Halogen-free antistatic agent and adhesive composition

Abstract

To provide an antistatic agent having high solvent solubility not only in hydrophobic solvents but also in hydrophilic solvents, the antistatic agent being capable of developing antistatic performance while retaining adhesive strength without impairing adhesion to a substrate upon coating.SOLUTION: The invention relates to an antistatic agent comprising an onium salt represented by formula (1), an adhesive composition containing the antistatic agent, and an antistatic resin. (In the formula, R1 is a branched or unbranched alkyl group having 1 to 12 carbon atoms. R2 is a methyl group, an ethyl group, or a hydrogen atom. R3 are each independently a methyl group or an ethyl group. n is 2 or 3).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an antistatic agent using a halogen-free onium salt consisting of a pyridinium cation and a trialkylsilylalkanesulfonic acid anion, and to a pressure-sensitive adhesive composition and an antistatic resin containing the same. [Background technology]

[0002] A known method for imparting antistatic properties to insulating resins is to coat the surface of a resin substrate with a conductive coating containing an antistatic agent. Examples of such antistatic agents include electron-conductive materials such as carbon black and ITO. However, when used in adhesives containing resins, these agents can cause problems with the hardness and transparency of the adhesive layer. Ion-conductive materials using onium salts are known as antistatic agents that impart conductivity while maintaining the transparency of the adhesive layer.

[0003] Ion-conductive materials are ionic compounds of anions and cations, and their properties have led to research into a variety of applications. By adjusting the type and amount of ion-conductive material added to insulating resins, it is possible to impart conductivity to the raw resin and to produce resin materials with different antistatic properties depending on the purpose.

[0004] Furthermore, onium salts have attracted attention because some have excellent properties such as nonvolatility, flame retardancy, and high ionic conductivity, and their physical properties and functions can be designed in a variety of ways.

[0005] As in Patent Documents 1 and 2 below, it is known that ionic liquids with fluorine-containing anions, such as bistrifluoromethanesulfonylimides and bisfluorosulfonylimides, are used to impart antistatic properties to adhesives and the like using onium salts. Antistatic agents using alkali metal salts containing halogens are also known, as in Patent Document 3. However, these antistatic agents contain halogens such as fluorine, which can cause corrosion to metals. In light of recent PFAS regulations, there is a demand for halogen-free antistatic agents that are not subject to PFAS regulations.

[0006] As a halogen-free onium salt, there has been a report of an antistatic agent for use in halogen-free pressure-sensitive adhesives, which uses dodecylbenzenesulfonic acid as the anion, as in Patent Document 4 below. However, halogen-free antistatic agents using dodecylbenzenesulfonic acid anions have low antistatic properties, and when the antistatic agent is applied to a pressure-sensitive adhesive, there is a problem with the surface resistance value. Furthermore, when a pressure-sensitive adhesive layer is formed, due to differences in polarity, dispersibility, and compatibility between the pressure-sensitive adhesive and the antistatic agent, the antistatic agent aggregates in a position near the interface with the substrate in the pressure-sensitive adhesive layer. The aggregated antistatic agent reduces the effective contact area between the pressure-sensitive adhesive and the substrate, resulting in a problem of reduced adhesion of the pressure-sensitive adhesive layer to the substrate.

[0007] Furthermore, halogen-free onium salts with trialkylsilylalkanesulfonic acid as the anion are known, as disclosed in Patent Documents 5 to 9 below. For example, Patent Documents 5 and 6 below use ammonium cations or phosphonium cations as the cations. However, antistatic agents combining these cations with trialkylsilylalkanesulfonic acid anions exhibit insufficient antistatic properties when combined with highly hydrophobic organic solvents during the preparation of adhesive inks. Furthermore, Patent Documents 8 and 9 below disclose ionic liquids combining trialkylsilylalkanesulfonic acid anions with pyridinium cations, but these have been used as additives for conductive metal pastes and as base oils for lubricating oils, and have not been used as antistatic agents for adhesive applications. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-290357 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-064146 [Patent Document 3] Japanese Patent Application Publication No. 2018-115328 [Patent Document 4] Japanese Patent Publication No. 2023-034983 [Patent Document 5] Special Publication No. 2005-535690 [Patent Document 6] Japanese Patent Application Laid-Open No. 2014-080388 [Patent Document 7] U.S. Patent No. 3,141,898 [Patent Document 8] Japanese Patent Application Publication No. 2019-139992 [Patent Document 9] International Publication No. 2009 / 020038 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide an antistatic agent that does not contain a halogen atom in its molecular structure, that has high solubility in both hydrophobic and hydrophilic solvents, and that exhibits antistatic properties while maintaining adhesive strength without impairing adhesion to a substrate when coated. [Means for solving the problem]

[0010] As a result of extensive research to solve the above-mentioned problems, the present inventors have discovered that by using an antistatic agent comprising an onium salt containing no halogen atoms, which uses a pyridinium cation and a trialkylsilylalkanesulfonic acid anion of a specific structure, it is possible to obtain an antistatic agent that has high solvent solubility, dispersibility in and compatibility with various resins, even when not only hydrophilic solvents such as methyl ethyl ketone but also highly hydrophobic organic solvents such as toluene are used in preparing an adhesive ink, and that has excellent antistatic properties when coated, as well as an antistatic adhesive resin that does not impair adhesion to a substrate while maintaining adhesive strength, and have thereby completed the present invention.

[0011] The present invention is as set forth in [1] to [6] below.

