TWI494394B - Adhesive layer and adhesive film - Google Patents

Description

Adhesive layer and adhesive film

The present invention relates to an adhesive layer for interlayer bonding or the like of an optical member, and an adhesive film using the adhesive layer. The adhesive layer has a film having a thickness of 1 μm to 20 μm, but has high adhesion and high adhesion.

In order to bond an optical member such as a polarizing plate or a retardation film to an adherend such as a liquid crystal cell by an adhesive layer, various adhesive films have been proposed (for example, refer to Patent Documents 1 and 2).

Patent Document 1 describes an optical adhesive composition containing a butyl acrylate or the like as a main component and containing an acrylamide compound or the like.

Patent Document 2 describes an optical device in which a (meth) acrylate having an alkyl group having 4 to 8 carbon atoms is used as a main component monomer, and a carboxyl group-containing monomer and a nitrogen-containing vinyl monomer are contained. Adhesive composition.

Further, in order to increase the refractive index of the adhesive layer, various adhesive films have been proposed through repeated studies (for example, refer to Patent Documents 3 to 8).

Patent Document 3 describes an optical adhesive composition having an aromatic ring and containing a tackifier having a refractive index of 1.51 to 1.75.

Patent Document 4 describes an adhesive sheet using an adhesive composition containing a copolymerizable polymer which is a copolymerizable polymer of an aromatic ring-containing acrylic modified monomer.

Patent Document 5 describes an optical adhesive composition containing a tackifier resin having an aromatic ring and an aromatic phosphate plasticizer.

Patent Document 6 describes an adhesive formed by curing an adhesive composition comprising: an acrylic resin; and an aromatic compound containing one ethylenically unsaturated group.

Patent Document 7 describes an optical element in which a retardation film and a birefringent plate are fixed to each other by an acrylic adhesive containing an aromatic monomer.

Patent Document 8 describes an adhesive composition containing a polyurethane resin obtained by reacting an aromatic diisocyanate with an aromatic polyester diol.

In recent years, in order to achieve thinning of an optical member, an adhesive film for interlayer bonding of an optical member is required to be an adhesive film in which the adhesive layer is a thin layer having a thickness of 20 μm or less.

Generally, the adhesive force of the adhesive layer is approximately proportional to the thickness of the adhesive layer. Therefore, if the thickness of the adhesive layer is made thinner, the adhesive force is lowered.

However, in recent years, it is required that the adhesive film has the same performance as that of the conventional adhesive film (the adhesive layer is a thick layer having a thickness of about 30 μm) even when the thickness of the adhesive layer is reduced, and for high temperature, The durability after standing for a long time in a high-humidity environment also has the same performance as that of the conventional adhesive film.

In addition, from the viewpoint of being able to reduce the thickness of the pressure-sensitive adhesive layer and forming an adhesive layer that does not require aging treatment (curing at a constant temperature), it is required to form a NCF (Non Carrier Film). It has a member structure of a "release film/adhesive layer/release film" including an adhesive layer from which a base material of an adhesive film is removed.

Further, in the conventional adhesive film, since the adhesive film is bonded to the adherend and then subjected to the aging treatment, the adhesion between the adherend and the adhesive layer can be improved.

However, the adhesive film of the NCF form has been subjected to the aging treatment of the adhesive layer, and thus the adhesion between the adherend and the adhesive layer is insufficient. Based on this, there is a problem that it is necessary to perform surface treatment such as corona treatment on the surface of the adherend.

There is therefore a need for an adhesive film that meets these requirements and overcomes these problems.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2012-177022

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2012-201734

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2007-084762

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2011-153169

[Patent Document 5] Japanese Patent Laid-Open Publication No. 2012-167188

[Patent Document 6] Japanese Patent Laid-Open Publication No. 2012-021148

[Patent Document 7] Japanese Patent Laid-Open Publication No. 2006-293281

[Patent Document 8] Japanese Patent Laid-Open Publication No. 2009-091522

The present invention has been made in view of the above circumstances, and an object of the invention is to provide an adhesive layer having high adhesion and high adhesion, and an adhesive film using the adhesive layer, although the film has a thickness of 1 μm to 20 μm.

