JP5600018B2 - Heat dissipation structure - Google Patents

Description

  The present invention relates to a heat dissipation structure for efficiently dissipating heat from heating elements of various devices such as electronic devices such as personal computers, mobile phones, and PDAs, and lighting and display devices such as LEDs and EL.

  In recent years, the performance of electronic devices such as personal computers, mobile phones, and PDAs, and lighting and display devices such as LEDs and EL has been remarkably improved, which is due to the significant performance improvements of arithmetic elements and light emitting elements. As described above, the amount of heat generation is remarkably increased with the improvement of the performance of the arithmetic element and the light emitting element, and how to dissipate heat in electronic devices, lighting, and display devices is an important issue. As a countermeasure against heat, it is important to provide a heat conductive material layer between the heating element and the radiator in order to transmit heat generated by the arithmetic element and the light emitting element to the radiator without loss and to dissipate through the radiator. .

  As a heat conductive material used for the purpose of such heat dissipation and heat transfer, for example, a soft heat dissipation sheet is known in which a heat conductive filler is highly filled and cured in a base rubber such as silicone rubber. A technique based on a combination of various heat conductive fillers and silicone rubber is disclosed (see Patent Documents 1 to 3).

  The heat-dissipating sheet for the purpose of such heat conduction requires not only the heat conduction of the material itself, but also the heat resistance with the heat-generating body and the heat-dissipating element, so the adhesion with the heat-generating body and the heat dissipating element Is considered important. When there is only one heating element on the substrate, the distance between the heating element and the heat radiating body is almost constant. It is possible. However, if there is a plurality of heating elements on the substrate and the heat dissipation is performed by one heat dissipation element, the distance between the heating element and the heat dissipation element may not be constant. Many. Therefore, when a heat radiating sheet having a constant thickness is used, there is a problem that it is difficult to arrange a plurality of heat generating elements so as to be in contact with one heat radiating element at the same time.

  In order to solve these problems, for example, Patent Document 4 discloses a room temperature curing type heat which can be cured at room temperature after applying a liquid material highly filled with a thermally conductive filler to silicone rubber before curing. A conductive silicone rubber composition is disclosed. Since such a composition is a liquid material, the adhesion between the heating element and the radiator is very good, and it can be used even when the distance between the heating element and the radiator is not constant. To preferred. However, since it is an uncured silicone rubber composition, there is a problem that volatilization of low molecular siloxane components and cyclic siloxane components increases during use. Problems have been pointed out that silicone resins often cause poor contact of electrical components and poor reading of precision devices such as hard disks due to volatilization of cyclic siloxane, which is a low molecular component. In addition, since the curing type is a moisture curing type, curing curing requires several hours or more, so that there is a problem that productivity is inferior.

  Patent Document 5 succeeds in obtaining a flexible flame-retardant heat-dissipating sheet by polymerizing and using an acrylic oligomer having a controlled molecular weight using an innovative polymerization method called living radical polymerization. There is no specific description regarding the method of using the thermosetting heat conductive composition in a liquid state.

  Moreover, in patent document 6, although it has succeeded in obtaining a flexible heat dissipation sheet similarly to patent document 5, there exists volatility in the flame retardance used in order to provide a flame retardance, or a softness | flexibility is supplemented. Therefore, since a plasticizer is used or a silicone resin is used as a curing agent, the volatile components cannot be reduced to a range where there is no practical problem. It is not described regarding the method of utilizing as a thermosetting heat conductive composition.

Japanese Patent Publication No. 6-55891 Japanese Examined Patent Publication No. 6-38460 Japanese Patent Publication No. 7-91468 JP 2004-352947 A JP 2009-179743 A JP 2006-278476 A

  As described above, there have been various problems in the prior art in which the heat conductive curable composition or the heat conductive grease is applied to the surface of the heat generator or the heat radiator. On the other hand, when using a pre-cured heat dissipation sheet, there is a problem that it is difficult to use when the distance between the heating element and the heat dissipation element is not constant, and heat dissipation sheets of various thicknesses are prepared in advance. It is possible to cope with the difference in distance to some extent, but the workability deteriorates due to the work of pasting various sheets, and it is necessary to prepare various sheets in advance. It causes cost increase.

  The present invention has excellent heat resistance and durability, has a low possibility of contact failure due to cyclic siloxane, which has been regarded as a problem in the prior art, is easy to apply, and short in heat treatment. It is an object of the present invention to obtain a heat dissipation structure using a thermosetting heat conductive composition that can be cured in time and can efficiently transfer the heat of the heating element to the heat dissipation body.

  That is, the present invention includes a plurality of heating elements, a substrate that fixes the plurality of heating elements, a radiator that is located opposite the heating element with respect to the substrate, the heating element, the substrate, and the heat dissipation. A thermally conductive material layer in contact with the body, the thermally conductive material layer covers the surfaces of the plurality of heating elements, and the thermally conductive material layer is polymerized between carbon-carbon double bonds A heat conductive curable composition containing at least the curable vinyl polymer (I) and the heat conductive filler (II) that are cured by the above-described method is used for any of the heating element, the substrate, and the heat radiator. The present invention relates to a heat dissipation structure characterized in that it is made of a material having a thermal conductivity of 0.9 W / mK or more, which is applied after contact and cured.

  In the heat dissipating structure according to the present invention, the distance between the plurality of heat generating elements and the heat dissipating element is not constant, and the difference in distance between the state where the distance between the two is the closest and the state where the both are the farthest Is preferably 0.1 mm or more.

  Furthermore, in the heat dissipating structure according to the present invention, the heat conductive curable composition has, on average, at least one crosslinkable (meth) acryloyl group that is cured by polymerization between carbon-carbon double bonds. The polymer (I), the thermally conductive filler (II), the initiator (III) of the vinyl polymer (I), and the plasticizer (IV) having a weight average molecular weight of 100 or more and 3000 or less, and at room temperature The viscosity before curing in is preferably 50 Pa · s or more.

  Furthermore, in the heat dissipation structure according to the present invention, a heat diffusion film including a graphite film is provided between the heat conductive material layer and the heat dissipation body, and the heat conductive material layer and the heat dissipation body are interposed via the heat diffusion film. Are preferably in contact with each other.

  Here, the state in which the thermally conductive material layer covers the surfaces of the plurality of heating elements is usually that 50% or more of the surface of the plurality of heating elements other than the portion in contact with the substrate is the thermally conductive material layer. This ratio is preferably 60% or more, more preferably 70% or more, still more preferably 80% or more, particularly preferably 90% or more, and most preferably 98% or more.

  According to the present invention, a heat dissipation structure that has a short processing time, good productivity, an extremely easy design of an electronic device, an excellent heat dissipation structure, and can diffuse the heat of a heating element to the outside. The body can be provided.

It is the schematic which shows an example of the thermal radiation structure concerning this invention. Here, (a) is a schematic cross-sectional view of the heat dissipation structure, and (b) is a schematic plan view showing a heating element, a substrate, and a thermally conductive material layer as viewed from the upper surface of the heat dissipation structure. It is the schematic which shows the other example of the thermal radiation structure concerning this invention. Here, (a) is a schematic cross-sectional view of the heat dissipation structure, and (b) is a schematic plan view showing a heating element, a substrate, and a thermally conductive material layer as viewed from the upper surface of the heat dissipation structure. It is the schematic which shows the further another example of the thermal radiation structure concerning this invention. Here, (a) is a schematic cross-sectional view of the heat dissipation structure, and (b) is a schematic plan view showing a heating element, a substrate, and a thermally conductive material layer as viewed from the upper surface of the heat dissipation structure. It is the schematic which shows an example of a typical heat dissipation structure. Here, (a) is a schematic cross-sectional view of a heat dissipation structure, and (b) is a schematic plan view showing a heating element, a substrate, a heat conductive material layer, and a heat diffusion film as seen from the top surface of the heat dissipation structure. is there. It is the schematic which shows an example of a typical heat dissipation structure. Here, (a) is a schematic cross-sectional view of a heat dissipation structure, and (b) is a schematic plan view showing a heating element, a substrate, a heat conductive material layer, and a heat diffusion film as seen from the top surface of the heat dissipation structure. is there. It is the schematic which shows an example of a typical heat dissipation structure. Here, (a) is a schematic cross-sectional view of a heat dissipation structure, and (b) is a schematic plan view showing a heating element, a substrate, a heat conductive material layer, and a heat diffusion film as seen from the top surface of the heat dissipation structure. is there.

