Adhesive agent composition and laminate with adhesive agent layer

Abstract

This adhesive agent composition comprises: a modified polyolefin-based resin (A) having a reactive functional group that reacts with an epoxy group; and an epoxy resin (B). The content of the epoxy resin (B) is 1-25 parts by mass with respect to 100 parts by mass of the modified polyolefin-based resin (A), and the weight average molecular weight Mw of the modified polyolefin-based resin (A) is 70,000-470,000. The adhesive agent composition has a storage modulus of 0.015 MPa or more at 200°C in the form of a cured product. The adhesive agent composition has a 180°-peel adhesion strength of 0.5 N / mm or more as measured on an adhesive test piece after being heated. This laminate with an adhesive agent layer comprises: an adhesive agent layer formed from an adhesive agent composition; and a base material film in contact with at least one surface of the adhesive agent layer.

Description

Adhesive composition and laminate with adhesive layer CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2023-220893, filed on December 27, 2023, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to an adhesive composition and a laminate with an adhesive layer.

[0003] In recent years, the demand for products related to flexible printed wiring boards (hereinafter also referred to as "FPCs") has increased along with the trend toward higher performance, smaller size, and lighter weight of electronic devices. Flexible printed wiring boards are flexible printed wiring boards that allow high-density, three-dimensional stacking of circuits in a limited space. Furthermore, by multi-layering flexible printed wiring boards, the area for wiring electronic circuits inside can be increased, and a large number of semiconductor components can be densely mounted on the surface.

[0004] When a flexible printed wiring board is produced, a laminate with an adhesive layer is used, in which an adhesive layer formed from an adhesive composition is laminated on a substrate film made of a resin film. When a flexible printed wiring board is multilayered, an adhesive composition is used for the lamination.

[0005] Demands for the performance of flexible printed wiring boards are becoming more stringent, and as transmission signal speeds increase, signals are becoming increasingly frequent. Accordingly, there is an increasing demand for flexible printed wiring boards to have low dielectric properties in the high-frequency range. To achieve this, various adhesive compositions have been developed.

[0006] For example, Patent Document 1 proposes a polyolefin-based adhesive composition that contains an acid-modified polyolefin and one or more compounds selected from the group consisting of an epoxy resin, an isocyanate compound, and a carbodiimide compound as an adhesive composition having low dielectric properties.

[0007] International Publication No. WO2021 / 0706060

[0008] However, although the cured product of the adhesive composition of Patent Document 1 has low dielectric properties and excellent initial adhesive strength, it may have insufficient heat resistance and adhesive strength after being left in a high-temperature environment for a long period of time. One possible method for improving the heat resistance and adhesive strength after being left in a high-temperature environment for a long period of time is to increase the amount of epoxy resin, which is the cured resin in the adhesive composition. However, this method increases the relative dielectric constant and deteriorates the dielectric properties.

[0009] The present disclosure has been made in view of such problems, and aims to provide an adhesive composition that provides a cured product with a low relative dielectric constant, excellent heat resistance, and excellent adhesive strength even after being placed in a high-temperature environment for a long period of time, as well as a laminate with an adhesive layer that uses the same.

[0010] The adhesive composition and the laminate with an adhesive layer according to the present disclosure are as follows.

[0011] [1] An adhesive composition comprising a modified polyolefin resin (A) having a reactive functional group that reacts with an epoxy group, and an epoxy resin (B), wherein the content of the epoxy resin (B) is 1 part by mass or more and 25 parts by mass or less per 100 parts by mass of the modified polyolefin resin (A), the modified polyolefin resin (A) has a weight average molecular weight Mw of 70,000 or more and 470,000 or less, the adhesive composition is cured under conditions of a curing temperature of 180°C and a curing time of 60 minutes, and the cured product of the adhesive composition has a storage modulus at 200°C of 0.015 MPa or more, and the adhesive composition is heat-treated at 200°C for 7 days to bond a polyimide substrate and a copper foil, and the heat-treated adhesive test specimen is then left to stand at 25°C and 65% RH for 24 hours, and the heat-treated adhesive test specimen satisfies JIS Z 10044-1:2001. An adhesive composition having a 180° peel adhesion strength of 0.5 N / mm or more, measured in accordance with ISO 6481 at a temperature of 23°C and a tensile speed of 50 mm / min. [2] The adhesive composition according to [1], wherein the cured product of the adhesive composition has a relative dielectric constant of 2.5 or less, measured at a frequency of 1 GHz. [3] The adhesive composition according to [1] or [2], wherein the modified polyolefin resin (A) is an acid-modified polyolefin resin. [4] The adhesive composition according to any one of [1] to [3], wherein the modified polyolefin resin (A) is a resin obtained by graft-modifying an unmodified polyolefin resin with a modifier containing an α,β-unsaturated carboxylic acid or a derivative thereof. [5] The adhesive composition according to [4], wherein the unmodified polyolefin resin is at least one selected from the group consisting of an ethylene-propylene copolymer, a propylene-butene copolymer, and an ethylene-propylene-butene copolymer. [6] The adhesive composition according to [4] or [5], wherein the unmodified polyolefin resin has a propylene unit content of 50 mol% or more and 9 mol% or less. [7] The adhesive composition according to any one of [1] to [6], wherein the epoxy resin (B) is a polyfunctional epoxy resin having an alicyclic skeleton.[8] A laminate with an adhesive layer, comprising an adhesive layer formed from the adhesive composition according to any one of [1] to [7], and a substrate film in contact with at least one surface of the adhesive layer.

[0012] In this disclosure, the term "adhesive layer" refers to a layer in a state before curing, in a B-stage state (i.e., a state in which a portion is in a semi-cured state where curing of the adhesive composition has begun, and curing of the adhesive composition progresses further by heating or the like), or in a state after the curing reaction has progressed to sufficiently form a crosslinked structure. Furthermore, the term "cured product" refers to a product in a state after the adhesive composition has been cured to sufficiently form a crosslinked structure.

[0013] The adhesive composition has the above-described configuration, and therefore, the adhesive composition, when cured, has a low relative dielectric constant, excellent heat resistance, and excellent adhesive strength even after being left in a high-temperature environment for a long period of time.

[0014] The laminate with an adhesive layer has the above-described configuration. Therefore, in the laminate with an adhesive layer, when the laminate is formed from a cured product of the adhesive composition, the adhesive layer has a low dielectric constant, excellent heat resistance, and excellent adhesive strength even after being placed in a high-temperature environment for a long period of time.

