JP2008129212A - Optical film, polarizing plate and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film having high optical transparency, good flexibility and good film conveyability, excellent in productivity, and useful particularly as a polarizer protective film, a polarizing plate using the optical film, having few defects on the appearance, and producible with good productivity, and a high-definition image display device using the polarizing plate. <P>SOLUTION: The optical film is obtained by crosslinking and curing an ionizing radiation curable resin composition comprising (A) 70-95 mass% of a monofunctional (meth)acrylic acid polymer having a weight average molecular weight of 50,000-80,000 and (B) 5-30 mass% of a polyfunctional compound having a radically polymerizable unsaturated double bond. The polarizing plate is obtained by forming the optical film on at least one surface of a polarizer. The image display device is obtained using the polarizing plate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical film formed by crosslinking and curing by irradiation with ionizing radiation such as various ultraviolet rays (UV-A, UV-B, UV-C), visible light, gamma rays, X-rays, electron beams, and the like. The present invention relates to a polarizing plate used as a protective film on one or both sides of a polarizer, and an image display device using the polarizing plate.

The polarizing plate is used in a liquid crystal display device or the like. Generally, the polarizing plate is composed of three layers in which protective films are laminated on both sides of a polarizer.
As the polarizer, a uniaxially oriented film in which iodine or a dye is adsorbed and dispersed in polyvinyl alcohol (hereinafter referred to as “PVA”) is usually used. Since this PVA polarizer shrinks due to heat and moisture and lowers the polarization function, it is a laminate in which protective films are bonded to both sides. The protective film has no birefringence, is optically isotropic, has high light transmittance, has excellent moisture resistance and heat resistance, has excellent mechanical properties, and has good flatness. In addition, good adhesion to the polarizer is required. For this purpose, a cellulose-based film has been conventionally used (see Patent Document 1).

Currently, triacetate (hereinafter referred to as “TAC”) is generally used as a cellulose film. However, the TAC film does not have sufficient resistance to moisture and heat, and when a polarizing plate using the TAC film as a polarizer protective film is used at high temperature or high humidity, the performance of the polarizing plate such as the degree of polarization and the hue deteriorates. is there.
Further, the TAC film produces a phase difference with respect to incident light in an oblique direction. Such a phase difference significantly affects viewing angle characteristics as the size of liquid crystal displays increases in recent years.
Further, since methylene chloride must be used as a solvent for the production of the TAC film, there are concerns about adverse effects on the environment and the like.

Further, as a polarizer protective film, a protective film for a polarizing plate formed of a polymer of styrenes, vinyl esters, maleic anhydrides, acrylic esters or methacrylic esters has been proposed (Patent Document 2 and 3). In particular, in terms of optical transparency, a (meth) acrylic resin that is a polymer such as acrylic acid esters and methacrylic acid esters is preferable.
However, since these are very hard and brittle in the film state, there is a possibility that breakage or the like may occur at the time of film conveyance, which causes a problem in conveyance property and poor productivity.

JP-A-7-120617 JP-A-9-197128 Japanese Patent Laid-Open No. 5-119217

The present invention has been made to solve the above-described conventional problems, and the object of the present invention is as follows.
(1) To provide an optical film particularly useful as a polarizer protective film having high optical transparency, good flexibility, good film transportability and excellent productivity,
(2) To provide a polarizing plate that can be produced with good productivity by using the optical film with few defects in appearance,
(3) To provide a high-quality image display device using the polarizing plate,
It is in.

As a result of intensive studies to achieve the above object, the present inventors have determined that an ionizing radiation curable resin composition containing a specific (meth) acrylic acid polymer and a compound having a radically polymerizable unsaturated double bond It has been found that the above problems can be solved by using an optical film obtained by crosslinking and curing a product. The present invention has been completed based on such findings.
That is, the present invention
[1] (A) 70 to 95% by mass of a monofunctional (meth) acrylic acid polymer having a weight average molecular weight of 50,000 to 80,000, and (B) a compound having a polyfunctional radically polymerizable unsaturated double bond An optical film obtained by crosslinking and curing an ionizing radiation curable resin composition containing 5 to 30% by mass;
[2] (B) The optical film according to [1], wherein the compound having a polyfunctional radically polymerizable unsaturated double bond is a polyfunctional (meth) acrylic acid polymer,
[3] A polarizing plate formed by forming the optical film according to [1] or [2] on at least one surface of a polarizer, and [4] An image display device using the polarizing plate according to [3]. ,
Is to provide.

  According to the present invention, even for incident light from an oblique direction, the phase difference is low, the optical transparency and mechanical strength are excellent, the flexibility is excellent, and the productivity is excellent. It is possible to provide an optical film particularly excellent as a polarizer protective film having excellent adhesion to the polarizer. Moreover, the polarizing plate using the polarizer protective film which consists of this optical film, and the polarizer formed from a PVA-type resin with few external appearance defects can be provided with sufficient productivity. Furthermore, a high quality image display device using the polarizing plate can be provided.

  The optical film of the present invention comprises (A) a monofunctional (meth) acrylic acid polymer having a weight average molecular weight of 50,000 to 80,000 (hereinafter sometimes referred to as component (A)) 70 to 95% by mass, and ( B) It is formed by crosslinking and curing an ionizing radiation curable resin composition containing 5 to 30% by mass of a compound having a polyfunctional radically polymerizable unsaturated double bond (hereinafter sometimes referred to as component (B)).

[(A) Monofunctional (meth) acrylic acid polymer]
The monofunctional (meth) acrylic acid polymer as the component (A) in the present invention is a homopolymer of a (meth) acrylic acid monomer or a monofunctional (meth) acrylic acid ester monomer or a co-polymer of a plurality of types of monomers. It is a coalescence. In addition, "(meth) acrylic acid" means "acrylic acid or methacrylic acid" here, and the thing similar to this also has the same meaning.

