Active energy ray-curable adhesive composition, adhesive layer, laminate, and article

Abstract

To provide an active energy ray-curable pressure-sensitive adhesive composition excellent in pressure-sensitive adhesive characteristics such as 180 ° pressure-sensitive adhesive force, constant load holding force and shear holding force, and capable of forming a pressure-sensitive adhesive layer excellent in removability and suppressed in bleed-out, to provide the pressure-sensitive adhesive layer, and to provide a laminate such as a pressure-sensitive adhesive tape having the pressure-sensitive adhesive layer.SOLUTION: An active energy ray-curable pressure-sensitive adhesive composition comprising a urethane (meth) acrylate resin (A) having an acryloyl group equivalent of 7000 to 40000 obtained by reacting a polyol (a), a polyisocyanate (b), and a (meth) acrylic compound (c) having a hydroxyl group, a nitrogen atom-containing (meth) acrylic monomer (B) capable of forming a homopolymer having a glass transition temperature of 15 °C. or higher, a (meth) acrylic monomer (C) capable of forming a homopolymer having a glass transition temperature of - 15 °C. or lower, a photopolymerization initiator (D), and a tackifier resin (E) having a softening point of 85 °C. or higher.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an active energy ray-curable pressure-sensitive adhesive composition, a pressure-sensitive adhesive layer, a laminate, and an article. More specifically, the present invention relates to an active energy ray-curable pressure-sensitive adhesive composition capable of forming a laminate such as a pressure-sensitive adhesive tape applicable to various fields such as the production of electronic devices and automotive parts, a pressure-sensitive adhesive and a pressure-sensitive adhesive layer comprising the composition, and an article having a structure bonded by the pressure-sensitive adhesive tape. [Background technology]

[0002] UV-curable adhesives do not usually contain solvents such as water, and do not require a solvent removal process when forming the adhesive layer. Furthermore, they do not require a maturation period to form a three-dimensional crosslinked structure, so they are attracting attention from the perspective of improving the production efficiency of final products manufactured using the adhesive and being environmentally friendly. Various studies have been conducted to improve the adhesive strength of ultraviolet-curable adhesives. For example, Patent Document 1 proposes an active energy ray-curable adhesive composition containing two ethylenically unsaturated monomers, a heterocycle-containing monomer and a hydroxyl group-containing monomer, in a specific ratio, which is said to have a good balance of adhesive strength and moist heat resistance. Patent Document 2 proposes a pressure-sensitive adhesive composition containing a specific urethane (meth)acrylate, a monofunctional monomer having a nitrogen atom and an unsaturated bond, and a monofunctional (meth)acrylate having a hydroxyl group, which is said to have excellent resistance to foaming and to be able to maintain adhesive strength even in high-temperature, high-humidity environments. Patent Document 3 proposes a resin composition for ultraviolet-curable pressure-sensitive adhesives that contains a specific amount of a specific (meth)acrylic monomer capable of forming a homopolymer with a predetermined glass transition temperature, and is said to be able to achieve both adhesive strength and holding power. Patent Document 4 proposes a resin composition for ultraviolet-curable pressure-sensitive adhesives that contains a urethane (meth)acrylate resin having a (meth)acryloyl group equivalent weight within a specific range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 013510 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-186450 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-136557 [Patent Document 4] Japanese Patent Application Laid-Open No. 2014-005368 Summary of the Invention [Problem to be solved by the invention]

[0004] Both the compositions disclosed in Patent Document 1 and Patent Document 2 contain a hydroxyl group-containing monomer as an ethylenically unsaturated monomer, but such a monomer is irritating to the skin, and therefore there is room for improvement in terms of the handleability of the composition and safety to the human body. On the other hand, pressure-sensitive adhesive tapes are used as a joining means with excellent workability and high adhesive reliability for fixing parts in various industrial fields such as office automation equipment, IT products, home appliances, and automobiles, for temporary fixing of parts, and for labeling to display product information. In recent years, from the perspective of protecting the global environment, there has been an increasing demand in various industrial fields such as home appliances and automobiles for the recycling and reuse of used products. Therefore, there is a need for an ultraviolet-curable pressure-sensitive adhesive that can form a pressure-sensitive adhesive layer that has improved adhesive properties, such as constant load holding power, required for on-board automotive parts, compared to the compositions disclosed in Patent Documents 1 to 4, while also having removability. There is also a demand for a pressure-sensitive adhesive tape that has such a function, in particular the function of being able to dismantle and reuse adherend parts without staining them with the pressure-sensitive adhesive components.

[0005] The present inventors have discovered that the above problems can be solved by a composition containing a specific urethane (meth)acrylate resin, a specific monomer, and a specific tackifier resin, and have arrived at the present invention. That is, an object of the present invention is to provide an active energy ray-curable pressure-sensitive adhesive composition that can form a pressure-sensitive adhesive layer that has excellent adhesive properties such as 180° adhesive strength, constant load holding strength, and shear holding strength, and that also has excellent removability and suppressed bleed-out. Another object of the present invention is to provide a pressure-sensitive adhesive and a pressure-sensitive adhesive layer comprising the active energy ray-curable pressure-sensitive adhesive composition, and a laminate such as a pressure-sensitive adhesive tape that includes the pressure-sensitive adhesive layer and is easily removable. Another object of the present invention is to provide an article having a structure adhered with the adhesive tape. [Means for solving the problem]

[0006] The present invention relates to the following [1] to

[11] . [1] A urethane (meth)acrylate resin (A) having an acryloyl group equivalent of 7,000 to 40,000, obtained by reacting a polyol (a), a polyisocyanate (b), and a (meth)acrylic compound having a hydroxyl group (c), a nitrogen atom-containing (meth)acrylic monomer (B) capable of forming a homopolymer having a glass transition temperature of 15°C or higher; a (meth)acrylic monomer (C) capable of forming a homopolymer having a glass transition temperature of −15° C. or lower; a photopolymerization initiator (D); An active energy ray-curable pressure-sensitive adhesive composition comprising a tackifier resin (E) having a softening point of 85°C or higher. [2] The active energy ray-curable pressure-sensitive adhesive composition according to [1], wherein the urethane (meth)acrylate resin (A) is a polyether-based urethane (meth)acrylate resin or a polyester-based urethane (meth)acrylate resin. [3] The active energy ray-curable pressure-sensitive adhesive composition according to [1] or [2], wherein the nitrogen atom-containing (meth)acrylic monomer (B) has an HSP value of 20 or more. [4] The active energy ray-curable pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the (meth)acrylic monomer (C) is a monomer having no hydroxyl group. [5] The active energy ray-curable pressure-sensitive adhesive composition according to any one of [1] to [4], wherein the tackifier resin (E) has an HSP value of 12 or more. [6] The active energy ray-curable pressure-sensitive adhesive composition according to any one of [1] to [5], which has a tan δ at 39°C of 0.25 or more. [7] A pressure-sensitive adhesive comprising the active energy ray-curable pressure-sensitive adhesive composition according to any one of [1] to [6]. [8] An adhesive layer comprising the active energy ray-curable adhesive composition according to any one of [1] to [6]. [9] A laminate having an adhesive layer formed from an adhesive comprising the active energy ray-curable adhesive composition according to any one of [1] to [6].

[10] The laminate according to [9], which is an adhesive tape having the adhesive layer on one or both sides of a substrate.

