Adhesive and Adhesive Composition, Adhesive Layer, Adhesive Sheet, Laminate, and Device with Adhesive Layer Using the Same

Abstract

An adhesive that can contribute to more petroleum resource conservation by increasing the proportion of environmentally friendly materials, an adhesive having heat resistance, heat and humidity resistance, and yellowing resistance, a low-viscosity adhesive capable of high solid content conversion, an adhesive sheet using the same, a laminate, and a device with an adhesive layer are provided. 【Means for solving the problem】 An adhesive containing an acrylic copolymer (A) which is a copolymer of a monomer mixture containing 2-octyl (meth)acrylate, an alkyl (meth)acrylate having 1 to 4 carbon atoms in the alkyl group, and a monomer having a carboxy group, or an adhesive composition containing the acrylic copolymer (A).

Description

Technical Field

[0001] The present invention relates to an adhesive and an adhesive composition, an adhesive layer, an adhesive sheet, a laminate, and a device with an adhesive layer using the same.

Background Art

[0002] An adhesive sheet having an adhesive layer formed from an adhesive is easy to handle, and thus is used in a wide range of fields from general fields such as labels and masking tapes to medical and optical fields. Further, adhesives have been used for bonding between members of various devices such as smartphones and televisions. Among them, adhesives used for applications assumed to be used for a long time, such as marking films, window films, automotive members, and optical displays, require durability such as heat resistance, heat and humidity resistance, and light resistance (yellowing resistance).

[0003] On the other hand, in order to conveniently coat at the time of producing an adhesive sheet, the adhesive is generally diluted and adjusted to a low viscosity for use. Regarding the solvent used for the viscosity adjustment, it is required to reduce the content as much as possible from the viewpoints of cost and handling. In addition, when the solid content of the adjusted solution is low, it tends to be difficult to coat the adhesive thicker and uniformly, and thus a low-viscosity adhesive having a higher solid content is required.

[0004] The adhesives described in Patent Document 1 and Patent Document 2 are adjusted to have a solid content of about 35%. As a result of the inventors' study, in the adhesives described in Patent Document 1 and Patent Document 2, when adjusted to a solid content of 35% or more, the viscosity becomes too high and coating becomes difficult, so the solid content could not be increased. As a result, the cost of the solvent used is high, and it is a major problem that it is difficult to apply the adhesive thickly.

[0005] In addition to the above-mentioned improvement in required performance, in the industries where pressure-sensitive sheets are used, the depletion of oil resources and the emission of carbon dioxide due to the combustion of oil-derived products are regarded as problems. Therefore, starting from the packaging material field, attempts are being made to save oil resources by using bio-derived materials instead of oil-derived materials in various industries such as the optical field and the semiconductor field. In an adhesive mainly composed of an acrylic copolymer, as a method for increasing the ratio of bio-derived materials, a method of copolymerizing a monomer mixture containing a (meth)acrylic acid alkyl ester monomer obtained by esterifying a linear alkyl alcohol produced from a biological source and (meth)acrylic acid to obtain an acrylic copolymer can be mentioned. Although increasing the ratio of environmentally friendly materials can contribute more to saving oil resources, the current situation is that only limited environmentally friendly materials are used, and there are problems in practical application.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] The problem to be solved by the present invention is an adhesive that can contribute more to saving oil resources by increasing the ratio of environmentally friendly materials, and has heat resistance, heat and humidity resistance, and yellowing resistance, and a low-viscosity adhesive and adhesive composition capable of high solid content conversion, an adhesive layer, a pressure-sensitive sheet, a laminate, and a device with an adhesive layer.

Means for Solving the Problems

[0008] As a result of intensive studies by the present inventors, it has been found that the problems of the present invention can be solved in the following aspects, and the present invention has been completed. That is, the present invention is composed of an acrylic copolymer (A) which is a copolymer of a monomer mixture containing 2-octyl (meth) acrylate (a1), an alkyl (meth) acrylate (a2) having 1 to 4 carbon atoms in the alkyl group, and a monomer (a3) having a carboxy group, and the content of (a1) in 100% by mass of the monomer mixture is 45% by mass or more and less than 90% by mass, the content of (a2) is 0.5% by mass or more and less than 20% by mass, and the content of (a3) is 0.5% by mass or more and less than 10% by mass. The present invention relates to an adhesive characterized by the above.

Effects of the Invention

[0009] The present invention provides an adhesive that can contribute to the conservation of petroleum resources, and also has heat resistance, heat and humidity resistance, and yellowing resistance, and a low-viscosity adhesive and an adhesive composition capable of high solid content conversion, an adhesive layer, an adhesive sheet, a laminate, and a device with an adhesive layer.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0011] The adhesive composition, adhesive sheet, and device provided with an adhesive layer according to the present disclosure have the following configurations [1] to

[15] .

[0012] [1] An adhesive containing an acrylic copolymer (A), wherein the acrylic copolymer (A) is a copolymer of a monomer mixture containing 2-octyl (meth) acrylate (a1), an alkyl (meth) acrylate (a2) having 1 to 4 carbon atoms in the alkyl group, and a monomer (a3) having a carboxy group, and the content of (a1) in 100% by mass of the monomer mixture is 45% by mass or more and less than 90% by mass, the content of (a2) is 0.5% by mass or more and less than 20% by mass, and the content of (a3) is 0.5% by mass or more and less than 10% by mass. [2] The adhesive according to [1], wherein the monomer mixture further contains a (meth) acrylic acid ester monomer (a4) having a cyclic structure, and the content of (a4) in 100% by mass of the monomer mixture exceeds 0% by mass and is less than 20% by mass. [3] An adhesive composition comprising the adhesive and a curing agent (B). [4] The adhesive composition according to [4], wherein the curing agent (B) contains at least one selected from the group consisting of an epoxy-based curing agent, a metal chelate-based curing agent, and an aziridine-based curing agent. [5] The adhesive composition according to [4] or [6], further comprising a silane coupling agent (C). [6] The adhesive composition according to any one of [4] to [8], further comprising an acrylic copolymer (D) having a weight average molecular weight of 50,000 or less, and the content of a monomer having a glass transition temperature of 90°C or higher in 100% by mass of the total monomers constituting the acrylic copolymer (D) is 80% by mass or more. [7] The adhesive composition according to

[10] , wherein the content of the acrylic copolymer (D) with respect to 100 parts by mass of the acrylic copolymer (A) is less than 20 parts by mass. [8] The adhesive composition according to any one of [4] to

[12] , wherein the gel fraction is 60% or more. [9] The adhesive composition according to any one of [4] to

[14] , wherein the biomass degree is 30% or more.

