KR102565135B1 - Polarizing plate - Google Patents

Abstract

In the present invention, the first protective film, the first adhesive layer, the polarizing film, the second adhesive layer and the second protective film are included in this order, and the glass transition temperature of the first adhesive layer is -15 ° C. or more and less than 60 ° C. , A polarizing plate having a glass transition temperature of the second adhesive layer of 60° C. or higher is provided.

Description

Polarizer {POLARIZING PLATE}

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

BACKGROUND OF THE INVENTION [0002] A polarizing plate widely used in an image display device represented by a liquid crystal display device or the like usually has a structure in which a protective film is laminated on both sides of a polarizing film. An adhesive is normally used for joining a polarizing film and a protective film. As adhesives for bonding protective films, water-based adhesives and active energy ray-curable adhesives are known.

In Japanese Unexamined Patent Publication No. 2010-286737, in a polarizing plate in which a protective film is bonded via an adhesive layer formed by curing a radically polymerizable composition on both sides of a polarizing film, the glass transition temperature of one adhesive layer is lowered, and the other side is lowered. It is described that by increasing the glass transition temperature of the adhesive layer, it is possible to provide a polarizing plate having good punching workability (small peeling at the end of the polarizing plate after punching) and excellent durability in a high temperature and high temperature, high humidity environment after punching. .

In general, a polarizing plate is manufactured as a long product (polarizing plate roll) by a roll-to-roll method, and then cut into a polarizing plate sheet having a size according to the screen size of an image display device to be applied, for example. , and is inserted into an image display device by being bonded to an image display element. Therefore, the polarizing plate is required to have workability such as when cutting into a single sheet (that peeling between the polarizing film and the protective film is unlikely to occur even by stress at the time of cutting or the like). In addition, the polarizing plate may be stored or transported for a certain period of time between the time it is cut into sheets and inserted into the image display device, but at this time, the storage/transport environment becomes relatively high in some cases. A polarizing plate sheet material exposed to a high-temperature environment tends to be easily deformed compared to a normal temperature environment, such as causing curl (curvature), for example, and the deformed polarizing plate sheet material is bonded to an image display element through an adhesive layer. In addition to poor handling (easiness of bonding), it is easy to cause a problem that air bubbles are mixed between the pressure-sensitive adhesive layer and the image display element.

Therefore, an object of the present invention is to provide a polarizing plate that exhibits good processability during cutting and the like and is less likely to cause curl (warp) even when placed under a high temperature environment.

The present invention provides the following polarizing plate.

[1] including 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 has a glass transition temperature of -15 ° C or more and less than 60 ° C, and the second adhesive layer has a glass transition temperature of 60 ° C or more.

[2] The polarizing plate according to [1], wherein the first adhesive layer has a glass transition temperature of 0°C or higher.

[3] The polarizing plate according to [1] or [2], wherein the second adhesive layer has a glass transition temperature of 80°C or higher.

[4] The polarizing plate according to any one of [1] to [3], wherein at least one of the first adhesive layer and the second adhesive layer is a cured product layer of an active energy ray-curable adhesive.

[5] The polarizing plate according to [4], wherein the active energy ray-curable adhesive contains a radically polymerizable compound.

[6] The first protective film and the second protective film are composed of a resin selected from the group consisting of polyester-based resins, polycarbonate-based resins, polyolefin-based resins, (meth)acrylic-based resins, and cellulose ester-based resins. The polarizing plate according to any one of [1] to [5].

[7] The polarizing plate according to [6], wherein the first protective film is composed of a (meth)acrylic resin, and the second protective film is composed of a polyolefin-based resin or a cellulose ester-based resin.

[8] The polarizing plate according to any one of [1] to [7], wherein at least one of the first protective film and the second protective film is a retardation film.

ADVANTAGE OF THE INVENTION According to this invention, while it has good processability at the time of cutting etc., it is possible to provide a polarizing plate that is hard to cause curl (curvature) even when placed in a high-temperature environment ("resistance to curl" in a high-temperature environment is good).

1 is a schematic cross-sectional view showing an example of the layer configuration of a polarizing plate according to the present invention.

Hereinafter, the polarizing plate according to the present invention will be described in detail.

(1) Configuration of polarizer

As shown in FIG. 1, the polarizing plate according to the present invention 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. ) in this order. That is, the first protective film 10 is laminated on one side of the polarizing film 30 through the first adhesive layer 15, and the second protective film 20 polarizes through the second adhesive layer 25. It is laminated on the other side of the film 30. The glass transition temperature Tg1 of the first adhesive layer 15 is -15°C or more and less than 60°C, and the glass transition temperature Tg2 of the second adhesive layer 25 is 60°C or more. The polarizing plate of the present invention having such a structure exhibits good workability (the film on the end face of the polarizing plate is difficult to peel when subjected to processing such as cutting or end face polishing) and curl resistance. In addition, this polarizing plate can also be excellent in durability (hereinafter also referred to as “cold-heat shock resistance”) when placed in an environment in which a high-temperature condition and a low-temperature condition are repeated.

Without being limited to the example of FIG. 1 , the polarizing plate according to the present invention may include other layers than those described above. Specific examples of other layers include, for example, an adhesive layer laminated on the outer surfaces of the first protective film 10 and/or the second protective film 20; a separate film laminated on the outer surface of this pressure-sensitive adhesive layer (also called a "release film"); a protective film laminated on the outer surface of the first protective film 10 and/or the second protective film 20 (also called a "surface protective film"); It is an optical functional film laminated on the outer surfaces of the first protective film 10 and/or the second protective film 20 through an adhesive layer or a pressure-sensitive adhesive layer.

The polarizing plate according to the present invention may be a long product of a polarizing plate having the above-mentioned layer structure or a winding roll thereof. In this case, workability refers to workability when cutting out a polarizing plate sheet from a long object or take-up roll, and curl resistance refers to curl resistance of the cut polarizing plate sheet, and cold and heat shock resistance refers to a long product or take-up roll. It refers to the cold-and-heat shock resistance of the polarizing plate sheet material, or the polarizing plate sheet cut therefrom.

Further, the polarizing plate according to the present invention may be a single sheet of the polarizing plate having the above-described layered structure. In this case, workability refers to processability when cutting out a sheet member of a smaller size from a polarizing plate sheet member or processability when polishing the end surface of a polarizing plate sheet member, and curl resistance and cold and heat shock resistance, respectively, polarizing plate sheet member or It refers to the curl resistance and cold and heat shock resistance of the polarizing plate sheet material of a smaller size cut therefrom.

(2) Polarizing film

The polarizing film 30 is a film having a function of selectively transmitting linearly polarized light in any one direction from natural light. For example, an iodine-based polarizing film obtained by adsorbing and orienting iodine on a polyvinyl alcohol-based resin film, a dye-based polarizing film obtained by adsorbing and orienting a dichroic dye on a polyvinyl alcohol-based resin film, and a dichroic dye in a lyotropic liquid crystal state. An application-type polarizing film obtained by coating and oriented/fixed is exemplified. These polarizing films are called absorption-type polarizing films because they selectively transmit linearly polarized light in one direction from natural light and absorb linearly polarized light in one direction. The polarizing film 30 is not limited to an absorption type polarizing film, but is a reflection type polarizing film that selectively transmits linearly polarized light in one direction from natural light and reflects the linearly polarized light in another direction, or a linear polarization film in another direction. A scattering type polarizing film that scatters polarized light may be used, but an absorption type polarizing film is preferable in terms of excellent visibility. Among them, an iodine-based polarizing film having excellent polarization degree and transmittance is more preferable.

As polyvinyl alcohol-type resin, what saponified polyvinyl acetate-type resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate and other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having an ammonium group.

The degree of saponification of the polyvinyl alcohol-based resin is usually about 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 may be used. The average degree of polymerization of the polyvinyl alcohol-based resin is usually about 1000 to 10000, preferably about 1500 to 5000. The average degree of polymerization of polyvinyl alcohol-based resin can be determined in accordance with JIS K 6726.

What produced this polyvinyl alcohol-type resin into a film is used as a raw film of the polarizing film 30. The method for forming a polyvinyl alcohol-based resin into a film is not particularly limited, and a known method is employed. The thickness of the polyvinyl alcohol-based raw film is, for example, 150 μm or less, and preferably 100 μm or less (eg, 50 μm or less).

The polarizing film 30 includes a step of uniaxially stretching a polyvinyl alcohol-based resin film; a step of adsorbing the dichroic dye by dyeing the polyvinyl alcohol-based resin film with the dichroic dye; a step of treating (crosslinking) the polyvinyl alcohol-based resin film to which the dichroic dye is adsorbed with an aqueous solution of boric acid; And it can manufacture by the method including the process of washing with water after treatment by boric acid aqueous solution.

Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing of the dichroic dye, simultaneously with dyeing, or after dyeing. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, you may perform uniaxial stretching in these multiple steps.

In uniaxial stretching, uniaxial stretching may be performed between rolls having different circumferential speeds, or uniaxial stretching may be performed using a hot roll. Further, uniaxial stretching may be dry stretching in which stretching is performed in the air, or wet stretching in which stretching is performed in a state where the polyvinyl alcohol-based resin film is swollen using a solvent or water. The stretching ratio is usually about 3 to 8 times.

As a method of dyeing a polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing the film in an aqueous solution containing the dichroic dye is employed. As the dichroic dye, iodine or a dichroic organic dye is used. On the other hand, it is preferable that the polyvinyl alcohol-based resin film is subjected to a treatment of being immersed in water before dyeing treatment.

As the dyeing treatment with iodine, a method in which a polyvinyl alcohol-based resin film is immersed in an aqueous solution containing iodine and potassium iodide is usually adopted. The content of iodine in this aqueous solution may be about 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide may be about 0.5 to 20 parts by weight per 100 parts by weight of water. In addition, the temperature of this aqueous solution may be about 20 to 40 °C. On the other hand, as a dyeing treatment with a dichroic organic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic organic dye is usually adopted. The aqueous solution containing a dichroic organic dye may contain inorganic salts, such as sodium sulfate, as a dyeing aid. The content of the dichroic organic dye in this aqueous solution may be about 1×10 ^-4 to 10 parts by weight per 100 parts by weight of water. The temperature of this aqueous solution may be about 20 to 80 °C.

As the boric acid treatment after dyeing with the dichroic dye, a method of immersing the dyed polyvinyl alcohol-based resin film in an aqueous solution containing boric acid is usually adopted. When using iodine as a dichroic dye, it is preferable that this aqueous solution containing boric acid contains potassium iodide. The amount of boric acid in the aqueous solution containing boric acid may be about 2 to 15 parts by weight per 100 parts by weight of water. The amount of potassium iodide in this aqueous solution may be about 0.1 to 20 parts by weight per 100 parts by weight of water. The temperature of this aqueous solution may be 50 ° C or higher, for example, 50 to 85 ° C.

