JP2006156935A - Heat dissipating sheet and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat dissipating sheet (for electronic apparatuses and electronic parts) which is thin and exhibits high heat dissipation characteristics and excellent electric insulation, and to provide its manufacturing method. <P>SOLUTION: The heat dissipating sheet is composed of alumina particles which are bound by binder resin with glass-transition temperature of -50 to 50°C. The mass ratio between the alumina particles and the binder resin is 70/30 to 91/9, and the thickness of the sheet is 50-150 μm. The sheet is formed by dissolving the binder resin in a solvent, homogeneously and finely dispersing the alumina particles in the solution, spreading the liquid, and drying it. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electronic component such as a large scale integrated circuit (LSI), a plasma display panel (PDP), an organic EL or an inorganic EL, a light emitting diode (LED), a fluorescent display tube (VFD) in an electronic device such as a personal computer or a cellular phone. ), Heat generated from display devices using cathode ray tubes (CRT), etc., or lighting fixtures using incandescent bulbs, fluorescent lamps, EL (organic or inorganic), LEDs, etc. are efficiently dissipated outward. The present invention relates to a heat dissipation sheet used and a method for manufacturing the same.

In recent years, high performance and multi-functionality of electronic devices are remarkable, and LSIs such as microprocessors (MPUs), image processing chips, and memories that are used are becoming more sophisticated. Because it was increasing, heat countermeasures became a problem.
Conventionally, it is common to use a heatsink such as a small fan motor when proper arrangement in the LSI device is sufficient, otherwise. However, thermal design is becoming difficult for electronic devices such as notebook computers and mobile phones that are particularly pursued to be thinner and lighter (smaller). And even for MPUs that previously did not require a heatsink, due to an increase in the amount of heat generation, it has become impossible to radiate heat without using a heatsink.
When providing a radiator in an electronic component such as an MPU, a heat radiating sheet made of a material having a high thermal conductivity is usually disposed between the electronic component and the radiator. This is because, when the electronic component and the radiator are directly joined, if a gap is generated between the electronic component and the radiator due to a minute warp of the joining surface of the radiator, the gap becomes a large heat conduction resistance. In addition, some users are concerned about the noise of fan motors, and notebook computers that are fanless by using only heat-dissipating sheets are now on the market.
In addition, in a display device such as a PDP, as the display brightness is increased, more heat is generated, the temperature of the display panel becomes higher, and the display quality characteristics of the display panel deteriorate. It has been proposed to provide a heat conductive sheet so as to be in close contact with the plate (see Patent Document 1), and has been put into practical use.
As described above, the heat dissipation sheet has become extremely important for heat countermeasures of electronic devices, electronic components, display devices, and the like.

Since the heat-dissipating sheet requires flexibility, a rubber-like one has been used. However, as a heat-dissipating sheet with increased thermal conductivity, a heat-dissipating sheet in which boron nitride is dispersed in a polyolefin-based rubber in recent years (Patent Document 2) And a heat-dissipating sheet (see Patent Document 3) in which graphitic carbon fibers having an average aspect ratio of less than 3 are dispersed in a matrix resin have been proposed.
If an electrically insulating material such as boron nitride or alumina is selected as the highly thermally conductive particles (inorganic filler) to be dispersed, an electrically insulating heat dissipation sheet can be obtained, and if an electrically conductive material such as graphite is selected. Electrically conductive heat-dissipating sheets can be obtained and used depending on the application.
These inorganic fillers, especially the latter graphitic carbon fiber, have a fairly high thermal conductivity, but in order to emphasize physical properties such as flexibility and mechanical strength of the heat dissipation sheet, the content of the inorganic filler in the heat dissipation sheet is The film thickness was not so high, and the film thickness was relatively thick, on the order of several hundred μm. That is, all of these heat radiating sheets inevitably have a low thermal resistance (high heat transmissivity) by increasing the thermal conductivity of the sheet to about 5 to 10 W / mK, thereby radiating heat. A design philosophy that enhances performance was adopted.

