DESCRIPTION POLARIZING PLATE COMPRISING LINEARLY POLARIZING FILM AND PHASE RETARDER [Field of invention] The present invention relates to a polarizing plate comprising a linearly polarizing film and a phase retarder, in which the polarizing film and the phase retarder are so arranged that their longitudinal directions may be essen- tially parallel to each other. The invention also relates to a circularly polarizing plate in which a linearly polar- izing film and a X./4 plate are so arranged that the absorp- tion axis of the film may be positioned at the angle of 45° to the slow axis of the X/4 plate.

Further, the invention relates to a liquid crystal display comprising an optical compensatory film, a circu- larly polarizing plate, and a liquid crystal cell in which nematic liquid crystal capable of bend alignment or hybrid alignment is sealed. The orientation vector of the liquid crystal changes its direction according to voltage applied to the liquid crystal cell. When the voltage is changed, the angle between the orientation vector and the substrate is changed.

[Background of invention] A liquid crystal display (LCD) has preferable charac- ters such as thin thickness, lightweight, and low power consumptions, compared with a cathode ray tube (CRT). The liquid crystal display, therefore, has been widely used in, for example, a notebook-size personal computer, a monitor, a TV set, a personal digital assistant (PDA), a cellular phone, a car navigation system or a video camera.

The most popular liquid crystal display comprises a cell of TN (twisted nematic) mode, in which twisted nematic liquid crystal is used. However, an image given by the TN mode display essentially fluctuates in color or contrast according to the viewing direction. Further, its response time is not fully satisfying.

U. S. Patent Nos. 4,583, 825 and 5,410, 422 disclose a liquid crystal display having a liquid crystal cell of bend alignment mode, in which rod-like liquid crystal molecules in upper part and ones in lower part are essentially re- versely (symmetrically) aligned. Since rod-like liquid crystal molecules in upper part and ones in lower part are symmetrically aligned, the liquid crystal cell of bend alignment mode has self-optical compensatory function.

Therefore, this mode is referred to as OCB (optically com- pensatory bend) mode.

The liquid crystal display of OCB mode must be equipped with an optical compensatory film, by which retar- dation of the displayed image seen frontally is cancelled and the viewing angle is enlarged. As the optical compen- satory film, a film comprising a transparent support and an optically anisotropic layer is described in Japanese Patent <BR> <BR> Provisional Publication No. 6 (1996) -214116, U. S. Patent Nos.

5,583, 679 and 5,646, 703, and West German Patent Publication No. 3911620A1.

In order to further improve the viewing angle of the OCB mode liquid crystal display, it has been studied to em- ploy an optical compensatory film used in a normal liquid crystal display. For example, U. S. Patent Nos. 5,805, 253, 6,064, 457 and W096/37804 (corresponding to European Patent Application No. 0783128A) disclose an optical compensatory film comprising an optically anisotropic layer of discotic liquid crystal. In those publications, an OCB mode liquid crystal display equipped with that film is also disclosed.

Because of the compensatory film having the anisotropic

layer of discotic liquid crystal, the disclosed liquid crystal display has a very wide viewing angle.

Further, a liquid crystal cell of HAN (hybrid-aligned- nematic) mode has been developed so that the above idea may be applied to a display of reflection type, and is proposed in the 42nd meeting (spring) of Japan Society Applied Phys- ics (29a-SZC-20,1995). In the liquid crystal cell of HAN mode, rod-like liquid crystal molecules in upper part of the bend alignment mode cell are oriented in hybrid align- ment. As the optical compensatory film for the HAN mode cell, a biaxially stretched film is proposed.

For further improving the viewing angle of the HAN mode display, Japanese Patent Provisional Publication No.

9 (1997) -21914 and Japanese Patent No. 3,118, 197 disclose an optical compensatory film having an optically anisotropic layer of discotic liquid crystal. In the patents, a HAN mode display equipped with the compensatory film is also disclosed.

The liquid crystal cell of OCB mode or HAN mode has a wide viewing angle and responds rapidly, as compared with a conventional liquid crystal cell (TN mode, STN mode), and hence has been used in a display of transmission type.

Further, it is also expected to develop a display of re- flection type or semi-transmission type comprising the cell of OCB mode or HAN mode. However, since a X/4 plate is in- dispensable in the display of reflection type or semi- transmission type, the production process is relatively complicated and the production yield is often lowered, as compared with the display of transmission type.

A liquid crystal cell of ECB (electrically controlled birefringence) mode, in which birefringent effect of liquid crystal is utilized to realize color displaying, is excel- lent in brightness and resolution of displayed images. It, therefore, is most widely used in a color TFT liquid crys- tal display, and described in many publications such as Ja-

panese Patent Provisional Publication No. 7 (1995)-230087 and"EL, PDP, and LCD displays (Japanese)", published by Toray Research Center (2001).

In a liquid crystal cell of OCB mode, HAN mode or ECB mode, the polarizing film must be placed so that the trans- mission axis of the film may be positioned at an angle of 20° to 70° to the rubbing direction for orienting the liq- uid crystal.

A polarizing plate generally comprises a polarizing film (which has polarizability) and a protective film lami- nated with an adhesive layer provided on one or each sur- face of the film. As a material for the polarizing film, polyvinyl alcohol (referred to as PVA) is mainly used. For example, after uniaxially stretched, a PVA film is colored with iodine or a dichromatic dye to prepare the polarizing film. Otherwise, after colored, the film may be stretched and crosslinked with a boron compound. As the protective film, a cellulose triacetate film is mainly used since it has high optically transparency and low birefringence.

The PVA film is normally stretched uniaxially in the longitudinal direction, and hence the prepared polarizing film (plate) has an absorption axis almost parallel to the longitudinal direction. Accordingly, for applying to an LCD of OCB mode, HAN mode or ECB mode, the polarizing plate prepared in the form of a roll must be stamped out obliquely at an angle of 20 to 70° to the longitudinal di- rection. Because of this oblique stamping, the whole pre- pared plate cannot be used. In fact, the end part of the rolled plate cannot be used. Particularly in making a lar- ge polarizing plate, the production yield is considerably lowered. Further, since it is difficult to reuse the re- maining polarizing plate (having many stamped holes), a large amount of waste is produced.

For solving the above problem, there have been pro- posed some methods for inclining the orientation axis of

polymer at a desired angle to the transferring direction of the film. Japanese Patent Publication No. 2000-9912 dis- closes a method for making the orientation axis oblique from the uniaxial stretching direction. In the method, while a plastic film is being laterally or longitudinally stretched, each edge of the film is stretched at a differ- ent speed in a longitudinal or lateral direction, respec- tively. However, if this method is performed with a tenter, the edges of the film must be transferred at different speeds. Consequently, the resultant film often has cramps (striped unevenness caused by inhomogeneous tensile stress), wrinkles and local unevenness of thickness, and hence it is difficult to realize the desired inclined angle (e. g., 45° in the case that the film is used in the polarizing plate).

On the other hand, if the difference between the transfer- ring speeds of edges is to be smaller, the stretching step must be performed in such a long production course to cost a lot.

In a method disclosed in Japanese Patent Provisional Publication No. 3 (1991) -182701, a continuous film is intro- duced into a course in which both edges of the film are held with plural pairs of holding means. The film is stretched with the holding means in a direction at the an- gle 8 to the transferring direction, to prepare a film hav- ing a stretching axis positioned at the angle 8 to the transferring direction. However, even in this method, the transferring speeds at both edges of the film are so dif- ferent from each other that the resultant film often has cramps and wrinkles. For relieving this trouble, it is ne- cessary to lengthen the course considerably. If so, how- ever, it also costs a lot.

Japanese Patent Provisional Publication No. 2 (1990)- 113920 proposes a method in which a film is introduced into a course comprising chucks arrayed in two lines. In the course, the chucks move on tenter rails so that each line

of chucks may run for a different distance. The film is transferred while the edges are being held between the lines of chucks, and thereby stretched in a direction oblique from the longitudinal transferring direction. How- ever, even a film stretched by this method often has cramps and wrinkles, and accordingly is unfavorable for optical uses.

[Summary of invention] An object of the present invention is to improve a po- larizing plate employable in an OCB mode liquid crystal display of semi-transmission type or in a HAN mode liquid crystal display of reflection type, and thereby to provide a polarizing plate which simplifies the production process and which improves the production yield of the display of semi-transmission type or reflection type.

Another object of the invention is to provide a method for obliquely stretching a polymer film, and thereby to im- prove the production yield of the polarizing plate.

A further object of the invention is to provide a po- larizing plate comprising a polymer film stretched oblique- ly by the above method. The aimed polarizing plate shows high performance and can be produced at a low cost.

A furthermore object of the invention is to provide a liquid crystal display of OCB mode, HAN mode or ECB mode comprising the above polarizing plate.

The present invention provides the following polariz- ing plates (1) to (4) and the following liquid crystal dis- plays (5) to (8).

(1) A polarizing plate which comprises a linearly polarizing film having a longitudinal direction and an ab- sorption axis, and a phase retarder having a longitudinal direction and a slow axis, wherein the longitudinal direc- tion of the linearly polarizing film is essentially paral- lel to the longitudinal direction of the phase retarder,

wherein the absorption axis of the linearly polarizing film is essentially parallel to the longitudinal direction of the linearly polarizing film, and wherein the slow axis of the phase retarder is essentially neither parallel nor per- pendicular to the longitudinal direction of the phase re- tarder.

(2) The polarizing plate as defined in (1), wherein the phase retarder is a X/4 plate, and wherein the slow ax- is of the phase retarder is positioned essentially at an angle of 45° to the longitudinal direction of the phase re- tarder.

(3) A polarizing plate which comprises a linearly polarizing film having a longitudinal direction and an ab- sorption axis, and a phase retarder having a longitudinal direction and a slow axis, wherein the longitudinal direc- tion of the linearly polarizing film is essentially paral- lel to the longitudinal direction of the phase retarder, wherein the absorption axis of the linearly polarizing film is essentially neither parallel nor perpendicular to the longitudinal direction of the linearly polarizing film, and wherein the slow axis of the phase retarder is essentially parallel to the longitudinal direction of the phase re- tarder.

(4) The polarizing plate as defined in (3), wherein the phase retarder is a X/4 plate, and wherein the absorp- tion axis of the linearly polarizing film is positioned es- sentially at an angle of 45° to the longitudinal direction of the linearly polarizing film.

(5) A liquid crystal display which comprises a liq- uid crystal cell and at least one polarizing plate, said liquid crystal cell comprising a pair of substrates each of which has a transparent electrode having a surface on which an orientation layer is provided, wherein nematic liquid crystal of bend alignment or hybrid alignment is sealed be- tween the orientation layers of the substrates, and wherein

the polarizing plate is clipped from the polarizing plate defined in one of (1) to (4).

(6) The liquid crystal display as defined in (5), wherein an optical compensatory film is provided between the liquid crystal cell and the polarizing plate, said op- tical compensatory film comprising a transparent support and an optically anisotropic layer of discotic liquid crys- tal oriented in a fixed alignment, and wherein the optical- ly anisotropic layer has such optical anisotropy that a Re (0°) retardation value is in the range of 10 to 60 nm (3525 nm), a Re (40°) retardation value is in the range of 80 to 130 nm (10525 nm) and a Re (-40°) retardation value is in the range of 10 to 60 nm (3525 nm).

The Re (0°), Re (40°) and Re (-40°) retardation values represent optically anisotropic values of the optical com- pensatory film. In a plane including the normal of the film and the direction giving the minimum retardation of the optically anisotropic layer, they are measured with a ray of 633 nm coming in the normal direction, in the direc- tion inclined at 40° from the normal to the side opposite to the direction giving the minimum retardation, and in the direction inclined at 40° from the normal to the direction giving the minimum retardation, respectively.

(7) The liquid crystal display as defined in (6), wherein the transparent support of the optical compensatory film has such optical anisotropy that a Re retardation val- ue is in the range of 10 to 70 nm and a Rth retardation value is in the range of 70 to 400 nm.

The Re and Rth retardation values are defined by the following formulas (I) and (II), respectively: (I) Re = (nx-ny) xd (II) Rth = {(nx+ny)/2-nx} xd in which nx is a refractive index along the show axis in the transparent support, ny is a refractive index along the traveling axis in the support, nz is a refractive index

along the depth of the support, and d is the thickness of the support in terms of nm.

(8) A liquid crystal display which comprises a po- larizing film prepared by continuously supplying an optical polymer film into a bent course in which, while both edges of the polymer film are held with holding means, the film is stretched under the conditions that: (i) the longitudinal stretching ratio is in the range of 1.2 to 10, (ii) the lateral stretching ratio is in the range of 1.1 to 20.0, (iii) the difference between longitudinal transferring speeds of the holding means at both edges is 1% or less, (iv) a state in which volatile content is 5% or more is present, and (v) the angle between the transferring direction and the essential stretching direction is in the range of 20° to 70° at the outlet of the course; characterized in that the liquid crystal display works according to OCB mode, HAN mode or ECB mode.