[10] An adhesive layer characterized by being obtained from the adhesive according to claim 1 or 2 or the adhesive composition.

[11] The adhesive layer is characterized in that the Haze is less than 2.0 after standing for 500 hours under the conditions of 60 °C and a relative humidity of 90%, and the Haze is less than 2.0 after standing for 500 hours under the conditions of 85 °C and a relative humidity of 85%.

[12] Δb after standing in an 85 °C atmosphere for 500 hours * The adhesive layer is characterized in that the value is 1.0 or less.

[13] An adhesive sheet comprising the adhesive layer and a release film.

[14] A laminate comprising the adhesive layer and a substrate.

[15] A device with an adhesive layer comprising the adhesive layer and a device.

[0013] Hereinafter, the adhesive and adhesive composition of the present invention, the adhesive layer, adhesive sheet, laminate, and device with an adhesive layer using the same will be described, but the present invention is not limited thereto. In this specification, (meth)acrylate includes acrylate and methacrylate, and (meth)acryloxy group includes acryloxy group and methacryloxy group. A monomer is a monomer having an ethylenically unsaturated group. In addition, the numerical range specified using "~" in this specification shall include the numerical values described before and after "~" as the range of the lower limit value and the upper limit value. Also, "film" and "sheet" shall not be distinguished by thickness. In other words, the "sheet" in this specification includes a thin film-like one, and the "film" in this specification includes a thick sheet-like one. Furthermore, the adherend refers to the object to which the adhesive layer of the adhesive sheet is attached. Unless otherwise noted, each of the various components appearing in this specification may be used alone or in combination of two or more.

[0014] In this specification, "2-octyl (meth)acrylate (a1)" may be abbreviated as "monomer (a1)", "alkyl (meth)acrylate (a2) with an alkyl group having 1 to 4 carbon atoms" as "monomer (a2)", "monomer (a3) having a carboxy group" as "monomer (a3)", and "(meth)acrylic acid ester monomer (a4) having a cyclic structure" as "monomer (a4)".

[0015] ≪Adhesive≫ The adhesive of the present invention contains an acrylic copolymer (A).

[0016] <Acrylic copolymer (A)> The acrylic copolymer (A) is a copolymer of a monomer mixture containing 2-octyl (meth)acrylate (a1), alkyl (meth)acrylate (a2) with an alkyl group having 1 to 4 carbon atoms, and monomer (a3) having a carboxy group, and is characterized in that the content of monomer (a1) in 100% by mass of the monomer mixture is 45% by mass or more and less than 90% by mass, the content of monomer (a2) is 0.5% by mass or more and less than 20% by mass, and the content of monomer (a3) is 0.5% by mass or more and less than 10% by mass.

[0017] [2-Octyl (meth)acrylate (a1)] 2-Octyl (meth)acrylate (a1) is a biomass monomer represented by the following formula (1). (Formula 1) JPEG0007697567000002.jpg52154 (R1 = H, CH3) The content rate of 2-octyl (meth)acrylate (a1) is 45 mass% or more and less than 90 mass% in 100 mass% of the monomer mixture. If the content rate of 2-octyl (meth)acrylate (a1) is less than 45 mass%, the viscosity of the adhesive increases, which is not preferable. The lower limit of the content rate of 2-octyl (meth)acrylate (a1) can obtain a desired effect if it is 45 mass% or more, preferably 55 mass% or more, more preferably 65 mass% or more. The higher the content rate of 2-octyl (meth)acrylate (a1), the more it can contribute to the conservation of petroleum resources, which is preferable. However, from the viewpoint of heat resistance, the preferable upper limit is less than 80 mass%, and more preferably less than 75 mass%.

[0018] [Alkyl (meth)acrylate (a2) having an alkyl group with 1 to 4 carbon atoms] The content rate of alkyl (meth)acrylate (a2) having an alkyl group with 1 to 4 carbon atoms is 0.5 mass% or more and less than 20 mass% in 100 mass% of the monomer mixture. If the content rate of alkyl (meth)acrylate (a2) having an alkyl group with 1 to 4 carbon atoms is 20 mass% or more, the viscosity of the adhesive increases, which is not preferable. The lower limit of the content rate of alkyl (meth)acrylate (a2) having an alkyl group with 1 to 4 carbon atoms can obtain a desired effect if it is 0.5 mass% or more, preferably 5 mass% or more, more preferably 8 mass% or more. By being in the above range, cohesion can be imparted to the adhesive layer, and the heat resistance is improved, which is preferable. However, from the viewpoint of viscosity, less than 18 mass% is preferable, and more preferably less than 16 mass%.

[0019] [Monomer (a3) having a carboxy group] The monomer (a3) having a carboxy group is not limited as long as it is a monomer having a carboxy group in the molecule. Specifically, (meth)acrylic acid, p-carboxybenzyl acrylate, β-carboxyethyl acrylate, maleic acid, monoethyl maleic acid, itaconic acid, citraconic acid, fumaric acid, etc. can be mentioned.

