JP2006169446A - Adhesive composition and cover lay film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive composition useful for an adhesive cured product excellent in heat resistance and for a cover lay film using the same, as well as useful for producing these products. <P>SOLUTION: The adhesive composition comprises (A) an epoxy resin, (B) a carboxylic acid-modified crosslinked acrylonitrile-butadiene rubber, (C) a curing agent, (D) a curing accelerator and (E) an inorganic filler. The cured product is made out of the composition and has a continuous phase, that is comprised of the cured epoxy resin, and a dispersed phase, that is comprised of the (B) component contained in the continuous phase and whose average grain diameter is not lager than 1 μm, and whose storage modulus is at least 200 MPa at 85°C. The cover lay film has an electrical insulating film layer and an adhesive layer comprised of the composition and placed on the film layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to an adhesive cured product having excellent heat resistance, a coverlay film using the cured product, and an adhesive composition useful for production thereof.

  With the increase in the density of electronic circuits and the downsizing of electronic devices, flexible copper-clad laminates are widely used in place of rigid copper-clad laminates that have been used in the past as thinner and more flexible materials. The market is growing year by year.

  After processing the copper foil of this flexible copper-clad laminate to form a wiring pattern, in order to cover and protect the wiring pattern formation surface, an electrically insulating film (coverlay) such as a polyimide film with an adhesive is used. Film). Properties required for these flexible copper-clad laminates and coverlay films (hereinafter referred to as flexible copper-clad laminates, etc.) include, for example, adhesion between an electrically insulating film and copper foil, heat resistance, and solvent resistance. Properties, electrical properties (migration resistance), dimensional stability, storage stability, flame retardancy, and the like.

  In recent years, flexible copper-clad laminates are often subjected to high-temperature and high-pressure loads due to the mounting of anisotropic conductive films (ACF) to increase the density of printed circuit boards. Etc. are also being studied for mounting on automobile electronic devices, and therefore further improvement in heat resistance of the flexible copper-clad laminate is required.

  As for flexible copper clad laminates, high heat resistance has been realized by using no adhesives instead of the conventional three-layer flexible copper clad laminates, which are bonded with polyimide film and copper foil. Single layer flexible copper clad laminates are rapidly spreading. On the other hand, with regard to the coverlay film, it has been attempted to use a material obtained by applying an epoxy resin adhesive to a polyimide film and B-staged in combination with a two-layer flexible copper-clad laminate. However, heat resistance is still insufficient.

  In addition, an epoxy resin adhesive containing an epoxy resin, an epoxy resin curing agent, a curing accelerator, and acrylonitrile-butadiene rubber (hereinafter referred to as NBR) modified with a carboxylic acid as an adhesive for the coverlay film Compositions are widely used. However, since NBR modified with carboxylic acid has a glass transition point (Tg) of around −50 ° C., even when the composition is sufficiently mixed with epoxy resin or the like and cured, the strength of the cured product obtained is Under the influence of NBR, as a result, the cured product has insufficient heat resistance.

  In addition, an epoxy resin composition containing an epoxy resin having a specific structure, a curing agent, an ion scavenger, and a core-shell type crosslinked rubber having an average particle size of 1 μm or less, and a coverlay film using the composition are proposed. However, the heat resistance is still insufficient.

JP 2003-213082 A

  An object of the present invention is to provide an adhesive cured product excellent in heat resistance, a coverlay film using the cured product, and an adhesive composition useful for the production thereof.

In order to solve the above problems, the present invention
(A) epoxy resin,
(B) a crosslinked acrylonitrile-butadiene rubber modified with a carboxylic acid,
(C) a curing agent,
(D) a curing accelerator, and (E) an adhesive composition comprising an inorganic filler,
I will provide a.

  Secondly, the present invention is a cured product of the adhesive composition, comprising a continuous phase composed of a cured epoxy resin, and a crosslinked acrylonitrile-butadiene rubber modified with the (B) carboxylic acid in the continuous phase. The cured product having a dispersed phase having an average particle size of 1 μm or less and a storage elastic modulus of 200 MPa or more at 85 ° C. is provided.

  Thirdly, the present invention provides a coverlay film having an electrically insulating film layer and an adhesive layer made of the adhesive composition provided on the film layer.

