JPH09328565A - Prepreg - Google Patents

Abstract

(57) [Summary] (Correction) [Solution] A plate-type viscometer was used to measure shear rate 1
The viscosity measured under the conditions of 0 rad / sec and a temperature of 130 ° C. is in the range of 5000 to 30000 poise for the first 5 minutes of measurement, and the viscosity after 20 minutes of measurement is 10,000 to 5000.
Consisting of a thermosetting resin composition in the range of 0 poise,
A prepreg composed of a thermosetting resin containing a polymaleimide compound naphthol, naphthalene diol, or a phenol resin containing at least one naphthalene skeleton, and an epoxy resin. Further, a prepreg made of a thermosetting resin containing a modified imide resin obtained by modifying with a compound having at least one active hydrogen in the molecule. [Effect] A prepreg which is excellent in plate thickness accuracy after press molding during production of a printed board and does not generate voids, and is particularly useful for producing a multilayer printed wiring board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated board for a printed wiring board, and more particularly to a prepreg excellent in resin flow characteristics during adhesive press molding when manufacturing a multilayer laminated board.

[0002]

2. Description of the Related Art As for printed wiring boards widely used for electric / electronic devices, communication devices, computing devices, etc., the wiring density has been advanced and the integration has been advanced.
Multilayer wiring laminates are being developed. The requirements of this multi-layer board include thinning and control of characteristic impedance. As a special shape of the multi-layer board, a rigid flex board combined with a flexible board, a part or a portion where an IC chip is mounted is made concave. Cavity type multilayer boards are required. In order to reduce the thickness of the multi-layer board and control the characteristic impedance, it is required that the board thickness accuracy of the laminated board and the inter-layer thickness accuracy be high. In order to increase the plate thickness accuracy, the resin flow characteristics of the prepreg used for manufacturing a multilayer board are important, and a prepreg that is generally called a non-flow type is used. Further, even when a rigid flex substrate or a cavity type multilayer substrate is manufactured, a non-flow type prepreg is used so that the resin does not flow to the connecting portion and the cavity portion of the flexible substrate.

[0003]

In the case of a non-flow type prepreg, an epoxy resin is usually used,
In order to control the flow characteristics, the reaction of the epoxy resin is promoted to increase the melt viscosity of the resin. With this method, the melt viscosity of the resin can be increased and the flow characteristics can be changed, but there is the problem that voids tend to occur during the production of multilayer boards because the viscosity rises rapidly during adhesive pressing and the gel time is shortened. . The present invention has been made in view of such circumstances, and an object thereof is to provide a prepreg in which a resin flow during molding of a multilayer board is small and voids are not generated.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result,
The viscosity when measured with a plate viscometer is high, the viscosity change during measurement is small, and the prepreg made of a thermosetting resin with a long gel time has no resin flow when forming a multilayer board, and voids do not occur. Heading, it came to complete the present invention.

That is, the viscosity measured by a plate viscometer at a shear rate of 10 rad / sec and a temperature of 130 ° C. is within the range of 5000 to 30000 poise for the first 5 minutes of measurement and 10000 after 20 minutes of measurement. ~ 500
A thermosetting resin having a gel time within the range of 00 poise, a gel time defined by the intersection of the storage elastic modulus and a loss elastic modulus of 20 minutes or more, and a gel time of 120 seconds or less measured on a 170 ° C. hot plate. It is a prepreg characterized by comprising a composition. In addition, this thermosetting resin composition,
(A) A prepreg containing a polymaleimide compound represented by the general formula (1). Further, the thermosetting resin composition is (a) a polymaleimide compound represented by the general formula (1), and (b) naphthol, dihydroxynaphthalene, or at least one phenol resin having a naphthalene skeleton, and / or ( c) A prepreg characterized by containing an epoxy resin having at least two epoxy groups in the molecule. Further, the thermosetting resin composition further comprises (a) the general formula (1)
A polymaleimide compound represented by (b) naphthol, dihydroxynaphthalene, or at least one phenol resin having a naphthalene skeleton, and / or (c) an epoxy resin having at least two epoxy groups in the molecule, and (D) A prepreg characterized by comprising a modified imide resin obtained by modifying with a compound having at least one active hydrogen in the molecule.

