JP2008303263A - Thermally conductive coating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermally conductive coating material having an excellent heat radiating property. <P>SOLUTION: The thermally conductive coating material having excellent thermal conductivity exceeding 3 W/(m×K) is obtained by combining a pitch-based carbon fiber filler which has high thermal conductivity and the surface of which is flat and substantially smooth, with a matrix consisting of a synthetic resin. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a paint using a pitch-based carbon fiber filler as a raw material. More specifically, after controlling the size (shape / dimension) and thermal conductivity of the pitch-based carbon fiber filler obtained by pulverizing a three-dimensional random mat-like pitch-based carbon fiber mat produced by the melt-blowing method, It is a composite thermal conductive paint, and is suitable as a heat dissipation material for heat-generating electronic components.

  High-performance carbon fibers can be classified into PAN-based carbon fibers made from polyacrylonitrile (PAN) and pitch-based carbon fibers made from a series of pitches. Carbon fibers are widely used in aerospace applications, construction / civil engineering applications, sports / leisure applications, etc., taking advantage of their extremely high strength and elastic modulus compared to ordinary synthetic polymers.

  Carbon fibers are said to have higher thermal conductivity and better heat dissipation than ordinary synthetic polymers. Carbon materials such as carbon fibers are said to achieve high thermal conductivity by phonon movement. Phonons are well transmitted in materials where crystals are developed. However, it cannot be said that commercially available PAN-based carbon fibers have sufficiently developed crystals, and their thermal conductivity is usually less than 200 W / (m · K), which is not necessarily preferable from the viewpoint of thermal management. I can not say. On the other hand, it is recognized that pitch-based carbon fibers have a high graphitization rate and thus grow well in crystals, and can easily achieve high thermal conductivity compared to PAN-based carbon fibers.

In recent years, with the increase in the density of heat-generating electronic components and the downsizing, thinning, and weight reduction of electronic devices such as portable personal computers, there has been an increasing demand for low heat resistance of heat dissipation members used in them. Therefore, it is required to make the heat dissipation member thinner. As a heat radiating member, a heat conductive sheet made of a hardened material filled with a heat conductive inorganic material powder, a heat conductive spacer made of a hardened material with a gel material filled with a heat conductive inorganic material powder and having flexibility A fluid heat conductive paste in which liquid silicone is filled with a heat conductive inorganic material powder is exemplified. Among these, those that can be easily thinned are heat conductive pastes.
In order to enable further thinning, it is necessary to use a solvent-soluble matrix as a matrix and to form a paint together with the thermally conductive filler, matrix and solvent.

In order to improve the thermal conductivity of the thermal conductive paint, it is only necessary to make the matrix densely packed with the thermal conductive material and to make it thin, and to reduce the thickness, the viscosity of the paint and the size of the filler should be adjusted. . Materials having excellent thermal conductivity include metal oxides such as aluminum oxide, boron nitride, aluminum nitride, magnesium oxide, zinc oxide, silicon carbide, quartz and aluminum hydroxide, metal nitride, metal carbide and metal hydroxide. It has been known. Patent Document 1 has a description of a coated body coated with a heat-dissipating coating film containing a metal-based filler such as titanium oxide as a heat-dissipating additive. However, the metal-based filler has a high specific gravity, and has a difficult property that the weight of the heat conductive paint is increased.
JP 2005-1393 A

  As described above, it is desirable to add a heat conductive material excellent in dispersibility to the paint from the viewpoint that a paint excellent in heat conductivity is required. Moreover, the heat conductive material used here is required to be a material having high heat conductivity and capable of maintaining the fiber state along the heat flow in the paint. Thus, since the paint is normally used at a high temperature, it is required to have heat dissipation and heat resistance and mechanical strength as a thermally conductive paint.

In view of improving the thermal conductivity of the thermally conductive coating material, the present inventors have found that the pitch-based carbon fiber filler has excellent dispersibility in the coating material and achieves good thermal conductivity. Reached.
That is, the problem of the present invention can be solved by a heat conductive coating material obtained by combining and diluting a pitch matrix carbon fiber filler, a resin matrix made of an organic polymer or an inorganic polymer, and a solvent as a heat conductive material.

