TWI668282B - Adhesive composition and adhesive film - Google Patents

Abstract

Provided are an adhesive composition capable of forming an adhesive layer having a good reworkability and high adhesion although being a thin film, and an adhesive film using the same. The adhesive composition includes an acrylic polymer of a copolymer having an acid value of 0.1 or less and a weight average molecular weight of 1 million or more, and (3) an isocyanate compound of a crosslinking agent, the acrylic polymer containing (1) selected from At least one or more (methyl groups) in a monomer group consisting of (meth) acrylic acid alkyl ester monomers having C1 to C14 alkyl groups and (meth) acrylic acid ester monomers containing aryl groups ) Acrylic acid ester monomer, containing at least 30 parts by weight or more of butyl acrylate in a total of 100 parts by weight (1), and containing no carboxyl-containing copolymerizable vinyl monomer but containing 0.1 to 3.5 with respect to (1) The content of (2) a hydroxyl group-containing copolymerizable vinyl monomer, and (3) the content of the crosslinking agent with respect to (1) is 0.01 to 0.8 parts by weight.

Description

Adhesive composition and adhesive film

The present invention relates to an adhesive composition and an adhesive film for bonding optical components such as polarizing plates.

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

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

Patent Document 2 describes an optical adhesive using a (meth) acrylate having an alkyl group having 4 to 8 carbon atoms as a main component monomer, a carboxyl group-containing monomer, and a nitrogen-containing vinyl monomer. combination.

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

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

Patent Document 4 describes an adhesive sheet including 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 including an aromatic ring-containing tackifying resin and an aromatic phosphate-based plasticizer.

Patent Document 6 describes an adhesive obtained by curing an adhesive composition, which includes: an acrylic resin; and an aromatic compound containing one ethylenically unsaturated group.

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

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

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Application Publication No. 2012-177022

Patent Document 2: Japanese Patent Application Publication No. 2012-201734

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

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

Patent Document 5: Japanese Patent Application Publication No. 2012-167188

Patent Document 6: Japanese Patent Application Publication No. 2012-021148

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

Patent Document 8: Japanese Patent Laid-Open No. 2009-091522

In recent years, in order to reduce the thickness of optical components, The adhesive film for interlayer bonding of optical components is required to be a thin adhesive film with an adhesive layer.

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 reduced, the adhesive force will be reduced accordingly.

However, in recent years, adhesive films are required to have the following properties: Even if the thickness of the adhesive layer is reduced, the adhesive film has the same adhesive force as a conventional adhesive film (the adhesive layer is a thick layer having a thickness of about 30 μm ). In terms of durability after being left for a long period of time in a high temperature and high humidity environment, it has performance equivalent to or higher than conventional adhesive films.

In addition, from the viewpoint of being able to reduce the thickness of the adhesive layer and forming an adhesive layer that does not require aging treatment (curing at a constant temperature), it is required to be in the form of an NCF (Non Carrier Film) It consists only of an adhesive layer with the adhesive film base material removed and has a "release film (release film) / adhesive layer / release film" component.

In addition, in the conventional adhesive film, since the aging treatment is performed after the adhesive film is bonded to the adherend, the adhesion between the adherend and the adhesive layer can be improved.

However, for an adhesive film in the form of NCF, since the aging treatment of the adhesive layer has been completed, the adhesion between the adherend and the adhesive layer is insufficient. For this reason, there is a problem that surface treatment such as corona treatment is required on the surface of the adherend.

Therefore, there is a need for an adhesive film that meets these requirements and overcomes these problems.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a thin film that has excellent reworkability and high resolvability. An adhesive composition for an adhesive adhesive layer, and an adhesive film using the adhesive composition.

In order to solve the above-mentioned problems, the adhesive composition of the present invention is characterized by using a hydroxyl group-containing copolymerizable vinyl monomer without using a carboxyl group as a functional group-containing monomer as butyl acrylate as an essential monomer and as a functional group-containing monomer. The copolymer of a copolymerizable vinyl monomer having a weight average molecular weight of 1 million or more uses an isocyanate compound as a crosslinking agent, and it is more preferable to use a silane coupling agent in combination.

