Crosslinking agent

Abstract

The present invention discloses a crosslinking agent. The crosslinking agent contains a (meth)acrylic resin which has a first structural unit derived from a (meth)acrylate that has a fluorine-containing organic group and a second structural unit derived from a (meth)acrylate that has a cyclic ether group.

Description

Crosslinking agent

[0001] The present disclosure relates to crosslinking agents.

[0002] In adhesive compositions, a crosslinking agent may be used in order to efficiently cure a curable resin such as a compound having a cyclic ether group (epoxy resin) (for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2022-151170

[0004] Polymers of compounds having a fluorine-containing organic group have attracted attention as materials exhibiting a low refractive index. The present inventors have focused on adhesive compositions containing a (meth)acrylate compound and an epoxy compound, and have investigated the curing reaction using a (meth)acrylate having a fluorine-containing organic group as the (meth)acrylate compound. As a result, it has been found that the adhesive strength of the cured product of the obtained adhesive composition tends to decrease, and furthermore, the infrared transmittance of the cured product of the adhesive composition also tends to decrease.

[0005] An object of the present disclosure is to provide a crosslinking agent that, when a compound having a fluorine-containing organic group is applied to an adhesive composition, can form a cured product of the adhesive composition that has sufficient adhesive strength and high infrared transmittance.

[0006] The present disclosure includes the following items [1] to [7]. [1] A crosslinking agent comprising a (meth)acrylic resin having a first structural unit derived from a (meth)acrylate having a fluorine-containing organic group and a second structural unit derived from a (meth)acrylate having a cyclic ether group. [2] The crosslinking agent according to [1], wherein the content of the first structural unit is 10 to 90 mol % based on all structural units of the (meth)acrylic resin, and the content of the second structural unit is 10 to 90 mol % based on all structural units of the (meth)acrylic resin. [3] The crosslinking agent according to [1] or [2], wherein the (meth)acrylate having a fluorine-containing organic group is a (meth)acrylate having a fluoroalkyl group. [4] The crosslinking agent according to [3], wherein the proportion of fluorine atoms in the fluoroalkyl group of the (meth)acrylate having a fluoroalkyl group is 80% or less based on the total amount of hydrogen atoms and fluorine atoms directly bonded to carbon atoms constituting the fluoroalkyl group. [5] The crosslinking agent according to any one of [1] to [4], wherein the (meth)acrylate having a cyclic ether group is at least one selected from the group consisting of (meth)acrylates having an epoxy group and (meth)acrylates having an oxetanyl group. [6] The crosslinking agent according to any one of [1] to [4], wherein the (meth)acrylate having a cyclic ether group is a (meth)acrylate having an alicyclic epoxy group. [7] The crosslinking agent according to any one of [1] to [6], wherein the (meth)acrylic resin has a weight average molecular weight of 10,000 to 60,000.

[0007] According to the present disclosure, a crosslinking agent is provided that, when a compound having a fluorine-containing organic group is applied to an adhesive composition, can form a cured product of the adhesive composition that has sufficient adhesive strength and high infrared transmittance.

[0008] Hereinafter, embodiments of the present disclosure will be described, but the present disclosure is not limited to the following embodiments.

[0009] 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 numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range may be replaced with the upper or lower limit of another numerical range. Furthermore, in a numerical range described in this specification, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. Furthermore, individually described upper and lower limits can be arbitrarily combined. In a numerical range described as "A to B," the numerical values ​​A and B at both ends are included as the lower and upper limits, respectively, in the numerical range. In this specification, for example, the term "10 or more" means "10" and "a number greater than 10," and this also applies when the numerical values ​​are different. Furthermore, for example, the term "10 or less" means "10" and "a number less than 10," and this also applies when the numerical values ​​are different.

[0010] In this specification, a (meth)acrylate compound refers to a compound having one or more (meth)acryloyl groups, and a (meth)acrylic resin refers to a (co)polymer having at least a structural unit derived from a (meth)acrylate compound. A (meth)acryloyl group refers to an acryloyl group or a corresponding methacryloyl group. The same applies to other similar expressions such as (meth)acrylate. Furthermore, "A or B" may include either A or B, or may include both.

