TW201708456A - Light-diffusing adhesive layer and light-diffusing adhesive film - Google Patents

Abstract

The present invention provides a light-diffusing adhesive layer that is an optical member which can be used instead of a conventional light-diffusing plate, and that has the function of a light-diffusing sheet and that can make the thickness of a display thinner, and a light-diffusing adhesive film using the same. The present invention is a light-diffusing adhesive layer having a light-diffusing function, wherein the light-diffusing adhesive layer is formed from an adhesive composition containing: a copolymer that includes: at least one alkyl (meth)acrylate monomer having a C1 to C14 alkyl group and, as a functional group-containing copolymerizable monomer, at least one selected from the group consisting of a hydroxyl group-containing copolymerizable monomer, a nitrogen-containing vinyl monomer, and an aromatic group-containing monomer; a cross-linking agent; and silicon-based particles, wherein the transmittance of the light-diffusing adhesive layer is 90% or more, the haze value is 40% or more, the refractive index is 1.47 or more, and the interface reflectance of the copolymer and the silicon-based particles is 0.01% or more.

Description

Light diffusing adhesive layer and light diffusing adhesive film

The present invention relates to a light diffusing adhesive layer and a light diffusing adhesive film using the light diffusing adhesive layer. More specifically, the present invention relates to a light-diffusing adhesive film which is mainly used as a constituent element in a liquid crystal display and which is bonded to an optical member and fixed. In particular, a light-diffusing adhesive layer having a function of a light-diffusing sheet laminated on a visible side of a liquid crystal display backlight and capable of being thinned (thickness of a display thickness) without using a light-diffusing sheet, and A light-diffusing adhesive film of the light-diffusing adhesive layer was used.

In recent years, the number of manufacturing and sales of liquid crystal displays centering on small and medium-sized sizes is gradually increasing. In addition, with the increase in demand for small and medium-sized liquid crystal displays, further simplification of the display structure and thinning of optical members are required, thereby reducing manufacturing costs and achieving thinning of the thickness of the display panel.

In order to adhere an optical member such as a polarizing plate or a phase difference plate to an adherend such as a liquid crystal cell by an adhesive layer, various adhesive films having excellent adhesion have been proposed (for example, see Patent Document 1 to 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 a monomer having a (meth) acrylate having an alkyl group having 4 to 8 carbon atoms as a main component, and having a carboxyl group-containing monomer and a nitrogen atom-containing vinyl monomer. Optical adhesive composition.

Further, various adhesive films which have been repeatedly studied in order to increase the refractive index of the adhesive layer have been proposed (for example, refer to Patent Documents 3 to 9).

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 comprising 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 comprising an aromatic ring-containing tackifying resin 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.

Patent Document 9 describes a light-diffusing adhesive composition obtained by adding a crosslinking agent such as an isocyanate or a light-diffusing agent composed of resin particles such as polystyrene resin particles to an adhesive resin such as an acrylate copolymer.

In recent years, in order to achieve thinning of an optical member, an adhesive film for bonding between layers of an optical member is required to be an adhesive film having a thickness of the adhesive layer as thin as 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 made thin, and the high temperature is high. In the high-humidity environment, the durability after standing for a long time also has the same performance as 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 is composed of only a member having an adhesive layer obtained by removing the adhesive film substrate and having a "release film/adhesive layer/release film".

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

However, in the case of the adhesive film using the NCF form, since the aging treatment of the adhesive layer has been completed, 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.

Prior art literature

Patent literature

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

Patent Document 2: JP-A-2012-201734

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

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

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

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

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

Patent Document 8: JP-A-2009-091522

Patent Document 9: Japanese Patent Laid-Open No. Hei 7-216328

Problem to be solved by the invention

An object of the present invention is to provide a light-diffusing adhesive layer and a light-diffusing adhesive film using the light-diffusing adhesive layer, wherein the light-diffusing adhesive layer is an optical member that can be used in place of a conventional light-diffusing sheet. It has the function of a light diffusion sheet, and can realize thinning of the thickness of the display.

Technical means of solving problems

In order to solve the above problems, the technical idea of the light-diffusing adhesive layer of the present invention is to form a light-diffusing adhesive layer by an adhesive layer comprising a copolymer and a crosslinking agent and cerium-based particles, wherein the copolymer comprises: At least one or more of alkyl (meth) acrylate monomers having an alkyl group having from C1 to C14; and a monomer having a copolymerizable functional group selected from a hydroxyl group-containing copolymerizable monomer At least one or more of a nitrogen atom-containing vinyl monomer and an aryl group-containing monomer.

Further, in order to solve the above problems, the present invention provides a light-diffusing adhesive layer which is a light-diffusing adhesive layer having a light diffusing function, and the light-diffusing adhesive layer is composed of a copolymer and a crosslinking agent and a ruthenium-based particle. The adhesive composition is formed.