[11] An article comprising at least two adherends and the laminate according to

[10] , which is an adhesive tape having the adhesive layer on both sides of the substrate, between the two adherends, wherein the two adherends are bonded via the laminate. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an active energy ray-curable pressure-sensitive adhesive composition that can form a pressure-sensitive adhesive layer that has excellent adhesive properties, excellent removability, and suppressed bleed-out. It is also possible to provide a pressure-sensitive adhesive and a pressure-sensitive adhesive layer made from the active energy ray-curable pressure-sensitive adhesive composition, as well as a laminate such as a pressure-sensitive adhesive tape that includes the pressure-sensitive adhesive layer and is easily removable. Furthermore, according to the present invention, it is possible to provide an article that has a structure adhered with the adhesive tape, which can be easily disassembled and whose parts can be reused. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present invention relates to a urethane (meth)acrylate resin (A) (hereinafter simply referred to as "urethane (meth)acrylate resin (A)") having an acryloyl group equivalent of 7,000 to 40,000, which is obtained by reacting a polyol (a), a polyisocyanate (b), and a (meth)acrylic compound (c) having a hydroxyl group, and a nitrogen atom-containing (meth)acrylic monomer (B) (hereinafter simply referred to as "nitrogen atom-containing (meth)acrylic monomer (B)") capable of forming a homopolymer having a glass transition temperature (Tg) of 15°C or higher. The active energy ray-curable pressure-sensitive adhesive composition (hereinafter also simply referred to as "the pressure-sensitive adhesive composition of the present invention") contains a (meth)acrylic monomer (B) capable of forming a homopolymer having a glass transition temperature (Tg) of -15°C or lower (hereinafter also simply referred to as "(meth)acrylic monomer (C)"), a photopolymerization initiator (D), and a tackifier resin (E) having a softening point of 85°C or higher (hereinafter also simply referred to as "tackifier resin (E)"). Hereinafter, embodiments of the present invention will be described in detail. In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In this specification, "(meth)acrylic" is a term that collectively refers to acrylic, methacrylic, and both. "(Meth)acrylate" is a term that collectively refers to acrylate, methacrylate, and both. First, each of the components of the pressure-sensitive adhesive composition of the present invention will be described.

[0009] [Urethane (meth)acrylate resin (A)] The urethane (meth)acrylate resin (A) contained in the pressure-sensitive adhesive composition of the present invention is obtained by reacting a polyol (a), a polyisocyanate (b), and a (meth)acrylic compound (c) having a hydroxyl group, and has an acryloyl group equivalent of 7,000 to 40,000. The urethane (meth)acrylate resin (A) has a (meth)acrylic group that undergoes radical polymerization upon irradiation with light, heating, etc., and the equivalent weight of the (meth)acrylic group, i.e., the acryloyl group equivalent weight, is in the range of 7,000 to 40,000, so that the adhesive layer formed from the pressure-sensitive adhesive composition of the present invention can achieve both excellent adhesive strength and holding power, and can also form an adhesive layer with excellent removability. The acryloyl group equivalent weight of the urethane (meth)acrylate resin (A) is preferably 8,000 to 35,000, and more preferably 9,000 to 30,000. The acryloyl group equivalent weight means the value obtained by dividing the total mass of the polyol (a), the polyisocyanate (b), and the (meth)acrylic compound (c) having a hydroxyl group by the equivalent weight of the (meth)acrylic group present in the urethane (meth)acrylate resin (A).

[0010] As the polyol (a), for example, polyether polyol, polyester polyol, polycarbonate polyol, polyacrylic polyol, etc. These may be used alone or in combination of two or more. Examples of polyether polyols include polytetramethylene glycol obtained by ring-opening polymerization of tetrahydrofuran; modified polytetramethylene glycol obtained by copolymerizing tetrahydrofuran with alkyl-substituted tetrahydrofuran or neopentyl glycol; and polyether polyols having an alicyclic structure. Furthermore, as the polyether polyol, a product obtained by addition polymerization of one or more alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, etc., to a compound having two or more active hydrogens may be used. Examples of such compounds having two or more active hydrogens include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 1,6-hexanediol, 2,5-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 2-methyl-1,3-propanediol, neopentyl glycol, ethanol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, glycerin, diglycerin, trimethylolpropane, ditrimethylolpropane, trimethylolpropane, 1,2,6-hexanetriol, triethanolamine, triisopropanolamine, pentaerythritol, dipentaerythritol, sorbitol, sucrose, ethylenediamine, N-ethyldiethylenetriamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,2-diaminobutane, 1,3-diaminobutane, 1,4-diaminobutane, diethylenetriamine, phosphoric acid, and acidic phosphate esters. Among these, polypropylene glycol and polytetramethylene glycol are preferred from the viewpoint that the adhesive layer formed from the adhesive composition of the present invention is likely to have both excellent adhesive strength and holding power.

[0011] Examples of polyester polyols include condensation polyester polyols, lactone polyester polyols, etc. Condensation polyester polyols are, for example, reaction products of low-molecular-weight polyhydric alcohols (low-molecular-weight polyols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, neopentyl glycol, hexanediol, cyclohexanedimethanol, glycerin, 1,1,1-trimethylolpropane, 1,2,5-hexanetriol, pentaerythritol, 1,4-cyclohexanedimethanol, and 1,3-propanediol, and sugars such as sorbitol) with polybasic carboxylic acids (glutaric acid, adipic acid, azelaic acid, fumaric acid, maleic acid, pimelic acid, suberic acid, sebacic acid, phthalic acid, terephthalic acid, isophthalic acid, dimer acid, pyromellitic acid, oligomer acid, hexahydrophthalic anhydride, and 1,4-cyclohexanedicarboxylic acid). Examples of lactone-based polyester polyols include polycaprolactone polyols obtained by ring-opening polymerization of lactones such as ε-caprolactone, α-methyl-ε-caprolactone, and ε-methyl-ε-caprolactone.

[0012] Examples of polycarbonate polyols include polycarbonate polyols obtained by reacting a carbonate (carbonic acid ester) such as a dialkyl carbonate (dimethyl carbonate, diethyl carbonate, etc.), ethylene carbonate, or diphenyl carbonate with a glycol such as diethylene glycol, ethylene glycol, triethylene glycol propanediol, propanediol, butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, octanediol, 1,4-butynediol, dipropylene glycol, tripropylene glycol, polytetramethylene ether glycol, 2-methyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 1,4-cyclohexanediglycol, or 1,4-cyclohexanedimethanol.

[0013] In producing the urethane (meth)acrylate resin (A), a chain extender containing an active hydrogen atom may be further used together with the polyol (a). Examples of such chain extenders include polyhydric alcohols such as ethylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 3,3'-dimethylolheptane, 1,4-cyclohexanedimethanol, neopentyl glycol, 3,3-bis(hydroxymethyl)heptane, diethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, sorbitol, and hydroquinone diethylol ether; and polyhydric amines such as ethylenediamine, propylenediamine, hexamethylenediamine, trimethylhexamethylenediamine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, diaminocyclohexane, methyldiaminocyclohexane, and norbornenediamine. These chain extenders may be used alone or in combination of two or more.

[0014] The weight-average molecular weight (Mw) of the polyol (a) is preferably in the range of 500 to 20,000, more preferably in the range of 1,500 to 15,000. It is preferable that the Mw of the polyol (a) is within the above range, from the viewpoint of imparting good cohesion and flexibility to the adhesive layer formed from the pressure-sensitive adhesive composition of the present invention. The Mw of the polyol (a) is a value measured using gel permeation chromatography (GPC) in terms of standard polystyrene.

[0015] Examples of the polyisocyanate (b) include aromatic diisocyanates such as xylylene diisocyanate, phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, and naphthalene diisocyanate; and aliphatic or alicyclic structure-containing diisocyanates such as hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, diisocyanatomethylcyclohexane, and tetramethylxylylene diisocyanate. These polyisocyanates may be used alone or in combination of two or more. Among these, isophorone diisocyanate and hexamethylene diisocyanate are more preferred, as they allow the adhesive layer formed from the pressure-sensitive adhesive composition of the present invention to easily achieve both excellent adhesive strength and holding power.

[0016] The hydroxyl group of the hydroxyl group-containing (meth)acrylic compound (c) reacts with the isocyanate group of the polyisocyanate (b), thereby introducing a (meth)acrylic group into the urethane (meth)acrylate resin (A). Examples of the hydroxyl group-containing (meth)acrylic compound (c) include hydroxyl group-containing (meth)acrylic acid alkyl esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl acrylate; hydroxyl group-containing polyfunctional (meth)acrylates such as trimethylolpropane di(meth)acrylate, pentaerythritol tri(meth)acrylate, and dipentaerythritol penta(meth)acrylate; hydroxyl group-containing acrylamide derivatives such as N-(2-hydroxyethyl)acrylamide; polyethylene glycol monoacrylate, polypropylene glycol monoacrylate, etc. Among these, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, and N-(2-hydroxyethyl)acrylamide are preferred from the viewpoints of availability, the ease with which the curing properties of the pressure-sensitive adhesive composition of the present invention are improved, and the adhesive layer formed easily exhibits both excellent adhesive strength and holding power.