In order to solve the above problems, the present invention has a technical idea of (meth) having an alkyl group having a carbon number of C1 to C14 in an adhesive layer obtained by crosslinking an adhesive composition comprising an acrylic polymer. a monomer having at least one of an alkyl acrylate monomer as a main component and containing at least one of a copolymerizable nitrogen-containing vinyl monomer as another copolymerizable monomer, which is toughened by copolymerization and crosslinking Adhesive and highly adherent adhesive layer.

Further, in order to solve the above problems, the present invention provides an adhesive layer which is obtained by crosslinking an adhesive composition comprising an acrylic polymer containing (meth)acrylic acid as a main component. At least one or more of the alkyl (meth)acrylic acid ester monomers having an alkyl group having a C1 to C14 alkyl group having at least one alkyl group and a aryl group-containing (meth) acrylate monomer, and containing At least one or more of the nitrogen-containing vinyl monomers of the other copolymerizable monomer, at least one of the carboxyl group-containing copolymerizable vinyl monomer and/or the hydroxyl group-containing copolymerizable vinyl monomer, Moreover, the thickness of the adhesive layer is 1 μm to 20 μm, and the thickness is 5 μm. The adhesion is 4.0 (N/25mm) or more.

Further, it is preferable that the adhesive composition comprises at least one or more of 70 to 95 parts by weight of (A) alkyl (meth) acrylate monomer having an alkyl group having from 1 to 4 carbon atoms. 100 parts by weight of the (meth) acrylate monomer as a main component of at least one of 5 to 30 parts by weight of the (B) aryl group-containing (meth) acrylate monomer, and 5 to 50 parts by weight (C) at least one of the nitrogen-containing vinyl monomers and at least 0.1 to 5 parts by weight of the (D) carboxyl group-containing copolymerizable vinyl monomer and/or the hydroxyl group-containing copolymerizable vinyl monomer One or more copolymers having a weight average molecular weight of 200,000 to 2,000,000; and 0.01 to 5 parts by weight of the (E) crosslinking agent.

In the adhesive composition, it is preferred that the content of one or more of the carboxyl group-containing copolymerizable vinyl monomers is 2.0 based on 100 parts by weight of the (meth) acrylate monomer as the main component. The content of one or more of the parts by weight or less and/or the hydroxyl group-containing copolymerizable vinyl monomer is 5.0 parts by weight or less.

Further, the adhesive layer preferably has a refractive index of 1.47 to 1.50.

Further, the present invention provides an adhesive film having a structure in which the adhesive layer is formed on one surface of a release film and has a release film/adhesive layer/release film.

Further, the present invention provides an adhesive film in which the above-mentioned adhesive layer is laminated on one surface of a substrate.

Moreover, the present invention provides a film for a peripheral member of a polarizing plate using the above adhesive film.

Further, the present invention provides a film for a touch panel using the above adhesive film.

Further, the present invention provides a film for an electronic paper using the above adhesive film.

Further, the present invention provides an organic EL (Electro-Luminescence) using the above adhesive film Use a membrane.

Further, the present invention provides an optical film with an adhesive layer formed by laminating the above-mentioned adhesive layer on at least one surface of an optical film.

According to the present invention, it is possible to satisfy the requirements in the prior art and overcome the problems in the prior art, and it is possible to provide an adhesive layer having high adhesion and high adhesion even in a film having a thickness of 1 μm to 20 μm and using the adhesive. Adhesive film of the layer.

Hereinafter, the present invention will be described based on preferred embodiments.

The adhesive layer of the present invention is obtained by crosslinking an adhesive composition comprising an acrylic polymer, wherein the (meth) acrylate monomer as a main component of the adhesive composition contains an alkyl group having a carbon number of C1. At least one or more of the (C) alkyl (meth) acrylate monomer and at least one of the aryl group-containing (meth) acrylate monomers, and containing nitrogen as another copolymerizable monomer At least one or more of a vinyl monomer, a carboxyl group-containing copolymerizable vinyl monomer, and/or a hydroxyl group-containing copolymerizable vinyl monomer, and the thickness of the adhesive layer is 1 μm. The adhesion at 20 μm and thickness 5 μm is 4.0 (N/25 mm) or more.