11a: heating element a, S _Ha : area of heating element a, T _Ca : outside temperature of the portion of the radiator closest to the heating element 11a, T _Ha : heating element a center temperature, 11b: heating element b, S _Hb : Area of the heating element b, T _Cb : Outer temperature of the portion of the radiator that is closest to the heating element 11b, T _Hb : Temperature at the center of the heating element b, 12: Substrate, S _S : Area of the substrate, 13: Heat dissipation Body, 14: heat conductive material layer, S _G : area of heat conductive material layer, 15: heat diffusion film, 16: graphite film, 17: adhesive layer, 18: protective film

  One embodiment of the heat dissipation structure of the present invention is described with reference to FIG. 1, including a heating element 11 a and a heating element 11 b, a substrate 12 for fixing the heating element 11, a radiator 13, and a thermally conductive material layer 14. The heat conductive material layer 14 is in contact with any of the heating elements 11a and 11b, the substrate 12, and the radiator 13, and covers the entire heating element 11.

  In the heat dissipation structure of the present embodiment, since the heating element 11 is covered with the heat conductive material layer 14 without coming into contact with air, the heat generated in the heating element is transmitted from the entire surface of the heating element to the radiator 13. Compared with the case where the heat conductive material layer 14 is in contact with only the top surface of the heating element, the heat transfer efficiency can be increased, and the temperature of the heating element can be kept lower. Further, since the heat conductive material layer 14 is a curable composition that can be applied, even when the distances between the plurality of heating elements 11a and 11b and the radiator 13 are not constant, the heat generated from both heating elements is efficiently obtained. It can be well transmitted to the radiator 13 and escaped.

  By using the curable composition which can be applied as the heat conductive material layer, the heat dissipating structure of the present embodiment can absorb the variation even when the dimension varies due to the tolerance of the heating element.

  Furthermore, the heat dissipation structure of the present embodiment employs a construction method in which the thermally conductive material layer is applied and cured after applying the curable composition that can be applied to any of the heating element, the substrate, and the radiator. As a result, not only when the height of the heating element varies, but also the liquid material can absorb the variation in dimensions due to the tolerance of the heating element, so even if there is variation in the height of the heating element, the heat diffusion film Can be made to follow the shape of the heating element, and a planar heat radiator can be used as it is. In addition, by using a thermally conductive curable composition that can be applied to the thermally conductive material layer, the thermal conductive material layer and the heating element can be securely adhered to each other, greatly reducing the thermal resistance between them. Will be.

  The form of the radiator 13 is not particularly limited, and is not limited to a form in which the substrate 12 covers the heating element 11 and the heat conductive material layer 14 as shown in FIG. It may be a form that is connected to. Moreover, as shown in FIG. 3, the structure which the heat radiator 11 and the board | substrate 12 whole cover with the heat radiator 13, ie, the structure where a heat radiator serves as a housing | casing, may be sufficient.

<Temperature of heating element>
The temperature of the heating element becomes lower as the heat generated from the heating element is efficiently transferred to the heat radiating body. The temperature of the heating element is preferably 130 ° C. or less, more preferably 120 ° C., and still more preferably 111 ° C. or less from the viewpoint of setting the temperature to the heat resistant temperature or less. If the temperature is 130 ° C. or higher, the function of the semiconductor element forming the heating element may become dull or malfunction. Depending on the electronic device, the heat-resistant temperature of the heating element may be limited to 120 ° C. or less.

<Distance between heating element and radiator>
As the distance between the heat generating element and the heat dissipating element increases, the thermal resistance increases and the temperature of the heat generating element increases. Therefore, it is important to select the distance between the heat generating body and the heat radiating body so that the temperature of the heat generating body does not become too high.

  The distance between the heating element and the radiator of the present invention is greater than 0 mm and 6.0 mm or less, preferably 0.01 mm or more and 5.0 mm or less, more preferably 0.03 mm or more and 3.0 mm or less. When the distance between the heat generating element and the heat radiating element is larger than 6.0 mm, the temperature of the heat generating element becomes too high because the temperature of the heat generating element cannot be efficiently transmitted to the heat radiating element. In addition, when the distance between the heating element and the radiator is 0 mm, that is, in direct contact with each other, there is no installation space for the heat conductive material layer, so that the variation in dimensions due to the tolerance of the heating element cannot be absorbed, and the thermal resistance is reduced. Reduction effect is small.

<Wattage of heating element>
The output (wattage) of the heating element of the present invention is 100 W or less, preferably 80 W or less, more preferably 50 W or less. When the output of the heating element is greater than 100 W, it is difficult to sufficiently release the heat of the heating element, so that the temperature of the heating element may rise to the heat resistant temperature or higher.

<Number of heating elements>
The present invention is capable of efficiently radiating heat even when a plurality of heating elements 11 are mounted on the substrate 12. Even when there is only one heating element on the substrate, it is possible to efficiently release heat by using the highly heat conductive curable composition as used in the present invention.
The distances between the plurality of heating elements and the radiators may be the same or different. Even if the distance between each heating element and the radiator is the same in design, the distance between the heating element and the heating element will be very small during actual use due to errors during installation, dimensional tolerance of the heating element, and variations in dimensions. Since a difference may arise, it is possible to cover the difference in the distance between a plurality of heat generating elements and a heat radiating element by using a highly heat conductive curable composition. However, if there is a slight dimensional variation, heat may be released with substantially the same efficiency even if a general heat radiating sheet is used. However, as the distance between each of the plurality of heating elements and the radiator increases, the workability for bonding various sheets deteriorates, and by increasing the adhesion surface between the sheets, air can be easily caught between the sheets. As a result, there is a problem that the thermal conductivity is lowered. Moreover, although it is not certain, at the time of sheet bonding, it is considered that the thermal conductivity is hindered by the bonding between the skins on the sheet surface. Therefore, the greater the difference in the distance between each of the plurality of heating elements and the radiator, the clearer the effect of the heat dissipation structure using the highly thermally conductive curable composition of the present case. When the difference between these distances is 0.1 mm or more, the effect of the high thermal conductive curable composition becomes clearer, which is preferable. When the distance between the plurality of heating elements and the radiator is not constant, the difference between the distance between the closest state and the farthest state is more preferably 0.2 mm or more, It is more preferably 0.5 mm or more, particularly preferably 1.0 mm or more, and most preferably 1.5 mm or more.

<Material of radiator>
Referring to FIG. 1, the material of the heat dissipating body 13 is preferable because the heat dissipating efficiency is increased as the material has higher thermal conductivity. Examples of preferable materials for the radiator include high heat conductive metals such as aluminum, copper and magnesium, high heat conductive carbon materials such as graphite and diamond, and high heat conductive ceramics such as alumina, aluminum nitride and silicon nitride. However, the present invention is not limited to these. The heat conductivity of the radiator is preferably 15 W / mK or more, more preferably 20 W / mK or more, further preferably 30 W / mK or more, and most preferably 100 W / mK or more, in order to improve heat dissipation. .

<Thermal conductive material layer>
Referring to FIG. 1, the heat conductive material layer 14 is in contact with any of the heat generating body 11, the substrate 12, and the heat radiating body 13, so that the entire heat generating body is covered with the heat conductive material layer. These contact surfaces need to be in close contact so that the thermal resistance is as small as possible. Thereby, the heat generated from the heating element can be efficiently transmitted to the heat radiating body. As the material of the heat conductive material layer, the heat resistance between the heat conductive material layer and the heating element / substrate / heat radiator is very small by curing after applying the heat conductive curable composition. Is possible.

<Thermal conductivity of the thermally conductive material layer>
Since the heat conductive material layer needs to conduct heat to the outside efficiently, it is necessary to use a material having high heat conductivity. Specifically, the thermal conductivity is 0.9 W / mK or more, preferably 1.0 W / mK or more, and more preferably 1.2 W / mK or more. By using such a high thermal conductivity material, it is possible to efficiently release the heat of the heating element as compared with the case where the heating element is in contact with air. In the case of using a curable composition as the material, the thermal conductivity measurement of the thermally conductive material layer is performed after sufficiently curing the material, and then hot disk method thermal conductivity measuring device TPA-501 manufactured by Kyoto Electronics Industry Co., Ltd. Can be measured at 23 ° C. by a method in which a 4φ size sensor is sandwiched between two disc-shaped samples having a thickness of 3 mm and a diameter of 20 mm.

<Viscosity of heat conductive material layer before curing>
The thermally conductive material layer is preferably coated with a curable composition having a fluidity but a relatively high viscosity having a viscosity before curing at room temperature of 50 Pa · s or more. When the viscosity before curing is low, such as 50 Pa · s or less, referring to FIG. The problem that property will fall arises. The viscosity before curing is preferably 100 Pa · s or more, more preferably 300 Pa · s or more, and most preferably 500 Pa · s or more. As the viscosity before curing, a value measured under the condition of 2 rpm using a BS type viscometer in an atmosphere of 23 ° C. is used. The upper limit of the viscosity before curing is not particularly limited, but if the viscosity is too high, application may be difficult, or air may be entrained during application, which may cause a decrease in thermal conductivity. Therefore, generally, a material having a viscosity of 10,000 Pa · s or less, preferably 6000 Pa · s or less is used.

<Heat conductive curable composition>
The thermally conductive curable composition comprises at least a curable vinyl polymer (I) that is cured by polymerization between carbon-carbon double bonds, and a thermally conductive filler (II). Is used. In addition to these, the radical initiator (III) for curing the curable liquid resin, the plasticizer (IV) having a weight average molecular weight of 100 or more and 3000 or less, or the heat conductive curable composition, if necessary. A heat aging inhibitor, a bulking agent, a thixotropic agent, an adhesion promoter, a dehydrating agent, a coupling agent, an ultraviolet absorber, an electromagnetic wave absorber, a filler, a solvent, and the like may be added.

  In this case, it is preferable from the viewpoint of productivity to use a thermally conductive curable composition by curing by polymerization of a carbon-carbon double bond. By using the composition, the processing time can be significantly shortened.

<Curable vinyl polymer>
As the curable vinyl polymer, a curable vinyl polymer having a reactive group in the molecule is used. Specific examples of the curable vinyl polymer include a curable acrylic resin and a curable methacrylic resin. Various reactive functional groups such as epoxy groups, hydrolyzable silyl groups, vinyl groups, acryloyl groups, SiH groups, urethane groups, carbodiimide groups, combinations of carboxylic anhydride groups and amino groups are used as reactive groups. be able to. When these are cured by a combination of two types of reactive groups, or by reaction of reactive groups with a curing catalyst, after preparing as a two-component composition, two components are applied when applied to a substrate or heating element. Curability can be obtained by mixing. Alternatively, in the case of a curable resin having a hydrolyzable silyl group, it can be cured by reacting with moisture in the air, so that it can be a one-component room temperature curable composition. In the case of a combination of a vinyl group, a SiH group, and a Pt catalyst, or in the case of a combination of a radical initiator and an acryloyl group, a one-component curable composition or a two-component curable composition is used, and then crosslinked. It can also be cured by heating to a temperature or applying crosslinking energy such as ultraviolet rays or electron beams.

  In this case, since it is easy to heat the whole heat dissipation structure to some extent, it is preferable to use a thermosetting composition. In the moisture curable composition, since the curing type is moisture curing, curing curing requires several hours or more, and thus the workability and productivity may be inferior.

<Curable vinyl resin>
Among the curable vinyl resins, it is preferable to use a curable acrylic resin because there is no problem of contamination in electronic equipment due to low molecular weight siloxane, and excellent heat resistance. As the curable acrylic resin, various known reactive acrylic resins can be used. Among these, it is preferable to use an acrylic oligomer having a reactive group at the molecular end. As these curable acrylic resins, a combination of a radical initiator and a curable acrylic resin produced by living radical polymerization, especially atom transfer radical polymerization, can be most preferably used. As an example of such a resin, Kaneka XMAP manufactured by Kaneka Corporation is well known.

<Curable vinyl resin having a (meth) acryloyl group at the terminal and a radical initiator>
Among the curable vinyl resins, the vinyl polymer of (I) has at least one crosslinkable (meth) acryloyl group per molecule at both ends or one end, and of those at the molecular ends. What can obtain the curable composition which can be hardened | cured by heat-processing by using the vinyl polymer (I) which is 0.8 or more on average, and initiator (III) is preferable. . The number of crosslinkable (meth) acryloyl groups in the vinyl polymer (I) is not particularly limited, but from the viewpoint of crosslinking, the average number of (meth) acryloyl groups is 1. 0 or more are preferable and 1.1 or more are more preferable. The upper limit is preferably 2.0 or less per molecule from the viewpoint of becoming flexible when cured.

  The initiator is not particularly limited, and examples thereof include a photopolymerization initiator, a thermal polymerization initiator, and a redox initiator. The photopolymerization initiator, the thermal polymerization initiator, and the redox initiator may be used alone or as a mixture of two or more. When used as a mixture, various initiators are used. It is preferable that the usage-amount of an agent exists in each below-mentioned range.

  As a photoinitiator, a photoradical initiator, a photoanion initiator, a near-infrared photoinitiator, etc. are mentioned, A photoradical initiator and a photoanion initiator are preferable, and a photoradical initiator is particularly preferable. Examples of the photo radical initiator include acetophenone, propiophenone, benzophenone, xanthol, fluorin, benzaldehyde, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4-methylacetophenone, 3-pentylacetophenone, 2, 2-diethoxyacetophenone, 4-methoxyacetophenone, 3-bromoacetophenone, 4-allylacetophenone, p-diacetylbenzene, 3-methoxybenzophenone, 4-methylbenzophenone, 4-chlorobenzophenone, 4,4′-dimethoxybenzophenone, 4 -Chloro-4'-benzylbenzophenone, 3-chloroxanthone, 3,9-dichloroxanthone, 3-chloro-8-nonylxanthone, benzoin, benzoy Methyl ether, benzoin butyl ether, bis (4-dimethylaminophenyl) ketone, benzylmethoxy ketal, 2-chlorothioxanthone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl- Phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl Examples include 2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, dibenzoyl and the like. Among these, α-hydroxy ketone compounds (for example, benzoin, benzoin methyl ether, benzoin butyl ether, 1-hydroxy-cyclohexyl-phenyl-ketone, etc.), phenyl ketone derivatives (for example, acetophenone, propiophenone, benzophenone, 3-methyl) Acetophenone, 4-methylacetophenone, 3-pentylacetophenone, 2,2-diethoxyacetophenone, 4-methoxyacetophenone, 3-bromoacetophenone, 4-allylacetophenone, 3-methoxybenzophenone, 4-methylbenzophenone, 4-chlorobenzophenone, 4,4′-dimethoxybenzophenone, 4-chloro-4′-benzylbenzophenone, bis (4-dimethylaminophenyl) ketone, etc.) are preferred.

  Examples of the photoanion initiator include 1,10-diaminodecane, 4,4′-trimethylenedipiperazine, carbamates and derivatives thereof, cobalt-amine complexes, aminooxyiminos, ammonium borates and the like. .

  As the near infrared photopolymerization initiator, a near infrared light absorbing cationic dye or the like may be used. As the near-infrared light absorbing cationic dye, near-infrared light which is excited by light energy in the region of 650 to 1500 nm, for example, disclosed in JP-A-3-111402, JP-A-5-194619, etc. It is preferable to use an absorbing cationic dye-borate anion complex or the like, and it is more preferable to use a boron sensitizer together.

