JP2008146005A - Optical film, polarizing plate and image display device - Google Patents

Abstract

An optical film having excellent optical properties such as low haze, excellent transparency, low birefringence, good mechanical strength and heat resistance, and excellent moisture permeability is provided.
An ionizing radiation curable composition containing (A) 80 to 97% by mass of an olefin binary or ternary copolymer and (B) 3 to 20% by mass of a compound having a radical polymerizable unsaturated double bond. It is an optical film formed by crosslinking and curing a resin composition.
[Selection figure] None

Description

  The present invention provides an optical film having excellent optical properties such as low haze, excellent transparency, low birefringence, good mechanical strength and heat resistance, and excellent moisture permeability, and the film on one side of a polarizer. Or it is related with the polarizing plate utilized as a protective film on both surfaces, and the image display apparatus using this polarizing plate.

  The polarizing plate is a material having a function of transmitting only light having a specific vibration direction and shielding other light, and is widely used as one of components constituting a liquid crystal display device, for example. As such a polarizing plate, what has the structure on which the polarizer and the protective film were laminated | stacked is generally used. The polarizer has a function of transmitting only light having a specific vibration direction. For example, a polyvinyl alcohol (hereinafter referred to as “PVA”) film is stretched and dyed with iodine or a dichroic dye. The film is generally used. Recently, a coating-type polarizer is also used.

By the way, the said protective film bears functions, such as holding a polarizer and giving practical intensity | strength to the whole polarizing plate, for example, writes triacetyl cellulose (henceforth "TAC") of a cellulose-type film. ) Film is generally used. Cellulose-based films have excellent optical uniformity such as good transparency and low birefringence, practical heat resistance, and excellent mechanical strength. ing.
In addition, since it has high moisture permeability, when it is bonded to a polarizer such as PVA, it is generally used as a polarizer protective film because it has good workability such as excellent moisture permeability of PVA and adhesive (for example, Patent Document 1).
However, since the cellulose-based film (for example, TAC film) has high water absorption, there have been problems such as deterioration in performance of the polarizer and dimensional stability due to water absorption.

  Thus, attempts have been made to improve dimensional stability by using a film material having a smaller water absorption rate than the conventional TAC film as a polarizer protective film. However, a polycarbonate film or polyethylene terephthalate film having a small water absorption has a problem that the photoelastic constant is large and the phase difference is changed by the action of external stress, so that the performance as a polarizing plate is deteriorated.

Further, a thermoplastic elastomer composition containing an olefin resin, a propylene copolymer, and a rubber component has been proposed as a composition excellent in friction resistance, transparency, and flexibility (see Patent Document 2).
However, when the above thermoplastic elastomer is used alone as a polarizer protective film, there is a drawback that elongation tends to occur alone, and even an isotropic material is stretched during film formation, Oriented, the in-plane retardation becomes higher than 10 nm, and a problem occurs in the function as a polarizing plate.

JP-A-7-120617 JP 2003-313434 A

  In view of the above problems, the present invention provides an optical film having excellent optical properties such as low haze, excellent transparency, low birefringence, etc., good mechanical strength and heat resistance, and excellent moisture permeability, and the optical film An object of the present invention is to provide a polarizing plate using, and an image display device using the polarizing plate.

As a result of intensive studies to achieve the above object, the present inventors have found that an ionizing radiation curable resin containing a compound having an olefin binary or ternary copolymer and a radically polymerizable unsaturated double bond. It has been found that the above problem can be solved by using an optical film obtained by crosslinking and curing the composition.
That is, the present invention
[1] An ionizing radiation curable resin containing (A) 80-97% by mass of an olefin binary or ternary copolymer and (B) 3-20% by mass of a compound having a radical polymerizable unsaturated double bond An optical film obtained by crosslinking and curing the composition;
[2] The optical film as described in [1] above, wherein the component (A) is a propylene-α-olefin copolymer,
[3] The optical film as described in [1] above, wherein the component (A) is a binary or ternary copolymer comprising the following component (a) and component (b) and / or component (c):
(A) an olefin (b) an α, β-unsaturated carboxylic acid, its anhydride, and an α, β-unsaturated carboxylic acid glycidyl ester, an unsaturated carboxylic acid (c) an unsaturated ester [4] The component (A) is at least one selected from the group consisting of a random copolymer of propylene and 1-butene, an ethylene-acrylic acid copolymer, and an ethylene-maleic anhydride-acrylic acid ester copolymer. 1],
[5] A polarizing plate formed by forming the optical film according to any one of [1] to [4] on at least one surface of a polarizer, and [6] the polarizing plate according to [5]. Image display device,
Is to provide.

