JP2011105793A - Pressure-sensitive adhesive, pressure-sensitive adhesive for optical member, optical member with pressure-sensitive adhesive layer, and image display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive, excellent in adhesiveness with optical laminates, especially between polarizing plates and glass substrates, even under the conditions of high temperature and high humidity or repeated environmental changes between a low temperature and a high temperature, so as not to cause foaming and peeling between pressure-sensitive adhesive layers and glass substrates, and excellent in durability to prevent a light-leaking phenomenon caused by contraction of a polarizing film, and the like. <P>SOLUTION: A pressure-sensitive adhesive composition [I], including an acrylic resin (A1) having a hydroxy group in its side chain, an acrylic resin (A2) having a carboxy group in its side chain, and an aromatic polyvalent isocyanate-based crosslinker (B), is crosslinked by means of the crosslinker (B) to obtain a pressure-sensitive adhesive, wherein the amount of the crosslinker (B) to be compounded is 0.3-5 pts.wt. based on 100 pts.wt. of the total amount of (A1) and (A2), and the gel fraction is 40-90%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pressure-sensitive adhesive, a pressure-sensitive adhesive for optical members, and an optical member with a pressure-sensitive adhesive layer obtained using the pressure-sensitive adhesive. Specifically, an optical film (polarizing film, retardation film, optical compensation film, brightness enhancement film, etc.) suitably used for liquid crystal display devices, organic EL display devices, image display devices such as PDP, etc. A pressure-sensitive adhesive for an optical member used for bonding an optical laminate in which a polarizing film is coated with a protective film such as a cellulose triacetate film and a glass substrate of a liquid crystal cell, and a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive for the optical member The present invention relates to an optical member with a pressure-sensitive adhesive layer, particularly a polarizing plate with a pressure-sensitive adhesive layer, and an image display device using the same.

  Conventionally, a polarizing film, for example, a polarizing plate coated with a cellulose film, for example, a cellulose triacetate film, on both sides of a polarizing film, for example, a polyvinyl alcohol film having a polarizing property, is a liquid crystal component that is aligned between two glass plates. Lamination is carried out on the surface of the sandwiched liquid crystal cell to form a liquid crystal display panel. This lamination to the liquid crystal cell surface is performed by bringing the pressure-sensitive adhesive layer provided on the polarizing plate surface into contact with the liquid crystal cell surface. This is usually done by pressing.

With regard to the pressure-sensitive adhesive used for optical members such as polarizing plates and retardation plates, durability is improved, that is, even when used under high temperature and high humidity, peeling between the optical member and the glass substrate may occur. It is required that foaming does not occur and light leakage (so-called “white spots”) due to dimensional changes of the substrate does not occur.
In order to solve such a problem, for example, in Patent Document 1, in the pressure-sensitive adhesive obtained by crosslinking reaction of an acrylic polymer containing a hydroxyl group and a carboxyl group with a crosslinking agent, the amount of the crosslinking agent used is less than usual. However, by suppressing the increase in the gel fraction, there has been proposed an adhesive that does not reduce the stress relaxation property of the adhesive layer and hardly causes light leakage.

JP 2004-91500 A

  However, the disclosed technique of Patent Document 1 has excellent adhesion between the optical laminate and the glass substrate under high temperature and high humidity conditions, and no foaming or peeling occurs between the adhesive and the glass substrate. Although a certain effect on durability that leaks are less likely to occur is observed, in recent years, liquid crystal display panels using optical members such as polarizing plates have been widely used as display devices for personal computers, liquid crystal televisions, car navigation systems, etc. Accordingly, in view of the situation in which the use in harsh environments is increasing, the performance in use under such an environment is not sufficient, and further improvement in durability has been demanded.

  In order to improve the durability, a method of increasing the molecular weight of the base polymer constituting the pressure-sensitive adhesive and a method of increasing the amount of the crosslinking agent used can be considered, but the former has a limitation of physically increasing the molecular weight. In the latter case, there is a problem that when the amount of the crosslinking agent used is increased, the gel fraction is increased and peeling or light leakage is likely to occur.

  Therefore, in the present invention, in such a background, even in a high temperature, high humidity environment, and repeated low temperature to high temperature environmental changes, the optical laminate, particularly the adhesive property between the polarizing plate and the glass substrate is excellent, A pressure-sensitive adhesive having excellent durability, such as prevention of light leakage caused by shrinkage of the polarizing film, in addition to no foaming or peeling between the agent layer and the glass substrate, An object is to provide an optical member with an adhesive layer and an image display device using the same.

  However, as a result of intensive research in view of such circumstances, the present inventors have made an acrylic resin containing a hydroxyl group in the side chain and a carboxyl group in the side chain as an acrylic resin in an adhesive composed of an acrylic resin and a crosslinking agent. When two types of acrylic resin containing a group are used in combination and a specific amount of a specific cross-linking agent is blended, the cross-linking agent is compared with a case where an acrylic resin having both a hydroxyl group and a carboxyl group is used alone. Since the gel fraction is less likely to increase with respect to the use ratio, it is possible to use a large amount of a crosslinking agent, and as a result, it is found that an optical member with an adhesive layer having excellent durability can be obtained. It came to complete.

That is, the gist of the present invention includes an acrylic resin (A1) containing a hydroxyl group in the side chain, an acrylic resin (A2) containing a carboxyl group in the side chain, and an aromatic polyvalent isocyanate crosslinking agent (B). The pressure-sensitive adhesive composition [I] is a pressure-sensitive adhesive formed by crosslinking with the crosslinking agent (B), and the amount of the crosslinking agent (B) is 0 with respect to 100 parts by weight of the total of (A1) and (A2) .3-5 parts by weight and a gel fraction of 40-90%.
Furthermore, it is related with the optical member with an adhesive layer containing the adhesive structure for optical members which uses the said adhesive, the adhesive layer containing this adhesive for optical members, and the laminated structure of an optical member.

  The pressure-sensitive adhesive of the present invention is excellent in various pressure-sensitive adhesive properties, and can be suitably used particularly as an optical member. It is a harsh environment of high temperature, high humidity, and repeated low-temperature to high-temperature environmental changes. Even under the optical laminate, especially excellent adhesion between the polarizing plate and the glass substrate, no foaming or peeling between the pressure-sensitive adhesive layer and the glass substrate, and further light leakage caused by contraction of the polarizing film An image display device such as a liquid crystal display panel that can prevent the phenomenon can be obtained.

The present invention will be described in detail below, but these show examples of desirable embodiments.
In the present invention, (meth) acryl means acryl or methacryl, (meth) acryloyl means acryloyl or methacryloyl, and (meth) acrylate means acrylate or methacrylate.

First, the pressure-sensitive adhesive composition of the present invention will be described.
The pressure-sensitive adhesive composition [I] of the present invention contains two types of acrylic resin (A1) containing a hydroxyl group in the side chain and acrylic resin (A2) containing a carboxyl group in the side chain as an acrylic resin. And an aromatic polyvalent isocyanate-based crosslinking agent (B) as a crosslinking agent.

  The acrylic resin (A1) containing a hydroxyl group in the side chain in the present invention (hereinafter sometimes abbreviated as “acrylic resin (A1)”) may be any acrylic resin containing a hydroxyl group in the side chain. For example, a method in which a hydroxyl group-containing monomer is copolymerized or homopolymerized, a functional group of an acrylic resin containing a functional group is reacted with a compound having both a functional group capable of reacting with the functional group and a hydroxyl group (post-modified) ) Produced by a method or the like.

