Pressure-sensitive adhesive composition

Abstract

To provide an adhesive composition, an adhesive film using the adhesive composition, and a surface protective film using the adhesive composition, wherein the adhesive composition has excellent adhesive performance such as balanced adhesive force at a low peeling speed and a high peeling speed, and can achieve both antistatic performance and anti-fouling performance.SOLUTION: An adhesive composition includes an acrylic polymer and an antistatic agent (F). The antistatic agent (F) is an ionic compound having a melting point of 25-80°C and represented by general formula (1) K+ A- [where, K+ is a cation and A- is one anion selected from the group consisting of imido group-free, trifluoromethane sulfonate ions and pentafluoroethane sulfonate ions]. The acrylic polymer is an acrylic polymer having a glass transition temperature of 0°C or less. Relative to 100 pts.wt. of the acrylic polymer, the ionic compound is contained at 0.01-10 pts.wt. as an essential component.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive composition containing an antistatic agent, and a pressure-sensitive adhesive film and a surface protection film using the same. More specifically, the present invention relates to a pressure-sensitive adhesive composition that has excellent adhesive performance, such as balanced adhesive strength at both low and high peel speeds, and is capable of achieving both antistatic performance and stain resistance, and a pressure-sensitive adhesive film and a surface protection film using the same. [Background technology]

[0002] Conventionally, in the manufacturing process of optical components such as polarizing plates, which are components of liquid crystal displays, a surface protection film is applied to temporarily protect the surface of the optical component. Such a surface protection film is used only in the manufacturing process of the optical component and is peeled off and removed from the optical component when the optical component is assembled into a liquid crystal display. Since such a surface protection film for protecting the surface of an optical component is used only in the manufacturing process of the optical component, it is also generally called a processing film.

[0003] The surface protection film used in the process of producing an optical component has an optically transparent polyethylene terephthalate (PET) resin film on one side of which an adhesive layer is formed, and a release-treated release film is attached to the surface of the adhesive layer to protect the adhesive layer until the surface protection film is attached to the optical component. Optical components such as polarizing plates, with the surface protection film attached, undergo product inspections that involve optical evaluation of the display performance, hue, contrast, and inclusion of foreign matter of the liquid crystal display panel. For this reason, the surface protection film is required to have the performance that the pressure-sensitive adhesive layer is free from air bubbles, foreign matter, and low-molecular-weight components of the pressure-sensitive adhesive composition, i.e., it is required to have contamination resistance. Furthermore, when peeling a surface protection film from an optical component such as a polarizing plate, there is concern that the static electricity generated when the pressure-sensitive adhesive layer is peeled off from the adherend may cause peeling electrification, which may lead to malfunctions in the electrical control circuits of liquid crystal displays. For this reason, the pressure-sensitive adhesive layer of a surface protection film is required to have excellent antistatic properties. Furthermore, in recent years, in addition to the conventionally used triacetyl cellulose (TAC), materials that are prone to peeling static electricity when peeling off the surface protective film of a polarizing plate, such as acrylic resins such as polymethyl methacrylate (PMMA), polyester resins such as polyethylene terephthalate (PET), cyclic olefin polymers, and polycarbonates, have been increasingly used as protective layers (sometimes called protective films) for the polarizers of polarizing plates. For this reason, the antistatic performance required for the pressure-sensitive adhesive layer of the surface protective film of a polarizing plate needs to be superior to that of conventional materials. Furthermore, when the surface protection film is finally peeled off from an optical component such as a polarizing plate, it is required to be able to be peeled off quickly, i.e., it is required that the adhesive strength does not change much depending on the peeling speed so that it can be peeled off quickly even at high speeds.

[0004] Thus, in recent years, in terms of ease of use when using a surface protection film, the adhesive layer that constitutes the surface protection film is required to have (1) a balance of adhesive strength at low and high peel speeds, (2) stain resistance, and (3) excellent antistatic properties. However, while it is possible to satisfy each of the required performances (1) to (3) for the adhesive layer constituting the surface protection film, it has been an extremely difficult task to simultaneously satisfy all of the required performances (1) to (3) required for the adhesive layer of the surface protection film.

[0005] To solve these problems, for example, the following proposals are known regarding (1) balancing adhesive strength at low and high peeling speeds, (2) having stain resistance, and (3) having excellent antistatic properties.

[0006] (1) With regard to balancing adhesive strength at low and high peel speeds, an acrylic pressure-sensitive adhesive layer, which is mainly composed of a copolymer of a (meth)acrylic acid alkyl ester having an alkyl group with 7 or less carbon atoms and a carboxyl group-containing copolymerizable compound and crosslinked with a crosslinking agent, has the problem that the pressure-sensitive adhesive transfers to the adherend after long-term adhesion and the adhesive strength to the adherend increases significantly over time. To avoid this, a pressure-sensitive adhesive layer is known which uses a copolymer of a (meth)acrylic acid alkyl ester having an alkyl group with 8 to 10 carbon atoms and a copolymerizable compound having an alcoholic hydroxyl group and crosslinks this with a crosslinking agent (Patent Document 1). Furthermore, a pressure-sensitive adhesive layer has been proposed in which a small amount of a copolymer of a (meth)acrylic acid alkyl ester and a carboxyl group-containing copolymerizable compound is blended with the same copolymer as above, and the resulting copolymer is crosslinked with a crosslinking agent. However, when used to protect the surface of a plastic plate or the like having a low surface tension and a smooth surface, there are problems such as peeling phenomena such as lifting due to heating during processing or storage, and poor removability when peeled at high speeds, which is the range of manual work.

[0007] In order to solve these problems, a pressure-sensitive adhesive composition has been proposed in which a copolymer of a monomer mixture obtained by adding a) 100 parts by weight of a (meth)acrylic acid alkyl ester, the main component of which is a (meth)acrylic acid alkyl ester having an alkyl group having 8 to 10 carbon atoms, b) 1 to 15 parts by weight of a carboxyl group-containing copolymerizable compound, and c) 3 to 100 parts by weight of a vinyl ester of an aliphatic carboxylic acid having 1 to 5 carbon atoms, is blended with a crosslinking agent in an amount equivalent to or greater than the amount of the carboxyl groups in the above-mentioned b) component (Patent Document 2). The pressure-sensitive adhesive composition described in Patent Document 2 does not experience peeling phenomena such as lifting during processing or storage, and in addition, the adhesive strength increases little over time, making it highly releasable; it can be releasable with little force even after long-term storage, particularly long-term storage under high-temperature conditions, without leaving any adhesive residue on the adherend, and can be releasable with little force even when peeled at high speed. However, in the pressure-sensitive adhesive composition described in Patent Document 2, the gel fraction of the pressure-sensitive adhesive layer in Examples 1 to 3 was 90%, and unpolymerized monomers or oligomers were likely to elute from the copolymer. Furthermore, Patent Document 2 does not mention antistatic properties or stain resistance, and there was a problem that it was difficult to improve the pressure-sensitive adhesive layer to have excellent antistatic properties and stain resistance when the adherend was a material that was prone to peel electrification.

[0008] Furthermore, with regard to (2) stain resistance, a pressure-sensitive adhesive composition has been disclosed that contains 100 parts by mass of a (meth)acrylic copolymer having a weight-average molecular weight of 100,000 or more and less than 1,000,000, which is composed of 0 part by mass or more and less than 0.5 part by mass of a carboxyl group-containing monomer, 0.6 to 9 parts by mass of a hydroxy group-containing (meth)acrylic monomer, and 99.4 to 90.5 parts by mass of a (meth)acrylic acid ester monomer; and 0.1 to 5 parts by mass of a carbodiimide crosslinking agent (Patent Document 3). The pressure-sensitive adhesive composition described in Patent Document 3 is characterized by using a carbodiimide-based crosslinking agent as a crosslinking agent for a (meth)acrylic copolymer of a specific composition. This provides the pressure-sensitive adhesive layer with a crosslinked structure that can adapt to shrinkage caused by pressure and temperature during autoclave treatment. As a result, the pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition is able to suppress or prevent foaming even under high-temperature and high-pressure conditions (during autoclave treatment), and is said to have excellent stain resistance and transparency. However, although the pressure-sensitive adhesive composition described in Patent Document 3 has improved stain resistance, it has not been possible to achieve both excellent adhesive performance and antistatic performance, and this remains a problem that needs to be solved.

[0009] Regarding (3) excellent antistatic performance, a method of kneading an antistatic agent into a substrate film is known as a method for imparting antistatic properties to a surface protective film. Examples of antistatic agents disclosed include (a) various cationic antistatic agents having cationic groups such as quaternary ammonium salts, pyridinium salts, and primary to tertiary amino groups, (b) anionic antistatic agents having anionic groups such as sulfonate groups, sulfate groups, phosphate groups, and phosphonate groups, (c) amphoteric antistatic agents such as amino acid-based and amino sulfate-based, (d) nonionic antistatic agents such as amino alcohol-based, glycerin-based, and polyethylene glycol-based, and (e) polymeric antistatic agents obtained by increasing the molecular weight of the above-mentioned antistatic agents (Patent Document 4). However, although the surface protection film described in Patent Document 4 describes imparting antistatic properties related to the adhesion of dirt to the adherend, it does not describe a solution for achieving both excellent adhesive properties and contamination resistance, and this remains a problem that needs to be solved.

[0010] In recent years, it has been proposed to incorporate an antistatic agent directly into a pressure-sensitive adhesive layer, rather than incorporating it into a substrate film or applying it to the surface of a substrate film. For example, an antistatic pressure-sensitive adhesive composition has been disclosed, which is characterized in that a salt having an anion having a fluoro group and a sulfonyl group is dispersed in a dissolved state in a polyetherester plasticizer containing a polyether group in the main chain (Patent Document 5). Patent Document 5 discloses that the pressure-sensitive adhesive composition uses as a plasticizer an ester formed from a mono- or dicarboxylic acid having a saturated or unsaturated acyclic hydrocarbon group and an alcohol having an acyclic hydrocarbon group with 1 to 20 carbon atoms, or an ester in which the unsaturated group in the unsaturated acyclic hydrocarbon group has been epoxidized. Such mono- or dicarboxylic acid having a saturated or unsaturated acyclic hydrocarbon group has a carbon number close to the carbon number of the acrylic monomer constituting the acrylic copolymer used in the pressure-sensitive adhesive layer, which improves compatibility with the antistatic pressure-sensitive adhesive composition and allows the plasticizer to be suitably retained in the acrylic antistatic pressure-sensitive adhesive composition, thereby suppressing bleed-out. However, although Patent Document 5 discloses techniques for improving antistatic performance and bleed-out, it does not disclose that the antistatic pressure-sensitive adhesive composition has excellent adhesive performance, such as a balance of adhesive strength at low peel speeds and high peel speeds, and the problem of obtaining a pressure-sensitive adhesive composition with excellent adhesive performance remains. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 63-225677 [Patent Document 2] Japanese Patent Application Publication No. 11-256111 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-122054 [Patent Document 4] Japanese Patent Application Publication No. 11-070629 [Patent Document 5] Japanese Patent Application Laid-Open No. 2014-118469 Summary of the Invention [Problem to be solved by the invention]

[0012] As described above, there is no prior art that simultaneously achieves the following for a pressure-sensitive adhesive layer that constitutes a surface protection film: (1) balancing adhesive strength at both low and high peel speeds, (2) having contamination resistance, and (3) having excellent antistatic properties. Furthermore, conventionally, there has been a trade-off between the antistatic performance of a pressure-sensitive adhesive layer formed using a pressure-sensitive adhesive composition with antistatic properties and the anti-contamination performance of the adherend in a surface protection film using the same, and it has been difficult to improve the anti-contamination performance while maintaining the antistatic performance. Furthermore, in recent years, the types of materials to which surface protective films are attached have increased, and the surface treatment conditions of the adherends have become more diverse, making it increasingly difficult to simultaneously achieve both contamination resistance and antistatic properties for all adherends.

[0013] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pressure-sensitive adhesive composition that has excellent adhesive performance, such as balanced adhesive strength, at both low and high peel speeds, as well as antistatic performance and stain resistance, and a pressure-sensitive adhesive film and a surface protection film using the same. [Means for solving the problem]

[0014] The inventors of the present invention have discovered that a pressure-sensitive adhesive composition containing, as an antistatic agent, an ionic compound that is solid at room temperature and has a trifluoromethanesulfonate anion or a pentafluoroethanesulfonate anion and a melting point of 25 to 80°C, can simultaneously exhibit antistatic properties and stain resistance to an adherend, thereby completing the present invention. The pressure-sensitive adhesive composition of the present invention contains, as an antistatic agent, an ionic compound that is solid at room temperature and has a trifluoromethanesulfonate anion or a pentafluoroethanesulfonate anion with a melting point of 25 to 80°C, and the pressure-sensitive adhesive film and surface protection film using the same achieve a balance between excellent adhesive performance, antistatic performance, and contamination resistance, thereby resolving the problems of the prior art.

[0015] In order to solve the above problems, the present invention provides a pressure-sensitive adhesive composition comprising an acrylic polymer, (F) an antistatic agent, and (C) a crosslinking agent, wherein the (F) antistatic agent is an ionic compound represented by the following general formula (1) and having a melting point of 25 to 80°C: K + A - (1) [In general formula (1), K + is a cation and A - is an anion selected from the group consisting of a trifluoromethanesulfonate anion and a pentafluoroethanesulfonate anion, which does not contain an imide group. The pressure-sensitive adhesive composition is characterized in that the acrylic polymer is an acrylic polymer having a glass transition temperature of 0°C or lower, and contains the ionic compound as an essential component in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the acrylic polymer.

[0016] The acrylic polymer is an acrylic polymer of a copolymer obtained by copolymerizing 0.01 to 10 parts by weight of at least one or more copolymerizable vinyl monomers (B-1) containing a hydroxyl group and / or 0.01 to 0.5 parts by weight of at least one or more copolymerizable vinyl monomers (B-2) containing a carboxyl group with 100 parts by weight of at least one or more (meth)acrylic acid ester monomers (A) having an alkyl group with 1 to 18 carbon atoms, and It is preferable that the pressure-sensitive adhesive composition contains at least one selected from the group consisting of isooctyl (meth)acrylate, isononyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate in a proportion of 50 parts by weight or more out of a total of 100 parts by weight of at least one type, and that the pressure-sensitive adhesive composition contains 0.1 to 10 parts by weight of a trifunctional or higher isocyanate compound as the (C) crosslinking agent relative to 100 parts by weight of the acrylic polymer, and that the pressure-sensitive adhesive composition further contains (D) a crosslinking accelerator which is a metal chelate compound, and (E) a keto-enol tautomer compound.

[0017] The surface resistivity of the pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition is 1.0 × 10 +12 and the peeling electrification voltage of the pressure-sensitive adhesive layer against a low refractive index layer formed on the surface of a PMMA substrate and a TAC substrate using a resin composition for forming a low refractive index layer containing a fluorine compound, and against a plain layer on which no treatment has been applied to the surface of the PMMA substrate and the TAC substrate, are both ±0.3 kV or less; the pressure-sensitive adhesive layer is attached to an adherend which is a polarizing plate having a protective layer laminated on a polarizer, the surface of which has been treated with a composition containing a fluorine compound for low reflection, and then left in an atmosphere of a temperature of 60°C and a humidity of 90% RH for 48 hours, and one day after removal from the atmosphere, the stain resistance to the surface of the adherend is "no staining"; and the adhesive strength of the pressure-sensitive adhesive layer to the low refractive index layer applied to the surface of the PMMA substrate is preferably 0.04 to 0.2 N / 25 mm at a slow peel speed of 0.3 m / min and 2.0 N / 25 mm or less at a fast peel speed of 30 m / min.

[0018] the (B-1) 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, N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, and N-hydroxyethyl(meth)acrylamide; The (B-2) carboxyl group-containing copolymerizable vinyl monomer is preferably at least one selected from the group consisting of (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxypropyl hexahydrophthalate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, carboxypolycaprolactone mono(meth)acrylate, and 2-(meth)acryloyloxyethyl tetrahydrophthalic acid.

[0019] The pressure-sensitive adhesive composition preferably contains 0.001 to 0.5 parts by weight of the crosslinking accelerator of the metal chelate compound (D) and 0.1 to 300 parts by weight of the keto-enol tautomer compound (E) relative to 100 parts by weight of the acrylic polymer, the crosslinking accelerator of the metal chelate compound (D) being at least one selected from the group consisting of aluminum chelate compounds, titanium chelate compounds, and iron chelate compounds, and the weight ratio of the (E) / the (D) is 70 to 1000.

[0020] The present invention also provides a pressure-sensitive adhesive film, characterized in that a pressure-sensitive adhesive layer obtained by crosslinking the above-mentioned pressure-sensitive adhesive composition is laminated on one surface of a resin film.

[0021] The present invention also provides a surface protection film using the above-mentioned pressure-sensitive adhesive film.

[0022] The present invention also provides a surface protection film for a polarizing plate, which uses the above-mentioned pressure-sensitive adhesive film.

[0023] The present invention also provides an optical film with a pressure-sensitive adhesive layer, comprising an optical film and a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition, laminated on at least one surface of the optical film.

[0024] The present invention also provides a pressure-sensitive adhesive film, wherein one surface of the resin film opposite to the surface on which the pressure-sensitive adhesive layer is formed is subjected to an antistatic treatment and an antifouling treatment. [Effects of the Invention]

[0025] The pressure-sensitive adhesive composition of the present invention has superior adhesive properties and excellent anti-static properties at peeling without deterioration over time, compared to conventional pressure-sensitive adhesive compositions for surface protection films. In particular, the surface protection film of the present invention has superior adhesive performance and excellent peel-off antistatic performance without deterioration over time compared to surface protection films made by conventional techniques, when the adherend is an antifouling layer containing a fluorine compound laminated on the surface of an optical film, or a low refractive index layer formed using a composition for forming a low refractive index layer containing a fluorine compound, and is significantly effective in achieving both antistatic performance and anti-fouling performance. In other words, the pressure-sensitive adhesive composition of the present invention and the surface protection film using the same have excellent adhesive properties and excellent antistatic properties against peeling without deterioration over time, and therefore have extremely high industrial utility value. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention will be described below based on preferred embodiments. The pressure-sensitive adhesive composition of the present embodiment is a pressure-sensitive adhesive composition containing an acrylic polymer, (F) an antistatic agent, and (C) a crosslinking agent, wherein the (F) antistatic agent is an ionic compound represented by the following general formula (1) and having a melting point of 25 to 80°C: K + A - (1) [In general formula (1), K + is a cation and A - is an anion selected from the group consisting of a trifluoromethanesulfonate anion and a pentafluoroethanesulfonate anion, which does not contain an imide group. The acrylic polymer is an acrylic polymer having a glass transition temperature of 0°C or lower, and is characterized in that the ionic compound is contained as an essential component in a ratio of 0.01 to 10 parts by weight per 100 parts by weight of the acrylic polymer.

[0027] The acrylic polymer used in the pressure-sensitive adhesive composition of the present embodiment is a main polymer of the pressure-sensitive adhesive composition, and is an acrylic polymer having a glass transition temperature of 0° C. or lower. The acrylic polymer is preferably a copolymer containing, as a main component, (A) a (meth)acrylic acid ester monomer having an alkyl group with 1 to 18 carbon atoms.

[0028] (A) Examples of the (meth)acrylic acid ester monomers having an alkyl group with 1 to 18 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, and methyl (meth)acrylate. Examples of the alkyl (meth)acrylate monomer include octadecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, cyclopentyl (meth)acrylate, and cyclohexyl (meth)acrylate. The alkyl group of the alkyl (meth)acrylate monomer may be linear, branched, or cyclic.

[0029] The acrylic polymer used in the pressure-sensitive adhesive composition of the present embodiment preferably contains at least one selected from the group consisting of isooctyl (meth)acrylate, isononyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate in a proportion of 50 parts by weight or more, more preferably 60 parts by weight or more, and particularly preferably 75 parts by weight or more, of a total of 100 parts by weight of at least one (meth)acrylic acid ester monomer (A) having an alkyl group with 1 to 18 carbon atoms.

[0030] The acrylic polymer used in the pressure-sensitive adhesive composition of this embodiment is preferably an acrylic polymer of a copolymer obtained by copolymerizing at least one copolymerizable vinyl monomer (B-1) containing a hydroxyl group and / or at least one copolymerizable vinyl monomer (B-2) containing a carboxyl group. The acrylic polymer may be copolymerized with at least one of the copolymerizable vinyl monomer (B-1) containing a hydroxyl group and the copolymerizable vinyl monomer (B-2) containing a carboxyl group, or may be copolymerized with both. The acrylic polymer is preferably an acrylic polymer of a copolymer obtained by copolymerizing 100 parts by weight of at least one (meth)acrylic acid ester monomer (A) having an alkyl group with 1 to 18 carbon atoms with 0.01 to 10 parts by weight of at least one (B-1) copolymerizable vinyl monomer containing a hydroxyl group and / or 0.01 to 0.5 parts by weight of at least one (B-2) copolymerizable vinyl monomer containing a carboxyl group.

[0031] The acrylic polymer used in the pressure-sensitive adhesive composition of this embodiment may be copolymerized with (B-1) a copolymerizable monomer containing a hydroxyl group. The (B-1) copolymerizable monomer containing a hydroxyl group is preferably 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, N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, etc. When copolymerizing (B-1) a copolymerizable monomer containing a hydroxyl group, the copolymer preferably contains 0.01 to 10.0 parts by weight, more preferably 0.5 to 7.0 parts by weight, and particularly preferably 1.0 to 6.0 parts by weight of (B-1) a copolymerizable monomer containing a hydroxyl group, relative to a total of 100 parts by weight of at least one (meth)acrylic acid ester monomer (A) having an alkyl group with 1 to 18 carbon atoms.

[0032] The acrylic polymer used in the pressure-sensitive adhesive composition of this embodiment may be copolymerized with (B-2) a copolymerizable monomer containing a carboxyl group. The (B-2) copolymerizable monomer containing a carboxyl group is preferably at least one selected from the group consisting of (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxypropyl hexahydrophthalate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, carboxypolycaprolactone mono(meth)acrylate, 2-(meth)acryloyloxyethyl tetrahydrophthalate, etc. When (B-2) a copolymerizable vinyl monomer containing a carboxyl group is copolymerized, it is preferably contained in an amount of 0.01 to 0.5 parts by weight, more preferably 0.01 to 0.4 parts by weight, and particularly preferably 0.01 to 0.3 parts by weight, per 100 parts by weight of at least one (meth)acrylic acid ester monomer (A) having an alkyl group with 1 to 18 carbon atoms.

[0033] The method for producing the acrylic polymer contained in the pressure-sensitive adhesive composition according to this embodiment is not particularly limited, and any known polymerization method, such as solution polymerization or emulsion polymerization, can be used as appropriate. The weight-average molecular weight of the acrylic polymer copolymer is, for example, 500,000 to 3,000,000. The acid value of the acrylic polymer is preferably 0.1 to 1.0, which can improve stain resistance. Here, the "acid value" is an index representing the acid content and is expressed as the number of milligrams of potassium hydroxide required to neutralize 1 g of a polymer containing a carboxyl group.

[0034] The pressure-sensitive adhesive composition according to this embodiment contains an antistatic agent (F). The antistatic agent (F) according to this embodiment is an ionic compound having a melting point of 25 to 80°C and represented by the following general formula (1).

[0035] K + A - (1) [In general formula (1), K + is a cation and A - is an anion selected from the group consisting of a trifluoromethanesulfonate anion and a pentafluoroethanesulfonate anion, which does not contain an imide group.

[0036] The ionic compound is preferably solid at room temperature. Room temperature is, for example, a temperature below 25° C., and specifically, the ionic compound is preferably solid at 23° C. The pressure-sensitive adhesive composition according to the present embodiment contains the ionic compound as an essential component in a ratio of 0.01 to 10 parts by weight per 100 parts by weight of the acrylic polymer.

[0037] In the general formula (1), the cation K + is preferably one cation selected from the group consisting of pyridinium, imidazolium, phosphonium, sulfonium, pyrrolidinium, guanidinium, ammonium, isouronium, thiouronium, piperidinium, pyrazolium, methylium, and morpholinium.

[0038] Specific examples of the (F) antistatic agent include 1-octyl-2-methylpyridinium trifluoromethanesulfonate salt, 1,2,3-trimethylimidazolium pentafluoroethanesulfonate salt, 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate salt, 1-hexyl-4-methylpyridinium pentafluoroethanesulfonate salt, 1-octyl-3-methylpyridinium trifluoromethanesulfonate salt, and n-octylpyridinium trifluoromethanesulfonate salt.

[0039] The pressure-sensitive adhesive composition according to this embodiment further contains a trifunctional or higher isocyanate compound as a crosslinking agent (C). Examples of trifunctional or higher isocyanate compounds include biuret-modified or isocyanurate-modified diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate, as well as adducts with trivalent or higher polyols such as trimethylolpropane and glycerin. The proportion of the trifunctional or higher isocyanate compound as the crosslinking agent (C) is preferably 0.1 to 10 parts by weight, and more preferably 0.1 to 6 parts by weight, per 100 parts by weight of the acrylic polymer.

[0040] The pressure-sensitive adhesive composition according to this embodiment may contain a (E) keto-enol tautomer compound. Examples of the (E) keto-enol tautomer compound include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate, and β-diketones such as acetylacetone, 2,4-hexanedione, and benzoylacetone. In pressure-sensitive adhesive compositions using a polyisocyanate compound as a crosslinking agent, these compounds block the isocyanate groups of the crosslinking agent, thereby suppressing excessive viscosity increase and gelation of the pressure-sensitive adhesive composition after the addition of the crosslinking agent, and thereby extending the pot life of the pressure-sensitive adhesive composition. The (E) keto-enol tautomer compound is preferably at least one selected from the group consisting of acetylacetone and ethyl acetoacetate. The (E) keto-enol tautomer compound is preferably contained in an amount of 0.1 to 300 parts by weight per 100 parts by weight of the acrylic polymer.

[0041] The pressure-sensitive adhesive composition according to this embodiment may contain (D) a crosslinking accelerator for a metal chelate compound. The (D) crosslinking accelerator for a metal chelate compound may be any substance that functions as a catalyst for the reaction (crosslinking reaction) between the copolymer and a polyisocyanate compound used as a crosslinking agent. The (D) crosslinking accelerator for a metal chelate compound is a compound in which one or more multidentate ligands L are bonded to a central metal atom M. The metal chelate compound may or may not have one or more monodentate ligands X bonded to the metal atom M. Specific examples of metal chelate compounds include iron tris(2,4-pentanedionato)(III), iron trisacetylacetonate, titanium trisacetylacetonate, ruthenium trisacetylacetonate, zinc bisacetylacetonate, aluminum trisacetylacetonate, zirconium tetrakisacetylacetonate, iron tris(2,4-hexanedionato)(III), zinc bis(2,4-hexanedionato), titanium tris(2,4-hexanedionato), aluminum tris(2,4-hexanedionato), and zirconium tetrakis(2,4-hexanedionato).

[0042] The crosslinking accelerator (D) of the metal chelate compound is preferably at least one metal chelate compound selected from the group consisting of aluminum chelate compounds, titanium chelate compounds, and iron chelate compounds, and the crosslinking accelerator (D) of the metal chelate compound is preferably contained in an amount of 0.001 to 0.5 parts by weight per 100 parts by weight of the acrylic polymer.

[0043] Unlike the crosslinking accelerator (D) of the metal chelate compound, the (E) keto-enol tautomer compound has the effect of inhibiting crosslinking, and therefore it is preferable to appropriately set the ratio of the (E) keto-enol tautomer compound to the (D) crosslinking accelerator of the metal chelate compound. To extend the pot life and improve the storage stability of the pressure-sensitive adhesive composition, the weight ratio of (E) / (D) is preferably 70 to 1,000, more preferably 70 to 700, and particularly preferably 70 to 300. Here, the weight ratio of (E) / (D) is the quotient obtained by dividing the weight parts of (E) by the weight parts of (D).

[0044] The pressure-sensitive adhesive composition according to this embodiment may contain (H) a polyether-modified siloxane compound as an optional component. The (H) polyether-modified siloxane compound is a siloxane compound having a polyether group, and has a general siloxane unit [—SiR 1 2-O-)], as well as siloxane units with polyether groups [—SiR 1 (R 2 O(R 3 O) n R 4 )-O-], where R 1 is one or more alkyl or aryl groups, R 2 and R 3 is one or more alkylene groups, R 4 indicates one or more alkyl groups, acyl groups, etc. (terminal groups). The polyether group is a polyoxyethylene group [(C2H4O) n ] and polyoxypropylene group [(C3H6O) nIn the siloxane unit having a polyether group, the terminal of the polyether group is an OH group (R 4 =H).

[0045] The polyether-modified siloxane compound (H) is preferably a polyether-modified siloxane compound having an HLB value of 6 to 12. The polyether-modified siloxane compound (H) is preferably contained in an amount of 0.01 to 0.5 parts by weight, more preferably 0.02 to 0.35 parts by weight, and particularly preferably 0.02 to 0.25 parts by weight, per 100 parts by weight of the acrylic polymer. The HLB value is the hydrophilic-lipophilic balance (hydrophilic-lipophilic ratio) as defined, for example, in JIS K3211 (Surfactant Terminology). Polyether-modified siloxane compounds can be obtained, for example, by grafting an organic compound having an unsaturated bond and a polyoxyalkylene group onto a polyorganosiloxane main chain having silicon hydride groups via a hydrosilylation reaction. Specific examples include dimethylsiloxane-methyl(polyoxyethylene)siloxane copolymers, dimethylsiloxane-methyl(polyoxyethylene)siloxane-methyl(polyoxypropylene)siloxane copolymers, and dimethylsiloxane-methyl(polyoxypropylene)siloxane polymers.

[0046] By incorporating the (H) polyether-modified siloxane compound into the pressure-sensitive adhesive composition, the adhesive strength and reworkability of the pressure-sensitive adhesive layer can be improved. The weight-average molecular weight of the (H) polyether-modified siloxane compound is preferably 10,000 or less. From the viewpoint of compatibility with acrylic polymers, the lower the HLB value and the lower the molecular weight, the better the compatibility. However, if the polyether-modified siloxane compound has a low molecular weight, it can achieve excellent antistatic properties even if it has a relatively high HLB value and somewhat low compatibility with the polymer.

[0047] The PSA composition of the present embodiment may contain, as appropriate, known additives such as surfactants, curing accelerators, plasticizers, fillers, curing retarders, processing aids, antioxidants, antioxidants, etc. These may be used alone or in combination of two or more.

[0048] The pressure-sensitive adhesive composition of this embodiment is suitable as a pressure-sensitive adhesive composition for a surface protection film to be attached to the protective layer of a polarizer of a polarizing plate. Here, the protective layer of the polarizer of the polarizing plate may be one selected from the group consisting of a TAC film, a PMMA film, and a PET film. Here, TAC is an abbreviation for triacetyl cellulose, PMMA is an abbreviation for polymethyl methacrylate, and PET is an abbreviation for polyethylene terephthalate. The surface treatment applied to the surface of the protective layer of the polarizer of the polarizing plate may be one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment, where AG stands for anti-glare, LR stands for low reflection, and AR stands for anti-reflection.

[0049] The pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of the present embodiment has a surface resistivity of 1.0×10 +12 Ω / □ or less is preferable, and 5.0×10 +11 It is more preferable that it is Ω / □ or less, and 1.0×10 +11 It is particularly preferable that the surface resistivity is Ω / □ or less. If the surface resistivity is high, the performance of dissipating static electricity generated when peeling the pressure-sensitive adhesive layer from the adherend is poor. Therefore, by sufficiently reducing the surface resistivity, the peeling electrification voltage caused by static electricity generated when peeling the pressure-sensitive adhesive layer from the adherend can be reduced, and the influence on the adherend can be suppressed.

[0050] The pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of the present embodiment preferably has a peel electrification voltage of ±0.3 kV or less, i.e., in the range of −0.3 to +0.3 kV, relative to a low refractive index layer formed using a resin composition for forming a low refractive index layer containing a fluorine compound. Examples of fluorine compounds used in the composition for forming a low refractive index layer include fluorine-containing copolymers, which are polymers of one or more of fluorinated olefins, fluorinated vinyl ethers, and fluorinated alkyl (meth)acrylates, and condensates of fluorinated alkyl group-containing silane compounds. The fluorine-containing copolymer may be copolymerized with a fluorinated monomer and a non-fluorinated monomer, such as an olefin, a vinyl ether, or a (meth)acrylate. The low refractive index layer may be combined with a high refractive index layer to form an antireflection layer.

[0051] When measuring the peel electrification voltage for the low refractive index layer, examples of the substrate on which the low refractive index layer is formed include a PMMA substrate and a TAC substrate. Furthermore, the pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of the present embodiment preferably exhibits a peel electrification voltage of ±0.3 kV or less, i.e., in the range of −0.3 to +0.3 kV, relative to a plain layer on which no treatment has been applied to the surface of a PMMA substrate or a TAC substrate.

[0052] Preferably, the pressure-sensitive adhesive layer is attached to an adherend, left in an atmosphere at a temperature of 60°C and a humidity of 90% RH for 48 hours, and then removed from the atmosphere for one day, and the contamination resistance of the adherend surface is "no contamination." Examples of the adherend include a polarizing plate in which a protective layer is laminated on a polarizer, and the surface of the protective layer is subjected to a low-reflection surface treatment with a composition containing a fluorine compound. The composition containing a fluorine compound used for the low-reflection surface treatment may be the same as or different from the resin composition for forming the low-refractive index layer containing the fluorine compound described above. Examples of the protective layer include a PMMA substrate and a TAC substrate.

[0053] The adhesive strength of the adhesive layer obtained by crosslinking the adhesive composition of this embodiment to the low refractive index layer applied to the surface of the PMMA substrate is preferably 0.04 to 0.2 N / 25 mm at a low peel speed of 0.3 m / min, and 2.0 N / 25 mm or less at a high peel speed of 30 m / min, and more preferably 0.2 to 1.6 N / 25 mm at a high peel speed of 30 m / min. This results in performance in which the adhesive strength varies little with peel speed, enabling rapid peeling even at high peel speeds. Furthermore, even when the surface protection film is temporarily peeled off for re-application, excessive force is not required, and it is easy to peel from the adherend.

[0054] The pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of the present embodiment preferably has a gel fraction of 95 to 100%, more preferably 97 to 100%. Such a high gel fraction of the pressure-sensitive adhesive layer prevents excessive adhesive strength at low peel speeds, reduces elution of unpolymerized monomers or oligomers from the copolymer, improves reworkability and durability at high temperatures and high humidity, and can suppress contamination of the adherend.

[0055] The pressure-sensitive adhesive film of this embodiment comprises a pressure-sensitive adhesive layer formed on one or both sides of a resin film by crosslinking the pressure-sensitive adhesive composition of this embodiment. The surface protection film of this embodiment comprises a pressure-sensitive adhesive layer formed on one side of a resin film by crosslinking the pressure-sensitive adhesive composition of this embodiment. The pressure-sensitive adhesive composition of this embodiment has excellent antistatic properties, an excellent balance of adhesive strength at low and high peel speeds, and also has stain resistance. Therefore, it can be suitably used as a surface protection film for polarizing plates.

[0056] As the base film of the pressure-sensitive adhesive layer and the release film (separator) that protects the adhesive surface, a resin film such as a polyester film can be used. One surface of the resin film, opposite to the surface on which the pressure-sensitive adhesive layer is formed, may be subjected to an antistatic treatment and an antifouling treatment. Examples of the antistatic treatment include coating or kneading an antistatic agent. Examples of the antifouling treatment include treatment with a silicone-based or fluorine-based release agent or coating agent, silica fine particles, or the like. The release film may be subjected to a release treatment with a silicone-based, fluorine-based, or long-chain alkyl-based release agent on the surface that faces the adhesive surface of the pressure-sensitive adhesive layer.

[0057] Furthermore, an optical film with a pressure-sensitive adhesive layer can be obtained by laminating a pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of the present embodiment on at least one surface of an optical film. Examples of optical films include polarizing films, retardation films, antireflection films, anti-glare films, ultraviolet absorbing films, infrared absorbing films, optical compensation films, and brightness enhancing films. Examples of devices to which optical members are applied include liquid crystal panels, organic EL panels, and touch panels. In the case of optical surface protection films such as surface protection films for polarizing plates and pressure-sensitive adhesive films, the substrate film and pressure-sensitive adhesive layer preferably have sufficient transparency. [Example]

[0058] The present invention will be specifically described below with reference to examples.

[0059] <Production of acrylic polymers> [Example 1] Nitrogen gas was introduced into a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, and the air in the reactor was replaced with nitrogen gas. Then, 100 parts by weight of 2-ethylhexyl acrylate, 6.0 parts by weight of 8-hydroxyoctyl acrylate, 0.1 parts by weight of acrylic acid, and a solvent (ethyl acetate) were added to the reactor. Then, 0.1 parts by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours, and the mixture was allowed to react at 65°C for 6 hours to obtain the acrylic polymer used in Example 1. [Examples 2 to 6 and Comparative Examples 1 to 3] The acrylic polymer solutions used in Examples 2 to 6 and Comparative Examples 1 to 3 were obtained in the same manner as the acrylic polymer solution used in Example 1, except that the monomer compositions were set as shown in (A), (B-1), and (B-2) in Table 1.

[0060] <Production of Pressure-Sensitive Adhesive Composition and Surface Protective Film> [Example 1] To the acrylic polymer solution of Example 1 prepared as described above, 2.5 parts by weight of a crosslinker (Coronate HX), 1.5 parts by weight of an antistatic agent (1-octyl-2-methylpyridinium trifluoromethanesulfonate salt), 0.1 parts by weight of a crosslinking catalyst (titanium trisacetylacetonate), and 8.5 parts by weight of acetylacetone were added and mixed by stirring to obtain a pressure-sensitive adhesive composition of Example 1. This pressure-sensitive adhesive composition was applied to a release film (a silicone resin-coated PET film) and then dried at 90°C to remove the solvent, yielding a 20 μm-thick pressure-sensitive adhesive layer. A pressure-sensitive adhesive layer with a release film was then transferred to the side of the substrate film (a PET film treated on one side with antistatic and antifouling properties) opposite the side treated with antistatic and antifouling properties, yielding a surface protection film of Example 1 having a laminate structure of "substrate film / pressure-sensitive adhesive layer / release film." [Examples 2 to 6 and Comparative Examples 1 to 3] Surface protection films of Examples 2 to 6 and Comparative Examples 1 to 3 were obtained in the same manner as the surface protection film of Example 1 above, except that the compositions of the additives were changed as shown in Table 1 (C) to (F).

[0061] [Table 1]

[0062] In Table 1, the parts by weight of each component were calculated relative to 100 parts by weight of the total of (A) (meth)acrylic acid ester monomers having an alkyl group with carbon atoms of 1 to 18. In Table 1, in each of the columns (C) to (F), the content (parts by weight) of each component is shown as a numerical value in parentheses ( ), with the acrylic polymer being 100 parts by weight. The compound names of the abbreviations of each component used in Table 1 are shown in Table 2. Coronate (registered trademark) HX, Coronate HL, and Coronate L are trade names of Tosoh Corporation, and Takenate (registered trademark) D-140N, D-127N, and D-110N are trade names of Mitsui Chemicals, Inc.

[0063] [Table 2]

[0064] Of the (F) antistatic agents, F-1 to F-6 and F-9 are ionic compounds with melting points of 25°C or higher and 80°C or lower that are solid at room temperature. F-7 and F-8 are ionic compounds with melting points above 80°C that are solid at room temperature.

[0065] <Test method and evaluation> The surface protection films of Examples 1 to 6 and Comparative Examples 1 to 3 were each aged for 7 days in an atmosphere at a temperature of 23° C. and a humidity of 50% RH, and then evaluated by the following test method.

[0066] <Adhesive strength test method> The release film was peeled off to expose the adhesive layer, and the surface protection film was then attached to the surface of a polarizing plate via the adhesive layer. After leaving it for one day, it was autoclaved at 50°C and 5 atmospheres for 20 minutes and then left at room temperature for a further 12 hours to prepare a sample for measuring adhesive strength. The resulting sample was peeled in the 180° direction using a tensile tester at a low speed (0.3 m / min) or a high speed (30 m / min), and the peel strength was measured and used as the adhesive strength. Here, the protective layer of the polarizer of the polarizing plate is made of one material selected from the group consisting of triacetyl cellulose (TAC), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET). In the LR polarizing plate and the AG-LR polarizing plate, the surface of the protective layer of the polarizer of the polarizing plate is subjected to a low-reflection surface treatment with a composition containing a fluorine compound.

[0067] <Surface resistivity test method> After aging the surface protection film and before bonding it to a polarizing plate, the release film was peeled off to expose the adhesive layer, and the surface resistivity of the adhesive layer was measured using a resistivity meter, Hiresta UP-HT450 (manufactured by Mitsubishi Chemical Analytech).

[0068] <Test method for peeling electrification voltage> The release film was peeled off to expose the pressure-sensitive adhesive layer, and the surface protection film was then attached to a polarizing plate having a low refractive index layer formed on the adherend surface using a composition for forming a low refractive index layer containing a fluorine compound.The surface protection film was peeled off at an angle of 180° at a pulling speed of 30 m / min, and the voltage (charged voltage) generated by charging the adherend was measured using high-precision static electricity sensors SK-035 and SK-200 (manufactured by Keyence Corporation).The maximum measured value was taken as the peeling charged voltage.

[0069] <Test method for stain resistance> A polarizing plate that had been subjected to low-reflection (LR) surface treatment was attached to one side of a glass plate via a pressure-sensitive adhesive layer (double-sided adhesive tape) using a laminating machine. A surface protection film was then attached to the surface of the polarizing plate using the laminating machine. After attachment to the adherend, the plate was left in an atmosphere of 60°C and 90% RH for 48 hours. After removal from the atmosphere, the surface protection film was peeled off and the state of contamination on the polarizing plate surface was visually inspected. The stain resistance was evaluated as follows: no staining on the polarizing plate surface was evaluated as "good," slight staining was evaluated as "fair," and significant staining was evaluated as "poor."

[0070] Table 3 shows the evaluation results for the surface protection films in Examples 1 to 6 and Comparative Examples 1 to 3. The "surface resistivity" is expressed in terms of "m×10 +n " is expressed as "mE+n" (where m is any real number and n is a positive integer). The column "Peeling electrification voltage" indicates the material (TAC or PMMA) and surface treatment (Plain or AG-LR) of the protective layer of the polarizer of the polarizing plate used in the test. "Plain" in "Surface treatment" means untreated. Similarly, the column "Stain resistance" indicates the material (PMMA) and surface treatment (AG-LR) of the protective layer of the polarizer of the polarizing plate used in the test.

[0071] [Table 3]

[0072] The surface protection films of Examples 1 to 6 had excellent adhesive performance, with an adhesive strength of 0.04 to 0.2 N / 25 mm at a low peel speed of 0.3 m / min to the adherend, which was a polarizing plate, and an adhesive strength of 2.0 N / 25 mm or less at a high peel speed of 30 m / min. In addition, the surface protection films of Examples 1 to 6 had a surface resistivity of the pressure-sensitive adhesive layer of 1.0 × 10 +12 The peeling voltage of the adhesive layer relative to a low refractive index layer formed using a composition for forming a low refractive index layer containing a fluorine compound was in the range of -0.3 to +0.3 kV, demonstrating excellent antistatic performance. Furthermore, the surface protection films of Examples 1 to 6 had excellent antistatic properties, with the peeling electrification voltage of the adhesive layer being within the range of −0.3 to +0.3 kV even when used on untreated PMMA substrates and TAC substrates that did not have a low refractive index layer. Furthermore, the surface protection films of Examples 1 to 6 were attached to the substrate, and then left in an atmosphere of 60°C and 90% RH for 48 hours. Even after being removed from the atmosphere and one day later, there was no contamination of the substrate, a polarizing plate that had been subjected to a low-reflection surface treatment, and the films also had excellent contamination resistance. That is, the evaluation results shown in Table 3 for the surface protection films of Examples 1 to 6 demonstrate that the problems of the present invention were solved.

[0073] The surface protection film of Comparative Example 1 contains an antistatic agent with a melting point exceeding 80° C. As a result, the surface protection film of Comparative Example 1 had a high adhesive strength of the pressure-sensitive adhesive layer, a high peeling electrification voltage, and poor stain resistance. Furthermore, the surface protection film of Comparative Example 2 contains an antistatic agent with a melting point exceeding 80° C. As a result, the surface protection film of Comparative Example 2 had a high adhesive strength of the pressure-sensitive adhesive layer, a high peeling electrification voltage, and poor stain resistance. Furthermore, the surface protection film of Comparative Example 3 contained an antistatic agent whose anion had an imide group, even though the melting point was 25 to 80° C. Therefore, the surface protection film of Comparative Example 3 had a high peeling electrification voltage against a PMMA substrate and poor stain resistance. As described above, the surface protection films of Comparative Examples 1 to 3 could not solve the problems of the present invention.

Claims

1. A pressure-sensitive adhesive composition comprising an acrylic polymer, (F) an antistatic agent, and (C) a crosslinking agent, The antistatic agent (F) is an ionic compound having a melting point of 25 to 80°C and represented by the following general formula (1): K ＋ ・A － (1) [In general formula (1), K ＋ is a cation, and A － is an anion not containing an imide group and selected from the group consisting of a trifluoromethanesulfonate anion and a pentafluoroethanesulfonate anion. the acrylic polymer has a glass transition temperature of 0°C or lower, The ionic compound is contained as an essential component in an amount of 0.01 to 10 parts by weight relative to 100 parts by weight of the acrylic polymer, the acrylic polymer is an acrylic polymer of a copolymer obtained by copolymerizing only 100 parts by weight in total of at least one (meth)acrylic acid ester monomer (A) having an alkyl group with 1 to 18 carbon atoms, 0.01 to 10 parts by weight in total of at least one (B-1) copolymerizable vinyl monomer containing a hydroxyl group, and either not containing a (B-2) copolymerizable vinyl monomer containing a carboxyl group or 0.1 to 0.5 parts by weight in total of at least one (B-2) copolymerizable vinyl monomer containing a carboxyl group, (A) contains 50 parts by weight or more of at least one monomer selected from the group consisting of isooctyl (meth)acrylate, isononyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate out of a total of 100 parts by weight of at least one (meth)acrylic acid ester monomer having an alkyl group with 1 to 18 carbon atoms; The pressure-sensitive adhesive composition, wherein the (B-1) hydroxyl group-containing copolymerizable vinyl monomer is at least one selected from the group consisting of 8-hydroxyoctyl(meth)acrylate, 6-hydroxyhexyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate, and N-hydroxyethyl(meth)acrylamide.

2. 10. A pressure-sensitive adhesive film comprising a resin film and a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition according to claim 1 laminated on one side of the resin film.

3. A surface protection film using the pressure-sensitive adhesive film according to claim 2.

4. A surface protection film for a polarizing plate, comprising the adhesive film according to claim 2 .

5. An optical film with a pressure-sensitive adhesive layer, comprising an optical film and a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition according to claim 1 laminated on at least one surface of the optical film.

6. The pressure-sensitive adhesive film according to claim 2 , wherein one surface of the resin film opposite to the surface on which the pressure-sensitive adhesive layer is formed is subjected to an antistatic treatment and an antifouling treatment.

Images