JP2014137477A - Polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate in which a first protective film made of a cycloolefin based resin, a polarizing film made of a polyvinyl alcohol based resin and a second protective film made of an acetyl-cellulose based resin are laminated in this order and which is excellent in heat resistance and moist-heat resistance when the polarizing plate is used while an adhesive layer having antistatic function is provided on the surface of the second protective film on the side opposite to the polarizing film.SOLUTION: The polarizing plate includes a first protective film made of a cycloolefin based resin and bonded to on one surface of a polarizing film through an adhesive and a second protective film made of an acetyl-cellulose based resin and bonded to the other surface of the polarizing film through the adhesive. The adhesive is formed of a photo-curable composition in which a cationic polymerization photoinitiator is blended into cationically polymerizable compound at a ratio of 2 pts.wt. or less of the former to 100 pts.wt. of the later on the first protective film side and the second protective film side.

Description

  The present invention relates to a polarizing plate in which a protective film made of a transparent resin is bonded to a polarizing film made of a polyvinyl alcohol resin.

  The polarizing plate is useful as one of the optical components constituting the liquid crystal display device. A polarizing plate usually has a structure in which protective films are laminated on both sides of a polarizing film, and is incorporated in a liquid crystal display device. It is also known that a protective film is provided only on one side of a polarizing film, but in many cases, a protective film is not a simple protective film on the other side but a film or layer having an optical function as another function. It is also formed. As a method for producing a polarizing film, a method in which a uniaxially stretched polyvinyl alcohol-based resin film dyed with a dichroic dye is treated with boric acid, followed by washing with water and drying is widely adopted.

  Usually, a protective film is bonded to the polarizing film immediately after the water washing treatment and the drying treatment. This is because the polarizing film after drying has a low physical strength, and once it is wound, there is a problem that it tends to tear in the processing direction. Therefore, usually, a water-based adhesive which is an aqueous solution of a polyvinyl alcohol resin is immediately applied to the polarizing film after the drying treatment, and protective films are simultaneously bonded to both surfaces of the polarizing film via this adhesive. Generally, a triacetyl cellulose film having a thickness of 30 to 100 μm is used as the protective film.

  The triacetyl cellulose film has high moisture permeability, and the polarizing plate bonded as a protective film has a problem of causing deterioration under wet heat, for example, at a temperature of 70 ° C. and a relative humidity of 90%. Therefore, it is also known that a protective film is made of a resin having a moisture permeability lower than that of triacetyl cellulose, for example, an amorphous polyolefin resin typically represented by a norbornene resin.

  When bonding a protective film made of a resin with low moisture permeability to a polyvinyl alcohol polarizing film, in an aqueous solution of a polyvinyl alcohol resin generally used as an adhesive for bonding a polyvinyl alcohol polarizing film and triacetyl cellulose There are problems that the adhesive strength is not sufficient or the appearance of the obtained polarizing plate becomes poor. This is because a resin film having a low moisture permeability is generally hydrophobic and water such as a solvent cannot be sufficiently dried due to a low moisture permeability. On the other hand, it is also known to bond different types of protective films on both surfaces of the polarizing film. For example, one surface of the polarizing film is made of a resin with low moisture permeability such as an amorphous polyolefin resin. There is also a proposal for bonding a protective film and bonding a protective film made of a highly moisture-permeable resin such as cellulose resin including triacetyl cellulose to the other surface of the polarizing film.

  Therefore, it provides high adhesion between a protective film made of a resin with low moisture permeability and a polyvinyl alcohol polarizing film, and high adhesion between a resin with high moisture permeability such as a cellulose resin and a polyvinyl alcohol polarizing film. There is an attempt to use an active energy ray-curable adhesive as an adhesive that gives force. For example, JP 2004-245925 A (Patent Document 1) discloses an adhesive mainly composed of an epoxy compound that does not contain an aromatic ring, and this adhesive is obtained by cationic polymerization by irradiation with active energy rays. It has been proposed to cure and bond the polarizing film and the protective film. JP 2008-257199 A (Patent Document 2) discloses a photocurable adhesive comprising a combination of an alicyclic epoxy compound and an epoxy compound having no alicyclic epoxy group, which is blended with a photocationic polymerization initiator. The technique which uses an agent for adhesion | attachment with a polarizing film and a protective film is disclosed.

  However, a polarizing plate produced using an adhesive having a composition specifically disclosed in Patent Document 1 or Patent Document 2 is discolored by sunlight or the heat of a backlight when applied to a liquid crystal display device. Are known. In particular, the above polarizing plate is a polarizing plate in which a cycloolefin resin film, a polarizing film, and an acetyl cellulose resin film are laminated. An adhesive with an antistatic function is provided on the acetyl cellulose resin film side to provide a liquid crystal display device. When applied, there is a problem that discoloration of the polarizing plate due to heat becomes remarkable.

JP 2004-245925 A JP 2008-257199 A

  Then, the subject of this invention is the polarizing plate in which the 1st protective film which consists of cycloolefin type resin, the polarizing film, and the 2nd protective film which consists of acetylcellulose type resins are laminated | stacked in this order, When a pressure-sensitive adhesive layer with an antistatic function is provided on the surface (the side opposite to the polarizing film), discoloration of the polarizing film due to heat is suppressed, and a polarizing plate excellent in wet heat resistance is provided.

  As a result of intensive studies to solve such problems, the inventors have used the first protective film and the adhesive used for bonding the second protective film and the polarizing film in the polarizing plate having the above-described configuration. About the 1st protective film side and the 2nd protective film side from the photocurable composition by which the photocationic polymerization initiator was mix | blended in the ratio of 2 weight part or less with respect to 100 weight part of cationic polymerizable compounds. It has been found that when the formed one is employed, a polarizing plate excellent in heat resistance and moist heat resistance can be obtained, and the present invention has been achieved.

  That is, in the polarizing plate of the present invention, a first protective film made of a cycloolefin resin is formed on one surface of a polarizing film made of a polyvinyl alcohol resin, and an acetyl cellulose resin is formed on the other surface of the polarizing film. Each of the second protective films is bonded via an adhesive, and a pressure-sensitive adhesive layer having an antistatic function is provided on the side opposite to the surface on which the polarizing film of the second protective film is bonded. The adhesive is a photocurable composition in which a photocationic polymerization initiator is blended at a ratio of 2 parts by weight or less with respect to 100 parts by weight of the cationically polymerizable compound on both the first protective film side and the second protective film side. It is formed from things.

  The cationically polymerizable compound constituting the photocurable composition may include an epoxy compound having at least one alicyclic epoxy group in the molecule.

  The photocationic polymerization initiator constituting the photocurable composition can have a gas phase acidity of 260 kcal / mol or less.

  Further, the above-mentioned photocationic polymerization initiator can be 4- (phenylthio) phenyldiphenylsulfonium tris (pentafluoroethyl) trifluorophosphate represented by the following formula (I).

  The pressure-sensitive adhesive layer having an antistatic function desirably contains an ionic compound having an anion having a fluorine atom.

  Thus, the obtained polarizing plate can suppress the variation | change_quantity of the single-piece | unit hue ab value of a polarizing plate at the time of heating at 90 degreeC for 48 hours, for example to 3 or less.

  Hereinafter, the present invention will be described in detail. In the polarizing plate of the present invention, a first protective film made of a cycloolefin resin is bonded to one surface of a polarizing film made of polyvinyl alcohol resin via an adhesive, and acetyl is attached to the other surface of the polarizing film. Adhesive having an antistatic function on the surface opposite to the polarizing film of the second protective film made of acetyl cellulose resin, wherein the second protective film made of cellulose resin is bonded via an adhesive. The agent is bonded. Each member and component which comprise a polarizing plate are demonstrated one by one.

