JPH11302545A - Silicone rubber composite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composite excellent in thermal conductivity and heat reliability, in particular in a specific direction and good in tackiness and adhesivity, by incorporating a silicone rubber base material with specific fiber of high thermal conductivity afforded with a degree of orientation. SOLUTION: This composite is obtained by incorporating (A) a silicone rubber base material consisting mainly of an organopolysiloxane with a viscosity before cured of pref. 0.01-100,000 Pa.s at room temperature of the average composition formula Ra SiO(4-a)-2 [R is a (substituted) 1-10C monovalent hydrocarbon; (a) is 1.85-2.10] with (B) 1-70 wt.% in terms of fiber volume content, of highly hermally conductive fiber 60-1,200 W/m.k in thermal conductivity and e.g. 0.1-100 mm in fiber length (e.g. in the form of a plain fabric, satin fabric, twill fabric of carbon fiber) followed by uniaxial orientation to effect curing the silicone rubber base material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicone rubber composite having high thermal conductivity and heat radiation, which reduces the contact resistance at the interface between a heat-generating electronic component and its heat radiating plate, and furthermore, the present invention relates to a specific material. The present invention relates to a heat-conducting silicone rubber composite suitable for efficiently dissipating or transferring heat in the direction described above, a method for producing the same, and a heat-conducting device.

[0002]

2. Description of the Related Art In recent years, with the miniaturization and high performance of portable information devices, especially notebook personal computers, the amount of heat generated by a CPU (Central Processing Unit) has also increased, and how this heat is released to the outside. That is, heat dissipation measures are the top priority.

Conventionally, as a heat dissipation measure for such a CPU, for example, a heat dissipation plate made of aluminum or the like to which a heat pipe is connected has been widely used. This heat sink is CP
It is necessary to fix it on the U, and a method of tightening with a screw is generally adopted.

However, in this case, inevitably, the CP
Since thermal resistance occurs at the contact interface between U and the heat sink,
The original performance of the heat dissipating component cannot be exhibited, and the heat dissipating property is also reduced. On the other hand, if the thermal resistance is too large, heat diffusion due to radiation from the CPU also increases, which may adversely affect peripheral components. Therefore, it is important to reduce the contact resistance between the CPU and the radiator plate and efficiently transmit heat to the radiator plate.

As means for reducing the contact thermal resistance,
JP-A-6-155517, JP-A-7-26635
No. 6, JP-A-8-238707, etc., in order to enhance thermal conductivity, metal powder or ceramic powder such as aluminum oxide, boron nitride, aluminum nitride or carbon such as natural graphite and carbon black. A heat-dissipating silicone rubber sheet in which an additive such as powder is added to an adhesive silicone rubber substrate has been proposed.

However, since the thermal conductivity of such a silicone rubber sheet is ultimately greatly affected by the frequency of contact between the additive particles, the high thermal conductivity inherent to the additive is not sufficiently exhibited, and the Although the thermal resistance is reduced, there is a problem that the heat radiation performance is still insufficient. on the other hand,
If the amount of the additive is increased in order to increase the contact frequency, there is also a problem that the base material is hardly cured or the adhesiveness of the finished rubber sheet is reduced. Also, since these heat-dissipating silicone rubber sheets are isotropic materials, the thermal conductivity in the in-plane direction and the thermal conductivity in the out-of-plane direction are almost equal,
It was not possible to selectively dissipate heat in a particular direction.

Japanese Patent Application Laid-Open No. 7-207160 discloses that a silicone polymer substrate is kneaded with a fine powder filler called a thickener and a metal or an alloy, and further mixed with a carbon material such as carbon fiber. A method for producing a silicone composition having excellent heat conductivity and conductivity is disclosed.

However, the above-mentioned carbon material is a component only for the purpose of improving or stabilizing the conductivity of the silicone composition, and is not disclosed as a component for improving the thermal conductivity. No method is disclosed for imparting excellent thermal conductivity to a silicone composition in a specific direction using fibers.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide excellent heat conductivity and heat dissipation, and high heat conductivity and heat dissipation in a specific direction. An object of the present invention is to provide a silicone rubber composite for heat conduction, a silicone rubber sheet, a method for producing the same, and a heat conduction device, which can have, and have good adhesion and adhesion.

[0010]

In order to achieve the above object, the silicone rubber composite of the present invention comprises a silicone rubber substrate containing a high thermal conductive fiber having a thermal conductivity of 60 to 1200 W / mk on a fiber volume content basis. And a silicone rubber composite compounded in an amount of 1 to 70% by weight, characterized in that at least a part of the high heat conductive fiber is unidirectionally or two-dimensionally oriented.

Further, the silicone rubber composite for heat conduction of the present invention is a silicone rubber composite comprising a silicone rubber substrate and 1 to 70% by weight of a high thermal conductive fiber in a fiber volume content. At least a part of the high thermal conductive fiber is unidirectionally or two-dimensionally oriented.

When the silicone rubber composite for heat conduction of the present invention is used as a silicone rubber sheet, the orientation of at least a part of the high heat conductive fiber has an out-of-plane component of the sheet, whereby the high heat conductive fiber At least one part penetrates the sheet. The highly thermally conductive fibers blended in the silicone rubber substrate are oriented in the out-of-plane direction and / or in-plane direction of the sheet.

The method for producing a silicone rubber composite for thermal conduction according to the present invention is characterized in that the silicone rubber substrate has a length of 0.1 to 100 mm.
After adding the high thermal conductive fiber of 1 mm, the high thermal conductive fiber is oriented in one direction to cure the silicone rubber substrate,
Alternatively, after laminating or depositing at least one kind of high thermal conductive fiber selected from fiber tow, fiber woven fabric, fiber unidirectional material or chopped fiber in a container, impregnating with a silicone rubber substrate and curing. .

