TW202032170A - Polarizing plate - Google Patents

Abstract

An objective of the present invention is to provide a polarizing plate in which discoloration of the polarizing plate is suppressed even in a severe environment.

As a solution, the polarizing plate of the present invention is a polarizing plate in which a thermoplastic resin film is bonded to at least one surface of a polarizing film via an adhesive layer, wherein

the adhesive is a cured product of a photocurable composition containing a cationic polymerizable compound and a photo-cationic polymerization initiator,

the photo-cationic polymerization initiator is contained in an amount of 0.5 to 1.5 parts by mass with respect to 100 parts by mass of the cationic polymerizable compound, and the cationic polymerizable compound contains 10 to 70% by mass of a bifunctional oxetane compound with respect to the total mass of the cationic polymerizable compound.

Description

Polarizer

The present invention relates to a polarizing plate in which a thermoplastic resin film is bonded to a polarizing film.

The polarizing plate can be used as one of the optical members constituting the liquid crystal display device. The polarizing plate usually has a structure in which a protective film is layered on at least one area of the polarizing film, and is installed in a liquid crystal display device. In addition, with regard to the manufacturing method of the polarizing film, a method of performing a boric acid treatment on a uniaxially stretched polyvinyl alcohol resin film dyed with a dichroic dye, followed by a water washing treatment and a drying treatment is widely used.

Generally, the polarizing film is bonded to the protective film immediately after the above-mentioned water washing treatment and drying treatment. This is because the physical strength of the dried polarizing film is weak, and once it is wound up, it will easily crack in the processing direction. Therefore, an adhesive is usually applied to the polarizing film after the drying process immediately, and the protective film is simultaneously bonded to both sides of the polarizing film via the adhesive.

The adhesive generally uses an aqueous adhesive containing a water-soluble resin such as polyvinyl alcohol-based resin as a main component, or an active energy ray-curable adhesive. Regarding the active energy ray-curable adhesive, Patent Document 1 describes a combination of an alicyclic epoxy compound and an epoxy compound not having an alicyclic epoxy group, and a photocationic polymerization initiator which is formulated together Light-curing adhesive. A technique for bonding a polarizing film and a protective film is disclosed.

[Prior Technical Literature]

[Patent Literature]

[Patent Document 1] JP 2008-257199 A

In recent years, in response to the diversification of mobile devices, durability in more severe environments has been required. In the polarizing plate described in Patent Document 1, it is known that there is a problem of discoloration of the polarizing plate in a severe environment (for example, when stored in a high temperature environment for a long time).

Therefore, the subject of the present invention is to provide a polarizing plate in which the discoloration of the polarizing plate is suppressed even in a severe environment.

The present invention includes the following inventions.

[1] A polarizing plate in which a thermoplastic resin film is bonded to at least one side of a polarizing film via an adhesive layer, wherein

The aforementioned adhesive is a cured product of a photocurable composition containing a cationic polymerizable compound and a photocationic polymerization initiator,

The aforementioned photocurable composition contains 0.5 to 1.5 parts by mass of a photocationic polymerization initiator relative to 100 parts by mass of the cationic polymerizable compound,

The aforementioned cationically polymerizable compound contains 10 to 70% by mass of the bifunctional oxetane compound with respect to the total mass of the cationically polymerizable compound.

[2] The polarizing plate according to [1], wherein the cationically polymerizable compound further contains an aliphatic epoxy compound in an amount of 10 to 70% by mass relative to the total mass of the cationically polymerizable compound.

[3] The polarizing plate according to [1] or [2], wherein the moisture permeability of the thermoplastic resin film at a temperature of 40°C and a relative humidity of 90% is 300 g/(m ² .24hr) or less.

The polarizing plate of the present invention is restrained from discoloration of the polarizing plate even in a severe environment.

The present invention will be described in detail below. The polarizing plate of the present invention is bonded to the thermoplastic resin film on at least one side of the polarizing film via an adhesive composed of a photocurable composition. The components and components of the polarizing plate are explained in order.

〔Polarizing Film〕

The polarizing film is composed of a polyvinyl alcohol resin film with a dichroic dye adsorbed and aligned. The polyvinyl alcohol-based resin constituting the polarizing film is obtained by saponifying a polyvinyl acetate-based resin. Examples of the polyvinyl acetate resin include polyvinyl acetate which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable with the vinyl acetate. Examples of other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of saponification of the polyvinyl alcohol-based resin is generally 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, for example, polyvinyl formaldehyde or polyvinyl acetal modified with aldehydes may also be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually 1,000 to 10,000, preferably in the range of 1,500 to 5,000.

The above-mentioned polarizing film is manufactured through the following steps: a step of uniaxially stretching a polyvinyl alcohol-based resin film; dyeing the polyvinyl alcohol-based resin film with a dichroic dye to adsorb the dichroic Pigment step: the step of treating the polyvinyl alcohol resin film with the dichroic pigment with boric acid aqueous solution.

The uniaxial extension step can be performed before dyeing with dichroic pigments, simultaneously with dyeing with dichroic pigments, or after dyeing with dichroic pigments . When uniaxial stretching is performed after dyeing with a dichroic dye, the uniaxial stretching may be performed before the boric acid treatment or may be performed during the boric acid treatment. In addition, it is also possible to perform uniaxial extension in these plural stages. When performing uniaxial stretching, it can be stretched through rollers with different peripheral speeds, or it can be stretched by wrapping the hot rollers. In addition, it may be dry stretching in the atmosphere, or wet stretching in a state swelled with a solvent. The stretching ratio is usually about 4 to 8 times.

When the polyvinyl alcohol-based resin film is dyed with a dichroic dye, for example, the polyvinyl alcohol-based resin film may be immersed in an aqueous solution containing the dichroic dye. Specifically, the dichroic dye system uses iodine or a dichroic organic dye.

When iodine is used as a dichroic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide for dyeing is usually adopted. In this aqueous solution, the content of iodine is usually about 0.01 to 0.5 parts by weight per 100 parts by weight of water, and the content of potassium iodide is usually about 0.5 to 10 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution is usually about 20 to 40°C, and the immersion time (dyeing time) in the aqueous solution is usually about 30 to 300 seconds.

On the other hand, when a dichroic organic dye is used as a dichroic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye for dyeing is generally adopted. In this aqueous solution, the content of the dichroic organic dye is usually about 1×10 ^-3 to 1×10 ^-2 parts by weight per 100 parts by weight of water. The aqueous solution may contain inorganic salts such as sodium sulfate. The temperature of the aqueous solution is usually about 20 to 80°C, and the immersion time (dyeing time) in the aqueous solution is usually about 30 to 300 seconds.

The boric acid treatment after dyeing by the dichroic dye is performed by immersing the dyed polyvinyl alcohol-based resin film in a boric acid aqueous solution. In the boric acid aqueous solution, the content of boric acid is usually about 2 to 15 parts by weight, preferably about 5 to 12 parts by weight per 100 parts by weight of water. When iodine is used as a dichroic dye, the boric acid aqueous solution preferably contains potassium iodide. In the boric acid aqueous solution, the content of potassium iodide per 100 parts by weight of water is usually about 2 to 20 parts by weight, preferably 5 to 15 parts by weight. 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 polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment is performed, for example, by immersing a polyvinyl alcohol-based resin film treated with boric acid in water. After washing with water, a drying process is performed to produce a polarizing film. The temperature of the water during the washing treatment is usually about 5 to 40°C, and the immersion time is usually about 2 to 120 seconds. The subsequent drying treatment is usually carried out using a hot air dryer or a far infrared heater. The drying temperature is usually 40 to 100°C. In addition, the drying treatment time is usually about 120 to 600 seconds.

The thickness of the finally obtained polarizing film composed of polyvinyl alcohol-based resin can be about 10 to 50 μm.

〔Thermoplastic resin film〕

The polarizing plate of the present invention is obtained by laminating a thermoplastic resin film on a polarizing film composed of a polyvinyl alcohol-based resin film described above through a photocurable composition, and curing the photocurable composition.

The thermoplastic resin film is preferably made of transparent resin. The thermoplastic resin film may be an unstretched film or a uniaxially or biaxially stretched film.

The main component of the thermoplastic resin film is preferably at least one resin selected from the group consisting of cellulose resin, acrylic resin, amorphous polyolefin resin, polyester resin, and polycarbonate resin.

The polyester resin is not particularly limited, but in terms of mechanical properties, solvent resistance, scratch resistance, and cost, it is particularly preferably polyethylene terephthalate. The so-called polyethylene terephthalate refers to a resin in which 80 mol% or more of the repeating unit is composed of ethylene terephthalate, and it may contain structural units derived from other copolymerization components.