Japanese Patent No. 3503625 Japanese Patent Laid-Open No. 7-246628 JP-A-9-283955

  Under such circumstances, the present invention provides a heat-dissipating sheet having a thin sheet thickness, good heat dissipation, and excellent electrical insulation (for electronic equipment and electronic parts), and an electrical insulating heat-dissipating sheet. The object is to provide a manufacturing method therefor.

As a result of studies for achieving the above object, the present inventors have found that heat dissipation performance by heat conduction of the heat dissipation sheet, that is, heat passing through the unit cross-sectional area per unit time when the temperature difference between the front and back of the heat dissipation sheet is constant. The flow rate is inversely proportional to the thermal resistance (the reciprocal of the heat transmissivity), and attention was paid to reducing the thermal resistance in order to improve the heat dissipation performance.
In view of the fact that the thermal resistance is proportional to [thickness / thermal conductivity] of the heat dissipation sheet, in order to lower the thermal resistance, there are two methods: a method of increasing the thermal conductivity and a method of reducing the thickness. I found that there was an option.
Incidentally, the conventional heat-dissipating sheet as described above has been exclusively selected to increase the thermal conductivity. In that case, however, a special and expensive high thermal conductivity material such as fibrous carbon fiber is required, or a special and difficult technique such as orienting the fiber in a specific direction in the sheet is required.
However, the present inventors also pay attention to the contribution of thickness, and firstly bind a high thermal conductivity material with as little binder resin as possible to achieve a certain level of high thermal conductivity and devise a film forming method. It has been found that a sufficient low thermal resistance can be realized even when a general-purpose high thermal conductivity material is used by using a thin heat sink sheet in combination, and the present invention has been completed.
In addition, as a heat dissipation mechanism of the heat dissipation sheet, in addition to heat conduction, there may be some contribution by infrared radiation, but the present inventors are particularly highly heat conductive materials in the heat dissipation sheet configured as described above. If a material with high thermal emissivity, such as alumina particles, is used, in addition to heat conduction inside the heat dissipation sheet, infrared radiation from the surface of the heat dissipation sheet can sufficiently contribute to heat dissipation, and better heat dissipation performance is achieved. Recognized that expression is possible. Even in this case, if the thickness of the heat radiating sheet is reduced, the heat is quickly transported to the surface where heat is exhausted by radiation, and the heat radiation efficiency is improved.
Such a heat radiating sheet is preferably produced by dispersing alumina particles in a resin solution obtained by dissolving a binder resin having a specific glass transition temperature in a solvent, and applying and drying the particles. By this method, a sheet having a low high alumina particle ratio and having excellent practical electrical insulation in terms of not only heat dissipation but also mechanical strength and flexibility can be easily obtained.
Here, the alumina particles are preferably spherical fine particles having an average particle diameter of 1 to 80 μm, and more preferably, the average particle diameter is 3 to 10 μm in order to obtain a heat dissipation sheet with excellent mechanical strength. The amount of the binder resin per unit surface area of the alumina particles is preferably 0.45 to 0.75 [g / m ² ].
The binder resin is preferably a polyester-based resin and an ethylene-vinyl acetate copolymer resin having a vinyl acetate unit ratio of 40 to 80 mol%. It is preferable for enhancing the thermal conductivity.

