Antistatic Surface Protection Film

Abstract

To provide an antistatic surface protective film which has balanced adhesive force at a low peeling speed and a high peeling speed and can achieve both antistatic and anti-fouling properties.SOLUTION: On one side of a base film 1, an adhesive layer 2 is formed. The adhesive layer is obtained by crosslinking an adhesive composition that contains an acrylic polymer and a crosslinker. The acrylic polymer is obtained by co-polymerizing (A) a total of 100 pts.wt. of alkyl (meth)acrylates with alkyl groups having 1 to 10 carbon atoms, where 2-ethylhexyl acrylate constitutes 50 pts.wt. or more and a total of one or more monofunctional methacrylate monomers with a homopolymer Tg of 0°C or higher constitutes 5-40 pts.wt. and (B) 1.0-6.0 pts.wt. of a copolymerizable monomer having hydroxy groups, without the inclusion of a copolymerizable monomer having carboxyl groups.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing an antistatic surface protective film suitable for use as a surface protective film for polarizing plates, etc. More specifically, the present invention relates to a method for producing an antistatic surface protective film that has balanced adhesive strength at both low and high peel speeds and is capable of achieving both antistatic performance and contamination resistance, and to an antistatic surface protective film. [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 for (1) balancing adhesive strength at low and high peeling speeds, (2) providing stain resistance, and (3) providing 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 a plasticizer consisting of 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 method for producing an antistatic surface protective film that has balanced adhesive strength at both low and high peel speeds and is capable of achieving both antistatic performance and contamination resistance, and an antistatic surface protective film. [Means for solving the problem]

[0014] To solve the above problems, the antistatic surface protection film of the present invention specifies a specific range of content of 2-ethylhexyl acrylate and a monofunctional methacrylate monomer, the homopolymer of which has a glass transition temperature (Tg) of 0° C. or higher, among (A) alkyl (meth)acrylates in which the alkyl group has carbon atoms of C1 to C10. Furthermore, the technical idea is that after a pressure-sensitive adhesive layer is laminated by coating and drying a pressure-sensitive adhesive composition, an appropriate amount of a liquid silicone compound and an antistatic agent are applied to the surface of the pressure-sensitive adhesive layer at 20° C., thereby reducing contamination of the adherend (improving contamination resistance) and reducing the peel electrification voltage when peeled off from the adherend, i.e., the optical film.

[0015] In order to solve the above problems, the present invention provides a method for producing an antistatic surface protective film, comprising the following steps (1) to (3): Step (1): A pressure-sensitive adhesive composition containing an acrylic polymer and a crosslinking agent, wherein the acrylic polymer has a weight-average molecular weight of 100 parts by weight 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 or more copolymerizable monomers having a hydroxyl group, and (F) 1.0 to 50 parts by weight of at least one or more polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomers constituting a polyalkylene glycol chain, without containing a copolymerizable monomer having a carboxyl group. a step of preparing an acrylic polymer comprising a copolymer having a molecular weight of more than 300,000 and not more than 1,000,000, the adhesive composition comprising 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 100 parts by weight of at least two or more alkyl (meth)acrylates (A) having a carbon number of C1 to C10 in the alkyl group, the adhesive composition further comprising (C) a tri- or higher functional isocyanate compound as the crosslinking agent, (D) a crosslinking retarder, and (E) a crosslinking accelerator other than a tin compound; Step (2): A step of preparing a pressure-sensitive adhesive layer by crosslinking the pressure-sensitive adhesive composition on one side of a substrate film made of a transparent resin; and step (3): attaching a release film, which is a resin film having a release agent layer containing an antistatic agent laminated on one side thereof, to the surface of the pressure-sensitive adhesive layer via the release agent layer, thereby transferring the antistatic agent from the release agent layer to the surface of the pressure-sensitive adhesive layer, the antistatic agent being formed by carrying out steps (1) to (3) in this order, wherein the release agent layer is formed from a resin composition containing a release agent mainly composed of dimethylpolysiloxane, a silicone-based compound that is liquid at 20°C, and an antistatic agent.

[0016] Furthermore, 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.

[0017] The antistatic agent in the release agent layer is preferably an alkali metal salt.

[0018] The present invention also provides an antistatic surface protective film comprising a substrate film made of a transparent resin and a pressure-sensitive adhesive layer formed on one side thereof by crosslinking a pressure-sensitive adhesive composition containing an acrylic polymer and a crosslinking agent, wherein the acrylic polymer is an acrylic polymer consisting of a copolymer having a weight-average molecular weight of more than 300,000 and not more than 1,000,000, obtained by copolymerizing 100 parts by weight of a total of at least two or more alkyl(meth)acrylates having an alkyl group of C1 to C10 carbon atoms, (B) 1.0 to 6.0 parts by weight of a total of at least one or more copolymerizable monomers having a hydroxyl group, and (F) 1.0 to 50 parts by weight of a total of at least one or more polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomers constituting a polyalkylene glycol chain, without containing a copolymerizable monomer having a carboxyl group, and wherein the (A) alkyl(meth)acrylates having an alkyl group of C1 to C10 carbon atoms are crosslinked. and (E) a crosslinking accelerator other than a tin compound, as a crosslinking accelerator; and a release film, which is formed by laminating a release agent layer containing an antistatic agent on one side of a resin film to the surface of the pressure-sensitive adhesive layer via the release agent layer, the antistatic agent from the release agent layer being transferred to the surface of the pressure-sensitive adhesive layer. The antistatic surface protection film is characterized in that the release agent layer is formed from a resin composition containing a release agent mainly composed of dimethylpolysiloxane, a silicone-based compound that is liquid at 20°C, and an antistatic agent.

[0019] Furthermore, 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.

[0020] The antistatic agent in the release agent layer is preferably an alkali metal salt.