Examples of other copolymerization components include dicarboxylic acid components and glycol components. Dicarboxylic acid components include isophthalic acid, p-β-hydroxyethoxy benzoic acid, 4,4'-dicarboxybiphenyl, 4,4'-dicarboxydiphenyl ketone, bis(4-carboxyl Phenyl)ethane, adipic acid, sebacic acid, isophthalic acid 5-sodium sulfonate and 1,4-dicarboxycyclohexane, etc. The glycol components include propylene glycol, butylene glycol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adducts of bisphenol A, polyethylene glycol, polypropylene glycol and polytetramethylene Base glycol and so on. These dicarboxylic acid components or diol components can also be used in combination of two or more types as needed. In addition, a hydroxycarboxylic acid such as p-hydroxybenzoic acid may be used in combination with the above-mentioned dicarboxylic acid component or diol component. Dicarboxylic acid components and/or glycol components having amide bonds, urethane bonds, ether bonds, carbonate bonds, etc., may also be used in small amounts as other copolymerization components.

The polyethylene terephthalate resin means a resin in which 80 mol% or more of the repeating unit is composed of ethylene terephthalate, and it may contain structural units derived from other copolymerization components. Other copolymerization components include: isophthalic acid, 4,4'-dicarboxybiphenyl, 4,4'-dicarboxydiphenyl ketone, bis(4-carboxyphenyl)ethane, adipic acid, Sebacic acid, isophthalic acid 5-sodium sulfonate, 1,4-dicarboxycyclohexane and other dicarboxylic acid components; propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, Glycol components such as ethylene oxide adducts of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. These dicarboxylic acids are It can be used in combination of two or more kinds of components or glycol components as needed. In addition, hydroxycarboxylic acids such as p-hydroxybenzoic acid or p-β-hydroxyethoxybenzoic acid may be used together with the above-mentioned carboxylic acid component or diol component. Dicarboxylic acid components and/or glycol components containing a small amount of amide bonds, urethane bonds, ether bonds, and carbonate bonds may also be used as other copolymerization components.

After the above-mentioned polyethylene terephthalate-based resin is formed into a film, by using the above-mentioned stretching treatment as a protective film, excellent mechanical properties, solvent resistance, scratch resistance, and cost can be obtained. Roller-shaped polarizing plate with reduced thickness.

Polycarbonate resin is a polyester formed by carbonic acid and glycol or bisphenol. Among them, aromatic polycarbonates having diphenylalkanes in the molecular chain are suitable for their excellent heat resistance, weather resistance, and acid resistance. Such polycarbonates can be exemplified from 2,2-bis(4-hydroxyphenyl)propane (alias bisphenol A), 2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4 -Hydroxyphenyl) cyclohexane, 1,1-bis(4-hydroxyphenyl)isobutane, or 1,1-bis(4-hydroxyphenyl)ethane-like bisphenols derived from polycarbonate ester.

As the manufacturing method of the polycarbonate resin film, any method such as a casting film method and a melt extrusion method can be used. Examples of specific manufacturing methods include: dissolving a polycarbonate resin in a suitable organic solvent to prepare a polycarbonate resin solution, and casting it on a metal support to form a mesh, and the mesh is After the object is peeled from the metal support, the peeled web is dried with hot air to obtain a film.

The acrylic resin is not particularly limited, but is generally a polymer with methacrylate as the main monomer, and a copolymer in which a small amount of other comonomer components are copolymerized is preferred. This copolymer can usually be obtained by polymerizing a monofunctional monomer containing methyl methacrylate and methyl acrylate in the coexistence of a radical polymerization initiator and a chain transfer agent. In addition, the acrylic resin can be copolymerized with a third monofunctional monomer.

The third monofunctional monomer that can be copolymerized with methyl methacrylate and methyl acrylate, for example, includes ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, and methyl methacrylate. Methacrylates other than methyl methacrylate such as benzyl acrylate, 2-ethylhexyl methacrylate and 2-hydroxyethyl methacrylate; ethyl acrylate, butyl acrylate, cyclohexyl acrylate , Phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate and other acrylates; 2-(hydroxymethyl)methyl acrylate, 2-(1-hydroxyethyl)acrylic acid Hydroxyalkyl acrylates such as methyl ester, ethyl 2-(hydroxymeth)acrylate and butyl 2-(hydroxymeth)acrylate; unsaturated acids such as methacrylic acid and acrylic acid; chlorostyrene and bromostyrene, etc. Halogenated styrenes; substituted styrenes such as vinyl toluene and α-methylstyrene; unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated acid anhydrides such as maleic anhydride and citraconic anhydride; phenyl horse Unsaturated imines, such as lyimines and cyclohexylmaleimines. These can be used individually, or a plurality of different ones can be used in combination.

When copolymerized with a multifunctional monomer, the multifunctional monomers that can be copolymerized with methyl methacrylate and methyl acrylate include, for example, ethylene glycol di(meth)acrylate, diethylene glycol di(methyl) Base) acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, nonaethylene glycol di(meth)acrylate and tetraethylene glycol di(meth)acrylate ) Ethylene glycol or its oligomers, such as acrylate, whose two terminal hydroxyl groups are esterified with acrylic acid or methacrylate; those whose two terminal hydroxyl groups of propylene glycol or its oligomers are esterified with acrylic acid or methacrylate; Alcohol di(meth)acrylate, hexanediol di(meth)acrylate, butanediol di(meth)acrylate and other diols whose hydroxyl groups are esterified with acrylic acid or methacrylate; bisphenol A , Alkylene oxide adducts of bisphenol A, or the two terminal hydroxyl groups of these halogen substitutes are esterified with acrylic acid or methacrylic acid; polyols such as trimethylolpropane and neopentylerythritol are esterified with acrylic acid or Methacrylate esterifiers, and those that make these terminal hydroxyl groups and glycidyl acrylate or glycidyl methacrylate epoxy groups ring-opening addition; make succinic acid, adipic acid, terephthalic acid, ortho Phthalic acid, these halogen substitutions Ring-opening addition of dibasic acids such as substances and these alkylene oxide adducts to the epoxy groups of glycidyl acrylate or glycidyl methacrylate; (meth) aryl acrylate; diethylene Aromatic divinyl compounds such as benzene, etc. Among them, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate can be preferably used.

The acrylic resin composed of such a composition may be modified by further reacting the functional groups possessed by the copolymer. Examples of the reaction include the intra-polymer chain demethanol condensation reaction between the methyl acrylate group of methyl acrylate and the hydroxyl group of methyl 2-(hydroxymeth)acrylate, and the reaction between the carboxyl group of acrylic acid and methyl 2-(hydroxymethyl)acrylate. The dehydration condensation reaction in the polymer chain of hydroxyl group.

The glass transition temperature of the acrylic resin is preferably in the range of 80 to 120°C. When the glass transition temperature of the acrylic resin is adjusted to the above range, the following methods can usually be adopted: the polymerization ratio of the methacrylate monomer to the acrylic monomer, the carbon chain length of the respective ester group, and The type of functional group and the polymerization ratio of the polyfunctional acrylic monomer to the entire monomer are appropriately selected.

Acrylic resin may contain well-known additives as needed. Known additives include, for example, lubricants, anti-caking agents, heat stabilizers, antioxidants, antistatic agents, lightfast agents, impact resistance improvers, surfactants, and the like. However, since the protective film laminated on the polarizing film needs transparency, the amount of these additives is preferably controlled to a minimum.

As the manufacturing method of the acrylic resin film, any method such as a melt extrusion method such as a melt casting method, a T-die method, or an expansion method, and a rolling method can be used. Among them, in view of obtaining a film with good surface properties, a method of forming a film by melt-extruding the raw material resin from, for example, a T-die and contacting at least one side of the obtained film with a roller or a belt is preferred.