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

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

  The uniaxial stretching step may be performed before dyeing with the dichroic dye, may be performed simultaneously with dyeing with the dichroic dye, or may be performed after dyeing with the dichroic dye. When uniaxial stretching is performed after dyeing with a dichroic dye, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Of course, it is also possible to perform uniaxial stretching in these plural stages. For uniaxial stretching, stretching may be performed between rolls having different peripheral speeds, or stretching may be performed by sandwiching between rolls. Moreover, the dry-type extending | stretching which extends | stretches in air | atmosphere may be sufficient, and the wet extending | stretching which extends | stretches in the state swollen with the solvent may be sufficient. The draw ratio is usually about 4 to 8 times.

  In order to dye the polyvinyl alcohol resin film with the dichroic dye, for example, the polyvinyl alcohol resin film may be immersed in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic organic dye is used as the dichroic dye.

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

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

  The boric acid treatment after dyeing with a dichroic dye is performed by immersing the dyed polyvinyl alcohol resin film in an aqueous boric acid solution. The boric acid content in the boric acid aqueous solution is usually about 2 to 15 parts by weight, preferably about 5 to 12 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye, this aqueous boric acid solution preferably contains potassium iodide. The content of potassium iodide in the boric acid aqueous solution is usually about 2 to 20 parts by weight, preferably 5 to 15 parts by weight per 100 parts by weight of water. The immersion time in the boric acid aqueous solution is usually about 100 to 1,200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C.

  The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment is performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. A drying process is performed after water washing, and a polarizing film is manufactured. The temperature of water in the water washing treatment is usually about 5 to 40 ° C., and the immersion time is usually about 2 to 120 seconds. The drying process performed after that is normally performed using a hot air dryer or a far-infrared heater. The drying temperature is usually 40 to 100 ° C. Moreover, the time of a drying process is about 120 to 600 seconds normally.

  Thus, the thickness of the polarizing film which consists of polyvinyl alcohol-type resin obtained can be about 10-50 micrometers.

[Protective film]
In the present invention, the first protective film made of cycloolefin resin is bonded to one side of the polarizing film made of polyvinyl alcohol resin described above via an adhesive, and acetyl is attached to the other side of the polarizing film. A second protective film made of a cellulose-based resin is bonded via an adhesive. Below, each protective film is demonstrated.

  The cycloolefin resin constituting the first protective film is, for example, a thermoplastic resin having a cycloolefin structural unit represented by norbornene, tetracyclododecene (also known as dimethanooctahydronaphthalene) or a derivative thereof. It is. In addition, it can be a hydrogenated product of the above-mentioned cycloolefin ring-opening polymer or a ring-opening copolymer using two or more kinds of cycloolefins, and cycloolefins and chain olefins or aromatics having a vinyl group. An addition copolymer with a compound may be used. In addition, a polar group may be introduced.

Commercially available thermoplastic cycloolefin resins are, for example, produced by TOPAS ADVANCED POLYMERS GmbH, Germany, and sold by "TOPAS" and JSR, which are sold by Polyplastics in Japan. “ARTON”, “ZEONEX” and “ZEONOR” sold by Nippon Zeon Co., Ltd., “Apel” sold by Mitsui Chemicals, etc. )

  In forming such a cycloolefin-based resin into a film, a known film forming method such as a solvent casting method or a melt extrusion method is appropriately used for film formation. A formed cycloolefin-based resin film and a cycloolefin-based resin film further stretched and provided with a phase difference are also commercially available. For example, "Arton Film" sold by JSR Corporation, "Zeonor Film" sold by Nippon Zeon Corporation, "Essina" and "SCA40" sold by Sekisui Chemical Co., Ltd. (Both are trade names) and these can be used preferably.

  In addition, the acetylcellulose-based resin constituting the second protective film is a resin in which at least a part of hydroxyl groups in cellulose is acetated, partly acetated, and partly esterified with another acid. It may be a mixed ester. Specific examples of the acetyl cellulose resin include triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate.

  These protective films may have various surface treatment layers such as a hard coat layer, an antireflection layer, an antiglare layer, and an antistatic layer on the surface opposite to the bonding surface with the polarizing film. The protective film can have a thickness of about 5 to 150 μm including the case where the surface treatment layer as described above is formed. The thickness is preferably 10 μm or more, preferably 120 μm or less, more preferably 100 μm or less.

[adhesive]
In the polarizing plate of the present invention, the first protective film is bonded to one surface of the polarizing film via an adhesive, and the second protection is applied to the other surface of the polarizing film via the adhesive. The film is bonded. This adhesive is formed from a photocurable composition in which a cationically polymerizable compound and a photocationic polymerization initiator are blended in a predetermined ratio.

(Cationically polymerizable compound)
The cationically polymerizable compound is a main component of the photocurable composition and becomes a component that gives an adhesive force by polymerization and curing. The cationically polymerizable compound may be any compound that cures by cationic polymerization, and particularly preferably includes an epoxy compound having at least two epoxy groups in the molecule. Examples of the epoxy compound include an aromatic epoxy compound having an aromatic ring in the molecule, an alicyclic compound having at least two epoxy groups in the molecule, and at least one of which is bonded to the alicyclic ring. An epoxy compound, which does not have an aromatic ring in the molecule, and one carbon atom of the epoxy group and the ring containing two carbon atoms to which it is bonded (usually an oxirane ring) is bonded to another aliphatic carbon atom And aliphatic epoxy compounds. Among these, those having an alicyclic epoxy compound as a main component are particularly preferable as the cationic polymerizable compound. When a cationically polymerizable compound having an alicyclic epoxy compound as a main component is used, a cured product (adhesive layer) having a high storage elastic modulus is given, and a protective film and a polarizing film are bonded via the cured product. In this case, the polarizing film is hardly broken.

  As described above, the alicyclic epoxy compound has at least two epoxy groups in the molecule, and at least one of them is bonded to the alicyclic ring. Here, the epoxy group bonded to the alicyclic ring is, as shown in the following formula (II), two bonds in which two bonds of the epoxy group (—O—) constitute the alicyclic ring. Each of the carbon atoms (usually adjacent carbon atoms). In the following formula (II), m represents an integer of 2 to 5.

A compound in which a group in the form of removing one or more hydrogen atoms in (CH ₂ ) _m in the above formula (II) is bonded to another chemical structure can be an alicyclic epoxy compound. Hydrogen constituting the alicyclic ring may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among these, a compound having an epoxycyclopentane ring [m = 3 in the above formula (II)] or an epoxycyclohexane ring [m = 4 in the above formula (II)] is preferable.

  Among the alicyclic epoxy compounds, alicyclic diepoxy compounds represented by the following formula (III) are preferable because they are easily available and have a large effect of increasing the storage elastic modulus of the cured product. The alicyclic diepoxy compound of the following formula (III) includes 3,4-epoxycyclohexylmethanol (the hydrogen atom constituting the cyclohexane may be substituted with an alkyl group having 1 to 6 carbon atoms), and 3,4 -An esterified product of epoxycyclohexanecarboxylic acid (the hydrogen atom constituting the cyclohexane may be substituted with an alkyl group having 1 to 6 carbon atoms).

Examples of the ester compound represented by the above formula (III) include 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (R ¹ = R ² = hydrogen atom), 3,4-epoxy-6-methylcyclohexyl. Examples include methyl 3,4-epoxy-6-methylcyclohexanecarboxylate (R ¹ = 6-methyl, R ² = 6-methyl).

