JP2014209162A - Polarizing plate and image display device - Google Patents

Abstract

A polyester film as a protective film for a polarizer and a hard coat layer laminated on the polyester film have excellent adhesion after wet heat aging and after light irradiation, and display unevenness after wet heat aging when incorporated in an image display device. Providing a polarizing plate that is suppressed and also suppresses rainbow unevenness when incorporated in an image display device. SOLUTION: A protective film, a polarizer containing polyvinyl alcohol, a polyester film, a hard coat layer side easy-adhesion layer, and a hard coat layer in this order, the polyester film is stretched in the width direction, The width of the polyester film is 1.4 m or more, the retardation Re in the in-plane direction of the polyester film is 4000 to 20000 nm, and the maximum direction of the in-plane elastic modulus of the polyester film and the absorption axis direction of the polarizer A polarizing plate in which the corners are 90 to 25 at both ends and the center in the width direction of the polyester film, the melting sub-peak temperature Tsm of the polyester film is 140 to 220 ° C., and a belt shape. [Selection] Figure 1

Description

  The present invention relates to a polarizing plate and an image display device including a protective film in which a hard coat layer is formed on the surface of a polyester film.

  Image display devices such as liquid crystal display (LCD), plasma display (PDP), electroluminescence display (OELD or IELD), field emission display (FED), touch panel, and electronic paper have a polarizer on the display screen side of the image display panel. Further, an optical laminate having functions such as antireflection and hard coat properties is provided on the outermost surface.

  Conventionally, a film made of a cellulose ester typified by triacetyl cellulose has been used as a light-transmitting substrate of such an optical laminate. This is because the retardation value of the cellulose ester is low, so that it has little influence on the display quality of the image display device and has an appropriate water permeability. Therefore, when producing a polarizing plate using an optical laminate, a polarizer This is based on the advantage that moisture remaining in the substrate can be dried through the optical laminate. Moreover, the point that the cellulose ester film is comparatively cheap also contributes. However, the cellulose ester film is inferior in heat-and-moisture resistance, and when the hard coat film is used as a polarizing plate protective film in a high-temperature and high-humidity environment, the polarizing plate function such as a polarizing function and a hue is lowered. Therefore, there has been a problem of display unevenness after aging with wet heat when a polarizing plate using such a hard coat film as a polarizing plate protective film is incorporated in an image display device.

  From the problem of such a cellulose ester film, an attempt has been made to use a polyester film such as polyethylene terephthalate having low water permeability for the cellulose ester film. It has been difficult to see rainbow unevenness by controlling the reflectance of the surface (see Patent Document 1) and increasing the retardation more than usual by stretching in a uniaxial direction (Patent Document 2).

  On the other hand, when used as a polarizing film, adhesion to the hard coat layer and adhesion to the polarizer (polarizer) are also required. Development of an easy adhesion layer for this uniaxially stretched polyester film Is also disclosed (Patent Document 3).

Japanese Patent No. 4878582 International Publication WO2011 / 162198 Japanese Patent No. 5051328

However, according to the study by the present inventors, when the adhesiveness of the easy-adhesion layer described in Patent Document 3 was evaluated, the maximum direction of the elastic modulus of polyester and the polarizer (polarizer), which is an actual configuration using a polarizing plate. It has been found that when the stretching direction of the film is greatly deviated from the orthogonal direction, the strain generated when the polarizing plate is cut increases, and the adhesion of the polyester film to the hard coat layer after wet heat aging is poor.
In particular, since a polyester film having a large retardation is difficult to determine the orientation axis in the width direction in a uniform direction in the process of roll-to-roll production, it is a belt-shaped (synonymous with a long length) bonded to a polarizer. When cut from the state in accordance with the form of use, some variation occurs between the absorption axis and transmission axis of the polarizer and the orientation axis of the polyester film.

  The problem to be solved by the present invention is that the adhesion between the polyester film and the hard coat layer is excellent even if there is a slight deviation from the direction in which the orientation axis of the polyester film and the absorption axis or transmission axis of the polarizer are determined. Another object of the present invention is to provide a polarizing plate in which display unevenness after wet heat aging when incorporated in an image display device is suppressed and rainbow unevenness when incorporated in an image display device is also suppressed.

As a result of intensive studies by the present inventors in order to solve the above problems, it is possible to suppress rainbow unevenness due to large in-plane retardation, and with a hard coat layer that can suppress display unevenness after aging due to material properties. Even when the polyester film is used with a film width greater than a specific width, the orientation axis and the absorption axis or transmission axis direction of the polarizer are slightly displaced from the determined direction, It has been found that all the above problems can be solved by controlling the melting sub-peak temperature Tsm to a specific range.
That is, the present invention which is a specific means for solving the above problems is as follows.

[1] a protective film;
A polarizer disposed on the protective film and comprising polyvinyl alcohol;
A polyester film disposed on a polarizer;
Hard coat layer side easy adhesion layer arranged on the polyester film,
A hard coat layer disposed on the hard coat layer side easy-adhesion layer,
The polyester film is stretched in the width direction,
The width of the polyester film is 1.4 m or more,
The in-plane direction retardation Re of the polyester film is 4000-20000 nm,
The angle formed by the maximum direction of the elastic modulus in the plane of the polyester film and the absorption axis direction of the polarizer is 90 ° ± 25 ° at both ends and the center in the width direction of the polyester film,
The melting sub-peak temperature Tsm of the polyester film is 140 to 220 ° C.,
A polarizing plate characterized by being strip-shaped.
[2] The polarizing plate according to [1] is preferably formed by uniaxially stretching a polyester film in the width direction.
[3] In the polarizing plate according to [1] or [2], it is preferable that the hard coat layer-side easy-adhesion layer contains at least one selected from a polyester resin, an acrylic resin, and a urethane resin.
[4] The polarizing plate according to any one of [1] to [3] preferably has a light transmittance of 15% or less at a wavelength of 380 nm of the polyester film.
[5] In the polarizing plate according to any one of [1] to [4], it is preferable that the hard coat layer-side easy-adhesion layer contains an ultraviolet absorber.
[6] In the polarizing plate according to any one of [1] to [5], the polyester film preferably contains an ultraviolet absorber.
[7] In the polarizing plate according to any one of [1] to [6], it is preferable that the hard coat layer-side easy-adhesion layer contains rutile-type titanium oxide fine particles.
[8] In the polarizing plate according to any one of [1] to [7], the hard coat layer-side easy-adhesion layer preferably contains an antioxidant.
[9] In the polarizing plate according to any one of [1] to [8], the hard coat layer-side easy-adhesion layer preferably contains an aliphatic polyester.
[10] In the polarizing plate according to any one of [1] to [9], the hard coat layer preferably contains an acrylate.
[11] The polarizing plate according to any one of [1] to [10] is preferably formed by coating a hard coat layer.
[12] In the polarizing plate according to any one of [1] to [11], a polarizer-side easy-adhesion layer is preferably disposed between the polarizer and the polyester film.
[13] An image display device comprising the polarizing plate according to any one of [1] to [12].

  According to the present invention, the adhesion after the wet heat aging of the polyester film as the protective film of the polarizer and the hard coat layer laminated on the polyester film is excellent, and the display unevenness after the wet heat aging when incorporated in the image display device. It is possible to provide a polarizing plate that is suppressed and also suppresses rainbow unevenness when incorporated in an image display device.

It is the schematic which shows the cross section of an example of the polarizing plate of this invention.

[Polarizer]
The polarizing plate of the present invention is a protective film, a polarizer disposed on the protective film and containing polyvinyl alcohol, a polyester film disposed on the polarizer, and a hard coat layer side easy adhesion disposed on the polyester film. The polyester film is stretched in the width direction, the width of the polyester film is 1.4 m or more, and the surface of the polyester film The retardation Re in the inward direction is 4000 to 20000 nm, and the angle formed by the maximum in-plane elastic modulus direction of the polyester film and the absorption axis direction of the polarizer is 90 ° at both the end and center in the width direction of the polyester film. It is ± 25 °, and the melting sub-peak temperature Tsm of the polyester film is 140 to 220 ° C. It is characterized in.
With such a configuration, the polarizing plate of the present invention has excellent adhesion after wet heat aging between the polyester film as the protective film of the polarizer and the hard coat layer laminated on the polyester film, and is incorporated into an image display device. Display unevenness after wet heat aging is suppressed, and rainbow unevenness when incorporated in an image display device is also suppressed.

<Configuration>
First, the structure of the polarizing plate of this invention is demonstrated based on drawing.
The polarizing plate of the present invention shown in FIG. 1 includes a polarizer 1 containing polyvinyl alcohol, a stretched polyester film 2 laminated on one side of the polarizer 1, and a hard coat layer side disposed on the polyester film 2. The hard coat layer 4 is provided on the easy adhesive layer 3b and the hard coat layer side easy adhesive layer 3b.
In the polarizing plate of the present invention, it is preferable that a polarizer-side easy-adhesion layer 3 a is disposed between the polarizer 1 and the polyester film 2, that is, the polyester film 2 is disposed on the polarizer 1 on the polarizer side. It is preferable to laminate via the easy adhesion layer 3a.
Further, the polarizing plate of the present invention is a protective film 10 laminated on the surface of the polarizer 1 opposite to the surface on which the stretched polyester film 2 is laminated via another easy adhesion layer (not shown). An optical compensation film (not shown) may be provided.

  The polarizing plate of the present invention has a strip shape. In the present specification, a belt-like shape is almost synonymous with a long shape, that is, a continuous film of several thousand meters. The polarizing plate of the present invention has an effect of obtaining a polarizing plate that can be continuously produced at a high speed and has a stable quality by being strip-shaped.

  Hereinafter, a preferable aspect is demonstrated about each member which comprises the polarizing plate of this invention, those manufacturing methods, etc.

<Polarizer>
The polarizer used in the present invention contains polyvinyl alcohol and is preferably made of polyvinyl alcohol. Although there is no restriction | limiting in particular as a manufacturing method of the said polarizer, Usually, the process of uniaxially stretching a polyvinyl alcohol-type resin film by a well-known method, and dyeing a polyvinyl alcohol-type resin film with a dichroic dye, dichroism It is manufactured through a step of adsorbing a dye, a step of treating a polyvinyl alcohol-based resin film adsorbed with a dichroic dye with an aqueous boric acid solution, and a step of washing with water after the treatment with an aqueous boric acid solution.

<Polyester film>
The polyester film used in the present invention is disposed on a polarizer and stretched in the width direction, the width is 1.4 m or more, the in-plane retardation Re is 4000 to 20000 nm, and the melting subpeak temperature Tsm. Is 140-220 ° C.
The polyester film used as the protective film for the polarizer is a film mainly composed of polyester, and may be a single layer film mainly composed of polyester, or a multilayer film having a layer mainly composed of polyester. It may be. Moreover, the surface treatment may be performed on both surfaces or one surface of these single layer films or multilayer films, and this surface treatment is performed by corona treatment, saponification treatment, heat treatment, ultraviolet irradiation, electron beam irradiation, or the like. Modification may be sufficient, and thin film formation by application | coating, vapor deposition, etc. of a polymer, a metal, etc. may be sufficient. The mass ratio of the polyester to the whole polyester film is usually 50 mass% or more, preferably 70 mass% or more, more preferably 90 mass% or more.

  Examples of the polyester include polyethylene terephthalate, polyethylene isophthalate, polyethylene 2,6-naphthalate, polybutylene terephthalate, and 1,4-cyclohexanedimethylene terephthalate, and two or more of them may be used as necessary. . Of these, polyethylene terephthalate is preferably used.