When the heat-conductive silicone rubber composite is formed into a sheet, the heat-conductive silicone rubber composite formed by any of the above methods is further cut substantially perpendicularly to the direction of orientation of the high heat conductive fibers. Then, it is formed by cutting it into a sheet.

A heat conducting device according to the present invention is characterized in that a heat generating portion and a heat radiating portion are connected to the heat conductive silicone rubber composite, and the orientation of at least one part of the high heat conductive fiber is an out-of-plane component of the sheet. In the case of a sheet shape having the following, the heat generating portion is connected to one surface of the sheet, and the heat radiating portion is connected to the other surface.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The silicone rubber substrate used in the present invention is not particularly limited, and known ones can be used. In particular, the viscosity at room temperature (25 ° C.) before curing is usually 0.1. 01 to 100,000 Pa · s, preferably 0.1 to 300 Pa · s, more preferably 0.3 to 10
0 Pa · s, more preferably 0.5 to 30 Pa · s. When the viscosity is less than 0.01 Pa · s, the oil separating property of the silicone rubber composition becomes large, and when it exceeds 100,000 Pa · s, the viscosity is too high, and the workability is undesirably reduced.

The silicone rubber substrate can be diluted or dissolved or dispersed with an aromatic or aliphatic solvent so as to have a viscosity that facilitates the work. As the silicone rubber substrate, either one-part curing type or two-part curing type can be used, but two-part curing type is preferably used.

In the present invention, the average composition formula R _a SiO
A silicone rubber base material containing an organopolysiloxane represented by _{(4-a) / 2} as a main component is preferably used. However, in the above average composition formula, R is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms (for example, a methyl group, an ethyl group, a propyl group, a butyl group, a 2-ethylbutyl group, an octyl group and the like). Alkyl group, vinyl group, alkenyl group such as allyl group and hexenyl group, cycloalkyl group such as cyclohexyl group and cyclopentyl group, aryl group such as phenyl group and tolyl group, and aralkyl group such as phenylethyl group. Represents a group in which part or all of the hydrogen atoms may be substituted with a halogen atom, a cyano group, or the like.)
Is preferably a positive number of 1.85 to 2.10.

The average degree of polymerization of the organopolysiloxane is preferably 100 to 20,000, particularly 300 to 2,000 for a liquid type, and 6,000 to 12,000 for a rubber type. Preferably, there is. If the average degree of polymerization of the organopolysiloxane is lower than 100, the mechanical strength after curing decreases, which is not preferable. The silicone rubber substrate of the present invention may not contain an inorganic filler, but may contain a general inorganic filler.

As the inorganic filler which can be blended with the silicone rubber substrate, generally, metal oxide, boron nitride and the like can be mentioned. Specifically, aluminum oxide, magnesium oxide, silicon dioxide, beryllium oxide, cubic Examples thereof include boron nitride, hexagonal boron nitride, silicon carbide, silicon nitride, copper powder, and aluminum powder. These may be used alone or in combination of two or more. In this case, the amount varies depending on the amount of the thermally conductive inorganic filler to be blended. However, the thermally conductive inorganic filler is usually 10 to 1000 parts by weight, preferably 100 to 100 parts by weight, per 100 parts by weight of the silicone rubber base material.
0 parts by weight can be blended.

Metal compounds such as aluminum hydroxide, iron oxide, titanium oxide and magnesium hydroxide, or platinum compounds such as platinum black, chloroplatinic acid, chloroplatinic acid and olefin And chloroplatinic acid complexes with vinyl siloxane, acetylene alcohol, etc., and chloroplatinic acid alcohol modified products. In the case of a metal compound such as aluminum hydroxide, the compounding amount can be usually 5 to 200 parts by weight with respect to 100 parts by weight of the silicone rubber base material. Usually, it can be 3 to 500 ppm in terms of platinum.

Silica gel, carbon black, calcium carbonate, quartz powder, diatomaceous earth, iron oxide,
Ferrite, zinc white, clay mineral, mica, smectite,
Lithium soap, aluminum soap and the like can be blended with the silicone rubber base material. Thus, the low-viscosity silicone rubber base material becomes grease-like, so that the orientation direction of the high heat conductive fiber can be effectively maintained. The compounding amount of the thickener can be usually 1 to 1000 parts by weight based on 100 parts by weight of the silicone rubber base material.

The silicone rubber substrate may be vulcanized at room temperature or thermal vulcanization under the temperature conditions at the time of vulcanization. In the vulcanization method, peroxide vulcanization, addition vulcanization, UV vulcanization,
Any of electron beam vulcanization and the like can be selected. Further, known additives such as a reinforcing agent, a dispersant, a heat resistance improver, a conductivity imparting agent, and a pigment may be added to these silicone rubber bases.

The high heat conductive fiber used in the present invention is used for the purpose of improving heat conductivity, and is usually a silicon carbide fiber,
Pitch-based carbon fibers, polyacrylonitrile-based carbon fibers, or rayon-based carbon fibers are used, but precursor fibers thereof can also be used. The pitch-based precursor fiber is a fiber after spinning, a fiber obtained by infusibilizing the fiber, or a pre-carbonized fiber obtained by pre-carbonizing.

