Method for producing optical film with pressure-sensitive adhesive layer

Abstract

To provide a method for manufacturing an adhesive layer-attached optical film that enables formation of an adhesive layer having excellent reworkability and high adhesion performance despite its thinness.SOLUTION: An acrylic polymer is a copolymer obtained by copolymerizing (A) a total of 100 pts.wt. of a monomer group consisting of alkyl (meth)acrylate monomers having C1-C14 alkyl groups and (meth)acrylate monomers having aromatic groups and (B) 0.1 to 3.5 pts.wt. of hydroxyl group-containing copolymerizable vinyl monomers, without including carboxyl group-containing copolymerizable vinyl monomers or amino group-containing (meth)acrylates, the copolymer having an acid value of 0.1 or less and a weight average molecular weight of 1 million or more. The polymer contains butyl acrylate of at least 30 pts.wt., and further contains an isocyanate compound of 0.01 to 0.8 pt.wt., and a silane coupling agent of 0.01 to 0.5 pt.wt.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an adhesive composition and an adhesive film used for bonding optical members such as polarizing plates.

Background Art

[0002] Various adhesive films have been proposed for bonding optical members such as polarizing plates and retardation plates to an adherend such as a liquid crystal cell via an adhesive layer (see, for example, Patent Documents 1 and 2). Patent Document 1 describes an optical adhesive composition containing a monomer having butyl acrylate or the like as a main component and containing an acrylamide compound or the like. Patent Document 2 describes an optical adhesive composition containing a monomer having a (meth)acrylate having an alkyl group having 4 to 8 carbon atoms as a main component and containing a carboxyl group-containing monomer and a nitrogen-containing vinyl monomer. In addition, various adhesive films have been proposed to increase the refractive index of the adhesive layer (see, for example, Patent Documents 3 to 8). Patent Document 3 describes an optical adhesive composition having an aromatic ring and containing a tackifier having a refractive index of 1.51 to 1.75. Patent Document 4 describes an adhesive sheet containing an adhesive composition containing a copolymerizable polymer of an acrylic acid-modified monomer containing an aromatic ring. Patent Document 5 describes an optical adhesive composition containing a tackifying resin having an aromatic ring and an aromatic phosphate plasticizer. Patent Document 6 describes an adhesive obtained by curing an adhesive composition containing an acrylic resin and an aromatic compound containing one ethylenically unsaturated group. Patent Document 7 describes an optical component obtained by fixing a retardation film and a birefringent plate to each other via an acrylic adhesive containing an aromatic monomer. Patent Document 8 describes an adhesive composition containing a urethane resin obtained by reacting an aromatic diisocyanate and an aromatic polyester diol.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, for the pressure-sensitive adhesive film used for laminating between optical members, in order to reduce the thickness of the optical member, it is required to use a pressure-sensitive adhesive film with a reduced thickness of the pressure-sensitive adhesive layer. Generally, since the adhesive strength of the pressure-sensitive adhesive layer is substantially proportional to the thickness of the pressure-sensitive adhesive layer, when the thickness of the pressure-sensitive adhesive layer is reduced, the adhesive strength will decrease accordingly.

[0005] However, the pressure-sensitive adhesive film required in recent years has the same adhesive strength as the conventional pressure-sensitive adhesive film (the thickness of the pressure-sensitive adhesive layer is as thick as about 30 μm) even when the thickness of the pressure-sensitive adhesive layer is reduced, and it is also required to have performance equal to or better than that of the conventional pressure-sensitive 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 an adhesive layer that does not require aging treatment (curing at a constant temperature) can be formed, it is required to adopt the form of NCF (Non Carrier Film) consisting only of the adhesive layer without the substrate of the adhesive film, having the member configuration of "release film / adhesive layer / release film".

[0006] Also, in the conventional adhesive film, after the adhesive film was laminated on the adherend, aging treatment was performed, so that the adhesion between the adherend and the adhesive layer could be improved. However, since the aging of the adhesive layer has already been completed in the adhesive film in the form of NCF, the adhesion between the adherend and the adhesive layer is insufficient. Therefore, there has been 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.

[0007] The present invention has been made in view of the above circumstances, and an object thereof is to provide an adhesive composition capable of forming an adhesive layer having excellent reworkability and high adhesion performance despite being a thin film, and an adhesive film using the same.