  Furthermore, the present invention is a heat conductive paint in which a pitch-based carbon fiber filler as a heat conductive material is combined with a curable resin, the observation surface with a scanning electron microscope is substantially smooth, and a hexagonal mesh surface. The crystal grain size derived from the growth direction is at least 5 nm, the thermal conductive paint contains 5 to 80 wt% of the pitch-based carbon fiber filler, and the thermal conductivity of the thermal conductive paint is at least 3 W / (m K), the carbon fiber is made from mesophase pitch, the average fiber diameter is 5 to 20 μm, the average fiber length is 5 to 6000 μm, and the fiber diameter dispersion percentage (CV value) with respect to the average fiber diameter is 5 to 20 It is also preferable that the pitch-based carbon fiber filler is included in an amount of 5 to 1000 parts by weight based on 100 parts by weight of the matrix.

  At least one selected from the group consisting of aluminum oxide, magnesium oxide, zinc oxide, boron nitride, aluminum nitride, aluminum oxynitride, quartz, and aluminum hydroxide with respect to 100 parts by weight of the pitch-based carbon fiber filler as the heat conductive material It is also preferable to further contain 1 to 500 parts by weight of an inorganic filler.

  Furthermore, at least one conductivity selected from the group consisting of 1 to 500 parts by weight of magnesium, gold, silver, copper, aluminum, iron, and graphite with respect to 100 parts by weight of the pitch-based carbon fiber filler as a heat conductive material. Including the filler is also included in the present invention.

  In addition, at least one conductivity selected from the group consisting of 1 to 50 parts by weight of magnesium, gold, silver, copper, aluminum, iron, and graphite with respect to 100 parts by weight of the pitch-based carbon fiber filler as the heat conductive material. And a matrix containing at least one resin selected from the group consisting of a silicone resin, an acrylic resin, a vinyl acetate copolymer, and a styrene-butadiene copolymer. This is a preferred embodiment.

  The present invention includes a step of immersing a pitch-based carbon fiber filler as a heat conductive material in a solvent, and at least one resin selected from the group consisting of a silicone resin, an acrylic resin, a vinyl acetate resin, and a styrene-butadiene copolymer. A method for producing a thermally conductive paint comprising a step of mixing with a matrix to obtain a mixture and a step of diluting the mixture with the same or different solvent as the solvent is also included. In the present invention, at least one selected from the group consisting of a pitch-based carbon fiber filler as a heat conductive material and aluminum oxide, magnesium oxide, zinc oxide, boron nitride, aluminum nitride, aluminum oxynitride, quartz, and aluminum hydroxide. A step of immersing the inorganic filler in a solvent, a step of mixing with a matrix made of at least one resin selected from the group consisting of a silicone resin, an acrylic resin, a vinyl acetate resin and a styrene-butadiene copolymer to obtain a mixture; Then, a method for producing a thermally conductive coating comprising the step of diluting the mixture with the same or different solvent as the solvent is also included.

  The thermal conductive paint of the present invention is a pitch-based carbon in which the spread of graphite crystals (crystal particle size derived from the growth direction of the hexagonal network surface) is controlled to a certain size or more and the surface shape is controlled to be smooth. By using a fiber filler, high thermal conductivity is possible, and handling properties as a paint are good.

Next, an embodiment of the present invention will be described.
Examples of the raw material for pitch-based carbon fibers used in the present invention include condensed polycyclic hydrocarbon compounds such as naphthalene and phenanthrene, condensed heterocyclic compounds such as petroleum-based pitch and coal-based pitch, and the like. Among them, condensed polycyclic hydrocarbon compounds such as naphthalene and phenanthrene are preferable, and optically anisotropic pitch, that is, mesophase pitch is particularly preferable. This is because the mesophase pitch is particularly preferable for improving the thermal conductivity of the carbon fiber because the degree of graphitization is easily improved when the graphitization treatment is performed.

  The softening point of the optically anisotropic pitch serving as the raw material pitch can be determined by the Mettler method, and is preferably 250 ° C. or higher and 350 ° C. or lower. When the softening point is lower than 250 ° C., fusion between fibers and large heat shrinkage occur during infusibilization. On the other hand, when the temperature is higher than 350 ° C., thermal decomposition of the pitch occurs and it becomes difficult to form a yarn.

  The optically anisotropic pitch can be fiberized by melt spinning after being melted and discharged from a nozzle and cooled. Specific examples of the spinning method include a normal spinning method in which a pitch discharged from a die is drawn by a winder, a melt blow method using hot air as an atomizing source, and a centrifugal spinning method in which a pitch is drawn using centrifugal force. Among these, the melt blow method is preferably used for reasons such as control of the radius of curvature and high productivity.

  The optically anisotropic pitch is melt-spun, then infusibilized, fired, pulverized as necessary, and finally graphitized to obtain a pitch-based carbon fiber filler. Hereinafter, each process will be described by taking the melt blow method as an example.

  In the present invention, the spinning temperature is desirably a temperature at which the viscosity of the optical anisotropic pitch is in the range of 30 to 250 poise. More preferably, the temperature is in the range of 50 to 200 poise. As the spinning nozzle, a nozzle having an introduction angle α of 10 to 55 ° and a ratio L / D of the discharge port length L to the discharge port diameter D in the range of 6 to 20 is preferably used. When the spinning condition is within this range, the shearing action applied to the optically anisotropic pitch in the molten state can arrange the aromatic ring molecules constituting the optically anisotropic pitch to some extent. When the spinning condition deviates from this condition, for example, when the shear force is stronger, such as when the viscosity is larger, the introduction angle is smaller, or when the L / D is larger, the alignment is excessively advanced and graphitized. In addition, the carbon fiber is fibrillated and easily broken. Conversely, under conditions where the effect of shearing force is small, such as when the viscosity is smaller, the introduction angle is larger, or the shearing force is smaller, such as when the L / D is smaller, the aromatic rings are not aligned so However, the degree of graphitization does not improve so much and high thermal conductivity cannot be obtained.

  The pitch fibers discharged (threaded out) from the nozzle holes are shortened by blowing a gas having a linear velocity of 100 to 10000 m per minute heated to 100 to 350 ° C. in the vicinity of the thinning point. As the gas to be blown, air, nitrogen, or argon can be used, but air is sufficient from the viewpoint of cost performance.

Pitch fibers are collected on a wire mesh belt to form a continuous mat-like material, and further cross-wrapped to form a three-dimensional random mat.
The three-dimensional random mat refers to a mat in which pitch fibers are entangled three-dimensionally in addition to being cross-wrapped. This entanglement is achieved in a cylinder called chimney while reaching the wire mesh belt from the nozzle. Since the linear fibers are entangled three-dimensionally, the characteristics of the fibers that normally exhibit only one-dimensional behavior are reflected three-dimensionally.

  The three-dimensional random mat made of pitch fibers thus obtained is infusible by a known method. Infusibilization is achieved at 200-350 ° C. using air or a gas with ozone, nitrogen dioxide, nitrogen, oxygen, iodine or bromine added to the air. Considering safety and convenience, it is preferable to carry out in the air. The infusibilized pitch fiber is fired at 600-1500 ° C. in vacuum or in an inert gas such as nitrogen, argon or krypton and then graphitized at 2000-3500 ° C. In many cases, the graphitization is carried out in low-cost nitrogen, and graphitization is generally performed by changing the type of inert gas according to the type of furnace used. After infusibilization or firing, the obtained fiber is pulverized as necessary. The pulverization can be performed by a known method. Specifically, a cutter, a ball mill, a jet mill, a crusher, or the like can be used. The pulverized carbon fiber is fired as necessary and then graphitized. The graphitization temperature is preferably 2000 to 3500 ° C. in order to increase the thermal conductivity of the carbon fiber. More preferably, it is 2300-3500 degreeC. It is preferable to put it in a graphite crucible at the time of graphitization because the physical and chemical action from the outside can be blocked. The graphite crucible is not limited in size and shape as long as the above-described carbon fiber can be put in a desired amount, but the oxidizing gas in the furnace during graphitization or cooling, or In order to prevent damage to the carbon fiber due to reaction with water vapor, a highly airtight one with a lid can be suitably used.

  The pitch-based carbon fiber filler used in the present invention preferably has a substantially smooth observation surface with a scanning electron microscope. Here, the term “smooth” means that surface irregularities are not confirmed, surface cracks are not confirmed, and filler cracks are not confirmed in observation with a scanning electron microscope. Here, “substantially” means that, for example, in the observation with an electron microscope, if there are 10 or less defect portions in the visual field (magnification 1000), it may be included a little. When the surface to be observed by a scanning electron microscope is substantially smooth, when a pitch-based carbon fiber filler and a matrix resin are mixed to create a thermally conductive paint, the interaction between the pitch-based carbon fiber filler and the matrix resin As a result, the viscosity of the heat conductive paint is reduced, and the handling property is improved. On the other hand, if the pitch-based carbon fiber filler is not smooth, the interaction between the pitch-based carbon fiber filler and the matrix resin increases, and as a result, the viscosity of the heat conductive paint increases and the handling property decreases.

