JP2007055217A - Easy-to-adhere polyester film for optical use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an easy-to-adhere polyester film for optical use which has a UV light transmittance high enough to be favorably used for a prism lens sheet of a liquid crystal display and exhibits an excellent adhesion to a prism lens layer, when proccessd into the prism lens sheet. <P>SOLUTION: The easy-to-adhere polyester film for optical use comprises a polyester film and coated layers on both the sides of the film and has a light transmittance of ≥88% for a 400 nm wavelength light. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optically easily adhesive polyester film, and more particularly to an optically easily adhesive polyester film that is suitably used as a prism lens sheet member of a liquid crystal display.

  Polyester films, especially biaxially stretched films of polyethylene terephthalate and polyethylene naphthalate, have excellent mechanical properties, heat resistance, and chemical resistance. Therefore, magnetic tape, ferromagnetic thin film tape, photographic film, packaging film, electronic parts It is widely used as a material such as a film for electric use, an electrical insulating film, a film for laminating a metal plate, a film to be pasted on the surface of a glass display, and a protective film for various members.

In recent years, polyester films are often used in various optical films, such as prism lens sheets for liquid crystal display members, touch panels, base films such as backlights, base films for antireflection films, electromagnetic wave shielding films for plasma displays, It is used for applications such as base films for organic EL displays and base films for explosion-proof displays. The base film used for such an optical film is required to have excellent transparency. Furthermore, excellent easy adhesion to a prism lens layer, a hard coat layer, an adhesive layer, an antireflection layer, a sputter layer and the like is required.
JP-A-63-37167

  In particular, in order to use it as a prism lens sheet member for a liquid crystal display, a high UV light transmittance is required in processing for forming a prism lens layer. However, UV light is shielded from the inherent light absorption characteristics of polyester, and it is difficult to obtain high transmittance.

  The present invention eliminates the problems of the prior art and can be suitably used for a prism lens sheet for a liquid crystal display. The prism lens layer has a high UV light transmittance and is processed into a prism lens sheet. It aims at providing the easily adhesive polyester film for optics which is excellent in adhesive force.

  That is, the present invention is an optically easy-adhesive polyester film comprising a polyester film and a coating layer provided on both sides thereof, and having a light transmittance of 88% or more at a wavelength of 400 nm.

  According to the present invention, it is possible to provide an easily adhesive polyester film for optical use that has a high UV light transmittance and is excellent in adhesive strength with a prism lens layer when processed into a prism lens sheet.

Hereinafter, the present invention will be described in detail.
[Polyester film]
In the present invention, the polyester constituting the polyester film is a linear saturated polyester synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof. Specific examples of such polyester include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), and polyethylene-2,6-naphthalate.

The polyester used for the polyester film may be a copolymer of these polyesters. The polyester is mainly used (for example, a component of 80 mol% or more), and a small proportion (for example, a component of 20 mol% or less) is used. It may be blended with a kind of resin. As the polyester, polyethylene terephthalate or polyethylene-2,6-naphthalate is particularly preferable because of a good balance between mechanical properties and optical properties.
The polyester may contain a colorant, an antistatic agent, an antioxidant, an organic lubricant, a catalyst, and an ultraviolet absorber. However, in the present invention, the polyester preferably contains no internal filler from the viewpoint of transparency.

The polyester film in the present invention is obtained by, for example, melt-extruding the above polyester into a film shape, cooling and solidifying with a casting drum to form an unstretched film, and this unstretched film is once or twice in the longitudinal direction at Tg to (Tg + 60) ° C. The total magnification is stretched so as to be 3 to 6 times, and then stretched so that the magnification is 3 to 5 times in the width direction at Tg to (Tg + 60) ° C., and further at 180 to 230 ° C. as necessary. It can be obtained by performing heat treatment for 1 to 60 seconds and performing reheat treatment while shrinking 0 to 20% in the width direction at a temperature lower by 10 to 20 ° C. than the heat treatment temperature. The glass transition temperature is abbreviated as Tg.
The thickness of the polyester film is preferably 25 to 300 [mu] m, particularly 50 to 250 [mu] m, in order to obtain the required strength when used as a prism lens sheet.

[Coating layer]
The easy-adhesive polyester film for optics of the present invention comprises coating layers on both sides of the above polyester film. The refractive index of this coating layer is preferably 1.20 to 1.55, more preferably 1.30 to 1.55. When the refractive index of the coating layer exceeds 1.55, the transmittance of UV light does not increase. On the other hand, it is technically difficult to make it less than 1.20.
The thickness of the coating layer is preferably 40 to 100 nm, more preferably 50 to 90 nm. When the coating thickness exceeds 100 nm, blocking tends to occur, which is not preferable. When the coating thickness is less than 40 nm, the UV light transmittance is not increased, which is not preferable.

  The optically easily adhesive polyester film of the present invention can achieve a light transmittance of 88% or more at a wavelength of 400 nm by providing a coating layer having a refractive index of 1.20 to 1.55 on both sides of the polyester film. If the light transmittance at a wavelength of 400 nm is less than 88%, it is difficult to process into a prism sheet. This optically easily adhesive polyester film can be obtained by forming a coating layer on both sides of the polyester.

[acrylic resin]
In order to make the refractive index within the range of the present invention, the coating layer provided on both sides of the polyester film is preferably made of an acrylic resin, and the glass transition point (Tg) of this acrylic resin is preferably 20 to 80 ° C., more preferably. Is 25-70 ° C. When the glass transition point is less than 20 ° C., the film blocking property is deteriorated, and when the glass transition point is higher than 80 ° C., the film forming property is deteriorated and the oligomer precipitation sealing property is deteriorated. The acrylic resin is preferably water-soluble or dispersible acrylic. The acrylic resin may contain some organic solvent.

  Such an acrylic resin can be produced by polymerizing the following acrylic monomers. Examples of acrylic monomers include alkyl acrylates and alkyl methacrylates (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, and cyclohexyl groups. Etc.); hydroxy-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate and 2-hydroxypropyl methacrylate; epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether; acrylic acid , Methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene sulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.) A monomer containing a carboxy group or a salt thereof; acrylamide, methacrylamide, N-alkyl acrylamide, N-alkyl methacrylamide, N, N-dialkyl acrylamide, N, N-dialkyl methacrylate (the alkyl group includes methyl group, ethyl Group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, etc.), N-alkoxyacrylamide, N-alkoxymethacrylamide, N, N-dialkoxy Acrylamide, N, N-dialkoxymethacrylamide (alkoxy groups include methoxy, ethoxy, butoxy, isobutoxy, etc.), acryloylmorpholine, N-methylolacrylamide, N-methylolmethacrylamide, -Monomers containing amide groups such as phenylacrylamide and N-phenylmethacrylamide; monomers of anhydrides such as maleic anhydride and itaconic anhydride; vinyl isocyanate, allyl isocyanate, styrene, α-methyl styrene, vinyl methyl ether, vinyl ethyl Examples include ethers, vinyltrialkoxysilanes, alkylmaleic acid monoesters, alkyl fumaric acid monoesters, alkylitaconic acid monoesters, acrylonitrile, methacrylonitrile, vinylidene chloride, ethylene, propylene, vinyl chloride, vinyl acetate, butadiene, etc. It is done.

  The acrylic resin can be produced according to the method described in Production Examples 1 to 3 of JP-A-63-37167. That is, a predetermined amount of sodium lauryl sulfonate as a surfactant and a predetermined amount of ion-exchanged water were charged into a four-necked flask and heated to 60 ° C. in a nitrogen stream, and then 0.5 parts of ammonium persulfate as a polymerization initiator Then, 0.2 part of sodium hydrogen nitrite is added, and a mixture of monomers capable of expressing a desired function is added dropwise over 3 hours while adjusting the liquid temperature to 60 to 70 ° C. In addition, an aqueous dispersion of an acrylic resin can be obtained by maintaining the reaction in the same temperature range for 2 hours while continuing the reaction with stirring and then cooling.

[Fine particles]
In the present invention, the coating layer provided on both sides of the polyester film preferably contains fine particles. The average particle diameter of the fine particles contained in the coating layer is, for example, 20 to 300 nm, preferably 60 to 300 nm, and more preferably 80 to 250 nm. If it exceeds 300 nm, it is not preferable because fine particles easily fall off, and if it is less than 60 nm, sufficient lubricity and scratch resistance may not be obtained. The fine particles are usually contained in the composition of the coating layer.

