JP7309964B2 - adhesive film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive film and a surface protective film containing a tocopherol-based antioxidant as an antioxidant added to develop the antioxidant function of the pressure-sensitive adhesive composition. More specifically, it relates to a pressure-sensitive adhesive composition containing a tocopherol-based compound as an antioxidant component. The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive film, and a surface protective film which are also excellent in deposition resistance.

Adhesives used as adhesive films are often produced by radical polymerization. If radicals or polymerization initiators remain in the adhesive after polymerization, not only the storage stability of the adhesive before film formation but also the adhesive layer after film formation will discolor over time. and other problems occur. In particular, adhesives for optical members are required to be colorless and transparent. For this reason, these problems have been overcome by adding various antioxidants to take advantage of their functions such as radical scavenging action and antioxidant action.

In recent years, there have been many demands for environmental measures in the field of pressure-sensitive adhesives as well. Conventional antioxidants, unlike lactone-based antioxidants, have problems such as being unusable from an environmental point of view, and countermeasures have been required. For example, a general antioxidant such as that described in Patent Document 1 is a dangerous substance whose handling is regulated by law because it generally has an adverse effect on the human body. In addition, conventional antioxidants are powdery at room temperature and easily precipitate even when dissolved in a solvent. As a result of pursuing the function of an antioxidant, if the amount added is inevitably large, defects such as precipitation from the adhesive layer have occurred.

Japanese Patent No. 5061898

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 composition, a pressure-sensitive adhesive film for optical members, and a surface protection film.
In addition to solving the above problems, the present invention provides an optical member for reducing the surface resistivity of the pressure-sensitive adhesive layer in order to reduce the peeling electrification voltage and facilitate the peeling of the surface protective film from the adherend. An object of the present invention is to provide a pressure-sensitive adhesive composition, a pressure-sensitive adhesive film for optical members, and a surface protection film.

In order to solve the above problems, the present invention contains an acrylic copolymer having a (meth)acrylic acid alkyl ester as a main component, a cross-linking agent, and an antioxidant, and the antioxidant is a tocopherol-based Provided is a pressure-sensitive adhesive composition for optical members containing a compound.

The tocopherol compounds are d-α-tocopherol, dl-α-tocopherol, d-β-tocopherol, dl-β-tocopherol, d-γ-tocopherol, dl-γ-tocopherol, d-δ-tocopherol, dl- δ-tocopherol, d-α-tocotrienol, dl-α-tocotrienol, d-β-tocotrienol, dl-β-tocotrienol, d-γ-tocotrienol, dl-γ-tocotrienol, d-δ-tocotrienol, dl-δ- It is preferably at least one selected from the compound group consisting of tocotrienols.

It is preferable that the pressure-sensitive adhesive composition for optical members further contains an ionic compound.

The cross-linking agent is preferably at least one cross-linking agent selected from a compound group consisting of a di- or more functional isocyanate-based cross-linking agent, a di- or more functional epoxy-based cross-linking agent, and an aluminum chelate-based cross-linking agent.

The acrylic copolymer comprises (A) at least one (meth)acrylic acid alkyl ester monomer having an alkyl group having C1 to C14 carbon atoms, and (B) a copolymerizable copolymer containing a hydroxyl group and/or a carboxyl group. and at least one vinyl monomer, and containing (C) 0.01 to 1.5 parts by weight of the tocopherol compound as an essential component with respect to 100 parts by weight of the acrylic copolymer. is preferred.

The acrylic copolymer comprises (A) at least one (meth)acrylic acid alkyl ester monomer having an alkyl group of C1 to C14 carbon atoms, and at least one copolymerizable vinyl monomer having a vinyl group, Preferably, (C) 0.01 to 1.5 parts by weight of the tocopherol compound is contained as an essential component with respect to 100 parts by weight of the acrylic copolymer.

The acrylic copolymer is composed of (A) at least two (meth)acrylic acid alkyl ester monomers in which the alkyl group has a carbon number of C1 to C14, and relative to 100 parts by weight of the acrylic copolymer and (C) 0.01 to 1.5 parts by weight of the tocopherol compound as an essential component.

