JP7116229B2 - Adhesive layer and adhesive film - Google Patents

Description

The present invention relates to a thin pressure-sensitive adhesive layer having a thickness of 1 μm to 20 μm and a pressure-sensitive adhesive film sandwiching the pressure-sensitive adhesive layer between release films, which is used for lamination between layers of optical members.

2. Description of the Related Art In recent years, various display devices, such as smart phones, tablet terminals, tablet PCs, etc., in which a capacitive touch panel is externally attached on a liquid crystal panel, are widely used. In such a display device, a physical space exists between the liquid crystal panel and the touch panel. Therefore, there is a problem that external light is reflected on the upper surface of the liquid crystal panel and the lower surface of the touch panel, and the visibility deteriorates especially in a bright environment such as outdoors.

As a method for solving the problem of deterioration in visibility, an in-cell display device (see, for example, Japanese Unexamined Patent Application Publication No. 2002-100002) has been proposed in which the function of a touch panel is incorporated into liquid crystal pixels. However, it has not been put to practical use because of the low yield of the product due to the complicated manufacturing process and the technical difficulty in improving the image display performance.

On the other hand, recently, an on-cell display device (see, for example, Patent Document 2) has been proposed. An on-cell display device forms a touch sensor composed of a transparent electrode pattern between a color filter and a polarizing plate, and incorporates a touch panel function between the color filter substrate and the polarizing plate. The on-sell method has the advantage that the yield of the product is less reduced. Therefore, the on-cell method is expected to develop in the future as a promising manufacturing technology for a liquid crystal panel incorporating a touch panel.

JP 2009-258182 A JP 2014-044501 A

In the various display devices described above, a pressure-sensitive adhesive layer is generally used for laminating the layers of the optical members. However, when the surface of at least one of the optical members is an optical member whose surface hardness is increased by surface treatment such as a hard coat layer (for example, the pencil hardness of the surface is 2H or more), it is used for bonding the optical members. If the pressure-sensitive adhesive layer is soft and thick, there is a problem that measurement errors occur when measuring the surface hardness of the laminate in which the optical member is bonded.
This is because when the hard coat layer of the laminated body of optical members is touched with a pencil, the base film of the optical member becomes thinner and the rigidity is lowered even if the surface hardness of the optical member itself is high. It is a phenomenon that the optical member is dented due to the fact that the pressure-sensitive adhesive layer is soft and the adhesive layer is soft, and the apparent surface hardness is lowered.

The present invention has been made in view of the above circumstances. An object of the present invention is to provide a pressure-sensitive adhesive layer and a pressure-sensitive adhesive film, which have both good properties and reworkability.

In order to solve the above problems, the present invention reduces the thickness of the adhesive layer to 1 μm to 20 μm compared to the conventional technology, and even the thin adhesive layer has the same adhesive strength as the conventional one. In order to do so, as the main component (meth)acrylic monomer, an alkyl (meth)acrylate monomer having an alkyl group having a carbon number of C1 to C14, a (meth)acrylate monomer having an aromatic group, and a nitrogen-containing vinyl monomer At least 40 parts by weight of butyl acrylate in a total of 100 parts by weight of at least one or more monomers selected from the acrylic monomer group consisting of a (meth)acrylate monomer having an alicyclic group, Furthermore, in order to reduce the corrosiveness of the pressure-sensitive adhesive layer, the technical idea is to use an acrylic polymer that does not contain a carboxyl group-containing copolymerizable vinyl monomer.