In the present specification, the term"essentially parallel", "essentially perpendicular"or"essentially at the angle of 45°"means the noticed angle is in the range of the strict anglet5°. Accordingly, the term"essentially neither parallel nor perpendicular"means the angle (angle on the smaller side, not more than 90°) is more than 5° and less than 85°.

According to the invention, the linearly polarizing film and the phase retarder can be laminated roll-to-roll in forming the polarizing plate. For producing a polariz- ing plate for a display of OCB mode, HAN mode or ECB mode or for a circularly polarizing plate, the polarizing film and the phase retarder (X/4 plate in the case of producing a circularly polarizing plate) must be laminated so that the absorption axis of the film may be positioned neither

parallel nor perpendicular to the slow axis of the retarder (k/4 plate). In fact, for producing a circularly polariz- ing plate, the absorption axis of the polarizing film must be positioned at 45° to the slow axis of the k/4 plate.

The linearly polarizing film in the form of a roll prepared in a conventional manner has an absorption axis parallel or perpendicular to the longitudinal direction, and also the phase retarder in the form of a roll prepared in a conven- tional manner has a slow axis parallel or perpendicular to the longitudinal direction. Therefore, in the roll-to-roll laminating procedure, it is impossible to place the absorp- tion axis of the film neither parallel nor perpendicular to the slow axis of the retarder. Accordingly, in a conven- tional production process, a chip stamped out of the line- arly polarizing film is laminated on one stamped out of the phase retarder.

According to the present invention, a phase retarder having a slow axis neither parallel nor perpendicular to the longitudinal direction or a linearly polarizing film having an absorption axis neither parallel nor perpendicu- lar to the longitudinal direction can be produced in the form of a roll. As a result, the invention makes it pos- sible to roll-to-roll laminate the polarizing film and the phase retarder so that the absorption axis of the film may be positioned neither parallel nor perpendicular to the slow axis of the retarder. Thus, a polarizing plate having the absorption axis neither parallel nor perpendicular to the slow axis (such as a circularly polarizing plate) can be produced through the roll-to-roll laminating procedure.

Being relatively simple and giving a high production yield at a low cost, the roll-to-roll laminating procedure is very advantageous as compared with the conventional method in which chips of the film and the retarder are laminated.

A liquid crystal display of bend alignment mode or HAN mode is a display of reflection type having a wide viewing

angle and responding rapidly. Therefore, if a circularly polarizing plate indispensable in the display is produced through a simple process with a high yield at a low cost, it is expected that-the display of bend alignment mode or HAN mode will be popularly used.

[Brief description of drawings] Fig. 1 is a schematic plan view illustrating an exam- ple of a method in which a polymer film is diagonally stretched.

Fig. 2 is a schematic plan view illustrating another example of a method in which a polymer film is diagonally stretched.

Fig. 3 is a schematic plan view illustrating still an- other example of a method in which a polymer film is diago- nally stretched.

Fig. 4 is a schematic plan view illustrating a further example of a method in which a polymer film is diagonally stretched.

Fig. 5 is a schematic plan view illustrating a still further example of a method in which a polymer film is di- agonally stretched.

Fig. 6 is a schematic plan view illustrating a yet still further example of a method in which a polymer film is diagonally stretched.

Fig. 7 is a schematic plan view showing a manner in which a conventional polarizing plate is formed by stamping out.

Fig. 8 is a schematic plan view showing a manner in which a polarizing plate of the invention is formed by stamping out.

[Detailed description of invention] (Liquid crystal cell) A liquid crystal cell of bend alignment mode or HAN mode is described in detail in Japanese Patent No.

3,118, 197.

The liquid crystal cell comprising liquid crystal ca- pable of bend alignment (namely, bend alignment cell) is a symmetrical cell, and a liquid crystal display having the cell essentially has a wide viewing angle. Also a liquid crystal display of reflection type comprising liquid crys- tal capable of HAN alignment essentially has a wide viewing angle.

A liquid crystal cell generally comprises a pair of substrates and nematic liquid crystal enclosed between them.

Each substrate has a transparent electrode on the surface.

In the bend alignment cell, nematic liquid crystal oriented in bend alignment when voltage is applied is used. The liquid crystal used in the bend alignment cell generally has positive dielectric anisotropy. The orientation vector of the nematic liquid crystal changes its direction accord- ing to the voltage applied to the liquid crystal cell.

When the voltage is changed, the angle between the orienta- tion vector and the substrate is changed. Normally, ac- cording as the voltage increases, the angle increases and the birefringence decreases to display an image. In the present specification, "liquid crystal in bend alignment" means that the orientation vectors (directors or optical axes) of the liquid crystal molecules in the liquid crystal layer are symmetrical (linearly symmetrical) based on the center line of the layer and, at the same time, that there is a bend part at least near the substrate. The term"bend part"means an area where a line formed by the directors near the substrate bends.

In other words, when the voltage is applied to a liq- uid crystal cell of bend alignment mode, directors of the

liquid crystal molecules near the lower substrate are al- most parallel to the substrate. The angle between the di- rector and the substrate increases with increase of dis- tance from the lower substrate, and the molecules posi- tioned in the central area (area where the distance from the lower substrate is almost equal to that from the upper one) have directors perpendicular or almost perpendicular to the substrate. According as the distance from the lower substrate further increases, the angle between the director and the substrate further increases. Finally, directors of the molecules near the upper substrate are almost parallel to the substrate. The directors in the central area may be oriented in twisted alignment. Further, the directors near or in contact with the upper or lower substrate may be in- clined from the substrate surface (namely, they may have tilt angles).

In the liquid crystal cell of bend alignment, the product (Anxd) of the refractive anisotropy of liquid crys- tal (An) and the thickness of liquid crystal layer (d) is preferably in the range of 100 to 2,000 nm, more preferably in the range of 150 to 1,700 nm, most preferably in the range of 500 to 1,500 nm. If the product is in the above ranges, both high brightness and a wide viewing angle are realized.

The HAN mode is well known in the field of liquid crystal displays. In a HAN alignment cell, the lower sub- strate is placed at the position corresponding to the cen- ter line of bend alignment cell. The lower substrate has an orientation layer that orients nematic liquid crystal in homeotropic alignment. Examples of the orientation layer include layers of deposited inorganic compounds, surface- active agents and organic silane compounds. Nematic liquid crystal used in the HAN alignment cell is oriented in hy- brid alignment when voltage is applied to the cell.

In the HAN alignment cell, it is preferred that the liquid crystal molecules on one substrate be essentially vertically aligned and that those on the other substrate be aligned at a pre-tilt angle of 0 to 45°. The product (Anxd) of the refractive anisotropy of liquid crystal (An) and the thickness of liquid crystal layer (d) is preferably in the range of 100 to 1,000 nm, more preferably in the range of 300 to 800 nm. The substrate vertically aligning the molecules may be either on the reflection board side or on the transparent electrode side.

The liquid crystal cell of bend alignment or HAN alignment has an area of self-optical compensating direc- tors. However, when even a display comprising the self- optical compensatory cell is very obliquely (particularly, upward and downward) seen, the transmittance through a dark part of displayed image increases to lower the contrast.

If the optical compensatory film of the invention is at- tached on the cell, the contrast of image seen obliquely is improved without lowering that seen frontally.

(Linearly polarizing film) For producing a circularly polarizing plate, a line- arly polarizing film is laminated on a X/4 plate so that the absorption axis of the film may be positioned at 45° to the slow axis of the plate. In order to produce the circu- larly polarizing plate through the roll-to-roll lamination, an oblong linearly polarizing film having the absorption axis inclined at 45° to the longitudinal direction and an oblong phase retarder having the slow axis parallel to the longitudinal direction are preferably used in combination.

Otherwise, an oblong linearly polarizing film having the absorption axis parallel to the longitudinal direction and an oblong phase retarder having the slow axis inclined at 45° to the longitudinal direction are also preferably used in combination.

There have been proposed some methods for inclining the orientation axis of polymer at a desired angle to the transferring direction of the film.

Japanese Patent Publication No. 2000-9912 discloses a method for making the orientation axis oblique from the uniaxial stretching direction. In the method, while a plastic film is being laterally or longitudinally stretched, each edge of the film is stretched at a different speed in a longitudinal or lateral direction, respectively.

In a method disclosed in Japanese Patent Provisional <BR> <BR> Publication No. 3 (1991) -182701, a continuous film is intro- duced into a course in which both edges of the film are held with plural pairs of holding means. The film is stretched with the holding means in a direction at a de- sired angle 0 to the transferring direction, to prepare a film having a stretching axis positioned at the angle 8 to the transferring direction.

Japanese Patent Provisional Publication No. 2 (1990)- 113920 proposes a method in which a film is introduced into a course comprising chucks arrayed in two lines. In the course, the chucks move on tenter rails so that each line of chucks may run for a different distance. The film is transferred while the edges are being held between the lines of chucks, and thereby stretched in a direction oblique from the longitudinal transferring direction.

Further, a polarizing plate may be subjected to rub- bing treatment to incline the transmission axis. Further- more, a polymer film may be obliquely stretched to produce an oblong polarizing film in the form of a roll, which is preferably used for producing a linearly polarizing film.

As a material for the linearly polarizing film, poly- vinyl alcohol (referred to as PVA) is mainly used. For ex- ample, after uniaxially stretched, a PVA film is colored with iodine or a dichromatic dye to prepare the polarizing film. Otherwise, after colored, the film may be stretched

and crosslinked with a boron compound. A film of polyene is also usable. For example, after stretched, the polyene film is dyed to prepare the polarizing film.

The linearly polarizing film having the absorption ax- is neither parallel nor perpendicular to the longitudinal direction can be produced, for example, in the following manner.

A polymer (normally, PVA) film is continuously sup- plied into a course in which both edges of the film are held with holding means, which stretch the film while run- ning in the longitudinal direction. The course satisfies the condition represented by the formula (1) : gL2-L1l>0. 4W.

In the formula (1), L1 is the travel from the starting position of holding one edge of the film to the releasing position, L2 is the travel from the starting position of holding the other edge to the releasing position, and W is the substantial width of the film at the terminal of stretching. In the course, the film is stretched while the supporting property of the film is kept in the presence of a sate in which volatile content is 5% or more. After the stretching procedure is completed, the film is made to shrink so that the amount of volatile matters may be low- ered. Thus formed film is wound up to a roll.

Figs. 1 and 2 each shows a schematic plan view for il- lustrating a typical example of a method in which polymer film is diagonally stretched.

The stretching method comprises the steps of (a) in- troducing a raw film in a direction indicated by an arrow (A), (b) stretching the film in a width direction thereof, and (c) transferring the stretched film to a subsequent step, that is to say, in a direction indicated by an arrow (b). The term"stretching step"as used hereinafter means the whole steps for performing the stretching method in- cluding these steps (a) to (c).

The film is continuously introduced in the direction indicated by (A) and first held at point B1 with a holding means on the left as seen from the upstream side. At this moment, the other edge of the-film is not held, so that no tension is developed in the width direction. That is to say, point B1 does not correspond to the substantial hold- ing initiation point.

In the invention, the substantial holding initiation point is defined by point at which both edges of the film are first held. The substantial holding initiation point is indicated by two points of holding initiation, point Al on the downstream side and point Cl at which a straight line roughly perpendicularly drawn from Al to a center line 11 (Fig. 10) or 21 (Fig. 2) of the film on the introduction side intersects a locus 13 (Fig. 1) or 23 (Fig. 2) of the holding means.

When holding means on both edges are transferred sub- stantially at the same speed, starting at these points, Al moves to A2, A3, An for each time unit, and Cl similarly moves to C2, C3, Cn. That is to say, stretching direction at that moment is indicated by a line connecting points An and Cn which the standard holding means pass at the same moment.

In the method of the invention, An is gradually delay- ed to Cn as shown in Figs. 1 and 2, so that the stretching direction slowly comes to be inclined from a direction per- pendicular to the transferring direction. The substantial holding release point of the invention is defined by two points, point Cx on the downstream side at which the film is released from the holding means and point Ay at which a straight line roughly perpendicularly drawn from Cx to a center line 12 (Fig. 1) or 22 (Fig. 2) of the film trans- ferred to a subsequent step intersect a locus 14 (Fig. 1) or 24 (Fig. 2) of the holding means on the opposite side.

The angle of the final stretching direction of the film is determined by the ratio of the difference Ay-Ax (that is to say, IL1-L21) in the travel between the right and left holding means at a substantial end point of the stretching step (the substantial holding release point) to the distance W between the substantial holding release points (the distance between Cx and Ay). Accordingly, the angle of inclination 9 made by the stretching direction and the transferring direction to the subsequent step satisfies the following equation: tanO = W/(Ay-Ax), that is to say, tan 6 = W/L1-L2I.