The optical film of the present invention has a small haze, excellent transparency, excellent optical properties such as low birefringence, good mechanical strength and heat resistance, and excellent moisture permeability. Further, it is excellent in various durability such as heat resistance, heat and humidity resistance, and a heat and cold cycle, and has no influence on the optical function of the polarizing plate, and is flexible and rich in elasticity. The component (B), which is an ionizing radiation curable component, contributes to various performance improvements. In addition, since the optical film of the present invention has resistance to external impacts and deformations, a polarizing plate with significantly improved strength and reliability as a liquid crystal display element can be obtained by being bonded to a polarizer. It is done.
Furthermore, the optical film of the present invention has a protective function equivalent to or higher than that of a conventionally used TAC film. In particular, the TAC film is hydrophilic and hardly moisture proof, whereas the optical film of the present invention is hydrophobic, so that the durability of the polarizing plate can be greatly improved. Therefore, the optical film of the present invention can be suitably used as a protective film laminated on one surface of the polarizing plate and bonded to the liquid crystal cell surface substrate, and can also be used as a protective film on the other surface side of the polarizing plate.

  The optical film of the present invention comprises (A) an olefin binary or ternary copolymer of 80 to 97% by mass, and (B) a compound having a radical polymerizable unsaturated double bond of 3 to 20% by mass. It is formed by crosslinking and curing a radiation curable resin composition.

[(A) olefin binary or ternary copolymer]
The binary or ternary copolymer which is the component (A) of the present invention is a copolymer of olefins such as ethylene, propylene and 1-butene, and other than olefins and olefins such as ethylene, propylene and 1-butene. The copolymer of the monomer of this is included.
Examples of the olefin copolymer include a binary copolymer of ethylene and propylene, a binary copolymer of α-olefin having 4 or more carbon atoms such as ethylene and 1-butene, and an α-olefin having propylene and 4 or more carbon atoms. And a terpolymer of ethylene-propylene-α-olefin having 4 or more carbon atoms. Among these, a binary copolymer of propylene and α-olefin having 4 or more carbon atoms. Is preferred.
Examples of the olefin having 4 or more carbon atoms include 1-butene, 1-hexene, 1-pentene, 1-heptene, octene-1, nonene-1, decene-1, 4-methylhexene-1, 4,4-dimethylpentene. -1,5-methylheptene-1,6-methylheptene-1,4-methyl-1-butene and 4-methylpentene-1 are preferable, and 1-butene is particularly preferable.

The copolymer may be a random copolymer or a block copolymer, but a random copolymer is more preferable from the viewpoint of maintaining transparency as an optical film.
That is, as the component (A) of the present invention, a random copolymer of propylene and 1-butene is particularly preferable.

The propylene-α-olefin copolymer which is a preferred embodiment in the present invention is usually produced by the following method. That is, it is produced by continuous multistage polymerization in which propylene homopolymerization using a tubular reactor is the first step, and is preferably obtained by continuously performing the following first to third steps.
(First step) A step of producing a propylene homopolymer in an amount of 2 to 15% by mass based on the total mass using a tubular reactor at a polymerization temperature of 5 to 40 ° C.
(2nd process) The process of copolymerizing a propylene and ethylene and manufacturing the copolymer which has a structural unit derived from a propylene and ethylene.
(Third step) A copolymer having a structural unit derived from propylene and ethylene by copolymerizing propylene with at least one olefin selected from ethylene and an α-olefin having 4 or more carbon atoms, propylene and 4 carbon atoms. A copolymer having a structural unit derived from the above α-olefin and at least one copolymer of propylene, an α-olefin having 4 or more carbon atoms and a copolymer having a structural unit derived from ethylene, The process of manufacturing so that the total amount with the copolymer manufactured by 2 processes may be 98-85 mass% of the polypropylene copolymer total mass.