In order to solve the above problems, the present invention provides a pressure-sensitive adhesive layer used for bonding optical members, wherein the pressure-sensitive adhesive layer crosslinks a pressure-sensitive adhesive composition containing an acrylic polymer and a crosslinking agent. and the acrylic polymer has (1) an alkyl (meth)acrylate monomer having an alkyl group with a carbon number of C1 to C14 as a main component (meth)acrylic monomer, and an aromatic group (meth) At least one monomer selected from the acrylic monomer group consisting of an acrylate monomer, a nitrogen-containing vinyl monomer, and an alicyclic (meth)acrylate monomer, of which 100 parts by weight in total, butyl acrylate at least 40 parts by weight or more, does not contain a carboxyl group-containing copolymerizable vinyl monomer, the Tg of the acrylic polymer is -35 ° C. or more and -10 ° C. or less, and the pressure-sensitive adhesive composition contains the main component A total of 100 parts by weight of a (meth)acrylic monomer and (2) 0.1 to 10 parts by weight of a hydroxyl group-containing copolymerizable vinyl monomer are copolymerized, the acid value is 0.1 or less, and the weight With respect to a total of 100 parts by weight of the acrylic polymer composed of a copolymer having an average molecular weight of 1,000,000 or more and the (meth)acrylic monomer as the main component, (3) 0.01 to 0.01 of an isocyanate compound alone as a cross-linking agent. 1.0 parts by weight of a silane coupling agent having at least one organic functional group selected from the group consisting of epoxy group, (meth)acryloxy group, mercapto group and amino group; 01 to 0.5 parts by weight, the gel fraction after crosslinking the acrylic polymer is 40 to 85%, the thickness of the adhesive layer is 1 μm to 20 μm, and the thickness An adhesive film obtained by transferring a 10 μm thick adhesive layer to one side of a 180 μm polarizing plate film was subjected to a peeling test against alkali-free glass in accordance with JIS Z0237 at a speed of 300 mm / min in the direction of 180 °. The pressure-sensitive adhesive layer having a thickness of 10 μm has an adhesive strength of 1.5 to 8.0 N/25 mm, and the refractive index of the pressure-sensitive adhesive layer is 1.47 to 1.50. Provide a pressure-sensitive adhesive layer.

The adhesive composition preferably further contains 0.01 to 0.5 parts by weight of a silane coupling agent.

The cross-linking agent contained in the pressure-sensitive adhesive composition is an isocyanate compound, and preferably contains at least one selected from trimethylolpropane adduct of tolylene diisocyanate and isocyanurate of hexamethylene diisocyanate. .

(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-hydroxyethyl (Meth) acrylate, at least one selected from the group of compounds consisting of.

It is preferable that the adhesive strength after being stored at 70° C. for 10 days after bonding the adhesive film to an adherend, alkali-free glass, is 10 N/25 mm or less.

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 an adhesive film for laminating a polarizing plate and a liquid crystal display panel or an organic electroluminescence display panel using the adhesive film.

The present invention also provides a polarizing plate with an adhesive layer using the adhesive film.

The present invention also provides a polarizing plate with a pressure-sensitive adhesive layer using the above pressure-sensitive adhesive film and using a retardation film having a retardation of λ/4 and/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, it is possible to provide a pressure-sensitive adhesive layer and a pressure-sensitive adhesive film that can maintain surface hardness even when used for lamination between layers of an optical member, and also have durability and reworkability.

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, which is used between an optical member having a surface pencil hardness of 2H or more and another optical member. , the acrylic polymer comprises (1) an alkyl (meth)acrylate monomer having an alkyl group having a carbon number of C1 to C14 and a (meth)acrylate monomer having an aromatic group as (meth)acrylic monomers as main components; , Nitrogen-containing vinyl monomers, and (meth)acrylate monomers having an alicyclic group, at least one or more monomers selected from the acrylic monomer group consisting of 100 parts by weight in total of 100 parts by weight, at least 40 parts by weight of butyl acrylate It contains more than parts by weight, does not contain a carboxyl group-containing copolymerizable vinyl monomer, the Tg of the acrylic polymer is -35 ° C. or more, and the pressure-sensitive adhesive composition contains the main component (meth)acrylic monomer A total of 100 parts by weight and (2) 0.1 to 10 parts by weight of a hydroxyl group-containing copolymerizable vinyl monomer are copolymerized, and have an acid value of 0.1 or less and a weight average molecular weight of 1,000,000 or more. (3) Contains 0.01 to 1.0 parts by weight of an isocyanate compound as a cross-linking agent with respect to a total of 100 parts by weight of the acrylic polymer composed of the copolymer and the (meth)acrylic monomer as the main component. The gel fraction after cross-linking the acrylic polymer is 40 to 85%, the thickness of the pressure-sensitive adhesive layer is 1 μm to 20 μm, and the pressure-sensitive adhesive layer with a thickness of 10 μm has an adhesive strength of 1.0 μm. 5 to 8.0 N/25 mm, and the measured value of the pencil hardness of the surface of the optical member is 2H, which is the same as the pencil hardness of the surface of the optical member. It is characterized by the above.