Although an upper edge of the film in Figs. 1 and 2 is held until 18 (Fig. 1) or 28 (Fig. 2) also after point Ay, the other edge is not held. Accordingly, no new stretching in the width direction is developed, so that 18 and 28 do not correspond to the substantial holding release point of the invention.

As described above, the substantial holding initiation points on both edges of the film are not simple holding points by the holding means on the right and left sides.

When the above-mentioned definition is more strictly de- scribed, the two substantial holding initiation points of the invention are each a point at which the straight line connecting either of the right and left holding points and the other holding point intersects at about right angles with the center line of the film introduced into the step of holding the film, and are defined as points positioned most upstream.

Similarly, the two substantial holding release points are each a point at which the straight line connecting ei- ther of the right and left holding points and the other holding point intersects at about right angles with the center line of the film sent out to the subsequent step, and are defined as points positioned most downstream.

The term"about right angles"as used herein means that the angle made by the center line of the film and the straight line connecting the right and left substantial holding initiation points or substantial holding release points is 900. 5°.

When it is tried that the difference in the travel be- tween the right and left holding means is given using a stretching machine of the tenter system like the invention, a great gap between the holding point held by the holding means and the substantial holding initiation point, or be- tween the release point from the holding means and the sub- stantial holding release point is sometimes developed by mechanical restrictions such as the length of a rail. How- ever, so long as the travel between the substantial holding initiation point and substantial holding release point de- fined above satisfies the relationship of equation (1), the object of the invention is attended.

In the above, the inclined angle of the orientation axis in the resulting stretched film can be controlled and adjusted by the ratio of the difference iLl-L21 in the travel between the right and left holding means to the out- let width W of step (c).

In the polarizing plates and the birefringent films, films oriented at 45° to the longitudinal directions are often desired. In this case, for obtaining an orientation angle of nearly 45°, it is preferable to satisfy the fol- lowing equation (2): 0. 9W < iLl-L21 < 1. 1W (2) It is more preferable to satisfy the following equa- tion (3): 0.97W < ILl-L21 < 1.03W (3) Specific examples of structures of the stretching steps are shown in Figs. 1 to 6 in which the polymer films are diagonally stretched satisfying the equation (1), and

these can be arbitrarily designed, taking installation coat and productivity into consideration.

The angel made by the direction (A) in which the film is introduced into the stretching step and the direction (B) in which the film is transferred to the subsequent step can be any numerical value. From the viewpoint that the total installation area of equipment including steps before and after stretching is minimized, it is preferred that this angle is as small as possible. The angle is prefera- bly within 3°, and more preferably within 0. 5°. For exam- ple, the structures shown in Figs. 1 and 4 can achieve this value.

In the method in which the running direction of the film is not substantially changed as described above, it is difficult to obtain an orientation angle of 45° to the lon- gitudinal direction, which is preferred in the polarizing plates and the birefringent films, only by enlarging the distance between the holding means. Thus, IL1-L21 can be increased by providing a step of shrinking the film after once stretched as shown in Fig. 1.

The stretch ratio is desirably from 1.1 to 20.0, and more desirably from 2 to 10. The subsequent shrinkage ra- tio is desirably 10% or more. Further, it is also preferred that stretching and shrinking are conducted two or more times as shown in Fig. 4, because ILl-L21 can be increased.

Furthermore, from the viewpoint of minimized installa- tion cost of the stretching step, a fewer bending cycles and a smaller bending angle of the locus of the holding means are preferred. From this viewpoint, it is preferred that the running direction of the film is bent with both edges of the film held so that the running direction of the film at an outlet of the step of holding both edges of the film is inclined at an angle of 40 to 50° to the substan-

tial stretching direction of the film as shown in Figs. 2, 3 and 5.

As an apparatus for stretching the film while holding both edges thereof in the invention, there is preferably used a tenter apparatus as shown in any one of Figs. 1 to 5.

In addition to the conventional two dimensional tenters, a stretching step of helically giving the difference in the travel of the holding means on both edges as shown in Fig.

6 can also be used.

In the tenter type stretching machine, chains to which clips are fixed move along rails in many cases. The later- ally uneven stretching method like the invention results in the deviation of terminal ends of the rails at an inlet and outlet of the step, which sometimes causes the film not to be held and released at the right and left edges thereof at the same time, as shown in Figs. 1 and 2. In this case, the substantial travel lengths L1 and L2 are not simple distance between the holding points and the release points, but the travel lengths of the portions in which both ends of the film are held with the holding means, as already stated.

When there is a difference in running speed between the right and left edges of the film at an outlet of the stretching step, wrinkles and local unevenness of film thickness are developed at the outlet of the stretching step. It is therefore desired that the right and left film holding means are substantially the same as with each other in transferring speed. The difference in transferring speed is preferably 1% or less, more preferably less than 0. 5%, and most preferably less than 0. 05%. The term "speed"as used herein means the length of a locus formed by each of the right and left holding means moving per min- ute. In a general tenter type stretching machine or the like, the unevenness of speed is generated on the order of seconds or less, depending on the cycle of sprocket teeth

driving a chain and the frequency of a drive motor, and an unevenness of several percents is often generated. However, this unevenness of speed does not correspond to the differ- ence in speed described in the invention.

Wrinkles and local unevenness of film thickness are developed according to the generation of the difference in the travel between the right and left holding means. For solving this problem, the invention comprises maintaining the supporting property of the polymer film, stretching the film in the presence of a state in which the volatile con- tent is 5% or more, and then, decreasing the volatile con- tent while shrinking the film. The term"maintaining the supporting property of the polymer film"as used herein means that the film can be held at both sides without im- pairment of film properties.

Further, the term"stretching the film in the presence of a state in which the volatile content is 5% or more" does not necessarily mean that a state in which the vola- tile content is 5% or more is maintained throughout the en- tire course of the stretching step, but means that the volatile content may be less than 5% in a part of the stretching step, as long as the stretching at a volatile content of 5% or more expresses the effect of the invention.

Methods for allowing the volatile matter to be contained in such a form include: a method for casting a film, thereby allowing the volatile matter such as water or a non-aqueous solvent to be contained; a method of immersing a film in the volatile matter such as water or a non-aqueous solvent, coating a film therewith, or spraying it on a film, before stretching; and a method of coating a film with the vola- tile matter such as water or a non-aqueous solvent during stretching. A film of a hydrophilic polymer such as poly- vinyl alcohol contains water in an atmosphere of high tem- perature and humidity, so that it can be allowed to contain the volatile matter by stretching after moisture condition-

ing in an atmosphere of high humidity, or by stretching un- der conditions of high humidity. Other than these methods, any means may also be used as long as the volatile content of a polymer film can be 5% or more.

The preferred volatile content varies according to the kind of polymer film. The maximum value of the volatile content may be any as long as the supporting property of the polymer film is maintained. The volatile content is preferably from 10% to 100% for polyvinyl alcohol, and preferably from 10% to 200% for a cellulose acylate.

The stretched film may be shrunk in either of the steps during and after stretching. Means for shrinking the film include a method of removing the volatile matter by elevation of temperature. However, any means may be used as long as the film is shrunk. The volatile content after drying is preferably 3% or less, more preferably 2% or less, and still more preferably 1. 5% or less.

A rail for restricting the locus of the holding means in the invention is often required to have a large bending curvature. For avoiding interference of the film holding means with each other or local stress concentration caused by sharp bending, it is preferred that the locus of the holding means draw a circular arc at a bend.

There is no particular limitation on the polymer film to be stretched in the invention. Films of appropriate po- lymers soluble in volatile solvent can be used. Examples of the polymers include PVA, polycarbonates, cellulose acy- lates and polysulfones.

Although there is no particular limitation on the thickness of the film before stretching, it is preferably from 1 pm to 1 mm, and particularly preferably from 20 pm to 200 pm, from the viewpoints of the stability of film holding and the uniformity of stretching.

Although the stretched film of the invention can be used for various purposes, it is suitably used as the po-

larizing film or the birefringent film by the characteris- tics that the orientation axis is inclined to the longitu- dinal direction. In particular, the polarizing film in which the orientation axis is inclined at 40 to 50°, more preferably 44 to 46°, to the longitudinal direction is preferably used as a polarizing plate for an LCD.

When the invention is used for the production of the polarizing film, PVA is preferably used as the polymer.

PVA is usually a product obtained by saponifying polyvinyl acetate. However, it may contain components copolymeriz- able with vinyl acetate, such as unsaturated carboxylic ac- ids, unsaturated sulfonic acids, olefins and vinyl ethers.

Modified PVA containing acetoacetyl groups, sulfonic acid groups, carbonyl groups and/or oxyalkylene groups can also be used.

Although there is no particular limitation on the de- gree of saponification of PVA, it is preferably from 80 to 100 mol%, and particularly preferably from 90 to 100 mol%, from the viewpoint of solubility. Further, although there is no particular limitation on the degree of polymerization of PVA, it is preferably from 100 to 10,000, and particu- larly preferably from 1,500 to 5,000.

The polarizing film is obtained by dying PVA, and the dying process is conducted by gas-phase or liquid-phase ad- sorption. When iodine is used as an example of the liquid- phase adsorption, a PVA film is immersed in an aqueous so- lution of iodine-potassium iodide. The amount of iodine is preferably from 0.1 to 20 g/liter, the amount of potassium iodide is preferably from 1 to 100 g/liter, and the weight ratio of iodine to potassium iodide is from 1 to 100. The dying time is preferably from 30 to 5,000 seconds, and the solution temperature is preferably from 5 to 50°C. As the dying method, there can be used any means, such as not only immersion, but also coating or spraying of an iodine or dye solution. The dying step may be situated either before or

after the stretching step of the invention. However, it is particularly preferred that the film be dyed in the liquid phase before the stretching step, because the film is prop- erly swelled to result in easy stretching.

Dying with a dichromatic dye as well as iodine is also preferred. Specific examples of the dichromatic dyes in- clude dye compounds such as azo-based dyes, stilbene-based dyes, pyrazolone-based dyes, triphenylmethane-based dyes, quinoline-based dyes, oxazine-based dyes, thiazine-based dyes and anthraquinone-based dyes. The dyes are preferably water-soluble, but are not limited thereto. Further, it is preferred that hydrophilic substituent groups such as sul- fonic acid groups, amino groups and hydroxyl groups are in- troduced into these dichromatic molecules. Specific exam- ples of the dichromatic molecules include C. I. Direct Yel- low 12, C. I. Direct Orange 39, C. I. Direct Orange 72, C. I.

Direct Red 39, C. I. Direct Red 79, C. I. Direct Red 81, C. I.

Direct Red 83, C. I. Direct Red 89, C. I. Direct Violet 48, C. I. Direct Blue 67, C. I. Direct Blue 90, C. I. Direct Green 59 and C. I. Direct Acid Red 37, and further include dyes described in Japanese Patent Provisional Publication Nos.

1 (1989) -161202, 1 (1989) -172906, 1 (1989) -172907, 1 (1989)-<BR> 183602,1 (1989) -248105,1 (1989) -265205 and 7 (1995)-261024.

These dichromatic molecules are used as free acids, alkali metal salts, ammonium salts or amine salts. A polarizing plate having various hues can be produced by compounding two or more kinds of these dichromatic molecules. A polar- izing element or polarizing plate containing a compound (dye) exhibiting black when a polarizing axis intersects at right angels, or containing various kinds of dichromatic molecules so as to show black is preferably excellent in both single plate transmittance and polarizing rate.

In the course of producing the polarizing film by stretching PVA, an additive for crosslinking PVA is prefer- ably used. In particular, when the diagonal stretching

method of the invention is used, the insufficiently hardened PVA film at the outlet of the stretching step sometimes causes deviation of the orientation direction of the PVA film due to tension given in the step. Accordingly, the film is preferably immersed in or coated with a solu- tion of a crosslinking agent in the step prior to stretch- ing or in the stretching step, thereby allowing the crosslinking agent to be contained in the film. As the crosslinking agents, there can be used agents described in U. S. Reissue Patent 232897, and most preferred are boric acid compounds.

The stretching method of the invention is also prefer- ably used in the production of a so-called polyvinylene- based polarizing film in which the polyene structure is formed by dehydration of PVA or dechlorination of polyvinyl chloride to obtain polarization caused by conjugated double bonds.

As the linearly polarizing film, a film of cellulose triacetate can be used. The cellulose triacetate film has such high optical transparency and such low birefringence that it is used as a protective film of optical compensa- tory film, phase retarder (1/4 plate) or normal polarizing plate.

The polarizing film produced in the invention is used as the polarizing plate by adhering a protective film or protective films to one or both sides thereof. There is no particular limitation on the kind of protective film. Ex- amples of the protective films that can be used in the in- vention include cellulose esters such as cellulose acetate, cellulose butyrate and cellulose propionate, polycarbonates, polyolefins, polystyrene and polyesters. The protective film of polarizing plate must have specific characters such as high transparency, proper moisture permeability, low bi- refringence and proper rigidity. From this viewpoint, cel-

lulose acylates are preferred, and cellulose acetate is particularly preferred.