These photopolymerization initiators may be used alone or in combination of two or more, or may be used in combination with other compounds. Specific examples of combinations with other compounds include combinations with amines such as diethanolmethylamine, dimethylethanolamine, and triethanolamine, and combinations with iodonium salts such as diphenyliodonium chloride, methylene blue, and the like. Examples include those combined with a dye and an amine.
In addition, when using the said photoinitiator, polymerization inhibitors, such as hydroquinone, hydroquinone monomethyl ether, benzoquinone, para tertiary butyl catechol, can also be added as needed.

  (III) When using a photoinitiator as a component, the addition amount does not have a restriction | limiting in particular, However, 0.001-10 with respect to 100 weight part of (I) component from the point of sclerosis | hardenability and storage stability. Part by weight is preferred. More preferably, it is about 0.025 to 7 parts by weight.

  Further, the thermal polymerization initiator is not particularly limited, and examples thereof include azo initiators, peroxide initiators, persulfate initiators and the like. Suitable peroxide initiators include, but are not limited to, benzoyl peroxide, acetyl peroxide, lauroyl peroxide, decanoyl peroxide, and the like.

  Suitable persulfate initiators include, but are not limited to, potassium persulfate, sodium persulfate, ammonium persulfate, and the like.

  A preferable thermal polymerization initiator is selected from the group consisting of an azo initiator and a peroxide initiator. More preferred are 2,2'-azobis (methylisobutylate), t-butyl peroxypivalate, di (4-t-butylcyclohexyl) peroxydicarbonate, and mixtures thereof.

  A thermal polymerization initiator may be used independently or may use 2 or more types together. When a thermal polymerization initiator is used as the component (III), the thermal polymerization initiator is present in a catalytically effective amount, and the amount added is not particularly limited, but is 100 parts by weight of the component (I) of the present invention. In some cases, it is preferably about 0.001 to 10 parts by weight, more preferably about 0.025 to 7 parts by weight.

  Furthermore, the redox (redox) initiator that can be used as the component (III) can be used in a wide temperature range. In particular, the following initiator species can be advantageously used at room temperature. Suitable redox initiators include, but are not limited to, combinations of the above persulfate initiators and reducing agents (sodium metabisulfite, sodium bisulfite, etc.); organic peroxides and tertiary amines. Combinations such as a combination of benzoyl peroxide and dimethylaniline, a combination of cumene hydroperoxide and anilines; a combination of organic peroxide and transition metal, such as a combination of cumene hydroperoxide and cobalt naphthate, and the like. Preferred redox initiators are a combination of organic peroxide and tertiary amine, a combination of organic peroxide and transition metal, and more preferably a combination of cumene hydroperoxide and anilines, cumene hydroperoxide. And cobalt naphthate.

  A redox initiator may be used independently or may use 2 or more types together. When a redox initiator is used as component (III), the redox initiator is present in a catalytically effective amount, and the amount added is not particularly limited, but is 100 parts by weight of component (I) of the present invention. In some cases, it is preferably about 0.001 to 10 parts by weight, more preferably about 0.025 to 7 parts by weight.

<Thermal conductive filler>
As the heat conductive filler (II) used in the heat conductive curable composition, a commercially available general good heat conductive filler can be used. Among them, carbon compounds such as graphite, diamond, and the like from various viewpoints such as thermal conductivity, availability, electrical insulating properties, electromagnetic shielding properties and electromagnetic wave absorption properties, filling properties, toxicity, etc .; aluminum oxide Metal oxides such as magnesium oxide, beryllium oxide, titanium oxide, zirconium oxide, and zinc oxide; metal nitrides such as boron nitride, aluminum nitride, and silicon nitride; metal carbides such as boron carbide, aluminum carbide, and silicon carbide; Metal hydroxides such as aluminum and magnesium hydroxide; metal carbonates such as magnesium carbonate and calcium carbonate; crystalline silica: calcined acrylonitrile polymer, calcined furan resin, calcined cresol resin, calcined polyvinyl chloride, sugar Baked product of organic polymer such as baked product of charcoal, baked product of charcoal; Zn ferrite Composite ferrite; Fe-Al-Si ternary alloy; metal powders, and the like preferably.

  Further, from the viewpoint of availability and thermal conductivity, graphite, aluminum oxide, magnesium oxide, boron nitride, aluminum nitride, silicon carbide, aluminum hydroxide, magnesium carbonate, and crystallized silica are more preferable, graphite, α-alumina, hexagonal Crystalline boron nitride, aluminum nitride, aluminum hydroxide, Mn—Zn soft ferrite, Ni—Zn soft ferrite, Fe—Al—Si ternary alloy (Sendust), carbonyl iron, iron nickel alloy (Permalloy) are more preferable Spheroidized graphite, round or spherical α-alumina, spheroidized hexagonal boron nitride, aluminum nitride, aluminum hydroxide, Mn—Zn soft ferrite, Ni—Zn soft ferrite, spherical Fe—Al—Si three Original alloy (Sendust), Carboni Particularly preferred is iron. When carbonyl iron is used in the present invention, reduced carbonyl iron powder is desirable. The reduced carbonyl iron powder is not a standard grade but a carbonyl iron powder classified into a reduced grade, and is characterized by a lower carbon and nitrogen content than the standard grade.

  In addition, these thermally conductive fillers are improved in dispersibility with respect to the resin, so that silane coupling agents (vinyl silane, epoxy silane, (meth) acryl silane, isocyanate silane, chlorosilane, aminosilane, etc.) and titanate coupling are used. Agents (alkoxy titanate, amino titanate, etc.) or fatty acids (caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, etc., sorbic acid, elaidic acid, oleic acid , Linoleic acid, linolenic acid, erucic acid and other unsaturated fatty acids) and resin acids (abietic acid, pimaric acid, levopimaric acid, neoapitic acid, parastrinic acid, dehydroabietic acid, isopimaric acid, sandaracopimaric acid, cormic acid, Secodehydroabietic acid, The hydroabietic acid) or the like, it is preferable that the surface has been treated.

  The amount of the heat conductive filler used is such that the heat conductivity of the heat conductive material obtained from the composition of the present invention can be increased, so that the volume ratio (%) of the heat conductive filler is high. Is preferably 25% by volume or more of the total composition. If it is less than 25% by volume, the thermal conductivity tends to be insufficient. When a higher thermal conductivity is desired, the amount of the thermally conductive filler used is more preferably 30% by volume or more in the total composition, more preferably 40% by volume or more, and 50% by volume. The above is particularly preferable. Moreover, it is preferable that the volume ratio (%) of a heat conductive filler becomes 90 volume% or less in the whole composition. When it is more than 90% by volume, the viscosity of the thermally conductive material layer before curing may become too high.

Here, the volume fraction (%) of the thermally conductive filler is calculated from the weight fraction and specific gravity of the resin component and the thermally conductive filler, and is obtained by the following equation. In the following formula, the thermally conductive filler is simply referred to as “filler”.
Filler volume ratio (volume%) = (filler weight ratio / filler specific gravity) ÷ [(resin weight ratio / resin weight specific gravity) + (filler weight ratio / filler specific gravity)] × 100
Here, the resin component refers to all components excluding the thermally conductive filler.

  Further, as one method for increasing the filling rate of the heat conductive filler to the resin, it is preferable to use two or more kinds of heat conductive fillers having different particle diameters in combination. In this case, it is preferable that the particle size ratio of the heat conductive filler having a large particle diameter and the heat conductive filler having a small particle diameter is about 100/5 to 100/20.

  These thermally conductive fillers can be used not only in the same type of thermally conductive filler, but also in combination of two or more different types. Moreover, you may use various fillers other than a heat conductive filler as needed to such an extent that the effect of this invention is not prevented. Various fillers other than the heat conductive filler are not particularly limited, but wood powder, pulp, cotton chips, asbestos, glass fiber, carbon fiber, mica, walnut shell powder, rice husk powder, diatomaceous earth, white clay, silica (Fumed silica, precipitated silica, fused silica, dolomite, silicic anhydride, hydrous silicic acid, amorphous spherical silica, etc.), reinforcing filler such as carbon black; diatomaceous earth, calcined clay, clay, talc, Titanium oxide, bentonite, organic bentonite, ferric oxide, aluminum fine powder, flint powder, activated zinc white, zinc powder, zinc carbonate and shirasu balloon, glass microballoon, organic microballoon of phenol resin and vinylidene chloride resin, PVC powder Fillers such as resin powder such as PMMA powder; asbestos, glass fiber and glass filament, Carbon fiber, Kevlar fiber, fibrous fillers such as polyethylene fiber and the like. Of these fillers, precipitated silica, fumed silica, fused silica, dolomite, carbon black, titanium oxide, talc and the like are preferable. Some of these fillers have a slightly function as a heat conductive filler, and the composition, such as carbon fiber, various metal powders, various metal oxides, various organic fibers, Some synthesis methods, crystallinity, and crystal structures can be used as excellent heat conductive fillers.

