KR20200063069A - Polarizing plate - Google Patents

Abstract

The present invention provides a polarizing plate in which discoloration of the polarizing plate is suppressed even in a harsh environment. In the polarizing plate, a thermoplastic resin film is bonded to at least one side of the polarizing film through an adhesive layer, wherein the adhesive is a cured product of a photocurable composition comprising a cationic polymerizable compound and a photocationic polymerization initiator. With respect to 100 parts by mass of the cationic polymerizable compound, 0.5 to 1.5 parts by mass of the photocationic polymerization initiator is included. The cationic polymerizable includes 10 to 70 mass % of a bifunctional oxetane compound with respect to the total mass of the cationic polymerizable compound.

Description

Polarizing plate {POLARIZING PLATE}

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

The polarizing plate is useful as one of the optical components constituting the liquid crystal display device. The polarizing plate usually has a structure in which a protective film is laminated on at least one side of the polarizing film, and is embedded in a liquid crystal display device. Moreover, as a manufacturing method of a polarizing film, the method of carrying out the boric-acid treatment of the uniaxially stretched polyvinyl alcohol-type resin film dyed with a dichroic dye, and continuing washing and drying is widely adopted.

Usually, the protective film is bonded to the polarizing film immediately after the above-mentioned water washing treatment and drying treatment. This is because the polarized film after drying has a weak physical strength and, once wound up, there is a problem such as being easily torn in the processing direction. Therefore, usually, an adhesive is immediately applied to the polarizing film after the drying treatment, and a protective film is simultaneously bonded to both sides of the polarizing film through the adhesive.

As the adhesive, an aqueous adhesive mainly composed of a water-soluble resin such as polyvinyl alcohol-based resin or an active energy ray-curable adhesive is used. As an active energy ray-curable adhesive, Patent Document 1 describes a photocurable adhesive compounded with a photocationic polymerization initiator by combining an alicyclic epoxy compound and an epoxy compound not having an alicyclic epoxy group. A technique for bonding a polarizing film and a protective film is disclosed.

[Patent Document 1] Japanese Patent Publication No. 2008-257199

Recently, with the diversification of mobile devices, durability in a more severe environment is required. It has been found that, in the polarizing plate described in Patent Document 1, there is a problem that the polarizing plate is discolored under harsh environments (for example, when stored in a high temperature environment for a long time).

Therefore, an object of the present invention is to provide a polarizing plate in which discoloration of the polarizing plate is suppressed even in harsh environments.

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 through an adhesive layer,

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

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

The cationic polymerizable compound is a polarizing plate characterized in that it contains 10 to 70 mass% of the bifunctional oxetane compound with respect to the total mass of the cationic polymerizable compound.

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

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

In the polarizing plate of the present invention, discoloration of the polarizing plate is suppressed even in harsh environments.

Hereinafter, the present invention will be described in detail. In the polarizing plate of the present invention, a thermoplastic resin film is bonded to at least one side of the polarizing film through an adhesive containing a photocurable composition. Each member and component constituting the polarizing plate will be sequentially described.

[Polarizing film]

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

The polarizing film described above is a step of uniaxially stretching a polyvinyl alcohol-based resin film, a process of dyeing a polyvinyl alcohol-based resin film with a dichroic dye, adsorbing the dichroic dye, and polyvinyl alcohol with a dichroic dye adsorbed It is manufactured through a process of treating a system resin film with an aqueous solution of boric acid.

The uniaxial stretching step 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 may be performed during boric acid treatment. Moreover, it is also possible to uniaxially stretch in these multiple steps. For uniaxial stretching, stretching may be performed between rolls having different circumferential speeds, or may be stretched by sandwiching between heat rolls. Further, dry stretching may be performed in the air, or wet stretching may be performed in a swollen state with a solvent. The draw ratio is usually about 4 to 8 times.

To dye the polyvinyl alcohol-based resin film with a dichroic dye, for example, the polyvinyl alcohol-based resin film may be immersed in an aqueous solution containing a dichroic dye. As the dichroic dye, iodine or a dichroic organic dye is specifically used.

When using iodine as a dichroic dye, a method of dyeing by immersing a polyvinyl alcohol-based 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 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 this aqueous solution is usually about 20 to 40°C, and the immersion time (dyeing time) in this 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 dyeing by dipping a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye is usually employed. The content of the dichroic organic dye in this aqueous solution is usually about 1×10 ^{-3 to} 1×10 ^-2 parts by weight per 100 parts by weight of water. This aqueous solution may contain inorganic salts, such as sodium sulfate. The temperature of this aqueous solution is usually about 20 to 80°C, and the immersion time (dyeing 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 polyvinyl alcohol-based resin film in a boric acid aqueous solution. The content of boric acid in the aqueous boric acid solution is usually about 2 to 15 parts by weight per 100 parts by weight of water, preferably about 5 to 12 parts by weight. When using iodine as a dichroic dye, it is preferable that this aqueous boric acid solution contains potassium iodide. The content of potassium iodide in the boric acid aqueous solution is usually about 2 to 20 parts by weight per 100 parts by weight of water, preferably 5 to 15 parts by weight. The immersion time in the aqueous boric acid 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 aqueous boric acid solution is usually 50°C or higher, preferably 50 to 85°C.

The polyvinyl alcohol-based resin film after the boric acid treatment is usually washed with water. The water washing treatment is performed by, for example, immersing a polyvinyl alcohol-based resin film treated with boric acid in water. After washing with water, a drying treatment is performed, and a polarizing film is produced. The temperature of the 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 after that is usually performed using a hot air dryer or a far infrared heater. The drying temperature is usually 40 to 100°C. Moreover, the time of a drying process is about 120-600 second normally.

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

[Thermoplastic resin film]

The polarizing plate of this invention is obtained by laminating|stacking a thermoplastic resin film through the photocurable composition to the polarizing film containing the polyvinyl alcohol-type resin film demonstrated above, and hardening a photocurable composition.

It is preferable that a thermoplastic resin film is formed from transparent resin. The thermoplastic resin film may be either a non-stretched 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-based resins, acrylic-based resins, amorphous polyolefin-based resins, polyester-based resins, and polycarbonate-based resins.

Although it does not specifically limit as polyester resin, Polyethylene terephthalate is especially preferable at the point of mechanical property, solvent resistance, scratch resistance, cost, etc. Polyethylene terephthalate means a resin composed of 80 mol% or more of repeating units composed of ethylene terephthalate, and may contain structural units derived from other copolymerization components.

Dicarboxylic acid component and diol component are mentioned as another copolymerization component. Dicarboxylic acid components include isophthalic acid, p-β-hydroxyethoxybenzoic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis(4-carboxyphenyl)ethane, And adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid, and 1,4-dicarboxycyclohexane. Examples of the diol component include propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adducts of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. These dicarboxylic acid components and diol components may be used in combination of two or more kinds, if necessary. Moreover, it is also possible to use together hydroxycarboxylic acid like p-hydroxybenzoic acid together with the said dicarboxylic acid component or diol component. As another copolymerization component, a small amount of a dicarboxylic acid component and/or a diol component having an amide bond, a urethane bond, an ether bond, a carbonate bond or the like may be used.

The polyethylene terephthalate-based resin means a resin in which 80 mol% or more of the repeating units are composed of ethylene terephthalate, and may contain structural units derived from other copolymerization components. As other copolymerization components, isophthalic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis(4-carboxyphenyl)ethane, adipic acid, sebacic acid, 5-sodium sulfoi Dicarboxylic acid components such as sophthalic acid and 1,4-dicarboxycyclohexane; And diol components such as propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. These dicarboxylic acid components and diol components can be used in combination of two or more kinds as necessary. Moreover, it is also possible to use together hydroxycarboxylic acids, such as p-hydroxybenzoic acid and p-β-hydroxyethoxybenzoic acid, together with the said dicarboxylic acid component and diol component. As other copolymerization components, dicarboxylic acid components and/or diol components containing a small amount of amide bonds, urethane bonds, ether bonds, carbonate bonds, and the like may be used.