  It is also effective to use the alicyclic epoxy compound and the aliphatic epoxy compound described above in combination. If the alicyclic epoxy compound is the main component and the aliphatic epoxy compound is used in combination with this as a cationically polymerizable compound, the adhesion between the polarizing film and the protective film is maintained while keeping the storage modulus of the cured product at a high value. It is possible to further improve the properties. As described above, the aliphatic epoxy compound here does not have an aromatic ring in the molecule, and one of the epoxy group and a ring containing two carbon atoms to which it is bonded (usually an oxirane ring). A compound in which a carbon atom is bonded to another aliphatic carbon atom. Examples thereof include polyglycidyl ethers of aliphatic polyhydric alcohols. Among these, a diglycidyl ether compound represented by the following formula (IV) is preferable because it is easily available and has a large effect of enhancing the adhesion between the polarizing film and the protective film.

  The diglycidyl ether compound represented by the above formula (IV) is a diglycidyl ether of alkylene glycol, wherein Z represents an alkylene group having 2 to 9 carbon atoms, and Z may be a straight chain or a branched chain. There may be.

  As the diglycidyl ether compound represented by the above formula (IV), for example, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,3-propanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, neopentyl Examples include glycol diglycidyl ether and 1,6-hexanediol diglycidyl ether.

  When the alicyclic epoxy compound and the aliphatic epoxy compound described above are used in combination, the blending ratio of both is 50 to 95% by weight of the alicyclic epoxy compound and the aliphatic based on the total amount of the cationic polymerizable compound. The epoxy compound is preferably 5% by weight or more. Of course, the sum of these does not exceed 100% by weight. By blending the alicyclic epoxy compound, for example, the alicyclic diepoxy compound of the above formula (III) at a ratio of 50% by weight or more of the whole cationic polymerizable compound, the storage modulus of the cured product at 80 ° C. is increased. Since it becomes 1,000 MPa or more, the polarizing film becomes difficult to break in the polarizing plate in which the polarizing film and the protective film are bonded via it.

  Moreover, the adhesiveness of a polarizing film and a protective film improves by mix | blending an aliphatic epoxy compound, for example, the diglycidyl ether compound of the said Formula (IV), 5weight% or more with respect to the whole cationically polymerizable compound. The blending ratio of the aliphatic epoxy compound is allowed up to 50% by weight based on the total amount of the cationic polymerizable compound when the cationic polymerizable compound is a two-component system of an alicyclic diepoxy compound and an aliphatic epoxy compound. However, if the amount is too large, the storage elastic modulus of the cured product is lowered and the polarizing film is easily cracked. Therefore, the amount is preferably 45% by weight or less based on the total amount of the cationic polymerizable compound.

  When the alicyclic diepoxy compound represented by the above formula (III) and the diglycidyl ether compound represented by the above formula (IV) described above are used in combination as the cationic polymerizable compound constituting the photocurable composition, In addition to these, other cationically polymerizable compounds may be included within the range described above. Examples of other cationically polymerizable compounds include epoxy compounds and oxetane compounds other than the above formulas (III) and (IV).

  The epoxy compounds other than the above formulas (III) and (IV) include an alicyclic epoxy compound having an epoxy group bonded to at least one alicyclic ring in the molecule other than the formula (III), and the formula (IV) Aliphatic epoxy compounds having an oxirane ring bonded to other aliphatic carbon atoms, aromatic epoxy compounds having an aromatic ring and an epoxy group in the molecule, and hydrogenated epoxy compounds in which the aromatic ring in the aromatic epoxy compound is hydrogenated and so on.

  As an alicyclic epoxy compound having an epoxy group bonded to at least one alicyclic ring in a molecule other than the above formula (III), for example, alkylene glycol and 3,4-epoxycyclohexanecarboxylic acid (on the cyclohexane ring) An esterified product of which an alkyl group may be bonded); an esterified product of a dicarboxylic acid and 3,4-epoxycyclohexylmethanol (which may have an alkyl group bonded to the cyclohexane ring); an alkylene glycol and 3, Etherified products with 4-epoxycyclohexylmethanol (which may have an alkyl group bonded to the cyclohexane ring); diepoxides of vinylcyclohexenes such as 4-vinylcyclohexene diepoxide and 1,2: 8,9-diepoxylimonene and so on.

  Examples of the aliphatic epoxy compound having an oxirane ring bonded to an aliphatic carbon atom other than the above formula (IV) include triglycidyl ether of glycerin, triglycidyl ether of trimethylolpropane, diglycidyl ether of polyethylene glycol, 2-ethyl Hexyl glycidyl ether.

  The aromatic epoxy compound having an aromatic ring and an epoxy group in the molecule can be a glycidyl ether of an aromatic polyhydroxy compound having at least two phenolic hydroxyl groups in the molecule. Examples include diglycidyl ether, diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol S, and glycidyl ether of phenol novolac resin.

  The hydrogenated epoxy compound in which the aromatic ring in the aromatic epoxy compound is hydrogenated is an aromatic polyhydroxy compound having at least two phenolic hydroxyl groups in the molecule as a raw material of the aromatic epoxy compound. The hydrogenated polyhydroxy compound obtained by selectively performing a hydrogenation reaction under pressure can be obtained by glycidyl etherification. Specific examples include diglycidyl ether of hydrogenated bisphenol A, hydrogenated bisphenol. Diglycidyl ether of F, diglycidyl ether of hydrogenated bisphenol S, and the like.

  Among these epoxy compounds other than those of formulas (III) and (IV), when compounding a compound that has an epoxy group bonded to an alicyclic ring and is classified as an alicyclic epoxy compound as defined above, The sum of the alicyclic diepoxy compound represented by the formula (III) is used within a range not exceeding 95% by weight based on the total amount of the cationically polymerizable compound.

  Moreover, the oxetane compound which can be any cationically polymerizable compound is a compound having a 4-membered ring ether (oxetanyl group) in the molecule, and specific examples thereof include the following compounds.

  3-ethyl-3-hydroxymethyloxetane, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, 3-ethyl-3- (phenoxymethyl) oxetane, di [(3-ethyl-3 -Oxetanyl) methyl] ether, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, 3-ethyl-3- (cyclohexyloxymethyl) oxetane, phenol novolac oxetane, 1,3-bis [(3-ethyloxetane -3-yl) methoxy] benzene, oxetanylsilsesquioxane, oxetanyl silicate and the like.

  By blending the oxetane compound at a ratio of 30% by weight or less based on the total amount of the cationic polymerizable compound, an effect of improving curability is expected compared to the case where only the epoxy compound is used as the cationic polymerizable compound. There are things you can do.

(Photocationic polymerization initiator)
A cationic photopolymerization initiator is blended with the cationically polymerizable compound as described above to obtain a photocurable composition. The photocurable composition undergoes cationic polymerization upon irradiation with active energy rays and is cured to give an adhesive layer. The cationic photopolymerization initiator is not particularly limited as long as it generates a cationic species or a Lewis acid upon irradiation with an active energy ray such as visible light, ultraviolet ray, X-ray, or electron beam, and initiates a polymerization reaction of the cationically polymerizable compound. Good. Since the photocationic polymerization initiator acts catalytically by light, it does not affect its storage stability and workability even when mixed with a cationically polymerizable compound. Examples of the photocationic polymerization initiator include aromatic diazonium salts, onium salts such as aromatic iodonium salts and aromatic sulfonium salts, and iron-arene complexes.

Examples of the aromatic diazonium salt include the following compounds.
Benzenediazonium hexafluoroantimonate,
Benzenediazonium hexafluorophosphate,
Benzenediazonium hexafluoroborate, etc.

Examples of the aromatic iodonium salt include the following compounds.
Diphenyliodonium tetrakis (pentafluorophenyl) borate,
Diphenyliodonium hexafluorophosphate,
Diphenyliodonium hexafluoroantimonate,
Di (4-nonylphenyl) iodonium hexafluorophosphate and the like.

Examples of the aromatic sulfonium salt include the following compounds.
Triphenylsulfonium hexafluorophosphate,
Triphenylsulfonium hexafluoroantimonate,
Triphenylsulfonium tetrakis (pentafluorophenyl) borate,
4,4′-bis [diphenylsulfonio] diphenyl sulfide bishexafluorophosphate,
4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexafluoroantimonate,
4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexafluorophosphate,
7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone hexafluoroantimonate,
7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate,
4-phenylcarbonyl-4′-diphenylsulfonio-diphenyl sulfide hexafluorophosphate,
4- (p-tert-butylphenylcarbonyl) -4′-diphenylsulfonio-diphenyl sulfide hexafluoroantimonate,
4- (p-tert-butylphenylcarbonyl) -4′-di (p-toluyl) sulfonio-diphenyl sulfide tetrakis (pentafluorophenyl) borate 4- (phenylthio) phenyldiphenylsulfonium tris (pentafluoroethyl) trifluorophosphate 4 -(Phenylthio) phenyldiphenylsulfonium hexafluorophosphate 4- (phenylthio) phenyldiphenylsulfonium trifluoromethanesulfonate and the like.

Examples of the iron-arene complex include the following compounds.
Xylene-cyclopentadienyl iron (II) hexafluoroantimonate,
Cumene-cyclopentadienyl iron (II) hexafluorophosphate,
Xylene-cyclopentadienyl iron (II) tris (trifluoromethylsulfonyl) methanide.

  These cationic photopolymerization initiators may be used alone or in combination of two or more. Among these, aromatic sulfonium salts are particularly preferably used because they have ultraviolet absorption characteristics even in a wavelength region near 300 nm, and thus can provide a cured product having excellent curability and good mechanical strength and adhesive strength. It is done.

Aromatic sulfonium salts constitute a photocationic polymerization initiator paired with a sulfonium cation (cation) and an anion (anion). As a measure of resin curability of this photocationic polymerization initiator, an anion is used. Gas phase acidity. Gas phase acidity is acidity in the gas phase and is defined as Gibbs energy change accompanying acid dissociation by IUPAC. This gas phase acidity can be calculated by a known method as described in, for example, “J. Am. Chem. Soc. 2000, 122, 5114-5124”. The gas phase acidity of typical anions of the above-mentioned sulfonium salts are BF ₄ ⁻ (288 kJ / mol), PF ₆ ⁻ (277 kJ / mol), SbF ₆ ⁻ (256 kJ / mol), (CF ₃ CF ₂ ) _3. PF ₃ ⁻ (256 kJ / mol), and considering the curability of these sulfonium salt resins, the gas phase acidity is preferably 260 kJ / mol or less.

  When the gas phase acidity exceeds 260 kJ / mol, the curability of the resin deteriorates. For example, even when the resin does not cure or the resin is apparently cured, the unreacted resin remaining in the cured resin film It is conceivable that the durability of the polarizing plate deteriorates due to the monomer. In order to reduce the amount of residual monomer, a method of increasing the amount of sulfonium salt added may be considered, but in this case, the amount of hydrogen fluoride by-produced by decomposition of the initiator increases, so that corrosion of the equipment and polarization Problems such as discoloration of the board occur.

  The compounding quantity of a photocationic polymerization initiator shall be 0.1-2 weight part with respect to 100 weight part of cationically polymerizable compounds. By blending 0.1 part by weight or more of the cationic photopolymerization initiator per 100 parts by weight of the cationically polymerizable compound, the cationically polymerizable compound can be sufficiently cured, and the resulting polarizing plate has high mechanical strength and adhesive strength. give. On the other hand, when the amount increases, the residual amount of the unreacted initiator, the solvent used as necessary to dissolve the initiator or the decomposition product of the initiator increases, and the physical properties of the cured product are impaired. In addition, since the amount of hydrogen fluoride by-produced by decomposition of the initiator increases, the polarizing film is deteriorated by heat, and the polarizing plate is discolored. Therefore, the amount of the cationic photopolymerization initiator is preferably 2 parts by weight or less per 100 parts by weight of the cationic polymerizable compound.

(Other components that can be blended in the photo-curable adhesive)
The photocurable adhesive may contain other components in addition to the cationic polymerizable compound and the photo cationic polymerization initiator described above. Examples of other components that can be incorporated include photosensitizers, photosensitizers, thermal cationic polymerization initiators, chain transfer agents, thermoplastic resins, flow regulators, antifoaming agents, leveling agents, organic solvents. and so on. Depending on the type of protective film to be bonded to the polarizing film, it may be preferable to blend a photosensitizer and further a photosensitization aid.

  The photosensitizer is a compound that exhibits maximum absorption at a wavelength longer than the maximum absorption wavelength exhibited by the photocationic polymerization initiator and promotes the polymerization initiation reaction by the photocationic polymerization initiator. As such a photosensitizer, an anthracene compound is preferably used. As anthracene compounds that can be used as photosensitizers, 9,10-dimethoxyanthracene, 9,10-diethoxyanthracene, 9,10-dipropoxyanthracene, 9,10-diisopropoxyanthracene, 9,10-dibutoxyanthracene 9,10-dipentyloxyanthracene, 9,10-dihexyloxyanthracene and the like.

  The photosensitizing assistant is a compound that further promotes the action of the photosensitizer. As such a photosensitizing assistant, naphthalene compounds are preferably used. 1,4-dimethoxynaphthalene, 1-ethoxy-4-methoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dipropoxynaphthalene, 1,4-dibutoxy as naphthalene compounds that can serve as photosensitizers And naphthalene.

  When blending these other components, the amount thereof is, for example, in the range of 10 parts by weight or less for each 100 parts by weight of the cationically polymerizable compound that is the main component of the photocurable adhesive, depending on the blending purpose. What is necessary is just to select suitably.

[Preparation of polarizing plate]
A 1st protective film and a 2nd protective film are bonded to a polarizing film through the adhesive bond layer formed from a photocurable composition, and let it be a polarizing plate. This bonding forms the coating layer of the photocurable composition demonstrated above in one or both of the bonding surface of a polarizing film and a protective film, and forms a polarizing film and these protective films through the coating layer. Bonding is performed by irradiating an application layer of the uncured photocurable composition with an active energy ray, and these protective films are fixed on the polarizing film.

  Various coating methods, such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater, can be used for forming the coating layer of the photocurable composition. Moreover, it can also employ | adopt the system which casts a photocurable composition in the meantime, supplying a polarizing film and a protective film continuously so that both bonding surfaces may become inside. Since each coating system has an optimum viscosity range, it is also a useful technique to adjust the viscosity using a solvent. There is no particular limitation on the type of the solvent for this purpose as long as it can dissolve the photocurable composition well without deteriorating the optical performance of the polarizing film. For example, organic solvents such as hydrocarbons typified by toluene and esters typified by ethyl acetate can be used.