Examples of (meth) acrylic acid ester monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and t-butyl (meth). acrylate, 2-ethylhexyl (meth) (meth) C ₁ -C ₁₈ alkyl esters of acrylic acid such as acrylate; hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxyl group, such as hydroxybutyl (meth) acrylate Containing (meth) acrylates; Nitrogen-containing (meth) acrylates such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate; Glycidyl (meth) acrylate, Tetrahydrofurfuryl (meth) acrylate DOO, containing functional groups such as morpholyl (meth) acrylate (meth) acrylate; isobornyl (meth) acrylate, alicyclic (meth) acrylates such as cyclohexyl (meth) acrylate. Among these, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl ( A (meth) acrylate etc. are preferable.

  The monofunctional (meth) acrylic acid polymer is polymerized by various methods known in the art such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. alone or in combination of two or more of the above monomers. can get. Further, it may be a copolymer with various monomers such as styrene, vinyltoluene, (meth) acrylonitrile and the like.

  It is essential that the weight average molecular weight of the monofunctional (meth) acrylic acid polymer is in the range of 50,000 to 80,000. When the weight average molecular weight is smaller than 50,000, the film forming strength at the time of producing an optical film is weak and the film is easily broken, so that it is not suitable as an optical film. On the other hand, when the weight average molecular weight is larger than 80,000, the flexibility is poor. Therefore, for example, when it is applied to a polarizing plate as a protective film for a polarizer, handling is difficult. From the above viewpoint, the weight average molecular weight of the monofunctional (meth) acrylic acid polymer is preferably in the range of 60,000 to 75,000.

  Content in the ionizing radiation curable resin composition of the said monofunctional (meth) acrylic acid polymer is the range of 70-95 mass%. When the content is less than 70% by mass, flexibility is poor and the film is easily broken, so that it is difficult to use as an optical film. On the other hand, when it exceeds 95% by mass, the film formation strength is weak when forming an optical film, and it is difficult to use it as an optical film. From the above viewpoint, the content of the monofunctional (meth) acrylic acid polymer in the ionizing radiation curable resin composition is more preferably in the range of 70 to 90% by mass.

[(B) Compound having a polyfunctional radically polymerizable unsaturated double bond]
Next, the compound having a polyfunctional radically polymerizable unsaturated double bond as the component (B) in the present invention is a compound that is cross-linked and cured by ionizing radiation, and specifically, a polyfunctional monomer. A polymerizable monomer, a polyfunctional oligomer, a polyfunctional polymer, etc. are mentioned, As a functional group which bridge | crosslinks and hardens | cures by ionizing radiation, a (meth) acryloyl group, an allyl group, or an epoxy group is mentioned.
The polysynthetic monomer is preferably a polyfunctional (meth) acrylic acid derivative having a radical polymerizable unsaturated group in the molecule, and more specifically a polyfunctional (meth) acrylate.

  Examples of the compound that crosslinks and cures by ionizing radiation include ultraviolet curable resins and electron beam curable resins. In the present invention, it is preferable to use electron beam curable resins. This is because a composition using an electron beam curable resin can be made solvent-free, is more preferable from the viewpoint of environment and health, and does not require an initiator for photopolymerization, so that stable curing characteristics can be obtained. .

  The polyfunctional (meth) acrylate is not particularly limited as long as it is a (meth) acrylate having two or more ethylenically unsaturated bonds in the molecule. Specifically, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) ) Acrylate, polyethylene glycol di (meth) acrylate, hydroxypivalate neopentyl glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate, caprolactone modified dicyclopentenyl di (meth) acrylate, ethylene oxide modified diphosphate ( (Meth) acrylate, allylated cyclohexyl di (meth) acrylate, isocyanurate di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene oxide modified trimethylo Propane tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide modified trimethylolpropane tri (meth) acrylate, tris ( Acryloxyethyl) isocyanurate, propionic acid modified dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tricyclodecane dimethanol diacrylate, ethylene oxide modified dipentaerythritol hexa (meth) acrylate, caprolactone modified di Examples include pentaerythritol hexa (meth) acrylate. These polyfunctional (meth) acrylates may be used singly or in combination of two or more.

  In the present invention, a monofunctional (meth) acrylate can be used in combination with the polyfunctional (meth) acrylate as long as the object of the present invention is not impaired, for the purpose of reducing the viscosity. Examples of the monofunctional (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, and cyclohexyl (meth) ) Acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isobornyl (meth) acrylate, and the like. These monofunctional (meth) acrylates may be used individually by 1 type, and may be used in combination of 2 or more type.

  Next, the polyfunctional oligomer (also called prepolymer) has a weight average molecular weight of about 300 to 5,000, and a radical polymerizable unsaturated bond such as a (meth) acryloyl group, an allyl group, or an epoxy group in the molecule. A polyurethane-based, polyester-based, polyether-based, polycarbonate-based, or poly (meth) acrylic acid ester-based polyfunctional oligomer (prepolymer) having the above can be used.

Examples of the polyfunctional oligomer include epoxy (meth) acrylates, urethane (meth) acrylates, polyester (meth) acrylates, and polyether (meth) acrylates.
Here, the epoxy (meth) acrylate oligomer can be obtained, for example, by reacting (meth) acrylic acid with an oxirane ring of a relatively low molecular weight bisphenol type epoxy resin or novolak type epoxy resin and esterifying it. it can. Further, a carboxyl-modified epoxy (meth) acrylate oligomer obtained by partially modifying this epoxy (meth) acrylate oligomer with a dibasic carboxylic acid anhydride can also be used.

