JP2018115340A - Adhesive layer and adhesive film - Google Patents

Abstract

A pressure-sensitive adhesive layer and a pressure-sensitive adhesive film are provided that do not cause an error in the measured value of the surface hardness of a laminate on which an optical member is bonded, and also have durability and reworkability. The acrylic polymer comprises (E) a hydroxyl group-containing copolymerizable vinyl monomer at a ratio of 0.1 to 10 parts by weight with respect to a total of 100 parts by weight of the acrylic monomers (A) to (D). And (C) the nitrogen-containing vinyl monomer is an (meth) acrylic monomer containing an amide bond or amino group, the acid value of the acrylic polymer is 0.1 or less, and the Tg of the acrylic polymer is − 35 ° C. or higher, and the pressure-sensitive adhesive composition contains 0.01 to 1.0 part by weight of an isocyanate compound as a crosslinking agent and 0.01 to 0.5 part by weight of a silane coupling agent. The gel fraction of the layer is 40 to 85%, the thickness of the pressure-sensitive adhesive layer is 1 μm to 20 μm, and the pressure-sensitive adhesive force of the pressure-sensitive adhesive layer having a thickness of 10 μm is 1.5 to 8.0 N / 25 mm. [Selection figure] None

Description

  The present invention relates to a thin adhesive layer having a thickness of 1 μm to 20 μm used for bonding between layers of optical members and the like, and an adhesive film in which the adhesive layer is sandwiched between release films.

  In recent years, various display devices having a capacitive touch panel externally attached to a liquid crystal panel, such as smartphones, tablet terminals, and tablet PCs, are widely used. In such a display device, a physical space exists between the liquid crystal panel and the touch panel. For this reason, external light etc. reflected on the upper surface of a liquid crystal panel or the lower surface of a touch panel, and there existed a problem that the visibility in bright environments, such as outdoors, fell.

  As a method for solving the problem that the visibility is lowered, an in-cell display device in which a function of a touch panel is incorporated in a liquid crystal pixel (see, for example, Patent Document 1) has been proposed. However, it has not been put into practical use because of a complicated manufacturing process and a decrease in product yield and technical difficulty in improving image display performance.

  On the other hand, recently, an on-cell display device (for example, see Patent Document 2) has been proposed. In the on-cell display device, a touch sensor including a transparent electrode pattern is formed between a color filter and a polarizing plate, and the function of the touch panel is formed between the color filter substrate and the polarizing plate. The on-cell method has an advantage that the yield of the product is less decreased. For this reason, the on-cell method is expected to develop in the future as a promising manufacturing technique for liquid crystal panels incorporating a touch panel.

JP 2009-258182 A JP 2014-045001 A

In the various display devices described above, a pressure-sensitive adhesive layer is generally used to bond the layers of the optical members. However, when the surface of at least one optical member is an optical member whose surface hardness is increased by surface treatment such as a hard coat layer (for example, the pencil hardness of the surface is 2H or more), it is used for bonding optical members. If the pressure-sensitive adhesive layer is soft and the pressure-sensitive adhesive layer is thick, there is a problem that a measurement error occurs when the surface hardness of the laminate on which the optical member is bonded is measured.
This is because the base film of the optical member is thinned and the rigidity is lowered even when the surface hardness of the optical member itself is high when touched with a pencil from the top of the hard coat layer of the laminate on which the optical member is bonded. This is a phenomenon in which the optical member is dented due to the softness of the pressure-sensitive adhesive layer and the apparent surface hardness is lowered.

  The present invention has been made in view of the above circumstances, and even when used for bonding between layers of an optical member, the measurement value of the surface hardness of the laminate on which the optical member is bonded does not cause an error and is durable. It is an object to provide a pressure-sensitive adhesive layer and a pressure-sensitive adhesive film that have both reproducibility and reworkability.

  In order to solve the above problems, the present invention reduces the thickness of the pressure-sensitive adhesive layer to 1 μm to 20 μm as compared with the prior art, and even with a thinned pressure-sensitive adhesive layer, In order to do this, as the main component (meth) acrylic monomer, an alkyl (meth) acrylate monomer having a C1-C14 alkyl group, a (meth) acrylate monomer having an aromatic group, a nitrogen-containing vinyl monomer, In addition, at least 40 parts by weight or more of butyl acrylate is contained in a total of 100 parts by weight of at least one monomer selected from the group of acrylic monomers consisting of a (meth) acrylate monomer having an alicyclic group, Furthermore, in order to reduce the corrosiveness of the pressure-sensitive adhesive layer, an acrylic polymer containing no carboxyl group-containing copolymerizable vinyl monomer is used. Is a technical idea.