The carbon fiber of the present invention contains, in addition to the precursor fiber, a fiber obtained by carbonizing the precursor fiber or a fiber obtained by graphitization. The processing temperature of the fiber varies depending on the individual process, but usually, the flame-proofing treatment or the infusibilizing treatment is 200 to 450 ° C in an oxidizing atmosphere, the pre-carbonizing treatment is 400 to 1000 ° C in a non-oxidizing atmosphere, and the carbonizing treatment is The graphitization treatment can be performed at 2000 to 3000 ° C. in a non-oxidizing atmosphere at 1000 to 1500 ° C.

The thermal conductivity of the high thermal conductive fiber used in the present invention is usually 5 to 1200 W / m · K, preferably 60 to 1200 W / m · K.
１1200 W / m · K, more preferably 100-120
0 W / m · K, more preferably 150 to 1200 W /
m · K, most preferably 300 to 1200 W / m · K can be used.

In the present invention, any of these high heat conductive fibers can be used, and among them, pitch-based carbon fibers which can easily exhibit high heat conductivity are particularly preferably used.

The pitch-based carbon fiber is usually used at a temperature of 2000 to 3300 ° C., preferably 2300 ° C. in a non-oxidizing atmosphere.
What has been graphitized at ３3300 ° C. is preferably used. As a method for obtaining economically inexpensive high thermal conductivity carbon fibers, pitch-based carbon fibers produced by heat treatment at 1500 to 2500 ° C. are chopped to a length of about 0.1 to 100 mm or without being chopped. 2500-330
Examples of using carbon fibers heat-treated at a temperature of 0 ° C. can be cited, but they can be chopped or not chopped after spinning, after infusibilization or after graphitization.

Also, a fiber whisker-like obtained by vapor-growing a fiber having an appropriate length may be used by infusibilizing, carbonizing, or graphitizing a fiber which is simultaneously chopped at the time of spinning or a fiber spun to a short length. Carbon fibers may be used.

In the present invention, continuous high heat conductive fibers are preferably used in order to impart anisotropic heat conductivity to the high heat conductive silicone rubber composite.

The continuous high heat conductive fiber is a high heat conductive fiber used in a cut state or in an uncut state, and is formed by molding a high heat conductive silicone rubber composition and finally forming a silicone such as a heat radiation sheet. Usually 0.1 to 10,000 more than the thickness when used as a rubber sheet
Times, preferably 2 to 10,000 times, more preferably 2 times.
It refers to a high thermal conductive fiber having a length of up to 1,000 times. In the present invention, continuous carbon fibers are particularly preferably used as the continuous high heat conductive fibers.

In the present invention, a silicone rubber sheet suitable as a heat radiating sheet can be produced by molding the above-mentioned high thermal conductive silicone rubber composition into a sheet. 10 mm, preferably 0.1 to 10 mm, more preferably 0.1 to 5 mm,
Most preferably, it is 0.2 to 3 mm. When the thickness is less than the above range, the strength of the obtained silicone rubber sheet is reduced. When the thickness is more than the above range, the ability to transmit heat to the heat radiating portion is reduced when the length of the high heat conductive fiber is short. The silicone rubber sheet may be used by crushing the sheet for contact with a heat radiating portion or a heat generating portion.

Further, in the present invention, the form of reinforcement by the continuous high heat conductive fiber is not particularly limited.
For example, arranging the fibers in one direction as the toe of the high heat conductive fibers, arranging in one direction by using a unidirectional material of the high heat conductive fibers, or shearing the high heat conductive fibers dispersed in the rubber base material. In addition, one-dimensional orientation that is oriented in one direction,
Two-dimensional orientation using woven fabric, random orientation in which chopped high thermal conductive fibers are randomly arranged or two-dimensional random orientation in which chopped high thermal conductive fibers are randomly deposited,
Alternatively, any combination of these can be used.

The high thermal conductive fiber can be used by mixing and dispersing it in a silicone rubber substrate as long as the fiber length is short. In this case, the fiber length is usually 0.005 to 100 m
m, preferably 0.1 to 100 mm, more preferably 0.5 to 50 mm, and still more preferably 1 to 10 mm.

At this time, the high heat conductive fiber can be used alone in the silicone rubber substrate, or can be used as a silicone rubber composition in combination with high heat conductive fibers having different lengths.

The fiber can be obtained by spinning a precursor fiber into a short length fiber or shortening a continuous fiber to a desired length to obtain a carbon fiber having the above fiber length. Any method can be adopted as a method of shortening the length of the fiber, and cutting, pulverization, or the like can be used.

In the case of short fibers, if the fiber length is less than the above range, it is not preferable because the original heat conduction characteristics of the high heat conductivity fiber cannot be utilized. On the other hand, when the ratio exceeds the above range, dispersibility in the rubber base material is reduced, and a silicone rubber composition having a uniform thermal conductivity cannot be obtained.

The highly thermally conductive silicone rubber composite of the present invention is characterized by having anisotropy in thermal conductivity. Highly heat conductive fibers have a property of having a considerably higher thermal conductivity in the fiber axis direction than other directions, that is, an anisotropic property of thermal conductivity. By utilizing this property, the thermal conductivity of the silicone rubber composite can be made anisotropic.
If the fiber in the silicone rubber composition containing the high thermal conductive fiber can be oriented in a specific direction, the fiber can have a considerably high thermal conductivity in the oriented direction, but the fiber is oriented. In those directions, the thermal conductivity becomes relatively low.

As a method for orienting the high heat conductive fiber, one-dimensional orientation, two-dimensional orientation, random orientation, two-dimensional random orientation and the like as described above can be adopted. Can be something.

