JP7763193B2 - adhesive composition - Google Patents

Description

The present invention relates to an adhesive composition. More specifically, it relates to an adhesive composition that can be used for bonding electronic components, etc.

BACKGROUND ART As electronic devices become smaller and lighter, the adhesive applications for electronic components and the like are becoming more diverse, and the demand for laminates with adhesive layers is increasing.
Furthermore, flexible printed circuit boards (hereinafter also referred to as FPCs), which are electronic components, are required to process large amounts of data at high speed, and are becoming increasingly compatible with high frequencies. The increased frequency of FPCs requires lower dielectric constants for their components, and low-dielectric substrate films and low-dielectric adhesives are being developed. In particular, to efficiently transmit signals with frequencies in the 6 GHz and 28 GHz bands used in fifth-generation mobile communication systems (hereinafter also referred to as 5G), substrate films and adhesives with low loss even in the 28 GHz millimeter-wave band are becoming increasingly important.

However, because the polarity of the main molecule of low-dielectric adhesives is low, they are less likely to exhibit adhesion (adhesion) with base films and other components related to electronic parts, and low-dielectric base films similarly tend to exhibit poor adhesion (adhesion) with adhesives, so there is a demand for improved adhesion.
Therefore, in order to meet the requirement for high adhesiveness while maintaining good electrical properties (low dielectric constant and low dielectric dissipation factor), a laminate has been proposed which uses an adhesive composition containing a carboxyl group-containing styrene-based elastomer (A) and an epoxy resin (B), and which comprises an adhesive layer made of the adhesive composition and a substrate film (see, for example, Patent Document 1).

International Publication No. 2016/017473

Low-dielectric adhesives also have the problem of being prone to resin flow due to the low polarity of the main molecule.
However, from the viewpoint of obtaining an adhesive composition that prevents resin flow, the above-mentioned Patent Document 1 cannot be said to be satisfactory, and there is room for improvement.

The present invention therefore aims to provide an adhesive composition for forming a low-dielectric adhesive layer that has good electrical properties (dielectric properties) compatible with 5G, exhibits good adhesion even to low-dielectric substrate films with poor adhesion, and combines heat resistance and chemical resistance (solvent resistance), and that can also suppress resin flow.

As a result of extensive research into solving the above-mentioned problems, the inventors discovered that by using an adhesive composition containing a modified styrene-based elastomer as the resin composition that is the main component of the adhesive composition and adjusting the melt flow rate (MFR) of the components other than the curing agent (resin composition) of the adhesive composition to a desired value, an adhesive composition containing a resin composition that exhibits the specified MFR can solve the above-mentioned problems, which led to the completion of the present invention.

The present invention includes the following aspects.
[1] A resin composition containing a modified styrene-based elastomer and a curing agent,
the content of the modified styrene-based elastomer relative to 100 parts by mass of the resin composition is 25 parts by mass or more,
The resin composition has a melt flow rate (200°C, load 21.60 kg) of 40 g/10 min or less.
[2] The adhesive composition according to [1], wherein the resin composition has a melt flow rate (200°C, load 21.60 kg) of 0.1 g/10 min or more.
[3] The adhesive composition according to [1] or [2], wherein the content of the curing agent per 100 parts by mass of the adhesive composition is 25 parts by mass or less.
[4] The adhesive composition according to any one of [1] to [3], wherein the modified styrene-based elastomer is a styrene-based elastomer containing a carboxy group.
[5] The adhesive composition according to any one of [1] to [3], wherein the modified styrene-based elastomer is a styrene-based elastomer containing an amino group.
[6] The adhesive composition according to any one of [1] to [5], wherein the resin composition contains at least two or more types of styrene-based elastomers.
[7] The adhesive composition according to any one of [1] to [6], wherein the curing agent contains an epoxy resin.
[8] The adhesive composition according to [7], wherein the curing agent contains an epoxy-modified styrene-butadiene copolymer.
[9] The adhesive composition according to any one of [1] to [8], wherein the resin composition contains a styrene-based elastomer having a weight average molecular weight (Mw) of 100,000 to 500,000.
[10] The adhesive composition according to any one of [1] to [9], wherein the resin composition contains a filler.
[11] The adhesive composition according to any one of [1] to [10], wherein the curing agent contains an organic peroxide.
[12] An adhesive layer obtained by curing the adhesive composition according to any one of [1] to [11], wherein the adhesive layer has a relative dielectric constant of 3 or less and a dielectric loss tangent of 0.005 or less, measured at a frequency of 28 GHz.
[13] A base film,
A laminate having an adhesive layer made of the adhesive composition according to any one of [1] to [11], or the adhesive layer according to [12].
[14] The laminate according to [13], wherein the substrate film contains a polyether ether ketone (PEEK) resin.
[15] A coverlay film with an adhesive layer comprising the laminate according to [13] or [14].
[16] A copper-clad laminate comprising the laminate according to [13] or [14].
[17] A printed wiring board comprising the laminate according to [13] or [14].
[18] A shielding film comprising the laminate according to [13] or [14].
[19] A printed wiring board with a shielding film comprising the laminate according to [13] or [14].

The present invention provides an adhesive composition for forming a low-dielectric adhesive layer that has good electrical properties (dielectric properties) compatible with 5G, exhibits good adhesion even to low-dielectric substrate films with poor adhesion, and combines heat resistance and chemical resistance (solvent resistance), and can also suppress resin flow.

The adhesive composition of the present invention, a laminate including an adhesive layer made of the adhesive composition, and electronic component-related components including the laminate are described in detail below. However, the description of the constituent elements described below is an example of one embodiment of the present invention and is not intended to be limiting.

(Adhesive composition)
The adhesive composition of the present invention contains a resin composition containing a modified styrene-based elastomer and a curing agent.
The content of the modified styrene-based elastomer relative to 100 parts by mass of the resin composition is 25 parts by mass or more.
The resin composition has a melt flow rate (200° C., load 21.60 kg) of 40 g/10 min or less.

The adhesive composition of the present invention may contain other components as needed.
The adhesive composition of the present invention exhibits good adhesion even though it is a low-dielectric adhesive composition, and is also excellent in heat resistance and chemical resistance (solvent resistance), and can also suppress resin flow.

<Resin composition>
The resin composition of the adhesive composition contains a styrene-based elastomer.
The resin composition may contain, in addition to the styrene-based elastomer, a resin component other than the styrene-based elastomer and other components.

<<Styrene-based elastomer>>
The styrene elastomer is a copolymer mainly composed of block and random structures of an unsaturated hydrocarbon and an aromatic vinyl compound, and a hydrogenated product thereof.
The low number of highly polar bonding groups in the molecule gives the composition good electrical properties (dielectric properties). Another advantage is that, compared to other types of elastomers, the molecular weight can be easily controlled, allowing for stable production of adhesive compositions with consistent properties.
Examples of aromatic vinyl compounds include styrene, t-butylstyrene, α-methylstyrene, divinylbenzene, 1,1-diphenylethylene, N,N-diethyl-p-aminoethylstyrene, vinyltoluene, etc. Examples of unsaturated hydrocarbons include ethylene, propylene, butadiene, isoprene, isobutene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, etc.
Specific examples of the styrene-based elastomer include a styrene-butadiene block copolymer, a styrene-ethylene propylene block copolymer, a styrene-butadiene-styrene block copolymer, a styrene-isoprene-styrene block copolymer, a styrene-ethylenebutylene-styrene block copolymer, and a styrene-ethylene propylene-styrene block copolymer.
Among the above copolymers, styrene-ethylenebutylene-styrene block copolymers and styrene-ethylenepropylene-styrene block copolymers are preferred from the viewpoints of being able to impart adhesive properties and electrical properties (dielectric properties) to the adhesive composition, and being able to relatively easily control the molecular structure and adjust the properties of the adhesive composition. Furthermore, the mass ratio of styrene/ethylenebutylene in the styrene-ethylenebutylene-styrene block copolymer and the mass ratio of styrene/ethylenepropylene in the styrene-ethylenepropylene-styrene block copolymer are preferably 10/90 to 60/40, and more preferably 30/70 to 60/40. When the mass ratio is 10/90 to 60/40, an adhesive composition with excellent adhesive properties can be obtained. When the mass ratio is 30/70 to 60/40, the interaction due to the skeleton derived from the aromatic vinyl compound is increased, improving compatibility with other resins. Furthermore, the increased cohesive force can also suppress resin flow.

