Composition, thermosetting adhesive, laminate, method for manufacturing laminate, flexible circuit board, and semiconductor device

Abstract

The present invention addresses the problem of providing: a composition having sufficient adhesive force and reduced dielectric loss tangent and warpage; a thermosetting adhesive; a laminate; a method for manufacturing the laminate; a flexible circuit board; and a semiconductor device.　This composition contains a thermosetting compound, and is characterized in that the benzoxazine content is 55 parts by mass or more with respect to 100 parts by mass of the thermosetting compound, and an elastomer and an organic filler are contained.

Description

Composition, thermosetting adhesive, laminate, method for manufacturing laminate, flexible circuit board and semiconductor device

[0001] The present invention relates to a composition, a thermosetting adhesive, a laminate, a method for producing a laminate, a flexible circuit board, and a semiconductor device. More specifically, the present invention relates to a composition having sufficient adhesive strength and reduced dielectric tangent and warpage.

[0002] In recent years, electronic devices have become more sophisticated and faster in processing speed, which has led to a demand for faster communication speeds. Specifically, the introduction and widespread use of fifth-generation mobile communication systems (5G) is expected. Development of electronic devices compatible with 5G is also underway.

[0003] 5G is allocated a frequency band below 6 GHz called the Sub-6 band and a frequency band above 24 GHz called the millimeter wave band. The amount of information that can be transmitted at one time increases the higher the radio wave frequency. Therefore, these 5G frequency bands are higher frequency bands than the previous generation 4G, and 5G electronic devices must be compatible with high frequency bands.

[0004] Circuit boards used in electronic devices and other devices require the use of materials with low transmission loss. Generally, it is believed that transmission loss in electrical signals is composed of the sum of dielectric loss, conductor loss, etc. Dielectric loss is caused by the dielectric properties of the insulating material surrounding the wiring. Conductor loss is caused by the shape of the conductor, skin resistance, characteristic impedance, etc. Dielectric loss increases as the frequency of radio waves increases, so using conventional materials increases dielectric loss. Therefore, there is a need to use materials with reduced dielectric loss that can suppress the increase in dielectric loss.

[0005] Dielectric loss depends on the dielectric constant and dielectric dissipation factor of a dielectric. Specifically, dielectric loss is proportional to the product of the square root of the dielectric constant and the dielectric dissipation factor of the dielectric. Therefore, the smaller the dielectric constant and dielectric dissipation factor, the smaller the dielectric loss value. Therefore, it is necessary to sufficiently reduce the dielectric constant and dielectric dissipation factor of materials for various electronic devices, particularly insulating materials, substrate materials, etc.

[0006] On the other hand, flexible copper clad laminates (FCCLs) are used for bendable flexible circuit boards (FPCs). The adhesives and insulating films used in these laminates, which have small dielectric constants and dielectric loss tangents, have relatively high water absorption rates. Therefore, the adhesives and insulating films tend to absorb water and expand, causing the copper clad laminate to curl.

[0007] Patent Document 1 discloses a technology relating to an adhesive composition for circuit boards that combines a specific resin and a filler and has a low relative dielectric constant and dielectric loss tangent. However, there is a large difference in water absorption between the adhesive and the insulating film used in the copper-clad laminate. As a result, when the adhesive and the insulating film absorb water and expand during processing or storage of the copper-clad laminate, they become significantly curved, making them difficult to handle. Furthermore, this problem is more pronounced the thinner the copper-clad laminate is.

[0008] Patent Document 2 discloses a technology relating to an adhesive resin composition containing a benzoxazine compound or the like. The water absorption rate of the adhesive resin composition was slightly reduced, but was still not sufficient. As a result, when the adhesive resin composition was made into a copper-clad laminate, the water absorption rate was still high, and there was a problem that the copper-clad laminate curved.

[0009] Patent Document 3 discloses a technology related to a thermosetting resin composition containing a benzoxazine compound. However, the thermoplastic resin composition has a low viscosity and is intended to be diluted with a solvent to form a resin solution for impregnation, and a porous substrate such as glass cloth is impregnated with this solution. Therefore, it has not been used for the purpose of bonding an insulating film to a copper plate.

[0010] JP 2018-82171 A JP 2010-195884 A JP 2016-196548 A

[0011] The present invention has been made in consideration of the above problems and circumstances, and an object of the present invention is to provide a composition, a thermosetting adhesive, a laminate, a method for manufacturing a laminate, a flexible circuit board, and a semiconductor device that have sufficient adhesive strength and reduced dielectric tangent and warpage.

[0012] The present inventors have investigated the causes of the above problems in order to solve the above problems. As a result, they have found that a composition containing a thermosetting compound has sufficient adhesive strength and can reduce dielectric tangent and warpage by containing 55 parts by mass or more of benzoxazine per 100 parts by mass of the thermosetting compound and also contains an elastomer and an organic filler, and have thus arrived at the present invention. That is, the above problems according to the present invention are solved by the following means.

[0013] 1. A composition containing a thermosetting compound, wherein the content of benzoxazine is 55 parts by mass or more per 100 parts by mass of the thermosetting compound, and the composition also contains an elastomer and an organic filler.

[0014] 2. The composition according to item 1, wherein the content of the organic filler is 50 parts by mass or less relative to 100 parts by mass of the thermosetting compound.

[0015] 3. The composition according to item 1, wherein the content of the elastomer is within a range of 10 to 50 parts by mass relative to 100 parts by mass of the thermosetting compound.

[0016] 4. The composition according to claim 1, wherein the organic filler contains polytetrafluoroethylene.

[0017] 5. The composition according to claim 1, wherein the elastomer is a block copolymer.

[0018] 6. The composition according to item 5, wherein the block copolymer is an acrylic triblock copolymer.

[0019] 7. The composition according to item 1, characterized in that the thermosetting compound contains an epoxy compound.

[0020] 8. The composition according to item 1, characterized in that it contains a bismaleimide as the thermosetting compound.

[0021] 9. A thermosetting adhesive comprising the composition according to any one of items 1 to 8.

[0022] 10. A laminate comprising a support, an adhesive layer, and a metal layer laminated in this order, wherein the adhesive layer contains a cured product of the thermosetting adhesive according to item 9.

[0023] 11. The laminate according to item 10, wherein the support contains a liquid crystal polymer or polyphenylene sulfide.

[0024] 12. A method for producing a laminate according to claim 10, comprising the step of applying the thermosetting adhesive.

[0025] 13. A flexible circuit board comprising the laminate according to claim 10.

[0026] 14. A semiconductor device comprising the flexible circuit board according to claim 13.

[0027] The above-described means of the present invention can provide a composition, a thermosetting adhesive, a laminate, a method for producing a laminate, a flexible circuit board, and a semiconductor device that have sufficient adhesive strength and reduced dielectric tangent and warpage.

[0028] The mechanism by which the effects of the present invention are manifested or the mechanism of action is not clear, but is speculated as follows.

[0029] As mentioned above, flexible copper clad laminates (FCCLs) must have sufficiently low dielectric constants and dielectric loss tangents, and must be able to reduce curvature and warpage in high-humidity environments. Curvature and warpage in high-humidity environments are thought to be caused by large differences in water absorption among the layers. Therefore, the adhesive layers used in FCCLs must have sufficiently low dielectric constants and dielectric loss tangents, and low water absorption.

[0030] Benzoxazine undergoes ring-opening polymerization upon heating to produce benzoxazine resin, which contains phenolic hydroxy groups and is a type of phenolic resin. Benzoxazine resin has a relatively low dielectric constant, dielectric loss tangent, and water absorption.

[0031] The organic filler has an extremely low dielectric loss tangent, and by using it in combination with the cured benzoxazine resin, the dielectric loss tangent of the adhesive layer can be further reduced.

[0032] Elastomers are polymeric compounds with rubber elasticity. When used in combination with benzoxazine resin before curing, they can adjust the viscosity of the composition. Furthermore, when used in combination with benzoxazine resin after curing, they can improve the adhesive strength of the adhesive layer.

[0033] The composition of the present invention contains the above-mentioned benzoxazine, an organic filler, and an elastomer. This allows the adhesive layer formed by curing the composition to have a sufficiently low dielectric constant and dielectric loss tangent. The composition of the present invention has a relatively high benzoxazine content of 55 parts by mass or more per 100 parts by mass of the thermosetting compound, which is believed to be a significant effect. Additionally, the composition of the present invention has sufficient adhesive strength and can reduce warpage.

[0034] Cross-sectional view of an example of a laminate (single-sided) of the present invention. Cross-sectional view of an example of a laminate (double-sided) of the present invention. Cross-sectional view of an example of a circuit board (single-sided structure) of the present invention. Cross-sectional view of an example of a circuit board (double-sided structure) of the present invention. Cross-sectional view of an example of a circuit board (multilayer structure) of the present invention.

[0035] The composition of the present invention is a composition containing a thermosetting compound, characterized in that the content of benzoxazine is 55 parts by mass or more per 100 parts by mass of the thermosetting compound, and the composition contains an elastomer and an organic filler. This feature is a technical feature common to or corresponding to the following embodiments.

[0036] In an embodiment of the present invention, from the viewpoint of adhesive strength, the content of the organic filler is preferably 50 parts by mass or less relative to 100 parts by mass of the thermosetting compound.

[0037] In an embodiment of the present invention, from the viewpoint of achieving both adhesive strength and dielectric loss tangent, the content of the elastomer is preferably within a range of 10 to 50 parts by mass relative to 100 parts by mass of the thermosetting compound.

[0038] In an embodiment of the present invention, from the viewpoint of dielectric loss tangent, the organic filler preferably contains polytetrafluoroethylene.

[0039] In an embodiment of the present invention, from the viewpoint of adhesive strength, the elastomer is preferably a block copolymer, and more preferably an acrylic triblock copolymer.

[0040] In an embodiment of the present invention, from the viewpoint of adhesive strength, it is preferable that the thermosetting compound contains an epoxy compound.

[0041] In an embodiment of the present invention, from the viewpoint of heat resistance, it is preferable that the thermosetting compound contains bismaleimide.

[0042] The thermosetting adhesive of the present invention is characterized by containing the above-described composition.

[0043] The laminate of the present invention is a laminate in which a support, an adhesive layer, and a metal layer are laminated in this order, and is characterized in that the adhesive layer contains a cured product of the thermosetting adhesive.

[0044] In an embodiment of the present invention, from the viewpoint of water absorption, the support preferably contains a liquid crystal polymer or polyphenylene sulfide.

[0045] The method for producing a laminate of the present invention is a method for producing the laminate, and is characterized by including a step of applying the thermosetting adhesive.

[0046] A flexible circuit board according to the present invention includes the laminate. A semiconductor device according to the present invention includes the flexible circuit board.

[0047] The present invention, its components, and embodiments and modes for carrying out the present invention will be described in detail below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0048] 1. Overview of the Composition The composition of the present invention is a composition containing a thermosetting compound, characterized in that the content of benzoxazine is 55 parts by mass or more per 100 parts by mass of the thermosetting compound, and the composition contains an elastomer and an organic filler.