  To smooth the observation surface of the pitch-based carbon fiber filler, the carbon fiber filler is pulverized and then graphitized to reduce defects in the pitch-based carbon fiber filler and to suppress the occurrence of defects. So smoothing can be achieved. Conversely, when pulverized after the graphitization treatment, the pitch-based carbon fiber filler has more defects, and defects are observed on the surface observed with a scanning electron microscope.

  The pitch-based carbon fiber filler used in the present invention needs to have a crystal grain size derived from the growth direction of the hexagonal network surface of 5 nm or more. The crystal grain size derived from the growth direction of the hexagonal mesh plane can be determined by a known method, and can be determined by diffraction lines from the (110) plane of the carbon crystal obtained by the X-ray diffraction method. The crystal grain size is important because heat conduction is mainly carried by phonons, and phonons are generated from crystals. More preferably, the crystal grain size is 20 nm or more, and more preferably 30 nm or more.

  The average fiber diameter of the three-dimensional random mat-like carbon fiber needs to be 5 to 20 μm. When the thickness is less than 5 μm, the mat shape may not be maintained, and productivity is low. When the fiber diameter exceeds 20 μm, unevenness in the infusibilization process becomes large and partial fusion may occur. More preferably, an average fiber diameter is 5-15 micrometers, More preferably, it is 7-12 micrometers.

  On the other hand, the average fiber length of the pitch-based carbon fiber filler is preferably 5 to 6000 μm. On the other hand, if the thickness is less than 5 μm, the characteristics as a fiber are lost, and sufficient thermal conductivity cannot be exhibited. On the other hand, when it exceeds 6000 μm, the entanglement of the fibers is remarkably increased, the viscosity of the heat conductive paint becomes high, and handling becomes difficult. More preferably, the average fiber length is 10 to 3000 μm, and more preferably 20 to 1000 μm.

  In addition, it is preferable that the CV value calculated | required as a percentage of fiber diameter dispersion | distribution with respect to an average fiber diameter is 5 to 20%. It is impossible in the process that the CV value falls below 5%. On the other hand, if the CV value exceeds 20%, there is a high possibility that fibers having a diameter of 20 μm or more that are likely to cause trouble due to infusibilization increase, which is not preferable from the viewpoint of productivity.

  The thermal conductivity of the thermal conductive paint according to the present invention can be measured by a known method. Among them, the probe method, hot disk method, and laser flash method are preferable, and the probe method is particularly simple and preferable. In general, the thermal conductivity of carbon fiber itself is several hundred W / (m · K), but when it is made into a composite, the thermal conductivity is drastically reduced due to the occurrence of defects, air contamination, and unexpected voids. To do. Therefore, it has been considered that it is difficult for the thermal conductivity as the thermal conductive coating material to substantially exceed 2 W / (m · K).

  On the other hand, in the present invention, this problem was solved by using a pitch-based carbon fiber filler, and a thermal conductivity of 3 W / (m · K) or more was realized as a paint. More preferably, the thermal conductivity is 5 W / (m · K) or more, and more preferably 8 W / (m · K) or more.

  The content rate of a pitch type carbon fiber filler is 5-1000 weight part of the said pitch type carbon fiber filler with respect to 100 weight part of matrices. On the other hand, if the content is less than 5 parts by weight, the thermal conductivity is low, and it is difficult to reduce the thermal resistance no matter how thin it is. On the other hand, when it exceeds 1000 parts by weight, the fluidity of the coating is lowered, and thinning becomes difficult. A more desirable content is 25 to 900 parts by weight.

  Moreover, as a heat conductive material other than pitch-based carbon fiber filler, metal oxides such as aluminum oxide, boron nitride, aluminum nitride, magnesium oxide, zinc oxide, silicon carbide, quartz, aluminum hydroxide, silver powder, metal nitride, metal Oxynitrides, metal carbides, metal hydroxides, or metals may be added as additives.

