JP2017047686A - Method for manufacturing flexible copper-clad laminated sheet and flexible copper-clad laminated sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of efficiently manufacturing a flexible copper-clad laminated sheet having excellent dielectric characteristics and high heat resistance and to provide a flexible copper-clad laminated sheet which has excellent dielectric characteristics and high heat resistance and can be efficiently manufactured.SOLUTION: There is provided a method for manufacturing a flexible copper-clad laminated sheet, which comprises: a step of applying an adhesive composition comprising (A) a carboxyl group-containing styrene-based elastomer and (B) a crosslinking compound having one or more epoxy groups and one or more vinyl groups and/or an isopropenyl group onto at least one surface of an insulation film; a step of heating the adhesive composition applied onto the insulation film to dry; a step of laminating a copper foil on the dried adhesive composition to form a laminate; and a step of irradiating the laminate with energy rays to cure the dried adhesive composition.SELECTED DRAWING: None

Description

  The present invention relates to a method capable of efficiently producing a flexible copper-clad laminate having excellent dielectric properties and high heat resistance, and flexible copper capable of efficiently producing excellent dielectric properties and high heat resistance. The present invention relates to a tension laminate.

  In recent years, there has been a demand for further miniaturization of electronic devices, and accordingly, a flexible circuit board that is lighter and can be bent is used instead of a rigid circuit board. It is becoming.

  Conventionally, flexible copper-clad laminates used in the production of flexible circuit boards have a tendency for adhesives to impair the dielectric properties, so avoid the use of adhesives and use thermoplastic insulating films and copper foils as high-temperature laminators. It was manufactured by pasting together directly. This method also has the advantage that it can be implemented at a lower cost than other methods. However, characteristics such as dielectric characteristics of the laminate obtained by the method depend greatly on the characteristics of the insulating film. Therefore, for example, liquid crystal polymer films are the mainstream as insulation films currently used for heat-fusion type copper clad laminates currently used for flexible circuit boards, but they are trying to further improve dielectric properties. In some cases, the material of the insulating film may be changed from a liquid crystal polymer to a fluororesin such as PTFE. However, in this case, since PTFE is a material having a large thermal contraction rate, it is difficult to satisfy the dimensional stability required for an electronic circuit board.

  In view of this, an adhesive has been developed that has better dielectric properties than an insulating film and can further improve the dielectric properties of a flexible copper-clad laminate. By bonding the insulating film and the copper foil using such an adhesive, a flexible copper clad laminate having improved dielectric properties can be produced. As such an adhesive, for example, Patent Document 1 discloses an adhesive composition containing a carboxy group-containing styrene elastomer and an epoxy resin. Patent Document 2 discloses a thermoplastic resin composition containing a saturated thermoplastic elastomer having a styrene unit and an epoxy resin.

International Publication No. 2014/147903 Pamphlet JP 2012-122046 A

  As described above, as a method for improving the overall dielectric characteristics of the flexible copper-clad laminate, there is a method of bonding an insulating film and a copper foil using an adhesive having excellent dielectric characteristics. In this manufacturing method, for example, when the adhesive described in Patent Documents 1 and 2 above is used, an adhesive composition layer is formed after forming a laminate of an insulating film, an adhesive composition layer, and a copper foil. It is necessary to sufficiently cure by heat treatment at a predetermined temperature and time. If the curing is insufficient, in the manufacturing process of the electronic circuit board, there is a problem that the curing of the adhesive proceeds in the process of applying heat such as a drying process at the time of circuit formation or solder reflow, and the base material is largely curled. The recommended temperature and recommended time for heat treatment when the adhesive proposed in Patent Documents 1 and 2 is completely cured are 100 to 200 ° C. for 30 to 240 minutes and 170 to 250 ° C. for 60 to 150 minutes, respectively. .

  Meanwhile, a roll-to-roll method has been developed as a method for efficiently mass-producing flexible copper-clad laminates at low cost. In the roll-to-roll method, for example, an adhesive is applied to an insulating film sent out from a roll state, the adhesive composition layer is heated and dried to form a B stage, and then the copper foil sent out from the roll state is also used. Laminate, cure the adhesive composition layer, and roll it up again. In this method, since the insulating film and the like continuously flow between the manufacturing apparatuses connected to each other and are finally wound up in a roll shape, it is possible to greatly reduce the labor and apparatus involved in the conveyance.

  When the low dielectric constant adhesive described in Patent Documents 1 and 2 is applied to the roll-to-roll method, the line speed cannot be increased when the heat treatment furnace is short in order to sufficiently cure the adhesive. In order to increase the line speed, it is necessary to enlarge the heat treatment furnace. In addition, for example, it is also conceivable that the adhesive composition layer is wound by winding an uncured long laminate to form a roll and heat-treating in that state in a batch furnace. However, in that case, a temperature difference is generated between the center portion and the outer portion of the scroll, and appearance defects such as shrinkage wrinkles due to curing shrinkage during curing and shrinkage wrinkles during cooling occur. In this case, a SUS foil having a thickness of about 100 μm is used as a spacer and wound together with the laminated plate to take measures against wrinkles that occur during curing shrinkage, but a step of winding the spacer is required. Therefore, it is not efficient.

  In addition, when the insulating film is melted and laminated to form a multilayer circuit board or during solder reflow, the adhesive layer decomposes and foams, resin flow occurs, and the adhesive strength with the copper foil is increased. If it is lost, the quality of the circuit board deteriorates, so the flexible copper-clad laminate is also required to have high heat resistance.

  Therefore, the present invention provides a method capable of efficiently producing a flexible copper-clad laminate having excellent dielectric properties and high heat resistance, and a flexible material having excellent dielectric properties and high heat resistance, and capable of efficient production. An object is to provide a copper-clad laminate.

This inventor repeated earnest research in order to solve the said subject. As a result, by combining a specific crosslinking compound with a carboxy group-containing styrenic elastomer as the composition of the adhesive composition, it becomes possible to cure in a short time using energy beam irradiation, and it has excellent dielectric properties and heat resistance. The present invention has been completed by finding that a flexible copper-clad laminate can be efficiently produced.
Hereinafter, the present invention will be described.

[1] A method for producing a flexible copper-clad laminate,
An adhesive composition comprising (A) a carboxy group-containing styrenic elastomer and (B) a crosslinking compound having one or more epoxy groups and one or more vinyl groups and / or isopropenyl groups on at least one side of an insulating film Applying step;
Drying the adhesive composition applied on the insulating film by heating;
A step of laminating a copper foil on the dry adhesive composition to form a laminate;
A method comprising the step of curing the dry adhesive composition by irradiating the laminate with an energy beam.

  [2] The method according to [1], wherein the adhesive composition further comprises (C) a bismaleimide compound.

  [3] In the above [2], the adhesive composition includes (A) 1 part by mass or more and 20 parts by mass or less of (C) the bismaleimide compound with respect to 100 parts by mass of the carboxy group-containing styrene elastomer. The method described.

  [4] The above [1], wherein the adhesive composition comprises (A) 0.1 to 10 parts by mass of (B) the crosslinking compound with respect to 100 parts by mass of the carboxy group-containing styrene elastomer. ] The method in any one of [3].

  [5] The method according to any one of [1] to [4], wherein ionizing radiation is used as the energy beam.

  [6] The method according to [5] above, wherein an acceleration voltage of the ionizing radiation is 300 kV or less, and a total irradiation dose is 100 kGy or more and 500 kGy or less.

  [7] The method according to any one of [1] to [6], wherein a thickness of the adhesive composition after curing is 5 μm or more and 100 μm or less.