The characters of the protective film can be desirably selected according to the usage. The protective film for normal LCD of transmission type preferably has the follow- ing characters. The thickness is preferably in the range of 5 to 500 pm, more preferably in the range of 20 to 200 Hm, particularly preferably in the range of 20 to 100 pm, form the viewpoint of handling and durability. The retar- dation value at 632.8 nm is preferably in the range of 0 to 150 nm, more preferably in the range of 0 to 20 nm, most preferably in the range of 0 to 5 nm. The slow axis of the protective film is preferably placed essentially parallel or perpendicularly to the absorption axis of the polarizing film, so as not to circularly polarize the linearly polar- ized light. However, if the protective film is designed to function as an element changing the polarized light such as a phase retarder, the slow axis of the protective film may be placed at any angle to the absorption axis of the polar- izing film.

The transmittance for visible light is preferably 60% or more, particularly preferably 90% or more. After the film is treated at 90°C for 120 hours, it shrinks in a di- mension decreasing ratio of preferably 0.3 to 0. 01%, more preferably 0.15 to 0. 01%. The tensile strength measured by a tensile test is preferably in the range of 50 to 1,000 Mpa, more preferably in the range of 100 to 300 Mpa. The moisture permeability is preferably in the range of 100 to 800 g/m2 day, more preferably in the range of 300 to 600 g/m2-day. Needless to say, the above values and ranges by no means restrict the invention.

Cellulose acylate preferably used for the protective film is described below in detail. In a preferred cellu- lose acylate, the degrees of substituted hydroxyl in cellu-

lose (substitution degrees) satisfy all the conditions rep- resented by the following formulas (I) to (IV): (I) 2.6 < A+B < 3.0 (II) 2.0 A < 3.0 (III) 0 < B s 0.8 (IV) 1.9 < A-B in which A is a substitution degree of acetyl group substi- tuting hydroxyl in cellulose, and B is a substitution de- gree of acyl group having 3 to 5 carbon atoms. Cellulose generally has three hydroxyls in one glucose unit, and hence the above substitution degrees are based on 3.0.

That is to say, the maximum substitution degree is 3.0. In cellulose triacetate, the substitution degree A is general- ly in the range of 2.6 to 3.0 (which means non-substituted hydroxyl is 0.4 at the most) and the degree B is 0. As a cellulose acylate used for the protective film of polariz- ing plate, a cellulose triacetate in which all the acyl groups are acetyls or which contains 2.0 or more of acetyls, 0.8 or less (particularly preferably 0.3 or less, in con- sideration of film property) of acyl groups and 0.4 or less of non-substituted hydroxyls is preferred. For determining the substitution degree, the amounts of acetic acid and fatty acid of 3 to 5 carbon atoms substituting the hydrox- yls in cellulose are measured and calculated according to ASTM : D-817-91.

Examples of the acyl group having 3 to 5 carbon atoms other than acetyl include propionyl (C2H5C0-), butyryl (n-, iso-C3H7CO-) and valeryl (n-, iso-, sec-, tert-C4HgCO-).

Among them, n-substituted groups are preferred and n- propionyl is particularly preferred because of mechanical strength of the resultant film and solubility. If the sub- stitution degree of acetyl group is low, the resultant film is poor in mechanical strength and durability against heat and moisture. If the substitution degree of acyl group having 3 to 5 carbon atoms is high, solubility of the cel-

lulose acylate to an organic solvent is improved. The cel- lulose acylate having the substitution degrees in the above ranges has preferable characters.

The (viscosity average) polymerization degree of cel- lulose acylate is preferably in the range of 200 to 700, more preferably in the range of 250 to 550. For determin- ing the viscosity average polymerization degree, the vis- cosity is measured with an Ostwald's viscometer. Form the obtained specific viscosity [], the viscosity average po- lymerization degree DP is calculated according to the for- mula: DP = []/Km in which Km is a constant 6x10-4.

Cellulose as the starting material for preparation of cellulose acylate can be obtained from cotton linters or wood pulp. A mixture of raw pulp can be also used.

The protective film of cellulose acylate is normally formed according to the solvent cast method, which compris- es the steps of dissolving the cellulose acylate and addi- tives in a solvent to prepare a thick solution (that is called'dope'), casting the solution on an endless support such as drum or band, and evaporating the solvent to form a film. The dope is preferably prepared so that the solid content may be in the range of 10 to 40 wt. %. The surface of the drum or band is preferably polished to give a mirror plane. The casting and drying steps of the solvent cast method are described in U. S. Patent Nos. 2,336, 310, 2,367, 603,2, 492,078, 2,492, 977,2, 492,978, 2,607, 704, 2,739, 069,2, 739,070, British Patent Nos. 640,731, 736,892, Japanese Patent Publication Nos. 45 (1970) -4554, 49 (1974)- 5614, Japanese Patent Provisional Publication Nos.

60 (1985) -176834, 60 (1985) -203430 and 62 (1987)-115035.

Two or more cellulose acylate solutions can be coop- eratively cast to form two or more layers. For example, two or more outlets are arranged at intervals along the running direction of the support, and from each outlet each cellulose acylate solution is cast to form a layered film

(Japanese Patent Provisional Publication Nos. 61 (1986)- 158414,1 (1989) -122419 and 11 (1999) -198285). Otherwise, cellulose acylate solutions may be cast from two outlets to form a film (Japanese Patent Publication No. 60 (1985)-27562, Japanese Patent Provisional Publication Nos. 61 (1986)-94724, <BR> <BR> 61 (1986) -947245, 61 (1986) -104813, 61 (1986) -158413 and<BR> 6 (1994) -134933). Further, a flow of high-viscous cellulose acylate solution may be enclosed with a flow of low-viscous one to form a layered flow, and the high-and low-viscous solutions in the layered flow may be simultaneously extrud- ed to produce a film (Japanese Patent Provisional Publica- tion No. 56 (1981)-162617).

Examples of the solvent in which cellulose acylate is <BR> <BR> dissolved include hydrocarbons (e. g. , benzene, toluene),<BR> hologenated hydrocarbons (e. g. , methylene chloride, chloro-<BR> benzene), alcohols (e. g. , methanol, ethanol, diethylene<BR> glycol), ketones (e. g. , acetone), esters (e. g. , ethyl ace- tate, propyl acetate) and ethers (tetrahydrofuran, methyl cellosolve). Hologenated hydrocarbons having 1 to 7 carbon atoms are preferred, and methylene chloride is most pre- ferred. From the viewpoint of solubility, property of re- leasing from the support, mechanical strength and optical character of the formed film, a mixed solvent of methylene chloride and one or more alcohols having 1 to 5 carbon at- oms is preferred. The amount of the alcohols is preferably in the range of 2 to 25 wt. %, more preferably in the range of 5 to 20 wt. % based on the total weight of the solvent.

Examples of the alcohols include methanol, ethanol, n- propanol, iso-propanol and n-butanol. Methanol, ethanol, n-propanol and mixture thereof are preferably used.

In addition to cellulose acylate, the dope may contain additives such as plasticizer, ultraviolet absorber, inor- ganic fine particles, salts of alkaline earth metals such as calcium and magnesium as thermal stabilizer, antistatic

agent, fire retardant, slipping agent, oil, releasing agent, and hydrolysis inhibiter of cellulose acylate.

As the plasticizer, phosphoric esters and carboxylic esters are used. Examples of the phosphoric esters include triphenyl phosphate (TPP), tricresyl phosphate (TCP), cre- syldiphenyl phosphate, octyldiphenyl phosphate, diphenyl- biphenyl phosphate, trioctyl phosphate and tributyl phos- phate. Typical examples of the carboxylic esters are phthalic esters and citric esters. Examples of the phthal- ic esters include dimethyl phthalate (DMP), diethyl phtha- late (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP). Examples of the citric esters include triethyl o- acetylcitrate (OACTE) and tributyl o-acetylcitrate (OACTB), acetyltriethyl citrate and acetyltributyl citrate.

Other carboxylic esters such as butyl oleate, methy- lacetyl ricinoleate, dibutyl sebacate and various trimel- litic esters such as trimethyl trimellitate are also usable.

Examples of the glycolic esters include triacetin, tribu- tyrin, butylphthalyl butylglycolate, ethylphthalyl ethyl- glycolate, methylphthalyl ethylglycolate and butylphthalyl butylglycolate. Triphenyl phosphate, biphenyldiphenyl phosphate, tricresyl phosphate, cresyldiphenyl phosphate, tributyl phosphate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diethylhexyl phtha- late, triacetin, ethylphthalyl ethylglycolate and trimethyl trimellitate are preferably used. In particular, triphenyl phosphate, biphenyldiphenyl phosphate, diethyl phthalate, ethylphthalyl ethylglycolate and trimethyl trimellitate are preferred. These may be used singly or in combination.

The amount of the plasticizer is in the range of preferably 5 to 30 wt. %, more preferably 8 to 16 wt. % based on the amount of the cellulose acylate. These may be added to- gether with cellulose acylate and the solvent when the dope

is prepared, or otherwise they may be added to the prepared dope.

The ultraviolet absorber can be desirably selected ac- cording to the aim. Examples of the ultraviolet absorber include salicylic ester-based agents, benzophenone-based agents, benztriazole-based agents, benzoate-based agents, cyanoacrylate-based agents and nickel complex salt-based agents. Benzophenone-based agents, benztriazole-based agents and salicylic ester-based agents are preferably used.

Examples of the benzophenone-based agents include 2,4- dihydroxybenzophenone, 2-hydroxy-4-acetoxybenzophenone, 2- hydroxy-4-methoxybenzophenone, 2, 2'-di-hydroxy-4- methoxybenzophenone, 2, 2'-di-hydroxy-4', 4- methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2- hydroxy-4-dodecyloxybenzophenone, and 2-hydroxy-4- (2- hydroxy-3-methacryloxy) propoxybenzophenone. Examples of the benztriazole-based agents include 2- (2'-hydroxy-3'- tert-butyl-5'-methylphenyl)-5-chlorobenztriazole, 2- (21- hydroxy-5'-tert-butylphenyl) benztriazole, 2-(2'-hydroxy- 3', 5'-di-tert-amylphenyl) benztriazole, 2-(2'-hydroxy-3', 5'- di-tert-butylphenyl) -5-chlorobenztriazole, and 2- (21- hydroxy-5'-tert-octylphenyl) benztriazole. Examples of the salicylic ester-based agents include phenyl salicylate, p- octylphenyl salicylate, and p-tert-butylphenyl salicylate.

Among them, 2-hydroxy-4-methoxybenzophenone, 2, 2'-di- hydroxy-4', 4-methoxybenzophenone, 2- (2'-hydroxy-3'-tert- butyl-5'-methylphenyl)-5-chlorobenztriazole, 2-(2'-hydroxy- 5'-tert-butylphenyl) benztriazole, 2- (2'-hydroxy-3', 5'-di- tert-amylphenyl) benztriazole, 2- (2'-hydroxy-3', 5'-di-tert- butylphenyl) -5-chlorobenztriazole are particularly pre- ferred.

It is particularly preferred that two or more agents absorbing light at different wavelengths be used to shield the plate from the ultraviolet light in a wide wavelength region. The amount of the ultraviolet absorber is prefera-

bly in the range of 0.01 to 5 wt. %, more preferably in the range of 0.1 to 3 wt. %, base on the amount of cellulose acylate. The absorber may be added to the solvent together with cellulose acylate, or otherwise may be added to the prepared dope. Preferably, immediately before casting, a solution of the ultraviolet absorber is mixed into the dope by means of, for example, a static mixer.

Examples of the inorganic fine particles include sil- ica, kaolin, talc, diatomaceous earth, quartz powder, cal- cium carbonate, barium sulfate, titanium oxide and alumina.

Before added into the dope, the fine particles are prefera- bly dispersed in a binder solution by means of, for example, high speed mixer, ball mill, attriter or supersonic disper- ser. As the binder, cellulose acylate is preferred. The fine particles are preferably dispersed together with other additives such as ultraviolet absorber. Any solvent may be used for dispersing the particles, but it is preferably similar to the solvent for the dope. The number average size of the particles is preferably in the range of 0.01 to 100 pm, 0.1 to 10 pm. The dispersion may be added in the stage of dissolving cellulose acylate or at other stages, but preferably is mixed into the dope by means of, for ex- ample, a static mixer immediately before casting.

As the releasing agent, surface active agents are pre- ferred. Examples of the surface active agents include phosphate-based agents, sulfonate-based agents, carbonate- based agents, nonionic agents and cationic agents. Other surface active agents may be used. Japanese Patent Provi- sional Publication No. 61 (1986) -243837 describes the re- leasing agents.