  Polyethylene terephthalate is a polyester having a structural unit derived from terephthalic acid as a dicarboxylic acid component and a structural unit derived from ethylene glycol as a diol component, and 80 mol% or more of all repeating units are preferably ethylene terephthalate. The structural unit derived from other copolymerization components may be included. Other copolymer components include isophthalic acid, p-β-oxyethoxybenzoic acid, 4,4′-dicarboxydiphenyl, 4,4′-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid , Dicarboxylic acid components such as sebacic acid, 5-sodium sulfoisophthalic acid, 1,4-dicarboxycyclohexane, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, bisphenol A ethylene oxide adduct, polyethylene glycol And diol components such as polypropylene glycol and polytetramethylene glycol. These dicarboxylic acid components and diol components can be used in combination of two or more if necessary. It is also possible to use an oxycarboxylic acid such as p-oxybenzoic acid in combination with the carboxylic acid component or diol component. As another copolymer component, a dicarboxylic acid component and / or a diol component containing a small amount of an amide bond, a urethane bond, an ether bond, a carbonate bond, or the like may be used. Polyethylene terephthalate can be produced by a direct polymerization method in which terephthalic acid and ethylene glycol and, if necessary, other dicarboxylic acid and / or other diol are directly reacted, dimethyl ester of terephthalic acid and ethylene glycol, and necessary Depending on the above, any production method such as a so-called transesterification method in which a dimethyl ester of another dicarboxylic acid and / or another diol is transesterified can be applied.

<Optical properties of polyester film>
The in-plane direction retardation Re (phase difference value) of the stretched polyester film is 4000 to 20000 nm, more preferably 5000 nm to 15000 nm. By setting the in-plane retardation value to 4000 nm or more, coloring from the front tends to be inconspicuous. The in-plane retardation value Re of the stretched polyester film is represented by the following formula (1).

Re = (na−nb) × d (1)
Here, na is the refractive index in the in-plane slow axis direction of the stretched polyester film, and nb is the in-plane fast axis direction (the direction perpendicular to the in-plane slow axis direction) of the stretched polyester film. , D is the thickness of the stretched polyester film.

  The retardation Rth in the thickness direction of the polyester film is preferably 4000 to 20000 nm, more preferably 5000 to 15000 nm, and particularly preferably 6000 to 15000 nm. In addition, retardation Rth of the thickness direction of a polyester film is represented by the method as described in the below-mentioned Example.

  The thickness of the polyester film thus obtained is preferably 20 to 100 μm, and more preferably 30 to 70 μm. When the thickness of the polyester film is less than 20 μm, handling tends to be difficult, and when the thickness exceeds 100 μm, the merit of thinning tends to be reduced.

<Physical properties of polyester film>
The polyester film has a melting sub-peak temperature (Tsm) of 140 to 220 ° C., preferably 150 ° C. or higher and lower than 220 ° C., more preferably 150 ° C. or higher and lower than 210 ° C., further preferably 150 ° C. or lower and 200 ° C. It is as follows. When the melting sub-peak temperature is 140 ° C. or higher, the thermal dimensional change (150 ° C., 30 minutes) is improved, and the hard coat layer is hardly cracked. On the other hand, when the temperature is 220 ° C. or less, the deviation between the maximum elastic modulus at the end and the stretching direction of the polarizer can be prevented from exceeding an allowable range.
Although there is no restriction | limiting in particular in order to obtain the polyester film which satisfies the conditions of this melting subpeak temperature, For example, it can obtain by manufacturing a film on the extending | stretching conditions shown to the manufacturing method of the below-mentioned polyester film.

<Other compounds in polyester>
The polyester film may be blended with known additives as necessary. Examples thereof include ultraviolet absorbers, particles, lubricants, antiblocking agents, heat stabilizers, antioxidants, antistatic agents, and light resistance. Agents, impact modifiers, lubricants, dyes, pigments and the like. However, when a polyester film is used as a base film for an antiglare film, transparency is generally required, so it is preferable to keep the additive amount to a minimum.

(UV absorber (for support))
In order to prevent the liquid crystal of the liquid crystal display from being deteriorated by ultraviolet rays, the polyester film may contain an ultraviolet absorber. 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.

  Moreover, as a commercial item, the said benzotriazole type | system | group ultraviolet absorber can be mentioned, for example, It can use as an emulsifier as needed or disperse | distributed to water as it is. In addition, New Coat UVA-204W (trade name, manufactured by Shin-Nakamura Chemical Co., Ltd.), SE-2538E (trade name, manufactured by Taisei Fine Chemical Co., Ltd.) and the like can be exemplified as water-based benzotriazole ultraviolet absorbers.

  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 '-(1,4-phenylene) bis [4H-3,1-benzoxazin-4-one] [In addition, 2,2'-p- Phenylenebis (3,1-benzoxazin-4-one)], 2,2′-m-phenylenebis (3,1-benzoxazin-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-benzoxazine-4 -One), 2,2 '-(2-chloro-p-phenylene) bis (3 , 1-benzoxazin-4-one), 2,2 ′-(1,4-cyclohexylene) bis (3,1-benzoxazin-4-one), 1,3,5-tri (3,1- Benzoxazin-4-on-2-yl) benzene, 1,3,5-tri (3,1-benzoxazin-4-on-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-dio 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-benzoxazin-4-one), 6,6′-bis (2- Phenyl-4H, 3,1-benzoxazin-4-one), 6,6′-methylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-methylenebis (2- Phenyl-4H, 3,1-benzoxazin-4-one), 6,6′-ethylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-ethylenebis ( 2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6′- Tylene bis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-butylene bis (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'-carbonylbis (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′-carbonyl Bis (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-benzoxazine-4 ON, 6,7′-methylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,7′-methylenebis (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 general formula (1), 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. Absent.

  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 general formula (1), 2,2 ′-(1,4-phenylene) bis [4H-3,1-benzoxazin-4-one] is particularly preferable in the present invention.

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

  Further, in the case of a polyester film having a multilayer structure, a film having at least a three-layer structure is preferable, 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.

  If the polyester film prevents the deterioration of the liquid crystal due to ultraviolet rays, as a guide, the light transmittance of the polyester film at a wavelength of 380 nm is preferably 15% or less, more preferably 10% or less, and still more preferably. 5% or less.

(particle)
The polyester film is preferably blended with particles mainly for the purpose of imparting easy slipping 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 of the particles include magnesium, kaolin, aluminum oxide, and titanium oxide. Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like. Furthermore, it is also possible to use precipitated particles in which a part of a metal compound such as a catalyst is precipitated and finely dispersed during the polyester film manufacturing process.

  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 0.01-3 micrometers normally, Preferably it is the range of 0.1-2 micrometers. If the average particle size is less than 0.01 μm, sufficient slipperiness cannot be imparted, or the particles may aggregate, resulting in insufficient dispersibility, which may reduce the transparency of the polyester film. . On the other hand, when the thickness exceeds 3 μm, the surface roughness of the polyester film becomes too rough, and a problem may occur when a functional layer such as a prism layer or a light diffusion layer is formed in a subsequent process.

  Furthermore, the particle content in the polyester film is usually in the range of 0.001 to 5 mass%, preferably 0.005 to 3 mass%. When the particle content is less than 0.001% by mass, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 5% by mass, the transparency of the polyester film is insufficient. There are cases.

  The method for adding particles to the polyester film is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for 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.

  Further, in order to impart haze to the polyester film, inorganic fine particles or organic fine particles may be blended in the polyester film. Inorganic fine particles include calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, silica, glass, talc, mica, white carbon, magnesium oxide, zinc oxide, and other inorganic particles, and these inorganic particles are surface treated with fatty acids. What has been applied can be cited as a representative one. The organic fine particles include melamine beads (refractive index 1.57), polymethyl methacrylate beads (refractive index 1.49), methyl methacrylate / styrene copolymer resin beads (refractive index 1.50 to 1.59). ), Polycarbonate beads (refractive index 1.55), polyethylene beads (refractive index 1.53), polyvinyl chloride beads (refractive index 1.46), silicone resin beads (refractive index 1.46) and the like are used. be able to.

<Method for producing polyester film>
Since the polyester film is stretched in the width direction, the polyester film production method is not particularly limited except for stretching in the width direction. In order to impart the above properties to the polyester film, it is preferably produced by the following method.
First, a polyester resin is melt-extruded into a film, cooled and solidified with a casting drum to form an unstretched polyester film, and if necessary, a coating solution for forming an easy-adhesion layer is applied, and this unstretched polyester film Is preferably stretched 3 to 10 times, preferably 3 to 7 times in the width direction at a temperature of Tg to (Tg + 60) ° C. of the polyester film. The polyester film is preferably uniaxially stretched in the width direction from the viewpoint of greatly expressing in-plane retardation Re.

  Next, it is preferable to perform heat treatment (referred to as heat setting here) at 140 ° C. or higher and 220 ° C. or lower for 1 to 60 seconds. The heat setting temperature is more preferably 150 ° C. or higher and 220 ° C. or lower, and particularly preferably 150 ° C. or higher and lower than 220 ° C.

  Furthermore, it is preferable to perform reheat treatment (referred to as relaxation treatment) while shrinking 0 to 20% in the longitudinal direction and / or the width direction at a temperature 10 to 20 ° C. lower than the heat setting temperature. In this method, since the film is less likely to come into contact with the roll, minute scratches and the like are less likely to occur on the film surface than in the method described above, which is advantageous for application to optical applications. The glass transition temperature of the film is expressed as Tg. When the heat setting temperature is 150 ° C. or more and less than 220 ° C., the deviation in the orientation direction of the polyester is reduced and the thermal dimensional change is also reduced, so that the hard coat layer is not easily peeled off or cracked.

When an unstretched polyester film is stretched in the width direction and heat-set, a bowing phenomenon that deforms in a bow shape in the film longitudinal direction occurs. Due to this bowing phenomenon, the stretched polyester film is displaced in the alignment direction between the central portion and the end portion in the width direction.
In the polyester film having a width of 1.4 m or more after stretching, the bowing phenomenon is remarkable, but the polyester film suppresses the thermal dimensional change by controlling the melting sub-peak temperature within the above-mentioned value range. .
In addition, although the upper limit of the width | variety after extending | stretching the said polyester film does not have a restriction | limiting in particular, For example, it can be 6 m or less in width.

In the polarizing plate of the present invention, the angle formed by the maximum direction of the elastic modulus in the plane of the polyester film and the absorption axis direction of the polyvinyl alcohol polarizer (generally the same as the stretching direction) is the end and center in the width direction of the polyester film. Is within 90 ° ± 25 °, so that the distortion caused by the angle between the orientation direction of the polyester film and the stretching direction of the polarizer is suppressed by the polyester film, so that the wet heat with the hard coat layer formed on the polyester film It becomes possible to obtain adhesion after aging.
The angle formed between the maximum in-plane elastic modulus direction of the polyester film and the absorption axis direction of the polarizer is more preferably 90 ° ± 20 °, and particularly preferably 90 ° ± 5 °.

<Hard coat layer>
The hard coat layer is provided on the surface of the polyester film in order to impart physical strength.

The polarizing plate of the present invention preferably has a hard coat layer formed by coating.
The hard coat layer is preferably formed using a composition for a hard coat layer containing an ionizing radiation curable resin which is a resin curable by ultraviolet rays and a photopolymerization initiator.

(resin)
Examples of the ionizing radiation curable resin include a compound having one or more unsaturated bonds such as a compound having an acrylate functional group, and the polarizing plate of the present invention has an acrylate hard coat layer. It is preferable from the viewpoint of improving the adhesion between the polyester film as the protective film for the polarizer and the hard coat layer laminated on the polyester film after wet heat aging. Examples of the compound having one unsaturated bond include ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, methylstyrene, N-vinylpyrrolidone and the like. Examples of the compound having two or more unsaturated bonds include polymethylolpropane tri (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (Meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and the like, and ethylene oxide ( A polyfunctional compound modified with EEO), or a reaction product of the polyfunctional compound and (meth) acrylate (for example, poly (meth) acrylate ester of polyhydric alcohol). It is possible. In the present specification, “(meth) acrylate” refers to methacrylate and acrylate.

  In addition to the above compounds, polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyds having a relatively low molecular weight (number average molecular weight of 300 to 80,000, preferably 400 to 5000) having an unsaturated double bond. Resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins, and the like can also be used as the ionizing radiation curable resin. The resin in this case includes all dimers, oligomers, and polymers other than monomers.

Preferred compounds as the acrylate include compounds having 3 or more unsaturated bonds. When such a compound is used, the crosslink density of the hard coat layer to be formed can be increased, and the coating hardness can be improved.
Specifically, in the present invention, pentaerythritol triacrylate, pentaerythritol tetraacrylate, polyester polyfunctional acrylate oligomer (3 to 15 functional), urethane polyfunctional acrylate oligomer (3 to 15 functional) and the like are used in appropriate combination. Is preferred.

