JP2022059896A - Heat-conductive resin composition, heat dissipation member, electronic apparatus, and method for producing heat-conductive resin composition - Google Patents

Abstract

To provide a heat-conductive resin composition for a heat dissipation member having high heat conductivity in a thickness direction, a heat dissipation member using the same, and an electronic apparatus using the same, and to provide a method for producing a heat-conductive resin composition for a heat dissipation member having high heat conductivity in a thickness direction at low cost.SOLUTION: A heat-conductive resin composition contains a first heat-conductive inorganic filler that is fibrous, a second heat-conductive inorganic filler having different shapes or sizes from the first heat-conductive filler, and a resin, in which a percentage content of the first heat-conductive inorganic filler is 0.1-10 wt.%, and a percentage content of the second heat-conductive inorganic filler is 60-88 wt.%, with respect to the solid content (component other than solvent contained in heat-conductive resin composition) in the heat-conductive resin composition.SELECTED DRAWING: Figure 1

Description

The present invention relates to a heat conductive resin composition having excellent heat conductivity in the thickness direction of the heat radiating member, a heat radiating member using the same, and an electronic device. The present invention also relates to a method for producing a thermally conductive resin composition.

In recent years, with the demand for higher functionality and smaller size and thinner electronic devices, the amount of heat generated from semiconductors mounted at high density has been increasing. For example, heat sinks and heat sink fins are indispensable for heat dissipation for stable operation of semiconductor devices used for controlling central arithmetic processing devices of personal computers and motors of electric vehicles, and members that connect semiconductor devices and heat sinks. There is a demand for a material that can achieve both insulation and thermal conductivity. Generally, a resin member sandwiched between a heating element such as a semiconductor package and a heat sink made of aluminum or copper has high insulating properties but extremely low thermal conductivity, and contributes to heat dissipation of semiconductor devices and the like. It was small.

In order to improve thermal conductivity while maintaining electrical insulation, a composite material in which a large amount of an inorganic filler having high thermal conductivity is filled in a resin is being developed. Known high thermal conductive inorganic fillers include boron nitride, alumina, alumina hydrate, aluminum nitride, silica, silicon nitride, magnesium oxide, silicon carbide, and titanium oxide. By changing the size, blending amount, etc., it is possible to realize electrical insulation and thermal conductivity according to the purpose.

A method of improving thermal conductivity by using a thermally conductive inorganic filler alone is known. According to Patent Document 1, when the filler particle size is small, the frequency of passing through the contact interface between the filler particles in the heat conduction path increases, and the heat conduction at such an interface is inferior to the heat conduction inside the filler particles. Therefore, it is described that it is preferable to use a filler having a large particle size. However, if the particle size is too large, the distance between the fillers becomes large and the electrical insulation tends to decrease, so that there is a limit to the improvement of the thermal conductivity by increasing the particle size.

Therefore, a method is known in which two or more types of thermally conductive inorganic fillers having different particle sizes are mixed to fill the gaps between the fillers having a large particle size and improve the content rate. According to Patent Document 2, the filling rate can be increased by mixing a heat conductive inorganic filler having an average particle size of 0.01 to 1 μm and a heat conductive inorganic filler having an average particle size of 1 to 10 μm. Have been described. However, even if the content is increased in this way, that is, even if the distance between the fillers is shortened, a resin component that prevents heat conduction exists between the fillers and continuously connects the gaps between the fillers having a large particle size. It is difficult to significantly improve the heat conductivity because a suitable heat conduction path cannot be formed. Further, if the particle size of the filler that fills the gaps between the fillers having a large particle size becomes too small, the cohesiveness becomes remarkably high, and the resin cannot enter between the agglomerated particles and voids (voids) are formed. There is a problem that the thermal conductivity is lowered.

In addition, by making the shape of the heat conductive inorganic filler fibrous with a large major axis / minor axis ratio (aspect ratio), it becomes easier to form a heat conductive path, and there is a method for improving heat conductivity. Are known. Patent Document 3 describes a highly thermally conductive material obtained by electrostatically spinning a spinning liquid containing an alumina source, producing an alumina fiber sheet by firing, and impregnating the alumina fiber sheet with a resin. However, since the alumina fibers in the high thermal conductivity material are oriented in the plane direction, the thermal conductivity in the plane direction is improved, but it is difficult to improve the thermal conductivity in the thickness direction. Further, since the high thermal conductive material of Patent Document 3 is produced by a method of impregnating an alumina fiber sheet with a resin, there is a problem that operability is poor, continuous production is difficult, and it is difficult to increase the area. There is. Further, since the content of alumina fiber, which is generally considered to be low in productivity, is as high as 20% by weight or more, there is a problem that the high thermal conductive material using the alumina fiber has low productivity.

Therefore, there is known a method of improving the thermal conductivity in the thickness direction and improving the operability by mixing a filler having a large aspect ratio and a filler having a small aspect ratio. Patent Document 4 describes a polymer-based filler having a filling factor of 30 to 60% by volume, a first thermally conductive filler having a filling factor of 25 to 60% by volume and an aspect ratio of 10 or more, and 10 A molding composition using a second thermally conductive filler having an aspect ratio of less than 5 by volume to 25% by volume is described. However, in the molding composition, since the proportion of the filler having a large aspect ratio is large, voids (voids) are likely to be formed due to the aggregation of the filler, and the thermal conductivity is likely to decrease, and the heat dissipation member is molded (particularly thermal pressure). During molding), the filler with a large aspect ratio tends to be oriented in the plane direction, the thermal conductivity in the thickness direction is insufficient, and the amount of the filler with a high aspect ratio with low productivity is large. There is a problem that the productivity of the molded composition tends to deteriorate.

Japanese Unexamined Patent Publication No. 11-45965 Japanese Unexamined Patent Publication No. 2011-23607 International Publication No. 2018/135517 Special Table 2002-535469

An object of the present invention is to provide a heat conductive resin composition for a heat radiating member having high thermal conductivity in the thickness direction, a heat radiating member using the same, and an electronic device using the same. Another object of the present invention is to provide a method for producing a heat conductive resin composition for a heat radiating member having high heat conductivity in the thickness direction with high productivity.

The present inventors have diligently studied to solve the above problems. As a result, a thermally conductive resin composition containing a fibrous first thermally conductive inorganic filler, a second thermally conductive inorganic filler, and a resin in a specific ratio is obtained, and the thermally conductive resin is obtained. It has been found that the problem of the present invention can be solved by producing the composition by a specific method, and the present invention has been completed.

The present invention includes the following aspects.
[1] A thermally conductive resin containing a fibrous first thermally conductive inorganic filler, a second thermally conductive inorganic filler having a shape or size different from that of the first thermally conductive filler, and a resin. In the composition, the content of the first heat conductive inorganic filler is 0 with respect to the solid content (components other than the solvent contained in the heat conductive resin composition) in the heat conductive resin composition. A heat conductive resin composition having a content of 1 to 10% by weight and a content of the second heat conductive inorganic filler of 60 to 88% by weight.
[2] The thermally conductive resin composition according to [1], wherein the first thermally conductive inorganic filler has an average fiber diameter of 0.05 to 5 μm and an average aspect ratio of 5 or more.
[3] When the average particle size of the second heat conductive inorganic filler is A and the average fiber diameter of the first heat conductive inorganic filler is B, the A / B is 5 or more. [1] Alternatively, the thermally conductive resin composition according to [2].
[4] The heat conductive resin composition according to any one of [1] to [3], wherein the shape of the second heat conductive inorganic filler is at least one selected from the group consisting of spheres and aggregates. thing.
[5] The first heat conductive inorganic filler is at least one selected from the group consisting of alumina, aluminum nitride, magnesium oxide, and silicon carbide, and the second heat conductive inorganic filler is boron nitride. The heat conductive resin composition according to any one of [1] to [4], which is at least one selected from the group consisting of silicon nitride, aluminum nitride, alumina, titanium oxide, magnesium oxide, and silicon carbide.
[6] The thermal conductivity according to any one of [1] to [5], wherein the resin is at least one selected from the group consisting of an epoxy resin, a silicone resin, an acrylic resin, a polyimide resin, and a fluororesin. Resin composition.
[7] A heat radiating member using the heat conductive resin composition according to any one of [1] to [6].
[8] An electronic device comprising the heat radiating member according to [7] and an electronic device having a heat generating portion or a cooling portion, and arranged in the electronic device so that the heat radiating member comes into contact with the heat generating portion.
[9] A step of preparing a spinning solution containing an inorganic compound, a step of spinning the spinning solution to prepare a precursor fiber, a step of firing the precursor fiber to prepare an inorganic fiber aggregate, and the above-mentioned inorganic. The step of crushing the fiber aggregate to produce the first heat conductive inorganic filler and the step of mixing the first heat conductive inorganic filler, the second heat conductive inorganic filler and the resin are performed. The method for producing a thermally conductive resin composition according to any one of [1] to [6], which comprises.

According to the present invention, it is possible to provide a heat conductive resin composition for a heat radiating member having high heat conductivity in the thickness direction. Further, according to the production method of the present invention, it is possible to provide a heat conductive resin composition for a heat radiating member having high heat conductivity in the thickness direction with high productivity.

It is a conceptual diagram of the heat conductive resin composition containing the first heat conductive inorganic filler, the second heat conductive inorganic filler, and a resin according to the Example of this invention. It is a conceptual diagram of the heat conductive resin composition containing the second heat conductive inorganic filler and resin according to Comparative Example 1 or Comparative Example 4 by this invention. It is a conceptual diagram of the heat-conducting resin composition containing the second heat-conducting inorganic filler, spherical alumina, and the resin according to Comparative Example 2 or Comparative Example 5 according to the present invention. FIG. 3 is a conceptual diagram of a heat conductive resin composition containing a first heat conductive inorganic filler, a second heat conductive inorganic filler, and a resin according to Comparative Example 3 according to the present invention. 6 is an X-ray diffraction image of fibrous alumina 1 to 3 and spherical alumina used in Examples or Comparative Examples of the present invention.

The thermally conductive resin composition of the present invention comprises a fibrous first thermally conductive inorganic filler, a second thermally conductive inorganic filler having a different shape or size from the first thermally conductive inorganic filler, and a resin. The content of the first heat conductive inorganic filler is 0.1 to 10% by weight with respect to the solid content in the heat conductive resin composition, and the second heat conductive inorganic is contained. The filler content is 60 to 88% by weight.

<First thermally conductive inorganic filler>
The first thermally conductive inorganic filler in the present invention has thermal conductivity and its shape is fibrous.
The "thermal conductivity" in the present invention means having a thermal conductivity of 1 W / (m · K) or more. Such inorganic materials include alumina, alumina hydrate, aluminum nitride, magnesium oxide, silicon carbide, silica, verilia, silicon nitride, boron nitride, magnesium oxide, titanium oxide, zirconium oxide, glass, carbon, graphite, etc. Examples include diamond, aluminum, nickel, titanium, gold, silver, copper, platinum, iron, or stainless steel. The materials of the first heat conductive inorganic filler of the present invention include alumina, aluminum nitride, magnesium oxide, and from the viewpoints of safety, heat conductivity, insulating property, processability into fibrous form, and availability. It is preferably at least one selected from the group consisting of silicon carbide, more preferably at least one selected from alumina, aluminum nitride, and magnesium oxide, and at least one selected from alumina and aluminum nitride. Is even more preferable.
Further, the "fibrous" in the present invention has an elongated shape, that is, has two minor axes and one major axis, and the length of the major axis is three times or more (aspect ratio) with respect to the length of the minor axis. Means that is 3 or more).

The average fiber diameter (average value of the length of the minor axis) of the first heat conductive inorganic filler is not particularly limited, but is preferably 0.05 to 5 μm, and preferably 0.1 to 3 μm. It is more preferably 0.1 to 2 μm, and even more preferably 0.1 to 2 μm. When the average fiber diameter of the first heat conductive inorganic filler is 0.05 μm or more, the cohesiveness is suppressed and a continuous heat conduction path is easily formed between the second heat conductive inorganic fillers, which is 5 μm. The following is preferable because it is possible to secure many contact points even with a small filling amount. The average fiber length of the first thermally conductive inorganic filler is not particularly limited, but is preferably 0.3 to 200 μm, more preferably 1 to 150 μm, and more preferably 2 to 100 μm. More preferred. When the average fiber length of the first heat conductive inorganic filler is 0.3 μm or more, it is preferable because a heat conduction path is easily formed, and when it is 200 μm or less, the interval of the second heat conductive inorganic filler is widened. It is preferable because it does not occur and the decrease in thermal conductivity can be suppressed. The average fiber diameter and average fiber length of the first heat conductive inorganic filler are determined by, for example, observing the first heat conductive inorganic filler with a scanning electron microscope and measuring the lengths of its major axis and minor axis. It can be calculated by taking the average value of the length of the minor axis as the average fiber diameter and the average value of the length of the major axis as the average fiber length.

The average aspect ratio of the first thermally conductive inorganic filler is not particularly limited, but is preferably 5 or more, more preferably 10 or more, and further preferably 15 or more. When the average aspect ratio of the first heat conductive inorganic filler is 5 or more, it is possible to form a continuous heat conduction path connecting the gaps of the filler having a large particle size, which is preferable. The upper limit of the average aspect ratio is not particularly limited, but is preferably 100 or less, more preferably 80 or less, and even more preferably 50 or less. When the average aspect ratio of the first heat conductive inorganic filler is 100 or less, it is easy to enter the gap between the second heat conductive inorganic fillers, and the space between the second heat conductive inorganic fillers is not widened. , It is preferable because it can suppress a decrease in thermal conductivity. The aspect ratio of the first thermally conductive inorganic filler can be calculated, for example, by dividing the average fiber length obtained by using a scanning electron microscope by the average fiber diameter.

When the first thermally conductive inorganic filler is alumina, the crystal structure thereof is not particularly limited, and γ-alumina, θ-alumina, δ-alumina, or α-alumina can be exemplified. From the viewpoint of thermal conductivity, α-alumina is preferable. When the first heat conductive inorganic filler is aluminum nitride, the crystal structure thereof is not particularly limited, and examples thereof include wurtzite structure (hexagonal system) and sphalerite structure (cubic crystal system). From the viewpoint of thermal conductivity and stability, the wurtzite structure (hexagonal system) is preferable. When the first thermally conductive inorganic filler is magnesium oxide, it preferably has a cubic structure from the viewpoint of high thermal conductivity. The crystal structure of the first thermally conductive inorganic filler can be determined from, for example, a diffraction image obtained by an X-ray diffraction method.

<Second thermally conductive filler>
The second heat conductive inorganic filler of the present invention is not particularly limited as long as it has heat conductivity and is different in shape or size from the first heat conductive filler. However, from the viewpoint of improving the thermal conductivity in the thickness direction, the second thermally conductive inorganic filler preferably has a different shape. Here, "the shape is different" means that the shape of the second thermally conductive inorganic filler is other than fibrous. Further, "different in size" means that the average fiber diameter of the first heat conductive inorganic filler and the average particle size of the second heat conductive inorganic filler are different.

The shape of the second heat conductive inorganic filler is not particularly limited, and examples thereof include plate shape, scale shape, rod shape, spherical shape, fibrous shape, tubular shape, quadruped shape, amorphous shape, and aggregate. In particular, from the viewpoint of improving thermal conductivity in the thickness direction, at least one selected from the group consisting of spheres and aggregates is preferable.

The average particle size of the second thermally conductive inorganic filler is not particularly limited, but is preferably 0.25 to 1000 μm, more preferably 1 to 500 μm, still more preferably 10 to 150 μm. .. If the average particle size of the second thermally conductive inorganic filler is 0.25 μm, the cohesiveness can be suppressed, the resin can easily penetrate into the gaps between the fillers, and voids can be suppressed, which is 1000 μm or less. If this is the case, a high filling rate can be secured and the thermal conductivity in the thickness direction can be increased, which is preferable. In the present invention, the average particle size of the second heat conductive inorganic filler is based on the particle size distribution measurement by the laser diffraction / scattering method. That is, when the powder is divided into two from a certain particle size by the wet method using the analysis by Franhofer diffraction theory and Mie's scattering theory, the large side and the small side have the same amount (volume basis). Is the average particle size. However, only when the shape of the second heat conductive inorganic filler is fibrous, the average particle size of the second heat conductive inorganic filler is determined by observing the second heat conductive inorganic filler with a scanning electron microscope and determining the length of its minor axis. It is the average value of the length of the minor axis when measured.

The relationship between the sizes of the first thermally conductive inorganic filler and the second thermally conductive inorganic filler is not particularly limited, but the average particle size of the second thermally conductive inorganic filler is A, and the first heat. When the average fiber diameter of the conductive inorganic filler is B, the A / B is preferably 5 or more, more preferably 20 or more, and further preferably 50 or more. When the A / B is 5 or more, a sufficient contact point can be formed even if the content of the first heat conductive inorganic filler is small, and high heat conductivity can be obtained, which is preferable. Further, as the upper limit of A / B, 1000 or less can be exemplified. When the A / B is 1000 or less, the first heat conductive inorganic filler facilitates the formation of a continuous heat conduction path between the second heat conductive inorganic fillers, which is preferable.

As the material of the second heat conductive inorganic filler, alumina, alumina hydrate, aluminum nitride, magnesium oxide, silicon carbide, silica, verilia, silicon nitride, boron nitride, magnesium oxide, titanium oxide, zirconium oxide, and glass. , Carbon, graphite, diamond, aluminum, nickel, titanium, gold, silver, copper, platinum, iron, or stainless steel can be exemplified. It is preferably at least one selected from the group consisting of boron nitride, silicon nitride, aluminum nitride, alumina, titanium oxide, magnesium oxide, and silicon carbide from the viewpoint of insulation, thermal conductivity, and stability in the atmosphere. Graphite Graphite At least one selected from the group consisting of graphite graphite boron nitride, aluminum nitride, silicon nitride, and alumina is more preferable, and boron nitride is even more preferable.

When the second thermally conductive inorganic filler is boron nitride, the crystal structure thereof is not particularly limited, and hexagonal or cubic can be exemplified. Hexagonal system is preferable from the viewpoint of easy availability. When the second heat conductive inorganic filler is aluminum nitride, the crystal structure thereof is not particularly limited, and examples thereof include wurtzite structure (hexagonal system) and sphalerite structure (cubic crystal system). From the viewpoint of thermal conductivity and stability, the wurtzite structure (hexagonal system) is preferable. When the second heat conductive inorganic filler is silicon nitride, the crystal structure thereof is not particularly limited, and α-silicon nitride, β-silicon nitride, or γ-silicon nitride can be exemplified. From the viewpoint of thermal conductivity, β-silicon nitride is preferable. When the second thermally conductive inorganic filler is alumina, the crystal structure thereof is not particularly limited, and γ-alumina, θ-alumina, δ-alumina, or α-alumina can be exemplified. From the viewpoint of thermal conductivity, α-alumina is preferable. The crystal structure of the second thermally conductive inorganic filler can be determined, for example, from the peak position of the diffraction image obtained by the X-ray diffraction method.

The first and second thermally conductive inorganic fillers are not particularly limited, but may be treated to physically or chemically change their surface functional groups. Specifically, the surface thereof may be surface-treated with a silane coupling agent, a titanium coupling agent, an aluminum coupling agent, a zirconium coupling agent, a zircoaluminate coupling agent, or the like. The functional group at the end of the coupling agent is not particularly limited, and examples thereof include amino, fluoro, acryloyl, epoxy, ureido, and acid anhydride, which may be appropriately selected depending on the properties of the resin to be used.

<Resin>
The resin of the present invention is not particularly limited, and may be a thermoplastic resin, a thermosetting resin, or a photocurable resin, and may be, for example, a polyolefin resin, a polyamide resin, or a polyester resin. Examples thereof include polycarbonate resin, polyacetal resin, aramid resin, polyurethane resin, vinyl chloride resin, polysulfone resin, cell roll resin, fluororesin, epoxy resin, silicone resin, acrylic resin, and polyimide resin. From the viewpoint of moldability, insulation, heat resistance, etc., it is preferably at least one selected from the group consisting of epoxy resin, silicone resin, acrylic resin, polyimide resin, and fluororesin, and the group consisting of epoxy resin and fluororesin. It is more preferable that it is at least one selected more.

Epoxy resins include dicyclopentadiene type epoxy resin, phosphorus-containing epoxy resin, naphthalene type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, and bisphenol A novolak type. Examples thereof include, but are not limited to, epoxy resins, biphenyl type epoxy resins, alicyclic epoxy resins, polyfunctional phenol diglycidyl ether compounds, and polyfunctional alcohol diglycidyl ether compounds, but are generally epoxy resins. Widely includes what is called. These may be used alone or in combination of two or more. Among them, those containing an epoxy resin having a liquid crystal property are preferable because high thermal conductivity can be obtained.

Examples of the silicone resin include dimethylpolysiloxane, methylphenylpolysiloxane, diphenylpolysiloxane, and modified silicone obtained by reacting various silicones thereof with an organic group. These silicone resins may be used alone or in combination of two or more.

Examples of the acrylic resin include compounds in which at least one monomer component selected from (meth) acrylic acid and an ester thereof is mixed with a polymer capable of dissolving or swelling in the monomer component. These acrylic resins may be used alone or in combination of two or more.

Examples of the polyimide resin include polyamide-imide resin, polyetherimide resin, polypyrromeldidiimide resin, and bismaleimide. These polyimide resins may be used alone or in combination of two or more.

Examples of the fluororesin include polytetrafluoroethylene [PTFE], tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer [PFA], tetrafluoroethylene / hexafluoropropylene copolymer [FEP], and ethylene / tetrafluoroethylene. Polymer [ETFE], ethylene / tetrafluoroethylene / hexafluoropropylene copolymer, polychlorotrifluoroethylene [PCTFE], chlorotrifluoroethylene / tetrafluoroethylene copolymer, ethylene / chlorotrifluoroethylene copolymer, Examples thereof include polyfluorinated vinylidene [PVDF] and vinylidene fluoride / hexafluoropropylene copolymer, but the present invention is not limited thereto, and broadly includes what is generally called a fluororesin. These may be used alone or in combination of two or more. Of these, polyvinylidene fluoride is preferable from the viewpoint of easy moldability and mechanical properties.

<Thermal conductive resin composition>
The thermally conductive resin composition of the present invention comprises a fibrous first thermally conductive inorganic filler and a second thermally conductive inorganic filler having a shape or size different from that of the first thermally conductive inorganic filler. The content of the first heat conductive inorganic filler is 0.1 to 10% by weight with respect to the solid content in the heat conductive resin composition containing the resin, and the second heat conductive inorganic filler is contained. The content of the heat is 60 to 88% by weight. The heat conductive resin composition having the above-mentioned structure has a fibrous first heat conduction in the gaps between the second heat conductive inorganic fillers contained in a large amount as compared with the first heat conductive inorganic filler. By entering a small amount of the sex inorganic filler, the formation of voids is suppressed, and the second heat conductive inorganic fillers are connected to each other by the first heat conductive inorganic filler to form a heat conduction path, and further, fibrous. Since the orientation of the first heat conductive inorganic filler having the above in the plane direction can be suppressed, high heat conductivity in the thickness direction can be realized.

Although not bound by a specific theory, the effects of the present invention will be described with reference to FIGS. 1 to 4.
In the constitution of the heat conductive resin composition of the present invention, a large amount of the second heat conductive inorganic filler is contained in the resin, and a small amount of the fibrous first heat conductive inorganic filler is contained in the gaps thereof. The state (Fig. 1). Therefore, the effect that the heat conductive path can be efficiently formed by the first heat conductive inorganic filler and the effect that voids due to aggregation are less likely to be formed due to the small amount of the first heat conductive inorganic filler. It is considered that the heat conductivity in the thickness direction can be improved by the effect that the first heat conductive inorganic filler is less likely to be oriented in the plane direction (arrow in FIG. 1; means that the heat conduction rate is high). .).
On the other hand, when the first thermally conductive inorganic filler is not used (FIG. 2) or when a small-sized spherical thermally conductive inorganic filler is used instead of the first thermally conductive inorganic filler (FIG. 3). , It is difficult to obtain high thermal conductivity because the ratio of heat conduction to the resin part with relatively low thermal conductivity increases (broken arrow in FIGS. 2 and 3; means that the heat conduction rate is slow). .). Further, in FIG. 3, even if the spherical heat conductive filler is increased in order to reduce the heat conduction ratio of the resin portion, voids are likely to be formed by these aggregations, and it is difficult to improve the heat conductivity. .. Further, even when the first heat conductive inorganic filler exceeding 10% by weight is used (FIG. 4), voids are likely to be formed by the aggregation of the first heat conductive inorganic fillers, and further, the first heat. It is considered difficult to obtain high thermal conductivity in the thickness direction because the conductive inorganic filler tends to be oriented in the plane direction (the arrow in the broken line in FIG. 4; means that the heat conduction rate is slow).
The essence of the present invention is to improve the thermal conductivity in the thickness direction by the synergistic action of the above-mentioned effects by setting the specific shape and content of the first and second thermally conductive inorganic fillers. The effect of the present invention obtained by such a synergistic action is not predicted in the prior art, and is a novel effect found in the present invention.

The content of the first heat conductive inorganic filler in the heat conductive resin composition of the present invention is relative to the solid content (components other than the solvent contained in the heat conductive resin composition) in the heat conductive resin composition. It is 0.1 to 10% by weight. If the content of the first heat conductive inorganic filler is 0.1% by weight, it is possible to form a continuous heat conduction path connecting the gaps of the filler having a large particle size, and if it is 10% by weight or less. , It is possible to suppress the aggregation of the filler and the orientation in the plane direction. From this point of view, it is preferably 0.5 to 9.5% by weight, more preferably 1 to 6% by weight, and even more preferably 1.5 to 4% by weight.

The content of the second heat conductive inorganic filler in the heat conductive resin composition of the present invention is relative to the solid content (components other than the solvent contained in the heat conductive resin composition) in the heat conductive resin composition. It is 60 to 88% by weight. When the content of the second heat conductive inorganic filler is 60% by weight or more, it is possible to have good heat conductivity in the thickness direction, and when it is 88% by weight or less, it is a processable heat conductive resin. It is preferable because the composition can be provided. From this point of view, it is more preferably 65 to 80% by weight, further preferably 70 to 80% by weight.

The content of the resin is not particularly limited as long as the content of the first and second thermally conductive inorganic fillers of the present invention is realized, but is preferably 2 to 40% by weight. It is more preferably 5 to 30% by weight, further preferably 10 to 25% by weight. When the resin content is 2% by weight or more, it is preferable because processing and molding are easy, and when it is 40% by weight or less, the thermal conductivity in the thickness direction can be increased, which is preferable.

The heat conductive resin composition of the present invention contains a first heat conductive inorganic filler, a second heat conductive inorganic filler, and as components other than the resin, a solvent, a curing agent, and the like, as long as the effects of the present invention are not impaired. Dispersants, polymer compounds, inorganic particles, metal particles, surfactants, antistatic agents, leveling agents, viscosity modifiers, tincture adjusters, adhesion improvers, epoxy hardeners, rust preventives, preservatives, antiseptic Additives such as molds, antioxidants, antioxidants, evaporation promoters, chelating agents, pigments, titanium blacks, carbon blacks, or dyes may be included.

The solvent contained in the heat conductive resin composition is not particularly limited, and water, methanol, ethanol, propanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-dimethylpropionamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, ethyl acetate, butyl acetate, propylene carbonate, diethylene carbonate, toluene, xylene, pyridine, tetrahydrofuran, dichloromethane, chloroform, 1,1,1,3 , 3,3-Hexafluoroisopropanol, formic acid, acetic acid and the like can be used. These may be appropriately selected in consideration of the solubility of the resin and the dispersibility of the filler, and may be used alone or in combination of two or more.

The curing agent contained in the heat conductive resin composition is not particularly limited, and is a polyfunctional acid anhydride, a styrene anhydride maleic acid resin (SMA), an amine-based curing agent, a thiol-based curing agent, a cyanate-based curing agent, and an activity. An ester-based curing agent, a phenol-based curing agent, or the like can be used. These may be appropriately selected depending on the reactivity and the characteristics of the heat radiating member to be obtained, and may be used alone or in combination of two or more.

The thermally conductive resin composition of the present invention is pelleted even in the form of powder (a powder mixture formed by mixing a first thermally conductive inorganic filler, a second thermally conductive inorganic filler, and a resin). It may be in the form of a liquid (for example, a pellet obtained by kneading a first heat conductive inorganic filler, a second heat conductive inorganic filler, and a resin) and the like (for example, the first heat conductivity). It may be a liquid composition such as a paint, an ink, or a varnish containing an inorganic filler, a second thermally conductive inorganic filler, a resin, and a solvent). The heat conductive resin composition of the present invention can be used for producing a heat radiating member (a cured heat conductive resin composition), and the heat conductive resin composition in an uncured or semi-cured state. Can also be used as a heat-dissipating paint, a heat-dissipating adhesive, a heat-dissipating filler, and the like.

<Heat dissipation member>
The heat radiating member of the present invention is obtained by molding the above-mentioned heat conductive resin composition into a shape suitable for an application and curing it, and has high thermal conductivity in the thickness direction, as well as heat resistance and chemical stability. Excellent in hardness and mechanical strength. The mechanical strength includes Young's modulus, tensile strength, tear strength, bending strength, flexural modulus, impact strength, and the like. Since it has such characteristics, it can be suitably used, for example, as a heat radiating member for electronic parts.

As the shape of the heat radiating member of the present invention, the shape of a sheet, a film, a thin film, a fiber, a non-woven fabric, a molded body and the like can be exemplified, but a sheet, a film or a thin film is preferable. The film thickness of the sheet in the present invention is 1 mm or more, the film thickness is 5 μm or more and less than 1 mm, preferably 10 to 500 μm, more preferably 20 to 300 μm, and the film thickness of the thin film is less than 5 μm. The film thickness may be appropriately changed according to the intended use.

The thermal conductivity in the thickness direction of the heat radiating member of the present invention is not particularly limited, but is preferably 3 W / (m · K) or more, and more preferably 5 W / (m · K) or more. Further, the thermal conductivity in the thickness direction of the heat radiating member of the present invention is preferably 20 times or more, more preferably 30 times or more, and 40 times more than the thermal conductivity in the thickness direction of the resin alone. The above is more preferable.

<Electronic equipment>
The electronic device of the present invention includes the above-mentioned heat dissipation member and an electronic device having a heat generating portion or a cooling portion. The heat radiating member may be arranged on the electronic device so as to come into contact with the heat generating portion. The heat dissipation member may be any of a heat dissipation electronic board, a heat dissipation plate, a heat dissipation sheet, a heat dissipation film, a heat dissipation adhesive, a heat dissipation molded product, etc., and the heat dissipation member has a three-dimensional structure using a mold or the like. It may be molded and used for parts where thermal expansion of precision machinery is a problem. In this way, the heat generated in the electronic device is dissipated by the heat radiating member, and the failure due to the heat is avoided, so that the life of the electronic device including the electronic device can be extended.

Examples of electronic devices include semiconductor devices. The heat radiating member has high heat resistance and high insulation in addition to high thermal conductivity. Therefore, it is particularly effective for an insulated gate bipolar transistor (IGBT), which requires a more efficient heat dissipation mechanism due to its high power among semiconductor elements. An IGBT is one of the semiconductor elements, which is a bipolar transistor in which a MOSFET is incorporated in a gate portion, and is used for power control. Electronic devices equipped with IGBTs include main conversion elements for high-power inverters, uninterruptible power supplies, variable voltage variable frequency control devices for AC motors, control devices for railway vehicles, electric transport equipment such as hybrid cars and electric cars, and IH. Examples include cookers.

<Manufacturing method of thermally conductive resin composition>
The method for producing the thermally conductive resin composition of the present invention is not particularly limited, but a step of preparing a spinning solution containing an inorganic compound (hereinafter, may be referred to as a “spinning solution preparation step”) and the spinning solution may be used. A step of spinning to produce a precursor fiber (hereinafter, may be referred to as a “spinning step”) and a step of firing a precursor fiber to produce an inorganic fiber aggregate (hereinafter, referred to as a “firing step”). There is), a step of crushing the inorganic fiber aggregate to produce a first heat conductive inorganic filler (hereinafter, may be referred to as a "crushing step"), and the first heat conductive inorganic filler. It is preferable to include a step of mixing the second heat conductive inorganic filler and the resin (hereinafter, may be referred to as a “mixing step”). According to this method, the shape, composition, and crystal structure of the first heat conductive inorganic filler can be controlled, and the heat conductive resin composition for a heat radiating member having high heat conductivity in the thickness direction is high. It becomes possible to manufacture with productivity.

<Spinning solution preparation process>
The spinning solution of the present invention is not particularly limited as long as it has spinnability and contains an inorganic compound, but even if it is a melt composed of the inorganic compound alone, the inorganic compound is dispersed or dissolved in a solvent. It may be a spinning solution, but from the viewpoint of reducing the average fiber diameter of the first heat conductive inorganic filler and improving the uniformity of the fiber diameter and composition, spinning in a state where the inorganic compound is dispersed or dissolved. It is preferable to use a solution, and it is more preferable to use a spinning solution in which the inorganic compound is dissolved in the solvent. The method for obtaining such a spinning solution is not particularly limited, and can be obtained by using known equipment such as a high-temperature melting furnace, a magnetic stirrer, a shaker, a planetary stirrer, or an ultrasonic device.

The inorganic compound is not particularly limited as long as the above-mentioned first heat conductive filler can be obtained, and silicon, aluminum, lithium, sodium, potassium, magnesium, calcium, strontium, barium, yttrium, lanthanum, titanium, zirconium, etc. Acetates, carbonates, nitrates, oxalic acids containing metal elements such as hafnium, vanadium, niobium, tantalum, chromium, tungsten, manganese, iron, cobalt, nickel, copper, silver, zinc, boron, indium, tin, lead and bismuth. Examples thereof include salts, sulfates, hydroxides, halides, or alkoxides. Among them, in order to improve the thermal conductivity of the first thermally conductive inorganic filler and improve the thermal conductivity in the thickness direction of the thermally conductive resin composition and the heat radiating member, the inorganic compounds are aluminum compounds, silicon compounds, and the like. And at least one inorganic compound selected from the group consisting of magnesium compounds. The aluminum compound is not particularly limited, and is not particularly limited. Aluminum acetate, aluminum carbonate, aluminum hydroxide, aluminum nitrate, aluminum chloride, aluminum oxide, or aluminum methoxyd, aluminum ethoxydo, aluminum normal propoxide, aluminum isopropoxide, aluminum normal. Aluminum alkoxides such as butoxide and aluminum-sec-butoxide can be exemplified. The silicon compound is not particularly limited, and examples thereof include silicon dioxide, silane alkoxides such as tetramethoxysilane and tetraethoxysilane, silicon carbide, and polycarbosilane. The magnesium compound is not particularly limited, and examples thereof include magnesium acetate, magnesium carbonate, magnesium hydroxide, magnesium nitrate, magnesium oxalate, magnesium chloride, magnesium oxide, and magnesium alkoxide. From the viewpoint of operability in the spinning solution preparation step, it is more preferable that the inorganic compound is at least one selected from the group consisting of aluminum alkoxide, silane alkoxide, polycarbosilane, magnesium acetate, magnesium carbonate, and magnesium alkoxide.

The spinning solution of the present invention is not particularly limited, but may contain a solvent for the purpose of improving the uniformity of the fiber diameter and composition and the spinnability. The solvent used in such a spinning solution preparation step is not particularly limited, and water, methanol, ethanol, propanol, 1-butanol, isobutanol, ethylene glycol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, acetone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, toluene, xylene, pyridine, tetrahydrofuran, dichloromethane, chloroform, 1,1,1,3,3,3-hexafluoroisopropanol , Formic acid, acetic acid, or propionic acid can be exemplified. These solvents may be used alone or in combination of two or more. The solvent used in the spinning solution preparation step preferably contains an alcohol solvent having a boiling point of 100 to 150 ° C. as a main component from the viewpoint of dispersibility, solubility and spinning stability of the inorganic compound. Here, "as a main component" means a component that occupies the largest proportion of the components constituting the solvent used in the spinning solution preparation step, and the component is preferably 50% by weight or more. , More preferably, it means that it occupies 85% by weight or more. When the boiling point of the solvent is 100 ° C. or higher, clogging of the nozzle due to volatilization of the solvent can be suppressed in the spinning process, and the spinning solution can be easily prepared by improving the solubility by heating in the spinning solution preparation step. If the temperature is 150 ° C. or lower, the solvent can be volatilized even when the fiber is spun at a high discharge rate, and a uniform precursor fiber can be obtained. The alcohol solvent having a boiling point of 100 to 150 ° C. is preferably 1-butanol, isobutanol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, and more preferably propylene glycol monomethyl ether.

The spinning solution of the present invention is not particularly limited, but may further contain a fiber-forming polymer for the purpose of improving spinnability. The fiber-forming polymer may have an action of promoting fibrosis of the spinning solution, and is selected from those that are soluble in the above solvent and decomposed by firing. As fiber-forming polymers, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, polyethylene, polypropylene, polyethylene terephthalate, polylactic acid, polyamide, polyurethane, polystyrene, polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyglycolic acid. , Polycaprolactone, cellulose, cellulose derivatives, chitin, chitosan, collagen, or copolymers or mixtures thereof. These fiber-forming polymers may be used alone or in combination of two or more. The fiber-forming polymer is preferably polyvinyl alcohol, polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, or polyacrylic acid, preferably polyvinylpyrrolidone, from the viewpoint of solubility in a solvent and degradability in a baking step. Is more preferable.

The spinning solution of the present invention is not particularly limited, but may contain a stabilizer for the purpose of stabilizing the spinning solution. The stabilizer is not particularly limited, but is preferably β-diketone, and more preferably acetylacetone. The content of the stabilizer is not particularly limited, but the molar ratio of the inorganic compound to the stabilizer is preferably 1: 0.3 to 1: 0.7, preferably 1: 0.5 to 1: 0.7. Is more preferable. When the molar ratio of the inorganic compound to the stabilizer is 1: 0.3 or more, hydrolysis of the inorganic compound can be suppressed and a stable spinning solution can be obtained for a long time, and when it is 1: 0.7 or less. , It is possible to suppress deterioration of spinnability due to excessive addition.

The concentration of the inorganic compound in the spinning solution of the present invention is not particularly limited, but is preferably 8 to 80% by weight, more preferably 10 to 60% by weight, based on the total weight of the spinning solution. It is more preferably 15 to 45% by weight. When the concentration of the inorganic compound with respect to the total weight of the spinning solution is 8% by weight or more, the stability and spinnability of the spinning solution can be improved and the spinning solution can be produced with high productivity, which is preferably 80% by weight or less. This is preferable because the viscosity of the spinning solution does not become too high, stable spinning can be performed, and fine fibers can be easily obtained.

Further, in the spinning solution of the present invention, the weight ratio of the fiber-forming polymer to the inorganic compound is not particularly limited, but is preferably 1: 3 to 1:20, preferably 1: 4 to 1:15. More preferably, it is more preferably 1: 5 to 1: 12.5. When the weight ratio of the fiber-forming polymer to the inorganic compound is 1: 3 or more, the ratio of the inorganic compound in the precursor fiber becomes large, and pores are less likely to be formed due to the disappearance of the fiber-forming polymer by firing. The uniform and dense first heat conductive inorganic filler is preferable because it can be obtained with high productivity, and when it is 20 or less, the fiber diameter of the first heat conductive filler can be reduced, which is preferable.

A component other than the above may be contained as a component of the spinning solution as long as the effect of the present invention is not significantly impaired, and a conductive auxiliary agent, a viscosity regulator, a pH adjuster, a preservative, a surfactant and the like may be contained. ..

<Spinning process>
Then, in the spinning step, the prepared spinning solution is spun to obtain precursor fibers. The spinning method is not particularly limited, and examples thereof include a dry spinning method, a wet spinning method, a melt spinning method, a spunbond method, a flash spinning method, a melt blown method, a rotary spinning method, and an electrostatic spinning method. The spinning method is preferable because the average fiber diameter of the first heat conductive inorganic filler can be reduced and the first heat conductive inorganic filler having a uniform fiber diameter, composition and crystal structure can be obtained. Therefore, even if the content of the first heat conductive inorganic filler is small, it is possible to form a continuous heat conduction path, the formation of voids is suppressed, and the heat conduction for the heat radiating member having high heat conductivity in the thickness direction. A sex resin composition can be obtained.
Hereinafter, a method for producing a thermally conductive resin composition using an electrostatic spinning method will be described, but the present invention is not limited thereto.

The electrostatic spinning method is a method in which a spinning solution is discharged and an electric field is applied to fiberize the discharged spinning solution to obtain fibers on a collector. Examples of the electrostatic spinning method include a method of extruding a spinning solution from a nozzle and applying an electric field to spin the spinning solution, a method of bubbling the spinning solution and applying an electric field to spin the spinning solution, and guiding the spinning solution to the surface of a cylindrical electrode. At the same time, a method of spinning by applying an electric field can be mentioned. According to this method, uniform fibers having a diameter of 10 nm to 10 μm can be obtained.

The discharge amount of the spinning solution is not particularly limited, but is preferably 0.1 to 10 mL / hr. A discharge rate of 0.1 mL / hr or more is preferable because sufficient productivity can be obtained, and a discharge rate of 10 mL / hr or less is preferable because uniform and fine fibers can be easily obtained. The polarity of the applied voltage may be positive or negative. Further, the magnitude of the voltage is not particularly limited as long as the fibers are formed, and for example, in the case of a positive voltage, a range of 5 to 100 kV can be exemplified. Further, the distance between the nozzle and the collector is not particularly limited as long as the fiber is formed, but the range of 5 to 50 cm can be exemplified. The collector may be any as long as it can collect the spun precursor fibers, and its material and shape are not particularly limited. As the material of the collector, a conductive material such as metal is preferably used. The shape of the collector is not particularly limited, and examples thereof include a flat plate shape, a shaft shape, and a conveyor shape. It is preferable that the collector has a conveyor shape because the precursor fibers can be continuously produced.

<Baking process>
Next, in the firing step, the precursor fibers obtained in the spinning step are fired to obtain an inorganic fiber aggregate.

In the firing step, by firing the precursor fiber, the fiber-forming polymer contained in the precursor fiber is thermally decomposed, and the metal element in the inorganic compound is oxidized, carbonized, or nitrided, resulting in high heat. Inorganic fiber aggregates having conductivity can be obtained. A general electric furnace can be used for firing. The firing atmosphere is not particularly limited, but whether it is carried out in an air atmosphere or an inert gas atmosphere such as nitrogen gas or argon gas, it is carried out in an air atmosphere for a certain period of time and then in an inert gas atmosphere. You may. The firing method may be one-step firing or multi-step firing.

The firing temperature is not particularly limited, but is preferably in the range of 600 to 1700 ° C, more preferably in the range of 800 to 1500 ° C, and even more preferably in the range of 1100 to 1500 ° C. When the firing temperature is 600 ° C. or higher, the firing is sufficient, the crystallization of the inorganic fiber aggregate proceeds, and the components other than the inorganic fiber aggregate are less likely to remain, so that a high-purity inorganic fiber aggregate can be obtained. If the temperature is 1700 ° C. or lower, the energy consumption can be kept low and the manufacturing cost can be suppressed. When the firing temperature is in the range of 1100 to 1500 ° C., the crystallinity of the inorganic fiber aggregate can be increased and the production cost can be sufficiently lowered. The firing time is not particularly limited, but may be fired for, for example, 1 to 24 hours. The rate of temperature rise is not particularly limited, but firing can be appropriately changed in the range of 5 to 50 ° C./min.

<Crushing process>
Next, in the pulverization step, the inorganic fiber aggregate obtained in the calcination step is pulverized to obtain a first thermally conductive inorganic filler. By pulverizing, it becomes easy to fill the resin or the like as a filler.

The crushing method is not particularly limited as long as it can maintain the fibrous shape, and examples thereof include ball mills, bead mills, jet mills, high-pressure homogenizers, planetary mills, rotary crushers, hammer crushers, cutter mills, stone mills, mortars, and screen mesh crushers. Although it may be dry or wet, screen mesh crushing is preferably used because it is easy to control a specific shape and size. Screen mesh crushing is a method in which an inorganic fiber aggregate is placed on a mesh having a predetermined opening and filtered with a brush or a spatula, or beads and an inorganic fiber aggregate such as alumina, zirconia, glass, PTFE, nylon, or polyethylene. An example of a method of applying vertical and / or horizontal vibration by placing and on a mesh can be illustrated. The mesh opening to be used is not particularly limited, but is preferably 20 to 1000 μm, and more preferably 50 to 500 μm. When the opening is 20 μm or more, it is preferable because the pulverization treatment time can be shortened, and when it is 1000 μm or less, it is preferable because coarse substances and agglomerates of the first heat conductive inorganic filler can be removed. The pulverization method and conditions may be appropriately changed for the required characteristics.

<Mixing process>
Next, in the mixing step, the heat conductive resin composition is obtained by mixing the first heat conductive inorganic filler obtained in the pulverization step, the above-mentioned second heat conductive inorganic filler, and the resin. ..

The mixing method is not particularly limited, and may be a dry method or a wet method. In the case of the dry method, it is preferable in that a thermally conductive resin composition can be obtained without the need for a solvent. In the case of the solution method, a heat conductive resin composition and a heat radiating member having a small variation in thermal conductivity can be obtained, which is preferable. As a method for producing a heat conductive resin composition by a dry method, for example, a first heat conductive inorganic filler, a second heat conductive inorganic filler, and a resin are blended at the above-mentioned concentrations and at room temperature. Examples thereof include a method of mixing using a dairy pot and a method of melt-kneading using a pelletizer or the like. As a method for producing a heat conductive resin composition by a wet method, for example, a first heat conductive inorganic filler, a second heat conductive inorganic filler, a resin, and a solvent are blended at the above-mentioned concentrations, and a magnetic stirrer is used. , A method of mixing using known equipment such as a shaker, a ball mill, a jet mill, a planetary stirrer, or an ultrasonic device may be mentioned, and the solvent may be evaporated after the mixing. The mixing conditions are not particularly limited, and for example, the mixing can be performed at 10 to 120 ° C. for 1 to 24 hours.

<Manufacturing method of heat dissipation member>
The heat radiating member of the present invention can be obtained by molding the heat conductive resin composition obtained as described above into a shape suitable for the intended use and curing the heat conductive resin composition. In the following, a method of manufacturing a film-shaped heat dissipation member can be exemplified. Hereinafter, a method for manufacturing a film-shaped heat radiating member will be described, but the present invention is not limited thereto.

When a powdery or pelletized heat conductive resin composition is used, for example, the heat conductive resin composition is sandwiched between stainless steel plates or placed in a mold of an arbitrary shape, and a predetermined temperature and pressure are applied by a compression molding machine. Examples thereof include a method of heat-pressing and curing by time, a method of curing by cooling and solidifying after melt molding, and a method of curing by irradiating ultraviolet rays. The compression molding conditions may be appropriately changed depending on the fluidity of the thermally conductive resin composition and the desired physical properties (which direction the thermal conductivity is emphasized, etc.), and the temperature at the time of compression molding is 60 to 60. Examples thereof include 250 ° C., a pressure of 1 to 30 MPa, and a time of 1 to 60 minutes.
When the heat conductive resin composition is partially cured (semi-cured state), the ease of handling can be further improved. For example, it is possible to form a semi-cured composition into a film shape, cut it into a desired shape, place it between suitable members, and bond them together.

When a liquid heat conductive resin composition is used, for example, a method of applying the resin composition on a support and curing the solvent by drying, and a method of heat curing or photocuring can be mentioned. The method of coating is not particularly limited, and a known method such as a spin coating method, a spray coating method, a roll coating method, a gravure coating method, or a cast coating method can be used. When patterning is required, it can be performed by using a known method such as an inkjet method, a screen printing method, or a flexographic printing method. The support to which the liquid heat conductive resin composition is applied is not particularly limited, and a glass substrate, an aluminum substrate, a copper substrate, a polymer film, or the like can be used. The heat radiating member may be left as a film on the support, but a support whose surface has been mold-released may be used in order to form a self-supporting film. The method for drying the solvent is not particularly limited, and examples thereof include induction heating, hot air circulation heating, vacuum drying, infrared rays, and microwave heating. As the drying conditions, for example, it may be dried at 40 to 150 ° C. for 1 to 180 minutes. The heat-dissipating member after drying can be further subjected to heat pressing or heat treatment for the purpose of suppressing voids. The hot pressing conditions are not particularly limited, and examples thereof include a pressing temperature of 60 to 250 ° C., a pressing pressure of 1 to 30 MPa, and a pressing time of 1 to 60 minutes. As the heat treatment conditions, for example, the heat treatment may be performed at 60 to 200 ° C. for 1 to 24 hours in an oven or the like.

Hereinafter, the present invention will be described in more detail by way of examples, but the following examples are merely intended as examples. The scope of the present invention is not limited to this embodiment.
The measurement method or definition of the physical property values used in the examples is shown below.

<Average fiber diameter, average fiber length, and aspect ratio of the first thermally conductive inorganic filler>
Observe the first heat-conducting inorganic filler using a scanning electron microscope (SU-8000) manufactured by Hitachi, Ltd., and use the image analysis function to observe the long axis of 50 or more first heat-conducting inorganic fillers. The length of the minor axis was measured, the average value of the length of the minor axis was defined as the average fiber diameter, the average value of the length of the major axis was defined as the average fiber length, and the average fiber length / average fiber diameter was defined as the average aspect ratio.
<Shape of second thermally conductive inorganic filler>
The shape of the second thermally conductive inorganic filler was observed using a scanning electron microscope (SU-8000) manufactured by Hitachi, Ltd.
<Average particle size of the second thermally conductive inorganic filler>
The average particle size of the second thermally conductive inorganic filler was measured using a laser diffraction / scattering type particle size distribution measuring device LA-950V2 manufactured by HORIBA, Ltd. For the measurement, after adding the measurement sample to pure water, the sample was irradiated with ultrasonic waves for 3 minutes, and a solution in which the sample was dispersed was used.
<Ratio of the average particle size of the second heat conductive filler to the average fiber diameter of the first heat conductive inorganic filler (A / B)>
A / B was calculated by dividing the average particle size A of the second thermally conductive inorganic filler measured by the above method by the average fiber diameter B of the first thermally conductive inorganic filler.
<Crystal structure of fibrous alumina and spherical alumina>
An X-ray diffraction image was obtained by irradiating the sample with CuKα rays using a Bruker X-ray diffractometer (D8 DISCOVER) and detecting the CuKα rays reflected from the sample. The crystal structure was determined from the peak position of the obtained X-ray diffraction image.
<Thermal conductivity in the thickness direction of the heat dissipation member>
The thermal conductivity (λ) in the thickness direction of the heat dissipation member was measured by the thermal diffusivity (measured with the eye phase thermal diffusivity measuring device manufactured by Hitachi High-Tech Science Co., Ltd.) and the specific heat (Co., Ltd.) according to JIS R1611. Measured by Perkin Elmer's diamond DSC type input assist type differential scanning calorific value measuring device) and specific gravity (measured by Alpha Mirage Co., Ltd. MD-300s type electronic diffusivity meter), and multiplied by these values. The thermal conductivity was calculated by combining them.

[Example 1]
<Preparation of fibrous alumina 1>
<Preparation of spinning solution>
While stirring 360 parts by weight of propylene glycol monomethyl ether, 16 parts by weight of polyvinylpyrrolidone was added and the mixture was stirred for 1 hour. Then, 20 parts by weight of acetylacetone was added, and after stirring for 30 minutes, 80 parts by weight of aluminum-sec-butoxide was added to prepare a spinning solution.
<Fiber production>
The spinning solution prepared by the above method was supplied to the nozzle at 2.5 ml / hr by a gear pump, and a voltage of 38 kv was applied to the nozzle to collect precursor fibers in a grounded collector. The distance between the nozzle and the collector was 23.5 cm. The electrostatically spun precursor fiber is heated to 1150 ° C. in air at a heating rate of 10 ° C./min, held at a firing temperature of 1150 ° C. for 2 hours, and then cooled to room temperature to obtain average fiber. A fibrous alumina aggregate having a diameter of 0.2 μm was prepared. Further, the obtained fibrous alumina aggregate was placed on a screen mesh having an opening of 300 μm, filtered with a brush and pulverized to produce fibrous alumina 1. The obtained fibrous alumina 1 was α-alumina and had an aspect ratio of 25 (average fiber diameter: 0.2 μm, average fiber length: 5 μm). The X-ray diffraction image of the obtained fibrous alumina 1 is shown in FIG.
<Preparation of thermally conductive resin composition>
Fibrous alumina 1 as the first heat conductive inorganic filler, boron nitride aggregate as the second heat conductive inorganic filler (manufactured by Momentive Performance Materials Japan (combined), (trade name) PolarTherm PTX-25) , Polyfluoride vinylidene (manufactured by Solvay Specialty Polymers Co., Ltd., Solef6010) as a resin, N, N-dimethylformamide as a solvent, and the content of the first thermally conductive inorganic filler with respect to the solid content in the thermally conductive resin composition. After mixing in the blending amounts shown in Table 1 so that the ratio is 1.9% by weight and the content of the second heat conductive inorganic filler is 73.9% by weight, N, N-dimethylformamide is evaporated. By allowing the heat conductive resin composition to be produced, a heat conductive resin composition was produced.
<Manufacturing of heat dissipation member>
A mold with a thickness of 5 mm and an opening of 20 mm × 20 mm is set in a small press (Mini test press manufactured by Toyo Seiki Seisakusho Co., Ltd., MP-SNH), and the heat conductive resin composition is put in the opening, and 200 A heat radiating member was prepared by pressing at 10 MPa at ° C. for 10 minutes. The thermal conductivity of the obtained heat radiating member in the thickness direction was 9.63 W / (m · K).

[Example 2]
Fibrous alumina 1 as the first heat conductive inorganic filler, boron nitride aggregate as the second heat conductive inorganic filler (manufactured by Momentive Performance Materials Japan (combined), (trade name) PolarTherm PTX-25) , Polyfluoride vinylidene (manufactured by Solvay Specialty Polymers Co., Ltd., Solef6010) as a resin, N, N-dimethylformamide as a solvent, and the content of the first thermally conductive inorganic filler with respect to the solid content in the thermally conductive resin composition. After mixing in the blending amounts shown in Table 1 so that the ratio is 3.6% by weight and the content of the second heat conductive inorganic filler is 73.2% by weight, N, N-dimethylformamide is evaporated. By allowing the heat conductive resin composition to be produced, a heat conductive resin composition was produced.
Next, a heat dissipation member was produced in the same manner as in Example 1. The thermal conductivity of the obtained heat radiating member in the thickness direction was 8.86 W / (m · K).

[Example 3]
Fibrous as in Example 1 except that acetylacetone in the spinning solution was 50 parts by weight, aluminum-sec-butoxide was 200 parts by weight, and the supply amount of the spinning solution in the spinning step was 5.5 ml / hr. Alumina 2 was produced. The obtained fibrous alumina 2 was α-alumina and had an aspect ratio of 20 (average fiber diameter: 0.5 μm, average fiber length: 10 μm). The X-ray diffraction image of the obtained fibrous alumina 2 is shown in FIG.
Next, a heat conductive resin composition and a heat radiating member were produced in the same manner as in Example 2 except that the fibrous alumina 2 was used as the first heat conductive inorganic filler. The thermal conductivity of the obtained heat radiating member in the thickness direction was 8.63 W / (m · K).

[Example 4]
Except that polyvinylpyrrolidone in the spinning solution was 28.8 parts by weight, acetylacetone was 54 parts by weight, aluminum-sec-butoxide was 216 parts by weight, the supply amount of the spinning solution in the spinning process was 7 mL / hr, and the applied voltage was 29 kV. Made fibrous alumina 3 in the same manner as in Example 1. The obtained fibrous alumina 3 was α-alumina and had an aspect ratio of 15 (average fiber diameter: 1.0 μm, average fiber length: 15 μm). The X-ray diffraction image of the obtained fibrous alumina 3 is shown in FIG.
Next, a heat conductive resin composition and a heat radiating member were produced in the same manner as in Example 2 except that the fibrous alumina 3 was used as the first heat conductive inorganic filler. The thermal conductivity of the obtained heat radiating member in the thickness direction was 7.61 W / (m · K).

[Example 5]
Fibrous alumina 1 as the first heat conductive inorganic filler, boron nitride aggregate as the second heat conductive inorganic filler (manufactured by Momentive Performance Materials Japan (combined), (trade name) PolarTherm PTX-25) , Polyfluoride vinylidene (manufactured by Solvay Specialty Polymers Co., Ltd., Solef6010) as a resin, N, N-dimethylformamide as a solvent, and the content of the first thermally conductive inorganic filler with respect to the solid content in the thermally conductive resin composition. After mixing in the blending amounts shown in Table 1 so that the ratio is 5.5% by weight and the content of the second heat conductive inorganic filler is 72.5% by weight, N, N-dimethylformamide is evaporated. By allowing the heat conductive resin composition to be produced, a heat conductive resin composition was produced.
Next, a heat dissipation member was produced in the same manner as in Example 1. The thermal conductivity of the obtained heat radiating member in the thickness direction was 8.45 W / (m · K).

[Example 6]
Fibrous alumina 1 as the first heat conductive inorganic filler, boron nitride aggregate as the second heat conductive inorganic filler (manufactured by Momentive Performance Materials Japan (combined), (trade name) PolarTherm PTX-25) , Polyfluoride vinylidene (manufactured by Solvay Specialty Polymers Co., Ltd., Solef6010) as a resin, N, N-dimethylformamide as a solvent, and the content of the first thermally conductive inorganic filler with respect to the solid content in the thermally conductive resin composition. After mixing in the blending amounts shown in Table 1 so that the ratio is 8.9% by weight and the content of the second heat conductive inorganic filler is 71.1% by weight, N, N-dimethylformamide is evaporated. By allowing the heat conductive resin composition to be produced, a heat conductive resin composition was produced.
Next, a heat dissipation member was produced in the same manner as in Example 1. The thermal conductivity of the obtained heat radiating member in the thickness direction was 6.60 W / (m · K).

[Comparative Example 1]
Boron nitride aggregate (Momentive Performance Materials Japan (combination), (trade name) PolarTherm PTX-25), polyvinylidene fluoride (Solvei Specialty Polymers Co., Ltd., Solef6010) as a resin, N, N as a solvent -Using dimethylformamide, the content of the first heat conductive inorganic filler with respect to the solid content in the heat conductive resin composition is 0% by weight, and the content of boron nitride aggregates is 74.8% by weight. , N, N-dimethylformamide was evaporated after mixing in the blending amounts shown in Table 1 to prepare a heat-conducting resin composition.
Next, a heat dissipation member was produced in the same manner as in Example 1. The thermal conductivity of the obtained heat radiating member in the thickness direction was 6.44 W / (m · K).

[Comparative Example 2]
In the same manner as in Example 6, except that spherical alumina (manufactured by Nikkei Kin Co., Ltd., LT-200, average particle size: 0.2 μm) was used instead of the first heat conductive inorganic filler. That is, the content of the first heat conductive inorganic filler with respect to the solid content in the heat conductive resin composition is 0% by weight, the content of the second heat conductive inorganic filler is 71.1% by weight, and the spherical alumina. A thermally conductive resin composition was prepared by mixing in the blending amounts shown in Table 1 so that the content was 8.9% by weight, and then evaporating N, N-dimethylformamide. The spherical alumina used was α-alumina from the X-ray diffraction image (FIG. 5).
Next, a heat dissipation member was produced in the same manner as in Example 6. The thermal conductivity of the obtained heat radiating member in the thickness direction was 6.46 W / (m · K).

[Comparative Example 3]
Fibrous alumina 1 as the first heat conductive inorganic filler, boron nitride aggregate as the second heat conductive inorganic filler (manufactured by Momentive Performance Materials Japan (combined), (trade name) PolarTherm PTX-25) , Polyfluoride vinylidene (manufactured by Solvay Specialty Polymers Co., Ltd., Solef6010) as a resin, N, N-dimethylformamide as a solvent, and the content of the first thermally conductive inorganic filler contained in the thermally conductive resin composition. The N, N-dimethylformamide is evaporated after mixing in the blending amounts shown in Table 1 so that 17.0% by weight and the content of the second heat conductive inorganic filler are 67.8% by weight. As a result, a thermally conductive resin composition was prepared.
Next, a heat dissipation member was produced in the same manner as in Example 1. The thermal conductivity of the obtained heat radiating member in the thickness direction was 5.53 W / (m · K).

Table 1 shows the physical property values of the first and second heat conductive inorganic fillers used in Examples 1 to 6 and Comparative Examples 1 to 3, the blending amount of each material, and the heat conductivity in the thickness direction of the heat radiating member. ..

Table 1

The thermally conductive resin composition of Examples 1 to 6 in which the fibrous alumina which is the first thermally conductive inorganic filler and the boron nitride aggregate which is the second thermally conductive inorganic filler are composed of a predetermined content. As a result, the thermal conductivity in the thickness direction of the product was improved by 2.5 to 49.5% as compared with Comparative Example 1 which did not contain the first thermally conductive inorganic filler.
Comparing Examples 2 to 4 in which the average fiber diameters of the fibrous alumina are different, the smaller the average fiber diameter, the higher the thermal conductivity in the thickness direction. It is considered that, at the same content rate, the smaller the average fiber diameter, the larger the number of fibrous aluminas and the more contact points with the boron nitride aggregates, so that the thermal conductivity in the thickness direction was improved.
Further, comparing Examples 1, 2, 5, and 6 in which the content of the fibrous alumina is different, the lower the content of the fibrous alumina, the higher the thermal conductivity in the thickness direction. It is considered that this is because when the content of the fibrous alumina increased, the fibrous alumina aggregated with each other and the contact point with the boron nitride aggregate decreased.
On the other hand, in Comparative Example 2 in which spherical alumina having a particle size of 0.2 μm was used instead of the first thermally conductive inorganic filler, the improvement in thermal conductivity in the thickness direction was 0.3% as compared with Comparative Example 1. There was almost no improvement. It is considered that it was difficult to form a heat conduction path as compared with fibrous alumina.
Further, in Comparative Example 3 in which the content of the fibrous alumina 1 exceeded 10% by weight, the thermal conductivity in the thickness direction was reduced by 14.1% as compared with Comparative Example 1. It is probable that the content of the fibrous alumina became too high, the distance between the boron nitride aggregates widened, and the thermal conductivity decreased.

[Example 7]
An epoxy resin (1-A) having a liquid crystallinity represented by the following formula (1-A) was synthesized by the method described in Japanese Patent No. 5084148.

次いで、第１の熱伝導性無機フィラーとして繊維状窒化アルミニウム（（株）Ｕ－ＭａＰ製、短繊維破砕タイプ、平均繊維径：２μｍ、平均繊維長：１００μｍ、平均アスペクト比：５０）、第２の熱伝導性無機フィラーとして窒化ホウ素凝集体（モメンティブ・パフォーマンス・マテリアルズ・ジャパン（合）製、（商品名）ＰｏｌａｒＴｈｅｒｍ ＰＴＸ－２５）、樹脂としてエポキシ樹脂（１－Ａ）、硬化剤としてアミン系硬化剤（和光純薬工業（株）製、４，４’－ジアミノ－１，２－ジフェニルエタン）を用い、熱伝導性樹脂組成物中の固形分に対する第１の熱伝導性無機フィラーの含有率が３．３重量％、第２の熱伝導性無機フィラーの含有率が８０．０％となるように、表２に記載の配合量で配合し、乳鉢で１０分間混合することで、熱伝導性樹脂組成物を作製した。
次いで、小型プレス(（株）東洋精機製作所製ミニテストプレス、ＭＰ－ＳＮＨ)に、厚みが１ｍｍで開口部が直径２５ｍｍの円形金型をセットし、熱伝導性樹脂組成物を開口部に入れ、１６０℃、１０ＭＰaで４５分間プレスし、樹脂を硬化させることで放熱部材を作製した。得られた放熱部材の厚み方向の熱伝導率は、１１．００Ｗ／（ｍ・Ｋ）であった。

Next, as the first heat conductive inorganic filler, fibrous aluminum nitride (manufactured by U-MaP Co., Ltd., short fiber crushing type, average fiber diameter: 2 μm, average fiber length: 100 μm, average aspect ratio: 50), second As a heat conductive inorganic filler, boron nitride aggregate (manufactured by Momentive Performance Materials Japan (combined), (trade name) PolarTherm PTX-25), epoxy resin (1-A) as a resin, and amine-based as a curing agent. Using a curing agent (4,4'-diamino-1,2-diphenylethane manufactured by Wako Pure Chemical Industries, Ltd.), the content of the first thermally conductive inorganic filler with respect to the solid content in the thermally conductive resin composition is contained. Mix in the blending amounts shown in Table 2 so that the ratio is 3.3% by weight and the content of the second heat conductive inorganic filler is 80.0%, and mix in a dairy pot for 10 minutes to heat. A conductive resin composition was prepared.
Next, set a circular die with a thickness of 1 mm and an opening of 25 mm in a small press (Minitest Press, MP-SNH manufactured by Toyo Seiki Seisakusho Co., Ltd.), and put the thermally conductive resin composition in the opening. , 160 ° C., 10 MPa for 45 minutes to cure the resin to produce a heat dissipation member. The thermal conductivity of the obtained heat radiating member in the thickness direction was 11.00 W / (m · K).

[Example 8]
Fibrous alumina 1 as the first heat conductive inorganic filler, boron nitride aggregate as the second heat conductive inorganic filler (manufactured by Momentive Performance Materials Japan (combined), (trade name) PolarTherm PTX-25) , Epoxy resin (1-A) is used as the resin, and an amine-based curing agent (4,4'-diamino-1,2-diphenylethane manufactured by Wako Pure Chemical Industries, Ltd.) is used as the curing agent, and the heat conductive resin composition is used. Table 2 shows that the content of the first heat conductive inorganic filler is 3.9% by weight and the content of the second heat conductive inorganic filler is 79.3% by weight with respect to the solid content in the material. The heat-conducting resin composition was prepared by blending in the blending amount of the above and mixing in a dairy pot for 10 minutes.
Next, a heat dissipation member was produced in the same manner as in Example 7. The thermal conductivity of the obtained heat radiating member in the thickness direction was 10.60 W / (m · K).

[Example 9]
Fibrous alumina 1 as the first heat conductive inorganic filler, boron nitride aggregate as the second heat conductive inorganic filler (manufactured by Momentive Performance Materials Japan (combined), (trade name) PolarTherm PTX-25) , Epoxy resin (1-A) is used as the resin, and an amine-based curing agent (4,4'-diamino-1,2-diphenylethane manufactured by Wako Pure Chemical Industries, Ltd.) is used as the curing agent, and the heat conductive resin composition is used. Table 2 shows that the content of the first heat conductive inorganic filler is 9.5% by weight and the content of the second heat conductive inorganic filler is 76.3% by weight with respect to the solid content in the material. The heat-conducting resin composition was prepared by blending in the blending amount of the above and mixing in a dairy pot for 10 minutes.
Next, a heat dissipation member was produced in the same manner as in Example 7. The thermal conductivity of the obtained heat radiating member in the thickness direction was 8.58 W / (m · K).

[Comparative Example 4]
Boron nitride agglomerates (manufactured by Momentive Performance Materials Japan (combined), (trade name) PolarTherm PTX-25), epoxy resin (1-A) as resin, amine-based curing agent as curing agent (Wako Pure Chemical Industries, Ltd.) (4,4'-diamino-1,2-diphenylethane) manufactured by Co., Ltd.), the content of the first heat conductive inorganic filler with respect to the solid content in the heat conductive resin composition is 0% by weight, and the setting is performed. A heat-conducting resin composition was prepared by blending in the blending amounts shown in Table 2 and mixing in a dairy pot for 10 minutes so that the content of the aggregate spherical boron nitride was 81.6% by weight.
Next, a heat dissipation member was produced in the same manner as in Example 7. The thermal conductivity of the obtained heat radiating member in the thickness direction was 8.20 W / (m · K).

[Comparative Example 5]
In the same manner as in Example 9, except that spherical alumina (manufactured by Nikkei Kin Co., Ltd., LT-200, average particle size: 0.2 μm) was used instead of the first heat conductive inorganic filler. That is, the content of the first heat conductive inorganic filler with respect to the solid content in the heat conductive resin composition is 0% by weight, the content of the second heat conductive inorganic filler is 76.3% by weight, and the spherical alumina. A heat conductive resin composition was prepared by blending in the blending amounts shown in Table 2 so that the content was 9.5% by weight and mixing in a dairy pot for 10 minutes.
Next, a heat dissipation member was produced in the same manner as in Example 7. The thermal conductivity of the obtained heat radiating member in the thickness direction was 7.86 W / (m · K).

The physical characteristic values of the first and second heat conductive inorganic fillers used in Examples 7 to 9 and Comparative Examples 4 to 5, the blending amount of each material, and the heat conductivity in the thickness direction of the heat conductive resin composition are determined. It is shown in Table 2.

Table 2

The thermally conductive resin compositions of Examples 6 to 9 in which the first thermally conductive inorganic filler and the second thermally conductive inorganic filler are composed of a predetermined content are the first thermally conductive inorganic filler. As a result, the thermal conductivity in the thickness direction was improved by 4.6 to 34.1% as compared with Comparative Example 4 containing no.
On the other hand, in Comparative Example 5 in which spherical alumina having a particle size of 0.2 μm was used instead of the first thermally conductive inorganic filler, the thermal conductivity in the thickness direction was reduced by 4.1% as compared with Comparative Example 4. .. This is probably because it was more difficult to form a heat conduction path than fibrous aluminum nitride or fibrous alumina.

Table 3 summarizes the production conditions of the fibrous aluminas 1 to 3 used in the examples.

Table 3

The heat conductive resin composition of the present invention has high heat conductivity in the thickness direction, and the amount of the first heat conductive inorganic filler added is smaller than that of the conventional method, so that it is easy and high. Can be manufactured with productivity. Therefore, it can be applied to various applications such as electronic / electrical equipment parts and automobile applications.

1 1st heat conductive inorganic filler 2 2nd heat conductive inorganic filler 3 Resin 4 Spherical alumina 5 Void (void)

Claims (9)

A thermally conductive resin composition containing a fibrous first thermally conductive inorganic filler, a second thermally conductive inorganic filler having a shape or size different from that of the first thermally conductive filler, and a resin. Therefore, the content of the first heat conductive inorganic filler is 0.1 to 0.1 or more with respect to the solid content (components other than the solvent contained in the heat conductive resin composition) in the heat conductive resin composition. A heat conductive resin composition having a content of 10% by weight and a content of the second heat conductive inorganic filler of 60 to 88% by weight. The heat conductive resin composition according to claim 1, wherein the first heat conductive inorganic filler has an average fiber diameter of 0.05 to 5 μm and an average aspect ratio of 5 or more. According to claim 1 or 2, when the average particle size of the second thermally conductive inorganic filler is A and the average fiber diameter of the first thermally conductive inorganic filler is B, the A / B is 5 or more. The heat conductive resin composition according to the above. The heat conductive resin composition according to any one of claims 1 to 3, wherein the shape of the second heat conductive inorganic filler is at least one selected from the group consisting of spheres and aggregates. The first heat conductive inorganic filler is at least one selected from the group consisting of alumina, aluminum nitride, magnesium oxide, and silicon carbide, and the second heat conductive inorganic filler is boron nitride and silicon nitride. The heat conductive resin composition according to any one of claims 1 to 4, which is at least one selected from the group consisting of aluminum nitride, alumina, titanium oxide, magnesium oxide, and silicon carbide. The heat conductive resin composition according to any one of claims 1 to 5, wherein the resin is at least one selected from the group consisting of an epoxy resin, a silicone resin, an acrylic resin, a polyimide resin, and a fluororesin. .. A heat radiating member using the heat conductive resin composition according to any one of claims 1 to 6. An electronic device comprising the heat radiating member according to claim 7 and an electronic device having a heat generating portion or a cooling portion, and arranged in the electronic device so that the heat radiating member comes into contact with the heat generating portion. A step of preparing a spinning solution containing an inorganic compound, a step of spinning the spinning solution to prepare a precursor fiber, a step of firing the precursor fiber to prepare an inorganic fiber aggregate, and a step of producing the inorganic fiber aggregate. A claim comprising a step of crushing a body to produce a first heat conductive inorganic filler and a step of mixing the first heat conductive inorganic filler, the second heat conductive inorganic filler, and the resin. Item 6. The method for producing a thermally conductive resin composition according to any one of Items 1 to 6.

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