In addition, in order to solve the above problems, the present invention provides an adhesive composition including an acrylic polymer as a copolymer having an acid value of 0.1 or less and a weight average molecular weight of 1 million or more; and (3 ) An isocyanate compound as a crosslinking agent, The acrylic polymer contains (1) a (meth) acrylic acid ester monomer selected from alkyl (meth) acrylic acid alkyl ester monomers having 1 to 14 carbon atoms in the alkyl group and an aromatic group-containing At least one or more of a monomer group composed of a (meth) acrylate monomer, and containing at least 30 parts by weight or more of butyl acrylate in a total of 100 parts by weight of the (meth) acrylate monomer, In addition, the acrylic polymer does not contain a carboxyl group-containing copolymerizable vinyl monomer, but contains (2) a hydroxyl group-containing copolymerization with respect to 100 parts by weight of the (meth) acrylate monomer in total. 0.1 ~ 3.5 parts by weight of vinyl monomer, The content of the isocyanate compound (3) as a crosslinking agent is 0.01 to 0.8 parts by weight based on 100 parts by weight of the (meth) acrylate monomer in total.

With respect to 100 parts by weight of the aforementioned (meth) acrylate mono It is preferable to further contain (4) a silane coupling agent in an amount of 0.01 to 0.5 parts by weight.

The isocyanate compound is preferably a trimethylolpropane adduct of toluene diisocyanate.

The (2) hydroxyl-containing copolymerizable vinyl monomer is preferably selected from the group consisting of 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and (meth) acrylic acid 4 -At least one or more of a compound group consisting of -hydroxybutyl ester and 2-hydroxyethyl (meth) acrylate.

In addition, the present invention provides an adhesive layer, which is an adhesive layer obtained by cross-linking the aforementioned adhesive composition. The cross-linked gel fraction is 40 to 75%, and the thickness of the adhesive layer is 25 μm . Adhesive force is 1.5 ~ 6.0N / 25mm.

Moreover, it is preferable that the adhesive force after adhering the said adhesive layer to an adherend at 70 degreeC x 10 days is 1.5-10N / 25mm.

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

In addition, the present invention provides an adhesive film for bonding a polarizing plate and a display panel, which uses the aforementioned adhesive film.

In addition, the present invention provides an adhesive layer which is used as an adhesive layer of a polarizing plate with an adhesive layer.

In addition, the present invention provides an adhesive layer used as an adhesive layer of a polarizing plate with an adhesive layer, and a phase having a phase difference of λ / 4 or λ / 2 is used as a constituent material of the polarizing plate. Poor film.

In addition, the present invention provides an optical film with an adhesive layer, wherein the aforementioned adhesive layer is laminated on at least one side of the optical film.

According to the present invention, it is possible to obtain an adhesive layer having both flexibility, rigidity, durability, and reworkability, and an adhesive film using the adhesive layer. The adhesive layer is characterized in that it is compatible with conventional adhesives. When the layer has a smaller amount of crosslinking agent and a smaller number of functional groups than the layer, it can be an adhesive layer having a high gel fraction after crosslinking.

Although the adhesive film of the present invention is a thin film, it has excellent reworkability and high adhesive properties.

[Practice of Invention]

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

The adhesive composition of the present invention includes an acrylic polymer as a copolymer having an acid value of 0.1 or less and a weight average molecular weight of 1 million or more; and (3) an isocyanate compound as a crosslinking agent, The acrylic polymer contains (1) a (meth) acrylic acid ester monomer selected from alkyl (meth) acrylic acid alkyl ester monomers having 1 to 14 carbon atoms in the alkyl group and an aromatic group-containing At least one or more of a monomer group composed of a (meth) acrylate monomer, and containing at least 30 parts by weight or more of butyl acrylate in a total of 100 parts by weight of the (meth) acrylate monomer, In addition, the acrylic polymer does not contain a carboxyl group-containing copolymerizable vinyl monomer, but contains (2) a hydroxyl group-containing copolymerization with respect to 100 parts by weight of the (meth) acrylate monomer in total. 0.1 ~ 3.5 parts by weight of vinyl monomer, With respect to a total of 100 parts by weight of the (meth) acrylate monomer, The content of said (3) isocyanate compound as a crosslinking agent is 0.01-0.8 weight part.