  The cured product obtained by curing the composition of the present invention is not only excellent in heat resistance but also excellent in peel strength, solder heat resistance, and the like. In particular, the cured product has a continuous phase composed of a cured epoxy resin, and a dispersed phase composed of crosslinked NBR modified with a carboxylic acid in the continuous phase and having an average particle size of 1 μm or less, and a storage elastic modulus of 85 ° C. In an embodiment at 200 MPa or more, the cured product has significantly excellent heat resistance. Therefore, since the coverlay film having the adhesive layer made of the composition of the present invention has the same characteristics as described above, it can be suitably used particularly for a flexible copper clad laminate.

<Adhesive composition>
Hereinafter, each component which comprises the adhesive composition of this invention is demonstrated in detail. In this specification, room temperature means 25 ° C. The nonvolatile component is a nonvolatile organic component and a nonvolatile inorganic solid component constituting a cured product obtained by curing the composition of the present invention. Specifically, the following mainly (A) to (E) Although it is a component and also includes a component that is optionally added, when the adhesive composition includes an organic solvent, the organic solvent is usually not included in the nonvolatile component.

[(A) Epoxy resin]
The epoxy resin as component (A) has at least two epoxy groups on average in one molecule. The epoxy resin may be modified with, for example, silicone, urethane, polyimide, polyamide, or the like, and may contain a bromine atom, a phosphorus atom, a sulfur atom, a nitrogen atom, or the like in the molecular skeleton. .

  The polystyrene-reduced weight average molecular weight of the epoxy resin of this component is not particularly limited, but is preferably in the range of 360 to 20,000 from the viewpoint of the adhesiveness of the composition and the heat resistance of the cured product. Moreover, it is preferable that the epoxy equivalent of this epoxy resin exists in the range of 180-10,000 from viewpoints of the adhesiveness of a composition, the heat resistance of hardened | cured material, etc.

  Examples of the epoxy resin of this component include, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, or those hydrogenated thereto; glycidyl ether type epoxy resins such as phenol novolac type epoxy resin and cresol novolac type epoxy resin; Glycidyl ester epoxy resin such as hexahydrophthalic acid glycidyl ester and dimer acid glycidyl ester; Glycidyl amine epoxy resin such as triglycidyl isocyanurate and tetraglycidyl diaminodiphenylmethane; Epoxidized polybutadiene, epoxidized soybean oil, CTBN modified epoxy resin, etc. A linear aliphatic epoxy resin; NBR-modified epoxy resin and the like, preferably bisphenol A type epoxy resin, bisphenol F type epoxy resin, E Nord novolak type epoxy resin, a cresol novolak type epoxy resin. As these commercial products, for example, Epicoat 828 (manufactured by Japan Epoxy Resin, two epoxy groups in one molecule), Epicron 830 (manufactured by Dainippon Ink and Chemicals, epoxy group in one molecule: 2 under the trade name) ), Epicoat 154 (manufactured by Japan Epoxy Resin, epoxy groups in one molecule: two or more), EOCN103S (manufactured by Nippon Kayaku, epoxy groups in one molecule: two or more), and the like.

  A brominated epoxy resin in which a bromine atom is bonded to a benzene ring in the molecule of a bisphenol A type epoxy resin is also effective because the flame retardancy of the cured product is improved. There are two types of commercially available brominated epoxy resins, one with a high bromine content and one with a low bromine content. For example, under the trade name, Epicoat 5050 (made by Japan Epoxy Resin, two epoxy groups in one molecule), Epicoat 5046 (manufactured by Japan Epoxy Resin, epoxy groups in one molecule: 2).

  Furthermore, a phosphorus-containing epoxy resin obtained by bonding a phosphorus atom to an epoxy resin using a reactive phosphorus compound is also effective as a material imparting flame retardancy. Since the phosphorus content rate in this phosphorus containing epoxy resin can provide the outstanding flame retardance to hardened | cured material, it is preferable that it is 3-4 mass%. Examples of the phosphorus-containing epoxy resin include 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (manufactured by Sanko Co., Ltd., trade name: HCA), or a phosphorus atom of this compound. Examples thereof include compounds obtained by reacting a compound obtained by replacing bonded active hydrogen atoms with hydroquinone (trade name: HCA-HQ, manufactured by Sanko Co., Ltd.) with the epoxy resin. As these commercial products, for example, under the trade name, FX305 (manufactured by Toto Kasei Co., Ltd., phosphorus content: 3% by mass, two epoxy groups in one molecule), Epicron EXA9710 (Dainippon Ink Chemical Co., Ltd.) Co., Ltd., phosphorus content: 3 mass%, epoxy groups in one molecule: 2) and the like.

