JP7697364B2 - Adhesive composition and laminate with adhesive layer - Google Patents

Description

The present invention relates to an adhesive composition and a laminate with an adhesive layer.

Capacitive sensors are used in touch sensors, fingerprint authentication, inspection work, and the like. For example, in fingerprint authentication, a semiconductor sensor element is provided on a substrate, and the difference in capacitance caused by the distance between the minute unevenness of a fingerprint and the sensor element is detected. In such capacitive sensors, the sensor element is generally sealed and protected by a sealant, but this sealant causes a decrease in the sensitivity of the sensor. In order to prevent the decrease in the sensitivity of the sensor, it has been proposed to mix a high dielectric inorganic filler into the sealant to increase the dielectric constant of the sealant (for example, Patent Document 1).
Various compositions are known as sealing materials for electronic components, and among them, curable epoxy adhesives are widely used.

JP 2018-141052 A

By combining an epoxy adhesive with a highly dielectric inorganic filler, the resulting sealing material (cured film) can exhibit a high dielectric constant and a high elastic modulus. However, the inventors' investigations have revealed that these sealing materials are poor in flexibility and may not exhibit sufficient adhesive strength (peel strength). Furthermore, the liquid viscosity of the adhesive before curing is likely to increase, leading to problems with handling.

The present invention aims to provide an adhesive composition that is easy to handle, and the resulting cured film exhibits a sufficiently high dielectric constant, and the cured film also has flexibility and excellent adhesion to an adherend. Another objective of the present invention is to provide a laminate with an adhesive layer that uses this adhesive composition.

The above object of the present invention can be achieved by the following means.
[1]
A composition comprising a polyamide compound (A), an epoxy resin (B), and a titanic acid compound (C),
The amine value of the polyamide compound (A) is 10 mgKOH/g or less,
the content of the titanic acid compound (C) is 60 to 610 parts by mass per 100 parts by mass of the polyamide compound (A);
An adhesive composition, wherein the dielectric constant of the cured product after the curing reaction is 4.0 or more.
[2]
The adhesive composition according to [1], wherein the titanic acid compound (C) has a dielectric constant of 100 or more.
[3]
The adhesive composition according to [1] or [2], wherein the titanate compound (C) is at least one of barium titanate, strontium titanate, and calcium titanate.
[4]
The adhesive composition according to any one of [1] to [3], further comprising a silane coupling agent.
[5]
The adhesive composition according to any one of [1] to [4], wherein the polyamide compound (A) has an acid value of 0.1 to 10 mgKOH/g.
[6]
The adhesive composition according to any one of [1] to [5], wherein the epoxy resin (B) has three or more epoxy groups in one molecule.
[7]
The adhesive composition according to any one of [1] to [6], wherein the epoxy resin (B) is a cresol novolac type epoxy resin.
[8]
The adhesive composition according to any one of [1] to [7], wherein the content of the epoxy resin (B) is 2 to 25 parts by mass per 100 parts by mass of the content of the polyamide compound (A).
[9]
A laminate with an adhesive layer, comprising a substrate film and an adhesive layer made of the adhesive composition according to any one of [1] to [8].

In the present invention, a numerical range expressed using "~" means a range that includes the numerical values written before and after "~" as the lower and upper limits. For example, when it is written as "A~B", the numerical range is "A or more and B or less".

In this invention and this specification, the term "adhesive layer" refers to a layer in a state before curing, in a B-stage state (i.e., a state in which a portion is in a semi-cured state where curing has begun, and curing can proceed further by heating, etc.), or in a state after the curing reaction has proceeded to sufficiently form a crosslinked structure. In addition, the terms "cured product" and "cured film" refer to an object or film in a state after the adhesive composition has been subjected to a curing reaction to sufficiently form a crosslinked structure.

The adhesive composition of the present invention has excellent handling properties, and the resulting cured film exhibits a sufficiently high dielectric constant, and this cured film is also flexible and has excellent adhesion to the adherend. In addition, the laminate with the adhesive layer of the present invention has a cured film obtained by curing the adhesive layer exhibits a sufficiently high dielectric constant, and this cured film is also flexible and has excellent adhesion to the adherend.

The following describes preferred embodiments of the adhesive composition of the present invention, but the present invention is not limited to the following embodiments except as specified in the present invention.

[Adhesive composition]
The adhesive composition of the present invention comprises a polyamide compound (A), an epoxy resin (B) and a titanic acid compound (C), the amine value of the polyamide compound (A) being 1 to 10 mgKOH/g, the content of the titanic acid compound (C) being 60 to 610 parts by mass per 100 parts by mass of the content of the polyamide compound (A), and the dielectric constant of the cured product after the curing reaction being 4.0 or more. Each component constituting the adhesive composition of the present invention will be described in order.

<Polyamide compound (A)>
The adhesive composition of the present invention contains one or more polyamide compounds as the polyamide compound (A). There is no particular limitation on the polyamide compound (A) used in the present invention, and a wide variety of polymers having a plurality of amide bonds in the polymer chain can be used. The polyamide compound (A) may have a polyether structure, a polyester structure, or the like in the polymer chain. The polyamide compound (A) can be synthesized, for example, by a dehydration condensation reaction of various dicarboxylic acids and diamines, self-condensation of aminocarboxylic acids, ring-opening polymerization of intramolecular cyclic compounds of aminocarboxylic acids, and a combination of these reactions. Commercially available products can also be widely used. As the polyamide compound (A) contained in the adhesive composition of the present invention, for example, nylon resins described in JP-A-2010-31220 can be suitably used. When the adhesive composition contains a solvent, it is preferable that the polyamide compound (A) is soluble in the solvent at room temperature (25° C.).
The polyamide compound may be a polyamide resin or a polyamide elastomer.

The adhesive composition of the present invention contains a polyamide compound as a base resin, and thus can effectively bring out the effect of improving the dielectric constant of the cured product by blending a titanic acid compound. The reason for this is unclear, but one possible reason is that the titanic acid compound can be uniformly dispersed in the polyamide compound in a small particle size state with a high dielectric constant due to the polarity of the structure (amide bond) unique to polyamide compounds.

