JP4432487B2 - Polarizing plate and manufacturing method thereof - Google Patents

Description

  The present invention relates to a polarizing plate in which a cycloolefin-based resin film is bonded to a polarizing film made of a polyvinyl alcohol-based resin, and a method for producing the same.

  A polarizing plate is usually a transparent resin film, for example, cellulose acetate typified by triacetyl cellulose, on an adhesive layer on one or both sides of a polarizing film made of a polyvinyl alcohol-based resin having a dichroic dye adsorbed and oriented. The protective film is laminated. This is bonded to a liquid crystal cell with an adhesive via another optical film as necessary to form a component of a liquid crystal display device.

  Liquid crystal display devices are used in various environments as their applications expand, and parts constituting the liquid crystal display devices are required to have high environmental resistance. For example, a liquid crystal display device for mobile use typified by a mobile phone is required to be able to be used under wet heat, and the polarizing plate used therein is also required to have high wet heat resistance. . However, the polarizing plate having the conventional structure has a problem that the polarizing performance is likely to be deteriorated and the interface between the polarizing film and the cellulose acetate-based film is easily peeled off when exposed to a wet and heat environment for a long time.

  For such problems, it has been proposed to use a thermoplastic cycloolefin-based resin as a protective film for a polarizing plate. For example, in Japanese Patent Laid-Open No. 5-212828 (Patent Document 1), a thermoplastic saturated norbornene resin sheet is laminated on at least one surface of a polyvinyl alcohol sheet via an acrylic adhesive, followed by thermocompression bonding. It is described that. JP-A-6-51117 (Patent Document 2) describes that a polarizing plate is formed by laminating a protective film made of a thermoplastic saturated norbornene resin on at least one surface of a polyvinyl alcohol polarizing film. Examples of adhesives used for this purpose include dry laminate adhesives obtained by mixing a polyurethane resin solution and a polyisocyanate resin solution, styrene butadiene rubber adhesives, and epoxy two-component curable adhesives. In addition, JP 2000-321430 A (Patent Document 3) discloses that at least one surface of a polyvinyl alcohol polarizing film has a ring shape through an adhesive layer that is a mixture of a polyvinyl alcohol adhesive and a two-component adhesive. It describes that a protective film made of an olefin resin is laminated to form a polarizing plate. Furthermore, in JP 2000-321432 A (Patent Document 4), a polarizing plate is obtained by bonding a polyvinyl alcohol polarizing film and a protective film made of a thermoplastic saturated norbornene resin with a polyurethane adhesive. Is described.

  However, an acrylic-based pressure-sensitive adhesive (also called a pressure-sensitive adhesive) has a thickness of 10 to 50 μm and has to be increased to some extent. Further, dry laminate adhesives, styrene butadiene rubber adhesives, epoxy two-component curable adhesives, and the like contain organic solvents, which have environmental and worker health problems. Furthermore, when an adhesive containing such an organic solvent is to be applied to a conventional polarizing plate manufacturing facility that does not use an organic solvent, it has been complicated to modify the facility, such as newly installing an explosion-proof facility. Furthermore, when a polyvinyl alcohol polarizing film and a cycloolefin resin film are bonded using a generally known polyvinyl alcohol-based, urethane-based, acrylic-based, vinyl acetate-based adhesive, etc. Sex was not always sufficient.

  On the other hand, it is mainly intended to use a conventional triacetyl cellulose as a protective film, and various proposals have been made for adhesion between it and a polyvinyl alcohol polarizing film. For example, in JP-A-8-101307 (Patent Document 5), a polyvinyl alcohol polarizing film and a support (protective film) are laminated via an adhesive composed of a polyester polyol and an aliphatic polyvalent isocyanate. A polarizing plate is described.