Especially, as said acrylic resin (A1), the copolymerization component containing a hydroxyl-containing monomer (a1) is copolymerized with another copolymerization component, or a hydroxyl-containing monomer (a1) is homopolymerized. It is preferable to use the product obtained from the viewpoint of easily obtaining an acrylic resin (A1) containing a hydroxyl group in the side chain when industrially produced.
Hereinafter, a case where the acrylic resin (A1) is produced by a method of copolymerizing the hydroxyl group-containing monomer (a1) will be described.

  Examples of the hydroxyl group-containing monomer (a1) include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8- Hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl acrylate and other (meth) acrylic acid hydroxyalkyl esters, diethylene glycol (meth) acrylate, polyethylene glycol mono (meth) Polyethylene glycol derivatives such as acrylate, polypropylene glycol derivatives such as polypropylene glycol mono (meth) acrylate, polyethylene glycol-polypropylene glycol -Oxyalkylene-modified monomers such as mono (meth) acrylate, poly (ethylene glycol-tetramethylene glycol) mono (meth) acrylate, poly (propylene glycol-tetramethylene glycol) mono (meth) acrylate, N-hydroxyethyl (meth) Primary hydroxyl group-containing monomers such as acrylamide; Secondary hydroxyl group-containing monomers such as 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate; 2,2 -Tertiary hydroxyl group-containing monomers such as dimethyl-2-hydroxyethyl (meth) acrylate.

  Among the hydroxyl group-containing monomers (a1), a primary hydroxyl group-containing monomer is preferable in terms of excellent reactivity with a crosslinking agent, and it is more preferable to use 2-hydroxyethyl (meth) acrylate. It is particularly preferable in that it is easy to produce with few impurities such as.

  As the hydroxyl group-containing monomer (a1) used in the present invention, it is also preferable to use a monomer having a content of di (meth) acrylate as an impurity of 0.5% or less, more preferably 0.2% or less. It is preferable to use less than 0.1%, specifically 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate.

  In the acrylic resin (A1) used in the present invention, the content of the hydroxyl group-containing monomer (a1) in the case of copolymerizing the hydroxyl group-containing monomer (a1) is 0.1 to 20% by weight based on the entire copolymerization component. The content is preferably 0.2 to 10% by weight, more preferably 0.5 to 3% by weight. If the content of the hydroxyl group-containing monomer (a1) is too large, the heat-and-moisture resistance tends to be inferior. If the content is too small, the crosslinking reaction cannot be efficiently performed, and foaming or the like tends to occur due to durability.

  As other copolymerization components other than the hydroxyl group-containing monomer (a1), a (meth) acrylic acid ester monomer (a2), if necessary, a functional group-containing monomer (a3) other than the hydroxyl group-containing monomer (a1) and other And a copolymerizable monomer (a4).

  Examples of the (meth) acrylic acid ester monomer (a2) include (meth) acrylic acid alkyl esters. For such (meth) acrylic acid alkyl ester, the alkyl group usually has 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, and particularly preferably 4 to 8 carbon atoms. Are methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-propyl (meth) acrylate, n-hexyl ( (Meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, Examples include isobornyl (meth) acrylate It is. Other (meth) acrylic acid ester monomers include aromatic (meth) acrylates such as phenyl (meth) acrylate, benzyl (meth) acrylate, and phenoxyethyl (meth) acrylate, and tetrahydrofurryl (meth) acrylate. It is done. These can be used alone or in combination of two or more.

  Among such (meth) acrylic acid alkyl esters (a2), n-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate are preferable in terms of copolymerizability, adhesive properties, ease of handling, and availability of raw materials. N-Butyl (meth) acrylate is preferably used because it is preferably used and more preferably has excellent durability.

  Examples of the functional group-containing monomer (a3) include acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, fumaric acid, acrylamide N-glycolic acid, cinnamic acid, and (meth) acrylic acid. Michael adducts (for example, acrylic acid dimer, methacrylic acid dimer, acrylic acid trimer, methacrylic acid trimer, acrylic acid tetramer, methacrylic acid tetramer, etc.), 2- (meth) acryloyloxyethyldicarboxylic acid monoester (for example, 2- Acryloyloxyethyl succinic acid monoester, 2-methacryloyloxyethyl succinic acid monoester, 2-acryloyloxyethyl phthalic acid monoester, 2-methacryloyloxyethyl phthalic acid monoester, 2-acryloyloxyethyl hexa Carboxyl group-containing monomers such as drophthalic acid monoester and 2-methacryloyloxyethyl hexahydrophthalic acid monoester); glycidyl group-containing monomers such as glycidyl (meth) acrylate and allyl glycidyl ether; acrylamide, methacrylamide, N- (n -Butoxyalkyl) acrylamide, N- (n-butoxyalkyl) methacrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, acrylamide Amide group-containing monomers such as -3-methylbutylmethylamine, dimethylaminoalkylacrylamide, dimethylaminoalkylmethacrylamide; dimethylaminoethyl (meth) acrylate, diethyl Amino group-containing monomers such as aminoethyl (meth) acrylate; nitrogen-containing monomers such as acryloylmorpholine; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid , Sulfonic acid group-containing monomers such as styrene sulfonic acid or salts thereof, and the like. These may be used alone or in combination of two or more.

  Examples of other copolymerizable monomers (a4) include acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene, Examples include vinyl pyridine, vinyl pyrrolidone, itaconic acid dialkyl ester, fumaric acid dialkyl ester, allyl alcohol, acrylic chloride, methyl vinyl ketone, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, and dimethylallyl vinylketone.

  As the content ratio of the copolymer component other than the hydroxyl group-containing monomer (a1), the (meth) acrylic acid ester monomer (a2) is preferably 50 to 99.9% by weight, particularly preferably 90 to 99.8% by weight. More preferably, it is 97 to 99.5% by weight, and the functional group-containing monomer (a3) other than the hydroxyl group-containing monomer (a1) is preferably 0 to 30% by weight, particularly preferably 0 to 5% by weight, and still more preferably. Is 0 to 1% by weight, and the other copolymerizable monomer (a4) is preferably 0 to 30% by weight, particularly preferably 0 to 15% by weight, and further preferably 0 to 10% by weight.

  The acrylic resin (A1) preferably contains substantially no carboxyl group-containing monomer as a copolymerization component other than the hydroxyl group-containing monomer (a1). It indicates that the content ratio of is 1% by weight or less, preferably not contained.

  For the purpose of increasing the molecular weight, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate A compound having two or more ethylenically unsaturated groups such as divinylbenzene can also be used in combination.

  In the present invention, the acrylic resin (A1) is produced by polymerizing the monomer components (a1) to (a4). In the polymerization, solution radical polymerization, suspension polymerization, bulk polymerization, It can be performed by a conventionally known method such as emulsion polymerization. For example, polymerization monomers such as the above hydroxyl group-containing monomer (a1), (meth) acrylic acid ester monomer (a2), other functional group-containing monomer (a3), and other copolymerizable monomer (a4) in an organic solvent Then, a polymerization initiator (azobisisobutyronitrile, azobisisovaleronitrile, benzoyl peroxide, etc.) is mixed or dropped and polymerized at reflux or at 50 to 90 ° C. for 2 to 20 hours.

