WO2022145369A1

WO2022145369A1 - Polarizing plate

Info

Publication number: WO2022145369A1
Application number: PCT/JP2021/048234
Authority: WO
Inventors: 智岩田; 智恵阪上
Original assignee: 住友化学株式会社
Priority date: 2020-12-28
Filing date: 2021-12-24
Publication date: 2022-07-07
Also published as: KR20230121917A; TW202235927A

Abstract

[Problem] To provide a polarizing plate in which protective films are affixed to both surfaces of a polarizing film, the polarizing plate exhibiting a small degree of curling or not being prone to curling even when placed in a high-humidity environment. [Solution] Provided is a polarizing plate including a first protective film, a first adhesive layer, a polarizing film, a second adhesive layer, and a second protective film in the stated order, the first adhesive layer being a cured product layer of a first cationically polymerizable adhesive including one or more types of cationic polymerization initiators, the second adhesive layer being a cured product layer of a second cationically polymerizable adhesive including one or more types of cationic polymerization initiators, the one or more cationic polymerization initiators included in the first cationically polymerizable adhesive including a first cationic polymerization initiator, the first cationic polymerization initiator being a borate salt comprising an anion component represented by formula (i), and the molecular weight of the first cationic polymerization initiator being greater than the molecular weight of the one or more types of cationic polymerization initiators included in the second cationically polymerizable adhesive.

Description

Polarizer

The present invention relates to a polarizing plate in which a protective film is bonded to both sides of a polarizing film via an adhesive layer.

A polarizing plate widely used in an image display device represented by a liquid crystal display device usually has a structure in which a protective film is laminated on both sides of a polarizing film. An adhesive is usually used for bonding the polarizing film and the protective film. As an adhesive for bonding a protective film, a water-based adhesive and an active energy ray-curable adhesive are known.

Japanese Patent Application Laid-Open No. 2015-140374 (Patent Document 1) describes (A) a compound containing an ester group and having two or more alicyclic epoxy groups in the molecule, (B) a fluoroalkylfluorophosphate anion or a penta. A photocationic polymerization initiator having a fluorophenylborate anion, a radiation curable composition containing (C) a compound having three or more hydroxyl groups in the molecule, and a polarizing film and a protective film adhered to each other using this composition. A polarizing plate made of an ester is described.

JP-A-2015-140374A

Generally, a polarizing plate is manufactured as a long object (polarizing plate roll) by a roll-to-roll method, and then cut into a polarizing plate sheet having a size corresponding to, for example, the screen size of an applied image display device. It is incorporated into an image display device by being attached to an image display element. The polarizing plate may be stored or transported for a certain period after being cut into a single-wafer body and before being incorporated into an image display device. In this case, the storage / transportation environment is relatively high humidity. May become. Polarized-plate single-wafers exposed to high-humidity environments are prone to curl.

An object of the present invention is to provide a polarizing plate in which protective films are bonded to both sides of a polarizing film, which is less likely to cause curl or has a small degree of curl even when placed in a high humidity environment. be.

The present invention provides the following polarizing plates.
[1] A polarizing plate containing a first protective film, a first adhesive layer, a polarizing film, a second adhesive layer, and a second protective film in this order.
The first adhesive layer is a cured product layer of the first cationic polymerization type adhesive containing one or more kinds of cationic polymerization initiators.
The second adhesive layer is a cured product layer of a second cationic polymerization type adhesive containing one or more kinds of cationic polymerization initiators.
The one or more kinds of cationic polymerization initiators contained in the first cationic polymerization type adhesive include the first cationic polymerization initiator.
The first cationic polymerization initiator has a cationic component and the following formula (i):

(In the formula, Y indicates an aryl group having 6 to 30 carbon atoms or a heterocyclic group having 4 to 30 carbon atoms, or a halogen atom, which may have a substituent (excluding a group containing a halogen atom). Phf represents a phenyl group in which at least one of the hydrogen atoms is substituted with at least one selected from a perfluoroalkyl group, a perfluoroalkoxy group, and a halogen atom. K is an integer of 0 to 4. be.)
It is a borate salt composed of an anion component represented by.
A polarizing plate having a molecular weight of the first cationic polymerization initiator larger than the molecular weight of one or more kinds of cationic polymerization initiators contained in the second cationic polymerization type adhesive.
[2] The polarizing plate according to [1], wherein the cation component is an aryl sulfonium ion.
[3] The first cationically polymerizable adhesive and the second cationically polymerizable adhesive further contain a cationically polymerizable compound.
The content of the one or more cationic polymerization initiators contained in the first cationic polymerization type adhesive and the content of the one or more kinds of cationic polymerization initiators contained in the second cationic polymerization type adhesive are as described above. The polarizing plate according to [1] or [2], which is 0.5 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the cationically polymerizable compound.
[4] The polarizing plate according to any one of [1] to [3], wherein the first protective film is composed of a (meth) acrylic resin or a cellulose ester resin.
[5] The polarizing plate according to any one of [1] to [4], further having an adhesive layer on the side of the second protective film opposite to the second adhesive layer side.

It is possible to provide a polarizing plate in which protective films are bonded to both sides of a polarizing film, which is less likely to cause curl or has a small degree of curl even when placed in a high humidity environment.

It is a schematic sectional drawing which shows an example of the layer structure of the polarizing plate which concerns on this invention.

Hereinafter, the polarizing plate according to the present invention (hereinafter, also simply referred to as “polarizing plate”) will be described in detail.

(1) Configuration of Polarizing Plate As shown in FIG. 1, the polarizing plate includes a first protective film 10, a first adhesive layer 15, a polarizing film 30, a second adhesive layer 25, and a second protective film 20. Include in order. That is, the first protective film 10 is laminated on one surface of the polarizing film 30 via the first adhesive layer 15, and the second protective film 20 is laminated on one surface of the polarizing film 30 via the second adhesive layer 25. It is laminated on.
The first adhesive layer 15 is preferably in contact with the first protective film 10 and the polarizing film 30. The second adhesive layer 25 is preferably in contact with the polarizing film 30 and the second protective film 20.

Not limited to the example of FIG. 1, the polarizing plate can include layers other than the above. Specific examples of other layers include, for example, a pressure-sensitive adhesive layer laminated on the outer surface of the first protective film 10 and / or the second protective film 20; a separate film laminated on the outer surface of the pressure-sensitive adhesive layer (“peeling). Also referred to as "film"); a protective film laminated on the outer surface of the first protective film 10 and / or the second protective film 20 (also referred to as "surface protective film"); first protective film 10 and / or second protective. An optically functional film or the like laminated on the outer surface of the film 20 via an adhesive layer or an adhesive layer.

The polarizing plate according to the present invention may be less likely to cause curl or have a small degree of curl even when placed in a high humidity environment. Hereinafter, the difficulty of curling is also referred to as "curl resistance", and the difficulty of curling or the small degree of curling is also referred to as "good curl resistance".

The polarizing plate may be a long object of the polarizing plate having the above-mentioned layer structure, a winding roll thereof, or a single-wafered body. The single-wafer body refers to a long object or a body cut out from the winding roll to a predetermined size, and usually has a rectangular shape such as a rectangle or a square.
When the polarizing plate is a long object or its winding roll, the curl resistance means the curl resistance of the long object or the single-wafer cut from the winding roll. When the polarizing plate is a single-wafer body, the curl resistance means the curl resistance of the single-wafer body or a smaller-sized single-wafer body cut from the single-wafer body.

(2) Polarizing film The polarizing film 30 is a film having a function of selectively transmitting linear polarization in one direction from natural light. For example, an iodine-based polarizing film in which iodine is adsorbed and oriented on a polyvinyl alcohol-based resin film, a dye-based polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film, and a dichroic dye in a Riotrovic liquid crystal state. Examples thereof include a coating type polarizing film coated with, oriented and immobilized. These polarizing films are called absorption type polarizing films because they selectively transmit linear polarization in one direction from natural light and absorb linear polarization in the other direction.

The polarizing film 30 is not limited to the absorption type polarizing film, but is a reflective polarizing film that selectively transmits linear polarization in one direction from natural light and reflects the linear polarization in the other direction, or linear polarization in the other direction. A scattering type polarizing film that scatters the particles may be used, but an absorption type polarizing film is preferable from the viewpoint of excellent visibility. Of these, an iodine-based polarizing film having excellent degree of polarization and transmittance is more preferable.