Examples of the (meth)acrylic acid alkyl ester monomer having an alkyl group having C1 to C14 include methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate. Isopropyl methacrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, amyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, ( Octyl methacrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, (meth)acrylic acid Anthracene ester, undecyl (meth)acrylate, dodecyl (meth)acrylate, (methyl) At least one of tridecyl acrylate, tetradecyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, and the like. The alkyl group in the alkyl (meth) acrylate monomer may be any of a straight chain, a branched chain, and a cyclic group. The proportion of the (meth) acrylate monomer having an alkyl group having a C1 to C14 alkyl group is preferably 50 to 95 parts by weight based on 100 parts by weight of the acrylic polymer (copolymer) of the binder composition.

Examples of the aryl group-containing (meth) acrylate monomer include benzyl (meth) acrylate, naphthyl (meth) acrylate, phenoxyethyl (meth) acrylate, and phenoxy (meth) acrylate. Butyl ester, 2-(1-naphthalenyloxy)ethyl (meth)acrylate, 2-(2-naphthalenyloxy)ethyl (meth)acrylate, 6-(1-naphthyloxy)(meth)acrylate Hexyl ester, 6-(2-naphthyloxy)hexyl (meth)acrylate, 8-(1-naphthalenyloxy)octyl (meth)acrylate, 8-(2-naphthyloxy)(meth)acrylate Base) octyl ester and the like. In order to obtain an adhesive layer having a high refractive index, at least one or more aryl group-containing (meth) acrylate monomers are preferably blended.

By mixing these aryl group-containing (meth) acrylate monomers with a monomer as a main component, that is, an alkyl (meth) acrylate monomer having an alkyl group having C1 to C14, it is possible to The refractive index of the obtained adhesive layer is adjusted to be adjusted, the refractive index difference between the optical members is reduced, and total reflection is reduced, whereby the total light transmittance can be improved. In the adhesive layer of the present invention, when the adhesive composition contains an aryl group-containing (meth) acrylate monomer, the content thereof is 100 parts by weight based on the (meth) acrylate monomer as a main component. Preferably, it is 5 to 30 parts by weight.

Examples of the nitrogen-containing vinyl monomer include N-vinylpyrrolidone, N-vinylcaprolactam, and (meth)acryl oxime. Cyclic nitrogen vinyl compound such as porphyrin; N-ethyl-N-methyl (meth) acrylamide, N-methyl-N-propyl (meth) acrylamide, N-methyl-N- Isopropyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (A a dialkyl-substituted (meth) acrylamide such as acrylamide, N,N-diisopropyl(meth)acrylamide or N,N-dibutyl(meth)acrylamide; N-ethyl-N-methylamine ethyl methacrylate, N-methyl-N-propylamine ethyl (meth) acrylate, N-methyl-N-isopropyl (meth) acrylate Amine ethyl ester, N,N-dimethylamine methyl (meth)acrylate, N,N-dimethylamine ethyl (meth)acrylate, N,N-dimethylamine (meth)acrylate Ester, N,N-dimethylamine butyl (meth)acrylate, N,N-dipropylamine ethyl (meth)acrylate, N,N-dibutylamineethyl (meth)acrylate, etc. Dialkylamine (meth)acrylate; N-ethyl-N-methylaminopropyl (meth) acrylamide, N-methyl-N-propylaminopropyl (methyl) acrylamide , N-methyl-N-isopropylaminopropyl (meth) acrylamide, N,N-dimethylaminopropyl (meth) propylene oxime , N,N-diethylaminopropyl (meth) acrylamide, N,N-dipropylaminopropyl (meth) acrylamide, N,N-dimethylamine ethyl (methyl And at least one of a dialkyl-substituted aminoalkyl (meth) acrylamide such as acrylamide or N,N-diethylamineethyl(meth)acrylamide.

