Adhesive composition

Abstract

Provided is an adhesive composition that is for forming a low-dielectric adhesive layer having heat resistance and being capable of preventing resin flow (resin flow-out properties), that exhibits excellent adhesiveness even with respect to a low-dielectric base material film having poor adhesiveness, and that has excellent electrical properties (dielectric properties) capable of handling 5G. Further, the adhesive composition can form an adhesive layer having superior adhesion-reliability even after being kept at 150°C for 168 hours.　The adhesive composition contains a resin composition including styrene-based elastomers. The styrene-based elastomers include a modified styrene-based elastomer. The styrene-based elastomers also include a styrene-based elastomer having a styrene ratio of 33 or more.

Description

[Technical Field]

[0001] This invention relates to an adhesive composition. More specifically, it relates to an adhesive composition that can be used for bonding electronic components and the like. [Background technology]

[0002] With the miniaturization and weight reduction of electronic devices, the applications for bonding electronic components and other materials have diversified, and the demand for laminates with adhesive layers is increasing. Furthermore, flexible printed circuit boards (FPCs), a type of electronic component, require high-speed processing of large amounts of data, and progress is being made in supporting high frequencies. Increasing the frequency of FPCs requires reducing the dielectric strength of the constituent elements, and development of low-dielectric substrate films and low-dielectric adhesives is underway. In particular, in order to efficiently transmit signals with frequencies in the 6GHz and 28GHz bands used in fifth-generation mobile communication systems (5G), substrate films and adhesives with low loss even in the 28GHz millimeter-wave band are becoming increasingly important.

[0003] However, low-dielectric adhesives have low polarity in their main component molecules, making it difficult for them to adhere well to substrate films and other components related to electronic parts. Similarly, low-dielectric substrate films can also have poor adhesion to adhesives, and there is a need to improve adhesion. Therefore, in order to have good electrical properties (low dielectric constant and low dielectric loss tangent) while meeting the requirement of high adhesion, a proposal has been made for a laminate comprising an adhesive layer made of an adhesive composition containing a carboxyl group-containing styrene elastomer (A) and an epoxy resin (B), and a substrate film (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2016 / 017473 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Incidentally, adhesives used in flexible printed circuit boards are required to maintain excellent adhesion even after prolonged exposure to high temperatures. To ensure reliable adhesion, for example, they must exhibit excellent adhesion even after 168 hours at 150°C. However, it was found that when the cured adhesive-coated laminate is left at 150°C for 168 hours, the storage modulus of the adhesive layer increases, causing it to harden and resulting in a decrease in adhesion. From the standpoint of providing an adhesive layer with excellent adhesion reliability even after 168 hours at 150°C, the adhesive described in Patent Document 1 above is not satisfactory and there is room for improvement.

[0006] Therefore, the present invention aims to provide an adhesive composition for forming a low-dielectric adhesive layer that has good electrical properties (dielectric properties) suitable for 5G, exhibits good adhesion even to low-dielectric substrate films with poor adhesion, and combines heat resistance and suppression of resin flow (resin leakage), and furthermore, can form an adhesive layer that exhibits excellent adhesion reliability even after 168 hours at 150°C. [Means for solving the problem]

[0007] As a result of diligent research to solve the above problems, the present inventors have discovered that by incorporating a specific styrene-based elastomer into the resin composition, which is the main component of the adhesive composition, the adhesive composition can solve the above problems, and have completed the present invention.

[0008] The present invention encompasses the following embodiments. [1] An adhesive composition comprising a resin composition containing a styrene-based elastomer, The styrene-based elastomer contains a modified styrene-based elastomer, and An adhesive composition in which the styrenic elastomer contains a styrenic elastomer having a styrene ratio of 33 or more. [2] The adhesive composition according to [1], wherein the styrene ratio of the styrenic elastomer is 40 or more. [3] The adhesive composition according to [1] or [2], wherein the content of the modified styrenic elastomer is 20 to 80 parts by mass with respect to 100 parts by mass of the resin composition. [4] The adhesive composition according to [1] or [2], wherein the content of the styrenic elastomer having a styrene ratio of 33 or more is 20 to 80 parts by mass with respect to 100 parts by mass of the resin composition. [5] The adhesive composition according to any one of [1] to [4], wherein the resin composition includes the modified styrenic elastomer and an unmodified styrenic elastomer. [6] The adhesive composition according to [5], wherein the styrenic elastomer having a styrene ratio of 33 or more is the unmodified styrenic elastomer. [7] The adhesive composition according to any one of [1] to [6], wherein the modified styrenic elastomer is a styrenic elastomer containing a carboxy group. [8] The adhesive composition according to any one of [1] to [6], wherein the modified styrenic elastomer is a styrenic elastomer containing an amino group. [9] The adhesive composition according to [6], wherein the weight average molecular weight of the unmodified styrenic elastomer having a styrene ratio of 33 or more is 50,000 or more.

[10] The adhesive composition according to [9], wherein the unmodified styrenic elastomer having a styrene ratio of 33 or more is a block copolymer.

[11] The adhesive composition according to

[10] , wherein the unmodified styrenic elastomer having a styrene ratio of 33 or more is a block copolymer containing a styrene-butadiene rubber (SBR) backbone.

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

[11] , wherein the adhesive composition contains the resin composition and a curing agent.

[13] The adhesive composition according to

[12] , wherein the content of the curing agent per 100 parts by mass of the resin composition is 20 parts by mass or less.

[14] The adhesive composition according to

[12] or

[13] , comprising an epoxy resin as the curing agent.

[15] The adhesive composition according to

[12] or

[13] , comprising a benzoxazine resin as the curing agent.

[16] The adhesive composition according to

[12] or

[13] , comprising a bismaleimide resin as the curing agent.

[17] An adhesive layer obtained by curing any of the adhesive compositions described in [1] to

[16] .

[18] The storage modulus of the adhesive layer at 25°C is 1.5 × 10⁻⁶ 7 ~3.0×10 7 The adhesive layer described in

[17] .

[19] The storage modulus of the adhesive layer after 168 hours at 150°C is 1.5 × 10⁻⁶ 7 ~3.0×10 7 The adhesive layer described in

[17] or

[18] .

[20] The adhesive layer according to any one of

[17] to

[19] , wherein the relative permittivity of the adhesive layer measured at a frequency of 28 GHz is 3.5 or less and the dielectric loss tangent is 0.005 or less.

[21] Base film and A laminate having an adhesive layer as described in any of

[17] to

[20] .

[22] The laminate according to

[21] , wherein the base film contains polyetheretherketone (PEEK) resin.

[23] Coverlay film with adhesive layer comprising the laminate described in

[21] or

[22] .

[24] A copper-clad laminate containing the laminate described in

[21] or

[22] .

[25] A printed circuit board including the laminate described in

[21] or

[22] . A shielding film comprising the laminate described in

[26]

[21] or

[22] .

[27] A printed circuit board with a shielding film, including the laminate described in

[21] or

[22] . [Effects of the Invention]

[0009] According to the present invention, an adhesive composition is provided for forming a low-dielectric adhesive layer that has good electrical properties (dielectric properties) suitable for 5G, exhibits good adhesion even to low-dielectric substrate films with poor adhesion, and combines heat resistance and suppression of resin flow (resin leakage), and further provides an adhesive composition that can form an adhesive layer that exhibits excellent adhesion reliability even after 168 hours at 150°C. [Modes for carrying out the invention]

[0010] The following describes in detail the adhesive composition of the present invention, the laminate containing an adhesive layer made of the adhesive composition, and the electronic component-related components containing the laminate. However, the description of the constituent elements described below is merely an example of one embodiment of the present invention and is not limited to these contents.