The polarizing film 30 is a step of uniaxially stretching a polyvinyl alcohol-based resin film; a step of adsorbing a bicolor dye by dyeing the polyvinyl alcohol-based resin film with a bicolor dye; polyvinyl alcohol on which the bicolor dye is adsorbed. It can be produced by a method including a step of treating (cross-linking) the based resin film with an aqueous boric acid solution; and a step of washing with water after the treatment with the aqueous boric acid solution. The draw ratio is usually about 3 to 8 times.

After washing with water, a drying treatment is performed to obtain a polarizing film 30. The drying process can be performed using a hot air dryer or a far-infrared heater. A polarizing plate can be obtained by adhering a protective film on both sides of the polarizing film 30 using an adhesive.

The thickness of the polarizing film 30 can be 40 μm or less, preferably 30 μm or less (for example, 20 μm or less). According to the methods described in JP-A-2000-338329 and JP-A-2012-159778, the thin-film polarizing film 30 can be manufactured more easily, and the thickness of the polarizing film 30 is, for example, 20 μm or less. Further, it can be 10 μm or less. The thickness of the polarizing film 30 is usually 2 μm or more. Reducing the thickness of the polarizing film 30 is advantageous for reducing the thickness of the polarizing plate and eventually the image display device.

(3) Protective film The first protective film 10 and the second protective film 20 are each translucent (preferably optically transparent) thermoplastic resin, for example, a chain polyolefin resin (polypropylene resin or the like). , Polyolefin-based resins such as cyclic polyolefin-based resins (norbornen-based resins, etc.); Cellulosic ester-based resins such as triacetyl cellulose and diacetyl cellulose; Polyester-based resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; It can be a resin film made of a based resin; a (meth) acrylic resin; or a mixture thereof, a copolymer, or the like.
Among them, the first protective film 10 and the second protective film 20 are each composed of a resin selected from the group consisting of a polyester resin, a polycarbonate resin, a polyolefin resin, a (meth) acrylic resin and a cellulose ester resin. Is preferable.
In the present specification, "(meth) acrylic" means methacrylic and / or acrylic, and "(meth)" in the case of "(meth) acrylate" or the like has the same meaning.

The first protective film 10 and the second protective film 20 may be either an unstretched film or a uniaxially or biaxially stretched film, respectively. The biaxial stretching may be simultaneous biaxial stretching in which the two stretching directions are simultaneously stretched, or sequential biaxial stretching in which the stretching is performed in a predetermined direction and then in the other direction. The first protective film 10 and / or the second protective film 20 may be a protective film having an optical function such as a retardation film. The retardation film is an optical functional film used for the purpose of compensating for the phase difference by a liquid crystal cell which is an image display element. For example, a retardation film to which an arbitrary retardation value is imparted by stretching a film made of the thermoplastic resin (uniaxial stretching or biaxial stretching, etc.) or forming a liquid crystal layer or the like on the film. Can be.

Examples of the chain polyolefin resin include homopolymers of chain olefins such as polyethylene resin and polypropylene resin, and copolymers composed of two or more kinds of chain olefins.

Cyclic polyolefin resin is a general term for resins containing norbornene, tetracyclododecene (also known as dimethanooctahydronaphthalene) or a cyclic olefin typified by a derivative thereof as a polymerization unit. Specific examples of the cyclic polyolefin resin include a ring-opened (co) polymer of a cyclic olefin and a hydrogenated product thereof, an addition polymer of a cyclic olefin, a cyclic olefin and a chain olefin such as ethylene and propylene, or a vinyl group. It is a copolymer with an aromatic compound having, and a modified (co) polymer obtained by modifying these with an unsaturated carboxylic acid or a derivative thereof. Among them, a norbornene-based resin using a norbornene-based monomer such as a norbornene or a polycyclic norbornene-based monomer is preferably used as the cyclic olefin.

The cellulose ester resin is a resin in which at least a part of the hydroxyl group in cellulose is esterified with acetate, and even if it is a mixed ester in which a part is esterified with acetate and a part is esterified with another acid. good. The cellulose ester-based resin is preferably an acetyl cellulose-based resin. Specific examples of the acetyl cellulose-based resin include triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate and the like.

The polyester-based resin is a resin other than the above-mentioned cellulose ester-based resin having an ester bond, and is generally composed of a polyvalent carboxylic acid or a derivative thereof and a polycondensate of a polyhydric alcohol. Specific examples of the polyester-based resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethylterephthalate, and polycyclohexanedimethylnaphthalate. Of these, polyethylene terephthalate is preferable. The polyethylene terephthalate means a resin in which 80 mol% or more of the repeating unit is composed of ethylene terephthalate.
The polycarbonate resin is a polyester formed from carbonic acid and glycol or bisphenol.

The (meth) acrylic resin can be a polymer containing a methacrylic acid ester as a main monomer (containing 50% by mass or more), and a small amount of other copolymerization components are copolymerized with the polymer. It is preferably a polymer. The (meth) acrylic resin is more preferably a copolymer of methyl methacrylate and methyl acrylate, and a third monofunctional monomer may be further copolymerized.

Examples of the third monofunctional monomer include methacrylic acid such as ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and 2-hydroxyethyl methacrylate. Methacrylic acid esters other than methyl; acrylic acid esters such as ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate; 2- Hydroxyalkylacrylic acid esters such as methyl (hydroxymethyl) acrylate, methyl 2- (1-hydroxyethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, butyl 2- (hydroxymethyl) acrylate; methacrylic. Unsaturated acids such as acids, acrylic acids; halogenated styrenes such as chlorostyrene and bromostyrene; substituted styrenes such as vinyltoluene and α-methylstyrene; unsaturated nitriles such as acrylonitrile and methacrylic acid. Acrylic acid anhydrides, unsaturated acid anhydrides such as citraconic acid anhydride; unsaturated imides such as phenylmaleimide and cyclohexylmaleimide can be mentioned. As the third monofunctional monomer, only one kind may be used alone, or two or more kinds may be used in combination.

The (meth) acrylic resin may be further copolymerized with a polyfunctional monomer. Examples of the polyfunctional monomer include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and nonaethylene glycol di (meth). Esteration of both terminal hydroxyl groups of ethylene glycol or its oligomer such as acrylate, tetradecaethylene glycol di (meth) acrylate with (meth) acrylic acid; both terminal hydroxyl groups of propylene glycol or its oligomer is (meth) acrylic acid. Esterated with (meth) acrylic acid; the hydroxyl group of a dihydric alcohol such as neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate, butanediol di (meth) acrylate; Bisphenol A, an alkylene oxide adduct of Bisphenol A, or esterified of both terminal hydroxyl groups of these halogen substituents with (meth) acrylic acid; polyhydric alcohols such as trimethylolpropane, pentaerythritol (meth) acrylic. Those esterified with an acid and those in which an epoxy group of glycidyl (meth) acrylate is ring-opened and added to these terminal hydroxyl groups; dibasic acids such as succinic acid, adipic acid, terephthalic acid, phthalic acid, and halogen substituents thereof. , And those in which an epoxy group of glycidyl (meth) acrylate is ring-opened and added to these alkylene oxide adducts; aryl (meth) acrylate; aromatic divinyl compounds such as divinylbenzene and the like can be mentioned. Of these, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate are preferably used.

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

The glass transition temperature of the (meth) acrylic resin is preferably 80 to 160 ° C. The glass transition temperature is the polymerization ratio of the methacrylic acid ester-based monomer and the acrylic acid ester-based monomer, the carbon chain length of each ester group, the types of functional groups having them, and the polyfunctional monomer for the entire monomer. It can be controlled by adjusting the polymerization ratio of the monomer. It is also effective to introduce a ring structure into the main chain of the polymer as a means for increasing the glass transition temperature of the (meth) acrylic resin. The ring structure is preferably a heterocyclic structure such as a cyclic acid anhydride structure, a cyclic imide structure and a lactone structure.