[0012] [1] An antistatic agent comprising an onium salt represented by formula (1). [ka] (In the formula, R1 is an optionally branched alkyl group having 1 to 12 carbon atoms, R2 is a methyl group, an ethyl group, or a hydrogen atom, and R3 is each independently a methyl group or an ethyl group, and n is 2 or 3.) [2] The antistatic agent according to [1], wherein the alkyl group for R1 in the formula (1) is a branched alkyl group. [3] The antistatic agent according to [1] or [2], wherein the onium salt represented by formula (1) is 1-(2-ethylhexyl)-3-methylpyridinium=3-(trimethylsilyl)-1-propanesulfonic acid or 1-(2-ethylhexyl)-3-methylpyridinium=3-(trimethylsilyl)-1-ethanesulfonic acid. [4] An antistatic resin comprising the antistatic agent according to any one of [1] to [3] and a resin. [5] A pressure-sensitive adhesive composition comprising the antistatic agent according to any one of [1] to [3] and an acrylic pressure-sensitive adhesive or a silicone pressure-sensitive adhesive. [6] The pressure-sensitive adhesive composition according to [5], characterized in that it contains 0.1 to 10 parts by mass of an antistatic agent per 100 parts by mass of the resin component of the acrylic pressure-sensitive adhesive or silicone pressure-sensitive adhesive. [Effects of the Invention]

[0013] The antistatic agent of the present invention has high solvent solubility, dispersibility in resins, and compatibility, even when a highly hydrophobic organic solvent such as toluene is used in addition to hydrophilic solvents such as methyl ethyl ketone when preparing an adhesive ink, and can exhibit excellent antistatic properties when coated. Therefore, the adhesive can be applied not only to acrylic-based adhesives but also to highly hydrophobic silicone-based adhesives. Furthermore, by using the antistatic agent of the present invention in an adhesive composition, it is possible to form an antistatic adhesive resin that maintains adhesive strength without impairing adhesion to the substrate, and the adhesive can be suitably used in surface protection films that protect the surfaces of optical components and electronic materials. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described below, but the present invention is not limited to the following embodiments.

[0015] [Onium salts] The antistatic agent of the present invention comprises an onium salt (pyridinium salt) represented by formula (1). This onium salt comprises a pyridinium cation and a trialkylsilylalkanesulfonate anion. [ka]

[0016] In the formula, R1 is an alkyl group having 1 to 12 carbon atoms, which may be branched. R2 is a methyl group, an ethyl group, or a hydrogen atom. Each R3 is independently a methyl group or an ethyl group. n is 2 or 3. R1 may be either linear or branched. Specific examples of R1 include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an s-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an s-pentyl group, an isopentyl group, a tert-pentyl group, a neopentyl group, an n-hexyl group, an s-hexyl group, an isohexyl group, a tert-hexyl group, a neohexyl group, a 2-ethylhexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, and an n-dodecyl group. Among these, a 2-ethylhexyl group is preferred as R1. Among R2, a methyl group is preferred. Furthermore, each R3 is independently a methyl group or an ethyl group, but it is preferred that all R3 are the same methyl group or ethyl group, and it is more preferred that all R3 are the same methyl group. n is preferably 3.

