Background to the Invention In electrophotography or electrostatic printing, an image is formed on a receiver medium by depositing onto a surface of the medium, in a suitable pattern, particulate toner, which consists of a dispersion of pigment in polymer, and fusing the toner into the surface to form an image. Such processes are generally carried out in an electrophotographic or electrostatic printer or copier. To produce a monochrome image, typically black and white, a single toner, typically black, is used. To produce a full colour image, a series of colour toners, cyan (C), magenta (M), yellow (Y) and black (K), are used.

Electrophotographic or electrostatic processes are used for forming images in this way on sheets of transparent receiver media for use in OHPs in which light is passed through the receiver sheet to project an image.

For black and white overhead projection purposes, OHP receiver sheets are usually in the form of a base film or substrate of polyester such as biaxially orientated poly (ethylene terephthalate) (PET) typically about 100, um thick (e. g. Melinex (Melinex is a Trade Mark) from ICI/DuPont) with a coating on the surface to promote adhesion of the toner to the base film. The coating is typically of an acrylic polymer and is either applied during the manufacture of the PET film or is coated off-line, i. e. as a separate step. The coating usually also contains filler to improve the handling properties and some antistatic agent (sometimes applied as an extra coating known as a supercoat). Such materials work well with black and white OHP images, where the aim of the toner is simply to block out projected light and hence project a dark area. Different considerations apply, however, in projecting colour images on an OHP. In this case light must be transmitted through a coloured block and accurately transmit the correct spectrum of light onto a screen. This must be achieved with minimum loss due to light scatter. It is therefore necessary for the coloured block on the film to be as transparent as possible. If the toner particles do not fuse adequately into the receiver sheet surface but instead stick to the surface and remain proud of the surface, there will be a haze in the film and scattering of the light at the surface of the film. This will cause the projected image on the screen to look dull and rather grey.

One convenient measure of the print quality of images on transparent media is the haze of the image. Haze is defined (British Standard 2782 Part 5) as the percentage of transmitted light that is deflected more than 2.5° (degrees) from the direction of the incoming beam.

For transparencies, the most noticeable effects caused by light scattering are in yellow portions of an image, which when projected, appear grey or brown on screen at high haze levels. Therefore measurements of the haze of yellow printed blocks are the best measure of print quality.

If conventional black and white OHP receiver sheets are used for colour OHP images, poor results are obtained. The present invention aims to provide a novel receiver medium, with particular application in the form of a transparent medium better suited for production of colour images for use in OHPs, but also more generally applicable without limitation to transparent media.

Summary of the Invention According to the present invention there is provided a receiver medium adapted to receive a colour toner image by an electrophotographic or electrostatic process, the receiver medium comprising a toner acceptance layer including a polymer or mixture of polymers in which the molecular weight (MW) is less than about 7,000 and the glass transition temperature (Tg) is greater than about 50°C, with MW and Tg being selected to satisfy equation (1) below: 0.0003 MW x e°°4Tg<20 (equation (1)) In equation (1), the value on the expression on the left hand side is preferably < 10, more preferably < 1. The significance of this equation will be discussed below.

The molecular weight of the polymer or mixture of polymers is preferably less than about 3,000, more preferably about 1,500 or less, with a value of about 500 representing a practical lower limit for providing a coherent coating of adequate mechanical strength.

The glass transition temperature of the polymer or mixture of polymers is preferably greater than about 60°C. However, for good print quality, the Tg should also be such that the toner acceptance layer is sufficiently soft at the surface temperature of the fuser within a copier or printer with which the receiver medium is to be used, so the Tg should not be too high. The Tg should preferably be less than this fuser surface temperature, which is typically between 150°C and 200°C.

For good adhesion between toner and the toner acceptance layer, the polymer or mixture of polymers should be selected to have a solubility parameter (SP) comparable to that of the toner (s) with which it is intended for use. The solubility parameter is a measure of the magnitude of the forces holding molecules together. It is derived from the latent heat of vaporisation minus the mechanical work done on vaporisation. This is divided by the molar volume to give what is known as the cohesive energy density. The solubility parameter is expressed as the square root of this value. It is well known that materials with similar solubility parameters tend to be compatible and that large differences in solubility parameter lead to poor compatibility. The higher the molecular weight of the toner, the less is the tolerance of differences between the SP values of the toner and of the polymer or mixture of polymers.