The (meth) acrylic resin may contain an additive if necessary. Examples of the additive include a lubricant, an antiblocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a light resistant agent, an impact resistance improving agent, a surfactant and the like. These additives may be contained in a protective film made of a thermoplastic resin other than the (meth) acrylic resin.

The (meth) acrylic resin may contain acrylic rubber particles which are impact-improving agents from the viewpoint of film-forming property on the film, impact resistance of the film, and the like. Acrylic rubber particles are particles containing an elastic polymer mainly composed of an acrylic acid ester as an essential component, and have a single-layer structure substantially composed of only this elastic polymer, or one elastic polymer. Examples thereof include a multi-layer structure having layers.

The first protective film 10 and / or the second protective film 20 may contain an ultraviolet absorber. When the polarizing plate is applied to an image display device such as a liquid crystal display device, the image display element is deteriorated by ultraviolet rays by arranging a protective film containing an ultraviolet absorber on the visible side of the image display element (for example, a liquid crystal cell). Can be suppressed. Examples of the ultraviolet absorber include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex salt compounds and the like.

The first protective film 10 and the second protective film 20 may be films made of the same resin or may be made of different resins. Further, the first protective film 10 and the second protective film 20 may be the same or different in terms of thickness, presence / absence of additives, their types, retardation characteristics, and the like.

The first protective film 10 and / or the second protective film 20 has a hard coat layer, an antiglare layer, an antireflection layer, a light diffusion layer, an antistatic layer, and an antistatic layer on the outer surface thereof (the surface opposite to the polarizing film 30). It may have a surface treatment layer (coating layer) such as a dirty layer and a conductive layer.

The thicknesses of the first protective film 10 and the second protective film 20 are usually 5 to 200 μm, preferably 10 to 120 μm, and more preferably 10 to 85 μm, respectively. Reducing the thickness of the first protective film 10 and the second protective film 20 is advantageous for reducing the thickness of the polarizing plate and the image display device. The thinner the protective film, the easier it is for the curl resistance to decrease. However, according to the present invention, the curl resistance of the polarizing plate can be effectively improved even if the thickness of the first protective film 10 and the second protective film 20 is thin. Can be done.

(4) Adhesive Layer The first adhesive layer 15 is a cured product layer of the first cationic polymerization type adhesive containing one or more kinds of cationic polymerization initiators, and the second adhesive layer 25 is one or more kinds. It is a cured product layer of the second cationic polymerization type adhesive containing a cationic polymerization initiator.
The first and second cationically polymerizable adhesives usually contain a cationically polymerizable compound and a cationically polymerizable initiator, respectively.
The cationic polymerization initiator generates a cationic species or Lewis acid by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, or electron beams, and initiates a polymerization reaction of a cationically curable compound.

The above-mentioned one or more cationic polymerization initiators contained in the first cationic polymerization type adhesive include the first cationic polymerization initiator. The first cationic polymerization initiator includes a cationic component and the following formula (i):

(In the formula, Y indicates an aryl group having 6 to 30 carbon atoms or a heterocyclic group having 4 to 30 carbon atoms, or a halogen atom, which may have a substituent (excluding a group containing a halogen atom). Phf represents a phenyl group in which at least one of the hydrogen atoms is substituted with at least one selected from a perfluoroalkyl group, a perfluoroalkoxy group, and a halogen atom. K is an integer of 0 to 4. When there are a plurality of Ys, the plurality of Ys may be the same or different. When there are a plurality of Phfs, the plurality of Rhfs may be the same or different.)
It is a borate salt composed of an anion component represented by.

The above-mentioned one or more kinds of cationic polymerization initiators contained in the first cationic polymerization initiator and the second cationic polymerization type adhesive are the above-mentioned one kind in which the molecular weight of the first cationic polymerization initiator is contained in the second cationic polymerization type adhesive. It is selected so as to be larger than the molecular weight of the above cationic polymerization initiator. The molecular weight of the first cationic polymerization initiator is larger than the molecular weight of the above-mentioned one or more kinds of cationic polymerization initiators contained in the second cationic polymerization type adhesive, that is, the molecular weight of the first cationic polymerization initiator is the second cationic polymerization. It means that it is larger than the molecular weight of any of the cationic polymerization initiators contained in the mold adhesive.

The first cationic polymerization type adhesive can contain two or more kinds of first cationic polymerization initiators. When the first cationic polymerization type adhesive contains two or more kinds of first cationic polymerization initiators, the molecular weight of at least one first cationic polymerization initiator is any of the cationic polymerization initiators contained in the second cationic polymerization type adhesive. Although it may be larger than the molecular weight of the agent, the molecular weight of all the first cationic polymerization initiators is the second cationic polymerization type from the viewpoint of providing a polarizing plate having good curl resistance even when placed in a high humidity environment. It is preferably larger than the molecular weight of any of the cationic polymerization initiators contained in the adhesive.

According to the present invention, it is possible to provide a polarizing plate having good curl resistance even when placed in a high humidity environment. In particular, the first protective film 10 side is concave and the second protective film 20 side is convex. It is possible to effectively suppress the curl. It is considered that such an action effect is caused by using the above-mentioned predetermined borate salt as the first cationic polymerization initiator and satisfying the above-mentioned predetermined relationship with respect to the molecular weight of the cationic polymerization initiator.

(4-1) Cationic Polymerization Initiator The first cationic polymerization type adhesive forming the first adhesive layer 15 contains one or more kinds of cationic polymerization initiators, and the one or more kinds of cationic polymerization initiators are the first. Contains a cationic polymerization initiator. The first cationic polymerization initiator is a borate salt composed of a cationic component and an anionic component represented by the above formula (i).
The first cationic polymerization initiator may contain one or more types of cationic components, and may contain one or more types of anionic components represented by the formula (i).

Examples of the perfluoroalkyl group in the formula (i) include a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, a nonafluorobutyl group, a perfluoropentyl group, a perfluorooctyl group, and the like having one carbon number. A linear perfluoroalkyl group having a number of 8 to 8, preferably 1 to 4; a branched perfluoroalkyl group having 3 to 8 carbon atoms, preferably 3 to 4 carbon atoms such as a heptafluoroisopropyl group and a nonafluoroisobutyl group. Examples thereof include a perfluorocycloalkyl group having 3 to 8 carbon atoms, preferably 3 to 4 carbon atoms such as a perfluorocyclopropyl group and a perfluorocyclobutyl group.

Examples of the perfluoroalkoxy group in the formula (i) include a trifluoromethoxy group, a pentafluoroethoxy group, a heptafluoropropoxy group, a nonafluorobutoxy group, a perfluoropentyloxy group, a perfluorooctyloxy group and the like. A linear perfluoroalkoxy group having 1 to 8, preferably 1 to 4; a branched chain having 3 to 8 carbon atoms, preferably 3 to 4 carbon atoms such as a heptafluoroisopropoxy group and a nonafluoroisobutoxy group. Examples thereof include a perfluoroalkoxy group.

Examples of the halogen atom in the formula (i) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

Examples of Rhf include pentafluorophenyl group (C ₆ F ₅ ), trifluorophenyl group (C ₆ H ₂ F ₃ ), tetrafluorophenyl group (C ₆ HF ₄ ), and trifluoromethyl phenyl group (CF ₃ C). ₆ H ₄ ), bis (trifluoromethyl) phenyl group ((CF ₃ ) ₂ C ₆ H ₃ ), pentafluoroethyl phenyl group (CF ₃ CF ₂ C ₆ H ₄ ), bis (pentafluoroethyl) phenyl group ( (CF ₃ CF ₂ ) ₂ C ₆ H ₃ ), Fluoro-trifluoromethyl phenyl group (CF ₃ C ₆ H ₃ F), Fluoro-bis (trifluoromethyl) phenyl group ((CF ₃ ) ₂ C ₆ H ₂ ) F), fluoro-pentafluoroethyl phenyl group (CF ₃ CF ₂ C ₆ H ₃ F), fluoro-bis (pentafluoroethyl) phenyl group ((CF ₃ CF ₂ ) ₂ C ₆ H ₂ F) and the like can be mentioned. ..

Rhf is preferably a phenyl group in which at least one hydrogen atom is substituted with a halogen atom, and more preferably a phenyl group in which at least one hydrogen atom is substituted with a fluorine atom.