[0049] The composition of the present invention has the property of being cured by the application of heat and also functions as an adhesive. The composition of the present invention has a reduced dielectric tangent and low water absorption, and is therefore preferably used as an adhesive in electronic devices. In particular, the composition of the present invention is preferably used as an adhesive for bonding a support such as a resin film to a metal layer, i.e., an adhesive for circuit boards.

[0050] 2. Composition of the Composition The composition of the present invention contains a thermosetting compound, an elastomer, and an organic filler. If necessary, other additives may be contained. The thermosetting compound, the elastomer, and the organic filler will be described below in order.

[0051] (1) Thermosetting Compound In the present invention, the thermosetting compound is not particularly limited as long as it has the property of being cured by heating. However, it must contain benzoxazine. Other examples of thermosetting compounds include epoxy compounds, bismaleimides, oxetanes, (meth)acrylic compounds, benzoguanamines, rosin-modified maleic acid, rosin-modified fumaric acid, melamine, urea compounds, and phenols. The molecular weight of these compounds is not particularly limited, and they may be monomers or resins.

[0052] In the present invention, benzoxazine is a main component of the thermosetting compound. Specifically, the content of benzoxazine is 55 parts by mass or more relative to 100 parts by mass of the thermosetting compound. The content of benzoxazine is preferably 60 parts by mass or more, and more preferably 70 parts by mass or more, relative to 100 parts by mass of the thermosetting compound.

[0053] (1.1) Benzoxazine In the present invention, the term "benzoxazine" refers to a compound having a benzoxazine ring, and is a general term for such compounds. In benzoxazines, the benzoxazine ring may have various substituents.

[0054] In benzoxazine, the oxazine ring opens due to heat, and a polymerization reaction proceeds. Therefore, it is preferable that the benzoxazine has a plurality of benzoxazine rings. By having a plurality of benzoxazine rings, a three-dimensional crosslinked structure can be formed, and adhesiveness can be improved.

[0055] The benzoxazine ring is represented by the following general formula (I).

[0056]

[0057] Among them, benzoxazine has a substituent R １ and R ２ It is preferred that the substituent R １ and R ２ Examples of benzoxazines having the formula (II) include compounds represented by the following general formula (II):

[0058]

[0059] (In general formula (II), R １ represents a hydrogen atom, a halogen atom, an amine group, a chain alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group having 3 to 8 carbon atoms, or an aryl group. ２ each independently represents a hydrogen atom, a halogen atom, an amine group, a linear alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group having 3 to 8 carbon atoms, or an aryl group. In the aromatic ring in general formula (II), a hydrogen atom is bonded to at least one of the carbon atoms at the ortho-position and the para-position to the carbon atom to which the oxygen atom is bonded.

[0060] R １ and R ２ The alkyl group or aryl group in may have a substituent, such as a halogen atom, an amine group, a chain alkyl group having 1 to 12 carbon atoms, or a cyclic alkyl group having 3 to 8 carbon atoms.

[0061] R １ Examples of R include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a cyclopentyl group, a cyclohexyl group, a phenyl group, an o-methylphenyl group, an m-methylphenyl group, a p-methylphenyl group, an o-ethylphenyl group, an m-ethylphenyl group, a p-ethylphenyl group, an o-t-butylphenyl group, an m-t-butylphenyl group, a p-t-butylphenyl group, an o-chlorophenyl group, and an o-bromophenyl group. １ is preferably a methyl group, an ethyl group, a propyl group, a phenyl group, or an o-methylphenyl group.

[0062] R ２ Preferred examples of R １ Preferred examples of the substituent of the aryl group include the same substituents as those of R １ The same substituents as those in the preferred examples of the above can be mentioned.

[0063] (1.1.1) Bifunctional benzoxazines Benzoxazines having two benzoxazine rings include two types of compounds represented by the following general formulas (III) and (IV). However, the benzoxazines having two benzoxazine rings are not limited thereto.

[0064]

[0065] (In general formula (III), Z １ The aromatic rings in the two benzoxazine rings may be directly bonded or condensed. １ Z as a linking group may be bonded via １ is -C(R ５ ) (R ６ ) -, -C(R ５ ) (aryl)-, —C(O)—, —S—, —O—, —S(O)—, —S(O) ２ -, a divalent heterocycle, or -[C(R ５ ) (R ６ ) )]x-arylene-[C(R７ ) (R ８ ) )]y-. ３ ~R ８ represents R in the above general formula (II). １ x and y each represent 0 or 1.

[0066] Among them, Z as a linking group １ is -C(R ５ ) (R ６ ) -, -C(R ５ )(aryl)-, —C(O)—, —S—, —O—, a divalent heterocycle, or —[C(R ５ ) (R ６ ) )]x-arylene-[C(R ７ ) (R ８ ) )]y- is preferred.

[0067] -C(R ５ In the linking group represented by (aryl)-, the aryl group is preferably a phenyl group.

[0068] -[C(R ５ ) (R ６ ) )]x-arylene-[C(R ７ ) (R ８ In the linking group represented by —C(R ))]y-, the number of arylene groups may be plural. ９ ) (R １０ )- may further have a linking group represented by R ９ and R １０ is the above R １ is synonymous with.

[0069] Among these, the arylene group is preferably a phenylene group. The groups bonded to the phenylene group may be arranged in the para or meta positions relative to each other.

[0070] Z as a linking group １ may be linear or non-linear, but is preferably linear. １ As shown in the above general formula (III), it is preferable that Z be bonded at the para position relative to the oxygen atom in the oxazine ring. However, the present invention is not limited thereto, and Z１ may be attached at the meta or ortho position relative to the oxygen atom in the oxazine ring.

[0071] Specifically, Z １ may be bonded at the para / para, para / meta, para / ortho, meta / meta, or ortho / meta positions. Here, "para / meta" means that the carbon atom at the "para" position relative to the oxygen atom in the oxazine ring and the carbon atom at the "meta" position relative to the oxygen atom in the oxazine ring are connected by the linking group Z １ This means that the bond is formed via the

[0072] The bifunctional benzoxazine may be a mixture of these isomers having different bonding positions. However, it is preferable that the majority of the mixture is the para / para isomer represented by the general formula (III). The content of the para / para isomer is preferably 75 mol% or more, more preferably 90 mol% or more, and even more preferably 99 mol% or more, based on the total number of moles of the isomer mixture.

[0073] R ５ ~R ８ is preferably a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a halogenated alkyl group. The alkyl group more preferably has 1 to 4 carbon atoms, and is more preferably a methyl group (—CH ３ The halogenated alkyl group is more preferably a fluorinated alkyl group, and more preferably a trifluoromethyl group (—CF ３ ) is preferred.

[0074] In the bifunctional benzoxazine represented by the general formula (III), Z as a linking group １ Specifically, -C(CH ３ ) ２ -, -CH ２ -, or 3,3-isobenzofuran-1(3H)-one, i.e., the bifunctional benzoxazine is preferably a benzoxazine derivative of bisphenol A, bisphenol F, or phenolphthalein.

[0075] The aromatic rings of the bifunctional benzoxazine may each independently have a substituent at a possible position. １ The substituent is preferably at the ortho position relative to the carbon atom bonded to the R １ It is preferable that the substituent has the same meaning as the following.

[0076]

[0077] (In general formula (IV), Z １ represents Z in the general formula (III). １ It is synonymous with R ３ and R ４ represents R in the above general formula (II). ２ is synonymous with

[0078] The benzoxazine of the present invention may be a compound having three or more benzoxazine rings. In the present invention, these benzoxazines may be contained alone or in combination of two or more.

[0079] These benzoxazines may be contained as a monomer, or may be contained as an oligomer in which several molecules of the monomer are polymerized.

[0080] Benzoxazine preferably forms a skeleton similar to that of phenolic resins through ring-opening polymerization. This provides excellent heat resistance (flame retardancy). Furthermore, a dense structure is formed, resulting in excellent dynamic properties, mechanical properties, low water absorption, and other properties. Regarding mechanical properties, high elasticity is obtained.

[0081] Commercially available benzoxazines may be used, such as bisphenol A benzoxazine "BA-BXZ" (manufactured by Konishi Chemical Co., Ltd.), bisphenol F benzoxazine "BF-BXZ" (manufactured by Konishi Chemical Co., Ltd.), bisphenol S benzoxazine "BS-BXZ" (manufactured by Konishi Chemical Co., Ltd.), P-d benzoxazine (manufactured by Shikoku Chemical Industry Co., Ltd.), Fa benzoxazine (manufactured by Shikoku Chemical Industry Co., Ltd.), and phenolphthalein benzoxazine.

[0082] Specific examples of the benzoxazine according to the present invention are shown below.

[0083]

[0084]

[0085]

[0086]

[0087] (1.2) Bismaleimide The thermoplastic resin according to the present invention preferably contains a bismaleimide in addition to the benzoxazine resin. The bismaleimide can react with the hydroxyl groups of the benzoxazine resin to form a three-dimensional crosslinked structure.

[0088] In the present invention, the term "bismaleimide" refers to a compound having two maleimide groups. The molecular weight of the bismaleimide is not particularly limited, and the bismaleimide may be a monomer or a resin.

[0089] Examples of bismaleimides include 4,4'-diphenylmethane bismaleimide, m-phenylene bismaleimide, bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenylene bismaleimide, 1,6'-bismaleimide-(2,2,4-trimethyl)hexane, 4,4'-diphenyl ether bismaleimide, 4,4'-diphenylsulfone bismaleimide, 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane bisphenol A bis(4-maleimidophenyl ether), etc. These may be contained alone or in combination of two or more.

[0090] Among these, bismaleimide preferably has a structure common to benzoxazine, which results in excellent compatibility in the composition. Furthermore, bismaleimide preferably has a relatively low dielectric constant and dielectric loss tangent.

[0091] The bismaleimide may be a commercially available product, such as "BAF-BMI" (manufactured by JFE Chemical Corporation), "BMI-3000", "BMI-1500", or "BMI-5000" (manufactured by Designer Molecules Inc.).

[0092] The content of the bismaleimide is preferably in the range of 0 to 45 parts by mass, more preferably in the range of 5 to 40 parts by mass, and further preferably in the range of 10 to 30 parts by mass, relative to 100 parts by mass of the thermosetting compound.

[0093] (1.3) Epoxy Compound The thermoplastic resin according to the present invention preferably contains an epoxy compound in addition to the benzoxazine resin. The epoxy compound can react with the hydroxyl groups of the benzoxazine resin to further form a three-dimensional crosslinked structure.

[0094] In the present invention, the term "epoxy compound" refers to a compound having at least one epoxy group. The molecular weight of the epoxy compound is not particularly limited, and the epoxy compound may be a monomer or a resin.

[0095] Examples of epoxy compounds include bisphenol A type epoxy resins, bisphenol F type epoxy resins, phenol novolac type epoxy resins, tert-butyl-catechol type epoxy resins, naphthalene type epoxy resins, naphthol type epoxy resins, naphthylene ether type epoxy resins, glycidylamine type epoxy resins, cresol novolac type epoxy resins, biphenyl type epoxy resins, linear aliphatic epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, spiro ring-containing epoxy resins, cyclohexanedimethanol type epoxy resins, dicyclopentadiene type epoxy resins, trimethylol type epoxy resins, aralkyl type epoxy resins, halogenated epoxy resins, etc. These may be contained alone or in combination of two or more.