The polyamide compound (A) preferably contains a piperazine component as a diamine component. By containing the piperazine component, the adhesion to flexible films such as polyimide films can be improved. In the polyamide compound (A), the proportion (content) of the piperazine component in the total diamine components is preferably 20 mol % or more, and more preferably 40 to 100 mol %.

The diamine components other than piperazine that may constitute the polyamide compound (A) are not particularly limited, and various diamine components can be incorporated as appropriate depending on the purpose. Examples include diamine components derived from ethylenediamine, tetramethylenediamine, hexamethylenediamine, heptamethylenediamine, p-diaminomethylcyclohexane, bis(p-aminocyclohexyl)methane, m-xylylenediamine, isophoronediamine, etc., but are not limited to these.

When the polyamide compound (A) contains a dicarboxylic acid component, the dicarboxylic acid component is not particularly limited and can be appropriately set according to the purpose. Examples of the dicarboxylic acid component include, but are not limited to, dicarboxylic acid components derived from adipic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, dimer acid, isophthalic acid, terephthalic acid, and sodium 5-sulfoisophthalate. From the viewpoint of solubility in a solvent, it is preferable to use all or part of a dicarboxylic acid with relatively low crystallinity, such as azelaic acid, undecanedioic acid, and dimer acid.

When the polyamide compound (A) contains an amino carboxylic acid component, the amino carboxylic acid component is not particularly limited and can be appropriately set according to the purpose. Examples of the amino carboxylic acid component include, but are not limited to, those derived from 11-aminoundecanoic acid, 12-aminododecanoic acid, 4-aminomethylbenzoic acid, 4-aminomethylcyclohexanecarboxylic acid, etc. In addition, examples of the intramolecular cyclic compounds of the above amino carboxylic acids include, but are not limited to, β-lactam, ε-caprolactam, laurinlactam, α-pyrrolidone, α-piperidone, etc.

Also, polyamide compounds (A) that are alcohol-soluble nylon resins obtained by introducing N-alkoxymethyl groups into polyamide bonds in the polyamide compound by adding formalin and alcohol are also preferred. The introduction of N-alkoxymethyl groups contributes to lowering the melting point, increasing flexibility, and improving solubility, and the introduction rate is determined according to the purpose.

In general, when the amine value of the polyamide compound (A) is high and the acid value is low, the reaction between the amino group and the epoxy group of the epoxy resin (B) is accelerated, and good curing properties can be obtained by short-term heat treatment. However, since the reaction proceeds even at room temperature, the reaction proceeds gradually immediately after mixing, and the liquid viscosity increases or gels, which tends to cause problems in handling. Therefore, in the present invention, the amine value of the polyamide compound (A) is controlled to 10 mgKOH/g or less. The amine value is preferably 9 mgKOH/g or less, and more preferably 8 mgKOH/g or less. The lower limit of the amine value of the polyamide compound (A) is not particularly limited, and it is also preferable that it is 0 mgKOH/g.
The acid value of the polyamide compound (A) is preferably from 0.1 to 10 mgKOH/g, and more preferably from 0.2 to 8 mgKOH/g.
The above-mentioned "amine value" means the number of mg of KOH equivalent to hydrochloric acid required to neutralize the amine present in 1 g of polyamide compound (A). Also, the "acid value" means the number of mg of KOH required to neutralize the acid present in 1 g of polyamide compound (A). Details of the method for measuring the amine value and the acid value will be described in the section [Examples] below.

The molecular weight and amine value of polyamide compound (A) can be adjusted, for example, by adjusting the charging ratio of diamine and dicarboxylic acid, reaction time, and degree of reduced pressure when synthesizing polyamide compound (A).

The content of polyamide compound (A) is preferably 10 to 65 mass %, more preferably 15 to 60 mass %, and even more preferably 17 to 50 mass %, of the total solid content of the adhesive composition (components excluding the solvent).

<Epoxy resin (B)>
The adhesive composition of the present invention contains one or more epoxy resins as the epoxy resin (B). The epoxy resin (B) plays the role of a crosslinking agent that cures the polyamide compound (A). There is no particular limitation on the type of epoxy resin (B), and epoxy resins used in epoxy adhesives can be widely applied.
Examples of the epoxy resin (B) include glycidyl ethers such as diglycidyl ether of bisphenol A and its oligomers, orthophthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, p-hydroxybenzoic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, succinic acid diglycidyl ester, adipic acid diglycidyl ester, sebacic acid diglycidyl ester, and trimellitic acid triglycidyl ester; ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, tetraphenyl glycidyl ether ethane, triphenyl glycidyl ether ethane, polyglycidyl ether of sorbitol, and polyglycidyl ether of polyglycerol, but are not limited thereto. Furthermore, novolac type epoxy resins such as phenol novolac type epoxy resins, cresol novolac type epoxy resins, and bisphenol A novolac type epoxy resins can be used, with cresol novolac type epoxy resins being preferred among these.

From the viewpoint of increasing the reactivity with the polyamide compound (A) and exhibiting high heat resistance, it is preferable to use an epoxy resin (B) having three or more epoxy groups in one molecule. The number of epoxy groups in one molecule of the epoxy resin (B) is preferably 3 to 10.

From the viewpoint of crosslinking density and heat resistance, the content of the epoxy resin (B) contained in the adhesive composition of the present invention is preferably 1 to 30 parts by mass, more preferably 2 to 25 parts by mass, more preferably 5 to 20 parts by mass, and even more preferably 7 to 15 parts by mass, per 100 parts by mass of the polyamide compound (A).

The adhesive composition of the present invention is usually dissolved in a solvent and used as a solution-type adhesive. The solvent is preferably one in which both the polyamide compound (A) and the epoxy resin (B) are soluble. Since the polyamide compound (A) is generally soluble in alcohol-based solvents and the epoxy resin (B) is generally soluble in ketone-based, ester-based, aromatic solvents, and chlorine-based solvents, the solvent can usually be selected from a mixture of an alcohol-based solvent and a ketone-based solvent, a mixture of an alcohol-based solvent and an ester-based solvent, a mixture of an alcohol-based solvent and an aromatic solvent, etc.