[0017] The urethane (meth)acrylate resin (A) is preferably a polyether-based urethane (meth)acrylate resin using at least a polyether polyol as the polyol (a), or a polyester-based urethane (meth)acrylate resin using at least a polyester polyol as the polyol (a). Use of a polyether-based urethane (meth)acrylate resin allows the adhesive layer formed from the pressure-sensitive adhesive composition of the present invention to have both excellent adhesive strength and holding power, and also improves the durability of the adhesive layer, particularly its hydrolysis resistance. The weight-average molecular weight (Mw) of the urethane (meth)acrylate resin (A) can be appropriately determined from the viewpoints of ensuring that the adhesive layer formed from the pressure-sensitive adhesive composition of the present invention has both excellent adhesive strength and holding power and excellent coating workability. When a polyether-based urethane (meth)acrylate resin is used as the urethane (meth)acrylate resin (A), the Mw is preferably 20,000 to 100,000, more preferably 30,000 to 70,000, and even more preferably 40,000 to 70,000. When a polyester-based urethane (meth)acrylate resin is used as the urethane (meth)acrylate resin (A), the Mw is preferably 10,000 to 50,000, more preferably 10,000 to 40,000, and even more preferably 15,000 to 30,000. The Mw of the urethane (meth)acrylate resin (A) is a value measured by gel permeation chromatography (GPC) and converted into a standard polystyrene value.

[0018] The urethane (meth)acrylate resin (A) can be produced, for example, by the following method. (1) In the absence of a solvent, polyol (a) and hydroxyl group-containing (meth)acrylic compound (c) are mixed, and then polyisocyanate (b) is added and reacted. (2) In the absence of a solvent, polyol (a) and polyisocyanate (b) are reacted to obtain a urethane prepolymer having isocyanate groups at the molecular terminals, and then hydroxyl group-containing (meth)acrylic compound (c) is added and reacted. In either case, the reaction temperature is preferably in the range of 20 to 120° C., and the reaction time is preferably about 30 minutes to 24 hours. Although a solvent may be used, it is preferable to carry out the reaction in the absence of a solvent, since this eliminates the need for solvent removal during production of the pressure-sensitive adhesive composition of the present invention, thereby simplifying the process. The reaction of polyol (a), polyisocyanate (b), and hydroxyl group-containing (meth)acrylic compound (c) is preferably carried out under conditions where the equivalent ratio between the total amount of hydroxyl groups in polyol (a) and the total amount of hydroxyl groups in hydroxyl group-containing (meth)acrylic compound (c) and the isocyanate groups in polyisocyanate (b) [isocyanate groups / total amount of hydroxyl groups] is 0.3 to 3.00, in order to control the molecular weight of the resulting urethane (meth)acrylate resin (A). When the reaction is carried out under conditions where the equivalent ratio exceeds 1, it is preferable to use alcohols such as monofunctional alcohols such as methanol, ethanol, propanol, and butanol; or bifunctional alcohols consisting of primary and secondary hydroxyl groups such as 1,2-propylene glycol and 1,3-butylene glycol, in order to deactivate the terminal isocyanate groups of the urethane (meth)acrylate resin (A) and adjust the equivalent ratio to fall within the aforementioned range. In producing the urethane (meth)acrylate resin (A), if necessary, polymerization inhibitors such as 3,5-di-tert-butyl-4-hydroxytoluene, hydroquinone, methylhydroquinone, hydroquinone monomethyl ether, p-tert-butylcatechol methoxyphenol, 2,6-di-tert-butylcresol, phenothiazine, tetramethylthiuram disulfide, diphenylamine, and dinitrobenzene; urethanization catalysts such as nitrogen-containing compounds such as triethylamine, triethylenediamine, and N-methylmorpholine, metal salts such as potassium acetate, zinc stearate, and tin octoate, and organometallic compounds such as dibutyltin dilaurate; and the like may be used.

[0019] In the pressure-sensitive adhesive composition of the present invention, the content of the urethane (meth)acrylate resin (A) is preferably in the range of 10 to 90 mass %, more preferably in the range of 20 to 70 mass %, and even more preferably in the range of 25 to 50 mass %, based on the total amount of the pressure-sensitive adhesive composition of the present invention. When the pressure-sensitive adhesive composition of the present invention contains the urethane (meth)acrylate resin (A) in the above-mentioned range, the pressure-sensitive adhesive composition is more likely to achieve a coating viscosity suitable for coating, and the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition is more likely to have excellent adhesive strength and holding power, which is preferable.

[0020] [Nitrogen atom-containing (meth)acrylic monomer (B)] As the nitrogen atom-containing (meth)acrylic monomer (B) capable of forming a homopolymer having a glass transition temperature (Tg) of 15°C or higher, from the viewpoint of providing an adhesive layer formed from the pressure-sensitive adhesive composition of the present invention with superior adhesive strength and holding power, a nitrogen-containing (meth)acrylic monomer capable of forming a homopolymer having a Tg of 55 to 160°C is preferred, and a nitrogen-containing (meth)acrylic monomer capable of forming a homopolymer having a Tg of 120 to 160°C is more preferred. Examples of such nitrogen-containing (meth)acrylic monomers include N,N-dimethylacrylamide (119°C), N,N-diethylacrylamide (81°C), N-isopropylacrylamide (134°C), N,N-dimethylaminopropylacrylamide (134°C), acryloylmorpholine (145°C), N-hydroxyethylacrylamide (98°C), N-vinylpyrrolidone (86°C), and N-acryloyloxyethylhexahydrophthalimide. The numbers in parentheses for each monomer are the Tg values ​​of the homopolymers of each monomer, as described in, for example, "Polymer Handbook (4th ed.)." These nitrogen-containing (meth)acrylic monomers (B) may be used alone or in combination of two or more. Among these, nitrogen-containing acrylic monomers are preferred from the viewpoint of improving the curability of the pressure-sensitive adhesive composition of the present invention, and acryloylmorpholine, N,N-dimethylacrylamide, N,N-dimethylaminopropylacrylamide, and N-acryloyloxyethylhexahydrophthalimide are preferred from the viewpoint of providing an adhesive layer formed from the pressure-sensitive adhesive composition of the present invention with superior adhesive strength and holding power, with acryloylmorpholine being more preferred.

[0021] The HSP value of the nitrogen-atom-containing (meth)acrylic monomer (B) is preferably 20 or more, more preferably 23 or more. The HSP value of the nitrogen-atom-containing (meth)acrylic monomer (B) is preferably 30 or less. When the HSP value of the nitrogen-atom-containing (meth)acrylic monomer (B) is within the above-mentioned range, it is believed that the polarity of the pressure-sensitive adhesive composition of the present invention can be easily controlled appropriately, and the compatibility of the constituent components, the urethane (meth)acrylate resin (A), the (meth)acrylic monomer (C), and the tackifier resin (E) described below, is improved. As a result, it is believed that the pressure-sensitive adhesive composition of the present invention has low haze and excellent transparency, the formed pressure-sensitive adhesive layer is likely to have excellent adhesive strength and holding power, and is likely to have excellent removability, and bleed-out of the tackifier resin (E) from the cured pressure-sensitive adhesive layer is also suppressed. Here, the HSP value means the Hansen solubility parameter, and its unit is (J / cm 3 ) 0.5 The HSP value is expressed as follows: The solubility parameter (SP value: δ) introduced by Hildebrand is multiplied by the dispersion term δ D , polar term δ P , and the hydrogen bond term δ H It is a parameter that takes into account the polarity of a substance and is expressed in three-dimensional space by dividing it into three components, and the relationship in the following equation holds. δ[(J / cm 3 ) 0.5 ]=(δ D 2 +δ P 2 +δ H 2 ) 0.5 The dispersion term δ D , polar term δ P , and the hydrogen bond term δ HMany of these have been calculated by Hansen and subsequent researchers, and are listed, for example, in pages VII-698 to 711 of the Polymer Handbook (4th edition). The Hansen solubility parameters for many solvents and resins have also been investigated, and are listed, for example, in the Industrial Solvents Handbook (by Wesley L. Archer). These solubility parameters can also be calculated using the Hansen Solubility Parameters in Practice (HSPiP) software. The dispersion term of the HSP of the nitrogen atom-containing (meth)acrylic monomer (B) is preferably 5 or more and 30 or less, more preferably 10 or more and 25 or less. The polarity term of the HSP of the nitrogen atom-containing (meth)acrylic monomer (B) is preferably 10 or more and 20 or less, more preferably 12 or more and 18 or less. Furthermore, the hydrogen bond term of the HSP of the nitrogen atom-containing (meth)acrylic monomer (B) is preferably 5 or more and 25 or less, more preferably 10 or more and 20 or less.