[0096] Among them, the epoxy compound is preferably a biphenyl-type epoxy resin, a naphthol-type epoxy resin, a phenol-type epoxy resin, a dicyclopentadiene-type epoxy resin, or an aralkyl-type epoxy resin. Furthermore, a biphenyl-type epoxy resin, a dicyclopentadiene-type epoxy resin, or a naphthol-type epoxy resin is more preferred, and a biphenyl-type epoxy resin is even more preferred. Specific examples include bisphenol A diglycidyl ether.

[0097] The epoxy compound preferably has a structure common to that of benzoxazine. This common structure results in excellent compatibility in the composition. Furthermore, the epoxy compound preferably has a relatively low dielectric constant and dielectric loss tangent.

[0098] The epoxy compound according to the present invention is not limited to the above resins as long as it has one or more epoxy groups in one molecule, but from the viewpoint of forming a three-dimensional crosslinked structure, it is preferable that the epoxy compound has many epoxy groups in one molecule.

[0099] The content of the epoxy compound is preferably in the range of 0 to 45 parts by mass, more preferably in the range of 3 to 30 parts by mass, and further preferably in the range of 5 to 20 parts by mass, relative to 100 parts by mass of the thermosetting compound.

[0100] (2) Elastomer The viscosity of the composition of the present invention can be adjusted by including an elastomer. Furthermore, the flexibility and adhesive strength of the cured adhesive layer can be improved. "Elastomer" refers to a polymeric compound that exhibits rubber elasticity at room temperature (25°C). "Rubber elasticity" refers to the property of a solid substance that is deformed by an external force and instantly returns to its original shape due to high internal stress.

[0101] Specifically, the term "elastomer" in the present invention refers to a polymer compound having a glass transition temperature in the range of -140 to 30°C and an elastic modulus at 25°C in the range of 0.3 to 50 MPa.

[0102] The glass transition temperature of an elastomer can be measured by the following method. Using a dynamic viscoelasticity measuring device, the loss tangent (tan δ) of the elastomer is measured under conditions of a temperature rise rate of 3°C / min and a vibration frequency of 1 Hz. The temperature at which the obtained loss tangent (tan δ) is maximum is defined as the glass transition temperature. The loss tangent (tan δ) is the value obtained by dividing the loss modulus (E") by the storage modulus (E') (tan δ = E" / E').

[0103] The elastic modulus of an elastomer can be measured by the following method: Using a dynamic viscoelasticity measuring device, the storage modulus (E') of an elastomer is measured under conditions of a temperature of 25°C and a frequency of 1 Hz.

[0104] The elastomer is preferably a block copolymer having a chemically crosslinked structure, specifically a structure in which soft segments and hard segments are covalently crosslinked. In this structure, the hard segments function as physical crosslinking points at temperatures below the glass transition temperature. The soft segments also exhibit elasticity. This structure relieves stress caused by volume changes. Furthermore, by using a triblock copolymer in which hard segments and soft segments are repeatedly bonded, the stress-relieving function can be further improved.

[0105] The viscosity of the composition of the present invention can be increased by including an elastomer, and the composition of the present invention can be applied to a support or a metal layer by coating.

[0106] Usually, adhesives with low viscosity that are difficult to apply by coating are used in the form of a prepreg. A prepreg is obtained by impregnating a substrate fiber (e.g., glass cloth) with a resin. Therefore, in addition to the properties of the adhesive, the properties of the substrate fiber are also significantly affected. However, the composition of the present invention does not require the form of a prepreg, and is therefore not affected by the properties of the substrate fiber.

[0107] Examples of elastomers include rubber materials and thermoplastic elastomers. Examples of rubber materials include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, nitrile rubber, chloroprene rubber, butyl rubber, acrylic rubber, ethylene-propylene rubber, hydrin rubber, urethane rubber, silicone rubber, and fluororubber. It is preferable that the rubber material be vulcanized.

[0108] Examples of thermoplastic elastomers include acrylic thermoplastic elastomers, styrene thermoplastic elastomers, olefin thermoplastic elastomers, urethane thermoplastic elastomers, polyester thermoplastic elastomers, polyamide thermoplastic elastomers, silicone thermoplastic elastomers, polyvinyl chloride thermoplastic elastomers, polybutadiene thermoplastic elastomers, trans-polyisoprene thermoplastic elastomers, fluororubber thermoplastic elastomers, chlorinated polyethylene thermoplastic elastomers, and derivatives thereof. These may be contained alone or in combination of two or more.

[0109] In thermoplastic elastomers, the hard segment component contributes to heat resistance and strength, while the soft segment component contributes to flexibility and toughness. Among these, from the viewpoints of flexibility and adhesiveness, the thermoplastic elastomer is preferably an acrylic triblock copolymer.

[0110] The acrylic triblock copolymer is a polymer having structural units derived from an acrylic acid ester. The acrylic triblock copolymer may also have structural units derived from a monomer other than an acrylic acid ester. The acrylic triblock copolymer may also have structural units derived from a plurality of different acrylic acid esters.

[0111] Examples of acrylic acid esters include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, cyclohexyl acrylate, octyl acrylate, decyl acrylate, lauryl acrylate, and benzyl acrylate.

[0112] The monomer other than the acrylic acid ester is preferably a vinyl-based monomer. Examples of the vinyl-based monomer include acrylonitrile, acrylamide, acrylic acid, methacrylic acid, methacrylic acid ester, styrene, ethylene, propylene, and butadiene. These may be contained alone or in combination of two or more.

[0113] The acrylic triblock copolymer preferably has a reactive functional group at the molecular end or in the molecular chain. From the viewpoint of adhesion to the metal layer, the reactive functional group is preferably an epoxy group, a hydroxy group, a carboxy group, an amino group, or an amide group. Furthermore, from the viewpoint of heat resistance and insulation reliability, the reactive functional group is preferably an epoxy group, a hydroxy group, or an amino group. Among these, the reactive functional group is preferably an epoxy group.

[0114] The weight-average molecular weight (Mw) of the acrylic triblock copolymer is not particularly limited. The weight-average molecular weight is preferably in the range of 10,000 to 2,000,000, and more preferably in the range of 50,000 to 1,200,000. The weight-average molecular weight is further preferably in the range of 100,000 to 900,000, and particularly preferably in the range of 500,000 to 900,000. A weight-average molecular weight of 10,000 or more makes it easy to maintain a low elastic modulus, and a weight-average molecular weight of 2,000,000 or less provides good compatibility and flowability.

[0115] Commercially available elastomers may be used, such as "CLARITY (registered trademark) LA2140" (acrylic block copolymer, manufactured by Kuraray Co., Ltd.) and "TUFTECH (registered trademark) H1041" (styrene-ethylenebutylene-styrene block copolymer, manufactured by Asahi Kasei Chemicals Corporation).

[0116] The content of the elastomer is preferably in the range of 0.1 to 50 parts by mass, more preferably in the range of 2 to 30 parts by mass, per 100 parts by mass of the thermosetting compound. Furthermore, the content of the elastomer is further preferably in the range of 5 to 30 parts by mass, particularly preferably in the range of 10 to 30 parts by mass, per 100 parts by mass of the thermosetting compound. By keeping the content within the above range, excellent compatibility between the elastomer and the thermosetting compound is achieved. Furthermore, cure shrinkage and thermal expansion can be reduced in the cured product of the composition of the present invention.

[0117] (3) Organic Filler The composition of the present invention can reduce the dielectric constant and dielectric loss tangent by containing an organic filler. Specifically, by containing an organic compound having both a low dielectric constant and a low dielectric loss tangent in the form of particles as a filler, the dielectric constant and dielectric loss tangent of the entire composition can be uniformly reduced.

[0118] In the present invention, the term "organic filler" refers to an organic compound that, when added, has the function of reducing the relative dielectric constant or dielectric loss tangent of the composition. The organic filler may be particulate, fibrous, or hollow resin particles. Among these, the organic filler is preferably particulate, and preferably has a number-average primary particle diameter of 1 μm or less. An example of a fibrous organic filler is nanofiber. The number-average primary particle diameter of the filler can be measured by the following method.

[0119] An SEM image of the filler sample is taken using a scanning electron microscope (manufactured by JEOL Ltd.), and a 10,000x magnified photograph of the SEM image is then imported into a scanner.

[0120] Next, from the obtained photographic image, images of 300 organic filler particles, excluding aggregated particles, are randomly binarized, and the horizontal Feret diameter of each is calculated. For example, this can be calculated using an automatic image processing analysis system "Luzex AP Software Ver. 1.32" (manufactured by Nireco Corporation). The average value of the horizontal Feret diameters of each of the organic filler particle images is then calculated, and this is taken as the number-average primary particle diameter. Here, "horizontal Feret diameter" refers to the length of the side parallel to the x-axis of the circumscribed rectangle when the particle images of the organic filler are binarized.

[0121] Examples of the organic filler include known organic fillers having a relatively low dielectric constant and dielectric loss tangent. The organic compound contained in the organic filler is not particularly limited, and examples thereof include polyethylene, polystyrene, urea-formalin resin, polyester, cellulose, acrylic resin, fluororesin, cured epoxy resin, crosslinked benzoguanamine resin, crosslinked acrylic resin, and crosslinked styrene. These may be contained alone or in combination of two or more.

[0122] From the viewpoint of adhesion to the metal layer, the organic filler is preferably fluororesin particles, polyester particles, or cellulose nanofibers. Among these, the organic filler is more preferably polytetrafluoroethylene (PTFE), methylsilicone, or polyphenylene ether particles. Alternatively, the organic filler may be liquid crystal polymer particles, which will be described later.

[0123] From the viewpoint of adhesion to the metal layer, the number average primary particle diameter of the organic filler is preferably in the range of 5 nm to 20 μm, more preferably in the range of 10 nm to 1 μm, further preferably in the range of 20 to 500 nm, particularly preferably in the range of 25 to 90 nm.

[0124] The organic filler may be a commercially available product, such as "NS-08" (polytetrafluoroethylene, manufactured by Nagoya Gosei Co., Ltd.) or "XYDAR (registered trademark) LF-31P" (liquid crystal polymer, volume average particle size: 5 μm, melting point: 320° C., manufactured by ENEOS Corporation).

[0125] The composition of the present invention may contain one type of organic filler alone or two or more types. From the viewpoints of the thermal expansion coefficient and adhesion to the metal layer, the content of the filler is preferably 50 parts by mass or less and preferably 1 part by mass or more relative to 100 parts by mass of the thermosetting compound. The content of the filler is more preferably in the range of 5 to 45 parts by mass, even more preferably in the range of 10 to 40 parts by mass, and particularly preferably in the range of 15 to 35 parts by mass.

[0126] (3.1) Fluorine Resin Particles Examples of fluororesin particles include polytetrafluoroethylene (PTFE), fluorinated ethylene-propylene copolymer (FEP), perfluoroalkoxy polymer (PFA), chlorotrifluoroethylene (CTFE), tetrafluoroethylene-chlorotrifluoroethylene copolymer (TFE / CTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polychlorotrifluoroethylene (PCTFE), and the like. Among these, polytetrafluoroethylene (PTFE, relative dielectric constant 2.1) is preferred from the viewpoint of low dielectric tangent and low relative dielectric constant. These may be used alone or in combination of two or more.