In the case that the cellulose acetate film is used as a protective film, the film is preferably made hydrophilic by subjecting the surface to saponification treatment, corona discharge treatment, flame treatment or glow dis- charge treatment, so as to enhance adhesion to a PVA resin.

Otherwise, the surface is coated with a solution containing a hydrophilic resin dissolved in a solvent compatible with cellulose acylate. For making the film surface hydrophilic, saponification treatment is preferred since it does not im- pair the planeness and properties of the film. The saponi- fication treatment is performed by, for example, immersing the film in an aqueous solution of alkali such as sodium hydroxide. After the treatment, the film is neutralized with an acid of low concentration and washed well with wa- ter.

On the protective film of polarizing plate, various functional layers may be provided. Examples of the func- tional layers include an optically anisotropic layer for compensating the viewing angle of LCD (described in Japane- se Patent Provisional Publication Nos. 4 (1992)-229828, <BR> <BR> 6 (1994) -75115 and 8 (1996) -50206), anti-glare layer or anti- reflection layer for improving recognizability of the dis- play, polymer-dispersed liquid crystal layer or cholesteric liquid crystal layer (which separates PS wave by anisotrop- ic scattering or anisotropic optical interference so as to improve the brightness of LCD), hard coating layer for im- proving anti-scratching property of the polarizing plate, gas-barrier layer for inhibiting moisture or oxygen from diffusing, adhesive layer for enhancing adhesion to the po- larizing film or the adhesive, and slipping layer.

The functional layer may be provided either on the po- larizing film side or on the opposite side. Which side to be provided on is desirably determined according to the us- age.

As the protective film, a functional film can be lami- nated on one or each surface of the polarizing film of the invention. Examples of the functional film include a phase retarder such as X/4 plate or k/2 plate, a light-diffusing film, a plastic cell having an electro-conductive layer on the side opposite to the polarizing plate, a brightness-

improving film having a function of anisotropic scattering or anisotropic optical interference, a reflection board, and a reflection board having a function of semi- transmittance.

As the protective film of polarizing plate, one of the above-described preferred protective films can be used.

Further, two or more of them may be laminated to use. On each surface of the polarizing film, the same protective film may be laminated. Otherwise, protective films provid- ed on both surfaces of the polarizing film may be different in function and property. Further, it is also possible to laminate a protective film on only one surface and to provide an adhesive layer for laminating a liquid crystal cell directly on the other surface. In that case, a re- leasable separator film is preferably laminated outside of the adhesive.

There is no particular limitation on an adhesive used for adhesion of the protective layer to the polarizing film.

Examples of the adhesives include PVA-based resins (includ- ing modified PVA containing acetoacetyl groups, sulfonic acid groups, carboxyl groups and/or oxyalkylene groups) and aqueous solutions of boron compounds. Of these, PVA-based resins are preferred. Aqueous solutions of boron compounds or potassium iodide may be added to PVA resins. The thick- ness of the adhesive layer is preferably from 0.01 to 10 pm, and particularly preferably from 0.05 to 5 pm, after drying.

Fig. 7 shows an example of the stamping of a conven- tional polarizing film, and Fig. 8 shows an example of the stamping of a polarizing film of the invention. In the conventional polarizing film, an absorption axis 71 of po- larization, that is to say, a stretching axis, agrees with a longitudinal direction 72, as shown in Fig. 7, whereas in the polarizing film of the invention, an absorption axis 81 of polarization, that is to say, a stretching axis, is in- clined at 45° to a longitudinal direction 82, as shown in

Fig. 8. This angle agrees with an angle made by an absorp- tion axis of the polarizing plate laminated on a liquid crystal cell in an LCD and a longitudinal or lateral direc- tion of the liquid crystal cell itself, which necessitates no diagonal stamping in the stamping step. Moreover, as seen from Fig. 8, the polarizing film of the invention is cut linearly along the longitudinal direction, so that it can also be produced by slitting along the longitudinal di- rection without stamping. Accordingly, the polarizing plate of the invention is also remarkably excellent in pro- ductivity.

In the polarizing plate of the invention, an adhesive layer may be provided for laminating on other members of an LCD. On the adhesive layer, a separator film is preferably laminated. The adhesive layer has not only optical trans- parency but also proper viscoelasticity and adhesive char- acter. Examples of materials for the adhesive layer in- clude acrylic copolymers, epoxy resins, polyurethane, sili- cone-based polymer, polyether, butyral-based resins, poly- amide resins, polyvinyl alcohol-based resins and synthetic rubber. From the material, the layer is formed and hardened according to drying method, chemical hardening method, thermal hardening method, fusing method and photo- hardening method. As the material, acrylic copolymers are preferred since their adhesive characters can be easily controlled and the layer formed from them is excellent in transparency, weatherability and durability.

From the viewpoint of increasing a contrast of the liquid crystal display, it is preferred that the polarizing plate of the invention has a higher transmittance and a higher degree of polarization. The transmittance is pref- erably 30% or more, and more preferably 40% or more, at 550 nm. The degree of polarization is preferably 95. 0% or more, more preferably 99. 0% or more, and particularly preferably 99. 9% or more, at 550 nm.

The liquid crystal display of the invention preferably comprises a liquid crystal cell and one polarizing film (or a pair of polarizing films). In the liquid crystal cell, liquid crystal is enclosed between a pair of substrates each of which has an orientation layer. The polarizing film has a transmission axis inclined from the longitudinal direction at an angle of preferably 20 to 70°, more pref- erably 40 to 50°, further preferably 44 to 46°. The longi- tudinal direction of the film is preferably parallel to the rubbing direction for aligning the liquid crystal. If the liquid crystal display comprises a pair of polarizing films, the absorption axes of the films are preferably crossed perpendicularly.

(Optical compensatory film) The optical compensatory film preferably comprises at least a transparent support and an optically anisotropic layer of discotic liquid crystal oriented in a fixed align- ment. The values Re (0°), Re (40°) and Re (-40°), which indi- cate optical anisotropy of the optically anisotropic layer, are preferably in the ranges of 3525 nm, 10525 nm and 3525 nm, respectively.

The above Re (0°), Re (40°) and Re (-40°) represent re- tardation values of the optical compensatory film. In a plane including the normal of the film and the direction giving the minimum retardation of the optically anisotropic layer, they are measured with a ray of 633 nm coming in the normal direction, in the direction inclined at 40° from the normal to the side opposite to the direction giving the minimum retardation, and in the direction inclined at 40° from the normal to the direction giving the minimum retar- dation, respectively.

(Transparent support) As the transparent support of the optical compensatory film, a polymer film having a light transmittance of 80% or more is preferably used. Preferably, the polymer film hardly shows birefringence even if external force is ap- plied. Examples of the polymer film include films of cel- <BR> <BR> lulose-based polymers, norbornene-based polymers (e. g. , Ar- tone [trade name] from JSR co., Ltd. and Zeonex [trade <BR> <BR> name] from Nippon Zeon Co. , Ltd. ), and polymethyl methacry- late. Cellulose-based polymers are preferred, cellulose esters are more preferred, and cellulose esters of lower fatty acids are further preferred. Here, the term"lower fatty acids"means fatty acids having 6 or less carbon at- oms. The number of carbon atoms is preferably 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose bu- tyrate). Cellulose acetate is preferred, and examples of the cellulose acetate include diacetyl cellulose and triacetyl cellulose. Cellulose esters of mixed fatty acids such as cellulose acetatepropionate and cellulose ac- etatebutyrate are also usable.

Generally, hydroxyl groups at 2-, 3-and 6-position of cellulose acylate are not equally substituted (namely, the substitution degree at each position is not equal to one third of the total substitution degree), and the substitu- tion degree at 6-position is apt to be relatively small.

In the cellulose acylate used in the invention, the substi- tution degree at 6-position is preferably larger than those at 2-and 3-positions.

The hydroxyl group at 6-position is substituted with acyl group in an amount of preferably 30% to 40%, more preferably 31% or more, most preferably 32% or more, based on the total substitution degree. Further, the substitu- tion degree of the acyl group at 6-position is preferably 0.88 or more.

The hydroxyl group at 6-position may be substituted with acyl group having 3 or more carbon atoms other than acetyl. Examples of the acyl groups having 3 or more car- bon atoms include propionyl, butyloyl, valeroyl, benzoyl and acryloyl. The substitution degree at each position can be measured by means of NMR.

Cellulose acylates prepared according to the methods described in Japanese Patent Provisional Publication No.

11 (1999) -5851 are usable for the invention.

(Retardation values of polymer film) Retardation values Re and Rth of the polymer film are defined by the following formulas (I) and (II): (I) Re = (nx-ny) xd (II) Rth = {(nx+ny)/2-nz} xd In the formulas (I) and (II), nx is a refractive index along the slow axis (i. e. , along the direction giving the maximum refractive index) in the film plane.

In the formulas (I) and (II), ny is a refractive index <BR> <BR> along the traveling axis (i. e. , along the direction giving the minimum refractive index) in the film plane.

In the formula (II), nz is a refractive index along the thickness direction of the film.

In the formulas (I) and (II), d is a thickness of the film in terms of nm.

In the invention, the values Re and Rth are preferably in the ranges of 10 to 70 nm and 70 to 400 nm, respectively.

The polymer film preferably has a birefringence value (An : nx-ny) in the range of 0.00025 to 0.00088, and the trans- parent support preferably has a birefringence value along the thickness direction { (nx+ny)/2-nz} in the range of 0.00088 to 0.005.

(Angle of slow axis in polymer film) The stretching direction of polymer film is defined as the standard line (0°), and the angle of the slow axis in the transparent support is defined as an angle between the slow axis and the standard line. In the case where a film in the form of a roll is laterally stretched, the lateral direction is the standard line. If the film is longitudi- nally stretched, the longitudinal direction is the standard line.

The average angle of slow axis is preferably 3° or less, more preferably 2° or less, most preferably 1° or less. A direction making the average angle of slow axis is defined as the average direction of slow axis.

The angle of slow axis has a standard deviation of preferably 1. 5° or less, more preferably 0. 8° or less, most preferably 0. 4° or less.

After electrified for a certain time, an LCD of trans- mission type equipped with an optical compensatory film of- ten displays an image framed with leaked light (what is called, "framewise unevenness"). This is caused by in- crease of transmittance at the peripheral part of the screen, and particularly when a black image is displayed it remarkably increases. Further, in an LCD of semi- transmission type, heat is generated at the backlight and unevenly distributed in the liquid crystal cell. The un- even thermal distribution changes the optical characters (retardation values, angle of slow axis) of the optical compensatory film, and thereby"framewise unevenness"is caused. When the temperature rises, the optical compensa- tory film expands or shrinks. However, the expansion or shrinkage is limited since the film is fixed on the liquid crystal cell or on the linearly polarizing film, and ac- cordingly the film is elastically deformed to change the optical characters.

In order to avoid"framewise unevenness", it is preferred to use a polymer film having high thermal conduc- tivity as the optical compensatory film. Examples of the polymer having high thermal conductivity include cellulose acetate [0. 22 W/ (m-°C)], low density polyethylene [0.34 W/(m-°C)], ABS [0. 36 W/(m-°C)] and polycarbonate [0.19 W/ °C)]. Cyclic olefin polymers such as Zeonex [0.20 W/ °C), from Nippon Zeon Co. , Ltd. ], Zeonor [0. 20<BR> W/ (m-°C), from Nippon Zeon Co. , Ltd. ] and Artone [0.20<BR> W/ °C), from JSR co. , Ltd. ] are also usable.

In consideration of optical and thermal characters, a film of cellulose acetate having an acetic acid content of 59.0 to 61. 5% is preferably used as the polymer film of the invention. The term"acetic acid content"means the amount of combined acetic acid per one unit weight of cellulose.

The acetic acid content is determined according to ASTM: D- 817-91 (tests of cellulose acetate).

The film of the invention is made of a polymer having a viscosity average polymerization degree (DP) of prefera- bly 250 or more, more preferably 290 or more. Further, it is also preferred for the polymer to have a narrow molecu- lar weight distribution of Mw/Mn (Mw and Mn are weight and number average molecular weights, respectively) determined by gel permeation chromatography. The value of Mw/Mn is preferably in the range of 1.0 to 1.7, more preferably in the range of 1.3 to 1.65, most preferably in the range of 1.4 to 1.6.

(Retardation-increasing agent) For adjusting the retardation of the polymer film, an aromatic compound having at least two aromatic rings is used as a retardation-increasing agent. As the re- tardation-increasing agent, triphenyltriazines are pre- ferred. Examples of them are described in Japanese Patent

Publication Nos. 2000-111914 and 2000-275434, and PCT/JP00/02619.

Two or more aromatic compounds may be used in com- bination. The aromatic ring may be either an aromatic hy- drocarbon ring or an aromatic heterocyclic ring.