<Plasticizer>
The plasticizer (IV) contained in the thermally conductive curable composition used for the thermally conductive material layer of the present invention is not particularly limited, but for the purpose of adjusting physical properties and properties, for example, dibutyl phthalate. , Phthalates such as diheptyl phthalate, di (2-ethylhexyl) phthalate, diisodecyl phthalate, butyl benzyl phthalate; non-aromatic dibasic esters such as dioctyl adipate, dioctyl sebacate, dibutyl sebacate, isodecyl succinate Aliphatic esters such as butyl oleate and methyl acetylricinolinate; esters of polyalkylene glycols such as diethylene glycol dibenzoate, triethylene glycol dibenzoate and pentaerythritol ester; tricresyl phosphate, tributyl phosphate Phosphates such as carbonate; trimellitic acid esters; polystyrenes such as polystyrene and poly-α-methylstyrene; polybutadiene, polybutene, polyisobutylene, butadiene-acrylonitrile, polychloroprene; chlorinated paraffins; alkyldiphenyl, Partially hydrogenated terphenyl and other hydrocarbon oils; process oils; polyethylene glycol, polypropylene glycol, ethylene oxide-propylene oxide copolymers, polyether polyols such as polytetramethylene glycol, and hydroxyl groups of these polyether polyols Polyethers such as alkyl derivatives in which the terminal or both terminals or all terminals are converted to alkyl ester groups or alkyl ether groups; Epoxidized soybean oil, epoxy benzyl stearate Epoxy group-containing plasticizers such as E-PS; dibasic alcohols such as sebacic acid, adipic acid, azelaic acid, and phthalic acid, and dihydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and dipropylene glycol Polyester plasticizers obtained from the following: vinyl polymers obtained by polymerizing vinyl monomers including acrylic plasticizers by various methods, and the like. These can be used alone or in admixture of two or more.

  The amount of the plasticizer (IV) used is preferably 5 to 800 parts by weight with respect to 100 parts by weight of the curable vinyl polymer (I) from the viewpoint of imparting elongation, workability, and preventing bleeding from the cured product.

  Moreover, as a property of the plasticizer used, it is desirable that a weight average molecular weight is 100 or more and 3000 or less. Preferably, it is 200 or more and 2000 or less. If it is 100 or less, the molecular weight is too low, the plasticizer flows out with time due to heat, and the initial physical properties cannot be maintained for a long time in many cases. Moreover, when molecular weight is too high, the viscosity of a curable composition will become high and workability | operativity will worsen.

  <Heat diffusion film> As another embodiment of the present invention, a heat diffusion film exists between the heat conductive material layer and the heat radiating body, and the heat conductive material layer and the heat radiating body are in contact with each other through the heat diffusion film. Also good. By using such a heat dissipation structure, the heat of the heating element can be transferred to the heat dissipation body after spreading in the lateral direction, so the heat dissipation efficiency is remarkably improved, and both the temperature of the heating element and the heat dissipation body It can be kept low. When the heat diffusion film is used, the area of the heat diffusion film is preferably as large as possible with respect to the area of the heat radiating body to which the heat diffusion film is attached.

<Graphite film>
As the heat diffusion film of the present invention, a film containing a graphite film is preferably used. The graphite film has a feature that it has a higher thermal conductivity in the plane direction than in the thickness direction. The thermal conductivity in the plane direction of the graphite film is 50 W / mK or more, preferably 100 W / mK or more, more preferably 200 W / mK or more, and most preferably 500 W / mK or more. On the other hand, the thermal conductivity in the thickness direction of the graphite film is 30 W / mK or less, preferably 20 W / mK or less, more preferably 10 W / mK or less. If the thermal conductivity in the thickness direction of the graphite film is greater than 30 W / mK, the heat generated from the heat generator is directly transmitted to the heat radiator before it diffuses. On the other hand, if the thermal conductivity in the thickness direction is 30 W / mK or less, it is preferable because the ratio of releasing the heat transmitted from the heating element in the thickness direction without much transmission is increased.

<Thermal diffusivity of graphite film>
The thermal diffusivity in the plane direction of the graphite film was measured by cutting the graphite film into a 4 mm × 40 mm sample shape using a thermal diffusivity measuring device (LacerPit manufactured by ULVAC-RIKO Co., Ltd.) by an optical alternating current method, and an atmosphere of 20 ° C. The measurement was performed at 10 Hz below. For measuring the thermal diffusivity in the thickness direction of the graphite film, LFA-502 manufactured by Kyoto Electronics Industry Co., Ltd. was used and measured by the laser flash method. The graphite film was cut to a diameter of 10 mm, and both sides of the film were blackened, and then the thermal diffusivity in the thickness direction was measured by a laser flash method at room temperature. Further, the heat capacity of the graphite film is calculated from a comparison with a reference standard substance Mo having a known heat capacity, and together with the density measured separately, the following formula (1)
λ = α × d × C _p (1)
Calculated from In Equation (1), λ represents thermal conductivity, α represents thermal diffusivity, d represents density, and C _p represents specific heat capacity.

<Protective film to be bonded to graphite film>
In some cases, the graphite film may fall off and contaminate the inside of the equipment. Moreover, since the graphite film exhibits electrical conductivity, there is a risk of causing a short circuit of the electronic device substrate. For these reasons, it is preferable that the graphite film of the present invention is used by being bonded to a protective film. The protective film is preferably a film in which an acrylic, silicone-based, epoxy-based, or polyimide-based adhesive or adhesive is formed on one surface of a film such as polyimide, polyethylene terephthalate, polyethylene, polypropylene, or polyester. Further, it may be a hot-melt type (thermoplastic) film such as polyester. A tape having a high thermal emissivity is preferable because the amount of heat transfer in non-contact increases when bonded. The resin tape has a low thermal conductivity, so it should be thin. In addition, about the surface which is in contact with the heat conductive material layer among heat diffusion films, since there is little possibility of causing the powder fall of a graphite film or a short circuit, it is not necessary to use a protective film. Although it is preferable not to use a protective film because the thermal conductivity is improved, it is necessary to remove only a part of the protective film at the time of manufacturing the heat diffusion film, which may cause an increase in production cost.

<Adhesive layer to be bonded to graphite film>
The heat diffused by the heat diffusing film including the graphite film is preferably used by being attached to the heat radiating body with an adhesive layer such as an adhesive or an adhesive. The material of the adhesive or adhesive used as the adhesive layer in the present invention is an acrylic, silicone, epoxy, or polyimide resin. Since such adhesives and adhesives have poor thermal conductivity, the adhesive layer should basically be thin.

<Method for producing graphite film>
The first method for producing a graphite film preferably used in the present invention is a graphite film obtained by pressing graphite powder into a sheet. In order for the graphite powder to be formed into a film, the powder needs to be in the form of flakes or scales. The most common method for producing such graphite powder is a method called an expanded (expanded graphite) method. In this method, graphite is immersed in an acid such as sulfuric acid to produce a graphite intercalation compound, which is then heat treated and foamed to separate the graphite layers. After peeling, the graphite powder is washed to remove the acid to obtain a thin film graphite powder. The graphite powder obtained by such a method is further subjected to rolling roll molding to obtain film-like graphite. The graphite film produced using expanded graphite obtained by such a method is flexible and has a high thermal conductivity in the film surface direction, so that it is preferably used for the purpose of the present invention.

  The second method for producing a graphite film preferably used in the present invention is produced by heat treatment of at least one resin selected from the group consisting of polyimide resin, polyparaphenylene vinylene resin, and polyoxadiazole resin. It is a thing. The resin most commonly used in this method is a polyimide resin. In the graphitization of resin films such as polyimide, the resin film that is a starting material is carbonized in nitrogen gas in a temperature range of about 1000 ° C. for about 30 minutes, and then argon is added. It can be obtained by graphitizing at least at a temperature of 2400 ° C. or higher, preferably 2700 ° C. or higher, more preferably 2800 ° C. or higher in an inert gas.

  The heat dissipating structure of the present invention can be used in an apparatus having a heating element inside, for example, an electronic device, a precision machine, an automobile and the like. In particular, it is suitable for small mobile devices such as mobile phones, notebook computers, and digital cameras among electronic devices.

  Embodiments and effects of the present invention will be described below with reference to examples, but the present invention is not limited thereto. In the following description, “part” means “part by weight” unless otherwise specified.

<Thermal conductive material layer>
[Synthesis Example 1 of Curable Acrylic Resin]
Synthesis example of n-butyl acrylate with both ends of acryloyl group: polymerization of n-butyl acrylate using cuprous bromide as catalyst, pentamethyldiethylenetriamine as ligand and diethyl-2,5-dibromoadipate as initiator Thus, a terminal bromine group poly (n-butyl acrylate) having a number average molecular weight of 22500 and a molecular weight distribution of 1.15 was obtained. 300 g of this polymer was dissolved in N, N-dimethylacetamide (300 mL), 8.3 g of potassium acrylate was added, and the mixture was heated and stirred at 70 ° C. for 3 hours in a nitrogen atmosphere. Butyl) (hereinafter referred to as polymer [1]) was obtained. N, N-dimethylacetamide in this mixed solution was distilled off under reduced pressure, toluene was added to the residue, and insolubles were removed by filtration. Toluene in the filtrate was distilled off under reduced pressure to purify the polymer [1]. The purified polymer [1] had a number average molecular weight of 22,800, a molecular weight distribution of 1.15, and an average terminal acryloyl group number of 2.0.

[Synthesis example 2 of curable acrylic resin]
Example of synthesis of n-butyl acrylate having one end of acryloyl group: polymerization of n-butyl acrylate using cuprous bromide as catalyst, pentamethyldiethylenetriamine as ligand and ethyl 2-bromobutyrate as initiator One-terminal bromine group poly (n-butyl acrylate) having an average molecular weight of 11800 and a molecular weight distribution of 1.08 was obtained. 1050 g of this polymer was dissolved in N, N-dimethylacetamide (1050 g), 19.7 g of potassium acrylate was added, and the mixture was heated and stirred at 70 ° C. for 3 hours in a nitrogen atmosphere to give poly (acrylic acid n-acrylate) with a acryloyl group at one end. Butyl) (hereinafter referred to as polymer [2]) was obtained. N, N-dimethylacetamide in this mixed solution was distilled off under reduced pressure, toluene was added to the residue, and insolubles were removed by filtration. The toluene in the filtrate was distilled off under reduced pressure to purify the polymer [2]. The number average molecular weight of the purified acryloyl group single terminal polymer [2] was 11900, the molecular weight distribution was 1.09, and the average terminal acryloyl group number was 0.90.

<Thermal conductive material layer>
[Production Example 1 of thermally conductive curable composition]
50 parts of the polymer [1] obtained in Synthesis Example 1, 50 parts of the polymer [2] obtained in Synthesis Example 2, 500 parts of BF-083 (aluminum hydroxide, Nippon Light Metal), 1 type of zinc oxide ( Zinc oxide (manufactured by Sakai Chemical Industry) 380 parts, Niper BW (benzoyl peroxide, manufactured by NOF Corporation) 1 part, TCP (tricresyl phosphate, manufactured by Daihachi Chemical Co., Ltd.) 100 parts, Adekastab AO-60 (pentaerythritol tetrakis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], made by ADEKA), mixed well, kneaded through three rolls three times, and thermally conductive material layer A composition A was obtained.
The composition A for heat conductive material was pressed at 150 ° C. for 15 minutes to obtain a heat radiation sheet having a thickness of 3 mm. The obtained heat radiation sheet had a thermal conductivity of 2.1 W / mK.

<Thermal conductive material layer>
[Production Example 2 of thermally conductive curable composition]
50 parts of the polymer [1] obtained in Synthesis Example 1, 50 parts of the polymer [2] obtained in Synthesis Example 2, 670 parts of BF-083 (aluminum hydroxide, Nippon Light Metal), perbutyl I (t- 4 parts butyl peroxyisopropyl monocarbonate, manufactured by NOF Corporation, 100 parts UP1021 (non-functional group type acrylic polymer, manufactured by Toagosei Co., Ltd.), ADK STAB AO-60 (pentaerythritol tetrakis [3- (3,5-di-t) -Butyl-4-hydroxyphenyl) propionate], made by Adeka), and mixed well, and further kneaded by passing three times through three rolls to obtain composition B for a heat conductive material layer. The composition B for a heat conductive material layer was pressed at 150 ° C. for 15 minutes to obtain a heat radiation sheet having a thickness of 3 mm. The obtained heat radiation sheet had a thermal conductivity of 1.7 W / mK.

<Thermal conductive material layer>
[Production Example 3 of thermally conductive curable composition]
50 parts of the polymer [1] obtained in Synthesis Example 1, 50 parts of the polymer [2] obtained in Production Example 2, 260 parts of PTX-60 (spherical boron nitride, manufactured by Momentive Performance Materials), perbutyl I ( 1 part of t-butyl peroxyisopropyl monocarbonate (manufactured by NOF Corporation), 100 parts of TCP (tricresyl phosphate, manufactured by Daihachi Chemical), ADK STAB AO-60 (pentaerythritol tetrakis [3- (3,5-di-t) -Butyl-4-hydroxyphenyl) propionate], made by Adeka), and mixed well, and further kneaded by passing three times through three rolls to obtain composition C for heat conductive material layer. The composition B for a heat conductive material layer was pressed at 150 ° C. for 15 minutes to obtain a heat radiation sheet having a thickness of 3 mm. The obtained heat radiation sheet had a thermal conductivity of 4.5 W / mK.

  The formulation and thermal conductivity of the compositions A to C for the heat conductive material layer are summarized in Table 1 below.

<Measurement of thermal conductivity of thermal conductive material layer by hot disk method>
Using a hot disk method thermal conductivity measuring device TPA-501 (manufactured by Kyoto Electronics Industry Co., Ltd.), a 4φ size sensor is sandwiched between two disk-shaped samples having a thickness of 3 mm and a diameter of 20 mm. The thermal conductivity was measured. When a curable composition was used as the thermally conductive material layer, the thermal conductivity was measured using the heat-dissipating sheet prepared in the production example of the thermally conductive curable composition.

<Graphite film> [Graphite film A]
[Preparation of Polyimide Film A] In a DMF (dimethylformamide) solution in which 1 equivalent of 4,4′-oxydianiline is dissolved, 1 equivalent of pyromellitic dianhydride is dissolved to obtain a polyamic acid solution (18.5). Mass%).

  While this solution was cooled, an imidation catalyst containing 1 equivalent of acetic anhydride, 1 equivalent of isoquinoline, and DMF was added to the carboxylic acid group contained in the polyamic acid to degas. Next, this mixed solution was applied onto an aluminum foil so as to have a predetermined thickness after drying. The mixed solution layer on the aluminum foil was dried using a hot air oven and a far infrared heater.

The drying conditions for film production when the finished thickness is 75 μm are shown below. The mixed solution layer on the aluminum foil was dried in a hot air oven at 120 ° C. for 240 seconds to form a self-supporting gel film. The gel film is peeled off from the aluminum foil, fixed to the frame, and heated in a hot air oven at 120 ° C. for 30 seconds, 275 ° C. for 40 seconds, 400 ° C. for 43 seconds, 450 ° C. for 50 seconds, and further with a far infrared heater 460 It was dried by heating stepwise at 23 ° C. for 23 seconds. As described above, a polyimide film A having a thickness of 75 μm (elasticity 3.1 GPa, water absorption 2.5%, birefringence 0.10, linear expansion coefficient 3.0 × 10 ⁻⁵ ° C. ⁻¹ ) was produced. .