Wherein the copolymer comprises at least one of an alkyl (meth) acrylate monomer having an alkyl group having from C1 to C14; and a monomer having a copolymerizable functional group selected from At least one or more of the group consisting of a hydroxyl group-containing copolymerizable monomer, a nitrogen atom-containing vinyl monomer, and an aryl group-containing monomer.

Further, the light-diffusing adhesive layer has a light transmittance of 90% or more, a haze value of 40% or more, a refractive index of 1.47 or more, and an interface reflectance of 0.01 between the copolymer and the ruthenium-based particles. %the above.

When the refractive index of the copolymer is n _a and the refractive index of the ruthenium particles is n _b , the interface reflectance (K) is K = ((n _{a -} n _b ) / (n _a + n _b )) ² To represent.

Further, it is preferable that the adhesion of the light-diffusing adhesive layer to the glass plate is 2.0 N/25 mm or more when the thickness is 20 μm.

Moreover, it is preferable that the adhesive composition contains a copolymer having a weight average molecular weight of 200,000 to 250,000, an isocyanate compound as a crosslinking agent, and an anthracene particle.

Wherein the copolymer is at least one or more and 5 to 30 parts by weight based on 70 to 95 parts by weight of the alkyl group of the C1-C14 alkyl (meth) acrylate monomer. 100 parts by weight of at least one of the above-mentioned (meth) acrylate monomers, at least one or more of 0.1 to 5 parts by weight of the hydroxyl group-containing copolymerizable vinyl monomer, and 0 to 50 parts by weight A copolymer of at least one of a vinyl monomer having a nitrogen atom.

The isocyanate compound as a crosslinking agent and 0.01 to 20 parts by weight of cerium-based particles are contained in an amount of 0.001 to 5 parts by weight based on 100 parts by weight of the above.

Moreover, it is preferable that the light-diffusing adhesive layer has a haze value of 40% or more and 90% or less.

Moreover, it is preferable that the ruthenium-based particles are one or more selected from the group consisting of cerium oxide particles, cerium oxide melamine core-shell particles, and fluorenone particles.

Moreover, the present invention provides a light-diffusing adhesive film comprising a light-diffusing adhesive layer formed on one surface of a release film and having a release film/light-diffusion adhesive layer/release film.

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

Further, the present invention provides an adhesive film for a peripheral member of a polarizing plate using the light-diffusing adhesive film.

Further, the present invention provides an adhesive film using the light-diffusing adhesive layer between layers between a polarizing plate and a brightness enhancing film.

Further, the present invention provides an optical film with an adhesive layer in which the light diffusion adhesive layer is laminated on at least one surface of the optical film.

Effect of the invention

According to the present invention, it is possible to provide a light-diffusing adhesive layer and a light-diffusing adhesive film using the light-diffusing adhesive layer, which satisfies the conventional requirements and overcomes the problems of the prior art, thereby An optical member that can be used in place of the conventional light diffusing plate has a function of a light diffusing sheet and can reduce the thickness of the display.

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

The light-diffusing adhesive layer of the present invention is characterized in that it is a light-diffusing adhesive layer having a light-diffusing function, and the light-diffusing adhesive layer is formed of an adhesive composition containing an acrylic polymer and a ruthenium-based particle. The light-transmitting adhesive layer has a light transmittance of 90% or more, a haze value of 40% or more, a refractive index of 1.47 or more, and an interface reflectance of 0.01% or more between the copolymer and the cerium-based particles.

Moreover, it is preferable that the light-diffusing adhesive layer has a haze value of 40% or more and 90% or less. Further, it is preferable that the light-diffusing adhesive layer is formed of an adhesive composition containing a copolymer (acrylic polymer) and a crosslinking agent and an anthracene-based particle, and the copolymer contains: an alkyl group having a carbon number of C1 At least one or more of the alkyl (meth) acrylate monomers of -C14; and a monomer containing a copolymerizable functional group selected from a hydroxyl group-containing copolymerizable monomer, a nitrogen atom-containing vinyl group At least one or more of the group consisting of a monomer and an aryl group-containing monomer.

Moreover, it is preferable that the above-mentioned adhesive composition contains a copolymer containing 0.1 to 5 parts by weight of a hydroxyl group-containing copolymer with respect to 100 parts by weight of the (meth) acrylate monomer as a main component. A copolymer of at least one of a vinyl monomer and at least one of 0 to 50 parts by weight of a nitrogen atom-containing vinyl monomer.

The (meth) acrylate monomer as a main component includes at least one or more of 70 to 95 parts by weight of the alkyl group having a C1-C14 alkyl (meth) acrylate monomer, and At least one or more of 5 to 30 parts by weight of the aryl (meth) acrylate monomer.

In addition, it is preferable that the adhesive composition contains 0.001 to 5 parts by weight of an isocyanate compound as a crosslinking agent, and 0.01 to 20 parts by weight of an anthracene based on 100 parts by weight of the (meth) acrylate monomer as a main component. particle.