For compatibility with polyester-based toners currently in use commercially, the polymer or mixture of polymers preferably has a solubility parameter in the range 18 to 28 JAcm3'2, more preferably in the range 20 to 25 J'2cm3'2, most preferably in the range 21 to 22 Jl'^cm3'2.

Where a mixture of polymers is used, values for molecular weight, glass transition temperature and solubility parameter of the mixture are calculated as a simple mathematical average based on the percentages by weight of different components in the mixture. For example, for a mixture of a% by weight of material A with a Tg of Ta with b% by weight of material B of Tg Tb, where a + b = 100%, then the average Tg is taken as aTa + bTb 100 Average MWs and SPs are calculated similarly.

The present invention is based on extensive experiments using transparent receiver media, with which it is harder to produce good quality prints than with opaque media. It has been found that it is possible to achieve good print performance, measured in terms of yellow haze values, using a polymer (or mixture of polymers) with a comparatively high Tg provided the MW is relatively low and equation (1) is satisfied. The Tg can be chosen to be sufficiently high so the toner acceptance layer is unlikely to soften or melt (with consequent risk of sticking) under normal conditions of storage and use, providing a robust receiver medium that is resistant to environmental changes, while still giving good print performance.

For typical toners currently in use commercially, equation (1) can be translated into values of % yellow haze (Y,. 1) of prints on the medium. The value of YH is approximately equal to the value of the expression on the left hand side of equation (1) + 10. Thus, where this expression is < 20, YH < 30 % ; where this expression is < 10, YH < 20% ; and where this expression is <1, YH<11%. A yellow haze value of 30% represents an acceptable maximum value for reasonable print quality, with lower values of YH indicating better print quality and so being preferred.

The findings of the invention are equally applicable to opaque receiver media, which are less sensitive to print quality than are transparent media. Opaque receiver media in accordance with the invention demonstrate good print quality in terms of brightness of colour and gloss.

Good results have been obtained using mixtures of polymers, particularly mixtures including one or more ketone aldehyde resins and derivatives, and/or one or more solid epoxy resins, and/or one or more saturated linear polyesters. Suitable ketone aldehyde resins and derivatives include those known as Synthetic Resin AP, TC, CA, SK and 1201 made by Huls and supplied by Allchem (Synthetic Resin AP etc are Trade Marks). The resin designated AP is an acetophenone formaldehyde resin, with SK being a hydrogenated version, CA being a cyclohexanone formaldehyde resin and 1201 being a urethane modified species. The TC resin is simply described as a ketone resin. Suitable solid epoxy resins include various bis-phenol A epi-chlorhydrin resins known as Epikote 1001, 1002,1004,1007 and 1009 made by Shell and supplied by Freeman Distribution (Epikote 1001 etc are Trade Marks). Suitable saturated linear polyesters include those known as Dynapol 850, 411 and 206 made by Huls and supplied by Allchem (Dynapol 850 etc are Trade Marks).

Mixtures including Synthetic Resin CA or Synthetic Resin AP are currently favoured.

Such mixtures preferably also include an Epikote solid epoxy resin, preferably Epikote 1009, and/or a Dynapol saturated linear polyester, preferably Dynapol 411.

The toner acceptance layer of receiver media in accordance with the invention can have adequate surface resistivity to prevent spurious images in use, desirably being around 10'0 oluns/square.

The toner acceptance layer desirably also includes a minor amount of particulate filler material, typically constituting an amount in the range 0.01 to 2% by weight of the weight of the toner acceptance layer. Inclusion of filler material gives the sheet a degree of surface roughness and prevents the surface of the sheet from being so smooth that it adheres to other smooth surfaces such as another similar sheet or a fuser roller. This also ensures reliable feed in a wide range of copiers and printers. The particulate filler material conveniently has a particle size in the range 1 to 301lm, preferably 1 to 10am, and may be of materials such as silica, particularly porous silica, polyethylene, or resin such as urea- formaldehyde resin. Good results have been obtained using, as filler materials, Tospearl 2000 polysiloxane spheres from Toshiba (Tospearl 2000 is a Trade Mark). Other possible filler materials include Syloid 244 (Syloid 244 is a Trade Mark) from Grace, which is a high porosity synthetic silica milled to a particle size of about 2um, Pergopak M3 (Pergopak M3 is a Trade Mark) from Omya Croxton and Garry, which is a milled urea- formaldehyde resin material with a particle size of about 3, um, Micro Pro 123 polyethylene powder filler (MicroPro 123 is a Trade Mark) from Micro Powders Inc./Kromachem, and Aerosil R972 (Aerosil R972 is a Trade Mark) from Degussa, which is a fumed silica.

