Thermal conductive sheet precursor, method for manufacturing a heat dissipation device, and heat dissipation device

Abstract

The present invention provides a thermal conductive sheet precursor that can be obtained to produce a thermal conductive sheet with low thermal resistance when assembled between a heat-generating element and a heat-dissipating element, a method for manufacturing a heat dissipation device using the thermal conductive sheet precursor, and a heat dissipation device capable of efficiently dissipating heat. [Solution] The thermal conductive sheet precursor of the present invention is characterized by comprising a thermoplastic resin (A) having a reactive group that reacts with an epoxy group, a reactive resin (B) having an epoxy group, a thermal latent epoxy curing agent (C), and a thermal conductive filler (D). Furthermore, the method for manufacturing the heat dissipation device of the present invention is characterized by comprising the steps of preparing a laminate comprising a heating element, the thermal conductive sheet precursor of the present invention, and a heat dissipation element, and heating the laminate under pressure to cure the thermal conductive sheet precursor.

Description

Technical Field

[0001] The present invention relates to a heat conduction sheet precursor, a method for manufacturing a heat dissipation device, and a heat dissipation device.

Background Art

[0002] In recent years, heat generation of electronic components such as plasma display panels (PDPs) and integrated circuit (IC) chips has increased with their higher performance. As a result, in electronic devices using such electronic components, it has become necessary to take measures against functional failures due to temperature rise of the electronic components.

[0003] As a measure against functional failures due to temperature rise of electronic components, generally, a method of promoting heat dissipation by attaching a heat dissipation body such as a metal heat sink, a heat dissipation plate, or heat dissipation fins to a heat generating body such as an electronic component is adopted. When using a heat dissipation body, in order to efficiently transfer heat from the heat generating body to the heat dissipation body, usually, a sheet-like member (heat conduction sheet) having a high thermal conductivity is interposed between the heat generating body and the heat dissipation body in a state where they are in close contact with each other. Therefore, a heat conduction sheet sandwiched between a heat generating body and a heat dissipation body has been required to exhibit excellent thermal conductivity under pressure due to being sandwiched.

[0004] Here, generally, in order to increase the thermal conductivity of a heat conduction sheet when used by sandwiching it between a heat generating body and a heat dissipation body, it is conceivable to reduce the thermal resistance value of the heat conduction sheet under pressure due to being sandwiched.

[0005] For example, Patent Document 1 discloses a technique for causing a heat conduction sheet containing a resin and a particulate carbon material to exhibit excellent thermal conductivity when used at a relatively low clamping pressure by setting the surface roughness of at least one main surface to a predetermined value or less and setting the thermal resistance value under pressure at a predetermined pressure to a predetermined value or less. Furthermore, Patent Document 2 discloses a thermal conductive sheet comprising a composition containing an organic polymer compound (A) having a predetermined glass transition temperature, an epoxy resin (B), a curing accelerator (C), and predetermined boron nitride particles (D), wherein the boron nitride particles (D) have excellent thermal conductivity and adhesion when the plane direction of the scales, the long axis direction of the ellipsoid, or the long axis direction of the rod are oriented in the thickness direction of the thermal conductive sheet. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2021-119606 [Patent Document 2] Japanese Patent Publication No. 2012-015273 [Overview of the project] [Problems that the invention aims to solve]

[0007] In recent years, there has been a demand for thermally conductive sheets to further reduce their thermal resistance when assembled between a heat-generating element and a heat-sinking element. However, with the conventional technology described above, it has been difficult to sufficiently reduce the thermal resistance of the thermally conductive sheet when assembled between a heat-generating element and a heat-sinking element.

[0008] Therefore, the present invention aims to provide a thermal conductive sheet precursor that can obtain a thermal conductive sheet with low thermal resistance when assembled between a heating element and a heat sink, a method for manufacturing a heat dissipation device using the thermal conductive sheet precursor, and a heat dissipation device capable of efficiently dissipating heat. [Means for solving the problem]

[0009] The inventors diligently conducted research with the aim of solving the above problems. As a result, the inventors newly discovered that a thermal conductive sheet with low thermal resistance when assembled between a heating element and a heat sink can be obtained by curing a thermal conductive sheet precursor containing a thermoplastic resin having a reactive group that reacts with an epoxy group, a reactive resin having an epoxy group, a thermal latent epoxy curing agent, and a thermal conductive filler, and thus completed the present invention.

[0010] In other words, the present invention aims to advantageously solve the above problems, and the present invention is a thermal conductive sheet precursor comprising [1] a thermoplastic resin (A) having a reactive group that reacts with epoxy groups, a reactive resin (B) having epoxy groups, a thermally latent epoxy curing agent (C), and a thermally conductive filler (D). The thermal conductive sheet precursor comprising the above-mentioned thermoplastic resin, a predetermined reactive resin, a thermally latent epoxy curing agent, and a thermally conductive filler can provide a thermal conductive sheet with low thermal resistance when assembled between a heating element and a heat sink.

[0011] [2] Preferably, the thermal conductive sheet precursor described in [1] further contains a curing accelerator (E). If the thermal conductive sheet precursor further contains a curing accelerator, the reaction rate can be accelerated to efficiently obtain a thermal conductive sheet, and the thermal resistance value when the obtained thermal conductive sheet is assembled between a heating element and a heat sink can be further reduced.

[0012] [3] The thermal conductive sheet precursor described in [1] or [2] above preferably has a gel fraction of 80% or more when heated at 150°C for 1 hour. If the gel fraction when heated under predetermined conditions is above a predetermined value, the thermal resistance value when the resulting thermal conductive sheet is assembled between the heating element and the heat sink can be further reduced. In this invention, the gel fraction can be measured by the method described in the examples.

[0013] [4] In any of the thermal conductive sheet precursors described in [1] to [3] above, the weight-average molecular weight of the thermoplastic resin (A) is preferably 2,000 or more and 200,000 or less. Thus, if the weight-average molecular weight of the thermoplastic resin (A) is within the above predetermined range, the thermal resistance value when the resulting thermal conductive sheet is assembled between the heating element and the heat sink can be further reduced. In this invention, the weight-average molecular weight of the thermoplastic resin (A) can be measured by the method described in the examples.

[0014] [5] In any of the thermal conductive sheet precursors described in [1] to [4] above, the thermal latent epoxy curing agent (C) is preferably a dicyandiamide or a reactive group-blocking type latent curing agent. If the thermal latent epoxy curing agent (C) is a dicyandiamide or a reactive group-blocking type latent curing agent, the thermal resistance value when the resulting thermal conductive sheet is assembled between a heating element and a heat sink can be further reduced.

[0015] [6] In any of the thermal conductive sheet precursors described in [1] to [5] above, it is preferable that the equivalent amount of epoxy groups contained in the reactive resin (B) relative to one equivalent amount of reactive groups contained in the thermoplastic resin (A) is 0.8 equivalents or more and 1.3 equivalents or less. If the equivalent amount of epoxy groups contained in the reactive resin (B) relative to one equivalent amount of reactive groups contained in the thermoplastic resin (A) is equal to or greater than the lower limit, the curing reaction can proceed sufficiently while maintaining the heat resistance of the thermal conductive sheet precursor. Furthermore, if the equivalent amount of epoxy groups contained in the reactive resin (B) relative to one equivalent amount of reactive groups contained in the thermoplastic resin (A) is equal to or less than the upper limit, the thermal resistance of the resulting thermal conductive sheet can be further reduced while maintaining the storage stability of the thermal conductive sheet precursor.

[0016] Moreover, the present invention aims to advantageously solve the above problems, and the present invention includes: a step of preparing a laminate in which a heating element, a heat conduction sheet precursor according to any one of the above [1] to [6], and a heat radiator are laminated; and a step of heating the laminate under pressure to cure the heat conduction sheet precursor. By curing the heat conduction sheet precursor under pressure while sandwiching it between the heating element and the heat radiator to form a heat conductive sheet, a heat dissipation device capable of efficiently dissipating heat can be manufactured.

[0017] Moreover, the present invention aims to advantageously solve the above problems, and the present invention is a heat dissipation device including: [8] a heating element; a heat radiator; and a cured product of the heat conduction sheet precursor according to any one of the above [1] to [6] sandwiched between the heating element and the heat radiator. A heat dissipation device provided with the cured product of the heat conduction sheet precursor described above can efficiently dissipate heat.

Effects of the Invention

[0018] According to the present invention, it is possible to provide a heat conduction sheet precursor capable of obtaining a heat conduction sheet having a low thermal resistance when assembled between a heating element and a heat radiator, a method for manufacturing a heat dissipation device using the heat conduction sheet precursor, and a heat dissipation device capable of efficiently dissipating heat.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described in detail. The heat conduction sheet precursor of the present invention can be cured by heating to form a heat conduction sheet. The heat conduction sheet precursor of the present invention can be suitably used, for example, in the method for manufacturing the heat dissipation device of the present invention. The heat dissipation device of the present invention includes a cured product of the heat conduction sheet precursor of the present invention as a heat conduction sheet.

[0020] (Heat Conduction Sheet Precursor) The heat-conductive sheet precursor of the present invention contains a thermoplastic resin (A) having a reactive group that reacts with an epoxy group, a reactive resin (B) having an epoxy group, a thermally latent epoxy curing agent (C), and a heat-conductive filler (D). Further, the heat-conductive sheet precursor of the present invention may or may not further contain at least one component selected from the group consisting of a curing accelerator (E) and other components.

[0021] The heat-conductive sheet obtained by using the heat-conductive sheet precursor containing the above components (A) to (D) has a low thermal resistance value and excellent thermal conductivity. Therefore, when the heat-conductive sheet is used in combination with a heat radiator such as a heat sink, a heat dissipation plate, a heat dissipation fin, etc., and a heat-generating body such as an electronic component, heat can be effectively dissipated from the heat-generating body through the heat-conductive sheet.

[0022] Here, the thermal resistance value of the heat-conductive sheet is considered to be the sum of the value of the bulk thermal resistance, which is the thermal resistance of the heat-conductive sheet itself, and the value of the interfacial thermal resistance at the interface between the heat-conductive sheet and the heat-generating body / heat radiator. For example, the value of the bulk thermal resistance of the heat-conductive sheet is derived from the composition and properties of the heat-conductive sheet, and is represented by the following formula (1): Value of bulk thermal resistance (K·m 2 / W) = thickness (m) / thermal conductivity (W / m·K) ··· (1). Also, the value of the interfacial thermal resistance of the heat-conductive sheet is derived from the adhesion (interfacial adhesion) at the interface between the heat-generating body and the heat radiator and the heat-conductive sheet, the difference in the bulk thermal resistance between the heat-generating body and the heat-conductive sheet, and the difference in the bulk thermal resistance between the heat radiator and the heat-conductive sheet. And the heat-conductive sheet precursor of the present invention is usually made into a heat-conductive sheet by heating under pressure in a state assembled between a heat radiator and a heat-generating body. Therefore, it is presumed that the obtained heat-conductive sheet adheres well to the heat radiator and the heat-generating body, and as a result, the interfacial thermal resistance decreases and the thermal resistance (the sum of the bulk thermal resistance and the interfacial thermal resistance) decreases.

[0023] <Thermoplastic resin (A) having a reactive group that reacts with an epoxy group> The thermoplastic resin (A) (hereinafter also simply referred to as "thermoplastic resin (A)") contained in the thermal conductive sheet precursor of the present invention, which has reactive groups that react with epoxy groups, is not particularly limited as long as it has reactive groups that can react with the epoxy groups of the reactive resin (B) having epoxy groups, which will be described later.

[0024] The reactive group that reacts with the epoxy group is not particularly limited, but examples include groups having active hydrogen and active ester groups. Examples of groups having active hydrogen include carboxyl groups, amino groups, hydroxyl groups, acid anhydride groups, and thiol groups. These may be used individually or in combination of two or more. Among these, the reactive group that reacts with the epoxy group is preferably a carboxyl group or an amino group, and more preferably a carboxyl group, from the viewpoint of reactivity.

[0025] The thermoplastic resin (A) is not particularly limited and includes, for example, thermoplastic resins having the above-mentioned reactive group, such as polybutene, polyisobutylene, butyl rubber, polybutadiene (BR), hydrogenated polybutadiene, acrylonitrile butadiene rubber (NBR), hydrogenated acrylonitrile butadiene rubber (HNBR), styrene butadiene rubber (SBR), acrylic rubber (ACM), ethylene acrylic rubber (AEM), isoprene rubber (IR), ethylene propylene rubber (EPDM), fluororubber (FKM), silicone rubber, and urethane rubber. These may be used individually or in combination of two or more. Among these, acrylonitrile butadiene rubber having the above-mentioned reactive group and acrylic rubber having the above-mentioned reactive group are preferred, acrylonitrile butadiene rubber having a carboxyl group and acrylic rubber having a carboxyl group are more preferred, and nitrile butadiene rubber having a carboxyl group is even more preferred.

[0026] The method for preparing the thermoplastic resin (A) is not particularly limited, and known methods can be used. For example, a method in which a monomer having the reactive group is polymerized when polymerizing a monomer for producing the thermoplastic resin (A); and a method in which the reactive group is introduced into the thermoplastic resin after it has been synthesized. Specifically, for example, methods for introducing a carboxyl group into a thermoplastic resin include a method in which an appropriate amount of an ethylenically unsaturated carboxylic acid such as maleic acid or maleic anhydride and / or an anhydride of the unsaturated carboxylic acid is copolymerized when polymerizing a monomer for producing the thermoplastic resin; and a method in which an appropriate amount of an ethylenically unsaturated carboxylic acid such as maleic acid or maleic anhydride and / or an anhydride of the unsaturated carboxylic acid and a peroxide are used in a grafting reaction after the thermoplastic resin has been synthesized.

[0027] Furthermore, the thermoplastic resin (A) can be either liquid or solid. For liquid thermoplastic resin (A), a thermoplastic resin (A) that is liquid at room temperature and atmospheric pressure can be used, and for solid thermoplastic resin (A), a thermoplastic resin (A) that is solid at room temperature and atmospheric pressure can be used. In this specification, "room temperature" refers to 23°C, and "atmospheric pressure" refers to 1 atm (absolute pressure).

[0028] <<Weight-average molecular weight of thermoplastic resin (A)>> The weight-average molecular weight of the thermoplastic resin (A) is not particularly limited, but from the viewpoint of further reducing the thermal resistance when the resulting heat conductive sheet is assembled between a heat generating element and a heat sink, it is preferably 2000 or more, more preferably 6000 or more, preferably 300000 or less, more preferably 200000 or less, even more preferably 100000 or less, and particularly preferably 60000 or less.

[0029] In the present invention, when two or more types of thermoplastic resin (A) are blended, the weight-average molecular weight of the thermoplastic resin (A) is the sum of the values ​​obtained by dividing the weight-average molecular weight of each type of thermoplastic resin by its blending ratio (the ratio when the total amount of each type of thermoplastic resin blended is set to 1).

[0030] <Reactive resin containing epoxy groups (B)> The reactive resin (B) having epoxy groups (hereinafter also simply referred to as "reactive resin (B)") included in the thermal conductive sheet precursor of the present invention is not particularly limited, and for example, an epoxy resin having one or more epoxy groups in one molecule can be used. Specific examples of epoxy resins include bisphenol-type epoxy resins (bisphenol A type diglycidyl ether, bisphenol F type diglycidyl ether, hydrogenated bisphenol A type diglycidyl ether, bisphenol S type diglycidyl ether, bisphenol AF type diglycidyl ether, etc.); dicyclopentadiene-type epoxy resins; trisphenol-type epoxy resins; naphthol novolac-type epoxy resins; phenol novolac-type epoxy resins; tert-butyl-catechol-type epoxy resins; naphthalene-type epoxy resins; naphthol-type epoxy resins; anthracene-type epoxy resins; glycidylamine-type epoxy resins; glycidyl ester-type epoxy resins; cresol novolac-type epoxy resins; biphenyl-type epoxy resins; linear aliphatic epoxy resins; epoxy resins having a butadiene structure; alicyclic epoxy resins; heterocyclic epoxy resins; spiro-ring-containing epoxy resins; cyclohexane-type epoxy resins; cyclohexanedimethanol-type epoxy resins; naphthylene ether-type epoxy resins; trimethylol-type epoxy resins; and tetraphenylethane-type epoxy resins. Biphenyl-type epoxy resins refer to epoxy resins having a biphenyl structure, where the biphenyl structure may have substituents such as alkyl groups, alkoxy groups, or aryl groups. These may be used individually or in combination of two or more. Among these, bisphenol-type epoxy resins are preferred.

[0031] Examples of commercially available reactive resin B include jER828 (epoxy equivalent 188 g / eq, weight-average molecular weight 370) and jER871 (epoxy equivalent 411 g / eq, weight-average molecular weight 260) from Mitsubishi Chemical Corporation, and YDF-8170C (epoxy equivalent 160 g / eq, weight-average molecular weight 320) from Toto Kasei Co., Ltd.

[0032] <<Composition Ratio>> The blending ratio of the reactive resin (B) in the thermal conductive sheet precursor of the present invention is not particularly limited, but is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 40 parts by mass or less, per 100 parts by mass of the thermoplastic resin (A). If the blending ratio of the reactive resin (B) is above the lower limit, the curing reaction can proceed sufficiently, and if the blending ratio of the reactive resin (B) is below the upper limit, crosslinking between epoxy groups can be suppressed and the flexibility of the thermal conductive sheet precursor can be maintained.

[0033] The epoxy equivalent of the reactive resin (B) is preferably 100 g / eq or more, more preferably 150 g / eq or more, and preferably 500 g / eq or less, and more preferably 450 g / eq or less. If the epoxy equivalent of the reactive resin (B) is above the lower limit, the resin can be sufficiently cured while maintaining the flexibility of the thermal conductive sheet precursor, and if the epoxy equivalent of the reactive resin (B) is below the upper limit, the curing reaction can proceed sufficiently. There are no particular restrictions on the method for measuring epoxy equivalent, but it can be measured by titration in accordance with JIS K 7236:2001 (Method for determining the epoxy equivalent of epoxy resin).

[0034] Furthermore, the equivalent amount of epoxy groups contained in the reactive resin (B) is preferably 0.8 equivalents or more, more preferably 1 equivalent or more, preferably 1.5 equivalents or less, more preferably 1.3 equivalents or less, and particularly preferably 1.2 equivalents or less, relative to 1 equivalent of reactive groups contained in the thermoplastic resin (A). If the equivalent amount of epoxy groups of the reactive resin (B) relative to 1 equivalent of reactive groups is above the above lower limit, the curing reaction can proceed sufficiently while maintaining the heat resistance of the thermal conductive sheet precursor. If the equivalent amount of epoxy groups of the reactive resin (B) is below the above upper limit, the thermal resistance of the resulting thermal conductive sheet can be further reduced while maintaining the storage stability of the thermal conductive sheet precursor.

[0035] Furthermore, the weight-average molecular weight of the reactive resin (B) relative to the weight-average molecular weight of the thermoplastic resin (A) is preferably 0.001 or higher, more preferably 0.005 or higher, particularly preferably 0.01 or higher, preferably 0.2 or lower, and more preferably 0.1 or lower. If the weight-average molecular weight of the reactive resin (B) relative to the thermoplastic resin (A) is above the lower limit, the thermal resistance of the resulting heat-conducting sheet can be further reduced, and if the weight-average molecular weight of the reactive resin (B) relative to the thermoplastic resin (A) is below the upper limit, the flexibility of the heat-conducting sheet precursor can be maintained. The reason why the thermal resistance can be further reduced if the weight-average molecular weight of the reactive resin (B) relative to the thermoplastic resin (A) is above the lower limit is not clear, but it is thought that when the weight-average molecular weight of the reactive resin (B) relative to the thermoplastic resin (A) is above the lower limit, the reactive resin (B) seeps out at the interface between the sheet and the adherend when the thermal conductive sheet precursor is heated under pressure and hardened, so the sheet surface becomes covered with the seeped reactive resin (B), which inhibits the thermal conductivity of the thermal conductive filler (D).

[0036] <Thermal latent epoxy curing agent (C)> The thermal latent epoxy curing agent (C) contained in the thermal conductive sheet precursor of the present invention is not particularly limited, and known thermal latent epoxy curing agents can be used. Here, "thermal latent epoxy curing agent" refers to a curing agent that does not exhibit the curing properties of epoxy resin at room temperature, but exhibits curing properties in response to external stimuli such as heat or pressure. A "thermal latent epoxy curing agent" exhibits curing properties when heated to a certain temperature or higher.

[0037] The heat-latent epoxy curing agent (C) used in the present invention preferably has a viscosity increase of 100% or less when mixed with a reactive resin (B) in a ratio of reactive resin (B) : heat-latent epoxy curing agent (C) = 100:20 (mass ratio) and stored at a temperature of 40°C, compared to the viscosity immediately after preparation of the mixture after 7 days of storage. More preferably, it is 70% or less, even more preferably 10% or less, and particularly preferably less than 0%. A curing agent with a viscosity increase of less than or equal to the above upper limit has its reaction with the reactive resin (B) suppressed during storage and can function suitably as a heat-latent epoxy curing agent (C). In this invention, the viscosity and viscosity increase of the mixture of the curing agent or curing accelerator and the reactive resin (B) can be measured and calculated by the method described in the examples.

[0038] Examples of thermal latent epoxy curing agents (C) include solid-disperse latent curing agents, reactive group-blocking latent curing agents, microencapsulated latent curing agents, elution-type latent curing agents, and ionic latent curing agents. Thermal latent epoxy curing agents (C) may be used alone or in combination of two or more types. Among these, solid-disperse latent curing agents and reactive group-block type latent curing agents are preferred. From the viewpoint of improving the storage stability of the thermal conductive sheet precursor while further reducing the thermal resistance value when the resulting thermal conductive sheet is assembled between the heating element and the heat sink, solid-disperse latent curing agents or reactive group-block type latent curing agents are more preferred.

[0039] Solid-dispersible latent curing agents are typically solids that are insoluble in reactive resins (B) at room temperature (25°C). By heating to a predetermined temperature, they can be solubilized by melting, thereby accelerating the curing reaction. Examples of solid-dispersible latent curing agents include dicyandiamide and its derivatives, organic acid hydrazides, diaminomaleonitrile and its derivatives, and boron trifluoride-amine complexes. Among these, dicyandiamide is preferred from the viewpoint of further reducing the thermal resistance value when the resulting heat-conducting sheet is assembled between a heating element and a heat sink.

[0040] Reaction group blocking type latent curing agents are latent curing agents that accelerate the curing reaction by releasing a curing agent containing reactive groups when heated to a temperature above a predetermined level, thereby eliminating the compound that was blocking the reactive groups. Examples of reaction group blocking type latent curing agents include reaction products of amine compounds and epoxy compounds (amine-epoxy adduct systems), and reaction products of amine compounds and isocyanate compounds or urea compounds (urea-type adduct systems). Examples of commercially available reaction group blocking type latent curing agents include Fujicure 7000, 7001, and 7002 manufactured by T&K TOKA Corporation.

[0041] Microencapsulated latent curing agents typically consist of a shell portion forming an outer shell and a core portion enclosed by the shell portion. The core portion contains a curing agent such as an amine-based curing agent. By heating or other means to a temperature above a predetermined level, the shell portion is broken, releasing the curing agent and accelerating the curing reaction. Examples of commercially available microencapsulated latent curing agents include Asahi Kasei's Novacure HX-3722, HX-3748, HX-3088, HX-3741, HX-3742, HX-5945HP, and HX-9322HP.

[0042] Dissolution-type latent curing agents are latent curing agents in which a curing agent, such as an amine-based curing agent, is encapsulated in a porous material. When heated to a temperature above a predetermined level, the curing reaction can be accelerated by the release of the curing agent. Examples of dissolution-type latent curing agents include molecular sieve-encapsulated curing agents.

[0043] Ionic latent curing agents contain organic acid salts of basic compounds and accelerate the curing reaction by generating basic compounds above a predetermined temperature through heating or other means. Examples of commercially available ionic latent curing agents include U-CAT SA1 and U-CAT1102 manufactured by Sunapro Co., Ltd.

[0044] The above-mentioned amine-based curing agent is not particularly limited as long as it has a nitrogen atom in its molecule, but for example, aromatic polyamine compounds having active hydrogen such as 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, m-phenylenediamine, m-xylylenediamine, and diethyltoluenediamine; aliphatic amines having active hydrogen such as diethylenetriamine, triethylenetetramine, isophoronediamine, bis(aminomethyl)norbornane, bis(4-aminocyclohexyl)methane, and dimer acid esters of polyethyleneimine; modified amines obtained by reacting these amines having active hydrogen with epoxy compounds, acrylonitrile, phenol and compounds such as formaldehyde and thiourea; and tertiary amines without active hydrogen such as dimethylaniline, dimethylbenzylamine, 2,4,6-tris(dimethylaminomethyl)phenol and monosubstituted imidazoles can be used.

[0045] <<Composition Ratio>> The proportion of the thermal latent epoxy curing agent (C) in the thermal conductive sheet precursor of the present invention is not particularly limited, but is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and preferably 10 parts by mass or less, and more preferably 8 parts by mass or less, per 100 parts by mass of thermoplastic resin (A). If the proportion of the thermal latent epoxy curing agent (C) is above the lower limit, the curing reaction can proceed sufficiently, and if the proportion of the thermal latent epoxy curing agent (C) is below the upper limit, the progress of side reactions can be suppressed, and the flexibility and storage stability of the thermal conductive sheet precursor can be maintained.

[0046] <Thermal conductive filler (D)> The thermally conductive filler (D) is a component that can enable the resulting thermally conductive sheet to exhibit excellent thermal conductivity. The thermally conductive filler (D) contained in the thermally conductive sheet precursor of the present invention is not particularly limited, and for example, particulate carbon materials and fibrous carbon materials can be used. Among these, the use of particulate carbon materials is preferred. Particulate carbon materials and fibrous carbon materials may be used in combination.

[0047] <<Particulate Carbon Material>> The particulate carbon material is not particularly limited, and for example, graphite such as natural graphite, artificial graphite, flaky graphite, flake graphite, acid-treated graphite, expandable graphite, and expanded graphite; carbon black; etc. may be used. These may be used individually or in combination of two or more. Among the particulate carbon materials, graphite is preferred, flaky graphite is more preferred, and expanded graphite is even more preferred. Using flaky graphite or expanded graphite can further improve the thermal conductivity when the resulting heat conductive sheet is assembled between a heating element and a heat sink. Expanded graphite, which can be suitably used as a particulate carbon material, can be obtained, for example, by chemically treating graphite such as flaky graphite with sulfuric acid to obtain expandable graphite, which is then heat-treated to expand it and then refined. Examples of expanded graphite include EC1500, EC1000, EC500, EC300, EC100, and EC50 (all are trade names) manufactured by Ito Graphite Industry Co., Ltd.

[0048] [Particle size of particulate carbon material] Furthermore, the particle size of the particulate carbon material is preferably 100 μm or more, more preferably 150 μm or more, and preferably 300 μm or less in volume average particle size. If the particle size of the particulate carbon material is above the lower limit, the particulate carbon material in the thermal conductive sheet precursor is more likely to orient in the desired direction and form good heat transfer paths. Therefore, the bulk thermal resistance of the resulting thermal conductive sheet can be lowered and higher thermal conductivity can be achieved. Also, if the particle size of the particulate carbon material is below the upper limit, the surface of the thermal conductive sheet precursor can be made smoother, and heat transfer from the heating element to the thermal conductive sheet when in contact with the heating element can be improved. In this invention, "volume-average particle diameter" can be measured in accordance with JIS Z8825 and represents the particle diameter at which the cumulative volume calculated from the smallest diameter side accounts for 50% of the particle size distribution (volume-based) measured by laser diffraction.

[0049] [Aspect ratio of particulate carbon material] Furthermore, the aspect ratio (major axis / minor axis) of the particulate carbon material is preferably 1 or more and 10 or less, and more preferably 1 or more and 5 or less. In this invention, the "aspect ratio of particulate carbon material" can be determined by observing the particulate carbon material with a scanning electron microscope (SEM), measuring the maximum diameter (long diameter) and the particle diameter in the direction perpendicular to the maximum diameter (short diameter) for any 50 particulate carbon materials, and calculating the average value of the ratio of the long diameter to the short diameter (long diameter / short diameter).

[0050] <<Fibrous carbon material>> The fibrous carbon material that can be contained in the thermal conductive sheet precursor of the present invention is not particularly limited, and examples include carbon nanotubes, vapor-grown carbon fibers, carbon fibers obtained by carbonizing organic fibers, and cut pieces thereof. These may be used individually or in combination of two or more.

[0051] Among the above, it is preferable to use fibrous carbon nanostructures such as carbon nanotubes as the fibrous carbon material, and it is more preferable to use fibrous carbon nanostructures containing carbon nanotubes. By using fibrous carbon nanostructures such as carbon nanotubes, the thermal conductivity and strength of the resulting thermal conductive sheet can be further improved.

[0052] Here, the fibrous carbon nanostructure containing carbon nanotubes, which can be suitably used as a fibrous carbon material, may consist solely of carbon nanotubes (hereinafter sometimes referred to as "CNTs"), or it may be a mixture of CNTs and fibrous carbon nanostructures other than CNTs. Furthermore, while the CNTs in the fibrous carbon nanostructure are not particularly limited, single-walled carbon nanotubes and / or multi-walled carbon nanotubes can be used, the CNTs are preferably single-walled to five-walled carbon nanotubes, and more preferably single-walled carbon nanotubes. Using single-walled carbon nanotubes can further improve the thermal conductivity and strength of the resulting thermal conductive sheet compared to using multi-walled carbon nanotubes.

[0053] [Average diameter (Av) of fibrous carbon nanostructures containing CNTs] The average diameter (Av) of the fibrous carbon nanostructures containing CNTs is preferably 0.5 nm or more, more preferably 1 nm or more, preferably 15 nm or less, and more preferably 10 nm or less. This is because if the average diameter (Av) of the fibrous carbon nanostructures containing CNTs is above the lower limit, aggregation of the fibrous carbon nanostructures containing CNTs can be suppressed and the dispersibility of the fibrous carbon nanostructures containing CNTs can be improved. Furthermore, if the average diameter (Av) of the fibrous carbon nanostructures containing CNTs is below the upper limit, the thermal conductivity and strength of the thermal conductive sheet can be sufficiently improved. The average diameter (Av) of fibrous carbon nanostructures containing CNTs can be determined by measuring the diameter (outer diameter) of 100 randomly selected fibrous carbon nanostructures containing CNTs using a transmission electron microscope. The average diameter (Av) of fibrous carbon nanostructures containing CNTs may be adjusted by changing the manufacturing method or manufacturing conditions of the fibrous carbon nanostructures containing CNTs, or by combining multiple types of fibrous carbon nanostructures containing CNTs obtained by different manufacturing methods.

[0054] [Average length of fibrous carbon nanostructures containing CNTs] Furthermore, it is preferable that the average length of the fibrous carbon nanostructure containing CNTs be 100 μm or more. In addition, from the viewpoint of suppressing damage such as fracture or breakage of CNTs during dispersion, it is preferable that the average length of the fibrous carbon nanostructure containing CNTs be 5000 μm or less.

[0055] <<Composition Ratio>> The amount of thermal conductive filler (D) blended is preferably 50 parts by mass or more, more preferably 80 parts by mass or more, preferably 300 parts by mass or less, and more preferably 250 parts by mass or less, per 100 parts by mass of the thermoplastic resin (A) described above. If the amount of thermal conductive filler (D) blended in the thermal conductive sheet precursor is above the lower limit above, the bulk thermal resistance of the resulting thermal conductive sheet can be further reduced. Also, if the amount of thermal conductive filler (D) blended in the thermal conductive sheet precursor is below the upper limit above, it is possible to suppress the thermal conductive sheet precursor from becoming excessively hard, and for example, the surface of the thermal conductive sheet precursor can be deformed more easily, further improving its ability to conform to heat-generating elements and heat-sinking elements. As a result, the resulting thermal conductive sheet can exhibit high thermal conductivity.

[0056] Furthermore, the thermal conductive sheet precursor of the present invention preferably contains 30 volume% or more of thermal conductive filler (D), more preferably 40 volume% or more, more preferably 55 volume% or less, and more preferably 50 volume% or less. If the volume percentage of thermal conductive filler (D) in the thermal conductive sheet precursor is within the above range, the thermal conductivity in the thickness direction of the resulting thermal conductive sheet will increase, allowing for even better heat transfer in the thickness direction of the thermal conductive sheet, while also ensuring the flexibility of the thermal conductive sheet precursor and further improving the thickness accuracy. In this invention, the content ratio (volume fraction) of the thermally conductive filler (D) can be measured by the method described in the examples.

[0057] <Curing accelerator (E)> The curing accelerator (E) optionally included in the heat conductive sheet precursor of the present invention is a component that can accelerate the curing reaction and increase the curing rate, while further reducing the thermal resistance value when the resulting heat conductive sheet is assembled between a heat generating element and a heat sink. The curing accelerator (E) is not particularly limited and includes urea-based curing accelerators, imidazole-based curing accelerators, phosphorus-based curing accelerators, guanidine-based curing accelerators, etc. Among these, imidazole-based curing accelerators and urea-based curing accelerators are preferred, and urea-based curing accelerators are more preferred. Furthermore, the curing accelerator (E) does not include any of the thermal latent epoxy curing agents (C) mentioned above.

[0058] Specific examples of urea-based curing accelerators include aliphatic dimethylureas such as 1,1-dimethylurea, 3-(4-chlorophenyl)-1,1-dimethylurea, 3-trifluoroethylphenyl-1,1-dimethylurea, 1-(3-{[(dimethylcarbamoyl)amino]methyl}-3,5,5-trimethylcyclohexyl)-3,3-dimethylurea, 4,4'-methylenebis(phenyldimethylurea), 1,1,3-trimethylurea, 3-ethyl-1,1-dimethylurea, 3-cyclohexyl-1,1-dimethylurea, and 3-cyclooctyl-1,1-dimethylurea. Among these, 1,1-dimethylurea is preferred.

[0059] The imidazole-based curing accelerator is not particularly limited, and examples include imidazole compounds and imidazole derivatives.

[0060] Examples of imidazole compounds include 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 1-cyanoethyl-2-phenylimidazolium trimellitate, and 2-phenyl-4,5-dihydroxymethylimidazole.

[0061] Examples of imidazole derivatives include adducts of imidazole compounds such as 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanurate adducts.

[0062] Specific examples of phosphorus-based curing accelerators include aliphatic phosphonium salts such as tetrabutylphosphonium bromide, tetrabutylphosphonium chloride, tetrabutylphosphonium acetate, tetrabutylphosphonium decanoate, tetrabutylphosphonium laurate, bis(tetrabutylphosphonium) pyromelitate, tetrabutylphosphonium hydrogen hexahydrophthalate, tetrabutylphosphonium 2,6-bis[(2-hydroxy-5-methylphenyl)methyl]-4-methylphenolate, and di-tert-butyldimethylphosphonium tetraphenylborate.

[0063] Examples of guanidine-based curing accelerators include dicyandiamide, 1-methylguanidine, 1-ethylguanidine, 1-cyclohexylguanidine, 1-phenylguanidine, 1-(o-tolyl)guanidine, dimethylguanidine, diphenylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]deca-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]deca-5-ene, 1-methylbiguanide, 1-ethylbiguanide, 1-n-butylbiguanide, 1-n-octadecylbiguanide, 1,1-dimethylbiguanide, 1,1-diethylbiguanide, 1-cyclohexylbiguanide, 1-allylbiguanide, 1-phenylbiguanide, and 1-(o-tolyl)biguanide.

[0064] <<Composition Ratio>> The amount of curing accelerator (E) added is preferably 1 part by mass or more, more preferably 3 parts by mass or more, preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of the thermoplastic resin (A) described above. If the proportion of curing accelerator (E) is above the lower limit, the curing reaction can proceed sufficiently, and if the proportion of curing accelerator (E) is below the upper limit, the resin can be sufficiently cured while maintaining the flexibility of the thermal conductive sheet precursor.

[0065] Furthermore, when the thermal conductive sheet precursor of the present invention contains both a thermal latent epoxy curing agent (C) and a curing accelerator (E), the total proportion of the thermal latent epoxy curing agent (C) and the curing accelerator (E) is preferably 4 parts by mass or more, more preferably 8 parts by mass or more, preferably 20 parts by mass or less, and more preferably 13 parts by mass or less, based on 100 parts by mass of the thermoplastic resin (A) described above. If the total proportion of the thermal latent epoxy curing agent (C) and the curing accelerator (E) is above the lower limit, the resin can be sufficiently cured, and if the total proportion of the thermal latent epoxy curing agent (C) and the curing accelerator (E) is below the upper limit, the curing reaction can be sufficiently carried out while maintaining the storage stability and flexibility of the thermal conductive sheet precursor.

[0066] <Other ingredients> Components that may be included in the thermal conductive sheet precursor of the present invention include known additives that can be used in the formation of a thermal conductive sheet. Additives that can be incorporated into the thermal conductive sheet precursor are not particularly limited, but include, for example, plasticizers such as fatty acid esters like sebacate ester; flame retardants such as red phosphorus-based flame retardants and phosphate ester-based flame retardants; toughness modifiers such as urethane acrylate; hygroscopic agents such as calcium oxide and magnesium oxide; adhesion enhancers such as silane coupling agents, titanium coupling agents and acid anhydrides; wettability enhancers such as nonionic surfactants and fluorine-based surfactants; ion trapping agents such as inorganic ion exchangers; and anti-aging agents such as aromatic secondary amines.

[0067] <<Composition Ratio>> If the thermal conductive sheet precursor further contains additives, the amount of additives can be, for example, 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of thermoplastic resin (A), and preferably 10 parts by mass or less.

[0068] <Properties of the thermal conductive sheet precursor> The thermal conductive sheet precursor preferably has a structure in which strips containing each of the above-mentioned components are bonded in parallel in one direction substantially perpendicular to the thickness direction of the thermal conductive sheet precursor (a direction at an angle of approximately 90° to the thickness direction). In the thermal conductive sheet precursor, since the thermal conductive filler (D) is oriented in the thickness direction, the thermal conductivity of the resulting thermal conductive sheet is improved. The width of the strips in this substantially vertical direction is preferably 1 mm or more, more preferably 1.2 mm or more, even more preferably 1.5 mm or more, preferably 3 mm or less, more preferably 2.8 mm or less, and even more preferably 2.5 mm or less. The width of the strips mentioned above may depend on the thickness of the primary sheet. Therefore, in thermal conductive sheet precursors where the width of the strips is greater than or equal to the lower limit, the number of layers, folds, or turns of the primary sheet is further reduced. As a result, such thermal conductive sheet precursors have an improved laminate formation rate, as described later, and improved productivity. On the other hand, in thermal conductive sheet precursors where the width of the strips is less than or equal to the upper limit, the thermal conductive filler (D) is well oriented in the thickness direction within the thermal conductive sheet precursor, so the thermal conductivity when the resulting thermal conductive sheet is assembled between a heating element and a heat sink is further improved.

[0069] <Gel fraction> The thermal conductive sheet precursor of the present invention preferably has a gel fraction of 80% or more, and more preferably 85% or more, when heated at 150°C for 1 hour. If the gel fraction is above the lower limit, the thermal resistance value when the resulting thermal conductive sheet is assembled between a heating element and a heat sink can be further reduced. The upper limit of the gel fraction can be, for example, 100% or less. The gel fraction can be adjusted, for example, by changing the proportions of thermoplastic resin (A), reactive resin (B), and heat-latent epoxy curing agent (C).

[0070] Furthermore, from the viewpoint of further reducing the thermal resistance value when the resulting thermal conductive sheet precursor is assembled between a heating element and a heat sink, the gel fraction of the thermal conductive sheet precursor of the present invention is preferably 68% or less, and more preferably 64% or less, before heating at 150°C for 1 hour.

[0071] Furthermore, from the viewpoint of further reducing the thermal resistance value when the resulting thermal conductive sheet precursor of the present invention is assembled between a heating element and a heat sink, it is preferable that the difference between the gel fraction after heating at 150°C for 1 hour and the gel fraction before heating at 150°C for 1 hour ([gel fraction after heating] - [gel fraction before heating]) is 15% or more, and more preferably 20% or more.

[0072] <Tackiness> The thermal conductive sheet precursor of the present invention exhibits a tack force of 60 N / cm when stored at 23°C for 7 days. 2 Preferably, it is 65 N / cm 2 It is preferable that the above conditions are met. Furthermore, the thermal conductive sheet precursor of the present invention exhibits a tack force of 30 N / cm when stored at 23°C for 30 days. 2 Preferably, it is 35 N / cm² or higher. 2 It is preferable that the above conditions are met. The tack force of the thermal conductive sheet precursor can be measured and calculated by the method described in the examples.

[0073] Furthermore, the thermal conductive sheet precursor of the present invention preferably has a reduction rate of tack strength after 30 days of storage relative to the tack strength after 7 days of storage at 23°C of 80% or less, more preferably 60% or less, and even more preferably 50% or less. In this invention, the reduction rate of tack force can be measured and calculated by the method described in the examples.

[0074] <thickness> The thermal conductive sheet precursor of the present invention preferably has a thickness of 0.05 mm or more, more preferably 0.08 mm or more, preferably 1 mm or less, more preferably 0.5 mm or less, particularly preferably 0.3 mm or less, and even more preferably 0.15 mm or less. If the thickness of the thermal conductive sheet precursor is below the above upper limit, the bulk thermal resistance value of the obtained thermal conductive sheet can be further reduced according to formula (1) above. In addition, if the thickness of the thermal conductive sheet precursor is below the above upper limit, the obtained thermal conductive sheet can be made thinner and adhere better to the heat-generating element and / or heat sink, so the interfacial thermal resistance value can be further reduced. Furthermore, if the thickness of the thermal conductive sheet precursor is above the above lower limit, the strength, durability and handling properties of the thermal conductive sheet precursor and the obtained thermal conductive sheet are superior.

[0075] <Method for manufacturing a thermal conductive sheet precursor> The thermal conductive sheet precursor of the present invention is not particularly limited and can be manufactured by a method comprising: a primary sheet molding step of forming a composition containing at least the thermoplastic resin (A), reactive resin (B), thermal latent epoxy curing agent (C), and thermal conductive filler (D) into a sheet to obtain a primary sheet; a laminate forming step of stacking a plurality of primary sheets in the thickness direction, or folding or winding the primary sheets to obtain a laminate; and a slicing step of slicing the laminate at an angle of 45° or less with respect to the stacking direction to obtain a secondary sheet. The method for manufacturing the thermal conductive sheet precursor described above may further include other steps besides those described above.

[0076] <Primary sheet molding process> In the primary sheet molding process, a composition comprising a thermoplastic resin (A), a reactive resin (B), a heat-latent epoxy curing agent (C), and a thermally conductive filler (D), and optionally further comprising at least one component selected from the group consisting of a curing accelerator (E) and other additives, is molded into a sheet to obtain a primary sheet. Here, the above components can be those described in the section on "thermally conductive sheet precursors."

[0077] [Preparation of composition] The composition is not particularly limited and can be prepared by mixing the above-mentioned components. Here, the preferred blending ratio of each component in the composition can be the same as that described in the section on "thermal conductive sheet precursor". The mixing of the above-mentioned components is not particularly limited and can be carried out using known mixing equipment such as a kneader; a mixer such as a Henschel mixer, Hobart mixer, or high-speed mixer; a twin-shaft kneader; rolls; etc.

[0078] Although the above-mentioned components may be added to the mixing apparatus all at once and mixed, it is preferable to add them in stages from the viewpoint of component dispersibility and low-temperature mixing. In particular, since the reactive resin (B) may have its reaction accelerated by heating, it is preferable to add it last during mixing.

[0079] The mixing temperature (temperature of the mixture) is preferably less than 60°C from the viewpoint of suppressing the reaction of the reactive resin (B). The lower limit of the mixing temperature is not particularly limited, but can be, for example, 5°C or higher. The mixing time can be, for example, 5 minutes or more and 60 minutes or less.

[0080] [Forming of the composition] The prepared composition is formed into a sheet. From the viewpoint of improving operability and moldability during molding, it is preferable to crush the composition beforehand using a crusher or the like before molding. The molding method is not particularly limited as long as it is a method in which pressure is applied to the composition and the composition is formed into a sheet, and can be a known pressure molding method such as press molding, rolling molding or extrusion molding. Among these, it is preferable to form the composition into a sheet by rolling molding, and more preferably to roll-form it into a sheet by passing it between rolls. From the viewpoint of suppressing the reaction of the reactive resin (B), it is preferable that the molding temperature (temperature of the components used for molding) be 50°C or lower. For example, when roll molding is performed, it is preferable that the roll temperature be 50°C or lower. Furthermore, the lower limit of the molding temperature is not particularly limited, but for example, it can be 5°C or higher. Furthermore, in the primary sheet formed by pressurizing the composition into a sheet, the thermally conductive filler (D) is mainly arranged in the in-plane direction, and it is presumed that the in-plane thermal conductivity of the primary sheet is improved.

[0081] <Laminate formation process> In the laminate formation process, multiple primary sheets obtained in the primary sheet molding process are stacked in the thickness direction, or the primary sheets are folded or wound to obtain a laminate in which multiple primary sheets containing the above-mentioned components are formed in the thickness direction. Here, the formation of a laminate by folding primary sheets is not particularly limited and can be done by folding the primary sheets to a certain width using a folding machine. The formation of a laminate by winding primary sheets is not particularly limited and can be done by winding the primary sheets around an axis parallel to the short or long direction of the primary sheets. Furthermore, the formation of a laminate by stacking primary sheets is not particularly limited and can be done using a stacking device. For example, by using a sheet stacking device (manufactured by Nikkiso Co., Ltd., product name "High Stacker"), it is possible to suppress the intrusion of air between layers, thereby efficiently obtaining a good laminate.

[0082] Furthermore, from the viewpoint of suppressing delamination, it is preferable to press the resulting laminate at a pressure of 0.05 MPa to 1.5 MPa in the lamination direction for 30 minutes to 90 minutes at a temperature of 20°C to 50°C.Hereinafter, the laminate before pressing may be referred to as the "first laminate," and the laminate after pressing may be referred to as the "second laminate." In obtaining a laminate, for example, when laminating primary sheets, it is necessary to heat and pressurize them to ensure good adhesion between the primary sheets. However, in the present invention, since a heat-latent epoxy curing agent (C) is used, curing during lamination can be prevented.

[0083] In laminates obtained by stacking, folding, or winding primary sheets, it is presumed that the thermally conductive fillers (D) are arranged in a direction substantially perpendicular to the stacking direction.

[0084] <Slicing process> In the slicing process, the laminate obtained in the laminate formation process is sliced ​​at an angle of 45° or less with respect to the lamination direction to obtain a secondary sheet consisting of slices of the laminate.

[0085] Here, the method for slicing the laminate is not particularly limited, and examples include the multi-blade method, laser processing method, water jet method, and knife processing method. Among these, the knife processing method is preferred because it makes it easier to make the thickness of the heat conductive sheet precursor uniform. The shape of the knife used in the knife processing method can be single-edged, double-edged, or asymmetrical, but a single-edged blade is preferred from the viewpoint of achieving thickness accuracy. Furthermore, the cutting tool used when slicing the laminate is not particularly limited, and a slicing member having a smooth surface with a slit and a blade portion protruding from the slit portion (for example, a plane or slicer with a sharp blade) can be used.

[0086] Furthermore, from the viewpoint of further improving the thermal conductivity of the resulting thermal conductive sheet, the slicing angle of the laminate is preferably 30° or less with respect to the lamination direction, more preferably 15° or less with respect to the lamination direction, and preferably approximately 0° with respect to the lamination direction (i.e., in the direction along the lamination direction). It is presumed that the thermal conductive filler (D) is arranged in the thickness direction within the secondary sheet obtained in this way.

[0087] <Thermal conductive sheet> The thermally conductive sheet of the present invention is a cured product of the thermally conductive sheet precursor described above, and is obtained by heating the thermally conductive sheet precursor. Each component in the thermally conductive sheet is derived from the thermally conductive sheet precursor.

[0088] The thermal conductive sheet preferably has a structure in which multiple strips are connected in parallel in one direction substantially perpendicular to the thickness direction of the thermal conductive sheet (a direction at an angle of approximately 90° to the thickness direction). In the thermal conductive sheet, the thermal conductive filler (D) is oriented in the thickness direction, thereby improving the thermal conductivity of the thermal conductive sheet. The above-mentioned strips are cured products of strips of the thermal conductive sheet precursor. Furthermore, the preferred thickness of the thermal conductive sheet and the preferred width of the thermal conductive sheet strips are the same as those described above in the section on "thermal conductive sheet precursor".

[0089] <Thermal resistance value> The thermal conductive sheet preferably has a thermal resistance value (°C / W) of 0.20 or less, more preferably 0.19 or less, and even more preferably 0.17 or less, measured under a pressure of 0.3 MPa by a metal foil lamination method. If the thermal resistance value of the thermal conductive sheet is below the above upper limit, it can exhibit excellent thermal conductivity when assembled between a heat-generating element and a heat-sinking element. In this invention, the thermal resistance value of the thermal conductive sheet obtained by the metal foil lamination method can be determined by the method described in the examples.

[0090] (Manufacturing method for heat dissipation devices) The method for manufacturing the heat dissipation device of the present invention includes a step of preparing a laminate comprising a heat-generating element, a heat-conducting sheet precursor, and a heat dissipation element stacked together (preparation step), and a step of heating the laminate under pressure to harden the heat-conducting sheet precursor (hardening step), and may optionally include other steps. According to the method for manufacturing a heat dissipation device of the present invention, it is possible to manufacture a heat dissipation device that can efficiently dissipate heat.

[0091] <Preparation process> In the preparation step, a stack is prepared, consisting of a heat-generating element, a heat-conducting sheet precursor, and a heat sink. Specifically, a stack is prepared in which the heat-conducting sheet precursor is sandwiched between the heat-generating element and the heat sink.

[0092] As a thermal conductive sheet precursor, the one described above in the "Thermal Conductive Sheet Precursor" section can be used. The heat-generating elements are not particularly limited and include, for example, integrated circuit elements such as CPUs, GPUs (Graphics Processing Units), DRAMs (Dynamic Random Access Memory), and flash memory, as well as electronic components that generate heat in electrical circuits, such as transistors and resistors. The heat dissipation material is not particularly limited and can be any heat sink or heat spreader used in combination with integrated circuit elements. Examples of materials for heat sinks and heat spreaders include copper and aluminum. In addition to heat spreaders and heat sinks, any heat dissipation material that conducts heat generated from a heat source to the outside can be used, such as heat sinks, coolers, die pads, printed circuit boards, cooling fans, Peltier elements, heat pipes, vapor chambers, metal covers, and housings.

[0093] The laminate of the heating element, the thermal conductive sheet precursor, and the heat sink is not particularly limited and can be obtained, for example, by placing the thermal conductive sheet precursor on the surface of the heating element, and then placing the heat sink on the surface of the thermal conductive sheet precursor. Alternatively, it may be obtained by placing the thermal conductive sheet precursor on the surface of the heat sink, and then placing the heating element on top of the thermal conductive sheet precursor. The thermal conductive sheet precursor may be a single sheet or multiple sheets stacked together.

[0094] <Curing process> In the curing process, the laminate obtained in the preparation process is heated under pressure to cure the thermal conductive sheet precursor. As a result, the thermal conductive sheet, which is the cured product of the thermal conductive sheet precursor, is obtained sandwiched between the heating element and the heat sink.

[0095] The heating temperature of the laminate is not particularly limited as long as it can cure the heat-conducting sheet precursor in the laminate, but is preferably 120°C or higher, more preferably 150°C or higher, preferably 200°C or lower, and more preferably 180°C or lower.

[0096] The heating time for the laminate is preferably 30 minutes or more, and more preferably 1 hour or more. There is no particular upper limit to the heating time for the laminate, but it is preferably 96 hours or less, and more preferably 2 hours or less.

[0097] The pressure applied when pressurizing the laminate (the pressure that presses the laminate in the stacking direction; absolute pressure) is preferably 0.2 MPa or higher, more preferably 0.3 MPa or higher, preferably 1.3 MPa or lower, and more preferably 1.1 MPa or lower.

[0098] <Other processes> Other steps that may be included in the method for manufacturing the heat dissipation device of the present invention include, for example, a step for manufacturing a thermal conductive sheet precursor. The step for manufacturing the thermal conductive sheet precursor can be the same as the "method for manufacturing a thermal conductive sheet precursor" described above, and is performed before the "preparation step" described above.

[0099] Thus, in the manufacturing method of the heat dissipation device of the present invention, a laminate consisting of a heating element, a heat conductive sheet precursor, and a heat sink is pressed in the direction of the laminate to bring the heat conductive sheet precursor into close contact with the heating element and the heat sink, and the heat conductive sheet precursor is cured to form a heat conductive sheet. As a result, in the resulting heat dissipation device, the heat conductive sheet adheres well to the heating element and the heat sink. Consequently, it is presumed that the above heat dissipation device has a lower interfacial thermal resistance at the interface between the heat conductive sheet and the heating element / heat sink compared to conventional heat dissipation devices in which the final heat conductive sheet is sandwiched between the heating element and the heat sink, and can efficiently dissipate heat.

[0100] (Heat dissipation device) The heat dissipation device manufactured by the manufacturing method of the present invention comprises a heating element, a heat sink, and a thermal conductive sheet sandwiched between the heating element and the heat sink. Here, the thermal conductive sheet is a cured product of the thermal conductive sheet precursor of the present invention described above. Since the heat dissipation device is equipped with a thermal conductive sheet which is a cured product of the thermal conductive sheet precursor of the present invention, it can efficiently dissipate heat. The preferred attributes of the thermal conductive sheet in the heat dissipation device are the same as those described above in the "Thermal Conductive Sheet" section. [Examples]

[0101] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" used to express quantities refer to mass unless otherwise specified. The various physical properties in the examples and comparative examples were measured and evaluated according to the following methods.

[0102] <Weight-average molecular weight of thermoplastic resin (A)> The weight-average molecular weight of thermoplastic resin (A) was determined on a standard polystyrene basis by gel permeation chromatography using tetrahydrofuran as the eluent. <Gel fraction> The thermal conductive sheet precursors (thickness: 300 μm) prepared in the examples and comparative examples were heated and cured in a vacuum oven at 150°C for 1 hour to obtain thermal conductive sheets. The weight of the obtained thermal conductive sheets was measured and designated as the weight before immersion X. The thermal conductive sheets were immersed in 50 ml of butyl acetate for 24 hours. After that, the thermal conductive sheets were carefully removed using tweezers (no rinsing or washing was performed during removal), placed on an aluminum tray, air-dried, and vacuum-dried at 90°C for 2 hours. The weight of the thermal conductive sheets after drying was measured and designated as the weight after immersion Y. The gel fraction was calculated using the weight before immersion X and the weight after immersion Y according to the following formula. Gel fraction = (Y / X) × 100 (%) Furthermore, any solvent other than butyl acetate may be used to immerse the thermal conductive sheet, as long as it dissolves the uncured resin but not the cured resin. Furthermore, "weight before immersion X" and "weight of sheet after immersion Y" each include the weight of the thermal conductive filler (D). Here, after immersion of the thermal conductive sheet in the solvent, the thermal conductive filler (D) may spill out along with the uncured resin dissolved in the solvent, but this spilled thermal conductive filler (D) is not included in "weight of sheet after immersion Y". Also, "weight of sheet after immersion Y" refers only to the weight of the portion of the thermal conductive sheet that maintains its sheet shape after immersion, and any portion that collapses and breaks apart after immersion is not included in "weight of sheet after immersion Y". Furthermore, the sheet size of the thermal conductive sheet to be measured for gel fraction is not particularly limited. <Percentage of thermally conductive filler (D) content (volume fraction)> The volume of each material used in the formation of the primary sheet was calculated by dividing its weight by its specific gravity. The percentage of thermally conductive filler (D) contained in the primary sheet (volume fraction) was then determined. The specific gravities of the products used in the examples and comparative examples are as follows. DN601:0.98 UC3510:1.06 H570:1.00 jER828:1.16 jER871:0.985 DYHARD 100SF: 1.4 Fujicure 7002: 1.14 DYHARD UR700: 1.23 2MAOKPW:1.53 EC100:2.25 <Thermal resistance value> [Thermal resistance value of thermal conductive sheet precursor (bulk thermal resistance value)] The thermal resistance values ​​of the thermal conductive sheet precursors (thickness: 100 μm) manufactured in the examples and comparative examples were measured using a thermal resistance tester (manufactured by Hitachi Technology & Services, Ltd., product name: "Thermal Resistance Measuring Device for Resin Materials"). Specifically, thermal conductive sheet precursors cut into approximately 1 cm squares were used as samples, and the thermal resistance values ​​of the thermal conductive sheet precursors were measured under various conditions, with a sample temperature of 50°C and a pressure of 0.3 MPa applied in the thickness direction. [Thermal resistance value by metal foil lamination method] Two Au-plated Cu foils (thickness: approximately 30 μm) were each cut into 18 mm squares, and then the thermal conductive sheet precursors (thickness: 100 μm) obtained in the examples and comparative examples were cut into 12 mm squares. Two metal plates with screw holes in the four corners were prepared, and one Au-plated Cu foil was placed in the center of one metal plate, with the thermal conductive sheet precursor placed on top of it. Furthermore, the other Au-plated Cu foil was placed on top of this thermal conductive sheet precursor, and the other metal plate was placed on top of this Au-plated Cu foil, thereby obtaining a laminate consisting of a metal plate / Au-plated Cu foil / thermal conductive sheet precursor / Au-plated Cu foil / metal plate. The four corners of the two metal plates were then fixed with screws, and the screws were tightened to a torque value of 4 cN·m to assemble the two metal plates. This assembly was placed in an oven and heated at a temperature of 150°C for 1 hour. The assembly was removed from the oven and left to room temperature. Subsequently, the screws were removed from the metal plate, and a metal foil laminate consisting of Au-plated Cu foil / thermal conductive sheet / Au-plated Cu foil was obtained. Next, grease was applied to the lower surface of the copper shaft of a thermal resistance tester (manufactured by Hitachi Technology & Services, Ltd., product name "Thermal Resistance Measuring Device for Resin Materials"). Grease was then applied to the upper surface of the metal foil laminate, and the upper surface of the metal foil laminate was attached to the upper surface of the copper shaft of the thermal resistance tester. Then, at a temperature of 50°C, the thermal resistance value was measured while a pressure of 0.3 MPa was applied in the thickness direction of the metal foil laminate. In the above metal foil lamination method, unlike when measuring the thermal resistance of a thermal conductive sheet alone, the thermal resistance at the interface with the metal foil is added to the bulk thermal resistance (thermal resistance of the thermal conductive sheet alone). Therefore, the measured thermal resistance value is considered to be the sum of the bulk thermal resistance value and the interfacial thermal resistance value at the interface between the thermal conductive sheet and the heat-generating / heat-sinking element. Furthermore, the value of the interfacial thermal resistance is thought to vary depending on the degree of adhesion between the thermal conductive sheet and the metal foil. The better the adhesion between the thermal conductive sheet and the metal foil, the lower the measured thermal resistance value will be, and the worse the adhesion, the greater the interfacial resistance and the higher the measured thermal resistance value will be. <Tackiness (Storage Stability)> The tack force on the surface of thermal conductive sheet precursors (thickness: 100 μm) prepared in the examples and comparative examples was measured using a tack device (TAC-1000, RHESCA). Specifically, the thermal conductive sheet precursors were stored at 23°C for 7, 14, or 30 days. Double-sided tape was attached to a 5 mm diameter probe, and a 4 mm diameter punched thermal conductive sheet precursor was attached to it. The sample-equipped probe was attached to the main body of the device, a silicon wafer was placed on the stage, and the tack value was evaluated at room temperature, a pressing pressure of 0.3 MPa, and a holding time of 10 seconds. The instantaneous maximum value (N) when peeling off the thermal conductive sheet precursor was read, and the value was measured over the sample area (0.1256 cm²). 2 By dividing by ), the tack value (N / cm²) after storage at 23°C for 7, 14, and 30 days can be obtained. 2 The following values ​​were calculated for each of them. Then, the decrease in tack force after 14 days and 30 days of storage relative to the initial value (tack force after 7 days of storage) was calculated using the following formula, and the storage stability of the thermal conductive sheet precursor was evaluated based on the following criteria. Tack strength reduction rate (%): 1 - ([Tack strength after 30 days of storage] or [Tack strength after 14 days of storage] / [Tack strength after 7 days of storage] × 100) A: The percentage decrease in tack strength after 30 days of storage relative to the initial value is 50% or less. B: The percentage decrease in tack strength after 30 days of storage relative to the initial value is between 50% and 60%. C: The percentage decrease in tack strength after 30 days of storage relative to the initial value is between 60% and 80%. D: The percentage decrease in tack strength after 30 days of storage relative to the initial value is over 80%. (Low temperature curing) The low-temperature curability of the thermal conductive sheet precursors produced in the examples and comparative examples was measured as follows and evaluated based on the following criteria. The thermal conductive precursor sheets (300 μm thick) obtained in the examples and comparative examples were heated and cured in a vacuum oven under three temperature and time conditions: 150°C for 1 hour (condition 1), 180°C for 1 hour (condition 2), and 180°C for 5 hours (condition 3; overheated to ensure sufficient curing) to obtain thermal conductive sheets. Next, the gel fraction of the thermal conductive sheets obtained by heating and curing under each condition was measured using the same procedure as described above for "gel fraction". Then, the low-temperature curability of the thermal conductive sheet precursors produced in the examples and comparative examples was evaluated based on the following criteria. A: The difference between "Gel fraction under Condition 3 (180°C for 5 hours)" and "Gel fraction under Condition 1 (150°C for 1 hour)" is 10 or less. B: The difference between "Gel fraction under condition 3 (180°C for 5 hours)" and "Gel fraction under condition 1 (150°C for 1 hour)" is greater than 10 and less than or equal to 30. C: The difference between "Gel fraction under condition 3 (180°C for 5 hours)" and "Gel fraction under condition 1 (150°C for 1 hour)" is greater than 30 and less than or equal to 60. D: "Gel fraction under condition 3 (180°C for 5 hours)" - "Gel fraction under condition 1 (150°C for 1 hour)" is greater than 60.

[0103] (Measurement of viscosity) The viscosity was determined for each of the following: the thermal latent epoxy curing agent (C) used in Examples 1-2 and 4-6 (product name "DYHARD® 100SF", manufactured by Alzchem; solid dispersion type latent curing agent, dicyandiamide); the thermal latent epoxy curing agent (C) used in Example 3 (product name "Fujicure 7002", manufactured by T&K TOKA; reactive group blocking type latent curing agent, amine compound); and the imidazole curing accelerator used in Example 6 and Comparative Example 1 (product name "2MAOK-PW", manufactured by Shikoku Chemicals Co., Ltd.). The viscosity was determined by the method described below and evaluated according to the criteria below. The results are shown in Table 1. The epoxy resin alone was used as a control. [Method for measuring viscosity] 100 parts by mass of epoxy resin (product name "jER828", manufactured by Mitsubishi Chemical Corporation) was mixed with 20 parts by mass of a curing agent or curing accelerator, and the resulting mixture was stored at a temperature of 40°C. At each of the following time points—immediately after preparation, after 3 days of storage, and after 7 days of storage—the viscosity (mPa·s) of the mixture was measured using a B-type viscometer (manufactured by Anton Paar) at room temperature (23°C) and a shear rate of 80¹ / s. The viscosity increase rate (%) was then calculated using the following formula. Thickening rate (%) = ([Viscosity after 7 days of storage] / [Viscosity immediately after preparation (initial)]) - 1 × 100) A: Thickening rate is less than 0% B: Thickness ratio greater than 0% and less than or equal to 10% C: Thickness ratio greater than 10% but less than or equal to 100% D: Thickness rate exceeds 100% [Table 1]

[0104] As shown in Table 1, the thermal latent epoxy curing agent (C) used in Examples 1 to 6 has a viscosity increase of 100% or less, indicating that it is a suitable thermal latent epoxy curing agent.

[0105] (Example 1) <Preparation of Composition> Using a kneader, a carboxy-modified liquid NBR (product name "DN601", weight-average molecular weight: 6000, molar amount of acidic functional groups per gram of resin: 0.86 mmol / g, manufactured by Nippon Zeon Co., Ltd.) as a thermoplastic resin (A), an epoxy resin (product name "jER828", manufactured by Mitsubishi Chemical Corporation) as a reactive resin (B), a solid-disperse latent curing agent (dicyandiamide, product name "DYHARD® 100SF", manufactured by AlzChem) as a thermal latent epoxy curing agent (C), a urea-based curing accelerator (product name "DYHARD® UR700", manufactured by AlzChem) as a curing accelerator (E), two types of antioxidants (product names "Nocrack CD" and "Nocrack MBZ", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), and expanded graphite (product name "EC100", manufactured by Ito Graphite Co., Ltd.) as a thermally conductive filler (D) were kneaded to obtain the composition. Specifically, powder A was prepared by pre-distributing 5 parts by mass of a heat-latent epoxy curing agent (C), 3 parts by mass of a curing accelerator (E), 2 parts by mass each of various antioxidants, and 203 parts by mass of a heat-conductive filler (D). The kneader was set to a temperature of 35°C, and 100 parts by mass of thermoplastic resin (A) and half of the powder A were added and kneaded for 3 minutes. Then, the remaining powder A was added and kneaded for 7 minutes. After that, 16.2 parts by mass of reactive resin (B) was added and kneaded for 8 minutes to obtain the composition. <Primary sheet molding process> Next, 600g of the obtained composition was rolled between rolls to form a sheet, thereby obtaining a primary sheet. The roll temperature was set to 50°C, and the line speed for roll transport was set to 1m / min. <Laminate formation process> Next, the obtained primary sheets were cut into 50mm x 50mm sections and stacked to a height of 55mm to obtain the first laminate. Subsequently, the obtained first laminate was vacuum-pressed in the stacking direction at a temperature of 50°C and a pressure of 1.1MPa for 1 hour to obtain the second laminate. <Slicing process> Next, while pressing the laminated surface of the second laminate with a pressure of 0.3 MPa, a woodworking slicer (manufactured by Marunaka Iron Works Co., Ltd., product name "Super Finishing Planer Super Mecha S") was used to slice the material at an angle of 0 degrees to the lamination direction (in other words, in the direction normal to the main surface of the laminated primary sheet), thereby obtaining a secondary sheet (thermal conductive sheet precursor) measuring 50 mm in length, 50 mm in width, and 100 μm in thickness. The thermal conductive sheet precursor is composed of strips joined in parallel in a direction perpendicular to the thickness direction of the thermal conductive sheet precursor (a direction at an angle of 90° to the thickness direction). The width of the strips in this approximately perpendicular direction is approximately the same as the thickness of the primary sheet. Furthermore, a thermal conductive sheet precursor measuring 50 mm in length, 50 mm in width, and 300 μm in thickness was also obtained for gel fraction measurement. Using the obtained thermal conductive sheet precursor, various measurements and evaluations were performed according to the above procedure. The results are shown in Table 2.

[0106] (Example 2) In preparing the composition, the amount of reactive resin (B) was changed from 16.2 parts by mass to 19.5 parts by mass, and the amount of thermally conductive filler (D) was changed from 203 parts by mass to 208 parts by mass. Except for these changes, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 2.

[0107] (Example 3) In preparing the composition, 5 parts by mass of a reactive group-blocking type latent curing agent (trade name "Fujicure 7002", manufactured by T&K TOKA; amine-based compound) was used instead of 5 parts by mass of a solid-disperse type latent curing agent (C) as the thermal latent epoxy curing agent (C), the amount of thermal conductive filler (D) was changed from 208 parts by mass to 206 parts by mass, and the curing accelerator (E) was not used. Except for these changes, various operations, measurements, and evaluations were carried out in the same manner as in Example 2. The results are shown in Table 2.

[0108] (Example 4) In preparing the composition, the reactive resin (B) was changed from 16.2 parts by mass of epoxy resin (trade name "jER828", manufactured by Mitsubishi Chemical Corporation) to 35.5 parts by mass of epoxy resin (trade name "jER871", manufactured by Mitsubishi Chemical Corporation), and the amount of thermally conductive filler (D) was changed from 203 parts by mass to 240 parts by mass. Otherwise, various operations, measurements, and evaluations were performed in the same manner as in Example 1. The results are shown in Table 2.

[0109] (Example 5) In preparing the composition, instead of 100 parts by mass of carboxy-modified liquid NBR (product name "DN601", manufactured by Nippon Zeon Co., Ltd.) as thermoplastic resin (A), 80 parts by mass of carboxy-containing acrylic rubber (product name "ARUFON UC3510", weight-average molecular weight: 2000, molar amount of acidic functional groups per gram of resin: 1.32 mmol / g, manufactured by Toagosei Co., Ltd.) and 20 parts by mass of carboxy-containing acrylic rubber (product name "HyTemp H570", weight-average molecular weight: 1,400,000, molar amount of acidic functional groups per gram of resin: 0.085 mmol / g, manufactured by Nippon Zeon Co., Ltd.) were used. The amount of reactive resin (B) was changed from 16.2 parts by mass to 21 parts by mass. A reactive group-blocking latent curing agent (product name "Fujicure 7002", T&K Except for using 3 parts by mass of an amine compound manufactured by TOKA Corporation, changing the amount of thermally conductive filler (D) from 203 parts by mass to 214 parts by mass, and not using a curing accelerator (E), various operations, measurements, and evaluations were performed in the same manner as in Example 1. The results are shown in Table 2. The weight-average molecular weight of the thermoplastic resin (A) in this example using the two types of thermoplastic resins (A) described above is [weight-average molecular weight of ARUFON UC3510 2000 × blending ratio 0.8] + [weight-average molecular weight of HyTemp H570 1,400,000 × blending ratio 0.2] = 280,320.

[0110] (Example 6) In preparing the composition, 3 parts by mass of an imidazole-based curing accelerator (trade name "2MAOK-PW", manufactured by Shikoku Chemicals, Inc.; reaction initiation temperature: 122°C) was used instead of 3 parts by mass of a urea-based curing accelerator (E), and the amount of thermally conductive filler (D) was changed from 203 parts by mass to 206 parts by mass. Otherwise, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 2.

[0111] (Comparative Example 1) In preparing the composition, the thermal latent epoxy curing agent (C) was not used, and the curing accelerator (E) was changed from 3 parts by mass of urea-based curing accelerator to 5 parts by mass of imidazole-based curing accelerator (product name "2MAOK-PW", manufactured by Shikoku Chemicals Co., Ltd.), and the amount of thermally conductive filler (D) was changed from 203 parts by mass to 200 parts by mass. Otherwise, various operations, measurements, and evaluations were performed in the same manner as in Example 1. The results are shown in Table 2.

[0112] (Comparative Example 2) In preparing the composition, 100 parts by mass of a thermoplastic resin (liquid NBR, trade name "Nipol 1312", manufactured by Nippon Zeon Co., Ltd.) that does not have reactive groups that react with epoxy groups was used instead of 100 parts by mass of thermoplastic resin (A). Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 2. [Table 2]

[0113] As shown in Table 2, Examples 1 to 6, which use a thermal conductive sheet precursor containing a thermoplastic resin (A), a reactive resin (B), a heat-latent epoxy curing agent (C), and a thermally conductive filler (D), can reduce the thermal resistance of the thermal conductive sheet when assembled between a heating element and a heat sink. [Industrial applicability]

[0114] According to the present invention, it is possible to provide a thermal conductive sheet precursor that can obtain a thermal conductive sheet with low thermal resistance when assembled between a heating element and a heat sink, a method for manufacturing a heat dissipation device using the thermal conductive sheet precursor, and a heat dissipation device capable of efficiently dissipating heat.

Claims

1. A thermal conductive sheet precursor comprising a thermoplastic resin (A) having a reactive group that reacts with an epoxy group, a reactive resin (B) having an epoxy group, a thermally latent epoxy curing agent (C), and a thermally conductive filler (D).

2. The thermal conductive sheet precursor according to claim 1, further comprising a curing accelerator (E).

3. The thermal conductive sheet precursor according to claim 1, wherein the gel fraction when heated at 150°C for 1 hour is 80% or more.

4. The thermal conductive sheet precursor according to claim 1, wherein the weight-average molecular weight of the thermoplastic resin (A) is 2,000 or more and 200,000 or less.

5. The thermal conductive sheet precursor according to claim 1, wherein the thermal latent epoxy curing agent (C) is dicyandiamide or a reactive group-blocking type latent curing agent.

6. The thermal conductive sheet precursor according to claim 1, wherein the equivalent amount of epoxy groups contained in the reactive resin (B) relative to 1 equivalent of reactive groups contained in the thermoplastic resin (A) is 0.8 equivalents or more and 1.3 equivalents or less.

7. A step of preparing a laminate comprising a heat-generating element, a heat-conducting sheet precursor according to any one of claims 1 to 6, and a heat-dissipating element, A method for manufacturing a heat dissipation device, comprising the step of heating the laminate under pressure to harden the heat conductive sheet precursor.

8. A heat dissipation device comprising a heating element, a heat sink, and a cured product of a thermal conductive sheet precursor according to any one of claims 1 to 6 sandwiched between the heating element and the heat sink.

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