TWI646349B - Method for manufacturing polarizer - Google Patents

Abstract

The present invention provides a method for producing a polarizing plate having excellent adhesion properties between a polarizing film and a protective film. In the method of producing a polarizing plate, at least one surface of a polarizing film having an iodine or a dichroic dye adsorbed to a polyvinyl alcohol-based resin film is attached, and a protective film formed of a thermoplastic resin is bonded by an ultraviolet curable adhesive. A method for producing a polarizing plate, comprising: a step (a) of contacting the protective film with water; and at least one film selected from the group consisting of the protective film and the polarizing film of the step (a), forming an ultraviolet curing type a step (b) of forming an adhesive layer formed of a second agent; a step of preparing a protective film and a polarizing film via the adhesive layer to obtain a laminated film; and irradiating the laminated film with ultraviolet rays to cause subsequent Step (d) of hardening the layer.

Description

Method for manufacturing polarizing plate

The present invention relates to a method of manufacturing a polarizing plate.

A polarizing film is used for an image display device such as a liquid crystal display device, an organic EL (electroluminescence) device, or a plasma display panel (PDP).

As a polarizing film, iodine or a dichroic dye is widely used for adsorption to a polyvinyl alcohol-based resin film, and it is usually bonded to a protective film to form a polarizing plate. For example, JP-A-2008-287207 (Patent Document 1) discloses a method in which a polarizing film is directly bonded to a polarizing film via an active energy ray-curable adhesive, and the adhesive is cured to produce a polarizing plate. However, the strength of the above-mentioned adhesives is not necessarily sufficient, and peeling or the like may occur.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] JP-A-2008-287207, in particular, paragraph 0098 and the like.

The present invention has been made in order to solve the above problems. A method for producing a polarizing plate which is excellent in adhesion of a polarizing film and a protective film formed of a thermoplastic resin.

In other words, the present invention provides a method for producing a polarizing plate which is bonded to at least one side of a polarizing film having an iodine or a dichroic dye adsorbed to a polyvinyl alcohol-based resin film, and bonded by an ultraviolet curing adhesive. A method for producing a polarizing plate comprising a protective film formed of a thermoplastic resin, comprising: a step (a) of contacting the protective film with water; and at least one selected from the group consisting of the protective film and the polarizing film of the step (a) a step (b) of forming an adhesive layer composed of an ultraviolet curable adhesive on a film; a step (c) of forming a laminated film by laminating a protective film and a polarizing film via an adhesive layer; The step (d) of irradiating the ultraviolet ray to harden the adhesive layer.

In the above production method, the protective film may include a step (a-1) of heating the protective film before the step (a) of contacting the water.

Further, the ultraviolet curable adhesive can be heated before the formation of the adhesive layer. Further, the ultraviolet curable adhesive is preferably a cationically polymerizable epoxy-based adhesive, and the epoxy-based adhesive is more preferably an epoxy resin containing no aromatic ring in the molecule. The epoxy-based adhesive may further contain a photocationic polymerization initiator in addition to the epoxy resin.

In the present invention, the thermoplastic resin constituting the protective film is Good for acrylic resin. Further, the protective film of the present invention preferably has a water content of from 0.2 to 5% by weight after the step of bringing the protective film into contact with water.

According to the present invention, a protective film made of a thermoplastic resin, in particular, a protective film made of an acrylic resin is brought into contact with water, whereby a polarizing film having a good adhesion property of the polarizing film and the protective film can be provided. The polarizing plate obtained by the present invention can be suitably used for a liquid crystal display device.

The present invention relates to a method of producing a polarizing plate by bonding a protective film made of a thermoplastic resin to a polarizing plate using an ultraviolet curable adhesive, and is characterized in that it comprises a step of bringing a protective film into contact with water, and is selected from a protective film and a polarizing film. a step of forming an adhesive layer on one surface of at least one film of the film to form an adhesive layer; a step of laminating a protective film and a polarizing film via an adhesive layer to obtain a laminated film; and a laminated film A step of irradiating ultraviolet rays to harden the adhesive layer.

[Polarizer]

The polarizing plate obtained by the production method of the present invention has a structure in which a protective film made of a thermoplastic resin is bonded to a polarizing film made of a polyvinyl alcohol-based resin by an ultraviolet curable adhesive.

(polarized film)

The polarizing film used in the present invention is composed of a polyvinyl alcohol-based resin, and specifically, a dichroic dye is adsorbed and aligned to a polyvinyl alcohol-based resin film. The polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin film can be saponified with a polyvinyl acetate-based resin. Examples of the polyvinyl acetate-based resin include, in addition to the homopolymer of vinyl acetate, a copolymer of vinyl acetate and another monomer copolymerizable therewith. As other monomers copolymerizable with vinyl acetate, for example, an unsaturated carboxylic acid, an olefin, a vinyl ether, an unsaturated sulfonic acid, an acrylamide having an ammonium group, or the like.

The degree of saponification of the polyvinyl alcohol-based resin is usually 85 mol% or more, preferably 98 mol% or more. Further, the polyvinyl alcohol-based resin may be a modified one, for example, a polyvinyl formal modified with an aldehyde, polyvinyl acetal, and polyvinyl butyral. The degree of polymerization of the polyvinyl alcohol-based resin is usually from about 1,000 to 10,000, preferably from about 1,500 to 5,000.

A film made of such a polyvinyl alcohol-based resin can be used as a polarizing film. The polyvinyl alcohol-based resin can be formed into a film by a conventionally suitable method. The film thickness of the germicidal film made of a polyvinyl alcohol-based resin is, for example, about 10 to 150 μm .

The polarizing film is usually subjected to a step of dyeing the dichroic dye by a dye film formed of a polyvinyl alcohol-based resin as described above, a dyeing step (dyeing step), and a polyvinyl alcohol having a dichroic dye adsorbed thereon. The resin film is treated with a boric acid aqueous solution (boric acid treatment step) and a water washing step (water washing treatment step) after the treatment step of the boric acid aqueous solution.

Moreover, when manufacturing a polarizing film, usually one-axis extension polyethylene The alcohol-based resin film may be carried out before the dyeing treatment step, or in the dyeing treatment step, or after the dyeing treatment step. When the one-axis extension is performed after the dyeing treatment step, the one-axis extension may be performed before the boric acid treatment step or in the boric acid treatment step. Of course, one-axis extension can also be performed at these multiple stages. One-axis extension can be extended between rollers with different rotational speeds, or extended by hot rollers. Further, it may be a dry stretching which is extended in the atmosphere, or a wet stretching in which the solvent is extended in an expanded state. The stretching ratio is usually about 3 to 8 times.

In the dyeing treatment step, the polyvinyl alcohol-based resin film is dyed by a dichroic dye, for example, by impregnating a polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic dye. As the dichroic dye, iodine, a dichroic dye or the like is used. The dichroic dye includes a dichroic direct dye composed of a diazo compound such as C.I. Direct Red 39, a dichroic direct dye, a arsenazo, an anthracene azo compound or the like. Further, the polyvinyl alcohol-based resin film is preferably subjected to immersion treatment of water before the dyeing treatment.

When iodine is used as the dichroic dye, a method in which a polyvinyl alcohol-based resin film is immersed in an aqueous solution containing iodine and potassium iodide and dyed is usually used. The iodine content of the aqueous solution is usually 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide is usually 0.5 to 20 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye, the temperature of the aqueous solution used for dyeing is usually 20 to 40 ° C, and the immersion time (dyeing time) of the aqueous solution is usually 20 to 1800 seconds.

On the other hand, when a dichroic dye is used as the dichroic dye, a method in which a polyvinyl alcohol-based resin film is immersed in an aqueous solution containing a water-soluble dichroic dye and dyed is usually used. The content of the dichroic dye of the solution, typically water per 100 parts by weight of 1 × 10 ^-4 to 10 parts by weight, preferably 1 × 10 ^-3 to 1 parts by weight, particularly preferred of 1 × 10 ^-3 to 1 × 10 ^-2 parts by weight. The aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing aid. When a dichroic dye is used as the dichroic dye, the temperature of the aqueous dyeing solution used for dyeing is usually 20 to 80 ° C, and the immersion time (dyeing time) of the aqueous solution is usually 10 to 1800 seconds.

