Adhesive main component and adhesive composition

Abstract

The object of the present invention is to provide an adhesive main component that has a moderately low viscosity when heated (e.g., 150°C) and excellent handling properties, and an adhesive composition containing the same that has excellent transparency, high tackiness, and low dielectric constant. [Solution] A main adhesive component containing a copolymer (A) comprising alkyl (alkyl with 16 to 32 carbon atoms) (meth)acrylate (a1), branched alkyl (alkyl with 8 to 10 carbon atoms) (meth)acrylate (a2), linear alkyl (alkyl with 1 to 4 carbon atoms) (meth)acrylate (a3), and nitrogen atom-containing monomer (a4) as constituent monomers.

Description

Technical Field

[0001] The present invention relates to an adhesive base resin 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 unit have been developed (for example, Patent Document 1). In recent years, in information device terminals such as smartphones, since high-speed data transmission is required, in order to suppress transmission delay, a reduction in the dielectric constant of the adhesive is required. 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 technology of Patent Document 1 does not achieve both low dielectric constant and transparency and have sufficient adhesiveness.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] 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 moderately low and excellent handling properties when heated (for example, 150°C), and an adhesive composition containing the same, which is excellent in transparency, has high adhesiveness, and has a low dielectric constant.

Means for Solving the Problems

[0005] The present inventors have conducted diligent studies to achieve the above objectives and have arrived at the present invention. Specifically, the present invention is an adhesive main component containing a copolymer (A) which includes alkyl (alkyl with 16 to 32 carbon atoms) (meth)acrylate (a1), branched alkyl (alkyl with 8 to 10 carbon atoms) (meth)acrylate (a2), linear alkyl (alkyl with 1 to 4 carbon atoms) (meth)acrylate (a3), and nitrogen atom-containing monomer (a4) as constituent monomers. [Effects of the Invention]

[0006] The main component of the adhesive of the present invention has a moderately low viscosity when heated (e.g., 150°C) and excellent handling properties. The adhesive composition containing the main component of the present invention has excellent transparency, high tackiness (especially on curved surfaces), and a low dielectric constant.

[0007] <Alkyl (alkyl group with 16-32 carbon atoms) (meth)acrylate (a1)> Examples of alkyl (alkyl with 16 to 32 carbon atoms) (meth)acrylate (a1) in the present invention include linear or branched alkyl (alkyl with 16 to 32 carbon atoms) (meth)acrylates, such as n-hexadecyl (meth)acrylate, 2-methylhexadecyl (meth)acrylate, 2-octyldecyl (meth)acrylate, 2-hexyldodecyl (meth)acrylate, 2-methylheptadecyl (meth)acrylate, 2-methyloctadecyl (meth)acrylate, n-eicosyl (meth)acrylate, 2-octyldodecyl (meth)acrylate, n-docosyl (meth)acrylate, 2-decyltetradecyl (meth)acrylate, 2-dodecylhexadecyl (meth)acrylate, and 2-tetradecyloctadecyl (meth)acrylate. In this invention, "(meth)acrylate" means "acrylate and / or methacrylate". Furthermore, (a1) may be used alone or in combination of two or more types.

[0008] Of the above (a1), preferred from the viewpoint of dielectric constant and transparency are branched alkyl (alkyl with 16 to 32 carbon atoms, preferably 20 to 32 carbon atoms) (meth)acrylate, a combination of branched alkyl (alkyl with 16 to 32 carbon atoms, preferably 20 to 32 carbon atoms) (meth)acrylate and linear (alkyl with 16 to 32 carbon atoms) (meth)acrylate, even more preferred is branched alkyl (alkyl with 16 to 32 carbon atoms, preferably 20 to 32 carbon atoms) (meth)acrylate, and particularly preferred is 2-decyltetradecyl (meth)acrylate. Furthermore, based on the weight of (a1), it is preferable that the branched alkyl (alkyl with 16 to 32 carbon atoms, preferably 20 to 32 carbon atoms) (meth)acrylate is 50% by weight or more.

[0009] <Branched alkyl (alkyl group with 8-10 carbon atoms) (meth)acrylate (a2)> Examples of branched alkyl (alkyl with 8 to 10 carbon atoms) (meth)acrylate (a2) in the present invention include 2-ethylhexyl (meth)acrylate, isononyl (meth)acrylate, and isodecyl (meth)acrylate. Furthermore, (a2) may be used alone or in combination of two or more types. Of the above (a2), 2-ethylhexyl (meth)acrylate is preferred from the viewpoint of holding power and adhesiveness on curved surfaces.

[0010] <Linear alkyl (alkyl group with 1-4 carbon atoms) (meth)acrylate (a3)> Examples of linear alkyl (alkyl group with 1 to 4 carbon atoms) (meth)acrylate (a3) ​​in the present invention include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and n-butyl (meth)acrylate. Furthermore, (a3) ​​may be used alone or in combination of two or more types. Of the above (a3), methyl (meth)acrylate and n-butyl (meth)acrylate are preferred from the viewpoint of holding power and adhesion on curved surfaces.

[0011] <Nitrogen atom-containing monomer (a4)> Examples of nitrogen atom-containing monomers (a4) in the present invention include (meth)acrylamide (a41), N-alkyl(meth)acrylamide (a42) having an alkyl group with 1 to 3 carbon atoms, N,N-dialkyl(meth)acrylamide (a43) having two alkyl groups, each with 1 to 3 carbon atoms, N-vinyl monomer (a44) which is a nitrogen-containing heterocyclic compound having a vinyl group, and N-(meth)acryloyl monomer (a45). Furthermore, (a4) may be used alone or in combination of two or more types.

[0012] Examples of N-alkyl(meth)acrylamides (a42) 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 N,N-dialkyl(meth)acrylamide (a43) 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.

[0013] Examples of N-vinyl monomers (a44), which are nitrogen-containing heterocyclic compounds 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-vinylimidazole, 4-vinylpyridine, 2-vinylpyridine, 2-vinylpyrazine, and N-vinyl-2-pyrrolidone. Examples of N-(meth)acryloyl monomers (a45) include 4-(meth)acryloylmorpholine, N-(meth)acryloylpyrrolidone, N-(meth)acryloylpiperidine, and N-(meth)acryloylpyrrolidine.

[0014] Among the above (a4), from the viewpoints of adhesive strength and adhesiveness to a curved surface, at least one selected from the group consisting of (a43), (a44) and (a45) is preferable, and more preferably, it is at least one selected from the group consisting of N,N-dimethylacrylamide, 4-acryloylmorpholine and N-vinyl-2-pyrrolidone.

[0015] <Copolymer (A)> The copolymer (A) in the present invention contains the alkyl (alkyl having 16 to 32 carbon atoms) (meth)acrylate (a1), the branched alkyl (alkyl having 8 to 10 carbon atoms) (meth)acrylate (a2), the linear alkyl (alkyl having 1 to 4 carbon atoms) (meth)acrylate (a3), and the nitrogen atom-containing monomer (a4) as constituent monomers. The copolymer (A) may also contain monomers other than the above (a1), (a2), (a3), and (a4), and examples thereof include a monomer (a5) having a carboxyl group and other monomers (a6).