[0017] Specific examples of the pyridinium cation constituting the onium salt represented by the formula (1) include 1-methylpyridinium cation, 1-ethylpyridinium cation, 1-propylpyridinium cation, 1-(1-methylethyl)pyridinium cation, 1-butylpyridinium cation, 1-(1-methylpropyl)pyridinium cation, 1-(2-methylpropyl)pyridinium cation, 1-(1,1-dimethylethyl)pyridinium cation, 1-pentylpyridinium cation, 1-(1-methylbutyl)pyridinium cation, 1-( 2-methylbutyl)pyridinium cation, 1-(3-methylbutyl)pyridinium cation, 1-(1,1-dimethylpropyl)pyridinium cation, 1-(2,2-dimethylpropyl)pyridinium cation, 1-hexylpyridinium cation, 1-(1-methylpentyl)pyridinium cation, 1-(2-methylpentyl)pyridinium cation, 1-(3-methylpentyl)pyridinium cation, 1-(4-methylpentyl)pyridinium cation, 1-(1,1-dimethylbutyl)pyridinium cation, 1-(2,2-dimethylpropyl)pyridinium cation 1-(3,3-dimethylbutyl)pyridinium cation, 1-(2-ethylhexyl)pyridinium cation, 1-heptylpyridinium cation, 1-octylpyridinium cation, 1-nonylpyridinium cation, 1-decylpyridinium cation, 1-undecylpyridinium cation, 1-dodecylpyridinium cation, 1,3-dimethylpyridinium cation, 1-ethyl-3-methylpyridinium cation, 1-propyl-3-methylpyridinium cation, 1-(1-methylethyl)- 3-methylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-(1-methylpropyl)-3-methylpyridinium cation, 1-(2-methylpropyl)-3-methylpyridinium cation, 1-(1,1-dimethylethyl)-3-methylpyridinium cation, 1-pentyl-3-methylpyridinium cation, 1-(1-methylbutyl)-3-methylpyridinium cation, 1-(2-methylbutyl)-3-methylpyridinium cation, 1-(3-methylbutyl)-3-methylpyridinium cation, 1-(1,1-dimethylpropyl)-3-methylpyridinium cation, 1-(2,2-dimethylpropyl)-3-methylpyridinium cation, 1-hexyl-3-methylpyridinium cation, 1-(1-methylpentyl)-3-methylpyridinium cation, 1-(2-methylpentyl)-3-methylpyridinium cation, 1-(3-methylpentyl)-3-methylpyridinium cation, 1-(4-methylpentyl)-3-methylpyridinium cation, 1-(1,1-dimethylbutyl)-3-methylpyridinium cation, 1-(2,2-dimethylbutyl) 1-(3,3-dimethylbutyl)-3-methylpyridinium cation, 1-(2-ethylhexyl)-3-methylpyridinium cation, 1-heptyl-3-methylpyridinium cation, 1-octyl-3-methylpyridinium cation, 1-nonyl-3-methylpyridinium cation, 1-decyl-3-methylpyridinium cation, 1-undecyl-3-methylpyridinium cation, 1-dodecyl-3-methylpyridinium cation, 1-methyl-3-ethylpyridinium cation, 1,3-diethylpyridinium pyridinium cation, 1-propyl-3-ethylpyridinium cation, 1-(1-methylethyl)-3-ethylpyridinium cation, 1-butyl-3-ethylpyridinium cation, 1-(1-methylpropyl)-3-ethylpyridinium cation, 1-(2-methylpropyl)-3-ethylpyridinium cation, 1-(1,1-dimethylethyl)-3-ethylpyridinium cation, 1-pentyl-3-ethylpyridinium cation, 1-(1-methylbutyl)-3-ethylpyridinium cation, 1-(2-methylbutyl)-3-ethylpyridinium cation, 1-(3-methylbutyl)-3-ethylpyridinium cation, 1-(1,1-dimethylpropyl)-3-ethylpyridinium cation, 1-(2,2-dimethylpropyl)-3-ethylpyridinium cation, 1-hexyl-3-ethylpyridinium cation, 1-(1-methylpentyl)-3-ethylpyridinium cation, 1-(2-methylpentyl)-3-ethylpyridinium cation, 1-(3-methylpentyl)-3-ethylpyridinium cation, 1-(4-methylpentyl)-3-ethylpyridinium cation, 1-(1,1-dimethylbutyl)-3-ethylpyridinium cation, 1-(2,2-dimethylbutyl)-3-ethylpyridinium cation, 1-(3,3-dimethylbutyl)-3-ethylpyridinium cation, 1-(2-ethylhexyl)-3-ethylpyridinium cation, 1-heptyl-3-ethylpyridinium cation, 1-octyl-3-ethylpyridinium cation, 1-nonyl-3-ethylpyridinium cation, 1-decyl-3-ethylpyridinium cation, 1-undecyl-3-ethyl Among these pyridinium cations, preferred are those in which R2 is a methyl group, such as 1,3-dimethylpyridinium cation, 1-ethyl-3-methylpyridinium cation, 1-propyl-3-methylpyridinium cation, 1-(1-methylethyl)-3-methylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-(1-methylpropyl)-3-methylpyridinium cation, 1-( 2-methylpropyl)-3-methylpyridinium cation, 1-(1,1-dimethylethyl)-3-methylpyridinium cation, 1-pentyl-3-methylpyridinium cation, 1-(1-methylbutyl)-3-methylpyridinium cation, 1-(2-methylbutyl)-3-methylpyridinium cation, 1-(3-methylbutyl)-3-methylpyridinium cation, 1-(1,1-dimethylpropyl)-3-methylpyridinium cation, 1-(2,2-dimethylpropyl)-3-methyl 1-hexyl-3-methylpyridinium cation, 1-(1-methylpentyl)-3-methylpyridinium cation, 1-(2-methylpentyl)-3-methylpyridinium cation, 1-(3-methylpentyl)-3-methylpyridinium cation, 1-(4-methylpentyl)-3-methylpyridinium cation, 1-(1,1-dimethylbutyl)-3-methylpyridinium cation, 1-(2,2-dimethylbutyl)-3-methylpyridinium cation, 1-(3,1-(3-dimethylbutyl)-3-methylpyridinium cation, 1-(2-ethylhexyl)-3-methylpyridinium cation, 1-heptyl-3-methylpyridinium cation, 1-octyl-3-methylpyridinium cation, 1-nonyl-3-methylpyridinium cation, 1-decyl-3-methylpyridinium cation, 1-undecyl-3-methylpyridinium cation, and 1-dodecyl-3-methylpyridinium cation are preferred, and R 2 is a methyl group and R1 has a branched carbon chain; 1-(1-methylethyl)-3-methylpyridinium cation, 1-(1-methylpropyl)-3-methylpyridinium cation, 1-(2-methylpropyl)-3-methylpyridinium cation, 1-(1,1-dimethylethyl)-3-methylpyridinium cation, 1-(1-methylbutyl)-3-methylpyridinium cation, 1-(2-methylbutyl)-3-methylpyridinium cation, 1-(3-methyl butyl)-3-methylpyridinium cation, 1-(1,1-dimethylpropyl)-3-methylpyridinium cation, 1-(2,2-dimethylpropyl)-3-methylpyridinium cation, 1-methylhexyl-3-methylpyridinium cation, 1-(1-methylpentyl)-3-methylpyridinium cation, 1-(2-methylpentyl)-3-methylpyridinium cation, 1-(3-methylpentyl)-3-methylpyridinium cation, 1-(4-methylpentyl)-3-methylpyridinium cation, 1-(1,1-dimethylbutyl)-3-methylpyridinium cation, 1-(2,2-dimethylbutyl)-3-methylpyridinium cation, 1-(3,3-dimethylbutyl)-3-methylpyridinium cation, and 1-(2-ethylhexyl)-3-methylpyridinium cation are preferred, with the 1-(2-ethylhexyl)-3-methylpyridinium cation being preferred from the standpoint of balance between antistatic performance and adhesive strength.

[0018] The pyridinium cation can be obtained, for example, from a pyridinium halide (halide) as a raw material. The pyridinium halide can be obtained by the same synthesis method as that for known quaternary ammonium halides (for example, synthesis examples of 1-butylpyridinium halide are described in Russian Journal of Organic Chemistry (2006), 42(7), 1068 and Journal of Physical Chemistry B (2015), 119(11), 4263, and synthesis examples of 1-butyl-3-methylpyridinium halide are described in Example 3 of JP-A-2016-510488, and synthesis examples of 1-(2-ethylhexyl)-3-methylpyridinium halide are described in Example 7). For example, pyridinium halide can be obtained by mixing pyridines and alkyl halides and heating as necessary.

[0019] Specific examples of the trialkylsilylalkanesulfonate anion that constitutes the onium salt represented by formula (1) include 3-(trimethylsilyl)-1-ethanesulfonate anion, 3-(trimethylsilyl)-1-propanesulfonate anion, 3-(triethylsilyl)-1-ethanesulfonate anion, and 3-(triethylsilyl)-1-propanesulfonate anion. Of these trialkylsilylalkanesulfonate anions, 3-(trimethylsilyl)-1-propanesulfonate anion and 3-(trimethylsilyl)-1-ethanesulfonate anion, in which all R3s are the same and are methyl groups, are more preferred.

