JP2005115028A - Layered body composed of adhesive layer and polarizing plate or retardation plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a layered body composed of an adhesive layer and a polarizing plate or a retardation plate, in which the foaming is not caused even in a high temperature or high temperature and high humidity environment, peeling is not caused on the interface of the objective body such as glass or a retardation plate, stress concentration induced by expansion, contraction or the like of a polarizing plate layer is reluxed, and color irregularity or a white void is not caused in a liquid crystal element. <P>SOLUTION: The layered body is obtained by forming an adhesive layer by applying and drying an acrylic adhesive and then laminating the layer on a polarizing plate or a retardation plate while the gel fraction of the adhesive layer is ≥80% of the saturated gel fraction. The acrylic adhesive is prepared by compounding an adhesive composition comprising an acrylic copolymer containing a carboxyl group and/or a hydroxyl group and having specified high molecular weight and a specified acrylic (co)polymer having specified low molecular weight with a crosslinking agent in an amount to produce 2 to 10 theoretical crosslinked points per one molecular chain of the copolymer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laminate comprising a pressure-sensitive adhesive layer and a polarizing plate or a retardation plate, which is used for adhering to an optical component such as a liquid crystal cell of a liquid crystal display device.

  A polarizing plate used for a liquid crystal element has a three-layer structure in which both surfaces of a polyvinyl alcohol-based polarizer are sandwiched between triacetyl cellulose-based protective films, but dimensional stability is poor due to the characteristics of these materials. In particular, it is remarkable under heat or wet heat conditions, and the dimensional change due to expansion and contraction of the polarizing plate is large. Therefore, under severe conditions, when the polarizing plate expands and contracts and the followability of the pressure-sensitive adhesive is insufficient, foaming or peeling due to this strain is likely to occur. In addition, since the internal stress caused by dimensional changes due to aging of the polarizing plate cannot be absorbed or relaxed, the distribution of residual stress acting on the polarizing plate becomes non-uniform, and stress is concentrated particularly on the periphery of the polarizing plate. As a result, the liquid crystal element surface becomes brighter or darker than the center, causing uneven color and white spots on the surface of the liquid crystal element.

  In order to solve the above problems, the pressure-sensitive adhesive used for adhering a polarizing plate or a retardation plate to a substrate is usually a small amount of a crosslinking agent added to a molecular weight-enhanced adhesive layer. It is made to be flexible and strong to withstand use. Furthermore, by adding a low molecular weight polymer to the pressure-sensitive adhesive, the residual stress acting on the polarizing plate is alleviated and uneven color and white spots are improved.

  Triacetyl cellulose (hereinafter abbreviated as TAC) used for a polarizing plate is generally produced by a solution casting method. Solvents used in this case include aliphatic hydrocarbons such as pentane and hexane, aromatic hydrocarbons such as benzene and toluene, halogenated hydrocarbons such as methyl chloride and methylene chloride, methanol and ethanol. Alcohols and esters such as methyl formate and ethyl formate are mainly used. Therefore, the aforementioned solvent remains in the TAC.

  Conventionally, an acrylic pressure-sensitive adhesive added with a crosslinking agent is formed on a release paper on a polarizing plate that uses the TAC produced as described above as a protective film, and is transferred immediately or in a state of being crosslinked in a small amount. The method is a general adhesive processing method. In particular, when adhesive processing is performed using an isocyanate compound as a cross-linking agent, if there is a large amount of residual solvent in the TAC, particularly alcohols, the isocyanate compound reacts with the residual solvent, and performance after curing the adhesive. Is unstable, and moisture adhering to the surface of the TAC causes the same problem.

  For example, regarding the control of the residual solvent, in JP-A-7-112446, in the production of a protective film for a polarizing plate comprising a cellulose triacetate film, a film drying temperature condition suitable for the amount of residual volatile components in the cellulose triacetate film It is shown. The amount of residual volatile matter in the polarizing plate protective film affects the birefringence of the protective film even during the production of the protective film. To keep the birefringence below 5 nm, the drying conditions of the protective film are strictly determined by the residual volatile content. Need to control. However, it is difficult to control the amount of volatile matter by solvent type only by controlling the drying conditions of the protective film by the amount of residual volatile matter, and the performance after curing the adhesive cannot be controlled.