Further, according to the present invention, a silicone rubber sheet having anisotropy in thermal conductivity can be obtained by using the above-mentioned high thermal conductive silicone rubber composition to form a cut surface after curing the silicone rubber. When used as a heat radiating sheet, it is important to transmit heat efficiently in the thickness direction of the sheet, and to cut the highly thermally conductive fibers to be oriented, preferably perpendicular to the fiber axis of as many of the fibers as possible. It is preferable to cut out in such a direction as to cut into pieces. For example, a carbon rubber tow, a carbon fiber woven fabric, a carbon fiber unidirectional material or a continuous carbon fiber selected from chopped carbon fibers is laminated or deposited in a container and then impregnated with a silicone rubber substrate and obtained after the silicone rubber substrate is cured. A silicone rubber composite in which the carbon fiber orientation is one-dimensional orientation, right-angle two-dimensional orientation, two-dimensional random orientation, or any combination thereof is cut in parallel to the laminating direction of the carbon fibers or parallel to the sedimentation direction. Can be cut out.

Here, the direction parallel to the laminating direction or the sedimentation direction is the thickness direction of the molding container when the fibers are deposited or laminated in the molding container, and is a direction that cuts the deposited or laminated fibers. More preferably, the orientation direction of a part or all of the cut fibers is perpendicular to the cut surface.

The method for molding the silicone rubber composition will be specifically described with reference to FIGS. FIG. 1 is a view showing one embodiment of a method for molding a silicone rubber composition according to the present invention. In the figure, 1 is a silicone rubber composition, 2 is a carbon fiber, 3 is a cut surface, and A is B indicates an out-of-plane direction of the heat dissipation sheet, and B indicates an in-plane direction.

FIG. 2 is a view showing an example of a heat conduction device according to the present invention. In FIG.
U and 6 indicate a personal computer housing, 7 indicates a silicone rubber sheet, and the same reference numerals as in FIG. 1 indicate the same members.

In this specification, the directions out of plane and in plane are defined assuming that the heat radiation sheet 7 is made of the high thermal conductive silicone rubber composition 1 as shown in FIG.
A heat generating component 5 and / or heat sink 4 as shown in FIG.
The direction substantially perpendicular to the plane direction of the (heat spreader) is an out-of-plane direction, and a heat-generating component as shown in B or /
A direction substantially parallel to the plane direction of the heat sink is defined as an in-plane direction. Although not shown, a plurality of heat sinks and / or CPs are provided on the silicone rubber sheet of the present invention.
A plurality of heat generating parts such as U can be connected, a silicone rubber sheet can be interposed between heat radiating plates and laminated, or a heat radiating part and a heat generating part can be connected to a personal computer housing with a silicone rubber sheet. .

When a tow or a unidirectional material is used as the carbon fiber 2, the tow of the carbon fiber 2 is aligned in one direction and deposited or laminated while the unidirectional material is oriented in the same direction. By impregnating and hardening, as shown in FIG. 1, by cutting out the surface 3 perpendicular to the orientation direction of the carbon fiber 2, the orientation direction of the carbon fiber 2, that is, the cut surface 3
High thermal conductivity can be selectively provided in a direction perpendicular to the substrate.

Using carbon fiber tow or unidirectional material,
When cut out in this manner, heat can be quickly diffused to the heat radiating section 4 such as a heat spreader located above the heat generating section 5 such as a CPU as shown in FIG.

Further, other cutting methods, for example, using a silicone rubber composition in which fibers are oriented in one direction or two dimensions, and cutting out a silicone rubber sheet in parallel with the direction of orientation of the high heat conductive fibers, a heating section. Heat can be quickly diffused into the sheet surface.

In the case where a woven fabric is used as the high thermal conductive fiber, for example, a plain woven fabric, a satin woven fabric, a twill woven fabric, etc. of carbon fiber are laminated and then impregnated with a silicone rubber base material. By cutting perpendicular to one orientation direction of the high heat conductive fiber to constitute, one direction of the fiber, namely, the direction perpendicular to the cut surface, and the orientation direction of the remaining uncut fibers in two directions. High thermal conductivity can be selectively provided.

When the fabric is cut out as described above using a woven fabric, not only can heat be quickly diffused to the heat radiating portion 4 located above the heat generating portion 5 in FIG. Due to the conductive fibers, local heating of the heat generating portion 5 can be diffused in a direction (B direction) parallel to the cut surface. In addition, a heat-dissipating sheet having a high thermal conductivity in a plane direction, which can prevent local heating, can be formed by cutting the heat-dissipating sheet perpendicularly to the laminating direction of the fabric.

The fiber length as described above is 0.005 to 10
0 mm, preferably 0.1 to 100 mm When the highly heat conductive fibers are slightly shorter and are randomly or unidirectionally oriented, the thickness of the heat radiation sheet finally cut out on the silicone rubber substrate is usually 0.1 to 0.1 mm. If high thermal conductive fibers having a length of 100 times, preferably 2 to 10 times, are dispersed and randomly cut two-dimensionally and cut out in parallel with the laminating direction of the fibers, a high thermal conductivity is obtained in the direction perpendicular to the sheet surface. In addition, it is possible to obtain a silicone rubber sheet having anisotropy in thermal conductivity within the sheet surface. Alternatively, if the silicone rubber base material and the fiber are mixed and kneaded, and then sheared by shearing after shearing and cutting in a direction perpendicular to the shearing direction, having a high thermal conductivity in a direction perpendicular to the sheet surface, In addition, a silicone rubber sheet having an isotropic thermal conductivity can be obtained within the sheet surface.