In order to distinguish it from the compound (D) described later, the nitrogen-containing vinyl monomer preferably does not contain a hydroxyl group, and more preferably does not contain a hydroxyl group or a carboxyl group. As such a monomer, preferred are the above-exemplified monomers, for example, an acrylic monomer containing an N,N-dialkyl substituted amine group or an N,N-dialkyl substituted decylamino group; N-vinyl group N-vinyl substituted indoleamines such as pyrrolidone and N-vinyl caprolactam; N-(methyl) propylene oxime An N-(meth)acrylinyl group such as a phenyl group is substituted with a cyclic amine.

Further, in the adhesive layer of the present invention, the nitrogen-containing vinyl monomer contained in the adhesive composition can impart the necessary adhesive force and durability to the adhesive layer. In the adhesive layer of the present invention, the content of the nitrogen-containing vinyl monomer contained in the adhesive composition is preferably 5 to 50 parts by weight based on 100 parts by weight of the (meth) acrylate monomer of the main component.

Further, in the adhesive layer of the present invention, as the nitrogen-containing vinyl monomer contained in the adhesive composition, it is particularly preferred to use N-vinylpyrrolidone or N,N-dimethyl(meth)acrylonitrile. Amine, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N, N-dibutyl(meth)acrylamide, N,N-dimethylaminopropyl (meth) acrylamide, N,N-diethylaminopropyl (meth) acrylamide, N , N-dimethylaminoethyl (meth) acrylamide, N-vinyl caprolactam, and the like.

Examples of the carboxyl group-containing copolymerizable vinyl monomer (carboxyl group-containing monomer) include (meth)acrylic acid, (meth)acrylic acid carboxyethyl ester, (meth)acrylic acid carboxypentyl ester, and 2-((). Methyl) propylene methoxyethyl hexahydrophthalic acid, 2-(methyl) propylene methoxy propyl hexahydrophthalic acid, 2-(methyl) propylene methoxyethyl phthalate Formic acid, 2-(methyl)propenyloxyethyl succinic acid, 2-(methyl) propylene oxiranyl ethyl maleic acid, carboxy polycaprolactone mono(meth) acrylate, 2-( At least one of methyl group acryloxyethyltetrahydrophthalic acid and the like.

Further, in the adhesive layer of the present invention, the carboxyl group-containing monomer contained in the adhesive composition can impart the necessary cohesive force to the adhesive layer. Adhesive composition in the adhesive layer of the present invention The content of the carboxyl group-containing monomer contained in the monomer is preferably 0.1 to 5 parts by weight based on 100 parts by weight of the (meth) acrylate monomer of the main component.

Examples of the hydroxyl group-containing copolymerizable vinyl monomer (hydroxyl group-containing monomer) include 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and (meth)acrylic acid. Hydroxyalkyl (meth)acrylates such as 4-hydroxybutyl ester and hydroxyethyl (meth)acrylate, N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, At least one or more of hydroxyl group-containing (meth) acrylamides such as N-hydroxyethyl (meth) acrylamide.

Further, in the adhesive layer of the present invention, the hydroxyl group-containing monomer contained in the adhesive composition is used as a copolymerizable monomer for reducing the content of a carboxyl group-containing monomer, and the carboxyl group-containing monomer The obtained adhesive layer affects the corrosiveness of the adherend which is easily corroded such as the ITO surface of the transparent conductive film. Therefore, the hydroxyl group-containing monomer can contribute to the adhesion of the adhesive layer and contribute to the reduction of corrosion. In the adhesive layer of the present invention, the content of the hydroxyl group-containing monomer contained in the adhesive composition is preferably 0.1 to 5 parts by weight based on 100 parts by weight of the (meth) acrylate monomer of the main component.

The copolymer of the adhesive composition used in the adhesive layer of the present invention preferably contains 5 to 50 parts by weight based on 100 parts by weight of the (meth) acrylate monomer as a main component (C). At least one or more of the nitrogen-containing vinyl monomers and 0.1 to 5 parts by weight of the (D) carboxyl group-containing copolymerizable vinyl monomer and/or the hydroxyl group-containing copolymerizable vinyl monomer, The (meth) acrylate monomer as a main component contains 70 to 95 parts by weight of at least one or more of (A) an alkyl (meth) acrylate monomer having an alkyl group having C1 to C14 and 5 At least one or more of the (B) aryl group-containing (meth) acrylate monomers are used in an amount of 30 parts by weight.

Further, it is preferably contained in an amount of 2.0 parts by weight or less and/or one or more kinds of hydroxyl groups containing one or more carboxyl group-containing copolymerizable vinyl monomers, based on 100 parts by weight of the (meth) acrylate monomer as a main component. The copolymerizable vinyl monomer is 5.0 parts by weight or less.

The polymerization method of the copolymer is not particularly limited, and a suitable known polymerization method such as a solution polymerization method or an emulsion polymerization method can be used. The weight average molecular weight of the copolymer is preferably from 200,000 to 2,000,000.

The above copolymer is preferably an acrylic polymer, preferably containing a (meth) acrylate monomer or 50 to 100% by weight of an acrylic monomer such as (meth)acrylic acid or (meth)acrylamide.

In the above adhesive composition, characteristics such as desired physical properties can be adjusted by blending the above-mentioned copolymer with a crosslinking agent and a suitable optional additive.

Examples of the crosslinking agent include biuret modified diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, and benzodimethyl diisocyanate. Or an isocyanurate-modified product; at least one of a polyisocyanate compound such as an adduct of a trivalent or higher polyhydric alcohol such as trimethylolpropane or glycerin; a metal chelate compound; an epoxy compound; . Further, the adhesive may be crosslinked by photocrosslinking such as ultraviolet rays.

In the case where a crosslinking agent is used to crosslink the copolymer, it is preferred that the copolymer has a functional group capable of crosslinking reaction with a crosslinking agent (a hydroxyl group or a carboxyl group may be selected depending on the kind of the crosslinking agent), and preferably. It is a monomer having these functional groups in a side chain. Further, it is preferred that the adhesive composition contains 0.01 to 5 parts by weight of the (E) crosslinking agent. Further, the basis of the parts by weight is the same as (A) to (D) in the above copolymer.

As other optional components, a decane coupling agent, an antioxidant, a surfactant, a curing accelerator, a plasticizer, a filler, a crosslinking catalyst, a crosslinking inhibitor, a curing inhibitor, a processing aid, and an anti-proof agent can be suitably blended. A well-known additive such as an aging agent. These additives may be used singly or in combination of two or more.

The pressure-sensitive adhesive layer of the present invention can be obtained by coating the above-mentioned pressure-sensitive adhesive composition on a substrate or a release film, and then crosslinking the pressure-sensitive adhesive composition.

It is desirable that the adhesive layer for interlayer bonding of the optical member is a thin adhesive layer, and it is preferable that the thickness of the above adhesive layer is from 1 μm to 20 μm. Further, in general, the adhesive force of the adhesive layer is substantially proportional to the thickness of the adhesive layer, but it is preferably 4.0 (N/25 mm) or more when the thickness is 5 μm. Further, when the thickness of the adhesive layer is not 5 μm, the "adhesion at a thickness of 5 μm" (N/25 mm) can be described as the thickness of the adhesive layer as T (μm), and the adhesive force of the adhesive layer is recorded. It is F (N/25 mm) and is estimated by the formula "(adhesion at thickness 5 μm) = 5F/T".

When the adhesive layer of the present invention is used for interlayer bonding or the like of an optical member, in order to reduce reflection of light on the interface between the adhesive layer and the optical member, it is desirable that the refractive index difference be as small as possible. Therefore, the refractive index of the above adhesive layer is preferably from 1.47 to 1.50.

The adhesive film of the present invention can be produced by forming the adhesive layer of the present invention on one side of a substrate or a release film.