The acrylic copolymer comprises (A) at least one (meth)acrylic acid alkyl ester monomer having an alkyl group having C1 to C14 carbon atoms, and (B) a copolymerizable copolymer containing a hydroxyl group and/or a carboxyl group. It consists of at least one vinyl monomer and at least one aromatic monomer, and (C) the tocopherol compound is added in an amount of 0.01 to 1.5 parts per 100 parts by weight of the acrylic copolymer. parts by weight, as an essential component.

The present invention also provides a pressure-sensitive adhesive film for optical members, comprising a substrate and a pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition for optical members on one side of the substrate.

Further, the present invention provides a pressure-sensitive adhesive film for optical members, characterized by using a pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition for optical members.

The present invention also provides a surface protection film using the pressure-sensitive adhesive film for optical members.

The present invention also provides a surface protective film for a polarizing plate, which uses the pressure-sensitive adhesive film for optical members.

The present invention also provides an optical surface protective film using the pressure-sensitive adhesive film for optical members.

The present invention also provides a pressure-sensitive adhesive film for bonding a polarizing plate and a display panel using the pressure-sensitive adhesive film for optical members.

The present invention also provides a pressure-sensitive adhesive film for laminating materials constituting a polarizing plate using the pressure-sensitive adhesive film for optical members.

Moreover, this invention provides the adhesive film for touchscreens using the said adhesive film for optical members.

The present invention also provides an electronic paper adhesive film using the optical member adhesive film.

According to the present invention, by using a pressure-sensitive adhesive composition containing a tocopherol-based compound as an antioxidant, it is possible to reduce costs and improve the above problems such as deposition resistance.

The present invention will be described below based on preferred embodiments.
The pressure-sensitive adhesive composition for an optical member of the present invention contains an acrylic copolymer containing a (meth)acrylic acid alkyl ester as a main component, a cross-linking agent, and an antioxidant. Contains system compounds. A tocopherol-based compound is generally vitamin E, which is also a naturally occurring chemical. For this reason, it has little adverse effect on the human body, is highly safe in handling, and is friendly to the environment. Moreover, since it is oil-soluble and liquid at room temperature, it is excellent in compatibility with the pressure-sensitive adhesive composition and in precipitation resistance.

The acrylic copolymer used in the pressure-sensitive adhesive composition for optical members of the present invention is preferably an acrylic polymer. Copolymers based on at least one type are preferred.
(A) Examples of (meth)acrylic acid alkyl ester monomers in which the alkyl group has C1 to C14 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (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 ( Alkyl (meth)acrylate monomers such as meth)acrylate, decyl (meth)acrylate, cyclopentyl (meth)acrylate and cyclohexyl (meth)acrylate can be mentioned. The alkyl group of the alkyl (meth)acrylate monomer may be linear, branched or cyclic.

The acrylic copolymer used in the present invention comprises (A) at least one (meth)acrylic acid alkyl ester monomer having an alkyl group with a carbon number of C1 to C14 and at least one other copolymerizable monomer. A copolymer composition can also be employed. In this case, other copolymerizable monomers include a copolymerizable vinyl monomer having a vinyl group, (B) a copolymerizable vinyl monomer having a hydroxyl group and/or a carboxyl group, and an aromatic monomer.

Examples of copolymerizable vinyl monomers containing hydroxyl groups include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6- Hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate and other hydroxyl group-containing (meth) acrylic acid esters, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl ( Examples include hydroxyl group-containing (meth)acrylamides such as meth)acrylamide, and at least one compound selected from these compound groups is preferable.
Copolymerizable vinyl monomers containing carboxyl groups include (meth)acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, and the like. At least one compound selected from these compound groups is preferred.
Examples of aromatic monomers include aromatic group-containing (meth)acrylic acid esters such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate, as well as styrene.
Examples of copolymerizable vinyl monomers other than the above include various vinyl monomers such as acrylamide, acrylonitrile, methyl vinyl ether, ethyl vinyl ether, vinyl acetate, and vinyl chloride.

