[DESCRIPTION]

[Invention Title]

OPTICAL FILMS, PHASE DIFFERNCE FILMS, AND LCD COMPRISING THE SAME

[Technical Field]

The present invention relates to an optical film, a retardation

film, a method of producing the same, and a polarizing plate and a liquid

crystal display device that includes the optical film or the retardation

film. More particularly, the present invention relates to an optical film

in which the mechanical properties and the optical properties are improved

and which includes a (meth)acryl based resin, a retardation film, a method

of producing the same, and a polarizing plate and a liquid crystal display

device that includes the optical film or the retardation film. This

application claims priority benefits from Korean Patent Application Nos.

10-2007-0058248, filed on June 14, 2007, and 10-2007-0109747, filed on

October 30, 2007, the entire content of which is fully incorporated herein

by reference.

[Background Art]

In the case of an acryl based resin, because of its low cost and

high transparency, it is useful as a resin for a film. However, an

acrylate film that includes an acryl based resin has a problem in that

since the aerylate film has the poor mechanical properties, it is

insufficient to produce the acrylate film as a desired film. In order

to improve this, an effort in which the acrylate film is produced by using

a material that is obtained by polymerizing the resin after a soft segment

is added to the acryl based resin has been made, but it is required that

a film having the desirable mechanical properties is developed.

In addition, the film that is produced by using the styrene based

resin is a material that shows an optical anisotropic property in which

a refractive index is increased in a direction that is vertical to the

alignment direction when the resin is stretched and aligned. It is known

that the resin is useful to produce the film having the positive thickness

retardation value (R _t h) by stretching it. In addition, the styrene based

resin has advantages of excellent economical efficiency and transparency.

However, there are problems of insufficient heat resistance and poor

mechanical properties, except that the film is produced in conjunction

with costly special monomer.

[Disclosure]

[Technical Problem]

The present inventors have studied to solve the problems occurring

in the related art and found that when a specific type of (meth)acryl based

copolymer is used to produce the film, the copolymer has excellent

mechanical properties and optical properties, so that it can be shown

excellent effect when it is applied as a material for optical film, and

in case of using more styrene resin, it can be shown high economical

efficiency and excellent properties when it is applied as an optical film

or a retardation film.

Therefore, it is an object of the present invention to provide an

optical film in which the mechanical properties are improved and which

includes a (meth)acryl based resin, a retardation film, a method of

producing the same, and a polarizing plate and a liquid crystal display

device that includes the optical film or the retardation film.

[Technical Solution]

In order to accomplish the above object, the present invention

provides an optical film comprising a graft copolymer that includes two

types or more of (meth)acrylic resins that have different glass transition

temperatures. The optical film may further comprise a resin that has

styrene or derivatives thereof.

In addition, the present invention provides a method of producing

an optical film comprising the steps of a) producing a first (meth)acryl

based resin comprising a first (meth)acryl based monomer ; b) intorducing

a functional group that is capable of being reacted with a radical to a

main chain of the first (meth)acryl based resin; c) radical polymerizing

a second (meth)acryl based monomer in respects to the modified first

(meth)acryl based resin that is obtained in step b) to produce a graft

copolymer in which the second (meth)acryl based resin that has the

different glass transition temperature from that of the first (meth)acryl

based resin is subjected to the graft polymerization in respects to the

first (meth)acryl based resin; and d) forming a film by using the graft

copolymer that is obtained in step c).

In step d), before the film is formed, the film can be formed by

blending the graft copolymer and the resin that has the styrene or the

derivatives thereof with each other and forming the film by using the

blended resin.

In addition, the present invention provides a retardation film

comprising a graft copolymer that includes two or more types of (meth)acryl

based resins in which glass transition temperatures are different from

each other; and a resin that has styrene or derivatives thereof, in which

a thickness retardation (R _t h) > 0, and an in-plane retardation (R _in ) ≠ 0.

In addition, the present invention provides a method of producing

the retardation fi Im comprising the steps of a) blending a graft copolymer

that includes two or more types of (meth)acryl based resins in which the

glass transition temperatures are different from each other and a resin

that has a styrene or derivatives thereof with each other; b) forming the

film by using the blending resin that is obtained in the step a); and c)

uniaxial Iy or biaxial Iy stretching the film.

In addition, the present invention provides a liquid crystal

display device comprising a liquid crystal cell ; a first polarizing plate

and a second polarizing plate that are positioned on both sides of the

liquid crystal cell; and one or more optical films that comprises a graft

copolymer that includes two types or more of (meth)acrylic resins that

have different glass transition temperatures and are positioned between

at least one of the first polarizing plate and the second polarizing plate

and the liquid crystal cell . The optical filmmay further comprise a resin

that has styrene or derivatives thereof.

In addition, the present invention provides a liquid crystal

display device that comprises the retardation film.

In addition, the present invention provides a polarizing plate

comprising an optical film that comprises a polarizer, and a graft

copolymer that includes two types or more of (meth)acrylic resins that

are positioned on a side or both sides of the polarizer as a protection

film and have different glass transition temperatures. The optical film

may further comprise a resin that has styrene or derivatives thereof.

In addition, the present invention provides a liquid crystal

display device comprising a liquid crystal cell ; a first polarizing plate

and a second polarizing plate that are positioned on both sides of the

liquid crystal cell", and at least one of the first polarizing plate and

the second polarizing plate is a polarizer and a polarizing plate that

includes an optical film that includes a graft copolymer that includes

two types or more of (meth)acrylic resins that have different glass

transition temperatures and is positioned on a side or both sides as a

protection film. The optical film may further comprise a resin that has

styrene or derivatives thereof.

[Advantageous Effects]

An optical film and a retardation film according to the present

invention comprises a graft copolymer comprising two types or more of

(meth)acryl based resins that have different glass transition

temperatures. Since the mechanical properties and the optical properties

are excellent, the film according to the present invention can be usefully

used for various puroposes, in particular, can be usefully used as the

protection film of the polarizing plate. Since the mechanical properties,

the heat resistance, and the optical properties are excellent , it isuseful

to simply produce an excellent liquid crystal display device at low cost.

[Description of Drawings]

FIG. 1 is a view that schematically illustrates a structure of a

liquid crystal display device in which an optical film according to the

present invention is applied as a protection film of a polarizing plate.

[Best Mode]

Hereinafter, the present invention will be described in more

detail .