[0127] The method for producing the fluororesin particles is not particularly limited, but emulsion polymerization is preferred. For example, the fluororesin particles can be produced by a commonly used method such as the method described in Fluororesin Handbook (edited by Satokawa Takaomi, published by Nikkan Kogyo Shimbun). The fluororesin particles produced by emulsion polymerization are aggregated and dried, and recovered as a fine powder in the form of secondary particles formed by aggregation of primary particles.

[0128] The average primary particle size of the fluororesin particles is preferably 1 μm or less, more preferably 0.5 μm or less, and even more preferably 0.3 μm or less. By having an average primary particle size of 1 μm or less, the particles are less likely to settle and can be stably dispersed even in a highly hydrophobic solvent. Although a smaller average primary particle size is preferable, from the viewpoint of ease of production, a size of 0.05 μm or more is preferred.

[0129] The term "average primary particle size" as used herein refers to the volume-based average particle size (50% volume diameter, median diameter) measured by a laser diffraction scattering method, a dynamic light scattering method, an image imaging method, or the like.

[0130] The average primary particle diameter of the fluororesin particles is preferably a value obtained by a laser diffraction scattering method, a dynamic light scattering method, etc. in the production stage. In the fine powder state after drying, the fluororesin particles are in the state of secondary particles, and the cohesion force between the primary particles is strong, making it difficult to easily measure the primary particle diameter by a laser diffraction scattering method, a dynamic light scattering method, etc. Therefore, the average primary particle diameter may be a value obtained by an image imaging method.

[0131] Examples of the measuring device and method include a dynamic light scattering method using a concentrated particle size analyzer "FPAR-1000" (manufactured by Otsuka Electronics Co., Ltd.), a laser diffraction scattering method using a particle size distribution measuring device "Microtrac" (manufactured by Nikkiso Co., Ltd.), and an image imaging method using image analysis particle size distribution measuring software "MacView" (manufactured by Mountec Co., Ltd.).

[0132] The content of the fluororesin in the fluororesin dispersion is preferably in the range of 5 to 70 mass %, more preferably in the range of 10 to 50 mass %, based on the total mass of the fluororesin dispersion.

[0133] When the content of the fluororesin in the fluororesin dispersion is 5% by mass or more, the amount of solvent is not too large, and an appropriate viscosity is maintained. Therefore, the fluororesin particles are less likely to settle and can be stably dispersed. Furthermore, when the content is 70% by mass or less, the fluororesin particles are less likely to aggregate and can be stably dispersed.

[0134] The fluorine-based additive that can be used in the fluororesin dispersion is not particularly limited as long as it has at least a fluorine-containing substituent and a hydrophobic group, and may further have a hydrophilic group.

[0135] The use of a fluorine-based additive reduces the surface tension of the highly hydrophobic solvent serving as the dispersion medium, improves the wettability of the fluororesin particle surface, and thereby improves the dispersibility of the fluororesin particles. Furthermore, the fluorine-containing substituents in the fluorine-based additive are adsorbed to the surface of the fluororesin particles, and the hydrophobic groups in the fluorine-based additive extend into the highly hydrophobic solvent. Therefore, the steric hindrance of the hydrophobic groups makes the fluororesin particles less likely to aggregate, resulting in more stable dispersion.

[0136] Examples of the fluorine-containing substituent in the fluorine-based additive include perfluoroalkyl groups and perfluoroalkenyl groups. Examples of the hydrophobic group include alkyl groups, phenyl groups, and siloxane groups, which may be used alone or in combination of two or more. Examples of the hydrophilic group include ethylene oxide, amide groups, ketone groups, carboxyl groups, and sulfone groups, which may be used alone or in combination of two or more.

[0137] Commercially available fluorine-based additives include the "Surflon (registered trademark) series" (manufactured by AGC Seimi Chemical Co., Ltd.), such as perfluoroalkyl group-containing Surflon (registered trademark) S-611, the "Megafac (registered trademark) series" (manufactured by DIC Corporation), such as Megafac (registered trademark) F-555, Megafac (registered trademark) F-558, and Megafac (registered trademark) F-563, and the Unidyne (Unidyne) series (manufactured by Daikin Industries, Ltd.), such as Unidyne (registered trademark) DS-403N. These may be used alone or in combination of two or more.

[0138] The content of the fluorine-based additive in the fluororesin dispersion is preferably in the range of 0.1 to 50 mass %, more preferably in the range of 5 to 35 mass %, and even more preferably in the range of 15 to 25 mass %, relative to the total mass of the fluororesin particles.

[0139] When the content of the fluorine-based additive in the fluororesin dispersion is 0.1% by mass or more, the surfaces of the fluororesin particles can be sufficiently wetted with the solvent, and when the content is 50% by mass or less, the dispersion can be prevented from foaming too much, which would reduce the efficiency of dispersion.

[0140] In the fluororesin particle dispersion, other surfactants may be used in combination with the above-mentioned fluorine-based additives, as long as the effects of the present invention are not impaired. The other surfactants are not particularly limited, and nonionic, anionic, cationic, and other surfactants can be used.

[0141] Examples of solvents that can be used for the fluororesin particle dispersion include acetone, methyl ethyl ketone, hexane, heptane, octane, 2-heptanone, cycloheptanone, cyclohexanone, cyclohexane, methylcyclohexane, ethylcyclohexane, methyl-n-pentyl ketone, methyl isobutyl ketone, methyl isopentyl ketone, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, ethylene glycol monoacetate, ethylene glycol monomethyl ether acetate, and ethylene glycol. Monoethyl ether acetate, diethylene glycol monoacetate, diethylene glycol diethyl ether, propylene glycol monoacetate, dipropylene glycol monoacetate, propylene glycol diacetate, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, cyclohexyl acetate, ethyl 3-ethoxypropionate, dioxane, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate ethyl, ethyl pyruvate, methyl methoxypropionate, ethyl ethoxypropionate, anisole, ethyl benzyl ether, cresyl methyl ether, diphenyl ether, dibenzyl ether, phenetole, butyl phenyl ether, benzene, ethylbenzene, diethylbenzene, pentylbenzene, isopropyl benzene, toluene, xylene, cymene, mesitylene, methanol, ethanol, isopropanol, butanol, methyl monoglycidyl ether, ethyl monoglycidyl ether, butyl monoglycidyl ether, phenyl monoglycidyl ether, methyl diglycidyl ether, ethyl diglycidyl ether, butyl diglycidyl ether, phenyl diglycidyl ether, methyl phenol monoglycidyl ether, ethyl phenol monoglycidyl ether, butyl phenol monoglycidyl ether, mineral spirits, 2-hydroxyethyl acrylate, tetrahydrofurfuryl acrylate, 4-vinylpyridine, 2-ethylhexyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl methacrylate,Examples of the surfactant include neopentyl glycol diacrylate, hexanediol diacrylate, trimethylolpropane triacrylate, methacrylate, methyl methacrylate, styrene, perfluorocarbon, hydrofluoroether, hydrochlorofluorocarbon, hydrofluorocarbon, perfluoropolyether, dimethylimidazoline, tetrahydrofuran, pyridine, formamide, acetanilide, dioxolane, o-cresol, m-cresol, p-cresol, phenol, N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, diethyl sulfoxide, dimethyl sulfone, diethyl sulfone, γ-butyrolactone, sulfolane, halogenated phenols, and various silicone oils. These may be used alone or in combination of two or more.

[0142] Among these, the solvent is preferably formamide, acetanilide, dioxolane, o-cresol, m-cresol, p-cresol, N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, γ-butyrolactone, sulfolane, halogenated phenols, xylene, or acetone.

[0143] Depending on the polarity of the solvent, some may be highly compatible with water, but if the water content is too high, it may hinder the dispersibility of the fluororesin particles in the solvent, causing an increase in viscosity and aggregation of the particles.

[0144] Therefore, the water content of the solvent as measured by the Karl Fischer method is preferably within a range of 0 to 5000 ppm by mass. The water content can be measured by the Karl Fischer method in accordance with JIS K 0068:2001, for example, using a Karl Fischer moisture meter "MCU-610" (manufactured by Kyoto Electronics Manufacturing Co., Ltd.).

[0145] By keeping the water content in the solvent within the above range, a fluororesin particle dispersion can be obtained that has a finer particle size, lower viscosity, and better storage stability. The water content in the solvent is preferably 3000 mass ppm or less, more preferably 2500 mass ppm or less, and even more preferably 2000 mass ppm or less. The water content in the solvent can be adjusted by a commonly used method for dehydrating organic solvents, such as using molecular sieves.

[0146] (4) Other Additives The composition of the present invention may contain other additives as needed. Examples of other additives include plasticizers, curing agents, curing accelerators, coupling agents, and flame retardants.

[0147] 3. Thermosetting Adhesive The thermosetting adhesive of the present invention is characterized by containing the above-described composition. When the above-described composition is used as a thermosetting adhesive, the composition may further contain additives as necessary. Furthermore, for example, the viscosity may be adjusted by further containing an organic solvent or the like in the composition. Examples of organic solvents include methylene chloride.

[0148] 4. Laminate The laminate of the present invention is a laminate in which a support, an adhesive layer, and a metal layer are laminated in this order, and is characterized in that the adhesive layer contains a cured product of the above-mentioned thermosetting adhesive.

[0149] 1 shows a cross-sectional view of an example of a laminate (single-sided) of the present invention. The laminate 100 is a single-sided metal-clad laminate in which a metal layer 101 is bonded to one side of a support 103 via an adhesive layer 102, and the metal layer is provided on only one side. Note that the laminate may have any layer other than the metal layer, adhesive layer, and support.

[0150] Figure 2 shows a cross-sectional view of an example of a laminate (double-sided) of the present invention. Laminate 110 is a double-sided metal-clad laminate in which metal layers 101 or 105 are bonded to both sides of support 103 via adhesive layers 102 or 104, respectively, and metal layers are provided on both sides. Note that the laminate may also have any layer other than the metal layer, adhesive layer, and support. Furthermore, it is sufficient that at least one of adhesive layers 102 and 104 contains a cured product of the thermosetting adhesive of the present invention.

[0151] The thickness of the laminate is not particularly limited, and is preferably within the range of 50 to 500 μm, and more preferably within the range of 100 to 300 μm. By having a thickness of 50 μm or more, it is possible to sufficiently reduce transmission loss when used in a circuit board. By having a thickness of 500 μm or less, it is possible to suppress a decrease in flexibility and productivity when used in a circuit board.

[0152] (1) Adhesive Layer The adhesive layer contains a cured product of the thermosetting adhesive. The adhesive layer preferably has a relatively low dielectric constant and dielectric loss tangent. Specifically, the dielectric constant at a frequency of 1 MHz under an environment of 22°C and 60% RH is preferably 3.0 or less, more preferably 2.6 or less, and even more preferably 2.3 or less.

[0153] The adhesive layer preferably has a dielectric loss tangent in the range of 0.00120 to 0.0150 at a frequency of 28 GHz in an environment of 22° C. and 60% RH. The dielectric loss tangent of the adhesive layer can be measured in the same manner as for the support, which will be described later.