The polyvinyl alcohol-based resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by immersing the polyvinyl alcohol-based resin film treated with boric acid in water. The temperature of the water in the water washing treatment is usually about 5 to 40°C. A drying process can be performed after washing with water, and the polarizing film 30 can be obtained. The drying treatment can be performed using a hot air dryer or a far-infrared heater. A polarizing plate can be obtained by bonding protective films to both surfaces of the polarizing film 30 using an adhesive.

Moreover, as another example of the manufacturing method of the polarizing film 30, the method of Unexamined-Japanese-Patent No. 2000-338329 or Unexamined-Japanese-Patent No. 2012-159778 is mentioned, for example. In this method, after applying a solution containing a polyvinyl alcohol-based resin to the surface of a base film to provide a resin layer, the laminated film composed of the base film and the resin layer is stretched, followed by dyeing treatment, crosslinking treatment, etc. Thus, a polarizer layer (polarizing film layer) is formed from the resin layer. After this light-polarizing laminated film which consists of a base film and a polarizer layer bonds a protective film to the surface of the polarizer layer, the base film is peeled off, and further, on the surface of the polarizer layer exposed by peeling of the base film, another layer is placed. It can be set as a polarizing plate by bonding a protective film.

The thickness of the polarizing film 30 may be 40 μm or less, preferably 30 μm or less (for example, 20 μm or less). On the other hand, according to the method described in Japanese Unexamined Patent Publication No. 2000-338329 or Japanese Unexamined Patent Publication No. 2012-159778, the thin polarizing film 30 can be more easily manufactured, and the thickness of the polarizing film 30 is, For example, it may be 20 μm or less, and furthermore, 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, consequently, the image display device.

(3) protective film

The first protective film 10 and the second protective film 20 are each made of a light-transmitting (preferably optically transparent) thermoplastic resin, such as a chain polyolefin-based resin (polypropylene-based resin, etc.), a cyclic polyolefin-based resin ( polyolefin-based resins such as norbornene-based resins and the like); cellulose ester-based resins such as triacetyl cellulose and diacetyl cellulose; polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; polycarbonate-based resin; (meth)acrylic resin; Alternatively, it may be a resin film made of a mixture or copolymer thereof. On the other hand, "(meth)acryl" means methacryl and/or acryl, and "(meth)" when referring to "(meth)acrylate" etc. has the same meaning. Among them, the first protective film 10 and the second protective film 20 are resins selected from the group consisting of polyester-based resins, polycarbonate-based resins, polyolefin-based resins, (meth)acrylic-based resins, and cellulose ester-based resins, respectively. It is preferable to be composed of.

The first protective film 10 and the second protective film 20 may each be an unstretched film or a uniaxially or biaxially stretched film. Biaxial stretching may be simultaneous biaxial stretching in which the film is simultaneously stretched in two stretching directions, or sequential biaxial stretching in which the film is stretched in a predetermined direction and then in another direction. The first protective film 10 and/or the second protective film 20 may also be protective films having an optical function such as a retardation film. The retardation film is an optical functional film used for the purpose of, for example, compensation of retardation by a liquid crystal cell serving as an image display element. For example, a retardation film having an arbitrary retardation value can be obtained by stretching the film made of the thermoplastic resin (eg, uniaxial stretching or biaxial stretching) or forming a liquid crystal layer or the like on the film.

Examples of the chain polyolefin-based resin include homopolymers of chain olefins such as polyethylene resins and polypropylene resins, as well as copolymers composed of two or more types of chain olefins.

The cyclic polyolefin-based resin is a general term for resins containing, as polymerized units, cyclic olefins such as norbornene, tetracyclododecene (another name: dimethanooctahydronaphthalene), or derivatives thereof as typical examples. Specific examples of cyclic polyolefin-based resins include ring-opening (co)polymers of cyclic olefins and their hydrogenated products, addition polymers of cyclic olefins, copolymers of cyclic olefins with chain olefins such as ethylene and propylene, or aromatic compounds having a vinyl group; and modified (co)polymers obtained by modifying them with unsaturated carboxylic acids or derivatives thereof. Among them, a norbornene-based resin using a norbornene-based monomer such as norbornene or a polycyclic norbornene-based monomer as the cyclic olefin is preferably used.

The cellulose ester-based resin is a resin in which at least one part of the hydroxyl groups in the cellulose is acetic acid esterified, and a mixed ester in which one part is acetic acid esterified and one part is esterified with another acid may be used. 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, and cellulose acetate butylate.

Polyester-type resin is resin other than the said cellulose ester-type resin which has an ester bond, and what consists of polycondensate of polyhydric carboxylic acid or its derivative(s) and polyhydric alcohol is common. Specific examples of the polyester-based resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate, and polycyclohexane. Contains dimethylnaphthalate. Among them, polyethylene terephthalate is preferably used from the viewpoints of mechanical properties, solvent resistance, scratch resistance, cost and the like. Polyethylene terephthalate means a resin in which 80 mol% or more of repeating units are constituted by ethylene terephthalate, and may contain structural units derived from other copolymerization components.

As another copolymerization component, a dicarboxylic acid component and a diol component are mentioned. As the dicarboxylic acid component, isophthalic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis(4-carboxyphenyl)ethane, adipic acid, sebacic acid, 5-sodium alcohol Poisophthalic acid, 1,4-dicarboxycyclohexane, etc. are mentioned. Examples of the diol component include propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, an ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. A dicarboxylic acid component and a diol component can also be used combining two or more types, respectively as needed. It is also possible to use a hydroxycarboxylic acid such as p-hydroxybenzoic acid or p-β-hydroxyethoxybenzoic acid in combination with the dicarboxylic acid component or diol component. As other copolymerization components, dicarboxylic acid components and/or diol components having amide bonds, urethane bonds, ether bonds, carbonate bonds and the like may be used in small amounts.

Polycarbonate-based resin is polyester formed from carbonic acid and glycol or bisphenol. Among them, an aromatic polycarbonate having diphenylalkane in its molecular chain is preferably used from the viewpoints of heat resistance, weather resistance and acid resistance. As polycarbonate, 2,2-bis (4-hydroxyphenyl) propane (aka bisphenol A), 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl) cyclo Polycarbonates derived from bisphenols such as hexane, 1,1-bis(4-hydroxyphenyl)isobutane, and 1,1-bis(4-hydroxyphenyl)ethane are exemplified.

The (meth)acrylic resin may be a polymer containing methacrylic acid ester as a main monomer (containing 50% by weight or more), and it is preferably a copolymer in which a small amount of other copolymerization components are copolymerized. 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 ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and 2-hydroxy methacrylate. methacrylic acid esters other than methyl methacrylate such as ethyl; acrylic 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 2-(hydroxymethyl)methyl acrylate, 2-(1-hydroxyethyl)methyl acrylate, 2-(hydroxymethyl)ethyl acrylate, and 2-(hydroxymethyl)butyl acrylate; unsaturated acids such as methacrylic acid and acrylic acid; halogenated styrenes such as chlorostyrene and bromostyrene; substituted styrenes such as vinyltoluene 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. A 3rd monofunctional monomer may be used individually by 1 type, and may use 2 or more types together.

A polyfunctional monomer may be further copolymerized with the (meth)acrylic resin. 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)acrylate, ethylene glycol such as tetradecaethylene glycol di(meth)acrylate, or those obtained by esterifying hydroxyl groups at both terminals of oligomers thereof with (meth)acrylic acid; What esterified the hydroxyl group of both terminals of propylene glycol or its oligomer with (meth)acrylic acid; What esterified the hydroxyl group of dihydric alcohol like neopentylglycol di(meth)acrylate, hexanediol di(meth)acrylate, and butanediol di(meth)acrylate with (meth)acrylic acid; bisphenol A, alkylene oxide adducts of bisphenol A, or those obtained by esterifying the hydroxyl groups at both terminals of halogen-substituted products thereof with (meth)acrylic acid; those obtained by esterification of polyhydric alcohols such as trimethylolpropane and pentaerythritol with (meth)acrylic acid, and those obtained by ring-opening addition of epoxy groups of glycidyl (meth)acrylate to terminal hydroxyl groups; dibasic acids such as succinic acid, adipic acid, terephthalic acid, phthalic acid, halogen-substituted products thereof, and alkylene oxide adducts thereof, etc., obtained by ring-opening addition of an epoxy group of glycidyl (meth)acrylate; aryl (meth)acrylate; aromatic divinyl compounds such as divinylbenzene; and the like. Especially, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate are used preferably.

The (meth)acrylic resin may be further modified by performing a reaction between the functional groups of the copolymer. As the reaction, for example, a demethanol condensation reaction in a polymer chain between 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 A dehydration condensation reaction in a polymer chain, etc. are mentioned.

The glass transition temperature of the (meth)acrylic resin is preferably 80 to 160°C. The glass transition temperature is determined by adjusting the polymerization ratio of the methacrylic acid ester monomer and the acrylic acid ester monomer, the carbon chain length of each ester group and the type of functional group they have, and the polymerization ratio of the polyfunctional monomer to the entire monomer. can be controlled by

In addition, as a means for increasing the glass transition temperature of (meth)acrylic resin, it is also effective to introduce a cyclic structure into the main chain of the polymer. The ring structure is preferably a heterocyclic structure such as a cyclic acid anhydride structure, a cyclic imide structure, and a lactone structure. Specifically, cyclic acid anhydride structures such as glutaric anhydride and succinic anhydride structures, cyclic imide structures such as glutarimide structures and succinimide structures, and lactone ring structures such as butyrolactone and valerolactone are exemplified. can As the content of the cyclic structure in the main chain is increased, the glass transition temperature of (meth)acrylic resin can be increased. A method of introducing a cyclic acid anhydride structure and a cyclic imide structure by copolymerizing a monomer having a cyclic structure such as maleic anhydride and maleimide, a method of introducing a cyclic acid anhydride structure by dehydration/demethanol condensation reaction after polymerization, It can be introduced by a method of reacting an amino compound to introduce a cyclic imide structure. The resin (polymer) having a lactone ring structure is obtained by preparing a polymer having a hydroxyl group and an ester group in the polymer chain, and then heating the hydroxyl group and ester group in the obtained polymer as necessary, such as an organic phosphorus compound. It can be obtained by a method of forming a lactone ring structure by cyclocondensation in the presence of a catalyst.

The (meth)acrylic resin may contain additives as needed. Examples of additives include lubricants, antiblocking agents, heat stabilizers, antioxidants, antistatic agents, light resistance agents, impact resistance modifiers, and surfactants.