  From the heat-resistant point, the content ratio of propylene and α-olefin in the propylene-α-olefin copolymer of the present invention is 5 to 50% by mass of α-olefin with respect to 95 to 50% by mass of propylene. preferable. From the above viewpoint, the α-olefin is more preferably 7 to 40% by mass with respect to 93 to 60% by mass of propylene.

  As a catalyst for producing a propylene-α-olefin copolymer, various Ziegler type catalysts can be used. When propylene is homopolymerized, it has a highly isotactic structure or syndiotactic. A copolymer obtained by polymerizing propylene and an α-olefin using a catalyst system that gives a polymer having a structure is preferred.

  Specific examples of the catalyst used for the polymerization include trivalent or tetravalent titanium halides, transition metal catalysts having these supported on various carriers, or two linked cyclopentadienyl groups or derivatives thereof. A catalyst system comprising a metallocene compound such as zirconium, hafnium, or titanium as an ligand and an organometallic compound is preferably used.

The binary or ternary copolymer as the component (A) of the present invention includes a copolymer of an olefin such as ethylene, propylene and 1-butene and a monomer other than the olefin as described above. Among these, a copolymer of an olefin and a monomer having a functional group such as a carboxyl group or an alkoxycarbonyl group, a so-called modified olefin copolymer is preferable. For example, (a) an olefin, (b) an α, β-unsaturated carboxylic acid, its anhydride, and an α, β-unsaturated carboxylic acid glycidyl ester, and (c) an unsaturated ester Examples thereof include binary copolymers and ternary copolymers using as a monomer. More specifically, a binary copolymer of the component (a) and the component (b), a binary copolymer of the component (a) and the component (c), the component (a), the component (b), and (C) The ternary copolymer of a component is mentioned.
These modified olefin copolymers may be random copolymers or block copolymers, but random copolymers are more preferable from the viewpoint of maintaining transparency as an optical film.

  As said (a) component, ethylene, propylene, 1-butene etc., and these mixtures can be used, and especially ethylene and / or propylene are preferable. Also, a mixed system of propylene and 1-butene, which are monomers used in the propylene-α-olefin copolymer, can be suitably used.

  As the α, β-unsaturated carboxylic acid and its anhydride in the component (b), acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid, maleic anhydride, itaconic anhydride, Citraconic anhydride and the like can be mentioned. Examples of the α, β-unsaturated carboxylic acid glycidyl ester include glycidyl acrylate and glycidyl methacrylate.

  Specific examples of the component (c) unsaturated ester include vinyl esters such as vinyl acetate and vinyl propionate; unsaturated carboxylic acid esters such as methyl acrylate, ethyl acrylate and methyl methacrylate.

  As the binary copolymer using the above components (a), (b) and (c) as monomers, an ethylene-acrylic acid copolymer is particularly preferable from the viewpoint of stability in synthesis and production cost. As the polymer, an ethylene-maleic anhydride-acrylic acid ester copolymer is particularly preferred from the viewpoint of stability in synthesis and production cost, as described above.

The modified olefin copolymer can be obtained by copolymerizing the above components by a known method such as high-pressure radical polymerization or emulsion polymerization.
In these copolymers, the content of (a) olefin 60 to 99 mol%, (b) unsaturated carboxylic acid 0.1 to 20 mol%, and (c) unsaturated ester 1 to 20 mol%. Is preferred. Within this range, the modified olefin copolymer can be synthesized stably.

The copolymer constituting the component (A) preferably has a melt flow rate (hereinafter referred to as “MFR”) of usually 1 ≦ MFR ≦ 100 g / 10 min (230 ° C.), more preferably 1 ≦ A range of MFR ≦ 50 g / 10 min, particularly 1 ≦ MFR ≦ 35 g / 10 min is preferable.
Furthermore, the copolymer constituting the component (A) preferably has a melting point (hereinafter referred to as “Tm”) measured by a suggestive thermal analyzer (DSC) of 120 ° C. or lower.
The molecular weight distribution (Mw / Mn) calculated from the weight average molecular weight (Mw) and the number average molecular weight (Mn) measured by gel permeation chromatography (GPC) is usually preferably 3 or less. Is preferably 2.8 or less, and particularly preferably 2.6 or less.