The acrylic polymer according to the present invention is a copolymer obtained by copolymerizing one or more monomers belonging to the first monomer group (main component monomers) and monomers belonging to the second monomer group (functional group monomers). It is a polymer. As monomers belonging to the first monomer group, an alkyl (meth)acrylate monomer having an alkyl group having C1 to C14 carbon atoms, an acrylate monomer having an aromatic group, a nitrogen-containing vinyl monomer, and an alicyclic (meth) At least one or more of the monomer group consisting of acrylate monomers can be used. At least one hydroxyl-containing copolymerizable vinyl monomer can be used as the monomer belonging to the second monomer group. In this specification, (meth)acrylate is a generic term for acrylate and methacrylate.

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, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, isohexyl (meth) acrylate, heptyl (meth) acrylate ) acrylate, isoheptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate ) acrylate, undecyl (meth) acrylate, isoundecyl (meth) acrylate, dodecyl (meth) acrylate, isododecyl (meth) acrylate, tridecyl (meth) acrylate, isotridecyl (meth) acrylate, tetradecyl (meth) acrylate, isotetradecyl (meth) acrylate ) at least one of acrylates and the like. The alkyl group of the alkyl (meth)acrylate monomer may be linear or branched.
The acrylic polymer according to the present invention uses butyl acrylate as an essential monomer. The acrylic polymer contains at least 40 parts by weight, more preferably 50 parts by weight or more, and particularly preferably 60 parts by weight or more of butyl acrylate in a total of 100 parts by weight of the monomers belonging to the first monomer group. is preferred.

In the adhesive composition according to the present invention, the (meth)acrylate monomer having an aromatic group includes benzyl (meth)acrylate, naphthyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxybutyl (meth)acrylate, 2 -(1-naphthyloxy)ethyl (meth)acrylate, 2-(2-naphthyloxy)ethyl (meth)acrylate, 6-(1-naphthyloxy)hexyl (meth)acrylate, 6-(2-naphthyloxy)hexyl At least one of (meth)acrylate, 8-(1-naphthyloxy)octyl(meth)acrylate, 8-(2-naphthyloxy)octyl(meth)acrylate and the like can be mentioned. 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 acrylic polymer according to the present invention preferably contains 30 parts by weight or less of a (meth)acrylate monomer having an aromatic group out of 100 parts by weight of the monomers belonging to the first monomer group.

In the pressure-sensitive adhesive composition of the pressure-sensitive adhesive layer according to the present invention, examples of the nitrogen-containing vinyl monomer include (meth)acrylic monomers containing an amide bond and (meth)acrylic monomers containing an amino group. More specifically, N-(meth)acryloylmorpholine, N-(meth)acryloylpiperazine, N-(meth)acryloylaziridine, N-(meth)acryloylazetidine, N-(meth)acryloylpyrrolidine, N-( Cyclic nitrogen vinyl compounds having an N-(meth)acryloyl-substituted heterocyclic structure, such as meth)acryloylpiperidine, N-(meth)acryloylazepane, N-(meth)acryloylazocane; (meth)acrylamide, N - unsubstituted or monoalkyl-substituted (meth)acrylamides such as methyl (meth)acrylamide, N-isopropyl (meth)acrylamide, Nt-butyl (meth)acrylamide; N,N-dimethyl (meth)acrylamide, N, N-diethyl (meth)acrylamide, N,N-dipropylacrylamide, N,N-diisopropyl (meth)acrylamide, N,N-dibutyl (meth)acrylamide, N-ethyl-N-methyl (meth)acrylamide, N- Dialkyl-substituted (meth)acrylamides such as methyl-N-propyl (meth)acrylamide and N-methyl-N-isopropyl (meth)acrylamide; N,N-dimethylaminomethyl (meth)acrylate, N,N-dimethylaminoethyl ( meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-dimethylaminoisopropyl (meth)acrylate, N,N-dimethylaminobutyl (meth)acrylate, N,N-diethylaminomethyl (meth)acrylate , N,N-diethylaminoethyl (meth)acrylate, N-ethyl-N-methylaminoethyl (meth)acrylate, N-methyl-N-propylaminoethyl (meth)acrylate, N-methyl-N-isopropylaminoethyl ( dialkylamino (meth)acrylates such as meth)acrylate, N,N-dibutylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate; N,N-dimethylaminopropyl (meth)acrylamide, N,N- Diethylaminopropyl (meth)acrylamide, N,N-dipropylaminopropyl (meth)acrylamide, N,N-diisopropylaminopropyl (meth)acrylamide, N-ethyl-N-methylaminopropyl (meth)acrylamide, N-methyl- N-propylaminopropyl (meth)acrylamide, N-methyl-N-isopropylamino At least one of N,N-dialkyl-substituted aminopropyl (meth)acrylamide such as propyl (meth)acrylamide; and (meth)acrylonitrile. As the nitrogen-containing vinyl monomer, those containing no hydroxyl group are preferable, and those containing neither hydroxyl group nor carboxyl group are more preferable. The acrylic polymer according to the present invention preferably contains 20 parts by weight or less of the nitrogen-containing vinyl monomer in the total 100 parts by weight of the monomers belonging to the first monomer group.

In the adhesive composition according to the present invention, the (meth)acrylate monomer having an alicyclic group includes cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, bicycloheptyl (meth)acrylate, and bicyclooctyl. At least one of (meth)acrylate, dimethylbicycloheptyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and the like can be mentioned. By blending a (meth)acrylate monomer with a saturated alicyclic group in the side chain like a cyclic alkyl (meth)acrylate monomer, the polarity of the acrylic polymer is lowered, contributing to its affinity for low-energy surfaces. . The acrylic polymer according to the present invention preferably contains 30 parts by weight or less of (meth)acrylate monomers having an alicyclic group in a total of 100 parts by weight of the monomers belonging to the first monomer group.

A monomer belonging to the second monomer group (functional group monomer) has a functional group capable of reacting with an isocyanate compound, which is used as a cross-linking agent. Such functional groups include carboxyl groups in addition to hydroxyl groups. However, from the viewpoint of avoiding adverse effects on corrosive adherends such as the ITO surface of the transparent conductive film, the acrylic polymer preferably does not contain a carboxyl group-containing copolymerizable vinyl monomer. The acid value of the acrylic polymer is preferably 0.1 or less.

In the adhesive composition according to the present invention, the hydroxyl group-containing copolymerizable vinyl monomers include 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy hydroxyl group-containing alkyl (meth)acrylates such as ethyl (meth)acrylate, and hydroxyl group-containing (meth)acrylamides such as N-hydroxy (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, and N-hydroxyethyl (meth)acrylamide at least one or more such as 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 selected from the group is preferred. The acrylic polymer according to the present invention preferably contains 0.1 to 10 parts by weight of a hydroxyl group-containing copolymerizable vinyl monomer with respect to a total of 100 parts by weight of the monomers belonging to the first monomer group. It is more preferable to contain up to 5.0 parts by weight, and it is particularly preferable to contain 0.2 to 4.0 parts by weight.

The polymerization method of the copolymer used as the acrylic polymer 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 an acrylic monomer such as a (meth)acrylate monomer. In the present invention, the glass transition temperature (hereinafter referred to as Tg) of the acrylic polymer is preferably −35° C. or higher. If the Tg is less than -35°C, reworkability and durability are lowered, which is not preferable. Furthermore, the Tg is more preferably -35°C to -10°C. If the Tg exceeds -10°C, the adhesive strength necessary for the present invention cannot be obtained, which is not preferred. Further, the weight average molecular weight of the acrylic polymer is preferably 1 million or more, more preferably in the range of 1 million to 2 million.

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.

Examples of cross-linking agents include buret-modified and isocyanurate-modified diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate; At least one or more polyisocyanate compounds such as adducts with polyols are included.

The content of the isocyanate compound used as the cross-linking agent is preferably 0.01 to 1.0 parts by weight with respect to 100 parts by weight of the monomers belonging to the first monomer group. As a cross-linking agent, only an isocyanate compound may be used. As the isocyanate compound, it is preferable to contain at least one selected from the trimethylolpropane adduct of tolylene diisocyanate and the isocyanurate of hexamethylene diisocyanate.

The adhesive composition preferably further contains a silane coupling agent. The silane coupling agent is a compound having at least one organic functional group and at least one hydrolyzable group in one molecule, wherein the hydrolyzable group is an alkoxy group or the like bonded to a silicon atom. 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.

The content of the silane coupling agent is preferably 0.01 to 0.5 parts by weight with respect to a total of 100 parts by weight of the monomers (monomers belonging to the first monomer group) excluding the hydroxyl group-containing copolymerizable vinyl monomer.

