JP2005208456A - Polarizing plate and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase adhesion strength between a protective film and a polarizing film by applying a proper adhesive on the respective surface in the process of laminating a cycloolefin resin film on one surface of a polarizing film made of a polyvinylalcohol resin and laminating a cellulose acetate film on the other surface to produce a polarizing plate. <P>SOLUTION: The polarizing plate is obtained by laminating a cycloolefin resin film on one surface of a polarizing film made of a polyvinyl alcohol resin via an aqueous first adhesive containing a polyester ionomer type urethane resin and a compound having a glycidyloxy group, and by laminating a cellulose acetate film on the other surface of the film via an aqueous second adhesive having a different composition from that of the first adhesive, for example, an aqueous solution of a polyvinyl alcohol resin. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  In the present invention, a cellulose acetate film is laminated on one surface of a polarizing film made of a polyvinyl alcohol resin via an adhesive layer, and a cycloolefin resin film is laminated on the other surface via an adhesive layer. The present invention relates to a polarizing plate and a manufacturing method thereof.

  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 JP-A-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 pressure-sensitive 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 in which a polyurethane resin solution and a polyisocyanate resin solution are mixed, 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 is complicated to modify the facility, such as newly installing an explosion-proof facility.

  On the other hand, polarizing plates often require functions such as scratch resistance, antistatic properties, antiglare properties, and antireflection properties on the surface. The cycloolefin-based resin film has insufficient functions because it is not always easy to impart a function to the surface of the protective film, which is made of a cellulose acetate-based resin such as a conventional triacetyl cellulose. Even if the function could be added, it was expensive. Therefore, a cellulose acetate-based resin is often desired for the protective film on at least one side of the polarizing plate.

  Conventionally, cellulose acetate-based resin is mainly intended to be a protective film, and various proposals have been made for adhesion between it and a polyvinyl alcohol-based polarizing film. As a water-based adhesive that does not contain an organic solvent, for example, JP-A-7-134212 (Patent Document 5) contains a predetermined amount of glyoxal in a polyvinyl alcohol adhesive that bonds a polyvinyl alcohol polarizing film and a protective film. JP-A-9-258023 (Patent Document 6) also contains a predetermined amount of a water-soluble epoxy compound in a polyvinyl alcohol adhesive that joins a polyvinyl alcohol polarizing film and a protective film. It is described that the adhesion is improved. However, when these polyvinyl alcohol-based adhesives are used to bond a polyvinyl alcohol-based polarizing film and a cycloolefin-based resin film, furthermore, generally known polyvinyl alcohol-based, urethane-based, acrylic-based, vinyl acetate-based adhesives, etc. Even when the agent was used, the adhesiveness was not always sufficient depending on the combination of both films.

Japanese Patent Laid-Open No. 5-212828 JP-A-6-511117 JP 2000-32430 A JP 2000-32432 A JP 7-134212 A Japanese Patent Laid-Open No. 9-258023

  An object of the present invention is to laminate a cycloolefin resin film on one surface of a polarizing film made of a polyvinyl alcohol resin via an adhesive layer and a cellulose acetate film on the other surface via an adhesive layer. When a polarizing plate is laminated, an appropriate adhesive is applied to each surface to increase the adhesive force between the polarizing film and each protective film. Another object of the present invention is to produce a polarizing plate in which a polyvinyl alcohol polarizing film and a protective 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 present inventors have used an aqueous mixture containing specific components as an adhesive for joining a polarizing film and a cycloolefin resin film, As an adhesive for bonding a cellulose acetate film, it is found that a polarizing plate excellent in adhesiveness between a polarizing film and a protective film can be obtained by using a water-based adhesive with a different composition. The invention has been reached.

  That is, according to the present invention, the first adhesive formed from a composition containing a polyester ionomer type urethane resin and a compound having a glycidyloxy group on one surface of a polarizing film made of a polyvinyl alcohol resin. Polarized light in which a cycloolefin-based resin film is laminated via a layer, and a cellulose acetate film is laminated on the other surface via a second adhesive layer having a composition different from that of the first adhesive layer A board is provided.