The weight-average molecular weight (Mw) of the styrene-based elastomer is preferably 100,000 to 500,000, with Mn being preferably 100,000 to 500,000. If the weight-average molecular weight is equal to or greater than the lower limit, excellent adhesive properties can be achieved. Furthermore, the increased frequency of entanglement between molecules controls the fluidity of the resin, thereby suppressing resin flow. If the weight-average molecular weight is equal to or less than the upper limit, the viscosity does not increase too much when dissolved in a solvent, making it easier to apply. Furthermore, compatibility with other resins, such as curing agents, is improved.
The weight average molecular weight is a value obtained by measuring the molecular weight by gel permeation chromatography (hereinafter also referred to as "GPC") and converting it into polystyrene equivalent.
The resin composition according to the present invention may contain two or more types of styrene-based elastomers.
For example, by using a modified styrene-based elastomer that has good surface adhesion to the adherend in combination with an unmodified styrene-based elastomer that allows the adhesive composition's elastic modulus to be adjusted for each temperature, it becomes possible to achieve high adhesion and control of fluidity.
In particular, modified styrene elastomers and unmodified styrene elastomers have similar molecular structures and are therefore highly compatible, and mixing these makes it easy to control adhesion and MFR.

<<<Modified styrene-based elastomer>>>
The resin composition that is the main component of the adhesive composition contains a modified styrene-based elastomer.
Modified styrene elastomers are copolymers primarily consisting of block and random structures of unsaturated hydrocarbons and aromatic vinyl compounds, and hydrogenated products thereof, to which substituents such as carboxyl groups, amino groups, epoxy groups, isocyanate groups, acryloyl groups, hydroxyl groups, mercapto groups, imide groups, and alkoxysilyl groups have been introduced.
The content of the modified styrene-based elastomer is 25 parts by mass or more relative to 100 parts by mass of the resin composition. When the content of the modified styrene-based elastomer is 25 parts by mass or more, adhesion due to the interaction of the substituents can be exhibited, and heat resistance and the like can be exhibited by sufficiently increasing the crosslink density.
Examples of modified styrene elastomers include carboxyl group-containing styrene elastomers and amino group-containing styrene elastomers, which will be described below.

<<<<<Carboxy group-containing styrene elastomers>>>>
Carboxy group-containing styrene elastomers have high adhesiveness, can impart flexibility to the cured product, and are effective as a component that imparts good electrical properties.
The adhesive composition contains a carboxyl group-containing styrene elastomer, which allows the flexible adhesive composition to conform sufficiently to the surface of the adherend, even if the adherend has good electrical properties and low polarity, such as a substrate film or metal foil, and the highly polar carboxyl group can exhibit adhesion, thereby improving the adhesion of the adhesive layer. Furthermore, because the carboxyl group-containing styrene elastomer is reactive, reacting it with a curing agent also improves the heat resistance and chemical resistance of the adhesive layer.
Furthermore, the inclusion of a carboxy group improves the dispersibility of the filler in the dispersion liquid.
The carboxyl group-containing styrene elastomer is a copolymer mainly consisting of block and random structures of unsaturated hydrocarbons and aromatic vinyl compounds, and a hydrogenated product thereof modified with an unsaturated carboxylic acid.
Specific examples of the types of aromatic vinyl compounds and unsaturated hydrocarbons and styrene-based elastomers are as described above in the section <<Styrene-based elastomers>>.

The modification of a carboxyl group-containing styrene elastomer can be carried out, for example, by copolymerizing an unsaturated carboxylic acid during polymerization of the styrene elastomer, or by heating and kneading the styrene elastomer and the unsaturated carboxylic acid in the presence of an organic peroxide.
Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid, maleic anhydride, and itaconic anhydride.
The amount of modification with the unsaturated carboxylic acid is preferably 0.1 to 10% by mass.
The acid value of the carboxyl group-containing styrene-based elastomer is preferably 0.1 to 25 mgKOH/g, and more preferably 0.5 to 23 mgKOH/g. When this acid value is 0.1 mgKOH/g or more, the adhesive composition cures sufficiently, and good adhesion and heat resistance are obtained. On the other hand, when the acid value is 30 mgKOH/g or less, the cohesive strength of the adhesive composition is suppressed, resulting in excellent adhesion and excellent electrical properties.

<<<<<Amino group-containing styrene elastomers>>>>
The inclusion of an amino group-containing styrene elastomer in the adhesive composition allows the amino group to exhibit strong interaction with the low-dielectric substrate film, increasing the reactivity of the adhesive composition and improving the adhesion of the adhesive layer. Furthermore, because the amino group-containing styrene elastomer is reactive, reacting it with a curing agent also improves the heat resistance and chemical resistance of the adhesive layer.
The amino group improves adhesion to metals.
The amino group-containing styrene elastomer is a copolymer mainly consisting of block and random structures of unsaturated hydrocarbons and aromatic vinyl compounds, and a hydrogenated product thereof, which is modified with an amine.
Specific examples of the types of aromatic vinyl compounds and unsaturated hydrocarbons and styrene-based elastomers are as described above in the section <<Styrene-based elastomers>>.

There are no particular limitations on the method for amine-modifying a styrene-based elastomer, and known methods can be used. Examples include a method of amine-modifying a (hydrogenated) block copolymer by polymerizing it using a polymerization initiator having an amino group, a method of amine-modifying a (hydrogenated) copolymer by using an unsaturated monomer having an amino group as a copolymerization raw material, and a method of amine-modifying a styrene-based elastomer containing a carboxyl group by reacting it with an amine modifier having two or more amino groups to form an amide structure or an imide structure.

From the viewpoint of ensuring good electrical properties (low dielectric constant, low dielectric loss) and adhesion (adhesion) of the adhesive composition, the total nitrogen content in the amino group-containing styrene-based elastomer is preferably 50 to 5000 ppm, and more preferably 200 to 3000 ppm. When the total nitrogen content is equal to or greater than the above lower limit, excellent adhesion can be achieved. When the total nitrogen content is equal to or less than the above upper limit, excellent electrical properties can be achieved.
The total nitrogen content in the amino group-containing styrene elastomer can be determined in accordance with JIS-K2609 using a trace nitrogen analyzer ND-100 (manufactured by Mitsubishi Chemical Corporation).

Only one type of modified styrene-based elastomer may be used, or two or more types may be contained.

<<Other resin components and other components>>
The resin component according to the present invention may contain, in addition to the styrene elastomer, a resin component other than the styrene elastomer and other components.