The retardation-increasing agent preferably has a molecular weight of 300 to 800.

If a cellulose acetate film is used as the polymer film, the aromatic compound is used in an amount of pref- erably 0.01 to 20 weight parts, more preferably 0.05 to 15 weight parts, further preferably 0.1 to 10 weight parts, based on 100 weight parts of cellulose acetate.

(Production of polymer film) A cellulose acetate film preferably used as the polym- er film can be produced according to the process described in Technology Publication No. 2001-1745 (Japanese), March 15,2001. Films of other polymers can be also produced in a similar manner.

(Stretching of polymer film) The produced polymer film can be stretched to control the retardation. The stretching ratio is preferably in the range of 3 to 100%.

The thickness of the polymer film is preferably in the range of 40 to 140 um, more preferably in the range of 70 to 120 pm.

The conditions of stretching can be adjusted to reduce the standard deviation of the angle of slow axis. There is no particular restriction on a method for stretching. For example, the film can be stretched with a tenter machine.

In that case, immediately after a film formed by solvent cast method is laterally stretched with a tenter machine, the condition of the film is controlled so that the angle of slow axis may have a small standard deviation. In de-

tail, immediately after stretched with the tenter machine, the film is kept at near the glass transition temperature with the tension maintained, to reduce the standard devia- tion of the angle of slow axis. If the film is kept at a temperature lower than the glass transition temperature, the standard deviation is increased.

Otherwise, when the film is longitudinally stretched roll-to-roll, the interval between the rolls can be length- ened to reduce the standard deviation.

(Surface treatment of polymer film) If used as the transparent protective film of polariz- ing plate, the polymer film is preferably subjected to sur- face treatment.

Examples of the surface treatment include corona dis- charge treatment, glow discharge treatment, flame treatment, acid or alkali treatment, and ultraviolet (W) treatment.

Acid or alkali treatment, namely saponification treatment is preferred.

(Orientation layer) The orientation layer has a function of giving an ori- entation direction of discotic liquid crystal in the opti- cally anisotropic layer.

Preferred examples of the orientation layer include a layer of an organic compound (preferably polymer) subjected to rubbing treatment, an obliquely deposited layer of an inorganic compound, and a layer having micro grooves. Fur- ther, a built-up film formed according to Langmuir-Blodgett technique (LB technique) from co-tricosanoic acid, dioctade- cyldimethylammoniumchloride or methyl stearate can be used as the orientation layer. In addition, a layer prepared by orienting dielectric materials by application of electric field or magnetic field can be employed as the orientation layer.

For preparing the orientation layer, a polymer film is preferably subjected to rubbing treatment. A polyvinyl al- cohol is preferred as the polymer of the film. A denatured polyvinyl alcohol having a hydrophobic group is particu- larly preferred. Since a hydrophobic group has affinity with discotic liquid crystal, the denatured polyvinyl alco- hol in which the hydrophobic group is introduced can align the molecules of discotic liquid crystal evenly. The hy- drophobic group is placed at the terminal of the main chain or at the side chain of polyvinyl alcohol.

The hydrophobic group is preferably an aliphatic group (preferably, alkyl group or alkenyl group) having 6 or more carbon atoms or an aromatic group.

If the hydrophobic group is placed at the terminal of the main chain, it is preferred to introduce a linking group between the terminal and the hydrophobic group. Ex- <BR> <BR> amples of the linking group include-S-, -C (CN) R1-,-NR2-, - CS-and a combination thereof. In the above, each of the R1 and R2 is independently hydrogen or an alkyl group hav- ing 1 to 6 carbon atoms.

If the hydrophobic group is placed at the side chain, a part of acetyl (-CO-CH3) in a vinyl acetate unit of poly- vinyl alcohol is replaced with an acyl group (-CO-R3) hav- ing 7 or more carbon atoms. In the above, the R3 is an aliphatic group having 6 or more carbon atoms or an aro- matic group.

The denatured polyvinyl alcohols are described in Ja- panese Patent Provisional publication No. 9 (1997)-152509.

Commercially available denatured polyvinyl alcohols (e. g., MP103, MP203, R1130, from Kuraray Co. , Ltd. ) may be used.

The (denatured) polyvinyl alcohol used in the inven- tion has a saponification degree of preferably 80% or more and a polymerization degree of preferably 200 or more.

The rubbing treatment is performed by rubbing the sur- face of the layer with paper or cloth along a certain di-

rection, to give the aligning function. Preferably, the layer is rubbed several times with cloth on which fibers having the same length and thickness are provided.

After discotic liquid crystal molecules in the opti- cally anisotropic layer are once aligned, they can keep the alignment even if the orientation layer is removed. There- fore, the optical compensatory film does not need to com- prise an orientation layer although the orientation layer is necessary for preparing the optical compensatory film.

If the orientation layer is provided between the transparent support and the optically anisotropic layer, an undercoating layer (adhesive layer) is preferably provided between the transparent support and the orientation layer.

(Optically anisotropic layer) The optically anisotropic layer is prepared from dis- cotic liquid crystal. A discotic liquid crystal molecule generally has optically negative uniaxiality. In the opti- cal compensatory film of the invention, the angle between the disc plane and the transparent support in each liquid crystal molecule preferably changes along the thickness (namely, the molecules are preferably oriented in hybrid alignment). There is no direction in which the retardation is 0 in the optically anisotropic layer, and this means the layer does not have an optical axis.

For forming the optically anisotropic layer, the dis- cotic liquid crystal molecules are preferably aligned with the aforementioned orientation layer and fixed with the alignment maintained.

The optically anisotropic layer has a thickness pref- erably in the range of 0.5 to 100 um, more preferably in the range of 0.5 to 30 pm.

The discotic liquid crystal molecule is described in various documents (C. Destrade et al, Mol. Crysr. Liq.

Cryst. , vol. 71, page 111 (1981); Japan Chemical Society,

Quarterly Chemical Review (written in Japanese), chapter 5 <BR> <BR> and chapter 10, section 2 (1994); B. Kohne et al. , Angew.<BR> <P>Chem. Soc. Chem. Comm. , page 1794 (1985) ; and J. Zhang et<BR> al. , J. Am. Chem. Soc. , vol. 116, page 2655 (1994) ). The polymerization reaction of the discotic liquid crystal molecule is described in Japanese Patent Provisional Publi- cation No. 8 (1996)-27284.

A polymerizable group is preferably bound to a dis- cotic core of the discotic liquid crystal molecule to cause the polymerization reaction of the compound. However, if the polymerizable group is directly bound to the discotic core, it is difficult to keep the alignment at the polym- erization reaction. Therefore, a linking group is prefera- bly introduced between the discotic core and the polymeriz- able group.

For fixing the aligned discotic liquid crystal molecules with the alignment maintained, photo- polymerization initiators are used. Examples of the photo polymerization initiators include a-carbonyl compounds (de- scribed in US Patent Nos. 2,367, 661,2, 367, 670), acyloin ethers (described in US Patent No. 2,448, 828), a- hydrocarbon substituted acyloin compounds (described in US Patent No. 2,722, 512), polycyclic quinone compounds (de- scribed in US Patent Nos. 2,951, 758,3, 046,127), combina- tions of triarylimidazoles and p-aminophenyl ketones (de- scribed in US Patent No. 3,549, 367), acridine or phenazine compounds (described in Japanese Patent Provisional Publi- <BR> <BR> cation No. 60 (1985) -105667 and US Patent No. 4,239, 850) and oxadiazole compounds (described in US Patent No. 4,212, 970).

The amount of the photo polymerization initiator is preferably in the range of 0.01 to 20 wt. %, and more pref- erably in the range of 0.5 to 5 wt. % based on the solid content of the coating solution.

The light irradiation for the photo polymerization is preferably conducted with an ultraviolet ray.

The exposure energy is preferably in the range of 20 to 50,000 mi per cm2, and more preferably in the range of 100 to 800 mi per cm2. The light irradiation can be con- ducted while the layer is heated to accelerate the photo polymerization reaction.

The protective film may be provided on the optically anisotropic layer.

(Phase retarder) The phase retarder preferably functions as a k/4 plate.

The A/4 plate must have a retardation value measured at 590 nm (Re590) in the range of 120 to 160 nm, and may consist of a single film or plural films. The plate pref- erably gives k/4 in a wide wavelength region, and prefera- bly consists of a single film in the form of a roll.

The k/4 plate must be laminated on a linearly polariz- ing film so that the slow axis of the plate may be posi- tioned at the angle of 45° to the absorption axis of the film, to form a circularly polarizing plate. In order to laminate them roll-to-roll, an oblong linearly polarizing film having the absorption axis inclined at 45° to the lon- gitudinal direction and an oblong k/4 plate having the slow axis parallel to the longitudinal direction are preferably used in combination. Otherwise, an oblong linearly polar- izing film having the absorption axis parallel to the lon- gitudinal direction and an oblong k/4 plate having the slow axis inclined at 45° to the longitudinal direction are also preferably used in combination.

Japanese Patent Provisional Publication Nos. 5 (1993)- <BR> <BR> 27118 and 5 (1993) -27119 disclose a phase retarder compris- ing a birefringencial film having high retardation and an- other birefringencial film having low retardation. The bi- refringencial films are laminated so that their optical ax- es may be perpendicularly crossed. If the difference of the retardation between the two films is B/4 in the whole

visible wavelength region, the phase retarder theoretically serves as a k/4 plate in the whole visible wavelength re- gion.

Japanese Patent Provisional Publication No. 10 (1998)- 68816 discloses a phase retarder comprising laminated two polymer films made of the same material. Each of the films gives X/2 at a certain wavelength, and thereby the phase retarder gives X/4 in a wide wavelength region.

Japanese Patent Provisional Publication No. 10 (1998)- 90521 also discloses a phase retarder comprising laminated two polymer films. This phase retarder also gives X/4 in a wide wavelength region.

The k/4 plate preferably consists of a single polymer film. In detail, the single film B/4 plate described in Japanese Patent Publication No. 2000-137116 and WO00/26705 is preferred. The shorter wavelength it is measured at, the smaller phase difference the B/4 plate gives.

The B/4 plate preferably has a Re retardation value measured at 450 nm (Re450) in the range of 100 to 125 nm and another Re retardation value measured at 590 nm (Re590) in the range of 120 to 160 nm. These Re retardation values satisfy preferably the condition of Re590-Re450 2 nm, more preferably the condition of Re590-Re450 5 nm, most preferably the condition of Re590-Re450 > 10 nm.

The Re retardation value measured at 450 nm (Re450) is preferably in the range of 108 to 125 nm, the Re retarda- tion value measured at 550 nm (Re550) is preferably in the range of 125 to 142 nm, the Re retardation value measured at 590 nm (Re590) is preferably in the range of 130 to 152 nm, and the Re550 and Re590 values satisfy preferably the condition of Re590-Re550 > 2 nm, more preferably the condi- tion of Re590-Re550 > 5 nm, most preferably the condition of Re590-Re550 10 nm. Further, Re550 and Re450 values preferably satisfy the condition of Re550-Re450 10 nm.

The retardation value (Re) is calculated according to the following formula: Re = (nx-ny) x d in which nx is a refractive index along the slow axis (di- rection giving the maximum refractive index) in the plane of the B/4 plate; ny is a refractive index in the direction perpendicular to the slow axis in the plane ; and d is the thickness of the B/4 plate in terms of nm.

The X/4 plate preferably consists of a single polymer film satisfying the condition of: 1 s (nx-nz)/ (nx-ny) 2 in which nx is a refractive index along the slow axis in the B/4 plane of the plate, ny is a refractive index per- pendicular to the slow axis in the plane of the B/4 plate, and nz is a refractive index in the thickness direction of the X/4 plate.

For producing the preferred B/4 plate having the aforementioned optical characters, a polymer film may be stretched. Otherwise, after coated with rod-like liquid crystal, a polymer film is subjected to rubbing treatment for aligning the rod-like liquid crystal molecules. The aligned molecules are fixed through, for example, photo po- lymerization, to form an optical anisotropic layer. Thus treated polymer films may be layered to form the X./4 plate.

The X/4 plate may be obliquely stretched or rubbed to con- trol the direction of the slow axis.

(X/4 plate consisting of single film) The thickness of the single film structuring the k/4 plate is preferably in the range of 5 to 1,000 pm, more preferably in the range of 10 to 500 Hm, further preferably in the range of 40 to 200 Hm, most preferably in the range of 70 to 120 pm.

(Polymer film)

As polymers for producing the polymer film, polymers described above as the material for the transparent support of optical compensatory film are usable.

Cellulose esters are preferred, and cellulose esters of lower fatty acids are further preferred as the polymers.

The term"lower fatty acids"means fatty acids having 6 or less carbon atoms. The number of carbon atoms is prefera- bly 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). Cellulose acetate is particularly preferred. Cellulose esters of mixed fatty acids such as cellulose acetatepropionate and cellulose acetatebutyrate are also usable.