[0154] From the viewpoints of dielectric properties, thermal expansion, and adhesion to the metal layer, it is preferable that the number density of the organic filler in the adhesive layer is higher inside than on the surface of the adhesive layer, where "number density" refers to the number of fillers per unit volume.

[0155] The method for forming the adhesive layer is not particularly limited. For example, a method can be used in which the thermosetting adhesive is applied to a support (or metal layer), and then a metal layer (or support) is attached to the opposite surface and thermally cured. Alternatively, the thermosetting adhesive can be applied to a support (or metal layer), and then thermally cured to form a support (or metal layer) on which an adhesive layer is laminated. Alternatively, the thermosetting adhesive can be applied to a release film, and then thermally cured to form an adhesive film (sheet).

[0156] The thickness of the adhesive layer is not particularly limited, but is preferably in the range of 10 to 50 μm, and more preferably in the range of 15 to 30 μm. When the thickness is 10 μm or more, sufficient adhesiveness can be obtained. When the thickness is 50 μm or less, transmission loss can be reduced and sufficient flexibility can be obtained.

[0157] (2) Support The support is not particularly limited, but is preferably an insulating film having a relatively low dielectric constant and dielectric loss tangent. Specifically, the support is preferably an insulating film having a volume resistivity of 1×10 １３ It is preferably Ω·cm or more. From the viewpoint of the effects of the present invention, the support is preferably a film with low water absorption.

[0158] (2.1) Structure of the Support The support is preferably a resin film, which may contain, as necessary, a surfactant, an inorganic filler, an organic filler, a plasticizer, a curing accelerator, a coupling agent, a pigment, a flame retardant, and the like.

[0159] The resin is not particularly limited as long as it has a relatively low relative dielectric constant and dielectric loss tangent. The resin may be a thermoplastic resin or a thermosetting resin.

[0160] Examples of resins include liquid crystal polymers (LCPs), polyphenylene sulfide, polyether ether ketone, polyimide, polyphenylene ether, polyethylene terephthalate, polyethylene naphthalate, polylactic acid, nylon, polyester, polyethersulfone, polycarbonate, polyarylate, aramid, polyamideimide, maleimide compounds, cyanate resins, benzocyclobutene resins, polycarbodiimides, etc. These may be contained alone or in combination of two or more.

[0161] From the viewpoint of reducing curvature or warpage of the laminate in a high-humidity environment and from the viewpoint of adhesion with a thermosetting adhesive containing benzoxazine as a main component, the resin is preferably a liquid crystal polymer (LCP), polyphenylene sulfide, polyether ether ketone, polyimide, or polyphenylene ether. Furthermore, from the viewpoint of water absorption, a liquid crystal polymer or polyphenylene sulfide is more preferable. When using polyimide as the support, it is preferable to select one with lower water absorption.

[0162] (2.1.1) Liquid Crystal Polymer In the present invention, the term "liquid crystal polymer" refers to a thermotropic liquid crystal polymer. Specifically, the term "liquid crystal polymer" refers to a thermoplastic resin that exhibits liquid crystal-like properties in a molten state, with linear molecular chains regularly arranged.

[0163] The liquid crystal polymer according to the present invention may be a liquid crystal polyester. Among them, a liquid crystal polyester containing structural units represented by the following formulae (a1), (a2), and (a3) ​​is preferred. (a1) —O—Ar １ -CO- (a2) -CO-Ar ２ -CO- (a3) ​​-X-Ar ３ -Y- (wherein, in formula (a1), Ar １ represents a 1,4-phenylene group, a 2,6-naphthylene group, or a 4,4′-biphenylene group. ２ represents a 1,4-phenylene group, a 1,3-phenylene group, or a 2,6-naphthylene group. ３represents a 1,4-phenylene group or a 1,3-phenylene group, X represents —NH—, and Y represents —O— or —NH—.]

[0164] The content of the structural unit represented by formula (a1) is preferably within a range of 30 to 80 mol % relative to 100 mol % of all structural units in the liquid crystal polyester, the content of the structural unit represented by formula (a2) is preferably within a range of 10 to 35 mol %, and the content of the structural unit represented by formula (a3) ​​is preferably within a range of 10 to 35 mol %.

[0165] The structural unit represented by formula (a1) is a structural unit derived from an aromatic hydroxycarboxylic acid, the structural unit represented by formula (a2) is a structural unit derived from an aromatic dicarboxylic acid, and the structural unit represented by formula (a3) ​​is a structural unit derived from an aromatic diamine or an aromatic amine having a phenolic hydroxyl group.

[0166] Among them, Ar １ is a 2,6-naphthylene group, and Ar ２ is a 1,3-phenylene group, and Ar ３ It is preferred that R is a 1,4-phenylene group and Y is —O—.

[0167] Examples of the structural unit represented by formula (a1) include structural units derived from p-hydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, 4-hydroxy-4'-biphenylcarboxylic acid, etc. Among these, a structural unit derived from 2-hydroxy-6-naphthoic acid is preferred. These may be contained alone or in combination of two or more.

[0168] The content of the structural unit represented by formula (a1) is preferably within a range of 30 to 80 mol %, more preferably within a range of 40 to 70 mol %, and even more preferably within a range of 45 to 65 mol %, relative to 100 mol % of all structural units in the liquid crystal polyester.

[0169] Examples of the structural unit represented by formula (a2) include structural units derived from terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, etc. Among these, a structural unit derived from isophthalic acid is preferred. These may be contained alone or in combination of two or more.

[0170] The content of the structural unit represented by formula (a2) is preferably within a range of 10 to 35 mol %, more preferably within a range of 15 to 30 mol %, and even more preferably within a range of 17.5 to 27.5 mol %, relative to 100 mol % of all structural units in the liquid crystal polyester.

[0171] Examples of the structural unit represented by formula (a3) ​​include structural units derived from 3-aminophenol, 4-aminophenol, 1,4-phenylenediamine, 1,3-phenylenediamine, 4-aminobenzoic acid, etc. Among these, a structural unit derived from 4-aminophenol is preferred. These may be contained alone or in combination of two or more.

[0172] The content of the structural unit represented by formula (a3) ​​is preferably within a range of 10 to 35 mol %, more preferably within a range of 15 to 30 mol %, and even more preferably within a range of 17.5 to 27.5 mol %, relative to 100 mol % of all structural units in the liquid crystal polyester.

[0173] The liquid crystal polyester can be produced, for example, by the method described in JP-A-2019-163431.

[0174] (2.2) Method for Producing Support The method for producing the support is not particularly limited, but a solution casting method is preferred. Any known solution casting method can be used. The solution casting method includes the following steps: 1) a step of preparing a coating solution; 2) a step of forming a coating film; and 3) a step of drying the coating film.

[0175] 1) Step of Preparing a Coating Liquid In the step of preparing a coating liquid, a coating liquid containing a resin, an additive, a solvent, etc. is prepared. The solvent is not particularly limited as long as it is a solvent in which the resin, etc. used dissolves or disperses. When the resin, etc. used is dissolved or dispersed in a solvent with a relatively low boiling point (for example, 150°C or less), it is preferable to use a low-boiling-point solvent. By using a low-boiling-point solvent, the manufacturing process temperature (particularly the drying temperature) of the support can be reduced, and thermal shrinkage can be reduced. The boiling point of the solvent is more preferably 120°C or less, even more preferably 90°C or less, and particularly preferably 70°C or less.

[0176] Examples of low-boiling point solvents include aromatic hydrocarbons (toluene, etc.), alcohols (methanol, ethanol, 2-propanol, 1-butanol, etc.), esters (ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, etc.), ethers (diethyl ether, propylene glycol monomethyl ether, ethylene glycol monoethyl ether, etc.), amides (dimethylformamide, N-methylpyrrolidone, etc.), ketones (acetone, methyl ethyl ketone, acetylacetone, cyclohexanone, etc.), halogenated hydrocarbons (methylene chloride, etc.), etc. These may be used alone or in combination of two or more.

[0177] The method for dissolving the resin in the solvent is not particularly limited. The resin to be used may be directly dissolved in the solvent, or the resin may be dissolved in the solvent by polymerizing a monomer in the solvent.

[0178] The method for adding the filler or the like to the solution obtained by dissolving the resin in the solvent is not particularly limited. The filler or the like may be added directly to the solution, or an aggregate of the filler or the like may be prepared and then added to the solution.

[0179] When the filler and other components added as needed are particles made of polymer (polymer particles), it is preferable to prepare an aggregate of polymer particles. A resin may be added to the aggregate, or the aggregate may be added to a solution in which a resin is dissolved. The aggregate of polymer particles can be obtained by spray-drying a slurry containing polymer particles, a surfactant, an inorganic powder, and an aqueous medium. The "surfactant" here refers to the surfactant used to form the aggregate.

[0180] The polymer particle aggregate can be prepared by, for example, the method described in JP 2010-138365 A. The polymer particle aggregate is composed of a plurality of polymer particles in which mutual connection (fusion) is suppressed. Therefore, when the polymer particle aggregate is dispersed in a solution in which a resin is dissolved in a solvent, it can be easily separated into polymer particles, and the polymer particle aggregate has excellent handleability and dispersibility.

[0181] The content of the resin in the coating liquid is preferably within a range of 5 to 60% by mass, more preferably within a range of 10 to 40% by mass, and even more preferably within a range of 10 to 30% by mass, relative to the total mass of the coating liquid.

[0182] When the resin content in the coating solution is 5% by mass or more, the coating solution is given sufficient viscosity, so that the coating film can be adjusted to a desired thickness when formed. Also, when the resin content is 60% by mass or less, unevenness in the thickness of the coating film can be suppressed when formed.

[0183] 2) Step of Forming a Coating Film In the step of forming a coating film, the coating liquid is applied onto a substrate to form a coating film.

[0184] The substrate is not particularly limited, and commercially available products may be used. Examples of commercially available substrate products include "Cerapeel (registered trademark) PJ101, PJ271, and HP2" (manufactured by Toray Industries, Inc.) and "Cosmoshine (registered trademark) A4160" (manufactured by Toyobo Co., Ltd.).

[0185] Alternatively, a film may be prepared in advance as a substrate, and the support according to the present invention may be prepared on the substrate.

[0186] The method for applying the coating liquid onto the substrate is not particularly limited, and examples of the application method include roll coating, rod bar coating, air knife coating, spray coating, and curtain coating.

[0187] 3) Step of drying the coating film In the step of drying the coating film, the coating film is dried to form a film. The method for drying the coating film is not particularly limited, and examples thereof include hot air, infrared rays, a heated roll, and microwaves.

[0188] The support according to the present invention preferably has a residual solvent content in the range of 200 to 3,000 ppm by mass, and it is preferable to select an appropriate drying method and drying conditions so that the residual solvent content falls within the above range. The residual solvent content is more preferably in the range of 400 to 2,000 ppm by mass, and even more preferably in the range of 500 to 1,500 ppm by mass. Although this depends on the type of solvent, the lower the residual solvent content, the less the impact on electrical properties. On the other hand, if the drying load is too high, productivity may decrease, so the drying load should be selected while considering the balance between performance and productivity.