  Japanese Patent Application Laid-Open No. 9-189810 discloses a manufacturing method in which an acrylic pressure-sensitive adhesive is applied to a release paper and dried, and the gel fraction is 70% or less of the saturated gel fraction and bonded to a polarizing plate or a retardation plate. Is disclosed. However, when the addition amount of the cross-linking agent is reduced to improve uneven color and white spots, the cross-linking agent affects the residual solvent and moisture when the gel fraction of the pressure-sensitive adhesive is 70% or less of the saturated gel fraction. The adhesive performance is not stable.

Further, in Patent Document 3 Japanese Patent Application Laid-Open No. 10-279907, generally, “100 parts by weight of a high molecular weight (meth) acrylic copolymer having a weight average molecular weight of 1,000,000 or more and a low molecular weight having a weight average molecular weight of 30,000 or less. An invention of “adhesive composition for polarizing plate comprising 20 to 200 parts by weight of (meth) acrylic (co) polymer” and 0.005 to 5 parts by weight of a polyfunctional compound is disclosed. The invention describes that a pressure-sensitive adhesive layer that can follow the dimensional change of the polarizing plate is formed so that uneven color and white spots are unlikely to occur in the liquid crystal element. However, in the present invention, it is necessary to make the addition amount of the polyfunctional compound small in order to make it difficult to generate uneven color and white spots, and a stable pressure-sensitive adhesive layer in the conventional production method of immediately pasting It is difficult to produce a polarizing plate or a retardation plate having
JP-A-7-112446 Japanese Patent Laid-Open No. 9-189810 JP-A-10-279907

  The object of the present invention is that foaming does not occur even in a high temperature or high temperature and humidity environment, peeling does not occur at the interface with the adherend such as glass or retardation plate, and stress concentration caused by expansion and contraction of the polarizing plate layer is alleviated. The present invention also provides a laminate comprising a pressure-sensitive adhesive layer and a polarizing plate or a retardation plate that does not cause uneven color and white spots in a liquid crystal element.

  As a result of extensive research, the present inventors have found that the degree of crosslinking of the pressure-sensitive adhesive crosslinked by the crosslinking agent significantly affects the optical performance of the final laminate, and the dimensions under heat and wet heat conditions. In order to make it difficult for foaming and peeling due to changes, color unevenness and white spots to occur, it is effective to crosslink the gel fraction of the crosslinked product to a specific ratio or higher and then attach it to the polarizing plate or retardation plate. The present invention has been found to be suitable.

  That is, the present invention applies an acrylic pressure-sensitive adhesive to a release film to form a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer has a gel fraction of 80% or more of the saturated gel fraction and is attached to a polarizing plate or a retardation plate. It is a laminated body formed together. Further, the acrylic pressure-sensitive adhesive has a weight average molecular weight of 800,000 to 2,000,000 comprising (A) (meth) acrylic acid alkyl ester monomer and carboxyl group and / or hydroxyl group-containing unsaturated monomer as main components. 100 parts by weight of a copolymer and (B) (meth) acrylic acid alkyl ester monomer as a main component, and a weight average molecular weight of 1000 to 300,000 (co) polymer 1 to 45 parts by weight. This is a pressure-sensitive adhesive composition obtained by blending a (co) polymer composition with a crosslinking agent (C) so that the number of theoretical crosslinking points per molecular chain of the copolymer (A) is 2 to 10. .

  The laminate obtained by cross-linking the gel fraction of the cross-linked product of the present invention so as to have a specific ratio or more and then bonding to the polarizing plate or the retardation plate is caused by expansion and contraction of the polarizing plate occurring under high temperature and high humidity conditions. Stress can be absorbed and relaxed sufficiently, and foaming and peeling, and uneven color and white spots can be prevented.

  Hereinafter, the configuration of the present invention will be described in detail. It is necessary that the gel fraction of the pressure-sensitive adhesive layer used in the laminate of the present invention is 80% or more of the saturated gel fraction. When the gel fraction is less than 80% of the saturated gel fraction, the reaction with the crosslinking agent is not sufficiently progressed, and thus the polarizing plate is bonded to the polarizing plate. It is impossible to stabilize the performance such as foaming and peeling due to dimensional changes under heat and wet heat conditions, color unevenness, white spots, etc.