An optical film according to the present invention is characterized

in that the optical film comprises a graft copolymer comprising two types

or more of (meth)acrylic resins that have different glass transition

temperatures. Since the optical film comprising the graft copolymer as

described above according to the present invention has the more excellent

mechanical properties and optical properties as compared to a conventional

acryl based film, the optical film according to the present invention can

be usefully used for various puroposes. In addition, the present invention

has the effect in which the mechanical properties of the film are improved

by adding the graft copolymer to the resin that has styrene or derivatives

thereof. In the present specification, it is construed that the

(meth)acryl based resin includes all the acryl based resin and the

methacryl based resin.

In the present invention, it is preferable that two types or more

of (meth)acryl based resins that have different glass transition

temperatures do not have compatibility to each other. It is preferable

that in the case of at least one of the (meth)acryl based resins, the glass

transition temperature is less than 0°C , and in the case of at least one

of the (meth)acryl based resins, the glass transition temperature is 0 ^° C

or more. It is preferable that the polymer chain forming a main chain

in the graft copolymer is the (meth)acryl based resin in which the glass

transition temperature is less than 0°C.

The (meth)acryl based resin is not limited, but may be produced

by polymerizing the (meth)acryl based monomer. If necessary, an

additional comonomer may be added.

As the (meth)acryl based monomer, it has an alkyl group having 1

to 12 carbon atoms, and preferably an alkyl group having 2 to 8 carbon

atoms, an alkylene group, and an aromatic substituent. Examples of the

(meth)acrylic acid ester based monomer that has the alkyl group having

1 to 12 carbon atoms may include monomers that are selected from the group

consisting of butyl acrylate, butyl methacrylate, 2-ethyl hexyl acrylate,

2-ethyl hexyl methacrylate, methyl acrylate, methyl methacrylate, ethyl

acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate,

iso-propyl acrylate, iso-propyl methacrylate, t-butyl acrylate, t-butyl

methacrylate, pentyl acrylate, pentyl methacrylate, n-octyl acrylate,

n-octyl methacrylate, iso-nonyl acrylate, iso-nonyl methacrylate,

n-tetradecyl acrylate, n-tetradecyl methacrylate, lauryl acrylate,

lauryl methacrylate, benzyl acrylate, benzyl methacrylate, and they may

be used alone or in a mixture of two or more species. However, the present

invention is not limited thereto.

In order to produce the (meth)acryl based resin, a (meth)acrylic

acid ester based monomer that has a functional group may be added.

Specific examples of the (meth)acrylic acid ester based monomer may

include a (meth)acrylic acid ester based monomer that includes hydroxy

such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate,

4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate,

2-hydroxyethylene glycol (meth)acrylate, 2-hydroxypropylene glycol

(meth)acrylate; a (meth)acrylic acid ester based monomer that includes

epoxy such as 2-glycidyl (meth)acrylate; and a (meth)acrylic acid ester

based monomer that icnludes carboxylic acid such as acrylic acid,

methacrylic acid, acrylic acid dimer, itaconic acid, maleic acid, maleic

anhydride, crotonic acid, β-carboxyethyl acrylate, and they may be used

alone or in a mixture of two or more species. However, the present

invention is not limited thereto.

The (meth)acryl based resin may further include, in addition to

the above monomer, other monomers. For example, a vinyl monomer that

includes a vinyl cyanide monomer, a maleimide monomer, and an aromatic

ring.

Acrylonitrile and the like are used as the vinyl cyanide monomer.

Examples of the maleimide monomer include N-phenyl maleimide,

N-cyclohexyl maleimide, N-methyl maleimide, N-butyl maleimide and the

like. Specific examples of the vinyl monomer that includes the aromatic

ring include one or more compounds that are selected from the group

consisting of a styrene based monomer, in detail, styrene, α-methyl

styrene, 3-methyl styrene, p-methyl styrene, p-ethyl styrene, p-propyl

styrene, 4-(p-methylphenyl) styrene, 1-vinyl naphthalene,

p-chlorostyrene, m-chlorostyrene and p-nitrostyrene, but not limited

thereto.

Any monomers in which the glass transition temperature of a

homopolymer of each of them is 0 ^° C may be used as the monomer that is

capable of producing the (meth)acryl based resin in which the glass

transition temperature is 0 ^° C or more among the monomers. In the present

invention, representatively, methylmethacrylate (MMA) may be mainly used.

It is preferable that the content of methylmethacrylate is in the amount

of 50 mole% or more in the (meth)acryl based resin.

In order to produce the (meth)acryl based resin that has the glass

transition temperature of 0°C or more, in addition to the above monomer,

a monomer in which the glass transition temperature of the homopolymer

is less than 0°C may be used as the comonomer. In this case, it may be

used while the amount thereof may be controlled so that the glass

transition temperature of the copolymer is 0°C or more.

In addition, among the monomers, a representative example of the

monomer that is capable of producing the (meth)acryl based resin in which

the glass transition temperature is less than 0°C may include

butylacrylate (BA), and in addition to this, examples of the monomer may

include butyl (meth)acrylate, ethyl (meth)acrylate, methyl

(meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate,

t-butyl (meth)acrylate, pentyl (meth)acrylate, n-octyl (meth)acrylate,

n-tetradecyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl

(meth)acrylate, benzyl (meth)acrylate and the like, and these monomers

may be used alone or in a mixture of two or more species.

In particular, in the case of when the (meth)acryl based resin in

which the glass transition temperature is less than 0°C forms a main chain

of the graft copolymer, a method in which a functional group that is capable

of being reactedwith radicals is introduced in the (meth)acryl based resin

in which the glass transition temperature is less than 0 ^° C may be used

so that the resin having the different glass transition temperature, for

example, the (meth)acryl based resin in which the glass transition

temperature is 0°C or more is subjected to the graft polymerization in

conjunction with the main chain of the copolymer. At this time, in order

to introduce a functional group that is capable of being reacted with

radicals in the (meth)acryl based resin in which the glass transition

temperature is less than 0°C, in addition to the above (meth)acryl based

monomer , it is preferable to add the (meth)acryl ic acid ester based monomer

that has the functional group.

Examples of the (meth)acrylic acid ester based monomer that has

the functional group may include a (meth)acrylic acid ester based monomer

that includes hydroxy such as 2-hydroxyethyl (meth)acrylate,

2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate,

6-hydroxyhexyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate,

2-hydroxypropylene glycol (meth)acrylate; a (meth)acrylic acid ester

based monomer that includes epoxy such as 2-glycidyl (meth)acrylate; and

a (meth)acrylic acid ester based monomer that icnludes a carboxylic acid

such as an acrylic acid, a methacrylic acid, an acrylic acid dimer, an

itaconic acid, a maleic acid, a maleic anhydride, a crotonic acid,

β-carboxyethyl acrylate, and they may be used alone or in a mixture of

two or more species. However, the present invention is not limited

thereto.