[0020] Of the onium salts represented by formula (1), it is preferable to use 1-(2-ethylhexyl)-3-methylpyridinium=3-(trimethylsilyl)-1-propanesulfonic acid or 1-(2-ethylhexyl)-3-methylpyridinium=3-(trimethylsilyl)-1-ethanesulfonic acid for the antistatic agent of the present invention.

[0021] The onium salt represented by the formula (1) can be produced by a known method so as to have the above structure. Examples of such methods include the following. The compound used in this reaction may be a commercially available product or one synthesized by a known method. [Method of producing onium salt] [ka]

[0022] The pyridines represented by the formula (2) can be selected from the group consisting of hydrogen, a methyl group, and an ethyl group at the 3-position of pyridine, and specific examples include 3-methylpyridine.

[0023] Specific examples of alkyl halides represented by formula (3) include 2-ethylhexyl alkyl groups and 3-(bromomethyl)heptane, in which the halogen is bromine. Here, the alkyl group can be selected from the group consisting of straight-chain or branched-chain alkyl groups having 1 to 12 carbon atoms. Specific examples of alkyl groups include methyl, ethyl, propyl, isopropyl, n-butyl, s-butyl, isobutyl, tert-butyl, n-pentyl, s-pentyl, isopentyl, tert-pentyl, neopentyl, n-hexyl, s-hexyl, isohexyl, tert-hexyl, neohexyl, 2-ethylhexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, and n-dodecyl groups. Examples of halogen ions include chloride ions, bromide ions, and iodide ions.

[0024] Specific examples of the pyridinium halide represented by the formula (4) include 1-(2-ethylhexyl)-3-methylpyridinium bromide, etc. Examples of halogen ions that form counter anions of the above cations include chloride ions, bromide ions, and iodide ions.

[0025] Examples of the metal salt of formula (5) include lithium 3-(trimethylsilyl)-1-propanesulfonate, sodium 3-(trimethylsilyl)-1-propanesulfonate, potassium 3-(trimethylsilyl)-1-propanesulfonate, etc. Examples of alkali metals and transition metals that form counter cations of the above anions include lithium, sodium, potassium, silver, etc.

[0026] The pyridinium halide represented by formula (4) may be synthesized as described above using pyridines represented by formula (2) and alkyl halides represented by formula (3), or may be commercially available without synthesis. When synthesizing the pyridinium cation represented by formula (4), the pyridines represented by formula (2) are quaternized with alkyl halides represented by formula (3) to obtain the pyridinium halide represented by formula (4).

[0027] The quaternization reaction of formula (2) using formula (3) may or may not require the use of a solvent. The solvent is not particularly limited as long as it does not affect the reaction. Specific examples include acetonitrile, methanol, ethyl acetate, benzene, toluene, xylene, diethyl ether, tetrahydrofuran, and 1,4-dioxane.

[0028] The amount of formula (3) used may be 0.7 mol or more per mol of formula (2), and is preferably 0.9 to 1.5 mol.

[0029] The reaction temperature in the quaternization reaction is usually 25°C or higher, preferably 30 to 150°C, and particularly preferably 60 to 120°C.

[0030] To isolate the compound (4), the unreacted raw materials and the solvent are removed.

[0031] The solution containing the isolated compound (4) is passed through a column packed with a cation exchange resin to convert it to the 1-(2-ethylhexyl)-3-methylpyridinium form. After thoroughly flushing with a solvent to confirm neutrality, a solution containing the compound (5) is passed through the column to carry out an ion exchange reaction. When using a commercially available pyridinium halide represented by formula (4), the solution is passed through a column packed with a cation exchange resin, and the ion exchange reaction is carried out in the same manner. Note that the conditions for these ion exchange reactions are not particularly limited, and conventional conditions can be used.

[0032] The solvent for the ion exchange reaction is not particularly limited as long as it does not affect the reaction. Specific examples include pure water, alcohol, acetonitrile, etc., and pure water is preferred.

[0033] To isolate the compound (6), the solvent is removed, and the isolated onium salt of the compound (6) can be used as an antistatic agent.

[0034] The antistatic agent of the present invention thus obtained is halogen-free because it does not contain a halogen in its molecular structure. Furthermore, the antistatic agent of the present invention, which is a combination of a trialkylsilylalkanesulfonate anion and a pyridinium cation, exhibits excellent antistatic performance, particularly excellent solubility in hydrophobic solvents and compatibility with hydrophobic resins, compared to antistatic agents using other onium salts.

[0035] [Adhesive composition and antistatic adhesive resin] By combining the antistatic agent of the present invention with a pressure-sensitive adhesive, a pressure-sensitive adhesive composition imparted with antistatic properties can be obtained. This pressure-sensitive adhesive composition imparted with antistatic properties becomes an antistatic adhesive resin when it is contained. This antistatic adhesive resin has excellent antistatic properties and does not impair adhesive properties. Specifically, when an acrylic polymer is used as the pressure-sensitive adhesive, the surface resistance value of the antistatic adhesive resin formed from the pressure-sensitive adhesive composition is 1×10 12 Ω or less, more preferably 1×10 11 Ω or less, and particularly good ones are 6×10 10When silicone polymer is used as adhesive, the resistance is 1×10 13 Ω or less, more preferably 1×10 12 Ω or less, and particularly good ones are 5×10 11 Ω or less. Furthermore, the adhesive strength is high while maintaining the adhesive strength. The surface resistance is measured with a resistivity meter, and the adhesive strength is measured with a tensile tester. Substrate adhesion can be evaluated by making an incision in the adhesive layer with a cutter knife or the like, rubbing the adhesive layer at the incision with the pad of a finger, and checking the degree to which the adhesive layer peels off from the substrate. Therefore, the adhesive composition of the present invention contains at least the pyridinium salt and an adhesive. The adhesive composition of the present invention also includes an adhesive ink prepared by dissolving the adhesive composition in a soluble organic solvent. The antistatic adhesive resin of the present invention also includes an adhesive sheet or adhesive film formed by applying the adhesive ink to a substrate, as well as a film peeled from the substrate. The antistatic adhesive resin of the present invention is also used as what is commonly called an adhesive layer.