Mixtures of filler materials may be used.

The toner acceptance layer desirably includes one or more anti-static materials with the aim of avoiding the need to use a supercoat. Suitable anti-static materials include one or more of lithium hydroxide and toluenesulphonic acid. Lithium ions provide both humectant properties and ionic conductivity. Diethylene glycol may also be included to assist these functions. Other anti-static materials include quaternised acrylates, nonyl phenol ethoxylate, sodium alkyl sulphonate and stearamide propyl methyl (3-hydroxy ethyl ammonium di-hydrogen phosphate. Suitable proprietary anti-static materials include Alcostat 1586, which is alkylarylpolyoxyethylene ammonium chloride, from Ciba Specialities (Alcostat 1586 is a Trade Mark), Cyastat SP35, which is stearamide propyl methyl p-hydroxy ethyl ammonium di-hydrogen phosphate, from Ciba Geigy (Cyastat SP35 is a Trade Mark), Aliquat 334, which comprises tricapry methyl ammonium chloride, from Cognis, Ireland (Aliquat 334 is a Trade Mark) and Atmer 190, which is a sodium salt of an alkyl sulphonic acid, from ICI Speciality Chemicals (Atmer 190 is a Trade Mark).

Flow agents such as silicones or acrylic ester polymers may optionally be included, particularly in conjunction with anti-static materials, to improve performance.

A supercoat may be provided in known manner on the toner acceptance layer if appropriate, e. g. to modify the surface resistivity.

The receiver medium typically comprises a substrate having a toner-receiving surface bearing a coating comprising the toner acceptance layer.

The substrate is typically in the form of a film or sheet of suitable material.

For transparent receiver media, e. g. for use with OHPs, the substrate should, of course, be transparent and usually comprises plastics material. In this case, the substrate is conveniently made of polyester, e. g. poly (ethyleneterephthalate) (PET) such as Melinex or poly (ethylenenaphthalate) (PEN). The substrate may alternatively be of polycarbonate.

A transparent receiver sheet will typically include one or more opaque portions for location by a photoelectric detector of a printer to facilitate correct feeding of the sheet, in known manner. Such an opaque portion may be produced by a pigmented or scattering stripe along one or more edges. Alternatively a strip of plain paper may be temporarily laminated behind the receiver sheet.

For opaque receiver media, the substrate can comprise a wide range of materials including paper, card, plastics film e. g. white polymer film, aluminised film, laminated materials etc. For transparent receiver media, the substrate typically has a thickness in the range 50 to 1501lu, e. g. about 100Am. For opaque receiver media, the substrate may be of similar, smaller or greater thickness.

The substrate may be pre-treated with an adhesion-promoting priming layer, e. g. of parachlorometacresol (PCMC), prior to application of the toner acceptance layer.

The toner acceptance layer ingredients are usually dissolved in a suitable solvent or solvent system (mixture of solvents) which can be any solvent or mixture of solvents that dissolve the materials and that is compatible with the other materials involved and coating technique used.

Suitable solvents include one or more of methanol, propanol, n-butanol, methyl ethyl ketone (MEK), acetone, toluene and water. A suitable solvent system for the preferred polymer mixtures mentioned above is a mixture of acetone and methyl ethyl ketone, e. g. as a 60/40 mixture by weight. Where water is used as the major solvent, it is desirable for the polymer materials to be in the form of a dispersion or latex.

The receiver medium may be produced by coating, e. g. by a roller coating technique, a solution of the toner acceptance layer ingredients dissolved in a suitable solvent system, e. g. acetone/methyl ethyl ketone, onto a substrate possibly pre-treated with an adhesion- promoting priming layer, e. g. of PCMC, followed by drying to produce the toner acceptance layer. A supercoat may be optionally provided on the toner acceptance layer.