A resin film such as a polyester film or the like can be used as the release film (separator) for forming the base film of the pressure-sensitive adhesive layer or the protective adhesive surface.

The base film can be formed on the surface of the resin film opposite to the side on which the adhesive layer is formed by an anthrone or a fluorine-based release agent, a coating agent, cerium oxide particles or the like. The antifouling treatment can be carried out by an antistatic treatment by application or mixing of an antistatic agent.

In the release film, a release treatment by an anthrone or a fluorine release agent is performed on the surface on the side where the adhesive surface of the adhesive layer is bonded.

The "release film/adhesive layer/release film" can be formed by bonding the surface of the release film to the mold release film on both surfaces of one adhesive layer. In this case, the release film on both sides can be peeled off sequentially or simultaneously to expose the adhesive surface, and can be bonded to an optical member such as an optical film. Examples of the optical film include a polarizing film, a retardation film, an antireflection film, an antiglare (antiglare) film, an ultraviolet absorbing film, an infrared absorbing film, an optical compensation film, and a brightness enhancement film.

The adhesive film of the present invention can be used for bonding various optical films, various optical films for touch panels, various optical films for electronic paper, various optical films for organic EL, and the like to peripheral members of liquid crystal displays mainly including polarizing plates.

Further, the above-mentioned adhesive layer may be laminated on at least one side of these optical films to prepare an optical film with an adhesive layer. Specifically, “optical film/adhesive layer/optical film”, “optical film/adhesive layer/release film”, “optical film/adhesive layer”, “optical film/adhesive layer/optical film” /Adhesive layer / optical film", "optical film / adhesive layer / optical film / adhesive layer / release film", "release film / adhesive layer / optical film / adhesive layer / release film", etc. Composition.

For example, in the case of an "optical film/adhesive layer/release film", in the case of having an adhesive layer protected by a release film, the release film is peeled off to expose an "optical film/adhesive layer". Adhesive layer, In combination with other optical films, it is possible to obtain a structure in which an adhesive layer is used for interlayer bonding such as "optical film/adhesive layer/optical film".

[Examples]

Hereinafter, the present invention will be specifically described by way of examples.

<Preparation of acrylic acid copolymer>

[Example 1]

Nitrogen gas was introduced into a reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube to replace the air in the reactor with nitrogen. Thereafter, 90 parts by weight of butyl acrylate, 10 parts by weight of phenoxyethyl acrylate, 10 parts by weight of diethyl acrylamide, 1.0 part by weight of acrylic acid, 1.0 part by weight of 4-hydroxybutyl acrylate, and a solvent were added to the reaction apparatus. Ethyl acetate) 60 parts by weight. Thereafter, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise thereto over 2 hours, and the mixture was reacted at 65 ° C for 6 hours to obtain an acrylic acid used in Example 1 having a weight average molecular weight of 500,000. Copolymer solution 1. A part of the acrylic copolymer was taken and used as an acid value measurement sample described later.

[Examples 2 to 5 and Comparative Examples 1 to 3]

Copolymerization with the above-mentioned acrylic acid used in Example 1 except that the composition of each monomer was adjusted as described in (A), (B), (C), (D-1) (D-2) of Table 1, respectively. The solution 1 was operated in the same manner, and the acrylic copolymer solutions used in Examples 2 to 5 and Comparative Examples 1 to 3 were obtained. Here, although the measurement results are not particularly shown, the copolymers contained in the acrylic copolymer solutions of Examples 2 to 5 and Comparative Examples 1 to 3 have a weight average molecular weight of 200,000 to 2,000,000.

<Preparation of Adhesive Composition, Adhesive Layer and Adhesive Film>

[Example 1]

In the acrylic copolymer solution 1 of Example 1 prepared as described above, 0.1 parts by weight of Coronate L-45 (addition of toluene diisocyanate (TDI) compound) and 0.1 weight of aluminum chelate (aluminum triacetate) were added. The mixture was stirred and mixed to obtain the adhesive composition of Example 1. This adhesive composition was applied onto a release film composed of a polyethylene terephthalate (PET) film coated with an anthrone resin, and then dried at 90 ° C to remove the solvent. Thereafter, by performing aging treatment for 7 days in an environment of 23 ° C and 50% RH, it was obtained that an adhesive was applied to one side of the release film. The adhesive film of Example 1 of the layer is obtained by crosslinking the adhesive composition.