[0016] Based on the total weight of the above (a1), (a2), (a3), and (a4), from the viewpoints of adhesiveness and low dielectric constant, (a1) is preferably 15 to 70% by weight, more preferably 20 to 60% by weight, (a2) is preferably 3 to 35% by weight, more preferably 5 to 20% by weight, (a3) is preferably 20 to 60% by weight, more preferably 25 to 50% by weight, and (a4) is preferably 1 to 15% by weight, more preferably 6 to 12% by weight.

[0017] Also, based on the weight of all the monomers constituting the copolymer (A), the total weight of (a1), (a2), (a3), and (a4) is preferably 90 to 100% by weight, more preferably 96 to 100% by weight, and particularly preferably 99 to 100% by weight.

[0018] 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. Also, (a5) may be used alone or in combination of two or more.

[0019] 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. The weight of the above (a5) is preferably 0 to 1.5% by weight, more preferably 0 to 0.5% by weight, based on the weight of all the monomers constituting the copolymer (A).

[0020] Examples of the other monomer (a6) include vinyl ester (a61), monomer (a62) having a hydroxyl group, etc. Examples of the vinyl ester (a61) include vinyl acetate, vinyl propionate and vinyl butyrate. Examples of the monomer (a62) having a hydroxyl group include hydroxyalkyl (meth)acrylate (a621) having a hydroxyalkyl group with 2 to 8 carbon atoms, monoesterified product of (meth)acrylic acid of polyalkylene glycol having an alkylene group with 2 to 8 carbon atoms (a622), etc.

[0021] Examples of (a621) include 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate and 2-hydroxybutyl (meth)acrylate. Examples of (a622) include polyethylene glycol mono(meth)acrylate. Also, (a6) may be used alone or in combination of two or more.

[0022] (a6) is preferably (a62) from the viewpoint of adhesiveness, more preferably 2-hydroxyethyl (meth)acrylate, and particularly preferably 2-hydroxyethyl acrylate. The weight of (a6) above is preferably 0 to 2.5% by weight, and more preferably 0 to 0.5% by weight, based on the total weight of the monomers constituting the copolymer (A).

[0023] The carboxyl group concentration of copolymer (A) is preferably 0.08 mol / kg or less, more preferably 0.07 mol / kg or less, particularly preferably 0.05 mol / kg or less, and most preferably 0.03 mol / kg or less. When the carboxyl group concentration of copolymer (A) is 0.08 mol / kg or less, it tends to be less corrosive to metal materials. The carboxyl group concentration of copolymer (A) may be 0 mol / kg, that is, the carboxyl group concentration of copolymer (A) is 0 mol / kg or more. Note that the carboxyl group concentration of copolymer (A) is the number of moles of carboxyl groups contained in copolymer (A) per unit weight of copolymer (A). The carboxyl group concentration can be calculated, for example, by measuring the acid value (KOH mg / g) of copolymer (A) in accordance with JIS K0070 and using the result. The carboxyl group concentration of copolymer (A) can be adjusted, for example, by selecting the type and weight ratio of component (a5) in the constituent monomers of copolymer (A).

[0024] Furthermore, the hydroxyl group concentration of copolymer (A) is preferably 0.05 mol / kg or less, more preferably 0.04 mol / kg, and particularly preferably 0.03 mol / kg or less. Copolymer (A) exhibits high heat resistance and tends to be less prone to thickening during high-temperature coating when its hydroxyl group concentration is 0.05 mol / kg or less. The hydroxyl group concentration of copolymer (A) refers to the number of moles of hydroxyl groups per unit weight of copolymer (A). This hydroxyl group concentration can be calculated by measuring the hydroxyl value (KOH mg / g) of copolymer (A) in accordance with JIS K0070. The hydroxyl group concentration of copolymer (A) can be adjusted, for example, by selecting the type and weight ratio of component (a62) in the constituent monomers of copolymer (A).

[0025] The weight-average molecular weight (Mw) (polystyrene equivalent) of copolymer (A), determined by gel permeation chromatography (GPC), is preferably 300,000 to 900,000, more preferably 350,000 to 800,000, and particularly preferably 400,000 to 700,000, from the viewpoint of improving tackiness and coating properties.

[0026] The measurement conditions for gel permeation chromatography (GPC) in this embodiment are as follows: - Device: "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% by weight tetrahydrofuran solution. -Solution injection volume: 100μl. -Flow rate: 1ml / min. -Measurement temperature: 40℃. -Detection device: refractive index detector. -Reference material: Standard polystyrene.

[0027] The glass transition temperature (Tg) of copolymer (A) is preferably -15°C to 10°C, and more preferably -10°C to 5°C, from the viewpoint of improving adhesion and coating properties. The above glass transition temperature (Tg) is the temperature at which the peak value of the loss coefficient (tanδ) obtained by measuring copolymer (A) under the following conditions using a viscoelasticity measuring device [e.g., model number MCR-302, manufactured by Anton Paar] is shown. - Jig: φ8mm parallel plate. - Sample thickness: 1 mm. Distortion: 1%. -Frequency: 1Hz. - Heating rate: 5°C / min. -Temperature range: -50°C to 180°C.

[0028] Furthermore, the glass transition temperature (Tg) of copolymer (A) can be appropriately adjusted by selecting the type and weight ratio of each monomer in the constituent monomers of copolymer (A). For example, (a1) and (a2) tend to have a low Tg. Also, nitrogen atom-containing monomers (a4) tend to have a high Tg. Furthermore, methacrylate monomers tend to have a higher Tg than acrylate monomers.

[0029] In the present invention, the storage modulus at 0°C (unit: kPa) is preferably 150 to 7,000 kPa, and more preferably 400 to 5,000 kPa, from the viewpoint of adhesion on curved surfaces at low temperatures. The storage modulus at 0°C (unit: kPa) can be measured using copolymer (A) under the following measurement conditions.

[0030] The storage modulus at 0°C was obtained by measuring copolymer (A) under the following conditions using a viscoelasticity measuring device [e.g., model number MCR-302, manufactured by Anton Paar]. - Jig: φ8mm parallel plate. - Sample thickness: 1 mm. Distortion: 1%. -Frequency: 1Hz. - Heating rate: 5°C / min. -Temperature range: -50°C to 180°C.

[0031] The above storage modulus at 0°C (unit: kPa) can be appropriately adjusted by selecting the type and weight ratio of each monomer in the copolymer (A). For example, (a1) and (a2) tend to have low storage moduli at 0°C. Also, nitrogen atom-containing monomers (a4) tend to have high storage moduli at 0°C. Furthermore, methacrylate monomers tend to have higher storage moduli at 0°C than acrylate monomers.

[0032] Copolymer (A) can be synthesized by polymerizing its constituent monomers using known polymerization methods, such as mass polymerization, solution polymerization, emulsion polymerization, or suspension polymerization. In this case, the constituent monomers can be polymerized in the presence of known polymerization initiators, such as azo-based polymerization initiators like azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), and azobisisovaleronitrile, or peroxide-based polymerization initiators such as benzoyl peroxide, di-t-butyl peroxide, and lauryl peroxide.

[0033] Of the polymerization methods described above, solution polymerization is preferred, in which the constituent monomers are polymerized in the presence of a solvent (S). Examples of solvents (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 acetate, and propylene glycol monomethyl ether acetate.

[0034] This solution polymerization yields a mixture of solvent (S) and copolymer (A). The solvent (S) and copolymer (A) in this mixture can be separated to obtain only copolymer (A). Alternatively, this mixture of solvent (S) and copolymer (A) can be used directly as the main adhesive component described later. Furthermore, the main adhesive component can be prepared by adjusting the solvent (S) content of the mixture as needed and adding appropriate additives as required.

[0035] <Adhesive main component (B)> The adhesive main component (B) of the present invention contains the copolymer (A). The adhesive main component of the present invention may contain only the copolymer (A), or it may contain the solvent (S), an aliphatic alcohol having 16 to 32 carbon atoms (T2), an antioxidant (T3), and other additives (T4). Each of these may be used individually or in combination of two or more.

[0036] When a solvent (S) is included, the amount is preferably 30% by weight or less, and more preferably 2% by weight or less, based on the weight of the main adhesive component, from the viewpoint of handling when it is used as a hot melt adhesive.

[0037] Including an aliphatic alcohol (T2) with 16 to 32 carbon atoms in the main component of the adhesive is preferable because it improves the heat resistance of the main component of the adhesive (suppresses the increase in molecular weight when heated) and improves the appearance of the adhesive sheet. Examples of aliphatic alcohols (T2) having 16 to 32 carbon atoms include n-hexadecyl alcohol, heptadecanol, n-octadecyl alcohol, isostearyl alcohol, oleyl alcohol, linoleyl alcohol, 2-decyltetradecyl alcohol, 2-dodecylhexadecyl alcohol, and 2-tetradecyloctadecyl alcohol. As for (T2), from the viewpoint of heat resistance and appearance, saturated aliphatic alcohols having 16 to 32 carbon atoms are preferred, more preferably branched alkyl alcohols having 16 to 32 carbon atoms, and particularly preferred is 2-decyltetradecyl alcohol. When an aliphatic alcohol (T2) having 16 to 32 carbon atoms is included, the amount is preferably 0.1 to 3.0% by weight, and more preferably 0.5 to 2.0% by weight, based on the weight of the main adhesive component, from the viewpoint of heat resistance and appearance.

[0038] In the adhesive main component of the present invention, it is preferable to contain an antioxidant (T3). The inclusion of an antioxidant (T3) is preferable because it can further suppress the generation of minute crosslinks in the cured product of the adhesive composition, and can suppress discoloration of the cured product and adhesive sheet at high temperatures. Examples of antioxidants (T3) in the present invention include hindered phenol antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, lactone-based antioxidants, and amine-based antioxidants.

[0039] Examples of hindered phenol antioxidants include 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 sulfur-based antioxidants include dilauryl 3,3'-thiodipropionate and distearyl 3,3'-thiodipropionate. Phosphorus-based antioxidants include, for example, organic phosphites which may have halogens. Examples of phosphorus-based antioxidants include triphenyl phosphite, triisodecyl phosphite, tris(2,4-di-t-butylphenyl) phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octyl phosphite, 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 and their halo-substituted derivatives. Examples of lactone-based antioxidants include reaction products of 5,7-di-t-butyl-3-hydroxybenzo[b]furan-2(3H)-one and o-xylene. Examples of amine-based antioxidants include hindered aromatic amines. Examples of amine-based antioxidants include octyldiphenylamine, Nn-butyl-p-aminophenol, and N,N-diisopropyl-p-phenylenediamine.

[0040] The antioxidant (T3) is preferably at least one selected from the group consisting of hindered phenol antioxidants, phosphorus antioxidants, and lactone antioxidants, from the viewpoint of suppressing the formation of crosslinks and suppressing discoloration. More preferably, it is at least one selected from the group consisting of hindered phenol antioxidants with a molecular weight of 700 to 2000 and phosphorus antioxidants with a molecular weight of 700 to 2000. Particularly preferred is a phosphorus antioxidant with a molecular weight of 700 to 2000, and most preferably 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.

[0041] In the present invention, when the main component of the adhesive contains an antioxidant (T3), the weight ratio of copolymer (A) to 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 viewpoint of suppressing the generation of crosslinks and preventing discoloration of the adhesive film.

[0042] When an antioxidant (T3) is included, the amount is preferably 0.05 to 5% by weight, and more preferably 0.1 to 1.0% by weight, based on the weight of the main adhesive component, from the viewpoint of preventing discoloration of the adhesive composition and adhesive film.

[0043] Other additives (T4) include tackifiers (N) such as terpene resins and rosin resins, plasticizers, fillers, pigments, and ultraviolet absorbers. If other additives (T4) are included, the amount is preferably 20% by weight or less, and more preferably 10% by weight or less, based on the weight of the main adhesive component, from the viewpoint of tackiness.

[0044] The adhesive main component of the present invention can be used, for example, as the adhesive main component of a hot-melt type adhesive. Since its viscosity is moderately low when heated (for example, 150°C), it can be softened or melted by heating (for example, 70-170°C), and then applied to a substrate as an adhesive composition in the presence of a photopolymerization initiator (D) described below, a polyfunctional (meth)acryloyl monomer (C) if necessary, and other additives, and further cured with active energy rays.

[0045] <Adhesive composition (X)> The adhesive composition (X) of the present invention contains the adhesive main component and a photopolymerization initiator (D). (D) may be one type or two or more types may be used in combination. In this invention, "light" means active energy rays, and "active energy rays" means electromagnetic waves or charged particle beams that have energy quanta, such as ultraviolet rays, electron beams, visible light, X-rays, and ion beams. Among these, ultraviolet rays or electron beams are preferred from the viewpoint of versatility, and ultraviolet rays are particularly preferred.

[0046] In the present invention, the photopolymerization initiator (D) includes those that generate radicals by abstracting hydrogen from other molecules such as copolymer (A) upon irradiation with active energy rays, thereby causing a crosslinking reaction of copolymer (A) in the main adhesive component. Examples of hydrogen abstraction type photopolymerization initiators include methyl benzoylformate, 4,4'-bis(diethylamino)benzophenone, benzophenone, and 4-methylbenzophenone. From the viewpoint of tackiness, a hydrogen abstraction type photopolymerization initiator (D) is preferred as the photopolymerization initiator (D).

[0047] Examples of commercially available hydrogen abstraction type photopolymerization initiators include Omnirad MBF (former Irgacure MBF) (methyl benzoylmate, IGM Resins BV photoinitiator), SB-PI 701 (4,4'-bis(diethylamino)benzophenone, Sanyo Trading Co., Ltd. photoinitiator), SB-PI 710 (benzophenone, Sanyo Trading Co., Ltd. photoinitiator), and SB-PI 712 (4-methylbenzophenone, Sanyo Trading Co., Ltd. photoinitiator).

[0048] In the present invention, the adhesive composition may contain a polyfunctional (meth)acryloyl monomer (C) for the purpose of adjusting the adhesive strength. (C) may be used alone or in combination of two or more types.

[0049] <Polyfunctional (meth)acryloyl monomer (C)> In the present invention, the polyfunctional (meth)acryloyl monomer (C) [hereinafter sometimes referred to as polyfunctional (meth)acrylate] is a compound having multiple (meth)acryloyl groups in its molecule. A (meth)acryloyl group is one or both of an acryloyl group and a methacryloyl group. Examples of (C) include a difunctional (meth)acryloyl monomer (C1), a trifunctional (meth)acryloyl monomer (C2), a tetrafunctional (meth)acryloyl monomer (C3), and a pentafunctional or more (meth)acryloyl monomer (C4).

[0050] Difunctional (meth)acryloyl monomers (C1) include those having two (meth)acryloyl groups in the molecule. Examples of (C1) include compounds having an esterified structure formed by the reaction of 1 mole of a compound having 2 to 20 carbon atoms and two or more hydroxyl groups with 2 moles of (meth)acrylic acid (C11); compounds having an esterified structure formed by the reaction of 1 mole of an alkylene oxide adduct of a compound having 2 to 20 carbon atoms and two or more hydroxyl groups with 2 moles of (meth)acrylic acid (C12); and compounds having an esterified structure formed by the reaction of 1 mole of a lactone adduct of a compound having 2 to 20 carbon atoms and two or more hydroxyl groups with 2 moles of (meth)acrylic acid (C13).

[0051] With respect to each of compound (C11), compound (C12), and compound (C13), examples of compounds having 2 to 20 carbon atoms and two or more hydroxyl groups include linear aliphatic alcohols having 2 to 20 carbon atoms, alicyclic alcohols having 3 to 20 carbon atoms, and aromatic hydroxyl group-containing compounds having 6 to 15 carbon atoms.

[0052] Examples of linear aliphatic alcohols having 2 to 20 carbon atoms include linear 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; linear aliphatic trihydric alcohols having 3 to 20 carbon atoms such as glycerin, trimethylolethane, and trimethylolpropane; and linear aliphatic tetrahydric to ochydric alcohols having 5 to 20 carbon atoms such as pentaerythritol, ditrimethylolpropane, sorbitol, mannitol, sorbitan, diglycerin, and dipentaerythritol.

[0053] 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.

[0054] Aromatic hydroxyl group-containing compounds with 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.

[0055] Regarding the compound (C12), the alkylene oxide preferably contains an alkylene oxide having 2 to 4 carbon atoms, and more specifically, examples include 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. From the viewpoint of adhesiveness, the alkylene oxide preferably contains at least one of EO and PO, and more preferably contains PO.

[0056] With respect to the compound (C12), it is preferable that the number of moles of alkylene oxide added per mole of the alkylene oxide adduct of a compound having 2 to 20 carbon atoms and two or more hydroxyl groups is between 1 mole and 40 moles.

[0057] Regarding the compound (C13), the lactone includes, for example, lactones having 2 to 12 carbon atoms, and more specifically, examples include acetolactone, propiolactone, butyrolactone, valerolactone, caprolactone, and laurolactone.

[0058] With respect to the compound (C13), it is preferable that the number of moles of lactone added per mole of a lactone adduct of a compound having 2 to 20 carbon atoms and two or more hydroxyl groups is 1 mole or more and 15 moles or less.

[0059] 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 compounds obtained by adding an alkylene oxide with 2 to 4 carbon atoms to cyclohexanemethanol, polypropylene glycol di(meth)acrylate, and polyethylene glycol di(meth)acrylate. Examples include ethylene glycol di(meth)acrylate, 2-ethyl-2-butyl-butanediol di(meth)acrylate, di(meth)acrylate of compounds obtained by adding an alkylene oxide having 2 to 4 carbon atoms to bisphenol A, di(meth)acrylate of compounds 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.

[0060] Trifunctional (meth)acrylic monomers (C2) include those having three (meth)acryloyl groups in the molecule. (C2) For example, A compound (C21) having the structure of an esterified product of 1 mole of a compound having 2 to 20 carbon atoms and 3 or more hydroxyl groups with 3 moles of (meth)acrylic acid; A compound (C22) having the structure of an esterified product of 1 mole of an alkylene oxide adduct of a compound having 2 to 20 carbon atoms and 3 or more hydroxyl groups, with 3 moles of (meth)acrylic acid; Examples include compounds (C23) having a structure in which 1 mole of a lactone adduct of a compound having 2 to 20 carbon atoms and 3 or more hydroxyl groups is esterified with 3 moles of (meth)acrylic acid.

[0061] With respect to each of compound (C21), compound (C22), and compound (C23), examples of compounds having 2 to 20 carbon atoms and 3 or more hydroxyl groups include, for example, the compounds having 3 or more hydroxyl groups among the compounds exemplified above as compounds having 2 to 20 carbon atoms and 2 or more hydroxyl groups with respect to (C1).

[0062] With respect to compound (C22), the compounds that may contain alkylene oxide may be the same as those in compound (C12) above, and the number of moles of alkylene oxide added may also be the same as those in compound (C12) above. Furthermore, with respect to compound (C23), the compounds that may contain lactone may be the same as those in compound (C13) above, and the number of moles of lactone added may also be the same as those in compound (C13) above.

[0063] Examples of (C2) include trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, tri(meth)acrylate of compounds in which an alkylene oxide having 2 to 4 carbon atoms is added to trimethylolpropane, glycerin tri(meth)acrylate, tri(meth)acrylate of compounds in which an alkylene oxide having 2 to 4 carbon atoms is added to glycerin, pentaerythritol tri(meth)acrylate, tri(meth)acrylate of compounds in which an alkylene oxide having 2 to 4 carbon atoms is added to pentaerythritol, dipentaerythulitol tri(meth)acrylate, tri(meth)acrylate of compounds in which an alkylene oxide having 2 to 4 carbon atoms is added to dipentaerythulitol, sorbitol tri(meth)acrylate, and tri(meth)acrylate of compounds in which an alkylene oxide having 2 to 4 carbon atoms is added to sorbitol.

[0064] Tetrafunctional (meth)acrylic monomers (C3) include those having four (meth)acryloyl groups in the molecule. (C3) For example, A compound (C31) having the structure of an esterified product of 1 mole of a compound having 2 to 20 carbon atoms and 4 or more hydroxyl groups with 4 moles of (meth)acrylic acid; A compound (C32) having the structure of an esterified product of 1 mole of an alkylene oxide adduct of a compound having 2 to 20 carbon atoms and 4 or more hydroxyl groups with 4 moles of (meth)acrylic acid; and Examples include compounds (C33) that have a structure in which 1 mole of a lactone adduct of a compound having 2 to 20 carbon atoms and 4 or more hydroxyl groups is esterified with 4 moles of (meth)acrylic acid.

[0065] With respect to each of compound (C31), compound (C32), and compound (C33), examples of compounds having 2 to 20 carbon atoms and four or more hydroxyl groups include, for example, the compounds having four or more hydroxyl groups among the compounds exemplified above as compounds having 2 to 20 carbon atoms and two or more hydroxyl groups with respect to (C1).

[0066] With respect to compound (C32), the compounds that may contain alkylene oxide may be the same as those in compound (C12) above, and the number of moles of alkylene oxide added may also be the same as those in compound (C12) above. Furthermore, with respect to compound (C33), the compounds that may contain lactone may be the same as those in compound (C13) above, and the number of moles of lactone added may also be the same as those in compound (C13) above.

[0067] Examples of (C3) include pentaerythritol tetra(meth)acrylate, tetra(meth)acrylate of compounds in which an alkylene oxide having 2 to 4 carbon atoms is added to pentaerythritol, sorbitol tetra(meth)acrylate, tetra(meth)acrylate of compounds in which an alkylene oxide having 2 to 4 carbon atoms is added to sorbitol, ditrimethylolpropane tetra(meth)acrylate, tetra(meth)acrylate of compounds in which an alkylene oxide having 2 to 4 carbon atoms is added to ditrimethylolpropane, dipentaerythritol tetra(meth)acrylate, and tetra(meth)acrylate of compounds in which an alkylene oxide having 2 to 4 carbon atoms is added to dipentaerythritol.

[0068] Five- or more functional (meth)acrylic monomers (C4) include those having five or more (meth)acryloyl groups in the molecule. (C4) For example, A compound (C41) having the structure of an esterified product of 1 mole of a compound having 2 to 20 carbon atoms and 5 or more hydroxyl groups with 5 or more moles of (meth)acrylic acid; Compounds (C42) having a structure in which 1 mole of an alkylene oxide adduct of a compound having 2 to 20 carbon atoms and 5 or more hydroxyl groups is esterified with 5 or more moles of (meth)acrylic acid; and Examples include compounds (C43) having a structure in which one mole of a lactone adduct of a compound having 2 to 20 carbon atoms and five or more hydroxyl groups is esterified with five or more moles of (meth)acrylic acid. With respect to each of compound (C41), compound (C42), and compound (C43), compounds having 2 to 20 carbon atoms and 5 or more hydroxyl groups include, for example, the compounds having 5 or more hydroxyl groups among the compounds exemplified above as compounds having 2 to 20 carbon atoms and 2 or more hydroxyl groups with respect to (C1).

[0069] With respect to compound (C42), the compounds that may contain alkylene oxide may be the same as those in compound (C12) above, and the number of moles of alkylene oxide added may also be the same as those in compound (C12) above. Furthermore, with respect to compound (C43), the compounds that may contain lactone may be the same as those in compound (C13) above, and the number of moles of lactone added may also be the same as those in compound (C13) above.

[0070] Examples of (C4) include sorbitol penta(meth)acrylate, penta(meth)acrylate of compounds in which an alkylene oxide having 2 to 4 carbon atoms is added to sorbitol, dipentaerythritol penta(meth)acrylate, penta(meth)acrylate of compounds in which an alkylene oxide having 2 to 4 carbon atoms is added to dipentaerythritol, dipentaerythritol hexa(meth)acrylate, hexa(meth)acrylate of compounds in which an alkylene oxide having 2 to 4 carbon atoms is added to dipentaerythritol, sorbitol hexa(meth)acrylate, hexa(meth)acrylate of compounds in which an alkylene oxide having 2 to 4 carbon atoms is added to sorbitol, and caprolactone-modified dipentaerythritol hexa(meth)acrylate.

[0071] In the present invention, (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, from the viewpoint of improving adhesiveness.

[0072] The molecular weight of (C) is preferably 150 to 600, and more preferably 200 to 550, from the viewpoint of improving adhesiveness. The molecular weight of (C) is the formula weight if (C) contains only one type of compound, and the number average molecular weight determined by gel permeation chromatography (GPC) if (C) contains two or more types of compounds.

[0073] The measurement conditions for gel permeation chromatography (GPC) in (C) of this embodiment are as follows: - Equipment: "Waters Alliance 2695" [manufactured by Waters]. - Columns: "Guardcolumn Super HL" (1 piece) and "TSKgel SuperH2000" (1 piece) [both manufactured by Tosoh Corporation]. - Sample solution: 0.25% by weight tetrahydrofuran solution. -Solution injection volume: 10μl. -Flow rate: 0.6ml / min. -Measurement temperature: 40℃. -Detection device: refractive index detector. -Reference substance: Standard polyethylene glycol.

[0074] The molecular weight per (meth)acryloyl group of (C) (molecular weight / number of (meth)acryloyl groups) is preferably 100 to 300, and more preferably 120 to 200, from the viewpoint of improving tackiness.

[0075] The adhesive composition of the present invention contains the main adhesive component of the present invention, a photopolymerization initiator (D), and optionally a polyfunctional (meth)acryloyl monomer (C).

[0076] From the viewpoint of adhesive strength, the content of copolymer (A) in the adhesive composition of the present invention is preferably 84 to 99.8% by weight, more preferably 87 to 99.8% by weight, even more preferably 90 to 99.8% by weight, and particularly preferably 95 to 99.4% by weight, based on the weight of the adhesive composition. From the viewpoint of adhesive strength, the content of the photopolymerization initiator (D) in the adhesive composition of the present invention is preferably 0.1 to 10% by weight, and more preferably 0.5 to 5% by weight, based on the weight of the adhesive composition. From the viewpoint of improving tackiness, the content of the polyfunctional (meth)acryloyl monomer (C) in the adhesive composition of the present invention is preferably 0.1 to 10% by weight, and more preferably 0.1 to 5% by weight, based on the weight of the adhesive composition. The weight ratio of the main adhesive component to the polyfunctional (meth)acryloyl monomer (C) in the adhesive composition [main adhesive component / (C)] is preferably 100 / 10 to 100 / 0.5, and more preferably 100 / 5 to 100 / 1, from the viewpoint of improving tackiness.

[0077] The adhesive composition of the present invention can be produced, for example, by mixing an adhesive main component containing the copolymer (A) of the present invention, a photopolymerization initiator (D), and optionally the polyfunctional (meth)acryloyl monomer (C).

[0078] The adhesive composition of the present invention may contain a solvent (S). That is, the adhesive composition may be a solution containing a solvent (S). For example, if the main component of the adhesive contains a solvent (S), the adhesive composition may also contain a solvent (S). The weight percentage of solvent (S) in the 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, relative to the weight of the adhesive composition, from the viewpoint of improving handling when used as a hot melt adhesive.

[0079] Furthermore, the adhesive composition of the present invention may contain additives as needed, to the extent that they do not impair the effects of the present disclosure. Examples of additives include the aforementioned aliphatic alcohols having 16 to 32 carbon atoms (T2), antioxidants (T3), other additives (T4), tackifiers such as terpene resins and rosin resins (N), plasticizers, fillers, pigments, ultraviolet absorbers, and the like.

[0080] When an aliphatic alcohol (T2) having 16 to 32 carbon atoms is included, the amount is preferably 0.1 to 3.0% by weight, and more preferably 0.5 to 2.0% by weight, based on the weight of the adhesive composition, from the viewpoint of heat resistance and appearance.

[0081] When an antioxidant (T3) is included, the amount is preferably 0.05 to 5% by weight, and more preferably 0.1 to 1.0% by weight, based on the weight of the adhesive composition, from the viewpoint of preventing discoloration of the adhesive film.

[0082] In the present invention, when the adhesive composition contains an antioxidant (T3), the weight ratio of copolymer (A) to 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 viewpoint of suppressing the generation of crosslinks and preventing discoloration of the adhesive film.

[0083] <Adhesive film> The adhesive composition of the present invention may be used, for example, in an adhesive film having an adhesive layer obtained by spreading the adhesive composition in layers and curing it. Alternatively, an adhesive film can also be prepared using the main adhesive component (B).

[0084] In the adhesive film, the thickness of the cured layer, which is made of the cured product of the 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.

[0085] The adhesive film may consist of, for example, only a cured layer, or it may comprise a film-like substrate and a cured layer overlapping this substrate.

[0086] Adhesive films can be manufactured by directly applying an adhesive composition to at least a portion of at least one side of a substrate using various coating devices, and then curing the adhesive composition by heating and / or using active energy rays (UV, electron beam, etc.).

[0087] A preferred mode of use is to soften or melt the adhesive composition by heating it (e.g., 130-180°C), apply it to a substrate, and then cure it with light (active energy rays, e.g., UV, electron beam, etc.), as shown in the examples described later. In other words, the adhesive composition can also be called an active energy ray curable hot melt adhesive composition.

[0088] The base material is, for example, in the form of a film or sheet. Examples of base materials include plastic film, plastic sheet, plastic foam, flat yarn, paper, metal plate, metal foil, woven fabric, nonwoven fabric, or wood. The plastic includes, for example, at least one selected from the group consisting of polyolefins such as polyethylene and polypropylene, polyurethane, polyethylene terephthalate, polyvinyl chloride, rayon, and polyamide. The paper is, for example, Japanese paper or crepe paper.

[0089] The main adhesive component of the present invention has a moderately low viscosity when heated (e.g., 150°C) and excellent handling properties. The adhesive composition containing the main adhesive component of the present invention has excellent transparency, high tackiness (especially on curved surfaces), and a low dielectric constant. Furthermore, the adhesive film having a cured layer made from the cured product of the adhesive composition has excellent tackiness. 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 protection, etc.), surface protection (protection of painted surfaces, etc.), medical use (bandages, etc.), and office use. Moreover, because the adhesive film has excellent tackiness on curved surfaces, it can also be suitably used for protecting curved substrates (curved displays, curved electronic circuit boards). [Examples]

[0090] The embodiment will be further described below with reference to examples and comparative examples, but the embodiment is not limited to these.

[0091] <Example 1> A reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping funnel, and nitrogen gas inlet tube was charged with 100 parts by weight of ethyl acetate as a solvent and the temperature was raised. Next, under solvent reflux, while blowing nitrogen into the reaction vessel, the monomer mixture having the following composition and initiator solution 1 having the following composition were continuously added dropwise to the reaction vessel using a dropping funnel over a period of 5 hours, thereby allowing radical polymerization to proceed in the reaction vessel. Composition of monomer-containing solution: 52 parts by weight of 2-decyltetradecyl methacrylate (a1-1), 6 parts by weight of 2-ethylhexyl acrylate (a2-1), 33 parts by weight of methyl acrylate (a3-1), and 9 parts by weight of N-vinyl-2-pyrrolidone (a4-1). Composition of reaction initiator solution 1: 0.10 parts by weight of 2,2'-azobis(2,4-dimethylvaleronitrile) [hereinafter sometimes abbreviated as V-65] and 20 parts by weight of ethyl acetate. After the dropwise addition was complete, while stirring the liquid in the reaction vessel at the same temperature, initiator solution 2 having the following composition was continuously added dropwise to the reaction vessel using a dropping funnel over a period of 1 hour. Subsequently, the polymerization reaction in the reaction vessel was continued for 1 hour under solvent reflux. Composition of initiator solution 2: 0.11 parts by weight of 2,2'-azobis(2,4-dimethylvaleronitrile) and 10 parts by weight of ethyl acetate.

[0092] Next, 1 part by weight of 2-decyltetradecyl alcohol (T2-1) and 0.5 parts by weight of tris(2,4-di-tert-butylphenyl) phosphite (T3-1) were added to the reaction vessel and stirred. Furthermore, the ethyl acetate was removed by distilling off the liquid in the reaction vessel by heating it to 130°C under reduced pressure. This prepared the main adhesive component (B-1) containing copolymer (A-1) in the reaction vessel. This main adhesive component (B-1) was removed from the reaction vessel. The weight-average molecular weight (Mw) of copolymer (A-1) was 450,000, the glass transition temperature (Tg) was 3°C, the carboxyl group concentration was 0 mol / kg, and the hydroxyl group concentration was 0 mol / kg.

[0093] <Examples 2-19, Comparative Example 1> The compositions of the monomer formulation solution, initiator solution 1, and initiator solution 2 were changed as shown in Table 1, and otherwise, each adhesive main component (B) containing each copolymer (A) was obtained in the same manner as in Example 1. The weight-average molecular weight, glass transition temperature, carboxyl group concentration, and hydroxyl group concentration of each copolymer (A) are shown in Table 1.

[0094] <Rating> The heat resistance and handling properties of each adhesive base (B) were evaluated. Furthermore, adhesive base coating films (Bα) and adhesive films (Bβ) were prepared, and their heat resistance, handling properties, transparency, dielectric constant, color, appearance, and corrosiveness were evaluated using the method described later. The results are shown in Table 1.

[0095] <Preparation of adhesive-based coating film (Bα)> Each adhesive base (B) is melted at 150°C and applied at an ambient temperature of 23°C to the surface of a 100 μm thick polyester film [Toray Industries, Inc., product name Lumirror Type T, polyethylene terephthalate (PET) film] using a slot coater at a rate of 100 g / m². 2 A coating film was prepared by applying the coating. This resulted in an adhesive-based coating film (Bα) comprising a polyester film and an adhesive-based coating film overlapping it.

[0096] <Preparation of adhesive-based coating film (Bβ)> The main adhesive component (B) was melted at 150°C and applied at an ambient temperature of 23°C to the surface of a 25 μm thick polyester film that had been treated with a release agent, using a slot coater at a rate of 100 g / m². 2 A coating film was prepared by applying the coating. This resulted in an adhesive-based coating film (Bβ) comprising a release polyester film and an adhesive-based coating film overlapping it.

[0097] <Examples 21-39, Comparative Example 21> The components shown in "Composition" of Table 2 were blended in a Henschel mixer for 3 minutes, and then melt-kneaded in a vented twin-screw extruder at 150°C, 100 rpm, and residence time of 3 minutes to obtain each adhesive composition (X). Adhesive films (Yα) and (Yβ) were prepared from each adhesive composition (X) and evaluated using the method described below. The results are shown in Table 2.

[0098] <Preparation of adhesive film (Yα)> Each adhesive composition (X) is melted at 150°C and applied at an ambient temperature of 23°C to the surface of a 100 μm thick polyester film [Toray Industries, Inc., product name Lumirror Type T, polyethylene terephthalate (PET) film] using a slot coater at a rate of 100 g / m². 2 A coating film was prepared by applying the coating using [a specific method]. This coating film was then treated with a UV irradiation device [Ushio Inc., model number UVC-02516S1AA01], using a metal halide lamp as the light source, to achieve an integrated light intensity of 2000 mJ / cm². 2 By irradiating the coating with ultraviolet light under these conditions, the coating film was cured, and a cured layer with a thickness of 100 μm was produced. This resulted in an adhesive film (Yα) comprising a polyester film and a cured layer superimposed thereon.

[0099] <Preparation of adhesive film (Yβ)> Each adhesive composition (X) is melted at 150°C and applied at an ambient temperature of 23°C to the surface of a 25 μm thick polyester film that has been treated with a release agent, using a slot coater at a rate of 100 g / m². 2 A coating film was prepared by applying the coating using [a specific method]. This coating film was then treated with a UV irradiation device [Ushio Inc., model number UVC-02516S1AA01], using a metal halide lamp as the light source, to achieve an integrated light intensity of 2000 mJ / cm². 2 By irradiating the coating with ultraviolet light under these conditions, the coating film was cured, and a cured layer with a thickness of 100 μm was prepared. This resulted in an adhesive film (Yβ) comprising a polyester film and a cured layer superimposed thereon.

[0100] <1> Heat resistance test A heat resistance test was conducted by leaving 100g of the main adhesive component (B) standing at 150°C under reduced pressure conditions of -100kPa for 7 hours. After that, the weight-average molecular weight was measured by gel permeation chromatography. The percentage change in the weight-average molecular weight after this heat resistance test from the weight-average molecular weight before the heat resistance test (shown in Table 1) was calculated using the following formula and evaluated according to the following criteria. Rate of change (%) = (Weight-average molecular weight after heat resistance test) × 100 / (Weight-average molecular weight before heat resistance test)

[0101] <Evaluation Criteria> AA: The rate of change is between 100% and 105%. A: The rate of change is between 105% and 110%. B: The rate of change is between 110% and 120%. C: The rate of change is 120% or more.

[0102] <2> Handling Each adhesive main component was temperature-controlled at 150°C for 3 hours using 100g of each component, and then filtered through industrial woven wire mesh with a mesh size of 0.196mm. The clogging of the wire mesh during filtration was evaluated according to the following criteria. <Evaluation Criteria> AA: No clogging in the wire mesh. A: There was some slight blockage in the wire mesh, but the removal speed did not decrease, and removal was possible. B: It was possible to remove it, but the wire mesh was clogged, which slowed down the removal speed. C: The wire mesh is jammed and cannot be removed.

[0103] <3> transparency A 25mm x 25mm film test piece was cut from either the adhesive-based coating film (Bβ) or the adhesive film (Yβ). This test piece was attached to a glass slide [S1111, manufactured by Matsunami Glass Industry Co., Ltd.], the release polyester film was peeled off, and the film was transferred. The transparency of the film attached to the glass was measured using a haze meter [NDH-300A, manufactured by Nippon Denshoku Industries] and evaluated according to the following criteria. In this evaluation, a score of A or higher is preferable.

[0104] <Evaluation Criteria> AA: Haze value less than 1% A: Haze value is between 1% and 3% B: Haze value is between 3% and 5% C: Haze value is 5% or higher

[0105] <4> Dielectric constant The dielectric constants of the adhesive main coating film (Bβ) and the adhesive film (Yβ) were measured under the following conditions. Equipment: TR-1100 type dielectric loss automatic measuring device manufactured by Ando Electric Co., Ltd. Solid electrode: SE-70 type solid electrode Measurement environment: 23°C, 50%RH

[0106] A disc-shaped sample with a diameter of φ=25 mm was cut from the adhesive main coating film (Bβ) and the adhesive film (Yβ), and its thickness was measured with a micrometer (D, in μm). The release film was peeled off, and the sample was placed between the main electrode and the counter electrode and measured at 1 kHz to record the capacitance (Cx, in pF). The dielectric constant was calculated by substituting the obtained values ​​into the following formula and evaluated according to the following evaluation criteria. In this evaluation, a value of A or higher is preferable. Dielectric constant = (14.39 × Cx × D) / 32400

[0107] <Evaluation Criteria> AA: Less than 3.5 A: 3.5 or higher and less than 3.7 B: 3.7 or higher and less than 4.0 C:4.0 or higher

[0108] <5> Coloring (b*) Film test pieces measuring 25 mm x 25 mm in plan view were cut from the adhesive main coating film (Bβ) and adhesive film (Yβ). These test pieces were attached to a glass slide [S1111, manufactured by Matsunami Glass Industry Co., Ltd.], the release polyester film was peeled off, and the film was transferred. The b* value of the film attached to this glass was measured using a haze meter [NDH-300A, manufactured by Nippon Denshoku Industries Co., Ltd.] and evaluated according to the following evaluation criteria. In this evaluation, a value of A or higher is preferable.

[0109] <Evaluation Criteria> AA: Less than 0.4 A: 0.4 or higher and less than 0.7 B: 0.7 or higher and less than 1.0 C:1.0 or more

[0110] <6> exterior The surface appearance of the hardened layers of the adhesive main coating film (Bα) and adhesive film (Yα) was visually observed and evaluated according to the following evaluation criteria. In this evaluation, a score of A or higher is preferable.

[0111] <Evaluation Criteria> AA: There are absolutely no uneven areas in the paint. A: There are slight inconsistencies in the paint application. B: There are some areas where the paint is unevenly applied. C: The paint job is uneven overall.

[0112] <7> Corrosion test Adhesive film test pieces with planar dimensions of 100 mm × 25 mm were cut from the adhesive main coating film (Bα) and adhesive film (Yα). A 0.18 mm thick polyethylene terephthalate film with an ITO (indium tin oxide) film overlaid on one side was also prepared. Under a 25°C atmosphere, the adhesive film test pieces and the polyethylene terephthalate film were placed on top of each other according to JIS Z0237-2009 "Test Method for Adhesive Tapes and Adhesive Sheets" so that the cured layer and the ITO film were in contact. Subsequently, a 2 kg load was applied to the polyethylene terephthalate film using a roller, and the roller was moved back and forth once on the polyethylene terephthalate film. This bonded the adhesive film test pieces and the polyethylene terephthalate film together to obtain a laminated film. The laminated film was left for 14 days under conditions of 25°C and 90% relative humidity, and then a 180° peel test was performed on an adhesive film test piece against polyethylene terephthalate film in an atmosphere of 25°C. Next, the electrical resistance (R1) of the ITO film on the polyethylene terephthalate film was measured. The electrical resistance (R0) of the ITO film on the polyethylene terephthalate film before lamination to the adhesive film test piece was also measured beforehand. Based on these results, the rate of change in the electrical resistance of the ITO film was calculated using the formula below, and the results were evaluated according to the evaluation criteria below. A smaller rate of change in resistance indicates lower corrosiveness and better performance. In this evaluation, a rating of A or higher is preferable. Rate of change (%) = (R1 - R0) × 100 / R0

[0113] <Evaluation Criteria> AA: Change rate less than 5%. A: A change of 5% or more, but less than 10%. B: Rate of change between 10% and 20%. C: Change rate of 20% or more.

[0114] <8> Adhesive strength (stickiness) A 100mm x 25mm adhesive film test piece was cut from the adhesive film (Yα). A 0.18mm thick polyethylene terephthalate film with an ITO (indium tin oxide) film on one side was also prepared. Under a 25°C atmosphere, the adhesive film test piece and the polyethylene terephthalate film were placed on top of each other according to the "Test Method for Adhesive Tapes and Adhesive Sheets" specified in JIS Z0237-2009, so that the cured layer and the ITO film were in contact. Next, a 2kg load was applied to the polyethylene terephthalate film using a roller, and the roller was moved back and forth once on the polyethylene terephthalate film. This bonded the adhesive film test piece and the polyethylene terephthalate film together to obtain a laminated film. The laminated film was left for one day at a temperature of 25°C and a relative humidity of 50%. Then, the 180° peel strength of an adhesive film test piece against polyethylene terephthalate film was measured at a width of 25 mm and a tensile speed of 300 mm / min in a 25°C atmosphere. The results were evaluated according to the following criteria. In this evaluation, a score of A or higher is preferable.

[0115] <Evaluation Criteria> AA: Larger than 15N / 25mm. A: Greater than 10N / 25mm and less than or equal to 15N / 25mm. B: Larger than 5N / 25mm and 10N / 25mm or smaller. C: 5N / 25mm or less.

[0116] <9> holding power A test piece of adhesive film (Yα) with planar dimensions of 100 mm × 12 mm was cut from the adhesive film (Yα). A stainless steel plate with planar dimensions of 100 mm × 100 mm was also prepared. The adhesive film (Yα) and the stainless steel plate were stacked so that the hardened layer and the stainless steel plate were in contact, and the contact area was 12 mm × 12 mm in planar dimensions. Next, a load of 2 kg was applied to the polyethylene terephthalate film using a roller, and the roller was moved back and forth once on the polyethylene terephthalate film. This bonded the adhesive film (Yα) and the stainless steel plate together to obtain a laminate. This laminate was left to stand in a 40°C atmosphere for 30 minutes. Next, in a 40°C atmosphere, the stainless steel plate was placed vertically so that the portion in contact with the adhesive film (Yα) was positioned downwards. In this state, a 1 kg downward load was applied for 24 hours to the upper edge of the adhesive film (Yα) at ​​the lower edge of the 88 mm x 12 mm portion of the stainless steel plate where the adhesive film (Yα) was not overlapping. Subsequently, the downward displacement (in mm) of the adhesive film (Yα) relative to the stainless steel plate was measured and evaluated according to the following evaluation criteria. Note that a smaller value indicates higher holding power.

[0117] <Evaluation Criteria> AA: 0.5mm or less. A: Greater than 0.5 mm and less than or equal to 1.0 mm. B: Greater than 1.0 mm and 2.0 mm or less. C: Exceeds 2.0mm.

[0118] <10> Adhesion on curved surfaces (curved surface peel test) A 40mm x 40mm adhesive film test piece was cut from the adhesive film (Yα). Five adhesive film test pieces were prepared and attached to five glass tubes with an outer diameter of 30mm, one of each wrapped around the tube. Next, each glass tube was left to stand for 24 hours in a 23°C atmosphere, and the length of the portion of the adhesive film that had peeled off the glass tube was measured. For each glass tube, the sum of the lengths of the peeled portions at one end and the peeled portions at the other end of the adhesive film was calculated. The average of the sums of these lengths for five glass tubes was calculated, and the results were evaluated according to the following evaluation criteria. A smaller value indicates better adhesion on curved surfaces. In this evaluation, a score of A or higher is preferable.

[0119] <Evaluation Criteria> AA: 0.5mm or less. A: Greater than 0.5 mm and less than or equal to 1.0 mm. B: Greater than 1.0 mm and 2.0 mm or less. C: Exceeds 2.0mm.

[0120] <11> Adhesion on curved surfaces at low temperatures (curved surface peeling test at low temperatures) Adhesive film test pieces measuring 40 mm x 40 mm in plan view were cut from adhesive film (Yα). Five adhesive film test pieces were left to stand for 24 hours in a 5°C atmosphere, and then attached to five glass tubes with an outer diameter of 30 mm, respectively, in a 5°C atmosphere. Next, each glass tube was left to stand for 24 hours in a 5°C atmosphere, and then the length of the portion of the adhesive film that had peeled off the glass tube was measured. For each glass tube, the sum of the lengths of the peeled portions at one end and the peeled portions at the other end of the adhesive film was calculated. The average of the sums of these lengths for five glass tubes was calculated, and the results were evaluated according to the following evaluation criteria. A smaller value indicates better adhesion on curved surfaces. In this evaluation, a score of A or higher is preferable.

[0121] <Evaluation Criteria> AA: 0.3mm or less. A: Over 0.3mm and 0.8mm or less. B: Greater than 0.8mm and less than or equal to 1.5mm. C: Exceeds 1.5mm.

[0122] [Table 1]

[0123] In Table 1, (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.

[0124] [Table 2]

[0125] The details of the polyfunctional (meth)acrylates and initiators in Table 2 are as follows. Polyfunctional (meth)acrylate (C-1): Product name Neomer TA-505, manufactured by Sanyo Chemical Industries, Ltd., triacrylate of the PO (propylene oxide) adduct of trimethylolpropane, number average molecular weight 460. Initiator (D-1): Product name SB-PI 712, manufactured by Sanyo Trading Co., Ltd., 4-methylbenzophenone.

[0126] The results in Tables 1 and 2 show that the main adhesive component of the present invention has superior handling properties compared to the comparative product. Furthermore, the adhesive composition of the present invention exhibits excellent transparency, high tackiness, particularly excellent tackiness on curved surfaces, and a low dielectric constant. Moreover, it exhibits minimal coating unevenness, excellent appearance, minimal discoloration, and no corrosiveness, making it extremely superior. [Industrial applicability]

[0127] The main adhesive component of the present invention has a moderately low viscosity when heated (e.g., 150°C) and excellent handling properties. The adhesive composition containing the main adhesive component of the present invention has excellent transparency, high tackiness (especially on curved surfaces), and a low dielectric constant. Furthermore, the adhesive film having a cured layer made from the cured product of the adhesive composition has excellent tackiness. 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 protection, etc.), surface protection (protection of painted surfaces, etc.), medical use (bandages, etc.), and office use. Moreover, because the adhesive film has excellent tackiness on curved surfaces, it can also be suitably used for protecting curved substrates (curved displays, curved electronic circuit boards).

Claims

1. The main component of the adhesive is a copolymer (A) containing alkyl (alkyl with 16 to 32 carbon atoms) (meth)acrylate (a1), branched alkyl (alkyl with 8 to 10 carbon atoms) (meth)acrylate (a2), linear alkyl (alkyl with 1 to 4 carbon atoms) (meth)acrylate (a3), and nitrogen atom-containing monomer (a4) as constituent monomers.

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

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

4. The adhesive main component according to claim 1, wherein the main component contains an aliphatic alcohol (T2) having 16 to 32 carbon atoms, and the content of the aliphatic alcohol (T2) in the main component is 0.1 to 3.0% by weight based on the weight of the main component.

5. The adhesive main component according to claim 1, wherein the storage modulus of the copolymer (A) at 0°C is 150 to 7,000 kPa.

6. The adhesive main component according to claim 1, wherein the weight-average molecular weight of the copolymer (A) is 300,000 to 900,000.

7. An adhesive composition comprising the adhesive main component according to any one of claims 1 to 6 and a photopolymerization initiator (D).

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