[0011] (Adhesive composition) The adhesive composition of the present invention includes a resin composition containing a styrene-based elastomer. The adhesive composition of the present invention may contain a resin composition and a curing agent.

[0012] <Resin composition> The styrene-based elastomer contained in the resin composition contains a modified styrene-based elastomer, and also contains a styrene-based elastomer with a styrene ratio of 33 or higher. The styrene elastomer may contain one or more modified styrene elastomers. The styrene elastomer may contain not only modified styrene elastomers but also unmodified styrene elastomers. The unmodified styrene-based elastomer may be present in one or more forms. In this invention, the present invention contains a styrene-based elastomer having a styrene ratio of 33 or more. The styrene-based elastomer having a styrene ratio of 33 or more may be either a modified styrene-based elastomer or an unmodified styrene-based elastomer. In the present invention, if the styrene ratio of the modified styrene elastomer is 33 or higher, that is, if the product contains a modified styrene elastomer with a styrene ratio of 33 or higher, it is sufficient to contain at least one such modified styrene elastomer, and it is also possible to contain other modified elastomers or other unmodified styrene elastomers. Furthermore, if the styrene ratio of the modified styrene elastomer is less than 33, an unmodified styrene elastomer with a styrene ratio of 33 or higher is included separately from the modified styrene elastomer. A preferred embodiment of the styrene-based elastomer of the present invention is a styrene-based elastomer containing a modified styrene-based elastomer and an unmodified styrene-based elastomer with a styrene ratio of 33 or more. The resin composition used in the present invention may contain, in addition to styrene-based elastomers, other resin components and other components.

[0013] <<Styrene-based elastomer>> The resin composition, which is the main component of the adhesive composition, contains a styrene-based elastomer. Styrene elastomers are copolymers mainly composed of unsaturated hydrocarbons and aromatic vinyl compounds with block and random structures, as well as hydrogenated versions thereof.

[0014] Examples of aromatic vinyl compounds include styrene, t-butylstyrene, α-methylstyrene, divinylbenzene, 1,1-diphenylethylene, N,N-diethyl-p-aminoethylstyrene, and vinyltoluene. Examples of unsaturated hydrocarbons include ethylene, propylene, butadiene, isoprene, isobutene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene. Specific examples of styrene-based elastomers include styrene-butadiene copolymers, styrene-ethylene propylene copolymers, and styrene-isoprene copolymers, as well as their block copolymers and water additives. These can impart adhesive properties and electrical properties (dielectric properties) to adhesive compositions, and their molecular structure can be relatively easily controlled, making it easy to adjust the properties of the adhesive composition. Among these, styrene-butadiene copolymers are preferred because their molecular weight is easily controllable and they allow for stable production of adhesive compositions with desired properties.

[0015] The styrene ratio, which is the weight ratio of styrene monomer units, is preferably 20 or higher, and more preferably 30 or higher. If the styrene ratio is 20 or higher, the adhesive composition can exhibit heat resistance. If the styrene ratio is 30 or higher, excellent adhesion can be achieved. Furthermore, it is preferable to include a styrene-based elastomer with a styrene ratio of 33 or higher, and more preferably a styrene-based elastomer with a styrene ratio of 40 or higher. When a styrene-based elastomer with a styrene ratio of 33 or higher is included, the compatibility with resin components other than the styrene-based elastomer and other components is improved, and the curing reaction occurs uniformly, resulting in excellent adhesion. In addition, the small change in storage modulus after 168 hours at 150°C suppresses the decrease in adhesion strength, ensuring excellent adhesion reliability of the adhesive layer. When a styrene-based elastomer with a styrene ratio of 40 or higher is included, the change in storage modulus after 168 hours at 150°C can be further reduced, resulting in even better adhesion reliability. The styrene-based elastomer preferably has a styrene ratio of 80 or less, and more preferably 60 or less. A styrene ratio of 80% or less enhances fluidity during heating, allowing the material to conform well to the surface of the base film and exhibit excellent adhesive strength. If the styrene ratio is 60% or less, styrene-based elastomers are readily available.

[0016] The measurement of the styrene ratio is 1This can be done using 1H NMR. For example, by using tetrachloromethane as the solvent, the integral values ​​of the peaks in the range of 6.5 ppm to 7.5 ppm corresponding to styrene, and the integral values ​​of the peaks in other ranges can be determined, and the styrene ratio can be calculated from the obtained values. In this application, the styrene ratio was calculated based on the styrene content (theoretical value) of the raw material.

[0017] Styrene-based elastomers with a styrene ratio of 33 or higher are not particularly limited in their type, whether modified or unmodified, and can be selected according to the purpose. A detailed explanation of unmodified styrene-based elastomers will be given later.

[0018] The weight-average molecular weight (Mw) of the styrene-based elastomer is preferably 50,000 to 300,000, and more preferably 100,000 to 300,000. If it is between 100,000 and 200,000, adhesion can be achieved, and if it is between 100,000 and 300,000, both adhesion and fluidity control can be achieved. The weight-average molecular weight is the value obtained by converting the molecular weight measured by gel permeation chromatography (hereinafter also referred to as "GPC") to a polystyrene equivalent.

[0019] Styrene-based elastomers with a styrene ratio of 33 or higher are more preferably styrene-based elastomers composed of a styrene-butadiene block copolymer containing a styrene-butadiene rubber (SBR) skeleton, from the viewpoint of being able to increase the styrene ratio and suppress changes in storage modulus.

[0020] The amount of styrene-based elastomer with a styrene ratio of 33 or higher contained in the resin composition used in the present invention is preferably 20 to 80 parts by mass, and more preferably 30 to 70 parts by mass, per 100 parts by mass of the resin composition. If the amount is 20 to 80, the change in storage modulus after 168 hours at 150°C can be suppressed, resulting in an adhesive composition with excellent adhesion. If the amount is 30 to 70, in addition to the above, resin flow can also be suppressed.

[0021] Styrene-based elastomers may be used individually or may contain two or more types.

[0022] <<Modified styrene-based elastomer>> Modified styrene elastomers are styrene elastomers into 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. Examples include styrene elastomers containing carboxyl groups and styrene elastomers containing amino groups, as described below. The inclusion of styrene elastomers containing carboxyl groups or styrene elastomers containing amino groups improves adhesion to metals and substrates. Furthermore, because carboxyl groups and amino groups can react with curing agents, this leads to improved heat resistance, chemical resistance, and even greater adhesion.

[0023] <<<Styrene-based elastomer containing carboxyl groups>>> Styrene-based elastomers containing carboxyl groups are effective as components that provide high adhesion, impart flexibility to cured products, and give good electrical properties. The inclusion of a styrene-based elastomer containing carboxyl groups in the adhesive composition allows the flexible adhesive composition to adequately conform to the surface of the substrate, such as a base film or metal foil, which has good electrical properties and low polarity. This allows the highly polar carboxyl groups to exhibit adhesion, thus improving the adhesion of the adhesive layer. Furthermore, because the styrene-based elastomer containing carboxyl groups is reactive, reacting it with a curing agent improves the heat resistance and chemical resistance of the adhesive layer. Furthermore, the presence of carboxyl groups improves the dispersibility of fillers when they are present in the dispersion. Styrene-based elastomers containing carboxyl groups are copolymers mainly consisting of block and random structures of unsaturated hydrocarbons and aromatic vinyl compounds, as well as hydrogenated versions thereof, modified with unsaturated carboxylic acids. The types of aromatic vinyl compounds and unsaturated hydrocarbons, as well as specific examples of styrene-based elastomers, are as described in the section above under "<<Styrene-based elastomers>>".