The urethane (meth) acrylate oligomer can be obtained, for example, by esterifying a polyurethane oligomer obtained by reaction of polyether polyol or polyester polyol and polyisocyanate with (meth) acrylic acid.
Polyester (meth) acrylate-based oligomers are obtained by esterifying the hydroxyl groups of polyester oligomers having hydroxyl groups at both ends obtained by condensation of polyvalent carboxylic acids and polyhydric alcohols with (meth) acrylic acid, It can be obtained by esterifying the terminal hydroxyl group of an oligomer obtained by adding alkylene oxide to carboxylic acid with (meth) acrylic acid.
The polyether (meth) acrylate oligomer can be obtained by esterifying the hydroxyl group of the polyether polyol with (meth) acrylic acid.

  In addition, polyfunctional oligomers include polybutadiene oligomers with high hydrophobicity that have (meth) acrylate groups in the side chain of polybutadiene oligomers, and silicone (meth) acrylate oligomers that have polysiloxane bonds in the main chain. In a molecule such as an aminoplast resin (meth) acrylate oligomer modified with an aminoplast resin having many reactive groups in a small molecule, or a novolak epoxy resin, bisphenol epoxy resin, aliphatic vinyl ether, aromatic vinyl ether, etc. There are oligomers having a cationic polymerizable functional group.

  Next, as the polyfunctional polymer, a urethane (meth) acrylate having a weight average molecular weight of about 1,000 to 300,000 and having a radical polymerizable double bond such as a (meth) acryloyl group, an allyl group, or an epoxy group. , Isocyanurate (meth) acrylate, polyester-urethane (meth) acrylate, epoxy (meth) acrylate, and the like can be applied.

  In the present invention, it is important that the resin composition containing the component (A) and the component (B) is cross-linked and cured by ionizing radiation. ) It preferably contains an acrylate monomer.

  Content of the said (B) component in the ionizing radiation-curable resin composition of this invention is the range of 5-30 mass%. When content of (B) component is less than 5 mass%, when forming an optical film, film-forming intensity | strength is weak and it is difficult to use as an optical film. On the other hand, when the content of the component (B) exceeds 30% by mass, the film is difficult to be used because it is poor in flexibility and easily breaks. From the above viewpoint, the content of the component (B) is more preferably in the range of 10 to 30% by mass.

[Other ingredients]
In addition, the ionizing radiation curable resin composition of the present invention may contain a monomer called a reactive diluent. The monomer is a monofunctional reactive diluent having a (meth) acryloyl group, an allyl group, or an epoxy group. Usually, an ionizing radiation curable resin composition has a high viscosity and cannot be applied unless it is adjusted with an organic solvent to lower the viscosity. However, when the monomer is contained in the ionizing radiation curable resin composition, the viscosity is lowered and it is not necessary to use a solvent. Therefore, the monomer can be used in a non-solvent (no solvent). The functional oligomer has the same effect.

When an ultraviolet curable resin composition is used as the component (B), about 0.1 to 5 parts by mass of a photopolymerization initiator is added to 100 parts by mass of the ionizing radiation curable resin composition. Is desirable.
The initiator for photopolymerization can be appropriately selected from those conventionally used and is not particularly limited. For example, for polymerizable monomers and polymerizable oligomers having radically polymerizable unsaturated groups in the molecule, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone , Dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, 4- (2-hydroxyethoxy) phenyl-2 (hydroxy-2-propyl) ketone, Non, p-phenylbenzophenone, 4,4′-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tertiarybutylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, Examples include 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal and the like.
Examples of the polymerizable oligomer having a cationic polymerizable functional group in the molecule include aromatic sulfonium salts, aromatic diazonium salts, aromatic iodonium salts, metallocene compounds, and benzoin sulfonic acid esters. Moreover, as a photosensitizer, p-dimethylbenzoic acid ester, tertiary amines, a thiol type sensitizer, etc. can be used, for example.

  Moreover, various additives can be mix | blended with the ionizing radiation-curable resin composition of this invention according to the desired physical property of the cured resin layer obtained. Examples of the additive include a weather resistance improver, an abrasion resistance improver, a polymerization inhibitor, a crosslinking agent, an infrared absorber, an antistatic agent, an adhesion improver, a leveling agent, a thixotrope, as long as the transparency is not affected. Examples include a property-imparting agent, a coupling agent, a plasticizer, an antifoaming agent, a filler, and a solvent.

Here, as the weather resistance improving agent, an ultraviolet absorber or a light stabilizer can be used.
The ultraviolet absorber may be either inorganic or organic, and as the inorganic ultraviolet absorber, titanium dioxide, cerium oxide, zinc oxide or the like having an average particle diameter of about 5 to 120 nm can be preferably used. Moreover, as an organic type ultraviolet absorber, benzotriazole type, for example, 2- (2-hydroxy-5-methylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-tert-) is specifically mentioned. Amylphenyl) benzotriazole, 3- [3- (benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl] propionic acid ester of polyethylene glycol, and the like.
On the other hand, examples of the light stabilizer include hindered amines, specifically 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2′-n-butylmalonate bis (1,2,2). , 6,6-pentamethyl-4-piperidyl), bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, tetrakis (2,2,6,6-tetramethyl-4-piperidyl)- 1,2,3,4-butanetetracarboxylate and the like.
Further, as the ultraviolet absorber or light stabilizer, a reactive ultraviolet absorber or light stabilizer having a polymerizable group such as a (meth) acryloyl group in the molecule can be used.

  Examples of the wear resistance improver include, for inorganic substances, spherical particles such as α-alumina, silica, kaolinite, iron oxide, diamond, and silicon carbide. Examples of the particle shape include a sphere, an ellipsoid, a polyhedron, a scale shape, and the like. Although there is no particular limitation, a spherical shape is preferable. Organic materials include synthetic resin beads such as cross-linked acrylic resin and polycarbonate resin. The particle size is usually about 30 to 200% of the film thickness of the optical film. Among these, spherical α-alumina is particularly preferable because it has high hardness and a large effect on improving wear resistance, and it is relatively easy to obtain spherical particles.