  About the weight average molecular weight of acrylic resin (A1), it is 100,000-3 million normally, Preferably it is 300,000-2 million, Most preferably, it is 600,000-2 million. If the weight average molecular weight is too small, the durability tends to deteriorate. If the weight average molecular weight is too large, a large amount of diluent solvent is required, which tends to be undesirable in terms of coating properties and cost.

  The degree of dispersion (weight average molecular weight / number average molecular weight) of the acrylic resin (A1) is preferably 20 or less, particularly preferably 15 or less, more preferably 10 or less, and particularly preferably 7 or less. preferable. When the degree of dispersion is too high, the durability of the pressure-sensitive adhesive layer tends to be inferior, and foaming or the like tends to occur. The lower limit of the degree of dispersion is usually 2 from the viewpoint of production limit.

  Furthermore, the glass transition temperature of the acrylic resin (A1) is preferably −80 to −20 ° C., particularly preferably −75 to −25 ° C., more preferably −60 to −30 ° C. If the glass transition temperature is too high, tackiness may occur. When it is too low, it tends to be inferior in heat resistance.

In addition, said weight average molecular weight is a weight average molecular weight by standard polystyrene molecular weight conversion, and it is a column in high performance liquid chromatography (The Japan Waters company "Waters 2695 (main body)" and "Waters 2414 (detector)"). : Shodex GPC KF-806L (exclusion limit molecular weight: 2 × 10 ⁷ , separation range: 100 to 2 × 10 ⁷ , theoretical plate number: 10,000 plates / piece, filler material: styrene-divinylbenzene copolymer, filler The particle size is 10 μm), and the degree of dispersion is determined from the weight average molecular weight and the number average molecular weight. The glass transition temperature is calculated from the Fox equation.

  The acrylic resin (A2) containing a carboxyl group in the side chain in the present invention (hereinafter sometimes abbreviated as “acrylic resin (A2)”) may be an acrylic resin containing a carboxyl group in the side chain. For example, a method in which a carboxyl group-containing monomer is copolymerized or homopolymerized, a compound having both a functional group capable of reacting with the functional group and a carboxyl group is reacted with a functional group of an acrylic resin containing a functional group ( Examples thereof include those produced by a post-modification method.

As the acrylic resin (A2), a copolymer component containing the carboxyl group-containing monomer (a′1) is copolymerized with other copolymer components, or the carboxyl group-containing monomer (a′1) is used alone. It is preferable to use a polymerized product because an acrylic resin (A2) containing a carboxyl group in the side chain can be easily obtained for industrial production.
Hereinafter, the case where the acrylic resin (A2) is produced by a method of copolymerizing the carboxyl group-containing monomer (a′1) will be described.

  Examples of the carboxyl group-containing monomer (a′1) include acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, fumaric acid, acrylamide N-glycolic acid, cinnamic acid, and (meth) acrylic acid. Michael adduct (eg, acrylic acid dimer, methacrylic acid dimer, acrylic acid trimer, methacrylic acid trimer, acrylic acid tetramer, methacrylic acid tetramer, etc.), 2- (meth) acryloyloxyethyl dicarboxylic acid monoester (eg, 2-acryloyl) Oxyethyl succinic acid monoester, 2-methacryloyloxyethyl succinic acid monoester, 2-acryloyloxyethyl phthalic acid monoester, 2-methacryloyloxyethyl phthalic acid monoester, 2-acryloyloxyethyl hexahydro Phthalic acid monoester, 2-methacryloyloxyethyl hexahydrophthalic acid monoester, etc.) and 2-carboxyethyl acrylate.

  Among the carboxyl group-containing monomers (a′1), (meth) acrylic acid and its Michael adduct are preferable, and acrylic acid is particularly preferable in terms of availability and stable production.

  In the acrylic resin (A2) used in the present invention, the content in the case of copolymerizing the carboxyl group-containing monomer (a′1) may be 0.5 to 30% by weight based on the entire copolymerization component. It is preferably 1 to 2012% by weight, more preferably 2 to 10% by weight. If the content of the carboxyl group-containing monomer (a′1) is too high, the adhesive strength tends to increase too much, or the cohesive strength tends to be insufficient and the durability tends to deteriorate. The rate tends to increase too much, and the durability and light leakage tend to deteriorate.

  As other copolymerization components other than the carboxyl group-containing monomer (a′1), a (meth) acrylic acid ester monomer (a′2), if necessary, a functional group other than the carboxyl group-containing monomer (a′1) And a monomer (a'3) and other copolymerizable monomers (a'4).

  As the (meth) acrylic acid ester monomer (a′2), the same ones as the above (meth) acrylic acid ester monomer (a2) can be used.

  Examples of the functional group-containing monomer (a′3) include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate. , 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, hydroxyalkyl esters of acrylic acid such as (4-hydroxymethylcyclohexyl) methyl acrylate, diethylene glycol (meth) acrylate, polyethylene glycol mono (meth) Polyethylene glycol derivatives such as acrylate, polypropylene glycol derivatives such as polypropylene glycol mono (meth) acrylate, polyethylene glycol-polypropylene glycol- Oxyalkylene-modified monomers such as poly (meth) acrylate, poly (ethylene glycol-tetramethylene glycol) mono (meth) acrylate, poly (propylene glycol-tetramethylene glycol) mono (meth) acrylate, N-hydroxyethyl (meth) acrylamide Primary hydroxyl group-containing monomers such as 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, secondary hydroxyl group-containing monomers such as 2-hydroxy-3-phenoxypropyl (meth) acrylate; Hydroxyl group-containing monomers such as tertiary hydroxyl group-containing monomers such as dimethyl-2-hydroxyethyl (meth) acrylate; glycidyl group-containing monomers such as glycidyl (meth) acrylate and allyl glycidyl ether; acrylamide, Tacrylamide, N- (n-butoxyalkyl) acrylamide, N- (n-butoxyalkyl) methacrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dimethylaminopropyl Amide group-containing monomers such as (meth) acrylamide, acrylamide-3-methylbutylmethylamine, dimethylaminoalkylacrylamide, dimethylaminoalkylmethacrylamide; amino groups such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate Monomer; Nitrogen-containing monomer such as acryloylmorpholine; Olefin sulfonic acid such as ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, 2-acrylamido-2-methylpropane Sulfonic acids, sulfonic acid group-containing monomers such as styrenesulfonic acid or salts thereof; and the like, used singly or in combination.

  As the other copolymerizable monomer (a′4), the same copolymerizable monomer (a4) as described above can be used.

  As the content ratio of the polymerization component other than the carboxyl group-containing monomer (a′1), the (meth) acrylic acid ester monomer (a′2) is preferably 70 to 99.9% by weight, particularly preferably 88 to 99. 0.5 wt%, more preferably 92 to 98 wt%, and the functional group-containing monomer (a′3) other than the carboxyl group-containing monomer (a′1) is preferably 0 to 10 wt%, particularly preferably 0. -1% by weight, more preferably 0% by weight, and the other copolymerizable monomer (a'4) is preferably 0-30% by weight, particularly preferably 0-15% by weight, more preferably 0-5% by weight. It is.