From the viewpoints of film-forming properties of the film or impact resistance of the film, the acrylic resin may contain acrylic rubber particles which are impact modifiers. The acrylic rubber particles referred to herein refer to particles with an elastic polymer mainly composed of acrylate as an essential component. Examples include those having a single-layer structure substantially composed of the elastic polymer, or those with the elastic polymer as an essential component. One-layer multi-layer structure. Examples of the elastic polymer include a crosslinked elastic copolymer which is composed of alkyl acrylate as a main component and copolymerized with other vinyl monomers and crosslinkable monomers copolymerizable with the alkyl acrylate. The alkyl acrylate as the main component of the elastic polymer includes, for example, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and other alkyl groups having a carbon number of about 1 to 8, especially preferred. An acrylate having an alkyl group with 4 or more carbon atoms is used. Other vinyl monomers that can be copolymerized with the alkyl acrylate include compounds having a polymerizable carbon-carbon double bond in the molecule, and more specifically, methacrylic acid such as methyl methacrylate Esters, aromatic vinyl compounds like styrene, vinyl cyanide compounds like acrylonitrile, etc. In addition, the crosslinkable monomer may be a crosslinkable compound having at least two polymerizable carbon-carbon double bonds in the molecule, and more specifically, examples include ethylene glycol di(meth)acrylate and butane (Meth)acrylates of polyols like alcohol di(meth)acrylate, alkenyl esters of (meth)acrylic acid like allyl (meth)acrylate, divinylbenzene, etc.

In addition, a laminate of a film made of an acrylic resin containing no rubber particles and a film made of an acrylic resin containing rubber particles may be used as the protective film. Acrylic resins are easily available on the market. For example, they are represented by trade names. Sumipex (manufactured by Sumitomo Chemical Co., Ltd.), Acrypet (manufactured by Mitsubishi Rayon Co., Ltd.), Delpet (manufactured by Asahi Kasei Co., Ltd.), Kuraray Co., Ltd.), Acryviewa (Nippon Shokubai Co., Ltd.), etc.

Examples of amorphous polyolefin-based resins include: using cyclopentadiene and olefins through the Diels-Alder reaction (Diels-Alder reaction) to obtain norcampine or its derivatives as monomers for ring opening Resin obtained by translocation polymerization, followed by hydrogenation; to use Tetracyclododecene or its derivatives obtained by the Diels-Alder reaction of dicyclopentadiene and olefins or methacrylates A resin obtained by ring-opening translocation polymerization as a monomer, followed by hydrogenation; using two or more selected from norbornene, tetracyclododecene and their derivatives, and other cyclic polyolefin monomers The resin obtained by carrying out ring-opening translocation copolymerization in the same way, followed by hydrogenation; obtained by the addition copolymerization of norbornene, tetracyclododecene or their derivatives with aromatic compounds having vinyl groups, etc. Resin etc. Examples of commercially available amorphous polyolefin resins include "Arton" of JSR Co., Ltd., "ZEONEX" and "ZEONOR" of Japan Zeon Co., Ltd., "APO" of Mitsui Chemicals Co., Ltd. and "Apel" and so on. When the amorphous polyolefin-based resin is formed into a film to form a film, a known method such as a solution casting method and a melt extrusion method can be suitably used in the film formation.

The cellulose resin is a resin in which at least a part of the hydroxyl groups in the cellulose is esterified with acetic acid, and may be a mixed ester in which a part is esterified with acetic acid and a part is esterified with another. The cellulose resin is preferably a cellulose ester resin, and more preferably a cellulose acetate resin. Specific examples of the cellulose acetate resin include cellulose triacetate, cellulose diacetate, cellulose acetate propionate, and cellulose acetate butyrate. Commercial products of films composed of such cellulose acetate resins include, for example, "FujitacTD80", "FujitacTD80UF" and "FujitacTD80UZ" manufactured by Fujifilm Co., Ltd., and "KC8UX2M" and "FujitacTD80UZ" manufactured by Konica Minolta Opto Co., Ltd. KC8UY" etc.

It is also possible to use a cellulose resin film to which an optical compensation function has been provided. The optical compensation film includes, for example, a film formed by containing a compound having a retardation adjustment function in a cellulose resin, a film obtained by coating a compound having a retardation adjustment function on the surface of the cellulose resin, and a film obtained by applying a retardation adjustment function to the cellulose resin. Films obtained by uniaxial or biaxial extension. If you cite examples of commercially available cellulose-based resin optical compensation films, There are "Wide Viewing Film WV BZ 438" and "Wide Viewing Film WV EA" manufactured by Fujifilm Co., Ltd., and "KC4FR-1" and "KC4HR-1" manufactured by Konica Minolta Opto Co., Ltd.

The thermoplastic resin film attached to one side of the polarizing film may contain an ultraviolet absorber. This is because by disposing the protective film containing the ultraviolet absorber on the viewing side of the liquid crystal cell, the liquid crystal cell can be protected from deterioration caused by ultraviolet rays.

In the present invention, the above-mentioned thermoplastic resin film is bonded using a photocurable composition to at least one side of the polarizing film. When the thermoplastic resin film is bonded to only one side of the polarizing film, for example, an adhesive layer for bonding to other members such as liquid crystal cells may be directly provided on the other side of the polarizing film.

On the other hand, when a thermoplastic resin film is bonded to both sides of a polarizing film, each thermoplastic resin film may be of the same type or different types.

The thermoplastic resin film attached to one side of the polarizing film is followed by using the photocurable composition described later, and the thermoplastic resin film attached to the other side of the polarizing film can be an adhesive layer formed of other photocuring compositions. And then.

The thermoplastic resin film can be easily bonded by saponification treatment, corona treatment, plasma treatment, anchor coating treatment, etc., on the bonding surface before being bonded to the polarizing film. In addition, the surface of the thermoplastic resin film on the opposite side to the bonding surface of the polarizing film may have various treatment layers such as a hard coat layer, an anti-reflection layer, and an anti-glare layer. The thickness of the thermoplastic resin film is usually in the range of about 5 to 200 μm, preferably 10 to 120 μm, more preferably 10 to 100 μm.

The moisture permeability of the thermoplastic resin film at a temperature of 40°C and a relative humidity of 90% is preferably 300g/(m ² .24hr) or less, more preferably 200g/(m ² .24hr), and still more preferably 100g/( m ² ．24hr). If the moisture permeability is less than 300g/(m ² .24hr), for example, the change in the transmittance under a high temperature and high humidity environment or the change in hue under a high temperature environment can be suppressed, which is preferable.

When laminating the thermoplastic resin film on both sides of the polarizing film, at least the viewing side (outermost surface) is attached under the conditions of a temperature of 40°C and a relative humidity of 90%. The moisture permeability is 300g/(m ² .24hr) or less the thermoplastic resin film is preferred, in order to double-sided polarizing film bonded at a temperature of 40 ℃, moisture permeability relative humidity was 90% of the 300g / (m ^2. 24hr) or less of the thermoplastic resin film better.

[Adhesive layer]

The polarizing plate of the present invention is one having a thermoplastic resin film bonded to one side of the above-mentioned polarizing film via an adhesive layer. The adhesive layer is formed of a photocurable composition prepared by mixing a cationic polymerizable compound and a photocationic polymerization initiator at a predetermined ratio.

(Cation polymerizable compound)

The cationic polymerizable compound is the main component of the photocurable composition and is a component that imparts adhesive force due to polymerization and curing. The cationically polymerizable compound includes a bifunctional oxetane compound.

(2-functional oxetane compound)

The bifunctional oxetane compound refers to a compound having two 4-membered cyclic ethers (oxetanyl groups) in the molecule, and examples thereof include the following compounds.

Bis[(3-ethyloxetan-3-yl)methyl]ether, bis[(3-methyloxetan-3-yl)methyl]ether, bis[(oxetane-3-yl)methyl]ether Butane-3-yl)methyl]ether, 1,4-bis[[(3-ethyloxetan-3-yl)methoxy]methyl]benzene, 1,4-bis[( 3-Ethyloxetan-3-yl)methoxy]benzene, 1,3-bis[(3-ethyloxetan-3-yl)methoxy]benzene, 1,2 -Bis[(3-ethyloxetan-3-yl)methoxy]benzene, 4,4'-bis[(3-ethyloxetan-3-yl)methoxy] Biphenyl, 2,2'-bis[(3-ethyloxetane-3-yl)methoxy]biphenyl, 1,1,1-gin[(3-ethyloxetane -3-yl)methoxymethyl]propane, 1,2-bis[(3-ethyloxetan-3-yl)methoxy]ethane, 1,2-bis[(3- Ethyloxetane-3-yl)methoxy]propane, 1,4-bis[(3-ethyloxetan-3-yl)methoxy]butane and 1,6- Bis[(3-ethyloxetan-3-yl)methoxy]hexane and the like.

Among them, when it is bis[(3-ethyloxetan-3-yl)methyl]ether, the photocurable composition has high reactivity and can change the elastic modulus of the resulting cured product at high temperatures. high. Therefore, the durability of the polarizing plate under high temperature conditions or high temperature and high humidity becomes higher, which is preferable.

In view of the low viscosity of the photocurable composition and excellent adhesion of the cured product of the photocurable composition, the molecular weight of the bifunctional oxetane compound is preferably 550 or less, and the molecular weight is more preferably 150 to 400. The molecular weight is more preferably 150 to 300.