That is, the present invention
(1) A heat dissipation sheet obtained by binding alumina particles with a binder resin having a glass transition temperature of −50 to 50 ° C., and the mass ratio of alumina particles / binder resin is 70/30 to 91/9 The heat dissipation sheet is characterized in that the sheet thickness is 50 to 150 μm;
(2) The heat dissipation sheet according to (1), wherein the alumina particles are spherical fine particles having an average particle diameter of 1 to 80 μm;
(3) The above (1), wherein the alumina particles are spherical fine particles having an average particle diameter of 3 to 10 μm, and the amount of the binder resin per unit surface area of the alumina particles is 0.45 to 0.75 [g / m ² ]. ) Heat dissipation sheet;
(4) In the above (1) to (3), the binder resin is at least one selected from a polyester resin and an ethylene-vinyl acetate copolymer resin having a vinyl acetate unit ratio of 40 to 80 mol%. Heat dissipation sheet;
(5) A heat-dissipating sheet with a releasable protective film in which the heat-dissipating sheet of (1) to (4) above is stuck on a releasable protective film;
(6) A composition for producing a heat-dissipating sheet comprising: 300 to 910 parts by mass of alumina particles; 100 parts by mass of a binder resin having a glass transition temperature of −50 to 50 ° C .; 200 to 3000 parts by mass of a solvent;
(7) A method for producing a heat-dissipating sheet, wherein the composition for producing a heat-dissipating sheet according to (6) is coated, and the solvent is dried and solidified to form a sheet;
Is to provide.

The heat-dissipating sheet of the present invention is formed by binding alumina, which is a material having good thermal conductivity, thermal radiation, and electrical insulation, with as little binder resin as possible and making the sheet thickness as thin as possible. Good heat dissipation and heat insulation by heat conduction and heat radiation.
Moreover, such a heat dissipation sheet can be suitably manufactured by dispersing alumina particles in a resin solution in which a binder resin having a specific glass transition temperature is dissolved in a solvent, and applying and drying the alumina particles. In addition to heat dissipation, it is possible to obtain a heat dissipation sheet having excellent practical electrical insulation not only in mechanical strength and flexibility.

The alumina used in the present invention is not particularly limited, but is sometimes referred to as spherical fine particles (hereinafter referred to as spherical alumina) from the standpoint of influence on sheet physical properties, mechanical wear, and easy increase in thermal conductivity by dense packing. ) Is preferred. In order to obtain a uniform dispersion state of alumina particles in a binder resin solution, which is a preferred production method of the present invention, and to obtain sufficient thin film formability, the average particle size is 1 to 80 μm, more preferably 1 to It is good to use a thing about 30 micrometers. That is, when the average particle size is 1 μm or more, uniform dispersion in the resin solution is facilitated, and an increase in the viscosity of the resin solution is prevented to improve coating suitability, thereby facilitating uniform film formation. On the other hand, when the average particle size is 80 μm or less, it is easy to reduce the thickness to 150 μm or less, and the contact area between the alumina particles is increased to easily obtain a high thermal conductivity. Further, the mechanical strength of the heat dissipation sheet can be prevented from being lowered.
In order to obtain a heat radiating sheet with excellent mechanical strength, the average particle diameter of the most preferable alumina particles is 3 to 10 μm, and the amount of the binder resin per unit surface area is 0.45 to 0 as described later. 0.75 [g / m ² ] is preferable.

  The binder resin used in the present invention needs to have a glass transition temperature (hereinafter referred to as Tg) of −50 to 50 ° C., and even more preferably, the solubility parameter (hereinafter referred to as SP value) is 8. It is preferably ~ 12. In particular, it is preferable that Tg is −30 to 10 ° C. and SP value is 8.5 to 11. When Tg is within this range, despite the high alumina particle content (low binder resin content), it is possible to ensure film-forming properties, flexibility, practical mechanical strength, etc. in the thin film of the heat dissipation sheet, Further, when the SP value is within these ranges, the alumina particles are easily dispersed uniformly in the binder resin solution with the solvent having the SP value within the range.