  The acrylic resin (A2) preferably contains substantially no hydroxyl group-containing monomer as a copolymerization component other than the carboxyl group-containing monomer (a′1). It indicates that the monomer content is 1% by weight or less, preferably not contained.

  For the purpose of increasing the molecular weight, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate A compound having two or more ethylenically unsaturated groups such as divinylbenzene can also be used in combination.

  In the present invention, the acrylic resin (A2) is produced by polymerizing the monomer components (a′1) to (a′4), and the polymerization is performed by a conventionally known method. For example, it can be manufactured by the same method as the acrylic resin (A1) described above.

  About the weight average molecular weight of acrylic resin (A2), it is 100,000-3 million normally, Preferably it is 300,000-2 million, Most preferably, it is 600,000-2 million. If the weight average molecular weight is too small, sufficient cohesive force tends not to be obtained. If the weight average molecular weight is too large, a large amount of diluent solvent is required, which tends to be undesirable in terms of coating properties and cost.

  The degree of dispersion (weight average molecular weight / number average molecular weight) of the acrylic resin (A2) is preferably 20 or less, particularly preferably 15 or less, more preferably 10 or less, and particularly preferably 7 or less. preferable. When the degree of dispersion is too high, the pressure-sensitive adhesive layer tends to be inferior in durability performance such as heat and moisture resistance and light leakage. The lower limit of the degree of dispersion is usually 2 from the viewpoint of production limit.

  Further, the glass transition temperature of the acrylic resin (A2) is preferably −80 to −20 ° C., particularly preferably −75 to −25 ° C., more preferably −60 to −30 ° C. If the glass transition temperature is too high, tackiness may occur. When it is too low, it tends to be inferior in heat resistance.

  In addition, said weight average molecular weight and glass transition temperature can be calculated | required similarly to the above.

  In the present invention, the small difference in weight average molecular weight between the acrylic resin (A1) and the acrylic resin (A2) can increase the cohesive force of the polymer network after crosslinking and improve the durability. Therefore, specifically, the ratio ((A1) / (A2)) of the weight average molecular weight of the acrylic resin (A1) and the acrylic resin (A2) is (A1) / (A2) = 0.5 to It is preferably 1.5, more preferably (A1) / (A2) = 0.8 to 1.2, and still more preferably (A1) / (A2) = 0.9 to 1.1.

Here, the content ratio (molar ratio) between the hydroxyl group and the carboxyl group contained in the pressure-sensitive adhesive composition [I] is preferably hydroxyl group / carboxyl group = 0.15 to 20, particularly preferably hydroxyl group / carboxyl. Group = 0.5-10, more preferably hydroxyl group / carboxyl group = 1.5-2.5. If the content ratio of the hydroxyl group with respect to the carboxyl group is too large, the gel fraction greatly increases depending on the amount of the crosslinking agent added, and the durability / light leakage tends to deteriorate. There is a tendency for power to rise too much.
The hydroxyl group and carboxyl group in the pressure-sensitive adhesive composition [I] are preferably functional groups substantially derived from the acrylic resin (A1) and the acrylic resin (A2). It may contain a derived functional group.

  Examples of the aromatic polyvalent isocyanate crosslinking agent (B) in the present invention (hereinafter sometimes abbreviated as “crosslinking agent (B)”) include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, and the like. Tolylene diisocyanate crosslinking agent, 1,3-xylylene diisocyanate, diphenylmethane-4,4-diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, and polyols such as these polyisocyanate compounds and trimethylolpropane Examples include adducts with compounds, burettes and isocyanurates of these polyisocyanate compounds. Among these, tolylene diisocyanate crosslinking agents are excellent in pot life and excellent in reactivity with hydroxyl groups and carboxyl groups. Prefer Properly, even adduct of tolylene diisocyanate with trimethylol propane being particularly preferred.

  The blending amount of the crosslinking agent (B) needs to be 0.3 to 5 parts by weight, preferably 0.5 to 100 parts by weight with respect to a total of 100 parts by weight of the acrylic resins (A1) and (A2). 2.5 parts by weight, more preferably 0.7 to 1.5 parts by weight. If the blending amount of the crosslinking agent is too large, durability and light leakage resistance tend to be deteriorated due to an increase in the gel fraction, and if it is too small, deterioration in durability, particularly foaming, is caused by a decrease in the gel fraction. It tends to happen easily.

  In the present invention, the pressure-sensitive adhesive composition [I] containing the acrylic resin (A1), the acrylic resin (A2), and the crosslinking agent (B) further comprises a silane coupling agent (C), a high refractive index. It is preferable to contain the rate compound (D).

In this invention, it is preferable at the point which the adhesiveness with respect to an optical member improves by containing a silane coupling agent (C) as a structural component of adhesive composition [I].
Examples of the silane coupling agent (C) include an epoxy group-containing silane coupling agent, a (meth) acryloyl group-containing silane coupling agent, a mercapto group-containing silane coupling agent, a hydroxyl group-based silane coupling agent, and a carboxyl group. Silane coupling agents, amino group silane coupling agents, amide group silane coupling agents, isocyanate group silane coupling agents, and the like. These may be used alone or in combination of two or more. Among these, an epoxy group-containing silane coupling agent and a mercapto group-containing silane coupling agent are preferably used, and the combined use of an epoxy group-containing silane coupling agent and a mercapto group-containing silane coupling agent also improves wet heat durability. It is preferable in that the adhesive strength does not increase too much.

  Specific examples of the epoxy group-containing silane coupling agent include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and γ-glycol. Sidoxypropylmethyldimethoxysilane, methyltri (glycidyl) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and the like can be mentioned. γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane.

  Specific examples of the mercapto group-containing silane coupling agent include γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, and γ-mercaptopropyldimethoxymethylsilane.

  As content of a silane coupling agent (C), it is 0.001-10 weight part normally with respect to a total of 100 weight part of acrylic resin (A1) and acrylic resin (A2), Preferably it is 0. 0.01 to 1 part by weight, particularly preferably 0.03 to 0.8 part by weight. If the content of the silane coupling agent (C) is too small, there is a tendency that the addition effect cannot be obtained. If the content is too large, the compatibility with the acrylic resin is deteriorated and the adhesive force and the cohesive force cannot be obtained. is there.

  In the present invention, containing a high refractive index compound (D) as a constituent of the pressure-sensitive adhesive composition [I] can control the birefringence of the pressure-sensitive adhesive and improve light leakage resistance. (Refer to WO / 1996/006370).

  The high refractive index compound (D) is preferably a compound containing an aromatic ring, a sulfur atom, a bromine atom, or an alkyl chain having 4 or more carbon atoms. Compounds containing chains are preferred. Specifically, it is preferable to use a phthalic acid compound, a trimellitic acid compound, a hindered phenol compound, a benzotriazole compound, a compound containing two or more aromatic rings, and particularly with an acrylic resin. A benzotriazole-based compound is preferable in terms of compatibility and durability.

  Examples of the phthalic acid compounds include dibutyl phthalate, diisobutyl phthalate, dioctyl phthalate, dinonyl phthalate, diisononyl phthalate, and didecyl phthalate, dialkyl phthalates, butyl octyl phthalate, and di- (2-ethylhexyl). ) Phthalate, diisooctyl phthalate and the like.