[0011] In this specification, the term "cyclic ether group" refers to a group obtained by removing one hydrogen atom directly bonded to a carbon atom from a compound having a cyclic ether such as oxirane or oxetane. The cyclic ether group may be a group obtained by removing one hydrogen atom directly bonded to a carbon atom from a compound having a three- or four-membered cyclic ether. Examples of such cyclic ether groups include epoxy groups (oxiranyl groups) and oxetanyl groups. The epoxy group includes alicyclic epoxy groups (epoxy groups formed together with two carbon atoms constituting an alicyclic ring) such as epoxycyclohexyl groups.

[0012] Unless otherwise specified, the materials exemplified below may be used alone or in combination of two or more. When a composition contains multiple substances corresponding to each component, the amount used or content of each component means the total amount of the multiple substances present in the composition, unless otherwise specified.

[0013] [Crosslinking Agent] The crosslinking agent of one embodiment includes a (meth)acrylic resin having a first structural unit derived from a (meth)acrylate having a fluorine-containing organic group and a second structural unit derived from a (meth)acrylate having a cyclic ether group. The crosslinking agent may be composed of the (meth)acrylic resin. The crosslinking agent of this embodiment can act as a compatibilizer that improves compatibility in an adhesive composition using a compound having a fluorine-containing organic group.

[0014] ((Meth)acrylic resin) The (meth)acrylate having a fluorine organic group that provides the first structural unit may be, for example, a (meth)acrylate having a fluoroalkyl group. Examples of the (meth)acrylate having a fluoroalkyl group include trifluoromethyl (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, 1,1,1,3,3,3-hexafluoro-2-propyl (meth)acrylate, perfluoroethylmethyl (meth)acrylate, perfluoropropylmethyl (meth)acrylate, perfluorobutylmethyl (meth)acrylate, perfluoropentylmethyl (meth)acrylate, perfluorohexylmethyl (meth)acrylate, perfluoroheptylmethyl (meth)acrylate, perfluorooctylmethyl (meth)acrylate, perfluorononylmethyl (meth)acrylate, perfluorodecylmethyl (meth)acrylate, perfluoroundecylmethyl (meth)acrylate, and perfluorododecylmethyl (meth)acrylate. acrylate, perfluorotridecylmethyl (meth)acrylate, perfluorotetradecylmethyl (meth)acrylate, 2-(trifluoromethyl)ethyl (meth)acrylate, 2-(perfluoroethyl)ethyl (meth)acrylate, 2-(perfluoropropyl)ethyl (meth)acrylate, 2-(perfluorobutyl)ethyl (meth)acrylate, 2-(perfluoropentyl)ethyl (meth)acrylate, 2-(perfluorohexyl)ethyl (meth)acrylate, 2-(perfluoroheptyl)ethyl (meth)acrylate, 2-(perfluorooctyl)ethyl (meth)acrylate, 2-(perfluorononyl)ethyl (meth)acrylate, 2-(perfluorotridecyl)ethyl (meth)acrylate, 2-(perfluorotetradecyl)ethyl (meth)acrylate, and the like.

[0015] In a (meth)acrylate having a fluoroalkyl group, the number of carbon atoms in the fluoroalkyl group may be, for example, 1 to 10, or 2 or more, or 8 or less, 6 or less, 4 or less, or 3 or less, from the viewpoint of compatibility in an adhesive composition to which a compound having a fluorine-containing organic group is applied. In a (meth)acrylate having a fluoroalkyl group, the number of carbon atoms in the fluoroalkyl group may be, for example, 2.

[0016] In a (meth)acrylate having a fluoroalkyl group, the proportion of fluorine atoms in the fluoroalkyl group is calculated based on the total amount of hydrogen atoms and fluorine atoms directly bonded to carbon atoms constituting the fluoroalkyl group. For example, the trifluoromethyl group of trifluoromethyl(meth)acrylate has three fluorine atoms and zero hydrogen atoms, and the proportion of fluorine atoms is 100%. For example, the 2,2,2-trifluoroethyl group of 2,2,2-trifluoroethyl(meth)acrylate has three fluorine atoms and two hydrogen atoms, and the proportion of fluorine atoms is 60%. From the viewpoint of compatibility in an adhesive composition using a compound having a fluorine-containing organic group, the proportion of fluorine atoms may be, for example, 100% or less, 90% or less, or 80% or less, or 30% or more, 40% or more, or 50% or more.