Other optional components include antioxidants, antistatic agents, surfactants, curing accelerators, plasticizers, fillers, cross-linking catalysts, cross-linking retarders, curing retarders, processing aids, anti-aging agents, etc. Additives can be appropriately blended. These may be used alone or in combination of two or more.

The pressure-sensitive adhesive layer according to 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 85%.

When the pressure-sensitive adhesive layer according to the present invention is used for lamination between layers of optical members, it is desirable that the pressure-sensitive adhesive layer is thin. The thickness of the adhesive layer is preferably 1 μm to 20 μm. Further, it is preferable that the pressure-sensitive adhesive layer having a thickness of 10 μm has an adhesive force of 1.5 to 8.0 N/25 mm. In general, the adhesive strength of the adhesive layer is approximately proportional to the thickness of the adhesive layer. Examples of adherends used in the adhesive force test include glass plates such as alkali-free glass, resin films, 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 of the release film that is 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 combining the release-treated surfaces of release films with both sides of one pressure-sensitive adhesive layer. In this case, by exposing the adhesive surface by peeling off the release films on both sides sequentially or simultaneously, 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 (antiglare) films, ultraviolet absorbing films, infrared absorbing films, optical compensation films, brightness enhancement films, and the like.

The pressure-sensitive adhesive layer according to the present invention can maintain the surface hardness of the adherend even if the pressure-sensitive adhesive layer is thick. For example, it can be suitably used in the case of an optical member having a pencil hardness of 2H or more on the surface. From the viewpoint of reworkability, the adhesive layer preferably has an adhesive strength of 10 N/25 mm or less after being stored at 70° C. for 10 days after bonding to the adherend.

The pressure-sensitive adhesive layer and pressure-sensitive adhesive film of the present invention are 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, and various optical films for organic EL. It can be used for laminating films and the like. 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. In the case of having an adhesive layer protected by a release film, the release film is peeled off to expose the adhesive layer like an "optical film/adhesive layer", which is then laminated with another optical film. , a configuration such as "optical film/adhesive layer/optical film" in which an adhesive layer is used for bonding between layers is obtained.

The pressure-sensitive adhesive film of the present invention is suitably used for bonding a polarizing plate and a display panel. Examples of display panels include liquid crystal panels and organic EL (electroluminescence) panels. The adhesive film of the present invention can be suitably 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. The pressure-sensitive adhesive layer of the present invention can be used for laminating the retardation film and the polarizing plate.

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 pipe to replace the air in the reactor with nitrogen gas. Then, 75 parts by weight of butyl acrylate, 25 parts by weight of t-butyl acrylate, 1.0 parts by weight of 8-hydroxyoctyl acrylate, and 60 parts by weight of a solvent (ethyl acetate) were added to the reactor. Thereafter, 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 to obtain an acrylic polymer solution used in Example 1.
[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.

<Production of adhesive composition, adhesive layer and adhesive film>
[Example 1]
0.2 parts by weight of Coronate HX (isocyanurate form of HDI) and 0.05 parts by weight of KBM-803 (3-mercaptopropyltrimethoxysilane) were added to the acrylic polymer solution of Example 1 produced as described above. In addition, the adhesive composition of Example 1 was obtained by stirring and mixing. After applying this adhesive composition on a release film (polyethylene terephthalate (PET) film coated with silicone resin), drying at 90 ° C. to remove the solvent, 23 ° C., 50% RH atmosphere A pressure-sensitive adhesive film of Example 1 having a pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition on one side of the release film was obtained by aging for 7 days under the same conditions.
[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, in group (1), alkyl (meth)acrylate monomers in which the alkyl group has C1 to C14 carbon atoms, a (meth)acrylate monomer having an aromatic group, a nitrogen-containing vinyl monomer, and an alicyclic The total amount of the monomer group consisting of the (meth)acrylate monomer was determined as 100 parts by weight. Also, the addition ratios of groups (2) to (4) are shown in parentheses in terms of parts by weight. Group (2) is a functional group-containing monomer, that is, a group of monomers consisting of a hydroxyl group-containing copolymerizable vinyl monomer and a carboxyl group-containing copolymerizable vinyl monomer. Group (3) is a cross-linking agent. Group (4) is a silane coupling agent.