For a transparent substrate, an opaque location portion may be included along one or more edges In a further aspect the invention thus provides a method of manufacturing a receiver medium adapted to receive a colour toner image by an electrophotographic or electrostatic process, comprising providing on a substrate a toner acceptance layer that includes a polymer or mixture of polymers in which the molecular weight (MW) is less than about 7,000 and the glass transition temperature (Tg) is greater than about 50°C, with MW and Tg being selected to satisfy equation (1) below: 0.0003 MW x e004Tg<20 (eguation (1)) The receiver medium may be used in conventional manner to receive a colour image e. g. for use in an OHP. This generally involves transferring colour toner particles to the toner acceptance layer, e. g. using a colour xerographic copier or printer in a process that typically involves passing the receiver medium through heated rollers to fuse the toner particles to each other and to ensure firm attachment to the receiver medium. Silicone oil is typically used as a lubricant to ensure that the toner particles do not adhere to the heated rollers.

In another aspect the invention thus provides a method of producing a receiver medium bearing a colour image, e. g. for projection by an overhead projector, comprising forming a colour toner image on a receiver medium in accordance with the invention.

The invention will be further described, by way of illustration, in the following Examples and with reference to the accompanying drawings, in which: Figure 1 is a graph of yellow haze (%) versus MW x e0.04Tg for a range of polymers and polymer mixtures; and Figure 2 is a graph of Tg (°C) versus molecular weight showing polymers exhibiting 20% and 30% yellow haze.

Example 1 A series of experimental receiver sheets were prepared, comprising transparent substrate coated with various polymers and polymer mixtures. A 20% solution of the polymer or polymer mixture was prepared in a 60/40 (by weight) mixture of acetone and methyl ethyl ketone. Each solution was coated onto a Melinex substrate (which is a transparent biaxially oriented polyethylene terephthalate film, 96pm thick, from DuPont) by means of a No 3 Meier bar to give a wet coating 24pLm thick. The sheets were dried in an oven at 100°C for 2 minutes. The resulting dry coat thickness was 3-4pm.

Test prints were made on the resulting receiver sheets, and also for comparison on a commercially available transparent receiver sheet with a toner acceptance layer comprising Diakon MG102, a polymethyl methacrylate (PMMA) resin from ICI Acrylics (Diakon MG102 is a Trade Mark). Prints were made using a Canon CLC800 colour copier using colour toner supplied for that copier. This particular copier was used because it is known to be a demanding copier that tends to give prints with high haze values. Yellow haze of the resulting prints was measured (in accordance with British Standard 2782 Part 5) using an XL211 Hazemeter (Gardner Neotech Instrument Division, USA). The results are shown in Table 1.

Table 1 Properties of Single Polymers and Mixtures Material % Material MW Tg (°C) J'Acm3'2 Yell. Haze (by wt) Sol. Par. (%) Epikote 1001 (1001) 100 1200 32 22. 03 11. 4 Synthetic Resin AP (AP) 100 1200 50 24. 7 14. 7 Epikote 1002 (1002) 100 1140 40 22. 03 15. 2 Epikote 1004 (1004) too 1480 49 22. 03 16. 4 Vinylite VYES*100'550053'23. 120. 7 Epikote 1007 (1007) 100 2900 67 22. 03 20. 9 Synthetic Resin CA 100 1300 75 23.25 20. 9 (CA) Synthetic Resin SK (SK) 100 1500 90 27. 16 28. 2 Dynapol 850 (D850) 100 15000 40 21. 8 33. 6 Dynapol 411 (D411) 100 16000 47 21.86 38. 9 Dynapol 206 (D206) 100 15000 67 24. 0 52. 8 Vinylite VROH* 100 8000 65 21.18 43.3 Diakon MG 102 100 60000 122 20. 32 45. 0 Vinylite VAGC* 100 15000 65 21. 18 59. 8 Ketjenflex MH* 100 580 36 22. 45 CA/1001 50 : 50 1250 53. 5 22. 64 10. 6 CA/1001 75 : 25 1275 64. 2 22. 94 12. 4 CA/1004 50 : 50 1390 62 22. 64 12. 6 SK/1002 50 : 50 1320 65 24. 6 13. 9 SK/1004 50 : 50 1490 69. 5 24. 6 14. 6 D411/ Ketjenflex MH 40 : 60 6748 41. 5 22. 19 16. 6 D850/1002 60 : 40 10006 40 21. 9 18. 9 CA/1007 50 : 50 2100 71 22. 64 19. 2 D411/1004 45 : 55 8014 48. 1 21. 9 19. 3 SK/1007 50 : 50 2200 78 24. 6 22. 4 D850/1002 73 : 27 12000 40 21. 86 25. 3 D206/1007 18 : 82 5000 67 22. 38 27. 3 D411/1004 59 : 41 10046 47. 8 21. 89 30. 4 D850/1002 90 : 10 14515 40 21. 82 38. 4 D206/1007 26 : 74 6046 67 22. 54 38. 9 SK/1009 50 : 50 2625 85. 0 24. 96 18. 7 L411/AP 20 : 80 3960 49. 4 24. 13 17. 5 *Vinylite VYES, VROH and VAGC are all vinyl chloride/vinyl acetate polymers from Union Carbide (Vinylite VYES etc are Trade Marks).