  The ionizing radiation curable resin is used in combination with a solvent-drying resin (a thermoplastic resin or the like, which is a resin that forms a film only by drying the solvent added to adjust the solid content during coating). You can also. By using a solvent-drying resin in combination, coating defects on the coated surface can be effectively prevented. The solvent-drying resin that can be used in combination with the ionizing radiation curable resin is not particularly limited, and a thermoplastic resin can be generally used.

  The thermoplastic resin is not particularly limited. For example, a styrene resin, a (meth) acrylic resin, a vinyl acetate resin, a vinyl ether resin, a halogen-containing resin, an alicyclic olefin resin, a polycarbonate resin, or a polyester resin. Examples thereof include resins, polyamide-based resins, cellulose derivatives, silicone-based resins, rubbers, and elastomers. The thermoplastic resin is preferably amorphous and soluble in an organic solvent (particularly a common solvent capable of dissolving a plurality of polymers and curable compounds). In particular, from the viewpoints of film forming properties, transparency, and weather resistance, styrene resins, (meth) acrylic resins, alicyclic olefin resins, polyester resins, cellulose derivatives (cellulose esters, etc.) and the like are preferable.

Moreover, the said composition for hard-coat layers may contain the thermosetting resin.
The thermosetting resin is not particularly limited. For example, phenol resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, unsaturated polyester resin, polyurethane resin, epoxy resin, aminoalkyd resin, melamine-urea cocondensation Examples thereof include resins, silicon resins, polysiloxane resins, and the like.

(Photopolymerization initiator)
The photopolymerization initiator is not particularly limited, and known ones can be used. For example, specific examples of the photopolymerization initiator include acetophenones, benzophenones, Michler benzoylbenzoate, α-amylo. Examples include oxime esters, thioxanthones, propiophenones, benzyls, benzoins, and acylphosphine oxides. In addition, it is preferable to use a mixture of photosensitizers, and specific examples thereof include n-butylamine, triethylamine, poly-n-butylphosphine, and the like.

  As the photopolymerization initiator, when the ionizing radiation curable resin is a resin system having a radical polymerizable unsaturated group, acetophenones, benzophenones, thioxanthones, benzoin, benzoin methyl ether, etc. may be used alone or in combination. It is preferable to use it. When the ionizing radiation curable resin is a resin system having a cationic polymerizable functional group, the photopolymerization initiator may be an aromatic diazonium salt, aromatic sulfonium salt, aromatic iodonium salt, metallocene compound, benzoin sulfone. It is preferable to use acid esters alone or as a mixture.

  As the photopolymerization initiator, in the case of an ionizing radiation curable resin having a radical polymerizable unsaturated group, 1-hydroxy-cyclohexyl-phenyl-ketone is compatible with the ionizing radiation curable resin, and yellowing is also caused. It is preferable for the reason that there are few.

  The content of the photopolymerization initiator in the hard coat layer composition is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the ionizing radiation curable resin. If it is less than 1 part by mass, the hardness of the hard coat layer in the optical laminate of the first invention may not be in the above-described range, and if it exceeds 10 parts by mass, up to the deep part of the coated film. This is because the ionizing radiation does not reach and internal curing is not promoted, and there is a risk that the pencil hardness of 3H or higher on the surface of the target hard coat layer may not be obtained.

  The minimum with more preferable content of the said photoinitiator is 2 mass parts, and a more preferable upper limit is 8 mass parts. When the content of the photopolymerization initiator is in this range, a hardness distribution does not occur in the film thickness direction, and uniform hardness is likely to occur.

(particle)
The hard coat layer can also serve as an antiglare layer (described later) provided with particles having an average particle size of 0.2 to 10 μm to provide an antiglare function (antiglare function).

(Characteristics of hard coat layer)
The film thickness of the hard coat layer can be appropriately designed depending on the application. The film thickness of the hard coat layer is preferably 0.2 to 10 μm, more preferably 0.5 to 7 μm.

  The hardness of the hard coat layer is preferably H or more, more preferably 2H or more, and most preferably 3H or more in a pencil hardness test according to JIS K-5400. Alternatively, the scratch resistance of the docoat layer is preferably as the wear amount of the test piece provided with the hard coat layer before and after the test is smaller in the Taber test according to JIS K-5400.

<Easily adhesive layer>
《Hard coat layer side easy adhesion layer》
The hard coat layer side easy-adhesion layer in the present invention has improved adhesion to various surface functional layers, and when used as a protective film on the front side of the front side polarizing plate, for example, the front side of a polyester film A hard coat layer, an antiglare layer, or the like can be effectively formed on the side opposite to the side where the polarizing film is bonded.

(resin)
In the polarizing plate of the present invention, the hard coat layer side easy-adhesion layer contains at least one selected from polyester resin, acrylic resin and urethane resin, and is laminated on a polyester film and a polyester film as a protective film for a polarizer. From the viewpoint of improving the adhesion of the coat layer with time after wet heat, it is preferable.
Moreover, it is more preferable that the hard-coat layer side easily bonding layer contains 2 or more types chosen from a polyester resin, an acrylic resin, and a urethane resin.

(1) Polyester resin The polyester resin used for the hard-coat layer side easily bonding layer in this invention consists of the following polyvalent carboxylic acid and a polyvalent hydroxy compound as main structural components, for example. 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-sodium sulfoterephthalic acid, 2-potassium sulfoterephthalic acid, 4-sodium sulfoisophthalic acid, 4-potassium sulfoisophthalic acid , 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutaric acid, succinic acid, trimellitic acid, trimesic acid, pyromellitic acid, trimellitic anhydride , Pyromellitic anhydride, phthalic anhydride, p -Hydroxybenzoic acid, trimellitic acid monopotassium salt and ester-forming derivatives thereof can be used. Examples of the polyvalent hydroxy compound include ethylene glycol, 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, Methylol - trimethylolpropane, sodium dimethylol ethyl sulfonate, potassium dimethylol ethyl sulfonate, dimethylol - potassium Rupuropion acid 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.

(1 ') Aliphatic polyester for hard coat layer side easy-adhesion layer As polyester for hard coat layer side easy adhesion layer, it is a polyester film as a protective film of a polarizer to use aliphatic polyester among the above-mentioned polyester resins. From the viewpoint of improving the adhesion between the hard coat layer laminated on the polyester film and the time after wet heat and the light resistance of the adhesion of the hard coat layer, alicyclic polyester is more preferred. The alicyclic polyester is composed of an alicyclic dicarboxylic acid as a main dicarboxylic acid component and an alicyclic diol as a main diol component.

(1′-1) Alicyclic dicarboxylic acid The alicyclic polyester is composed of an alicyclic dicarboxylic acid as a main dicarboxylic acid component. Here, the main dicarboxylic acid component means 80 mol% or more, preferably 90 mol% or more per total dicarboxylic acid component. Within this range, an easy-adhesion layer excellent in both heat resistance can be obtained.

  The alicyclic dicarboxylic acid is one in which two carboxyl groups are bonded to the alicyclic structure. Specifically, for example, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,4-decahydronaphthalenedicarboxylic acid, 1,5-decahydronaphthalenedicarboxylic acid 2,6-decahydronaphthalenedicarboxylic acid and 2,7-decahydronaphthalenedicarboxylic acid. Among these, 1,4-cyclohexanedicarboxylic acid is preferable because the molding temperature of the obtained polyester is close to the molding temperature of the conventional polyester and is easily available industrially. 1,4-Cyclohexanedicarboxylic acid has a trans form and a cis form as isomers, but the ratio of the trans form of 1,4-cyclohexanedicarboxylic acid to the cis form is preferably 80 from the viewpoint of heat resistance of the obtained polyester. / 20 to 100/0, more preferably 85/15 to 100/0, and particularly preferably 90/10 to 100/0.

  In addition to the alicyclic carboxylic acid, the alicyclic polyester may contain an aromatic dicarboxylic acid and / or an aliphatic dicarboxylic acid at a ratio of 20 mol% or less per total dicarboxylic acid component.

  Specific examples of the aromatic dicarboxylic acid include terephthalic acid, phthalic acid, isophthalic acid, phenylenedioxycarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, and 4,4′-diphenyl. Examples thereof include ketone dicarboxylic acid, 4,4′-diphenoxyethanedicarboxylic acid, 4,4′-diphenylsulfone dicarboxylic acid, and 2,6-naphthalenedicarboxylic acid. Specific examples of the aliphatic dicarboxylic acid include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecadicarboxylic acid, and dodecadicarboxylic acid.

(1′-2) Diol Component The alicyclic polyester is composed of an alicyclic diol as a main diol component. Here, the main diol component means 80 mol% or more, preferably 90 mol% or more, more preferably 95 mol% or more, particularly preferably 97 mol% or more, based on the total diol component. Within this range, an easy-adhesion layer excellent in both transparency and heat resistance can be obtained.

  As an alicyclic diol, two hydroxy groups are bonded to an alicyclic structure, and an alicyclic diol in which two hydroxyl groups are bonded to a five-membered or six-membered ring is preferable. When the alicyclic diol is a 5-membered or 6-membered alicyclic diol, the heat resistance of the resulting polyester can be improved.

  Examples of the 5-membered alicyclic diol include 1,2-cyclopentanedimethanol, 1,3-cyclopentanedimethanol, bis (hydroxymethyl) tricyclo, and [5.2.1.0] decane. be able to.

  Examples of the 6-membered alicyclic diol include 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, Mention may be made of 6-membered ring diols such as 1,4-cyclohexanedimethanol and 2,2-bis (4-hydroxycyclohexyl) -propane.

  Among these alicyclic diols, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol are preferable, and 1,4-cyclohexanedimethanol is particularly preferable. 1,4-Cyclohexanedimethanol is highly reactive because the methylol group is in the para position, it is easy to obtain a polyester with a high polymerization degree, a polyester with a high glass transition temperature is obtained, and it is an industrial product and is available. This is because there is an advantage that it is easy. 1,4-Cyclohexanedimethanol has a trans isomer and a cis isomer, and a molar ratio of the trans isomer to the cis isomer is preferably in the range of 60/40 to 100/0.

  Examples of the diol component other than the alicyclic diol constituting the alicyclic polyester include aliphatic diols such as ethylene glycol, propylene glycol, butanediol, pentanediol, and hexanediol.

  In the alicyclic polyester, it is preferable that 80 mol% or more of the dicarboxylic acid component is occupied by the alicyclic dicarboxylic acid and 80 mol% or more of the diol component is occupied by the alicyclic diol. The alicyclic dicarboxylic acid of the alicyclic polyester is preferably cyclohexane dicarboxylic acid, and the alicyclic diol is preferably cyclohexane dimethanol. The most preferred alicyclic polyester is an alicyclic polyester in which 80 mol% or more of the dicarboxylic acid component is occupied by cyclohexanedicarboxylic acid and 80 mol% or more of the diol component is occupied by cyclohexanedimethanol.

(2) Acrylic resin The acrylic resin used for the hard coat layer side easy-adhesion layer in the present invention is a polymerizable monomer having a carbon-carbon double bond, as typified by an acrylic or methacrylic monomer. It is the polymer which becomes. 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.

  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-methylolacrylamide or (meth) acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene, vinyl propionate Various vinyl esters such as: Various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, etc .; Phosphorus-containing vinyl monomers; Various such as vinyl chloride and biridene chloride And various conjugated dienes such as butadiene.

(3) Urethane resin As the urethane resin used for the hard coat layer side easy-adhesion layer in the present invention, various urethane resins described in the polarizer-side easy adhesive layer described later can be used.

  In the present invention, the total content of the polyester resin, acrylic resin, and urethane resin in the hard coat layer side easy-adhesion layer is usually 10% by mass or more, preferably 30 to 95% by mass, and more preferably 40 to 95%. It is the range of mass%. When the amount is less than 10% by mass, sufficient adhesion to a hard coat layer or a surface functional layer such as an antiglare layer described later may not be obtained.

(4) Other binder polymers In the present invention, the hard coat layer-side easy-adhesion layer can be used in combination with a binder polymer other than polyester resin, acrylic resin or urethane resin in order to improve the coating surface state and transparency. It is.

