JP2010013580A - High-thermal conductivity composite and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-thermal conductivity composite comprising a matrix resin constituting the matrix, and a high-thermal conductivity filler having anisotropy in the shape, and exhibiting a desired thermal conductivity even when the content of the filler is small; and to provide a method for producing the composite. <P>SOLUTION: The high-thermal conductivity composite is obtained by curing a mixture of the high-thermal conductivity filler having a surface-modifier not having affinity with the matrix resin and attached to the surface, and the matrix resin raw material. As a result, the filler forms a network structure in the matrix resin. The absolute value of the difference of the SP values between the matrix resin and the surface modifier is preferably regulated so as to be ≥0.5. Alternatively, the high-thermal conductivity composite is produced by stirring a mixture of a matrix resin raw material and a high-thermal conductivity filler while keeping the viscosity at ≥15 Pa s, and curing the resultant mixture. As a result, the filler forms a network structure in the matrix resin. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a resin / filler composite having excellent thermal conductivity and a method for producing the same.

  In recent years, resin products used in the automotive field, the electrical and electronic field, and the like have become necessary to take some heat dissipation measures against heat generation due to downsizing and high performance of the products. For example, device heat generation per unit volume of a wiring board tends to increase with downsizing of electronic devices, higher mounting density, and higher speed of operation. An increase in the temperature of an electronic device decreases its characteristics, lifespan, and the like, and consequently affects the reliability of the electronic device itself. The tendency in the power circuit is particularly strong, and how to dissipate the heat of the heat generating device is an important issue in order to improve the reliability of the power circuit.

  For this reason, the resin material used for a wiring board requires high heat dissipation. As the resin material, a filler having a high thermal conductivity, for example, a resin / filler composite in which a particulate metal, alloy or ceramic is dispersed in a matrix resin is generally used.

  For example, Patent Document 1 discloses a resin composition in which a metal fiber or a low melting point alloy powder that is melted and joined in a network is dispersed in a thermoplastic resin.

Moreover, in patent document 2, the mixed powder containing resin, a low melting-point alloy, and a filler is shape | molded at normal temperature, Then, the molded object is heated at the temperature which a low-melting-point alloy melts completely, and fillers are welded with a low-melting-point alloy. By doing so, the thermal conductivity of the molded body is increased.
JP 2004-135495 A Japanese Patent Laid-Open No. 6-196684

  As described above, by dispersing fine inorganic particles and metal particles having high thermal conductivity as fillers in the matrix resin, a resin / filler composite exhibiting high thermal conductivity as a whole can be obtained. However, when a particulate filler is added to the resin, the filler is likely to be uniformly dispersed in the resin, resulting in a structure in which a resin matrix having low thermal conductivity is interposed between the particles. For this reason, the particles are discontinuously dispersed and the desired thermal conductivity may not be obtained. As described in Patent Document 1, even if a fibrous filler (metal fiber) is used, the filler tends to be discontinuous simply by dispersing the filler in the resin. Therefore, if the filler content is increased in order to improve the thermal conductivity of the composite, the resin content decreases, so the flexibility, impact resistance, moldability, workability, etc. of the composite decrease. There is a problem.

  Moreover, since patent document 1 and patent document 2 contain the low melting-point alloy whose heat conductivity is small compared with a filler, it is difficult to increase the heat conductivity of a composite_body | complex largely. Furthermore, in patent document 2, in order to weld fillers, it is necessary to enlarge the content rate of a low melting-point alloy. However, even if the content of the low-melting-point alloy is increased, there is a problem that the resin content is decreased and the mechanical properties of the composite are decreased.

  Therefore, in view of the above problems, the present inventors are composed of a matrix resin and a highly thermally conductive filler dispersed in the matrix resin, and can achieve a desired thermal conductivity even when the filler content is low. It is an object to provide a high thermal conductive composite and a method for producing the same.

The high thermal conductive composite of the present invention is a high thermal conductive composite comprising a matrix resin constituting a matrix and a high thermal conductive filler having anisotropy in shape,
The high thermal conductivity fillers are in direct contact with each other, and the high thermal conductivity filler forms a network structure in the matrix resin.

Further, the method for producing a high thermal conductive composite of the present invention is a method for producing a high thermal conductive composite comprising a matrix resin constituting a matrix and a high thermal conductive filler having anisotropy in shape,
A filler surface modification step of attaching a surface modifier having an absolute value of a solubility parameter (SP value) difference with the matrix resin of 0.5 or more to the surface of the high thermal conductive filler;
A mixture preparation step of preparing a mixture of the high thermal conductive filler and matrix resin raw material whose surface is modified;
A molding step of molding the mixture;
It is characterized by comprising.