  Further, according to the present invention, the one side of a polarizing film made of a polyvinyl alcohol-based resin is cyclohexane via a water-based first adhesive containing a polyester-based ionomer-type urethane resin and a compound having a glycidyloxy group. A polarizing plate is produced by laminating an olefin-based resin film and laminating a cellulose acetate-based film on the other surface via an aqueous second adhesive having a composition different from that of the first adhesive. A method is also provided. Here, the water-based adhesive can be used in a form that does not substantially contain an organic solvent.

  According to the present invention, a cycloolefin-based resin film is laminated on one surface of a polyvinyl alcohol-based polarizing film, and a cellulose acetate-based film is laminated on the other surface as a protective film, and the polarizing film and both protective films are bonded. A polarizing plate having excellent properties can be produced. 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. In the polarizing plate of the present invention, a cycloolefin resin film is laminated on one surface of a polarizing film made of polyvinyl alcohol resin via a first adhesive layer, and a second adhesive layer is formed on the other surface. It is manufactured by laminating a cellulose acetate film. Specifically, the polarizing film made of a polyvinyl alcohol-based resin is obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol-based resin film. In the present invention, as the first adhesive layer for joining the polarizing film and the cycloolefin resin film, a mixture of a polyester ionomer type urethane resin and a compound having a glycidyloxy group is employed, and the polarizing film and acetic acid are used. As a 2nd adhesive bond layer joined to a cellulose film, the thing of a composition different from a 1st adhesive bond layer is employ | adopted.

  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 or 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 immersing and dyeing a polyvinyl alcohol-based 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, this 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 resin film is laminated on one surface of the polarizing film via a first adhesive layer, and a cellulose acetate film is laminated on the other surface via a second adhesive layer. Laminated 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. It may be 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 cycloolefin resin film may be stretched uniaxially or biaxially. In this case, the draw ratio is usually about 1.1 to 5 times, preferably 1.1 to 3 times.

  The cellulose acetate film used as the other protective film in the present invention is a cellulose part or a complete acetate ester, and examples thereof include a triacetyl cellulose film and a diacetyl cellulose film. Commercially available triacetyl cellulose films include "Fujitack TD80", "Fujitack TD80UF" and "Fujitack TD80UZ" sold by Fuji Photo Film Co., Ltd., "KC8UX2M" sold by Konica Minolta Opto and There is “KC8UY”.

  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. Therefore, a suitable thickness of the cycloolefin-based resin film is, for example, about 5 to 200 μm, preferably 10 to 150 μm, more preferably 20 to 100 μm. On the other hand, the thickness of the cellulose acetate film is usually about 20 to 200 μm.

  The protective film made of these cycloolefin-based resin and / or cellulose acetate-based resin has antiglare treatment, hard coat treatment, antistatic treatment, antireflection treatment, etc. on the surface opposite to the surface to be attached to the polarizing film. Surface treatment may be performed. In addition, a coat layer made of a liquid crystalline compound or a high molecular weight compound thereof may be formed.

  A cycloolefin-based resin film as described above is provided on one side of the polarizing film via a first adhesive layer, and the other side is also provided via a second adhesive layer. Cellulose acetate films as described above are laminated to form a polarizing plate.