The boric acid treatment step is carried out by immersing the polyvinyl alcohol-based resin film dyed with the dichroic dye in an aqueous boric acid solution. The amount of boric acid in the aqueous boric acid solution is usually 2 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. When iodine is used as the dichroic dye in the dyeing treatment step, the aqueous boric acid solution used in the boric acid treatment step preferably contains potassium iodide. At this time, the amount of potassium iodide in the aqueous boric acid solution is usually 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight per 100 parts by weight of water. The immersion time for the aqueous boric acid solution is usually from 60 to 1200 seconds, preferably from 150 to 600 seconds, more preferably from 200 to 400 seconds. The temperature of the aqueous boric acid solution is usually 50 ° C or higher, preferably 50 to 85 ° C, more preferably 60 to 80 ° C.

Then, in the water washing treatment step, an excess of boric acid, iodine or the like is removed from the polyvinyl alcohol-based resin film after the boric acid treatment, for example, by immersing the film in water. The temperature of the water to be washed is usually 5 to 40 ° C, and the immersion time is usually 1 to 120 seconds. After the water washing treatment, the film was subjected to a drying treatment to obtain a polarizing film. Drying treatment, for example using hot air drying Dry machine, far infrared heater, etc. The temperature of the drying treatment is usually from 30 to 100 ° C, preferably from 50 to 80 ° C. The drying time is usually 60 to 600 seconds, preferably 120 to 600 seconds.

The thickness of the obtained polarizing film is usually in the range of 5 to 40 μm , more preferably 5 to 30 μm .

(protective film)

The protective film used in the present invention is a film for physically and chemically protecting a polarizing film, and is composed of a thermoplastic resin. Examples of the thermoplastic resin include olefin-based resins such as polyethylene, polypropylene, and polyvinyl chloride; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; and polycarbonate resins; a cycloolefin-based resin such as a decene-based resin; a polyurethane resin; an acrylic resin such as polyacrylate or polymethacrylate; and diethylamino cellulose and triethylenesulfonyl cellulose (TAC) A transparent polymer material such as a cellulose resin. Among them, a polyolefin resin, a polyester resin, a polycarbonate resin, a cycloolefin resin, an acrylic resin, and a cellulose resin are used to effectively increase the polarizing film and the protective film by the polarizing plate obtained by the present invention. It is suitable for the adhesiveness, and is particularly suitable as an acrylic resin. Further, the thermoplastic resin may contain an additive such as an ultraviolet absorber, an antioxidant, a plasticizer or the like as needed. The thermoplastic resin can be formed into a film by a conventional method such as a cast film method or an extrusion method.

The above-mentioned cycloolefin-based resin refers to a thermoplastic resin having a monomer unit composed of a cycloolefin of a norbornene or a polycyclic norbornene-based monomer. Resin. The cycloolefin resin may be a hydrogenated product of a ring-opening polymer using a single cyclic olefin, a hydrogenated product of a ring-opening copolymer using two or more kinds of cyclic olefins, and may be a cyclic olefin and a chain olefin and/or have a vinyl group. An addition polymer such as an aromatic compound. Further, it is also effective to introduce a polar group into the main chain or the side chain.

As a commercially available thermoplastic cycloolefin resin, "Topas", which is manufactured by Polyplastics Co., Ltd., "Arton" (registered trademark) sold by JSR, and Japan ZEON (share), manufactured by Topas Advanced Polymers GmbH. "ZEONOR" (registered trademark) and "ZEONEX" (registered trademark) and "APL" (registered trademark) sold by Mitsui Chemicals Co., Ltd. (all of which are trade names) can be used as appropriate.

Further, as the acrylic resin described above, a methyl methacrylate-based resin can be suitably used. The methyl methacrylate-based resin is a polymer containing 50% by weight or more of a structural unit derived from methyl methacrylate when the total amount of the resin is 100% by weight. The structural unit derived from methyl methacrylate is all contained in the resin, and is preferably contained in an amount of 70% by weight or more. Further, a methyl methacrylate homopolymer obtained by separately polymerizing methyl methacrylate may also be used.

The methyl methacrylate-based resin may be a copolymer of methyl methacrylate and a monomer copolymerizable therewith as long as it contains 50% by weight or more of a structural unit derived from methyl methacrylate. . As a monomer copolymerizable with methyl methacrylate, such as ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, methacrylic acid 2-ethylhexyl ester and Methyl acrylate other than methyl methacrylate such as 2-hydroxyethyl methacrylate; methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, acrylic acid 2 Acrylates such as ethylhexyl ester and 2-hydroxyethyl acrylate; unsaturated acids such as methacrylic acid and acrylic acid; halogenated styrenes such as chlorostyrene and bromostyrene; such as vinyl toluene and α-methyl Alkyl styrene such as styrene or the like is substituted for styrene; acrylonitrile, methacrylonitrile, maleic anhydride, phenyl maleimide, cyclohexylmaleimide or the like. These monomers may be used alone or in combination of two or more.

A rubbery polymer may be added to the above methyl methacrylate resin. The acrylic resin film can be made soft by the addition of the rubbery polymer. Thereby, when the film is formed, the operation of winding the film by the tension is applied, and the problem that the stress is concentrated on a part of the film to cause cracking or cutting of the film at the end portion of the film can be avoided, and the film can be efficiently produced. Further, even when it is bonded to the polarizing film, it is possible to suppress breakage of the film, and the operation of the film is facilitated by avoiding the problem of cutting the film.

The rubbery polymer may, for example, be an acrylic multilayer structure or a graft copolymer obtained by graft-polymerizing an ethylenically unsaturated monomer with a rubber component. The acrylic multilayer structure is a multilayer structure having a rubber elastic layer or an elastomer layer inside and a hard layer as the outermost layer. The rubber-elastic layer or the layer of the elastomer may be, for example, 20 to 60% by weight based on the total weight of the rubber-like polymer. The acrylic multilayer structure may have a structure in which a hard layer is further provided as the innermost layer.

a rubber-elastic layer or a layer of elastomer, converted from glass A layer composed of an acrylic polymer having a point (Tg) of less than 25 °C. The acrylic polymer forming a rubber elastic layer or an elastomer layer may be composed of one or more kinds of lower alkyl (meth)acrylate, lower alkyl alkoxylate, and cyanoethyl (meth)acrylate. An ethylenically unsaturated monomer such as an ester, acrylamide, a hydroxyl lower alkyl (meth)acrylate or (meth)acrylic acid, and allyl (meth)acrylate, ethylene glycol di(meth)acrylate , butanediol di(meth)acrylate, diallyl phthalate, triallyl cyanurate, urea allyl propionate, divinylbenzene, maleic acid diene A crosslinked polymer obtained by polymerizing a polyfunctional monomer such as propyl ester, trimethylolpropane tri(meth)acrylate or allyl cinnamate.

The hard layer is a layer composed of an acrylic polymer having a Tg of 25 ° C or higher. As such an acrylic polymer, for example, a homopolymer of an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms, and an alkyl methacrylate as a main component, and other alkyl methacrylates, a copolymer of a copolymerizable monofunctional monomer such as an alkyl acrylate, styrene, substituted styrene, acrylonitrile or methacrylonitrile. Further, the acrylic polymer forming the hard layer may be a crosslinked polymer copolymerized by adding a polyfunctional monomer to the monofunctional monomer. Examples of such an acrylic polymer include those described in JP-A-55-27576, JP-A-6-80739, and JP-A-987868.