[Examples 2 to 5 and Comparative Examples 1 to 3]

The adhesive films of Examples 2 to 5 and Comparative Examples 1 to 3 were obtained in the same manner as in the adhesive film of Example 1 except that the composition of the additive was adjusted as described in (E) of Table 1.

In Table 1, the numerical value in the parentheses indicates the numerical value of the weight parts of the (C) group to the (E) group obtained by setting the total weight of the group (A) and the group (B) to 100 parts by weight.

Further, the names of the compounds corresponding to the abbreviations of the respective components used in Table 1 are shown in Table 2. Here, Coronate (registered trademark) L-45 is the trade name of Japan Polyurethane Industry Co., Ltd., and D-11ON is the trade name of Mitsui Chemicals Co., Ltd. TDI refers to toluene diisocyanate and XDI refers to benzenedimethyl diisocyanate.

<Test method and evaluation>

The release film (PET film coated with an oxime resin) was peeled off from the adhesive films of Examples 1 to 5 and Comparative Examples 1 to 3 to expose the adhesive layer, and the adhesive layer was transferred to one side of the polarizing plate (film). on.

<Method for measuring adhesion>

The adhesive layer was transferred to one side of a polarizing plate (film) having a thickness of 180 μm to obtain an adhesive film (an optical film with an adhesive layer) as a sample.

The adhesive film was attached to a non-tin surface of soda lime glass washed with acetone using a pinch roller. Thereafter, the autoclave treatment was carried out under the conditions of 50 ° C and 0.5 MPa × 20 minutes, and then returned to an environment of 23 ° C × 50% RH, and the peeling strength of the adhesive film after one hour passed was measured by a tensile tester. According to JIS Z0237 "Adhesive tape, adhesive sheet test method", the measurement will be carried out at a speed of 300 mm/min. The peel strength at the time of peeling in the 180° direction serves as the adhesive force of the adhesive layer of the adhesive film.

<Test method for adhesion>

The adhesive layer of the adhesive film of the sample after the measurement of the adhesive force was visually confirmed, and the adhesion was judged in a state of being peeled off from the polarizing plate (film) of the base material layer.

○. . The adhesive layer did not fall off from the substrate layer at all.

△. . A part of the adhesive layer separates from the substrate layer and falls off.

×. . The adhesive layer is detached from the substrate layer and adheres to the glass of the adherend.

<Test method for durability>

A 10 cm square adhesive film prepared by the same method as the measurement of the adhesive force was applied to the non-tin surface of the soda lime glass in the same manner to obtain a sample. The sample was placed in an environment of 60° C.×90% RH for 250 hours, and then taken out to an environment of 23° C.×50% RH, and the state of the adhesive film after 1 hour was visually observed to determine the durability.

○. . The adhesive film did not cause peeling and foaming at all.

△. . A part of the adhesive film is peeled off and foamed.

×. . The entire adhesive film is peeled and foamed.

<Method for Measuring Refractive Index>

The refractive index of the adhesive layer at 23 ° C was measured using an Abbe refractometer (manufacturer: ERMA, model: ER-2S).

The evaluation results are shown in Table 3.

In the adhesive films of Examples 1 to 5, the adhesive layer having a thickness of 5 μm had an adhesive force of 4.0 N/25 mm or more, and the refractive index of the adhesive layer was in the range of 1.47 to 1.50, and was excellent in adhesion and durability. That is, the adhesive films of Examples 1 to 5 can satisfy the required requirements and overcome the problems.

Using the adhesive composition of Example 1, an adhesive film having an adhesive layer thickness of 3 μm, 5 μm, 10 μm, 15 μm, and 20 μm was prepared in the same manner, and the adhesive force of the adhesive layer was measured, and the results are shown in the table. 4 in. It is understood that the adhesive force of the adhesive layer using the adhesive composition of Example 1 is substantially proportional to the thickness of the adhesive layer as is well known.