In the adhesive composition of the present invention, as the (meth) acrylic acid alkyl ester monomer having an alkyl group of C1 to C14, examples include (meth) acrylic acid methyl ester and (meth) acrylic acid. Ethyl ester, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, amyl (meth) acrylate, (meth) acrylic acid Hexyl ester, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, (formyl) (Isyl) isononyl acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, (formyl) At least one type of tetradecyl acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, or the like. The alkyl group in the (meth) acrylic acid alkyl ester monomer may be any of linear, branched, and cyclic.

In a total of 100 parts by weight of the (meth) acrylic acid ester monomer, the total content of the alkyl (meth) acrylic acid ester monomer having C1 to C14 in the alkyl group is preferably 70 parts by weight or more, and may be 100 parts by weight. The proportion of the (meth) acrylic acid alkyl ester monomer having C1 to C14 in the alkyl group is preferably 50 to 99.9 parts by weight based on 100 parts by weight of the acrylic polymer (copolymer) of the adhesive composition. In the present invention, butyl acrylate is used as an essential monomer. It is preferable that the content of butyl acrylate is at least 30 parts by weight or more in a total of 100 parts by weight of the (meth) acrylate monomer.

In addition, in the present invention, for the adhesive composition, the (meth) acrylic acid alkyl group having a carbon number of C1 to C14 in the alkyl group is 100 parts by weight in total. The content of the methyl acrylate monomer in the (meth) acrylate monomer composed of one or more of the ester monomers is 20 parts by weight or more, and the refractive index of the adhesive layer can be increased to 1.47 or more.

In the adhesive composition of the present invention, as the (meth) acrylate monomer, there may be one or more of (aryl) group-containing (meth) acrylate monomers. Examples of the aryl group-containing (meth) acrylate monomer include benzyl (meth) acrylate, naphthyl (meth) acrylate, phenoxyethyl (meth) acrylate, and phenoxy (meth) acrylate Butyl ester, 2- (1-naphthyloxy) ethyl (meth) acrylate, 2- (2-naphthyloxy) ethyl (meth) acrylate, 6- (1-naphthyloxy) (meth) acrylate ) Hexyl ester, 6- (2-naphthyloxy) hexyl (meth) acrylate, 8- (1-naphthyloxy) octyl (meth) acrylate, 8- (2-naphthyloxy) (meth) acrylate Octyl ester and the like. In order to obtain an adhesive layer having a high refractive index, it is preferable to mix at least one or more aryl group-containing (meth) acrylate monomers.

By mixing these aryl group-containing (meth) acrylic acid ester monomers with C1-C14 alkyl (meth) acrylic acid alkyl ester monomers, the obtained adhesive layer can be refracted It is possible to improve the total light transmittance by adjusting the refractive index to reduce the refractive index difference between the optical components and reduce the total reflection. In the adhesive layer of the present invention, when the adhesive composition includes an aryl group-containing (meth) acrylate monomer, the aryl group-containing ( The content of the meth) acrylate monomer is 5 to 30 parts by weight.

In addition, by co-polymerizing an aryl group-containing (meth) acrylate monomer and containing 20 parts by weight or more of a methyl acrylate monomer in a total of 100 parts by weight of the (meth) acrylate monomer, the adhesive is improved. Effect of the layer's refractive index In contrast, the refractive index of the adhesive layer can be further increased.

In addition, as described above, as a method of increasing the refractive index of the adhesive layer, there are two methods including a method of containing 20 parts by weight or more of a methyl acrylate monomer in a total of 100 parts by weight of the (meth) acrylate monomer. And a method of copolymerizing an aryl group-containing (meth) acrylate monomer; Each method can be used independently, but it is more preferable to use the two methods together.

In the adhesive composition of the present invention, the acrylic polymer as the functional group-containing monomer does not include a carboxyl group-containing copolymerizable vinyl monomer, but includes a hydroxyl group-containing copolymerizable vinyl monomer. As the functional group-containing monomer, only a hydroxyl-containing copolymerizable vinyl monomer may be used.

