KR20200039643A - Adhesive film - Google Patents

Abstract

The present invention relates to an adhesive layer having an excellent rework property and a high adhesion property despite being a thin film, and an adhesive film using the same. The adhesive layer contains an alkyl (meta) acrylate monomer having C1-C14 carbon numbers of an alkyl group and/or a (meta) acrylate monomer having an aromatic group (1); contains at least 30 parts by weight or more of butyl acrylate in the (1); excludes a carboxyl group containing copolymerizable vinyl monomer; contains 0.1-3.5 parts by weight of a hydroxyl containing copolymerizable vinyl monomer (2) for the (1); contains an acrylic polymer which 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 0.01-0.8 parts by weight of an isocyanate compound as a crosslinking agent (3) for the (1). The adhesive layer includes 40-75% of a gel fraction after crosslinking, 1-25 μm of a thickness, and 1.5-6.0 N/25mm of an adhesive force of 25 μm thickness.

Description

Adhesive film {ADHESIVE FILM}

The present invention relates to an adhesive layer and an adhesive film used for bonding optical members such as polarizing plates.

Various adhesive films have been proposed to adhere optical members such as polarizing plates and retardation plates to adherends such as liquid crystal cells via an adhesive layer (see, for example, Patent Documents 1 to 2).

Patent Document 1 discloses an optical pressure-sensitive adhesive composition containing butyl acrylate or the like as a main component monomer and containing an acrylamide compound or the like.

Patent document 2 discloses an optical pressure-sensitive adhesive composition containing (meth) acrylate having an alkyl group having 4 to 8 carbon atoms as a main component monomer, and containing a carboxyl group-containing monomer and a nitrogen-containing vinyl monomer.

Further, in order to increase the refractive index of the pressure-sensitive adhesive layer, various pressure-sensitive adhesive films have been proposed (see, for example, Patent Documents 3 to 8).

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

Patent document 4 discloses an adhesive sheet containing an adhesive composition comprising a copolymerizable polymer of an acrylic acid-modified monomer having an aromatic ring.

Patent Document 5 discloses an optical pressure-sensitive adhesive composition containing an tackifying resin having an aromatic ring and an aromatic phosphate ester plasticizer.

Patent document 6 describes an adhesive in which an adhesive composition containing an acrylic resin and an aromatic compound having one ethylenically unsaturated group is cured.

Patent Document 7 describes an optical component formed by fixing a retardation film and a birefringent plate to each other via an acrylic pressure-sensitive adhesive containing an aromatic monomer.

Patent document 8 discloses an adhesive composition comprising a urethane resin formed by reacting an aromatic diisocyanate with an aromatic polyester diol.

Japanese Patent Application Publication No. 2012-177022 Japanese Patent Application Publication 2012-201734 Japanese Patent Publication No. 2007-084762 Japanese Patent Application Publication No. 2011-153169 Japanese Patent Application Publication 2012-167188 Japanese Patent Application Publication No. 2012-021148 Japanese Patent Publication No. 2006-293281 Japanese Patent Application Publication No. 2009-091522

In recent years, what is required for the pressure-sensitive adhesive film used to bond the layers of the optical member is to make the pressure-sensitive adhesive film with a thin thickness of the pressure-sensitive adhesive layer in order to promote thinning of the optical member.

In general, since the adhesive force of the pressure-sensitive adhesive layer is approximately proportional to the thickness of the pressure-sensitive adhesive layer, when the thickness of the pressure-sensitive adhesive layer is reduced, the adhesive force is lowered.

However, the pressure-sensitive adhesive film required in recent years has the same adhesive strength as that of a conventional pressure-sensitive adhesive film (the thickness of the pressure-sensitive adhesive layer is about 30 µm) even when the thickness of the pressure-sensitive adhesive layer is thin, and is left for a long time in an atmosphere of high temperature and high humidity. It is also required to have a performance equal to or higher than that of the conventional adhesive film for the durability afterwards.