  In order to solve the above-mentioned problems, the present invention is obtained by crosslinking a pressure-sensitive adhesive composition made of an acrylic polymer used between layers of an optical member having a pencil hardness of 2H or more and another optical member. In the pressure-sensitive adhesive layer, the acrylic polymer has (1) an alkyl (meth) acrylate monomer having a C1-C14 alkyl group as a main component (meth) acrylic monomer and an aromatic group (meta ) Of the total 100 parts by weight of at least one monomer selected from the group of acrylic monomers consisting of an acrylate monomer, a nitrogen-containing vinyl monomer, and an (meth) acrylate monomer having an alicyclic group, butyl Containing at least 40 parts by weight of acrylate, no carboxyl group-containing copolymerizable vinyl monomer, Tg of the polymer is −35 ° C. or higher, and the pressure-sensitive adhesive composition comprises 100 parts by weight of the (meth) acrylic monomer as the main component and (2) 0.1% of the hydroxyl group-containing copolymerizable vinyl monomer. And 10 parts by weight of an acrylic polymer made of a copolymer having an acid value of 0.1 or less and a weight average molecular weight of 1 million or more, and the (meth) acrylic monomer as the main component. (3) containing 0.01 to 1.0 part by weight of an isocyanate compound alone as a crosslinking agent, and further comprising a group consisting of an epoxy group, a (meth) acryloxy group, a mercapto group, and an amino group 0.01-0.5 part by weight of a silane coupling agent having an organic functional group selected from the group consisting of 0.01 to 0.5 parts by weight, and the gel fraction after crosslinking the acrylic polymer is 40 85% of the pressure-sensitive adhesive layer having a thickness of 1 μm to 20 μm, and a pressure-sensitive adhesive film obtained by transferring a pressure-sensitive adhesive layer having a thickness of 10 μm to one surface of a polarizing film having a thickness of 180 μm with respect to non-alkali glass. The peel test is performed in accordance with JIS Z0237 at a speed of 300 mm / min in the direction of 180 °, and the adhesive strength of the obtained 10 μm-thick adhesive layer is 1.5 to 8.0 N / 25 mm. Measured value of pencil hardness on the surface of the hard coat layer of the sample obtained by bonding non-alkali glass to the other surface of the polarizing plate having a hard coat layer having a hardness of 2H on one surface via the adhesive layer. Provides a pressure-sensitive adhesive layer characterized by being 2H or more.

  It is preferable that the pressure-sensitive adhesive composition further contains 0.01 to 0.5 parts by weight of a silane coupling agent.

  The crosslinking agent contained in the pressure-sensitive adhesive composition is an isocyanate compound, and preferably contains at least one selected from a trimethylolpropane adduct of tolylene diisocyanate and an isocyanurate of hexamethylene diisocyanate. .

  (2) Hydroxyl-containing copolymerizable vinyl monomer in the pressure-sensitive adhesive composition is 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl. It is preferable that it is at least 1 or more types selected from the compound group which consists of (meth) acrylate.

  The adhesive strength after the adhesive film is bonded to non-alkali glass as an adherend and stored at 70 ° C. for 10 days is preferably 10 N / 25 mm or less.

  Moreover, this invention provides the adhesive film characterized by the said adhesive layer being formed in the single side | surface of a release film, and being the structure of a release film / adhesive layer / release film.

  Moreover, this invention provides the adhesive film characterized by the said adhesive layer being laminated | stacked on the single side | surface of a base material.

  Moreover, this invention provides the adhesive film for bonding with a polarizing plate and a liquid crystal display panel or an organic electroluminescent display panel in which the said adhesive film was used.

  Moreover, this invention provides the polarizing plate with an adhesive layer in which the said adhesive film was used.

  The present invention also provides a polarizing plate with a pressure-sensitive adhesive layer in which the pressure-sensitive adhesive film is used and a retardation film having a phase difference of λ / 4 and / or λ / 2 is used as a constituent material.

  Moreover, this invention provides the optical film with an adhesive layer by which the said adhesive layer is laminated | stacked on the at least one surface of the optical film.

  ADVANTAGE OF THE INVENTION According to this invention, even if it uses for bonding between the layers of an optical member, the adhesive layer and adhesive film which can maintain surface hardness and also have durability and rework property can be provided.

Hereinafter, the present invention will be described based on preferred embodiments.
The pressure-sensitive adhesive layer of the present invention is a pressure-sensitive adhesive layer formed by crosslinking a pressure-sensitive adhesive composition made of an acrylic polymer used between layers of an optical member having a pencil hardness of 2H or more and another optical member. The acrylic polymer is (1) an alkyl (meth) acrylate monomer having a C1-C14 alkyl group as a main component (meth) acrylic monomer, and a (meth) acrylate monomer having an aromatic group. , At least 40 of butyl acrylate in a total of 100 parts by weight of at least one monomer selected from the group of acrylic monomers consisting of a nitrogen-containing vinyl monomer and an (meth) acrylate monomer having an alicyclic group. It contains at least parts by weight and does not contain a carboxyl group-containing copolymerizable vinyl monomer. Is −35 ° C. or higher, and the pressure-sensitive adhesive composition comprises a total of 100 parts by weight of the main component (meth) acrylic monomer, and (2) 0.1 to 10 parts by weight of a hydroxyl group-containing copolymerizable vinyl monomer. And an acrylic polymer composed of a copolymer having an acid value of 0.1 or less and a weight average molecular weight of 1,000,000 or more, and the (meth) acrylic monomer as the main component. Part (3) containing 0.01 to 1.0 part by weight of an isocyanate compound as a crosslinking agent, the gel fraction after crosslinking the acrylic polymer is 40 to 85%, The thickness of the pressure-sensitive adhesive layer is 1 μm to 20 μm, the pressure-sensitive adhesive force of the pressure-sensitive adhesive layer having a thickness of 10 μm is 1.5 to 8.0 N / 25 mm, and the optical member is alkali-free through the pressure-sensitive adhesive layer. Of the surface to be bonded to the glass Measurements of the brush hardness, wherein the is the same 2H least pencil hardness of the surface of the optical member.

