Thermosetting resin composition, coverlay film, adhesive sheet, and flexible printed wiring board

Abstract

This thermosetting resin composition contains: an epoxy resin that is solid at 25°C; an epoxy resin that is non-solid at 25°C; a finely particulate rubber that is dispersed in the non-solid epoxy resin; a setting agent; an inorganic filler; and a polyurethane derived from a polycarbonate diol. The finely particulate rubber is contained at a quantity of 3-15 parts by mass relative to the total parts by mass of the solid epoxy resin and the non-solid epoxy resin. The acid value of the polyurethane derived from the polycarbonate diol is 10-30 mg KOH / g. The weight average molecular weight of the polyurethane derived from the polycarbonate diol is 15,000-60,000.

Description

[Technical field]

[0001] The present invention relates to a thermosetting resin composition, a coverlay film, an adhesive sheet, and a flexible printed wiring board. [Background technology]

[0002] Examples of sheet-like electronic materials constituting electronic devices include coverlay films, adhesive sheets, flexible printed wiring boards, etc. Such electronic materials are required to have a good balance of physical properties such as peel strength (hereinafter also referred to as peel strength), electrical properties such as electrical insulation reliability (hereinafter also referred to as migration properties), heat resistance properties such as solder heat resistance, and flame retardant properties (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-187810 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, sheet-like electronic materials are further required to be easily and efficiently processed, and to have excellent electrical insulation reliability under harsh conditions. Here, being easily and efficiently processed means being able to perform thermocompression bonding in a short time (hereinafter also referred to as quick press). Also, having excellent electrical insulation reliability under harsh conditions means having excellent electrical insulation reliability in an evaluation of electrical insulation reliability under high stress conditions of, for example, 110°C, 85% RH, and DC50V, i.e., BHAST (Biased Highly Accelerated temperature and humidity Stress Test).

[0005] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a thermosetting resin composition, a coverlay film, an adhesive sheet, and a flexible printed wiring board that can be quickly pressed and have excellent electrical insulation reliability in BHAST. [Means for solving the problem]

[0006] As a result of intensive research into achieving the above-mentioned object, the present inventors have found that the above-mentioned object can be achieved by a thermosetting resin composition comprising an epoxy resin that is solid at 25°C, an epoxy resin that is non-solid at 25°C, fine particle rubber dispersed in the non-solid epoxy resin, a curing agent, an inorganic filler, and a polyurethane derived from a polycarbonate diol, wherein the content of the fine particle rubber is 3 to 15 parts by mass relative to the total parts by mass of the solid epoxy resin and the non-solid epoxy resin, the acid value of the polyurethane derived from the polycarbonate diol is 10 to 30 mgKOH / g, and the weight average molecular weight of the polyurethane derived from the polycarbonate diol is 15,000 to 60,000, and thus have completed the present invention.

[0007] That is, the present invention is as follows. [1] A thermosetting resin composition comprising an epoxy resin that is solid at 25°C, an epoxy resin that is non-solid at 25°C, fine particle rubber dispersed in the non-solid epoxy resin, a curing agent, an inorganic filler, and a polyurethane derived from a polycarbonate diol, wherein the content of the fine particle rubber is 3 to 15 parts by mass relative to the total parts by mass of the solid epoxy resin and the non-solid epoxy resin, the acid value of the polyurethane derived from the polycarbonate diol is 10 to 30 mgKOH / g, and the weight average molecular weight of the polyurethane derived from the polycarbonate diol is 15,000 to 60,000.

[0008] [2] The thermosetting resin composition according to the above [1], wherein the fine particle rubber is composed of core-shell polymer particles.

[0009] [3] The thermosetting resin composition according to the above [1] or [2], wherein the number of parts by mass of the fine particle rubber and the non-solid epoxy resin is 15 to 40 parts by mass when the total number of parts by mass of the solid epoxy resin and the non-solid epoxy resin is 100 parts by mass.

[0010] [4] The thermosetting resin composition according to any one of the above [1] to [3], wherein the number of parts by mass of the polyurethane derived from the polycarbonate diol is 50 to 100 parts by mass when the total number of parts by mass of the solid epoxy resin and the non-solid epoxy resin is 100 parts by mass.

[0011] [5] The thermosetting resin composition according to any one of the above [1] to [4], wherein the number of parts by mass of the inorganic filler is 60 to 150 parts by mass when the total number of parts by mass of the solid epoxy resin and the non-solid epoxy resin is 100 parts by mass.

[0012] [6] A coverlay film comprising a substrate and an adhesive layer laminated on one side of the substrate, the adhesive layer comprising the thermosetting resin composition according to any one of [1] to [5] above.

[0013] [7] An adhesive sheet comprising the thermosetting resin composition according to any one of [1] to [5] above.

