Curable adhesive composition and curable adhesive sheet

Abstract

Provided is a curable adhesive composition comprising a binder resin (A) having a reactive functional group, a poly(phenylene ether) resin (B) having a vinyl group and a number-average molecular weight of 1,500 or higher but lower than 5,000, and a polyfunctional compound (C) having two or more unsaturated hydrocarbon groups each having a double bond at the end.

Description

Curable adhesive composition and curable adhesive sheet

[0001] The present invention relates to a curable adhesive composition and a curable adhesive sheet.

[0002] In recent years, flexible printed circuit boards (FPCs) have been used as wiring components in response to the trend toward smaller and lighter electronic devices. FPCs can be manufactured by, for example, forming an electrical circuit by etching the copper foil of a copper-clad laminate, in which copper foil is laminated to an insulating resin film such as polyimide. For such FPCs, a cover lay sheet having an insulating resin substrate and an adhesive layer is laminated to the copper foil on which the electrical circuit is formed to protect the electrical circuit. As an example of such a cover lay sheet, Patent Document 1 discloses an invention relating to a laminate with an adhesive layer, which includes a substrate film and, on at least one surface of the substrate film, an adhesive layer made of an adhesive composition containing a carboxyl group-containing styrene-based elastomer and an epoxy resin.

[0003] Japanese Patent Application Laid-Open No. 2018-150541

[0004] The laminate described in Patent Document 1 is said to have high adhesion to, for example, a substrate film made of a polyimide resin or the like and copper foil, but further improvement, including in other properties, is required. In other words, there is a need for a curable adhesive composition that can form an adhesive layer or a cured product thereof that has excellent various properties and can be suitably applied to cover lay sheet applications.

[0005] The present invention provides a curable adhesive composition comprising a binder resin having a reactive functional group, a polyphenylene ether resin having a vinyl group and a number-average molecular weight within a predetermined range, and a polyfunctional compound having two or more unsaturated hydrocarbon groups having a double bond at the terminal, and a curable adhesive sheet having an adhesive layer formed from the curable adhesive composition. Specifically, one aspect of the present invention is as follows: [1] A curable adhesive composition comprising: a binder resin (A) having a reactive functional group; a polyphenylene ether resin (B) having a vinyl group and a number-average molecular weight of 1,500 or more but less than 5,000; and a polyfunctional compound (C) having two or more unsaturated hydrocarbon groups having a double bond at the terminal. [2] The curable adhesive composition according to claim 1, further comprising a cationic polymerization initiator (D). [3] The curable adhesive composition according to item [1] or [2], wherein the content of component (B) is 99.0 parts by mass or less per 100 parts by mass of the total amount of component (A). [4] The curable adhesive composition according to any one of [1] to [3] above, wherein the content of component (A) is more than 20% by mass, based on the total amount of active ingredients in the curable adhesive composition. [5] The curable adhesive composition according to any one of [1] to [4] above, further comprising a crosslinking agent (E) capable of reacting with the reactive functional group of component (A). [6] The curable adhesive composition according to any one of [1] to [5] above, wherein the total content of components (A), (B), and (C) is 50% by mass or more, based on the total amount of active ingredients in the curable adhesive composition. [7] The curable adhesive composition according to any one of [1] to [6] above, wherein the total content of components (B) and (C) is less than 100 parts by mass, based on 100 parts by mass of the total amount of component (A). [8] The curable adhesive composition according to any one of [1] to [7] above, wherein component (C) is a polyfunctional compound having a heterocyclic structure. [9] The curable adhesive composition according to any one of [1] to [8] above, wherein component (C) is a polyfunctional compound having two or more of the unsaturated hydrocarbon groups and further containing a saturated hydrocarbon group.

[10] The curable adhesive composition according to any one of [1] to [9] above, wherein component (C) includes a polyfunctional compound (C1) having two of the unsaturated hydrocarbon groups.

[11] The curable adhesive composition according to the above

[10] , wherein component (C1) is a polyfunctional compound having two unsaturated hydrocarbon groups and one saturated hydrocarbon group.

[12] The curable adhesive composition according to any one of the above [1] to

[11] , wherein component (C) comprises a compound (C11) represented by the following general formula (c-11): (In the above formula, R ａ represents a saturated hydrocarbon group.)

[13] The curable adhesive composition according to any one of [1] to

[12] above, wherein component (A) comprises an olefin-based resin (A1) having a reactive functional group.

[14] The curable adhesive composition according to any one of [1] to

[13] above, wherein the content of the inorganic filler is 0 to 30 mass%, based on the total amount of active ingredients of the curable adhesive composition.

[15] A curable adhesive sheet having an adhesive layer formed from the curable adhesive composition according to any one of [1] to

[14] above.

[16] The curable adhesive sheet according to

[15] above, wherein the adhesive layer can be cured by heating to form a cured product.

[17] The curable adhesive sheet according to

[15] or

[16] above, which is used as a coverlay sheet.

[0006] A preferred embodiment of the curable adhesive composition of the present invention can form an adhesive layer or a cured product thereof that has an excellent balance of various properties (e.g., adhesive strength, dielectric properties, effect of suppressing bleeding of adhesive components, etc.) that can be suitably applied to coverlay sheets.

[0007] 2 is a schematic cross-sectional view in the thickness direction of a curable adhesive sheet according to an embodiment of the present invention, showing an example of the configuration of the adhesive sheet. FIG. 3 is a schematic view showing the state of a test sample after heat pressing, for explaining the procedure for evaluating the exudation of adhesive components.

[0008] The numerical ranges described herein can be arbitrarily combined with upper and lower limit values. For example, when a numerical range is described as "preferably 20 to 120, more preferably 40 to 90," the ranges "20 to 90" and "40 to 120" are also included in the numerical ranges described herein. Furthermore, when a numerical range is described as "preferably 20 or more, more preferably 40 or more, and preferably 120 or less, more preferably 90 or less," the ranges "20 to 90" and "40 to 120" are also included in the numerical ranges described herein. In addition, for example, a numerical range described herein as "60 to 100" means a range of "60 or more and 100 or less." Furthermore, when specifying the upper and lower limit values ​​described herein, the numerical range from the lower limit value to the upper limit value can be specified by appropriately selecting from the respective options and combining them arbitrarily. In addition, multiple combinations of the various requirements described as preferred aspects of the present specification can be used.

[0009] In this specification, for example, "(meth)acrylate" is used as a term that refers to both "acrylate" and "methacrylate," and the same applies to other similar terms. In this specification, the "active ingredient" of a curable adhesive composition refers to the components contained in the curable adhesive composition excluding dilution solvents such as water and organic solvents. In this specification, the number average molecular weight (Mn) is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene, and specifically, is a value measured based on the method described in the examples.

[0010] [Configuration of Curable Adhesive Composition] The curable adhesive composition of the present invention contains a binder resin (A) having a reactive functional group (hereinafter also referred to as "component (A)"), a polyphenylene ether resin (B) having a vinyl group and a number average molecular weight of 1500 or more and less than 5000 (hereinafter also referred to as "component (B)"), and a polyfunctional compound (C) having two or more unsaturated hydrocarbon groups having a terminal double bond (hereinafter also referred to as "component (C)").

[0011] A curable adhesive sheet having an adhesive layer is attached to an adherend such as a circuit board, cured to form a cured product, and then bonded to the adherend. In this process, further improvement in the adhesive strength of the cured product to an adherend such as a circuit board is desired. In recent years, communication devices such as smartphones have increasingly used higher-frequency electrical signals to handle larger volumes of data. Because electrical signals in the high-frequency range (e.g., 1 GHz or higher) are easily converted to heat, higher frequencies of electrical signals tend to increase transmission loss. Therefore, in order to transmit high-frequency electrical signals at high speed with reduced transmission loss, low dielectric properties (low dielectric constant and low dielectric dissipation factor) are also required for the cured product obtained by curing the adhesive layer of a coverlay sheet that protects a circuit board. Furthermore, during the bonding process in which the adhesive layer of a curable adhesive sheet is attached to an adherend such as a circuit board and cured to bond the adhesive to the adherend, the adhesive components of the adhesive layer may seep out from the edges of the sheet, resulting in contamination of areas not intended to come into contact with the curable adhesive sheet. Under these circumstances, the curable adhesive composition of one embodiment of the present invention contains components (A), (B), and (C), and is a composition capable of forming an adhesive layer or a cured product thereof that has a good balance of various properties such as adhesive strength, low dielectric properties, and the effect of suppressing bleeding of adhesive components, thereby solving the above-mentioned problems.

[0012] The curable adhesive composition of one embodiment of the present invention preferably further contains one or more selected from the group consisting of a cationic polymerization initiator (D) (hereinafter also referred to as "component (D)"), a crosslinking agent (E) (hereinafter also referred to as "component (E)") capable of reacting with the reactive functional group of component (A), and a silane coupling agent (F) (hereinafter also referred to as "component (F)"). In addition, the curable adhesive composition of one embodiment of the present invention may contain additives other than these components (A) to (F) as long as the effects of the present invention are not impaired.

[0013] In one embodiment of the curable adhesive composition of the present invention, from the viewpoint of providing a composition capable of forming an adhesive layer or a cured product thereof that exhibits a well-balanced improvement in various properties, such as adhesive strength, low dielectric properties, and adhesive component bleeding-suppression effect, the total content of components (A), (B), and (C) relative to the total amount of active ingredients in the curable adhesive composition is preferably 50% by mass or more, more preferably 55% by mass or more, more preferably 60% by mass or more, more preferably 65% ​​by mass or more, even more preferably 70% by mass or more, even more preferably 75% by mass or more, still more preferably 80% by mass or more, still more preferably 85% by mass or more, and particularly preferably 90% by mass or more, and may also be 100% by mass or less, 99.99% by mass or less, 99.90% by mass or less, 99.70% by mass or less, or 99.50% by mass or less.

[0014] From the above viewpoints, in the curable adhesive composition of one embodiment of the present invention, the total content of components (A), (B), (C), (D), (E), and (F) is preferably 50% by mass or more, more preferably 55% by mass or more, more preferably 60% by mass or more, more preferably 65% ​​by mass or more, even more preferably 70% by mass or more, even more preferably 75% by mass or more, even more preferably 80% by mass or more, still more preferably 85% by mass or more, and particularly preferably 90% by mass or more, and may be 100% by mass or less, based on the total amount of active ingredients in the curable adhesive composition. Below, details of each component contained in the curable adhesive composition of one embodiment of the present invention will be described.

[0015] <Component (A): Binder Resin> The curable adhesive composition of one embodiment of the present invention contains a binder resin (A) having a reactive functional group. By using a composition containing the binder resin (A), an adhesive layer formed from the composition is less likely to experience the phenomenon of adhesive components seeping out from the edges during the adhesion process in which the composition is applied to an adherend such as a circuit board and cured to bond the adherend. In other words, by containing the binder resin (A), the curable adhesive composition of one embodiment of the present invention can form an adhesive layer that is highly effective in suppressing the seepage of adhesive components. The binder resin (A) may be used alone or in combination of two or more types.

[0016] In the curable adhesive composition of one aspect of the present invention, the content of component (A) is preferably greater than 20% by mass, more preferably 22% by mass or more, more preferably 25% by mass or more, more preferably 27% by mass or more, even more preferably 30% by mass or more, even more preferably 35% by mass or more, even more preferably 40% by mass or more, and still more preferably 45% by mass or more, based on the total amount (100% by mass) of the active ingredients of the curable adhesive composition, from the viewpoint of forming a composition that can form an adhesive layer that is highly effective in suppressing bleeding of adhesive ingredients and a composition that can form a cured product with further improved low dielectric properties.

