Pressure-sensitive adhesive composition, and pressure-sensitive adhesive film, surface protection film, and pressure-sensitive adhesive layer-attached optical film using the same

Abstract

To provide an adhesive composition which has an adhesive strength well balanced between low speed peeling and high speed peeling, and achieves both anti-static performance and anti-staining performance, an adhesive film, a surface protective film, and an optical film with an adhesive layer.SOLUTION: An adhesive composition contains an acrylic polymer produced by copolymerizing (A) 100 pts.wt. of a total of at least two or more 1-10C alkyl (meth)acrylates, (B) 1.0-6.0 pts.wt. of a hydroxy group-containing monomer, (C) 0.01-0.6 pt.wt. of a carboxy group-containing monomer, having an acid value of 0.1-1.0 and a weight average molecular weight of 300,000 or higher and 1,000,000 or lower, an ionic compound with a melting point of 25-80°C, and trifunctional or higher isocyanate compound. Adhesive strength of an adhesive layer formed by crosslinking of the adhesive composition is 0.01-0.1 N / 25 mm in the case of low speed peeling and 1.0 N / 25 mm or lower in the case of high speed peeling.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive composition suitable for use in surface protection films such as surface protection films for polarizing plates, and to 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 balanced adhesive strength at both low and high peel speeds and is capable of achieving both antistatic performance and anti-fouling performance, and to 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 such optical components has an adhesive layer formed on one side of an optically transparent polyethylene terephthalate (PET) resin film, and a release-treated release film is attached to the surface of the adhesive layer of the surface protection film to protect the adhesive layer until it 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 performance requirements for the surface protection film include the absence of air bubbles or foreign matter in the pressure-sensitive adhesive layer and the ability to reduce adhesion of low-molecular-weight components of the pressure-sensitive adhesive composition to the surface of the adherend, i.e., 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 could 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) Regarding balancing adhesive strength at low and high peel speeds, acrylic pressure-sensitive adhesive layers, which are primarily 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, have had problems with the adhesive transferring to the adherend over long periods of adhesion and with a significant increase in adhesive strength to the adherend over time. To avoid these problems, a pressure-sensitive adhesive layer with a gel fraction of 60% or more, 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 crosslinked with a crosslinking agent, and a surface protection member provided with this pressure-sensitive adhesive layer is known (Patent Document 1). However, the pressure-sensitive adhesive layer described in Patent Document 1 has a problem in that it does not completely solve the problem of the adhesive strength to the adherend increasing over time. Also known is a pressure-sensitive adhesive layer prepared by blending a small amount of a copolymer of a (meth)acrylic acid alkyl ester and a carboxyl group-containing copolymerizable compound with the above-mentioned copolymer and crosslinking the resulting mixture with a crosslinking agent. However, when these pressure-sensitive adhesive layers are used to protect the surface of a plastic plate or the like having a low surface tension and a smooth surface, they have the problems of peeling, such as lifting, caused by heating during processing or storage, and poor removability due to their high adhesive strength at high peeling speeds, which are 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). In the adhesive layer obtained by crosslinking the adhesive composition described in Patent Document 2, peeling phenomena such as lifting do not occur during processing or storage, and furthermore, the adhesive strength increases little over time, resulting in excellent removability, and the adhesive layer can be removably peeled with little force even after long-term storage, particularly long-term storage under a high-temperature atmosphere, without leaving any adhesive residue on the adherend, and can be removably peeled with little force even when peeled at high speed. However, in the pressure-sensitive adhesive layer obtained by crosslinking 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 all 90%, and the adhesive strength at slow peel speeds was prone to become excessive, and unpolymerized monomers or oligomers were prone to elution from the pressure-sensitive adhesive layer. Furthermore, Patent Document 2 does not disclose any information regarding antistatic properties and stain resistance, and there was a problem in 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 generating static electricity upon peeling.

[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 makes it possible to provide a pressure-sensitive adhesive layer with a crosslinked structure that can adapt to shrinkage caused by pressure and temperature during autoclave treatment. As a result, a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition described in Patent Document 3 is said to be able to suppress or prevent foaming even under high-temperature and high-pressure conditions (during autoclave treatment), and to have excellent stain resistance and transparency. However, although the adhesive layer obtained by crosslinking the adhesive composition described in Patent Document 3 has improved stain resistance, it has not yet been possible to achieve both excellent adhesive performance by balancing adhesive strength at low and high peel speeds 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 a technique for improving antistatic performance and bleed-out in a pressure-sensitive adhesive layer obtained by crosslinking an antistatic pressure-sensitive adhesive composition, it does not disclose that excellent adhesive performance can be obtained by balancing adhesive strength at low and high peel speeds, and the problem of obtaining a pressure-sensitive adhesive layer 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 solves the problems of simultaneously achieving the following required properties for the adhesive layer that constitutes a surface protection film: (1) balancing adhesive strength at 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 of the adherends to which surface protection films are attached have increased, and the surface treatment conditions of the adherends have become more diverse. As a result, it has become increasingly difficult for the pressure-sensitive adhesive layer constituting the surface protection film to balance adhesive strength with all adherends, particularly at the above-mentioned (1) slow and fast peel speeds, and (2) to have contamination resistance.

[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 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. [Means for solving the problem]

[0014] The inventors of the present invention have reconsidered the type of compound to be copolymerized with an acrylic polymer in an adhesive composition used in a surface protection film for polarizing plates, the adhesive composition containing an acrylic polymer, an antistatic agent, and a crosslinking agent, and have worked diligently to improve the above-mentioned problem of achieving both (1) a balance of adhesive strength at both low and high peel speeds, and (2) stain resistance. As a result, it was found that the above problems (1) and (2) can be simultaneously solved by specifying the content ratio of 2-ethylhexyl acrylate and a monofunctional methacrylate monomer whose homopolymer has a glass transition temperature (Tg) of 0°C or higher within a specific range among (A) alkyl (meth)acrylates having an alkyl group with a carbon number of C1 to C10. Furthermore, the present invention was completed by making the adhesive composition contain an antistatic agent.