In the present specification, the description of the content of the monomer (including) monomer in the acrylic polymer (copolymer) mainly means that the monomer is copolymerized in the acrylic polymer (copolymer), but the raw material is not excluded. A part of the monomer remains in the acrylic polymer (copolymer) in an unreacted state.

The (meth)acrylic acid alkyl ester monomer having an alkyl group having from C1 to C14 may, for example, be methyl (meth)acrylate, ethyl (meth)acrylate or propyl (meth)acrylate. , isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, amyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate , octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, (methyl ) decyl acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, ( At least one of cyclopentyl methyl methacrylate and cyclohexyl (meth) acrylate. The alkyl group in the alkyl (meth) acrylate monomer may be any of a linear chain, a branched chain, and a cyclic group. The ratio of the alkyl (meth) acrylate monomer having an alkyl group having a C1 to C14 alkyl group is preferably 70 to 95 parts by weight based on 100 parts by weight of the (meth) acrylate monomer of the main component.

Examples of the aryl group-containing copolymerizable vinyl monomer (aryl group-containing monomer) include benzyl (meth)acrylate, naphthyl (meth)acrylate, and phenoxyethyl (meth)acrylate. Phenyloxybutyl (meth)acrylate, 2-(1-naphthalenyloxy)ethyl (meth)acrylate, 2-(2-naphthyloxy)ethyl (meth)acrylate, (meth)acrylic acid 6 -(1-naphthyloxy)hexyl ester, 6-(2-naphthalenyloxy)hexyl (meth)acrylate, 8-(1-naphthalenyloxy)octyl (meth)acrylate, (meth)acrylic acid An aryl group-containing acrylic monomer such as 8-(2-naphthyloxy)octyl ester, ethylene glycol o-phenyl phenyl ether acrylate, polyethylene glycol o-phenyl phenyl ether acrylate, or the like Base vinyl monomer. In order to obtain an adhesive layer having a high refractive index, it is preferred to blend at least one or more aryl group-containing monomers.

By mixing these aryl group-containing monomers with an alkyl (meth) acrylate monomer having an alkyl group having a C1-C14 alkyl group as a main component monomer, the obtained light-diffusing adhesive layer can be obtained. The refractive index is increased and 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 light-diffusing adhesive layer of the present invention, when the adhesive composition comprises an aryl group-containing monomer, an aryl group-containing monomer is preferred with respect to 100 parts by weight of the (meth) acrylate monomer as a main component. The content is 5 to 30 parts by weight.

Examples of the vinyl monomer containing a nitrogen atom include a cyclic nitrogen-vinyl compound such as N-vinylpyrrolidone, N-vinylcaprolactam, or (meth)acryloquinone morpholine; 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,N-di Dialkyl substituted (meth) acrylamide such as isopropyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide; N-ethyl-N (meth) acrylate -methylaminoethyl ester, N-methyl-N-propylamine ethyl (meth)acrylate, N-methyl-N-isopropylamine ethyl (meth)acrylate, (meth)acrylic acid N , N-dimethylaminomethyl ester, N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N (meth)acrylate - dimethylamine butyl ester, N,N-dipropylamine ethyl (meth)acrylate, N,N-dibutylamine ethyl (meth)acrylate, etc. Dialkylamine methyl methacrylate; N-ethyl-N-methylaminopropyl (meth) acrylamide, N-methyl-N-propylaminopropyl (meth) acrylamide, N-methyl-N-isopropylaminopropyl (meth) acrylamide, N,N-dimethylaminopropyl (meth) acrylamide, N,N-diethylaminopropyl ( Methyl) acrylamide, N,N-dipropylaminopropyl (meth) acrylamide, N,N-dimethylamine ethyl (meth) acrylamide, N,N-diethyl At least one of dialkyl substituted aminoalkyl (meth) acrylamide such as amine ethyl (meth) acrylamide or the like.

In order to distinguish it from the hydroxyl group-containing copolymerizable monomer to be described later, the nitrogen atom-containing vinyl monomer is preferably a monomer having no hydroxyl group, and more preferably a monomer having no 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-vinylpyrrolidone, An N-vinyl substituted indoleamine such as N-vinyl caprolactam or an N-(meth)acrylinyl substituted cyclic amine such as N-(meth)acryloquinone.

Further, in the light-diffusing adhesive layer of the present invention, the nitrogen-containing vinyl monomer contained in the acrylic polymer of the adhesive composition can impart the necessary adhesive force and durability to the light-diffusing adhesive layer. In the light-diffusing adhesive layer of the present invention, a nitrogen atom-containing vinyl monomer contained in the aforementioned acrylic polymer of the adhesive composition is preferred with respect to 100 parts by weight of the (meth) acrylate monomer as a main component. The content of the body is 0 to 50 parts by weight.

Further, in the light-diffusing adhesive layer of the present invention, it is particularly preferable to use N-vinylpyrrolidone or N,N-di as the nitrogen atom-containing vinyl monomer contained in the acrylic polymer as the adhesive composition. Methyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) acrylamide, N, N-diisopropyl (A Acrylamide, N,N-dibutyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, N,N-diethylaminopropyl ( Methyl) acrylamide, N,N-dimethylamine ethyl (meth) acrylamide, N-vinyl caprolactam, and the like.

The carboxyl group-containing copolymerizable vinyl monomer (carboxyl group-containing copolymerizable monomer) may, for example, be (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl methacrylate or 2-( Methyl) propylene methoxyethyl hexahydrophthalic acid, 2-(methyl) propylene methoxy propyl hexahydrophthalic acid, 2-(methyl) propylene methoxyethyl phthalate Formic acid, 2-(methyl) propylene methoxyethyl succinic acid, 2-(methyl) propylene oxiranyl ethyl maleic acid, carboxy polycaprolactone mono (meth) acrylate, 2- (A) At least one of acryloxyethyltetrahydrophthalic acid and the like.

Further, in the light-diffusing adhesive layer of the present invention, the carboxyl group-containing copolymerizable monomer contained in the acrylic polymer of the adhesive composition can impart a necessary cohesive force to the light-diffusing adhesive layer. In the light-diffusing adhesive layer of the present invention, the acrylic polymer of the adhesive composition may not contain a carboxyl group-containing copolymerizable monomer, but when it is contained, it is contained as a main component with respect to 100 parts by weight. The content of the acrylate monomer, preferably a carboxyl group-containing copolymerizable monomer, is from 0 to 5 parts by weight.

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

Further, in the light-diffusing adhesive layer of the present invention, the hydroxyl group-containing copolymerizable monomer contained in the acrylic polymer of the adhesive composition can be used as a monomer for reducing a carboxyl group-containing copolymerizable monomer. The copolymerizable monomer is used, and the carboxyl group-containing monomer causes the obtained light-diffusing adhesive layer to have a corrosive effect on the easily corroded adherend such as ITO (indium tin oxide) surface of the transparent conductive film. . Therefore, the hydroxyl group-containing copolymerizable monomer can contribute to the improvement of the adhesion of the light-diffusing adhesive layer and the reduction of corrosion. In the light-diffusing adhesive layer of the present invention, a hydroxyl group-containing copolymerizable monomer contained in the aforementioned acrylic polymer of the adhesive composition is preferred with respect to 100 parts by weight of the (meth) acrylate monomer as a main component. The content of the body is 0.1 to 5 parts by weight.

The acrylic polymer of the adhesive composition used in the light-diffusing adhesive layer of the present invention is preferably at least one selected from the group consisting of alkyl (meth)acrylic acid alkyl ester monomers having an alkyl group having from C1 to C14. And at least one selected from the group consisting of a hydroxyl group-containing copolymerizable monomer, a nitrogen atom-containing vinyl monomer, and an aryl group-containing monomer as a monomer having a copolymerizable functional group, The copolymer having a weight average molecular weight of 200,000 to 2.5 million is formed.

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 2,500,000.

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

In the above-mentioned adhesive composition, by blending the ruthenium-based particles as a light-diffusing agent into the above copolymer (acrylic polymer), desired optical characteristics (light transmittance, haze value) can be imparted. Further, by blending a crosslinking agent and a suitable optional additive, properties such as desired physical properties can be adjusted.

The ruthenium-based particles may be selected from individual particles or composite particles containing a ruthenium compound, and specific examples thereof include ruthenium dioxide particles, cerium oxide melamine core-shell particles, fluorenone particles, and silicate glass particles. It is preferably one or more selected from the group consisting of cerium oxide particles, cerium oxide nucleocide core-shell particles, and anthrone particles. The cerium oxide melamine core-shell particle is a composite particle having a core of melamine and a shell of cerium oxide. This composite particle has a structure in which fine particles (nanoparticles) of colloidal cerium oxide are closely packed on the surface of melamine particles. Examples of the fluorenone particles include fluorenone resin particles, fluorenone rubber particles, and crosslinked fluorenone particles.

The adhesive composition used in the light-diffusing adhesive layer of the present invention preferably contains 0.01 to 20 parts by weight of cerium-based particles per 100 parts by weight of the (meth) acrylate monomer as a main component.

The crosslinking agent may, for example, be a biuret of diisocyanate such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate or benzodimethyl diisocyanate. 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; At least one of the above. Further, the adhesive may be crosslinked by photocrosslinking such as ultraviolet rays.

When a crosslinking agent is used to crosslink the copolymer, it is preferred that the copolymer has a functional group capable of undergoing a 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 is preferably contained on the side. Chains have monomers with these functional groups. Moreover, it is preferable that the adhesive composition contains 0.001 to 5 parts by weight of an isocyanate compound as a crosslinking agent with respect to 100 parts by weight of the (meth) acrylate monomer as a main component.