Examples of the hydroxyl-containing copolymerizable vinyl monomer include 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Hydroxyl-containing (meth) acrylic acid alkyl esters such as 2-hydroxyethyl (meth) acrylate; N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, At least one or more of hydroxyl-containing (meth) acrylamides such as N-hydroxyethyl (meth) acrylamide and the like.

Among these, it is preferable that the hydroxyl-containing copolymerizable vinyl monomer is selected from the group consisting of 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. And at least one of the compound group consisting of 2-hydroxyethyl (meth) acrylate.

In addition, in the adhesive layer of the present invention, the hydroxyl group-containing copolymerizable vinyl monomer contained in the adhesive composition can be used as a copolymerizable ethylene for reducing the content of the carboxyl group-containing copolymerizable vinyl monomer. Based monomer, and the carboxyl group-containing copolymerizable vinyl monomer makes the obtained adhesive layer conductive to transparent The ITO surface of the film is corrosive, which is easily corroded. Therefore, the hydroxyl-containing copolymerizable vinyl monomer can help improve the adhesion of the adhesive layer and reduce the corrosiveness. In the adhesive layer of the present invention, the content of the hydroxyl-containing copolymerizable vinyl monomer in the adhesive composition is preferably 0.1 to 3.5 parts by weight based on 100 parts by weight of the (meth) acrylate monomer in total.

The acrylic polymer of the adhesive composition used in the adhesive layer of the present invention is a copolymer having an acid value of 0.1 or less and a weight average molecular weight of 1 million or more, and contains (1) as a (meth) acrylate monoester At least one selected from the group consisting of an alkyl (meth) acrylic acid ester monomer having 1 to 14 carbon atoms in the alkyl group and an aromatic (meth) acrylic acid ester-containing monomer And the content of butyl acrylate is at least 30 parts by weight or more in a total of 100 parts by weight of the (meth) acrylate monomer, In addition, the acrylic polymer does not contain a carboxyl group-containing copolymerizable vinyl monomer, but contains (2) a hydroxyl group-containing copolymerization with respect to 100 parts by weight of the (meth) acrylate monomer in total. 0.1 to 3.5 parts by weight of a vinyl monomer.

The polymerization method of the copolymer is not particularly limited, and an appropriate known polymerization method such as a solution polymerization method or an emulsion polymerization method can be used. The acrylic polymer preferably contains 50 to 100% by weight of an acrylic monomer such as a (meth) acrylate monomer or a (meth) acrylamide.

The said adhesive composition can adjust characteristics, such as a required physical-property value, by mix | blending a crosslinking agent and an appropriate arbitrary additive with the said acrylic polymer.

As the (3) crosslinking agent, hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, Modified biuret or isocyanurate of diisocyanates such as xylylene diisocyanate, adducts of trivalent or higher polyhydric alcohols such as trimethylolpropane or glycerol, etc. At least one of polyisocyanate compounds. The acrylic polymer preferably contains a hydroxyl group as a functional group capable of performing a crosslinking reaction with the isocyanate compound of the crosslinking agent, and further preferably contains a monomer having these functional groups on a side chain. Moreover, it is preferable that an adhesive composition contains 0.01-0.8 weight part of isocyanate compounds with respect to 100 weight part of (meth) acrylate monomers in total. As the (3) crosslinking agent, only an isocyanate compound may be used. The isocyanate compound is preferably an adduct of toluene diisocyanate, and particularly preferably a trimethylolpropane adduct of toluene diisocyanate.

The adhesive composition preferably further contains (4) a silane coupling agent. (4) The silane coupling agent may be a compound having at least one organic functional group and at least one hydrolyzable group in one molecule, and the hydrolyzable group is an alkoxy group or the like bonded to a silicon atom. Preferably, the silane coupling agent has at least one organic functional group selected from the group consisting of an epoxy group, a (meth) acrylfluorenyl group, a mercapto group, and an amino group. Here, the (meth) acryloxy group means acryloxy group (CH ₂ = CHCOO-) or a methacryloxy group (CH ₂ = C (CH ₃ ) COO-).