[0015] In order to solve the above-mentioned problems, the present invention provides a pressure-sensitive adhesive composition comprising a first acrylic polymer, a crosslinking agent, and an ionic compound, wherein the first acrylic polymer is a copolymer of (A) 100 parts by weight of at least two or more alkyl(meth)acrylates having a carbon number of C1 to C10 in the alkyl group, (B) 1.0 to 6.0 parts by weight of at least one or more copolymerizable monomers having a hydroxyl group, and (C) 0.01 to 0.6 parts by weight of at least one or more copolymerizable monomers having a carboxyl group, and has an acid value of 0.1 to 1.0 and a weight-average molecular weight of more than 300,000. The adhesive composition is an acrylic polymer consisting of a copolymer of more than 1 million carbon atoms, and contains 50 parts by weight or more of 2-ethylhexyl acrylate and 5 to 40 parts by weight of one or more monofunctional methacrylate monomers having a homopolymer Tg of 0°C or higher out of a total of 100 parts by weight of at least two or more alkyl (meth)acrylates (A) whose alkyl group has carbon atoms of C1 to C10, and the adhesive composition is characterized in that it contains a tri- or higher functional isocyanate compound as the crosslinking agent, a crosslinking retarder, and a crosslinking catalyst other than a tin compound as the crosslinking catalyst.

[0016] A surface protection film formed by laminating a 15 μm thick adhesive layer obtained by crosslinking the adhesive composition on one side of a 38 μm thick polyester film is attached to the surface of a polarizing plate, and then the surface protection film is peeled from the polarizing plate. The adhesive strength at a low peeling speed of 0.3 m / min is preferably 0.01 to 0.1 N / 25 mm, and at a high peeling speed of 30 m / min is preferably 1.0 N / 25 mm or less.

[0017] The monofunctional methacrylate monomer having a homopolymer Tg of 0°C or higher is preferably at least one selected from the group consisting of n-butyl methacrylate, isobutyl methacrylate, s-butyl methacrylate, t-butyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, ethyl methacrylate, and methyl methacrylate.

[0018] It is preferable that the pressure-sensitive adhesive composition further contains a second acrylic polymer, the second acrylic polymer being a copolymer obtained by copolymerizing (a) at least one or more (meth)acrylic acid ester monomers having an alkyl group with a carbon number of C1 to C18, (b) at least one or more copolymerizable monomers having a hydroxyl group, and (c) at least one or more mono(meth)acrylic acid ester monomers having a polyalkylene glycol chain, and that the pressure-sensitive adhesive composition contains 0.1 to 5.0 parts by weight of the second acrylic polymer per 100 parts by weight of the total of the at least two or more (A) alkyl (meth)acrylates having an alkyl group with a carbon number of C1 to C10.

[0019] It is preferable that the pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer used in a surface protection film for a polarizing plate, that the protective layer of the polarizer of the polarizing plate is one selected from the group consisting of a TAC-based film, a PMMA-based film, and a PET-based film, and that the surface treatment applied to the surface of the protective layer of the polarizer of the polarizing plate is one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment.

[0020] It is preferable that the ionic compound is an ionic compound having a melting point of 25 to 80°C, the cation of the ionic compound is pyridinium, and the pressure-sensitive adhesive composition 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 first acrylic polymer.

[0021] The pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition has a surface resistivity of 1.0×10 +12 Ω / □ or less, the peeling electrification voltage of the pressure-sensitive adhesive layer relative to a low refractive index layer formed using a composition for forming a low refractive index layer containing a fluorine compound is within the range of +0.3 to −0.3 kV; It is preferable that the polarizing plate be bonded to a surface substrate that is one selected from the group consisting of TAC-based films, PMMA-based films, and PET-based films, and that the surface treatment applied to the surface of the surface substrate is one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment.The polarizing plate is then left to stand for two days in an atmosphere at a temperature of 60°C and a humidity of 90% RH, removed, and then peeled off one day later, and there is no contamination.

[0022] the (B) hydroxyl group-containing copolymerizable 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 (C) carboxyl group-containing copolymerizable 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 tetrahydrophthalate.

[0023] It is preferable that the crosslinking retarder is a keto-enol tautomer compound, and the crosslinking retarder is contained in a proportion of 0.1 to 300 parts by weight relative to 100 parts by weight of the first acrylic polymer; the crosslinking catalyst is 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 catalyst is contained in a proportion of 0.001 to 0.5 parts by weight relative to 100 parts by weight of the first acrylic polymer; and the weight ratio of the crosslinking retarder / the crosslinking catalyst is 80 to 1000.

[0024] The pressure-sensitive adhesive composition preferably contains 0.01 to 0.5 parts by weight of a polyether-modified siloxane compound having an HLB value of 6 to 12 and a weight-average molecular weight of 10,000 or less, relative to 100 parts by weight of the first acrylic polymer.

[0025] The second acrylic polymer is a copolymer having a weight average molecular weight of more than 300,000 and not more than 800,000, obtained by copolymerizing 2.0 to 12.0 parts by weight of at least one copolymerizable monomer containing a hydroxyl group and 1 to 30 parts by weight of at least one polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer with respect to 100 parts by weight of (a) at least one (meth)acrylic acid ester monomer having an alkyl group carbon number of C1 to C18, and (b) 1 to 30 parts by weight of at least one polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer. It is preferable that the ratio (b-1) / (B-1) of the total parts by weight of the at least one copolymerizable monomer containing a hydroxyl group (B) contained in the first acrylic polymer relative to 100 parts by weight of the first acrylic polymer to the total parts by weight of the at least one copolymerizable monomer containing a hydroxyl group (b) contained in the second acrylic polymer relative to 100 parts by weight of the second acrylic polymer is within the range of 1.0 to 2.0.