The (meth)acrylic resin may contain acrylic rubber particles as an impact improver from the viewpoint of the film formability to the film and the impact resistance of the film. Acrylic rubber particles are particles containing an acrylic acid ester-based elastomer as an essential component, and include those having a single-layer structure substantially composed only of the elastomer or those having a multi-layer structure containing the elastomer as one layer. there is. As an example of this elastic polymer, a crosslinked elastic copolymer obtained by copolymerizing alkyl acrylate as a main component with other vinyl monomers and crosslinkable monomers copolymerizable therewith can be given. Examples of the alkyl acrylate serving as the main component of the elastomer include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, etc., having an alkyl group having about 1 to 8 carbon atoms, and alkyl acrylate having an alkyl group of 4 or more carbon atoms. This is preferably used. Examples of other vinylic 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, styrene and aromatic vinyl compounds such as the same, vinyl cyan compounds such as acrylonitrile, and the like. Examples of the crosslinkable monomer include crosslinkable compounds having at least two polymerizable carbon-carbon double bonds in the molecule, and more specifically, ethylene glycol di(meth)acrylate, butanediol di(meth)acrylate and (meth)acrylates of polyhydric alcohols, alkenyl esters of (meth)acrylic acid such as allyl (meth)acrylates, and divinylbenzene.

A laminate of a film made of (meth)acrylic resin containing no rubber particles and a film made of (meth)acrylic resin containing rubber particles can also be used as a protective film. In addition, a (meth)acrylic resin layer formed on one side or both sides of a retardation developing layer made of a resin different from the (meth)acrylic resin and exhibiting a retardation may be used as a protective film.

The first protective film 10 and/or the second protective film 20 may contain an ultraviolet absorber. When a polarizing plate is applied to an image display device such as a liquid crystal display device, it is possible to suppress deterioration of the image display device by ultraviolet rays by disposing a protective film containing an ultraviolet absorber on the viewer side of the image display device (for example, a liquid crystal cell). can Examples of the ultraviolet absorber include salicylic acid ester-based compounds, benzophenone-based compounds, benzotriazole-based compounds, cyanoacrylate-based compounds, and nickel complex salt-based compounds.

The first protective film 10 and the second protective film 20 may be films composed of the same resin or films composed of different resins. In one example of the combination of the first protective film 10 and the second protective film 20, the first protective film 10 bonded through the first adhesive layer 15 having a lower glass transition temperature is a (meth)acrylic A combination in which the second protective film 20 made of resin and bonded via the second adhesive layer 25 having a higher glass transition temperature is composed of polyolefin-based resin or cellulose ester-based resin. In this way, when the first protective film 10 and the second protective film 20 are compared, the protective film having lower mechanical properties (breaking stress) is passed through the first adhesive layer 15 having a lower glass transition temperature. By laminating on the polarizing film 30, workability can be further improved. In addition, the first protective film 10 and the second protective film 20 may be the same or different in thickness, the presence or absence of additives, their types, and retardation characteristics.

The first protective film 10 and/or the second protective film 20, on the outer surface (the surface opposite to the polarizing film 30), has a hard coat layer, an anti-glare layer, an antireflection layer, a light diffusion layer, an antistatic layer, You may have a surface treatment layer (coating layer) like an antifouling layer and a conductive layer.

The thickness of the first protective film 10 and the second protective film 20 is usually 5 to 200 μm, preferably 10 to 120 μm, and more preferably 10 to 85 μm. 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, consequently, the image display device. The thinner the protective film, the lower the resistance to heat and cold shock. However, according to the present invention, even if the thickness of the first protective film 10 and the second protective film 20 is thin, the heat and cold resistance of the polarizing plate can be effectively improved.

(4) adhesive layer

The glass transition temperature Tg1 of the first adhesive layer 15 is -15°C or more and less than 60°C, and the glass transition temperature Tg2 of the second adhesive layer 25 is 60°C or more. When the glass transition temperatures of the first adhesive layer 15 and the second adhesive layer 25 satisfy this relationship, the processability and curl resistance of the polarizing plate can be highly compatible. In addition, it is possible to improve the cold and thermal shock resistance of the polarizing plate. The glass transition temperature of the adhesive layer is measured by a differential scanning calorimeter (DSC), and an example of the measurement method is the method described in the section of Examples described later.

The glass transition temperature Tg1 of the first adhesive layer 15 is preferably less than 55°C, more preferably less than 50°C, still more preferably less than 45°C, mainly from the viewpoint of workability and also taking into account curl resistance. On the other hand, when the glass transition temperature Tg1 is too low, even when the glass transition temperature Tg2 of the second adhesive layer 25 is within a predetermined range, the polarizing plate is inferior in cold and heat shock resistance, and the polarizing film 30 has cracks, cracks, etc. problems may occur. From the viewpoint of heat and cold shock resistance and furthermore, from the viewpoint of curl resistance, the glass transition temperature Tg1 is preferably -10°C or higher, more preferably -5°C or higher, still more preferably 0°C or higher, particularly preferably 5°C or higher. am.

The glass transition temperature Tg2 of the second adhesive layer 25 is preferably 70 ° C. or higher, more preferably 80 ° C. or higher, mainly from the viewpoint of durability of the polarizing plate, particularly cold and heat shock resistance, and furthermore, considering curl resistance, More preferably, it is 90 degreeC or more, Especially preferably, it is 95 degreeC or more. When the glass transition temperature Tg2 is 60°C or higher, sufficient heat and cold shock resistance can be obtained, and occurrence of problems such as cracks and cracks in the polarizing film 30 can be suppressed, and curl resistance is also advantageous. On the other hand, if the glass transition temperature Tg2 is too high, the second adhesive layer 25 becomes brittle, and even when the glass transition temperature Tg1 of the first adhesive layer 15 is within a predetermined range, workability is reduced, resulting in poor processing. Sometimes problems arise. For this reason, the glass transition temperature Tg2 is preferably 200°C or lower, more preferably 180°C or lower, still more preferably 160°C or lower.

From the standpoint of mainly improving curl resistance, the glass transition temperatures Tg1 and Tg2 are each within the above ranges, and the difference between the two (Tg2 - Tg1) is preferably 120°C or less, and more preferably 100°C or less. Tg2-Tg1 is more preferably 90°C or lower, still more preferably 80°C or lower. Further, setting the Tg2-Tg1 to 10°C or higher, or even 20°C or higher (for example, 50°C or higher, particularly 55°C or higher) is advantageous for combining good processability, curl resistance, and cold and heat shock resistance.

The adhesive forming the first adhesive layer 15 and the second adhesive layer 25 is not particularly limited as long as the predetermined glass transition temperatures Tg1 and Tg2 can be obtained, and a water-based adhesive, heat or ultraviolet light, visible light, and curable adhesives that are cured by irradiation with active energy rays such as electron beams and X-rays. A curable adhesive contains a curable (polymerizable) compound as a main component. Specific examples of the water-based adhesive are those obtained by dissolving or dispersing a polyvinyl alcohol-based resin or urethane resin as a main component in water, such as polyvalent aldehydes, melamine-based compounds, zirconia compounds, zinc compounds, glyoxal, and water-soluble epoxy resins. You may contain a curable component or a crosslinking agent. In the case of using a curable adhesive (including a case where a water-based adhesive contains a curable component or a crosslinking agent), an adhesive layer formed therefrom is a cured material layer of the curable adhesive.

Among the above, a curable adhesive is preferable, and an active energy ray-curable adhesive is more preferable, since the drying step of removing the solvent by heating can be omitted. Water-based adhesives and heat-curable adhesives require a heating process, and this heating may cause curling of the polarizing plate. In the form of a polarizing plate using an active energy ray-curable adhesive, a form in which at least one of the first adhesive layer 15 and the second adhesive layer 25 is a cured product layer of an active energy ray-curable adhesive is exemplified. It is preferable that both the first adhesive layer 15 and the second adhesive layer 25 are cured product layers of an active energy ray-curable adhesive.

The glass transition temperatures Tg1 and Tg2 of the first adhesive layer 15 and the second adhesive layer 25 can be adjusted according to the following guidelines, for example. That is, when forming an adhesive layer with a curable adhesive, a compound whose glass transition temperature of the cured product is close to the target glass transition temperature of the adhesive layer is usually selected as the curable compound contained in the curable adhesive as a main component. The glass transition temperature of the cured product of the curable compound mainly depends on the structure of the curable compound or the combination of the curable compounds. For example, when the curable compound contains an alicyclic epoxy compound or an aromatic epoxy compound, the glass transition temperature of the curable compound tends to be high, and when it contains an aliphatic epoxy compound, the glass transition temperature tends to be low. The glass transition temperature of the adhesive layer can also be adjusted by the degree of crosslinking of the curable compound, and for example, when the amount of the trifunctional or higher functional curable compound is increased, the glass transition temperature of the adhesive layer tends to increase. The glass transition temperature of the adhesive layer can also be adjusted by adding components other than the main component to the curable adhesive. For example, when a polymer component (thermoplastic resin or the like) is added, the glass transition temperature of the adhesive layer tends to be lowered.

Curable adhesives, if classified according to their curing mode, are cationic polymerizable adhesives containing a cationic polymerizable compound as the curable compound, radical polymerizable adhesives containing a radical polymerizable compound as the curable compound, cationic polymerizable compounds, and radical curable adhesives. and hybrid type curable adhesives containing both polymerizable compounds. Specific examples of the cationically polymerizable compound include epoxy compounds having one or more epoxy groups in the molecule, oxetane compounds having one or more oxetane rings in the molecule, and vinyl compounds. Further, specific examples of the radically polymerizable compound include (meth)acrylic compounds and vinyl compounds having one or more (meth)acryloyl groups in the molecule. The curable adhesive may contain one or two or more cationically polymerizable compounds, and/or one or two or more radically polymerizable compounds.

(4-1) cationic polymerization type adhesive

The cationically polymerizable compound, which is the main component of cationically polymerizable adhesives, is a compound or oligomer that undergoes a cationic polymerization reaction by heating or irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays, and is cured. A cetane compound, a vinyl compound, etc. can be illustrated. Among them, a preferable cationically polymerizable compound is an epoxy compound. An epoxy compound is a compound having one or more, preferably two or more epoxy groups in a molecule. An epoxy compound may be used individually by 1 type, and may use 2 or more types together. As an epoxy compound, an alicyclic epoxy compound, an aromatic epoxy compound, a hydrogenation epoxy compound, an aliphatic epoxy compound, etc. are mentioned. Especially, 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.

An alicyclic epoxy compound is a compound having one or more epoxy groups bonded to an alicyclic ring in a molecule. "Epoxy group bonded to an alicyclic ring" means a crosslinked oxygen atom -O- in a 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 a plurality of hydrogen atoms removed from (CH ₂ ) _m in the formula (I) is bonded to another chemical structure can be an alicyclic epoxy compound. One or a plurality of hydrogen atoms in (CH ₂ ) _m may be suitably substituted with a linear alkyl group such as a methyl group or an ethyl group.

Among them, an alicyclic epoxy compound having an epoxycyclopentane structure [m = 3 in the formula (I)] or an epoxycyclohexane structure [m = 4 in the formula (I)] is the glass of the cured product. It has a high transition temperature and is advantageous in increasing the glass transition temperature of the adhesive layer, and is also advantageous in terms of adhesiveness between the polarizing film and the protective film. Below, the specific example of an alicyclic epoxy compound is given. Here, the compound names are given first, and then the corresponding chemical formulas are shown, and the same symbols are assigned to the compound names and the corresponding chemical formulas.