<<<Resin components other than styrene-based elastomers>>>
The resin composition according to the present invention may contain, for example, a thermoplastic resin other than the styrene-based elastomer to an extent that the function of the adhesive composition is not affected.
Examples of the other thermoplastic resins include phenoxy resins, polyamide resins, polyimide resins, bismaleimide resins, polyester resins, polycarbonate resins, polyphenylene oxide resins, polyurethane resins, polyacetal resins, polyethylene-based resins, polypropylene-based resins, polybutadiene-based resins, polyvinyl-based resins, fluorine-based resins, etc. These thermoplastic resins may be used alone or in combination of two or more.
Depending on the compatibility between the styrene elastomer and the other thermoplastic resins, the resin flow and MFR values described below may change, and these can be adjusted by the compounding method.

<<<Other ingredients>>>
The resin composition according to the present invention may contain, for example, other components in addition to the styrene-based elastomer.
Other components that may be included include, for example, fillers, fibers, tackifiers, flame retardants, heat aging inhibitors, leveling agents, defoamers, inorganic fillers, and pigments, to the extent that they do not affect the functionality of the adhesive composition.
Depending on the dispersibility of the styrene elastomer with other components, the resin flow and MFR values described below may change, and this can be adjusted by the compounding and dispersion methods.

<<<<<Filler>>>>
The adhesive composition of the present invention preferably contains a filler.
As the filler according to the present invention, inorganic fillers are preferred from the viewpoint of heat resistance and control of the mechanical properties of the adhesive composition, and as inorganic fillers, silicon-based inorganic fillers and boron nitride are preferred from the viewpoint of electrical properties. Furthermore, as silicon-based inorganic fillers, for example, mica and talc are preferred, which enable control of the mechanical properties of the adhesive composition even with a small amount and also have excellent electrical properties.
Furthermore, as the filler according to the present invention, an organic filler is preferred from the viewpoint of, for example, dispersibility and brittleness, and as the organic filler, a styrene-based spherical filler is preferred from the viewpoint of electrical properties, and a styrene-based hollow filler is more preferred.
Furthermore, as the filler according to the present invention, for example, an engineering plastic resin filler is preferred from the viewpoint of dielectric properties, and as the engineering plastic resin filler, fluororesin powder, liquid crystal polymer powder, and syndiotactic polystyrene powder are preferred from the viewpoint of chemical resistance.
These may be used alone or in combination of two or more.
The content of the filler contained in the adhesive composition of the present invention is preferably 0.5 to 25 parts by volume, and more preferably 1 to 15 parts by volume, per 100 parts by volume of the resin composition.
The shape of the filler is not particularly limited and can be appropriately selected depending on the purpose. For example, the inorganic filler may be a spherical inorganic filler or a non-spherical inorganic filler, but from the viewpoint of the coefficient of thermal expansion (CTE) and film strength, a non-spherical inorganic filler is preferred. The shape of the non-spherical inorganic filler may be any three-dimensional shape other than a spherical shape (approximately perfect sphere), and examples thereof include plate-like, scale-like, columnar, chain-like, and fibrous shapes. Among these, from the viewpoint of the coefficient of thermal expansion (CTE) and film strength, plate-like and scale-like inorganic fillers are preferred, and plate-like inorganic fillers are more preferred.

Examples of the above fibers include carbon fiber, glass fiber, aramid fiber, cellulose fiber, etc. These fibers may be used alone or in combination of two or more types.

Examples of the tackifier include coumarone-indene resin, terpene resin, terpene-phenol resin, rosin resin, p-t-butylphenol-acetylene resin, phenol-formaldehyde resin, xylene-formaldehyde resin, petroleum-based hydrocarbon resin, hydrogenated hydrocarbon resin, and turpentine-based resin. These tackifiers may be used alone or in combination of two or more.

The above flame retardant may be either an organic flame retardant or an inorganic flame retardant. Examples of organic flame retardants include phosphorus-based flame retardants such as melamine phosphate, melamine polyphosphate, guanidine phosphate, guanidine polyphosphate, ammonium phosphate, ammonium polyphosphate, ammonium amido phosphate, ammonium amido polyphosphate, carbamate phosphate, carbamate polyphosphate, aluminum trisdiethylphosphinate, aluminum trismethylethylphosphinate, aluminum trisdiphenylphosphinate, zinc bisdiethylphosphinate, zinc bismethylethylphosphinate, zinc bisdiphenylphosphinate, titanyl bisdiethylphosphinate, titanium tetrakisdiethylphosphinate, titanyl bismethylethylphosphinate, titanium tetrakismethylethylphosphinate, titanyl bisdiphenylphosphinate, and titanium tetrakisdiphenylphosphinate; nitrogen-based flame retardants such as triazine-based compounds such as melamine, melam, and melamine cyanurate, cyanuric acid compounds, isocyanuric acid compounds, triazole-based compounds, tetrazole compounds, diazo compounds, and urea; and silicon-based flame retardants such as silicone compounds and silane compounds. Examples of inorganic flame retardants include metal hydroxides such as aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, barium hydroxide, and calcium hydroxide; metal oxides such as tin oxide, aluminum oxide, magnesium oxide, zirconium oxide, zinc oxide, molybdenum oxide, and nickel oxide; zinc carbonate, magnesium carbonate, barium carbonate, zinc borate, and hydrated glass. Two or more of these flame retardants can be used in combination.

The above-mentioned heat aging inhibitors include 2,6-di-tert-butyl-4-methylphenol, n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate, tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane, pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenol, triethylene glycol-bis[3 phenol-based antioxidants such as 3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate; 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-tert-butylphenyl)phosphite. These may be used alone or in combination of two or more.

Examples of the inorganic filler include powders made of titanium oxide, aluminum oxide, zinc oxide, carbon black, silica, copper, silver, etc. These may be used alone or in combination of two or more.

<<Characteristics of Resin Composition>>
The melt flow rate (MFR) of the resin composition is 40 g/10 min or less under the measurement conditions of 200° C. and a load of 21.60 kg.
Here, MFR is a value that indicates the fluidity of a resin composition, and the larger the value, the higher the fluidity.
The MFR is measured using an extrusion type plastometer specified in JIS K6760, and the measurement method conforms to the method specified in JIS K7210 (1976). In the present invention, the measurement is performed under the conditions of 200°C and a load of 21.6 kg.
The temperature condition for measuring MFR is 200°C, taking into consideration that the thermocompression bonding temperature generally set when mounting the adhesive layer is 150 to 200°C and that the higher the temperature, the more likely resin flow occurs.The load condition for measurement is 21.60 kg, a standard load close to the thermocompression bonding pressure of 2 to 3 MPa generally set when mounting the adhesive layer.
The MFR of the resin composition is preferably 40 g/10 min or less, more preferably 10 g/10 min or less, even more preferably 5 g/10 min or less, and even more preferably 3 g/10 min or less, under measurement conditions of 200°C and a load of 21.60 kg. Furthermore, the MFR is more preferably 0.1 g/10 min or more. An MFR of 40 g/10 min or less can suppress resin flow. An MFR of 10 g/10 min or less can suppress resin flow even when the amount of curing agent is increased, and heat resistance can be improved by further increasing the crosslink density. An MFR of less than the above upper limit can further reduce resin flow. An MFR of 0.1 g/10 min or more can conform to unevenness in the pattern of a printed wiring board.

<Curing agent>
The curing agent reacts with the resin composition to increase the crosslink density of the resin composition, thereby enabling the adhesive to exhibit high adhesion to the adherend and heat resistance of the cured product. The curing agent is composed of a crosslinking agent that reacts with the resin composition to form a crosslinked structure, and may optionally contain a reaction accelerator that accelerates the reaction between the resin composition and the crosslinking agent.
The content of the curing agent is preferably 25 parts by mass or less per 100 parts by mass of the adhesive composition (the sum of the resin composition and the curing agent), from the viewpoint of being within a suitable range for enabling the effect of the MFR of the resin composition to be exerted and enabling the performance of the adhesive to be exerted.
The content of the curing agent is more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less. If the content of the curing agent is equal to or less than the above upper limit, the resin flow can be further controlled to be small, and the adhesion and dielectric properties can be improved. Furthermore, from the viewpoint of sufficient crosslinking and the development of adhesiveness, heat resistance, etc., the content of the curing agent is more preferably 0.05 parts by mass or more.