When the silicone rubber composite is cut out and the rubber is soft and difficult to cut out, the compound can be cooled and cut out to a temperature at which it can be cut out. As a cooling means, a refrigerator, a freezer, ice, dry ice, liquid nitrogen, liquid helium and the like can be used. Examples of the cutting method include cutting with a plow such as a planer or a saw blade such as a circular saw, water jet cutting, or laser cutting.

In the present invention, the fiber volume content of the high thermal conductive silicone rubber composite is usually 1 to 70%, preferably 2 to 70%, more preferably 2 to 60%, and still more preferably 2 to 50%. is there.

When the fiber volume content is less than the above range, it is difficult to uniformly arrange the fibers in the base material and the material becomes non-uniform, and at the same time, a desired thermal conductivity cannot be obtained. This is not preferred.
Further, when the fiber volume content exceeds the above range, the penetration of the silicone rubber substrate between the fibers, or the dispersion of the fibers in the silicone rubber substrate is not sufficiently obtained, and the curability or moldability, uniformity is reduced. This is not preferable because the silicone rubber composite is remarkably reduced, and a silicone rubber composite having good adhesion and uniform heat conductivity cannot be obtained.

The fiber volume content is appropriately determined within the above range according to the purpose of use of the silicone rubber composite. For example, when high thermal conductivity is required for the silicone rubber composite, the fiber volume content is 10 to 70%, preferably 10 to 50% by weight, and adhesion to other members is required. In the case, the fiber volume content is 1 to 30%,
Preferably it is 2 to 30%, more preferably 3 to 10%.

In the present invention, the silicone rubber composite having high thermal conductivity is preferably flexible and has high thermal conductivity.

In the present invention, the fiber length is 0.005 to 100 mm, preferably 0.1 to 100 m.
The production of a highly thermally conductive silicone rubber sheet when using a highly thermally conductive fiber slightly shorter than m is performed as follows.

First, the silicone rubber base material which becomes a rubber-like elastic body after the above-mentioned curing is plasticized and mixed with the above-mentioned high heat conductive fibers so that the fibers are uniformly dispersed and mixed. This plasticizing and mixing step is performed using, for example, mixers such as a mixing roll, an internal mixer, and a kneader.

The mixture having undergone the mixing and plasticizing steps is then subjected to the orientation of the high heat conductive fibers uniformly dispersed and blended in the mixture. This orientation is for example a screw pump,
The shearing is performed by applying shear to the plasticized mixture by a gear pump, a plunger pump, or the like, and plastically deforming the plasticized mixture in a certain direction. This orientation can also be carried out using a conventional synthetic resin or synthetic rubber molding apparatus, for example, an extrusion molding machine, an injection molding machine, a calender molding machine, or the like.

The silicone rubber composition mixed and kneaded into a large number of pipes arranged in parallel having a diameter of 0.1 to 10 times the fiber length in order to efficiently give shear and orient the fibers is subjected to a differential pressure. Extruded and passed through the pipe.

In this way, it is possible to obtain a silicone rubber composite in which highly thermally conductive fibers are oriented substantially parallel to the flow axis direction in a molded article made of a rubber-like elastic body.

The silicone rubber composite obtained is vulcanized because of insufficient crosslinking and curing reaction. The method of vulcanization is arbitrary, but for example, the vulcanization can be performed by heating at 180 ° C to 300 ° C. In this case, heat vulcanization at about 200 to 260 ° C. for about 10 minutes can be used.

In the present invention, a silicone rubber sheet suitable as a heat radiating sheet can be produced by slicing a highly heat-conductive silicone rubber composite into a sheet.

In order to obtain the desired silicone rubber sheet having high thermal conductivity in the thickness direction, it is preferable to orient a large number of high heat conductive fibers in the thickness direction of the sheet. The high thermal conductive silicone resin composite obtained as a specific example has a desired thickness along a plane substantially perpendicular to the orientation direction of the high thermal conductive fibers in the composite, that is, a plane perpendicular to the shearing direction by the pipe. Can be sliced into a sheet shape. At the time of slicing, the silicone resin composite can be heated or cooled.

The high thermal conductive silicone rubber sheet of the present invention obtained by processing the high thermal conductive silicone rubber composition into a sheet is obtained by penetrating an infinite number of high thermal conductive fibers in the sheet. When manufactured by the above-described method, it is buried in a partially unpenetrated state. The proportion of partially unfinished fibers depends on the length of the fibers used, the thickness of the sheet, the temperature at the time of slicing, and the like.

Preferably, the silicone rubber sheet of the present invention is obtained by orienting highly thermally conductive fibers in a direction parallel to the thickness direction of the sheet. Here, when the fiber oriented in one direction is cut perpendicular to the in-plane direction of the sheet by shearing or the like, the fiber becomes too hard, the rubber hardness increases, and the followability to the uneven surface is deteriorated, and the heat generating portion is formed. And the adhesiveness to the heat radiating portion is deteriorated, which causes thermal resistance. Therefore, when processing the highly heat conductive silicone rubber composite in which the fibers are oriented in one direction into a sheet, it is preferable to slice the diagonal slightly from the direction perpendicular to the fiber axis. In the silicone rubber sheet sliced in this way, the fibers are oriented substantially perpendicularly and slightly obliquely to the sheet surface. Thereby, the adhesion and the flexibility with the heat generating portion and the heat radiating portion can be improved without changing the fiber content. Although the slicing angle depends on the fiber length and the sheet thickness because the fibers need to penetrate the sheet, it is preferable that the slicing angle be shifted about 0 ° to about 10 ° obliquely from the direction perpendicular to the fiber axis.