Examples of the fine particles include calcium carbonate, magnesium carbonate, calcium oxide, zinc oxide, magnesium oxide, silicon oxide, sodium silicate, aluminum hydroxide, iron oxide, zirconium oxide, barium sulfate, titanium oxide, tin oxide, and antimony trioxide. Inorganic fine particles such as carbon black and molybdenum disulfide; organic fine particles such as acrylic cross-linked polymer, styrene cross-linked polymer, silicone resin, fluororesin, benzoguanamine resin, phenol resin, and nylon resin can be used. One of these may be used, or two or more may be used.
The content of the fine particles in the coating layer is preferably 0.1 to 10% by weight per 100% by weight of the composition of the coating layer. If it is less than 0.1% by weight, sufficient lubricity and scratch resistance cannot be obtained, and if it exceeds 10% by weight, the cohesive strength of the coating film becomes low and the adhesiveness deteriorates, which is not preferable.

[Crosslinking agent]
It is preferable that a crosslinking agent is blended in the composition of the coating layer. As the crosslinking agent, epoxy, oxazoline, melamine and isocyanate are preferable. One of these may be used, or two or more may be used.

  Examples of the epoxy crosslinking agent include polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidylamine compounds, and the like. Examples of the polyepoxy compounds include sorbitol, polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether. , Diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, diepoxy compound, for example, neopentyl glycol diglycidyl ether, 1,6-hexanediol Diglycidyl ether, resorcin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene group Coal diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl ether, monoepoxy compound, for example, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, glycidyl amine compound N, N, N ′, N ′,-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N-diglycidylamino) cyclohexane and the like.

  As the oxazoline crosslinking agent, a polymer containing an oxazoline group is preferable. It can be prepared by polymerization with addition polymerizable oxazoline group-containing monomers alone or with other monomers. Addition polymerizable oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, Examples include 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, and the like. Among these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially. The other monomer is not limited as long as it is a monomer copolymerizable with an addition-polymerizable oxazoline group-containing monomer, such as alkyl acrylate, alkyl methacrylate (the alkyl group includes a methyl group, an ethyl group, an n-propyl group, an isopropyl group, (meth) acrylic acid esters such as n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group); acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, Unsaturated carboxylic acids such as styrenesulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); Unsaturated nitriles such as acrylonitrile, methacrylonitrile; acrylamide, methacrylamide, N-alkyl Acrylamide, N-alkyl methacrylate N, N-dialkylacrylamide, N, N-dialkylmethacrylate (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl Groups, cyclohexyl groups, etc.); vinyl esters such as vinyl acetate, vinyl propionate, acrylic acid, methacrylic acid with polyalkylene oxide added to the ester moiety; methyl vinyl ether, ethyl vinyl ether, etc. Vinyl ethers; α-olefins such as ethylene and propylene; Halogen-containing α and β-unsaturated monomers such as vinyl chloride, vinylidene chloride and vinyl fluoride; α and β-unsaturations such as styrene and α-methylstyrene An aromatic monomer etc. can be mentioned.

  The melamine crosslinking agent is preferably a compound obtained by reacting methylol melamine derivative obtained by condensing melamine and formaldehyde with ether such as methyl alcohol, ethyl alcohol or isopropyl alcohol as a lower alcohol and a mixture thereof. Examples of the methylol melamine derivative include monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, hexamethylol melamine and the like.

  Examples of isocyanate crosslinking agents include tolylene diisocyanate, diphenylmethane-4,4′-diisocyanate, metaxylylene diisocyanate, hexamethylene-1,6-diisocyanate, 1,6-diisocyanate hexane, tolylene diisocyanate and hexanetriol. Products, adducts of tolylene diisocyanate and trimethylolpropane, polyol-modified diphenylmethane-4,4'-diisocyanate, carbodiimide-modified diphenylmethane-4,4'-diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, 3,3'- Vitrilene-4,4 'diisocyanate, 3,3' dimethyldiphenylmethane-4,4'-diisocyanate, metaphenylene diisocyanate, etc. Can.

When a crosslinking agent is blended in the composition of the coating layer, the blending ratio of the crosslinking agent is preferably 0.1 to 30% by weight, more preferably 10 to 25% by weight per 100% by weight of the composition of the coating layer. If it is less than 0.1% by weight, the cohesive strength of the coating film may not be exhibited, and the adhesiveness may be insufficient. If it exceeds 30% by weight, the coating film becomes very hard, stress relaxation is reduced, adhesion is not exhibited, and when a coated film is collected and used, foreign matter due to a crosslinked product may be generated, which is not preferable.
The crosslinking agent for the coating layer is preferably an oxazoline crosslinking agent because it is easy to handle and the pot life of the coating solution is relatively long.