  Specific examples of the binder polymer include polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches and the like.

(Crosslinking agent)
Furthermore, in the hard coat layer side easy-adhesion layer, a crosslinking agent can be used in combination as long as the gist of the present invention is not impaired. By using a cross-linking agent, the easy-adhesion layer becomes stronger, so that the moisture and heat 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.

(particle)
The hard coat layer side easy-adhesion layer may contain particles for the purpose of improving the blocking property and slipperiness of the easy-adhesion layer, such as inorganic particles such as silica, alumina, metal oxide, or crosslinked polymer particles. Organic particles such as

(UV absorber for hard coat layer side easy adhesion layer)
In the polarizing plate of the present invention, the hard coat layer-side easy-adhesion layer contains an ultraviolet absorber, and the adhesion between the polyester film as a polarizer protective film and the hard coat layer laminated on the polyester film after wet heat aging From the viewpoints of improving and improving the light resistance of the adhesion of the hard coat layer, it is preferable.
Examples of the UV absorber for the hard coat layer side easy-adhesion layer include benzotriazole-based UV absorbers, triazine-based UV absorbers, and benzophenone-based UV absorbers.

  As a benzotriazole type ultraviolet absorber, the said benzotriazole type ultraviolet absorber can be mentioned as a commercial item, for example, It can be used as it is disperse | distributed to water as it is, using an emulsifier as needed. In addition, New Coat UVA-204W (trade name, manufactured by Shin-Nakamura Chemical Co., Ltd.), SE-2538E (trade name, manufactured by Taisei Fine Chemical Co., Ltd.) and the like can be exemplified as water-based benzotriazole ultraviolet absorbers.

  Examples of the triazine-based ultraviolet absorber include the above-mentioned triazine-based ultraviolet absorber, and the triazine-based ultraviolet absorber can be used by using an emulsifier as needed or dispersed in water as it is. In addition, TINUVIN477-DW (trade name, manufactured by BASF Japan), Shine Guard TA-22 (trade name, manufactured by Senka), and the like can be given.

  As the benzophenone-based ultraviolet absorber, the benzophenone-based ultraviolet absorber can be used by using an emulsifier as needed or dispersed in an aqueous solvent as it is. As the aqueous medium, water or a mixed solvent of water and a water-soluble organic solvent such as alcohol can be used. In the case of using a mixed solvent of water and a water-soluble organic solvent, the ratio of the water-soluble organic solvent is preferably 10% by mass or less based on the entire aqueous medium. The usage-amount of a ultraviolet absorber is 5-25 mass% of a normal composition normally in conversion of solid content, Preferably it is 5-20 mass%.

(Material for adjusting the refractive index)
Furthermore, when a clear surface functional layer such as a hard coat layer is formed in the hard coat layer side easy-adhesion layer, a material that adjusts the refractive index is used in order to reduce interference unevenness due to external light. It is also possible. 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 metal compounds described above, in the polarizing plate of the present invention, it is preferable that the hard coat layer-side easy-adhesion layer contains rutile-type titanium oxide fine particles described later.
Among the organic compounds having the metal element, an organic compound having a titanium element or a zirconium element is preferable in terms of particularly good coatability and transparency, and more preferably water-soluble when considering application to in-line coating. Titanium chelate compounds, water-soluble zirconium chelate compounds and the like are preferably used.

  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 polyester resin, acrylic resin, or urethane fat contained in the hard coat layer-side easy-adhesion layer. Among these, polyester resins can easily use many aromatic compounds because of their structures. Among the aromatic compounds, naphthalene rings and bisphenol A compounds are useful because they can efficiently increase the refractive index of the easily adhesive 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.

In the polarizing plate of the present invention, the hard coat layer-side easy-adhesion layer contains rutile-type titanium oxide fine particles as described above, and a hard coat layer laminated on a polyester film as a polarizer protective film and a polyester film From the viewpoints of improving the adhesiveness of the film after wet heat and improving the light resistance of the adhesiveness of the hard coat layer.
In the present invention, the crystal system of the titanium oxide fine particles is preferably a rutile type. When the titanium oxide fine particles are of a crystal system other than the rutile type, such as an anatase type, the light resistance against external light is deteriorated. The crystal system of titanium oxide is measured using an X-ray diffractometer. When the titanium oxide fine particles are composed of a plurality of crystal systems, the case where the rutile type peak intensity ratio exceeds 50%, preferably 60%, is regarded as the rutile type titanium oxide fine particles.

  The content of the rutile-type titanium oxide fine particles in the easy adhesion layer is, for example, 0.5 to 75% by mass, preferably 0.5 to 55% by mass, more preferably 1 to 50 per 100% by mass of the total mass of the easy adhesion layer. % By mass. When the content of the titanium oxide fine particles exceeds 75% by mass, the cohesive force of the coating layer decreases and the adhesiveness deteriorates, which is not preferable, and when it is less than 0.5% by mass, the refractive index of the easy-adhesive layer decreases, When a hard coat layer is formed thereon, interference unevenness appears and becomes unfavorable.

  The average primary particle diameter of the rutile-type titanium oxide fine particles is preferably 4 to 25 nm, more preferably 5 to 25 nm. If the average primary particle diameter exceeds 25 nm, optical scattering occurs and the transparency of the easy-adhesion layer is unfavorable. On the other hand, if the average primary particle diameter is less than 4 nm, the aggregation of fine particles increases and the secondary particle diameter increases, resulting in optical scattering. Occurs, and the transparency of the easy-adhesion layer deteriorates, which is not preferable. In addition, the average primary particle diameter of the fine particles in the present invention is the number average primary particle diameter.

As rutile type titanium oxide fine particles, those having a refractive index of preferably 1.70 to 3.00, more preferably 1.90 to 2.80 are used. When the refractive index is less than 1.70, the volume fraction of the fine particles with respect to the polymer binder is increased, the cohesive force of the easy-adhesion layer is lowered, which is not preferable, and when the refractive index exceeds 3.00, a very special substance is obtained. It is difficult and undesirable to use industrially.
The rutile-type titanium oxide fine particles are preferably used as an aqueous dispersion in order to reduce environmental burden and handle easily during application.

(Antioxidant for hard coat layer side easy adhesion layer)
In the polarizing plate of the present invention, it is preferable that the hard coat layer side easy-adhesion layer contains an antioxidant. With this embodiment, the polyester film as a polarizer protective film and the hard coat layer laminated on the polyester film have excellent adhesion after wet heat aging, and the hard coat layer has excellent adhesion and light resistance, and at the same time, UV transmittance. The polyester film can be obtained.

  Antioxidants are radical scavengers (primary agents) that trap the generated radicals to prevent oxidation, or peroxide decomposers (secondary agents) that decompose the generated peroxides to prevent oxidation. Indicates. Examples of the radical scavenger include phenol-based antioxidants and amine-based antioxidants, and examples of the peroxide decomposer include phosphorus-based antioxidants and sulfur-based antioxidants. Examples of phenolic antioxidants include triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5 -Di-t-butyl-4-hydroxyphenyl) propionate], pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N, N′-hexa Methylenebis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide), 3,5-di-tert-butyl-4-hydroxyben Le phosphonate - diethyl ester, hindered phenolic antioxidants and the like. Examples of amine-based antioxidants include polymers of oxalic acid and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, sebacic acid-bis- (1,2,2,6,6). -Pentamethyl-4-piperidine), methyl sebacate- (1,2,2,6,6-pentamethyl-4-piperidine), poly [[6-[(1,1,3,3-tetramethylbutyl) Amino] -1,3,5-triazine-2,4-diyl] [(2,2,6,6-tetramethyl-4-piperidinyl) imino] [1,6-hexanediyl] [(2,2, 6,6-tetramethyl-4-piperidinyl) imino]], sebacic acid-bis- (2,2,6,6-tetramethyl-4-piperidine) and the like, hindered amine antioxidants (hindered amine light stabilizers, HALS) etc. . Examples of phosphorus antioxidants include trialkyl phosphites, alkyl allyl phosphites, triallyl phosphites, and the like. Examples of the sulfur-based antioxidant include sulfur dioxide and sulfite. Among these, from the viewpoint of excellent balance between light resistance and ultraviolet light transmittance, phenolic antioxidants and amine antioxidants are preferable, and hindered phenolic antioxidants and hindered amine antioxidants are particularly preferable. Moreover, it is preferable to use these aqueous dispersions from a viewpoint of handleability.

  In the hard-coat layer side easily bonding layer of this invention, it is also possible to use a commercial item as it is as an antioxidant. Examples of such commercially available products include TINUVIN (registered trademark) 123-DW, IRGANOX (registered trademark) 1010, 1035, and 1076 manufactured by BASF Corporation.

  Content of antioxidant in a hard-coat layer side easily bonding layer is 0.1 to 40 mass parts with respect to 100 mass parts in total of a polyester resin, a urethane resin, and an acrylic resin. By setting the content of the antioxidant in the above range, light resistance can be improved while maintaining excellent transparency and maintaining excellent ultraviolet transmittance. When there is too little content, it is inferior to light resistance. From such a viewpoint, the content of the antioxidant in the transparent conductive coating layer is more preferably 0.15 parts by mass or more with respect to a total of 100 parts by mass of the polyester resin, the urethane resin, and the acrylic resin. The amount is particularly preferably 0.18 parts by mass or more. On the other hand, when there is too much content, the transparency improvement effect will become low. Moreover, it is inferior to ultraviolet transmittance. From such a viewpoint, the content of the antioxidant is more preferably 30 parts by mass or less and 20 parts by mass or less with respect to 100 parts by mass in total of the polyester resin, the urethane resin, and the acrylic resin. Particularly preferred.

  The antioxidant content will be described in more detail. When the antioxidant is a phenolic antioxidant, the content of the antioxidant in the coating composition for an easy-adhesion layer is polyester resin, urethane resin, and acrylic resin. Is preferably from 0.1 parts by weight to 2 parts by weight, more preferably from 0.2 parts by weight to 1 part by weight, and more preferably from 0.2 parts by weight to 0. The amount is particularly preferably 5 parts by mass or less. When the antioxidant is an amine-based antioxidant, the content of the antioxidant in the easy-adhesion layer coating composition is 5 with respect to a total of 100 parts by mass of the polyester resin, urethane resin, and acrylic resin. It is preferably no less than 40 parts by mass and more preferably no less than 10 parts by mass and no greater than 30 parts by mass, and particularly preferably no less than 10 parts by mass and no greater than 20 parts by mass. By adopting such a combination of an antioxidant and a content, it is possible to further improve light resistance while maintaining excellent transparency and maintaining excellent ultraviolet transmittance.

《Polarizer side easy adhesion layer》
The polarizer-side easy-adhesion layer in the present invention is a layer for improving adhesiveness with various functional layers, for example, adhesiveness with various adhesives used for laminating a polarizer and a polyester film. Can be used to improve.

In order to improve the adhesion between the polyester film and the adhesive layer, the present inventors have examined compounds such as urethane resin and polyvinyl alcohol. As a result of further investigations, it has been found that the adhesiveness is relatively improved in the easy-adhesion layer using a combination of polyester resin or urethane resin and polyvinyl alcohol. On the other hand, as a result of various investigations of the crosslinking agent, it is possible to achieve comparative adhesion by combining an isocyanate compound or an oxazoline compound and polyvinyl alcohol, or an isocyanate compound or oxazoline compound and a urethane resin, and devising the composition ratio. It was also found that the performance was improved. By combining these results and using polyester resin or urethane resin, polyvinyl alcohol, isocyanate compound, or oxazoline compound together, surprisingly the adhesion is greatly improved and easy adhesion that can be used for polarizer protection Succeeded in forming a layer.
As the polyester resin contained in the polarizer-side easy-adhesion layer in the present invention, it is possible to use a polyester resin or an aliphatic polyester resin used in the hard coat layer-side easy-adhesion layer.

  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.

  Among the above polyols, polycarbonate polyols are more preferably used in order to improve the adhesiveness with various adhesive layers.

  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-Bisaminomethylcyclohexane Alicyclic diamines, and the like of.