When the silicone rubber sheet according to the present invention is deformed so as to reduce its thickness, the above-mentioned non-penetrated high heat conductive fibers are made to penetrate one after another, so as to come into contact with both of the heat generating surface and the heat radiating surface. Therefore, the amount of heat transported by the high thermal conductive fiber, which is the main thermal conductor of the silicone rubber sheet according to the present invention, is greatly increased. Therefore, the silicone rubber sheet according to the present invention is desirably used by being deformed so as to reduce its thickness by applying a pressing force in an out-of-plane direction or stretching in an in-plane direction.

The heat conductivity of the highly heat-conductive silicone rubber sheet of the present invention in the out-of-plane direction is usually 0.3 to 850 W / m ·
K, preferably 0.5 to 560 W / m · K, more preferably 3 to 560 W / m · K, and still more preferably 4 to 56 W / m · K.
0 W / m · K. The thermal conductivity in the in-plane direction of the high thermal conductivity silicone rubber sheet is usually 0.15 to 1.5 W / m · K when the thermal conductivity in the in-plane direction is constant. In this case, the ratio of the thermal conductivity in the out-of-plane direction / in-plane direction is usually 2-5.
A value of 500, preferably 10 to 3500 is particularly preferred for using a silicone rubber sheet as an anisotropic heat conductive heat radiating sheet.

The heat conductivity in the in-plane direction of the highly heat-conductive silicone rubber sheet of the present invention is usually 0.15 to 450 W / W when the heat conductivity in the in-plane direction is anisotropic in the plane and is not constant.
m · K, preferably 0.15 to 250 W / m · K. In this case, the ratio of the thermal conductivity in the out-of-plane direction / in-plane direction is usually 1 to 5500, preferably 1 to 3500, and the high thermal conductive silicone rubber sheet is used as an anisotropic thermal conductive heat radiating sheet. Is particularly preferred.

The hardness of the silicone rubber composite obtained by the present invention can be generally 1 to 100, preferably 5 to 50 as Asker C hardness. What is Asker C hardness?
SRIS 0101 (Japan Rubber Association) or JIS
It refers to the hardness measured using a spring type hardness tester Asker C type according to S6050. If the hardness of the silicone rubber composite is less than 1, it is too soft, and if it exceeds 100, it is not preferable because the adhesion to other parts such as a heat generating part and a heat radiating part is insufficient.

When connecting the heat generating portion and the heat radiating portion to the silicone rubber composite or the silicone rubber sheet of the present invention, an adhesive may be used. The components of the pressure-sensitive adhesive are not particularly limited, but a silicone-based pressure-sensitive adhesive is preferably used, and an additive such as a vulcanizing agent may be appropriately added thereto.

[0071]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. [Example 1] A pitch-based graphitized carbon fiber having a thermal conductivity of about 600 W / m · K and a thermal conductivity of about 50 W / m · K, previously cut into a length of about 95 mm in a 100 × 100 × 100 mm Teflon resin container. m · K pitch-based carbon fiber
(treated at 3000 ° C. in an r atmosphere) was unidirectionally filled so that the volume content was 45% in the container. Next, a silicone rubber substrate having a viscosity before curing of 0.7 Pa · s is poured into the container to a height of 90 mm,
Defoaming and curing were performed to obtain a carbon fiber reinforced silicone rubber composite. The final fiber volume content was 50%. After taking out the obtained silicone rubber composite from the container, as shown in FIG. 1, it was cut out to a thickness of 3 mm in a direction perpendicular to the oriented carbon fibers to obtain a high thermal conductive silicone rubber sheet.

When the thermal conductivity was measured in the out-of-plane direction and in-plane direction of the sheet, respectively,
Good carbon fiber reinforced anisotropic high thermal conductivity silicone rubber with excellent thermal conductivity in a specific direction of W / m · K, in-plane direction 0.20 W / m · K, and out-of-plane / in-plane direction ratio of about 1300 A sheet was obtained. In addition, the measurement of the thermal conductivity in an Example was all measured by the laser flash method based on JISR1611.

Example 2 100 × 100 × 100 mm
Pitch-based carbonized carbon fiber with a thermal conductivity of about 60 W / m · K (pitch-based carbon fiber with a thermal conductivity of about 50 W / m · K, cut into a Teflon resin container of about Medium at 3000 ° C)
Filling was performed in one direction so that the volume content was 45% in the container. Next, a silicone rubber base material having a viscosity of 0.7 Pa · s before curing was poured into the container to a height of 90 mm, and defoaming and curing were performed to obtain a carbon fiber reinforced silicone rubber composite. The final fiber volume content is 50%
Met. The obtained material was taken out of the container, and Example 1 was obtained.
In the same manner as in the above, a high thermal conductive silicone rubber sheet was obtained. When the thermal conductivity in the out-of-plane direction and the in-plane direction of the sheet were measured, the out-of-plane direction was 28 W / m · K, and the in-plane direction was 0.1 W / m · K.
At 19 W / m · K, a good carbon fiber reinforced anisotropic high thermal conductivity silicone rubber sheet having excellent thermal conductivity in a specific direction having an out-of-plane direction / in-plane direction ratio of 147 was obtained.

Example 3 100 × 100 × 100 mm
Was filled in one direction with the pitch-based graphitized carbon fiber used in Example 1 previously cut to a length of about 95 mm so as to have a volume content of 15% in the container. Next, the viscosity before curing is 0.7 Pa
・ 90mm high in the container with silicone rubber base material
The mixture was defoamed and cured to obtain a carbon fiber reinforced silicone rubber composite. The final fiber volume content was 17%. The obtained silicone rubber composite was taken out of the container, and a high heat conductive silicone rubber sheet was obtained in the same manner as in Example 1. When the thermal conductivity in the out-of-plane direction and the in-plane direction of the sheet were measured, the out-of-plane direction was 107 W / m · K, and the in-plane direction was 0.19 W / m · K.
Thus, a good carbon fiber reinforced anisotropic high thermal conductivity silicone rubber sheet having excellent thermal conductivity in a specific direction having an out-of-plane direction / in-plane direction ratio of 563 was obtained.