In addition, in that the thickness of the pressure-sensitive adhesive layer can be reduced and that the pressure-sensitive adhesive layer that does not need to be subjected to aging treatment (curing at constant temperature) can be formed, the pressure-sensitive adhesive layer consists of only the pressure-sensitive adhesive layer. It has been desired to form a non-carrier film (NCF) having a member structure of "release film / adhesive layer / release film".

In addition, in the conventional adhesive film, since the aging treatment is performed after bonding the adhesive film to the adherend, it is possible to improve the adhesion between the adherend and the pressure-sensitive adhesive layer.

However, in the adhesive film in the form of NCF, since the aging of the pressure-sensitive adhesive layer has already been completed, the adhesion between the adherend and the pressure-sensitive adhesive layer is insufficient. For this reason, there is a problem that it is necessary to perform surface treatment such as corona treatment on the surface of the adherend.

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

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an adhesive layer having excellent rework performance and high adhesion performance and an adhesive film using the same despite being a thin film.

In order to solve the above problems, the pressure-sensitive adhesive layer according to the present invention uses butyl acrylate as an essential monomer as the pressure-sensitive adhesive composition, does not use a carboxyl group-containing copolymerizable vinyl monomer as a functional group-containing monomer, and uses a hydroxyl group-containing copolymerizable vinyl monomer. It is characterized by using an isocyanate compound as a crosslinking agent, more preferably a silane coupling agent, for a copolymer having a weight average molecular weight of 1 million or more.

In addition, in order to solve the above problems, the present invention provides a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition made of an acrylic polymer, wherein the pressure-sensitive adhesive composition is (1) a (meth) acrylate monomer having an alkyl group having C1 to C14 alkyl. It contains at least 1 sort (s) or more selected from the monomer group which consists of a (meth) acrylate monomer and a (meth) acrylate monomer which has an aromatic group, and at least 30 butyl acrylates in 100 parts by weight of the total of the (meth) acrylate monomers. It contains 0.1 to 3.5 parts by weight of (2) a hydroxyl group-containing copolymerizable vinyl monomer, based on 100 parts by weight of the above-mentioned (meth) acrylate monomer, and does not contain a carboxyl group-containing copolymerizable vinyl monomer. Is 0.1 or less, and an acrylic polymer having a weight average molecular weight of 1 million or more, and (meth) (3) A pressure-sensitive adhesive composition containing 0.01 to 0.8 parts by weight of an isocyanate compound as a crosslinking agent, based on 100 parts by weight of the acrylate monomer, the gel fraction after crosslinking is 40 to 75%, and the thickness of the pressure-sensitive adhesive layer is 1 µm. It provides a pressure-sensitive adhesive layer characterized in that the adhesive force of the pressure-sensitive adhesive layer of 25 µm to 25 µm is 1.5 to 6.0 N / 25 mm.

Moreover, it is preferable to contain 0.01-0.5 weight part of (4) silane coupling agents with respect to 100 weight part of the said (meth) acrylate monomer in the said adhesive composition.

Moreover, it is preferable that the isocyanate compound in the said adhesive composition is a trimethylolpropane adduct of tolylene diisocyanate.

In addition, (2) hydroxyl group-containing copolymerizable vinyl monomer in the pressure-sensitive adhesive composition is 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxy butyl (meth) acrylate, 2 -It is preferable that it is at least 1 sort (s) or more selected from the compound group which consists of hydroxyethyl (meth) acrylates.

Moreover, it is preferable that the adhesive force after 70 degreeCx10 days after bonding the said adhesive layer to an adherend is 1.5-10 N / 25 mm.

In addition, the present invention provides a pressure-sensitive adhesive film, characterized in that the pressure-sensitive adhesive layer is formed on one side of the release film, and is composed of a release film / adhesive layer / release film.

In addition, the present invention provides an adhesive film characterized in that the pressure-sensitive adhesive layer is laminated on one side of the substrate.

In addition, the present invention provides an adhesive film used for bonding the polarizing plate and the display panel on which the adhesive film is used.

In addition, the present invention provides a polarizing plate is formed on the pressure-sensitive adhesive layer is used the adhesive film.

In addition, the present invention provides a polarizing plate in which the pressure-sensitive adhesive layer is used, wherein the pressure-sensitive adhesive layer is used, and a phase difference film having a phase difference of λ / 4 or λ / 2 is used as a constituent material.

In addition, the present invention provides an optical film on which at least one side of the optical film is provided with a pressure-sensitive adhesive layer on which the pressure-sensitive adhesive layer is laminated.

According to the present invention, the adhesive layer having a high gel fraction after crosslinking is reduced while reducing the amount of crosslinking agent and functional group, compared to the conventional adhesive layer, and the adhesive layer has flexibility, rigidity, durability and rework properties, and The used adhesive film can be obtained.

Although the adhesive film of the present invention is a thin film, it has excellent rework performance and high adhesion performance.

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

The pressure-sensitive adhesive layer of the present invention is a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition made of an acrylic polymer, wherein the pressure-sensitive adhesive composition is (1) an alkyl (meth) acrylate monomer having C1 to C14 carbon atoms as the (meth) acrylate monomer. And at least one selected from the group of monomers consisting of (meth) acrylate monomers having an aromatic group, and at least 30 parts by weight of butyl acrylate, and a carboxyl group, in 100 parts by weight of the total of (meth) acrylate monomers. It contains 0.1 to 3.5 parts by weight of (2) hydroxyl group-containing copolymerizable vinyl monomer, and contains 0.1 to 3.5 parts by weight of the hydroxyl group-containing copolymerizable vinyl monomer, based on 100 parts by weight of the (meth) acrylate monomer. An acrylic polymer having an average molecular weight of 1 million or more copolymer and the (meth) acrylate monomer With respect to 100 parts by weight in total, (3) a pressure-sensitive adhesive composition containing 0.01 to 0.8 parts by weight of an isocyanate compound as a crosslinking agent, the gel fraction after crosslinking is 40 to 75%, and the thickness of the pressure-sensitive adhesive layer is 1 μm to 25 μm. , It characterized in that the adhesive strength of the pressure-sensitive adhesive layer of 25㎛ is 1.5 ~ 6.0N / 25㎜.

In the pressure-sensitive adhesive composition according to the present invention, alkyl (meth) acrylate monomers having C1 to C14 carbon atoms in the alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and isopropyl (Meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, iso Octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl ( And at least one or more of meta) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, cyclopentyl (meth) acrylate, and cyclohexyl (meth) acrylate. The alkyl group of the alkyl (meth) acrylate monomer may be linear, branched or cyclic.

Of 100 parts by weight of the (meth) acrylate monomer, the total number of alkyl (meth) acrylate monomers having C1 to C14 carbon atoms in the alkyl group is preferably 70 parts by weight or more, and may be 100 parts by weight. The alkyl (meth) acrylate monomer having C1 to C14 carbon atoms in the alkyl group preferably has a proportion of 50 to 99.9 parts by weight of 100 parts by weight of the acrylic polymer (copolymer) of the pressure-sensitive adhesive composition. In the present invention, butyl acrylate is used as an essential monomer. It is preferable to contain at least 30 parts by weight of butyl acrylate among 100 parts by weight of the (meth) acrylate monomer.

Furthermore, in the present invention, the monomer of methyl acrylate is 20 in 100 parts by weight of the (meth) acrylate monomer in which the pressure-sensitive adhesive composition is composed of one or more of alkyl (meth) acrylate monomers having C1 to C14 alkyl groups. By containing in a proportion of parts by weight or more, the refractive index of the pressure-sensitive adhesive layer can be increased to 1.47 or more.

The pressure-sensitive adhesive composition according to the present invention may further contain at least one (meth) acrylate monomer having an aromatic group as the (meth) acrylate monomer. Examples of the (meth) acrylate monomer having an aromatic group include benzyl (meth) acrylate, naphthyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxybutyl (meth) acrylate, and 2- (1- Naphthyloxy) ethyl (meth) acrylate, 2- (2-naphthyloxy) ethyl (meth) acrylate, 6- (1-naphthyloxy) hexyl (meth) acrylate, 6- (2-naphthyl And oxy) hexyl (meth) acrylate, 8- (1-naphthyloxy) octyl (meth) acrylate, 8- (2-naphthyloxy) octyl (meth) acrylate, and the like. In order to obtain an adhesive layer having a high refractive index, it is preferable to blend at least one of (meth) acrylate monomers having an aromatic group.

By mixing the (meth) acrylate monomer having these aromatic groups with an alkyl (meth) acrylate monomer having C 1 to C 14 carbon atoms, the refractive index of the resulting pressure-sensitive adhesive layer can be increased and adjusted, reducing the difference in refractive index between optical members, The total light transmittance can be improved by reducing total reflection. In the pressure-sensitive adhesive layer according to the present invention, in the case where the pressure-sensitive adhesive composition contains a (meth) acrylate monomer having an aromatic group, it is preferably contained in a proportion of 5 to 30 parts by weight, out of 100 parts by weight of the total of (meth) acrylate monomers. Do.

In addition, by copolymerizing the (meth) acrylate monomer having an aromatic group, the effect of increasing the refractive index of the pressure-sensitive adhesive layer by incorporating a methylacrylate monomer in a proportion of 20 parts by weight or more out of 100 parts by weight of the (meth) acrylate monomer It is possible to further increase the refractive index of the pressure-sensitive adhesive layer.

In addition, as described above, as a method of increasing the refractive index of the pressure-sensitive adhesive layer, a method of containing a monomer of methyl acrylate in a proportion of 20 parts by weight or more out of 100 parts by weight of (meth) acrylate monomer, and (meth) having an aromatic group There are two methods of copolymerizing the acrylate monomer, and each method can be employed alone, but it is more preferable to use the two methods in combination.

In the pressure-sensitive adhesive composition of the present invention, the acrylic polymer does not contain a carboxyl group-containing copolymerizable vinyl monomer as a functional group-containing monomer, and contains a hydroxyl group-containing copolymerizable vinyl monomer. As the functional group-containing monomer, only a hydroxyl group-containing copolymerizable vinyl monomer may be used.

Examples of the hydroxyl-containing copolymerizable vinyl monomer include 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxy Alkyl (meth) acrylates containing hydroxyl groups such as ethyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, etc. And hydroxyl group-containing (meth) acrylamides.

Among them, hydroxyl-containing copolymerizable vinyl monomers include 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxyethyl (metha) It is preferable that it is at least 1 sort (s) or more selected from the compound group which consists of acrylates.

In addition, in the pressure-sensitive adhesive layer according to the present invention, the hydroxyl group-containing copolymerizable vinyl monomer contained in the pressure-sensitive adhesive composition is believed to affect the corrosive properties of the transparent conductive film, such as the ITO surface, which are easily corroded. It can be used as a copolymerizable monomer for reducing the content of the contained copolymerizable vinyl monomer. For this reason, the hydroxyl group-containing copolymerizable vinyl monomer can help to improve the adhesive strength of the pressure-sensitive adhesive layer and also to reduce corrosiveness. In the pressure-sensitive adhesive layer according to the present invention, the hydroxyl group-containing copolymerizable vinyl monomer contained in the pressure-sensitive adhesive composition is preferably 0.1 to 3.5 parts by weight, out of 100 parts by weight of the (meth) acrylate monomer.

The acrylic polymer of the pressure-sensitive adhesive composition used in the pressure-sensitive adhesive layer of the present invention is (1) a (meth) acrylate monomer as an alkyl (meth) acrylate monomer having a C1 to C14 alkyl group and a (meth) acrylate monomer having an aromatic group. It contains at least 1 sort (s) or more chosen from the group of monomers which consists, and, in 100 weight part of the said (meth) acrylate monomer, it contains at least 30 weight part or more of butyl acrylate, and does not contain a carboxyl group-containing copolymerizable vinyl monomer. It is a copolymer which contains 0.1-3.5 weight part of (2) hydroxyl group-containing copolymerizable vinyl monomers with respect to 100 weight part of (meth) acrylate monomers, has an acid value of 0.1 or less, and a weight average molecular weight of 1 million or more.

The polymerization method of the copolymer is not particularly limited, and a suitable 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 (meth) acrylate monomer or (meth) acrylamide.

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

(3) Examples of the crosslinking agent include, for example, burette-modified products of diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate, and isocyanurate modified products. And at least one polyisocyanate compound such as trimethylolpropane or an adduct with trivalent or higher polyols such as glycerin. It is preferable that the acrylic polymer has a hydroxyl group as a functional group capable of crosslinking reaction with an isocyanate compound of a crosslinking agent, and it is also preferable to contain a monomer having these functional groups in a side chain. Moreover, it is preferable that the adhesive composition contains 0.01-0.8 weight part of isocyanate compounds with respect to 100 weight part of (meth) acrylate monomers in total. (3) You may use only an isocyanate compound as a crosslinking agent. As the isocyanate compound, an adduct of tolylene diisocyanate is preferred, and a trimethylolpropane adduct of tolylene diisocyanate is particularly preferred.

It is preferable that the said adhesive composition contains (4) silane coupling agent further. (4) As a silane coupling agent, the compound which has at least 1 organic functional group in 1 molecule, and at least 1 hydrolysable group, and the said hydrolysable group is the alkoxy group couple | bonded with the silicon atom etc. is mentioned. It is preferable that the silane coupling agent has at least one organic functional group selected from the group consisting of an epoxy group, (meth) acryloxy group, mercapto group, and amino group. Here, (meth) acryloxy group means acryloxy group (CH ₂ = CHCOO-) or methacryloxy group (CH ₂ = C (CH ₃ ) COO-).

Examples of the silane coupling agent having an epoxy group include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidyl Doxypropyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethylmethyldimethoxysilane, 2- (3,4-epoxycyclo Hexyl) ethylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 5,6-epoxyhexyltrimethoxysilane, 5,6-epoxyhexylmethyldimethoxysilane, 5,6 -Epoxyhexyl methyl diethoxysilane, 5,6-epoxyhexyl triethoxysilane, etc. are mentioned.

Examples of the silane coupling agent having a (meth) acryloxy group include 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropylmethyldimethoxysilane, and 3- (meth) acryloxy And propyltriethoxysilane, 3- (meth) acryloxypropylmethyldiethoxysilane, 3- (meth) acryloxypropyldimethylethoxysilane, and 3- (meth) acryloxypropyldimethylmethoxysilane.

Examples of the silane coupling agent having a mercapto group include 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, and 3-mercaptopropyl And triethoxysilane.

Examples of the silane coupling agent having an amino group include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and N-2- (amino Ethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldiethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N- 2- (aminoethyl) -3-aminopropyl triethoxysilane, 3- (methylamino) propyl trimethoxysilane, 3- (methylamino) propyl triethoxysilane, etc. are mentioned.

Moreover, the alkoxy oligomer (silicone alkoxy oligomer) etc. which contain the said organic functional group and oligomerized can also be used as a silane coupling agent.

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

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

The adhesive layer of this invention can be obtained by apply | coating the said adhesive composition to a base material or a release film, and crosslinking an adhesive composition. The gel fraction of the pressure-sensitive adhesive layer after crosslinking is preferably 40 to 75%.

When used for interlayer bonding of an optical member, it is preferable that it is a thin pressure-sensitive adhesive layer, and the thickness of the pressure-sensitive adhesive layer is preferably 1 μm to 25 μm, more preferably 5 μm to 25 μm. Further, in general, the adhesive strength of the pressure-sensitive adhesive layer is approximately proportional to the thickness of the pressure-sensitive adhesive layer, but it is preferable that the pressure-sensitive adhesive strength of the pressure-sensitive adhesive layer having a thickness of 25 μm is 1.5 to 6.0 N / 25 mm. Moreover, it is preferable that the adhesive force of 70 to 10 days after bonding the adhesive layer to the adherend is 1.5 to 10 N / 25 mm. As an adherend, a glass plate, such as an alkali free glass, a resin film, etc. are mentioned.

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

The adhesive film of this invention can be manufactured by forming the adhesive layer of this invention on one side of a base material or a release film.

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

The base film may be subjected to an antistatic treatment by anti-fouling treatment with a silicone-based, fluorine-based release agent or coating agent, silica fine particles, or an antistatic agent, etc., on a surface opposite to the side on which the pressure-sensitive adhesive layer of the resin film is formed.

