JP2012188605A - Thermally conductive adhesive composition and thermally conductive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermally conductive adhesive composition that has high thermal conductivity and excellent productivity.SOLUTION: The thermally conductive adhesive composition contains an adhesive member that has adhesion, wherein the thermally conductive adhesive composition further contains a thermally conductive filler that is dispersed in the adhesive member and has insulation properties. The thermally conductive filler has Mohs hardness of 6 or larger and heat conductivity of 40 W/mK or larger.

Description

  The present invention relates to a heat conductive pressure-sensitive adhesive composition and a heat conductive pressure-sensitive adhesive sheet, and in particular, a heat conductive pressure-sensitive adhesive composition used when sticking a heat sink or a heat sink to an electronic device or the like, and a heat The present invention relates to a conductive adhesive sheet.

  2. Description of the Related Art Conventionally, a heat radiating member such as a heat sink or a heat sink is attached to an electronic device that generates heat, and efficient heat radiation is performed. In attaching the heat dissipating member, a heat conductive adhesive in which a heat conductive filler for increasing heat conductivity is dispersed in an adhesive such as an epoxy resin has been used. However, there was a process of fixing the heat radiating member until the heat conductive adhesive was cured, and there was a problem in work efficiency. In order to omit the curing time, a heat conductive pressure-sensitive adhesive sheet in which a heat conductive pressure-sensitive adhesive in which a heat conductive filler is dispersed in a pressure-sensitive adhesive is applied in a sheet shape has been used (Japanese Patent Laid-Open No. 6-88061). (Patent Document 1)). Aluminum oxide is used as a heat conductive filler in a commercially available heat conductive adhesive sheet. In addition, the following technologies relating to the heat conductive adhesive sheet using materials other than aluminum oxide are disclosed.

  According to Japanese Patent Laid-Open No. 11-269438 (Patent Document 2), 50 parts by weight or more of a (meth) acrylic acid alkyl ester monomer having an alkyl group having 4 to 14 carbon atoms and a copolymerizable polar vinyl monomer Hydrated metal compound for 100 parts of pressure-sensitive adhesive composition consisting of 100 parts of an acrylic copolymer or partial polymer prepared from a monomer mixture essentially comprising 5 to 10 parts and 10 to 100 parts of tackifying resin An electrically insulating thermally conductive flame retardant pressure sensitive adhesive and pressure sensitive adhesive tape characterized by containing 50 to 250 parts are disclosed. Further, according to WO 2007/148729 (Patent Document 3), liquid rubber, at least one of styrene rubber and amorphous olefin resin, tackifier resin, and graphite are included as essential components, and the inclusion of graphite Disclosed is a thermally conductive thermoplastic pressure-sensitive adhesive composition characterized in that the amount is in the range of 30 to 75% by weight relative to the total mass of the composition.

JP-A-6-88061 JP-A-11-269438 WO2007 / 148729

  The properties required for such a heat conductive pressure-sensitive adhesive or pressure-sensitive adhesive sheet include high thermal conductivity and high adhesiveness depending on its use. Moreover, since it may be used also in the location where insulation is requested | required, the high insulation of heat conductive adhesive itself is also requested | required. Since the graphite used for the heat conductive adhesive composition disclosed in Patent Document 3 has no insulating property, there is anxiety in use in applications that require insulating properties.

  In addition, unlike the heat conductive adhesive, the heat conductive pressure-sensitive adhesive sheet needs to be processed into the shape of the heat radiating member using a punching blade in advance. In this case, if the filler dispersed in the heat conductive adhesive sheet is harder than the punching blade, damage to the punching blade is increased. As a result, the life of the punching blade is shortened, resulting in a decrease in productivity and an increase in cost due to an increase in the number of times the punching blade is maintained. While the general Mohs hardness of stainless steel is 6, the Mohs hardness of aluminum oxide disclosed in Patent Document 1 is 9.