A: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,

B: 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate;

C: Ethylenebis(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-tetraoxatrispiro[5.2.2.5.2.2]henicosan;

I: 3-(3,4-epoxycyclohexyl)-8,9-epoxy-1,5-dioxaspiro[5.5]undecane;

J: 4-vinylcyclohexene dioxide,

K: limonene dioxide,

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 a molecule. Specific examples thereof include bisphenol-type epoxy compounds or oligomers thereof, such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenyl F, and diglycidyl ether of bisphenol S; novolak-type epoxy resins such as phenol novolac epoxy resin, cresol novolac epoxy resin, and hydroxybenzaldehyde phenol novolac epoxy resin; polyfunctional epoxy compounds such as glycidyl ether of 2,2',4,4'-tetrahydroxydiphenylmethane and glycidyl ether of 2,2',4,4'-tetrahydroxybenzophenone; Polyfunctional epoxy resins such as epoxidized polyvinylphenol are included.

The hydrogenated epoxy compound is a glycidyl ether of a polyol having an alicyclic ring, and a nucleus hydrogenated polyhydroxy compound obtained by selectively hydrogenating an aromatic polyol to an aromatic ring under pressure in the presence of a catalyst is glycidyl ether it may be angry Specific examples of the aromatic polyol include, for example, bisphenol-type compounds such as bisphenol A, bisphenol F, and bisphenol S; novolak-type resins such as phenol novolac resin, cresol novolac resin, and hydroxybenzaldehyde phenol novolak resin; Polyfunctional compounds such as tetrahydroxydiphenylmethane, tetrahydroxybenzophenone, and polyvinylphenol are included. It can be set as glycidyl ether by making epichlorohydrin react with the alicyclic polyol obtained by carrying out the hydrogenation reaction to the aromatic ring of an aromatic polyol. Among the hydrogenated epoxy compounds, diglycidyl ether of hydrogenated bisphenol A is preferable.

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

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

Specifically, the aliphatic diepoxy compound represented by the formula (II) is a diglycidyl ether of an alkanediol, a diglycidyl ether of an oligoalkylene glycol having a repetition number of up to about 4, or a diglycidyl diol of an alicyclic diol. It is glycidyl ether.

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

The oxetane compound, which is one of the cationically polymerizable compounds, is a compound containing one or more oxetane rings (oxetanyl groups) in the molecule, and its specific example is 3-ethyl-3-hydroxymethyloxetane (oxetane alcohol ), 2-ethylhexyloxetane, 1,4-bis[{(3-ethyloxetan-3-yl)methoxy}methyl]benzene (also called xylylenebisoxetane), 3-ethyl- 3[{(3-ethyloxetan-3-yl)methoxy}methyl]oxetane, 3-ethyl-3-(phenoxymethyl)oxetane, 3-(cyclohexyloxy)methyl-3-ethyloxetane Contains cetane. An oxetane compound may be used as a main component of a cationically polymerizable compound, or may be used in combination with an epoxy compound. By using an oxetane compound together, a cure rate and adhesiveness can be improved in some cases.

Examples of the vinyl compound that can be a cationically polymerizable compound include aliphatic or alicyclic vinyl ether compounds, and specific examples thereof include n-amyl vinyl ether, i-amyl vinyl ether, n-hexyl vinyl ether, vinyl ethers of alkyl or alkenyl alcohols having 5 to 20 carbon atoms, such as n-octyl vinyl ether, 2-ethylhexyl vinyl ether, n-dodecyl vinyl ether, stearyl vinyl ether, and oleyl vinyl ether; hydroxyl group-containing vinyl ethers such as 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, and 4-hydroxybutyl vinyl ether; vinyl ethers of monoalcohols having aliphatic or aromatic rings, such as cyclohexyl vinyl ether, 2-methylcyclohexyl vinyl ether, cyclohexylmethyl vinyl ether, and benzyl vinyl 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, trimethylol propane divinyl ether, trimethylol propane trivinyl ether, 1,4-dihydroxycyclohexane monovinyl ether, 1,4-dihydroxycyclohexane divinyl ether, 1,4-dihydroxymethyl mono-polyvinyl ethers of polyhydric alcohols such as cyclohexane monovinyl ether and 1,4-dihydroxymethylcyclohexane divinyl ether; polyalkylene glycol mono-divinyl ethers such as diethylene glycol divinyl ether, triethylene glycol divinyl ether, and diethylene glycol monobutyl monovinyl ether; Other vinyl ethers, such as glycidyl vinyl ether and ethylene glycol vinyl ether methacrylate, are included. A vinyl compound may be used as a main component of a 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 together, the curing speed or the viscosity reduction of an adhesive agent can be improved in some cases.

The cationically polymerizable adhesive may further contain other cationically polymerizable compounds other than those described above, such as cyclic lactone compounds, cyclic acetal compounds, cyclic thioether compounds, and spiroorthoester compounds.

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 polymerizable adhesive (including the case of a hybrid type curable adhesive) is 100% by weight, the content of the cationically polymerizable compound (The content of all cationically polymerizable compounds contained in the cationically polymerizable adhesive, and when two or more cationically polymerizable compounds are contained, the total content thereof) is preferably 50% by weight or more, and more preferably 60% by weight or more. It is preferable, and it is more preferable that it is 70 weight% or more. Also, as described above, the cationic polymerization type adhesive may further contain a polymer component (such as a thermoplastic resin). Thereby, the glass transition temperature of the adhesive layer can be lowered or the adhesiveness between the polarizing film and the protective film can be improved.

The cationic polymerization type adhesive may be active energy ray curable or heat curable, but since the step of heating can be omitted and curling of the polarizing plate due to this heating can be prevented, it is preferably active energy ray curable. In the case of imparting active energy ray curability to a cationically polymerizable adhesive containing a cationically polymerizable compound, it is preferable to incorporate a photocationic polymerization initiator into the adhesive. The photocationic polymerization initiator generates a cationic species or a Lewis acid by irradiation of active energy rays such as visible light, ultraviolet rays, X-rays or electron beams, thereby initiating a polymerization reaction of a cationically curable compound. Since a photocationic polymerization initiator acts catalytically with light, even if it is mixed with a photocationic curable compound, it is excellent in storage stability and workability. Examples of the compound that generates cationic species or Lewis acids by irradiation with active energy rays include onium salts such as aromatic iodonium salts and aromatic sulfonium salts, aromatic diazonium salts, and iron-arene complexes.

The aromatic iodonium salt is a compound having a diaryliodonium cation, and as the cation, a diphenyliodonium cation is typically exemplified. The aromatic sulfonium salt is a compound having a triarylsulfonium cation, and examples of the cation include triphenylsulfonium cation and 4,4'-bis(diphenylsulfonio)diphenylsulfide cation. there is. The aromatic diazonium salt is a compound having a diazonium cation, and as the cation, a benzenediazonium cation is typically exemplified. In addition, the iron-arene complex is typically a cyclopentadienyl iron (II) arene cation complex salt.

The cations described above pair with an anion to form a photocationic polymerization initiator. Examples of the anion constituting the photocationic polymerization initiator include special phosphorus anion [(Rf) _n PF _6-n ] ^- , hexafluorophosphate anion PF ₆ ^- , hexafluoroantimonate anion SbF ₆ ^- , pentafluoro rhohydroxyantimonate anion SbF ₅ (OH) ^- , hexafluoroacenate anion AsF ₆ ^- , tetrafluoroborate anion BF ₄ ^- , tetrakis(pentafluorophenyl)borate anion B(C ₆ F ₅ ) ₄ ^- back. Among them, from the viewpoint of the curability of the cationically polymerizable compound and the safety of the resulting adhesive layer, a special phosphorus anion [(Rf) _n PF _{6 -n} ] ^- or a hexafluorophosphate anion PF ₆ ^- is preferable.

A photocationic polymerization initiator may be used individually by 1 type, and may use 2 or more types together. Among them, aromatic sulfonium salts have ultraviolet absorbing properties even in the wavelength range of around 300 nm, and thus are excellent in curability and can provide cured products having good mechanical strength and adhesive strength, so they are preferably used.

The compounding amount of the photocationic polymerization initiator is usually 0.5 to 10 parts by weight, preferably 6 parts by weight or less, based on 100 parts by weight of the cationically polymerizable compound. By blending 0.5 parts by weight or more of the photocationic polymerization initiator, the cationically polymerizable compound can be sufficiently cured, and high mechanical strength and adhesive strength can be imparted to the obtained polarizing plate. On the other hand, if the amount is excessively increased, the hygroscopicity of the cured product increases due to an increase in the ionic substance in the cured product, and there is a possibility that the durability of the polarizing plate decreases.

As described above, a hybrid type curable adhesive can be obtained by adding a cationically polymerizable compound to a cationically polymerizable adhesive and containing a radically polymerizable compound. By using the radically polymerizable compound together, the effect of increasing the hardness and mechanical strength of the adhesive layer can be expected, and furthermore, the viscosity and curing rate of the curable adhesive can be further easily adjusted.

(4-2) radical polymerization adhesive

The radical polymerizable compound, which is the main component of the radical polymerization type adhesive, refers to a compound or oligomer that undergoes a radical polymerization reaction by heating or irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays, and is cured. Specifically, ethylene Compounds having sexually unsaturated bonds are exemplified. As the compound having an ethylenically unsaturated bond, besides the (meth)acrylic compound having one or more (meth)acryloyl groups in the molecule, styrene, styrenesulfonic acid, vinyl acetate, vinyl propionate, N-vinyl-2-pyrrolidone and The same vinyl compound etc. are mentioned. Especially, a preferable radically polymerizable compound is a (meth)acrylic compound.

The (meth)acrylic compound is obtained by reacting two or more kinds of a (meth)acrylate monomer having at least one (meth)acryloyloxy group in a molecule, a (meth)acrylamide monomer, and a functional group-containing compound, and (meth)acryloyl group-containing compounds such as (meth)acryloligomers having at least two (meth)acryloyl groups are exemplified. The (meth)acrylic oligomer is preferably a (meth)acrylate oligomer having at least two (meth)acryloyloxy groups in the molecule. A (meth)acrylic compound may be used individually by 1 type, and may use 2 or more types together.

As the (meth)acrylate monomer, a monofunctional (meth)acrylate monomer having one (meth)acryloyloxy group in the molecule and a bifunctional (meth)acrylate having two (meth)acryloyloxy groups in the molecule monomers and polyfunctional (meth)acrylate monomers having three or more (meth)acryloyloxy groups in the molecule.