[0017] The content of the first structural unit may be 10 to 90 mol %, 20 to 90 mol %, 30 to 90 mol %, or 40 to 90 mol %, based on all structural units of the (meth)acrylic resin, from the viewpoint of compatibility in an adhesive composition to which a compound having a fluorine-containing organic group is applied.

[0018] The (meth)acrylate having a cyclic ether group that provides the second structural unit may be, for example, at least one selected from the group consisting of (meth)acrylates having an epoxy group and (meth)acrylates having an oxetanyl group. Examples of (meth)acrylates having an epoxy group include (meth)acrylates having an alicyclic epoxy group such as 3,4-epoxycyclohexylmethyl (meth)acrylate, and (meth)acrylates having an epoxy group other than an alicyclic epoxy group such as glycidyl (meth)acrylate. Examples of (meth)acrylates having an oxetanyl group include (3-ethyloxetan-3-yl)methyl (meth)acrylate. The (meth)acrylate having a cyclic ether group may be, for example, a (meth)acrylate having an alicyclic epoxy group.

[0019] In the (meth)acrylic resin, the content of the second structural unit may be 10 to 90 mol %, 10 to 80 mol %, 10 to 70 mol %, or 10 to 60 mol % based on all structural units of the (meth)acrylic resin, from the viewpoint of crosslinkability with an epoxy compound or the like.

[0020] The (meth)acrylic resin may have structural units other than the first structural unit and the second structural unit, as long as the effects of the present disclosure are not impaired. Examples of compounds that provide such structural units include monofunctional (meth)acrylates having one (meth)acryloyl group, such as alkyl(meth)acrylates having an alkyl group, (meth)acrylates having an aromatic group, (meth)acrylates having an alicyclic group, (meth)acrylates having a nitrogen-oxygen heterocyclic group, alkoxypolyalkylene glycol (meth)acrylates, polyalkylene glycol mono(meth)acrylates, and (meth)acrylates having a siloxane skeleton; polyfunctional (meth)acrylates having two or more (meth)acryloyl groups, such as aliphatic poly(meth)acrylates and aromatic poly(meth)acrylates; and compounds having a radical polymerizable group other than a (meth)acryloyl group, such as styrene, 4-methylstyrene, vinylpyridine, vinylpyrrolidone, vinyl acetate, cyclohexylmaleimide, and phenylmaleimide.

[0021] The content of the other structural units may be 0 to 40 mol %, 0 to 30 mol %, 0 to 20 mol %, or 0 to 10 mol % based on all structural units of the (meth)acrylic resin.

[0022] The weight average molecular weight (Mw) of the (meth)acrylic resin may be, for example, 1,000 to 200,000, 3,000 or more, 5,000 or more, or 10,000 or more, and may be 150,000 or less, 100,000 or less, 60,000 or less, or 50,000 or less. The weight average molecular weight (Mw) is a polystyrene-equivalent value measured by gel permeation chromatography (GPC) using a calibration curve with standard polystyrene. The weight average molecular weight (Mw) can be measured, for example, by the method described in the Examples.

[0023] (Method for Producing (Meth)acrylic Resin) The (meth)acrylic resin can be obtained, for example, by radical polymerization using a solution polymerization method. More specifically, it can be obtained by polymerizing, in a solvent, monomers including a (meth)acrylate having a cyclic ether group and a (meth)acrylate having a fluorine-containing organic group.

