Heat dissipation material

Abstract

Provided is a heat dissipation material comprising a mesogen/silicon compound (co)polymer having a number average molecular weight of 1,000-500,000, represented by general formula (1). ##STR00001##
(Ar is a mesogen group selected from the structure represented by the following formulas. ##STR00002##
a represents a positive number from 0.5 to 1, b represents a number from 0 to 0.5 (with the caveat that a and b each represent the ratio of each number of repeating units in molecules, and a+b=1). R.sub.1 is independently a monovalent hydrocarbon group which does not independently include a C.sub.1-8 aliphatic unsaturated bond. R.sub.2 is independently a hydrogen atom, Si(CH.sub.3).sub.3, Si(CH.sub.3).sub.2(OH), Si(CH.sub.3).sub.2(CHCH) or Si(CH.sub.3).sub.2(CH.sub.2CHCH.sub.2)). This heat dissipation material has excellent thermal conductivity, and further shows good thermoplastic properties and has excellent moldability, and hence can be suitably used as a resin material for heat dissipation materials and semiconductor devices and electronic parts in particular.

Claims

1. A heat dissipation material comprising a mesogen/silicon compound (co)polymer composition containing 100 to 1,500 parts by mass of a thermally conductive filler with respect to 100 parts by mass of a mesogen/silicon compound (co)polymer having a number average molecular weight of 1,000 to 500,000, represented by the following general formula (1): ##STR00015## wherein Ar represents a mesogen group selected from structures represented by the following formulas: ##STR00016## a represents a positive number of 0.5 to 1, and b represents a number of 0 to 0.5, with the proviso that a and b each represent a ratio of each number of repeating units to the sum of the total repeating units in a molecule, and a+b=1, R.sub.1s each independently represent a C.sub.1-8 monovalent hydrocarbon group free of aliphatic unsaturated bond, and R.sub.2s each independently represent a hydrogen atom, Si(CH.sub.3).sub.3, Si(CH.sub.3).sub.2(OH), Si(CH.sub.3)2(CHCH.sub.2), or Si(CH.sub.3).sub.2(CH.sub.2CHCH.sub.2).

2. The heat dissipation material according to claim 1, wherein the mesogen/silicon compound (co)polymer composition has fluidity, in a temperature range of the melting point to the melting point +50 C. of the mesogen/silicon compound (co)polymer represented by the general formula (1).

3. The heat dissipation material according to claim 1 or 2, wherein the mesogen/silicon compound (co)polymer composition has thermal conductivity of 1 W/m.Math.K or more.

4. A heat dissipation material comprising a mesogen/silicon compound (co)polymer composition containing 100 to 1,500 parts by mass of a thermally conductive filler with respect to 100 parts by mass of a mesogen/silicon compound (co)polymer having a number average molecular weight of 1,000 to 500,000, said mesogen/silicon compound (co)polymer being represented by the following general formula (1): ##STR00017## wherein each R.sub.1 independently represents methyl or a C.sub.2-8 monovalent hydrocarbon group free of aliphatic unsaturated bond, each R.sub.2 independently represents a hydrogen atom, Si(CH.sub.3).sub.3, Si(CH.sub.3).sub.2(OH), Si(CH.sub.3).sub.2(CHCH.sub.2), or Si(CH.sub.3).sub.2(CH.sub.2CHCH.sub.2), Ar represents a mesogen group of structure represented by the following formula: ##STR00018## a represents a positive number of 0.5 to 1, and b represents a number of 0 to 0.5, with the proviso that each of a and b represents a ratio of each number of repeating units to the sum of the total repeating units in a molecule, and a+b=1.

Description

EXAMPLES

(1) Hereinafter, the present invention is described with reference to Synthesis Examples, Examples, and Comparative Examples. However, the present invention is not limited thereto.

(2) First, Synthesis Examples of a monomer as a raw material of a mesogen/silicon compound (co)polymer used in the present invention are shown. These monomers are synthesized by a known method.

Synthesis Example 1

Synthesis of 1,4-bis(hydroxydimethylsilyl)benzene

(3) In a 5 L separable flask equipped with a reflux tube and a 1 L dropping funnel, 500 mL of tetrahydrofuran, 2,500 mL of methyl ethyl ketone, 7.8 g of 5% by mass palladium-carrying carbon, and 172.8 g of deionized water were put, and the temperature was raised to 50 C. Subsequently, 757.6 g of 1,4-bis(dimethylsilyl)benzene (trade name Silphenylene C, manufactured by Shin-Etsu Chemical Co., Ltd.) was put in the dropping funnel, and dropwise addition was performed over four hours. After completion of the dropwise addition, aging was performed for five hours, the catalyst was removed by filtration, and the filtrate was concentrated to obtain a white solid. Subsequently, recrystallization purification was performed using a mixed solvent of 3 L of hexane and 500 mL of tetrahydrofuran to obtain 596.9 g of 1,4-bis(hydroxydimethylsilyl)benzene (yield 68%).
.sup.1H-NMR (400 MHz, CDCl.sub.3) 7.61 (s, 4H), 1.95 (brs, 2H), 0.41 (s, 12H)

Synthesis Example 2

Synthesis of 4,4-bis(hydroxydimethylsilyl)biphenyl

(4) To a 3 L eggplant flask equipped with a reflux tube, 48 g of magnesium, 1 L of dry tetrahydrofuran, and a few drops of 1,2-dibromoethane were added, and the resulting mixture was heated under reflux under a nitrogen atmosphere. Subsequently, 250 g of 4,4-dibromobiphenyl was added thereto, and the resulting mixture was heated under reflux for one hour to prepare a Grignard reagent. This Grignard reagent was transferred dropwise to a 3 L four-necked flask including 170 g of dimethylchlorosilane and 200 mL of tetrahydrofuran in an ice bath over one hour. After completion of the dropwise addition, a reaction was allowed to proceed overnight at room temperature. The residue was removed with a Kiriyama funnel, and then the resulting product was purified by distillation at 140-150 C./1 mmHg to obtain 4,4-bis(dimethylsilyl) biphenyl.

(5) Using this 4,4-bis(dimethylsilyl) biphenyl as a raw material, 130 g of 4,4-bis(hydroxydimethylsilyl) biphenyl was obtained in a similar manner to the above synthesis method of 1,4-bis(hydroxydimethylsilyl)benzene (yield 47%).
.sup.1H-NMR (400 MHz, CDCl.sub.3) 7.68 (d, 4H), 7.60 (d, 4H), 1.76 (brs, 2H), 0.45 (s, 12H)

Example 1

(6) To a 1 L eggplant flask equipped with a Dean Stark trap, 100 g of 1,4-bis(hydroxydimethylsilyl)benzene obtained in Synthesis Example 1, 800 mL of benzene, and 4 g of 1,1,3,3-tetramethylguanidine di-2-ethylhexanoate were added, and the resulting mixture was heated under reflux for 24 hours. Thereafter, the resulting solution was added dropwise to 3 L of methanol, and reprecipitation purification was performed to obtain 88 g of a white powder PTMPS (mesogen/silicon compound polymer) represented by the following chemical formula (2). An yield of 90%, number average molecular weight (Mn)=80,000, polydispersity index (PDI)=1.7, thermal conductivity=0.25 W/m.Math.K, and melting point (mp)=125 C. were obtained. This polymer is referred to as polymer 1.

(7) ##STR00010##
wherein n is a number such that the number average molecular weight is within the above range.

Example 2

(8) To a 1 L eggplant flask equipped with a Dean Stark trap, 100 g of 4,4-bis(hydroxydimethylsilyl) biphenyl obtained in Synthesis Example 2, 800 mL of benzene, and 4 g of 1,1,3,3-tetramethylguanidine di-2-ethylhexanoate were added, and the resulting mixture was heated under reflux for 24 hours. Thereafter, the resulting solution was added dropwise to 3 L of methanol, and reprecipitation purification was performed to obtain 76 g of a white powder resin (mesogen/silicon compound polymer) represented by the following chemical formula (3). An yield of 79%, Mn=5,000, PDI=1.8, thermal conductivity=0.35 W/m.Math.K, and mp=210 C. were obtained. This polymer is referred to as polymer 2.

(9) ##STR00011##
wherein n is a number such that the number average molecular weight is within the above range.

Example 3

(10) To a 1 L eggplant flask equipped with a Dean Stark trap, 80 g of 1,4-bis(hydroxydimethylsilyl)benzene obtained in Synthesis Example 1, 14.67 g of 1,1,3,3-tetramethyl-1,3-dihydroxydisiloxane, 800 mL of benzene, and 4 g of 1,1,3,3-tetramethylguanidine di-2-ethylhexanoate were added, and the resulting mixture was heated under reflux for 24 hours. Thereafter, the resulting solution was added dropwise to 3 L of methanol, and reprecipitation purification was performed to obtain 82 g of a white powder resin (mesogen/silicon compound copolymer) represented by the following chemical formula (4). An yield of 87%, Mn=160,000, PDI=2.0, thermal conductivity=0.20 W/m.Math.K, and mp=90 C. were obtained. This polymer is referred to as polymer 3.

(11) ##STR00012##

Example 4

(12) To a 1 L eggplant flask equipped with a Dean Stark trap, 106.9 g of 4,4-bis(hydroxydimethylsilyl) biphenyl obtained in Synthesis Example 2, 14.67 g of 1,1,3,3-tetramethyl-1,3-dihydroxydisiloxane, 800 mL of benzene, and 4 g of 1,1,3,3-tetramethylguanidine di-2-ethylhexanoate were added, and the resulting mixture was heated under reflux for 24 hours. Thereafter, the resulting solution was added dropwise to 3 L of methanol, and reprecipitation purification was performed to obtain 100 g of a white powder resin (mesogen/silicon compound copolymer) represented by the following chemical formula (5). An yield of 85%, Mn=24,000, PDI=2.2, thermal conductivity=0.26 W/m.Math.K, and mp=140 C. were obtained. This polymer is designated polymer 4.

(13) ##STR00013##

Example 5

(14) In a planetary mixer, 50 g of the above polymer 1 and 185 g of spherical alumina (DAW-0745, manufactured by Denka Co., Ltd.) were put, were heated and mixed at 180 C., were poured into a mold of 60 mm60 mm6 mm, and were subjected to press molding at 150 C. for 10 minutes to obtain composition 1. Composition 1 had thermal conductivity of 1.58 W/m.Math.K.

Example 6

(15) In a planetary mixer, 50 g of the above polymer 2 and 185 g of spherical alumina (DAW-0745, manufactured by Denka Co., Ltd.) were put, were heated and mixed at 220 C., were poured into a mold of 60 mm60 mm6 mm, and were subjected to press molding at 220 C. for 10 minutes to obtain composition 2. Composition 2 had thermal conductivity of 2.14 W/m.Math.K.

Example 7

(16) In a planetary mixer, 50 g of the above polymer 3 and 185 g of spherical alumina (DAW-0745, manufactured by Denka Co., Ltd.) were put, were heated and mixed at 180 C., were poured into a mold of 60 mm60 mm6 mm, and were subjected to press molding at 150 C. for 10 minutes to obtain composition 3. Composition 3 had thermal conductivity of 1.28 W/m.Math.K.

Example 8

(17) In a planetary mixer, 50 g of the above polymer 4 and 185 g of spherical alumina (DAW-0745, manufactured by Denka Co., Ltd.) were put, were heated and mixed at 180 C., were poured into a mold of 60 mm60 mm6 mm, and were subjected to press molding at 150 C. for 10 minutes to obtain composition 4. Composition 4 had thermal conductivity of 1.61 W/m.Math.K.

Comparative Example 1

(18) In a planetary mixer, 48 g of a dimethylsilicone oil having both terminals blocked with alkenyl groups and having viscosity of 1,000 mPa.Math.s, 1.96 g of an organohydrogenpolysiloxane containing four hydrogen atoms directly bonded to silicon atoms (molar ratio between terminal alkenyl group and SiH group=1:1), and 185 g of spherical alumina (DAW-0745, manufactured by Denka Co., Ltd.) were put, and were mixed at room temperature for 30 minutes, 0.05 g of a 0.5% by mass Karstedt's catalyst toluene solution was added thereto, and the resulting mixture was further mixed for five minutes. This product was poured into a mold of 60 mm60 mm6 mm, and was subjected to press molding at 150 C. for 10 minutes to obtain cured product 5. Cured product 5 had thermal conductivity of 1.08 W/m.Math.K.

Comparative Example 2

(19) To a 1 L eggplant flask equipped with a Dean Stark trap, 20 g of 1,4-bis(hydroxydimethylsilyl)benzene obtained in Synthesis Example 1, 80 g of 1,1,3,3-tetramethyl-1,3-dihydroxydisiloxane, 800 mL of benzene, and 4 g of 1,1,3,3-tetramethylguanidine di-2-ethylhexanoate were added, and the resulting mixture was heated under reflux for 24 hours. Thereafter, the resulting solution was added dropwise to 3 L of methanol, and reprecipitation purification was performed to obtain 68 g of a highly viscous transparent liquid represented by the following chemical formula (6). An yield of 75%, Mn=240,000, and PDI=2.5 were obtained. This liquid was cooled to 30 C., but did not become a solid, and the thermal conductivity thereof could not be measured.

(20) ##STR00014##

(21) Various physical properties (hardness, tensile strength, and elongation) were evaluated using polymers 1 to 4, compositions 1 to 4, and cured product 5 obtained in the above Examples 1 to 8 and Comparative Example 1. In addition, the melting points of compositions 1 to 4 and cured Product 5 were measured. The results are indicated in Table 1 below. Incidentally, for various physical properties, a sheet of 100 mm100 mm2 mm was prepared by press molding at 150 C. for 10 minutes, and measurement was performed using an automatic hardness meter and a tensile tester. Note that conditions for physical property measurement were in accordance with JIS K 6249.

(22) TABLE-US-00001 TABLE 1 Comparative Example Example 1 2 3 4 5 6 7 8 1 Polymer Polymer Polymer Polymer Composition Composition Composition Composition Cured 1 2 3 4 1 2 3 4 product 5 Hardness D57 D65 D38 D52 D71 D78 D55 D69 A38 Tensile strength: 22 28 12 17 21 25 15 24 1 MPa Elongation: % 56 21 92 49 3 4 3 3 106 Thermal conductivity: 0.25 0.35 0.20 0.26 1.58 2.14 1.28 1.61 1.08 W/m .Math. K Melting point: C. 125 210 90 140 130 210 92 150 None

(23) These results indicate that the heat dissipation material (Examples 1 to 4) consisting of the mesogen/silicon compound (co)polymer according to the present invention has thermal conductivity of 0.35 to 0.20 W/m.Math.K which is better than that of a dimethylsilicone resin (Literature value 0.18 W/m.Math.K) generally used as a conventional heat dissipation material, and also has excellent mechanical physical properties. Furthermore, the heat dissipation material (Examples 5 to 8) consisting of a composition containing the mesogen/silicon compound (co)polymer (resin) according to the present invention and a thermally conductive filler (filler) has thermoplastic properties, and therefore has better moldability than dimethyl silicone rubber (Comparative Example 1) requiring chemical crosslinking. It is known that the thermal conductivity of the heat dissipation material (Examples 5 to 8) consisting of a composition containing a resin and a filler is dramatically improved as the thermal conductivity of the resin is increased. Also in the resin of the present invention, the thermal conductivity after addition of a filler is largely improved as compared with a combination of a usual dimethyl silicone resin and a filler. From these facts, the heat dissipation material consisting of the mesogen/silicon compound (co)polymer of the present invention and the heat dissipation material consisting of a composition containing the (co)polymer and a thermally conductive filler are suitable as heat dissipation materials, and can be suitably used particularly as a resin material for semiconductor devices and electronic parts.