The adhesive film of Comparative Example 1 may be because the adhesive composition does not contain a nitrogen-containing monomer, and the adhesive layer having a thickness of 5 μm has a weak adhesive force. Further, since the aryl group-containing (meth) acrylate monomer is not contained, the adhesive layer has a low refractive index. Moreover, adhesion and durability are also poor.

The adhesive film of Comparative Example 2 may be because the amount of the copolymerizable vinyl monomer having a carboxyl group in the adhesive composition is too large, and the adhesive layer having a thickness of 5 μm is weak. Further, since the aryl group-containing (meth) acrylate monomer is not contained, the adhesive layer has a low refractive index. Moreover, adhesion and durability are also poor.

The adhesive film of Comparative Example 3 may be because the adhesive composition contains neither a carboxyl group-containing copolymerizable vinyl monomer nor a hydroxyl group-containing copolymerizable vinyl monomer, and the adhesive layer having a thickness of 5 μm is adhered. The force is weak, and the adhesion and durability are also poor.

Thus, the adhesive films of Comparative Examples 1 to 3 did not satisfy the required requirements and overcome the problems of the prior art.

Claims (11)

An adhesive layer obtained by crosslinking an adhesive composition containing an acrylic polymer, wherein the adhesive composition contains an alkyl carbon of a (meth) acrylate monomer as a main component At least one or more of the alkyl (meth) acrylate monomers having a C1 to C14 atomic number and at least one of the aryl group-containing (meth) acrylate monomers, and containing as other copolymerizable monomers At least one or more of the nitrogen-containing vinyl monomers, and at least one of the carboxyl group-containing copolymerizable vinyl monomer and/or the hydroxyl group-containing copolymerizable vinyl monomer, and further, the adhesive layer The thickness is 1 μm to 20 μm, and the adhesion at a thickness of 5 μm is 4.0 N/25 mm or more. The adhesive layer according to claim 1, wherein the adhesive composition comprises: (meth)acrylic acid alkyl group having 70 to 95 parts by weight of (A) alkyl group having C1 to C14 carbon atoms 100 weight of (meth) acrylate monomer as a main component of at least one or more of the ester monomers and at least one or more of 5 to 30 parts by weight of the (B) aryl group-containing (meth) acrylate monomer And containing 5 to 50 parts by weight of one or more of (C) nitrogen-containing vinyl monomers and 0.1 to 5 parts by weight of (D) carboxyl group-containing copolymerizable vinyl monomer and/or hydroxyl group-containing At least one of the polymerizable vinyl monomers has a weight average molecular weight of 200,000 to 2,000,000 copolymers; and 0.01 to 5 parts by weight of the (E) crosslinking agent. The adhesive layer according to claim 1 or 2, wherein the carboxyl group-containing copolymerized ethylene is 100 parts by weight of the (meth) acrylate monomer as the main component in the adhesive composition. The content of one or more of the content of one or more of the base monomers is 2.0 parts by weight or less and/or the hydroxyl group-containing copolymerizable vinyl monomer is 5.0 parts by weight or less. The adhesive layer of claim 1 or 2, wherein the adhesive layer has a refractive index of 1.47 to 1.50. An adhesive film formed by forming an adhesive layer according to any one of claims 1 to 4 on one side of a release film, and having a release film/adhesive layer/release film. An adhesive film obtained by laminating an adhesive layer according to any one of claims 1 to 4 on one side of a substrate. A film for a peripheral member of a polarizing plate which uses an adhesive film as disclosed in claim 5 or 6. A film for a touch panel using an adhesive film as disclosed in claim 5 or 6. A film for electronic paper using an adhesive film as disclosed in claim 5 or 6. A film for an organic EL which uses an adhesive film as disclosed in claim 5 or 6. An optical film having an adhesive layer formed by laminating an adhesive layer according to any one of claims 1 to 4 on at least one side of the optical film.