  In the present invention, the content of the copolymer constituting the component (A) in the ionizing radiation curable resin composition is in the range of 80 to 97% by mass. When the content is less than 80% by mass, the film-forming property is low when forming an optical film, and it is difficult to use as an optical film. On the other hand, when the content exceeds 97% by mass, the heat resistance is inferior, the film is stretched during film formation, the in-plane retardation is increased, and the optical film of the present invention is used as a protective film for a polarizing plate. In this case, the performance as a polarizing plate is lowered. From the above viewpoint, the content of the copolymer constituting the component (A) in the ionizing radiation curable resin composition is more preferably in the range of 80 to 95% by mass.

[(B) Compound having radically polymerizable unsaturated double bond]
Next, the compound having a radical polymerizable unsaturated double bond as the component (B) in the present invention is a compound that is crosslinked and cured by ionizing radiation, and examples thereof include a polymerizable monomer, a functional oligomer, and a functional polymer. Examples of the functional group that is crosslinked and cured by ionizing radiation include a (meth) acryloyl group, an allyl group, and an epoxy group.
Here, ionizing radiation refers to various ultraviolet rays (UV-A, UV-B, UV-C), visible light, gamma rays, X-rays, electron beams, and the like.

  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 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. In the present invention, “(meth) acrylate” means “acrylate or methacrylate”.
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 lowering the viscosity. Examples of monofunctional (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl ( Examples include meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and isobornyl (meth) acrylate. These monofunctional (meth) acrylates may be used alone or in combination of two or more.

  Next, the functional oligomer (also referred to as prepolymer) has a molecular weight (weight average) of about 300 to 5,000, and is radically polymerizable such as (meth) acryloyl group, allyl group, or epoxy group in the molecule. Polyurethanes, polyesters, polyethers, polycarbonates, poly (meth) acrylates with double bonds can be applied, and oligomers with radically polymerizable unsaturated groups in the molecule, such as epoxy (meth) acrylates , Urethane (meth) acrylate, polyester (meth) acrylate, and polyether (meth) acrylate.

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. . 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.
Examples of polyester (meth) acrylate oligomers include esterification of hydroxyl groups of polyester oligomers having hydroxyl groups at both ends obtained by condensation of polycarboxylic acid and polyhydric alcohol with (meth) acrylic acid, It can be obtained by esterifying the terminal hydroxyl group of an oligomer obtained by adding an alkylene oxide to a 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.

  Furthermore, other functional oligomers include polybutadiene (meth) acrylate oligomers with high hydrophobicity having (meth) acrylate groups in the side chains of polybutadiene oligomers, silicone (meth) acrylate oligomers with polysiloxane bonds in the main chain, In aminoplast resin (meth) acrylate oligomer modified by aminoplast resin with many reactive groups in small molecule, or in novolak type epoxy resin, bisphenol type epoxy resin, aliphatic vinyl ether, aromatic vinyl ether, etc. Examples include oligomers having a cationic polymerizable functional group.

  Next, as the functional polymer, urethane (meth) having a molecular weight (weight average) 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. Acrylate, isocyanurate (meth) acrylate, polyester-urethane (meth) acrylate, epoxy (meth) acrylate, and the like are applicable.

  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 3-20 mass%. When content of (B) component is less than 3 mass%, the effect of hardening by ionizing radiation is small, the produced optical element is soft, and it is difficult to use as an optical film. On the other hand, when the content of the component (B) exceeds 20% by mass, the component (A) and the component (B) are separated and film formation becomes impossible. From the above viewpoint, the content of the component (B) is more preferably in the range of 5 to 20% 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 3 to 20% 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]
Hereafter, the manufacturing method of the optical film of this invention is explained in full detail, referring FIG.1 and FIG.2.
The above-mentioned component (A), component (B) and various additives are usually uniformly kneaded at a predetermined ratio under heating to prepare an ionizing radiation curable resin composition. Next, using the ionizing radiation curable resin composition, an uncured film is prepared by various molding methods such as an extrusion molding method, a casting method, a T-die extrusion molding method, an inflation method, and an injection molding method, and then ionization is performed. The film is cured by irradiation with radiation.