[0024] Modification of styrene-based elastomers containing carboxyl groups can be carried out, for example, by copolymerizing them with an unsaturated carboxylic acid during polymerization. Alternatively, it can be done by heating and kneading the styrene-based elastomer and the unsaturated carboxylic acid in the presence of an organic peroxide. Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid, maleic anhydride, and itaconic anhydride. The amount of modification by unsaturated carboxylic acid is preferably 0.1 to 10% by mass. The acid value of the styrene-based elastomer containing a carboxyl group is preferably 0.1 to 25 mgKOH / g, and more preferably 0.5 to 23 mgKOH / g. When the acid value is 0.1 mgKOH / g or higher, the adhesive composition hardens sufficiently, and good adhesion and heat resistance are obtained. On the other hand, when the acid value is 30 mgKOH / g or lower, the cohesive force of the adhesive composition is suppressed, resulting in excellent tackiness and excellent electrical properties.

[0025] <<<Styrene-based elastomer containing amino groups>>> The inclusion of a styrene-based elastomer containing amino groups in the adhesive composition allows the amino groups to strongly interact with the low-dielectric substrate film, increasing the reactivity of the adhesive composition and improving the adhesion of the adhesive layer. Furthermore, because the styrene-based elastomer containing amino groups is reactive, reacting it with a curing agent also improves the heat resistance and chemical resistance of the adhesive layer. Because it contains amino groups, its adhesion to metals is improved. Styrene-based elastomers containing amino groups are copolymers mainly consisting of block and random structures of unsaturated hydrocarbons and aromatic vinyl compounds, as well as hydrogenated versions thereof, that have been modified with amines. The types of aromatic vinyl compounds and unsaturated hydrocarbons, as well as specific examples of styrene-based elastomers, are as described in the section above under "<<Styrene-based elastomers>>".

[0026] The method for amine-modifying styrene-based elastomers is not particularly limited, and known methods can be used. Examples include amine-modification by polymerizing a (hydrogenated) block copolymer using a polymerization initiator having an amino group, amine-modification of a (hydrogenated) copolymer by using an unsaturated monomer having an amino group as a copolymerizing raw material, and amine-modification by reacting a styrene-based elastomer containing a carboxyl group with an amine modifier having two or more amino groups to form an amide structure or / or an imide structure.

[0027] 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 styrene-based elastomer containing amino groups is preferably 50 to 5000 ppm, and more preferably 200 to 3000 ppm. If the total nitrogen content is above the lower limit, excellent adhesion can be achieved. If the total nitrogen content is below the upper limit, the electrical properties are excellent. The total nitrogen content in a styrene-based elastomer containing amino groups can be determined using a trace nitrogen analyzer, model ND-100 (manufactured by Mitsubishi Chemical Corporation), in accordance with JIS-K2609.

[0028] The amount of modified styrene-based elastomer contained in the resin composition used in the present invention is preferably 20 to 80 parts by mass, and more preferably 30 to 70 parts by mass, per 100 parts by mass of the resin composition. Within this range, an adhesive composition with excellent adhesion can be obtained.

[0029] <<Unmodified styrene-based elastomer>> The resin composition used in the present invention may contain an unmodified styrene elastomer in addition to a modified styrene elastomer. A styrene-based elastomer with a styrene ratio of 33 or higher may be an unmodified styrene-based elastomer. Unmodified styrene-based elastomers may be used alone or may contain two or more types. A preferred embodiment of the resin composition used in the present invention is a resin composition containing a modified styrene elastomer and an unmodified styrene elastomer having a styrene ratio of 33 or more.

[0030] In the resin composition used in this invention, by using a modified styrene-based elastomer with good surface adhesion to the adherend and an unmodified styrene-based elastomer that allows for temperature-dependent adjustment of the storage modulus of the adhesive composition, it is possible to achieve high adhesion, control of fluidity, and suppression of changes in the storage modulus. In particular, by including a modified styrene elastomer and an unmodified styrene elastomer with similar molecular structures, a resin composition with good compatibility and adhesive properties can be obtained.

[0031] <<Other resin components>> The resin composition used in the present invention may contain other resin components in addition to the styrene-based elastomer described above. The resin composition according to the present invention may contain, for example, other thermoplastic resins other than styrene-based elastomers, to an extent that does not affect the function of the adhesive composition. Examples of other thermoplastic resins mentioned above include phenoxy resins, polyamide resins, polyester resins, polycarbonate resins, polyphenylene oxide resins, polyurethane resins, polyacetal resins, polyethylene resins, polypropylene resins, polybutadiene resins, and polyvinyl resins. These thermoplastic resins may be used individually or in combination of two or more types. The resin flow rate may change depending on the compatibility between the styrene-based elastomer and the other thermoplastic resins mentioned above, and this can be adjusted by changing the compounding method.

[0032] <<Other ingredients>> The resin composition used in the present invention may contain other components in addition to resin components such as styrene elastomers and the other resin components mentioned above. Other components may include, for example, fillers, tackifiers, flame retardants, heat aging inhibitors, leveling agents, defoamers, inorganic fillers, and pigments, in amounts that do not affect the function of the adhesive composition. The resin flow rate may change depending on the dispersibility of the styrene elastomer with other components, and this can be adjusted by changing the formulation and dispersion method.

[0033] <<<Filler>>> The adhesive composition of the present invention preferably contains a filler. As fillers 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, mica and talc are preferred, for example, as they can control the mechanical properties of the adhesive composition even in small amounts and also have excellent electrical properties. Furthermore, as fillers according to the present invention, organic fillers are preferred from the viewpoint of dispersibility and brittleness, and as organic fillers, styrene-based spherical fillers are preferred from the viewpoint of electrical properties, and styrene-based hollow fillers are more preferred. These can be used individually or in combination of two or more types. The filler content in the adhesive composition of the present invention is preferably 0.5 to 25 parts by volume per 100 parts by volume of the resin composition, 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 spherical or non-spherical, but from the viewpoint of thermal expansion coefficient (CTE) and film strength, non-spherical inorganic fillers are preferred. The shape of the non-spherical inorganic filler can be any three-dimensional shape other than spherical (approximately perfectly spherical), such as plate-like, flake-like, columnar, chain-like, or fibrous. Among these, plate-like and flake-like inorganic fillers are preferred from the viewpoint of thermal expansion coefficient (CTE) and film strength, and plate-like inorganic fillers are more preferred.

[0034] Examples of the tackifiers mentioned above include coumarone-indene resin, terpene resin, terpene-phenol resin, rosin resin, pt-butylphenol-acetylene resin, phenol-formaldehyde resin, xylene-formaldehyde resin, petroleum hydrocarbon resin, hydrogenated hydrocarbon resin, turpentine resin, and the like. These tackifiers may be used individually or in combination of two or more.

[0035] The above-mentioned 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 phosphate, ammonium polyphosphate, carbamate phosphate, carbamate polyphosphate, aluminum tris-diethylphosphinate, aluminum tris-methylethylphosphinate, aluminum tris-diphenylphosphinate, zinc bis-diethylphosphinate, zinc bis-methylethylphosphinate, zinc bis-diphenylphosphinate, titanyl bis-diethylphosphinate, titanium tetrakis-diethylphosphinate, titanyl bis-methylethylphosphinate, titanium tetrakis-methylethylphosphinate, titanyl bis-diphenylphosphinate, and titanium tetrakis-diphenylphosphinate; nitrogen-based flame retardants such as triazine compounds like melamine, melam, and melamine cyanurate, as well as cyanuric acid compounds, isocyanuric acid compounds, triazole 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; and zinc carbonate, magnesium carbonate, barium carbonate, zinc borate, and hydrated glass. Two or more of these flame retardants can be used in combination.

[0036] 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), and triethylene glycol-bis[3 Examples include phenol-based antioxidants such as -(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 individually or in combination of two or more.