In addition, Table 2 shows the compound names of the abbreviations of the components used in Table 1. Coronate (registered trademark) HX and L are trade names of Nippon Polyurethane Industry Co., Ltd. KBM-403, KBM-802 and KBM-803 are trade names of Shin-Etsu Chemical Co., Ltd. TDI means tolylene diisocyanate, TMP means trimethylolpropane and HDI means hexamethylene diisocyanate.

<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 10 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>
A sample of the acrylic polymer was dissolved in a solvent (a mixture of diethyl ether and ethanol at a volume ratio of 2:1) to prepare a measurement sample. The measurement sample is subjected to potentiometric titration with a potassium hydroxide ethanol solution having a concentration of about 0.1 mol / l using a potentiometric automatic titrator (manufactured by Kyoto Electronics Industry, AT-610) to neutralize the sample. The amount of potassium hydroxide ethanol solution required was measured. Then, the acid value of the acrylic polymer 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 S of 0.1 mol/l potassium hydroxide ethanol solution = mass of solid content of sample (g)

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

<Durability test method>
A 10 cm square adhesive film prepared by the same method as the method for measuring adhesive strength was bonded to a non-tin surface of alkali-free glass washed with acetone with a pressure bonding roll to prepare a measurement sample. After leaving the prepared measurement sample in a predetermined atmosphere (80 ° C. dry atmosphere or 60 ° C. × 90% RH atmosphere) for 250 hours, remove it in a 23 ° C. × 50% RH atmosphere, and after 1 hour, the state of the adhesive film was visually observed to determine the durability. Criteria for visual observation were as follows.
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 left for 1 hour, the adhesive strength of the adhesive film was measured to determine the reworkability. The reworkability criteria were as follows.
◯: 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).

<Method for measuring pencil hardness>
A pressure-sensitive adhesive layer having a predetermined thickness (Table 4) is transferred to a polarizing plate having a hard coat layer with a pencil hardness of 2H on the surface to obtain a sample. After bonding the polarizing plate to the alkali-free glass via the adhesive layer of the sample, a pencil hardness test was performed on the surface of the sample in accordance with JIS K5600 scratch hardness (pencil method). The pencil hardness of the surface of the hard coat layer in the layer structure of "/adhesive layer/non-alkali glass" was measured.

Tables 3 and 4 show the evaluation results. Although the results are not shown, the acid value of the acrylic polymer was 0.1 or less in Examples 1 to 5 and Comparative Examples 2 to 3 in which no carboxyl group-containing copolymerizable vinyl monomer was used. Moreover, the weight average molecular weights of the acrylic polymers were all 1,000,000 or more.

In the adhesive films of Examples 1 to 5, which are adhesive films according to the present invention, the acrylic polymer contains at least 40 parts by weight or more of butyl acrylate out of a total of 100 parts by weight of the main component (meth)acrylic monomer. is doing. In addition, the acrylic polymers of Examples 1 to 5 do not contain a carboxyl group-containing copolymerizable vinyl monomer, the Tg of the acrylic polymer is -35 ° C. or higher, the acid value is 0.1 or lower, and the weight average It has a molecular weight of 1,000,000 or more and a gel fraction of 40 to 85% after cross-linking. In addition, the pencil hardness of the surface of the polarizing plate bonded to the non-alkali glass via the adhesive layer was still 2H in appearance. As a result, the use of the pressure-sensitive adhesive film according to the present invention does not cause an error in the measured value of the surface hardness of the laminate in which the optical member is bonded.
Further, the pressure-sensitive adhesive layers of Examples 1 to 5 had a pressure-sensitive adhesive strength of 1.5 to 8.0 N/25 mm and excellent durability. In addition, after bonding the adhesive films of Examples 1 to 5 to the adherend, the adhesive strength after storage at 70 ° C. for 10 days is 10 N / 25 mm or less, so reworkability is also excellent. rice field. That is, the adhesive films of Examples 1 to 5 were able to overcome the requirements and problems in the prior art.

Since the adhesive film of Comparative Example 1 contained a carboxyl group-containing copolymerizable vinyl monomer in the acrylic polymer, the acid value of the acrylic polymer was greater than 0.1. In addition, the pressure-sensitive adhesive film of Comparative Example 1 does not contain butyl acrylate in the acrylic polymer, the content of the cross-linking agent is excessive, and the Tg of the acrylic polymer is lower than -35 ° C., so that the reworkability is slightly poor. The durability at 60°C x 90% RH was poor. Moreover, the pencil hardness of the surface of the polarizing plate bonded to the non-alkali glass via the pressure-sensitive adhesive layer decreased from 2H to H in appearance.