  The acrylic polymer according to the present invention is a copolymer obtained by copolymerizing one or more monomers belonging to the first monomer group (main component monomers) and one or more monomers belonging to the second monomer group (functional group monomers). It is a polymer. As a monomer belonging to the first monomer group, an alkyl (meth) acrylate monomer having an alkyl group of C1 to C14, an acrylate monomer having an aromatic group, a nitrogen-containing vinyl monomer, and an alicyclic (meth) At least one monomer group consisting of acrylate monomers can be used. As the monomer belonging to the second monomer group, at least one of hydroxyl group-containing copolymerizable vinyl monomers can be used. In the present specification, (meth) acrylate is a general term for acrylate and methacrylate.

In the pressure-sensitive adhesive composition according to the present invention, the alkyl (meth) acrylate monomer having an alkyl group having C1 to C14 may be methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) ) Acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, isohexyl (meth) acrylate, heptyl (meth) ) Acrylate, isoheptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) ) Acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, isoundecyl (meth) acrylate, dodecyl (meth) acrylate, isododecyl (meth) acrylate, tridecyl (meth) acrylate, isotridecyl (meth) acrylate , Tetradecyl (meth) acrylate, isotetradecyl (meth) acrylate, and the like. The alkyl group of the alkyl (meth) acrylate monomer may be linear or branched.
The acrylic polymer according to the present invention uses butyl acrylate as an essential monomer. The acrylic polymer contains butyl acrylate in a proportion of at least 40 parts by weight, more preferably 50 parts by weight or more, particularly preferably 60 parts by weight or more, out of a total of 100 parts by weight of the monomers belonging to the first monomer group. Is preferred.

  In the pressure-sensitive adhesive composition according to the present invention, as the (meth) acrylate monomer having an aromatic group, benzyl (meth) acrylate, naphthyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxybutyl (meth) acrylate, 2 -(1-naphthyloxy) ethyl (meth) acrylate, 2- (2-naphthyloxy) ethyl (meth) acrylate, 6- (1-naphthyloxy) hexyl (meth) acrylate, 6- (2-naphthyloxy) hexyl Examples thereof include at least one or more of (meth) acrylate, 8- (1-naphthyloxy) octyl (meth) acrylate, and 8- (2-naphthyloxy) octyl (meth) acrylate. In order to obtain a pressure-sensitive adhesive layer having a high refractive index, it is preferable to blend at least one (meth) acrylate monomer having an aromatic group. The acrylic polymer according to the present invention preferably contains a (meth) acrylate monomer having an aromatic group in a proportion of 30 parts by weight or less, out of a total of 100 parts by weight of the monomers belonging to the first monomer group.

  In the pressure-sensitive adhesive composition of the pressure-sensitive adhesive layer according to the present invention, examples of the nitrogen-containing vinyl monomer include (meth) acrylic monomers containing amide bonds, (meth) acrylic monomers containing amino groups, and the like. More specifically, N- (meth) acryloylmorpholine, N- (meth) acryloylpiperazine, N- (meth) acryloylaziridine, N- (meth) acryloylazetidine, N- (meth) acryloylpyrrolidine, N- ( Cyclic nitrogen vinyl compounds having a heterocyclic structure substituted with N- (meth) acryloyl, such as (meth) acryloylpiperidine, N- (meth) acryloylazepane, N- (meth) acryloylazocan; (meth) acrylamide, N -Unsubstituted or monoalkyl-substituted (meth) acrylamide such as methyl (meth) acrylamide, N-isopropyl (meth) acrylamide, Nt-butyl (meth) acrylamide; N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyla Rilamide, N, N-diisopropyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide, N-ethyl-N-methyl (meth) acrylamide, N-methyl-N-propyl (meth) acrylamide, N-methyl- Dialkyl-substituted (meth) acrylamides such as N-isopropyl (meth) acrylamide; N, N-dimethylaminomethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) Acrylate, N, N-dimethylaminoisopropyl (meth) acrylate, N, N-dimethylaminobutyl (meth) acrylate, N, N-diethylaminomethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N- Ethyl-N-methyl Minoethyl (meth) acrylate, N-methyl-N-propylaminoethyl (meth) acrylate, N-methyl-N-isopropylaminoethyl (meth) acrylate, N, N-dibutylaminoethyl (meth) acrylate, t-butylamino Dialkylamino (meth) acrylates such as ethyl (meth) acrylate; N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide, N, N-dipropylaminopropyl (meth) acrylamide, N, N-diisopropylaminopropyl (meth) acrylamide, N-ethyl-N-methylaminopropyl (meth) acrylamide, N-methyl-N-propylaminopropyl (meth) acrylamide, N-methyl-N-isopropylamino Examples thereof include at least one or more of N, N-dialkyl-substituted aminopropyl (meth) acrylamide such as propyl (meth) acrylamide; (meth) acrylonitrile. As the nitrogen-containing vinyl monomer, those containing no hydroxyl group are preferred, and those containing no hydroxyl group and carboxyl group are more preferred. The acrylic polymer according to the present invention preferably contains a nitrogen-containing vinyl monomer in a proportion of 20 parts by weight or less, out of a total of 100 parts by weight of the monomers belonging to the first monomer group.

  In the pressure-sensitive adhesive composition according to the present invention, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, bicycloheptyl (meth) acrylate, bicyclooctyl are used as the (meth) acrylate monomer having an alicyclic group. Examples thereof include at least one or more of (meth) acrylate, dimethylbicycloheptyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and the like. By blending a (meth) acrylate monomer with a saturated alicyclic group in the side chain, like a cyclic alkyl (meth) acrylate monomer, the polarity of the acrylic polymer is lowered, contributing to affinity for low-energy surfaces. . The acrylic polymer according to the present invention preferably contains a (meth) acrylate monomer having an alicyclic group in a proportion of 30 parts by weight or less, out of a total of 100 parts by weight of the monomers belonging to the first monomer group.

  The monomer (functional group monomer) belonging to the second monomer group has a functional group that can react with an isocyanate compound, which is used as a crosslinking agent. Such a functional group includes a carboxyl group in addition to a hydroxyl group. However, it is preferable that the acrylic polymer does not contain a carboxyl group-containing copolymerizable vinyl monomer from the viewpoint of avoiding the influence on the corrosiveness to the corroded adherend such as the ITO surface of the transparent conductive film. The acid value of the acrylic polymer is preferably 0.1 or less.

  In the pressure-sensitive adhesive composition according to the present invention, examples of the hydroxyl group-containing copolymerizable vinyl monomer include 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxy. Hydroxyl group-containing alkyl (meth) acrylates such as ethyl (meth) acrylate, and hydroxyl group-containing (meth) acrylamides such as N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, and N-hydroxyethyl (meth) acrylamide And at least one of them. Among them, the compound in which the hydroxyl group-containing copolymerizable vinyl monomer is 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate It is preferably at least one selected from the group. The acrylic polymer according to the present invention preferably contains 0.1 to 10 parts by weight of the hydroxyl group-containing copolymerizable vinyl monomer with respect to a total of 100 parts by weight of the monomers belonging to the first monomer group. It is more preferable to contain -5.0 weight part, and it is especially preferable to contain 0.2-4.0 weight part.

  The polymerization method of the copolymer used as the acrylic polymer is not particularly limited, and a known polymerization method such as a solution polymerization method or an emulsion polymerization method can be used as appropriate. The acrylic polymer preferably contains 50 to 100% by weight of an acrylic monomer such as a (meth) acrylate monomer. In the present invention, the glass transition temperature (hereinafter referred to as Tg) of the acrylic polymer is preferably −35 ° C. or higher. If Tg is less than -35 ° C, reworkability and durability are deteriorated. Furthermore, Tg is more preferably −35 ° C. to −10 ° C. When Tg exceeds -10 ° C, the adhesive force required for the present invention cannot be obtained, which is not preferable. The weight average molecular weight of the acrylic polymer is preferably 1 million or more, and more preferably in the range of 1 million to 2 million.

  The pressure-sensitive adhesive composition can adjust properties such as required physical property values by blending the acrylic polymer with a crosslinking agent or an appropriate additive as appropriate.

  As the crosslinking agent, for example, a buret modified product of a diisocyanate such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, an isocyanurate modified product, trimethylol propane, or a trivalent or higher valent compound such as glycerin. Examples include at least one polyisocyanate compound such as an adduct with a polyol.

  As for content of the isocyanate compound used as a crosslinking agent, 0.01-1.0 weight part is preferable with respect to a total of 100 weight part of the monomer which belongs to a 1st monomer group. As the cross-linking agent, only an isocyanate compound may be used. The isocyanate compound preferably contains at least one selected from a trimethylolpropane adduct of tolylene diisocyanate and an isocyanurate of hexamethylene diisocyanate.

The pressure-sensitive adhesive composition preferably further contains a silane coupling agent. As the silane coupling agent, a compound having at least one organic functional group and at least one hydrolyzable group in one molecule, wherein the hydrolyzable group is an alkoxy group bonded to a silicon atom, or the like. Can be mentioned. It is preferable that the silane coupling agent has at least one organic functional group selected from the group consisting of an epoxy group, a (meth) acryloxy group, a mercapto group, and an amino group. Here, the (meth) acryloxy group means an acryloxy group (CH ₂ ═CHCOO—) or a methacryloxy group (CH ₂ ═C (CH ₃ ) COO—).