[0024] The solvent can be appropriately selected from organic solvents commonly used in the field of radical polymerization. The solvent may be a solvent having a cyclic ether group (epoxy group or oxetanyl group) but no radical polymerizable group, since the crosslinking agent ((meth)acrylic resin) can be directly used in the polymerization reaction for the curing reaction of a curable resin such as a compound (epoxy resin) having a cyclic ether group without isolating the crosslinking agent ((meth)acrylic resin) (without removing or replacing the solvent). Examples of the solvent include those commonly used in the field of epoxy resin diluents. Examples of the solvent include epoxy resins that are liquid at 25°C. The solvent may be, for example, an aliphatic diglycidyl ether.

[0025] In this specification, the radical polymerizable group refers to a group having a carbon-carbon double bond. Examples of the radical polymerizable group include a (meth)acryloyl group, a vinyl group, an allyl group, a styryl group, an alkenyl group, an alkenylene group, and a maleimide group.

[0026] Examples of aliphatic diglycidyl ethers include diglycidyl ethers having an alkylene group, such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, and 1,6-hexanediol diglycidyl ether; diglycidyl ethers having an oxyalkylene group, such as diethylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, and polyethylene glycol diglycidyl ether; and diglycidyl ethers having a cycloalkylene group, such as hydrogenated bisphenol A diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, and diglycidyl-1,2-cyclohexanedicarboxylate.

[0027] The amount of the solvent used can be appropriately determined depending on the type of monomer, reaction conditions, solid content concentration, etc.

[0028] When polymerizing the monomers, a thermal radical generator, an additive, etc. may be added as needed.

[0029] Examples of the thermal radical generator include organic peroxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropyl carbonate, t-amylperoxy-2-ethylhexanoate, and t-butylperoxy-2-ethylhexanoate; and azo compounds such as 2,2'-azobis(isobutyronitrile), 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl-2,2'-azobis(2-methylpropionate).

[0030] The amount of the thermal radical generator to be added may be appropriately set depending on the type of monomer, reaction conditions, etc., and is not particularly limited, but may be 100 to 200,000 ppm by mass, 1,000 to 100,000 ppm by mass, or 10,000 to 80,000 ppm by mass based on the total amount of the monomers.

[0031] Examples of the additives include chain transfer agents, antioxidants, light stabilizers, weather stabilizers, ultraviolet absorbers, radical scavengers, etc. The amount of the additives added is not particularly limited, but may be 0.001 to 2% by mass or 0.005 to 1% by mass based on the total amount of the monomers.

[0032] The polymerization temperature may be 40 to 120° C., 50 to 100° C., or 60 to 90° C. The polymerization time may be 0.1 to 24 hours, 0.5 to 20 hours, or 1 to 12 hours.

[0033] According to the crosslinking agent of the present disclosure, when a compound having a fluorine-containing organic group is applied to an adhesive composition, it becomes possible to form a cured product of the adhesive composition that has sufficient adhesive strength and high infrared transmittance.

[0034] The present disclosure will be described in more detail below with reference to examples, although the present disclosure is not limited to these examples.

[0035] [Synthesis of (meth)acrylic resin (crosslinking agent)] The following raw materials were prepared. (Meth)acrylate compounds M-3F: trifluoroethyl methacrylate (Light Ester M-3F, manufactured by Kyoeisha Chemical Co., Ltd.) TTA-15: 3,4-epoxycyclohexylmethyl methacrylate (manufactured by Sun Chemical Co., Ltd.) BA: butyl acrylate (manufactured by Toagosei Co., Ltd.) MMA: methyl methacrylate (Acryester (registered trademark) M, manufactured by Mitsubishi Chemical Corporation) GMA: glycidyl methacrylate (manufactured by Mitsubishi Gas Chemical Company, Inc.) Thermal radical generator V-601: dimethyl-2,2'-azobis(2-methylpropionate) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Solvent NPG(D): neopentyl glycol diglycidyl ether (Epogose (registered trademark) NPG(D)) (manufactured by Yokkaichi Synthetic Co., Ltd.) BisF: Bisphenol F epoxy resin (EPICLON (registered trademark) 830, manufactured by DIC Corporation, liquid at 25°C)

[0036] Example 1-1 84.06 g of M-3F and 98.12 g of TTA-15 (molar ratio of M-3F / TTA-15 = 50% / 50%), 10.17 g of V-601, and 23.72 g of NPG (D) were mixed to prepare a mixture (a-1). Separately, 1.82 g of V-601 was dissolved in 7.29 g of NPG (D) to prepare a solution (b-1).