  Examples of the trimellitic acid-based compound include trimellitic acid esters obtained by condensing three carboxylic acids of trimellitic acid with alcohols, specifically, trimethyl trimellitic acid, triethyl trimellitic acid, Tripropyl trimellitic acid, tributyl trimellitic acid, triamyl trimellitic acid, trihexyl trimellitic acid, triheptyl trimellitic acid, tri-n-octyl trimellitic acid, tri-2-ethylhexyl trimellitic acid, trinonyl trimellitic acid, tri Mellitic acid tris (decyl), trimellitic acid tris (dodecyl), trimellitic acid tris (tetradecyl), trimellitic acid tris (C8-C12 mixed alkyl), trimellitic acid tris (C7-C9 mixed alkyl), trimellitic acid Trila Such as Lil, and the like.

  Examples of the hindered phenol compound include triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], pentaerythritol-tetrakis [3- (3,5- Di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 1,6-hexanediol-bis [3- (3 5-di-t-butyl-4-hydroxyphenyl) propionate], ethylenebis (oxyethylene) bis [3- (5-t-butyl-4-hydroxy-m-tolyl) propionate], hexamethylene-bis [3 -(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], isooctyl-3- 3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 3,9-bis [2- {3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, N, N′-hexane-1,6-diylbis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionamide], N, N′-hexamethylenebis ( 3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine, diethyl [(3 5-bis (1,1-dimethylethyl) -4-hydroxyphenyl) methyl] phosphate, 3,5-di-tert-butyl-4-hydroxybenzyl phosphonate-diethyl ester, 3,3 ′, 3 ″ , 5,5 ′, 5 ″ -hexa-t-butyl-a, a ′, a ″-(mesitylene-2,4,6-triyl) tri-p-cresol, 1,1,3-tris ( 2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethyl) isocyanuric acid, 1,3,5- Tris (4-sec-butyl-3-hydroxy-2,6-dimethyl) isocyanuric acid, 1,3,5-tris (4-neopentyl-3-hydroxy-2,6-dimethyl) isocyanuric acid, 2,2 ′ -Methylenebis (4 -Methyl-6-t-butylphenol), 4,4'-butylidenebis (4-methyl-6-t-butylphenol), tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate, Tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate, polycondensate of p-chloromethylstyrene and p-cresol, polycondensate of p-chloromethylstyrene and divinylbenzene, p -An isobutylene reaction product of cresol and divinylbenzene polycondensate is exemplified.

  Examples of the benzotriazole-based compound include 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (3,5-di-tert-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -p-cresol, 2- (2H-benzotriazole-2- Yl) -4,6-bis (1-methyl-1-phenylethyl) phenol, 2- [5-chloro (2H) -benzotriazol-2-yl] -4-methyl-6- (tert-butyl) phenol 2- (2H-benzotriazol-2-yl) -4,6-di-tert-butylphenol, 2- (2H-benzotriazol-2-yl) -4- (1,1 3,3-tetramethylbutyl) phenol, 2- (2H-benzotriazol-2-yl) -4-methyl-6- (3,4,5,6-tetrahydrophthalimidylmethyl) phenol, methyl 3- ( 3- (2H-benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl) propionate / polyethylene glycol 300 reaction product, 2- (2H-benzotriazol-2-yl) -6- ( Linear and side chain dodecyl) -4-methylphenol, 2- (2H-benzotriazol-2-yl) -4,6-di-tert-pentylphenol, 2- (2H-benzotriazol-2-yl)- 6- (1-methyl-1-phenylethyl) -4- (1,1,3,3-tetramethylbutyl) phenol, 2- (2-hydroxy- 4-octyloxyphenyl) -2H-benzotriazole, 2- (2-hydroxy-5-tert-butylphenyl) -2H-benzotriazole, 5% 2-methoxy-1-methylethyl acetate 95% benzenepropanoic acid, 3 -(2H-benzotriazol-2-yl) -5- (1,1-1,1-dimethylethyl) -4-hydroxy, C7-9 side chain and linear alkyl ester, octyl-3- [3-tert -Butyl-4-hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5- (5-chloro -2H-benzotriazol-2-yl) phenyl] propionate. In addition to those exemplified above, Tinuvin 360, Tinuvin P, Tinuvin 234, Tinuvin 326, Tinuvin 320, Tinuvin 329, Tinuvin 213, Tinuvin 571, Tinuvin 328, Tinuvin PS, Tinuvin 99-2, Tin (Kemipro Kasei), Sumisorb 250 (manufactured by Sumitomo Chemical), SEESORB 704, SEESORB 707 (all manufactured by Cypro Chemical), CISORB 5228 (manufactured by Double Bond Chemical Co., Ltd.) and the like can be suitably used.

  Among these, octyl-3- [3-t-butyl-4-hydroxy-5- (5-chloro-2H-benzotriazole-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-t- A mixture of butyl-4-hydroxy-5- (5-chloro-2H-benzotriazole-2-yl) phenyl] propionate (“TINUVIN109” manufactured by Ciba Specialty Chemicals) is preferred.

Examples of the compound containing two or more aromatic rings include biphenyl, diphenylsulfone, 4-phenylphenol, benzoin, diphenyl sulfide, diphenyl ether, 4-hydroxybiphenyl-4′-carboxylic acid, 4,4′-biphenol, 4,4′-dihydroxydiphenylmethane, 4-α-cumylphenol, diphenylacetylene, azobenzene, dibenzofuran, diphenylmethane, benzyl benzoate, diphenyl phthalate, N- (4-methoxybenzylidene) -4-acetoxyaniline, 4- [ (Methoxybenzylidene) amino] azobenzene, 4,4′-sulfonyldiphenol, 4-phenoxyphenol, 4′-methoxybenzylideneaminostilbene, bisphenol A, benzylidenephenylamine, N, N '-Dibenzylidenehydrazine, transstilbene, p-dianisalbenzidine, terephthalbis- (p-phenetidine), carbazole, 1,4-diphenyl-1,3-butadiene, 1,4-diphenyl-1,3,5 -Hexadiene, fluorene, dibenzothiophene and the like.
Moreover, you may use the compound which has an aromatic ring and a urethane bond, For example, the reaction material of the isocyanate compound and alcohol containing an aromatic ring and the reaction material of the alcohol and aromatic compound containing an aromatic ring are mentioned.

  The weight average molecular weight of the high refractive index compound (D) is usually 10,000 or less, preferably 500 or less, particularly preferably 100 to 2000, and particularly preferably 200 to 1000. If the weight average molecular weight is too high, the polymer does not align well between the polymers and the birefringence adjusting effect tends to be difficult to obtain, and if it is too low, the durability tends to decrease.

  As content of a high refractive index compound (D), it is 5-100 weight part normally with respect to a total of 100 weight part of acrylic resin (A1) and acrylic resin (A2), More preferably, it is 10-10 weight part. 50 parts by weight, particularly preferably 20 to 40 parts by weight. If the content of the high-refractive-index low-molecular compound (D) is too small, the light leakage resistance tends to decrease, and if it is too large, durability tends to decrease due to insufficient cohesive force.

The pressure-sensitive adhesive composition [I] further includes an antistatic agent, other acrylic pressure-sensitive adhesives, other pressure-sensitive adhesives, urethane resin, rosin, rosin ester, and hydrogenated rosin as long as the effects of the present invention are not impaired. Tackifiers such as esters, phenol resins, aromatic modified terpene resins, aliphatic petroleum resins, alicyclic petroleum resins, styrene resins, xylene resins, colorants, fillers, anti-aging agents, UV absorbers Conventionally known additives such as functional dyes, and compounds that cause coloration or discoloration by irradiation with ultraviolet rays or radiation can be blended.
In addition to the above additives, a small amount of impurities contained in the raw materials for producing the constituent components of the pressure-sensitive adhesive composition [I] may be contained.

  Examples of the antistatic agent include cation type antistatic agents of quaternary ammonium salts such as imidazolium salts and tetraalkylammonium sulfonates, aliphatic sulfonates, higher alcohol sulfate esters, higher alcohol alkylene oxide adduct sulfuric acid. Anionic antistatic agents such as ester salts, higher alcohol phosphate esters, higher alcohol alcohol alkylene oxide adduct phosphate esters, potassium bis (fluorosulfonyl) imide, lithium bis (trifluorosulfonyl) imide, lithium chloride, etc. Examples thereof include alkali metal salts, alkaline earth metal salts, higher alcohol alkylene oxide adducts, polyalkylene glycol fatty acid esters and the like.

  In the present invention, the pressure-sensitive adhesive composition [I] preferably contains the acrylic resins (A1) and (A2) as the main components. It means that the total of acrylic resins is usually 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more based on the total amount of the pressure-sensitive adhesive composition [I]. The upper limit is usually 99.9% by weight.

  Thus, the pressure-sensitive adhesive composition [I] used in the present invention is obtained, and the pressure-sensitive adhesive composition [I] is crosslinked to become the pressure-sensitive adhesive of the present invention.

  The pressure-sensitive adhesive of the present invention is obtained by crosslinking a pressure-sensitive adhesive composition [I] containing an acrylic resin (A1), an acrylic resin (A2), and a crosslinking agent (B) as essential components. Crosslinking (chemical crosslinking) is performed by the reaction of the functional group of the resin (A1) and the functional group of the acrylic resin (A2) with the crosslinking agent (B).

  In the present invention, the pressure-sensitive adhesive composition obtained by crosslinking the pressure-sensitive adhesive composition [I] needs to have a gel fraction of 40 to 90%, from the viewpoint of the balance between durability and light leakage resistance. Preferably it is 45-80%, More preferably, it is 50-70%, Most preferably, it is 50-60%. If the gel fraction is too low, durability tends to be insufficient due to insufficient cohesive force, and if the gel fraction is too high, cohesive force tends to increase and light leakage resistance tends to decrease. Moreover, when adhesive composition [I] contains a non-crosslinking component, it is preferable that the gel fraction only by a crosslinking component ((A1), (A2), (B)) will be 70 to 90%. .

  In adjusting the gel fraction of the pressure-sensitive adhesive to the above range, for example, it is achieved by adjusting the type and amount of the crosslinking agent, adjusting the composition ratio of the hydroxyl group and the carboxyl group in the composition, and the like. . Moreover, since the gel fraction changes with each interaction, the ratio between the crosslinking agent and the functional group amount needs to be balanced.

  The gel fraction is a measure of the degree of crosslinking, and is calculated, for example, by the following method. That is, a pressure-sensitive adhesive sheet (not provided with a separator) in which a pressure-sensitive adhesive layer is formed on a polymer sheet (for example, polyethylene terephthalate film or the like) as a base material is wrapped with a 200-mesh SUS wire mesh, and 23 in toluene. The weight percentage of the insoluble pressure-sensitive adhesive component immersed in the wire mesh at 24 ° C. for 24 hours is defined as the gel fraction. However, the weight of the substrate is subtracted.

  In this invention, the optical member with an adhesive layer can be obtained by laminating and forming the adhesive layer which consists of said adhesive on an optical member (for example, optical laminated body).

  It is preferable that the optical member with the pressure-sensitive adhesive layer is further provided with a release sheet on the surface opposite to the optical member surface of the pressure-sensitive adhesive layer.

  Moreover, when using the optical member with an adhesive layer for practical use, the said release sheet is peeled and used. And as said release sheet, it is preferable to use a silicon-type release sheet.

In preparing the optical member with the pressure-sensitive adhesive layer, for the method of crosslinking the pressure-sensitive adhesive composition [I], [1] The pressure-sensitive adhesive composition [I] is applied on the optical member, dried, and then released. A method of pasting a mold sheet and performing an aging treatment, [2] By applying a pressure-sensitive adhesive composition [I] on a release sheet, drying, and then pasting an optical member and performing an aging treatment. Can be done. Among these, the method [2] is preferable from the viewpoint of not damaging the substrate, workability and stable production.

  The aging treatment is carried out to balance the physical properties of the adhesive. As aging conditions, the temperature is usually from room temperature to 70 ° C., and the time is usually from 1 day to 30 days. What is necessary is just to carry out on conditions, such as 1 day-20 days at 23 degreeC, 3-10 days at 23 degreeC, 1 day-7 days at 40 degreeC.

  When applying the pressure-sensitive adhesive composition [I], it is preferable to dilute the pressure-sensitive adhesive composition [I] in a solvent, and the dilution concentration is preferably 5 to 60% by weight, particularly preferably 10%. ~ 30% by weight. The solvent is not particularly limited as long as it can dissolve the pressure-sensitive adhesive composition [I]. Examples thereof include ester solvents such as methyl acetate, ethyl acetate, methyl acetoacetate, and ethyl acetoacetate, acetone Further, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, aromatic solvents such as toluene and xylene, and alcohol solvents such as methanol, ethanol and propyl alcohol can be used. Among these, ethyl acetate and methyl ethyl ketone are preferably used from the viewpoints of solubility, drying property, price, and the like.

  In addition, the application of the pressure-sensitive adhesive composition [I] can be performed by conventional methods such as roll coating, die coating, gravure coating, comma coating, and screen printing.

  Moreover, 5-300 micrometers is preferable normally, and, as for the thickness of the adhesive layer in the optical member with an adhesive layer obtained, 10-50 micrometers is especially preferable, Furthermore, 12-30 micrometers is preferable. If the thickness of the pressure-sensitive adhesive layer is too thin, the adhesive physical properties tend to be difficult to stabilize, and if it is too thick, the entire optical member tends to be too thick.

  The optical member with the pressure-sensitive adhesive layer of the present invention has a release sheet, and after the release sheet has been peeled off, the pressure-sensitive adhesive layer surface is bonded to a glass substrate and used for, for example, a liquid crystal display panel.

  In the present invention, the adhesive strength of the pressure-sensitive adhesive layer is appropriately determined according to the material of the adherend, etc., but for example, as the adhesive strength after one day has passed, the adhesive layer is adhered to a glass substrate. Preferably has an adhesive strength of 0.2 N / 25 mm to 20 N / 25 mm, more preferably 0.5 N / 25 mm to 10 N / 25 mm, and after 14 days, 0.2 N / 25 mm to 30 N / 25 mm. It preferably has an adhesive force, and more preferably 5 N / 25 mm to 20 N / 25 mm.

