JP2019085436A - Adhesive composition for optical film, adhesive layer for optical film and optical film with adhesive layer - Google Patents

Abstract

To provide an adhesive composition for an optical film that can form, on an adherend (an optical film), an adhesive layer for an optical film capable of suppressing the occurrence of foaming, peeling and the like and excellent in durability and reworkability even when exposed to heating/humidification conditions.SOLUTION: An adhesive composition for an optical film contains a (meth)acrylic polymer and a crosslinking agent. The (meth)acrylic polymer contains as monomer units an amide group-containing monomer and an alkoxy group-containing alkyl (meth)acrylate in which the alkoxy group-containing alkyl (meth)acrylate is contained in an amount of 20 to 80 mass% based on 100 mass% of the total amount of monomer units constituting the (meth)acrylic polymer.SELECTED DRAWING: None

Description

  The present invention relates to a pressure-sensitive adhesive composition for an optical film, a pressure-sensitive adhesive layer for an optical film, and an optical film with a pressure-sensitive adhesive layer. As the optical film, it is possible to use a polarizing film (polarizing plate), a retardation film, an optical compensation film, a brightness enhancement film, or a laminate of these.

  In the liquid crystal display device and the like, it is indispensable to dispose polarizing elements on both sides of the liquid crystal cell from the image forming system, and generally, a polarizing film is attached. In addition to polarizing films, various optical elements have come to be used for liquid crystal panels in order to improve the display quality of displays. For example, a retardation film for preventing coloring, a viewing angle widening film for improving the viewing angle of a liquid crystal display, or a brightness enhancement film for enhancing the contrast of the display may be used. These films are collectively referred to as optical films.

  When sticking an optical member such as the optical film to a liquid crystal cell, a pressure-sensitive adhesive is usually used. Also, the adhesion between the optical film and the liquid crystal cell or the optical film is usually in close contact with a pressure-sensitive adhesive in order to reduce the loss of light. In such a case, the adhesive has an advantage such as not requiring a drying step to fix the optical film, so the pressure-sensitive adhesive is a pressure-sensitive adhesive layer provided with an adhesive layer in advance as an adhesive layer on one side of the optical film. Films are commonly used. A release film is usually attached to the pressure-sensitive adhesive layer of the pressure-sensitive adhesive layer-attached optical film.

  As the necessary characteristics required for the pressure-sensitive adhesive layer, heating is performed in a state in which the pressure-sensitive adhesive layer is bonded to an optical film, or in a state in which an optical film with a pressure-sensitive adhesive layer is further bonded to a glass substrate of a liquid crystal panel. Under the humidified conditions, high durability is required. For example, in an endurance test by heating / humidifying which is usually performed as an environmental acceleration test, high problems such as foaming, peeling, and floating due to the pressure-sensitive adhesive layer do not occur. Adhesion reliability etc. are required.

  In particular, the pressure-sensitive adhesive layer and the optical film with the pressure-sensitive adhesive layer used for automotive displays such as car navigation used in outdoor and high temperature vehicles are expected to have high adhesion reliability and durability at high temperature Sex is required.

  In addition, the optical film (for example, a polarizing film) tends to shrink due to the heat treatment. The shrinkage of the polarizing film causes a problem that the pressure-sensitive adhesive layer itself is also deformed.

  Various pressure-sensitive adhesive compositions for forming the pressure-sensitive adhesive layer of the pressure-sensitive adhesive layer-attached optical film have been proposed (for example, Patent Document 1).

JP 2012-158702 A

  Patent Document 1 proposes a pressure-sensitive adhesive composition in which 4 to 20 parts by mass of an isocyanate-based crosslinking agent is blended with 100 parts by mass of an acrylic polymer containing a polar monomer, such as an aromatic ring-containing monomer and an amide group-containing monomer. ing. However, since the pressure-sensitive adhesive composition of Patent Document 1 contains a large proportion of the crosslinking agent, peeling tends to easily occur in the durability test.

  Therefore, according to the present invention, even when the adherend (optical film) is exposed to heating and humidifying conditions, the occurrence of foaming and peeling can be suppressed, and the durability (heat resistance and moisture resistance) can be suppressed. An object of the present invention is to provide a pressure-sensitive adhesive composition for an optical film which can obtain a pressure-sensitive adhesive layer for an optical film which is excellent in peeling resistance) and reworkability.

  Moreover, this invention aims at providing the adhesive film with an adhesive layer which has the adhesive layer for said optical films, and the adhesive layer for said optical films.

  As a result of intensive studies to solve the above problems, the present inventors have found the following pressure-sensitive adhesive composition for an optical film, and came to complete the present invention.

  That is, the pressure-sensitive adhesive composition for an optical film of the present invention is a pressure-sensitive adhesive composition for an optical film containing a (meth) acrylic polymer and a crosslinking agent, and the (meth) acrylic polymer is used as a monomer unit 20. The alkoxy group-containing alkyl (meth) acrylate containing an amide group-containing monomer and an alkoxy group-containing alkyl (meth) acrylate, relative to 100% by mass in total of monomer units constituting the (meth) acrylic polymer It is characterized by containing 80 mass%. The "pressure-sensitive adhesive composition for an optical film" may be hereinafter simply referred to as "pressure-sensitive adhesive composition".

  The pressure-sensitive adhesive composition for an optical film of the present invention comprises 0.9 to 7% by mass of the amide group-containing monomer and 100% by mass of the total amount of monomer units constituting the (meth) acrylic polymer, and It is preferable to contain 25-75 mass% of group containing alkyl (meth) acrylate.

  The pressure-sensitive adhesive composition for an optical film of the present invention comprises 0.9 to 3% by mass of the amide group-containing monomer and 100% by mass of the total amount of monomer units constituting the (meth) acrylic polymer, and It is preferable to contain 35-75 mass% of group containing alkyl (meth) acrylate.

  The pressure-sensitive adhesive composition for an optical film of the present invention comprises the amide group-containing monomer in an amount of 0.9 to 3% by mass with respect to 100% by mass of the total amount of monomer units constituting the (meth) acrylic polymer The alkoxy group-containing alkyl (meth) acrylate is preferably contained in an amount of 50 to 75% by mass.

  In the pressure-sensitive adhesive composition for an optical film of the present invention, preferably, the (meth) acrylic polymer does not contain a carboxyl group-containing monomer as a monomer unit.

  The pressure-sensitive adhesive layer for an optical film of the present invention is preferably formed of the pressure-sensitive adhesive composition for an optical film.

  The pressure-sensitive adhesive layer-attached optical film of the present invention preferably has the pressure-sensitive adhesive layer for an optical film on at least one side of the optical film.

  The pressure-sensitive adhesive layer for an optical film formed of the pressure-sensitive adhesive composition for an optical film according to the present invention, such as foaming or peeling, is a case where it is exposed to heating and humidification conditions in a state of being attached to the optical film. It is possible to suppress the occurrence, and to obtain high adhesion reliability, reworkability and durability (heat resistance, moisture resistance, peel resistance), which is useful. In addition, even when an optical film with a pressure-sensitive adhesive layer using the pressure-sensitive adhesive layer for an optical film is exposed to heating and humidifying conditions, display unevenness caused by foaming and peeling can be suppressed, which is useful. .

It is an example of the schematic sectional drawing of the polarizing film with an adhesive layer of this invention.

<(Meth) acrylic polymer>
The pressure-sensitive adhesive composition for an optical film of the present invention contains a (meth) acrylic polymer, and the (meth) acrylic polymer contains, as monomer units, an amide group-containing monomer, and an alkoxy group-containing alkyl (meth) acrylate And containing 20 to 80% by mass of the alkoxy group-containing alkyl (meth) acrylate relative to 100% by mass in total of monomer units constituting the (meth) acrylic polymer. In addition, (meth) acrylate means an acrylate and / or a methacrylate, and (meth) of this invention is the same meaning.

  The alkoxy group-containing alkyl (meth) acrylate is not particularly limited. For example, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, methoxytriethylene glycol acrylate, 3-methoxypropyl acrylate, acrylic acid 3 -Ethoxypropyl, 4-methoxybutyl acrylate, 4-ethoxybutyl acrylate and the like can be mentioned. The alkoxy group-containing alkyl (meth) acrylate can be used alone or in combination of two or more.

  The alkoxy group-containing alkyl (meth) acrylate is contained in an amount of 20 to 80% by mass, preferably 22 to 80% by mass, based on 100% by mass of the total amount of monomer units constituting the (meth) acrylic polymer. Is 25 to 78% by mass, more preferably 25 to 75% by mass, particularly preferably 35 to 75% by mass, and most preferably 50 to 75% by mass. When the content of the alkoxy group-containing monomer is less than 20% by mass, reworkability and durability (heat resistance, moisture resistance, peeling resistance) become insufficient. On the other hand, when it exceeds 80% by mass, the moisture content of the pressure-sensitive adhesive becomes high, and the foam resistance becomes insufficient.

  The amide group-containing monomer is preferably a compound containing an amide group in the structure and containing a polymerizable unsaturated double bond such as (meth) acryloyl group or vinyl group. The amide group-containing monomer is not particularly limited. For example, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-isopropylacrylamide, N-methyl (meth) ) Acrylamide, N-butyl (meth) acrylamide, N-hexyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylol-N-propane (meth) acrylamide, aminomethyl (meth) acrylamide, aminoethyl (meth) acrylamide ) Acrylamide-based monomers such as acrylamide, mercaaptomethyl (meth) acrylamide, mercaptoethyl (meth) acrylamide; N- (meth) acryloyl morpholine, N- (meth) acryloyl piperidine, N- (meth) acrylo N- acryloyl heterocyclic monomers such Rupirorijin; N- vinylpyrrolidone, N- vinyl-containing lactam monomers such as N- vinyl -ε- caprolactam. The amide group-containing monomer is preferable for satisfying the durability, and among the amide group-containing monomers, in particular, an N-vinyl group-containing lactam monomer is preferable for satisfying the durability and reworkability.

  The amide group-containing monomer is preferably contained in an amount of 0.1 to 15% by mass, more preferably 0.3 to 12% by mass, based on 100% by mass of the total amount of monomer units constituting the (meth) acrylic polymer. It is more preferably 0.5 to 10% by mass, particularly preferably 0.9 to 7% by mass, and most preferably 0.9 to 3% by mass. If the mass ratio of the amide group-containing monomer (in particular, the N-vinyl group-containing lactam monomer) falls within the above range, reworkability and durability (heat resistance, moisture resistance, peeling resistance) can be particularly satisfied. . In addition, when it exceeds 15 mass%, it is unpreferable from the point of rework property.

  The pressure-sensitive adhesive composition for an optical film of the present invention is a pressure-sensitive adhesive composition for an optical film comprising a (meth) acrylic polymer and a crosslinking agent, wherein the (meth) acrylic polymer is an amide group as a monomer unit. The alkoxy group-containing alkyl (meth) acrylate is contained in an amount of 100 to 80% by mass based on the total amount of monomer units constituting the (meth) acrylic polymer containing the monomer and the alkoxy group-containing alkyl (meth) acrylate. Although it is characterized in that it contains by mass%, the compounding amount of the amide group-containing monomer and the alkoxy group-containing alkyl (meth) acrylate is 100 mass% in total of the monomer units constituting the (meth) acrylic polymer To 0.9% by mass to 7% by mass of the amide group-containing monomer, and It is preferable to contain 25 to 75% by mass of (meth) acrylate, and 0.9 to 3% by mass of the amide group-containing monomer with respect to 100% by mass in total of monomer units constituting the (meth) acrylic polymer, And it is more preferable to contain 35-75 mass% of said alkoxy group containing alkyl (meth) acrylates, The said amide group containing monomer is 100 mass% of monomer units whole quantity which comprises the said (meth) acrylic-type polymer. It is further preferable to contain 0.9 to 3% by mass and 50 to 75% by mass of the alkoxy group-containing alkyl (meth) acrylate. By using the amide group-containing monomer and the alkoxy group-containing alkyl (meth) acrylate in combination, adhesion can be improved without using a carboxyl group-containing monomer which contributes to improvement in adhesion, and durability It is excellent also in the properties (heat resistance, moisture resistance, peeling resistance) and reworkability, which is a preferable embodiment. Furthermore, by using both monomers in combination within the above range, adhesion is further improved, reworkability is excellent, and in addition to this, a monomer having an acidic functional group such as a carboxyl group-containing monomer is not used. Also, it is excellent in metal corrosion resistance (for example, ITO corrosion resistance when using ITO for an adherend), which is a preferable embodiment.

  The (meth) acrylic polymer preferably contains an alkyl (meth) acrylate as a monomer unit, in addition to the amide group-containing monomer and the alkoxy group-containing alkyl (meth) acrylate. As said alkyl (meth) acrylate, the C1-C18 thing of linear or branched alkyl group can be illustrated. For example, as the alkyl group, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, amyl group, hexyl group, cyclohexyl group, heptyl group, 2-ethylhexyl group, isooctyl group, nonyl group, decyl Groups, isodecyl groups, dodecyl groups, isomyristyl groups, lauryl groups, tridecyl groups, pentadecyl groups, hexadecyl groups, heptadecyl groups, octadecyl groups, and the like. These can be used alone or in combination. The average carbon number of these alkyl groups is preferably 3 to 9.

  The alkyl (meth) acrylate is preferably contained in an amount of 1 to 75% by mass, more preferably 3 to 70% by mass, based on 100% by mass of the total amount of monomer units constituting the (meth) acrylic polymer. Preferably it is 5-65 mass%. It is preferable to set the mass ratio of the alkyl (meth) acrylate in the above range in order to secure the adhesiveness.

  Moreover, it is preferable that the said (meth) acrylic-type polymer contains a hydroxyl group containing monomer as a monomer unit. The hydroxyl group-containing monomer is preferably a compound containing a hydroxyl group in the structure and containing a polymerizable unsaturated double bond such as (meth) acryloyl group or vinyl group. Specific examples of the hydroxyl group-containing monomer include, for example, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8- Examples include hydroxyalkyl (meth) acrylates such as hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, and (4-hydroxymethylcyclohexyl) -methyl acrylate. Among the hydroxyl group-containing monomers, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are preferable in terms of durability, and 4-hydroxybutyl (meth) acrylate is particularly preferable.

  The hydroxyl group-containing monomer is preferably 0.01 to 7% by mass, more preferably 0.1 to 5% by mass, based on 100% by mass of the total amount of monomer units constituting the (meth) acrylic polymer. It is more preferably 0.3 to 3% by mass. If the mass ratio of the hydroxyl group-containing monomer is less than 0.01% by mass, crosslinking of the pressure-sensitive adhesive layer may be insufficient, and the durability and the adhesion properties may not be satisfied. May not be satisfied. In particular, since the hydroxyl group-containing monomer is highly reactive with the intermolecular crosslinking agent, it is preferably used in terms of the improvement of the cohesiveness and heat resistance of the obtained pressure-sensitive adhesive layer, and the reworkability.

  The (meth) acrylic polymer preferably contains an aromatic ring-containing monomer as a monomer unit. The aromatic ring-containing monomer is preferably a compound containing an aromatic ring structure in its structure and containing a (meth) acryloyl group (hereinafter sometimes referred to as an aromatic ring-containing (meth) acrylate). The aromatic ring includes a benzene ring, a naphthalene ring or a biphenyl ring. In particular, the aromatic ring-containing monomer can satisfy the durability and can improve display unevenness due to light leakage.

  Specific examples of the aromatic ring-containing monomer include styrene, p-tert-butoxystyrene, and p-acetoxystyrene.

  Specific examples of the aromatic ring-containing (meth) acrylate include, for example, benzyl (meth) acrylate, phenyl (meth) acrylate, o-phenylphenol (meth) acrylate phenoxy (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxy Propyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, ethylene oxide modified nonylphenol (meth) acrylate, ethylene oxide modified cresol (meth) acrylate, phenol ethylene oxide modified (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) ) Acrylate, methoxybenzyl (meth) acrylate, chlorobenzyl (meth) acrylate, cresyl (meth) acrylate, polystilil Those having a benzene ring such as (meth) acrylate; hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth) acrylate, 2-naphthoxyethyl acrylate, 2- (4-methoxy-1-naphthoxy) ethyl (meth) Those having a naphthalene ring such as acrylate; and those having a biphenyl ring such as biphenyl (meth) acrylate.

  The aromatic ring-containing (meth) acrylate is preferably benzyl (meth) acrylate or phenoxyethyl (meth) acrylate, particularly preferably phenoxyethyl (meth) acrylate, from the viewpoint of adhesion properties and durability.

  The amount of the aromatic ring-containing monomer is preferably 3 to 25% by mass, more preferably 8 to 22% by mass, and further preferably 12 with respect to 100% by mass of the total amount of monomer units constituting the (meth) acrylic polymer. -20 mass%. If the mass ratio of the aromatic ring-containing monomer is within the above range, display unevenness due to light leakage can be sufficiently suppressed, and the durability is also excellent, which is preferable. When the mass ratio of the aromatic ring-containing monomer exceeds 25% by mass, display unevenness is rather insufficiently suppressed, and the durability is also reduced.

  The (meth) acrylic polymer may contain, as a monomer unit, a carboxyl group-containing monomer generally at 0.3% by mass or less. When the carboxyl group-containing monomer is contained, the adhesion can be expected to be improved, but the metal corrosion resistance (for example, the ITO corrosion resistance) required when sticking to ITO may not be satisfied. Preferably, the (meth) acrylic polymer does not contain a carboxyl group-containing monomer as a monomer unit.

  When the (meth) acrylic polymer contains the carboxyl group-containing monomer as a monomer unit, the carboxyl group-containing monomer contains a carboxyl group in the structure, and (meth) acryloyl group, vinyl The compound is preferably a compound containing a polymerizable unsaturated double bond such as a group. Specific examples of the carboxyl group-containing monomer include (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid and the like. Among the above-mentioned carboxyl group-containing monomers, acrylic acid is preferable from the viewpoint of copolymerizability, cost and adhesive property. If a small amount of the carboxyl group-containing monomer is used, an increase in adhesion with time can be suppressed, and adhesion can be improved. In addition, when using the said carboxyl group-containing monomer, it is preferable to apply to the use which metal corrosion resistance is not requested | required.

  In the (meth) acrylic polymer, it is not particularly required to contain other monomer units in addition to the monomer units, but for the purpose of improving adhesiveness and heat resistance, (meth) acryloyl group Alternatively, one or more copolymerizable monomers having a polymerizable functional group having an unsaturated double bond such as a vinyl group can be introduced by copolymerization.

  Specific examples of such copolymerizable monomers include: acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; caprolactone adduct of acrylic acid; allyl sulfonic acid, 2- (meth) acrylamido-2-methyl Sulfonic acid group-containing monomers such as propanesulfonic acid, (meth) acrylamidopropanesulfonic acid, sulfopropyl (meth) acrylate and the like; phosphoric acid group-containing monomers such as 2-hydroxyethyl acryloyl phosphate and the like.

  Also, alkylaminoalkyl (meth) acrylates such as aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, etc .; methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate Alkoxyalkyl (meth) acrylates such as meta) acrylate; N- (meth) acryloyloxymethylene succinimide, N- (meth) acryloyl-6-oxyhexamethylene succinimide, N- (meth) acryloyl-8-oxyoctamethylene succinimide and the like Succinimide-based monomers of the following: maleimide-based monomers such as N-cyclohexyl maleimide, N-isopropyl maleimide, N-lauryl maleimide and N-phenyl maleimide; N-methyl itaconimide, N Itaconimide-based monomers such as ethyl itaconimide, N-butyl itaconimide, N-octyl itaconimide, N-2-ethylhexyl itaconimide, N-cyclohexyl itaconimide, N-lauryl thioconimide, etc. are also examples of monomers for modification purpose It can be mentioned.

  Furthermore, as modifying monomers, vinyl monomers such as vinyl acetate and vinyl propionate; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing (meth) acrylates such as glycidyl (meth) acrylate; polyethylene glycol (meth) Glycol (meth) acrylates such as acrylate, polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate; tetrahydrofurfuryl (meth) acrylate, fluorine (meth) acrylate, silicone (meth) And (meth) acrylate monomers such as acrylate and 2-methoxyethyl acrylate can also be used. Furthermore, isoprene, butadiene, isobutylene, vinyl ether and the like can be mentioned.

  Furthermore, as a copolymerizable monomer other than the above-mentioned, the silane type monomer containing a silicon atom, etc. are mentioned. Examples of silane monomers include 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane 8-vinyloctyl triethoxysilane, 10-methacryloyloxydecyl trimethoxysilane, 10-acryloyloxydecyl trimethoxysilane, 10-methacryloyloxydecyl triethoxysilane, 10-acryloyloxydecyl triethoxysilane, and the like.

  Further, as a copolymerizable monomer, tripropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, bisphenol A diglycidyl ether di (meth) acrylate, neo Pentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate And (meth) acryloyl esters of (meth) acrylic acid and polyhydric alcohol such as caprolactone-modified dipentaerythritol hexa (meth) acrylate , A polyfunctional monomer having two or more unsaturated double bonds such as a vinyl group, or a skeleton such as polyester, epoxy, urethane etc. as a functional group similar to a monomer component and unsaturated such as a (meth) acryloyl group or a vinyl group It is also possible to use polyester (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate or the like in which two or more double bonds are added.

  The above copolymerized monomer is preferably about 0 to 10% by mass, more preferably about 0 to 7% by mass, based on 100% by mass of the total amount of monomer units constituting the (meth) acrylic polymer. More preferably, it is about 0 to 5% by mass.

  The weight-average molecular weight (Mw) of the (meth) acrylic polymer is preferably 900,000 to 3,000,000, and in view of durability, particularly heat resistance, the weight-average molecular weight is more preferably 1,000,000 to 2,800,000. It is more preferably 1.2 million to 2.6 million, and particularly preferably 1.4 million to 2.4 million. When the weight average molecular weight (Mw) is less than 900,000, the low molecular weight polymer component increases, the crosslink density of the gel (pressure-sensitive adhesive layer) becomes high, and along with this, the pressure-sensitive adhesive layer becomes hard and stress relaxation Is not preferred. On the other hand, when the weight average molecular weight is more than 3,000,000, the increase in viscosity and the gelation during the polymerization of the polymer are not preferable.

  The polydispersity (molecular weight distribution, weight average molecular weight (Mw) / number average molecular weight (Mn)) of the (meth) acrylic polymer is preferably 6 or less, more preferably 2.5 to 5.5. And more preferably 3 to 5. When the polydispersity (Mw / Mn) exceeds 6, a large amount of low molecular weight polymer is required, and in order to increase the gel fraction of the pressure-sensitive adhesive layer, it is necessary to use a large amount of crosslinking agent. An excess of the crosslinking agent reacts with the gelled polymer to increase the crosslink density of the gel (pressure-sensitive adhesive layer), which causes the pressure-sensitive adhesive layer to be hard and the stress relaxation property is impaired, which is not preferable. Also, when the amount of low molecular weight polymer is large and the amount of uncrosslinked polymer or oligomer (sol content) is large, the pressure sensitive adhesive layer is formed by the uncrosslinked polymer segregated in the vicinity of the adhesive layer interface in contact with the adherend. It is speculated that a fragile layer will be formed inside, but when the pressure-sensitive adhesive layer is exposed to a heated and humidified environment, the pressure-sensitive adhesive layer is broken near the fragile layer and the pressure-sensitive adhesive layer is peeled off. The degree of polydispersity (Mw / Mn) is preferably adjusted to 6 or less. The weight average molecular weight (Mw) and the degree of polydispersity (Mw / Mn) are measured by GPC (gel permeation chromatography) and determined from values calculated by polystyrene conversion.