  The first adhesive used for joining the polarizing film and the cycloolefin resin film is a mixture of a polyester ionomer type urethane resin and a compound having a glycidyloxy group. The polyester-based ionomer type urethane resin here 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 ring-opening polymerization reaction of a cyclic ester compound such as ε-caprolactone, or a copolyester thereof, in addition to a polyester obtained by a dehydration condensation reaction between a glycol component and an acid component. 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 not impairing 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 less than 5,000, sufficient strength of the adhesive layer cannot be obtained, and if it is more than 300,000, the viscosity of the resulting dispersion as an aqueous dispersion increases, making it 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 this aqueous adhesive is preferably 2,000 mPa · sec or less, more preferably 1,000 mPa · sec or less, and particularly preferably 500 mPa · sec or less. The lower the viscosity, the easier the application of the adhesive and the better the appearance of the resulting polarizing plate. 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, particularly 20% by weight or more and 50% by weight or less from the viewpoint of viscosity and adhesive strength. Even more 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, in addition to the polyester ionomer type urethane resin as described above, a compound having a glycidyloxy group is blended to form a first adhesive for joining the polarizing film and the cycloolefin resin film. . By using the compound having such a glycidyloxy group in combination, the adhesion between the polarizing film and the cycloolefin-based resin film is improved. The glycidyloxy group here is a group represented by the following formula, and should be called a 2,3-epoxypropoxy group purely.

  The glycidyloxy group is particularly preferably ether-bonded. The compound having a glycidyloxy group preferably has at least two glycidyloxy groups in the molecule. Examples thereof include polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl ether, neodymium. Pentyl 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, trimethylol group Pan triglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, sorbitan polyglycidyl ether, polyglycerol polyglycidyl ether. The compound having a glycidyloxy group preferably has a weight average molecular weight of 5,000 or less. Examples of commercially available compounds having a glycidyloxy group include “CR-5L” sold by Dainippon Ink and Chemicals, Inc.

  The mixing ratio of the polyester ionomer type urethane resin and the compound having a glycidyloxy group is such that the compound having a glycidyloxy group is in the range of about 5 to 100 parts by weight with respect to 100 parts by weight of the solid content of the polyester ionomer type urethane resin. It is preferable to select appropriately so that the compound having a glycidyloxy group is 5 to 60 parts by weight, particularly 5 to 30 parts by weight. If the ratio of the compound having a glycidyloxy group is too low, sufficient adhesive strength cannot be obtained, and if the ratio is too high, the viscosity of the adhesive becomes high and handling becomes difficult.

  A water-based adhesive containing a polyester ionomer-type urethane resin and a compound having a glycidyloxy group does not require the use of an organic solvent, so there is no risk of causing environmental or worker health problems. At the same time, the use of a compound having a glycidyloxy group gives high adhesive strength.

  On the other hand, the second adhesive for joining the polarizing film and the cellulose acetate-based film may be any water-based adhesive that firmly bonds both. The above-mentioned polyester ionomer type urethane resin can also be used for the second adhesive. However, in this case, it is not necessary to use a compound having a glycidyloxy group, and therefore, the composition is different from that of the first adhesive layer.

  When a polyester ionomer type urethane resin is used as the second adhesive, a compound having an isocyanato group, particularly a polyisocyanate compound having at least two isocyanato groups in the molecule, is used in order to increase adhesion to a cellulose acetate film. It is preferable to use together. Examples of such isocyanato group-containing compounds include monomers or oligomers such as 2,4-tolylene diisocyanate, phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, and the like. The reaction material of a compound and a polyol is mentioned. Examples of the polyol used for this purpose include 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, and the like. The molecular weight of these isocyanato group-containing compounds is preferably 5,000 or less in terms of weight average molecular weight, even if they are a reaction product with the above oligomer or polyol. Examples of suitable commercially available isocyanato group-containing compounds include “Hydran Assist C1” sold by Dainippon Ink and Chemicals, Inc.

  The mixing ratio of the polyester ionomer type urethane resin and the isocyanato group-containing compound is suitably set so that the isocyanate group-containing compound is in the range of about 5 to 100 parts by weight with respect to 100 parts by weight of the solid content of the polyester ionomer type urethane resin. It is preferable to select, and more preferably, the isocyanato group-containing compound is selected in the range of 5 to 60 parts by weight, particularly 5 to 30 parts by weight. If the ratio of the isocyanato group-containing compound is too low, sufficient adhesive strength cannot be obtained. If the ratio is too high, the viscosity of the adhesive becomes high and handling becomes difficult.