  Patent Document 2 discloses a thermally conductive adhesive composition using a hydrated metal compound such as aluminum hydroxide as a thermally conductive filler in order to simultaneously impart thermal conductivity and flame retardancy to a thermally conductive adhesive sheet. Is disclosed. In general, the Mohs hardness of a hydrated metal compound such as aluminum hydroxide is as low as about 3, but the thermal conductivity is very low as less than 10 W / m · K. When a thermally conductive adhesive sheet having a thermal conductivity of about 0.6 W / m · K is prepared using such a thermally conductive filler with low thermal conductivity, a large amount of thermally conductive filler is required. As the heat conductive filler content with respect to the heat conductive pressure-sensitive adhesive composition increases, the adhesiveness decreases, so that there is a limit to the heat conductive filler content. Therefore, efficient production of a heat conductive adhesive composition and a heat conductive adhesive sheet is attained by using the heat conductive filler which has high heat conductivity.

  An object of the present invention is to provide a heat conductive pressure-sensitive adhesive composition having high heat conductivity and good productivity.

  Another object of the present invention is to provide a heat conductive pressure-sensitive adhesive sheet having high heat conductivity and good productivity.

  The inventor of the present application disperses an insulating heat conductive filler having a lower hardness than the punching blade and having a high thermal conductivity in an adhesive member, thereby providing a heat conductive adhesive having high thermal conductivity and good productivity. It has been found that an agent composition can be formed.

  The thermally conductive adhesive composition according to the present invention is a thermally conductive adhesive composition including an adhesive member having adhesiveness, and includes a thermally conductive filler dispersed in the adhesive member and having insulating properties, The Mohs hardness of the conductive filler is 6 or less, and the thermal conductivity of the thermally conductive filler is 40 W / m · K or more.

  Moreover, in the other situation of this invention, the heat conductive adhesive sheet is provided with the above-mentioned heat conductive adhesive composition, and is formed in the sheet form.

  Generally, stainless steel having a Mohs hardness of about 6 is used for the punching blade. Therefore, by making the Mohs hardness of the heat conductive filler 6 or less, it is possible to remove the heat conductive adhesive sheet when processing it into the shape of the heat radiating member. Damage to the blade can be reduced. If it does so, it can suppress that the abrasion degree of a blade is decreased, the lifetime of a blade is shortened, and the maintenance cycle of a blade can be lengthened. Moreover, if the heat conductivity of a heat conductive filler is 40 W / m * K or more, a heat conductive adhesive sheet can be produced efficiently. Therefore, such a heat conductive adhesive composition and a heat conductive adhesive sheet have high heat conductivity, and productivity is favorable.

It is a schematic sectional drawing of the heat conductive adhesive sheet containing the heat conductive adhesive composition which concerns on one Embodiment of this invention. It is a graph which shows the relationship between the heat conductivity of a heat conductive adhesive sheet, and the content rate of a heat conductive filler.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a heat conductive pressure-sensitive adhesive sheet containing a heat conductive pressure-sensitive adhesive composition according to an embodiment of the present invention.

  With reference to FIG. 1, the heat conductive adhesive sheet 11 which concerns on one Embodiment of this invention is a sheet form, has a predetermined thickness, and is the 1st as a peeling film comprised from a thermoplastic resin etc. Film 12, a second film 13 as a release film which is similarly composed of a thermoplastic resin, and the like, and a thermally conductive adhesive composition disposed between the first film 12 and the second film 13. 14. The heat conductive pressure-sensitive adhesive composition 14 includes a pressure-sensitive adhesive member 15 and a plurality of heat conductive fillers 16 contained so as to be dispersed between the pressure-sensitive adhesive members 15. The thickness of the thermally conductive pressure-sensitive adhesive composition 14 is preferably as small as possible considering the efficiency of heat dissipation, and is set to be about 50 to 300 μm.

  Here, the detailed structure of the heat conductive adhesive composition 14 contained in the heat conductive adhesive sheet 11 which concerns on one Embodiment of this invention is demonstrated. With reference to FIG. 1 again, the heat conductive adhesive composition 14 is a structure provided with the adhesive member 15 which has adhesiveness, and the several heat conductive filler 16. As shown in FIG.

  The adhesive member 15 uses an acrylic adhesive, a rubber adhesive, a silicon adhesive, a polyester adhesive, or the like, but the adhesive is not specified in the present invention.

  The plurality of thermally conductive fillers 16 are so-called additives, and the shape thereof is granular and substantially spherical. The thermally conductive filler 16 is appropriately dispersed and contained in the adhesive member 15 having adhesiveness. Such a heat conductive filler 16 having a predetermined particle size distribution is prepared, added into the adhesive member 15, and appropriately dispersed by stirring or the like. About the average particle diameter of the heat conductive filler 16, a 1-30 micrometers thing is selected, for example. When the average particle diameter of the heat conductive filler 16 is smaller than 1 μm, it is difficult to disperse the heat conductive filler 16. Moreover, when the average particle diameter of the filler 16 is larger than 30 micrometers, the surface roughness of an adhesive sheet will become large and sufficient adhesive force will not be obtained.

  Here, the filler 16 is configured such that the Mohs hardness of the filler is 6 or less and the thermal conductivity of the filler is 40 W / m · K or more. Specifically, heat conductive fillers that meet the conditions of insulation, Mohs hardness of 6 or less, and thermal conductivity of 40 W / m · K or more include magnesium oxide, zinc oxide, hexagonal boron nitride, and the like. These thermally conductive fillers may be used alone or in combination. That is, the material of the thermally conductive filler is composed of at least one material selected from the group consisting of magnesium oxide, zinc oxide, and boron nitride. Dispersing these thermally conductive fillers can reduce damage to the punching blade when processing the thermally conductive adhesive sheet into the shape of the heat dissipation member. If it does so, it can suppress that the abrasion degree of a punching blade is decreased, the lifetime of a punching blade becomes short, and can lengthen the maintenance cycle of a punching blade. Therefore, productivity can be improved. Moreover, such a heat conductive adhesive composition 14 has insulation, and it is a high level without a problem also about heat conductivity.

  Specifically, the material of the heat conductive filler 16 is, for example, magnesium oxide. Magnesium oxide has a Mohs hardness of about 6. Therefore, when processing a heat conductive adhesive sheet into the shape of a heat radiating member, productivity can be made favorable. Moreover, about heat conductivity, it is about 50 W / m * K, and the heat conductive adhesive composition and heat conductive adhesive sheet which have high heat conductivity can be produced efficiently.

  For the purpose of improving dispersibility in an adhesive, etc., a coupling treatment to a heat conductive filler, a stearic acid treatment, and the like may be appropriately performed.

(Adjustment of heat conductive adhesive composition)
As an adhesive member, 100 parts by weight of a solvent-based acrylic adhesive (P-815, Nichiei Kako Co., Ltd., solid content 55%) is added to the addition amount of the heat conductive filler shown in Table 1, and stirred until uniform. By doing this, the heat conductive adhesive composition solution was obtained. As the thermally conductive filler, two kinds of magnesium oxides having different average particle diameters (P-WR2, manufactured by Kamijima Chemical Co., Ltd., average particle diameter 3 μm, specific gravity 3.58, thermal conductivity 51.1 W / m · K, and Kamijima Chemical Industry Co., Ltd. SL-WR2, average particle diameter 10 micrometers, specific gravity 3.58, and thermal conductivity 51.1 W / m * K) were used. As comparative examples, aluminum oxide (A30 manufactured by Nippon Light Metal Co., Ltd., average particle size 5 μm, specific gravity 3.98, thermal conductivity 30 W / m · K) and aluminum hydroxide were used.