[Production method]
In the present invention, the composition used for coating the coating layer is in the form of an aqueous coating solution such as an aqueous solution, aqueous dispersion or emulsion to form a coating layer (hereinafter sometimes referred to as “coating film”). Are preferably used. In order to form the coating layer, if necessary, other resins than the above composition, for example, an antistatic agent, a coloring agent, a surfactant, an ultraviolet absorber, and a crosslinking agent may be blended.

  The solid content concentration of the aqueous coating liquid used in the present invention is usually 20% by weight or less, preferably 1 to 10% by weight. If it is less than 1% by weight, the coatability to the polyester film may be insufficient, and if it exceeds 20% by weight, the stability of the coating liquid and the appearance of the coating layer may be deteriorated.

Application of the aqueous coating liquid to the polyester film can be carried out at an arbitrary stage, but it is preferably carried out in the process of producing the polyester film, and it is further preferable to apply it to the polyester film before orientation crystallization is completed. preferable.
Here, the polyester film before the crystal orientation is completed is an unstretched film, a uniaxially oriented film in which the unstretched film is oriented in either the longitudinal direction or the transverse direction, and further in two directions, the longitudinal direction and the transverse direction. And a low-stretch stretched orientation (a biaxially stretched film before the orientation crystallization is completed by finally re-stretching in the machine direction or the transverse direction). Especially, it is preferable to apply | coat the aqueous coating liquid of the said composition to an unstretched film or the uniaxially stretched film orientated to one direction, and to perform longitudinal stretch and / or horizontal stretch, and heat setting as it is. An aqueous coating solution of the above composition is applied to an unstretched film or a uniaxially stretched film oriented in one direction, and the film is stretched by a simultaneous biaxial stretching method in which longitudinal stretching and transverse stretching are simultaneously performed, and further heat-set. You may give it. According to this method, damage to the film can be prevented.

When applying an aqueous coating solution to a film, as a pretreatment for improving the coating properties, the film surface is subjected to physical treatment such as corona surface treatment, flame treatment, plasma treatment, etc., or chemically combined with the composition. It is preferable to use an inert surfactant as a wetting agent.
Such surfactants promote the wetting of the aqueous coating liquid to the polyester film and improve the stability of the coating liquid. For example, polyoxyethylene-fatty acid ester, sorbitan fatty acid ester, glycerin fatty acid ester, fatty acid metal Examples include anionic and nonionic surfactants such as soaps, alkyl sulfates, alkyl sulfonates, and alkyl sulfosuccinates. The surfactant is preferably contained in the composition forming the coating layer in an amount of 1 to 10% by weight.

The coating amount of the coating liquid is preferably such an amount that the thickness of the coating layer is in the range of 40 to 100 nm, preferably 50 to 90 nm. If the thickness of the coating layer is less than 40 nm, the adhesive strength is insufficient, and if it exceeds 100 nm, blocking may occur or the haze value may be increased.
As a coating method, any known coating method can be applied. For example, a roll coating method, a gravure coating method, a roll brush method, a spray coating method, an air knife coating method, an impregnation method, and a curtain coating method can be provided. These may be used alone or in combination.

Hereinafter, the present invention will be described in more detail with reference to examples.
Various physical properties were evaluated by the following methods.
(1) Light transmittance at a wavelength of 400 nm Using a spectrophotometer UV-3101PC manufactured by Shimadzu Corporation, the light transmittance at a wavelength of 400 nm was measured under the conditions of a scanning speed of 200 nm, a slit width of 20 nm, and a sampling pitch of 1.0 nm. .

(2) Coating layer thickness The film was cut into small pieces, embedded with an epoxy resin, and the film cross section was cut into a thickness of 50 nm with a microtome. This was stained with 2% osmic acid at 60 ° C. for 2 hours. The cross section of the dyed film was observed with a transmission electron microscope (LEM-2000), and the coating layer thickness was measured.

(3) Refractive index The coating material was evaporated to dryness, and the refractive index of the coating material at a wavelength of 633 nm was measured using a laser refractometer (METRICICON PRIM COUPER Model 2010).