<<Crosslinking agent>>
Examples of crosslinking agents include epoxy resins, isocyanate resins, phenolic resins, cyanate resins, polyamides, polyurethanes, organic peroxides, silane coupling agents, benzoxazines, allyl compounds, and propenyl compounds. The crosslinking agent can be appropriately selected depending on the purpose, but from the viewpoint of being able to cure the adhesive composition at a moderate curing temperature and exhibit heat resistance, epoxy resins are preferred. From the viewpoint of being able to improve the crosslinking density of the adhesive composition without containing highly polar functional groups and further improve the adhesion (adhesion), heat resistance, and chemical resistance of the adhesive layer, organic peroxides are preferred. Only one type of crosslinking agent may be used, or two or more types may be contained.

<<<Epoxy resin>>>
The epoxy resin is a component that reacts with the carboxy group in the carboxy group-containing styrene-based elastomer or the amino group in the amino group-containing styrene-based elastomer, thereby imparting high adhesion to the adherend and heat resistance to the cured adhesive.

Examples of epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, and hydrogenated versions thereof; glycidyl ester-based epoxy resins such as phthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, p-hydroxybenzoic acid glycidyl 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 ester, and the like. Examples of epoxy resins that can be used include, but are not limited to, glycidyl ether-based epoxy resins such as glycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, tetraphenylglycidyl ether ethane, triphenylglycidyl ether ethane, polyglycidyl ether of sorbitol, and polyglycerol polyglycidyl ether; glycidyl amine-based epoxy resins such as triglycidyl isocyanurate and tetraglycidyldiaminodiphenylmethane; and linear aliphatic epoxy resins such as epoxidized polybutadiene and epoxidized soybean oil. Additionally, novolac-type epoxy resins such as xylene structure-containing novolac epoxy resins, naphthol novolac-type epoxy resins, phenol novolac epoxy resins, o-cresol novolac epoxy resins, and bisphenol A novolac epoxy resins can also be used.
These epoxy resins may be used alone or in combination of two or more.

Specific examples of novolac-type epoxy resins include "YX7700" (xylene structure-containing novolac-type epoxy resin) manufactured by Mitsubishi Chemical Corporation, "NC7000L" (naphthol novolac-type epoxy resin) manufactured by Nippon Kayaku Co., Ltd., "ESN485" (naphthol novolac-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd., "N-690" (cresol novolac-type epoxy resin) manufactured by DIC Corporation, and "N-695" (cresol novolac-type epoxy resin) manufactured by DIC Corporation.

It is more preferable that the epoxy resin is an epoxy-modified resin. This is because it has good compatibility with the base resin (resin composition) containing a styrene-based elastomer, and can exert a resin flow suppression effect without compromising the effect of adjusting the MFR of the base resin.

<<<<Epoxy-modified resin>>>>
The epoxy-modified resin is preferably an epoxy-modified resin having a structure represented by the following formula (1).
(At least one of ^R1 and ^R2 is a substituent other than H, and at least one of ^R3 and ^R4 is a substituent other than H.)
The epoxy-modified resin having the structure represented by the above formula (1) has a faster reaction rate of the epoxy structure with the carboxy group in the carboxy group-containing styrene-based elastomer or the amino group in the amino group-containing styrene-based elastomer, or of self-polymerization, compared to ordinary epoxy resins, and is therefore effective as a component that imparts high adhesion to adherends and heat resistance to the cured adhesive.

A preferred embodiment of the epoxy-modified resin is an epoxy-modified resin having a structure represented by the following formula (2):

( ^R5 and ^R6 each independently represent hydrogen or an alkyl group having 10 or less carbon atoms. When a plurality of structures represented by the above formula (2) are present in the epoxy-modified resin, ^R5 in each formula (2) may be the same or different, and ^R6 in each formula (2) may be the same or different. * represents a bonding group.)
From the viewpoint of reducing steric hindrance near the epoxy group and allowing the reaction to proceed sufficiently, it is more preferable that R ⁵ and R ⁶ in the above formula (2) are both hydrogen.

It is preferable that the epoxy-modified resin contains unsaturated bonds other than aromatic rings, such as olefin skeletons or vinyl groups. Unsaturated bonds other than aromatic rings, such as olefin skeletons or vinyl groups, can be incorporated into reactions involving epoxy groups to accelerate the reaction rate and increase crosslink density. As a result, heat resistance and chemical resistance can be improved even with small amounts added. Furthermore, unsaturated bonds other than aromatic rings can be crosslinked by radical polymerization, increasing the crosslink density of the epoxy-modified resin and improving heat resistance and chemical resistance.

A preferred embodiment of the epoxy-modified resin is an epoxy-modified resin having a structure represented by the following formula (3):

( ^R7 and ^R8 each independently represent hydrogen or an alkyl group having 10 or less carbon atoms. When a plurality of structures represented by the above formula (3) are present in the epoxy-modified resin, ^R7 in each formula (3) may be the same or different, and ^R8 in each formula (3) may be the same or different. * represents a bonding group.)
In the above formula (3), it is more preferable that R ⁷ and R ⁸ are both hydrogen.

The epoxy-modified resin is preferably an epoxy-modified resin having a structure represented by the above formula (1) and a structure represented by the above formula (3), and more preferably an epoxy-modified resin having a structure represented by the above formula (2) and a structure represented by the above formula (3).

Preferred embodiments of the epoxy-modified resin include epoxy-modified resins having at least one of the structures represented by formula (4) and formula (5) below. It is also preferable for the resin to have both the structure represented by formula (4) and the structure represented by formula (5) below.

( ^R9 and ^R10 each independently represent hydrogen or an alkyl group having 10 or less carbon atoms. When a plurality of structures represented by the above formula (4) are present in the epoxy-modified resin, ^R9 in each formula (4) may be the same or different, and ^R10 in each formula (4) may be the same or different. * represents a bonding group.)
In the above formula (4), it is more preferable that R ⁹ and R ¹⁰ are both hydrogen.

(R ¹¹ and R ¹² each independently represent hydrogen or an alkyl group having 10 or less carbon atoms. When a plurality of structures represented by the above formula (5) are present in the epoxy-modified resin, R ¹¹ in each formula (5) may be the same or different, and R ¹² in each formula (5) may be the same or different. * represents a bonding group.)
In the above formula (5), it is more preferable that R ¹¹ and R ¹² are both hydrogen.

The epoxy-modified resin is preferably an epoxy-modified resin having a structure represented by the above formula (1) and at least one of the structures represented by the above formula (4) and the structure represented by the above formula (5), and is more preferably an epoxy-modified resin having a structure represented by the above formula (2) and at least one of the structures represented by the above formula (4) and the structure represented by the above formula (5).
Also preferred are epoxy-modified resins having a structure represented by the above formula (1) or (2), a structure represented by the above formula (3), and at least one of a structure represented by the above formula (4) and a structure represented by the above formula (5).