  Examples of the polymerization inhibitor include hydroquinone, p-benzoquinone, hydroquinone monomethyl ether, pyrogallol, and t-butylcatechol. Examples of the crosslinking agent include a polyisocyanate compound, an epoxy compound, a metal chelate compound, an aziridine compound, and an oxazoline compound. Used.

As the filler, for example, barium sulfate, talc, clay, calcium carbonate, aluminum hydroxide and the like are used.
As the infrared absorber, for example, a dithiol metal complex, a phthalocyanine compound, a diimmonium compound, or the like is used.

[Method for producing optical film]
Hereinafter, the manufacturing method of the optical film of this invention is explained in full detail, referring FIGS.
The above-mentioned component (A), component (B) and various additives are homogeneously mixed at a predetermined ratio to prepare a coating liquid comprising an ionizing radiation curable resin composition. The viscosity of the coating solution is not particularly limited as long as it is a viscosity capable of forming the uncured resin layer 6 on the surface of the substrate 4 by a coating method described later.

The coating solution prepared in this way is a gravure coating method, a bar coating method, a roll coating method, a micro gravure coating method, a reverse coating method, a roll brush method, a spray coating method, an air knife coating method, a comma coating method, A known method such as an impregnation method, or a curtain coating method or the like is applied alone or in combination, and applied to the substrate (FIG. 1A).
When an aqueous coating liquid is used, a slight amount of an organic solvent may be included for the purpose of maintaining the stability of the coating liquid. Preferably, coating is performed by a comma coating method, and the uncured resin layer 6 is formed on the substrate 4.
The coating amount is appropriately determined according to the required thickness of the optical film, but usually the thickness after curing is in the range of 10 to 150 μm. When the thickness is 10 μm or more, sufficient strength can be obtained when the optical film is used as a protective film for a polarizer. On the other hand, when the thickness is 150 μm or less, the production is easy and there is no cost problem. From the above viewpoint, the thickness of the optical film is more preferably in the range of 30 to 100 μm.

There is no restriction | limiting in particular as the base material 4 used here, For example, it has a mold release property which shows the surface tension of 40 dyn / cm or less at 20 degreeC, and is a normal transfer material which has sufficient self-holding property. Any film that can be used can be suitably used. Specific examples include polyester films such as polyethylene terephthalate films; polyolefin films such as polyethylene films and polypropylene films; polycarbonate films; polyvinylidene fluoride films, polyvinyl fluoride films, polyhexafluoropropylene films, poly (heptafluoroisopropyl (meth)) Fluorine-based resin films such as acrylate films; silicon-containing polymer films such as polyoxydimethylsilylene, polyoxymethylsilylene, polyoxydimethylsilylene-α, ω-dibutanoic acid, polyoxyvinylsilylene; polystyrene films, polyamide films, polyamides Resin films such as imide film, polyvinyl chloride film, cellulose acetate film; cellophane paper, glass Western paper such as thin paper; Japanese paper; and these composite film-like materials.
Among these films, when used as a protective film for a polarizer, a biaxially stretched polyester film having surface smoothness and low cost is desirable.

Although the thickness of the base material 4 is not specifically limited, In order to suppress generation | occurrence | production of a wrinkle and a crack with respect to an optical film, it is preferable normally that it is the range of 4-150 micrometers, and is the range of 12-120 micrometers. Is more preferable, and the range of 16 to 100 μm is more preferable.
In particular, when used as a protective film for a polarizer, a range of 16 to 100 μm, which has shape retention and is less likely to wrinkle, is desirable.

When the release property of the optical film 1 from the base material 4 is insufficient, a release treatment can be performed on the surface of the base material 4. Examples of the treatment agent used for the mold release treatment include mold release waxes such as paraffin wax; silicone resin, melamine resin, urea resin, urea-melamine resin, cellulose resin, benzoguanamine resin, and the like. Mold resin; various surfactants can be used.
The mold release treatment can be performed by a known method using the above treatment agent. For example, the treatment agent alone or mixed with a solvent or the like, applied onto a substrate according to a normal printing method such as a gravure printing method, a screen printing method, or an offset printing method, dried, and further cured as necessary ( The release layer can be formed by heating, ultraviolet irradiation, electron beam irradiation, or radiation irradiation.

  Next, the uncured resin layer 6 formed on the substrate 4 is irradiated with ionizing radiation 5 such as an electron beam and ultraviolet rays by the above-described method to cure the uncured resin layer 6 (FIG. 1B). )), To obtain the optical film 1 of the present invention (FIG. 1 (c)). Here, when an electron beam is used as the ionizing radiation 5, the acceleration voltage can be appropriately selected according to the resin used and the thickness of the layer, but is usually 100 to 1000 keV, preferably uncured at an acceleration voltage of about 70 to 300 kV. It is preferable to cure the resin layer 6.

In electron beam irradiation, the transmission capability increases as the acceleration voltage increases. Therefore, when a base material that deteriorates due to an electron beam is used as the base material 4, the transmission depth of the electron beam and the uncured resin layer 6 are increased. By selecting an accelerating voltage so that the thicknesses of the base material 4 are substantially equal, it is possible to suppress irradiation of the base material 4 with an extra electron beam and minimize deterioration of the base material 4 due to the excess electron beam. You can stay.
The irradiation dose is preferably such that the crosslinking density of the uncured resin layer 6 is saturated, and is usually selected in the range of 5 to 300 kGy (0.5 to 30 Mrad), preferably 10 to 50 kGy (1 to 5 Mrad). When the irradiation amount is 5 kGy or more, the monomer reaction sufficiently occurs and curing is sufficient. On the other hand, when the irradiation amount is 300 kGy or less, the cured resin layer or the substrate is not damaged. The atmosphere during curing is preferably performed at an oxygen concentration of 500 ppm or less, and more preferably 200 ppm or less.