(4) Adhesiveness with prism lens layer “KZ9590” manufactured by JSR Co., Ltd. is poured into a mold on which a prism lens pattern is formed, and the polyester film obtained thereon is adhered with the coated surface facing the prism resin, The polyester film surface was irradiated with UV light having an intensity of 35 cd for 10 seconds to cure the resin, and a prism lens layer having an apex angle of 95 degrees, a pitch of 50 μm, and a height of 3 μm was formed. The obtained prism lens surface is subjected to a cross cut (100 squares of 1 mm ² ) and a cellophane tape (made by Nichiban Co., Ltd.) with a width of 24 mm is applied on the prism lens surface. After peeling off, the peeled surface was observed and evaluated according to the following criteria.
5: Peeling area is less than 10% …… Adhesive strength is very good 4: Peeling area is 10% or more and less than 20% …… Adhesive strength is good 3: Peeling area is 20% or more and less than 30% …… Adhesive strength is somewhat good 2: Peeling Area is 30% or more and less than 40% …… Adhesive force failure 1: Peeling area is 40% or more …… Adhesive strength is extremely poor

(5) Luminance The prism sheet obtained in the evaluation of (3) above was incorporated into a commercially available LCD backlight (LG Electronics 15 inch monitor (FLATRON L1515S)), and the luminance was measured. For luminance measurement, a luminance meter (BM-7 manufactured by Topcon Corporation) was used. If the transmittance of the UV light is low, the prism lens is poorly formed and the luminance does not increase. The luminance when the prism sheet was not used was set to 100%, and the luminance increase rate when the prism sheet was used and the resin curing of the prism lens layer were evaluated according to the following criteria.
○: Brightness increase rate is 126% or more …… Resin curing is extremely good Δ: Brightness increase rate is 120% or more and 125% or less …… Resin curing is good ×: Brightness increase rate is less than 120% …… Resin curing is poor

(6) Blocking resistance Two films were overlapped so that the coated surfaces were in contact with each other, and a pressure of 0.6 kg / cm ² was applied to the film for 17 hours in an atmosphere of 60 ° C. and 80% RH. Then, it peeled and the blocking resistance was evaluated according to the following criteria by its peeling force.
○: Peeling force <340 mN / 5 cm …… Good blocking resistance Δ: 340 mN / 5 cm ≦ Peeling force <380 mN / 5 cm.

(7) Intrinsic viscosity Intrinsic viscosity ([η] dl / g) was measured with an o-chlorophenol solution at 25 ° C.

[Example 1]
Molten polyethylene terephthalate ([η] = 0.62 dl / g, Tg = 78 ° C.) is extruded from a die, cooled with a cooling drum by a conventional method to form an unstretched film, and then stretched 3.2 times in the machine direction. Then, an aqueous coating solution having a coating concentration of 4% shown in Table 1 was uniformly applied to both surfaces with a roll coater.
The molten polyethylene terephthalate used did not contain fine particles as a lubricant.

The film provided with the coating layer was subsequently dried at 95 ° C., stretched 3.5 times at 120 ° C. in the transverse direction, shrunk 3% in the width direction at 220 ° C., and heat-fixed. An adhesive polyester film was obtained. The evaluation results are shown in Table 2.
Furthermore, “KZ9590” manufactured by JSR Corporation is poured into a mold on which a prism lens pattern is formed, and the optically easy-adhesive polyester film obtained thereon is adhered so that the coating layer is on the prism resin side. Then, UV light having an intensity of 35 cd was irradiated from the polyester film side for 10 seconds to cure the resin, and a prism lens layer having an apex angle of 95 degrees, a pitch of 50 μm, and a height of 3 μm was formed into a prism sheet. The adhesion between the prism lens layer of the obtained prism sheet and the polyester film was evaluated. The evaluation results are shown in Table 2.

[Examples 2 and 3]
A prism sheet was prepared by obtaining an optically easy-adhesive polyester film in the same manner as in Example 1 except that a coating film was formed using the coating agents shown in Table 1. The evaluation results are shown in Table 2.

[Example 4]
Molten polyethylene terephthalate ([η] = 0.62 dl / g, Tg = 78 ° C.) was extruded from a die, cooled with a cooling drum by a conventional method to form an unstretched film, and then the coating concentrations shown in Table 1 on both sides thereof A 6% aqueous coating solution was uniformly applied with a roll coater. This coated film was subsequently dried at 95 ° C., stretched at 100 ° C. at the same time in the longitudinal direction by 3.4 times and in the transverse direction by 3.6 times, and shrunk by 2% in the longitudinal and width directions at 225 ° C. This was fixed to obtain an optically easy-adhesive polyester film having a polyester film thickness of 100 μm and a coating layer thickness of 80 nm, and a prism sheet was prepared. The evaluation results are shown in Table 2.

[Comparative Examples 1-3]
A prism sheet was prepared by obtaining an optically easy-adhesive polyester film in the same manner as in Example 1 except that a coating film was formed using the coating agents shown in Table 1. The evaluation results are shown in Table 2.

