JP7339371B2 - adhesive film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive layer and a pressure-sensitive adhesive film used for lamination between layers of optical members. More specifically, the present invention relates to a pressure-sensitive adhesive layer having high adhesive strength and high adhesion performance in spite of being a thin film with a thickness of 1 μm to 20 μm, and a pressure-sensitive adhesive film using the same.

Various adhesive films have been proposed for bonding optical members such as polarizing plates and retardation plates to adherends such as liquid crystal cells via adhesive layers (see, for example, Patent Documents 1 and 2).
Patent Document 1 describes an optical pressure-sensitive adhesive composition containing butyl acrylate or the like as a main monomer and containing an acrylamide compound or the like.
Patent Document 2 discloses an optical pressure-sensitive adhesive composition containing a (meth)acrylate having an alkyl group having 4 to 8 carbon atoms as a main component monomer, a monomer having a carboxyl group, and a vinyl monomer having a nitrogen atom. Are listed.
In addition, in order to increase the refractive index of the pressure-sensitive adhesive layer, pressure-sensitive adhesive films have been proposed in various ways (see Patent Documents 3 to 8, for example).
Patent Document 3 describes an optical adhesive composition containing a tackifier having an aromatic ring and a refractive index of 1.51 to 1.75.
Patent Document 4 describes a pressure-sensitive adhesive sheet containing a pressure-sensitive adhesive composition containing a copolymerizable polymer of an acrylic acid-modified monomer having an aromatic ring.
Patent Document 5 describes an optical pressure-sensitive adhesive composition containing a tackifying resin having an aromatic ring and an aromatic phosphoric ester plasticizer.
Patent Document 6 describes a pressure-sensitive adhesive obtained by curing a pressure-sensitive adhesive composition containing an acrylic resin and an aromatic compound having one ethylenically unsaturated group.
Patent Document 7 describes an optical component in which a retardation film and a birefringent plate are adhered to each other via an acrylic pressure-sensitive adhesive containing an aromatic monomer.
Patent Document 8 describes a pressure-sensitive adhesive composition containing a urethane resin obtained by reacting an aromatic diisocyanate with an aromatic polyester diol.

JP 2012-177022 A JP 2012-201734 A JP 2007-084762 A JP 2011-153169 A JP 2012-167188 A JP 2012-021148 A JP 2006-293281 A JP 2009-091522 A

In recent years, there is a demand for adhesive films used for bonding between layers of optical members. It is to be
In general, the adhesive strength of the adhesive layer is approximately proportional to the thickness of the adhesive layer, and therefore, when the thickness of the adhesive layer is reduced, the adhesive strength is lowered accordingly.

However, the adhesive film that has been in demand in recent years has an adhesive force equivalent to that of a conventional adhesive film (thickness of the adhesive layer is about 30 μm) even if the thickness of the adhesive layer is thin. In addition, it is required that the adhesive film has a performance equal to or higher than that of the conventional adhesive film in terms of durability after being left for a long time in an atmosphere of high temperature and high humidity.
In addition, since the thickness of the adhesive layer can be reduced and the adhesive layer can be formed without the need for aging treatment (curing at a constant temperature), the adhesive layer can be formed without the adhesive film base material. NCF (Non Carrier Film) having a member configuration of "release film/adhesive layer/release film" is required.

In addition, since the conventional pressure-sensitive adhesive film is subjected to aging treatment after bonding the pressure-sensitive adhesive film to the adherend, it is possible to improve the adhesion between the adherend and the pressure-sensitive adhesive layer.
However, since the pressure-sensitive adhesive film in the form of NCF has already completed aging of the pressure-sensitive adhesive layer, the adhesion between the adherend and the pressure-sensitive adhesive layer is insufficient. Therefore, there is a problem that the surface of the adherend needs to be subjected to surface treatment such as corona treatment.
A cling film that overcomes these requirements and problems is needed.

The present invention has been made in view of the above circumstances, and provides a pressure-sensitive adhesive layer having high adhesive strength and high adhesion performance despite being a thin film with a thickness of 1 μm to 20 μm, and a pressure-sensitive adhesive film using the same. The task is to provide

In order to solve the above problems, the present invention provides a pressure-sensitive adhesive layer obtained by cross-linking a pressure-sensitive adhesive composition comprising an acrylic polymer, wherein at least one alkyl (meth)acrylate monomer having a C1 to C14 alkyl group has The seed is used as a main component monomer, and at least one or more vinyl monomers having a copolymerizable nitrogen atom are included as other copolymerizable monomers, and copolymerized and crosslinked. The technical idea is to provide an adhesive layer that also has adhesion performance.