The gel fraction referred to in the present invention is about 30 mg of pressure-sensitive adhesive collected in a sample bottle at the time of sticking, added with 50 cc of toluene and soaked at room temperature for 24 hours, and then filtered the contents of the sample bottle with a 200 mesh metal net. The residue on the metal net is dried at 100 ° C. for 2 hours, and the dry weight is measured.
Gel fraction (% by weight) = (Dry weight / Adhesive sampling weight) × 100

  The saturated gel fraction in the present invention refers to a pressure-sensitive adhesive film that is applied on a release paper so that the dry coating thickness is 25 μm and dried at 90 ° C. for 60 seconds in an atmosphere of 23 ° C. × 60% RH. The gel fraction measured after 15-day standing curing shall be said.

  The copolymer (A) constituting the acrylic pressure-sensitive adhesive layer of the laminate of the present invention is a pressure-sensitive adhesive mainly comprising a (meth) acrylic acid alkyl ester monomer and a carboxyl group and / or a hydroxyl group-containing monomer. Agent composition. Specifically, the (meth) acrylic acid alkyl ester monomer used is methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, 2- Examples include ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate, and the like. At least one selected from these groups can be used.

  The carboxyl group and / or hydroxyl group-containing monomer used in the copolymer (A) is specifically a (meth) acrylic acid, itaconic acid, maleic acid, maleic anhydride, Examples thereof include fumaric acid and fumaric anhydride, and at least one selected from these groups can be used. (Meth) acrylic acid is preferred. Specific examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, caprolactone-modified (meth) acrylate, polyethylene glycol (meta ) Acrylate, polypropylene glycol (meth) acrylate, and the like, and at least one selected from these groups can be used. The carboxyl group-containing monomer and the hydroxyl group-containing monomer can be used alone or in combination. The usage-amount of a carboxyl group and / or a hydroxyl-containing monomer is 0.01 to 10 weight% with respect to the monomer whole quantity. If the amount used is less than 0.01% by weight, the degree of cross-linking is small and deviation at normal temperature is likely to occur, and if the amount used exceeds 10% by weight, the stress due to expansion and contraction of the polarizing plate layer Concentration cannot be absorbed or relaxed sufficiently. Preferably it is 0.1-7.0 weight%. More preferably, it is 0.5 to 5% by weight.

  It is necessary that the copolymer (A) constituting the acrylic pressure-sensitive adhesive layer of the laminate of the present invention has a weight average molecular weight of 800,000 to 2,000,000. When the weight average molecular weight is less than 800,000, even if a crosslinking agent is used, the cohesive force is insufficient and foaming or peeling off from the polarizing plate is likely to occur. When the weight average molecular weight exceeds 2 million, the stress concentration resulting from the expansion and contraction of the polarizing plate layer cannot be sufficiently absorbed and relaxed, the coating viscosity becomes too high, and the workability is inferior.

  The (co) polymer (B) mainly composed of (meth) acrylic acid alkyl ester constituting the acrylic pressure-sensitive adhesive layer of the laminate of the present invention is uneven in color due to minute distortion caused by a change in the size of the polarizing plate. -It is an essential component for preventing foaming or peeling due to dimensional changes under high temperature and humidity conditions without exacerbating the white spot phenomenon. The effect of the (co) polymer (B) has a role of plasticizing the copolymer (A) by entering between the copolymers (A) forming the network structure by the crosslinking agent because the average molecular weight is small. It is thought to have the effect of improving the durability, elasticity and flexibility, and preventing uneven color and white spots.

  The (meth) acrylic acid alkyl ester monomer used in the (co) polymer (B) constituting the acrylic pressure-sensitive adhesive layer of the laminate of the present invention is the (meth) acrylic used in the copolymer (A). Acid alkyl ester monomers can be used. Preferably, it does not have a functional group-containing monomer.

  The weight average molecular weight of the (co) polymer (B) constituting the acrylic pressure-sensitive adhesive layer of the laminate of the present invention needs to be 1000 to 300,000. When the weight average molecular weight is less than 1000, the cohesive force is reduced, which causes foaming and peeling. If it exceeds 300,000, the flexibility is lowered and it is difficult to prevent uneven color and white spots.

  The usage-amount of the (co) polymer (B) which comprises the acrylic adhesive layer of the laminated body of this invention needs 1-45 weight part with respect to 100 weight part of copolymers (A). When the amount used is less than 1 part by weight, it is difficult to sufficiently absorb and relax the stress concentration caused by the expansion and contraction of the polarizing plate layer. If the amount used exceeds 45 parts by weight, the cohesive force is reduced, causing foaming and peeling. Preferably it is 5-45 weight part.