An example of a monofunctional (meth)acrylate monomer is an alkyl (meth)acrylate. In the alkyl (meth)acrylate, the alkyl group may be straight chain or branched as long as it has 3 or more carbon atoms. Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, t -Butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc. are mentioned. Also, aralkyl (meth)acrylates such as benzyl (meth)acrylate; (meth)acrylates of terpene alcohol such as isobornyl (meth)acrylate; (meth)acrylates having a tetrahydrofurfuryl structure such as tetrahydrofurfuryl (meth)acrylate; Cyclohexyl (meth) acrylate, cyclohexylmethyl methacrylate, dicyclopentanyl acrylate, dicyclopentenyl (meth) acrylate, 1,4-cyclohexanedimethanol monoacrylate, such as by adding a cycloalkyl group to the alkyl group (meth)acrylate having; aminoalkyl (meth)acrylates such as N,N-dimethylaminoethyl (meth)acrylate; 2-phenoxyethyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, ethylcarbitol (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate having an ether linkage at the alkyl moiety (meth)acrylate can also be used as a monofunctional (meth)acrylate monomer.

Moreover, the monofunctional (meth)acrylate which has a hydroxyl group in an alkyl moiety, and the monofunctional (meth)acrylate which has a carboxyl group in an alkyl moiety can also be used. Specific examples of the monofunctional (meth)acrylate having a hydroxyl group at the alkyl moiety include 2-hydroxyethyl (meth)acrylate, 2- or 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, ) acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, trimethylolpropane mono(meth)acrylate, and pentaerythritol mono(meth)acrylate. Specific examples of the monofunctional (meth)acrylate having a carboxyl group at the alkyl moiety include 2-carboxyethyl (meth)acrylate, ω-carboxy-polycaprolactone (n≒2) mono(meth)acrylate, 1-[ 2-(meth)acryloyloxyethyl]phthalic acid, 1-[2-(meth)acryloyloxyethyl]hexahydrophthalic acid, 1-[2-(meth)acryloyloxyethyl]succinic acid, 4-[ 2-(meth)acryloyloxyethyl]trimellitic acid, N-(meth)acryloyloxy-N',N'-dicarboxymethyl-p-phenylenediamine.

The (meth)acrylamide monomer is preferably a (meth)acrylamide having a substituent at the N-position, and a typical example of the substituent at the N-position is an alkyl group, which forms a ring together with the nitrogen atom of (meth)acrylamide. It may be formed, and this ring may have an oxygen atom as a ring member in addition to the carbon atom and the nitrogen atom of (meth)acrylamide. In addition, a substituent such as alkyl or oxo (=O) may be bonded to the carbon atoms constituting the ring.

Specific examples of the N-substituted (meth)acrylamide include N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-n-butyl (meth)acrylamide, N-alkyl (meth)acrylamides such as N-t-butyl (meth)acrylamide and N-hexyl (meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide. Also, the N-substituent may be an alkyl group having a hydroxyl group, and examples thereof include N-hydroxymethyl (meth)acrylamide, N-(2-hydroxyethyl)(meth)acrylamide, and N-(2-hydroxyl). propyl) (meth) acrylamide; and the like. In addition, as specific examples of the N-substituted (meth)acrylamide forming the above 5- or 6-membered ring, N-acryloylpyrrolidine, 3-acryloyl-2-oxazolidinone, 4-acryloylmol Folin, N-acryloylpiperidine, N-methacryloylpiperidine, and the like.

Examples of the bifunctional (meth)acrylate monomer include alkylene glycol di(meth)acrylates, polyoxyalkylene glycol di(meth)acrylates, halogen-substituted alkylene glycol di(meth)acrylates, and di(meth)acrylates of aliphatic polyols. )Acrylates, di(meth)acrylates of hydrogenated dicyclopentadiene or tricyclodecanedialkanol, di(meth)acrylates of dioxane glycol or dioxane dialkanol, alkylene oxide adducts of bisphenol A or bisphenol F Di(meth)acrylate, epoxydi(meth)acrylate of bisphenol A or bisphenol F, etc. are mentioned.

For more specific examples of the bifunctional (meth)acrylate monomer, ethylene glycol di(meth)acrylate, 1,3-butanedioldi(meth)acrylate, 1,4-butanedioldi(meth)acrylate, 1, 6-Hexanedioldi(meth)acrylate, 1,9-nonanedioldi(meth)acrylate, neopentylglycoldi(meth)acrylate, trimethylolpropanedi(meth)acrylate, pentaerythritol di(meth)acrylate Acrylates, ditrimethylolpropane di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate )Acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, silicon di(meth)acrylate, neopentyl glycol hydroxypivalate Di(meth)acrylate of ester, 2,2-bis[4-(meth)acryloyloxyethoxyethoxyphenyl]propane, 2,2-bis[4-(meth)acryloyloxyethoxy Toxycyclohexyl] propane, hydrogenated dicyclopentadienyl di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, 1,3-dioxane-2,5-diyl di(meth)acrylate [alias : Dioxane glycol di(meth)acrylate], acetal compound of hydroxypivalaldehyde and trimethylolpropane [chemical name: 2-(2-hydroxy-1,1-dimethylethyl)-5-ethyl-5-hydroxy oxymethyl-1,3-dioxane] di(meth)acrylate, tris(hydroxyethyl)isocyanurate di(meth)acrylate, 1,4-cyclohexanedimethanol diacrylate, and the like.

Examples of trifunctional or higher polyfunctional (meth)acrylate monomers include glycerin tri(meth)acrylate, alkoxylated glycerin tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, and ditrimethylolpropane tri(meth)acrylate. Rate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate , poly(meth)acrylates of trifunctional or higher functional aliphatic polyols such as dipentaerythritol hexa(meth)acrylate, etc. Tri(meth)acrylate of adduct, tri(meth)acrylate of alkylene oxide adduct of trimethylolpropane, 1,1,1-tris[(meth)acryloyloxyethoxyethoxy]propane, tris(hydroxy) Roxyethyl) isocyanurate tri(meth)acrylate, etc. are mentioned.

On the other hand, (meth)acrylic oligomers include urethane (meth)acrylic oligomers, polyester (meth)acrylic oligomers, epoxy (meth)acrylic oligomers, and the like.

A urethane (meth)acrylic oligomer is a compound having a urethane bond (-NHCOO-) and at least two (meth)acryloyl groups in a molecule. Specifically, a urethanization reaction product of polyisocyanate and a hydroxyl-containing (meth)acrylic monomer each having at least one (meth)acryloyl group and at least one hydroxyl group in the molecule, or a terminal obtained by reacting a polyol with polyisocyanate It may be a urethanization reaction product of an isocyanato group-containing urethane compound and a (meth)acryl monomer each having at least one (meth)acryloyl group and at least one hydroxyl group in the molecule.

The hydroxyl group-containing (meth)acryl monomer used in the urethanization reaction may be, for example, a hydroxyl group-containing (meth)acrylate monomer, and specific examples thereof include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, glycerine di(meth)acrylate, trimethylolpropanedi(meth)acrylate , pentaerythritol tri(meth)acrylate and dipentaerythritol penta(meth)acrylate. Specific examples other than the hydroxyl group-containing (meth)acrylate monomer include N-hydroxyalkyl (meth)acrylamide monomers such as N-hydroxyethyl (meth)acrylamide and N-methylol (meth)acrylamide. .

Examples of polyisocyanates used in the urethanization reaction with hydroxyl group-containing (meth)acrylic monomers include hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, and the like. Among diisocyanates, diisocyanates obtained by hydrogenating aromatic isocyanates (e.g., hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate, etc.), di- or tri-isocyanates such as triphenylmethane triisocyanate, dibenzylbenzene triisocyanate, and polyisocyanates obtained by polymerizing the diisocyanates described above.

Moreover, as a polyol used in order to set it as a terminal isocyanato group containing urethane compound by reaction with polyisocyanate, aromatic, aliphatic, or an alicyclic polyol, polyester polyol, polyether polyol, etc. can be used. Examples of aliphatic and alicyclic polyols include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, trimethylolethane, trimethylolpropane, and ditrimethylol. Propane, pentaerythritol, dipentaerythritol, dimethylol heptane, dimethylol propionic acid, dimethylol butanoic acid, glycerin, hydrogenated bisphenol A, etc. are mentioned.

Polyester polyol is obtained by dehydration condensation reaction of the polyol described above with polybasic carboxylic acid or its anhydride. Examples of polybasic carboxylic acids or their anhydrides are indicated by appending "(anhydrous)" to those that can be anhydrides, such as (anhydrous) succinic acid, adipic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, (anhydrous) There are trimellitic acid, (anhydrous) pyromellitic acid, (anhydrous) phthalic acid, isophthalic acid, terephthalic acid, and hexahydro (anhydrous) phthalic acid.

The polyether polyol may be, in addition to polyalkylene glycol, a polyoxyalkylene-modified polyol obtained by reacting an alkylene oxide with the above-described polyol or dihydroxybenzenes.

A polyester (meth)acrylic oligomer is a compound having an ester bond and at least two (meth)acryloyl groups (typically (meth)acryloyloxy groups) in the molecule. Specifically, it can be obtained by a dehydration condensation reaction using (meth)acrylic acid, a polybasic carboxylic acid or an anhydride thereof, and a polyol. Examples of polybasic carboxylic acids or their anhydrides used in the dehydration condensation reaction are indicated by appending "(anhydrous)" to an anhydride, such as (anhydrous) succinic acid, adipic acid, (anhydrous) maleic acid, (anhydrous) Itaconic acid, (anhydrous) trimellitic acid, (anhydrous) pyromellitic acid, hexahydro (anhydrous) phthalic acid, (anhydrous) phthalic acid, isophthalic acid, terephthalic acid, and the like. In addition, as polyols used in the dehydration condensation reaction, 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, trimethylolethane, trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, dimethylolheptane, dimethylolpropionic acid, dimethylolbutanoic acid, glycerin, hydrogenated bisphenol A, and the like.

Epoxy (meth)acrylic oligomers can be obtained, for example, by an addition reaction between polyglycidyl ether and (meth)acrylic acid, and have at least two (meth)acryloyloxy groups in the molecule. As the polyglycidyl ether used for the addition reaction, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A diglycidyl ether etc. are mentioned.

The radical polymerization type adhesive may be active energy ray curable or heat curable, but is preferably active energy ray curable. In the case of imparting active energy ray curability to a radical polymerization type adhesive containing a radical polymerization compound, it is preferable to blend an optical radical polymerization initiator into the adhesive. The photo-radical polymerization initiator initiates a polymerization reaction of a radical curable compound by irradiation of active energy rays such as visible light, ultraviolet rays, X-rays or electron beams. Photoradical polymerization initiators may be used individually by 1 type, and may use 2 or more types together.

Specific examples of the photoradical polymerization initiator include acetophenone, 3-methylacetophenone, benzyldimethylketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-methyl- acetophenone-based initiators such as 1-[4-(methylthio)phenyl-2-morpholinopropan-1-one and 2-hydroxy-2-methyl-1-phenylpropan-1-one; benzophenone-based initiators such as benzophenone, 4-chlorobenzophenone, and 4,4'-diaminobenzophenone; benzoin ether-based initiators such as benzoin propyl ether and benzoin ethyl ether; thioxanthone-based initiators such as 4-isopropylthioxanthone; In addition, xanthone, fluorenone, camphaquinone, benzaldehyde, and anthraquinone are included.