[0015] Hereinafter, one embodiment of the present disclosure will be described, but the present disclosure is not limited to the example of the following embodiment. Furthermore, the lower limit and upper limit of the numerical ranges shown below can be arbitrarily combined.

[0016] 1. Adhesive Composition The adhesive composition of this embodiment contains a modified polyolefin resin (A) having a reactive functional group that reacts with an epoxy group, and an epoxy resin (B). In the adhesive composition of this embodiment, the content of the epoxy resin (B) is 1 part by mass or more and 25 parts by mass or less per 100 parts by mass of the modified polyolefin resin (A), and the weight average molecular weight Mw of the modified polyolefin resin (A) is 70,000 or more and 470,000 or less. The adhesive composition of this embodiment is cured under conditions of a curing temperature of 180°C and a curing time of 60 minutes, and the cured product of the adhesive composition has a storage modulus at 200°C of 0.015 MPa or more. Adhesion test pieces obtained by bonding a polyimide substrate and a copper foil using the adhesive composition are heat-treated at 200°C for 7 days and then allowed to stand at 25°C and 65% RH for 24 hours. The heat-treated adhesion test pieces have a 180° peel strength of 0.5 N / mm or more, as measured in accordance with JIS C6481 at 23°C and a tensile speed of 50 mm / min. The adhesive composition of this embodiment will now be described in detail.

[0017] 1.1 Modified Polyolefin Resin (A) In the adhesive composition of this embodiment, the modified polyolefin resin (A) is an important adhesive component that serves as the base of the adhesive composition.

[0018] The modified polyolefin resin (A) has a reactive functional group that reacts with an epoxy group. That is, the modified polyolefin resin (A) can be said to be an unmodified polyolefin resin into which a reactive functional group that reacts with an epoxy group has been introduced, or can be said to be a resin obtained by modifying an unmodified polyolefin resin with a modifier having a reactive functional group that reacts with an epoxy group, or can be said to be a resin obtained by modifying an unmodified polyolefin resin so as to have reactivity with the epoxy resin (B).

[0019] Examples of reactive functional groups that react with epoxy groups include groups having active hydrogen, active ester groups, etc. Examples of groups having active hydrogen include carboxy groups, amino groups, hydroxyl groups, acid anhydride groups, and thiol groups. These can be used alone or in combination of two or more. From the viewpoint of reactivity, etc., the reactive functional group that reacts with epoxy groups is preferably a carboxy group or an amino group, and more preferably a carboxy group.

[0020] The modified polyolefin resin (A) is preferably an acid-modified polyolefin resin, and specifically, it can be a resin having a portion derived from an unmodified polyolefin resin and a graft portion derived from a modifying agent, and is preferably a resin obtained by graft-modifying an unmodified polyolefin resin with a modifying agent containing an α,β-unsaturated carboxylic acid or a derivative thereof.

[0021] The production of the modified polyolefin resin (A) by graft modification (graft polymerization) can be carried out by known methods, and a radical initiator may be used during production. Examples of methods for producing the modified polyolefin resin (A) include a solution method in which an unmodified polyolefin resin is heated and dissolved in a solvent such as toluene, and the modifier and radical initiator are added, and a melt method in which the unmodified polyolefin resin, modifier, and radical initiator are melt-kneaded using a Banbury mixer, kneader, extruder, or the like. The method for using the unmodified polyolefin resin, modifier, and radical initiator is not particularly limited, and they may be added to the reaction system all at once or sequentially. Furthermore, when producing the modified polyolefin resin (A), a modification aid for improving the graft efficiency of the modifier such as an α,β-unsaturated carboxylic acid, a stabilizer for adjusting the resin stability, and the like may also be used.

[0022] The unmodified polyolefin resin used in producing the modified polyolefin resin (A) is not particularly limited as long as it has a structural unit derived from an olefin, but homopolymers or copolymers having 2 to 20 carbon atoms, such as ethylene, propylene, butene, pentene, hexene, heptene, octene, and 4-methyl-1-pentene, are preferably used. The unmodified polyolefin resin is more preferably a homopolymer or copolymer of an olefin having 2 to 6 carbon atoms. Specific examples of the unmodified polyolefin resin include ethylene-propylene copolymers, propylene-butene copolymers, and ethylene-propylene-butene copolymers. These can be used alone or in combination of two or more.

[0023] Specifically, the unmodified polyolefin resin used in producing the modified polyolefin resin (A) is preferably an unmodified polypropylene resin. In this case, the modified polyolefin resin (A) can be a resin having a portion derived from the unmodified polypropylene resin and a graft portion derived from a modifier, and is preferably a resin obtained by graft-modifying an unmodified polypropylene resin with a modifier containing an α,β-unsaturated carboxylic acid or a derivative thereof. The unmodified polypropylene resin is not particularly limited as long as it has structural units derived from propylene and is not modified with a modifier such as an α,β-unsaturated carboxylic acid or a derivative thereof. However, a copolymer of propylene and an olefin having 2 to 20 carbon atoms, such as ethylene, butene, pentene, hexene, heptene, octene, or 4-methyl-1-pentene, is preferably used. The unmodified polypropylene resin is more preferably a copolymer of propylene and an olefin having 2 to 6 carbon atoms.

[0024] The content ratio of the structural units in the unmodified polyolefin resin and the unmodified polypropylene resin can be selected arbitrarily. From the viewpoint of advantageous adhesion to poorly adhesive adherends, the modified polyolefin resin (A) is preferably a modified resin of at least one unmodified polypropylene resin selected from the group consisting of ethylene-propylene copolymer, propylene-butene copolymer, and ethylene-propylene-butene copolymer. From the viewpoint of obtaining excellent adhesive properties, it is preferable to use an unmodified polypropylene resin having a propylene unit content of 50 mol% or more and 98 mol% or less. When the propylene unit content is within the above-mentioned range, flexibility can be imparted to the bonded joint after bonding two members.