Specific examples of the solvent include alcohol-based solvents (alcohol compounds) such as methanol, ethanol, i-propyl alcohol, n-propyl alcohol, i-butyl alcohol, n-butyl alcohol, benzyl alcohol, ethylene glycol methyl ether, propylene glycol methyl ether, diethylene glycol monomethyl ether, and diacetone alcohol; ketone-based solvents (ketone compounds) such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, and cyclohexanone; aromatic solvents (aromatic compounds) such as toluene, xylene, ethylbenzene, and mesitylene; ester-based solvents (ester compounds) such as methyl acetate, ethyl acetate, ethylene glycol monomethyl ether acetate, and 3-methoxybutyl acetate; and chlorine-based solvents (chlorine compounds) such as chloroform, carbon tetrachloride, dichloromethane, and trichloroethylene. In addition, in order to improve the solubility of the polyamide compound (A), it is also possible to use solvents to which water, phenol, formic acid, acetic acid, or the like has been added. Among these solvents, a mixed solvent in which an alcohol-based solvent and one or more other solvents are used in combination is preferred as the solvent for the adhesive composition of the present invention. Examples of such mixed solvents include methanol/toluene mixed solvent, i-propyl alcohol/toluene mixed solvent, i-isopropyl alcohol/dichloromethane mixed solvent, etc. The proportion of the alcohol-based solvent in the total solvent amount of the adhesive composition of the present invention is preferably 30 to 80 mass % from the viewpoint of the solubility of the polyamide compound (A) and the epoxy resin (B).

<Titanic acid compound (C)>
The adhesive composition of the present invention contains one or more titanic acid compounds as the titanic acid compound (C). The titanic acid compound (C) is an inorganic filler contained in the adhesive composition of the present invention in the form of particles. The titanic acid compound is preferably a composite oxide of titanic acid and an alkaline earth metal. Examples of the titanic acid compound include barium titanate, strontium titanate, calcium titanate, and magnesium titanate.

In the adhesive composition of the present invention, the content of the titanic acid compound (C) is 60 to 610 parts by mass, preferably 70 to 610 parts by mass, more preferably 100 to 610 parts by mass, even more preferably 150 to 600 parts by mass, and even more preferably 200 to 500 parts by mass, per 100 parts by mass of the polyamide compound (A), from the viewpoints of high dielectric properties and good adhesiveness.

The dielectric constant ε (measurement frequency: 1 MHz) of the titanic acid compound (C) is preferably 100 or more, more preferably 120 or more, and even more preferably 150 or more. The upper limit of the dielectric constant ε of the titanic acid compound (C) is not particularly limited, but it is usually practical to set it to 15,000 or less. The dielectric constant ε of the titanic acid compound (C) can be determined by the method described in the section [Examples] below.

The adhesive composition of the present invention contains a combination of a polyamide compound (A) and an epoxy resin (B), and further contains a combination of a titanic acid compound (C), which suppresses an increase in the liquid viscosity of the adhesive composition and provides excellent handleability. The adhesive layer formed using this composition exhibits strong adhesion to the adherend due to the curing reaction, and can also achieve a higher dielectric constant. Furthermore, the flexibility of the encapsulant can be ensured, making it applicable to flexible devices.

<Characteristics of Adhesive Composition>
The dielectric constant of the adhesive composition according to the present invention is 4.0 or more, preferably 4.5 or more, more preferably 5.0 or more, even more preferably 8.0 or more, and even more preferably 10.0 or more. The upper limit of the dielectric constant is not particularly limited, but is usually 100.0 or less. The dielectric constant of the cured product of the adhesive composition can be determined by the method described in the section [Examples] below.

The peel strength of the cured product of the adhesive composition according to the present invention is preferably 10.0 N/cm or more, and more preferably 11.0 N/cm or more. The upper limit of the peel strength is not particularly limited, but is usually 50.0 N/cm or less. The peel strength can be determined by the method described in the [Examples] section below.

The liquid viscosity of the adhesive composition according to the present invention is preferably 100 to 30,000 mPa·s, more preferably 100 to 25,000 mPa·s, even more preferably 150 to 25,000 mPa·s, and even more preferably 200 to 25,000 mPa·s. The liquid viscosity can be determined by the method described in the Examples section below.

The elastic modulus of the cured product of the adhesive composition according to the present invention is preferably 0.1 to 5.2 GPa, more preferably 0.8 to 4.0 GPa, even more preferably 1.2 to 3.7 GPa, even more preferably 1.3 to 3.0 GPa, even more preferably 1.9 to 2.0 GPa, and even more preferably 2.4 to 2.5 GPa. The elastic modulus (tensile test) can be determined by the method described in the [Examples] section below.

<Other ingredients>
In addition to the polyamide compound (A), the epoxy resin (B), and the titanic acid compound (C), additives may be added to the adhesive composition of the present invention for various purposes such as improving adhesion and solution properties. Examples of additives include coupling agents, antioxidants, UV absorbers, flame retardants, fillers other than the titanic acid compound (C), leveling agents, defoamers, thickeners, dyes, etc. Such additives can be added when or after the raw materials are dissolved in a solvent.

Examples of coupling agents include silane-based coupling agents (silane coupling agents) such as vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, and 3-isocyanatopropyltriethoxysilane, titanate-based coupling agents (titanate coupling agents), aluminate-based coupling agents (aluminate coupling agents), and zirconium-based coupling agents (zirconium coupling agents).

The content of the coupling agent is preferably 0.5 to 3.0 parts by mass, and more preferably 1.0 to 2.0 parts by mass, per 100 parts by mass of the polyamide compound (A).

Examples of antioxidants include phenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol, n-octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate, and tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, sulfur-based antioxidants such as dilauryl-3,3'-thiodipropionate and dimyristyl-3,3'-dithiopropionate, and phosphorus-based antioxidants such as trisnonylphenyl phosphite and tris(2,4-di-t-butylphenyl)phosphite.