[0022] In the pressure-sensitive adhesive composition of the present invention, the content of the nitrogen-atom-containing (meth)acrylic monomer (B) is preferably in the range of 10 to 300 parts by mass, more preferably 50 to 200 parts by mass, per 100 parts by mass of the urethane (meth)acrylate resin (A). When the content of the nitrogen-atom-containing (meth)acrylic monomer (B) is in the above-mentioned range, the curability of the pressure-sensitive adhesive composition of the present invention can be improved, and the formed pressure-sensitive adhesive layer is more excellent in both adhesive strength and holding power, and is also more likely to have excellent removability.

[0023] [(Meth)acrylic monomer (C)] As the (meth)acrylic monomer (C) capable of forming a homopolymer having a glass transition temperature (Tg) of -15°C or less, a (meth)acrylic monomer capable of forming a homopolymer having a Tg of -20 to -80°C is more preferred, from the viewpoint that the adhesive layer formed from the adhesive composition of the present invention has better adhesive strength and holding power. Examples of such (meth)acrylic monomers include ethyl acrylate (-24°C), n-propyl acrylate (-37°C), n-butyl acrylate (-54°C), sec-butyl acrylate (-22°C), isobutyl acrylate (-24°C), 2-ethylbutyl acrylate (-50°C), n-pentyl acrylate (-57°C), isoamyl acrylate (-45°C), n-hexyl acrylate (-57°C), n-heptyl acrylate (-60°C), 2-ethylhexyl acrylate (-70°C), n-octyl acrylate (-65°C), isooctyl acrylate (-58°C), isononyl acrylate (-58°C), isodecyl acrylate (-62°C), lauryl acrylate (-23°C), ... Examples of suitable Tg values ​​include stearyl acrylate (-58°C), 2-methoxyethyl acrylate (-50°C), 3-methoxypropyl acrylate (-75°C), 2-methoxybutyl acrylate (-32°C), 3-methoxybutyl acrylate (-56°C), 2-ethoxyethyl acrylate (-24°C), 2-ethoxypropyl acrylate (-24°C), 2-ethoxybutyl acrylate (-24°C), 2-hydroxyethyl acrylate (-15°C), 4-hydroxybutyl acrylate (-32°C), ethyl carbitol acrylate (-67°C), phenoxyethyl acrylate (-22°C), 2-hydroxyethyl (meth)acrylate (-15°C), and 4-hydroxybutyl (meth)acrylate (-32°C). The parenthesized numbers for each monomer indicate the Tg values ​​of the homopolymers of the respective monomers, as described in, for example, "Polymer Handbook (4th ed.)." These (meth)acrylic monomers (C) may be used alone or in combination of two or more. Among these, acrylic monomers are preferred from the viewpoint of improving the curing properties of the pressure-sensitive adhesive composition of the present invention, and n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, and isodecyl acrylate are more preferred from the viewpoint of providing a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention with superior adhesive strength and holding power.

[0024] Furthermore, the (meth)acrylic monomer (C) is more preferably a monomer having no hydroxyl group, from the viewpoint of improving the handleability of the pressure-sensitive adhesive composition of the present invention, particularly from the viewpoint of reducing skin irritation and achieving excellent safety.

[0025] In the pressure-sensitive adhesive composition of the present invention, the content of the (meth)acrylic monomer (C) is preferably in the range of 10 to 300 parts by mass, more preferably 50 to 200 parts by mass, per 100 parts by mass of the urethane (meth)acrylate resin (A). When the content of the (meth)acrylic monomer (C) is in the above range, the curability of the pressure-sensitive adhesive composition of the present invention can be improved, and the pressure-sensitive adhesive layer formed is likely to have excellent adhesive strength and holding power.

[0026] The pressure-sensitive adhesive composition of the present invention may contain vinyl monomers other than the nitrogen atom-containing (meth)acrylic monomer (B) and the (meth)acrylic monomer (C) described above, as long as the effects of the present invention are not impaired. Such other vinyl monomers include (meth)acrylic acid, N-methylolacrylamide, acrylonitrile, N-vinylformamide, itaconic acid (anhydride), maleic acid (anhydride), fumaric acid, crotonic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, and isobutyl methacrylate. butyl (meth)acrylate, n-pentyl methacrylate, isopentyl methacrylate, neopentyl methacrylate, n-hexyl methacrylate, n-heptyl methacrylate, isoheptyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, nonyl methacrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl methacrylate, isobornyl (meth)acrylate, dodecyl (meth)acrylate, phenyl methacrylate Examples of the alkyl acrylate include vinyl acrylate, glycidyl methacrylate, benzyl (meth)acrylate, trifluoromethylmethyl (meth)acrylate, 2-trifluoromethylethyl (meth)acrylate, 2-perfluoroethylethyl (meth)acrylate, 2-perfluoroethyl-2-perfluorobutylethyl (meth)acrylate, 2-perfluoroethyl (meth)acrylate, perfluoromethyl (meth)acrylate, diperfluoromethylmethyl (meth)acrylate, 2-perfluoromethyl-2-perfluoroethylethyl (meth)acrylate, 2-perfluorohexylethyl (meth)acrylate, 2-perfluorodecylethyl (meth)acrylate, 2-perfluorohexadecylethyl (meth)acrylate, styrene, p-methylstyrene, ethylstyrene, propylstyrene, isopropylstyrene, p-tert-butylstyrene, vinyl acetate, vinyl propionate, and vinyl pivalate.

[0027] [Photopolymerization initiator (D)] The photopolymerization initiator (D) generates radicals upon irradiation with light, heating, or the like, and initiates radical polymerization of the urethane (meth)acrylate resin (A), the nitrogen atom-containing (meth)acrylic monomer (B), and the (meth)acrylic monomer (C). Examples of the photopolymerization initiator (D) include acetophenones such as 4-phenoxydichloroacetophenone, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 4-(2-hydroxyethoxy)-phenyl(2-hydroxy-2-propyl)ketone, 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propanone, and 2,2-dimethoxy-2-phenylacetophenone; benzoins such as benzoin methyl ether, benzoin isoethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, and 4-benzoyl-4'-methyldiphenyl thioxanthones such as thioxanthone, 2-chlorothioxanthone, 2,4-dichlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, and 2,4-diisopropylthioxanthone; anthraquinones such as 4,4'-dimethylaminothioxanthone, 4,4'-diethylaminobenzophenone, α-acyloxime ester, benzyl, methylbenzoyl formate, and 2-ethylanthraquinone; acylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide; and 3,3',4,4'-tetra(tert-butyloperoxycarbonyl)benzophenone and acrylated benzophenone. These photopolymerization initiators (D) may be used alone or in combination of two or more. Among these, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide are preferred, from the viewpoints of excellent compatibility with the nitrogen atom-containing (meth)acrylic monomer (B) and (meth)acrylic monomer (C) used in the present invention, improving the curing properties of the pressure-sensitive adhesive composition of the present invention, and providing a pressure-sensitive adhesive layer formed with superior adhesive strength and holding power. In the pressure-sensitive adhesive composition of the present invention, the content of the photopolymerization initiator (D) is not particularly limited as long as it is an amount that can crosslink at least 60 mass% of the polymerization components including the urethane (meth)acrylate resin (A), the nitrogen-containing (meth)acrylic monomer (B), and the (meth)acrylic monomer (C), and is typically in the range of 0.1 to 20 mass parts, more preferably 0.5 to 15 mass parts, and even more preferably 0.5 to 10 mass parts, per 100 mass parts of the urethane (meth)acrylate resin (A). When the content of the photopolymerization initiator (D) is within the above range, the polymerization components are less likely to remain unreacted and the amount of unreacted photopolymerization initiator (D) is reduced, which tends to improve the handleability of the pressure-sensitive adhesive composition of the present invention and tends to suppress performance deterioration over time of an adhesive layer formed from the pressure-sensitive adhesive composition of the present invention.