Another method for producing the high thermal conductive composite of the present invention is a method for producing a high thermal conductive composite comprising a matrix resin constituting the matrix and a high thermal conductive filler having anisotropy in shape,
A mixture preparation step of preparing a mixture of the high thermal conductive filler and the matrix resin raw material;
A stirring step of stirring the mixture obtained in the mixture preparation step while maintaining the viscosity of the mixture at 15 Pa · s or higher;
A molding step of molding the mixture after stirring;
It is characterized by comprising.

  The high thermal conductivity composite of the present invention is composed of a matrix resin constituting the matrix and a high thermal conductivity filler having anisotropy in shape, and the high thermal conductivity fillers are in direct contact with each other so as to have high thermal conductivity. The filler forms a network structure in the matrix resin. The network structure formed by the high thermal conductive filler is a three-dimensional network formed in the matrix resin by direct contact between the high thermal conductive fillers, and serves as a path for transferring heat. That is, the formation of a network structure by the high thermal conductivity filler in the matrix resin leads to an improvement in the thermal conductivity of the high thermal conductivity composite of the present invention.

  In the method for producing a high thermal conductive composite of the present invention, the high thermal conductive filler is attached to the surface thereof with a surface modifier having an absolute value of a difference in solubility parameter (SP value) from the matrix resin of 0.5 or more. And then mixed with the matrix resin raw material. A highly thermally conductive filler to which a surface modifier that is not easily compatible with the matrix resin is attached is difficult to disperse uniformly in the matrix resin. As a result, the highly thermally conductive filler forms a network structure in the matrix resin.

  Alternatively, in the method for producing a high thermal conductive composite according to the present invention, the mixture of the matrix resin and the high thermal conductive filler is stirred while maintaining the viscosity at 15 Pa · s or more. Since the mixture is stirred while maintaining a high viscosity, the mixture is sheared more slowly than usual, and the high thermal conductive filler tends to form a network structure in the matrix resin.

  The best mode for carrying out the highly heat-conductive composite of the present invention and the method for producing the same will be described below.

  The high thermal conductive composite of the present invention comprises a matrix resin constituting a matrix and a high thermal conductive filler having anisotropy in shape.

  The matrix resin may be appropriately selected according to the use of the high thermal conductive composite, but is preferably a thermosetting resin. As the thermosetting resin, an epoxy resin is preferably used. Specific examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, and novolac type epoxy. An acrylic resin (thermoplastic resin) may be used. Specific examples of the acrylic resin include polymethyl methacrylate and polyacrylonitrile. These resin materials may be used alone or in admixture of two or more.

  The high thermal conductive filler is not particularly limited as long as it has high thermal conductivity and anisotropy in shape. In other words, any high thermal conductive filler (hereinafter abbreviated as “filler”) having an aspect ratio (long side / short side) of more than 1, preferably 10 or more can be used. The specific shape is preferably fibrous, scale-like or whisker. These fillers may be used alone or in combination of two or more.

  Furthermore, in addition to a filler having anisotropy in shape, a particulate filler having an aspect ratio of about 1 may be used. By using both the filler having anisotropy in the shape and the particulate filler, the contact point between the fillers forming the network structure is reinforced, and the effect as a path for transferring heat is improved.

The filler preferably has a thermal conductivity of 10 W / m · K or more, more preferably 10 to 2000 W / m · K, and 100 to 2000 W / m · K. In particular, when a highly heat conductive composite is used as a heat radiating member of an electronic device, insulation is necessary. Therefore, it is preferable to use a highly insulating high heat conductive filler that has both heat conductivity and insulation. Specifically, the electrical resistivity is preferably 1 × 10 ⁵ Ω · cm or more, and more preferably 1 × 10 ⁵ to 1 × 10 ¹⁵ Ω · cm. Examples of materials having such characteristics include alumina (Al ₂ O ₃ ), aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ), silicon carbide (SiC), cubic boron nitride (cBN), and the like. One or more of these can be used. Of these, aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ), or silicon carbide (SiC) is particularly preferable. When used together with particulate filler, the filler having anisotropic shape and the particulate filler may be fillers made of the same material or fillers made of different materials. May be.

  Although there is no limitation in particular in the usage-amount of a filler, when the high heat conductive composite body is 100 weight%, it is good to contain a filler 5 to 40 weight% further 15 to 30 weight%. When the filler content is less than 5% by weight, the filler is difficult to form a network structure, so that thermal conductivity is difficult to develop. As the filler content increases, the thermal conductivity improves. However, if the filler content exceeds 40% by weight, the resin content decreases, so that flexibility, impact resistance, moldability, workability, and the like decrease. As will be described later, the high thermal conductivity composite of the present invention can provide the desired thermal conductivity even if the filler content is smaller than usual, so that the filler content is 15% by weight or less. May be suppressed to 10% by weight or less.

  In addition to the filler having anisotropy in the shape described above, in the case where a particulate filler is also used, the particulate filler is contained in an amount of 10% by weight or less when the entire high thermal conductive composite is taken as 100% by weight. Good. In particular, when the content is 5 to 10% by weight, the thermal conductivity of the high thermal conductive composite of the present invention is further improved.

  By the way, usually, when preparing a mixture composed of a matrix resin raw material and a filler, a matrix resin and a filler having high affinity are used, or the filler is subjected to a surface treatment so as to improve the affinity. It is common. Moreover, in order to improve the dispersibility of the filler in a matrix resin, it is common to sufficiently stir after the preparation. However, in this invention, before preparing the mixture of matrix resin and a filler, the surface modifier which does not have affinity with a matrix resin is made to adhere to the surface of a filler. Alternatively, the viscosity of the mixture of the matrix resin and the filler is kept higher than before and stirred. As a result, the filler forms a network structure in the matrix resin. Below, each high heat conductive composite is demonstrated.

  The high thermal conductive composite of the present invention includes a high thermal conductive filler and a matrix resin raw material on which a surface modifier having an absolute value of a difference in solubility parameter (SP value) from the matrix resin of 0.5 or more is adhered. It is preferable to form a mixture of That is, the high thermal conductive composite of the present invention includes a filler surface modification step in which a surface modifier having an SP value difference with the matrix resin of 0.5 or more is attached to the surface of the high thermal conductive filler. It is manufactured through a mixture preparation step for preparing a mixture of a highly thermally conductive filler whose surface is modified and a matrix resin raw material, and a molding step for molding the mixture.

  The surface modifier used in the filler surface modification step is not particularly limited as long as it has a low affinity with the matrix resin and is incompatible with the matrix resin. By modifying the surface of the filler using a surface modifier having a low affinity with the matrix resin, the filler is not uniformly dispersed in the mixture, but forms a network structure in the matrix resin. In addition, if a filler having anisotropy in shape is used, a network structure having contacts at both ends in the longitudinal direction of the filler is easily formed. Therefore, even if the filler content is smaller than usual, a high thermal conductive composite having desired thermal conductivity can be obtained.

Note that a solubility parameter (SP value) is used as a factor for determining the strength of affinity. The SP value (unit: (cal / cm ³ ) ^1/2 ) is determined from the cohesive energy density (CED) indicating the intermolecular binding force. That is, it is calculated from the square root of the heat of vaporization required to evaporate one molar volume of liquid. The absolute value of the difference in SP value between the matrix resin and the surface modifier is preferably 0.5 or more, more preferably 1 or more. If the absolute value of the difference in SP value is less than 0.5, the filler is uniformly dispersed in the matrix resin, so that it is difficult to form a network structure. On the other hand, when it exceeds 4, aggregation of fillers becomes remarkable and it becomes difficult to form a network structure. Therefore, the absolute value of the difference in SP value between the matrix resin and the surface modifier is preferably 4 or less, and more preferably 3 or less.

  Moreover, if it is a surface modifier that can be used in a liquid state, in the filler surface modification step, the surface modifier can be adhered to the filler surface simply by injecting the surface modifier into a container filled with the filler. Further, the surface modifier may be adsorbed on the filler surface by heating the filler and the surface modifier in contact with each other. The surface modifying agent needs to remain attached to the surface of the filler at least until the filler is mixed with the matrix resin in the mixture preparation step. Therefore, a liquid with low volatility may be selected as the surface modifier. Further, it is desirable that the surface modifier has a low reactivity with the matrix resin. That is, preferable surface modifiers are acetonitrile, propylene glycol monomethyl ether (PGME) and propylene glycol monomethyl ether acetate (PGMEA), dimethylformamide (DMF), dimethylacetamide, n-butanol, etc., and the matrix to be used among them. You may use individually 1 type with low affinity with resin, or may use 2 or more types together. Specifically, if the matrix resin is acrylic (SP value: 9 to 10), acetonitrile (SP value: 11.9), PGME (SP value: 10.6) and PGMEA (SP) are used as the surface modifier. It is desirable to use one or more of the values: 8.7).

  Since the surface modifying agent may be attached to the surface of the filler, desirably attached to the entire surface of the filler, the amount used may be appropriately selected according to the type and amount of the filler used. If the amount of the surface modifier used is defined, it is desirable to use 2% by weight or more when the filler to be used (including the amount when using a granular filler) is 100% by weight. Desirably, it is 3 to 5% by weight.

  In the mixture preparation step, a mixture of a filler whose surface is modified and a matrix resin raw material is prepared. If the matrix resin is a thermosetting resin, a liquid composed of low-molecular monomers and having an appropriate viscosity is used as the matrix resin raw material, the matrix resin raw material and the surface-modified filler, and a curing agent as necessary. Add. The filler is not uniformly dispersed in the mixture and forms a network structure. In the mixture preparation step, it is desirable to use a kneader such as a roll or a kneader.

  The high thermal conductive composite of the present invention is formed by stirring a mixture of a matrix resin raw material and a high thermal conductive filler while maintaining the viscosity at 15 Pa · s or higher. That is, the high thermal conductive composite of the present invention comprises a mixture preparation step for preparing a mixture of a high thermal conductive filler and a matrix resin raw material, and a mixture obtained in the mixture preparation step, wherein the viscosity of the mixture is 15 Pa · s or more. It is manufactured through a stirring process for maintaining and stirring, and a molding process for molding the mixture after stirring.

  In the stirring process, if the viscosity of the mixture of the filler and the matrix resin is kept at 15 Pa · s or higher, preferably 20 Pa · s or higher, the mixture is stirred with a high viscosity, so that only moderate shearing occurs in the mixture. Absent. When sheared and stirred more gently than usual, the filler is not uniformly dispersed in the mixture, and the formation of a network structure is promoted even when the surface modifier is not attached to the surface of the filler. In addition, as described above, when a filler having anisotropy in shape is used, a network structure having both ends in the longitudinal direction of the filler as contacts is easily formed. Therefore, even if the filler content is smaller than usual, a high thermal conductive composite having desired thermal conductivity can be obtained. In addition, if the upper limit of the viscosity of a mixture is prescribed | regulated, 60 Pa.s or less and also 40 Pa.s or less are desirable. When the viscosity exceeds 60 Pa · s, the filler is likely to aggregate and a network structure is not formed.

  The viscosity of the mixture in the stirring step depends on the shear rate during stirring. Therefore, the shear rate when stirring the mixture is preferably 1 to 50 / s, more preferably 3 to 30 / s. In order to control the viscosity of the mixture and the shear rate during stirring, it is necessary to appropriately select the temperature of the mixture and the number of rotations of stirring. Specifically, if the temperature of the mixture is 50 ° C., the number of rotations during stirring is preferably 10 to 100 rpm, more preferably 30 to 80 rpm. The mixture is preferably stirred for 0.01 to 1 hour, more preferably 0.1 to 0.5 hour. The longer the stirring time, the easier it is for the filler to be uniformly dispersed in the mixture. Therefore, when the stirring time exceeds 1 hour, it is difficult to form a network structure with the filler.

  Moreover, although the usage-amount of a desirable filler is as having already stated, when stirring in the state where the viscosity of a mixture is high, when the whole highly heat conductive composite shall be 100 weight%, a filler is 6-40 weight. % Or even 8 to 20% by weight. If the filler content is less than 6% by weight, even if the mixture is stirred while maintaining a high viscosity, the effect of promoting the formation of a network structure is small, so that the thermal conductivity is hardly exhibited.

  Further, it is desirable that the temperature of the mixture is 30 to 70 ° C, more preferably 45 to 55 ° C. If it is less than 30 ° C., the viscosity of the mixture is too high and it is difficult to form a network structure. On the other hand, when the temperature exceeds 70 ° C., the viscosity of the mixture decreases and the mixture tends to flow, and the effect of promoting the formation of a network structure is reduced.

  In addition, when performing a stirring process, you may make a surface modifier adhere to the surface of a filler previously before a mixture preparation process (filler surface modification process). At this time, the absolute value of the difference in SP value between the desired matrix resin and the surface modifier is as described above, but in the case of stirring while maintaining the viscosity of the mixture at 15 Pa · s or higher in the subsequent stirring step. For this, it is desirable that the difference in SP value is 3 or less, more preferably 2 or less. If the absolute value of the difference in SP value exceeds 3, even if stirring is performed at a high viscosity, the effect of promoting the formation of a network structure is small, and depending on the stirring conditions, the network structure may collapse from the state before stirring. Therefore, it is not desirable.

  The forming step is a step of forming the mixture into a desired shape. Depending on the type of matrix resin, the mixture may be cooled and solidified, or reacted by applying energy such as heat to the mixture to cure the mixture, thereby fixing the mixture in a desired shape. In addition, what is necessary is just to select curing conditions suitably according to the matrix resin to be used. The high thermal conductive composite of the present invention is applied to a base material, dried and cured to form a film, or formed into a film shape or a plate shape, and used for an electronic device. It can be applied to matrix resin and solder resist resin.