By film-forming the polyethylene terephthalate-based resin and then performing the stretching treatment as described above as a protective film, mechanical properties, solvent resistance, scratch resistance, cost, etc. are excellent, and a roll-type polarizing plate with reduced thickness. Can get

The polycarbonate-based resin is a polyester formed of carbonic acid and glycol or bisphenol. Among them, aromatic polycarbonates having diphenyl alkanes in the molecular chain are preferably used because of their excellent heat resistance, weather resistance and acid resistance. As such a polycarbonate, 2,2-bis(4-hydroxyphenyl)propane (aka bisphenol A), 2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl) Polycarbonates derived from bisphenols such as cyclohexane, 1,1-bis(4-hydroxyphenyl)isobutane, or 1,1-bis(4-hydroxyphenyl)ethane are exemplified.

As a manufacturing method of a polycarbonate resin film, you may use any method, such as a flexible film forming method and a melt extrusion method. As an example of a specific manufacturing method, a polycarbonate-based resin is dissolved in a suitable organic solvent to form a polycarbonate-based resin solution, which is flexible on a metal support to form a web, and the web is peeled off from the metal support and then peeled off. And a method of obtaining a film by hot-air drying the web.

Although the acrylic resin is not particularly limited, it is generally a polymer having a methacrylic acid ester as a main monomer, and it is preferably a copolymer in which a small amount of other comonomer components are copolymerized. This copolymer can usually be obtained by polymerizing a monofunctional monomer containing methyl methacrylate and methyl acrylate in the presence of a radical polymerization initiator and a chain transfer agent. Moreover, an acrylic resin can copolymerize a 3rd monofunctional monomer.

Examples of the third monofunctional monomer copolymerizable with methyl methacrylate and methyl acrylate include, for example, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, and methacryl. Methacrylic acid esters other than methyl methacrylate, such as 2-ethylhexyl acid and 2-hydroxyethyl methacrylate; Acrylic acid esters such as ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate; Hydroxyalkyl acrylic acid esters such as methyl 2-(hydroxymethyl)acrylate, methyl 2-(1-hydroxyethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, and butyl 2-(hydroxymethyl)acrylate ; Unsaturated acids such as methacrylic acid and acrylic acid; Halogenated styrenes such as chlorostyrene and bromostyrene; 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; And unsaturated imides such as phenyl maleimide and cyclohexyl maleimide. These may be used alone, or different plural types may be used in combination.

When copolymerizing a polyfunctional monomer, examples of the polyfunctional monomer capable of copolymerizing methyl methacrylate and methyl acrylate include, for example, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and triethylene glycol. Di(meth)acrylate, tetraethylene glycol di(meth)acrylate, nonaethylene glycol di(meth)acrylate, and tetradecaethylene glycol di(meth)acrylate, such as ethylene glycol or oligomers at both terminal hydroxyl groups Esterified with acrylic acid or methacrylic acid; Esterified with hydroxyl or acrylic acid at both ends of propylene glycol or oligomers thereof; Esters of hydroxyl groups of dihydric alcohols such as neopentyl glycol di(meth)acrylate, hexanediol di(meth)acrylate, and butanediol di(meth)acrylate with acrylic acid or methacrylic acid; Esters of bisphenol A, bisphenol A alkylene oxide adducts, or both terminal hydroxyl groups of these halogen substituents with acrylic acid or methacrylic acid; Polyhydric alcohols such as trimethylolpropane and pentaerythritol are esterified with acrylic acid or methacrylic acid, and those terminal hydroxyl groups are cyclically added with glycidyl acrylate or glycidyl methacrylate epoxy groups; Dibasic acids such as succinic acid, adipic acid, terephthalic acid, phthalic acid, and halogen substituents thereof, and those obtained by ring-opening addition of epoxy groups of glycidyl acrylate or glycidyl methacrylate to alkylene oxide adducts; Aryl (meth)acrylate; And aromatic divinyl compounds such as divinylbenzene. Among them, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate are preferably used.

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

The glass transition temperature of the acrylic resin is preferably in the range of 80 to 120°C. In order to adjust the glass transition temperature of the acrylic resin to the above range, usually, the polymerization ratio of the methacrylic acid ester-based monomer and the acrylic acid ester-based monomer, the length of the carbon chain of each ester group and the type of functional groups thereof, and the whole monomer A method of appropriately selecting the polymerization ratio of the polyfunctional acrylic monomer for the polymer or the like is employed.

The acrylic resin may contain known additives as necessary. Examples of known additives include lubricants, anti-blocking agents, heat stabilizers, antioxidants, antistatic agents, light resistance agents, impact resistance improvers, surfactants, and the like. However, since transparency is required as a protective film laminated on a polarizing film, it is preferable to limit the amount of these additives to a minimum.

As a manufacturing method of an acrylic resin film, you may use any method, such as melt-casting method, melt-extrusion method, such as T-die method and inflation method, a calendar method. Especially, the method of forming a film by making the raw material resin melt-extruded from a T die, for example, and forming a film by contacting at least one surface of the obtained film-like material with a roll or a belt is obtained.

The acrylic resin may contain acrylic rubber particles, which are impact-improving agents, from the viewpoint of film forming properties to the film and impact resistance of the film. The acrylic rubber particles referred to herein are particles having an acrylic polymer as an essential component as an essential component, and have a single-layer structure consisting essentially of only this elastomer, or a multilayer structure comprising this elastomer as one layer. have. As an example of such an elastic polymer, a crosslinked elastic copolymer which has an alkylacrylate as a main component and copolymerizes other vinyl monomers and crosslinkable monomers copolymerizable therewith is mentioned. Examples of the alkyl acrylate which is the main component of the elastic polymer include, for example, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and the like, wherein the alkyl group has about 1 to 8 carbon atoms, particularly carbon number. An acrylate having 4 or more alkyl groups is preferably used. Other vinyl monomers copolymerizable with this alkyl acrylate include compounds having one polymerizable carbon-carbon double bond in the molecule, and more specifically, methacrylic acid esters such as methyl methacrylate and styrene. The same aromatic vinyl compound, vinyl cyan compound, such as acrylonitrile, etc. are mentioned. Further, examples of the crosslinkable monomer include crosslinkable compounds having at least two polymerizable carbon-carbon double bonds in a molecule, and more specifically, ethylene glycol di(meth)acrylate and butanediol di(meth)acrylic. And (meth)acrylates of polyhydric alcohols such as rate, alkenyl ester of (meth)acrylic acid such as allyl (meth)acrylate, divinylbenzene, and the like.

In addition, a laminate of a film containing an acrylic resin containing no rubber particles and a film containing an acrylic resin containing rubber particles can also be used as a protective film. Commercially available acrylic resins can be easily obtained. For example, each product name is Sumipex (manufactured by Sumitomo Chemical Co., Ltd.), Acripet (manufactured by Mitsubishi Rayon Co., Ltd.), Delpet (Asahi Kasei Co., Ltd.). And Shikigaisha), parapets (manufactured by Kabushiki Kaisha Shakurare), and Arch Reviewer (manufactured by Kabushiki Kaisha Nihon Shokubai).

The amorphous polyolefin-based resin is a resin obtained by subjecting ring-opening metathesis polymerization of norbornene or a derivative thereof obtained by the Diels-Alder reaction from cyclopentadiene and olefins as a monomer, followed by hydrogenation; A resin obtained by ring-opening metathesis polymerization of tetracyclododecene or a derivative thereof obtained by Diels-Alder reaction from dicyclopentadiene and olefins or methacrylic acid esters as a monomer, followed by hydrogenation; A resin obtained by subjecting to ring-opening metathesis copolymerization similarly using two or more kinds selected from norbornene, tetracyclododecene and derivatives thereof, and other cyclic polyolefin monomers; And resins obtained by addition copolymerization of an aromatic compound having a vinyl group and the like with norbornene, tetracyclododecene or a derivative thereof. Examples of commercially available amorphous polyolefin-based resins include "Atone" from JSR Co., "ZEONEX" and "ZEONOR" from Nippon Xeon, "APO" and "Apel" from Mitsui Chemicals. And so on. When an amorphous polyolefin-based resin is formed into a film, a known method such as a solvent casting method or a melt extrusion method is appropriately used for the film formation.

The cellulose-based resin is a resin in which at least a part of hydroxyl groups in cellulose are acetic acid esterified, and may be a mixed ester in which a part is acetic acid esterified and a part is esterified with another acid. The cellulose-based resin is preferably a cellulose ester-based resin, and more preferably an acetylcellulose-based resin. Triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate are mentioned as a specific example of an acetyl cellulose type resin. Commercially available products of the film containing such an acetylcellulose resin include, for example, “FujiTak TD80”, “FujiTak TD80UF” and “FujiTak TD80UZ” manufactured by Fujifilm Co., Ltd., manufactured by Konica Minolta Opto Co., Ltd. And KC8UX2M" and "KC8UY".

It is also possible to use a cellulose-based resin film provided with an optical compensation function. As such an optical compensation film, for example, a film containing a compound having a phase difference adjustment function in a cellulose-based resin, a compound having a phase difference adjustment function applied on the surface of the cellulose-based resin, or obtained by stretching the cellulose-based resin uniaxially or biaxially And films. Examples of commercially available optical compensation films of cellulose-based resins are "Wide View Film WV BZ 438" and "Wide View Film WV EA" manufactured by Fujifilm Co., Ltd., and "KC4FR" manufactured by Konica Minolta Opto Co., Ltd. -1" and "KC4HR-1".

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

In the present invention, the thermoplastic resin film described above is bonded to at least one surface of the polarizing film using a photocurable composition. When the thermoplastic resin film is bonded to only one side of the polarizing film, for example, it may take the form of directly attaching an adhesive layer for bonding to another member such as a liquid crystal cell on the other side of the polarizing film.

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

The thermoplastic resin film bonded to one side of the polarizing film is adhered using a photocurable composition, which will be described later, but the thermoplastic resin film bonded to the other side of the polarizing film uses an adhesive layer formed of another photocurable composition. May be adhered.

The thermoplastic resin film may be subjected to bi-adhesion treatment such as saponification treatment, corona treatment, primer treatment, and anchor coating treatment on the bonding surface prior to bonding to the polarizing film. Moreover, you may have various processing layers, such as a hard-coat layer, an antireflection layer, and an anti-glare layer, on the surface opposite to the bonding surface of a thermoplastic resin film to a polarizing film. 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 thermoplastic resin film preferably has a moisture permeability of 300 g/(m ² ·24 hr) or less at a temperature of 40° C. and a relative humidity of 90%, more preferably 200 g/(m ² ·24 hr) or less. , More preferably 100 g/(m ² ·24 hr) or less. A moisture permeability of 300 g/(m ² ·24 hr) or less is preferable because, for example, a change in transmittance under a high temperature and high humidity environment and a change in color under a high temperature environment can be suppressed.

When a thermoplastic resin film is bonded to both sides of a polarizing film, a thermoplastic resin film having a moisture permeability of 300 g/(m ² ·24 hr) or less at a temperature of 40° C. and a relative humidity of 90% is at least on the viewing side (outermost surface). It is preferable to bond, and it is more preferable to bond a thermoplastic resin film having a moisture permeability of 300 g/(m ² ·24 hr) or less on both surfaces of the polarizing film at a temperature of 40°C and a relative humidity of 90%.

[Adhesive layer]

In the polarizing plate of the present invention, a thermoplastic resin film is bonded to one side of the polarizing film through an adhesive layer. This adhesive layer is formed of a photocurable composition in which a cationic polymerizable compound and a photocationic polymerization initiator are blended in a predetermined ratio.

(Cationic polymerizable compound)

The cationically polymerizable compound is a main component of the photocurable composition, and is a component that provides adhesion by polymerization curing. As a cationic polymerizable compound, a bifunctional oxetane compound is included.

(Bifunctional oxetane compound)

The bifunctional oxetane compound is a compound having two quaternary ring ethers (oxetanyl groups) in a molecule, and examples thereof include the following compounds.

Bis[(3-ethyloxetan-3-yl)methyl]ether, bis[(3-methyloxetan-3-yl)methyl]ether, bis[(oxetan-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-ethyl Oxetan-3-yl)methoxy]biphenyl, 2,2′-bis[(3-ethyloxetan-3-yl)methoxy]biphenyl, 1,1,1-tris[(3-ethylox Cetane-3-yl)methoxymethyl]propane, 1,2-bis[(3-ethyloxetan-3-yl)methoxy]ethane, 1,2-bis[(3-ethyloxetan-3-yl )Methoxy]propane, 1,4-bis[(3-ethyloxetan-3-yl)methoxy]butane and 1,6-bis[(3-ethyloxetan-3-yl)methoxy]hexane, etc. .

Especially, in the case of bis[(3-ethyloxetan-3-yl)methyl]ether, the reactivity of the photocurable composition is high, and the elastic modulus at high temperature of the obtained cured product can be made high. Therefore, since the durability of the polarizing plate under high temperature conditions and high temperature and high humidity increases, it is preferable.

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

As the bifunctional oxetane compound, one type may be used, or two or more types may be used.

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

(Aliphatic epoxy compound)

The photocurable composition in the present invention may further contain an aliphatic epoxy compound as a cationic polymerizable compound. When a bifunctional oxetane compound and an aliphatic epoxy compound are used together as a cationic polymerizable compound, the adhesion between the polarizing film and the protective film can be further increased while maintaining the storage elastic modulus of the cured product of the photocurable composition at a high value. The aliphatic epoxy compound referred to herein is a compound in which one carbon atom among two carbon atoms contained in an epoxy group is bonded to another aliphatic carbon atom. Examples thereof include polyglycidyl ethers of alkane polyols and polyglycidyl ethers of polyalkylene glycols.

Examples of polyglycidyl ethers of polyalkylene glycols include diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, and tripropylene glycol diglycidyl ether. Can be heard.

As a specific example of the polyglycidyl ether of an alkane polyol, it is a compound represented by following formula (IV).

In the formula (IV), Z represents an alkylene group having 2 to 10 carbon atoms, Z may be a straight chain or a branched chain, or may be a ring structure. Z has 2 to 6 carbon atoms, and more preferably 4 to 6 carbon atoms.

As the compound represented by the formula (IV), for example, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,3-propanediol diglycidyl ether, 1,4-butanediol diglycidyl Ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, 1,9-nonanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, 1,4-cyclo And hexane dimethanol diglycidyl ether.

Other aliphatic epoxy compounds include triglycidyl ether of glycerin, triglycidyl ether of trimethylolpropane, pentaerythritol polyglycidyl ether and dipentaerythritol polyglycidyl ether, 2-ethylhexylglycidyl Ether, hydroquinone diglycidyl ether, resorcin diglycidyl ether, and the like.