[0036] The pressure-sensitive adhesive in the present invention includes not only pressure-sensitive adhesives such as acrylic polymers, but also pressure-sensitive adhesives such as silicone polymers, pressure-sensitive adhesives such as urethane polymers obtained by reacting polyols such as polyether polyols with polyisocyanate compounds, and pressure-sensitive adhesives such as rubber polymers such as isoprene rubber. Among these pressure-sensitive adhesives, acrylic or silicone pressure-sensitive adhesives are preferred as pressure-sensitive adhesives to be combined with the antistatic agent of the present invention.

[0037] Examples of acrylic polymers include those containing an acrylic polymer whose main component is an acrylate or methacrylate having an alkyl group having 1 to 14 carbon atoms. Examples include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, isobutyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and n-octyl acrylate.

[0038] The mass-average molecular weight of the acrylic polymer is 100,000 to 5,000,000, preferably 200,000 to 4,000,000, and more preferably 300,000 to 3,000,000. If the mass-average molecular weight is less than 100,000, the cohesive strength of the pressure-sensitive adhesive composition may be reduced. On the other hand, if it exceeds 5,000,000, the fluidity of the polymer decreases, resulting in insufficient wettability to the adherend and causing peeling. The mass-average molecular weight can be measured by gel permeation chromatography (GPC).

[0039] The copolymer can be obtained by a general acrylic polymer polymerization method such as solution polymerization, emulsion polymerization, bulk polymerization, or suspension polymerization, and may be any of a random copolymer, a block copolymer, a graft copolymer, or the like.

[0040] Furthermore, by appropriately crosslinking the acrylic polymer, a pressure-sensitive adhesive composition having an adhesive layer with excellent heat resistance can be obtained. Crosslinking methods include adding a crosslinking agent to the acrylic pressure-sensitive adhesive. Examples of crosslinking agents include isocyanate compounds, epoxy compounds, aziridine compounds, and metal chelate compounds.

[0041] The isocyanate compound is a compound having at least two isocyanate groups (-NCO) in the molecule. Specific examples include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate, alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate, aromatic diisocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate and xylylene diisocyanate, and isocyanate adducts such as a trimethylolpropane / tolylene diisocyanate trimer adduct, a trimethylolpropane / hexamethylene diisocyanate trimer adduct and an isocyanurate of hexamethylene diisocyanate.

[0042] Epoxy compounds are compounds that have at least two epoxy groups in the molecule. Specific examples include bisphenol A epoxy resin, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, 1,6-hexanediol diglycidyl ether, and N,N-diglycidylaniline.

[0043] Aziridine compounds are compounds that have at least two three-membered ring skeletons, also known as ethyleneimines, each consisting of one nitrogen atom and two carbon atoms. Specific examples include diphenylmethane-4,4'-bis(1-aziridinecarboxamide), toluene-2,4-bis(1-aziridinecarboxamide), triethylenemelamine, isophthaloylbis-1-(2-methylaziridine), tris-1-aziridinylphosphine oxide, hexamethylene-1,6-bis(1-aziridinecarboxamide), trimethylolpropane-tri-β-aziridinylpropionate, and tetramethylolmethane-tri-β-aziridinylpropionate.

[0044] Examples of metal chelate compounds include compounds in which acetylacetone or ethyl acetoacetate is coordinated with a polyvalent metal such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, or zirconium.

[0045] The content of the crosslinking agent is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5.0 parts by mass, relative to 100 parts by mass of the adhesive. If the content is less than 0.01 part by mass, crosslinking is insufficient, resulting in a decrease in the cohesive strength of the adhesive composition and insufficient heat resistance. On the other hand, if the content exceeds 10 parts by mass, the cohesive strength of the polymer is high, reducing fluidity and resulting in insufficient wettability to the adherend, which can cause peeling.

[0046] The pressure-sensitive adhesive composition of the present invention may contain a surfactant made of an alkylene oxide group-containing compound. The alkylene oxide group-containing compound is a compound having an alkylene oxide group, and specific examples thereof include alkylene oxide group-containing surfactants, alkylene oxide group-containing polyether polymers, and alkylene glycol group-containing (meth)acrylic polymers. Among these, alkylene oxide group-containing surfactants are preferably used because of their good compatibility with acrylic polymers.

[0047] Examples of alkylene oxide group-containing surfactants include nonionic surfactants such as polyoxyalkylene fatty acid esters, polyoxyalkylene sorbitan fatty acid esters, polyoxyalkylene sorbitol fatty acid esters, polyoxyalkylene alkyl ethers, polyoxyalkylene alkyl allyl ethers, polyoxyalkylene alkylphenyl ethers, polyoxyalkylene derivatives, polyoxyalkylene alkylamines, and polyoxyalkylene alkylamine fatty acid esters; anionic surfactants such as polyoxyalkylene alkyl ether sulfates, polyoxyalkylene alkyl ether phosphates, polyoxyalkylene alkylphenyl ether sulfates, and polyoxyalkylene alkylphenyl ether phosphates; and cationic surfactants and zwitterionic surfactants having alkylene oxide groups. Furthermore, the surfactants may have reactive substituents such as (meth)acryloyl groups and allyl groups in the molecule.

[0048] The alkylene oxide group-containing compound may be used alone or in combination of two or more kinds. The amount of the compound added is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, per 100 parts by mass of the acrylic polymer.

[0049] The pressure-sensitive adhesive composition of the present invention may contain a silane compound, which can improve adhesion to substrates such as films and glass.

[0050] Examples of silane compounds include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyldimethoxymethylsilane, and 3-glycidoxypropylethoxydimethylsilane. Two or more of these may be used in combination.