[0021] Furthermore, it is preferred that the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer constituting the (F) polyalkylene glycol chain 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 is at least one selected from the group consisting of polyalkylene glycol mono(meth)acrylate, methoxypolyalkylene glycol (meth)acrylate, and ethoxypolyalkylene glycol (meth)acrylate.

[0022] Furthermore, it is preferable that the antistatic surface protective film is used as a surface protective film for a polarizing plate, and that the protective layer of the polarizer of the polarizing plate, which serves as an adherend in the use of the surface protective film for a polarizing plate, is at least 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 at least one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment.

[0023] Furthermore, it is preferable that 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.

[0024] It is also preferred that the (D) crosslinking retarder is a keto-enol tautomer compound, and the (D) crosslinking retarder is contained in a proportion of 0.1 to 300 parts by weight relative to 100 parts by weight of the acrylic polymer; the (E) crosslinking accelerator 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 (E) crosslinking accelerator is contained in a proportion of 0.001 to 0.5 parts by weight relative to 100 parts by weight of the acrylic polymer; and the (D) / (E) weight parts ratio is 80 to 1000.

[0025] 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 per 100 parts by weight of the acrylic polymer.

[0026] The silicone compound in the release agent layer is preferably a polyether-modified silicone.

[0027] The antistatic agent in the release agent layer is preferably a Li salt, and is at least one selected from the group consisting of LiTFSI, LiFSI, and LiTF. [Effects of the Invention]

[0028] The antistatic surface protective film of the present invention causes little contamination of an adherend and its contamination resistance to the adherend does not change over time. Furthermore, according to the present invention, even if the adherend is an optical film such as an LR polarizing plate or an AG-LR polarizing plate whose surface has been treated with an anti-contamination agent such as a silicone compound or a fluorine compound, the peeling electrification voltage generated when the antistatic surface protective film is peeled off from the adherend can be kept low, and an antistatic surface protective film having excellent peel-off antistatic performance without deterioration over time can be provided.

[0029] According to the antistatic surface protection film of the present invention, even in a surface protection film for polarizing plates using PMMA as a substrate, it is possible to achieve both (1) a balance of adhesive strength at low and high peel speeds and (2) contamination resistance. Furthermore, by specifying the content ratio of 2-ethylhexyl acrylate and monofunctional methacrylate monomers, the homopolymer of which 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, it is possible to achieve both (1) a balance of adhesive strength at both low and high peel speeds, and (2) contamination resistance, particularly in surface protection films for polarizing plates using PMMA as a base material.

[0030] It is unclear why the inclusion of one or more monofunctional methacrylate monomers whose homopolymer Tg is 0°C or higher contributes to (1) balancing adhesive strength at both slow and fast peel speeds and (2) 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, thereby significantly improving adhesive performance in a crosslinked state; and, when the protective layer of the polarizer of a polarizing plate, which is the adherend in a surface protection film for polarizing plates, is a PMMA-based film, the affinity with methyl methacrylate, the main component of the PMMA-based film, is improved. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a cross-sectional view illustrating the concept of an antistatic surface protective film of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a state in which the release film has been peeled off from the antistatic surface protective film of the present invention. [Figure 3] FIG. 1 is a cross-sectional view showing one embodiment of an optical component of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] The present invention will be described in detail below based on embodiments. 1 is a cross-sectional view showing the concept of an antistatic surface protection film of this embodiment. This antistatic surface protection film 10 has a pressure-sensitive adhesive layer 2 formed on one surface of a transparent substrate film 1. A release film 5, which has a release agent layer 4 formed on the surface of a resin film 3, is attached to the surface of this pressure-sensitive adhesive layer 2.

[0033] The substrate film 1 used in the antistatic surface protection film 10 according to this embodiment is made of a transparent and flexible resin. This allows for visual inspection of the optical component, which is the adherend, with the antistatic surface protection film attached to the optical component. The transparent resin film used as the substrate film 1 is preferably a polyester film such as polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, or polybutylene terephthalate. In addition to polyester films, films made of other resins can also be used as long as they have the required strength and optical suitability. The substrate film 1 may be a non-stretched film or a uniaxially or biaxially stretched film. The stretch ratio of the stretched film and the axial orientation angle formed by crystallization of the stretched film may be controlled to specific values.

[0034] The thickness of the substrate film 1 used in the antistatic surface protection film 10 according to this embodiment is not particularly limited, but a thickness of, for example, about 12 to 100 μm is preferred, and a thickness of about 20 to 50 μm is more preferred as it is easier to handle. If necessary, an antifouling layer for preventing surface contamination, an antistatic layer, a hard coat layer for preventing scratches, etc. may be provided on the surface of the base film 1 opposite to the surface on which the pressure-sensitive adhesive layer 2 is formed. The surface of the base film 1 may also be subjected to an adhesion-enhancing treatment such as surface modification by corona discharge or application of an anchor coating agent.

[0035] Furthermore, the adhesive layer 2 used in the antistatic surface protection film 10 according to this embodiment is not particularly limited as long as it adheres to the surface of the adherend, can be easily peeled off after use, and is unlikely to contaminate the adherend. However, taking into consideration durability after application to an optical film, it is common to use an acrylic adhesive layer in which an acrylic polymer is crosslinked.

[0036] The pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer 2 is an acrylic polymer having a weight average molecular weight of more than 300,000, obtained by copolymerizing (A) 100 parts by weight 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 or more copolymerizable monomers containing a hydroxyl group, and (F) 1.0 to 50 parts by weight of at least one or more polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomers constituting a polyalkylene glycol chain, without containing a copolymerizable monomer having a carboxyl group. The adhesive composition is an acrylic polymer consisting of a copolymer of 100,000 or less 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 100 parts by weight of a total of at least two or more alkyl (meth)acrylates (A) whose alkyl group has carbon atoms of C1 to C10, and the adhesive composition further contains (C) a tri- or higher functional isocyanate compound as the crosslinking agent, (D) a crosslinking retarder, and (E) a crosslinking accelerator other than a tin compound as a crosslinking accelerator.

[0037] Examples of the alkyl (meth)acrylates in which the carbon number of the alkyl group in (A) is 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).

[0038] The 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 the (A) alkyl (meth)acrylates in which the number of carbon atoms in the alkyl group is C1 to C10, examples of the monofunctional methacrylate monomer 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, and 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 are 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.

[0039] The (B) copolymerizable monomer containing a hydroxyl group used in the 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 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) relative to 100 parts by weight of the total of (A).

[0040] The acrylic polymer is preferably copolymerized with a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer that constitutes the (F) polyalkylene glycol chain. Furthermore, the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer may be added to the pressure-sensitive adhesive composition as a component separate from the acrylic polymer. In either case, the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer can function as an antistatic aid.

[0041] The 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 the acrylic polymer. It may be a polyalkylene glycol mono(meth)acrylate in which the other hydroxyl group remains as OH, or an alkoxy polyalkylene glycol mono(meth)acrylate in which the other hydroxyl group is converted to an alkyl ether. Note that polyalkylene glycol mono(meth)acrylate falls under the category of (F) above, and therefore is not classified as (B) above even if it contains a hydroxyl group.

[0042] 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.

[0043] The polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer preferably 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 the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer. The polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer preferably contains a diester content of 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 the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer.

[0044] 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.

[0045] The acrylic polymer is preferably obtained by copolymerizing at least one polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer 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, more preferably 1 to 35 parts by weight, and particularly preferably 1 to 25 parts by weight, per 100 parts by weight of the total of (A).

[0046] The method for producing the acrylic polymer is not particularly limited, and known polymerization methods such as solution polymerization and emulsion polymerization can be used as appropriate. The acrylic polymer preferably has a weight-average molecular weight of more than 300,000 and not more than 1,000,000. The acrylic polymer is copolymerized without containing a copolymerizable monomer having a carboxyl group. The acid value of the acrylic polymer is preferably 0.1 to 1.0. This improves 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.

[0047] The pressure-sensitive adhesive composition according to this embodiment further contains (C) a trifunctional or higher isocyanate compound as a crosslinking agent. Examples of the trifunctional or higher isocyanate compound (C) 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 (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.

[0048] The pressure-sensitive adhesive composition according to this embodiment contains a crosslinking retarder (D). Examples of the crosslinking retarder (D) 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 that block the isocyanate groups of the trifunctional or higher isocyanate compound (C), thereby suppressing excessive viscosity increase and gelation of the pressure-sensitive adhesive composition after the addition of a crosslinking agent, and thereby extending the pot life of the pressure-sensitive adhesive composition. The crosslinking retarder (D) is preferably at least one selected from the group consisting of acetylacetone and ethyl acetoacetate. The crosslinking retarder (D) is preferably contained in an amount of 0.1 to 300 parts by weight per 100 parts by weight of the acrylic polymer.

[0049] The pressure-sensitive adhesive composition according to this embodiment contains a crosslinking accelerator (E) other than a tin compound. The crosslinking accelerator (E) may be any substance that functions as a catalyst for the reaction (crosslinking reaction) between the acrylic polymer and the crosslinking agent when the trifunctional or higher isocyanate compound (C) is used as the crosslinking agent. The crosslinking accelerator (E) 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).

[0050] The crosslinking accelerator (E) 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 content of the crosslinking accelerator (E) is preferably 0.001 to 0.5 parts by weight per 100 parts by weight of the acrylic polymer.

[0051] Contrary to the crosslinking accelerator (E), the crosslinking retarder (D) has the effect of inhibiting crosslinking, and therefore it is preferable to appropriately set the ratio of the crosslinking retarder (D) to the crosslinking accelerator (E). To extend the pot life and improve the storage stability of the pressure-sensitive adhesive composition, the weight ratio of (D) / (E) is preferably 80 to 1000, more preferably 80 to 700, and particularly preferably 80 to 300. Here, the weight ratio of (D) / (E) is the quotient obtained by dividing the weight parts of (D) by the weight parts of (E).

[0052] The pressure-sensitive adhesive composition according to the present embodiment may contain, as an optional component, (G) a polyether-modified siloxane compound. The 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).

[0053] The polyether-modified siloxane compound preferably has an HLB value of 6 to 12. The 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 acrylic polymer. The HLB value is the hydrophilic-lipophilic balance (hydrophilic-lipophilic ratio) as defined, for example, in JIS K3211 (surfactant terminology).

[0054] The polyether-modified siloxane compound can be obtained, for example, by grafting an organic compound having an unsaturated bond and a polyoxyalkylene group onto a polyorganosiloxane main chain having a silicon hydride group via a hydrosilylation reaction. Specific examples include dimethylsiloxane-methyl(polyoxyethylene)siloxane copolymer, dimethylsiloxane-methyl(polyoxyethylene)siloxane-methyl(polyoxypropylene)siloxane copolymer, and dimethylsiloxane-methyl(polyoxypropylene)siloxane polymer.

[0055] By incorporating the 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 polyether-modified siloxane compound is preferably 10,000 or less. From the viewpoint of compatibility with the acrylic polymer, 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, the HLB value is relatively high and even if the compatibility with the acrylic polymer is somewhat low, excellent antistatic properties can be obtained.

[0056] 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.

[0057] The thickness of the pressure-sensitive adhesive layer 2 used in the antistatic surface protection film 10 according to this embodiment is not particularly limited, but is preferably about 5 to 40 μm, and more preferably about 10 to 30 μm. It is preferable that the pressure-sensitive adhesive layer 2 have a weak adhesive strength, i.e., a peel strength (adhesive strength) of about 0.03 to 0.3 N / 25 mm, to the surface of the adherend, since this provides excellent operability when peeling the antistatic surface protection film from the adherend. Furthermore, the peel strength of the release film 5 from the pressure-sensitive adhesive layer 2 is preferably 0.2 N / 50 mm or less, since this provides excellent operability when peeling the release film 5 from the antistatic surface protection film 10.