  The production of such (meth) acrylic polymers can be appropriately selected from known production methods such as solution polymerization, bulk polymerization, emulsion polymerization, and various radical polymerizations. Among them, solution polymerization is preferable from the viewpoint of simplicity and versatility. preferable. The (meth) acrylic polymer to be obtained may be any of a random copolymer, a block copolymer, a graft copolymer and the like.

  In solution polymerization, for example, ethyl acetate, toluene or the like is used as a polymerization solvent. As a specific example of solution polymerization, the reaction is carried out under a stream of an inert gas such as nitrogen, usually with a polymerization initiator at about 50 to 70 ° C., for about 10 minutes to 30 hours. In particular, by shortening the polymerization time to about 30 minutes, the adhesion reliability of the pressure-sensitive adhesive can be improved by suppressing the formation of low molecular weight oligomers generated at the late stage of polymerization.

  The polymerization initiator, chain transfer agent, emulsifier and the like used for radical polymerization are not particularly limited and can be appropriately selected and used. The weight average molecular weight of the (meth) acrylic polymer can be controlled by the amount of the polymerization initiator and the chain transfer agent used, and the reaction conditions, and the amount used can be appropriately adjusted according to the type of these.

<Polymerization initiator>
As a polymerization initiator, for example, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [2- (5-methyl-2) -Imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis (2-methylpropionamidine) disulfate, 2,2'-azobis (N, N'-dimethylene isobutylamidine), 2,2 Azo initiators such as' -azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate (manufactured by Wako Pure Chemical Industries, Ltd., VA-057), persulfates such as potassium persulfate and ammonium persulfate , Di (2-ethylhexyl) peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butylperoxydika -Carbonate, t-butylperoxy neodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3- Tetramethylbutylperoxy-2-ethylhexanoate, di (4-methylbenzoyl) peroxide, dibenzoylperoxide, t-butylperoxyisobutyrate, 1,1-di (t-hexylperoxy) cyclohexane, Peroxide initiator such as t-butyl hydroperoxide, peroxide initiator such as hydrogen peroxide, combination of persulfate and sodium bisulfite, combination of peroxide such as peroxide and sodium ascorbate, and reducing agent in combination Although a redox type initiator etc. can be mentioned, it is not limited to these

  The polymerization initiators may be used alone or in combination of two or more, but the total content is 0.005 to about 100 parts by mass of the total amount of the monomer components. The amount is preferably about 1 part by mass, and more preferably about 0.02 to 0.5 parts by mass.

  In addition, as the polymerization initiator, for example, a (meth) acrylic polymer having the weight average molecular weight (Mw) and the polydispersity (Mw / Mn) is produced using 2,2′-azobisisobutyronitrile. For this purpose, the amount of the polymerization initiator used is preferably about 0.06 to 0.2 parts by mass, more preferably 0.08 to 0.175 parts by mass, with respect to 100 parts by mass of the total amount of the monomer components. It is preferable to have a degree.

  Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol and the like. The chain transfer agent may be used alone or as a mixture of two or more, but the total content is 0.1 parts by mass with respect to 100 parts by mass of the total amount of the monomer components. Less than or equal to.

  Moreover, as an emulsifier used when carrying out the emulsion polymerization, for example, anionic emulsifiers such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecyl benzene sulfonate, ammonium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, etc., polyoxy Nonionic emulsifiers, such as ethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene polyoxypropylene block polymer, etc. are mentioned. These emulsifiers may be used alone or in combination of two or more.

  Furthermore, reactive emulsifiers into which a radical polymerizable functional group such as propenyl group or allyl ether group has been introduced can be used as the emulsifier, and specifically, Aqualon HS-10, HS-20, KH-10, BC-05, BC-10, BC-20 (all from Dai-ichi Kogyo Seiyaku Co., Ltd.), Adekaria Soap SE10N (manufactured by Asahi Denka Co., Ltd.), etc. may be mentioned. Reactive emulsifiers are preferred because they are incorporated into the polymer chain after polymerization, which improves the water resistance. The amount of the emulsifier used is preferably 0.3 to 5 parts by mass, more preferably 0.5 to 1 parts by mass from the viewpoint of polymerization stability or mechanical stability, with respect to 100 parts by mass of the total amount of the monomer components.

<Crosslinking agent>
The pressure-sensitive adhesive composition for an optical film of the present invention is characterized by containing a crosslinking agent, preferably containing an isocyanate crosslinking agent and / or a peroxide crosslinking agent, and more preferably an isocyanate crosslinking agent and an peroxide crosslinking agent. It is using together and containing an oxide type crosslinking agent. By using an isocyanate-based crosslinking agent or a peroxide-based crosslinking agent, a (meth) acrylic polymer of high molecular weight can be prepared, and a pressure-sensitive adhesive layer excellent in stress relaxation properties can be obtained. It is preferable because it can be suppressed. In particular, by using a peroxide-based crosslinking agent, it becomes difficult to peel off, which is a preferable embodiment. Moreover, although there is no problem in practical use, when an isocyanate type crosslinking agent is used alone, it takes time to crosslink the pressure sensitive adhesive, and there is a possibility that productivity may be lowered.

  As said isocyanate type crosslinking agent, the compound which has an isocyanate group at least 2 can be used. For example, known aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates and the like generally used for the urethanization reaction may be used.

  Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4- Trimethyl hexamethylene diisocyanate etc. are mentioned.

  Examples of the alicyclic isocyanate include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate Hydrogenated tetramethyl xylylene diisocyanate and the like can be mentioned.

  Examples of the aromatic diisocyanate include phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 4'- toluidine diisocyanate, 4, 4'- diphenyl ether diisocyanate, 4, 4'- diphenyl diisocyanate, 1, 5- naphthalene diisocyanate, xylylene diisocyanate etc. are mentioned.

  Further, as the isocyanate-based crosslinking agent, a multimer (dimer, trimer, pentamer, etc.) of the diisocyanate, a urethane modified product reacted with a polyhydric alcohol such as trimethylolpropane, a urea modified product, Biuret modified products, alphanate modified products, isocyanurate modified products, carbodiimide modified products and the like.

  As a commercial item of the isocyanate type crosslinking agent, for example, trade names "Millionate MT", "Millionate MTL", "Millionate MR-200", "Millionate MR-400", "Corronate L", "Corronate HL", "Corronate HX" [or more, Made by Tosoh Corporation]; trade name "Takenate D-110N" "Takenate D-120N" "Takenate D-140N" "Takenate D-160N" "Takenate D-165N" "Takenate D-170HN" "Takenate D-178N" " Takenate 500, "Takenate 600" [above, Mitsui Chemicals, Inc.]; and the like. These compounds may be used alone or in combination of two or more.

  As said isocyanate type crosslinking agent, aliphatic polyisocyanate and the aliphatic polyisocyanate type compound which is its modified body are preferable. The aliphatic polyisocyanate compound has a crosslinked structure richer in flexibility than other isocyanate crosslinking agents, easily relaxes the stress associated with expansion / contraction of the optical film, and is less likely to be peeled off in the durability test. Especially as an aliphatic polyisocyanate type compound, hexamethylene diisocyanate and its modified substance are preferable.

  The peroxide-based crosslinking agent (simply referred to as a peroxide) may be a base polymer ((meth) acrylic polymer) of a pressure-sensitive adhesive composition by generating radically active species by heating or light irradiation. Any crosslinking agent can be used as long as it promotes crosslinking, but in consideration of workability and stability, it is preferable to use a peroxide having a half-life temperature of 80 to 160 ° C. for 1 minute, and 90 to It is more preferred to use a peroxide which is 140 ° C.

  As a peroxide which can be used, for example, di (2-ethylhexyl) peroxydicarbonate (one-minute half-life temperature: 90.6 ° C.), di (4-t-butylcyclohexyl) peroxydicarbonate (1 Half-life temperature: 92.1 ° C), di-sec-butylperoxydicarbonate (one-minute half-life temperature: 92.4 ° C), t-butyl peroxy neodecanoate (one-minute half-life temperature: 103) .5 ° C), t-hexylperoxypivalate (one-minute half-life temperature: 109.1 ° C), t-butylperoxypivalate (one-minute half-life temperature: 110.3 ° C), dilauroyl peroxide (one-minute half-life temperature: 110.3 ° C) 1 minute half-life temperature: 116.4 ° C.), di-n-octanoyl peroxide (1 minute half-life temperature: 117.4 ° C.), 1,1,3,3-tetramethylbutyl peroxide Oxy-2-ethylhexanoate (one-minute half-life temperature: 124.3 ° C), di (4-methylbenzoyl) peroxide (one-minute half-life temperature: 128.2 ° C), dibenzoyl peroxide (one-minute half-life Temperature: 130.0 ° C.), t-butyl peroxyisobutyrate (one-minute half-life temperature: 136.1 ° C.), 1,1-di (t-hexylperoxy) cyclohexane (one-minute half-life temperature: 149.2 ° C.) and the like. Among them, since the crosslinking reaction efficiency is particularly excellent, di (4-t-butylcyclohexyl) peroxydicarbonate (one-minute half-life temperature: 92.1 ° C.), dilauroyl peroxide (one-minute half-life temperature: 116. 4 ° C.), dibenzoyl peroxide (one-minute half-life temperature: 130.0 ° C.), etc. are preferably used.

  In addition, the half life of peroxide is an index showing the decomposition rate of peroxide, and refers to the time until the remaining amount of peroxide is halved. The decomposition temperature for obtaining the half life at any time and the half life time at any temperature are described in the manufacturer catalog etc. For example, “Organic peroxide catalog 9th edition of Nippon Oil and Fats Co., Ltd. (May 2003) and the like.

  In addition, as a measuring method of the peroxide decomposition amount which remained after reaction processing, it can measure, for example by HPLC (high performance liquid chromatography).

  More specifically, for example, about 0.2 g each of the pressure-sensitive adhesive composition after reaction treatment is taken out, immersed in 10 mL of ethyl acetate, shaken and extracted at 120 rpm for 3 hours at 25 ° C. with a shaker, and then room temperature Let stand for 3 days. Then, add 10 mL of acetonitrile, shake at 120 rpm for 30 minutes at 25 ° C., filter through a membrane filter (0.45 μm), and inject about 10 μL of the extract into HPLC for analysis. The amount of peroxide can be used.

  The amount of the crosslinking agent used is preferably 0.01 to 3 parts by mass, more preferably 0.03 to 2 parts by mass, and further preferably 0.05 to 2 parts by mass with respect to 100 parts by mass of the (meth) acrylic polymer. 1 part by mass is preferred. In addition, if the crosslinking agent is less than 0.01 parts by mass, the pressure-sensitive adhesive layer may be insufficiently crosslinked, and the durability and the adhesion properties may not be satisfied. On the other hand, if more than 3 parts by mass, the pressure-sensitive adhesive layer becomes too hard Durability tends to decrease.

  The compounding ratio of the isocyanate-based crosslinking agent to the peroxide-based crosslinking agent (isocyanate-based crosslinking agent: peroxide-based crosslinking agent) is preferably 0: 100 to 50: 50, and more preferably 0: 100 to 40: 60. preferable.

  The pressure-sensitive adhesive composition for an optical film of the present invention can contain a silane coupling agent. Durability can be improved by using a silane coupling agent. Specific examples of the silane coupling agent include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3, Epoxy group-containing silane coupling agent such as 4-epoxycyclohexyl) ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl- Amino group-containing silane coupling agents such as N- (1,3-dimethylbutylidene) propylamine, N-phenyl-γ-aminopropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltritriol (Meth) acrylics such as ethoxysilane Containing silane coupling agents, such as isocyanate-containing silane coupling agent such as 3-isocyanate propyl triethoxysilane and the like. As the silane coupling agent exemplified above, an epoxy group-containing silane coupling agent is preferable.

  In addition, as the silane coupling agent, one having a plurality of alkoxysilyl groups in the molecule can also be used. Specifically, for example, Shin-Etsu Chemical X-41-1053, X-41-1059A, X-41-1056, X-41-1805, X-41-1818, X-41-1810, X-40. -2651 and the like. A silane coupling agent having a plurality of alkoxysilyl groups in these molecules is difficult to volatilize, and is effective for improving the durability because it has a plurality of alkoxysilyl groups, and is preferable. The silane coupling agent having a plurality of alkoxysilyl groups in the molecule is preferably one having an epoxy group in the molecule, and more preferably two or more epoxy groups in the molecule. Silane coupling agents having a plurality of alkoxysilyl groups in the molecule and having an epoxy group tend to have good durability. Specific examples of silane coupling agents having a plurality of alkoxysilyl groups in the molecule and having an epoxy group include X-4-1105, X-41-1059A, X-41-1056 manufactured by Shin-Etsu Chemical Co., Ltd. Shin-Etsu Chemical Co., Ltd. X-41-1056 having a high epoxy group content is preferred.

  The silane coupling agent may be used alone or as a mixture of two or more, but the total content is the above relative to 100 parts by mass of the (meth) acrylic polymer. As a silane coupling agent, 0.001-5 mass parts is preferable, 0.01-1 mass part is more preferable, 0.02-1 mass part is still more preferable, 0.05-0.6 mass part is especially preferable. If it is in the said range, it will become the quantity which improves durability and it holds the adhesive force to glass etc. moderately, and is preferable.

  Furthermore, the pressure-sensitive adhesive composition for an optical film may contain other known additives as long as the properties are not impaired. For example, antistatic agents (ions such as ionic liquids and alkali metal salts) may be contained. Compounds), colorants, powders such as pigments, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet light An absorber, a polymerization inhibitor, an inorganic or organic filler, a metal powder, a particulate form, a foil, etc. can be suitably added according to the use to be used. Moreover, you may employ | adopt the redox system which added the reducing agent in the range which can be controlled. These additives are preferably used in an amount of 5 parts by mass or less, further 3 parts by mass or less, and further 1 part by mass or less with respect to 100 parts by mass of the (meth) acrylic polymer.

<Pressure-sensitive adhesive layer>
The pressure-sensitive adhesive composition for an optical film can be formed by the pressure-sensitive adhesive composition for an optical film, and in forming the pressure-sensitive adhesive layer, the crosslinking treatment temperature and the crosslinking treatment time can be adjusted It is preferable to fully consider the effects of

  The crosslinking temperature and the crosslinking time can be adjusted depending on the crosslinking agent used. The crosslinking temperature is preferably 170 ° C. or less.

  The crosslinking treatment may be performed at a temperature at the drying step of the pressure-sensitive adhesive layer, or may be separately performed after the drying step by separately providing a crosslinking treatment step.

  The crosslinking time can be set in consideration of productivity and workability, but is usually about 0.2 to 20 minutes, and preferably about 0.5 to 10 minutes.

<Optical film with adhesive layer>
The pressure-sensitive adhesive layer-carrying optical film of the present invention preferably has the pressure-sensitive adhesive layer for an optical film formed on at least one side of the optical film. The optical film with a pressure-sensitive adhesive layer using the pressure-sensitive adhesive layer for an optical film is useful because it can suppress display unevenness caused by foaming or peeling even when exposed to heating and humidifying conditions. In addition, as the optical film, a polarizing film (polarizing plate), a retardation film, an optical compensation film, a brightness enhancement film, or a laminate of these may be used.

  The pressure-sensitive adhesive layer may be formed, for example, by applying the pressure-sensitive adhesive composition to a release-treated separator or the like, removing the polymerization solvent or the like by drying to form a pressure-sensitive adhesive layer, The pressure-sensitive adhesive composition is applied to an optical film, and a polymerization solvent or the like is removed by drying to form a pressure-sensitive adhesive layer on the optical film. In addition, in application | coating of an adhesive, you may newly add 1 or more types of solvent other than a polymerization solvent suitably.

<Separator>
A silicone release liner is preferably used as the release-treated separator. In the step of applying and drying the pressure-sensitive adhesive composition of the present invention on such a liner to form a pressure-sensitive adhesive layer, as a method of drying the pressure-sensitive adhesive, an appropriate method is appropriately adopted depending on the purpose. obtain. Preferably, the method of heat-drying the film | membrane (coating film) which apply | coated the said adhesive composition is used. The heating and drying temperature is preferably 40 to 200 ° C., more preferably 50 to 180 ° C., and particularly preferably 70 to 170 ° C. By making heating temperature into said range, the adhesive which has the outstanding adhesion characteristic can be obtained.

  As the drying time, any appropriate time may be employed. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, and particularly preferably 10 seconds to 5 minutes.

  Moreover, an adhesive layer can be formed after forming an anchor layer on the surface of an optical film, or performing various easy adhesion processes, such as a corona treatment and a plasma treatment. Further, the surface of the pressure-sensitive adhesive layer may be subjected to an easy adhesion treatment.

  Various methods are used as a method of forming the pressure-sensitive adhesive layer. Specifically, for example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, die coater etc. Methods such as extrusion coating may be mentioned.

  The thickness of the pressure-sensitive adhesive layer is not particularly limited, and is, for example, about 1 to 100 μm. Preferably, it is 2 to 50 μm, more preferably 2 to 40 μm, and still more preferably 5 to 35 μm.

  When the pressure-sensitive adhesive layer is exposed, the pressure-sensitive adhesive layer may be protected with a release-treated sheet (separator) until it is practically used.

  As a constituent material of the separator, for example, plastic films such as polyethylene, polypropylene, polyethylene terephthalate, polyester film, porous materials such as paper, cloth, non-woven fabric, nets, foam sheets, metal foils, laminates thereof, etc. Although an appropriate thin film etc. can be mentioned, a plastic film is used suitably from the point which is excellent in surface smoothness.

  The plastic film is not particularly limited as long as it is a film capable of protecting the pressure-sensitive adhesive layer, and for example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride film A polymer film, a polyethylene terephthalate film, a polybutylene terephthalate film, a polyurethane film, an ethylene-vinyl acetate copolymer film and the like can be mentioned.

  The thickness of the separator is generally 5 to 200 μm, preferably about 5 to 100 μm. The separator may be, if necessary, a release agent of silicone type, fluorine type, long chain alkyl type or fatty acid amide type, release by silica powder etc., antifouling treatment, coating type, kneading type, evaporation type Etc. can also be performed. In particular, the peelability from the pressure-sensitive adhesive layer can be further enhanced by appropriately performing the peeling treatment such as silicone treatment, long-chain alkyl treatment, fluorine treatment and the like on the surface of the separator.

  In addition, the sheet | seat which carried out the peeling process used in preparation of said optical film with an adhesive layer can be used as a separator of an optical film with an adhesive layer as it is, and can be simplified in a process surface.

<Image display device>
In the present invention, an image display apparatus using at least one optical film with a pressure-sensitive adhesive layer can also be obtained. As the optical film, those used for forming an image display device such as a liquid crystal display device are used, and the type thereof is not particularly limited. For example, a polarizing film is mentioned as said optical film. The polarizing film may include a polarizer, and one having a transparent protective film on one side or both sides of the polarizer may be used.

  The polarizer is not particularly limited, and various types of polarizers can be used. As a polarizer, for example, a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, or an ethylene / vinyl acetate copolymer-based partially saponified film, dichroism of iodine or a dichroic dye Examples thereof include those obtained by adsorbing a substance and uniaxially stretched, and dehydrated products of polyvinyl alcohol and dehydrochlorinated products of polyvinyl chloride such as polyene-based oriented films. Among these, a polarizer made of a polyvinyl alcohol film and a dichroic substance such as iodine is preferable.

  A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine and uniaxially stretching it may be prepared, for example, by dyeing the polyvinyl alcohol-based film by immersing it in an aqueous solution of iodine and stretching it to 3 to 7 times the original length. it can. It can also be immersed in an aqueous solution such as potassium iodide which may contain boric acid, zinc sulfate, zinc chloride and the like as required. Furthermore, before dyeing, the polyvinyl alcohol-based film may be dipped in water and rinsed if necessary. In addition to being able to wash the stains and antiblocking agents on the surface of the polyvinyl alcohol film by washing the polyvinyl alcohol film with water, it is also possible to prevent unevenness such as uneven dyeing by swelling the polyvinyl alcohol film. is there. The stretching may be performed after staining with iodine, may be stretching while staining, or may be stretched and then stained with iodine. It can also be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

  The thickness of the polarizer is preferably 5 to 40 μm. From the viewpoint of thinning, the thickness is more preferably 30 μm or less, and still more preferably 25 μm or less. Such a thin polarizer has less thickness unevenness, excellent visibility, and less dimensional change, so it is excellent in durability even under heating and humidifying conditions, and foaming and peeling hardly occur, and further, It is preferable that the thickness as a polarizing film can be reduced.

  As a thin polarizer, typically, the specification of Japanese Patent Application Laid-Open Nos. 51-069644, 2000-338329, WO 2010/100917, PCT / JP2010 / 001460, or Japanese Patent Application No. 2010- Examples thereof include thin polarizing films described in Japanese Patent Application Laid-Open No. 269002 and Japanese Patent Application No. 2010-263692. These thin polarizing films can be obtained by a manufacturing method including the steps of stretching a polyvinyl alcohol resin (hereinafter, also referred to as a PVA resin) layer and a stretching resin base material in the state of a laminate and dyeing. With this manufacturing method, even if the PVA-based resin layer is thin, it is possible to stretch without any problems such as breakage due to stretching by being supported by the stretching resin base material.

  Among the thin polarizing films described above, among the processes of stretching in the state of a laminate and the process of dyeing, WO2010 / 100917 pamphlet, in that it can be stretched at high magnification to improve polarization performance. Preferred are those obtained by the process comprising drawing in an aqueous solution of boric acid as described in the specification of JP2010 / 001460, or Japanese Patent Application No. 2010-269002 and Japanese Patent Application No. 2010-263692, particularly What is obtained by the manufacturing method which includes the process of air-drawing auxiliary | assistant before extending | stretching in the boric-acid aqueous solution which is described in Japanese Patent Application No. 2010-269002 specification and Japanese Patent Application No. 2010-263692 specification is preferable.

  As a material which comprises a transparent protective film, the thermoplastic resin which is excellent in transparency, mechanical strength, heat stability, water blocking property, isotropy etc. is used, for example. Specific examples of such thermoplastic resin include cellulose resin such as triacetyl cellulose, polyester resin, polyether sulfone resin, polysulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, (meth) acrylic resin, cyclic Polyolefin resin (norbornene resin), polyarylate resin, polystyrene resin, polyvinyl alcohol resin, and mixtures thereof are mentioned. In addition, although a transparent protective film is bonded together by an adhesive layer on one side of the polarizer, (meth) acrylic, urethane, acrylic urethane, epoxy, silicone as a transparent protective film on the other side. A thermosetting resin such as a resin or an ultraviolet curable resin can be used. The transparent protective film may contain one or more types of any appropriate additive. Examples of the additive include ultraviolet light absorbers, antioxidants, lubricants, plasticizers, mold release agents, coloring inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, colorants and the like. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by mass, more preferably 50 to 99% by mass, still more preferably 60 to 98% by mass, and particularly preferably 70 to 97% by mass. . When content of the said thermoplastic resin in a transparent protective film is 50 mass% or less, there exists a possibility that the high transparency etc. which a thermoplastic resin originally has can not fully be expressed.

  The adhesive used to bond the polarizer and the transparent protective film is not particularly limited as long as it is optically transparent, and various types of aqueous, solvent, hot melt, radical curable and cationic curable types are used. However, water-based adhesives or radical curing adhesives are preferred.

  In addition, as an optical film, for example, for formation of a liquid crystal display device such as a reflection plate, an anti-transmission plate, a retardation film (including a wave plate such as 1⁄2 or 1⁄4), a visual compensation film, a brightness enhancement film, etc. What becomes an optical layer which may be used is mentioned. These may be used alone as an optical film, or may be used as one layer or two or more layers laminated to the polarizing film in practical use.

  An optical film in which the above optical layer is laminated on a polarizing film can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. It is excellent in stability, assembly work, etc., and there is an advantage that the manufacturing process of a liquid crystal display etc. can be improved. An appropriate adhesion means such as an adhesive layer may be used for lamination. When bonding the polarizing film and the other optical layers, the optical axes thereof can be set at an appropriate arrangement angle in accordance with the target retardation characteristics and the like.

  The pressure-sensitive adhesive layer-carrying optical film of the present invention can be preferably used for the formation of various image display devices such as liquid crystal display devices. The formation of the liquid crystal display can be performed according to the prior art. That is, in general, a liquid crystal display device is formed by appropriately assembling a display panel such as a liquid crystal cell, an adhesive film with an adhesive layer, and an optional component such as an illumination system and incorporating a drive circuit. In the present invention, there is no particular limitation except that the pressure-sensitive adhesive layer-attached optical film according to the present invention is used, and the method may be conventional. The liquid crystal cell may also be of any type such as TN type, STN type, π type, VA type, or IPS type.

  It is possible to form an appropriate liquid crystal display device such as a liquid crystal display device in which an adhesive film with an adhesive layer is disposed on one side or both sides of a display panel such as a liquid crystal cell, or a backlight or a reflector for an illumination system. . In that case, the pressure-sensitive adhesive layer-attached optical film according to the present invention can be disposed on one side or both sides of a display panel such as a liquid crystal cell. When optical films are provided on both sides, they may be the same or different. Furthermore, when forming a liquid crystal display device, one or more appropriate components such as a diffusion layer, an antiglare layer, an antireflective film, a protective plate, a prism array, a lens array sheet, a light diffusion sheet, and a backlight are provided at appropriate positions. Two or more layers can be arranged.

  EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples. All parts and% in each example are based on mass. The room temperature standing conditions which are not particularly specified below are all 23 ° C. × 65% RH.

<Measurement of weight average molecular weight (Mw) of (meth) acrylic polymer>
The weight average molecular weight (Mw) of the (meth) acrylic polymer was measured by GPC (gel permeation chromatography). The polydispersity (Mw / Mn, molecular weight distribution) of the (meth) acrylic polymer was also measured in the same manner.
・ Analyzer: HLC-8120 GPC manufactured by Tosoh Corporation
・ Column: Tosoh Corporation, G7000H _XL + GMH _XL + GMH _XL
・ Column size: Each 7.8mmφ × 30cm in total 90cm
・ Column temperature: 40 ° C
・ Flow rate: 0.8mL / min
Injection volume: 100 μL
Eluent: Tetrahydrofuran Detector: Differential Refractometer (RI)
Standard sample: polystyrene

<Preparation of Polarizing Film (Polarizing Plate)>
A 60 μm thick polyvinyl alcohol film was stretched up to 3 times between rolls with different speed ratios while dyeing at 30 ° C. in a 0.3% iodine solution for 1 minute. Thereafter, the film was stretched to a total draw ratio of 6 times while being immersed for 0.5 minutes in an aqueous solution containing 60% of boric acid at 4% concentration and potassium iodide at 10% concentration. Subsequently, after washing | cleaning by immersing in 30 degreeC and the aqueous solution containing 1.5% density | concentration potassium iodide for 10 seconds, drying was performed at 50 degreeC for 4 minutes, and the 22-micrometer-thick polarizer was obtained. A saponified triacetylcellulose (TAC) film having a thickness of 40 μm was bonded to both sides of the polarizer with a polyvinyl alcohol-based adhesive to prepare a polarizing film (polarizing plate).

Example 1
(Preparation of (meth) acrylic polymer (A1))
20 parts of 2-methoxyethyl acrylate, 62.1 parts of butyl acrylate, 1 part of 4-hydroxybutyl acrylate, phenoxyethyl acrylate 16 in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler A monomer mixture containing part, 0.9 part of N-vinyl-pyrrolidone was charged. Furthermore, 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator is charged with 85 parts of ethyl acetate and 15 parts of toluene with respect to 100 parts of the monomer mixture (solid content), and the frame is gently stirred. While introducing nitrogen gas while replacing with nitrogen, the liquid temperature in the flask is maintained at around 55 ° C and polymerization reaction is performed for 6 hours, weight average molecular weight (Mw) 2.26 million, polydispersity (Mw / Mn) A solution of 4.6 (meth) acrylic polymer (A1) was prepared.

(Preparation of pressure-sensitive adhesive composition)
0.1 parts of an isocyanate-based crosslinking agent (Takenate D-160N, trimethylolpropane hexamethylene diisocyanate manufactured by Mitsui Chemicals, Inc.) with respect to 100 parts of the solid content of the solution of the (meth) acrylic polymer (A1) obtained above And 0.3 part of a peroxide-based crosslinking agent (Niper BMT, manufactured by NOF Corp., benzoyl peroxide), silane coupling agent (X-41-1810, manufactured by Shin-Etsu Chemical Co., Ltd., thiol group-containing silicate oligomer) 0 One part was blended to prepare a solution of the acrylic pressure-sensitive adhesive composition.

(Preparation of polarizing film with pressure-sensitive adhesive layer)
Then, the solution of the acrylic pressure-sensitive adhesive composition is treated with a silicone-based release agent on one side of a polyethylene terephthalate film (separator film: MRF 38, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) The solution was applied to a thickness of 20 μm and dried at 155 ° C. for 1 minute to form an adhesive layer on the surface of the separator film. Subsequently, the pressure-sensitive adhesive layer formed on the separator film was transferred to the produced polarizing film to produce a polarizing film with a pressure-sensitive adhesive layer.

(Preparation of (meth) acrylic polymer (A2) to (A8))
(Preparation of (meth) acrylic polymer (A1)) (meth) acrylic polymer (A2) to (A8) in the same manner except that the monomer composition of the feed is changed as shown in Table 1 Solution was prepared.

(Preparation of (meth) acrylic polymer (A9))
In (Preparation of (meth) acrylic polymer (A1)), as shown in Table 1, the monomer composition of charged is 76 parts of butyl acrylate, 16 parts of phenoxyethyl acrylate, 7 parts of N-vinyl-pyrrolidone, 4-hydroxybutyl A solution of (meth) acrylic polymer (A9) was prepared in the same manner as in 1 part of acrylate, and the like.

(Preparation of (meth) acrylic polymer (A10))
In (Preparation of (meth) acrylic polymer (A1)), as shown in Table 1, 50 parts of 2-methoxyethyl acrylate, 49 parts of butyl acrylate, 1 part of 4-hydroxybutyl acrylate, etc. Similarly, a solution of (meth) acrylic polymer (A10) was prepared.

(Preparation of (meth) acrylic polymer (A11))
In (Preparation of (meth) acrylic polymer (A1)), as shown in Table 1, the monomer composition of the feed is 90 parts of 2-methoxyethyl acrylate, 9 parts of butyl acrylate, 1 part of 4-hydroxybutyl acrylate, and others Similarly, a solution of (meth) acrylic polymer (A11) was prepared.

<Examples 2 to 10, Comparative Examples 1 to 3>
In Examples 2 to 10 and Comparative Examples 1 to 3, as shown in Table 1, as in Example 1, the types of monomers, their use proportions are changed, and the manufacturing conditions are controlled. Solutions of (meth) acrylic polymers (A2) to (A11) having the polymer physical properties (weight-average molecular weight (Mw) and polydispersity (Mw / Mn)) shown were prepared.
In addition, as shown in Table 1, an acrylic pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that the amount of the crosslinking agent used was changed with respect to the obtained solution of each (meth) acrylic polymer. Solution was prepared. In addition, about the polymerization initiator and silane coupling agent which have no description of a compounding quantity in a table | surface, the same amount as Example 1 was used.
Furthermore, using the solution of the acrylic pressure-sensitive adhesive composition, as shown in Table 1, a polarizing film with a pressure-sensitive adhesive layer was produced in the same manner as Example 1.

  The following evaluation was performed about the polarizing film with an adhesive layer obtained by the said Example and comparative example. The evaluation results are shown in Table 2.

<Durability test>
What cut the polarizing film with an adhesive layer obtained by the said Example and comparative example into 15 inch size was made into the sample. ITO glass (Geomatec Co., Ltd.) formed by depositing the sample on a 0.7 mm thick non-alkali glass (manufactured by Corning, EG-XG) to have a film thickness of 20 nm at a Sn ratio of 3% It bonded to a 0.7 mm alkali free glass (manufactured by Corning, EG-XG) using a laminator. Then, the sample was autoclaved at 50 ° C. and 0.5 MPa for 15 minutes to completely adhere the sample to the adherend. The treated sample is treated for 500 hours under each atmosphere of 105 ° C. and 65 ° C. × 95% RH, and then, it is placed between the polarizing film, the ITO glass, and the alkali-free glass. The appearance was visually evaluated according to the following criteria.
(Evaluation criteria)
◎: No change in appearance such as foaming or peeling at all. There is no problem in practical use.
○: Slight peeling or foaming at the end, but no problem in practical use.
Δ: Peeling or foaming at the end, but there is no problem in practical use unless it is a special application.
X: Remarkable peeling at the end, and there is a problem in practical use.

<Reworkability>
What cut | judged the polarizing film with an adhesive layer into length 120 mm x width 25 mm was made into the sample. The laminator was applied to ITO glass (Geomatec Co., Ltd.) which was formed to have a film thickness of 20 nm with a Sn ratio of 3% on a 0.7 mm thick alkali-free glass (manufactured by Corning, EG-XG). The adhesion of the sample was measured after complete adhesion by using a paste and then autoclaving at 50 ° C., 5 atm for 15 minutes. The adhesion is measured by using a tensile tester (Autograph SHIMAZU AG-1 10KN) to peel off the sample at a peel angle of 90 ° and a peel rate of 300 mm / min (N / 25 mm, measuring length 80 mm). It asked by doing. The measurement was performed twice and the average value was taken as the measurement value.
(Evaluation criteria)
:: Adhesive strength less than 10 N (no problem in practical use)
Good: Adhesive strength less than 10 to 13 N (no problem in practical use)
:: Adhesive strength less than 13 to 16 N (no problem in practical use)
X: Adhesive strength 16 N or more (there is a problem in practical use)

（評価基準）
○：抵抗値変化が１．２０以下
×：抵抗値変化が１．２０より大きい <Metal corrosion resistance (ITO corrosion resistance)>
What cut the polarizing film with an adhesive layer into 15 mm x 15 mm was made into the sample. The sample is attached to the center of a 20 mm × 20 mm ITO glass (Diomatec Co., Ltd. product) formed to a film thickness of 20 nm with a Sn ratio of 3% and autoclaved at 50 ° C and 5 atm for 15 minutes It was used as a measurement sample of corrosion resistance. The resistance value of the obtained measurement sample was measured using a measuring device described later, and this was taken as the “initial resistance value”.
Thereafter, the measurement sample was put into an environment of 65 ° C. × 95% RH for 500 hours, and the resistance value was measured to obtain “resistance value after wet heat”. In addition, the said resistance value measured using the product made by Accent Optical Technologies, and HL5500PC. From the “initial resistance value” and the “resistance value after wet heat” measured as described above, “resistance value change” was calculated by the following equation and evaluated according to the following criteria.

(Evaluation criteria)
○: change in resistance is 1.20 or less ×: change in resistance is greater than 1.20

Abbreviations etc. in Table 1 are described below.
MEA: 2-methoxyethyl acrylate BA: butyl acrylate PEA: phenoxyethyl acrylate NVP: N-vinyl-pyrrolidone AA: acrylic acid HBA: 4-hydroxybutyl acrylate isocyanate D160: Takenate D-160N (trimethylolpropane manufactured by Mitsui Chemicals, Inc. Adducts of hexamethylene diisocyanate)
Peroxide: nyper BMT (benzoyl peroxide) manufactured by NOF Corporation

  From the results in Table 2, in all the Examples, by using the pressure-sensitive adhesive layer for an optical film formed using a pressure-sensitive adhesive composition containing a (meth) acrylic polymer containing a specific monomer in a specific ratio, It has been confirmed that the durability (heat resistance, moisture resistance, peeling resistance) and reworkability are excellent. Moreover, by not using a carboxyl group-containing monomer, it confirmed that it was excellent also in metal corrosion resistance (ITO corrosion resistance), and it was confirmed that it is practical also in the use as which these characteristics are required. .

  On the other hand, in Comparative Examples, by using a (meth) acrylic polymer which does not contain a specific monomer or does not contain a specific monomer in a specific ratio, those which can simultaneously satisfy all the evaluation items of durability It was not obtained.

1 adhesive layer 2 separator 3 polarizer 4 and 4 'protective film 5 polarizing film (polarizing plate)
10 Polarizing film with adhesive layer

Claims (7)

An adhesive composition for an optical film, comprising a (meth) acrylic polymer and a crosslinking agent,
The (meth) acrylic polymer contains, as monomer units, an amide group-containing monomer and an alkoxy group-containing alkyl (meth) acrylate.
A pressure-sensitive adhesive composition for an optical film, comprising 20 to 80% by mass of the alkoxy group-containing alkyl (meth) acrylate relative to a total amount of 100% by mass of monomer units constituting the (meth) acrylic polymer.   0.9-7 mass% of the amide group-containing monomer and 25-75 mass of the alkoxy group-containing alkyl (meth) acrylate relative to the total amount of 100 mass% of monomer units constituting the (meth) acrylic polymer %. 2. The pressure-sensitive adhesive composition for an optical film according to claim 1, wherein the composition comprises   0.9 to 3% by mass of the amide group-containing monomer and 35 to 75% by mass of the alkoxy group-containing alkyl (meth) acrylate based on 100% by mass in total of monomer units constituting the (meth) acrylic polymer %. 3. The pressure-sensitive adhesive composition for an optical film according to claim 1 or 2, characterized in that   0.9 to 3 mass% of the amide group-containing monomer and 50 to 75 mass of the alkoxy group-containing alkyl (meth) acrylate, based on 100 mass% of the total amount of monomer units constituting the (meth) acrylic polymer The pressure-sensitive adhesive composition for an optical film according to any one of claims 1 to 3, which is contained in an amount of 50%.   The pressure-sensitive adhesive composition for an optical film according to any one of claims 1 to 4, wherein the (meth) acrylic polymer does not contain a carboxyl group-containing monomer as a monomer unit.   A pressure-sensitive adhesive layer for an optical film, comprising the pressure-sensitive adhesive composition for an optical film according to any one of claims 1 to 5. An optical film with a pressure-sensitive adhesive layer, comprising the pressure-sensitive adhesive layer for an optical film according to claim 6 on at least one side of the optical film.

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