[0025] The modifier may include an α,β-unsaturated carboxylic acid and its derivative. Examples of the α,β-unsaturated carboxylic acid include maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, aconitic acid, and norbornene dicarboxylic acid. Derivatives of unsaturated carboxylic acids include acid anhydrides, acid halides, amides, imides, and esters. Preferred modifiers include itaconic anhydride, maleic anhydride, aconitic anhydride, and citraconic anhydride, with itaconic anhydride and maleic anhydride being particularly preferred in terms of adhesiveness. When a modifier is used, it is sufficient to use one or more selected from α,β-unsaturated carboxylic acids and their derivatives. Examples of the modifier include a combination of one or more α,β-unsaturated carboxylic acids and one or more derivatives thereof, a combination of two or more α,β-unsaturated carboxylic acids, or a combination of two or more derivatives of α,β-unsaturated carboxylic acids.

[0026] The modifying agent may contain other compounds (other modifying agents) in addition to the α,β-unsaturated carboxylic acid, etc., depending on the purpose. Examples of the other compounds (other modifying agents) include (meth)acrylic acid esters represented by the following formula (1), (meth)acrylic acid, other (meth)acrylic acid derivatives, aromatic vinyl compounds, cyclohexyl vinyl ether, etc. These other compounds may be used alone or in combination of two or more. CH２ =CR1COOR2 (1) (In formula (1), R1 is a hydrogen atom or a methyl group, and R2 is a hydrocarbon group.)

[0027] In formula (1) representing the (meth)acrylic acid ester, R1 is a hydrogen atom or a methyl group, preferably a methyl group. R2 is a hydrocarbon group, preferably an alkyl group having 8 to 18 carbon atoms. Examples of compounds represented by formula (1) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and benzyl (meth)acrylate. These compounds may be used alone or in combination of two or more. In this embodiment, it is preferable to use a modifier that further contains a (meth)acrylic acid ester having an alkyl group having from 8 to 18 carbon atoms, as this improves heat resistance. In particular, it is preferable to use a modifier that contains octyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, or stearyl (meth)acrylate.

[0028] Examples of (meth)acrylic acid derivatives other than (meth)acrylic acid esters include hydroxyethyl (meth)acrylate, glycidyl (meth)acrylate, and isocyanate-containing (meth)acrylic acid. Examples of aromatic vinyl compounds include styrene, o-methylstyrene, p-methylstyrene, and α-methylstyrene. The combined use of an α,β-unsaturated carboxylic acid or its derivative with another modifier as the modifier can improve the graft rate of the modifier, improve solubility in solvents, and further improve adhesion. When a modifier other than the (meth)acrylic acid ester represented by formula (1) is used, it is desirable that the amount used does not exceed the total amount of the α,β-unsaturated carboxylic acid and its derivative and the (meth)acrylic acid ester.

[0029] As described above, the modified polyolefin resin (A) may have at least a graft moiety derived from a modifier. Hereinafter, the content of the graft moiety contained in the modified polyolefin resin (hereinafter also referred to as "graft mass") will be described.

[0030] The modified polyolefin resin (A) may have a graft moiety derived from an α,β-unsaturated carboxylic acid or a derivative thereof. In the modified polyolefin resin (A), the graft mass of the graft moiety derived from an α,β-unsaturated carboxylic acid or a derivative thereof is preferably 0.1% by mass or more and 20% by mass or less, and more preferably 0.2% by mass or more and 18% by mass or less, relative to 100% by mass of the modified polyolefin resin (A), from the viewpoint of adhesiveness. A graft mass of 0.1% by mass or more provides excellent solubility in solvents and particularly excellent adhesion to adherends made of metals and the like. Furthermore, a graft mass of 20% by mass or less provides sufficient adhesion to adherends made of resins and the like.

[0031] The graft mass derived from an α,β-unsaturated carboxylic acid or a derivative thereof in the modified polyolefin resin (A) can be determined by alkali titration. However, when the derivative of the α,β-unsaturated carboxylic acid is an imide or the like having no acid group, the graft mass can be determined by Fourier transform infrared spectroscopy.

[0032] When the modified polyolefin resin (A) contains a graft moiety derived from the (meth)acrylic acid ester represented by the above formula (1), the graft mass is preferably from 0.1 to 30% by mass, more preferably from 0.3 to 25% by mass, relative to 100% by mass of the modified polyolefin resin (A). When the graft mass is from 0.1 to 30% by mass, the solubility in solvents is excellent and the adhesion to adherends can be further improved.

[0033] When the modifying agent contains a (meth)acrylic acid ester represented by the formula (1), the graft mass in the resulting modified polyolefin resin (A) can be determined by Fourier transform infrared spectroscopy.

[0034] The radical initiator used in the production of the modified polyolefin resin (A) can be appropriately selected from known radical initiators. For example, it is preferable to use an organic peroxide such as benzoyl peroxide, dicumyl peroxide, lauroyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, or cumene hydroperoxide.

[0035] Examples of the modifying aid that can be used in producing the modified polyolefin resin (A) include divinylbenzene, hexadiene, dicyclopentadiene, etc. Examples of the stabilizer that can be used include hydroquinone, benzoquinone, nitrosophenylhydroxy compounds, etc.

[0036] The weight-average molecular weight Mw of the modified polyolefin resin (A) is 70,000 or more and 470,000 or less. When the lower limit of the weight-average molecular weight Mw of the modified polyolefin resin (A) is 70,000 or more, the cohesive force is good even after exposure to high temperatures, and excellent adhesive strength can be exhibited. From the viewpoint of solvent resistance at the bonded joint after bonding, the lower limit of the weight-average molecular weight Mw of the modified polyolefin resin (A) is preferably 72,000 or more, more preferably 75,000 or more, and even more preferably 80,000 or more. On the other hand, when the upper limit of the weight-average molecular weight Mw of the modified polyolefin resin (A) is 470,000 or less, excellent fluidity is achieved, and the varnish can be easily handled when forming a thin film layer. The upper limit of the weight-average molecular weight Mw of the modified polyolefin resin (A) is preferably 430,000 or less, more preferably 400,000 or less, and even more preferably 380,000 or less, from the viewpoints of initial adhesive strength, solubility in solvents, etc. The upper and lower limits of the weight-average molecular weight Mw can be combined in any manner.

[0037] The acid value of the modified polyolefin resin (A) is preferably 0.1 mgKOH / g or more and 50 mgKOH / g or less, more preferably 0.5 mgKOH / g or more and 40 mgKOH / g or less, and even more preferably 1.0 mgKOH / g or more and 30 mgKOH / g or less. When the acid value of the modified polyolefin resin (A) is within the above range, the adhesive composition is sufficiently cured, and good adhesion, heat resistance, and low dielectric properties are obtained.