Japanese Patent Laid-Open No. 5-212828 JP-A-6-511117 JP 2000-32430 A JP 2000-32432 A JP-A-8-101307

  An object of the present invention is to use a suitable adhesive to increase the adhesive strength of both when a protective film made of a cycloolefin resin is laminated on a polyvinyl alcohol polarizing film to form a polarizing plate. Another object of the present invention is to produce a polarizing plate in which a polyvinyl alcohol polarizing film and a cycloolefin resin film are firmly bonded using a water-based adhesive that does not substantially contain an organic solvent. .

  As a result of diligent research under such a purpose, the inventors of the present invention used a mixture containing specific components as an adhesive when laminating a protective film composed of a cycloolefin resin on a polyvinyl alcohol polarizing film. By using it, it discovered that the polarizing plate excellent in the adhesiveness of a polarizing film and a protective film was obtained, and reached | attained this invention.

That is, according to the present invention, there is provided a polarizing plate in which a cycloolefin resin film is laminated on at least one surface of a polarizing film made of a polyvinyl alcohol resin via an adhesive layer, and the adhesive layer is made of a polyester ionomer. There is provided a polarizing plate comprising a composition in which 5 to 30 parts by weight of an oxetane compound and an epoxy compound are blended with respect to 100 parts by weight of the type urethane resin.

Here, cyclo olefin resin films, can either be placed on one side of the polarizing film may be disposed on both surfaces of the polarizing film. When a cycloolefin resin film is laminated on one surface of the polarizing film, a protective film made of a resin other than the cycloolefin resin, for example, a cellulose acetate film can be laminated on the other surface.

Further, according to the present invention, a method for producing a polarizing plate by laminating a cycloolefin-based resin film via a water-based adhesive on a polarizing film made of a polyvinyl alcohol-based resin , the water-based adhesive being a polyester-based 5-30 parts by weight of an oxetane compound and an epoxy compound were blended with 100 parts by weight of the solid content of the urethane resin in an aqueous dispersion in which the ionomer-type urethane resin was dispersed in water and the viscosity was 500 mPa · sec or less . A method for producing a polarizing plate is also provided. Here, the water-based adhesive can be used in a form that does not substantially contain an organic solvent.

  According to this invention, compared with the case where the conventional adhesive agent is used, the polarizing plate excellent in the adhesiveness of the protective film which consists of a polyvinyl-alcohol-type polarizing film and a cycloolefin type resin can be manufactured. In addition, since it is not necessary to use an organic solvent in the production of this polarizing plate, it is excellent in terms of environment and safety and hygiene, and is manufactured with the same equipment as a polarizing plate made of a conventional transparent protective film / polarizing film. And there is no need for large capital investment.

  Hereinafter, the present invention will be described in detail. A polarizing plate is manufactured by laminating | stacking a transparent protective film through the adhesive bond layer on the single side | surface or both surfaces of the polarizing film which consists of polyvinyl alcohol-type resin. Specifically, the polarizing film made of polyvinyl alcohol resin is obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol resin film. In the present invention, a cycloolefin resin film is used as a protective film laminated on at least one surface of the polarizing film, and a composition in which a urethane resin, an oxetane compound and an epoxy compound are blended is used as an adhesive layer. To do.

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

  A film obtained by forming such a polyvinyl alcohol resin is used as a raw film of a polarizing film. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. Although the film thickness of a polyvinyl alcohol-type raw film is not specifically limited, For example, it is about 10 micrometers-150 micrometers.

  A polarizing film usually has a step of uniaxially stretching such a polyvinyl alcohol resin film, a step of dyeing a polyvinyl alcohol resin film with a dichroic dye and adsorbing the dichroic dye, and a dichroic dye adsorbed. It is manufactured through a step of treating the polyvinyl alcohol-based resin film with a boric acid aqueous solution and a step of washing with water after the treatment with the boric acid aqueous solution.

  Uniaxial stretching may be performed before dyeing, simultaneously with dyeing, or after dyeing. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Of course, it is also possible to perform uniaxial stretching in these plural stages. In uniaxial stretching, it may be uniaxially stretched between rolls having different peripheral speeds, or may be uniaxially stretched using a hot roll. Further, it may be dry stretching such as stretching in the air, or may be wet stretching in which stretching is performed in a state swollen with a solvent. The draw ratio is usually about 3 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 dye is used as the dichroic dye. In addition, it is preferable that the polyvinyl alcohol-type resin film performs the immersion process to water before a dyeing process.

  When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol resin film by dipping in an aqueous solution containing iodine and potassium iodide is usually employed. The iodine content in this aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water, and the potassium iodide content is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. . The temperature of the aqueous solution used for dyeing is usually about 20 to 40 ° C., and the immersion time (dyeing time) in this aqueous solution is usually about 20 to 1,800 seconds.

On the other hand, when a dichroic dye is used as the dichroic dye, a method of dyeing by immersing a polyvinyl alcohol resin film in an aqueous solution containing a water-soluble dichroic dye is usually employed. The content of the dichroic dye in this aqueous solution is usually about 1 × 10 ⁻⁴ to 10 parts by weight, preferably about 1 × 10 ⁻³ to 1 part by weight per 100 parts by weight of water. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the aqueous dye solution used for dyeing is usually about 20 to 80 ° C., and the immersion time (dyeing time) in this aqueous solution is usually about 10 to 1,800 seconds.

  The boric acid treatment after dyeing with the dichroic dye is performed by immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution. The amount of boric acid in the boric acid-containing 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, the boric acid-containing aqueous solution preferably contains potassium iodide. The amount of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight, preferably about 5 to 12 parts by weight per 100 parts by weight of water. The immersion time in the boric acid-containing aqueous solution is usually about 60 to 1,200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C., more preferably 60 to 80 ° 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. The temperature of water in the water washing treatment is usually about 5 to 40 ° C., and the immersion time is usually about 1 to 120 seconds. After washing with water, a drying process is performed to obtain a polarizing film. The drying process is usually performed using a hot air dryer or a far infrared heater. The temperature of the drying treatment is usually about 30 to 100 ° C, preferably 50 to 80 ° C. The time for the drying treatment is usually about 60 to 600 seconds, preferably about 120 to 600 seconds.

  In this way, the polyvinyl alcohol resin film is subjected to uniaxial stretching, dyeing with a dichroic dye, and boric acid treatment to obtain a polarizing film. The thickness of this polarizing film is about 5 to 40 μm. In the present invention, a cycloolefin-based resin film is laminated on at least one surface of the polarizing film via an adhesive layer to form a polarizing plate.

  The cycloolefin resin is a thermoplastic resin having a monomer unit made of a cyclic olefin (cycloolefin) such as norbornene or a polycyclic norbornene monomer. This cycloolefin-based resin 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, as well as cycloolefins and chain olefins or vinyl groups. An addition copolymer with an aromatic compound having Those having a polar group introduced are also effective.

  When a copolymer of a cycloolefin and a chain olefin or an aromatic compound having a vinyl group is used, examples of the chain olefin include ethylene and propylene, and examples of the aromatic compound having a vinyl group Examples thereof include styrene, α-methylstyrene, and nuclear alkyl-substituted styrene. In such a copolymer, the monomer unit composed of cycloolefin may be 50 mol% or less, for example, about 15 to 50 mol%. In particular, when a ternary copolymer of a cycloolefin, a chain olefin, and an aromatic compound having a vinyl group is used, the amount of monomer units composed of cycloolefin can be relatively small. In such a terpolymer, the unit of monomer composed of a chain olefin is usually about 5 to 80 mol%, and the unit of monomer composed of an aromatic compound having a vinyl group is usually about 5 to 80 mol%.

  Examples of commercially available thermoplastic cycloolefin resins include “Topas” sold by Ticona in Germany, “Arton” sold by JSR Co., Ltd., and sold by Nippon Zeon Co., Ltd. There are "ZEONOR", "ZEONEX", "Appel" sold by Mitsui Chemicals. Such a cycloolefin-based resin is formed into a film, and a known method such as a solvent casting method or a melt extrusion method is appropriately used for forming the film. Formed cycloolefin resin films are also available on the market, such as “Essina” and “SCA40” sold by Sekisui Chemical Co., Ltd., “Zeonor Film” sold by Optes Co., Ltd. There is.