[0020] The content rate of the monomer (a3) having a carboxy group is 0.5 mass% or more and less than 10 mass% in 100 mass% of the monomer mixture. It is preferably 2 mass% or more and less than 8 mass%, and more preferably 3 mass% or more and less than 6 mass%. By having the monomer (a3) having a carboxy group at 0.5 mass% or more, curing can be promoted, wet heat whitening can be suppressed, and the cohesive force of the adhesive layer can be increased to impart heat resistance. Also, by making the monomer (a3) having a carboxy group less than 10 mass%, an increase in the viscosity of the solution can be suppressed.

[0021] [Monomer (a4) having a cyclic structure] The monomer mixture constituting the acrylic copolymer (A) may further contain a monomer (a4) having a cyclic structure. Examples of the monomer (a4) having a cyclic structure include cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, etc. When the monomer (a4) having a cyclic structure is included, its content rate is preferably more than 0 mass% and less than 20 mass% in 100 mass% of the monomer mixture, and more preferably 5 mass% or more and less than 12.5 mass%. By being within the above range, heat resistance, wet heat resistance, and suppression of an increase in the viscosity of the solution can be imparted. It is preferable to use isobornyl (meth)acrylate which is a biomass monomer in consideration of the environment.

[0022] [Other monomers] The other monomers may be monomers other than 2-octyl (meth)acrylate (a1), alkyl (meth)acrylate (a2) having 1 to 4 carbon atoms in the alkyl group, monomer (a3) having a carboxy group, and monomer (a4) having a cyclic structure, and are not particularly limited. Also, as for the other monomers, it is preferable to use (meth)acrylate which is a biomass monomer in consideration of the environment, and it is more preferable to use (meth)acrylate having a high biomass degree.

[0023] Examples of other monomers include acrylamide, N,N-dimethylacrylamide, methacrylonitrile, acrylonitrile, diacetone acrylamide, stearyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and the like. Stearyl (meth)acrylate and lauryl (meth)acrylate, which are biomass monomers, are preferred.

[0024] Other monomers may or may not be contained. When contained, the content is less than 50% by mass in 100% by mass of the monomer mixture. By setting the content to less than 50% by mass, an increase in the viscosity of the adhesive can be suppressed. In terms of suppressing the increase in viscosity, the content is preferably 40% by mass or less, and more preferably 20% by mass or less.

[0025] (Production of Acrylic Copolymer (A)) The acrylic copolymer (A) can be produced by polymerizing the monomer mixture. For the polymerization, known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, and suspension polymerization are possible, but solution polymerization is preferred. Solvents used in solution polymerization are preferably, for example, acetone, methyl acetate, ethyl acetate, toluene, xylene, anisole, methyl ethyl ketone, cyclohexanone, and the like. The polymerization temperature is preferably a boiling point reaction at 60 to 120°C. Also, the polymerization time is preferably about 5 to 12 hours.

[0026] The polymerization initiator used for the polymerization is preferably a radical polymerization initiator. Radical polymerization initiators are generally peroxides and azo compounds. Examples of peroxides include dialkyl peroxides such as di-t-butyl peroxide, dicumyl peroxide, t-butyl cumyl peroxide, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, 2,5-di(t-butylperoxy)hexin-3; Peroxy esters such as t-butyl peroxybenzoate, t-butyl peroxyacetate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane; ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide; Peroxyketals such as 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, n-butyl-4,4-bis(t-butylperoxy)valerate; Hydroperoxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylcyclohexane-2,5-dihydroperoxide; Diacyl peroxides such as benzoyl peroxide, decanoyl peroxide, lauroyl peroxide, 2,4-dichlorobenzoyl peroxide; Peroxydicarbonates such as bis(t-butylcyclohexyl) peroxydicarbonate and the like can be mentioned.

[0027] Examples of azo compounds include 2,2'-azobisbutyronitriles such as 2,2'-azobisisobutyronitrile (abbreviation: AIBN), 2,2'-azobis(2-methylbutyronitrile); 2,2'-azobisvaleronitriles such as 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile); 2,2'-azobispropionitriles such as 2,2'-azobis(2-hydroxymethylpropionitrile); 1,1'-azobisalkannitriles such as 1,1'-azobis(cyclohexane-1-carbonitrile) and the like can be mentioned.

[0028] The polymerization initiator is preferably used in an amount of 0.01 to 10 parts by mass, more preferably 0.1 to 2 parts by mass, based on 100 parts by mass of the monomer mixture.

[0029] (Weight-average molecular weight (Mw)) The Mw of the acrylic copolymer (A) is not particularly limited, but is preferably 1.8 million or less, more preferably 1 million or less. The Mw is a value in terms of polystyrene measured by gel permeation chromatography (GPC).

[0030] <<Adhesive composition>> The adhesive composition of the present invention contains an adhesive containing an acrylic copolymer (A) and a curing agent (B). Further, it can contain a silane coupling agent (C) and an acrylic copolymer (D) having a weight-average molecular weight of 50,000 or less, if necessary.

[0031] <<Curing agent (B)>> The adhesive composition of the present invention contains a curing agent (B), and the curing agent (B) is not particularly limited as long as it can provide a crosslinked structure to the adhesive composition and can be used. By blending the curing agent, the cohesive force of the adhesive layer is improved, and the adhesive strength, heat resistance, and light resistance are improved. The curing agent (B) preferably contains at least one selected from the group consisting of epoxy curing agents, metal chelate-based curing agents, and aziridine-based curing agents. By containing at least one, the cohesive force of the adhesive can be moderately increased, which is preferable in that it hardly adversely affects other physical properties.

[0032] Examples of the epoxy-based curing agent include glycerin diglycidyl ether, 1,6-hexanediol diglycidyl ether, N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidylaminophenylmethane, and the like.

[0033] Examples of the metal chelate-based curing agent include aluminum organic compounds and zirconium compounds. Specific examples of commercially available products include, for example, aluminum chelate D, aluminum chelate A (both manufactured by Kawaken Fine Chemicals Co., Ltd.), ZC-750 (manufactured by Matsumoto Fine Chemical Co., Ltd.), and the like.

[0034] Examples of aziridine-based curing agents include tris(1-aziridinepropionic acid) 1,1,1-propanetriyltrimethylene, 2-[[[3-(2-methylaziridin-1-yl)propionyl]oxy]methyl]-2-ethylpropane-1,3-diol bis[3-(2-methylaziridin-1-yl)propionate], and the like.

[0035] The curing agent (B) is preferably contained in an amount of 0.02 to 4 parts by mass, more preferably 0.04 to 1 part by mass, based on 100 parts by mass of the acrylic copolymer (A). When the content is 0.02 parts by mass or more, the cohesive force is further improved, and when it is 4 parts by mass or less, it is easier to balance the cohesive force and flexibility, so sufficient adhesive strength and heat resistance can be easily obtained.

[0036] <Silane coupling agent (C)> The pressure-sensitive adhesive composition of the present invention preferably contains a silane coupling agent (C). By including the silane coupling agent (C), the adhesive strength, heat resistance, and resistance to wet heat whitening can be improved. The silane coupling agent (C) is preferably contained in an amount of 0.05 to 0.2 parts by mass based on 100 parts by mass of the acrylic copolymer (A). By setting it to 0.05 to 0.2 parts by mass, it becomes easy to balance heat resistance and resistance to wet heat whitening.

[0037] Examples of the silane coupling agent (C) include alkoxysilane compounds having a (meth)acryloxy group, alkoxysilane compounds having a vinyl group, alkoxysilane compounds having an amino group, alkoxysilane compounds having a mercapto group, or alkoxysilane compounds having an epoxy group. Specific examples of commercially available products include, for example, KBM-403 (3-glycidoxypropyltrimethoxysilane), KBE-403 (3-glycidoxypropyltriethoxysilane), KBM-303 (2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane) (the above are manufactured by Shin-Etsu Chemical Co., Ltd.), and the like.

[0038] <Acrylic copolymer (D) having a weight average molecular weight of 50,000 or less> From the viewpoint of heat resistance, the pressure-sensitive adhesive composition of the present invention preferably further contains an acrylic copolymer (D). The acrylic copolymer (D) has a weight average molecular weight (Mw) of 50,000 or less, and in a total of 100% by mass of the monomer mixture constituting the acrylic copolymer (D), the content of a monomer having a glass transition temperature of the homopolymer of 90°C or higher (hereinafter also referred to as a high Tg monomer) is 80% by mass or more. By having an Mw of 50,000 or less for the acrylic copolymer (D), it is compatible with the acrylic copolymer (A), and the heat resistance can be improved while suppressing an increase in HAZE. The Mw of the acrylic copolymer (D) is preferably 30,000 or less. By containing 80% by mass or more of a high Tg monomer in the acrylic copolymer (D), cohesive force is imparted to the pressure-sensitive adhesive layer and the heat resistance is improved. The content of the high Tg monomer in a total of 100% by mass of the monomer mixture may be 100% by mass, but is preferably 99.5% by mass or less.

[0039] Examples of monomers having a glass transition temperature of the homopolymer of 90°C or higher include isobornyl (meth)acrylate, methyl methacrylate, acryloylmorpholine, N,N-dimethylacrylamide, and the like. From the viewpoint of saving petroleum resources, it is preferable to use isobornyl (meth)acrylate, which is a biomass monomer.

[0040] As monomers other than isobornyl (meth)acrylate constituting the acrylic copolymer (D), various monomers described in the description of the acrylic copolymer (A) can be used.

[0041] The acrylic copolymer (D) can be produced by polymerizing a monomer mixture in the same manner as the acrylic copolymer (A). Polymerization can be carried out by known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, and suspension polymerization, but solution polymerization is preferred. Solvents used in solution polymerization are preferably, for example, acetone, methyl acetate, ethyl acetate, toluene, xylene, anisole, methyl ethyl ketone, cyclohexanone, etc. The polymerization temperature preferably involves a boiling point reaction at 60 to 120°C. Also, the polymerization time is preferably about 5 to 12 hours. A chain transfer agent can also be added as necessary.

[0042] The acrylic copolymer (D) is preferably less than 20 parts by mass with respect to 100 parts by mass of the acrylic copolymer (A). By being less than 20 parts by mass, appropriate cohesive force can be imparted to the pressure-sensitive adhesive layer and the heat resistance can be improved.

[0043] In the pressure-sensitive adhesive composition of the present invention, various resins, chlorinated polyolefins, oils, softeners, dyes, pigments, antioxidants, and ultraviolet absorbers described later can be added as optional components as long as the problems can be solved.

[0044] Examples of the chlorinated polyolefin include chlorinated polypropylene, acid-modified chlorinated polypropylene, acrylic-modified chlorinated polypropylene, chlorinated polyethylene, chlorinated ethylene-vinyl acetate copolymer, etc. From the viewpoint of good compatibility with acrylic copolymers, etc. and effectively reducing polarity, chlorinated polypropylene or chlorinated ethylene-vinyl acetate copolymer is preferred. Specifically, as commercially available products, for example, Super Cron 390S (chlorinated polypropylene, chlorine content 36%), Super Cron BX (chlorinated EVA, chlorine content 18%) (both manufactured by Nippon Paper Industries Co., Ltd.) can be mentioned.

[0045] The pressure-sensitive adhesive composition of the present invention preferably has a gel fraction of 60% or more. However, depending on the application, it can also be used even if the gel fraction is 60% or less. The measurement method of the gel fraction will be described in detail in the examples.