Ketjenflex MH is a toluene sulphonamide formaldehyde resin from Akzo (Ketjenflex is a Trade Mark). Ketjenflex MH is difficult to print due to its low Tg and softening point, so no yellow haze value was determined.

The results show that the printed yellow haze is related to the molecular weight and Tg of the coated polymer or polymer mixture. It was found that the function of molecular weight and Tg that best fitted the data, with a standard deviation of 0.92, was equation (2) below: Yen a MW x e°. oaTg (equation (2)) This function was plotted against yellow haze for the experimental data obtained, and the resulting graph is shown as Figure 1.

By measuring the slope and intercept of the graph of Figure 1, equation (3) below, relating yellow haze to molecular weight and Tg was derived.

YH = 0.0003 MW x e° + 10.4 (equation (3)) where == yellow haze, MW = molecular weight of a polymer or average molecular weight of a polymer mixture (calculated as described above), and Tg = glass transition temperature of a polymer or average glass transition temperature of a polymer mixture (calculated as described above).

Equation (3) thus allows an appropriate molecular weight for a polymer or mixture of polymers to be calculated to provide a chosen level of yellow haze (say 20%) using a material of particular desired Tg. Rearranging equation (3): <BR> <BR> YH10 4<BR> MW = (equation (4))<BR> 0.0003 x e0.04Tg This allows a definition to be shown graphically of what polymers will give acceptable print performance in colour laser printers and copiers. The example below applies to copiers that operate at the bottom end of the fuser temperature range, this being the most critical as far as print performance is concerned. The graph shown in Figure 2 is drawn from data calculated from equation (4) and shows the coating polymers properties within which an acceptable yellow haze is obtained.

If the preferred limits of Tg and MW are chosen, an area bounded by the curve generated by equation (4) defines all the polymers or mixtures thereof which give a yellow printed haze of less than or equal to 30%. Polymers that are close to the diagonal edge or that have solubility parameters (SP) at either extreme will tend to 30% haze.

Equation (3) also allows the printed yellow haze for any given polymer or polymer mixture to be predicted. Also, if desirable limits for molecular weight, glass transition temperature and solubility parameter are chosen a three dimensional wedge shaped space can be defined within which the polymer or mixture of polymers will give an acceptable printed yellow haze performance.

Equation (1) is derived from equation (3). Rearranging equation (3): YH-10. 4 = 0.0003 MW x e'-04Tg (equation (5)) As noted above, a YH value of 30% represents an acceptable maximum value for reasonable print quality on a transparent receiver medium. Substituting Yn<30 in equation (5) gives equation (1), thus defining the relationship between MW and Tg to give aYHOf <30% Example 2 In order to make fully functional transparency films, it is known to be necessary to control the surface resistivity of the material, desirably to be around 101° ohms/square, to prevent spurious images, and also to provide for good toner adhesion without sticking to the fuser roller. A number of test formulations were made up, coated, printed and tested as described previously in Example 1, although it was often necessary to add a small amount of methanol to the solution in order to bring the antistatic agent into solution. Further tests on prints were conducted as follows: The surface resistivity (SR) was measured by means of a Milli-to 2 resistivity meter (Dr Thiedig & Co, Germany) (Milli-to 2 is a Trade Mark).

Toner adhesion was measured by folding the printed blocks, flattening the fold and rubbing the line of the fold with tissue. The width of removed material was then recorded. A value of 0. 5mm or less was acceptable, with a value of Omm being preferred. Feeding OK means that single sheets did not jam in the Canon CLC800 printer. Static pattern refers to artefacts that appear in the image if spurious charges are generated by transport through the printer or other handling and indicate that the surface resistivity is too high. These generally appear as holes in the toner where the applied charge has been nullified by a previously induced charge.