  (A) The epoxy resin of a component may be used individually by 1 type, or may use 2 or more types together.

[(B) Crosslinked NBR modified with carboxylic acid]
The crosslinked NBR modified with the carboxylic acid component (B) gives the cured product the same level of peel strength, solder heat resistance, and the like as before, and also provides excellent heat resistance.

  The average particle size of the primary particles of the crosslinked NBR is not particularly limited, but is usually 100 nm or less because this component easily forms a dispersed phase having an average particle size of 1 μm or less in the cured product.

  The carboxyl group introduced by modifying the crosslinked NBR with a carboxylic acid may be present at the molecular chain terminal or at the molecular chain non-terminal.

  In the crosslinked NBR modified with the carboxylic acid of this component, the content of at least acrylonitrile and butadiene contained, and the content of the carboxyl group introduced by modification with the carboxylic acid as described above are not particularly limited. However, it is preferably as follows. The acrylonitrile content is usually 10 to 35% by mass. The butadiene content is usually 65 to 85% by mass. The carboxyl group content is usually 0.1 to 10% by mass, and when the cured product is applied to a cover lay film, the flowability, solder heat resistance and stability become more excellent, and preferably 0.5 to 1% by mass.

  The crosslinked NBR modified with carboxylic acid may be produced by any method, and is usually obtained by copolymerizing acrylonitrile, butadiene and a carboxylic acid monomer having a polymerizable unsaturated double bond. Although it is produced, it is one that is partially crosslinked by adding a crosslinkable monomer in the copolymerization stage. If necessary, it may be in the form of particles after crosslinking. Examples of the carboxylic acid monomer having a polymerizable unsaturated double bond include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid and the like, preferably acrylic acid, methacrylic acid, more preferably Is acrylic acid.

  Specific examples of the crosslinked NBR modified with the carboxylic acid of this component include, for example, XER-91 (manufactured by JSR) under the trade name.

  Although the compounding quantity of (B) component is not specifically limited, It is 20-100 mass parts normally with respect to 100 mass parts of (A) component, Preferably it is 25-75 mass parts, More preferably, it is 30-60 masses. Part. When this range is satisfied, the cured product can easily form a preferable phase structure described later (that is, in the cured product, the cured epoxy resin forms a continuous phase, and the crosslinked NBR forms a dispersed phase having an average particle size of 1 μm or less. Therefore, the cured product has the same level of peel strength and solder heat resistance as those of the prior art, and even better heat resistance.

  The crosslinked NBR modified with the carboxylic acid (B) may be used alone or in combination of two or more.

[(C) curing agent]
The curing agent as component (C) is not particularly limited as long as it has been conventionally used as a curing agent for epoxy resins. Examples of the curing agent include a polyamine curing agent, an acid anhydride curing agent, and a phenol resin curing agent. Examples of polyamine curing agents include aliphatic amine curing agents such as diethylenetriamine, tetraethylenetetramine, and tetraethylenepentamine; alicyclic amine curing agents such as isophoronediamine; diaminodiphenylmethane, diaminodiphenylsulfone (DDS), Aromatic amine curing agents such as phenylenediamine; dicyandiamide and the like. Examples of the acid anhydride curing agent include phthalic anhydride, pyromellitic anhydride, trimellitic anhydride, hexahydrophthalic anhydride, and the like. Examples of phenolic resin-based curing agents include phenol novolac resin (Showa High Polymer Co., Ltd., trade name: Shonor BRG-558), triazine phenolic resin (Dainippon Ink Co., Ltd., trade name: LA4055, containing nitrogen atom) Flame retardant resin). Among these, as the curing agent, aromatic amines and phenolic resins are preferable from the viewpoints of reactivity and adhesiveness of the adhesive composition and heat resistance of the cured product.

  Although the compounding quantity of (C) component is not specifically limited, It is 1-80 mass parts normally with respect to 100 mass parts of (A) component, Preferably it is 3-60 mass parts.

  (C) The hardening | curing agent of a component may be used individually by 1 type, or may use 2 or more types together.