  Thus, as a first adhesive for bonding the polarizing film and the cycloolefin-based resin film and a second adhesive for bonding the polarizing film and the cellulose acetate-based film, respectively, polyester-based ionomer type urethane A resin-containing composition can be used. However, when a urethane resin is used as an adhesive, sufficient adhesion is achieved only after pasting at room temperature or higher for at least half a day, usually several days or longer. Strength is obtained. Therefore, when the adhesive layer is in an uncured state, there are limitations on operations such as cutting and pasting to other films, and the manufacturing cost may be increased particularly when manufacturing with a wide width.

  Therefore, if a polyvinyl alcohol-based resin is used as the second adhesive for joining the polarizing film and the cellulose acetate film, the interface between the polarizing film and the cellulose acetate film is stable immediately after the production of the polarizing plate. Adhesive strength is obtained. Due to this adhesive force, it becomes possible to easily perform operations such as cutting and pasting even immediately after production, where the adhesive force at the interface between the other polarizing film and the cycloolefin-based resin film is weak.

  In this case, an aqueous solution of a polyvinyl alcohol resin is used as the second adhesive. Polyvinyl alcohol resins are modified such as partially saponified polyvinyl alcohol and fully saponified polyvinyl alcohol, as well as carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol, and amino group-modified polyvinyl alcohol. Polyvinyl alcohol resin may be used.

  The density | concentration of the polyvinyl alcohol-type resin in an adhesive agent is about 1-10 weight part normally with respect to 100 weight part of water, Preferably it is 1-5 weight part. In order to improve adhesiveness, it is preferable to add a curable component or a crosslinking agent such as glyoxal or water-soluble epoxy resin to the polyvinyl alcohol-based adhesive. The water-soluble epoxy resin is, for example, a polyamide polyamine epoxy obtained by reacting a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine with a polycarboxylic acid such as adipic acid and epichlorohydrin. It can be a resin. Commercially available products of such polyamide polyamine epoxy resins include “Smiles Resin 650” and “Smiles Resin 675” sold by Sumitomo Chemical Co., Ltd., and “WS-” sold by Japan PMC Co., Ltd. 525 ”. The addition amount of these curable components or crosslinking agents is usually 1 to 100 parts by weight, preferably 1 to 50 parts by weight, with respect to 100 parts by weight of the polyvinyl alcohol resin. If the amount added is small, the effect of improving the adhesiveness is reduced, while if the amount added is large, the adhesive layer tends to be brittle.

  The method of joining the polarizing film and the protective film with an adhesive may be generally known, for example, by casting, Meyer bar coating, gravure coating, die coating, dip coating, spraying, etc. The method of apply | coating an adhesive agent to the adhesive surface of a polarizing film and / or a protective film, and superimposing both is mentioned. 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.

  Moreover, in order to improve adhesiveness, surface treatments such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, and saponification treatment may be appropriately performed on the adhesion 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. Further, after drying, it is preferable to cure at room temperature or slightly higher temperature, for example, at a temperature of about 20 to 50 ° C. for about 12 to 600 hours, particularly in order to increase the adhesive strength of the adhesive layer made of urethane resin. 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 is greater than 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) Production of Polarizing Film 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 was uniaxially stretched about 5 times in a dry process, and further maintained a tension state. The sample was immersed in pure water at 60 ° C. for 1 minute, and then immersed in an aqueous solution having an iodine / potassium iodide / water weight ratio 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.

(B) Preparation of Adhesive Polyester ionomer-type urethane resin aqueous emulsion (“Hydran AP-20” manufactured by Dainippon Ink & Chemicals, Inc., solid content concentration 30%, viscosity 30 mPa · sec) A polyurethane adhesive (A) was prepared by adding 5 parts of “CR-5L” manufactured by Dainippon Ink & Chemicals, Inc., which is a functional glycidyl ether.