  In adhering the polarizing film and the protective film, the corona discharge treatment, the plasma treatment, the flame treatment, the primer treatment, and the anchor coating are performed on one or both of the bonding surfaces before forming the coating layer of the adhesive composition. Easy adhesion treatment such as treatment may be performed.

The light source used for irradiating the coating layer of the photocurable composition with active energy rays may be any one that generates ultraviolet rays, electron beams, X-rays, and the like. In particular, for example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, a metal halide lamp or the like having a light emission distribution at a wavelength of 400 nm or less is preferably used. The irradiation intensity of the active energy ray to the photocurable composition is determined for each target composition and is not particularly limited, but the irradiation intensity in the wavelength region effective for activating the initiator is 0. It is preferable that it is 0.1-100 mW / cm < ² >. When the light irradiation intensity to the photocurable composition is less than 0.1 mW / cm ² , the reaction time becomes too long, and when it exceeds 100 mW / cm ² , the heat radiated from the lamp and the photocurable composition The heat generated during the polymerization may cause yellowing of the photocurable composition or deterioration of the polarizing film. The light irradiation time to the photocurable composition is controlled for each composition to be cured and is not particularly limited, but the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is 10 to 5, It is preferably set to be 000 mJ / cm ² . When the integrated light quantity to the photocurable composition is less than 10 mJ / cm ² , active species derived from the initiator are not sufficiently generated, and the resulting adhesive layer may be insufficiently cured, When the integrated light quantity exceeds 5,000 mJ / cm ² , the irradiation time becomes very long, which is disadvantageous for improving productivity.

  When a protective film is bonded to both sides of the polarizing film, the active energy ray may be irradiated from either side of the protective film. For example, one protective film contains an ultraviolet absorber and the other protective film When the ultraviolet absorber is not contained, it is preferable to irradiate the active energy rays from the protective film side not containing the ultraviolet absorber in order to effectively use the irradiated active energy rays and increase the curing rate.

  The thickness of the adhesive layer formed by curing the photocurable composition is usually 20 μm or less, preferably 10 μm or less, more preferably 5 μm or less. When the adhesive layer becomes thick, the reaction rate of the adhesive composition decreases, and the wet heat resistance of the polarizing plate tends to deteriorate.

[Optical properties of polarizing plate]
The polarizing plate of the present invention employs a photocurable composition in which 2 parts or less of the cationic photopolymerization initiator is blended with respect to 100 parts by weight of the cationic polymerizable compound in the adhesive layer constituting the polarizing plate, It is resistant to deterioration even when exposed to high temperature conditions and has excellent heat resistance. For example, even after performing a heating test that is allowed to stand for 48 hours in an environment at a temperature of 90 ° C., the ab value represented by the root mean square value of the a value and b value of the transmitted hue is kept in the range of 0.5 to 3. be able to.

The above-mentioned transmission hue means the hue of light transmitted from the other surface when light is applied from one surface of the polarizing plate. The hue here can be expressed by a value and b value in the Lab color system, and is measured using standard light. In the present invention, the measured transmission hue of the polarizing plate is measured on the acetyl cellulose film of the polarizing plate having protective films (cycloolefin film and acetyl cellulose film in the examples described later) on both sides of the polarizing film. A pressure-sensitive adhesive layer is provided, and the pressure-sensitive adhesive layer side is bonded to a glass plate. The Lab color system is represented by Hunter's lightness index L and hues a and b as described in “5.5 Accelerated weather resistance test” of JIS K 5981: 2006 “Synthetic resin powder coating”. Is. As a concept similar to the Lab color system, JIS Z 8729: 2004 "Color Display method - L ^* a ^* b ^* color system and L ^* u ^* v ^* color system" as defined in L ^* a ^* b ^{* Although} there is a color system, the Lab color system is adopted in the present invention. The values of the lightness index L and the hues a and b are calculated from the tristimulus values X, Y and Z defined in JIS Z 8722: 2009 “Color Measurement Method—Reflection and Transmission Object Color” by the following formula. .

L = 10Y ^1/2
a = 17.5 (10.2 XY) / Y ^1/2
b = 7.0 (Y-0.847Z) / Y1 / ² .

In the Lab color system, the hue a value and b value can indicate positions corresponding to saturation, and when the hue a value increases, the hue changes to red, and when the hue b value increases, the hue changes to yellow. Each changes. The ab value representing the hue is calculated by the following equation (V).
ab = (a ² + b ² ) ^1/2 (V)

The polarizing plate of the present invention has an ab value represented by the root mean square value of the a value and b value of the transmitted hue even after a heating test that is allowed to stand for 48 hours in an environment at a temperature of 90 ° C. Therefore, the polarizing plate does not turn yellow even under such a high temperature environment, and the durability is excellent.

The single transmittance (Ty) is a transmittance when natural light is incident on one film. The natural light incident upon measuring the single transmittance can be divided into linearly polarized light orthogonal to the transmission axis of the film and linearly polarized light parallel to the transmission axis. If the transmittance when linearly polarized light orthogonal to the transmission axis (that is, parallel to the absorption axis) is incident is kc, and the transmittance when linearly polarized light parallel to the transmission axis is incident is kp, the single transmittance Ty is Since it is the average of the transmittance when linearly polarized light orthogonal to the transmission axis is incident and the transmittance when linearly polarized light parallel to the transmission axis is incident, it can be expressed by the following formula (VI) (expressed as a percentage display) If this is the case, multiply this by 100).
Single transmittance Ty = (kc + kp) / 2 (VI)

[Laminated optical member]
The polarizing plate of the present invention can be made into a laminated optical member by laminating optical layers having optical functions other than the polarizing plate. Typically, a laminated optical member is obtained by laminating and attaching an optical layer to a protective film of a polarizing plate via an adhesive or a pressure-sensitive adhesive. In addition, for example, the present invention is applied to one surface of a polarizing film. Accordingly, the protective film can be bonded via the photocurable composition, and the optical layer can be laminated and bonded to the other surface of the polarizing film via the adhesive or the pressure-sensitive adhesive. In the latter case, if the photocurable composition defined in the present invention is used as an adhesive for adhering the polarizing film and the optical layer, the optical layer can simultaneously be a protective film defined in the present invention.

  As an example of the optical layer laminated on the polarizing plate, for the polarizing plate arranged on the back side of the liquid crystal cell, the reflective layer is laminated on the opposite side of the polarizing plate from the side facing the liquid crystal cell. A layer, a transflective layer, a light diffusion layer, a light collector, a brightness enhancement film, and the like. In addition, for both the polarizing plate disposed on the front side of the liquid crystal cell and the polarizing plate disposed on the back side of the liquid crystal cell, a retardation plate laminated on the side of the polarizing plate facing the liquid crystal cell, etc. There is.

  The reflective layer, transflective layer, or light diffusion layer is a reflective polarizing plate (optical member), a transflective polarizing plate (optical member), or a diffusing polarizing plate (optical member), respectively. Is provided. The reflective polarizing plate is used in a liquid crystal display device of a type that reflects and displays incident light from the viewing side. Since a light source such as a backlight can be omitted, the liquid crystal display device can be easily thinned. The transflective polarizing plate is used as a reflection type in a bright place and used in a liquid crystal display device that displays light from a backlight in a dark place. The optical member as the reflective polarizing plate can form a reflective layer by attaching a foil or a vapor deposition film made of a metal such as aluminum to a protective film on a polarizing film, for example. The optical member as a transflective polarizing plate can be formed by using the reflective layer as a half mirror, or by adhering a reflective plate containing a pearl pigment or the like and exhibiting light transmittance to the polarizing plate. On the other hand, an optical member as a diffusion type polarizing plate can be applied by various methods such as a method of performing a mat treatment on a protective film on a polarizing plate, a method of applying a resin containing fine particles, and a method of adhering a film containing fine particles. Use to form a fine relief structure on the surface.