[0028] [Tackifying resin (E)] The tackifier resin (E) contained in the pressure-sensitive adhesive composition of the present invention has a softening point of 85°C or higher. Such a softening point is preferably 100°C or higher, and more preferably 110°C or higher. The softening point of the tackifier resin (E) is preferably 200°C or lower, and more preferably 170°C or lower. When the softening point of the tackifier resin (E) is within the above range, the adhesive layer formed from the pressure-sensitive adhesive composition of the present invention can have good adhesiveness at around room temperature (0 to 40°C) and exhibit good heat durability. The softening point of the tackifier resin (E) in the present invention means a value determined by the ring and ball method in accordance with JIS K 5902. The HSP value of the tackifier resin (E) is preferably 12 or more, more preferably 15 or more, and even more preferably 17 or more. The HSP value of the tackifier resin (E) is preferably 30 or less, more preferably 25 or less, and even more preferably 22 or less. The definition and details of the HSP value are as described above in the explanation of the HSP value of the nitrogen atom-containing (meth)acrylic monomer (B). The inclusion of a tackifier resin (E) having an HSP value within the above-described range tends to improve compatibility with the urethane (meth)acrylate resin (A), nitrogen-containing (meth)acrylic monomer (B), and (meth)acrylic monomer (C) constituting the pressure-sensitive adhesive composition of the present invention, making it easier to appropriately control the polarity of the pressure-sensitive adhesive composition of the present invention. As a result, the pressure-sensitive adhesive composition of the present invention has low haze and excellent transparency, and the pressure-sensitive adhesive layer formed has excellent adhesive strength and holding power. Furthermore, even after the pressure-sensitive adhesive composition of the present invention is cured to form a pressure-sensitive adhesive layer, bleed-out of the tackifier resin (E) is suppressed, resulting in excellent removability. Therefore, an article in which at least two adherends are bonded via a laminate (adhesive tape) having an adhesive layer formed from the pressure-sensitive adhesive composition of the present invention, as described below, firmly fixes the adherends together, and when disassembly is desired, the adhesive layer does not remain on the adherends, allowing for clean peeling.

[0029] Examples of the tackifying resin (E) include various tackifying resins such as rosin, polymerized rosin, polymerized rosin ester, rosin phenol, stabilized rosin ester, disproportionated rosin ester, hydrogenated rosin ester, terpene, terpene phenol, petroleum resin, C5 / C9 petroleum resin, process oil, polybutene, polyester, (meth)acrylate, etc. These tackifying resins may be used alone or in combination of two or more. Commercially available tackifier resins (E) can be used, and tackifier resins that satisfy the softening point and preferably the HSP value ranges described above can be used as the tackifier resin (E) in the pressure-sensitive adhesive composition of the present invention.

[0030] In the pressure-sensitive adhesive composition of the present invention, the content of the tackifier resin (E) is preferably in the range of 5 to 200 parts by mass, more preferably 10 to 110 parts by mass, per 100 parts by mass of the urethane (meth)acrylate resin (A), from the viewpoint of enabling the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention to have excellent adhesive strength and holding power and also good removability. The content of the tackifier resin is preferably in the range of 5 to 40% by mass, more preferably 5 to 30% by mass, based on the total pressure-sensitive adhesive composition of the present invention.

[0031] The pressure-sensitive adhesive composition of the present invention may further contain other additives, such as antioxidants, antiaging agents, colorants such as pigments and dyes, crosslinking agents, thickeners, leveling agents, film-forming aids, infrared absorbers, ultraviolet absorbers, and water repellents, as necessary, within the range that does not impair the effects of the present invention.

[0032] [Adhesive and adhesive layer] The present invention also relates to a pressure-sensitive adhesive comprising the pressure-sensitive adhesive composition of the present invention. The pressure-sensitive adhesive of the present invention can be widely applied in various fields such as the production of electronic devices and automotive parts, construction supplies, and medical supplies. The adhesive layer can be formed by applying the adhesive comprising the adhesive composition of the present invention onto a substrate by a known coating method such as roll coating, knife coating, bar coating or die coating. The pressure-sensitive adhesive comprising the pressure-sensitive adhesive composition of the present invention can also be applied to a substrate using, for example, a dispenser to form a pressure-sensitive adhesive layer. When forming a pressure-sensitive adhesive layer on a substrate using a dispenser, the application speed is not particularly limited, and from the viewpoint of balancing workability and productivity, for example, a speed of 5 mm / min or more is preferred, and 10 mm / min or more is more preferred. Furthermore, to reduce the viscosity and improve applicability immediately before application to the substrate, shear stress may be applied to the pressure-sensitive adhesive composition of the present invention using a screw dispenser. The screw rotation speed when applying shear stress is preferably 50 rpm or more, more preferably 100 rpm or more. The screw rotation speed is preferably 1000 rpm or less, and more preferably 900 rpm or less. When forming a pressure-sensitive adhesive layer on a substrate using a dispenser, the pressure-sensitive adhesive composition of the present invention may be heated as needed.

[0033] The pressure-sensitive adhesive composition of the present invention is applied to a substrate to form a pressure-sensitive adhesive layer, and then cured with active energy rays to form the pressure-sensitive adhesive layer. Examples of active energy rays include visible light, ultraviolet light, infrared light, microwaves, EUV, semiconductor laser light, and excimer lasers (KrF, ArF). Among these, curing by irradiation with ultraviolet light or the like is preferred. Examples of light sources that can be used for ultraviolet rays include metal halide lamps, xenon lamps, carbon arc lamps, chemical lamps, low-pressure mercury lamps, high-pressure mercury lamps, and UV-LED lamps. From the viewpoint of extremely low heat generation and environmental protection that can accommodate mercury-free trends, it is more preferable to cure the composition by irradiating it with light from a UV-LED lamp, preferably a UV-LED lamp with a main peak wavelength of approximately 365 to 405 nm that can provide sufficient illuminance. The irradiation energy of light using a UV-LED is 100 to 5000 mJ / cm. 2 The range is preferably 500 to 3000 mJ / cm 2 The range of 1000 to 2000 mJ / cm is more preferable. 2 The range is more preferable.

[0034] The present invention also provides an adhesive layer comprising the pressure-sensitive adhesive composition of the present invention, in other words, an adhesive layer formed by applying the pressure-sensitive adhesive composition of the present invention and curing the applied active energy rays. The adhesive layer of the present invention has excellent adhesive strength and holding power, and also has excellent removability due to suppressed bleed-out of the tackifier resin (E). The thickness of the adhesive layer is preferably in the range of 10 to 5 mm, more preferably in the range of 20 to 2000 μm, from the viewpoints of adhesive strength to the adherend and film uniformity during solution coating. The thickness of the adhesive layer is the average value obtained by measuring the thickness at any five positions. From the viewpoint of exhibiting good 180° adhesive strength, the tan δ of the adhesive layer at 39°C is preferably 0.25 or more, more preferably in the range of 0.25 to 1.5, even more preferably in the range of 0.3 to 1.4, and particularly preferably in the range of 0.4 to 1.3. As a result of analyzing the correlation between the 180° adhesive strength and tan δ at each temperature, the present inventors found that there is a strong correlation between tan δ at 39°C and the 180° adhesive strength. When the tan δ of the adhesive layer of the present invention at 39°C is within the above range, the wettability to the adherend and the elasticity to peel from the adherend are well balanced, making it easier to exhibit good 180° adhesive strength. The tan δ of the adhesive layer can be adjusted by the types, combinations, and blending ratios of the urethane (meth)acrylate resin (A), nitrogen atom-containing (meth)acrylic monomer (B), (meth)acrylic monomer (C), photopolymerization initiator (D), and tackifier resin (E) that constitute the adhesive composition of the present invention, as well as the amount of crosslinking agent (gel fraction) added if necessary. The tan δ of the adhesive layer can be determined by dynamic viscoelasticity measurement in the examples described below.

