JP5755768B2 - Laminated polyester film - Google Patents

Description

  The present invention relates to a laminated polyester film, and in particular, relates to a laminated polyester film suitably used as a member for protecting a polarizing plate used in a liquid crystal display.

  In recent years, liquid crystal displays have been widely used as display devices for televisions, personal computers, digital cameras, mobile phones and the like. The liquid crystal display has a front-side polarizing plate // liquid crystal // rear-side polarizing plate, where the display side is the front side and the opposite side (backlight side) is the rear side. The polarizing plate usually has a configuration in which a protective film or the like is bonded to a polarizing film of a polyvinyl alcohol film which is uniaxially stretched (protective film / polarizing film / protective film). The protective films disposed on the front and rear surfaces of the polarizing film constituting the front polarizing plate are designated as protective film A and protective film B, respectively, and the protective films disposed on the front and rear surfaces of the polarizing film constituting the rear polarizing plate. Assuming that the film is a protective film C and a protective film D, respectively, the overall configuration is as follows: from the front side, protective film A / front side polarizing film / protective film B // liquid crystal // protective film C / rear side polarizing film / protective Film D is obtained.

As the protective film, a triacetyl cellulose film (hereinafter sometimes abbreviated as a TAC film) is often used because it has high transparency and optical isotropy.
However, it is inferior in dimensional stability and heat-and-moisture resistance, and has the disadvantage that the surface must be saponified beforehand with an alkaline solution in order to adhere to the polarizing film. As liquid crystal displays increase in size and quality in recent years, improvement in mechanical strength and stability under high-temperature and high-humidity environments is required. The need to avoid quality degradation has emerged. Further, since the alkali treatment uses a high-concentration alkaline solution, it is not preferable in terms of work safety and environmental protection.

  In order to solve these problems, materials other than the TAC film such as a norbornene film have been studied (Patent Documents 1 and 2). However, since a film made of another material does not use a general-purpose resin, there is a problem that the cost is high. Then, the method of using the polyester film which is general purpose resin which can ensure dimensional stability, does not require the process of the alkali treatment which has various problems, and also has no problem also in cost is also proposed.

  However, the polyester film alone has a drawback that the adhesiveness between the polarizing film and the adhesive used for bonding the protective film is poor. In order to improve the adhesion of the polyester film, a configuration in which an anchor layer is provided has also been proposed, but there is no specific disclosure, and depending on the adhesive, it is difficult to ensure sufficient adhesion. (Patent Documents 3 to 5).

JP-A-6-511117 JP 2006-227090 A JP 2002-116320 A JP-A-8-271733 JP-A-8-271734

  The present invention has been made in view of the above circumstances, and the problem to be solved is that it can solve various problems of the TAC film, has good adhesiveness with an adhesive, and is a protective film for a polarizing film. It is providing the laminated polyester film which can be utilized suitably as.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the use of a laminated polyester film having a specific configuration can easily solve the above-described problems, and have completed the present invention.

That is, the gist of the present invention includes polyvinyl alcohol, an oxazoline compound, and an isocyanate compound, and the weight ratio of polyvinyl alcohol: oxazoline compound: isocyanate compound is 1.0 to 8.0: 1.0 to 8. 0.0: It exists in the laminated polyester film characterized by having the coating layer which is the range of 1.0-8.0 on a polyester film, and having an adhesive bond layer on the said coating layer.

  According to the laminated polyester film of the present invention, for example, a laminated polyester film excellent in adhesive strength with an adhesive for bonding a protective film for a polarizing plate and a polarizing film can be provided, and its industrial value is high.

  The polyester film constituting the laminated polyester film in the present invention may have a single layer structure or a multilayer structure, and may have four or more layers as long as it does not exceed the gist of the present invention other than a two-layer or three-layer structure. It may be a multilayer, and is not particularly limited.

  The polyester used in the present invention may be a homopolyester or a copolyester. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical polyester includes polyethylene terephthalate and the like. On the other hand, examples of the dicarboxylic acid component of the copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (for example, p-oxybenzoic acid). 1 type or 2 types or more are mentioned, As a glycol component, 1 type or 2 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexane dimethanol, neopentyl glycol, is mentioned.

  The polyester film of the present invention may contain an ultraviolet absorber in order to prevent the liquid crystal of the liquid crystal display from being deteriorated by ultraviolet rays. The ultraviolet absorber is not particularly limited as long as it is a compound having ultraviolet absorbing ability and can withstand the heat applied in the production process of the polyester film.

  As the ultraviolet absorber, there are an organic ultraviolet absorber and an inorganic ultraviolet absorber. From the viewpoint of transparency, an organic ultraviolet absorber is preferable. Although it does not specifically limit as an organic type ultraviolet absorber, For example, a benzotriazole type, a cyclic imino ester type, a benzophenone type etc. are mentioned. From the viewpoint of durability, benzotriazole and cyclic imino ester are more preferable. It is also possible to use two or more ultraviolet absorbers in combination.

  Examples of the benzotriazole-based ultraviolet absorbers include, but are not limited to, 2- [2′-hydroxy-5 ′-(methacryloyloxymethyl) phenyl] -2H-benzotriazole, 2- [2 '-Hydroxy-5'-(methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-5 '-(methacryloyloxypropyl) phenyl] -2H-benzotriazole, 2- [2'- Hydroxy-5 '-(methacryloyloxyhexyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-tert-butyl-5'-(methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2 -[2'-hydroxy-5'-tert-butyl-3 '-(methacryl Yloxyethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′-(methacryloyloxyethyl) phenyl] -5-chloro-2H-benzotriazole, 2- [2′-hydroxy-5 ′ -(Methacryloyloxyethyl) phenyl] -5-methoxy-2H-benzotriazole, 2- [2'-hydroxy-5 '-(methacryloyloxyethyl) phenyl] -5-cyano-2H-benzotriazole, 2- [2 '-Hydroxy-5'-(methacryloyloxyethyl) phenyl] -5-tert-butyl-2H-benzotriazole, 2- [2'-hydroxy-5 '-(methacryloyloxyethyl) phenyl] -5-nitro-2H -Benzotriazole and the like.