  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 a skeleton of a urethane resin to form an ionomer is preferable because it is excellent in the storage stability of the liquid and the water resistance, transparency, and adhesion of the easily adhesive layer obtained. 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 easy-adhesive layer obtained in addition to excellent stability in a liquid state before coating.

  Polyvinyl alcohol contained in the polarizer-side easy-adhesion layer in the present invention has a polyvinyl alcohol moiety, including, for example, modified compounds partially acetalized or butyralized with respect to polyvinyl alcohol, Conventionally 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 easy-adhesion layer may be lowered. Further, 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 in the range of 70 to 99.9 mol% is practically used.

The isocyanate compound contained in the polarizer-side easy-adhesion layer in the invention refers to a compound having an isocyanate group in the molecule, and may be a low molecule or a polymer.
Further, diisocyanates or trifunctional or higher functional isocyanate compounds can be used. Specifically, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 1,4-naphthalene Diisocyanate, 1,5-naphthalene diisocyanate, phenylene diisocyanate, tetramethylxylylene diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4 ' -Diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate Aromatic diisocyanates such as nates, aromatic aliphatic diisocyanates such as xylylene diisocyanate, isophorone diisocyanate and 4,4-dicyclohexylmethane diisocyanate, alicyclic diisocyanates such as 1,3-bis (isocyanatomethyl) cyclohexane, hexa And methylene diisocyanates and aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate, and trimers of these isocyanate compounds.
As the crosslinking agent used in the present invention, a blocked isocyanate compound is also preferable. By adding the blocked isocyanate compound, it is possible to improve the temporal stability of the coating solution.
The blocked isocyanate compound can be prepared by subjecting the isocyanate compound and the blocking agent to an addition reaction by a conventionally known method. Examples of the isocyanate blocking agent include phenols such as phenol, cresol, xylenol, resorcinol, nitrophenol, and chlorophenol; thiophenols such as thiophenol and methylthiophenol; oximes such as acetoxime, methyl etiketooxime, and cyclohexanone oxime. Alcohols such as methanol, ethanol, propanol and butanol; halogen-substituted alcohols such as ethylene chlorohydrin and 1,3-dichloro-2-propanol; tertiary alcohols such as t-butanol and t-pentanol Lactams such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, β-propyllactam; rapizoles such as 3,5-dimethylrapizole; aromatic amines; Bromide such; acetylacetone, acetoacetic esters, active methylene compounds such as malonic acid ethyl ester; mercaptans; imines; ureas; diaryl compounds; and sodium bisulfite and the like.

  The oxazoline compound contained in the polarizer-side easy-adhesion layer in the present invention is a compound having an oxazoline group in the molecule. 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.

  Content of the polyester resin or the compound derived from a urethane resin which occupies for a polarizer side easily bonding layer is 10-80 mass% normally, Preferably it is 15-75 mass%, More preferably, it is 20-50 mass%. When the amount of the polyester resin or the urethane resin is out of the above range, the adhesive force between the polyester film and the adhesive layer may not be sufficiently obtained.

  Content of the compound derived from the polyvinyl alcohol which occupies for a polarizer side easily bonding layer is 10-80 mass% normally, Preferably it is 15-60 mass%, More preferably, it is 20-50 mass%. When the amount is less than 10% by mass, 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 isocyanate compound or the compound derived from the oxazoline compound in the polarizer-side easy-adhesion layer is usually 10 to 80% by mass, preferably 15 to 60% by mass, and more preferably 20 to 40% by mass. When the amount is less than 10% by mass, the easy-adhesion layer becomes brittle due to a small amount of the crosslinking component, and the heat-and-moisture resistance may be reduced. Adhesion and adhesiveness with the adhesive layer may not be sufficient.

  In the polarizer-side easy-adhesion layer, a binder polymer other than a polyester resin, a urethane resin, or polyvinyl alcohol can be used in combination in order to improve the coating surface state and transparency.

  In the present invention, the “binder polymer” is a number average molecular weight (Mn) measured by gel permeation chromatography (GPC) according to a polymer compound safety evaluation flow scheme (sponsored by the Chemical Substance Council in November 1985). It is defined as a polymer compound of 1000 or more and having a film-forming property.

  Specific examples of the binder polymer include acrylic resin, polyvinyl (polyvinyl chloride, polyvinyl pyrrolidone, vinyl chloride vinyl acetate copolymer, etc.), polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches and the like.

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

  A 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.

  As an epoxy compound, the compound containing an epoxy group in a molecule | numerator, its prepolymer, and hardened | cured material are mentioned, for example. 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 crosslinking agents, in particular, by using an epoxy compound in combination, the easy-adhesion layer is strengthened, and an improvement in adhesion and wet heat resistance can be expected. These cross-linking agents preferably have water solubility or water dispersibility in consideration of application to in-line coating.

  Further, the polarizer-side easy-adhesion layer may contain particles for the purpose of improving the blocking property and slipperiness of the easy-adhesion layer, such as inorganic particles such as silica, alumina, metal oxide, or crosslinked polymer particles. Organic particles, and the like.

<< Other Additives Used for Easy Adhesive Layer >>
Furthermore, in the range not impairing the gist of the present invention, the polarizer-side easy-adhesion layer and the hard coat layer-side easy-adhesion layer may be provided with an antifoaming agent, a coating property improver, a thickener, an organic lubricant, An inhibitor, an ultraviolet absorber, an antioxidant, a foaming agent, a dye, a pigment and the like may be contained.

  In addition, the coating composition for an easy-adhesion layer used in the present invention may contain a surfactant, a crosslinking agent, a dispersant, a thickener, a film forming aid, an antiblocking agent, and the like as necessary.

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

<< Method for Producing Easy Adhesive Layer >>
When providing an easy-adhesion layer by in-line coating, the above-mentioned series of compounds is applied as an aqueous solution or water dispersion, and a coating solution adjusted to a solid content concentration of about 0.1 to 50% by mass is applied onto the polyester film. It is preferable to produce a polyester film as described above. 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 hard coat layer side easy adhesion layer of the polyester film in the present invention is usually in the range of 0.002 to 1.0 μm, more preferably 0.02 to 0.5 μm, and further preferably 0.03 to 0.2 μm. It is. 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.

  The film thickness of the polarizer-side easy-adhesion layer of the polyester film in the present invention is usually in the range of 0.002 to 1.0 μm, more preferably 0.03 to 0.5 μm, and still more preferably 0.04 to 0.2 μm. is there. 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, a method for providing an easy-adhesion layer may be a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, or curtain coating. As for the coating method, there is a description example in “Coating method” published by Yoji Harasaki in 1979.

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

  On the other hand, when an easy-adhesion layer is provided by in-line coating, it is usually preferable to perform heat treatment 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 using a polyester film as a protective film for a polarizer in a polarizing plate, generally, the polarizer is bonded to the polarizer-side easy-adhesion layer side via an adhesive for adhering the polarizer.
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.

  For example, polyvinyl alcohol which is uniaxially stretched and dyed with iodine or the like is preferably laminated as a polarizer on the prepared adhesive layer. A polarizing plate can be obtained by laminating a protective film or a retardation film on the opposite side of the polarizer.

[Image display device]
The image display device of the present invention includes the polarizing plate of the present invention.
Examples of the image display device include a liquid crystal display (LCD), a plasma display (PDP), an electroluminescence display (OELD or IELD), a field emission display (FED), a touch panel, and electronic paper. These image display devices preferably include the polarizing plate of the present invention on the display screen side of the image display panel.

<Liquid crystal display device>
The liquid crystal display device preferably includes the polarizing plate of the present invention and a liquid crystal display element. Here, the liquid crystal display element is typically a liquid crystal panel having a liquid crystal cell in which liquid crystal is sealed between upper and lower substrates and displaying an image by changing the alignment state of the liquid crystal by applying a voltage. The polarizing plate of the present invention can be applied to various known displays such as a display panel, a CRT display, and an organic EL display. In the liquid crystal display device, it is preferable that the polarizing plate of the present invention is disposed on the visual recognition side with respect to the liquid crystal display element with the hard coat layer side facing outside. The polyester film may be directly bonded to the surface of the liquid crystal display element. When the liquid crystal panel is used as a liquid crystal display element, for example, as described above, the polyester film is bonded to the surface of the liquid crystal panel via a polarizer. You can also. Thus, when the polarizing plate of the present invention having a polyester film is applied to a liquid crystal display element, the polyester film and the hard coat layer are excellent in adhesion durability after wet heat aging, and a conventional protective film is used. The strength of the liquid crystal display element is reinforced more than the case, and the warpage of the liquid crystal display element can be prevented.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[Example 1]
<Synthesis of raw material polyester>
(Raw material polyester 1)
As shown below, by directly reacting terephthalic acid and ethylene glycol to distill off water, esterify, and then use a direct esterification method in which polycondensation is performed under reduced pressure, raw polyester 1 ( Sb catalyst system PET) was obtained.

(1) Esterification reaction In a first esterification reactor, 4.7 tons of high-purity terephthalic acid and 1.8 tons of ethylene glycol are mixed over 90 minutes to form a slurry, and continuously at a flow rate of 3800 kg / h. It supplied to the 1st esterification reaction tank. Further, an ethylene glycol solution of antimony trioxide was continuously supplied, and the reaction was carried out at a reaction vessel temperature of 250 ° C. with stirring and an average residence time of about 4.3 hours. At this time, antimony trioxide was continuously added so that the amount of Sb added was 150 ppm in terms of element.

  This reaction product was transferred to a second esterification reaction vessel, and reacted with stirring at a temperature in the reaction vessel of 250 ° C. and an average residence time of 1.2 hours. To the second esterification reaction tank, an ethylene glycol solution of magnesium acetate and an ethylene glycol solution of trimethyl phosphate are continuously supplied so that the added amount of Mg and the added amount of P are 65 ppm and 35 ppm in terms of element, respectively. did.

(2) the polycondensation reaction above-obtained esterification reaction product supplied to the first polycondensation reaction vessel continuously stirring, the reaction temperature 270 ° C., the reaction vessel pressure 20 torr (2.67 × 10 ^{- 3} MPa) and polycondensation with an average residence time of about 1.8 hours.

Further, the mixture was transferred to the second double condensation reaction tank, and while stirring in this reaction tank, the reaction tank temperature was 276 ° C., the reaction tank pressure was 5 torr (6.67 × 10 ⁻⁴ MPa), and the residence time was about 1.2 hours. The reaction (polycondensation) was performed under the conditions.

Subsequently, it was further transferred to the third triple condensation reaction tank. In this reaction tank, the reaction tank temperature was 278 ° C., the reaction tank pressure was 1.5 torr (2.0 × 10 ⁻⁴ MPa), and the residence time was 1.5 hours. The reaction product (polyethylene terephthalate (PET)) was obtained by reaction (polycondensation) under the following conditions.

  Next, the obtained reaction product was discharged into cold water in a strand form and immediately cut to prepare polyester pellets (cross section: major axis: about 4 mm, minor axis: about 2 mm, length: about 3 mm).

  The obtained polymer had IV = 0.63. This polymer was designated as raw material polyester 1 (hereinafter abbreviated as PET1).

(Raw material polyester 2)
10 parts by weight of the dried UV absorber (2,2 ′-(1,4-phenylene) bis (4H-3,1-benzoxazin-4-one), 90 parts by weight of PET1 (IV = 0.63) The mixture was mixed and pelletized in the same manner as the production of PET1 using a kneading extruder to obtain a raw material polyester 2 containing an ultraviolet absorber (hereinafter abbreviated as PET2).