[0026] It is preferable that the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer has an average repeat number of 3 to 14 alkylene oxides constituting the polyalkylene glycol chain, the diester content in the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer is 0.2% or less, and the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer contains at least one selected from the group consisting of polyalkylene glycol mono(meth)acrylate, methoxypolyalkylene glycol (meth)acrylate, and ethoxypolyalkylene glycol (meth)acrylate in a proportion of 1 to 50 parts by weight per 100 parts by weight of the second acrylic polymer.

[0027] The present invention also provides a pressure-sensitive adhesive film, characterized in that a pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition described above is laminated on one side of a resin film.

[0028] The present invention also provides a surface protection film using the above-mentioned pressure-sensitive adhesive film.

[0029] The present invention also provides a surface protection film for a polarizing plate, which uses the above-mentioned pressure-sensitive adhesive film.

[0030] The present invention also provides an optical film with a pressure-sensitive adhesive layer, which comprises 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.

[0031] 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]

[0032] In the pressure-sensitive adhesive composition according to the present invention, the first acrylic polymer contains 50 parts by weight or more of 2-ethylhexyl acrylate and 5 to 40 parts by weight of one or more monofunctional methacrylate monomers having a homopolymer Tg of 0° C. or higher, out of a total of 100 parts by weight of (A) at least two or more alkyl (meth)acrylates whose alkyl groups have carbon atoms of C1 to C10. This makes it possible, particularly in a surface protection film for polarizing plates using PMMA as a substrate, to simultaneously achieve (1) a balance of adhesive strength at both slow and fast peel speeds, and (2) stain resistance. It is not clear why the inclusion of one or more monofunctional methacrylate monomers whose homopolymers have a Tg of 0°C or higher in the pressure-sensitive adhesive composition of the present invention contributes to (1) balancing adhesive strength at both low and high peel speeds, and (2) providing stain resistance. Possible reasons for this include the fact that these methacrylate monomers produce polymers with high Tg despite not having polar functional groups such as carboxyl or amide groups, or long-chain alkyl groups exceeding C10, which significantly improves adhesive performance in the crosslinked state, and also the fact that they have improved affinity with methyl methacrylate, the main component of PMMA-based films. DETAILED DESCRIPTION OF THE INVENTION

[0033] 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, a crosslinking agent, and an ionic compound, wherein the acrylic polymer is (A) 100 parts by weight of a total of at least two or more alkyl (meth)acrylates having an alkyl group carbon number of C1 to C10, (B) 1.0 to 6.0 parts by weight of at least one copolymerizable monomer containing a hydroxyl group; (C) 0.01 to 0.6 parts by weight of at least one copolymerizable monomer containing a carboxyl group; an acrylic polymer comprising a copolymer having an acid value of 0.1 to 1.0 and a weight average molecular weight of more than 300,000 and not more than 1,000,000, (A) the composition contains 50 parts by weight or more of 2-ethylhexyl acrylate and 5 to 40 parts by weight of one or more monofunctional methacrylate monomers having a homopolymer Tg of 0°C or higher out of a total of 100 parts by weight of at least two or more alkyl (meth)acrylates having an alkyl group with a carbon number of C1 to C10; The pressure-sensitive adhesive composition is characterized by containing a tri- or higher functional isocyanate compound as the crosslinking agent, a crosslinking retarder, and a crosslinking catalyst other than a tin compound as the crosslinking catalyst.

[0034] 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 may be referred to as a first acrylic polymer when distinguishing it from a second acrylic polymer described below. The first acrylic polymer is an acrylic polymer having a glass transition temperature (Tg) of 0°C or lower. The first acrylic polymer is preferably a copolymer containing, as a main component, an alkyl (meth)acrylate (A) having an alkyl group with a carbon number of C1 to C10.

[0035] (A) Examples of the alkyl (meth)acrylate having an alkyl group with a carbon number of C1 to C10 include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (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, cyclopentyl (meth)acrylate, and cyclohexyl (meth)acrylate. The alkyl group of these alkyl (meth)acrylates may be either acyclic (straight-chain or branched) or cyclic (monocyclic or polycyclic).

[0036] The first acrylic polymer preferably contains, out of a total of 100 parts by weight of (A), 50 parts by weight or more of 2-ethylhexyl acrylate and 5 to 40 parts by weight of a total of one or more monofunctional methacrylate monomers having a homopolymer Tg of 0°C or higher. In addition, 2-ethylhexyl acrylate is preferably contained in an amount of 50 parts by weight or more, more preferably 60 parts by weight or more, and particularly preferably 70 parts by weight or more, of a total of 100 parts by weight of (A). Furthermore, among (A) alkyl (meth)acrylates having an alkyl group with a carbon number of C1 to C10, examples of monofunctional methacrylate monomers having a Tg of 0°C or higher include one or more selected from the group consisting of n-butyl methacrylate, isobutyl methacrylate, s-butyl methacrylate, t-butyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, ethyl methacrylate, methyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, n-hexyl methacrylate, isohexyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, and dicyclopentamethacrylate. Among these monofunctional methacrylate monomers having a Tg of 0°C or higher, methacrylate monomers having an alkyl group with a carbon number of C1 to C6 are preferred, and methacrylate monomers having an alkyl group with a carbon number of C1 to C4 are more preferred, with one or more selected from the group consisting of n-butyl methacrylate, isobutyl methacrylate, s-butyl methacrylate, t-butyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, ethyl methacrylate, and methyl methacrylate being particularly preferred. The total amount of one or more monofunctional methacrylate monomers having a Tg of 0°C or higher is preferably 5 to 40 parts by weight, more preferably 8 to 40 parts by weight, and particularly preferably 10 to 35 parts by weight, out of 100 parts by weight of the total of (A). In the following description, when the Tg of a monomer is simply referred to, it may refer to the Tg of the homopolymer.

[0037] The (B) copolymerizable monomer containing a hydroxyl group used in the first acrylic polymer 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, and the like. The first acrylic polymer preferably contains 1.0 to 6.0 parts by weight, more preferably 2.0 to 6.0 parts by weight, and particularly preferably 2.5 to 5.5 parts by weight of at least one copolymerizable monomer containing a hydroxyl group (B) per 100 parts by weight of the total of (A).