  The electron beam source is not particularly limited. For example, various electron beam accelerators such as a cockroft Walton type, a bandegraft type, a resonant transformer type, an insulated core transformer type, a linear type, a dynamitron type, a high frequency type, etc. It is used to irradiate with an electron beam by the ecultron curtain method, the beam scanning method, or the like. An apparatus “Electro Curtain” (trade name) [Iwasaki Electric Co., Ltd.] that can irradiate a uniform electron beam in a curtain form from a linear filament is preferable.

  When ultraviolet rays are used as the ionizing radiation 5, those containing ultraviolet rays having a wavelength of 190 to 380 nm are irradiated. There is no restriction | limiting in particular as an ultraviolet-ray source, For example, a high pressure mercury lamp, a low pressure mercury lamp, a metal halide lamp, a carbon arc lamp etc. are used. The wavelength of the ultraviolet (UV) lamp used for ultraviolet curing may be selected according to the adhesive composition. The irradiation amount may be irradiated according to the material and amount of the composition, the output of the UV lamp, and the processing speed.

  The optical film 1 thus formed has various functions by adding various additives, for example, a so-called hard coat function, anti-fogging coat function, anti-fouling coat having high hardness and scratch resistance. A function, an antiglare coating function, an antireflection coating function, an ultraviolet shielding coating function, an infrared shielding coating function, and the like can also be imparted.

  The optical film of the present invention can be preferably used for forming various devices such as an image display device. In general, an image display device is formed by appropriately assembling components such as a liquid crystal cell, an optical film, and an illumination system as necessary, and incorporating a drive circuit. There is no particular limitation on the configuration of the image display device except that it is used. For example, an appropriate image display device such as an image display device in which a polarizing plate or an optical film is arranged on one side or both sides of a liquid crystal cell, or a device using a backlight or a reflector as an illumination system is exemplified. As the liquid crystal cell, any type such as a TN type, an STN type, or a π type can be used. In constructing the image display device, for example, a single layer of appropriate parts such as a diffusion plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, and a backlight are provided at appropriate positions. Alternatively, two or more layers can be arranged.

[Polarizer]
The polarizing plate according to the present invention is obtained by, for example, laminating the optical film of the present invention on one or both sides of a polarizer in which a dichroic dye is adsorbed and oriented on a uniaxially stretched PVA resin film. Here, the optical film is bonded to a polarizer and functions as a protective film.
The method for laminating the optical film and the polarizer is performed through an adhesive layer formed of an adhesive. As an adhesive for forming this adhesive layer, a PVA adhesive, an epoxy adhesive, an acrylic adhesive, a polyolefin grafted with an unsaturated carboxylic acid or an anhydride thereof, or a polyolefin blended with the grafted polyolefin System adhesives and the like. In addition, an adhesive having transparency, for example, an adhesive such as polyvinyl ether or rubber can be used.

The PVA-based adhesive contains a PVA-based resin and a cross-linking agent. Examples of the PVA-based resin include PVA obtained by saponifying polyvinyl acetate and its derivatives, and a single copolymer having a copolymerizable property with vinyl acetate. Examples thereof include a saponified product of a copolymer with a monomer, a modified PVA obtained by acetalizing, urethanizing, etherifying, grafting or phosphoric esterifying PVA. These PVA resins can be used singly or in combination of two or more. Monomers copolymerizable with vinyl acetate include (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, (meth) acrylic acid and other unsaturated carboxylic acids and esters thereof, ethylene and propylene, etc. α-olefin, (meth) allylsulfonic acid (soda), sulfonic acid soda (monoalkylmalate), disulfonic acid soda alkylmalate, N-methylolacrylamide, acrylamide alkylsulfonic acid alkali salt, N-vinylpyrrolidone, N- Examples include vinyl pyrrolidone derivatives.
The degree of polymerization of the PVA-based resin is not particularly limited, but since the adhesiveness and the like are improved, the average degree of polymerization is about 100 to 3000, preferably 500 to 3000, and the average saponification degree is about 85 to 100 mol%, preferably It is preferable to use about 90-100 mol%.

  Examples of the epoxy adhesive include a hydrogenated epoxy resin, an alicyclic epoxy resin, and an aliphatic epoxy resin. The epoxy resin may further contain a compound that promotes cationic polymerization, such as okitacenes and polyols.

  Acrylic adhesives include acrylic esters such as butyl acrylate, ethyl acrylate, methyl acrylate and 2-ethylhexyl acrylate, and α-mono such as acrylic acid, maleic acid, itaconic acid, methacrylic acid and crotonic acid. Those mainly composed of copolymers with olefin carboxylic acids (including those added with vinyl monomers such as acrylonitrile, vinyl acetate and styrene) are particularly preferred because they do not interfere with the polarization characteristics of the polarizer. .

  Further, a polyolefin grafted with an unsaturated carboxylic acid or an anhydride thereof or a polyolefin blended with the grafted polyolefin can also be used as an adhesive. Examples of polyolefins used for grafting include low density polyethylene, high density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymer, and ethylene-1-butene copolymer. , Propylene-1-butene copolymer, and mixtures thereof. Examples of the unsaturated carboxylic acid or anhydride thereof used for polyolefin grafting include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, citraconic acid, citraconic anhydride, itaconic acid, and itaconic anhydride. The modified polyolefin thus obtained may be used as it is, but can also be used by blending with polyolefin.

  The adhesive layer is formed by applying an adhesive on either or both sides of the optical film and the polarizer. The thickness of the adhesive layer is preferably 0.01 to 10 μm, more preferably 0.03 to 5 μm.

  Moreover, when bonding the said optical film with a polarizer, an easily bonding process can be performed for the adhesive improvement to the surface which contact | connects the polarizer of an optical film. Examples of the easy adhesion treatment include surface treatment such as corona treatment, plasma treatment, low-pressure UV treatment, and saponification treatment, and a method of forming an anchor layer, and these can be used in combination. Among these, a corona treatment, a method of forming an anchor layer, and a method of using these in combination are preferable.

  Next, an adhesive layer is formed on the surface subjected to the easy adhesion treatment as described above, and the optical film of the present invention and the polarizer are bonded through the adhesive layer. This bonding can be performed by a roll laminator or the like. The heating drying temperature and drying time are appropriately determined according to the type of adhesive.

  In laminating the optical film of the present invention and the polarizer, the optical film may be peeled off from the substrate and pasted to the polarizer (FIG. 2 (a)), or the polarizer and the optical film were pasted together. You may peel off a base material later (FIG.2 (b)). Furthermore, in the form of a coating solution dissolved or dispersed in a solvent, the ionizing radiation curable resin according to the present invention is directly applied to the surface of the polarizer by the above-described coating method, and is crosslinked and cured by irradiation with ionizing radiation. A protective film can be formed by adhering to a polarizer (FIG. 3).

A PVA resin generally used as a resin constituting a polarizer can be obtained by saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate resin include, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymerization of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids.
The degree of saponification of the PVA-based resin is usually 85 to 100 mol%, preferably 98 to 100 mol%. This PVA-based resin may be further modified. For example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the PVA resin is usually in the range of 1,000 to 10,000, preferably 1,500 to 10,000.

  The polarizing plate is a step of uniaxially stretching the PVA-based resin film as described above, a step of dyeing the PVA-based resin film with a dichroic dye, and adsorbing the dichroic dye, a PVA on which the dichroic dye is adsorbed A process of treating a resin film with an aqueous boric acid solution, a process of washing with a boric acid aqueous solution and washing with water, and applying a protective film to a uniaxially stretched PVA resin film on which dichroic dyes are adsorbed and oriented by applying these processes It is manufactured through a process of combining.

  Uniaxial stretching may be performed before dyeing with a dichroic dye, may be performed simultaneously with dyeing with a dichroic dye, or may be performed after dyeing with a dichroic dye. When uniaxial stretching is performed after dyeing with a dichroic dye, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, it is also possible to perform uniaxial stretching in these several steps. For uniaxial stretching, rolls having different peripheral speeds may be uniaxially stretched or uniaxially stretched using a hot roll. Moreover, the dry-type extending | stretching which extends | stretches in air | atmosphere may be sufficient, and the wet extending | stretching which extends | stretches in the state swollen with the solvent may be sufficient. The draw ratio is usually about 4 to 8 times.

In order to dye the PVA resin film with the dichroic dye, for example, the PVA resin film may be immersed in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic dye is used as the dichroic dye.
When iodine is used as the dichroic dye, a method of immersing and dyeing a PVA resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is usually about 0.01 to 0.5 parts by mass per 100 parts by mass of water, and the content of potassium iodide is usually about 0.5 to 10 parts by mass per 100 parts by mass of water. It is. The temperature of this aqueous solution is usually about 20 to 40 ° C., and the immersion time in this aqueous solution is usually about 30 to 300 seconds.

On the other hand, when a dichroic dye is used as the dichroic dye, a method of immersing and dyeing a PVA resin film in an aqueous solution containing a water-soluble dichroic dye is usually employed. The content of the dichroic dye in this aqueous solution is usually about 1 × 10 ⁻³ to 1 × 10 ⁻² parts by mass per 100 parts by mass of water. This aqueous solution may contain an inorganic salt such as sodium sulfate. The temperature of this aqueous solution is usually about 20 to 80 ° C., and the immersion time in this aqueous solution is usually about 30 to 300 seconds.
The boric acid treatment after dyeing with a dichroic dye is performed by immersing the dyed PVA resin film in an aqueous boric acid solution. The boric acid content in the boric acid aqueous solution is usually about 2 to 15 parts by mass, preferably about 5 to 12 parts by mass per 100 parts by mass of water.
When iodine is used as the dichroic dye, the aqueous boric acid solution preferably contains potassium iodide. The content of potassium iodide in the boric acid aqueous solution is usually about 2 to 20 parts by mass, preferably 5 to 15 parts by mass per 100 parts by mass of water. The immersion time in the boric acid aqueous solution is usually about 100 to 1,200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C.

The PVA resin film after boric acid treatment is usually washed with water. The water washing treatment is performed, for example, by immersing a boric acid-treated PVA resin film in water. After washing with water, a drying process is performed to obtain a polarizer. The temperature of water in the water washing treatment is usually about 5 to 40 ° C., and the immersion time is usually about 2 to 120 seconds. The drying process performed thereafter is usually performed using a hot air dryer or a far infrared heater. The drying temperature is usually 40 to 100 ° C. The processing time in the drying process is usually about 120 to 600 seconds.
In this way, a polarizer comprising a PVA resin film in which iodine or dichroic dye is adsorbed and oriented is obtained.

[Image display device]
The polarizing plate of the present invention is used by being bonded to, for example, a liquid crystal cell. In FIG. 4, the structural example of the liquid crystal cell which has the polarizing plate of this invention is shown. In FIG. 4, 7 indicates a liquid crystal cell. Examples of the liquid crystal cell 7 include an active matrix drive type typified by a thin film transistor type and a simple matrix drive type typified by a twist nematic type and a super twist nematic type. A retardation plate 8 is laminated on the liquid crystal cell 7 via an adhesive layer (not shown), and a polarizing plate 9 of the present invention is provided on the retardation cell 8 via an adhesive layer (not shown). Are stacked. The polarizing plate 9 has a polarizer 3 at the center, and a protective film 1 composed of the optical film of the present invention is laminated on both surfaces of the polarizing plate 9 with an adhesive layer 2 interposed therebetween. When laminating the polarizing plate and the liquid crystal cell of the present invention, an adhesive layer may be provided on the polarizing plate in advance.