[0058] Furthermore, the release film 5 used in the antistatic surface protection film 10 according to this embodiment has a release agent layer 4 formed on one side of the resin film 3 from a resin composition containing a release agent whose main component is dimethylpolysiloxane, a silicone-based compound that is liquid at 20°C, and an antistatic agent.

[0059] Examples of the resin film 3 include polyester film, polyamide film, polyethylene film, polypropylene film, and polyimide film, but polyester film is particularly preferred because of its excellent transparency and relatively low price. The resin film may be an unstretched film or a uniaxially or biaxially stretched film. Furthermore, the stretching ratio of the stretched film and the axial orientation angle formed by crystallization of the stretched film may be controlled to a specific value. The thickness of the resin film 3 is not particularly limited, but is preferably about 12 to 100 μm, and more preferably about 20 to 50 μm, as this is easy to handle. If necessary, the surface of the resin film 3 may be subjected to an easy-adhesion treatment such as surface modification by corona discharge or application of an anchor coating agent.

[0060] The release agent containing dimethylpolysiloxane as a main component that constitutes the release agent layer 4 includes known silicone-based release agents such as addition reaction type, condensation reaction type, cationic polymerization type, and radical polymerization type. Examples of commercially available products as addition reaction type silicone-based release agents include KS-776A, KS-847T, KS-779H, KS-837, KS-778, and KS-830 (manufactured by Shin-Etsu Chemical Co., Ltd.), SRX-211, SRX-345, SRX-357, SD7333, SD7220, SD7223, LTC-300B, LTC-350G, and LTC-310 (manufactured by Dow Corning Toray Co., Ltd.). Examples of commercially available products as condensation reaction type release agents include SRX-290 and SYLOFF-23 (manufactured by Dow Corning Toray Co., Ltd.). Examples of commercially available cationic polymerization products include TPR-6501, TPR-6500, UV9300, VU9315, and UV9430 (manufactured by Momentive Performance Materials), and X62-7622 (manufactured by Shin-Etsu Chemical Co., Ltd.). Examples of commercially available radical polymerization products include X62-7205 (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0061] Examples of silicone-based compounds that are liquid at 20°C and that constitute the release agent layer 4 include polyether-modified silicones, alkyl-modified silicones, and carbinol higher fatty acid ester-modified silicones. In this embodiment, in order to improve the antistatic properties of the surface of the pressure-sensitive adhesive layer, a silicone-based compound that is liquid at 20°C and that is compatible with the release agent layer, which is mainly composed of dimethylpolysiloxane, is used. Among modified silicone compounds, polyether-modified silicones are preferred for use in this embodiment. The polyether chain in the polyether-modified silicone is composed of ethylene oxide, propylene oxide, or the like. For example, by selecting the molecular weight of the polyethylene oxide used in the side chain, physical properties such as compatibility with the silicone release agent and antistatic effect can be adjusted. In addition, examples of commercially available polyether-modified silicone products include KF-351A, KF-352A, KF-353, KF-354L, KF-355A, and KF-642 (manufactured by Shin-Etsu Chemical Co., Ltd.), SH8400, SH8700, and SF8410 (manufactured by Dow Corning Toray Co., Ltd.), TSF-4440, TSF-4441, TSF-4445, TSF-4446, and TSF-4450 (manufactured by Momentive Performance Materials), and BYK-300, BYK-306, BYK-307, BYK-320, BYK-325, and BYK-330 (manufactured by BYK-Chemie). The amount of silicone compound that is liquid at 20°C to be added to a release agent whose main component is dimethylpolysiloxane will vary depending on the type of silicone compound and its degree of compatibility with the release agent, but can be set taking into consideration the desired peel electrification voltage, contamination resistance to the adherend, adhesive properties, etc. when the antistatic surface protection film is peeled from the adherend.

[0062] The antistatic agent constituting the release agent layer 4 is preferably one that has good dispersibility in the release agent solution whose main component is dimethylpolysiloxane and does not inhibit the hardening of the release agent whose main component is dimethylpolysiloxane. Alkali metal salts are suitable as such antistatic agents. Examples of the alkali metal salts include metal salts of lithium, sodium, and potassium. Specific examples include Li + , Na + , K. + and a cation consisting of Cl - , Br - , I - , BF4 - , PF6 - , SCN - , ClO4 - , CF3SO3 - , (FSO2)2N - , (CF3SO2)2N - , (C2F5SO2)2N - , (CF3SO2)3C -A metal salt composed of an anion consisting of the following is preferably used. In particular, the antistatic agent in the release agent layer 4 is a Li salt, and is preferably at least one selected from the group consisting of LiTFSI, LiFSI, and LiTF. Here, LiTFSI represents Li(CF3SO2)2N. LiFSI represents Li(FSO2)2N. LiTF represents LiCF3SO3. These alkali metal salts may be used alone or in combination of two or more. A compound containing a polyoxyalkylene structure may be added to stabilize the ionic substance. The amount of antistatic agent added to a release agent containing dimethylpolysiloxane as a main component varies depending on the type of antistatic agent and the degree of affinity with the release agent, but can be set taking into consideration the desired peeling electrification voltage, contamination resistance to the adherend, adhesive properties, etc. when peeling the antistatic surface protective film from the adherend.

[0063] There are no particular limitations on the method for mixing the dimethylpolysiloxane-based release agent with the polyether-modified silicone and antistatic agent. Any of the following methods may be used: adding the polyether-modified silicone and antistatic agent to the dimethylpolysiloxane-based release agent, mixing them, and then adding and mixing a catalyst for curing the release agent; diluting the dimethylpolysiloxane-based release agent with an organic solvent, then adding and mixing the polyether-modified silicone, antistatic agent, and catalyst for curing the release agent; or diluting the siloxane-based release agent with an organic solvent, adding and mixing a catalyst, and then adding and mixing the polyether-modified silicone and antistatic agent. If necessary, adhesion improvers such as silane coupling agents or materials that enhance the antistatic effect, such as compounds containing polyoxyalkylene groups, may be added.