[0037] Examples of the inorganic fillers mentioned above include powders consisting of titanium dioxide, aluminum oxide, zinc oxide, carbon black, silica, copper, and silver. These may be used individually or in combination of two or more.

[0038] <Hardening agent> The curing agent can increase the storage modulus of the adhesive composition by reacting with the resin composition or by polymerization of curing agents with each other. By increasing the crosslinking density of the resin composition, high adhesion to the adherend and heat resistance of the cured adhesive can be achieved. The curing agent consists of a crosslinking agent that reacts with the resin composition to form a crosslinked structure, and may optionally contain a reaction accelerator to promote the reaction between the resin composition and the crosslinking agent. From the viewpoint of ensuring high adhesion and achieving low dielectric properties, the curing agent content is preferably 20 parts by mass or less per 100 parts by mass of the resin composition.

[0039] <<Crosslinking agent>> Examples of crosslinking agents include benzoxazine resins, bismaleimide resins, epoxy resins, isocyanate resins, phenolic resins, cyanate resins, polyamides, polyurethanes, organic peroxides, and silane coupling agents. While the crosslinking agent can be appropriately selected depending on the purpose, benzoxazine resins and epoxy resins are preferred from the viewpoint of enabling the adhesive composition to cure at a suitable curing temperature and exhibiting heat resistance. Bismaleimide resins are preferred from the viewpoint of improving the crosslinking density of the adhesive composition without containing highly polar functional groups, thereby further improving the adhesion and heat resistance of the adhesive layer. Only one crosslinking agent may be used, or two or more may be included.

[0040] <<<Benzoxazine resin>>> Since benzoxazine resin reacts with styrene-based elastomers containing the above-mentioned carboxyl groups, styrene-based elastomers containing the above-mentioned amino groups, bismaleimide resin, etc., the crosslinking density is improved, and further adhesion and heat resistance of the adhesive layer can be imparted. Examples of benzoxazine resins 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 types may be combined. The nitrogen atom of the oxazine ring may be bonded to a phenyl group, methyl group, cyclohexyl group, etc. Specific examples of benzoxazine resins include "Benzoxazine Fa," "Benzoxazine Pd," and "Benzoxazine ALP-d" manufactured by Shikoku Chemicals, Inc., and "Cashew Benzoxazine Resin CR-276" manufactured by Tohoku Chemicals, Inc.

[0041] <<<Bismaleimide resin>>> Bismaleimide resin has a structure containing two maleimide groups, and its presence of maleimide groups improves adhesion to metals. Furthermore, because it has unsaturated bonds, it can be crosslinked and reacts with carboxyl groups in styrene-based elastomers containing carboxyl groups, amino groups in styrene-based elastomers containing amino groups, and benzoxazine resins, etc. This improves the crosslinking density, enabling the realization of even greater adhesion and stable heat resistance.

[0042] Examples of bismaleimide resins include 1-methyl-2,4-bismaleimidebenzene, N,N'-m-phenylenebismaleimide, N,N'-p-phenylenebismaleimide, N,N'-m-toluenebismaleimide, N,N'-4,4-biphenylenebismaleimide, N,N'-4,4-(3,3'-dimethyl-biphenylene)bismaleimide, and N,N'-4,4-(3,3'-dimethyldiphenylmethane)bismaleimide. Examples include N,N'-4,4-(3,3'-diethyldiphenylmethane)bismaleimide, N,N'-4,4-diphenylmethanebismaleimide, N,N'-4,4-diphenylpropanebismaleimide, N,N'-4,4-diphenyletherbismaleimide, N,N'-3,3-diphenylsulfonebismaleimide, and polymers obtained by polymerizing amine-modified products such as dimer acids and trimer acids with maleic anhydride or pyromellitic acid.

[0043] <<<Epoxy resin>>> The epoxy resin is a component that reacts with the carboxyl groups in the styrene-based elastomer containing the carboxyl groups mentioned above, or with the amino groups in the styrene-based elastomer containing the amino groups mentioned above, to exhibit high adhesion to the adherend and heat resistance of the cured adhesive.

[0044] Examples of epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, or hydrogenated versions thereof; glycidyl ester epoxy resins such as diglycidyl phthalate, diglycidyl isophthalate, diglycidyl terephthalate, glycidyl p-hydroxybenzoate, diglycidyl tetrahydrophthalate, diglycidyl succinate, diglycidyl adipic acid, diglycidyl sebacate, and triglycidyl trimellitic acid; ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, and 1,4-butanediol diglycidyl ether. Examples of epoxy resins include glycidyl ether-based epoxy resins such as glycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, tetraphenyl glycidyl ether ethane, triphenyl glycidyl ether ethane, sorbitol polyglycidyl ether, and polyglycerol polyglycidyl ether; glycidylamine-based epoxy resins such as triglycidyl isocyanurate and tetraglycidyldiaminodiphenylmethane; and linear aliphatic epoxy resins such as epoxidized polybutadiene and epoxidized soybean oil, but are not limited to these. In addition, novolac-type epoxy resins such as xylene structure-containing novolac epoxy resin, naphthol novolac-type epoxy resin, phenol novolac epoxy resin, o-cresol novolac epoxy resin, and bisphenol A novolac epoxy resin can also be used. These epoxy resins may be used individually or in combination of two or more.

[0045] Specific examples of novolak-type epoxy resins include, for example, "YX7700" (xylene structure-containing novolak-type epoxy resin) manufactured by Mitsubishi Chemical Corporation, "NC7000L" (naphthol novolak-type epoxy resin) manufactured by Nippon Kayaku Co., Ltd., "ESN485" (naphthol novolak-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd., "N-690" (cresol novolak-type epoxy resin) manufactured by DIC Corporation, "N-695" (cresol novolak-type epoxy resin) manufactured by DIC Corporation, and the like.

[0046] It is more preferable that the epoxy resin is an epoxy-modified resin. This is because it has good compatibility with the main agent (resin composition) containing a styrene-based elastomer and can exhibit the effect of suppressing resin flow without impairing the effect of adjusting the MFR of the main agent.

[0047] <<<<Epoxy-modified resin>>>> As the epoxy-modified resin, for example, it is preferable that it is an epoxy-modified resin having a structure represented by the following formula (1). [[]]END]]

Chemical formula

[0048] Preferable embodiments of the epoxy-modified resin include an epoxy-modified resin having a structure represented by the following formula (e).

[0049] [ka] (R 5 and R 6 Each of these independently represents either hydrogen or an alkyl group with 10 or fewer carbon atoms. If multiple structures represented by formula (2) exist in the epoxy-modified resin, then R in each of the formulas (2) 5 These can be the same or different, and in each case, R in equation (2) 6 These 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, in formula (2) above, R 5 and R 6 However, it is preferable that both are hydrogen.

[0050] Epoxy-modified resins preferably contain unsaturated bonds in addition to aromatic rings such as olefin skeletons and vinyl groups. These unsaturated bonds, other than aromatic rings, can be incorporated into reactions involving epoxy groups, thereby accelerating the reaction rate and increasing the crosslinking density. As a result, heat resistance and chemical resistance can be improved even with smaller formulations. Furthermore, crosslinking these unsaturated bonds via radical polymerization can increase the crosslinking density of the epoxy-modified resin, further improving heat resistance and chemical resistance.

[0051] A preferred embodiment of the epoxy-modified resin is an epoxy-modified resin having a structure represented by the following formula (3).

[0052] [ka] (R 7 and R 8 Each of these independently represents hydrogen or an alkyl group with 10 or fewer carbon atoms. If multiple structures represented by formula (3) exist in the epoxy-modified resin, then R in each of the formulas (3) 7 These can be the same or different, and in each equation (3), R 8These may be the same or different. (* represents a bonding group.) In equation (3) above, R 7 and R 8 However, it is preferable that both are hydrogen.