[(D) Curing accelerator]
The curing accelerator as component (D) is not particularly limited as long as it promotes the reaction between (A) the epoxy resin and (C) the curing agent. Examples of the curing accelerator include imidazole compounds, triorganophosphines, phosphonium salts, tertiary amines, borofluorides, octylates, and the like. Examples of imidazole compounds include 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, and ethyl isocyanate compounds of these compounds, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2 -Phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole and the like. Examples of the triorganophosphine include triphenylphosphine, tributylphosphine, tris (p-methylphenyl) phosphine, tris (p-methoxyphenyl) phosphine, tris (p-ethoxyphenyl) phosphine, triphenylphosphine / triphenylborate, And triorganophosphines such as tetraphenylphosphine and tetraphenylborate. Examples of phosphonium salts include quaternary phosphonium salts. Examples of the tertiary amine include triethyleneammonium triphenylborate and the tetraphenylborate salt thereof. Examples of the borofluoride include zinc borofluoride, tin borofluoride, nickel borofluoride, and the like. Examples of the octylate include tin octylate and zinc octylate. Among these, borofluoride is preferable.

  Although the compounding quantity of (D) component is not specifically limited, It is 0.1-30 mass parts normally with respect to 100 mass parts of (A) component, Preferably it is 1-20 mass parts, Most preferably, it is 1- 5 parts by mass.

  (D) The hardening accelerator of a component may be used individually by 1 type, or may use 2 or more types together.

[(E) inorganic filler]
The (E) component inorganic filler is a component blended for the purpose of assisting in flame retardancy of cured products, improving peel strength (cohesive peeling of the adhesive after curing), stabilizing moisture absorption resistance, and the like. is there. Although this inorganic filler will not be specifically limited if it is conventionally used for the coverlay film, What acts also as a flame-retardant adjuvant is preferable.

  Specific examples of inorganic fillers include metal hydroxides such as aluminum hydroxide and magnesium hydroxide; metal oxides such as silicon dioxide, aluminum oxide and molybdenum oxide; boric acid compounds such as zinc borate and magnesium borate Etc. Among these, metal hydroxides such as aluminum hydroxide and magnesium hydroxide; metal oxides such as silicon dioxide, aluminum oxide, and molybdenum oxide are preferable because they act as flame retardant aids. Aluminum hydroxide, hydroxide Magnesium is particularly preferred.

  In order to improve the adhesion and water resistance of these inorganic fillers to the resin matrix and to improve the heat resistance, moisture absorption resistance, etc. of the cured product, the surface of the inorganic filler is a silane coupling agent or titanate. Hydrophobic treatment with a system coupling agent or the like is preferred.

  Although the compounding quantity of (E) component is not specifically limited, Preferably it is 5-60 mass parts with respect to a total of 100 mass parts of the non-volatile component in a composition, More preferably, it is 10-50 mass parts. By satisfy | filling this range, the adhesiveness of the composition obtained and the heat resistance of hardened | cured material will become a better thing.

  (E) The inorganic filler of a component may be used individually by 1 type, or may use 2 or more types together.

[Other ingredients]
In addition to the components (A) to (E), other components may be added. Specific examples thereof include a halogen-free phosphorus-based flame retardant and an NBR vulcanizing agent. Examples of the phosphorus-based flame retardant include SP-703 (manufactured by Shikoku Kasei) and the like under the trade name. Examples of the NBR vulcanizing agent include zinc oxide (ZnO).

-Rubber other than component (B) Furthermore, a rubber other than component (B) may be used in combination with the composition of the present invention as long as the heat resistance of the cured product is not impaired. Examples of the rubber other than the component (B) include acrylic rubber and NBR. Specific examples of this NBR include non-crosslinked NBR modified with a carboxylic acid (for example, NIPPOL 1072 (trade name) manufactured by ZEON CORPORATION), hydrogenated NBR (for example, ZETPOL 2020 manufactured by ZEON CORPORATION (commercial product) Non-crosslinked NBR such as name)). Examples of this acrylic rubber include acrylic rubber modified with carboxylic acid (03-72-23 (trade name) manufactured by Kyodo Kagaku). These rubbers other than the component (B) may be used alone or in combination of two or more.

  The rubber other than the component (B) is a range in which the cured epoxy resin in the cured product forms a continuous layer and (B) the crosslinked NBR modified with the carboxylic acid is not prevented from being dispersed to an average particle size of 1 μm or less. Specifically, it is 0-10 mass parts normally with respect to 100 mass parts of (A) component.