The release film is subjected to a release treatment with a silicone-based, fluorine-based release agent or the like on the side of the pressure-sensitive adhesive layer that is aligned with the adhesion surface.

It is also possible to form a "release film / adhesive layer / release film" by aligning the surfaces on which both sides of one pressure-sensitive adhesive layer are subjected to a release treatment of a release film. In this case, the release films on both sides are sequentially or simultaneously peeled to expose the adhesive surface, whereby it is possible to bond with optical members such as optical films. Examples of the optical film include a polarizing film, a retardation film, an antireflection film, an anti-glare (anti-glare) film, an ultraviolet absorbing film, an infrared absorbing film, an optical compensation film, and a brightness enhancing film.

The pressure-sensitive adhesive film of the present invention can be used for bonding various optical films for peripheral members of liquid crystal display devices mainly comprising polarizing plates, various optical films for touch panels, various optical films for electronic paper, and various optical films for organic EL.

Moreover, it can be set as the optical film in which the adhesive layer in which the said adhesive layer was laminated | stacked is formed 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" and the like.

For example, in the case of having an adhesive layer protected by a release film, such as "optical film / adhesive layer / release film", the release film is peeled to expose the adhesive layer like "optical film / adhesive layer", and other optical By bonding to the film, a structure such as "optical film / adhesive layer / optical film" in which the pressure-sensitive adhesive layer is used for interlayer bonding is obtained.

The adhesive film of the present invention is preferably used for bonding of a polarizing plate and a display panel. For example, it is used as an adhesive layer of the polarizing plate in which the adhesive layer is formed. A retardation film having a phase difference of λ / 4 or λ / 2 may be used as a constituent material of the polarizing plate.

Example

Hereinafter, the present invention will be described in detail through examples.

<Production of acrylic polymers>

[Example 1]

Nitrogen gas was introduced into a reaction device equipped with a stirrer, a thermometer, a reflux cooler, and a nitrogen introduction tube, and air in the reaction device was replaced with nitrogen gas. Then, 60 parts by weight of a solvent (ethyl acetate) was added to the reaction apparatus together with 100 parts by weight of butyl acrylate and 0.2 parts by weight of 8-hydroxyoctyl acrylate. Thereafter, 0.1 part by weight of azobisisobutyronitrile was added dropwise over 2 hours as a polymerization initiator, and reacted at 65 ° C for 6 hours to obtain an acrylic polymer solution (1) used in Example 1 having a weight average molecular weight of 1 million or more. Got. A part of the acrylic polymer was collected and used as a measurement sample for the acid value described later.

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

Examples 2 to 5 and Comparative Example 1 were made in the same manner as in the acrylic polymer solution (1) used in Example 1, except that the monomer compositions were as described in Groups (1) and (2) in Table 1, respectively. The acrylic polymer solution used for -3 was obtained. Moreover, although the measurement result is not specifically shown, the weight average molecular weight of the acrylic polymer contained in the acrylic polymer solution of Examples 2-5 and Comparative Examples 1-3 is 1 million or more.

<Production of adhesive composition, adhesive layer and adhesive film>

[Example 1]

With respect to the acrylic polymer solution (1) of Example 1 prepared as described above, 0.2 parts by weight of coronate L (trimethylolpropane (TMP) adduct of tolylene diisocyanate (TDI) compound), KBM-403 (3- Glycidoxypropyltrimethoxysilane) 0.05 parts by weight was added and stirred and mixed to obtain the pressure-sensitive adhesive composition of Example 1. This adhesive composition is coated on a release film made of a polyethylene terephthalate (PET) film coated with a silicone resin, and then dried at 90 ° C to remove the solvent, followed by aging for 7 days in an atmosphere of 23 ° C, 50% RH to crosslink the pressure-sensitive adhesive composition. The adhesive film of Example 1 which has the adhesive layer of thickness 25 micrometers formed on one side of a release film was obtained.

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

The adhesive films of Examples 2 to 5 and Comparative Examples 1 to 3 were made in the same manner as the adhesive films of Example 1, except that the composition of the additives was as described in Groups (3) and (4) in Table 1, respectively. Got.