The aliphatic epoxy compound is preferably a compound represented by formula (IV) because it is easy to obtain and has a large effect of increasing the adhesion between the polarizing film and the thermoplastic resin film. Specifically, compounds having Z having 4 to 6 carbon atoms such as 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, and 1,6-hexanediol diglycidyl ether are preferably used. .

As the aliphatic epoxy compound, one type 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 both is preferably 10 to 90 mass% of the aliphatic epoxy compound, based on the total amount of the cationic polymerizable compound, and 15 to 80 It is more preferable that it is a mass %, and it is still more preferable that it is 15-50 mass %. Of course, these totals do not exceed 100% by mass. When an aliphatic epoxy compound (for example, the compound represented by the formula (IV)) is blended at a ratio of 10% by mass or more of the entire cationic polymerizable compound, the adhesive strength with the thermoplastic resin film is excellent. In view of the low viscosity and adhesion of the photocurable composition, the aliphatic epoxy compound is preferred in many cases, but when it exceeds 90% by mass, the storage elastic modulus at 80°C of the cured product of the photocurable composition becomes low, and through it, polarization The durability of the polarizing plate in which the film and the protective film are bonded is poor in the cold heat shock test.

(Other cationic curable components)

The photocurable composition may contain other cationically curable components. Other cationically curable components include aromatic epoxy compounds, hydrogenated epoxy compounds in which aromatic rings in aromatic epoxy compounds are hydrogenated, alicyclic epoxy compounds, monofunctional oxetane compounds, and the like.

In the present invention, the aromatic epoxy compound refers to a compound in which a glycidyl ether group or a glycidyl ester group is directly bonded to an aromatic ring. Specific examples thereof include bisphenol A type epoxy, bisphenol F type epoxy resin, bisphenol S type epoxy, bisphenol A and bisphenol F and epichlorohydrin polycondensation epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy And resins, bisphenol A novolac-type epoxy resins, and bisphenol F novolac-type epoxy resins.

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. Further, for the same reason, the weight average molecular weight of the aromatic epoxy compound (hereinafter referred to as "Mw") is preferably 400 to 50,000, more preferably 1,000 to 10,000, and even more preferably 2,000 to 5,000. In addition, Mw in this invention means Mw of polystyrene conversion measured by gel permeation chromatography (GPC).

The aromatic epoxy compounds may be used alone or in combination of two or more.

When using an aromatic epoxy compound together, the content is preferably contained in an amount of 1 to 25% by mass based on the total mass of the cationic polymerizable compound. When content is 1 mass% or more, adhesiveness with a thermoplastic resin film improves. On the other hand, when the content exceeds 25% by mass, the viscosity of the composition becomes high, and the coating property is deteriorated. The preferable content is 3 to 20% by mass, more preferably 5 to 15% by mass, based on the total mass of the cationic polymerizable compound.

The hydrogenated epoxy compound is a hydrogenated polyhydroxy compound obtained by subjecting the aromatic polyhydroxy compound having at least two phenolic hydroxyl groups to a molecule which is a raw material of the above-mentioned aromatic epoxy compound to perform a hydrogenation reaction selectively under pressure in the presence of a catalyst. It is glycidyl etherified. Specific examples thereof include diglycidyl ether of bisphenol A hydrogenated, diglycidyl ether of bisphenol F hydrogenated, diglycidyl ether of bisphenol S hydrogenated, and the like.

An alicyclic epoxy compound means a compound containing at least two alicyclic epoxy groups in a molecule. The alicyclic epoxy group is a group represented by the following formula (II) (in formula (II), it represents an integer of m=2 to 5), specifically, an epoxycyclopentyl group, an epoxycyclohexyl group, and the like. have.

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

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

As a compound represented by Formula (III), 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6- And methyl cyclohexane carboxylate.

When using an alicyclic epoxy compound together, it is preferable that the content of the alicyclic epoxy compound is small from the viewpoint of heat and moisture resistance. Specifically, the alicyclic epoxy compound is preferably less than 30% by mass, more preferably less than 15% by mass, and even more preferably 1 to 10% by mass relative to the total mass of the cationic polymerizable compound.

(Photocationic polymerization initiator)

The photocurable composition undergoes cationic polymerization by irradiation with active energy rays, and cures to provide an adhesive layer. The photocationic polymerization initiator may be a cationic species or Lewis acid generated by irradiation of active energy rays such as visible light, ultraviolet light, X-rays, or electron beams, and initiate polymerization reaction of the cationic polymerizable compound. Since the photocationic polymerization initiator acts catalytically by light, even when mixed with a cationic polymerizable compound, its storage stability and workability are not affected. Examples of the photocationic polymerization initiator include an aromatic diazonium salt, an onium salt such as an aromatic iodonium salt or an aromatic sulfonium salt, and an iron-arene complex.

As an aromatic diazonium salt, the following compounds are mentioned, for example.

Benzenediazonium hexafluoroantimonate,

Benzenediazonium hexafluorophosphate,

Benzenediazonium hexafluoroborate and the like.

As an aromatic iodonium salt, the following compounds are mentioned, for example.

Diphenyl iodonium tetrakis (pentafluorophenyl) borate,

Diphenyliodonium hexafluorophosphate,

Diphenyl iodonium hexafluoroantimonate,

Di(4-nonylphenyl)iodonium hexafluorophosphate,

Di(4-alkylphenyl) iodonium hexafluorophosphate,

Tolylkyl iodonium tetrakis (pentafluorophenyl) borate,

Di(4-t-butylphenyl)iodonium hexafluorophosphate,

Di(4-t-butylphenyl) iodonium hexafluoroantimonate,

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

As an aromatic sulfonium salt, the following compounds are mentioned, for example.

Triphenylsulfonium hexafluorophosphate,

Triphenylsulfonium hexafluoroantimonate,

Triphenylsulfonium tetrakis(pentafluorophenyl) borate,

4,4'-bis[diphenylsulfonio]diphenylsulfide bishexafluorophosphate,

4,4'-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenylsulfide bishexafluoroantimonate,

4,4'-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenylsulfide bishexafluorophosphate,

7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthone hexafluoroantimonate,

7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthone tetrakis(pentafluorophenyl)borate,

4-phenylcarbonyl-4'-diphenylsulfonio-diphenylsulphide hexafluorophosphate,

4-(p-tert-butylphenylcarbonyl)-4'-diphenylsulfonio-diphenylsulfide hexafluoroantimonate,

4-(p-tert-butylphenylcarbonyl)-4'-di(p-toluyl)sulfonio-diphenylsulfide tetrakis(pentafluorophenyl)borate

4-(phenylthio)phenyldiphenylsulfonium tris(pentafluoroethyl)trifluorophosphate

4-(phenylthio)phenyldiphenylsulfonium hexafluorophosphate

4-(phenylthio)phenyldiphenylsulfonium trifluoromethanesulfonate, and the like.

Examples of the iron-allen complex include the following compounds.

Xylene-cyclopentadienyl iron(II) hexafluoroantimonate,

Cumene-cyclopentadienyl iron(II) hexafluorophosphate,

Xylene-cyclopentadienyl iron(II) tris(trifluoromethylsulfonyl)methanide and the like.

These photocationic polymerization initiators can be obtained as commercial 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), Kayard PCI-220, PCI- 620 [manufactured by Nihon Kayaku Co., Ltd.], Irgacure 250 (manufactured by Chiba 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 Industries, Ltd.], BBI-102, BBI-103, TPS-102, TPS-103, DTS-102, DTS-103 [Midorika Gaku Co., Ltd. ] And the like.