Organic solvent The above components (A) to (E) and optionally added components may be used as they are or dissolved or dispersed in an organic solvent, and the composition is dissolved or dispersed (hereinafter simply referred to as “solution”). ) May be used as prepared. Examples of the organic solvent include N, N-dimethylacetamide, methyl ethyl ketone (MEK), N, N-dimethylformamide, cyclohexanone, N-methyl-2-pyrrolidone, toluene, methanol, ethanol, isopropanol, THF, acetone and the like. Preferably, MEK and toluene are used.

  These organic solvents may be used alone or in combination of two or more.

  The total concentration of nonvolatile components in the adhesive composition containing the organic solvent is usually 10 to 45% by mass, preferably 20 to 40% by mass. When this concentration satisfies such a range, the adhesive composition has good applicability to a substrate such as an electrical insulating film, so that it has excellent workability without causing unevenness during coating and the environment. It is also excellent in terms of surface and economy.

[Preparation method]
The above components (A) to (E) and other components optionally added may be mixed by any means, but are usually mixed using, for example, a pot mill, a ball mill, a homogenizer, a super mill or the like. . At this time, the mixing condition of each component is not particularly limited, but it is desirable that the cured product obtained by curing the composition is mixed so as to form the following preferable phase structure.

[Phase structure]
The cured product obtained by curing the composition has a structure in which a cured epoxy resin becomes a continuous phase and a crosslinked NBR modified with a carboxylic acid becomes a dispersed phase. This continuous phase particularly contributes to improving the heat resistance of the cured product, and the dispersed phase particularly contributes to improving the flexibility of the cured product. The average particle size of this dispersed phase is usually 1 μm or less, preferably 0.1 to 0.8 μm. When this range is satisfied, the rubber component is uniformly dispersed in the cured product, and the cured epoxy resin becomes a continuous phase. Further, the storage elastic modulus at 85 ° C. of the cured product is preferably 200 MPa or more. When the average particle diameter of these dispersed phases and the storage modulus of the cured product satisfy the above ranges at the same time, the cured product has particularly excellent heat resistance, peel strength and solder heat resistance.

<Coverlay film>
The said composition can be used for manufacture of a coverlay film.

Configuration The configuration of the coverlay film having an adhesive layer made of a cured product of the adhesive composition of the present invention includes an electrically insulating film layer and an adhesive layer provided on the film layer. . Specifically, for example, a two-layer structure having an electrically insulating film layer and an adhesive layer; a three-layer structure having an electrically insulating film layer, an adhesive layer, and a release material layer can be given. The thickness of the adhesive layer can be selected depending on the purpose of use, but is usually 5 to 45 μm, preferably 5 to 35 μm, particularly preferably 15 to 25 μm in a dry state.

  The electrically insulating film constituting the electrically insulating film layer is not particularly limited as long as it is usually used for flexible copper-clad laminates and coverlay films. Specific examples thereof include polyimide film, polyethylene terephthalate (PET) film, polyester film, polyparabanic acid film, polyether ether ketone film, polyphenylene sulfide film, aramid film; glass fiber, aramid fiber, polyester fiber, etc. This is impregnated with a matrix epoxy resin, polyester resin, or diallyl phthalate resin, and film-like or sheet-like and bonded with copper foil. Heat resistance, dimensional stability, mechanical properties (elastic modulus) Polyimide film, polyparabanic acid film, and polyphenylene sulfide film are preferable, and a polyimide film is particularly preferable.

  The thickness of the electrically insulating film layer may be selected arbitrarily depending on the purpose of use, but is usually 12.5 to 75 μm, preferably 12.5 to 50 μm, particularly preferably 12.5 to 25 μm. In addition, in order to improve adhesion to the adhesive layer, clean the film surface, improve dimensional stability, etc., surface treatment such as low-temperature plasma treatment, corona discharge treatment, sandblast treatment, etc. is performed on one or both sides of this film. May be.

  The release material constituting the release material layer is not particularly limited as long as it can be removed without impairing the shape of the adhesive layer. Specific examples thereof include polyethylene (PE) film, polypropylene (PP) film, polymethylpentene (TPX) film; PE film and PP film with silicone release material; PE resin-coated paper, PP resin-coated paper, TPX resin-coated paper Etc. The release material may have any thickness, but is preferably 13 to 75 μm for a film and 50 to 200 μm for paper.

〔Production method〕
Next, the coverlay film manufacturing method of the present invention will be described by taking a coverlay film having a three-layer structure using an organic solvent as a preferred embodiment as an example.