Examples of the silane coupling agent having an epoxy group include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-epoxy Propoxypropylmethyldimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- ( 3,4-epoxycyclohexyl) ethylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethylmethyldiethoxysilane, 2- (3,4-epoxy (Cyclohexyl) ethyltriethoxysilane, 5,6-epoxyhexyltrimethoxysilane, 5,6-epoxyhexylmethyldimethoxysilane Alkane, 5,6-epoxyhexylmethyldiethoxysilane, 5,6-epoxyhexyltriethoxysilane and the like.

Examples of the silane coupling agent having a (meth) acrylic fluorenyloxy group include 3- (meth) acryloxypropyltrimethoxysilane, and 3- (meth) acryloxypropylmethyl Dimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 3- (meth) acryloxypropylmethyldiethoxysilane, 3- (methyl) ) Acryloxypropyldimethylethoxysilane, 3- (meth) acryloxypropyldimethylmethoxysilane, and the like.

Examples of the silane coupling agent having a mercapto group include 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, 3 -Mercaptopropyltriethoxysilane and the like.

Examples of the silane coupling agent having an amino group include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N -2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldiethoxysilane, N-2- ( (Aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltriethoxysilane, 3- (methylamino) propyltrimethoxysilane, 3- (methylamino) propyltriethoxysilane and the like.

In addition, an alkoxy oligomer (silyloxy oligomer) or the like containing the organic functional group and oligomerized may be used as the silane coupling agent.

The content of the (4) silane coupling agent is preferably 0.01 to 0.5 parts by weight based on 100 parts by weight of the (meth) acrylate monomer in total.

As other optional components, antioxidants, Known additives such as surfactants, curing accelerators, plasticizers, fillers, crosslinking catalysts, crosslinking inhibitors, curing inhibitors, processing aids, and anti-aging agents. These may be used alone or in combination of two or more.

The adhesive layer of the present invention can be obtained by coating the adhesive composition on a substrate or a release film and then crosslinking the adhesive composition. The gel fraction of the crosslinked adhesive layer is preferably 40 to 75%.

In the case of interlayer bonding of optical components, etc., a thin adhesive layer is desirable. The thickness of the adhesive layer is preferably 1 μm to 25 μm , and more preferably 5 μm to 25 μm . In addition, the adhesive force of the adhesive layer is generally approximately proportional to the thickness of the adhesive layer, but the adhesive force of the adhesive layer having a thickness of 25 μm is preferably 1.5 to 6.0 N / 25 mm. In addition, it is preferable that the adhesive force after bonding the adhesive layer to the adherend at 70 ° C. × 10 days is 1.5 to 10 N / 25 mm. Examples of the adherend include glass plates such as non-glass, resin films, and the like.

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

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

As a base film for forming an adhesive layer or a release film (separator) for protecting an adhesive surface, a resin film such as a polyester film can be used.

For the base film, the surface of the resin film opposite to the side where the adhesive layer is formed can be protected with a silicone-based, fluorine-based release agent or coating agent, or silica particles. Dirt treatment, coating or mixing with antistatic agent Antistatic treatment performed.

The release film is subjected to a release treatment with a silicone-based, fluorine-based release agent, or the like on the surface to be bonded to the adhesive surface of the adhesive layer.

A mold release film / adhesive layer / release film can be formed by laminating the release film-treated surfaces on both sides of one adhesive layer. In this case, by peeling the release films on both sides sequentially or simultaneously to expose the adhesive surface, it is possible to adhere to optical components such as optical films. Examples of the optical film include a polarizing film, a retardation film, an anti-reflection film, an anti-glare film, an ultraviolet absorbing film, an infrared absorbing film, an optical compensation film, and a brightness enhancement film.

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

In addition, the above-mentioned adhesive layer can be laminated on at least one side of these optical films to produce an optical film with an adhesive layer. Specifically, "optical film / adhesive layer / optical film", "optical film / adhesive layer / release film", "optical film / adhesive layer", "optical film / adhesive layer / optical film" / Adhesive layer / optical film "," optical film / adhesive layer / optical film / adhesive layer / release film "," release film / adhesive layer / optical film / adhesive layer / release film ", etc. Composition.

For example, in the case of "optical film / adhesive layer / release film", in the case of having an adhesive layer protected by a release film, peeling off the release film exposes a film like "optical film / adhesive layer" The adhesive layer is bonded to other optical films to obtain a structure such as "optical film / adhesive layer / optical film" using the adhesive layer for interlayer bonding.