Further, as the acrylic copolymer used in the present invention, (A) a copolymer composition comprising at least two (meth)acrylic acid alkyl ester monomers having alkyl groups of C1 to C14 carbon atoms may be employed. can. In this case, the copolymer composition can be obtained without using a copolymerizable vinyl monomer other than (A) a (meth)acrylic acid alkyl ester monomer having an alkyl group of C1 to C14 carbon atoms.

The polymerization method of the acrylic 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 copolymer preferably has a weight average molecular weight of 200,000 to 2,000,000.

In the pressure-sensitive adhesive composition for optical members of the present invention, the acrylic copolymer is preferably crosslinked when forming the pressure-sensitive adhesive layer. For cross-linking, the pressure-sensitive adhesive composition for optical members may contain a known cross-linking agent, or may be cross-linked by photo-crosslinking such as ultraviolet (UV) light. As the cross-linking agent, one or more cross-linking agents selected from the group of compounds consisting of di- or more functional isocyanate-based cross-linking agents, di- or more functional epoxy-based cross-linking agents, and aluminum chelate-based cross-linking agents are preferable. When a cross-linking agent is used, it is preferably contained in an amount of 0.1 to 5 parts by weight with respect to 100 parts by weight of the acrylic copolymer.

A tocopherol-based compound is contained as an antioxidant used in the pressure-sensitive adhesive composition for optical members of the present invention. A tocopherol-based compound is generally vitamin E, which is also a naturally occurring chemical. For this reason, it has little adverse effect on the human body, is highly safe in handling, and is friendly to the environment. Moreover, since it is oil-soluble and liquid at room temperature, it is excellent in compatibility with the pressure-sensitive adhesive composition and in precipitation resistance.
As the tocopherol compound used in the present invention, since it is used by being blended in the pressure-sensitive adhesive composition for optical members (it is not metabolized like in the human body), the ferryl hydroxyl group of tocopherol is not changed to an ester or the like. , a compound having a ferrulic hydroxyl group is preferred. Examples include tocopherols and tocotrienols. Tocopherols and tocotrienols are known to be classified into natural compounds (d-form), non-natural compounds (l-form), and racemic forms (dl-form) which are equivalent mixtures thereof. ing. Natural compounds (d-form) and racemic forms (dl-form) are preferred because some of them are used as food additives and the like.
Specific tocopherol compounds include d-α-tocopherol, dl-α-tocopherol, d-β-tocopherol, dl-β-tocopherol, d-γ-tocopherol, dl-γ-tocopherol and d-δ-tocopherol. , dl-δ-tocopherol, d-α-tocotrienol, dl-α-tocotrienol, d-β-tocotrienol, dl-β-tocotrienol, d-γ-tocotrienol, dl-γ-tocotrienol, d-δ-tocotrienol, dl At least one selected from the group of compounds consisting of -δ-tocotrienol. Two or more tocopherol compounds may be used in combination. As a food additive, what is called "mixed tocopherol" is a mixture mainly composed of d-α-tocopherol, d-β-tocopherol, d-γ-tocopherol and d-δ-tocopherol, and is called "tocotrienol". What are called are mixtures based on d-α-tocotrienol, d-β-tocotrienol, d-γ-tocotrienol and d-δ-tocotrienol.
The pressure-sensitive adhesive composition for optical members of the present invention preferably contains 0.01 to 1.5 parts by weight of a tocopherol compound with respect to 100 parts by weight of the acrylic copolymer.

The pressure-sensitive adhesive composition for optical members of the present invention preferably contains an antistatic agent in order to impart antistatic performance. The antistatic agent is preferably solid at normal temperature (eg, 30°C), and more specifically, the antistatic agent is an ionic compound having a melting point of 30-50°C. The antistatic agent may be a quaternary ammonium salt ion compound containing an acryloyl group.
Since these antistatic agents have low melting points and long-chain alkyl groups, they are presumed to have high affinity with acrylic polymers.