  [8] The method according to any one of [1] to [7], wherein the insulating film is a liquid crystal polymer film.

  [9] The method according to any one of [1] to [8], wherein the thickness of the insulating film is 10 μm or more and 100 μm or less.

[10] including an insulating film and copper foil,
Adhesive composition comprising (A) a carboxy group-containing styrenic elastomer and (B) a crosslinking compound having one or more epoxy groups and one or more vinyl groups and / or isopropenyl groups on at least one side of the insulating film. The said copper foil is adhere | attached with the thing, The flexible copper clad laminated board characterized by the above-mentioned.

  [11] The flexible copper-clad laminate according to [10], wherein the adhesive composition further includes (C) a bismaleimide compound.

  [12] The flexible copper-clad laminate as described in [10] or [11] above, wherein the adhesive composition has a thickness after curing of 5 μm or more and 100 μm or less.

  [13] The flexible copper clad laminate according to any one of [10] to [12], wherein the insulating film has a thickness of 10 μm or more and 100 μm or less.

  [14] The flexible copper clad laminate according to any one of [10] to [13], wherein the insulating film is a liquid crystal polymer film.

  The adhesive composition used in the present invention not only exhibits excellent dielectric properties and high heat resistance, but also cures in a short time by irradiation with energy rays. Thus, the method of the present invention enables efficient production of flexible copper clad laminates. In addition, the flexible copper clad laminate produced by the method of the present invention is excellent in dielectric properties and heat resistance. Therefore, the present invention is very industrially excellent as a technology capable of efficiently producing a flexible copper-clad laminate having excellent dielectric characteristics and high heat resistance, which has been increasingly demanded in recent years.

FIG. 1 is a schematic view showing a flexible copper-clad laminate according to the present invention. FIG. 2 is a schematic view showing an example of producing a multilayer circuit board using the flexible copper-clad laminate and the adhesive sheet according to the present invention. FIG. 3 is a schematic view showing an example of producing a multilayer circuit board by melting an insulating film of a flexible copper-clad laminate according to the present invention.

Hereinafter, the method of the present invention will be described step by step.
1. Step of preparing the adhesive composition In the method of the present invention, it is preferable to prepare the adhesive composition in advance. Specifically, the components of the adhesive composition are mixed until uniform. For example, the raw material of adhesive composition is thrown into mixers, such as a homomixer, a planetary mixer, and a fencil mixer, and the method of mixing for predetermined time is mentioned.

The adhesive composition used in the method of the present invention comprises at least (A) a carboxy group-containing styrenic elastomer, and (B) one or more epoxy groups and one or more vinyl groups (—CH═CH ₂ ) and / or isoforms. A crosslinking compound having a propenyl group (—C (CH ₃ ) ═CH ₂ ) is included. The combination of the carboxy group-containing styrenic elastomer (A) and the crosslinking compound (B) makes it possible to quickly cure the adhesive composition layer by irradiation of energy rays, and as a result, efficient flexible copper-clad laminates. Manufacturing becomes possible.

  In the present invention, a styrene elastomer having a carboxy group in its molecular structure is used as the main component constituting the adhesive composition. The carboxy group-containing styrene-based elastomer is obtained by modifying a copolymer mainly composed of a block and a random structure of an aromatic vinyl compound and a conjugated diene compound, and a hydrogenated product thereof with an unsaturated carboxylic acid. Examples of the aromatic vinyl compound include styrene, t-butylstyrene such as pt-butylstyrene, α-methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylstyrene, N, N-diethyl- Examples thereof include p-aminoethylstyrene and vinyltoluene. The conjugated diene compound is not particularly limited as long as it can impart rubber elasticity to polystyrene, and examples thereof include butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene and the like. be able to.

  The modification of the styrene elastomer with the unsaturated carboxylic acid can be performed, for example, by copolymerizing the unsaturated carboxylic acid during the polymerization of the styrene elastomer. Moreover, it can also carry out by heating and mixing a styrene-type elastomer and unsaturated carboxylic acid in presence of an organic peroxide. Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid, maleic anhydride, itaconic anhydride, fumaric anhydride, and the like. The amount of modification with unsaturated carboxylic acid is usually about 0.1% by mass or more and 10% by mass or less with respect to the entire carboxy group-containing styrene elastomer.

  The acid value of the carboxy group-containing styrene-based elastomer is preferably from 0.1 mgKOH / g to 20 mgKOH / g. If the acid value is less than 0.1 mg KOH / g, the adhesive composition may be insufficiently cured, and good adhesiveness and heat resistance may not be obtained. On the other hand, when the acid value exceeds 20 mgKOH / g, the adhesion strength and the dielectric properties may be deteriorated. As said acid value, 0.5 mgKOH / g or more is more preferable, 1.0 mgKOH / g or more is further more preferable, 18 mgKOH / g or less is more preferable, 15 mgKOH / g or less is more preferable.

  The molecular weight of the carboxy group-containing styrenic elastomer may be adjusted as appropriate, but for example, the weight average molecular weight is preferably 10,000 or more and 500,000 or less. When the weight average molecular weight is in the range of 10,000 or more and 500,000 or less, excellent adhesion and dielectric properties can be exhibited. The weight average molecular weight is preferably 30,000 or more, more preferably 50,000 or more, more preferably 300,000 or less, and still more preferably 200,000 or less. In addition, the weight average molecular weight in this invention shall mean the value which converted the molecular weight measured by the gel permeation chromatography in polystyrene.

  Specific examples of the styrene elastomer constituting the carboxy group-containing styrene elastomer include styrene-butadiene block copolymer, styrene-ethylenepropylene block copolymer, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene. Examples thereof include a block copolymer, a styrene-ethylenebutylene-styrene block copolymer, and a styrene-ethylenepropylene-styrene block copolymer. Among the copolymers, styrene-ethylenebutylene-styrene block copolymers and styrene-ethylenepropylene-styrene block copolymers are preferable from the viewpoints of adhesiveness and dielectric properties. The mass ratio of styrene / ethylene butylene in the styrene-ethylene butylene-styrene block copolymer and the mass ratio of styrene / ethylene propylene in the styrene-ethylene propylene-styrene block copolymer are 10/90 to 50/50. Preferably there is. When the mass ratio of styrene is less than 10%, the adhesiveness and heat resistance of the adhesive composition may be reduced. On the other hand, if it exceeds 50%, the dielectric properties may be deteriorated.

  The crosslinking compound (B) used in the present invention has one or more epoxy groups and one or more vinyl groups and / or isopropenyl groups, and crosslinks the carboxy group-containing styrene elastomer (A) to form an adhesive layer. Harden. In the present invention, by combining the carboxy group-containing styrene elastomer (A) and the crosslinking compound (B), curing in a short time using energy ray irradiation is possible, and flexible with excellent dielectric properties and heat resistance. A copper-clad laminate can be produced efficiently.

  According to the inventor's experimental knowledge, even a crosslinking compound having a plurality of epoxy groups and the like and capable of crosslinking the carboxy group-containing styrenic elastomer (A) has an epoxy group and a vinyl and / or isopropenyl group. Without both, efficient curing in a short time is difficult. The crosslinking compound (B) is mainly composed of a polymer containing an epoxy group and a vinyl group and / or an isopropenyl group at the terminal and / or side chain of the polymer, and an epoxy group and a vinyl group and / or an isopropenyl group. They are classified as those bonded via a linker group. Moreover, a glycidyl group can be mentioned as a group containing an epoxy group, an acryloyl group can be mentioned as a group containing a vinyl group, and a methacryloyl group can be mentioned as a group containing an isopropenyl group.