Example 4 100 × 100 × 100 mm
A plain woven fabric made of the pitch-based graphitized carbon fiber used in Example 1 previously cut into a size of 95 × 95 mm was laminated on a Teflon resin container of the above, so that the volume content was 45% in the container. did. Next, a silicone rubber base material having a viscosity of 0.7 Pa · s before curing was poured into the container to a height of 90 mm, and defoaming and curing were performed to obtain a carbon fiber reinforced silicone rubber composite. The final fiber volume content was 50%. The obtained silicone rubber composite was taken out of the container and cut out vertically into carbon fibers in one direction of the carbon fibers oriented in two directions to obtain a highly thermally conductive silicone rubber sheet. When the thermal conductivity was measured by adjusting the out-of-plane direction and the in-plane direction of the sheet, the out-of-plane direction was 58 W / m · K, and the in-plane direction was 0.19 to 5
At 8 W / m · K, a good carbon fiber reinforced anisotropic high thermal conductivity silicone rubber sheet having anisotropy in thermal conductivity in the out-of-plane direction and in-plane direction was obtained.

Example 5 100 × 100 × 100 mm
Was randomly filled with the pitch-based graphitized carbon fiber used in Example 1 previously cut to a length of 10 mm so as to have a volume content of 45% in the container. Next, the viscosity before curing is 0.7 Pa
・ 90mm high in the container with silicone rubber base material
The mixture was defoamed and cured to obtain a carbon fiber reinforced silicone rubber composite. The final fiber volume content was 50%. The obtained silicone rubber composite was taken out of the container and cut out in the laminating direction of the carbon fibers to obtain a highly thermally conductive silicone rubber sheet. When the thermal conductivity in the out-of-plane direction and the in-plane direction of the sheet were measured, the out-of-plane direction was 1.6 W / m · K, and the in-plane direction was 0.19 to 1.6 W.
/ M · K, a good carbon fiber reinforced anisotropic high thermal conductivity silicone rubber sheet having anisotropy of thermal conductivity in the out-of-plane direction and in-plane direction was obtained.

Example 6 The viscosity before curing was 0.7 Pa ·
s, a pitch-based carbon fiber having a thermal conductivity of about 650 W / m · K and a length of about 3 mm (a thermal conductivity of about 50 W / m · K, a length of about 3 m) as a thermal conductive filler.
m pitch-based carbon fiber was heat-treated at 3000 ° C. for 2 hours in an inert atmosphere) and added to the base material by 7% by weight, and sufficiently stirred and dispersed and mixed by a mixing roll. The mixture was subjected to stress, plastically deformed in a certain direction, and extruded while the fibers were uniaxially oriented. The obtained 200 × 100 × 300 silicone rubber molded body is cured (250 ° C., 10 minutes) and then sliced into a sheet along a plane perpendicular to the oriented fiber, and the 0.3 mm thick fiber is cut in the thickness direction. To obtain a silicone rubber sheet oriented in the following manner. When the thermal conductivity in the out-of-plane direction of the obtained rubber sheet was measured by a laser flash method,
It was 15 W / m · K.

Example 7 The silicone rubber molded product obtained in Example 1 was sliced into a sheet along a plane perpendicular to the oriented fiber after curing (250 ° C., 10 minutes), and the thickness was 3 mm. A silicone rubber sheet having 0.0 mm fibers oriented in the thickness direction was obtained. When the thermal conductivity of the obtained rubber sheet in the out-of-plane direction was measured by a laser flash method, it was 2.4.
W / m · K.

Example 8 The same silicone rubber substrate as in Example 1 was used as a heat-conductive filler, with a heat conductivity of about 650.
Pitch-based carbon fiber with a W / m · K and length of about 3 mm (heat conductivity of pitch-based carbon fiber with a thermal conductivity of about 50 W / m · K and a length of about 3 mm at 3000 ° C. for 2 hours in an inert atmosphere) Is added to the base material by 13% by weight, and the mixture is sufficiently stirred and dispersed and mixed by a mixing roll. Then, the mixture is subjected to stress by an extruder and plastically deformed in a certain direction.
The fibers were extruded while being uniaxially oriented.
After curing the obtained 200 × 100 × 300 silicone rubber molded article (250 ° C., 10 minutes), it is sliced into a sheet along a plane perpendicular to the oriented fiber, and has a thickness of 0.3 mm.
To obtain a silicone rubber sheet having the fibers oriented in the thickness direction. When the thermal conductivity of the obtained rubber sheet in the out-of-plane direction was measured by a laser flash method, it was 20 W / m · K.

Example 9 The silicone rubber molded product obtained in Example 3 was cured (250 ° C., 10 minutes) and then sliced into a sheet along a plane perpendicular to the oriented fiber, and the thickness was 3. A silicone rubber sheet having 0 mm fibers oriented in the thickness direction was obtained. When the thermal conductivity of the obtained rubber sheet in the out-of-plane direction was measured by a laser flash method, it was 5.0 W.
/ M · K.

