JP7132402B2 - Adhesive layer and optical film with adhesive layer - Google Patents

Description

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

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

In recent years, an adhesive film used for bonding between layers of optical members is required to be an adhesive film with a thin adhesive layer in order to reduce the thickness of the optical member. is.
In general, the adhesive strength of the adhesive layer is approximately proportional to the thickness of the adhesive layer, and therefore, when the thickness of the adhesive layer is reduced, the adhesive strength is lowered accordingly.

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

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

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

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 a pressure-sensitive adhesive composition, does not use a carboxyl group-containing copolymerizable vinyl monomer as a functional group-containing monomer, and contains a hydroxyl group. It is characterized by using an isocyanate compound as a cross-linking agent for a copolymer having a weight average molecular weight of 1,000,000 or more using a copolymerizable vinyl monomer, and more preferably using a silane coupling agent together.

Further, in order to solve the above problems, the present invention provides a pressure-sensitive adhesive layer formed by cross-linking a pressure-sensitive adhesive composition comprising an acrylic polymer, wherein the pressure-sensitive adhesive composition comprises (1) a (meth)acrylate as a main component As a monomer, at least one selected from the monomer group consisting of alkyl (meth)acrylate monomers having C1 to C14 carbon atoms in the alkyl group and (meth)acrylate monomers having an aromatic group, Of the total 100 parts by weight of the (meth)acrylate monomers of the component, at least 30 parts by weight of butyl acrylate and a total of 100 parts by weight of the (meth)acrylate monomer as the main component without containing a carboxyl group-containing copolymerizable vinyl monomer (2) 0.1 to 3.5 parts by weight of a hydroxyl group-containing copolymerizable vinyl monomer, an acid value of 0.1 or less, and a weight average molecular weight of 1,000,000 or more. Containing (3) 0.01 to 0.8 parts by weight of an isocyanate compound as a cross-linking agent with respect to a total of 100 parts by weight of the combined acrylic polymer and the (meth)acrylate monomer as the main component. A pressure-sensitive adhesive composition having a gel fraction of 40 to 75% after cross-linking, a thickness of the pressure-sensitive adhesive layer of 1 μm to 25 μm, and an adhesive strength of the pressure-sensitive adhesive layer having a thickness of 25 μm of 1.5 Provide a pressure-sensitive adhesive layer characterized by ˜6.0 N/25 mm.

Further, it is preferable that (4) 0.01 to 0.5 parts by weight of a silane coupling agent is contained in the adhesive composition with respect to a total of 100 parts by weight of the (meth)acrylate monomer as the main component. .

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

Further, (2) the hydroxyl group-containing copolymerizable vinyl monomer in the adhesive composition is 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2- It is preferably at least one selected from the compound group consisting of hydroxyethyl (meth)acrylate.

Further, it is preferable that the pressure-sensitive adhesive layer has an adhesive strength of 1.5 to 10 N/25 mm after 10 days at 70° C. after bonding the pressure-sensitive adhesive layer to the adherend.

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

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

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

In addition, the present invention provides a polarizing plate with an adhesive layer using the adhesive film.

The present invention also provides a pressure-sensitive adhesive layer-attached polarizing plate using the above pressure-sensitive adhesive film and using a retardation film having a retardation of λ/4 or λ/2 as a constituent material.

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

According to the present invention, the amount of cross-linking agent and the amount of functional groups are reduced compared to conventional pressure-sensitive adhesive layers, and the resulting pressure-sensitive adhesive layer has a high gel fraction after cross-linking. A pressure-sensitive adhesive layer having both durability and reworkability and a pressure-sensitive adhesive film using the same can be obtained.
The pressure-sensitive adhesive film of the present invention has excellent reworkability and high adhesion performance in spite of being a thin film.

The present invention will be described below based on preferred embodiments.
The pressure-sensitive adhesive layer of the present invention is a pressure-sensitive adhesive layer formed by cross-linking a pressure-sensitive adhesive composition comprising an acrylic polymer, wherein the pressure-sensitive adhesive composition contains (1) an alkyl group as a main component (meth)acrylate monomer. containing at least one or more selected from a group of monomers consisting of alkyl (meth)acrylate monomers having C1 to C14 carbon atoms and (meth)acrylate monomers having an aromatic group, and the (meth)acrylate as the main component Of the total 100 parts by weight of the monomers, at least 30 parts by weight of butyl acrylate and no carboxyl group-containing copolymerizable vinyl monomer, with respect to a total of 100 parts by weight of the (meth)acrylate monomer as the main component, ( 2) Acrylic polymer which is a copolymer containing 0.1 to 3.5 parts by weight of a hydroxyl group-containing copolymerizable vinyl monomer, having an acid value of 0.1 or less and a weight average molecular weight of 1,000,000 or more and (3) 0.01 to 0.8 parts by weight of an isocyanate compound as a cross-linking agent with respect to a total of 100 parts by weight of the (meth)acrylate monomer as the main component. The gel fraction after cross-linking is 40 to 75%, the thickness of the adhesive layer is 1 μm to 25 μm, and the adhesive strength of the adhesive layer with a thickness of 25 μm is 1.5 to 6.0 N/25 mm. It is characterized by