  In the high thermal conductive composite of the present invention and the method for producing the same described above, a desirable network structure is a network size of 10 μm or more, 20 μm or more, and further 30 μm or more. The network size is the maximum length of the diagonal line of each net that can be discriminated when the cross section of the high thermal conductive composite is observed with a scanning electron microscope (SEM) in a field of view of about 200 μm × 300 μm. Average value.

  As mentioned above, although embodiment of the highly heat conductive composite_body | complex of this invention and its manufacturing method was described, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.

  Hereinafter, the present invention will be specifically described with reference to examples of the high thermal conductive composite of the present invention and the production method thereof.

[Example 1]
Methyl acrylate (“3Bond 3057J” manufactured by ThreeBond Co., Ltd., SP value: 9.3) as a matrix resin raw material and silicon carbide (SiC) whisker (“Toka Whisker” manufactured by Tokai Carbon Co., Ltd.) average diameter 0.3 to 1 as a filler 4 μm, fiber length 5 to 30 μm), acetonitrile (SP value: 11.9) was used as a surface treatment agent for the filler, and a highly heat-conductive composite film was formed on the surface of the substrate by the following procedure.

<Filler surface modification process>
20 g of SiC whiskers were prepared and filled into transparent vials. Next, acetonitrile was injected into the transparent vial so as to be 3% by weight with respect to 100% by weight of SiC whiskers. The obtained mixture of SiC whisker and acetonitrile was pulverized and mixed with an ultrasonic homogenizer, and then heated to 60 ° C. to adsorb and immobilize acetonitrile on the surface of the SiC whisker.

<Mixture preparation process>
A mixture of 10 g of the surface-modified filler and 90 g of methyl acrylate was prepared. The filler content was 10% by weight when the high thermal conductive composite was taken as 100% by weight. Three passes of kneading with three rolls were performed.

<Molding process>
The obtained mixture was applied to the surface of a glass substrate (30 mm × 30 mm), and the coated surface was irradiated with UV, and then heated at 130 ° C. for 1 hour. Thus, sample # 01 having a coating made of a high thermal conductive composite having a thickness of 200 μm on the surface of the substrate was obtained.

[Example 2]
Sample # 02 was obtained in the same manner as in Example 1 except that propylene glycol monomethyl ether (PGME, SP value: 10.6) was used as the surface treatment agent. Below, a filler surface modification | reformation process is demonstrated.

  20 g of SiC whiskers were prepared and filled into transparent vials. Next, PGME was inject | poured into the transparent vial so that it might become 3 weight% with respect to 100 weight% of SiC whiskers. The obtained mixture of SiC whisker and PGME was pulverized and mixed with an ultrasonic homogenizer, and then heated to 70 ° C. to adsorb and immobilize PGME on the surface of the SiC whisker.

[Example 3]
Sample # 03 was obtained in the same manner as in Example 1 except that propylene glycol monomethyl ether acetate (PGMEA, SP value: 8.7) was used as the surface treatment agent. Below, a filler surface modification | reformation process is demonstrated.

  20 g of SiC whiskers were prepared and filled into transparent vials. Next, PGME was inject | poured into the transparent vial so that it might become 3 weight% with respect to 100 weight% of SiC whiskers. The obtained mixture of SiC whisker and PGMEA was pulverized and mixed with an ultrasonic homogenizer, and then heated to 70 ° C. to adsorb and immobilize PGMEA on the surface of the SiC whisker.

[Comparative Example 1]
Sample # C1 was obtained in the same manner as in Example 1 except that the surface modifier was not used, that is, the surface modification step was not performed.

[Evaluation]
[Observation of network structure]
The cross sections of the coatings of Samples # 01 to # 03 and # C1 were observed. Cross-sectional observation was performed with a scanning electron microscope (SEM). The obtained SEM images are shown in FIGS.

  In samples # 01 to # 03 subjected to the filler surface modification step, a network structure formed by the filler was observed, but not in sample # C1 (FIG. 4).

  Further, the network size was calculated from the obtained SEM image. The network size was calculated by measuring the diagonal length of each net that can be discriminated in the SEM images shown in FIGS. The maximum value, minimum value, and average value of the network size are shown in FIG. In FIG. 5, the horizontal axis (SP value difference) is the absolute value of the SP value difference between the matrix resin and the surface treatment agent.

  The average value of the network size was 48 μm for # 01, 26 μm for # 02, and 18 μm for # 03. That is, it has been found that the larger the absolute value of the SP value difference between the matrix resin and the filler, the easier it is to form a network structure having a larger network size.