The blending amount of the radical photopolymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 to 6 parts by weight, based on 100 parts by weight of the radical polymerizable compound. By blending 0.5 parts by weight or more of the photoradical polymerization initiator, the radically polymerizable compound can be sufficiently cured, and high mechanical strength and adhesive strength can be imparted to the obtained polarizing plate. On the other hand, if the amount is excessively increased, there is a possibility that the durability of the polarizing plate is lowered.

(4-3) Additives

The adhesive forming the first adhesive layer 15 and/or the second adhesive layer 25 may contain other additives as needed. Specific examples of additives include ion trapping agents, antioxidants, chain transfer agents, polymerization accelerators (polyols, etc.), sensitizers, sensitizers, light stabilizers, tackifiers, thermoplastic resins, fillers, flow regulators, plasticizers, antifoaming agents, and leveling agents. , A silane coupling agent, a colorant, an antistatic agent, a UV absorber, and a thermal polymerization initiator. On the other hand, a thermal polymerization initiator is used instead of a photopolymerization initiator when preparing a thermally curable adhesive. A photopolymerization initiator and a thermal polymerization initiator may be used in combination. Examples of the ion trapping agent include inorganic compounds such as powdery bismuth, antimony, magnesium, aluminum, calcium, titanium, and mixtures thereof, and examples of the antioxidant include hindered phenolic antioxidants. can

(4-4) Coating of adhesive and adhesion between polarizing film and protective film

The first protective film 10 is laminated and adhered to one side of the polarizing film 30 via the first adhesive layer 15, and the second adhesive layer 25 is applied to the other side of the polarizing film 30. The polarizing plate according to the present invention may be obtained by laminating and adhering the second protective film 20 through the bonding process. The first protective film 10 and the second protective film 20 (hereinafter collectively referred to simply as "protective films") may be laminated and bonded on one side in stages, or the protective films on both sides may be bonded in one step. Lamination bonding may be used.

The bonding between the polarizing film 30 and the protective film is specifically, applying an adhesive to the bonding surface of the polarizing film 30 and/or the bonding surface of the protective film, and overlapping both films through the coating layer of the adhesive, For example, after bonding by pressing from above and below using a bonding roll or the like, the adhesive layer is dried (for example, in the case of a water-based adhesive), cured by irradiating active energy rays (in the case of an active energy ray-curable adhesive), or heated It can be bonded by curing (in the case of a heat curable adhesive). Even when an active energy ray-curable adhesive is used, heat treatment may be performed simultaneously with active energy ray irradiation or after active energy ray irradiation. Prior to 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 a saponification treatment, a corona discharge treatment, a plasma treatment, a flame treatment, a priming treatment, or an anchor coating treatment to facilitate adhesion. treatment may be performed.

For the formation of the coated layer of the adhesive, various coating methods such as doctor blade, wire bar, die coater, comma coater, and gravure coater can be used. In addition, while supplying the polarizing film 30 and the protective film continuously so that the bonding surfaces of both are inside, a method of casting an adhesive therebetween can also be adopted.

From the viewpoint of coatability, the adhesive forming the first adhesive layer 15 and the second adhesive layer 25 preferably 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 of a solvent-free type, but may contain an organic solvent in order to adjust the viscosity to suit the coating method employed.

Moreover, you may heat at least one of a protective film and an adhesive agent in the process of forming the coating layer of an adhesive agent, or the process of overlapping and bonding polarizing film 30 and a protective film. Thereby, the adhesiveness between the polarizing film 30 and the protective film, especially the adhesiveness between the protective film and the adhesive layer is improved. Specific examples of the heating include heating of a protective film, heating of an adhesive, heating of a laminate in which the polarizing film 30 and the protective film are laminated via an uncured or undried adhesive layer, and the like. As a method of heating the protective film or laminate, for example, a method of passing a long protective film or laminate through a device that emits radiant heat such as an infrared heater sequentially, or heating a long protective film or laminate using a blower or the like. A method of spraying a gas may be cited. Moreover, as a method of heating an adhesive agent, the method of supplying the heated adhesive agent to a coating device after previously heating and keeping an adhesive agent warm in a storage tank is mentioned, for example. It is preferable that it is 30-80 degreeC, and, as for the temperature which heats a protective film, an adhesive agent, or a laminated body, it is more preferable that it is 40-60 degreeC. If the heating temperature exceeds 80°C, there is a risk that the protective film, adhesive or laminate may deteriorate due to heat. In addition, when the heating temperature is less than 30°C, the effect of improving the adhesion between the protective film and the polarizing film 30 tends to be insufficient.

When the coating layer of the adhesive is formed on the protective film, the moisture content of the protective film according to the dry weight method is preferably 0.2 to 5% by weight. When the moisture content is within the above range, especially when the adhesive is a cationically polymerized adhesive, the reactivity of the adhesive tends to be improved and the adhesion between the protective film and the polarizing film 30 is improved.

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

The intensity of irradiation of active energy rays to the adhesive layer is determined for each adhesive composition, and it is preferable that the intensity of light irradiation in a wavelength region effective for activating the photopolymerization initiator is 0.1 to 1000 mW/cm 2 . If the light irradiation intensity is too low, the reaction time becomes long. On the other hand, if the light irradiation intensity is too large, yellowing of the adhesive layer or deterioration of the polarizing film 30 due to heat radiated from the lamp and heat generated during polymerization of the adhesive. , or the skin defect of the protective film may be caused. In addition, the light irradiation time to the adhesive is also controlled for each adhesive composition, but it is preferable to set the integrated light amount expressed as the product of the light irradiation intensity and the light irradiation time to be 10 to 5000 mJ/cm 2 . If the amount of integrated light is too small, generation of active species derived from the photopolymerization initiator is not sufficient, and there is a possibility that the adhesive layer obtained may be insufficiently cured. easy to be at a disadvantage

The timing of laminating the protective film to the polarizing film 30 through the coating layer of the adhesive and the timing of curing or drying the coating layer are not particularly limited. For example, after laminating one protective film, the coating layer may then be cured or dried, then the other protective film may be laminated, and the coating layer may be cured or dried. Alternatively, after laminating the protective films on both sides sequentially or simultaneously, the coating layers on both sides may be cured or dried simultaneously. In addition, you may apply an active energy ray from either protective film side. For example, when one protective film contains a UV absorber and the other protective film does not contain a UV absorber, it is preferable to irradiate active energy rays from the side of the protective film that does not contain the UV absorber. By irradiating in this way, the irradiated active energy ray can be effectively used and the curing speed can be increased.

The thickness of the first and second adhesive layers 15 and 25 after curing or drying is usually 20 μm or less, preferably 10 μm or less, more preferably 5 μm or less, and particularly preferably 3 μm or less. When the thickness of the first and second adhesive layers 15 and 25 is excessively large, the reaction rate of the adhesive tends to decrease and the heat-and-moisture resistance of the polarizing plate tends to deteriorate. The thickness of the first and second adhesive layers 15 and 25 is usually 0.01 μm or more, preferably 0.1 μm or more. The thickness of the first adhesive layer 15 and the second adhesive layer 25 may be the same or different.

(5) Other components of the polarizer

(5-1) Optical Functional Film

The polarizing plate may have other optical functional films other than the polarizing film 30 for imparting desired optical functions, and a suitable example thereof is a retardation film. As described above, although the first protective film 10 and/or the second protective film 20 may serve as a retardation film, a retardation film may be laminated separately from the protective film. In the latter case, the retardation film may be laminated on the outer surfaces of the first protective film 10 and/or the second protective film 20 through an adhesive layer or an adhesive layer.

Specific examples of the retardation film include a birefringent film composed of a stretched film of a light-transmitting thermoplastic resin, a film in which discotic liquid crystals or nematic liquid crystals are aligned and fixed, and a liquid crystal layer formed on a base film. The base film is usually a thermoplastic resin film, and as the thermoplastic resin, a cellulose ester-based resin such as triacetyl cellulose is preferably used.

As the thermoplastic resin forming the birefringent film, those described for the protective film can be used. For example, in the case of using a cellulose ester-based resin, a method of forming a film by incorporating a compound having a retardation adjusting function into a cellulose ester-based resin, and a compound having a retardation adjusting function on the surface of a cellulose ester-based resin film A birefringent film can be obtained by a coating method or a method of uniaxially or biaxially stretching a cellulose ester-based resin. As the thermoplastic resin forming the birefringent film, other thermoplastic resins such as polyvinyl alcohol-based resin, polystyrene-based resin, polyarylate-based resin, and polyamide-based resin may be used.

The retardation film may be used in combination of two or more sheets for the purpose of controlling optical properties such as widening the bandwidth. Further, it is also possible to use a substantially optically isotropic zero retardation film as the retardation film, not limited to a film having optical anisotropy. The zero retardation film refers to a film in which both the in-plane retardation value R _e and the thickness direction retardation value R _th are -15 to 15 nm. The in-plane retardation value R _e and the thickness direction retardation value R _th referred to herein are values at a wavelength of 590 nm.

The in-plane retardation value R _e and the thickness direction retardation value R _th are respectively expressed by the following formula:

R _e =(n _x -n _y )×d

R _th =[(n _x +n _y )/2-n _z ]×d

is defined as In the formula, n _x is the refractive index in the film in-plane slow axis direction (x-axis direction), n _y is the film in-plane fast axis direction (y-axis direction orthogonal to the x-axis in-plane) refractive index, n _z is the film thickness is the refractive index in the direction (the z-axis direction perpendicular to the film plane), and d is the thickness of the film.

For the zero retardation film, the thermoplastic resins described in relation to the protective film and the birefringent film can be used. A resin film made of a polyester-based resin can be used. Among them, cellulose ester-based resins and polyolefin-based resins are preferably used because control of the retardation value is easy and acquisition is also easy.

Examples of other optical functional films (optical members) that can be included in the polarizing plate are light collecting plates, brightness enhancing films, reflective layers (reflection films), transflective layers (transflective reflective films), light diffusion layers (light diffusion films), and the like. These are generally installed when the polarizing plate is a polarizing plate disposed on the rear side (backlight side) of the liquid crystal cell.

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

A luminance improving film is used for the purpose of improving luminance in a liquid crystal display device to which a polarizing plate is applied. Specifically, a reflective polarization separation sheet designed to generate an anisotropy in reflectance by laminating a plurality of thin films having different refractive index anisotropy, an orientation film of cholesteric liquid crystal polymer or an alignment liquid crystal layer thereof supported on a base film. circularly polarized light separation sheets; and the like.

The reflective layer, the transflective layer, and the light diffusing layer are provided to make the polarizing plate into a reflective, transflective, or diffusive optical member, respectively. A reflective polarizing plate is used for a liquid crystal display device that displays by reflecting incident light from the viewing side, and since a light source such as a backlight can be omitted, the liquid crystal display device can be easily reduced in thickness. A transflective type polarizing plate is used in a liquid crystal display device of a type that is reflective in bright light and displays with light from a backlight in a dark place. Further, the diffusion-type polarizing plate is used for a liquid crystal display device in which display defects such as moire fringe are suppressed by imparting light diffusivity. The reflective layer, the semi-transmissive reflective layer, and the light-diffusing layer can be formed by known methods.