These photocationic polymerization initiators may be used alone or in combination of two or more. Among these, aromatic sulfonium salts are particularly preferably used because they have ultraviolet absorbing properties even in the wavelength region around 300 nm, and are excellent in curing properties and can provide a cured product having good mechanical strength and adhesive strength.

The blending amount of the photocationic polymerization initiator is 0.5 to 1.5 parts by mass based on 100 parts by mass of the cationic polymerizable compound. By mixing 0.5 part by mass or more (more preferably, 0.7 part by mass or more) of photocationic polymerization initiator per 100 parts by mass of the cationic polymerizable compound, the cationic polymerizable compound can be sufficiently cured, and high mechanical strength and adhesive strength to the obtained polarizing plate In addition to providing, it becomes excellent in durability under a high temperature and high humidity environment. On the other hand, when the amount increases, the residual amount of the unreacted initiator or the solvent used as necessary to dissolve the initiator or the decomposition product of the initiator increases, so that the physical properties of the cured product are damaged, and the polarizing plate is discolored under a high temperature environment. Therefore, the amount of the photocationic polymerization initiator is preferably 1.5 parts by mass or less per 100 parts by mass of the cationic polymerizable compound.

(Other ingredients)

The photocurable composition may contain other components in addition to the cationic polymerizable compound and photocationic polymerization initiator described above. Examples of other ingredients that can be blended include photosensitizers, photosensitizers, thermocationic polymerization initiators, chain transfer agents, thermoplastic resins, flow modifiers, antifoaming agents, leveling agents, organic solvents, silane coupling agents, polymers, and the like. Depending on the type of the protective film bonded to the polarizing film, it may be desirable to blend a photosensitizer and, moreover, 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 accelerates the polymerization initiation reaction by the photocationic polymerization initiator. Anthracene-based compounds are preferably used as such photosensitizers. As anthracene-based compounds that can be photosensitizers, 9,10-dimethoxyanthracene, 9,10-diethoxyanthracene, 9,10-dipropoxyanthracene, 9,10-diisopropoxyanthracene, 9,10- And dibutoxyanthracene, 9,10-dipentyloxyanthracene, and 9,10-dihexyloxyanthracene.

The photosensitizer is a compound that further promotes the action of the photosensitizer. As such a photosensitizer, a naphthalene-based compound is preferably used. As a naphthalene-based compound that can be a photosensitizer, 1,4-dimethoxynaphthalene, 1-ethoxy-4-methoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dipropoxynaphthalene, 1, 4-dibutoxynaphthalene, etc. are mentioned.

When blending these other components, the amount may be appropriately selected in accordance with the blending purpose in a range of, for example, 10 parts by mass or less, respectively, with respect to 100 parts by mass of the cationic polymerizable compound which is a main component of the photocurable composition.

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

The water content of the photocurable composition is preferably 3% by mass or less, more preferably 2% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less, based on the total amount of the photocurable composition. When the water content of the photocurable composition exceeds 3% by mass, the curability of the photocurable composition tends to deteriorate. Therefore, the adhesiveness between the thermoplastic resin film and the polarizing film immediately after the production of the polarizing plate is lowered, and there is a tendency for lifting and peeling to occur.

[Production of the polarizing plate]

The thermoplastic resin film is bonded to the polarizing film through an adhesive layer formed from the photocurable composition, thereby forming a polarizing plate. In this bonding, the coating layer of the photocurable composition described above is formed on one or both of the bonding surfaces of the polarizing film and the thermoplastic resin film, the polarizing film and these protective films are bonded through the coating layer, and the uncured sight It is made by hardening by irradiating an active energy ray to the coating layer of a chemical conversion composition, and fixing these thermoplastic resin films on a polarizing film.

Various coating methods, such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater, can be used for formation of the coating layer of a photocurable composition. Further, while continuously supplying the polarizing film and the thermoplastic resin film so that the bonding surfaces of both are inside, a method of softening the photocurable composition therebetween can also be employed. Since each coating method has a suitable viscosity range, it is also a useful technique to adjust the viscosity using a solvent. There is no particular limitation on the type of the solvent for this, as long as it does not degrade the optical performance of the polarizing film and dissolves the photocurable composition satisfactorily. For example, organic solvents such as hydrocarbons represented by toluene and esters represented by ethyl acetate can be used.

In adhering the polarizing film and the thermoplastic resin film, before or after forming the coating layer of the photocurable composition on one or both of the bonding surfaces, corona discharge treatment, plasma treatment, flame treatment, primer treatment, anchor coating treatment and The same easy adhesion treatment may be performed.

The light source used for irradiating active energy rays to the coating layer of the photocurable composition may be any one that generates ultraviolet rays, electron beams, X-rays, and the like. In particular, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, metal halide lamps, etc., which have a light emission distribution at a wavelength of 400 nm or less, are suitably used. The irradiation intensity of the active energy ray to the photocurable composition is determined for each target composition, and is not particularly limited, but it is preferable that the irradiation intensity of the wavelength region effective for activation of the initiator is 0.1 to 100 mW/cm 2. When the light irradiation intensity to the photocurable composition is less than 0.1 mW/cm 2, the reaction time becomes too long, and when it exceeds 100 mW/cm 2, the photocurability is caused by heat radiating from the lamp and heat generated during polymerization of the photocurable composition. There is a possibility of causing yellowing of the composition or deterioration of the polarizing film. The light irradiation time to the photocurable composition is controlled for each composition to be cured, and is not particularly limited, but is preferably set so that the accumulated light amount expressed as a product of the irradiation intensity and the irradiation time is 10 to 5,000 mJ/cm 2. . When the accumulated light amount to the photocurable composition is less than 10 mJ/cm 2, the generation of active species derived from the initiator is not sufficient, and thus the curing of the resulting adhesive layer may be insufficient, while the accumulated light amount exceeds 5,000 mJ/cm 2 If it does, the irradiation time becomes very long, which is disadvantageous for improving productivity.

When a thermoplastic resin film is bonded to both surfaces of a polarizing film, irradiation of active energy rays may be performed on either side of the thermoplastic resin film, but, for example, one thermoplastic resin film contains an ultraviolet absorber, and the other thermoplastic resin film is ultraviolet light. When it does not contain an absorbent, it is preferable to irradiate an active energy ray from the thermoplastic resin film side which does not contain an ultraviolet absorber effectively using the irradiated active energy ray and increasing the curing rate.

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 is thick, durability in the heat resistant environment and in the high temperature and high humidity environment tends to deteriorate.

[Laminated optical member]

The polarizing plate of this invention can laminate|stack the optical layer which has an optical function other than a polarizing plate, and can be set as a laminated optical member. Typically, a laminated optical member is formed by laminating and adhering an optical layer to a thermoplastic resin film of a polarizing plate through an adhesive layer or an adhesive layer, but, for example, through a photocurable composition according to the present invention on one side of a polarizing film, for example. The thermoplastic resin film may be bonded and the optical layer may be laminated and bonded to the other side of the polarizing film through an adhesive or an adhesive. In the latter case, as the adhesive layer for adhering the polarizing film and the optical layer, a cured product of the photocurable composition specified in the present invention may be used, or an adhesive layer formed from other known adhesives may be used.

For example, an optical layer laminated on a polarizing plate, for a polarizing plate disposed on the back side of a liquid crystal cell, a reflective layer, a semi-transmissive reflective layer, a light diffusing layer, a light converging plate, laminated on the opposite side to the side facing the liquid crystal cell of the polarizing plate, And brightness enhancing films. In addition, for any one of the polarizing plate disposed on the front side of the liquid crystal cell and the polarizing plate disposed on the back side of the liquid crystal cell, there are retardation plates stacked on the side facing the liquid crystal cell of the polarizing plate.