[Measurement of thermal conductivity]
The thermal conductivity of samples # 01 to # 03 and # C1 was measured. The measurement was performed by measuring the temperature difference between the upper and lower surfaces of the substrate and the coating in the thickness direction using a thermal diffusivity measuring device (Mobile 1u) manufactured by Eye Phase Co., Ltd. The measurement result of thermal conductivity is shown in FIG.

  The larger the network size, that is, the larger the absolute value of the SP value difference between the matrix resin and the filler, the higher the thermal conductivity.

[Example 4]
The same methyl acrylate as described above as a matrix resin raw material (“ThreeBond 3057J” manufactured by ThreeBond Co., Ltd.), the same SiC whisker as described above (“Toka Whisker” manufactured by Tokai Carbon Co., Ltd.), and PGME as a surface treatment agent for the filler, A high thermal conductive composite film was formed on the surface of the substrate by the following procedure.

<Filler surface modification process>
20 g of SiC whiskers were prepared and filled into transparent vials. Next, PGME was inject | poured into the transparent vial so that it might become 3 weight% with respect to 100 weight% of SiC whiskers. The obtained mixture of SiC whisker and PGME was pulverized and mixed with an ultrasonic homogenizer, and then heated to 70 ° C. to adsorb and immobilize PGME on the surface of the SiC whisker.

<Mixture preparation process>
A mixture of 6 g of filler with modified surface and 194 g of methyl acrylate was prepared. The filler content was 3% by weight when the high thermal conductive composite was taken as 100% by weight. Three passes of kneading with three rolls were performed.

<Stirring step>
The resulting mixture was heated to 50 ° C. With the mixture kept at 50 ° C., the mixture was stirred using a stirrer. As a stirrer, a general stirrer was used. The stirrer was rotated at 63 rpm and stirred at a shear rate of 10 [1 / s] for a predetermined time to obtain a high thermal conductive composite. The viscosity of the mixture at this time was 15 Pa · s. The stirring time is shown in Table 1.

<Molding process>
The obtained mixture was applied to the surface of a glass substrate (30 mm × 50 mm), and the coated surface was irradiated with UV, and then heated at 130 ° C. for 1 hour. In this way, three types of samples # 04-1 to # 3-3 having a coating made of a high thermal conductive composite having a thickness of 200 μm on the surface of the substrate were obtained.

[Example 5]
Samples # 05-1 to 3 were obtained in the same manner as in Example 4 except that the filler content was 5% by weight when the high thermal conductive composite was 100% by weight. The viscosity of the mixture in the stirring step was 14 Pa · s.

[Example 6]
Samples # 06-1 and # 06-2 were obtained in the same manner as in Example 4 except that the filler content when the high thermal conductive composite was 100% by weight was changed to 7% by weight. The viscosity of the mixture in the stirring step was 17 Pa · s.

[Example 7]
Samples # 07-1 to 4 were obtained in the same manner as in Example 4 except that the filler content was 10% by weight when the high thermal conductive composite was 100% by weight. The viscosity of the mixture in the stirring step was 19 Pa · s.

[Example 8]
Samples # 08-1 to 4 were obtained in the same manner as in Example 4 except that the filler content was 15 wt% when the high thermal conductive composite was 100 wt%. The viscosity of the mixture in the stirring step was 27 Pa · s.

[Example 9]
Samples # 09-1 to 4 were obtained in the same manner as in Example 4 except that the filler content when the high thermal conductive composite was 100% by weight was 20% by weight. The viscosity of the mixture in the stirring step was 40 Pa · s.

[Example 10]
Samples # 10-1 to # 3 were obtained in the same manner as in Example 4 except that the filler content was 27% by weight when the high thermal conductive composite was 100% by weight. The viscosity of the mixture in the stirring step was 60 Pa · s.

[Example 11]
Samples # 11-1 to 4 were obtained in the same manner as in Example 7 except that acetonitrile was used as the surface modifier. The viscosity of the mixture in the stirring step was 19 Pa · s.

  In Table 1, # 01 and # 11-1, and # 02 and # 07-1 are the same sample.

  For reference, the viscosity when the shear rate is changed from 0 to 100 [1 / s] for the resin compositions having different filler contents is shown in FIG. The filler contents were 0 (no filler), 5 wt%, 7 wt%, 10 wt%, 25 wt%, and 30 wt%, respectively. For the measurement of viscosity, a viscoelasticity measuring device (Rheo Stress 6000) manufactured by Eiko Seiki Co., Ltd. was used. The greater the filler content, the higher the viscosity of the resin composition. Moreover, the viscosity of the resin composition decreased as the shear rate increased.

  Further, the thermal conductivity of each sample was measured by the same method as described above. The results are shown in FIG. 8 and FIG.

  In Examples 4 to 11, when the stirring time was 0 hour (no stirring), the filler that had undergone the surface modification step formed a network structure in the matrix resin. In particular, when the filler content was 10% by weight or more, high thermal conductivity was exhibited. On the other hand, if the filler content exceeds 20% by weight, it is estimated that there is no significant difference in thermal conductivity.

  In Example 4 and Example 5, since the viscosity of the mixture in the stirring step was 15 Pa · s or less, no great change in thermal conductivity occurred even when stirring was performed. In Example 6 where the mixture was stirred at 17 Pa · s, it can be estimated that the thermal conductivity was improved by stirring for 0.1 hour as compared with the case where stirring was not performed. Similarly, also in Examples 7 to 10, by selecting the stirring time appropriately, the thermal conductivity was improved as compared with the case where stirring was not performed.

  In Example 11, acetonitrile was used as the surface modifier. When stirring was not performed (# 11-1), a network structure having a larger network size was formed in the filler (FIG. 1). However, even when stirring was performed under the same conditions as in Example 7, no improvement in thermal conductivity was observed. That is, when the SP value difference between the matrix resin and the filler is large, the formation of the network structure was not promoted even when stirring was performed with a high viscosity.

[Example 12]
The same methyl acrylate as the above as the raw material of the matrix resin, the same SiC whisker as the filler as described above, and dimethylformamide (DMF, SP value: 12.1) as the surface treatment agent for the filler are used. A conductive composite film was formed.

<Filler surface modification process>
20 g of SiC whiskers were prepared and filled into transparent vials. Next, DMF was injected into the transparent vial so as to be 3% by weight with respect to 100% by weight of SiC whiskers. The obtained mixture of SiC whisker and DMF was pulverized and mixed with an ultrasonic homogenizer, and then heated to 70 ° C. to adsorb and immobilize DMF on the surface of the SiC whisker.

<Mixture preparation process>
A mixture of surface modified filler and methyl acrylate was prepared. Eight types of mixtures were prepared by changing the filler content from 5 to 40% by weight in increments of 5% by weight when the high thermal conductive composite was 100% by weight. Three passes of kneading with three rolls were performed.

<Stirring step>
The resulting mixture was heated to 50 ° C. With the mixture kept at 50 ° C., the mixture was stirred using a stirrer. As a stirring device, a general stirring device was used, and the number of revolutions of the stirring bar was 63 rpm. Stirring was performed at a shear rate of 10 [1 / s] for 0.1 hour to obtain a highly heat conductive composite.

<Molding process>
The obtained mixture was applied to the surface of a glass substrate (30 mm × 50 mm), and the coated surface was irradiated with UV, and then heated at 130 ° C. for 1 hour. In this manner, eight types of samples having a coating made of a high thermal conductive composite having a thickness of 200 μm on the surface of the substrate were obtained.

[Example 13]
Eight types of samples were obtained in the same manner as in Example 12 except that the stirring step was not performed.

[Comparative Example 2]
A sample was prepared in the same manner as in Example 13 except that the filler content was 0% by weight.

  The thermal conductivity of each sample of Examples 12 and 13 and Comparative Example 2 was measured by the same method as described above. The measurement result is shown in FIG. 10 together with the result of the sample prepared without performing the stirring step. In FIG. 10, ◇ indicates the thermal conductivity of each sample of Example 12, and ◯ indicates the thermal conductivity of each sample of Example 13 and Comparative Example 2. Moreover, the improvement rate of the heat conductivity by performing a stirring process is shown by ♦ with the heat conductivity of each sample.

  Regardless of the presence or absence of the stirring step, the thermal conductivity increased as the filler content increased. It was also found that when the filler content was 10% by weight or more, the formation of a network structure was promoted by stirring and the thermal conductivity was greatly improved. On the other hand, the greater the filler content, the easier it is for the filler to aggregate, making it difficult to form a network structure. However, if it is 40 wt% or less, and less than 35 wt%, the thermal conductivity is increased by stirring. Improved.

It is a drawing substitute photograph which shows the cross-sectional observation result of the film which consists of a high heat conductive composite of sample # 01 (Example 1). It is a drawing substitute photograph which shows the cross-sectional observation result of the film which consists of a high heat conductive composite of sample # 02 (Example 2). It is a drawing substitute photograph which shows the cross-sectional observation result of the film which consists of a highly heat conductive composite of sample # 03 (Example 3). It is a drawing substitute photograph which shows the cross-sectional observation result of the resin film of sample # C1 (comparative example 1). It is a graph which shows the network size with respect to the absolute value of the difference of SP value of matrix resin and a surface treating agent about sample # 01- # 03. It is a graph which shows the heat conductivity with respect to network size about sample # 01- # 03. It is a graph which shows a viscosity when changing a shear rate to 0-100 [1 / s] about the mixture from which filler content differs. It is a graph which shows the change of the heat conductivity with respect to stirring time. It is a graph which shows the change of the heat conductivity with respect to stirring time. It is a graph which shows the change of the heat conductivity with respect to filler content.