[0053] The epoxy-modified resin is preferably an epoxy-modified resin having the structure represented by formula (1) and the structure represented by formula (3), and more preferably an epoxy-modified resin having the structure represented by formula (2) and the structure represented by formula (3).

[0054] A preferred embodiment of the epoxy-modified resin is an epoxy-modified resin having at least one of the structures represented by formula (4) and formula (5) below. It is also preferable to have both the structure represented by formula (4) and the structure represented by formula (5) below.

[0055] [ka] (R 9 and R 10 Each of these independently represents either hydrogen or an alkyl group with 10 or fewer carbon atoms. If multiple structures represented by formula (4) exist in the epoxy-modified resin, then R in each of the formulas (4) 9 These can be the same or different, and in each equation (4), R 10 These may be the same or different. (* represents a bonding group.) In equation (4) above, R 9 and R 10 However, it is preferable that both are hydrogen.

[0056] [ka] (R 11 and R 12 Each of these independently represents hydrogen or an alkyl group with 10 or fewer carbon atoms. If multiple structures represented by formula (5) exist in the epoxy-modified resin, the R in each of the formulas (5)11 These can be the same or different, and in each equation (5), R 12 These may be the same or different. (* represents a bonding group.) In equation (5) above, R 11 and R 12 However, it is preferable that both are hydrogen.

[0057] The epoxy-modified resin is preferably an epoxy-modified resin having a structure represented by formula (1), a structure represented by formula (4), and a structure represented by formula (5), and more preferably an epoxy-modified resin having a structure represented by formula (2), a structure represented by formula (4), and a structure represented by formula (5). Furthermore, epoxy-modified resins having at least one of the structures represented by formula (1) or formula (2) above, the structure represented by formula (3) above, and the structure represented by formula (4) above and the structure represented by formula (5) above are also preferred.

[0058] Furthermore, the epoxy-modified resin is preferably an epoxy-modified organic compound obtained by modifying an organic compound containing unsaturated bonds. By modifying an organic compound containing unsaturated bonds, the structure represented by formula (1) and the unsaturated bonds can coexist within the molecule depending on the modification rate, making it easier to impart the effect of unsaturated bonds to the reaction of the epoxy structure, in addition to aromatic rings such as olefin skeletons and vinyl groups. Here, an effective method for modifying organic compounds containing unsaturated bonds into epoxy-modified organic compounds is the reaction of forming an epoxy skeleton with a peroxide. Examples of peroxides 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 unsaturated bonds. The epoxy-modified elastomer can impart flexibility to the cured product and suppress the reduction in toughness of the cured product due to epoxy curing, thereby maintaining adhesion when the laminate is bent and not reducing heat resistance or chemical resistance. Furthermore, it is preferable that the epoxy-modified resin is a styrene-based elastomer. This is because, when the epoxy-modified resin is a styrene-based elastomer, along with 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 carboxyl groups in the styrene-based elastomer containing the carboxyl groups and the amino groups in the styrene-based elastomer containing the amino groups can proceed efficiently.

[0059] Furthermore, the epoxy-modified resin is preferably a styrene-based elastomer. In epoxy-modified resins having the structures represented by formula (1) and formula (2) above, it is also preferable that they have styrene structural units in addition to the structures represented by formulas (3) to (5) above. The epoxy-modified resin, along with the styrene-based elastomer contained in the adhesive resin composition of the present invention, is a styrene-based elastomer. This improves compatibility when the two are mixed, allowing for efficient reaction with the carboxyl groups in the styrene-based elastomer containing the carboxyl groups and the amino groups in the styrene-based elastomer containing the amino groups.

[0060] Examples of epoxy-modified resins include alicyclic epoxy compounds having alicyclic epoxy groups such as epoxycyclohexane, epoxidized polybutadiene, and epoxy compounds of styrene-butadiene block copolymers. In particular, epoxy compounds of styrene-butadiene block copolymers are preferred. Because styrene-butadiene block copolymers contain unsaturated bonds, the structure represented by formula (1) and unsaturated bonds can coexist within the molecule, making it easier to impart the effect of unsaturated bonds to the reaction of epoxy structures, in addition to aromatic rings such as olefin skeletons and vinyl groups. Commercially available epoxy compounds can be used as epoxy-modified resins, such as Celoxide 2021P, Celoxide 2081, Celoxide 2000 (manufactured by Daicel Corporation), Epolide GT401, Epolide PB3600, Epolide PB4700 (manufactured by Daicel Corporation), and Epofriend AT501, Epofriend CT310 (manufactured by Daicel Corporation).

[0061] The weight-average molecular weight (Mw) of the epoxy-modified resin is preferably 30,000 or more, and more preferably 50,000 or more. If the weight-average molecular weight is 30,000 or more, softening of the adhesive composition can be suppressed, and resin flow during heat bonding can be prevented. If the weight-average molecular weight is 50,000 or more, the flexibility of the epoxy-modified resin is improved, and the toughness of the cured product is improved. 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. If the weight-average molecular weight is 200,000 or less, compatibility with styrene-based elastomers is further improved. If the weight-average molecular weight is 160,000 or less, the storage modulus of the adhesive composition can be lowered, and it can conform to the shape of the adherend.

[0062] <<<Organic peroxide>>> By including organic peroxides, the crosslinking density of the adhesive composition can be improved without including highly polar functional groups, thereby further enhancing the adhesion, heat resistance, and chemical resistance of the adhesive layer. Unsaturated bonds, acryloyl groups, bismaleimide groups, and unsaturated bonds other than aromatic rings, such as the olefin skeleton and vinyl groups in the aforementioned epoxy-modified resin, can be crosslinked by radical polymerization using radicals generated from organic peroxides, thereby improving the adhesion, heat resistance, and chemical resistance of the adhesive layer. Furthermore, radicals generated from organic peroxides have high hydrogen abstraction ability and can crosslink hydrogenated styrene-based elastomers, thus improving the crosslinking density of the adhesive composition without containing highly polar functional groups.

[0063] Examples of organic peroxides include benzoyl peroxide, lauroyl peroxide, t-butyl peroxypivalate, t-butyl peroxyethyl hexanoate, 1,1'-bis-(t-butylperoxy)cyclohexane, t-amylperoxy-2-ethylhexanoate, and t-hexylperoxy-2-ethylhexanoate.

[0064] Furthermore, examples of the coupling agents mentioned above include silane-based coupling agents such as vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxylane, 3-ureidopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-isocyanetopropyltriethoxysilane, and imidazolesilane; titanate-based coupling agents; aluminate-based coupling agents; and zirconium-based coupling agents. These may be used individually or in combination of two or more.

[0065] <<Reaction Accelerator>> The above-mentioned reaction accelerators are used, for example, to accelerate the reaction between styrene elastomers, particularly modified styrene elastomers, and crosslinking agents. Examples of reaction accelerators that can be used include tertiary amine reaction accelerators, tertiary amine salt reaction accelerators, and imidazole reaction accelerators.

[0066] Examples of tertiary amine reaction accelerators include benzyldimethylamine, 2-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol, tetramethylguanidine, triethanolamine, N,N'-dimethylpiperazine, triethylenediamine, and 1,8-diazabicyclo[5.4.0]undecene.

[0067] Examples of tertiary amine salt reaction accelerators include formate, octylate, p-toluenesulfonate, o-phthalate, phenol salt, or phenol novolac resin salt of 1,8-diazabicyclo[5.4.0]undecene, and formate, octylate, p-toluenesulfonate, o-phthalate, phenol salt, or phenol novolac resin salt of 1,5-diazabicyclo[4.3.0]nonene.