The average acetic acid content (acetylation degree) of cellulose acetate is preferably in the range of 45.0 to 62. 5%, more preferably in the range of 55.0 to 61. 0%, most preferably in the range of 59.0 to 60. 0%.

(Retardation-increasing agent) A retardation-increasing agent can be incorporated in- to the polymer (preferably, cellulose acetate) film, to control the retardation values. As the retardation- increasing agent, triphenyltriazine-based compounds (which are used in the optical compensatory film) can be used.

However, a preferred retardation-increasing agent is a rod- like compound having at least one aromatic ring, for exam- ple, 1,4-cyclohexanedicarboxylic p-n-heptylphenol diester.

The amount of the retardation increasing agent is preferably in the range of 0.05 to 20 weight parts, more preferably in the range of 0.1 to 10 weight parts, further preferably in the range of 0.2 to 5 weight parts, most preferably in the range of 0.5 to 2 weight parts, based on 100 weight parts of polymer. Two or more retardation in- creasing agents may be used in combination.

The retardation-increasing agent preferably has the maximum absorption band in the wavelength region of 250 to

400 nm, and also preferably has essentially no absorption band in the visible wavelength region.

Further, the polymer film is preferably stretched to control the refractive indexes (refractive indexes nx, ny and nz in the film plane along the slow axis, along the traveling axis and along the thickness direction, respec- tively). The film can be obliquely stretched in the same manner as the PVA film described above, so that the slow axis may be inclined at 45° to the longitudinal direction.

(X/4 plate of coating type) As the X/4 plate, a k/4 plate of coating type de- scribed in Japanese Patent Publication No. 2001-21720 can be used. Comprising two optically anistropic layers and a twisted structure provided between them, the k/4 plate of coating type has remarkably improved character in a wide wavelength region.

The two optically anistropic layers are preferably bi- refringent films or layers comprising liquid crystal. More preferably at least one of the optically anistropic layers is a layer comprising liquid crystal, and most preferably both layers are layers comprising liquid crystal. The op- tical characters of the layer comprising liquid crystal are more easily controlled than those of the birefringent film.

In the anistropic layer comprising liquid crystal, the slow axis can be oriented by the rubbing direction of liq- uid crystal molecules. If the amount and kind of liquid crystal is properly controlled, the retardation value can be strictly adjusted.

The optically anistropic layer has a thickness and an orientation birefringence whose product measured at 550 nm (namely, at the midst of visible wavelength region) is in the range of 150 to 350 nm. In the twisted structure, the twist angle is in the range of 3 to 45°. The product of the thickness and the orientation birefringence corresponds

to the retardation value in plane if the layer does not have the twisted structure.

(Birefringent film) The other optical anisotropic layer is preferably a birefringent film giving a phase difference of 60 to 170 nm at 550 nm (namely, at the midst of visible wavelength re- gion).

Examples of polymers for the birefringent film include polyolefin (e. g., polyethylene, polypropylene, norbornene- based polymers), polyvinyl chloride, polystyrene, polyacry- lonitrile, polysulfone, polyarylate, polyvinyl alcohol, po- lymethacrylic esters, polyacrylic polymers, and cellulose esters. Copolymers or mixture thereof are also usable.

The optical anisotropy of the film is preferably given by stretching. The film is preferably uniaxially stretched.

The uniaxial stretching is preferably a longitudinal stretching in which two or more rolls are differentially rotated or a lateral stretching in which both edges of the film are held and laterally stretched with a tenter machine.

Two or more films may be laminated so that the resultant layered film can satisfy the above conditions. The polymer film is preferably formed by the solvent cast method, to reduce unevenness of the film. The thickness of the film is preferably in the range of 20 to 500 nm, more preferably in the range of 50 to 200 nm, most preferably in the range of 50 to 100 nm.

(Circularly polarizing plate) The X/4 plate and the linearly polarizing film are laminated so that the slow axis of the plate may be posi- tioned essentially at 45° to the absorption axis of the film, to produce a circularly polarizing plate. If the ab- sorption axis of the film is inclined from the longitudinal direction essentially at 45°, the slow axis of the plate is

preferably essentially parallel to the longitudinal direc- tion. If the absorption axis of the film is essentially parallel to the longitudinal direction, the slow axis of the plate is preferably inclined from the longitudinal di- rection essentially at 45°.

The angle between the slow of the plate and the ab- sorption axis of the film is preferably in the range of 41 to 49°, more preferably in the range of 42 to 48°, further preferably in the range of 43 to 47°, most preferably in the range of 44 to 46°.

Thus, the k/4 plate and the linearly polarizing film are laminated to produce a layered composition. On the back surface of the composition, a protective film is pref- erably provided. The protective film is preferably made of a transparent polymer (having an optical transmittance of 80% or more). Examples of the transparent polymer include <BR> <BR> polyolefins (e. g. , Artone, Zeonex, Zeonor [trade names]), cellulose acetate, polycarbonate, polyacrlate, polysulfone and polyethersulfone). Commercially available transparent polymers and films thereof are also usable.

The slow axis of the protective film is positioned preferably essentially parallel to the absorption axis of the linearly polarizing film.

The linearly polarizing film and the k/4 plate, or the linearly polarizing film and the protective film are lami- nated with an adhesive. The adhesive is preferably an aqueous solution of polyvinyl alcohol-based resin or of bo- ron compound, more preferably an aqueous solution of poly- vinyl alcohol-based resin. As the polyvinyl alcohol-based resin, a denatured polyvinyl alcohol in which a functional group other than alcohol (e. g. , acetoacetyl, sulfo, car- boxyl or alcoxy) is introduced may be used. The layer of adhesion has a dry thickness of preferably 0.01 to 10 pm, more preferably 0.05 to 5 Hm.

(Liquid crystal display) The liquid crystal display of the invention may be designed normally white mode (in which a bright or dark im- age is displayed when the applied voltage is low or high, respectively) or normally black mode (in which a dark or bright image is displayed when the applied voltage is low or high, respectively).

If the invention is applied to a display of reflection type or semi-transmission type, the active matrix mode is preferred to the simple matrix mode. It is more preferred to adopt TFT (thin film transistor), TFD (thin film diode) or MIM (metal insulator metal) mode. In the case of TFT mode, cold polysilicon or grain boundary silicon is prefer- ably used.

The liquid crystal display is described in detail in various documents or publications, for example,"Handbook of Liquid Crystal Devise (Japanese)", 142nd committee, Japan Society for the Promotion of Science, Nikkan Kogyou Shinbun <BR> <BR> publishing Co. , Ltd.;"Liquid Crystal, Application (Japa-<BR> nese) ", Okano, Baifukan publishing Co. , Ltd.;"Color Liquid<BR> Crystal Display (Japanese) ", Kobayashi, Sangyo Shuppan pub-<BR> lishing Co. , Ltd.;"Liquid Crystal Display in Next Genera- tion (Japanese)", Uchida, Kogyou Chosakai publishing Co., Ltd.;"The Latest Liquid Crystal Display (Japanese) ", the group of young liquid crystal scholars, Sigma publishing <BR> <BR> Co. , Ltd.; and"Liquid Crystal: Groundwork and New Applica- tion of LCD (Japanese)", the group of young liquid crystal scholars, Sigma publishing Co. , Ltd.

[Example 1] (Preparation of HAN mode liquid crystal cell) On a glass substrate provided with an ITO electrode, a polyimide layer was formed and the surface of the layer was subjected to rubbing treatment to form an orientation layer.

Independently, SiO was deposited on another glass substrate

provided with an ITO electrode to form an orientation layer.

The two glass plates were faced to each other, and combined so as to have the gap between the plates of 4.8 Hm.

Nematic liquid crystal (An = 0.1396 ; trade name: ZLI1132, available from Merck & Co. , Inc. ) was inserted into the gap, to prepare a liquid crystal cell of HAN mode. The retarda- tion of the produced liquid crystal layer was 671 nm.

(Preparation of k/4 plate in the form of a roll) At room temperature, 120 weight parts of cellulose triacetate (average acetic acid content: 59. 5%), 9.36 weight parts of triphenyl phosphate, 4.68 weight parts of biphenyldipehenyl phosphate, 1.00 weight part of retarda- tion increasing agent (trans-1, 4-cyclohexanedi-carboxylic 4-n-heptylphenol diester), 543.14 weight parts of methylene chloride, 99.35 weight parts of methanol and 19.87 weight parts were mixed and dissolved to prepare a solution (dope).

The dope was cast onto a moving stainless band, and introduced to drying zones to dry at 25°C for 1 minute and at 45°C for 5 minutes. Thus formed film contained the sol- vents remaining in the amount of 30 wt. %. After peeled from the band, the film was wound up at a higher winding speed than the transferring speed of the band to stretch at 130°C. In this longitudinal stretching, the film was let to shrink laterally. After stretched, the film was intro- duced to a drying zone to dry at 120°C for 30 minutes and then wound up. Thus formed film contained the solvents re- maining in the amount of 0.1 wt. %.

The obtained film in the form of a roll had the thick- ness of 101 pm, and its retardation value Re was measured at 450 nm, 550 nm and 590 nm by means of an ellipsometer (M-150, Japan Spectrum Co. , Ltd. ) to find 119.3 nm, 137.2 nm and 142.7 nm, respectively. The slow axis of the film was parallel to the transferring (longitudinal, stretching) direction.

Further, the refractive indexes were measured with an Abbe's refractometer, and the angle dependence of retarda- tion was also measured. From the obtained data, nx (re- fractive index along the show axis), ny (refractive index perpendicular to the slow axis) and nz (refractive index along the depth) were determined at 550 nm to find that (nx-nz)/ (nx-ny) was 1.60.

(Preparation of linearly polarizing film in the form of a roll) A PVA film was immersed at 25°C for 240 seconds in an aqueous solution containing 2.0 g/liter of iodine and 4.0 g/liter of potassium iodide, and further 25°C for 60 sec- onds in an aqueous solution containing 10 g/liter of boric acid. After the immersed film was stretched by means of a tenter machine at the stretching ratio of 5.3, the film was dried to shrink at 80°C with the width kept at a constant.

The film was then released from the tenter, and wound up.

The contents of water in the film before and after drying were 31% and 1. 5%, respectively.

The difference between the transferring speeds of left and right edge was less than 0. 05%, and the angle between the center line of the film introduced into the course (tenter machine) and that of the film sent out to the sub- sequent step was 46°. As the outlet of the course, any wrinkle or deformation was not observed in the film.

The obtained linearly polarized film had a slow axis inclined at 45° to the transferring (longitudinal) direc- tion. The transmittance and the polarizability of the film were 43. 7% and 99. 97%, respectively, at 550 nm.

(Preparation of circularly polarizing plate) A commercially available triacetyl cellulose film (Fu- jitac TD80, Fuji Photo Film Co. , Ltd. ) and the above X/4 plate were immersed at 55°C in a 1.5 N NaOH aqueous solu-

tion for 1 minute, to saponify both surfaces of the film and the plate. One surface of each of the film of the plate was coated with a polyvinyl alcohol-based adhesive layer of 30 pm thickness, and the above linearly polarizing film was roll-to-roll sandwiched and laminated with the triacetyl cellulose film and the X/4 plate. Thus obtained layered composition was dried at 80°C to produce a circu- larly polarizing plate having the thickness of approx. 241 Jim.

(Preparation of optical compensatory sheet) The following components were poured into a mixing tank, and stirred and heated to dissolve each component.

Thus, a cellulose triacetate solution was prepared.

Cellulose triacetate solution Cellulose acetate (acetic acid content: 60. 9%) 100 weight parts Triphenyl phosphate (plasticizer) 8.1 weight parts Biphenyldiphenyl phosphate (plasticizer) 3.6 weight parts Methylene chloride (first solvent) 338 weight parts Methanol (second solvent) 27 weight parts 15 Weight parts of the following retardation increas- ing agent, 80 weight parts of methylene chloride and 20 weight parts of methanol were poured into another mixing tank, and stirred and heated to prepare a retardation in- creasing agent solution.

(Retardation increasing agent)

52 Weight parts of the prepared retardation increasing agent solution and 477 weight parts of the cellulose ace- tate solution were mixed and stirred to prepare a dope.

The prepared dope was cast by means of a band-casting machine. When the amount of the solvent remaining in the formed film reached 50 wt. %, the film was peeled from the band. The film was laterally stretched by 17% at 130°C, and held at 130°C for 30 seconds with the width maintained.

Then, the film was released from the holding means to pro- duce a triacetate film.

The optical characters of the prepared cellulose ace- tate film were measured at the wavelength of 550 nm by <BR> <BR> means of an ellipsometer (M-150, Japan Spectrum Co. , Ltd.), to find the Re and Rth values. The angles of slow axes were measured by means of an optical birefringence analyzer (KOBRA-21ADH, Oji Scientific Instrument Co. , Ltd. ) at ten points laterally positioned at an equal interval, and aver- aged. The standard deviation of the angles of slow axes was also obtained.