  Examples of the crosslinking compound (B) containing an epoxy group, a vinyl group and / or an isopropenyl group at the terminal and / or side chain of the polymer include epoxidized polybutadiene. Polybutadiene contains trans-1,4-addition units, cis-1,4-addition units, and 1,2-addition units as described below, and can be substantially controlled by adjusting reaction conditions such as the type of catalyst. The structure can be controlled, such as polybutadiene composed of only such units, or polybutadiene having many of these units.

  Epoxidized polybutadiene is polybutadiene obtained by partially or completely epoxidizing (epoxy-modifying) a carbon-carbon double bond of polybutadiene. Epoxidized polybutadiene is usually in a liquid state, and the polybutadiene constituting the epoxidized polybutadiene may be 1,2-polybutadiene or 1,4-polybutadiene. However, in the present invention, an epoxidized polybutadiene containing a 1,2-addition unit and a part of the vinyl group in the 1,2-addition unit is epoxidized, and has both an epoxy group and a vinyl group. Use.

  The epoxy modification of polybutadiene can be carried out by reacting polybutadiene with an epoxidizing agent. Examples of the epoxidizing agent include peracids and hydroperoxides. Examples of peracids include performic acid, peracetic acid, perbenzoic acid, and trifluoroperacetic acid, and examples of hydroperoxides include hydrogen peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. It is done.

  The molecular weight of the epoxidized polybutadiene may be appropriately adjusted. For example, the weight average molecular weight may be 250 or more and 20000 or less. From the viewpoint of curing efficiency of the adhesive composition and workability during coating, 500 or more and 10,000 or less are preferable.

The linker group of the crosslinking compound (B) in which the epoxy group and the vinyl group and / or isopropenyl group are bonded via a linker group is not particularly limited, and examples thereof include a C _1-6 alkylene group and an amino group. (—NH—), imino group (> C═N— or —N═C <), ether group (—O—), thioether group (—S—), carbonyl group (—C (═O) —), Thionyl group (—C (═S) —), ester group (—C (═O) —O— or —O—C (═O) —), amide group (—C (═O) —NH— or — NH—C (═O) —), sulfoxide group (—S (═O) —), sulfonyl group (—S (═O) ₂ —), sulfonylamide group (—NH—S (═O) ₂ —, or -S (= O) _2- NH-) and a group in which two or more of these are bonded can be exemplified. When two or more of these groups are bonded to form the linker group, the number of bonds is preferably 30 or less or 25 or less, and more preferably 20 or less or 15 or less. Other linker groups include C _6-10 cycloalkylene groups such as cyclohexalene; C _6-12 arylene groups such as phenylene groups, naphthylene groups, and biphenylene groups; heteroaryl groups such as pyridylene groups, thienylene groups, and indylene groups; Mention may be made of saturated heterocyclyl groups such as oxalene, dioxalene, 1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione.

  In the crosslinking compound (B) in which the epoxy group and the vinyl group and / or isopropenyl group are bonded via a linker group, the upper limit of the number of epoxy groups and vinyl groups and / or isopropenyl groups is that of the linker group. It may be determined depending on the type and the like, and may be adjusted as appropriate. For example, it may be 1 or more and 10 or less, respectively, 5 or less is preferable, and 3 or 2 is more preferable.

  The epoxy equivalent of the crosslinking compound (B) is not particularly limited, but can usually be 100 equivalents or more and 1500 equivalents or less. From the viewpoint of adhesiveness and dielectric properties of the adhesive composition, those of 150 equivalents or more and 500 equivalents or less are preferable. In this invention, an epoxy equivalent is the gram number (g / eq) of the epoxy compound containing an epoxy group of 1 gram equivalent, and can measure it according to the method of JISK7236.

  The addition amount of the crosslinking compound (B) is preferably in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the carboxy group-containing styrene elastomer (A). If the ratio is less than 0.1 parts by mass, the effect of improving the curing efficiency of the adhesive composition may be difficult to be exhibited. On the other hand, when the ratio exceeds 10 parts by mass, the adhesive composition after curing may have a relative dielectric constant of 2.5 and a dielectric loss tangent of more than 0.005. As the said ratio, 0.5 mass part or more is more preferable, 1 mass part or more is more preferable, 5 mass parts or less are more preferable, and 3 mass parts or less are more preferable.

  The adhesive composition used in the method of the present invention preferably contains a bismaleimide compound (C) in addition to the carboxy group-containing styrene elastomer (A) and the crosslinking compound (B), which are essential components. By further blending a bismaleimide compound, it becomes possible to further accelerate the curing of the adhesive composition by energy beam irradiation.

  The bismaleimide compound has a chemical structure in which two maleimide groups are bonded by a divalent organic group. Specifically, 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-phenylenebismaleimide, 1,6'-bismaleimide- (2,2,4-trimethyl) hexane and the like.

  From the viewpoint of solubility in a solvent, 1,6′-bismaleimide- (2,2,4-trimethyl) hexane and bis (3-ethyl-5-methyl-4-maleimidophenyl) methane are preferable, and dielectric properties are more preferable. In addition, 1,6′-bismaleimide- (2,2,4-trimethyl) hexane is preferable from the viewpoint of curing efficiency by energy rays.

  The addition amount of the bismaleimide compound is preferably in the range of 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the carboxy group-containing styrene elastomer (A). If the said ratio is 1 mass part or more, the hardening promotion effect | action of an adhesive composition will be more reliably exhibited. On the other hand, if it exceeds 20 parts by mass, the adhesive strength and dielectric properties may be reduced. As said ratio, 3 mass parts or more are more preferable, 10 mass parts or less are more preferable, and 5 mass parts or less are more preferable.

  In addition, you may mix | blend a general component with the adhesive composition for manufacturing a flexible copper clad laminated board. For example, a solvent may be used. When the adhesive composition of the present invention is a solution or dispersion containing a solvent, it is possible to smoothly apply an insulating film and form an adhesive layer, and easily form an adhesive layer having a desired thickness. Can be obtained.

  The solvent is not particularly limited as long as it has an appropriate solubility in at least the carboxy group-containing styrene elastomer (A) and the crosslinking compound (B) and is volatile and relatively easy to distill off. For example, aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, chlorobenzene, mesitylene; methanol, ethanol, isopropyl alcohol, n-propyl alcohol, isobutyl alcohol, n-butyl alcohol, benzyl alcohol, ethylene glycol monomethyl ether Alcohol solvents such as propylene glycol monomethyl ether, diethylene glycol monomethyl ether, diacetone alcohol; acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexane Cyclohexanone, ketone solvents such as isophorone; methyl acetate, ethyl acetate, ethylene glycol monomethyl ether acetate, esters such as 3-methoxybutyl acetate; hexane, heptane, cyclohexane, aliphatic hydrocarbon solvents such as methyl cyclohexane. These solvents may be used alone or in combination of two or more.

  If necessary, tackifiers, flame retardants, curing accelerators, photopolymerization initiators, coupling agents, heat aging inhibitors, leveling agents, antifoaming agents, inorganic fillers, pigments, etc. It can be blended to such an extent that it does not affect the function of the product. However, it should be noted that the addition of these components may contribute to deterioration of dielectric properties and inhibition of curing of the adhesive composition. For example, polymerization initiators and curing accelerators can cause loss of dielectric properties and should not be used as long as sufficient curing is possible.

  Examples of the tackifier include coumarone / indene resin, terpene resin, terpene phenol resin, rosin resin, pt-butylphenol / acetylene resin, phenol / formaldehyde resin, xylene / formaldehyde resin, petroleum hydrocarbon resin, hydrogenation Examples thereof include hydrocarbon resins and terpin resins. These tackifiers may be used alone or in combination of two or more.

  As the flame retardant, either an organic flame retardant or an inorganic flame retardant may be used. Examples of the organic flame retardant include melanin phosphate, melanin polyphosphate, guanidine phosphate, ammonium phosphate, ammonium phosphate, ammonium amidophosphate, ammonium amidophosphate, carbamate phosphate, carbamate polyphosphate, trisdiethylphosphine Aluminum acid, aluminum trismethylethylphosphinate, aluminum trisdiphenylphosphinate, zinc bisdiethylphosphinate, zinc bismethylethylphosphinate, zinc bisdiphenylphosphinate, titanyl bisdiethylphosphinate, titanium tetrakisdiethylphosphinate, bismethylethyl Titanyl phosphinate, titanium tetrakismethylethylphosphinate, titanyl bisdiphenylphosphinate, tetrakisdiphenylphosphite Phosphorus flame retardants such as titanium acid; Triazine compounds such as melanin, melam, and melamine cyanurate; and nitrogen flame retardants such as cyanuric acid compounds, isocyanuric acid compounds, triazole compounds, tetrazole compounds, diazo compounds, and urea; silicone Examples thereof include silicon-based flame retardants such as compounds and silane compounds. Inorganic flame retardants include metal hydroxides such as aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, barium hydroxide, calcium hydroxide; tin oxide, aluminum oxide, magnesium oxide, zirconium oxide, zinc oxide, molybdenum oxide And metal oxides such as nickel oxide; zinc carbonate, magnesium carbonate, barium carbonate, zinc borate, hydrated glass, and the like. These flame retardants may be used alone or in combination of two or more.

  The curing accelerator is used for the purpose of accelerating the reaction between the carboxy group-containing styrene elastomer (A) and the crosslinking compound (B) at the time of heating and drying after the adhesive composition is applied to the insulating film. However, when the adhesive composition is completely cured by irradiating it with energy rays, the addition amount needs special attention because it may inhibit the curing even if the addition amount is 1 part by mass or less. As the curing accelerator, tertiary amine-based curing accelerators, tertiary amine salt-based curing accelerators, and imidazole-based curing accelerators can be used.

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

  Tertiary amine salt curing accelerators include 1,8-diazabicyclo [5.4.0] undecene formate, octylate, p-toluenesulfonate, o-phthalate, phenol salt or phenol Examples include novolak salt resins and 1,5-diazabicyclo [4.3.0] nonene formate, octylate, p-toluenesulfonate, o-phthalate, phenol salt, and phenol novolac resin salt.

  Examples of the imidazole curing accelerator include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-methyl-4-ethylimidazole, 2-phenylimidazole, 2-phenyl- 4-methylimidazole, 1-benzyl-2-phenylimidazole, 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine, 2,4-diamino-6- [ 2'-Undecylimidazolyl- (1 ')]-ethyl-s-triazine, 2,4-diamino-6- [2'-ethyl-4'-methylimidazolyl- (1')]-ethyl-s-triazine 2,4-diamino-6- [2'-methylimidazolyl- (1 ')]-ethyl-s-triazine isocyanuric acid adduct 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole and the like.

  As the photopolymerization initiator, a photopolymerization initiator conventionally used in the field of energy beam curable resin compositions can be used. For example, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1- Hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone, Oligo {2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone}, 2-hydroxy-1- {4- [4- (2-hydroxy-2-methylpropionyl) benzyl] phenyl } Acetophenones such as 2-methylpropan-1-one; benzoin, benzoin methyl ester Benzoins such as ter, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether; benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 3,3 ', 4 , 4′-Tetra (t-butylperoxycarbonyl) benzophenone, 2,4,6, -trimethylbenzophenone, 4-benzoyl-N, N-dimethyl-N- [2- (1-oxo-2-propenyloxy) ethyl Benzophenones such as benzenemethananium bromide and (4-benzoylbenzyl) trimethylammonium chloride; 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dic Thioxanthones such as rothioxanthone, 1-chloro-4-propoxythioxanthone, 2- (3-dimethylamino-2-hydroxy) -3,4-dimethyl-9H-thioxanthone-9-one mesochloride; oxyphenylacetic acid 2- Examples include [2-oxo-2-phenyl-acetoxy-ethoxy] ethyl ester, oxyphenylacetic acid 2- [2-hydroxy-ethoxy] ethyl ester, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, and the like. It is done.

  As a coupling agent, vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2- (Aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3-isocyanatopropyltriethoxysilane, imidazolesilane, etc. Silane coupling agents; titanate coupling agents, aluminate coupling agents, zirconium coupling agents, and the like. These may be used alone or in combination of two or more.

  Examples of heat aging inhibitors include 2,6-di-tert-butyl-4-methylphenol, n-octadecyl-3- (3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) propionate, tetrakis [Methylene-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] phenolic antioxidants such as methane; dilauryl-3,3′-thiodipropionate, dimyristyl-3,3 ′ -Sulfur antioxidants such as dithiopropionate; phosphorus antioxidants such as trisnonylphenyl phosphite and tris (2,4-di-tert-butylphenyl) phosphite. These may be used alone or in combination of two or more.

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

  The adhesive composition according to the present invention needs to have at least a dielectric property after curing that is superior to that of an insulating film. Specifically, those having a relative dielectric constant of 2.5 or less and a dielectric loss tangent of 0.005 or less after curing are preferable. The relative dielectric constant is more preferably 2.4 or less, and the dielectric loss tangent is more preferably 0.003 or less. In order to satisfy this characteristic, for example, the styrene / ethylene butylene ratio of the carboxy group-containing styrene elastomer (A) is lowered, the addition amount of the crosslinking compound (B) is reduced, and the bismaleimide compound is also obtained. It is preferable not to blend (C) or to reduce the amount of addition. However, in this case, there is a possibility that the adhesion between the insulating film and the copper foil may be insufficient.

  The solid content concentration of the adhesive composition according to the present invention is preferably in the range of 3% by mass or more and 80% by mass or less from the viewpoint of workability including coating film formability. When the solid content concentration exceeds 80% by mass, the viscosity of the composition may be too high, and it may be difficult to apply uniformly. The solid content concentration is more preferably in the range of 10% by mass to 50% by mass.

2. Next, the obtained adhesive composition is applied on at least one surface of the insulating resin film.

  The insulating film used in the present invention is a flexible insulating resin film. The insulating film used in the present invention is preferably a wholly aromatic resin film having good radiation resistance. When using an aliphatic hydrocarbon resin film, when the irradiation dose of energy rays exceeds 200 kGy, the mechanical strength of the insulating film may decrease due to overcrosslinking or decomposition. Examples of the material for the insulating film include a liquid crystal polymer resin, a polyimide resin, a polyether ether ketone resin, and a polyphenylene sulfide resin. Among these, a liquid crystal polymer film and a polyimide film are preferable from the viewpoint of characteristics such as dielectric properties and dimensional change required as a flexible copper clad laminate, and a liquid crystal polymer film is more preferable from the viewpoint of low water absorption.

  The liquid crystal polymer includes a thermotropic liquid crystal polymer exhibiting liquid crystallinity in a molten state and a rheotropic liquid crystal polymer exhibiting liquid crystallinity in a solution state. In the present invention, any liquid crystal polymer can be used, but a thermotropic liquid crystal polymer is preferably used because it is thermoplastic and is superior in high-frequency characteristics.

  Among the thermotropic liquid crystal polymers, a thermotropic liquid crystal polyester (hereinafter simply referred to as “liquid crystal polyester”) is, for example, an aromatic hydroxycarboxylic acid as an essential monomer and reacted with a monomer such as an aromatic dicarboxylic acid or aromatic diol. It is an aromatic polyester obtained by this, and exhibits liquid crystallinity when melted. Typical examples thereof include type I [Formula (1)] synthesized from parahydroxybenzoic acid (PHB), phthalic acid, and 4,4′-biphenol, PHB and 2,6-hydroxynaphthoic acid. Type II [Formula (2)] synthesized from the above, Type III [Formula (3)] synthesized from PHB, terephthalic acid, and ethylene glycol.

  In the present invention, among them, I-type liquid crystal polyester and II-type liquid crystal polyester are preferable because they are superior in heat resistance and hydrolysis resistance. In the above formula (1), isophthalic acid is preferable as phthalic acid.

  The thickness of the insulating film in the present invention may be appropriately adjusted, but is preferably 10 μm or more and 100 μm or less. If the said thickness is 10 micrometers or more, sufficient intensity | strength as a base film can be ensured. In addition, when the thickness is 12 μm or more, interlayer insulation in the case of a multilayer board can be ensured more reliably. On the other hand, the upper limit of the thickness is not particularly limited, but if it is too thick, the entire electronic circuit board may be heavy, and drawing processing may be difficult. The thickness is more preferably 11 μm or more, further preferably 12 μm or more, more preferably 50 μm or less, and further preferably 20 μm or less.

  The manufacturing method of the insulating film used by this invention is not specifically limited, What is necessary is just to use a conventional method. For example, the liquid crystal polymer film may be produced by a conventionally known method such as a T-die method or an inflation method by a melt extrusion method. In addition, when the anisotropy of the liquid crystal polymer film produced by these methods is high, the anisotropy can be reduced by biaxial stretching or the like.

  You may mix | blend an inorganic filler with the insulating film used by this invention. For example, the liquid crystal polymer film used as an insulating film in the present invention is preferably substantially composed of only a liquid crystal polymer due to dielectric properties and the like, but the liquid crystal polymer exhibits strong anisotropy when subjected to shear stress, As needed, you may add the inorganic filler for relieving the anisotropy of the molecular orientation which arises when melt-processing a liquid crystal polymer. By introducing such an inorganic filler for relaxation of alignment, for example, the surface of the liquid crystal polymer after being extruded becomes smooth, and uniform alignment is easily obtained. In addition, in order to control the color tone of the insulating film, a colored inorganic filler may be added.

  The orientation relaxation or colored inorganic filler that may be blended in the insulating film is not particularly limited, but for example, inorganic composed of talc, mica, aluminum oxide, titanium oxide, silicon oxide, silicon nitride, carbon black, etc. A filler can be mentioned. The shape of the inorganic filler is not particularly limited, and examples thereof include a spherical shape, a plate shape, a rod shape, a needle shape, and an indeterminate shape. The size of the inorganic filler is preferably 50 nm or more and 10 μm or less. In addition, the magnitude | size of the said inorganic filler says the value of the volume average particle diameter calculated | required from the particle size distribution measurement.

  Since the inorganic filler for relaxing orientation and coloring of the insulating film may impair the dielectric properties of the base film, the ratio of the inorganic filler to the entire insulating film (the total of the polymer and filler constituting the insulating film) Is preferably 20% by mass or less. By making the said ratio 20 mass% or less, the dielectric characteristic of an insulating film can be made excellent.

  The thermal linear expansion coefficient in the planar direction of the insulating film is preferably 3 ppm / ° C. or higher and 30 ppm / ° C. or lower, and the ratio between the thermal linear expansion coefficient in one direction of the planar direction and the thermal linear expansion coefficient in the direction orthogonal to the direction. Is preferably 0.4 or more and 2.5 or less. By adjusting the thermal linear expansion coefficient and the ratio within the above range, the thermal stress, mechanical strength, and dielectric anisotropy can be more reliably reduced in the plane direction, and warpage can be more reliably generated. It can be made excellent as a material for an electronic circuit board, such as being able to be suppressed. For example, the warp of the insulating film can be suppressed to 10% or less. Such “warpage” can be determined in accordance with JIS C6481, and specifically, the film is placed on a horizontal table, the center of the film is in contact with the table, and the four corners are lifted from the table. The maximum value is obtained by measuring the distance between the four corners and the base, and the percentage value is obtained by dividing this value by the length of the side of the film. Moreover, when measuring the thermal linear expansion coefficient of a plane direction, each thermal linear expansion coefficient of the extrusion direction (MD direction) of an insulating film and the direction (TD direction) orthogonal to MD direction, and the thermal linear expansion coefficient of metal foil, If the difference is large, the laminate tends to be warped. Therefore, it is preferable to measure the thermal expansion coefficient in both the MD direction and the TD direction. The thermal linear expansion coefficient can be adjusted by extrusion conditions and stretching operations. The thermal linear expansion coefficient can be measured by a thermomechanical analysis method (TMA method). For example, “Q400” manufactured by TA Instruments Inc. is used as a thermomechanical measurement device, the sample shape is 4 mm wide, the distance between chucks is 15 mm, and a load of 0.1 N is applied to a temperature of 170 ° C. When the temperature is raised from 170 ° C. to room temperature at a temperature drop rate of 10 ° C./min, the chuck-to-chuck distance between 100 ° C. and 50 ° C. is raised. The coefficient of thermal expansion is measured from the change.

  As a method for applying the adhesive composition to the insulating film, for example, conventional methods such as gravure coating, die coating, knife coating, and the like can be used.

  It is preferable to adjust the coating amount of the adhesive composition so that the thickness after curing is about 5 μm or more and 100 μm or less. When the thickness of the adhesive layer after curing is less than 5 μm, the dielectric properties of the copper clad laminate may not be sufficient. On the other hand, if it is thicker than 100 μm, it is necessary to increase the transmission of energy rays during curing, and in the case of ionizing radiation, it is necessary to increase the acceleration voltage. As thickness of the adhesive bond layer after hardening, 10 micrometers or more and 50 micrometers or less are more preferable.

  Further, the coating amount of the adhesive composition is such that the ratio (y / x) of the thickness (y) after curing of the adhesive composition to the thickness (x) of the insulating film is 1 or more and 5 or less. It is preferable to configure. When the ratio is smaller than 1, the dielectric properties may not be sufficient when the copper clad laminate is used. On the other hand, when it is larger than 5, there is a possibility of causing a problem that the adhesive composition curls greatly due to cure shrinkage of the adhesive composition. The ratio is more preferably 1 or more and 3 or less.

  The adhesive composition is applied to at least one side of the insulating film. That is, when the object to be manufactured is a single-sided copper-clad laminate, the adhesive composition may be applied to one side of the insulating film. In the case of a double-sided copper-clad laminate, the adhesive is applied to both sides of the insulating film. Apply the composition.

3. Next, the adhesive composition applied on the insulating film is dried by heating. More specifically, by heating, each component positively starts to react and does not cure, but the solvent contained in the adhesive composition is distilled off to such an extent that tackiness is lost. The state of the adhesive composition is generally referred to as “B stage”, but in the present invention, it is referred to as “dry adhesive composition”.

  For drying the adhesive composition, a general drying apparatus such as a circulating hot air drying furnace may be used. The drying conditions such as temperature and time may be appropriately determined according to the type and amount of the solvent blended in the adhesive composition. For example, the temperature is about 60 ° C. or higher and 150 ° C. or lower for 1 minute or longer, 30 It can be about a minute or less.

4). Semi-curing process of dry adhesive composition layer Although the implementation of this process is optional, the adhesive composition layer dried in the drying process 3 is irradiated with energy rays before being laminated with copper foil, and completely cured. It may be semi-cured to such an extent that it does not.

  When laminating a copper foil on the adhesive composition dried in the drying step, tackiness (surface tackiness) may be a problem. In this case, tackiness can be reduced by semi-curing the adhesive composition in this step. In addition, when a relatively high energy dose is required for complete curing of the adhesive composition, when the high energy dose is irradiated at once, there may be a problem that the insulating film generates heat and heat wrinkles are generated. In this case, this step makes it possible to reduce the energy dose irradiated at a time.

  The energy rays are those that impart energy to the constituent components of the adhesive composition to promote the curing reaction, and for example, ionizing radiation, γ rays, ultraviolet rays, and the like can be used. In the case of the laminate, ionizing radiation and γ rays are preferable from the viewpoint of permeability to the insulating film, and ionizing radiation is more preferable from the viewpoint of curing efficiency.

  The irradiation amount of the energy rays is adjusted so that the adhesive composition can be cured to the extent that the above effect is obtained while preventing the adhesive composition from being completely cured. Specifically, it is preferable to obtain a sol fraction representing the degree of curing in the adhesive layer, and to adjust the energy ray irradiation amount so that the sol fraction is 30% or more and 70% or less. The sol fraction is more preferably 40% or more and 60% or less.

In the present invention, the sol fraction can be measured by the following procedure. That is, after the adhesive composition layer of the measurement sample is semi-cured or cured, it is immersed in a solvent such as toluene. Since components not involved in curing are easily dissolved in the solvent, the sol fraction can be calculated from the mass of the sample before immersion in the solvent and the sample dried after immersion in the solvent by the following formula. In addition, when measuring a sol fraction after hardening an adhesive composition layer after laminating | stacking copper foil by a subsequent process, it shall immerse in a solvent, after removing copper foil by an etching.
Sol fraction [%] = [(mass before soaking−mass after soaking / drying) / (mass before soaking)] × 100

  In this step, for example, in the case of ionizing radiation, the irradiation dose is preferably about 25 kGy to 200 kGy, more preferably about 50 kGy to 150 kGy.

5). Next, a copper foil is laminated on the dried adhesive composition, and an insulating film, a dry adhesive composition layer or a semi-cured adhesive composition layer, and a copper foil are laminated in this order. A laminated body is formed.

  If copper foil is generally used with a copper clad laminated board, it can be used without a restriction | limiting in particular. For example, the thickness of about 5 μm or more and 70 μm or less can be used. As copper foil, what consists only of copper may be used, and what contains other metal components, such as a copper alloy, which has copper as a main component may be used.

  In order for the circuit board using the copper clad laminate obtained by the present invention to exhibit good high frequency characteristics, the surface roughness on the side in contact with the adhesive layer in the copper foil is preferably low. From this viewpoint, the surface roughness Rz of the mat surface of the copper foil is preferably 2.5 μm or less, and more preferably 1.5 μm or less.

  The copper foil is preferably thermocompression bonded to the dry adhesive composition layer or the semi-cured adhesive composition layer. The conditions for thermocompression bonding may be appropriately adjusted according to the composition of the dry adhesive composition layer or the semi-cured adhesive composition layer. 5 MPa or less and about 0.1 second or more and 10 minutes or less, and when the method of the present invention is carried out by a roll-to-roll method, it is about 0.1 second or more and 5 seconds or less. be able to.

  In the case of carrying out the method of the present invention in a roll-to-roll system, for example, after laminating a roll-shaped copper foil on a dry adhesive composition layer or a semi-cured adhesive composition layer, This can be done through heated rolls.

6). Next, the adhesive composition is completely cured by irradiating the laminated body of the insulating film, the dry adhesive composition layer or the semi-cured adhesive composition layer, and the copper foil with energy rays. .

  What is necessary is just to adjust suitably the intensity of the energy beam irradiated in this process so that a dry adhesive composition layer or a semi-hardened adhesive composition layer can fully harden | cure. For example, when ionizing radiation is used as the energy beam, the acceleration voltage is preferably 300 kV or less. When the acceleration voltage exceeds 300 kV, the energy of the ionizing radiation increases, and the temperature of the substrate during irradiation rises, which may cause problems such as decomposition of components of the adhesive composition and heat wrinkles. On the other hand, if the acceleration voltage is too low, electrons may not pass through the substrate and stay inside the substrate, which may cause Lichtenberg discharge (discharge breakdown). The acceleration voltage is more preferably 100 kV or more and 200 kV or less.

  What is necessary is just to adjust suitably the total irradiation dose to the laminated body of energy rays so that a dry adhesive composition layer or a semi-hardened adhesive composition layer can fully harden | cure. For example, in the case of ionizing radiation, the irradiation dose is preferably 100 kGy or more and 500 kGy or less. When the said irradiation dose is less than 100 kGy, hardening of adhesive composition is inadequate and there exists a possibility that favorable adhesiveness and heat resistance may not be obtained. On the other hand, in the case of over 500 kGy, there is a possibility that good adhesiveness and heat resistance may not be obtained due to decomposition of the adhesive layer. The irradiation dose is more preferably 200 kGy or more and 300 kGy or less.

  In the method of the present invention, it is preferable to set the curing conditions so that the sol fraction of the adhesive layer after this step is less than 25%.

  The flexible copper-clad laminate produced by the method of the present invention described above is composed of an insulating film that is flexible and excellent in dielectric properties, and also has excellent dielectric properties in the adhesive layer. As a whole, it can be said that it has excellent dielectric characteristics such as low dielectric constant and low dielectric loss tangent.

  The adhesive layer of the flexible copper clad laminate according to the present invention contains a carboxy group-containing styrene elastomer as a main component. In this carboxy group-containing styrene elastomer, if the styrene content is high, the adhesion with the insulating film is improved, but the curing efficiency is lowered. On the other hand, when the acid value is increased to improve the curing efficiency, the adhesion of the insulating film is lowered. In the present invention, even when a carboxy group-containing styrene elastomer having a high styrene content and high adhesion to an insulating film is used, one or more epoxy groups and one or more vinyls that can be cured by irradiation with energy rays. The crosslinking compound (B) having a group and / or isopropenyl group is blended to improve the curing efficiency. As a result, an adhesive layer having excellent heat resistance can be formed even after a short time of curing, and a flexible copper-clad laminate can be produced by a roll-to-roll method. Conventionally, as a typical curing aid, triallyl isocyanurate (“TAIC” manufactured by Nippon Kasei Co., Ltd.) or unsaturated liquid rubber has been used. The auxiliaries cannot cure the carboxy group-containing styrene elastomer, but tend to inhibit the curing, and the crosslinking compound (B) is optimal for efficient curing of the carboxy group-containing styrene elastomer. Has been found. That is, by the combination of the carboxy group-containing styrenic elastomer (A) and the crosslinking compound (B), the cured adhesive layer according to the present invention not only has excellent dielectric properties but also the adhesive composition according to the present invention. Can be sufficiently cured with an energy ray in a short time, and the cured adhesive layer is also excellent in heat resistance.

  In the adhesive layer after curing according to the present invention, it is unclear how the carboxy group-containing styrene elastomer is crosslinked by the crosslinking compound (B), and the polymer structure is currently analyzed. There is no way to do it.

  A schematic view of a flexible copper clad laminate according to the present invention is shown in FIG. In FIG. 1, the adhesive layer is formed on the entire surface of the resin film, and the copper foil is bonded. A desired circuit can be formed by etching the copper foil layer to obtain a flexible circuit board. In addition, a multilayer circuit board can be formed by stacking the flexible circuit boards.

  For example, as shown in FIG. 2, after etching the copper foil layer of the flexible copper-clad laminate according to the present invention into a desired pattern, adhesion of glass cloth-impregnated prepreg, bonding sheet or the like with the obtained two flexible circuit boards The adhesive sheet is cured by sandwiching the sheet and heating and pressing from above and below to obtain a multilayer circuit board. As the lower circuit board in the multilayer circuit board of FIG. 2 (3), an existing multilayer circuit board using a film made of a thermosetting resin or a thermoplastic resin is shown.

  As another aspect, after etching the copper foil layer of the flexible copper clad laminate according to the present invention into a desired pattern, the obtained flexible circuit board is laminated as shown in FIG. 3 without using an adhesive sheet. Then, by heating and pressing from above and below, a part of the insulating film is melted, and the insulating film and the circuit surface and / or the insulating film are bonded to each other to obtain a multilayer circuit board. Thus, when an adhesive sheet is not used, the insulating film is particularly preferably a liquid crystal polymer film which is a thermoplastic resin and has high heat resistance. As the lower circuit board in the multilayer circuit board of FIG. 3 (3), an existing multilayer circuit board using a film made of a thermosetting resin or a thermoplastic resin is shown.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

Examples 1 to 9: Production of flexible copper-clad laminate (1) Preparation of adhesive composition By adding each raw material with a composition shown in Table 1 to a 1000 mL flask with a stirrer and stirring at room temperature for 6 hours. A liquid adhesive composition having a solid content concentration of 20% was prepared.

In Table 1, the resin materials used are as follows.
Carboxy group-containing styrene elastomer 1
A maleic acid-modified styrene-ethylenebutylene-styrene block copolymer (“Tuftec (registered trademark) M1913” manufactured by Asahi Kasei Chemicals Corporation) was used. The copolymer has an acid value of 10 mg KOH / g, a styrene / ethylene butylene ratio of 30/70, and a weight average molecular weight of 150,000.
Carboxy group-containing styrene elastomer 2
A maleic acid-modified styrene-ethylenebutylene-styrene block copolymer ("Tuftec (registered trademark) M1911" manufactured by Asahi Kasei Chemicals Corporation) was used. The copolymer has an acid value of 2 mg KOH / g, a styrene / ethylene butylene ratio of 30/70, and a weight average molecular weight of 150,000.
Carboxy group-containing styrene elastomer 3
A maleic acid-modified styrene-ethylenebutylene-styrene block copolymer ("Tuftec (registered trademark) M1943" manufactured by Asahi Kasei Chemicals Corporation) was used. The copolymer has an acid value of 10 mg KOH / g, a styrene / ethylene butylene ratio of 20/80, and a weight average molecular weight of 170,000.

Crosslinking Compound 1- Epoxidized Polybutadiene “RICON 657” manufactured by Clay Valley Company was used. The epoxidized polybutadiene has a weight average molecular weight of 1500 and an epoxy equivalent of 230 to 250.
Compound 2 for crosslinking 2-epoxidized polybutadiene “NISSO-PB JP-100” manufactured by Nippon Soda Co., Ltd. was used. The weight average molecular weight of this epoxidized polybutadiene is 1300, the epoxy equivalent is 190 to 210, the number of epoxy groups per molecule is 4 to 7, and the number of side chain vinyl groups per molecule is 16 to 25.
Crosslinking compound 3-Allyl-epoxidized isocyanuric acid 1-allyl-3,5-diglycidyl-isocyanuric acid ("MA-DGIC" manufactured by Shikoku Kasei Co., Ltd.) was used. The molecular weight of this crosslinking compound is 281 and the epoxy equivalent is 281.
Crosslinking compound 4-Allyl-epoxidized isocyanuric acid 1,3-diallyl-5-glycidyl-isocyanuric acid (“DA-DGIC” manufactured by Shikoku Kasei Co., Ltd.) was used. This crosslinked compound has a molecular weight of 265 and an epoxy equivalent of 132.
Crosslinking compound 5-Allyl-epoxidized alkylene glycol 4-hydroxybutyl acrylate glycidyl ether (manufactured by Nippon Kasei Co., Ltd.) was used. This crosslinked compound has a molecular weight of 200 and an epoxy equivalent of 200.

Bismaleimide compound 1
1,6′-Bismaleimide- (2,2,4-trimethyl) hexane (“BMI-TMH” manufactured by Daiwa Kasei Kogyo Co., Ltd.) was used. The solubility of this bismaleimide compound in a solvent is 10 g / 100 g solvent when the solvent is toluene at 25 ° C., and 13 g / 100 g solvent when methyl ethyl ketone at 25 ° C. is used. Here, the solubility is a value indicating the amount of solute dissolved in 100 g of solvent.
Bismaleimide compound 2
Bis (3-ethyl-5-methyl-4-maleimidophenyl) methane (“BMI-70” manufactured by Keii Kasei Co., Ltd.) was used. The solubility of this bismaleimide compound in the solvent is 8 g / 100 g solvent when the solvent is toluene at 25 ° C., and 37 g / 100 g solvent when the solvent is methyl ethyl ketone at 25 ° C.

(2) Coating The above liquid adhesive composition was roll-coated on the surface of a liquid crystal polymer film having a thickness of 13 μm. Subsequently, this film with a coating film was left still in an oven and dried at 110 ° C. for 10 minutes to obtain an insulating film with a dry adhesive composition layer having a total thickness of 50 μm.

(3) Copper foil laminate 18 μm electrolytic copper foil (“F1-WS” manufactured by Furukawa Electric Co., Ltd., Rz = 1.5 μm) was used for the dry adhesive composition layer of the above insulating film with a dry adhesive composition layer. Lamination was carried out so as to be in surface contact with the surface, and thermocompression bonding was performed for 5 minutes under the conditions of 120 ° C. and a pressure of 2 MPa to perform copper foil lamination.

(4) Curing of Dry Adhesive Composition Layer by Energy Beam Irradiation 1 to 100 kGy of ionizing radiation with an acceleration voltage of 200 kV in a nitrogen atmosphere until the total dose becomes 100 to 300 kGy shown in Table 1 in a nitrogen atmosphere. Irradiation was performed 3 times to obtain a flexible copper-clad laminate.

Comparative Examples 1 to 12: Production of flexible copper clad laminate A flexible copper clad laminate was produced in the same manner as in Examples 1 to 6 except that the composition of the liquid adhesive composition was changed as shown in Table 2. Specifically, only a carboxy group-containing styrene elastomer was used, or a carboxy group-containing styrene elastomer and a liquid rubber were used in combination.

In Table 2, the resin materials other than the resin materials used in the above examples are as follows.
Liquid rubber 1
1,2-polybutadiene homopolymer (“NISSO-PB B3000” manufactured by Nippon Soda Co., Ltd.) was used.
Liquid rubber 2
Maleic acid-modified polybutadiene (“RICON 131MA10” manufactured by Clay Valley) was used.
Liquid rubber 3
A methacrylate-modified liquid polyisoprene (“Kuraprene (registered trademark) UC-203” manufactured by Kuraray Co., Ltd.) was used.

TAIC
Triallyl isocyanurate (“TAIC” manufactured by Nippon Kasei Co., Ltd.) was used as the polyfunctional monomer.

Epoxy compound 1
A dicyclopentadiene skeleton-containing epoxy resin (“EPICLON HP-7200” manufactured by DIC) was used.
Epoxy compound 2
1,3,5-triglycidyl-isocyanuric acid (“TEPIC-L” manufactured by Nissan Chemical Co., Ltd.) was used.

