JP2007263987A - Polarizing plate protection film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate protection film that is excellent in environment-resistant dimensional stability and has retardation property as an optical compensation function, excellent stability of the retardation property and preferable adherence to a polarizer. <P>SOLUTION: The polarizer protection film has a thin layer of a hydrophilic polymer compound on the outermost surface on one surface of a transparent thermoplastic synthetic polymer film, and a crosslinked resin cured layer between the thin layer and the transparent thermoplastic synthetic polymer film. The transparent film is a birefringent film satisfying expressions (1): 0≤(nx-ny)×d≤300 nm and (2) -150≤ä(nx+ny)/2-nz}×d≤400 nm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a protective film for a polarizing plate, and more particularly to a protective film for a polarizing plate that has excellent durability such as chemical resistance and environmental resistance and has a function as optical compensation.

  Conventionally, a triacetate cellulose-based resin film has been used as a protective film for polarizing plates, but in recent years polarizing plates have been used in various applications and various environments, resulting in unprecedented harsh usage conditions. Is expected to have a function to withstand Currently, protective films for polarizing plates made of triacetate cellulose-based resin films are still used, but dimensional shrinkage occurs under environmental tests at high temperatures and high humidity, resulting in functional deterioration and shrinkage of the polarizer. Due to the generation of stress, it is a big problem to affect the image quality of a liquid crystal display element used as a polarizing plate application.

  Furthermore, until now, a polarizing plate having an optical compensation function was created by laminating a retardation film with a polarizing plate with an adhesive, but in order to realize further cost reduction of a liquid crystal display element, Reduction of the number of points and processing man-hours is desired, and efforts have been made to develop a retardation function as a protective film function of a polarizing plate. For this purpose, a film obtained by stretching a triacetate cellulose-based resin film to give a phase difference is also used, and a material intended to provide an optical compensation function for a polarizing plate protective film of a polarizing plate. Development has been carried out (for example, see Patent Document 1 below).

However, since a triacetate cellulose-based resin film is used as a base material, the deterioration of optical characteristics in the environmental resistance test is remarkable, and the problem of dimensional stability still remains. As a result, a polarizing plate protective film having an excellent environmental resistance and excellent dimensional stability and having retardation characteristics as an optical compensation function has not been obtained.
JP 2003-279729 A

  The present invention is for a polarizing plate having excellent dimensional stability in environmental resistance, having retardation characteristics as an optical compensation function, excellent stability of the retardation characteristics, and good adhesion to a polarizer. It is to provide a protective film.

  In order to solve the above problems, the present inventor has intensively studied a protective film for polarizing plates, and paid attention to the adhesiveness between a polarizer having a polarizing function and a film having retardation characteristics, and a film having the retardation characteristics. did. And in adhesiveness of a polarizer and such a film, it discovered that it was important to use a hydrophilic material and a crosslinkable resin together, and to provide each layer which consists of them in a specific order, and a polarizing plate. Has succeeded in providing a protective film.

で表されることを特徴とする上記［５］の偏光板用保護フィルム（但し、Ｒ_１およびＲ_２はそれぞれ独立に水素原子、ハロゲン原子及び炭素数１〜３の炭化水素基から選ばれる少なくとも１種の基である）。
［７］ ヒドロキシ化合物（Ｉ）からなる組成比の割合が、全体の５〜９５ｍｏｌ％を占める共重合ポリカーボネートであることを特徴とする上記［６］の偏光板用保護フィルム。
［８］ 共重合ポリカーボネートが、２種類以上の共重合ポリカーボネートを含む組成物であり、該組成物の粘度平均分子量が２０００〜１０００００であることを特徴とする上記［６］〜［７］のいずれかの偏光板用保護フィルム。 That is, the present invention can be achieved by the following [1] to [7].
[1] A film for laminating with a polarizer, comprising a crosslinked resin cured layer and a thin layer made of a hydrophilic polymer compound in this order on one side of a transparent thermoplastic synthetic polymer film, and the polymer The film has the following formulas (1) and (2)
_{0 ≦ (n x -n y)} × d ≦ 300nm (1)
0 <{(n _x + n _y ) / 2−n _z } × d ≦ 400 nm (2)
A protective film for a polarizing plate, which is a birefringent film satisfying the above requirements.
(In the above formulas (1) and (2), _nx and _ny are each independently the main refractive index in the plane of the film, _nz is the refractive index in the thickness direction of the film, and d is the film thickness. is there.)
[2] The protective film for polarizing plate according to [1], wherein the hydrophilic polymer compound is mainly a polyvinyl alcohol derivative.
[3] The protection for polarizing plate according to any one of [1] to [2], wherein the crosslinked resin cured layer is a layer obtained by curing a mixture in which a phenoxy resin and an isocyanate compound are present simultaneously. the film.
[4] The protective film for a polarizing plate according to any one of the above [1] to [3], wherein the thin layer made of the hydrophilic polymer compound is on the outermost surface of one side of the transparent thermoplastic synthetic polymer film.
[5] The protective film for a polarizing plate according to any one of [1] to [4], wherein the transparent thermoplastic synthetic polymer film is made of a polycarbonate resin.
[6] The hydroxy compound which is a monomer component in which the polycarbonate resin is a copolymerized polycarbonate is represented by the following formula (I)

The protective film for polarizing plate according to [5], wherein R ₁ and R ₂ are each independently selected from a hydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 3 carbon atoms. One group).
[7] The protective film for polarizing plate according to [6], wherein the composition ratio of the hydroxy compound (I) is a copolymerized polycarbonate occupying 5 to 95 mol% of the whole.
[8] Any of the above [6] to [7], wherein the copolymer polycarbonate is a composition containing two or more kinds of copolymer polycarbonates, and the viscosity average molecular weight of the composition is 2000 to 100,000. A protective film for such a polarizing plate.

  According to the present invention, the transparent thermoplastic synthetic polymer film has a thin layer made of a hydrophilic polymer compound on the outermost surface, and a crosslinked resin is interposed between the thin layer and the transparent thermoplastic synthetic polymer film. By having a hardened layer, it is possible to provide a protective film for a polarizing plate excellent in dimensional stability in environmental resistance. In addition, it is possible to provide a protective film for a polarizing plate that has retardation characteristics as an optical compensation function, has excellent stability of the retardation characteristics, and has good adhesion to a polarizer. In producing the polarizing plate having the above, it is possible to reduce the number of members and the number of processing steps, thereby achieving an effect of further reducing the cost of the members of the liquid crystal display element.