  The weight average molecular weight is a molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC) (model: LC-10ADVP, manufactured by Shimadzu Corporation, column: KF-G, KF-806M).

  The crosslinking agent (C) added to the acrylic pressure-sensitive adhesive of the laminate of the present invention can use a compound that reacts with a carboxyl group and / or a hydroxyl group, and is necessary for increasing the cohesive strength of the pressure-sensitive adhesive. As a crosslinking agent that can be used, a glycidyl compound having at least two glycidyl groups in one molecule, an isocyanate compound having two or more isocyanate groups in one molecule, and an aziridine compound having at least two aziridinyl groups in one molecule An oxazoline compound having an oxazoline group in one molecule, a metal chelate compound, a butylated melamine compound, or the like can be used. Preferred are glycidyl compounds, isocyanate compounds and aziridine compounds.

  The amount of use must be blended so that the number of theoretical crosslinking points per molecular chain of the copolymer (A) is 2 to 10. When the number of theoretical crosslinking points is less than 2, the cohesive force of the pressure-sensitive adhesive is low, which causes foaming or peeling. When the number of theoretical crosslinking points exceeds 10, it is difficult to sufficiently absorb and relax the stress concentration caused by the expansion and contraction of the polarizing plate layer.

In addition, the calculation method of the number of theoretical bridge | crosslinking points can be calculated | required from the following formula.
Number of moles of polymer of copolymer (A) = weight of copolymer (A) / number of moles of reactive group in weight average molecular weight crosslinking agent of copolymer (A) = weight of blended crosslinking agent × unit weight The number of reactive groups of the crosslinking agent per theoretical number of crosslinking points = number of moles of reactive groups of the crosslinking agent / number of moles of polymer

  The glycidyl compound that can be used as the crosslinking agent used in the acrylic pressure-sensitive adhesive of the laminate of the present invention is a glycidyl compound having at least two glycidyl groups in one molecule. Specifically, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether , Tetraglycidylxylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, etc. A glycidyl compound is mentioned, At least 1 sort (s) chosen from these groups can be used.

  The isocyanate compound that can be used as the crosslinking agent used in the acrylic pressure-sensitive adhesive of the laminate of the present invention is an isocyanate compound having at least two isocyanate groups in one molecule. Specific examples include tolylene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and prepolymers modified from these, and at least one selected from these groups can be used. A non-yellowing type of hexamethylene diisocyanate or isophorone diisocyanate is preferable.

  The aziridine compound that can be used as the crosslinking agent used in the acrylic pressure-sensitive adhesive of the laminate of the present invention is an aziridine compound having at least two aziridinyl groups in one molecule. Specifically, 1,1 ′-(methylene-di-p-phenylene) bis-3,3-aziridylurea, 1,1 ′-(hexamethylene) bis-3,3-aziridylurea, ethylenebis (2-aziridinyl) Lupropionate), tris (1-aziridinyl) phosphine oxide, 2,4,6-triaziridinyl-1,3,5-triazine, trimethylolpropanthris (2-aziridinylpropionate), etc. Is mentioned. At least one selected from these groups can be used.

  For the acrylic pressure-sensitive adhesive of the laminate of the present invention, a silane compound containing a mercaptoalkyl group and an alkoxy group simultaneously in the molecule can be used. By using a silane compound containing a mercaptoalkyl group and an alkoxy group in the molecule at the same time, the adhesion to the glass substrate surface as the adherend can be further improved. Specific examples of the silane compound containing a mercaptoalkyl group and an alkoxy group in the molecule used in the present invention include γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, mercaptobutyltrimethoxysilane, γ -Mercaptopropylmethyldimethoxysilane, mercapto group-containing alkoxysilane oligomer and the like. At least one selected from these groups can be used.

  The amount of the silane compound containing a mercaptoalkyl group and an alkoxy group at the same time in the molecule used in the acrylic pressure-sensitive adhesive of the laminate of the present invention is 0.01-2 with respect to 100 parts by weight of the copolymer (A). Parts by weight. When the amount used is less than 0.01 parts by weight, the effect of enhancing the adhesion to the glass substrate surface, which is the adherend, is small, and when it exceeds 2 parts by weight, the pressure-sensitive adhesive layer is peeled off.