[0014] [8] A flexible printed wiring board comprising a substrate on which wiring is formed, and a coverlay film composed of a base material and an adhesive layer laminated on one side of the base material, the coverlay film being provided so that the adhesive layer is in contact with the surface of the substrate on which the wiring is formed, the coverlay film being the coverlay film described in [6] above. Effect of the Invention

[0015] According to the present invention, it is possible to provide a thermosetting resin composition, a coverlay film, an adhesive sheet, and a flexible printed wiring board that can be quickly pressed and have excellent electrical insulation reliability in BHAST. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a plan view showing a wiring pattern employed in a characteristic evaluation test of a flexible printed wiring board using the thermosetting resin composition of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, a detailed description will be given of a mode for carrying out the present invention (hereinafter, referred to as an embodiment). The following embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be carried out by appropriately modifying it within the scope of its gist.

[0018] (Thermosetting resin composition) The thermosetting resin composition of the present invention is preferably used mainly as a resin composition for electronic materials such as coverlay films, adhesive sheets, and flexible printed wiring boards.

[0019] The thermosetting resin composition of the embodiment includes an epoxy resin that is solid at 25° C., an epoxy resin that is non-solid at 25° C., fine particle rubber dispersed in the non-solid epoxy resin, a curing agent, an inorganic filler, and a polyurethane derived from a polycarbonate diol. The content of the fine particle rubber is 3 to 15 parts by mass relative to the total parts by mass of the solid epoxy resin and the non-solid epoxy resin, the acid value of the polyurethane derived from the polycarbonate diol is 10 to 30 mgKOH / g, and the weight average molecular weight of the polyurethane derived from the polycarbonate diol is 15,000 to 60,000.

[0020] (Epoxy resin) The epoxy resin contained in the thermosetting resin composition of the embodiment includes both an epoxy resin that is solid at 25°C and an epoxy resin that is non-solid at 25°C, from the viewpoints of uniformly mixing the thermosetting resin composition, spreading the resin into fine grooves between wirings (hereinafter also referred to as wiring embedding ability), improving the electrical insulation reliability after the thermosetting resin composition is cured, and imparting heat resistance.

[0021] From the viewpoint of increasing reactivity and from the viewpoint of increasing the electrical insulation reliability after the thermosetting resin composition is cured, the epoxy resin in a solid state at 25°C has two or more epoxy groups in one molecule, and the epoxy equivalent is preferably 150 to 500 g / eq, more preferably 150 to 350 g / eq. Examples of epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, novolac type epoxy resins, amine type epoxy resins, biphenyl type epoxy resins, and alicyclic epoxy resins, each of which has an epoxy equivalent within the above-mentioned range. From the viewpoint of electrical insulation reliability and flame retardancy, bisphenol A type epoxy resins are preferred, and biphenyl type epoxy resins are more preferred. Two or more types of epoxy resins may be used. In addition, the epoxy resin in a solid state at 25°C may be dissolved in an organic solvent in advance to facilitate mixing with other materials contained in the thermosetting resin composition. The epoxy equivalent of the epoxy resin can be measured in accordance with JIS K7236 2001.

[0022] The content of the epoxy resin solid at 25°C is preferably 60 to 85 parts by mass when the total of the epoxy resins (epoxy resin solid at 25°C and epoxy resin non-solid at 25°C) contained in the thermosetting resin composition is 100 parts by mass. When the content of the epoxy resin solid at 25°C is within the range of 60 to 85 parts by mass, for example, when the thermosetting resin composition is processed into a sheet and the cured state of the thermosetting resin composition is made into a semi-cured state (B stage), tackiness (stickiness) can be suppressed. Furthermore, air (air bubbles) mixed in during quick pressing can be reduced. Here, the parts by mass used in the present invention means parts by mass converted into non-volatile content. The parts by mass converted into non-volatile content means, for example, parts by mass of the resin (non-volatile content) excluding volatile components such as organic solvents contained in the resin. In addition, the semi-cured state (B stage) means a state in which the curing reaction of the thermosetting resin composition has progressed halfway but has not progressed completely.

[0023] The epoxy resin that is non-solid at 25°C means an epoxy resin that is fluid at 25°C. From the viewpoint of increasing the dispersibility of the fine particle rubber and from the viewpoint of increasing the peel strength of the sheet-like electronic material composed of the thermosetting resin composition, the non-solid epoxy resin has two or more epoxy groups in one molecule, and the epoxy equivalent is preferably 100 to 400 g / eq, more preferably 150 to 350 g / eq. The epoxy resin has an epoxy equivalent within the above-mentioned range, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, amine type epoxy resin, and alicyclic epoxy resin. Two or more kinds of epoxy resins may be used. From the viewpoint of heat resistance, bisphenol A type epoxy resin is preferred, and phenol novolac type epoxy resin is more preferred. In addition, from the viewpoint of expressing physical properties such as the peel strength of the sheet-like electronic material composed of the thermosetting resin composition, it is preferable to use a non-solid epoxy resin in which the fine particle rubber is uniformly dispersed at 25°C before preparing the thermosetting resin composition.