The reflective layer, the semi-transmissive reflective layer, or the light-diffusing layer is provided to form a reflective polarizing plate (optical member), a transflective polarizing plate (optical member), or a diffusing polarizing plate (optical member), respectively. The reflective polarizing plate is used for a liquid crystal display device of a type that reflects and displays incident light from the viewer side, and since a light source such as a backlight can be omitted, it is easy to thin the liquid crystal display device. In addition, the semi-transmissive polarizing plate is used in a liquid crystal display device of a type that displays a reflection type in a spot and a light from a backlight in a dark place. The optical member as a reflective polarizing plate can form a reflective layer, for example, by attaching a foil or a vapor-deposited film containing a metal such as aluminum to a protective film on the polarizing film. The optical member as a semi-transmissive polarizing plate can be formed by using the above-mentioned reflective layer as a half mirror or by attaching a pearlescent pigment or the like to a reflective plate that exhibits light transmission to the polarizing plate. On the other hand, the optical member as a diffusion type polarizing plate uses various methods such as a method of performing a matt treatment on a protective film on a polarizing plate, a method of applying a resin containing fine particles, a method of bonding a film containing fine particles, and the like. A fine uneven structure is formed on the surface.

Moreover, an optical member as a polarizing plate for both reflection and diffusion can also be formed, and in such a case, for example, a method such as providing a reflective layer reflecting the uneven structure on the fine concavo-convex structure surface of the diffusion-type polarizing plate can be adopted. The reflective layer having a fine concavo-convex structure has advantages such as diffusing incident light by diffuse reflection, preventing directionality and glare, and suppressing unevenness in contrast. In addition, the resin layer or film containing fine particles has an advantage such that incident light and its reflected light diffuse when passing through the fine particle containing layer, and can suppress contrast unevenness. The reflective layer reflecting the surface fine concavo-convex structure can be formed by directly depositing a metal on the surface of the fine concavo-convex structure by methods such as vacuum deposition, ion plating, deposition such as sputtering or plating. The fine particles to be blended to form the surface fine concavo-convex structure include, for example, inorganic fine particles such as silica, aluminum oxide, titanium oxide, zirconia, tin oxide, indium oxide, cadmium oxide, and antimony having an average particle diameter of 0.1 to 30 µm, crosslinking Or organic-based fine particles such as a non-crosslinked polymer.

The light collecting plate is used for the purpose of optical path control and the like, and can be formed as a prism array sheet, a lens array sheet, or a dot laying sheet.

The luminance-enhancing film is used for the purpose of improving luminance in a liquid crystal display device. For example, a reflective polarization separation sheet designed to produce anisotropy in reflectivity by laminating a plurality of thin film films having different anisotropy of refractive index. And a circularly polarized separating sheet in which an alignment film of a cholesteric liquid crystal polymer or an alignment liquid crystal layer is supported on a film substrate.

On the other hand, the retardation plate as the optical layer described above is used for the purpose of compensating for the retardation by the liquid crystal cell. Examples thereof include a birefringent film including a stretched film of various plastics, a film in which a discotic liquid crystal or nematic liquid crystal is aligned and fixed, and a liquid crystal layer formed on the film substrate. When a liquid crystal layer is formed on a film substrate, a cellulose-based resin film such as triacetyl cellulose is preferably used as the film substrate.

Examples of the plastic forming the birefringent film include, for example, amorphous polyolefin-based resins, polycarbonate-based resins, acrylic-based resins, and chain polyolefin-based resins such as polypropylene, polyvinyl alcohol, polystyrene, polyarylate, and polyamide. Can be. The stretched film may be treated in an appropriate manner such as uniaxial or biaxial. In addition, a retardation plate may be used in combination of two or more sheets for the purpose of controlling optical characteristics such as broadband.

In the laminated optical member, an optical layer other than a polarizing plate is preferably used because an optical compensation can be effectively performed when applied to a liquid crystal display device. The retardation value (in-plane and thickness direction) of the retardation plate may be appropriately selected depending on the liquid crystal cell to be applied.

The laminated optical member can be formed as a laminate of two or more layers by combining a polarizing plate and one or two or more layers selected according to the purpose of use from the various optical layers described above. In that case, the various optical layers forming the laminated optical member are integrated with the polarizing plate using an adhesive layer or an adhesive layer, but the adhesive or adhesive used therefor is not particularly limited as long as the adhesive layer or adhesive layer is formed satisfactorily. . It is preferable to use an adhesive (also referred to as a pressure-sensitive adhesive) from the viewpoint of ease of adhesion work or prevention of occurrence of optical distortion. As the pressure-sensitive adhesive, an acrylic polymer, a silicone polymer, polyester, polyurethane, polyether or the like can be used as the base polymer. Among them, like an acrylic adhesive, it has excellent optical transparency, maintains proper wettability and cohesiveness, has excellent adhesion to a substrate, furthermore has weatherability and heat resistance, etc., lifting and peeling under conditions of heating or humidification, etc. It is preferable to select and use the one that does not cause the peeling problem. In the acrylic adhesive, an acrylic monomer containing a functional group containing an alkyl ester of (meth)acrylic acid having an alkyl group having 20 or less carbon atoms, such as a methyl group, an ethyl group, or a butyl group, and (meth)acrylic acid or (hydroxy)ethyl (meth)acrylate. , Acrylic copolymers having a weight average molecular weight of 100,000 or more, which are blended so that the glass transition temperature is preferably 25° C. or less, and more preferably 0° C. or less, are useful as the base polymer.

Formation of the pressure-sensitive adhesive layer on the polarizing plate is, for example, dissolving or dispersing the pressure-sensitive adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare a solution of 10 to 40% by mass, and coating it directly on the polarizing plate, or protect in advance. It can be carried out by forming a pressure-sensitive adhesive layer on a film and then attaching it to a polarizing plate. The thickness of the pressure-sensitive adhesive layer is determined depending on the adhesive strength and the like, but a range of about 1 to 50 µm is suitable.

In addition, a filler, a pigment or a colorant, an antioxidant, an antistatic agent, an ultraviolet absorber, etc. which may contain glass fibers, glass beads, resin beads, metal powder, or other inorganic powders may be blended in the adhesive layer, if necessary. Examples of the ultraviolet absorber include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex salt compounds.

Examples of the antistatic agent include ionic compounds, conductive fine particles, and conductive polymers. Among these, suitable antistatic agents may be used alone or in combination of two or more. Of course, two or more types of antistatic agents classified as ionic compounds may be used in combination, two or more types of antistatic agents classified as conductive fine particles may be used in combination, and two or more types of antistatic agents classified as conductive polymers may be used. It can also be used.

Among the antistatic agents described above, since compatibility with the solvent is excellent, an ionic compound is preferably used.

Ionic compounds can be classified into ionic compounds having an organic cation, ionic compounds having an inorganic cation, ionic compounds having an organic anion, and ionic compounds having an inorganic anion. Examples of the organic cations include pyridinium cations, imidazolium cations, ammonium cations, sulfonium cations, phosphonium cations, and the like. Lithium, potassium, etc. are mentioned as an inorganic cation. The cation component constituting the ionic compound may be an inorganic anion or an organic anion, but is preferably an organic cation from the viewpoint of compatibility with a (meth)acrylic resin. On the other hand, as the anion component constituting the ionic compound, an inorganic anion or an organic anion may be used, but since an ionic compound having excellent antistatic performance is provided, an anion component containing a fluorine atom is preferable. As an anion component containing a fluorine atom, a hexafluorophosphate anion [(PF ₆ ^-)], bis (methanesulfonyl trifluoromethanesulfonyl) imide anion _{[(CF 3 SO 2) 2} N -] anion, bis ( and the like can be ^{anion-sulfonyl} fluorophenyl) imide anion _{[(FSO 2) 2 N]} .