  When the optical film of the present invention is used as a protective film for a polarizer, the uncured resin layer 1 is produced directly on the polarizer 3 by the above-described various molding methods, and this is irradiated with ionizing radiation 2. There is a method of producing a protective film 4 by curing (see FIG. 1). Moreover, as shown in FIG. 2, the uncured resin layer 1 (uncured film) is prepared by the above-described various molding methods, and the protective film 4 is prepared in advance by irradiating it with ionizing radiation 2, and thereafter Alternatively, it may be bonded to the polarizer 3 through the adhesive layer 5.

  About the thickness of the optical film of this invention, the range of 10-200 micrometers is preferable. When the thickness is 10 μm or more, the strength as a protective film of the polarizer is sufficiently ensured, and when it is 200 μm or less, sufficient flexibility is obtained, and since it is lightweight, handling is easy. It is also advantageous in terms of cost. From the above viewpoint, the thickness of the optical film is more preferably 30 to 150 μm.

  In the present invention, the protective film 4 is obtained by irradiating the uncured resin layer 1 with ionizing radiation such as an electron beam and ultraviolet rays to cure the uncured resin layer 1. When an electron beam is used as the ionizing radiation 2, the acceleration voltage of the electron beam can be appropriately selected according to the resin used and the thickness of the layer, but is usually 100 to 1,000 keV, preferably about 70 to 300 kV. It is preferable to cure the uncured resin layer. 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.

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

  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 bonding the optical film of the present invention to one side or both sides of a polarizer. Here, the optical film is bonded to a polarizer and functions as a protective film. The optical film of the present invention has an in-plane retardation of 10 nm or less, and the in-plane retardation can be set to 6 nm or less by optimizing the above materials. Therefore, when the optical film of the present invention is used as a protective film for a polarizing plate, there is an advantage that the influence of optical compensation of the protective film is small.

As the polarizer used in the polarizing plate of the present invention, any polarizer may be used as long as it has a function of transmitting only light having a specific vibration direction. For example, a polyvinyl alcohol film is stretched, and iodine or two-color Polyvinyl alcohol polarizers dyed with reactive dyes; polyene polarizers such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride; reflective polarizers using cholesteric liquid crystals; thin film crystal film polarizers Among them, polyvinyl alcohol polarizers are preferably used.
Examples of the polyvinyl alcohol polarizer include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, ethylene / vinyl acetate copolymer partially saponified films, iodine and dichroic dyes, etc. A dichroic substance is adsorbed and uniaxially stretched. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic substance such as iodine is preferably used. The thickness of these polarizers is not particularly limited, and is generally about 1 to 100 μm.

A PVA resin suitably used as a resin constituting the polarizer can be obtained by saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate resin include not only polyvinyl acetate which is a homopolymer of vinyl acetate, but also 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, for example, a step of uniaxially stretching a PVA resin film as described above, a step of dyeing a PVA resin film with a dichroic dye, and adsorbing the dichroic dye, and a dichroic dye adsorbing A process of treating the prepared PVA resin film with an aqueous boric acid solution, a process of washing with water after the treatment with an aqueous boric acid solution, and a uniaxially stretched PVA resin film on which dichroic dyes are adsorbed and oriented by applying these steps Manufactured through a process of laminating films.

  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.

As a method of pasting an optical film and a polarizer, as mentioned above, it is performed through an adhesive layer.
As an adhesive for forming the 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 system blended with the grafted polyolefin Examples include adhesives. 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 crosslinking agent. Examples of the PVA-based resin include PVA obtained by saponifying polyvinyl acetate and its derivatives, and a monomer copolymerizable with vinyl acetate. And a modified PVA obtained by subjecting PVA to acetalization, urethanization, etherification, grafting, or phosphoric esterification. These PVA resins can be used singly or in combination of two or more. Examples of 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, and α- such as ethylene and propylene. Olefin, (meth) allylsulfonic acid (soda), sulfonic acid soda (monoalkylmalate), disulfonic acid soda alkylmalate, N-methylolacrylamide, acrylamide alkylsulfonic acid alkali salt, N-vinylpyrrolidone, N-vinylpyrrolidone Derivatives and the like.
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 3,000, preferably 500 to 3,000, and the average degree of saponification is 85 to 100 mol%. It is preferable to use a material having a degree of about 90 to 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 a copolymer with an olefin carboxylic acid (including those added with vinyl monomers such as acrylonitrile, vinyl acetate and styrene) are particularly preferred because they do not impair the polarizing properties 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 may also be used by blending with other polyolefins.