  Examples of the silane coupling agent having an epoxy group include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropyl. Triethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 5,6-epoxyhexyltrimethoxysilane, 5,6-epoxyhexylmethyldimethoxysilane, 5,6-epoxyhexylmethyldiethoxysilane, 5,6- Epoxy hex Such as triethoxy silane. Examples of the silane coupling agent having a (meth) acryloxy group include 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropylmethyldimethoxysilane, and 3- (meth) acryloxypropyltriethoxy. Examples thereof include silane, 3- (meth) acryloxypropylmethyldiethoxysilane, 3- (meth) acryloxypropyldimethylethoxysilane, and 3- (meth) acryloxypropyldimethylmethoxysilane. Examples of the silane coupling agent having a mercapto group include 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, and 3-mercaptopropyltriethoxysilane. Examples of the silane coupling agent having an amino group include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-2- (aminoethyl)- 3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldiethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) ) -3-aminopropyltriethoxysilane, 3- (methylamino) propyltrimethoxysilane, 3- (methylamino) propyltriethoxysilane and the like. Moreover, the oligomerized alkoxy oligomer (silicone alkoxy oligomer) containing the said organic functional group etc. can also be used as a silane coupling agent.

  The content of the silane coupling agent is preferably 0.01 to 0.5 parts by weight with respect to a total of 100 parts by weight of monomers (monomers belonging to the first monomer group) excluding the hydroxyl group-containing copolymerizable vinyl monomer.

  As other optional components, known antioxidants, antistatic agents, surfactants, curing accelerators, plasticizers, fillers, crosslinking catalysts, crosslinking retarders, curing retarders, processing aids, anti-aging agents, etc. Additives can be appropriately blended. These may be used alone or in combination of two or more.

  The pressure-sensitive adhesive layer according to the present invention can be obtained by applying the pressure-sensitive adhesive composition to a substrate or a release film and then crosslinking the pressure-sensitive adhesive composition. The gel fraction of the pressure-sensitive adhesive layer after crosslinking is preferably 40 to 85%.

  When the pressure-sensitive adhesive layer according to the present invention is used for bonding between layers of optical members, it is desirable that the pressure-sensitive adhesive layer be a thin pressure-sensitive adhesive layer. The thickness of the pressure-sensitive adhesive layer is preferably 1 μm to 20 μm. Moreover, it is preferable that the adhesive force of a 10-micrometer-thick adhesive layer is 1.5-8.0N / 25mm. In general, the adhesive strength of the pressure-sensitive adhesive layer is substantially proportional to the thickness of the pressure-sensitive adhesive layer. Examples of the adherend used for the adhesion test include glass plates such as non-alkali glass and resin films.

  When the pressure-sensitive adhesive layer according to the present invention is used for bonding between layers of an optical member, it is desirable that the difference in refractive index is as small as possible in order to reduce the reflection of light rays at the interface between the pressure-sensitive adhesive layer and the optical member. . For this reason, it is preferable that the refractive index of the said adhesive layer is 1.47-1.50.

  The pressure-sensitive adhesive film of the present invention can be produced by forming the pressure-sensitive adhesive layer of the present invention on one side of a substrate or a release film. As the base film used for forming the pressure-sensitive adhesive layer and the release film (separator) for protecting the pressure-sensitive adhesive surface, a resin film such as a polyester film can be used. On the base film, on the side opposite to the side where the adhesive layer of the resin film is formed, antifouling treatment with silicone-based, fluorine-based release agent or coating agent, silica fine particles, etc., application of antistatic agent, An antistatic treatment such as kneading can be performed.

  The release film is subjected to release treatment with a silicone-based or fluorine-based release agent or the like on the surface of the pressure-sensitive adhesive layer that is to be combined with the pressure-sensitive adhesive surface. A structure of “release film / adhesive layer / release film” can also be obtained by combining the surfaces of the release layer with the release film subjected to the release treatment. In this case, the release films on both sides can be bonded to an optical member such as an optical film by separating the release films sequentially or simultaneously to expose the adhesive surface. Examples of the optical film include a polarizing film, a retardation film, an antireflection film, an antiglare (antiglare) film, an ultraviolet absorption film, an infrared absorption film, an optical compensation film, and a brightness enhancement film.

  Since the pressure-sensitive adhesive layer according to the present invention can maintain the surface hardness of the adherend even when the pressure-sensitive adhesive layer is thick, at least one of the adherends has increased the surface hardness by a hard coat layer or the like ( For example, when the surface is an optical member (such as pencil hardness of 2H or more), it can be suitably used. From the viewpoint of reworkability, it is preferable that the adhesive strength after the adhesive layer is bonded to the adherend and stored at 70 ° C. for 10 days is 10 N / 25 mm or less.

  The pressure-sensitive adhesive layer and pressure-sensitive adhesive film of the present invention are various optical films for peripheral members of liquid crystal display devices mainly comprising polarizing plates, various optical films for touch panels, various optical films for electronic paper, and various opticals for organic EL. It can be used for bonding films and the like. Moreover, it can be set as the optical film with an adhesive layer by which the said adhesive layer is laminated | stacked on the at least one surface of these optical films. If you have a pressure-sensitive adhesive layer protected by a release film, peel off the release film, expose the pressure-sensitive adhesive layer as "optical film / pressure-sensitive adhesive layer", and paste it with another optical film. A configuration such as “optical film / pressure-sensitive adhesive layer / optical film” in which the pressure-sensitive adhesive layer is used for bonding between layers is obtained.