The antistatic agent, which is an ionic compound having a melting point of 30 to 50° C., is an ionic compound having a cation and an anion, wherein the cation is pyridinium cation, imidazolium cation, pyrimidinium cation, pyrazolium cation, pyrrolidinium cation, nitrogen-containing onium cations such as nium cations and ammonium cations _, phosphonium cations, sulfonium cations ^, etc., ^and RC ₆ H ₄ SO ₃ ⁻ ), perchlorate (ClO ₄ ⁻ ), tetrafluoroborate (BF ₄ ⁻ ), and other compounds that are inorganic or organic anions. A compound having a melting point of 30 to 50° C. can be obtained by selecting the chain length of the alkyl group and the position and number of substituents. The cation is preferably a quaternary nitrogen-containing onium cation, such as quaternary pyridinium cations such as 1-alkylpyridinium (the carbon atoms at positions 2 to 6 may be substituted or unsubstituted), 1, quaternary imidazolium cations such as 3-dialkylimidazolium (carbon atoms at positions 2, 4 and 5 may be substituted or unsubstituted); quaternary ammonium cations such as tetraalkylammonium; .

The acryloyl group-containing quaternary ammonium salt type ionic compound is an ionic compound having a cation and an anion, wherein the cation is (meth)acryloyloxyalkyltrialkylammonium [R ₃ N ⁺ -C _n H _2n -OCOCQ =CH ₂ , where Q=H or CH ₃ , R=alkyl] (meth)acryloyl group-containing quaternary ammonium, and the anions are hexafluorophosphate (PF ₆ ⁻ ), thiocyanate ( SCN ⁻ ), organic sulfonates (RSO ₃ ⁻ ), perchlorates (ClO ₄ ⁻ ), tetrafluoroborates (BF ₄ ⁻ ), F-containing imide salts ( ^RF ₂ N ⁻ ), and other inorganic Alternatively, a compound that is an organic anion can be used. R ^F of the F-containing imide salt (R ^F ₂ N ⁻ ) includes a perfluoroalkanesulfonyl group such as a trifluoromethanesulfonyl group and a pentafluoroethanesulfonyl group, and a fluorosulfonyl group. Examples of F-containing imide salts include bis(fluorosulfonyl)imide salt [(FSO ₂ ) ₂ N ⁻ ], bis(trifluoromethanesulfonyl)imide salt [(CF ₃ SO ₂ ) ₂ N ⁻ ], bis(pentafluoroethanesulfonyl ) and bissulfonylimide salts such as imide salts [(C ₂ F ₅ SO ₂ ) ₂ N ⁻ ].

The antistatic agent, which is an ionic compound with a melting point of 30 to 50° C., is not particularly limited. Specific examples of ionic compounds having a pyridinium cation and having a melting point of 30 to 50° C. include 1-octylpyridinium dodecylbenzenesulfonate, 1-dodecylpyridinium thiocyanate, and 3-methyl-1-dodecylpyridinium phosphorus hexafluoride. acid salts, 1-dodecylpyridinium dodecylbenzenesulfonate, 4-methyl-1-octylpyridinium hexafluorophosphate and the like.
Further, specific examples of the acryloyl group-containing quaternary ammonium salt ion compound include dimethylaminomethyl (meth)acrylate hexafluorophosphate methyl salt [(CH ₃ ) ₃ N ⁺ CH ₂ OCOCQ=CH ₂ PF ₆ ⁻ , where Q=H or CH ₃ ], dimethylaminoethyl (meth)acrylate bis(trifluoromethanesulfonyl)imidomethyl salt [(CH ₃ ) ₃ N ⁺ (CH ₂ ) ₂ OCOCQ=CH _2. (CF ₃ SO ₂ ) ₂ N ⁻ where Q=H or CH ₃ ], dimethylaminomethyl (meth)acrylate bis(fluorosulfonyl)imide methyl salt [(CH ₃ ) ₃ N ⁺ CH ₂ OCOCQ=CH _2. (FSO ₂ ) ₂ N ⁻ , where Q=H or CH ₃ ] and the like.
Further, the ionic compound having a melting point of 30 to 50° C. is 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the main component (meth)acrylate monomer that is the combination of (A) and (B). It is preferably contained in the proportion of parts.