  Examples of the cyclic imino ester-based ultraviolet absorber include, but are not limited to, 2-methyl-3,1-benzoxazin-4-one, 2-butyl-3,1-benzoxazine-4, for example. -One, 2-phenyl-3,1-benzoxazin-4-one, 2- (1- or 2-naphthyl) -3,1-benzoxazin-4-one, 2- (4-biphenyl) -3, 1-benzoxazin-4-one, 2-p-nitrophenyl-3,1-benzoxazin-4-one, 2-m-nitrophenyl-3,1-benzoxazin-4-one, 2-p-benzoyl Phenyl-3,1-benzoxazin-4-one, 2-p-methoxyphenyl-3,1-benzoxazin-4-one, 2-o-methoxyphenyl-3,1-benzoxazin-4-one, -Cyclohexyl-3,1-benzoxazin-4-one, 2-p- (or m-) phthalimidophenyl-3,1-benzoxazin-4-one, N-phenyl-4- (3,1-benzoxazine -4-On-2-yl) phthalimide, N-benzoyl-4- (3,1-benzoxazin-4-one-2-yl) aniline, N-benzoyl-N-methyl-4- (3,1- Benzoxazin-4-one-2-yl) aniline, 2- (p- (N-methylcarbonyl) phenyl) -3,1-benzoxazin-4-one, 2,2′-bis (3,1-benzo Oxazin-4-one), 2,2′-ethylenebis (3,1-benzoxazin-4-one), 2,2′-tetramethylenebis (3,1-benzoxazin-4-one), 2, 2'-Decame Renbis (3,1-benzoxazin-4-one, 2,2'-p-phenylenebis (3,1-benzoxazin-4-one), 2,2'-m-phenylenebis (3,1-benzo Oxazin-4-one), 2,2 ′-(4,4′-diphenylene) bis (3,1-benzoxazin-4-one), 2,2 ′-(2,6- or 1,5-naphthylene) ) Bis (3,1-benzoxazin-4-one), 2,2 ′-(2-methyl-p-phenylene) bis (3,1-benzoxazin-4-one), 2,2 ′-(2 -Nitro-p-phenylene) bis (3,1-benzoxazin-4-one), 2,2 '-(2-chloro-p-phenylene) bis (3,1-benzoxazin-4-one), 2 , 2 '-(1,4-cyclohexylene) bis (3,1-benzoo Sadin-4-one), 1,3,5-tri (3,1-benzoxazin-4-one-2-yl) benzene, 1,3,5-tri (3,1-benzoxazin-4-one) -2-yl) naphthalene, 2,4,6-tri (3,1-benzoxazin-4-one-2-yl) naphthalene, 2,8-dimethyl-4H, 6H-benzo (1,2-d; 5,4-d ′) bis (1,3) -oxazine-4,6-dione, 2,7-dimethyl-4H, 9H-benzo (1,2-d; 4,5-d ′) bis (1 , 3) -Oxazine-4,9-dione, 2,8-diphenyl-4H, 8H-benzo (1,2-d; 5,4-d ′) bis (1,3) -oxazine-4,6- Dione, 2,7-diphenyl-4H, 9H-benzo (1,2-d; 4,5-d ′) bis (1,3) -oxazine 4,6-dione, 6,6′-bis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-bis (2-ethyl-4H, 3,1-benzoxazine) -4-one), 6,6'-bis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6'-methylenebis (2-methyl-4H, 3,1-benzoxazine) -4-one), 6,6'-methylenebis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6'-ethylenebis (2-methyl-4H, 3,1-benzo) Oxazin-4-one), 6,6′-ethylenebis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6′-butylenebis (2-methyl-4H, 3,1- Benzoxazin-4-one), 6,6′-butylenebis (2- Phenyl-4H, 3,1-benzoxazin-4-one), 6,6′-oxybis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-oxybis (2- Phenyl-4H, 3,1-benzoxazin-4-one), 6,6′-sulfonylbis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-sulfonylbis ( 2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6′-carbonylbis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-carbonyl Bis (2-phenyl-4H, 3,1-benzoxazin-4-one), 7,7′-methylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 7,7′- Methylenebis (2-phenyl-4H 3,1-benzoxazin-4-one), 7,7′-bis (2-methyl-4H, 3,1-benzoxazin-4-one), 7,7′-ethylenebis (2-methyl-4H) , 3,1-benzoxazin-4-one), 7,7′-oxybis (2-methyl-4H, 3,1-benzoxazin-4-one), 7,7′-sulfonylbis (2-methyl-) 4H, 3,1-benzoxazin-4-one), 7,7′-carbonylbis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,7′-bis (2-methyl) -4H, 3,1-benzoxazin-4-one), 6,7'-bis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6,7'-methylenebis (2-methyl- 4H, 3,1-benzoxazin-4-one), 6,7 ′ Methylene bis (2-phenyl-4H, 3,1-benzoxazin-4-one), and the like.

  Among the above compounds, when considering the color tone, a benzoxazinone-based compound which is difficult to be yellowed is preferably used. As an example thereof, a compound represented by the following general formula (1) is more preferably used. It is done.

In the above formula, R represents a divalent aromatic hydrocarbon group, and X ¹ and X ² are each independently selected from hydrogen or the following functional group group, but are not necessarily limited thereto.

Functional group: alkyl group, aryl group, heteroaryl group, halogen, alkoxyl group, aryloxy group, hydroxyl group, carboxyl group, ester group, nitro group Among the compounds represented by the above structural formula, in the present invention, 2,2 ′-(1,4-phenylene) bis [4H-3,1-benzoxazin-4-one] is particularly preferred.

  The amount of the ultraviolet absorber to be contained in the laminated polyester film of the present invention is usually 10.0% by weight or less, preferably 0.3 to 3.0% by weight. When an ultraviolet absorber in an amount exceeding 10.0% by weight is contained, the ultraviolet absorber may bleed out on the surface, which may cause deterioration of surface functionality such as adhesion deterioration.

  In the case of a multilayer film, it is preferably at least a three-layer structure, and the ultraviolet absorber is preferably blended in the intermediate layer. By blending an ultraviolet absorber in the intermediate layer, the compound can be prevented from bleeding out to the film surface, and as a result, properties such as film adhesion can be maintained.

  When used as a protective film for a polarizing film, if the laminated polyester film of the present invention prevents deterioration of the liquid crystal due to ultraviolet rays, as a guideline, the light transmittance at a wavelength of 380 nm is preferably 10% or less, more preferably. Is 5% or less. The light transmittance at a wavelength of 380 nm can be adjusted by changing the type and amount of the above-described ultraviolet absorber.

  In the polyester layer of the film of the present invention, it is preferable to blend particles mainly for the purpose of imparting slipperiness and preventing scratches in each step. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples include inorganic particles such as magnesium, kaolin, aluminum oxide, and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin, and benzoguanamine resin. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color, etc. These series of particles may be used in combination of two or more as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.01-5 micrometers normally, Preferably it is the range of 0.1-3 micrometers. If the average particle size is less than 0.01 μm, the slipperiness may not be sufficiently imparted, or the particles may be aggregated to make the dispersibility insufficient, thereby reducing the transparency of the film. On the other hand, when the thickness exceeds 5 μm, the surface roughness of the film becomes too rough, and a defect may occur in a subsequent process.

  Furthermore, the content of particles in the polyester layer is usually in the range of 0.0001 to 5% by weight, preferably 0.0003 to 3% by weight. When the particle content is less than 0.0001% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 5% by weight, the transparency of the film is insufficient. There is a case.

  The method for adding particles to the polyester layer is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage of producing the polyester constituting each layer, but it is preferably added after completion of esterification or transesterification.

  Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  In addition to the above-mentioned particles, conventionally known antioxidants, antistatic agents, thermal stabilizers, lubricants, dyes, pigments, and the like can be added to the polyester film in the present invention as necessary.

  Although the thickness of the polyester film in this invention will not be specifically limited if it is a range which can be formed into a film as a film, Usually, 10-200 micrometers, Preferably it is the range of 25-50 micrometers.

  Next, although the manufacture example of the polyester film in this invention is demonstrated concretely, it is not limited to the following manufacture examples at all. That is, a method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method or a liquid application adhesion method is preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7.0 times, preferably 3.0 to 6.0 times. Next, the film is stretched in the direction perpendicular to the first stretching direction. In that case, the stretching temperature is usually 70 to 170 ° C., and the stretching ratio is usually 3.0 to 7.0 times, preferably 3.5 to 6 times. .0 times. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  In the present invention, the simultaneous biaxial stretching method can be adopted for the production of the polyester film constituting the laminated polyester film. The simultaneous biaxial stretching method is a method in which the above-mentioned unstretched sheet is usually stretched and oriented in the machine direction and the width direction at a temperature controlled normally at 70 to 120 ° C., preferably 80 to 110 ° C. Is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area magnification. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, a conventionally known stretching method such as a screw method, a pantograph method, or a linear driving method can be employed.

  Next, formation of the coating layer which comprises the laminated polyester film in this invention is demonstrated. Regarding the coating layer, it may be provided by in-line coating which treats the film surface during the process of forming a polyester film, or offline coating which is applied outside the system on a once produced film may be adopted. Since the coating can be performed simultaneously with the film formation, the production can be handled at a low cost, and therefore in-line coating is preferably used.

  The in-line coating is not limited to the following, but for example, in the sequential biaxial stretching, the coating treatment can be performed particularly before the lateral stretching after the longitudinal stretching is finished. When the coating layer is provided on the polyester film by in-line coating, it is possible to apply at the same time as the film formation, and the coating layer can be processed at a high temperature in the heat treatment process of the polyester film after stretching. Performances such as adhesion to various surface functional layers that can be formed on the layer and heat-and-moisture resistance can be improved. Moreover, when coating before extending | stretching, the thickness of an application layer can also be changed with a draw ratio, and compared with offline coating, thin film coating can be performed more easily. That is, a film suitable as a polyester film can be produced by in-line coating, particularly coating before stretching.

  In the present invention, it is an essential requirement to have a coating layer containing a polyvinyl alcohol, an oxazoline compound and an isocyanate compound (hereinafter sometimes abbreviated as a first coating layer) on a polyester film. is there.

  The first coating layer of the film of the present invention is a coating layer for improving adhesiveness with various functional layers. For example, various adhesives used for bonding the polarizing film and the laminated polyester film of the present invention together. It can be used to improve the adhesion with the agent.

  The present inventors examined polyvinyl alcohol for improving the adhesion with the adhesive layer, but the coating layer formed with polyvinyl alcohol alone had no adhesion. Then, when the combination of various materials was examined, it became clear that adhesiveness improved comparatively if it combined polyvinyl alcohol and an oxazoline type compound, and devised the composition ratio. However, it is still not sufficient adhesiveness, and when further searching for a coating layer that improves adhesion by using in combination with these two kinds of compounds, surprisingly, by using an isocyanate compound in combination, Adhesiveness was greatly improved and a coating layer usable for protecting a polarizing film was successfully formed.

  The polyvinyl alcohol contained in the first coating layer of the film of the present invention has a polyvinyl alcohol moiety, and includes, for example, modified compounds partially acetalized or butyralized with respect to polyvinyl alcohol. Known polyvinyl alcohol can be used. The degree of polymerization of polyvinyl alcohol is not particularly limited, but is usually 100 or more, preferably 300 to 40,000. When the degree of polymerization is less than 100, the water resistance of the coating layer may decrease. Moreover, the saponification degree of polyvinyl alcohol is not particularly limited, but a polyvinyl acetate saponified product in a range of 70 mol% or more, preferably 70 to 99.9 mol% is practically used.

  The oxazoline-based compound contained in the first coating layer of the film of the present invention is a compound having an oxazoline group in the molecule and a compound derived therefrom. In particular, a polymer containing an oxazoline group is preferable, and it can be prepared by polymerization of an addition polymerizable oxazoline group-containing monomer alone or with another monomer. 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, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, and the like can be mentioned, and one or a mixture of two or more thereof can be used. 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. For example, alkyl (meth) acrylate (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, styrene Unsaturated carboxylic acids such as sulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); Unsaturated nitriles such as acrylonitrile, methacrylonitrile; (meth) acrylamide, N-alkyl ( (Meth) acrylamide, N, N-dialkyl (meth) acrylamide, As the alkyl group, unsaturated amides such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group and cyclohexyl group); vinyl acetate Vinyl esters such as vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α, β-unsaturated monomers such as vinyl chloride, vinylidene chloride and vinyl fluoride And α, β-unsaturated aromatic monomers such as styrene and α-methylstyrene, and the like, and one or more of these monomers can be used.

  Moreover, improvement in coating film strength and improvement in wet heat resistance can be expected when the number of hydrophilic groups such as polyalkylene glycol components is small and the amount of oxazoline groups is large.

  The isocyanate compound contained in the first coating layer of the film of the present invention is a compound derived from an isocyanate derivative represented by isocyanate or blocked isocyanate. Examples of isocyanate include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate, and aromatic rings such as α, α, α ′, α′-tetramethylxylylene diisocyanate. Aliphatic isocyanates such as aliphatic isocyanate, methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylene bis (4-cyclohexyl isocyanate), isopropylidene dicyclohexyl diisocyanate Ne Alicyclic isocyanates such as bets are exemplified. Further, polymers and derivatives such as burettes, isocyanurates, uretdiones, and carbodiimide modified products of these isocyanates are also included. These may be used alone or in combination. Among the above isocyanates, aliphatic isocyanates or alicyclic isocyanates are more preferable than aromatic isocyanates in order to avoid yellowing due to ultraviolet rays.

  When used in the state of blocked isocyanate, the blocking agent includes, for example, bisulfites, phenolic compounds such as phenol, cresol, and ethylphenol, and alcohols such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, and ethanol. Compounds, active methylene compounds such as dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate and acetylacetone, mercaptan compounds such as butyl mercaptan and dodecyl mercaptan, lactam compounds such as ε-caprolactam and δ-valerolactam , Amine compounds such as diphenylaniline, aniline, ethyleneimine, acetanilide, acid amide compounds of acetic acid amide, formaldehyde, acetoald Examples include oxime compounds such as oxime, acetone oxime, methyl ethyl ketone oxime, and cyclohexanone oxime, and these may be used alone or in combination of two or more.

  In addition, the isocyanate compound in the present invention may be used alone, or may be used as a mixture or bond with various polymers. In the sense of improving the dispersibility and crosslinkability of the isocyanate compound, it is preferable to use a mixture or a bond with a polyester resin or a urethane resin.

  The content of polyvinyl alcohol in the first coating layer of the present invention is usually 10 to 80% by weight, preferably 10 to 60% by weight, and more preferably 15 to 45% by weight. If it is less than 10% by weight, the adhesiveness with the adhesive layer may not be sufficient due to a small amount of the polyvinyl alcohol component. Sexuality may not be sufficient.

  The content of the oxazoline-based compound in the first coating layer of the present invention is usually 10 to 80% by weight, preferably 10 to 60% by weight, and more preferably 15 to 30% by weight. If the amount is less than 10% by weight, the coating layer becomes brittle due to a small amount of the crosslinking component, and the heat-and-moisture resistance may decrease. And adhesiveness with the adhesive layer may not be sufficient.

  Content of the isocyanate type compound which occupies for the 1st application layer of the film of this invention is 10 to 80 weight% normally, Preferably it is 15 to 70 weight%, More preferably, it is 20 to 50 weight%. If the amount is less than 10% by weight, the coating layer becomes brittle due to a small amount of the crosslinking component, and the heat-and-moisture resistance may decrease. And adhesiveness with the adhesive layer may not be sufficient.

  The weight ratio of polyvinyl alcohol: oxazoline compound: isocyanate compound contained in the first coating layer of the film of the present invention is usually 1.0 to 8.0: 1.0 to 8.0: 1.0 to 8. 0, preferably 1.0-4.0: 1.0-3.0: 1.0-6.5, more preferably 1.0-3.0: 1.0-2.0: 1 The range is from .0 to 4.0.

  In the first coating layer of the film of the present invention, a polymer other than polyvinyl alcohol can be used in combination in order to improve the coating surface state and transparency.

  Specific examples of the polymer include polyester resin, acrylic resin, urethane resin, polyvinyl (polyvinyl chloride, vinyl chloride vinyl acetate copolymer, etc.), polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches and the like. It is done.

  Furthermore, a crosslinking agent other than the oxazoline-based compound and the isocyanate-based compound can be used in combination in the first coating layer as long as the gist of the present invention is not impaired. Various known compounds can be used as the crosslinking agent, and examples thereof include melamine compounds, epoxy compounds, carbodiimide compounds, and the like.

  The melamine compound is a compound having a melamine skeleton in the compound. For example, an alkylolated melamine derivative, a compound partially or completely etherified by reacting an alcohol with an alkylolated melamine derivative, and a mixture thereof can be used. As alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like are preferably used. Moreover, as a melamine compound, either a monomer or a multimer more than a dimer may be sufficient, or a mixture thereof may be used. Further, a product obtained by co-condensing urea or the like with a part of melamine can be used, and a catalyst can be used to increase the reactivity of the melamine compound.

  Examples of the epoxy compound include a compound containing an epoxy group in the molecule, a prepolymer and a cured product thereof. Examples include condensates of epichlorohydrin with hydroxyl groups and amino groups such as ethylene glycol, polyethylene glycol, glycerin, polyglycerin, and bisphenol A, and polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidylamine compounds, and the like. is there. Examples of the polyepoxy compound include sorbitol, polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, trimethylol. Examples of the propane polyglycidyl ether and diepoxy compound include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether. Ether, polypropylene glycol diglycidyl ether, Ritetramethylene glycol diglycidyl ether and monoepoxy compounds include, for example, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and glycidyl amine compounds such as N, N, N ′, N ′,-tetraglycidyl-m. -Xylylenediamine, 1,3-bis (N, N-diglycidylamino) cyclohexane and the like.

  Among these cross-linking agents, improvement of adhesion and heat-and-moisture resistance can be expected by using an epoxy compound in combination. These cross-linking agents preferably have water solubility or water dispersibility in consideration of application to in-line coating.

  Further, the first coating layer preferably contains particles for the purpose of improving the blocking property and slipperiness of the coating layer, and the average particle size is preferably in the range of 1 μm or less from the viewpoint of the transparency of the film. Is 0.7 μm or less, more preferably 0.2 μm or less. From the viewpoint of blocking properties and slipperiness, the average particle size is preferably in the range of 0.01 μm or more, more preferably in the range of 0.03 μm or more, and still more preferably in the range of 0.05 μm or more. Specific examples of the particles include silica, alumina, kaolin, calcium carbonate, titanium oxide, and organic particles. Among them, silica is particularly preferable. The content of the particles in the coating layer depends on the average particle diameter, but is preferably in the range of 0.1 to 30% by weight, more preferably in the range of 0.5 to 10% by weight, and further preferably 1 to 6%. It is in the range of wt%.

  In the present invention, a coating layer containing a resin (hereinafter abbreviated as a second coating layer) is provided on the surface of the polyester film opposite to the surface having a coating layer containing polyvinyl alcohol, an oxazoline compound, and an isocyanate compound. May be provided).

  It is preferable to provide the 2nd application layer of the film of this invention in order to improve adhesiveness with various surface functional layers depending on a use. For example, when used as a protective film on the front side of the front side polarizing plate (the above-mentioned protective film A), for example, a hard coat layer or an antiglare layer on the front side of the polyester film (the side opposite to the side to be bonded to the polarizing film) It is a coating layer which can form etc. effectively.

  Conventionally known resins can be used as the resin contained in the second coating layer, but polyester resins, acrylic resins, urethane resins, and the like are preferable from the viewpoint of improving adhesion to various surface functional layers. Used.

  The polyester resin that can be contained in the second coating layer includes, for example, the following polyvalent carboxylic acid and polyvalent hydroxy compound as main components. That is, as the polyvalent carboxylic acid, terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4′-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, and 2,6 -Naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalic acid, 5-sodium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutar Acid, succinic acid, trimellitic acid, trimesic acid, pyromellitic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, trimellitic acid monopotassium salt and ester-forming derivatives thereof can be used. As the polyvalent hydroxy compound, ethylene Recall, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,5-pentanediol , Neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol, bisphenol A-ethylene glycol adduct, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol Polytetramethylene glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, potassium dimethylolpropionate, and the like can be used. One or more compounds may be appropriately selected from these compounds, and a polyester resin may be synthesized by a conventional polycondensation reaction.

  The acrylic resin that can be contained in the second coating layer is a polymer composed of a polymerizable monomer having a carbon-carbon double bond, as typified by acrylic and methacrylic monomers. These may be either a homopolymer or a copolymer. Moreover, the copolymer of these polymers and other polymers (for example, polyester, polyurethane, etc.) is also included. For example, a block copolymer or a graft copolymer. Alternatively, a polymer (possibly a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyester solution or a polyester dispersion is also included. Similarly, a polymer (in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyurethane solution or polyurethane dispersion is also included. Similarly, a polymer obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in another polymer solution or dispersion (in some cases, a polymer mixture) is also included. In order to improve the total light transmittance more efficiently, it is also possible to use a fluorine atom-containing compound having a low refractive index.

  The polymerizable monomer having a carbon-carbon double bond is not particularly limited, but particularly representative compounds include, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, citracone. Various carboxyl group-containing monomers such as acids, and salts thereof; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, monobutyl hydroxyl fumarate, Various hydroxyl group-containing monomers such as monobutylhydroxy itaconate; various monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate ( (Meth) acrylic acid esters; Various nitrogen-containing compounds such as meth) acrylamide, diacetone acrylamide, N-methylol acrylamide or (meth) acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene, vinyl acetate, propion Various vinyl esters such as vinyl acid; various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, etc .; phosphorus-containing vinyl monomers; vinyl chloride, biliden chloride, Various vinyl halides such as vinyl fluoride, vinylidene fluoride, trifluorochloroethylene, tetrafluoroethylene, chlorotrifluoroethylene and hexafluoropropylene; various conjugated dienes such as butadiene That.

  The urethane resin that can be contained in the second coating layer is a polymer compound having a urethane resin in the molecule. Usually, urethane resin is prepared by reaction of polyol and isocyanate. Examples of the polyol include polycarbonate polyols, polyester polyols, polyether polyols, polyolefin polyols, and acrylic polyols. These compounds may be used alone or in combination.

  Polycarbonate polyols are obtained from a polyhydric alcohol and a carbonate compound by a dealcoholization reaction. Examples of the polyhydric alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentane. Diol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decane Diol, neopentyl glycol, 3-methyl-1,5-pentanediol, 3,3-dimethylol heptane and the like can be mentioned. Examples of the carbonate compound include dimethyl carbonate, diethyl carbonate, diphenyl carbonate, and ethylene carbonate. Examples of polycarbonate polyols obtained from these reactions include poly (1,6-hexylene) carbonate, poly (3- And methyl-1,5-pentylene) carbonate.

  Polyester polyols include polycarboxylic acids (malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, isophthalic acid, etc.) or their acid anhydrides. Product and polyhydric alcohol (ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol 2-methyl-2-propyl-1 3-propanediol, 1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol 1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2-hexyl-1,3-propanediol, cyclohexane Diol, bishydroxymethylcyclohexane, dimethanolbenzene, bishydroxyethoxybenzene, alkyl dialkanolamine, lactone diol, etc.).

  Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, and the like.

  Examples of the polyisocyanate compound used for obtaining the urethane resin include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate, α, α, α ′, α ′. -Aliphatic diisocyanates having aromatic rings such as tetramethylxylylene diisocyanate, aliphatic diisocyanates such as methylene diisocyanate, propylene diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl Methanzi Cyanate, alicyclic diisocyanates such as isopropylidene dicyclohexyl diisocyanates. These may be used alone or in combination.

  A chain extender may be used when synthesizing the urethane resin, and the chain extender is not particularly limited as long as it has two or more active groups that react with an isocyanate group. Alternatively, a chain extender having two amino groups can be mainly used.

  Examples of the chain extender having two hydroxyl groups include aliphatic glycols such as ethylene glycol, propylene glycol and butanediol, aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene, and esters such as neopentyl glycol hydroxypivalate. And glycols such as glycols. Examples of the chain extender having two amino groups include aromatic diamines such as tolylenediamine, xylylenediamine, and diphenylmethanediamine, ethylenediamine, propylenediamine, hexanediamine, 2,2-dimethyl-1,3- Propanediamine, 2-methyl-1,5-pentanediamine, trimethylhexanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10- Aliphatic diamines such as decane diamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, dicyclohexylmethanediamine, isoprobilitincyclohexyl-4,4′-diamine, 1,4-diaminocyclohexane, 1 , 3-Bisaminomethylcyclohexa And alicyclic diamines such as

The urethane resin in the present invention may use a solvent as a medium, but preferably uses water as a medium. In order to disperse or dissolve the urethane resin in water, there are a forced emulsification type using an emulsifier, a self-emulsification type in which a hydrophilic group is introduced into the urethane resin, and a water-soluble type. In particular, a self-emulsification type in which an ionic group is introduced into the skeleton of a urethane resin to form an ionomer is preferable because of excellent storage stability of the liquid and water resistance, transparency, and adhesion of the resulting coating layer.
Examples of the ionic group to be introduced include various groups such as a carboxyl group, sulfonic acid, phosphoric acid, phosphonic acid, quaternary ammonium salt, and the like, and a carboxyl group is preferable. As a method for introducing a carboxyl group into a urethane resin, various methods can be taken in each stage of the polymerization reaction. For example, there are a method of using a carboxyl group-containing resin as a copolymer component during prepolymer synthesis, and a method of using a component having a carboxyl group as one component such as polyol, polyisocyanate, and chain extender. In particular, a method in which a desired amount of carboxyl groups is introduced using a carboxyl group-containing diol depending on the amount of this component charged is preferred. For example, dimethylolpropionic acid, dimethylolbutanoic acid, bis- (2-hydroxyethyl) propionic acid, bis- (2-hydroxyethyl) butanoic acid and the like are copolymerized with a diol used for polymerization of a urethane resin. Can do. The carboxyl group is preferably in the form of a salt neutralized with ammonia, amine, alkali metal, inorganic alkali or the like. Particularly preferred are ammonia, trimethylamine and triethylamine. In such a polyurethane resin, a carboxyl group from which the neutralizing agent has been removed in the drying step after coating can be used as a crosslinking reaction point by another crosslinking agent. Thereby, it is possible to further improve the durability, solvent resistance, water resistance, blocking resistance, and the like of the obtained coating layer, as well as excellent stability in a liquid state before coating.

  In the film of the present invention, when the second coating layer is provided, the resin content in the second coating layer is preferably 10% by weight or more, more preferably 30 to 95% by weight, and still more preferably 40 to 95%. It is in the range of wt%.

  Furthermore, it is also possible to use a crosslinking agent in the second coating layer as long as the gist of the present invention is not impaired. By using a cross-linking agent, the coating layer becomes strong, so that the heat and moisture resistance and the scratch resistance may be further improved. Examples of the crosslinking agent include melamine compounds, epoxy compounds, oxazoline compounds, isocyanate compounds, carbodiimide compounds, and the like. These cross-linking agents may be used alone or in combination of two or more. Furthermore, when consideration is given to application to in-line coating, it is preferable to have water solubility or water dispersibility.

  Further, the second coating layer may contain particles for the purpose of improving the blocking property and slipperiness of the coating layer, and the same particles as those used in the first coating layer can be used.

  Furthermore, when a clear surface functional layer such as a hard coat layer is formed in the second coating layer, it is possible to use a material that adjusts the refractive index in order to reduce interference unevenness due to external light. It is. Specifically, the material for adjusting the refractive index is a high refractive index material in the present invention. Examples of the high refractive index material include metal compounds, aromatic-containing organic compounds, sulfur atoms, bromine atoms and the like.