[Transparent thermoplastic polymer film]
The transparent thermoplastic synthetic polymer film used in the present invention may be any one that can be used as a protective film for a polarizing plate, and is transparent, mechanical strength, thermal stability, moisture shielding property, isotropic Those excellent in the above are preferable. Examples of materials that give a transparent thermoplastic synthetic polymer film include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, acrylic polymers such as polymethyl methacrylate, polystyrene, acrylonitrile / styrene copolymer (AS resin), and the like. Examples thereof include styrene-based polymers and polycarbonate-based polymers. In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyethersulfone polymers, polyetheretherketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers, or blends of the above polymers Examples of the polymer that forms the protective film for a polarizing plate are also exemplified. At this time, as a protective film for polarizing plate, it is necessary to have a thin film and sufficient strength, and suitable materials in this respect include polycarbonate polymers, norbornene resin polymers, norbornene polymers, polyarylate polymers, Polysulfone-based polymers and the like are preferable, and a polarizing plate protective film made of a polycarbonate-based polymer is particularly preferable.

  In particular, the polycarbonate-based polymer as a transparent thermoplastic synthetic polymer film suitably used in the present invention is a polyester of carbonic acid and glycol or dihydric phenol, usually carbonic acid and 2,2′-bis (4-hydroxy). There are various aromatic polycarbonates having a structural unit of (phenyl) -propane (commonly called bisphenol-A). However, the present invention is not limited to this, and for example, 1,1-bis (4-hydroxyphenyl) -Alkylcycloalkane, 1,1-bis (3-substituted-4-hydroxyphenyl) -alkylcycloalkane, 1,1-bis (3,5-substituted-4-hydroxyphenyl) -alkylcycloalkane, 9,9 -At least one divalent pheno selected from the group consisting of bis (4-hydroxyphenyl) fluorenes Polycarbonate copolymer homopolymer Le a monomer component, a mixture of phenol -A polycarbonate to monomer component, copolymerized polycarbonates to the dihydric phenol and bisphenol -A and monomer components.

  Specific examples of 1,1-bis (4-hydroxyphenyl) -alkylcycloalkane include 1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 1,1-bis (4-hydroxyphenyl) ) -3,3-dimethyl-5,5-dimethylcyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3-dimethyl-5-methylcyclopentane, and the like.

  1,1-bis (3-substituted-4-hydroxyphenyl) -alkylcycloalkane includes 1,1-bis (4-hydroxyphenyl) -alkyl substituted with an alkyl group having 1 to 12 carbon atoms or a halogen group. Cycloalkanes such as 1,1-bis (3-methyl-4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 1,1-bis (3-ethyl-4-hydroxyphenyl) -3,3- Dimethyl-5,5-dimethylcyclohexane, 1,1-bis (3-chloro-4-hydroxyphenyl) -3,3-dimethyl-4-methylcyclohexane, 1,1-bis (3-bromo-4-hydroxyphenyl) ) -3,3-dimethyl-5-methylcyclopentane.

  1,1-bis (3,5-substituted-4-hydroxyphenyl) -alkylcycloalkane includes 1,1-bis (4-hydroxyphenyl) substituted with an alkyl group having 1 to 12 carbon atoms or a halogen group. Alkylcycloalkanes such as 1,1-bis (3-methyl-4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 1,1-bis (3,5-dichloro-4-hydroxyphenyl)- 3,3-dimethyl-5-methylcyclohexane, 1,1-bis (3-ethyl-5-methyl-4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 1,1-bis (3,5- Dimethyl-4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 1,1-bis (3,5-dimethyl-4-hydroxyphenyl) -3,3-di Chill -5-methyl cyclopentane, and the like.

  Examples of 9,9-bis (4-hydroxyphenyl) fluorenes include 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, Examples include 9-bis (3-ethyl-4-hydroxyphenyl) fluorene.

  Furthermore, as other bisphenol components, 2,2′-bis (4-hydroxyphenyl) propane (bisphenol-A), 4,4 ′-(α-methylbenzylidene) bisphenol, bis (4-hydroxyphenyl) methane, 2 , 2′-bis (4-hydroxyphenyl) butane, 3,3′-bis (4-hydroxyphenyl) pentane, 4,4′-bis (4-hydroxyphenyl) hebutane, 4,4′-bis (4- Hydroxyphenyl) 2,5-dimethylhebutane, bis (4-hydroxyphenyl) methylphenylmethane, bis (4-hydroxyphenyl) diphenylmethane, 2,2′-bis (4-hydroxyphenyl) octane, bis (4-hydroxy) Phenyl) octane, bis (4-hydroxyphenyl) 4-fluorophenylmethane, 2, '-Bis (3-fluoro-4-hydroxyphenyl) propane, bis (3,5-dimethyl-4hydroxyphenyl) methane, 2,2'-bis (3,5-dimethyl-4-hydroxyphenyl) propane, bis ( 3,5-dimethyl-4-hydroxyphenyl) phenylethane, bis (3-methyl-4-hydroxyphenyl) diphenylmethane and the like. These can be used alone or in admixture of two or more.

  In addition to the bisphenol component, the polycarbonate contains a polyester carbonate using a small amount of aliphatic or aromatic dicarboxylic acid as a comonomer of the acid component. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, p-xylene glycol, bis (4-hydroxyphenyl) -methane, 1,1′-bis (4-hydroxyphenyl) -ethane, and 1,1′-. Bis (4-hydroxyphenyl) -butane, 2,2′-bis (4-hydroxyphenyl) -butane and the like can be mentioned. Of these, terephthalic acid and isophthalic acid are preferred.

  The molecular weight of the polycarbonate used is preferably one having a viscosity average molecular weight of 2000 to 100,000, more preferably 5000 to 70000, and still more preferably 7000 to 50000. This is expressed as a specific viscosity measured at 20 ° C. in a methylene chloride solution having a concentration of 0.7 g / dl, and is 0.07 to 2.70, preferably 0.15 to 1.80, more preferably 0.7. 20 to 1.30. A film having a viscosity average molecular weight of less than 2000 is not suitable because the resulting film becomes brittle, and a film having a viscosity average molecular weight of 100,000 or more is not preferable because processability to the film becomes difficult.

で表される繰り返し単位及び下記式（ＩＩＩ） As the polycarbonate used in the present invention, in particular, the following formula (II)

And a repeating unit represented by the following formula (III)

で表される繰り返し単位からなるポリカーボネートが好ましい。このポリカーボネートは共重合体であっても混合物であってもよい。

Polycarbonate consisting of repeating units represented by This polycarbonate may be a copolymer or a mixture.

In the formula (II), R _{3 to} R ₁₀ are each independently at least one group selected from a hydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 6 carbon atoms. Examples of the hydrocarbon group include alkyl groups such as a methyl group and an ethyl group, and aryl groups such as a phenyl group. X is the following formula

であり、Ｒ_１９およびＲ_２０はそれぞれ独立に水素原子、ハロゲン原子及び炭素数１〜３の炭化水素基から選ばれる少なくとも１種の基である。かかる炭化水素基としては、メチル基、エチル基等のアルキル基、フェニル基等のアリール基が挙げられる。

R ₁₉ and R ₂₀ are each independently at least one group selected from a hydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 3 carbon atoms. Examples of the hydrocarbon group include alkyl groups such as a methyl group and an ethyl group, and aryl groups such as a phenyl group.

In the above formula (III), R _{11 to} R ₁₈ are each independently at least one group selected from a hydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 22 carbon atoms. Examples of the hydrocarbon group include alkyl groups such as a methyl group and an ethyl group, and aryl groups such as a phenyl group. Y is the following formula group

から選ばれる少なくとも１種の基である。ここでＲ_２１〜Ｒ_２３、Ｒ_２５及びＲ_２６はそれぞれ独立に水素原子、ハロゲン原子及び炭素数１〜２２の炭化水素基から選ばれる少なくとも１種の基であり、Ｒ_２４及びＲ_２７は炭素数１〜２０の炭化水素基から選ばれる少なくとも１種の基である。炭素数１〜２２の炭化水素基及び炭素数１〜２０の炭化水素基としては、例えば、メチル基、エチル基等のアルキル基、フェニル基等のアリール基が挙げられる。

At least one group selected from the group consisting of Here, R _{21 to} R ₂₃ , R ₂₅ and R ₂₆ are each independently at least one group selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms, and R ₂₄ and R ₂₇ are carbon atoms. It is at least one group selected from the hydrocarbon groups of number 1-20. Examples of the hydrocarbon group having 1 to 22 carbon atoms and the hydrocarbon group having 1 to 20 carbon atoms include alkyl groups such as a methyl group and an ethyl group, and aryl groups such as a phenyl group.

Ar _{1 to} Ar ₃ are each independently at least one group selected from aryl groups having 6 to 10 carbon atoms. Examples of the aryl group include a phenyl group and a naphthyl group.

  In the polycarbonate composed of the repeating units represented by the above formulas (II) and (III), the content of (II) is preferably 5 to 95 mol% of the entire repeating units. In this polycarbonate, when the content of (II) is less than 5 mol%, the birefringence of the polymer film becomes large, so that it is difficult to obtain an in-plane uniform retardation film. On the other hand, when the content of (II) exceeds 95 mol% of the whole, the film is easily broken and becomes brittle, and is not suitable as a film having a retardation. More preferably, the content of (II) is preferably 20 to 80 mol%, and more effectively, the content of (II) is preferably 30 to 70 mol%. In particular, in applications in which characteristics with a larger retardation value are required for shorter wavelengths, it is suitable that the content of (II) is 30 to 55 mol%, and characteristics with smaller retardation values for shorter wavelengths are required. In such applications, it is suitable that the content of (II) is 55 to 70 mol%.

  Among these, in the above formula (III), 1,1-bis (3-methyl-4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 2,2′-bis (4-hydroxyphenyl) -propane ( (Also referred to as bisphenol A) is preferably used, and the copolymer polycarbonate composed of 9,9-bis (4-hydroxyphenyl) fluorene (also referred to as biscresol fluorene) in the above formula (I) has heat resistance and dimensional stability. , Excellent in transparency.

  In addition, in the transparent thermoplastic synthetic polymer film used in the present invention, polymer modification such as heat stabilizer, antioxidant, ultraviolet absorber, light stabilizer, transparent nucleator, permanent antistatic agent, fluorescent brightener, etc. The agent may be present in the film at the same time.

  The transparent thermoplastic synthetic polymer film of the present invention has good transparency, preferably a haze value of 5% or less and a total light transmittance of 85% or more.

  The glass transition temperature of the transparent thermoplastic synthetic polymer film is usually from 160 to 260 ° C., preferably from 170 to 250 ° C., particularly preferably from 180 to 240 ° C. At temperatures lower than that, the dimensional stability is poor, Moreover, since the temperature control of a extending process becomes very difficult at the temperature beyond it, manufacture becomes difficult.

The transparent thermoplastic synthetic polymer film of the present invention is a birefringent film having a retardation at the same time as a protective film for a polarizing plate, but the birefringence that is an optical characteristic thereof is represented by a retardation value, It is divided into inner retardation (R value) and thickness direction retardation (K value). These R value and K value are defined by the following formulas (a) and (b), respectively.
_{R = Δn × d = (n} x -n y) × d (a)
K = ((n _x + _ny ) / 2−n _z ) × d (b)
The unit of R value and K value is nm. _{n x,} n y, n _z is defined herein as follows.
n _x: maximum refractive index in the film plane n _y: refractive index of the direction perpendicular to the direction showing the maximum refractive index in the film plane n _z: film normal direction refractive index (the main stretching direction when monoaxial stretching (In the case of biaxial stretching, it means the direction of stretching so that the degree of orientation increases, and in terms of chemical structure, it refers to the orientation direction of the polymer main chain.)

  The transparent thermoplastic synthetic polymer film in the present invention may be an optical uniaxial or biaxial film having a phase difference.

[Method for producing transparent thermoplastic synthetic polymer film]
The production method of the transparent thermoplastic synthetic polymer film used for the protective film for polarizing plate of the present invention is not particularly limited, and a film produced using any known film production method can be used. is there. For example, any of a film by an extrusion method, a film by a solution cast method, a film by a calendar method, and the like may be used. In the present invention, a uniaxially stretched film or a biaxially stretched film may be used, but a film obtained by a solution casting method is preferred because it has excellent surface accuracy and optical isotropy and small anisotropy. Can be suitably used.

  The thickness of the protective film for polarizing plate is generally 500 μm or less, preferably 1 to 300 μm or less, particularly preferably 5 to 200 μm.

  The surface of the protective film for polarizing plate to which the polarizer is not adhered may be subjected to a hard coat layer, antireflection treatment, anti-sticking treatment, or treatment for diffusion or antiglare.

  The hard coat treatment is performed for the purpose of preventing the polarizing plate from being scratched. For example, the surface of the transparent protective film is coated with a cured film excellent in hardness and slipping properties by an appropriate ultraviolet curable resin such as acrylic or silicone. It can be formed by a method to be added to. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. The anti-sticking treatment is performed for the purpose of preventing adhesion with the adjacent layer.

  Anti-glare treatment is applied for the purpose of preventing external light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, the surface is roughened by sandblasting or embossing. It can be formed by imparting a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a method or a compounding method of transparent fine particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle size of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles made of a crosslinked or uncrosslinked polymer, etc. are used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing polarized transmitted light to expand a viewing angle or the like.

  The protective film for polarizing plate is preferably subjected to a surface treatment before bonding. Examples of the surface treatment include corona discharge treatment, ultraviolet irradiation treatment, and the like, and it is preferable that the surface state is preferably 65 ° or less, more preferably 60 ° or less, with a water droplet contact angle on the film surface.

[Hydrophilic polymer compound]
The hydrophilic polymer compound in the present invention is literally a polymer having an affinity for water, such as a hydrophilic cellulose derivative (for example, methylcellulose, carboxymethylcellulose, hydroxycellulose, etc.), a polyvinyl alcohol derivative (for example, polyvinyl alcohol). , Vinyl acetate-vinyl alcohol copolymer, polyvinyl acetal, polyvinyl homar, polyvinyl benzal, etc.), natural polymer compounds (eg, gelatin, casein, gum arabic, etc.), hydrophilic polyester derivatives (eg, partially sulfone) Polyethylene terephthalate, etc.) and polyvinyl derivatives (for example, poly-N-vinylpyrrolidone, polyacrylamide, polyvinylimidazole, polyvinylpyrazole, etc.). These may be used alone or in combination of two or more. The hydrophilic polymer compound is preferably a compound having a composition similar to that of a polarizer (usually a polyvinyl alcohol derivative (for example, polyvinyl alcohol)).

  The hydrophilic polymer compound may be dissolved by heating at the time of dissolution in order to improve solubility using water as a solvent. The dissolution concentration is about 2 to 50 parts by weight, preferably 5 to 30 parts by weight, when water is 100 parts by weight. When there is a cross-linked resin cured layer formed by curing a cross-linkable resin as a lower layer, the hydrophilic polymer compound is applied onto the heat-fixed layer and then heat-set. 1 minute or more is required at 100 ° C., preferably 100 ° C. for 5 minutes or more, more preferably holding at 100 ° C. for 10 minutes or more forms a thin layer as an adhesive layer without peeling To be good to do.

  In order to form a thin layer, it is possible to use a coating on one side of the transparent thermoplastic synthetic polymer film, in particular, a commonly used wet coating method. Represents a means of laminating deposits with a uniform film thickness on the film surface by coating uniformly on the film and drying, specifically spin coating method, Mayer bar coating method, forward rotation roll coating method , A gravure roll coating method, a reverse roll coating method, etc. are shown, and any of these methods may be used.

[Crosslinked resin cured layer]
In the present invention, when having a crosslinked resin cured layer obtained by curing a crosslinkable resin between the transparent thermoplastic synthetic polymer film and a thin layer comprising a hydrophilic polymer compound, Adhesiveness with the thin layer is further improved.

  The cured cross-linked resin layer obtained by curing the cross-linkable resin is a layer obtained by curing the cross-linkable resin through a cross-linking reaction or the like by external excitation energy, but by irradiation with active rays such as ultraviolet rays and electron beams. Examples thereof include an actinic radiation curable resin to be cured and a heat crosslinkable resin that initiates a crosslinking reaction by heat, and any of them may be used.

  Typical examples of the actinic radiation curable resin include an ultraviolet curable resin. Examples thereof include an ultraviolet curable polyester acrylate resin, an ultraviolet curable acrylic urethane resin, an ultraviolet curable methacrylate ester resin, and an ultraviolet curable resin. Examples thereof include a curable polyester acrylate resin and an ultraviolet curable polyol acrylate resin. In particular, UV curable polyol acrylate resins are good, such as trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, alkyl-modified dipenta. Photopolymerizable monomer oligomers such as erythritol pentaerythritol are preferred. These polyol acrylate resins are highly crosslinkable and have high curability, high hardness and low cure shrinkage, low odor and low toxicity, and are relatively safe.

  Examples of electron beam curable resins are preferably those having an acrylate-based functional group, such as relatively low molecular weight polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, spiroacetal resins. , Polybutadiene resin, polythiol polyene resin and the like.

  Examples of the thermosetting resin include epoxy resin, phenoxy resin, phenoxy ether resin, phenoxy ester resin, acrylic resin, melamine resin, phenol resin, and urethane resin, or a mixture thereof. Among these, an epoxy resin, a phenoxy resin, a phenoxy ether resin, and a phenoxy ester resin-containing composition are preferable. Furthermore, among these, what has a phenoxy-type resin can be used suitably, and the mixture of a phenoxy-type resin and a polyfunctional isocyanate compound is suitable.

で示される繰り返し単位からなるフェノキシ樹脂、フェノキシエーテル樹脂、フェノキシエステル樹脂から選択した少なくとも１種類のフェノキシ樹脂である。ここで、R_２８〜R_３３は、同一または異なる水素または炭素数１から３のアルキル基、R_３４は炭素数２から５のアルキレン基、Xはエーテル基、エステル基、ｍは０から３の整数、ｎは２０から３００の整数をそれぞれ意味する。 The phenoxy resin is represented by the following general formula (IV)

At least one phenoxy resin selected from a phenoxy resin, a phenoxy ether resin, and a phenoxy ester resin each having a repeating unit represented by formula (1). Here, R _{28 to} R ₃₃ are the same or different hydrogen or an alkyl group having 1 to 3 carbon atoms, R ₃₄ is an alkylene group having 2 to 5 carbon atoms, X is an ether group, an ester group, and m is 0 to 3 An integer, n means an integer of 20 to 300, respectively.

Of these, those in which R ₂₈ and R ₂₉ are methyl groups, R ₃₀ , R ₃₁ , R ₃₂ , and R ₃₃ are hydrogen and R ₃₄ is a pentylene group are preferred from the viewpoint of easy synthesis and cost.