The adhesive film of Comparative Example 2 contained no butyl acrylate in the acrylic polymer, had a Tg of the acrylic polymer lower than -35°C, and contained an excessive amount of cross-linking agent. In addition, probably because the gel fraction after cross-linking is high, the adhesive strength of the adhesive layer with a thickness of 10 μm is less than 1.5 N / 25 mm, the durability at 80 ° C dry is slightly poor, and the durability at 60 ° C x 90% RH was nasty. Moreover, the pencil hardness of the surface of the polarizing plate bonded to the non-alkali glass via the pressure-sensitive adhesive layer decreased from 2H to H in appearance.

Since the adhesive film of Comparative Example 3 does not contain a hydroxyl group-containing copolymerizable vinyl monomer and a carboxyl group-containing copolymerizable vinyl monomer in the acrylic polymer, the gel fraction after cross-linking is 0% even if a cross-linking agent is used. (substantially not crosslinked). In addition, the Tg of the acrylic polymer was lower than -35°C, the adhesive strength was very high, and the reworkability and durability were poor. Moreover, the pencil hardness of the surface of the polarizing plate bonded to the non-alkali glass via the pressure-sensitive adhesive layer decreased from 2H to H in appearance.

Thus, the adhesive films of Comparative Examples 1-3 could not overcome the requirements and problems in the prior art.

Claims (5)

A pressure-sensitive adhesive layer used for bonding optical members,
The pressure-sensitive adhesive layer is obtained by cross-linking a pressure-sensitive adhesive composition containing an acrylic polymer and a cross-linking agent,
The acrylic polymer is
(1) as main component (meth)acrylic monomers, an alkyl (meth)acrylate monomer having an alkyl group having C1 to C14 carbon atoms, a (meth)acrylate monomer having an aromatic group, and a nitrogen-containing vinyl monomer; At least 40 parts by weight of butyl acrylate in a total of 100 parts by weight of a (meth)acrylate monomer having an alicyclic group and at least one or more monomers selected from the acrylic monomer group consisting of does not contain a group-containing copolymerizable vinyl monomer,
The acrylic polymer has a Tg of −35° C. or more and −10° C. or less,
The pressure-sensitive adhesive composition is obtained by copolymerizing a total of 100 parts by weight of the main component (meth)acrylic monomer and (2) 0.1 to 10 parts by weight of a hydroxyl group-containing copolymerizable vinyl monomer. , with respect to a total of 100 parts by weight of an acrylic polymer composed of a copolymer having an acid value of 0.1 or less and a weight average molecular weight of 1 million or more, and the (meth)acrylic monomer as the main component, (3) Contains 0.01 to 1.0 parts by weight of an isocyanate compound alone as a cross-linking agent, and at least one organic functional group selected from the group consisting of an epoxy group, a (meth)acryloxy group, a mercapto group, and an amino group. containing a silane coupling agent having a group in a proportion of 0.01 to 0.5 parts by weight,
The gel fraction after cross-linking the acrylic polymer is 40 to 85%,
The pressure-sensitive adhesive layer has a thickness of 1 μm to 20 μm,
An adhesive film obtained by transferring an adhesive layer with a thickness of 10 μm to one side of a polarizing plate film with a thickness of 180 μm was subjected to a peeling test against alkali-free glass in accordance with JIS Z0237 at 300 mm / min in the direction of 180 °. The pressure-sensitive adhesive layer with a thickness of 10 μm obtained by performing at a speed has an adhesive strength of 1.5 to 8.0 N / 25 mm,
The pressure-sensitive adhesive layer, wherein the refractive index of the pressure-sensitive adhesive layer is 1.47 to 1.50. (2) the hydroxyl group-containing copolymerizable vinyl monomer is selected from 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate; 2. The pressure-sensitive adhesive layer according to claim 1, wherein at least one compound selected from the group consisting of: 3. A pressure-sensitive adhesive film, wherein the pressure-sensitive adhesive layer according to claim 1 is formed on one side of a release film, and has a structure of release film/adhesive layer/release film. A pressure-sensitive adhesive film comprising the pressure-sensitive adhesive layer according to claim 1 or 2 laminated on one side of a substrate. A polarizing plate with an adhesive layer, wherein the adhesive film according to claim 3 is used.