  The thickness of the protective film is preferably thin. However, if it is too thin, the strength is lowered and the processability is inferior. On the other hand, if it is too thick, the transparency is lowered or the weight of the polarizing plate is increased. Occurs. Accordingly, the appropriate thickness of the protective film, particularly the cycloolefin-based resin film is, for example, about 5 to 200 μm, preferably 10 to 150 μm, more preferably 20 to 100 μm.

  The protective film made of such a cycloolefin-based resin may be bonded to one side of the polarizing film or may be bonded to both sides. When a protective film made of a cycloolefin resin is bonded to both surfaces of the polarizing film, the two protective films may be of the same type or different types. When a protective film made of a cycloolefin resin is bonded to one surface of the polarizing film, a protective film made of a resin other than the cycloolefin resin can be bonded to the opposite surface. An example of a suitable protective film made of a resin other than the cycloolefin-based resin is a cellulose acetate-based resin film that has been widely used for a protective film for a polarizing plate. The cellulose acetate-based resin film can be, for example, a triacetyl cellulose film or a diacetyl cellulose film. Triacetyl cellulose films include “Fujitack TD80”, “Fujitack TD80UF” and “Fujitack TD80UZ” sold by Fuji Photo Film Co., Ltd., “KC8UX2M” and “KC8UY” sold by Konica Minolta Opto Co., Ltd. "and so on. The thickness of the cellulose acetate-based protective film is about 20 to 200 μm. Other examples of protective films made of resins other than cycloolefin resins include optical films such as films made of polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, and films made of polycarbonate resins. A film excellent in transparency can also be mentioned.

  In addition, in the said protective film, surface treatments, such as a glare-proof process, a hard-coat process, an antistatic process, and an antireflection process, may be given to the surface on the opposite side to the surface stuck to a polarizing film. In addition, a coat layer made of a liquid crystalline compound or a high molecular weight compound thereof may be formed. These surface treatment layers and coat layers can be applied to the surface of one of the polarizing films when a protective film made of a cycloolefin resin is bonded to both surfaces of the polarizing film. In the case where a protective film made of a resin is bonded and a protective film made of another resin is bonded to the other surface, it can be applied to the surface of any protective film.

  In the present invention, a cycloolefin resin film as described above is laminated on at least one surface of a polarizing film made of a polyvinyl alcohol resin as described above via an adhesive layer to form a polarizing plate. . A cycloolefin resin film can be laminated on one side of the polarizing film, and a protective film made of a resin other than the cycloolefin resin can be laminated on the other side. The adhesive used here, particularly the adhesive used for bonding to the cycloolefin-based resin film, is a composition in which a urethane resin, an oxetane compound, and an epoxy compound are blended. When a protective film made of a resin other than a cycloolefin resin is laminated on one side of a polarizing film, the adhesive for that purpose is not necessarily limited to those specified here, but in general, both sides are the same for ease of construction. It is advantageous to use an adhesive.

Examples of the urethane resin include polyether urethane resins, polyester urethane resins, and acrylic urethane resins. In the present invention , polyester ionomer type urethane resins are employed . A polyester ionomer type urethane resin is a urethane resin having a polyester skeleton, into which a small amount of an ionic component (hydrophilic component) is introduced. Such an ionomer type urethane resin is suitable as a water-based adhesive because it is emulsified directly in water without using an emulsifier to form an emulsion. Polyester ionomer urethane resins are known per se, and are described, for example, in JP-A-7-97504 as examples of polymer dispersants for dispersing phenolic resins in an aqueous medium. Such a polyester ionomer type urethane resin can be manufactured by the following method, for example.