[0047] The content of the component (B) in the composition is preferably 95% by mass or less, particularly preferably 50% by mass or more, and may further be 52% by mass or more, 55% by mass or more, 57% by mass or more, 60% by mass or more, 62% by mass or more, or 65% by mass or more. From the viewpoint of sufficiently containing component (B) and component (C) to obtain a composition that can form a cured product with improved adhesive strength, the content is preferably 95% by mass or less, more preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, even more preferably 75% by mass or less, still more preferably 72% by mass or less, and particularly preferably 70% by mass or less.

[0017] The number average molecular weight (Mn) of the binder resin (A) used in one embodiment of the present invention is, from the viewpoint of improving film-forming properties and providing a composition that can improve the shape stability of the adhesive layer, preferably 10,000 or more, more preferably 12,000 or more, more preferably 15,000 or more, even more preferably 20,000 or more, still more preferably 25,000 or more, still more preferably 30,000 or more, still more preferably 32,000 or more, particularly preferably 35,000 or more, and even more preferably 37,000 or more, 39,000 or more.

[0044] The molecular weight may be 0 or more, 40,000 or more, 42,000 or more, or 45,000 or more. Furthermore, from the viewpoint of improving the solubility of component (A) in a diluting solvent and providing a composition with excellent coatability when the composition is in the form of a solution, the molecular weight is preferably 200,000 or less, more preferably 150,000 or less, more preferably 100,000 or less, even more preferably 80,000 or less, even more preferably 70,000 or less, still more preferably 60,000 or less, and particularly preferably 55,000 or less.

[0018] The binder resin (A) used in one embodiment of the present invention may have a reactive functional group as a side chain relative to the main chain resin. Examples of the reactive functional group possessed by the binder resin (A) include a carboxyl group, a carboxylic acid anhydride structure, a carboxylic acid ester, a hydroxyl group, an epoxy group, an amide group, an ammonium group, a nitrile group, an amino group, an imide group, an isocyanate group, an acetyl group, a thiol group, a sulfonic acid group, a phosphonic acid group, a nitro group, a halogen atom, and an alkoxysilyl group. The reactive functional group possessed by the binder resin (A) may be composed of one type alone or a combination of two or more types. Among these, the reactive functional group of the binder resin (A) is preferably a group selected from a carboxy group, a group having a carboxylic acid anhydride structure, an epoxy group, an amide group, an ammonium group, a nitrile group, an amino group, an imide group, an isocyanate group, an acetyl group, a thiol group, an ether group, a thioether group, a sulfone group, a phosphone group, a nitro group, a urethane group, a halogen atom, and an alkoxysilyl group. From the viewpoint of obtaining a composition that can form a cured product having superior adhesive strength, a group selected from a carboxy group and a group having a carboxylic acid anhydride structure is more preferred. From the viewpoint of obtaining a composition that can form a cured product that is superior in adhesive strength and low dielectric properties, a group having a carboxylic acid anhydride structure is even more preferred.

[0019] Examples of resins that form the main chain of the binder resin (A) include polyolefin-based resins, phenoxy-based resins, polyimide-based resins, polyamideimide-based resins, polyvinyl butyral-based resins, polycarbonate-based resins, styrene-based resins, etc. Among these, from the viewpoint of improving film-forming properties and providing a composition that can improve the shape stability of the adhesive layer, as well as providing a composition that can form a cured product with further improved low dielectric properties, the binder resin (A) used in one embodiment of the present invention preferably contains one or more selected from polyolefin-based resins having reactive functional groups and styrene-based resins having reactive functional groups, and more preferably contains at least a polyolefin-based resin (A1) having a reactive functional group.

[0020] In the curable adhesive composition of one embodiment of the present invention, the content of the polyolefin resin (A1) is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, more preferably 70 to 100 mass%, even more preferably 80 to 100 mass%, even more preferably 85 to 100 mass%, still more preferably 90 to 100 mass%, and particularly preferably 95 to 100 mass%, relative to the total amount (100 mass%) of component (A) contained in the curable adhesive composition, from the viewpoint of obtaining a composition that can form a cured product with excellent low dielectric properties.

[0021] The polyolefin resin (A1) used in one embodiment of the present invention may be any polymer having structural units derived from an olefin monomer, and may be a polymer consisting only of structural units derived from an olefin monomer, or may be a copolymer having structural units derived from an olefin monomer and structural units derived from a monomer copolymerizable with the olefin monomer.

[0022] The olefin monomer constituting the polyolefin resin (A1) may be an α-olefin having 2 or more carbon atoms, preferably an α-olefin having 2 to 8 carbon atoms, more preferably at least one selected from ethylene, propylene, 1-butene, isobutylene, and 1-hexene, and even more preferably at least one selected from ethylene and propylene. These olefin monomers may be used alone or in combination of two or more.

[0023] Furthermore, examples of the monomer copolymerizable with the olefin-based monomer constituting the polyolefin-based resin (A1) include vinyl acetate, (meth)acrylic acid ester, styrene, etc. These monomers may be used alone or in combination of two or more.

[0024] Specific examples of the polyolefin resin (A1) used in one embodiment of the present invention include very low density polyethylene (VLDPE), low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), linear low density polyethylene, polypropylene (PP), ethylene-propylene copolymer, olefin elastomer (TPO), ethylene-vinyl acetate copolymer (EVA), ethylene-(meth)acrylic acid copolymer, and ethylene-(meth)acrylic acid ester copolymer.

[0025] The binder resin (A) used in one embodiment of the present invention may be a modified resin obtained by subjecting a main chain resin to modification treatment using a modifying agent to introduce the above-mentioned reactive functional group. Specific modified resins include, for example, acid-modified resins into which acid groups have been introduced and resins into which hydroxyl groups have been introduced. From the viewpoint of obtaining a composition capable of forming a cured product having superior adhesive strength, acid-modified resins into which acid groups have been introduced are preferred, and from the viewpoint of obtaining a composition capable of forming a cured product having superior adhesive strength and low dielectric properties, acid anhydride-modified resins into which acid anhydride structures have been introduced are more preferred.

[0026] Acid-modified resins or acid anhydride-modified resins (hereinafter also referred to as "unsaturated carboxylic acids, etc.") can be obtained, for example, by reacting an unsaturated carboxylic acid, etc. with a resin that serves as a main chain, thereby introducing a carboxy group or a carboxylic acid anhydride structure and graft-modifying it. The method for introducing the unsaturated carboxylic acid, etc. into the resin is not particularly limited, and examples include a method in which the resin and the unsaturated carboxylic acid, etc. are heated to a temperature equal to or higher than the melting point of the resin in the presence of a radical generator such as an organic peroxide or an azonitrile, thereby melting and reacting them, or a method in which the resin and the unsaturated carboxylic acid, etc. are dissolved in an organic solvent, and then heated and stirred in the presence of a radical generator, thereby reacting them.

[0027] Examples of unsaturated carboxylic acids include maleic acid, fumaric acid, itaconic acid, citraconic acid, glutaconic acid, tetrahydrophthalic acid, and aconitic acid. Examples of unsaturated carboxylic acid anhydrides include maleic anhydride, itaconic anhydride, glutaconic anhydride, citraconic anhydride, aconitic anhydride, norbornene dicarboxylic anhydride, and tetrahydrophthalic anhydride. These may be used alone or in combination of two or more. Among these, maleic anhydride is preferred from the viewpoint of forming a composition capable of forming a cured product having excellent adhesive strength and low dielectric properties.

[0028] The amount of the unsaturated carboxylic acid or the like to be reacted with the resin is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 3 parts by mass, and even more preferably 0.2 to 1 part by mass, relative to 100 parts by mass of the resin, from the viewpoint of obtaining a composition that can form a cured product that is superior in adhesive strength and low dielectric properties.

[0029] <Component (B): Polyphenylene Ether Resin> The curable adhesive composition of one embodiment of the present invention contains a polyphenylene ether resin (B) having a vinyl group and a number average molecular weight of 1,500 or more and less than 5,000. The curable adhesive composition of one embodiment of the present invention contains the polyphenylene ether resin (B) together with a polyfunctional compound (C) described below, thereby forming a cured product that has improved adhesive strength while improving heat resistance and low dielectric properties. The polyphenylene ether resin (B) may be used alone or in combination of two or more types.

[0030] In the curable adhesive composition of one embodiment of the present invention, the content of component (B) is, from the viewpoint of forming a composition that can form a cured product with improved adhesive strength, preferably 1 part by mass or more, more preferably 3 parts by mass or more, more preferably 5 parts by mass or more, more preferably 7 parts by mass or more, even more preferably 10 parts by mass or more, even more preferably 12 parts by mass or more, even more preferably 15 parts by mass or more, still more preferably 17 parts by mass or more, and particularly preferably 20 parts by mass or more, relative to 100 parts by mass of the total amount of component (A). Furthermore, from the viewpoint of forming a composition that can form an adhesive layer that is highly effective in suppressing bleeding of adhesive components and a cured product with good low dielectric properties, the content of component (B) is preferably less than 99 parts by mass, more preferably 95 parts by mass or less, more preferably 90 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 70 parts by mass or less, even more preferably 60 parts by mass or less, even more preferably 50 parts by mass or less, still more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less.

[0031] In the curable adhesive composition of one embodiment of the present invention, the content of component (B) relative to the total amount (100 mass%) of the curable adhesive composition is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, more preferably 1.0 mass% or more, more preferably 3.0 mass% or more, even more preferably 5.0 mass% or more, even more preferably 7.0 mass% or more, even more preferably 10.0 mass% or more, still more preferably 12.0 mass% or more, and particularly preferably 15.0 mass% or more, from the viewpoint of forming a composition that can form an adhesive layer that is highly effective in suppressing bleeding of adhesive components and a composition that can form a cured product with good low dielectric properties, the content of component (B) is preferably less than 50 mass%, more preferably 45 mass% or less, more preferably 40 mass% or less, more preferably 35 mass% or less, even more preferably 30 mass% or less, even more preferably 27 mass% or less, even more preferably 25 mass% or less, still more preferably 22 mass% or less, and particularly preferably 20 mass% or less.

[0032] From the viewpoint of providing a composition that can form a cured product having good low dielectric properties and further improved adhesive strength, the number average molecular weight (Mn) of the polyphenylene ether resin (B) used in one embodiment of the present invention is 1,500 or more, but is preferably 1,600 or more, more preferably 1,700 or more, more preferably 1,800 or more, even more preferably 1,900 or more, still more preferably 2,000 or more, and particularly preferably 2,100 or more. Furthermore, from the viewpoint of providing a composition that has good solubility in a diluent solvent and excellent coatability when the composition is in the form of a solution, the number average molecular weight (Mn) is less than 5,000, but is preferably 4,900 or less, more preferably 4,800 or less, more preferably 4,700 or less, even more preferably 4,600 or less, even more preferably 4,500 or less, still more preferably 4,400 or less, particularly preferably 4,300 or less, and may even be 4,200 or less, 4,000 or less, 3,700 or less, 3,500 or less, 3,300 or less, or 3,000 or less.

[0033] The polyphenylene ether resin (B) used in one embodiment of the present invention may be a resin having a structural unit represented by at least one of the following general formula (bi) and formula (b-ii) in the main chain.