The binder resin used in the present invention is not particularly limited as long as it satisfies the above Tg range or the SP value range. However, in order to obtain a heat-dissipating sheet having excellent electrical insulation, the binder resin is used. As physical properties, the volume resistivity value is preferably 1 × 10 ¹² Ω or more, and more preferably 1 × 10 ¹⁴ Ω or more.
Such a binder resin may be polyurethane, polyolefin, acrylic resin, various synthetic rubbers, etc., but in addition to easy solubility in a solvent, coating suitability of a composition dissolved in a solvent (viscosity, etc.) Polyester resins and ethylene-vinyl acetate copolymer resins are particularly preferred from the viewpoint of the mechanical strength, weather resistance, heat resistance, and the like of the sheet.

As the polyester-based resin, in addition to satisfying the above Tg range or further the SP value range, it is amorphous from the viewpoint of sheet flexibility and easy solubility in a solvent (for producing the heat-dissipating sheet of the present invention). Quality polyester resin is preferable, and saturated polyester is preferable from the viewpoint of weather resistance.
Examples of such saturated polyesters include polyesters of saturated dibasic acids such as succinic acid and adipic acid and saturated dihydric alcohols such as ethylene glycol and 1.6 hexanediol. The number average molecular weight of the saturated polyester is preferably 5,000 to 50,000.
From the viewpoint of preventing dioxin generation and preventing contact failure due to low molecular siloxane, a polyester resin that is halogen-free and siloxane-free is preferable.

As the ethylene-vinyl acetate copolymer resin, one satisfying the above Tg range or further the SP value range is used. However, from the viewpoints of flexibility and heat resistance of the heat dissipation sheet, those in the range of elastomer called EVM (ISO 1692 (1995)) in which the ratio of vinyl acetate units is 40 to 80 mol% are particularly preferable. The number average molecular weight of the ethylene-vinyl acetate copolymer resin is preferably 50,000 to 500,000.
Since the EVM elastomer has high heat resistance, there is an advantage that the thermal stability of the heat radiating sheet is particularly excellent when it is used.
In addition, like a polyester-type resin, it is preferable that it is halogen-free and siloxane-free from a viewpoint of prevention of dioxin generation | occurrence | production and a contact failure by low molecular siloxane.

The heat dissipation sheet of the present invention has a mass ratio of the alumina particles / the binder resin (hereinafter sometimes referred to as PV ratio) of 70/30 to 91/9, preferably 70/30 to 80/20, and In the formulation (thermal conductivity of about 1.5 to 2 W / mK), the sheet thickness is 50 to 150 μm, preferably 80 to 120 μm in order to obtain a sufficiently low thermal resistance.
That is, in order to increase thermal conductivity and thermal radiation, the content of alumina particles is increased and the sheet thickness is made as thin as possible. If the alumina particle / binder resin ratio (PV ratio) is lower than 70/30, thermal conductivity and thermal radiation are insufficient, and if it is higher than 91/9, it becomes difficult to obtain a sheet having practical mechanical strength. .
Further, if the sheet thickness is thicker than 150 μm, the thermal resistance in the sheet thickness direction is large, and in the case where the thermal conductivity obtained from the composition of the present invention is about 1.5 to 2 W / mK, the heat dissipation due to thermal conduction becomes insufficient. If it is thinner than 50 μm, film formation becomes difficult, and at the same time, a sheet with practical mechanical strength cannot be obtained.
Moreover, the high alumina particle ratio with respect to this binder resin can improve the heat resistance of a thermal radiation sheet.
In order to obtain a heat radiating sheet having excellent mechanical strength (typically tensile strength), the average particle size of alumina particles is 3 to 10 μm, and the amount of binder resin per unit surface area is 0.45. It is preferable that it is -0.75 [g / m < ² >]. This is because the mechanical strength of the heat-dissipating sheet of the present invention depends on the average particle diameter of alumina particles and the amount of binder resin per unit surface area, as specifically shown in the examples and comparative examples described later. This is because the value of 1 exhibits sufficient mechanical strength within the above range.
Here, the binder resin amount per unit surface area is the amount B of alumina particles added to the binder resin amount C (hereinafter also referred to as filler amount) in the heat-radiating sheet of the present invention and the composition for producing a heat-radiating sheet. And the value divided by the specific surface area A of the alumina particles, defined as C / (A * B). The unit of the binder resin amount C / (A * B) per unit surface area is obtained by dividing the unit of the binder resin amount C and the filler amount B by the unit of the surface area in the specific surface area.
For example, if the unit of binder resin amount C and filler amount B is [g] and the unit of specific surface area is [m ² / g], the unit of C / (A * B) is [g] / ([m ² / g] * [g]) = [g / m ² ].