The epoxy-modified resin is preferably an epoxy-modified organic compound obtained by modifying an organic compound containing an unsaturated bond. By modifying the organic compound containing an unsaturated bond, the structure represented by formula (1) and the unsaturated bond can coexist in the molecule depending on the modification rate, and the effect of the unsaturated bond can be easily imparted to the reaction of the epoxy structure in addition to the olefin skeleton and aromatic ring such as a vinyl group.
Here, a method for modifying an organic compound containing an unsaturated bond into an epoxy-modified organic compound is effectively a reaction in which an epoxy skeleton is formed using a peroxide. Examples of the peroxide that can be used include percarboxylic acid compounds such as performic acid, peracetic acid, and perpropionic acid.
The epoxy-modified resin is preferably an epoxy-modified elastomer obtained by modifying an elastomer containing an unsaturated bond. The epoxy-modified elastomer can impart flexibility to the cured product and suppress the decrease in toughness of the cured product due to epoxy curing, thereby maintaining adhesion when the laminate is bent and preventing a decrease in heat resistance or chemical resistance.

Furthermore, the epoxy-modified resin is preferably a styrene-based elastomer.
In the epoxy-modified resin having the structure represented by the above formula (1) or (2), it is also preferable that the resin has a styrene structural unit in addition to the structures represented by the above formulas (3) to (5).
Since the epoxy-modified resin is a styrene-based elastomer as well as the styrene-based elastomer contained in the adhesive resin composition of the present invention, compatibility is improved when the two are mixed, and the reaction with the carboxy group in the carboxy group-containing styrene-based elastomer and the amino group in the amino group-containing styrene-based elastomer can proceed efficiently.

Examples of epoxy-modified resins include alicyclic epoxy compounds having an alicyclic epoxy group such as epoxycyclohexane, epoxidized polybutadiene, and epoxy compounds of styrene-butadiene block copolymers.
Among these, an epoxy compound of a styrene-butadiene block copolymer is more preferred. Because the styrene-butadiene block copolymer contains an unsaturated bond, the structure represented by formula (1) and the unsaturated bond can coexist in the molecule, and the effect of the unsaturated bond can be easily imparted to the reaction of the epoxy structure in addition to the effect of the olefin skeleton and aromatic ring such as the vinyl group.
As the epoxy-modified resin, commercially available epoxy compounds can also be used, and examples thereof include CELLOXIDE 2021P, CELLOXIDE 2081, CELLOXIDE 2000 (manufactured by Daicel Corporation), EPOLEAD GT401, EPOLEAD PB3600, EPOLEAD PB4700 (manufactured by Daicel Corporation), EPOFRIEND AT501, and EPOFRIEND CT310 (manufactured by Daicel Corporation).

The weight-average molecular weight (Mw) of the epoxy-modified resin is preferably 30,000 or more, and more preferably 50,000 or more. A weight-average molecular weight of 30,000 or more can suppress softening of the adhesive composition and prevent resin flow during heat and pressure bonding. A weight-average molecular weight of 50,000 or more improves the flexibility of the epoxy-modified resin and the toughness of the cured product. Furthermore, the weight-average molecular weight (Mw) of the epoxy-modified resin is preferably 200,000 or less, and more preferably 160,000 or less. A weight-average molecular weight of 200,000 or less further improves compatibility with styrene-based elastomers. A weight-average molecular weight of 160,000 or less can reduce the elastic modulus of the adhesive composition, allowing it to conform to the shape of the adherend.

<<<Organic peroxide>>>
The curing agent of the present invention preferably contains an organic peroxide, which can improve the crosslink density of the adhesive composition without containing a highly polar functional group, thereby further improving the adhesion (adhesion), heat resistance, and chemical resistance of the adhesive layer.
The unsaturated bonds and acryloyl groups contained in the resin composition, and unsaturated bonds other than aromatic rings, such as the olefin skeleton and vinyl group contained in the above-mentioned epoxy-modified resin, can crosslink the resin components even by radical polymerization using radicals generated from organic peroxides, thereby further improving the adhesion (adhesion), heat resistance, and chemical resistance of the adhesive layer.
Furthermore, the radicals generated from the organic peroxide have a high hydrogen abstraction ability and can crosslink hydrogenated styrene-based elastomers, so the crosslink density of the adhesive composition can be further improved without containing highly polar functional groups.

Examples of organic peroxides include benzoyl peroxide, lauroyl peroxide, t-butyl peroxypivalate, t-butylperoxyethylhexanoate, 1,1'-bis-(t-butylperoxy)cyclohexane, t-amylperoxy-2-ethylhexanoate, and t-hexylperoxy-2-ethylhexanoate.

Further examples of the coupling agent include silane-based 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, 3-isocyanatopropyltriethoxysilane, and imidazole silane; titanate-based coupling agents; aluminate-based coupling agents; and zirconium-based coupling agents. These may be used alone or in combination of two or more.

Examples of the benzoxazine include 6,6-(1-methylethylidene)bis(3,4-dihydro-3-phenyl-2H-1,3-benzoxazine) and 6,6-(1-methylethylidene)bis(3,4-dihydro-3-methyl-2H-1,3-benzoxazine), and two or more may be used in combination. The nitrogen atom of the oxazine ring may be bonded to a phenyl group, methyl group, cyclohexyl group, or the like. Specific examples of benzoxazine resins include "Benzoxazine F-a," "Benzoxazine P-d," and "Benzoxazine ALP-d" manufactured by Shikoku Chemicals Corporation, and "CR-276" and "BZ-LB-MDA" manufactured by Tohoku Chemical Industry Co., Ltd. These may be used alone or in combination of two or more.

Specific examples of the allyl compounds include "Resitop SBA02A," "Resitop APG-LC," "Resitop LVA01," "Resitop FATC809," and "Resitop FTC809AE," all manufactured by Gunei Chemical Industry Co., Ltd. These may be used alone or in combination of two or more.

Specific examples of the propenyl compounds include "Resitop BPN01S" manufactured by Gunei Chemical Industry Co., Ltd. These may be used alone or in combination of two or more.

<<Reaction accelerator>>
The reaction accelerator is used for the purpose of accelerating the reaction between a styrene elastomer, particularly a modified styrene elastomer, and a crosslinking agent. Examples of the reaction accelerator that can be used include a tertiary amine reaction accelerator, a tertiary amine salt reaction accelerator, and an imidazole reaction accelerator.

Tertiary amine reaction accelerators include benzyldimethylamine, 2-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol, tetramethylguanidine, triethanolamine, N,N'-dimethylpiperazine, triethylenediamine, 1,8-diazabicyclo[5.4.0]undecene, etc.

Examples of tertiary amine salt-based reaction accelerators include the formate, octylate, p-toluenesulfonate, o-phthalate, phenolate, or phenol novolac resin salt of 1,8-diazabicyclo[5.4.0]undecene, and the formate, octylate, p-toluenesulfonate, o-phthalate, phenolate, or phenol novolac resin salt of 1,5-diazabicyclo[4.3.0]nonene.

Imidazole-based reaction accelerators include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-methyl-4-ethylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2' 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, etc. These curing accelerators may be used alone or in combination of two or more.

(adhesive layer)
The adhesive layer according to the present invention comprises the adhesive composition according to the present invention.
The adhesive composition that forms the adhesive layer is allowed to cure.
The curing method is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include thermal curing.
The thickness of the adhesive layer is not particularly limited and can be appropriately selected depending on the purpose. For example, it is preferably 3 μm or more, more preferably 5 μm or more. It is also preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less. If the thickness of the adhesive layer is 3 μm or more, sufficient adhesion can be exerted, and if it is 5 μm or more, it can follow the steps of the pattern of the printed wiring board. If the thickness of the adhesive layer is 50 μm or less, the laminate can be made thinner, and if it is 30 μm or less, the resin flow can be accurately controlled.