  When it is desired to control the volume resistance value of the heat conductive paint, an electrically insulating inorganic filler can be added. Specific examples include metal oxides such as aluminum oxide, magnesium oxide and zinc oxide, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, and metal nitrides such as boron nitride and aluminum nitride. Aluminum oxide, magnesium oxide, zinc oxide, boron nitride, aluminum nitride, aluminum oxynitride, quartz, and aluminum hydroxide can be preferably used. These inorganic fillers may be used alone or in combination of two or more. Moreover, as addition amount of an inorganic filler, it can add in 1-2500 weight part with respect to 100 weight part of pitch-type carbon fiber fillers, Preferably it is the range of 1-500 weight part, More preferably, it is 1-50. It can be added in the range of parts by weight. Deviating from the above range is not preferable because there is a problem that the handling property of the paint is lowered or a desired volume resistance value cannot be obtained. That is, in the thermally conductive coating material of the present invention, aluminum oxide, magnesium oxide, zinc oxide, boron nitride, aluminum nitride, aluminum oxynitride, quartz, and hydroxylated with respect to 100 parts by weight of pitch-based carbon fiber filler as a heat conductive material. It is preferable to further include 1 to 500 parts by weight, more preferably 1 to 50 parts by weight of at least one inorganic filler selected from the group consisting of aluminum.

  On the other hand, when it is desired to control the electrical conductivity of the thermally conductive paint, a conductive filler such as a metal, an alloy thereof, or graphite can be added. Among these, magnesium, gold, silver, copper, aluminum, iron or graphite can be preferably used. These may be used alone or in combination of two or more. Above all, as the graphite, scale-like, expanded graphite, natural graphite, expanded products of expanded graphite, and the like can be used as appropriate. Moreover, as addition amount of an electroconductive filler, it can add in the range of 1-2500 weight part with respect to 100 weight part of pitch-type carbon fiber fillers, Preferably it is the range of 1-500 weight part, More preferably, it is 1-50. It can be added in the range of parts by weight. When it deviates from the above-mentioned range, there is a problem that the handleability of the paint is lowered or the desired electric conductivity cannot be obtained, which is not preferable. That is, in the heat conductive paint of the present invention, 1 to 500 parts by weight, more preferably 1 to 50 parts by weight of magnesium, gold, silver, copper, and aluminum are used with respect to 100 parts by weight of the pitch-based carbon fiber filler as a heat conductive material. It is preferable to include at least one conductive filler selected from the group consisting of iron, graphite, and graphite.

  The heat conductive paint of the present invention preferably has a rate of 0.1 to 15 Pa · S (1 to 150 poise) at a shear rate of 1.7 (1 / S). More preferably, it is 0.3 to 10 Pa · S (30 to 100 poise). When it is less than 0.1 Pa · S (1 poise), the fluidity of the paint is too high and flows out immediately, which is unsuitable as a paint. If it exceeds 15 Pa · S (150 poise), the fluidity is too low, and thinning becomes difficult. However, when thinning is not required, the viscosity may be increased up to 50 Pa · S. However, more preferably, the viscosity should be suppressed to about 30 Pa · S. In addition, although a viscosity can be measured using a well-known method, specifically, it can measure using a B-type viscometer, for example.

The resin used as the matrix used in the present invention has characteristics such as airtightness and insulation. By using these as a matrix, a highly reliable heat conductive paint can be obtained. Although there is no restriction | limiting in particular in these matrices, Specifically, a silicone resin, an acrylic resin, a vinyl acetate resin, and a styrene-butadiene copolymer are generally used. That is, it is preferable that the thermally conductive coating material of the present invention contains at least one resin selected from the group consisting of a silicone resin, an acrylic resin, a vinyl acetate resin, and a styrene-butadiene copolymer as a matrix. These can be copolymerized and used as necessary. The silicone resin may be any of thermosetting type, thermoplastic type, and oil type.
The solvent used in the present invention is not particularly limited, but needs to have high affinity with the matrix.

  The heat conductive paint of the present invention can be produced by kneading the above materials with a universal mixing stirrer, kneader or the like and diluting with a solvent. At this time, the pitch-based carbon fiber filler is immersed in a solvent with high affinity to the matrix to reduce the volume, and by mixing and kneading the matrix here, the amount of solvent required for dilution is suppressed, and further thickening is suppressed. it can.

