JP2012251151A - Epoxy resin composition and epoxy resin varnish, bonding sheet and cover-lay film using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition excellent in flexibility and flame retardancy, and to provide an epoxy resin varnish, a bonding sheet and a cover-lay film using the composition.SOLUTION: The epoxy resin composition comprises (a) an epoxy resin, (b) a curing agent and (c) a phenolic hydroxy group-containing aromatic polyamide-polybutadiene-acrylonitrile copolymer. In the composition: the (a) component is a trishydroxyphenylmethane type epoxy resin; the (b) component is composed of 10(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide only; phenolic hydroxy groups in the (b) component are included by 0.5 mol or more with respect to 1.0 mol of epoxy groups in the (a) component; and the compounding rate of the (c) component is 5 to 300 pts.mass with respect to 100 pts.mass of the total of the (a) component and the (b) component.

Description

  The present invention relates to an epoxy resin composition suitable for manufacturing a printed circuit board and an epoxy resin varnish, a bonding sheet, and a coverlay film using the same, and has particularly excellent flexibility, adhesiveness, and heat resistance. The present invention relates to an epoxy resin composition having flame retardancy, an epoxy resin varnish, a bonding sheet, and a coverlay film using the same.

  As an epoxy resin composition having flame retardancy, for example, a phosphorus-modified flame retardant epoxy resin composition containing an epoxy resin, a phosphorus-containing compound and a curing agent (see Patent Document 1), (A) 2 in one molecule A thermosetting epoxy resin composition comprising an epoxy resin having at least one epoxy group, (B) a curing agent having a phenolic hydroxyl group, and (C) an imidazole compound having a hydroxyl group as a curing accelerator (patent) Reference 2), a resin composition containing a specific proportion of an epoxy resin and a phosphorus-based flame retardant having a reactive phenolic hydroxyl group, and having a reaction rate of 80% or more between the epoxy resin and the flame retardant (patent) Document 3) has been proposed. In these compounds, for example, 10 (2,5-dihydroxyphenyl) -10H-9oxa-10-phosphaphenanthrene-10-oxide is used as the phosphorus-containing compound. Although these materials can provide flame retardancy, these compositions have a problem in flexibility.

  To solve this problem, an adhesive sheet or film (see Patent Document 4) characterized by having an island-island structure (microphase separation structure) in which an epoxy resin becomes an island, an epoxy resin, a curing agent, a phenolic hydroxyl group-containing polyamide-poly A flame retardant non-halogen epoxy resin composition (Patent Document 5) in which a (butadiene-acrylonitrile) copolymer, a flame retardant imparting agent, and an ion scavenger are essential components has been proposed.

  However, these products have a poor balance between flexibility, heat resistance, and flame retardancy, and have not been able to satisfy the respective characteristics at a high level at the same time.

JP 2000-80251 JP 2002-241473 A JP 2003-286332 A JP 2004-176003 A JP 2002-69270 A

  The present invention provides these problems, that is, to provide an epoxy resin composition excellent in flexibility, heat resistance and flame retardancy, and an epoxy resin varnish, a bonding sheet and a coverlay film using the same. And

  As a result of intensive studies to solve the above problems, the present inventors have used an epoxy resin composition containing a specific epoxy resin, a curing agent, and a phenolic hydroxyl group-containing aromatic polyamide-polybutadiene-acrylonitrile copolymer. The present epoxy resin varnish, bonding sheet, and coverlay film were found to be excellent in flexibility, heat resistance, and flame retardancy, and completed the present invention.

  That is, the present invention provides the following epoxy resin composition and an epoxy resin varnish, a bonding sheet, and a coverlay film using the same.

[1] An epoxy resin composition containing (a) an epoxy resin, (b) a curing agent, and (c) a phenolic hydroxyl group-containing aromatic polyamide-polybutadiene-acrylonitrile copolymer, wherein the component (a) is trishydroxy It is a phenylmethane type epoxy resin, and the component (b) consists only of 10 (2,5-dihydroxyphenyl) -10H-9oxa-10-phosphaphenanthrene-10-oxide, The phenolic hydroxyl group in the component (b) is 0.5 mol or more with respect to 1.0 mol of the epoxy group, and the blending ratio of the component (c) is the ratio between the component (a) and the component (b). An epoxy resin composition characterized by being 5 to 300 parts by mass with respect to 100 parts by mass in total.