  Furthermore, an optical member can be formed as a polarizing plate for both reflection and diffusion. In that case, for example, a method of providing a reflective layer reflecting the concavo-convex structure on the fine concavo-convex structure surface of the diffusing polarizing plate is adopted. it can. The reflective layer having a fine concavo-convex structure has advantages such that incident light is diffused by irregular reflection, directivity and glare can be prevented, and uneven brightness can be suppressed. In addition, the resin layer or film containing fine particles also has an advantage that incident light and its reflected light are diffused when passing through the fine particle-containing layer, and light and dark unevenness can be suppressed. The reflective layer reflecting the surface fine concavo-convex structure can be formed by directly attaching a metal to the surface of the fine concavo-convex structure by a method such as vapor deposition such as vacuum deposition, ion plating, sputtering, or plating. The fine particles to be blended for forming the surface fine concavo-convex structure are, for example, silica, aluminum oxide, titanium oxide, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide having an average particle diameter of 0.1 to 30 μm. It can be inorganic fine particles, organic fine particles such as crosslinked or non-crosslinked polymers, and the like.

  The light collector is used for the purpose of optical path control and can be formed as a prism array sheet, a lens array sheet, or a dot-attached sheet.

  The brightness enhancement film is used for the purpose of improving the brightness in a liquid crystal display device. For example, a plurality of thin film films having different refractive index anisotropies are laminated to produce anisotropy in reflectance. Examples thereof include a reflective polarization separation sheet designed as described above, an oriented film of a cholesteric liquid crystal polymer, and a circularly polarized light separation sheet in which the oriented liquid crystal layer is supported on a film substrate.

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

  Examples of the plastic forming the birefringent film include amorphous polyolefin resins, polycarbonate resins, acrylic resins, chain polyolefin resins such as polypropylene, polyvinyl alcohol, polystyrene, polyarylate, polyamide, and the like. It is done. The stretched film can be processed by an appropriate method such as uniaxial or biaxial. Note that two or more retardation plates may be used in combination for the purpose of controlling optical characteristics such as broadening the bandwidth.

  Of the laminated optical members, those including a retardation plate as an optical layer other than the polarizing plate are preferably used because they can effectively ensure optical security when applied to a liquid crystal display device. The optimum retardation value (in-plane and thickness direction) of the retardation plate may be selected according to the liquid crystal cell to be applied.

  The laminated optical member can be a laminate of two layers or three or more layers by combining a polarizing plate and one or more layers selected from the various optical layers described above according to the purpose of use. In that case, the various optical layers forming the laminated optical member are integrated with the polarizing plate using an adhesive or pressure-sensitive adhesive, but the adhesive or pressure-sensitive adhesive layer used for this purpose is good. As long as it is formed, there is no particular limitation. It is preferable to use a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive) from the viewpoint of easy bonding work and prevention of optical distortion. As the pressure-sensitive adhesive, those having an acrylic polymer, a silicone polymer, polyester, polyurethane, polyether, or the like as a base polymer can be used. Among them, like acrylic adhesives, it has excellent optical transparency, retains appropriate wettability and cohesion, has excellent adhesion to substrates, and has weather resistance and heat resistance. However, it is preferable to select and use a material that does not cause peeling problems such as floating and peeling under the conditions of heating and humidification. In acrylic adhesives, alkyl esters of (meth) acrylic acid having an alkyl group having 20 or less carbon atoms such as methyl, ethyl and butyl groups, and (meth) acrylic acid and hydroxyethyl (meth) acrylate Based on an acrylic copolymer having a weight average molecular weight of 100,000 or more, which is blended with a functional group-containing acrylic monomer comprising a glass transition temperature of preferably 25 ° C. or less, more preferably 0 ° C. or less. Useful as a polymer.

  The pressure-sensitive adhesive layer is formed on the polarizing plate by, for example, 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, which is directly on the polarizing plate. It can be carried out by a coating method, a method in which an adhesive layer is previously formed on a protective film, and transferred onto a polarizing plate. The thickness of the pressure-sensitive adhesive layer is determined according to the adhesive force and the like, but a range of about 1 to 50 μm is appropriate.

  In addition, the pressure-sensitive adhesive layer is optionally filled with glass fiber, glass beads, resin beads, metal powder, other inorganic powders, pigments, colorants, antioxidants, antistatic agents, ultraviolet absorbers. Etc. may be blended. Examples of ultraviolet absorbers include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex compounds.

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

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

  The ionic compound can be classified into an ionic compound having an organic cation, an ionic compound having an inorganic cation, an ionic compound having an organic anion, and an ionic compound having an inorganic anion. Examples of ionic compounds having an organic cation are listed below by classification according to the structure of the organic cation.

Pyridinium salt:
1-butylpyridinium tetrafluoroborate,
1-butylpyridinium hexafluorophosphate,
1-butyl-3-methylpyridinium tetrafluoroborate,
1-butyl-3-methylpyridinium trifluoromethanesulfonate,
1-butyl-3-methylpyridinium bis (trifluoromethanesulfonyl) imide,
1-butyl-3-methylpyridinium bis (pentafluoroethanesulfonyl) imide,
1-butyl-4-methylpyridinium hexafluorophosphate,
1-hexylpyridinium tetrafluoroborate,
1-hexylpyridinium hexafluorophosphate,
1-hexyl-4-methyl-pyridinium bis (fluorosulfonyl) imide,
1-octylpyridinium hexafluorophosphate,
1-butylpyridinium N- (trifluoromethanesulfonyl) trifluoroacetamide,
1-butyl-3-methylpyridinium N- (trifluoromethanesulfonyl) trifluoroacetamide and the like.

Imidazolium salt:
1-ethyl-3-methylimidazolium tetrafluoroborate,
1-ethyl-3-methylimidazolium hexafluorophosphate,
1-ethyl-3-methylimidazolium acetate,
1-ethyl-3-methylimidazolium trifluoroacetate,
1-ethyl-3-methylimidazolium heptafluorobutyrate,
1-ethyl-3-methylimidazolium trifluoromethanesulfonate,
1-ethyl-3-methylimidazolium perfluorobutane sulfonate,
1-ethyl-3-methylimidazolium p-toluenesulfonate,
1-ethyl-3-methylimidazolium dicyanamide,
1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide,
1-ethyl-3-methylimidazolium bis (pentafluoroethanesulfonyl) imide,
1-ethyl-3-methylimidazolium tris (trifluoromethanesulfonyl) methanide,
1-ethyl-3-methylimidazolium N- (trifluoromethanesulfonyl) trifluoroacetamide,
1-butyl-3-methylimidazolium methanesulfonate,
1-butyl-3-methylimidazolium tetrafluoroborate,
1-butyl-3-methylimidazolium hexafluorophosphate,
1-butyl-3-methylimidazolium trifluoroacetate,
1-butyl-3-methylimidazolium heptafluorobutyrate,
1-butyl-3-methylimidazolium trifluoromethanesulfonate,
1-butyl-3-methylimidazolium perfluorobutane sulfonate,
1-butyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide,
1-hexyl-3-methylimidazolium bromide,
1-hexyl-3-methylimidazolium chloride,
1-hexyl-3-methylimidazolium tetrafluoroborate,
1-hexyl-3-methylimidazolium hexafluorophosphate,
1-hexyl-3-methylimidazolium trifluoromethanesulfonate,
1-octyl-3-methylimidazolium tetrafluoroborate,
1-octyl-3-methylimidazolium hexafluorophosphate,
1-hexyl-2,3-dimethylimidazolium tetrafluoroborate,
1,2-dimethyl-3-propylimidazolium bis (trifluoromethanesulfonyl) imide and the like.

Pyrrolidinium salt:
1-butyl-1-methylpyrrolidinium hexafluorophosphate and the like.

Quaternary ammonium salt:
Tetrabutylammonium hexafluorophosphate,
Tetrabutylammonium p-toluenesulfonate,
Tetrahexylammonium bis (trifluoromethanesulfonyl) imide,
N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium tetrafluoroborate,
N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide,
Diallyldimethylammonium tetrafluoroborate,
Diallyldimethylammonium trifluoromethanesulfonate,
Diallyldimethylammonium bis (trifluoromethanesulfonyl) imide,
Diallyldimethylammonium bis (pentafluoroethanesulfonyl) imide,
Diallyldimethylammonium N- (trifluoromethanesulfonyl) trifluoroacetamide,
Glycidyltrimethylammonium trifluoromethanesulfonate,
Glycidyltrimethylammonium bis (trifluoromethanesulfonyl) imide, glycidyltrimethylammonium bis (pentafluoroethanesulfonyl) imide,
Glycidyltrimethylammonium N- (trifluoromethanesulfonyl) trifluoroacetamide,
N, N-dimethyl-N-ethyl-N-propylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dimethyl-N-ethyl-N-butylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dimethyl-N-ethyl-N-pentylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dimethyl-N-ethyl-N-hexylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dimethyl-N-ethyl-N-heptylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dimethyl-N-ethyl-N-nonylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dimethyl-N, N-dipropylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dimethyl-N-propyl-N-butylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dimethyl-N-propyl-N-pentylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dimethyl-N-propyl-N-hexylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dimethyl-N-propyl-N-heptylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dimethyl-N-butyl-N-hexylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dimethyl-N-butyl-N-heptylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dimethyl-N-pentyl-N-hexylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dimethyl-N, N-dihexylammonium bis (trifluoromethanesulfonyl) imide,
Trimethylheptylammonium bis (trifluoromethanesulfonyl) imide,
N, N-diethyl-N-methyl-N-propylammonium bis (trifluoromethanesulfonyl) imide,
N, N-diethyl-N-methyl-N-pentylammonium bis (trifluoromethanesulfonyl) imide,
N, N-diethyl-N-methyl-N-heptylammonium bis (trifluoromethanesulfonyl) imide,
N, N-diethyl-N-propyl-N-pentylammonium bis (trifluoromethanesulfonyl) imide,
Triethylpropylammonium bis (trifluoromethanesulfonyl) imide,
Triethylpentylammonium bis (trifluoromethanesulfonyl) imide,
Triethylheptylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dipropyl-N-methyl-N-ethylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dipropyl-N-methyl-N-pentylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dipropyl-N-butyl-N-hexylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dipropyl-N, N-dihexylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dibutyl-N-methyl-N-pentylammonium bis (trifluoromethanesulfonyl) imide,
N, N-dibutyl-N-methyl-N-hexylammonium bis (trifluoromethanesulfonyl) imide,
Trioctylmethylammonium bis (trifluoromethanesulfonyl) imide,
Trioctylmethylammonium hexafluorophosphate,
N-methyl-N-ethyl-N-propyl-N-pentylammonium bis (trifluoromethanesulfonyl) imide,
(2-hydroxyethyl) trimethylammonium bis (trifluoromethanesulfonyl) imide,
(2-hydroxyethyl) trimethylammonium dimethylphosphinate and the like.

Examples of the ionic compound having an inorganic cation include the following.
Lithium bromide,
Lithium iodide,
Lithium tetrafluoroborate,
Lithium hexafluorophosphate,
Lithium thiocyanate,
Lithium perchlorate,
Lithium trifluoromethanesulfonate,
Lithium bis (trifluoromethanesulfonyl) imide,
Lithium bis (pentafluoroethanesulfonyl) imide,
Lithium tris (trifluoromethanesulfonyl) methanide,
Potassium bis (fluorosulfonyl) imide and the like.

  The ionic compound having an organic cation and the ionic compound having an inorganic cation exemplified above each have a counter ion (anion). Thus, examples of the ionic compound having an organic anion and the ionic compound having an inorganic anion described above can be found in the compounds listed above.

When the anionic component constituting the ionic compound is hexafluorophosphate,
In particular, the hue change of the polarizing film due to the heat of the polarizing film composed of a cycloolefin-based resin film, a polarizing film, and an acetylcellulose-based resin film becomes remarkable, and in this case, the effect of the photocurable adhesive of the present invention is particularly confirmed.

  The laminated optical member can be disposed on one side or both sides of the liquid crystal cell. The liquid crystal cell to be used is arbitrary. For example, a liquid crystal display device using various liquid crystal cells such as an active matrix drive type typified by a thin film transistor type and a simple matrix drive type typified by a super twisted nematic type. Can be formed. A pressure-sensitive adhesive is usually used for bonding the laminated optical member and the liquid crystal cell.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In the examples, “parts” and “%” representing the content or amount used are based on weight unless otherwise specified. Moreover, the cationically polymerizable compound, the silane coupling agent, and the photocationic polymerization initiator used in the following examples are as follows, and are denoted by respective symbols below.

(A) Cationic polymerizable compound (a1) 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate: obtained from Daicel Chemical Industries, Ltd., trade name “Celoxide 2021P”. In Table 1 below, it is abbreviated as “(a1)”.
(A2) 1,4-butanediol diglycidyl ether: obtained from Nagase ChemteX Corporation, trade name “EX-214L”. In Table 1 below, it is abbreviated as “(a2)”.

(B) Photocationic polymerization initiator (b1) 4- (phenylthio) phenyldiphenylsulfonium tris (pentafluoroethyl) trifluorophosphate: a compound represented by the formula (I). In Table 1 below, it is abbreviated as “(b1)”.
(B2) 4- (phenylthio) phenyldiphenylsulfonium hexafluorophosphate: obtained from San Apro Co., Ltd., trade name “CPI-100P”. In Table 1 below, it is abbreviated as “(b2)”.
(B3) 4- (phenylthio) phenyldiphenylsulfonium trifluoromethanesulfonate: obtained from San Apro Co., Ltd., trade name “PAG-TF”. In Table 1 below, it is abbreviated as “(b3)”.

[Examples 1 and 2, Comparative Examples 1 to 3]
(1) Preparation of photocurable composition After mixing each component by the mixture ratio (a part is a part) shown in Table 1, it degas | defoamed and prepared the photocurable compositions 1-5. In addition, a photocationic polymerization initiator was mix | blended as a 50% propylene carbonate solution, and displayed in Table 1 with the solid content.

(2) Curability of adhesive The photocurable compositions 1 to 5 prepared in (1) are applied to the surface of a 50 μm thick cycloolefin film [trade name “ZEONOR” manufactured by Nippon Zeon Co., Ltd.] Coating was performed using a bar coater so that the film thickness after curing was about 2.5 μm. From the photocurable composition side of the photocurable composition-coated film, the integrated light amount is 500 mJ / cm ² using an ultraviolet irradiation device with a belt conveyor (using a “D bulb” manufactured by Fusion UV Systems). The adhesive layer was formed by irradiating ultraviolet rays so as to cure the photocurable composition. The finger touch on the surface of the adhesive layer after curing was confirmed, and the curability when there was no stickiness was good (◯), and the curability when there was stickiness was judged as poor (×). The results are summarized in Table 1.