[0035] The present invention also provides a laminate having an adhesive layer formed from an adhesive comprising the adhesive composition of the present invention. Such a laminate may have a substrate, or may be an adhesive tape consisting of an adhesive layer alone without a substrate, and is not particularly limited. The pressure-sensitive adhesive tape of the present invention has an adhesive layer formed from the pressure-sensitive adhesive composition of the present invention, and thus has excellent adhesive properties such as adhesive strength and holding power, and also has excellent removability due to suppressed bleed-out. Therefore, the pressure-sensitive adhesive tape of the present invention can be used as a pressure-sensitive adhesive tape with excellent removability, which allows the adherends to be easily separated or dismantled after a certain period of time has elapsed after being applied to the adherends and fixed thereto. Here, "excellent removability" means that when the adherends are separated or dismantled, cohesive failure does not occur within the adhesive layer, but rather the adhesive layer exhibits good releasability at the interface between the adherend and the adhesive layer. This also encompasses the fact that the components constituting the pressure-sensitive adhesive composition of the present invention, such as the tackifier resin (E), do not remain on the adherend, and the tape can be peeled off without damaging the adherend, allowing the adherend to be recycled. Furthermore, the pressure-sensitive adhesive tape of the present invention has a low content of volatile components, which reduces the adverse effects on the external environment caused by smoke, etc., when fixing adherends to each other or when peeling and dismantling the tape, and is also excellent in terms of safety for workers during dismantling.

[0036] The shape of the substrate is not particularly limited as long as it allows application of the pressure-sensitive adhesive composition, and examples thereof include flat, foil, sheet, plate, curved, uneven, etc. Examples of substrates that can be appropriately selected and used depending on the application of the pressure-sensitive adhesive tape include plastic films such as polypropylene film, ethylene-propylene copolymer film, polyester film, polyvinyl chloride film, cellophane, polyimide, polycarbonate (PC), polystyrene (PS), etc.; foam sheets made of foams such as polyurethane foam, polyethylene foam, polypropylene foam, ethylene-vinyl acetate copolymer foam, butyl rubber foam, polyacrylate foam, etc.; woven and nonwoven fabrics made by spinning alone or in combination various fibrous materials (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, semi-synthetic fibers such as acetate, metal fibers such as stainless steel, etc.); paper such as kraft paper, Japanese paper, crepe paper, etc.; and metal foils such as aluminum foil and copper foil. The plastic film may be a non-stretched film, a uniaxially stretched film, or a biaxially stretched film. The surface of the substrate on which the adhesive layer is to be formed may be subjected to an adhesion-improving treatment such as application of a primer or corona discharge treatment. The laminate of the present invention is preferably a pressure-sensitive adhesive tape, which is a laminate consisting of a film or sheet-like substrate and a pressure-sensitive adhesive layer formed on one or both sides of the substrate, the pressure-sensitive adhesive layer being made of the pressure-sensitive adhesive composition of the present invention. In this case, the thickness of the substrate can be appropriately selected depending on the purpose, and is usually preferably in the range of 1 μm to 2000 μm.

[0037] When the laminate of the present invention is an adhesive tape, the laminate may have a release layer (also referred to as a release sheet or release liner). Examples of the release layer include glassine paper, kraft paper, clay-coated paper, paper laminated with a film such as polyethylene, paper coated with a resin such as polyvinyl alcohol or an acrylic ester copolymer, and synthetic resin films such as polyester or polypropylene coated with a fluororesin or silicone resin. The release layer may be present on one or both sides of the adhesive tape of the present invention.

[0038] When the laminate of the present invention is an adhesive tape, as long as the outermost layers (excluding the release layer) positioned opposite each other in the thickness direction have adhesive surfaces that can be bonded to an adherend, the laminate may have other layers in addition to the adhesive layer and the base layer, such as functional layers having functions such as insulating properties, heat insulation properties, impact resistance, waterproofing properties, or heat shielding properties.

[0039] The laminate of the present invention may have the following exemplary configurations, but is not limited to these. In the following laminate configurations, " / " represents a laminate interface, and for example, in "Layer A / Layer B," Layer A and Layer B are adjacent to each other, i.e., are in direct contact with each other. ·Adhesive layer / base material layer ·Peel layer / adhesive layer / peel layer ·Release layer / functional layer / adhesive layer / release layer Release layer / functional layer / adhesive layer / functional layer / release layer ·Release layer / Adhesive layer / Base layer ·Adhesive layer / base layer / functional layer ·Adhesive layer / functional layer / base material layer ·Release layer / Adhesive layer / Functional layer / Base layer / Functional layer · Peel layer / adhesive layer / base layer / adhesive layer ·Adhesive layer / base material layer / adhesive layer ·Adhesive layer / base material layer / functional layer / adhesive layer ·Release layer / Adhesive layer / Base layer / Adhesive layer / Release layer · Peel layer / adhesive layer / base layer / functional layer / adhesive layer ·Release layer / Adhesive layer / Functional layer / Base material layer / Adhesive layer / Release layer ·Release layer / Adhesive layer / Functional layer / Base layer / Functional layer / Adhesive layer / Release layer

[0040]

[0033] There are no particular limitations on the method for producing the laminate of the present invention. For example, the laminate of the present invention, which is a pressure-sensitive adhesive tape, can be produced by applying the pressure-sensitive adhesive composition of the present invention to a substrate to form a pressure-sensitive adhesive layer, overlaying a release sheet on the pressure-sensitive adhesive layer, and then irradiating with active energy rays from the release sheet side to form a pressure-sensitive adhesive layer. Here, the pressure-sensitive adhesive composition of the present invention can be further applied to the opposite side of the substrate layer to form a pressure-sensitive adhesive layer, overlaying a release sheet, and then irradiating with active energy rays from the release sheet side to form a pressure-sensitive adhesive layer, thereby producing the pressure-sensitive adhesive tape of the present invention, which is a laminate having pressure-sensitive adhesive layers on both sides of the substrate. Alternatively, the pressure-sensitive adhesive composition of the present invention can be applied to a release sheet to form a pressure-sensitive adhesive layer, the formed pressure-sensitive adhesive layer is bonded to one or both sides of a sheet-like substrate, and then active energy rays are irradiated from the release sheet side to form a pressure-sensitive adhesive layer, thereby producing the laminate of the present invention, which is a pressure-sensitive adhesive tape. Furthermore, the laminate of the present invention may be produced by subjecting the pressure-sensitive adhesive composition of the present invention to extrusion molding, press molding, injection molding or the like, and then irradiating it with active energy rays.

[0041] When the laminate of the present invention, which is an adhesive tape, has adhesive layers on both sides excluding the release layer, adherends can be stuck to both sides of the adhesive tape, and it can be suitably used for joining adherends together. The pressure-sensitive adhesive tape of the present invention has excellent adhesive properties such as 180° adhesive strength (180° peel adhesive strength), constant load holding strength, and shear holding strength, as well as excellent removability, and therefore can be suitably used, for example, for bonding rigid adherends to each other and for separating adherends from each other. For example, the pressure-sensitive adhesive tape can be suitably used in applications where peeling of the adhesive tape is required for separating parts for the purpose of reuse or recycling, specifically as an adhesive tape for fixing parts of various products in industrial applications such as electronic devices, automobiles, building materials, office automation, and home appliances, and can improve work efficiency when separating parts or removing labels. Furthermore, the laminate of the present invention, which is an adhesive tape, has a low content of volatile components, reduces adverse effects on the external environment, and is removably and easily peelable.

[0042] [Goods] The present invention also provides an article comprising at least two adherends and, between the two adherends, an adhesive tape which is the adhesive layer of the present invention alone, or an adhesive tape having the adhesive layer of the present invention on both sides of a substrate, and the laminate of the present invention, in which the two adherends are adhered via the adhesive tape. The adherend may be rigid or flexible like a film, etc. The material and shape of the adherend are not particularly limited, and examples include plate-shaped adherends made of resin, glass, or metal, housings, covers, and parts having any of these on the adherend surface. The two adherends bonded via the pressure-sensitive adhesive tape may be the same or different. As a method for bonding the adherends, a method in which an adherend is attached to each adhesive surface of the pressure-sensitive adhesive tape of the present invention and the two adherends are bonded together can be mentioned. There are no particular restrictions on the articles, but from the viewpoint of effectively utilizing the effects of the pressure-sensitive adhesive tape of the present invention, for example, in-vehicle parts, electronic devices, parts built into electronic devices, etc. are preferred. In a plan view of the article, the adhesive tape may be attached to the entire adhesion surface, which is the surface of the adherend facing the adhesive tape, or the adhesive tape may be attached to only a part of the adhesion surface of the adherend.