[0189] The qualitative and quantitative determination of the residual solvent amount in the film of the present invention can be performed by headspace gas chromatography. In headspace gas chromatography, a sample is sealed in a container and heated, and the gas in the container is quickly injected into a gas chromatograph while the container is filled with volatile components. Mass spectrometry is then performed to identify the compounds and quantify the volatile components. The volatile components are quantified by creating a calibration curve in advance using samples with known concentrations and comparing the peak areas of the volatile components obtained by measurement with the calibration curve.

[0190] The measurement conditions are as follows: Headspace device: HP7694 Head Space Sampler (manufactured by Hewlett-Packard) Temperature conditions: transfer line 140°C, loop temperature 140°C Sample amount: 0.8 g / 20 mL vial GC: HP5890 (manufactured by Hewlett-Packard) MS: HP5971 (manufactured by Hewlett-Packard) Column: HP-624 (30 m x inner diameter 0.25 mm) Oven temperature: initial temperature 40°C (holding time 3 minutes), heating rate 10°C / min, ultimate temperature 140°C (holding time 30 minutes) Measurement mode: SIM (select ion monitor) mode

[0191] The obtained support may be further stretched. The support may be stretched in only one direction (uniaxial stretching) or in two perpendicular directions (biaxial stretching). Preferably, the support is stretched in two directions, that is, the width direction (TD direction) of the film and the machine direction (MD direction) perpendicular to the width direction.

[0192] The stretching ratio, for example, [stretching ratio in TD direction / stretching ratio in MD direction] is preferably in the range of 1.0 to 3.0. The stretching ratios in the TD direction and MD direction are each preferably in the range of 1.01 to 3.5 times, and more preferably in the range of 1.01 to 1.3 times. The higher the stretching ratio, the greater the residual stress in the resulting film tends to be. The stretching ratio is defined as [(stretching direction size of film after stretching) / (stretching direction size of film before stretching)].

[0193] When the glass transition temperature of the resin used in the film is Tg, the stretching temperature is preferably (Tg-65)°C or more and (Tg+60)°C or less. The stretching temperature is more preferably (Tg-50)°C or more and (Tg+50)°C or less, and even more preferably (Tg-30)°C or more and (Tg+50)°C or less.

[0194] When the stretching temperature is (Tg-30)°C or higher, the film tends to have flexibility suitable for stretching and is less likely to be subjected to excessive tension during stretching. When the stretching temperature is (Tg+60)°C or lower, an appropriate residual stress tends to remain in the stretched film and the generation of bubbles due to evaporation of the solvent in the film can be suppressed.

[0195] The film can be stretched in the MD direction by, for example, a method in which a plurality of rolls are provided with different peripheral speeds and the difference in peripheral speed is utilized (roll method).The film can be stretched in the TD direction by, for example, a method in which both ends of the film are fixed with clips or pins and the distance between the clips or pins is increased in the direction of travel (tenter method).

[0196] (2.3) Physical Properties of Support (2.3.1) Thickness The thickness of the support according to the present invention is preferably in the range of 12.5 to 100.0 μm, more preferably in the range of 25.0 to 50.0 μm. By keeping the thickness within the above range, the circuit board can be made thin, and transmission loss can be reduced.

[0197] (2.3.2) Dielectric Loss Tangent The support according to the present invention preferably has a dielectric loss tangent in the range of 0.0010 to 0.0150 at a frequency of 28 GHz under an environment of 22°C and 60% RH. The lower the dielectric loss tangent (the closer to 0), the more preferable the support.

[0198] The dielectric loss tangent at a frequency of 28 GHz in an environment of 22° C. and 60% RH is preferably in the range of 0.0010 to 0.0150, and more preferably in the range of 0.0010 to 0.0070.

[0199] The dielectric loss tangent can be adjusted to a desired value by appropriately selecting the type, content, etc. of the material used in the support. In addition, the dielectric loss tangent can be adjusted to a desired value by the manufacturing method and manufacturing conditions of the support.

[0200] (Method for Measuring Dielectric Tangent) The dielectric tangent of the support can be measured in accordance with JIS R1641:2007. A test piece of 100 mm x 120 mm in size is prepared for the support, and prior to measurement, it is stored in an environment of a temperature of 22±1°C and a humidity of 60±5% RH for 90 hours. Thereafter, the dielectric tangent is measured at a frequency of 28 GHz using a cylindrical cavity resonator method.

[0201] (2.3.3) Transmission Loss The support according to the present invention preferably has a transmission loss of 1.5 dB / 10 mm or less, more preferably 0.5 dB / 10 mm or less, at a frequency of 28 GHz in an environment of 23° C. and 65% RH. Since the transmission loss is 1.5 dB / 10 mm or less, that is, the support has sufficient suppression of deterioration and attenuation of signals such as electricity, light, and sound flowing on the circuit board, it can also be used in 5G-compatible communication devices.

[0202] (Method for Measuring Transmission Loss) One side of a support (one of the two sides), an adhesive component such as an adhesive sheet, and a 2 μm thick copper plate are laminated together with the adhesive sheet in the middle. Note that an adhesive sheet and copper plate with known transmission loss values ​​are used. For example, this is heat-pressed under conditions of 90°C, 0.5 MPa, and 0.5 minutes. This is then cured at 180°C, 2.0 MPa, and 5 minutes, followed by post-curing at 180°C for 1 hour, to obtain a laminate in which the film, the cured adhesive sheet, and the copper plate are laminated in this order.

[0203] Thereafter, a microstrip line with a wiring width of 140 μm and a length of 100 mm is formed as a circuit pattern on the copper foil layer surface by chemical etching so that the characteristic impedance is 50 Ω, and this is used as a sample. The sample is left for 24 hours in an environment with a temperature of 23 ° C and a humidity of 65% RH. Immediately after leaving it, the transmission loss (dB / 10 mm) at 28 GHz is measured using a network analyzer "8722ES" (manufactured by Agilent Technology Inc.) and a probe "ACP40-250" (manufactured by Cascade Microtec Inc.). The transmission loss of the support alone is obtained by subtracting the transmission losses of the adhesive sheet and copper plate from the transmission loss of the resulting laminate.

[0204] (3) Metal Layer The metal used for the metal layer is not particularly limited and examples thereof include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof. Among these, from the viewpoints of electrical resistance and long-term stability, the metal is preferably copper or a copper alloy.

[0205] The thickness of the metal layer is not particularly limited, and when a metal foil such as a copper foil is used, the thickness is preferably 35 μm or less, and more preferably in the range of 5 to 25 μm. From the viewpoints of production stability and handling, the thickness of the metal foil is preferably 5 μm or more.

[0206] When copper foil is used, it may be rolled copper foil or electrolytic copper foil, or a commercially available copper foil may be used. Furthermore, the metal foil may be surface-treated with, for example, siding, aluminum alcoholate, aluminum chelate, or a silane coupling agent for the purpose of, for example, rust prevention or improving adhesive strength. Rolled copper foil with high surface smoothness is preferred.

[0207] Furthermore, a carrier-attached metal foil containing two or more layers of metal foil may be used as the metal foil. Examples of carrier-attached metal foils include carrier-attached copper foils consisting of a carrier-attached copper foil (thickness: 10 to 35 μm) and an ultra-thin copper foil (thickness: 2 to 5 μm) laminated on the carrier-attached copper foil via a release layer. By using such carrier-attached copper foil, it is possible to form fine patterns using MSAP (modified semi-additive process). The release layer is preferably a metal layer containing nickel or chromium, or a multilayer metal layer in which such metal layers are laminated. Examples of carrier-attached metal foils include "FUTF-5DAF-2" (manufactured by Fukuda Metal Foil & Powder Co., Ltd.).

[0208] (4) Method for Producing a Laminate The method for producing a laminate of the present invention includes a step of applying the thermosetting adhesive. The thermosetting adhesive has sufficient viscosity so that it can be applied by coating.

[0209] Examples of methods for producing the laminate of the present invention include a method in which a metal foil is heat-pressurized to a support via the thermosetting adhesive. Another method involves applying the thermosetting adhesive to a support (or metal layer) and then thermosetting it to form a support (or metal layer) on which an adhesive layer is laminated. Thereafter, a metal layer (or support) is laminated to the surface of the adhesive layer opposite to the surface in contact with the support (or metal layer). Another method involves applying the thermosetting adhesive to a release film and then thermosetting it to form an adhesive film (sheet). Then, a method involves laminating the support and metal layer via the adhesive film.

[0210] Examples of methods for producing a double-sided metal clad laminate include the following: After forming a single-sided metal clad laminate, two single-sided metal clad laminates are stacked with the supports facing each other and then heat-pressurized to bond them together; and, after forming a single-sided metal clad laminate, a metal layer is heat-pressurized to the surface of the support opposite to the surface to which the metal layer is attached via the thermosetting adhesive.

[0211] Thermocompression bonding is preferably carried out under the following conditions. The temperature is preferably within the range of 90 to 250°C, and more preferably within the range of 150 to 190°C. The pressure is preferably within the range of 0.5 to 5.0 MPa, and more preferably within the range of 1.0 to 3.0 MPa. The thermocompression bonding time is preferably within the range of 0.5 to 150 minutes, and more preferably within the range of 5 to 60 minutes. Note that the thermocompression bonding may be carried out in multiple stages by changing the curing conditions. This thermocompression bonding process is also called a vacuum pressing process.

[0212] To accelerate the curing, a post-cure may be performed after the thermocompression bonding at a temperature in the range of 150 to 190°C for 5 to 90 minutes. The curing conditions may be varied to perform the curing in multiple stages. The thermocompression bonding step and the post-cure step are collectively referred to as the integration step.

[0213] 5. Flexible Circuit Board The flexible circuit board of the present invention is characterized by having the above-described laminate. Specifically, one or more metal layers of the above-described laminate are processed into a pattern to form a wiring layer (conductor circuit layer), thereby making it possible to produce a flexible flexible circuit board.

[0214] Flexible printed circuits (FPCs) are thin and highly flexible, allowing them to be bent. Furthermore, flexible printed circuits can be used for three-dimensional wiring and dynamic wiring within devices, contributing to the reduction of thickness, size, and weight of electronic devices.

[0215] (1) Structure of Flexible Circuit Board Flexible circuit board structures include a single-sided structure using a single-sided metal clad laminate, a double-sided structure using a double-sided metal clad laminate, and a multilayer structure in which laminates are combined to form three or more metal layers. Each structure will be described below, but the flexible circuit board of the present invention may include any layer other than the metal layer, adhesive layer, and support. Furthermore, it is sufficient that at least one of the adhesive layers disposed between the support and the adhesive layer contains a cured product of the thermosetting adhesive of the present invention. For convenience, the metal layer 201 and the adhesive layer 202 are collectively referred to as the wiring layer 206.

[0216] 3 shows a cross-sectional view of an example of a flexible circuit board (single-sided structure) according to the present invention. Circuit board 200 can be produced by pattern printing on laminate 100. Note that metal layer 201, adhesive layer 202, and support 203 correspond to metal layer 101, adhesive layer 102, and support 103 described above.