[0037] A flask equipped with a stirrer, dropping funnel, condenser, thermometer, and gas inlet tube was charged with 163.2 g of NPG (D), and the mixture was stirred under a nitrogen atmosphere while replacing the gas, and the temperature was raised to 85°C. Next, mixture (a-1) was added dropwise to the flask over 2 hours. After the dropwise addition was completed, the mixture was stirred at 85°C for 20 minutes, after which solution (b-1) was added and stirred for an additional 7 hours. Next, with continued stirring, the mixture was cooled to room temperature (25°C) to obtain a solution containing the (meth)acrylic resin (crosslinking agent A) of Example 1-1. The solids concentration was 50% by mass. The solids content of the (meth)acrylic resin-containing solution refers to the components other than the solvent of the (meth)acrylic resin-containing solution.

[0038] Example 1-2 141.02 g of M-3F and 41.15 g of TTA-15 (molar ratio of M-3F / TTA-15 = 80% / 20%), 10.17 g of V-601, and 23.72 g of NPG (D) were mixed to prepare a mixture (a-2). A solution containing the (meth)acrylic resin (crosslinking agent B) of Example 1-2 was obtained by the same procedure as in Example 1-1, except that mixture (a-1) was replaced with mixture (a-2). The solids concentration was 50% by mass.

[0039] Example 1-3 121.43 g of M-3F and 60.75 g of TTA-15 (molar ratio of M-3F / TTA-15 = 70% / 30%), 10.17 g of V-601, and 23.72 g of NPG (D) were mixed to prepare a mixture (a-3). A solution containing a (meth)acrylic resin (crosslinking agent C) of Example 1-3 was obtained by the same procedure as in Example 1-1, except that mixture (a-1) was replaced with mixture (a-3). The solids concentration was 50% by mass.

[0040] Example 1-4 48.63 g of M-3F and 132.44 g of TTA-15 (molar ratio of M-3F / TTA-15 = 30% / 70%), 10.17 g of V-601, and 23.72 g of NPG (D) were mixed to prepare a mixture (a-4). A solution containing a (meth)acrylic resin (crosslinking agent D) of Example 1-4 was obtained by the same procedure as in Example 1-1, except that mixture (a-1) was replaced with mixture (a-4). The solids concentration was 50% by mass.

[0041] Example 1-5 32.01 g of M-3F and 149.45 g of TTA-15 (molar ratio of M-3F / TTA-15 = 20% / 80%), 10.17 g of V-601, and 23.72 g of NPG (D) were mixed to prepare a mixture (a-5). A solution containing a (meth)acrylic resin (crosslinking agent E) of Example 1-5 was obtained by the same procedure as in Example 1-1, except that mixture (a-1) was replaced with mixture (a-5). The solids concentration was 50% by mass.

[0042] Example 1-6 144.38 g of M-3F and 42.13 g of TTA-15 (molar ratio of M-3F / TTA-15 = 80% / 20%), 5.78 g of V-601, and 24.11 g of NPG (D) were mixed to prepare a mixture (a-6). Separately, 1.87 g of V-601 was dissolved in 7.46 g of NPG (D) to prepare a solution (b-2).

[0043] A flask equipped with a stirrer, dropping funnel, condenser, thermometer, and gas inlet tube was charged with 162.44 g of NPG (D), and the mixture was stirred under a nitrogen atmosphere while replacing the gas, and the temperature was raised to 85°C. Next, mixture (a-6) was added dropwise to the flask over 2 hours. After the dropwise addition was completed, the mixture was stirred at 85°C for 20 minutes, and then solution (b-2) was added and stirred for an additional 7 hours. Next, with continued stirring, the mixture was cooled to room temperature (25°C) to obtain a solution containing the (meth)acrylic resin (crosslinking agent F) of Example 1-6. The solids concentration was 50% by mass.