[0024] The content of the epoxy resin that is non-solid at 25° C. is preferably 15 to 40 parts by mass, more preferably 15 to 35 parts by mass, and even more preferably 15 to 30 parts by mass, when the total amount of the epoxy resins (epoxy resins that are solid at 25° C. and epoxy resins that are non-solid at 25° C.) contained in the thermosetting resin composition is taken as 100 parts by mass. When the content of the epoxy resin that is non-solid at 25° C. is within the range of 15 to 40 parts by mass, the peel strength of the sheet-like electronic material composed of the thermosetting resin composition can be maintained at a high level.

[0025] (Fine particle rubber) The fine particle rubber is preferably a core-shell polymer particle composed of a core layer and a shell layer covering the surface of the core layer.

[0026] The polymer constituting the core layer is a polymer having rubber-like elasticity. Examples of the polymer having rubber-like elasticity include diene rubber, acrylic rubber, styrene rubber, and polysiloxane rubber. The core layer may be composed of two or more kinds of polymers.

[0027] The polymer constituting the shell layer may be a (co)polymer obtained by copolymerizing one or more components selected from (meth)acrylic acid ester monomers, aromatic vinyl monomers, cyanide vinyl monomers, unsaturated acid derivatives, (meth)acrylamide derivatives, and maleimide derivatives. The polymer constituting the shell layer is bonded to the polymer constituting the core layer by graft polymerization. This allows a part or the whole surface of the core layer to be stably covered with the shell layer, preventing re-aggregation of the core-shell polymer particles.

[0028] From the viewpoint of compatibility with the epoxy resin, it is preferable that a functional group that reacts with the resin or curing agent contained in the thermosetting resin composition is introduced into the polymer constituting the shell layer. Examples of the functional group include a hydroxyl group, a carboxyl group, and an epoxy group, and from the viewpoint of improving compatibility with the epoxy resin, an epoxy group is preferable.

[0029] From the viewpoint of improving dispersibility, the size of the fine particle rubber is preferably 0.05 to 1 μm in average particle size.

[0030] The content of the fine particle rubber is preferably 3 to 15 parts by mass, more preferably 3 to 13 parts by mass, and even more preferably 3 to 10 parts by mass, when the total of the epoxy resins (solid epoxy resins at 25° C. and non-solid epoxy resins at 25° C.) contained in the thermosetting resin composition is taken as 100 parts by mass. By having the content of the fine particle rubber within the range of 3 to 15 parts by mass, the peel strength of the sheet-like electronic material composed of the thermosetting resin composition can be maintained at a high level without decreasing the electrical insulation reliability after the thermosetting resin composition is cured.

[0031] From the viewpoint of uniformly dispersing the fine particle rubber in the thermosetting resin composition, it is preferable to use fine particle rubber dispersed in an epoxy resin that is non-solid at 25°C.

[0032] Examples of fine particle rubber dispersed in a non-solid epoxy resin at 25° C. include MX-136, MX-153, MX-154, MX-170, MX-217, MX-257, MX-416, MX-451, MX-551, MX-960, and MX-965 manufactured by Kaneka Corporation.

[0033] (hardening agent) The curing agent is preferably one that cures the epoxy resin. Examples of the curing agent include diaminodiphenylmethane (DDM), diaminodiphenylsulfone (DDS), diaminodiphenylether (DDE), hexamethylenediamine, dicyandiamide, and phenol novolac. Among these, dicyandiamide is preferred from the viewpoint of ease of control of the curing reaction, and diaminodiphenylsulfone is more preferred. Two or more curing agents may be used.

[0034] From the viewpoint of improving wiring embedding properties and enhancing electrical insulation reliability after the thermosetting resin composition is cured, the equivalent of the curing agent is preferably 0.3 to 0.8 equivalents, and more preferably 0.3 to 0.6 equivalents, relative to 1 equivalent of the epoxy group of the epoxy resin (solid epoxy resin at 25° C. and non-solid epoxy resin at 25° C.) contained in the thermosetting resin composition.

[0035] (Inorganic filler) Examples of inorganic fillers include aluminum hydroxide, magnesium hydroxide, and silica. Among these, magnesium hydroxide is preferred, and aluminum hydroxide is more preferred, from the viewpoint of improving flame retardancy and wiring embedding properties, and from the viewpoint of imparting tack-free properties required for quick pressing. Two or more inorganic fillers may be used.

[0036] From the viewpoint of improving flame retardancy and wiring embedding property, and from the viewpoint of imparting tack-free property, the content of the inorganic filler is preferably 60 to 150 parts by mass, more preferably 60 to 120 parts by mass, and even more preferably 70 to 100 parts by mass, relative to 100 parts by mass of the total epoxy resins (epoxy resins that are solid at 25° C. and epoxy resins that are non-solid at 25° C.) contained in the thermosetting resin composition.