<Manufacture of polyester film>
-Film forming process-
After drying 90 parts by mass of the raw material polyester 1 (PET1) and 10 parts by mass of the raw material polyester 2 (PET2) containing an ultraviolet absorber to a moisture content of 20 ppm or less, the hopper 1 of the uniaxial kneading extruder 1 having a diameter of 50 mm is used. And melted to 300 ° C. with the extruder 1 (intermediate layer II layer).
Moreover, after drying PET1 to a water content of 20 ppm or less, it was put into a hopper 2 of a single screw kneading extruder 2 having a diameter of 30 mm and melted at 300 ° C. by the extruder 2 (outer layer I layer, outer layer III layer).
These two kinds of polymer melts are respectively passed through a gear pump and a filter (pore diameter 20 μm), and then the polymer extruded from the extruder 1 is extruded into an intermediate layer (II layer) in a two-type three-layer confluence block. The polymer extruded from the machine 2 was laminated so as to be outer layers (I layer and III layer), and extruded from a die having a width of 120 mm into a sheet shape.
The molten resin was extruded from the die under the conditions that the pressure fluctuation was 1% and the temperature distribution of the molten resin was 2%. Specifically, the back pressure was increased by 1% with respect to the average pressure in the barrel of the extruder, and the piping temperature of the extruder was heated at a temperature 2% higher than the average temperature in the barrel of the extruder.
The molten resin extruded from the die was extruded onto a cooling cast drum set at a temperature of 25 ° C., and was brought into close contact with the cooling cast drum using an electrostatic application method. It peeled using the peeling roll arrange | positioned facing the cooling cast drum, and the unstretched polyester film 1 was obtained. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thicknesses of the I layer, the II layer, and the III layer was 10:80:10.

-Formation of an easy adhesion layer-
(1) Formation of hard coat layer side easy-adhesion layer The following compounds were mixed in the following ratio to prepare coating liquid H1 for hard coat layer-side easy adhesive layer.

・ Coating liquid H1 for hard coat layer side easy adhesion layer
Polyester resin: (IC) 60 parts by mass Acrylic resin: (II) 25 parts by mass Melamine compound: (VIB) 10 parts by mass Particles: (VII) 5 parts by mass Details of the compounds used are shown below.
・ Polyester resin: (IC)
Polyester resin sulfonic acid aqueous dispersion monomer composition copolymerized with monomers of the following 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%)

・ Acrylic resin: (II)
Aqueous dispersion of acrylic resin polymerized with monomers of the following composition Ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylol acrylamide / acrylic acid = 65/21/10/2/2 (mass%) emulsion polymer ( Emulsifier: Anionic surfactant)
-Urethane resin: (IIIB)
400 parts by weight of a polycarbonate polyol composed of 1,6-hexanediol and diethyl carbonate having a number average molecular weight of 2000, 10.4 parts by weight of neopentyl glycol, 58.4 parts by weight of isophorone diisocyanate, 74.3 parts by weight of dimethylol butanoic acid. An aqueous dispersion of urethane resin obtained by neutralizing a prepolymer consisting of parts by mass with triethylamine and extending the chain with isophoronediamine.
Melamine compound: (VIB) hexamethoxymethylmelamine Particles: (VII) Silica sol having an average particle size of 65 nm

(2) Formation of polarizer-side easy-adhesion layer The following compounds were mixed in the following ratio to prepare a coating liquid P1 for polarizer-side easy-adhesion.
(2-1) Synthesis of copolymer polyester resin (A-1) Dimethyl terephthalate 194.2 parts by mass Dimethyl isophthalate 184.5 parts by mass Dimethyl-5-sodium sulfoisophthalate 14.8 parts by mass Diethylene glycol 233.5 parts by mass Ethylene glycol 136.6 parts by mass Tetra-n-butyl titanate 0.2 parts by mass The above compound was charged, and a transesterification reaction was performed at a temperature of 160 ° C to 220 ° C over 4 hours. Next, the temperature was raised to 255 ° C., and the pressure of the reaction system was gradually reduced, followed by reaction for 1 hour 30 minutes under a reduced pressure of 30 Pa to obtain a copolymerized polyester resin (A-1).

(2-2) Preparation of polyester aqueous dispersion (Aw-1) Copolyester resin (A-1) 30 parts by mass Ethylene glycol n-butyl ether 15 parts by mass Dissolved. After the resin was completely dissolved, 55 parts by mass of water was gradually added to the polyester solution while stirring. After the addition, the solution was cooled to room temperature while stirring to prepare a milky white polyester aqueous dispersion (Aw-1) having a solid content of 30% by mass.

(2-3) Preparation of aqueous polyvinyl alcohol solution (Bw-1) 90 parts by mass of water was added, and while stirring, polyvinyl alcohol resin (manufactured by Kuraray) having a saponification degree of 88% and a polymerization degree of 500 (B-1) 10 masses Part was added gradually. After the addition, the solution was heated to 95 ° C. while stirring to dissolve the resin. After dissolution, the mixture was cooled to room temperature with stirring to prepare a polyvinyl alcohol aqueous solution (Bw-1) having a solid content of 10% by mass.

Polyisocyanate compound having isocyanurate structure made from hexamethylene diisocyanate (Duranate TPA manufactured by Asahi Kasei Chemicals)
100 parts by mass Propylene glycol monomethyl ether acetate 55 parts by mass Polyethylene glycol monomethyl ether (average molecular weight 750) 30 parts by mass The above compound was charged and held at 70 ° C. for 4 hours in a nitrogen atmosphere. Thereafter, the reaction solution temperature was lowered to 50 ° C., and 47 parts by mass of methyl ethyl ketoxime was added dropwise. The infrared spectrum of the reaction solution was measured to confirm that the absorption of the isocyanate group had disappeared, and a block polyisocyanate aqueous dispersion (C-1) having a solid content of 75% by mass was obtained.

The following coating agent was mixed and the coating liquid P1 for polarizer side easy adhesion which the mass ratio of polyester-type resin (A) / polyvinyl alcohol-type resin (B) becomes 70/30 was produced.
Water 40.61 mass%
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 11.67 mass%
Polyvinyl alcohol aqueous solution (Bw-1) 15.00 mass%
Block isocyanate-based crosslinking agent (C-1) 0.67% by mass
Particles (silica sol with an average particle diameter of 100 nm, solid content concentration 40% by mass)
1.25% by mass
Catalyst (organotin-based compound solid concentration 14% by mass) 0.3% by mass
Surfactant (silicon-based, solid content concentration 10% by mass) 0.5% by mass

(3) Application of easy-adhesion layer on both surfaces of polyester film By reverse roll method, the following coating liquid H1 for hard-coat layer-side easy-adhesion layer is applied to one side of unstretched polyester film 1, and polarizer is applied to the other surface. The coating solution P1 for side adhesion was applied while adjusting the coating amount after drying so that both sides would be 0.12 g / m ² .

-Transverse stretching process-
(Preheating part)
The preheating temperature was 90 ° C., and the mixture was heated to a temperature at which stretching was possible.

(Extension part)
The unstretched polyester film 1 coated and preheated with an easy-adhesion layer is guided to a tenter (transverse stretching machine), and the ends of the film are gripped with clips, while the TD direction (film width direction, The film was transversely stretched under the following conditions in the transverse direction) to obtain a film having a width of 5 m.
"conditions"
-Transverse stretching temperature: 90 ° C
・ Horizontal stretch ratio: 4.3 times

(Heat fixing part)
Next, a heat setting treatment was performed while controlling the film surface temperature of the polyester film within the following range.
<Condition>
・ Heat setting temperature: 180 ℃
・ Heat setting time: 15 seconds

(Heat relaxation part)
The polyester film after heat setting was heated to the following temperature to relax the film.
-Thermal relaxation temperature: 170 ° C
-Thermal relaxation rate: TD direction (film width direction, lateral direction) 2%

(Cooling section)
Next, the polyester film after heat relaxation was cooled at a cooling temperature of 50 ° C.

(Recover film and split film)
After cooling, the polyester film 1 was divided into 1.4 m widths in the width direction, and the chuck portion was trimmed. Then, after extruding (knurling) at a width of 10 mm on both ends of each divided roll, it was wound up 2000 m at a tension of 18 kg / m. The divided samples were defined as an end A, a center B, and an end C from one end side.
As described above, strip-shaped (long) uniaxially stretched polyester films 1-A, 1-B, and 1-C having a thickness of 100 μm and a width of 1.4 m were manufactured.

<Formation by applying a hard coat layer>
Then, the dry film thickness of the mixed coating liquid (acryl-1) having the following composition is applied to the surface of the polyester film 1-A, 1-B, 1-C coated with the coating liquid H1 for the hard-coat layer-side easy-adhesion layer. It was applied and dried so as to have a thickness of 5 μm, and cured by irradiation with ultraviolet rays to form a hard coat layer.
Dipentaerythritol hexaacrylate 85 parts by mass 2-hydroxy-3-phenoxypropyl acrylate 15 parts by mass photopolymerization initiator (trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals)
5 parts by weight methyl ethyl ketone 200 parts by weight

<Strip (long) polarizing plate processing>
A commercially available cellulose acetate film (ZRD40, manufactured by Fuji Film Co., Ltd.) was prepared as a polarizing plate protective film, and continuously passed through a 1.5 N aqueous sodium hydroxide solution and immersed at 55 ° C. for 2 minutes. It wash | cleaned in the room temperature water-washing tub, and neutralized using 0.1 N sulfuric acid at 30 degreeC. Again, it was washed in a water bath at room temperature and further dried with hot air at 100 ° C. In this way, the surface of the cellulose acetate film was saponified.
Subsequently, a roll-shaped polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in the conveying direction in an aqueous iodine solution and dried to obtain a polarizer having a thickness of 20 μm.
Polarizers of the above saponified cellulose acetate film and strip (long) polyester film samples 1-A, 1-B and 1-C using a 3% aqueous solution of polyvinyl alcohol (Kuraray PVA-117H) as an adhesive The surface on which the coating liquid P1 for the side easy-adhesion layer is applied is the polarizer side, and is bonded in a roll-to-roll manner with the polarizer in between, and both sides of the polarizer are protected by a film. I got a plate. The obtained three polarizing plates were used as the polarizing plate of Example 1.
In the evaluation of the misalignment angle between the maximum direction of the elastic modulus in the polyester film surface described later and the absorption axis of the PVA polarizer, a polarizing plate produced using the polyester film sample 1-A and the polyester film sample 1-B are used. And the polarizing plate manufactured using the polyester film sample 1-C was evaluated.
On the other hand, as a representative example in other evaluations, an image using a polyester film sample 1-A, a polarizing plate manufactured using the polyester film sample 1-A, and a polarizing plate manufactured using the polyester film sample 1-A. The display device was evaluated.
In addition, other examples, reference examples, and comparative examples described later were similarly evaluated.

[Examples 2 to 9]
The polarizing plates of Examples 2 to 9 were produced in the same manner as in Example 1 except that the production conditions of the polarizing plate of Example 1 were changed as shown in Table 1 below. In addition, Re and Rth of the polyester film were controlled to be the values shown in Table 1 below by polarizing the stretching condition in the width direction.

[Example 10]:
(Easily adhesive layer including emulsion)
The same procedure as in Example 1 was conducted except that 35% of the entire resin was mixed with UV-absorbing emulsion (New Coat UVA-204W: manufactured by Shin-Nakamura Chemical Co., Ltd.) in the easy-adhesion coating solution H1 for the hard-coat layer easy-adhesion layer. A polarizing plate of Example 10 was produced.

[Example 11]
(Easily adhesive layer containing titanium oxide)
Example in which rutile-type titanium oxide (TTO51 (A): primary particle size 20 nm, manufactured by Ishihara Sangyo Co., Ltd.) was mixed in the easy-adhesion coating liquid H1 for the hard-coat layer-side easy-adhesive layer with 50% by mass based on the entire resin. In the same manner as in Example 1, a polarizing plate of Example 11 was produced.

[Example 12]
(An easy-adhesive layer containing an antioxidant)
Example 1 except that a hindered amine-based antioxidant (TINUVIN123-DW: 30% aqueous dispersion manufactured by BASF) was mixed in the easy-adhesion coating solution H1 for the hard-coat layer-side easy-adhesive layer with respect to the entire resin. Similarly, the polarizing plate of Example 12 was produced.

[Example 13]
(Easily adhesive layer containing aliphatic polyester, etc.)
Example 13 was carried out in the same manner as in Example 1 except that the following coating solution for the hard coat layer side easy-adhesion layer was added to the easy-adhesion coating solution H1 for hard coat layer side easy-adhesion layer. A polarizing plate was prepared.
<Prescription>
・ The following polyester 13 90 mass%
・ Oxazoline cross-linking agent (trade name Epocross WS-300, manufactured by Nippon Shokubai Co., Ltd.) 5% by mass
・ Polyoxyethylene (n = 7) lauryl ether (trade name NAROACTY N-70, manufactured by Sanyo Chemical Industries, Ltd.) 5% by mass
The polyester 13 is a polyester in which the acid component is composed of 95 mol% of 1,4-cyclohexanedicarboxylic acid / 5 mol% of 5-sodiumsulfoisophthalic acid and the glycol component is 100 mol% of 1,4-cyclohexanedimethanol. (Tg = 45 ° C., average molecular weight 14,000). Polyester 13 was produced as follows according to the method described in Example 1 of JP-A-06-116487. That is, 38 parts of dimethyl 1,4-cyclohexanedicarboxylate, 3 parts of dimethyl 5-sodium sulfoisophthalate, and 58 parts of 1,4-cyclohexanedimethanol were charged into a reactor, and 0.05 parts of tetrabutoxytitanium was added thereto. Then, the temperature was controlled at 230 ° C. in a nitrogen atmosphere, and the produced methanol was distilled off to conduct a transesterification reaction. Next, the temperature of the reaction system was gradually raised to 255 ° C., and the pressure inside the system was reduced to 1 mmHg to carry out a polycondensation reaction, whereby polyester 13 was obtained.

[Example 14]
(Other easily adhesive layer)
The polarizing plate of Example 14 except that instead of the coating liquid H1 for easy adhesion on the hard coat layer side, the coating liquid H2 for easy adhesion layer on the hard coat layer side having the following composition was used. Was made.
・ Coating liquid H2 for hard coat layer side easy adhesion layer
Polyester resin: (above IC) 50 parts by mass Urethane resin: (above IIIB) 17 parts by mass Melamine compound: (above VIB) 30 parts by mass Particles: (above VII) 3 parts by mass

[Example 15]
In Example 1, the polarizing plate of Example 15 was produced like Example 1 except having changed the easy-adhesion prescription as follows.
-Formation of an easy adhesion layer-
(1) Formation of hard coat layer side easy-adhesion layer The following compounds were mixed in the following ratio to prepare a coating liquid H11 for a hard coat layer-side easy adhesive layer.
-Coating liquid H11 for hard coat layer side easy adhesion layer
Water 65 parts by mass polyester resin: (A11 below, solid content 25% by mass) 25 parts by mass surfactant (E11 below, solid content 1% by mass) 3 parts by mass Particles: (F below, solid content 10% by mass) 2 parts by mass Part lubricant: (G below, solid content 30% by mass) 5 parts by mass Details of the compounds used are shown below.
・ Polyester resin: (A11)
A sulfonic acid-based aqueous dispersion monomer composition of a polyester resin copolymerized with a monomer having the following composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / triethylene glycol / Diethylene glycol = 66/30/4 // 40/30/30 (mol%), Tg = 45 ° C.
Surfactant: (E11) sulfosuccinic acid surfactant (manufactured by NOF Corporation, Rapisol A-90)
Particles: (F) Silica sol with an average particle size of 180 nm Lubricant: (G) Carnauba wax

(2) Formation of polarizer-side easy-adhesion layer The following compounds were mixed in the following ratio to prepare a coating liquid P11 for polarizer-side easy-adhesion.
(2-1) Preparation of aqueous polyvinyl alcohol solution (A13) 90 parts by mass of water was added, and 10 parts by mass of polyvinyl alcohol resin (manufactured by Kuraray) having a saponification degree of 73% and a polymerization degree of 500 was gradually added with stirring. After the addition, the solution was heated to 95 ° C. while stirring to dissolve the resin. After dissolution, the mixture was cooled to room temperature with stirring to prepare a polyvinyl alcohol aqueous solution (A13) having a solid content of 10% by mass.
The following coating agent is mixed, and a coating liquid P11 for easily adhering to the polarizer, in which the mass ratio of polyester resin (A11) / polyvinyl alcohol resin (A13) / isocyanate compound (B11) is 40/30/40, is obtained. Produced.
Water 47.4 parts by mass Polyester aqueous dispersion (A11, solid content 25% by mass) 12 parts by mass polyvinyl alcohol aqueous solution (A13, solid content 10% by mass) 22 parts by mass isocyanate compound (B11 below, solid content 27% by mass) 11 parts by mass particles (F, solid content concentration 10% by mass) 1 part by mass catalyst (organotin compound solid content 10% by mass) 0.1 parts by mass surfactant (E12 below, solid content concentration 1% by mass) 3 masses Part aqueous sodium hydrogen carbonate solution (solid concentration 3.3 mass%) 3.5 parts by mass The details of the compounds used are shown below.
・ Isocyanate compound: (B11)
34 parts by mass of hexamethylene diisocyanate was added to 200 parts by mass of the polyester of ethylene oxide adduct of bisphenol A and maleic acid, the reaction was carried out, and 73 parts by mass of a 30% by mass aqueous sodium bisulfite solution was added and stirred. Thereafter, a blocked isocyanate compound diluted with water.
-Surfactant: (E12) Polyethylene oxide surfactant (Sanyo Chemical Industries, NAROACTY CL-95)

[Examples 16 to 23]
The polarizing plates of Examples 16 to 23 were produced in the same manner as in Example 15 except that the production conditions of the polarizing plate of Example 15 were changed as shown in Table 2 below. The Re and Rth of the polyester film were controlled to be the values shown in Table 2 below by polarizing the stretching condition in the width direction.

[Example 24]
(Easily adhesive layer including emulsion)
A UV absorbing emulsion (New Coat UVA-204W: manufactured by Shin-Nakamura Chemical Co., Ltd.) was mixed in the easy-adhesion coating solution H11 for the hard coat layer-side easy-adhesive layer in the same manner as in Example 15 except that 35% of the total resin was mixed. And the polarizing plate of Example 24 was produced.

[Example 25]
(Easily adhesive layer containing titanium oxide)
Example in which rutile-type titanium oxide (TTO51 (A): primary particle size 20 nm, manufactured by Ishihara Sangyo Co., Ltd.) was mixed in the easy-adhesion coating solution H11 for the hardcoat layer-side easy-adhesive layer with 50% by mass based on the entire resin. In the same manner as in Example 15, a polarizing plate of Example 25 was produced.

[Example 26]
(An easy-adhesive layer containing an antioxidant)
Example 15 except that a hindered amine antioxidant (TINUVIN123-DW: 30% aqueous dispersion manufactured by BASF) was mixed in the easy-adhesion coating solution H11 for the hard-coat layer-side easy-adhesive layer with respect to the entire resin. Similarly, the polarizing plate of Example 26 was produced.

[Example 27]
(Easily adhesive layer containing aliphatic polyester, etc.)
Example 27 was carried out in the same manner as in Example 15 except that the coating liquid for hard coat layer side easy adhesion layer obtained by adding the following aliphatic ester or the like to the easy adhesion coating liquid H11 for hard coat layer side easy adhesion layer was used. A polarizing plate was prepared.
<Prescription>
・ The following polyester 13 90 mass%
・ Oxazoline cross-linking agent (trade name Epocross WS-300, manufactured by Nippon Shokubai Co., Ltd.) 5% by mass
・ Polyoxyethylene (n = 7) lauryl ether (trade name NAROACTY N-70, manufactured by Sanyo Chemical Industries, Ltd.) 5% by mass
The polyester 13 is a polyester in which the acid component is composed of 95 mol% of 1,4-cyclohexanedicarboxylic acid / 5 mol% of 5-sodiumsulfoisophthalic acid and the glycol component is 100 mol% of 1,4-cyclohexanedimethanol. (Tg = 45 ° C., average molecular weight 14,000). Polyester 13 was produced as follows according to the method described in Example 1 of JP-A-06-116487. That is, 38 parts of dimethyl 1,4-cyclohexanedicarboxylate, 3 parts of dimethyl 5-sodium sulfoisophthalate, and 58 parts of 1,4-cyclohexanedimethanol were charged into a reactor, and 0.05 parts of tetrabutoxytitanium was added thereto. Then, the temperature was controlled at 230 ° C. in a nitrogen atmosphere, and the produced methanol was distilled off to conduct a transesterification reaction. Next, the temperature of the reaction system was gradually raised to 255 ° C., and the pressure inside the system was reduced to 1 mmHg to carry out a polycondensation reaction, whereby polyester 13 was obtained.

[Example 28]
(Other easily adhesive layer)
The polarizing plate of Example 28 except that instead of the coating liquid H11 for easy adhesion on the hard coat layer side, the coating liquid H2 for easy adhesion layer on the hard coat layer side having the following composition was used. Was made.
・ Coating liquid H12 for hard coat layer side easy adhesion layer
Water 61.4 parts by mass Polyester resin: (A11, solid content 25% by mass) 15 parts by mass acrylic resin: (A12 below, solid content 30% by mass) 5 parts by mass Isocyanate compound: (B11, solid content 27% by mass) 5 Part by mass Surfactant (E11, solid content 1% by mass) 3 parts by mass Particle: (F, solid content 10% by mass) 2 parts by mass Lubricant: (G, solid content 30% by mass) 5 parts by mass Catalyst (Organic tin system) Compound: Solid content: 10% by mass) 0.1 part by mass Aqueous sodium hydrogen carbonate solution (solid content: 3.3% by mass) 3.5 parts by mass Details of the compounds used are shown below.
・ Acrylic resin: (A12)
Aqueous dispersion of acrylic resin polymerized with monomers of the following composition Ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylol acrylamide / acrylic acid = 65/21/10/2/2 (mass%) emulsion polymer ( Emulsifier: Anionic surfactant)

[Example 29]
(Other easily adhesive layers)
The polarizing plate of Example 29 except that instead of the coating liquid H11 for easy adhesion on the hard coat layer side, the coating liquid H13 for easy adhesion layer on the hard coat layer side having the following composition was used. Was made.
・ Coating liquid H13 for hard coat layer side easy adhesion layer
Water 46.4 parts by mass Isocyanate compound: (B11, solid content 27% by mass) 25 parts by mass surfactant (E11, solid content 1% by mass) 3 parts by mass Particles: (F, solid content 10% by mass) 2 parts by mass Lubricant: (G, solid content 30% by mass) 5 parts by mass catalyst (organotin compound solid content 10% by mass) 0.1 part by mass sodium hydrogen carbonate aqueous solution (solid content concentration 3.3% by mass) 3.5 parts by mass

[Example 30]
(Other easily adhesive layer)
The polarizing plate of Example 30 in the same manner as in Example 1 except that instead of the coating liquid H11 for easy adhesion on the hard coat layer side, the coating liquid H14 for easy adhesion layer on the hard coat layer side having the following composition was used. Was made.
-Coating liquid H14 for hard coat layer side easy adhesion layer
Water 61.4 parts by mass Polyester resin: (A11, solid content 25% by mass) 15 parts by mass Naphthalene ring-containing polyester resin: (manufactured by Kyoyo Chemical Industry Plus Coat Z-592, solid content 25% by mass) 5 parts by mass Isocyanate compound: (B11, solid content 27 mass%) 5 mass parts surfactant (E11, solid content 1 mass%) 3 mass parts particles: (F, solid content 10 mass%) 2 mass parts lubricant: (G, solid content 30 mass%) %) 5 parts by mass catalyst (organotin compound solid content 10% by mass) 0.1 part by mass sodium hydrogen carbonate aqueous solution (solid content concentration 3.3% by mass) 3.5 parts by mass

[Example 31]
In Example 15, the polarizing plate of Example 31 was used in the same manner except that the unstretched polyester film 2 obtained by molding a polyester film by single layer extrusion was used instead of the unstretched polyester film 1 as described below. Was made.
-Film forming process-
After drying 90 parts by mass of the raw material polyester 1 (PET1) and 7 parts by mass of the raw material polyester 2 (PET2) containing an ultraviolet absorber to a moisture content of 20 ppm or less, the hopper 1 of the uniaxial kneading extruder 1 having a diameter of 50 mm is used. And melted at 300 ° C. with the extruder 1.
The polymer melts were respectively passed through a gear pump and a filter (pore diameter: 20 μm), and then extruded into a sheet form from a die having a width of 120 mm by a single layer block.
The molten resin was extruded from the die under the conditions that the pressure fluctuation was 1% and the temperature distribution of the molten resin was 2%. Specifically, the back pressure was increased by 1% with respect to the average pressure in the barrel of the extruder, and the piping temperature of the extruder was heated at a temperature 2% higher than the average temperature in the barrel of the extruder.
The molten resin extruded from the die was extruded onto a cooling cast drum set at a temperature of 25 ° C., and was brought into close contact with the cooling cast drum using an electrostatic application method. It peeled using the peeling roll arrange | positioned facing the cooling cast drum, and the unstretched polyester film 2 of width 5m was obtained.