(3) Production of Polarizing Plate A polarizing plate was produced using the photocurable compositions 1 to 4 in which the adhesive of the above (2) had good curability. The surface of a cycloolefin film [trade name “ZEONOR” manufactured by Nippon Zeon Co., Ltd.] having a thickness of 50 μm is subjected to corona discharge treatment, and the above photocurable composition is applied to the corona discharge treatment surface using a bar coater. Articles 1 to 4 were each coated so that the film thickness after curing was about 2.5 μm. A polyvinyl alcohol-iodine polarizing film was bonded to the coated surface of the photocurable composition. Further, a corona discharge treatment was applied to a bonding surface of a 40 μm thick acetylcellulose-based film [trade name “N-TAC KC4FR-1” manufactured by Konica Minolta Opto Co., Ltd.], and a cycloolefin was applied to the corona discharge treatment surface. The same photocurable composition as that used for the system film was coated with a bar coater so that the film thickness after curing was about 2.5 μm. The polarizing film by which the cycloolefin film produced above was bonded on the single side | surface was bonded to the application surface of the photocurable composition on the polarizing film side, and the laminated body was produced. From the acetylcellulose film side of this laminate, ultraviolet rays were irradiated using an ultraviolet irradiation device with a belt conveyor (the lamp used a “D bulb” manufactured by Fusion UV Systems Co., Ltd.) so that the integrated light amount was 500 mJ / cm ^2. The photocurable composition was cured to form an adhesive layer. In this way, a polarizing plate in which a protective film was bonded to both surfaces of the polarizing film via an adhesive was produced.

  Next, an adhesive layer was formed on each polarizing plate prepared in (3) to prepare a polarizing plate with an adhesive. In the following examples, the following were used as the isocyanate-based crosslinking agent, silane coupling agent, and antistatic agent, respectively.

<Isocyanate-based crosslinking agent>
Coronate L: Trimethylolpropane adduct of tolylene diisocyanate in ethyl acetate solution (solid content: 75%), obtained from Nippon Polyurethane Co., Ltd.

<Silane coupling agent>
KBM-403: 3-glycidoxypropyltrimethoxysilane, liquid, obtained from Shin-Etsu Chemical Co., Ltd.

<Antistatic agent>
N-hexylpyridinium hexafluorophosphate, a compound represented by the following formula (VII) and having a melting point of 45 ° C.

(4) Production of polarizing plate with pressure-sensitive adhesive layer Acrylic system obtained by adding an isocyanate-based crosslinking agent, a silane coupling agent, and an antistatic agent to a copolymer of butyl acrylate, methyl acrylate, acrylic acid, and hydroxyethyl acrylate An organic solvent solution of an adhesive was prepared. The thickness after drying with a die coater on the release treatment surface of a 38 μm-thick polyethylene terephthalate film (trade name “SP-PLR382020” (release film) manufactured by Lintec Co., Ltd.) that has been subjected to release treatment. Was applied to give a sheet-like pressure sensitive adhesive with a release film. Next, the surface (adhesive surface) opposite to the separator of the sheet-like pressure-sensitive adhesive obtained above was bonded to the surface of the acetylcellulose film of the polarizing plate prepared in (2) above with a laminator, and then the temperature was 23. Curing was carried out for 7 days under the conditions of ° C. and relative humidity of 65% to obtain a polarizing film with an adhesive.

(5) Evaluation of optical properties of polarizing plate The polarizing plate with adhesive prepared in (4) above is cut into a size of 30 mm × 30 mm and bonded to an alkali-free glass (trade name “EAGLE XG” manufactured by Corning). Then, the a value and b value of each transmitted hue were measured. Measurement is performed using a UV-visible spectrophotometer “UV-2450” manufactured by Shimadzu Corporation with an optional accessory “film holder with polarizing film” set, and transmission through a polarizing plate in the wavelength range of 380 nm to 780 nm. The spectrum was obtained, and the a value and b value of the transmission hue and the transmittance Ty were calculated by software “UV-Probe” attached to the spectrophotometer. Based on this measured value, the ab value of the transmitted hue was calculated according to the following equation.

(6) Evaluation of heat resistance of polarizing plate The polarizing plate produced in the above (4) was subjected to a heating test for 48 hours in a heating environment at a temperature of 90 ° C., and the transmitted hue a value and b in the polarizing plate after the test The value was measured. The measurement and the calculation of the ab value were performed by the same method as in (4) above. Table 2 shows the change Δab value of the transmitted hue before and after the heat resistance test. The results are summarized in Table 2. Δab in the table represents a change in the hue of the polarizing plate, and when the value is 3 or more, when the polarizing plate is applied to a liquid crystal display device, the color change of the polarizing plate can be noticed visually. Means.

    Δab = ab value after heating test−ab value before heating test

(6) Moisture and heat resistance evaluation of polarizing plate The polarizing plate produced in the above (4) is subjected to a test for 48 hours in a humid heat environment at a temperature of 60 ° C. and a relative humidity of 90%. It was measured. Measurement and calculation of Ty were performed in the same manner as in (4) above. Table 2 shows the change ΔTy in transmittance before and after the wet heat resistance test. In the table, ΔTy represents a change in the single transmittance of the polarizing plate. When the numerical value is 2 or more, it means that a defect occurs in the appearance of the polarizing plate.

  From Table 2, the first protective film made of cycloolefin-based resin, the polarizing film made of polyvinyl alcohol-based resin, and the second protective film made of acetylcellulose-based resin were each bonded via an adhesive. In the case where a pressure-sensitive adhesive layer having an antistatic function is provided on the surface of the plate opposite to the polarizing film of the second protective film made of acetylcellulose-based resin, the adhesive is used with respect to 100 parts by weight of the cationic polymerizable compound. It was confirmed that good heat resistance and heat-and-moisture resistance were exhibited by setting the addition amount of the photocationic polymerization initiator to 2 parts or less.

Claims (6)

A first protective film made of a cycloolefin resin is bonded to one surface of a polarizing film made of a polyvinyl alcohol resin through an adhesive, and a second film made of an acetylcellulose resin is attached to the other surface of the polarizing film. Two protective films are bonded via an adhesive,
An adhesive layer having an antistatic function is provided on the side opposite to the surface on which the polarizing film of the second protective film is bonded,
The adhesive is a photocurable composition in which the cationic photopolymerization initiator is blended at a ratio of 2 parts by weight or less with respect to 100 parts by weight of the cationic polymerizable compound on both the first protective film side and the second protective film side. A polarizing plate formed from the composition.   2. The polarizing plate according to claim 1, wherein the cationically polymerizable compound constituting the photocurable composition contains an epoxy compound having at least one alicyclic epoxy group in the molecule.   The polarizing plate according to claim 1, wherein the photocationic polymerization initiator constituting the photocurable composition has a gas phase acidity of 260 kcal / mol or less. The photocationic polymerization initiator has the following formula (I)

The polarizing plate according to claim 3, which is 4- (phenylthio) phenyldiphenylsulfonium tris (pentafluoroethyl) trifluorophosphate represented by:   The polarizing plate according to claim 1, wherein the pressure-sensitive adhesive layer having an antistatic function contains an ionic compound having an anion having a fluorine atom.   The polarizing plate according to any one of claims 1 to 5, wherein a change amount of a single hue ab value when held at a temperature of 90 ° C for 48 hours is 3 or less.