[0064] The mixing ratio of the dimethylpolysiloxane-based release agent to the polyether-modified silicone and antistatic agent is not particularly limited, but a weight ratio of approximately 5 to 100 parts by weight of the polyether-modified silicone and antistatic agent (solids) per 100 parts by weight of the dimethylpolysiloxane-based release agent is preferred. If the amount of polyether-modified silicone and antistatic agent added (solids) is less than 5 parts by weight per 100 parts by weight of the dimethylpolysiloxane-based release agent, the amount of antistatic agent transferred to the surface of the adhesive layer will be reduced, making it difficult for the adhesive to exhibit its antistatic function. Furthermore, if the amount of polyether-modified silicone and antistatic agent added (solids) exceeds 100 parts by weight per 100 parts by weight of the dimethylpolysiloxane-based release agent, the dimethylpolysiloxane-based release agent, along with the polyether-modified silicone and antistatic agent, will be transferred to the surface of the adhesive layer, potentially reducing the adhesive properties of the adhesive.

[0065] The method for forming the pressure-sensitive adhesive layer 2 on the base film 1 of the antistatic surface protection film 10 according to this embodiment and the method for laminating the release film 5 thereto may be any known method, and are not particularly limited. Specific examples include (1) a method in which a resin composition for forming the pressure-sensitive adhesive layer 2 is applied to one side of the base film 1, dried to form a pressure-sensitive adhesive layer, and then laminating the release film 5, and (2) a method in which a resin composition for forming the pressure-sensitive adhesive layer 2 is applied to the surface of the release film 5, dried to form a pressure-sensitive adhesive layer, and then laminating the base film 1, and either method may be used.

[0066] The pressure-sensitive adhesive layer 2 may be formed on the surface of the base film 1 by a known method. Specifically, known coating methods such as reverse coating, comma coating, gravure coating, slot die coating, Mayer bar coating, and air knife coating can be used. Similarly, the release agent layer 4 may be formed on the resin film 3 by a known method. Specifically, known coating methods such as gravure coating, Mayer bar coating, and air knife coating can be used.

[0067] Fig. 2 is a cross-sectional view showing a state in which the release film 5 has been peeled off from the antistatic surface protection film 10. By peeling the release film 5 off from the antistatic surface protection film 10 shown in Fig. 1, part of the antistatic agent 7 contained in the release agent layer 4 of the release film 5 is transferred (adhered) to the surface of the pressure-sensitive adhesive layer 2 of the antistatic surface protection film 10. Therefore, in Fig. 2, the antistatic agent transferred to the surface of the pressure-sensitive adhesive layer 2 of the antistatic surface protection film is schematically shown by spots indicated by the reference numeral 7. In the antistatic surface protection film of this embodiment, when the antistatic surface protection film 11 shown in Figure 2 with the release film peeled off is attached to an adherend, the antistatic agent 7 transferred to the surface of the pressure-sensitive adhesive layer 2 comes into contact with the surface of the adherend. This makes it possible to keep the peeling electrification voltage low when the antistatic surface protection film is peeled off from the adherend again. In addition to the antistatic agent 7, a silicone-based compound that is liquid at 20°C may be transferred from the release agent layer 4 to the surface of the pressure-sensitive adhesive layer 2.

[0068] FIG. 3 is a cross-sectional view showing an example of the optical component of this embodiment. The release film 5 is peeled off from the antistatic surface protection film 10 according to this embodiment, and the pressure-sensitive adhesive layer 2 is exposed. The film is then attached to an optical component 8 as an adherend via the pressure-sensitive adhesive layer 2 . FIG. 3 shows an optical component 20 to which the antistatic surface protective film 10 of this embodiment is attached. Examples of optical components include optical films such as polarizing plates, retardation plates, lens films, polarizing plates that also function as retardation plates, and polarizing plates that also function as lens films. These optical components are used as components of liquid crystal display devices such as liquid crystal display panels, optical systems for various instruments, and the like. Other examples of optical components include optical films such as antireflection films, hard coat films, and transparent conductive films for touch panels. In particular, the antistatic surface protective film can be suitably used as an antifouling surface protective film to be attached to the antifouling surface of optical films such as low-reflection polarizing plates (LR polarizing plates) and anti-glare low-reflection polarizing plates (AG-LR polarizing plates), whose surfaces have been treated with antifouling treatments such as silicone compounds or fluorine compounds. According to the optical component of this embodiment, when the antistatic surface protective film 10 is peeled off from the adherend, that is, the optical component (optical film), the peeling electrification voltage can be kept sufficiently low, so there is no risk of damaging circuit components such as driver ICs, TFT elements, and gate line driving circuits, and production efficiency in the process of manufacturing liquid crystal display panels, etc. can be improved and the reliability of the production process can be maintained.

[0069] The antistatic surface protective film 10 of this embodiment is suitable as a surface protective film for polarizing plates. The pressure-sensitive adhesive layer 2 of the antistatic surface protective film 10 may be attached to a protective layer of a polarizer of a polarizing plate. Here, the protective layer of the polarizer of the polarizing plate, which serves as an adherend in the use of the surface protective film for polarizing plates, may be at least one selected from the group consisting of TAC-based films, PMMA-based films, and PET-based films. Here, TAC is an abbreviation for triacetyl cellulose, PMMA is an abbreviation for polymethyl methacrylate, and PET is an abbreviation for polyethylene terephthalate. In addition, the surface of the protective layer of the polarizer of the polarizing plate, which is the adherend in the use of the surface protective film for 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.