[0046] The pressure-sensitive adhesive composition of the present invention contains an acrylic copolymer (A) which is a copolymer of a monomer mixture containing a specific monomer, thereby suppressing the increase in viscosity when using the acrylic copolymer and ensuring heat resistance and heat and humidity resistance. As a result, the amount of the organic solvent used for viscosity adjustment during coating can be significantly reduced compared to the conventional amount. The Mw of the acrylic copolymer (A) can be adjusted as appropriate. In the present invention, when the Mw of the acrylic copolymer (A) is 600,000 to 1,000,000, the viscosity at a solid content of 35% (±1) is preferably 6000 mPas·s or less. The method for preparing the solid content and the method for measuring the viscosity will be described in detail in the examples.

[0047] ≪Pressure-sensitive adhesive layer≫ The pressure-sensitive adhesive layer is a layer obtained from the pressure-sensitive adhesive or pressure-sensitive adhesive composition of the present invention. The method for forming the pressure-sensitive adhesive layer is not particularly limited and is the same as the coating method described in the description of the pressure-sensitive adhesive sheet described later.

[0048] The pressure-sensitive adhesive layer of the present invention preferably has durability such as heat resistance and heat and humidity resistance in order to be applied to long-term use such as an optical display. As heat resistance and heat and humidity resistance, the Haze after standing for 500 hours under the conditions of 60°C and 90% relative humidity is less than 2.0, the Haze after standing for 500 hours under the conditions of 85°C and 85% relative humidity is less than 2.0, and the Δb * value is 1.0 or less, and it is preferable that foaming or floating derived from the pressure-sensitive adhesive layer does not occur under the above conditions. The measurement method will be described in detail in the examples.

[0049] ≪Pressure-sensitive adhesive sheet≫ The pressure-sensitive adhesive sheet includes a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive or pressure-sensitive adhesive composition of the present invention and a release film.

[0050] The pressure-sensitive adhesive sheet of the present invention may have any configuration in which a release film is formed on one or both sides of the pressure-sensitive adhesive layer.

[0051] <Release film> The release film is not particularly limited, but a transparent plastic substrate can be preferably used. Examples of the material of the transparent plastic substrate include plastics such as polyester such as polyethylene terephthalate (PET), acrylic resin such as polymethyl methacrylate (PMMA), polycarbonate, triacetyl cellulose, polysulfone, polyarylate, and polycycloolefin. The plastic materials can be used alone or in combination of two or more.

[0052] As the release film, among the transparent plastic substrates as described above, a transparent plastic substrate having excellent heat resistance, that is, a transparent plastic substrate in which deformation is suppressed or prevented under severe conditions such as high temperature and high temperature and high humidity can be preferably used. As the transparent plastic substrate, a PET film or sheet is particularly preferable.

[0053] The thickness of the release film is preferably less than 200 μm. Although the thickness should be adjusted according to the handling of the members to be used, being less than 200 μm makes the texture of the material not too strong, facilitates winding into a roll shape, and can be used comfortably when bonding with a sheet or the like.

[0054] Since the pressure-sensitive adhesive sheet of the present invention has excellent heat resistance and heat and humidity resistance, it can be used for fixing the outside and inside of various devices such as personal computers, mobile phones, and home appliances. Although not particularly limited, it can be used for fixing to dissimilar materials of the device, such as polyolefins including polyethylene and polypropylene, resins such as polycarbonate and phenol, metals such as iron, stainless steel (SUS), aluminum and copper, and others such as cement, mortar, glass, non-woven fabric, woven fabric, paper, rubber, and foam sheet.

[0055] For the coating of the adhesive or the adhesive composition, an appropriate liquid medium can also be added to adjust the viscosity. Specifically, for example, hydrocarbon solvents such as toluene, xylene, hexane, heptane, etc.; ester solvents such as ethyl acetate, butyl acetate, etc.; ketone solvents such as acetone, methyl ethyl ketone, etc.; halogenated hydrocarbon solvents such as dichloromethane, chloroform, etc.; ether solvents such as diethyl ether, methoxytoluene, dioxane, etc., or other hydrocarbon solvents, etc. can be mentioned. However, water and alcohol need to be used carefully because they may cause inhibition of the reaction between the acrylic copolymer (A) and the isocyanate-based curing agent.

[0056] The coating method is not particularly limited, and various coating methods such as a Meyer bar, an applicator, a brush, a spray, a roller, a gravure coater, a die coater, a lip coater, a comma coater, a knife coater, a reverse coater, a spin coater, etc. can be mentioned. Also, the drying and curing method is not particularly limited, and those using hot air drying, infrared rays, a vacuum method, or active energy rays can be mentioned, but from the viewpoint of outgas resistance, hot air or steam heating at 60 to 180 °C is preferable.

[0057] The thickness of the adhesive layer is preferably 2 to 1,000 μm, and more preferably 5 to 500 μm. Note that the adhesive layer may be a single layer or in any form of lamination of two or more layers.

[0058] ≪Laminate≫ The laminate of the present invention includes a base material and an adhesive layer. The adhesive layer is formed using the adhesive sheet of the present invention. Specifically, for example, the release film can be peeled off from the adhesive sheet of the present invention, and the adhesive layer can be attached to the base material to form a laminate.

[0059] <Base material> The base material refers to the object to which the adhesive layer of the adhesive sheet having an adhesive layer is attached, and is not limited to a specific one. As an example, polyolefins including polyethylene and polypropylene, resins such as polycarbonate and phenol, metals such as iron, stainless steel (SUS), aluminum and copper, and other materials such as cement, mortar, glass, non-woven fabric, woven fabric, paper, rubber, foam sheet, and laminates thereof can be used. The adhesive and the adhesive composition of the present invention exhibit excellent adhesive strength to at least one type of adherend. The thickness of the base material is not particularly limited. For example, it is preferably less than 500 μm, more preferably 10 to 200 μm, and even more preferably 25 to 150 μm.

[0060] FIG. 1 shows an example of a schematic cross-sectional view partially showing the laminate of the present invention. In FIG. 1, 3 is the base material, 1 is the adhesive layer, and 4 and 5 are devices.

