JP2002128864A - Flame retardant resin composition and its applications - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flame retardant resin composition which is suitable for a copper-clad laminate used for an electronic circuit load or a sealing material, a molding material, a casting material, an adhesive, an electric insulating coating material used for an electronic component, has excellent thermostability and flame retardancy and is free from a halogenous flame retarder. SOLUTION: The flame retardant resin composition contains (a) a cyanate compound shown by formula (1) (wherein, R1 is -CH2-, -C(CH3)2-, -C(CF3)2-, -CH(CH3)-, -O-, -S-, or direct bond. R2 and R3 are -H, -CH3, -C2H5, or -CF3) and/or a prepolymer made from the same, (b) a multifunctional epoxy resin and (c) a guanidine compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition having a low dielectric constant, a low dielectric loss tangent, and excellent heat resistance and flame retardancy. It is suitable for use in applications such as:

More specifically, the present invention relates to a resin composition for producing a copper-clad laminate used for an electronic circuit board and a sealing material, a molding material, a casting material, an adhesive, and an electric insulating paint used for an electronic component. It is useful as a material and the like, and is used for a flame-retardant resin composition not using a halogen-based flame retardant.

[0003]

2. Description of the Related Art In recent years, printed wiring boards mounted on computers, communication devices and the like have been increasingly densified and thinned, and high heat resistance and insulation properties have been required. In addition, a material having a low dielectric constant and a low dielectric loss tangent has been demanded in order to cope with an increase in signal speed and an increase in frequency. Cyanate resin and BT
Resin (bismaleimide-triazine resin) is a resin material that has both high heat resistance and low dielectric properties. It is known that blending an epoxy resin with them can reduce water absorption, improve adhesiveness, and improve workability. Have been. Furthermore, if the cyanate ester resin or BT resin alone is used, the UL (Unde)
rwriterLaboratorys) Standard V-
Since a flame retardancy of 0 level cannot be achieved, halogenated epoxy resins, especially brominated epoxy resins, are added as flame retardants. However, when a brominated epoxy resin is used at a high temperature for a long period of time, a halide is dissociated, which may cause corrosion of wiring. Further, the use of halogen has been regarded as a problem from the viewpoint of environmental safety, and alternative materials have been studied.

[0004]

[Problems to be Solved by the Invention] Heat resistance suitable for copper clad laminates used for electronic circuit boards and materials for sealing materials, molding materials, casting materials, adhesives, and electric insulating paints used for electronic components It is an object of the present invention to provide a flame-retardant resin composition having excellent flame retardancy and not using a halogen-based flame retardant.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a flame-retardant resin composition which simultaneously satisfies the above-mentioned properties can be obtained. . That is, the present invention relates to the formula (1)

Embedded image (Wherein R ₁ is -CH _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -CH (CH ₃ )
-, -O-, -S-, or a direct bond. R ₂ and R ₃ are -H, -CH
_3, -C ₂ H _5, or show a -CF _3). A) a flame-retardant resin composition comprising a cyanate compound represented by the formula (1) and / or a prepolymer (a), a polyfunctional epoxy resin (b), and a guanidine compound (c) using the same as a raw material;
(2) The flame-retardant resin composition according to (1), which contains the phosphorus-containing compound (d), and (3) the content of the guanidine compound (c) is (c) / (a) = 0.01 to 0. .2 (1)
Or (4) the flame-retardant resin composition according to any one of (1) to (3), wherein the guanidine compound is dicyandiamide. , (5) the content of the phosphorus-containing compound (d) is (d) / (a) = 0.1 to
The flame-retardant resin composition according to any one of (2) to (4), which is 0.6, and any one of (6) (1) to (5).
The varnish of the flame-retardant resin composition obtained by dissolving the flame-retardant resin composition according to the above item in a solvent, and the varnish of the flame-retardant resin composition according to any one of the items (1) to (5). Cured product, (8)
(9) A build-up printed circuit board using the flame-retardant resin composition according to any one of (1) to (5) for an interlayer insulating layer, (9) any one of (1) to (5). And a metal foil with a resin for a build-up printed wiring board using the flame-retardant resin composition described above.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The flame-retardant resin composition of the present invention contains a cyanate compound and / or a prepolymer (a), a polyfunctional epoxy resin (b) and a guanidine compound (c) using the same as a raw material. .