Examples of the aryl group having 6 to 30 carbon atoms in Y in the formula (i) include a phenyl group, a biphenyl group, a naphthyl group, an anthrasenyl group, a phenanthrenyl group and the like.
The heterocyclic group having 4 to 30 carbon atoms in Y in the formula (i) is a group obtained by removing one hydrogen atom from the heterocyclic ring having 4 to 30 carbon atoms. Examples of the heterocycle include a heterocycle containing an oxygen atom such as an oxetane ring, a tetrahydrofuran ring and a morpholin ring; a heterocycle containing a sulfur atom such as a thiophene ring and a thiazole ring; and a nitrogen atom such as a pyrrole ring, an imidazoline ring and an indole ring. Examples include heterocycles including.

The substituent that Y may have is a group other than the group containing a halogen atom, for example, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, and a group having 1 to 6 carbon atoms. Examples thereof include an alkoxy group, an alkylthio group having 1 to 6 carbon atoms, an arylthio group having 6 to 12 carbon atoms, and an alkylcarbonyl group having 2 to 7 carbon atoms. When Y has a plurality of substituents, each of these substituents may be the same or different.

k is preferably an integer of 0 to 2, more preferably an integer of 0 or 1.
It is more preferably 0.

When there are a plurality of Phfs (when k represents an integer of 0 to 2), the plurality of Rhfs are preferably the same group, and all Rhfs are phenyl groups in which at least one hydrogen atom is substituted with a fluorine atom. Is more preferable.

Among them, from the viewpoint of curl resistance of the polarizing plate, the anion component represented by the formula (i) is an anion in which k is 0 and Rhf is a phenyl group in which at least one hydrogen atom is substituted with a halogen atom. It is preferably a component, and more preferably an anionic component in which k is 0 and Rhf is a pentafluorophenyl group (C ₆ F ₅ ). The anion component of the first cationic polymerization initiator is preferably tetrakis (pentafluorophenyl) borate anion B (C ₆ F ₅ ) 4- ^or the like.

Examples of the cationic component of the first cationic polymerization initiator include aryl sulfonium ions, aryl iodonium ions, aryl diazonium ions and the like. Examples of the aryl sulfonium ion include a triphenyl sulfonium cation, a 4,4'-bis (diphenyl sulfonio) diphenyl sulfide cation and the like. Examples of the aryl iodonium ion include a diphenyl iodonium cation. Examples of the aryl diazonium ion include a benzenediazonium cation.
Of these, aryl sulfonium ions are preferable from the viewpoint of curl resistance of the polarizing plate. From the viewpoint of curl resistance of the polarizing plate, the cationic component of the first cationic polymerization initiator more preferably contains 4,4'-bis (diphenylsulfonate) diphenylsulfide cation.

From the viewpoint of curl resistance of the polarizing plate, it is preferable that the first cationic polymerization type adhesive contains only the first cationic polymerization initiator as the cationic polymerization initiator.

The molecular weight of the first cationic polymerization type initiator may be 900 or more, 1000 or more, 1500 or more, 1900 or more, or 3000 or less. Well, it may be 2500 or less.

The second cationically polymerizable adhesive forming the second adhesive layer 25 contains one or more cationic polymerization initiators. As described above, the cationic polymerization initiator contained in the second cationic polymerization type adhesive is the above-mentioned one or more kinds of cationic polymerization initiators in which the molecular weight of the first cationic polymerization initiator is contained in the second cationic polymerization type adhesive. It is selected to be larger than the molecular weight. Hereinafter, one or more types of cationic polymerization initiators contained in the second cationic polymerization type adhesive are also collectively referred to as “second cationic polymerization initiator”.
The second cationic polymerization initiator may contain one or more types of cationic components, and may contain one or more types of anionic components.

Specifically, examples of the second cationic polymerization initiator include aryl sulfonium salts, aryl iodonium salts, aryl diazonium salts, iron-allene complexes and the like.
Examples of the cation component constituting the aryl sulfonium salt include aryl sulfonium ions such as triphenyl sulfonium cation and 4,4'-bis (diphenyl sulfonate) diphenyl sulfide cation. Examples of the cation component constituting the aryliodonium salt include aryliodonium ions such as diphenyliodonium cations. Examples of the cation component constituting the aryldiazonium salt include aryldiazonium ions such as benzenediazonium cations. The iron-arene complex is, for example, cyclopentadienyl iron (II) arene cationic complex salt.

In one preferred embodiment, the cationic component of the first cationic polymerization initiator and the cationic component of the second cationic polymerization initiator are both from the viewpoint of curl resistance of the polarizing plate and adhesion between the polarizing film and the protective film. It is an aryl sulfonium ion. In one preferred embodiment, the cationic component of the first cationic polymerization initiator and the cationic component of the second cationic polymerization initiator are both triphenylsulfonium cations and / or 4,4'-bis (diphenylsulfonate) diphenylsulfides. It is a cation.

The anion component constituting the second cationic polymerization initiator includes a special phosphorus anion [(Rf) _n PF _6-n ] ^- (n represents an integer of 1 to 6 and Rf represents an alkyl halide group). Hexafluorophosphate anion PF _6- , hexafluoroantimonate anion SbF _6- ^, pentafluorohydroxyantimonate anion SbF ₅ (OH) ^- ^, hexafluoroarsenate anion AsF _6- ^, tetrafluoroborate anion BF _4- ^, tetrakis (penta). Fluorophenyl) Borate anion B (C ₆ F ₅ ) ₄ ^- etc. A preferred example is the hexafluorophosphate anion PF ₆ ⁻ .

From the viewpoint of curl resistance of the polarizing plate, in one preferred embodiment, the anion component of the first cationic polymerization initiator is the anion represented by the above formula (i), and the anion of the second cationic polymerization initiator. ^The component is PF _6- . From the viewpoint of curl resistance of the polarizing plate, in one preferred embodiment, the anionic component of the first cationic polymerization initiator is B ₍ C6 F ₅ ) _4- ^, and the anionic component of the second cationic polymerization initiator. Is ^PF _6- .
From the viewpoint of curl resistance of the polarizing plate, the cationic polymerization initiator contained in the second cationic polymerization type adhesive preferably does not have an anion component represented by the above formula (i), and is not a borate anion. Is more preferable.

The molecular weight of the second cationic polymerization initiator is not particularly limited as long as it is smaller than the molecular weight of the first cationic polymerization initiator, but it may be 1000 or less, 800 or less, or 600 or less. , 200 or more.

The content of the cationic polymerization initiator contained in the first cationically polymerizable adhesive (the total content of two or more kinds of cationic polymerization initiators if they are contained) and the cation contained in the second cationically polymerizable adhesive. The content of the polymerization initiator (when two or more kinds of cationic polymerization initiators are contained, the total content thereof) is usually 0.5 parts by mass or more and 10 parts by mass with respect to 100 parts by mass of the cationically polymerizable compound. It is 5 parts by mass or less, preferably 0.5 parts by mass or more and 5 parts by mass or less, and more preferably 1.0 part by mass or more and 5 parts by mass or less. From the viewpoint of the wet and heat durability of the polarizing plate, the content is more preferably 1.3 parts by mass or more.
If the amount of the cationic polymerization initiator is excessively large, the amount of ionic substances in the adhesive layer increases, so that the hygroscopicity of the adhesive layer increases, and the durability of the polarizing plate may decrease.

(4-2) Cationic Polymerizable Compound The cationically polymerizable compound contained in the first cationically polymerizable adhesive and the second cationically polymerizable adhesive is irradiated with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. A compound or oligomer in which the cationic polymerization reaction proceeds and is cured, and examples thereof include an epoxy compound, an oxetane compound, and a vinyl compound. Among them, the preferable cationically polymerizable compound is an epoxy compound. The epoxy compound is a compound having one or more, preferably two or more epoxy groups in the molecule. Only one type of epoxy compound may be used alone, or two or more types may be used in combination. Examples of the epoxy compound include an alicyclic epoxy compound, an aromatic epoxy compound, a hydrogenated epoxy compound, and an aliphatic epoxy compound. Above all, from the viewpoint of weather resistance, curing speed and adhesiveness, the epoxy compound preferably contains an alicyclic epoxy compound or an aliphatic epoxy compound, and more preferably contains an alicyclic epoxy compound.
The first cationically polymerizable adhesive and the second cationically polymerizable adhesive may contain one or more cationically polymerizable compounds.

The alicyclic epoxy compound is a compound having one or more epoxy groups bonded to the alicyclic ring in the molecule. The "epoxide group bonded to the alicyclic ring" means a bridging oxygen atom-O- in the structure represented by the following formula (I). In the following formula (I), m is an integer of 2 to 5.

A compound in which one or more hydrogen atoms in the (CH ₂ ) _m in the above formula (I) are removed and a group bonded to another chemical structure can be an alicyclic epoxy compound. One or more hydrogen atoms in (CH ₂ ) _m may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group.

Among them, the alicyclic epoxy compound having an epoxycyclopentane structure [m = 3 in the above formula (I)] and an epoxycyclohexane structure [m = 4 in the above formula (I)] is a cured glass. The transition temperature is high, which is advantageous in increasing the glass transition temperature of the adhesive layer, and is also advantageous in terms of the adhesiveness between the polarizing film and the protective film. Specific examples of the alicyclic epoxy compound are given below. Here, the compound names are first listed, and then the chemical formulas corresponding to the respective compounds are shown, and the compound names and the corresponding chemical formulas are given the same reference numerals.

A: 3,4-Epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,
B: 3,4-Epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate,
C: Ethylene bis (3,4-epoxycyclohexanecarboxylate),
D: Bis (3,4-epoxycyclohexylmethyl) adipate,
E: Bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate,
F: Diethylene glycol bis (3,4-epoxycyclohexylmethyl ether),
G: Ethylene glycol bis (3,4-epoxycyclohexylmethyl ether),
H: 2,3,14,15-Diepoxy-7,11,18,21-Tetraoxatrispyro [5.2.2.5.2.2] Heneicosane,
I: 3- (3,4-epoxycyclohexyl) -8,9-epoxy-1,5-dioxaspiro [5.5] undecane,
J: 4-Vinylcyclohexene dioxide,
K: Limonene Geoxide,
L: Bis (2,3-epoxycyclopentyl) ether,
M: Dicyclopentadiene dioxide.

An aromatic epoxy compound is a compound having an aromatic ring and an epoxy group in the molecule. Specific examples thereof include bisphenol type epoxy compounds such as bisphenol A diglycidyl ether, bisfer F diglycidyl ether, and bisphenol S diglycidyl ether or oligomers thereof; phenol novolac epoxy resin, cresol novolac epoxy resin, hydroxybenzaldehyde phenol novolac. Novolak type epoxy resin such as epoxy resin; polyfunctional epoxy such as 2,2', 4,4'-tetrahydroxydiphenylmethane glycidyl ether, 2,2', 4,4'-tetrahydroxybenzophenone glycidyl ether Compounds; Containing polyfunctional epoxy resins such as epoxidized polyvinylphenol.

The hydrogenated epoxy compound is a glycidyl ether of a polyol having an alicyclic ring, and is a nuclear hydrogenated poly obtained by selectively hydrogenating an aromatic polyol in the aromatic ring under pressure in the presence of a catalyst. The hydroxy compound can be glycidyl etherified. Specific examples of the aromatic polyol include bisphenol type compounds such as bisphenol A, bisfer F and bisphenol S; novolak type resins such as phenol novolac resin, cresol novolak resin and hydroxybenzaldehyde phenol novolac resin; tetrahydroxydiphenylmethane and tetrahydroxy. Contains polyfunctional compounds such as benzophenone and polyvinylphenol. A glycidyl ether can be obtained by reacting an alicyclic polyol obtained by hydrogenating the aromatic ring of an aromatic polyol with epichlorohydrin. Among the hydrogenated epoxy compounds, the diglycidyl ether of hydrogenated bisphenol A can be mentioned.

The aliphatic epoxy compound is a compound having at least one oxylan ring (3-membered cyclic ether) bonded to an aliphatic carbon atom in the molecule. For example, monofunctional epoxy compounds such as butyl glycidyl ether and 2-ethylhexyl glycidyl ether; 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4- Bifunctional epoxy compounds such as cyclohexanedimethanol diglycidyl ether; trifunctional or higher functional epoxy compounds such as trimethylolpropane triglycidyl ether and pentaerythritol tetraglycidyl ether; alicyclic such as 4-vinylcyclohexenedioxide and limonendioxide. There are epoxy compounds having one epoxy group directly bonded to the formula ring and an oxylan ring bonded to an aliphatic carbon atom. Of these, a bifunctional epoxy compound (also referred to as an aliphatic diepoxy compound) having two oxylan rings bonded to an aliphatic carbon atom in the molecule is preferable from the viewpoint of adhesiveness between the polarizing film and the protective film. Such a suitable aliphatic diepoxy compound can be represented by, for example, the following formula (II).

Y in the above formula (II) is an alkylene group having 2 to 9 carbon atoms, an alkylene group having 4 to 9 total carbon atoms intervening with an ether bond, or a divalent group having 6 to 18 carbon atoms having an alicyclic structure. It is a hydrocarbon group of.

Specifically, the aliphatic diepoxy compound represented by the above formula (II) is a diglycidyl ether of an alkane diol, a diglycidyl ether of an oligoalkylene glycol up to about 4 repetitions, or a diglycidyl ether of an alicyclic diol. Is.

Specific examples of the diol (glycol) capable of forming the aliphatic diepoxy compound represented by the above formula (II) are listed below. Alcandiols include ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, and 1,4-butanediol. , Neopentyl glycol, 3-methyl-2,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentane Diol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3,5-heptanediol, 1,8-octanediol, 2-methyl-1,8 -There are octanediol, 1,9-nonanediol and the like. Examples of the oligoalkylene glycol include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol and the like. Examples of the alicyclic diol include cyclohexanediol such as 1,2-cyclohexanediol, 1,3-cyclohexanediol, and 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1, There are cyclohexanedimethanol and the like such as 4-cyclohexanedimethanol.

An oxetane compound, which is one of the cationically polymerizable compounds, is a compound containing one or more oxetane rings (oxetaneyl groups) in the molecule, and specific examples thereof are 3-ethyl-3-hydroxymethyloxetane (oxetane alcohol). Also called), 2-ethylhexyloxetane, 1,4-bis [{(3-ethyloxetane-3-yl) methoxy} methyl] benzene (also called xylylenebis oxetane), 3-ethyl-3 [{( 3-Ethyloxetane-3-yl) methoxy} methyl] oxetane, 3-ethyl-3- (phenoxymethyl) oxetane, 3- (cyclohexyloxy) methyl-3-ethyloxetane. The oxetane compound may be used as the main component of the cationically polymerizable compound, or may be used in combination with the epoxy compound. By using an oxetane compound in combination, the curing speed and adhesiveness may be improved.

Examples of the vinyl compound that can be a cationically polymerizable compound include an aliphatic or alicyclic vinyl ether compound, and specific examples thereof include n-amyl vinyl ether, i-amyl vinyl ether, n-hexyl vinyl ether, and n-octyl vinyl ether. , 2-Ethylhexyl vinyl ether, n-dodecyl vinyl ether, stearyl vinyl ether, oleyl vinyl ether and other alkyl or alkenyl alcohol vinyl ethers having 5 to 20 carbon atoms; 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether and the like. Hydroxyl group-containing vinyl ether; monoalcohol vinyl ether having an aliphatic ring or aromatic ring such as cyclohexyl vinyl ether, 2-methylcyclohexylvinyl ether, cyclohexylmethylvinyl ether, benzylvinyl ether; glycerol monovinyl ether, 1,4-butanediol monovinyl ether, 1, 4-Butanediol divinyl ether, 1,6-hexanediol divinyl ether, neopentyl glycol divinyl ether, pentaerythritol divinyl ether, pentaerythritol tetravinyl ether, trimethylolpropane divinyl ether, trimethylolpropanetrivinyl ether, 1,4-dihydroxycyclohexane Mono-polyvinyl ethers of polyvalent alcohols such as monovinyl ether, 1,4-dihydroxycyclohexanedivinyl ether, 1,4-dihydroxymethylcyclohexanemonovinyl ether, 1,4-dihydroxymethylcyclohexanedivinyl ether; diethylene glycol divinyl ether, triethylene glycol di Polyalkylene glycol mono-divinyl ethers such as vinyl ethers and diethylene glycol monobutyl monovinyl ethers; other vinyl ethers such as glycidyl vinyl ethers and ethylene glycol vinyl ether methacrylates. The vinyl compound may be used as a main component of the cationically polymerizable compound, or may be used in combination with an epoxy compound, or an epoxy compound and an oxetane compound. By using a vinyl compound in combination, it may be possible to improve the curing speed and the low viscosity of the adhesive.

The cationically polymerizable adhesive can further contain other cationically polymerizable compounds other than the above, such as a cyclic lactone compound, a cyclic acetal compound, a cyclic thioether compound, and a spiro ortho ester compound.

From the viewpoint of the adhesiveness between the polarizing film and the protective film, when the total amount of the curable compound contained in the cationically polymerized adhesive is 100% by mass in the first and second cationically polymerized adhesives, the cationic polymerization is carried out. The content of the sex compound (the content of all the cationically polymerizable compounds contained in the cationically polymerizable adhesive, and the total content of two or more kinds of cationically polymerizable compounds when they are contained) is 50 mass by mass. % Or more, more preferably 60% by mass or more, further preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 100% by mass. preferable.

The cationically polymerizable compound contained in the first cationically polymerizable adhesive and the cationically polymerizable compound contained in the second cationically polymerizable adhesive may be of the same type or different from each other.

(4-3) Additives The first and / or second cationically polymerized adhesives may contain other additives, if necessary. Examples of the additive include an ion trapping agent, an antioxidant, a chain transfer agent, a polymerization accelerator (polyol, etc.), a sensitizer, a sensitizing aid, a light stabilizer, a tackifier, a thermoplastic resin, and a filler. , Flow conditioner, plasticizer, defoaming agent, leveling agent, silane coupling agent, dye, antistatic agent, ultraviolet absorber.

(4-4) Coating of Adhesive and Adhesion between Polarizing Film and Protective Film The first protective film 10 is laminated and adhered to one surface of the polarizing film 30 via the first adhesive layer 15, and the polarizing film 30 is laminated. The polarizing plate according to the present invention can be obtained by laminating and adhering the second protective film 20 to the other surface of the film via the second adhesive layer 25. The first protective film 10 and the second protective film 20 (collectively referred to as simply "protective film") may be laminated and adhered one side at a time, or the protective films on both sides may be laminated in one step. It may be glued.

To bond the polarizing film 30 and the protective film, specifically, an adhesive is applied to the bonding surface of the polarizing film 30 and / or the bonding surface of the protective film, and both are coated via the coating layer of the adhesive. This can be done by stacking the films of the above, pressing them from above and below using, for example, a bonding roll or the like, bonding them, and then irradiating them with active energy rays to cure them. When the active energy ray-curable adhesive is used, the heat treatment may be performed at the same time as the irradiation with the active energy ray or after the irradiation with the active energy ray. Before forming the coating layer of the adhesive, one or both of the bonding surfaces of the polarizing film 30 and the protective film are subjected to saponification treatment, corona discharge treatment, plasma treatment, flame treatment, primer treatment, and anchor coating treatment. The easy-adhesion treatment such as the above may be applied.

For the formation of the coating layer of the adhesive, for example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Further, it is also possible to adopt a method in which the polarizing film 30 and the protective film are continuously supplied so that the bonding surface of both is on the inside, and the adhesive is spread between them.

From the viewpoint of coatability, it is preferable that the adhesive forming the first adhesive layer 15 and the second adhesive layer 25 has a low viscosity. Specifically, the viscosity at 25 ° C. is preferably 1000 mPa · s or less, more preferably 500 mPa · s or less, still more preferably 100 mPa · s or less. The adhesive may be solvent-free, but may contain an organic solvent in order to adjust the viscosity to be suitable for the coating method to be adopted.

The light source of the active energy ray may be, for example, one that generates ultraviolet rays, electron beams, X-rays, or the like. The active energy ray is preferably ultraviolet light. As the ultraviolet light source, a light source having a light emission distribution having a wavelength of 400 nm or less is preferable, and examples thereof include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excited mercury lamp, and a metal halide lamp. be able to.

The intensity of irradiating the adhesive layer with active energy rays is determined for each adhesive composition, but the intensity of irradiating light in the wavelength region effective for activating the photopolymerization initiator is 0.1 to 1000 mW / cm ² . It is preferable to do so. If the light irradiation intensity is too low, the reaction time will be too long, while if the light irradiation intensity is too high, the heat radiated from the lamp and the heat generated during the polymerization of the adhesive will cause yellowing and polarization of the adhesive layer. There is a possibility that the film 30 may be deteriorated or the protective film may be poorly skinned. The light irradiation time to the adhesive is also controlled for each adhesive composition, but the integrated light amount expressed as the product of the light irradiation intensity and the light irradiation time is set to be 10 to 5000 mJ / cm ² . Is preferable. If the integrated light intensity is too small, the active species derived from the photopolymerization initiator may not be sufficiently generated, and the resulting adhesive layer may be insufficiently cured. On the other hand, if the integrated light intensity is too large, the light intensity may be insufficient. The irradiation time becomes very long, which tends to be disadvantageous for improving productivity.

The timing of laminating the protective film on the polarizing film 30 via the coating layer of the adhesive and the timing of curing the coating layer are not particularly limited. For example, after laminating one protective film, the coating layer can be continuously cured, and then the other protective film can be laminated to cure the coating layer. Alternatively, after laminating both protective films sequentially or simultaneously, the coating layers on both sides may be cured at the same time. Further, the irradiation of the active energy rays may be performed from either protective film side. For example, when one protective film contains an ultraviolet absorber and the other protective film does not contain an ultraviolet absorber, it is preferable to irradiate active energy rays from the protective film side that does not contain the ultraviolet absorber. By irradiating in this way, the irradiated active energy rays can be effectively used and the curing rate can be increased.

The thickness of the first and second

adhesive layers

15 and 25 after curing is usually 20 μm or less, preferably 10 μm or less, more preferably 5 μm or less, still more preferably less than 5 μm, and particularly preferably 3 μm or less. If the thicknesses of the first and second

adhesive layers

15 and 25 are excessively large, the reaction rate of the adhesive tends to decrease, and the wet and heat durability of the polarizing plate tends to deteriorate. The thicknesses of the first and second

adhesive layers

15 and 25 are usually 0.01 μm or more, preferably 0.1 μm or more, and more preferably 0.5 μm or more. If the thickness of the first and second

adhesive layers

15 and 25 is too thin, the first adhesive layer and the second adhesive may have fine defects (fine dust, fine dust, etc.) on the polarizing film 30. Other layers (first protective film 10, second protective film 20, etc.) laminated via the layer may also be affected by fine defects. The first adhesive layer 15 and the second adhesive layer 25 may have the same thickness or different thicknesses.

(5) Preferred Configuration of Polarizing Plate The curl resistance effect can be effectively obtained even when placed in a high humidity environment. In particular, the first protective film 10 side is concave and the second protective film 20 side is concave. Since the convex curl can be effectively suppressed, the polarizing plate preferably has the following configuration, for example.
[A] The first protective film 10 and the second protective film 20 are films made of different resins.
[B] In the above [a], the first protective film 10 is a (meth) acrylic resin film or a cellulose ester resin film.
[C] In the above [b], the second protective film 20 is a cyclic polyolefin resin film.
[D] In any of the above [a] to [c], the first cationic polymerization initiator is a borate salt composed of a cationic component which is an arylsulfonium ion and an anion component represented by the above formula (i). The second cationic polymerization initiator contains a cationic polymerization initiator containing PF ₆ ⁻ as an anionic component.
[E] In the above [d], the first cationic polymerization initiator is a borate salt composed of a cationic component which is an aryl sulfonium ion ^and an anion component which is B (C ₆ F ₅ ) _4- .
[F] In the above [d] or [e], the second cationic polymerization initiator contains a cationic polymerization initiator composed of a cationic component which is an aryl sulfonium ion and an anionic component which is PF ₆ ⁻ .
[G] In any of the above [a] to [f], the first cationic polymerization type adhesive contains only the first cationic polymerization initiator, and the second cationic polymerization type adhesive contains a cationic component which is an aryl sulfonium ion. It contains only a cationic polymerization initiator composed of an anionic component of PF ₆ ⁻ .
[H] In the above [g], the cationic component of the first cationic polymerization initiator is a triphenylsulfonium cation and / or a 4,4'-bis (diphenylsulfonio) diphenylsulfide cation, and the second cationic polymerization type adhesive. The cationic component of the cationic polymerization initiator contained in the above is a triphenylsulfonium cation and / or a 4,4'-bis (diphenylsulfonio) diphenylsulfide cation.