When an antistatic agent is added to the pressure-sensitive adhesive composition for optical members to provide antistatic performance, the pressure-sensitive adhesive layer for optical members laminated with the pressure-sensitive adhesive composition for optical members has an antistatic performance. , the surface resistivity of the adhesive layer is preferably 1.0×10 ⁺¹² Ω/□ or less, more preferably 5.0×10 ⁺¹¹ Ω/□ or less. If the surface resistivity is high, the performance of releasing static electricity generated by electrification during peeling is inferior. Therefore, by sufficiently reducing the surface resistivity, the peeling electrification voltage caused by static electricity, which is generated when the adherend peels off the adhesive layer, is reduced, which affects the control electronic circuit of the adherend. can be suppressed.

In the pressure-sensitive adhesive composition for optical members of the present invention, the acrylic copolymer is preferably crosslinked when forming the pressure-sensitive adhesive layer. In order to crosslink the acrylic copolymer of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition preferably contains a known cross-linking agent. The cross-linking agent used in the present invention is one or more cross-linking agents selected from the group of compounds consisting of di- or more functional isocyanate-based cross-linking agents, di- or more functional epoxy-based cross-linking agents, and aluminum chelate-based cross-linking agents. Preferably. The cross-linking agents may be used singly or in combination of two or more.

The difunctional or higher isocyanate compound may be a polyisocyanate compound having at least two or more isocyanate (NCO) groups in one molecule, such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate. Diisocyanates such as isocyanate (compounds having two NCO groups in one molecule) burette-modified products and isocyanurate-modified products, trivalent or higher polyols such as trimethylolpropane and glycerin (at least three or more in one molecule and an adduct (polyol-modified compound) with (a compound having an OH group of ).
In addition, the tri- or more functional isocyanate compound is a polyisocyanate compound having at least 3 or more isocyanate (NCO) groups in one molecule, particularly an isocyanurate of a hexamethylene diisocyanate compound, an isocyanurate of an isophorone diisocyanate compound, It is preferably at least one selected from the compound group consisting of an adduct of a hexamethylene diisocyanate compound, an adduct of an isophorone diisocyanate compound, a burette of a hexamethylene diisocyanate compound, and a burette of an isophorone diisocyanate compound.
The bifunctional or higher isocyanate cross-linking agent is preferably contained in an amount of 0.01 to 5.0 parts by weight, more preferably 0.02 to 3.0 parts by weight, with respect to 100 parts by weight of the acrylic copolymer. should be included.

Bifunctional or more functional epoxy compounds include, for example, bisphenol type epoxy resins such as bisphenol A type epoxy resin and bisphenol F type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, glycidyl ether type epoxy resin, glycidylamine. type epoxy resins, and the like. Among these, bisphenol type epoxy resins such as bifunctional bisphenol A type and bisphenol F type are more preferable because they are liquid with low viscosity and easy to handle.
In addition, the bifunctional or higher epoxy compound specifically includes glycerin poly (eg di, tri) glycidyl ether, sorbitol polyglycidyl ether, pentaerythritol poly (eg di, tri, tetra) glycidyl ether, trimethylolpropane poly glycidyl ether and the like.
The difunctional or higher epoxy compound is preferably contained in an amount of 0.01 to 5.0 parts by weight, more preferably 0.02 to 3.0 parts by weight, based on 100 parts by weight of the acrylic copolymer. It's good to be