The cyanate compound used in the present invention is
It means a compound of the formula (1) having two or more cyanate groups in the molecule. In the present invention, the cyanate compound itself and / or a prepolymer derived therefrom can be used as the component (a). As the prepolymer, those obtained by heating the compound of the formula (1) can be used. These cyanate compounds and their prepolymers can be obtained by known methods.
Commercial products such as CyB-30 and AroCyB-40 (manufactured by Asahi Chiba) are available.

Specific examples of the cyanate compound of the formula (1) that can be used in the present invention include bis (3,5-dimethyl-4-cyanatephenyl) methane, bis (4-cyanatephenyl) methane and bis (3-methyl4 -Cyanate phenyl) methane, bis (3-ethyl 4-cyanate phenyl) methane, 1,1-bis (4-cyanate phenyl) ethane, 2,2-bis (4-cyanate phenyl) propane, di (4-cyanate phenyl) ) Ether, di (4-cyanatephenyl) thioether, 4,
4- {1,3-phenylenebis (1-methylethylidene)} bisphenyl cyanate, 4,4-dicyanate-diphenyl, 2,2-bis (4-cyanatophenyl) -1,1,1,3,3,3 -Hexafluoropropane and the like. Examples of the cyanate ester of a trihydric phenol include 1,1,1-tris (4-cyanatephenyl) ethane and bis (3,5-dimethyl-).
4-cyanatephenyl) -4-cyanatephenyl-
1,1,1-ethane and the like can be mentioned.

[0009] Among these cyanate compounds, which cyanate compound is to be used is appropriately selected from properties having a required property or a wide range of properties from a liquid to a solid at room temperature depending on the structure according to the application. Although it is not particularly limited, it is preferable to use 2,2-bis (4-cyanatophenyl) propane or a cyanate compound containing this prepolymer as a main component in terms of productivity, handleability, cost, and the like. It is particularly preferable because it is good. Pre-polymerization of the cyanate compound (generally forming a cyclic trimer) in advance is suitable for lowering the dielectric constant and preventing recrystallization when the varnish is used. The content of the cyanate compound and / or the prepolymer (a) using the same as a raw material is preferably 30 to 90% by weight, more preferably 50 to 80% by weight of the whole composition excluding the solvent component.

The polyfunctional epoxy resin (b) in the present invention
As, for example, novolak type epoxy resin, bisphenol type epoxy resin, biphenyl type epoxy resin, fluorene type epoxy resin, resorcinol type epoxy resin,
Polyglycol type epoxy resins and the like can be mentioned. Preferably, it is a novolak type epoxy resin. Specific examples thereof include EPPN-201 (phenol novolak type epoxy resin manufactured by Nippon Kayaku Co., Ltd.), EOCN-104S,
EOCN-1020 (cresol novolak type epoxy resin manufactured by Nippon Kayaku Co., Ltd.), NC-7000, NC-
7300 (Novolak type epoxy resin having a phenol skeleton and a naphthol skeleton, manufactured by Nippon Kayaku Co., Ltd.), EP
PN-501H, EPPN-502H (manufactured by Nippon Kayaku Co., Ltd., novolak type epoxy resin having a triphenylmethane skeleton), NC-3000 (manufactured by Nippon Kayaku Co., Ltd.)
A novolak type epoxy resin having a phenol skeleton and a biphenyl skeleton), an alkyl novolak type epoxy resin,
A styrenated phenol novolak type epoxy resin, a bisphenol novolak type epoxy resin, an aralkylphenol novolak type epoxy resin and the like are exemplified. These epoxy resins may be used alone or in combination of two or more. The content of the polyfunctional epoxy resin (b) is preferably from 5 to 40% by weight, more preferably from 10 to 20% by weight of the total composition excluding the solvent component.

