JP2012067221A - Insulating sheet and laminated structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulating sheet which is used in bonding a thermal conductor having a thermal conductivity of 10 W/m K or more to an electrically conductive layer, excels in handling properties in an uncured state, further has a low elastic modulus of a cured product after curing, and excels in the thermal conductivity of the cured product.SOLUTION: The insulating sheet is used in bonding a thermal conductor having a thermal conductivity of 10 W/m K or more to an electrically conductive layer. The insulating sheet includes a polyvinyl acetal resin having a weight average molecular weight of 10,000 or more, a curable compound having an epoxy group or an oxetane group, a curing agent, and a filler having a thermal conductivity of 10 W/m K or more.

Description

  The present invention relates to an insulating sheet used for adhering a thermal conductor having a thermal conductivity of 10 W / m · K or more to a conductive layer, and more specifically, has excellent handling properties in an uncured state, Further, the present invention relates to an insulating sheet having a low elastic modulus of a cured product after curing and excellent thermal conductivity of the cured product, and a laminated structure using the insulating sheet.

  In electronic devices and communication devices, printed wiring boards having an insulating layer are used. The insulating layer is formed using a paste-like or sheet-like insulating adhesive material.

  As an example of the insulating adhesive material, Patent Document 1 below includes a resin composition and an adhesive film including an epoxy resin, a cyanate ester resin, an adduct of a guanidine compound and an epoxy resin, and a metal-based curing catalyst. It is disclosed. The resin composition and the adhesive film may contain a polymer resin and an inorganic filler. Polymer resins include polyvinyl acetal resin, phenoxy resin, polyimide resin, polyamideimide resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, polyphenylene ether resin, polycarbonate resin, polyetheretherketone resin and polyester resin. Is listed.

  Patent Document 2 below discloses a liquid epoxy resin having two or more epoxy groups, a liquid aromatic epoxy resin having three or more epoxy groups, and a specific amino group-containing phosphate ester compound. And a resin composition and an adhesive film containing an organic polymer component and an inorganic filler are disclosed. Examples of the organic polymer component include polyvinyl acetal resin, phenoxy resin, polyamide resin, and polyaminoimide resin.

JP 2010-90237 A JP 2009-295589 A

  In recent years, miniaturization and high performance of electric devices have been advanced. For this reason, in the printed wiring board used for the said electronic device and communication apparatus, multilayering and a thin film are progressing, and the mounting density of an electronic component is high. Along with this, a large amount of heat is easily generated from the electronic components, and the need to dissipate the generated heat is increasing. In order to dissipate heat, the insulating layer of the printed wiring board needs to have high thermal conductivity.

  However, in the conventional printed wiring board using the insulating adhesive material described in Patent Documents 1 and 2, the insulating layer has a low thermal conductivity, and sufficient heat dissipation may not be obtained. Furthermore, the elastic modulus of the insulating layer may be too high. For this reason, when the insulating layer is exposed to a high temperature in a reflow process or the like, a crack may occur in the insulating layer.

  Furthermore, the adhesive films described in Patent Documents 1 and 2 may have low handling properties.

  The object of the present invention is to adhere a heat conductor having a thermal conductivity of 10 W / m · K or more to a conductive layer, and has excellent handling properties in an uncured state, and further a cured product after curing. An insulating sheet having a low elastic modulus and excellent thermal conductivity of the cured product, and a laminated structure using the insulating sheet.

  According to a wide aspect of the present invention, there is provided an insulating sheet used for bonding a thermal conductor having a thermal conductivity of 10 W / m · K or more to a conductive layer, and a polyvinyl acetal having a weight average molecular weight of 10,000 or more. There is provided an insulating sheet comprising a resin, a curable compound having an epoxy group or an oxetane group, a curing agent, and a filler having a thermal conductivity of 10 W / m · K or more.

  The polyvinyl acetal resin is preferably polyvinyl butyral. The glass transition temperature of the polyvinyl acetal resin is preferably 40 ° C. or higher and 75 ° C. or lower. It is preferable that the content rate of the hydroxyl group of the said polyvinyl acetal resin is 20 mol% or more and 40 mol% or less.

  The filler preferably has a new Mohs hardness of 9 or less.

  The curing agent preferably does not have an aromatic skeleton. The curing agent is preferably an acid anhydride represented by any of the following formulas (1) to (4) or dicyandiamide.

  In said formula (4), R1 and R2 show hydrogen, a C1-C5 alkyl group, or a hydroxyl group, respectively.

  The insulating sheet according to the present invention preferably further contains an antioxidant.

  The laminated structure according to the present invention includes a heat conductor having a thermal conductivity of 10 W / m · K or more, an insulating layer laminated on at least one surface of the heat conductor, and the heat conduction of the insulating layer. A conductive layer laminated on the surface opposite to the surface on which the body is laminated, and the insulating layer is formed by curing an insulating sheet configured according to the present invention.

  The heat conductor is preferably a metal.

  The insulating sheet according to the present invention includes a polyvinyl acetal resin having a weight average molecular weight of 10,000 or more, a curable compound having an epoxy group or an oxetane group, a curing agent, and a filler having a thermal conductivity of 10 W / m · K or more. Therefore, the handleability of the insulating sheet in an uncured state can be enhanced. Furthermore, the elastic modulus of the cured product formed by curing the insulating sheet according to the present invention can be lowered, and the thermal conductivity of the cured product can be increased.

  In the laminated structure according to the present invention, a conductive layer is laminated on at least one surface of a thermal conductor having a thermal conductivity of 10 W / m · K or more via an insulating layer. Since it forms by hardening the insulating sheet comprised according to invention, the heat from the conductive layer side is easy to be transmitted to the said heat conductor through an insulating layer. For this reason, heat can be efficiently dissipated by the heat conductor.

FIG. 1 is a partially cutaway front sectional view schematically showing a laminated structure according to an embodiment of the present invention.

  Details of the present invention will be described below.

  The insulating sheet according to the present invention has a polyvinyl acetal resin (A) having a weight average molecular weight of 10,000 or more, a curable compound (B) having an epoxy group or an oxetane group, a curing agent (C), and a thermal conductivity. And a filler (D) that is 10 W / m · K or more.

  By adopting the above composition, the handleability of the insulating sheet in an uncured state can be enhanced. Furthermore, the elastic modulus of the hardened | cured material of an insulating sheet can be made low, and heat conductivity can be made high.

  Hereinafter, first, details of each component contained in the insulating sheet according to the present invention will be described.

(Polyvinyl acetal resin (A))
The polyvinyl acetal resin (A) contained in the insulating sheet according to the present invention is not particularly limited as long as the weight average molecular weight is 10,000 or more. A conventionally known polyvinyl acetal resin can be used as the polyvinyl acetal resin. As for polyvinyl acetal resin (A), only 1 type may be used and 2 or more types may be used together.

  The polyvinyl acetal resin (A) is excellent in compatibility with the curable compound (B) having an epoxy group or an oxetane group. For example, the polyvinyl acetal resin (A) is sufficiently compatible with the curable compound (B) having an epoxy group or an oxetane group, and the polyvinyl acetal resin (A) and the curable compound (B) are in phase in the insulating sheet. Hard to separate. For this reason, the elasticity modulus of the hardened | cured material of an insulating sheet becomes low. Furthermore, the heat resistance and adhesiveness of the hardened | cured material of an insulating sheet also become high.

  The polyvinyl acetal resin (A) can be produced, for example, by acetalizing polyvinyl alcohol with an aldehyde. The polyvinyl alcohol can be produced, for example, by saponifying polyvinyl acetate. The saponification degree of the polyvinyl alcohol is generally 80 to 99.8 mol%.

  The number of carbon atoms of the acetal group contained in the polyvinyl acetal resin is not particularly limited. The aldehyde used when manufacturing the said polyvinyl acetal resin is not specifically limited. The carbon number of the acetal group in the polyvinyl acetal resin is preferably 3 or 4. When the carbon number of the acetal group in the polyvinyl acetal resin is 3 or more, the glass transition temperature of the insulating sheet is sufficiently low.

  The aldehyde is not particularly limited. In general, an aldehyde having 1 to 10 carbon atoms is preferably used as the aldehyde. Examples of the aldehyde having 1 to 10 carbon atoms include n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, 2-ethylbutyraldehyde, n-hexylaldehyde, n-octylaldehyde, n-nonylaldehyde, n- Examples include decyl aldehyde, formaldehyde, acetaldehyde, and benzaldehyde. Among these, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-hexylaldehyde or n-valeraldehyde is preferable, propionaldehyde, n-butyraldehyde or isobutyraldehyde is more preferable, and n-butyraldehyde is still more preferable. As for the said aldehyde, only 1 type may be used and 2 or more types may be used together.

  The polyvinyl acetal resin (A) is preferably polyvinyl butyral. By using polyvinyl butyral, the glass transition temperature of the insulating sheet can be further lowered.

  The glass transition temperature of the polyvinyl acetal resin (A) is preferably 40 ° C. or higher and 75 ° C. or lower. When the glass transition temperature of the polyvinyl acetal resin (A) is 40 to 75 ° C., thermal degradation of the polyvinyl acetal resin can be suppressed, and the elastic modulus of the cured product can be further reduced.

  The hydroxyl group content (hydroxyl group amount) of the polyvinyl acetal resin (A) is preferably 10 mol% or more, more preferably 15 mol% or more, still more preferably 20 mol% or more, preferably 40 mol% or less, more preferably. It is 35 mol% or less, and particularly preferably 30 mol% or less. When the hydroxyl group content is not less than the above lower limit, the handling property of the insulating sheet in an uncured state becomes high, and the handling of the insulating sheet becomes easy. When the hydroxyl group content is not more than the above upper limit, the heat resistance of the cured product is further increased.

  The hydroxyl group content of the polyvinyl acetal resin (A) is particularly preferably 20 mol% or more and 40 mol% or less, and most preferably 20 mol% or more and 30 mol% or less. When the hydroxyl group content is 20 to 40 mol% or 20 to 30 mol%, the compatibility between the polyvinyl acetal resin (A) and the curable compound (B) is further enhanced, and the dispersion of the filler (D) is further increased. Sex is also higher.

  The content of hydroxyl groups in the polyvinyl acetal resin (A) is a molar fraction obtained by dividing the amount of ethylene groups to which hydroxyl groups are bonded by the total amount of ethylene groups in the main chain. The amount of ethylene group to which the hydroxyl group is bonded can be determined, for example, by measuring the amount of ethylene group to which the hydroxyl group of polyvinyl alcohol as a raw material is bonded in accordance with JIS K6726 “Testing method for polyvinyl alcohol”. it can.

  The acetylation degree (acetyl group amount) of the polyvinyl acetal resin (A) is preferably 3 mol% or less. When the acetylation degree is not more than the above upper limit, the heat resistance of the cured product is further increased.

  The degree of acetylation is obtained by subtracting the amount of ethylene groups to which acetal groups are bonded and the amount of ethylene groups to which hydroxyl groups are bonded from the total amount of ethylene groups of the main chain, The mole fraction obtained by dividing by. The amount of ethylene group to which the acetal group is bonded can be measured, for example, according to JIS K6728 “Testing method for polyvinyl butyral”.

  The degree of acetalization of the polyvinyl acetal resin (in the case of polyvinyl butyral, the degree of butyralization) is preferably 60 mol% or more, more preferably 63 mol% or more, preferably 90 mol% or less, more preferably 85 mol% or less, More preferably, it is 80 mol% or less. When the degree of acetalization is not less than the above lower limit, compatibility and moisture resistance can be improved. When the degree of acetalization is less than or equal to the above upper limit, the reaction time required for producing a polyvinyl acetal resin is shortened.

  The degree of acetalization is a mole fraction obtained by dividing the amount of ethylene groups to which acetal groups are bonded by the total amount of ethylene groups in the main chain.

  The degree of acetalization is obtained by measuring the amount of acetyl group and the amount of vinyl alcohol by a method based on JIS K6728 “Testing method for polyvinyl butyral” or by a method using nuclear magnetic resonance (NMR). The molar fraction can be calculated from the result, and then calculated by subtracting the amount of acetyl group and the amount of vinyl alcohol from 100 mol%.

  When the polyvinyl acetal resin is a polyvinyl butyral resin, the degree of acetalization (degree of butyralization) and the amount of acetyl group are calculated from the results measured by a method according to JIS K6728 “Testing methods for polyvinyl butyral”. obtain.

  The weight average molecular weight of the polyvinyl acetal resin (A) is 10,000 or more. The weight average molecular weight of the polyvinyl acetal resin (A) is more preferably 20000 or more, further preferably 30000 or more, preferably 1000000 or less, more preferably 250,000 or less. When the weight average molecular weight of the polyvinyl acetal resin (A) is 10,000 or less, the insulating sheet is likely to be thermally deteriorated. As the weight average molecular weight of the polyvinyl acetal resin (A) is larger, the thermal deterioration of the insulating sheet can be suppressed. When the weight average molecular weight of the polyvinyl acetal resin (A) is not more than the above upper limit, the compatibility between the polyvinyl acetal resin (A) and another resin is further enhanced. As a result, the handling property of the insulating sheet and the heat resistance of the cured product of the insulating sheet are further enhanced.

  The content of the polyvinyl acetal resin (A) is 20% by weight or more and 60% by weight or less in the total 100% by weight of all the resin components in the insulating sheet (hereinafter sometimes abbreviated as “all resin component X”). Is preferred. The content of the polyvinyl acetal resin (A) in the total 100% by weight of all the resin components X is more preferably 30% by weight or more, and more preferably 50% by weight or less. When the content of the polyvinyl acetal resin (A) is not less than the above lower limit, the handleability of the insulating sheet in an uncured state is further enhanced. When the content of the polyvinyl acetal resin (A) is not more than the above upper limit, the dispersibility of the filler (D) is increased. The total resin component X refers to the total of the polyvinyl acetal resin (A), the curable compound (B), the curing agent (C), and other resin components added as necessary. The total resin component X does not contain the filler (D). All the resin components X contain an antioxidant (E).

(Curable compound having epoxy group or oxetane group (B))
The curable compound (B) contained in the insulating sheet according to the present invention is not particularly limited as long as it has an epoxy group or an oxetane group. As the curable compound (B) having an epoxy group or an oxetane group, a conventionally known epoxy compound or oxetane compound can be used. Oxetane groups are also called oxetanyl groups. The curable compound (B) is cured by the action of the curing agent (C). As for a curable compound (B), only 1 type may be used and 2 or more types may be used together.

  The curable compound (B) may contain an epoxy compound (B1) having an epoxy group, or may contain an oxetane compound (B2) having an oxetane group.

  From the viewpoint of further improving the heat resistance and dielectric breakdown characteristics of the cured product, the curable compound (B) preferably has an aromatic skeleton.

  Specific examples of the epoxy compound (B1) having an epoxy group include an epoxy monomer having a bisphenol skeleton, an epoxy monomer having a dicyclopentadiene skeleton, an epoxy monomer having a naphthalene skeleton, an epoxy monomer having an adamantane skeleton, and an epoxy having a fluorene skeleton. Examples of the monomer include an epoxy monomer having a biphenyl skeleton, an epoxy monomer having a bi (glycidyloxyphenyl) methane skeleton, an epoxy monomer having a xanthene skeleton, an epoxy monomer having an anthracene skeleton, and an epoxy monomer having a pyrene skeleton. These hydrogenated products or modified products may be used. As for an epoxy compound (B1), only 1 type may be used and 2 or more types may be used together.

  Examples of the epoxy monomer having a bisphenol skeleton include an epoxy monomer having a bisphenol A type, bisphenol F type, or bisphenol S type bisphenol skeleton.

  Examples of the epoxy monomer having a dicyclopentadiene skeleton include dicyclopentadiene dioxide and a phenol novolac epoxy monomer having a dicyclopentadiene skeleton.

  Examples of the epoxy monomer having a naphthalene skeleton include 1-glycidylnaphthalene, 2-glycidylnaphthalene, 1,2-diglycidylnaphthalene, 1,5-diglycidylnaphthalene, 1,6-diglycidylnaphthalene, 1,7-diglycidyl. Naphthalene, 2,7-diglycidylnaphthalene, triglycidylnaphthalene, 1,2,5,6-tetraglycidylnaphthalene and the like can be mentioned.

  Examples of the epoxy monomer having an adamantane skeleton include 1,3-bis (4-glycidyloxyphenyl) adamantane and 2,2-bis (4-glycidyloxyphenyl) adamantane.

  Examples of the epoxy monomer having a fluorene skeleton include 9,9-bis (4-glycidyloxyphenyl) fluorene, 9,9-bis (4-glycidyloxy-3-methylphenyl) fluorene, and 9,9-bis (4- Glycidyloxy-3-chlorophenyl) fluorene, 9,9-bis (4-glycidyloxy-3-bromophenyl) fluorene, 9,9-bis (4-glycidyloxy-3-fluorophenyl) fluorene, 9,9-bis (4-Glycidyloxy-3-methoxyphenyl) fluorene, 9,9-bis (4-glycidyloxy-3,5-dimethylphenyl) fluorene, 9,9-bis (4-glycidyloxy-3,5-dichlorophenyl) Fluorene and 9,9-bis (4-glycidyloxy-3,5-dibromophenyl) Fluorene, and the like.

  Examples of the epoxy monomer having a biphenyl skeleton include 4,4'-diglycidylbiphenyl and 4,4'-diglycidyl-3,3 ', 5,5'-tetramethylbiphenyl.

  Examples of the epoxy monomer having a bi (glycidyloxyphenyl) methane skeleton include 1,1′-bi (2,7-glycidyloxynaphthyl) methane, 1,8′-bi (2,7-glycidyloxynaphthyl) methane, 1,1′-bi (3,7-glycidyloxynaphthyl) methane, 1,8′-bi (3,7-glycidyloxynaphthyl) methane, 1,1′-bi (3,5-glycidyloxynaphthyl) methane 1,8'-bi (3,5-glycidyloxynaphthyl) methane, 1,2'-bi (2,7-glycidyloxynaphthyl) methane, 1,2'-bi (3,7-glycidyloxynaphthyl) Examples include methane and 1,2′-bi (3,5-glycidyloxynaphthyl) methane.

  Examples of the epoxy monomer having a xanthene skeleton include 1,3,4,5,6,8-hexamethyl-2,7-bis-oxiranylmethoxy-9-phenyl-9H-xanthene.

  Specific examples of the oxetane compound (B2) having an oxetane group include, for example, 4,4′-bis [(3-ethyl-3-oxetanyl) methoxymethyl] biphenyl, 1,4-benzenedicarboxylate bis [(3- Ethyl-3-oxetanyl) methyl] ester, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, and oxetane-modified phenol novolac. As for an oxetane compound (B2), only 1 type may be used and 2 or more types may be used together.

  The weight average molecular weight of the curable compound (B) is preferably less than 10,000. The weight average molecular weight of the curable compound (B) is preferably 200 or more, more preferably 600 or less, and still more preferably 550 or less. When the weight average molecular weight of the curable compound (B) is not less than the above lower limit, the volatility of the curable compound (B) is lowered, and the handleability of the insulating sheet is further enhanced. When the weight average molecular weight of the curable compound (B) is not more than the above upper limit, the adhesiveness of the cured product is further enhanced. Furthermore, the insulating sheet is hard and not easily brittle, and the adhesiveness of the cured product is further enhanced.

  In the total 100% by weight of all the resin components X, the content of the curable compound (B) is preferably 10% by weight or more and 60% by weight or less. The content of the curable compound (B) in 100% by weight of the total resin component X is more preferably 20% by weight or more, and more preferably 50% by weight or less. When the content of the curable compound (B) is not less than the above lower limit, the adhesiveness and heat resistance of the cured product are further increased. When the content of the curable compound (B) is not more than the above upper limit, the handling property of the insulating sheet is further enhanced.

(Curing agent (C))
The curing agent (C) contained in the insulating sheet according to the present invention is not particularly limited as long as the insulating sheet can be cured. The curing agent (C) is preferably a thermosetting agent. As for a hardening | curing agent (C), only 1 type may be used and 2 or more types may be used together.

  Examples of the curing agent (C) include a phenol resin, an acid anhydride having an aromatic skeleton or an alicyclic skeleton, a water additive of the acid anhydride, or a modified product of the acid anhydride. Dicyandiamide is also used as the curing agent (C). By using these curing agents, a cured product having an excellent balance of heat resistance, moisture resistance and electrical properties can be obtained. These curing agents are thermosetting agents.

  From the viewpoint of further reducing the elastic modulus of the cured product, the curing agent (C) is preferably an acid anhydride, a water additive of the acid anhydride or a modified product of the acid anhydride, or dicyandiamide.

  The phenol resin is not particularly limited. Specific examples of the phenol resin include phenol novolak, o-cresol novolak, p-cresol novolak, t-butylphenol novolak, dicyclopentadiene cresol, polyparavinylphenol, bisphenol A type novolak, xylylene modified novolak, decalin modified novolak, Examples include poly (di-o-hydroxyphenyl) methane, poly (di-m-hydroxyphenyl) methane, and poly (di-p-hydroxyphenyl) methane. Among these, from the viewpoint of further enhancing the flexibility of the insulating sheet and the flame retardancy of the cured product, a phenol resin having a melamine skeleton, a phenol resin having a triazine skeleton, or a phenol resin having an allyl group is preferable.

  Examples of commercially available phenol resins include MEH-8005, MEH-8010, and MEH-8015 (all of which are manufactured by Meiwa Kasei Co., Ltd.), YLH903 (manufactured by Japan Epoxy Resin Co., Ltd.), LA-7052, LA-7054, and LA-7751. LA-1356 and LA-3018-50P (all of which are manufactured by DIC), PS6313 and PS6492 (manufactured by Gunei Chemical Co., Ltd.), and the like.

  An acid anhydride having an aromatic skeleton, a water additive of the acid anhydride, or a modified product of the acid anhydride is not particularly limited. Examples of the acid anhydride having an aromatic skeleton, a water addition of the acid anhydride, or a modified product of the acid anhydride include, for example, a styrene / maleic anhydride copolymer, benzophenone tetracarboxylic acid anhydride, pyromellitic acid anhydride, Trimellitic anhydride, 4,4'-oxydiphthalic anhydride, phenylethynylphthalic anhydride, glycerol bis (anhydrotrimellitate) monoacetate, ethylene glycol bis (anhydrotrimellitate), methyltetrahydrophthalic anhydride Examples include acid, methylhexahydrophthalic anhydride, and trialkyltetrahydrophthalic anhydride. Of these, methyl nadic acid anhydride or trialkyltetrahydrophthalic anhydride is preferable. By using methyl nadic acid anhydride or trialkyltetrahydrophthalic anhydride, the water resistance of the cured product can be increased.

  Examples of commercially available acid anhydrides having an aromatic skeleton, water additives of the acid anhydrides, or modified products of the acid anhydrides include SMA Resin EF30, SMA Resin EF40, SMA Resin EF60, and SMA Resin EF80 (any of the above Also manufactured by Sartomer Japan), ODPA-M and PEPA (all manufactured by Manac), Ricacid MTA-10, Ricacid MTA-15, Ricacid TMTA, Ricacid TMEG-100, Ricacid TMEG-200, Ricacid TMEG-300, Ricacid TMEG-500, Ricacid TMEG-S, Ricacid TH, Ricacid HT-1A, Ricacid HH, Ricacid MH-700, Ricacid MT-500, Ricacid DSDA and Ricacid TDA-100 (all of which are manufactured by Shin Nippon Rika Co., Ltd.) PICLON B4400, EPICLON B650, and EPICLON B570 (all manufactured by both DIC Corporation).

  From the viewpoint of further reducing the elastic modulus of the cured product, the curing agent (C) preferably does not have an aromatic skeleton. From the viewpoint of further reducing the elastic modulus of the cured product, the curing agent (C) is an acid anhydride having no aromatic skeleton, a water additive of the acid anhydride or a modified product of the acid anhydride, or Dicyandiamide is preferred. Dicyandiamide has no aromatic skeleton. From the viewpoint of further reducing the elastic modulus of the cured product, the curing agent (C) is an acid anhydride having an alicyclic skeleton, a water additive of the acid anhydride or a modified product of the acid anhydride, or dicyandiamide. It is more preferable that By using dicyandiamide, the glass transition temperature of the insulating sheet is further lowered.

  From the viewpoint of further reducing the elastic modulus of the cured product, the curing agent (C) is an acid anhydride having a polyalicyclic skeleton, a water additive of the acid anhydride or a modified product of the acid anhydride, or An acid anhydride having an alicyclic skeleton obtained by addition reaction of a terpene compound and maleic anhydride, a water additive of the acid anhydride or a modified product of the acid anhydride, or dicyandiamide is preferable. In addition, the use of these curing agents further increases the flexibility of the cured product and the moisture resistance and adhesion of the cured product.

  Examples of the acid anhydride having an alicyclic skeleton, a water addition of the acid anhydride, or a modified product of the acid anhydride include methyl nadic acid anhydride, acid anhydride having a dicyclopentadiene skeleton, and the acid anhydride And the like.

  Examples of commercially available acid anhydrides having the alicyclic skeleton, water additions of the acid anhydrides, or modified products of the acid anhydrides include Ricacid HNA and Ricacid HNA-100 (all of which are manufactured by Shin Nippon Rika Co., Ltd.) , And EpiCure YH306, EpiCure YH307, EpiCure YH308H, EpiCure YH309 (all of which are manufactured by Japan Epoxy Resin Co., Ltd.) and the like.

  The curing agent (C) is more preferably an acid anhydride represented by any of the following formulas (1) to (4) or dicyandiamide. By using this preferable curing agent, the flexibility of the cured product and the moisture resistance or adhesion of the cured product are further increased.

  In said formula (4), R1 and R2 show hydrogen, a C1-C5 alkyl group, or a hydroxyl group, respectively.

  In order to adjust the curing speed or the physical properties of the cured product, the curing agent and the curing accelerator may be used in combination.

  The said hardening accelerator is not specifically limited. Specific examples of the curing accelerator include tertiary amines, imidazoles, imidazolines, triazines, organic phosphorus compounds, quaternary phosphonium salts and diazabicycloalkenes such as organic acid salts. Examples of the curing accelerator include organometallic compounds, quaternary ammonium salts, metal halides, and the like. Examples of the organometallic compounds include zinc octylate, tin octylate and aluminum acetylacetone complex.

  Examples of the curing accelerator include a high melting point imidazole curing accelerator, a high melting point dispersion type latent curing accelerator, a microcapsule type latent curing accelerator, an amine salt type latent curing accelerator, and a high temperature dissociation type and thermal cation. A polymerization type latent curing accelerator or the like can be used. As for the said hardening accelerator, only 1 type may be used and 2 or more types may be used together.

  Examples of the high melting point dispersion type latent accelerator include amine addition type accelerators in which dicyandiamide or amine is added to an epoxy monomer or the like. Examples of the microcapsule type latent accelerator include a microcapsule type latent accelerator in which the surface of an imidazole, phosphorus or phosphine accelerator is coated with a polymer. Examples of the high-temperature dissociation type and thermal cationic polymerization type latent curing accelerator include Lewis acid salts and Bronsted acid salts.

  The curing accelerator is preferably a high melting point imidazole curing accelerator. By using a high melting point imidazole curing accelerator, the reaction system can be easily controlled, and the curing speed of the insulating sheet and the physical properties of the cured product can be more easily adjusted. A high-melting-point curing accelerator having a melting point of 100 ° C. or higher is excellent in handleability. Accordingly, the melting accelerator preferably has a melting point of 100 ° C. or higher.

  In a total of 100% by weight of all the resin components X, the content of the curing agent (C) is preferably 10% by weight or more and 40% by weight or less. In the total 100% by weight of all the resin components X, the content of the curing agent (C) is more preferably 12% by weight or more, more preferably 25% by weight or less. When the content of the curing agent (C) is not less than the above lower limit, it is easy to sufficiently cure the insulating sheet. When the content of the curing agent (C) is not more than the above upper limit, it becomes difficult to generate an excessive curing agent (C) that does not participate in curing. For this reason, the heat resistance and adhesiveness of hardened | cured material become still higher.

(Filler (D))
The filler (D) contained in the insulating sheet according to the present invention is not particularly limited as long as the thermal conductivity is 10 W / m · K or more. By using this filler (D), the thermal conductivity of the cured product can be increased. As a result, the heat dissipation of the cured product is increased. As for a filler (D), only 1 type may be used and 2 or more types may be used together.

  When the thermal conductivity of the filler (D) is smaller than 10 W / m · K, it is difficult to sufficiently increase the thermal conductivity of the cured product. The thermal conductivity of the filler (D) is preferably 15 W / m · K or more, more preferably 20 W / m · K or more. The upper limit of the thermal conductivity of the filler (D) is not particularly limited. Inorganic fillers having a thermal conductivity of about 300 W / m · K are widely known, and inorganic fillers having a thermal conductivity of about 200 W / m · K are easily available.

  From the viewpoint of further improving the heat dissipation of the cured product, the filler (D) is preferably an inorganic filler.

  The filler (D) is preferably at least one selected from the group consisting of alumina, synthetic magnesite, crystalline silica, boron nitride, aluminum nitride, silicon nitride, silicon carbide, zinc oxide and magnesium oxide. More preferred is at least one selected from the group consisting of boron nitride, aluminum nitride, silicon nitride, silicon carbide, zinc oxide and magnesium oxide. By using these preferable fillers, the heat dissipation of the cured product can be further enhanced.

  The filler (D) is more preferably at least one selected from the group consisting of spherical alumina, crushed alumina and spherical aluminum nitride, and more preferably spherical alumina or spherical aluminum nitride. By using these preferable fillers, the heat dissipation of the cured product can be further enhanced.

  The new Mohs hardness of the filler (D) is preferably 12 or less, more preferably 9 or less.

  When the new Mohs hardness of the filler (D) is 9 or less, the workability of the cured product can be further enhanced.

  From the viewpoint of further improving the workability of the cured product, since the new Mohs hardness is 9 or less, the filler (D) is at least selected from the group consisting of synthetic magnesite, crystalline silica, zinc oxide, and magnesium oxide. One type is preferable.

  The filler (D) may be a spherical filler or a crushed filler. The filler (D) is particularly preferably spherical. In the case of a spherical filler, since it can be filled with high density, the heat dissipation of the cured product can be further enhanced.

  Examples of the crushed filler include crushed alumina. The crushed filler can be obtained, for example, by crushing a massive inorganic substance using a uniaxial crusher, a biaxial crusher, a hammer crusher, a ball mill, or the like. By using the crushed filler, the filler in the insulating sheet is likely to have a structure that is bridged or effectively brought close together. Therefore, the thermal conductivity of the cured product of the insulating sheet can be further enhanced. Moreover, the crushed filler is generally cheaper than a normal filler. For this reason, the cost of an insulating sheet can be reduced by using the crushed filler.

  The average particle size of the crushed filler is preferably 12 μm or less. If the average particle diameter exceeds 12 μm, the crushed filler cannot be dispersed with high density in the insulating sheet, and the dielectric breakdown characteristics of the cured product of the insulating sheet may deteriorate. The average particle size of the crushed filler is more preferably 10 μm or less, and preferably 1 μm or more. If the average particle size of the crushed filler is too small, it may be difficult to fill the crushed filler with high density.

  The aspect ratio of the crushed filler is not particularly limited. The aspect ratio of the crushed filler is preferably 1.5 or more and 20 or less. Fillers with an aspect ratio of less than 1.5 are relatively expensive. Therefore, the cost of the insulating sheet increases. When the aspect ratio is 20 or less, filling of the crushed filler is easy.

  The aspect ratio of the crushed filler can be determined, for example, by measuring the crushed surface of the filler using a digital image analysis type particle size distribution measuring device (trade name: FPA, manufactured by Nippon Luft).

  When the filler (D) is a spherical filler, the average particle diameter of the spherical filler is preferably 0.1 μm or more and 40 μm or less. When the average particle size is 0.1 μm or more, the filler (D) can be easily filled at a high density. When the average particle size is 40 μm or less, the dielectric breakdown characteristics of the cured product are further enhanced.

  The “average particle diameter” is an average particle diameter obtained from a volume average particle size distribution measurement result measured by a laser diffraction particle size distribution measuring apparatus.

  In 100% by volume of the insulating sheet, the content of the filler (D) is preferably 20% by volume or more and 90% by volume or less. When the content of the filler (D) is 20 to 90% by volume, the heat dissipation property of the cured product is further enhanced, and the handling property of the insulating sheet is further improved. From the viewpoint of further improving the heat dissipation of the cured product, the content of the filler (D) in 100% by volume of the insulating sheet is particularly preferably 30% by volume or more. The content of the filler (D) in 100% by volume of the insulating sheet is more preferably 35% by volume or more, more preferably 85% by volume or less, still more preferably 80% by volume or less, particularly preferably 70% by volume or less, and most preferably. Is 60% by volume or less. When the content of the filler (D) is not less than the above lower limit, the heat dissipation of the cured product is further enhanced. When the content of the filler (D) is not more than the above upper limit, the handling property of the insulating sheet is further enhanced.

(Antioxidant (E))
From the viewpoint of further improving the heat resistance of the cured product, the insulating sheet according to the present invention more preferably contains an antioxidant (E). As for antioxidant (E), only 1 type may be used and 2 or more types may be used together.

  Examples of the antioxidant (E) include phenol-based antioxidants, phosphorus-based antioxidants, amine-based antioxidants, sulfur-based antioxidants, and lactone-based antioxidants. From the viewpoint of further increasing the heat resistance of the cured product, the antioxidant (E) is at least one selected from the group consisting of phenolic antioxidants, phosphorus antioxidants, and amine antioxidants. The phenolic antioxidant is more preferable.

  Specific examples of the phenolic antioxidant include pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], thiodiethylenebis [3- (3,5-di-). tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N, N′-hexane-1,6-diylbis [3- ( 3,5-di-tert-butyl-4-hydroxyphenyl) propionamide], benzenepropanoic acid, 3,5-bis (1,1-dimethylethyl) -4-hydroxy C7-C9 side chain alkyl ester, 3, 3 ′, 3 ″, 5,5 ′, 5 ″ -hexa-tert-butyl-a, a ′, a ″-(mesitylene-2 4,6-triyl) tri-p-cresol, 4,6-bis (dodecylthiomethyl) -o-cresol, 4,6-bis (octylthiomethyl) -o-cresol, ethylenebis (oxyethylene) bis [ 3- (5-tert-butyl 4-hydroxy-m-tolyl) propionate], hexamethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,3,5- Tris (3,5-di-tert-butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 1,3,5-tris [( 4-tert-butyl-3-hydroxy-2,6-xylyl) methyl] -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 2,6-di-tert -Butyl-4- [4,6-bis (octylthio) -1,3,5-triazin-2-ylamino] phenol and diethyl {[3,5-bis (1,1-dimethylethyl) -4-hydroxy Phenyl] methyl} phosphonate and the like.

  Examples of the phosphorus antioxidant include cyclohexylphosphine and triphenylphosphine. Furthermore, specific examples of the phosphorus antioxidant include tris (2,4-di-tert-butylphenyl) phosphite, tris {2-[(2,4,8,10-tetra-tert-butyldibenzo). [D, f] [1,3,2] dioxaphosphine-6-yl) oxy] ethyl} amine, bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite, bis [2 , 4-Bis (1,1-dimethylethyl) -6-methylphenyl] ethyl ester phosphorous acid and tetrakis (2,4-di-tert-butylphenyl) (1,1-biphenyl) -4,4 ′ -Diyl bisphosphonite etc. are mentioned.

  Specific examples of the amine antioxidant include triethylamine, dicyandiamide, melamine, ethyldiamino-S-triazine, 2,4-diamino-S-triazine, 2,4-diamino-6-tolyl-S-triazine, 2 , 4-diamino-6-xylyl-S-triazine, quaternary ammonium salt derivatives, and the like.

  Specific examples of the lactone antioxidant include a reaction product of 3-hydroxy-5,7-di-tert-butyl-furan-2-one and o-xylene.

  Examples of commercially available phenolic antioxidants include IRGANOX 1010, IRGANOX 1035, IRGANOX 1076, IRGANOX 1135, IRGANOX 245, IRGANOX 259, IRGANOX 295 (all of which are manufactured by Ciba Japan), ADK STAB AO-30, ADK STAB AO-40, ADK STAB AO-50, ADK STAB AO-60, ADK STAB AO-70, ADK STAB AO-80, ADK STAB AO-90, ADK STAB AO-330 (all of which are manufactured by ADEKA), Sumilizer GA-80, and Sumizer MD -S, Sumilizer BBM-S, Sumilizer GM, Sumilizer GS (F), Sumilizer GP , All manufactured by Sumitomo Chemical Co., Ltd.), HOSTANOX O10, HOSTANOX O16, HOSTANOX O14, HOSTANOX O3 (all are manufactured by Clariant), Antage BHT, Antage W-300, Antage W-400, Antage W500 (and above, any As well as SEENOX 224M and SEENOX 326M (all of which are manufactured by Sipro Kasei Co., Ltd.).

  Commercially available products of the above phosphorus antioxidants include Adeastab PEP-4C, Adeastab PEP-8, Adeastab PEP-24G, Adeastab PEP-36, Adeastab HP-10, Adeastab 2112, Adeastab 260, Adeastab 522A, Adeastab 1178, Adeastab 1500, Adeastab C, Adeastab 135A, Adeastab 3010, Adeastab TPP (all are made by ADEKA), Sandstub P-EPQ, Hostanox PAR24 (all are made by Clariant), and JP-312L, JP-318 -0, JPM-308, JPM-313, JPP-613M, JPP-31, JPP-2000PT, JPH-3800 (all of which are manufactured by Johoku Chemical Industry Co., Ltd.) Etc. The.

  The content of the antioxidant (E) in the total 100% by weight of the total resin component X is preferably 0.01% by weight or more and 5.0% by weight or less. In the total 100% by weight of all resin components X, the content of the antioxidant (E) is more preferably 0.05% by weight or more, more preferably 3% by weight or less. When the content of the antioxidant (E) is not less than the above lower limit, the heat resistance of the cured product is further increased. When the content of the antioxidant (E) is not more than the above upper limit, it is difficult to generate an excessive antioxidant (E) that does not greatly contribute to the improvement of heat resistance.

(Other ingredients)
The insulating sheet according to the present invention may contain rubber particles. By using the rubber particles, the stress relaxation property and flexibility of the insulating sheet can be enhanced.

  The insulating sheet according to the present invention may contain a dispersant. Use of the dispersant can further enhance the thermal conductivity and dielectric breakdown characteristics of the cured product.

  The dispersant preferably has a functional group containing a hydrogen atom having hydrogen bonding properties. When the dispersing agent has a functional group containing a hydrogen atom having hydrogen bonding properties, the thermal conductivity and dielectric breakdown characteristics of the cured product can be further enhanced. Examples of the functional group containing a hydrogen atom having hydrogen bonding include a carboxyl group (pKa = 4), a phosphoric acid group (pKa = 7), a phenol group (pKa = 10), and the like.

  The pKa of the functional group containing a hydrogen atom having hydrogen bonding property is preferably 2 or more, more preferably 3 or more, preferably 10 or less, more preferably 9 or less. When the pKa of the functional group is not less than the lower limit, the acidity of the dispersant does not become too high. Therefore, the storage stability of the insulating sheet is further enhanced. When the pKa of the functional group is not more than the above upper limit, the function as the dispersant is sufficiently fulfilled, and the thermal conductivity and dielectric breakdown characteristics of the cured product are further enhanced.

  The functional group containing a hydrogen atom having hydrogen bonding properties is preferably a carboxyl group or a phosphate group. In this case, the thermal conductivity and dielectric breakdown characteristics of the cured product are further enhanced.

  Specific examples of the dispersant include a polyester carboxylic acid, a polyether carboxylic acid, a polyacrylic carboxylic acid, an aliphatic carboxylic acid, a polysiloxane carboxylic acid, a polyester phosphoric acid, and a polyether type. Examples thereof include phosphoric acid, polyacrylic phosphoric acid, aliphatic phosphoric acid, polysiloxane phosphoric acid, polyester phenol, polyether phenol, polyacrylic phenol, aliphatic phenol, and polysiloxane phenol. As for the said dispersing agent, only 1 type may be used and 2 or more types may be used together.

  In 100% by weight of the insulating sheet, the content of the dispersant is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, preferably 20% by weight or less, more preferably 10% by weight or less. . When the content of the dispersant is not less than the above lower limit and not more than the upper limit, aggregation of the filler (D) can be suppressed, and the heat dissipation and dielectric breakdown characteristics of the cured product can be further enhanced.

  In order to further improve the handling property, the insulating sheet according to the present invention may contain a base material such as glass cloth, glass nonwoven fabric, and aramid nonwoven fabric. However, even if the base material is not included, the insulating sheet has a self-supporting property at room temperature (23 ° C.) and an excellent handling property. Therefore, the insulating sheet preferably does not contain a base material, and particularly preferably does not contain glass cloth. When an insulating sheet does not contain the said base material, the thickness of an insulating sheet can be made thin and the thermal conductivity of hardened | cured material can be improved further. Furthermore, when an insulating sheet does not contain the said base material, various processes, such as a laser processing or a drilling process, can also be easily performed to an insulating sheet as needed. In addition, self-supporting means that the shape of a sheet can be maintained and handled as a sheet even if there is no support such as a PET film or copper foil.

  The insulating sheet according to the present invention may contain a styrene polymer, a (meth) acrylic polymer, a phenoxy resin, or the like.

  Furthermore, the insulating sheet according to the present invention may contain a tackifier, a plasticizer, a coupling agent, a thixotropic agent, a flame retardant, a photosensitizer, a colorant, and the like as necessary.

(Insulating sheet)
The insulating sheet according to the present invention is used for bonding a heat conductor having a thermal conductivity of 10 W / m · K or more to a conductive layer.

  The manufacturing method of the insulating sheet which concerns on this invention is not specifically limited. The insulating sheet can be obtained, for example, by forming a mixture obtained by mixing the above-described materials into a sheet shape by a method such as a solvent casting method or an extrusion film forming method. Defoaming is preferred when forming into a sheet.

  The thickness of the insulating sheet is not particularly limited. The thickness of the insulating sheet is preferably 10 μm or more, more preferably 50 μm or more, further preferably 70 μm or more, preferably 300 μm or less, more preferably 200 μm or less, and still more preferably 120 μm or less. When the thickness is not less than the above lower limit, the insulating property of the cured product of the insulating sheet is increased. When the thickness is less than or equal to the above upper limit, the heat dissipation becomes high when the metal body is bonded to the conductive layer.

  The glass transition temperature Tg of the insulating sheet in an uncured state is preferably 25 ° C. or lower. When the glass transition temperature is 25 ° C. or lower, the insulating sheet is hard and not easily brittle at room temperature. For this reason, the handleability of the insulating sheet in an uncured state is enhanced.

  When the insulating sheet is cured, the tensile elastic modulus at 25 ° C. of the cured product of the insulating sheet is preferably 15000 MPa or less, more preferably 10,000 MPa or less. When the tensile elastic modulus at 25 ° C. of the cured product of the insulating sheet is not more than the above upper limit, the cured product of the insulating sheet is not too hard and brittle, and cracks or the like are hardly generated in the cured product of the insulating sheet.

  The tensile elastic modulus can be measured, for example, in a tensile mode using a DMA device (DVA-200, manufactured by IT Measurement Control Co., Ltd.). Moreover, when measuring the tensile elasticity modulus of the hardened | cured material of an insulating sheet, the hardened | cured material of an insulating sheet is obtained by making it harden | cure by the temperature of two steps of 120 degreeC for 1 hour and then 200 degreeC for 1 hour.

  The thermal conductivity of the cured product of the insulating sheet is preferably 0.7 W / m · K or more, more preferably 1.0 W / m · K or more, and further preferably 1.5 W / m · K or more. The heat dissipation of the hardened | cured material of an insulating sheet becomes high enough that heat conductivity is more than the said minimum.

  The dielectric breakdown voltage of the cured product of the insulating sheet is preferably 30 kV / mm or more, more preferably 40 kV / mm or more, still more preferably 50 kV / mm or more, particularly preferably 80 kV / mm or more, and most preferably 100 kV / mm or more. is there. If the dielectric breakdown voltage is too low, the insulating property may be lowered when the insulating sheet is used for a large current application such as for a power element.

(Laminated structure)
The insulating sheet according to the present invention constitutes an insulating layer of a laminated structure in which a conductive layer is laminated via an insulating layer on at least one side of a thermal conductor having a thermal conductivity of 10 W / m · K or more. Is preferably used.

  In FIG. 1, an example of the laminated structure using the insulating sheet which concerns on one Embodiment of this invention is shown.

  The laminated structure 1 shown in FIG. 1 is opposite to the heat conductor 2, the insulating layer 3 laminated on one surface 2a of the heat conductor 2, and the surface of the insulating layer 3 on which the heat conductor 2 is laminated. And a conductive layer 4 laminated on the surface on the side. The insulating layer 3 is formed by curing the insulating sheet according to the present invention. The heat conductivity of the heat conductor 2 is 10 W / m · K or more.

  It is only necessary that the insulating layer 3 and the conductive layer 4 are laminated in this order on at least one surface 2a of the heat conductor 2, and the insulating layer and the conductive layer are also formed on the other surface 2b of the heat conductor 2. You may laminate | stack in order.

  In the laminated structure 1, since the insulating layer 3 has a high thermal conductivity, heat from the conductive layer 4 side is easily transmitted to the thermal conductor 2 through the insulating layer 3. In the laminated structure 1, heat can be efficiently dissipated by the heat conductor 2.

  For example, after bonding a metal body to each conductive layer such as a laminated board or multilayer wiring board provided with copper circuits on both sides, copper foil, copper plate, semiconductor element or semiconductor package via an insulating sheet, the insulating sheet is cured. By doing so, the laminated structure 1 can be obtained.

  The heat conductor whose heat conductivity is 10 W / m · K or more is not particularly limited. Examples of the heat conductor having a thermal conductivity of 10 W / m · K or more include aluminum, copper, alumina, beryllia, silicon carbide, silicon nitride, aluminum nitride, and graphite sheet. Especially, it is preferable that the heat conductor whose said heat conductivity is 10 W / m * K or more is copper or aluminum. Copper or aluminum is excellent in heat dissipation.

  The insulating sheet according to the present invention is suitably used for bonding a heat conductor having a thermal conductivity of 10 W / m · K or more to a conductive layer of a semiconductor device in which a semiconductor element is mounted on a substrate.

  The insulating sheet according to the present invention adheres a heat conductor having a thermal conductivity of 10 W / m · K or more to a conductive layer of an electronic component device in which electronic component elements other than semiconductor elements are mounted on a substrate. Also preferably used.

  When the semiconductor element is a power device element for a large current, the cured product of the insulating sheet is required to be more excellent in insulation or heat resistance. Therefore, the insulating sheet of this invention is used suitably for such a use.

  Hereinafter, the present invention will be clarified by giving specific examples and comparative examples of the present invention. The present invention is not limited to the following examples.

  The following materials were prepared.

[Polyvinyl acetal resin (A)]
(1) Polyvinyl butyral 1 (manufactured by Sekisui Chemical Co., Ltd., trade name: BL-5, weight average molecular weight 32000, glass transition temperature 62 ° C., hydroxyl group content 21 mol%, acetylation degree 3 mol% or less, butyral degree) 77 mol% or more)
(2) Polyvinyl butyral 2 (manufactured by Sekisui Chemical Co., Ltd., trade name: BM-S, weight average molecular weight 53,000, glass transition temperature 60 ° C., hydroxyl group content 22 mol%, acetylation degree 4 to 6 mol%, butyral) Degree 73 mol%)
(3) Polyvinyl butyral 3 (manufactured by Sekisui Chemical Co., Ltd., trade name: BH-S, weight average molecular weight 66000, glass transition temperature 64 ° C., hydroxyl group content 22 mol%, acetylation degree 4-6 mol%, butyralization Degree 73 mol%)

[Polymers other than polyvinyl acetal resin (A)]
Epoxy group-containing acrylic resin (manufactured by NOF Corporation, trade name: Marproof G-0130S, Mw = 9000, Tg = 69 ° C.)

[Epoxy compound having epoxy group (B1)]
(1) Bisphenol A type liquid epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., trade name: Epicoat 828US, Mw = 370)
(2) Bisphenol F type liquid epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., trade name: Epicoat 806L, Mw = 370)
(3) Trifunctional glycidyldiamine type liquid epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., trade name: Epicoat 630, Mw = 300)
(4) Fluorene skeleton epoxy resin (manufactured by Osaka Gas Chemical Co., Ltd., trade name: ONCOAT EX1011, Mw = 486)
(5) Naphthalene skeleton liquid epoxy resin (manufactured by DIC, trade name: EPICLON HP-4032D, Mw = 304)
(6) Hexahydrophthalic acid skeleton liquid epoxy resin (manufactured by Nippon Kayaku Co., Ltd., trade name: AK-601, Mw = 284)
(7) Bisphenol A type solid epoxy resin (product name: 1003, Mw = 1300, manufactured by Japan Epoxy Resin Co., Ltd.)

[Oxetane compound having oxetane group (A2)]
(1) Oxetane resin containing benzene skeleton (manufactured by Ube Industries, trade name: etanacol OXTP, Mw = 362.4)

[Curing agent (C)]
(1) Alicyclic skeleton acid anhydride (manufactured by Shin Nippon Chemical Co., Ltd., trade name: MH-700)
(2) Aromatic skeleton acid anhydride (manufactured by Sartomer Japan, trade name: SMA resin EF60)
(3) Polyalicyclic skeleton acid anhydride (manufactured by Shin Nippon Rika Co., Ltd., trade name: HNA-100)
(4) Terpene-based skeleton acid anhydride (manufactured by Japan Epoxy Resin, trade name: Epicure YH-306)
(5) Biphenyl skeleton phenolic resin (Madewa Kasei Co., Ltd., trade name: MEH-7851-S)
(6) Allyl group-containing skeletal phenol resin (manufactured by Japan Epoxy Resin, trade name: YLH-903)
(7) Triazine skeleton phenolic resin (manufactured by DIC, trade name: Phenolite KA-7052-L2)
(8) Melamine skeleton phenolic resin (manufactured by Gunei Chemical Industry Co., Ltd., trade name: PS-6492)
(9) Dicyandiamide (trade name: DICY7, manufactured by Japan Epoxy Resin Co., Ltd.)

[Filler (D)]
(1) 5 μm crushed alumina (crushed filler, manufactured by Nippon Light Metal Co., Ltd., trade name: LT300C, average particle diameter 5 μm, maximum particle diameter 15 μm, thermal conductivity 36 W / m · K, new Mohs hardness 12)
(2) 2 μm crushed alumina (crushed filler, manufactured by Nippon Light Metal Co., Ltd., trade name: LS-242C, average particle diameter 2 μm, maximum particle diameter 20 μm, thermal conductivity 36 W / m · K, new Mohs hardness 12)
(3) Spherical alumina (Denka Co., Ltd., trade name: DAM-10, average particle size 10 μm, maximum particle size 30 μm, thermal conductivity 36 W / m · K, new Mohs hardness 12)
(4) Synthetic magnesite (Kamishima Chemical Co., Ltd., trade name: MSL, average particle diameter 6 μm, maximum particle diameter 20 μm, thermal conductivity 15 W / m · K, new Mohs hardness 3.5)
(5) Aluminum nitride (manufactured by Toyo Aluminum Co., Ltd., trade name: TOYALNITE-FLX, average particle diameter 14 μm, maximum particle diameter 30 μm, thermal conductivity 200 W / m · K new Mohs hardness 11)
(6) Crystalline silica (manufactured by Tatsumori Co., Ltd., trade name: Crystallite CMC-12, average particle size 5 μm, maximum particle size 20 μm, thermal conductivity 10 W / m · K, new Mohs hardness 9)
(7) Silicon carbide (manufactured by Shinano Electric Smelting Co., Ltd., trade name: Shinano Random GP # 700, average particle diameter 17 μm, maximum particle diameter 70 μm, thermal conductivity 125 W / m · K, new Mohs hardness 13)
(8) Zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd., trade name: LPZINC-5, average particle diameter 5 μm, maximum particle diameter 20 μm, thermal conductivity 54 W / m · K, new Mohs hardness 5)
(9) Magnesium oxide (manufactured by Sakai Chemical Industry Co., Ltd., trade name: SMO Large Particle, average particle size 1.1 μm, maximum particle size 7 μm, thermal conductivity 35 W / m · K, new Mohs hardness 6)

[Fillers other than filler (D)]
(1) Fused silica (manufactured by Tokuyama Corporation, trade name SE15, average particle size 15 μm, new Mohs hardness 7)

[Antioxidant (E)]
(1) Phenol antioxidant (Ciba, trade name: IRGANOX1010)

[Dispersant]
(1) Acrylic dispersant (manufactured by Big Chemie Japan, trade name: Disperbyk-2070, pKa has a carboxyl group of 4)
(2) Polyether-based dispersant (manufactured by Enomoto Kasei Co., Ltd., trade name: ED151, pKa has 7 phosphate groups)

[Additive]
(1) Epoxysilane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KBE403)

[solvent]
(1) Methyl ethyl ketone

(Examples 1-30 and Comparative Examples 1-4)
Using a homodisper type stirrer, each raw material was blended in the proportions shown in Tables 1 to 5 below (the blending unit is parts by weight) and kneaded to prepare an insulating material.

  The insulating material was applied to a release PET sheet having a thickness of 50 μm so as to have a thickness of 100 μm, and dried in an oven at 90 ° C. for 30 minutes to produce an insulating sheet on the PET sheet.

(Evaluation)
(1) Handling property A laminate sheet having a PET sheet and an insulating sheet formed on the PET sheet was cut into a size of 460 mm x 610 mm to obtain a test sample. Using the obtained test sample, handling properties when the insulating sheet before thermosetting was peeled from the PET sheet at room temperature (23 ° C.) were evaluated according to the following criteria.

[Handling criteria]
○: The insulating sheet is not deformed and can be easily peeled. Δ: The insulating sheet can be peeled, but the sheet is stretched or broken. ×: The insulating sheet cannot be peeled.

(2) Glass transition temperature Using a differential scanning calorimeter “DSC220C” (manufactured by Seiko Instruments Inc.), the glass transition temperature of the insulating sheet in an uncured state was measured at a rate of temperature increase of 3 ° C./min.

(3) Thermal conductivity The thermal conductivity of the insulating sheet was measured using a thermal conductivity meter “quick thermal conductivity meter QTM-500” manufactured by Kyoto Electronics Industry Co., Ltd.

(4) Solder heat resistance test An insulating sheet is sandwiched between an aluminum plate having a thickness of 1.5 mm and an electrolytic copper foil having a thickness of 35 μm, and while maintaining a pressure of 4 MPa with a vacuum press machine at 120 ° C. for 1 hour, further at 200 ° C. The insulating sheet was press-cured for 1 hour to form a copper-clad laminate. The obtained copper-clad laminate was cut into a size of 50 mm × 60 mm to obtain a test sample. The obtained test sample was floated in a solder bath at 288 ° C. with the copper foil side facing down, and the time until the copper foil swelled or peeled off was measured and judged according to the following criteria.

[Criteria for solder heat resistance test]
○: No swelling or peeling even after 10 minutes ○: Swelling or peeling occurs after 3 minutes and before 10 minutes Δ: Swelling or after 3 minutes and before 3 minutes Peeling occurs ×: Swelling or peeling occurs before 1 minute elapses

(5) Dielectric breakdown voltage The insulation sheet was cut out to a size of 100 mm × 100 mm to obtain a test sample. The obtained test sample was cured in an oven at 120 ° C. for 1 hour and further in an oven at 200 ° C. for 1 hour to obtain a cured product of an insulating sheet. An AC voltage was applied using a withstand voltage tester (MODEL7473, manufactured by EXTECH Electronics) so that the voltage increased at a rate of 1 kV / second between the cured products of the insulating sheet. The voltage at which the cured product of the insulating sheet was broken was defined as the dielectric breakdown voltage.

(6) Workability An insulating sheet is sandwiched between an aluminum plate having a thickness of 1.5 mm and an electrolytic copper foil having a thickness of 35 μm, and the pressure of 4 MPa is maintained with a vacuum press machine at 120 ° C. for 1 hour, and further at 200 ° C. The insulating sheet was press cured for a time to form a copper-clad laminate. The obtained copper-clad laminate was router-processed using a drill with a diameter of 2.0 mm (Union Tool, RA series) under conditions of a rotation speed of 30000 and a table feed speed of 0.5 m / min. The processing distance until the flash was generated was measured, and the workability was evaluated according to the following criteria.

[Criteria for workability]
○○: Machining of 20m or more without burring ○: Machining of 5m or more and less than 20m without burring △: Machining of 1m or more but less than 5m without burring × By machining of less than 1m Burr occurs

(7) Elastic modulus After cutting the insulating sheet into a size of 5 mm × 50 mm, it was cured in an oven at 120 ° C. for 1 hour and at 200 ° C. for 1 hour to prepare a test sample. Using this test sample, in a DMA apparatus (DVA-200, manufactured by IT Measurement & Control Co., Ltd.) under tension mode, distance between chucks of 24 mm, heating rate of 5 ° C. per minute, measurement frequency of 10 Hz and 1% strain. The temperature-storage elastic modulus (E ′) when the temperature was raised to −60 to 320 ° C. was read. From the measured value obtained, the tensile elastic modulus at 25 ° C. of the cured product of the insulating sheet was evaluated.

  The results are shown in Tables 1 to 5 below.

DESCRIPTION OF SYMBOLS 1 ... Laminated structure 2 ... Thermal conductor 2a ... 1st surface 2b ... 2nd surface 3 ... Insulating layer 4 ... Conductive layer

Claims (10)

An insulating sheet used for bonding a thermal conductor having a thermal conductivity of 10 W / m · K or more to a conductive layer,
A polyvinyl acetal resin having a weight average molecular weight of 10,000 or more;
A curable compound having an epoxy group or an oxetane group;
A curing agent;
An insulating sheet comprising a filler having a thermal conductivity of 10 W / m · K or more.   The insulating sheet according to claim 1, wherein the polyvinyl acetal resin is polyvinyl butyral.   The insulating sheet of Claim 1 or 2 whose glass transition temperature of the said polyvinyl acetal resin is 40 degreeC or more and 75 degrees C or less.   The insulating sheet according to any one of claims 1 to 3, wherein the content of hydroxyl groups in the polyvinyl acetal resin is 20 mol% or more and 40 mol% or less.   The insulating sheet according to claim 1, wherein the filler has a new Mohs hardness of 9 or less.   The insulating sheet according to claim 1, wherein the curing agent does not have an aromatic skeleton. The insulating sheet according to any one of claims 1 to 6, wherein the curing agent is an acid anhydride or dicyandiamide represented by any of the following formulas (1) to (4).

In said formula (4), R1 and R2 show hydrogen, a C1-C5 alkyl group, or a hydroxyl group, respectively.   The insulating sheet according to any one of claims 1 to 7, further comprising an antioxidant. A thermal conductor having a thermal conductivity of 10 W / m · K or more;
An insulating layer laminated on at least one surface of the thermal conductor;
A conductive layer laminated on a surface opposite to the surface on which the thermal conductor of the insulating layer is laminated,
The laminated structure in which the said insulating layer is formed by hardening the insulating sheet of any one of Claims 1-8.   The laminated structure according to claim 9, wherein the heat conductor is a metal.

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