The pressure-sensitive adhesive composition for optical members of the present invention contains an acrylic copolymer containing a (meth)acrylic acid alkyl ester as a main component, a cross-linking agent, and an antioxidant. When the acrylic copolymer has a carboxyl group or a hydroxyl group, cross-linking between these functional groups and the aluminum chelate compound occurs.
As the aluminum chelate compound that can be used in the present invention, keto-enol tautomer aluminum salts such as acetylacetonate aluminum salt and ethyl acetoacetate aluminum salt are preferable. It is preferably used as one having excellent functions.
Ketoenol tautomers Ketoenol tautomers used in aluminum salts include β-diketones such as acetylacetone, β-ketocarboxylic acid esters such as ethyl acetoacetate, methyl acetoacetate, oleyl acetoacetate, and alkyl acetoacetate. is mentioned.
Specific examples of keto-enol tautomeric aluminum salts include aluminum tris(acetylacetonate), aluminum tris(ethylacetoacetate), aluminum monoacetylacetonate bis(ethylacetoacetate), aluminum monoacetylacetonate bis-oleyl Acetoacetate, ethylacetoacetate aluminum diisopropylate, alkylacetoacetate aluminum diisopropylate, and the like.

Furthermore, as other components, known additives such as silane coupling agents, antioxidants, surfactants, curing accelerators, plasticizers, fillers, curing retarders, processing aids, anti-aging agents, etc. may be appropriately blended. can be done. These can be used alone or in combination of two or more.

The pressure-sensitive adhesive film for optical members of the present invention can be produced by forming a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition for optical members 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 pressure-sensitive adhesive layer and the release film (separator) for protecting the pressure-sensitive 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.
The pressure-sensitive adhesive layer of the pressure-sensitive adhesive film for bonding various optical films such as polarizing plates and retardation films to optical parts such as liquid crystal cells and other optical films preferably has sufficient transparency. In the case of an optical surface protective film such as a polarizing plate surface protective film, the base film and the pressure-sensitive adhesive layer preferably have sufficient transparency.

When the adhesive film has a base film, the adhesive film of the present invention is, for example, a surface protective film, a surface protective film for a polarizing plate, an optical surface protective film, an optical film with an adhesive, a polarizing plate with an adhesive, or the like. It can be suitably used for

When the adhesive film does not have a base film, by matching the release-treated surfaces of the release film to both sides of one adhesive layer, "release film / adhesive layer / release film ” can also be configured. 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.
In this case, the adhesive film of the present invention can be used for bonding a polarizing plate and a display panel. Examples of display panels include liquid crystal display devices and organic EL devices, but are not limited to these.
Further, the pressure-sensitive adhesive film for optical members of the present invention includes a pressure-sensitive adhesive film for laminating materials constituting a polarizing plate, various optical films for peripheral members of liquid crystal display devices mainly composed of polarizing plates, pressure-sensitive adhesive films for touch panels, and electronic paper. It can be used as an adhesive film for organic EL, an adhesive film for organic EL, and the like.

Also, an optical film with a pressure-sensitive adhesive layer can be obtained by laminating the pressure-sensitive adhesive layer on at least one surface of these optical films. Specifically, "optical film / adhesive layer / optical film", "optical film / adhesive layer / release film", "optical film / adhesive layer", "optical film / adhesive layer / optical film / adhesive layer/optical film”, “optical film/adhesive layer/optical film/adhesive layer/release film”, “release film/adhesive layer/optical film/adhesive layer/release film”, etc. configuration.
For example, like "optical film/adhesive layer/release film", if it has an adhesive layer protected by a release film, peel off the release film, "optical film/adhesive layer" By exposing the pressure-sensitive adhesive layer and bonding it to another optical film, a configuration such as "optical film/pressure-sensitive adhesive layer/optical film" in which the pressure-sensitive adhesive layer is used for bonding between layers can be obtained.

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

<Production of acrylic copolymer>
[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 2-ethylhexyl acrylate, 2.0 parts by weight of 6-hydroxyhexyl acrylate, and 100 parts of 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 8 hours to obtain the acrylic copolymer solution of Example 1 having a weight average molecular weight of 500,000. got 1.
[Examples 2-7 and Comparative Examples 1-2]
The acrylic copolymer solution 1 used in Example 1 above was prepared in the same manner as in Example 1, except that the monomer compositions were as described in Table 1 (A), (A'), and (B). Thus, acrylic copolymer solutions used in Examples 2-7 and Comparative Examples 1-2 were obtained.