Further, in order to impart antistatic properties to the pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition may contain an antistatic agent such as one or two or more kinds of ionic compounds. The antistatic agent is preferably a solid at normal temperature (for example, 25 ° C). More specifically, the antistatic agent is an ionic compound having a melting point of 25 to 50 °C. The antistatic agent may be a quaternary ammonium salt type ionic compound containing an acrylonitrile group.

Since these antistatic agents have a low melting point and a long-chain alkyl group, they are presumed to have high affinity with an acrylic polymer.

When the antistatic property is imparted, the surface resistivity of the adhesive layer obtained by crosslinking the above-mentioned adhesive composition is preferably 5.0 × 10 ^{+ 10} Ω / □ or less.

The antistatic agent having an ionic compound having a melting point of 25 to 50 ° C is an ionic compound having a cation and an anion, and examples of the cation include a pyridinium cation, an imidazolium cation, a pyrimidine cation, a pyrazolium cation, and a pyrrole. a nitrogen-containing phosphonium cation such as a phosphonium cation or an ammonium cation, or a phosphonium cation or a phosphonium cation, and the anion is hexafluorophosphate (PF ₆ ^- ), thiocyanate (SCN ^- ), alkylbenzenesulfonate (RC ₆ H _{4 )} A compound of an inorganic or organic anion such as SO ₃ ^- ), perchlorate (ClO ₄ ^- ) or tetrafluoroborate (BF ₄ ^- ). A compound having a melting point of 25 to 50 ° C can be obtained by selecting the chain length of the alkyl group or the position and number of the substituent. The cation is preferably a quaternary nitrogen sulfonium cation, and examples thereof include a quaternary pyridinium cation such as 1-alkylpyridinium (having a substituent or a substituent at a carbon atom of 2 to 6), and 1,3-di A quaternary imide cation such as a quaternary imidazolium cation or a tetraalkylammonium such as a tetrazolium imidazolium (having a substituent having a carbon atom at the 2, 4 or 5 position or a substituent) may be used.

The quaternary ammonium salt-containing ionic compound containing an acrylonitrile group is an ionic compound having a cation and an anion, and examples thereof include a (meth)acryloxyalkylalkyltrialkylammonium (R ₃ N ^{+ )} -C _n H _2n -OCOCQ=CH ₂ , wherein Q=H or CH ₃ , R=alkyl), etc. (meth)acryloyl group-containing quaternary ammonium; anion is hexafluorophosphate (PF ₆ ^- ) , thiocyanate (SCN ^- ), organic sulfonate (RSO ₃ ^- ), perchlorate (ClO ₄ ^- ), tetrafluoroborate (BF ₄ ^- ), fluorinated atom ruthenium (R ^F ₂ N ^- ) A compound of an inorganic or organic anion. (PEI) as the root (R ^F ₂ N ^-) fluorine atoms, R ^F, include trifluoromethanesulfonic acyl, sulfo pentafluoroethyl acyl group such as a perfluoroalkyl sulfonic acyl, acyl-fluoro-sulfo . Examples of the fluorinated atom-containing quinary imine group include bis(fluorosulfonyl) ruthenium root [(FSO ₂ ) ₂ N ^- ], bis(trifluoromethanesulfonyl) fluorenylene root [(CF). ₃ SO ₂ ) ₂ N ^- ], bis(sulfonylsulfonyl) quinone imine [(C ₂ F ₅ SO ₂ ) ₂ N ^- ), etc.

The antistatic agent for the ionic compound having a melting point of 25 to 50 ° C is not particularly limited. Specific examples of the ionic compound having a pyridinium cation having a melting point of 25 to 50 ° C include 1-octylpyridinium dodecylbenzenesulfonate and 1-dodecylpyridinium thiocyanate. , 3-methyl-1-dodecylpyridinium hexafluorophosphate, 1-dodecylpyridinium dodecylbenzenesulfonate, 4-methyl-1-octylpyridinium hexafluorophosphate Salt and so on.

Further, specific examples of the acryl-based quaternary ammonium salt-containing ionic compound include dimethylaminomethyl (meth) acrylate hexafluorophosphate methyl salt [(CH ₃ ) ₃ N ⁺ CH ₂ OCOCQ=CH ₂ •PF ₆ ^- , wherein Q=H or CH ₃ ], dimethylaminoethyl (meth) acrylate bis(trifluoromethanesulfonyl) fluorene imine methyl salt [(CH) ₃ ) ₃ N ⁺ (CH ₂ ) ₂ OCOCQ=CH ₂ •(CF ₃ SO ₂ ) ₂ N ^- , wherein Q=H or CH ₃ ], dimethylaminomethyl (meth)acrylate bis (fluorine) Sulfhydryl) quinone imine methyl salt [(CH ₃ ) ₃ N ⁺ CH ₂ OCOCQ=CH ₂ • (FSO ₂ ) ₂ N ^- , wherein Q = H or CH ₃ ] and the like.

In addition, in the case where the ionic compound having a melting point of 25 to 50 ° C is contained in the above-mentioned adhesive composition, it is preferably 100 parts by weight of the (meth) acrylate monomer as the main component. The content ratio thereof is 0.1 to 5.0 parts by weight.