[0037] (Polyurethane derived from polycarbonate diol) The polyurethane derived from the polycarbonate diol contained in the thermosetting resin composition of the embodiment has at least one polycarbonate skeleton in the molecule. The number of polycarbonate skeletons is not particularly limited as long as the polyurethane is derived from the polycarbonate diol. By having at least one polycarbonate skeleton in the polyurethane molecule, hydrolysis of the polyurethane is suppressed in a high temperature and high humidity environment after the thermosetting resin composition is cured. This makes it possible to ensure high electrical insulation reliability after the thermosetting resin composition is cured. In addition, the thermosetting resin composition of the present invention is given film properties by containing the polyurethane derived from the polycarbonate diol. This gives the necessary flexibility to sheet-like electronic materials such as coverlay films and adhesive sheets.

[0038] The polycarbonate diol may be represented by the following general formula (1).

[0039] [ka] (R represents an alkylene group having 1 to 10 carbon atoms, and m represents an integer of 1 to 20.)

[0040] From the viewpoint of suppressing hydrolysis of polyurethane in a high temperature and high humidity environment after the thermosetting resin composition is cured, and from the viewpoint of improving the peel strength of a sheet-like electronic material composed of the thermosetting resin composition, it is preferable that the carbon number of R in the general formula (1) is 1 to 10 and m is 1 to 20.

[0041] Polycarbonate diol-derived polyurethane can be obtained by polymerizing polycarbonate diol represented by general formula (1) with polyisocyanate. The polyisocyanate is not particularly limited as long as it is a polyisocyanate that can react with polycarbonate diol represented by general formula (1) to form polyurethane. Examples of polyisocyanates include aromatic diisocyanates such as tolylene-2,4-diisocyanate, 4-methoxy-1,3-phenylene diisocyanate, 2,4-diisocyanate diphenyl ether, 4,4'-methylenebis(phenylene diisocyanate) (MDI), 2,4'-methylenebis(phenylene diisocyanate), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), and 1,5-naphthalene diisocyanate; aliphatic diisocyanates such as methylene diisocyanate and 1,6-hexane diisocyanate (HDI); and alicyclic diisocyanates such as 1,4-cyclohexylene diisocyanate, 4,4'-methylenebis(cyclohexyl diisocyanate), and isophorone diisocyanate (IPDI).

[0042] The polyisocyanate may be a compound obtained by reacting these isocyanate compounds with low molecular weight polyols or polyamines to convert the functional groups at the terminals into isocyanate groups. The polyisocyanates may be used alone or in combination of two or more kinds of polyisocyanates. From the viewpoints of heat resistance, flexibility, and reactivity, isophorone diisocyanate is preferred.

[0043] The polyurethane derived from the polycarbonate diol is preferably acidic from the viewpoint of improving the peel strength of the sheet-like electronic material composed of the thermosetting resin composition. The polyurethane derived from the acidic polycarbonate diol preferably has a hydroxyl group, a sulfo group, or a carboxyl group in the molecular chain (mainly the side chain) of the polyurethane, and more preferably has a carboxyl group from the viewpoint of improving the reactivity with the epoxy resin and from the viewpoint of improving the electrical properties of the thermosetting resin composition after curing. The acidity can be indicated by the acid value.

[0044] The acid value of the polyurethane derived from the polycarbonate diol is 10 to 30 mgKOH / g, preferably 10 to 25 mgKOH / g. By having the acid value of the polyurethane derived from the polycarbonate diol be 10 to 30 mgKOH / g, the wiring embedding property is improved, and the peel strength of the sheet-like electronic material composed of the thermosetting resin composition is improved.

[0045] The acid value of the polyurethane derived from the polycarbonate diol can be measured in accordance with JIS K0070.

[0046] From the viewpoint of increasing the peel strength of a sheet-like electronic material composed of a thermosetting resin composition, the content of the polyurethane derived from polycarbonate diol is preferably 50 to 100 parts by mass, more preferably 60 to 90 parts by mass, and even more preferably 70 to 80 parts by mass, relative to 100 parts by mass of the total epoxy resins (epoxy resins that are solid at 25°C and epoxy resins that are non-solid at 25°C) contained in the thermosetting resin composition.

[0047] The weight average molecular weight of the polyurethane derived from the polycarbonate diol is preferably 15,000 to 60,000, more preferably 30,000 to 60,000, and even more preferably 35,000 to 60,000. When the weight average molecular weight of the polyurethane derived from the polycarbonate diol is 15,000 to 60,000, the flexibility of the thermosetting resin composition after curing is improved, and the wiring embedding property is good. The weight average molecular weight of the polyurethane derived from the polycarbonate diol can be measured by gel permeation chromatography (GPC) using standard polystyrene having an average molecular weight of about 500 to about 1,000,000.