  The copolymer (A) constituting the acrylic pressure-sensitive adhesive layer of the laminate of the present invention can be usually produced by bulk polymerization or solution polymerization. Solution polymerization is preferred. Examples of the solvent used include organic solvents such as ethyl acetate, toluene, n-hexane, acetone, and methyl ethyl ketone, which are usually used for solution polymerization reactions. The polymerization initiator used in the polymerization may be a polymer azo polymerization initiator alone or the polymerization initiator and other azobisisobutyronitrile, azobisvaleronitrile, etc. for the polymerization reaction of the copolymer (A). An azobis compound can be used in combination.

  The (co) polymer (B) constituting the acrylic pressure-sensitive adhesive layer of the laminate of the present invention can be produced by the same method, bulk polymerization, solution polymerization, living polymerization and the like as the copolymer (A). . For example, in radical polymerization in a solvent, the amount of polymerization initiator used is about 5 to 30 times the amount used when polymerizing a normal pressure-sensitive adhesive. Further, mercaptans such as lauryl mercaptan, α-methylstyrene dimer Etc. are used. Further, the target (co) polymer (B) can be obtained by fractional precipitation using a solvent such as heptane in order to narrow the molecular weight dispersion. A low molecular weight polymer can also be obtained by a living polymerization method. Furthermore, a known low molecular weight type solventless acrylic polymer obtained by a bulk polymerization method can also be used.

  You may mix | blend various things as needed for the purpose of adjusting the adhesiveness of the copolymer (A) which comprises the acrylic adhesive layer of the laminated body of this invention. Specific examples used for blending include terpene, terpene-phenol, coumarone indene, styrene, rosin, xylene, phenol, petroleum and other tackifying resins, antioxidants, UV absorbers , Fillers, pigments and the like.

  The laminate of the present invention can be produced by the following production method. The acrylic adhesive of the present invention is applied to a polyester release film of 20 to 50 μm with a commonly used coating apparatus such as a roll coating apparatus so that the dry coating thickness is 10 to 50 μm, preferably 15 to 40 μm. And dried at 80 to 120 ° C. for 30 to 120 seconds to produce an adhesive sheet. The surface of the pressure-sensitive adhesive is protected with the above-mentioned polyester release film, and the gel fraction relative to the saturated gel fraction immediately after normal drying is 10-60%. It is preferable to cure for 3 to 7 days or more in an atmosphere of ° C. The laminate of the present invention can be obtained by removing the release film on one side of the pressure-sensitive adhesive sheet after curing and transferring it to a polarizing plate.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not restrict | limited by this. In the examples and comparative examples, “part” or “%” means “part by weight” or “% by weight” unless otherwise specified.

Production Example 1 (Copolymer A-1)
After nitrogen gas is sealed in a reactor equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen introduction tube, 70 parts of ethyl acetate, 15 parts of acetone, 99 parts of butyl acrylate, 1 part of acrylic acid, azo polymerization 0.1 part of initiator 2,2′-azobisisobutyronitrile (trade name V-60, Wako Pure Chemical Industries, Ltd.) is charged. The reaction is carried out for 8 hours at the reflux temperature of the solvent in a nitrogen gas stream with stirring. After completion of the reaction, 315 parts of toluene is added and cooled to room temperature. A copolymer A-1 having a viscosity of 7,000 mPa · s, a solid content of 20.0%, and a weight average molecular weight of 1.35 million was obtained.

Production Example 2 (Copolymer A-2)
Manufacture example 2 obtained copolymer A-2 like manufacture example 1 except changing the kind and quantity of a monomer as shown in Table 1. The analytical values are shown in Table 1.

Production Example 3 (Copolymer B-1)
After nitrogen gas was sealed in the same reactor as in Production Example 1, 60 parts of ethyl acetate, 10 parts of acetone, 100 parts of butyl acrylate, 0.2 part of lauryl mercaptan, azo-based polymerization initiator 2,2′-azobisiso 0.1 part of butyronitrile (trade name V-60, Wako Pure Chemical Industries, Ltd.) is charged. The reaction was carried out for 4.5 hours at the reflux temperature of the solvent in a nitrogen gas stream while stirring. After completion of the reaction, 80 parts of toluene is added and cooled to room temperature. A copolymer B-1 having a viscosity of 300 mPa · s, a solid content of 40.0%, and a weight average molecular weight of 200,000 was obtained.