[0038] The content of the modified polyolefin resin (A) is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, and even more preferably 65 parts by mass or more, per 100 parts by mass of the solid content of the adhesive composition. By having the content of the modified polyolefin resin (A) be 50 parts by mass or more, it is possible to easily exhibit good adhesive properties. The content of the modified polyolefin resin (A) is preferably 99 parts by mass or less, per 100 parts by mass of the solid content of the adhesive composition.

[0039] 1.2 Epoxy Resin (B) In the adhesive composition of this embodiment, the epoxy resin (B) reacts with reactive functional groups such as carboxyl groups contained in the modified polyolefin resin (A), and is an important component for imparting adhesion to adherends and heat resistance to the cured adhesive.

[0040] Examples of the epoxy resin (B) include bisphenol A type epoxy resins, bisphenol F type epoxy resins, and hydrogenated versions thereof; glycidyl ester-based epoxy resins such as orthophthalic 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, propylene glycol diglycidyl ether, and 1,4-butanediol. Examples of epoxy resins that can be used include, but are not limited to, glycidyl ether-based epoxy resins such as diol diglycidyl 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; glycidylamine-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 phenol novolac epoxy resin, o-cresol novolac epoxy resin, and bisphenol A novolac epoxy resin can also be used.

[0041] Examples of the epoxy resin (B) include brominated bisphenol A epoxy resins, phosphorus-containing epoxy resins, dicyclopentadiene skeleton-containing epoxy resins, naphthalene skeleton-containing epoxy resins, anthracene-type epoxy resins, tertiary butylcatechol-type epoxy resins, triphenylmethane-type epoxy resins, tetraphenylethane-type epoxy resins, biphenyl-type epoxy resins, and bisphenol S-type epoxy resins. These epoxy resins (B) may be used alone or in combination of two or more. Among the epoxy resins (B), epoxy resins without glycidylamino groups are preferred because they improve the storage stability of the laminate with the adhesive layer. Furthermore, as the epoxy resin (B), polyfunctional epoxy resins with alicyclic skeletons are preferred, and epoxy resins with dicyclopentadiene skeletons are more preferred, since they provide adhesive compositions with excellent dielectric properties.

[0042] The epoxy resin (B) preferably has two or more epoxy groups in one molecule. This is because a crosslinked structure is formed by reaction with the modified polyolefin resin (A), thereby exhibiting high heat resistance. Furthermore, when an epoxy resin having two or more epoxy groups is used, the degree of crosslinking with the modified polyolefin resin (A) is sufficient, resulting in sufficient heat resistance.

[0043] The content of the epoxy resin (B) is 1 part by mass or more and 25 parts by mass or less per 100 parts by mass of the modified polyolefin resin (A). This makes it possible to maintain heat resistance while keeping the relative dielectric constant of the cured product low. From the viewpoints of peel strength, heat resistance, etc., the lower limit of the content of the epoxy resin (B) is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more. Furthermore, from the viewpoint of suppressing a decrease in low dielectric properties, etc., the upper limit of the content of the epoxy resin (B) is preferably 20 parts by mass or less, more preferably 17.5 parts by mass or less, and even more preferably 15 parts by mass or less. The upper and lower limits of the content of the epoxy resin (B) can be combined in any manner.

[0044] 1.3 Other Components In addition to the modified polyolefin resin (A) and epoxy resin (B) described above, the adhesive composition of the present embodiment may contain other thermoplastic resins, tackifiers, flame retardants, curing agents, curing accelerators, coupling agents, heat aging inhibitors, inorganic fillers, leveling agents, antifoaming agents, pigments, ultraviolet absorbers, lubricants, solvents, and the like, to the extent that the functionality of the adhesive composition is not affected.

[0045] (Thermoplastic Resin) Examples of the other thermoplastic resins include polyolefin resins, styrene elastomers, phenoxy resins, polyamide resins, polyester resins, polycarbonate resins, polyphenylene oxide resins, polyurethane resins, polyacetal resins, and polyvinyl resins. These thermoplastic resins may be used alone or in combination of two or more.

[0046] Specific examples of polyolefin resins include ethylene-α-olefin copolymers such as ethylene-propylene terpolymers (EPDM, EPT), ethylene-propylene copolymers (EPM), ethylene-butene copolymers, ethylene-propylene-butene copolymers, ethylene-1-hexene copolymers, and ethylene-1-octene copolymers, as well as the unmodified polyolefin resins described above in the section on modified polyolefin resin (A). These may be used alone or in combination of two or more.

[0047] Specific examples of styrene-based elastomers include styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-butene-styrene-styrene block copolymer (SEBSS), styrene-isobutylene-styrene block copolymer (SIBS), and styrene-isoprene-styrene block copolymer (SIS). These may be used alone or in combination of two or more.

[0048] (Tackifier) ​​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, turpentine-based resin, etc. These tackifiers may be used alone or in combination of two or more.

[0049] (Flame Retardant) The 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. These flame retardants may be used alone or in combination of two or more.

[0050] (Curing Agent) Examples of the curing agent include, but are not limited to, amine-based curing agents and acid anhydride-based curing agents. Examples of the amine-based curing agent include melamine resins such as methylated melamine resin, butylated melamine resin, and benzoguanamine resin, dicyandiamide, and 4,4'-diphenyldiaminosulfone. Examples of the acid anhydride include aromatic acid anhydrides and aliphatic acid anhydrides. These curing agents may be used alone or in combination of two or more.

[0051] The content of the curing agent is preferably 1 part by mass or more and 100 parts by mass or less, and more preferably 5 parts by mass or more and 70 parts by mass or less, relative to 100 parts by mass of the epoxy resin (B).

[0052] (Curing Accelerator) The curing accelerator can be used for the purpose of accelerating the reaction between the modified polyolefin resin (A) and the epoxy resin (B), and examples of the curing accelerator that can be used include tertiary amine curing accelerators, tertiary amine salt curing accelerators, and imidazole curing accelerators.

[0053] Examples of the tertiary amine curing accelerator 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.

[0054] Examples of the tertiary amine salt curing accelerator include formate, octylate, p-toluenesulfonate, o-phthalate, phenolate, and phenol novolac resin salt of 1,8-diazabicyclo[5.4.0]undecene; and formate, octylate, p-toluenesulfonate, o-phthalate, phenolate, and phenol novolac resin salt of 1,5-diazabicyclo[4.3.0]nonene.

[0055] Examples of the imidazole curing accelerator 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.

[0056] When the adhesive composition of this embodiment contains a curing accelerator, the content of the curing accelerator is preferably 1 part by mass or more and 15 parts by mass or less, more preferably 1 part by mass or more and 10 parts by mass or less, and even more preferably 2 parts by mass or more and 5 parts by mass or less, relative to 100 parts by mass of the epoxy resin (B). When the content of the curing accelerator is within the above range, it is possible to easily exhibit excellent adhesiveness and heat resistance.

[0057] (Coupling Agent) 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-isocyanatepropyltriethoxysilane, 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.

[0058] (Heat Aging Resistant) Examples of the heat aging inhibitor include antioxidants, and specific examples thereof 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 Examples of antioxidants include phenol-based antioxidants such as ethylene glycol-bis[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 antioxidants may be used alone or in combination of two or more.

[0059] (Inorganic Filler) Examples of the inorganic filler include powders of titanium oxide, aluminum oxide, zinc oxide, carbon black, silica, talc, copper, silver, etc. These may be used alone or in combination of two or more.

[0060] (Lubricant) Examples of the lubricant include oleic acid amide, stearic acid amide, erucic acid amide, etc. These may be used alone or in combination of two or more.

[0061] (Solvent) The adhesive composition of this embodiment can be produced by mixing the modified polyolefin resin (A), the epoxy resin (B), and, if necessary, other components. The mixing method is not particularly limited as long as the adhesive composition becomes homogeneous. Since the adhesive composition is preferably used in the form of a solution or dispersion, a solvent such as an organic solvent is usually also used.

[0062] 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, 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. When the adhesive composition contains a solvent and is a solution or dispersion (resin varnish) in which the components are dissolved or dispersed in the solvent, coating onto a substrate film and forming an adhesive layer can be carried out smoothly, and an adhesive layer of the desired thickness can be easily obtained.

[0063] When the adhesive composition of the present embodiment contains a solvent such as an organic solvent, the solid content is preferably in the range of 5% by mass to 50% by mass, more preferably 10% by mass to 40% 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 easy. In the present disclosure, "solid content" means the components excluding the solvent.

[0064] 1.4 Storage Modulus of Cured Adhesive Composition The adhesive composition of this embodiment is cured at a curing temperature of 180°C for a curing time of 60 minutes, and the cured product of the adhesive composition has a storage modulus of 0.015 MPa or more at 200°C. The storage modulus measured under these conditions is a physical property closely related to the heat resistance of the cured adhesive composition and the adhesive strength after being left in a high-temperature environment for a long period of time. Details of the method for measuring the storage modulus will be described in detail in the Examples below.

[0065] If the storage modulus is less than 0.015 MPa, the heat resistance of the cured product of the adhesive composition and the adhesive strength after being left in a high-temperature environment for a long period of time will decrease. From the viewpoints of the heat resistance of the cured product of the adhesive composition and the adhesive strength after being left in a high-temperature environment for a long period of time, the lower limit of the storage modulus is preferably 0.02 MPa or more, more preferably 0.06 MPa or more, and even more preferably 0.1 MPa or more. Furthermore, from the viewpoints of preventing deterioration of flexibility due to a decrease in flexibility, the upper limit of the storage modulus is preferably 2.5 MPa or less, more preferably 2.3 MPa or less, and even more preferably 2.1 MPa or less. The upper and lower limits of the storage modulus can be combined in any manner.

[0066] 1.5 180° Peel Adhesion Strength of Heat-Treated Adhesive Test Pieces The adhesive composition of this embodiment is used to bond a polyimide substrate to a copper foil. The adhesive test pieces are then heat-treated at 200°C for 7 days and then left to stand at 25°C and 65% RH for 24 hours. The heat-treated adhesive test pieces have a 180° peel adhesion strength of 0.5 N / mm or more, as measured in accordance with JIS C6481 at 23°C and a tensile speed of 50 mm / min. The 180° peel adhesion strength of the heat-treated adhesive test pieces measured under these conditions is a physical property closely related to the adhesive strength of the cured product of the adhesive composition after it has been placed in a high-temperature environment for a long period of time. Details of the method for measuring the 180° peel adhesion strength of the heat-treated adhesive test pieces are described in detail in the Examples below.

[0067] The lower limit of the 180° peel adhesive strength of the adhesive test piece after the heat treatment is preferably 0.55 N / mm or more, more preferably 0.6 N / mm or more, and even more preferably 0.7 N / mm or more, from the viewpoint of improving the adhesive strength after the cured product of the adhesive composition is placed in a high-temperature environment for a long period of time.

[0068] 1.6 Dielectric Properties of Cured Adhesive Composition 1.6.1 Dielectric Constant of Cured Adhesive Composition The adhesive composition of this embodiment preferably has a dielectric constant (Dk, εr) of 2.5 or less when measured at a frequency of 1 GHz. A dielectric constant of 2.5 or less allows the adhesive composition to be used suitably in FPC-related products, which have stringent dielectric property requirements in response to the recent trend toward faster signal speeds and higher signal frequencies. The dielectric constant is preferably 2.45 or less, more preferably 2.4 or less, and even more preferably 2.35 or less. The dielectric constant can be adjusted by the type and content of each component in the adhesive composition. Details of the method for measuring the dielectric constant will be described in detail in the Examples below.

[0069] 1.6.2 Dielectric Loss Tangent of Cured Product of Adhesive Composition The adhesive composition of this embodiment preferably has a dielectric loss tangent (Df, tanδ) of 0.01 or less when measured at a frequency of 1 GHz. If the dielectric loss tangent is 0.01 or less, the adhesive composition can be suitably used in FPC-related products, which have strict requirements for dielectric properties in response to the recent trend toward even faster signal speeds and higher signal frequencies. The dielectric loss tangent is preferably 0.008 or less, more preferably 0.007 or less, and even more preferably 0.005 or less. The dielectric loss tangent can be measured in the same manner as the method for measuring the relative dielectric constant, which will be described in detail in the Examples below.

[0070] 2. Laminate with Adhesive Layer The laminate with an adhesive layer of this embodiment comprises an adhesive layer formed from the adhesive composition described above and a substrate film in contact with at least one side of the adhesive layer. The state of the adhesive layer is as defined above. The laminate with an adhesive layer of this embodiment will be specifically described below.

[0071] One embodiment of the adhesive layer-attached laminate is a coverlay film, which is typically a laminate in which an adhesive layer is formed on at least one surface of a substrate film, making it difficult to peel the substrate film and the adhesive layer from each other.