[0034] In the above general formula (bi) or (b-ii), R ａ１ and R ａ２ are each independently a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom), an alkyl group having 1 to 6 carbon atoms, or a phenyl group, preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, even more preferably an alkyl group having 1 to 3 carbon atoms, even more preferably a methyl group or an ethyl group, and particularly preferably a methyl group. ａ１ and R ａ２ Examples of the alkyl group having 1 to 6 carbon atoms that can be selected as m1 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a t-butyl group, an s-butyl group, an isobutyl group, an n-pentyl group, an n-hexyl group, etc. m1 and m2 each independently represent an integer of 0 to 4, preferably an integer of 0 to 3, more preferably an integer of 0 to 2, and even more preferably 2.

[0035] From the viewpoint of obtaining a composition capable of forming a cured product having good low dielectric properties and further improved adhesive strength, the polyphenylene ether resin (B) used in one embodiment of the present invention is preferably a resin having a skeleton represented by the following formula (b-1) as the main chain:

[0036] In the above general formula (b-1), R ａ１ and R ａ２ , and m1 and m2 are the same as defined in the above general formula (bi) or formula (b-ii), and the types and numerical ranges of preferred groups are also the same. X is a divalent organic group, and at least one hydrogen atom of the organic group may be substituted with a substituent. p1 and p2 are each independently an integer of 0 or more, and p1 + p2 is an integer of 1 or more. * indicates the bonding position with the terminal group.

[0037] Examples of divalent hydrocarbon groups that can be selected as X include alkylene groups having 1 to 20 carbon atoms, oxyalkylene groups having 1 to 20 carbon atoms, alkenylene groups having 1 to 20 carbon atoms, cycloalkylene groups having 3 to 10 ring carbon atoms, cycloalkenylene groups having 3 to 10 ring carbon atoms, phenylene groups, biphenylene groups, terphenylene groups, naphthylene groups, and groups formed by combining two or more of these groups. The alkylene groups, oxyalkylene groups, and alkenylene groups may be linear or branched. The alkylene groups, oxyalkylene groups, and alkenylene groups may have a substituent selected from a halogen atom, a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, and a cycloalkyl group having 3 to 10 carbon atoms. In addition, the above cycloalkylene group, cycloalkenylene group, phenylene group, biphenylene group, terphenylene group, and naphthylene group may have a substituent selected from a halogen atom, an alkyl group having 1 to 6 carbon atoms, an oxyalkyl group having 1 to 6 carbon atoms, and an alkenyl group having 1 to 6 carbon atoms.

[0038] Among these, from the viewpoint of obtaining a composition capable of forming a cured product with improved adhesive strength, X is preferably a group represented by the following formula (b-2).

[0039] In the above general formula (b-2), R ｂ１ and R ｂ２ are each independently a halogen atom (fluorine atom, chlorine atom, bromine atom, or iodine atom), an alkyl group having 1 to 6 carbon atoms, an oxyalkyl group having 1 to 6 carbon atoms, or an alkenyl group having 1 to 6 carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, even more preferably an alkyl group having 1 to 3 carbon atoms, even more preferably a methyl group or an ethyl group, and particularly preferably a methyl group. ｂ１ and R ｂ２ Examples of the alkyl group having 1 to 6 carbon atoms that can be selected as n1 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a t-butyl group, an s-butyl group, an isobutyl group, an n-pentyl group, an n-hexyl group, etc. n1 and n2 each independently represent an integer of 0 to 4, preferably an integer of 0 to 3, more preferably an integer of 1 to 3, and even more preferably 3.

[0040] In the above general formula (b-2), A represents a single bond or a divalent hydrocarbon group. Examples of divalent hydrocarbon groups that can be selected as A include alkylene groups having 1 to 20 carbon atoms, oxyalkylene groups having 1 to 20 carbon atoms, alkenylene groups having 1 to 20 carbon atoms, cycloalkylene groups having 3 to 10 ring carbon atoms, and cycloalkenylene groups having 3 to 10 ring carbon atoms. The alkylene groups, oxyalkylene groups, and alkenylene groups may be linear or branched. The hydrocarbon groups that can be selected as A may have the above-mentioned substituents. Among these, from the viewpoint of obtaining a composition that can form a cured product with improved adhesive strength, A is preferably a single bond or an alkylene group having 1 to 20 carbon atoms, and more preferably a single bond.

[0041] From the viewpoint of obtaining a composition capable of forming a cured product having improved adhesive strength, the polyphenylene ether resin (B) used in one embodiment of the present invention is more preferably a resin having, as a main chain, a skeleton represented by the following formula (b-3):

[0042] In the above general formula (b-3), R ａ１ and R ａ２ is the same as defined in the above general formula (bi) or (b-ii), and the types and ranges of preferred groups are also the same. ｂ１ and R ｂ２ is the same as defined in the general formula (b-2) above, and the types and numerical ranges of the preferred groups are also the same. p1 and p2 are each independently an integer of 0 or more, and p1 + p2 is an integer of 1 or more. * indicates the bonding position with the terminal group. Note that, in the general formula (b-3) above, ａ１ , R ａ２ , R ｂ１ , and R ｂ２ are each independently preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, even more preferably an alkyl group having 1 to 3 carbon atoms, still more preferably a methyl group or an ethyl group, and particularly preferably a methyl group.

[0043] Since the polyphenylene ether resin (B) used in one embodiment of the present invention has a vinyl group, a cured product formed from the curable adhesive composition has low dielectric properties, excellent crosslinkability, and excellent heat resistance. The vinyl group contained in the polyphenylene ether resin (B) may be one that constitutes a part of a hydrocarbon-based substituent, such as a vinylbenzyl group or a vinylnaphthyl group. In other words, the polyphenylene ether resin (B) is formed by bonding a vinyl group or a vinyl-group-containing hydrocarbon group to a polyphenylene ether skeleton.

[0044] From the viewpoint of obtaining a composition capable of forming a cured product having excellent low dielectric properties, crosslinkability, and heat resistance, the polyphenylene ether resin (B) used in one embodiment of the present invention is preferably a resin having vinyl groups or vinyl group-containing hydrocarbon groups at both terminals of the main chain. The polyphenylene ether resin (B) having vinyl groups or vinyl group-containing hydrocarbon groups at both terminals of the main chain can be obtained by forming a polyphenylene ether skeleton as the main chain and then introducing vinyl groups or vinyl group-containing hydrocarbon groups to both terminals. Specifically, a difunctional phenol compound and a monofunctional phenol compound are reacted to obtain a polymer having phenolic hydroxyl groups at both terminals, and then the terminal phenolic hydroxyl groups are vinylbenzyl-etherified using 4-(chloromethyl)styrene, thereby obtaining the polyphenylene ether resin (B) having vinylbenzyl groups at both terminals of the polyphenylene ether skeleton.

[0045] The polyphenylene ether resin (B) used in one embodiment of the present invention is preferably a compound represented by the following general formula (b-4). p1 and p2 are each independently an integer of 0 or greater, and p1+p2 is an integer of 1 or greater.

[0046] The polyphenylene ether resin (B) used in one embodiment of the present invention may be a commercially available product, such as OPE-2St (a compound represented by the above general formula (b-4)) manufactured by Mitsubishi Gas Chemical Company, Inc.

[0047] <Component (C): Polyfunctional Compound> The curable adhesive composition of one embodiment of the present invention contains a polyfunctional compound (C) having two or more unsaturated hydrocarbon groups with a terminal double bond. The polyfunctional compound (C) in the present invention excludes compounds corresponding to components (A) and (B). By forming a composition containing the polyfunctional compound (C) together with the polyphenylene ether resin (B), a cured product can be formed that exhibits a well-balanced improvement in low dielectric properties and adhesive strength. In particular, since the polyfunctional compound (C) has two or more unsaturated hydrocarbon groups, a crosslinked structure is formed in the resulting cured product, thereby enabling the formation of a cured product with further improved adhesive strength. The polyfunctional compound (C) may be used alone or in combination of two or more types.

[0048] In the curable adhesive composition of one embodiment of the present invention, the content of component (C) is, from the viewpoint of forming a composition that can form a cured product exhibiting a well-balanced improvement in low dielectric properties and adhesive strength, preferably 1 part by mass or more, more preferably 3 parts by mass or more, more preferably 5 parts by mass or more, more preferably 7 parts by mass or more, even more preferably 10 parts by mass or more, even more preferably 12 parts by mass or more, even more preferably 15 parts by mass or more, still more preferably 17 parts by mass or more, and particularly preferably 20 parts by mass or more, relative to 100 parts by mass of the total amount of component (A); and, from the viewpoint of forming a composition that can form an adhesive layer with excellent adhesion, preferably less than 99 parts by mass, more preferably 95 parts by mass or less, more preferably 90 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 70 parts by mass or less, even more preferably 60 parts by mass or less, even more preferably 50 parts by mass or less, still more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less.

[0049] In the curable adhesive composition of one embodiment of the present invention, the content of component (C) is, relative to the total amount (100 mass%) of the active ingredients of the curable adhesive composition, preferably 0.1 mass% or more, more preferably 0.5 mass% or more, more preferably 1.0 mass% or more, more preferably 3.0 mass% or more, even more preferably 5.0 mass% or more, even more preferably 7.0 mass% or more, even more preferably 10.0 mass% or more, still more preferably 12.0 mass% or more, and particularly preferably 15.0 mass% or more, from the viewpoint of a composition that can form an adhesive layer with excellent adhesion, preferably less than 50 mass%, more preferably 45 mass% or less, more preferably 40 mass% or less, more preferably 35 mass% or less, even more preferably 30 mass% or less, even more preferably 27 mass% or less, even more preferably 25 mass% or less, still more preferably 22 mass% or less, and particularly preferably 20 mass% or less.

[0050] In the curable adhesive composition of one embodiment of the present invention, from the viewpoint of forming a composition capable of forming a cured product having a well-balanced improvement in low dielectric properties, adhesive strength, and heat resistance, the content ratio of component (B) to component (C) [(B) / (C)], in mass ratio, is preferably 5 / 95 or more, more preferably 10 / 90 or more, more preferably 15 / 85 or more, more preferably 20 / 80 or more, even more preferably 25 / 75 or more, even more preferably 30 / 70 or more, even more preferably 35 / 65 or more, still more preferably 40 / 60 or more, particularly preferably 45 / 55 or more, and is preferably 95 / 5 or less, more preferably 90 / 10 or less, more preferably 85 / 15 or less, more preferably 80 / 20 or less, even more preferably 75 / 25 or less, even more preferably 70 / 30 or less, even more preferably 65 / 35 or less, still more preferably 60 / 40 or less, particularly preferably 55 / 45 or less.

[0051] In the curable adhesive composition of one embodiment of the present invention, the total content of component (B) and component (C) is, relative to 100 parts by mass of component (A), preferably less than 100 parts by mass, more preferably 95 parts by mass or less, more preferably 90 parts by mass or less, more preferably 85 parts by mass or less, even more preferably 80 parts by mass or less, even more preferably 75 parts by mass or less, even more preferably 70 parts by mass or less, still more preferably 65 parts by mass or less, and particularly preferably 60 parts by mass or less, from the viewpoint of a composition that can form an adhesive layer that has a high effect of suppressing bleeding of the adhesive components; and, from the viewpoint of a composition that can form a cured product with improved adhesive strength, preferably 2 parts by mass or more, more preferably 5 parts by mass or more, more preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, even more preferably 25 parts by mass or more, even more preferably 30 parts by mass or more, still more preferably 35 parts by mass or more, and particularly preferably 40 parts by mass or more.