[0070] In the antistatic surface protection film 10 of this embodiment, the surface resistivity of the pressure-sensitive adhesive layer 2 obtained by crosslinking the pressure-sensitive adhesive composition to which the antistatic agent of the release agent layer 4 has been transferred is 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 of the pressure-sensitive adhesive layer 2 is Ω / □ or less. If the surface resistivity of the pressure-sensitive adhesive layer 2 is high, the pressure-sensitive adhesive layer 2 will be poor in terms of its ability to dissipate static electricity generated when peeling it from an adherend. Therefore, by making the surface resistivity of the pressure-sensitive adhesive layer 2 sufficiently small, the peeling electrification voltage that occurs in conjunction with static electricity generated when peeling the pressure-sensitive adhesive layer 2 from an adherend can be reduced, thereby suppressing its influence on the adherend.

[0071] In the antistatic surface protective film 10 of this embodiment, the pressure-sensitive adhesive layer 2, obtained by crosslinking the pressure-sensitive adhesive composition to which the antistatic agent of the release agent layer 4 has been transferred, preferably has a peel electrification voltage 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 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.

[0072] 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. In the antistatic surface protection film 10 of this embodiment, the pressure-sensitive adhesive layer 2 obtained by crosslinking the pressure-sensitive adhesive composition to which the antistatic agent of the release agent layer 4 has been transferred 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.

[0073] The pressure-sensitive adhesive layer 2 is preferably adhered 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 without contamination. Examples of the adherend include polarizing plates 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 a fluorine compound described above. Examples of the protective layer and surface treatment include the protective layer of the polarizer described above and a surface treatment applied to its surface. Specific examples include polarizing plates in which the surface substrate is a type selected from the group consisting of a TAC film, a PMMA film, and a PET film, and the surface treatment applied to the surface of the surface substrate is a type selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment.

[0074] In the antistatic surface protection film 10 of this embodiment, the antistatic surface protection film 10 is formed by laminating a 15 μm thick adhesive layer 2, which is obtained by crosslinking the adhesive composition to which the antistatic agent of the release agent layer 4 has been transferred, to one side of a 38 μm thick polyester film. After the antistatic surface protection film 10 is bonded to the surface of a polarizing plate, the antistatic surface protection film 10 exhibits an adhesive strength of 0.01 to 0.1 N / 25 mm at a low peeling speed of 0.3 m / min, preferably an adhesive strength of 1.0 N / 25 mm or less at a high peeling speed of 30 m / min, and more preferably an adhesive strength of 0.2 to 0.8 N / 25 mm at a high peeling speed of 30 m / min. This allows for minimal change in adhesive strength with peeling speed, enabling rapid peeling even at high peeling speeds. Furthermore, when the antistatic surface protection film 10 is temporarily peeled off for re-adhesion, it is easily peeled off from the adherend without requiring excessive force.

[0075] In the antistatic surface protection film 10 of this embodiment, the gel fraction of the pressure-sensitive adhesive layer 2 obtained by crosslinking the pressure-sensitive adhesive composition to which the antistatic agent of the release agent layer 4 has been transferred is preferably 95 to 100%, and more preferably 97 to 100%. Such a high gel fraction of the pressure-sensitive adhesive layer 2 prevents excessive adhesive strength at low peel speeds, reduces elution of unpolymerized monomers or oligomers from the pressure-sensitive adhesive layer 2, improves reworkability and durability at high temperatures and high humidity, and can suppress contamination of the adherend.

[0076] The pressure-sensitive adhesive film of this embodiment comprises a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition of this embodiment on one or both sides of a resin film. The surface protection film of this embodiment comprises a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition of this embodiment on one side of a resin film. The surface protection film of this embodiment becomes an antistatic surface protection film by transferring the antistatic agent of the release agent layer 4 to the surface of the pressure-sensitive adhesive layer 2, and thus has excellent antistatic properties. Furthermore, the antistatic surface protection film of this embodiment has an excellent balance of adhesive strength at both low and high peel speeds, and also has contamination resistance. Therefore, it can be suitably used as a surface protection film for polarizing plates.

[0077] Furthermore, an optical film with a pressure-sensitive adhesive layer can be obtained by laminating, on at least one surface of an optical film, a pressure-sensitive adhesive layer 2 obtained by crosslinking the pressure-sensitive adhesive composition to which the antistatic agent of the release agent layer 4 has been transferred. 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]

[0078] The present invention will be specifically described below with reference to examples.

[0079] <Production of Pressure-Sensitive Adhesive Composition> [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, 80 parts by weight of 2-ethylhexyl acrylate, 20 parts by weight of n-butyl methacrylate, 4.5 parts by weight of 8-hydroxyoctyl acrylate, 10 parts by weight of polypropylene glycol monoacrylate (n=12), 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, yielding an acrylic polymer solution of Example 1. To this acrylic polymer solution, 8.5 parts by weight of acetylacetone was added and stirred, and then 2.0 parts by weight of Coronate HX (an isocyanurate of a hexamethylene diisocyanate compound), 0.1 parts by weight of titanium trisacetylacetonate, and 0.05 parts by weight of a polyether-modified siloxane compound (HLB=7) were added and mixed with stirring to obtain the adhesive composition of Example 1.

[0080] [Examples 2 to 6 and Comparative Examples 1 to 4] The pressure-sensitive adhesive compositions of Examples 2 to 6 and Comparative Examples 1 to 4 were obtained in the same manner as Example 1, except that the formulation of the pressure-sensitive adhesive composition of Example 1 was changed as shown in Table 1. In the case of the pressure-sensitive adhesive compositions of Comparative Examples 1 and 2, a compound shown in the "antistatic agent" column in Table 2 was further added to the pressure-sensitive adhesive composition. The acrylic polymers of Examples 1 to 6 and Comparative Examples 1 to 3 were copolymers having a weight-average molecular weight of more than 300,000 and not more than 1,000,000. The acrylic polymer of Comparative Example 4 was a copolymer having a weight-average molecular weight of 100,000.