(5-2) Adhesive layer

The polarizing plate according to the present invention may contain a pressure-sensitive adhesive layer for bonding it to an image display element such as a liquid crystal cell or another optical member. The pressure-sensitive adhesive layer may 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.

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

Formation of the pressure-sensitive adhesive layer on the polarizing plate is, for example, by dissolving or dispersing the pressure-sensitive adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare a 10 to 40% by weight solution, and directly applying this to the target surface of the polarizing plate to form a pressure-sensitive adhesive layer. It can be formed by a method of forming, a method of forming an adhesive layer in a sheet form on a separate film subjected to release treatment, and attaching it to the target surface of a polarizing plate. The thickness of the pressure-sensitive adhesive layer is determined depending on its adhesive strength and the like, but is suitably in the range of about 1 to 50 μm, preferably 2 to 40 μm.

The polarizing plate may include the above-described separator film. The separation film may be a film made of polyethylene-based resins such as polyethylene, polypropylene-based resins such as polypropylene, and polyester-based resins such as polyethylene terephthalate. Among them, a stretched film of polyethylene terephthalate is preferable.

The pressure-sensitive adhesive layer may contain fillers made of glass fibers, glass beads, resin beads, metal powder or other inorganic powders, pigments, colorants, antioxidants, ultraviolet absorbers, antistatic agents, and the like, as necessary.

Examples of the antistatic agent include ionic compounds, conductive fine particles, and conductive polymers, but ionic compounds are preferably used. The cation component constituting the ionic compound may be an inorganic anion or an organic anion, but it is preferably an organic cation from the viewpoint of compatibility with (meth)acrylic resin. Examples of organic cations include pyridinium cations, imidazolium cations, ammonium cations, sulfonium cations, and phosphonium cations. On the other hand, the anion component constituting the ionic compound may be an inorganic anion or an organic anion, but an anion component containing a fluorine atom is preferable because it gives an ionic compound excellent in antistatic performance. As the anion component containing a fluorine atom, hexafluorophosphate anion [(PF ₆ ^- )], bis(trifluoromethanesulfonyl)imide anion [(CF ₃ SO ₂ ) ₂ N ^- ] anion, bis(fluoro rosulfonyl)imide anion [(FSO ₂ ) ₂ N ^- ] anion; and the like.

(5-3) Protection film

The polarizing plate according to the present invention may include a protection film for temporarily attaching and protecting its surface (protective film surface). A protection film is peeled off for every adhesive layer it has, after a polarizing plate is bonded to an image display element or another optical member, for example.

The protection film is composed of a base film and an adhesive layer laminated thereon. Regarding the pressure-sensitive adhesive layer, the above contents are cited. The resin constituting the base film may be, for example, a thermoplastic resin such as a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, a polyester-based resin such as polyethylene terephthalate or polyethylene naphthalate, and a polycarbonate-based resin. there is. Preferably, they are polyester-based resins, such as polyethylene terephthalate.

The polarizing plate of this invention can be bonded to image display elements, such as a liquid crystal cell, through an adhesive layer. As a liquid crystal cell, an IPS type, a VA type, etc. are mentioned.

[Example]

Hereinafter, examples and comparative examples will be described to explain the present invention more specifically, but the present invention is not limited by these examples. In the following examples, the following were used as the radically polymerizable compound, photoradical polymerization initiator, and additive constituting the adhesive.

(radical polymerizable compound)

[1] Curable compound 1: dicyclopentanyl acrylate (trade name “FA-513AS” obtained from Hitachi Chemical Co., Ltd., glass transition temperature: 120° C.);

[2] Curable compound 2: 1,4-cyclohexanedimethanol monoacrylate (trade name "CHDMMA" obtained from Nippon Kasei Co., Ltd., glass transition temperature 18 ° C.),

[3] Curable compound 3: hydroxyethyl acrylate (trade name "HEA" obtained from Osaka Yuki Kogyo Co., Ltd., glass transition temperature -15 ° C),

[4] curable compound 4: 4-hydroxybutyl acrylate (trade name “4HBA” obtained from Osaka Yuki Kogyo Co., Ltd., glass transition temperature -32° C.);

[5] Curable compound 5: N,N-dimethylacrylamide (trade name “DMAA” obtained from KJ Chemical Co., Ltd., glass transition temperature: 119° C.),

[6] Curable compound 6: N-(2-hydroxyethyl)acrylamide (trade name “HEAA” obtained from KJ Chemical Co., Ltd., glass transition temperature 98° C.),

[7] Curable compound 7: polyethylene glycol #600 diacrylate (trade name “A-600” obtained from Shin-Nakamura Chemical Industry Co., Ltd., glass transition temperature -23° C.),

[8] curable compound 8: ethoxylated glycerin triacrylate (trade name “A-GLY-20E” obtained from Shin-Nakamura Chemical Industry Co., Ltd.);

[9] Curable compound 9: ω-carboxy-polycaprolactone (n≒2) monoacrylate (trade name “M-5300” obtained from Toagosei Co., Ltd., glass transition temperature -41° C.),

[10] Curable compound 10: UV-curable urethane acrylate resin (trade name "UV-3000B" obtained from Nippon Kosei Chemical Industry Co., Ltd., glass transition temperature -39°C).

[11] curable compound 11: dipentaerythritol hexaacrylate (trade name “A-DPH” obtained from Shin-Nakamura Chemical Industry Co., Ltd.);

[12] Curable compound 12: UV-curable urethane acrylate resin (trade name “UV-3700B” obtained from Nippon Kosei Chemical Co., Ltd.).

On the other hand, the above-mentioned ethoxylated glycerin triacrylate (trade name "A-GLY-20E") has the following structural formula.

In addition, the above-described ultraviolet curable urethane acrylate resin (trade name "UV-3000B") is an ultraviolet curable resin mainly composed of urethane acrylate, and has a viscosity of 45000 to 65000 mPa·s/60°C and a molecular weight (Mw) of 18000, the number of oligomeric functional groups is 2.

In addition, the above-mentioned ultraviolet curable urethane acrylate resin (trade name "UV-3700B") is an ultraviolet curable resin mainly composed of urethane acrylate, and has a viscosity of 30000 to 60000 mPa·s/60°C and a molecular weight (Mw) of 38000, the number of oligomeric functional groups is 2.

(Photoradical polymerization initiator)

[13] Initiator 1: 2-methyl-1-[4-(methylthio)phenyl]-2-morifolinopropan-1-one (trade name “Irgacure 907” obtained from BASF).

(additive)

[14] Additive 1: Silicone-based leveling agent (trade name "SH710" obtained from Toray Dow Corning Co., Ltd.).

<Production Examples 1 to 6: Preparation of UV curable adhesive>

The above-described radically polymerizable compound, photoradical polymerization initiator, and additives were weighed in a 20 mL screw tube at the blending ratios shown in Table 1 (numerals in Table 1 represent parts by weight), mixed and defoamed, and formed into a liquid state. UV curable adhesives A to F were prepared, respectively.

<Production Examples 7 to 8: Preparation of UV curable adhesive>

The above-described radically polymerizable compound, photoradical polymerization initiator, and additives were weighed in a 20 mL screw tube at the blending ratios shown in Table 2 (numerals in Table 2 represent parts by weight), mixed and defoamed, and formed into a liquid state. UV-curable adhesives G and H were prepared, respectively.

<Production Example 9: Production of (meth)acrylic resin film>

A (meth)acrylic resin, which is a copolymer obtained by copolymerizing methyl methacrylate and methyl acrylate at a weight ratio of 96:4, was prepared. In addition, the innermost layer is made of a hard polymer polymerized with methyl methacrylate and a small amount of allyl methacrylate, and the middle layer is polymerized with butyl acrylate as a main component and also with styrene and a small amount of allyl methacrylate. acrylic particles with a three-layer structure in which the outermost layer is made of a hard polymer polymerized with methyl methacrylate and a small amount of ethyl acrylate, and the average particle diameter up to the middle layer of the elastic body is 240 nm. rubber particles were prepared.

The above-described (meth)acrylic resin and the above-mentioned acrylic rubber particles are blended in a weight ratio of 70:30, preparing a pallet to which a benzotriazole-based ultraviolet absorber is added, and while melt-kneading this with a twin screw extruder, 100 weight of the pallet 0.05 part by weight of stearic acid, which is a lubricant, was added to the mixture and mixed to obtain a pellet of a (meth)acrylic resin composition. This pallet is fed into a 65 mmφ single screw extruder, extruded through a T-shaped die at a set temperature of 275 ° C, and both sides of the extruded film-shaped molten resin are sandwiched between two polishing rolls with mirror surfaces set at a temperature of 45 ° C. to cool Thus, a (meth)acrylic resin film having a thickness of 80 μm was produced. The transmittance at a wavelength of 380 nm of the obtained (meth)acrylic resin film was 25% or less.

<Examples 1 to 3, Comparative Examples 1 to 5>

(1) Fabrication of polarizer

Corona discharge treatment was performed on one side of the (meth)acrylic resin film (first protective film) produced in Production Example 9, and the corona discharge treatment surface was used as a first adhesive (adhesive for forming the first adhesive layer). The adhesives shown in Table 3 were applied using a bar coater to a thickness of about 2.5 μm after curing. Next, a polyvinyl alcohol (PVA)-iodine-based polarizing film having a thickness of 25 µm was bonded to the coated surface. Subsequently, a retardation film having a thickness of 50 μm made of a cyclic polyolefin resin (norbornene resin) [trade name “ZEONOR” manufactured by Nippon Zeon Co., Ltd., in-plane retardation value _Re at a wavelength of 590 nm: 52 nm] (second One side of the protective film) was subjected to corona discharge treatment, and an adhesive similarly described in Table 3 was applied to the corona discharge treated side as the second adhesive (adhesive forming the second adhesive layer) to a thickness of about 2.5 μm after curing. It was coated using a bar coater to become. On the coated surface, a polarizing film with a (meth)acrylic resin film produced above was stacked from the polarizing film side, pressed using a bonding roll, and bonded to obtain a laminate. With respect to this laminated body, on the side of the cyclic polyolefin-based resin film, an ultraviolet irradiation device equipped with a belt conveyor (a "D bulb" manufactured by Fusion UV Systems was used as a lamp) was used so that the integrated light amount was 250 mJ/cm2 (UVB). Ultraviolet rays were irradiated so that the polarizing plate was produced by curing the adhesive layer on both sides.