<Method of manufacturing adhesive layer>
An adhesive layer can be produced by forming the adhesive composition into a film.
The adhesive composition can be produced by mixing a resin composition containing a modified styrene-based elastomer and a curing agent. The mixing method is not particularly limited as long as the adhesive composition is homogeneous. Since the adhesive composition is preferably used in the form of a solution or dispersion, a solvent is usually also used.
Examples of solvents include alcohols such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol, isobutyl alcohol, n-butyl alcohol, benzyl alcohol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, and diacetone alcohol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, and isophorone; aromatic hydrocarbons such as toluene, xylene, ethylbenzene, and mesitylene; esters such as methyl acetate, ethyl acetate, butyl acetate, ethylene glycol monomethyl ether acetate, and 3-methoxybutyl acetate; and aliphatic hydrocarbons such as hexane, heptane, cyclohexane, and methylcyclohexane. These solvents may be used alone or in combination of two or more. Adding a small amount of cyclohexanone to toluene, which is particularly capable of dissolving low-polarity resins, improves compatibility with curing agents and the like, allowing for a uniform adhesive layer.
When the adhesive composition is a solution or dispersion containing a solvent (resin varnish), coating onto a substrate film and formation of an adhesive layer can be carried out smoothly, and an adhesive layer of the desired thickness can be easily obtained.
When the adhesive composition contains a solvent, the solid content is preferably in the range of 3 to 80% by mass, more preferably 10 to 50% by mass, from the viewpoint of workability including the formation of the adhesive layer. When the solid content is 80% by mass or less, the viscosity of the solution is appropriate, and uniform application is facilitated.
In a more specific embodiment of the method for producing an adhesive layer, a resin varnish containing the adhesive composition and a solvent is applied to the surface of a substrate film to form a resin varnish layer, and then the solvent is removed from the resin varnish layer to form a B-stage adhesive layer. Here, the B-stage adhesive layer refers to an adhesive composition in an uncured state or a semi-cured state in which a portion of the adhesive composition has begun to cure, and refers to a state in which curing of the adhesive composition progresses further by heating or the like.
Here, the method for applying the resin varnish onto the substrate film is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include spraying, spin coating, dipping, roll coating, blade coating, doctor roll method, doctor blade method, curtain coating, slit coating, screen printing, inkjet method, and dispensing method.
The adhesive layer in the B-stage state can be further heated or the like to form a cured adhesive layer.

<Characteristics of the adhesive layer>
If the resin flow of the adhesive layer is large, during the mounting and manufacturing of coverlay films, printed wiring boards, and printed wiring boards with shielding films, the adhesive layer may flow out during thermocompression bonding, blocking the through-holes and preventing electrical continuity. Furthermore, in copper-clad laminates and shielding films, resin leakage from the edges during thermocompression bonding or uneven pressure distribution can cause wrinkled patterns due to resin flow. To prevent these defects, the resin flow of the adhesive layer made of the adhesive composition of the present invention is preferably 0.25 mm or less, and more preferably 0.10 mm or less. If the resin flow is 0.25 mm or less, the adhesive can be used in commonly used through-holes with a diameter of 0.5 mm or more. If the resin flow is 0.10 mm or less, the adhesive can be used in through-holes with a diameter of 0.2 to 0.5 mm, which are expected to be used in the future, and can also be expected to prevent wrinkles in copper-clad laminates and shielding films.
The adhesive layer obtained by curing the adhesive composition of the present invention preferably has a relative dielectric constant (εr) at a frequency of 28 GHz of 3 or less, more preferably 2.7 or less.The adhesive layer preferably has a dielectric loss tangent (tanδ) at a frequency of 28 GHz of 0.005 or less, more preferably 0.0025 or less, and even more preferably 0.002 or less.
If the dielectric constant is 3 or less and the dielectric dissipation factor is 0.005 or less, the material can be used in high-frequency FPC-related products that require strict electrical properties. Furthermore, if the dielectric constant is 2.7 or less and the dielectric dissipation factor is 0.0025 or less, the material can satisfy the electrical properties expected of components of 5G-compatible high-frequency FPC-related products, exhibiting electrical properties equivalent to those of LCP, making it suitable for use in 5G high-frequency FPC-related products that require strict electrical properties. Furthermore, if the dielectric dissipation factor is 0.002 or less, high-frequency FPC-related products with even improved transmission properties can be manufactured.

[Relative permittivity and dielectric loss tangent]
The dielectric constant and dielectric loss tangent of the adhesive layer can be measured using a network analyzer MS46122B (manufactured by Anritsu) and an open resonator Fabry-Perot DPS-03 (manufactured by KEYCOM) by the open resonator method at a temperature of 23°C and a frequency of 28 GHz.

(Laminate)
The laminate of the present invention comprises a substrate film and the above-described adhesive layer on at least one surface of the substrate film.

<Base film>
The substrate film used in the present invention can be selected depending on the application of the laminate. For example, when the laminate is used as a coverlay film or a copper-clad laminate (CCL), examples of the substrate film include polyimide films, polyether ether ketone films, polyphenylene sulfide films, aramid films, polyethylene naphthalate films, and liquid crystal polymer films. Among these, polyimide films, polyether ether ketone (PEEK) films, polyethylene naphthalate films, and liquid crystal polymer films are preferred from the viewpoints of adhesiveness and electrical properties.
The storage modulus of the base film at 200°C is preferably 1 x 10 ^or more. Resin flow is accompanied by deformation of the edges of the base film, and the greater the deformation, the greater the resin flow. Therefore, the higher the storage modulus at the compression bonding temperature, the more the resin flow of the adhesive composition can be suppressed.

Furthermore, when the laminate of the present invention is used as a bonding sheet, the base film must be a release film, such as polyethylene terephthalate film, polyethylene film, polypropylene film, silicone release-treated paper, polyolefin resin-coated paper, TPX (polymethylpentene) film, and fluorine-based resin film.

When the laminate of the present invention is used as a shielding film, the base film must be a film with electromagnetic wave shielding ability, such as a laminate of a protective insulating layer and a metal foil.

(Coverlay film)
A preferred embodiment of the laminate according to the present invention is a coverlay film.
When manufacturing an FPC, a laminate with an adhesive layer called a "coverlay film" is usually used to protect the wiring portion. This coverlay film has an insulating resin layer and an adhesive layer formed on the surface of the insulating resin layer.
For example, a coverlay film is a laminate in which the adhesive layer is formed on at least one surface of the base film, and peeling of the base film and the adhesive layer is generally difficult.
The thickness of the base film included in the coverlay film is preferably 5 to 100 μm, more preferably 5 to 50 μm, and even more preferably 5 to 30 μm. If the thickness of the base film is equal to or less than the upper limit, the coverlay film can be made thinner. If the thickness of the base film is equal to or greater than the lower limit, the printed wiring board can be easily designed and handled.
As a method for producing a coverlay film, for example, a resin varnish containing the adhesive composition and a solvent is applied to the surface of the base film to form a resin varnish layer, and then the solvent is removed from the resin varnish layer, thereby producing a coverlay film having a B-stage adhesive layer formed thereon.
The drying temperature when removing the solvent is preferably 40 to 250°C, more preferably 70 to 170°C.
Drying is carried out 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, known films such as polyethylene terephthalate film, polyethylene film, polypropylene film, silicone release-treated paper, polyolefin resin-coated paper, TPX film, and fluorine-based resin film can be used.
The coverlay film according to the present invention uses the low-dielectric adhesive composition of the present invention, which enables high-speed transmission in electronic devices and also provides excellent adhesion stability to electronic devices.

(Bonding sheet)
A preferred embodiment of the laminate according to the present invention is a bonding sheet.
The bonding sheet is a sheet in which the adhesive layer is formed on the surface of a release film (substrate film). The bonding sheet may also be in a form in which the adhesive layer is provided between two release films. When using the bonding sheet, the release film is peeled off. The release film may be the same as that described in the above (coverlay film) section.
The thickness of the substrate film included in the bonding sheet is preferably 5 to 100 μm, more preferably 25 to 75 μm, and even more preferably 38 to 50 μm. If the thickness of the substrate film is within the above range, the bonding sheet is easy to manufacture and easy to handle.
A bonding sheet can be produced, for example, by applying a resin varnish containing the adhesive composition and a solvent to the surface of a release film and drying it in the same manner as in the case of the coverlay film.
The bonding sheet according to the present invention uses the low-dielectric adhesive composition of the present invention, which enables high-speed transmission in electronic devices and also provides excellent adhesive stability to electronic devices.

(Copper-clad laminate (CCL))
A preferred embodiment of the laminate according to the present invention is a copper-clad laminate obtained by laminating a copper foil to the adhesive layer in the laminate according to the present invention.
A copper-clad laminate is formed by laminating a copper foil to the above-mentioned laminate, and is composed of, for example, a base film, an adhesive layer, and a copper foil in this order. The adhesive layer and the copper foil may be formed on both sides of the base film.
The adhesive composition used in the present invention also has excellent adhesion to articles containing copper.
The copper-clad laminate of the present invention uses the low-dielectric adhesive composition of the present invention, and therefore enables high-speed transmission in electronic devices and has excellent adhesive stability.

One method for producing a copper-clad laminate is to bring the adhesive layer of the laminate into face-to-face contact with copper foil, thermally laminate the laminate at 80°C to 200°C, and then cure the adhesive layer by after-curing. After-curing conditions can be, for example, 100°C to 200°C in an inert gas atmosphere for 30 minutes to 4 hours. The copper foil is not particularly limited, and electrolytic copper foil, rolled copper foil, etc. can be used.

(Printed wiring board)
A preferred embodiment of the laminate of the present invention is a printed wiring board obtained by laminating copper wiring to the adhesive layer in the laminate of the present invention.
A printed wiring board can be obtained by forming an electronic circuit on the copper-clad laminate.
The printed wiring board is formed by bonding a base film and copper wiring using the laminate, and is composed of the base film, adhesive layer, and copper wiring in that order. The adhesive layer and copper wiring may be formed on both sides of the base film.
For example, a printed wiring board is manufactured by using a heat press or the like to attach a coverlay film via an adhesive layer to a surface having wiring portions.
The printed wiring board according to the present invention uses the low-dielectric adhesive composition of the present invention, and therefore enables high-speed transmission in electronic devices and has excellent adhesive stability.
A method for producing the printed wiring board according to the present invention includes, for example, contacting the adhesive layer of the laminate with copper wiring, performing thermal lamination at 80°C to 200°C, and then curing the adhesive layer by after-curing. The after-curing conditions can be, for example, 100°C to 200°C and 30 minutes to 4 hours. The shape of the copper wiring is not particularly limited, and an appropriate shape can be selected as desired.

(Shielding film)
A preferred embodiment of the laminate according to the present invention is a shielding film.
Shielding film is a film used to shield various electronic devices, such as computers, mobile phones, and analytical equipment, in order to cut out electromagnetic noise that can affect these devices and cause them to malfunction. It is also called electromagnetic wave shielding film.
The electromagnetic wave shielding film is formed by laminating, for example, an insulating resin layer, a metal layer, and the adhesive layer according to the present invention in this order.
The shielding film of the present invention uses the low-dielectric adhesive composition of the present invention, which enables high-speed transmission in electronic devices and also provides excellent adhesion stability to electronic devices.

(Printed wiring board with shielding film)
A preferred embodiment of the laminate according to the present invention is a printed wiring board with a shielding film.
A printed wiring board with a shielding film is a printed wiring board having a printed circuit provided on at least one surface of the substrate, and the electromagnetic wave shielding film is attached to the printed wiring board.
A printed wiring board with a shielding film includes, for example, a printed wiring board, an insulating film adjacent to the surface of the printed wiring board on which the printed circuit is provided, and the electromagnetic wave shielding film.
The printed wiring board with a shielding film according to the present invention uses the low-dielectric adhesive composition of the present invention, and therefore enables high-speed transmission in electronic devices and has excellent adhesive stability.

The present invention will be described in further detail below with reference to examples, but the scope of the present invention is not limited to these examples. In the following, parts and percentages are by weight unless otherwise specified.

(Carboxy group-containing styrene elastomer)
Kraton FG1901 (maleic acid-modified styrene-ethylene butylene-styrene block copolymer) manufactured by Kraton Corp. The copolymer had an acid value of 19 mg KOH/g, a styrene/ethylene butylene ratio of 30/70, and a weight-average molecular weight of 81,000.
(Amino group-containing styrene elastomer)
The product used was "Tuftec MP10" (amine-modified styrene-ethylene butylene-styrene copolymer) manufactured by Asahi Kasei Corporation. The styrene/ethylene butylene ratio of this copolymer was 30/70, and the weight-average molecular weight was 78,000. The total nitrogen content of this copolymer was 430 ppm (μg/g).
(Carboxy-free styrene-based elastomer)
The copolymer used was "Tuftec P1500" (hydrogenated styrene-based elastomer) manufactured by Asahi Kasei Corporation. The copolymer had an acid value of 0 mgKOH/g, a styrene/ethylene butylene ratio of 30/70, and a weight average molecular weight of 67,000.
(Unmodified styrene elastomer)
Kraton G1651 (styrene-ethylenebutylene-styrene block copolymer) manufactured by Kraton Corp. The copolymer had an acid value of 0 mgKOH/g, a styrene/ethylenebutylene ratio of 33/67, and a weight-average molecular weight of 136,700.
(Unmodified styrene elastomer)
The product used was "A1535" (hydrogenated styrene-butadiene copolymer) manufactured by Kraton Corp. The acid value of this copolymer was 0 mgKOH/g and the weight average molecular weight was 135,700.
(Curing agent: epoxy modified resin)
The product used was "Epofriend CT310" (epoxidized styrene-butadiene block copolymer) manufactured by Daicel Corporation. The styrene/ethylene-butylene ratio of this copolymer was 40/60, the weight-average molecular weight was 93,000, and the epoxy equivalent was 2125 g/eq.
(hardening agent: organic peroxide)
As the organic peroxide, a peroxyester manufactured by NOF Corporation under the trade name "Perbutyl E" was used.
(solvent)
A mixed solvent of toluene and cyclohexanone (mass ratio = 97:3) was used.
(Base film)
The substrate film used was "Shin-Etsu Sepla Film PEEK" (polyether ether ketone, thickness 50 μm) manufactured by Shin-Etsu Polymer Co., Ltd. The storage modulus of the substrate film at 200° C. was 5×10 ⁸ .
(electrolytic copper foil)
The electrolytic copper foil used was "TQ-M7-VSP" manufactured by Mitsui Mining & Smelting Co., Ltd. (electrolytic copper foil, thickness 12 μm, shiny side Rz 1.27 μm, shiny side Ra 0.197 μm, shiny side Rsm 12.95 μm). The surface roughness of the shiny side was determined from a roughness curve measured using a laser microscope in accordance with JIS B 0601:2013 (ISO 4287:1997 Amd.1:2009).
(Release film)
As the release film, NP75SA (silicone release PET film, 75 μm) manufactured by Panac Corporation was used.