[0048] (Other ingredients) The thermosetting resin composition of the embodiment may further contain other additives, etc. Examples of the other additives include imidazole accelerators such as 2-methylimidazole, N-benzyl-2-methylimidazole, and 2-undecylimidazole, Lewis acid complexes such as boron trifluoride monoethylamine, polyamines, and curing accelerators such as melamine resins, dispersants, softeners, antioxidants, pigments, dyes, and silane coupling agents.

[0049] (Coverlay film) A coverlay film is used, for example, to protect wiring formed on a substrate. The coverlay film is composed of a base material and an adhesive layer laminated on one side of the base material. The adhesive layer may be provided on both sides of the film-like base material. According to a coverlay film having this configuration, the wiring surfaces of multiple substrates can be protected by one coverlay film. Furthermore, the substrate can be multi-layered.

[0050] The substrate constituting the coverlay film is a film-like substrate, and has a thickness of 2 to 75 μm.

[0051] Examples of the substrate for the coverlay film include polyimide (PI)-based substrates, polyamide (PA)-based substrates, polyethylene naphthalate (PEN)-based substrates, polyamideimide (PAI)-based substrates, polyethylene terephthalate (PET)-based substrates, polyphenylene sulfide (PPS)-based substrates, and liquid crystal (LCP)-based substrates. From the viewpoints of flame retardancy, electrical insulation reliability, heat resistance, and elastic modulus, polyimide (PI)-based substrates are preferred. In addition, the surface of the substrate can be subjected to a surface modification treatment such as a corona treatment or a plasma treatment. This modifies the surface of the substrate, improving the adhesion between the adhesive layer and the substrate.

[0052] The adhesive layer is made of the thermosetting resin composition of the embodiment. The adhesive layer has a thickness of 5 to 50 μm after drying. The cured state of the thermosetting resin composition constituting the adhesive layer is a semi-cured state (B stage).

[0053] The coverlay film is produced by the following procedure. A solution containing a thermosetting resin composition is prepared by dissolving the thermosetting resin composition in an organic solvent. The solution is applied onto a film-like substrate. Next, the solution is heated until the thermosetting resin composition reaches a semi-cured state (B stage). After cooling, a coverlay film is obtained in which an adhesive layer composed of the thermosetting resin composition is formed on the film-like substrate. The heating conditions are 100 to 250°C and 5 seconds to 30 minutes, and are adjusted depending on the coating thickness.

[0054] Examples of organic solvents include alcohols such as methanol and ethanol; glycols such as ethylene glycol and propylene glycol; glycol monoalkyl ethers such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether; glycol dialkyl ethers such as ethylene glycol dimethyl ether and ethylene glycol diethyl ether; alkyl esters such as methyl acetate, ethyl acetate, propyl acetate, and methyl acetoacetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; aliphatic hydrocarbons such as hexane, cyclohexane, and octane; amides such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone; and cyclic ethers such as tetrahydrofuran and dioxane.

[0055] The coating device is not particularly limited, and any known coater can be used, such as a die coater, a comma coater, or a gravure coater.

[0056] When the thickness of the adhesive layer constituting the coverlay film is 5 μm or less, the coverlay film can be produced by the following procedure. First, an adhesive layer is formed on the surface of a release film that has been subjected to a release treatment so that the thickness after drying is 5 μm. Then, a film-like substrate to be used for the coverlay film is prepared separately, and the substrate and the adhesive layer are laminated so that their surfaces meet. Next, the obtained laminate is heated and pressurized, and only the release film is peeled off. This makes it possible to obtain a coverlay film with an adhesive layer thickness of 5 μm.

[0057] (Adhesive sheet) The adhesive sheet is an adhesive material made of the thermosetting resin composition of the embodiment formed into a sheet shape.

[0058] The adhesive layer constituting the adhesive sheet has a thickness of 5 to 50 μm.

[0059] The adhesive sheet is produced by the following procedure. A solution containing a thermosetting resin composition is prepared by dissolving the thermosetting resin composition in an organic solvent. The solution is applied to the release-treated surface of a film-like substrate that has been subjected to a release treatment. Next, the solution is heated until the thermosetting resin composition reaches a semi-cured state (B stage). After cooling, an adhesive sheet is obtained in which an adhesive layer composed of the thermosetting resin composition is formed on the film-like substrate. The heating conditions are 100 to 250°C and 5 seconds to 30 minutes, and are adjusted according to the coating thickness. When in use, the film-like substrate is peeled off from the adhesive layer.

[0060] Examples of the treatment agent for release treatment used on the substrate that has been subjected to release treatment include silicone-based treatment agents and fluorine-based treatment agents.

[0061] Another example of an adhesive sheet configuration is one in which adhesive layers are provided on both sides of a film-like substrate from the viewpoint of improving rigidity and electrical insulation reliability.