One type of bifunctional oxetane compound may be used, or two or more types may be used.

Based on the total mass of the cationically polymerizable compound, the bifunctional oxetane compound is preferably formulated in a ratio of 10 to 70% by mass. When the content of the bifunctional oxetane compound is 10% by mass or less, the curability of the photocurable composition decreases, and when it is 70% by mass or more, the adhesive force to the thermoplastic resin film decreases. A preferable content is based on the total amount of the cationically polymerizable compound, and the bifunctional oxetane compound is 15 to 65% by mass, more preferably 25 to 55% by mass.

(Aliphatic epoxy compound)

The photocurable composition in the present invention may further contain an aliphatic epoxy compound as a cationically polymerizable compound. When a bifunctional oxetane compound and aliphatic epoxy compound are used together as a cationic polymerizable compound, the storage elastic modulus of the cured product of the photocurable composition can be maintained at a high value, and the polarizing film can be further improved Adhesion to the protective film. The aliphatic epoxy compound here refers to a compound in which one of the two carbon atoms contained in the epoxy group is bonded to other aliphatic carbon atoms. Examples thereof include polyglycidyl ether of alkane polyol and polyglycidyl ether of polyalkylene glycol.

Examples of polyglycidyl ethers of polyalkylene glycol include diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, and tripropylene glycol diglycidyl ether. Ether etc.

A specific example of the polyglycidyl ether of alkane polyol is a compound represented by the following formula (IV).

In the above formula (IV), Z represents an alkylene group having a carbon number of 2 to 10, and Z may be linear or branched, and may also be a ring structure. Z preferably has a carbon number of 2-6, and more preferably 4-6.

The compound represented by the above formula (IV) includes, for example, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,3-propanediol diglycidyl ether, 1,4-butanediol diglycidyl ether Ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, 1,9-nonanediol diglycidyl ether, cyclohexane dimethanol diglycidyl ether, 1 , 4-Cyclohexane dimethanol diglycidyl ether and so on.

Other aliphatic epoxy compounds include glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, neopentyl erythritol polyglycidyl ether, and dineopentaerythritol polyglycidyl ether. -Ethylhexyl glycidyl ether, hydroquinone diglycidyl ether, resorcinol diglycidyl ether, etc.

The aliphatic epoxy compound is preferably a compound represented by formula (IV) from the viewpoint of being easily available and having a greater effect of improving the adhesion between the polarizing film and the thermoplastic resin film. Specifically, it is preferable to use 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, etc. Z is carbon number 4 to Compound of 6.

One type of aliphatic epoxy compound may be used, or two or more types may be used.

When a bifunctional oxetane compound and an aliphatic epoxy compound are used together, the blending ratio of the two is based on the total amount of the cationic polymerizable compound, and the aliphatic epoxy compound It is preferably 10 to 90% by mass, more preferably 15 to 80% by mass, and even more preferably 15 to 50% by mass. Of course, the sum of these will not exceed 100% by mass. By blending an aliphatic epoxy compound (for example, the compound represented by the above formula (IV)) at a ratio of 10% by mass or more in the total cationically polymerizable compound, the adhesion to the thermoplastic resin film becomes excellent. From the viewpoint of low viscosity and adhesive force of the photocurable composition, although the aliphatic epoxy compound is more preferably, when it exceeds 90% by mass, the cured product of the photocurable composition has storage elasticity at 80°C The modulus becomes lower, and the durability of the polarizing plate in which the polarizing film and the protective film are bonded via the cured product of the photocurable composition will deteriorate in the cold and hot impact test.

(Other cationic hardening ingredients)

The photocurable composition may contain other cationic curable components. Examples of other cation curable components include aromatic epoxy compounds, hydrogenated epoxy compounds in which the aromatic ring in the aromatic epoxy compound is hydrogenated, alicyclic epoxy compounds, and monofunctional oxetane compounds.

In the present invention, the term "aromatic epoxy compound" means a compound in which a glycidyl ether group or a glycidyl ester group is directly bonded to an aromatic ring. Specific examples include bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, epoxy resin formed by polycondensation of bisphenol A, bisphenol F and epichlorohydrin, Phenolic novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolac type epoxy resin, and bisphenol F novolac type epoxy resin.

From the viewpoint of adhesion to the thermoplastic resin film, the number of epoxy groups contained in one molecule of the aromatic epoxy compound is preferably 2 or more. In addition, for the same reason, the weight average molecular weight (hereinafter referred to as "Mw") of the aromatic epoxy compound is preferably 400 to 50,000, more preferably 1,000 to 10,000, and still more preferably 2,000 to 50,000. In addition, Mw in the present invention refers to Mw converted into polystyrene measured by gel permeation chromatography (GPC).

The aromatic epoxy compound may be used alone, or two or more kinds may be used.

When an aromatic epoxy compound is used in combination, its content is preferably 1 to 25% by mass relative to the total mass of the cationically polymerizable compound. By making the content 1% by mass or more, the adhesion to the thermoplastic resin film is improved. On the other hand, when the content exceeds 25% by mass, the viscosity of the composition increases, and the paintability deteriorates. A preferable content is 3 to 20% by mass relative to the total mass of the cationically polymerizable compound, and more preferably 5 to 15% by mass.

The hydrogenated epoxy compound is prepared by selectively hydrogenating an aromatic polyhydroxy compound having at least two phenolic hydroxyl groups in the molecule, which is a raw material of the above-mentioned aromatic epoxy compound, in the presence of a catalyst and under pressure. The resulting hydrogenated polyhydroxy compound is glycidyl etherified. Specific examples thereof include diglycidyl ether of hydrogenated bisphenol A, diglycidyl ether of hydrogenated bisphenol F, and diglycidyl ether of hydrogenated bisphenol S.

The so-called alicyclic epoxy compound refers to a compound containing at least two alicyclic epoxy groups in the molecule. The so-called alicyclic epoxy group refers to a group represented by the following formula (II) (in formula (II), m = an integer from 2 to 5), specifically, epoxycyclopentyl, epoxy ring Hexyl etc.

The alicyclic epoxy compound is preferably a compound represented by formula (III).

(式中，R¹及R²分別獨立地表示碳數1至6的烷基。)

(In the formula, R ¹ and R ² each independently represent an alkyl group having 1 to 6 carbon atoms.)

The compound represented by formula (III) can include 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate, 3,4-epoxy-6-methylcyclohexylmethyl 3, 4-epoxy-6-methylcyclohexane carboxylate, etc.

When an alicyclic epoxy compound is used in combination, from the viewpoint of moisture and heat resistance, it is preferable that the content of the alicyclic epoxy compound is smaller. Specifically, with respect to the total mass of the cationic polymerizable compound, the alicyclic epoxy compound is preferably less than 30% by mass, more preferably less than 15% by mass, and more preferably 1 to 10% by mass. .

(Photocationic polymerization initiator)

The photocurable composition system undergoes cationic polymerization due to the irradiation of active energy rays and hardens to be applied to the adhesive layer. The photocationic polymerization initiator may be one that generates cationic species or Lewis acid due to irradiation of visible light, ultraviolet rays, X-rays, or active energy rays such as electron beams, and initiates the polymerization reaction of the cationic polymerizable compound. Since the photocationic polymerization initiator has a catalytic effect due to light, even if it is mixed with the cationic polymerizable compound, it will not affect its storage stability or workability. Examples of the photocationic polymerization initiator include onium salts of aromatic diazonium salts, aromatic iodonium salts or aromatic sulfonium salts, iron-arene complexes, and the like.

Examples of the aromatic diazonium salt include the following compounds.

Benzene diazonium hexafluoroantimonate,

Benzene diazonium hexafluorophosphate,

Benzene diazonium hexafluoroborate and so on.

Examples of the aromatic iodonium salt include the following compounds.

Diphenyl iodonium tetra (pentafluorophenyl) borate,

Diphenyl iodonium hexafluorophosphate,

Diphenyl iodonium hexafluoroantimonate,

Bis (4-nonylphenyl) iodonium hexafluorophosphate,

Bis(4-alkylphenyl) iodonium hexafluorophosphate,

Tolylcumyl iodonium tetrakis (pentafluorophenyl) borate,

Bis(4-tertiary butylphenyl) iodonium hexafluorophosphate,

Bis(4-tertiary butylphenyl) iodonium hexafluoroantimonate,

(4-Methylphenyl)[4-(2-methylpropyl)phenyl]-hexafluorophosphate and the like.

Examples of the aromatic sulfonium salt include the following compounds.