The laminated optical member can be disposed on one side or both sides of the liquid crystal cell. The liquid crystal cell to be used is arbitrary, and various liquid crystal cells can be used to form a liquid crystal display device, such as an active matrix driving type represented by a thin film transistor type or a simple matrix driving type represented by a super twisted nematic type. Can be. An adhesive is usually used for adhesion of the laminated optical member and the liquid crystal cell.

Example

Examples will be described below to more specifically describe the present invention, but the present invention is not limited to these examples. In the examples, "parts" and "%" indicating the content to the amount used are based on mass unless otherwise specified. In addition, the cationically polymerizable compound, photocationic polymerization initiator, and leveling agent used in the following examples are as follows, and are indicated by the following symbols.

(A) Cationic polymerizable compound

(a1) 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane: obtained from Toagosei Corporation, trade name "OXT-221". In Table 1 described later, "(a1)" is abbreviated.

(a2) 1,4-butanediol diglycidyl ether: obtained from Nagase Chemtex Co., Ltd., trade name "EX-214L". In Table 1 described later, "(a2)" is abbreviated.

(B) Photocationic polymerization initiator

(b1) 4-(phenylthio)phenyldiphenylsulfonium hexafluorophosphate: obtained from San Apro Corporation, trade name "CPI-100P". In Table 1 described later, "(b1)" is abbreviated. In addition, CPI-100P was used as a 50% propylene carbonate solution, and Table 1 lists its solid content.

[Examples 1 to 3 and Comparative Example 1]

[Preparation Examples 1 to 4]

(1) Preparation of photocurable composition

After mixing each component in the compounding ratio shown in Table 1, it was defoamed and photocurable compositions 1-3 were prepared.

(2) Preparation of polarizing plate

[Example 1]

A polarizing plate was manufactured using the photocurable composition 1. The surface of the 50 µm-thick cycloolefin-based film (trade name "ZEONOR" manufactured by Nippon Zeon Co., Ltd.) was subjected to corona discharge treatment, and the photocurable composition 1 described above was applied to the corona discharge treatment surface using a bar coater. It was coated so that the film thickness after curing was about 1.5 µm. A polyvinyl alcohol-iodine polarizing film was bonded to the coated surface of the photocurable composition. Further, a corona discharge treatment was performed on the bonding surface of the protective film containing 80 µm-thick (meth)acrylic resin (PMMA) containing a UV absorber (trade name "Technology S001", manufactured by Sumitomo Chemical Co., Ltd.), On the surface of the corona discharge treatment, the same photocurable composition 1 used for the cycloolefin-based film was coated with a bar coater so that the film thickness after curing was about 1.5 µm. On the coated surface of the photocurable composition, a polarizing film in which the cycloolefin film produced above was bonded to one side was bonded on the polarizing film side to produce a laminate. From the cycloolefin-based film side of this layered product, an ultraviolet ray so that the accumulated light amount (UVB) becomes 200 mJ/cm 2 using an ultraviolet irradiation device with a belt conveyor attached (the lamp uses “D bulb” manufactured by Fusion UV Systems). Was irradiated, and the photocurable composition was cured to form an adhesive layer. In this way, a polarizing plate in which a protective film was bonded to each side of the polarizing film through an adhesive was produced.

[Example 2]

A polarizing plate was manufactured using the photocurable composition 1. The surface of the 50 µm-thick cycloolefin-based film (trade name "ZEONOR" manufactured by Nippon Zeon Co., Ltd.) was subjected to corona discharge treatment, and the photocurable composition 1 described above was applied to the corona discharge treatment surface using a bar coater. Each was coated so that the film thickness after curing was about 1.5 µm. A polyvinyl alcohol-iodine polarizing film was bonded to the coated surface of the photocurable composition. Further, a corona discharge treatment was performed on the bonding surface of a triacetylcellulose (TAC)-based film (trade name "TD60UL", manufactured by Fujifilm Co., Ltd.) having a thickness of 60 µm containing an ultraviolet absorber, and the surface of the corona discharge treatment was cyclo. The same photocurable composition used for the olefin-based film was coated with a bar coater so that the film thickness after curing was about 1.5 µm. On the coated surface of the photocurable composition, a polarizing film in which the cycloolefin film produced above was bonded to one side was bonded on the polarizing film side to produce a laminate. From the cycloolefin-based film side of this layered product, ultraviolet light is applied so that the accumulated light amount (UVB) becomes 200 mJ/cm 2 using an ultraviolet irradiation device with a belt conveyor attached (the lamp uses “D bulb” manufactured by Fusion UV Systems). Was irradiated, and the photocurable composition was cured to form an adhesive layer. In this way, a polarizing plate in which a protective film was bonded to each side of the polarizing film through 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 replaced with the photocurable composition 2.

[Comparative Example 1]

A polarizing plate was produced in the same manner as in Example 1 except that the photocurable composition 1 was replaced with the photocurable composition 3.

The moisture permeability at a temperature of 40°C and a relative humidity of 90% of the thermoplastic resin film was measured by the cup method specified in JIS Z0208.

PMMA: 60 g/(㎡·24 hr)

TAC: 520 g/(㎡·24 hr)

COP: 5.8 g/(㎡·24 hr)

(3) Preparation of polarizing plate with adhesive layer

After the corona treatment was performed on the cycloolefin-based film surface of the polarizing plate prepared in (2), and an acrylic pressure-sensitive adhesive having a thickness of 25 μm was bonded by a laminator, it was cured for 7 days under conditions of a temperature of 23° C. and a relative humidity of 65%. , To obtain a polarizing film with an adhesive.

(4) Evaluation of optical properties of polarizer

The polarizing plate with adhesive prepared in (3) was cut to a size of 30 mm×30 mm, bonded to an alkali free glass (trade name “EAGLE XG” manufactured by Corning), and the b value of each transmitted color was measured. For measurement, a polarizing plate in a wavelength range of 380 nm to 780 nm was used by setting an "visible film holder with polarizing film" as an optional accessory to an ultraviolet visible spectrophotometer "UV-2450" manufactured by Shimadzu Corporation. The transmission spectrum was calculated, and the b value, which is the transmission color, was calculated by the software "UV-Probe" attached to the spectrophotometer.

(5) Evaluation of heat resistance of polarizing plate

The polarizing plate produced in the above (4) was subjected to a heating test in which the temperature was set to stand for 48 hours in a heating environment at 90° C., and the transmitted color b value of the polarizing plate after testing was measured. Measurement and calculation of the b value were performed in the same manner as in (4) above. The absolute value (|Δb|) value of the difference in the transmission color before and after the heat resistance test was calculated according to the following equation.

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

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

Δb rate of change in each example (%)

=|{(|Δb|) in each example-(|Δb| in Comparative Example 1)}|/(|Δb| in Comparative Example 1)×100

In addition, in any of the Examples and Comparative Examples, Δb showed a positive value.

Table 1 shows the results.

From Table 1, in a polarizing plate in which a thermoplastic resin film is bonded to at least one side of a polarizing film through an adhesive, the adhesive contains 10 to 70% by mass of a bifunctional oxetane compound in a cationic polymerizable compound, and also a cation It was confirmed that it exhibited good heat resistance by including 0.5 to 1.5 parts by mass of the photocationic polymerization initiator with respect to 100 parts by mass of the polymerizable compound.