Further, in order to solve the above problems, the present invention provides a pressure-sensitive adhesive layer obtained by cross-linking a pressure-sensitive adhesive composition containing an acrylic polymer and a cross-linking agent, wherein the acrylic polymer comprises (A) an alkyl group 70 to 95 parts by weight of at least one alkyl (meth)acrylate monomer having a carbon number of C1 to C14, and (B) at least one (meth)acrylate monomer having an aromatic group. 5 to 30 parts by weight, and at least one or more of (C) a vinyl monomer having no hydroxyl group or carboxyl group and having a nitrogen atom, as another copolymerizable monomer, with respect to the total 100 parts by weight. and (D) 0.1 to 10 parts by weight of at least one copolymerizable vinyl monomer having a hydroxyl group, and a copolymerizable vinyl monomer having a carboxyl group. It is a copolymer with a weight average molecular weight of 200,000 to 2,000,000 copolymerized without containing, and the (C) vinyl monomer having no hydroxyl group or carboxyl group and having a nitrogen atom is N-vinylpyrrolidone, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-dipropyl (meth)acrylamide, N,N-diisopropyl (meth)acrylamide, N,N-dibutyl (meth)acrylamide, At least one compound selected from the group consisting of N,N-diethylaminopropyl(meth)acrylamide, N,N-dimethylaminoethyl(meth)acrylamide, and N-vinylcaprolactam, and the cross-linking agent is trifunctional isocyanate. The pressure-sensitive adhesive layer is a compound, the pressure-sensitive adhesive layer has a thickness of 1 μm to 20 μm, and a refractive index of 1.47 to 1.50.

Moreover, when the thickness of the pressure-sensitive adhesive layer is 20 μm, it is preferable that the initial adhesive strength after lamination is 3.0 (N/25 mm) or more.

Moreover, it is preferable that the said adhesive composition contains an antistatic agent.

Also, the antistatic agent is preferably an ionic compound having a melting point of 25 to 50°C.

Further, the adhesive composition contains 0.1 to 5.0 parts by weight of an ionic compound having a melting point of 25 to 50° C., and the adhesive layer has a surface resistivity of 5.0×10 ⁺¹⁰ Ω/□ or less. Preferably.

The present invention also provides a pressure-sensitive adhesive film, wherein the pressure-sensitive adhesive layer is formed on one side of a release film and has a configuration of release film/adhesive layer/release film.

The present invention also provides a pressure-sensitive adhesive film comprising the pressure-sensitive adhesive layer laminated on one side of a substrate.

The present invention also provides a film for bonding a polarizing plate and a display panel using the pressure-sensitive adhesive film.

Moreover, this invention provides the film for touchscreens using the adhesive film.

The present invention also provides an electronic paper film using the pressure-sensitive adhesive film.

The present invention also provides an optical film with a pressure-sensitive adhesive layer, in which the pressure-sensitive adhesive layer is laminated on at least one surface of an optical film.

According to the present invention, by overcoming the conventional requirements and problems, a pressure-sensitive adhesive layer having high adhesive strength and high adhesion performance despite a thin film with a thickness of 1 μm to 20 μm, and a pressure-sensitive adhesive layer using the same I can provide the film.

The present invention will be described below based on preferred embodiments.
The pressure-sensitive adhesive layer of the present invention is a pressure-sensitive adhesive layer obtained by cross-linking a pressure-sensitive adhesive composition comprising an acrylic polymer, wherein the acrylic polymer is a (meth)acrylate monomer as a main component, and the alkyl group has a carbon number of C1. containing at least one or more alkyl (meth)acrylate monomers of ∼C14 and at least one (meth)acrylate monomer having an aromatic group, and as other copolymerizable monomer, a vinyl monomer having a nitrogen atom It is a copolymer containing at least one or more and at least one or more copolymerizable vinyl monomers having a hydroxyl group, the cross-linking agent for cross-linking the pressure-sensitive adhesive composition is a trifunctional isocyanate compound, and the pressure-sensitive adhesive The thickness of the agent layer is 1 μm to 20 μm, and when the thickness is 20 μm, the initial adhesive strength after bonding is 3.0 (N/25 mm) or more, and the refractive index is 1.47 to 1.50. characterized by being
In this specification, the statement that the acrylic polymer (copolymer) contains (includes) a monomer mainly means that the monomer is copolymerized in the acrylic polymer (copolymer), It is not excluded that part of the raw material monomer remains unreacted in the acrylic polymer (copolymer).