  Such a heat-dissipating sheet of the present invention is a composition in which alumina particles are uniformly dispersed in a solution in which a binder resin is dissolved in a solvent. A thin heat dissipation sheet can be obtained. That is, in the present invention, by using a solvent, the fluidity of the alumina particles and the binder resin mixture is enhanced, and the thin film coating suitability is imparted. And after coating and film-forming this composition, the solvent contained is dried and removed, whereby the film thickness of the solidified heat-dissipating sheet is reduced by the amount of the solvent, and the film is further thinned.

The solvent used in the production of the heat dissipation sheet of the present invention is preferably a solvent having an SP value of 8 to 12, and more preferably 8.5 to 11. When the SP value is within this range, the binder resin having the SP value within that range is well dissolved and the dispersibility of the alumina particles is also good.
Such a solvent is not particularly limited as long as the SP value is within this range, but methyl ethyl ketone (SP value: 9.3), toluene (SP value: 8.9), ethyl acetate (SP value: 9.1) and the like. It is preferably used from the viewpoints of drying property after coating, fluidity of the coating agent, and the like.
These solvents may be used alone or in combination of two or more.
Furthermore, as a composition (coating agent) for producing the heat-radiating sheet of the present invention, as long as it does not impair the solution state of the binder resin, it is necessary for the purpose of adjusting the fluidity of the coating agent and the drying speed. Thus, an appropriate amount of a diluting solvent, a slow-drying solvent or the like having an SP value outside the above range can be added.

The composition for producing the heat-radiating sheet of the present invention is prepared by dissolving 300 parts by mass of alumina particles in a solution obtained by dissolving 100 parts by mass of a binder resin having a glass transition temperature of −50 to 50 ° C. in 200 to 3000 parts by mass of a solvent. Is uniformly and finely dispersed and mixed using a dissolver or the like.
The applicability of the composition depends on the type and amount of each component of the composition, but is greatly influenced by the type and amount of the solvent, the shape / particle size and amount of the alumina particles, among others.
In order to easily obtain a heat-dissipating sheet having a thin sheet thickness of 50 to 150 μm according to the present invention by the coating method suitably used in the present invention, the optimum solvent blending amount (composition fluidity, thickness shrinkage during drying) In order to evaluate the relationship between the amount of the solvent and the total composition, the solvent amount in the composition is 16.5 to 88.3% by mass, and the alumina particle diameter is 1 to 80 μm. The viscosity of the alumina particle-dispersed resin solution (coating agent) is preferably about 50 to 10,000 mPas (B-type viscometer (60 rotations)).

  In the heat dissipation sheet of the present invention, a flame retardant such as a metal hydrate, a colorant, a curing agent such as isocyanate, etc., as long as it does not have a large adverse effect on the heat dissipation characteristics (thermal conductivity, heat radiation). An appropriate amount of a dispersant, microsilica and the like may be appropriately selected and blended.