The graft copolymer obtained by graft-polymerizing an ethylenically unsaturated monomer with a rubber component preferably contains 5 to 80% by weight of a structural unit derived from a rubber component (thus, contains 95 to 20% by weight of ethylenic unsaturation) Monomeric structural unit). As the rubber component, for example, a diene rubber such as polybutadiene rubber, acrylonitrile/butadiene copolymer rubber, styrene/butadiene copolymer rubber, or the like; polybutyl acrylate, polypropyl acrylate, and poly An acrylic rubber such as 2-ethylhexyl acrylate; and an ethylene/propylene/non-conjugated diene rubber. Two or more types of components can be used as the rubber component. Examples of the ethylenically unsaturated monomer include styrene, acrylonitrile, and alkyl (meth)acrylate. Among them, an acrylic unsaturated monomer such as acrylonitrile or an alkyl (meth)acrylate is preferably used. As such a graft copolymer, those described in JP-A-55-147514 and JP-A-47-9740 can be used.

When the protective film made of the acrylic resin as described above is subjected to the step of bringing the protective film described later into contact with water, the effect of improving the adhesion property tends to be easily exhibited.

The above-mentioned cellulose-based resin means a partially esterified or fully esterified cellulose, for example, cellulose acetate, propionate, butyrate, and a mixed ester thereof. More specifically, for example, triethyl fluorenyl cellulose, diethyl acetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate, and the like. Among them, triethylenesulfonyl cellulose is suitable because it is easy to bond and easy to obtain.

Commercially available products, such as "Fujitac (registered trademark) TD80", "Fujitac (registered trademark) TD80UF", "Fujitac (registered trademark) TD80UZ", and Konica, manufactured by Fujifilm Co., Ltd. "KC8UX2M" and "KC8UY" (all of which are trade names) manufactured by Minolta Co., Ltd.

The protective film is preferably 200 μm or less, more preferably 100 μm or less, still more preferably 20 μm or more, and still more preferably 30 μm or more from the viewpoint of thinness and weight reduction of the polarizing plate. In the production method of the present invention, for example, a roll-shaped roll-shaped protective film can be wound up using a long protective film.

(UV curing adhesive)

The adhesive used for forming the adhesive layer between the protective film and the polarizing film is usually, for example, a water-based adhesive or an ultraviolet-curable adhesive. However, in the present invention, an ultraviolet-curable adhesive is used.

When the ultraviolet-curable adhesive is classified according to the type of curing, for example, a radical polymerization type adhesive or a cationic polymerization type adhesive, and the like, for example, an acrylic resin-based adhesive or a ring may be used depending on the chemical type of the hardening component. An oxygen-based adhesive or the like. In the present invention, any of these may be used, or a mixture of two or more of these may be used, and a cationically polymerizable epoxy-based adhesive is suitably used from the viewpoints of ease of handling, adhesion strength obtained, and the like. Here, the term "epoxy resin" refers to a compound or polymer which has an epoxy group in a molecule and is hardened by a ring-opening polymerization reaction of an epoxy group, and according to the practice in the field, even a monomer is called Epoxy resin.

The epoxy resin contained in the ultraviolet curable adhesive is suitably used for an epoxy resin which does not contain an aromatic ring in the molecule from the viewpoints of weather resistance, refractive index, and cationic polymerizability. Examples of the epoxy resin which does not contain an aromatic ring in the molecule include a hydrogenated epoxy resin, an alicyclic epoxy resin, and an aliphatic epoxy resin.

Hydrogenated epoxy resin can be touched by aromatic epoxy resin It is obtained by selectively performing a nuclear hydrogenation reaction under pressure and in the presence of a medium. Examples of the aromatic epoxy resin include a bisphenol epoxy resin such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and diepoxypropyl ether of bisphenol S; Phenolic resin type epoxy resin such as phenolic resin (novolak) epoxy resin, cresol novolac resin epoxy resin, and hydroxybenzaldehyde phenolic phenolic resin epoxy resin; epoxypropyl ether of tetrahydroxyphenylmethane, tetrahydroxydiphenyl A polyfunctional epoxy resin such as a glycidyl ether of a ketone or an epoxidized polyvinyl phenol. Among them, a glycidyl ether of hydrogenated bisphenol A is preferably used as the hydrogenated epoxy resin.

The alicyclic epoxy resin refers to an epoxy resin having one or more epoxy groups bonded to an alicyclic ring in the molecule. The epoxy group bonded to the alicyclic ring, as shown in the following formula (I), means that the two bonding bonds of the epoxy group (-O-) are directly bonded to the two constituting the alicyclic ring. Carbon atoms (usually adjacent carbon atoms). In the following formula (I), m is an integer of 2 to 5.

The compound having a form in which one or a plurality of hydrogen atoms in the (CH ₂ ) _m of the above formula (I) is removed can be an alicyclic epoxy resin. The hydrogen constituting the alicyclic ring may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among them, from the adhesive having a good bonding strength to the polarizing film and the protective film, the structure having an epoxycyclocyclopentane (m=3 in the above formula (I)) and having an epoxycyclohexane structure ( The epoxy resin of m=4 in the above formula is preferred. Specific examples of the alicyclic epoxy resin are disclosed below. Here, the names of the compounds are listed first, and the corresponding chemical formulas are respectively shown, and the names of the compounds and the chemical formulas corresponding thereto are given the same symbols.

A: 3,4-epoxycyclohexylmethyl ester of 3,4-epoxycyclohexanecarboxylic acid; B: 3,4-ring of 3,4-epoxy-6-methylcyclohexanecarboxylic acid Oxy-6-methylcyclohexylmethyl ester; C: bis(3,4-epoxycyclohexanecarboxylic acid) ethyl ester; D: adipic acid bis(3,4-epoxycyclohexyl Ester); 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-tetraoxide trispirate [ 5.2.2.5.2.2] eicosane; I: 3-(3,4-epoxycyclohexyl)-8,9-epoxy-1,5-dioxospiro[5.0]undecane; J: 4-vinyl dicyclohexene oxide; K: liminene; L: bis(2,3-epoxycyclopentyl) ether; M: dicyclopentadiene dioxide or the like.

Among them, ethylene glycol bis(3,4-epoxycyclohexylmethyl ether) is preferred because it is relatively easy to obtain.

Further, examples of the aliphatic epoxy resin include a polyepoxypropyl ether of an aliphatic polyol or an alkylene oxide adduct thereof. More specifically, for example, diepoxypropyl ether of 1,4-butanediol; diepoxypropyl ether of 1,6-hexanediol; triepoxypropyl ether of glycerol; trihydroxypropane Triepoxypropyl ether; diepoxypropyl ether of polyethylene glycol; diepoxypropyl ether of propylene glycol; and monoepoxypropyl group of aliphatic polyol such as ethylene glycol, propylene glycol and glycerin Ether, etc.

In the present invention, the epoxy resin may be used alone or in combination of two or more.

The epoxy equivalent is a measure of the amount of epoxy groups of each epoxy resin. The epoxy equivalent means a mass of a resin containing one equivalent of an epoxy group, and if the value is low, it can be judged that the amount of the functional group is large. The epoxy equivalent was measured by dissolving a precisely weighed resin sample in chloroform, adding acetic acid and a tetraethylammonium bromide solution, and then performing potentiometric titration with a 0.1 mol/liter perchloric acid acetic acid standard solution. When a perchloric acid-acetic acid standard solution is added, perchloric acid is reacted with tetraethylammonium bromide to form hydrogen bromide. The generated hydrogen bromide reacts with an epoxy group. All of the epoxy groups were reacted, and when hydrogen bromide became excessive, the end point of the measurement was measured, and the epoxy equivalent was measured.

The epoxy resin used in the present invention has an epoxy equivalent of usually from 30 to 3,000 g/equivalent, preferably from 50 to 1,500 g/equivalent. When the epoxy equivalent is less than 30 g/equivalent, the flexibility of the adhesive layer after curing may be low or the strength may be lowered. On the other hand, more than 3000g / when When it is used, there is a possibility that the compatibility with other components contained in the adhesive is lowered.

In the present invention, as described above, the epoxy resin is preferably a cationically polymerized one. Therefore, it is preferred that the ultraviolet curable adhesive contains a photocationic polymerization initiator. The photocationic polymerization initiator generates a cationic substance or a Lewis acid by irradiation with ultraviolet rays to initiate polymerization of an epoxy group. Any form of photocationic polymerization initiator can be used.