[0217] 4 shows a cross-sectional view of an example of a flexible circuit board (double-sided structure) according to the present invention. Circuit board 210 can be produced by printing a pattern on laminate 110. Metal layers 201 and 205, adhesive layers 202 and 204, and support 203 correspond to metal layers 101 and 105, adhesive layers 102 and 104, and support 103 described above.

[0218] 5 shows a cross-sectional view of an example of a flexible circuit board (multilayer structure) according to the present invention. Circuit board 220 can be produced by printing a pattern on a laminate and laminating it via adhesive layer 207. Metal layer 201, adhesive layer 202, and support 203 correspond to metal layer 101, adhesive layer 102, and support 103 described above. Adhesive layer 207 also preferably contains a cured product of the thermosetting adhesive according to the present invention.

[0219] (2) Manufacturing Method of Flexible Circuit Board Examples of the manufacturing method of the flexible circuit board of the present invention include a method of processing a metal foil into a predetermined transmission circuit by etching, and a method of processing a metal foil into a predetermined transmission circuit by electrolytic plating. Examples of electrolytic plating methods include a semi-additive process (SAP method) and a modified semi-additive process (MSAP method).

[0220] In the manufacturing of flexible circuit boards, the unnecessary photoresist layer is finally peeled off and the flexible circuit board is washed. The difference in surface free energy between the two opposing surfaces of the base film is relatively small, and the wettability is similar, meaning that the two surfaces can be washed to the same degree, which is thought to prevent the photoresist layer from remaining and reduce transmission loss in the circuit board.

[0221] The film of the present invention may be used not only as a base film but also as a coverlay film, which can protect the circuit electrically, mechanically, chemically, and thermally.

[0222] 6. Semiconductor Device A semiconductor device of the present invention is characterized by comprising the flexible circuit board described above.

[0223] The flexible circuit board can be suitably used in electronic devices such as computers, mobile phones, digital cameras, and televisions.

[0224] In addition to the flexible circuit board, the composition of the present invention can also be used as an adhesive in electronic circuits including passive devices, sensor elements, light-emitting elements, liquid crystal displays, electrophoretic displays, image display elements (e.g., self-luminous displays), wireless or wired communication elements, computing elements, memory elements, MEMS elements, solar cells, thin film transistors, etc. These are preferably included in electronic devices. Examples of the passive devices include transistors, active elements (e.g., diodes), resistors, capacitors, inductors, etc. The sensor elements sense pressure, temperature, light, humidity, etc.

[0225] The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. In the examples, the terms "parts" and "%" are used, but they represent "parts by mass" or "% by mass" unless otherwise specified. In the following examples, operations were carried out at room temperature (25°C) unless otherwise specified.

[0226] 1. Details of Each Compound Details of each compound used in the examples are shown below.

[0227] (benzoxazine)

[0228]

[0229] (Bismaleimide) M1: 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane bisphenol A bis(4-maleimidophenyl ether)

[0230]

[0231] (Epoxy compound) EP1: bisphenol A diglycidyl ether

[0232]

[0233] (Elastomer) EL1: Acrylic block copolymer "CLARITY (registered trademark) LA2140" (manufactured by Kuraray Co., Ltd.) EL2: Styrene block copolymer (styrene-ethylenebutylene-styrene block copolymer) "TUFTECH (registered trademark) H1041" (manufactured by Asahi Kasei Chemicals Corporation) EL3: Olefin random copolymer

[0234] The olefin random copolymer (EL3) was obtained by the following procedure: First, a propylene-ethylene random copolymer containing 97 mol % of propylene units and 3 mol % of ethylene units was synthesized using a metallocene catalyst as a polymerization catalyst.

[0235] The following components were kneaded and reacted using a twin-screw extruder with the maximum temperature of the cylinder set to 170°C: Propylene-ethylene random copolymer 100.0 parts by mass, maleic anhydride 1.0 part by mass, lauryl methacrylate 0.5 part by mass, di-t-butyl peroxide 0.8 part by mass

[0236] The extruder was degassed under reduced pressure to remove any remaining unreacted material, thereby synthesizing an olefin random copolymer having a weight-average molecular weight of 150,000 and an acid value of 10 mgKOH / g.

[0237] (Fillers) F1: Polytetrafluoroethylene (PTFE) "NS-08" (manufactured by Nagoya Synthetic Co., Ltd.) F2: Silica "SC2500-SPJ" (volume average particle size: 0.5 μm, manufactured by Admatechs Co., Ltd.) F3: Liquid crystal polymer (LCP) "XYDAR (registered trademark) LF-31P" (volume average particle size: 5 μm, melting point: 320°C, manufactured by ENEOS Corporation) For the PTFE filler of F1, the following solution was prepared. An appropriate amount of dichloromethane was added to 100 parts by mass of a 10% by mass methanol solution "NS-08" (manufactured by Nagoya Synthetic Co., Ltd.). Next, the methanol was distilled off under reduced pressure to prepare a 20% by mass dichloromethane solution of the filler (filler solution).

[0238] 2. Preparation of Compositions (1) Preparation of Composition 8 The following components were mixed with stirring to prepare Composition 8: Benzoxazine (BO1) 70.0 parts by mass Bismaleimide (M1) 20.0 parts by mass Epoxy compound (EP1) 10.0 parts by mass Elastomer (EL1) 30.0 parts by mass Filler (F1) 30.0 parts by mass Methylene chloride 250.0 parts by mass A filler solution was added so that the amount of filler (solid content) added was 30.0 parts by mass.

[0239] (2) Preparation of Compositions 1 to 7 and 9 to 22 Compositions 1 to 7 and 9 to 22 were prepared using the same procedure as for preparing composition 8, except that the types and contents of each component were changed as shown in Tables I and II. The configurations of compositions 18 and 19 were the same as those of composition 8.

[0240] The composition of each composition is shown in Tables I and II below. In Tables I and II, "-" indicates that the corresponding component is not contained. In Table I, "Content" indicates the content [parts by mass] of each of the benzoxazine, bismaleimide, and epoxy compound relative to 100 parts by mass of the total thermosetting compounds. In Table II, "Content" indicates the content [parts by mass] of each of the elastomer and filler relative to 100 parts by mass of the total thermosetting compounds.

[0241]

[0242]

[0243] 3. Preparation of Laminate (1) Preparation of Support (1.1) Preparation of Support 1 (LCP) (1.1.1) Synthesis of Liquid Crystalline Polyester Resin 1 The following components were placed in a polymerization vessel equipped with a stirring blade, and potassium acetate and magnesium acetate were also added as catalysts: 60.0 mol% 6-hydroxy-2-naphthoic acid (HNA), 20.0 mol% 4,4-dihydroxybiphenyl (BP), 15.5 mol% terephthalic acid (TPA), and 4.5 mol% 2,6-naphthalenedicarboxylic acid (NADA).

[0244] The polymerization vessel was purged with nitrogen by vacuum-injecting nitrogen three times, and the following components were then added to the polymerization vessel. The mixture in the polymerization vessel was heated to 150°C and the acetylation reaction was carried out under reflux for 2 hours. Acetic anhydride: 1.08 molar equivalents per mole of hydroxyl groups in the above components.

[0245] After the acetylation was completed, the polymerization vessel in which acetic acid had been distilled was heated at a rate of 0.5°C / min, and when the melt temperature in the vessel reached 310°C, the polymer was taken out and cooled to solidify. The obtained polymer was pulverized to a size that could pass through a sieve with 2.0 mm openings, thereby obtaining a prepolymer.

[0246] Next, using a heater in an oven (manufactured by Yamato Scientific Co., Ltd.), the temperature of the prepolymer obtained above was raised from room temperature to 300°C over 7 hours. The temperature of the prepolymer was maintained at 300°C for 1 hour to carry out solid-state polymerization. Thereafter, the obtained polymer was allowed to cool naturally at room temperature to obtain liquid crystalline polyester resin 1 (LCP1).

[0247] Using a polarizing microscope, a sample of the liquid crystalline polyester resin 1 obtained above was heated and melted on a heating stage, and the presence or absence of optical anisotropy was confirmed to indicate liquid crystallinity. The polarizing microscope used was a polarizing microscope "BH-2" (manufactured by Olympus Corporation) equipped with a microscope hot stage "FP82HT" (manufactured by Mettler).

[0248] (1.1.2) Preparation of Dispersion Liquid Crystalline Polyester Resin 1 obtained above was pulverized using a jet mill to obtain powder particles with an average particle size of 7 μm. The following components were mixed, and the powder particles were dispersed by stirring to obtain a dispersion. The following dispersion medium was prepared by mixing organic solvent 1: methyl ethyl ketone (boiling point 80°C) and organic solvent 2: methyl isobutyrate (boiling point 92°C) in a mass ratio of 8:2 (methyl ethyl ketone:methyl isobutyrate). The boiling point difference between the two organic solvents was 12°C. Powder particles: 10 parts by mass Dispersion medium: 90 parts by mass

[0249] (1.1.3) Coating of Dispersion The dispersion obtained above was coated onto a continuously transported rolled copper foil having a thickness of 25 μm, so as to form a coating film having a dry thickness of 30 μm.

[0250] (1.1.4) Removal of Dispersion Medium The coating film was dried for 2 minutes and 30 seconds in a dryer at 60°C. When the coating film surface was rubbed with a finger at the dryer outlet, the liquid crystalline polyester resin 1 powder came off. In other words, it was confirmed that the liquid crystalline polyester resin 1 powder particles were not fused at this stage. Note that some of the dispersion medium remained in the coating film after drying. The drying time was adjusted so that the amount of residual dispersion medium in the coating film when it entered the next annealing section would be within the range of 10 to 30 mass %, and also depending on the type and mixing ratio of the solvents constituting the dispersion medium.

[0251] (1.1.5) Heat Treatment The dried coating film (powder particle dispersion layer) was placed in an annealing section under a nitrogen atmosphere with the dispersion medium still remaining, and heat-treated in the annealing zone at 350°C for 1 hour. The annealing section was equipped with a temperature-raising zone, an annealing zone, and a slow-cooling zone, from the upstream side, and the coating film was heated throughout the annealing section. Under a nitrogen atmosphere, heating was performed with hot air from both the substrate (copper foil) side and the coating film side. The amount of residual dispersion medium in the coating film when it entered the annealing section was 10% by mass. After the heat treatment, the copper foil portion was edging using iron chloride, and the film was taken up to obtain a support 1.

[0252] (1.2) Preparation of Support 2 (PEEK) The following components were added to a 300 mL autoclave (equipped with a stirrer, a valve for introducing N2 gas, and a thermocouple). The proportion (mol %) per substance amount of each component used and the amount (mol) of the substance actually used are shown below. 4,4'-Difluorobenzophenone 17.4 mol % (0.150 mol) Hydroquinone 17.4 mol % (0.150 mol) Diphenyl sulfone (DPS) 47.7 mol % (0.413 mol) K ２ CO ３ 0.9 mol% (0.008 mol) Na ２ CO ３ 16.6 mol% (0.144 mol)

[0253] After that, N ２ The mixture was stirred and heated while flowing gas at a flow rate of 100 mL / min to polymerize polyether ether ketone (PEEK). The temperature conditions were as follows: The mixture was heated at a rate of 3°C / min in the range of 30 to 180°C and at a rate of 1°C / min in the range of 180 to 320°C, and the mixture was held at 320°C for 4 hours. After the polymerization reaction was completed, the polyether ether ketone (PEEK) was cooled to room temperature and pulverized to obtain flake-like PEEK powder. The obtained PEEK powder was washed five times with 300 mL of water.