  The adhesive strength is measured as follows, for example. About a polarizing plate with an adhesive layer, it cut | judged to width 25mm width, peels a release film, presses the adhesive layer side to a non-alkali glass plate (Corning company make, "Corning 1737"), and a polarizing plate A glass plate is bonded. Then, after performing an autoclave process (50 degreeC, 0.5 MPa, 20 minutes), 23 degreeC and 50% R. H. Then, after leaving for 24 hours (or 24 days), a 180 ° C. peel test is performed.

  Examples of the optical member in the present invention include an optical film suitably used for an image display device such as a liquid crystal display device, an organic EL display device, and a PDP. Examples of such an optical film include a polarizing plate and a retardation. Examples thereof include a plate, an elliptically polarizing plate, an optical compensation film, a brightness enhancement film, and a laminate of these. Among them, a polarizing plate is particularly effective in the present invention.

  The polarizing plate used in the present invention is usually a laminate of a cellulose triacetate film as a protective film on both sides of a polarizing film. The polarizing film has an average degree of polymerization of 1,500 to 10,000, A uniaxially stretched film dyed with an aqueous solution of iodine-potassium iodide or a dichroic dye using a film made of a polyvinyl alcohol resin having a degree of conversion of 85 to 100 mol% as a raw film (usually 2 to 10 times, preferably Is a stretching ratio of about 3 to 7 times.

  The polyvinyl alcohol resin is usually produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate, but a small amount of unsaturated carboxylic acid (including salt, ester, amide, nitrile, etc.), olefins, vinyl ether And a component copolymerizable with vinyl acetate, such as an unsaturated sulfonate. Moreover, what is called polyvinyl acetal resin and polyvinyl alcohol derivatives, such as polybutyral resin and polyvinyl formal resin, which are obtained by reacting polyvinyl alcohol with an aldehyde in the presence of an acid are also exemplified.

  The pressure-sensitive adhesive of the present invention can also be used as various displays for word processors, computers, mobile phones, televisions, etc .; optical parts such as polarizing plates and laminates corresponding thereto; and pressure-sensitive adhesives for temporary surface protection of electronic substrates and the like. is there.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In the examples, “parts” and “%” mean weight basis unless otherwise specified.

  First, various acrylic resins were prepared as follows. In addition, regarding the measurement of the weight average molecular weight of acrylic resin, dispersion degree, and glass transition temperature, it measured according to the above-mentioned method. In addition, regarding the measurement of a viscosity, it measured according to the 4.5.3 rotational viscometer method of JISK5400 (1990).

[Preparation of acrylic resin] (See Table 1)
[Acrylic resin (A1-1)]
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 1.5 parts of 2-hydroxyethyl acrylate (a1), 98.5 parts of butyl acrylate (a2), and After charging 85 parts of ethyl acetate and 45 parts of acetone, heating and refluxing was started, 0.03 part of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and the mixture was reacted at ethyl acetate refluxing temperature for 3 hours. Diluted acrylic resin (A1-1) solution (weight average molecular weight (Mw) 1.7 million, dispersity (Mw / Mn) 3.4, glass transition temperature -53 ° C., solid content 17%, viscosity 8000 mPa · s ( 25 ° C.).

[Acrylic resin (A1-2)]
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 5 parts of 2-hydroxyethyl acrylate (a1), 95 parts of butyl acrylate (a2), and 100 parts of ethyl acetate , 45 parts of acetone was added, and after heating to reflux, 0.03 part of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, reacted for 3 hours at the reflux temperature of ethyl acetate, diluted with ethyl acetate and acrylic. Resin (A1-2) solution (weight average molecular weight (Mw) 1580,000, dispersity (Mw / Mn) 3.7, glass transition temperature -50 ° C., solid content 18%, viscosity 8,000 mPa · s (25 ° C. )).

[Acrylic resin (A2-1)]
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, acrylic acid (a1 ′) 5 parts, butyl acrylate (a′2) 95 parts, and ethyl acetate 85 parts , 45 parts of acetone was added, and after heating to reflux, 0.03 part of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, reacted for 3 hours at the reflux temperature of ethyl acetate, diluted with ethyl acetate and acrylic. Resin (A2-1) solution (weight average molecular weight (Mw) 1.7 million, dispersity (Mw / Mn) 3.4, glass transition temperature -53 ° C., solid content 17%, viscosity 8000 mPa · s (25 ° C.)) Got.

[Acrylic resin (A2-2)]
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, acrylic acid (a1 ′) 10 parts, butyl acrylate (a′2) 90 parts, and ethyl acetate 85 parts , 45 parts of acetone was added, and after heating to reflux, 0.03 part of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, reacted for 3 hours at the reflux temperature of ethyl acetate, diluted with ethyl acetate and acrylic. Resin (A2-2) solution (weight average molecular weight (Mw) 1.6 million, dispersity (Mw / Mn) 3.4, glass transition temperature -46 ° C., solid content 18%, viscosity 8000 mPa · s (25 ° C.)) Got.

[Acrylic resin (A′-1)]
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 1.5 parts of 2-hydroxyethyl acrylate, 98 parts of butyl acrylate, 0.5 part of acrylic acid and ethyl acetate 85 parts and 45 parts of acetone were added, and after heating and refluxing was started, 0.03 part of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, reacted at ethyl acetate reflux temperature for 3 hours, and then diluted with ethyl acetate. Acrylic resin (A′-1) solution (weight average molecular weight (Mw) 1.7 million, dispersity (Mw / Mn) 3.4, glass transition temperature −53 ° C., solid content 17%, viscosity 8000 mPa · s (25 ° C)).

[Crosslinking agent (B)]
The following were prepared as a crosslinking agent (B-1).
・ 55% ethyl acetate solution of trimethylolpropane tolylene diisocyanate adduct (manufactured by Nippon Polyurethane Co., Ltd., “Coronate L-55E”)

[Silane coupling agent (C)]
The following were prepared as the silane compound (C-1).
・ Γ-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., “KBM403”)

[High refractive index compound (D)]
The following were prepared as the high refractive index compound (D-1).
・ Benzotriazole compounds (manufactured by Ciba Specialty Chemicals, “TINUVIN109”)
The following were prepared as the high refractive index low molecular compound (D-2).
・ Diisononyl phthalate ("DINP", manufactured by J-Plus Co., Ltd.)

[Examples 1-9, Comparative Examples 1-3]
Each component prepared and prepared as described above was blended in the proportions shown in Table 2 below to prepare a pressure-sensitive adhesive composition as a pressure-sensitive adhesive forming material for optical members, and this was diluted with methyl ethyl ketone ( Viscosity [500 to 10000 mPa · s (25 ° C.)]) An adhesive composition solution was prepared.

  And after apply | coating the said adhesive composition solution to the polyester-type release sheet so that the thickness after drying may be set to 25 micrometers, and drying for 3 minutes at 90 degreeC, the formed adhesive composition layer side is made into polyethylene. Transferred onto a terephthalate (PET) film (thickness 38 μm), then 23 ° C. × 65% R.D. H. The film was aged for 10 days under the above conditions to obtain a PET film with an adhesive layer.

  Using the PET film with the pressure-sensitive adhesive layer thus obtained, the gel fraction was measured and evaluated according to each method shown below. These results are also shown in Table 2 below.