[0043] Although one embodiment of the pressure-sensitive adhesive composition, pressure-sensitive adhesive, pressure-sensitive adhesive layer, laminate, pressure-sensitive adhesive tape, and article of the present invention has been described above, the present invention is not limited to the configuration of the above-described embodiment. For example, the pressure-sensitive adhesive composition, laminate, pressure-sensitive adhesive tape, and article of the present invention may have any other optional components in addition to the configuration of the above-described embodiment, or may be substituted with any other components that produce the same effect. [Example]

[0044] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the following examples. Materials used in the examples are shown below.

[0045] Urethane (meth)acrylate resin (A) [Synthesis Example 1] A polyester polyol prepared using a mixture of adipic acid and isophthalic acid as the acid component and a mixture of 1,3-propanediol and 3-methyl-1,5-pentanediol as the diol component, and N-(2-hydroxyethyl)acrylamide were added to a reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet tube, and thermometer. The internal temperature was raised to 40°C and trimethylhexamethylene diisocyanate was added, followed by raising the temperature to 80°C over 1 hour and stirring at 80°C for a further 12 hours. After confirming that the isocyanate groups in the reaction mixture had disappeared, the mixture was cooled to obtain Resin A1, which was the urethane (meth)acrylate resin (A). The resulting resin A1 had an acryloyl group equivalent of 10,000, Mw of 20,000, and Tg of -32°C.

[0046] [Synthesis Example 2] Polypropylene glycol and 2-hydroxyethyl acrylate were added to the same reaction vessel as in Synthesis Example 1. The internal temperature was raised to 40°C, and isophorone diisocyanate was added, after which the temperature was raised to 80°C over 1 hour and the mixture was stirred at 80°C for a further 12 hours. After confirming that the isocyanate groups in the reaction mixture had disappeared, the mixture was cooled to obtain Resin A2 as the urethane (meth)acrylate resin (A). The resulting resin A2 had an acryloyl group equivalent of 26,500, Mw of 53,000, and Tg of -61°C.

[0047] [Synthesis Example 3] Polytetramethylene ether glycol and 2-hydroxyethyl acrylate were added to the same reaction vessel as in Synthesis Example 1. The internal temperature was raised to 40°C, and isophorone diisocyanate was added, after which the temperature was raised to 80°C over 1 hour and the mixture was stirred at 80°C for a further 12 hours. After confirming that the isocyanate groups in the reaction mixture had disappeared, the mixture was cooled to obtain Resin A3 as the urethane (meth)acrylate resin (A). The resulting resin A3 had an acryloyl group equivalent of 7,000, Mw of 14,000, and Tg of -71°C.

[0048] [Synthesis Example 4] A polyester polyol consisting of a mixture of polycaprolactone and diethylene glycol and 2-hydroxyethyl acrylate were added to the same reaction vessel as in Synthesis Example 1. The internal temperature was raised to 40°C and isophorone diisocyanate was added, after which the temperature was raised to 80°C over 1 hour and the mixture was stirred at 80°C for a further 12 hours. After confirming that the isocyanate groups in the reaction mixture had disappeared, the mixture was cooled to obtain Resin A4. The resulting resin A4 had an acryloyl group equivalent of 6250, Mw of 12500, and Tg of -57°C.

[0049] Nitrogen-containing (meth)acrylic monomer (B) The HSP value of each monomer was calculated using HSPiP software. Monomer B1: acryloylmorpholine (monomer HSP value 22.3, Tg 145°C when homopolymer is formed) Monomer B2: N-vinylpyrrolidone (monomer HSP value 20.8, Tg 86°C when homopolymer is formed) Monomer B3: N,N-diethylacrylamide (HSP value of the monomer: 19.2, Tg when homopolymer is formed: 81°C) (Meth)acrylic monomer (C) Monomer C1: n-octyl acrylate (Tg -65°C when homopolymer is formed) <Photopolymerization initiator (D)> Initiator D1: "Omnirad184" (trade name, manufactured by IGM RESINS BV, 1-hydroxycyclohexyl phenyl ketone)

[0050] <Tackifying resin (E)> The following commercially available products were used: The HSP value of each commercially available product was measured using the Hansen ball method. Tackifying resin E1: "Reactol UV-2000R" (product name, manufactured by LAWTER, polyester resin, softening point 120°C, HSP value 22.6) Tackifying resin E2: "YS Polystar G125" (trade name, manufactured by Yasuhara Chemical Co., Ltd., terpene phenol resin, softening point 120-130°C, HSP value 18.5) Tackifying resin E3: "Reactol UV-T90" (product name, manufactured by LAWTER, polyester resin, softening point 88°C, HSP value 22.6) Tackifying resin E4: "YS Polystar TH130" (trade name, manufactured by Yasuhara Chemical Co., Ltd., terpene phenol resin, softening point 125-135°C, HSP value 18.0) Tackifying resin E5: "YS Polystar T80" (trade name, manufactured by Yasuhara Chemical Co., Ltd., terpene phenol resin, softening point 80°C, HSP value 18.0)

[0051] 1. Preparation example of active energy ray-curable adhesive composition [Example 1] A pressure-sensitive adhesive composition (1) was obtained by mixing 100 parts by mass of resin A1 as the urethane (meth)acrylate resin (A), 80 parts by mass of monomer B1 as the nitrogen atom-containing (meth)acrylic monomer (B), 110 parts by mass of monomer C1 as the (meth)acrylic monomer (C), 1.5 parts by mass of initiator D1 as the photopolymerization initiator (D), and 20 parts by mass of tackifying resin E1 as the tackifying resin (E).

[0052] [Examples 2 to 10] Pressure-sensitive adhesive compositions (2) to (10) were obtained in the same manner as in Example 1, except that the components and their amounts were changed as shown in Table 1. [Comparative Examples 1 to 6] Pressure-sensitive adhesive compositions (C1) to (C6) were obtained in the same manner as in Example 1, except that the components and their amounts were changed as shown in Table 1.

[0053] 2. Evaluation 2-1. Viscosity of the adhesive composition The viscosity of the pressure-sensitive adhesive composition obtained in each of the Examples and Comparative Examples was measured using a Brookfield viscometer in an environment of 23°C.

[0054] 2-2. Gel fraction of pressure-sensitive adhesive composition The pressure-sensitive adhesive composition obtained in each Example and Comparative Example was applied to the surface of a release-treated polyethylene terephthalate film (release PET75) having a thickness of 75 μm so that the film thickness after UV irradiation would be 42 μm. Then, using a UV irradiation device, the film was exposed to an integrated light intensity of 1400 mJ / cm at a wavelength of 300 to 390 nm. 2 An adhesive layer was obtained by irradiating ultraviolet light under the conditions of 0.015 to 0.015. A test piece measuring 4 cm wide x 3 cm long was cut from the obtained adhesive layer, its mass was measured, and then it was immersed in toluene at 23°C for 24 hours. The test piece was removed, dried, and the mass of the insoluble matter was measured, and the gel fraction was calculated using the following formula. Gel fraction (mass%) = [(mass of adhesive layer after immersion) / (mass of adhesive layer before immersion)] × 100

[0055] 2-3. Tan δ of adhesive layer formed from adhesive composition The tan δ of the adhesive layer was determined by dynamic viscoelasticity measurement. Specifically, adhesive layers formed from the adhesive compositions obtained in each Example and Comparative Example in the same manner as in 2-2 above were stacked to a thickness of approximately 2 mm and punched out into a circle with a diameter of 8 mm to prepare a test specimen. Parallel plates with a diameter of 8 mm were attached to a viscoelasticity testing machine (ARESG2, manufactured by TA Instruments Japan), and the above test specimen was sandwiched between them. Measurements were then taken at a frequency of 1 Hz and a heating rate of 5°C / min from 30°C to 200°C to determine tan δ at each temperature, with the value at 39°C being used.