When the polarizing plate is incorporated in the image display device, the polarizing plate is typically arranged so that the first protective film 10 side is the visual recognition side and the second protective film 20 side is the image display element side.

(6) Other Components of Polarizing Plate (6-1) Optical Functional Film The polarizing plate can be provided with an optical functional film other than the polarizing film 30 for imparting a desired optical function. A suitable example thereof is a retardation film. As described above, the first protective film 10 and / or the second protective film 20 can also serve as the retardation film, but the retardation film can also be laminated separately from the protective film. In the latter case, the retardation film can be laminated on the outer surface of the first protective film 10 and / or the second protective film 20 via the pressure-sensitive adhesive layer and the adhesive layer.

Specific examples of the retardation film include a birefringent film composed of a stretched film of a translucent thermoplastic resin, a film in which a discotic liquid crystal or a nematic liquid crystal is oriented and fixed, and the above liquid crystal layer on a base film. Includes those formed. The base film is usually a thermoplastic resin film, and a cellulose ester resin such as triacetyl cellulose is preferably used as the thermoplastic resin.

Examples of other optically functional films (optical members) that may be included in the polarizing plate include a condenser plate, a brightness improving film, a reflective layer (reflective film), a semi-transmissive reflective layer (semi-transmissive reflective film), and a light diffusing layer (light). Diffusing film) etc. These are generally provided when the polarizing plate is a polarizing plate arranged on the back surface side (backlight side) of the liquid crystal cell.

(6-2) Adhesive Layer The polarizing plate according to the present invention may include an adhesive layer for attaching the polarizing plate to an image display element such as a liquid crystal cell or another optical member. The pressure-sensitive adhesive layer can be laminated on the outer surface of the protective film. The pressure-sensitive adhesive layer may be laminated on the outer surface of the first protective film, or may be laminated on the outer surface of the second protective film.

When the polarizing plate has a pressure-sensitive adhesive layer, it is preferable that the polarizing plate has a pressure-sensitive adhesive layer on the side opposite to the side of the second adhesive layer 25 in the second protective film 20. This pressure-sensitive adhesive layer is typically a pressure-sensitive adhesive layer for adhering a polarizing plate to an image display element.

As the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer, a (meth) acrylic resin, a silicone-based resin, a polyester-based resin, a polyurethane-based resin, a polyether-based resin, or the like as a base polymer can be used. Among them, a (meth) acrylic pressure-sensitive adhesive is preferably used from the viewpoints of transparency, adhesive strength, reliability, weather resistance, heat resistance, reworkability and the like. The (meth) acrylic pressure-sensitive adhesive includes (meth) acrylic acid alkyl esters having an alkyl group having 20 or less carbon atoms such as a methyl group, an ethyl group and a butyl group, and (meth) acrylic acid and (meth) acrylic acid. A functional group-containing (meth) acrylic monomer such as hydroxyethyl is blended so that the glass transition temperature is preferably 25 ° C. or lower, more preferably 0 ° C. or lower, and the weight average molecular weight is 100,000 or more (meth). Acrylic resins are useful as base polymers.

For the formation of the pressure-sensitive adhesive layer on the polarizing plate, for example, the pressure-sensitive adhesive composition is dissolved or dispersed in an organic solvent such as toluene or ethyl acetate to prepare a solution of 10 to 40% by mass, and this is used as the target surface of the polarizing plate. A method of forming an adhesive layer by directly coating on a sheet, or a method of forming an adhesive layer in the form of a sheet on a separate film that has been subjected to a mold release treatment and transferring it to the target surface of the polarizing plate. It can be done by such as. The thickness of the pressure-sensitive adhesive layer is determined according to the adhesive strength and the like, but is appropriately in the range of about 1 to 50 μm, preferably 2 to 40 μm.

The polarizing plate may include the above-mentioned separate film. The separate film can be a film made of a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate, or the like. Of these, a stretched film of polyethylene terephthalate is preferable.

The pressure-sensitive adhesive layer contains, if necessary, a filler made of glass fiber, glass beads, resin beads, metal powder or other inorganic powder, a pigment, a colorant, an antioxidant, an ultraviolet absorber, an antioxidant, and the like. It may have been done.

(6-3) Protective film The polarizing plate according to the present invention may include a protective film for temporarily adhering and protecting the surface (protective film surface) thereof. After the polarizing plate is attached to, for example, an image display element or another optical member, the protective film is peeled off and removed together with the pressure-sensitive adhesive layer contained therein.

The protect film is composed of a base film and an adhesive layer laminated on the base film. The above description is cited for the pressure-sensitive adhesive layer. The resin constituting the base film is, for example, a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate, or a thermoplastic resin such as a polycarbonate resin. be able to. A polyester resin such as polyethylene terephthalate is preferable.

The polarizing plate of the present invention can be attached to an image display element such as a liquid crystal cell via an adhesive layer. Examples of the liquid crystal cell include an IPS type and a VA type. Further, the polarizing plate of the present invention can be bonded to an organic EL panel as an antireflection polarizing plate via an adhesive layer.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these examples. In the following examples, the following are used as the cationically polymerizable compound constituting the cationically polymerizable adhesive and the cationically polymerizable initiator.

[1] Cationic polymerizable compound A-1: 3', 4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (manufactured by Daicel Corporation, trade name "CEL2021P")
[2] Cationic Polymerizable Compound A-2: Neopentyl Glycol Diglycidyl Ether (manufactured by Nagase ChemteX Corporation, trade name "EX-211L")
[3] Cationic polymerizable compound A-3: 4-hydroxybutyl vinyl ether (manufactured by Nippon Carbide, trade name "HBVE")
[4] Cationic Polymerizable Compound A-4: Methyl Methacrylate-Glyzyl Methacrylic Acid Ether Copolymer (Cationic Polymerizable Polymer) (manufactured by NOF CORPORATION, trade name "Marproof G-01100")
[5] Cationic Polymerization Initiator B-1: A cationic polymerization initiator composed of the following cationic component and anionic component. A mixture of a compound having a molecular weight of 1050 and a compound having a molecular weight of 1915 (manufactured by Estchem Co., Ltd., trade name "PAG-20008").

[6] Cationic polymerization initiator B-2: A cationic polymerization initiator composed of the following cationic and anionic components. Molecular weight 517 (manufactured by Sun Appro Co., Ltd., trade name "CPI-100P")

<Production Examples 1 to 14: Preparation of Cationic Polymerized Adhesive>
The cationically polymerizable compounds and cationic polymerization initiators shown in Table 1 were mixed at the blending ratios shown in Table 1 and defoamed to prepare liquid cationically polymerizable adhesives A to N, respectively. The numerical values in Table 1 indicate parts by mass. The cationic polymerization initiators B-1 and B-2 were blended as a 50% by mass propylene carbonate solution, and the numerical values shown in Table 1 are the amounts of the solid content contained therein.

<Examples 1 to 7, Comparative Examples 1 to 2>
(1) Preparation of Polarizing Plate One side of the first protective film shown in Table 2 is subjected to corona discharge treatment, and the first cationically polymerizable adhesive shown in Table 2 is applied to the corona discharge treated surface using a bar coater. The coating was applied so that the thickness after curing was about 5 μm. Next, a polyvinyl alcohol (PVA) -iodine-based polarizing film having a thickness of 25 μm was attached to the coated surface. Next, one side of the second protective film shown in Table 2 is subjected to corona discharge treatment, and the thickness of the second cationically polymerizable adhesive shown in Table 2 after curing is applied to the corona discharge treated surface using a bar coater. Was applied so that the thickness was about 5 μm. The polarizing film with the first protective film produced above was laminated on the coated surface on the polarizing film side, and pressed and bonded using a bonding roll to obtain a laminated body. From the second protective film side of this laminated body, the integrated light intensity is 200 mJ / cm ² (UVB) using an ultraviolet irradiation device with a belt conveyor [the lamp uses a "D valve" manufactured by Fusion UV Systems). A polarizing plate was produced by irradiating ultraviolet rays so as to obtain the above, and curing the adhesive layers on both sides.