In order to produce the (meth)acryl based resin in which the glass

transition temperature is less than 0°C , in addition to the above monomer,

a monomer in which the glass transition temperature of the homopolymer

is 0°C or more may be used as the comonomer. In this case, it may be used

while the amount thereof may be controlled so that the glass transition

temperature of the copolymer is less than 0°C.

In the present invention, in the graft copolymer that includes two

or more types of (meth)acryl based resins in which the the glass transition

temperatures are different from each other, the (meth)acryl based resin

in which the glass transition temperature is low may form a main chain

of the (meth)acryl based resin, and the (meth)acryl based resin in which

the glass transition temperature is high may form a side chain, and vice

versa. In the present invention, it is preferable that in the graft

copolymer, the (meth)acryl based resin in which the glass transition

temperature is low form a main chain of the (meth)acryl based resin, and

the (meth)acryl based resin in which the glass transition temperature is

high may form a side chain. For example, in the graft copolymer, one or

more types of (meth)acryl based resins in which the glass transition

temperature is less than 0 ^° C may form a main chain, and one or more types

of (meth)acryl based resins in which the glass transition temperature is

0°C or more may form a side chain.

In the graft copolymer, a weight average molecular weight is

preferably in the range of 50000 to 2000000, and more preferably in the

range of 50000 to 500000, and a number average molecular weight is

preferably in the range of 10000 to 1000000, and more preferably in the

range of 10000 to 300000.

In the present invention, the content ratio of the (meth)acryl

based resin in which the glass transition temperature is less than 0°C

and the (meth)acryl based resin in which the glass transition temperature

is 0°C or more is in the range of 95:5 to 5:95, and more preferably 90:10

to 10: 90.

In the present invention, as the resin that has the styrene or

derivatives thereof, the resin is not particularly limited if the resin

includes 30 % by weight or more of styrene or derivatives thereof therein.

In detail, examples of the resin that has styrene or derivatives thereof

and is capable of being used in the present invention may include

polystyrene, SAN (styrene acrylonitrile copolymer) and the like.

In the present invention, the graft polymer and the resin that has

styrene or derivatives thereof can be mixed with each other in a weight

ratio in the range of 95:5 to 5:95, and in particular, in order to show

the desired physical properties, it is preferable that styrene or

derivatives thereof is included in an amount of 20 % by weight or more

in the blending resin that is obtained after the blending.

According to an embodiment of the present invention, it is provided

a method of producing an optical film, which includes a) producing a first

(meth)acryl based resin that includes a first (meth)acryl based monomer ;

b) intorducing a functional group that is capable of being reacted with

a radical to a main chain of the first (meth)acryl based resin; c) radical

polymerizing a second (meth)acryl based monomer in respects to the

modified first (meth)acryl based resin that is obtained in the step b)

to produce a graft copolymer in which the second (meth)acryl based resin

that has the different glass transition temperature from that of the first

(meth)acryl based resin is subjected to the graft polymerization in

respects to the first (meth)acryl based resin; and d) forming the film

by using the graft copolymer that is obtained in the step c).

Before the film is formed in the step d) , after the graft copolymer

and the resin that has the styrene or the derivatives thereof is blended

with each other, the film may be formed by using the blended resin.

The step a) is a step for producing the first (meth)acryl based

resin, and in order to introduce the functional group that is capable of

being reacted with the radical to the main chain of the first (meth)acryl

based resin in the step b), which is performed in a next process, it is

preferable that the (meth)acrylic acid ester based monomer having various

functional groups is added to the first (meth)acryl based monomer.

Preferable examples of the (meth)acrylic acid ester based monomer that

has the functional group may include a (meth)acrylic acid ester based

monomer that includes hydroxy such as 2-hydroxyethyl (meth)acrylate,

2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate,

6-hydroxyhexyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate,

and 2-hydroxypropylene glycol (meth)acrylate; a (meth)acrylic acid ester

based monomer that includes epoxy such as 2-glycidyl (meth)acrylate! and

a (meth)acrylic acid ester based monomer that icnludes a carboxylic acid

such as an acrylic acid, a methacrylic acid, an acrylic acid dimer, an

itaconic acid, a maleic acid, a maleic anhydride, a crotonic acid,

β-carboxyethyl aerylate, but is not limited thereto. The amount of the

(meth)acrylic acid ester based monomer that has the functional group which

is added to produce the first (meth)acryl based resin is in the range of

0.1-50 mol%, and more preferably in the range of 0.1 - 10 mol%.

Subsequently, the step b) is a step in which a functional group

that is capable of being reacted with a radical is introduced into the

main chain of the first (meth)acryl based resin that is produced in the

step a). Examples of the functional group that is capable of being reacted

with the radical include the -SH group.

In detail, in an embodiment of the step b), as a method for

introducing the -SH group to the first (meth)acryl based resin, a method

that comprises a step for esterifying a hydroxy group or a carboxylic group

and amercaptoacetic acid, mercapto alcohol , or mercapto ester in the resin

under the presence or absence of a catalyst may be used. In this step,

the amount of the -SH group that is capable of being introudced in respects

to the first (meth)acryl based resin may be various according to the

reaction condition. For example, the concentration of the -SH group may

be variously introduced by controlling the degree of esterification in

the amount of 0.1 - 100mole%, andmore preferably 50 - 100mole% in respects

to the functional group of the whole hydroxy group or the carboxyl group.

Examples of the catalyst that is capable of being used in the step

b) may representatively include an acid catalyst. Examples of the acid

catalyst that is capable of being used according to this may include an

inorganic salt of a sulfuric acid or a chloric acid, an organic acid such

as a methane sulfonic acid, a paratoluene sulfonic acid and the like, a

Lewis acid such as a boronic acid and the like and the like. The amount

of the acid catalyst that is used in the step b) is not limited.

The first (raeth)acryl based resin into which the mercapto group

is introduced may act as a chain transfer agent in the course of a next

radical polymerizing, and function to provide an active site of the graft

polymerization (see [Journal of Polymer Science 1959, ρ411 - 423]).

In the step c), a second (meth)acryl based monomer may be added

in respects to the modified first (meth)acryl based resin that is obtained

in the step b) and radical polymerized to produce a graft copolymer in

which the second (meth)acryl based resin that has the different glass

transition temperature from that of the first (meth)acryl based resin is

subjected to the graft polymerization in respects to the first (meth)acryl

based resin.