In Table 1, the types of monomers are indicated by the following abbreviations.
Monomer BA: Butyl acrylate MA: Methyl acrylate MMA: Methyl methacrylate AAc: Acrylic acid 2HEMA: 2 Hydroxyethyl methacrylate

  The weight average molecular weight in Table 1 is a molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC) (model: LC-10ADVP, manufactured by Shimadzu Corporation, column: KF-G, KF-806M).

  The (co) polymer (B) used in the acrylic pressure-sensitive adhesive layer of the laminate of the present invention is a low molecular weight type of a commercially available product (trade name Alfon, manufactured by Toagosei Co., Ltd.) as shown in Table 2 below. Solvent acrylic polymers can also be used.

The solid content of 100 parts by weight of the copolymer A-1 solution obtained in Production Example 1 was mixed with the solid content of 40 parts by weight of the polymer B-1 solution obtained in Production Example 5, Furthermore, 0.08 parts by weight of a solid content of biuret type of hexamethylene diisocyanate (trade name Duranate 24A-100, manufactured by Asahi Kasei Kogyo Co., Ltd.) is added as a crosslinking agent and stirred well. The prepared pressure-sensitive adhesive solution was applied to a polyester release film (38 μm) so that the dry coating thickness was 25 μm, and dried at 90 ° C. for 60 seconds to obtain a pressure-sensitive adhesive sheet. The adhesive was protected with a polyester release film (38 μm) and aged in an atmosphere of 23 ° C. and 65% RH for 7 days. The release film on one side was peeled off and transferred to a polarizing plate to obtain a polarizing plate sample. The obtained polarizing plate sample was cut into 80 mm × 150 mm so that the absorption axis was 45 ° with respect to the long side of the polarizing plate, and a pressure of 5 kg / cm ² was applied to one side of the glass plate at 50 ° C. As a result of leaving the test sample that was held for a minute to be bonded in an atmosphere of 90 ° C., 60 ° C., and 90% RH for 500 hours and examining the occurrence of foaming and peeling, both were good. The obtained polarizing plate sample was placed on both surfaces of the glass plate so that the absorption axis was orthogonal, a pressure of 5 kg / cm ² was applied at 50 ° C., and the test sample was held for 18 minutes and bonded to 90 ° C. As a result of examining the state of occurrence of uneven color and white spots, it was good. Moreover, the gel fraction at the time of bonding was 30%, the saturated gel fraction was 35%, and the gel fraction at the time of bonding was 86% of the saturated gel fraction. The number of theoretical crosslinking points was 6 / one polymer. The heat resistance, heat-and-moisture resistance, color unevenness and white spot test were all good. The results are shown in Table 3.

  In Example 2, the amounts of copolymer A-1, polymer B-1 and crosslinking agent were blended as shown in Table 3, and γ-mercaptopropyltrimethoxysilane (Nihon Unicar Co., Ltd.), which is a silane compound, was added. Manufactured, trade name: AZ-6129) Except for adding 0.3 parts by weight, it was adjusted and tested in the same manner as in Example 1. All the results were good. The results are shown in Table 3.

  Example 3 was prepared and tested in exactly the same manner as Example 1, except that Alfon UP-1000 was blended as shown in Table 3 instead of the polymer B-1 of Example 2. All the results were good. The results are shown in Table 3.

  In Example 4, as shown in Table 3, the copolymer (A) is A-2, the (co) polymer (B) is Alfone UP-1000, and the crosslinking agent (C) is N, N, N ′, N The test was carried out in the same manner as in Example 1, except that '-tetraglycidyl m-xylenediamine (trade name Tetrad X, manufactured by Mitsubishi Gas Chemical Co., Ltd.) was used. All the results were good. The results are shown in Table 3.

Comparative Example 1
In Comparative Example 1, the prepared pressure-sensitive adhesive solution was applied to a polyester release film (38 μm) so that the thickness of the dried coating film was 25 μm, and dried at 90 ° C. for 60 seconds, just like Example 1. A sheet was obtained. The sample was immediately transferred to a polarizing plate and aged for 7 days in an atmosphere of 23 ° C. and 65% RH to obtain a polarizing plate sample. As a result of the test, the balance of cohesive force was not sufficient, and heat-resistant and heat-and-moisture-resistant foaming, uneven color, and white spots were observed. Moreover, the gel fraction at the time of bonding was 10%, the saturated gel fraction was 35%, and the gel fraction at the time of bonding was 29% of the saturated gel fraction. The number of theoretical crosslinking points was 6 / one polymer. The results are shown in Table 4.