[0062] Another example of the adhesive sheet is a prepreg in which a substrate such as a woven fabric or nonwoven fabric is impregnated with a thermosetting resin composition in order to improve the rigidity and electrical insulation reliability. The prepreg is produced by the following procedure. First, a woven fabric or nonwoven fabric made of fibers such as glass fiber is prepared as the substrate. Next, a solution containing a thermosetting resin composition in which the thermosetting resin composition is dissolved in an organic solvent is prepared. The substrate is impregnated with the solution. The substrate is pulled out of the solution and heated until the attached thermosetting resin composition reaches the B stage. After cooling, a B stage prepreg is obtained.

[0063] The adhesive sheet can be used as an interlayer adhesive for bonding substrates such as flexible printed wiring boards, etc. Furthermore, the adhesive sheet can protect the wiring by covering the wiring.

[0064] (Flexible Printed Circuit Board) A flexible printed wiring board comprises a substrate on which wiring is formed, and a coverlay film composed of a base material and an adhesive layer laminated on one side of the base material, with the coverlay film being provided so that the adhesive layer is in contact with the surface of the substrate on which the wiring is formed.

[0065] The wiring formed on the substrate is, for example, wiring formed by etching the copper layer of a copper-plated laminate or a copper-clad laminate. The wiring formed on another substrate may be wiring formed by inkjet printing using conductive ink. The material of the wiring may be other metals such as silver and zinc instead of copper.

[0066] The thickness of the substrate used in the flexible printed wiring board is not particularly limited, but is 15 to 200 μm in order for the substrate to have flexibility.

[0067] A flexible printed wiring board is manufactured by the following procedure. A substrate on which wiring is formed, and a coverlay film composed of a base material and an adhesive layer laminated on one side of the base material are prepared. Next, the coverlay film is laminated so that the adhesive layer is in contact with the surface of the substrate on which wiring is formed, and then heated and pressed. In this way, a flexible printed wiring board is obtained. The heating and pressing conditions are 120 to 250°C, 5 seconds to 120 minutes, and 1 to 10 MPa, and are set according to the laminate configuration. EXAMPLES

[0068] The present invention will be described in more detail with reference to the following examples, which are not to be construed as limiting the present invention in any way.

[0069] The following components were used as the resin compositions in the examples and comparative examples. (Epoxy resin) (1) Epoxy resin A: a biphenyl type epoxy resin that is solid at 25°C, with an epoxy equivalent of 290 g / eq (manufactured by Nippon Kayaku Co., Ltd., NC3000H), (2) Epoxy resin B: non-solid bisphenol A type epoxy resin at 25°C, epoxy equivalent 190g / eq (DIC Corporation, Epicron 850), (3) Epoxy resin C: A non-solid microparticle rubber dispersed epoxy resin (phenol novolac type) at 25°C, with an epoxy equivalent of 231 g / eq and containing 25 parts by mass of microparticle rubber (polybutadiene rubber, average particle size 0.1 μm) per 100 parts by mass of total solids (Kaneka Corporation, MX-217); (4) Epoxy resin D: non-solid fine particle rubber dispersed epoxy resin (bisphenol A type) at 25°C, epoxy equivalent 294g / eq, fine particle rubber (polybutadiene rubber, average particle size 0.1μm) content 37 parts by mass per 100 parts by mass of total solids (manufactured by Kaneka Corporation, MX-257).

[0070] (hardening agent) Diaminodiphenylsulfone: amine value 62 g / eq (Konishi Chemical Industry Co., Ltd., 3,3'-DAS).

[0071] (Inorganic filler) Aluminum hydroxide (Nippon Light Metal Co., Ltd., BF013).

[0072] (Polyurethane derived from polycarbonate diol) [Synthesis of Polyurethane A derived from Polycarbonate Diol] A 1-liter flask equipped with a stirrer, a thermometer, and a cooling tube was charged with 250.0 g of (a) carbonate-based polyol (Ube Industries, Ltd., Ethanacole (registered trademark) UH-100 (hydroxyl value 112 mgKOH / g)), 32.1 g of (b) dimethylolpropanoic acid, and 104.2 g of (c) isophorone diisocyanate. In addition, as a solvent, dimethylacetamide equivalent to 10% by mass of the total amount of (a), (b), and (c) and toluene equivalent to 45% by mass of the total amount of (a), (b), and (c) were added and stirred at 100 ° C. Thereafter, the mixture was reacted until no NCO groups remained, and then methyl ethyl ketone equivalent to 45% by mass of the total amount of (a), (b), and (c) was added to obtain a polyurethane resin solution having a resin content of 45% by mass.

[0073] Polyurethanes B to J derived from polycarbonate diol were synthesized in the same manner as in the synthesis of polyurethane A derived from polycarbonate diol, except that the amount of each component added was changed as shown in Table 1.

[0074] [Table 1]

[0075] (Other softening ingredients) (1) Polyester-based polyurethane K: number average molecular weight 13,000, acid value 35 mgKOH / g (manufactured by Toyobo Co., Ltd., UR-3500), (2) Acrylonitrile butadiene rubber L: acid value 40 mg KOH / g (manufactured by JSR Corporation, JSR XER-32C).