In the step c), the addition amount of the modified first

(meth)acryl based resin that is obtained in the step b) may be generally

variously controlled in the range of 1 to 50 parts by weight in respects

to 100 parts by weight of the second (meth)acryl basedmonomer . The second

(meth)acryl based monomer means a (meth)acryl based monomer that is

capable of being included in the second (meth)acryl based resin that has

the different glass transition temperature from that of the first

(meth)acryl based resin, and an example thereof is as described above.

In the method of producing the optical film according to the present

invention, the first (meth)acryl based resin is a (meth)acryl based resin

in which the glass transition temperature is less than 0°C , and the second

(meth)acryl based resin is a (meth)acryl based resin in which the glass

transition temperature is more than 0°C.

In the step c) , in addition to the second (meth)acryl basedmonomer ,

the (meth)acrylic acid ester based monomer that has the functional group

maybe further added. Preferable examples of the (meth)acrylic acid ester

based monomer that has the functional group are the same as those that

are capable of being used in the step a).

As a radical polymerization in the step c, a method that is known

in the art maybe used, and the scope of the present invention is not limited

to the polymerization method. For example, a bulk polymerization, a

solution polymerization, a suspension polymerization, an emulsion

polymerization and the like may be possible, but are not limited thereto.

As the polymerization initiator, for example, an initiator that

is activated by heating or an initiator that is activated by light may

be used. In detail, the initiator that is activated by heating such as

an azo compound such as azobisGsobutylonitri Ie) , a peroxid compound such

as benzoyl peroxide and the like, or an initiator that is activated by

light such as benzophenone, benzoine ethyl ether, 2,2'-dimetoxy-2-phenyl

acetophenoen and the like may be used, but are not limited thereto. The

amount of the polymerization initiator is not limited, but in order to

obtain an appripriate molecular weight of the graft copolymer that is

obtained finally, in general , in respects to the second (meth)acryl based

monomer, it is preferable that the weight ratio is in the range of 0.01

to 5, and more preferably, the weight ratio is in the range of 0.1 to 1.

Inaddition, in order to appropriately control the molecular weight ,

a chain transfer agent may be added. As an appropriate chain transfer

agent, a mercaptane system such as dodecyl mercaptane, lauryl mercaptane

or alpha methyl styrene dimer and the like are appropriate.

The reaction temperature of the polymerization may vary slightly

for the balance in respects to the other polymerization conditions, and

may be generally in the range of 30 ~ 130"C , preferably 40 ~ 120 ⁰ C , and

more preferably 40 ~ 90°C. In addition, the reaction time is different

according to the reaction conditions such as the reaction temperature,

the type of monomer, or the concentration, but may be generally in the

range of 2 ~ 24 hours. While the radical polymerization is performed,

the block copolymer may further include a filler, a reinforcing agent,

a stabilizer, a coloring agent, and antioxidant, if necessary.

Examples of the solvent that is used in the polymerization may

include ethers such as tetrahydrofuran, diethyl ether, and dioxane,

hydrocarbons such as n-hexane, petroleum ether, toluene, bezene, and

xylene, alcohols such as methanol, ethanol, and isopropanol, ketones such

as acetone, methyl ethyl ketone, and methyl isobutylketone, acetonitrile,

N,N-dimethyl formamide, and dimethyl sulfoxide. Such solvents may be used

singly or in combination of two or more. The polymerization reaction is

preferably performed under inert gas atmosphere. Examples of the inert

gas may include nitrogen gas and argon gas.

In the above method, the molecular weight, the degree of graft and

thermal stability of the graft copolymer can be controlled by controlling

the amount of a precursor, a polymerization initiator, and the second

(meth)acryl based monomer for intorducing a functional group that is

capable of being reacted with a radical to a main chain of the first

(meth)acryl based resin.

In step d) , the graft copolymer may be used to produce the optical

film by using a general film producing method such as an extrusion shaping

method, an inflation shaping method, or a solution softening method as

a primary shaping processing process. It is preferable that the optical

film is used itself, that is, while the optical film is not stretched,

for the industrial used, and in the next step, a retardation difference

may be provided by a stretching processing operation that is a secondary

shaping processing process to use the optical film as the retardation film.

In step d), in the case of when the copolymer is blendedwith styrene

or the derivatives thereof, the blending condition is not particularly

limited, and may be applied to an extrusion process that is generally

applied.

In addition, when the optical film according to the present

invention is produced, in addition to the above graft copolymer to improve

the productivity, a commercialized aery1 resin may be mixed. At this time,

the mixing ratio of the graft copolymer and the acryl based resin is not

particularly limited, and may be mixed in the range inwhich the mechanical

properties of the obtained optical film are not reduced. Preferably, the

mixing is possible so that the weight ratio between the graft copolymer

and the acryl based resin is in the range of 95:5 to 5:95, and more

preferably, the weight ratio is in the range of 80:20 to 20:80. In the

case of when the weight ratio of the acryl based resin is exceeded 95%,

it cannot have physical properties that are appropriate for the use as

the optical film. The specific type of the the acryl based resin is not

particularly limited, and a commercial type may be used. For example,

polymethyl methacrylate (PMMA) and the like may be used.

In the case of producing the film by using an extrusion shaping

method as the primary shaping process method, the film that has a

predetermined thickness can be produced by passing it through a thin

interval of a die that is called as a T -die. At this time, in order to

prevent poorness of the appearance by bubbling of the gas, it is preferable

that the graft copolymer is preliminarilyheated and dried at a temperature

in the range of 80 to 130 ^° C . It is preferable that the extrusion shaping

is performed at a temperature that is sufficiently higher than a glass

transition temperature in which the graft copolymer is melted and flows

in order to suppress the alignment of the molecular chain. After passing

through the die, in order to cool and solidify the film that is present

in a melted state, a low temperature metal roller or a steal belt may be

used.

In the case of when the film is produced by using the solution

softening method as the primary shaping processing method, a solvent that

is capable of being used by each resin may be selected, and if necessary,

a plurality of solvents may be used. Specific examples of the solvent

that is capable of being used in the solution softening method may include

methylene chloride, chloroform, chlorobenzene, 1,4-dioxane,

1,3-dioxolane, tetrahydrofurane and the like, but are not limited thereto.