Claims (21)

A high thermal conductive composite comprising a matrix resin constituting the matrix and a high thermal conductive filler having anisotropy in shape,
The high thermal conductivity filler is in direct contact with each other, and the high thermal conductivity filler forms a network structure in the matrix resin.   The high thermal conductive composite according to claim 1, comprising 5 to 40% by weight of the high thermal conductive filler when the whole is taken as 100% by weight.   A mixture of the high thermal conductive filler and the matrix resin raw material having a surface modifier adhering to the surface with an absolute value of a difference in solubility parameter (SP value) from the matrix resin of 0.5 or more is formed. The high thermal conductive composite according to claim 1 or 2.   The high thermal conductive composite according to claim 3, wherein an absolute value of a difference in solubility parameter (SP value) between the matrix resin and the surface modifier is 0.5 or more and 4 or less.   The high thermal conductivity according to claim 3, wherein the matrix resin is acrylic, and the surface modifier is one or more of acetonitrile, propylene glycol monomethyl ether (PGME) and propylene glycol monomethyl ether acetate (PGMEA). Complex.   The high thermal conductive composite according to claim 1 or 2, wherein the mixture of the matrix resin raw material and the high thermal conductive filler is stirred while maintaining the viscosity at 15 Pa · s or more, and then the mixture is molded.   The highly heat conductive composite according to claim 6, wherein the viscosity of the mixture during stirring is 20 Pa · s or more and 60 Pa · s or less.   The high thermal conductive composite according to claim 6, wherein the mixture is stirred at a shear rate of 1 to 50 / s.   The high thermal conductive composite according to claim 1, wherein the matrix resin is a thermosetting resin.   The high thermal conductive composite according to claim 1, wherein the matrix resin is acrylic or epoxy.   The high thermal conductive composite according to claim 1, wherein the high thermal conductive filler has a fibrous shape, a scale shape, or a whisker. The high heat conductive filler is a high insulating high heat conductive filler having a thermal conductivity of 10 to 2000 W / m · K and an electrical resistivity of 1 × 10 ⁵ to 1 × 10 ¹⁵ Ω · cm. High thermal conductivity composite.   The high thermal conductive composite according to claim 12, wherein the thermal conductive filler is a silicon carbide (SiC) whisker. A method for producing a high thermal conductive composite comprising a matrix resin constituting a matrix and a high thermal conductive filler having anisotropy in shape,
A filler surface modification step of attaching a surface modifier having an absolute value of a solubility parameter (SP value) difference with the matrix resin of 0.5 or more to the surface of the high thermal conductive filler;
A mixture preparation step of preparing a mixture of the high thermal conductive filler and matrix resin raw material whose surface is modified;
A molding step of molding the mixture;
A process for producing a highly heat-conductive composite comprising:   The method for producing a high thermal conductivity composite according to claim 14, wherein an absolute value of a difference in solubility parameter (SP value) between the matrix resin and the surface modifier is 0.5 or more and 4 or less. A method for producing a high thermal conductive composite comprising a matrix resin constituting a matrix and a high thermal conductive filler having anisotropy in shape,
A mixture preparation step of preparing a mixture of the high thermal conductive filler and the matrix resin raw material;
A stirring step of stirring the mixture obtained in the mixture preparation step while maintaining the viscosity of the mixture at 15 Pa · s or higher;
A molding step of molding the mixture after stirring;
A process for producing a highly heat-conductive composite comprising:   The high heat conductivity according to claim 16, wherein the mixture preparation step is a step of preparing the mixture so that the high heat conductive filler is 6 to 40% by weight when the high heat conductive composite is 100% by weight. A method for producing a composite.   The method for producing a high thermal conductivity composite according to claim 16, wherein the viscosity of the mixture during stirring is 20 Pa · s or more and 60 Pa · s or less.   The method for producing a high thermal conductivity composite according to claim 16, wherein the stirring step is a step of stirring the mixture at a shear rate of 1 to 50 / s.   The method for producing a high thermal conductivity composite according to claim 16, wherein the stirring step is a step of stirring the mixture for 0.01 to 1 hour.   A high thermal conductive composite obtained by the method according to claim 14.