Halogen-free antistatic agent and adhesive composition

Abstract

Provided are: an antistatic agent comprising an ammonium salt represented by formula (1); an adhesive composition containing said antistatic agent; and an antistatic agent or the like having excellent resin compatibility and antistatic properties imparted by means of an antistatic resin. (In the formula, R1 through R4 may be the same or different and are 1-13C alkyl groups, and the total number of carbon atoms in the alkyl groups R1 through R4 is 12-16.)

Description

Halogen-free antistatic agent and adhesive composition

[0001] The present invention relates to an antistatic agent using an onium salt containing no halogen atoms and consisting of a tetraalkylammonium cation and a bis(oxalatoborate) anion, and to a pressure-sensitive adhesive composition and an antistatic resin containing the same.

[0002] As a method for imparting antistatic properties to insulating resins, a method of coating the surface of a resin substrate with a conductive coating film containing an antistatic agent is known. Examples of the antistatic agent include electron conductive materials such as carbon black and ITO, but when used in adhesives using resins, they have 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 antistatic agents made from ionic compounds of anions and cations, and their properties have led to research into a variety of applications. By adding different types and amounts of ion-conductive materials to insulating resins, the electrical resistance of the raw resin can be reduced, resulting in resin materials with different antistatic properties tailored to the intended purpose.

[0004] In addition, onium salts have attracted attention because they 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. Due to these properties, onium salts are used as antistatic agents for various resins.

[0005] It is known that ionic liquids having fluorine-containing anions, such as bistrifluoromethanesulfonylimides and bisfluorosulfonylimides, are used to impart antistatic properties to adhesives and the like using onium salts, as in Patent Documents 1 and 2. However, these antistatic agents contain halogens such as fluorine, which can cause corrosion of metals and, in view of recent PFAS regulations, halogen-free antistatic agents are desired; as in Patent Document 3, antistatic agents whose anions do not contain fluorine are used in carrier tape applications in the semiconductor field.

[0006] It is known that halogen-free onium salts are inferior in physical properties to onium salts containing general fluorine-containing anions. For example, a halogen-free antistatic agent using a tetraalkylammonium cation and a dodecylbenzenesulfonate anion, as disclosed in Patent Document 4, has low antistatic properties, and when the antistatic agent is applied to a pressure-sensitive adhesive, there is a problem with the surface resistance value.

[0007] Patent Document 5 discloses an antistatic agent using a quaternary ammonium cation and a bis(oxalate)borate anion. Patent Document 5 assumes that the quaternary ammonium cation may have a structure with a hydrocarbon group having a halogen substituent, and does not consider halogen-free antistatic agents. Regarding halogen-free antistatic agents, known are those in which the quaternary ammonium cation is a tetraalkylammonium cation. However, with these halogen-free antistatic agents, if the total number of carbon atoms in the alkyl groups in the tetraalkylammonium cation is too small, the moist heat resistance and adhesive strength deteriorate when the antistatic agent is applied to an adhesive. If the total number of carbon atoms is too large, the antistatic performance deteriorates, and there are problems with the surface resistance value when the antistatic agent is applied to an adhesive.

[0008] JP 2005-290357 A JP 2013-064146 A JP 2022-109631 A JP 2023-034983 A JP 2019-108414 A

[0009] The present invention aims to provide an antistatic agent that does not contain halogen in its molecular structure, has excellent resin compatibility, and exhibits sufficient antistatic properties even when added in small amounts. It also aims to provide an adhesive composition that is excellent in transparency and has low haze, and an antistatic adhesive resin that is excellent in moisture and heat resistance, by using such an antistatic agent in an adhesive.

[0010] As a result of extensive research, the present inventors have found that, among antistatic agents comprising a tetraalkylammonium cation and a bisoxalate borate anion, by using a tetraalkylammonium cation in which the total number of carbon atoms in the alkyl groups in the tetraalkylammonium cation is 12 to 16, it is possible to obtain an antistatic agent having excellent resin compatibility and antistatic performance, a pressure-sensitive adhesive composition having excellent transparency and small haze, and an antistatic adhesive resin having excellent moisture and heat resistance while maintaining adhesive strength, and have completed the present invention.

[0011] The present invention is described in the following [1] to [6].

[0012] [1] An antistatic agent comprising a quaternary ammonium salt represented by formula (1): (In the formula, R １ ~R ４ are alkyl groups having 1 to 13 carbon atoms, which may be the same or different, and R １ ~R ４ The total number of carbon atoms in the alkyl groups is 12 to 16.) [2] The antistatic agent according to [1], wherein the quaternary ammonium salt represented by formula (1) is tetrabutylammonium bisoxalatoborate or tetrapropylammonium bisoxalatoborate. [3] An antistatic resin comprising the antistatic agent according to any one of [1] to [2] and a resin. [4] A pressure-sensitive adhesive composition comprising the antistatic agent according to any one of [1] to [2] and an acrylic pressure-sensitive adhesive. [5] The pressure-sensitive adhesive composition according to [4], wherein the antistatic agent is contained in an amount of 0.1 to 10 parts by mass per 100 parts by mass of the resin component of the acrylic pressure-sensitive adhesive. [6] An antistatic adhesive resin obtained by coating the pressure-sensitive adhesive composition according to any one of [4] to [5], wherein the surface resistance of the resin is 1.0 x 10 １０ An antistatic adhesive resin characterized by having a resistance of less than Ω.

[0013] The antistatic agent of the present invention has high resin compatibility and can exhibit sufficient antistatic properties even when added in a small amount. Therefore, when the antistatic agent of the present invention is used in a pressure-sensitive adhesive composition, it is possible to form an antistatic pressure-sensitive adhesive resin that has excellent moisture and heat resistance and transparency while maintaining adhesive strength and has low haze, and the antistatic agent can be used in surface protection films that protect the surfaces of optical components and electronic materials.

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

[0015] [Quaternary Ammonium Salt] The antistatic agent of the present invention comprises a quaternary ammonium salt represented by formula (1): This quaternary ammonium salt comprises a tetraalkylammonium cation and a bisoxalatoborate anion.

[0016] In formula (1), R １ ~R ４ are alkyl groups having 1 to 13 carbon atoms, which may be the same or different, and R １ ~R ４ The total number of carbon atoms in the alkyl group is 12 to 16. The alkyl group may be either linear or branched. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a cyclopropyl group, a butyl group, a s-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, and a tridecyl group.

[0017] Specific examples of the tetraalkylammonium cation represented by the formula (1) include tetrapropylammonium cation, tetrabutylammonium cation, trimethylnonylammonium cation, trimethyldecylammonium cation, trimethylundecylammonium cation, trimethyldodecylammonium cation, trimethyltridecylammonium cation, triethylhexylammonium cation, triethylheptylammonium cation, triethyloctylammonium cation, triethylnonylammonium cation, triethyldecylammonium cation, tripropylbutylammonium cation, tripropylpentylammonium cation, tripropylhexylammonium cation, tripropylheptylammonium cation, tributylmethylammonium cation, tributylethylammonium cation, tributylpropylammonium cation, tripentylmethylammonium cation, dimethyldipentylammonium cation, dimethyldihexylammonium cation, dimethyldiheptylammonium cation, dipropyldibutylammonium cation, Ammonium cation, dipropyldipentylammonium cation, dimethylethyloctylammonium cation, dimethylethylnonylammonium cation, dimethylethyldecylammonium cation, dimethylethylundecylammonium cation, dimethylethyldodecylammonium cation, dimethylpropylheptylammonium cation, dimethylpropyloctylammonium cation, dimethylpropylnonylammonium cation, dimethylpropyldecylammonium cation, dimethylpropylundecylammonium cation, dimethylbutylhexylammonium cation, dimethylbutylheptylammonium cation, dimethylbutyloctylammonium cation, dimethylbutylnonylammonium cation, dimethylbutyldecylammonium cation, dimethylpentylhexylammonium cation, dimethylpentylheptylammonium cation, dimethylpentyloctylammonium cation, dimethylpentylnonylammonium cation, dimethylhexylheptylammonium cation, dimethylhexyloctylammonium cation,diethylmethylheptylammonium cation, diethylmethyloctylammonium cation, diethylmethylnonylammonium cation, diethylmethyldecylammonium cation, diethylmethylundecylammonium cation, diethylpropylpentylammonium cation, diethylpropylhexylammonium cation, diethylpropylheptylammonium cation, diethylpropyloctylammonium cation, diethylpropylnonylammonium cation, dipropylmethylpentylammonium cation, dipropylmethylhexylammonium cation, dipropylmethylheptylammonium cation, dipropylmethyloctylammonium cation, dipropylmethylnonylammonium cation, dipropylethylbutylammonium cation, dipropylethylpentylammonium cation, dipropylethylhexylammonium cation, dipropylethylheptylammonium cation, dipropylethyloctylammonium cation, dipropylbutylpentylammonium cation, dipropylbutylhexylammonium cation, dibutylmethylpropylpentylammonium cation, dibutylmethylpentylammonium cation, dibutylmethylhexylammonium cation, dibutylmethylheptylammonium cation, dibutylethylpropylammonium cation, dibutylethylpentylammonium cation, dibutylethylhexylammonium cation, dibutylpropylpentylammonium cation, methylethylpropylhexylammonium cation, methylethylpropylheptylammonium cation, methylethylpropyloctylammonium cation, methylethylpropylnonylammonium cation, methylethylpropyldecylammonium cation, methylethylbutylpentylammonium cation, methylethylbutylhexylammonium cation, methylethylbutylheptylammonium cation, methylethylbutyloctylammonium cation, methylethylbutylnonylammonium cation, methylethylpentylhexylammonium cation, methylethylpentylheptylammonium cation, methylethylpentyloctylammonium cation,Examples of the tetraalkylammonium cation include methylethylhexylheptylammonium cation, methylpropylbutylpentylammonium cation, methylpropylbutylhexylammonium cation, methylpropylbutylheptylammonium cation, methylpropylbutyloctylammonium cation, methylpropylpentylhexylammonium cation, methylpropylpentylheptylammonium cation, methylbutylpentylhexylammonium cation, ethylpropylbutylpentylammonium cation, ethylpropylbutylhexylammonium cation, ethylpropylbutylheptylammonium cation, and ethylpropylpentylhexylammonium cation. Of these tetraalkylammonium cations, preferred are tetrapropylammonium cation, tetrabutylammonium cation, trimethylnonylammonium cation, trimethyldecylammonium cation, trimethyldodecylammonium cation, tributylmethylammonium cation, and dimethylhexyloctylammonium cation. In terms of the balance between antistatic performance and resin compatibility, and moist heat resistance, more preferred are tetrapropylammonium cation (wherein the total number of carbon atoms in the alkyl groups is 12) and tetrabutylammonium cation (wherein the total number of carbon atoms in the alkyl groups is 16).

[0018] In formula (1), the anion represents bisoxalatoborate.

[0019] For the antistatic agent of the present invention, among the onium salts represented by formula (1), it is preferable to use tetrabutylammonium bisoxalatoborate or tetrapropylammonium bisoxalatoborate.

[0020] The onium salt represented by the above formula (1) can be produced by a known method so as to have the above structure. Examples of such a method include the following method. The compound used in this reaction may be a commercially available product or one synthesized by a known method. [Production method of onium salt]

[0021] Specific examples of the tetraalkylammonium cation represented by the formula (2) include tetrapropylammonium cation, tetrabutylammonium cation, trimethylnonylammonium cation, trimethyldecylammonium cation, trimethyldodecylammonium cation, tributylmethylammonium cation, dimethylhexyloctylammonium cation, etc. Examples of halides that form counter anions of the above cations include chloride ions, bromide ions, and iodide ions.

[0022] Examples of the metal salt of formula (3) include lithium bis(oxalato)borate, sodium bis(oxalato)borate, potassium bis(oxalato)borate, etc. Examples of the alkali metals and transition metals that form counter cations of the above anions include lithium, sodium, potassium, silver, etc.

[0023] The amount of the compound of formula (3) used in the ion exchange reaction is usually 0.8 moles or more, preferably 0.9 to 1.8 moles, more preferably 1.0 to 1.2 moles, per mole of the compound of formula (2).

[0024] The ion exchange reaction is usually carried out in a solvent. There are no particular limitations on the solvent as long as it does not affect the reaction. Specific examples of the solvent include pure water, acetonitrile, ethyl acetate, benzene, toluene, xylene, diethyl ether, tetrahydrofuran, and 1,4-dioxane, with pure water and acetonitrile being preferred.

[0025] The order of mixing the formula (2), the formula (3), and the solvent is not particularly limited, and the formula (3) may be added after mixing the formula (2) and the solvent, or the formula (3) may be mixed with the solvent and then the formula (2) may be added.

[0026] The reaction temperature in the ion exchange reaction is usually 10°C or higher, preferably 10 to 60°C, and particularly preferably 15 to 50°C.

[0027] To isolate Formula (4) from the reaction solution after the reaction is complete, the solvent and the inorganic salt produced are removed from the reaction solution. If the inorganic salt precipitates in the resulting reaction solution, the reaction solution is filtered to remove the precipitated inorganic salt, and then Formula (4) is isolated by an appropriate combination of unit operations such as concentration, filtration, and extraction. The isolated Formula (4) can be used as an antistatic agent.

[0028] 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 combines a bisoxalatoborate anion with a tetraalkylammonium cation skeleton in which the total number of carbon atoms in the alkyl groups in the tetraalkylammonium cation is 12 to 16, has lower ionic conductivity than when a tetraalkylammonium cation skeleton in which the total number of carbon atoms in the alkyl groups in the tetraalkylammonium cation is greater than 12 to 16, and exhibits excellent compatibility with resins and hydrophobicity, thereby providing good antistatic performance, compared to when a tetraalkylammonium cation skeleton in which the total number of carbon atoms in the alkyl groups is less than 12 to 16 is selected.

[0029] [Adhesive composition and antistatic adhesive resin] By combining the antistatic agent of the present invention with an acrylic adhesive, an adhesive composition imparted with antistatic properties can be obtained. This adhesive composition imparted with antistatic properties becomes an antistatic adhesive resin by incorporating it. This antistatic adhesive resin has excellent antistatic properties, excellent transparency, and low haze. This antistatic adhesive resin also has improved moisture and heat resistance while maintaining adhesive strength. Specifically, the surface resistance of the antistatic adhesive resin formed from the adhesive composition is 5.0 × 10 10 Ω or less, more preferably 1.0 × 10 10The viscosity is Ω or less, the transparency is a transmittance of 90% or more, and the haze value is 2.0% or less, preferably 1.5% or less. Furthermore, the change in adhesive strength between before and after the addition of an antistatic agent is less than 10%, and when the antistatic adhesive resin is subjected to a moist heat resistance test, the change in haze between before and after the test is less than 10%. Surface resistance is measured with a resistivity meter, transmittance and haze with a haze meter, and adhesive strength with a tensile tester. The moist heat resistance test can be performed by measuring the haze value with a haze meter after exposure to constant temperature and humidity conditions. Therefore, the adhesive composition of the present invention contains at least the above-mentioned quaternary ammonium salt and an acrylic adhesive. The adhesive composition of the present invention also includes an adhesive ink prepared by dissolving the above-mentioned adhesive composition in a soluble organic solvent. The antistatic adhesive resin of the present invention also includes adhesive sheets and adhesive films formed by applying the above-mentioned adhesive ink to a substrate, as well as those peeled from the substrate. The antistatic adhesive resin of the present invention is used as what is usually called an adhesive layer.

[0030] The acrylic pressure-sensitive adhesive of the present invention preferably contains an acrylic polymer whose main component is an acrylate or methacrylate having an alkyl group having 1 to 14 carbon atoms. Specific 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.

[0031] The acrylic polymer 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.

[0032] 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.

[0033] 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.

[0034] Epoxy compounds are compounds having at least two epoxy groups in the molecule. Specific examples include bisphenol A epoxy resins, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, 1,6-hexanediol diglycidyl ether, and N,N-diglycidylaniline.

[0035] Aziridine compounds are compounds that have at least two three-membered ring skeletons, each consisting of one nitrogen atom and two carbon atoms, also known as ethyleneimines. 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.

[0036] 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.

[0037] 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 acrylic pressure-sensitive 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 pressure-sensitive 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 may cause peeling.

[0038] 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.

[0039] 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.

[0040] The alkylene oxide group-containing compound may be used alone or in combination of two or more. The blending amount 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. If the blending amount is less than 0.01 part by mass, bleeding may occur.

[0041] 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.

[0042] 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.

[0043] The amount of the quaternary ammonium salt 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 acrylic pressure-sensitive adhesive. By setting the amount in this range, a pressure-sensitive adhesive composition with even more excellent electrical properties can be obtained.

[0044] 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.

[0045] 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. These pressure-sensitive adhesive compositions or pressure-sensitive adhesive inks can be applied to substrates such as resin films or glass, and then dried as necessary to prepare pressure-sensitive adhesive sheets having a pressure-sensitive adhesive layer formed on the surface of these substrates. The thickness of the pressure-sensitive adhesive layer is preferably 3 to 100 μm, more preferably 5 to 50 μm.

[0046] [Adhesive Ink] Examples of organic solvents used in the adhesive ink as the 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. Among these, toluene, MEK, ethyl acetate, butyl acetate, and IPA are particularly preferred.

[0047] [Substrate] 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.

[0048] [Method for producing pressure-sensitive adhesive sheet] Examples of a method 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 150° C. or lower, from the viewpoint of promoting curing of the liquid film.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] [Antistatic Resin] As described above, the antistatic agent of the present invention can be combined with an acrylic adhesive to obtain a pressure-sensitive adhesive composition 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 acrylic adhesives, as well as synthetic resins such as polyethylene terephthalate, polypropylene, and polycarbonate, as well as various adhesives or release agents (silicone-based adhesives, urethane-based adhesives, rubber-based adhesives, silicone-based release agents, fluorine-based release agents, acrylic-based release agents, etc.). The performance of the antistatic resin of the present invention is similar to that of the adhesive layer (antistatic adhesive resin) described above.

[0053] 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 an acrylic adhesive, or a synthetic resin such as polyethylene terephthalate, polypropylene, or polycarbonate, or various adhesives or release agents (such as silicone adhesives, urethane adhesives, rubber adhesives, silicone release agents, fluorine-based release agents, or acrylic release agents), the antistatic resin can be obtained by mixing the resin with the acrylic adhesive. Furthermore, if an acrylic resin monomer is used as the resin raw material, the antistatic resin of the present invention can be obtained by adding a photopolymerization initiator to a solution containing the acrylic resin monomer and the antistatic agent of the present invention, and then applying the solution to the surface of the resin, and irradiating the resin with ultraviolet light.

[0054] 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.

[0055] [Preparation of Antistatic Agent] Tetrabutylammonium bisoxalatoborate was prepared as follows.

[0056] 16 g of tetrabutylammonium bromide and 15 g of acetonitrile were placed in a four-neck flask, and 10 g of lithium bis(oxalato)borate was added to the mixture, followed by stirring for 1 hour at 40° C. After removing the solvent by concentration, the mixture was washed with butyl acetate and pure water, and then concentrated again to obtain 20 g (yield 94%) of tetrabutylammonium bis(oxalato)borate (the total number of carbon atoms in the alkyl groups is 16).

[0057] Example 1 Preparation of adhesive ink Acrylic adhesive (2030U, manufactured by Soken Chemical & Engineering Co., Ltd., non-volatile content 15%): 40 g Curing agent (isocyanate compound, Y-75, manufactured by Soken Chemical & Engineering Co., Ltd., non-volatile content 75%): 0.32 g Antistatic agent (tetrabutylammonium bisoxalatoborate): 0.03 g The above composition was diluted with MEK to a non-volatile content concentration of 15 parts by mass to prepare an adhesive ink.

[0058] Example 2 An adhesive ink was prepared without changing the procedure of Example 1 except that 0.06 g of the antistatic agent was used instead of 0.03 g.

[0059] Example 3 An adhesive ink was prepared without changing the amount of antistatic agent used in Example 1, except that 0.12 g was used instead of 0.03 g.

[0060] Example 4 An adhesive ink was prepared without changing the amount of antistatic agent used in Example 1, except that 0.60 g was used instead of 0.03 g.

[0061] [Preparation of Antistatic Agent] Tetrapropylammonium bisoxalatoborate was prepared as follows.

[0062] 13 g of tetrapropylammonium bromide and 15 g of acetonitrile were placed in a four-neck flask, and 10 g of lithium bis(oxalato)borate was added to the mixture, followed by stirring for 1 hour at 40° C. After the solvent was removed by concentration, the mixture was washed with butyl acetate and pure water, and then concentrated again to obtain 17 g (yield 93%) of tetrapropylammonium bis(oxalato)borate (the total number of carbon atoms in the alkyl groups was 12).

[0063] Example 5 An adhesive ink was prepared without changing the process of Example 1 except that tetrapropylammonium bisoxalatoborate was used instead of the antistatic agent.

[0064] Example 6 An adhesive ink was prepared without changing the procedure of Example 5 except that 0.06 g of the antistatic agent was used instead of 0.03 g.

[0065] Example 7 An adhesive ink was prepared without changing the procedure of Example 5 except that 0.12 g of the antistatic agent was used instead of 0.03 g.

[0066] Example 8 An adhesive ink was prepared without changing the amount of antistatic agent used in Example 5, except that 0.60 g was used instead of 0.03 g.

[0067] [Preparation of Antistatic Agent] Tetraethylammonium bisoxalatoborate was prepared as follows.

[0068] 10 g of tetraethylammonium bromide and 15 g of acetonitrile were placed in a four-neck flask, and 10 g of lithium bis(oxalato)borate was added to the mixture, followed by stirring for 1 hour at 40° C. After removing the solvent by concentration, the mixture was washed with butyl acetate and pure water, and then concentrated again to obtain 13 g (yield 86%) of tetraethylammonium bis(oxalato)borate (the total number of carbon atoms in the alkyl groups is 8).

[0069] Comparative Example 1 An adhesive ink was prepared without changing the process of Example 1 except that tetraethylammonium bisoxalatoborate was used instead of the antistatic agent.

[0070] Comparative Example 2 An adhesive ink was prepared without changing the amount of the antistatic agent used in Comparative Example 1, except that 0.06 g was used instead of 0.03 g.

[0071] Comparative Example 3 An adhesive ink was prepared without changing the amount of the antistatic agent used in Comparative Example 1, except that 0.12 g was used instead of 0.03 g.

[0072] Comparative Example 4 An adhesive ink was prepared without changing the ingredients in Comparative Example 1 except that 0.60 g of the antistatic agent was used instead of 0.03 g.

[0073] [Preparation of Antistatic Agent] Trimethylhexadecylammonium bisoxalatoborate was prepared as follows.

[0074] 18 g of trimethylhexadecylammonium bromide and 15 g of acetonitrile were placed in a four-neck flask, and 10 g of lithium bis(oxalato)borate was added to the mixture, followed by stirring for 1 hour at 40° C. After the solvent was removed by concentration, the mixture was washed with ethyl acetate and pure water, and then concentrated again to obtain 22 g (yield 94%) of trimethylhexadecylammonium bis(oxalato)borate (the total number of carbon atoms in the alkyl groups was 19).

[0075] Comparative Example 5 An adhesive ink was prepared without changing the process of Example 1 except that trimethylhexadecylammonium bisoxalatoborate was used instead of the antistatic agent.

[0076] Comparative Example 6 An adhesive ink was prepared without changing the amount of the antistatic agent used in Comparative Example 5, except that 0.06 g was used instead of 0.03 g.

[0077] Comparative Example 7 An adhesive ink was prepared without changing the amount of the antistatic agent used in Comparative Example 5, except that 0.12 g was used instead of 0.03 g.

[0078] Comparative Example 8 An adhesive ink was prepared without changing the ingredients in Comparative Example 5 except that 0.60 g of the antistatic agent was used instead of 0.03 g.

[0079] [Preparation of Antistatic Agent] Trioctylmethylammonium bisoxalatoborate was prepared as follows.

[0080] 20 g of trioctylmethylammonium chloride and 15 g of acetonitrile were placed in a four-neck flask, and 10 g of lithium bis(oxalato)borate was added to the mixture, followed by stirring for 1 hour at 40° C. After the solvent was removed by concentration, the mixture was washed with butyl acetate and pure water, and then concentrated again to obtain 22 g (yield 87%) of trioctylmethylammonium bis(oxalato)borate (the total number of carbon atoms in the alkyl groups was 25).

[0081] Comparative Example 9 An adhesive ink was prepared without changing the process of Example 1 except that trioctylmethylammonium bisoxalatoborate was used instead of the antistatic agent.

[0082] Comparative Example 10 An adhesive ink was prepared without changing the amount of the antistatic agent used in Comparative Example 9, except that 0.06 g was used instead of 0.03 g.

[0083] Comparative Example 11 An adhesive ink was prepared without changing the amount of the antistatic agent used in Comparative Example 9, except that 0.12 g was used instead of 0.03 g.

[0084] Comparative Example 12 An adhesive ink was prepared without changing the ingredients of Comparative Example 9 except that 0.60 g of the antistatic agent was used instead of 0.03 g.

[0085] [Preparation of Antistatic Agent] Tetrabutylammonium dodecylbenzenesulfonate was prepared as follows.

[0086] 16 g of tetrabutylammonium bromide, 18 g of sodium dodecylbenzenesulfonate, and 15 g of pure water were placed in a four-neck flask and stirred for 15 hours at 60° C. After the solvent was removed by concentration, the mixture was washed with ethyl acetate and pure water, and then concentrated again to obtain 23 g of tetrabutylammonium dodecylbenzenesulfonate (yield 82%).

[0087] Comparative Example 13 An adhesive ink was prepared without changing the process of Example 1 except that tetrabutylammonium dodecylbenzenesulfonic acid was used instead of the antistatic agent.

[0088] Comparative Example 14 An adhesive ink was prepared without changing the amount of the antistatic agent used in Comparative Example 13, except that 0.06 g was used instead of 0.03 g.

[0089] Comparative Example 15 An adhesive ink was prepared without changing the antistatic agent used in Comparative Example 13 except that 0.12 g was used instead of 0.03 g.

[0090] Comparative Example 16 An adhesive ink was prepared without changing the antistatic agent used in Comparative Example 13, except that 0.60 g was used instead of 0.03 g.

[0091] [Preparation of Antistatic Agent] Tetrapropylammonium dodecylbenzenesulfonate was prepared as follows.

[0092] 13 g of tetrapropylammonium bromide, 18 g of sodium dodecylbenzenesulfonate, and 15 g of pure water were placed in a four-neck flask and stirred for 15 hours at 60° C. After the solvent was removed by concentration, the mixture was washed with ethyl acetate and pure water, and then concentrated again to obtain 20 g of tetrapropylammonium dodecylbenzenesulfonate (yield 80%).

[0093] Comparative Example 17 An adhesive ink was prepared without changing the process of Example 1 except that tetrapropylammonium dodecylbenzenesulfonic acid was used instead of the antistatic agent.

[0094] Comparative Example 18 An adhesive ink was prepared without changing the amount of the antistatic agent used in Comparative Example 17, except that 0.06 g was used instead of 0.03 g.

[0095] Comparative Example 19 An adhesive ink was prepared without changing the antistatic agent used in Comparative Example 17, except that 0.12 g was used instead of 0.03 g.

[0096] Comparative Example 20 An adhesive ink was prepared without changing the ingredients of Comparative Example 17 except that 0.60 g of the antistatic agent was used instead of 0.03 g.

[0097] [Coating Conditions] The adhesive ink was coated onto a PET film using a bar coater to a thickness of approximately 25 μm after drying, and then dried in a hot air dryer at 120° C. for 3 minutes to prepare a test piece (adhesive film).

[0098] [Measurement of Surface Resistivity] Using a Hirester UP (manufactured by Mitsubishi Chemical Analytech Corporation, product name "MCP-HT450"), a probe was pressed against the coated surface of the test piece at a temperature of 23±2°C, a humidity of 50±5% RH, and an applied voltage of 100 V, and the stable surface resistance value was measured after 30 seconds had elapsed.

[0099] [Measurement of Transmittance and Haze Value] The transmittance and haze of the adhesive layer side of the adhesive film from which the separator had been peeled off were measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH5000").

[0100] [Measurement of Adhesive Strength] A measurement sample (a 25 mm wide adhesive film pressed onto a SUS304 steel plate with a 2 kg roller) was peeled in a 180° direction at a peeling speed (300 mm / min) using a tensile tester (manufactured by Shimadzu Corporation, product name "AUTOGRAPH AGS-X 100 N"), and the measured peel strength was taken as adhesive strength. The adhesive strength was evaluated according to the following evaluation criteria using the rate of change in adhesive strength in the adhesive film before and after the addition of the antistatic agent. Furthermore, the test was conducted only on samples where the antistatic agent was added at 10% relative to the resin solids content.

[0101] Evaluation criteria: ◯: The rate of change in adhesive strength of the adhesive film before and after the addition of the antistatic agent is less than 10%. ×: The rate of change in adhesive strength of the adhesive film before and after the addition of the antistatic agent is 10% or more.

[0102] [Humidity and Heat Resistance Test] The haze of a measurement sample (a 25 mm wide adhesive film stored at 60°C and 80% RH for 500 hours) was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH5000") and evaluated according to the following evaluation criteria.

[0103] Evaluation criteria: ◯: The rate of change in haze value before and after the moist heat resistance test was less than 10%. ×: The rate of change in haze value before and after the moist heat resistance test was 10% or more.

[0104] The results of Examples 1 to 8 and Comparative Examples 1 to 20 are shown in Table 1.

[0105] As described above, the adhesive compositions of Examples 1 to 8 of the present invention have a surface resistance value (1×10) sufficient for providing an antistatic adhesive film (antistatic adhesive resin) even when added in a small amount of 10% or less relative to the resin solid content. 10 The film had a resistance of less than Ω, and further satisfied the resin compatibility criteria of a haze value of 1.5% or less and a transmittance of 90% or more. Furthermore, no problems were observed with the moist heat resistance. Furthermore, the adhesive strength remained almost unchanged from before addition, even when 10% of the antistatic agent was added. On the other hand, Comparative Examples 1 to 4 met the surface resistance criteria, but the moist heat resistance and adhesive strength changed significantly, resulting in bleedout. In Comparative Examples 5 to 12, the antistatic adhesive film (antistatic adhesive resin) met the haze, transmittance, and moist heat resistance criteria with the addition of a small amount of 1% or less relative to the resin solids, but the surface resistance was high. Therefore, the amount of antistatic agent added was increased to reduce the surface resistance, but the haze and transmittance performance decreased and the adhesive strength changed significantly. Furthermore, in Comparative Examples 13 to 20, the anion in Examples 1 to 8 was changed to dodecylbenzenesulfonic acid, but none of the criteria required for the antistatic performance-imparted adhesive film (antistatic adhesive resin) made from the intended antistatic performance-imparted adhesive composition were met.

[0106] In particular, comparing Examples 1-8 and Comparative Examples 1-12, which are both tetraalkylammonium bisoxalatoborate salt antistatic agents, it is believed that Comparative Examples 1-4, in which the total number of carbon atoms in the tetraalkylammonium is only 8, have poor hydrophobicity and therefore poor resin compatibility. When made into an antistatic adhesive film (antistatic adhesive resin), both the haze value and transmittance decreased, and adhesive strength and moist heat resistance properties significantly changed. In Comparative Examples 5-12, in which the total number of carbon atoms is 19 and 25, the increased molecular weight likely affected the electrical conductivity of the antistatic agent, resulting in high surface resistance when made into an antistatic adhesive film (antistatic adhesive resin). Therefore, specifying the total number of carbon atoms in the alkyl groups in the tetraalkylammonium cation to 12-16, including embodiments of the present invention, is believed to be effective in satisfying all criteria for surface resistance, resin compatibility, adhesive strength, and moist heat resistance.

[0107] The present invention can be used as a surface protection film for protecting the surface of an optical member.

Claims

1. An antistatic agent comprising a quaternary ammonium salt represented by formula (1): (In the formula, R １ ~R ４ may be the same or different and are alkyl groups having 1 to 13 carbon atoms, １ ~R ４ The total number of carbon atoms in the alkyl group is 12 to 16.

2. The antistatic agent according to claim 1, wherein the quaternary ammonium salt represented by formula (1) is tetrabutylammonium bisoxalatoborate or tetrapropylammonium bisoxalatoborate.

3. An antistatic resin comprising the antistatic agent according to claims 1 or 2 and a resin.

4. A pressure-sensitive adhesive composition comprising the antistatic agent according to claim 1 or 2 and an acrylic pressure-sensitive adhesive.

5. The adhesive composition according to claim 4, 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 adhesive.

6. A pressure-sensitive adhesive sheet containing the pressure-sensitive adhesive composition according to claim 4, having a surface resistance of 1.0 x 10 １０ An antistatic adhesive resin characterized by having a resistance of less than Ω.

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