In particular , in order to control the volatilization rate, a good solvent

and a poor solvent may be combined with each other in respects to the graft

copolymer. When the drying in the solution softening method, according

to the settlement of the heating condition, bubbles or inner voids are

not formed in the film, and it is preferable that the concentration of

the residual solvent is 0.1 wt% or less.

It is preferable that the thickness of the optical film that is

produced by using the primary shaping processing by the above method is

in the range of 30 to 500 μm (micrometers).

In the case of when the optical film that is produced as described

above is additionally stretched, if the glass transition temperature of

the graft copolymer is Tg, it may be performed at a temperature in the

range of Tg - 20°C - Tg + 30°C. The glass transition temperature means

a temperature in the range of a temperature at which the storage elasticity

of the graft copolymer starts to be reduced to allow the loss elasticity

to be higher than the storage elasticity to a temperature at which the

alignment of the polymer chains becomes loose and thus vanishes. The

glass transition temperature may be measured by using a differential

scanning calorimeter (DSC).

The present invention provides a retardation film that comprises

a graft copolymer that includes two or more types of (meth)acryl based

resins in which glass transition temperatures are different from each

other; and a resin that has styrene or derivatives thereof. In the

retardation film, a thickness retardation (R _t h) > 0, and an in-plane

retardation (R; _n ) φ 0. It is preferable that the thickenss of the

retardation film is in the range of 30 to 200 μm (micrometers). It is

preferable that the in-plane retardation value of the retardation film

is in the range of 0 to +400 nm and the value of the thickness retardation

is in the range of 0 to +400 nm.

In the specification of the present invention, the thickness

retardation (R _t h) and the in-plane retardation (R; _n ) are defined as the

following equations:

R _th = d{n _z - (n _x + n _y )/2}

Ri _n = d(n _x - n _y )

wherein, the χ-axis direction refractive index is n _x , the y-axis

direction refractive index is %, the thickness direction refractive index

is n _z , and the thickness of the film is d.

The retardation film according to the present invention may be

produced by after the film is shaped as described in the production method

of the optical film, (c) further uniaxial Iy or biaxial Iy stretching the

film. In the present invention, the film that includes the components

as described above may be uniaxial Iy stretched or uniaxial Iy stretched

while the stretching ratios of the biaxises to provide the retardation

film in which the thickness retardation (R _t h) > 0 and the in-plane

retardation (Rj _n ) ≠ 0. The retardation film may provide optical

properties that are required in a liquid crystal display device, in

particular, an IPS type of the liquid crystal display device.

The stretching, if the glass transition temperature of the blending

resin is Tg, may be performed at a temperature in the range of Tg - 20 ⁰ C

~ Tg + 3O ⁰ C . The glass transition temperature means a temperature in the

range of a temperature at which the storage elasticity of the block

copolymer starts to be reduced to allow the loss elasticity to be higher

than the storage elasticity to a temperature at which the alignment of

the polymer chains becomes loose and thus vanishes. The glass transition

temperature may be measured by using a differential scanning calorimeter

(DSC) .

The stretching rate can be appropriately controlled according to

the retardation and the thickness of the film. In general, the strethcing

can be performed while the stretching rate that is calculated by the

following eqaution is in the range of 50 %/min to 500 %/min.

[Equation]

stretching speed (%/min) = {(width direction dimension after

stretching / width direction dimension before stretching) - 1} x 100 (%)

/ tiem needed for stretching (min)

In the method of producing the retardation film according to the

present invention, the stretching ratio may be appropriatly controlled

according to the retardation and the thickness of the film, and in general ,

the stretching can be performed in the range of 10% to 100%.

In addition, the present invention provides a liquid crystal

display device that comprises a liquid crystal cell; a first polarizing

plate and a second polarizing plate that are positioned on both sides of

the liquid crystal cell; and one or more optical films according to claim

1 or 2 that are positioned between at least one of the first polarizing

plate and the second polarizing plate and the liquid crystal cell and

include the graft copolymer that includes two or more types of the

(meth)acryl based resins in which the glass transition temperatures are

different from each other. Theoptical film may further include the resin

that includes styrene or derivatives thereof.

In addition, the present invention provides a liquid crystal

display that includes the retardation film.

In addition, the present invention provides a polarizing plate that

includes an optical film that comprises a polarizer and a graft copolymer

that includes two types or more of (meth)acrylic resins that are positioned

on a side or both sides of the polarizer as a protection film and have

different glass transition temperatures. The optical film may further

include a resin that has styrene or derivatives thereof.

In the case of disposing the optical film according to the present

invention to only one side of polarizer as the protection film, a

protection film that is known in the art may be positioned on the other

side thereof. Examples of the protection film disposed as a protection

film to the other side may include a triacetate cellulose (TAC) film, an

ROMP (ring opening metathesis polymerization) polynorbornene-based film,

an HROMP (ring opening metathesis polymerization followed by

hydrogenation) polymer film, which is obtained by hydrogenating a ring

opening metathesis polymerized cycloolefine-based polymer, a polyester

film, and an addition polymerization polynorbornene-based film. In

addition, a film made from a transparent polymer may be available as the

protection film, but is not limited thereto.

As a polarizer, a film which contains iodine or dichromatic dyes

and is made of polyvinyl alcohol (PVA) may be used. The polarizer may

be produced by applying iodine or dichromatic dyes on the PVA film.

However, the production method of the polarizing plate is not limited.

In the specification, the polarizer does not include the protective film,

and the polarizing plate includes the polarizer and the protective film.

In the polarizing plate according to the present invention, the

protection film and the polarizer may be combined by using the method that

is known in the art.

For example, the combination of the protection film and the

polarizer may be performedby using an attachment process using an adhesive.

That is, first, the adhesive is coated on the surface of the PVA film that

is the protective film of the polarizer or the polarizer by using a roll

coater, a gravure coater , abarcoater, a knife coater , a capillary coater,

or the like. Before the adhesive is completely dried, the protective film

and the polarizer are combined with each other using heat pressing or

pressing at normal temperature by means of a combination roll. When a

hot melt type adhesive is used, it is required that the heat pressing roll

is used.

Examples of the adhesive which is capable of being used to combine

the protection film and the polarizer include, but are not limited to,

a one- or two-liquid type polyvinyl alcohol (PVA) adhesive, a polyurethane

based adhesive, an epoxy based adhesive, a styrene-butadiene rubber (SBR)

based adhesive, a hot melt type adhesive and the like. If the polyurethane

based adhesive is to be used, it is preferable to use the polyurethane

based adhesive produced by using an aliphatic isocyanate compound which

does not cause yellowing due to light. If an one- or two-Iiquid type dry

laminate adhesive or an adhesive having relatively low reactivity in

respects to isocyanate and a hydroxy group is used, a solution type

adhesive which is diluted with an acetate solvent, a ketone solvent, an

ether solvent, or an aromatic solvent may be used. In this connection,

it is preferable that the adhesive have low viscosity of 5000 cps or less.