A photocationic polymerization initiator is added, and the method of curing the adhesive by ultraviolet rays is hardened at a normal temperature, and the point at which the polarizing film is less likely to change due to heat or the point where the protective film and the polarizing film are joined by high bonding strength is caused. It is beneficial. Since the photocationic polymerization initiator acts as a catalyst by light, even if it is further mixed with an epoxy resin, the adhesion retention property and handleability are excellent.

The photocationic polymerization initiator is not particularly limited, and examples thereof include an onium salt such as an aromatic diazonium salt, an aromatic onium salt, and an aromatic onium salt, and an iron-aromatic hydrocarbon complex.

Examples of the aromatic diazonium salt include benzene diazonium hexafluoroantimonate, benzene diazonium hexafluorophosphate, and benzene diazonium hexafluoroborate.

As the aromatic sulfonium salt, for example, diphenylsulfonium sulfonium (pentafluorophenyl)borate, diphenylsulfonium hexafluorophosphate, diphenylsulfonium hexafluoroantimonate, bis(4-mercaptobenzene hexafluorophosphate) Base) 錪 salt and so on.

As the aromatic phosphonium salt, for example, triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, bis(hexafluorophosphate) 4,4' - bis(diphenylfluorene)diphenyl sulfide, bis(hexafluoroantimonate) 4,4'-bis[bis(β-hydroxyethoxy)phenylhydrazine]diphenyl sulfide, bis(hexafluorophosphorus) Acid) 4,4'-bis[bis(β-hydroxyethoxy)phenylhydrazine]diphenyl sulfide, hexafluoroantimonic acid 7-[bis(p-tolyl)indole]-2-isopropylsulfuric acid Thioxanthone, tetrakis(pentafluorophenyl)borate 7-[bis(p-tolyl)purine]-2-isopropylthioxanthone, 4-phenylcarbonyl-4'-hexafluorophosphate Diphenyl sulfonium-diphenyl sulfide, hexafluoroantimonate 4-(p-butylphenylcarbonyl)-4'-diphenylanthracene-diphenyl sulfide, tetrakis(pentafluorophenyl)borate 4 -(p-T-butylphenylcarbonyl)-4'-bis(p-tolyl)indole-diphenyl sulfide.

As an iron-aromatic complex, for example, xylene hexafluoroantimony-cyclopentadienyl iron (II), cumene hexafluoro-cyclopentadienyl iron (II), xylene-cyclopentadienyl iron ( II) - Refractory (trifluoromethylsulfonyl) metal complexes and the like.

The commercially available product of the photo-cationic polymerization initiator can be easily obtained. For each of the product names, for example, "KAYALITE (registered trademark) PCI-220" and "KAYALITE (registered trademark)" manufactured by Nippon Kayaku Co., Ltd. PCI-620", "UVI-6990" manufactured by Dow Chemical Co., Ltd., "ADEKA OPTOMER (registered trademark) SP-150" by ADEKA, "ADEKA OPTOMER (registered trademark) SP-170", Japan Soda (share) "DPI-101" made by "CI-5102", "CIT-1370", "CIT-1682", "CIP-1866S", "CIP-2048S", "CIP-2064S", and Green Chemical Co., Ltd. , "DPI-102", "DPI-103", "DPI-105", "MPI-103", "MPI-105", "BBI-101", "BBI-102", "BBI-103", " BBI-105", "TPS-101", "TPS-102", "TPS-103", "TPS-105", "MDS-103", "MDS-105", "DTS-102", "DTS- 103", "PI-2074" made by Rhodia Corporation. Among them, "CI-5102" manufactured by Japan Soda Co., Ltd. is one of the preferred photocationic polymerization initiators.

The above photocationic polymerization initiators can be used separately It can be used alone or in combination of two or more. Among these, the aromatic onium salt is preferred because it has ultraviolet light absorption characteristics in a wavelength region of 300 nm or more, and has good curability, and a cured product having good mechanical strength and adhesion strength can be obtained.

The compounding amount of the photocationic polymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 part by weight or more, and preferably 15 parts by weight or less based on 100 parts by weight of the epoxy resin. When the amount of the photocationic polymerization initiator is less than 0.5 part by weight, the curing is insufficient, and the mechanical strength or the subsequent strength tends to be lowered. In addition, when the amount of the photocationic polymerization initiator is more than 20 parts by weight, the ionic substance in the cured product increases, the hygroscopicity of the cured product becomes high, and the durability of the polarizing plate may be lowered.

When a photocationic polymerization initiator is used, the ultraviolet curable adhesive may further contain a photosensitizer as needed. By using a photosensitizer to increase the reactivity of cationic polymerization, the mechanical strength and the strength of the cured product can be improved. Examples of the photosensitizer include a carbonyl compound, an organic sulfur compound, a persulfide compound, a redox compound, an azo and a diazo compound, a halide, a photoreducible dye, and the like. Specific examples include benzoin methyl ether, benzoin isopropyl ether, and benzoin derivatives such as α,α-dimethoxy-α-phenylacetophenone; diphenyl ketone and 2,4-dichloro bis Phenyl ketone, o-benzoin benzoic acid methyl ester, 4,4'-bis(dimethylamino)diphenyl ketone, and 4,4'-bis(diethylamino)diphenyl ketone a phenyl ketone derivative; a thioxanthone derivative such as 2-chlorothiazinone or 2-isopropylthioxanthone; an anthracene derivative such as 2-chloroindole and 2-methylindole ; N-methyl acridone and N-butyl acridone Acridine derivatives; and α,α-diethoxyacetophenone, diphenylethylenedione, Fluorenone, Xanthone, uranium compounds, halides, and the like. However, it is not limited to these. These photo sensitizers may be used alone or in combination of two or more. The light sensitizer is preferably contained in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the ultraviolet curable adhesive.

The ultraviolet curable adhesive may further contain a compound which promotes cationic polymerization such as oxetane or vinyl ether or a polyhydric alcohol.

Oxetane is a compound having a 4-membered cyclic ether in the molecule. As an example of oxetane, for example, 3-ethyl-3-hydroxymethyloxetane, 1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl Benzo, 3-ethyl-3-(phenoxymethyl)oxetane, bis[(3-ethyl-3-oxetanyl)methyl]ether, 3-ethyl- 3-(2-ethylhexyloxymethyl)oxetane, phenol novolac oxetane, and the like. A commercially available product of such oxetane can be easily obtained, and each of the trade names is, for example, "Aron oxetane (registered trademark) OXT-101" and "Aron oxetane (registered trademark) OXT, manufactured by Toago Corporation. -121", "Aron oxetane (registered trademark) OXT-211", "Aron oxetane (registered trademark) OXT-221", "Aron oxetane (registered trademark) OXT-212", and the like. The oxetane is usually contained in the ultraviolet curable adhesive in an amount of from 5 to 95% by weight, preferably from 30 to 70% by weight.

As the vinyl ether, a vinyl ether having a monofunctional group having one vinyl group in the molecule and a polyfunctional vinyl ether having two or more vinyl groups in the molecule can be used. Moreover, other than the vinyl group such as a hydroxyl group, a carboxyl group, an epoxy group or the like may be used as needed. Functional base.

Specific examples of the monofunctional vinyl ether include, for example, propyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexyl vinyl ether, dicyclopentadienyl vinyl ether, tricyclodecane vinyl ether, Benzyl vinyl ether, ethoxylated ethyl vinyl ether, ethoxylated butyl vinyl ether, ethyl cyclohexane dimethanol monovinyl ether, ethyl diethylene glycol monovinyl ether. Further, specific examples of the vinyl ether having a hydroxyl group include, for example, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, diethylene glycol monovinyl ether, 1,4-cyclohexanedimethanol monovinyl ether, dipropylene glycol monovinyl ether. As the vinyl ether having an epoxy group, for example, glycidyl ethyl vinyl ether, glycidyl butyl vinyl ether, glycidyl cyclohexane dimethanol monovinyl ether, glycidyl diethylene glycol Alcohol monovinyl ether and the like.