[0081] In each column of Table 1 and the "Antistatic Agent" section of Table 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. "(D) / (E)" in Table 2 indicates the ratio by weight. In addition, in each of columns (B) to (G) of Table 1, the content (parts by weight) of each component is shown in parentheses ( ) when the total parts by weight of the acrylic polymer calculated as the sum of the parts by weight of (A), (B), and (F) is taken as 100 parts by weight. In addition, in the "Antistatic Agent" section of Table 2, LiTFSI represents Li(CF3SO2)2N, and LiTF represents LiCF3SO3.

[0082] [Table 1]

[0083] [Table 2]

[0084] The compound names of the abbreviations of the components (A) to (G) used in Table 1 are shown in Table 3. Coronate (registered trademark) HX, Coronate HL, and Coronate L are product names of Tosoh Corporation, and Takenate (registered trademark) D-140N and D-110N are product names of Mitsui Chemicals, Inc. Furthermore, among the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomers constituting the (F) polyalkylene glycol chain, F-1 to F-3 are monomers having a diester content of 0.2 wt% or less, and F-4 is a monomer having a diester content of 0.8 wt%. The value of n indicates the average repeat number of alkylene oxide. Furthermore, among the (G) polyether-modified siloxane compounds, G-1 to G-6 have a weight average molecular weight of 10,000 or less.

[0085] [Table 3]

[0086] <Preparation of antistatic surface protection film> [Example 1] 5 parts by weight of an addition reaction type silicone (manufactured by Toray Dow Corning Co., Ltd., product name: SRX-345), 0.15 parts by weight of a polyether-modified silicone (manufactured by Toray Dow Corning Co., Ltd., product name: SH8400), 0.5 parts by weight of lithium bis(trifluoromethanesulfonyl)imide salt (LiTFSI) as an antistatic agent, 95 parts by weight of a 1:1 mixed solvent of toluene and ethyl acetate, and 0.05 parts by weight of a platinum catalyst (manufactured by Toray Dow Corning Co., Ltd., product name: SRX-212 Catalyst) were combined and stirred to prepare a coating material for forming the release agent layer of Example 1. The coating material for forming the release agent layer of Example 1 was applied to the surface of a 38 μm-thick polyethylene terephthalate film using a Mayer bar to a dried thickness of 0.2 μm, and the mixture was dried in a hot air circulating oven at 120°C for 1 minute to obtain the release film of Example 1. The pressure-sensitive adhesive composition of Example 1 was applied to the surface of a 38 μm-thick polyethylene terephthalate film so that the dried thickness would be 15 μm, and then dried for 2 minutes in a hot air circulating oven at 100°C to form a pressure-sensitive adhesive layer. The release agent layer (silicone-treated surface) of the release film of Example 1 prepared above was then attached to the surface of this pressure-sensitive adhesive layer. The resulting pressure-sensitive adhesive film was kept warm in an environment of 40°C for 5 days to cure the pressure-sensitive adhesive, thereby obtaining the antistatic surface protection film of Example 1.

[0087] [Examples 2 to 6] The paints for forming the release agent layers of Examples 2 to 6 were obtained in the same manner as in Example 1, except that the compositions of the paints for forming the release agent layers of Example 1 were each as shown in Table 4. In addition, antistatic surface protection films of Examples 2 to 6 were obtained in the same manner as Example 1, except that the adhesive composition and the paint forming the release agent layer of Example 1 were replaced with the adhesive compositions and the paint forming the release agent layer of Examples 2 to 6, respectively.

[0088] [Comparative Example 1] 5 parts by weight of addition reaction type silicone (manufactured by Toray Dow Corning Co., Ltd., product name: SRX-345), 95 parts by weight of a 1:1 mixed solvent of toluene and ethyl acetate, and 0.05 parts by weight of a platinum catalyst (manufactured by Toray Dow Corning Co., Ltd., product name: SRX-212 Catalyst) were combined, stirred, and mixed to prepare a coating material for forming the release agent layer of Comparative Example 1. The coating material for forming the release agent layer of Comparative Example 1 was applied to the surface of a polyethylene terephthalate film with a thickness of 38 μm using a Mayer bar so that the thickness after drying would be 0.2 μm, and the coating was dried in a hot air circulating oven at 120°C for 1 minute to obtain the release film of Comparative Example 1. The adhesive composition of Comparative Example 1 was applied to the surface of a 38 μm-thick polyethylene terephthalate film so that the dried thickness would be 15 μm, and then dried for 2 minutes in a hot air circulating oven at 100°C to form an adhesive layer. The release agent layer (silicone-treated surface) of the release film of Comparative Example 1 prepared above was then attached to the surface of this adhesive layer. The resulting adhesive film was kept warm in an environment of 40°C for 5 days to cure the adhesive, thereby obtaining an antistatic surface protection film of Comparative Example 1.

[0089] Comparative Example 2 An antistatic surface protection film of Comparative Example 2 was obtained in the same manner as Comparative Example 1, except that the adhesive composition of Comparative Example 1 was replaced with the adhesive composition of Comparative Example 2. [Comparative Examples 3 to 4] The paints for forming the release agent layers of Comparative Examples 3 and 4 were obtained in the same manner as in Example 1, except that the compositions of the paints for forming the release agent layers of Example 1 were each as shown in Table 4. Furthermore, the antistatic surface protection films of Comparative Examples 3 and 4 were obtained in the same manner as in Example 1, except that the adhesive composition and paint for forming the release agent layer of Example 1 were changed to the adhesive compositions and paints for forming the release agent layers of Comparative Examples 3 and 4, respectively. In the "Antistatic Agent" section of Table 4, LiTFSI represents Li(CF3SO2)2N, LiFSI represents Li(FSO2)2N, and LiTF represents LiCF3SO3.

[0090] [Table 4]

[0091] <Test method and evaluation> The antistatic 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. In the antistatic surface protection films of Examples 1 to 6 and Comparative Examples 3 and 4, the antistatic agent in the release agent layer can be transferred to the surface of the pressure-sensitive adhesive layer by peeling off the release film. In Comparative Examples 1 and 2, the antistatic agent is contained throughout the entire pressure-sensitive adhesive layer.

[0092] <Adhesive strength test method> The release film was peeled off to expose a 15 μm thick adhesive layer. The antistatic surface protection film was then attached to the surface of a polarizing plate via the adhesive layer, left for one day, then 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.

[0093] <Surface resistivity test method> After aging the antistatic 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 (registered trademark) UP-HT450 (manufactured by Mitsubishi Chemical Analytech).

[0094] <Test method for peeling electrification voltage> The release film was peeled off to expose the pressure-sensitive adhesive layer, and the antistatic 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 antistatic surface protection film was peeled off at an angle of 180° at a tensile 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.

[0095] <Test method for stain resistance> A polarizing plate having the surface substrate and surface treatment (untreated for Plain) shown in Table 6 was bonded to one side of a glass plate using a laminator via a pressure-sensitive adhesive layer (double-sided pressure-sensitive adhesive tape). An antistatic surface protective film was then bonded to the surface of the polarizing plate using the laminator. After bonding 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 antistatic surface protective film was peeled off and the surface of the polarizing plate was visually inspected for contamination. 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."

[0096] Tables 5 and 6 show the evaluation results for the antistatic surface protection films of Examples 1 to 6 and Comparative Examples 1 to 4. The "surface resistivity" in Table 5 is "m×10 +n " is expressed as "mE+n" (where m is any real number and n is a positive integer).

[0097] [Table 5]

[0098] [Table 6]

[0099] The antistatic 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 between adhesive strength at low and high peel speeds. In addition, in the antistatic surface protection films of Examples 1 to 6, the antistatic agent in the release agent layer is transferred to the surface of the pressure-sensitive adhesive layer, so the surface resistivity of the pressure-sensitive adhesive layer is 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 antistatic surface protection films of Examples 1 to 6 were attached to an adherend, 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 had passed, no contamination occurred on the adherend, i.e., various polarizing plates, and the films also had excellent contamination resistance. That is, the evaluation results shown in Tables 5 and 6 demonstrate that the antistatic surface protection films of Examples 1 to 6 were able to solve the problems of the present invention.

[0100] The antistatic surface protection film of Comparative Example 1 (in which the Tg of the monofunctional methacrylate monomer copolymerized with the acrylic polymer was less than 0°C, the entire pressure-sensitive adhesive layer contained an antistatic agent, and the release agent layer did not contain a silicone-based compound that was liquid at 20°C or an antistatic agent) had slightly poor contamination resistance. Furthermore, the antistatic surface protection film of Comparative Example 2 (in which the monofunctional methacrylate monomer and hydroxyl group-containing monomer copolymerized with the acrylic polymer were in excess, the acrylic polymer did not contain the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer that constitutes the polyalkylene glycol chain, the entire pressure-sensitive adhesive layer contained an antistatic agent, and the release agent layer did not contain the silicone compound that was liquid at 20°C or the antistatic agent) had high adhesive strength, high peeling electrification voltage, and poor contamination resistance. Furthermore, the antistatic surface protection film of Comparative Example 3 (in which the acrylic polymer did not contain a methacrylate monomer having a Tg of 0°C or higher and a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer constituting a polyalkylene glycol chain, but contained a carboxyl group-containing monomer) had high adhesive strength, high surface resistance, high peeling electrification voltage, and poor contamination resistance. Furthermore, the antistatic surface protection film of Comparative Example 4 (in which the weight-average molecular weight of the acrylic polymer is small) had poor stain resistance. As described above, the antistatic surface protection films of Comparative Examples 1 to 4 could not solve the problems of the present invention. [Explanation of symbols]

[0101] 1...base film, 2...adhesive layer, 3...resin film, 4...release agent layer, 5...release film, 7...antistatic agent, 8...adherend (optical component), 10...antistatic surface protective film, 11...antistatic surface protective film with release film removed, 20...optical component with antistatic surface protective film attached.

Claims

1. An antistatic surface protective film comprising a substrate film made of a transparent resin and a pressure-sensitive adhesive layer formed on one side thereof, the pressure-sensitive adhesive layer being formed by crosslinking a pressure-sensitive adhesive composition containing an acrylic polymer and a crosslinking agent, The acrylic polymer (A) 100 parts by weight of a total of at least two or more alkyl (meth)acrylates whose alkyl groups have carbon atoms of 1 to 10, (B) 1.0 to 6.0 parts by weight of at least one copolymerizable monomer containing a hydroxyl group; an acrylic polymer comprising a copolymer having a weight average molecular weight of more than 300,000 and not more than 1,000,000, obtained by copolymerizing the above without containing a copolymerizable monomer having a carboxyl group, (A) contains 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, and 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, the acrylic polymer is copolymerized with (F) a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer that constitutes a polyalkylene glycol chain, a release film, which has a resin film on one side of which a release agent layer containing an alkali metal salt as an antistatic agent, laminated to the surface of the pressure-sensitive adhesive layer via the release agent layer, and the antistatic agent in the release agent layer is transferred to the surface of the pressure-sensitive adhesive layer; An antistatic surface protective film, characterized in that the release agent layer is formed from a resin composition containing a release agent mainly composed of dimethylpolysiloxane, a silicone-based compound that is liquid at 20°C, and an antistatic agent.

2. 2. The antistatic surface protective film according to claim 1, wherein the pressure-sensitive adhesive composition contains (C) a tri- or higher functional isocyanate compound as the crosslinking agent.

3. 3. The antistatic surface protection film according to claim 1, wherein the silicone compound in the release agent layer is a polyether-modified silicone.

4. The antistatic surface protective film according to any one of claims 1 to 3, characterized in that the antistatic agent in the release agent layer is a Li salt, and is at least one selected from the group consisting of LiTFSI, LiFSI, and LiTF.

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