The alumina particle-dispersed resin solution (coating agent), which is a composition for producing the heat-dissipating sheet of the present invention, is coated on a releasable film such as a resin film with a release layer using a normal coating machine or the like. Then, it is made into a sheet by being dried by a far-infrared radiation heater, hot air blowing or the like.
As the release layer, melamine resin or the like is used. As the resin film, a polyester resin such as polyethylene terephthalate is used.
Of course, a higher heat conductivity of the formed heat dissipation sheet is preferable in terms of heat dissipation performance. However, in the present invention, the thermal conductivity of the heat-dissipating sheet is about 1 W / mK or more, more preferably 1.5 W / mK or more because it is designed to reduce the thermal resistance by reducing the thickness of the heat-dissipating sheet to 150 μm or less. Thus, the heat dissipation performance required for practical use can be obtained. Due to the combination of the thickness and thermal conductivity and the thermal radiation property of alumina, the heat radiation performance equivalent to that of a conventional heat radiation sheet having a thickness of 500 μm and a thermal conductivity of about 5 W / mK can be obtained. If a thin film is formed using the composition having the above composition, this degree of thermal conductivity can be easily obtained.
The thermal conductivity is measured according to a known method such as a method defined in JIS A 1412, a laser flash method, or the like.

  The heat-dissipating sheet thus obtained can be peeled off from the releasable film, or can be in the form of a product for use as a heat-dissipating sheet with the releasable film as a protective film.

  Moreover, the heat-radiation sheet of this invention is good also as a structure which further provided the adhesive layer in the upper surface or lower surface of the heat-radiation sheet, and this raises the convenience at the time of product use.

  The heat-dissipating sheet of the present invention is affixed to a back surface, a side surface or the like of a heating element such as an electronic component such as an LSI or a display device such as a PDP at a position that does not hinder assembly, light emission, image display, or the like. Thereby, the heat-radiation sheet of this invention expresses the heat-radiation mechanism according to the usage form. For example, when used by being stacked or connected to a heat exhaust system such as a heat sink, a water-cooled or air-cooled cooler, the heat-dissipating sheet of the present invention serves as a passage for transferring heat from the heating element to the heat exhaust system. Heat is released exclusively from the heat exhaust system by heat conduction and / or heat radiation. On the other hand, when using the heat radiating sheet alone of the present invention, the heat transferred from the heat generating element in the thickness direction and in-plane direction of the heat radiating sheet by heat conduction exclusively to the heat radiation from the surface of the heat radiating sheet and the surrounding atmosphere. It is released to the outside by heat conduction.

Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
Polyester A (amorphous saturated copolyester; manufactured by Toyobo Co., Ltd., trade name: “Byron 300”, Tg: 6 ° C., number average molecular weight in a container equipped with a 300 ml stirring mixer 23000, specific gravity 1.20, SP value 10.96, volume resistivity 1.3 × 10 ¹⁵ Ω) dissolved in 35% by mass in a mixed solvent of methyl ethyl ketone / toluene, 20 parts by mass of alumina particles (average particle diameter) : 3 μm) 28 parts by mass was added and mixed well to obtain a uniform slurry (alumina particles / binder resin mass ratio (PV ratio) = 80/20). To this slurry, 52 parts by mass of methyl ethyl ketone was further added and stirred and mixed to obtain a coating liquid in which alumina fine particles were uniformly dispersed.
The obtained coating liquid was applied onto the release agent layer of the release agent-coated PET film by a coating machine (applicator), dried with hot air, and the contained solvent was removed by drying to obtain a heat dissipation sheet. .
Table 1 shows the physical properties and the like of the obtained heat dissipation sheet.

The density (g / cm ² ) of the heat dissipation sheet was calculated by measuring the film thickness and weight (mass) (g) of the sheet cut to a size of 5.0 × 10.0 cm.
The thermal conductivity was measured by a method in which the thermal diffusivity was obtained by a laser flash method, and the thermal conductivity was calculated as the product of the thermal diffusivity and the heat capacity (density × specific heat) (Example 2 and subsequent examples) The same).
The SP value was determined by the FEDORS method.
The tensile strength and tensile breaking elongation of the heat radiation sheet were determined in accordance with JIS K7113.
Sheet workability was evaluated based on whether or not the heat dissipation sheet could be peeled from the release film while maintaining its shape.