  Moreover, as a polyfunctional isocyanate compound, what contains two or more isocyanate groups is required, and the following can be illustrated. 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, tolylene diisocyanate-trimethylolpropane adduct, t-cyclohexane-1,4-diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, hexamethylene diisocyanate, 1,3,6-hexamethylene triisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane-4, 4′-diisocyanate, hydrogenated diphenylmethane-4, 4 '-Diisocyanate, lysine diisocyanate, lysine ester triisocyanate, triphenylmethane triisocyanate, tris ( Socyanate phenyl) thiophosphate, m-tetramethylxylylene diisocyanate, p-tetramethylxylylene diisocyanate, 1,6,11-undecane triisocyanate, 1,8-diisocyanate-4-isocyanatomethyloctane, bicycloheptane triisocyanate, Examples thereof include polyisocyanates such as 2,2,4-trimethylhexamethylene isocyanate, 2,4,4-trimethylhexamethylene diisocyanate, mixtures thereof, and polyhydric alcohol adducts. Among these, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, tolylene diisocyanate-trimethylolpropane adduct and hexamethylene diisocyanate are particularly preferable from the viewpoint of versatility and reactivity.

  The cured crosslinked resin layer can be obtained by mixing a phenoxy resin and a polyfunctional isocyanate compound. In that case, it is good also as a heat-crosslinking resin solution suitable for application | coating by melt | dissolving and mixing using the solvent which melt | dissolves both well, for example, methyl ethyl ketone, methyl isobutyl ketone, cellosolve acetate, ethyl acetate etc. Then, this thermoplastic resin solution is formed on a plastic film by a wet coating method and cured by heat treatment, whereby a cured layer having good adhesion to the polyvinyl alcohol resin can be obtained.

  A particularly preferred composition is a heat-crosslinkable resin that is a mixture in which a phenoxy resin and a polyfunctional isocyanate compound are present simultaneously. Regarding the mixed composition, the number of moles of hydroxyl groups in the phenoxy resin is within the above-mentioned polyfunctional isocyanate compound. The value [NCO / OH] obtained by dividing the number of isocyanate moles in the range of 0.2 to 3 is excellent in adhesion to the polyvinyl alcohol resin layer.

  The thickness of the thin layer is usually 0.01 to 30 μm, preferably 0.05 to 10 μm. If it is thinner than 0.01 μm, it is difficult to uniformly apply to the film, which is inconvenient. On the other hand, if it is thicker than 30, there is a problem that a crack occurs with respect to the bending of the film.

[Application fields of protective films for polarizing plates]
The protective film for polarizing plates of the present invention has the thin layer on one surface of the transparent thermoplastic synthetic polymer film, preferably on the outermost surface via a crosslinked resin cured layer. Such a thin layer is bonded to a polarizer to provide a polarizing plate. The side of the polarizer surface that is not bonded to the thin layer is also usually protected by some film.

  The protective film for polarizing plate of the present invention is used as a polarizing plate having an optical compensation function, and can form a liquid crystal display device having a wide viewing angle and excellent display quality such as contrast, and twisted nematic mode. , A vertical alignment mode, an OCB (Optically Compensated Bend) alignment mode, a TFT liquid crystal display device such as an in-plane switching mode, or the like can be used. In practical use, it can be used for all applications used as a polarizing plate. For example, in the case of a liquid crystal display device, a backlight, a reflector or a transflective reflector is used in an illumination system. A transmission type, a reflection type, a transflective type, or the like can be formed. Examples of display devices using other polarizing plates include liquid crystal projectors, ferroelectric liquid crystals, those using antiferroelectric liquid crystals, and organic EL display devices. May be used for

  In the polarizing plate mounted with the protective film for polarizing plate of the present invention, the pressure-sensitive adhesive layer is used for bonding with the liquid crystal panel, but the pressure-sensitive adhesive layer exposed surface is provided with the pressure-sensitive adhesive layer on the polarizing plate, A separator is temporarily attached and covered for the purpose of preventing contamination.

  The adhesive layer is, for example, an adhesive such as a natural or synthetic resin, particularly a tackifier resin, a filler or pigment made of glass fiber, glass beads, metal powder, or other inorganic powder, a colorant, an antioxidant, or the like. You may contain the additive of being added to a layer. Moreover, the adhesion layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient. Attachment of the adhesive layer to the polarizing plate can be performed by an appropriate method. As an example thereof, for example, an adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of an appropriate solvent alone or a mixture such as toluene and ethyl acetate is prepared. Examples thereof include a method in which an adhesive layer is formed on a polarizing plate or an optical film by an appropriate developing method such as a casting method or a coating method, and then transferred onto the polarizing plate or the optical film. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 to 500 μm, preferably 2 to 200 μm, particularly preferably 10 to 100 μm.

  As the separator of the adhesive layer, for example, a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foamed sheet or metal foil, an appropriate thin leaf body such as a laminate thereof, if necessary, a silicone type or a long mirror alkyl type, It is possible to have an appropriate one according to the prior art, such as one coated with an appropriate release agent such as fluorine-based or molybdenum sulfide.

The material characteristic values and the like described in the present specification are obtained by the following evaluation methods.
(1) Measurement of R value and K value The phase difference R value, which is the product of birefringence Δn and film thickness d, and the phase difference K value perpendicular to the in-plane direction are the product name “KOBRA21” manufactured by Oji Scientific Instruments. -ADH ". R values are measured when the surface of the incident light and the film is _{vertical, R = Δn · d = (} n x -n y) × d, K = ((n x + n y) / 2-n z) Xd. The unit of R value and K value is nm. _{n x,} n y, n _z is defined herein as follows.
_nx : maximum refractive index in the film plane _ny : refractive index in the direction perpendicular to the direction showing the maximum refractive index in the film plane _nz : refractive index in the film normal direction

(2) Adhesive evaluation with polyvinyl alcohol 15 parts of polyvinyl alcohol resin (Kuraray PVA117, polymerization degree 1700, saponification degree 98.5) was dissolved by heating in a predetermined amount of 85 parts of water to prepare a polyvinyl alcohol solution. This polyvinyl alcohol solution was applied onto a protective film for a polarizing plate and then subjected to the Mayer bar coating method. Furthermore, it dried for 5 minutes in 60 degreeC oven, and laminated | stacked the 6-micrometer-thick polyvinyl alcohol resin layer. The adhesive property of the protective film for polarizing plate obtained by this polyvinyl alcohol resin layer and the examples and comparative examples was peeled off in the vertical direction by sticking a Nichiban cellophane tape to a region cross-cut to 100 pieces of 1 mm each. Evaluation was made based on whether or not peeling occurred in some cases.
×: Adhesiveness insufficient 1/100 peeling occurs ○: Adherence secured No peeling

(3) Evaluation method of dimensional stability Regarding the dimensional change of the protective film for polarizing plate, as an evaluation device, a real-time scanning laser microscope manufactured by Lasertec Co., Ltd .: trade name “1LM21D” is used, and an initial and heat resistance test. Later dimensions were measured. The test conditions were observed up to 1000 hr for 80 ° C. DRY and 60 ° C. and 90% RH, respectively. The evaluation criteria were three stages: no change, contraction, and expansion.

(4) Evaluation as a polarizing plate A sample having good adhesion to polyvinyl alcohol in the present invention was used as a protective film for polarizing plate to prepare a polarizing plate according to the following method, and a characteristic test on environmental resistance was conducted. did.
A 120 μm thick polyvinyl alcohol film was immersed in an aqueous solution containing 1 part of iodine, 2 parts of potassium iodide, and 4 parts of boric acid, and stretched 4 times at 50 ° C. to obtain a polarizing film. In the following steps (i) to (v), a polarizer (hereinafter sometimes referred to as a polarizing film) and a protective film for a polarizing plate were bonded together to produce a polarizing plate.
[Method of making polarizing plate]
(I) It arrange | positions on a glass plate on the thin layer of the protective film for polarizing plates cut out by 30 cm of longitudinal directions, and the width direction 18 cm.
(Ii) The polarizing film having the same size as the protective film for polarizing plate is immersed in a polyvinyl alcohol adhesive layer having a solid content of 2 wt% for 1 to 2 seconds.
(Iii) The excess adhesive adhering to the polarizing film of (ii) above is lightly removed, placed on the protective film sample of (i) above, and further cut into the same size and the protective film for polarizing plate and the adhesive Laminate them so that they touch each other.
(Iv) Excess adhesive and bubbles are removed from the end of the laminate of the polarizing film and the polarizing plate protective film laminated in (iii) above with a hand roller and bonded together. The pressure of the hand roller was about 2-3 kg / cm ² and the roller speed was about 2 m / min.
(V) The sample obtained in (iv) was left in an oven at 80 ° C. for 2 minutes to obtain a polarizing plate.

(5) Optical properties [Measurement of degree of polarization]
The transmittance was measured using Hitachi, Ltd., trade name “U-4000 Spectrophotometer”. In the measurement, the parallel and orthogonal transmittances were measured using two polarizing plates, and the degree of polarization was determined as follows. The parallel transmittance is a transmittance measured by overlapping two sheets so that the absorption axis of the polarizer is parallel. The orthogonal transmittance is a transmittance measured by overlapping two sheets so that the absorption axis of the polarizer is perpendicular. It is.
Polarization degree = {(H1-H2) / (H1 + H2)} ^1/2
H1: Parallel transmittance, H2: Orthogonal transmittance [Environmental resistance test of polarizing plate]
The test conditions were 80 ° C. DRY and 60 ° C. and 90% RH, each observed up to 1000 hr, and the optical characteristics were evaluated by the change in polarization degree before and after the test.
When the change in the degree of polarization was within 1%, the environmental resistance was judged as “good” and judged as “good”, and the others were judged as “poor” and judged as deteriorated.

(6) Optical compensation effect of liquid crystal display device The optical compensation effect was examined using a liquid crystal monitor VL-151VA manufactured by Fujitsu Limited.
The polarizing plate obtained by this invention was comprised on the back surface of the liquid crystal cell so that the arrangement | positioning of a slow axis might be equal similarly to a commercially available state. The surface used the structure of a commercial item.
As an evaluation, the contrast and viewing angle characteristics are compared with those of commercially available products, and those with an optical compensation effect are evaluated as good (◯), and those with no optical compensation are evaluated as bad (×). It was.

[Example 1]
A reactor equipped with a stirrer, thermometer and reflux condenser was charged with an aqueous sodium hydroxide solution and ion-exchanged water, and 1,1-bis (3-methyl-4-hydroxyphenyl) -3,3,5-trimethylcyclohexane and Biscresol fluorene was dissolved at a ratio of 50:50 (mol%) and a small amount of hydrosulfide was added. Next, methylene chloride was added thereto, and phosgene was blown in at about 20 ° C. over about 60 minutes. Further, p-tert-butylphenol was added for emulsification, triethylamine was added, and the mixture was stirred at 30 ° C. for about 3 hours to complete the reaction. After completion of the reaction, the organic phase was collected, and methylene chloride was evaporated to obtain a copolymerized polycarbonate. The composition ratio of the obtained copolymer polycarbonate was almost equal to the amount of monomer charged. Moreover, the glass transition point temperature of this resin was 236 degreeC.

  This copolymer polycarbonate was dissolved in methylene chloride to prepare an 18 wt% dope solution. This dope solution was cast on a steel drum, which was continuously peeled off and dried, and this was uniaxially stretched 1.8 times in the longitudinal direction at 230 ° C. with a roll stretching machine. The film thickness of the obtained uniaxially stretched film was 115 μm, and the residual solvent amount was 1.3% by weight. This retardation film was subjected to a transverse stretching process 2.1 times in the transverse direction at 240 ° C. with a tenter. The stretched film obtained by this sequential biaxial stretching had retardation values of R = 52 nm and K = 273 nm.

  A crosslinked resin cured layer was formed on the stretched film using a crosslinkable resin. The hardened layer was made by mixing 20 parts of PKHM-30, a phenoxy resin made by Union Carbide Corporation, 40 parts of methyl ethyl ketone and 20 parts of 2-ethoxyethyl acetate. 20 parts of Coronate L was mixed to prepare a coating solution. This coating solution was applied by the Meyer bar coating method and heat-treated at 130 ° C. for 5 minutes to form a cured layer having a thickness of 2 μm.

  Further, a thin layer made of a hydrophilic polymer compound was formed on the crosslinked resin cured layer. For the thin layer, a PVA aqueous solution obtained by heating and dissolving 15 parts of polyvinyl alcohol resin (Kuraray PVA117, polymerization degree 1700, saponification degree 98.5) in a predetermined amount of 85 parts of water was used as a coating solution. This coating solution is applied by the Meyer bar coating method, heat-treated at 100 ° C. for 5 minutes to form a thin layer having a thickness of 2 μm, and a hydrophilic polymer compound is formed on the outermost surface of the transparent thermoplastic synthetic polymer film. A polarizing plate protective film having a thin layer was obtained.

  With respect to this protective film for polarizing plate, dimensional stability was evaluated up to 1000 hr for 80 ° C. DRY and 60 ° C. and 90% RH, but no dimensional change was observed. At the same time, changes in the optical characteristics of the phase difference value and the K value were measured, but no change was observed.

  The adhesion test of this protective film for polarizing plates and polyvinyl alcohol was performed. A polyvinyl alcohol solution is applied to the surface having a thin layer of the protective film for polarizing plate by the Mayer bar coating method, dried in an oven at 60 ° C. for 5 minutes, and a polyvinyl alcohol layer having a thickness of 10 μm is applied to the polarizing plate. Formed on a protective film. An adhesion test between the polyvinyl alcohol layer and the protective film for polarizing plate was performed by a cross-cut test, but no peeling was observed and good adhesion was obtained.

Subsequently, the polarizing plate was produced using the said polarizing plate film.
When the thus prepared sample of Example 1 was evaluated, it was confirmed that the adhesiveness was good, the degree of polarization was 99.2%, and the film had sufficient properties as a polarizing plate. Also, in the environmental resistance test at 80 ° C. DRY and 60 ° C. 90% 1000 hr, the polarization degree characteristic was not seen and it was good.

  A polarizing plate using the polarizing plate protective film obtained in the present invention was mounted on a liquid crystal monitor. At this time, bonding was carried out via an adhesive so that the polarizing plate protective film of the present invention was installed on the liquid crystal cell side. When the display screen of the liquid crystal monitor thus obtained was confirmed, it had good contrast and a wide viewing angle.

[Example 2]
A reactor equipped with a stirrer, thermometer and reflux condenser was charged with an aqueous sodium hydroxide solution and ion-exchanged water, and bisphenol A and biscresol fluorene were dissolved at a ratio of 50:50 (mol%), and a small amount of hydrosulfide was added. Was added. Next, methylene chloride was added thereto, and phosgene was blown in at about 20 ° C. over about 60 minutes. Further, p-tert-butylphenol was added for emulsification, triethylamine was added, and the mixture was stirred at 30 ° C. for about 3 hours to complete the reaction. After completion of the reaction, the organic phase was collected, and methylene chloride was evaporated to obtain a copolymerized polycarbonate. The composition ratio of the obtained copolymer polycarbonate was almost equal to the amount of monomer charged. Moreover, the glass transition temperature of this resin was 213 degreeC.

  This copolymer polycarbonate was dissolved in methylene chloride to prepare an 18 wt% dope solution. This dope solution was cast on a steel drum, which was continuously peeled off and dried, and uniaxially stretched 1.8 times in the machine direction at 210 ° C. with a roll stretching machine. The film thickness of the obtained uniaxially stretched film was 119 μm, and the residual solvent amount was 1.2% by weight. This retardation film was subjected to a transverse stretching step 2.1 times in the transverse direction at 217 ° C. with a tenter. The stretched film obtained by this sequential biaxial stretching had retardation values of R = 49 nm and K = 268 nm.

Next, a polarizing plate protective film was obtained in the same manner as in Example 1.
Further, the polarizing plate protective film was evaluated in the same manner as in Example 1, but the same good results as in Example 1 were obtained.

  A polarizing plate using the polarizing plate protective film obtained in the present invention was mounted on a liquid crystal monitor. At this time, bonding was carried out via an adhesive so that the polarizing plate protective film of the present invention was installed on the liquid crystal cell side. When the display screen of the liquid crystal monitor thus obtained was confirmed, it had good contrast and a wide viewing angle.

[Comparative Example 1]
As in Example 2, a copolymerized polycarbonate obtained by using bisphenol A and biscresol fluorene in a ratio of 50:50 (mol%) was used.
This copolymer polycarbonate was dissolved in methylene chloride to prepare an 18 wt% dope solution. This dope solution was cast on a steel drum, which was continuously peeled off and dried, and uniaxially stretched 1.8 times in the machine direction at 210 ° C. with a roll stretching machine. The film thickness of the obtained uniaxially stretched film was 119 μm, and the residual solvent amount was 1.2% by weight. This retardation film was subjected to a transverse stretching step 2.1 times in the transverse direction at 217 ° C. with a tenter. The stretched film obtained by this sequential biaxial stretching had retardation values of R = 51 nm and K = 273 nm.

Here, this stretched film was used as a protective film for a polarizing plate as it was.
With respect to this protective film for polarizing plate, dimensional stability was evaluated up to 1000 hr for 80 ° C. DRY and 60 ° C. and 90% RH, but no dimensional change was observed. At the same time, changes in the optical characteristics of the phase difference value and the K value were measured, but no change was observed.

  The adhesion test of this protective film for polarizing plates and polyvinyl alcohol was performed. A polyvinyl alcohol solution is applied to the surface having a thin layer of the protective film for polarizing plate by the Mayer bar coating method, dried in an oven at 60 ° C. for 5 minutes, and a polyvinyl alcohol layer having a thickness of 10 μm is applied to the polarizing plate. Formed on a protective film. When the adhesion test between the polyvinyl alcohol layer and the protective film for polarizing plate was performed by a cross-cut test, the polyvinyl alcohol layer was completely peeled off, and sufficient adhesion between the protective film for polarizing plate and the polyvinyl alcohol was not obtained. .

[Comparative Example 2]
As in Example 2, a copolymerized polycarbonate obtained by using bisphenol A and biscresol fluorene in a ratio of 50:50 (mol%) was used.

  This copolymer polycarbonate was dissolved in methylene chloride to prepare an 18 wt% dope solution. This dope solution was cast on a steel drum, which was continuously peeled off and dried, and uniaxially stretched 1.8 times in the machine direction at 210 ° C. with a roll stretching machine. The film thickness of the obtained uniaxially stretched film was 119 μm, and the residual solvent amount was 1.2% by weight. This retardation film was subjected to a transverse stretching step 2.1 times in the transverse direction at 217 ° C. with a tenter. The stretched film obtained by this sequential biaxial stretching had retardation values of R = 54 nm and K = 270 nm.

  Next, a cured layer was formed on the stretched film using a crosslinkable resin. The hardened layer is a mixture of 20 parts of PKHM-30, a phenoxy resin made by Union Carbide Corporation, 40 parts of methyl ethyl ketone as a solvent and 20 parts of 2-ethoxyethyl acetate. 20 parts of Coronate L was mixed to prepare a coating solution. This coating solution was applied by the Meyer bar coating method and heat-treated at 130 ° C. for 5 minutes to form a cured layer having a thickness of 2 μm. Here, the stretched film having a cured layer thus obtained was used as a protective film for a polarizing plate.

  With respect to this protective film for polarizing plate, dimensional stability was evaluated up to 1000 hr for 80 ° C. DRY and 60 ° C. and 90% RH, but no dimensional change was observed. At the same time, changes in the optical characteristics of the phase difference value and the K value were measured, but no change was observed.

  Next, the adhesiveness test of this protective film for polarizing plates and polyvinyl alcohol was done. A polyvinyl alcohol solution is applied to the surface having a thin layer of the protective film for polarizing plate by the Mayer bar coating method, dried in an oven at 60 ° C. for 5 minutes, and a polyvinyl alcohol layer having a thickness of 10 μm is applied to the polarizing plate. Formed on a protective film. When the adhesion test between the polyvinyl alcohol layer and the protective film for polarizing plate was performed by a cross-cut test, the polyvinyl alcohol layer was completely peeled off, and sufficient adhesion between the protective film for polarizing plate and the polyvinyl alcohol was not obtained. .

[Comparative Example 3]
As in Example 2, a copolymerized polycarbonate obtained by using bisphenol A and biscresol fluorene in a ratio of 50:50 (mol%) was used.

  This copolymer polycarbonate was dissolved in methylene chloride to prepare an 18 wt% dope solution. This dope solution was cast on a steel drum, which was continuously peeled off and dried, and uniaxially stretched 1.8 times in the machine direction at 210 ° C. with a roll stretching machine. The film thickness of the obtained uniaxially stretched film was 119 μm, and the residual solvent amount was 1.2% by weight. This retardation film was subjected to a transverse stretching step 2.1 times in the transverse direction at 217 ° C. with a tenter. The stretched film obtained by this sequential biaxial stretching had retardation values of R = 54 nm and K = 270 nm.

  Next, a thin layer made of a hydrophilic polymer compound was formed on the stretched film. For the thin layer, a PVA aqueous solution obtained by heating and dissolving 15 parts of polyvinyl alcohol resin (Kuraray PVA117, polymerization degree 1700, saponification degree 98.5) in a predetermined amount of 85 parts of water was used as a coating solution. This coating solution is applied by the Meyer bar coating method, heat-treated at 100 ° C. for 5 minutes to form a thin layer having a thickness of 2 μm, and composed of a hydrophilic polymer compound on the outermost surface of one side of the transparent thermoplastic synthetic polymer film. A protective film for a polarizing plate having a thin layer was obtained. Here, the stretched film having a thin layer thus obtained was used as a protective film for a polarizing plate.

  With respect to this protective film for polarizing plate, dimensional stability was evaluated up to 1000 hr for 80 ° C. DRY and 60 ° C. and 90% RH, but no dimensional change was observed. At the same time, changes in the optical characteristics of the phase difference value and the K value were measured, but no change was observed.

  Next, the adhesiveness test of this protective film for polarizing plates and polyvinyl alcohol was done. A polyvinyl alcohol solution is applied to the surface having a thin layer of the protective film for polarizing plate by the Mayer bar coating method, dried in an oven at 60 ° C. for 5 minutes, and a polyvinyl alcohol layer having a thickness of 10 μm is applied to the polarizing plate. Formed on a protective film. When the adhesive test between the polyvinyl alcohol layer and the protective film for polarizing plate is performed by a cross-cut test, the polyvinyl alcohol layer and the thin layer are all peeled off, and the adhesive property between the protective film for polarizing plate and the polyvinyl alcohol is sufficient. Was not obtained.

  The protective film for polarizing plate of the present invention is used as a polarizing plate having an optical compensation function, and can form a liquid crystal display device having a wide viewing angle and excellent display quality such as contrast, and twisted nematic mode. , A vertical alignment mode, an OCB (Optically Compensated Bend) alignment mode, a TFT liquid crystal display device such as an in-plane switching mode, or the like can be used. In practical use, it can be used for all applications used as a polarizing plate. For example, in the case of a liquid crystal display device, a backlight, a reflector or a transflective reflector is used in an illumination system. A transmission type, a reflection type, a transflective type, or the like can be formed. Examples of display devices using other polarizing plates include liquid crystal projectors, ferroelectric liquid crystals, those using antiferroelectric liquid crystals, and organic EL display devices.

Claims (8)

A film for laminating with a polarizer, comprising a cured crosslinked resin layer and a thin layer composed of a hydrophilic polymer compound in this order on one side of a transparent thermoplastic synthetic polymer film, and the polymer film comprising: Formulas (1) and (2)
_{0 ≦ (n x -n y)} × d ≦ 300nm (1)
_{-150 ≦ {(n x + n} y) / 2-n z} × d ≦ 400nm (2)
A protective film for a polarizing plate, which is a birefringent film satisfying the above requirements.
(In the above formulas (1) and (2), _nx and _ny are each independently the main refractive index in the plane of the film, _nz is the refractive index in the thickness direction of the film, and d is the film thickness. is there.)   The protective film for a polarizing plate according to claim 1, wherein the hydrophilic polymer compound is mainly a polyvinyl alcohol derivative.   The protective film for a polarizing plate according to claim 1, wherein the crosslinked resin cured layer is a layer obtained by curing a mixture in which a phenoxy resin and an isocyanate compound are present simultaneously.   The protective film for polarizing plates in any one of Claims 1-3 in which the thin layer which consists of a hydrophilic high molecular compound exists in the outermost surface of the at least single side | surface of a transparent thermoplastic synthetic polymer film.   The said transparent thermoplastic synthetic polymer film consists of polycarbonate-type resin, The protective film for polarizing plates in any one of Claims 1-4 characterized by the above-mentioned. The polycarbonate compound is composed of a copolymerized polycarbonate, and the hydroxy compound that is a monomer component constituting the copolymerized polycarbonate is represented by the following formula (I):

The protective film for a polarizing plate according to claim 5, wherein R ₁ and R ₂ are each independently selected from a hydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 3 carbon atoms. At least one group).   The protective film for a polarizing plate according to claim 6, wherein the composition ratio of the hydroxy compound (I) is a copolymerized polycarbonate occupying 5 to 95 mol% of the whole.   8. The polarizing plate according to claim 6, wherein the copolymer polycarbonate is a composition containing two or more kinds of copolymer polycarbonates, and the viscosity average molecular weight of the composition is 2000 to 100,000. Protective film.