Preferably, the adhesive has excellent storage stability and light

transmittance of 90% or more at a wavelength of 400 to 800 nm.

A gluing agent may be used as long as it has desirable adhesiveness.

It is preferable that the gluing agent is sufficiently cured by heat or

ultraviolet rays after the combination so that mechanical strength

required in the adhesive is ensured, and interfacial adhesion strength

is large so that stripping does not occur as long as any one of both sides

of the film to which the gluing agent is attached is not destroyed.

Specific examples of the gluing agent may include natural rubber,

synthetic rubber, or elastomer having excellent optical transparency, a

vinyl chloride/vinyl acetate copolymer, polyvinyl alkyl ether,

polyacrylate, denatured polyolefin gluing agent, and a curable adhesive

containing a curing agent such as isocyanate.

In addition, the present invention provides a liquid crystal

display device that comprises a liquid crystal cell; a first polarizing

plate and a second polarizing plate that are positioned on both sides of

the liquid crystal cell; and at least one of the first polarizing plate

and the second polarizing plate is a polarizer and a polarizing plate that

is positioned on a side or both sides as a protection film and includes

the optical film including the graft copolymer that includes two or more

types of the (meth)acryl based resins in which the glass transition

temperatures are different from each other. The optical film may further

include the resin that includes styrene or derivatives thereof.

The optical film or the retardation film may be positioned in the

liquid crystal display device by one or two pieces. It is preferable that

the liquid crystal display device according to the present invention is

an IPS mode.

If the above liquid crystal display device is watched through

exemplified FIG. 1, it is as follows. In FIG. 1, the optical film

according to the present invention may be positioned as the protection

film on a side or both sides of the polarizing film of at least one of

the polarizing plate 11 and the polarizing plate 12. The optical film

according to the present invention may be positioned as the inner

protection film or as the outer protection film. In FIG. 1, the

retardation film is shown, but the presence of the retardation film is

not necessary. In addition, in FIG.1, a backlight is positioned at the

polarizing plate 12, but the backlight may be positioned at the polarizing

plate 11.

The liquid crystal display device that includes the polarizing

plate according to the present invention as described above may further

comprise the optical film according to the present invention between the

polarizing plate and the liquid crystal cell.

A better understanding of the present invention will be described

in light of the following Examples which are set forth to illustrate, but

are not to be construed to limit the present invention.

[Mode for Invention]

Example 1 - Production of the graft copolymer

1. Production of the first acryl based resin [A]

93 g of butylacrylate, 7 g of 2-hydroxyethylacrylate, 43 g of

toluene and 0.2 g of the initiator AIBN, and 0.1 g of 1-octylmercaptane

were dropped at 70°C into the reactor having the volume of 250 ml for 4

hours, and additionally polymerized for 3 hours at 95 ^° C to produce the

polymer. The unreacted monomer in the solution was measured by using the

gas chromatography, and it was confirmed that the conversion ratio was

98% (molecular weight: Mw = 215k, Mn = 70k).

2. Introduction of the functional group capable of being reacted

with the radical to the main chain of the first acryl based resin

200 g of toluene was further added to 200 g of the first acryl based

resin [A] solution, 1 g of the p-toluene sulfonic acid, and 6 g of the

thioglycolic acid were put thereinto after the reaction was finished, it

was dropped to methanol , and they were reacted for 4 hours whi Ie they were

refluxed. Subsequently, after toluene was added to the precipitate, it

was heated to remove methanol in the polymer as the azeotrope. Through

this process, the first acryl based resin [A ¹ ] polymer solution that had

SH could be obtained.

3. Graft polymerization

32 g of the modified first acryl based resin [A'] solution (TSC

40%), 79.17 g of MMA, 4.17 g of MA, 0.26 g of AIBN were put into the

polymerization device that had the volume of 250 mL, and were reacted for

12 hours while maintaining under the nitrogen atmosphere at 70°C. After

the reaction was finished, the polymerization solution was precipitated

in methanol to obtain the graft copolymer (copolymer 1).

The copolymers 2 and 3 were subjected to the polymerization as

described in the following Table 1 to obtain the polymer in which the second

(meth)acryl based resin was grafted in respects to the first (meth)acryl

based resin.

[Table 1]

Examples 2 to 4 - Production of the graft copolymer

1. Production of the first acryl based resins [B], [C], [D]

The amounts were the same as Example 1, except that the amounts

of butylacrylate, 2-hydroxyethylacrylate, toluene, initiator AIBN, and

1-octylmercaptane were used as described in the following Table 2.

[Table 2]

1) 4-hydroxybutylacrylate

2. Introudction of the functional group capable of being reacted

with the radical into the main chain of the first acryl based resin

The same thing as Example 1 was used, except for the description

in Table 3 to produce the modified first acryl based resins [B'], [C]

and [D'] that had various contents of functional groups and the molecular

weights.

[Table 3]

Acid catalyst: p-toluene sulfonic acid

3. Graft polymerization

(1) Copolymer 4 and 5

20 g of the modified first acryl based resin [B ¹ ] solution (TSC

50%), 95 g of MMA, 5 g of MA, 0.26 g of AIBN, and 140 g of toluene were

put into the polymerization device that had the volume of 250 mL, and they

were reacted with each other for 12 hours while maintaining at 70°C under

the nitrogen atmosphere. After the reaction was finished, the

polymerization solution was precipitated in methanol to obtain the graft

copolymer (copolymer 4 and 5).

[Table 4]

(2) Copolymers 6 to 8

20 g of the modified first acryl based resin [C] solution (TSC

50%), 72 g of MMA, 9 g of AN (acrylonitrile), 9 g of CHMI

(N-cyclohexylmaleimide), 0.24 g of AIBN, and 90 g of toluene were put into

the the polymerization device that had the volume of 250 mL, and they were

reacted with each other while increasing to the reaction temperature from

70 ^° C to 80°C for 4 hours under the nitrogen atmosphere, increasing to the

reaction temperature from 80 ^° C to 100 ^° C for 4 hours, and maintaining for

1 hour. After the reaction was finished, the polymerization solution was

precipitated in methanol to obtain the graft copolymers. The graft

copolymers were dried at 90 ^° C in the oven to obtain the final polymers

(copolymer 6 to 8).