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 antibiotic may be suitably blended. A well-known additive such as an aging agent. These may be used alone or in combination of two or more.

The light-diffusing adhesive layer of the present invention can be obtained by applying the above-mentioned pressure-sensitive adhesive composition to a substrate or a release film (release film) and then crosslinking the pressure-sensitive adhesive composition.

The adhesive layer for interlayer bonding or the like of the optical member is desirably a thin adhesive layer, and it is preferable that the light-diffusing adhesive layer has a thickness of 1 μm to 20 μm. Further, in general, the adhesive force of the adhesive layer is approximately proportional to the thickness of the adhesive layer. However, in the present invention, when the thickness of the light-diffusing adhesive layer is 20 μm, the adhesion to the glass plate is 2.0 N/25 mm or more. In addition, when the thickness of the adhesive layer is not 20 μm, the "adhesion at a thickness of 20 μm" (N/25 mm) is such that the thickness of the adhesive layer is set to T (μm) and the adhesive layer is adhered. The force is set to F (N/25 mm) and is estimated by the formula "(adhesion at a thickness of 20 μm) = 20 × F / T".

When the light-diffusing adhesive layer of the present invention is used for interlayer bonding or the like of an optical member, the light-transmitting adhesive layer preferably has a light transmittance of 90% or more, a haze value of 40% or more, and a refractive index of 1.47 or more. . The haze value is preferably 40% or more and 90% or less. In order to reduce light reflection on the interface between the light-diffusing 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 light-diffusing adhesive layer is preferably 1.47 to 1.50.

Further, in order to secure a haze value of 40% or more, it is necessary to diffuse light inside the light-diffusing adhesive layer. Therefore, it is preferable that the interface reflectance between the copolymer and the cerium-based particles is 0.01% or more. Here, when the refractive index of the copolymer is n _a and the refractive index of the ruthenium particles is n _b , the interface reflectance (K) is expressed as follows (Formula 1).

Further, when the interface reflectance K is expressed in percentage (%), 100 times of the right side value can be further calculated. [Math 1]

Further, when the copolymer contains mixed particles composed of two different cerium-like particles (A, B), the interface reflectance (K ₂ ) is determined according to the following formula (Formula 2). [Math 2] (Formula 2)

here,

K ₂ : interface reflectance between copolymer and mixed particles (%)

K _A : interface reflectance between copolymer and particle A (%)

K _B : interface reflectance between copolymer and particle B (%)

A ₁ : ratio of addition of particles A in the mixed particles (% by weight)

B ₁ : ratio of addition of particles B in the mixed particles (% by weight)

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

As the release film (separator) for forming the base film of the light-diffusing adhesive layer or the protective adhesive surface, a resin film such as a polyester film or the like can be used.

The base film can be subjected to a release agent or a coating agent of an anthrone or a fluorine, a ceria particle, or the like on a surface of the resin film opposite to the side on which the light diffusion adhesive layer is formed. The antifouling treatment can be carried out by an antistatic treatment by coating 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 adhesion surface of the light-diffusing adhesive layer is bonded.

The surface of the release film that has been subjected to the release treatment by bonding the release film to both surfaces of the light-diffusing adhesive layer can form a "release film/light diffusion adhesive layer/release film". 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 anti-glare film, an ultraviolet absorbing film, an infrared absorbing film, an optical compensation film, and a brightness enhancement film. For example, it is preferred to use a light diffusing adhesive layer between the layers of the polarizing plate and the brightness enhancing film.

The light-diffusing 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 for peripheral members of liquid crystal displays mainly including polarizing plates. in.

Further, an optical film having an adhesive layer may be prepared by laminating the light-diffusing adhesive layer on at least one surface of these optical films. Specifically, "optical film / light diffusing adhesive layer / optical film", "optical film / light diffusing adhesive layer / release film", "optical film / light diffusing adhesive layer", "optical film / Light diffusing adhesive layer / optical film / light diffusing adhesive layer / optical film", "optical film / light diffusing adhesive layer / optical film / light diffusing adhesive layer / release film", "release film / light diffusion" The composition of the adhesive layer/optical film/light diffusion adhesive layer/release film. When an adhesive layer is provided on both surfaces of the optical film, it is also possible to provide only one side of the optical diffusing adhesive layer.

For example, in the case of a light-diffusing adhesive layer protected by a release film like the "optical film/light-diffusion adhesive layer/release film", the release film is peeled off to expose an image like "optical film/light diffusion adhesion". A light-diffusing adhesive layer such as a "agent layer" is bonded to another optical film, whereby a light-diffusing adhesive layer can be used for interlayer bonding such as "optical film/light diffusion adhesive layer/optical film". Composition.

Example

Hereinafter, the present invention will be specifically described based on examples.