[0052] The number of carbon atoms in each of the unsaturated hydrocarbon groups contained in the polyfunctional compound (C) used in one embodiment of the present invention is preferably 2 to 10, more preferably 2 to 7, even more preferably 2 to 5, still more preferably 2 to 4, and particularly preferably 2 to 3. Examples of the unsaturated hydrocarbon group include a vinyl group, an allyl group, a 3-butenyl group, a 4-pentenyl group, a 5-hexenyl group, an isopropenyl group, a 1-methyl-2-propenyl group, a vinylbenzyl group, and a vinylnaphthyl group. Among these, the unsaturated hydrocarbon group contained in the polyfunctional compound (C) is preferably an allyl group.

[0053] The number of unsaturated hydrocarbon groups contained in the polyfunctional compound (C) used in one embodiment of the present invention is 2 or more, but from the viewpoint of making the crosslinked structure appropriately sparse and providing a composition that can form a cured product in which the generation of cracks is suppressed, and from the viewpoint of making a composition that can suppress cure shrinkage in the adhesion step in which the adhesive layer becomes a cured product and reduce warpage of the plate-like member that is the adherend, such as a circuit board, the number is preferably 2 to 4, more preferably 2 to 3, and even more preferably 2.

[0054] From the viewpoint of obtaining a composition capable of forming a cured product having improved low dielectric properties and adhesive strength in a more balanced manner, the polyfunctional compound (C) used in one embodiment of the present invention is preferably a polyfunctional compound having two or more of the unsaturated hydrocarbon groups and further having a saturated hydrocarbon group. From the above viewpoint, the number of saturated hydrocarbon groups possessed by the polyfunctional compound (C) used in one embodiment of the present invention is preferably 1 or more, more preferably 1 to 4, even more preferably 1 to 3, still more preferably 1 to 2, and particularly preferably 1.

[0055] Examples of the saturated hydrocarbon group include an alkyl group and an alkyl group substituted with an alkoxy group. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a t-butyl group, an s-butyl group, an isobutyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, and an n-pentadecyl group. The number of carbon atoms in the alkyl group is preferably 1 to 20, more preferably 4 to 18, even more preferably 6 to 16, and still more preferably 8 to 15.

[0056] Examples of the alkyl group substituted with an alkoxy group include a methoxymethyl group, an ethoxymethyl group, a 2-methoxyethoxymethyl group, a benzyloxymethyl group, etc. The number of carbon atoms in the alkyl group substituted with an alkoxy group is preferably 2 to 15, more preferably 2 to 12, and even more preferably 3 to 10.

[0057] The polyfunctional compound (C) used in one embodiment of the present invention preferably includes a polyfunctional compound (C1) having two unsaturated hydrocarbon groups. As described above, a composition containing such a polyfunctional compound (C1) having two unsaturated hydrocarbon groups can be a composition that can form a cured product in which cracking is suppressed and warping of the adherend, such as a plate-like member such as a circuit board, is reduced, and can also be a composition that can form a cured product with further improved low dielectric properties and adhesive strength. From the above perspective, it is more preferable that the polyfunctional compound (C1) is a polyfunctional compound having two unsaturated hydrocarbon groups and at least one saturated hydrocarbon group.

[0058] From the above viewpoints, in the curable adhesive composition of one embodiment of the present invention, the content of the polyfunctional compound (C1) is preferably 30 to 100 mass%, more preferably 40 to 100 mass%, more preferably 50 to 100 mass%, more preferably 60 to 100 mass%, even more preferably 70 to 100 mass%, even more preferably 80 to 100 mass%, even more preferably 85 to 100 mass%, still more preferably 90 to 100 mass%, and particularly preferably 95 to 100 mass%, relative to the total amount (100 mass%) of component (C) contained in the curable adhesive composition.

[0059] The polyfunctional compound (C) used in one embodiment of the present invention is preferably a polyfunctional compound having a heterocyclic skeleton. By including a polyfunctional compound having a heterocyclic skeleton, a composition can be obtained that can form a cured product with improved low dielectric properties and adhesive strength. Specific examples of the heterocyclic skeleton include an isocyanurate skeleton and a glycoluril skeleton.

[0060] Examples of the polyfunctional compound (C) used in one embodiment of the present invention include a compound having an isocyanurate skeleton represented by the following general formula (c-1) and a compound having a glycoluril skeleton represented by the following general formula (c-2).

[0061] In the general formula (c-1), R １１ ~R １３ are each independently an unsaturated hydrocarbon group having a double bond at a terminal, or a saturated hydrocarbon group, and R１１ ~R １３ At least two of the above are unsaturated hydrocarbon groups. ２１ ~R ２６ are each independently a hydrogen atom, an unsaturated hydrocarbon group having a double bond at the terminal, or a saturated hydrocarbon group, and R ２１ ~R ２６ At least two of R are the unsaturated hydrocarbon groups. １１ ~R １３ and R ２１ ~R ２６ Specific examples of the unsaturated hydrocarbon group and saturated hydrocarbon group that can be selected as are as described above, and the preferred range of the number of carbon atoms is also as described above.

[0062] From the viewpoint of being a composition capable of forming a cured product in which cracking is suppressed and warpage of the adherend, such as a plate-like member such as a circuit board, is reduced, and also capable of forming a cured product having further improved low dielectric properties and adhesive strength, the polyfunctional compound (C) used in one aspect of the present invention preferably includes a compound having an isocyanurate skeleton represented by the general formula (c-1) above, and more preferably includes a compound (C11) having an isocyanurate skeleton represented by the following general formula (c-11):

[0063] In the above general formula (c-11), R ａ is a saturated hydrocarbon group, and specific examples are as described above. ａ is preferably an alkyl group. The alkyl group preferably has 1 to 20 carbon atoms, more preferably 4 to 18 carbon atoms, even more preferably 6 to 16 carbon atoms, and even more preferably 8 to 15 carbon atoms.

[0064] From the above viewpoints, in the curable adhesive composition of one aspect of the present invention, the content of compound (C11) is preferably 30 to 100 mass%, more preferably 40 to 100 mass%, more preferably 50 to 100 mass%, more preferably 60 to 100 mass%, even more preferably 70 to 100 mass%, even more preferably 80 to 100 mass%, even more preferably 85 to 100 mass%, still more preferably 90 to 100 mass%, and particularly preferably 95 to 100 mass%, relative to the total amount (100 mass%) of component (C) contained in the curable adhesive composition.

[0065] The polyfunctional compound (C) used in one embodiment of the present invention may be a commercially available product. Specific examples of commercially available products include L-DAIC (product name, manufactured by Shikoku Chemical Industry Co., Ltd., a compound represented by the general formula (c-11) above), TAIC (registered trademark) (product name, manufactured by Mitsubishi Chemical Corporation, a compound represented by the R １１ ~R １３ is an allyl group), TAG (product name, manufactured by Shikoku Chemicals Corporation, compound represented by the above general formula (c-2)), etc.

[0066] The molecular weight of the polyfunctional compound (C) used in one embodiment of the present invention is preferably 100 or more, more preferably 150 or more, even more preferably 200 or more, still more preferably 230 or more, and particularly preferably 270 or more, from the viewpoint of obtaining a composition that easily forms a cured product having the desired physical properties, and is preferably 1000 or less, more preferably 800 or less, even more preferably 700 or less, still more preferably 600 or less, and particularly preferably 500 or less, from the viewpoint of obtaining a composition that easily forms an adhesive layer that is easy to apply at room temperature.

[0067] The boiling point of the polyfunctional compound (C) used in one embodiment of the present invention is preferably 175 to 350° C., more preferably 200 to 300° C. The 5% weight loss temperature of the polyfunctional compound (C) used in one embodiment of the present invention is preferably 175 to 350° C., more preferably 200 to 300° C.

[0068] Furthermore, from the viewpoint of obtaining a composition that can form a cured product with excellent low dielectric properties and that can easily form an adhesive layer that is easy to apply at room temperature, the polyfunctional compound (C) used in one embodiment of the present invention is preferably a compound that is liquid at 25° C. In this specification, the term "compound that is liquid at 25° C." refers to a compound that has fluidity at 25° C., and specifically refers to a compound that has a viscosity of 2 to 10,000 mPa s as measured at 25° C. and 1.0 rpm using an E-type viscometer.

[0069] <Component (D): Cationic Polymerization Initiator> The curable adhesive composition of one embodiment of the present invention preferably further contains a cationic polymerization initiator (D). By forming the curable adhesive composition into which the cationic polymerization initiator (D) is contained, the polymerization reaction of components (B) and (C) can be sufficiently progressed, and the storage stability of the formed adhesive layer can be improved. The cationic polymerization initiator (D) may be used alone or in combination of two or more types.

[0070] In the curable adhesive composition of one embodiment of the present invention, the content of component (D) is, from the viewpoint of allowing the polymerization reaction of components (B) and (C) to proceed sufficiently and forming an adhesive layer with improved storage stability, preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, more preferably 0.10 parts by mass or more, even more preferably 0.15 parts by mass or more, even more preferably 0.20 parts by mass or more, still more preferably 0.25 parts by mass or more, and particularly preferably 0.30 parts by mass or more, relative to 100 parts by mass of the total amount of components (B) and (C). Also, the content of component (D) is preferably 6.0 parts by mass or less, more preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, even more preferably 2.0 parts by mass or less, even more preferably 1.5 parts by mass or less, still more preferably 1.0 part by mass or less, and particularly preferably 0.70 parts by mass or less.

[0071] The cationic polymerization initiator (D) used in one embodiment of the present invention may be a thermal cationic polymerization initiator or a photo-induced cationic polymerization initiator. However, from the viewpoint of enabling polymerization to be carried out in a simple process, a thermal cationic polymerization initiator is preferred.

[0072] The thermal cationic polymerization initiator used in one embodiment of the present invention is a compound capable of generating a cationic species that initiates polymerization upon heating, and examples thereof include sulfonium salts, quaternary ammonium salts, phosphonium salts, diazonium salts, iodonium salts, etc. These thermal cationic polymerization initiators may be used alone or in combination of two or more.

[0073] Examples of sulfonium salts include triphenylsulfonium tetrafluoroborate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluoroarsinate, tris(4-methoxyphenyl)sulfonium hexafluoroarsinate, diphenyl(4-phenylthiophenyl)sulfonium hexafluoroarsinate, etc. Commercially available sulfonium salts can also be used, such as ADEKAOPTON SP-150, ADEKAOPTON SP-170, ADEKAOPTON CP-66, ADEKAOPTON CP-77 (all manufactured by ADEKA Corporation), SAN-AID SI-60L, SAN-AID SI-80L, SAN-AID SI-100L, SAN-AID SI-B2A, SAN-AID SI-B3 (all manufactured by Sanshin Chemical Industry Co., Ltd.), CYRACURE UVI-6974, ... Examples of suitable grease include UVI-6990 (manufactured by Union Carbide), UVI-508, UVI-509 (manufactured by General Electric Company), FC-508, FC-509 (manufactured by Minnesota Mining and Manufacturing Company), CD-1010, CD-1011 (manufactured by Thurstomer Corporation), and CI series products (manufactured by Nippon Soda Co., Ltd.).

[0074] Examples of quaternary ammonium salts include tetrabutylammonium tetrafluoroborate, tetrabutylammonium hexafluorophosphate, tetrabutylammonium hydrogen sulfate, tetraethylammonium tetrafluoroborate, tetraethylammonium p-toluenesulfonate, N,N-dimethyl-N-benzylanilinium hexafluoroantimonate, N,N-dimethyl-N-benzylanilinium tetrafluoroborate, N,N-dimethyl-N-benzylpyridinium hexafluoroantimonate, N,N-diethyl-N-benzyltrifluoromethanesulfonate, N,N-dimethyl-N-(4-methoxybenzyl)pyridinium hexafluoroantimonate, and N,N-diethyl-N-(4-methoxybenzyl)toluidinium hexafluoroantimonate.