(1) A method of obtaining an ionomer resin by emulsifying a hydrophilic group-containing polyurethane resin obtained by reacting a hydrophilic group-containing compound (A), a polyester polyol (B) and a polyisocyanate (C) in water;
(2) Hydrophilic group-containing compound (A), polyester polyol (B) and polyisocyanate (C) are reacted to disperse the terminal isocyanate group-containing urethane polymer into which the hydrophilic group has been introduced, and reacted with polyamine. To obtain an ionomer resin.

  Examples of the hydrophilic group-containing compound (A) used herein include sulfonic acid group-containing compounds such as 2-hydroxyethanesulfonic acid, sulfosuccinic acid, sulfanilic acid, and 2,4-diaminotoluenesulfonic acid, Carboxylic acid group-containing compounds such as dimethylolpropionic acid, dihydroxymaleic acid, 3,4-diaminobenzoic acid, polyoxyethylene glycol or polyoxyethylene-polyoxypropylene copolymer having at least one active hydrogen in the polymer Examples include coalesced glycol.

  The polyester polyol (B) is a polyester obtained by a dehydration condensation reaction between a glycol component and an acid component, a polyester obtained by a ring-opening polymerization reaction of a cyclic ester compound such as ε-caprolactone, or a copolymer polyester thereof. Can be. The glycol component used in the polyester polyol includes ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6 -Hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (molecular weight 300 to 6,000), dipropylene glycol, tripropylene glycol, 2,2-diethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-pentyl-2-propyl-1,3-propanediol, 2-butyl-2-hexyl-1,3-propanediol, 2-ethyl-1 , 3-Hexanediol Bishydroxyethoxybenzene, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, bisphenol A, hydrogenated bisphenol A, and the like hydroquinone and their alkylene oxide adducts. Acid components include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid , Phthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, 1,2-bis (phenoxy) ethane-p, p'- Examples include dicarboxylic acids, anhydrides and ester-forming derivatives of these dicarboxylic acids, p-hydroxybenzoic acid, p- (2-hydroxyethoxy) benzoic acid, and ester-forming derivatives of these hydroxycarboxylic acids.

  The polyester ionomer type urethane resin may be a combination of the above-described polyester polyol and other high molecular weight polyol components or low molecular weight active hydrogen-containing compounds in a range that does not impair the effects of the present invention. Good. Examples of the high molecular weight polyol include polyether polyol, polycarbonate polyol, polyacetal polyol, polyacrylate polyol, polyesteramide polyol, and polythioether polyol. Examples of the low molecular weight active hydrogen-containing compound include polyhydroxy compounds such as ethylene glycol, neopentyl glycol, 1,6-hexanediol, glycerin and trimethylolpropane, and diamine compounds such as ethylenediamine and piperazine. Especially, it is a preferable form to use a low molecular weight active hydrogen containing compound together.

  The polyisocyanate (C) is a compound having at least two isocyanato groups in the molecule. Specifically, for example, 2,4-tolylene diisocyanate, phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 1 , 6-hexamethylene diisocyanate, isophorone diisocyanate and the like.

  The reaction of these hydrophilic group-containing compound (A), polyester polyol (B) and polyisocyanate (C) can be carried out in the absence of a solvent, but can also be carried out in an organic solvent. The obtained resin is neutralized with a non-volatile base such as sodium hydroxide or potassium hydroxide, an amine such as triethylamine or dimethylethanolamine, or ammonia, and water is added thereto to add a polyester ionomer. An aqueous dispersion of type urethane resin is obtained.

  When the polyester ionomer type urethane resin is obtained in a state containing an organic solvent by using an organic solvent in the reaction, it is advantageous to use the polyester after removing the organic solvent by distillation or the like. Since this urethane resin is an ionomer type, an extremely fine and stable colloid can be formed in water, and it becomes an aqueous adhesive containing no organic solvent.

  The polyester-based ionomer-type urethane resin preferably has a weight average molecular weight of 5,000 or more, more preferably 10,000 to 300,000. If the weight average molecular weight is 5,000 or less, sufficient strength of the adhesive layer cannot be obtained, and if it is higher than 300,000, the viscosity when it is used as an aqueous dispersion becomes high, and it becomes difficult to handle.