  The adhesive film of this invention is used suitably for bonding of a polarizing plate and a display panel. Examples of the display panel include a liquid crystal panel and an organic EL (electroluminescence) panel. The adhesive film of this invention can be used suitably as an adhesive layer of a polarizing plate with an adhesive layer. As a constituent material of the polarizing plate, a retardation film having a retardation of λ / 4 or λ / 2 may be used. The pressure-sensitive adhesive layer of the present invention can be used for bonding the retardation film and the polarizing plate.

  Hereinafter, the present invention will be specifically described with reference to examples.

<Manufacture of acrylic polymer>
[Example 1]
Nitrogen gas was introduced into a reactor equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, and the air in the reactor was replaced with nitrogen gas. Thereafter, 75 parts by weight of butyl acrylate, 25 parts by weight of t-butyl acrylate, 1.0 part by weight of 8-hydroxyoctyl acrylate and 60 parts by weight of a solvent (ethyl acetate) were added to the reactor. Thereafter, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was dropped over 2 hours and reacted at 65 ° C. for 6 hours to obtain an acrylic polymer solution used in Example 1.
[Examples 2 to 5 and Comparative Examples 1 to 3]
Examples 2 to 5 and Examples 2 to 5 were carried out in the same manner as in the acrylic polymer solution 1 used in Example 1 except that the monomer compositions were as described in groups (1) and (2) in Table 1. An acrylic polymer solution used in Comparative Examples 1 to 3 was obtained.

<Manufacture of an adhesive composition, an adhesive layer, and an adhesive film>
[Example 1]
0.2 parts by weight of coronate HX (HDI isocyanurate) and 0.05 parts by weight of KBM-803 (3-mercaptopropyltrimethoxysilane) were added to the acrylic polymer solution of Example 1 produced as described above. In addition, the mixture was stirred and mixed to obtain the pressure-sensitive adhesive composition of Example 1. After applying this pressure-sensitive adhesive composition onto a release film (polyethylene terephthalate (PET) film coated with a silicone resin), the solvent was removed by drying at 90 ° C., and an atmosphere at 23 ° C. and 50% RH. The adhesive film of Example 1 which has an adhesive layer formed by bridge | crosslinking an adhesive composition on the single side | surface of a release film was obtained by aging for 7 days below.
[Examples 2 to 5 and Comparative Examples 1 to 3]
Examples 2 to 5 and Comparative Example 1 were carried out in the same manner as the adhesive film of Example 1 except that the compositions of the additives were as described in groups (3) and (4) of Table 1. -3 adhesive films were obtained.

  In Table 1, an alkyl (meth) acrylate monomer having an alkyl group of C1 to C14, a (meth) acrylate monomer having an aromatic group, a nitrogen-containing vinyl monomer, and an alicyclic group of (1) group. The total of the monomer group consisting of the (meth) acrylate monomer was 100 parts by weight. Moreover, the numerical value of a weight part is shown enclosed with a parenthesis as an addition ratio from (2) group to (4) group. Group (2) is a monomer group comprising functional group-containing monomers, that is, a hydroxyl group-containing copolymerizable vinyl monomer and a carboxyl group-containing copolymerizable vinyl monomer. (3) Group is a crosslinking agent. (4) Group is a silane coupling agent.

  In addition, Table 2 shows the names of the abbreviations of each component used in Table 1. Coronate (registered trademark) HX and L are trade names of Nippon Polyurethane Industry Co., Ltd., and KBM-403, KBM-802 and KBM-803 are trade names of Shin-Etsu Chemical Co., Ltd. TDI means tolylene diisocyanate, TMP means trimethylolpropane, and HDI means hexamethylene diisocyanate.

<Test method and evaluation>
From the adhesive films in Examples 1 to 5 and Comparative Examples 1 to 3, the release film (PET film coated with silicone resin) was peeled off to expose the adhesive layer, and the adhesive on one side of the polarizing plate (film) The layer was transferred.

<Measurement method of adhesive strength>
A pressure-sensitive adhesive layer having a thickness of 10 μm was transferred to one side of a polarizing plate (film) having a thickness of 180 μm to obtain a pressure-sensitive adhesive film (optical film with a pressure-sensitive adhesive layer) as a sample. The obtained adhesive film was bonded to a non-tin surface washed with non-alkali glass acetone with a pressure roll and autoclaved under conditions of 50 ° C. and 0.5 MPa × 20 minutes, and then an atmosphere of 23 ° C. × 50% RH. Returned to 1 hour. The peel strength of the subsequent adhesive film was measured with a tensile tester in accordance with JIS Z0237 “Test method for adhesive tape / adhesive sheet”, and the peel strength when peeled at a rate of 300 mm / min in the 180 ° direction was It was set as the adhesive force (N / 25mm) of the adhesive layer of an adhesive film.