The adhesive film of the present invention can be preferably used for bonding a polarizing plate and a display panel. For example, it is used as an adhesive layer of a polarizing plate with an adhesive layer. As a constituent material of the polarizing plate, a retardation film having a retardation of λ / 4 or λ / 2 can be used.

[Example]

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

<Production of acrylic polymer>

[Example 1]

Nitrogen was introduced into a reaction device 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, 100 parts by weight of butyl acrylate, 0.2 parts by weight of 8-hydroxyoctyl acrylate, and 60 parts by weight of a solvent (ethyl acetate) were simultaneously added to the reaction device. Then, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours, and the mixture was reacted at 65 ° C. for 6 hours to obtain a weight average molecular weight of 1 million or more, which was used in Example 1. Acrylic polymer solution 1. A part of the acrylic polymer was taken and used as an acid value measurement sample described later.

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

Except that the composition of each monomer was adjusted separately as described in the groups (1) and (2) in Table 1, the same operation as in the acrylic polymer solution 1 used in Example 1 described above was performed to obtain The acrylic polymer solutions in Examples 2 to 5 and Comparative Examples 1 to 3. Although the measurement results are not particularly shown, the weight average molecular weight of the acrylic polymer contained in the acrylic polymer solutions of Examples 2 to 5 and Comparative Examples 1 to 3 was 1 million or more.

<Manufacture of an adhesive composition, an adhesive layer, and an adhesive film>

[Example 1]

To the acrylic polymer solution 1 of Example 1 manufactured as described above, 0.2 parts by weight of Coronate L ( L) (Toluene diisocyanate (TDI) compound trimethylolpropane (TMP) adduct), 0.05 parts by weight of KBM-403 (3-glycidoxypropyltrimethoxysilane), and stirred Thus, the adhesive composition of Example 1 was obtained. This adhesive composition was coated on a release film composed of a polyethylene terephthalate (PET) film coated with a silicone resin, and then dried at 90 ° C to remove the solvent, and then And cured for 7 days in an environment of 23 ° C and 50% RH, thereby obtaining Example 1 having an adhesive layer having a thickness of 25 μm and having a thickness of 25 μm , which was crosslinked with the adhesive composition on one side of the release film Adhesive film.

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

Except that the composition of the additives was adjusted separately as described in groups (3) and (4) of Table 1, the same operation as in the adhesive film of Example 1 described above was carried out to obtain Examples 2 to 5 and Comparative Examples 1 to 3 adhesive film.

In Table 1, the values in parentheses indicate the values of parts (2) to (4) obtained by setting the total weight of the (1) group to 100 parts by weight, and used as (2) to (4) ) Group addition ratio.

In addition, the compound names corresponding to the abbreviations of the respective components used in Table 1 are shown in Table 2. In addition, Coronate ( , Registered trademark) L is the trade name of Nippon Polyurethane Industry Co., Ltd., D-110N is the trade name of Mitsui Chemicals Co., Ltd., KBM-403 and KBM-803 are Shin-Etsu Chemical Industry Co., Ltd. Product name. TDI refers to toluene diisocyanate, TMP refers to trimethylolpropane, and XDI refers to xylylene diisocyanate. In Tables 1 and 2, the carboxyl group-containing copolymerizable vinyl monomer and the hydroxyl group-containing copolymerizable vinyl monomer are included in the group (2).

<Test method and evaluation>

The release film (PET film coated with silicone resin) was peeled from the adhesive films of Examples 1 to 5 and Comparative Examples 1 to 3 to expose the adhesive layer, and the adhesive layer was transferred to a single sheet of a polarizing plate (film). Surface.

<Method for measuring adhesive force>

An adhesive layer having a thickness of 25 μm was transferred to one side of a polarizing plate (film) having a thickness of 180 μm , and an adhesive film (optical film with an adhesive layer) was obtained as a sample.