[0051] Silicone-based polymers can also be used, including mixtures of organic and silicone-based polymers or copolymer resins. Curable silicone-based resins can be either "addition reaction" resins, which are heat-cured in the presence of a platinum catalyst using an organohydrogenpolysiloxane and an organopolysiloxane containing alkenyl groups, or "peroxide-cured" resins, which are crosslinked and cured with an organic peroxide such as benzoyl peroxide. However, addition reaction resins, which do not use peroxides and do not produce decomposition products, are preferred. The "addition reaction" resin is preferably one that contains a first polydimethylsiloxane having at least two alkenyl groups per molecule and a second polydimethylsiloxane having at least two hydrosilyl groups per molecule.

[0052] Examples of the curing catalyst include platinum-based catalysts, such as chloroplatinic acid, an alcohol solution of chloroplatinic acid, a reaction product of chloroplatinic acid and an alcohol solution, a reaction product of chloroplatinic acid and an olefin compound, a reaction product of chloroplatinic acid and a vinyl group-containing siloxane compound, a platinum-olefin complex, a platinum-vinyl group-containing siloxane complex, and a platinum-phosphorus complex.

[0053] The amount of the curing catalyst to be added is usually 0.1 to 1 part by mass, preferably 0.3 to 0.6 parts by mass, in terms of the amount of platinum element, relative to the silicone resin component.

[0054] The amount of the onium salt (antistatic agent) represented by formula (1) in the pressure-sensitive adhesive composition of the present invention is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, per 100 parts by mass of the resin component of the pressure-sensitive adhesive. By setting the amount in this range, a pressure-sensitive adhesive composition with even more excellent electrical properties can be obtained.

[0055] The pressure-sensitive adhesive composition of the present invention can be used in combination with other binder resins, antioxidants, ultraviolet absorbers, lubricants, etc., within the scope of not impairing the effects of the present invention.

[0056] When preparing a pressure-sensitive adhesive sheet having a substrate on which an adhesive layer is formed as an antistatic adhesive resin, the pressure-sensitive adhesive composition of the present invention may be applied directly to the substrate, or a pressure-sensitive adhesive ink prepared by dissolving the pressure-sensitive adhesive composition in a soluble organic solvent may be applied to the substrate. The pressure-sensitive adhesive composition or the pressure-sensitive adhesive ink may be applied to a substrate such as a resin film or glass, and then dried as necessary to prepare a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed on the surface of the substrate. The thickness of the pressure-sensitive adhesive layer is preferably 3 to 100 μm, more preferably 5 to 50 μm.

[0057] [Adhesive ink] Examples of organic solvents used in the pressure-sensitive adhesive ink as the pressure-sensitive adhesive composition include alcohol-based solvents such as methanol, ethanol, propanol, isopropanol, isopropyl alcohol (IPA), and butanol; glycol-based solvents such as ethylene glycol, propylene glycol, butylene glycol, polyethylene glycol, polypropylene glycol, and polyoxyethylene-polyoxypropylene copolymers; ether alcohol-based solvents such as monomethyl ether, monoethyl ether, monopropyl ether, monoisopropyl ether, and monobutyl ether of the glycol-based solvents; polyether-based solvents such as dimethyl ether, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, methyl ethyl ether, methyl propyl ether, methyl isopropyl ether, methyl butyl ether, ethyl propyl ether, ethyl isopropyl ether, and ethyl butyl ether of the glycol-based solvents; ketone-based solvents such as methyl ethyl ketone (MEK), methyl isobutyl ketone, and cyclohexanone; ester-based solvents such as methyl acetate, ethyl acetate, and butyl acetate; and hydrocarbon-based solvents such as hexane, heptane, octane, cyclopentane, cyclohexane, toluene, and xylene. The organic solvent is preferably one that can dissolve the antistatic agent of the present invention and the adhesive used well. These may be used alone or in combination, taking into consideration the boiling point, solubility with the resin, coatability to the substrate, etc. For example, toluene, MEK, ethyl acetate, butyl acetate, IPA, etc. are preferred for acrylic adhesives, and toluene, xylene, etc. are preferred for silicone adhesives.

[0058] [Base material] Examples of the substrate include a polyethylene terephthalate (PET) film, a polycarbonate film, a polystyrene film, an acrylic film, a cellulose triacetate film, a polyethylene film, and a polypropylene film.

[0059] [How to make adhesive sheets] Examples of methods for applying a pressure-sensitive adhesive composition or the like to a substrate include roll coating, gravure coating, reverse coating, die coating, comma coating, etc. When drying is performed to remove the solvent from the liquid film coated on the substrate or the like, the temperature is preferably 50° C. or higher and 140° C. or lower, from the viewpoint of promoting curing of the liquid film.

[0060] For the purpose of protecting the adhesive surface, a separator can be attached to the surface of the adhesive layer as needed. The separator can be paper or a plastic film, with plastic film being preferred because of its excellent surface smoothness.

[0061] Examples of plastic films include polyethylene films, polypropylene films, polybutene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, polyethylene terephthalate films, polybutylene terephthalate films, and polyurethane films.

[0062] The pressure-sensitive adhesive composition of the present invention and a pressure-sensitive adhesive sheet (antistatic pressure-sensitive adhesive resin) prepared using the same can be used for plastic products, etc. In particular, they can be used as a surface protection film for protecting the surfaces of optical components such as polarizing plates, wavelength plates, optical compensation films, light diffusion sheets, and reflective sheets used in liquid crystal displays, etc., as well as protective films for electronic materials and semiconductor components.

[0063] [Antistatic resin] As described above, the antistatic agent of the present invention can be combined with a pressure-sensitive adhesive to obtain a pressure-sensitive adhesive composition imparted with antistatic properties. However, it is also possible to simply incorporate this agent into various resins to impart conductivity to the resin, thereby producing an antistatic resin. Examples of resins that can incorporate the antistatic agent of the present invention include resins that can be used as pressure-sensitive adhesives, as well as synthetic resins such as polyethylene terephthalate, polypropylene, and polycarbonate, and various release agents (silicone-based release agents, fluorine-based release agents, acrylic release agents, etc.). The performance of the antistatic resin of the present invention is similar to that of the above-mentioned pressure-sensitive adhesive layer (antistatic adhesive resin).