<Method for measuring acid value>
A sample of the acrylic polymer was dissolved in a solvent (a mixture of diethyl ether and ethanol at a volume ratio of 2: 1) to obtain a measurement sample. In order to neutralize the sample by performing potentiometric titration of the measurement sample with a potassium hydroxide ethanol solution having a concentration of about 0.1 mol / l using an automatic potentiometric titrator (AT-610, manufactured by Kyoto Electronics Industry). The amount of potassium hydroxide ethanol solution required was measured. And the acid value of acrylic polymer was calculated | required from the following formula.
Acid value = (B × f × 5.611) / S
B = Amount of 0.1 mol / l potassium hydroxide ethanol solution used for titration (ml)
f = factor of 0.1 mol / l potassium hydroxide ethanol solution = mass of solid content of sample (g)

<Method for measuring gel fraction>
After the aging is completed, the mass of the pressure-sensitive adhesive layer of the measurement sample before being bonded to the polarizing plate is accurately measured, immersed in toluene for 24 hours, and then filtered through a 200 mesh wire net. Then, after drying a filtered material at 100 degreeC for 1 hour, the mass of the residue was measured correctly and the gel fraction of the adhesive layer (adhesive layer after bridge | crosslinking) was computed from the following formula | equation.
Gel fraction (%) = insoluble partial mass (g) / mass of adhesive layer (g) × 100

<Durability test method>
A 10 cm square pressure-sensitive adhesive film prepared by the same method as the method for measuring adhesive strength was bonded to a non-tin surface washed with non-alkali glass acetone with a pressure-bonding roll to prepare a measurement sample. The prepared measurement sample is left in a predetermined atmosphere (80 ° C. dry atmosphere or 60 ° C. × 90% RH atmosphere) for 250 hours, then taken out in a 23 ° C. × 50% RH atmosphere, and after 1 hour, the state of the adhesive film Was visually observed to determine durability. The criteria for visual observation were as follows.
○ ・ ・ There is no peeling or foaming of the adhesive film.
Δ ·· Peeling and foaming occurred on part of the adhesive film.
× ·· Peeling and foaming occurred on the entire adhesive film.

<Test method for reworkability>
A sample prepared by laminating a 10 cm square adhesive film prepared by the same method as the measurement of adhesive strength on the non-tin surface of non-alkali glass by the same method was left in an atmosphere of 70 ° C. for 10 days, and then 23 The reworkability was judged by measuring the adhesive strength of the adhesive film after taking it out in an atmosphere at 0 ° C. and leaving it for 1 hour. The criteria for determining reworkability were as follows.
○ ·· Adhesive strength after 10 days at 70 ° C. is 1.5 to 10 N / 25 mm.
Δ ·· 70 ° C. × 10 days later, the adhesive strength is greater than 10 N / 25 mm, but 20 N / 25 mm or less.
× · The adhesive strength after 70 ° C. × 10 days is greater than 20 N / 25 mm (cannot be removed).

<Measuring method of pencil hardness>
A pressure-sensitive adhesive layer having a predetermined thickness (Table 4) is transferred to a polarizing plate having a hard coat layer with a pencil hardness of 2H on its surface to prepare a sample. After pasting the polarizing plate to the alkali-free glass through the adhesive layer of the sample, the pencil hardness test of the sample surface is performed according to the scratch hardness (pencil method) of JIS K5600. The pencil hardness of the surface of the hard coat layer in the layer configuration of “/ adhesive layer / alkali-free glass” was measured.

  Tables 3 and 4 show the evaluation results. In addition, although a result is not shown in particular, the acid value of the acrylic polymer was 0.1 or less in Examples 1 to 5 and Comparative Examples 2 to 3 in which no carboxyl group-containing copolymerizable vinyl monomer was used. The weight average molecular weight of the acrylic polymer was 1 million or more.

In the adhesive films of Examples 1 to 5, which are the adhesive films according to the present invention, the acrylic polymer contains at least 40 parts by weight of butyl acrylate out of a total of 100 parts by weight of the main component (meth) acrylic monomer. doing. Moreover, the acrylic polymer of Examples 1-5 does not contain a carboxyl group-containing copolymerizable vinyl monomer, the acrylic polymer has a Tg of −35 ° C. or higher, an acid value of 0.1 or lower, and a weight average. The molecular weight is 1 million or more, and the gel fraction after crosslinking is 40 to 85%. Moreover, the pencil hardness of the surface of the polarizing plate bonded to the non-alkali glass via the pressure-sensitive adhesive layer was apparently 2H. Thereby, if the adhesive film concerning this invention is used, an error will not arise in the measured value of the surface hardness of the laminated body which bonded the optical member.
Moreover, the adhesive force of Examples 1-5 was 1.5-8.0 N / 25mm in the adhesive force of the 10-micrometer-thick adhesive layer, and was excellent in durability. Moreover, after bonding the adhesive film of Examples 1-5 to a to-be-adhered body, it is excellent also in rework property because the adhesive force after storing at 70 degreeC x 10 days is 10 N / 25mm or less. It was. That is, according to the adhesive films of Examples 1 to 5, the requirements and problems in the prior art could be overcome.