In the present invention, the guanidine compound (c)
Is used as a flame-retardant component. Examples of the guanidine compound include dicyandiamide and 1- (o-tolyl) biguanide, and dicyandiamide is preferable. The content of the guanidine compound (c) in the flame-retardant resin composition is preferably (c) / (a) = 0.02 to 0.2. If it is 0.02 or less, the flame retardancy is insufficient, and if it is 0.2 or more, the moisture absorption and dielectric properties of the cured product are adversely affected.

In the present invention, the use of the phosphorus-containing compound (d) as a flame retardant-imparting component is preferred because higher levels of flame retardancy can be imparted and the amount of guanidine compound used can be reduced. . The phosphorus-containing compound may be a reaction type or an addition type. The phosphorus-containing compound referred to herein includes a phosphorus-containing epoxy resin. Specific examples of the phosphorus-containing compound include trimethyl phosphate, triethyl phosphate, tricresyl phosphate, trixylylenyl phosphate, cresyl diphenyl phosphate, cresyl 2,6-dixylylenyl phosphate, and 1,3-phenylene bis (diphenyl phosphate). ), Phosphate esters such as 1,3-phenylenebis (dixylylenylphosphate), 1,4-phenylenebis (dixylylenylphosphate), and 4,4′-biphenyl (dixylylenylphosphate);
Phosphanes such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10 (2,5-dihydroxyphenyl) -10H-9-oxa-10-phosphaphenanthrene-10-oxide, Phosphorus-containing epoxy resins obtained by reacting epoxy resins with the active hydrogens of the phosphanes, red phosphorus, etc., are preferred. Phosphates, phosphanes and active hydrogens of the epoxy resins and the phosphanes are preferred. And a phosphorus-containing epoxy resin obtained by reacting with 1,4-phenylenebis (dixylenylphosphate), 1,4-phenylenebis (dixylylenylphosphate), and 4,4′- Reaction of biphenyl (dixylylenyl phosphate), epoxy resin with active hydrogen of the phosphane It is a phosphorus-containing epoxy resin obtained by the reaction. The content of the phosphorus-containing compound (d) in the flame-retardant resin composition is (d) / (a) / = 0.1 to 0.6.
Is preferred. If it is less than 0.1, the flame retardancy is insufficient,
If it is 0.6 or more, the moisture absorption and the dielectric properties of the cured product are adversely affected.

[0013] The thermosetting resin composition of the present invention may optionally contain an ion scavenger. The ion scavenger is preferably an inorganic compound having an ion-capturing ability. The ion-capturing ability mentioned here is to reduce ionic impurities by capturing phosphoric acid, organic acid anions, halogen anions, alkali metal cations, alkaline earth metal cations and the like. As a specific example of the ion trapping material, BiOx (OH) y (NO3) z
[Where x is 0.9 to 1.1, y is 0.6 to 0.8, z
Is a positive number of 0.2 to 0.4], MgxAl (OH)
2x + 3y-2zCOz.mH2O [where x, y, z
Is a positive number satisfying 2x + 3y-2z ≧ 0, and m is a positive number], zirconium phosphate, antimony pentoxide, bismuth oxide and the like. These may be used alone or in combination of two or more. The maximum particle size of these ion scavengers is preferably 5 μm or less, more preferably 1 μm or less.

The thermosetting resin composition of the present invention may optionally contain a binder resin. Binder resin, acetal resin, acrylic resin, epoxy-nylon resin, NB
Examples include, but are not limited to, R-phenol-based resins, epoxy-NBR-based resins, polyamide-based resins, polyimide-based resins, silicone-based resins, and the like. The compounding amount of the binder resin is desirably limited to a range that does not impair the flame retardancy and heat resistance, and is usually 0.05 to 50 parts by weight, preferably 0.1 to 50 parts by weight, based on 100 parts by weight of the target resin component.
05 to 20 parts by weight are used as needed.

[0015] A curing accelerator can be added to the thermosetting resin composition of the present invention, if necessary. The curing accelerator is not particularly limited, and examples thereof include organometallic salts or metal-organic complexes of iron, copper, zinc, cobalt, nickel, manganese, and tin, and imidazoles. Specific examples of the organic metal salt or metal organic complex include zinc naphthenate, cobalt naphthenate, copper naphthenate, lead naphthenate, zinc naphthenate,
Metal chelate compounds such as tin octylate, zinc octylate, lead acetylacetonate, copper acetylacetonate, cobalt acetylacetonate, dibutyltin maleate and the like. Examples of imidazoles include 2-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 2-heptadecylimidazole,
Phenyl-4-methylimidazole, 1-benzyl-2
-Phenylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1
-Cyanoethyl-2-undecylimidazole, 2,4
-Diamino-6 (2'-methylimidazole (1 '))
Ethyl-s-triazine, 2,4-diamino-6 (2 ′
-Undecylimidazole (1 ′)) ethyl-s-triazine, 2,4-diamino-6 (2′-ethyl, 4-methylimidazole (1 ′)) ethyl-s-triazine,
2,4-diamino-6 (2′-methylimidazole (1 ′)) ethyl-s-triazine / isocyanuric acid adduct, 2: 3 of 2-methylimidazole isocyanuric acid
Adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-3,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 1-cyanoethyl-2-phenyl-
Various imidazoles of 3,5-dicyanoethoxymethylimidazole, and those imidazoles and phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, naphthalenedicarboxylic acid, maleic acid,
Salts with polyvalent carboxylic acids such as oxalic acid may be mentioned. The curing accelerator is usually used in an amount of 0.01 to 100 parts by weight of the resin component.
5 parts by weight, preferably 0.1 to 3 parts by weight are used as needed.

A filler may be used in the flame-retardant resin composition of the present invention. As fillers, fused silica, crystalline silica, silicon carbide, silicon nitride, boron nitride, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, mica, talc, clay, alumina, magnesium oxide, zirconium oxide, aluminum hydroxide,
Magnesium hydroxide, calcium silicate, aluminum silicate, lithium aluminum silicate, zirconium silicate, barium titanate, glass fiber, carbon fiber, molybdenum disulfide, asbestos and the like, preferably fused silica,
Crystalline silica, silicon nitride, boron nitride, calcium carbonate,
Barium sulfate, calcium sulfate, mica, talc, clay, alumina and aluminum hydroxide. These fillers may be used alone or in combination of two or more.

A coloring agent, a coupling agent, a leveling agent and the like can be appropriately added to the flame-retardant resin composition of the present invention according to the purpose. Halogen-based flame retardants are preferred in view of the object of the present invention. Absent. The colorant is not particularly limited, and may be phthalocyanine, azo, disazo, quinacridone, anthraquinone, flavanthrone, perinone, perylene, dioxazine, condensed azo, various azomethine-based organic dyes, titanium oxide, lead sulfate, chromium yellow, zinc yellow. , Chromium vermillion, valve shell, cobalt violet, dark blue, ultramarine, carbon black, chrome green, chromium oxide, cobalt green, and other inorganic pigments.

As coupling agents, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyl Trimethoxysilane, N- (2-
(Aminoethyl) 3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) 3-aminopropylmethyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, vinyltrimethoxysilane, N Silane-based cups such as-(2- (vinylbenzylamino) ethyl) 3-aminopropyltrimethoxysilane hydrochloride, 3-methacryloxypropyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane Ring agent, isopropyl (N-ethylaminoethylamino) titanate, isopropyl triisostearoyl titanate, titanium di (dioctyl pyrophosphate) oxyacetate, tetraisopropyl di (dioctyl phosphate) Site) titanate, neoalkoxy tri (p-N- (β- aminoethyl) aminophenyl)
Titanium-based coupling agents such as titanate, Zr-acetylacetonate, Zr-methacrylate, Zr-propionate, neoalkoxy zirconate, neoalkoxytris neodecanoyl zirconate, neoalkoxytris (dodecanoyl) benzenesulfonyl zirconate, neoalkoxy Tris (ethylenediaminoethyl) zirconate, neoalkoxytris (m-aminophenyl) zirconate, ammonium zirconium carbonate, Al-acetylacetonate, Al-methacrylate, zirconium such as Al-propionate, or an aluminum-based coupling agent. Preferred is a silicon-based coupling agent. By using a coupling agent, a cured product having excellent moisture resistance reliability and a small decrease in adhesive strength after moisture absorption can be obtained.