[0064] The antistatic resin of the present invention can be produced in the same manner as antistatic resins using conventional known antistatic agents. For example, if the resin is a synthetic resin such as polyethylene terephthalate, polypropylene, or polycarbonate, or a release agent (such as a silicone-based release agent, a fluorine-based release agent, or an acrylic-based release agent), in addition to a resin that serves as an adhesive, the antistatic resin can be obtained by mixing it with the resin. Furthermore, if an acrylic resin monomer is used as the resin raw material, a solution containing the acrylic resin monomer and the antistatic agent of the present invention is prepared by adding a photopolymerization initiator to the solution, and the solution is applied to the surface of the resin, and the resin is then irradiated with ultraviolet light to obtain the antistatic resin of the present invention. [Example]

[0065] The present invention will be described in detail below by way of examples, but the present invention is not limited to these examples in any way.

[0066] [Production of antistatic agents] The onium salts used in the antistatic agents were prepared according to the following synthesis examples.

[0067] (Synthesis Example 1) 15.0 g of 3-methylpyridine and 31.1 g of ethylhexyl bromide were mixed with stirring and reacted for 15 hours at 100° C. After that, the mixture was concentrated to obtain 44.3 g of 1-(2-ethylhexyl)-3-methylpyridinium bromide (yield 96%).

[0068] Next, a 20 mL column was packed with cation exchange resin Diaion PK216H (Mitsubishi Chemical Corporation), and an aqueous solution of 20 g of 1-(2-ethylhexyl)-3-methylpyridinium bromide dissolved in 100 mL of water was passed through to convert it to the 1-(2-ethylhexyl)-3-methylpyridinium form. After the conversion, water was thoroughly poured through the column, and after confirming that the eluate was neutral, an aqueous solution of 6.10 g of sodium 3-trimethylsilyl-1-propanesulfonate (Tokyo Chemical Industry Co., Ltd.) dissolved in 100 mL of water was passed through the column. The eluate was concentrated to obtain 10.1 g of 1-(2-ethylhexyl)-3-methylpyridinium = 3-trimethylsilyl-1-propanesulfonic acid (90% yield).

[0069] (Synthesis Example 2) 11.1 g (yield 92%) of 1-butyl-3-methylpyridinium 3-trimethylsilyl-1-propanesulfonic acid was obtained in the same manner as in Synthesis Example 1, except that 1-(2-ethylhexyl)-3-methylpyridinium bromide described in Synthesis Example 1 was replaced with 1-butyl-3-methylpyridinium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0070] (Synthesis Example 3) 10.8 g (yield 88%) of 1-butyl-pyridinium 3-trimethylsilyl-1-propanesulfonic acid was obtained in the same manner as in Synthesis Example 1, except that 1-(2-ethylhexyl)-3-methylpyridinium bromide described in Synthesis Example 1 was replaced with 1-butyl-pyridinium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0071] (Synthesis Example 4) 9.5 g (yield 88%) of 1-(2-ethylhexyl)-3-methylpyridinium = 3-trimethylsilyl-1-ethanesulfonate was obtained in the same manner as in Synthesis Example 1, except that sodium 3-trimethylsilyl-1-propanesulfonate described in Synthesis Example 1 was replaced with sodium 3-trimethylsilyl-1-ethanesulfonate (manufactured by Sigma-Aldrich).

[0072] (Synthesis Example 5) Equimolar amounts of 1-butyl-3-methylpyridinium bromide and lithium bis(trifluoromethylsulfonyl)imide (Tokyo Chemical Industry Co., Ltd.) were added to water to perform salt exchange. After that, the solution was separated with chloroform, and the organic layer was washed with water and then concentrated to remove the chloroform, producing 1-butyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide.

[0073] (Synthesis Example 6) 1-Butyl-3-methylpyridinium trifluoromethanesulfonate was prepared in the same manner as in Synthesis Example 5, except that lithium bis(trifluoromethylsulfonyl)imide acid described in Synthesis Example 5 was replaced with lithium trifluoromethanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0074] (Synthesis Example 7) Tetraethylammonium 3-trimethylsilyl-1-propanesulfonic acid was prepared in the same manner as in Synthesis Example 1, except that 1-(2-ethylhexyl)-3-methylpyridinium bromide described in Synthesis Example 1 was replaced with tetraethylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0075] (Synthesis Example 8) 1-Butyl-3-methylpyridinium dodecylbenzenesulfonate was prepared in the same manner as in Synthesis Example 5, except that lithium bis(trifluoromethylsulfonyl)imide described in Synthesis Example 5 was replaced with dodecylbenzenesulfonic acid (manufactured by Kanto Chemical Co., Inc.).

[0076] [Preparation of adhesive ink] The adhesive ink was prepared as follows.

[0077] Example 1 0.06 g of the compound of Synthesis Example 1 used as an antistatic agent, 20 g of an acrylic adhesive SK Dyne 1495 (manufactured by Soken Chemical & Engineering Co., Ltd., non-volatile content 30%), and 0.48 g of an isocyanate curing agent L-45K (manufactured by Soken Chemical & Engineering Co., Ltd., non-volatile content 50%) were mixed together, and the mixture was diluted with 19 g of toluene to prepare an adhesive ink.

[0078] Example 2 An adhesive ink was prepared without changing the antistatic agent of Example 1 except that the compound of Synthesis Example 2 was used.

[0079] Example 3 An adhesive ink was prepared without changing the antistatic agent of Example 1 except that the compound of Synthesis Example 3 was used.

[0080] Example 4 An adhesive ink was prepared without changing the antistatic agent of Example 1 except that the compound of Synthesis Example 4 was used.

[0081] Example 5 An adhesive ink was prepared without making any changes to the composition of Example 1 except that the toluene solvent was changed to MEK.

[0082] (Comparative Example 1) An adhesive ink was prepared without changing the antistatic agent of Example 1 except that the compound of Synthesis Example 5 was used.

[0083] (Comparative Example 2) An adhesive ink was prepared without changing the antistatic agent of Example 1 except that the compound of Synthesis Example 6 was used.