(2) Measurement of the glass transition temperature Tg of the adhesive layer

Two stretched films of a cyclic polyolefin-based resin having a thickness of 25 µm ["Zeonoa Film" sold by Nippon Zeon Co., Ltd.] were prepared and used as they were without corona treatment. Then, the UV curable adhesive prepared using a bar coater was coated on the surface of one stretched film so that the film thickness after curing was 2 μm, and another stretched film was overlaid on the coated surface. On one side of the cyclic polyolefin-based resin film of this bonded product, an ultraviolet irradiation device equipped with a belt conveyor (a "D bulb" manufactured by Fusion UV Systems was used as a lamp) irradiated ultraviolet light so that the integrated light amount was 250 mJ/cm 2 . By irradiation, the UV-curable adhesive was cured. Next, the stretched film with the cured product sandwiched therebetween was peeled off, and 5 mg of the cured product was collected, placed in an aluminum lid container, pressed tightly, and sealed to prepare a sample for measurement.

Differential Scanning Calorimeter (DSC) ["EXSTAR-6000 DSC6220" sold by SI Nanotechnology Co., Ltd.] is set with a container containing the above measurement sample, and while purging nitrogen gas, the temperature is from 20 ° C to -60 ° C. After lowering the temperature to °C, holding for 1 minute after reaching -60 °C, raising the temperature at a rate of 10 °C/min from -60 °C to 150 °C, and immediately lowering the temperature to 20 °C when reaching 150 °C. Then, from the DSC curve when the temperature is raised from -60 ° C to 150 ° C, the midpoint glass transition temperature specified in JIS K 7121-1987 “Method for Measuring Transition Temperature of Plastics” is obtained, and this is obtained as an ultraviolet curable adhesive to be measured. The glass transition temperature of the adhesive layer (cured product) formed by The glass transition temperature of the first adhesive layer formed of the first adhesive is Tg1, and the glass transition temperature of the second adhesive layer formed of the second adhesive is Tg2.

(3) Evaluation of curl resistance under high temperature environment of polarizing plate

A sheet material having a size of 80 mm × 80 mm was cut out from the polarizing plate prepared in (1) above. After the sheet was left overnight in an environment of a temperature of 23°C and a relative humidity of 60%, it was placed under a drying condition of a temperature of 80°C for 10 minutes, and then placed in an environment of a temperature of 23°C and a relative humidity of 60% for 3 hours. measured The amount of curl was obtained as the average value of the four obtained values by placing the curved sheet member on a horizontal pedestal so as to be convex downward, and measuring the heights from the pedestal to the four corner portions of the sheet member with a ruler, respectively. Based on the amount of curl obtained, curl resistance was evaluated according to the following criteria. The evaluation results are shown in Table 3.

A: The amount of curl is less than 5 mm.

B: The amount of curl is 5 mm or more and less than 10 mm,

C: The amount of curl is 10 mm or more.

(4) Evaluation of workability of polarizer

Using a blade of 800 mm × 800 mm manufactured by Dumbbell, punching was performed from the first protective film side of the polarizing plate, and the state of lifting and peeling at the end of the polarizing plate was visually observed, and workability was evaluated based on the following criteria. . The evaluation results are shown in Table 3.

A: There is no lifting or peeling at the end of the polarizing plate.

B: There exists lifting or peeling at the edge part of a polarizing plate.

(5) Formation of pressure-sensitive adhesive layer

An organic solvent solution of a (meth)acrylic pressure-sensitive adhesive obtained by adding an isocyanate-based crosslinking agent, a silane coupling agent, and an antistatic agent to (meth)acrylic resin, which is a copolymer of butyl acrylate, methyl acrylate, acrylic acid, and hydroxyethyl acrylate, , The release treatment surface of a 38 μm-thick separation film made of polyethylene terephthalate subjected to release treatment [trade name “SP-PLR382052” obtained from Lintec Co., Ltd.], so that the thickness after drying with a die coater is 20 μm Coating was carried out to produce a sheet-like pressure-sensitive adhesive with a separate film. Next, after bonding the surface (adhesive surface) opposite to the separate film of the sheet-like pressure-sensitive adhesive obtained above to the surface of the cyclic polyolefin-based resin film of the polarizing plate produced in the above (1) with a laminator, the temperature is 23 ° C. and the relative humidity is 65%. It was cured for 7 days under the conditions of, and a polarizing plate having an adhesive layer was obtained.

(6) Evaluation of cold and heat shock resistance of polarizing plate

A sheet of 200 mm × 150 mm in size was cut out from the polarizing plate having the pressure-sensitive adhesive layer prepared in (5) above, and bonded to alkali-free glass [trade name "EAGLEXG" manufactured by Corning] from the pressure-sensitive adhesive layer side, followed by a cold-heat shock test. It was set as the measurement sample for (heat shock test). Four of these measurement samples were prepared for each polarizing plate sheet member. The cold-heat shock test was conducted by repeating a total of 100 cycles of holding at -40°C for 30 minutes, then raising the temperature to 70°C and holding for 30 minutes as one cycle. The said cold-and-heat shock test was done about 4 measurement samples, and the cold-and-heat shock resistance was evaluated by the ratio with respect to the total number of samples (4) in which cracks or cracks were observed in the polarizing film after the test. The evaluation results are shown in Table 3.

<Examples 4 to 6>

(1-1) Production of polarizing plate (Example 4)

Corona discharge treatment was performed on one side of the (meth)acrylic resin film (first protective film) produced in Production Example 9, and the corona discharge treatment surface was used as a first adhesive (adhesive for forming the first adhesive layer). The adhesives shown in Table 4 were applied using a bar coater to a thickness of about 2.5 μm after curing. Next, a polyvinyl alcohol (PVA)-iodine-based polarizing film having a thickness of 25 µm was bonded to the coated surface. Next, corona discharge treatment was applied to one side of a retardation film (trade name “KC4CR” manufactured by Konica Minolta Co., Ltd.) (second protective film) having a thickness of 40 μm made of acetyl cellulose resin, and the corona discharge treatment surface was , As the second adhesive (adhesive for forming the second adhesive layer), the adhesive shown in Table 4 was similarly coated using a bar coater so that the thickness after curing was about 2.5 μm. On the coated surface, a polarizing film with a (meth)acrylic resin film produced above was stacked from the polarizing film side, pressed using a bonding roll, and bonded to obtain a laminate. With respect to this laminated body, on the side of the acetyl cellulose-based resin film, using an ultraviolet irradiation device equipped with a belt conveyor ("D Bulb" manufactured by Fusion UV Systems as a lamp was used), the accumulated light amount was 250 mJ/cm2 (UVB ), the adhesive layer on both sides was cured and a polarizing plate was produced.

(1-2) Production of polarizing plate (Examples 5 to 6)

Corona discharge treatment was performed on one side of the (meth)acrylic resin film (first protective film) produced in Production Example 9, and the corona discharge treatment surface was used as a first adhesive (adhesive for forming the first adhesive layer). The adhesives shown in Table 4 were applied using a bar coater to a thickness of about 2.5 μm after curing. Next, a polyvinyl alcohol (PVA)-iodine-based polarizing film having a thickness of 25 µm was bonded to the coated surface. Subsequently, a retardation film having a thickness of 50 μm made of a cyclic polyolefin resin (norbornene resin) [trade name “ZEONOR” manufactured by Nippon Zeon Co., Ltd., in-plane retardation value Re: 52 nm at a wavelength of 590 nm] (second protection Film) was subjected to corona discharge treatment, and on the corona discharge treated surface, the adhesive similarly described in Table 4 as the second adhesive (adhesive forming the second adhesive layer) was cured to a thickness of about 2.5 μm. It was coated using a bar coater as much as possible. On the coated surface, a polarizing film with a (meth)acrylic resin film produced above was stacked from the polarizing film side, pressed using a bonding roll, and bonded to obtain a laminate. With respect to this laminated body, on the side of the cyclic polyolefin-based resin film, an ultraviolet irradiation device equipped with a belt conveyor (the lamp uses a “D bulb” manufactured by Fusion UV Systems Co., Ltd.) was used to obtain a cumulative amount of light of 250 mJ/cm 2 (UVB). Ultraviolet rays were irradiated so that the polarizing plate was produced by curing the adhesive layer on both sides.

(2) Measurement of the glass transition temperature Tg of the adhesive layer

In the same manner as in (2) of <Examples 1 to 3 and Comparative Examples 1 to 5>, the glass transition temperature Tg1 of the first adhesive layer formed of the first adhesive and the second adhesive layer formed of the second adhesive The glass transition temperature Tg2 was measured.

(3) Evaluation of curl resistance under high temperature environment of polarizing plate

It was carried out in the same way as (3) of <Examples 1-3 and Comparative Examples 1-5>, and curl resistance was evaluated about the polarizing plate obtained in Examples 4-6. The evaluation results are shown in Table 4.

(4) Evaluation of workability of polarizer

In the same manner as in (4) of <Examples 1 to 3 and Comparative Examples 1 to 5>, workability was evaluated for the polarizing plates obtained in Examples 4 to 6. The evaluation results are shown in Table 4.

(5) Formation of pressure-sensitive adhesive layer

A polarizing plate having an adhesive layer was obtained using the polarizing plate obtained in Examples 4 to 6 in the same manner as in (5) of <Examples 1 to 3 and Comparative Examples 1 to 5>. On the other hand, the sheet-like pressure-sensitive adhesive was bonded to the surface of the cyclic polyolefin-based resin film or the surface of the acetyl cellulose-based resin film of the polarizing plate.

(6) Evaluation of cold and heat shock resistance of polarizing plate

It was carried out in the same way as (6) of <Examples 1-3 and Comparative Examples 1-5>, and the cold-heat shock resistance was evaluated about the polarizing plate obtained in Examples 4-6. The evaluation results are shown in Table 4.

Claims (8)

A first protective film, a first adhesive layer, a polarizing film, a second adhesive layer and a second protective film in this order,
The glass transition temperature of the first adhesive layer is -15 ° C or more and less than 60 ° C, and the glass transition temperature of the second adhesive layer is 60 ° C or more and 200 ° C or less,
A polarizing plate having a difference between a glass transition temperature of the second adhesive layer and a glass transition temperature of the first adhesive layer of 10 ° C. or more and 120 ° C. or less. The polarizing plate according to claim 1 , wherein the first adhesive layer has a glass transition temperature of 0° C. or higher. The polarizing plate according to claim 1 , wherein the second adhesive layer has a glass transition temperature of 80° C. or higher. The polarizing plate according to claim 1, wherein at least one of the first adhesive layer and the second adhesive layer is a cured material layer of an active energy ray-curable adhesive. The polarizing plate of claim 4, wherein the active energy ray-curable adhesive includes a radical polymerizable compound. The method of claim 1, wherein the first protective film and the second protective film are resins selected from the group consisting of polyester-based resins, polycarbonate-based resins, polyolefin-based resins, (meth)acrylic-based resins, and cellulose ester-based resins. A polarizing plate composed of. The polarizing plate according to claim 6, wherein the first protective film is made of a (meth)acrylic resin, and the second protective film is made of a polyolefin-based resin or a cellulose ester-based resin. The polarizing plate according to claim 1, wherein at least one of the first protective film and the second protective film is a retardation film.

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