Specific examples of the bifunctional vinyl ether include ethylene glycol divinyl ether, butanediol divinyl ether, 1,3-propanediol divinyl ether, and 1,4-butanediol divinyl ether. 1,5-pentanediol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, tetraethylene glycol divinyl ether, cyclohexanediol divinyl ether, cyclohexyl Alkane dimethanol divinyl ether, hydrogenated bisphenol A divinyl ether, and the like. Among these divinyl ether compounds, a divinyl ether of an alkanediol or an oligoalkylene oxide is preferable, and it is preferable to have diethylene glycol divinyl ether especially from the point which is easy to acquire, etc..

Specific examples of the trifunctional vinyl ether include, for example, trimethylolpropane trivinyl ether, trimethylolpropane ethoxylated trivinyl ether, and the like.

The above polyol is preferably one in which no acidic base other than a phenolic hydroxyl group is present in the molecule. Examples of such a polyol include a polyol compound having no functional group other than a hydroxyl group, a polyvalent polyol compound, a polycaprolactone polyol compound, a polyol compound having a phenolic hydroxyl group, a polycarbonate polyol, and the like. The molecular weight of the polyols is usually 48 or more, preferably 62 or more, more preferably 100 or more, and still more preferably 1,000 or less. The polyol is usually contained in an ultraviolet curable adhesive in an amount of 50% by weight or less, preferably 30% by weight or less.

The ultraviolet curable adhesive may further contain other additives such as an ion trapping agent, an antioxidant, a chain transfer agent, a sensitizer, an adhesion-imparting agent, a thermoplastic resin, a filler, a flow regulator, and the like, without impairing the effects of the present invention. Plasticizer, defoamer, etc. Examples of the ion scavenger include inorganic compounds such as powdered lanthanoid, lanthanide, magnesium, aluminum, calcium, and titanium, and the like. As an antioxidant, a hindered phenol type antioxidant, etc. are mentioned, for example.

[Method of Manufacturing Polarizing Plate]

A method of producing a polarizing plate of the present invention is characterized by comprising the following steps (a) to (d).

(a) a step of bringing the protective film into contact with water; (b) a step of applying an ultraviolet curable adhesive to form an adhesive layer on one surface of at least one film selected from the group consisting of a protective film and a polarizing film; The protective film and the polarizing film are laminated via the adhesive layer to form a laminate a step of filming; and (d) a step of irradiating the laminated film with ultraviolet rays to harden the adhesive layer.

In the following description, the step (a) of bringing the protective film into contact with water is referred to as "step (a)", and the step (b) of forming the adhesive layer on the one surface of the protective film by applying the ultraviolet curable adhesive to the adhesive layer is referred to as "step (a)". In the step (b), the step (c) of bonding the protective film and the polarizing film to form the laminated film via the adhesive layer is referred to as "step (c)", and the laminated film is irradiated with ultraviolet rays to harden the adhesive layer. Step (d) is referred to as "step (d)". Each step will be described in detail.

<Step (a)>

In the step (a), the protective film is brought into contact with water. This step is, for example, a method in which a protective film is passed through a humidified tank, and steam is blown off, or water is blown off by spraying or the like, and the protective film is immersed in water and carried out in water. By this step, for example, the moisture content of the protective film can be adjusted. When adjusting the moisture content of the protective film, in the air of the temperature and humidity of the manufacturing environment of the polarizing plate (in the environment), the moisture content in the protective film is higher than the water content (balanced moisture content) in an equilibrium state in the environment. Preferably. Step (a) may be carried out at a stage earlier than step (d) to be described later, and may be carried out initially, or after step (b) or step (c), and preferably before step (b). Further, when the step (a) is carried out after the step (b) or the step (c), it is preferred to carry out the step (a) in the atmosphere.

By the step (a), a polarizing plate which improves the adhesion of the polarizing film and the protective film can be obtained. This effect is more remarkable when the protective film is an acrylic resin film.

When the step (a) is carried out in the atmosphere, it is preferably carried out at a temperature of from 25 to 80 ° C, more preferably from 25 to 50 ° C, more preferably from 30 to 50 ° C. When the temperature exceeds 80 ° C, the protective film, the ultraviolet curable adhesive or the polarizing film may be deteriorated by heat. Further, when the temperature is less than 25 ° C, it becomes difficult to increase the moisture content of the protective film. Further, when the step (a) is carried out in the atmosphere, it is preferably carried out in an environment having a relative humidity of 60 to 90%, and more preferably in an environment having a relative humidity of 70 to 90%. When the relative humidity is less than 60%, it becomes difficult to increase the moisture content of the protective film. On the other hand, when the relative humidity exceeds 90%, water droplets adhere to the protective film, which is a cause of defects such as water droplets remaining on the protective film, and excessive moisture may affect the hardening of the adhesive.

The treatment time in the step (a) in the atmosphere is preferably 0.2 seconds or longer, more preferably 1 second or longer, still more preferably 5 seconds or longer. Further, the treatment time is preferably 1 hour or shorter, more preferably 10 minutes or shorter, and still more preferably 5 minutes or shorter. When the treatment time is less than 0.2 second, the adhesiveness between the adhesive and the polarizing film tends to be insufficiently improved, and when it is more than 1 hour, the productivity tends to be lowered.

The production method of the present invention may further comprise the step (a-1) of heating the protective film composed of the thermoplastic resin before the step (a). Hereinafter, the step (a-1) of heating the protective film made of a thermoplastic resin is referred to as "step (a-1)".

The step (a-1) is carried out for the purpose of uniformizing the unevenness on the surface of the protective film. The temperature of the heated film is preferably a temperature below the glass transition point (Tg) of the resin constituting the protective film, which is 5 to 45 ° C lower than the glass transition point. The temperature is better. When the temperature is too low, it is difficult to obtain an effect of uniformizing the surface, and at a temperature exceeding the glass transition point, it is difficult to transport the film in a manufacturing apparatus due to film stretching. Further, the heating time is preferably 0.2 seconds or more, more preferably 1 second or more, and still more preferably 5 seconds or longer. Further, the heating time is preferably 1 hour or less, more preferably 10 minutes or less, and still more preferably 5 minutes or less. The heating of the protective film varies depending on the type of the film and the manufacturing environment, and therefore it may be carried out at an appropriate temperature and time in accordance with the protective film to be used. The heating of the protective film is usually carried out under a non-contact condition in which the protective film is not exposed to water, for example, in an environment having a relative humidity of 20% or less.

A method of heating the protective film, for example, a method in which a long protective film taken up from a roll-shaped protective film is sequentially passed through a heated bath, and a heated air is blown to a long protective film using a hair dryer or the like. When the step (a-1) is carried out, it is preferred to carry out the step of bringing the protective film into contact with water. By performing the step (a-1), the surface quality of the protective film can be improved, and a polarizing plate having a uniform surface quality can be obtained. .

In the production method of the present invention, in the above step (a-1), after the step (a-1), the step (a) of bringing the protective film into contact with water is performed.

The moisture content of the protective film of the step (a) described above is usually 0.2 to 5% by weight, preferably 0.4 to 2% by weight, more preferably 0.6 to 1.6% by weight. This moisture content becomes the range after performing the step (a) regardless of the implementation of the step (a-1).

The water content of the protective film is a converted value calculated from a moisture measurement value (a value measured by an infrared moisture rate meter) measured by a light transmission method. In the present specification, the moisture content of the protective film is as follows Calculated by the formula. First, a plurality of protective films having different conditions in the step (a) are prepared, and the protective films are measured by a light penetrating method, and then dried by a dry weight method (drying at 105 ° C for 1 hour, by weight before and after drying) The water content of the protective film was determined by the difference in moisture content, and the correction line was prepared by the measured value of the light penetrating method and the water content by the dry weight method. The water content of the protective film was calculated from the measured value of the measured value of the light penetration method to calculate the water content.

As the infrared moisture meter, for example, a diffuse reflection type infrared film thickness meter (RX-300) manufactured by Kurabo Industries, Ltd., an infrared multicomponent meter (IM series IRMA 1100S) manufactured by Chino, or the like can be used.