In Table 1, the numerical values of the parts by weight are shown in parentheses as the addition ratio from the group (2) to the group (4), which was obtained by setting the total number of groups (1) to 100 parts by weight.

In addition, Table 2 shows the compound names of the abbreviations of the components used in Table 1. Incidentally, Coronate (registered trademark) L is a trade name of Nihon Polyurethane Industry Co., Ltd., D-110N is a trade name of Mitsui Chemical Co., Ltd., and KBM-403 and KBM-803 are trade names of Shin-Etsu Chemical Co., Ltd. TDI means tolylene diisocyanate, TMP means trimethylolpropane, and XDI means xylylene diisocyanate. In Table 1 and Table 2, the carboxyl group-containing copolymerizable vinyl monomer was described in group (2) together with the hydroxyl group-containing copolymerizable vinyl monomer.

<Test method and evaluation>

The release film (silicone resin coated PET film) was peeled 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 transferred to one side of the polarizing plate (film).

<Method of measuring adhesive force>

An adhesive layer having a thickness of 25 μm was transferred to one surface of a polarizing plate (film) having a thickness of 180 μm to obtain an adhesive film (an optical film on which an adhesive layer was formed) serving as a sample.

The obtained adhesive film was adhered to a non-tin surface washed with acetone of an alkali-free glass with a pressing roll, autoclaved under conditions of 50 ° C and 0.5 MPa x 20 minutes, and then returned to an atmosphere of 23 ° C x 50% RH, and for 1 hour. Passed. The peel strength of the subsequent adhesive film was measured by a tensile tester in accordance with JIS Z0237 "Adhesive Tape / Adhesive Sheet Test Method", and the peel strength when peeled at a rate of 300 mm / min in the 180 ° direction was an adhesive film. It was set as the adhesive force (N / 25 mm) of the pressure-sensitive adhesive layer.

<Measurement method of acid value>

The acid value of the acrylic polymer is dissolved in a sample (a mixture of diethyl ether and ethanol in a volume ratio of 2: 1), using a potentiometric automatic titration device (Kyoto Electronics Industry Co., Ltd., AT-610) to have a concentration of about 0.1. Potentiometric titration was performed with a mol / L potassium hydroxide ethanol solution to measure the amount of potassium hydroxide ethanol solution needed to neutralize the sample. And the acid value was calculated | required from the following formula.

Acid value = (B × f × 5.611) / S

B = amount of 0.1 mol / l potassium hydroxide ethanol solution used in titration (ml)

f = 0.1mol / ℓ Potassium hydroxide solution

S = mass of sample solids (g)

<Measurement method of gel fraction>

After the aging is finished, 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 200 mesh wire mesh. Thereafter, the filtrate was dried at 100 ° C. for 1 hour, the mass of the residue was accurately measured, and the gel fraction of the pressure-sensitive adhesive layer (pressure-sensitive adhesive after cross-linking) was calculated from the following formula.

Gel fraction (%) = insoluble partial mass (g) / adhesive mass (g) x 100

<Durability test method>

A sample prepared by bonding an adhesive film of 10 cm in width and a non-tinned surface of an alkali-free glass in the same manner as in the measurement of the adhesive force in a predetermined atmosphere (80 ° C dry atmosphere, or 60 ° C x 90% RH) After leaving for 250 hours under the atmosphere), the mixture was taken out under an atmosphere of 23 ° C x 50% RH, and after 1 hour, the state of the adhesive film was visually observed to determine durability.

There is no peeling or foaming of the adhesive film.

Δ ... Peeling and foaming are occurring on a part of the adhesive film.

Peeling and foaming are occurring in the whole of the adhesive film.

<Test method of rework property>

A sample prepared by bonding an adhesive film of 10 cm in width and a non-tinned surface of an alkali-free glass in the same manner as in the measurement of the adhesive force was left in an atmosphere of 70 ° C. for 10 days, and then taken out under an atmosphere of 23 ° C., The rework property was determined by measuring the adhesive strength of the adhesive film after standing for 1 hour.

The adhesive strength after 70 占 폚 x 10 days was 1.5 to 10 N / 25 mm.