Examples of ultraviolet absorbers include benzotriazole-based ultraviolet absorbers such as 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and 2-[(2'-hydroxy-3',5'-bis(α,α-dimethylbenzyl)phenyl]-benzotriazole, benzophenone-based ultraviolet absorbers such as 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, and 2-hydroxy-4-n-octylbenzophenone, and phenyl salicylate. Examples include salicylate-based UV absorbers, cyanoacrylate-based UV absorbers such as ethyl-2-cyano-3,3-diphenylacrylate, oxalic anilide-based UV absorbers such as 2-ethoxy-2'-ethyl oxalic acid bisanilide, and hindered amine-based UV absorbers such as bis-[2,2,6,6-tetramethyl-4-piperidine]sebacate and bis-[N-methyl-2,2,6,6-tetramethyl-4-piperidinyl]sebacate.

Examples of flame retardants include bromine-based flame retardants such as tetrabromobisphenol A, hexabromobenzene, decabromodiphenyl ether, hexabromocyclododecane, bis(pentabromophenyl)ethane, and bis(tetrabromophthalimide)ethane; aromatic phosphate ester-based flame retardants such as triphenyl phosphate, 2-ethylhexyl diphenyl phosphate, and cresyl diphenyl phosphate; aromatic condensed phosphate esters such as 1,3-phenylene bis(diphenyl phosphate), 1,3-phenylene bis(dixylenyl)phosphate, and bisphenol A bis(diphenyl phosphate); halogen-containing phosphate ester-based flame retardants such as tris(dichloropropyl)phosphate; red phosphorus-based flame retardants such as red phosphorus; inorganic flame retardants such as aluminum hydroxide, magnesium hydroxide, and antimony trioxide; silicone-based flame retardants; and boron-based flame retardants.

Examples of fillers include calcium carbonate, titanium oxide, zinc oxide, talc, calcium carbonate, carbon black, silica, copper powder, aluminum powder, silver powder, etc.

In the present invention, the adhesive composition containing the polyamide compound (A), the epoxy resin (B) and the titanic acid compound (C) is preferably dissolved in the above-mentioned solvent together with the above-mentioned optional additives and used as a solution-type adhesive. When used as a solution-type adhesive, the resin concentration of the adhesive composition (the total concentration (mass %) of the polyamide compound (A) and the epoxy resin (B)) is preferably 10 to 35 mass %, more preferably 15 to 30 mass %.

[Laminate with adhesive layer]
The laminate with an adhesive layer according to the present invention comprises an adhesive layer made of the above-mentioned adhesive composition, and a substrate film in contact with at least one surface of the adhesive layer.

One embodiment of the laminate with an adhesive layer according to the present invention is a coverlay film. A coverlay film has an adhesive layer formed on at least one surface of a base film.

When the laminate with the adhesive layer is a coverlay film, examples of the base film include polyimide film, polyether ether ketone film, polyphenylene sulfide film, aramid film, polyethylene naphthalate film, and liquid crystal polymer film. Among these, polyimide film, polyethylene naphthalate film, and liquid crystal polymer film are preferred from the viewpoints of adhesion and electrical properties.

Such substrate films are commercially available, and for polyimide films, "Kapton (registered trademark)" manufactured by DuPont-Toray Co., Ltd., "Xenomax (registered trademark)" manufactured by Toyobo Co., Ltd., "Upilex (registered trademark)-S" manufactured by Ube Industries, Ltd., "Apical (registered trademark)" manufactured by Kaneka Corporation, etc. can be used. For polyethylene naphthalate films, "Teonex (registered trademark)" manufactured by Teijin DuPont Films Co., Ltd. can be used. For liquid crystal polymer films, "Vexstar (registered trademark)" manufactured by Kuraray Co., Ltd., "Viac (registered trademark)" manufactured by Primatec Co., Ltd., etc. can be used. The substrate film can also be made by forming the corresponding resin into a film of the desired thickness.

As a method for producing a coverlay film, for example, a resin varnish containing the above-mentioned adhesive composition and a solvent is applied to the surface of a base film such as a polyimide film to form a resin varnish layer, and then the solvent is removed from this resin varnish layer, thereby producing a coverlay film having an adhesive layer formed thereon.
The drying temperature when removing the solvent is preferably 40 to 250° C., and more preferably 70 to 170° C. Drying is performed by passing the laminate coated with the adhesive composition through a furnace in which hot air drying, far-infrared heating, high-frequency induction heating, or the like is performed.
If necessary, a release film may be laminated on the surface of the adhesive layer for storage, etc. As the release film, a typical film such as a polyethylene terephthalate film, a polyethylene film, a polypropylene film, silicone release-treated paper, a polyolefin resin-coated paper, a polymethylpentene (TPX) film, or a fluorine-based resin film may be used.

Another embodiment of the laminate with an adhesive layer is a bonding sheet. The bonding sheet also has the above-mentioned adhesive layer formed on the surface of a base film, but a release film is used as the base film. The bonding sheet may also have an adhesive layer between two release films. When using the bonding sheet, the release film is peeled off. The release film may be the same as the one described above.

Such release films are also commercially available, and examples that can be used include "Lumirror (registered trademark)" manufactured by Toray Advanced Film Co., Ltd., "Toyobo Ester (registered trademark) Film" manufactured by Toyobo Co., Ltd., "Aflex (registered trademark)" manufactured by Asahi Glass Co., Ltd., and "Opulent (registered trademark)" manufactured by Mitsui Chemicals Tocello Co., Ltd.

One method for producing a bonding sheet is, for example, to apply a resin varnish containing the adhesive composition and a solvent to the surface of a release film, and then dry it in the same manner as for the coverlay film.

The thickness of the substrate film is preferably 5 to 100 μm, more preferably 5 to 50 μm, and even more preferably 5 to 30 μm, in order to make the laminate with the adhesive layer thinner.

The thickness of the adhesive layer is preferably from 5 to 100 μm, more preferably from 10 to 70 μm, and even more preferably from 10 to 50 μm.
The thicknesses of the substrate film and adhesive layer are selected depending on the application, but the substrate film tends to be thinner in order to improve electrical properties. In general, when the substrate film is thin and the adhesive layer is thick, the laminate with the adhesive layer is more likely to warp and the workability is reduced, but the laminate with the adhesive layer of the present invention hardly warps even when the substrate film is thin and the adhesive layer is thick. In the laminate with the adhesive layer of the present invention, the ratio (D1/D2) of the thickness of the adhesive layer (D1) to the thickness of the substrate film (D2) is preferably 1 to 10, more preferably 1 to 5 or less. Furthermore, it is preferable that the thickness of the adhesive layer is thicker than the thickness of the substrate film.

Another embodiment of the laminate with an adhesive layer is a copper-clad laminate. The copper-clad laminate is a laminate in which a polyimide film as a base film and a copper foil are laminated together using the adhesive layer. That is, the copper-clad laminate is a laminate composed of a base film, an adhesive layer, and a copper foil in this order. In the copper-clad laminate, the adhesive layer and the copper foil may be formed on both sides of the base film. That is, the copper-clad laminate may be a laminate having an adhesive layer and a copper foil, in this order, on one side and the other side of the base film. Since the adhesive composition of the present invention has excellent adhesion to an article containing copper, the copper-clad laminate has excellent stability as an integrated product. The adhesive layer contained in the copper-clad laminate of the present invention may be made of a cured product or an uncured product.
The thickness of the adhesive layer in the copper-clad laminate is preferably 5 to 45 μm, and more preferably 10 to 35 μm.

A method for producing a copper-clad laminate can be, for example, to bring the adhesive layer of the coverlay film into surface contact with copper foil, perform thermal lamination at 80 to 150°C, and then harden the adhesive layer by after-curing. The after-curing conditions can be, for example, 100 to 200°C and 30 minutes to 4 hours. The copper foil is not particularly limited, and electrolytic copper foil, rolled copper foil, etc. can be used.

[Article with adhesive layer]
The article with an adhesive layer according to the present invention is an article having an adhesive layer made of the above-mentioned adhesive composition. A preferred embodiment of the present invention is an electromagnetic shielding material having an adhesive layer. This can prevent malfunction of electronic devices due to electromagnetic noise, leakage of confidential information due to interception of communication waves, etc. As a method for producing the electromagnetic shielding material of the present invention, for example, a method of bonding a high dielectric bonding sheet having an adhesive layer to a shielding material can be applied.
The thickness of the adhesive layer in the electromagnetic wave shielding material is preferably 5 to 100 μm, and more preferably 10 to 70 μm.

Other examples of articles with an adhesive layer include antenna substrates, capacitors, capacitance-type sensors, piezoelectric film speakers, etc., which have an adhesive layer made of the above-mentioned adhesive composition.

The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In the following, "parts" and "%" are by weight unless otherwise specified.

[Preparation of adhesive composition]
Example 1
An adhesive solution (adhesive composition) was prepared by adding and mixing 100 parts by mass of polyamide compound a (acid value: 7 mg KOH/g, amine value: 3 mg KOH/g), 10 parts by mass of o-cresol novolac epoxy resin (trade name: EPICLON N-665, manufactured by DIC Corporation), 1.11 parts by mass of an epoxy silane coupling agent (trade name: SH-6040, manufactured by DuPont Toray Specialty Materials Inc.), and 67.1 parts by mass of barium titanate (trade name: BT-05, manufactured by Sakai Chemical Industry Co., Ltd., dielectric constant: 4590) to 394 parts by mass of a mixed solvent of methanol/toluene = 1/1 (mass ratio).

Example 2
An adhesive solution was prepared in the same manner as in Example 1, except that the amount of barium titanate added was changed to 151 parts by mass.

Example 3
An adhesive solution was prepared in the same manner as in Example 1, except that the amount of barium titanate added was changed to 259 parts by mass.

Example 4
An adhesive solution was prepared in the same manner as in Example 1, except that the amount of barium titanate added was changed to 404 parts by mass.

Example 5
An adhesive solution was prepared in the same manner as in Example 1, except that the amount of barium titanate added was changed to 606 parts by mass.

Example 6
An adhesive solution was prepared in the same manner as in Example 1, except that polyamide compound a was changed to polyamide compound b (acid value: 1 mg KOH/g, amine value: 4.5 mg KOH/g) and the amount of barium titanate added was changed to 404 parts by mass.

Example 7
An adhesive solution was prepared in the same manner as in Example 1, except that polyamide compound a was changed to polyamide compound c (acid value: 1 mg KOH/g, amine value: 4.5 mg KOH/g) and the amount of barium titanate added was changed to 404 parts by mass.

Example 8
An adhesive solution was prepared in the same manner as in Example 1, except that 67.1 parts by mass of barium titanate was changed to 322 parts by mass of strontium titanate (product name: ST-A, manufactured by Fuji Titanium Industry Co., Ltd., dielectric constant: 300).

<Example 9>
An adhesive solution was prepared in the same manner as in Example 1, except that 67.1 parts by mass of barium titanate was changed to 276 parts by mass of calcium titanate (product name: CT-3, manufactured by Kyoritsu Materials Co., Ltd., dielectric constant: 180).

Example 10
An adhesive solution was prepared in the same manner as in Example 4, except that the amount of o-cresol novolac type epoxy resin added was changed to 2 parts by mass.

Example 11
An adhesive solution was prepared in the same manner as in Example 4, except that the amount of o-cresol novolac type epoxy resin was changed to 25 parts by mass.

<Comparative Example 1>
An adhesive composition was prepared by mixing 100 parts by mass of epoxy resin (trade name: Epicoat 828, manufactured by Mitsubishi Chemical Corporation), 25 parts by mass of diethylene glycol diglycidyl ether (trade name: SR-2EGS, manufactured by Sakamoto Yakuhin Kogyo Co., Ltd.), 48.5 parts by mass of modified aliphatic polyamine (trade name: Fujicure FXJ-8074-D, manufactured by T&K Toka Corporation), 1.5 parts by mass of aminopropyltriethoxysilane (trade name: A-1100, manufactured by Nippon Shokubai Sangyo Co., Ltd.), and 97.2 parts by mass of barium titanate (trade name: BT-05, manufactured by Sakai Chemical Industry Co., Ltd.).

<Comparative Example 2>
An adhesive composition was prepared by mixing 100 parts by mass of epoxy resin (trade name: Epicoat 807, manufactured by Mitsubishi Chemical Corporation), 19 parts by mass of m-phenylenediamine (trade name: Epicure Z, manufactured by Mitsubishi Chemical Corporation), 1.84 parts by mass of an epoxy silane coupling agent (trade name: KBM-402, manufactured by Shin-Etsu Chemical Co., Ltd.), 0.79 parts by mass of a titanate coupling agent (trade name: KR-46B, manufactured by Ajinomoto Fine-Techno Co., Ltd.), and 426 parts by mass of barium titanate (trade name: BT-05, manufactured by Sakai Chemical Industry Co., Ltd.).

<Comparative Example 3>
An adhesive solution (adhesive composition) was prepared by adding and mixing 100 parts by mass of acid-modified polyolefin resin (product name: Auroren 500S, manufactured by Nippon Paper Industries Co., Ltd.), 0.1 parts by mass of dioctyltin dilaurate (manufactured by Kishida Chemical Co., Ltd.), 10 parts by mass of hexamethylene diisocyanate (product name: Duranate TKA-100, manufactured by Asahi Kasei Corporation), and 78.2 parts by mass of barium titanate (product name: BT-05, manufactured by Sakai Chemical Industry Co., Ltd.) to 567 parts by mass of a mixed solvent of methylcyclohexane/methyl ethyl ketone = 3.7/1 (mass ratio).

<Comparative Example 4>
An adhesive composition was prepared by mixing 100 parts by mass of acrylic polymer (product name: UH-2041, manufactured by Toagosei Co., Ltd.), 0.1 parts by mass of dioctyltin dilaurate (manufactured by Kishida Chemical Co., Ltd.), 102 parts by mass of hexamethylene diisocyanate (product name: Duranate AE-700-100, manufactured by Asahi Kasei Corporation), and 66.7 parts by mass of barium titanate (product name: BT-05, manufactured by Sakai Chemical Industry Co., Ltd.).

<Comparative Example 5>
An adhesive solution was prepared in the same manner as in Example 1, except that 121 parts by mass of silica (product name: Excelica SE-1, manufactured by Tokuyama Corporation) was used instead of 67.1 parts by mass of barium titanate.

<Comparative Example 6>
An adhesive solution was prepared in the same manner as in Example 1, except that 154 parts by mass of boron nitride (product name: PCTP-2, manufactured by Saint-Gobain) was added instead of 67.1 parts by mass of barium titanate.

<Comparative Example 7>
An adhesive solution was prepared in the same manner as in Example 1, except that the amount of barium titanate added was changed to 35 parts by mass.

<Comparative Example 8>
An adhesive solution was prepared in the same manner as in Example 1, except that the amount of barium titanate added was changed to 908 parts by mass.

<Comparative Example 9>
An adhesive solution was prepared in the same manner as in Example 1, except that barium titanate was not added.

[Evaluation method]
<Method for measuring the amine value of a polyamide compound>
The polyamide compound was dissolved in a mixed solution of 20 ml of 1-butanol and 20 ml of toluene, and an automatic titration apparatus "AT-510" manufactured by Kyoto Electronics Manufacturing Co., Ltd. was used, to which an "APB-510-01B" manufactured by the same company was connected as a burette. Potentiometric titration was performed using a 0.1 mol/L 2-propanolic hydrochloric acid solution as the titration reagent, and the mg of hydrochloric acid and the equivalent amount of KOH per 1 g of the polyamide compound were calculated.

<Method for measuring the acid value of a polyamide compound>
1 g of polyamide compound was dissolved in 40 ml of benzyl alcohol, and an automatic titration apparatus "AT-510" manufactured by Kyoto Electronics Manufacturing Co., Ltd. was used, to which an "APB-510-20B" manufactured by the same company was connected as a burette. Potentiometric titration was performed using a 0.01 mol/L benzyl alcohol-based KOH solution as the titration reagent, and the number of mg of KOH per 1 g of polyamide compound was calculated.

<Method of measuring dielectric constant>
(Cured Products of Adhesive Compositions Prepared in Examples 1 to 11 and Comparative Examples 5 to 9)
A 38 μm-thick release polyethylene terephthalate film was prepared, and the adhesive composition was roll-coated on one surface of the film. The coated film was then placed in an oven and dried at 90° C. for 3 minutes to form a coating (adhesive layer) with a thickness of 50 μm. The coating was then placed in an oven and heat-treated at 150° C. for 30 minutes. This heat treatment allowed the curing reaction (crosslinking reaction) of the coating to proceed sufficiently. The release film was then peeled off to prepare a test piece (50×50 mm).
The dielectric constant (ε) was measured using a network analyzer 85071E-300 (manufactured by Agilent Technologies) by the split post dielectric resonator method (SPDR method) at a temperature of 23° C. and a frequency of 10 GHz.

(Cured products of adhesive compositions prepared in Comparative Examples 1 and 2)
A 38 μm-thick release polyethylene terephthalate film was prepared, and the adhesive composition was roll-coated on one surface of the film. The coated film was then placed in an oven and dried at 90° C. for 3 minutes to form a coating (adhesive layer) with a thickness of 50 μm. The coating was then placed in an oven and heat-treated at 130° C. for 5 minutes. This heat treatment allowed the curing reaction (crosslinking reaction) of the coating to proceed sufficiently. The release film was then peeled off to prepare a test piece (50×50 mm).
The dielectric constant (ε) was measured using a network analyzer 85071E-300 (manufactured by Agilent Technologies) by the split post dielectric resonator method (SPDR method) at a temperature of 23° C. and a frequency of 10 GHz.

(Cured product of adhesive composition prepared in Comparative Example 3)
A 38 μm-thick release polyethylene terephthalate film was prepared, and the adhesive composition was roll-coated on one surface of the film. The coated film was then placed in an oven and dried at 90° C. for 3 minutes to form a coating (adhesive layer) with a thickness of 50 μm. The coating was then placed in an oven and cured at 40° C. for 1 day. This curing allowed the curing reaction (crosslinking reaction) of the coating to proceed sufficiently. The release film was then peeled off to prepare a test piece (50×50 mm).
The dielectric constant (ε) was measured using a network analyzer 85071E-300 (manufactured by Agilent Technologies) by the split post dielectric resonator method (SPDR method) at a temperature of 23° C. and a frequency of 10 GHz.

(Cured product of adhesive composition prepared in Comparative Example 4)
A 38 μm-thick release polyethylene terephthalate film was prepared, and the adhesive composition was roll-coated on one surface of the film. The coated film was then placed in an oven and dried at 90° C. for 3 minutes to form a coating (adhesive layer) with a thickness of 50 μm. The coating was then placed in an oven and heat-treated at 80° C. for 1 hour. This heat treatment allowed the curing reaction (crosslinking reaction) of the coating to proceed sufficiently. The release film was then peeled off to prepare a test piece (50×50 mm).
The dielectric constant (ε) was measured using a network analyzer 85071E-300 (manufactured by Agilent Technologies) by the split post dielectric resonator method (SPDR method) at a temperature of 23° C. and a frequency of 10 GHz.

(Titanic acid compound (C))
A barium titanate sheet made of titanic acid compound (C) was polished to a thickness of 0.4 mm, then cut into a size of 1.5 mm x 4 mm, silver electrodes were provided on both sides, and the dielectric constant was measured electrically at a frequency of 1 MHz and at temperatures ranging from room temperature (25°C) to 500°C.

<Method for measuring peel strength>
(Cured Products of Adhesive Compositions Prepared in Examples 1 to 11 and Comparative Examples 5 to 9)
A rolled copper foil with a thickness of 35 μm was prepared, and the adhesive composition was roll-coated on its surface. The film with the coating was then placed in an oven and dried at 90° C. for 3 minutes to form a coating (adhesive layer) with a thickness of 50 μm, and a copper foil with an adhesive layer was obtained. Thereafter, a copper-clad laminate with a polyimide layer of 57 μm was superimposed so that the polyimide layer side was in surface contact with the surface of the adhesive layer of the copper foil with an adhesive layer, and laminated under conditions of a temperature of 120° C. and a pressure of 0.5 MPa. Next, this laminate (copper-clad laminate with polyimide/adhesive layer/copper foil) was heated and pressed for 30 minutes under conditions of a temperature of 150° C. and a pressure of 3 MPa to obtain a substrate for evaluating peel adhesion strength. The evaluation substrate was cut to prepare adhesion test pieces of a predetermined size. To evaluate the adhesiveness, the 90° peel adhesive strength (N/cm) was measured when peeling the rolled copper foil from the adhesive test piece at a temperature of 23° C. and a tensile speed of 50 mm/min in accordance with JIS C 6481:2015. The width of the adhesive test piece during the measurement was 10 mm.

(Cured products of adhesive compositions prepared in Comparative Examples 1 and 2)
A rolled copper foil with a thickness of 35 μm was prepared, and the adhesive composition was roll-coated on its surface. The film with the coating was then placed in an oven and dried at 90° C. for 3 minutes to form a coating (adhesive layer) with a thickness of 50 μm, and a copper foil with an adhesive layer was obtained. Thereafter, a copper-clad laminate with a polyimide layer of 57 μm was superposed so that the polyimide layer side was in surface contact with the surface of the adhesive layer of the copper foil with an adhesive layer, and laminated under conditions of a temperature of 120° C. and a pressure of 0.5 MPa. Next, this laminate (copper-clad laminate with polyimide/adhesive layer/copper foil) was heated and pressed for 3 minutes under conditions of a temperature of 130° C. and a pressure of 3 MPa, to obtain a substrate for evaluating peel adhesion strength. The evaluation substrate was cut to prepare adhesion test pieces of a predetermined size. To evaluate the adhesiveness, the 90° peel adhesive strength (N/cm) was measured when peeling the rolled copper foil from the adhesive test piece at a temperature of 23° C. and a tensile speed of 50 mm/min in accordance with JIS C 6481:2015. The width of the adhesive test piece during the measurement was 10 mm.

(Cured product of adhesive composition prepared in Comparative Example 3)
A rolled copper foil having a thickness of 35 μm was prepared, and the adhesive composition was roll-coated on its surface. The film with the coating was then placed in an oven and dried at 90° C. for 3 minutes to form a coating (adhesive layer) having a thickness of 50 μm, and a copper foil with an adhesive layer was obtained. Thereafter, a copper-clad laminate with a polyimide layer having a thickness of 57 μm was superposed so that the polyimide layer side was in surface contact with the surface of the adhesive layer of the copper foil with the adhesive layer, and lamination was performed under conditions of a temperature of 80° C., a pressure of 0.4 MPa, and a speed of 0.5 m/min. Next, the coating was placed in an oven and aged at 40° C. for one day to obtain a substrate for evaluation of peel adhesion strength. The evaluation substrate was cut to prepare adhesion test pieces of a predetermined size. To evaluate the adhesiveness, the 90° peel adhesive strength (N/cm) was measured when peeling the rolled copper foil from the adhesive test piece at a temperature of 23° C. and a tensile speed of 50 mm/min in accordance with JIS C 6481:2015. The width of the adhesive test piece during the measurement was 10 mm.

(Cured product of adhesive composition prepared in Comparative Example 4)
A rolled copper foil having a thickness of 35 μm was prepared, and the adhesive composition was roll-coated on its surface. The film with the coating was then placed in an oven and dried at 90° C. for 3 minutes to form a coating (adhesive layer) having a thickness of 50 μm, and a copper foil with an adhesive layer was obtained. Thereafter, a copper-clad laminate with a polyimide layer having a thickness of 57 μm was superposed so that the polyimide layer side was in surface contact with the surface of the adhesive layer of the copper foil with the adhesive layer, and lamination was performed under conditions of a temperature of 80° C., a pressure of 0.4 MPa, and a speed of 0.5 m/min. Next, the coating was placed in an oven and heat-treated at 80° C. for 1 hour to obtain a substrate for evaluation of peel adhesion strength. The evaluation substrate was cut to prepare adhesion test pieces of a predetermined size. To evaluate the adhesiveness, the 90° peel adhesive strength (N/cm) was measured when peeling the rolled copper foil from the adhesive test piece at a temperature of 23° C. and a tensile speed of 50 mm/min in accordance with JIS C 6481:2015. The width of the adhesive test piece during the measurement was 10 mm.

<Method of measuring coatability (liquid viscosity)>
The liquid viscosity of the adhesive composition was measured under the following conditions using a TVE-20H viscometer (salt water/plate type, manufactured by Toki Sangyo Co., Ltd.), which is an E-type viscometer (cone-plate type viscometer). If the liquid viscosity was 30,000 mPa·s or less, it was determined that the coatability was good.
- Measurement conditions -
Cone shape: angle 3° x R9.7', radius 20mm
Temperature: 25℃±0.5℃

<How to measure flexibility>
(Tensile test)
Test pieces were prepared in the same manner as in the measurement of the electrical properties (dielectric constant and dielectric tangent) described above, and tensile tests were performed using Shimadzu Corporation's "Autograph AG-Xplus" with a fixture distance of 40 mm, a gauge distance of 20 mm, a tensile speed of 5 mm/min, and 23°C. The strain was measured in real time using a camera. The strain from the origin to the yield point was divided into 10 parts, and the slope of the tangent in each section was calculated by the least squares method to calculate the tensile modulus.
(Bending test)
Test pieces prepared in the same manner as in the tensile test were wrapped around an iron bar having a diameter of 2 mm in a bending resistance test (cylindrical mandrel method) conforming to JIS K5600-5-1:2018, and visually observed for the occurrence of cracks. Test pieces in which no cracks were observed were rated as "○", and those in which cracks were observed were rated as "×".

The compositions of the adhesive compositions of Examples 1 to 11 and Comparative Examples 1 to 9 are shown in Tables 1 and 2, and the results of the various measurements described above for the adhesive compositions of Examples 1 to 11 and Comparative Examples 1 to 9 are shown in Table 3.

(Notes to Table 1)
- Values in the table: parts by weight - The numbers in parentheses for the filler column are the volume percent of the solid content

(Notes to Table 2)
Values in the table: parts by weight. The figures in parentheses for the filler column are the volume % of the solid content.
"Dioctyltin dilaurate" is omitted from Table 2.

(Notes to Table 3)
The "-" in Comparative Example 1 means that the adhesive composition solidified 15 minutes after application, and the coatability (liquid viscosity) could not be measured.

In Comparative Example 5, which did not contain a titanic acid compound as a filler but contained silica particles, the dielectric constant of the cured product could not be increased to a desired level. The same was true for Comparative Example 6, which contained boron nitride as a filler, and Comparative Example 9, which did not contain a filler.
Furthermore, even if a titanic acid compound is blended as a filler, if the amount is small, the dielectric constant of the cured product cannot be increased to a desired level (Comparative Example 7).On the other hand, if the amount of titanic acid compound blended is too large, the liquid viscosity increases, resulting in poor handling properties and poor peel strength of the cured product (Comparative Example 8).
Furthermore, even if a desired amount of titanic acid compound was blended as a filler, when the base resin (matrix resin) did not contain a polyamide compound and the base resin was only an epoxy resin, and a curing agent was used to cause a reaction, the curing reaction proceeded too quickly, resulting in extremely poor handling properties, and the obtained cured product was hard and had poor flexibility (Comparative Examples 1 and 2).
In addition, when an epoxy resin was not used as the base resin, but instead the base resin was made of a polyolefin resin or an acrylic polymer having reactive groups, and these were reacted with a polyisocyanate to cause a curing reaction, the dielectric constant could not be increased to the desired level even when a titanic acid compound was added, and the peel strength was also poor (Comparative Examples 3 and 4).
In contrast, all of the adhesive compositions defined in the present invention had excellent handleability, and the resulting cured products fully exploited the high dielectric properties of the titanic acid compound, exhibited a high dielectric constant, and the cured products were flexible and had excellent adhesion to the adherend (Examples 1 to 11).

Claims (9)

A composition comprising a polyamide compound (A), an epoxy resin (B), and a titanic acid compound (C),
The amine value of the polyamide compound (A) is 10 mgKOH/g or less,
the content of the titanic acid compound (C) is 60 to 610 parts by mass per 100 parts by mass of the polyamide compound (A);
An adhesive composition, wherein the dielectric constant of the cured product after the curing reaction is 4.0 or more. The adhesive composition according to claim 1, wherein the titanic acid compound (C) has a dielectric constant of 100 or more. The adhesive composition according to claim 1 or 2, wherein the titanate compound (C) is at least one of barium titanate, strontium titanate, and calcium titanate. The adhesive composition according to any one of claims 1 to 3, which contains a silane coupling agent. The adhesive composition according to any one of claims 1 to 4, wherein the acid value of the polyamide compound (A) is 0.1 to 10 mgKOH/g. The adhesive composition according to any one of claims 1 to 5, wherein the epoxy resin (B) has three or more epoxy groups in one molecule. The adhesive composition according to any one of claims 1 to 6, wherein the epoxy resin (B) is a cresol novolac type epoxy resin. The adhesive composition according to any one of claims 1 to 7, wherein the content of the epoxy resin (B) is 2 to 25 parts by mass per 100 parts by mass of the content of the polyamide compound (A). A laminate with an adhesive layer comprising a substrate film and an adhesive layer made of the adhesive composition according to any one of claims 1 to 8.