The obtained adhesive film was adhered to a non-tin surface of a non-durable glass washed with acetone by a pressure roller, and then subjected to autoclave treatment at 50 ° C, 0.5 MPa × 20 minutes, and then returned to 23 ° C × 50 % RH, 1 hour passed. The peeling strength of the subsequent adhesive film was measured using a tensile tester in accordance with JIS Z0237 "Test Method for Adhesive Tapes and Adhesive Sheets", and the peeling strength when peeled in a 180 ° direction at a speed of 300 mm / min was taken as the Adhesive force of the adhesive layer (N / 25mm).

<Method for measuring acid value>

The acid value of the acrylic polymer was determined as follows: A sample was dissolved in a solvent (a solvent in which diethyl ether and ethanol were mixed at a volume ratio of 2: 1), and an automatic titration device (AT-610, Kyoto) was used. (Produced by Electronics Industries, Ltd.), potentiometric titration was performed with a potassium hydroxide ethanol solution having a concentration of about 0.1 mol / L, and the amount of potassium hydroxide ethanol solution required for neutralizing the sample was measured. Then, the acid value was obtained by the following formula.

Acid value = (B × f × 5.611) / S

B = 0.1 mol / L potassium hydroxide ethanol solution used in titration (mL)

f = 0.1mol / L factor of potassium hydroxide ethanol solution (factor)

S = Quality of the solid content of the sample (g)

<Method for measuring gel fraction>

Accurately measure the quality of the test sample after the aging is completed and before the polarizing plate is attached. After immersing in toluene for 24 hours, it is filtered through a 200-mesh wire mesh. Then, after the filtered matter was dried at 100 ° C. for 1 hour, the quality of the residue was accurately measured, and the gel fraction of the adhesive layer (adhesive after crosslinking) was calculated according to the following formula.

Gel fraction (%) = quality of insoluble portion (g) / quality of adhesive (g) × 100

<Durability test method>

A 10 cm square adhesive film prepared by the same method as that used for measuring the adhesive force was attached to the non-tin surface of a non-tin glass in the same manner to prepare a sample, and the sample was placed in a predetermined environment (80 ° C). After 250 hours in a dry environment or an environment of 60 ° C. × 90% RH), take it out to an environment of 23 ° C. × 50% RH and visually observe the state of the adhesive film after 1 hour to judge the durability.

○: No peeling or foaming occurred in the adhesive film.

Δ: Part of the adhesive film was peeled and foamed.

×: Peeling and foaming occurred in the entire adhesive film.

<Test method for reworkability>

A 10 cm square adhesive film prepared by the same method as that used for measuring the adhesive force was attached to the non-tin surface of non-tinted glass in the same manner to prepare a sample, and the sample was placed in an environment at 70 ° C. 10 After a few days, it was taken out to an environment of 23 ° C., and the adhesive force of the adhesive film after standing for 1 hour was measured to determine reworkability.

(Circle): The adhesive force after 70 degreeC x 10 days is 1.5-10N / 25mm.

△: Adhesion at 70 ° C × 10 days is greater than 10N / 25mm but less than 20N / 25mm.

×: Adhesion at 70 ° C × 10 days is greater than 20N / 25mm (unpeelable).

The evaluation results are shown in Table 3. Regarding the acid value, it was confirmed that the acrylic polymers of Examples 1 to 5 and Comparative Examples 2 and 3 having no carboxyl group-containing copolymerizable vinyl monomers had an acid value of 0.1 or less and had a carboxyl group-containing copolymerization The acrylic polymer of Comparative Example 1 of the vinyl monomer had an acid value of more than 0.1.

In the adhesive films of Examples 1 to 5, the adhesive force of the adhesive layer with a thickness of 25 μm was in the range of 1.5 to 6.0 N / 25 mm, and the gel fraction of the adhesive layer after crosslinking was 40 to 75%. In addition, it has excellent adhesion and durability. In addition, the adhesive force in the range of 1.5 to 10 N / 25 mm after bonding to the adherend at 70 ° C for 10 days is also excellent in reworkability. That is, the adhesive films of Examples 1 to 5 can meet the required requirements and can overcome the problems existing in the prior art.