Regarding the melting characteristics which are the characteristics of the present invention,
The press temperature condition for molding the multilayer plate is 120
After being held at ℃ to 140 ℃ for 10 to 30 minutes, it is common to raise the temperature to about 200 ℃ which is the curing temperature, and the melting property of the resin at the first holding time is that the resin does not protrude during molding, It is important in producing void-free multilayer laminates. The feature of the present invention relates to the melting characteristics of the resin at 120 to 130 ° C. Viscosity measured with a plate viscometer is 130 ° C, and shear rate is 10 rad / sec. The melt viscosity is such that the first 5 minutes is 5,000 to 30,000 poise and the viscosity after 20 minutes is 10,000 to 50,000 poise. There is something. In other words, 13
It has a high viscosity at 0 ° C, and has a melting property such that the viscosity does not change much in about 20 minutes. Furthermore, gelation does not occur in this 20 minutes. Initial viscosity is 5000
If it is less than poise, the resin component will flow out at the time of pressing, and the desired high-thickness thickness accuracy and the desired multi-layer laminate without resin protrusion cannot be obtained. If it is more than 30,000 poise, the viscosity is too high and voids are generated. Also, the initial viscosity is 5000
Even if the resin composition is up to 30,000 poise, the resin composition will be 50,000 poise or more while being left at 130 ° C.
Voids occur because the viscosity is excessively increased during pressing. Further, even if the viscosity is within an appropriate range, if the gel time defined by the intersection of the storage elastic modulus and the loss elastic modulus is within 15 minutes, bubbles cannot be sufficiently removed and voids are generated. Furthermore, the gel time measured with a 170 ° C. hot plate is 12
When the time is 0 seconds or more, the curing characteristics at the time of pressing are poor, the curing requires a long time, and the productivity is poor.

As the (a) polymaleimide compound used in the present invention, any compound having two or more maleimide groups in one molecule can be used. Examples of such polymaleimide compounds include N, N '-[1,3- (2-methylphenylene)] bismaleimide, N, N'-(1,4-phenylene) bismaleimide, bis (4-maleimide) Phenyl) methane, bis (3-methyl-4-maleimidophenyl) methane, bis (4-maleimidophenyl) ether, bis (4-
Maleimidophenyl) sulfone, bis (4-maleimidophenyl) sulfide, bis (4-maleimidophenyl) ketone, bis (4-maleimidocyclohexyl) methane, 1,
4-bis (4-maleimidophenyl) cyclohexane, 1,4-
Bis (maleimidomethyl) cyclohexane, 1,4-bis (
Maleimidomethyl) benzene, 1,3-bis (4-maleimidophenoxy) benzene, 1,3-bis (3-maleimidophenoxy) benzene, bis [4- (3-maleimidophenoxy) phenyl] methane, bis [4- ( 4-maleimidophenoxy) phenyl] methane, 1,1-bis [4- (3-maleimidophenoxy)
Phenyl] ethane, 1,1-bis [4- (4-maleimidophenoxy) phenyl] ethane, 1,2-bis [4- (3-maleimidophenoxy) phenyl] ethane, 1,2-bis [4- (4 -Maleimidophenoxy) phenyl] ethane, 2,2-bis [4- (3-maleimidophenoxy) phenyl] propane, 2,2-bis [4-
(4-Maleimidophenoxy) phenyl] propane, 2,2-
Bis [4- (3-maleimidophenoxy) phenyl] butane,
2,2-bis [4- (4-maleimidophenoxy) phenyl] butane, 2,2-bis [4- (3-maleimidophenoxy) phenyl]-
1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4-
Maleimidophenoxy) phenyl] -1,1,1,3,3,3 hexafluoropropane, 4,4'-bis (3-maleimidophenoxy) biphenyl, 4,4'-bis (4-maleimidophenoxy) biphenyl, bis [4- (3-maleimidophenoxy) phenyl] ketone, bis [4- (4-maleimidophenoxy) phenyl] ketone, bis [4- (3-maleimidophenoxy) phenyl] sulfide, bis [4- (4-maleimidophenoxy) phenyl] ketone ) Phenyl] sulfide, bis [4- (3-maleimidophenoxy) phenyl] sulfoxide, bis [4- (4-maleimidophenoxy) phenyl] sulfoxide, bis [4- (3-maleimidophenoxy) phenyl] sulfone, bis [4 -(Four-
Maleimidophenoxy) phenyl] sulfone, bis [4-
(3-Maleimidophenoxy) phenyl] ether, bis
[4- (4-maleimidophenoxy) phenyl] ether, 1,
4-bis [4- (4-maleimidophenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-maleimidophenoxy) -α, α-dimethylbenzyl] benzene, 1,4- Screw
[4- (3-maleimidophenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (3-maleimidophenoxy)-
α, α-Dimethylbenzyl] benzene, 1,4-bis [4- (4-
Maleimidophenoxy) -3,5-dimethyl-α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-maleimidophenoxy) -3,5-dimethyl-α, α-dimethylbenzyl] benzene, 1 , 4-bis [4- (3-maleimidophenoxy) -3,5-dimethyl-α, α-dimethylbenzyl] benzene, 1,3-bis [4- (3-maleimidophenoxy) -3,5-dimethyl- α, α
-Dimethylbenzyl] benzene, general formula (2)

[0008]

Embedded image (In the formula, n is 0 to 10 on average), and a polymaleimide compound represented by the general formula (3)

[0009]

Embedded image (Wherein, m is an average value of 0 to 10). These polymaleimide compounds may be used alone or as a mixture of two or more.

As the component (b), any phenol resin having naphthol, dihydroxynaphthalene, or at least one naphthalene skeleton can be used. The phenol resin having a naphthalene skeleton will be exemplified below. A reaction product of naphthols or naphthols such as dihydroxynaphthalene with phenols such as phenol, cresol, resorcinol, dihydroxybiphenyl or naphthols with aldehydes such as formaldehyde, acetaldehyde, benzaldehyde, hydroxybenzaldehyde, glucoxal, alkanedial. Examples include certain novolac resins and aralkyl resins that are reaction products of the above naphthols with aralkyl alcohol derivatives or aralkyl halide derivatives, and one or a mixture of two or more of these naphthols, dihydroxynaphthalenes, and phenol resins is used. .

As the epoxy resin as the component (c),
All epoxy compounds having two or more epoxy groups in the molecule can be used. Examples of such an epoxy compound include phenols such as phenol, cresol, resorcinol, and naphthol, or phenols obtained by halogenating them, and aldehydes such as formaldehyde, acetaldehyde, benzaldehyde, tolualdehyde, glyoxal, and alkandial. An epoxy resin obtained by reacting a reaction product obtained by condensation reaction with epichlorohydrin. An epoxy resin obtained by reacting a reaction product of the above phenols with an aralkyl alcohol derivative or an aralkyl halide derivative and epichlorohydrin. Furthermore, 2 in 1 molecule shown below
Epoxy resins derived from compounds having one or more active hydrogens, such as bisphenol A, bisphenol F, resorcin, bishydroxydiphenyl ether,
Polyhydric phenols such as bishydroxybiphenyl, bishydroxynaphthalene and trihydroxyphenylmethane, polyhydric alcohols such as ethylene glycol, neopentyl glycol, glycerin, trimethylolpropane, pentaerythritol, diethylene glycol and polypropylene glycol; ethylenediamine, aniline, Amines such as bis (4-aminophenyl) methane;
Epoxy resins obtained by reacting polychlorocarboxylic acids such as adipic acid, phthalic acid and isophthalic acid with epichlorohydrin are exemplified. One or a mixture of two or more of these epoxy resins can be used. In addition, various halogenated epoxy resins such as a brominated phenol novolak resin and a brominated bisphenol A type epoxy resin can be used.

In the composition of the present invention, the component (a), a polymaleimide compound represented by the general formula (1), and the component (b) are used.
Component naphthols or phenolic resins and (c)
The compounding amount of the component epoxy resin is such that the total amount of the component (b) and the component (c) is 10 to 100 parts by weight of the component (a).
500 parts by weight, preferably 25 to 300 parts by weight,
The equivalent ratio of the epoxy resin of the component (c) to the naphthol or the phenol resin of the component (b) is in the range of 0.1 to 10, preferably 0.5 to 2.0.

The resin composition of the present invention may optionally contain a phenol resin having no naphthalene skeleton such as a phenol novolac resin or a phenol aralkyl resin, an amine represented by diaminodiphenylmethane, diaminodiphenylsulfone, dicyandiamide or the like. Phthalic acid,
An acid anhydride such as pyromellitic dianhydride can also be used in combination.

As the component (d) used for producing the modified imide resin, any compound having at least one active hydrogen in the molecule can be used. Compounds having at least one active hydrogen in the molecule include phenol, bisphenol A, bisphenol F, cresol, resorcinol, naphthol, phenols such as dihydroxynaphthol, aniline, aminophenol,
One alcohol in one molecule such as phenylenediamine, ethylenediamine, amines such as bis (4-aminophenyl) methane, glycidol, glycerin diglycidyl ether, ethylene glycol monoglycidyl ether, resorcinol monoglycidyl ether, naphthoresorcinol monoglycidyl ether, etc. A compound comprising an acidic or phenolic OH group and one or more epoxy groups,
Compounds having an OH group and an acetylene group such as propargyl alcohol are exemplified.

As a method for producing the modified imide resin,
(A) a polymaleimide resin as a component, (b) a component,
The components (c) and (d) are simultaneously heated to 80 to 200 ° C.
In general, the mixture is heated and mixed for 0.1 to 10 hours, but may be further mixed by heating in an organic solvent. In the case of heating and mixing in an organic solvent, it is generally 50 to 200 ° C. and 0.1 to 2 depending on the boiling point of the organic solvent to be used.
0 hours. Although the content of the modified imide resin is not clear, it is considered to be mainly oligomerization of the polymaleimide resin. In the modification, it is difficult to produce a stable modified imide resin only with the component (b) and / or the component (c) or only the component (d) with respect to the component (a).

The component (d) is preferably used in an amount of 5 to 100 parts by weight with respect to 100 parts by weight of the polymaleimide resin, but 10 to 30 is particularly used for the purpose of maintaining heat resistance.
It is preferable to use parts by weight.

The amount of the naphthols or phenolic resin as the component (b) and the epoxy resin as the component (c) is (a)
The total amount of the components (b) and (c) is 10 to 500 parts by weight, preferably 25 to 300, relative to 100 parts by weight of the components.
It is a part by weight, and the equivalent ratio of the epoxy resin of the component (c) to the phenol resin of the component (b) is in the range of 0.1 to 10, preferably in the range of 0.5 to 2.0.

In the present invention, when the resin composition is cured, it is desirable to include a curing accelerator,
As such a curing accelerator, 2-methylimidazole,
Imidazoles such as 2-methyl-4-ethylimidazole and 2-heptadecylimidazole; amines such as triethanolamine, triethylenediamine and N-methylmorpholine; organic phosphines such as tributylphosphine, triphenylphosphine and tolylphosphine. ;
Tetraphenylphosphonium tetraphenylborate,
Tetraphenylboron salts such as triethylammonium tetraphenylborate; and 1,8-diaza-bicyclo (5,4,0) undecene-7 and derivatives thereof. These curing accelerators may be used alone or in combination of two or more, and if necessary, an organic peroxide or an azo compound may be used in combination. The content of these curing accelerators is 0.005 to 100 parts by weight of the resin.
Used in the range of 10 parts by weight.

In addition to the above-mentioned various components, the resin material of the present invention may be used for imide resins such as diallyl phthalate, triallyl isocyanurate, o, o'-diallyl bisphenol A, bisphenol A diallyl ether and bisphenol A dicyanate, if necessary. Commonly used reactive diluents; various silicone oils; flame retardants such as bromine compounds, antimony and phosphorus; fillers such as silica, talc, alumina and aluminum nitride, polyether sulfones, polyphenylene ethers, aromatic polyesters A linear polymer such as polysulfone, polyphenylene sulfide, polyetheretherketone, polyimide, polyetherimide, polyamideimide, polyparabanic acid, and other appropriate additives may be added.

In order to produce a prepreg using the resin composition of the present invention as described above, the resin resin composition (a) component, (b) component, (c) component, curing accelerator and other The additives are dissolved in a solvent to form a resin varnish. Alternatively, the component (a), the component (b), the component (c) and the component (e)
A modified imide resin composed of components and other additives are dissolved in a solvent to form a resin varnish. The concentration of the thermosetting resin composition in the varnish is preferably 40 to 80% by weight. As the solvent used at this time, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether,
Propylene glycol monomethyl ether, ethylene glycol monobutyl ether, N, N-dimethylformamide, N, N-dimethylacetamide, dioxane,
Acetone, N-methyl-2-pyrrolidone, dimethyl sulfoxide, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane, 2-heptanone and the like can be used.

As the base material, all known base materials such as glass cloth, carbon fiber, organic fiber cloth, glass non-woven cloth and paper can be used. After applying and impregnating the varnish on the substrate, a prepreg is manufactured through a drying step, but the application method, impregnation method, and drying method are not particularly limited. The drying conditions are appropriately determined depending on the boiling point of the solvent used. However, a high temperature is not preferable, and the amount of the residual solvent in the prepreg is desirably 1% by weight or less.

The laminated plate is manufactured by heating and pressurizing one or a plurality of the above prepregs which are stacked, and at this time, a metal foil or a metal plate is stacked on one or both outermost layers. be able to. The heating temperature is 1
00 to 300 ° C, pressurization pressure is 5 to 100 kg /
cm2 is desirable. Copper, aluminum, iron, stainless steel or the like can be used as the metal foil or metal plate. Further, a laminated board for a multilayer printed wiring board may be formed by using an inner layer core material.

[0023]

The present invention will be described below in more detail with reference to examples. In addition, the test method of the performance in an Example is as follows. -Viscosity: Plate-type viscometer (Dynamic Spectrometer RDS-2 manufactured by Rheometrics Co., Ltd.) Measurement conditions Temperature 130 ° C Rotation speed 10rad /
Second-Gel time (1): Calculated from the intersection of the storage elastic modulus and the loss elastic modulus during viscosity measurement.・ Gel time (2): 1 according to JIS-C6481
Measured on a 70 ° C hot plate.・ Plate thickness accuracy: 35 μm thick copper foil is laid on both sides of 10 prepregs, 130 ° C, 20 minutes (pressure: contact pressure) 180
After forming a copper-clad laminate by press molding under conditions of 90 ° C. and 90 minutes (pressure: 40 kg / cm 2), the difference in sheet thickness between the central portion and the end portion of the laminated sheet was measured by a micrometer.・ Number of voids: IPC-TM-6 with 35μ copper foil
A prepreg and a copper foil were laid on a 0.2 mm thick core material on which 50 comb-shaped electrodes were formed, the copper foil was removed by etching after pressing under the same press conditions as the measurement of plate thickness accuracy, and X-ray The number of generated voids was measured.

The raw materials used in Examples and Comparative Examples were as follows. -Polymaleimide compound: bis (4-maleimidophenyl) methane (manufactured by Mitsui Toatsu Chemicals, Inc.)-Dihydroxynaphthalene: 1,6-naphthalenediol (manufactured by Kanto Chemicals, Inc.)-Phenolic resin (1): naphtholzai Lock (manufactured by Mitsui Toatsu Chemicals, Inc.) ・ Phenol resin (2): Naphthol, cresol novolac resin (Kayahard NHN (manufactured by Nippon Kayaku Co., Ltd.) ・ Epoxy resin; Bisphenol A epoxy resin (Epicoat 1001, oil conversion) Shell Epoxy Co., Ltd.-Glycidol; Epiol OH (Nippon Oil & Fats Co., Ltd.)-Curing accelerator; 2 ethyl 4-methyl imidazole (2E4MZ)
, Manufactured by Shikoku Kasei Co., Ltd. ・ Epoxy resin prepreg: R1776 (manufactured by Matsushita Electric Works Ltd.) 100μ thick ・ Polyamino bismaleimide resin prepreg: R477
5 (Matsushita Electric Works, Ltd.) 100 μ thick Modified imide resin prepreg: BT830 (Mitsubishi Gas Chemical Co., Ltd.) 100 μ thick

Production Example of Modified Imido Resin (1) In a reaction vessel equipped with a stirrer, a thermometer and a cooler, 100 parts by weight of polymaleimide resin, 30 parts by weight of naphthol zylok, 50 parts by weight of epoxy resin, and glycidol 2
Insert 0 parts by weight and 100 parts by weight of methyl ethyl ketone and react at 80 ° C. for 10 hours to obtain modified imide resin (1)
I got

Examples 1 to 3 and Comparative Examples 1 to 3 The compositions (parts by weight) shown in Table 1 were dissolved in a flask to obtain a thermosetting resin varnish. The thermosetting resin varnish thus obtained was impregnated in a glass cloth (100 μm thick) of 104 g / m ² and dried at 150 ° C. for 5 minutes to obtain a prepreg of about 190 g / m ² . The viscosity characteristics of the obtained prepreg resin, gel time, plate thickness accuracy,
Table 2 shows the number of voids generated. For comparison, an epoxy resin prepreg (Comparative Example 1), a polyamino bismaleimide resin prepreg (Comparative Example 2), and a modified imide resin prepreg (Comparative Example 3) were also evaluated in the same manner, and the results are shown in Table 2. . Compared with the present invention, Comparative Examples 1 and 3
In the case of 1, the plate thickness accuracy was poor because the viscosity was too low, and some voids occurred because the gel time (1) was short. In the case of Comparative Example 2, the plate thickness accuracy is good due to the high viscosity, but voids are often generated due to the large increase in viscosity. As described above, the characteristics of both the plate thickness accuracy and the non-occurrence of voids are not satisfied as compared with the present embodiment.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

As described in Examples and Comparative Examples, the prepreg according to the present invention has good plate thickness accuracy after press molding and does not generate voids, and is particularly suitable for multilayer printed wiring boards. It is effective as a prepreg.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location H05K 1/03 610 H05K 1/03 610T (72) Inventor Kenji Shima 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Address: Mitsui Toatsu Chemical Co., Ltd. (72) Inventor, Hitoshi Sakuraba, 1190, Kasama-cho, Sakae-ku, Yokohama, Kanagawa Prefecture Mitsui Toatsu Chemical Co., Ltd. (72) Inventor: Kotaro Asahina, 1190, Kasama-cho, Sakae-ku, Yokohama, Kanagawa Prefecture Mitsui Toatsu Inside Chemical Co., Ltd.

Claims (5)

[Claims] 1. A shear rate of 1 using a plate viscometer.
Thermosetting resin composition having a viscosity measured at 0 rad / sec and a temperature of 130 ° C. within the range of 5000 to 30,000 poise for the initial 5 minutes of measurement and within the range of 10,000 to 50,000 poise after 20 minutes of measurement A prepreg characterized by being made of objects. 2. The gel time defined by the intersection of the storage elastic modulus and the loss elastic modulus is 1 when measured with a plate type viscometer.
A prepreg comprising the thermosetting resin composition according to claim 1, which has a gel time of 30 seconds or longer at 30 ° C. and a gel time of 120 seconds or shorter as measured on a 170 ° C. hot plate. 3. The thermosetting resin composition according to claim 1 or 2, wherein (a) is a polymaleimide compound represented by the general formula (1) (In the formula, R 1 is an m-valent organic group, Xa and Xb are hydrogen atoms,
A prepreg, which contains the same or different monovalent atoms or groups selected from a halogen atom and an organic group, and m is an integer of 2 or more). 4. The thermosetting resin composition according to claim 1 or 2, wherein (a) a polymaleimide compound represented by the general formula (1) and (b) naphthol, dihydroxynaphthalene, or at least one. Is a prepreg containing a phenol resin having a naphthalene skeleton, and / or (c) an epoxy resin having at least two epoxy groups in the molecule. 5. The thermosetting resin composition according to claim 1 or 2, wherein (a) the polymaleimide compound represented by the general formula (1), (b) naphthol, dihydroxynaphthalene, or at least one. Is modified by a phenol resin having a naphthalene skeleton, and / or (c) an epoxy resin having at least two epoxy groups in the molecule, and (d) a compound having at least one active hydrogen in the molecule. A prepreg containing an imide resin.