The results are set forth in Table 1.

TABLE 1 Transparent Re Rth Standard deviation of angles support value value of slow axes Example 1 40 nm 220 nm 1. 4° Example 2 40 nm 220 nm 1. 3° On the above-prepared cellulose acetate film, a 1.0 N KOH solution (solvent: isopropyl alcohol/propylene gly- col/water = 75/13/12 wt/%) was applied by means of a wire- bar coater of #3. After heated at 60°C for 10 seconds, the surface was washed with water applied by means of a wire- bar coater of #1. 6 and further 500 ml/m2 of water at 40°C sprayed from a nozzle. Immediately after that, the water on the film was three times blown out with air-knife. The surface was then dried with hot air at 100°C, to prepare a cellulose triacetate film having a saponified surface.

On the saponified surface of the cellulose triacetate film, a coating solution prepared by dissolving 2.0 g of the following denatured polyvinyl alcohol in 36 g of water and adding 12 g of methanol and 0.1 g of glutaric aldehyde (crosslinking agent) was applied by means of a wire-bar coater of #14, and dried with hot air at 60°C for 60 sec- onds and 90°C for 160 seconds to form an orientation layer on the cellulose triacetate film in the form of a roll.

The orientation layer was then subjected to rubbing treatment parallel to the transferring (longitudinal) di- rection.

(Denatured polyvinyl alcohol)

To prepare a coating solution, 38.4 g of the following discotic (liquid crystal) compound, 4.1 g of ethylene oxide denatured trimethlolpropanetriacrylate (V#360, Osaka Or- <BR> <BR> ganic Chemicals Co. , Ltd. ), 0.8 g of cellulose acetate bu- tyrate (CAB-551-0.2, Eastman Chemical), 0.2 g of cellulose acetate butyrate (CAB-531-1, Eastman Chemical), 1.5 g of a photopolymerization initiator (Irgacure 907, Ciba-Geigy) and 0.5 g of a sensitizer (Kayacure DETX, Nippon Kayaku Co., <BR> <BR> Ltd. ) were dissolved in 102 g of methyl ethyl ketone. The coating solution was then applied on the orientation layer (subjected to rubbing treatment at 45° to the longitudinal direction) by means of a wire bar coater of #3. The thus- treated film was fixed on a metal frame, and heated in a thermostat at 130°C for 2 minutes to orient molecules of the discotic compound in monodomain discotic nematic phase.

The film was then irradiated at 130°C for 1 minute with an ultraviolet ray emitted from a high-pressure mercury lamp of 120 W/cm, so as to polymerize the discotic liquid crys- tal molecules. The film was cooled to room temperature.

Thus, an optically anisotropic layer was formed to prepare an optical compensatory film.

(Discotic liquid crystal compound)

The retardation values Re (0°), Re (40°) and Re (-40°) were measured in the normal direction, in the direction in- clined at 40° from the normal, and in the direction in- clined at-40, respectively, in the plane including the rubbing direction and the normal. The results are set for- th in Table 2.

TABLE 2 Optical compensatory film Re (0°) Re (-40°) Re (40°) Example 1 38 nm 42 nm 83 nm Example 2 40 nm 44 nm 87 nm (Preparation of HAN mode LCD of reflection type) On a reflection board used in a commercially available LCD of reflection type, a liquid crystal cell of HAN mode was laminated. The optical compensatory film was laminated on the cell with an acrylic adhesive, so that the cellulose triacetate side of the film might be in contact with the cell. The rubbing direction of the cell was positioned

anti-parallel to the rubbing direction of the film. Fur- ther on the laminated film, the circularly polarizing plate was laminated with an acrylic adhesive, so that the k/4 plate of the polarizing plate might be in contact with the film. The slow axis of the k/4 plate was positioned paral- lel to the rubbing direction of the cell. Thus, a HAN mode LCD of reflection type was produced. The produced liquid crystal display had the following constitution.

Circularly polarizing plate Protective film (TD80U) Linearly polarizing film (PVA/I2) Phase retarder (X/4 plate) Optical compensatory film Transparent support (cellulose triacetate film) Optically anisotropic layer (discotic liquid crystal layer) HAN mode liquid crystal cell Reflection board Voltage (white: 2V, black: 6V) was applied to the liq- uid crystal cell, and an image was displayed and frontally seen to measure a front contrast ratio by means of a meter (EZ-Contrast 160D, ELDIM). The viewing angle giving a con- trast ratio of 5 or more was leftward-rightward (perpen- dicularly to the rubbing direction). The results were set forth in Table 3.

TABLE 3 Liquid crystal display Front contrast ratio Viewing angle Example 1 15 120° Example 2 12 100° [Example 2] (Preparation of bent alignment mode liquid crystal cell) On a glass substrate provided with an ITO electrode, aluminum was deposited except for leaving a part for a win- dow to form a diffusing refraction board with the window for sub-transmission. A polyimide layer was formed on the board and the surface of the layer was subjected to rubbing treatment to form an orientation layer. Independently, an- other polyimide film was provided on another glass sub- strate provided with an ITO electrode to form an orienta- tion layer. The two glass plates were faced to each other, and combined so as to have the gap between the plates of 10 pm. Nematic liquid crystal (An = 0.1396 ; trade name: <BR> <BR> ZLI1132, available from Merck & Co. , Inc. ) was inserted in- to the gap, to prepare a liquid crystal cell of bent align- ment mode. The retardation of the produced liquid crystal layer was 698 nm.

The following components were mixed to prepare a solu- tion, in which powder of cellulose triacetate (mean parti- cle size: 2 mm) was gradually added with stirring.

Cellulose triacetate solution Cellulose triacetate (acetic acid content: 60. 5%) 100 weight parts Triphenyl phosphate (plasticizer) 6.8 weight parts Biphenyldiphenyl phosphate (plasticizer) 4.9 weight parts Methyl acetate (first solvent) 240 weight parts Cyclohexanone (second solvent) 100 weight parts Methanol (third solvent) 25 weight parts Ethanol (forth solvent) 25 weight parts Silica particles (mean size: 20 nm) 0.5 weight part The retardation-increasing agent used in Example 1 6.7 weight parts The mixture was left at room temperature (25°C) for 3 hours. The obtained inhomogeneous gel was cooled at-70°C for 6 hours, and then heated to 50°C to obtain a dope.

From the dope, a cellulose triacetate film was formed in the same manner as in Example 1. The optical characters and the thermal conductivity of the formed film are set forth in Table 1.

The cellulose acetate film was immersed in a 1.5 N NaOH aqueous solution at 55°C for 2 minutes. After washed in a water bath at room temperature, the film was neutral- ized with 0.1 N sulfuric acid at 30°C. The film was then washed again in a water bath at room temperature, and dried with hot air at 100°C. Thus the surfaces of the cellulose acetate film were saponified.

On one surface of the saponified film, an orientation layer was formed and subjected to rubbing treatment in the same manner as in Example 1.

To prepare a coating solution, 41.0 g of the discotic liquid crystal compound used in Example 1,4. 0 g of ethyle- ne oxide denatured trimethlolpropanetriacrylate (V#360, Osaka Organic Chemicals Co. , Ltd. ), 0.90 g of cellulose acetate butyrate (CAB-551-0.2, Eastman Chemical), 0.23 g of cellulose acetate butyrate (CAB-531-1, Eastman Chemical), 1.35 g of a photopolymerization initiator (Irgacure 907, Ciba-Geigy) and 0.45 g of a sensitizer (Kayacure DETX, Nip- pon Kayaku Co. , Ltd. ) were dissolved in 102 g of methyl ethyl ketone. The coating solution was then applied on the orientation layer by means of a wire bar coater of #3. The thus-treated film was fixed on a metal frame, and heated in a thermostat at 130°C for 2 minutes to orient molecules of the discotic compound in monodomain discotic nematic phase.

The film was then irradiated at 130°C for 1 minute with an ultraviolet ray emitted from a high-pressure mercury lamp of 120 W/cm, so as to polymerize the discotic liquid crys- tal molecules. The film was cooled to room temperature.

Thus, an optically anisotropic layer was formed to prepare an optical compensatory film.

The retardation values Re (0°), Re (40°) and Re (-40°) were measured in the normal direction, in the direction in- clined at 40° from the normal, and in the direction in- clined at-40, respectively, in the plane including the rubbing direction and the normal. The results were set forth in Table 2.

(Preparation of linearly polarizing film) A PVA film was immersed at 25°C for 240 seconds in an aqueous solution containing 2.0 g/liter of iodine and 4.0 g/liter of potassium iodide, and further 25°C for 60 sec- onds in an aqueous solution containing 10 g/liter of boric

acid. After the immersed film was stretched by means of a tenter machine at the stretching ratio of 7.4, the film was dried to shrink at 80°C with the width kept at a constant.

The film was then released from the tenter, and wound up.

The contents of water in the film before and after drying were 30% and 1. 3%, respectively.

The obtained linearly polarized film had a slow axis parallel to the transferring (longitudinal) direction. The transmittance and the polarizability of the film were 43. 9% and 99. 96%, respectively, at 550 nm.

(Preparation of k/4 plate) The following coating solution was applied by means of a bar coater on a cellulose triacetate film similar to that used in the optical compensatory film of Example 1, and dried at 130°C for 3 minutes to form a vertical orientation layer having 0.5 um thickness.

Solution for vertical orientation layer Polyamic acid denatured with steroid 5.0 wt. % N-methyl-2-pyrrolidone 25.0 wt. % Ethylene glycol monobutyl ether 25.0 wt. % Methyl ethyl ketone 45.0 wt. % The film having the formed vertical orientation layer was wound up to a roll, and subjected to rubbing treatment at 45° to the transferring (longitudinal) direction. On the vertical orientation layer, the following coating solu- tion was applied and irradiated for 1 second with an ultra- violet ray emitted from a high pressure mercury lamp of 500 W/cm2 to produce a k/4 plate having the retardation value

of 138 nm and a slow axis inclined at 45° to the longitudi- nal direction in plane.

Solution for optically anisotropic layer Discotic liquid crystal used in Example 1 32.6 wt. % Cellulose acetatebutylate 0.2 wt. % Trimethylol propanetriacrylate 3.2 wt. % Irgacure 907 (Ciba-Geigy) 0.4 wt. % Kayacure DETX (Nippon Kayaku Co. , Ltd. ) 1.1 wt. % The following chiral agent (C-2) 0.35 wt. % Methyl ethyl ketone 62.5 wt. % Chiral agent (C-2) (Preparation of circularly polarizing plate) Both surfaces of each of a commercially available cel- lulose triacetate film (Fujitac TD80, Fuji Photo Film Co., <BR> <BR> Ltd. ) and the above k/4 plate were saponified in the same manner as in Example 1. The cellulose triacetate side sur- face of each of the film of the plate was coated with a polyvinyl alcohol-based adhesive layer of approx. 30 pm

thickness, and the above linearly polarizing film was roll- to-roll sandwiched and laminated with the triacetyl cellu- lose film and the X/4 plate. Thus obtained layered compo- sition was dried at 80°C to produce a circularly polarizing plate having the thickness of approx. 241 pm.

(Preparation of OCB alignment mode LCD of semi-transmission type) On each side of a liquid crystal cell of bend align- ment mode, the optical compensatory film was laminated with an acrylic adhesive, so that the cellulose triacetate side of the film might be in contact with the cell. The rubbing direction of the cell was positioned parallel to the rub- bing direction of the film. Further on the film, the cir- cularly polarizing plate was laminated with an acrylic ad- hesive, so that the k/4 plate of the polarizing plate might be in contact with the film. The slow axis of the k/4 plate was positioned anti-parallel to the rubbing direction of the cell. On the reflection board side, a prism sheet and a diffusing plate were successively laminated to provide a backlight unit. Thus, a LCD of semi-transmission type was produced. The produced liquid crystal display had the following constitution.

Circularly polarizing plate Protective film (TD80U) Linearly polarizing film (PVA/I2) Phase retarder (k/4 plate) Optical compensatory film Transparent support (cellulose triacetate film) Optically anisotropic layer (discotic liquid crystal layer)

Liquid crystal cell of bend alignment mode (CB mode) Optical compensatory film Optically anisotropic layer (discotic liquid crystal layer) Transparent support (cellulose triacetate film) Circularly polarizing plate Phase retarder (x/4 plate) Linearly polarizing film (PVA/I2) Protective film (TD80U) Prism sheet Diffusing board Backlight Voltage (white: 2V, black: 6V) was applied to the liq- uid crystal cell, and an image was displayed and frontally seen to measure a front contrast ratio by means of a meter (EZ-Contrast 160D, ELDIM). The viewing angle giving a con- trast ratio of 5 or more was measured leftward-rightward (perpendicularly to the rubbing direction). The results were set forth in Table 3.