Example 1
The components constituting the adhesive layer shown in Table 1 were contained in the proportions shown in Table 1, and these components were dissolved in a solvent to prepare a resin varnish with a solids concentration of 15 mass %.
The components constituting the resin composition in the adhesive composition and the MFR of the resin composition are as shown in Table 1. Table 1 also shows the content ratio of the resin composition and the curing agent.
Next, the surface of the substrate film was subjected to a corona treatment.
The resin varnish prepared above was applied to the surface of a substrate film, dried in an oven at 130°C for 4 minutes, and the solvent was evaporated to form an adhesive layer (25 μm), resulting in an adhesive-attached substrate film. The adhesive layer of the adhesive laminate was placed in contact with the shiny side of the electrolytic copper foil, and thermal lamination was performed at 150°C to obtain a pre-cured adhesive laminate. The pre-cured adhesive laminate was after-cured at 150°C for 1 hour to cure the adhesive layer, resulting in a cured adhesive laminate.

The MFR of the resin composition of Example 1 was measured.
The resin flow (mm) of the cured adhesive laminate of Example 1 was measured.
After curing, the adhesive strength (N/cm) between the electrolytic copper foil and the substrate film of the adhesive laminate of Example 1 was measured.
The relative dielectric constant and dielectric loss tangent at a frequency of 28 GHz were also measured for the adhesive layer in the cured adhesive laminate of Example 1.

[MFR of resin composition]
A resin composition varnish having a solids concentration of 15% by mass was prepared by dissolving the components of the resin composition in the proportions shown in Table 1 in a solvent. The resin composition varnish was roll-coated onto a release film, and the coated film was then placed in an oven and dried at 130°C for 4 minutes to form a resin composition film (thickness: 50 μm). The resin composition film was peeled from the release film and cut to prepare a sample for MFR measurement.
The MFR was measured using an extrusion type plastometer specified in JIS K6760, and the measurement method conformed to the method specified in JIS K7210 (1976). In Example 1, the measurement was performed at 200°C under a load of 21.60 kg.

[Resin flow (mm)]
Three holes with a diameter of 5 mm were made in an adhesive-attached substrate film (adhesive layer 25 μm, 30 mm×90 mm) using a belt punch.
The laminate was placed on the shiny side of an electrolytic copper foil so as to be in contact with it, and then heat-laminated at 150°C, and pressed at 180°C, 3 MPa, and 3 minutes. The length of the resin protruding onto the copper foil was measured at 12 points (4 points x 3 locations) using a microscope, and the average value was recorded.
Microscope (KEYENCE Digital Microscope VHX-500): Lens magnification 300x

[Adhesion strength (N/cm)]
The adhesive strength was measured by cutting the cured adhesive laminate into a 25 mm wide test piece, and measuring the peel strength when peeling the electrolytic copper foil from the adhesive-attached substrate film fixed to a support at a peel speed of 0.3 m/min and a peel angle of 180° in accordance with JIS Z0237:2009 (Test methods for adhesive tapes and adhesive sheets).

[Solder heat resistance test]
In the solder heat resistance test, the cured adhesive laminate was floated in a solder bath at 288°C for 10 seconds three times with the substrate film side facing up, and any abnormal appearance such as swelling or peeling of the adhesive layer was checked.
The heat resistance of the laminate was evaluated according to the following evaluation criteria.
◎ No abnormalities (no dissolution).
○ No abnormalities are found in the final product, but the adhesive layer softens during the test.
△: No peeling, but the adhesive layer has softened and a "stain pattern" has formed.
× Peeling off.

[Relative permittivity and dielectric loss tangent]
The dielectric constant and dielectric loss tangent of the adhesive layer were measured using a network analyzer MS46122B (manufactured by Anritsu) and an open-type resonator Fabry-Perot DPS-03 (manufactured by KEYCOM) using the open-type resonator method at a temperature of 23 ° C and a frequency of 28 GHz. The measurement sample was prepared by roll-coating a resin varnish onto a release film, and then placing the coated film in an oven and drying it at 110 ° C for 4 minutes to form a B-stage adhesive layer (thickness 50 μm). Next, this adhesive layer was thermally laminated at 150 ° C so that the adhesive surfaces were in contact with each other to form a pre-cured adhesive film (thickness 100 μm). This pre-cured adhesive film (thickness 100 μm) was placed in an oven and subjected to a heat-curing treatment at 150 ° C for 60 minutes to produce a cured adhesive film (100 mm x 100 mm). After curing, the release film was peeled off from the adhesive film, and the relative dielectric constant and dielectric loss tangent of the adhesive layer were measured.

The results of each measurement are shown in Table 1. In Table 1, "na" indicates that the material did not flow and measurement was not possible.

(Examples 2 to 11)
Laminates of Examples 2 to 11 were prepared in the same manner as in Example 1, except that the types and blending amounts of the components constituting the adhesive layer in Example 1 were changed as shown in Table 1.
The laminate thus produced was evaluated in the same manner as in Example 1.
The results are shown in Table 1.

(Comparative Examples 1 to 5)
Laminates of Comparative Examples 1 to 5 were prepared in the same manner as in Example 1, except that the types and blending amounts of the components constituting the adhesive layer in Example 1 were changed as shown in Table 1.
The laminate thus produced was evaluated in the same manner as in Example 1.
The results are shown in Table 1.

As shown in the examples, the adhesive layer made of the adhesive composition of the present invention exhibits good electrical properties (dielectric properties) that are compatible with 5G, and also has excellent adhesion, heat resistance, and solvent resistance, and can also suppress resin flow.

Laminates having an adhesive layer made from the adhesive composition of the present invention can be suitably used in the manufacture of FPC-related products for electronic devices such as smartphones, mobile phones, optical modules, digital cameras, game consoles, laptops, and medical devices.

Claims (9)

an adhesive layer made of an adhesive composition containing a resin composition including a modified styrene-based elastomer and a curing agent,
the modified styrene-based elastomer is a styrene-based elastomer containing a carboxy group or a styrene-based elastomer containing an amino group,
the curing agent is at least one selected from the group consisting of epoxy resins, isocyanate resins, phenolic resins, cyanate resins, polyamides, polyurethanes, organic peroxides, silane coupling agents, benzoxazines, allyl compounds, and propenyl compounds;
the content of the modified styrene-based elastomer relative to 100 parts by mass of the resin composition is 25 parts by mass or more and 75 parts by mass or less ,
the content of the curing agent per 100 parts by mass of the adhesive composition is 25 parts by mass or less,
the resin composition has a melt flow rate (200°C, load 21.60 kg) of 0.1 g/10 min or more and 10 g/10 min or less;
An adhesive layer obtained by curing the adhesive composition, wherein the adhesive layer has a relative dielectric constant of 3 or less and a dielectric loss tangent of 0.005 or less, measured at a frequency of 28 GHz. The adhesive layer according to claim 1 , wherein the resin composition contains at least two or more types of styrene-based elastomers. 2. The adhesive layer according to claim 1, wherein the epoxy resin of the curing agent is an epoxy-modified styrene-butadiene copolymer. The adhesive layer according to claim 1 , wherein the resin composition comprises a styrene-based elastomer having a weight average molecular weight (Mw) of 100,000 to 500,000. A base film;
A laminate comprising the adhesive layer according to any one of claims 1 to 4 . The laminate according to claim 5 , wherein the substrate film contains a polyether ether ketone (PEEK) resin. A coverlay film with an adhesive layer, comprising the laminate according to claim 5 or 6 . A copper clad laminate comprising the laminate according to claim 5 or 6 . A printed wiring board comprising the laminate according to claim 5 or 6 .