Examples of alkyl (meth)acrylate monomers having C1 to C14 carbon atoms in the alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl At least one of (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, etc. species or more. The alkyl group of the alkyl (meth)acrylate monomer may be linear, branched or cyclic. (A) the alkyl (meth)acrylate monomer having an alkyl group having C1 to C14 carbon atoms, and (B) the (meth)acrylate monomer having an aromatic group in a ratio of 70 to 95 parts per 100 parts by weight combined. Parts by weight are preferred.

Examples of (meth)acrylate monomers having an aromatic group include benzyl (meth)acrylate, naphthyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxybutyl (meth)acrylate, 2-(1-naphthyloxy)ethyl (meth)acrylate. ) acrylate, 2-(2-naphthyloxy) ethyl (meth) acrylate, 6-(1-naphthyloxy) hexyl (meth) acrylate, 6-(2-naphthyloxy) hexyl (meth) acrylate, 8-(1- naphthyloxy)octyl (meth)acrylate, 8-(2-naphthyloxy)octyl (meth)acrylate, ethylene glycol o-phenylphenyl ether (meth)acrylate, polyethylene glycol o-phenylphenyl ether (meth)acrylate and the like. . In order to obtain a pressure-sensitive adhesive layer with a high refractive index, it is preferable to blend at least one (meth)acrylate monomer having an aromatic group.
The refractive index of the adhesive layer obtained by mixing the (meth)acrylate monomer having these aromatic groups with an alkyl (meth)acrylate monomer having an alkyl group having a carbon number of C1 to C14, which is the monomer of the main component. can be adjusted by increasing the refractive index difference between the optical members, and the total light transmittance can be improved by reducing the total reflection.
Further, in the pressure-sensitive adhesive layer according to the present invention, (B) the (meth)acrylate monomer having an aromatic group is 100 parts by weight of the (meth)acrylate monomer as the main component, which is the combination of (A) and (B). Among them, it is preferable to contain 5 to 30 parts by weight.

Examples of vinyl monomers having a nitrogen atom include cyclic nitrogen vinyl compounds such as N-vinylpyrrolidone, N-vinylcaprolactam, (meth)acryloylmorpholine, 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 (meth)acrylamide, N, Dialkyl-substituted (meth)acrylamides such as N-diisopropyl (meth)acrylamide, N,N-dibutyl (meth)acrylamide, N-ethyl-N-methylaminoethyl (meth)acrylate, N-methyl-N-propylaminoethyl ( meth)acrylate, N-methyl-N-isopropylaminoethyl (meth)acrylate, N,N-dimethylaminomethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl ( dialkylamino (meth)acrylates such as meth)acrylate, N,N-dimethylaminobutyl (meth)acrylate, N,N-dipropylaminoethyl (meth)acrylate, N,N-dibutylaminoethyl (meth)acrylate, N - Ethyl-N-methylaminopropyl (meth)acrylamide, N-methyl-N-propylaminopropyl (meth)acrylamide, N-methyl-N-isopropylaminopropyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide ) acrylamide, N,N-diethylaminopropyl (meth)acrylamide, N,N-dipropylaminopropyl (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylamide, N,N-diethylaminoethyl (meth)acrylamide, etc. and at least one dialkyl-substituted aminoalkyl (meth)acrylamide.

The vinyl monomer having a nitrogen atom preferably does not have a hydroxyl group, and more preferably does not have a hydroxyl group and a carboxyl group, so as to be distinguishable from the compound (D) described later. Such monomers include the monomers exemplified above, for example, acrylic monomers having N,N-dialkyl-substituted amino groups and N,N-dialkyl-substituted amide groups; -vinyl-substituted lactams; N-(meth)acryloyl-substituted cyclic amines such as N-(meth)acryloylmorpholine are preferred.

In addition, in the pressure-sensitive adhesive layer according to the present invention, the vinyl monomer having a nitrogen atom contained in the acrylic polymer of the pressure-sensitive adhesive composition can impart necessary adhesive strength and durability to the pressure-sensitive adhesive layer. . In the pressure-sensitive adhesive layer according to the present invention, the vinyl monomer having a nitrogen atom to be contained in the acrylic polymer of the pressure-sensitive adhesive composition is a (meth)acrylate monomer as a main component combining the above (A) and the above (B). It is preferably 2 to 50 parts by weight with respect to 100 parts by weight.
In the pressure-sensitive adhesive layer according to the present invention, the vinyl monomer having a nitrogen atom to be contained in the acrylic polymer of the pressure-sensitive adhesive composition includes N-vinylpyrrolidone, N,N-dimethyl(meth)acrylamide, 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-vinylcaprolactam and the like are particularly preferably used.