[0044] Comparative Example 1-1 182.17 g of M-3F (molar ratio of M-3F / TTA-15 = 100% / 0%), 10.17 g of V-601, and 23.72 g of NPG (D) were mixed to prepare a mixture (a-7). A solution containing a (meth)acrylic resin (crosslinking agent a) of Comparative Example 1-1 was obtained by the same procedure as in Example 1-1, except that mixture (a-1) was replaced with mixture (a-7). The solids concentration was 50% by mass.

[0045] Comparative Example 1-2 95.41 g of BA, 82.81 g of MMA, and 11.76 g of GMA (molar ratio of BA / MMA / GMA = 45% / 50% / 5%), 2.28 g of V-601, and 24.42 g of NPG (D) were mixed to prepare a mixture (a-8). A solution containing the (meth)acrylic resin (crosslinking agent b) of Comparative Example 1-2 was obtained by the same procedure as in Example 1-6, except that mixture (a-6) was replaced with mixture (a-8). The solids concentration was 50% by mass.

[0046] Comparative Example 1-3 A solution containing a (meth)acrylic resin (crosslinking agent c) of Comparative Example 1-3 was obtained in the same manner as in Comparative Example 1-2, except that the solvent was changed from NPG (D) to BisF. The solid content concentration was 50 mass%.

[0047] [Evaluation of (meth)acrylic resin] (Measurement of viscosity (25°C)) The viscosity of a solution containing a (meth)acrylic resin at 25°C was measured at a rotation speed of 10 rpm after setting a sample volume of 0.5 to 1.0 mL in an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., product name: VISCOMETER-TV22, applicable cone-plate rotor: 3° × R17.65). The results are shown in Table 1.

[0048] (Measurement of weight average molecular weight (Mw)) A solution containing a (meth)acrylic resin was dissolved in tetrahydrofuran (THF) to prepare a 0.2 mass % THF solution as a sample for Mw measurement. Mw was measured by gel permeation chromatography (GPC) and calculated by conversion using a calibration curve of standard polystyrene. The GPC conditions are shown below. The results are also shown in Table 1. Measuring apparatus: Shodex (registered trademark) GPC-101 (manufactured by Resonac Co., Ltd.) Detector: Differential refractometer Shodex RI-71S (manufactured by Resonac Co., Ltd.) Column: Shodex LF-804 + LF-804 (manufactured by Resonac Co., Ltd.) Column temperature: 40°C Eluent: tetrahydrofuran (THF) Flow rate: 1 mL / min

[0049] (Observation of Resin Solution) The solution containing the (meth)acrylic resin was visually observed, and transparent solutions were evaluated as "A," and opaque solutions were evaluated as "B." The results are shown in Table 1.

[0050]

[0051] [Preparation of Adhesive Compositions] <Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-3> The adhesive compositions of Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-3, each containing a (meth)acrylate compound, an epoxy compound, a crosslinking agent, and a photoacid generator, were prepared by mixing the components in the amounts (unit: parts by mass) shown in Table 2 using a planetary mixer (5 minutes / 1500 rpm).

[0052] The details of each raw material are as follows: (Meth)acrylate compounds V-13F: 1H,1H,2H,2H-tridecafluorooctyl acrylate (2-(perfluorohexyl)ethyl acrylate) (manufactured by Osaka Organic Chemical Industry Ltd.) 4-HBA: 4-hydroxybutyl acrylate (manufactured by Osaka Organic Chemical Industry Ltd.) 2-MTA: 2-methoxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Ltd.) Epoxy compounds NPG(D): neopentyl glycol diglycidyl ether (Epogose (registered trademark) NPG(D)) (manufactured by Yokkaichi Synthetic Co., Ltd.) 2021P: 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (Celloxide (registered trademark) 2021P, manufactured by Daicel Corporation) BisF: bisphenol F type epoxy resin (EPICLON (registered trademark) 830, manufactured by DIC Corporation, liquid at 25°C) Crosslinking agent (Meth)acrylic resins (crosslinking agents A to F and a to c) of Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-3 Photoacid generator CPI-110P: sulfonium salt (manufactured by San-Apro Co., Ltd.)

[0053] The amounts of the (meth)acrylic resins (crosslinking agents A to F and a to c) of Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-3, which are crosslinking agents, and the epoxy compounds NPG (D) and BisF added were prepared using the solution containing the (meth)acrylic resin (crosslinking agent) obtained above.

[0054] [Evaluation of Adhesive Composition] (Measurement of Shear Strength) A 50 μm thick spacer film was placed on a glass slide to give dimensions of 5 mm wide x 5 mm thick x 50 μm thick, and the adhesive composition was applied to the glass slide. A glass chip with a width of 7 mm x 7 mm and a thickness of 1.0 mm was placed on the applied adhesive composition, and an LED lamp (manufactured by Ushio Inc., wavelength: 365 nm) was used to illuminate the adhesive composition at 30 mW / cm. ２ The adhesive composition was irradiated with light for 30 seconds. The shear strength was measured using a bond tester (Nordson, product name: DAGE4000) at a shear rate of 180 mm / min, using a sample taken 270 seconds after the end of light irradiation. The results are shown in Table 2.

[0055] (Measurement of infrared transmittance) The infrared transmittance of the cured adhesive composition was measured at a wavelength of 1,310 nm using a spectrophotometer (manufactured by Agilent Technologies, product name: Cary 7000). Measurement samples were prepared by the following procedure. First, a 500 μm thick spacer film was placed on a release film so that the dimensions were 50 mm wide x 50 mm long and 500 μm thick, and the adhesive composition was applied onto the release film. Next, an LED lamp (manufactured by Ushio Inc., wavelength: 365 nm) was used to measure the infrared transmittance at 30 mW / cm. ２ The adhesive composition was irradiated with light for 30 seconds, and 600 seconds after the end of the light irradiation, the adhesive composition was peeled off from the release film to prepare a measurement sample. Glass used as the substrate was used as a baseline. When the infrared transmittance was 85% or higher, the adhesive composition was evaluated as excellent in infrared transmittance, earning an "A" rating, and when it was less than 85%, a "B" rating. The results are shown in Table 2.

[0056]

[0057] As shown in Table 2, the adhesive compositions of Examples 2-1 to 2-6 had higher shear strength and higher infrared transmittance of the cured products than the adhesive compositions of Comparative Examples 2-1 to 2-3. These results confirm that when a crosslinking agent according to the present disclosure is used in conjunction with a compound having a fluorine-containing organic group in an adhesive composition, it is possible to form a cured adhesive composition having sufficient adhesive strength and high infrared transmittance.

Claims

1. A crosslinking agent comprising a (meth)acrylic resin having a first structural unit derived from a (meth)acrylate having a fluorine-containing organic group, and a second structural unit derived from a (meth)acrylate having a cyclic ether group.

2. The crosslinking agent according to claim 1, wherein the content of the first structural unit is 10 to 90 mol % based on all structural units of the (meth)acrylic resin, and the content of the second structural unit is 10 to 90 mol % based on all structural units of the (meth)acrylic resin.

3. The crosslinking agent according to claim 1 or 2, wherein the (meth)acrylate having a fluorine-containing organic group is a (meth)acrylate having a fluoroalkyl group.

4. The crosslinking agent according to claim 3, wherein the proportion of fluorine atoms in the fluoroalkyl group of the (meth)acrylate having a fluoroalkyl group is 80% or less based on the total amount of hydrogen atoms and fluorine atoms directly bonded to carbon atoms constituting the fluoroalkyl group.

5. The crosslinking agent according to claim 1 or 2, wherein the (meth)acrylate having a cyclic ether group is at least one selected from the group consisting of (meth)acrylates having an epoxy group and (meth)acrylates having an oxetanyl group.

6. The crosslinking agent according to claim 1 or 2, wherein the (meth)acrylate having a cyclic ether group is a (meth)acrylate having an alicyclic epoxy group.

7. The crosslinking agent according to claim 1 or 2, wherein the (meth)acrylic resin has a weight average molecular weight of 10,000 to 60,000.

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