<Manufacture of Acrylic 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, thereby replacing the air in the reaction device with nitrogen. Then, 85 parts by weight of butyl acrylate, 10 parts by weight of benzyl acrylate, 5 parts by weight of benzyl methacrylate, 1.5 parts by weight of 6-hydroxyhexyl acrylate, and 10 parts by weight of diethyl benzene were added to the reaction apparatus. Acrylamide and 60 parts by weight of a solvent (ethyl acetate) were simultaneously added. Then, 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 copolymer of Example 1 having a weight average molecular weight of 700,000. Solution 1. A part of the acrylic copolymer was used as an acid value measurement sample to be described later.

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

Except that the composition of each monomer was adjusted as described in (A), (B), (C), and (D) of Table 1, the same procedure as in the above-described acrylic copolymer solution 1 used in Example 1 was carried out. The acrylic copolymer solutions used in Examples 2 to 5 and Comparative Examples 1 to 3 were obtained.

<Preparation of Adhesive Composition, Light-Diffusion Adhesive Layer, and Light-Diffusing Adhesive Film>

[Example 1]

In the acrylic copolymer solution 1 of Example 1 produced as described above, 0.2 part by weight of Coronate HX (isocyanurate of hexamethylene diisocyanate compound) and 3.0 parts by weight of cerium oxide melamine core shell were added. The particles (particle diameter: 2 μm, refractive index: 1.65) were stirred and mixed to obtain the pressure-sensitive adhesive composition of Example 1. The adhesive composition is applied onto a release film composed of a polyethylene terephthalate (PET) film coated with an fluorenone resin, and then dried at a temperature of 90 ° C to remove the solvent, and then, After aging for 7 days in an environment of 23° C. and 50% RH, the light of Example 1 having a light-diffusing adhesive layer (thickness: 20 μm) obtained by crosslinking the adhesive composition on one surface of the release film was obtained. Spread the adhesive film.

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

Except that the composition of the additive was adjusted as described in (E) and (F) of Table 1, the same procedure as in the light diffusion adhesive film of Example 1 was carried out, and Examples 2 to 5 and Comparative Example 1 were obtained. 3 light diffuses the adhesive film. 【Table 1】

In Table 1, the numerical values in parentheses indicate the parts by weight of the respective components. The parts by weight are determined by the total amount of the (meth)acrylic monomers in which the main component is set, that is, the total of the components (A) and (B) is 100 parts by weight.

Further, the compound names corresponding to the abbreviations of the respective components used in Table 1 are shown in Table 2. Here, Coronate (registered trademark) HX, Coronate HL, and Coronate L-45 are trade names of Japan Polyurethane Co., Ltd., and D-110N is a trade name of Mitsui Chemicals Co., Ltd. HDI refers to hexamethylene diisocyanate, TDI refers to toluene diisocyanate, and XDI refers to benzenedimethyl diisocyanate. 【Table 2】

<Test method and evaluation>

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

<Method for measuring adhesion>

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

The light-diffusing adhesive film was bonded to the non-tin surface of the soda lime glass washed with acetone by a pinch roller, and subjected to autoclave treatment at 50 ° C and 0.5 MPa × 20 minutes. Then, it was returned to an environment of 23 ° C × 50% RH, and the peeling strength of the light diffusion adhesive film after one hour passed was measured by a tensile tester according to JIS Z0237 "Adhesive tape, adhesive sheet test method", and was 300 mm. The peel strength at which the speed of /min is peeled off in the 180° direction serves as the adhesion of the light-diffusing adhesive layer of the light-diffusing adhesive film.

<Method for Measuring Refractive Index of Light-Diffusing Adhesive Layer>

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

<Method for measuring interface reflectance>

The refractive index n _{a of the} copolymer is considered to be equal to the refractive index of the light-diffusing adhesive layer measured in the previous item, and the refractive index of the ruthenium-like particles is set to n _b , by calculating the mathematical formula ((n _{a -} n _{b )} / (n _a + n _b )) ² × 100 (%), and the interface reflectance between the copolymer and the ruthenium-based particles was determined. When the light-diffusing adhesive layer contains two kinds of quinone particles, it is calculated according to the above (Formula 2).

<Method for measuring light transmittance>

Method for Measuring Light Transmittance: The light transmittance of the light-diffusing adhesive layer was measured in accordance with JIS K7105, "Test Method for Optical Properties of Plastics".

<Method for measuring haze value>

Method for measuring haze value: The haze value of the light-diffusing adhesive layer was measured in accordance with JIS K7136, "Haze Calculation Method for Plastic-Transparent Material".

<Test method for durability>

A 10 cm square adhesive film prepared in the same manner as the adhesion measurement was applied to a non-tin surface of soda lime glass to prepare a sample, which was placed in an environment of 80 ° C × 90% RH. After 250 hours, the mixture was taken out to an environment of 23 ° C × 50% RH, and the state of the light-diffusing adhesive film after 1 hour was visually observed to judge the durability.

○: Peeling and foaming of the light diffusion adhesive film were not produced at all.

