JP7333852B2 - adhesive film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive composition having excellent antistatic properties and a pressure-sensitive adhesive film using the same.

Conventionally, in optical members such as polarizing plates and retardation plates, which are members constituting liquid crystal displays, surface protective films for temporarily protecting the surfaces of optical members, optical members between optical members or other optical members have been used. A lamination film is used to be laminated to a member. These pressure-sensitive adhesive films may be used only in the process of manufacturing optical members, or may be incorporated into final products such as liquid crystal displays.

If static electricity is generated when the adhesive film is peeled off from an optical member such as a polarizing plate or retardation plate, there is a concern that the static electricity generated by peeling will affect the failure of the electrical control circuit of the liquid crystal display. There is a demand for excellent antistatic performance against

For excellent antistatic performance, a method of kneading an antistatic agent into a base film is disclosed as a method for imparting antistatic performance to a surface protective film. Antistatic agents include, for example, (a) quaternary ammonium salts, pyridinium salts, various cationic antistatic agents having cationic groups such as primary to tertiary amino groups, (b) sulfonic acid groups, sulfuric acid Anionic antistatic agents having anionic groups such as ester bases, phosphate ester bases and phosphonate bases, (c) amphoteric antistatic agents such as amino acid-based and aminosulfate-based antistatic agents, (d) amino alcohol-based and glycerin-based , a nonionic antistatic agent such as polyethylene glycol, and (e) a polymeric antistatic agent obtained by increasing the molecular weight of the above antistatic agent (Patent Document 1).
In recent years, it has been proposed to incorporate such an antistatic agent into the base film, or directly into the pressure-sensitive adhesive layer instead of applying it to the surface of the base film.

JP-A-11-070629

A polarizing plate used for a liquid crystal display or the like uses a polyvinyl alcohol (PVA) layer containing iodine molecules (I ₂ ) as a polarizer, and on both sides thereof, triacetyl cellulose (TAC), COP (cycloolefin polymer), acrylic, A structure in which a resin film using a material with excellent optical properties (such as transparency) such as polypropylene (PP) is laminated as a protective layer (sometimes called a protective film for a polarizer) is generally used. Furthermore, the resin film of the protective layer may also function as a retardation film.

In recent years, as liquid crystal displays and the like have become thinner, polarizing plates and TAC films, which are protective films constituting the polarizing plates, tend to become thinner. By thinning the TAC film or the like, when the adhesive film having antistatic performance is attached to the polarizing plate, the ionic compound in the additive component contained in the adhesive composition and the iodine contained in the polarizer are affected by the interaction of As a result, the iodine compound precipitates in the polarizer, causing a problem of fading of the polarizing plate (polarizer).

The present invention has been made in view of the above circumstances, does not react with iodine contained in the polarizer of the polarizing plate, can suppress the fading of the polarizing plate, excellent antistatic adhesive composition, and it An object of the present invention is to provide an adhesive film using

In order to solve the above problems, the pressure-sensitive adhesive composition of the present invention uses an ionic compound that is solid at a temperature of 25 ° C. and contains an organic iodine compound as an antistatic agent. In addition, when the adhesive layer is attached to the polarizing plate, the iodine contained in the polarizer of the polarizing plate does not react with the antistatic agent, so that the fading of the polarizing plate can be suppressed.

In order to solve the above problems, the present invention provides a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive polymer, a cross-linking agent, and an antistatic agent, wherein the pressure-sensitive adhesive polymer contains (A) the number of carbon atoms in the alkyl group A copolymer composition containing at least one C1 to C14 (meth)acrylic acid alkyl ester monomer and another copolymerizable vinyl monomer, wherein the antistatic agent has a melting point of 25°C to 50°C. and containing an ionic compound that is solid at a temperature of 25° C., the ionic compound comprising a cation and an anion, and containing an organic iodine compound.

Preferably, the organic iodine compound is contained in either the cation or the anion, or both the cation and the anion.

The other copolymerizable vinyl monomer of the adhesive polymer is at least one of (B) a copolymerizable vinyl monomer containing no carboxyl group and containing a hydroxyl group and a copolymerizable vinyl monomer having a vinyl group, With respect to 100 parts by weight of the copolymer composition, (C) 0.1 to 10 parts by weight of the ionic compound, and 0.01 to 5 parts by weight of a bifunctional or higher isocyanate compound as a cross-linking agent, is preferably contained as an essential component.

The other copolymerizable vinyl monomer of the pressure-sensitive adhesive polymer is at least one aromatic monomer, and (C) the ionic compound is 0.1 per 100 parts by weight of the copolymer composition. 10 parts by weight and 0.01 to 5 parts by weight of a bifunctional or higher isocyanate compound as a cross-linking agent are preferably contained as essential components.

Further, the present invention is characterized in that the pressure-sensitive adhesive layer formed by laminating the pressure-sensitive adhesive composition on one side of a substrate has a surface resistivity of 1.0×10 ⁺¹² Ω/□ or less. To provide a self-adhesive film.

Further, the present invention provides a pressure-sensitive adhesive film having a pressure-sensitive adhesive layer formed on one side of a base material using the pressure-sensitive adhesive composition, and after bonding to an adherend via the pressure-sensitive adhesive layer, the pressure-sensitive adhesive film is heated at 70°C x 10°C. The pressure-sensitive adhesive film is characterized in that the pressure-sensitive adhesive layer has a pressure-sensitive adhesive strength of 1.5 to 10 N/25 mm after curing for a day.

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

Further, the present invention is characterized in that a pressure-sensitive adhesive layer is formed on one side of a release film using the pressure-sensitive adhesive composition, and has a configuration of release film/adhesive layer/release film. To provide self-adhesive film.

The present invention also provides a pressure-sensitive adhesive layer that is formed using the pressure-sensitive adhesive composition and that is used for bonding a polarizing plate and a display panel.

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

Further, in the present invention, as a constituent material of the polarizing plate protective film, a retardation film made of a triacetate-based material or a COP-based material has a thickness of 40 μm or less, and two or more layers are laminated on both sides of the polarizing plate. Provided is the pressure-sensitive adhesive layer used in a polarizing plate having a total thickness of 150 μm or less for the polarizing plate protective film or the retardation film and the layers included therebetween.

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

According to the present invention, the pressure-sensitive adhesive composition does not impair the pressure-sensitive adhesive performance under durability conditions, etc., and can suppress the discoloration of the polarizer, and the pressure-sensitive adhesive composition and the pressure-sensitive adhesive film using the same have excellent antistatic performance. can provide. Therefore, it has become possible to solve the above-mentioned problems that the conventional pressure-sensitive adhesive composition containing an ionic compound antistatic agent has.

The present invention will be described below based on preferred embodiments.
The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive polymer, a cross-linking agent, and an antistatic agent, wherein the antistatic agent has a melting point of 25 ° C. to 50 ° C. It is characterized by containing an ionic compound that is solid at 25° C., the ionic compound comprising a cation and an anion, and containing an organic iodine compound.

The ionic compound according to the present invention is preferably an ionic compound consisting of an anion and a cation, more preferably an ionic compound consisting of an organic anion and an organic cation.

The organic iodine compound contained in the ionic compound according to the present invention is an organic compound having a bond between carbon and iodine (CI bond). Organic iodine compounds include organic iodides (RI), iodosyl compounds (R-IO), iodonium compounds (R ₂ I ⁺ X ⁻ ), and the like. Here, R represents an organic group. X represents an anion for the iodonium cation. Iodine in the organic iodine compound is preferably contained as a substituent in the ionic compound, and a monovalent monoatomic iodine group (chemical formula: I-, English name: iodo-) is particularly preferred. The iodine substituent may be contained in any portion, such as an aliphatic group such as an alkyl group, an aromatic ring such as benzene, or a heterocycle such as pyridine or imidazole.

Also, the organic iodine compound is preferably contained in either the cation or the anion of the ionic compound, or in both the cation and the anion. The ionic compound may be a combination of an organic anion having a CI bond and an organic or inorganic cation having no CI bond, or an organic cation having a CI bond and an organic cation having no CI bond. A combination with an organic anion or an inorganic anion may be used, or a combination of an organic anion having a CI bond and an organic cation having a CI bond may be used.

The ionic compound that has a melting point of 25° C. to 50° C. and is solid at a temperature of 25° C. includes pyridinium cations, imidazolium cations, pyrimidinium cations, pyrazolium cations, pyrrolidinium cations, and ammonium cations. Nitrogen-containing onium cations such as cations, and compounds such as phosphonium cations and sulfonium cations can be mentioned. Specifically, the anions are phosphate hexafluoride (PF ₆ ^- ), thiocyanate (SCN ^- ), alkylbenzenesulfonate (RC ₆ H ₄ SO ₃ ^- ), perchlorate (ClO ₄ ^- ), tetrafluoroborate (BF ₄ ⁻ ), bis(fluorosulfonyl)imide salt (FSI), bis(trifluoromethanesulfonyl)imide salt (TFSI), trifluoromethanesulfonate (TF) and other inorganic or organic Compounds that are anions are included. It is preferably solid at room temperature (for example, 25°C), and an ionic compound having a melting point of 25°C to 50°C can be obtained by selecting the chain length of the alkyl group, the position and number of substituents, and the like. 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), and 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; .

Organic cations containing iodine include pyridinium cations, imidazolium cations, pyrimidinium cations, pyrazolium cations, pyrrolidinium cations, ammonium cations, phosphonium cations, and sulfonium cations. It is sufficient to have one or two or more, and examples thereof include iodopyridinium cations, iodoimidazolium cations, iodopyrimidinium cations, iodopyrazolium cations, iodopyrrolidinium cations, and iodoalkylammonium cations.

As the iodine-containing organic anions, organic anions such as aromatic sulfonate anions, aliphatic sulfonate anions, and carboxylate anions may have one or more I-substituents, iodobenzenesulfonate anions. , iodoalkanesulfonate anions, iodocarboxylate anions, and the like.

The pressure-sensitive adhesive composition according to the present invention contains an organic iodine compound in a proportion of 0.1 to 10 parts by weight with respect to 100 parts by weight of the copolymer composition (main polymer) constituting the pressure-sensitive adhesive polymer. It preferably contains an ionic compound that is solid at a temperature of 25°C with a melting point of 25°C to 50°C. Since these ionic compounds have low melting points and long-chain alkyl groups, they are presumed to have high affinity with acrylic copolymers. Therefore, as an antistatic agent, a pressure-sensitive adhesive composition having excellent antistatic properties can be obtained.

As the adhesive polymer, an acrylic copolymer (acrylic polymer) is preferable, and in particular, at least one (A) (meth)acrylic acid alkyl ester monomer having an alkyl group having a carbon number of C1 to C14 is added to the copolymer composition. Copolymers containing 50 parts by weight or more per 100 parts by weight of the product are preferred.

(A) Examples of (meth)acrylic acid alkyl ester monomers in which the alkyl group has C1 to C14 carbon atoms include 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, isodecyl (meth)acrylate, undecyl ( meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate and the like.
(A) The ratio of the (meth)acrylic acid alkyl ester monomer having an alkyl group of C1 to C14 carbon atoms is preferably 50 parts by weight or more in 100 parts by weight of the copolymer composition.

(A) The copolymerizable monomer to be copolymerized with the (meth)acrylic acid alkyl ester monomer having an alkyl group of C1 to C14 carbon atoms is a copolymerizable vinyl monomer having an unsaturated polymerizable group such as a vinyl group. are mentioned. The copolymerizable vinyl monomer may have a hydroxyl group, an amino group, an amide group, an ether group, an aromatic group, etc. as other functional groups. Two or more functional groups other than the polymerizable group may be contained in one molecule of each monomer.

(B) Examples of the hydroxyl group-containing copolymerizable vinyl monomer include hydroxyl group-containing (meth)acrylates such as hydroxyalkyl (meth)acrylates, and hydroxyl group-containing (meth)acrylamides such as hydroxyalkyl (meth)acrylamides. A copolymerizable vinyl monomer containing a hydroxyl group preferably does not contain a carboxyl group.
Hydroxyl group-containing (meth)acrylates include 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate and the like.
The hydroxyl group-containing (meth)acrylamide includes N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide and the like.
The ratio of (B) the hydroxyl-containing copolymerizable vinyl monomer is preferably 0.1 to 10 parts by weight per 100 parts by weight of the copolymer composition.

Copolymerizable vinyl monomers having an aromatic group include (meth)acrylates having an aromatic group, as well as aromatic monomers such as styrene and methylstyrene.
(Meth)acrylates having an aromatic group include benzyl (meth)acrylate, naphthyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxybutyl (meth)acrylate, 2-(1-naphthyloxy)ethyl (meth) Acrylates, 2-(2-naphthyloxy)ethyl (meth)acrylate, 6-(1-naphthyloxy)hexyl (meth)acrylate, 6-(2-naphthyloxy)hexyl (meth)acrylate, 8-(1-naphthyl) oxy)octyl (meth)acrylate, 8-(2-naphthyloxy)octyl (meth)acrylate and the like. In order to obtain a pressure-sensitive adhesive layer with a high refractive index, it is preferable to blend at least one aromatic monomer.

Examples of copolymerizable vinyl monomers other than the above include copolymerizable vinyl monomers containing a carboxyl group such as (meth)acrylic acid, copolymerizable vinyl monomers containing a polyether group such as polyalkylene glycol mono(meth)acrylate, Nitrogen-containing copolymerizable vinyl monomers such as N-vinylpyrrolidone, (meth)acrylamide, and (meth)acrylonitrile can be mentioned.

The combination of copolymerizable vinyl monomers in the copolymer constituting the pressure-sensitive adhesive component is not particularly limited, but at least one (meth)acrylic acid alkyl ester monomer having an alkyl group with a carbon number of C1 to C14 and a hydroxyl group. A copolymer containing at least one copolymerizable vinyl monomer, a copolymer containing at least one (meth)acrylic acid alkyl ester monomer having an alkyl group having a carbon number of C1 to C14, and another vinyl group. at least one of (meth)acrylic acid alkyl ester monomers having alkyl groups of C1 to C14 carbon atoms, and at least one copolymerizable vinyl monomer containing a hydroxyl group. a copolymer comprising a seed and at least one other copolymerizable vinyl monomer having a vinyl group, at least one (meth)acrylic acid alkyl ester monomer having an alkyl group of C1 to C14 carbon atoms, and an aromatic A copolymer consisting of at least one group-based monomer, at least one (meth)acrylic acid alkyl ester monomer having an alkyl group having a carbon number of C1 to C14, at least one aromatic monomer, and a hydroxyl group. A copolymer comprising at least one copolymerizable vinyl monomer, at least one (meth)acrylic acid alkyl ester monomer having an alkyl group having a carbon number of C1 to C14, and at least one aromatic monomer. and at least one other copolymerizable vinyl monomer having a vinyl group, and the like.

The copolymerizable vinyl monomer preferably contains at least one monomer having a functional group such as a hydroxyl group as a functional group capable of reacting with the cross-linking agent. It is preferable that the acrylic copolymer does not contain a carboxyl group-containing copolymerizable vinyl monomer and contains a hydroxyl group-containing copolymerizable vinyl monomer. As the functional group-containing monomer, only a hydroxyl group-containing copolymerizable vinyl monomer may be used.

As the cross-linking agent, a bifunctional or higher isocyanate compound is preferable. The isocyanate compound having a functionality of 2 or more may be at least one or two or more selected from polyisocyanate compounds having at least two or more isocyanate (NCO) groups in one molecule. Polyisocyanate compounds are classified into aliphatic isocyanates, aromatic isocyanates, acyclic isocyanates, alicyclic isocyanates, and the like, and any of them may be used. The bifunctional isocyanate compound may be a polyurethane compound having an isocyanate group produced by reacting a diisocyanate compound and a diol compound.

Examples of trifunctional or higher isocyanate compounds include bifunctional isocyanate compounds (compounds having two NCO groups in one molecule) with burette modification and isocyanurate modification, trimethylolpropane (TMP), glycerin and the like. and an adduct (polyol modified product) with a polyol (compound having at least 3 or more OH groups in one molecule). It is also possible to use only a trifunctional isocyanate compound or only a bifunctional isocyanate compound as a bifunctional or higher isocyanate compound. Moreover, it is also possible to use a trifunctional isocyanate compound and a bifunctional isocyanate compound together.

Difunctional or higher isocyanate compounds include bifunctional isocyanate compounds such as tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate, and hydrogenated xylylene diisocyanate, and modified products thereof ( trifunctional or higher isocyanate compounds consisting of adducts, burettes, isocyanurates, etc.).

The pressure-sensitive adhesive composition according to the present invention preferably contains a bifunctional or higher isocyanate compound as a cross-linking agent in a proportion of 0.01 to 5 parts by weight with respect to 100 parts by weight of the copolymer composition.

The pressure-sensitive adhesive composition according to the present invention includes, as components other than the above, a crosslinking catalyst such as a metal chelate compound, a crosslinking inhibitor such as a ketoenol tautomer compound, a surfactant, a curing accelerator, a plasticizer, a filler, and a curing agent. Known additives such as retarders, processing aids, anti-aging agents, and antioxidants can be added as appropriate. These are used alone or in combination of two or more.

The pressure-sensitive adhesive layer of the invention can be formed using the pressure-sensitive adhesive composition of the invention. After bonding to an adherend via the adhesive layer and curing at 70° C. for 10 days, the adhesive strength of the adhesive layer is preferably 1.5 to 10 N/25 mm. Examples of the adherend include an optical glass plate such as alkali-free glass.

In the pressure-sensitive adhesive layer formed by laminating the pressure-sensitive adhesive composition on one side of a substrate, the surface resistivity of the pressure-sensitive adhesive layer is preferably 1.0×10 ⁺¹² Ω/□ or less. If the surface resistivity of the pressure-sensitive adhesive layer 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 the static electricity generated when the adherend peels off the pressure-sensitive adhesive layer is reduced, and the electric control circuit of the adherend is not affected. can be suppressed.

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

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

The pressure-sensitive adhesive film of the present invention is suitably used for bonding a polarizing plate and a display panel. Examples of display panels include liquid crystal panels and organic EL 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 of the retardation film include triacetate-based materials such as TAC, COP-based materials, and the like. The polarizing plate may have a configuration such as “retardation film/polarizer/retardation film”. In this case, the thickness can be reduced as compared with the case where the polarizing plate of "protective layer/polarizer/protective layer" is further laminated with a retardation film. A protective film that can be removed by peeling may be provided on one or both sides of the polarizing plate.

According to the present invention, even if an adhesive film is attached to a polarizing plate, it is possible to suppress the deterioration of the polarization characteristics due to escape of iodine molecules contained in the polarizer. From the viewpoint of thinning the polarizing plate, the thickness of the retardation film is 40 μm or less, and two or more polarizing plate protective films or retardation films laminated on both sides of the polarizing plate, and a layer contained therebetween. and (total thickness of the polarizing plate) is preferably 150 μm or less. Between two or more polarizing plate protective films or retardation films, a polarizer composed of a PVA layer containing iodine, etc., an adhesive layer, etc. may be included. The total thickness of the polarizing plate may be the thickness of the portion to be incorporated in the final product such as a liquid crystal display (the thickness excluding the portion not to be incorporated), and may not include the polyester protective film or the like.

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. Thereafter, 100 parts by weight of butyl acrylate, 3.0 parts by weight of 6-hydroxyhexyl acrylate, and a solvent (ethyl acetate) were added to the reactor. After that, azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours and reacted at 65° C. for 6 hours to obtain an acrylic copolymer solution used in Example 1.
[Examples 2 to 4 and Comparative Examples 1 to 3]
Examples 2 to 4 and 4 were prepared in the same manner as the acrylic copolymer solution used in Example 1 above, except that the compositions of the monomers were set as shown in Table 1 (A) and (B), respectively. Acrylic copolymer solutions used in Comparative Examples 1 to 3 were obtained.

<Production of adhesive composition and adhesive film>
[Example 1]
After adding 2.0 parts by weight of 1-nonylpyridinium 2-iodobenzenesulfonate to the acrylic copolymer solution of Example 1 produced as described above and stirring, Coronate HX (an isocyanurate of a hexamethylene diisocyanate compound 1.0 parts by weight of component) was added and mixed with stirring to obtain a pressure-sensitive adhesive composition of Example 1. After applying this pressure-sensitive adhesive composition onto a release film made of a polyethylene terephthalate (PET) film coated with a silicone resin, the solvent is removed by drying at 90° C., and the thickness of the pressure-sensitive adhesive layer is 25 μm. A sticky sheet was obtained.
After that, the pressure-sensitive adhesive sheet is transferred to the opposite side of the antistatic and antifouling treated side of the polyethylene terephthalate (PET) film having one side antistatic and antifouling treated. The adhesive film of Example 1 having a laminated structure of "PET film/adhesive layer/releasing film (silicone resin-coated PET film)" was obtained.
[Examples 2 to 4 and Comparative Examples 1 to 3]
Examples 2 to 4 and Comparative Examples 1 to 2 were prepared in the same manner as in the adhesive film of Example 1 above, except that the composition of the additive was set as described in Table 2 for "crosslinking agent" and (C). 3 was 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 of Group (A) being 100 parts by weight. Group (A) consists of (meth)acrylic acid alkyl ester monomers or aromatic monomers having alkyl groups of C1 to C14 carbon atoms. Group (B) consists of copolymerizable vinyl monomers containing a hydroxyl group or a carboxyl group. Group (C) consists of ionic compounds.

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 are trade names of Nippon Polyurethane Industry Co., Ltd.

<Test method and evaluation>
After aging the adhesive films in Examples 1 to 4 and Comparative Examples 1 to 3 for 7 days in an atmosphere of 23 ° C. and 50% RH, the release film (silicone resin-coated PET film) was peeled off, and the adhesive The exposed layer was used as a sample for surface resistivity measurement.
Furthermore, the pressure-sensitive adhesive film with the pressure-sensitive adhesive layer exposed was attached to the surface of a polarizing plate with the pressure-sensitive adhesive layer interposed therebetween to obtain a sample for measurement of adhesive strength.

<Surface resistivity>
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 Analytech) is used. was used to measure the surface resistivity (Ω/□) of the adhesive layer.

<Adhesive strength>
After the adhesive layer (film) was attached to the polarizing plate, the polarizing plate with the adhesive layer was attached to non-alkali glass manufactured by Corning (trade name: Eagle XG). After that, the sample was allowed to stand in an atmosphere of 70°C for 10 days, then taken out to room temperature and left for another 1 hour.
<Fadeability>
After the adhesive layer (film) was attached to the polarizing plate, the polarizing plate with the adhesive layer was attached to non-alkali glass manufactured by Corning (trade name: Eagle XG). Then, after standing in an atmosphere of 85° C. and 85% RH for 100 hours, the plate was taken out to room temperature, and after standing for 1 hour, the degree of fading of the polarizing plate was observed. As for the evaluation target criteria, the case where the polarizing plate was not discolored was evaluated as "○", the case where the polarizing plate was partially discolored was evaluated as "Δ", and the case where the polarizing plate was discolored was evaluated as "x".

Table 3 shows the evaluation results. In addition, the surface resistivity was expressed by a method of setting "m×10 ⁺ⁿ " to "mE+n" (where m is an arbitrary real number and n is a positive integer).
The types of polarizing plates are as follows.
Polarizing plate A (total thickness 135 μm, retardation film: TAC with a thickness of 40 μm)
Polarizing plate B (total thickness 115 μm, retardation film: TAC with a thickness of 25 μm)
Polarizing plate C (total thickness 90 μm, retardation film: TAC with a thickness of 20 μm)
Polarizing plate D (total thickness 135 μm, retardation film: COP with a thickness of 40 μm)
Polarizing plate E (total thickness 180 μm, retardation film: TAC with a thickness of 80 μm)

The adhesive films of Examples 1 to 4 had low surface resistivity, moderate adhesive strength, and did not fade even when the polarizing plate was thin. That is, it simultaneously satisfies all of the required performances of (1) not impairing adhesive performance under durability conditions, etc., (2) being able to suppress discoloration of polarizing plates, and (3) being excellent in antistatic properties.

Since the pressure-sensitive adhesive films of Comparative Examples 1 and 3 did not contain an ionic organic iodine compound, fading of the polarizing plate could not be suppressed.
Since the pressure-sensitive adhesive film of Comparative Example 2 did not contain an ionic compound, it had a high surface resistivity and did not have antistatic properties. In addition, probably because the copolymer of the adhesive component is a copolymer of a copolymerizable vinyl monomer containing a carboxyl group, after curing at 70 ° C. for 10 days after bonding to the adherend, the adhesive The adhesion of the layers became very strong.
As described above, the pressure-sensitive adhesive films of Comparative Examples 1 to 3 (1) do not impair the adhesive performance under durability conditions, etc., (2) can suppress fading of the polarizing plate, and (3) have excellent antistatic properties. , could not satisfy all the required performance simultaneously.

Claims (3)

A pressure-sensitive adhesive film in which a pressure-sensitive adhesive layer is formed using a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive polymer, a cross-linking agent, and an antistatic agent,
The adhesive polymer is an acrylic polymer,
The antistatic agent contains an ionic compound that has a melting point of 25° C. to 50° C. and is solid at a temperature of 25° C. The ionic compound consists of a cation and an anion and contains an organic iodine compound. An adhesive film characterized by: A pressure-sensitive adhesive layer is formed on one side of the release film using a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive polymer, a cross-linking agent, and an antistatic agent,
The adhesive polymer is an acrylic polymer,
The antistatic agent contains an ionic compound that has a melting point of 25° C. to 50° C. and is solid at a temperature of 25° C. The ionic compound consists of a cation and an anion and contains an organic iodine compound. , a pressure-sensitive adhesive film having a configuration of release film/adhesive layer/release film. A pressure-sensitive adhesive layer is formed on at least one side of a substrate using a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive polymer, a cross-linking agent, and an antistatic agent,
The adhesive polymer is an acrylic polymer,
The antistatic agent contains an ionic compound that has a melting point of 25° C. to 50° C. and is solid at a temperature of 25° C. The ionic compound consists of a cation and an anion and contains an organic iodine compound. An adhesive film characterized by: