Adhesive main agent and adhesive composition

Abstract

To provide: an adhesive main agent that has a suitably low viscosity when heated and has excellent handleability; and an adhesive composition using the same, which has excellent transparency, high adhesivity, and a low dielectric constant.SOLUTION: An adhesive main agent comprises a copolymer (A) that comprises, as constituent monomers, a long-chain alkyl (meth)acrylate (a1), a short-chain alkyl (meth)acrylate (a2), and a nitrogen atom-containing monomer (a3), where the (a1) has a C12-18 linear alkyl group, the (a2) has a C1-4 linear alkyl group and, in the constituent monomers of the copolymer (A), there are included, as the (a1), at least two components having linear alkyl groups with different carbon numbers.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an adhesive base and an adhesive composition.

Background Art

[0002] Conventionally, natural rubber-based adhesives or acrylic-based adhesives are known as adhesives for adhesive tapes or adhesive sheets. As acrylic-based adhesives, (co)polymers having a specific alkyl (meth)acrylate as an essential constituent monomer have been developed (for example, Patent Document 1). In recent years, in information device terminals such as smartphones, since high-speed data transmission has been demanded, in order to suppress transmission delay, a reduction in the dielectric constant of the adhesive has been demanded. On the other hand, since an adhesive is used for a member that requires visibility such as a display of a smartphone or the like, transparency of the adhesive is required. However, even the technique of Patent Document 1 does not achieve both a low dielectric constant and transparency and have sufficient adhesiveness.

[0003] In recent years, for the purpose of suppressing the use of solvents for environmental protection, studies on hot melt adhesives have been advanced (for example, Patent Document 2). A hot melt adhesive is used by heating an adhesive base containing a (meth)acrylate polymer to soften or melt it, adding a photoinitiator, applying it to a base material or the like, and irradiating it with light or the like. However, when the adhesive base is heated, there is a problem that the viscosity is high and the handleability is poor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide an adhesive base resin having a viscosity that is appropriately low and excellent handleability when heated (for example, at 150°C), and an adhesive composition that contains the same and has excellent transparency, high adhesiveness, and a low dielectric constant.

Means for Solving the Problems

[0006] As a result of intensive studies to achieve the above object, the present inventors have reached the present invention. That is, the present invention is an adhesive base resin containing a copolymer (A) containing a long-chain alkyl (meth)acrylate (a1), a short-chain alkyl (meth)acrylate (a2), and a nitrogen atom-containing monomer (a3) as constituent monomers, wherein the (a1) has a linear alkyl group having 12 to 18 carbon atoms, the (a2) has a linear alkyl group having 1 to 4 carbon atoms, the constituent monomers of the copolymer (A) contain at least two components having different carbon numbers of the linear alkyl group as the (a1), and the weight ratio (a11 / a12) is 1.5 to 3.0 in the combination of the weight of the component (a11) having the largest content weight as the (a1) in the constituent monomers of the copolymer (A) and the weight of any one component (a12) among the components having different carbon numbers from the carbon number of the linear alkyl group of the (a11); an adhesive composition containing the adhesive base resin and a photopolymerization initiator (D).

Effects of the Invention

[0007] The adhesive base resin of the present invention has a viscosity that is appropriately low and excellent handleability when heated (for example, at 150°C), and the adhesive composition containing the adhesive base resin of the present invention has excellent transparency, high adhesiveness (particularly adhesiveness on a curved surface), and a low dielectric constant.

Modes for Carrying Out the Invention

[0008] The main adhesive agent of the present invention is a main adhesive agent containing a copolymer (A) having a long-chain alkyl (meth)acrylate (a1), a short-chain alkyl (meth)acrylate (a2), and a nitrogen atom-containing monomer (a3) as constituent monomers, wherein (a1) has a linear alkyl group with 12 to 18 carbon atoms, wherein (a2) has a linear alkyl group with 1 to 4 carbon atoms, the constituent monomers of the copolymer (A) contain at least two components with different carbon numbers of the linear alkyl group as (a1), and in the combination of the weight of the component (a11) having the largest content weight as (a1) in the constituent monomers of the copolymer (A) and the weight of any one component (a12) among the components with different carbon numbers from the carbon number of the linear alkyl group possessed by (a11), the weight ratio (a11 / a12) is 1.5 to 3.0. In the present invention, the main adhesive agent is one that functions as an adhesive by undergoing a crosslinking reaction with a photopolymerization initiator (D).

[0009] <Copolymer (A)> In the present invention, the copolymer (A) contains a long-chain alkyl (meth)acrylate (a1) having a linear alkyl group with 12 to 18 carbon atoms, a short-chain alkyl (meth)acrylate (a2) having a linear alkyl group with 1 to 4 carbon atoms, and a nitrogen atom-containing monomer (a3) as constituent monomers, and the constituent monomers of the copolymer (A) contain at least two components with different carbon numbers of the linear alkyl group as (a1). When a monomer having a long straight-chain alkyl group with 12 to 18 carbon atoms is used as a constituent monomer of the copolymer (A), the elastic modulus of the copolymer (A) increases, and the adhesive composition containing the same tends to have good holding power and adhesiveness on a curved surface. However, the crystallinity of the copolymer (A) increases, and the handleability of the adhesive base and the transparency of the adhesive composition tend to decrease. In the present invention, by using monomers having carbon chains of different lengths as the long straight-chain alkyl group in a specific weight ratio, it has been found that high adhesiveness of the adhesive composition, handleability of the adhesive base, and transparency of the adhesive composition can be improved. Furthermore, in addition to two or more kinds of the long-chain alkyl (meth)acrylate (a1), by using a short-chain alkyl (meth)acrylate (a2) and a nitrogen atom-containing monomer (a3) in combination, it has been found that high adhesiveness can be exhibited particularly on a curved surface. In the present invention, “(meth)acrylate” means “acrylate and / or methacrylate”.

[0010] The long-chain alkyl (meth)acrylate (a1) has a straight-chain alkyl group with 12 to 18 carbon atoms. Examples thereof include n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, n-pentadecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-heptadecyl (meth)acrylate, and n-octadecyl (meth)acrylate.

[0011] In the present invention, the constituent monomer of the copolymer (A) contains at least two components having different carbon numbers of the straight-chain alkyl group as (a1). As the combination of (a1) (the combination of the component (a11) having the largest content weight and the component (a12) other than (a11)), from the viewpoint of dielectric constant, it is preferable to combine those having a carbon number difference of 2 to 4 in the straight-chain alkyl group, and more preferably, the combination of n-hexadecyl (meth)acrylate and n-octadecyl (meth)acrylate is preferable.

[0012] Examples of the short-chain alkyl (meth)acrylate (a2) include those having a linear alkyl group with 1 to 4 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and n-butyl (meth)acrylate. (a2) is preferably at least one selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, and n-butyl (meth)acrylate, more preferably at least one selected from the group consisting of methyl acrylate, ethyl acrylate, and n-butyl acrylate, and particularly preferably methyl acrylate, from the viewpoints of the handleability of the pressure-sensitive adhesive main agent, the adhesive strength, and the adhesiveness to a curved surface. (a2) may be used alone or in combination of two or more.

[0013] Examples of the nitrogen atom-containing monomer (a3) include (meth)acrylamide (a31), N-alkyl (meth)acrylamide (a32) having an alkyl group with 1 to 3 carbon atoms, N,N-dialkyl (meth)acrylamide (a33) having two alkyl groups each with 1 to 3 carbon atoms, N-vinyl monomer (a34) which is a nitrogen-containing heterocyclic compound having a vinyl group, and N-(meth)acryloyl monomer (a35). (a3) may be used alone or in combination of two or more. Examples of the N-alkyl (meth)acrylamide (a32) having an alkyl group with 1 to 3 carbon atoms include N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, and N-propyl (meth)acrylamide. Examples of the N,N-dialkyl (meth)acrylamide (a33) having two alkyl groups each with 1 to 3 carbon atoms include N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, and N,N-dipropyl (meth)acrylamide. Examples of the N-vinyl monomer (a34), which is a nitrogen-containing heterocyclic compound having a vinyl group, include N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N-vinyl-2-pyrrolidone, N-vinylimidazole, 1-vinylimidazole, 4-vinylpyridine, 2-vinylpyridine, 2-vinylpyrazine, and N-vinyl-2-pyrrolidone. Examples of the N-(meth)acryloyl monomer (a35) include 4-(meth)acryloylmorpholine, N-(meth)acryloylpyrrolidone, N-(meth)acryloylpiperidine, and N-(meth)acryloylpyrrolidine. (a3) is preferably at least one selected from the group consisting of (a33), (a34), and (a35), and more preferably at least one selected from the group consisting of N,N-dimethylacrylamide, 4-acryloylmorpholine, and N-vinyl-2-pyrrolidone, from the viewpoints of the handleability of the pressure-sensitive adhesive main agent, the adhesive strength, and the adhesiveness to a curved surface.

[0014] In the present invention, the copolymer (A) contains a long-chain alkyl (meth)acrylate (a1) having a linear alkyl group with 12 to 18 carbon atoms, a short-chain alkyl (meth)acrylate (a2) having a linear alkyl group with 1 to 4 carbon atoms, and a nitrogen atom-containing monomer (a3) as constituent monomers, but may contain constituent monomers other than (a1), (a2), and (a3). Examples thereof include a branched alkyl (meth)acrylate (a4) having a branched alkyl group with 3 to 18 carbon atoms, a monomer (a5) having a carboxyl group, and other monomers (a6). (a4), (a5), and (a6) may each be used alone or in combination of two or more.

[0015] Examples of the branched alkyl (meth)acrylate (a4) having a branched alkyl group with 3 to 18 carbon atoms include those having a branched alkyl group with 3 to 18 carbon atoms, such as isopropyl (meth)acrylate, isobutyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, isododecyl (meth)acrylate, isotridecyl (meth)acrylate, isotetradecyl (meth)acrylate, isopentadecyl (meth)acrylate, isohexadecyl (meth)acrylate, isoheptadecyl (meth)acrylate, isooctadecyl (meth)acrylate, and the like. From the viewpoint of handleability, (a4) is preferably isobutyl (meth)acrylate, neopentyl (meth)acrylate, or 2-ethylhexyl (meth)acrylate, and more preferably 2-ethylhexyl (meth)acrylate.

[0016] Examples of the monomer (a5) having a carboxyl group include monobasic acids such as (meth)acrylic acid and crotonic acid, polybasic acids such as maleic acid, itaconic acid, and fumaric acid, anhydrides of the above polybasic acids, and monoalkyl esters of the above polybasic acids. From the viewpoint of adhesiveness, (a5) is preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic anhydride, and itaconic acid, and more preferably acrylic acid.

[0017] Examples of the other monomer (a6) include vinyl esters (a61) and monomers having a hydroxyl group (a62). Examples of (a61) include vinyl acetate, vinyl propionate, and vinyl butyrate. Examples of (a62) include hydroxyalkyl (meth)acrylates (a621) having a hydroxyalkyl group with 2 to 8 carbon atoms and mono (meth)acrylate esters (a622) of polyalkylene glycols having an alkylene group with 2 to 8 carbon atoms. Examples of (a621) include 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and the like. Examples of (a622) include polyethylene glycol mono (meth)acrylate and the like. From the viewpoint of adhesiveness, (a6) is preferably (a62), more preferably 2-hydroxyethyl (meth)acrylate, and particularly preferably 2-hydroxyethyl acrylate.

[0018] From the viewpoint of dielectric constant, the weight ratio of the long-chain alkyl (meth)acrylate (a1) in the constituent monomers of the copolymer (A) is preferably 35 to 75% by weight, more preferably 45 to 65% by weight, based on the total weight of the constituent monomers. From the viewpoints of handleability of the main adhesive agent, adhesive strength, and adhesion to a curved surface, the weight ratio of the short-chain alkyl (meth)acrylate (a2) in the constituent monomers of the copolymer (A) is preferably 15 to 55% by weight, more preferably 20 to 40% by weight, based on the total weight of the constituent monomers. From the viewpoints of handleability of the main adhesive agent, adhesive strength, and adhesion to a curved surface, the weight ratio of the nitrogen atom-containing monomer (a3) in the constituent monomers of the copolymer (A) is preferably 3 to 20% by weight, more preferably 5 to 15% by weight, based on the total weight of the constituent monomers. From the viewpoint of the balance between adhesiveness and dielectric constant, the total weight ratio of (a1), (a2), and (a3) in the constituent monomers of the copolymer (A) is preferably 70 to 100% by weight, more preferably 80 to 95% by weight, based on the total weight of the constituent monomers.

[0019] From the viewpoint of the balance between adhesiveness and handleability, the weight ratio of the branched alkyl (meth)acrylate (a4) having a branched alkyl group with 3 to 18 carbon atoms in the constituent monomers of the copolymer (A) is preferably 0 to 30% by weight, more preferably 5 to 15% by weight, based on the total weight of the constituent monomers. From the perspective of corrosiveness, the weight ratio of the monomer (a5) having a carboxyl group in the constituent monomers of the copolymer (A) is preferably 0 to 0.5% by weight, more preferably 0 to 0.3% by weight, based on the total weight of the constituent monomers. From the perspective of adhesiveness, the weight ratio of the other monomer (a6) in the constituent monomers of the copolymer (A) is preferably 0 to 5% by weight, more preferably 0 to 3% by weight, based on the total weight of the constituent monomers. From the perspective of adhesiveness, the total weight ratio of (a4), (a5) and (a6) in the constituent monomers of the copolymer (A) is preferably 0 to 30% by weight, more preferably 5 to 20% by weight, based on the total weight of the constituent monomers.

[0020] In the present invention, at least two components having different carbon numbers of linear alkyl groups are contained as the component (a1) in the constituent monomers of the copolymer (A). In the combination of the weight of the component (a11) having the largest content weight as the component (a1) in the constituent monomers of the copolymer (A) and the weight of any one component (a12) among the components having different carbon numbers from the carbon number of the linear alkyl group of the (a11), the weight ratio (a11 / a12) is 1.5 to 3.0. When the weight ratio (a11 / a12) is less than 1.5 or exceeds 3.0, the transparency deteriorates. From the perspective of transparency, the weight ratio (a11 / a12) is preferably 1.8 to 2.7.

[0021] In the present invention, the carboxyl group concentration of the copolymer (A) is preferably 0.08 mol / kg or less, more preferably 0.05 mol / kg or less, and particularly preferably 0.03 mol / kg or less. When the carboxyl group concentration of the copolymer (A) is 0.08 mol / kg or less, the metal material tends to be less likely to corrode. The carboxyl group concentration of the copolymer (A) may be 0 mol / kg, that is, the carboxyl group concentration of the copolymer (A) is 0 mol / kg or more. The carboxyl group concentration of the copolymer (A) is the number of moles of carboxyl groups contained in the copolymer (A) per unit weight of the copolymer (A). The carboxyl group concentration can be calculated, for example, from the result of measuring the acid value (KOH mg / g) of the copolymer (A) according to JIS K0070. The carboxyl group concentration of the copolymer (A) can be adjusted, for example, by selecting the type and adjusting the weight ratio of the (a5) component in the constituent monomers of the copolymer (A).

[0022] In the present invention, the hydroxyl group concentration of the copolymer (A) is preferably 0.05 mol / kg or less, more preferably 0.03 mol / kg or less. When the hydroxyl group concentration of the copolymer (A) is 0.05 mol / kg or less, the heat resistance is high and the viscosity is less likely to increase during high-temperature coating. The hydroxyl group concentration of the copolymer (A) may be 0 mol / kg, that is, the hydroxyl group concentration of the copolymer (A) is 0 mol / kg or more. The hydroxyl group concentration of the copolymer (A) is the number of moles of hydroxyl groups contained in the copolymer (A) per unit weight of the copolymer (A). This hydroxyl group concentration can be calculated from the result of measuring the hydroxyl value (KOH mg / g) of the copolymer (A) according to JIS K0070. The hydroxyl group concentration of the copolymer (A) can be adjusted, for example, by selecting the type and adjusting the weight ratio of the (a62) component in the constituent monomers of the copolymer (A).

[0023] The weight average molecular weight (polystyrene conversion) of the copolymer (A) determined by gel permeation chromatography (GPC) is preferably 100,000 to 500,000, more preferably 150,000 to 400,000, still more preferably 200,000 to 400,000, from the viewpoints of the handleability of the pressure-sensitive adhesive main agent, the improvement of the adhesiveness of the pressure-sensitive adhesive composition, and the improvement of the coatability. The measurement conditions for gel permeation chromatography (GPC) in this embodiment are as follows. - Apparatus: "HLC-8120GPC" [manufactured by Tosoh Corporation]. - Columns: "Guardcolumn HXL-H" (1 piece) and "TSKgel GMHXL" (2 pieces) [both manufactured by Tosoh Corporation]. - Sample solution: 0.25 wt% tetrahydrofuran solution. - Solution injection volume: 100 μl. - Flow rate: 1 ml / min. - Measurement temperature: 40°C. - Detection device: Refractive index detector. - Reference substance: Standard polystyrene.

[0024] The glass transition temperature (Tg) of the copolymer (A) is preferably -15°C or higher and 10°C or lower, more preferably -10°C or higher and 5°C or lower, from the viewpoints of the handleability of the pressure-sensitive adhesive base resin, the improvement of the adhesive strength of the pressure-sensitive adhesive composition, and the improvement of the coatability. The above glass transition temperature (Tg) is the temperature indicating the peak value of the loss coefficient (tanδ) obtained by measuring the copolymer (A) under the following conditions using a viscoelasticity measuring device [for example, model number MCR-302, manufactured by Anton Paar]. - Fixture: φ8 mm parallel plate. - Sample thickness: 1 mm. - Strain: 1%. - Frequency: 1 Hz. - Heating rate: 5°C / min. - Temperature range: From -50°C to 180°C. Also, the glass transition temperature (Tg) of the copolymer (A) can be appropriately adjusted by selecting the types of the respective monomers in the constituent monomers of the copolymer (A) and adjusting the weight ratio. That is, for example, among the long-chain alkyl (meth)acrylates (a1), those having an alkyl group with 12 carbon atoms, the branched alkyl (meth)acrylates (a4) having a branched alkyl group with 3 to 18 carbon atoms, and n-butyl acrylate each tend to have a low Tg. Also, among the long-chain alkyl (meth)acrylates (a1), those having an alkyl group with 13 or more carbon atoms, methyl (meth)acrylate, and the nitrogen atom-containing monomer (a3) each tend to have a high Tg. Furthermore, methacrylate monomers tend to have a higher Tg than acrylate monomers.

[0025] The copolymer (A) can be synthesized by polymerizing the constituent monomers by a known polymerization method, such as bulk polymerization, solution polymerization, emulsion polymerization, or suspension polymerization. In this case, in the presence of a known polymerization initiator, such as an azo-based polymerization initiator like azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), azobisisovaleronitrile, or a peroxide-based polymerization initiator like benzoyl peroxide, di-t-butyl peroxide, lauryl peroxide, the constituent monomers can be polymerized.

[0026] Among the above polymerization methods, solution polymerization in which the constituent monomer is polymerized in the presence of a solvent (S) is preferred. Examples of the solvent (S) include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; halogenated hydrocarbons such as dichloromethane, trichloroethane, trichloroethylene, tetrachloroethylene, and dichloropropane; alcohols such as methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol, and diacetone alcohol; ethers such as diethyl ether, diisopropyl ether, dioxane, and tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, and cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, and ethyl butyrate; and polyols and their derivatives such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and propylene glycol monomethyl ether acetate. By this solution polymerization, a mixture of the solvent (S) and the copolymer (A) is obtained. The solvent (S) and the copolymer (A) in this mixture can be separated to obtain only the copolymer (A). Further, the mixture of the solvent (S) and the copolymer (A) can be used as it is as the main component of the adhesive described later. Also, the main component of the adhesive can be prepared by adjusting the content ratio of the solvent (S) in the mixture as necessary and adding appropriate additives to the mixture as necessary.

[0027] <Main component of the adhesive> The main component of the adhesive of the present invention contains the copolymer (A). The main component of the adhesive of the present invention may contain only the copolymer (A), or may contain the solvent (S), inorganic sulfate (T1), aliphatic alcohol having 12 to 18 carbon atoms (T2), antioxidant (T3), and other additives (T4). These may be used alone or in combination of two or more.

[0028] When containing a solvent (S), from the viewpoint of handling in the case of a hot melt adhesive, it is preferably 30% by weight or less, more preferably 2% by weight or less, based on the weight of the main adhesive component.

[0029] It is preferable that the main adhesive component contains an inorganic sulfate (T1) because it can suppress coloring reduction during the production of the main adhesive component and the increase in coloring over time during heating. Examples of the inorganic sulfate (T1) include sulfates such as sodium sulfate, potassium sulfate, calcium sulfate, and barium sulfate. From the viewpoint of coloring reduction, sodium sulfate is preferable as the inorganic sulfate (T1). When containing an inorganic sulfate (T1), from the viewpoint of the balance between coloring reduction and transparency, it is preferably 0.001 to 0.03% by weight, more preferably 0.002 to 0.02% by weight, based on the weight of the main adhesive component. The amount of the inorganic sulfate can be determined by measuring the sulfur content under the following measurement conditions by X-ray fluorescence analysis. <Measurement Conditions> Apparatus: Fully automatic wavelength dispersive X-ray fluorescence analyzer [「Axios」, manufactured by Spectris Co., Ltd.] X-ray excitation conditions: Voltage 50 kV, current 40 mA Measurement chamber atmosphere: Helium

[0030] It is preferable that the main adhesive component contains an aliphatic alcohol (T2) having 12 to 18 carbon atoms because it has the effects of improving the heat resistance of the main adhesive component (suppressing the increase in molecular weight during heating) and improving the appearance of the adhesive sheet. Examples of the aliphatic alcohol (T2) having 12 to 18 carbon atoms include lauryl alcohol, tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol (also referred to as n-hexadecyl alcohol), palmitoleyl alcohol, heptadecanol, stearyl alcohol (also referred to as n-octadecyl alcohol), isostearyl alcohol, oleyl alcohol, linoleyl alcohol, and the like. (T2) is preferably a linear aliphatic alcohol having 12 to 18 carbon atoms from the viewpoints of heat resistance and appearance, more preferably a linear saturated aliphatic alcohol having 14 to 18 carbon atoms, and particularly preferably cetyl alcohol and stearyl alcohol. Further, it is preferable to contain two kinds of aliphatic alcohols having different carbon number differences, and more preferably to contain two kinds of aliphatic alcohols having a carbon number difference of 2 to 4. When containing an aliphatic alcohol (T2) having 12 to 18 carbon atoms, from the viewpoints of heat resistance and appearance, 0.01 to 1.5% by weight is preferable, and more preferably 0.02 to 1.0% by weight based on the weight of the main component of the adhesive.

[0031] In the main component of the adhesive of the present invention, it is preferable to contain an antioxidant (T3). By containing the antioxidant (T3), the generation of minute crosslinked products in the cured product of the adhesive composition can be further suppressed, and the coloring of the cured product and the adhesive sheet at high temperatures can be suppressed, which is preferable. Examples of the antioxidant (T3) in the present invention include hindered phenol antioxidants, sulfur antioxidants, phosphorus antioxidants, lactone antioxidants, amine antioxidants, and the like. Examples of the hindered phenol antioxidant include tris(2,4-di-tert-butylphenyl)phosphite, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, 2,6-di-t-butyl-p-cresol, 2,2'-methylenebis(4-methyl-6-t-butylphenol), triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], and octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate. Examples of the sulfur antioxidant include dilauryl 3,3'-thiodipropionate and distearyl 3,3'-thiodipropionate. The phosphorus-based antioxidant contains, for example, an organic phosphite which may have a halogen. Examples of the phosphorus-based antioxidant include triphenyl phosphite, triisodecyl phosphite, tris(2,4-di-t-butylphenyl) phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl) octyl phosphite, and their halo-substituted products. Examples of the lactone-based antioxidant include the reaction product of 5,7-di-t-butyl-3-hydroxybenzofuran-2(3H)-one and o-xylene. The amine-based antioxidant contains, for example, a hindered aromatic amine. Examples of the amine-based antioxidant include octyldiphenylamine, N-n-butyl-p-aminophenol, and N,N-diisopropyl-p-phenylenediamine.

[0032] From the viewpoints of suppressing the generation of crosslinked products and suppressing coloring, the antioxidant (T3) is preferably at least one selected from the group consisting of hindered phenol-based antioxidants, phosphorus-based antioxidants, and lactone-based antioxidants. More preferably, it is at least one selected from the group consisting of a hindered phenol-based antioxidant having a molecular weight of 700 or more and 2000 or less and a phosphorus-based antioxidant having a molecular weight of 700 or more and 2000 or less. Particularly preferably, it is a phosphorus-based antioxidant having a molecular weight of 700 or more and 2000 or less. Most preferably, they are tris(2,4-di-tert-butylphenyl) phosphite and 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane.

[0033] When the main component of the adhesive in the present invention contains the antioxidant (T3), the weight ratio of the copolymer (A) to the antioxidant (T3) [copolymer (A): antioxidant (T3)] is preferably 100:0.001 to 100:3, more preferably 100:0.005 to 100:1, and particularly preferably 100:0.01 to 100:0.5 from the viewpoints of suppressing the generation of crosslinked products and preventing the coloring of the adhesive film.

[0034] When containing the antioxidant (T3), from the viewpoint of preventing the coloring of the pressure-sensitive adhesive composition and the pressure-sensitive adhesive film, 0.05 to 5% by weight is preferable, and more preferably 0.1 to 1.0% by weight, based on the weight of the pressure-sensitive adhesive main agent.

[0035] Examples of the other additives (T4) include tackifier (N) such as terpene resin and rosin resin, plasticizer, filler, pigment, and ultraviolet absorber. When containing the other additives (T4), from the viewpoint of tackiness, 20% by weight or less is preferable, and more preferably 10% by weight or less, based on the weight of the pressure-sensitive adhesive main agent.

[0036] The pressure-sensitive adhesive main agent of the present invention can be used, for example, as the pressure-sensitive adhesive main agent of a hot melt type pressure-sensitive adhesive. Since the viscosity when heated (for example, 150 ° C) is appropriately low, it is heated (for example, 70 to 170 ° C) to be softened or melted, and the photoinitiator (D) described below, if necessary, a polyfunctional (meth) acryloyl monomer (C) and other additives are allowed to coexist to form a pressure-sensitive adhesive composition, which is then applied to a substrate and further cured with active energy rays for use.

[0037] <Pressure-sensitive adhesive composition> The pressure-sensitive adhesive composition of the present invention contains the pressure-sensitive adhesive main agent and a photoinitiator (D). One kind of (D) may be used, or two or more kinds may be used in combination. In the present invention, "light" means active energy rays, and "active energy rays" means those having energy quanta among electromagnetic waves or charged particle beams, and examples include ultraviolet rays, electron beams, visible light, X-rays, ion beams, etc. Among them, from the viewpoint of versatility, ultraviolet rays or electron beams are preferable, and ultraviolet rays are particularly preferable.

[0038] In the present invention, the photoinitiator (D) includes those capable of generating radicals by extracting hydrogen from other molecules such as the copolymer (A) upon irradiation with active energy rays, and causing a crosslinking reaction of the copolymer (A) in the main component of the pressure-sensitive adhesive. Examples thereof include hydrogen abstraction type photoinitiators such as methyl benzoylformate, 4,4'-bis(diethylamino)benzophenone, benzophenone, and 4-methylbenzophenone. From the viewpoint of adhesiveness, the photoinitiator (D) is preferably a hydrogen abstraction type photoinitiator.

[0039] Commercially available products of such hydrogen abstraction type photoinitiators include Omnirad MBF (former Irgacure MBF) (methyl benzoylformate, a photoinitiator manufactured by IGM Resins B.V.), SB-PI 701 (4,4'-bis(diethylamino)benzophenone, a photoinitiator manufactured by Sanyo Trading Co., Ltd.), SB-PI 710 (benzophenone, a photoinitiator manufactured by Sanyo Trading Co., Ltd.), SB-PI 712 (4-methylbenzophenone, a photoinitiator manufactured by Sanyo Trading Co., Ltd.), and the like.

[0040] In the present invention, the pressure-sensitive adhesive composition may contain a polyfunctional (meth)acryloyl monomer (C) for the purpose of adjusting the adhesive strength. One kind of (C) may be used, or two or more kinds may be used in combination. <Polyfunctional (meth)acryloyl monomer (C)> In the present invention, the polyfunctional (meth)acryloyl monomer (C) is a compound having a plurality of (meth)acryloyl groups in the molecule. The (meth)acryloyl group means one or both of an acryloyl group and a methacryloyl group. Examples of (C) include bifunctional (meth)acryloyl monomer (C1), trifunctional (meth)acryloyl monomer (C2), tetrafunctional (meth)acryloyl monomer (C3), and pentafunctional or higher (meth)acryloyl monomer (C4).

[0041] The bifunctional (meth)acryloyl monomer (C1) includes those having two (meth)acryloyl groups in the molecule. (C1) includes, for example, an esterification product (C11) of 1 mol of a compound having 2 to 20 carbon atoms and two or more hydroxyl groups and 2 mol of (meth)acrylic acid; a compound (C12) having a structure of an esterification product obtained by reacting 1 mol of an alkylene oxide adduct of a compound having 2 to 20 carbon atoms and two or more hydroxyl groups with 2 mol of (meth)acrylic acid; and a compound (C13) having a structure of an esterification product obtained by reacting 1 mol of a lactone adduct of a compound having 2 to 20 carbon atoms and two or more hydroxyl groups with 2 mol of (meth)acrylic acid, etc. are mentioned.

[0042] Regarding each of the compound (C11), the compound (C12), and the compound (C13), the compound having 2 to 20 carbon atoms and two or more hydroxyl groups includes, for example, a chain aliphatic alcohol having 2 to 20 carbon atoms, an alicyclic alcohol having 3 to 20 carbon atoms, and an aromatic hydroxyl group-containing compound having 6 to 15 carbon atoms, etc.

[0043] Examples of the chain aliphatic alcohol having 2 to 20 carbon atoms include chain aliphatic dihydric alcohols having 2 to 20 carbon atoms such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, dodecanediol, tetradecanediol, neopentyl glycol, and 2,2-diethyl-1,3-propanediol; chain aliphatic trihydric alcohols having 3 to 20 carbon atoms such as glycerin, trimethylolethane, and trimethylolpropane; and chain aliphatic 4- to 8-valent alcohols having 5 to 20 carbon atoms such as pentaerythritol, ditrimethylolpropane, sorbitol, mannitol, sorbitan, diglycerin, and dipentaerythritol, etc.

[0044] The alicyclic alcohols having 3 to 20 carbon atoms include, for example, dihydric alcohols such as 1,3 - cyclopentanediol, 1,4 - cyclohexanediol, 1,4 - cyclohexanedimethanol, 1,4 - cycloheptanediol, and 2,2 - bis(4 - hydroxycyclohexyl)propane; and trihydric alcohols such as 1,3,5 - cyclohexanetriol and the like.

[0045] The aromatic - hydroxyl - group - containing compounds having 6 to 15 carbon atoms include, for example, pyrogallol, catechol, resorcinol, hydroquinone, dihydroxynaphthalene, bisphenol A, bisphenol F, bisphenol S, and 1,3,5 - triazine - 2,4,6 - triol and the like.

[0046] Regarding compound (C12), the alkylene oxide is preferably an alkylene oxide having 2 to 4 carbon atoms. More specifically, for example, ethylene oxide (hereinafter, "ethylene oxide" may be referred to as EO), 1,2 - propylene oxide (hereinafter, "1,2 - propylene oxide" may be referred to as PO), 1,3 - propylene oxide, 1,2 - butylene oxide, 1,3 - butylene oxide, 1,4 - butylene oxide, and 2,3 - butylene oxide and the like can be mentioned. From the viewpoint of adhesiveness, the alkylene oxide preferably contains at least one of EO and PO, and more preferably contains PO. Further, in compound (C12), the alkylene oxide is preferably EO and / or PO from the viewpoint of adhesiveness, and more preferably PO.

[0047] Regarding compound (C12), the number of moles of alkylene oxide added per mole in the alkylene oxide adduct of a compound having 2 to 20 carbon atoms and having two or more hydroxyl groups is preferably 1 mole or more and 40 moles or less.

[0048] Regarding the compound (C13), the lactone contains, for example, lactones having 2 to 12 carbon atoms. More specifically, examples include acetolactone, propiolactone, butyrolactone, valerolactone, caprolactone, laurolactone, and the like.

[0049] Regarding the compound (C13), the number of moles of lactone added per mole in the lactone adduct of a compound having 2 to 20 carbon atoms and two or more hydroxyl groups is preferably 1 mole or more and 15 moles or less.

[0050] Examples of (C1) include 1,6 - hexanediol di(meth)acrylate, 1,10 - decanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 2,4 - dimethyl - 1,5 - pentanediol di(meth)acrylate, butylethylpropanediol di(meth)acrylate, di(meth)acrylate of a compound obtained by adding an alkylene oxide having 2 to 4 carbon atoms to cyclohexanemethanol, polypropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, 2 - ethyl - 2 - butyl - butanediol di(meth)acrylate, di(meth)acrylate of a compound obtained by adding an alkylene oxide having 2 to 4 carbon atoms to bisphenol A, di(meth)acrylate of a compound obtained by adding an alkylene oxide having 2 to 4 carbon atoms to bisphenol F, 1,4 - butanediol di(meth)acrylate, 2 - ethyl - 2 - butyl - propanediol di(meth)acrylate, and 1,9 - nonanediol di(meth)acrylate, etc.

[0051] The trifunctional (meth)acrylic monomer (C2) includes those having three (meth)acryloyl groups in the molecule. Examples of (C2) include Compound (C21) having a structure of an esterified product of 1 mole of a compound having 2 to 20 carbon atoms and three or more hydroxyl groups with 3 moles of (meth)acrylic acid; A compound (C22) having a structure of an esterified product of 1 mol of an alkylene oxide adduct of a compound having 2 to 20 carbon atoms and three or more hydroxyl groups with 3 mol of (meth)acrylic acid; and Examples thereof include a compound (C23) having a structure of an esterified product of 1 mol of a lactone adduct of a compound having 2 to 20 carbon atoms and three or more hydroxyl groups with 3 mol of (meth)acrylic acid.

[0052] Regarding each of the compound (C21), the compound (C22), and the compound (C23), examples of the compound having 2 to 20 carbon atoms and three or more hydroxyl groups include compounds having three or more hydroxyl groups among the compounds exemplified as the compounds having 2 to 20 carbon atoms and two or more hydroxyl groups regarding the above (C1).

[0053] Regarding the compound (C22), the alkylene oxide may be the same as in the case of the above compound (C12), and the number of moles of the added alkylene oxide may also be the same as in the case of the above compound (C12). Regarding the compound (C23), the lactone may be the same as in the case of the above compound (C13), and the number of moles of the added lactone may also be the same as in the case of the above compound (C13).

[0054] Examples of (C2) include trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, tri(meth)acrylate of a compound obtained by adding an alkylene oxide having 2 to 4 carbon atoms to trimethylolpropane, glycerin tri(meth)acrylate, tri(meth)acrylate of a compound obtained by adding an alkylene oxide having 2 to 4 carbon atoms to glycerin, pentaerythritol tri(meth)acrylate, tri(meth)acrylate of a compound obtained by adding an alkylene oxide having 2 to 4 carbon atoms to pentaerythritol, dipentaerythritol tri(meth)acrylate, tri(meth)acrylate of a compound obtained by adding an alkylene oxide having 2 to 4 carbon atoms to dipentaerythritol, sorbitol tri(meth)acrylate, and tri(meth)acrylate of a compound obtained by adding an alkylene oxide having 2 to 4 carbon atoms to sorbitol, and the like.

[0055] Examples of the tetrafunctional (meth)acrylic monomer (C3) include those having four (meth)acryloyl groups in the molecule. Examples of (C3) include, a compound (C31) having a structure of an esterified product of 1 mol of a compound having 2 to 20 carbon atoms and four or more hydroxyl groups and 4 mol of (meth)acrylic acid; a compound (C32) having a structure of an esterified product of 1 mol of an alkylene oxide adduct of a compound having 2 to 20 carbon atoms and four or more hydroxyl groups and 4 mol of (meth)acrylic acid; and a compound (C33) having a structure of an esterified product of 1 mol of a lactone adduct of a compound having 2 to 20 carbon atoms and four or more hydroxyl groups and 4 mol of (meth)acrylic acid, and the like.

[0056] Regarding each of the compound (C31), the compound (C32), and the compound (C33), examples of the compound having 2 to 20 carbon atoms and four or more hydroxyl groups include compounds having four or more hydroxyl groups among the compounds exemplified as the compounds having 2 to 20 carbon atoms and two or more hydroxyl groups regarding the above (C1).

[0057] Regarding the compound (C32), the alkylene oxide may be the same as in the case of the above compound (C12), and the number of moles of the added alkylene oxide may also be the same as in the case of the above compound (C12). Regarding the compound (C33), the lactone may be the same as in the case of the above compound (C13), and the number of moles of the added lactone may also be the same as in the case of the above compound (C13).

[0058] (C3) includes, for example, pentaerythritol tetra(meth)acrylate, tetra(meth)acrylate of a compound obtained by adding an alkylene oxide having 2 to 4 carbon atoms to pentaerythritol, sorbitol tetra(meth)acrylate, tetra(meth)acrylate of a compound obtained by adding an alkylene oxide having 2 to 4 carbon atoms to sorbitol, ditrimethylolpropane tetra(meth)acrylate, tetra(meth)acrylate of a compound obtained by adding an alkylene oxide having 2 to 4 carbon atoms to ditrimethylolpropane, dipentaerythritol tetra(meth)acrylate, and tetra(meth)acrylate of a compound obtained by adding an alkylene oxide having 2 to 4 carbon atoms to dipentaerythritol, and the like.

[0059] The penta-functional or higher (meth)acrylic monomer (C4) includes those having five or more (meth)acryloyl groups in the molecule. (C4) includes, for example Compound (C41) having a structure of an esterified product of 1 mole of a compound having 2 to 20 carbon atoms and five or more hydroxyl groups and 5 moles or more of (meth)acrylic acid; Compound (C42) having a structure of an esterified product of 1 mole of an alkylene oxide adduct of a compound having 2 to 20 carbon atoms and five or more hydroxyl groups and 5 moles or more of (meth)acrylic acid; and Compound (C43) having a structure of an esterified product of 1 mole of a lactone adduct of a compound having 2 to 20 carbon atoms and five or more hydroxyl groups and 5 moles or more of (meth)acrylic acid, and the like. Regarding each of compound (C41), compound (C42), and compound (C43), examples of the compound having 2 to 20 carbon atoms and five or more hydroxyl groups include the compounds having five or more hydroxyl groups among the compounds exemplified as the compounds having 2 to 20 carbon atoms and two or more hydroxyl groups regarding the above (C1).

[0060] Regarding compound (C42), the alkylene oxide may be the same as in the case of the above compound (C12), and the number of moles of added alkylene oxide may also be the same as in the case of the above compound (C12). Also, regarding compound (C43), the lactone may be the same as in the case of the above compound (C13), and the number of moles of added lactone may also be the same as in the case of the above compound (C13).

[0061] Examples of (C4) include sorbitol penta(meth)acrylate, penta(meth)acrylate of a compound obtained by adding an alkylene oxide having 2 to 4 carbon atoms to sorbitol, dipentaerythritol penta(meth)acrylate, penta(meth)acrylate of a compound obtained by adding an alkylene oxide having 2 to 4 carbon atoms to dipentaerythritol, dipentaerythritol hexa(meth)acrylate, hexa(meth)acrylate of a compound obtained by adding an alkylene oxide having 2 to 4 carbon atoms to dipentaerythritol, sorbitol hexa(meth)acrylate, hexa(meth)acrylate of a compound obtained by adding an alkylene oxide having 2 to 4 carbon atoms to sorbitol, and caprolactone-modified dipentaerythritol hexa(meth)acrylate, etc.

[0062] In the present invention, from the viewpoint of improving adhesiveness, (C) is preferably a compound having 2 to 6 (meth)acryloyl groups in the molecule, and more preferably a compound having 2 to 5 (meth)acryloyl groups in the molecule.

[0063] The molecular weight of (C) is preferably 150 or more and 600 or less, more preferably 200 or more and 550 or less, from the viewpoint of improving adhesiveness. The molecular weight of (C) is the chemical formula weight when (C) contains only one type of compound, and is the number average molecular weight determined by gel permeation chromatography (GPC) when (C) contains two or more types of compounds. The measurement conditions of gel permeation chromatography (GPC) for (C) in this embodiment are as follows. - Apparatus: "Waters Alliance 2695" [manufactured by Waters]. - Columns: "Guardcolumn Super H-L" (1 piece) and "TSKgel SuperH2000 (1 piece)" [both manufactured by Tosoh Corporation]. - Sample solution: 0.25 wt% tetrahydrofuran solution. - Solution injection volume: 10 μl. - Flow rate: 0.6 ml / min. - Measurement temperature: 40 °C. - Detection device: Refractive index detector. - Standard substance: Standard polyethylene glycol.

[0064] The molecular weight per (meth)acryloyl group of (C) (molecular weight / number of (meth)acryloyl groups) is preferably 100 or more and 300 or less, more preferably 120 or more and 200 or less, from the viewpoint of improving adhesiveness.

[0065] The pressure-sensitive adhesive composition of the present invention contains the pressure-sensitive adhesive main agent of the present invention, a photopolymerization initiator (D), and, if necessary, a polyfunctional (meth)acryloyl monomer (C).

[0066] The content of the copolymer (A) in the pressure-sensitive adhesive composition of the present invention is preferably 84 to 99.8% by weight, more preferably 87 to 99.8% by weight, still more preferably 90 to 99.8% by weight, and particularly preferably 95 to 99.4% by weight, based on the weight of the pressure-sensitive adhesive composition, from the viewpoint of adhesive strength. From the viewpoint of adhesive strength, the content of the photopolymerization initiator (D) in the pressure-sensitive adhesive composition of the present invention is preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight, based on the weight of the pressure-sensitive adhesive composition. From the viewpoint of improving adhesiveness, the content of the polyfunctional (meth)acryloyl monomer (C) in the pressure-sensitive adhesive composition of the present invention is preferably 0.1 to 10% by weight, more preferably 0.1 to 5% by weight, based on the weight of the pressure-sensitive adhesive composition. From the viewpoint of improving adhesiveness, the weight ratio of the main pressure-sensitive adhesive agent to the polyfunctional (meth)acryloyl monomer (C) in the pressure-sensitive adhesive composition [main pressure-sensitive adhesive agent / (C)] is preferably 100 / 10 to 100 / 0.5, more preferably 100 / 5 to 100 / 1.

[0067] The pressure-sensitive adhesive composition of the present invention can be produced, for example, by mixing a pressure-sensitive adhesive main agent containing the copolymer (A) of the present invention, a photopolymerization initiator (D), and, if necessary, the polyfunctional (meth)acryloyl monomer (C).

[0068] The pressure-sensitive adhesive composition of the present invention may contain a solvent (S). That is, the pressure-sensitive adhesive composition may be a solution containing the solvent (S). For example, when the pressure-sensitive adhesive main agent contains the solvent (S), the pressure-sensitive adhesive composition also contains the solvent (S). From the viewpoint of improving handleability when making a hot-melt pressure-sensitive adhesive, the weight ratio of the solvent (S) in the pressure-sensitive adhesive composition of the present invention is preferably 50% by weight or less, more preferably 5% by weight or less, and particularly preferably 1% by weight or less, based on the weight of the pressure-sensitive adhesive composition.

[0069] Further, the pressure-sensitive adhesive composition of the present invention may contain additives as necessary, as long as the effects of the present disclosure are not impaired. Examples of the additives include the aforementioned inorganic sulfate (T1), aliphatic alcohols having 12 to 18 carbon atoms (T2), antioxidants (T3), other additives (T4), tackifiers (N) such as terpene resins and rosin resins, plasticizers, fillers, pigments, ultraviolet absorbers, and the like.

[0070] When containing inorganic sulfate (T1), from the viewpoint of the balance between coloring reduction and transparency, based on the weight of the pressure-sensitive adhesive composition, 0.001 to 0.03% by weight is preferable, and more preferably 0.002 to 0.02% by weight.

[0071] When containing an aliphatic alcohol (T2) having 12 to 18 carbon atoms, from the viewpoints of heat resistance and appearance, based on the weight of the pressure-sensitive adhesive composition, 0.01 to 1.5% by weight is preferable, and more preferably 0.02 to 1.0% by weight.

[0072] When containing an antioxidant (T3), from the viewpoint of preventing coloring of the pressure-sensitive adhesive film, based on the weight of the pressure-sensitive adhesive composition, 0.05 to 5% by weight is preferable, and more preferably 0.1 to 1.0% by weight.

[0073] In the present invention, when the pressure-sensitive adhesive composition contains an antioxidant (T3), the weight ratio of the copolymer (A) to the antioxidant (T3) [copolymer (A): antioxidant (T3)] is preferably 100:0.001 to 100:3, more preferably 100:0.005 to 100:1, and particularly preferably 100:0.01 to 100:0.5 from the viewpoints of suppressing the generation of crosslinked products and preventing coloring of the pressure-sensitive adhesive film.

[0074] <Pressure-sensitive adhesive film> The pressure-sensitive adhesive composition of the present invention may be used, for example, as a pressure-sensitive adhesive film having a pressure-sensitive adhesive layer applied and cured in a layer form.

[0075] In the pressure-sensitive adhesive film, the thickness of the cured layer made of the cured product of the pressure-sensitive adhesive composition is preferably 10 μm or more and 200 μm or less, and more preferably 20 μm or more and 100 μm or less.

[0076] The pressure-sensitive adhesive film may be composed of, for example, only a cured product, or may include a film-like base material and a cured layer overlapping the base material.

[0077] The pressure-sensitive adhesive film can be produced by directly applying a pressure-sensitive adhesive composition to at least a part of at least one side of a substrate using various coating devices, and then curing the pressure-sensitive adhesive composition by heating and / or active energy rays (such as UV rays, electron beams, etc.).

[0078] As a preferred usage mode, as in the following examples, the pressure-sensitive adhesive composition is heated (for example, to 130 to 180 °C) to be softened or melted, then applied to the substrate, and further cured by light (active energy rays, such as UV rays, electron beams, etc.). That is to say, the pressure-sensitive adhesive composition can also be said to be an active energy ray-curable hot melt pressure-sensitive adhesive composition.

[0079] The substrate is, for example, in the form of a film or a sheet. The substrate is, for example, a plastic film, a plastic sheet, a plastic foam, a flat yarn, paper, a metal plate, a metal foil, a woven fabric, a non-woven fabric, or wood, etc. The plastic includes at least one selected from the group consisting of polyolefins such as polyethylene and polypropylene, polyurethane, polyethylene terephthalate, polyvinyl chloride, rayon, and polyamide, etc. The paper is, for example, Japanese paper or crepe paper.

[0080] The main agent of the pressure-sensitive adhesive of the present invention has an appropriately low viscosity when heated (for example, to 150 °C) and excellent handleability. The pressure-sensitive adhesive composition containing the main agent of the pressure-sensitive adhesive of the present invention has excellent transparency, high adhesiveness (especially adhesiveness on a curved surface), a low dielectric constant, and an adhesive film having a cured layer composed of a cured product of the pressure-sensitive adhesive composition has excellent adhesiveness. Therefore, the adhesive film can be suitably used for various applications such as packaging (packaging of frozen foods, bundling of vegetables, etc.), marking (automobile moldings, emblems, marks, etc.), masking (glass sealing, building curing, etc.), surface protection (protection of painted surfaces, etc.), medical use (band-aids, etc.), and office use. Furthermore, since the adhesive film has excellent adhesiveness on a curved surface, it can also be suitably used for protecting curved substrates (curved displays, curved electronic substrates).

Examples

[0081] Hereinafter, the present embodiment will be further described by way of examples and comparative examples, but the present embodiment is not limited thereto.

[0082] <Example 1> 100 parts by weight of ethyl acetate as a solvent was charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping funnel and a nitrogen gas introduction tube, and the temperature was raised. Next, while blowing nitrogen into the reaction vessel under solvent reflux, a monomer mixture solution having the following composition and an initiator solution 1 having the following composition were continuously dropped into the reaction vessel using a dropping funnel over 5 hours to cause radical polymerization to proceed in the reaction vessel. Composition of monomer mixture solution: 15 parts by weight of n-octadecyl methacrylate (a1-1), 35 parts by weight of n-hexadecyl methacrylate (a1-2), 36 parts by weight of methyl acrylate (a2-1), 9 parts by weight of N-vinyl-2-pyrrolidone (a3-1), and 5 parts by weight of 2-ethylhexyl acrylate (a4-1). Composition of initiator solution 1: 0.20 part by weight of 2,2'-azobis(2,4-dimethylvaleronitrile) [hereinafter may be abbreviated as V-65] and 20 parts by weight of ethyl acetate. After completion of dropping, while stirring the liquid in the reaction vessel at the same temperature, an initiator solution 2 having the following composition was continuously dropped into the reaction vessel using a dropping funnel over 1 hour. Thereafter, the polymerization reaction in the reaction vessel was continued for 1 hour under solvent reflux. Composition of initiator solution 2: 0.11 part by weight of 2,2'-azobis(2,4-dimethylvaleronitrile) and 10 parts by weight of ethyl acetate. Next, 0.01 part by weight of sodium sulfate (T1-1), 0.1 part by weight of n-octadecyl alcohol (T2-1), 0.4 part by weight of n-hexadecyl alcohol (T2-2), and 0.5 part by weight of tris(2,4-di-tert-butylphenyl) phosphite (T3-1) were added to the reaction vessel and stirred. Furthermore, under reduced pressure, the liquid in the reaction vessel was heated to 130 ° C to distill off ethyl acetate. Thereby, an adhesive base (B-1) containing a copolymer (A-1) was prepared in the reaction vessel. This adhesive base (B-1) was taken out from the reaction vessel. The weight average molecular weight (Mw) of the copolymer (A-1) was 280,000, the glass transition temperature (Tg) was 3°C, the carboxy group concentration was 0 mol / kg, and the hydroxyl group concentration was 0 mol / kg.

[0083] <Examples 2 to 26, Comparative Examples 1 to 5> The compositions of the monomer mixture solution, initiator solution 1, and initiator solution 2 were changed as shown in Tables 1 to 2, and otherwise, in the same manner as in Example 1, adhesive base agents (B-2) to (B-26) or (Comp. A-1) to (Comp. A-5) each containing the copolymer (A-2) to (A-26) or (Comp. A-1) to (Comp. A-5) were obtained. The weight average molecular weight, glass transition temperature, carboxy group concentration, and hydroxyl group concentration of each of the copolymers (A-2) to (A-26) and (Comp. A-1) to (Comp. A-5) are shown in Tables 1 to 2.

[0084] <Evaluation> The heat resistance and handleability of the adhesive base agents (B-1) to (B-26) and (Comp. B-1) to (Comp. B-5) were evaluated. Further, the following adhesive base agent coating films (Bα) and adhesive base agent coating films (Bβ) were prepared, and the transparency, dielectric constant, coloring, appearance, and corrosiveness were evaluated by the methods described below. The results are shown in Tables 1 to 2.

[0085] <1> Heat resistance test After conducting a heat resistance test in which each of the adhesive base agents (B-1) to (B-26) and (Comp. B-1) to (Comp. B-5) was allowed to stand for 7 hours under reduced pressure conditions of 100 g, 150°C, and a gauge pressure of -100 kPa, the weight average molecular weight was measured by gel permeation chromatography. The change rate of the weight average molecular weight after this heat resistance test from the weight average molecular weight before the heat resistance test (the weight average molecular weight shown in Tables 1 to 2) was calculated by the following formula and evaluated according to the following criteria. Change rate (%) = (Weight average molecular weight after heat resistance test) / (Weight average molecular weight before heat resistance test) × 100 <Evaluation criteria> AA: The change rate is 100% or more and less than 105%. A: The change rate is 105% or more and less than 110%. B: The change rate is 110% or more and less than 120%. C: The change rate is 120% or more.

[0086] <2> Handling property Each of the adhesive main agents (B-1) to (B-26) and (Ratio B-1) to (Ratio B-5) was heated at 150 °C for 3 hours, and then filtered through an industrial wire mesh with an opening size of 0.196 mm. The clogging of the wire mesh during filtration was evaluated according to the following criteria. <Evaluation criteria> AA: No clogging of the wire mesh. A: Slight clogging was observed in the wire mesh, but the extraction speed did not decrease and it was possible to extract. B: It was possible to extract, but clogging of the wire mesh was observed and the extraction speed decreased. C: The wire mesh became clogged and it was impossible to extract.

[0087] <Preparation of the adhesive main agent coating film (Bα)> Each of the adhesive main agents (B-1) to (B-26) and (Ratio B-1) to (Ratio B-5) was melted at 150 °C, and at an environmental temperature of 23 °C, using a slot coater on the surface of a polyester film with a thickness of 100 μm [manufactured by Toray Industries, Inc., product name Lumirror Type T, polyethylene terephthalate (PET) film], it was coated at a coating amount of 100 g / m 2 to form a coating film. Thus, an adhesive main agent coating film (Bα) comprising a polyester film and an adhesive main agent coating film overlapping it was obtained.

[0088] <Preparation of the adhesive main agent coating film (Bβ)> Each of the adhesive main agents (B-1) to (B-26) and (Ratio B-1) to (Ratio B-5) was melted at 150 °C, and at an environmental temperature of 23 °C, using a slot coater on the surface of a polyester film with a thickness of 25 μm that had been subjected to a release treatment on the surface, it was coated at a coating amount of 100 g / m 2 to form a coating film. Thus, an adhesive main agent coating film (Bβ) comprising a release polyester film and an adhesive main agent coating film overlapping it was obtained.

[0089]

Table 1

[0090]

Table 2

[0091] In Tables 1 to 2, (T3-1) is tris(2,4-di-tert-butylphenyl) phosphite, and (T3-2) is 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane.

[0092] <Examples 41 to 67, Comparative Examples 41 to 45> The compounding components shown in the "Formulation Composition" of Tables 3 to 4 were blended with a Henschel mixer for 3 minutes, and then melt-kneaded with a twin-screw extruder with a vent at 150 °C, 100 rpm, and a residence time of 3 minutes to obtain pressure-sensitive adhesive compositions (X-1) to (X-27) and (Ratio X-1) to (Ratio X-5). From each of the pressure-sensitive adhesive compositions (X-1) to (X-27) and (Ratio X-1) to (Ratio X-5), the following pressure-sensitive adhesive films (Yα) and pressure-sensitive adhesive films (Yβ) were produced and evaluated by the method described below. The results are shown in Tables 3 to 4.

[0093] <Production of Pressure-Sensitive Adhesive Film (Yα)> Each of the pressure-sensitive adhesive compositions (X-1) to (X-27) and (Ratio X-1) to (Ratio X-5) was melted at 150 °C, and under an environmental temperature of 23 °C, using a slot coater on the surface of a polyester film [manufactured by Toray Industries, Inc., product name Lumirror Type T, polyethylene terephthalate (PET) film] with a thickness of 100 μm, it was coated at a coating amount of 100 g / m 2 to form a coating film. Using a UV irradiation device [manufactured by USHIO INC., model number UVC-02516S1AA01] for this coating film and using a metal halide lamp as the light source, an integrated light quantity of 2000 mJ / cm 2By irradiating with ultraviolet rays under the conditions described above, the coating film was cured to produce a cured layer with a thickness of 100 μm. As a result, an adhesive film (Yα) comprising a polyester film and a cured layer overlapping therewith was obtained.

[0094] <Production of Adhesive Film (Yβ)> Each of the adhesive compositions (X-1) to (X-27) and (Ratio X-1) to (Ratio X-5) was melted at 150 °C, and using a slot coater on the surface of a polyester film with a release treatment on the surface having a thickness of 25 μm under an environmental temperature of 23 °C, it was coated at an application amount of 100 g / m 2 to form a coating film. For this coating film, a UV irradiation device [manufactured by USHIO INC., model number UVC-02516S1AA01] was used, and a metal halide lamp was used as the light source, and ultraviolet rays were irradiated under the condition of an integrated light amount of 2000 mJ / cm 2 to cure the coating film and produce a cured layer with a thickness of 100 μm. As a result, an adhesive film (Yβ) comprising a polyester film and a cured layer overlapping therewith was obtained.

[0095]

Table 3

[0096]

Table 4

[0097] Note that the details of the polyfunctional (meth)acrylate and initiator in Tables 3 to 4 are as follows. Polyfunctional (meth)acrylate (C-1): Product name Neo Mer TA-505, manufactured by Sanyo Chemical Industries, Ltd., triacrylate of a PO (propylene oxide) adduct of trimethylolpropane, number average molecular weight 460. Polyfunctional (meth)acrylate (C-2): Manufactured by Osaka Organic Chemical Industry Co., Ltd., 1,6-hexanediol diacrylate, number average molecular weight 226. Initiator (D-1): Product name SB-PI 712, manufactured by Sanyo Trading Co., Ltd., 4-methylbenzophenone.

[0098] <3>Transparency A film test piece with a planar dimension of 25 mm × 25 mm was cut out from the pressure-sensitive adhesive base resin coating film (Bβ) or the pressure-sensitive adhesive film (Yβ). This test piece was attached to a slide glass ["S1111" manufactured by Matsunami Glass Industry Co., Ltd.], and the release polyester film was peeled off and transferred. The transparency of the film attached to this glass was measured with a haze meter ["NDH-300A" manufactured by Nippon Denshoku Industries Co., Ltd.] and evaluated according to the following evaluation criteria. In this evaluation, it is preferably A or higher. <Evaluation Criteria> AA: Haze value is less than 1% A: Haze value is 1% or more and less than 3% B: Haze value is 3% or more and less than 5% C: Haze value is 5% or more

[0099] <4>Dielectric Constant The dielectric constants of the pressure-sensitive adhesive base resin coating film (Bβ) and the pressure-sensitive adhesive film (Yβ) were measured under the following conditions. Apparatus: TR-1100 type automatic dielectric loss measuring apparatus manufactured by Ando Electric Co., Ltd. Solid electrode: SE-70 type solid electrode Measurement environment: 23°C, 50% RH A disk with a diameter of φ = 25 mm was cut out from the pressure-sensitive adhesive base resin coating film (Bβ) and the pressure-sensitive adhesive film (Yβ), and the thickness was measured with a micrometer (D, unit: μm). The release film was peeled off, sandwiched between the main electrode and the counter electrode, and measured at 1 kHz, and the capacitance (Cx, unit: pF) was recorded. The dielectric constant was calculated by substituting the obtained numerical values into the following formula. Dielectric constant = (14.39 × Cx × D) / 32400 It was evaluated according to the following evaluation criteria. In this evaluation, it is preferably A or higher. <Evaluation Criteria> AA: Less than 3.2 A: 3.2 or more and less than 3.5 B: 3.5 or more and less than 3.8 C: 3.8 or more

[0100] <5>Coloration (b*) From the base adhesive coating film (Bβ) and the pressure-sensitive adhesive film (Yβ), a film test piece with a planar dimension of 25 mm × 25 mm was cut out. This test piece was pasted onto a slide glass ["S1111" manufactured by Matsunami Glass Industry Co., Ltd.], the release polyester film was peeled off and transferred. The b* value of the film pasted on this glass was measured with a haze meter ["NDH-300A" manufactured by Nippon Denshoku Industries Co., Ltd.] and evaluated according to the following evaluation criteria. In this evaluation, it is preferably A or higher. <Evaluation Criteria> AA: Less than 0.4 A: 0.4 or more and less than 0.7 B: 0.7 or more and less than 1.0 C: 1.0 or more

[0101] <6> Appearance The appearance of the surface of the cured layer of the base adhesive coating film (Bα) and the pressure-sensitive adhesive film (Yα) was visually observed and evaluated according to the following evaluation criteria. In this evaluation, it is preferably A or higher. <Evaluation Criteria> AA: There is no coating unevenness at all. A: There is slight coating unevenness. B: There is partial coating unevenness. C: There is overall coating unevenness.

[0102] <7> Corrosion Test An adhesive film test piece with a planar dimension of 100 mm × 25 mm was cut out from the base adhesive film (Bα) and the adhesive film (Yα). Also, a polyethylene terephthalate film with a thickness of 0.18 mm having an ITO (indium tin oxide) film laminated on one side was prepared. In an atmosphere at 25°C, based on JIS Z0237-2009 "Test Methods for Adhesive Tapes and Adhesive Sheets", the adhesive film test piece and the polyethylene terephthalate film were overlapped so that the cured layer and the ITO film were in contact. Subsequently, while applying a load of 2 kg with a roller on the polyethylene terephthalate film, the roller was reciprocated once on the polyethylene terephthalate film. Thereby, the adhesive film test piece and the polyethylene terephthalate film were bonded together to obtain a laminated film. This laminated film was left standing for 14 days under the conditions of a temperature of 25°C and a relative humidity of 90%, and then, in an atmosphere at 25°C, a 180° peel test of the adhesive film test piece with respect to the polyethylene terephthalate film was conducted. Subsequently, the electrical resistance value (R1) of the ITO film on the polyethylene terephthalate film was measured. Also, the electrical resistance value (R0) of the ITO film on the polyethylene terephthalate film before being bonded to the adhesive film test piece was measured in advance. Based on these, the change rate of the electrical resistance value of the ITO film was calculated by the following formula, and the result was evaluated according to the following evaluation criteria. Note that the smaller the change rate of the resistance value, the smaller the corrosiveness, which means it is good. In this evaluation, it is preferably A or above. Change rate (%) = (R1 - R0) / R0 × 100 <Evaluation Criteria> AA: Change rate less than 5%. A: Change rate 5% or more and less than 10%. B: Change rate 10% or more and less than 20%. C: Change rate 20% or more.

[0103] <8>Adhesive Strength (Adhesiveness) An adhesive film test piece with a planar dimension of 100 mm × 25 mm was cut out from the adhesive film (Yα). Also, a polyethylene terephthalate film with a thickness of 0.18 mm having an ITO (indium tin oxide) film laminated on one side was prepared. In an atmosphere at 25°C, based on the "Test Methods for Adhesive Tapes and Adhesive Sheets" specified in JIS Z0237-2009, the adhesive film test piece and the polyethylene terephthalate film were overlapped so that the cured layer and the ITO film were in contact. Subsequently, while applying a load of 2 kg with a roller on the polyethylene terephthalate film, the roller was reciprocated once on the polyethylene terephthalate film. Thereby, the adhesive film test piece and the polyethylene terephthalate film were bonded together to obtain a laminated film. This laminated film was left standing for 1 day under the conditions of a temperature of 25°C and a relative humidity of 50%, and then, in an atmosphere at 25°C, the 180° peel strength of the adhesive film test piece with respect to the polyethylene terephthalate film was measured under the conditions of a width of 25 mm and a tensile speed of 300 mm / min. The results were evaluated according to the following evaluation criteria. In this evaluation, it is preferably A or higher. <Evaluation Criteria> AA: Greater than 15 N / 25 mm. A: Greater than 10 N / 25 mm and less than or equal to 15 N / 25 mm. B: Greater than 5 N / 25 mm and less than or equal to 10 N / 25 mm. C: Less than or equal to 5 N / 25 mm.

[0104] <9>Retention Force An adhesive film test piece with a planar dimension of 100 mm × 12 mm was cut out from the adhesive film (Yα). Also, a stainless steel plate with a planar dimension of 100 mm × 100 mm was prepared. The adhesive film (Yα) and the stainless steel plate were overlapped such that the cured layer was in contact with the stainless steel plate and the contact area was 12 mm × 12 mm in plan view. Subsequently, while applying a load of 2 kg with a roller on a polyethylene terephthalate film, the roller was reciprocated once on the polyethylene terephthalate film. Thereby, the adhesive film (Yα) and the stainless steel plate were bonded together to obtain a laminate. This laminate was allowed to stand in an atmosphere at 40°C for 30 minutes. Next, in an atmosphere at 40°C, the stainless steel plate was set vertically so that the portion where the adhesive film (Yα) was in contact was placed downward. In this state, at the lower end of the 88 mm × 12 mm portion of the stainless steel plate where the adhesive film (Yα) was not overlapped, a load of 1 kg directed downward was applied to the upper end of the adhesive film (Yα) for 24 hours. Subsequently, the downward displacement (unit: mm) of the adhesive film (Yα) with respect to the stainless steel plate was measured and evaluated according to the following evaluation criteria. Note that the smaller the numerical value, the higher the holding force. <Evaluation Criteria> AA: 0.5 mm or less. A: Exceeding 0.5 mm and 1.0 mm or less. B: Exceeding 1.0 mm and 2.0 mm or less. C: Exceeding 2.0 mm.

[0105] <10>Adhesiveness on a Curved Surface (Curved Surface Peeling Test) An adhesive film test piece with a planar dimension of 40 mm × 40 mm was cut out from the adhesive film (Yα). Five adhesive film test pieces were prepared and attached to five glass tubes with an outer diameter of 30 mm so as to be wound around them respectively. Next, each glass tube was allowed to stand in a 23°C atmosphere for 24 hours, and then the length of the portion of the pressure-sensitive adhesive film test piece that peeled off from the glass tube was measured. For each glass tube, the sum of the length of the peeled portion at one end of the pressure-sensitive adhesive film test piece and the length of the peeled portion at the other end was calculated. The average value of the sum of the lengths for 5 glass tubes was calculated, and the result was evaluated according to the following evaluation criteria. Note that the smaller the numerical value, the better the adhesiveness on the curved surface. In this evaluation, it is preferably A or higher. <Evaluation Criteria> AA: 0.5 mm or less. A: Exceeding 0.5 mm and 1.0 mm or less. B: Exceeding 1.0 mm and 2.0 mm or less. C: Exceeding 2.0 mm.

[0106] From the results in Tables 1 to 4, it can be seen that the main adhesive agents of Examples 1 to 26 of the present invention are excellent in handleability. Furthermore, it can be seen that they have high transparency, a low dielectric constant, little coating unevenness, excellent appearance, little coloring, low corrosiveness, high heat resistance, and are extremely excellent. Also, it can be seen that the pressure-sensitive adhesive sheet obtained by curing the pressure-sensitive adhesive composition of Examples 41 to 67 of the present invention is excellent in transparency, has high adhesiveness, particularly excellent adhesiveness on a curved surface, and has a low dielectric constant. Furthermore, it can be seen that it has little coating unevenness, excellent appearance, little coloring, low corrosiveness, and is extremely excellent. On the other hand, it can be seen that the main adhesive agent of Comparative Example 1 using only one kind of (a1), Comparative Examples 2 to 3 where the weight ratio (a11 / a12) is outside the range, and Comparative Examples 4 to 5 not containing (a2) or (a3), and the sheet obtained by curing the pressure-sensitive adhesive composition using the same are inferior in any one of the performances.

Industrial Applicability

[0107] The main adhesive of the present invention has a viscosity that is moderately low when heated (for example, 150 ° C), is excellent in handleability, the adhesive composition containing the main adhesive of the present invention is excellent in transparency, has high adhesiveness (especially adhesiveness on a curved surface), has a low dielectric constant, and the adhesive film having a cured layer made of a cured product of the adhesive composition is excellent in adhesiveness. Therefore, the adhesive film can be suitably used for various applications such as packaging (packaging of frozen foods, bundling of vegetables, etc.), marking (automobile moldings, emblems, marks, etc.), masking (glass sealing, construction curing, etc.), surface protection (coating surface protection, etc.), medical use (band-aids, etc.) and office use. Furthermore, since the adhesive film is excellent in adhesiveness on a curved surface, it can also be suitably used for protecting curved substrates (curved displays, curved electronic substrates).

Claims

1. An adhesive main agent containing a copolymer (A) containing a long-chain alkyl (meth)acrylate (a1), a short-chain alkyl (meth)acrylate (a2), and a nitrogen atom-containing monomer (a3) as constituent monomers, wherein the (a1) has a linear alkyl group having 12 to 18 carbon atoms, the (a2) has a linear alkyl group having 1 to 4 carbon atoms, at least two components having different carbon numbers of the linear alkyl group are contained as the (a1) in the constituent monomers of the copolymer (A), and the weight of the component (a11) having the largest content weight as the (a1) in the constituent monomers of the copolymer (A) and the carbon number of the linear alkyl group of the (a11) are different from those of any one of the components (a12) of the components having different carbon numbers. An adhesive main agent in which the weight ratio (a11 / a12) is 1.5 to 3.0 in the combination with the weight of the component (a12).

2. The adhesive main agent according to claim 1, wherein the carboxyl group concentration of the copolymer (A) is 0.08 mol / kg or less.

3. The adhesive main agent according to claim 1, wherein the hydroxyl group concentration of the copolymer (A) is 0.05 mol / kg or less.

4. The adhesive main agent according to claim 1, containing an inorganic sulfate (T1) in the adhesive main agent, and the content of the inorganic sulfate (T1) in the adhesive main agent is 0.001 to 0.03% by weight based on the weight of the adhesive main agent.

5. The adhesive main agent according to claim 1, containing an aliphatic alcohol (T2) having 12 to 18 carbon atoms in the adhesive main agent, and the content of the aliphatic alcohol (T2) in the adhesive main agent is 0.01 to 1.5% by weight based on the weight of the adhesive main agent.

6. The adhesive main agent according to claim 1, wherein the weight average molecular weight of the copolymer (A) is 200,000 to 400,000.

7. An adhesive composition containing the adhesive main agent according to any one of claims 1 to 6 and a photoinitiator (D).

Images