When the obtained polarizing plate is incorporated in an image display device, the polarizing plate is arranged so that the second protective film (phase difference film) side is the image display element side and the first protective film side is the visual recognition side. To.

The details of the first protective film and the second protective film shown in Table 2 are as follows.
[1] Protective film a: A (meth) acrylic resin film having a thickness of 60 μm containing an ultraviolet absorber. The (meth) acrylic resin constituting the film is a copolymer obtained by copolymerizing methyl methacrylate and methyl acrylate at a mass ratio of 96: 4.
[2] Protective film b: Cellulose ester-based resin film with a thickness of 60 μm (manufactured by Fuji Photo Film Co., Ltd., trade name “TG”)
[3] Protective film c: A retardation film having a thickness of 50 μm made of a cyclic polyolefin resin (norbornene resin) (manufactured by Nippon Zeon Corporation, trade name “ZEONOR”).
[4] Protective film d: A retardation film having a thickness of 40 μm made of (meth) acrylic resin (manufactured by LG Chem Co., Ltd., trade name “GA-01”).

(2) Evaluation of curl resistance of the polarizing plate in a high humidity environment From the polarizing plate produced in (1) above, a single-wafer body having a size of 8 cm × 8 cm was cut out in an environment of a temperature of 25 ° C. and a relative humidity of 55%. .. In this single-wafer body, a set of two opposing sides is parallel to the absorption axis direction of the polarizing film. At this time, the sheet-fed body was not curled (curl amount 0 mm). After leaving this sheet-fed body in an environment of a temperature of 25 ° C. and a relative humidity of 90% for 2 hours, the curl amount of the sheet-fed body was measured. The amount of curl was obtained by placing a curved sheet of leaf on a horizontal table so that it was convex downward, and measuring the height from the table to the four corners of the sheet with a ruler. It was calculated as the average value of the points. Based on the obtained curl amount, the curl resistance was evaluated according to the following criteria. The evaluation results are shown in Table 2.

5: No curl or curl amount is 1 mm or less 4: Curl amount is more than 1 mm and 2 mm or less 3: Curl amount is more than 2 mm and 5 mm or less 2: Curl amount is more than 5 mm and 20 mm or less 1: The curl is too strong and the polarizing plate is curled up.

(3) Formation of adhesive layer (meth) An organic solvent solution of an acrylic adhesive is dried on the release-treated surface of a separate film having a thickness of 38 μm made of polyethylene terephthalate that has undergone a mold release treatment with a die coater. Was applied so that the thickness of the adhesive was 20 μm to prepare a sheet-like adhesive with a separate film. Next, the surface of the second protective film of the polarizing plate produced in (1) above is subjected to a corona discharge treatment, and the surface of the corona discharge treated surface is opposite to the surface of the sheet-like pressure-sensitive adhesive obtained above (adhesive). The surface) was bonded with a laminator and then cured at a temperature of 23 ° C. and a relative humidity of 65% for 7 days to obtain a polarizing plate having an adhesive layer.

(4) Evaluation of Moist Heat Durability of Polarizing Plate A single-wafer body having a size of 3 cm × 3 cm was cut out from the polarizing plate having the pressure-sensitive adhesive layer prepared in (3) above. In this single-wafer body, a set of two opposing sides is parallel to the absorption axis direction of the polarizing film. The separate film was peeled off from this sheet-fed body, and the exposed pressure-sensitive adhesive layer surface was attached to a glass substrate. For the glass substrate, Corning's non-alkali glass product name "Eagle XG" was used. The obtained optical laminate was measured for MD transmittance and TD transmittance in the wavelength range of 380 to 780 nm using a spectrophotometer with an integrating sphere (manufactured by Nippon Spectroscopy Co., Ltd., product name "V7100"). The single transmittance at the wavelength was calculated. The calculated single transmittance is corrected for luminosity factor by the double field (C light source) of JIS Z ₈₇₀₁ : 1999 "Color display method _- XYZ color system and _X10 Y10 Z10 color system", and the humidity and heat endurance. The luminous efficiency correction single transmittance (Ty) before the test was determined. The optical laminate was set in a spectrophotometer with an integrating sphere so that the first protective film surface side of the polarizing plate was the detector side and the light entered from the glass substrate side.

The simple substance transmittance (%) is calculated by the following formula:
It is defined by the simple substance transmittance (λ) = (Tp (λ) + Tc (λ)) / 2.
Tp (λ) is the transmittance (%) of the measurement sample measured in relation to the linear polarization of the incident wavelength λ (nm) and the parallel Nicol.
Tc (λ) is the transmittance (%) of the measurement sample measured in relation to the linear polarization of the incident wavelength λ (nm) and the cross Nicol.

Next, the optical laminate was placed in a moist heat environment with a temperature of 80 ° C. and a relative humidity of 90% for 48 hours, and further subjected to a moist heat durability test in which the optical laminate was placed in an environment with a temperature of 23 ° C. and a relative humidity of 60% for 24 hours. After the moist heat endurance test, the luminous efficiency correction single transmittance Ty was determined by the same method as before the moist heat endurance test.
The amount of change in Ty was calculated from the luminous efficiency correction unit transmittance Ty after the wet heat durability test and before the test based on the following formula, and the wet heat durability was evaluated according to the following criteria. The evaluation results are shown in Table 2.
Ty change amount (%) = | Ty (after wet heat durability test) -Ty (before wet heat durability test) |

4: Ty change amount is 1.0% or less 3: Ty change amount is more than 1.0% and 2.0% or less 2: Ty change amount is more than 2.0% and 3.0% or less 1 : Ty change amount is more than 3.0%

10 first protective film, 15 first adhesive layer, 20 second protective film, 25 second adhesive layer, 30 polarizing film.

Claims

A polarizing plate containing a first protective film, a first adhesive layer, a polarizing film, a second adhesive layer, and a second protective film in this order.
The first adhesive layer is a cured product layer of the first cationic polymerization type adhesive containing one or more kinds of cationic polymerization initiators.
The second adhesive layer is a cured product layer of a second cationic polymerization type adhesive containing one or more kinds of cationic polymerization initiators.
The one or more kinds of cationic polymerization initiators contained in the first cationic polymerization type adhesive include the first cationic polymerization initiator.
The first cationic polymerization initiator has a cationic component and the following formula (i):

(In the formula, Y indicates an aryl group having 6 to 30 carbon atoms or a heterocyclic group having 4 to 30 carbon atoms, or a halogen atom, which may have a substituent (excluding a group containing a halogen atom). Phf represents a phenyl group in which at least one of the hydrogen atoms is substituted with at least one selected from a perfluoroalkyl group, a perfluoroalkoxy group, and a halogen atom. K is an integer of 0 to 4. be.)
It is a borate salt composed of an anion component represented by.
A polarizing plate having a molecular weight of the first cationic polymerization initiator larger than the molecular weight of one or more kinds of cationic polymerization initiators contained in the second cationic polymerization type adhesive.
The polarizing plate according to claim 1, wherein the cation component is an aryl sulfonium ion.
The first cationically polymerizable adhesive and the second cationically polymerizable adhesive further contain a cationically polymerizable compound.
The content of the one or more kinds of cationic polymerization initiators contained in the first cationic polymerization type adhesive and the content of the one or more kinds of cationic polymerization initiators contained in the second cationic polymerization type adhesive are as described above. The polarizing plate according to claim 1 or 2, wherein the amount is 0.5 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the cationically polymerizable compound.
The polarizing plate according to any one of claims 1 to 3, wherein the first protective film is composed of a (meth) acrylic resin or a cellulose ester resin.
The polarizing plate according to any one of claims 1 to 4, further comprising an adhesive layer on the side of the second protective film opposite to the second adhesive layer side.