[2] An epoxy resin varnish comprising the epoxy resin composition according to [1].

[3] A bonding sheet comprising an adhesive layer containing the epoxy resin composition according to [1] provided on a substrate.

[4] A coverlay film, wherein an adhesive layer containing the epoxy resin composition according to [1] is provided on an insulating base film.

  The epoxy resin composition of the present invention and the epoxy resin varnish, bonding sheet, and coverlay film using the epoxy resin composition have heat resistance and flow resistance, and are excellent in flame retardancy and flexibility, so that yield and product reliability are improved. The sex can be greatly improved. Therefore, the epoxy resin composition of the present invention can provide an epoxy resin varnish, a bonding sheet, and a coverlay film that are extremely useful particularly for the production of flexible printed circuit boards.

  Hereinafter, although the form for implementing the epoxy resin composition of this invention and the epoxy resin varnish, bonding sheet, and coverlay film using the same is demonstrated concretely, this invention is not limited to the following forms. Absent.

[1] Epoxy resin The trishydroxyphenylmethane type epoxy resin used in the present invention is represented by the following formula (1).

［式（１）中ｎは０〜１である。］

[In Formula (1), n is 0-1. ]

  As this epoxy resin, those which are solid at normal temperature are preferred, and those having an epoxy equivalent of 190 g / eq or less are particularly preferred from the viewpoint of heat resistance and flame retardancy. In addition, the epoxy resin may be other epoxy resins, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type or cresol novolac type epoxy resin, alicyclic epoxy resin, hydrogenated bisphenol, as long as the present invention is not inhibited. A-type or AD-type epoxy resin, propylene glycol diglycidyl ether, pentaerythritol polyglycidyl ether and other aliphatic epoxy resins, epoxy resins obtained from aliphatic or aromatic carboxylic acids and epichlorohydrin, aliphatic or aromatic amines, Used in combination with epoxy resins obtained from epichlorohydrin, heterocyclic epoxy resins, spiro ring-containing epoxy resins, epoxy-modified resins, bisphenol S-type epoxy resins, biphenol-type epoxy resins, etc. It may be.

[2] Curing Agent As the curing agent used in the epoxy resin composition of the present invention, 10 (2,5-dihydroxyphenyl) -10H-9oxa-10-phosphaphenanthrene-10-oxide is used alone. The use ratio of the curing agent is preferably such that the phenolic hydroxyl group is 0.5 or more with respect to 1.0 mol of the epoxy group in the epoxy resin. A particularly preferable range is 0.6 or more.

[3] Phenolic hydroxyl group-containing aromatic polyamide-polybutadiene-acrylonitrile copolymer The phenolic hydroxyl group-containing aromatic polyamide-polybutadiene-acrylonitrile copolymer used in the epoxy resin composition of the present invention is a phenolic hydroxyl group-containing aromatic polyamide. -Polybutadiene-acrylonitrile copolymer dicarboxylic acid component having a hydroxyl group, for example, 5-hydroxyisophthalic acid, 4-hydroxyisophthalic acid, 2-hydroxyphthalic acid, 3-hydroxyphthalic acid, 2-hydroxyterephthalic acid, phenolic hydroxyl group Examples of dicarboxylic acids having no phthalic acid include phthalic acid, isophthalic acid, terephthalic acid, dicarboxyl naphthalene, succinic acid, fumaric acid, glutaric acid, adipic acid, 1,3-dichlorohexanedicarboxylic acid, 4,4′- Diamines such as 3,3′-diamine-4,4′-dihydroxyphenylmethane, 2,2-bis (3-amino-4-hydroxy) for phenyldicarboxylic acid, 3,3′-methylenedibenzoic acid and the like Phenyl) hexafluoropropane, 2,2-bis (3-amino-4-hydroxyphenyl) difluoromethane, 3,4-diamino-1,5-benzenediol, 3,3'-dihydroxy-4,4'-diaminobis Phenyl, 3,3'-diamino-4,4'-dihydroxybiphenyl, 2,2-bis (3-amino-4-hydroxyphenyl) ketone, 2,2-bis (3-amino-4-hydroxyphenyl) sulfide 2,2-bis (3-amino-4-hydroxyphenyl) ether, 2,2-bis (3-amino-4-hydroxyphenyl) sulfone, , 2-bis (3-amino-4-hydroxyphenyl) propane, 2,2-bis (3-hydroxy-4-aminophenyl) propane, 2,2-bis (3-hydroxy-4-aminophenyl) methane, etc. 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, diaminonaphthalene, piperazine, hexanetylenediamine, tetramethylenediamine, m- Xylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminobenzophenone, 2,2'-bis (4-aminophenyl) propane, 3,3'-diaminodiphenylsulfone, 3,3'-diaminodiphenyl, etc. For example, phosphites and Using a condensing agent in the presence of a lysine derivative, the mixture is heated and stirred under an inert atmosphere such as nitrogen in an organic solvent typified by N-methyl-2-pyrrolidone, and a condensation reaction is performed. A polyamide-polybutadiene-acrylonitrile copolymer is produced. Among these, it is preferable to use a compound represented by the following formula (2).