[0072] Examples of the substrate film included in the laminate with an adhesive layer include a polyimide film, a polyether ether ketone film, a polyphenylene sulfide film, an aramid film, a polyethylene naphthalate film, a liquid crystal polymer film, etc. Among these, from the viewpoints of adhesiveness and electrical properties, a polyimide film, a polyethylene naphthalate film, and a liquid crystal polymer film are preferred.

[0073] As a method for producing a laminate with an adhesive layer, for example, a resin varnish containing the above-mentioned adhesive composition and a solvent is applied to the surface of a substrate film such as a polyimide film to form a resin varnish layer, and then the solvent is removed from this resin varnish layer, thereby producing a laminate with an adhesive layer having a B-stage adhesive layer formed thereon.

[0074] The drying temperature when removing the solvent is preferably 40 to 250° C., more preferably 70 to 170° C. Drying can be carried out by passing the laminate coated with the adhesive composition through a furnace that performs hot air drying, far-infrared heating, high-frequency induction heating, or the like.

[0075] 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, polymethylpentene (TPX) film, and fluororesin film can be used.

[0076] Another embodiment of the laminate with an adhesive layer is a bonding sheet. The bonding sheet also has the above-mentioned adhesive layer formed on the surface of a substrate film, but the substrate film functions as a release film. The bonding sheet may also have an adhesive layer between two release films. The release films are peeled off when the bonding sheet is used. The release films may be the same as those described above.

[0077] 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.

[0078] The thickness of the adhesive layer can be preferably 5 μm or more and 100 μm or less, more preferably 10 μm or more and 70 μm or less, and even more preferably 10 μm or more and 50 μm or less, in order to fully exhibit adhesive strength. The thickness of the base film can be preferably 5 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less, and even more preferably 5 μm or more and 30 μm or less, in order to reduce the thickness of the laminate with the adhesive layer.

[0079] 3. Flexible Copper-Clad Laminate The flexible copper-clad laminate of this embodiment includes a substrate film on one side of the adhesive layer of the above-mentioned adhesive layer-attached laminate and a copper foil on the other side of the adhesive layer. Specifically, the flexible copper-clad laminate can be configured by bonding a substrate film and a copper foil together using the above-mentioned adhesive layer-attached laminate. That is, the flexible copper-clad laminate can be configured by laminating a substrate 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 substrate film. Since the above-mentioned adhesive composition has excellent adhesion to copper-containing articles, the flexible copper-clad laminate has excellent stability as an integrated product.

[0080] A method for producing a flexible copper-clad laminate includes, for example, bringing the adhesive layer of the adhesive layer-attached laminate into surface contact with copper foil, performing thermal lamination at a temperature of, for example, 80°C to 150°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 copper foil is not particularly limited, and electrolytic copper foil, rolled copper foil, etc. can be used.

[0081] 4. Flexible Flat Cable The flexible flat cable of this embodiment includes a substrate film on one side of the adhesive layer of the above-mentioned adhesive layer-attached laminate, and copper wiring on the other side of the adhesive layer. Specifically, the flexible flat cable can be configured by bonding the substrate film and copper wiring together using the above-mentioned adhesive layer-attached laminate. That is, the flexible flat cable can be configured by laminating the substrate film, adhesive layer, and copper wiring in this order. The adhesive layer and copper wiring may be formed on both sides of the substrate film. Because the above-mentioned adhesive composition has excellent adhesion to copper-containing articles, the flexible flat cable has excellent stability as an integrated product.

[0082] One method for producing a flexible flat cable is to contact the adhesive layer of the adhesive layer-attached laminate with copper wiring, perform thermal lamination at a temperature of 80°C to 150°C, and then harden 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 can be selected appropriately as desired.

[0083] The present disclosure will be described in more detail based on examples, but the present disclosure is not limited thereto. In the following, parts and percentages are by mass unless otherwise specified.

[0084] 1. Evaluation Method (1) Weight-average molecular weight Mw GPC measurement was performed under the following conditions to determine the weight-average molecular weight Mw of the modified polyolefin resin (A). The weight-average molecular weight Mw was calculated by converting the retention time measured by GPC into the retention time of standard polystyrene. Apparatus: Alliance 2695 (manufactured by Waters Corporation) Columns: 2 TSKgel SuperMultiporeHZ-H, 2 TSKgel SuperHZ2500 (manufactured by Tosoh Corporation) Column temperature: 40°C Eluent: tetrahydrofuran 0.35 ml / min Detector: RI (differential refractive index detector)

[0085] (2) Acid Value 1 g of modified polyolefin resin (A) was dissolved in 30 ml of toluene, and an automatic titrator "AT-510" manufactured by Kyoto Electronics Manufacturing Co., Ltd., connected to an "APB-510-20B" manufactured by the same company as a burette, was used. Potentiometric titration was performed using a 0.01 mol / L benzyl alcohol-based KOH solution as the titration reagent, and the number of mg of KOH per 1 g of resin was calculated.

[0086] (3) Storage Modulus of Resin Composition The storage modulus of the resin composition was measured using a viscoelasticity measuring device (Hitachi High-Tech Science Corporation, "DMA7100"). Specifically, a 38 μm-thick release PET film was prepared, and the predetermined liquid adhesive composition listed in Table 1 was applied to its release-treated surface. The coated film was then placed in an oven and dried at 90°C for 3 minutes to form a B-stage adhesive layer (50 μm thick), yielding an adhesive-attached laminate. The adhesive-attached laminate was then placed in an oven and cured at 180°C for 60 minutes to form a C-stage adhesive layer (50 μm thick). The release PET film was then peeled off, and a test piece consisting of the cured adhesive composition was cut into a width of 5 mm and a length of 50 mm. Next, dynamic viscoelasticity measurement was performed on this test piece at a frequency of 10 Hz, and the storage modulus at 200°C was measured when the temperature was raised from -70°C to 240°C at a temperature rise rate of 2°C / min.