[Table 5]

(3) Copolymers 9 to 12

20 g of the modified first acryl based resin [D ¹ ] solution (TSC

50%), 85.5 g of MMA, 4.5 g of MA, 0.2 g of AIBN, and 90 g of toluene were

put into the the polymerization device that had the volume of 250 mL, and

they were reacted with each other while increasing to the reaction

temperature from 60 ^° C to 80°C for 8 hours under the nitrogen atmosphere.

After the reaction was finished, the polymerization solution was

precipitated in methanol to obtain the graft copolymers. The graft

copolymers were dried at 90 ^° C in the oven to obtain the final polymers

(copolymer 9 to 12)

[Table 6]

<Production of the film>

7.5 g of the graft copolymer that was produced in Preparation

Example was put into 42.5 g of dichloroethane, and agitated for 24 hours

at 30 ^° C to produce the uniform solution. It was filtered by using the

filter that had the size of 5 μm (micrometers) to remove the insoluble

material and the dust, and the 15 wt% casting solution was produced. The

casting solution was poured to the glass plate for a LCD substrate,

subjected to the casting at a rate of 0.3 m/min by using the doctor blade,

and dried at the room temperature for 60 min. Next, at 60 °C for 60 min

and at 115 ⁰ C for 90 min, it was dried to remove the solvent , and the polymer

film was removed. The physical properties of the produced film are

described in the following Table 7. The whole transmittance and the haze

of the film were measured by using the reflectance-transmittance meter

(HR-100, Murakami color research Lab.). In each case, the whole

transmittance of the film was 90% or more, and the haze was the same as

the results of the following Table 7. In addition, since the graft

copolymer films that were obtained in each case were not bent when they

were folded, it could be seen that the degree of roughness was more improved

as compared to the known polymethyl methacrylate resin.

[Table 7]

Type of the Thickness of the transmittance Haze (%) Toughness copolymer film (μm) (ft)

Copolymer 1 96 92 0.2 Tough

Copolymer 2 90 93 0.3 Tough

Copolymer 3 80 91 0.4 Tough

Copolymer 4 66 93 0.3 Tough

Copolymer 5 87 91 0.4 Tough

Copolymer 6 86 90 0.4 Tough

Copolymer 7 74 90 0.4 Tough

Copolymer 10 87 92 0.5 Tough

In addition, the results after the fi Im of the graft copolymer that

was produced in the above Examples are described in the following Table

8. If the results were examined, it could be seen that since the in-plane

retardation and the thickness retardation are low, it could be suitable

to use as the optical film.

[Table 8]

the graft copolymer

1. Production of the graft copolymer

1) Production of the first acryl based resin [E]

97.5 g of butyl acrylate, 2.5 g of 2-hydroxybutyl acrylate, 43 g

of toluene and 0.2 g of the initiator AIBN, and 0.12 g of 1-octylmercaptane

were dropped at 80 ^° C to the reactor that had the volume of 250 ml for 4

hours, and additionally polymerized for 3 hours at 95°C to produce the

polymer. The unreacted monomer in the solution was measured by using the

gas chromatography, and it was confirmed that the conversion ratio was

98% (molecular weight: Mw = 95k, Mn = 39k).

2) Introduction of the functional group capable of being reacted

with the radical, to the main chain of the first acryl based resin

260 g of toluene was put into 140 g of the first acryl based resin

[E] solution that was produced in 1), 1 g of the p-toluene sulfonic acid,

and 3.5 g of the thioglycolic acid were put thereinto, and theywere reacted

with each other for 4 hours while they were refluxed. After the reaction

was finished, they were dropped to methanol and precipitated.

Subsequently, toluene was added to the precipitate, and heated to remove

methanol in the polymer as the azeotrope. Through this process, the first

acryl based resin [E'] polymer solution including SH could be obtained.

3) Graft polymerization

32gof the modified first acryl based resin[E' ] solution (TSC 40%)

that was obtained in the step 2), 79.17 g of MMA, 4.17 g of MA, and 0.26

g of AIBN were put into the polymerization device that had the volume of

25OmL, and they were reacted with each other for 12 hours while maintaining

at 70°C . After the reaction was finished, the polymerization solution

was precipitated in methanol to obtain the graft copolymer 13.

2. Blending of the SAN resin and the graft copolymer

100 g of the graft copolymer 5 and 300 g of SAN (LG Chemicals

(trademark: SAN80HF)) were uniformly mixed with each other and pushed by

using a single screw extruder to produce a pellet in which two resins were

mixed with each other.

Example 6 - Blending of the styrene based resin (SAN resin) and

the graft copolymer

1. Production of the graft copolymer

1) Production of the first acryl based resin [F]

70 g of butyl acrylate, 3 g of 2-hydroxybutyl acrylate, 27 g of

styrene, 30 g of toluene and 0.3 g of the initiator AIBN, and 0.1 g of

1-octylmercaptane were dropped at 70°C to the reactor that had the volume

of 250 ml for 4 hours, and additionally polymerized for 3 hours at 95°C

to produce the polymer. The unreacted monomer in the solution was

measured by using the gas chromatography, and it was confirmed that the

conversion ratio was 98% (molecular weight: Mw = 170k, Mn = 62k).

2) Introduction of the functional group that was capable of being

reacted with the radical , to the main chain of the first acryl based resin

200 g of toluene was additionally put into 200 g of the first acryl

based resin [F] solution that was produced in (1), 1 g of the p-toluene

sulfonic acid, and 6 g of the thioglycolic acid were put thereinto, and

they were reacted with each other for 4 hours while they were refluxed.

After the reaction was finished, they were dropped to methanol and

precipitated. Subsequently, toluene was added to the precipitate, and

heated to remove methanol in the polymer as the azeotrope. Through this

process, the first acryl based resin [F'] polymer solution including SH

could be obtained.

3) Graft polymerization

32 g of the modified first acryl based resin [F'] solution (TSC

40%), 79.17 g of MMA, 4.17 g of MA, and 0.26 g of AIBN were put into the

polymerization device that had the volume of 250 mL, and they were reacted

with each other for 12 hours while maintaining at 70°C under the nitrogen

atmosphere. After the reaction was finished, the polymerization solution

was precipitated in hexane to obtain the graft copolymer 14.

2. Blending of the SAN resin and the graft copolymer

100 g of the graft copolymer 14 and 300 g of SAN (LG Chemicals

(trademark: SAN80HF)) were uniformly mixed with each other and pushed by

using a single screw extruder to produce a pel let in which two resins were

mixed with each other.