Triphenylsulfonium hexafluorophosphate,

Triphenylsulfonium hexafluoroantimonate,

Triphenylsulfonium (pentafluorophenyl) borate,

4,4'-bis[diphenylsulfonyl]diphenyl sulfide bishexafluorophosphate,

4,4'-bis[bis(β-hydroxyethoxy)phenylsulfonyl]diphenyl sulfide bishexafluoroantimonate,

4,4'-bis[bis(β-hydroxyethoxy)phenylsulfonyl]diphenyl sulfide bishexafluorophosphate,

7-[Bis(p-tolylmethyl)sulfonyl]-2-isopropylthioxanthone hexafluoroantimonate,

7-[Bis(p-tolyl)sulfonyl]-2-isopropylthioxanthone 4(pentafluorophenyl) borate,

4-phenylcarbonyl-4'-diphenylsulfonyl-diphenyl sulfide hexafluorophosphate,

4-(p-tert-butylphenylcarbonyl)-4'-diphenylsulfonyl-diphenyl sulfide hexafluoroantimonate,

4-(p-tert-butylphenylcarbonyl)-4’-bis(p-tolyl)sulfonyl-diphenyl sulfide 4-(pentafluorophenyl)borate

4-(Phenylthio)phenyldiphenylsulfonium ginseng(pentafluoroethyl)trifluorophosphate

4-(Phenylthio)phenyldiphenylsulfonium hexafluorophosphate

4-(phenylthio)phenyldiphenylsulfonium trifluoromethanesulfonate and the like.

Examples of iron-arene complexes include the following compounds.

Xylene-cyclopentadienyl iron(II) hexafluoroantimonate,

Cumene-cyclopentadienyl iron (II) hexafluorophosphate,

Xylene-cyclopentadienyl iron (II) ginseng (trifluoromethylsulfonyl) methyl body and the like.

These photocationic polymerizable initiators can be obtained from commercially available products. For example, Adeka Optomer SP-100, SP-150, SP-152, SP-170, SP-172 [manufactured by ADEKA Co., Ltd.], photo-initiator 2074 (manufactured by Rhodia), Kayarad PCI-220, PCI-620 [Manufactured by Nippon Kayaku Co., Ltd.], Irgacure250 (manufactured by CIBA Japan), CPI-100P, CPI-110P, CPI-101A, CPI-200K, CPI-210S (manufactured by San-Apro Co., Ltd.), WPI-113, WPI-116 [manufactured by Wako Pure Chemical Industry Co., Ltd.]), BBI-102, BBI-103, TPS-102, TPS-103, DTS-102, DTS-103 [manufactured by Green Chemical Co., Ltd.], etc.

These photocationic polymerization initiators may be used alone, or two or more of them may be mixed and used. Among these, aromatic sulfonium salts in particular also have ultraviolet absorbing properties in the wavelength region around 300 nm, so they are excellent in curability and can impart a cured product with good mechanical strength or adhesive strength, and are therefore suitable.

The compounding amount of the photocationic polymerization initiator is 0.5 to 1.5 parts by mass relative to 100 parts by mass of the cationic polymerizable compound. By preparing 0.5 parts by mass or more (more preferably 0.7 parts by mass or more) of the photocationic polymerization initiator per 100 parts by mass of the cationically polymerizable compound, the cationically polymerizable compound can be sufficiently cured, and the resulting polarizing plate Provides high mechanical strength and adhesive strength, and at the same time has excellent durability in high temperature and high humidity environments. On the other hand, when the amount increases, the residual amount of unreacted starter, solvents used as necessary to dissolve the starter, or decomposition products of the starter will increase, thereby impairing the physical properties of the hardened product. Discolor the polarizer in a high temperature environment. Accordingly, the amount of the photocationic polymerization initiator is preferably 1.5 parts by mass or less per 100 parts by mass of the cationically polymerizable compound.

(Other ingredients)

The photocurable composition also contains other components in addition to the cationic polymerizable compound and photocationic polymerization initiator described above. Examples of other ingredients that can be adjusted include photosensitizers, photosensitizers, thermal cationic polymerization initiators, chain transfer agents, thermoplastic resins, flow regulators, defoamers, leveling agents, organic solvents, silane coupling Agents, polymers, etc. Depending on the type of protective film attached to the polarizing film, it is sometimes better to formulate a photosensitizer or even a photosensitizer.

The photosensitizer is a compound that exhibits maximum absorption at a wavelength longer than the maximum absorption wavelength indicated by the photocationic polymerization initiator, and the photocationic polymerization initiator promotes the initiation of polymerization. For such photosensitizer, it is preferable to use an onion-based compound. The onion-based compounds that can become photosensitizers include 9,10-dimethoxy onion, 9,10-diethoxy onion, 9,10-dipropoxy onion, and 9,10-diisopropoxy onion. , 9,10-dibutoxy onion, 9,10-dipentyloxy onion, 9,10-dihexyloxy onion, etc.

The photosensitizer is a compound that further promotes the action of the photosensitizer. As such a photosensitizing auxiliary agent, it is preferable to use a naphthalene compound. Naphthalene compounds that can be photosensitizers include 1,4-dimethoxynaphthalene, 1-ethoxy-4-methoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dipropylene Oxynaphthalene, 1,4-dibutoxynaphthalene, etc.

When these other components are blended, the amount is relative to 100 parts by mass of the cationically polymerizable compound which is the main component of the photocurable composition, and for example, it may be appropriately selected from the range of 10 parts by mass or less according to the purpose of blending.

The viscosity of the photocurable composition in the present invention is not particularly limited, and is preferably 10 to 1000 mPa at 25°C. s. From the viewpoint of paintability and thinning of the coating layer, it is more preferably 15 to 500 mPa. s, and more preferably 20 to 100 mPa. s. The viscosity in the present invention is the measured value measured by the E-type viscometer.

The moisture content of the photocurable composition relative to the total amount of the photocurable composition is preferably 3% by mass or less, more preferably 2% by mass or less, still more preferably 1% by mass or less, particularly preferably 0.5% by mass or less . When the moisture content of the photocurable composition exceeds 3% by mass, the curability of the photocurable composition will deteriorate. tendency. Therefore, the adhesion between the thermoplastic resin film and the polarizing film immediately after the production of the polarizing plate is reduced, and there is a tendency for warping or peeling.

[Production of Polarizing Plate]

The thermoplastic resin film is bonded to the polarizing film via the adhesive layer formed of the photocurable composition to form a polarizing plate. This bonding is performed by forming the coating layer of the photocurable composition described above on one or both sides of the bonding surface of the polarizing film and the thermoplastic resin film, and the polarizing film is interposed between the coating layer It is bonded to these protective films, and the coating layer of the uncured photocurable composition is irradiated with active energy rays to be cured to fix the thermoplastic resin film on the polarizing film.

When forming the coating layer of the photocurable composition, for example, various coating methods such as doctor blades, wire bars, die coaters, chipped wheel coaters, and gravure coaters can be used. In addition, a method in which the polarizing film and the thermoplastic resin film are continuously supplied with the bonding surface of the two facing inward, and the photocurable composition may be streamed. Since each coating method has the most suitable viscosity range, it is also a useful technique to use a solvent to adjust the viscosity. Therefore, as long as the solvent does not lower the optical performance of the polarizing film and dissolves the photocurable composition well, the type is not particularly limited. For example, organic solvents such as hydrocarbons represented by toluene and esters represented by ethyl acetate can be used.

When bonding the polarizing film and the thermoplastic resin film, before forming the coating layer of the photocurable composition on one or both sides of the bonding surface of the two, it may be subjected to corona discharge treatment, plasma treatment, flame treatment, and primer treatment. Coating and anchor coating are easy to follow.

The light source used to irradiate the coating layer of the photocurable composition with active energy rays may be any one that generates ultraviolet rays, electron beams, X-rays, and the like. It is especially suitable for use with luminous distribution below 400nm, such as low pressure mercury lamp, medium pressure mercury lamp, high pressure mercury lamp, ultra high pressure mercury lamp, chemical lamp, black light lamp, microwave excited mercury lamp, metal halide lamp, etc. The irradiation intensity of the active energy rays of the photocurable composition is determined according to the composition of each target, and is not particularly limited, but the irradiation intensity of the wavelength region where the activation of the initiator is effective is preferably 0.1 to 100mW/ cm ² . When the light irradiation intensity to the photocurable composition is less than 0.1mW/cm ² , the reaction time will become too long, and if it exceeds 100 mW/cm ² , the heat radiated from the lamp and the heat generated by the polymerization of the photocurable composition will cause There is a possibility of yellowing of the photocurable composition or deterioration of the polarizing film. The light irradiation time of the photocurable composition is controlled by each composition to be cured, and there is still no particular limitation. However, the cumulative light amount represented by the product of the irradiation intensity and the irradiation time is set to be 10 to 5,000 mJ/cm ² good. When the cumulative amount of light to the photocurable composition is less than 10mJ/cm ² , the production of active species derived from the initiator is insufficient, and the curing of the resulting adhesive layer may become insufficient. On the other hand, the cumulative amount of light exceeds At 5,000mJ/cm ² , the irradiation time will become very long, which is not conducive to productivity improvement.