[0038] The (C) copolymerizable monomer having a carboxyl group used in the first acrylic polymer 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, and the like. The first acrylic polymer preferably contains 0.01 to 0.6 parts by weight, more preferably 0.01 to 0.5 parts by weight, and particularly preferably 0.01 to 0.4 parts by weight of at least one copolymerizable monomer (C) containing a carboxyl group, relative to 100 parts by weight of the total of (A).

[0039] The method for producing the first acrylic polymer is not particularly limited, and any known polymerization method such as solution polymerization or emulsion polymerization can be used as appropriate. The first acrylic polymer preferably has a weight-average molecular weight of more than 300,000 and not more than 1,000,000. The first acrylic polymer also preferably has an acid value of 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.

[0040] The pressure-sensitive adhesive composition according to this embodiment contains an antistatic agent (G). The antistatic agent (G) according to this embodiment is preferably an ionic compound having a melting point of 25 to 80°C. The ionic compound is preferably solid at room temperature. Room temperature is, for example, a temperature below 25°C, and specifically, an ionic compound that is solid at 23°C is preferred. The pressure-sensitive adhesive composition according to this embodiment preferably 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 first acrylic polymer.

[0041] The anion of the ionic compound is hexafluorophosphate (PF6 - ), thiocyanate (SCN - ), perchlorate (ClO4 - ), tetrafluoroborate (BF4 - ), inorganic anions such as carboxylates (RCOO - ), sulfonates (RSO3 - ), alkoxide or phenoxide salts (RO - ), organic imide salts (RN - ), methide salt (R3C - ), organic borate salts (R4B - ) and other organic anions. R contained in each general formula of the organic anion is an organic group which may have fluorine substitution. Examples of the organic group include at least one of an alkyl group, an alkoxy group, an aromatic group (an aryl group, an aralkyl group, etc.), an aliphatic or aromatic carbonyl group, and an aliphatic or aromatic sulfonyl group. In the organic group contained in the anion, some or all of the hydrogen atoms may be substituted with one or more halogen atoms such as fluorine atoms.

[0042] The cation of the ionic compound may be one selected from the group consisting of pyridinium, imidazolium, phosphonium, sulfonium, pyrrolidinium, guanidinium, ammonium, isouronium, thiouronium, piperidinium, pyrazolium, methylium, and morpholinium. The cation of the ionic compound is preferably pyridinium. The organic group contained in the cation may have some or all of the hydrogen atoms substituted with one or more halogen atoms such as fluorine atoms. When the anion and / or cation of the ionic compound contains an organic group such as an alkyl group, an ionic compound having a melting point of 25 to 80°C can be obtained by selecting the chain length of the alkyl group, the position and number of the substituents, etc.

[0043] Specific examples of the ionic compound include 1-octylpyridinium hexafluorophosphate, 1-nonylpyridinium hexafluorophosphate, 2-methyl-1-dodecylpyridinium hexafluorophosphate, 3-methyl-1-dodecylpyridinium hexafluorophosphate, 1-octylpyridinium dodecylbenzenesulfonate, 1-dodecylpyridinium thiocyanate, 1-dodecylpyridinium dodecylbenzenesulfonate, 4-methyl-1-octylpyridinium hexafluorophosphate, 1-nonylpyridinium 2-iodobenzenesulfonate, 4,5-diiodo-1-butyl-3-methylimidazolium hexafluorophosphate, 2-methyl-1-dodecylpyridinium 2-iodobenzenesulfonate, and 4,5-diiodo-1-butyl-3-methylimidazolium. 3-Iodobenzenesulfonate salt, 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, n-octylpyridinium trifluoromethanesulfonate salt, 1-propyl-3-methylpyridinium nonafluorobutanesulfonate salt, 3-methyl-1-octylpyridinium nonafluorobutanesulfonate salt, methyltrioctylammonium tris(pentafluorobenzenesulfonyl)methide salt, 1-ethyl-3-methylimidazolium tetrakispentafluorophenylborate salt, 1-butyl-1-methylpiperidinium Examples thereof include bis(pentafluorobenzenesulfonyl)imide salts.

[0044] The pressure-sensitive adhesive composition according to this embodiment further contains a trifunctional or higher isocyanate compound as a crosslinking agent (D). 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 (D) 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 first acrylic polymer.

[0045] The pressure-sensitive adhesive composition according to this embodiment may contain a crosslinking retarder (E). Examples of the crosslinking retarder (E) 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. These are keto-enol tautomer compounds, and in pressure-sensitive adhesive compositions containing a polyisocyanate compound as a crosslinking agent, blocking the isocyanate groups of the crosslinking agent (D) can suppress excessive viscosity increase and gelation of the pressure-sensitive adhesive composition after the addition of the crosslinking agent, thereby extending the pot life of the pressure-sensitive adhesive composition. The crosslinking retarder (E) is preferably at least one selected from the group consisting of acetylacetone and ethyl acetoacetate. The crosslinking retarder (E) is preferably contained in an amount of 0.1 to 300 parts by weight per 100 parts by weight of the first acrylic polymer.

[0046] The pressure-sensitive adhesive composition according to this embodiment may contain a crosslinking catalyst other than a tin compound as the crosslinking catalyst (F). The crosslinking catalyst (F) may be any substance that functions as a catalyst for the reaction (crosslinking reaction) between the acrylic polymer and the crosslinking agent when a polyisocyanate compound is used as the crosslinking agent. The crosslinking catalyst (F) is preferably a metal chelate compound. The 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).

[0047] The crosslinking catalyst (F) 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 catalyst (F) is preferably contained in an amount of 0.001 to 0.5 parts by weight per 100 parts by weight of the first acrylic polymer.

[0048] Since the (E) crosslinking retarder has the effect of inhibiting crosslinking, in contrast to the (F) crosslinking catalyst, it is preferable to appropriately set the ratio of the (E) crosslinking retarder to the (F) crosslinking catalyst. To extend the pot life and improve the storage stability of the PSA composition, the weight ratio of (E) / (F) is preferably 80 to 1000, more preferably 80 to 700, and particularly preferably 80 to 300. Here, the weight ratio of (E) / (F) is the quotient obtained by dividing the weight parts of (E) by the weight parts of (F).

[0049] 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) n In the siloxane unit having a polyether group, the terminal of the polyether group is an OH group (R 4 =H).

[0050] The (H) polyether-modified siloxane compound is preferably a polyether-modified siloxane compound having an HLB value of 6 to 12. The (H) polyether-modified siloxane compound 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 first 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.

[0051] 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.

[0052] The pressure-sensitive adhesive composition according to this embodiment may contain a second acrylic polymer as an optional component. When the pressure-sensitive adhesive composition further contains a second acrylic polymer copolymerized with a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer, the compatibility between the ionic compound and the acrylic polymer is improved, resulting in further improvements in antistatic performance and stain resistance. Examples of the second acrylic polymer include copolymers of (a) at least one (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C1 to C18, (b) at least one copolymerizable monomer containing a hydroxyl group, and (c) at least one mono(meth)acrylic acid ester monomer containing a polyalkylene glycol chain.

[0053] Examples of (a) (meth)acrylic acid ester monomers having an alkyl group with a carbon number of C1 to C18 used in the second acrylic polymer include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, and isooctyl (meth)acrylate. Examples of the alkyl group include methyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, cyclopentyl (meth)acrylate, and cyclohexyl (meth)acrylate. The alkyl group (a) may be acyclic (straight-chain or branched) or cyclic (monocyclic or polycyclic). It is also possible to select the same compound or ratio of (a) the (meth)acrylic acid ester monomer in which the alkyl group has a carbon number of C1 to C18 used in the second acrylic polymer as (A) the alkyl (meth)acrylate in which the alkyl group has a carbon number of C1 to C10 used in the first acrylic polymer. Alternatively, (a) may contain a compound different from (A). Furthermore, even if the monomers are the same compound, the proportion in (a) may be different from the proportion in (A). For example, the second acrylic polymer may be a copolymer in which alkyl methacrylate is not copolymerized. Furthermore, the second acrylic polymer may be a copolymer in which a (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C11 to C18 is not copolymerized, or the second acrylic polymer may contain a (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C11 to C18.

[0054] The (b) hydroxyl group-containing copolymerizable monomer used in the second acrylic polymer 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, and the like. The second acrylic polymer preferably contains 2.0 to 12.0 parts by weight, more preferably 3.0 to 12.0 parts by weight, and particularly preferably 4.0 to 12.0 parts by weight of at least one copolymerizable monomer containing a hydroxyl group, per 100 parts by weight of the at least one (meth)acrylic acid ester monomer having a carbon number of C1 to C18 in the alkyl group (a). The hydroxyl group-containing copolymerizable monomer (b) used in the second acrylic polymer may be the same compound or in the same proportion as the hydroxyl group-containing copolymerizable monomer (B) used in the first acrylic polymer. Alternatively, (b) may contain a compound different from (B). Furthermore, even if the monomers are the same compound, the proportion in (b) may be different from the proportion in (B).

[0055] The second acrylic polymer used in the pressure-sensitive adhesive composition of the present embodiment contains (c) a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer. In the pressure-sensitive adhesive composition of the present embodiment, the second acrylic polymer containing (c) a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer functions as an antistatic adjuvant. The first acrylic polymer may be a copolymer in which no polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer is copolymerized, or it may be a copolymer in which the same polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer as the second acrylic polymer is copolymerized. The second acrylic polymer is preferably contained in an amount of 0.1 to 5.0 parts by weight, more preferably 0.1 to 3.5 parts by weight, and particularly preferably 0.1 to 2.5 parts by weight, relative to 100 parts by weight of the total of at least two or more alkyl (meth)acrylates (A) used in the first acrylic polymer, each having an alkyl group with a carbon number of C1 to C10.

[0056] The (c) polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer may be a compound in which one of the multiple hydroxyl groups of a polyalkylene glycol is esterified as a (meth)acrylic acid ester. Since the (meth)acrylic acid ester group serves as a polymerizable group, it can be copolymerized with a second acrylic polymer. It may be a polyalkylene glycol mono(meth)acrylate in which the other hydroxyl group remains OH, or an alkoxy polyalkylene glycol mono(meth)acrylate in which the other hydroxyl group is converted to an alkyl ether. Note that since polyalkylene glycol mono(meth)acrylate falls under (c), it is not classified as (B) or (b) even if it contains a hydroxyl group.

[0057] The polyalkylene glycol constituting the polyalkylene glycol chain may be any glycol compound having one or more alkylene groups, and examples thereof include polyethylene glycol, polypropylene glycol, polybutylene glycol, polyethylene glycol-polypropylene glycol, polyethylene glycol-polybutylene glycol, polypropylene glycol-polybutylene glycol, and polyethylene glycol-polypropylene glycol-polybutylene glycol.

[0058] It is preferable that (c) the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer has an average repeat number of alkylene oxides constituting the polyalkylene glycol chain of 3 to 14. The "average repeat number of alkylene oxides" refers to the average number of repeating alkylene oxide units in the "polyalkylene glycol chain" portion contained in the molecular structure of (c) the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer. Furthermore, the diester content in (c) the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer is preferably 0.2% or less. The "diester content in the monomer" refers to the content (wt%) of polyalkylene glycol di(meth)acrylic acid ester contained in (c) the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer.

[0059] (c) The polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer is preferably at least one selected from the group consisting of polyalkylene glycol mono(meth)acrylate, methoxypolyalkylene glycol (meth)acrylate, and ethoxypolyalkylene glycol (meth)acrylate. The second acrylic polymer preferably contains 1 to 30 parts by weight, more preferably 2 to 30 parts by weight, and particularly preferably 5 to 25 parts by weight of (c) polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer per 100 parts by weight of the (a) at least one or more (meth)acrylic acid ester monomers having an alkyl group with a carbon number of C1 to C18.

[0060] The method for producing the second acrylic polymer is not particularly limited, and any known polymerization method such as solution polymerization or emulsion polymerization can be used as appropriate. The second acrylic polymer is preferably a copolymer having a weight-average molecular weight of more than 300,000 and not more than 800,000. The weight-average molecular weight of the second acrylic polymer may be approximately the same as that of the first acrylic polymer, or may be larger or smaller than that of the first acrylic polymer. The second acrylic polymer may have a functional group capable of reacting with (D) a crosslinking agent. The second acrylic polymer may be a copolymer in which a copolymerizable monomer containing a carboxyl group has not been copolymerized, or may be a copolymer in which a copolymerizable monomer containing a carboxyl group similar to that of the first acrylic polymer has been copolymerized. The (D) crosslinking agent may be involved in crosslinking between the first acrylic polymer and the second acrylic polymer.

[0061] The ratio (b-1) / (B-1) of the total parts by weight of (B) at least one copolymerizable monomer containing a hydroxyl group contained in the first acrylic polymer relative to 100 parts by weight of the first acrylic polymer to the total parts by weight of (b) at least one copolymerizable monomer containing a hydroxyl group contained in the second acrylic polymer relative to 100 parts by weight of the second acrylic polymer is preferably within a range of 1.0 to 2.0.

[0062] 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.

[0063] The pressure-sensitive adhesive composition of this embodiment is suitable as a pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer used in a surface protection film for a polarizing plate. The pressure-sensitive adhesive layer of the surface protection film may be attached to a protective layer of a polarizer of the polarizing plate. Here, the protective layer of the polarizer of the polarizing plate may be at least 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 of the protective layer of the polarizer of the polarizing plate may be subjected to at least one surface treatment 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.

[0064] 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 It is preferable that the resistance is Ω / □ or less, 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.

[0065] The pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of the present embodiment preferably exhibits a peel electrification voltage in the range of +0.3 to -0.3 kV relative to a low refractive index layer formed using a 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 obtained by copolymerizing a fluorinated monomer with a non-fluorinated monomer such as an olefin, vinyl ether, or (meth)acrylate. The low refractive index layer may be combined with a high refractive index layer to form an antireflection layer.

[0066] When measuring the peeling 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 peeling electrification voltage in the range of +0.3 to -0.3 kV relative to a plain layer on the surface of a PMMA substrate or a TAC substrate that has not been treated in any way.

[0067] It is preferable that the pressure-sensitive adhesive layer is not contaminated when it is attached to an adherend such as a polarizing plate, left in an atmosphere at a temperature of 60°C and a humidity of 90%RH for 2 days (48 hours), removed from the atmosphere, and peeled off after one day. An example of the adherend is 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 and surface treatment include the protective layer of the polarizer described above and the surface treatment applied to its surface.

[0068] A surface protection film formed by laminating a 15 μm thick adhesive layer obtained by crosslinking the adhesive composition of this embodiment to one side of a 38 μm thick polyester film is adhered to the surface of a polarizing plate. When the surface protection film is then peeled from the polarizing plate, the adhesive strength at a low peel speed of 0.3 m / min is preferably 0.01 to 0.1 N / 25 mm, and at a high peel speed of 30 m / min, the adhesive strength is preferably 1.0 N / 25 mm or less, and more preferably 0.2 to 1.6 N / 25 mm at a high peel speed of 30 m / min. This allows for minimal change in adhesive strength with peel speed, enabling rapid peeling even at high peel speeds. Furthermore, even when the surface protection film is peeled off for re-application, it is easily peeled off from the adherend without requiring excessive force.

[0069] 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 suppresses contamination of the adherend.

[0070] 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.

[0071] 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.

[0072] 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]

[0073] The present invention will be specifically described below with reference to examples.

[0074] <Production of first acrylic polymer> [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, 70 parts by weight of 2-ethylhexyl acrylate, 30 parts by weight of n-butyl methacrylate, 5.5 parts by weight of 8-hydroxyoctyl acrylate, 0.2 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 a first acrylic polymer used in Example 1. [Examples 2 to 6 and Comparative Examples 1 to 4] The first acrylic polymer solutions used in Examples 2 to 6 and Comparative Examples 1 to 4 were obtained in the same manner as the first acrylic polymer solution used in Example 1 above, except that the monomer compositions were set as shown in (A), (B), and (C) in Table 1. The first acrylic polymer used in Examples 1 to 6 and Comparative Examples 1 to 4 was a copolymer having a weight average molecular weight of more than 300,000 and not more than 1,000,000.

[0075] <Production of Pressure-Sensitive Adhesive Composition and Surface Protective Film> [Example 1] To the first acrylic polymer solution of Example 1 prepared as described above, 2.0 parts by weight of a crosslinker (Coronate HX), 9 parts by weight of acetylacetone, 0.1 parts by weight of a crosslinking catalyst (titanium trisacetylacetonate), 0.9 parts by weight of an antistatic agent (3-methyl-1-octylpyridinium nonafluorobutanesulfonate salt), 0.05 parts by weight of a polyether-modified siloxane compound (HLB=7), and 0.2 parts by weight of a copolymer having a weight average molecular weight (Mw) of 600,000, which was copolymerized in a weight ratio of 100:8:15 between 2-ethylhexyl acrylate, 8-hydroxyoctyl acrylate, and methoxypolyethylene glycol acrylate (n=8), 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. Then, an adhesive layer with a release film was transferred to the side of the base film (a PET film with one side treated for antistatic and antifouling properties) opposite the side treated for antistatic and antifouling properties, thereby obtaining the surface protection film of Example 1, which has a laminated structure of "base film / adhesive layer / release film." [Examples 2 to 6 and Comparative Examples 1 to 4] The surface protection films of Examples 2 to 6 and Comparative Examples 1 to 4 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 (D) to (H) and (J) in Tables 1 and 2, respectively. In the surface protection films of Examples 1 to 6 and Comparative Examples 1 to 4, the gel fraction of the pressure-sensitive adhesive layer was in the range of 95 to 100%.

[0076] [Table 1]

[0077] [Table 2]

[0078] In Tables 1 and 2, the parts by weight of each component were calculated relative to 100 parts by weight of the total of (A) alkyl (meth)acrylates having alkyl groups with carbon numbers of C1 to C10. In Tables 1 and 2, in each of the columns (B) to (H) and (J), 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 the components (A) to (H) used in Tables 1 and 2 are shown in Table 3. Coronate (registered trademark) HX, HL, and 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.

[0079] [Table 3]

[0080] Among the (G) antistatic agents, G-1 to G-4 have a melting point of 25°C or higher and 80°C or lower, and are ionic compounds that are solid at room temperature. G-5 has a melting point of over 80°C, and is an ionic compound that is solid at room temperature. Furthermore, among the (H) polyether-modified siloxane compounds, H-1 to H-6 have a weight average molecular weight of 10,000 or less.

[0081] The compositions and molecular weights (Mw) of the monomers constituting the second acrylic polymer shown in column (J) of Table 2 are shown in Table 4. The compound names of the abbreviations of each component used in Table 4 are shown in Table 5. In Table 4, the parts by weight of each component were calculated with the total of (a) being 100 parts by weight. Furthermore, in each of columns (b) to (c), the content ratio (parts by weight) calculated with the total of the second acrylic polymer being 100 parts by weight is shown in parentheses ( ).

[0082] [Table 4]

[0083] [Table 5]

[0084] (c) Among the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomers, I-1 to I-3 are monomers having a diester content of 0.2 wt% or less, and I-4 is a monomer having a diester content of 0.8 wt%. The value of n indicates the average repeat number of alkylene oxide.

[0085] <Test method and evaluation> The surface protection films of Examples 1 to 6 and Comparative Examples 1 to 4 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.

[0086] <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 polymethyl methacrylate (PMMA) having an AG-LR treated layer.

[0087] <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).

[0088] <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.

[0089] <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 2 days (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 "Good," and significant staining was evaluated as "Poor."

[0090] Table 6 shows the evaluation results for the surface protection films in Examples 1 to 6 and Comparative Examples 1 to 4. "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 "Stain resistance" column indicates the material (TAC, PMMA, PET) and surface treatment (untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment) of the protective layer of the polarizer of the polarizing plate used in the test. "Plain" in "surface treatment" means untreated.

[0091] [Table 6]

[0092] The surface protection films of Examples 1 to 6 had an adhesive strength of 0.01 to 0.1 N / 25 mm at a low peel speed of 0.3 m / min to the adherend, i.e., a polarizing plate, and an adhesive strength of 1.0 N / 25 mm or less at a high peel speed of 30 m / min, demonstrating excellent adhesive performance by achieving a balance of adhesive strength at both low and high peel speeds. 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 were attached to the substrate, and then left for 48 hours in an atmosphere at a temperature of 60°C and a humidity of 90% RH. Even after being removed from the atmosphere and one day had passed, there was no contamination of the various polarizing plates that were the substrate, and the films also had excellent contamination resistance. That is, the evaluation results shown in Table 6 demonstrate that the surface protection films of Examples 1 to 6 were able to solve the problems of the present invention.

[0093] The surface protection film of Comparative Example 1 (wherein the Tg of the monofunctional methacrylate monomer copolymerized with the first acrylic polymer was less than 0° C.) exhibited poor stain resistance to adherends other than TAC. Furthermore, the surface protection film of Comparative Example 2 (containing an excess of hydroxyl group-containing monomer copolymerized with the first acrylic polymer) had a high adhesive strength at low peel speeds and poor stain resistance compared to PMMA. Furthermore, the surface protection film of Comparative Example 3 (in which the first acrylic polymer did not contain a methacrylate monomer with a Tg of 0°C or higher, the proportion of carboxyl group-containing monomers was excessive, and the melting point of the antistatic agent exceeded 80°C) had a high adhesive strength at a high peel speed, a high peel electrification voltage, and poor contamination resistance. Furthermore, the surface protection film of Comparative Example 4 (in Tables 1 and 2, the components (B) to (H) and (J) are the same as those of Example 3, except that the component (A) of Comparative Example 4 does not contain a methacrylate monomer with a Tg of 0°C or higher) had a higher adhesive strength at a high peel speed, a higher peel electrification voltage, and poorer contamination resistance to PMMA than the surface protection film of Example 3. From the comparison of the performance of the surface protection film of Comparative Example 4 with that of Example 3, it became clear that the inclusion of one or more monofunctional methacrylate monomers having a homopolymer Tg of 0°C or higher in the pressure-sensitive adhesive composition of the present invention contributes to achieving both (1) a balance of adhesive strength at low and high peel speeds, and (2) stain resistance. Furthermore, the surface protection films of Comparative Examples 1 to 4 were unable to solve the problems of the present invention.

Claims

1. A pressure-sensitive adhesive composition comprising a first acrylic polymer, a crosslinking agent, and an ionic compound, The first acrylic polymer is (A) 100 parts by weight of a total of at least two or more alkyl (meth)acrylates having an alkyl group with a carbon number of C1 to C10; (B) 1.0 to 6.0 parts by weight of at least one copolymerizable monomer containing a hydroxyl group; (C) 0.01 to 0.6 parts by weight of at least one copolymerizable monomer containing a carboxyl group; an acrylic polymer comprising a copolymer having an acid value of 0.1 to 1.0 and a weight average molecular weight of more than 300,000 and not more than 1,000,000, (A) contains 50 parts by weight or more of 2-ethylhexyl acrylate and 5 to 40 parts by weight of one or more monofunctional methacrylate monomers having a homopolymer Tg of 0°C or higher, out of a total of 100 parts by weight of at least two or more alkyl (meth)acrylates having an alkyl group with a carbon number of C1 to C10; the ionic compound has a melting point of 25 to 80°C, the pressure-sensitive adhesive composition contains a tri- or higher functional isocyanate compound as the crosslinking agent, A pressure-sensitive adhesive composition characterized in that, when a surface protection film is laminated to a surface of a polarizing plate, in which a pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition is laminated to a thickness of 15 μm on one side of a polyester film having a thickness of 38 μm, and the surface protection film is then peeled from the polarizing plate, the adhesive strength at a low peeling speed of 0.3 m / min is 0.01 to 0.1 N / 25 mm, and the adhesive strength at a high peeling speed of 30 m / min is 1.0 N / 25 mm or less.

2. The adhesive composition described in Claim 1, characterized in that the monofunctional methacrylate monomer having a Tg of 0°C or higher of the homopolymer is one or more selected from the group of compounds consisting of n-butyl methacrylate, isobutyl methacrylate, s-butyl methacrylate, t-butyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, ethyl methacrylate, and methyl methacrylate.

3. the pressure-sensitive adhesive composition further comprises a second acrylic polymer, The second acrylic polymer is (a) at least one (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C1 to C18; (b) at least one copolymerizable monomer containing a hydroxyl group; (c) a copolymer obtained by copolymerizing at least one polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer, 3. The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive composition contains 0.1 to 5.0 parts by weight of the second acrylic polymer per 100 parts by weight of the total of at least two or more alkyl (meth)acrylates (A) having an alkyl group with a carbon number of C1 to C10.

4. the pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer used in a surface protection film for a polarizing plate, The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the protective layer of the polarizer of the polarizing plate is one selected from the group consisting of a TAC-based film, a PMMA-based film, and a PET-based film, and the surface treatment applied to the surface of the protective layer of the polarizer of the polarizing plate is one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment.

5. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein a cation of the ionic compound is pyridinium, and the pressure-sensitive adhesive composition 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 first acrylic polymer.

6. The pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition has a surface resistivity of 1.0×10 ＋１２ Ω / □ or less, the peeling electrification voltage of the pressure-sensitive adhesive layer relative to a low refractive index layer formed using a composition for forming a low refractive index layer containing a fluorine compound is within the range of +0.3 to −0.3 kV; 6. The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the surface substrate is one selected from the group consisting of a TAC-based film, a PMMA-based film, and a PET-based film, and the surface treatment applied to the surface of the surface substrate is one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment.

7. The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive composition is adhered to a polarizing plate, left to stand for two days in an atmosphere at a temperature of 60°C and a humidity of 90% RH, removed, and then peeled off after one day has passed.

7. the (B) hydroxyl group-containing copolymerizable 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 pressure-sensitive adhesive composition according to any one of claims 1 to 6, wherein the (C) carboxyl group-containing copolymerizable monomer is 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 tetrahydrophthalate.

8. the pressure-sensitive adhesive composition contains a crosslinking retarder and a crosslinking catalyst other than a tin compound; the crosslinking retarder is a keto-enol tautomer compound; The crosslinking retarder is contained in an amount of 0.1 to 300 parts by weight relative to 100 parts by weight of the first acrylic polymer, the crosslinking catalyst is at least one metal chelate compound selected from the group consisting of aluminum chelate compounds, titanium chelate compounds, and iron chelate compounds; the crosslinking catalyst is contained in an amount of 0.001 to 0.5 parts by weight relative to 100 parts by weight of the first acrylic polymer, 8. The pressure-sensitive adhesive composition according to claim 1, wherein the weight ratio of the crosslinking retarder to the crosslinking catalyst is 80 to 1000.

9. The pressure-sensitive adhesive composition according to any one of claims 1 to 8, characterized in that the pressure-sensitive adhesive composition contains 0.01 to 0.5 parts by weight of a polyether-modified siloxane compound having an HLB value of 6 to 12 and a weight-average molecular weight of 10,000 or less, relative to 100 parts by weight of the first acrylic polymer.

10. The second acrylic polymer is (a) per 100 parts by weight of at least one (meth)acrylic acid ester monomer having an alkyl group carbon number of C1 to C18, (b) 2.0 to 12.0 parts by weight of at least one copolymerizable monomer containing a hydroxyl group; (c) a copolymer having a weight average molecular weight of more than 300,000 and not more than 800,000, obtained by copolymerizing 1 to 30 parts by weight of at least one polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer; 4. The pressure-sensitive adhesive composition according to claim 3, wherein a ratio (b-1) / (B-1) of a total part by weight of the at least one or more hydroxyl group-containing copolymerizable monomers (B) contained in the first acrylic polymer relative to a total of 100 parts by weight of the first acrylic polymer to a total part by weight of the at least one or more hydroxyl group-containing copolymerizable monomers (b) contained in the second acrylic polymer relative to a total of 100 parts by weight of the second acrylic polymer is within a range of 1.0 to 2.

0.

11. the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer has an average repeat number of alkylene oxides constituting the polyalkylene glycol chain of 3 to 14, the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer has a diester content of 0.2% or less, 11. The pressure-sensitive adhesive composition according to claim 3 or 10, wherein the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer is at least one selected from the group consisting of polyalkylene glycol mono(meth)acrylate, methoxypolyalkylene glycol (meth)acrylate, and ethoxypolyalkylene glycol (meth)acrylate, in an amount of 1 to 50 parts by weight per 100 parts by weight of the second acrylic polymer.

12. 12. 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.

13. A surface protection film using the pressure-sensitive adhesive film according to claim 12.

14. A surface protection film for a polarizing plate, comprising the pressure-sensitive adhesive film according to claim 12.

15. 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 any one of claims 1 to 11, laminated on at least one surface of the optical film.

16. The pressure-sensitive adhesive film according to claim 12, 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.

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