  Applications of the thermally conductive paint of the present invention include heat dissipating members for electronic parts, thermally conductive fillers, insulating fillers for temperature measurement, and the like. For example, the thermally conductive paint of the present invention is used to transfer heat from heat-generating electronic components such as MPUs, power transistors and transformers to heat-radiating components such as heat-dissipating fins and heat-dissipating fans. Used by being sandwiched between heat dissipation components. As a result, heat transfer between the heat-generating electronic component and the heat-dissipating component is improved, and malfunction of the heat-generating electronic component can be reduced in the long term. Or it can use suitably for the connection of a heat pipe and a heat sink, and the connection of the module and heat sink with which various heat generating bodies were incorporated.

  Prior to kneading, the pitch-based carbon fiber filler can be used as a surface modified by oxidation treatment such as electrolytic oxidation, or by treatment with a coupling agent or sizing agent. Also, by applying electroless plating method, electrolytic plating method, physical vapor deposition method such as vacuum deposition, sputtering, ion plating, chemical vapor deposition method, painting, dipping, mechanochemical method for mechanically fixing fine particles, etc. A metal or ceramic coated on the surface may be used. Hereinafter, the present invention will be described in more detail with reference to examples.

Examples are shown below, but the present invention is not limited thereto.
In addition, each value in a present Example was calculated | required according to the following method.
(1) The average fiber diameter of the pitch-based carbon fiber filler was measured from 60 graphitized pitch-based carbon fiber fillers using a scale under an optical microscope according to JIS R7607, and obtained from the average value.
(2) The average fiber length of the pitch-based carbon fiber filler was determined by extracting the pitch-based carbon fiber filler that had undergone graphitization, measuring 2000 pieces with a length measuring device under an optical microscope, and calculating the average value.
(3) The crystal size of the pitch-based carbon fiber filler was determined by the Gakushin method by measuring reflection from the (110) plane appearing in X-ray diffraction.
(4) The surface of the pitch-based carbon fiber filler was observed with a scanning electron microscope.
(5) The thermal conductivity of the thermally conductive coating was determined by the probe method using QTM-500 manufactured by Kyoto Electronics Co., Ltd., by coating the coating on the reference plate to a thickness of 1 mm.
(6) The electrical conductivity of the thermally conductive coating was measured with a Loresta EP or Hiresta from Dia Instruments.
(7) The viscosity of the heat conductive paint was measured with a B-type viscometer.

[Example 1]
A pitch made of a condensed polycyclic hydrocarbon compound was used as a main raw material. The optical anisotropy ratio was 100%, and the softening point was 283 ° C. Using a spinneret having a hole with a diameter of 0.2 mm, heated air was ejected from the slit at a linear velocity of 5500 m / min, and the melt pitch was pulled to produce a pitch fiber having an average diameter of 14.5 μm. The spun fibers were collected on a belt to form a mat, and then a three-dimensional random mat made of pitch-based fibers having a basis weight of 320 g / m ^{2 by} cross wrapping.

This three-dimensional random mat was heated from 170 ° C. to 285 ° C. at an average heating rate of 2 ° C./min to be infusible and further fired at 800 ° C. This three-dimensional random mat was pulverized at 800 rpm using a cutter (manufactured by Turbo Kogyo) and graphitized at 3000 ° C.
The average fiber diameter of the graphitic carbon fiber filler after graphitization was 9.8 μm, and the ratio of the fiber diameter dispersion to the average fiber diameter was 12%. The average fiber length was 50 μm. The crystal size derived from the growth direction of the hexagonal network surface was 70 nm. The surface of the pitch-based carbon fiber filler observed with a scanning electron microscope was smooth.

50 parts by weight of acetone and 80 parts by weight of pitch-based carbon fiber filler are mixed, 20 parts by weight of an acrylic resin (trade name “Udouble S5000” manufactured by Nippon Shokubai Co., Ltd.) is added to this mixture, and 30 minutes using a planetary mixer While kneading, vacuum degassing was performed, and 300 parts by weight of acetone was further added and diluted to produce a coating material.
When the heat conductivity of the produced heat conductive paint was measured, it was 5.9 W / (m · K), and the electric conductivity was 1.7 × 10 ⁴ Ω / □ (Ω / sq.). The viscosity was 1.0 Pa · S.

[Example 2]
A pitch-based carbon fiber filler was produced in the same manner as in Example 1.
50 parts by weight of hexane and 80 parts by weight of a pitch-based carbon fiber filler are mixed, and 20% by weight of a silicone resin (trade name “TSF451-100” manufactured by Toshiba Silicone Co., Ltd.) is added to this mixture, and then mixed with a planetary mixer. Vacuum defoaming was performed while kneading for a minute, and the kneaded product was diluted with 300 parts by weight of hexane (1: 1) to obtain a heat conductive paint.
It was 6.7 W / (m * K) when the heat conductivity of the obtained heat conductive coating material was measured. Further, the electric conductivity was 2.4 × 10 ⁴ Ω / □ (Ω / sq.), And the viscosity was 0.9 Pa · S.