In the pressure-sensitive adhesive composition according to the present invention, the alkyl (meth)acrylate monomers having C1 to C14 alkyl groups include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, ) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate ) acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, cyclopentyl (meth)acrylate , cyclohexyl (meth)acrylate and the like. The alkyl group of the alkyl (meth)acrylate monomer may be linear, branched or cyclic.
Of the total 100 parts by weight of the main component (meth)acrylate monomers, the total amount of alkyl (meth)acrylate monomers having alkyl groups of C1 to C14 carbon atoms is preferably 70 parts by weight or more, and may be 100 parts by weight. The proportion of the alkyl (meth)acrylate monomer having an alkyl group of C1 to C14 carbon atoms is preferably 50 to 99.9 parts by weight with respect to 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 that at least 30 parts by weight or more of butyl acrylate is contained in a total of 100 parts by weight of the (meth)acrylate monomers as the main component.
Further, in the present invention, the pressure-sensitive adhesive composition is composed of one or more alkyl (meth)acrylate monomers in which the alkyl group has C1 to C14 carbon atoms. , the refractive index of the pressure-sensitive adhesive layer can be increased to 1.47 or more by containing 20 parts by weight or more of the methyl acrylate monomer.

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

The refractive index of the adhesive layer obtained by mixing the (meth)acrylate monomer having these aromatic groups with an alkyl (meth)acrylate monomer having an alkyl group having a carbon number of C1 to C14, which is the monomer of the main component. can be adjusted by increasing the refractive index difference between the optical members, and the total light transmittance can be improved by reducing the total reflection. In the pressure-sensitive adhesive layer according to the present invention, when the pressure-sensitive adhesive composition contains a (meth)acrylate monomer having an aromatic group, 5 to 30 parts by weight of the total 100 parts by weight of the main component (meth)acrylate monomer It is preferable to contain it in the ratio of 1 part.
In addition, by copolymerizing a (meth)acrylate monomer having an aromatic group, a methyl acrylate monomer is contained at a rate of 20 parts by weight or more in the total 100 parts by weight of the (meth)acrylate monomers as the main component. The refractive index of the pressure-sensitive adhesive layer can be increased more than the effect of increasing the refractive index of the pressure-sensitive adhesive layer.
Further, as described above, as a method for increasing the refractive index of the pressure-sensitive adhesive layer, 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 main component (meth)acrylate monomer; There are two methods, a method of copolymerizing a (meth)acrylate monomer having an aromatic group, and each method can be employed alone, but it is more preferable to use the two methods together.

In the pressure-sensitive adhesive composition of the present invention, the acrylic polymer does not contain a carboxyl group-containing copolymerizable vinyl monomer as functional group-containing monomers, but 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 hydroxyl group-containing copolymerizable vinyl monomers include hydroxyl groups such as 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate. At least one or more of hydroxyl group-containing (meth)acrylamides such as containing alkyl (meth)acrylates, N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, etc. mentioned.
Among them, compounds in which the hydroxyl group-containing copolymerizable vinyl monomer is composed of 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate. At least one or more selected from the group is preferable.
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 prevents the resulting pressure-sensitive adhesive layer from corroding easily corroding adherends such as the ITO surface of the transparent conductive film. It can be used as a copolymerizable monomer for reducing the content of a carboxyl group-containing copolymerizable vinyl monomer, which is said to affect the properties. Therefore, the hydroxyl group-containing copolymerizable vinyl monomer can be used to improve the adhesive strength of the adhesive layer and reduce corrosiveness. In the pressure-sensitive adhesive layer according to the present invention, the hydroxyl group-containing copolymerizable vinyl monomer contained in the pressure-sensitive adhesive composition is 0.1 to 3.5 parts by weight out of 100 parts by weight in total of the main component (meth)acrylate monomer. is preferably