Results are given in Tables 2 and 3 below, which set out the amount (in grams) of materials used in various test formulations and results obtained. Molecular weight, Tg and solubility parameter data for the various mixtures are given in Table 1.

Table 2 Materials 069 070 071 073 074 075 076 Synthetic Resin SK 20 10 Synthetic Resin CA 20 15 15 10 Synthetic Resin AP 20 Epikote 1002 10 Epikote 1001 5 10 Surcol SP6* 10 Alcostat 1586 3 3 3 Cyastat SP35 5. 7 5. 7 5. 7 5. 7 5. 7 5. 7 5. 7 Tospearl 2000 0.04 0.04 0.04 0.04 0.4 0.4 0. 04 Propanol 10 10 Acetone 30 30 50 MEK 10 10 10 Methanol 80 80 80 75 40 40 20 Y haze % 27. 1 20. 35 14. 6 44.3 (poor) 12. 4 10. 6 13. 9 Feed ok ok ok ok ok ok ok S.R. 2x1011 1x1013 2.5x1010 1x1012 1.5x1010 1.6x1010 >1014 Toner Adhes. poor lmm poor 1mm poor 3mm poor lmm poor lmm 0. 5mm 0. 5mm Coat thick (llm) 3. 5 3. 5 3. 5 3. 5 3. 5 3. 5 3. 5 Static pattern yes yes yes yes no no no *Surcol SP6 is a quaternised acrylic resin from Ciba Specialities (Surcol SP6 is a Trade Mark). This material functions both as a coating polymer and as an anti-static material, as it has a moderate Tg and is a cationic quaternised polymer. However, the high yellow haze value indicates that this material has a high molecular weight, and so needs to be combined with one or more other polymers of low molecular weight and low Tg to give acceptable yellow haze results, which is impractical.

Table 3 Materials 077 078 079 080 081 091 Dynapol 411 4 Synthethic Resin SK 10 10 10 Synthetic Resin CA 10 10 Synthetic Resin AP 16 Epikote 1002 Epikote 1007 10 10 Epikote 1004 10 10 Epikote 1009 10 Aliquat 334 3 3 Atmer 190* 0. 88 Cyastat SP35 5. 7 5. 7 5. 7 Tospearl 2000 0. 04 0. 04 0. 04 0. 04 0. 04 Micro Pro 123 0. 07 Aerosil R972 0. 008 Acetone 50 50 50 50 50 48 MEK 10 10 30 10 30 32 Methanol 20 20 20 Y haze (%) 22. 4 19. 2 14. 6 12. 6 18. 7 17. 5 Feed ok ok ok ok ok ok S. R. 2*0x10l° 1. 5x10l3 9.7x10 lxl0l4 9.7x10"5. 3x10" Toner Adhes. 0.5mm 0.5mm 0.5nun 0.5mm 0.5mm 0 mm Coat thick (lem) 3. 5 3. 5 3. 5 3. 5 3. 5 3. 5 Static pattern no yes no yes no no *Atmer 190 is used as a 20% solution in toluene/butanol.

Example 3 A currently preferred formulation is that identified above as 081. This formulation was made by placing the solvents, 30g of MEK and 50g of acetone, in a container with a magnetic follower and stirring by means of a magnetic stirrer. The Epikote 1009 (lOg) and the Synthetic Resin SK (lOg) were then added and the mixture was stirred until dissolved. The antistat Aliquat 334 was added and stirred until dissolved. Finally the filler Tospearl T2000 (0.04g) was added and this was stirred until thoroughly dispersed.

Coating on Melinex film was carried out as described in Example 1.

Example 4 Another currently preferred formulation is that identified above as 091. This was made up in the same way as before by placing the solvents, 32g MEK and 48g of acetone, in a container with a magnetic follower. This was then placed on a magnetic stirrer and the 4g of Dynapol 411 and the 16g of Synthetic Resin AP were added whilst stirring. When this was dissolved 0.88g of the 20% Atmer 190 solution was added along with the 0.07g of Micro Pro 123 and the 0.007g of Aerosil R972 and these were stirred until dispersed.

Coating on Melinex film was carried out as described in Example 1.