<Step (b)>

In the step (b), an ultraviolet curable adhesive is applied to one surface of the protective film and/or the polarizing film of the step (a) to form an adhesive layer. The protective film which has passed through the step (a), as described above, is usually in a water content of 0.2 to 5% by weight. The coating layer may be formed on the bonding surface of the protective film and the polarizing film, or may be formed on the bonding surface of the polarizing film and the protective film, or may be formed in both, but in the manufacturing method of the present invention, It is preferable that the bonding surface of the protective film and the polarizing film form an adhesive layer. For the application of the second agent, for example, various coating methods such as a doctor blade, a wire bar, a slit coater, a notch coater, and a gravure coater can be used. In each coating method, it is also a useful technique to adjust the viscosity of the adhesive using a solvent because of the optimum viscosity. It is preferred to use it in a solvent system without lowering the optical properties of the polarizing film and dissolving the adhesive well. Specific examples of the solvent are not particularly limited, and examples thereof include an organic solvent such as a hydrocarbon such as toluene or an ester such as ethyl acetate.

In the step (b), the ultraviolet curable adhesive can be heated before coating. When the ultraviolet curable adhesive is heated, the viscosity is lowered, and it is easy to apply to the adherend, and after the adhesive is cured, the adhesion to the adherend can be improved, which is preferable. After the application of the adhesive, it may be heated. In this case, after the adhesive is cured, the adhesion to the adherend can be improved.

Further, before the formation of the adhesive layer, an easy subsequent treatment such as a corona treatment, a plasma treatment, a primer treatment, an anchor coating treatment, or the like can be performed on the surface on which the protective film or the adhesive layer of the polarizing film is formed.

<Step (c)>

In the step (c), the protective film is bonded to the polarizing film via the adhesive layer formed in the step (b) to obtain a laminated film. The laminated film system may have a structure in which a protective film is laminated on one surface or both surfaces of the polarizing film. When the protective film is laminated on both sides of the polarizing film, the two protective films may be the same or different. Further, the protective film may be laminated on the surface of the polarizing film, and the optical compensation film may be laminated on the other surface of the polarizing film.

<Step (d)>

In the step (d), the laminated film obtained in the above step (c) is irradiated with ultraviolet rays. The adhesive layer composed of the ultraviolet curable adhesive is cured by irradiation with ultraviolet rays. For the ultraviolet light source, for example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, or the like having a light-emitting distribution of a wavelength of 400 nm or less can be used. Metal halide lamps, etc.

The light irradiation intensity of the adhesive layer composed of the ultraviolet curable adhesive is determined by the composition of each ultraviolet curable adhesive, and the irradiation intensity in the wavelength region effective for the activation of the polymerization initiator is 0.1 to 500 mW/ Cm ^{2 is} preferred. When the light irradiation intensity is less than 0.1 mW/cm ² , the reaction time is too long, and when it exceeds 500 mW/cm ² , yellowing of the adhesive may occur due to heat radiated from the lamp and heat generation during polymerization of the ultraviolet curable adhesive. Deterioration of the polarizing film. The composition of each ultraviolet curable adhesive can be controlled by the light irradiation time of the adhesive layer composed of the ultraviolet curable adhesive, and is not particularly limited, but is accumulated as a product of the irradiation intensity and the irradiation time. The amount of light is preferably set to 10 to 5000 mJ/cm ² . When the cumulative amount of the ultraviolet curable adhesive is less than 10 mJ/cm ² , the generation of the active material from the initiator is insufficient, and the curing of the adhesive may become insufficient. On the other hand, when it exceeds 5000 mJ/cm<^2> , the irradiation time becomes very long, and there exists a tendency for the productivity improvement to it.

The curing of the adhesive layer by ultraviolet irradiation is preferably carried out under the conditions of various functions of the polarizing plate which does not lower the degree of polarization of the polarizing film, the transmittance, the hue, and the transparency of the protective film and the optical compensation film. The thickness of the adhesive layer after hardening is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less.

The above steps (a-1) and (a) to (d) are usually carried out in a clean room. Further, the above steps (b) to (d) are usually carried out in an environment of a temperature of 20 to 27 ° C and a relative humidity of 40% to 62%.

The polarizing plate can be manufactured by the manufacturing method demonstrated above. The polarizing plate may be configured such that the protective film is bonded only to one surface of the polarizing film, or the protective film may be bonded to both surfaces of the polarizing film.

The protective film is bonded only to the polarizing plate on one side of the polarizing film, and the optical compensation film can be laminated on the surface of the polarizing film opposite to the surface to which the protective film is bonded. The adhesive for bonding the polarizing film and the optical compensation film, for example, an aqueous adhesive containing a polyvinyl alcohol resin or an amine ester resin, which is different from the ultraviolet curing adhesive, may be an ultraviolet curing adhesive. When the same adhesive as the ultraviolet curable adhesive used for bonding the polarizing film and the protective film is used, the production efficiency can be improved and the type of the raw material can be reduced.

The optical compensation film may, for example, be a cellulose resin such as triethylenesulfonyl cellulose (TAC); an olefin resin such as polyethylene, polypropylene or polyvinyl chloride; polyethylene terephthalate and polynaphthalene; A polyester resin such as ethylene dicarboxylate; a cycloolefin resin such as a decene-based resin; and an optical compensation film made of an acrylic resin such as polyacrylate or polymethacrylate.

For example, the cellulose-based resin film contains a film having a compound having a function of adjusting a phase difference, and the film of a compound having a function of adjusting a phase difference is applied to the film; A film obtained by one-axis stretching or biaxially stretching a cellulose resin film or the like. As an optical compensation film made of a cellulose-based resin film, for example, "WV FILM WIDE VIEW EA80" manufactured by Fujifilm Co., Ltd., "KC4FR-1" manufactured by Konica Minolta Co., Ltd., " KC4HR-1" (above, all are trade names) and so on.

The thickness of the optical compensation film composed of the cellulose resin film is not particularly limited, but is preferably in the range of 20 to 90 μm , more preferably 30 to 90 μm . When the thickness is less than 20 μm , the operation of the film is difficult. On the other hand, when it exceeds 90 μm , the workability tends to be poor, and the thickness and weight of the obtained polarizing plate tend to be disadvantageous.

The optical compensation film composed of a cycloolefin resin may, for example, be a cyclic olefin resin film which is extended by one axis or biaxially. In the liquid crystal panel for a large liquid crystal television, particularly in a liquid crystal panel having a liquid crystal cell of a vertical alignment (VA) mode, when the polarizing plate obtained by the present invention is used, the extension of the cycloolefin resin film is obtained from the optical compensation film. The point of optical characteristics and durability is also suitable.

When the thickness of the optical compensation film composed of the extended cycloolefin resin is too thick, the workability tends to be poor, and the transparency is lowered, and the thickness and weight of the polarizing plate tend to be difficult. Therefore, the thickness of the film is preferably about 20 to 80 μm .

Further, the optical compensation film may be subjected to a corona treatment, a plasma treatment, a primer treatment, an anchor coating treatment, or the like on the surface on which the adhesive layer is formed, similarly to the protective film and the polarizing film, before the formation of the adhesive. Easy to proceed.

The polarizing plate described above can form an adhesive layer (or an adhesive layer) used for bonding to a liquid crystal cell or the like. The adhesive layer may be a surface opposite to the surface on which the protective film formed on the protective film or the polarizing film is laminated. Further, a surface on the opposite side to the surface on which the protective film is laminated in the polarizing film is laminated, and a protective film or an optical compensation film is laminated thereon to form an adhesive layer (or Primer layer). Further, an optical functional film is laminated on the polarizing film, the protective film laminated on the polarizing film, or the optical compensation film, and an adhesive layer (or an adhesive layer) may be formed on the laminated optical functional film.

As the adhesive to be used for the adhesive layer, a conventionally known adhesive can be used, and examples thereof include an acrylic adhesive, an amine ester adhesive, and a polyoxygen adhesive. Among them, an acrylic adhesive can be preferably used from the viewpoints of transparency, adhesion, reliability, and reworkability. In the adhesive layer, such an adhesive is applied, for example, to an organic solvent solution, and applied to a substrate film (for example, a protective film, a polarizing film, etc.) by a slit coater or a gravure coater, and dried. Can be set. Further, it may be provided by a method in which a sheet-like adhesive formed on a plastic film (referred to as a release film) subjected to a release treatment is transferred to a base film. The thickness of the adhesive layer is preferably in the range of 2 to 40 μm .