The acrylic polymer of the pressure-sensitive adhesive composition used in the pressure-sensitive adhesive layer of the present invention includes (1) an alkyl (meth)acrylate monomer having an alkyl group having a carbon number of C1 to C14 as a main component (meth)acrylate monomer and an aromatic containing at least one selected from the monomer group consisting of (meth)acrylate monomers having a group, and at least 30 parts by weight of butyl acrylate out of the total 100 parts by weight of the main component (meth)acrylate monomers (2) 0.1 to 3.0 parts by weight of (2) a hydroxyl group-containing copolymerizable vinyl monomer with respect to a total of 100 parts by weight of the (meth)acrylate monomer as the main component, which does not contain a carboxyl group-containing copolymerizable vinyl monomer. A copolymer having an acid value of 0.1 or less and a weight average molecular weight of 1,000,000 or more.

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

The pressure-sensitive adhesive composition can be adjusted in properties such as required physical properties by blending a cross-linking agent and optional additives with the acrylic polymer described above.
(3) Examples of the cross-linking agent include burette-modified and isocyanurate-modified diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate, trimethylolpropane, and glycerin. At least one or more polyisocyanate compounds such as adducts with polyols having a valency or higher can be used. The acrylic polymer preferably has a hydroxyl group as a functional group capable of cross-linking reaction with the isocyanate compound of the cross-linking agent, and preferably contains monomers having these functional groups in side chains. In addition, the pressure-sensitive adhesive composition preferably contains 0.01 to 0.8 parts by weight of the isocyanate compound with respect to a total of 100 parts by weight of the (meth)acrylate monomer as the main component. (3) As a cross-linking agent, only an isocyanate compound may be used. As the isocyanate compound, an adduct of tolylene diisocyanate is preferable, and a trimethylolpropane adduct of tolylene diisocyanate is particularly preferable.

The pressure-sensitive adhesive composition preferably further contains (4) a silane coupling agent. (4) The silane coupling agent has 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. Certain compounds are mentioned. The silane coupling agent preferably 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, the (meth)acryloxy group means an acryloxy group (CH ₂ ═CHCOO—) or a methacryloxy group (CH ₂ ═C(CH ₃ )COO—).

Silane coupling agents having an epoxy group include, for example, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropyl. triethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 5,6-epoxyhexyltrimethoxysilane, 5,6-epoxyhexylmethyldimethoxysilane, 5,6-epoxyhexylmethyldiethoxysilane, 5,6- Epoxyhexyltriethoxysilane and the like are included.
Silane coupling agents having a (meth)acryloxy group include, for example, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropyltriethoxy silane, 3-(meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropyldimethylethoxysilane, 3-(meth)acryloxypropyldimethylmethoxysilane and the like.
Silane coupling agents having a mercapto group include, for example, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldiethoxysilane and 3-mercaptopropyltriethoxysilane.
Silane coupling agents having an amino group include, for example, 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 oligomerized alkoxy oligomer (silicone alkoxy oligomer) containing the organic functional group can also be used as the silane coupling agent.

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

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

The pressure-sensitive adhesive layer of the present invention can be obtained by applying the pressure-sensitive adhesive composition to a substrate or a release film, and then crosslinking the pressure-sensitive adhesive composition. The gel fraction of the adhesive layer after cross-linking is preferably 40 to 75%.
When used for lamination between layers of an optical member, the adhesive layer is preferably thin, and the thickness of the adhesive layer is preferably 1 μm to 25 μm, more preferably 5 μm to 25 μm. In general, the adhesive strength of the adhesive layer is approximately proportional to the thickness of the adhesive layer. is preferred. Furthermore, it is preferable that the adhesive strength after 10 days at 70° C. is 1.5 to 10 N/25 mm after bonding the adhesive layer to the adherend. Examples of the adherend include a glass plate such as alkali-free glass, a resin film, and the like.

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

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

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

The pressure-sensitive adhesive film of the present invention is used to attach various optical films for peripheral members of liquid crystal display devices, mainly polarizing plates, various optical films for touch panels, various optical films for electronic paper, various optical films for organic EL, etc. Can be used in combination.
Also, an optical film with a pressure-sensitive adhesive layer, in which the pressure-sensitive adhesive layer is laminated on at least one surface of these optical films, can be obtained. Specifically, "optical film / adhesive layer / optical film", "optical film / adhesive layer / release film", "optical film / adhesive layer", "optical film / adhesive layer / optical film / adhesive layer/optical film”, “optical film/adhesive layer/optical film/adhesive layer/release film”, “release film/adhesive layer/optical film/adhesive layer/release film”, etc. configuration.
For example, when having an adhesive layer protected by a release film, such as "optical film/adhesive layer/release film", the release film is peeled off and "optical film/adhesive layer" is formed. By exposing the pressure-sensitive adhesive layer and laminating it with another optical film, a structure such as "optical film/adhesive layer/optical film" in which the pressure-sensitive adhesive layer is used for lamination between layers can be obtained.
The pressure-sensitive adhesive film of the present invention is suitably 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 may be used.