[Examples 32-46]
In each of Examples 16-30, each of Examples 16-30 was carried out in the same manner as Examples 16-30, except that unstretched polyester film 2 produced by the method described in Example 31 was used instead of unstretched polyester film 1. 32-46 polarizing plates were produced.
However, in Example 38, the usage-amount of PET2 described in Example 31 was 14 mass parts.

[Comparative Examples 1 and 2]
In Example 1, the polarizing plates of Comparative Examples 1 and 2 were produced in the same manner as in Example 1 except that the heat setting temperature was changed to the temperature described in Table 3 below.

[Comparative Example 10]
Before applying an easily bonding layer to a polyester film, the polarizing plate of the comparative example 10 was produced like Example 1 except having extended | stretched the polyester film 3 times to the vertical direction.

[Reference Example 1]
For Example 1, instead of the polyester film, a commercially available cellulose acetate film saponified in the same manner as ZRD40 (TD80, manufactured by Fuji Film, no easy adhesion) was used in the same manner as in Example 1 for reference. The polarizing plate of Example 1 was produced.

[Characteristics of polyester film, evaluation of polarizing plate and liquid crystal display]
Characteristic evaluation of the polyester film used for the polarizing plate of each example, reference example, and comparative example, and evaluation of the polarizing plate and liquid crystal display device of each example, reference example, and comparative example were performed by the following methods.
The obtained results are shown in Tables 1 to 3 below.

<Melting sub-peak temperature (Tsm)>
Using DSC220 manufactured by Seiko Denshi Kogyo Co., Ltd., a DSC curve is drawn at a rate of temperature increase of 20 ° C./min using a polyester film sample amount of 10 mg. (Tsm).

<Re, Rth>
In-plane retardation is defined as the product (ΔNxy × d) of anisotropy of biaxial refractive index (ΔNxy = | Nx−Ny |) and film thickness d (nm) on the film. It is a parameter indicating the optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) was determined by the following method. Using two polarizing plates, the orientation axis direction of the film was determined, and a 4 cm × 2 cm rectangle was cut out so that the orientation axis directions were perpendicular to each other, and used as a measurement sample. With respect to this sample, the biaxial refractive index (Nx, Ny) perpendicular to each other and the refractive index (Nz) in the thickness direction were determined by an Abbe refractometer (NAGO-4T, measurement wavelength 589 nm, manufactured by Atago Co., Ltd.). The absolute value (| Nx−Ny |) of the refractive index difference between the axes was defined as the refractive index anisotropy (ΔNxy). The thickness d (nm) of the film was measured using an electric micrometer (manufactured by Fine Reef, Millitron 1245D), and the unit was converted to nm. Retardation (Re) was determined from the product (ΔNxy × d) of refractive index anisotropy (ΔNxy) and film thickness d (nm).
Thickness direction retardation is obtained by multiplying two birefringences ΔNxz (= | Nx−Nz |) and ΔNyz (= | Ny−Nz |) by film thickness d when viewed from the cross section in the film thickness direction. It is a parameter which shows the average of retardation obtained. Thickness direction retardation (Rth) is obtained by calculating Nx, Ny, Nz and film thickness d (nm) in the same manner as the measurement of retardation, and calculating the average value of (ΔNxz × d) and (ΔNyz × d). )

<380 nm transmittance>
Using a spectrophotometer (UV-3100PC type manufactured by Shimadzu Corporation), the light transmittance in the wavelength region of 300 to 500 nm of each film was measured using the air layer as a standard, and the light transmittance at a wavelength of 380 nm was determined.

<Heat shrinkage>
A sample of 350 mm in the longitudinal (MD) direction of the polyester film and 50 mm in the width direction is cut out, marked at 300 mm intervals near both ends in the longitudinal direction of the sample, and fixed at one end to an oven adjusted to a temperature of 150 ° C. Left free for 30 minutes. The distance between the gauge points was measured in the take-out chamber (this length is assumed to be S), and the thermal contraction rate (MD heat yield) in the MD direction was determined by the following formula.
MD heat yield (%) = (300−S) / 300 × 100
The thermal shrinkage rate in the MD direction of the polyester film is preferably 3.0% or less, more preferably 2.0% or less, and more preferably 1.0% or less from the viewpoint of suppressing peeling of the hard coat layer. It is particularly preferred that

<Evaluation of deviation angle between maximum direction of elastic modulus in plane of polyester film and absorption axis of PVA polarizer>
(1) Measurement of maximum direction of in-plane elastic modulus The maximum direction of in-plane elastic modulus of a polyester film was measured using a sound velocity measuring device “SST-2501, Nomura Corporation” at 25 ° C. and 60% relative humidity. The film was conditioned for 2 hours or more in an atmosphere of 25 ° C. and the relative humidity was 60%, and the sound speed was measured by dividing the 360 ° direction into 32 directions, and the maximum velocity direction was the maximum in-plane elastic modulus direction. It was.
The maximum direction of the in-plane elastic modulus was determined for the end A of the polyester film sample produced in each example and comparative example, the center B of the polyester film sample, and the end C of the polyester film sample.

(2) About the polarizing plate manufactured using the edge part A of the polyester film sample, the polarizing plate manufactured using the center B of the polyester film sample, and the polarizing plate manufactured using the end part C of the polyester film sample, The deviation angle between the maximum direction of the elastic modulus in the plane of the polyester film and the absorption axis of the PVA polarizer was determined by the following method. That is, when the reference direction is the transport direction (MD direction) when the polarizer and each polyester film sample are bonded by roll-to-roll among the absorption axes of the PVA polarizer, each polyester film surface from the MD direction. The angle measured toward the maximum direction of the elastic modulus was determined.

<Hard coat adhesion evaluation>
The polarizing plates of each Example, Reference Example, and Comparative Example were cut to 55 inches with a Thomson blade and left for 24 hours in a condition 1: 60 ° C. and 90% relative humidity (hard coat adhesion after wet heat aging) Evaluation).
Condition 2: Xenon irradiation was performed for 12 hours (light resistance evaluation of hard coat adhesion).
Make a 10 × 10 cross-cut so as to include the edge of the polarizing plate of Condition 1 or Condition 2, and then apply a 18 mm wide tape (Cello Tape (registered trademark), Elpac (registered trademark) LP manufactured by Nichiban Co., Ltd.) −18) was attached, and the peeled surface after abrupt peeling at a 180 ° peel angle was observed.
The result was evaluated as A when no peeling of the hard coat layer was observed and B as a part where peeling was observed.
The hard coat adhesion evaluation after wet heat aging of Condition 1 is practically required to be A evaluation.
The light resistance evaluation of the hard coat adhesion of Condition 2 is preferably A evaluation.

<Display unevenness after aging at 60 ° C. and 90%>
The upper and lower polarizing plates of the IPS mode liquid crystal cell (manufactured by LGD 42LS5600) were peeled off, and the produced polarizing plates of Examples, Reference Examples and Comparative Examples were attached so that the ZRD 40 was on the liquid crystal cell side. The crossed nicols were arranged so that the transmission axis of the upper polarizing plate was in the vertical direction and the transmission axis of the lower polarizing plate was in the horizontal direction.
The produced LCD panel was put into Celco (manufactured by ESPEC) for 72 hours under the conditions of 60 ° C. and 90% relative humidity, and unevenness of black display at the time of taking out was observed.
The results were evaluated as A if black display unevenness was not observed, B being slightly observed, and C being clearly observed. Practically, it is necessary to have an A or B evaluation, and an A evaluation is preferable.

<Rainbow unevenness evaluation>
The panel on which the polarizing plates of Examples, Reference Examples and Comparative Examples were bonded together was observed through the polarizing plate.
The results were evaluated as A if no rainbow-like color unevenness was observed, B being slightly observed, and C being clearly observed. Practically, it is necessary to have an A or B evaluation, and an A evaluation is preferable.

From the above Tables 1 to 3, the polarizing plate of the present invention is excellent in adhesion between a polyester film as a protective film of a polarizer and a hard coat layer laminated on the polyester film after wet heat aging, and incorporated in an image display device. It was found that display unevenness after aging with heat and heat was suppressed, and rainbow unevenness when incorporated in an image display device was also suppressed.
On the other hand, from Comparative Example 1, the melting sub-peak temperature Tsm of the polyester film exceeds the upper limit defined in the present invention, and the deviation angle between the maximum direction of the elastic modulus in the polyester film plane and the absorption axis of the PVA polarizer is the present invention. When it exceeds the specified range, it was found that the adhesion of the hard coat layer after wet heat aging was insufficient.
From Comparative Example 2, it was found that when the melting sub-peak temperature Tsm of the polyester film was lower than the lower limit defined in the present invention, the adhesion of the hard coat layer after wet heat aging was insufficient.
From Comparative Example 10, it was found that when the retardation Re in the in-plane direction of the polyester film was lower than the lower limit specified in the present invention, the suppression of rainbow unevenness when incorporated in an image display device was insufficient.
From Reference Example 1, it was found that when a highly water-permeable cellulose acylate film was used instead of the polyester film, display unevenness after wet heat aging when incorporated into an image display device was insufficient.
In addition, in the hard coat adhesion evaluation, in the case where the partial peeling of the hard coat layer was observed, peeling occurred at the end portion (1 mm) of the polarizing plate.

DESCRIPTION OF SYMBOLS 1 Polarizer 2 Polyester film 3a Polarizer side easy-adhesion layer 3b Hard-coat layer side easy-adhesion layer 4 Hard-coat layer 10 Protective film

Claims (13)

A protective film;
A polarizer disposed on the protective film and comprising polyvinyl alcohol;
A polyester film disposed on the polarizer;
A hard coat layer side easy adhesion layer disposed on the polyester film;
A hard coat layer disposed on the hard coat layer side easy adhesion layer,
The polyester film is stretched in the width direction,
The width of the polyester film is 1.4 m or more,
In-plane retardation Re of the polyester film is 4000-20000 nm,
The angle formed by the maximum direction of the elastic modulus in the plane of the polyester film and the absorption axis direction of the polarizer is 90 ° ± 25 ° at both ends and the center in the width direction of the polyester film,
The melting sub-peak temperature Tsm of the polyester film is 140 to 220 ° C.,
A polarizing plate characterized by being strip-shaped.   The polarizing plate according to claim 1, wherein the polyester film is uniaxially stretched in the width direction.   The polarizing plate according to claim 1 or 2, wherein the hard coat layer side easy-adhesion layer contains at least one selected from a polyester resin, an acrylic resin, and a urethane resin.   The polarizing plate as described in any one of Claims 1-3 whose light transmittance in wavelength 380nm of the said polyester film is 15% or less.   The polarizing plate as described in any one of Claims 1-4 with which the said hard-coat layer side easily bonding layer contains a ultraviolet absorber.   The polarizing plate as described in any one of Claims 1-5 in which the said polyester film contains a ultraviolet absorber.   The polarizing plate as described in any one of Claims 1-6 in which the said hard-coat layer side easily bonding layer contains a rutile type titanium oxide microparticle.   The polarizing plate as described in any one of Claims 1-7 in which the said hard-coat layer side easily bonding layer contains antioxidant.   The polarizing plate as described in any one of Claims 1-8 in which the said hard-coat layer side easily bonding layer contains aliphatic polyester.   The polarizing plate as described in any one of Claims 1-9 in which the said hard-coat layer contains an acrylate.   The polarizing plate according to claim 1, wherein the hard coat layer is formed by coating.   The polarizing plate as described in any one of Claims 1-11 with which the polarizer side easily bonding layer was arrange | positioned between the said polarizer and the said polyester film.   An image display device comprising the polarizing plate according to claim 1.

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