[0068] Examples of imidazole 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, and 2,4-diamino-6-[2' Examples include undecylimidazolyl-(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 isocyanurate adduct, 2-phenylimidazole isocyanurate adduct, 2-phenyl-4,5-dihydroxymethylimidazole, and 2-phenyl-4-methyl-5-hydroxymethylimidazole. These curing accelerators may be used alone or in combination of two or more.

[0069] (adhesive layer) The adhesive layer according to the present invention is formed using the adhesive composition of the present invention described above. The adhesive composition forms an adhesive layer and can be cured. There are no particular limitations on the curing method; it can be appropriately selected depending on the purpose, for example, thermal curing. The thickness of the adhesive layer is not particularly limited and can be appropriately selected depending on the purpose, but 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 achieved, and if it is 5 μm or more, it can follow steps such as patterns on printed circuit boards. If the thickness of the adhesive layer is 50 μm or less, thinning of the laminate is possible, and if it is 30 μm or less, the resin flow can be accurately controlled.

[0070] <Method for manufacturing the adhesive layer> An adhesive layer can be manufactured by forming the above adhesive composition into a film. The above adhesive composition can be manufactured by mixing a resin composition containing each of the styrene-based elastomers described above with a curing agent. The mixing method is not particularly limited, as long as the adhesive composition becomes uniform. Since the adhesive composition is preferably used in solution or dispersion form, 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 individually or in combination of two or more. In particular, adding a small amount of cyclohexanone to toluene, which can dissolve resins with low polarity, improves compatibility with curing agents and other components, allowing for a more uniform adhesive layer. If the adhesive composition is a solvent-containing solution or dispersion (resin varnish), coating onto the substrate film and forming the 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 concentration 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 concentration is 80% by mass or less, the viscosity of the solution is appropriate, and it is easy to apply uniformly. A more specific embodiment of the method for manufacturing the adhesive layer is to apply a resin varnish containing the above-mentioned adhesive composition and solvent to the surface of a substrate film to form a resin varnish layer, and then remove the solvent from the resin varnish layer to form a B-stage adhesive layer. Here, a B-stage adhesive layer refers to a state in which the adhesive composition is uncured or partially cured, and in which the curing of the adhesive composition progresses further due to heating or the like. There are no particular restrictions on the method of applying the resin varnish to the substrate film, and it can be appropriately selected depending on the purpose. Examples include the spray method, spin coating method, dip method, roll coating method, blade coating method, doctor roll method, doctor blade method, curtain coating method, slit coating method, screen printing method, inkjet method, and dispensing method. The above-mentioned B-stage adhesive layer can be further heated or otherwise treated to form a hardened adhesive layer.

[0071] <Characteristics of the adhesive layer> The relative permittivity (εr) of the adhesive layer obtained by curing the adhesive composition of the present invention at a frequency of 28 GHz is preferably 3.5 or less, and more preferably 2.7 or less. The dielectric loss tangent (tanδ) of the adhesive layer at a frequency of 28 GHz is preferably 0.005 or less, more preferably 0.0025 or less, and even more preferably 0.002 or less. If the relative permittivity is 3.5 or less and the dielectric loss tangent is 0.005 or less, it can be used in high-frequency FPC-related products with stringent electrical characteristics. Furthermore, if the relative permittivity is 2.7 or less and the dielectric loss tangent is 0.0025 or less, it can satisfy the electrical characteristics expected of components in 5G-compatible high-frequency FPC-related products, achieving electrical characteristics equivalent to LCP, and can be suitably used in 5G high-frequency FPC-related products with stringent electrical characteristics. Moreover, if the dielectric loss tangent is 0.002 or less, it becomes possible to manufacture high-frequency FPC-related products with even more improved transmission characteristics.

[0072] [Relative permittivity and dielectric loss tangent] The relative permittivity and dielectric loss tangent of the adhesive layer can be measured using the open-type resonator method with a network analyzer MS46122B (Anritsu) and an open-type resonator Fabry-Perot DPS-03 (KEYCOM) at a temperature of 23°C and a frequency of 28 GHz.

[0073] The storage modulus at 25°C of the adhesive layer obtained by curing the adhesive composition of the present invention is 1.5 × 10⁻⁶ 7 ~3.0×10 7 It is preferable that the storage modulus is within the above range, which allows for the maintenance of adhesion when the laminate is formed. Furthermore, the storage modulus at 25°C after the adhesive layer has been subjected to 150°C for 168 hours is 1.5 × 10⁻⁶. 7 ~3.0×10 7 It is preferable that the storage modulus is within the above range, which allows for the maintenance of adhesion when the laminate is formed. The storage modulus value should not be too high or too low; it is necessary to maintain a storage modulus that is just right to contribute to adhesion. If the storage modulus of the adhesive layer is within the above range, the effect of suppressing fluctuations in the storage modulus after 168 hours at 150°C by the resin composition used in the present invention can be fully demonstrated.

[0074] (Laminated structure) The laminate of the present invention comprises a base film and the adhesive layer on at least one surface of the base film.

[0075] <Base film> The base 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 copper-clad laminate (CCL), examples include polyimide film, polyetheretherketone film, polyphenylene sulfide film, aramid film, polyethylene naphthalate film, and liquid crystal polymer film. Among these, polyimide film, polyetheretherketone (PEEK) film, polyethylene naphthalate film, and liquid crystal polymer film are preferred from the viewpoint of adhesion and electrical properties. The storage modulus of the base film at 200°C is 1 × 10⁻⁶. 8 The above is preferable. 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 bonding temperature, the more the resin flow of the adhesive composition can be suppressed.

[0076] Furthermore, when the laminate of the present invention is used as a bonding sheet, the base film must be a release film, and examples include polyethylene terephthalate film, polyethylene film, polypropylene film, silicone release treated paper, polyolefin resin coated paper, TPX (polymethylpentene) film, and fluororesin film.

[0077] When the laminate of the present invention is used as a shielding film, the base film must be a film that has electromagnetic wave shielding ability, and examples include a laminate of a protective insulating layer and a metal foil.

[0078] (Coverlay film) A coverlay film is a preferred embodiment of the laminate according to the present invention. When manufacturing FPCs (Flexible Printed Circuits), a laminate with an adhesive layer called a "coverlay film" is typically used to protect the wiring. This coverlay film comprises an insulating resin layer and an adhesive layer formed on its surface. 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 the base film and the adhesive layer are generally difficult to separate. 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 below the above upper limit, the coverlay film can be made into a thin film. If the thickness of the base film is above the above lower limit, the design of the printed circuit board can be easily performed and handling is also good. As a method for producing a coverlay film, for example, a resin varnish containing the above-mentioned adhesive composition and solvent can be applied to the surface of the base film to form a resin varnish layer, and then the solvent can be removed from the resin varnish layer to produce a coverlay film in which a B-stage adhesive layer has been formed. 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 that is subjected to hot air drying, far-infrared heating, and high-frequency induction heating, etc. If necessary, a release film may be laminated onto the surface of the adhesive layer for storage purposes. Known release films such as polyethylene terephthalate film, polyethylene film, polypropylene film, silicone release treated paper, polyolefin resin coated paper, TPX film, and fluororesin film can be used. Because the coverlay film according to the present invention uses the low dielectric adhesive composition of the present invention, it enables high-speed transmission in electronic devices and also exhibits excellent adhesive stability with electronic devices.

[0079] (Bonding sheet) A preferred embodiment of the laminate according to the present invention is a bonding sheet. A bonding sheet has the adhesive layer described above formed on the surface of a release film (base film). Alternatively, the bonding sheet may have an adhesive layer between two release films. When using the bonding sheet, the release film is peeled off. The release film can be the same as that described in the (coverlay film) section above. The thickness of the base 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 base film is within the above range, the bonding sheet is easy to manufacture and easy to handle. One method for manufacturing a bonding sheet is to apply a resin varnish containing the above-mentioned adhesive composition and solvent to the surface of a release film and dry it in the same manner as in the case of the coverlay film. Because the bonding sheet according to the present invention uses the low dielectric adhesive composition of the present invention, it enables high-speed transmission of electronic devices and also exhibits excellent adhesive stability with electronic devices.