Examples of copolymerizable vinyl monomers having a hydroxyl group (monomers having a hydroxyl group) include 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, hydroxyethyl Hydroxyalkyl (meth)acrylates such as (meth)acrylates, and (meth)acrylamides having a hydroxyl group such as N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, and N-hydroxyethyl(meth)acrylamide at least one or more such as
Further, in the pressure-sensitive adhesive layer according to the present invention, the monomer having a hydroxyl group to be contained in the acrylic polymer of the pressure-sensitive adhesive composition is such that the resulting pressure-sensitive adhesive layer adheres easily to corroding surfaces such as the ITO surface of the transparent conductive film. It can be used as a copolymerizable monomer to reduce the content of monomers having carboxyl groups, which are said to affect corrosiveness to the body. Therefore, a monomer having a hydroxyl group can be used to improve the adhesive strength of the adhesive layer and reduce corrosiveness. In the pressure-sensitive adhesive layer according to the present invention, the monomer having a hydroxyl group to be contained in the acrylic polymer of the pressure-sensitive adhesive composition is the main component (meth)acrylate monomer 100, which is a combination of (A) and (B). It is preferably 0.1 to 10 parts by weight.

The copolymer of the pressure-sensitive adhesive composition used for the pressure-sensitive adhesive layer of the present invention contains 70 to 95 parts by weight of (A) at least one alkyl (meth)acrylate monomer having an alkyl group having C1 to C14 carbon atoms. and (B) 5 to 30 parts by weight of a combination of at least one (meth)acrylate monomer having an aromatic group, and 100 parts by weight of (C) a vinyl monomer having a nitrogen atom. and (D) at least one copolymerizable vinyl monomer having a hydroxyl group, preferably 0.1 to 10 parts by weight.
Moreover, it is preferable that the acrylic polymer does not contain a copolymerizable vinyl monomer having a carboxyl group as its monomer. If the polymer has a carboxyl group, the acid may corrode an adherend such as ITO.

The polymerization method of the copolymer is not particularly limited, and known polymerization methods such as a solution polymerization method and an emulsion polymerization method can be used as appropriate. The weight average molecular weight of the copolymer is preferably 200,000 to 2,000,000.
The copolymer is preferably an acrylic polymer, and preferably contains 50 to 100% by weight of acrylic monomers such as (meth)acrylate monomers and (meth)acrylamides.
It is preferable that the adhesive layer has a gel fraction of 50 to 70%.

The pressure-sensitive adhesive composition can be adjusted in properties such as required physical properties by blending the copolymer with a cross-linking agent and optional additives.
Examples of cross-linking agents include buret-modified and isocyanurate-modified diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate; (E) trifunctional isocyanate compounds such as adducts with polyols are preferred.

Examples of trifunctional isocyanate compounds include isocyanurate compounds of hexamethylene diisocyanate compounds, isocyanurate compounds of isophorone diisocyanate compounds, adduct compounds of hexamethylene diisocyanate compounds, adduct compounds of isophorone diisocyanate compounds, burette compounds of hexamethylene diisocyanate compounds, and isophorone diisocyanate compounds. buret form, isocyanurate form of tolylene diisocyanate compound, isocyanurate form of xylylene diisocyanate compound, isocyanurate form of hydrogenated xylylene diisocyanate compound, adduct form of tolylene diisocyanate compound, adduct form of xylylene diisocyanate compound, water At least one or more of adducts of the added xylylene diisocyanate compound is preferable.

When cross-linking a copolymer using a trifunctional isocyanate compound, the copolymer preferably has a cross-linking reactive functional group (especially a hydroxyl group) with a cross-linking agent. It is preferable to contain a monomer that has In addition, the pressure-sensitive adhesive composition preferably contains (E) 0.001 to 1 part by weight of a trifunctional isocyanate compound as a cross-linking agent. The standards for parts by weight are the same as (A) to (D) in the copolymer.

The pressure-sensitive adhesive composition of the present invention can contain an antistatic agent in order to impart antistatic performance. The antistatic agent is preferably solid at room temperature (eg, 25°C), more specifically, the antistatic agent is an ionic compound having a melting point of 25-50°C. The antistatic agent may be a quaternary ammonium salt type ionic compound having an acryloyl group.
Since these antistatic agents have low melting points and long-chain alkyl groups, they are presumed to have high affinity with acrylic polymers.
When antistatic performance is imparted, the surface resistivity of the pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition is preferably 5.0×10 ⁺¹⁰ Ω/□ or less.

The antistatic agent which is an ionic compound having a melting point of 25 to 50° C. is an ionic compound having a cation and an anion, wherein the cation is pyridinium cation, imidazolium cation, pyrimidinium cation, pyrazolium cation, nitrogen ^- containing onium cations such as pyrrolidinium cations and ammonium cations, phosphonium cations, _sulfonium cations ^, etc., and Examples include compounds that are inorganic or organic anions such as salts (RC ₆ H ₄ SO ₃ ⁻ ), perchlorates (ClO ₄ ⁻ ), tetrafluoroborate (BF ₄ ⁻ ), and the like. A compound having a melting point of 25 to 50° C. can be obtained by selecting the chain length of the alkyl group and the position and number of substituents. The cation is preferably a quaternary nitrogen-containing onium cation, such as quaternary pyridinium cations such as 1-alkylpyridinium (the carbon atoms at positions 2 to 6 may be substituted or unsubstituted), 1, quaternary imidazolium cations such as 3-dialkylimidazolium (carbon atoms at positions 2, 4 and 5 may be substituted or unsubstituted); quaternary ammonium cations such as tetraalkylammonium; .

The quaternary ammonium salt-type ionic compound having an acryloyl group is an ionic compound having a cation and an anion, wherein the cation is (meth)acryloyloxyalkyltrialkylammonium [R ₃ N ⁺ -C _n H _2n —OCOCQ=CH ₂ , where Q=H or CH ₃ , R=alkyl] is a quaternary ammonium having a (meth)acryloyl group, and the anions are phosphate hexafluoride (PF ₆ ⁻ ), thiocyanate (SCN ⁻ ), organic sulfonate (RSO ₃ ⁻ ), perchlorate (ClO ₄ ⁻ ), tetrafluoroborate (BF ₄ ⁻ ), imide salt having a fluorine atom ( ^RF ₂ N ^- ) and other inorganic or organic anion compounds. R ^F of the imide salt (R ^F ₂ N ⁻ ) having a fluorine atom includes a perfluoroalkanesulfonyl group such as a trifluoromethanesulfonyl group and a pentafluoroethanesulfonyl group, and a fluorosulfonyl group. Examples of imide salts having a fluorine atom include bis(fluorosulfonyl)imide salt [(FSO ₂ ) ₂ N ⁻ ], bis(trifluoromethanesulfonyl)imide salt [(CF ₃ SO ₂ ) ₂ N ⁻ ], bis(pentafluoro and bissulfonylimide salts such as ethanesulfonyl)imide salt [(C ₂ F ₅ SO ₂ ) ₂ N ⁻ ].

The antistatic agent, which is an ionic compound having a melting point of 25 to 50° C., is not particularly limited. Specific examples of ionic compounds having a pyridinium cation and having a melting point of 25 to 50° C. include 1-octylpyridinium dodecylbenzenesulfonate, 1-dodecylpyridinium thiocyanate, and 3-methyl-1-dodecylpyridinium hexafluoride. phosphate, 1-dodecylpyridinium dodecylbenzenesulfonate, 4-methyl-1-octylpyridinium hexafluorophosphate and the like.
Further, specific examples of the quaternary ammonium salt-type ionic compound having an acryloyl group include dimethylaminomethyl (meth)acrylate methyl hexafluorophosphate [(CH ₃ ) ₃ N ⁺ CH ₂ OCOCQ=CH ₂ . PF ₆ ⁻ , where Q=H or CH ₃ ], dimethylaminoethyl (meth)acrylate bis(trifluoromethanesulfonyl)imidomethyl salt [(CH ₃ ) ₃ N ⁺ (CH ₂ ) ₂ OCOCQ=CH _2. (CF ₃ SO ₂ ) ₂ N ⁻ where Q=H or CH ₃ ], dimethylaminomethyl (meth)acrylate bis(fluorosulfonyl)imide methyl salt [(CH ₃ ) ₃ N ⁺ CH ₂ OCOCQ=CH _2. (FSO ₂ ) ₂ N ⁻ with Q═H or CH ₃ ] and the like.
Further, the ionic compound having a melting point of 25 to 50° C. is 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the (meth)acrylate monomer that is the main component of the combination of (A) and (B). It is preferably contained in parts by weight.

A silane coupling agent is preferably added to the pressure-sensitive adhesive composition of the present invention when it is used for bonding an optical member to a display panel or the like. Silane coupling agents to be added include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-methacryloxysilane. propylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, vinyltriacetoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3- glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, vinyltrichlorosilane, 3- Mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2 -(aminoethyl)-3-aminopropyltrimethoxysilane, 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, and the like. These silane coupling agents can be used singly or in combination of two or more. The amount added is usually 0.001 to 5 parts by weight per 100 parts by weight of the pressure-sensitive adhesive composition. preferably.

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

The pressure-sensitive adhesive layer of 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.
When used for lamination between layers of optical members, it is desirable that the pressure-sensitive adhesive layer has a small thickness, and the thickness of the pressure-sensitive adhesive layer is preferably 1 μm to 20 μm. In general, the adhesive strength of the adhesive layer is approximately proportional to the thickness of the adhesive layer. is preferably
When the pressure-sensitive adhesive layer of the present invention is attached as an optical member to, for example, a polarizing plate (polarizing film), the adhesive force to the polarizing plate is desirably at least the above lower limit. In general, polarizing films are mainly composed of polyvinyl alcohol (PVA) films to which iodine has been adsorbed, and some have a saponified triacetyl cellulose (TAC) or polyethylene terephthalate (PET) protective layer on the surface. . Therefore, it is desirable that the adhesive layer of the present invention has an adhesive force to an adherend such as saponified triacetyl cellulose (TAC) that is at least the lower limit value described above.

When the pressure-sensitive adhesive layer according to the present invention is used for lamination between layers of an optical member, it is desirable that the difference in refractive index is as small as possible in order to reduce reflection of light rays at the interface between the pressure-sensitive adhesive layer and the optical member. . Therefore, the refractive index of the adhesive layer is preferably 1.47 to 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 release film.
A resin film such as a polyester film can be used as the base film used for forming the pressure-sensitive adhesive layer and the release film (separator) for protecting the pressure-sensitive adhesive surface.
On the side of the base film opposite to the side of the resin film on which the pressure-sensitive adhesive layer is formed, silicone-based or fluorine-based release agents or coating agents, antifouling treatment with silica fine particles, etc., antistatic agent coating, Antistatic treatment such as kneading can be applied.

The release film is subjected to release treatment with a silicone-based or fluorine-based release agent or the like on the side to be matched with the adhesive surface of the adhesive layer.
A configuration of "release film/adhesive layer/release film" can also be obtained by putting the release-treated surfaces of the release films on both sides of one pressure-sensitive adhesive layer. In this case, by peeling off the release films on both sides sequentially or simultaneously to expose the adhesive surface, it becomes possible to bond with an optical member such as an optical film. Examples of optical films include polarizing films, retardation films, antireflection films, antiglare films, ultraviolet absorbing films, infrared absorbing films, optical compensation films, brightness enhancement films, and the like.

The adhesive film of the present invention can be used for bonding a polarizing plate and a display panel. Examples of display panels include liquid crystal display devices and organic EL devices, but are not limited to these.
Further, the pressure-sensitive adhesive film of the present invention includes various optical films for peripheral members of liquid crystal display devices, mainly polarizing plates, various optical films for touch panels, various optical films for electronic paper, various optical films for organic EL, and the like. can be used for bonding.
Also, an optical film with a pressure-sensitive adhesive layer can be obtained by laminating the pressure-sensitive adhesive layer on at least one surface of these optical films. 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. configuration.
For example, like "optical film/adhesive layer/release film", if it has an adhesive layer protected by a release film, peel off the release film, "optical film/adhesive layer" By exposing the pressure-sensitive adhesive layer and laminating it with another optical film, a configuration such as "optical film/adhesive layer/optical film" in which the pressure-sensitive adhesive layer is used for lamination between layers can be obtained.

EXAMPLES The present invention will be specifically described below with reference to examples.

<Production of acrylic copolymer>
[Example 1]
Nitrogen gas was introduced into a reactor equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet tube to replace the air in the reactor with nitrogen gas. Then, 90 parts by weight of butyl acrylate, 10 parts by weight of benzyl acrylate, 10 parts by weight of N-vinylpyrrolidone, 2.5 parts by weight of 6-hydroxyhexyl acrylate, and 60 parts by weight of a solvent (ethyl acetate) were added to the reactor. Thereafter, 0.1 parts by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours, and reacted at 65° C. for 6 hours to obtain an acrylic copolymer solution having a weight average molecular weight of 500,000 and used in Example 1. got 1. A part of the acrylic copolymer was sampled and used as a sample for acid value measurement, which will be described later.
[Examples 2 to 5 and Comparative Examples 1 to 3]
Examples 2 to 5 and Comparative Examples 2 to 5 and Comparative An acrylic copolymer solution was obtained for use in Examples 1-3. Although no specific measurement results are shown, the weight-average molecular weight of the copolymers contained in the acrylic copolymer solutions of Examples 2-5 and Comparative Examples 1-3 is in the range of 200,000 to 2,000,000.

<Production of adhesive composition, adhesive layer and adhesive film>
[Example 1]
To the acrylic copolymer solution 1 of Example 1 produced as described above, 0.5 parts by weight of Coronate HX (an isocyanurate of a hexamethylene diisocyanate compound) was added and mixed with stirring to prepare an adhesive composition of Example 1. got stuff After applying this pressure-sensitive adhesive composition onto a release film made of a polyethylene terephthalate (PET) film coated with a silicone resin, drying at 90°C to remove the solvent, followed by drying at 23°C in an atmosphere of 50% RH. By aging for 7 days, a pressure-sensitive adhesive film of Example 1 having a pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition on one side of the release film was obtained.
[Examples 2 to 5 and Comparative Examples 1 to 3]
Examples 2 to 5 and Comparative Examples 1 to 3 were prepared in the same manner as in the adhesive film of Example 1 above, except that the compositions of the additives were respectively as described in (E) and (F) in Table 1. was obtained.

In Table 1, the addition ratios of groups (C) to (F) are calculated based on the total of groups (A) and (B) being 100 parts by weight. However, in Example 3, the total of Groups (A) and (B) was 110 parts by weight, in Example 5, the total of Groups (A) and (B) was 90 parts by weight, and in Comparative Example 2, The total amount of groups (A) and (C) is 100 parts by weight.
In addition, Table 2 shows the compound names of the abbreviations of the components used in Table 1. Coronate (registered trademark) HX, HL and L-45 are trade names of Nippon Polyurethane Industry Co., Ltd., and D-110N is a trade name of Mitsui Chemicals, Inc. HDI means hexamethylene diisocyanate, TDI means tolylene diisocyanate and XDI means xylylene diisocyanate.

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

<Method for measuring adhesive strength>
The pressure-sensitive adhesive layer was transferred to one side of a polarizing plate (film) having a thickness of 180 μm to obtain a sample pressure-sensitive adhesive film (optical film with pressure-sensitive adhesive layer).
The adhesive film was attached to the non-tin surface of soda lime glass washed with acetone with a pressure bonding roll, autoclaved under the conditions of 50 ° C. and 0.5 MPa for 20 minutes, and then returned to an atmosphere of 23 ° C. and 50% RH. The peel strength of the adhesive film after 1 hour was measured with a tensile tester in accordance with JIS Z0237 "Adhesive tape/adhesive sheet test method", and the peel strength when peeled at a speed of 300 mm / min in the 180 ° direction. was taken as the adhesive strength of the adhesive layer of the adhesive film.

<Gel fraction>
After aging, the mass of the measurement sample before bonding to the polarizing plate is accurately measured, immersed in toluene for 24 hours, and then filtered through a wire mesh of 200 mesh. Then, after drying the filtrate at 100° C. for 1 hour, the mass of the residue was accurately measured, and the gel fraction of the adhesive layer (adhesive after cross-linking) was calculated from the following formula.
Gel fraction (%) = mass of insoluble portion (g) / mass of adhesive (g) x 100

<Test method for adhesion>
The pressure-sensitive adhesive layer of the sample pressure-sensitive adhesive film after measuring the pressure-sensitive adhesive strength was visually observed, and the adhesion was determined by the state in which the substrate layer was removed from the polarizing plate (film).
Good: The pressure-sensitive adhesive layer did not come off from the substrate layer at all.
Δ: Part of the pressure-sensitive adhesive layer was lifted and dropped from the substrate layer.
x: The pressure-sensitive adhesive layer fell off from the substrate layer and was transferred to the adherend glass.

<Reworkability>
A sample prepared by bonding a 10 cm square adhesive film prepared by the same method as the adhesive force measurement to the non-tin surface of soda lime glass by the same method was left in a dry atmosphere at 70 ° C. for 24 hours. After the adhesive film was removed from the glass plate, the adhesive residue on the surface of the adherend was visually observed.
◯: No adhesive residue was observed.
Δ: Adhesive residue was slightly observed.
x: Adhesive residue was clearly observed.

<Durability test method>
A sample prepared by bonding a 10 cm square adhesive film prepared by the same method as the adhesive force measurement to the non-tin surface of soda lime glass by the same method was placed in an atmosphere of 60 ° C. x 90% RH for 250 hours. After standing, the adhesive film was taken out in an atmosphere of 23° C.×50% RH, and after 1 hour, the state of the adhesive film was visually observed to judge the durability.
Good: No peeling or foaming of the adhesive film.
(triangle|delta)... Peeling and foaming generate|occur|produce in a part of adhesion film.
x: Peeling and foaming occurred over the entire adhesive film.

<Method for measuring refractive index>
The refractive index of the adhesive layer at 23° C. is measured with an Abbe refractometer (manufacturer name: ERMA, model: ER-2S).

<Method for measuring surface resistivity>
After aging, before bonding to the polarizing plate, the release film (silicone resin-coated PET film) is peeled off to expose the adhesive layer, and a resistivity meter Hiresta UP-HT450 (manufactured by Mitsubishi Chemical Analytic Tech) is used. The surface resistivity of the adhesive layer was measured.

Table 3 shows the evaluation results. In addition, the surface resistivity was expressed by a method of setting "m×10 ⁺ⁿ " to "mE+n" (where m is an arbitrary real number and n is a positive integer).

In the adhesive films of Examples 1 to 5, the initial adhesive strength of the adhesive layer with a thickness of 20 μm is 3.0 N/25 mm or more, and the refractive index of the adhesive layer is in the range of 1.47 to 1.50. , adhesion, reworkability, and durability were also excellent. That is, the adhesive films of Examples 1-5 were able to overcome the requirements and problems. Also, the pressure-sensitive adhesive films of Examples 3 to 5 have surface resistivities of 5.0×10 ⁺¹⁰ Ω/□ or less, which are sufficient to have antistatic performance.

The pressure-sensitive adhesive film of Comparative Example 1 has a high gel fraction and a weak initial pressure-sensitive adhesive layer with a thickness of 20 μm. Moreover, since it does not contain a (meth)acrylate monomer having an aromatic group, the pressure-sensitive adhesive layer has a low refractive index. Moreover, it was inferior also in adhesiveness and durability.
The pressure-sensitive adhesive film of Comparative Example 2 has a low gel fraction and a weak pressure-sensitive adhesive layer with a thickness of 5 μm. Moreover, since it does not contain a (meth)acrylate monomer having an aromatic group, the pressure-sensitive adhesive layer has a low refractive index. In addition, the adhesiveness, reworkability and durability were also inferior.
The adhesive film of Comparative Example 3 had a low gel fraction and was inferior in reworkability and durability.
Thus, the adhesive films of Comparative Examples 1-3 could not overcome the conventional requirements and problems.

Claims (1)

A pressure-sensitive adhesive film in which a pressure-sensitive adhesive layer obtained by cross-linking a pressure-sensitive adhesive composition containing an acrylic polymer, an antistatic agent, and a cross-linking agent is laminated on one side of a substrate,
The acrylic polymer is
(A) 70 to 95 parts by weight of at least one alkyl (meth)acrylate monomer having an alkyl group with a carbon number of C1 to C14;
(B) 5 to 30 parts by weight of a combination of at least one (meth)acrylate monomer having an aromatic group and 100 parts by weight in total, as another copolymerizable monomer,
(C) 2 to 50 parts by weight of a combination of at least one vinyl monomer having no hydroxyl group or carboxyl group and having a nitrogen atom;
(D) A weight average molecular weight obtained by copolymerizing 0.1 to 10 parts by weight of at least one copolymerizable vinyl monomer having a hydroxyl group without containing a copolymerizable vinyl monomer having a carboxyl group. It is a copolymer of 200,000 to 2,000,000,
The cross-linking agent is a trifunctional isocyanate compound,
The adhesive film is
When the thickness is 20 μm, the initial adhesive strength of the lamination is 3.0 (N / 25 mm) or more,
The initial adhesive strength is a value measured by the following adhesive strength measurement method,
The adhesive layer has a refractive index of 1.47 to 1.50,
The pressure-sensitive adhesive film, wherein the pressure-sensitive adhesive layer has a surface resistivity of 5.0×10 ⁺¹⁰ Ω/□ or less.
[Method for measuring adhesive strength]
An adhesive layer to be measured was transferred to one side of a polarizing plate (film) having a thickness of 180 μm to obtain an adhesive film. The adhesive film was laminated and autoclaved under the conditions of 50 ° C. and 0.5 MPa for 20 minutes, then returned to the atmosphere of 23 ° C. and 50% RH for 1 hour. Adhesive sheet test method”, and the peel strength when peeled at a speed of 300 mm / min in the direction of 180 ° with a tensile tester is taken as adhesive strength.