The polyester ionomer type urethane resin is used as a water-based adhesive in a state of being dispersed in water. The viscosity of the aqueous adhesive, 2,000 mPa · sec or less, more and even not preferable handling than 1,000 mPa · sec. The lower the viscosity, the easier the application of the adhesive and the better the appearance of the resulting polarizing plate, so that it is more preferably 500 mPa · sec or less . The solid content concentration of the polyester ionomer type urethane resin in this water-based adhesive is preferably in the range of 10 to 70% by weight from the viewpoint of viscosity and adhesive strength, and in particular, 20% by weight or more and 50% by weight or less. Is preferred.

  Polyethylene glycol, polyoxyethylene, or a surfactant may be further added to the aqueous dispersion of the polyester ionomer type urethane resin. Furthermore, water-soluble resins such as polyhydroxyethyl methacrylate, polyhydroxyethyl acrylate, polyacrylic acid, and polyvinyl alcohol resins may be added.

  Examples of commercially available polyester ionomer type urethane resins suitable for use in the present invention include “Hydran AP-20” and “Hydran APX-101H” sold by Dainippon Ink and Chemicals, Inc. .

In the present invention, above-described in addition to the port Riesuteru based ionomer type urethane resin, using an aqueous adhesive containing an oxetane compound and an epoxy compound. By using the oxetane compound and the epoxy compound in combination, the adhesion between the polarizing film and the cycloolefin-based resin film is improved.

  The oxetane compound is a compound having a 4-membered ring ether, that is, an oxetane ring in the molecule. Examples include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [{(3-ethyl-3-oxetanyl) methoxy} methyl] benzene, 3-ethyl-3- (phenoxymethyl) oxetane, bis [(3-Ethyl-3-oxetanyl) methyl] ether, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, 3-ethyl-3-[(3-triethoxysilylpropoxy) methyl] oxetane, oxetanyl Examples include silsesquioxane and phenol novolac oxetane. Here, the oxetanyl silsesquioxane is obtained by hydrolytic condensation of a silane compound having an oxetanyl group, for example, the aforementioned 3-ethyl-3-[(3-triethoxysilylpropoxy) methyl] oxetane. It is a network-like polysiloxane compound having a plurality of oxetanyl groups. Among these oxetane compounds, 3-ethyl-3-hydroxymethyloxetane excellent in water dispersion performance is preferable. Examples of commercially available oxetane compounds include “OXT-101” sold by Toagosei Co., Ltd.

  The epoxy compound is a compound having a three-membered ether, that is, an epoxy ring in the molecule. Examples thereof include polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, diglycerin diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, resorcin diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol Polyglycidyl ether, sorbitan polyglycidyl ether, pe Taerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycyl Sidoxypropylmethyldiethoxysilane and the like can be mentioned. Among these, those excellent in water dispersion performance are preferable. Examples of commercially available epoxy compounds include “CR-5L” sold by Dainippon Ink Chemical Co., Ltd., “Epolite 40E” and “Epolite 80MF” sold by Kyoeisha Chemical Co., Ltd. There are “KBM-303”, “KBM-403” and “KBE-403” sold by Shin-Etsu Chemical Co., Ltd., respectively.

The mixing ratio of the urethane resin, an oxetane compound and an epoxy compound, relative to 100 parts by weight of the solid content of the urethane resin, you select as oxetane compounds and epoxy compounds is in the range of respectively are 5 to 30 parts by weight. If the ratio of the oxetane compound and the epoxy compound is too low, sufficient adhesive strength cannot be obtained. If the ratio is too large, the stability of the adhesive is reduced and the viscosity of the adhesive is increased, making it difficult to handle. Become.

  As described above, the present invention has a great feature in using an aqueous adhesive containing a urethane resin, an oxetane compound and an epoxy compound. Since this water-based adhesive does not require the use of organic solvents, there is no risk of causing environmental or worker health problems, and the combined use of an oxetane compound and an epoxy compound results in high adhesive strength. Is obtained.