[0080] (Copper-clad laminate (CCL)) A preferred embodiment of the laminate according to the present invention is a copper-clad laminate obtained by bonding copper foil to an adhesive layer in the laminate of the present invention. The copper-clad laminate is formed by laminating copper foil onto the above-mentioned laminate, and is composed, for example, in the order of base film, adhesive layer, and copper foil. The adhesive layer and copper foil may be formed on both sides of the base film. The adhesive composition used in this invention also exhibits excellent adhesion to articles containing copper. The copper-clad laminate according to the present invention uses the low-dielectric adhesive composition of the present invention, enabling high-speed transmission in electronic devices and providing excellent adhesive stability.

[0081] One method for manufacturing copper-clad laminates involves bringing the adhesive layer of the laminate into surface contact with the copper foil, 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 for 30 minutes to 4 hours under an inert gas atmosphere. The copper foil is not particularly limited, and electrolytic copper foil, rolled copper foil, etc., can be used.

[0082] (Printed circuit board) A preferred embodiment of the laminate according to the present invention is a printed circuit board in which copper wiring is bonded to an adhesive layer in the laminate of the present invention. A printed circuit board is obtained by forming electronic circuits on the copper-clad laminate mentioned above. A printed circuit board is constructed by laminating a base film and copper wiring using the above-mentioned 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 circuit board is manufactured by using a heat press or the like to attach a coverlay film to the surface having the wiring portion via an adhesive layer. Because the printed circuit board according to the present invention uses the low dielectric adhesive composition of the present invention, it enables high-speed transmission in electronic devices and has excellent adhesive stability. One method for manufacturing a printed circuit board according to the present invention is to bring the adhesive layer of the laminate into contact with the copper wiring, perform heat lamination at 80°C to 200°C, and then cure the adhesive layer by after-curing. The after-curing conditions can be, for example, 100°C to 200°C for 30 minutes to 4 hours. The shape of the copper wiring is not particularly limited, and an appropriate shape may be selected as desired.

[0083] (Shielding film) A preferred embodiment of the laminate according to the present invention is a shield film. Shielding film is a film used to shield various electronic devices, such as computers, mobile phones, and analytical instruments, by cutting out electromagnetic noise that can affect them and cause malfunctions. It is also called electromagnetic shielding film. The electromagnetic wave shielding film is formed by laminating, for example, an insulating resin layer, a metal layer, and an adhesive layer according to the present invention in this order. Because the shielding film according to the present invention uses the low dielectric adhesive composition of the present invention, it enables high-speed transmission of data in electronic devices and also exhibits excellent adhesive stability with electronic devices.

[0084] (Printed circuit board with shielding film) A preferred embodiment of the laminate according to the present invention is a printed circuit board with a shielding film. A printed circuit board with a shielding film is a printed circuit board on which printed circuits are provided on at least one side of the board, with the electromagnetic wave shielding film attached to it. A printed circuit board with a shielding film comprises, for example, a printed circuit board, an insulating film adjacent to the side of the printed circuit board on which the printed circuit is provided, and the electromagnetic wave shielding film. The printed circuit board with a shielding film according to the present invention uses the low-dielectric adhesive composition of the present invention, thereby enabling high-speed transmission of electronic devices and providing excellent adhesive stability. [Examples]

[0085] The present invention will be further described below with reference to examples, but the scope of the present invention is not limited to these examples. In the following, parts and % are by mass unless otherwise specified.

[0086] (Styrene-based elastomer containing carboxyl groups) The product used was Kraton FG1901 (maleic acid-modified hydrogenated styrene-butadiene copolymer), manufactured by Kraton. This copolymer has an acid value of 19 mgKOH / g, a styrene ratio of 30, and a weight-average molecular weight of 81,000. (Styrene-based elastomer containing amino groups) The product used was "ToughTec MP10" (amine-modified hydrogenated styrene-butadiene copolymer) manufactured by Asahi Kasei Corporation. The styrene ratio of this copolymer was 30, and the weight-average molecular weight was 78,000. The total nitrogen content of this copolymer was 430 ppm (μg / g). (Unmodified styrene elastomer) We used Kraton's product name "A1535" (hydrogenated styrene-butadiene copolymer). This copolymer has a styrene ratio of 58 and a weight-average molecular weight of 135,700. (Unmodified styrene elastomer) We used Kraton's product name "A1536" (hydrogenated styrene-butadiene copolymer). This copolymer has a styrene ratio of 42 and a weight-average molecular weight of 140,506. (Unmodified styrene elastomer) We used "ToughTec P1500" (hydrogenated styrene elastomer), a product manufactured by Asahi Kasei Corporation. The styrene ratio of this copolymer is 30, and the weight-average molecular weight is 67,000. (Unmodified styrene elastomer) We used Kraton's product name "Kraton G1651" (styrene-ethylenebutylene-styrene block copolymer). This copolymer has a styrene ratio of 33 and a weight-average molecular weight of 136,700. (Hardening agent: epoxy-modified resin) We used "Epofriend CT310" (epoxidized styrene-butadiene block copolymer), manufactured by Daicel Corporation. This copolymer has a styrene / ethylene-butylene ratio of 40 / 60, a weight-average molecular weight of 93,000, and an epoxy equivalent of 2125 g / eq. (Hardening agent: Bismaleimide resin) The product used was "SLK-3000-T50," manufactured by Shin-Etsu Chemical Co., Ltd. Its weight-average molecular weight is 138.77. (Hardening agent: Benzoxazine resin) The product name "Pd" manufactured by Shikoku Chemicals, Inc. was used. (solvent) A mixed solvent consisting of toluene and cyclohexanone (mass ratio = 97:3) was used. (Base film) As the base film, we used "Shin-Etsu Sepla Film PEEK" (polyether ether ketone, 50 μm thick) manufactured by Shin-Etsu Polymer Co., Ltd. The storage modulus of the base film at 200°C was 5 × 10⁻⁶. 8 That was the case. (electrolytic copper foil) As the electrolytic copper foil, we used "TQ-M7-VSP" (electrolytic copper foil, thickness 12 μm, glossy surface Rz 1.27 μm, glossy surface Ra 0.197 μm, glossy surface Rsm 12.95 μm) manufactured by Mitsui Mining & Smelting Co., Ltd. The surface roughness of the glossy surface was measured using a laser microscope, and the value was determined from this roughness curve based on JIS B 0601:2013 (ISO 4287:1997 Amd.1:2009). (Release film) As the release film, we used NP75SA (silicone release PET film, 75 μm) manufactured by Panac Co., Ltd.

[0087] (Example 1) A resin varnish was prepared by dissolving the components of the adhesive layer shown in Table 1 in the proportions shown in Table 1, and having a solid content concentration of 15% by mass. The components constituting the resin composition in the adhesive composition are shown in Table 1. The proportions of the resin composition and the curing agent are also shown in Table 1.

[0088] The relative permittivity and dielectric loss tangent of the adhesive layer obtained by curing using the resin varnish of Example 1 were measured at a frequency of 28 GHz. The elastic modulus at 25°C was measured for the adhesive layer obtained by curing with the resin varnish of Example 1. Furthermore, the storage modulus of the adhesive layer obtained by curing with the resin varnish of Example 1 was measured after 168 hours at 150°C.