[0087] (4) Dielectric Properties (Dielectric Constant) of Cured Adhesive Compositions A 38 μm-thick release PET film was prepared, and the liquid adhesive composition listed in Table 1 was applied to its release-treated surface. The coated film was then placed in an oven and dried at 90°C for 3 minutes to form a 50 μm-thick coating (adhesive layer), yielding an adhesive layer. The adhesive layer was then placed in an oven and cured at 180°C for 60 minutes. The release film was then peeled off to obtain a test piece (100 mm x 80 mm) made of the cured adhesive composition. The dielectric constants (Dk, εr) were measured using a network analyzer 85071E-300 (manufactured by Agilent Technologies) by the split post dielectric resonator method (SPDR method) at a temperature of 23°C and a frequency of 1 GHz. A dielectric constant of 2.5 or less was deemed to be a low dielectric constant and was rated "A." When the dielectric constant was greater than 2.5, the cured product was deemed to have a high dielectric constant and was marked with "C."

[0088] (5) Solder heat resistance of cured adhesive composition The test was conducted under the following conditions in accordance with JIS C 6481 "Test method for copper-clad laminates for printed wiring boards." Each adhesive test piece was cut into 25 mm squares and heated at 120°C for 30 minutes. The adhesive test piece was then floated with the copper-clad laminate film facing up in a solder bath at 280°C for 10 seconds, and the foaming state on the surface of the adhesive test piece was observed. The adhesive test piece was then removed from the solder bath, allowed to stand at room temperature for 10 seconds, and then floated again in a solder bath at 280°C for 10 seconds, and the foaming state on the surface of the adhesive test piece was observed. The number of times the adhesive test piece was floated in the solder bath was counted, and this procedure was repeated up to 10 times. The upper limit of the number of times at which foaming was not observed in the adhesive test piece was taken as the temperature for solder heat resistance. When foaming was not observed in the adhesive test piece two or more times, the adhesive test piece was deemed to have excellent heat resistance and was rated "A." When no bubbles were observed in the adhesive test piece once, the heat resistance was deemed poor and was given a grade of "C." Note that this solder heat resistance evaluation evaluates heat resistance under stricter conditions than the solder heat resistance evaluation in Patent Document 1.

[0089] (6) Peel Adhesion Strength of Cured Product of Adhesive Composition A copper-clad laminate (a laminate of a 25 μm-thick polyimide film and an 18 μm-thick copper foil) was prepared, and the surface of the polyimide film was roll-coated with a predetermined liquid adhesive composition listed in Table 1. The coated film was then placed in an oven and dried at 90°C for 3 minutes to form a B-stage adhesive layer (25 μm thick), yielding a laminate with an adhesive layer. A 35 μm-thick rolled copper foil was then placed on top of the adhesive layer of the laminate so that it was in surface contact with the adhesive layer, and lamination was performed at a temperature of 120°C, a pressure of 0.4 MPa, and a speed of 0.5 m / min. This laminate (copper-clad laminate / adhesive layer / copper foil) was then heat-cured for 60 minutes at a temperature of 180°C and a pressure of 3 MPa to yield a flexible copper-clad laminate. The resulting flexible copper-clad laminate was then heat-treated in an oven at 200°C for 7 days, and then placed in a thermostatic chamber at 25°C and 65% RH for 24 hours. The flexible copper-clad laminate was then cut into heat-treated adhesive test specimens of a predetermined size. To evaluate adhesiveness, the 180° peel strength (N / mm) of the heat-treated copper-clad laminate was measured at 23°C and a tensile speed of 50 mm / min according to JIS C 6481 "Test Methods for Copper-Clad Laminates for Printed Wiring Boards." The width of the adhesive test specimens used for the measurement was 10 mm.

[0090] When the 180° peel strength of the heat-treated adhesive test piece was 0.5 N / mm or more, the adhesive strength after being left in a high-temperature environment for a long period of time was evaluated as excellent and was given a grade of "A." When the 180° peel strength of the heat-treated adhesive test piece was less than 0.5 N / mm, the adhesive strength after being left in a high-temperature environment for a long period of time was evaluated as poor and was given a grade of "C."

[0091] 2. Raw Materials for Adhesive Composition The following raw materials for the adhesive composition were prepared: (1) Modified Polyolefin Resin (A) Acid-modified polypropylene resins (a1) to (a11) were prepared as the modified polyolefin resin (A) by the method described below.

[0092] 100 parts by mass of propylene / 1-butene copolymer (molar ratio: propylene / 1-butene = 70 / 30) was heated and melted in a four-neck flask under a nitrogen atmosphere. Then, while maintaining the temperature in the system at 170°C and stirring, 1.5 parts by mass of maleic anhydride as an unsaturated carboxylic acid and 1.2 parts by mass of dicumyl peroxide as a radical generator were added over one hour, followed by a reaction for one hour. After completion of the reaction, the resulting reaction product was poured into a large amount of acetone to solidify the resin. This resin was finely chopped and processed into pellets. Next, this pelletized resin was mixed with acetone in an amount three times the mass of the resin and stirred for one hour at 50°C to wash the resin. The resin was then recovered and further washed in the same manner to remove free maleic anhydride. The washed resin was then dried under reduced pressure in a vacuum dryer to obtain modified polyolefin resin (a4). The resulting acid-modified polyolefin resin (a4) as the modified polyolefin resin (A) had a weight average molecular weight Mw of 150,000 and an acid value of 10 mgKOH / g.

[0093] In addition, 100 parts by mass of a propylene-ethylene random copolymer composed of 97 mol% propylene units and 3 mol% ethylene units, produced using a metallocene catalyst as a polymerization catalyst, 0.5 parts by mass of maleic anhydride, 0.3 parts by mass of lauryl methacrylate, and 0.4 parts by mass of di-t-butyl peroxide were kneaded and reacted using a twin-screw extruder with the maximum cylinder temperature set to 170°C. The mixture was then degassed under reduced pressure in the extruder to remove any remaining unreacted material, yielding a modified polyolefin resin (a6). The resulting modified polyolefin resin (a6) had a weight-average molecular weight Mw of 200,000 and an acid value of 13 mgKOH / g.

[0094] In preparing the acid-modified polyolefin resin (a4), the amount of maleic anhydride, the amount of dicumyl peroxide, the reaction time, etc. were adjusted to prepare acid-modified polyolefin resins (a1) to (a3), (a5), and (a7) to (a11) having a weight-average molecular weight Mw of 60,000 to 500,000, as shown in Table 1 below. In preparing the acid-modified polyolefin resin (a6), the weight-average molecular weight Mw and acid value could be adjusted by adjusting the amount of maleic anhydride, the amount of di-t-butyl peroxide, the reaction time, etc., as described above. The acid values ​​of the acid-modified polyolefin resins (a1) to (a8) and (a10) were in the range of 0.1 mgKOH / g or more and 50 mgKOH / g or less. The acid-modified polyolefin resin (a9) and the acid-modified polyolefin resin (a11) have weight-average molecular weights Mw outside the range specified in the present disclosure and therefore do not fall under the category of "modified polyolefin resin (A)" as defined in the present disclosure. However, for the sake of convenience, they are included in the description of "modified polyolefin resin (A)" in this example.