The optical functional film is laminated on the polarizing film via an adhesive, and laminated on the protective film or the optical compensation film on the polarizing film. An optical functional film is applied, for example, to a surface of a substrate, to an optical compensation film in which a liquid crystal compound is aligned, and a light-reflecting polarizing film that transmits light having a polarized light and reflects a polarized light having opposite properties; and a polycarbonate-based resin a retardation film comprising: a retardation film comprising a cycloolefin resin; a film having an anti-glare function having an uneven shape on the surface; a film having a surface anti-reflection function; and a reflective film having a reflective function on the surface; A semi-transmissive reflective film or the like for the reflection function and the transmission function.

A commercial product corresponding to an optical compensation film coated with a liquid crystal compound on the surface of a substrate, and a product name such as Fujifilm "WV film" sold by the film (stock), "NH film" sold by JX Nippon Mining & Energy Co., Ltd., "NR film", etc. A commercially available product of a reflective polarizing film that reflects light having a polarized light of the opposite nature, which is a light-transmitting light, and a "DBEF" available from Sumitomo 3M Co., Ltd., manufactured by 3M Co., Ltd., respectively. "," APF" and so on. In addition, as a commercial product corresponding to a retardation film made of a cycloolefin-based resin, "Arton film" ("Arton" is a registered trademark of the company) sold under the trade name, for example, JSR (share), "Escena" (registered trademark) sold by Sekisui Chemical Industry Co., Ltd., "ZEONOR film" (registered trademark) sold by Japan ZEON Co., Ltd., etc.

[Liquid Crystal Display Device]

The polarizing plate manufactured by the present invention is suitably used for a liquid crystal display device. The liquid crystal display device is provided with a liquid crystal panel. The liquid crystal panel includes a liquid crystal cell and a polarizing plate laminated on one surface or both surfaces of the liquid crystal cell, and the liquid crystal cell and the polarizing plate are bonded together via the adhesive layer as described above. In the liquid crystal panel, the polarizing plate manufactured by the present invention is provided only on the surface of one side of the liquid crystal cell, and a conventionally suitable polarizing plate can be used as the polarizing plate provided on the other surface of the liquid crystal cell. The liquid crystal panel provided in the liquid crystal display device may be provided with an anti-glare treatment, a hard coating treatment, or an anti-reflection, for example, a polarizing plate provided on the front side of the liquid crystal cell (on the side of the liquid crystal display device and opposite to the backlight). Treated polarizing plates, etc.

In the liquid crystal display device, a configuration other than the liquid crystal panel may be a suitable configuration of a conventional liquid crystal display device, for example, a backlight, a light diffusing plate, and a liquid crystal panel are sequentially provided, and sequentially It has a backlight, a light diffusing plate, a light diffusing film, and a liquid crystal panel.

According to the production method of the present invention, in the step (a), the protective film that has been in contact with water absorbs moisture, but in the step (c), the protective film that absorbs moisture is laminated with the polarizing film via the adhesive layer. The moisture absorbed by the protective film is considered to act on the ultraviolet curable adhesive or the polarizing film which forms the adhesive layer, and the adhesive force is improved.

[Examples]

The present invention will now be described in more detail by way of examples, but the invention is not limited thereto. In addition, in the example, the content and the % and the amount of the usage amount are shown, and unless otherwise specified, it is a weight basis.

In the following examples, the water content of the protective film is a converted value calculated from a moisture measurement value (a value measured by an infrared moisture rate meter) measured by a light transmission method. Specifically, first, a protective film which is stored for a predetermined period of time in an environment having a temperature of 23° C. and a relative humidity of 60%, and a protective film having a temperature of 23° C. and a relative humidity of 90% are stored for a predetermined period of time. The measured value of the protective film by the light penetration method and the moisture content by the dry weight method are used to prepare a calibration line, and then, in the embodiment, the measured value of the protective film by the light penetration method after the step of contacting the water, The water content was calculated by comparing the calibration line with the measured value of the light-transmissive method of the protective film before the formation of the adhesive layer (temperature: 23 ° C, relative humidity: 60%), and the water content was calculated by comparing the correction line. Further, as an infrared moisture meter, an infrared multicomponent meter (IM series IRMA1100S) manufactured by Chino was used.

[Manufacturing Example 1: Production of Protective Film]

In a glass reaction vessel having an internal volume of 5 L, 1700 parts of ion-exchanged water, 0.7 parts of sodium carbonate, and 0.3 parts of sodium persulfate were placed, and the mixture was stirred under a nitrogen gas stream to add sodium dialkyl sulfosuccinate [Kao (share)). The product "PELEX (registered trademark) OT-P"] 4.46 parts, 150 parts of ion-exchanged water, 150 parts of methyl methacrylate, and 0.3 parts of allyl methacrylate. Then, the stirring temperature was raised to 75 ° C and stirred for 150 minutes.

Then, a mixture of 689 parts of butyl acrylate, 162 parts of styrene, and 17 parts of allyl methacrylate, and 0.85 parts of sodium persulfate, "PELEX (registered trademark) OT-P" 7.4 parts, and ion-exchanged water were added over 90 minutes. 50 parts of the mixture was further polymerized for 90 minutes. After the completion of the polymerization, a mixture of 326 parts of methyl acrylate and 14 parts of ethyl acrylate was added over 30 minutes, and 30 parts of ion-exchanged water in which 0.34 parts of sodium persulfate was dissolved was added. After the addition was completed, the mixture was kept for another 60 minutes, and the polymerization was completed. The obtained reaction product was poured into a 0.5% aluminum chloride aqueous solution to aggregate the polymer. This was washed with water for 5 times, and then dried to obtain an acrylic multilayer polymer.

80 parts of a copolymer of methyl methacrylate/methyl acrylate having a polymerization ratio of 96/4 and a refractive index of 1.49, and 20 parts of the acrylic composition of the acrylic multilayer polymer produced above was added to Hanschel The machine was mixed with a Henschel mixer, melt-kneaded by a vented one-axis extruder (screw diameter: 65 mm), and extruded at a resin temperature of 260 ° C. The extruded resin was pressed against an elastic roller set at 80 ° C. A protective film having a thickness of 80 μm was formed through a roller unit (three elastic polishing rollers, a horizontal roller). Further, in the extrusion molding, a T-die having a lip width of 1400 mm and a lip gap of 1 mm was used.

[Production Example 2: Production of polarizing film]

A polyvinyl alcohol film having a thickness of 75 μm and an average degree of polymerization of 2400 and a saponification degree of 99.9 mol% or more was immersed in pure water at 30° C., and then immersed in a weight ratio of iodine/potassium iodide/water of 0.02/2. /100 and an aqueous solution having a water temperature of 30 °C. Then, it was immersed in an aqueous solution of potassium iodide/boric acid/water in a weight ratio of 12/5/100 and a water temperature of 56.5 °C. Subsequently, the mixture was washed with pure water at 8 ° C, and then dried at 65 ° C to produce a polarizing film in which iodine was adsorbed to the polyvinyl alcohol film. The extension was mainly carried out in the steps of dyeing iodine and boric acid treatment, and the total stretching ratio was 5.3 times.

[Production Example 3: Production of ultraviolet curable adhesive]

As the ultraviolet curable adhesive, a cationic polymerization type epoxy-based adhesive is used. In the preparation, the curable component (A) and the photocationic polymerization initiator (B) which are contained in the adhesive are used as follows.

(A) a hardenable component contained in an adhesive

(a1) alicyclic epoxy resin: 3,4-epoxycyclohexyl methyl ester of 3,4-epoxycyclohexanecarboxylic acid: obtained by DAICEL Chemical Industry Co., Ltd. under the trade name "Celloxide (registered trademark) 2021P", Table 1 is described as (a1).

(a2) Aliphatic Epoxy Resin: 1,4-Butanediol Diepoxypropyl Ether: Nagase Chemtex (share), trade name "DENACOL (registered trademark) EX-121", Table 1 It is described as (a2).

(a3) Vinyl ether: diethylene glycol divinyl ether: from Japanese carbide Industrial (share) acquisition, Table 1 is described as (a3).

The above three types of curable components are those of a cationic polymerization type, and each has a structure of the following formula.

(a3) CH ₂ =CH-O-(CH ₂ ) ₂ -O-(CH ₂ ) ₂ -O-CH=CH ₂

(B) Photocationic polymerization initiator

Triarylsulfonium salt photocationic polymerization initiator: Obtained from SAN-APRO (share) in the form of a 50% propylene carbonate solution, trade name "CPI-100P".

70 parts of the alicyclic epoxy resin (a1), 15 parts of the aliphatic epoxy resin (a2), and 15 parts of the vinyl ether (a3) were blended, and 4.5 parts of the photocationic polymerization initiator was further mixed as a solid component. Defoaming was carried out to prepare a photocurable adhesive liquid. For the prepared adhesive, a viscosity of 25 ° C was measured using a rotary viscoelasticity measuring device "Physica MCR301" manufactured by Anton Paar Co., Ltd. The results are shown in Table 1.

[Example 1]

The protective film obtained in Production Example 1 was placed in a constant temperature and humidity oven set to a temperature of 40 ° C and humidified to a relative humidity of 90% for 1 hour [step (a)]. The water content of the protective film after this step was 1.2%. Next, the surface of the protective film The corona discharge treatment was carried out, and the ultraviolet curable adhesive obtained in Production Example 3 was applied onto the corona discharge treated surface to form an adhesive layer [step (b)]. Furthermore, the ultraviolet curable adhesive obtained in the production example 3 was applied to one side of the cycloolefin resin film [product name "Zeonor film" (a) of the Japanese ZEON Co., Ltd. to form an adhesive layer [ Step (b)]. Then, the protective film and the cycloolefin-based resin film were bonded to each other on both surfaces of the polarizing film obtained in Production Example 2 in an environment of 23 ° C, and an acrylic resin film/adhesive layer/polarizing film was obtained. a laminate film composed of an adhesive layer/cycloolefin resin film [step (c)]. Then, ultraviolet rays are irradiated from the surface of the cycloolefin resin film to cure the adhesive layer, and a polarizing plate is produced [step (d)].

[Embodiment 2]

A polarizing plate was produced in the same manner as in Example 1 except that the protective film obtained in Production Example 1 was placed in a constant temperature and humidity oven set to a temperature of 30 ° C and humidified to a relative humidity of 60% for 20 seconds [step (a)]. . The water content of the protective film was 0.8%.

[Comparative Example 1]

A polarizing plate was produced in the same manner as in Example 1 except that the protective film obtained in Production Example 1 was placed in a constant temperature oven set to a temperature of 95 ° C for 60 seconds. The moisture content of the protective film taken out from the oven was 0.1%. Furthermore, the relative humidity in the oven is less than 10%.

[Comparative Example 2]

The protective film obtained in Production Example 1 was not subjected to heating treatment, and was not carried out. A polarizing plate was produced in the same manner as in Example 1 except for the step (a). The moisture content of the protective film taken out from the oven was 0.3%.

(180 degree peel test of polarizing plate)

With respect to the polarizing plates produced in the above examples and comparative examples, the peel strength between the protective film and the polarizing film was measured in the following manner. The produced polarizing plate was allowed to stand for 300 hours after the production, and cut into a size of 200 mm × 25 mm to prepare a test piece. The peeling strength between the protective film obtained in Production Example 1 and the polarizing film was measured on the exposed surface of the protective film obtained in Production Example 1, and an acrylic pressure-sensitive adhesive layer was provided, and bonded to the glass plate via the adhesive layer. A cutting blade was placed between the polarizing film and the protective film obtained in Production Example 1, and a notch was placed, and the protective film was peeled off from the longitudinal end by 30 mm, and the peeled portion was sandwiched by the jaw portion of the testing machine. In the test piece of this state, in the environment of a temperature of 23 ° C and a relative humidity of 55%, according to JIS K6854-2: 1999 "Adhesive - Peeling and Penetration Strength Test Method - Part 2: 180 degree peeling", the grip moving speed is At 300 mm/min, a 180-degree peel test was performed, and an average peeling force of a length of 170 mm excluding the grip of the grip portion was obtained. The results are shown in Table 1.

For the protective film and the polarizing film which were peeled off after the 180-degree peeling test in each of the examples and the comparative examples, the infrared absorption spectrum of each peeling surface was measured by an FT-IR apparatus ("640-IR" manufactured by Varian Co., Ltd.). , to investigate whether there is adhesive residue. As a result, in Examples 1 and 2, no adhesive remained on the side of the protective film, and only the adhesive remained on the side of the polarizing film. From this, it is considered that the peeling occurs between the adhesive layer and the protective film. Further, in Comparative Example 1 and Comparative Example 2, the adhesive agent remained on the side of the polarizing film, and the adhesive remained only on the side of the protective film. From this point of view, it is considered that the peeling occurs between the adhesive layer and the polarizing film.

From the results of Table 1, the protective film is subjected to step (a). Examples 1 and 2 showed good adhesion in the 180 degree peel test. On the other hand, in Comparative Examples 1 and 2 in which the protective film was not subjected to the step (a), the adhesion was lowered as compared with Examples 1 and 2. In this case, when the protective film, particularly the acrylic resin film, is treated with contact water, it has been confirmed that the effect of improving the adhesion between the polarizing film and the protective film is obtained.

Claims (10)

A method for producing a polarizing plate comprising at least one side of a polarizing film having an iodine or a dichroic dye adsorbed to a polyvinyl alcohol-based resin film, and bonded to a thermoplastic resin by an ultraviolet curable adhesive A method for producing a polarizing plate, comprising: a step (a) of contacting the protective film with water; and forming at least one film selected from the protective film and the polarizing film of the step (a). a step (b) of forming an adhesive layer composed of an ultraviolet curable adhesive; a step (c) of forming a laminated film by laminating a protective film and a polarizing film via the adhesive layer; and irradiating the laminated film with ultraviolet rays And step (d) of hardening the adhesive layer. The method for producing a polarizing plate according to claim 1, wherein the step (a) of bringing the protective film into contact with water comprises the step (a-1) of heating the protective film. The method of producing a polarizing plate according to claim 1, wherein the ultraviolet curable adhesive is heated before the formation of the adhesive layer. The method for producing a polarizing plate according to claim 1, wherein the ultraviolet curable adhesive is an epoxy-based adhesive. The method for producing a polarizing plate according to claim 4, wherein the epoxy-based adhesive comprises an epoxy resin containing no aromatic ring in the molecule. The method for manufacturing a polarizing plate according to claim 4, wherein The epoxy-based adhesive further contains a photocationic polymerization initiator in addition to the epoxy resin. The method for producing a polarizing plate according to any one of claims 1 to 6, wherein the thermoplastic resin is an acrylic resin. The method for producing a polarizing plate according to claim 7, wherein the protective film after the step (a) has a water content of 0.2 to 5% by weight. The method for producing a polarizing plate according to any one of claims 1 to 6, wherein the step (a) is carried out at a temperature of 25 to 80 ° C and a relative humidity of 60 to 90%. . A method for producing a polarizing plate comprising at least one side of a polarizing film having an iodine or a dichroic dye adsorbed to a polyvinyl alcohol-based resin film, and bonded to a thermoplastic resin by an ultraviolet curable adhesive A method of producing a polarizing plate, comprising: a polarizing film and at least one film selected from the group consisting of a polarizing film and a protective film having a water content of 0.4 to 5% by weight, forming an adhesive composed of an ultraviolet curing adhesive; Step (b) of the layer; a step (c) of forming a laminated film by laminating a protective film and a polarizing film via the adhesive layer; and a step (d) of irradiating the laminated film with ultraviolet rays to cure the adhesive layer .