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

<Production of acrylic polymer>
[Example 1]
Nitrogen gas was introduced into a reactor equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet tube to replace the air in the reactor with nitrogen gas. 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 added to the reactor. After that, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours, and reacted at 65° C. for 6 hours. A solution 1 was obtained. A part of the acrylic polymer was sampled and used as a sample for acid value measurement, which will be described later.
[Examples 2 to 5 and Comparative Examples 1 to 3]
Examples 2 to 5 and Examples 2 to 5 and An acrylic polymer solution used in Comparative Examples 1 to 3 was obtained. Although no particular measurement results are shown, the acrylic polymer contained in the acrylic polymer solutions of Examples 2 to 5 and Comparative Examples 1 to 3 had a weight average molecular weight of 1,000,000 or more.

<Production of adhesive composition, adhesive layer and adhesive film>
[Example 1]
With respect to the acrylic polymer solution 1 of Example 1 produced as described above, 0.2 parts by weight of Coronate L (trimethylolpropane (TMP) adduct of tolylene diisocyanate (TDI) compound), KBM-403 (3- 0.05 part by weight of glycidoxypropyltrimethoxysilane) was added and mixed with stirring to obtain a pressure-sensitive adhesive composition of Example 1. After applying this adhesive composition on a release film made of a polyethylene terephthalate (PET) film coated with a silicone resin, drying at 90 ° C. to remove the solvent, and then under an atmosphere of 23 ° C. and 50% RH. A pressure-sensitive adhesive film of Example 1 having a 25 μm-thick pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition on one side of the release film was obtained by aging at for 7 days.
[Examples 2 to 5 and Comparative Examples 1 to 3]
Examples 2 to 5 and Comparative Example 1 were prepared in the same manner as in the adhesive film of Example 1 above, except that the compositions of the additives were respectively as described in Groups (3) and (4) in Table 1. ~3 sticky films were obtained.

In Table 1, the addition ratios of groups (2) to (4) are calculated based on the total of group (1) being 100 parts by weight, and the numerical values of parts by weight are shown in parentheses.
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 Nippon Polyurethane Industry Co., Ltd., D-110N is a trade name of Mitsui Chemicals, Inc., and KBM-403 and KBM-803 are trade names of Shin-Etsu Chemical Co., Ltd. is. TDI means tolylene diisocyanate, TMP means trimethylolpropane and XDI means xylylene diisocyanate. In Tables 1 and 2, the carboxyl group-containing copolymerizable vinyl monomer is listed in group (2) together with the hydroxyl group-containing copolymerizable vinyl monomer.

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

<Method for measuring adhesive strength>
A pressure-sensitive adhesive layer having a thickness of 25 μm was transferred onto one side of a polarizing plate (film) having a thickness of 180 μm to obtain a sample pressure-sensitive adhesive film (optical film with a pressure-sensitive adhesive layer).
The resulting adhesive film was laminated with a pressure bonding roll to a non-tin surface of alkali-free glass washed with acetone, autoclaved under the conditions of 50 ° C. and 0.5 MPa for 20 minutes, and then in an atmosphere of 23 ° C. and 50% RH. It was put back down and allowed to pass for 1 hour. The peel strength of the adhesive film after that is measured by a tensile tester in accordance with JIS Z0237 "Adhesive tape/adhesive sheet test method", and the peel strength when peeled at a speed of 300 mm / min in the 180 ° direction is The adhesive strength (N/25 mm) of the adhesive layer of the adhesive film was used.