[0061] In the laminate shown in FIG. 1, the base material is attached to the device via the adhesive layer.

[0062] <Manufacture of laminate> The method for manufacturing the laminate can be, for example, peeling one-sided release film from an adhesive sheet having release films on both sides of the adhesive layer and attaching the adhesive layer to the base material to form a laminate. Also, after directly forming the adhesive layer on the base material, the adhesive layer of the base material or another adhesive sheet can be attached to the adhesive layer to form a laminate.

[0063] <Device with adhesive layer> The device with an adhesive layer of the present invention only needs to include the above-mentioned adhesive layer and the device, and is not particularly limited. The device with an adhesive layer can be manufactured using, for example, the adhesive sheet or laminate of the present invention. That is, the configuration can be an adhesive layer / device, a base material / adhesive layer / device, etc. Or, a configuration such as device 1 / adhesive layer / device 2 in which different devices 1 and 2 are bonded via an adhesive layer may also be acceptable.

[0064] Figure 2 shows an example of a schematic cross-sectional view partially showing a device with an adhesive layer, which is an example of the use of the adhesive sheet of the present invention. In Figure 2, 3 is a base material, 1 is an adhesive layer, 4 is device 1, and 5 is device 2. Note that the configuration of the device with an adhesive layer is not limited to Figure 2.

[0065] In the device with an adhesive layer shown in Figure 3, the base material is attached to the release film via the adhesive layer (adhesive layer) of the present invention. In this way, it can be commercialized with the release film provided, and can also be used in the intermediate processes of commercialization.

[0066] The uses of the device with an adhesive layer are not particularly limited, and examples include all household appliances such as personal computers, mobile phones, televisions, tablets, and smart watches.

[0067] In view of the current trend towards environmentally friendly materials, the adhesives and adhesive compositions of the present invention can be made into adhesives and adhesive compositions that are partially or entirely derived from biological materials by using biomass monomers as the monomers constituting the acrylic copolymer (A) and acrylic copolymer (D). The biomass content is preferably 30% or more. More preferably 39% or more, and even more preferably 60% or more. The higher the biomass content, the higher the usefulness as an environmentally friendly material. The calculation method of the biomass content is described in the examples.

Examples

[0068] Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to these examples. In the examples, unless otherwise specified, "parts" means "parts by mass" and "%" means "mass %". Also, the compounding amounts in the tables are in parts by mass, and except for solvents, they are values in terms of non-volatile components. Note that the blanks in the tables indicate that they are not compounded. Incidentally, it is common general knowledge that the viscosity of the pressure-sensitive adhesive composition increases or decreases depending on the Mw of the acrylic copolymer (A) contained, and since the Mw of the acrylic copolymer (A) can be adjusted as appropriate, it is not realistic to confirm the effects of the present invention in all Mw ranges of the acrylic copolymer (A). Therefore, the Mw of the acrylic copolymer (A) described in the examples was produced and evaluated so as to be 600,000 to 1,000,000.

[0069] <Measurement of weight-average molecular weight (Mw) and Mw classification evaluation method> The weight-average molecular weight (Mw) was measured by gel permeation chromatography (GPC). As the apparatus, a GPC apparatus: LC-GPC system "Prominence" manufactured by Shimadzu Corporation was used. Also, as the column, TSKgel α-M manufactured by Tosoh Corporation was used, and two columns were connected in series. As the eluent, N,N-dimethylformamide (DMF) was used, and the measurement was carried out at 40°C. The determination of Mw was carried out by conversion using polystyrene with a known Mw as a standard substance.

[0070] (Production of acrylic copolymer) <Example 1: Production of (A-1)> Using a reaction apparatus equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer, ethyl acetate was added as a polymerization solvent into the reaction vessel, 85 parts of 2-octyl acrylate (2-OA) as monomer (a1), 10 parts of methyl acrylate (MA) as monomer (a2), and 5 parts of acrylic acid (AA) as monomer (a3) were added, and the mixture was stirred to prepare a monomer mixture. 0.02 parts of azobisisobutyronitrile (hereinafter, AIBN) was added as an initiator and mixed, and polymerization was carried out at about 80°C for 6 hours under a nitrogen atmosphere. After completion of the reaction, it was cooled and diluted with ethyl acetate to obtain an acrylic copolymer solution. The obtained acrylic copolymer is designated as (A-1).

[0071] <Production of Examples 2 to 32 (A-2 to A-32) and Comparative Examples 1 to 6 (A'-1 to A'-6)> Acrylic copolymers (A-2 to A-32, A'-1 to A'-6) were produced in the same manner as the production of the acrylic copolymer (Example 1), except that the composition and compounding amounts (parts by mass) described in Tables 1 to 3 were changed.

[0072]

Table 1

[0073]

Table 2

[0074]

Table 3

[0075] The abbreviations described in Tables 1 to 3 are as follows. Note that the description is only for those for which the biomass content has been confirmed. [2-Octyl (meth) acrylate (a1)] 2-OA: 2-Octyl acrylate (biomass content 73%) 2-OMA: 2-Octyl methacrylate (biomass content 67%) [Alkyl (meth) acrylate with 1 to 4 carbon atoms in the alkyl group (a2)] MA: Methyl acrylate (alkyl group has 1 carbon atom) MMA: Methyl methacrylate (alkyl group has 1 carbon atom) TBA: t-Butyl acrylate (alkyl group has 4 carbon atoms) [Monomer having a carboxy group (a3)] AA: Acrylic acid MAA: Methacrylic acid [Monomer having a cyclic structure (a4)] IBXA: Isobornyl acrylate (biomass content 76%) IBXMA: Isobornyl methacrylate (biomass content 71%) BZA: Benzyl acrylate [Other monomers] 2EHA: 2-Ethylhexyl acrylate LA: Lauryl acrylate (biomass content 80%) DMAA: N,N-Dimethylacrylamide

[0076] <Production Example 1: Production of (D-1)> Using a reaction apparatus equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping tube, 100 parts of toluene as a polymerization solvent was charged into the reaction vessel, and a mixture of 100 parts of isobornyl methacrylate, 15 parts of methyl ethyl ketone as a polymerization solvent, and 2 parts of AIBN as an initiator was added to the dropping vessel and dropped over about 2 hours. Polymerization was carried out at about 90 °C for 6 hours under a nitrogen atmosphere. After the reaction was completed, it was cooled and diluted with ethyl acetate, and the resulting acrylic copolymer was designated as D-1. Also, the results of measuring the weight average molecular weight (Mw) of the obtained acrylic copolymer are shown in Table 4.