The adhesive film of Comparative Example 1 may be because the (meth) acrylate monomer does not contain butyl acrylate, and has a carboxyl-containing copolymerizable vinyl monomer as a functional group-containing monomer, and has a high gel fraction. For this reason, the adhesive layer with a thickness of 25 μm has strong adhesion, and has poor durability and reworkability under 60 ° C × 90% RH environment.

The adhesive film of Comparative Example 2 may have a high gel fraction due to the excessive blending amount of the hydroxyl-containing copolymerizable vinyl monomer in the adhesive composition, and its durability in the 60 ° C. × 90% RH environment was poor. In addition, the durability and reworkability in a dry environment at 80 ° C are also slightly inferior.

Since the adhesive film of Comparative Example 3 has neither a carboxyl group-containing copolymerizable vinyl monomer nor a hydroxyl group-containing copolymerizable vinyl monomer in the adhesive composition, the acrylic polymer does not cross The adhesive strength of the adhesive layer with a gel fraction of 0 and a thickness of 25 μm is very strong. As a result, durability and reworkability are inferior.

In this way, the adhesive films of Comparative Examples 1 to 3 were unable to meet the conventional requirements and overcome the problems that existed in the past.

Claims (11)

An adhesive layer is an adhesive layer formed by cross-linking an adhesive composition containing an acrylic polymer and a cross-linking agent, wherein the acrylic polymer is selected from a total of 100 parts by weight of At least one or more (methyl groups) in a monomer group consisting of (meth) acrylic acid alkyl ester monomers having C1 to C14 alkyl groups and (meth) acrylic acid ester monomers containing aryl groups ) Acrylic acid ester monomer, and 0.1 to 3.5 parts by weight of a hydroxyl-containing copolymerizable vinyl monomer, the acid value obtained by copolymerization without containing a carboxyl-containing copolymerizable vinyl monomer is 0.1 or less The copolymer having a weight-average molecular weight of 1 million or more contains butyl (meth) acrylate in a proportion of at least 30 parts by weight or more in a total of 100 parts by weight of the (meth) acrylate monomer, and contains 20 weight Parts or more of (meth) acrylic acid methyl ester monomers or aryl group-containing (meth) acrylic acid ester monomers in a proportion of 5 to 30 parts by weight, based on 100 parts by weight of the (meth) acrylic acid Ester monomer, the adhesive composition contains 0.01 to 0.8 parts by weight of an isocyanate compound Said cross-linking agent, a refractive index of 1.47 to 1.50. The adhesive layer according to item 1 of the scope of patent application, wherein the adhesive composition further contains 0.01 to 0.5 parts by weight of silane with respect to 100 parts by weight of the (meth) acrylate monomer in total. Coupling agent. The adhesive layer according to item 1 or 2 of the patent application scope, wherein the isocyanate compound is a trimethylolpropane adduct of toluene diisocyanate. The adhesive layer according to item 1 or 2 of the patent application scope, wherein the hydroxyl-containing copolymerizable vinyl monomer is selected from the group consisting of 8-hydroxyoctyl (meth) acrylate, (meth) At least one or more compounds selected from the group consisting of 6-hydroxyhexyl acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxyethyl (meth) acrylate. According to the adhesive layer described in item 1 or 2 of the patent application scope, the gel fraction after crosslinking is 40 to 75%, and the adhesive force of the adhesive layer with a thickness of 25 μm is 1.5 to 6.0 N / 25 mm. The adhesive layer according to item 5 of the patent application scope, wherein the adhesive force after the adhesive layer is adhered to the adherend at 70 ° C. × 10 days is 1.5 to 10 N / 25 mm. An adhesive film is formed by laminating an adhesive layer according to any one of claims 1 to 6 of a patent application scope on one side of a substrate. An adhesive film for bonding a polarizing plate and a display panel uses the adhesive film described in item 7 of the scope of patent application. The adhesive layer according to item 5 of the scope of patent application is used as an adhesive layer of a polarizing plate with an adhesive layer. The adhesive layer described in item 5 of the scope of patent application is used as an adhesive layer of a polarizing plate with an adhesive layer, and a material having λ / 4 or λ / 2 is used as a constituent material of the polarizing plate. Phase difference retardation film. An optical film with an adhesive layer is provided with at least one side of the optical film laminated with the adhesive layer according to any one of claims 1 to 6.