  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.

[Image display device]
The polarizing plate of the present invention is used by being bonded to, for example, a liquid crystal cell. In FIG. 3, the structural example of the liquid crystal cell which has the polarizing plate of this invention is shown. In FIG. 3, 6 indicates a liquid crystal cell. Examples of the liquid crystal cell 6 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 6 via an adhesive layer (not shown), and a polarizing plate 7 of the present invention is formed thereon via an adhesive layer (not shown). Are stacked. The polarizing plate 7 has a polarizer 3 at the center, and a protective film 4 made of the optical film of the present invention is laminated on both surfaces of the polarizing plate 7 with an adhesive layer 5 interposed therebetween. When laminating the polarizing plate 7 and the retardation plate 8 and the retardation plate 8 and the liquid crystal cell 6 of the present invention, an adhesive layer may be provided on the polarizing plate 7, the retardation plate 8 and the liquid crystal cell 6 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 film such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foamed sheet or metal foil, and a laminate thereof, if necessary, silicone-based or long-chain alkyl-based, 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.

  In addition, the polarizing plate of the present invention, which is bonded to at least one surface of the polarizer as the protective film of the polarizer of the present invention, is provided on the other surface of the polarizer as necessary. Can be laminated, and films made of other resins can be laminated. Examples of other resin films include TAC films, polyethersulfone films, polyarylate films, polyethylene terephthalate films, polynaphthalene terephthalate films, polycarbonate films, cyclic polyolefin films, maleimide resin films, fluorine resin films, and the like. Can be mentioned. The film made of the other resin may be a retardation film having a specific retardation.

The polarizing plate of the present invention is preferably a laminate having at least one hard coat layer in order to improve surface properties and scratch resistance. Examples of the hard coat layer include a hard coat layer made of, for example, a silicone resin, an acrylic resin, an acrylic silicone resin, an ultraviolet curable resin, a urethane hard coat agent, etc. Among them, transparency, scratch resistance, From the viewpoint of chemical resistance, a hard coat layer made of an ultraviolet curable resin is preferable. One or more of these hard coat layers can be used.
Examples of the ultraviolet curable resin include one or more ultraviolet curable resins selected from ultraviolet curable acrylic urethane, ultraviolet curable epoxy acrylate, ultraviolet curable (poly) ester acrylate, ultraviolet curable oxetane, and the like.
As for the thickness of a hard-coat layer, 0.1-100 micrometers is preferable, Especially preferably, it is 1-50 micrometers, More preferably, it is 2-20 micrometers. Further, a primer treatment can be performed between the hard coat layers.

[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.

[Applied to touch panel]
The optical film of this invention can be used conveniently also for the polarizing plate of a touchscreen. In general, a touch panel is a device in which an operator operates a device or a system by touching a transparent surface provided at the top of a display screen with a pen or a finger. Touching the screen directly has become more and more popular in recent years because it is more direct and intuitive than pressing the cursor with a direction key to confirm the position. . In recent years, the growth of mobile terminals such as mobile phones and PDAs (Personal Digital Assistants) has been remarkable, and there is a strong demand for visibility under the sunlight and thin and light weight. Became. There are various types of touch panels, and they are properly used depending on their advantages and disadvantages. The touch panel includes a resistive film method, an optical method, a capacitive coupling method (also called an analog capacitive coupling method), an infrared method, an ultrasonic method, and an electromagnetic induction method. Here, an example of a resistive film type touch panel will be described.