Means for Solving the Problems

[0008] In order to solve the above problems, the adhesive composition according to the present invention uses butyl acrylate as an essential monomer, 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. For a copolymer having a weight average molecular weight of 1,000,000 or more, an isocyanate compound is used as a crosslinking agent, and more preferably, a silane coupling agent is used in combination.

[0009] Also, in order to solve the above problems, the present invention provides an acrylic polymer which contains (1) at least one selected from a monomer group consisting of an alkyl (meth)acrylate monomer having 1 to 14 carbon atoms in the alkyl group and a (meth)acrylate monomer having an aromatic group as the main component (meth)acrylate monomer, and contains at least 30 parts by weight or more of butyl acrylate out of a total of 100 parts by weight of the main component (meth)acrylate monomer, does not contain a carboxyl group-containing copolymerizable vinyl monomer, and contains (2) 0.1 to 3.5 parts by weight of a hydroxyl group-containing copolymerizable vinyl monomer with respect to 100 parts by weight of the total of the main component (meth)acrylate monomers, and is a copolymer 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 crosslinking agent with respect to 100 parts by weight of the total of the main component (meth)acrylate monomers, thereby providing an adhesive composition.

[0010] Furthermore, it is preferable to contain (4) 0.01 to 0.5 parts by weight of a silane coupling agent with respect to 100 parts by weight of the total of the main component (meth)acrylate monomers.

[0011] Also, it is preferable that the isocyanate compound is a trimethylolpropane adduct of tolylene diisocyanate.

[0012] Also, it is preferable that the (2) hydroxyl group-containing copolymerizable vinyl monomer is at least one selected from the group consisting of 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate.

[0013] The present invention also provides an adhesive layer obtained by crosslinking the above adhesive composition, wherein the gel fraction after crosslinking is 40 to 75%, and the adhesive strength of the adhesive layer having a thickness of 25 μm is 1.5 to 6.0 N / 25 mm.

[0014] Also, after laminating the adhesive layer onto the adherend, the adhesive strength after 10 days at 70°C is preferably 1.5 to 10 N / 25 mm.

[0015] Further, the present invention provides an adhesive film characterized in that the adhesive layer is laminated on one side of a base material.

[0016] Furthermore, the present invention provides an adhesive film used for bonding a polarizing plate and a display panel, which uses the above-mentioned adhesive film.

[0017] Moreover, the present invention provides the above-mentioned adhesive layer used as an adhesive layer of a polarizing plate with an adhesive layer.

[0018] In addition, the present invention provides the above-mentioned adhesive layer used as an adhesive layer of a polarizing plate with an adhesive layer, in which a retardation film having a retardation of λ / 4 or λ / 2 is used as a constituent material of the polarizing plate.

[0019] Also, the present invention provides an optical film with an adhesive layer, in which the adhesive layer is laminated on at least one surface of the optical film.

Advantages of the Invention

[0020] According to the present invention, it is characterized in that an adhesive layer with a high gel fraction after crosslinking is obtained while reducing the amount of crosslinking agent and the amount of functional groups compared with the conventional adhesive layer, and an adhesive layer having flexibility, rigidity, durability, and reworkability, and an adhesive film using the same can be obtained. The adhesive film of the present invention has excellent reworkability and high adhesion performance despite being a thin film.

Embodiments for Carrying Out the Invention

[0021] Hereinafter, the present invention will be described based on preferred embodiments. The pressure-sensitive adhesive composition of the present invention contains: (1) as the main component (meth)acrylate monomer, at least one or more selected from the group of monomers consisting of an alkyl (meth)acrylate monomer having an alkyl group with 1 to 14 carbon atoms and a (meth)acrylate monomer having an aromatic group. Among a total of 100 parts by weight of the (meth)acrylate monomers as the main component, butyl acrylate is at least 30 parts by weight or more, and it does not contain a carboxyl group-containing copolymerizable vinyl monomer. With respect to a total of 100 parts by weight of the (meth)acrylate monomers as the main component, (2) a hydroxyl group-containing copolymerizable vinyl monomer is 0.1 to 3.5 parts by weight. It contains an acrylic polymer which is a copolymer having an acid value of 0.1 or less and a weight average molecular weight of 1,000,000 or more, and with respect to a total of 100 parts by weight of the (meth)acrylate monomers as the main component, (3) an isocyanate compound is 0.01 to 0.8 parts by weight as a crosslinking agent, and is characterized by this.