[Preparation Example 4-10]

(1) Preparation of photocurable composition

After mixing each component at the compounding ratio shown in Table 2, it was defoamed to prepare photocurable compositions 4 to 10.

In addition, the abbreviation in Table 2 represents the compound described below, respectively.

(A) Cationic polymerizable compound

(a1) 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane: obtained from Toagosei Corporation, trade name "OXT-221". In Table 2, "(a1)" is abbreviated.

(a2) 1,4-butanediol diglycidyl ether: obtained from Nagase Chemtex Co., Ltd., trade name "EX-214L". In Table 2, "(a2)" is abbreviated.

(a3) Neopentyl glycol diglycidyl ether: obtained from Nagase Chemtex Co., Ltd., trade name "EX-211L". In Table 2, "(a3)" is abbreviated.

(a4) Pentaerythritol polyglycidyl ether: obtained from Nagase Chemtex Co., Ltd., trade name "EX-411". In Table 2, "(a4)" is abbreviated.

(a5) 3',4'-epoxycyclohexylmethyl 3,4-cyclohexanecarboxylate: obtained from Daicel Chemical Co., Ltd., trade name "Celloxide 2021P". In Table 2, "(a5)" is abbreviated.

(B) Photocationic polymerization initiator

(b1) 4-(phenylthio)phenyldiphenylsulfonium hexafluorophosphate: obtained from San Apro Corporation, trade name "CPI-100P". In Table 2, "(b1)" is abbreviated. In addition, CPI-100P was used as a 50% propylene carbonate solution, and Table 2 lists the solid content.

[Example 4]

(2) Preparation of polarizing plate

Corona discharge treatment was performed on the surface of [trade name "ZEONOR" manufactured by Nippon Zeon Co., Ltd.) of a 50 µm-thick cycloolefin-based resin film, and a photocurable composition 4 was applied to the corona discharge treatment surface using a bar coater. It was coated so that the film thickness after curing was about 1.5 µm. A polyvinyl alcohol-iodine polarizing film was bonded to the coated surface of the photocurable composition 4. Further, a corona discharge treatment was performed on the bonding surface of the protective film containing 80 µm-thick (meth)acrylic resin (PMMA) containing a UV absorber (trade name "Technology S001", manufactured by Sumitomo Chemical Co., Ltd.), On the surface of the corona discharge treatment, the photocurable composition 4 was coated with a bar coater so that the film thickness after curing was about 1.5 µm. On the coated surface of the photocurable composition 4, a polarizing film in which the cycloolefin film produced above was bonded to one side was bonded on the polarizing film side, thereby producing a laminate. From the cycloolefin-based film side of this layered product, ultraviolet light is applied so that the accumulated light amount (UVB) becomes 200 mJ/cm 2 using an ultraviolet irradiation device with a belt conveyor attached (the lamp uses “D bulb” manufactured by Fusion UV Systems). Was irradiated, and the photocurable composition was cured to form an adhesive layer, and a polarizing plate in which a protective film was bonded through adhesive on both sides of the polarizing film was produced.

[Example 5]

A polarizing plate was produced in the same manner as in Example 5, except that the photocurable composition 4 was replaced with the photocurable composition 5.

[Example 6]

A polarizing plate was produced in the same manner as in Example 5, except that the photocurable composition 4 was replaced with the photocurable composition 6.

[Example 7]

A polarizing plate was produced in the same manner as in Example 5, except that the photocurable composition 4 was replaced with the photocurable composition 7.

[Example 8]

A polarizing plate was produced in the same manner as in Example 5, except that the photocurable composition 4 was replaced with the photocurable composition 8.

[Example 9]

A polarizing plate was produced in the same manner as in Example 5, except that the photocurable composition 4 was replaced with the photocurable composition 9.

[Example 10]

A polarizing plate was produced in the same manner as in Example 5, except that the photocurable composition 4 was replaced with the photocurable composition 10.

(3) Preparation of polarizing plate with adhesive layer

After the corona treatment was performed on the cycloolefin-based film surface of the polarizing plate prepared in (2), and an acrylic pressure-sensitive adhesive having a thickness of 25 μm was bonded by a laminator, it was cured for 7 days under conditions of a temperature of 23° C. and a relative humidity of 65%. , A polarizing film with an adhesive was obtained.

(4) Evaluation of optical properties of polarizer

The polarizing plate with an adhesive prepared in (3) was cut to a size of 30 mm×30 mm, bonded to an alkali free glass (trade name "EAGLE XG" manufactured by Corning), and the b value of each transmitted color was measured. For measurement, a polarizing plate in a wavelength range of 380 nm to 780 nm was used by setting an "visible film holder with polarizing film" as an optional accessory to an ultraviolet visible spectrophotometer "UV-2450" manufactured by Shimadzu Corporation. The transmission spectrum was calculated, and the b value, which is the transmission color, was calculated by the software "UV-Probe" attached to the spectrophotometer.

(5) Evaluation of heat resistance of polarizing plate

The polarizing plate produced in the above (4) was subjected to a heating test in which the temperature was set to stand for 48 hours in a heating environment at 90° C., and the transmitted color b value of the polarizing plate after testing was measured. Measurement and calculation of the b value were performed in the same manner as in (4) above. The absolute value (|Δb|) value of the difference in the transmission color before and after the heat resistance test was calculated according to the following equation.

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

Next, the "Δb change rate (improvement rate)" (%) of each example based on |Δb| of Comparative Example 1 was determined from the obtained value of |Δb|. Table 2 shows the calculated value of the Δb change rate. The larger the Δb change rate, the better the heat resistance.

Δb rate of change in each example (%)

=|{(|Δb|) in each example-(|Δb| in Comparative Example 1)}|/(|Δb| in Comparative Example 1)×100

In addition, in any of the Examples and Comparative Examples, Δb showed a positive value.

Table 2 shows the results.

(6) Evaluation of heat and moisture resistance of the polarizing plate

The polarizing plate produced in the above (4) was subjected to a heat and moisture resistance test that was allowed to stand for 48 hours in a high temperature and high humidity environment at a temperature of 80°C and a relative humidity of 90%, and the luminous intensity corrected group transmittance Ty value of the polarizing plate after the test was measured. Measurement and calculation of the Ty value were performed in the same manner as in (4) above. The absolute value (|ΔTy|) value of the difference in the visibility transmittance simple substance transmittance Ty before and after the heat-resistant heat test was calculated according to the following equation.

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

In addition, in any of the examples and comparative examples, ΔTy showed a positive value.

Table 3 shows the results.

Claims (3)

As a polarizing plate is a thermoplastic resin film is bonded to at least one side of the polarizing film through an adhesive layer,
The adhesive is a cured product of a photocurable composition comprising a cationic polymerizable compound and a photocationic polymerization initiator,
The photocurable composition contains 0.5 to 1.5 parts by mass of a photocationic polymerization initiator with respect to 100 parts by mass of the cationic polymerizable compound,
The cationic polymerizable compound is a polarizing plate characterized in that it contains 10 to 70% by mass of the bifunctional oxetane compound with respect to the total mass of the cationic polymerizable compound. The polarizing plate of claim 1, wherein the cationic polymerizable compound further comprises 10 to 70 mass% of an aliphatic epoxy compound based on the total mass of the cationic polymerizable compound. The polarizing plate according to claim 1 or 2, wherein the thermoplastic resin film has a moisture permeability of 300 g/(m ² ·24 hr) or less at a temperature of 40°C and a relative humidity of 90%.