<Method for measuring acid value>
The acid value of the acrylic polymer was determined by dissolving the sample in a solvent (mixture of diethyl ether and ethanol at a volume ratio of 2:1) and measuring the acid value with an automatic potentiometric titrator (AT-610, manufactured by Kyoto Electronics Industry Co., Ltd.). 1 Using the above potentiometric titrator, 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 to neutralize the sample was measured. Then, the acid value was obtained from the following formula.
Acid value = (B x f x 5.611) / S
B = amount of 0.1 mol/l potassium hydroxide ethanol solution used for titration (ml)
f = factor of 0.1 mol/l potassium hydroxide ethanol solution S = mass of solid content of sample (g)

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

<Durability test method>
A sample prepared by bonding a 10 cm square adhesive film prepared by the same method as the measurement of adhesive strength to the non-tin surface of alkali-free glass in the same manner was placed in a predetermined atmosphere (80 ° C. dry atmosphere, or 60 ° C. After being left for 250 hours under an atmosphere of 90% RH and 23° C., it was taken out under an atmosphere of 50% RH at 23° C. After 1 hour, the state of the adhesive film was visually observed to judge the durability.
Good: No peeling or foaming of the adhesive film.
(triangle|delta)... Peeling and foaming generate|occur|produce in a part of adhesion film.
x: Peeling and foaming occurred over the entire adhesive film.

<Reworkability test method>
A 10 cm square adhesive film prepared in the same manner as for measuring adhesive force was laminated to the non-tin surface of alkali-free glass in the same manner. C., and after standing for 1 hour, the adhesive strength of the adhesive film was measured to judge the reworkability.
◯: Adhesive strength after 10 days at 70° C. is 1.5 to 10 N/25 mm.
Δ: The adhesive strength after 70° C.×10 days is greater than 10 N/25 mm, but is 20 N/25 mm or less.
x: Adhesive strength after 70°C x 10 days is greater than 20 N/25 mm (cannot be peeled off).

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

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

The pressure-sensitive adhesive film of Comparative Example 1 did not contain butyl acrylate as a main component (meth)acrylate monomer, and contained a carboxyl group-containing copolymerizable vinyl monomer as a functional group-containing monomer. The pressure-sensitive adhesive layer with a thickness of 25 μm had a strong adhesive force, and was inferior in durability and reworkability in an atmosphere of 60° C.×90% RH.
The pressure-sensitive adhesive film of Comparative Example 2 had poor durability in an atmosphere of 60°C x 90% RH, probably because the amount of the hydroxyl group-containing copolymerizable vinyl monomer blended in the pressure-sensitive adhesive composition was too large and the gel fraction was high. Also, the durability in a dry atmosphere at 80° C. and the reworkability were slightly inferior.
In the pressure-sensitive adhesive film of Comparative Example 3, since the pressure-sensitive adhesive composition does not contain a carboxyl group-containing copolymerizable vinyl monomer or a hydroxyl group-containing copolymerizable vinyl monomer, the acrylic polymer is not crosslinked, and the gel fraction is 0. The adhesive strength of the adhesive layer with a thickness of 25 μm is very strong. As a result, the durability and reworkability were inferior.
Thus, the adhesive films of Comparative Examples 1-3 could not overcome the conventional requirements and problems.

Claims (3)

In the pressure-sensitive adhesive layer obtained by cross-linking a pressure-sensitive adhesive composition containing an acrylic polymer and (C) a cross-linking agent,
The acrylic polymer is
(A) the main component (meth)acrylate monomer is selected from a monomer group consisting of an alkyl (meth)acrylate monomer having an alkyl group with a carbon number of C1 to C14 and a (meth)acrylate monomer having an aromatic group; For a total of 100 parts by weight of at least two or more,
(B) an acid value obtained by copolymerizing 0.1 to 3.5 parts by weight of a hydroxyl group-containing copolymerizable vinyl monomer without containing a carboxyl group-containing copolymerizable vinyl monomer and an amino group-containing (meth)acrylate; is 0.1 or less and is an acrylic polymer that is a copolymer having a weight average molecular weight of 1,000,000 or more,
Containing 30 parts by weight or more of butyl acrylate in a total of 100 parts by weight of the (meth)acrylate monomer as the main component (A),
With respect to a total of 100 parts by weight of the (A) main component (meth)acrylate monomer, 0.01 to 0.8 parts by weight of an isocyanate compound as the (C) crosslinking agent and (D) a silane coupling agent 0.01 to 0.5 parts by weight,
The adhesive layer has a gel fraction of 40 to 75% after cross-linking, a thickness of 1 μm to 25 μm, and an adhesive strength of 1.5 to 6.5 μm. 0 N/25 mm, and an adhesive strength of 1.5 to 10 N/25 mm after 10 days at 70° C. after bonding the adhesive layer to an adherend. A polarizing plate with an adhesive layer, wherein the adhesive layer according to claim 1 is used. An optical film with a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer according to claim 1 is laminated on at least one surface of an optical film.