[0254] The obtained PEEK powder was melt-extruded at about 400° C. using a 90 mmφ single-screw extruder, and the melt was quenched with a cooling roll at about 100° C. to obtain a support 2 having a thickness of 100 μm.

[0255] (1.3) Preparation of Support 3 (PPS) The following components were mixed to prepare resin pellets primarily composed of polyphenylene sulfide (PPS). The melt viscosity of polyphenylene sulfide (PPS) was measured at a temperature of 310°C and a shear rate of 1200 / sec. Specifically, approximately 20 g of dried PPS polymer was used as a sample, and the melt viscosity was measured using a capillary rheometer "Capilograph (registered trademark) 1-C" (manufactured by Toyo Seiki Seisaku-sho). A 1 mmφ x 10 mm flat die capillary was used. The sample was introduced into the apparatus and held at 310°C for 5 minutes, after which the melt viscosity of the sample was measured.

[0256] Polyphenylene sulfide (melt viscosity 160 Pa·s) 100.0 parts by mass Filler (calcium carbonate "NITOREX #30PS" (manufactured by Nitto Funka Kogyo Co., Ltd., average particle size 0.7 μm)) 0.3 parts by mass Calcium stearate 0.2 parts by mass

[0257] The following components were mixed using a blender to obtain a PPS resin composition: 100.0 parts by mass of the above resin pellets; 1.2 parts by mass of s-PS resin pellets "XAREC (registered trademark) S-104" (manufactured by Idemitsu Kosan Co., Ltd.). The above PPS resin composition was heated to 310°C to melt and filtered through a disk filter with 40 μm openings. The molten PPS resin composition was extruded through a die and cooled on a metal drum whose surface was maintained at 40°C to obtain a resin sheet with a thickness of 360 μm.

[0258] The obtained resin sheet was preheated by contacting it with a metal roll whose surface temperature was adjusted to within a range of 80 to 90 ° C. Thereafter, on a metal roll whose surface temperature was adjusted to 93 ° C., inter-roll stretching was performed so that the resin sheet's length in the longitudinal direction was 3.5 times. The film stretched in the longitudinal direction was introduced into a tenter stretching machine and stretched in the transverse direction by 2.9 times in an atmosphere of 93 ° C. After stretching, the film was immediately heat-set at 250 ° C. for 100 seconds while being relaxed by 4% in the transverse direction, to obtain a support 3 having a thickness of 40 μm.

[0259] (2) Preparation of Laminate (2.1) Preparation of Laminate 8 The composition 8 obtained above was applied to a support 1 so that the thickness of the (adhesive layer) after curing of the composition would be 25 μm. Then, a copper foil having a thickness of 35 μm was laminated via the composition 8, and these were subjected to heat-pressure bonding at 200° C. and 2.0 MPa for 90 minutes. Then, a laminate 8 having a support, an adhesive layer, and a metal layer was obtained.

[0260] (2.2) Preparation of Laminates 1 to 7 and 9 to 22 Laminates 1 to 7 and 9 to 22 were prepared in the same manner as in the preparation method of Laminate 8, except that the support and composition were changed as shown in Tables I and II.

[0261] 4. Evaluation The following evaluations were carried out for each of the obtained laminates.

[0262] (1) Adhesion Strength For each of the obtained laminates, the peel strength when peeling off the metal layer (copper foil) was measured using a force gauge "DPRS-2TR" (manufactured by Imada Co., Ltd.), and the adhesive strength of the adhesive layer was evaluated. The peel strength was measured in accordance with Section 7 "Performance Test" of the JPCA Electric Circuit Board Standards, Third Edition, under the following conditions. Jig: 90-degree peel jig "P90-200N-BB" (manufactured by Imada Co., Ltd.) Pull speed: 50 mm / min

[0263] The obtained peel strength was evaluated according to the following criteria. A grade of D or higher (A to D) was considered acceptable. A: Peel strength is 9 N / cm or higher. B: Peel strength is 7 N / cm or higher and less than 9 N / cm. C: Peel strength is 5 N / cm or higher and less than 7 N / cm. D: Peel strength is 3 N / cm or higher and less than 5 N / cm. E: Peel strength is less than 3 N / cm.

[0264] (2) Dielectric Loss Tangent The dielectric loss tangent of each laminate was measured in accordance with JIS R1641:2007. A test piece measuring 100 mm x 120 mm was prepared for each laminate and stored for 90 hours at a temperature of 22±1°C and a humidity of 60±5% RH before measurement. Thereafter, the dielectric loss tangent was measured at a frequency of 28 GHz using a cylindrical cavity resonator method.

[0265] The obtained dielectric dissipation factor was evaluated according to the following criteria. A grade of D or higher (A to D) was considered acceptable. A: The dielectric dissipation factor is 0.004 or less. B: The dielectric dissipation factor is greater than 0.004 and less than 0.005. C: The dielectric dissipation factor is greater than 0.005 and less than 0.007. D: The dielectric dissipation factor is greater than 0.007 and less than 0.010. E: The dielectric dissipation factor is greater than 0.010.

[0266] (3) Heat Resistance Test pieces measuring 10 cm x 10 cm were prepared for each of the obtained laminates. Then, using a simultaneous differential thermal and gravimetric analyzer in a nitrogen atmosphere, the test pieces were heated from 30°C to 550°C at a constant heating rate (10°C / min), and the change in mass was measured. The simultaneous differential thermal and gravimetric analyzer used was a "TG / DTA 6200" (manufactured by Seiko Instruments Inc.).

[0267] Using the mass of the test piece at 200°C as the reference, the temperature at which the mass loss rate, as defined by the following formula, becomes 5%, was defined as Td°C: Mass loss rate [%] = {(M200 - MT) / M200} x 100 (where M200 represents the mass of the test piece at 200°C, and MT represents the mass of the test piece at T°C).

[0268] The obtained temperature (Td°C) at which the mass loss rate reached 5% was evaluated according to the following criteria. A grade of D or higher (A to D) was considered acceptable. A: The temperature (Td°C) at which the mass loss rate reached 5% was 380°C or higher. B: The temperature (Td°C) at which the mass loss rate reached 5% was 350°C or higher and lower than 380°C. C: The temperature (Td°C) at which the mass loss rate reached 5% was 300°C or higher and lower than 350°C. D: The temperature (Td°C) at which the mass loss rate reached 5% was 260°C or higher and lower than 300°C. E: The temperature (Td°C) at which the mass loss rate reached 5% was lower than 260°C.

[0269] (4) Warpage A test piece measuring 10 cm x 10 cm was prepared for each of the obtained laminates. After conditioning the laminate with the support side facing downward at 23°C and a relative humidity of 50% for 24 hours, the amount of lift at each of the four corners was measured. When the warpage was convex, the specimen was turned upside down and measured. When the warpage was concave, it was considered positive, and when the warpage was convex, it was considered negative.

[0270] The average value (absolute value) X of the obtained measurements at the four corners was evaluated according to the following criteria. A grade of D or higher (A to D) was considered pass. A: The average value X is 5 mm or less. B: The average value X is more than 5 mm and 10 mm or less. C: The average value X is more than 10 mm and 15 mm or less. D: The average value X is more than 15 mm and 25 mm or less. E: The average value X is more than 25 mm.

[0271] (5) Water Absorption Rate A test piece with a diameter of 10 cm was prepared for each of the obtained laminates. In accordance with JIS K7209:2000, the test piece was immersed in water at 23°C for 24 hours, and the water absorption rate, as defined by the following formula, was measured from the change in mass before and after immersion. The lower the water absorption rate, the better. (Formula) Water absorption rate [%] = {(mass after immersion - mass before immersion) / mass before immersion} x 100

[0272] The construction and evaluation results of each laminate are shown in Table III.

[0273]

[0274] From the examples and comparative examples, it is clear that the composition of the present invention has sufficient adhesive strength and can reduce the dielectric tangent and warpage.

[0275] A comparison of Laminates 8 and 17 reveals that the dielectric loss tangent can be reduced by including polytetrafluoroethylene in the organic filler.

[0276] A comparison of laminates 8, 20 and 21 shows that the adhesive strength can be improved by using a block copolymer as the elastomer, and further by using an acrylic triblock copolymer as the elastomer.

[0277] A comparison of Laminates 1 and 4 shows that the adhesive strength can be improved by including an epoxy compound as a thermosetting compound.

[0278] A comparison of Laminates 4 and 5 shows that the inclusion of bismaleimide as a thermosetting compound can improve heat resistance.

[0279] A comparison of Laminates 8 and 18 to 19 shows that the water absorption rate can be reduced by including a liquid crystal polymer or polyphenylene sulfide in the support.

[0280] The present invention can provide a composition having sufficient adhesive strength and reduced dielectric tangent and warpage, thereby providing a flexible circuit board and a semiconductor device that can be used even in high frequency bands.

[0281] REFERENCE SIGNS LIST 100 Metal clad laminate (single-sided) 101 Metal layer 102 Adhesive layer 103 Support 104 Adhesive layer 105 Metal layer 110 Metal clad laminate (double-sided) 200 Circuit board (single-sided structure) 201 Metal layer 202 Adhesive layer 203 Support 204 Adhesive layer 205 Metal layer 206 Wiring layer 207 Adhesive layer 210 Circuit board (double-sided structure) 220 Circuit board (multi-layer structure)

Claims

1. A composition containing a thermosetting compound, the content of benzoxazine being 55 parts by mass or more per 100 parts by mass of the thermosetting compound, and the composition containing an elastomer and an organic filler.

2. The composition according to claim 1, characterized in that the content of said organic filler is 50 parts by mass or less per 100 parts by mass of said thermosetting compound.

3. The composition according to claim 1, characterized in that the content of the elastomer is within the range of 10 to 50 parts by mass per 100 parts by mass of the thermosetting compound.

4. The composition according to claim 1, characterized in that the organic filler contains polytetrafluoroethylene.

5. The composition according to claim 1, wherein the elastomer is a block copolymer.

6. The composition according to claim 5, wherein said block copolymer is an acrylic triblock copolymer.

7. The composition according to claim 1, characterized in that it contains an epoxy compound as the thermosetting compound.

8. The composition according to claim 1, characterized in that it contains bismaleimide as the thermosetting compound.

9. A thermosetting adhesive comprising the composition according to any one of claims 1 to 8.

10. A laminate comprising a support, an adhesive layer and a metal layer laminated in this order, wherein the adhesive layer contains a cured product of the thermosetting adhesive according to claim 9.

11. The laminate according to claim 10, wherein the support contains a liquid crystal polymer or polyphenylene sulfide.

12. A method for producing a laminate according to claim 10, comprising the step of applying the thermosetting adhesive.

13. A flexible circuit board comprising the laminate according to claim 10.

14. A semiconductor device comprising the flexible circuit board according to claim 13.

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