(Adjustment of heat conductive adhesive sheet)
The thermally conductive pressure-sensitive adhesive composition solution was applied onto a 25 μm polyethylene terephthalate film that had been peel-treated so that the thickness after drying was as shown in Table 1, and was covered with a 25 μm polyethylene terephthalate film that had been peel-treated after drying. A sheet was obtained.

(Evaluation method)
Thermal conductivity was measured by a temperature gradient method and a hot wire method. Adhesive strength was a 25 mm x 150 mm test sample lined with a 25 µm polyethylene terephthalate film, applied to a stainless steel plate with a reciprocating pressure of 2 kg rubber roller, and allowed to stand in an atmosphere of 23 ° C and 50% humidity for 24 hours. It peeled at 180 degree peeling and the peeling speed of 300 mm / min (min), and measured.

(Comparative Examples 3 and 4)
Based on the blend composition of Examples 7 and 8 in Patent Document 2, the specific gravity of aluminum hydroxide is 2.42, the specific gravity of acrylic copolymer, tackifier resin, photocrosslinker, and photoinitiator is 1, and the filler is contained. The rate was calculated. As the thermal conductivity, the measurement results of Examples 7 and 8 in Patent Document 2 were used as they were.

  FIG. 2 shows the relationship between the heat conductivity of the heat conductive pressure-sensitive adhesive sheet and the content of the heat conductive filler in order to clarify the difference in the material of the heat conductive filler. In FIG. 2, the vertical axis indicates the thermal conductivity (W / m · K) of the heat conductive adhesive sheet, and the horizontal axis indicates the content (volume%) of the heat conductive filler.

  Referring to Table 1 and FIG. 2, for example, when the content of the thermally conductive filler is approximately 28% by volume, in Example 2, the thermal conductivity is 0.58 W / m · K. On the other hand, in Comparative Example 1, it was 0.44 W / m · K, and in Comparative Example 3, it was 0.4 W / m · K and did not reach 0.5 W / m · K. In Example 1, the thermal conductivity is 0.55 W / m · K although the thermal conductive filler is 25% by volume. Thus, when the thermally conductive filler according to Examples 1 to 5 is used, high thermal conductivity can be realized while reducing the content of the thermally conductive filler. Here, as the content of the heat conductive filler increases, the value of the adhesive strength decreases. Therefore, it is preferable to select the heat conductive filler to be used and the content thereof depending on the application.

  Although the embodiments of the present invention have been described with reference to the drawings, the present invention is not limited to the illustrated embodiments. Various modifications and variations can be made to the illustrated embodiment within the same range or equivalent range as the present invention.

  The thermally conductive adhesive composition and the thermally conductive adhesive sheet according to the present invention are effectively used when high thermal conductivity and good productivity are required.

  DESCRIPTION OF SYMBOLS 11 Thermal conductive adhesive sheet, 12, 13 Release film, 14 Thermal conductive adhesive composition, 15 Adhesive member, 16 Filler.

Claims (5)

A thermally conductive adhesive composition comprising an adhesive member having adhesiveness,
Including a thermally conductive filler dispersed in the adhesive member and having an insulating property;
The Mohs hardness of the thermally conductive filler is 6 or less,
The heat conductive adhesive composition whose heat conductivity of the said heat conductive filler is 40 W / m * K or more. The heat conductive adhesive composition according to claim 1, wherein the material of the heat conductive filler is composed of at least one material selected from the group consisting of magnesium oxide, zinc oxide, and boron nitride. The heat conductive adhesive composition of Claim 1 or 2 whose average particle diameter of the said heat conductive filler is 1-30 micrometers. The content of the heat conductive filler with respect to the whole of the heat conductive adhesive composition is 40 to 70% by volume,
The heat conductive adhesive composition in any one of Claims 1-3 whose heat conductivity of the said heat conductive adhesive composition is 0.6 W / m * K or more. The heat conductive adhesive composition in any one of Claims 1-4 is provided,
The heat conductive adhesive composition sheet formed in the sheet form.

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