  Since the pressure-sensitive adhesive film of Comparative Example 1 contained a carboxyl group-containing copolymerizable vinyl monomer in the acrylic polymer, the acid value of the acrylic polymer was greater than 0.1. The pressure-sensitive adhesive film of Comparative Example 1 does not contain butyl acrylate in the acrylic polymer, the content of the crosslinking agent is excessive, and the Tg of the acrylic polymer is lower than −35 ° C. The durability at 60 ° C. × 90% RH was poor. Moreover, the pencil hardness of the surface of the polarizing plate bonded to the non-alkali glass through the pressure-sensitive adhesive layer apparently decreased from 2H to H.

  In the pressure-sensitive adhesive film of Comparative Example 2, the acrylic polymer did not contain butyl acrylate, the Tg of the acrylic polymer was lower than -35 ° C, and the content of the crosslinking agent was excessive. In addition, because the gel fraction after crosslinking is high, the adhesive strength of the 10 μm thick adhesive layer is less than 1.5 N / 25 mm, the durability at 80 ° C. dry is slightly poor, and the durability at 60 ° C. × 90% RH The nature was bad. Moreover, the pencil hardness of the surface of the polarizing plate bonded to the non-alkali glass through the pressure-sensitive adhesive layer apparently decreased from 2H to H.

  Since the pressure-sensitive adhesive film of Comparative Example 3 does not contain a hydroxyl group-containing copolymerizable vinyl monomer and a carboxyl group-containing copolymerizable vinyl monomer in the acrylic polymer, the gel fraction after crosslinking is 0% even when a crosslinking agent is used. (Substantially not crosslinked). Further, the Tg of the acrylic polymer was lower than -35 ° C, the adhesive strength was very large, and the reworkability and durability were poor. Moreover, the pencil hardness of the surface of the polarizing plate bonded to the non-alkali glass through the pressure-sensitive adhesive layer apparently decreased from 2H to H.

  As described above, the pressure-sensitive adhesive films of Comparative Examples 1 to 3 could not overcome the requirements and problems in the prior art.

Claims (5)

An adhesive layer used for bonding optical members,
The pressure-sensitive adhesive layer is formed by crosslinking a pressure-sensitive adhesive composition containing an acrylic polymer and a crosslinking agent,
The acrylic polymer is
(A) an alkyl (meth) acrylate monomer having an alkyl group with C1-C14 carbon atoms,
(B) a (meth) acrylate monomer having an aromatic group;
(C) a nitrogen-containing vinyl monomer containing no hydroxyl group and no carboxyl group;
(D) a (meth) acrylate monomer having an alicyclic group,
And at least one monomer selected from the group of acrylic monomers consisting of: (E) a hydroxyl group-containing copolymerizable vinyl monomer; and
Is an acrylic polymer comprising a copolymer having a weight average molecular weight of 1,000,000 or more, copolymerized without containing a carboxyl group-containing copolymerizable vinyl monomer,
The acrylic polymer is at a ratio of 0.1 to 10 parts by weight of at least one of the (E) hydroxyl group-containing copolymerizable vinyl monomers with respect to 100 parts by weight of the total of (A) to (D). Containing
The nitrogen-containing vinyl monomer containing no (C) hydroxyl group and carboxyl group is at least one selected from the group consisting of a (meth) acrylic monomer containing an amide bond and a (meth) acrylic monomer containing an amino group. More than a kind of compound,
The acid value of the acrylic polymer is 0.1 or less,
Tg of the acrylic polymer is −35 ° C. or more,
The pressure-sensitive adhesive composition comprises 0.01 to 1.0 parts by weight of an isocyanate compound as the cross-linking agent with respect to 100 parts by weight of the total of (A) to (D).
The pressure-sensitive adhesive composition further comprises a silane coupling agent in a proportion of 0.01 to 0.5 parts by weight with respect to a total of 100 parts by weight of the (A) to (D).
The gel fraction of the pressure-sensitive adhesive layer after crosslinking the pressure-sensitive adhesive composition is 40 to 85%,
A peel test of the pressure-sensitive adhesive film obtained by transferring a pressure-sensitive adhesive layer having a thickness of 10 μm on one side of a polarizing film having a thickness of 1 μm to 20 μm and having a thickness of 1 μm to 20 μm was performed on a non-alkali glass. In accordance with Z0237, the adhesive is carried out at a speed of 300 mm / min in the direction of 180 °, and the adhesive force of the obtained adhesive layer having a thickness of 10 μm is 1.5 to 8.0 N / 25 mm. layer.   The (E) hydroxyl group-containing copolymerizable vinyl monomer is selected from 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxyethyl (meth) acrylate. The pressure-sensitive adhesive layer according to claim 1, wherein the pressure-sensitive adhesive layer is at least one selected from the group of compounds.   The pressure-sensitive adhesive film according to claim 1, wherein the pressure-sensitive adhesive layer is formed on one side of a release film, and has a structure of release film / pressure-sensitive adhesive layer / release film.   A pressure-sensitive adhesive film, wherein the pressure-sensitive adhesive layer according to claim 1 or 2 is laminated on one side of a substrate.   The polarizing plate with an adhesive layer in which the adhesive film of Claim 3 was used.