[Comparative Example 4]
An optically easy-adhesive polyester film was obtained in the same manner as in Example 2 except that the coating layer was provided only on one side and the prism layer was provided on the opposite side of the coating layer to prepare a prism sheet. The evaluation results are shown in Table 2.

[Comparative Example 5]
An optically easy-adhesive polyester film was obtained in the same manner as in Example 2 except that the coating layer was not formed and the prism layer was directly provided on the surface where the coating layer was not provided, and a prism sheet was prepared. The evaluation results are shown in Table 2.

acrylic resin:
It consists of 60 mol% methyl methacrylate / 30 mol% ethyl acrylate / 2 mol% 2-hydroxyethyl acrylate / 5 mol% N-methylolacrylamide (Tg = 40 ° C.). The acrylic was produced as follows according to the method described in Production Examples 1 to 3 of JP-A-63-37167. That is, 302 parts of ion-exchanged water was charged into a four-necked flask and the temperature was raised to 60 ° C. in a nitrogen stream, then 0.5 parts of ammonium persulfate and 0.2 parts of sodium bisulfite were added as a polymerization initiator, Further, a monomer mixture of 46.7 parts of methyl methacrylate, 23.3 parts of ethyl acrylate, 4.5 parts of 2-hydroxyethyl acrylate, and 3.4 parts of N-methylol acrylamide was added over 3 hours with a liquid temperature of 60 to It was added dropwise while adjusting to 70 ° C. After completion of dropping, the reaction was continued with stirring while maintaining the same temperature range for 2 hours, and then cooled to obtain an aqueous dispersion of acrylic 1 having a solid content of 25%.

Polyester resin:
The acid component is composed of 75 mol% of 2,6-naphthalenedicarboxylic acid / 20 mol% of isophthalic acid / 5 mol% of 5-sodium sulfoisophthalic acid, and the glycol component is composed of 90 mol% of ethylene glycol / 10 mol% of diethylene glycol (Tg). = 80 ° C., average molecular weight 15000). Polyester 1 was produced as follows. That is, 51 parts of dimethyl 2,6-naphthalenedicarboxylate, 11 parts of dimethyl isophthalate, 4 parts of dimethyl 5-sodium sulfoisophthalate, 31 parts of ethylene glycol and 2 parts of diethylene glycol were charged into a reactor. 05 parts were added, the temperature was controlled at 230 ° C. under a nitrogen atmosphere, and the resulting methanol was distilled off to conduct a transesterification reaction. Next, the temperature of the reaction system was gradually raised to 255 ° C. in a polymerization kettle with high motor torque of the stirrer, and the inside of the system was reduced in pressure by 1 mmHg to carry out a polycondensation reaction to obtain polyester 1 having an intrinsic viscosity of 0.56. 25 parts of this polyester was dissolved in 75 parts of tetrahydrofuran, and 75 parts of water was dropped into the resulting solution under high-speed stirring at 10,000 rpm to obtain a milky white dispersion, and then this dispersion was subjected to a reduced pressure of 20 mmHg. Distilled and the tetrahydrofuran was distilled off. An aqueous dispersion of polyester 1 was obtained.

Cross-linking agent:
Glycerol polyglycidyl ether (trade name Denacol EX-313, manufactured by Nagase ChemteX Corporation)
Fine particles 1:
Acrylic filler (average particle size: 200 nm) (trade name Mx-200W manufactured by Nippon Shokubai Co., Ltd.)
Fine particle 2:
Acrylic filler (average particle size: 50 nm) (trade name MX-50W manufactured by Nippon Shokubai Co., Ltd.)
Wetting agent:
Polyoxyethylene (n = 7) lauryl ether (trade name NAROACTY N-70, manufactured by Sanyo Kasei Co., Ltd.)

  The optically easy-adhesive polyester film of the present invention can be suitably used for various optical applications, and can be particularly suitably used as a prism lens sheet member for a liquid crystal display.

Claims (4)

  An easily adhesive polyester film for optics, comprising a polyester film and a coating layer provided on both sides thereof, and having a light transmittance at a wavelength of 400 nm of 88% or more.   The easily adhesive polyester film for optics according to claim 1, wherein the coating layer has a refractive index of 1.20 to 1.55.   The easily adhesive polyester film for optics according to claim 1 or 2, which is used for a prism lens sheet member of a liquid crystal display.   The easily adhesive polyester film for optics according to any one of claims 1 to 3, produced by a simultaneous biaxial stretching method.