[0022] In the pressure-sensitive adhesive composition according to the present invention, examples of the alkyl (meth)acrylate monomer having an alkyl group with 1 to 14 carbon atoms include at least one or more of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)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, 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, etc. The alkyl group of the alkyl (meth)acrylate monomer may be linear, branched, or cyclic. Out of a total of 100 parts by weight of the (meth)acrylate monomers as the main components, the total of the alkyl (meth)acrylate monomers having an alkyl group with 1 to 14 carbon atoms is preferably 70 parts by weight or more, and may be 100 parts by weight. The alkyl (meth)acrylate monomer having an alkyl group with 1 to 14 carbon atoms is preferably in a proportion of 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. Out of a total of 100 parts by weight of the (meth)acrylate monomers as the main components, it is preferable to contain at least 30 parts by weight or more of butyl acrylate. Further, in the present invention, by the pressure-sensitive adhesive composition containing the methyl acrylate monomer in a proportion of 20 parts by weight or more out of a total of 100 parts by weight of the (meth)acrylate monomers as the main components composed of one or more of the alkyl (meth)acrylate monomers having an alkyl group with 1 to 14 carbon atoms, the refractive index of the pressure-sensitive adhesive layer can be increased to 1.47 or more.

[0023] The pressure-sensitive adhesive composition according to the present invention may further contain one or more of the (meth)acrylate monomers having an aromatic group as the (meth)acrylate monomers as the main components. Examples of the (meth)acrylate monomer having an aromatic group include 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 (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 having a high refractive index, it is preferable to blend at least one or more of the (meth)acrylate monomers having an aromatic group.

[0024] By mixing these (meth)acrylate monomers having aromatic groups with an alkyl (meth)acrylate monomer having 1 to 14 carbon atoms in the alkyl group, which is the main component monomer, the refractive index of the resulting pressure-sensitive adhesive layer can be increased and adjusted, the refractive index difference between optical members can be reduced, and total internal reflection can be reduced to improve the total light transmittance. 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, it is preferably contained in a proportion of 5 to 30 parts by weight within a total of 100 parts by weight of the main component (meth)acrylate monomer. Also, by copolymerizing a (meth)acrylate monomer having an aromatic group, the refractive index of the pressure-sensitive adhesive layer can be further increased compared to the effect of increasing the refractive index of the pressure-sensitive adhesive layer by containing a methyl acrylate monomer in a proportion of 20 parts by weight or more within a total of 100 parts by weight of the above-mentioned main component (meth)acrylate monomer. Also, as described above, as a method for increasing the refractive index of the pressure-sensitive adhesive layer, there are two methods: a method of containing a methyl acrylate monomer in a proportion of 20 parts by weight or more within a total of 100 parts by weight of the main component (meth)acrylate monomer, and a method of copolymerizing a (meth)acrylate monomer having an aromatic group. Each method can be adopted alone, but it is more preferable to use these two methods in combination.

[0025] In the pressure-sensitive adhesive composition of the present invention, the acrylic polymer does not contain a carboxyl group-containing copolymerizable vinyl monomer as the functional group-containing monomer, and contains a hydroxyl group-containing copolymerizable vinyl monomer. As the functional group-containing monomer, only the hydroxyl group-containing copolymerizable vinyl monomer may be used.

[0026] Examples of the hydroxyl group-containing copolymerizable vinyl monomer include at least one or more of hydroxyl group-containing alkyl (meth) acrylates such as 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, and hydroxyl group-containing (meth) acrylamides such as N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, and the like. Among them, it is preferable that the hydroxyl group-containing copolymerizable vinyl monomer is at least one selected from the group consisting of 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate. 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 can be used as a copolymerizable monomer for reducing the content of the carboxyl group-containing copolymerizable vinyl monomer, which is said to affect the corrosiveness of the resulting pressure-sensitive adhesive layer against a corrosive adherend such as the ITO surface of a transparent conductive film. Therefore, the hydroxyl group-containing copolymerizable vinyl monomer can be used to improve the adhesive strength of the pressure-sensitive adhesive layer and reduce the 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 within a total of 100 parts by weight of the main component (meth) acrylate monomer.

[0027] The acrylic polymer of the pressure-sensitive adhesive composition used in the pressure-sensitive adhesive layer of the present invention contains, as (1) the main component (meth)acrylate monomer, at least one or more selected from the group of monomers consisting of an alkyl (meth)acrylate monomer having an alkyl group with 1 to 14 carbon atoms and a (meth)acrylate monomer having an aromatic group. Among the total 100 parts by weight of the (meth)acrylate monomers as the main component, butyl acrylate is at least 30 parts by weight or more, and it does not contain a carboxyl group-containing copolymerizable vinyl monomer. With respect to the total 100 parts by weight of the (meth)acrylate monomers as the main component, (2) it contains 0.1 to 3.5 parts by weight of a hydroxyl group-containing copolymerizable vinyl monomer, and it is a copolymer having an acid value of 0.1 or less and a weight average molecular weight of 1,000,000 or more.

[0028] The polymerization method of the copolymer is not particularly limited, and known polymerization methods such as solution polymerization method and emulsion polymerization method can be appropriately used. The acrylic polymer preferably contains 50 to 100% by weight of acrylic monomers such as (meth)acrylate monomers and (meth)acrylamides.

[0029] For the pressure-sensitive adhesive composition, by blending a cross-linking agent and optionally any additives with the above acrylic polymer, properties such as required physical property values can be adjusted. (3) Examples of the crosslinking agent include at least one or more polyisocyanate compounds such as biuret-modified products and isocyanurate-modified products of diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate, and adducts with polyols having a trivalent or higher valence such as trimethylolpropane and glycerin. It is preferable that the acrylic polymer has a hydroxyl group as a functional group capable of undergoing a crosslinking reaction with the isocyanate compound of the crosslinking agent, and it is also preferable to contain a monomer having these functional groups in the side chain. Further, it is preferable that the pressure-sensitive adhesive composition contains 0.01 to 0.8 parts by weight of the isocyanate compound with respect to 100 parts by weight in total of the (meth)acrylate monomers as the main components. (3) Only an isocyanate compound may be used as the crosslinking agent. As the isocyanate compound, an adduct of tolylene diisocyanate is preferable, and in particular, an adduct of tolylene diisocyanate with trimethylolpropane is preferable.

[0030] The pressure-sensitive adhesive composition preferably further contains (4) a silane coupling agent. (4) Examples of the silane coupling agent include compounds having at least one organic functional group and at least one hydrolyzable group in one molecule, and the hydrolyzable group is an alkoxy group bonded to a silicon atom or the like. It is preferable that the silane coupling agent has at least one kind of organic functional group selected from the group consisting of an epoxy group, a (meth)acryloxy group, a mercapto group, and an amino group. Here, the (meth)acryloxy group means an acryloxy group (CH2=CHCOO-) or a methacryloxy group (CH2=C(CH3)COO-).

[0031] Examples of the silane coupling agent having an epoxy group include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltriethoxysilane, 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. Examples of the silane coupling agent having a (meth)acryloxy group include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropyldimethylethoxysilane, ............ Examples of the silane coupling agent having a mercapto group include 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, 3-mercaptopropyltriethoxysilane, and the like. Examples of the silane coupling agent having an amino group include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldiethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-(methylamino)propyltrimethoxysilane, 3-(methylamino)propyltriethoxysilane, and the like. In addition, oligomerized alkoxy oligomers (silicone alkoxy oligomers) containing the organic functional group can also be used as silane coupling agents.

[0032] (4) The content of the silane coupling agent is preferably 0.01 to 0.5 parts by weight of the silane coupling agent with respect to 100 parts by weight in total of the (meth)acrylate monomers as the main components.

[0033] As other optional components, known additives such as antioxidants, surfactants, curing accelerators, plasticizers, fillers, crosslinking catalysts, crosslinking retardants, curing retardants, processing aids, and anti-aging agents can be appropriately blended. These may be used alone or in combination of two or more.

[0034] 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 pressure-sensitive adhesive layer after crosslinking is preferably 40 to 75%. When used for bonding between layers of optical members, etc., it is desirable to have a thin pressure-sensitive adhesive layer. The thickness of the pressure-sensitive adhesive layer is preferably 1 μm to 25 μm, more preferably 5 μm to 25 μm. Generally, the adhesive strength of the pressure-sensitive adhesive layer is substantially proportional to the thickness of the pressure-sensitive adhesive layer, but the adhesive strength of the pressure-sensitive adhesive layer with a thickness of 25 μm is preferably 1.5 to 6.0 N / 25 mm. Further, after bonding the pressure-sensitive adhesive layer to the adherend, the adhesive strength after 70 °C × 10 days is preferably 1.5 to 10 N / 25 mm. Examples of the adherend include glass plates such as non-alkali glass and resin films.

[0035] When the pressure-sensitive adhesive layer according to the present invention is used for bonding between layers of optical members, etc., in order to reduce the reflection of light at the interface between the pressure-sensitive adhesive layer and the optical member, it is desirable that the difference in refractive index be as small as possible. For this reason, the refractive index of the pressure-sensitive adhesive layer is preferably 1.47 to 1.50.

[0036] 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 surface of a substrate or a release film. As the base film used for forming the adhesive layer and the release film (separator) for protecting the adhesive surface, resin films such as polyester films can be used. On the surface of the base film opposite to the side where the adhesive layer of the resin film is formed, anti-fouling treatment with silicone-based, fluorine-based release agents, coating agents, silica fine particles, etc., and antistatic treatment by applying or incorporating antistatic agents can be performed.

[0037] On the surface of the release film that is joined to the adhesive surface of the adhesive layer, a release treatment is performed with a silicone-based or fluorine-based release agent. By aligning the surfaces of the release films that have been subjected to the release treatment on both sides of one adhesive layer, a structure of "release film / adhesive layer / release film" can also be formed. In this case, by sequentially or simultaneously peeling off the release films on both sides to expose the adhesive surface, it becomes possible to bond with optical members such as optical films. Examples of optical films include polarizing films, retardation films, antireflection films, antiglare films, ultraviolet absorption films, infrared absorption films, optical compensation films, brightness enhancement films, etc.

[0038] The adhesive film of the present invention can be used for bonding various optical films for peripheral members of liquid crystal display devices mainly including polarizing plates, various optical films for touch panels, various optical films for electronic papers, various optical films for organic ELs, etc. Moreover, it can be made into an optical film with an adhesive layer in which the adhesive layer is laminated on at least one surface of these optical films. Specifically, structures such as "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" can be mentioned. 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 to expose the adhesive layer as in "optical film / adhesive layer", and by laminating with another optical film, a structure such as "optical film / adhesive layer / optical film" in which the adhesive layer is used for interlayer lamination can be obtained. The pressure-sensitive adhesive film of the present invention is suitably used for laminating a polarizing plate and a display panel. For example, it is used as the 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.

Example

[0039] Hereinafter, the present invention will be specifically described with reference to examples.

[0040] <Production of acrylic polymer> [Example 1] Nitrogen gas was introduced into a reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube to replace the air in the reaction apparatus 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 reaction apparatus. 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 Acrylic Polymer Solution 1 used in Example 1 having a weight average molecular weight of 1,000,000 or more. A part of the acrylic polymer was collected and used as a sample for measuring the acid value described later. [Examples 2 to 5 and Comparative Examples 1 to 3] Acrylic polymer solutions used in Examples 2 to 5 and Comparative Examples 1 to 3 were obtained in the same manner as Acrylic Polymer Solution 1 used in Example 1 above, except that the monomer composition was made as described in groups (1) and (2) of Table 1. Although the measurement results are not particularly shown, the weight average molecular weight of the acrylic polymers contained in the acrylic polymer solutions of Examples 2 to 5 and Comparative Examples 1 to 3 is 1,000,000 or more.

[0041] <Manufacture of Adhesive Composition, Adhesive Layer, and Adhesive Film> [Example 1] To 1 part by weight of the acrylic polymer solution of Example 1 manufactured as described above, 0.2 part by weight of Coronate L (trimethylolpropane (TMP) adduct of tolylene diisocyanate (TDI) compound) and 0.05 part by weight of KBM-403 (3-glycidoxypropyltrimethoxysilane) were added and stirred and mixed to obtain the adhesive composition of Example 1. After applying this adhesive composition onto a release film made of a silicone resin-coated polyethylene terephthalate (PET) film, the solvent was removed by drying at 90°C, and then aging was performed for 7 days in an atmosphere of 23°C and 50% RH to crosslink the adhesive composition, thereby obtaining an adhesive film of Example 1 having an adhesive layer with a thickness of 25 μm on one side of the release film. [Examples 2 to 5 and Comparative Examples 1 to 3] Adhesive films of Examples 2 to 5 and Comparative Examples 1 to 3 were obtained in the same manner as the adhesive film of Example 1 described above, except that the composition of the additives was made as described in groups (3) and (4) of Table 1, respectively.

[0042]

Table 1

[0043] In Table 1, the numerical values in parts by weight are shown enclosed in parentheses as the addition ratios from group (2) to group (4), obtained by setting the total of group (1) to 100 parts by weight. In addition, the compound names of the abbreviations of the respective components used in Table 1 are shown in Table 2. Note that Coronate (registered trademark) L is a product name of Nippon Polyurethane Industry Co., Ltd., D-110N is a product name of Mitsui Chemicals, Inc., and KBM-403 and KBM-803 are product names of Shin-Etsu Chemical Co., Ltd. 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 described in group (2) together with the hydroxyl group-containing copolymerizable vinyl monomer.

[0044]

Table 2

[0045] <Test method and evaluation> From the pressure-sensitive adhesive films in Examples 1 to 5 and Comparative Examples 1 to 3, the release film (PET film coated with a silicone resin) was peeled off to expose the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer was transferred to one side of a polarizing plate (film).

[0046] <Method for measuring adhesive strength> A 25-μm-thick pressure-sensitive adhesive layer was transferred to one side of a polarizing plate (film) with a thickness of 180 μm to obtain a pressure-sensitive adhesive film (optical film with a pressure-sensitive adhesive layer) as a sample. The obtained pressure-sensitive adhesive film was bonded to the non-tin surface washed with acetone of non-alkali glass with a pressure roller, autoclaved under the conditions of 50 °C and 0.5 MPa for 20 minutes, then returned to the atmosphere of 23 °C × 50% RH, and allowed to stand for 1 hour. The peel strength of the subsequent pressure-sensitive adhesive film was measured by a tensile tester in accordance with JIS Z0237 "Test method for adhesive tapes and adhesive sheets", and the peel strength when peeling at a speed of 300 mm / min in the 180° direction was taken as the adhesive strength (N / 25 mm) of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film.

[0047] <Method for measuring acid value> The acid value of the acrylic polymer was determined by dissolving the sample in a solvent (a mixture of diethyl ether and ethanol in a volume ratio of 2:1), using a potentiometric automatic titrator (manufactured by Kyoto Electronics Industry Co., Ltd., AT-610), performing potentiometric titration with a potassium hydroxide ethanol solution having a concentration of about 0.1 mol / l using the above potentiometric titrator, and measuring the amount of the potassium hydroxide ethanol solution required to neutralize the sample. Then, the acid value was determined from the following formula. Acid value = (B × f × 5.611) / S B = Amount (ml) of 0.1 mol / l potassium hydroxide ethanol solution used for titration f = Factor of 0.1 mol / l potassium hydroxide ethanol solution S = Mass (g) of solid content of the sample

[0048] <Method for Measuring Gel Fraction> After the aging is completed, accurately measure the mass of the measurement sample before laminating it to the polarizing plate. Immerse it in toluene for 24 hours and then filter it through a 200-mesh wire mesh. Then, dry the filtrate at 100 °C for 1 hour, accurately measure the mass of the residue, and calculate the gel fraction of the adhesive layer (crosslinked adhesive) from the following formula. Gel fraction (%) = Mass of insoluble part (g) / Mass of adhesive (g) × 100

[0049] <Test Method for Durability> A 10 cm square adhesive film prepared in the same manner as the measurement of adhesive strength, and a sample prepared by laminating it to the non-tin surface of non-alkali glass in the same manner, were left in a predetermined atmosphere (80 °C dry atmosphere or 60 °C × 90% RH atmosphere) for 250 hours, then taken out into a 23 °C × 50% RH atmosphere, and the state of the adhesive film was visually observed 1 hour later to determine the durability. ○·· There is no peeling or foaming of the adhesive film at all. △·· Peeling and foaming have occurred in a part of the adhesive film. ×·· Peeling and foaming have occurred throughout the adhesive film.

[0050] <Test Method for Reworkability> A 10 cm square adhesive film prepared in the same manner as the measurement of adhesive strength, and a sample prepared by laminating it to the non-tin surface of non-alkali glass in the same manner, were left in an atmosphere of 70 °C for 10 days, then taken out into an atmosphere of 23 °C, and the adhesive strength of the adhesive film after standing for 1 hour was measured to determine the reworkability. ○·· The adhesive strength after 70 °C × 10 days is 1.5 to 10 N / 25 mm. △·· The adhesive strength after 70 °C × 10 days is greater than 10 N / 25 mm but 20 N / 25 mm or less. ×·· The adhesive strength after 70 °C × 10 days is greater than 20 N / 25 mm (it cannot be peeled off).

[0051] Table 3 shows the evaluation results. Regarding the acid value, it was confirmed that the acid values of the acrylic polymers in Examples 1 to 5 and Comparative Examples 2 and 3, which do not contain a carboxyl group-containing copolymerizable vinyl monomer, were 0.1 or less, and the acid value of the acrylic polymer in Comparative Example 1, which contains a carboxyl group-containing copolymerizable vinyl monomer, was greater than 0.1.

[0052]

Table 3

[0053] For the pressure-sensitive adhesive films of Examples 1 to 5, the adhesive strength of the 25-μm-thick adhesive layer was 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 the adhesion and durability were excellent. Also, after bonding to the adherend, the adhesive strength after 70°C × 10 days was in the range of 1.5 to 10 N / 25 mm, so the reworkability was also excellent. That is, the pressure-sensitive adhesive films of Examples 1 to 5 could overcome the requirements and problems.

[0054] The pressure-sensitive adhesive film of Comparative Example 1 did not contain butyl acrylate as the main component (meth)acrylate monomer and contained a carboxyl group-containing copolymerizable vinyl monomer as the functional group-containing monomer. Because of the high gel fraction, the adhesive strength of the 25-μm-thick adhesive layer was strong, and it was inferior in durability and reworkability in an atmosphere of 60°C × 90% RH. The pressure-sensitive adhesive film of Comparative Example 2 had too much content of the hydroxyl group-containing copolymerizable vinyl monomer in the adhesive composition. Because of the high gel fraction, it was inferior in durability in an atmosphere of 60°C × 90% RH and was also slightly inferior in durability and reworkability in an 80°C dry atmosphere. The pressure-sensitive adhesive film of Comparative Example 3 did not contain either a carboxyl group-containing copolymerizable vinyl monomer or a hydroxyl group-containing copolymerizable vinyl monomer in the adhesive composition. Therefore, the acrylic polymer did not crosslink, the gel fraction was 0, and the adhesive strength of the 25-μm-thick adhesive layer was very strong. As a result, it was inferior in durability and reworkability. Thus, the pressure-sensitive adhesive films of Comparative Examples 1 to 3 could not overcome the conventional requirements and problems.

Claims

1. A method for manufacturing an optical film with an adhesive layer, which uses an adhesive film formed by laminating an adhesive layer obtained by crosslinking an adhesive composition containing an acrylic polymer and a crosslinking agent on one surface of a release film, peeling off the release film, and bonding the adhesive layer to an optical film, wherein the acrylic polymer is a copolymer having an acid value of 0.1 or less and a weight average molecular weight of 1,000,000 or more, which is obtained by copolymerizing (A) at least one or more selected from the monomer group consisting of an alkyl (meth)acrylate monomer having an alkyl group with 1 to 14 carbon atoms and a (meth)acrylate monomer having an aromatic group, in a total of 100 parts by weight, and (B) 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, and in the total of 100 parts by weight of at least one or more selected from the monomer group consisting of the (A) alkyl (meth)acrylate monomer having an alkyl group with 1 to 14 carbon atoms and the (meth)acrylate monomer having an aromatic group, the total of the alkyl (meth)acrylate monomer having an alkyl group with 1 to 14 carbon atoms is 100 parts by weight, containing butyl acrylate at a ratio of at least 30 parts by weight or more and containing a methyl acrylate monomer at a ratio of 20 parts by weight or more, the adhesive composition further contains, with respect to a total of 100 parts by weight of at least one or more selected from the monomer group consisting of the (A) alkyl (meth)acrylate monomer having an alkyl group with 1 to 14 carbon atoms and the (meth)acrylate monomer having an aromatic group, 0.01 to 0.8 parts by weight of an isocyanate compound as the crosslinking agent and 0.01 to 0.5 parts by weight of a silane coupling agent, the silane coupling agent has at least one type of organic functional group selected from the group consisting of an epoxy group, a (meth)acryloxy group, and a mercapto group, the thickness of the adhesive layer is 1 to 25 μm, and the optical film with an adhesive layer is characterized in that after bonding to the non-tin surface of non-alkali glass, the adhesive strength of the adhesive layer after 70°C × 10 days is 1.5 to 10 N / 25 mm.

2. ​ The method for manufacturing an optical film with an adhesive layer according to claim 1, wherein the optical film is a polarizing plate.

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