[0077] <Production of Production Examples 2 and 3> Acrylic copolymers (D-2) and (D'-1) were produced in the same manner as in Production Example 1, except that the composition and blending amounts (parts by mass) described in Table 4 were changed.

[0078]

Table 4

[0079] The abbreviations described in Table 4 are as follows. [Monomer with Tg of homopolymer ≥ 90 °C] IBXA: Isobornyl acrylate (Tg: 97 °C) IBXMA: Isobornyl methacrylate (Tg: 180 °C) DMAA: N,N-Dimethylacrylamide (Tg: 119 °C) [Other monomers] CHA: Cyclohexyl acrylate (Tg: 15 °C) 2EHA: 2-Ethylhexyl acrylate (Tg: -70 °C)

[0080] <Example 33> To 100 parts of the acrylic copolymer (A-1), 0.05 part of "Tetrad-X" (manufactured by Mitsubishi Gas Chemical Company, an epoxy-based curing agent) was blended as the curing agent (B) to obtain an adhesive composition. Using a comma coater, the obtained adhesive composition was applied onto a release liner (SP-PET-O1-BU: manufactured by Mitsui Chemicals Toagosei Co., Ltd.) with a thickness of 38 μm as a release sheet so that the dried thickness became 25 μm, dried at 110°C for 3 minutes, and then a release liner (SP-PET-O3-B3: manufactured by Mitsui Chemicals Toagosei Co., Ltd.) with a thickness of 75 μm was laminated as a release sheet to the adhesive layer. In this state, it was aged at 23°C for 7 days to obtain an adhesive sheet.

[0081] <Examples 34 to 75, Comparative Examples 7 to 12> As shown in Table 5, except that the types and blending amounts of the acrylic copolymer (A), the curing agent (B), the silane coupling agent (C), and the acrylic copolymer (D) were changed, adhesive compositions and adhesive sheets were obtained in the same manner as in Example 33, respectively.

[0082] <Measurement of gel fraction> The 38-μm release liner of the obtained adhesive sheet was peeled off, and the adhesive layer was laminated onto a PET film (manufactured by Toyobo Co., Ltd., Cosmo Shine A-4360, thickness 100 μm) as a base material, and a test adhesive sheet with a size of 30 mm in width × 100 mm in length was prepared. Further, the 75-μm release liner on the other surface of the adhesive sheet was peeled off to prepare a test piece, and its weight was measured. The test piece was immersed in ethyl acetate at 23°C for 24 hours, taken out from ethyl acetate, and dried at 150°C for 30 minutes. The weight of the dried test piece was measured, and the gel fraction was calculated using the following formula (1). In Table 5, "60%<" means that the gel fraction is more than 60%. Gel fraction (weight%) = 100 × (W2 - W0) / (W1 - W0) ····(1) (W0: weight of the base material (PET film), W1: weight of the test piece before immersion, W2: weight of the test piece after immersion and drying)

[0083] <Calculation of biomass degree> The biomass content of the pressure-sensitive adhesive composition was calculated using the following formula (2) (in the case of a two-component monomer (A, B) system). Biomass content = {(Aw × Ab) + (Bw × Bb)} / (Aw + Bw) ···· (2) Aw: Weight of monomer A, Bw: Weight of monomer B Ab: Biomass content of monomer A (%), Bb: Biomass content of monomer B (%) When the biomass content was specified within a range, the minimum value was used for the above calculation.

[0084] The materials used in the examples and comparative examples are described below. <Hardener (B)> Tetrad X: An epoxy-based hardener manufactured by Mitsubishi Gas Chemical Company Aluminum chelate A: A metal chelate-based hardener manufactured by Kawaken Fine Chemical Co., Ltd. PZ-33: An aziridine-based hardener manufactured by Nippon Shokubai Co., Ltd.

[0085] <Silane coupling agent (C)> KBE-403: (3-Glycidoxypropyltriethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0086] For the pressure-sensitive adhesives and pressure-sensitive adhesive compositions obtained in Examples 32 to 75 and Comparative Examples 7 to 12, evaluations of low viscosity, heat resistance, moisture and heat whitening resistance, and yellowing resistance were carried out by the following methods. The results are shown in Table 6.

[0087] <Low viscosity> For the pressure-sensitive adhesives and pressure-sensitive adhesive compositions of Examples 32 to 75 and Comparative Examples 7 to 12, the viscosity was measured by the following method, and the low viscosity was evaluated according to the following evaluation criteria. The solid content of the acrylic copolymer contained was adjusted to 35% (±1) of the solid content, and the viscosity was measured using a Brookfield viscometer (rotor number: M3, rotation speed: 12 rpm). The adjustment of the solid content was carried out using ethyl acetate. [Evaluation criteria] A: Viscosity less than 3,000 mPas·s: Excellent B: Viscosity is 3,000 mPas·s or more and less than 4,000 mPas·s: Good C: Viscosity is 4,000 mPas·s or more and less than 5,000 mPas·s: Usable D: Viscosity is 5,000 mPas·s or more: Unusable