Examples 2-10, Comparative Examples 1-4
A coating solution having each composition described in Table 1 was obtained by the same operation as in Example 1, and a heat dissipation sheet was obtained by the same operation as in Example 1.
Table 1 shows the physical properties and the like of the obtained heat dissipation sheet.
Polyester B is manufactured by Toyobo Co., Ltd., trade name: “Byron 200” (Tg: 67 ° C., number average molecular weight 17000, specific gravity 1.26, SP value 11.73, volume specific resistance value 7.2. × 10 ¹⁶ Ω) is an amorphous saturated copolyester, and the polyester C is
Prototype urethane-modified polyester manufactured by Toyobo Co., Ltd.

As can be seen from the results in Table 1, when the Tg of the binder resin is higher than 50 ° C., the sheet becomes hard and brittle, and when it is lower than −50 ° C., the mechanical strength is insufficient and the sheet shape cannot be maintained (hence the tensile strength). Neither strength nor tensile fracture elongation can be measured), and neither is suitable as a heat dissipation sheet (Comparative Examples 1 and 2).
Further, when the alumina particle / binder resin mass ratio (PV ratio) is lower than 70/30, the thermal conductivity is low (less than 1 W / mK), and when it is higher than 91/9, the mechanical strength is insufficient and the sheet shape is maintained. Neither is suitable as a heat dissipation sheet (Comparative Examples 3 and 4).

Examples 11-18
Except for using EVM as the binder resin, the same operation as in Example 1 was performed to obtain a coating liquid having an average particle size of alumina particles and a PV ratio shown in Table 2, and a heat dissipation sheet was obtained by the same operation as in Example 1. (Film thickness: 100 μm).
Table 2 shows the physical properties and the like of the obtained heat radiation sheet.

Examples 19-34
The amount of the binder resin per unit surface area of the fillers (alumina particles) shown in Tables 3 and 4 for alumina particles having an average particle diameter of 3 μm and 10 μm was the same as in Example 1 except that EVM was used as the binder resin. C / A * B) g / m ² , and a PV ratio coating solution were obtained, and a heat dissipation sheet was obtained by the same operation as in Example 1 (film thickness: 100 μm).
Tables 3 and 4 show the physical properties and the like of the obtained heat radiation sheet.

As can be seen from the results in Tables 2 to 4, in order to obtain a heat radiating sheet having excellent mechanical strength, the average particle diameter of alumina particles is 3 to 10 μm, and the amount of binder resin per unit surface area is 0.45. It is preferable that it is -0.75 [g / m < ² >].

Claims (7)

  A heat dissipation sheet formed by binding alumina particles with a binder resin having a glass transition temperature of −50 to 50 ° C., wherein the mass ratio of alumina particles / binder resin is 70/30 to 91/9, and the sheet thickness Is a heat-dissipating sheet.   The heat dissipation sheet according to claim 1, wherein the alumina particles are spherical fine particles having an average particle diameter of 1 to 80 μm. ^2. The heat dissipation according to claim 1, wherein the alumina particles are spherical fine particles having an average particle diameter of 3 to 10 μm, and the amount of the binder resin per unit surface area of the alumina particles is 0.45 to 0.75 [g / m ² ]. Sheet.   The heat-radiating sheet according to claim 1, wherein the binder resin is at least one selected from a polyester resin and an ethylene-vinyl acetate copolymer resin having a vinyl acetate unit ratio of 40 to 80 mol%.   A heat-dissipating sheet with a releasable protective film, wherein the heat-dissipating sheet according to claim 1 is adhered on a releasable protective film.   A composition for producing a heat-dissipating sheet, comprising: 300 to 910 parts by mass of alumina particles; 100 parts by mass of a binder resin having a glass transition temperature of -50 to 50 ° C; 200 to 3000 parts by mass of a solvent.   A method for manufacturing a heat dissipation sheet, wherein the composition for manufacturing a heat dissipation sheet according to claim 6 is coated, and the solvent is dried and solidified to form a sheet.