Curing accelerator An imidazole-based curing accelerator (“Cureazole (registered trademark) C11-Z” manufactured by Shikoku Kasei Co., Ltd.) was used.

Test Example 1: Curing degree of adhesive layer-sol fraction measurement The copper foil surface of the flexible copper-clad laminate produced above was removed by etching with ferric chloride to produce a test piece. The obtained test piece was cut into a size of 25 mm square, and the mass before swelling was measured. Next, the test piece was immersed in 50 mL of toluene at 40 ° C. for 8 hours to swell. After the test piece that reached the swelling equilibrium was dried at 80 ° C. for 30 minutes, the mass was measured. The sol fraction was calculated using the following formula, and the degree of cure was determined. Table 3 shows the calculated sol fraction values.
Sol fraction [%] = [(mass before swelling−mass after swelling / drying) / (mass before swelling)] × 100
The sol fraction indicates the ratio of the unreacted residue of the styrene elastomer that is soluble in the toluene solvent or the entire cured product of the styrene elastomer that is insufficiently cured. The lower the value, the more the curing proceeds. Can be judged. If the sol fraction is less than 25%, it can be said that the curing is relatively sufficiently advanced. However, if the sol fraction is 25% or more, the curing is insufficient, and the solder heat resistance and the electronic circuit board are reduced. There arises a problem that the adhesive layer flows out in the pressing step when manufacturing the material.

Test Example 2: Solder heat resistance-solder swell test The flexible copper-clad laminate produced above was cut into 25 mm squares, and a temperature of 121 was measured using a pressure cooker test (PCT) apparatus ("Autoclave SP510" manufactured by Yamato Scientific Co., Ltd.). The treatment was performed at 0 ° C. and a pressure of 2 atm for 30 minutes. Next, after floating for 20 seconds on a 260 ° C. molten solder with the copper foil surface facing up, the presence or absence of swelling inside the liquid crystal polymer film and the adhesive layer as an insulating film was examined visually. In Table 3, when there is no swelling observed in both the liquid crystal polymer film and the adhesive layer, it is described as “No”, and at least one of which swelling is confirmed is described as “Yes”.

Test Example 3: Peel Strength Measurement The flexible copper-clad laminate prepared above was cut into 10 mm × 60 mm to obtain a test piece. In order to evaluate adhesiveness, in accordance with JIS C 6481, under the conditions of 23 ° C. and a tensile speed of 50 mm / min, the 180 ° peel adhesion strength (N / mm). The results are shown in Table 3.

  In addition, all the peeling interfaces of the tested flexible copper-clad laminates are between the liquid crystal polymer film and the adhesive layer, and the peel adhesion strength between the copper foil and the adhesive layer is higher than that between the liquid crystal polymer film and the adhesive layer. It became clear. Also, if the peel strength is 0.5 N / mm or more, it is called an etching bite in which an etchant enters between the copper foil and the adhesive layer in the etching process when forming a circuit on the copper foil laminate. There is no problem.

Test Example 4: Dielectric characteristics—dielectric constant measurement and dielectric loss tangent measurement Each adhesive composition was applied to one side of a copper foil having a thickness of 18 μm and then dried, and ionizing radiation with an acceleration voltage of 200 kV was applied at 100 kGy in nitrogen atmosphere Irradiation was repeated until the total dose reached 200 kGy to cure the adhesive composition. Thereafter, the copper foil was removed by etching to prepare a sample piece for measurement. Next, using a network analyzer (“E5071C” manufactured by Agilent), the relative permittivity and dielectric loss tangent of the cured adhesive were measured under the conditions of a cavity resonator perturbation method at 23 ° C. and a frequency of 3 GHz. The results are shown in Table 3.

Test Example 5: Measurement of dimensional change rate The flexible copper-clad laminate prepared above was cut into 120 mm squares to obtain test pieces. About the obtained test piece, the dimensional change rate after copper foil etching was measured based on JISC6481. The distance between scores during measurement was 100 mm. The results are shown in Table 3.

  As shown in Table 3, regardless of the example and the comparative example, the produced flexible copper-clad laminate has excellent dielectric properties, and has a low dimensional change rate and excellent dimensional stability. The reason is considered to be due to the characteristics of the carboxy group-containing styrene-based elastomer that is the main component of the adhesive layer.

  Moreover, since the peel adhesion strength between the liquid crystal polymer film-adhesive layer and the copper foil-adhesive layer was about the same in the examples and the comparative examples, the reaction at these boundaries proceeded by energy beam irradiation. it was thought.

  On the other hand, the degree of cure of the adhesive layer of the comparative example was inadequate, and solder swelling was observed except for one example. This is considered to be because the component was decomposed and foamed by heat treatment because the curing of the adhesive composition did not proceed sufficiently. In addition, even when solder blistering is not observed, resin flow may occur during heat treatment for multilayering or solder reflow by melting the insulation film, or the adhesive strength with copper foil may be reduced. There is a risk.

  In contrast, despite the short-time curing, the degree of cure of the adhesive layer of the flexible copper clad laminate according to the present invention is sufficient. It can be expected that there is no decrease in the adhesive strength with copper foil.

  1: resin film, 2: adhesive layer, 3: copper foil, 4: circuit board, 5: adhesive sheet, 6: multilayer circuit board

Claims (14)

A method for producing a flexible copper clad laminate,
An adhesive composition comprising (A) a carboxy group-containing styrenic elastomer and (B) a crosslinking compound having one or more epoxy groups and one or more vinyl groups and / or isopropenyl groups on at least one side of an insulating film Applying step;
Drying the adhesive composition applied on the insulating film by heating;
A step of laminating a copper foil on the dry adhesive composition to form a laminate;
A method comprising the step of curing the dry adhesive composition by irradiating the laminate with an energy beam.   The method of claim 1, wherein the adhesive composition further comprises (C) a bismaleimide compound.   The method according to claim 2, wherein the adhesive composition contains (B) the bismaleimide compound in an amount of 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the carboxy group-containing styrene elastomer (A).   The said adhesive composition contains 0.1 to 10 mass parts of (B) the said crosslinking compound with respect to 100 mass parts of (A) said carboxy-group containing styrene-type elastomers. The method according to any one.   The method according to claim 1, wherein ionizing radiation is used as the energy beam.   The method according to claim 5, wherein an acceleration voltage of the ionizing radiation is 300 kV or less and a total irradiation dose is 100 kGy or more and 500 kGy or less.   The method according to claim 1, wherein the adhesive composition has a thickness after curing of 5 μm or more and 100 μm or less.   The method according to claim 1, wherein the insulating film is a liquid crystal polymer film.   The method according to claim 1, wherein the insulating film has a thickness of 10 μm or more and 100 μm or less. Including insulation film and copper foil,
Adhesive composition comprising (A) a carboxy group-containing styrenic elastomer and (B) a crosslinking compound having one or more epoxy groups and one or more vinyl groups and / or isopropenyl groups on at least one side of the insulating film. The said copper foil is adhere | attached with the thing, The flexible copper clad laminated board characterized by the above-mentioned.   The flexible copper clad laminate according to claim 10, wherein the adhesive composition further contains (C) a bismaleimide compound.   The flexible copper-clad laminate according to claim 10 or 11, wherein a thickness of the adhesive composition after curing is 5 µm or more and 100 µm or less.   The thickness of the said insulating film is 10 micrometers or more and 100 micrometers or less, The flexible copper clad laminated board in any one of Claims 10-12.   The flexible copper clad laminate according to claim 10, wherein the insulating film is a liquid crystal polymer film.

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