△: Part of the light-diffusing adhesive film was peeled off and foamed.

×: Peeling and foaming occurred in the entirety of the light-diffusing adhesive film.

The measurement results of Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 3. 【table 3】

In the light-diffusing adhesive films of Examples 1 to 5, when the thickness of the light-diffusing adhesive layer was 20 μm, the adhesion to the glass plate was 2.0 N/25 mm or more. Further, the light-diffusing adhesive layer has a refractive index of 1.47 or more and a light transmittance of 90% or more, and the interface reflectance between the copolymer and the cerium-based particles is 0.01% or more, and the haze value is 40% or more. Durability is also excellent. That is, the light-diffusing adhesive films of Examples 1 to 5 can satisfy the required requirements and overcome the problems.

For reference, using the same light-diffusing adhesive composition as in Examples 1 to 5, a light-diffusing adhesive film having a thickness of the light-diffusing adhesive layer of 10 μm, 13 μm, 15 μm, and 20 μm was produced in the same manner. The light transmittance and haze value of the light-diffusing adhesive layer were measured, and the results are shown in Table 4. The light transmittance of the light-diffusing adhesive layer using the light-diffusing adhesive composition does not depend on the film thickness of the adhesive layer, but it is understood that the haze value is lowered when the thickness of the adhesive layer is thin. 【Table 4】

The adhesive film of Comparative Example 1 has a low refractive index because the monomer composition of the acrylic polymer is a single 2EHA; and the interface reflectance is 0% because the refractive index of the copolymer is equal to the refractive index of the ruthenium-based particles. For the sake of this, the haze value is low. Moreover, the durability is also poor.

In the adhesive film of Comparative Example 2, the content of the alkyl (meth)acrylate monomer having a C1 to C14 alkyl group is low, and the content of the ruthenium particles is large, and the adhesion is low and the light transmittance is high. The rate is low and the durability is also poor.

In the adhesive film of Comparative Example 3, since the content of the quinone particles was small, the haze value was low, and the adhesive composition was not crosslinked, and the durability was also poor.

As described above, the adhesive films of Comparative Examples 1 to 3 could not satisfy the proposed requirements and overcome the problems existing in the past.

Claims (8)

A light diffusing adhesive layer having a light diffusing function, the light diffusing adhesive layer being formed of an adhesive composition containing a copolymer and a crosslinking agent and an anthracene particle, the copolymer being a carbon atom of an alkyl group a monomer having a number of C1 to C14 alkyl (meth) acrylate monomers; and a monomer having a copolymerizable functional group selected from a hydroxyl group-containing copolymerizable monomer and a nitrogen atom-containing monomer a copolymer having a weight average molecular weight of 200,000 to 2.5 million obtained by copolymerizing at least one or more monomers selected from the group consisting of a vinyl monomer and an aryl group-containing monomer, wherein the thickness of the light-diffusing adhesive layer is The transmittance at 20 μm is 90% or more, and the haze value is 40% or more and 90% or less, and the content of the ruthenium-based particles is 0.01 to 20 parts by weight based on 100 parts by weight of the copolymer. The light-diffusing adhesive layer according to claim 1, wherein when the thickness of the light-diffusing adhesive layer is 20 μm, the adhesion to the glass plate is 2.0 N/25 mm or more. The light-diffusing adhesive layer according to claim 1 or 2, wherein the adhesive composition comprises a copolymer and an isocyanate compound as the crosslinking agent, and the copolymer is 70 to 95 parts by weight. At least one or more monomers having an alkyl group having a C1-C14 alkyl (meth) acrylate monomer, and at least 5 to 30 parts by weight of an aryl group-containing (meth) acrylate monomer 100 parts by weight of one or more monomers, at least one of 0.1 to 5 parts by weight of at least one of the hydroxyl group-containing copolymerizable vinyl monomers, and at least at least 0 to 50 parts by weight of the nitrogen atom-containing vinyl monomer a copolymer obtained by copolymerizing one or more monomers, wherein the content of the isocyanate compound as the crosslinking agent is 0.001 to 5 parts by weight based on 100 parts by weight of the copolymer, and the cerium particles are selected from two One or more of the group consisting of cerium oxide particles, cerium oxide melamine core-shell particles, and anthrone particles. A light-diffusing adhesive film which is formed by forming a light-diffusing adhesive layer according to any one of claims 1 to 3 on one side of a release film, and having a release film/light diffusion adhesive layer/release film Composition. A light-diffusing adhesive film obtained by laminating the light-diffusing adhesive layer according to any one of claims 1 to 3 on one surface of a substrate. An adhesive film for a peripheral member of a polarizing plate, which uses the light-diffusing adhesive film described in claim 5. An adhesive film using the light-diffusing adhesive layer according to any one of claims 1 to 3 between the layers of the polarizing plate and the brightness enhancement film. An optical film having an adhesive layer, wherein the light-diffusing adhesive layer according to any one of claims 1 to 3 is laminated on at least one surface of the optical film.