[0075] Examples of phosphonium salts include ethyltriphenylphosphonium hexafluoroantimonate and tetrabutylphosphonium hexafluoroantimonate.

[0076] Examples of diazonium salts include AMERICURE (manufactured by American Can Co.), ULTRASET (manufactured by Adeka Corporation), and the like.

[0077] Examples of iodonium salts include diphenyliodonium hexafluoroarsinate, bis(4-chlorophenyl)iodonium hexafluoroarsinate, bis(4-bromophenyl)iodonium hexafluoroarsinate, phenyl(4-methoxyphenyl)iodonium hexafluoroarsinate, etc. Commercially available iodonium salts can also be used, such as UV-9310C (manufactured by Toshiba Silicones Co., Ltd.), Photoinitiator 2074 (manufactured by Rhone-Poulenc), UVE series products (manufactured by General Electric Co.), and FC series products (manufactured by Minnesota Mining and Manufacturing Co.).

[0078] When the curable adhesive composition of one embodiment of the present invention contains a cationic polymerization initiator (D), at least a portion of the cationic polymerization initiator (D) may be a high-temperature reactive thermal cationic polymerization initiator that exhibits an exothermic peak top temperature of more than 120°C when differential scanning calorimetry is performed under the following conditions: (Differential Scanning Calorimetry Conditions) A measurement sample is a mixture containing 0.1 part by mass of the cationic polymerization initiator to be measured, 100 parts by mass of bisphenol A diglycidyl ether, and 0.1 part by mass of γ-butyrolactone, and differential scanning calorimetry is performed from 30°C to 300°C at a heating rate of 10°C / min to measure the peak temperature of the exothermic peak.

[0079] Commercially available high-temperature reactive thermal cationic polymerization initiators include, for example, San-Aid SI-B3, San-Aid SI-B4, San-Aid SI-B5, and San-Aid SI-150 (all manufactured by Sanshin Chemical Industry Co., Ltd.).

[0080] <Reactive Curing Agent Other Than Cationic Polymerization Initiator (D)> The curable adhesive composition of one embodiment of the present invention may contain a reactive curing agent other than the cationic polymerization initiator (D) in place of or together with the cationic polymerization initiator (D), within a range that does not impair the effects of the present invention. When the curable adhesive composition of one embodiment of the present invention contains the cationic polymerization initiator (D), the content of the other reactive curing agent may be 0 to 90 parts by mass, 0 to 50 parts by mass, 0 to 40 parts by mass, 0 to 30 parts by mass, 0 to 20 parts by mass, 0 to 10 parts by mass, 0 to 5.0 parts by mass, 0 to 2.0 parts by mass, 0 to 1.0 parts by mass, 0 to 0.10 parts by mass, 0 to 0.010 parts by mass, or 0 to 0.0010 parts by mass, relative to 100 parts by mass of the total amount of component (D). On the other hand, when the curable adhesive composition of one embodiment of the present invention does not contain the cationic polymerization initiator (D), the content of the other reactive curing agent may be 0.01 parts by mass or more, 0.05 parts by mass or more, 0.10 parts by mass or more, 0.15 parts by mass or more, 0.20 parts by mass or more, 0.25 parts by mass or more, or 0.30 parts by mass or more, relative to 100 parts by mass of the total amount of component (B) and component (C), or may be 6.0 parts by mass or less, 5.0 parts by mass or less, 3.0 parts by mass or less, 2.0 parts by mass or less, 1.5 parts by mass or less, 1.0 part by mass or less, or 0.70 parts by mass or less.

[0081] Examples of the reactive curing agent (D) other than the cationic polymerization initiator include amine compounds such as benzylmethylamine and 2,4,6-trisdimethylaminomethylphenol; imidazole compounds such as 2-methylimidazole, 2-ethyl-4-methylimidazole, and 2-heptadecylimidazole; Lewis acids such as boron trifluoride-monoethylamine complex and boron trifluoride-piperazine complex; and peroxides such as di(t-butylperoxy)diisopropylbenzene.

[0082] <Component (E): Crosslinking Agent> The curable adhesive composition of one embodiment of the present invention preferably further contains a crosslinking agent (E) capable of reacting with the reactive functional group of component (A). By forming a composition containing the crosslinking agent (E) in addition to component (A), an adhesive layer having a high effect of suppressing bleeding of adhesive components can be formed. In other words, during the process of forming an adhesive layer from a coating film formed from the curable adhesive composition, the crosslinking agent (E) reacts with the reactive functional group possessed by the binder resin (A), forming a crosslinked structure within the coating film, thereby forming an adhesive layer that is resistant to fluidization even when heated. As a result, the formed adhesive layer is less likely to leak adhesive components from the edges during the bonding process in which the adhesive layer is applied to an adherend such as a circuit board, cured, and bonded to the adherend. The crosslinking agent (E) may be used alone or in combination of two or more types.

[0083] In the curable adhesive composition of one embodiment of the present invention, the content of component (E) is, from the viewpoint of forming a composition that can form an adhesive layer that has a higher effect of suppressing bleeding of adhesive components, preferably 0.01 parts by mass or more, more preferably 0.03 parts by mass or more, more preferably 0.05 parts by mass or more, more preferably 0.07 parts by mass or more, even more preferably 0.10 parts by mass or more, even more preferably 0.15 parts by mass or more, even more preferably 0.20 parts by mass or more, still more preferably 0.25 parts by mass or more, and particularly preferably 0.30 parts by mass or more, relative to 100 parts by mass of the total amount of component (A); and from the viewpoint of forming a composition that can form an adhesive layer with excellent adhesion, the content of component (E) is preferably 10.0 parts by mass or less, more preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, more preferably 5.0 parts by mass or less, even more preferably 4.0 parts by mass or less, even more preferably 3.0 parts by mass or less, even more preferably 2.5 parts by mass or less, still more preferably 2.0 parts by mass or less, and particularly preferably 1.5 parts by mass or less.

[0084] The molecular weight of the crosslinking agent (E) used in one aspect of the present invention is preferably 1,000 or less, more preferably 800 or less, even more preferably 700 or less, still more preferably 600 or less, and particularly preferably 500 or less, from the viewpoint of increasing the probability of reaction with component (A), facilitating the formation of a crosslinked structure, and providing a composition that can form an adhesive layer that is more effective in suppressing the bleeding of adhesive components.Furthermore, from the viewpoint of adjusting the molecular weight so that the crosslinking agent (E) can be retained within the adhesive layer by heating in the drying step of forming the adhesive layer, and providing a composition that can exert the effects of adding the crosslinking agent (E), the molecular weight is preferably 100 or more, more preferably 150 or more, even more preferably 200 or more, still more preferably 250 or more, and particularly preferably 300 or more.

[0085] The crosslinking agent (E) used in one embodiment of the present invention is appropriately selected depending on the type of reactive functional group possessed by component (A), and examples thereof include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, metal chelate-based crosslinking agents, and aziridine-based crosslinking agents. Among these, from the viewpoint of storage stability, the crosslinking agent (E) used in one embodiment of the present invention is preferably at least one selected from isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-based crosslinking agents. Furthermore, from the viewpoint of obtaining a composition capable of forming a cured product with further improved low dielectric properties, the crosslinking agent (E) used in one embodiment of the present invention is preferably a crosslinking agent having an isocyanurate skeleton.

[0086] The isocyanate crosslinking agent is preferably a compound having two or more isocyanate groups in the molecule, and examples thereof include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, diphenylmethane-4,4-diisocyanate, isophorone diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, adducts of these polyisocyanate compounds with polyol compounds such as trimethylolpropane, and biuret and isocyanurate forms of these polyisocyanate compounds.

[0087] The epoxy crosslinking agent is preferably a compound having two or more epoxy groups in the molecule, and examples thereof include 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, and diglycidylamine.

[0088] Examples of the metal chelate crosslinking agent include chelate compounds having metal ions that function as crosslinking points. Examples of the metal ions include aluminum ions, zirconium ions, titanium ions, zinc ions, iron ions, and tin ions. Among these, aluminum chelate compounds are preferred as the metal chelate crosslinking agent, including aluminum tris(acetylacetonate), acetylacetonate aluminum bis(ethylacetoacetate), diisopropoxyaluminum monooleylacetoacetate, and monoisopropoxyaluminum bisoleylacetoacetate.

[0089] Among these, from the viewpoint of obtaining a composition capable of forming an adhesive layer having a higher effect of suppressing bleeding of adhesive components and a cured product having further improved low dielectric properties, the crosslinking agent (E) used in one embodiment of the present invention is preferably an isocyanate-based crosslinking agent, more preferably an isocyanurate of a polyisocyanate compound, and even more preferably one or more selected from an isocyanurate of 1,5-pentamethylene diisocyanate [1,3,5-tris(5-isocyanatopentyl)-1,3,5-triazine-2,4,6-trione] and an isocyanurate of 1,6-hexamethylene diisocyanate [1,3,5-tris(6-isocyanatohexyl)-1,3,5-triazine-2,4,6-trione].

[0090] <Component (F): Silane Coupling Agent> The curable adhesive composition of one embodiment of the present invention preferably further contains a silane coupling agent (F). By using a composition containing a silane coupling agent, a cured product with improved adhesive strength can be formed. The silane coupling agent (F) may be used alone or in combination of two or more types.

[0091] In the curable adhesive composition of one embodiment of the present invention, the content of component (F) is preferably 0.001 parts by mass or more, more preferably 0.005 parts by mass or more, more preferably 0.01 parts by mass or more, more preferably 0.03 parts by mass or more, even more preferably 0.05 parts by mass or more, still more preferably 0.07 parts by mass or more, even more preferably 0.10 parts by mass or more, still more preferably 0.12 parts by mass or more, and particularly preferably 0.01 parts by mass or more, based on 100 parts by mass of the total amount of component (A), from the viewpoint of forming a composition that can form a cured product with excellent adhesive strength even in a high-temperature and high-humidity environment. It is preferably 0.15 parts by mass or more, and from the viewpoint of suppressing the amount of outgassing that can be generated in a high-temperature, high-humidity environment and providing a composition that can form a cured product that maintains good adhesive strength, it is preferably 6.0 parts by mass or less, more preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, more preferably 3.0 parts by mass or less, even more preferably 2.0 parts by mass or less, even more preferably 1.5 parts by mass or less, even more preferably 1.0 part by mass or less, still more preferably 0.80 parts by mass or less, and particularly preferably 0.60 parts by mass or less.

[0092] The silane coupling agent (E) used in one embodiment of the present invention is preferably an organosilicon compound having at least one alkoxysilyl group in the molecule. Specific examples of the silane coupling agent include silane coupling agents having a (meth)acryloyl group, such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane; vinyltrimethoxysilane, vinyltriethoxysilane, dimethoxymethyl Silane coupling agents having a vinyl group such as vinyl silane, diethoxymethyl vinyl silane, trichlorovinyl silane, vinyl tris(2-methoxyethoxy) silane; silane coupling agents having an epoxy group such as 2-(3,4-epoxycyclohexyl) ethyl trimethoxy silane, 3-glycidoxypropyl trimethoxy silane, 3-glycidoxypropyl methyl diethoxy silane, 3-glycidoxypropyl triethoxy silane, 8-glycidoxyoctyl trimethoxy silane; silane coupling agents having a styryl group such as p-styryl trimethoxy silane, p-styryl triethoxy silane; N-(2-aminoethyl)-3-aminopropyl methyl dimethoxy silane, N-(2-aminoethyl)-3-aminopropyl tri ... Silane coupling agents having an amino group, such as i-ethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride; silane coupling agents having a ureido group, such as 3-ureidopropyltrimethoxysilane and 3-ureidopropyltriethoxysilane; silane coupling agents having a halogen atom, such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane; silane coupling agents having a mercapto group, such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane;Examples of suitable silane coupling agents include silane coupling agents having a sulfide group, such as bis(trimethoxysilylpropyl)tetrasulfide and bis(triethoxysilylpropyl)tetrasulfide; silane coupling agents having an isocyanate group, such as 3-isocyanatepropyltrimethoxysilane and 3-isocyanatepropyltriethoxysilane; silane coupling agents having an allyl group, such as allyltrichlorosilane, allyltriethoxysilane and allyltrimethoxysilane; and silane coupling agents having a hydroxyl group, such as 3-hydroxypropyltrimethoxysilane and 3-hydroxypropyltriethoxysilane.

[0093] <Cyclic Ether Compound> The curable adhesive composition of one embodiment of the present invention may further contain a cyclic ether compound, or may be a composition that does not contain a cyclic ether compound. The cyclic ether compound may be any compound having a cyclic ether group. Examples of the cyclic ether group include an oxirane group (epoxy group), an oxetane group (oxetanyl group), a tetrahydrofuryl group, and a tetrahydropyranyl group. In this specification, the oxirane group includes groups having an oxirane structure, such as a glycidyl group, a glycidyl ether group, and an epoxycyclohexyl group. The cyclic ether compound may be used alone, or two or more types may be used in combination.

[0094] Compositions containing cyclic ether compounds have the property of being able to form cured products with excellent adhesive strength, but the cured products tend to have large values ​​of dielectric constant and dielectric dissipation factor, and therefore poor low-dielectric properties. However, the curable adhesive composition of one embodiment of the present invention contains the above-mentioned components (A) to (C), and therefore has the property of being able to form cured products with improved adhesive strength and low-dielectric properties in a well-balanced manner. Therefore, the curable adhesive composition of one embodiment of the present invention does not need to contain a cyclic ether compound, which would cause a decrease in low-dielectric properties.

[0095] In the curable adhesive composition of one embodiment of the present invention, the content of the cyclic ether compound may be less than 5.0 mass%, less than 3.0 mass%, less than 1.0 mass%, less than 0.50 mass%, less than 0.10 mass%, less than 0.010 mass%, less than 0.0010 mass%, less than 0.00010 mass%, or less than 0.000010 mass%, relative to the total amount (100 mass%) of the active ingredients of the curable adhesive composition. Furthermore, in the curable adhesive composition of one embodiment of the present invention, the content of the cyclic ether compound may be less than 5.0 parts by mass, less than 3.0 parts by mass, less than 1.0 part by mass, less than 0.50 parts by mass, less than 0.10 parts by mass, less than 0.010 parts by mass, less than 0.0010 parts by mass, less than 0.00010 parts by mass, or less than 0.000010 parts by mass, relative to 100 parts by mass of the total amount of components (A) to (C) included in the curable adhesive composition.

[0096] <Inorganic Filler> The curable adhesive composition of one embodiment of the present invention may further contain an inorganic filler, or may be a composition that does not contain an inorganic filler. Examples of inorganic fillers include silica, alumina, talc, aluminum hydroxide, magnesium hydroxide, titanium oxide, mica, aluminum borate, barium sulfate, boron nitride, forsterite, zinc oxide, magnesium oxide, and calcium carbonate. These inorganic fillers may be used alone or in combination of two or more.

[0097] However, in the curable adhesive composition of one embodiment of the present invention, the smaller the content of the inorganic filler, the more preferable. In the curable adhesive composition of one embodiment of the present invention, the content of the inorganic filler may be 0 to 30 mass%, 0 to 20 mass%, 0 to 10 mass%, 0 to 5.0 mass%, 0 to 2.0 mass%, 0 to 1.0 mass%, 0 to 0.1 mass%, 0 to 0.01 mass%, or 0 to 0.001 mass%, relative to the total amount (100 mass%) of the active ingredients of the curable adhesive composition. Furthermore, in the curable adhesive composition of one embodiment of the present invention, the content of the inorganic filler may be less than 50 parts by mass, less than 30 parts by mass, less than 10 parts by mass, less than 5.0 parts by mass, less than 1.0 parts by mass, less than 0.1 parts by mass, less than 0.01 parts by mass, less than 0.001 parts by mass, or less than 0.0001 parts by mass, relative to 100 parts by mass of the total amount of components (A) to (C) contained in the curable adhesive composition.

[0098] <Other Additives> The curable adhesive composition of one embodiment of the present invention may contain additives other than the above-described components, as long as the effects of the present invention are not impaired. Examples of other additives include ultraviolet absorbers, antistatic agents, light stabilizers, antioxidants, resin stabilizers, pigments, extenders, and softeners. These additives may be used alone or in combination of two or more. The content of these additives can be appropriately set depending on the type of additive. For example, the content of each additive may be 0.001 to 30 parts by mass, 0.005 to 20 parts by mass, 0.01 to 10 parts by mass, or 0.03 to 5 parts by mass, relative to 100 parts by mass of the total amount of component (A) contained in the curable adhesive composition.

[0099] <Liquid Active Ingredient> The curable adhesive composition of one embodiment of the present invention preferably contains an active ingredient that is liquid at 25° C. By using a composition that contains a liquid active ingredient, the adhesive properties of the adhesive layer that is formed can be improved.

[0100] In one embodiment of the curable adhesive composition of the present invention, from the viewpoint of forming a composition capable of forming an adhesive layer with excellent adhesion, the content of active ingredients that are liquid at 25°C, relative to the total amount (100 mass%) of active ingredients in the curable adhesive composition, is preferably 5.0 mass% or more, more preferably 7.0 mass% or more, even more preferably 10 mass% or more, still more preferably 12 mass% or more, and particularly preferably 14 mass% or more, and is also preferably 50 mass% or less, more preferably 40 mass% or less, even more preferably 35 mass% or less, still more preferably 30 mass% or less, and particularly preferably 25 mass% or less.

[0101] From the viewpoint of obtaining a composition capable of forming an adhesive layer with excellent adhesion and capable of forming a cured product with improved low dielectric properties and adhesive strength, it is preferred that at least one of the active ingredients that are liquid at 25°C contained in the curable adhesive composition of one embodiment of the present invention is a polyfunctional compound (C). In the curable adhesive composition of one embodiment of the present invention, the content of the polyfunctional compound (C) relative to the total amount (100% by mass) of active ingredients that are liquid at 25°C is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, and may also be 100% by mass or less, 99.9% by mass or less, 99.5% by mass or less, 99.0% by mass or less, 98.5% by mass or less, or 98.0% by mass or less.

[0102] <Dilution Solvent> The curable adhesive composition of one embodiment of the present invention may be in the form of a solution by further adding a dilution solvent. Examples of the dilution solvent used in one embodiment of the present invention include aromatic hydrocarbon solvents such as benzene and toluene; ester solvents such as ethyl acetate and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; aliphatic hydrocarbon solvents such as n-pentane, n-hexane, and n-heptane; and alicyclic hydrocarbon solvents such as cyclopentane, cyclohexane, and methylcyclohexane. These dilution solvents may be used alone or in combination of two or more. Note that these dilution solvents may be the solvents used in the synthesis of components (A) and (B), or one or more solvents other than the solvents used in the synthesis of components (A) and (B) may be added.

[0103] When the curable adhesive composition of one embodiment of the present invention is in the form of a solution, the concentration of the active ingredient in the curable adhesive composition is appropriately set so as to achieve a desired viscosity, taking into consideration factors such as coatability. The active ingredient concentration may be 0.01% by mass or more, 0.05% by mass or more, 0.10% by mass or more, 0.50% by mass or more, 1.0% by mass or more, 3.0% by mass or more, 5.0% by mass or more, or 10% by mass or more, relative to the total amount (100% by mass) of the curable adhesive composition, or may be 80% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, 40% by mass or less, or 30% by mass or less.

[0104] [Curable adhesive sheet] A curable adhesive sheet of one embodiment of the present invention has an adhesive layer formed from the curable adhesive composition of one embodiment of the present invention described above. The adhesive layer can be cured by undergoing a curing step. The curable adhesive sheet of one embodiment of the present invention is not particularly limited as long as it has a configuration including the adhesive layer. For example, it may be a curable adhesive sheet having an adhesive layer on at least one side of a substrate, or a curable adhesive sheet having a configuration in which the adhesive layer is sandwiched between two release sheets.

[0105] FIG. 1 is a schematic cross-sectional view in the thickness direction of a curable adhesive sheet showing an example of the configuration of one embodiment of the present invention. Specific configurations of curable adhesive sheets of one embodiment of the present invention include, for example, a substrate-attached curable adhesive sheet 1 having an adhesive layer 10 on one surface side of a substrate 20, as shown in FIG. 1( a). Alternatively, a substrate-attached curable adhesive sheet 2 having a first adhesive layer 11 and a second adhesive layer 12 on both surface sides of the substrate 20, as shown in FIG. 1( b), may be used. Note that in one embodiment of the present invention, the substrate 20 and the adhesive layer 10 may be directly laminated together, as in the curable adhesive sheet 1 shown in FIG. 1( a), or another layer may be present between the substrate 20 and the adhesive layer 10. This also applies to the substrate 20 and the first adhesive layer 11, and the substrate 20 and the second adhesive layer 12 in the curable adhesive sheet 2 shown in FIG. 1( b).

[0106] Furthermore, as shown in Figure 1(c), a curable adhesive sheet according to one embodiment of the present invention may have a configuration similar to that of curable adhesive sheet 1, in which a release sheet 30 is further laminated on the adhesive surface of adhesive layer 10, resulting in a curable adhesive sheet 3 with a substrate. Similarly, the configuration of curable adhesive sheet 2 shown in Figure 1(b) may also be a curable adhesive sheet in which a release sheet is laminated on the adhesive surface of each of first adhesive layer 11 and second adhesive layer 12. In this configuration, the two release sheets are preferably made of materials adjusted to have different peel strengths.

[0107] 1(d), the curable adhesive sheet of one embodiment of the present invention may have a configuration similar to that of a substrate-free curable adhesive sheet 4, in which the adhesive layer 10 is sandwiched between a first release sheet 31 and a second release sheet 32 ​​without using a substrate. The materials of the first release sheet 31 and the second release sheet 32 ​​of this curable adhesive sheet 4 may be the same or different, but are preferably adjusted so that the release strengths of the release sheets 31 and 32 are different. Other examples include curable adhesive sheets having a configuration in which an adhesive layer is provided on one side of a release-treated surface and the sheet is wound into a roll.

[0108] The adhesive layer, substrate, and release sheet constituting the curable adhesive sheet of one embodiment of the present invention are described in detail below. Note that, in this specification, the thicknesses of the adhesive layer, substrate, and release sheet are values ​​measured in accordance with JIS K7130 (1999), and can be measured using a known thickness meter.

[0109] <Adhesive Layer> The adhesive layer of the curable adhesive sheet of one embodiment of the present invention is a layer formed from the curable adhesive composition of one embodiment of the present invention described above. In the curable adhesive sheet of one embodiment of the present invention, the thickness of the adhesive layer is, from the viewpoint of forming a cured product having a thickness sufficient to protect a circuit board, preferably 1.0 μm or more, more preferably 3.0 μm or more, more preferably 5.0 μm or more, more preferably 7.0 μm or more, even more preferably 10 μm or more, even more preferably 12 μm or more, even more preferably 15 μm or more, still more preferably 17 μm or more, particularly preferably 20 μm or more, and is preferably 60 μm or less, more preferably 55 μm or less, more preferably 50 μm or less, even more preferably 45 μm or less, still more preferably 40 μm or less, particularly preferably 35 μm or less.

[0110] The adhesive layer of the curable adhesive sheet of one embodiment of the present invention is curable and can therefore be formed into a cured product. The curing method of the adhesive layer can be adjusted depending on the type of reactive curing agent such as component (D), and may be a thermal curing method or a photocuring method, and can be selected appropriately depending on the application. For example, when the curable adhesive sheet of one embodiment of the present invention is used as a coverlay sheet to form a cured product for protecting a circuit board, a thermal curing method is preferred.

[0111] <Substrate> The curable adhesive sheet of one embodiment of the present invention may have a substrate. The substrate of the curable adhesive sheet of one embodiment of the present invention is not particularly limited and may be appropriately selected depending on the application, but a resin film is preferred. Examples of resin components constituting the resin film include polyimide, polyamide, polyamideimide, polyphenylene ether, polyether ketone, polyether ether ketone, polyolefin, polyester, polycarbonate, polysulfone, polyether sulfone, polyphenylene sulfide, polyarylate, acrylic resin, cycloolefin polymer, aromatic polymer, polyurethane polymer, and liquid crystal polymer film.

[0112] The thickness of the substrate is not particularly limited and may be appropriately selected depending on the application, but is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 12 μm or more, still more preferably 15 μm or more, and particularly preferably 17 μm or more, and is preferably 500 μm or less, more preferably 400 μm or less, even more preferably 300 μm or less, still more preferably 200 μm or less, and particularly preferably 150 μm or less.

[0113] <Release Sheet> The curable adhesive sheet of one embodiment of the present invention may have a release sheet. The release sheet functions as a protective film for the adhesive layer until the curable adhesive sheet is used. Furthermore, when the curable adhesive sheet is a sheet without a substrate, the release sheet functions as a support in the manufacturing process of the curable adhesive sheet. Note that when the curable adhesive sheet of one embodiment of the present invention is used, the release sheet is usually peeled off and removed.

[0114] The release sheet of one embodiment of the present invention includes a release layer formed by applying a release agent to the surface of a release film substrate. Examples of release film substrates include paper substrates such as glassine paper, coated paper, and fine paper; laminated paper obtained by laminating a thermoplastic resin such as polyethylene to these paper substrates; and plastic films such as polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, polypropylene resin, and polyethylene resin. Examples of release agents include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins, long-chain alkyl resins, alkyd resins, and fluorine-containing resins. The thickness of the release sheet is not particularly limited, but is typically 20 to 250 μm.

[0115] [Method for producing a curable adhesive sheet] The method for producing the curable adhesive sheet of one embodiment of the present invention is not particularly limited, and the sheet can be produced by applying the curable adhesive composition of one embodiment of the present invention to the substrate or release sheet described above by a known application method. From the viewpoint of improving the coatability to the substrate or release sheet, it is preferable to dilute the curable adhesive composition of one embodiment of the present invention with a dilution solvent to form a solution.

[0116] Examples of methods for applying the curable adhesive composition to a substrate or a release sheet include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[0117] After applying the curable adhesive composition to a substrate or a release sheet to form a coating film, it is preferable to carry out a drying treatment. Examples of drying methods include hot air drying, heat roll drying, and infrared irradiation. The formed coating film is preferably dried by heating at a temperature of 80°C to 150°C for 30 seconds to 5 minutes (preferably 40 seconds to 3 minutes, and more preferably 45 seconds to 2 minutes). After this drying process, an adhesive layer can be formed on the substrate or release sheet.

[0118] In addition, when the curable adhesive composition used for forming the adhesive layer contains a crosslinking agent (E), in order to complete the crosslinking reaction, it is preferable to go through a seasoning process of holding for a certain period (for example, about 1 day to 14 days).

[0119] Specific manufacturing methods according to the configuration of the curable adhesive sheet of one aspect of the present invention include the following methods. As a manufacturing method of the curable adhesive sheet 1 as shown in Fig. 1(a), a method having a step of directly applying the above-mentioned curable adhesive composition on one surface of the base material 20 to form the adhesive layer 10 can be mentioned. Further, a method may be adopted which includes a step of directly applying the above-mentioned curable adhesive composition on the release-treated surface of the release sheet to form the adhesive layer 10, a step of bonding the base material 20 to the surface on which the adhesive layer 10 is exposed, and a step of removing the release sheet.

[0120] As a manufacturing method of the curable adhesive sheet 2 as shown in Fig. 1(b), a method having a step of directly applying the above-mentioned curable adhesive composition on both surfaces of the base material 20 to form the first adhesive layer 11 and the second adhesive layer 12 can be mentioned. Further, a method may be adopted which includes a step of preparing two sheets each having an adhesive layer formed by directly applying the above-mentioned curable adhesive composition on the release-treated surface of the release sheet, a step of bonding each adhesive layer to both surfaces of the base material 20, and a step of removing the release sheet.

[0121] As a manufacturing method of the curable adhesive sheet 3 as shown in Fig. 1(c), a method having a step of laminating the release sheet 30 on the surface of the adhesive layer 10 of the curable adhesive sheet 3 manufactured as described above can be mentioned. Further, a method may be adopted which includes a step of directly applying the above-mentioned curable adhesive composition on the release-treated surface of the release sheet 30 to form the adhesive layer 10, and a step of bonding the adhesive layer 10 and the base material 20.

[0122] As a method for manufacturing the curable adhesive sheet 4 as shown in Fig. 1(d), there is a method having a step of directly applying the above-described curable adhesive composition onto the release surface of the release sheet 31 to form the adhesive layer 10, and a step of laminating another release sheet 32 onto the exposed surface of this adhesive layer 10. As described above, it is preferable to adjust the release sheets 31 and 32 so that their release forces are different.

[0123] 〔Properties of the curable adhesive sheet〕The adhesive layer of the curable adhesive sheet according to one aspect of the present invention can become a cured product by curing. The formed cured product is excellent in adhesive strength and low dielectric properties.

[0124] After laminating the adhesive layer of the curable adhesive sheet according to one aspect of the present invention onto a copper foil and then curing the adhesive layer, the adhesive strength of the cured product with respect to the copper foil (hereinafter, also simply referred to as "adhesive strength of the cured product") is preferably 0.75 kgf / cm or more, more preferably 0.78 kgf / cm or more, more preferably 0.80 kgf / cm or more, still more preferably 0.85 kgf / cm or more, still more preferably 0.88 kgf / cm or more, even more preferably 0.90 kgf / cm or more, particularly preferably 0.92 kgf / cm or more, and further, it may be 0.95 kgf / cm or more or 0.97 kgf / cm or more. In this specification, the adhesive strength of the cured product means a value measured based on the method described in the examples below.

[0125] The relative dielectric constant of the cured product obtained by curing the adhesive layer of the curable adhesive sheet according to one aspect of the present invention at 23°C and 1 GHz is preferably less than 2.36, more preferably 2.35 or less, still more preferably 2.34 or less, even more preferably less than 2.33, and particularly preferably 2.32 or less. There is no particular lower limit for the relative dielectric constant of the cured product at 23°C and 1 GHz, and for example, it may be 1.50 or more, 1.60 or more, 1.70 or more, 1.80 or more, 1.90 or more, or 2.00 or more.

[0126] The dielectric loss tangent at 23°C and 1 GHz of the cured product obtained by curing the adhesive layer of the curable adhesive sheet of one embodiment of the present invention is preferably less than 0.005, more preferably 0.004 or less, more preferably 0.003 or less, even more preferably less than 0.001, still more preferably 0.0009 or less, and particularly preferably 0.0008 or less. There is no particular lower limit to the dielectric loss tangent at 23°C and 1 GHz of the cured product, and it may be, for example, 0.00001 or more, 0.00003 or more, 0.00005 or more, 0.00007 or more, or 0.0001 or more.

[0127] In this specification, the relative dielectric constant and dielectric loss tangent of the cured product refer to values ​​measured based on the method described in the examples below.

[0128] Furthermore, in the curable adhesive sheet of one embodiment of the present invention, after the adhesive layer is applied to an adherend such as a circuit board, during the adhesion process of curing the adhesive layer to adhere to the adherend, the adhesive component of the adhesive layer can be suppressed from seeping out from the edge of the sheet, thereby preventing contamination of the adherend. For the curable adhesive sheet of one embodiment of the present invention, the seepage distance of the adhesive component measured according to the method described in the Examples below is preferably 200 μm or less, more preferably 150 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, even more preferably 30 μm or less, still more preferably 25 μm or less, and particularly preferably 20 μm or less.

[0129] [Method of using a curable adhesive sheet, and method of manufacturing a circuit board with a cured product] The cured product obtained by curing the adhesive layer of a curable adhesive sheet of one embodiment of the present invention has high adhesive strength and also has excellent low dielectric properties in the high frequency range. Furthermore, during the adhesion process from the adhesive layer to the cured product, oozing of adhesive components is effectively suppressed, preventing contamination of the adherend. Therefore, the curable adhesive sheet of one embodiment of the present invention is preferably used when forming components in devices that require low dielectric properties, and is particularly preferably used as a coverlay sheet to protect circuit boards. Examples of circuit boards include flexible printed circuit boards (FPCs).

[0130] Furthermore, because the adhesive layer of the curable adhesive sheet of one embodiment of the present invention has the above-mentioned properties, the present invention can also provide the following [1] and [2]. [1] A method for using a curable adhesive sheet, comprising an adhesion step of laminating the adhesive layer of the curable adhesive sheet of one embodiment of the present invention to a circuit board, curing the adhesive layer to form a cured product, and adhering the cured product to the circuit board. [2] A method for producing a circuit board with a cured product, comprising an adhesion step of laminating the adhesive layer of the curable adhesive sheet of one embodiment of the present invention to a circuit board, curing the adhesive layer to form a cured product, and adhering the cured product to the circuit board.

[0131] The curing method in [1] and [2] above may be a thermal curing method or a photocuring method, and is selected depending on the type of components contained in the curable adhesive composition that forms the adhesive layer. However, a thermal curing method is preferred. The heating temperature during thermal curing is preferably 80 to 200°C, more preferably 90 to 190°C, and even more preferably 100 to 180°C, and the heating time is preferably 10 minutes to 12 hours, more preferably 30 minutes to 6 hours, and even more preferably 40 minutes to 3 hours. Furthermore, it is preferable to perform a heat press when performing the heat press. The pressure during the heat press is preferably 0.1 to 10 MPa, more preferably 0.5 to 8.0 MPa, and even more preferably 1.0 to 5.0 MPa.

[0132] When the adhesive layer is cured by a photocuring method, the adhesive layer can be cured by irradiating it with energy rays such as ultraviolet rays.

[0133] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples. The physical properties were measured by the methods shown below.

[0134] [Number average molecular weight (Mn)] Measurement was performed using a gel permeation chromatograph (manufactured by Tosoh Corporation, product name "HLC-8320 GPC") under the following conditions, and the value measured in terms of standard polystyrene was used. (Measurement conditions) Column: "TSK gel guard column super H-H", "TSK gel super HM-H", "TSK gel super HM-H", and "TSK gel super H2000" connected in sequence (all manufactured by Tosoh Corporation) Column temperature: 40°C Developing solvent: tetrahydrofuran Flow rate: 1.0 mL / min

[0135] Examples 1 to 3, Comparative Example 1 (1) Preparation of Curable Adhesive Compositions The components shown in Table 1 were blended in the amounts (active ingredient ratios) shown in Table 1 and dissolved in toluene to prepare curable adhesive compositions so as to achieve the desired active ingredient concentrations. Details of each component used in preparing the curable adhesive compositions are as follows. <Component (A): Binder Resin> - "Modified Polyolefin": A solution containing a maleic anhydride-modified α-olefin polymer having an Mn of 47,000 (corresponding to the above-mentioned component (A1), solid at 25°C) (manufactured by Mitsui Chemicals, Inc., product name "UNISTOR H-200"). <Component (B): Polyphenylene Ether Resin> - "Polyphenylene Ether Resin (1)": A solution containing a vinylbenzyl-modified polyphenylene ether having an Mn of 2,200 (a compound represented by the above-mentioned general formula (b-4), solid at 25°C) (manufactured by Mitsubishi Gas Chemical Company, Inc., product name "OPE-2St 2200"). "Polyphenylene ether resin (2)": a solution containing a vinylbenzyl-modified polyphenylene ether having Mn=4,000 (a compound represented by the general formula (b-4) above, solid at 25°C). <Component (B'): Polyphenylene ether resin> "Polyphenylene ether resin (3)": a solution containing a vinylbenzyl-modified polyphenylene ether having Mn=1,200 (a compound represented by the general formula (b-4) above, solid at 25°C) (manufactured by Mitsubishi Gas Chemical Company, Inc., product name "OPE-2St 1200"). <Component (C): Polyfunctional compound> "Polyfunctional compound (1)": a solution containing a vinylbenzyl-modified polyphenylene ether having Mn=1,200 (a compound represented by the general formula (b-4) above, solid at 25°C). ａis an alkyl group having 8 to 15 carbon atoms. Product name: "L-DAIC", manufactured by Shikoku Chemicals Corporation, molecular weight: 377.27, liquid at 25°C. "Polyfunctional compound (2)": a compound represented by the general formula (c-1) above, wherein R １１ ~R １３ is an allyl group. Manufactured by Mitsubishi Chemical Corporation, product name "TAIC (registered trademark)", molecular weight = 249.27, liquid at 25°C. <Component (D): Cationic polymerization initiator> - "Thermal cationic polymerization initiator": thermal cationic polymerization initiator (manufactured by Sanshin Chemical Industry Co., Ltd., product name "Sanaid SI-B3"), solid at 25°C. <Component (E): Crosslinking agent> - "Isocyanate crosslinking agent": 1,3,5-tris(5-isocyanatopentyl)-1,3,5-triazine-2,4,6-trione (manufactured by Mitsui Chemicals, Inc., product name "Stabio D-370N"), molecular weight = 462, liquid at 25°C. <Component (F): Silane Coupling Agent> - "Silane coupling agent": 8-glycidoxyoctyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd., product name "KBM4803"), liquid at 25°C.

[0136] (2) Preparation of Curable Adhesive Sheet The curable adhesive composition prepared in (1) above was applied to the release-treated surface of a first release sheet (manufactured by Lintec Corporation, product name "SP-PET752150") to form a coating film, and the coating film was dried at 100°C for 2 minutes to form an adhesive layer 25 μm thick. Furthermore, the exposed surface of the formed adhesive layer was bonded to the release-treated surface of a second release sheet (manufactured by Lintec Corporation, product name "SP-PET381130") to obtain a curable adhesive sheet having the same configuration as the curable adhesive sheet 4 shown in Figure 1(d).

[0137]

[0138] The curable adhesive sheet prepared in (2) above was used to measure the following physical properties. The results are shown in Table 2.

[0139] (1) Measurement of adhesive strength of cured product One release sheet was peeled from the curable adhesive sheet prepared by the procedures of the Examples and Comparative Examples, and the exposed surface of the adhesive layer was superimposed on the shiny side of copper foil (manufactured by Mitsui Mining & Smelting Co., Ltd., product name "Electrolytic Copper Foil", thickness: 35 μm), and the resulting sheet was laminated at 100 ° C. using a thermal laminator. The sheet was cut into a size of 10 mm length x 100 mm width, and copper foil was laminated on the adhesive layer to obtain a copper foil-attached curable adhesive sheet. The other release sheet was then peeled from the copper foil-attached curable adhesive sheet, and the exposed surface of the adhesive layer was laminated to a 25 μm-thick modified polyimide film (manufactured by PI Advanced Materials, FG grade) using a thermal laminator at 100 ° C. to obtain a laminate consisting of copper foil / adhesive layer / modified polyimide film laminated in this order. Next, this laminate was heat-pressed for 1 hour under conditions of 160°C and 5 MPa to thermally cure the adhesive layer and obtain a cured product as a measurement sample. This measurement sample was tested using a precision universal testing machine (manufactured by Shimadzu Corporation, product name "Autograph AG-IS") to peel the copper foil and cured product laminate of the measurement sample from the modified polyimide film under conditions of a peel angle of 90° and a peel rate of 50 mm / min, and the value measured when this was taken as the "adhesive strength of the cured product."

[0140] (2) Measurement of the dielectric constant and dielectric loss tangent of the cured product. Multiple curable adhesive sheets prepared according to the procedures of the Examples or Comparative Examples were prepared, and the release sheets were removed as appropriate. Multiple adhesive layers were stacked to form an adhesive layer approximately 1 mm thick, resulting in a laminate having a first release sheet, an approximately 1 mm thick adhesive layer, and a second release sheet in this order. This laminate was then heated at 160°C for 1 hour to cure the approximately 1 mm thick adhesive layer. The two release sheets were then removed to obtain a cured product, which served as a measurement sample. The dielectric constant and dielectric loss tangent of the cured product were measured at 23°C and 1 GHz using an RF impedance material analyzer (Keysight Technologies, product name "E4991A"). In this specification, 1 GHz is used as an example of a high-frequency range.

[0141] (3) Measurement of Adhesive Layer Oozing Distance One release sheet was peeled from a curable adhesive sheet prepared by the procedure of an Example or Comparative Example, and the exposed surface of the adhesive layer was bonded to a modified polyimide film (manufactured by PI Advanced Materials, FG grade, thickness 25 μm) using a thermal laminator at 100 ° C., and then cut to a size of 100 mm length x 100 mm width to obtain a curable adhesive sheet having the same configuration as the curable adhesive sheet 3 shown in Figure 1 (c) , in which the release sheet / adhesive layer / modified polyimide film were laminated in this order. Next, the other release sheet was also peeled from this laminate, and the exposed surface of the adhesive layer was placed on the shiny side of a copper foil (manufactured by Mitsui Mining & Smelting Co., Ltd., product name "Electrolytic Copper Foil", thickness: 35 μm) that was wider than the exposed surface, and the two were laminated using a thermal laminator at a temperature of 100 ° C. to obtain a test sample in which the copper foil / adhesive layer / modified polyimide film were laminated in this order. This test sample was subjected to a 20-minute heat press treatment under conditions of 171°C and 1.38 MPa, after which the test sample was cooled to room temperature, and the exudation distance of the adhesive component was measured as follows. (Measurement of Exudation Distance of Adhesive Component) Figure 2 is a schematic diagram showing the state of the test sample after heat pressing to explain the procedure for evaluating the exudation of adhesive components, where (a) is a schematic plan view of the test sample when viewed from above, and (b) is a schematic cross-sectional view of the test sample when cut vertically along line A-A' in (a). In the prepared test sample, the area of ​​the copper foil 100 is larger than the areas of the adhesive layer 10 and the polyimide film substrate 20. Therefore, if the adhesive component exudes, it will spread beyond the outer edge of the polyimide film substrate 20 as shown in Figure 2(a) and will adhere to the copper foil 100 that is not bonded to the adhesive layer 10. Here, the test sample after heat pressing was viewed in plan using a digital microscope to observe the adhesive component that had seeped out from the outer edge of the polyimide film substrate 20, and the distance from the outer edge to the point where the adhesive component had seeped out the furthest (the length indicated by X in Figure 2(a)) was measured as the "adhesive component seepage distance." It can be said that the shorter this "adhesive component seepage distance," the greater the effect of suppressing the seepage of the adhesive component.

[0142]

[0143] As can be seen from Table 2, the cured products formed from the curable adhesive compositions prepared in Examples 1 to 3 had high adhesive strength and low values ​​of dielectric constant and dielectric dissipation factor, resulting in excellent low dielectric properties. It was also confirmed that the adhesive layers formed from the curable adhesive compositions prepared in Examples 1 to 3 were highly effective in suppressing the bleeding of adhesive components. On the other hand, the cured product formed from the curable adhesive composition prepared in Comparative Example 1 had inferior adhesive strength compared to Examples 1 to 3.

[0144] 1, 2, 3, 4 Curable adhesive sheet 10, 11, 12 Adhesive layer 20 Substrate 30, 31, 32 Release sheet 100 Copper foil

Claims

1. A binder resin (A) having a reactive functional group, A polyphenylene ether resin (B) having a vinyl group and a number average molecular weight of 1,500 or more and less than 5,000, and A polyfunctional compound (C) having two or more unsaturated hydrocarbon groups having a double bond at the terminal A curable adhesive composition containing the same.

2. The curable adhesive composition according to claim 1, further containing a cationic polymerization initiator (D).

3. The curable adhesive composition according to claim 1 or 2, wherein the content of the component (B) is 99.0 parts by mass or less with respect to 100 parts by mass of the total amount of the component (A).

4. The curable adhesive composition according to claim 1 or 2, wherein the content of the component (A) is more than 20% by mass with respect to the total amount of the active ingredients of the curable adhesive composition.

5. The curable adhesive composition according to claim 1 or 2, further containing a crosslinking agent (E) capable of reacting with the reactive functional group of the component (A).

6. The curable adhesive composition according to claim 1 or 2, wherein the total content of the component (A), the component (B) and the component (C) is 50% by mass or more with respect to the total amount of the active ingredients of the curable adhesive composition.

7. The curable adhesive composition according to claim 1 or 2, wherein the total content of the component (B) and the component (C) is less than 100 parts by mass with respect to 100 parts by mass of the total amount of the component (A).

8. The curable adhesive composition according to claim 1 or 2, wherein the component (C) is a polyfunctional compound having a heterocyclic structure.

9. The curable adhesive composition according to claim 1 or 2, wherein the component (C) is a polyfunctional compound having two or more of the unsaturated hydrocarbon groups and further containing a saturated hydrocarbon group.

10. The curable adhesive composition according to claim 1 or 2, wherein the component (C) contains a polyfunctional compound (C1) having two of the unsaturated hydrocarbon groups.

11. The curable adhesive composition according to claim 10, wherein the component (C1) is a polyfunctional compound having two of the unsaturated hydrocarbon groups and one saturated hydrocarbon group.

12. The curable adhesive composition according to claim 1 or 2, wherein the component (C) contains a compound (C11) represented by the following general formula (c-11). 【Chemical 1】 (In the above formula, R ａ represents a saturated hydrocarbon group.)

13. The curable adhesive composition according to claim 1 or 2, wherein the component (A) contains an olefin resin (A1) having a reactive functional group.

14. The curable adhesive composition according to claim 1 or 2, wherein the content of the inorganic filler is 0 to 30% by mass based on the total amount of the active ingredients of the curable adhesive composition.

15. A curable adhesive sheet having an adhesive layer formed from the curable adhesive composition according to claim 1 or 2.

16. The curable adhesive sheet according to claim 15, wherein the adhesive layer can be cured by heating to obtain a cured product.

17. The curable adhesive sheet according to claim 15, which is used as a coverlay sheet.

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