<Production of pressure-sensitive adhesive composition for optical members and pressure-sensitive adhesive film>
[Example 1]
2.0 parts by weight of Coronate HL (an adduct of a hexamethylene diisocyanate (HDI) compound) was added to the acrylic copolymer solution 1 produced as described above (including 100 parts by weight of the acrylic copolymer). The mixture was stirred and mixed to obtain a pressure-sensitive adhesive composition for an optical member of Example 1. After applying this pressure-sensitive adhesive composition for optical members onto a release film made of a polyethylene terephthalate (PET) film coated with a silicone resin, the solvent was removed by drying at 90° C., and the thickness of the pressure-sensitive adhesive layer was 25 μm. An adhesive film was obtained.
After that, the antistatic and antifouling treated side of the polyethylene terephthalate (PET) film on one side is transferred to the side opposite to the antistatic and antifouling treated side, and the adhesive film is transferred to the surface opposite to the antistatic and antifouling treated side. An adhesive film of Example 1 having a laminated structure of "PET film/adhesive layer/release film (silicone resin-coated PET film)" was obtained.
[Examples 2-7 and Comparative Examples 1-2]
Examples 2 to 7 and Examples 2 to 7 and Adhesive films of Comparative Examples 1 and 2 were obtained.

In Table 1, the compounding ratio of each component is indicated by enclosing the numerical values in parentheses in parts by weight obtained based on the total amount of (A) and (A') being 100 parts by weight. In addition, Table 2 shows the compound names of the abbreviations of the components used in Table 1.
Coronate (registered trademark) HX, HL and L-45 are trade names of Nippon Polyurethane Industry Co., Ltd. TETRAD (registered trademark)-X is a trade name of Mitsubishi Gas Chemical Co., Ltd. Duranate (registered trademark) Trademark) 24A-100 is a trade name of Asahi Kasei Chemicals Corporation. Denacol (registered trademark) EX-121 is a trade name of a monofunctional epoxy compound (2-ethylhexyl glycidyl ether) manufactured by Nagase ChemteX Corporation. IRGANOX® 1010 is a trade name for a hindered phenolic antioxidant from BASF.

<Test method and evaluation>
After aging the adhesive films in Examples 1 to 7 and Comparative Examples 1 and 2 in an atmosphere of 23 ° C. and 50% RH for 7 days, the release film (silicone resin-coated PET film) was peeled off, and the adhesive layer was removed. The exposed adhesive film was used as a sample for surface resistivity measurement.
Furthermore, the adhesive film with the adhesive layer exposed is attached to the surface of the polarizing plate attached to the liquid crystal cell via the adhesive layer, left to stand for one day, and then autoclaved at 50 ° C., 5 atmospheres, and 20 minutes. Then, the sample was left at room temperature for 12 hours and used as a test sample for adhesive strength.

<Surface resistivity of adhesive layer>
After aging, before bonding to the polarizing plate, the release film (silicone resin-coated PET film) is peeled off to expose the adhesive layer, and a resistivity meter Hiresta UP-HT450 (manufactured by Mitsubishi Chemical Analytic Tech) is used. The surface resistivity of the adhesive layer was measured.

<Adhesive strength>
The adhesive film with the adhesive layer exposed above was cut into an adhesive film with a width of 25 mm, attached to the surface of the polarizing plate, and then peeled at 30 m / min using a tensile tester in the 180 ° direction. The peel strength measured by peeling at the speed was defined as the adhesive strength.

<Storage stability of adhesive composition for optical member>
After leaving the pressure-sensitive adhesive composition for optical members obtained above in an atmosphere of 50° C. for one month, the viscosity of the pressure-sensitive adhesive composition for optical members is measured, and the storage stability is evaluated based on whether or not there is an increase in viscosity. confirm. The evaluation criteria were as follows: "○" when the viscosity change was less than 20%, "Δ" when the change was 20% or more and less than 50%, and "X" when the change was 50% or more.