[Example 3]
A pitch-based carbon fiber filler was produced in the same manner as in Example 1.
50 parts by weight of water and 80 parts by weight of pitch-based carbon fiber filler are mixed, 20% by weight of a styrene-butadiene copolymer (trade name “Nipol LX407AS” manufactured by Nippon Zeon Co., Ltd.) is added thereto, and a planetary mixer is used. The mixture was vacuum degassed while mixing for 30 minutes to obtain a heat conductive paint.
The heat conductivity of the obtained heat conductive paint was measured and found to be 5.1 W / (m · K). The electrical conductivity was 1.8 × 10 ⁴ Ω / □ (Ω / sq.), And the viscosity was 1.1 Pa · S.

[Example 4]
A pitch-based carbon fiber filler was produced in the same manner as in Example 1.
50 parts by weight of water and 80 parts by weight of pitch-based carbon fiber filler are mixed, and 20% by weight of vinyl acetate resin (trade name “Sumikaflex” manufactured by Sumitomo Chemical Co., Ltd.) is added to this mixture, and then a planetary mixer is used. A heat conductive coating was produced by vacuum degassing while mixing for 30 minutes.
It was 5.8 W / (m * K) when the heat conductivity of the manufactured heat conductive coating material was measured. The electrical conductivity was 1.8 × 10 ⁴ Ω / □ (Ω / sq.), And the viscosity was 1.0 Pa · S.

[Example 5]
A pitch-based carbon fiber filler was produced in the same manner as in Example 1.
30 parts by weight of hexane, 60 parts by weight of pitch-based carbon fiber filler, 20 parts by weight of boron nitride, and 20 parts by weight of a silicone resin (trade name “TSF451-100” manufactured by Toshiba Silicone Co., Ltd.) were used. The paint was produced by vacuum defoaming while mixing for minutes.
It was 5.4 W / (m * K) when the heat conductivity of the produced heat conductive coating material was measured. The electric conductivity was 1.9 × 10 ⁷ Ω / □ (Ω / sq.). The viscosity was 0.8 Pa · S.

[Example 6]
A three-dimensional random mat-like carbon fiber was produced in the same manner as in Example 1.
50 parts by weight of hexane, 60 parts by weight of pitch-based carbon fiber filler, 20 parts by weight of silver powder, and 20 parts by weight of silicone resin (trade name “TSF451-100” manufactured by Toshiba Silicone Co., Ltd.) using a planetary mixer for 30 minutes The paint was produced by vacuum defoaming while mixing.
It was 6.7 W / (m * K) when the heat conductivity of the produced heat conductive coating material was measured. The electric conductivity was 1.2 × 10 ² Ω / □ (Ω / sq.). The viscosity was 1.0 Pa · S.

[Comparative Example 1]
A paint was produced in the same manner as in Example 1 except that the content of the pitch-based carbon fiber filler was 3%.
It was 0.5 W / (m * K) when the heat conductivity of the shape | molded heat conductive coating material was measured. The electric conductivity was 1.9 × 10 ⁹ Ω / □ (Ω / sq.). The viscosity was 0.5 Pa · S. Since the amount of the pitch-based carbon fiber filler was less than 5%, it did not have sufficient thermal conductivity.

[Comparative Example 2]
A paint was prepared in the same manner as in Example 1 except that acetone, pitch-based carbon fiber filler, and acrylic resin were mixed at the same time.
The heat conductivity of the molded heat conductive paint was measured and found to be 4.7 W / (m · K). The electric conductivity was 2.6 × 10 ⁴ Ω / □ (Ω / sq.). The viscosity was 20.0 Pa · S. Since the pitch-based carbon fiber filler was not previously diluted after being dispersed in advance, the dispersibility of the pitch-based carbon fiber filler was poor, the viscosity increased, and the handling property decreased.

[Comparative Example 3]
A paint was prepared in the same manner as in Example 1 except that the three-dimensional random mat-like carbon fiber was pulverized after graphitization to obtain a pitch-based carbon fiber filler. At this time, the surface of the pitch-based carbon fiber filler was not smooth.
The heat conductivity of the molded heat conductive paint was measured and found to be 5.6 W / (m · K). The electric conductivity was 2.4 × 10Ω / □ (Ω / sq.). The viscosity was 16.0 Pa · S. Since the surface of the pitch-based carbon fiber filler was not smooth, the viscosity was high and the handling property was low.

  The thermal conductive paint of the present invention can exhibit high thermal conductivity by controlling the spread of graphite crystals to a certain size or more and using a pitch-based carbon fiber filler with controlled surface properties, and has excellent handling properties. This makes it possible to apply to heat-dissipating members. Furthermore, by improving the adhesion to the heat radiation sheet for electronic parts, the heat exchanger, etc., the heat conduction efficiency can be improved and the weight can be reduced.

Claims (10)

  A heat conductive paint comprising a pitch-based carbon fiber filler as a heat conductive material and a matrix made of an organic polymer or an inorganic polymer resin.   The pitch-based carbon fiber filler according to claim 1 has a substantially smooth observation surface with a scanning electron microscope, a crystal size derived from the growth direction of the hexagonal network surface is 5 nm or more, and the thermally conductive paint Thermal conductivity, comprising 5 to 1000 parts by weight of the pitch-based carbon fiber filler with respect to 100 parts by weight of the matrix, and having a thermal conductivity of 3 W / (m · K) or more. Paint.   The pitch-based carbon fiber filler is made of mesophase pitch as a raw material, the average fiber diameter is 5 to 20 μm, the average fiber length is 5 to 6000 μm, and the percentage of the fiber diameter dispersion with respect to the average fiber diameter (CV value) is 5 to 20%. The heat conductive coating material of Claim 1 or Claim 2.   At least one selected from the group consisting of aluminum oxide, magnesium oxide, zinc oxide, boron nitride, aluminum nitride, aluminum oxynitride, quartz, and aluminum hydroxide with respect to 100 parts by weight of the pitch-based carbon fiber filler as the heat conductive material The heat conductive paint according to any one of claims 1 to 3, further comprising 1 to 500 parts by weight of an inorganic filler.   At least one selected from the group consisting of aluminum oxide, magnesium oxide, zinc oxide, boron nitride, aluminum nitride, aluminum oxynitride, quartz, and aluminum hydroxide with respect to 100 parts by weight of the pitch-based carbon fiber filler as the heat conductive material The thermally conductive paint according to claim 4, further comprising 1 to 50 parts by weight of an inorganic filler.   At least one conductive filler selected from the group consisting of 1 to 500 parts by weight of magnesium, gold, silver, copper, aluminum, iron, and graphite with respect to 100 parts by weight of the pitch-based carbon fiber filler as a heat conductive material. The heat conductive paint according to any one of claims 1 to 5.   At least one conductive filler selected from the group consisting of 1 to 50 parts by weight of magnesium, gold, silver, copper, aluminum, iron, and graphite with respect to 100 parts by weight of the pitch-based carbon fiber filler as a heat conductive material. The thermally conductive paint according to claim 6, which is contained.   The thermally conductive paint according to any one of claims 1 to 7, comprising at least one resin selected from the group consisting of a silicone resin, an acrylic resin, a vinyl acetate resin, and a styrene-butadiene copolymer as a matrix.   A step of immersing a pitch-based carbon fiber filler as a heat conductive material in a solvent; and a matrix made of at least one resin selected from the group consisting of a silicone resin, an acrylic resin, a vinyl acetate resin, and a styrene-butadiene copolymer; A method for producing a thermally conductive paint, comprising: a step of obtaining a mixture by mixing, and a step of diluting the mixture with a solvent that is the same as or different from the solvent.   A pitch-based carbon fiber filler as a heat conductive material, and at least one inorganic filler selected from the group consisting of aluminum oxide, magnesium oxide, zinc oxide, boron nitride, aluminum nitride, aluminum oxynitride, quartz, and aluminum hydroxide; At least one selected from the group consisting of a step of soaking in a solvent, an immersion material comprising the pitch-based carbon fiber filler and the inorganic filler, and a silicone resin, an acrylic resin, a vinyl acetate resin, and a styrene-butadiene copolymer. A method for producing a thermally conductive coating, comprising: a step of mixing a matrix made of a seed resin to obtain a mixture; and a step of diluting the mixture with a solvent that is the same as or different from the solvent.