As the leveling agent, acrylates such as ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate having a molecular weight of 4000 to 12 are used.
000 oligomers, epoxidized soybean fatty acid, epoxidized aviethyl alcohol, hydrogenated castor oil, modified silicone, anionic / nonionic surfactant, and the like.

The flame-retardant resin composition of the present invention comprises, for example, a cyanate compound and / or a prepolymer (a), a polyfunctional epoxy resin (b), a guanidine compound (c), and a phosphorus compound as a raw material. After mixing the compound (d), a curing accelerator, a binder resin, an ion scavenger, a filler, a coupling agent, a coloring agent, a leveling agent, and the like using a Henschel mixer, a planetary mixer, or the like,
It can be obtained by uniformly dispersing with a two-roll, kneader, extruder, sand grinder or the like.

Further, the flame-retardant resin composition of the present invention comprises, for example, a cyanate compound and / or a prepolymer (a), a polyfunctional epoxy resin (b), and a guanidine compound (c) using the same as a raw material. A varnish can be obtained by uniformly mixing a phosphorus-containing compound (d), a curing accelerator, a binder resin, an ion scavenger, a filler, a coupling agent, a coloring agent, a leveling agent, and the like in a solvent.
Examples of the solvent used include amide solvents such as γ-butyrolactones, N-methylpyrrolidone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide, N, N-dimethylimidazolidinone and the like. , Sulfones such as tetramethylene sulfone, ether solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, ethylene glycol diethyl ether, propylene glycol diethyl ether, propylene glycol monomethyl ether monoacetate, tetrahydrofuran and dioxane; ketones such as methyl ethyl ketone and methyl isobutyl ketone And aromatic solvents such as toluene and xylene. These solvents may be used alone or in combination of two or more. It is desirable to contain an amide-based or sulfone-based solvent from the viewpoint of easily dissolving the guanidine compound (c). The solid content concentration in the obtained varnish is usually 10 to 80% by weight, preferably 30 to 70% by weight.
% By weight.

In order to obtain a cured product of the flame-retardant resin composition of the present invention, the composition may be heat-cured under conditions suitable for the curing system. Assuming use for a printed circuit board, curing conditions at 170 ° C. for about 1 hour are generally used.

The build-up printed wiring board using the flame-retardant resin composition of the present invention for an interlayer insulating layer can be manufactured by a known method, and is not particularly limited. For example, a hard laminated board serving as a core After laminating a resin-attached metal foil using the flame-retardant resin composition of the present invention, etching,
It is obtained by forming wirings and vias by plating.

The resin-attached metal foil for a build-up printed wiring board using the flame-retardant resin composition of the present invention for an interlayer insulating layer can be produced by a known method, and is not particularly limited. It can be obtained by applying the flame-retardant resin composition of the present invention to an electrolytic copper foil with a comma coater and removing the solvent with an inline dryer.

[0025]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples and comparative examples, “parts” means parts by weight.

In the evaluation of the build-up printed wiring board in the embodiment, the flame retardancy was UL (Underwriter).
The glass transition temperature was measured by TM7000 manufactured by Vacuum Riko Co., Ltd. in accordance with the standards of (Laboratory).

Examples 1 to 3 and Comparative Example 1 The compositions shown in Table 1 were prepared as the thermosetting resin varnish compositions. Each obtained varnish was applied to an electrolytic copper foil (thickness 35).
μm (made by Furukawa Electric) with a comma coater so that the thickness after drying becomes 75 μm.
The solvent was removed under the conditions of heating and drying at 0 ° C. for 2 minutes to obtain a copper foil with resin. Non-halogen FR-4 substrate (TCL-W-555 manufactured by Toshiba Chemical Co., Ltd.) from which copper foil has been removed by etching.
This resin-coated copper foil was adhered to both surfaces of an MU thickness of 0.4 mm by a hot press and cured (cured at a pressure of 1 Pa and a temperature of 170 ° C. for 1 hour) to obtain a sample for a flame retardancy test. Table 1 Comparative Examples Example 11 12 23 Mixing ratio (parts by weight) Cyanate compound varnish 133 133 133 133 Polyfunctional epoxy resin A 20 20-20 Polyfunctional epoxy resin B-20-DICY 777-Phosphorus-containing compound A -30 30 30 Catalyst 1 11 1 Binder resin 20 20 20 20 DMF 90 90 90 90 Evaluation of build-up printed wiring board Flame retardant UL94 V-1 V-0 V-0 V-2 Glass transition temperature (° C)>200>200>200> 200 Cyanate compound varnish: Cyanate resin prepolymer B-40S (manufactured by Asahi Ciba Co., Ltd., bisphenol A dicyanate resin, trimerization ratio 40%, solid content 75% MEK solution) Polyfunctional epoxy resin A: EPPN -502H (with a triphenylmethane skeleton manufactured by Nippon Kayaku Co., Ltd.) Novolak type epoxy resin) Polyfunctional epoxy resin B: EPPN-201 (Phenol novolak type epoxy resin manufactured by Nippon Kayaku Co., Ltd.) DICY: Dicyandiamide (Nippon Carbide Co., Ltd.) Phosphorus compound A: FP-500 (Asahi Denka Co., Ltd.) Binder resin: BPAM-01 (CTBN modified polyamide resin manufactured by Nippon Kayaku Co., Ltd.) Catalyst: 8% Nikka Octic zinc (Zinc 2-ethylhexylate mineral spirit solution manufactured by Nippon Kagaku Sangyo Co., Ltd.)

[0028]

According to the present invention, a flame-retardant resin composition having excellent heat resistance and flame retardancy was obtained as is apparent from the results shown in Table 1.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 3/46 H05K 3/46 TF term (Reference) 4F100 AB01B AB17 AK01A AK53A AL05A BA02 EH46 EH462 EJ42 EJ422 EJ86 EJ862 GB43 JJ03 JJ07 JJ07A JL08 YY00A 4J002 CD011 CD031 CD041 CD051 CD061 CD202 DA058 ER027 ET006 EW018 EW028 EW038 EW048 FD010 FD090 FD146 FD147 FD150 FD200 FD312 FD316 FD318 AD01 AF01 AJ008 AA12 AA15 AA32 BB01 CC09 CC31 DD03 EE31 HH16 HH18

Claims (9)

[Claims] (1) Formula (1) (Wherein R ₁ is -CH _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -CH (CH ₃ )
-, -O-, -S-, or a direct bond. R ₂ and R ₃ are -H, -CH
_3, -C ₂ H _5, or show a -CF _3). And / or a prepolymer (a), a polyfunctional epoxy resin (b), and a guanidine compound (c) using the same as a raw material. 2. The composition according to claim 1, which contains a phosphorus-containing compound (d).
3. The flame-retardant resin composition according to item 1. 3. The method according to claim 1, wherein the content of the guanidine compound (c) is (c).
The flame-retardant resin composition according to claim 1, wherein /(a)=0.01 to 0.2. 4. The flame-retardant resin composition according to claim 1, wherein the guanidine compound is dicyandiamide. 5. The method according to claim 1, wherein the content of the phosphorus-containing compound (d) is (d) /
The flame-retardant resin composition according to any one of claims 2 to 4, wherein (a) is 0.1 to 0.6. 6. A flame-retardant resin composition varnish obtained by dissolving the flame-retardant resin composition according to any one of claims 1 to 5 in a solvent. 7. A cured product of the flame-retardant resin composition according to claim 1. 8. A build-up printed wiring board using the flame-retardant resin composition according to any one of claims 1 to 5 for an interlayer insulating layer. 9. A resin-attached metal foil for a build-up printed wiring board using the flame-retardant resin composition according to any one of claims 1 to 5.