[0088] <Heat resistance> After preparing a test piece by cutting the obtained adhesive sheet into a size of 25 mm in width and 100 mm in length, the 38 μm release liner of the test piece was peeled off in an atmosphere of 23°C and 50% relative humidity (also described as 23°C - 50%RH), and it was pressure-bonded onto SUS with a hand roller of 2 kg weight reciprocated once so that the adhesion area became 25 mm in width × 40 mm in length. After standing for 24 hours in an atmosphere of 23°C - 50%RH, a load of 500 g was applied and it was left standing in an 80°C environment for 10 hours. The displacement of the test piece after 10 hours was evaluated using a microscope. S: No displacement of the test piece: Excellent A: Displacement of the test piece exceeds 0 mm and is less than 0.1 mm: Good B: Displacement of the test piece is 0.1 mm or more and less than 0.4 mm: Good C: Displacement of the test piece is 0.4 mm or more and less than 1.0 mm: Usable D: Displacement of the test piece is 1.0 mm or more: Unusable

[0089] <Moist heat whitening property> The 38-μm release liner of the obtained adhesive sheet was peeled off, and in an atmosphere of 23°C - 50% RH, the adhesive layer was laminated onto a glass plate using a laminator. Next, the other 75-μm release liner of the adhesive sheet was peeled off and laminated onto the glass plate using the same laminator as above. By applying a pressure of 0.5 MPa in an atmosphere of 50°C and holding for 20 minutes, a test piece laminated in the order of glass plate / adhesive layer / glass plate was prepared and left in an environment of 60°C and a relative humidity of 90% (also described as 60°C - 90% RH) and 85°C and a relative humidity of 85% (also described as 85°C - 85% RH) for 500 hours. Each was cooled at 23°C - 50% RH for 1 hour to obtain a test piece. The HAZE of each test piece was measured and evaluated according to the following criteria. The HAZE was measured using a Turbidimeter NDH5000W manufactured by Nippon Denshoku Industries Co., Ltd. [Evaluation Criteria] A: HAZE is less than 0.5. Excellent B: HAZE is 0.5 or more and less than 1.0. Good C: HAZE is 1.0 or more and less than 2.0. Fair D: HAZE is 2.0 or more. Not usable

[0090] [Yellowing Resistance] The 38-μm release liner of the obtained adhesive sheet was peeled off, and in an atmosphere of 23°C - 50% RH, the adhesive layer was laminated onto a glass plate using a laminator. Next, the other 75-μm release liner of the adhesive sheet was peeled off and laminated onto the glass plate using the same laminator as above. By applying a pressure of 0.5 MPa in an atmosphere of 50°C and holding for 20 minutes, a test piece laminated in the order of glass plate / adhesive layer / glass plate was prepared and left in an environment of 85°C for 500 hours. After cooling it at 23°C - 50% RH for 1 hour, the b * value was measured, and the Δb * value was calculated using the following formula. The b * value was measured using a SE6000 manufactured by Nippon Denshoku Industries Co., Ltd. Δb * value = [b value after standing for 500 hours] - [b value before the test] * value] - [b value before the test] * value] [Evaluation Criteria] A: Δb* The value is 1.0 or less: Good. D: Δb * The value exceeds 1.0. It cannot be used.

[0091]

Table 5

[0092]

Table 6

Explanation of Symbols

[0093] The symbols in Figures 1, 2, and 3 are explained below. 1 Adhesive layer 2 Release film 3 Substrate 4 Device 1 5 Device 2

Claims

1. A pressure-sensitive adhesive composition comprising an adhesive containing an acrylic copolymer (A) and a curing agent (B), The acrylic copolymer (A) is a copolymer of a monomer mixture containing 2-octyl(meth)acrylate (a1), an alkyl(meth)acrylate (a2) having an alkyl group with 1 to 4 carbon atoms, a monomer (a3) ​​having a carboxy group, and a monomer (a4) having a cyclic structure; A pressure-sensitive adhesive composition, characterized in that the content of (a1) is 45% by mass or more and less than 90% by mass, the content of (a2) is 0.5% by mass or more and less than 20% by mass, the content of (a3) ​​is 0.5% by mass or more and less than 10% by mass, and the content of (a4) is 5% by mass or more and less than 20% by mass, based on 100% by mass of a monomer mixture.

2. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the curing agent (B) comprises at least one selected from the group consisting of epoxy-based curing agents, metal chelate-based curing agents, and aziridine-based curing agents.

3. 2. The pressure-sensitive adhesive composition according to claim 1, further comprising a silane coupling agent (C).

4. The pressure-sensitive adhesive composition according to claim 1, further comprising an acrylic copolymer (D) having a weight average molecular weight of 50,000 or less, wherein the content of monomers having a homopolymer glass transition temperature of 90°C or higher is 80% by mass or more relative to a total of 100% by mass of a monomer mixture constituting the acrylic copolymer (D).

5. 5. The pressure-sensitive adhesive composition according to claim 4, wherein the content of the acrylic copolymer (D) is less than 20 parts by mass based on 100 parts by mass of the acrylic copolymer (A).

6. 2. The pressure-sensitive adhesive composition according to claim 1, which has a gel fraction of 60% or more.

7. 2. The pressure-sensitive adhesive composition according to claim 1, having a biomass ratio of 30% or more.

8. A pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition according to any one of claims 1 to 7.

9. The pressure-sensitive adhesive layer according to claim 8, which has a haze of less than 2.0 after standing for 500 hours under conditions of 60°C and a relative humidity of 90%, and a haze of less than 2.0 after standing for 500 hours under conditions of 85°C and a relative humidity of 85%.

10. The pressure-sensitive adhesive layer according to claim 8, which has a Δb* value of 1.0 or less after standing in an 85° C. atmosphere for 500 hours.

11. A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer according to claim 8 and a release film.

12. A laminate comprising the pressure-sensitive adhesive layer according to claim 8 and a substrate.

13. A device with an adhesive layer, comprising the adhesive layer according to claim 8 and a device.

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