Example 7 - Blending of the styrene based resin (SAN resin) and

the graft copolymer

1. Blending of the SAN resin and the graft copolymer

210 g of the graft copolymer 14 that was produced in Example 6 and

90 g of SAN were uniformly mixed with each other and pushed by using a

single screw extruder to produce a pellet in which two resins were mixed

with each other.

Example 8 - Blending of the styrene based resin (SAN resin) and

the graft copolymer

1. Blending of the SAN resin and the graft copolymer

210 g of the graft copolymer 13 that was produced in Example 5 and

90 g of SAN (LG Chemicals (trademark: SAN80HF)) were uniformly mixed with

each other and pushed by using a single screw extruder to produce a pel let

in which two resins were mixed with each other.

Example 9 - Blending of the styrene based resin (SAN resin) and

the graft copolymer

1. Production of the graft copolymer

1) Production of the first acryl based resin [G]

77 g of butyl acrylate, 3 g of 2-hydroxybutyl acrylate, 20 g of

styrene, 30 g of toluene and 0.3 g of the initiator AIBN, and 0.08 g of

1-octylmercaptane were dropped at 70°C to the reactor that had the volume

of 250 ml for 4 hours, and additionally polymerized for 3 hours at 95°C

to produce the polymer. The unreacted monomer in the solution was

measured by using the gas chromatography, and it was confirmed that the

conversion ratio was 98% (molecular weight: Mw = 190k, Mn = 90k).

2) Introduction of the functional group that was capable of being

reacted with the radical , to the main chain of the first acryl based resin

400 g of toluene was additionally put into 200 g of the first acryl

based resin [G] solution, 1 g of the p-toluene sulfonic acid, and 6 g of

the thioglycolic acid were put thereinto, and they were reacted with each

other for 4 hours while they were refluxed. After the reaction was

finished, they were dropped to methanol and precipitated. Subsequently,

toluene was added to the precipitate, and heated to remove methanol in

the polymer as the azeotrope. Through this process, the first acryl based

resin [G'] polymer solution including SH could be obtained.

3) Graft polymerization

40 g of the modified first acryl based resin [G'] solution (TSC

33%), 79.17 g of MMA, 4.17 g of MA, and 0.26 g of AIBN were put into the

polymerization device that had the volume of 250 raL, and they were reacted

with each other for 12 hours while maintaining at 70 ^° C under the nitrogen

atmosphere. After the reaction was finished, the polymerization solution

was precipitated in hexane to obtain the graft copolymer 15.

2. Blending of the SAN resin and the graft copolymer

100 g of the graft copolymer 15 and 300 g of SAN (LG Chemicals

(trademark: SAN80HF)) were uniformly mixed with each other and pushed by

using a single screw extruder to produce a pellet in which two resins were

mixed with each other.

Example 10 - Blending of the styrene based resin (SAN resin) and

the graft copolymer

1. Blending of the SAN resin and the graft copolymer

200 g of the graft copolymer 15 that was produced in Example 9 and

100 g of SAN (LG Chemicals (trademark: SAN80HF)) were uniformly mixed with

each other and pushed by using a single screw extruder to produce a pellet

in which two resins were mixed with each other.

Example 11 - Blending of the styrene based resin (SAN resin) and

the graft copolymer

1. Production of the graft copolymer

1) Production of the first acryl based resin [H]

77 g of butyl acrylate, 3 g of 2-hydroxybutyl acrylate, 20 g of

styrene, 30 g of toluene and 0.3 g of the initiator AIBN, and 0.08 g of

1-octylmercaptane were dropped at 70"C to the reactor that had the volume

of 250 ml for 4 hours, and additionally polymerized for 3 hours at 95°C

to produce the polymer. The unreacted monomer in the solution was

measured by using the gas chromatography, and it was confirmed that the

conversion ratio was 98% (molecular weight: Mw = 190k, Mn = 90k).

2) Introduction of the functional group that was capable of being

reacted with the radical , to the main chain of the first acryl based resin

400 g of toluene was additionally put into 200 g of the first acryl

based resin [H] solution, 1 g of the p-toluene sulfonic acid, and 6 g of

the thioglycolic acid were put thereinto, and they were reacted with each

other for 4 hours with refluxing. After the reaction was finished, they

were dropped to methanol and precipitated. Subsequently, toluene was

added to the precipitate, and heated to remove methanol in the polymer

as the azeotrope. Through this process, the first acryl based resin [H']

polymer solution including SH could be obtained.

3) Graft polymerization

40 g of the modified first acryl based resin [H'] solution (TSC

33%), 75.17 g of MMA, 4.17 g of MA, 4 g of CHMI, and 0.26 g of AIBN were

put into the polymerization device that had the volume of 250 mL, and they

were reacted with each other for 12 hours while maintaining at 70°C under

the nitrogen atmosphere. After the reaction was finished, the

polymerization solution was precipitated in hexane to obtain the graft

copolymer 16.

2. Blending of the SAN resin and the graft copolymer

100 g of the graft copolymer 16 and 300 g of SAN (LG Chemicals

(trademark: SAN80HF)) were uniformly mixed with each other and pushed by

using a single screw extruder to produce a pellet in which two resins were

mixed with each other.

Example 12 - Blending of the styrene based resin (SAN resin) and

the graft copolymer

1. Blending of the SAN resin and the graft copolymer

200 g of the graft copolymer 16 that was produced in Example 11

and 100 g of SAN (LG Chemicals (trademark: SAN80HF)) were uniformly mixed

with each other and pushed by using a single screw extruder to produce

a pellet in which two resins were mixed with each other.

Production of the film and stretching>

10 g of the blended pellet was processed by using the hot press

to produce the film having the thickness in the range of 100 μm

(micrometers) to 132 μm (micrometers) under the conditions of 240 ^° C and

150 bar. This film was stretched under the following conditions to

produce the retardation film. The stretching conditions and the

retardation values of the produced films are described in the following

Table 9.

[Table 9]

[Industrial Applicability]

The optical film and the retardation film according to the present

invention includes the graft copolymer that includes two or more types

of (meth)acryl based resins in which the glass transition temperatures

are different from each other. Since the mechanical properties and the

optical properties are excellent, the film according to the present

invention can be usefully used for various puroposes, in particular, can

be usefully used as the protection film of the polarizing plate. Since

the mechanical properties, the resistance to heat, and the optical

properties are excellent, it is useful to simply produce a liquid crystal

display device in which a performance is excellent at low cost.