When laminating a thermoplastic resin film on both sides of a polarizing film, the active energy rays can be irradiated from either side of the thermoplastic resin film, but for example, one thermoplastic resin film contains an ultraviolet absorber, while the other thermoplastic resin film does not contain ultraviolet absorbers. It is preferable to irradiate active energy rays from the side of the thermoplastic resin film that does not contain an ultraviolet absorber in order to effectively use the irradiated active energy rays to increase the curing speed.

The thickness of the adhesive layer formed by curing the photocurable composition is usually 20 μm or less, preferably 10 μm or less, and more preferably 5 μm or less. When the adhesive layer becomes thicker, the durability in a heat-resistant environment and a high-temperature and high-humidity environment tends to deteriorate.

[Layered Optical Components]

The polarizing plate of the present invention can be used as a laminated optical member by laminating optical layers having optical functions other than the polarizing plate. Typically, a thermoplastic resin film attached to a polarizing plate is laminated with an optical layer via an adhesive layer or an adhesive layer to serve as a laminated optical component. However, it can be cured by light, for example, on one side of the polarizing film according to the present invention. The thermoplastic resin film is laminated on the other side of the polarizing film with an adhesive or The optical layer is laminated and attached to the adhesive. In the latter case, the adhesive layer for attaching the polarizing film to the optical layer may be a cured product of the photocurable composition specified in the present invention, or an adhesive formed of other known adhesives Floor.

Taking the example of the optical layer laminated on the polarizing plate, for the polarizing plate arranged on the back side of the liquid crystal cell, there is a reflective layer laminated on the opposite side of the polarizing plate and the side facing the liquid crystal cell, semi-transmissive reflection Layer, light diffusion layer, light collection plate, brightness enhancement film, etc. In addition, for any one of the polarizing plate arranged on the front side of the liquid crystal cell and the polarizing plate arranged on the back side of the liquid crystal cell, there is a phase difference plate laminated on the side of the polarizing plate facing the liquid crystal cell.

The reflective layer, semi-transmissive reflective layer or light diffusion layer is used as a reflective polarizer (optical member), semi-transmissive reflective polarizer (optical member), or diffused polarizer (optical member), respectively And the setter. The reflective polarizer is used in a liquid crystal display device that reflects incident light from the viewing side to display. It is possible to omit light sources such as a backlight, and therefore it is easy to make the liquid crystal display device thinner. In addition, the semi-transmissive polarizing plate is used as a reflective type in bright places, and a liquid crystal display device that displays light from the backlight in dark places. As an optical member of a reflective polarizer, for example, a protective film made of aluminum or other metal may be additionally provided with a foil or a vapor-deposited film on the protective film on the polarizing film to form a reflective layer. The optical member as a semi-transmissive polarizing plate can be formed by using the above-mentioned reflective layer as a semi-reflective mirror, or attaching a reflective plate containing pearlescent pigments and the like and exhibiting translucency to the polarizing plate. On the other hand, as the optical member of the diffusion type polarizing plate, various methods such as a method of applying a matting treatment to the protective film on the polarizing plate, a method of coating a resin containing particles, and a method of bonding a film containing particles are used. The surface forms a fine uneven structure.

In addition, it is also possible to form an optical member as a polarizing plate for both reflection and diffusion. In this case, for example, it can be used to provide a reflective layer reflecting the uneven structure on the surface of the diffuse polarizer. Methods. The reflective layer with fine concavo-convex structure diffuses incident light by diffuse reflection to prevent directivity or glare, and has the advantage of suppressing uneven brightness. In addition, the resin layer or film containing fine particles also has the following advantage: the incident light and its reflected light diffuse when penetrating the layer containing fine particles, and the unevenness of brightness and darkness can be suppressed. The reflective layer reflecting the fine uneven structure on the surface can be formed by, for example, vacuum evaporation, ion plating, sputtering evaporation or plating, etc., by directly attaching metal to the surface of the fine uneven structure. The fine particles prepared to form the surface fine uneven structure can be, for example, inorganic fine particles such as silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, and antimony oxide with an average particle diameter of 0.1 to 30 μm. , Such as cross-linked or non-cross-linked polymer organic particles.

The light-collecting plate is used by the user to control the optical path, and can be formed as an array sheet, a lens array sheet, or a dotted sheet.

Brightness-enhancing film is used to increase the brightness of liquid crystal display devices. An example of it can be a reflective type designed by laminating a plurality of thin films with different refractive index anisotropy to produce anisotropy in reflectance. Polarized light separation sheet, circularly polarized light separation sheet supported by the alignment film of cholesteric liquid crystal polymer or its alignment liquid crystal layer on the film substrate.

On the other hand, the phase difference plate as the above-mentioned optical layer is used for the purpose of compensating the phase difference by the liquid crystal cell. Examples include birefringent films composed of stretched films of various plastics, films in which discotic liquid crystals or nematic liquid crystals are aligned and fixed, and those having the above-mentioned liquid crystal layer formed on a film substrate. When the liquid crystal layer is formed on the film substrate, it is preferable to use a cellulose resin film such as cellulose triacetate as the film substrate.

The plastic forming the birefringent film includes, for example, amorphous polyolefin resins, polycarbonate resins, acrylic resins, chain polyolefin resins such as polypropylene, polyvinyl alcohol, polystyrene, Polyacrylate, polyamide, etc. The stretched film may be processed by a suitable method such as uniaxial or biaxial. In addition, for the purpose of controlling optical characteristics such as broadband, the phase difference plate can be used in combination with two or more sheets.

Among the laminated optical members, it is preferable to use a phase difference plate as an optical layer other than the polarizing plate, because it can effectively guarantee optical protection when applied to a liquid crystal display device. The retardation value (in-surface and thickness direction) of the retardation plate can be selected as the most suitable as long as it matches the applied liquid crystal cell.

The laminated optical member can combine a polarizing plate and one or more layers selected from the above-mentioned various optical layers according to the purpose of use to form a laminated body of two or more layers. At this time, the various optical layers forming the laminated optical member are those integrated with the polarizing plate using an adhesive layer or an adhesive layer, but the adhesive or adhesive used here is capable of forming an adhesive layer or adhesion well The agent layer is not particularly limited. From the viewpoints of ease of access to work or prevention of optical strain, it is preferable to use an adhesive (also called a pressure sensitive adhesive). The adhesive can use acrylic polymer, silicone polymer, polyester, polyurethane, polyether, etc. as the matrix polymer. Among them, it is preferable to use an acrylic adhesive, which has excellent optical transparency, maintains appropriate wettability or cohesive force, excellent adhesion to the substrate, and has weather resistance or heat resistance. Or those who do not have peeling problems such as lifting or peeling under humid conditions. In the acrylic adhesive, an alkyl ester of (meth)acrylic acid having an alkyl group with a carbon number of 20 or less such as a methyl group, an ethyl group, or a butyl group, and a (meth)acrylic acid or (meth)acrylic acid hydroxyl group Functional group-containing acrylic monomers such as ethyl esters are formulated such that the glass transition temperature is preferably 25°C or less, and more preferably 0°C or less, and is an acrylic copolymer with a weight average molecular weight of 100,000 or more. Suitable for use as a matrix polymer.

The formation of the adhesive layer on the polarizing plate can be carried out, for example, by dissolving or dispersing an organic solvent such as toluene or ethyl acetate in the adhesive composition to prepare a 10 to 40% by mass solution, and applying it directly The method of mounting on the polarizing plate; or, forming an adhesive on the protective film in advance Agent layer, and then transfer the adhesive layer to the polarizing plate. The thickness of the adhesive layer is determined in accordance with its adhesive strength, etc., but it is preferably in the range of about 1 to 50 μm.

In addition, fillers, pigments or colorants, antioxidants, antistatic agents, ultraviolet absorbers, etc., including glass beads or glass beads, resin beads, metal powder or other inorganic powders, etc. can be prepared in the adhesive layer as needed. Examples of ultraviolet absorbers include salicylate-based compounds, benzophenone-based compounds, benzotriazole-based compounds, cyanoacrylate-based compounds, and nickel complex salt-based compounds.