The pressure-sensitive adhesive for laminating the polarizing plate and the liquid crystal cell of the present invention is not particularly limited. For example, an acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is a base polymer. Can be appropriately selected and used.
The pressure-sensitive adhesive is required to be excellent in optical transparency, suitable wettability, cohesiveness, adhesive properties such as adhesion, weather resistance, heat resistance and the like. Furthermore, the moisture absorption rate is low in terms of preventing foaming and peeling due to moisture absorption, reducing optical properties due to thermal expansion differences, preventing warping of liquid crystal cells, and, in turn, forming a high-quality and durable image display device. Therefore, a pressure-sensitive adhesive layer having excellent heat resistance is required. At present, an acrylic pressure-sensitive adhesive is most preferable in consideration of these required properties.

  Examples of the pressure-sensitive adhesive include natural and synthetic resins, in particular, tackifier resins, fillers and pigments made of glass fibers, glass beads, metal powders, other inorganic powders, colorants, antioxidants, and the like. Etc. may be contained. Moreover, the adhesive layer which contains microparticles | fine-particles and shows light diffusibility may be sufficient.

The application of the pressure-sensitive adhesive to the polarizing plate of the present invention is not particularly limited, and can be performed by an appropriate method. For example, a pressure-sensitive adhesive solution of about 10 to 40% by mass 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 or ethyl acetate is prepared, and the resulting solution is allowed to flow. A method of coating directly on the polarizing plate of the present invention by an appropriate development method such as a rolling method or a coating method, or forming an adhesive layer on a releasable base film according to this method and applying it to the present invention. The method of transferring to a polarizing plate is mentioned.
As the coating method, various methods such as gravure coating, bar coating, roll coating, reverse roll coating, comma coating and the like are possible, but gravure coating is the most common.

The pressure-sensitive adhesive layer can also be provided on one or both sides of the polarizing plate of the present invention as a superimposed layer of different compositions or types. Moreover, when providing in both surfaces, the adhesive does not need to be the same composition in the front and back of the polarizing plate of this invention, and it is not necessary to be the same thickness. It can also be set as the adhesive layer of a different composition and different thickness.
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 μm to 500 μm, preferably 5 μm to 200 μm, particularly preferably 10 μm to 100 μm.

  The exposed surface of the pressure-sensitive adhesive layer is preferably temporarily covered with a release film for the purpose of preventing the contamination until it is put to practical use. Thereby, it can prevent contacting an adhesive layer in the usual handling state. As the releasable film, for example, an appropriate thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foamed sheet, metal foil, laminate thereof, or the like, silicone type or long chain alkyl type Conventionally known materials such as those coated with an appropriate release agent such as fluorine-based or molybdenum sulfide can be used.

  In the present invention, the polarizer, the protective film layer, the pressure-sensitive adhesive layer, and the like include, for example, salicylic acid ester compounds, benzophenol compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Ultraviolet absorbing ability may be imparted by a method of treating with an ultraviolet absorber.

[Application to organic EL display devices]
The polarizing plate of the present invention can be suitably used for an organic EL display device.
Generally, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitter (organic electroluminescent light emitter). Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Or, a structure having various combinations such as a stacked body of an electron injection layer composed of such a light emitting layer and a perylene derivative, a stacked body of these hole injection layer, light emitting layer, and electron injection layer is known. Yes.

In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the phosphor material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be predicted from this, the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.
In an organic EL display device, in order to extract light emitted from the organic light emitting layer, at least one of the electrodes must be transparent, and a transparent electrode usually formed of a transparent conductor such as indium tin oxide (ITO) is used as an anode. It is used as On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

  In the organic EL display device having such a configuration, the organic light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL display device looks like a mirror surface.

  In an organic EL display device comprising an organic electroluminescent light emitting device comprising a transparent electrode on the surface side of an organic light emitting layer that emits light upon application of a voltage and a metal electrode on the back side of the organic light emitting layer, the surface of the transparent electrode The polarizing plate of the present invention can be provided on the side, and a birefringent layer (retardation plate) can be provided between the transparent electrode and the polarizing plate.

Since the polarizing plate of the present invention has a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized from the outside by the polarization action. In particular, if the birefringent layer is composed of a λ / 4 plate and the angle between the polarizing direction of the polarizing plate and the birefringent layer is adjusted to π / 4, the mirror surface of the metal electrode can be completely shielded. .
That is, only the linearly polarized light component of the external light incident on the organic EL display device is transmitted by the polarizing plate. This linearly polarized light generally becomes elliptically polarized light by the birefringent layer, but becomes circularly polarized light when the birefringent layer is a λ / 4 plate and the angle formed by the polarization direction with the polarizing plate is π / 4. This circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized light again at the birefringent layer. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by this example.
(Evaluation methods)
1. Film forming strength: When peeled off from the release PET film (base material), the produced optical film was “◯” when it was peeled without breaking, and “×” when the film was broken.
2. Flexibility: When the optical film was bent by hand, when the film was not cracked or scratched, “◯” was given, and when the film was cracked or scratched, “X” was given.
3. Evaluation of retardation The in-plane retardation was measured at an incident angle of 0 to ± 50 degrees using a retardation measuring instrument (“KOBRA-21ADH” manufactured by Oji Scientific Instruments). In addition, the phase difference at the time of using a TAC film as a reference example was measured together. The results are shown in Table 1 and FIG.