[0089] [Relative permittivity and dielectric loss tangent] The dielectric constant and dielectric loss tangent of the adhesive layer were measured using the open-type resonator method with a network analyzer MS46122B (Anritsu) and an open-type resonator Fabry-Perot DPS-03 (KEYCOM) at a temperature of 23°C and a frequency of 28 GHz. For the measurement sample, a resin varnish was roll-coated onto a release film, and then this coated film was placed in an oven and dried at 110°C for 4 minutes to form a B-stage adhesive layer (thickness 50 μm). Next, this adhesive layer was heat-laminated at 150°C with the adhesive surfaces in contact to form a pre-cured adhesive film (thickness 100 μm). This pre-cured adhesive film (thickness 100 μm) was placed in an oven and heat-cured at 150°C for 60 minutes to produce a cured adhesive film (100 mm × 100 mm). After curing, the release film was peeled off the adhesive film, and the relative permittivity and dielectric loss tangent of the adhesive layer were measured.

[0090] [Storage modulus (Pa)] The storage modulus of the adhesive layer was measured using a viscoelasticity measuring device (RSA-G2, TA Instruments) with a measurement frequency of 1 Hz and a heating rate of 5 °C / min, in accordance with JIS K7244. For the measurement sample, a resin varnish was roll-coated onto a release film, and this coated film was then placed in an oven and dried at 110 °C for 4 minutes to form a B-stage adhesive layer (50 μm thick). Next, this adhesive layer was heat-laminated at 120 °C with the adhesive surfaces in contact to form a pre-cured adhesive film (100 μm thick), and a pre-cured adhesive film (100 mm × 100 mm) was prepared. The release film was peeled off the adhesive film, and the storage modulus (Pa) of the pre-cured adhesive layer was measured. Furthermore, a pre-curing adhesive film (100 μm thick) was placed in an oven and heat-cured at 150°C for 60 minutes to produce a cured adhesive film (100 mm x 100 mm). The release film was peeled off the adhesive film and the storage modulus (Pa) of the cured adhesive layer was measured. Similarly, the storage modulus (Pa) of the cured adhesive layer was measured after 168 hours at 150°C.

[0091] Using the resin varnish from Example 1, a laminate with adhesive after curing was prepared by the following method. The surface of the base film was subjected to corona treatment. The resin varnish prepared above was applied to the surface of the base film and dried in an oven at 130°C for 4 minutes to evaporate the solvent, forming an adhesive layer (25 μm) and obtaining an adhesive-backed base film (adhesive-backed laminate). The adhesive layer of the adhesive-backed laminate was placed in contact with the glossy surface of the electrolytic copper foil and heat-laminated at 150°C to obtain an adhesive-backed laminate before curing. The adhesive layer of the adhesive-backed laminate before curing was cured by after-curing at 150°C for 1 hour to obtain a cured adhesive-backed laminate.

[0092] The initial adhesion force (N / cm) between the electrolytic copper foil and the substrate film of the adhesive-coated laminate in Example 1 after curing was measured. The adhesion strength (N / cm) of the cured adhesive laminate of Example 1 was measured after a heat resistance test at 150°C for 168 hours. A solder heat resistance test was performed on the adhesive-coated laminate from Example 1 after curing. The resin flow rate (resin leakage rate) (mm) of the adhesive-coated laminate after curing in Example 1 was measured.

[0093] [Initial adhesion force (N / cm)] Adhesion strength was measured by cutting a 25mm wide test specimen from the cured adhesive-coated laminate and, in accordance with JIS Z0237:2009 (Test Methods for Adhesive Tapes and Adhesive Sheets), by measuring the peel strength when peeling the electrolytic copper foil from the adhesive-coated base film fixed to the support at a peeling speed of 0.3m / min and a peeling angle of 180°.

[0094] [Adhesion strength after heat resistance test (N / cm)] The adhesion strength after the heat resistance test was measured by cutting the cured adhesive laminate into a 25mm wide test specimen, and after 168 hours at 150°C, measuring the peel strength when peeling the electrolytic copper foil from the adhesive-coated base film fixed to the support at a peeling speed of 0.3m / min and a peeling angle of 180°, in accordance with JIS Z0237:2009 (Test method for adhesive tapes and adhesive sheets).

[0095] [Heat resistance test evaluation] The adhesion strength after the heat resistance test was evaluated according to the following criteria. ○ 5N / cm or more △ 3N / cm or more and less than 5N / cm × Less than 3 N / cm

[0096] [Solder heat resistance test] For the solder heat resistance test, the cured adhesive-coated laminate was cut into 30mm x 30mm test specimens. With the base film side facing up, these specimens were floated in a 288°C solder bath for 10 seconds x 3 times, and any abnormal appearance such as blistering 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). ○ Although no abnormalities were found in the end, softening of the adhesive layer was observed during the test. △ Although there is no peeling, the adhesive layer has softened, creating a "stain pattern." × It is peeling off.

[0097] [Resin flow (resin flow rate) (mm)] After curing, the adhesive-coated laminate was cut to create a 30mm x 90mm test specimen, and three 5mm diameter holes were punched into it using a belt punch. The electrolytic copper foil was placed on top of the glossy surface, and thermal lamination was performed at 150°C. It was then pressed at 180°C, 3 MPa for 3 minutes. The length of the resin that protruded 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

[0098] The results of each measurement are shown in Table 1.

[0099] (Examples 2 to 13) Laminates of Examples 2 to 13 were prepared in the same manner as in Example 1, except that the types and amounts of components constituting the adhesive layer were changed as shown in Tables 1 and 2. The fabricated laminate was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

[0100] (Comparative Example 1 to Comparative Example 4) Laminates of Comparative Examples 1 to 4 were prepared in the same manner as in Example 1, except that the types and amounts of components constituting the adhesive layer were changed as shown in Table 2. The fabricated laminate was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0101] [Table 1]

[0102] [Table 2]

[0103] As shown in the examples, the adhesive layer made from 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 suppression of resin flow (resin leakage), and further exhibits excellent adhesion reliability even after 168 hours at 150°C. [Industrial applicability]

[0104] Laminates having an adhesive layer made of 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, laptop computers, and medical devices.

Claims

1. An adhesive composition for printed circuit boards, comprising a resin composition containing a styrene-based elastomer, The aforementioned styrene elastomer contains a modified styrene elastomer. The styrene-based elastomer contains a styrene-based elastomer having a styrene ratio of 33 to 80. The content of the styrene-based elastomer, in which the styrene ratio is 33 or more and 80 or less per 100 parts by mass of the resin composition, is 30 to 70 parts by mass. The adhesive composition contains the resin composition and a curing agent. The curing agent comprises a benzoxazine resin, An adhesive composition wherein the content of the curing agent is 20 parts by mass or less per 100 parts by mass of the resin composition.

2. The adhesive composition according to claim 1, wherein the resin composition contains the modified styrene elastomer and the unmodified styrene elastomer.

3. The adhesive composition according to claim 2, wherein the styrene-based elastomer having a styrene ratio of 33 to 80 is the unmodified styrene-based elastomer.

4. An adhesive layer obtained by curing the adhesive composition described in claim 1.

5. The storage modulus of the adhesive layer at 25°C after 168 hours at 150°C is 1.5 × 10⁻⁶. ７ ~3.0 x 10 ７ The adhesive layer according to claim 4, wherein the material is Pa.

6. The adhesive layer according to claim 5, wherein the relative permittivity of the adhesive layer, measured at a frequency of 28 GHz, is 3.5 or less, and the dielectric loss tangent is 0.005 or less.

7. A base film and A laminate having an adhesive layer according to any one of claims 4 to 6.

8. The laminate according to claim 7, wherein the base film contains polyetheretherketone (PEEK) resin.

9. A printed circuit board comprising the laminate described in claim 7.

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