  Generally, a method of adhering a polarizing film and a protective film made of a cycloolefin resin with an adhesive, and a method of adhering both when a protective film made of a resin other than a cycloolefin resin is laminated on one side of a polarizing film are generally used. The adhesive may be applied to the adhesive surface of the polarizing film and / or protective film by, for example, casting method, Meyer bar coating method, gravure coating method, die coating method, dip coating method, spraying method, etc. And a method of superimposing the two. The casting method is a method in which a polarizing film or a protective film, which is an object to be coated, is moved in a generally vertical direction, a substantially horizontal direction, or an oblique direction between the two, and an adhesive is allowed to flow down and spread on the surface. It is. After applying the adhesive, the polarizing film and the protective film are sandwiched by nip rolls and bonded together.

  In order to improve adhesion, surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, and saponification treatment may be appropriately performed on the adhesive surface of the polarizing film and / or the protective film. Examples of the saponification treatment include a method of immersing in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

  After laminating the polarizing film and the protective film, a drying process is performed. The drying process is performed, for example, by blowing hot air, and the temperature at that time is appropriately selected from the range of about 40 to 100 ° C., preferably 60 to 100 ° C. The drying time is about 20 to 1,200 seconds. After drying, it is preferable to carry out curing at room temperature or slightly higher temperature, for example, at a temperature of about 20 to 50 ° C. for about 12 to 600 hours. The thickness of the adhesive layer after drying is usually about 0.001 to 5 μm, preferably 0.01 μm or more, preferably 2 μm or less, more preferably 1 μm or less. When the thickness of the adhesive layer exceeds 5 μm, the appearance of the polarizing plate tends to be poor.

  In the polarizing plate of the present invention, an optical functional film may be attached to the surface of the protective film via an adhesive. As an optical functional film, for example, a liquid crystal compound is applied to the surface of a base material, an optical compensation film that is oriented, a reflection that transmits a certain kind of polarized light, and reflects polarized light that shows the opposite property. Type polarized light separation film, retardation film made of polycarbonate resin, retardation film made of cyclic polyolefin resin, film with anti-glare function having concavo-convex shape on surface, film with surface antireflection treatment, reflection having reflection function on surface Examples thereof include a film and a transflective film having both a reflection function and a transmission function. Commercially available products corresponding to the optical compensation film coated with a liquid crystal compound on the substrate surface and aligned are "WV film" sold by Fuji Photo Film Co., Ltd. and Nippon Oil Corporation. There are “NH film” and “NR film” (both are trade names) on the market. A commercial product equivalent to a reflective polarizing separation film that transmits certain types of polarized light and reflects polarized light exhibiting the opposite properties is Minnesota Mining and Manufacturing (3M) (Sumitomo 3M Limited in Japan). "DBEF" (trade name) sold by In addition, “ARTON” sold by JSR Co., Ltd., “ESCINA” sold by Sekisui Chemical Co., Ltd. as a commercial product corresponding to a retardation film made of cyclic polyolefin resin. There is "Zeonor Film" (all trade names) sold by Optes.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these examples. In the examples, “%” and “part” representing the content or amount used are based on weight unless otherwise specified.

Example 1
A polyvinyl alcohol film having an average degree of polymerization of about 2,400 and a saponification degree of 99.9 mol% or more and a thickness of 75 μm is uniaxially stretched about 5 times in a dry manner, and further maintained at 60 ° C. with pure water at 60 ° C. And then immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100 at 28 ° C. for 60 seconds. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72 ° C. for 300 seconds. Subsequently, it was washed with pure water at 26 ° C. for 20 seconds and then dried at 65 ° C. to obtain a polarizing film in which iodine was adsorbed and oriented on polyvinyl alcohol.