Resistive touch panels include a glass / glass type and a glass / film type. In the glass / glass type, a glass substrate with a transparent conductive layer and a glass substrate with a transparent conductive layer are held via a space, and this is mounted on the display surface. The glass / film type is a type of touch panel in which an upper glass substrate with a transparent conductive layer is replaced with an optical film because a lighter / thinner one is desired in an in-vehicle or portable touch panel.
FIG. 4 shows a glass / glass type touch panel, and FIG. 5 shows a glass / film type touch panel.
If a linearly polarizing plate or a circularly polarizing plate made by combining a polarizing plate with a λ / 4 plate is used on the outermost surface of the touch panel, sufficient strength can be obtained as a touch panel, and visibility can be improved due to the antireflection effect. Will improve. The polarizing plates of the touch panel are 9 in FIG. 4 and 17 in FIG. The optical film of this invention can be used conveniently for the polarizing plate of these touch panels.
A polarizing plate and a λ / 4 plate comprising the optical film of the present invention and a polarizer are laminated so that the angle between the slow axis in the plane of the λ / 4 plate and the polarizing axis of the polarizing plate is substantially 45 °. A circularly polarizing plate is then obtained. Substantially 45 degrees means 40 to 50 degrees. The angle between the slow axis in the plane of the λ / 4 plate and the polarization axis of the polarizing film is preferably 41 to 49 degrees, more preferably 42 to 48 degrees, and 43 to 47 degrees. Is more preferable, and is most preferably 44 to 46 degrees.
The optical film of the present invention can be used for any of the upper, lower and lower outer layers (lightweight reduction film provided with ITO) of the polarizing plate. There are two types of anti-reflection for touch panels: linearly polarized light type and circularly polarized light type (linearly polarized light has a higher reflectance than circularly polarized light). Can also be used.
The circularly polarizing plate or linearly polarizing plate using the optical film of the present invention can be used for both transmissive and reflective touch panels.

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 property: “O” when the film was normally wound by T-die extrusion, and “X” when the film was wrinkled, punctured, or had some bleed from the resin.
2. Evaluation of in-plane retardation The in-plane retardation was measured using a phase difference measuring device (“KOBRA-WR” manufactured by Oji Scientific Instruments) at a wavelength of 589.3 nm and an incident angle of 0 degree.
3. Heat resistance and moisture resistance Polarized light comprising a polyvinyl alcohol-based resin film in which iodine is adsorbed and oriented using PVA obtained by saponifying polyvinyl acetate as an optical film obtained in Example 1 and Comparative Example 3. It adhered to both sides of the child to obtain a polarizing plate.
A 150 mm square test piece was cut out from the polarizing plate, and as an evaluation of heat resistance, the appearance of the polarizing plate after maintaining at 80 ° C. for 1,000 hours was observed. The case where yellowing did not occur was indicated as “◯”, and the case where yellowing occurred was indicated as “x”.
In addition, as an evaluation of moisture resistance, the appearance of the polarizing plate was observed after being held at 70 ° C. and a relative humidity of 95% for 1,000 hours. The case where adhesion peeling did not occur in the inner portion of about 2 mm from the periphery of the polarizing plate was indicated as “◯”, and the case where adhesion peeling occurred was indicated as “x”.

Example 1
Tricyclodecane dimethanol diacrylate (hereinafter referred to as “A-DCP”) which is an acrylic oligomer in 90% by mass of a propylene / 1-butene random copolymer (trade name: Tafmer XR110J, manufactured by Mitsui Chemicals, Inc.) ( A 10% by mass liquid of Shin-Nakamura Chemical Co., Ltd., trade name: NK Ester A-DCP) was added and compounded at a processing temperature of 185 ° C. The pellets produced by compounding were T-die extruded at a processing temperature of 170 ° C. and a take-up roll temperature of 50 ° C. to a thickness of 100 μm to obtain an uncured film. Next, an optical film was obtained by irradiating this with an electron beam at an intensity of 50 kGy and curing the oligomer with an electron beam.
The optical film was evaluated by the above evaluation method. The results are shown in Table 1.

Example 2
An optical film was obtained in the same manner as in Example 1 except that the content of the propylene / 1-butene random copolymer was 95% by mass and the content of A-DCP was 5% by mass. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

Example 3
An optical film was obtained in the same manner as in Example 1 except that the content of the propylene / 1-butene random copolymer was 80% by mass and the content of A-DCP was 20% by mass. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

Example 4
Aside from using trimethylolpropane triacrylate of trifunctional acrylate (hereinafter referred to as “A-TMPT”) (manufactured by Shin-Nakamura Kogyo Co., Ltd., trade name: NK ester A-TMPT ”) instead of A-DCP. An optical film was obtained in the same manner as in Example 1. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

Example 5
Except for the hexafunctional acrylate dipentaerystol hexaacrylate (hereinafter referred to as “A-DPH”) (manufactured by Shin-Nakamura Kogyo Co., Ltd., trade name: NK ester A-DPH ”) instead of A-DCP. Obtained an optical film in the same manner as in Example 1. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