[Production of Carbonized Film A]
A 75 μm-thick polyimide film A is sandwiched between graphite plates, heated to 1000 ° C. in a nitrogen atmosphere using an electric furnace, and then heat-treated at 1000 ° C. for 1 hour for carbonization treatment (carbonization treatment). Film A was obtained.

[Production of Graphite Film A]
A carbonized film A (length: 200 mm × width: 200 mm; area: 400 cm ² ) is sandwiched from above and below by a plate-like smooth graphite plate of length 270 mm × width 270 mm × thickness 3 mm, and a graphite container of 300 mm × width 300 mm × thickness 60 mm It was held in (container A) and heated until the temperature of container A reached 3000 ° C., and carbonized film A was graphitized to produce a graphite film. The graphite film after this heat treatment was compressed in the thickness direction with a single plate press to obtain a graphite film A. The plane direction thermal diffusivity was 9.0 cm ² / s, the plane direction thermal conductivity was 1150 W / mK, the thickness direction thermal conductivity was 5.0 W / mK, and the thickness was 40 μm.

[Graphite film B]
The graphite film B is a graphite film “λ300 μm product” manufactured by Geltech Co., Ltd. The plane direction thermal diffusivity was 3.0 cm ² / s, the plane direction thermal conductivity was 210 W / mK, the thickness direction thermal conductivity was 50 W / mK, and the thickness was 300 μm.

<Measurement of thermal conductivity of graphite film>
The thermal conductivity of the graphite films A and B is expressed by the following formula (1)
λ = α × d × C _p (1)
Calculated from In Equation (1), λ represents thermal conductivity, α represents thermal diffusivity, d represents density, and C _p represents specific heat capacity. The thermal diffusivity, density, and specific heat capacity of the graphite film were determined by the following method.

<Measurement of thermal diffusivity in the surface direction of graphite film by optical alternating current method>
The progress of graphitization was determined by measuring the thermal diffusivity in the surface direction of the film. The higher the thermal diffusivity, the more remarkable the graphitization. The thermal diffusivity was measured at 10 Hz in a 20 ° C. atmosphere by cutting a graphite film into a 4 mm × 40 mm sample shape using a thermal diffusivity measuring apparatus (LaserPit manufactured by ULVAC-RIKO Co., Ltd.) using an optical alternating current method. .

<Measurement of thermal diffusivity and thermal conductivity in the thickness direction of graphite film by laser flash method>
For measuring the thermal diffusivity and thermal conductivity in the thickness direction of the graphite film by the laser flash method, LFA-502 manufactured by Kyoto Electronics Industry Co., Ltd. based on JIS R1611-1997 was used. The graphite film was cut to a diameter of 10 mm, and both surfaces of the film were graphitized (graphitized), and then the thermal diffusivity was measured in the thickness direction by a laser flash method at room temperature. Moreover, the heat capacity of the graphite film was calculated from comparison with a reference standard substance Mo having a known heat capacity. The thermal conductivity in the thickness direction was calculated from the measured thermal diffusivity, density and heat capacity in the thickness direction of the graphite film.

<Density measurement of graphite film>
The density of the graphite film was calculated by dividing the mass (g) of the graphite film by the volume (cm ³ ) calculated by the product of the vertical, horizontal and thickness of the graphite film. In addition, the average value measured by arbitrary 10 points | pieces was used for the thickness of a graphite film. The higher the density, the more remarkable the graphitization.

<Measurement of graphite film thickness>
As a method of measuring the thickness of the graphite film, a film of 50 mm × 50 mm was used in a constant temperature room at room temperature (25 ° C.) using a thickness gauge (HEIDENHAIN-CERTO manufactured by HEIDENHAIN Co., Ltd.) at any 10 points. Were measured and averaged to obtain a measured value.

<Specific heat measurement of graphite film>
The specific heat of the graphite film was measured from 20 ° C. to 260 ° C. under a temperature rising condition of 10 ° C./min using a thermal analysis system manufactured by SII Nano Technology Co., Ltd. and a differential scanning calorimeter DSC220CU.

Example 1
Referring to FIG. 1, a heating element 11 a having a width of 5 mm × 5 mm × thickness 1 mm made of silicon and having an output of 1.5 W, and a heating element having a width of 5 mm × 5 mm × thickness of 1.2 mm made of silicon and having an output of 1.0 W 11b, fixed to a substrate 12 made of epoxy resin having a width of 30 mm × 20 mm × thickness of 0.8 mm and having a container shape. Aluminum having a thickness of 1.2 mm, a width of 35 mm × 25 mm, and a height of 10 mm so as to be supported at a position facing the heating element 11 with a distance Da of 1.00 mm and a distance Db of 0.80 mm. A radiator 13 made of A6061 and having a thermal conductivity of 180 W / mK is attached. By completely covering the heating elements 11a and 11b and in contact with the substrate 12 and the heat radiating body 13, the thermally conductive curable composition A is filled and applied with care so as not to include an air layer, and cured. The heat conductive material layer 14 was provided. For such a heat dissipation structure, the temperature T _H (° C.) at the center of the heating element after 600 seconds from the start of heat generation (when it reaches a constant temperature state) and the part of the heat dissipation element closest to the heating element (this part Was measured by measuring the temperature T _C (° C.) of the heating element (located directly above the center of the heating element). The central temperature T _Ha of the heating element 11a is 92.2 ° C., the outer temperature T _{Ca of the} portion of the heat dissipation element closest to the heating element 11a is 82.5 ° C., and the central temperature T _Hb of the heating element 11b is 86.1. The outer temperature T _{Cb of the} part closest to the heating element 11b in the heat dissipation body was 81.9 ° C.

(Example 2)
Except for changing the substrate 12 to the shape shown in FIG. 2, the heat dissipating property of the heat dissipating structure was evaluated in the same configuration as in Example 1. The center temperature T _Ha of the heating element 11a is 104.8 ° C., the outer temperature T _{Ca of the} part of the radiator closest to the heating element 11a is 84.9 ° C., and the center temperature T _Hb of the heating element 11b is 95.9. The outer temperature T _{Cb of the} part closest to the heating element 11b among the heat dissipation elements was 84.2 ° C.

(Example 3)
Referring to FIG. 3, heating element 11a made of silicon having a width of 5 mm × 5 mm × thickness 1 mm and having an output of 1.5 W, and heating element 11a having a width of 5 mm × 5 mm × thickness of 1.2 mm made of silicon. 11b, 30 mm × 20 mm wide × 0.8 mm thick epoxy resin and fixed to a plate-shaped substrate 12. It is made of SUS405 with a width of 100 mm × 50 mm × thickness of 1.0 mm so as to be supported at a position facing the heating element 11 with a distance Da of 1.00 mm and a distance Db of 0.80 mm. A 27 W / mK heat radiator 13 is attached so as to wrap the entire substrate 12. By completely covering both the heating elements 11a and 11b and in contact with the substrate 12 and the heat radiating body 13, the heat conductive curable composition A is filled and applied with care so as not to include an air layer, and cured. A thermally conductive material layer 14 was provided. For such a heat dissipation structure, the temperature T _H (° C.) at the center of the heating element after 600 seconds from the start of heat generation (when it reaches a constant temperature state) and the part of the heat dissipation element closest to the heating element (this part Was measured by measuring the temperature T _C (° C.) of the heating element (located directly above the center of the heating element). The central temperature T _Ha of the heating element 11a is 82.4 ° C., the outer temperature T _{Ca of the} portion of the radiator closest to the heating element 11a is 70.3 ° C., and the central temperature T _Hb of the heating element 11b is 73.6. The outside temperature T _{Cb of the} part closest to the heating element 11b in the heat dissipation body was 67.0 ° C.