Examples of antistatic agents include ionic compounds, conductive fine particles, and conductive polymers. Among these, suitable antistatic agents can be used individually or in combination of two or more kinds. In addition, of course, two or more antistatic agents classified as ionic compounds can be used in combination, and two or more antistatic agents classified as conductive fine particles can also be used in combination. It can also be classified as conductive polymer. Two or more antistatic agents are used in combination.

Among the antistatic agents described above, ionic compounds are preferably used in terms of excellent compatibility with solvents.

Ionic compounds can be classified into ionic compounds having organic cations, ionic compounds having inorganic cations, ionic compounds having organic anions, and ionic compounds having inorganic anions. Examples of organic cations include pyridinium cations, imidazolium cations, ammonium cations, sulfonium cations, and phosphonium cations. Examples of inorganic cations include lithium and potassium. The cationic component constituting the ionic compound may be an inorganic anion or an organic anion, but from the viewpoint of compatibility with the (meth)acrylic resin, an organic cation is preferred. On the other hand, the anion component constituting the ionic compound may be an inorganic anion or an organic anion, but from the viewpoint of imparting an ionic compound with excellent antistatic properties, an anion component containing a fluorine atom is preferred. An anionic component containing a fluorine atom include hexafluorophosphate anion [(PF ₆ ^-)], bis (trifluoromethane sulfonic acyl) imide anion _{[(CF 3 SO 2) 2} N -] anion, a bis (fluorosulfonyl acyl) imide anion ^{_{[(FSO 2) 2 N -}} ] anion.

The laminated optical member can be arranged on one side or both sides of the liquid crystal cell. The liquid crystal cell used is arbitrary. For example, various liquid crystal cells such as an active matrix drive type represented by a thin film transistor type and a simple matrix drive type represented by a super-twisted nematic type can be used. To form a liquid crystal display device. Adhesives are usually used when bonding the laminated optical member and the liquid crystal cell.

(Example)

The following examples are used to illustrate the present invention more specifically, but the present invention is not limited by these examples. In the example, the "parts" and "%" that indicate the content or usage amount are quality standards unless otherwise specified. In addition, the cationic polymerizable compound, photocationic polymerization initiator, and leveling agent used in the following examples are as follows, and each is indicated by a symbol below.

(A) Cationic polymerizable compound

(a1) 3-Ethyl-3{[(3-ethyloxetane-3-yl)methoxy]methyl}oxetane: Obtained from Toa Gosei Co., Ltd., trade name " OXT-221". It is abbreviated as "(a1)" in Table 1 described later.

(a2) 1,4-Butanediol diglycidyl ether: Obtained from Nagase ChemteX Co., Ltd., trade name "EX-214L". It is abbreviated as "(a2)" in Table 1 below.

(B) Photocationic polymerization initiator

(b1) 4-(Phenylthio)phenyldiphenylsulfonium Hexafluorophosphate: Obtained from San-Apro Co., Ltd. under the trade name "CPI-100P". It is abbreviated as "(b1)" in Table 1 described later. In addition, CPI-100P is used as a 50% propylene carbonate solution, and its solid content is described in Table 1.

[Examples 1 to 3, Comparative Example 1]

[Modulation examples 1 to 4]

(1) Preparation of photocurable composition

After mixing the components according to the blending ratio shown in Table 1, defoaming was performed to prepare photocurable compositions 1 to 3.

(2) Production of polarizing plate

[Example 1]

The above-mentioned photocurable composition 1 was used to produce a polarizing plate. Corona discharge treatment was applied to the surface of a cycloolefin-based film [trade name "ZEONOR" manufactured by Japan Zeon Co., Ltd.] with a thickness of 50 μm, and the photocurable composition 1 was used as a cured film using a bar coater. It is coated on the corona discharge treatment surface so that the thickness becomes about 1.5 μm. A polyvinyl alcohol-iodine-based polarizing film was bonded to the coating surface of the photocurable composition. In addition, corona is applied to the bonding surface of a protective film composed of (meth)acrylic resin (PMMA) [trade name "Technolloy S001", manufactured by Sumitomo Chemical Co., Ltd.] with a thickness of 80 μm containing ultraviolet absorber After discharge treatment, the same photocurable composition 1 as that used for the cycloolefin-based film was applied to the corona discharge treatment surface using a bar coater so that the film thickness after curing would be approximately 1.5 μm. The polarizing film in which the cycloolefin film was bonded to one side of the prepared polarizing film was bonded to the coated surface of the photocurable composition from the polarizing film side to prepare a laminate. From the cycloolefin-based film side of the laminate, use an ultraviolet irradiation device with a conveyor (the lamp uses "D bulb" manufactured by Fusion UV Systems) to irradiate the cumulative light intensity (UVB) to 200mJ/cm ² The ultraviolet rays harden the photocurable composition to form an adhesive layer. In this way, a polarizing plate in which a protective film was bonded on both sides of the polarizing film via an adhesive was produced.

[Example 2]

The above-mentioned photocurable composition 1 was used to produce a polarizing plate. Corona discharge treatment was applied to the surface of a cycloolefin-based film [trade name "ZEONOR" manufactured by Japan Zeon Co., Ltd.] with a thickness of 50 μm, and the photocurable composition 1 was cured using a bar coater. Coating on the corona discharge treatment surface so that the thickness becomes about 1.5 μm. A polyvinyl alcohol-iodine-based polarizing film was bonded to the coating surface of the photocurable composition. In addition, corona discharge treatment was applied to the bonding surface of a 60μm-thick triacetate cellulose (TAC) film [trade name "TD60UL", manufactured by Fujifilm Co., Ltd.] containing ultraviolet absorbers, and bar coating was used The machine applies the same photocurable composition as that used for the cycloolefin-based film to the corona discharge treatment surface so that the film thickness after curing becomes about 1.5 μm. The polarizing film in which the cycloolefin film was bonded to one side of the prepared polarizing film was bonded to the coated surface of the photocurable composition from the polarizing film side to prepare a laminate. From the cycloolefin-based film side of the laminate, use an ultraviolet irradiation device with a conveyor (the lamp uses "Dbulb" manufactured by Fusion UV Systems) to irradiate the accumulated light (UVB) to 200mJ/cm ² The ultraviolet rays harden the photocurable composition to form an adhesive layer. In this manner, a polarizing plate in which a protective film was bonded on both sides of the polarizing film via an adhesive was produced.

[Example 3]

A polarizing plate was produced in the same manner as in Example 1, except that the photocurable composition 1 was changed to the photocurable composition 2.

[Comparative Example 1]

Except for changing the photocurable composition 1 to the photocurable composition 3, the polarizing plate was produced in the same manner as in Example 1.

The moisture permeability of the thermoplastic resin film at a temperature of 40°C and a relative humidity of 90% is measured by the cylindrical flat plate method specified in JIS Z 0208.

PMMA: 60g/(m ² ．24hr)

TAC: 520g/(m ² ．24hr)

COP: 5.8g/(m ² ．24hr)

(3) Production of polarizing plate with adhesive layer

After corona treatment is applied to the cycloolefin film surface of the polarizing plate produced in (2) above, an acrylic adhesive with a thickness of 25μm is bonded by a laminator, and then cured at a temperature of 23°C and a relative humidity of 65% After 7 days, a polarizing film with adhesive was obtained.

(4) Evaluation of the optical characteristics of the polarizer

Cut the adhesive-attached polarizing plate produced in (3) above into a size of 30mm×30mm, and attach it to alkali-free glass [trade name "EAGLE XG" manufactured by Corning Corporation] to measure the respective penetrating hue The b value. The measurement is performed using the UV-Visible Spectrophotometer "UV-2450" manufactured by Shimadzu Corporation, which is equipped with the optional accessory "Film holder with polarizing film" to obtain the polarizing plate in the wavelength range of 380nm to 780nm For the penetration spectrum, the b value of the penetration hue is calculated by the software "UV-Probe" attached to the spectrophotometer.

(5) Heat resistance evaluation of polarizing plate

The polarizing plate produced in (4) above was allowed to stand for 48 hours in a heating environment at a temperature of 90°C for a heating test, and the penetration hue b value of the polarizing plate after the test was measured. The measurement and the calculation of the b value were performed in the same manner as in (4) above. The absolute value (|Δb|) of the difference in the penetration hue before and after the heat resistance test is calculated according to the following formula.

|Δb|=|b value after heating test-b value before heating test|

Next, from the obtained value of |Δb|, the "Δb change rate (improvement rate)" (%) of each example based on the |Δb| of Comparative Example 1 was obtained according to the following equation. The calculated value of the Δb change rate is shown in Table 1. The larger the Δb change rate, the better the heat resistance.

Change rate of Δb of each case (%)=|{(|Δb| of each case)-(|Δb| of Comparative Example 1)}|/(|Δb| of Comparative Example 1)×100

In addition, Δb shows a positive value in all Examples and Comparative Examples.

The results are shown in Table 1.

[Table 1]

It can be confirmed from Table 1 that in a polarizing plate in which a thermoplastic resin film is bonded to at least one side of the polarizing film via an adhesive, the adhesive is made to contain 10 to 70% by mass of bifunctional oxygen in a cationically polymerizable compound. Etidine compounds containing 0.5 to 1.5 parts by mass of the photocationic polymerization initiator relative to 100 parts by mass of the cationically polymerizable compound exhibit good heat resistance.

[Modulation example 4-10]

(1) Preparation of photocurable composition

After mixing each component according to the compounding ratio shown in Table 2, it defoamed and prepared the photocurable composition 4-10.

In addition, the abbreviations in Table 2 respectively indicate the compounds described below.

(A) Cationic polymerizable compound

(a1) 3-Ethyl-3{[(3-ethyloxetane-3-yl)methoxy]methyl}oxetane: Obtained from Toa Gosei Co., Ltd., trade name " OXT-221". It is abbreviated as "(a1)" in Table 2.

(a2) 1,4-Butanediol diglycidyl ether: Obtained from Nagase ChemteX Co., Ltd., trade name "EX-214L". It is abbreviated as "(a2)" in Table 2.

(a3) Neopentyl glycol diglycidyl ether: Obtained from Nagase ChemteX Co., Ltd., trade name "EX-211L". It is abbreviated as "(a3)" in Table 3.

(a4) Neopentyl erythritol polyglycidyl ether: obtained from Nagase ChemteX Co., Ltd., trade name "EX-411". It is abbreviated as "(a4)" in Table 2.

(a5) 3',4'-epoxycyclohexylmethyl 3,4-cyclohexane carboxylate: obtained from Daicel Chemical Co., Ltd., trade name "Celloxide 2021P". It is abbreviated as "(a5)" in Table 2.

(B) Photocationic polymerization initiator

(b1) 4-(Phenylthio)phenyldiphenylsulfonium Hexafluorophosphate: Obtained from San-Apro Co., Ltd. under the trade name "CPI-100P". It is abbreviated as "(b1)" in Table 2. In addition, CPI-100P is used as a 50% propylene carbonate solution, and its solid content is described in Table 2.

[Example 4]

(2) Production of polarizing plate

Corona discharge treatment was applied to the surface of a cycloolefin resin film with a thickness of 50 μm [trade name "ZEONOR" manufactured by Japan Zeon Co., Ltd.], and the photocurable composition 4 was cured using a bar coater. It is coated on the corona discharge treatment surface so that the film thickness becomes about 1.5 μm. A polyvinyl alcohol-iodine-based polarizing film was bonded to the coating surface of the photocurable composition 4. In addition, corona discharge was applied to the bonding surface of a protective film composed of (meth)acrylic resin (PMMA) [trade name "Technolloy S001", manufactured by Sumitomo Chemical Co., Ltd.] containing ultraviolet absorber and having a thickness of 80 μm After treatment, the photocurable composition 4 was coated on the corona discharge treatment surface using a bar coater so that the film thickness after curing became about 1.5 μm. The polarizing film in which the cycloolefin film was bonded to one side of the prepared polarizing film was bonded to the coated surface of the photocurable composition 4 from the polarizing film side to produce a laminate. From the cycloolefin-based film side of the laminate, use the UV irradiation device attached to the conveyor (the lamp uses the "D bulb" manufactured by Fusion UV Systems) to irradiate the cumulative amount of light (UVB) to 200mJ/cm ² Ultraviolet rays harden the photocurable composition to form an adhesive layer, and produce a polarizing plate in which a protective film is bonded on both sides of the polarizing film with the adhesive interposed therebetween.

[Example 5]

Except that the photocurable composition 4 was changed to the photocurable composition 5, the polarizing plate was produced in the same manner as in Example 5.

[Example 6]

The polarizing plate was produced in the same manner as in Example 5 except that the photocurable composition 4 was changed to the photocurable composition 6.

[Example 7]

The polarizing plate was produced in the same manner as in Example 5 except that the photocurable composition 4 was changed to the photocurable composition 7.

[Example 8]

The polarizing plate was produced in the same manner as in Example 5 except that the photocurable composition 4 was changed to the photocurable composition 8.

[Example 9]

Except that the photocurable composition 4 was changed to the photocurable composition 9, the polarizing plate was produced in the same manner as in Example 5.

[Example 10]

Except for changing the photocurable composition 4 to the photocurable composition 10, a polarizing plate was produced in the same manner as in Example 5.

(3) Production of polarizing plate with adhesive layer

After corona treatment is applied to the cycloolefin film surface of the polarizing plate produced in (2) above, an acrylic adhesive with a thickness of 25μm is bonded by a laminator, and then cured at a temperature of 23°C and a relative humidity of 65% After 7 days, a polarizing film with adhesive was obtained.

(4) Evaluation of the optical characteristics of the polarizer

The polarizing plate with adhesive produced in (3) above was cut into a size of 30mm×30mm, and then laminated with alkali-free glass [trade name "EAGLE XG" manufactured by Corning Corporation] to measure the respective penetrating hues b value. The measurement is performed using the UV-Visible Spectrophotometer "UV-2450" manufactured by Shimadzu Corporation, which is equipped with the optional accessory "Film holder with polarizing film" to obtain the polarizing plate in the wavelength range of 380nm to 780nm For the penetration spectrum, the b value of the penetration hue is calculated by the software "UV-Probe" attached to the spectrophotometer.

(5) Heat resistance evaluation of polarizing plate

The polarizing plate produced in (4) above was allowed to stand for 48 hours in a heating environment at a temperature of 90°C for a heating test, and the penetration hue b value of the polarizing plate after the test was measured. The measurement and the calculation of the b value were performed in the same manner as in (4) above. The absolute value (|Δb|) of the difference in the penetration hue before and after the heat resistance test is calculated according to the following formula.

|Δb|=|b value after heating test-b value before heating test|

Next, from the obtained value of |Δb|, the "Δb change rate (improvement rate)" (%) of each example based on the |Δb| of Comparative Example 1 was obtained according to the following equation. The calculated value of Δb change rate is shown in Table 2. The larger the Δb change rate, the better the heat resistance.

Change rate of Δb of each case (%)=|{(|Δb| of each case)-(|Δb| of Comparative Example 1)}|/(|Δb| of Comparative Example 1)×100

In addition, Δb shows a positive value in all Examples and Comparative Examples.

The results are shown in Table 2.

[Table 2]

(6) Evaluation of resistance to humidity and heat of polarizer

The polarizing plate produced in (4) above was allowed to stand for 48 hours in a high temperature and high humidity environment with a temperature of 80°C and a relative humidity of 90% to conduct a damp and heat resistance test, and the visibility correction monomer transmittance Ty value of the polarizing plate after the test was measured. . The measurement and the calculation of the Ty value were performed in the same manner as in (4) above. The absolute value (|ΔTy|) of the difference in visibility correction monomer transmittance Ty before and after the damp heat resistance test is calculated according to the following formula.

|ΔTy|=|Ty value after heating test-Ty value before heating test|

In addition, ΔTy shows a positive value in all the examples and comparative examples.

The results are shown in Table 3.

[table 3]

Claims (3)

A polarizing plate is formed by laminating at least one side of a polarizing film with a thermoplastic resin film via an adhesive layer, wherein: The aforementioned adhesive is a cured product of a photocurable composition containing a cationic polymerizable compound and a photocationic polymerization initiator, The aforementioned photocurable composition contains 0.5 to 1.5 parts by mass of a photocationic polymerization initiator relative to 100 parts by mass of the cationic polymerizable compound, The aforementioned cationically polymerizable compound contains 10 to 70% by mass of the bifunctional oxetane compound with respect to the total mass of the cationically polymerizable compound. The polarizing plate according to the first item of the patent application, wherein the cationically polymerizable compound further contains an aliphatic epoxy compound in an amount of 10 to 70% by mass relative to the total mass of the cationically polymerizable compound. The polarizing plate as described in item 1 or 2 of the scope of patent application, wherein the moisture permeability of the thermoplastic resin film at a temperature of 40°C and a relative humidity of 90% is 300 g/(m ² .24hr) or less.