Example 10 The silicone rubber sheet having a thickness of about 2 mm obtained in Example 4 was mixed with 100 parts by weight of a silicone adhesive and 4 parts by weight of a vulcanizing agent on both sides.
Each was applied with a thickness of 20 μm, heated at 230 ° C. for 30 minutes, and then cooled to obtain an adhesive silicone rubber sheet. When the thermal conductivity in the out-of-plane direction of the obtained rubber sheet was measured by a laser flash method, 4.9 W / m.
-K, which was almost the same as in Example 4.

Comparative Example 1 100 × 100 × 100 mm
In a Teflon resin container, the viscosity before curing is 0.7Pa
The silicone rubber substrate, which was s, was poured into the container to a height of 90 mm, defoamed and cured to obtain a silicone rubber single material. From the obtained material, a sheet was cut out in the same thickness as in Example 1, and two types of samples were prepared and the thermal conductivity was measured. As a result, the value was 0.17 W / m · K.

Comparative Example 2 100 × 100 × 100 mm
Was filled in one direction with the pitch-based graphitized carbon fibers used in Example 1 previously cut to a length of about 95 mm so as to have a volume content of 80% in the container. Next, the viscosity before curing is 0.7 Pa
・ 90mm high in the container with silicone rubber base material
The mixture was defoamed and cured to obtain a carbon fiber reinforced silicone rubber composite. However, when the material was taken out of the container, the silicone rubber base material did not reach the bottom of the container and did not sufficiently penetrate between the carbon fibers. And thus could not be used as a carbon fiber reinforced anisotropic high thermal conductivity silicone rubber sheet.

Comparative Example 3 Only the silicone rubber substrate used in Example 6 was directly extruded by an extruder. The obtained 200 × 100 × 300 silicone rubber molded body was cured (250 ° C., 10 minutes) and then sliced into a sheet to obtain a 0.3 mm thick silicone rubber sheet. When the thermal conductivity of the obtained rubber sheet was measured by a laser flash method, it was 0.16 W / m · K.

[0085]

According to the present invention, a fiber-reinforced anisotropic material having excellent thermal conductivity and heat dissipation, high heat conductivity and heat dissipation in a specific direction, and good adhesion and adhesion. High thermal conductive silicone rubber composites can be produced.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a method for molding a silicone rubber composition according to the present invention.

FIG. 2 is a diagram showing an example of a heat conduction device according to the present invention.

[Explanation of symbols]

1: silicone rubber composition, 2: carbon fiber, 3: cut surface, 4: heat sink, 5: CPU, 6: personal computer housing,
7: silicone rubber sheet, A: out-of-plane direction, B: in-plane direction.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] January 19, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0078

[Correction method] Change

[Correction contents]

Example 7 The silicone rubber molded product obtained in Example 6 was sliced into a sheet along a plane perpendicular to the oriented fibers after curing (250 ° C., 10 minutes), and the thickness was 3 mm. A silicone rubber sheet having 0.0 mm fibers oriented in the thickness direction was obtained. When the thermal conductivity of the obtained rubber sheet in the out-of-plane direction was measured by a laser flash method, it was 2.4.
W / m · K.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0079

[Correction method] Change

[Correction contents]

Example 8 A silicone rubber base material similar to that of Example 6 was used as a heat conductive filler, with a heat conductivity of about 650.
Pitch-based carbon fiber of W / m · K, length of about 3 mm (heat-treated pitch-based carbon fiber of thermal conductivity of about 50 W / m · K, length of about 3 mm at 3000 ° C. for 2 hours in an inert atmosphere) Is added to the base material by 13% by weight, and the mixture is sufficiently stirred and dispersed and mixed by a mixing roll. Then, the mixture is subjected to stress by an extruder and plastically deformed in a certain direction.
The fibers were extruded while being uniaxially oriented.
After curing the obtained 200 × 100 × 300 silicone rubber molded article (250 ° C., 10 minutes), it is sliced into a sheet along a plane perpendicular to the oriented fiber, and has a thickness of 0.3 mm.
To obtain a silicone rubber sheet having the fibers oriented in the thickness direction. When the thermal conductivity of the obtained rubber sheet in the out-of-plane direction was measured by a laser flash method, it was 20 W / m · K.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0080

[Correction method] Change

[Correction contents]

Example 9 The silicone rubber molded product obtained in Example 8 was cured (250 ° C., 10 minutes) and then sliced into a sheet along a plane perpendicular to the oriented fiber, and the thickness was 3. A silicone rubber sheet having 0 mm fibers oriented in the thickness direction was obtained. When the thermal conductivity of the obtained rubber sheet in the out-of-plane direction was measured by a laser flash method, it was 5.0 W.
/ M · K.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0081

[Correction method] Change

[Correction contents]

Example 10 The silicone rubber sheet having a thickness of about 2 mm obtained in Example 9 was mixed with 100 parts by weight of a silicone adhesive and 4 parts by weight of a vulcanizing agent on both sides.
Each was applied with a thickness of 20 μm, heated at 230 ° C. for 30 minutes, and then cooled to obtain an adhesive silicone rubber sheet. When the thermal conductivity in the out-of-plane direction of the obtained rubber sheet was measured by a laser flash method, 4.9 W / m.
-K, which was hardly different from that of Example 9.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yutaka Sanogawa 1-3-12 Nishi-Shimbashi, Minato-ku, Tokyo Japan Oil Co., Ltd.

Claims (1)

[Claims] 1. A silicone rubber substrate having a thermal conductivity of 60 to 1
A silicone rubber composite comprising a high thermal conductive fiber of 200 W / m · k in a fiber volume content of 1 to 70% by weight, wherein at least a part of the high thermal conductive fiber is unidirectionally or two-dimensionally oriented. A silicone rubber composite comprising: