Laminate, adhesive composition, and circuit board material

Abstract

To provide an adhesive composition that enables formation of an adhesive layer exhibiting excellent heat resistance, a low dielectric loss tangent, and a high retention rate of adhesion strength before and after a damp-heat durability test, and to provide a laminate and a circuit board material produced using the adhesive composition.SOLUTION: A laminate having an adhesive layer on at least one surface of a substrate or a conductor layer, the adhesive layer being a cured product of an adhesive composition containing a polyester resin (A), a polyepoxy compound (B), and a filler (C), and the dielectric loss tangent (Df) of the adhesive layer at 10 GHz (23°C, 50% RH environment) being 0.005 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminate having an adhesive layer made of a cured product of an adhesive composition containing a polyester resin. More specifically, the present invention relates to a laminate having an adhesive layer that has excellent heat resistance, a low dielectric loss tangent, and a high retention rate of adhesive strength before and after a wet heat durability test. The present invention also relates to a circuit board material having this laminate. The present invention also relates to an adhesive composition suitable for the adhesive layer of this laminate. [Background technology]

[0002] Polyester resins are excellent in heat resistance, chemical resistance, durability, and mechanical strength, and are therefore used in a wide range of fields, including films, PET bottles, fibers, toner, electrical components, adhesives, and pressure-sensitive adhesives. Polyester-based resins are known to have high polarity due to their polymer structure, and therefore exhibit excellent adhesive properties to polar polymers such as polyester, polyvinyl chloride, polyimide, and epoxy resin, as well as to metal materials such as copper and aluminum. Utilizing this property, polyester-based resins are being considered for use as adhesives for producing laminates of metal and plastic.

[0003] Patent Document 1 proposes a thermosetting adhesive sheet that exhibits excellent dimensional stability during curing and excellent post-curing adhesion, heat resistance, flexibility, electrical insulation, low dielectric constant, and low dielectric loss tangent. This thermosetting adhesive sheet is formed from a thermosetting composition containing a resin (e.g., a polyester resin) having a total amount of reactive functional groups capable of reacting with at least one of an organometallic compound and an epoxy group-containing compound and functional groups having a heteroatom other than halogen of 0.01 mmol / g or more and 9 mmol / g or less, an organometallic compound, and a trifunctional or higher epoxy group-containing compound.

[0004] Patent Document 2 proposes a copolymerized polyester that has excellent resistance to moist heat and cationic acids, compatibility with epoxy resins, and adhesive properties, and an adhesive composition containing the same. This copolymerized polyester is composed of an aromatic dicarboxylic acid component, a dimer diol, a first glycol, a second glycol or an oxyacid, and an alkylene glycol having 2 to 10 carbon atoms.

[0005] Patent Document 3 proposes an adhesive composition that has excellent long-term durability in a humid and hot environment and also has high adhesive properties, and that contains a polyester resin (A1) that satisfies the requirements of an ester bond concentration of 7 mmol / g or less, an acid value of 3 mgKOH / g or more, and a glass transition temperature (Tg) of -5°C or more. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2017-031301 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-183365 [Patent Document 3] International Publication No. 2021 / 079670 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, in the field of electronic materials such as flexible copper-clad laminates and flexible printed circuit boards, the physical properties required for the adhesive layers used therein include excellent adhesion, heat resistance, and durability against humidity and heat, and in addition, with the increasing frequency of transmission signals, there is a strong demand for low dielectric properties such as even lower dielectric constant and lower dielectric dissipation factor, especially lower dielectric dissipation factor. However, when resins are designed with the aim of improving heat resistance or durability against heat and humidity, the dielectric loss tangent tends to increase, making it difficult to achieve both of these properties at a high level.

[0008] For example, the technology disclosed in Patent Document 1 uses a large amount of polycarboxylic acid or polyhydric alcohol having a long-chain alkyl group in order to reduce the dielectric constant, dielectric loss tangent, and water absorption rate, which causes problems such as reduced adhesiveness. Furthermore, Patent Document 1 does not take into consideration long-term durability in a humid and hot environment, and further improvements are required.

[0009] When a copper-clad laminate or the like is produced using the adhesive composition disclosed in Patent Document 2, it is expected that the long-term durability in a humid and hot environment will be relatively excellent. However, the copolymer polyester in question contains an ether bond-containing glycol such as polypropylene glycol as a copolymerization component, or the copolymer does not have an acid value that serves as a reaction site with an epoxy resin. For this reason, the copolymer polyester in question has problems such as poor adhesiveness and heat resistance.

[0010] The adhesive composition disclosed in Patent Document 3 solves these problems, but further improvement in low dielectric tangent is desired.

[0011] The present invention provides an adhesive composition that can form an adhesive layer that has excellent heat resistance and a low dielectric tangent, and that exhibits a high rate of adhesive strength retention before and after a wet heat durability test, as well as a laminate and a circuit board material that use this adhesive composition. [Means for solving the problem]

[0012] The present inventors have discovered that by controlling the dielectric loss tangent (Df) of a cured product of an adhesive composition containing a polyester resin (A), a polyepoxy compound (B), and a filler (C), it is possible to obtain a laminate that has excellent heat resistance, contributes to low transmission loss, and exhibits a high retention rate of adhesive strength before and after a moist heat durability test.

[0013] The present invention provides the following.

[0014] [1] A laminate having an adhesive layer on at least one surface of a substrate or a conductor layer, the adhesive layer is a cured product of an adhesive composition containing a polyester resin (A), a polyepoxy compound (B), and a filler (C), The laminate has a dielectric loss tangent (Df) of the adhesive layer at 10 GHz (under an environment of a temperature of 23°C and a relative humidity of 50% RH) of 0.005 or less.

[0015] [2] The laminate according to [1], wherein the filler (C) contains a fluorine-containing polymer powder (C1) and / or a clay mineral (C2).

[0016] [3] The laminate according to [1] or [2], wherein the content of the polyepoxy compound (B) in the adhesive composition is an amount such that the epoxy equivalent of the polyepoxy compound (B) relative to the carboxyl groups of the polyester resin (A) is 0.8 or more but less than 2.

[0017] [4] The laminate according to any one of [1] to [3], wherein the polyester resin (A) has an acid value of 3 mgKOH / g or more and a glass transition temperature of −5° C. or more.

[0018] [5] The laminate according to any one of [1] to [4], wherein the polyester resin (A) contains a structural unit derived from a polycarboxylic acid and a structural unit derived from a polyhydric alcohol.

[0019] [6] The laminate according to [5], wherein the polyester resin (A) contains, as the structural unit derived from a polycarboxylic acid, a structural unit derived from an aromatic polycarboxylic acid.

[0020] [7] The laminate according to any one of [1] to [6], wherein the content of the filler (C) in the adhesive composition is 1 to 100 parts by weight per 100 parts by weight of the polyester resin (A).

[0021] [8] The laminate according to any one of [1] to [7], wherein the substrate is at least one selected from the group consisting of polyimide film, polyether ether ketone film, polyphenylene sulfide film, aramid film, polyethylene naphthalate film, liquid crystal polymer film, polyethylene terephthalate film, polyethylene film, polypropylene film, silicone release-treated paper, polyolefin resin-coated paper, polymethylpentene film, and fluorine-based resin film.

[0022] [9] The laminate according to any one of [1] to [8], further comprising a conductor laminated thereon.

[0023]

[10] A circuit board material having the laminate according to any one of [1] to [9].

[0024]

[11] An adhesive composition containing a polyester resin (A), a polyepoxy compound (B), and a filler (C), An adhesive composition, wherein the dielectric loss tangent (Df) at 10 GHz (under an environment of a temperature of 23°C and a relative humidity of 50%) of the cured product of the adhesive composition is 0.005 or less.

[0025]

[12] The adhesive composition according to

[11] , wherein the filler (C) contains a fluorine-containing polymer powder (C1) and / or a clay mineral (C2).

[0026]

[13] The adhesive composition according to

[11] or

[12] , wherein the content of the polyepoxy compound (B) is such that the epoxy equivalent of the polyepoxy compound (B) relative to the carboxyl groups of the polyester resin (A) is 0.8 or more and less than 2.

[0027]

[14] The adhesive composition according to any one of

[11] to

[13] , wherein the polyester resin (A) has an acid value of 3 mgKOH / g or more and a glass transition temperature of -5°C or more.

[0028]

[15] The adhesive composition according to

[14] , wherein the polyester resin (A) has an acid value of 5 mgKOH / g or more and a glass transition temperature of -5°C or more.

[0029]

[16] The adhesive composition according to any one of

[11] to

[15] , wherein the polyester resin (A) contains a structural unit derived from a polycarboxylic acid and a structural unit derived from a polyhydric alcohol.

[0030]

[17] The adhesive composition according to

[16] , wherein the polyester resin (A) contains a structural unit derived from an aromatic polycarboxylic acid as the structural unit derived from a polycarboxylic acid.

[0031]

[18] The adhesive composition according to any one of

[11] to

[17] , wherein the content of the filler (C) is 1 to 100 parts by weight per 100 parts by weight of the polyester resin (A). [Effects of the Invention]

[0032] The adhesive layer of the laminate of the present invention has excellent heat resistance, contributes to low transmission loss, and maintains a high rate of adhesive strength before and after a wet heat durability test. Furthermore, the adhesive composition of the present invention can form an adhesive layer that is excellent in heat resistance, contributes to low transmission loss, and maintains a high rate of adhesive strength before and after a wet heat durability test.

[0033] The laminate of the present invention is particularly suitable as a laminate obtained by bonding and integrating a metal and a plastic with an adhesive layer, for example, a flexible laminate such as a flexible copper-clad laminate or a flexible printed circuit board, a coverlay, a bonding sheet, etc., and is particularly suitable for use as a circuit board material for a flexible printed wiring board, etc. Such a circuit board material is highly reliable and has excellent long-term durability in a humid and hot environment. DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention will be described in detail below, with the following description showing an example of a preferred embodiment of the present invention.

[0035] In the present invention, the term "class" added after the name of a compound is a concept that encompasses not only the compound but also derivatives of the compound. For example, the term "carboxylic acids" includes not only carboxylic acids but also carboxylic acid derivatives such as carboxylic acid salts, carboxylic acid anhydrides, carboxylic acid halides, and carboxylic acid esters.

[0036] [Adhesive composition] The adhesive composition of the present invention contains a polyester resin (A), an epoxy compound (B), and a filler (C), and the cured product thereof exhibits a specific dielectric dissipation factor (Df).

[0037] [Polyester resin (A)] The polyester resin (A) preferably contains a structural unit derived from a polycarboxylic acid and a structural unit derived from a polyhydric alcohol in the molecule, and particularly preferably is obtained by ester bonding a polycarboxylic acid and a polyhydric alcohol.

[0038] <Polycarboxylic acids> Examples of the polycarboxylic acids in the polycarboxylic acids include aromatic polycarboxylic acids described below; alicyclic polycarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,2-cyclohexanedicarboxylic acid and their acid anhydrides; and aliphatic polycarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, and dodecanedioic acid. One or more types of polycarboxylic acids can be used.

[0039] The polycarboxylic acids preferably contain aromatic polycarboxylic acids. Examples of aromatic polycarboxylic acids include monocyclic aromatic polycarboxylic acids such as terephthalic acid, isophthalic acid, dimethyl terephthalate, dimethyl isophthalate, and orthophthalic acid; polycyclic aromatic polycarboxylic acids such as biphenyldicarboxylic acid, naphthalenedicarboxylic acid, and dimethyl naphthalenedicarboxylate; and among polycyclic aromatic polycarboxylic acids, condensed polycyclic aromatic polycarboxylic acids such as naphthalenedicarboxylic acid and dimethyl naphthalenedicarboxylate, and derivatives thereof (aromatic dicarboxylic acids). Other examples include aromatic oxycarboxylic acids such as p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid.

[0040] Furthermore, aromatic polycarboxylic acids having three or more functional groups that are introduced into the polyester resin (A) for the purpose of imparting a branched skeleton or an acid value are also included in the aromatic polycarboxylic acids. Examples of trifunctional or higher functional aromatic carboxylic acids include trimellitic acid, trimesic acid, ethylene glycol bis(anhydrotrimellitate), glycerol tris(anhydrotrimellitate), trimellitic anhydride, pyromellitic dianhydride, oxydiphthalic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride, and 2,2'-bis[(dicarboxyphenoxy)phenyl]propane dianhydride.

[0041] Among the polycarboxylic acids, polycyclic aromatic polycarboxylic acids are preferred from the viewpoint of dielectric properties, and condensed polycyclic aromatic polycarboxylic acids are particularly preferred. Among the condensed polycyclic aromatic polycarboxylic acids, dimethyl naphthalenedicarboxylate is particularly preferred. Among the monocyclic aromatic polycarboxylic acids, terephthalic acid, dimethyl terephthalate, isophthalic acid, and dimethyl isophthalate are preferred. In order to reduce the crystallinity and ensure stability after dissolution in a solvent, it is preferable to use a plurality of polycarboxylic acids.

[0042] The content of aromatic polycarboxylic acids relative to the total polycarboxylic acids is preferably 25 mol% or more, more preferably 40 mol% or more, even more preferably 70 mol% or more, and particularly preferably 90 mol% or more. The aromatic polycarboxylic acids may account for 100 mol%. If the content of aromatic carboxylic acids is too low, the long-term durability in a humid and hot environment tends to be insufficient and the low dielectric tangent tends to be inferior.

[0043] The content (molar ratio) of aromatic polycarboxylic acids relative to the total polycarboxylic acids can be calculated from the following formula. Aromatic polycarboxylic acid content (mol%) = (aromatic polycarboxylic acids (moles) / polycarboxylic acids (moles)) × 100

[0044] The content of the structural units derived from aromatic polycarboxylic acids in the entire polyester resin (A) is preferably 15 to 70% by weight, more preferably 20 to 65% by weight, even more preferably 25 to 60% by weight, and particularly preferably 30 to 55% by weight. If the content of the structural units derived from aromatic polycarboxylic acids is too low, the initial adhesion tends to be insufficient and the dielectric loss tangent tends to be poor. If the content of the structural units derived from aromatic polycarboxylic acids is too high, the initial adhesion tends to be insufficient.

[0045] The polycarboxylic acids preferably also contain trivalent or higher polycarboxylic acids having 0 or 1 acid anhydride group. The carboxyl group in such polycarboxylic acids preferably has a valence of 3 to 6, more preferably 3 to 4. Examples of such polycarboxylic acids include the above-mentioned trifunctional or higher aromatic polycarboxylic acids having 0 or 1 acid anhydride group. Examples include trimellitic anhydride, trimellitic acid, and trimesic acid. Among these, those having 1 acid anhydride group are preferred, with trimellitic anhydride being particularly preferred. Among the trivalent or higher polycarboxylic acids having 0 or 1 acid anhydride group, examples other than aromatic polycarboxylic acids include hydrogenated trimellitic anhydride.

[0046] In view of the hygroscopicity of the polyester resin (A), the content of aromatic dicarboxylic acids having sulfonic acid groups, such as sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, and 5(4-sulfophenoxy)isophthalic acid, and aromatic dicarboxylic acid salts having sulfonate groups, such as their metal salts and ammonium salts, relative to the total amount of polycarboxylic acids is preferably 10 mol % or less, more preferably 5 mol % or less, even more preferably 3 mol % or less, particularly preferably 1 mol % or less, and most preferably 0 mol %.

[0047] <Polyhydric alcohols> Examples of polyhydric alcohols include dimer diols, bisphenol skeleton-containing monomers, aliphatic polyhydric alcohols, alicyclic polyhydric alcohols, and aromatic polyhydric alcohols. One or more types of polyhydric alcohols can be used.

[0048] In the present invention, the compound constituting the polyester resin (A) preferably contains a dimer diol as a polyhydric alcohol. Examples of dimer diols include dimer diols which are reduction products of dimer acids (mainly those having 36 to 44 carbon atoms) derived from oleic acid, linoleic acid, linolenic acid, erucic acid, etc., and hydrogenated products thereof. Among these, hydrogenated products are preferred from the viewpoint of suppressing gelation during the production of the polyester resin (A).

[0049] The content of dimer diol relative to the total polyhydric alcohols is preferably 2 to 80 mol%, more preferably 5 to 70 mol%, even more preferably 7 to 65 mol%, and particularly preferably 10 to 60 mol%. If the content of dimer diols is too low, the low moisture absorption and dielectric properties tend to be inferior. If the content of dimer diols is too high, the initial adhesion tends to be insufficient.

[0050] The content of the structural units derived from dimer diols in the entire polyester resin (A) is preferably 5 to 70% by weight, more preferably 10 to 60% by weight, even more preferably 12 to 55% by weight, and particularly preferably 15 to 50% by weight. If the content of the structural units derived from dimer diols is too low, the low moisture absorption and dielectric properties tend to be inferior. If the content of the structural units derived from dimer diols is too high, the initial adhesion tends to be insufficient.

[0051] Examples of bisphenol skeleton-containing monomers include bisphenol A, bisphenol B, bisphenol E, bisphenol F, bisphenol AP, bisphenol BP, bisphenol P, bisphenol PH, bisphenol S, bisphenol Z, 4,4'-dihydroxybenzophenone, bisphenol fluorene, bisphenylphenol fluorene, and hydrogenated versions thereof, as well as glycols such as ethylene oxide adducts and propylene oxide adducts obtained by adding one to several moles of ethylene oxide or propylene oxide to the hydroxyl groups of bisphenols. Among these, bisphenol fluorene and bisphenylphenol fluorene having a condensed polycyclic aromatic skeleton are preferred from the viewpoint of low dielectric properties, and ethylene oxide adducts are preferred from the viewpoint of reactivity. In particular, ethylene oxide adducts containing 2 to 3 moles are preferred from the viewpoints of heat resistance, low moisture absorption, and long-term durability in a humid and hot environment, and bisphenoxyethanol fluorene and bisphenylphenoxyethanol fluorene are most preferred.

[0052] Examples of aliphatic polyhydric alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-ethyl-2-butylpropanediol, dimethylolheptane, 2,2,4-trimethyl-1,3-pentanediol, etc. Among these, it is preferable to use those having 5 or less carbon atoms from the viewpoint of dielectric properties.

[0053] Examples of alicyclic polyhydric alcohols include 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, tricyclodecanediol, tricyclodecane dimethanol, spiroglycol, etc. Among these, polycyclic alcohols are preferred from the viewpoint of low dielectric properties, and tricyclodecane dimethanol is more preferred.

[0054] Examples of aromatic polyhydric alcohols include paraxylene glycol, metaxylene glycol, orthoxylene glycol, 1,4-phenylene glycol, and ethylene oxide adducts of 1,4-phenylene glycol.

[0055] Among the above polyhydric alcohols, it is preferable to use polyhydric alcohols having a side chain from the viewpoint of solvent solubility and solution stability. Examples of polyhydric alcohols having a side chain include bisphenol A, bisphenol B, bisphenol E, bisphenol AP, bisphenol BP, bisphenol P, bisphenol PH, bisphenol S, bisphenol Z, bisphenol fluorene, bisphenylphenol fluorene, and hydrogenated products thereof; ethylene oxide adducts and propylene oxide adducts obtained by adding 1 to several moles of ethylene oxide or propylene oxide to the hydroxyl groups of bisphenols; aliphatic polyhydric alcohols having a side chain such as 1,2-propylene glycol, 2-methyl-1,3-propanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-ethyl-2-butylpropanediol, dimethylolheptane, and 2,2,4-trimethyl-1,3-pentanediol; and alicyclic polyhydric alcohols having a side chain such as tricyclodecanediol, tricyclodecane dimethanol, and spiroglycol.

[0056] The content of the polyhydric alcohol having a side chain is preferably 10 mol % or more, more preferably 20 mol % or more, and even more preferably 30 mol % or more, with the upper limit being 95 mol %, based on the total amount of polyhydric alcohols. The content of the structural unit derived from a polyhydric alcohol having a side chain is preferably 5% by weight or more, more preferably 10% by weight or more, and even more preferably 15% by weight or more, with the upper limit being 50% by weight, based on the entire polyester resin (A). If the content of the polyhydric alcohol having a side chain is too low, the solvent solubility and the solution stability of the resulting polyester resin (A) solution tend to decrease.

[0057] The content of structural units derived from ether bond-containing glycols other than bisphenol skeleton-containing monomers, such as diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, is preferably 20% by weight or less, more preferably 15% by weight or less, even more preferably 10% by weight or less, particularly preferably 8% by weight or less, and most preferably 5% by weight or less, based on the total weight of the polyester resin (A), from the viewpoints of heat resistance, low moisture absorption, and long-term durability in a humid and hot environment.

[0058] In addition to the polycarboxylic anhydride described below, the polyester resin (A) may be copolymerized with at least one selected from the group consisting of trifunctional or higher polycarboxylic acids and trifunctional or higher polyhydric alcohols, if necessary, for the purpose of introducing a branched skeleton. When a cured product is obtained by reacting the polyester resin (A) with the polyepoxy compound (B) described below, the introduction of a branched skeleton increases the terminal group concentration (reaction points) of the resin, allowing for a cured product with high crosslink density and strength to be obtained.

[0059] In this case, examples of trifunctional or higher polyvalent carboxylic acids include trimellitic acid, trimesic acid, ethylene glycol bis(anhydrotrimellitate), glycerol tris(anhydrotrimellitate), trimellitic anhydride, pyromellitic dianhydride, oxydiphthalic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride, and 2,2'-bis[(dicarboxyphenoxy)phenyl]propane dianhydride. Examples of trifunctional or higher polyhydric alcohols include glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol. One or more of the tri- or higher functional polycarboxylic acids and the tri- or higher functional polyhydric alcohols can be used.

[0060] When at least one selected from the group consisting of trifunctional or higher polycarboxylic acids and trifunctional or higher polyhydric alcohols is used separately from the polycarboxylic acid anhydride described below, the content of the trifunctional or higher polycarboxylic acids relative to the total polycarboxylic acids, or the content of the trifunctional or higher polyhydric alcohol relative to the total polyhydric alcohols, is preferably in the range of 0.1 to 5 mol %, more preferably 0.1 to 3 mol %. If the content of either or both is too high, the mechanical properties such as elongation at break of the adhesive layer formed from the adhesive composition tend to decrease, and gelation also tends to occur during polymerization.

[0061] <Production of Polyester Resin (A)> The polyester resin (A) can be produced by a known method, for example, by subjecting a polycarboxylic acid and a polyhydric alcohol to an esterification reaction, optionally in the presence of a catalyst, to obtain a polyester resin, and then introducing an acid value into the polyester resin.

[0062] Examples of methods for introducing an acid value into a polyester resin include a method of introducing a carboxylic acid into the resin by acid addition after an esterification reaction or reduced-pressure polycondensation. If a monocarboxylic acid, dicarboxylic acid, or polyfunctional carboxylic acid compound is used for the acid addition, a decrease in molecular weight may occur due to ester exchange, and therefore it is preferable to use a compound having at least one carboxylic acid anhydride. Examples of the carboxylic acid anhydride include succinic anhydride, maleic anhydride, orthophthalic anhydride, 2,5-norbornene dicarboxylic acid anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic dianhydride, oxydiphthalic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, 3,3',4,4'-diphenyltetracarboxylic acid dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic acid dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride, and 2,2'-bis[(dicarboxyphenoxy)phenyl]propane dianhydride.

[0063] When the total structural units derived from polycarboxylic acids constituting a polyester resin are taken as 100 mol %, adding more than 15 mol % of acid can cause gelation. Acid addition methods include adding the acid directly in bulk and adding the polyester resin in solution. The reaction in bulk is fast, but adding a large amount can cause gelation, and the reaction occurs at high temperatures, so care must be taken to prevent oxidation by blocking oxygen gas. On the other hand, adding the acid in solution is slow, but allows for the stable introduction of a large number of carboxyl groups.

[0064] In order to obtain a polyester resin having a carboxy group in the side chain, a method of reacting a polycarboxylic acid anhydride with a hydroxyl group-containing prepolymer obtained by copolymerizing a polycarboxylic acid other than a polycarboxylic acid anhydride with a polyhydric alcohol is preferred from the viewpoint of productivity.

[0065] The polyester resin (A) can also be produced by another well-known method, for example, by subjecting a polycarboxylic acid and a polyhydric alcohol to an esterification reaction, optionally in the presence of a catalyst, to obtain a prepolymer, followed by polycondensation and further depolymerization.

[0066] The temperature for the esterification reaction between the polycarboxylic acids and the polyhydric alcohols is usually 180 to 280° C., and the reaction time is usually 60 minutes to 8 hours.

[0067] The temperature in the polycondensation is usually 220 to 280° C., and the reaction time is usually 20 minutes to 4 hours. The polycondensation is preferably carried out under reduced pressure.

[0068] For depolymerization, it is preferable to use a trivalent or higher polycarboxylic acid having 0 or 1 acid anhydride group from the viewpoint of initial adhesiveness. Examples of trivalent or higher polycarboxylic acids having 0 or 1 acid anhydride group include compounds such as trimellitic acid, trimellitic anhydride, hydrogenated trimellitic anhydride, and trimesic acid. Preferred are trivalent or higher polycarboxylic acids having 1 acid anhydride group from the viewpoint of suppressing a decrease in molecular weight, such as trimellitic anhydride and hydrogenated trimellitic anhydride. Trimellitic anhydride is particularly preferred from the viewpoint of a low dielectric loss tangent. The temperature for depolymerization is usually 200 to 260°C, and the reaction time is usually 10 minutes to 3 hours.

[0069] When the structural units derived from all polycarboxylic acids constituting the polyester resin are taken as 100 mol %, depolymerization using more than 20 mol % of trivalent or higher polycarboxylic acids having 0 or 1 acid anhydride group can significantly reduce the molecular weight of the resin. Therefore, when the structural units derived from all polycarboxylic acids constituting the polyester resin are taken as 100 mol %, depolymerization is preferably performed using 20 mol % or less of trivalent or higher polycarboxylic acids having 0 or 1 acid anhydride group, more preferably 1 to 15 mol %, even more preferably 2 to 10 mol %, and particularly preferably 3 to 9 mol %.

[0070] <Ester bond concentration of polyester resin (A)> The ester bond concentration of the polyester resin (A) is preferably 10 mmol / g or less, more preferably 1 to 9 mmol / g, even more preferably 2 to 8.5 mmol / g, particularly preferably 2.5 to 8 mmol / g, and especially preferably 3 to 7.5 mmol / g. If the ester bond concentration is too high, the low moisture absorption and long-term durability in a humid and hot environment will be insufficient, whereas if the ester bond concentration is too low, the initial adhesiveness will be insufficient.

[0071] The definition and measurement method of the ester bond concentration are as follows. The ester bond concentration (mmol / g) refers to the number of moles of ester bonds in 1 g of polyester resin, and can be calculated from the amounts charged, for example. The calculation method is to divide the number of moles of the smaller of the charged amounts of polycarboxylic acids and polyhydric alcohols by the total weight of the resin, and an example of the calculation formula is shown below. When the amounts of the polycarboxylic acids and the polyhydric alcohols charged are equal in molar amount, either of the following calculation formulas may be used. When a monomer having both a carboxyl group and a hydroxyl group is used, or when polyester is produced from caprolactone or the like, the calculation method will be changed appropriately.

[0072] (When the amount of polycarboxylic acids is less than the amount of polyhydric alcohols) Ester bond concentration (mmol / g) = [(A1 / a1×m1+A2 / a2×m2+A3 / a3×m3……) / Z]×1000 A: Amount of polycarboxylic acids (g) a: Molecular weight of polycarboxylic acids m: number of carboxylic acid groups per molecule of polycarboxylic acids Z: Finished weight (g)

[0073] (When the amount of polyhydric alcohols is less than the amount of polycarboxylic acids) Ester bond concentration (mmol / g) = [(B1 / b1×n1+B2 / b2×n2+B3 / b3×n3……) / Z]×1000 B: Amount of polyhydric alcohol (g) b: Molecular weight of polyhydric alcohols n: number of hydroxyl groups per molecule of polyhydric alcohol Z: Finished weight (g)

[0074] The ester bond concentration can also be measured by a known method using NMR or the like.

[0075] The concentration of polar groups other than ester bonds and reactive functional groups is preferably low from the viewpoint of low moisture absorption and long-term durability in a humid and hot environment. Other polar groups include, for example, an amide group, an imide group, a urethane group, a urea group, an ether group, and a carbonate group.

[0076] The total concentration of amide groups, imide groups, urethane groups, and urea groups is preferably 3 mmol / g or less, more preferably 2 mmol / g or less, even more preferably 1 mmol / g or less, particularly preferably 0.5 mmol / g or less, and most preferably 0.2 mmol / g or less. Examples of the ether group include an alkyl ether group and a phenyl ether group. From the viewpoint of low moisture absorption and long-term durability in a humid and hot environment, it is particularly preferable to reduce the concentration of alkyl ether groups. The alkyl ether group concentration is preferably 3 mmol / g or less, more preferably 2 mmol / g or less, even more preferably 1.5 mmol / g or less, particularly preferably 1 mmol / g or less, and most preferably 0.5 mmol / g or less. The phenyl ether group concentration is preferably 5 mmol / g or less, more preferably 4 mmol / g or less, even more preferably 3 mmol / g or less, and particularly preferably 2.5 mmol / g or less. The carbonate group concentration is preferably 3 mmol / g or less, more preferably 2 mmol / g or less, even more preferably 1 mmol / g or less, particularly preferably 0.5 mmol / g or less, and most preferably 0.2 mmol / g or less.

[0077] <Dielectric properties of polyester resin (A)> (Dielectric loss tangent (Df)) The polyester resin (A) preferably has a dielectric loss tangent (Df) at a frequency of 10 GHz under an environment of a temperature of 23°C and a relative humidity of 50%RH of 0.005 or less, more preferably 0.0045 or less, even more preferably 0.004 or less, still more preferably 0.0035 or less, and particularly preferably 0.003 or less. If the dielectric loss tangent is too high, the transmission loss of the resulting laminate increases.

[0078] (Dielectric constant (Dk)) The dielectric constant (Dk) of the polyester resin (A) at a frequency of 10 GHz under an environment of a temperature of 23°C and a relative humidity of 50% RH is preferably 2.9 or less, more preferably 2.8 or less, even more preferably 2.7 or less, and particularly preferably 2.6 or less. If the dielectric constant is too high, the resulting laminate tends to have a poor transmission speed or large transmission loss.

[0079] The dielectric constant and dielectric loss tangent of polyester resin (A) can be determined by the cavity resonator perturbation method using a network analyzer. If polyester resin (A) is highly adhesive and it is difficult to prepare a measurement sample for it alone, it can be measured sandwiched between films, and the dielectric properties of polyester resin (A) alone can be calculated by subtracting the film's weight.

[0080] <Acid value of polyester resin (A)> The acid value of the polyester resin (A) is preferably 3 mgKOH / g or more, more preferably 4 mgKOH / g or more, even more preferably 5 mgKOH / g or more, particularly preferably 6 mgKOH / g or more, and particularly preferably 7 mgKOH / g or more, while the acid value of the polyester resin (A) is preferably 60 mgKOH / g or less, more preferably 40 mgKOH / g or less, even more preferably 30 mgKOH / g or less, and particularly preferably 20 mgKOH / g or less. If the acid value of the polyester resin (A) is too low, when the adhesive composition contains a polyepoxy compound (B), the number of crosslinking points with the polyepoxy compound (B) is insufficient, resulting in a low degree of crosslinking and insufficient heat resistance.If the acid value of the polyester resin (A) is too high, the hygroscopicity and long-term durability in a humid and hot environment decrease, and a large amount of the polyepoxy compound (B) is required for curing, which tends to result in inferior dielectric properties, which have become increasingly popular in recent years.

[0081] The definition and measurement method of the acid value are as follows. The acid value (mgKOH / g) can be determined by dissolving 1 g of polyester resin in 30 g of a mixed solvent of toluene / methanol (for example, toluene / methanol=7 / 3 by volume) and performing neutralization titration according to JIS K0070. In the present invention, the acid value of the polyester resin (A) is determined by the content of carboxy groups in the resin.

[0082] <Glass transition temperature (Tg) of polyester resin (A)> The glass transition temperature (Tg) of the polyester resin (A) is preferably −5° C. or higher, more preferably 0° C. or higher, even more preferably 3° C. or higher, particularly preferably 5° C. or higher, especially preferably 7° C. or higher, and most preferably 10° C. or higher. On the other hand, the glass transition temperature (Tg) of the polyester resin (A) is preferably 100° C. or lower, more preferably 80° C. or lower, even more preferably 60° C. or lower, especially preferably 40° C. or lower, and especially preferably 30° C. or lower. If the glass transition temperature (Tg) of the polyester-based resin (A) is too low, the initial adhesion and tack-free property tend to be insufficient, whereas if the glass transition temperature (Tg) of the polyester-based resin (A) is too high, the initial adhesion and flexibility tend to be insufficient.

[0083] The glass transition temperature (Tg) was measured as follows. The glass transition temperature (Tg) can be determined by measurement using a differential scanning calorimeter under the following measurement conditions: a measurement temperature range of −70 to 140° C., and a temperature rise rate of 10° C. / min.

[0084] <Peak top molecular weight (Mp) and weight average molecular weight (Mw) of polyester resin (A)> The peak top molecular weight (Mp) of the polyester resin (A) is preferably 5,000 to 150,000, more preferably 10,000 to 100,000, still more preferably 15,000 to 70,000, and particularly preferably 25,000 to 40,000. If the peak top molecular weight (Mp) is too low, the low moisture absorption, tack-free properties, and long-term durability in a humid and hot environment tend to be insufficient, and problems such as the polyester resin in the adhesive layer flowing and seeping out during press processing when producing flexible laminates such as flexible copper-clad laminates and flexible printed circuit boards tend to occur.If the peak top molecular weight (Mp) is too high, the initial adhesion tends to be insufficient, and the solution viscosity during application tends to be too high, making it difficult to obtain a uniform coating film.

[0085] The weight average molecular weight (Mw) of the polyester resin (A) is preferably 5,000 to 300,000, more preferably 10,000 to 200,000, still more preferably 20,000 to 150,000, and particularly preferably 25,000 to 100,000. If the weight-average molecular weight (Mw) is too low, the low moisture absorption, tack-free properties, and long-term durability in a humid and hot environment tend to be insufficient, and problems such as the polyester resin in the adhesive layer flowing and seeping out during press processing when producing flexible laminates such as flexible copper-clad laminates and flexible printed circuit boards tend to occur.If the weight-average molecular weight (Mw) is too high, the initial adhesion tends to be insufficient, and the solution viscosity during application tends to be too high, making it difficult to obtain a uniform coating film.

[0086] The peak top molecular weight (Mp) and the weight average molecular weight (Mw) were measured by the following methods. The peak top molecular weight (Mp) and weight average molecular weight (Mw) can be measured using a high performance liquid chromatography (manufactured by Tosoh Corporation, "HLC-8320GPC") using two columns (TSKgel SuperMultipore HZ-M (exclusion limit molecular weight: 2 × 106, number of theoretical plates: 16,000 plates / column, packing material: styrene-divinylbenzene copolymer, packing particle size: 4 μm)) in series, and calculated in terms of the molecular weight of standard polystyrene.

[0087] <Water absorption rate (wt%) of polyester resin (A)> The water absorption rate of the polyester resin (A) is preferably 2% by weight or less, more preferably 1% by weight or less, even more preferably 0.8% by weight or less, and particularly preferably 0.6% by weight or less. If the water absorption rate is too high, the durability against humidity and heat and the insulating reliability tend to decrease, and the dielectric properties tend to be poor. Poor dielectric properties mean that the values ​​of the relative dielectric constant and the dielectric loss tangent do not decrease, or the values ​​increase.

[0088] The water absorption rate was measured as follows. The polyester resin solution (before the addition of the polyepoxy compound (B) and filler (C)) is applied to a release film using an applicator and dried at 120°C for 10 minutes to produce a sheet with a polyester resin layer with a dry thickness of 65 μm. This sheet is cut into a size of 7.5 cm x 11 cm, and the polyester resin layer side of the sheet is laminated onto a glass plate, after which the release film is peeled off. This process is repeated six times to obtain a test plate with a 390 μm-thick polyester resin layer on the glass plate. The test plate thus obtained is immersed in purified water at 23°C for 24 hours, then removed, the surface water is wiped off, and dried for 2 hours at 70°C. The necessary weight is measured in each of these steps, and the water absorption rate (wt%) is calculated from the weight change according to the following formula. Water absorption rate (weight%)=(cd)×100 / (ba) a: Weight of the glass plate alone b: Initial weight of test plate c: Weight of the test plate immediately after removing it from the purified water and wiping off the water d: Weight of test plate after drying at 70°C for 2 hours

[0089] <Polyester resin (A) content> The adhesive composition of the present invention may contain only the polyester resin (A) as the polyester resin, or may contain polyester resins other than the polyester resin (A), but the content of the polyester resin (A) in the adhesive composition of the present invention is preferably more than 50% by weight, more preferably 70% by weight or more, still more preferably 85% by weight or more, or may even be 100% by weight, of the total polyester resins. If the content of the polyester resin (A) is too low, the low moisture absorption and long-term durability in a humid and hot environment tend to be insufficient, and the low dielectric tangent tends to be inferior.

[0090] [Polyepoxy compound (B)] The adhesive composition of the present invention contains a polyepoxy compound (B). When the adhesive composition of the present invention contains the polyepoxy compound (B), the epoxy groups in the polyepoxy compound (B) react with the carboxy groups in the polyester resin (A) to cause curing, thereby obtaining an adhesive layer that not only has excellent adhesive strength but also excellent solder heat resistance.

[0091] The equivalent weight of the epoxy groups of the polyepoxy compound (B) in the adhesive composition relative to the carboxy groups of the polyester resin (A) in the adhesive composition is preferably less than 2, more preferably 1.9 or less, even more preferably 1.7 or less, and particularly preferably 1.5 or less. On the other hand, the equivalent weight of the epoxy groups of the polyepoxy compound (B) in the adhesive composition relative to the carboxy groups of the polyester resin (A) in the adhesive composition is preferably 0.1 or more, more preferably 0.3 or more, even more preferably 0.5 or more, and most preferably 0.8 or more. If the equivalent weight is too large, the initial adhesion and low moisture absorption tend to be insufficient, the dielectric properties tend to be poor, and the solder heat resistance tends to be deteriorated, whereas if the equivalent weight is too small, the long-term durability in a humid and hot environment and the solder heat resistance tend to be insufficient.

[0092] The equivalent weight of epoxy groups relative to carboxy groups (COOH) can be calculated from the acid value of the polyester resin (A) and the epoxy equivalent weight (g / eq) of the blended polyepoxy compound (B) using the following formula: Equivalent of epoxy group to COOH =(e÷WPE) / (AV÷56.1÷1000×P) e: Weight (g) of polyepoxy compound (B) used in the formulation WPE: Epoxy equivalent (g / eq) of polyepoxy compound (B) AV: Acid value of polyester resin (A) (mgKOH / g) p: Weight (g) of polyester resin (A) used in the blend

[0093] The epoxy equivalent WPE of the polyepoxy compound (B) is preferably 500 g / eq or less, more preferably 350 g / eq or less, even more preferably 250 g / eq or less, and particularly preferably 200 g / eq or less. If the epoxy equivalent of the polyepoxy compound (B) is too high, the crosslink density after curing will be low, resulting in poor solder heat resistance, and the dielectric properties will tend to be poor because a large amount of polyepoxy compound (B) must be added to achieve high crosslink density. The epoxy equivalent WPE of the polyepoxy compound (B) is usually 50 g / eq or more. In the present invention, the "epoxy equivalent (WPE)" is defined as "the weight of an epoxy resin containing one equivalent of epoxy groups" and can be measured in accordance with JIS K7236.

[0094] Examples of the polyepoxy compound (B) include nitrogen-containing polyepoxy compounds such as glycidyl amine-type compounds, such as tetraglycidyl diaminodiphenylmethane, triglycidyl p-aminophenol, tetraglycidyl bisaminomethylcyclohexane, and N,N,N',N'-tetraglycidyl-m-xylenediamine. Other examples include bifunctional glycidyl ethers, such as bisphenol A diglycidyl ether, bisphenol S diglycidyl ether, and brominated bisphenol A diglycidyl ether; multifunctional glycidyl ethers, such as phenol novolac glycidyl ether and cresol novolac glycidyl ether; glycidyl esters, such as hexahydrophthalic acid glycidyl ester and dimer acid glycidyl ester; and alicyclic or aliphatic epoxides, such as triglycidyl isocyanurate, 3,4-epoxycyclohexylmethylcarboxylate, epoxidized polybutadiene, and epoxidized soybean oil. Polyepoxy compounds (B) can be used singly or in combination.

[0095] When the adhesive composition of the present invention contains a nitrogen-containing polyepoxy compound (nitrogen-containing polyepoxy compound) as the polyepoxy compound (B), the coating film of the adhesive composition can be brought to a B-stage (semi-cured state) by heating at a relatively low temperature, and the fluidity of the B-stage film tends to be suppressed, improving workability in the bonding operation. Furthermore, the effect of suppressing foaming of the B-stage film is expected, which is preferable.

[0096] Filler The adhesive composition of the present invention contains a filler (C). By containing the filler (C), an adhesive having not only excellent adhesive strength but also excellent solder heat resistance can be obtained. In addition, various functionalities such as flame retardancy can be imparted.

[0097] The filler is not particularly limited, but examples of the shape include spherical, powdery, fibrous, needle-like, and scale-like shapes.

[0098] Examples of fillers include fluorine-based polymer powders such as polyvinylidene fluoride (PVDF), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), and fluororubber (FKM), polyethylene powder, polyacrylic ester powder, epoxy resin powder, polyamide powder, polyurethane powder, and polysiloxane powder, as well as polymer fillers such as multilayer core-shell structures using silicone, acrylic, styrene-butadiene rubber, and butadiene rubber; (Poly)phosphate compounds such as melamine phosphate, melamine polyphosphate, guanidine phosphate, guanidine polyphosphate, ammonium phosphate, ammonium polyphosphate, ammonium amide phosphate, ammonium amide polyphosphate, carbamate phosphate, and carbamate polyphosphate; organic phosphate ester compounds, phosphazene compounds, phosphonic acid compounds; phosphinic acid compounds such as aluminum diethylphosphinate, aluminum methylethylphosphinate, aluminum diphenylphosphinate, aluminum ethylbutylphosphinate, aluminum methylbutylphosphinate, and aluminum polyethylenephosphinate; phosphine oxide compounds, phosphorus-based flame-retardant fillers such as phosphorus oxide compounds, phosphorane compounds, and phosphoramide compounds; Nitrogen-based flame-retardant fillers such as benzoguanamine, melamine, melam, melem, melon, melamine cyanurate, cyanuric acid compounds, isocyanuric acid compounds, triazole compounds, tetrazole compounds, diazo compounds, and urea; Inorganic fillers such as silica, silicon nitride, boron nitride, aluminum nitride, calcium hydrogen phosphate, calcium phosphate, glass flakes, hydrated glass, calcium titanate, sepiolite, magnesium sulfate, aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, barium hydroxide, calcium hydroxide, titanium oxide, tin oxide, aluminum oxide, magnesium oxide, zirconium oxide, zinc oxide, molybdenum oxide, antimony oxide, nickel oxide, zinc carbonate, magnesium carbonate, calcium carbonate, barium carbonate, zinc borate, and aluminum borate; kaolinite group clay minerals (halloysite, kaolinite, endelite, dickite, nacrite, etc.), antigorite group clay minerals (antigorite, chrysotile, etc.), smectite group clay minerals (montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, stevensite, etc.), vermiculite group clay minerals (vermiculite, etc.), mica or mica group clay minerals (muscovite, phlogopite, and other micas, margarite, tetrasilylic mica, taeniolite, etc.), talc, clay, hydrotalcite, wollastonite, xonotlite, synthetic mica, and other clay minerals; Examples include: The filler (C) can be used alone or in combination of two or more.

[0099] Among these fillers, fluoropolymer powder (C1) and / or clay mineral (C2) are preferred from the viewpoint of further reducing the dielectric constant and dielectric dissipation factor and further improving the effects of the present invention. By including fluoropolymer powder (C1) and / or clay mineral (C2), an adhesive can be obtained that not only has high initial adhesive strength but also low dielectric properties and high adhesive strength even after a humidity and heat durability test. Furthermore, from the viewpoint of dispersibility in the polyester resin (A), clay minerals are more preferred, and mica is particularly preferred.

[0100] Examples of the fluorine-based polymer powder (C1) include polyvinylidene fluoride (PVDF), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), fluororubber (FKM), etc. These may be used alone or in combination of two or more. The fluoropolymer powder (C1) is preferred from the viewpoint of further reducing the dielectric constant and dielectric loss tangent and further improving the effects of the present invention, and among these, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer is particularly preferred from the viewpoint of adhesiveness and compatibility and dispersibility with the polyester resin (A). The incorporation of the fluoropolymer powder makes it possible to obtain a cured product that is excellent in balance not only with dielectric properties but also with adhesiveness, flexibility, electrical insulation, and heat resistance.

[0101] Examples of clay minerals (C2) include kaolinite clay minerals (halloysite, kaolinite, endelite, dickite, nacrite, etc.), antigorite clay minerals (antigorite, chrysotile, etc.), smectite clay minerals (montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, stevensite, etc.), vermiculite clay minerals (vermiculite, etc.), mica or mica clay minerals (muscovite, phlogopite, and other micas, margarite, tetrasilylic mica, taeniolite, etc.), talc, clay, hydrotalcite, wollastonite, xonotlite, synthetic mica, etc. These may be used alone or in combination of two or more. Among these clay minerals (C2), mica clay minerals and synthetic mica are preferred, and synthetic mica is more preferred, in terms of dispersibility in the polyester resin (A).

[0102] The average particle size of these fillers (C) is preferably 0.1 μm to 25 μm. When a filler having an average particle size close to 0.1 μm is used, the modifying effect of the filler is easily obtained, and further, the dispersibility and stability of the dispersion are easily improved. When a filler having an average particle size close to 25 μm is used, the mechanical properties of the cured film are easily improved.

[0103] [Adhesive composition formulation] The adhesive composition of the present invention contains a polyester resin (A), a polyepoxy compound (B), and a filler (C), and exhibits the effects of low transmission properties, low moisture absorption, tack-free properties, initial adhesion, and excellent long-term durability under humid and hot environments.

[0104] The content of the polyepoxy compound (B) in the adhesive composition of the present invention may be any amount that satisfies the aforementioned suitable equivalent ratio of epoxy groups in the polyepoxy compound (B) to carboxy groups in the polyester resin (A). More specifically, the content of the polyepoxy compound (B) is preferably 0.5 to 30 parts by weight, more preferably 1 to 20 parts by weight, even more preferably 1.5 to 15 parts by weight, and particularly preferably 1.8 to 5 parts by weight, per 100 parts by weight of the polyester resin (A). If the content of the polyepoxy compound (B) is too low, heat resistance and long-term durability under humid and hot environments tend to be insufficient. If the content of the polyepoxy compound (B) is too high, initial adhesion and low moisture absorption tend to be insufficient, and dielectric properties tend to be poor.

[0105] The content of the filler (C) in the adhesive composition of the present invention is preferably 1 to 100 parts by weight, more preferably 5 to 90 parts by weight, even more preferably 10 to 80 parts by weight, particularly preferably 15 to 70 parts by weight, and especially preferably 20 to 60 parts by weight, per 100 parts by weight of the polyester resin (A). A filler (C) content within the above range is preferred because it can reduce the dielectric loss tangent and improve long-term durability in a humid and hot environment without impairing adhesiveness. If the filler (C) content is too high, adhesiveness tends to decrease.

[0106] [catalyst] The adhesive composition of the present invention containing the polyepoxy compound (B) may contain a catalyst for curing.

[0107] Examples of the catalyst include imidazole compounds such as 2-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, and 1-cyanoethyl-2-ethyl-4-methylimidazole; tertiary amines such as triethylamine, triethylenediamine, N'-methyl-N-(2-dimethylaminoethyl)piperazine, 1,8-diazabicyclo(5,4,0)-undecene-7, 1,5-diazabicyclo(4,3,0)-nonene-5,6-dibutylamino-1,8-diazabicyclo(5,4,0)-undecene-7; and compounds obtained by converting these tertiary amines into amine salts with phenol, octylic acid, quaternized tetraphenylborate salts, or the like; cationic catalysts such as triallylsulfonium hexafluoroantimonate and diaryliodonium hexafluoroantimonate; and triphenylphosphine. Among these, tertiary amines such as 1,8-diazabicyclo(5,4,0)-undecene-7 and 1,5-diazabicyclo(4,3,0)-nonene-5,6-dibutylamino-1,8-diazabicyclo(5,4,0)-undecene-7, and compounds obtained by converting these tertiary amines into amine salts with phenol, octylic acid, quaternized tetraphenylborate salts, etc., are preferred in terms of thermosetting properties, heat resistance, adhesion to metals, and storage stability after blending. These catalysts may be used alone or in combination.

[0108] When the adhesive composition of the present invention contains a catalyst, the amount of the catalyst is preferably 0.01 to 1 part by weight per 100 parts by weight of the polyester resin (A). Within this range, the catalytic effect on the reaction between the polyester resin (A) and the polyepoxy compound (B) is further enhanced, and strong adhesive performance can be obtained.

[0109] [solvent] The adhesive composition of the present invention may contain a solvent in order to adjust the viscosity of the adhesive composition appropriately and to facilitate handling when forming a coating film. The solvent is used to ensure ease of handling and workability when molding the adhesive composition, and there are no particular restrictions on the amount used.

[0110] Examples of the solvent include ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone, and cyclohexanone; esters such as ethyl acetate; ethers such as ethylene glycol monomethyl ether; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; alcohols such as methanol and ethanol; alkanes such as hexane and cyclohexane; aromatics such as toluene and xylene. Only one solvent may be used, or two or more solvents may be mixed in any combination and ratio.

[0111] [Other ingredients] The adhesive composition of the present invention may contain other components in addition to the components listed above to further improve its functionality, such as coupling agents such as silane coupling agents, ultraviolet inhibitors, antioxidants, plasticizers, fluxes, flame retardants, colorants, dispersants, emulsifiers, elasticity reducing agents, diluents, antifoaming agents, ion trapping agents, leveling agents, and catalysts.

[0112] When the adhesive composition of the present invention contains these other components, the content of the other components is preferably 40% by weight or less, more preferably 0.05 to 30% by weight, even more preferably 0.1 to 20% by weight, and particularly preferably 0.2 to 10% by weight.

[0113] [Dielectric properties of adhesive composition] <Dielectric loss tangent (Df)> The dielectric loss tangent (Df) of a cured product of the adhesive composition of the present invention at a frequency of 10 GHz under an environment of a temperature of 23°C and a relative humidity of 50% RH is 0.005 or less, preferably 0.004 or less, more preferably 0.0038 or less, even more preferably 0.0036 or less, still more preferably 0.0034 or less, particularly preferably 0.0032 or less, especially preferably 0.0030 or less, and most preferably 0.0028 or less. If the dielectric loss tangent is too high, the transmission loss will increase when used in a laminate.

[0114] <Dielectric constant (Dk)> The dielectric constant (Dk) of the cured product of the adhesive composition of the present invention at a frequency of 10 GHz under an environment of a temperature of 23°C and a relative humidity of 50% RH is preferably 3.0 or less, more preferably 2.9 or less, even more preferably 2.8 or less, and particularly preferably 2.7 or less. If the dielectric constant is too high, when used in a laminate, the transmission speed tends to be reduced and the transmission loss tends to be large.

[0115] The dielectric loss tangent and relative permittivity of the cured product of the adhesive composition of the present invention can be measured by a cavity resonator perturbation method using a network analyzer. If the adhesive composition is so adhesive that it is difficult to prepare a measurement sample alone, the adhesive composition can be sandwiched between films and measured, and the dielectric properties of the adhesive composition alone can be calculated by subtracting the film content.

[0116] The following methods can be used to obtain an adhesive composition having excellent dielectric properties, with a dielectric loss tangent and a relative dielectric constant that are equal to or lower than the above upper limit. (1) Use a polyester resin (A) with low dielectric tangent and dielectric constant. (2) The formulation should be designed to contain fewer polar groups that deteriorate dielectric properties. (3) A low dielectric filler is used in combination as the filler (C).

[0117] [Adhesive layer] The adhesive layer obtained by curing the adhesive composition of the present invention exhibits the effects of excellent initial adhesion, low moisture absorption, and long-term durability under humid and hot environments.

[0118] In the present invention, "curing" means intentionally curing the adhesive composition by heat and / or light, etc., and the degree of curing can be controlled depending on the desired physical properties and application. The degree of curing can be confirmed by the gel fraction of the adhesive, and the gel fraction is preferably 50% or more, more preferably 60% or more, particularly preferably 70% or more, and even more preferably 75% or more. If the gel fraction is too low, the heat resistance and long-term durability under humid and hot environments tend to be insufficient. The gel fraction mentioned above refers to the weight percentage of the insoluble cured component of the adhesive composition relative to the weight of the cured product before immersion in methyl ethyl ketone at 23° C. for 24 hours.

[0119] The method for curing or semi-curing the adhesive composition of the present invention varies depending on the components and their amounts in the adhesive composition, but typically involves heating at 80 to 200°C for 10 minutes to 10 hours.

[0120] [Application] The adhesive composition of the present invention has excellent initial adhesion, low moisture absorption, and long-term durability in a humid and hot environment, and is therefore effective for bonding substrates made of various materials such as resins and metals. In particular, the adhesive composition is suitable as an adhesive for producing a laminate of a metal layer and a plastic layer, for example, an adhesive used for bonding electronic materials described below.

[0121] [Laminate] The laminate of the present invention is a laminate having an adhesive layer on at least one surface of a substrate or a conductor layer, the adhesive layer being a cured product of an adhesive composition containing a polyester resin (A), a polyepoxy compound (B), and a filler (C), and the adhesive layer (hereinafter sometimes referred to as the "adhesive layer of the present invention") exhibits a specific dielectric loss tangent (Df).

[0122] [Adhesive composition] The adhesive composition of the present invention described above can be used as the adhesive composition constituting the adhesive layer of the laminate of the present invention, and the curing method for forming the adhesive layer is also as described above.

[0123] [Dielectric properties of adhesive layer] <Dielectric loss tangent (Df)> The adhesive layer of the present invention has a dielectric loss tangent (Df) at a frequency of 10 GHz under an environment of a temperature of 23°C and a relative humidity of 50%RH of 0.005 or less, preferably 0.004 or less, more preferably 0.0038 or less, even more preferably 0.0036 or less, still more preferably 0.0034 or less, particularly preferably 0.0032 or less, particularly preferably 0.0030 or less, and most preferably 0.0028 or less. If the dielectric loss tangent is too high, the transmission loss of the laminate increases.

[0124] <Dielectric constant (Dk)> The adhesive layer of the present invention preferably has a dielectric constant (Dk) of 3.0 or less at a frequency of 10 GHz under an environment of a temperature of 23°C and a relative humidity of 50%RH, more preferably 2.9 or less, even more preferably 2.8 or less, and particularly preferably 2.7 or less. If the dielectric constant is too high, the laminate tends to have a poor transmission speed and a large transmission loss.

[0125] The dielectric loss tangent and relative dielectric constant of the adhesive layer of the present invention can be measured by the same method as the above-mentioned method for measuring the cured product of the adhesive composition of the present invention.

[0126] The method for obtaining an adhesive layer having excellent dielectric properties, in which the dielectric loss tangent and further the relative dielectric constant are not more than the above upper limit, is as described above as a method for obtaining an adhesive composition having excellent dielectric properties for the adhesive composition of the present invention, and the following method can be mentioned for the adhesive composition for forming the adhesive layer of the present invention. (1) The adhesive composition contains a polyester resin (A) having a low dielectric tangent and dielectric constant. (2) The adhesive composition is designed to have a small amount of polar groups that deteriorate the dielectric properties. (3) A low dielectric filler is used in combination as the filler (C).

[0127] Adhesive Layer Thickness The thickness of the adhesive layer of the present invention varies depending on the application of the laminate, but is usually 1 to 200 μm.

[0128] [Method for forming adhesive layer] The adhesive layer of the present invention can be produced by applying the adhesive composition of the present invention to a substrate or conductive layer, as described below. More specifically, the resin composition is applied to the substrate or conductive layer, and then dried under specific conditions (temperature: 80 to 180°C, time: 2 to 30 minutes) until it reaches a semi-cured state (hereinafter also referred to as B-stage) to obtain the adhesive layer. The thickness of the coating film varies depending on the application, but may be approximately 1 to 200 μm. The application method is not particularly limited, and examples include methods using a comma coater, die coater, gravure coater, and roll coater. Note that a fully cured (C-stage) adhesive layer can be obtained by laminating a B-stage adhesive layer to another substrate or conductive layer using a laminator or press, followed by treatment under specific curing conditions (temperature: 80 to 200°C, pressure: 0 to 3 MPa, time: 10 to 600 minutes). In the laminate of the present invention, the adhesive layer of the present invention may be formed on only one surface of the substrate or the conductor layer, or may be formed on both surfaces.

[0129] [Base material] The substrate of the laminate of the present invention is not particularly limited. Specific examples of the substrate include polyimide films, polyether ether ketone films, polyphenylene sulfide films, aramid films, polyethylene naphthalate films, liquid crystal polymer films, polyethylene terephthalate films, polyethylene films, polypropylene films, silicone release-treated paper, polyolefin resin-coated paper, polymethylpentene films, and fluorine-based resin films, which are preferred when the laminate of the present invention is used as a flexible laminate described below. These substrates may be used alone or in combination of two or more. For example, two or more of the substrates may be laminated together. In this case, the adhesive layer of the present invention may be formed between the substrates.

[0130] Of the above-mentioned substrates, polyimide films, polyether ether ketone films, polyphenylene sulfide films, aramid films, polyethylene naphthalate films, liquid crystal polymer films, polyethylene terephthalate films, polyethylene films, polypropylene films, polymethylpentene films, and fluorine-based resin films are preferred, and among these, from the viewpoints of adhesiveness and electrical properties, polyimide films, polyethylene naphthalate films, and liquid crystal polymer films are more preferred, and polyimide films and liquid crystal polymer films are even more preferred.

[0131] There are no particular restrictions on the thickness of the substrate, and it is designed appropriately depending on the application of the laminate and the material of the substrate used, but from the viewpoint of obtaining sufficient mechanical strength while making the laminate thin and flexible, it is preferably in the range of 1 to 500 μm, particularly 3 to 100 μm, and even more particularly 5 to 50 μm.

[0132] [Conductor Layer] Examples of conductors that form the conductor layer include foils made of ordinary copper or copper alloys, stainless steel or its alloys, nickel or nickel alloys (including 42 alloy), and aluminum or aluminum alloys. Copper foils, such as rolled copper foils and electrolytic copper foils, are commonly used as common circuit board materials, and are also preferably used in the present invention. The surface of these metal foils may be coated with an anti-rust layer, a heat-resistant layer, or an adhesive layer. The thickness of the metal foil is not particularly limited, and may be any thickness that can provide sufficient functionality depending on the application. The conductor layer may be formed in a pattern as a circuit, or may be formed in a plane.

[0133] The thickness of the conductor layer is usually about 1 to 100 μm.

[0134] [Other layers] The laminate of the present invention may have other layers in addition to the adhesive layer of the present invention and the substrate or conductor layer. The other layer is preferably a substrate or a conductor layer, particularly when the laminate of the present invention is used as a circuit board material.

[0135] The laminate of the present invention may also have a release layer in contact with the adhesive layer of the present invention. Examples of the release film that can be used to form the release layer include polyolefin films such as polyethylene and polypropylene; polyester films such as polyethylene terephthalate and polyethylene naphthalate; polyimide films; and resin films whose main components are polycarbonate films. The thickness of the release film is preferably from 1 to 300 μm, more preferably from 5 to 200 μm, still more preferably from 10 to 150 μm, and particularly preferably from 20 to 120 μm. The release film may be subjected to a matte treatment, a corona treatment, or an antistatic treatment on the surface that comes into contact with the adhesive layer of the present invention.

[0136] The laminate of the present invention may further include one or more adhesive layers, insulating layers, and conductor layers other than those described above.

[0137] [Application] Examples of uses of the laminate of the present invention include electronic materials such as flexible copper-clad laminates, coverlays, bonding sheets, and resin-coated copper foils. Examples of products produced by laminating electronic materials include flexible laminates such as flexible printed circuit boards, multilayer printed wiring boards, laminates for electric and electronic circuits such as capacitors, underfill materials, interchip fills for 3D-LSI, insulating sheets, heat dissipation substrates, etc. In addition, the laminate of the present invention can be used as a material for circuit boards, but is not limited thereto. The flexible laminate is, for example, a laminate obtained by sequentially laminating a flexible substrate, an adhesive layer, and a conductive metal layer made of copper, aluminum, an alloy thereof, etc., and the adhesive of the present invention can be used as the adhesive constituting the adhesive layer. In addition to the various layers described above, the flexible laminate may further include other insulating layers, other adhesive layers, and other conductive metal layers.

[0138] One embodiment of the laminate of the present invention is a circuit board material. Other embodiments of the laminate of the present invention include flexible copper-clad laminates, coverlay films, bonding sheets, and resin-coated copper foils.

[0139] [Circuit board material] The circuit board material as one embodiment of the laminate of the present invention can be produced, for example, by the following method. The adhesive layer of the present invention is formed on a substrate or a conductor layer, and a conductor or substrate is further laminated thereon, after which a circuit is formed using a photoresist or the like, and the required number of such layers are laminated. The lamination of the substrate and the conductor layer may be performed by directly overlapping conductive metal foils, by adhering the conductive metal foils with the adhesive composition of the present invention, by forming a conductive metal layer by plating or sputtering, or by combining these methods. [Example]

[0140] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples as long as it does not depart from the gist of the invention. In the following, "parts" and "%" are by weight.

[0141] The ratio (mol%) of aromatic polycarboxylic acids to the total polycarboxylic acids (referred to as "aromatic acid content" in Table 1-B), ester bond concentration (mmol / g), water absorption (%), glass transition temperature (Tg) (°C), acid value (mgKOH / g), peak top molecular weight (Mp), weight average molecular weight (Mw), dielectric properties, and epoxy group equivalent to COOH (epoxy / COOH) were measured according to the description in this specification.

[0142] [Production of polyester resin] The compositions (molar ratios) shown in Table 1-A below are the composition ratios (resin composition ratios) of the finished products, and are the relative ratios (molar ratios) of the amounts of the constituent monomers of the resulting polyester resins.

[0143] <Production Example 1: Production of Polyester Resin (A-1)> Thermometer, stirrer, rectification column, nitrogen inlet tube equipped reactor, as polycarboxylic acids terephthalic acid (TPA) 53.8 parts (0.3238 mol), isophthalic acid (IPA) 212.7 parts (1.2802 mol), trimellitic anhydride (TMAn) 3.1 parts (0.0161 mol), as polyhydric alcohols 2-methyl-1,3-propanediol (2MPG) 58.4 parts (0.6480 mol), neopentyl glycol (NPG) 140.1 parts (1.3452 mol), dimer diol "Pripol 2033" (P2033) (manufactured by Croda) 102.9 parts (0.1944 mol), tetrabutyl titanate 0.1 parts as a catalyst was charged, the internal temperature was raised to 260 ° C. over 2 hours, and the esterification reaction was carried out at 260 ° C. for 1.5 hours. Next, 0.1 parts of tetrabutyl titanate was added as a catalyst, the pressure in the system was reduced to 2.5 hPa, and a polymerization reaction was carried out over 2 hours. Thereafter, the internal temperature was lowered to 240°C, and 9.0 parts (0.0468 mol) of trimellitic anhydride (TMAn) was added, and a depolymerization reaction was carried out at 240°C for 1 hour to obtain a polyester resin (A-1).

[0144] <Production Example 2: Production of Polyester Resin (A-2)> A polyester resin (A-2) was obtained in the same manner as in Production Example 1, except that the resin composition was changed as shown in Table 1-A.

[0145] The resin compositions (structural units derived from components) and physical properties of the obtained polyester resins (A-1) and (A-2) are shown in Tables 1-A and 1-B. In Table 1-A, the abbreviations are as follows: "TPA": Terephthalic acid "IPA": Isophthalic acid "NDCM": 2,6-naphthalenedicarboxylic acid dimethyl "TMAn": Trimellitic anhydride "EG": Ethylene glycol "2MPG": 2-methyl-1,3-propanediol "NPG": Neopentyl glycol "TCD-DM": Tricyclodecanedimethanol "P2033": Dimer diol "Pripol 2033" (manufactured by Croda)

[0146] [Table 1]

[0147] <Polyepoxy compound (B)> The following polyepoxy compounds (B) were prepared. (B-1): Metaxylenediamine type epoxy resin "TETRAD-X" (Mitsubishi Gas Chemical Company, Inc.) (WPE = 98 (g / eq)) (B-2): Glycidylamine epoxy resin "jER-604" (Mitsubishi Chemical Corporation) (WPE = 118 (g / eq)) (B-3): Para-aminophenol type epoxy resin "jER-630" (Mitsubishi Chemical Corporation) (WPE = 98 (g / eq)) (B-4): Phenol novolac epoxy resin "YDPN-638" (Nippon Steel Chemical & Material Co., Ltd.) (WPE = 177 (g / eq))

[0148] <Filler (C)> The following filler (C) was prepared: (C-1): Synthetic mica "Micromica MK-100" (manufactured by Katakura Co-op Agri Co., Ltd.) (average particle size = 6 μm) (C-2): Fluorine-based polymer powder "EA-2000" (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) (AGC) (average particle size: 2-3 μm)

[0149] [Production of adhesive composition] An adhesive composition was produced using the polyester resin (A-1), the polyepoxy compound (B) and the filler (C) as follows.

[0150] Example 1 A polyester resin (A-1) solution (100 parts as solid content) was mixed with 3.2 parts of a polyepoxy compound (B-1) (solid content) and 30 parts of a filler (C-1), and the mixture was further diluted with methyl ethyl ketone to a solid content of 40%, followed by stirring and mixing to obtain an adhesive composition.

[0151] <Examples 2 to 6, Comparative Examples 1 to 3> An adhesive composition was obtained in the same manner as in Example 1, except that the resin composition shown in Table 2 was used.

[0152] The adhesive compositions obtained were evaluated as follows, and the results are shown in Tables 2 and 3.

[0153] [Laminate fabrication] The adhesive composition prepared above was applied to a 50 μm-thick polyimide film "Kapton 200H" (manufactured by DuPont-Toray Co., Ltd.) with an applicator and then dried at 120°C for 5 minutes to form an adhesive layer with a dry thickness of 25 μm. Next, a 30 μm-thick rolled copper foil was laminated to the adhesive layer surface of the adhesive-coated polyimide film (lamination conditions: 170°C, 0.2 MPa, feed rate 1.5 m / min), and then heat-treated and cured in an oven at 160°C for 4 hours to obtain a laminate. For convenience, the laminate (polyimide film / adhesive layer / rolled copper foil) laminated with rolled copper foil will be referred to as "PI / Cu."

[0154] [evaluation] <Gel fraction> The polyimide film with the adhesive layer obtained above was heat-treated at 160°C for 4 hours to cure, and then cut into a 4 cm x 4 cm size. This was wrapped in a 200-mesh SUS wire netting and immersed in methyl ethyl ketone at 23°C for 24 hours, and the weight percentage of the insoluble adhesive component remaining in the wire netting relative to the weight of the adhesive before immersion was taken as the gel fraction.

[0155] <Dispersibility> The polyimide film with the adhesive layer obtained above was cured by heat treatment at 160° C. for 4 hours, and then the compatibility of the resin and the dispersibility of the filler in the resulting adhesive layer were visually inspected. The evaluation criteria were as follows: A: Dispersed and dissolved, no agglomerates observed B: Dispersed, but fine aggregates are visible to the naked eye C: Dispersed, but many aggregates visible to the naked eye D: Not dispersed

[0156] <Initial adhesive strength> The PI / Cu obtained above was cut into 1 cm wide pieces to be used as test pieces. The test pieces were fixed to 2 mm thick glass plates using double-sided tape, and the tensile peel strength (N / cm) of the test pieces was measured using a peel tester under an environment of 23°C and 50% RH (peel speed: 50 mm / min, peel angle: 180°). The evaluation criteria were as follows: ◎:8N / cm or more ○: 6N / cm or more, less than 8N / cm △: 4N / cm or more, less than 6N / cm ×: Less than 4N / cm

[0157] <Moist heat durability> The test pieces prepared in the same manner as above were placed in a thermo-hygrostat at 85°C and 85% RH, and after a predetermined time (240, 500, or 1000 hours), they were removed and left to stand overnight in an environment of 23°C and 50% RH. The tensile peel strength (N / cm) was then measured in the same manner as the initial adhesive strength described above. The percentage of the adhesive strength after the moist heat treatment to the initial adhesive strength was taken as the "retention rate (%)." The absolute value of the adhesive strength was evaluated using the same evaluation criteria as for the initial adhesive strength. The adhesive strength retention rate was evaluated based on the following evaluation criteria. ◎: Retention rate is 80% or more ○: Retention rate is 60% or more but less than 80% △: Retention rate is 40% or more but less than 60% ×: Retention rate is less than 40%

[0158] <Dielectric constant (Dk) / dielectric loss tangent (Df)> The adhesive composition prepared above was applied to a 38 μm thick PET film using an applicator, dried at 120°C for 5 minutes, and then heat-treated and cured in an oven at 160°C for 4 hours to produce a 50 μm thick cured film.The values ​​at 10 GHz for this cured film were measured using a cavity resonator perturbation method with a network analyzer.

[0159] <Transmission loss> The transmission loss of a laminate is the sum of conductor loss and dielectric loss, and the dielectric loss is proportional to the square root of the dielectric constant (Dk) of the dielectric layer and the dielectric loss tangent (Df). Therefore, to evaluate the effect on transmission loss, the coefficient E of the dielectric loss term of transmission loss was set to the following formula, and its value was calculated from the dielectric constant (Dk) and dielectric loss tangent (Df) at 10 GHz. E=(Dk) 1 / 2 ×Df The evaluation criteria were as follows: If the evaluation was A or B, the transmission loss of the laminate was good. A:E ≦ 0.004 B: 0.004 < E ≦ 0.007 C: 0.007 < E ≦ 0.009 D:0.009 < E

[0160] [Table 2]

[0161] [Table 3]

[0162] From the above results, it can be seen that the laminate of the present invention and the adhesive composition of the present invention can provide a laminate having an adhesive layer with low transmission loss and a high rate of retention of adhesive strength before and after a moist heat durability test.

[0163] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application Nos. 2021-197875, 2021-197876 and 2021-197877, filed on December 6, 2021, and are incorporated by reference in their entirety.

Claims

1. A laminate having an adhesive layer on at least one surface of a substrate or a conductor layer, the adhesive layer is a cured product of an adhesive composition containing a polyester resin (A), a polyepoxy compound (B), and a filler (C), The laminate, wherein the adhesive layer has a dielectric loss tangent (Df) at 10 GHz (under an environment of a temperature of 23°C and a relative humidity of 50% RH) of 0.005 or less.

2. The laminate according to claim 1, wherein the filler (C) contains a fluoropolymer powder (C1) and / or a clay mineral (C2).

3. 3. The laminate according to claim 1, wherein the content of the polyepoxy compound (B) in the adhesive composition is an amount such that the epoxy equivalent of the polyepoxy compound (B) relative to the carboxy groups of the polyester resin (A) is 0.8 or more and less than 2.

4. The laminate according to any one of claims 1 to 3, wherein the polyester resin (A) has an acid value of 3 mgKOH / g or more and a glass transition temperature of -5°C or more.

5. The laminate according to any one of claims 1 to 4, wherein the polyester resin (A) contains a structural unit derived from a polycarboxylic acid and a structural unit derived from a polyhydric alcohol.

6. The laminate according to claim 5 , wherein the polyester resin (A) contains a structural unit derived from an aromatic polycarboxylic acid as the structural unit derived from a polycarboxylic acid.

7. The laminate according to any one of claims 1 to 6, wherein the content of the filler (C) in the adhesive composition is 1 to 100 parts by weight per 100 parts by weight of the polyester-based resin (A).

8. The laminate according to any one of claims 1 to 7, wherein the substrate is at least one selected from the group consisting of a polyimide film, a polyether ether ketone film, a polyphenylene sulfide film, an aramid film, a polyethylene naphthalate film, a liquid crystal polymer film, a polyethylene terephthalate film, a polyethylene film, a polypropylene film, silicone release-treated paper, a polyolefin resin-coated paper, a polymethylpentene film, and a fluorine-based resin film.

9. The laminate according to any one of claims 1 to 8, further comprising a conductor laminated thereon.

10. A circuit board material comprising the laminate according to any one of claims 1 to 9.

11. An adhesive composition comprising a polyester resin (A), a polyepoxy compound (B), and a filler (C), An adhesive composition, wherein a cured product of the adhesive composition has a dielectric loss tangent (Df) at 10 GHz (under an environment of a temperature of 23°C and a relative humidity of 50%) of 0.005 or less.

12. The adhesive composition according to claim 11, wherein the filler (C) contains a fluoropolymer powder (C1) and / or a clay mineral (C2).

13. The adhesive composition according to claim 11 or 12, wherein the content of the polyepoxy compound (B) is such that the epoxy equivalent of the polyepoxy compound (B) relative to the carboxyl groups of the polyester resin (A) is 0.8 or more and less than 2.

14. The adhesive composition according to any one of claims 11 to 13, wherein the polyester resin (A) has an acid value of 3 mgKOH / g or more and a glass transition temperature of -5°C or more.

15. The adhesive composition according to claim 14, wherein the polyester resin (A) has an acid value of 5 mgKOH / g or more and a glass transition temperature of −5° C. or more.

16. The adhesive composition according to any one of claims 11 to 15, wherein the polyester resin (A) contains a structural unit derived from a polycarboxylic acid and a structural unit derived from a polyhydric alcohol.

17. The adhesive composition according to claim 16, wherein the polyester resin (A) contains a structural unit derived from an aromatic polycarboxylic acid as the structural unit derived from a polycarboxylic acid.

18. The adhesive composition according to any one of claims 11 to 17, wherein the content of the filler (C) is 1 to 100 parts by weight per 100 parts by weight of the polyester-based resin (A).

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