  Separately, Toagosei, an oxetane compound, is added to 100 parts of an aqueous emulsion of polyester ionomer type urethane resin (“Hydran AP-20” manufactured by Dainippon Ink and Chemicals, Inc., solid content concentration 30%, viscosity 30 mPa · sec). 5 parts of “OXT-101” (chemical name: 3-ethyl-3-hydroxymethyloxetane) manufactured by KK, “KBM-303” (chemical name: 2) manufactured by Shin-Etsu Chemical Co., Ltd., which is an epoxy compound 5 parts of-(3,4-epoxycyclohexyl) ethyltrimethoxysilane) was added to obtain an adhesive. A protective film of 40 μm thickness made of corona-treated norbornene resin (“Zeonor film” manufactured by Optes Co., Ltd.) is bonded to both sides of the previously obtained polarizing film via the adhesive. And dried at 80 ° C. for 5 minutes to obtain a polarizing plate. Thereafter, it was cured at 40 ° C. for 6 days. A cutter blade was inserted in the transmission axis direction at an angle of 45 ° with respect to the normal direction of the film on the surface of the polarizing plate, and peeling of the polarizing film and the protective film was attempted, but no peeling occurred.

Example 2
A protective film to be bonded to the polarizing film is a 100 μm-thick “Zeonor film” made of a norbornene-based resin that has been subjected to corona treatment on one side, and a thickness made of triacetylcellulose that has been subjected to surface saponification treatment on the other side. A polarizing plate was produced in the same manner as in Example 1 except that the film was 80 μm thick (“Fujitac” film manufactured by Fuji Photo Film Co., Ltd.) and the curing time was 8 days at 40 ° C. With respect to the obtained polarizing plate, a peel test was attempted in the same manner as in Example 1. However, both surfaces did not peel at all.

Example 3
The same procedure as in Example 1 was performed except that “CR-5L” (polyfunctional glycidyl ether) manufactured by Dainippon Ink & Chemicals, Inc. was used instead of the epoxy compound “KBM-303”. A polarizing plate was prepared. The obtained polarizing plate was subjected to a peel test in the same manner as in Example 1, but did not peel at all.

Comparative Example 1
A polarizing plate was produced in the same manner as in Example 1 except that the epoxy compound “KBM-303” was not blended in the adhesive. In the obtained polarizing plate, the protective film was easily peeled off.

Comparative Example 2
In 100 parts of water, 3 parts of carboxyl group-modified polyvinyl alcohol (“Kuraray Poval KL318” manufactured by Kuraray Co., Ltd.) and water-soluble polyamide epoxy resin (“Smiles Resin 650” manufactured by Sumitomo Chemical Co., Ltd. (solid content concentration) (30% aqueous solution) A polarizing plate was produced in the same manner as in Example 1 except that 1.5 parts was added to obtain an adhesive and the curing time was 4 days at 40 ° C. The obtained polarizing plate was The protective film was easily peeled off.

Claims (5)

A polarizing plate in which a cycloolefin resin film is laminated on at least one surface of a polarizing film made of a polyvinyl alcohol resin via an adhesive layer,
The adhesive layer is composed of a composition in which 5 to 30 parts by weight of an oxetane compound and an epoxy compound are blended with 100 parts by weight of a polyester ionomer type urethane resin. The polarizing plate according to claim 1 , wherein the cycloolefin resin film is laminated on one side of the polarizing film, and the cellulose acetate film is laminated on the other side . The polarizing plate of claim 1 Symbol placement cycloolefin resin film on both sides is the product layer of the polarizing film. A polarizing film comprising a polyvinyl alcohol-based resin, through a water-based adhesive laminating cycloolefin resin film, a method of manufacturing a polarizing plate,
The aqueous adhesive contains an oxetane compound and an epoxy compound with respect to 100 parts by weight of the solid content of the urethane resin in an aqueous dispersion in which a polyester ionomer type urethane resin is dispersed in water and the viscosity is 500 mPa · sec or less. A method for producing a polarizing plate , comprising 5 to 30 parts by weight of each . The method according to claim 4, wherein the water-based adhesive is substantially free of an organic solvent .