[Gel fraction]
After the obtained PET film with the pressure-sensitive adhesive layer is cut into 40 × 40 mm, the release sheet is peeled off and the pressure-sensitive adhesive layer side is bonded to a 50 × 100 mm SUS mesh sheet (200 mesh), and then the SUS mesh sheet. The sample was wrapped from the center with respect to the longitudinal direction, and the sample was wrapped. Then, the gel fraction was measured by weight change when immersed in a sealed container containing 250 g of toluene.

Next, the pressure-sensitive adhesive composition solutions of Examples 1 to 9 and Comparative Examples 1 to 4 were applied to a polyester release sheet so that the thickness after drying was 25 μm, and dried at 90 ° C. for 3 minutes. The formed pressure-sensitive adhesive composition layer was transferred onto a polarizing plate (thickness 190 μm), and then 23 ° C. × 65% R.D. H. The film was aged for 10 days under the above conditions to obtain a polarizing plate with an adhesive layer.
For the polarizing plate, “MLP38U” manufactured by Biei Imaging Co., Ltd. was used by cutting it at 45 ° C. with respect to the stretching axis.

  Using the polarizing plate with the pressure-sensitive adhesive layer thus obtained, durability (wet heat resistance test, heat cycle test, heat resistance test) and adhesive strength were measured and evaluated according to the following methods. These results are shown in Table 3 below.

〔durability〕
The release sheet of the obtained polarizing plate with the pressure-sensitive adhesive layer was peeled off, and the pressure-sensitive adhesive layer side was pressed against a non-alkali glass plate (Corning Corp., Eagle XG) to bond the polarizing plate and the glass plate. Thereafter, autoclave treatment (50 ° C., 0.5 MPa, 20 minutes) was performed, and thereafter foaming, peeling, and light leakage phenomenon were evaluated in the following durability tests (wet heat resistance test, heat cycle test, heat resistance test).
For the heat resistance test only, the same sample was bonded to both the front and back surfaces so that the polarizing plate was crossed Nicol, and was used for light leakage observation.
The test piece size used was 20 cm × 15 cm.

〔An endurance test〕
(1) Moisture and heat resistance test 60 ° C., 90% R.D. H. Endurance test for 150 hours (2) Heat cycle test Endurance test for 75 cycles, with the operation of leaving at -35 ° C for 60 minutes, then leaving at 70 ° C for 60 minutes (3) Heat test-1
Durability test at 90 ° C for 150 hours (4) Heat resistance test-2 (light leakage)
Light leakage at 80 ° C for 150 hours

〔Evaluation criteria〕
(Foam)
○: Foam is hardly seen △ ... Foam is slightly seen × ... Foam is seen a lot (peeling)
○: Peeling less than 0.5 mm or occurrence of a lift mark Δ ... Peeling of 0.5 mm or more and less than 10 mm, or generation of a lift mark × ... Peeling of 10 mm or more, or a lift mark of 10 mm or more Occurrence (light leakage)

○ ・ ・ ・ light leakage is hardly seen △ ・ ・ ・ light leakage is slightly generated × ・ ・ ・ light leakage is large on 4 sides

[Adhesive strength: 1 day later]
About the prepared polarizing plate with an adhesive layer, it cuts to width 25mm width, peels off a release film, presses the adhesive layer side to a non-alkali glass board (Corning company make, "Corning 1737"), and polarized light The plate and the glass plate were bonded together. Thereafter, autoclaving (50 ° C., 0.5 MPa, 20 minutes) was performed, and 23 ° C. 50% R.D. H. A 180 ° C. peel test was performed after leaving the sample for 24 hours. In the peelability, it is desired that the adhesive strength is small, and the target is 10 N / 25 mm or less after one day.
[Adhesive strength: 14 days later]
The same treatment as that after one day was performed, and 23 ° C., 50% R.D. H. After leaving for 14 days under the conditions, a 180 degree peel test was conducted. In long-term peelability, it is desired that the adhesive strength is small, and after 14 days, the target is 20 N / 25 mm or less and no trace.

The pressure-sensitive adhesives of Examples 1 to 9 were excellent in balance between durability performance and pressure-sensitive adhesive properties as compared with the pressure-sensitive adhesives of Comparative Examples 1 to 3.
In particular, Example 1 in which an acrylic resin (A1) containing a hydroxyl group in the side chain and an acrylic resin (A2) containing a carboxyl group in the side chain is used as an acrylic resin, and has both a hydroxyl group and a carboxyl group. When comparing Comparative Example 1 using the acrylic resin (A′-1), the gel fraction of Example 1 containing a larger amount of the crosslinking agent is lower, and as a result, light leakage of the heat resistance test. It can be seen from Table 3 that it is excellent in the test and the suppression of increase in adhesive strength over time.

  The pressure-sensitive adhesive of the present invention has high durability, does not cause foaming or peeling in a severe environment, is excellent in light leakage resistance, and further has a small increase in adhesive strength with time of application. It is very useful as an adhesive for optical members. Furthermore, the optical member with an adhesive layer and an image display apparatus can be obtained using them.

Claims (11)

Adhesive composition [I] containing an acrylic resin (A1) containing a hydroxyl group in the side chain, an acrylic resin (A2) containing a carboxyl group in the side chain, and an aromatic polyvalent isocyanate crosslinking agent (B) Is an adhesive formed by crosslinking with a crosslinking agent (B),
The blending amount of the crosslinking agent (B) is 0.3 to 5 parts by weight with respect to a total of 100 parts by weight of (A1) and (A2), and the gel fraction is 40 to 90%. Adhesive.   The acrylic resin (A1) containing a hydroxyl group in the side chain is obtained by copolymerizing a copolymer component containing 0.1 to 20% by weight of the hydroxyl group-containing monomer (a1). Adhesive   The pressure-sensitive adhesive according to claim 1 or 2, wherein the acrylic resin (A1) containing a hydroxyl group in the side chain does not substantially contain a carboxyl group-containing monomer as a copolymerization component.   The acrylic resin (A2) containing a carboxyl group in the side chain is obtained by copolymerizing a copolymer component containing 0.5 to 30% by weight of the carboxyl group-containing monomer (a'1). Item 3. The pressure-sensitive adhesive according to item 1 or 2.   The pressure-sensitive adhesive according to claim 1 or 4, wherein the acrylic resin (A2) containing a carboxyl group in the side chain does not substantially contain a hydroxyl group-containing monomer as a copolymerization component.   The pressure-sensitive adhesive according to any one of claims 1 to 5, wherein the ratio (molar ratio) between the hydroxyl group and the carboxyl group contained in the pressure-sensitive adhesive composition [I] is hydroxyl group / carboxyl group = 0.15 to 20. .   The blending ratio of the acrylic resin (A1) containing a hydroxyl group in the side chain and the acrylic resin (A2) containing a carboxyl group in the side chain is (A1) :( A2) = 50: 50 to 95: 5. The pressure-sensitive adhesive according to any one of claims 1 to 6.   A pressure-sensitive adhesive for optical members, comprising the pressure-sensitive adhesive according to claim 1.   The pressure-sensitive adhesive for optical members according to claim 8, wherein the optical member is a polarizing plate.   An optical member with a pressure-sensitive adhesive layer, comprising a laminated structure of a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive for optical members according to claim 8 or 9, and an optical member.   An image display device comprising the optical member with an adhesive layer according to claim 10.