Example 6
An optical film in the same manner as in Example 1 except that an ethylene-acrylic acid copolymer (manufactured by Nippon Polyethylene Co., Ltd., trade name Lexpearl EAA / A3100) was used instead of the propylene / 1-butene random copolymer. Got. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

Example 7
Example except that instead of propylene / 1-butene random copolymer, an ethylene-maleic anhydride-acrylic acid ester terpolymer (manufactured by Nippon Polyethylene Co., Ltd., trade name Lexpearl ET / ET220X) was used. In the same manner as in Example 1, an optical film was obtained. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

Comparative Example 1
An optical film was obtained in the same manner as in Example 1 except that the content of the propylene / 1-butene random copolymer was 99% by mass and the content of A-DCP was 1% by mass. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

Comparative Example 2
An optical film was obtained in the same manner as in Example 1 except that the content of the propylene / 1-butene random copolymer was 75% by mass and the content of A-DCP was 25% by mass. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

Comparative Example 3
An optical film was obtained in the same manner as in Example 1 except that only the propylene / 1-butene random copolymer was used. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

* 1 Measurement not possible due to film formation failure

According to the present invention, it is possible to provide an optical film having excellent optical properties such as low haze, excellent transparency, low birefringence, excellent mechanical strength and heat resistance, and excellent moisture permeability. In addition, it has excellent durability such as heat resistance, moist heat resistance and cold heat cycle, and can improve the polarization degree of the polarizing plate without affecting the optical function of the polarizing plate. In addition, an optical film rich in elasticity can be provided.
Further, since the optical film of the present invention has resistance to external impacts and deformations, the strength and reliability as a liquid crystal display element can be remarkably improved by using the optical film by being bonded to a polarizer. A polarizing plate can be provided.
Furthermore, the optical film of the present invention is more hydrophobic than the conventionally used TAC film, whereas the optical film of the present invention is hydrophobic, whereas the optical film of the present invention is hydrophobic. The durability of the polarizing plate can be greatly improved. Therefore, the optical film of the present invention can be suitably used as a protective film laminated on at least one surface of the polarizing plate and bonded to the liquid crystal cell surface substrate, and can also be used as a protective film on the other side of the polarizing plate. it can.

It is a schematic diagram which shows the manufacturing process of the polarizing plate of this invention. It is a schematic diagram which shows the manufacturing process of the polarizing plate of this invention. 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 schematic diagram which shows the structural example of the touch panel (glass / glass type) of a resistive film system. It is a schematic diagram which shows the structural example of the touch panel (glass / film type) of a resistive film system.

Explanation of symbols

1. 1. Uncured resin layer Ionizing radiation Polarizer 4. 4. Protective film Adhesive layer 6. 6. Liquid crystal cell Polarizing plate 8. Phase difference plate (birefringent plate)
9. Touch panel polarizing plate Antireflection film 11. λ / 4 plate 12. Polarizer protective film [top]
12 '. Polarizer protective film [bottom]
13. Polarizer (PVA)
14 Glass 15. ITO protective film 16. Polarizer protective film [Shimogai]
17. Touch panel polarizing plate

Claims (6)

  An ionizing radiation curable resin composition containing (A) 80 to 97% by mass of an olefin binary or ternary copolymer and (B) 3 to 20% by mass of a compound having a radical polymerizable unsaturated double bond. An optical film obtained by crosslinking and curing.   The optical film according to claim 1, wherein the component (A) is a propylene-α-olefin copolymer. The optical film according to claim 1, wherein the component (A) is a binary or ternary copolymer comprising the following component (a), component (b) and / or component (c).
(A) an olefin (b) an α, β-unsaturated carboxylic acid, an anhydride thereof, and an unsaturated carboxylic acid (c) an unsaturated ester selected from the group consisting of an α, β-unsaturated carboxylic acid glycidyl ester   The component (A) is at least one selected from the group consisting of a random copolymer of propylene and 1-butene, an ethylene-acrylic acid copolymer, and an ethylene-maleic anhydride-acrylic acid ester copolymer. Item 5. The optical film according to Item 1.   The polarizing plate formed by forming the optical film in any one of Claims 1-4 on the at least single side | surface of a polarizer.   An image display device using the polarizing plate according to claim 5.

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