  First, an adhesive composition (solution state) prepared by previously mixing the components (A) to (E) with other components optionally added and an organic solvent is electrically converted using a reverse roll coater, a comma coater or the like. Apply to one side of insulating film. The adhesive composition is semi-cured by removing the organic solvent in the adhesive composition by heating the film coated with this adhesive composition through an in-line dryer at 80 to 160 ° C. for 2 to 10 minutes. State. Next, the application surface of the adhesive composition of the film and the release material are pressure-bonded and laminated with a roll laminator to form a coverlay film. The release material is peeled off during use. The “semi-cured state” means a state in which the composition is dried or a state in which the curing reaction proceeds in a part thereof.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.

Examples and comparative examples
For each component of the adhesive composition, a mixture was prepared using the types shown in Table 1 in the compounding amounts (parts by mass) shown in the same table. This mixture was dissolved in a mixed solvent of MEK / toluene, stirred and mixed so as to be uniform, and an adhesive composition (solution state) having a total concentration of nonvolatile components of 35% by mass was prepared.

  Next, an applicator is applied to the adhesive composition (solution state) on a polyimide film (manufactured by Toray DuPont, trade name: Kapton V, thickness: 25 μm) so that the thickness after drying is 25 μm. Applied. Thereafter, MEK and toluene were removed under a heating and drying condition at 90 ° C. for 10 minutes in a blowing oven, whereby the adhesive composition was made into a semi-cured state to obtain a coverlay film. Using this coverlay film, characteristics were evaluated according to the following measurement / evaluation methods.

[Measurement and evaluation method]
1. Peel strength
According to JIS C6481, press machine (processing conditions; temperature: 160 ° C, pressure: 50 kg / cm ² ) with a glossy surface of 35 µm thick electrolytic copper foil (manufactured by Japan Energy) and the adhesive layer of the coverlay film. Time: 40 minutes) and after-curing at 150 ° C. for 4 hours to prepare a test sample. This sample is cut to a size of 1cm in width and 15cm in length to make a test piece. The polyimide film surface of the test piece is fixed, and an electrolytic copper foil is placed in a direction of 90 degrees at 50mm / min at 25 ° C. The minimum value of the load when peeled continuously at a speed of was measured and taken as the peel strength (N / cm).

2. Solder heat resistance (normal condition, moisture absorption)
The test sample prepared in the section “1. Peel strength” was cut into 25 mm squares to prepare test pieces. With respect to solder heat resistance (normal state), the test piece was floated on a solder bath for 30 seconds, and then the appearance of the test piece was visually confirmed to check for swelling and peeling. This operation was repeated while changing the temperature of the solder bath, and the maximum temperature (° C.) at which the sample did not swell and peel off was measured. Solder heat resistance (moisture absorption) was determined by leaving a test piece prepared in the same manner as the solder heat resistance (normal state) measurement for 24 hours in an atmosphere at a temperature of 40 ° C. and a relative humidity of 90%. After floating on the solder bath for 30 seconds, the appearance of the test piece was visually confirmed to check for swelling, peeling, and the like. This operation was repeated while changing the temperature of the solder bath, and the maximum temperature (° C.) at which the sample did not swell and peel off was measured.

3. Phase structure After dyeing an adhesive-attached film obtained by removing the electrolytic copper foil of the test sample prepared in the section “1. Peel strength” by etching treatment with osmium oxide, a transmission electron microscope (manufactured by JEOL, trade name: JEM-1010) was used to observe the phase structure of the cured product. By observation of the cured product with a transmission electron microscope, it was confirmed that the cured epoxy resin formed a continuous phase and the crosslinked NBR formed a dispersed phase having an average particle size of 1 μm or less.

4). Heat resistance (storage modulus)
The adhesive solution was applied to a glossy surface of 35 μm thick electrolytic copper foil (manufactured by Japan Energy) using an applicator so that the thickness after drying was 25 μm. Then, the adhesive composition was made into a semi-cured state by removing MEK and toluene in the adhesive solution in a blast oven under heating and drying conditions at 90 ° C. for 10 minutes. A glossy surface of 35 μm thick electrolytic copper foil (manufactured by Japan Energy Co., Ltd.) is adhered to the surface to which the adhesive composition is applied, and is pressed under conditions of 160 ° C. × 50 kgf / cm ² × 40 minutes, and further 160 ° C. × After cure for 3 hours. Then, the electrolytic copper foil was removed by etching the entire surface to prepare a cured adhesive film for measuring storage elastic modulus. Next, using this film, it was measured at 85 ° C. under the conditions of tensile measurement mode, frequency: 5 Hz, temperature increase rate: 10 ° C./min, using a viscoelasticity measuring device (trade name: RSAIII, manufactured by TA Instruments). The storage elastic modulus (MPa) was measured. It is evaluated that the higher the storage elastic modulus, the higher the film strength of the cured product and the better the heat resistance.