Separately, in 100 parts of water, 3 parts of carboxyl group-modified polyvinyl alcohol (“Kuraray Poval KL318” manufactured by Kuraray Co., Ltd.) and a water-soluble polyamide epoxy resin (“Smiles Resin 650” manufactured by Sumitomo Chemical Co., Ltd. (solid) An aqueous solution having a partial concentration of 30%) 1.5 parts was added to obtain a polyvinyl alcohol-based adhesive.

(C) Production and evaluation of polarizing plate Protection of 100 μm thickness made of norbornene-based resin subjected to corona treatment on one side of the polarizing film obtained in (a) via the polyurethane-based adhesive (A) A film is bonded, and a protective film having a thickness of 80 μm made of triacetyl cellulose subjected to a surface saponification treatment is bonded to the other surface via the polyvinyl alcohol-based adhesive, and 80 ° C. And dried for 7 minutes to obtain a polarizing plate. On the surface of this polarizing plate, a cutter blade was inserted in the direction of the transmission axis at an angle of 45 ° with respect to the normal direction of the film, and when the peeling of the polarizing film and the protective film was attempted, the norbornene-based resin film was peeled off. However, the triacetyl cellulose film did not peel at all. Thereafter, the polarizing plate without the cutter blade was cured at 40 ° C. for 9 days. About the polarizing plate after curing, when the peeling test of the protective film was done by the method similar to the above, neither side peeled at all.

Example 2
An aqueous emulsion “Hydran AP-20” of the same polyester ionomer type urethane resin used in (b) of Example 1 was added to “Hydran” manufactured by Dainippon Ink & Chemicals, Inc., which is an isocyanato group-containing compound. 7.5 parts of Assister C-1 ″ and 30 parts of water were added to obtain a polyurethane-based adhesive (B). A polarizing plate was prepared in the same manner as in (c) of Example 1 except that this polyurethane adhesive (B) was used instead of the polyvinyl alcohol adhesive, and further cured at 40 ° C. for 9 days. The polarizing plate after curing was subjected to a peel test in the same manner as in Example 1. As a result, the norbornene resin film and the triacetyl cellulose film did not peel at all.

Claims (9)

  Cycloolefin resin via a first adhesive layer formed from a composition containing a polyester ionomer type urethane resin and a compound having a glycidyloxy group on one surface of a polarizing film made of a polyvinyl alcohol resin A polarizing plate, wherein a film is laminated, and a cellulose acetate film is laminated on the other surface through a second adhesive layer having a composition different from that of the first adhesive layer.   The polarizing plate according to claim 1, wherein the second adhesive layer contains a polyester ionomer type urethane resin and is formed from a composition having a composition different from that of the first adhesive layer.   The polarizing plate according to claim 2, wherein the second adhesive layer is formed from a composition containing a polyester ionomer type urethane resin and a polyisocyanate compound.   The polarizing plate according to claim 1, wherein the second adhesive layer is formed from a composition containing a polyvinyl alcohol-based resin.   On one surface of a polarizing film made of polyvinyl alcohol resin, a cycloolefin resin film is laminated via an aqueous first adhesive containing a polyester ionomer type urethane resin and a compound having a glycidyloxy group, A method for producing a polarizing plate, comprising: laminating a cellulose acetate film on the other surface through an aqueous second adhesive having a composition different from that of the first adhesive.   The method according to claim 5, wherein the second adhesive contains a polyester ionomer type urethane resin and is a water-based adhesive having a composition different from that of the first adhesive.   The method according to claim 6, wherein the second adhesive is a water-based adhesive containing a polyester-based ionomer-type urethane resin and a polyisocyanate compound.   The method according to claim 5, wherein the second adhesive is an aqueous solution of a polyvinyl alcohol-based resin. The method according to any one of claims 5 to 8, wherein the first adhesive and the second adhesive are substantially free of an organic solvent.