  Examples of the metal compound include titanium oxide, zinc oxide, tin oxide, antimony oxide, yttrium oxide, zirconium oxide, indium oxide, cerium oxide, ATO (antimony / tin oxide), and ITO (indium / tin oxide). Aluminum such as metal oxide, aluminum acetylacetonate, hydroxyaluminum diacetate, dihydroxyaluminum acetate; tetranormal butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, tetramethyl titanate, titanium acetylacetate Nato, titanium tetraacetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate, titanium triethanolamine Titanium such as iron acetate and titanium ethyl acetoacetate; Iron such as iron acetylacetonate and iron acetate; Cobalt such as cobalt acetylacetonate; Copper acetate, copper acetate monohydrate, copper acetate multihydrate, copper acetyl Coppers such as acetonate; zincs such as zinc acetate, zinc acetate dihydrate, zinc acetylacetonate hydrate; zirconium acetate, zirconium normal propylate, zirconium normal butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetate Examples thereof include organic compounds having a metal element such as zirconium and zirconium compounds such as narate and zirconium bisacetylacetonate. These may be used alone or in combination of two or more.

  Among the above metal compounds, an organic compound having a titanium element or a zirconium element is preferable in terms of particularly good coatability and transparency, and more preferably a water-soluble titanium chelate compound when considering application to in-line coating, A water-soluble zirconium chelate compound or the like is preferably used. In addition, fine particles of titanium oxide or zirconium oxide are also preferably used in that the stability of the coating liquid and effective adjustment of the refractive index are possible.

  Examples of aromatic-containing organic compounds include compounds having a high proportion of benzene rings such as condensed polycyclic aromatic compounds, bisphenol A compounds, biphenyl compounds, and fluorene compounds, which can be exemplified by naphthalene rings and anthracene rings. Examples thereof include compounds, ultraviolet absorber-containing compounds such as benzophenone and benzotriazole, and various heteroaromatic ring compounds. These may be used alone or in combination of two or more. An aromatic compound is effective because it can be incorporated into a resin capable of forming the second coating layer. Among these, polyester resins can easily use many aromatic compounds because of their structures. Among aromatic compounds, naphthalene ring and bisphenol A compound are useful because they can efficiently increase the refractive index of the coating layer. A melamine compound that can be used as a crosslinking agent is a compound having a high ratio of heteroaromatic rings, and is also a compound effective for increasing the refractive index.

  Furthermore, as long as the gist of the present invention is not impaired, the first coating layer and the second coating layer have an antifoaming agent, coating property improving agent, thickening agent, organic lubricant, antistatic agent, ultraviolet absorption as necessary. Agents, antioxidants, foaming agents, dyes, pigments and the like may be contained.

  Analysis of various components in the coating layer can be performed by surface analysis such as TOF-SIMS.

  When providing a coating layer by in-line coating, the above-mentioned series of compounds is applied as an aqueous solution or dispersion, and the coating solution adjusted to a solid content concentration of about 0.1 to 50% by weight as a guide is applied onto the polyester film. It is preferable to produce a laminated polyester film. Moreover, in the range which does not impair the main point of this invention, a small amount of organic solvents may be contained in the coating liquid for the purpose of improving dispersibility in water, improving film-forming properties, and the like. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

  The film thickness of the 1st coating layer and the 2nd coating layer of the laminated polyester film in this invention is 0.002-1.0 micrometer normally, More preferably, it is 0.03-0.5 micrometer, More preferably, it is 0.04-0. The range is 2 μm. If the film thickness is less than 0.002 μm, sufficient adhesion may not be obtained, and if it exceeds 1.0 μm, the appearance, transparency, and film blocking properties may be deteriorated.

  In the present invention, as a method for providing the coating layer, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating or the like can be used.

  In the present invention, the drying and curing conditions for forming the coating layer on the polyester film are not particularly limited. For example, when the coating layer is provided by off-line coating, it is usually 3 to 40 at 80 to 200 ° C. The heat treatment may be performed for 2 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds.

  On the other hand, when the coating layer is provided by in-line coating, heat treatment is usually performed at 70 to 280 ° C. for 3 to 200 seconds as a guide.

  Further, irrespective of off-line coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as required. The polyester film constituting the laminated polyester film in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  When the laminated polyester film of the present invention is used as, for example, a protective film for a polarizing film in a polarizing plate, generally, the polarizing film is bonded to the first coating layer via an adhesive for adhering the polarizing film. . As the adhesive, conventionally known ones can be used, for example, acrylic compounds such as polyvinyl alcohol, polyvinyl butyral and polybutyl acrylate, and epoxy having an alicyclic epoxy group exemplified by glycidyl group and epoxycyclohexane. System compounds and the like.

  On the prepared adhesive layer, for example, polyvinyl alcohol that is uniaxially stretched and dyed with iodine or the like is bonded as a polarizing film. A protective film, a retardation film, or the like can be bonded to the opposite side of the polarizing film to form a polarizing plate.

  Moreover, it is also possible to form a surface functional layer such as a hard coat layer or an antiglare layer on the side opposite to the first coating layer side of the polyester film (if there is a second coating layer). Although it does not specifically limit as a material used for a surface functional layer, For example, hardened | cured materials, such as reactive silicon compounds, such as monofunctional (meth) acrylate, polyfunctional (meth) acrylate, and tetraethoxysilane, are mentioned. Among these, from the viewpoint of achieving both productivity and hardness, a polymerization cured product of a composition containing an ultraviolet curable polyfunctional (meth) acrylate is particularly preferable.

  It does not specifically limit as a composition containing a ultraviolet curable polyfunctional (meth) acrylate. For example, a mixture of one or more known ultraviolet curable polyfunctional (meth) acrylates, those commercially available as ultraviolet curable hard coat materials, or the range that does not impair the purpose of this embodiment other than these, What added the other component further can be used.

  The UV-curable polyfunctional (meth) acrylate is not particularly limited. For example, dipentaerythritol hexa (meth) acrylate, tetramethylolmethanetetra (meth) acrylate, tetramethylolmethanetri (meth) acrylate, (Meth) acryl derivatives of polyfunctional alcohols such as trimethylolpropane tri (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,6-bis (3-acryloyloxy-2-hydroxypropyloxy) hexane And polyethylene glycol di (meth) acrylate and urethane (meth) acrylate.

  Other components contained in the composition containing an ultraviolet curable polyfunctional (meth) acrylate are not particularly limited. Examples thereof include inorganic or organic fine particles, polymerization initiators, polymerization inhibitors, antioxidants, antistatic agents, dispersants, surfactants, light stabilizers, and leveling agents. In addition, when the film is dried after film formation in the wet coating method, an arbitrary amount of solvent can be added.

  As a method for forming the surface functional layer, when an organic material is used, a general wet coat method such as a roll coat method or a die coat method is employed. The formed hard coat layer can be subjected to a curing reaction by heating, irradiation with active energy rays such as ultraviolet rays and electron beams as necessary.

When the laminated polyester film of the present invention is used for a polarizing plate, the layer structure exemplified above is a surface functional layer / second coating layer / polyester film / first coating layer / adhesive / polarizing film / protective film. .

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measurement method and evaluation method used in the present invention are as follows.