Comparative Example 2
Comparative Example 2 was prepared in exactly the same manner as in Example 2 to prepare a test sample, which was immediately transferred to a polarizing plate and tested in the same manner as Comparative Example 1. As a result, heat-resistant firing was observed, and uneven color and white spots were bad. The gel fraction at the time of pasting was 53% of the saturated gel fraction, and the number of theoretical crosslinking points was 2.3 / one polymer molecule. The results are shown in Table 4.

In Tables 3 and 4, the crosslinking agent and the silane compound are indicated by the following abbreviations.
Crosslinking agent C-1: Asahi Kasei Co., Ltd. product name Duranate 24A-100
Number of functional groups: 3
NCO content (wt%): 23.5
NCO content (g / g): 0.235
NCO content (eq / g): 0.0056 (the number of reactive groups of the crosslinking agent per unit weight)
C-2: Mitsubishi Gas Chemical Co., Ltd. trade name Tetrad X
Number of functional groups: 4
Epoxy equivalent: 90
Epoxy content (wt%): 47.8
Epoxy content (g / g): 0.478
Epoxy content (eq / g): 0.0111 (crosslinker reactive group per unit weight)
number)
Silane compound: Nippon Unicar Co., Ltd. product name AZ-6129

Test method Heat resistance and moist heat resistance The heat resistance of the pressure-sensitive adhesive sheet was obtained by applying the pressure-sensitive adhesive solution of the present invention to a polyester release film (38 μm) so that the dry coating thickness was 25 μm and drying at 90 ° C. for 60 seconds. Got. The pressure-sensitive adhesive was aged in an atmosphere of 23 ° C. and 65% RH for 7 days, and then transferred onto a 190 μm polarizing film to obtain a polarizing plate sample. The obtained polarizing plate sample was cut into 80 mm × 150 mm so that the absorption axis was 45 ° with respect to the long side of the polarizing plate, and a pressure of 5 kg / cm ² was applied to one side of the glass plate at 50 ° C. It was set as the test sample which was hold | maintained and stuck together. The test sample is left in a thermostat at 90 ° C. for 500 hours, returned to room temperature, and observed for foaming and peeling. For heat and moisture resistance, the test sample obtained as described above is left in a constant temperature and humidity chamber at 60 ° C. and 95% RH for 500 hours, returned to room temperature, and observed for the occurrence of foaming and peeling.
○: No change in appearance such as foaming or peeling.
Δ: Little change in appearance such as foaming and peeling.
X: Appearance changes such as foaming and peeling are considerable.

Color unevenness / white spot test A polarizing plate sample obtained in the same manner as heat resistance was placed on both sides of a glass plate so that the absorption axis was perpendicular, and a pressure of 5 kg / cm ² was applied at 50 ° C., The test sample held for 18 minutes and bonded together is observed for uneven color and white spots after being left in an atmosphere of 90 ° C. for 500 hours.
○: Uneven color and white spots are not recognized at all.
Δ: Color unevenness and white spots are slightly noticeable.
X: Color unevenness and white spots are large.

  It can be used for the production of polarizing plates and retardation plates that are free from foaming and peeling, uneven color and white spots caused by strain due to crosslinking or residual stress of the polarizing plates and retardation plates.

Claims (2)

  A laminate in which an acrylic adhesive is applied to a release film and dried to form an adhesive layer, and the adhesive layer has a gel fraction of 80% or more of the saturated gel fraction and is bonded to a polarizing plate or a retardation plate. body.   (A) (meth) acrylic acid alkyl ester monomer, and 100 parts by weight of a copolymer having a weight average molecular weight of 800,000 to 2,000,000 having a carboxyl group and / or a hydroxyl group-containing unsaturated monomer as main components (B) a (co) polymer composition comprising 1 to 45 parts by weight of a (co) polymer having a weight average molecular weight of 1000 to 300,000 having a (meth) acrylic acid alkyl ester monomer as a main component, The acrylic pressure-sensitive adhesive obtained by blending the crosslinking agent (C) so that the number of theoretical crosslinking points per molecular chain of the copolymer (A) is 2 to 10 is used. The laminated body as described in.