Example 1
(1) Preparation of monofunctional acrylic acid polymer solution As a monofunctional acrylic acid polymer, an acrylic acid copolymer ("Dainal BR64" manufactured by Mitsubishi Rayon Co., Ltd., weight average molecular weight 65,000, glass transition point (hereinafter referred to as "monofunctional acrylic polymer") A monofunctional acrylic acid polymer solution was prepared using 55 ° C. and a theoretical oxidation value of 2 mg KOH / g). Methyl ethyl ketone (MEK) was used as a solvent, and the acrylic acid copolymer was added thereto so that the solid content was 30% by mass, followed by stirring and dissolving at 60 ° C. with a hot stirrer.

(2) Preparation of ionizing radiation-curable resin composition 90% by mass of the monofunctional acrylic acid polymer solution prepared in (1) and a compound having a polyfunctional radically polymerizable unsaturated double bond as tricyclodecane dimethanol di An ionizing radiation curable resin composition was prepared by mixing 10% by mass of acrylate (hereinafter referred to as “A-DCP”, “NK-ester A-DCP” manufactured by Shin-Nakamura Chemical Co., Ltd.).

(3) Production of optical film The ionizing radiation-curable resin composition prepared in (2) above is applied onto a substrate (untreated biaxially stretched polyester film, “E5001” manufactured by Toyobo Co., Ltd., 50 μm thickness) with an applicator. It was applied and dried by blowing off the solvent in an oven. Drying was performed at 80 ° C. for 2 minutes.
Subsequently, the electron beam was irradiated using the electron beam irradiation apparatus (Iwasaki Electric Co., Ltd. make, "electro curtain"), and the coating film was hardened. The measurement conditions were a line speed of 10 m / min, an irradiation energy of 30 kGy (HV = 165 kV, 1.4 mA), and an oxygen concentration of 200 ppm.
The optical film was evaluated by the above evaluation method. The results are shown in Table 1.

Examples 2-6 and Comparative Examples 1-4
Kind of monofunctional acrylic acid polymer, kind of compound having polyfunctional radically polymerizable unsaturated double bond, and inclusion of compound having monofunctional acrylic acid polymer and polyfunctional radically polymerizable unsaturated double bond An optical film was produced in the same manner as in Example 1 except that the amount was changed as described in Table 1. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

* 1 BR64; acrylic acid copolymer, “Dynar BR64” manufactured by Mitsubishi Rayon Co., Ltd., weight average molecular weight 65,000, Tg 55 ° C., theoretical oxidation value 2 mgKOH / g
* 2 BR77: Acrylic acid copolymer, “Dainal BR77” manufactured by Mitsubishi Rayon Co., Ltd., weight average molecular weight 65,000, Tg 80 ° C., theoretical oxidation value 18.5 mgKOH / g
* 3 BR60; acrylic acid copolymer, “Dynar BR60” manufactured by Mitsubishi Rayon Co., Ltd., weight average molecular weight 70,000, Tg 75 ° C., theoretical oxidation value 1 mgKOH / g
* 4 BR83: Acrylic acid copolymer, “Dainal BR83” manufactured by Mitsubishi Rayon Co., Ltd., weight average molecular weight 40,000, Tg 105 ° C., theoretical oxidation value 2 mgKOH / g
* 5 BR73: Acrylic acid copolymer, “Dainal BR73” manufactured by Mitsubishi Rayon Co., Ltd., weight average molecular weight 85,000, Tg 100 ° C., theoretical oxidation value 3 mgKOH / g
* 6 A-DCP; Tricyclodecane dimethanol diacrylate, “NK-Ester A-DCP” manufactured by Shin-Nakamura Chemical Co., Ltd.
* 7 A-TMPT; trimethylolpropane triacrylate, “NK-ester A-TMPT” manufactured by Shin-Nakamura Chemical Co., Ltd.
* 8 A-DPH: dipentaerythritol hexaacrylate, “NK-ester A-DPH” manufactured by Shin-Nakamura Chemical Co., Ltd.

  According to the present invention, the phase difference is low even with respect to incident light from an oblique direction, the optical transparency and mechanical strength are excellent, the flexibility is good, the productivity is excellent, and the PVA resin is formed. An optical film that is excellent in adhesiveness with a polarizer and that is particularly suitable for a polarizer protective film can be provided. In addition, a polarizing plate with few appearance defects can be provided with high productivity by using the optical film and a polarizer formed of a PVA resin. Furthermore, a high-quality image display device using such a polarizing plate can be provided.

It is a schematic diagram which shows the manufacturing process of the optical film of this invention. It is a schematic diagram which shows the process of bonding an optical film to a polarizer. It is a schematic diagram which shows the process of forming the protective film which consists of an optical film of this invention in a polarizer. It is a schematic diagram which shows the structural example of the liquid crystal cell which has the polarizing plate of this invention. It is a figure which shows the evaluation result of a phase difference.

Explanation of symbols

1. Optical film (protective film)
2. 2. Adhesive layer Polarizer 4. Base material 5. Ionizing radiation Ionizing radiation curable resin layer (uncured resin layer)
7). Liquid crystal cell 8. Phase difference plate (birefringent plate)
9. Polarizing plate 10. Optical element

Claims (4)

  (A) 70 to 95% by mass of a monofunctional (meth) acrylic acid polymer having a weight average molecular weight of 50,000 to 80,000 and (B) compounds 5 to 30 having a polyfunctional radically polymerizable unsaturated double bond An optical film obtained by crosslinking and curing an ionizing radiation curable resin composition containing mass%.   (B) The optical film according to claim 1, wherein the compound having a polyfunctional radically polymerizable unsaturated double bond is a polyfunctional (meth) acrylic acid polymer.   A polarizing plate formed by forming the optical film according to claim 1 or 2 on at least one surface of a polarizer.   An image display device using the polarizing plate according to claim 3.

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