注）配合量の単位は質量部

Note) Unit of compounding amount is parts by mass

  In the table, components (A) to (E) and other components are as follows.

・ (A) Epoxy resin (1) Bisphenol A type epoxy resin (trade name: Epicoat 828, manufactured by Japan Epoxy Resin, 2 epoxy groups in one molecule)
(2) Bisphenol A type epoxy resin (trade name: Epicoat 828EL, made by Japan Epoxy Resin, 2 epoxy groups in one molecule)
(3) Bromine-containing epoxy resin (trade name: Epicoat 5046, manufactured by Japan Epoxy Resin, 2 epoxy groups in one molecule)
(4) Bromine-containing epoxy resin (trade name: Epicoat 5050, manufactured by Japan Epoxy Resin, 2 epoxy groups in one molecule)
(5) Chelate-modified epoxy resin (trade name: EP-49-20, manufactured by Asahi Denka, epoxy groups in one molecule: 2 or more)
(6) NBR modified epoxy resin (trade name: EPR-50-30, manufactured by Asahi Denka, epoxy groups in one molecule: 2 or more)
(7) Ortho-cresol novolac type epoxy resin (trade name: EOCN-103S, manufactured by Nippon Kayaku, epoxy groups in one molecule: 2 or more)
・ (B) Cross-linked NBR
(1) Crosslinked NBR modified with carboxylic acid (trade name: XER-91, manufactured by JSR)
・ (C) Curing agent (1) Phenol novolac resin (Brand name: BRG-558, manufactured by Dainippon Ink and Chemicals)
(2) Diamine-based curing agent (4,4′-diaminodiphenylsulfone (DDS))
・ (D) Curing accelerator (1) Imidazole-based curing accelerator (trade name: 2E4MZ, manufactured by Shikoku Chemicals)
(2) Tin borofluoride (Stella Chemical)
・ (E) Inorganic filler (1) Aluminum hydroxide (trade name: Hygielite H43STE, Showa Denko)
・ Other components (1) Core-shell type cross-linked butadiene (trade name: EXL2655, manufactured by Rohm and Haas)
(2) Core-shell type cross-linked acrylic rubber (trade name: EXL2314, manufactured by Rohm and Haas)
(3) Non-bridging hydrogenated NBR (trade name: Zetpol 2020, manufactured by Nippon Zeon)
(4) Non-crosslinked carboxyl group-containing NBR (trade name: PNR-1H, manufactured by JSR, high-purity product)
(5) Aromatic phosphoric ester amide (phosphorous flame retardant, trade name: SP-703, manufactured by Shikoku Chemicals)
(6) Zinc oxide (NBR vulcanizing agent, ZnO)

<Evaluation>
The compositions prepared in the examples satisfy the requirements of claim 1, and the cured or coverlay film is excellent in peel strength and solder heat resistance, and further has a storage elastic modulus at 85 ° C. Was 200 MPa or more, and was excellent in heat resistance.
On the other hand, the composition prepared in the comparative example does not contain the essential component (B) among the requirements of claim 1, and the cured product or coverlay film has a peel strength and a solder heat resistance. And at least one characteristic of heat resistance at high temperatures was inferior to that prepared in the examples.

Claims (4)

(A) epoxy resin,
(B) a crosslinked acrylonitrile-butadiene rubber modified with a carboxylic acid,
(C) a curing agent,
An adhesive composition comprising (D) a curing accelerator and (E) an inorganic filler.   2. A cured product of the adhesive composition according to claim 1, wherein the average particle is composed of a continuous phase composed of a cured epoxy resin and a crosslinked acrylonitrile-butadiene rubber modified with the (B) carboxylic acid in the continuous phase. The cured product having a dispersed phase having a diameter of 1 μm or less and a storage elastic modulus of 200 MPa or more at 85 ° C.   The coverlay film which has an electrically insulating film layer and the adhesive bond layer which consists of an adhesive composition of Claim 1 provided on this film layer. The coverlay film according to claim 3, wherein the electrically insulating film layer is a polyimide film layer.