[0095] (2) Epoxy resin (B) Dicyclopentadiene skeleton-containing epoxy resin (b1) (hereinafter also referred to as DCPD-type epoxy resin (b1)) (manufactured by DIC Corporation, "EPICLON HP-7200")

[0096] (3) Others: Curing accelerator (imidazole-based curing accelerator) (manufactured by Shikoku Chemicals Corporation, "Curesol C11Z"); Solvent (a mixed solvent of toluene and methylcyclohexane (mass ratio = 20:80)). The amount of solvent was adjusted appropriately so that the solids concentration of the adhesive composition would be 15 to 30 mass %.

[0097] 3. Production and Evaluation of Adhesive Compositions The above raw materials were added to a 1000 ml flask equipped with a stirrer in the prescribed proportions shown in Table 1, and a solvent was added. The mixture was dissolved by stirring at room temperature (25°C) for 6 hours to prepare and evaluate each adhesive composition. The results are shown in Table 1.

[0098] 4. Production and Evaluation of Laminates with Adhesive Layers Using the above adhesive compositions, laminates with adhesive layers were produced and evaluated as described in the explanations for each evaluation method above. The results are shown in Table 1.

[0099]

[0100] Table 1 reveals the following. Specifically, in Sample 1C, the weight-average molecular weight Mw of the modified polyolefin resin (A) was less than 70,000, and the storage modulus of the cured product at 200°C was 0.01 MPa. Therefore, Sample 1C had insufficient heat resistance and adhesive strength after being left in a high-temperature environment for a long period of time. This is thought to be because exposure to high temperatures reduces the cohesive force, making it impossible to fully demonstrate adhesive strength.

[0101] In Sample 2C, the weight average molecular weight Mw of the modified polyolefin resin (A) exceeded 470,000. Therefore, it was difficult to dissolve the adhesive composition of Sample 2C in a solvent to form a varnish, and it was not possible to roll-coat the adhesive composition onto a substrate film. In other words, Sample 2C had poor processability when forming a thin film of the adhesive composition, and therefore it was not possible to evaluate the cured product in the first place.

[0102] In Sample 3C, the content of epoxy resin (B) exceeded 25 parts by mass relative to 100 parts by mass of modified polyolefin resin (A). Therefore, Sample 3C had an excessively high ratio of the epoxy resin (cured resin) relative to the modified polyolefin resin (A), resulting in a high dielectric constant. Furthermore, the excessive amount of epoxy resin caused the cured product to harden, tending to reduce adhesive strength after long-term storage in a high-temperature environment.

[0103] In contrast, the adhesive compositions of Samples 1 to 12 satisfy the requirements set forth in the present disclosure. Therefore, it was confirmed that the cured products of Samples 1 to 12 have a low dielectric constant, excellent heat resistance, and excellent adhesive strength after long-term exposure to high-temperature environments. Furthermore, Sample 12, in which the weight-average molecular weight Mw of the modified polyolefin resin (A) is closest to the upper limit of 470,000, could be prepared to a state suitable for roll coating by using a larger amount of solvent when forming a varnish than Samples 1 to 11. These results confirmed that, from the standpoints of varnish handling and the formation of a stable thin film layer on a substrate film, it is preferable for the weight-average molecular weight Mw of the modified polyolefin resin (A) to be less than 430,000.

[0104] Based on the above results, it can be said that the present disclosure can provide an adhesive composition that produces a cured product with a low dielectric constant, excellent heat resistance, and excellent adhesive strength even after being left in a high-temperature environment for a long period of time, as well as a laminate with an adhesive layer that uses the same.

[0105] The present disclosure is not limited to the above-described embodiments and examples, and various modifications are possible without departing from the spirit of the present disclosure. Furthermore, the configurations shown in the above-described embodiments and examples can be combined in any manner.

Claims

1. An adhesive composition containing a modified polyolefin resin (A) having a reactive functional group that reacts with an epoxy group and an epoxy resin (B), wherein the content of the epoxy resin (B) is 1 part by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the modified polyolefin resin (A), the weight average molecular weight Mw of the modified polyolefin resin (A) is 70,000 or more and 470,000 or less, the storage elastic modulus of the cured product of the adhesive composition cured under the conditions of a curing temperature of 180 ° C and a curing time of 60 minutes is 0.015 MPa or more at 200 ° C, and for an adhesion test piece obtained by adhering a polyimide substrate and a copper foil using the adhesive composition, after heat treatment at a temperature of 200 ° C for 7 days, and then further standing at a temperature of 25 ° C and a humidity of 65% RH for 24 hours, the 180 ° peel adhesion strength measured at a temperature of 23 ° C and a tensile speed of 50 mm / min in accordance with JIS C6481 is 0.5 N / mm or more. Adhesive composition.

2. The adhesive composition according to claim 1, wherein the relative permittivity of the cured product of the adhesive composition measured at a frequency of 1 GHz is 2.5 or less.

3. The adhesive composition according to claim 1, wherein the modified polyolefin resin (A) is an acid-modified polyolefin resin.

4. The adhesive composition according to claim 1, wherein the modified polyolefin resin (A) is a resin obtained by graft-modifying an unmodified polyolefin resin with a modifier containing an α,β-unsaturated carboxylic acid or a derivative thereof.

5. The adhesive composition according to claim 4, wherein the unmodified polyolefin resin is at least one selected from the group consisting of an ethylene-propylene copolymer, a propylene-butene copolymer, and an ethylene-propylene-butene copolymer.

6. The adhesive composition according to claim 5, wherein the content ratio of propylene units in the unmodified polyolefin resin is 50 mol% or more and 98 mol% or less.

7. The adhesive composition according to claim 1, wherein the epoxy resin (B) is a polyfunctional epoxy resin having an alicyclic skeleton.

8. A laminate with an adhesive layer comprising an adhesive layer formed from the adhesive composition according to any one of claims 1 to 7 and a substrate film in contact with at least one surface of the adhesive layer.

Images