[0084] (Comparative Example 3) An adhesive ink was prepared without changing the antistatic agent of Example 1 except that the compound of Synthesis Example 7 was used.

[0085] Comparative Example 4 An adhesive ink was prepared without changing the antistatic agent of Example 5 except that the compound of Synthesis Example 7 was used.

[0086] (Comparative Example 5) An adhesive ink was prepared without changing the antistatic agent of Example 1 except that the compound of Synthesis Example 8 was used.

[0087] Example 6 0.4 g of the compound of Synthesis Example 1 used as an antistatic agent, 20 g of silicone-based adhesive X-40-3306 (manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.1 g of platinum-based catalyst CAT-PL-50T (manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed together and diluted with 80 g of toluene to prepare an adhesive ink.

[0088] Example 7 An adhesive ink was prepared without changing the antistatic agent of Example 6 except that the compound of Synthesis Example 2 was used.

[0089] Example 8 An adhesive ink was prepared without changing the antistatic agent of Example 6 except that the compound of Synthesis Example 3 was used.

[0090] Example 9 An adhesive ink was prepared without changing the antistatic agent of Example 6 except that the compound of Synthesis Example 4 was used.

[0091] (Comparative Example 6) An adhesive ink was prepared without changing the antistatic agent of Example 6 except that the compound of Synthesis Example 5 was used.

[0092] (Comparative Example 7) An adhesive ink was prepared without changing the antistatic agent of Example 6 except that the compound of Synthesis Example 6 was used.

[0093] (Comparative Example 8) An adhesive ink was prepared without changing the antistatic agent of Example 6 except that the compound of Synthesis Example 7 was used.

[0094] Comparative Example 9 An adhesive ink was prepared without changing the antistatic agent of Example 6 except that the compound of Synthesis Example 8 was used.

[0095] [Coating conditions] The adhesive ink was coated onto a PET film using a bar coater to a thickness of approximately 20 μm after drying, and heated at 130° C. for 3 minutes to prepare a test piece.

[0096] [Surface resistance measurement] The surface resistance of the coated surface of the test piece was measured at room temperature, 50% RH, and an applied voltage of 100 V using a resistivity meter, Hirester UP (MCP-HT450).

[0097] [Adhesion test] An adhesive film test piece was attached to a stainless steel plate (SUS304, the same below) so that the attachment area was 25 mm wide x 100 mm long [one round trip with a 2 kg load roller, the same below], and using a tensile tester at room temperature (23°C) in accordance with JIS Z0237, the force (N / 25 mm) required to peel the tape from the stainless steel plate at a speed of 300 mm / min and an angle of 180° was measured, and the adhesive strength (unit: N / 25 mm) was evaluated.

[0098] [Evaluation of adhesion to substrate] After leaving the test piece in a thermostatic chamber at room temperature (25°C) and 50% RH for one day, a cross-shaped cut (30mm x 30mm) was made in the adhesive layer on the coated surface with a cutter knife. The adhesive layer at the cut site was then rubbed with the pad of a finger to check the degree of peeling of the adhesive layer from the substrate.

[0099] The adhesion was evaluated according to the following criteria. ◯: The adhesive layer in the rubbed area did not detach from the substrate. △: Approximately 20 to 80% of the adhesive layer in the rubbed area was detached from the substrate. ×: 80% or more of the adhesive layer in the rubbed area was detached from the substrate.

[0100] The results of Examples 1 to 9 and Comparative Examples 1 to 9 are shown in Table 1. [Table 1]

[0101] As can be seen from Table 1, for both the acrylic and silicone adhesives, Examples 1 to 9 had lower surface resistance, no decrease in adhesive strength, and excellent adhesion to the substrate compared to Comparative Examples 1 to 9. Furthermore, for the acrylic adhesives, Examples 1 and 5 confirmed good surface resistance, adhesive strength, and substrate adhesion for both toluene, a highly hydrophobic solvent, and MEK, a highly hydrophilic solvent. Furthermore, when Examples 1 to 3 and 6 to 8 were compared, 1-(2-ethylhexyl)-3-methylpyridinium = 3-trimethylsilyl-1-propanesulfonic acid exhibited particularly good properties.

[0102] Compared with the halogen-free antistatic agent tetraethylammonium=3-trimethylsilyl-1-propanesulfonate, the antistatic agent of the Examples had superior surface resistance values, and compared with 1-butyl-3-methylpyridinium=dodecylbenzenesulfonate, the Examples had superior surface resistance values ​​and adhesion to substrates. [Industrial Applicability]

[0103] The present invention can be suitably used as a surface protection film for protecting the surfaces of electronic components and optical members.

Claims

1. An antistatic agent comprising an onium salt represented by formula (1): 【Chemistry 1】 (In the formula, R1 is an alkyl group having 1 to 12 carbon atoms, which may be branched; R2 is a methyl group, an ethyl group, or a hydrogen atom; R3 is independently a methyl group or an ethyl group; and n is 2 or 3.)

2. 2. The antistatic agent according to claim 1, wherein the alkyl group for R1 in formula (1) is a branched alkyl group.

3. 2. The antistatic agent according to claim 1, wherein the onium salt represented by formula (1) is 1-(2-ethylhexyl)-3-methylpyridinium=3-(trimethylsilyl)-1-propanesulfonic acid or 1-(2-ethylhexyl)-3-methylpyridinium=3-(trimethylsilyl)-1-ethanesulfonic acid.

4. An antistatic resin comprising the antistatic agent according to any one of claims 1 to 3 and a resin.

5. A pressure-sensitive adhesive composition comprising the antistatic agent according to any one of claims 1 to 3 and an acrylic pressure-sensitive adhesive or a silicone pressure-sensitive adhesive.

6. 6. The pressure-sensitive adhesive composition according to claim 5, further comprising 0.1 to 10 parts by mass of an antistatic agent per 100 parts by mass of the resin component of the acrylic pressure-sensitive adhesive or silicone pressure-sensitive adhesive.

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