(1) Measuring method of intrinsic viscosity of polyester 1 g of polyester from which other polymer components and pigments incompatible with polyester have been removed are precisely weighed, and 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) is added. And dissolved at 30 ° C.

(2) Measuring method of average particle size (d ₅₀ : μm) Integration (weight basis) 50 in equivalent spherical distribution measured using centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type, manufactured by Shimadzu Corporation) % Was defined as the average particle size.

(3) Method for measuring film thickness of coating layer The surface of the coating layer was dyed with RuO ₄ and embedded in an epoxy resin. Thereafter, the section prepared by ultramicrotomy stained with RuO _4, a coating layer cross-section was measured by using a TEM (Hitachi Ltd. H-7650, accelerating voltage 100 V).

(4) Adhesive evaluation method A 5 wt% aqueous solution of polyvinyl alcohol having a polymerization degree of 1000 and a saponification degree of 98.5 mol% as an adhesive was applied to the surface of the first coating layer of the laminated polyester film so that the dry film thickness was 2 μm. It dried and it was set as the adhesive bond layer. A 10 × 10 cross-cut is put on the adhesive layer, and a tape having a width of 24 mm (Cello tape (registered trademark), Elpac (registered trademark) LP-24 manufactured by Nichiban Co., Ltd.) is pasted thereon, 180 After peeling off suddenly at a peeling angle of 5 degrees, the peeled surface is observed. If the peeled area is 5% or less, ◎ if it exceeds 5% and 20% or less, ○, if it exceeds 20% and 50% or less, Δ, 50 When it exceeded%, it was set as x.

(5) Hard coat layer adhesion evaluation method (HC adhesion)
85 parts by mass of dipentaerythritol hexaacrylate, 15 parts by mass of 2-hydroxy-3-phenoxypropyl acrylate, photopolymerization initiator (trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals) on the second coating layer surface of the laminated polyester film A mixed coating solution of 200 parts by mass of methyl ethyl ketone was applied and dried so as to have a dry film thickness of 5 μm, and cured by irradiation with ultraviolet rays to form a hard coat layer. The obtained film was left in an environment of 60 ° C. and 90% RH for 50 hours. Then, a 10 × 10 cross cut was made, and a 18 mm wide tape (Cello Tape (registered trademark), Elpac (registered trademark) LP-18, manufactured by Nichiban Co., Ltd.) was applied thereon, with a 180 degree peeling angle. The peeled surface after abrupt peeling was observed, and if the peeled area was less than 5%, it was rated as ◯ if it was 5% or more but less than 20%, and × if it was 20% or more.

(6) Antiglare layer adhesion evaluation method (AG adhesion)
On the second coating layer surface of the laminated polyester film, a dry film thickness is obtained by mixing a mixed solution of 100 parts by mass of an anti-glare coating solution (Nucle Paint (registered trademark) NAG-1000, solid content concentration 50% by weight, manufactured by Nippon Paint Co., Ltd.) and 70 parts by mass of methyl ethyl ketone. It was applied and dried to a thickness of 5 μm and cured by irradiating with ultraviolet rays to form an antiglare layer. The obtained film was left in an environment of 60 ° C. and 90% RH for 50 hours. Then, a 10 × 10 cross cut was made, and a 18 mm wide tape (Cello Tape (registered trademark), Elpac (registered trademark) LP-18, manufactured by Nichiban Co., Ltd.) was applied thereon, with a 180 degree peeling angle. The peeled surface after abrupt peeling was observed, and if the peeled area was less than 5%, it was rated as ◯ if it was 5% or more but less than 20%, and × if it was 20% or more.

(7) Measurement of transmittance at a wavelength of 380 nm Using a spectrophotometer (UV-3100PC type, manufactured by Shimadzu Corporation), the scan rate is low, the sampling pitch is 2 nm, and the light transmittance is continuously measured in the wavelength range of 300 to 700 nm. The light transmittance at a wavelength of 380 nm was detected.

The polyester used in the examples and comparative examples was prepared as follows.
<Method for producing polyester (A)>
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is placed in the reactor, the reaction start temperature is set to 150 ° C., and the methanol is distilled off gradually. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.04 part by weight of ethyl acid phosphate to this reaction mixture, 0.04 part by weight of antimony trioxide was added, and a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester (A) was 0.63.

<Method for producing polyester (B)>
In the method for producing polyester (A), after adding 0.04 part by weight of ethyl acid phosphate, 0.2 part by weight of silica particles dispersed in ethylene glycol having an average particle diameter of 2 μm and 0.04 part by weight of antimony trioxide And polyester (B) was obtained using the same method as the production method of polyester (A) except that the polycondensation reaction was stopped at the time corresponding to the intrinsic viscosity of 0.65. The obtained polyester (B) had an intrinsic viscosity of 0.65.

<Method for producing polyester (C)>
Polyester (A) is subjected to a vented twin screw extruder and 2,2 ′-(1,4-phenylene) bis [4H-3,1-benzoxazin-4-one] (manufactured by CYTEC Co., Ltd.) as an ultraviolet absorber. CYASORB UV-3638 (molecular weight 369 benzoxazinone type) was supplied to a concentration of 10% by weight and melt-kneaded to form chips, thereby preparing an ultraviolet absorber master batch polyester (C). The intrinsic viscosity of the obtained polyester (C) was 0.59.

Examples of compounds constituting the coating layer are as follows.
(Example compounds)
・ Polyvinyl alcohol: (I)
Polyvinyl alcohol having a saponification degree of 88 mol% and a polymerization degree of 500

・ Oxazoline compounds: (IIA)
Acrylic polymer Epocros WS-500 (manufactured by Nippon Shokubai) having an oxazoline group and a polyalkylene oxide chain. Oxazoline group amount of about 4.5 mmol / g.
・ Oxazoline compounds: (IIB)
Oxazoline group-containing acrylic polymer Epocros WS-300 (manufactured by Nippon Shokubai). The amount of oxazoline group is about 7.7 mmol / g.

・ Isocyanate compounds: (IIIA)
158 parts by weight of hexamethylene diisocyanate trimer, 26 parts by weight of methoxypolyethylene glycol (OH value = 81 mg KOH / g), 27.8 parts by weight of diethyl diethylene glycol and 0.001 part by weight of dioctyltin laurate were reacted at 85 ° C. Thereafter, the mixture was allowed to cool, and 66 parts by weight of methyl ethyl ketone oxime was added dropwise to react. Subsequently, 115 parts by weight of 1,6-hexamethylenediol-based polycarbonate diol (OH value = 56 mgKOH / g), 1.2 parts by weight of trimethylolpropane (OH value = 1254 mgKOH / g), dimethylolpropionic acid (OH value = 837 mgKOH) / G) 7.6 parts by weight and 50 parts by weight of dimethyldipropylene glycol were added, and after stirring, 40.3 parts by weight of isophorone diisocyanate was added and reacted. After allowing to cool, 8.2 parts by weight of hexamethylene diisocyanate trimer was added, and after stirring, 5.8 parts by weight of triethylamine was added and stirred. A block isocyanate compound obtained by dropping 450 parts by weight of water into this mixed solution and dropping and stirring 21 parts by weight of a 15% aqueous diethylenetriamine solution.
・ Isocyanate compounds: (IIIB)
33.6 parts by weight of hexamethylene diisocyanate was added to 200 parts by weight of a polyester (molecular weight 2000) of bisphenol A ethylene oxide 2 mol adduct and maleic acid, and reacted at 100 ° C. for 2 hours. Then, the temperature of the system was once lowered to 50 ° C., 73 parts by weight of a 30% aqueous sodium bisulfite solution was added, the mixture was stirred at 45 ° C. for 60 minutes, and then diluted with 718 parts by weight of water.

・ Polyester resin: (IVA)
Monomer composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / 1,4-butanediol / Diethylene glycol = 56/40/4 // 70/20/10 (mol%)
・ Polyester resin: (IVB)
Aqueous dispersion of polyester resin having condensed polycyclic aromatic compound copolymerized with the following composition: Monomer composition: (acid component) 2,6-naphthalenedicarboxylic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene Glycol / diethylene glycol = 92/8 // 80/20 (mol%)

Acrylic resin: (V) Aqueous dispersion of acrylic resin polymerized with the following composition: ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylol acrylamide / acrylic acid = 65/21/10/2/2 (% by weight) Emulsion polymer (emulsifier: anionic surfactant)

-Urethane resin: (VIA)
Hydran AP-40 (manufactured by DIC), which is a carboxylic acid water-dispersed polyester polyurethane resin
-Urethane resin: (VIB)
400 parts of polycarbonate polyol composed of 1,6-hexanediol and diethyl carbonate having a number average molecular weight of 2000, 10.4 parts of neopentyl glycol, 58.4 parts of isophorone diisocyanate, and 74.3 parts of dimethylolbutanoic acid. An aqueous dispersion of urethane resin obtained by neutralizing a prepolymer with triethylamine and extending the chain with isophoronediamine.

Epoxy compound: (VIIA) Denacol EX-521 (manufactured by Nagase ChemteX), which is polyglycerol polyglycidyl ether.
Melamine compounds: (VIIB) hexamethoxymethylmelamine Particles: (VIII) Silica sol with an average particle size of 65 nm

Example 1:
A mixed raw material obtained by mixing polyester (A) and (B) at a ratio of 90% and 10%, respectively, is used as a raw material for the outermost layer (surface layer), and polyesters (A) and (C) are at a ratio of 85% and 15%, respectively. Each of the mixed raw materials is fed to two extruders as a raw material for the intermediate layer, melted at 285 ° C., and then two types and three layers (surface layer / intermediate layer / The unstretched sheet was obtained by coextrusion and cooling and solidification in the layer structure of the surface layer. Next, the film was stretched 3.4 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid A1 shown in Table 1 below was applied to one side of the longitudinally stretched film (first coating layer). The coating liquid B1 shown in Table 2 below is applied to the opposite surface (formation of the second coating layer), led to a tenter, stretched 4.3 times at 120 ° C in the transverse direction, and heat-treated at 225 ° C. Thereafter, the polyester is loosened by 2% in the lateral direction and has a thickness of 38 μm (surface layer: 4 μm, intermediate layer: 30 μm) having a first coating layer of 0.05 μm and a second coating layer of 0.10 μm (after drying). A film was obtained. When the obtained polyester film was evaluated, the adhesion of the first coating layer was good, the adhesion of the second coating layer was also good, and the transmittance at 380 nm was 4%, absorbing ultraviolet rays. It was confirmed that The properties of this film are shown in Table 3 below.

Examples 2 to 23:
In Example 1, it manufactured like Example 1 except having changed the coating composition into the coating composition shown in Table 1 and Table 2, and obtained the polyester film. The finished polyester film was as shown in Table 3.

Example 24:
A mixed raw material obtained by mixing polyester (A) and (B) at a ratio of 90% and 10%, respectively, is used as a raw material for the outermost layer (surface layer), and polyesters (A) and (C) are at a ratio of 80% and 20%, respectively. A polyester film was obtained in the same manner as in Example 1 except that the mixed raw material was used as a raw material for the intermediate layer. The completed polyester film is as shown in Table 3. Further, the transmittance at 380 nm was 1%, and it was confirmed that ultraviolet rays were absorbed.

Example 25:
A mixed raw material in which polyesters (A) and (B) are mixed at a ratio of 90% and 10%, respectively, is used as a raw material for the outermost layer (surface layer), and polyesters (A) and (C) are respectively at a ratio of 90% and 10%. A polyester film was obtained in the same manner as in Example 1 except that the mixed raw material was used as a raw material for the intermediate layer. The completed polyester film is as shown in Table 3. Further, the transmittance at 380 nm was 9%, and it was confirmed that ultraviolet rays were absorbed.

Example 26:
Example 1 except that a mixed raw material in which polyesters (A) and (B) are mixed at a ratio of 90% and 10%, respectively, is used as a raw material for the outermost layer (surface layer) and polyester (A) is used as a raw material for the intermediate layer. In the same manner, a polyester film was obtained. The finished polyester film was as shown in Table 3.

Comparative Examples 1-7:
In Example 1, it manufactured like Example 1 except having changed the coating composition into the coating composition shown in Table 1 and Table 2, and obtained the polyester film. When the completed laminated polyester film was evaluated, it was as shown in Table 4 and was poor in adhesion and adhesion.

Comparative Example 8:
In Comparative Example 1, a polyester film was obtained in the same manner as in Comparative Example 1 except that the second coating layer was not provided. When the completed laminated polyester film was evaluated, it was as shown in Table 4 and was poor in adhesion and adhesion.

  The film of the present invention can be suitably used for, for example, a protective film for a polarizing film used for a liquid crystal display and various adhesives and applications requiring good adhesion.

Claims (5)

It contains polyvinyl alcohol, an oxazoline compound, and an isocyanate compound, and the weight ratio of polyvinyl alcohol: oxazoline compound: isocyanate compound is 1.0 to 8.0: 1.0 to 8.0: 1.0 to 8 A laminated polyester film having a coating layer in the range of 0.0 on the polyester film and an adhesive layer on the coating layer. The laminated polyester film according to claim 1, wherein the polyester film contains an ultraviolet absorber. A coating layer containing at least one selected from a polyester resin, an acrylic resin, and a urethane resin is provided on the side opposite to the side having the coating layer containing the polyvinyl alcohol, the oxazoline compound, and the isocyanate compound of the polyester film. The laminated polyester film according to claim 1, wherein the laminated polyester film is provided. 4. The laminated polyester film according to claim 3, further comprising a hard coat layer or an antiglare layer on the coating layer containing at least one selected from a polyester resin, an acrylic resin, and a urethane resin. 5. The laminated polyester film according to claim 3, wherein a high refractive index material is contained in the coating layer containing at least one selected from a polyester resin, an acrylic resin, and a urethane resin.