（式（２）中、ｘ、ｙ、ｚ、ｌ、ｍ及びｎは、それぞれ平均重合度であって、ｘ＝３〜７、ｙ＝１〜４、ｚ＝５〜１５、ｌ＋ｍ＝２〜２００の整数をそれぞれ示し、ｍ／（ｌ＋ｍ）≧０．０４である。）で示される共重合体である。

(In the formula (2), x, y, z, l, m, and n are average polymerization degrees, respectively, and x = 3 to 7, y = 1 to 4, z = 5 to 15, l + m = 2 to 2. Each represents an integer of 200, and m / (l + m) ≧ 0.04).

  This is necessary for imparting flexibility and adhesiveness, and by adding it, it is possible to impart flexibility to the cured product and at the same time increase the adhesive strength with other flexible substrate constituent materials. The blending ratio of the phenolic hydroxyl group-containing aromatic polyamide-polybutadiene-acrylonitrile copolymer is preferably in the range of 5 to 300 parts by mass with respect to 100 parts by mass of the total amount of the epoxy resin and the curing agent. If there is less phenolic hydroxyl group-containing aromatic polyamide-polybutadiene-acrylonitrile copolymer than this range, flexibility and adhesiveness will decrease, and if it exceeds this range, electrical properties and handling properties when varnished will decrease. It is not preferable. A particularly preferable blending ratio is in the range of 10 to 150 parts by mass from the viewpoints of flexibility, adhesiveness, electrical characteristics, and handling properties in varnish.

[4] Other components Other additives can be added to the epoxy resin composition of the present invention as necessary. Examples of the additive include phosphorus compounds such as triphenylphosphine, such as triethylamine, tetraethanolamine, 1,8-diaza-bicyclo [5.4.0] -7-undecene (DBU), N, N-dimethyl. Tertiary amine compounds such as benzylamine, 1,1,3,3-tetramethylguanidine, 2-ethyl-4-methylimidazole, N-methylpiperazine, such as 1,8-diaza-bicyclo [5.4. 0] -7-undecenium tetraphenylborate and other boron-based compounds such as curing accelerators, plasticizers such as natural waxes, synthetic waxes and metal salts of long-chain aliphatic acids, acid amides, esters, Release agents such as paraffins, stress relaxation agents such as nitrile rubber and butadiene rubber, antimony trioxide, antimony pentoxide, tin oxide, hydroxylation Inorganic flame retardants such as molybdenum oxide, zinc borate, barium metaborate, red phosphorus, aluminum hydroxide, magnesium hydroxide, calcium aluminate, tetrabromobisphenol A, tetrabromophthalic anhydride, hexabromobenzene, brominated phenol novolak, etc. Brominated flame retardants, silane coupling agents, titanate coupling agents, coupling agents such as aluminum coupling agents, fused silica, crystalline silica, low α-ray silica, glass flakes, glass beads, glass balloons, Talc, alumina, calcium silicate, aluminum hydroxide, calcium carbonate, barium sulfate, magnesia, silicon nitride, boron nitride, ferrite, rare earth cobalt, gold, silver, nickel, copper, lead, iron powder, iron oxide, sand iron, etc. Metal powder, graphite, carbon, petal, yellow Inorganic fillers such as lead or conductive particles, colorants such as dyes and pigments, inorganic fibers such as carbon fibers, glass fibers, boron fibers, silicon carbide fibers, alumina fibers, silica alumina fibers, aramid fibers, polyester fibers , Organic fibers such as cellulose fiber, carbon fiber, oxidation stabilizer, light stabilizer, moisture resistance improver, thixotropy imparting agent, diluent, antifoaming agent, other various resins, tackifier, antistatic agent, Examples thereof include a lubricant and an ultraviolet absorber. Among them, the silane coupling agent is preferably used in terms of adhesion between the epoxy resin and the filler. Moreover, it is preferable to use aluminum hydroxide etc. when providing a flame retardance and flow resistance.

  The epoxy resin composition of the present invention can be obtained by mixing an epoxy resin, a curing agent, a phenolic hydroxyl group-containing polyamide-polybutadiene-acrylonitrile copolymer, and various additives as required. When using as a sheet | seat, it is set as a coating liquid by mixing each said component uniformly in a predetermined ratio in a solvent. Examples of the solvent in this case include organic solvents such as toluene, ethanol, cellosolve, tetrahydrofuran, N-methyl-2-pyrrolidone, and dimethylformamide.

  Curing of the epoxy resin composition of the present invention is mainly carried out by heat curing. For example, it is used in combination with a catalyst around room temperature, room temperature curing caused by oxygen or moisture, photocuring caused by an acid generated by ultraviolet irradiation, or the like. It is also possible.

  The epoxy resin composition of the present invention can be preferably used as an adhesive constituting a bonding sheet or a coverlay film in addition to an epoxy resin varnish.

  The structure of the bonding sheet is a three-layer structure composed of a release film / adhesive / release film or a two-layer structure composed of a release film / adhesive, and the thickness of the adhesive is generally 5 to 100 μm. It can be appropriately selected depending on the usage situation.

  The structure of the coverlay film is a three-layer structure composed of an electrically insulating film / adhesive / release material or a two-layer structure composed of an electrically insulating film / adhesive, and the thickness of the adhesive is 5 to 100 μm. It can be appropriately selected depending on the usage situation.

  Examples of the electrically insulating film that can be used in the present invention include polyimide films, PET (polyethylene terephthalate) films, polyester films, polyparabanic acid films, polyether ether ketone films, polyphenylene sulfide films, aramid films, and liquid crystal polymer films. Of these, a polyimide film, an aramid film, and a liquid crystal polymer film are preferable in view of heat resistance, dimensional stability, mechanical properties, and the like. The thickness of the film is usually in the range of 4.2 to 75 μm, but an appropriate thickness may be used as necessary. In addition, one or both surfaces of these films may be subjected to a surface treatment such as a low temperature plasma treatment, a corona discharge treatment, or a sand blast treatment.

  Examples of the release material usable in the present invention include polyethylene film, polypropylene film, polymethylpentene (TPX) film, PET film, polyethylene film with silicone release agent, polypropylene film and PET film, polyethylene resin-coated paper, polypropylene resin coat Paper and TPX resin-coated paper, and the like. The thickness of the release material is preferably 13 to 75 μm for a film base and 50 to 200 μm for a paper base. used.

  The flexible printed wiring board material has a three-layer structure composed of metal foil / adhesive / electrically insulating film, and the thickness of the adhesive is generally 10 to 100 μm. You can choose.

  Examples of the metal foil used at this time include electrolytic copper foil, rolled copper foil, aluminum foil, tungsten foil, and iron foil. Generally, from the viewpoint of workability, flexibility, electrical conductivity, etc., the electrolytic copper foil and Rolled copper foil is used. The thickness of the metal foil is generally 18 to 70 μm, but can be appropriately selected according to use.

  Hereinafter, a method for producing the above-described coverlay film will be described. A coating solution comprising the epoxy resin composition of the present invention is prepared by the following procedure, and this coating solution is applied to the electrical insulating film using a roll coater, a comma coater or the like. This is passed through an in-line dryer and heat-treated at 40 to 160 ° C. for 1 to 20 minutes to remove the solvent in the adhesive and form an adhesive layer. The adhesive-coated surface of the release agent with the adhesive and the release material are pressure-bonded by a heating roll. Generally the application | coating thickness of an adhesive agent should just be 5-100 micrometers in a dry state. In addition, when the thickness of the electrical insulating film to be used is less than 25 μm, it is opposite to the surface on which the adhesive layer of the electrical insulating film is formed in order to transport the film at the time of application and to suppress smearing of the adhesive layer. It is preferable to apply the coating liquid after reinforcing it with a carrier sheet or the like in which a pressure-sensitive adhesive layer is provided on a substrate on the side surface.

<Preparation of coating solution>
(1) A phenolic hydroxyl group-containing aromatic polyamide-polybutadiene-acrylonitrile copolymer, an inorganic filler used as required, and a coupling agent are placed in a solvent and stirred.
(2) A curing agent is added to (1) and further mixed.
(3) Next, an epoxy resin dissolved in a solvent is added to the above (2) and mixed uniformly.

  Furthermore, the manufacturing method of the bonding sheet of this invention apply | coats the coating liquid which consists of the epoxy resin composition of this invention prepared above to a mold release material using a roll coater, a comma coater, etc. This is passed through an in-line dryer and heat-treated at 40 to 160 ° C. for 1 to 20 minutes to remove the solvent in the adhesive and form an adhesive layer. The adhesive-coated surface of the release agent with the adhesive and the release material are pressure-bonded by a heating roll. Generally the application | coating thickness of an adhesive agent should just be 5-100 micrometers in a dry state.

Hereinafter, the epoxy resin composition of the present invention and the coverlay film using the same will be described in detail with reference to examples, but the epoxy resin composition of the present invention and other coverlay films using the same will be described in these examples. It is not limited by.
In addition, about the cover-lay film of an Example, a reference example, and a comparative example, six items, a flame retardance, a bendability, an electrical property, heat resistance, embedding property, and a oozing property, were evaluated. These items were evaluated by the following methods.

(1) Flame retardancy The prepared coverlay film was pressed and cured at 160 ° C. and a load of 40 kgf / cm ² for 60 minutes, and the flame retardancy of the sample was evaluated according to the UL94 test method.
○: VTM-0
Δ: VTM-1
X: VTM-2

(2) Bendability The prepared coverlay film was pressed and cured at 160 ° C. and a load of 40 kgf / cm ² for 60 minutes, and the state where it was bent at 180 ° was visually evaluated according to the following criteria.
○: No cracks are observed in the bent part ×: Cracks are observed in the bent part

(3) Electrical characteristics After applying to a JIS2 comb electrode and curing, the electrode was observed after 85 hours, 95%, applied voltage 20 V, 100 hours.
○: The electrode is not thinned, discolored, or rusted.
X: The electrode is thinned, discolored, or rusted.

(4) Heat resistance (glass transition temperature)
The produced coverlay film was processed into 3 mm × 15 mm, and measured using the TMA4000S (manufactured by MACSCIENCE) under the following conditions by the TMA method.
<Conditions>
Temperature increase rate: 5 ° C / min Load: -5 to -10g
○: 160 ° C or higher × 159 ° C or lower

(5) Embeddability L / S 100 μm / 100 μm electrode and bonding sheet were observed at 160 ° C. for 1 hour at 40 kgf / cm ² after hot press curing and the cross section was observed.
○: There is no void and the resin has entered between the lines.
X: There is a gap.

(6) Permeability The bonding sheet cut to 40 mm □ was hot-pressed at 160 ° C. for 1 hour at 40 kgf / cm ² and the shape after curing was observed.
○: Within 40 ± 3mm □: 44mm □ or more

Reference example 1
Phenolic hydroxyl group-containing aromatic polyamide-polybutadiene-acrylonitrile copolymer (solid content 40% DMF solution product) 243 parts by mass, hydroxyphenylmethane type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., trade name “EPPN502H”) 100 parts by mass, Curing agent [10 (2,5-dihydroxyphenyl) -10H-9oxa-10-phosphaphenanthrene-10-oxide (manufactured by Sanko Co., Ltd., trade name “HCA-HQ”) 65.1 parts by mass and biphenyl type naphthol novolak 29.9 parts by mass of resin (made by Meiwa Kasei Co., Ltd., trade name “MEH-7851-3H”)] 95 parts by mass, 1 part by mass of 2-methylimidazole were mixed and dissolved in 400 parts by mass of a mixture of methyl ethyl ketone and dimethylformamide. An adhesive layer forming coating solution was prepared.
This coating solution is preliminarily plasma-treated on one side of an aramid film (manufactured by Teijin Advanced Films, trade name “Aramika”, thickness of 4.2 μm), applied to the plasma-treated surface, and dried (100 ° C., 3 minutes) And a coverlay film having a film thickness of about 60 μm was produced. The physical properties of this product are shown in Table 1.

Example 1
In Reference Example 1, the curing agent was 95 parts by mass of 10 (2,5-dihydroxyphenyl) -10H-9oxa-10-phosphaphenanthrene-10-oxide (manufactured by Sanko Co., Ltd., trade name “HCA-HQ”), A coverlay film was prepared in the same manner as in Reference Example 1 except that the biphenyl type naphthol novolak resin was not used. The physical properties of this product are shown in Table 1.

Reference example 2
In Reference Example 1, the curing agent was 47.5 parts by mass of 10 (2,5-dihydroxyphenyl) -10H-9oxa-10-phosphaphenanthrene-10-oxide (manufactured by Sanko Co., Ltd., trade name “HCA-HQ”). A coverlay film was prepared in the same manner as in Reference Example 1 except that 47.5 parts by mass of biphenyl type naphthol novolak resin (Maywa Kasei Co., Ltd., trade name “MEH-7851-3H”) was used. The physical properties of this product are shown in Table 1.

Comparative Example 1
A coverlay film was produced in the same manner as in Reference Example 1 except that the bisphenol A type epoxy resin (manufactured by Dainippon Ink and Chemicals, trade name “EPICLON850S”) was used as the epoxy resin in Reference Example 1. The physical properties of this product are shown in Table 1.

Comparative Example 2
In Reference Example 1, the curing agent was a novolak type phenol resin (manufactured by Nippon Kayaku Co., Ltd., trade name “Kayahard TPM, hydroxyl group equivalent 97 g / eq”, 56.7 parts by mass, and the curing accelerator was 2-phenyl-4-methyl-5. -1 part by mass of hydroxymethylimidazole, 10 (2,5-dihydroxyphenyl) -10H-9 oxa-10-phosphaphenanthrene-10-oxide (trade name “HCA-HQ” 85 parts by mass as a flame retardant imparting agent Except for the use, a coverlay film was produced in the same manner as in Reference Example 1. Table 1 shows the physical properties of this coverlay film.

Comparative Example 3
A coverlay film was produced in the same manner as in Reference Example 1 except that the phenolic hydroxyl group-containing aromatic polyamide-polybutadiene-acrylonitrile copolymer was not used in Reference Example 1. The physical properties of this product are shown in Table 1.

  From the results in Table 1, it can be seen that the cover lay film of the present invention has a performance satisfying both flame retardancy and flexibility. Since the adhesive layer is excellent in the embedding of the adhesive, and the pressure-sensitive adhesive layer does not ooze out even by the heating press at the time of application, it can be seen that a high-quality printed circuit board is obtained.

  The present invention relates to an epoxy resin composition suitable for producing printed wiring boards, and an epoxy resin varnish, a bonding sheet, and a coverlay film using the same, and particularly has heat resistance, flow resistance, and flame retardancy. Since it is excellent in flexibility, it is possible to improve both yield and product reliability when manufacturing a printed circuit board.

Claims (4)

In the epoxy resin composition containing (a) an epoxy resin, (b) a curing agent, and (c) a phenolic hydroxyl group-containing aromatic polyamide-polybutadiene-acrylonitrile copolymer,
The component (a) is a trishydroxyphenylmethane type epoxy resin,
The component (b) consists only of 10 (2,5-dihydroxyphenyl) -10H-9oxa-10-phosphaphenanthrene-10-oxide,
The phenolic hydroxyl group in the component (b) is 0.5 mol or more with respect to 1.0 mol of the epoxy group in the component (a),
The proportion of the component (c) is 5 to 300 parts by mass with respect to 100 parts by mass of the total amount of the component (a) and the component (b).   An epoxy resin varnish comprising the epoxy resin composition according to claim 1.   A bonding sheet comprising an adhesive layer containing the epoxy resin composition according to claim 1 on a substrate.   A coverlay film comprising an adhesive layer containing the epoxy resin composition according to claim 1 provided on an insulating base film.