[0076] In the examples and comparative examples, the evaluation and measurement methods were as follows.

[0077] <Peel strength> (1) Sample preparation procedure (1-1) Preparation of coverlay film A resin composition that would become an adhesive layer was applied to one side of a 12.5 μm thick polyimide film (Kaneka Corporation, Apical 12.5NPI) so that the thickness after drying would be 25 μm, and the film was dried at 160° C. for 10 minutes until it reached a semi-cured state (B stage). Then, a release PET film was laminated on the adhesive layer side at 100° C. to obtain a coverlay film with a release PET film.

[0078] (1-2) Preparation of measurement samples The release PET film was peeled off from the coverlay film prepared in (1-1), and the adhesive layer surface was bonded to the glossy surface of rolled copper foil (JX Nippon Mining & Metals Corporation, BHY-22B-T, thickness 35 μm), and heated and pressed at 185°C, 3.0 MPa, and for 60 seconds. After that, it was heated in an oven at 160°C for 1 hour to obtain a measurement sample.

[0079] (2)Measurement method The measurement sample prepared in (1-2) was cut to a width of 10 mm and a length of 100 mm, and the peel strength in the 180° direction (parallel to the surface of the measurement sample) was measured under the following measurement conditions using an autograph AGS-500 manufactured by Shimadzu Corporation. The measurement conditions were copper foil drawing and a test speed of 50 mm / min. The evaluation criteria were as follows: Excellent: Peel strength is 10N / cm or more. Good: Peel strength is 7N / cm or more and less than 10N / cm. Poor: Peel strength is less than 7N / cm.

[0080] <Electrical insulation reliability (BHAST)> (1) Sample preparation procedure (1-1) Preparation of coverlay film A resin composition that would become an adhesive layer was applied to one side of a 12.5 μm thick polyimide film (Kaneka Corporation, Apical 12.5NPI) so that the thickness after drying would be 15 μm, and the film was dried at 160° C. for 10 minutes until it reached a semi-cured state (B stage). Then, a release PET film was laminated on the adhesive layer side at 100° C. to obtain a coverlay film with a release PET film.

[0081] (1-2) Preparation of the substrate The shiny copper foil side of a two-layer board (PNS H0509RAC, manufactured by Arisawa Manufacturing Co., Ltd.) was etched to obtain an adherend with a wiring pattern shown in Figure 1, in which the wiring width (L) and spacing (S) were each 20 μm (hereinafter referred to as L / S=20 / 20).

[0082] (1-3) Preparation of measurement samples The release PET film was peeled off from the coverlay film prepared in (1-1), and the adhesive layer was laminated so that the surface of the adhesive layer faced the surface of the adherend prepared in (1-2) on which the wiring was formed, and the laminate was heated and pressurized at 185°C, 3.0 MPa, and for 60 seconds. After that, the laminate was heated in an oven at 160°C for 1 hour to obtain a measurement sample.

[0083] (2)Measurement method One end of the wiring was connected to the equipment wiring so that a voltage was applied to the wiring pattern. After connection, the wiring was visually inspected for the presence or absence of short circuits, dentite, and other changes in appearance after 200 hours under conditions of 110°C, 85% RH, and DC 50V. The evaluation criteria were as follows: Excellent: After 200 hours, there was no short circuit or change in appearance. Good: After 200 hours, no short circuit occurred, but there was a change in appearance. Poor: A short circuit occurred before 200 hours had elapsed, and there was also a change in appearance.

[0084] <Wiring burial ability> (1) Sample preparation procedure (1-1) Preparation of coverlay film A resin composition that would become an adhesive layer was applied to one side of a 12.5 μm thick polyimide film (Kaneka Corporation, Apical 12.5NPI) so that the thickness after drying would be 15 μm, and the film was heated at 160° C. for 10 minutes until it reached a semi-cured state (B stage). Then, a release PET film was laminated on the adhesive layer side at 100° C. to obtain a coverlay film with a release PET film.

[0085] (1-2) Preparation of the substrate The adherend was a two-layer substrate consisting of an electrolytic copper foil (manufactured by JX Nippon Mining & Metals, thickness 18 μm) with a 25 μm thick polyimide layer formed on the rough surface. The shiny copper foil surface of the substrate was etched to obtain wiring patterns with L / S=50 / 50, 60 / 60, 70 / 70, 80 / 80, 90 / 90, and 100 / 100.

[0086] (2) Evaluation method The release PET film was peeled off from the coverlay film prepared in (1-1), and the surface of the adhesive layer was laminated to face the surface of the adherend prepared in (1-2) on which the wiring was formed, and the laminate was subjected to thermocompression bonding (quick press) under conditions of 185°C, 3.0 MPa, 30 seconds, and 185°C, 3.0 MPa, 60 seconds, respectively. The laminated sample was then heated in an oven at 160°C for 1 hour. The laminated sample was then cooled, and the sample was cut perpendicular to the longitudinal direction of the wiring. The cut surface was polished and observed with an optical microscope to evaluate whether the wiring embedding was good or not. The evaluation criteria were as follows: Excellent: The quick press molding time was 30 seconds, and the resin was spread evenly between the wiring grooves. Good: When the quick press molding time was 30 seconds, the resin did not penetrate into the grooves between the wires, but after 60 seconds the resin penetrated. Poor: In both cases where the quick press molding time was 30 seconds and 60 seconds, the resin did not reach the grooves between the wiring.

[0087] Example 1 70 parts by mass of epoxy resin A and 30 parts by mass of epoxy resin C were added to a container to make the total mass of the epoxy resins 100 parts by mass. To this, 10.4 parts by mass of a curing agent and a polyurethane derived from polycarbonate diol were added. B 75 parts by mass of aluminum hydroxide, 90 parts by mass of Department, yes As an organic solvent, 400 parts by mass of methyl ethyl ketone was added, and the mixture was then stirred at room temperature to obtain a thermosetting resin composition.

[0088] (Example 2) to (Example 13), (Comparative Example 1) to (Comparative Example 11) As shown in Tables 2 and 3, thermosetting resin compositions were obtained by changing the type and content of each component in the same manner as in Example 1. The unit of content in the tables is parts by mass unless otherwise specified.

[0089] [Table 2]

[0090] [Table 3]

[0091] As shown in Table 2, the thermosetting resin compositions of Examples 1 to 13 were excellent in processability (wiring embedding ability) by quick pressing and also excellent in electrical insulation reliability in BHAST. Furthermore, in the solder heat resistance evaluation, Examples 1 to 13 showed no swelling or peeling even when contacted with a solder bath at 260°C for 60 seconds or more, and had excellent solder heat resistance. Furthermore, all of the Examples had the UL94 standard V-0 grade, which is a flame retardancy rating required for sheet-like electronic materials.

[0092] The solder heat resistance was evaluated by <Peel strength> (1) A measurement sample (laminate) prepared according to the sample preparation procedure was floated in a solder bath set at 260°C so that the copper foil surface of the laminate was in contact with the solder bath. This state was maintained for 60 seconds or more, and the presence or absence of blistering and peeling was visually confirmed.

[0093] The present invention allows various embodiments and modifications without departing from the broad spirit and scope of the present invention. The above-described embodiments are for the purpose of explaining the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is indicated by the claims, not the embodiments. Various modifications made within the scope of the claims and within the scope of the meaning of the invention equivalent thereto are considered to be within the scope of the present invention.

Claims

1. The epoxy resin includes an epoxy resin that is solid at 25° C., an epoxy resin that is non-solid at 25° C., fine particle rubber dispersed in the non-solid epoxy resin, a curing agent, an inorganic filler, and a polyurethane derived from a polycarbonate diol, the content of the fine particle rubber is 3 to 15 parts by mass when the total number of parts by mass of the solid epoxy resin and the non-solid epoxy resin is 100 parts by mass, The acid value of the polyurethane derived from the polycarbonate diol is 10 to 30 mgKOH / g; The thermosetting resin composition, wherein the weight average molecular weight of the polyurethane derived from the polycarbonate diol is 15,000 to 60,000.

2. The thermosetting resin composition according to claim 1 , wherein the fine particle rubber is composed of core-shell polymer particles.

3. 3. The thermosetting resin composition according to claim 1, wherein the number of parts by mass of the fine particle rubber and the non-solid epoxy resin is 15 to 40 parts by mass when the total number of parts by mass of the solid epoxy resin and the non-solid epoxy resin is 100 parts by mass.

4. The thermosetting resin composition according to any one of claims 1 to 3, wherein the number of parts by mass of the polyurethane derived from the polycarbonate diol is 50 to 100 parts by mass when the total number of parts by mass of the solid epoxy resin and the non-solid epoxy resin is 100 parts by mass.

5. The thermosetting resin composition according to any one of claims 1 to 4, wherein the number of parts by mass of the inorganic filler is 60 to 150 parts by mass when the total number of parts by mass of the solid epoxy resin and the non-solid epoxy resin is 100 parts by mass.

6. A coverlay film comprising a substrate and an adhesive layer laminated on one side of the substrate, the adhesive layer comprising the thermosetting resin composition according to claim 1 .

7. An adhesive sheet comprising the thermosetting resin composition according to claim 1 .

8. A flexible printed wiring board comprising: a substrate on which wiring is formed; and a coverlay film composed of a base material and an adhesive layer laminated on one side of the base material, the coverlay film being provided so that the adhesive layer is in contact with the surface of the substrate on which the wiring is formed, A flexible printed wiring board, wherein the coverlay film is the coverlay film according to claim 6.

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