[0056] 2-4. 180° adhesive strength (180° peel adhesive strength) (1) The pressure-sensitive adhesive composition obtained in each Example and Comparative Example was applied to the surface of a 75 μm-thick polyethylene terephthalate film (release PET75) whose surface had been subjected to a release treatment, so that the film thickness after UV irradiation would be 42 μm, and another release PET75 was attached to the coated surface. Next, ultraviolet light was irradiated from above using a UV irradiation device to produce a pressure-sensitive adhesive sheet in which two sheets of release PET75 were laminated via an adhesive layer. The ultraviolet light irradiation was carried out so that the integrated light intensity at a wavelength of 300 to 390 nm after passing through the release PET75 was 1400 mJ / cm. 2 The test was carried out under the following conditions. (2) One of the release PET75 films constituting the pressure-sensitive adhesive sheet obtained above was peeled off, and a 25 μm-thick polyethylene terephthalate film (PET25) was attached to the adhesive layer surface to produce a pressure-sensitive adhesive film (laminate). This pressure-sensitive adhesive film (laminate) was then cut into 20 mm widths to produce pressure-sensitive adhesive tapes. The release PET75 was peeled off from the pressure-sensitive adhesive tape, and the adhesive layer surface was attached to a stainless steel plate (SUS304 with a hairline finish using #360 sandpaper). A 2 kg roller was rolled back and forth on the top surface of the pressure-sensitive adhesive tape, and the tape was then left to stand for 1 hour at 23°C and 50% RH to produce a test piece in which the pressure-sensitive adhesive tape and stainless steel plate were bonded together. Next, using a Tensilon tensile tester, the strength of the pressure-sensitive adhesive tape was measured when it was peeled off in a 180° direction at a pulling rate of 300 mm / min with the stainless steel plate constituting the test piece fixed in place.

[0057] 2-5. Shear holding strength In the above-mentioned 2-4(1), one release PET75 was peeled from the pressure-sensitive adhesive sheet prepared from the pressure-sensitive adhesive composition obtained in each Example and Comparative Example, and the surface of the adhesive layer was lined with 50 μm thick aluminum foil under an environment of 23°C and 50% RH, and the adhesive tape was cut into a length of 100 mm and a width of 20 mm. The release PET75 was peeled from the cut adhesive tape, and the surface of the adhesive layer was attached to a stainless steel plate (SUS304 with a hairline finish using #360 sandpaper) with an adhesive area of ​​20 mm x 20 mm (4 cm 2 ) and a 2 kg roller was rolled back and forth once on the top surface of the cut adhesive tape, and then the tape was left to stand for 1 hour in an environment of 23°C and 50% RH to prepare a test piece in which a part of the cut adhesive tape was pressure-bonded to the stainless steel plate. Next, the stainless steel plate side of the test piece was fixed to a holding force meter in an environment of 70°C, and then the portion of the test piece that was not attached to the stainless steel plate of the cut adhesive tape was folded over, a 500 g weight was attached, and the test piece was left in an environment of 70°C to measure the time until the cut adhesive tape peeled off (fell off). Note that when the test piece was held for 1,440 minutes, the test was terminated at that point.

[0058] 2-6. Constant load holding power In the above-mentioned 2-4(1), one release PET75 was peeled from the pressure-sensitive adhesive sheet prepared from the pressure-sensitive adhesive composition obtained in each Example and Comparative Example, and the adhesive surface was backed with PET25 in an environment of 23°C and 50% RH, and then cut into a pressure-sensitive adhesive tape 100 mm long and 10 mm wide. The release PET75 was peeled from the cut pressure-sensitive adhesive tape, and the adhesive surface was attached to a stainless steel plate (SUS304 with a hairline finish using #360 sandpaper) so that the adhesive length was 50 mm. A 2 kg roller was run back and forth across the top surface of the cut pressure-sensitive adhesive tape, and the tape was then allowed to stand for 1 hour in an environment of 40°C to prepare a test piece in which a portion of the cut pressure-sensitive adhesive tape was pressure-bonded to the stainless steel plate. Next, the stainless steel plate side of the test piece was fixed to a constant load holding force meter so that the adhesive tape side was facing downward, and then a 100 g weight was attached to the part of the test piece where the cut adhesive tape was not attached to the stainless steel plate, and the test piece was left in an environment of 23 ° C and 50% RH, and the time until the cut adhesive tape peeled (fell) was measured. Note that when the test was held for 180 minutes, the test was terminated.

[0059] 2-7.Removability In the above-mentioned 2-4(1), one release PET75 was peeled from the pressure-sensitive adhesive sheet prepared from the pressure-sensitive adhesive composition obtained in each Example and Comparative Example, and the surface of the adhesive layer was backed with PET25 in an environment of 23°C and 50% RH, and then cut into a pressure-sensitive adhesive tape 120 mm long and 10 mm wide. The release PET75 was peeled from the cut pressure-sensitive adhesive tape, and the surface of the adhesive layer was attached to a stainless steel plate (SUS304 with a BA finish). A 2 kg roller was rolled back and forth over the top of the cut pressure-sensitive adhesive tape once, and the tape was then left to stand for 72 hours in an environment of 23°C and 50% RH to prepare a test piece in which the cut pressure-sensitive adhesive tape and the stainless steel plate were pressure-bonded. Next, with the stainless steel plate of the test piece fixed, the cut adhesive tape was peeled off in a 135° direction at a pulling speed of 20 m / min, and the presence or absence of adhesive residue or contamination on the stainless steel plate was evaluated as follows. ◯: Peeled off at the interface between the adhesive layer and the stainless steel plate without leaving any adhesive residue or contamination. ×: Destruction occurred within the adhesive layer, or peeling occurred between the PET25 and adhesive layer, resulting in adhesive residue and contamination.

[0060] The results are summarized in Table 1. The adhesive layer formed from the adhesive composition satisfying the requirements of the present invention has excellent and well-balanced adhesive properties such as 180° adhesive strength, constant load holding strength, and shear holding strength, and also has excellent removability.

[0061] [Table 1] [Industrial Applicability]

[0062] The active energy ray-curable pressure-sensitive adhesive composition of the present invention has excellent adhesive properties and can form a pressure-sensitive adhesive layer with excellent removability and suppressed bleed-out. Therefore, a laminate such as a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed from the active energy ray-curable pressure-sensitive adhesive composition of the present invention can be suitably used in applications where peeling of the pressure-sensitive adhesive tape is required when separating components for the purpose of reuse or recycling, for example, as a pressure-sensitive adhesive tape for fixing components of various products in industrial applications such as electronic devices, automobiles, building materials, office automation, and home appliances, and improves work efficiency when separating components or removing labels.

Claims

1. a urethane (meth)acrylate resin (A) having an acryloyl group equivalent weight of 7,000 to 40,000, obtained by reacting a polyol (a), a polyisocyanate (b), and a (meth)acrylic compound (c) having a hydroxyl group; a nitrogen atom-containing (meth)acrylic monomer (B) capable of forming a homopolymer having a glass transition temperature of 15°C or higher; a (meth)acrylic monomer (C) capable of forming a homopolymer having a glass transition temperature of −15° C. or lower; a photopolymerization initiator (D); An active energy ray-curable pressure-sensitive adhesive composition comprising a tackifier resin (E) having a softening point of 85°C or higher.

2. 2. The active energy ray-curable pressure-sensitive adhesive composition according to claim 1, wherein the urethane (meth)acrylate resin (A) is a polyether-based urethane (meth)acrylate resin or a polyester-based urethane (meth)acrylate resin.

3. The active energy ray-curable pressure-sensitive adhesive composition according to claim 1, wherein the nitrogen atom-containing (meth)acrylic monomer (B) has an HSP value of 20 or more.

4. The active energy ray-curable pressure-sensitive adhesive composition according to claim 1 , wherein the (meth)acrylic monomer (C) is a monomer having no hydroxyl group.

5. The active energy ray-curable pressure-sensitive adhesive composition according to claim 1, wherein the tackifier resin (E) has an HSP value of 12 or more.

6. The active energy ray-curable pressure-sensitive adhesive composition according to claim 1, which has a tan δ at 39°C of 0.25 or more.

7. A pressure-sensitive adhesive comprising the active energy ray-curable pressure-sensitive adhesive composition according to any one of claims 1 to 6.

8. An adhesive layer comprising the active energy ray-curable adhesive composition according to any one of claims 1 to 6.

9. A laminate having an adhesive layer formed from an adhesive comprising the active energy ray-curable adhesive composition according to any one of claims 1 to 6.

10. The laminate according to claim 9 , which is an adhesive tape having the adhesive layer on one or both sides of a substrate.

11. An article comprising at least two adherends and the laminate according to claim 10, which is an adhesive tape having the adhesive layer on both sides of the substrate, disposed between the two adherends, wherein the two adherends are bonded via the laminate.

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