The adhesive strength after Δ · 70 ° C. × 10 days is greater than 10 N / 25 mm, but less than 20 N / 25 mm.

The adhesive force after 10 days at 70 占 폚 was greater than 20 N / 25 mm (cannot be peeled off).

Table 3 shows the evaluation results. As to the acid value, the acrylic polymer of Comparative Example 1 containing the carboxyl group-containing copolymerizable vinyl monomer is 0.1 or less, and the acrylic polymer of Examples 1 to 5 and Comparative Examples 2 and 3 not containing a carboxyl group-containing copolymerizable vinyl monomer is 0.1 or less. It was confirmed that the acid value of was greater than 0.1.

The adhesive films of Examples 1 to 5 had a thickness of 25 µm and the adhesive strength of the adhesive layer in the range of 1.5 to 6.0 N / 25 mm, the gel fraction of the adhesive layer after crosslinking was 40 to 75%, and excellent adhesion and durability. In addition, the rework property was excellent because the adhesive strength after 70 ° C. x 10 days after bonding to the adherend was in the range of 1.5 to 10 N / 25 mm. That is, the adhesive films of Examples 1 to 5 were able to overcome the requirements and problems.

The adhesive film of Comparative Example 1 does not contain butyl acrylate as a (meth) acrylate monomer, contains a carboxyl group-containing copolymerizable vinyl monomer as a functional group-containing monomer, and is because of a high gel fraction or of a 25 µm thick adhesive layer. The adhesive strength was strong, and the durability and rework property were poor in an atmosphere of 60 ° C x 90% RH.

The pressure-sensitive adhesive film of Comparative Example 2 is because the amount of the hydroxyl group-containing copolymerizable vinyl monomer in the pressure-sensitive adhesive composition is too large, the gel fraction is high, the durability in an atmosphere of 60 ° C. × 90% RH falls, and the durability and dryness in an 80 ° C. dry atmosphere. The workability was also slightly off.

Since the adhesive film of Comparative Example 3 does not contain a carboxyl group-containing copolymerizable vinyl monomer or a hydroxyl group-containing copolymerizable vinyl monomer in the adhesive composition, the acrylic polymer is not crosslinked, the gel fraction is 0, and the adhesive force of the adhesive layer having a thickness of 25 μm This is very strong. As a result, durability and rework property were inferior.

As described above, in the adhesive films of Comparative Examples 1 to 3, conventional requirements and problems could not be overcome.

Claims (2)

In the pressure-sensitive adhesive film formed by cross-linking the pressure-sensitive adhesive composition containing an acrylic polymer and a crosslinking agent (C) on one side of the substrate,
The acrylic polymer
(A) 100 parts by weight of at least one or more selected from the group consisting of a monomer group consisting of an alkyl (meth) acrylate monomer having a C1 to C14 carbon atom and a (meth) acrylate monomer having an aromatic group as the (meth) acrylate monomer; ,
(B) 0.1 to 3.5 parts by weight of only a hydroxyl group-containing copolymerizable vinyl monomer as a functional group-containing monomer, an acid value of 0.1 or less, and a copolymer having a weight average molecular weight of 1 million or more,
Of the total 100 parts by weight of (A), it is made by containing butyl acrylate in a proportion of 30 parts by weight or more,
As the functional group-containing monomer, the hydroxyl group-containing copolymerizable vinyl monomer includes hydroxyl group-containing alkyl (meth) acrylates, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, and N-hydroxy At least one compound selected from the group consisting of ethyl (meth) acrylamide, 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) It comprises at least one compound selected from the group consisting of acrylates,
The pressure-sensitive adhesive composition is made of 0.01 to 0.8 parts by weight of the isocyanate compound as the crosslinking agent (C) and 0.01 to 0.5 parts by weight of the silane coupling agent, based on 100 parts by weight of the total (A),
The adhesive film, characterized in that the gel fraction after crosslinking of the pressure-sensitive adhesive layer is 40 to 75%. An optical film in which an adhesive layer in which the adhesive layer of the adhesive film of claim 1 is laminated is formed on at least one side of the optical film.