<Discoloration of adhesive film>
A pressure-sensitive adhesive film obtained by laminating a 25 μm-thick pressure-sensitive adhesive layer on transparent PET is left in an atmosphere at 50° C. for one month, and then the discoloration of the pressure-sensitive adhesive layer is checked. The evaluation criteria were as follows: colorless and transparent, "good"; slightly yellowing, "fair"; and yellowing, "bad".

<Precipitation resistance of adhesive film>
An adhesive film obtained by laminating an adhesive layer having a thickness of 25 μm on transparent PET is left in an atmosphere of 50° C. for 2 weeks, then left in an atmosphere of 0° C. for 2 weeks, and then the antioxidant is precipitated from the adhesive film. Check status. The evaluation criteria were as follows: "○" when the antioxidant was not precipitated at all, "Δ" when the antioxidant was slightly precipitated, and "X" when the antioxidant was precipitated.

Table 3 shows the evaluation results. In addition, the surface resistivity of the pressure-sensitive adhesive layer was expressed by a system where "m×10 ⁺ⁿ " is "mE+n" (where m is an arbitrary real number and n is a positive integer).

The pressure-sensitive adhesive compositions for optical members and the pressure-sensitive adhesive films of Examples 1 to 7 contain a tocopherol-based compound as an antioxidant in the pressure-sensitive adhesive composition for optical members, so that the pressure-sensitive adhesive composition for optical members is storage stable. All of the properties, the discoloration property of the adhesive film, and the deposition resistance of the adhesive film were good.
Further, the adhesive films of Examples 2 and 5 to 7 contained an ionic compound as an antistatic agent in the adhesive composition for optical members, but as shown in Table 3, the surface resistivity was , 5.0×10 ⁺¹¹ Ω/□ or less, and has the effect of reducing the peeling electrification voltage.
From this, it was found that the antistatic performance of the ionic compound in the present invention is effective without being inhibited by the tocopherol compound as an antioxidant.
In addition, since the pressure-sensitive adhesive composition for optical members and the pressure-sensitive adhesive film of Comparative Example 1 do not contain an antioxidant in the pressure-sensitive adhesive composition for optical members, the storage stability of the pressure-sensitive adhesive composition for optical members and the pressure-sensitive adhesive film had a problem with discoloration.
Since the pressure-sensitive adhesive composition for optical members and the pressure-sensitive adhesive film of Comparative Example 2 contain a hindered phenol-based antioxidant as an antioxidant in the pressure-sensitive adhesive composition for optical members, there is a problem in the deposition resistance of the pressure-sensitive adhesive film. was there.

The pressure-sensitive adhesive composition for optical members of the present invention uses a tocopherol-based compound that has little adverse effect on the human body as an antioxidant, and also has excellent antistatic performance and deposition resistance, so it is safe and It is possible to provide a pressure-sensitive adhesive film and a surface protective film for optical members that are excellent in practical use, and have great industrial utility value.

Claims (1)

A pressure-sensitive adhesive layer obtained by cross-linking a pressure-sensitive adhesive composition containing an acrylic copolymer containing (meth)acrylic acid alkyl ester as a main component, a cross-linking agent, an antioxidant, and an ionic compound is laminated. is an adhesive film,
The antioxidant is d-α-tocopherol, dl-α-tocopherol, d-β-tocopherol, dl-β-tocopherol, d-γ-tocopherol, dl-γ-tocopherol, d-δ-tocopherol, dl- δ-tocopherol, d-α-tocotrienol, dl-α-tocotrienol, d-β-tocotrienol, dl-β-tocotrienol, d-γ-tocotrienol, dl-γ-tocotrienol, d-δ-tocotrienol, dl-δ- At least one tocopherol-based compound selected from the group of compounds consisting of tocotrienols,
The pressure-sensitive adhesive film, wherein the surface resistivity of the pressure-sensitive adhesive film is 5.0×10 ⁺¹¹ Ω/□ or less.