Example 4
Referring to FIG. 4, a silicon heating element 11 a having a width of 5 mm × 5 mm × thickness 1 mm made of silicon and a heating element 11 a having a width of 5 mm × 5 mm × thickness 1.2 mm made of silicon 11b, 30 mm × 20 mm wide × 0.8 mm thick epoxy resin and fixed to a plate-shaped substrate 12. It is made of SUS405 with a width of 100 mm × 50 mm × thickness of 1.0 mm so that it is supported at a position facing the heating element 11 with a distance Da of 1.10 mm and a distance Db of 0.90 mm. A 27 W / mK heat radiator 13 is attached so as to wrap the entire substrate 12. The surface of the radiator facing the heating element is composed of a graphite layer 16 made of graphite film A, an adhesive layer 17 made of acrylic adhesive having a thickness of 30 μm, and a protective film 18 made of PET film having a thickness of 30 μm. A thermal diffusion film 15 of × 40 mm × 100 μm thickness is affixed. By completely covering the heating elements 11a and 11b and in contact with the substrate 12 and the heat diffusion film 15, the heat conductive curable composition A is filled, applied, and cured so as not to include an air layer. The heat conductive material layer 14 was provided. For such a heat dissipation structure, the temperature T _H (° C.) at the center of the heating element after 600 seconds from the start of heat generation (when it reaches a constant temperature state) and the part of the heat dissipation element closest to the heating element (this part Was measured by measuring the temperature T _C (° C.) of the heating element (located directly above the center of the heating element). The center temperature T _Ha of the heating element 11a is 77.8 ° C., the outer temperature T _{Ca of the} portion closest to the heating element 11a in the radiator is 60.9 ° C., and the center temperature T _Hb of the heating element 11b is 69.7 ° C. The outside temperature T _{Cb of the} part closest to the heating element 11b in the heat dissipation body was 59.8 ° C.

(Example 5)
Except that the thermally conductive curable composition B was applied and cured as the thermally conductive material layer 15, the heat dissipation property of the heat dissipation structure having the same configuration as in Example 1 was evaluated. The central temperature T _Ha of the heating element 11a is 94.3 ° C., the outer temperature T _{Ca of the} portion of the radiator closest to the heating element 11a is 82.7 ° C., and the central temperature T _Hb of the heating element 11b is 87.0. The outside temperature T _{Cb of the} part closest to the heating element 11b in the heat dissipation body was 82.0 ° C.

(Example 6)
Except that the heat conductive curable composition C was applied as the heat conductive material layer 15 and then cured, the heat dissipation of the heat dissipation structure having the same configuration as in Example 1 was evaluated. The center temperature T _Ha of the heating element 11a is 87.2 ° C., the outer temperature T _{Ca of the} part of the radiator closest to the heating element 11a is 82.7 ° C., and the center temperature T _Hb of the heating element 11b is 84.0. The outside temperature T _{Cb of the} part closest to the heating element 11b in the heat dissipation body was 82.0 ° C.

(Example 7)
On the surface of the radiator that faces the heating element, a graphite layer 16 made of graphite film B, an adhesive layer 17 made of an acrylic adhesive having a thickness of 30 μm, and a protective film 18 made of a PET film having a thickness of 30 μm. Except that the 40 mm × 360 μm thick thermal diffusion film 15 was attached, the heat dissipation performance of the heat dissipation structure having the same configuration as in Example 5 was evaluated. The central temperature T _Ha of the heating element 11a is 76.9 ° C., the outer temperature T _{Ca of the} portion of the radiator closest to the heating element 11a is 60.0 ° C., and the central temperature T _Hb of the heating element 11b is 68.9 ° C. The outside temperature T _{Cb of the} part closest to the heating element 11b in the heat dissipation body was 59.0 ° C.

(Comparative Example 1)
Referring to FIG. 5, heating element 11a made of silicon having a width of 5 mm × 5 mm × thickness 1 mm and having an output of 1.5 W, and heating element 11a having a width of 5 mm × 5 mm × thickness of 1.2 mm made of silicon. 11b, fixed to a substrate 12 made of epoxy resin having a width of 30 mm × 20 mm × thickness of 0.8 mm and having a container shape. Aluminum having a thickness of 1.2 mm, a width of 35 mm × 25 mm, and a height of 10 mm so as to be supported at a position facing the heating element 11 with a distance Da of 1.00 mm and a distance Db of 0.80 mm. A radiator 13 made of A6061 and having a thermal conductivity of 180 W / mK is attached. The heat conductive material layer 14a and the heat conductive material layer 14a and the heat conductive material layer 14a and the heat conductive material layer 14a can be cured by being filled and applied with care so as not to include an air layer while being in contact with only the heat generators 11a and 11b and the heat radiator 13. 14b was provided. For such a heat dissipation structure, the temperature T _H (° C.) at the center of the heating element after 600 seconds from the start of heat generation (when it reaches a constant temperature state) and the part of the heat dissipation element closest to the heating element (this part Was measured by measuring the temperature T _C (° C.) of the heating element (located directly above the center of the heating element). The center temperature T _Ha of the heating element 11a is 96.8 ° C., the outer temperature T _Ca of the heat radiator closest to the heating element 11a is 83.3 ° C., and the center temperature T _Hb of the heating element 11b is 88.0. The outside temperature T _{Cb of the} part closest to the heating element 11b in the heat dissipation body was 82.5 ° C.

(Comparative Example 2)
Referring to FIG. 6, heating element 11a made of silicon having a width of 5 mm × 5 mm × thickness 1 mm and having an output of 1.5 W, and heating element 11a having a width of 5 mm × 5 mm × thickness of 1.2 mm made of silicon 11b, 30 mm × 20 mm wide × 0.8 mm thick epoxy resin and fixed to a plate-shaped substrate 12. Aluminum having a thickness of 1.2 mm, a width of 35 mm × 25 mm, and a height of 10 mm so as to be supported at a position facing the heating element 11 with a distance Da of 1.00 mm and a distance Db of 0.80 mm. The heat conductivity 180W / mK radiator 13 made from A6061 is attached. The heat conductive material layers 14a and 14b are formed by a method in which the heat conductive curable composition A is filled, applied and cured with care not to include an air layer in a state where the heat generators 11a and 11b are in contact with only the heat radiator 13. Was provided. For such a heat dissipation structure, the temperature T _H (° C.) at the center of the heating element after 600 seconds from the start of heat generation (when it reaches a constant temperature state) and the part of the heat dissipation element closest to the heating element (this part Was measured by measuring the temperature T _C (° C.) of the heating element (located directly above the center of the heating element). The central temperature T _Ha of the heating element 11a is 125.5 ° C., the outer temperature T _Ca of the heat radiator closest to the heating element 11a is 86.8 ° C., and the central temperature T _Hb of the heating element 11b is 108.0. The outer temperature T _{Cb of the} part closest to the heating element 11b among the heating element and the heating element was 85.9 ° C.

  In Comparative Example 1 and Comparative Example 2, the heat conductive material layer does not sufficiently cover the heating element, and the heat conductive material layer is not in contact with the substrate. Yes.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Claims (2)

A plurality of heat generators, a substrate for fixing the plurality of heat generators, a heat dissipator located at a position opposite to the heat generator relative to the substrate, and heat conductivity in contact with the heat generator, the substrate and the heat dissipator. A heat diffusion film including a graphite film between the heat conductive material layer and the heat dissipating body. However, the thermally conductive material layer and the radiator are in contact via the thermal diffusion film, and the thermally conductive material layer is cured by polymerization between carbon-carbon double bonds. After the thermal conductive curable composition containing at least the coalescence (I) and the thermal conductive filler (II) is applied so as to be in contact with any of the heating element, the substrate, and the radiator, the resin is cured. Material with a thermal conductivity of 0.9 W / mK or higher A heat dissipation structure,
The distance between the plurality of heat generating elements and the heat dissipating element is not constant, and the difference between the distance between the closest distance and the farthest distance is 0.1 mm or more. A heat dissipation structure. Start of vinyl polymer (I), heat conductive filler (II), and vinyl polymer (I) having an average of at least one crosslinkable (meth) acryloyl group in the thermally conductive curable composition 2. The heat dissipation structure according to claim 1, comprising at least an agent (III) and a plasticizer (IV), and having a viscosity before curing at room temperature of 50 Pa · s or more.

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