TW201621027A - Thermally conductive sheet - Google Patents

Abstract

Provided is a thermally conductive sheet which exhibits excellent handling properties, and which is capable of excellently transmitting, in the in-plane direction and the vertical direction, heat from a heat-generating electronic component. This thermally conductive sheet is characterized by being obtained by impregnating/filling the holes in a graphite sheet with a thermosoftening silicone resin which is substantially solid at room temperature.

Description

Thermally conductive sheet

The present invention relates to a thermally conductive sheet which is excellent in heat conductivity from a heat-generating electronic component, and particularly excellent in thermal conductivity in an in-plane direction (that is, a direction horizontal or parallel to a sheet surface).

An LSI wafer such as a CPU, a driver IC, or a memory used in an electronic device such as a personal computer generates a large amount of heat due to miniaturization, high integration, and the like, and the temperature of the wafer is increased by the heat. Will cause poor operation of the chip. Therefore, a large number of heat radiating members have been proposed for suppressing an increase in temperature.

In addition, in recent years, portable electronic terminals such as smart phones or tablet PCs are rapidly developing and popularizing. If the heat generated from the memory or the wafer is efficiently transmitted to the back surface of the electronic terminal, a deviation in temperature distribution occurs on the back surface of the terminal, and only heat is felt in the portion. A smart phone that has a direct contact with the skin, and hopes to solve such a situation as much as possible and to uniformize the temperature distribution. In such a case, the film having excellent thermal conductivity in the in-plane direction represented by the graphite sheet is interposed in the memory or by the following method. The heat generated from the heat generating body can be quickly diffused between the heat generating body such as a wafer and the back surface of the electronic terminal. However, the graphite flakes are very brittle, and there is a case where the graphite component is peeled off or the graphite powder is scattered. Moreover, when the thickness is thin, workability is difficult. Further, since the surface of the graphite sheet does not have viscosity, it has a drawback that it is difficult to mount.

In order to solve the above problems, there has been proposed a method in which a resin layer for imparting insulation, imparting adhesion, and improving workability is laminated to one side or both sides. However, in this method, by laminating a resin layer having a low thermal conductivity to a graphite sheet having a good heat conductivity, the heat dissipation characteristics of the graphite sheet are impaired. There is also a proposal to laminate a thermally conductive resin layer to one side or both sides of a graphite sheet, but it is formed by laminating or heat-pressing an adhesive tape or a thermosoftening sheet of an existing formed body. The fine voids on the outside of the graphite sheet can be filled, and the internal voids cannot be filled.

In addition, there is also a proposal to fill the surface of the graphite sheet by immersing a liquid having a high fluidity and internal voids to reduce the thermal resistance. However, in the use environment, repeated heating and cooling, due to repeated expansion and contraction, the liquid will Exudation (pumping-out phenomenon due to thermal cycling) causes an increase in thermal resistance or poor adhesion.

Further, as a prior art related to the present invention, for example, the following documents may be mentioned.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2014-3141

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2004-363432

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thermally conductive sheet which can convey heat from a heat-generating electronic component to an in-plane direction and a vertical direction and has good handleability.

In order to achieve the above object, the present inventors have found through in-depth review that a thermosoftening polyoxyxene resin which is substantially solid at room temperature (25 ° C ± 5 ° C) (ie, a non-liquid material having no self-flowing property) Or a thermally softening polysiloxane resin obtained by dispersing a thermally conductive filler, diluting the formulation with a solvent, impregnating the graphite sheet, and volatilizing the solvent to obtain a pore of the graphite sheet. The heat-conductive sheet is impregnated and filled with a thermosoftening polyoxyxylene resin or a thermally conductive filler as a dispersion of a thermally softening polyoxymethylene resin composition, and the thermally conductive sheet has a peeling resistance of the graphite component. Or the effect of the scattering of the graphite powder, and since the surface has a certain viscosity, the mountability is excellent, and the heat dissipation characteristics in the in-plane direction and the vertical direction are excellent, and thus the present invention has been completed.

Accordingly, the present invention provides the following thermally conductive sheet.

[1]. A thermally conductive sheet characterized by being substantially solid at room temperature The thermosoftening polyoxymethylene resin is impregnated and filled in the pores of the graphite sheet.

[2] The thermally conductive sheet according to the above [1], wherein the thermosoftening polyoxynoxy resin contains a difunctional siloxane structural unit (D unit) and a trifunctional sesquiterpene structural unit ( T unit).

[3] The thermally conductive sheet according to the above [2], wherein the thermosoftening polydecane resin is a formula

D ¹ _m T _p D ² _n

(wherein D ¹ represents (CH ₃ ) ₂ SiO units, T represents (C ₆ H ₅ )SiO _3/2 units, and D ² represents (CH ₃ )(CH ₂ =CH)SiO units, m, p, n is a positive number, (m + n) / p (mole ratio) = 0.25 ~ 4.0, (m + n) / m (mole ratio) = 1.0 ~ 4.0 range).

[4] The thermally conductive sheet according to the above [1], wherein the thermosoftening polysiloxane resin contains a monofunctional decyloxy structural unit (M unit) and a difunctional decane structural unit (D unit). And trifunctional sesquiterpene structural units (T units).

[5] The thermally conductive sheet according to the above [4], wherein the thermosoftening polydecane resin is a formula

M _l D ¹ _m T _p D ² _n

(Wherein, M represents-based (CH _{3) 3} SiO _1/2 unit, D ¹ represents-based (CH _{3) 2} SiO unit, T represents a line (C ₆ H ₅₎ SiO _3/2 unit, D ² are diagrams ( CH ₃ )(CH ₂ =CH)SiO unit, l, m, p, n are positive numbers, (m+n)/p (möer ratio)=0.25~4.0, (m+n)/m (möer ratio ) = 1.0 ~ 4.0, l / (m + n) (mole ratio) = 0.001 ~ 0.1 range).

[6] The thermally conductive sheet according to the above [1], wherein the thermosoftening polysiloxane resin contains a monofunctional decyloxy structural unit (M unit) and a difunctional decane structural unit (D unit). And tetrafunctional structural units (Q units).

[7] The thermally conductive sheet according to the above [6], wherein the thermosoftening polysiloxane resin is of the following formula

M _l D ¹ _m Q _q D ² _n

(wherein M represents (CH ₃ ) ₃ SiO _1/2 units, D ¹ represents (CH ₃ ) ₂ SiO units, Q represents SiO _4/2 units, and D ² represents (CH ₃ ) (CH ₂ =CH) SiO unit, l, m, q, n is a positive number, (m + n) / q (mole ratio) = 0.25 ~ 4.0, (m + n) / m (mr ratio) = 1.0 ~ 4.0, l/(m+n) (mole ratio) = range of 0.001 to 0.1).

[8] The thermally conductive sheet according to the above [1], wherein the thermosoftening polysiloxane resin is composed of only M unit and T unit, or only M unit and Q unit, and the heat is The softening polyoxyxene resin is combined with a high viscosity polyoxygenated oil or a raw rubbery polyoxynitride.

[9] The thermally conductive sheet according to any one of the above [1], wherein the thermosoftening polydecane resin further inhibits the fluidization of the thermosoftening polyoxymethylene resin. The amount of the range is adjusted to disperse and disperse the thermal conductive filler.

[10] The thermally conductive sheet according to the above [9], wherein the thermally conductive filler is added in an amount of from 1 to 100 parts by mass based on 100 parts by mass of the thermosoftening polydecane resin.

[11] The thermally conductive sheet according to any one of the above [1] to [10] wherein The softening point of the thermosoftening polyoxymethylene resin is 40 to 120 °C.

[12] The thermally conductive sheet according to any one of the above [1], wherein the thermosoftening polyanthracene resin has an average molecular weight of 500 to 10,000.

[13] The thermally conductive sheet according to any one of [1] to [12] wherein the thermal conductivity in the in-plane direction is 100 W/m‧K or more.

The thermally conductive sheet of the present invention has an effect of preventing peeling of the graphite component or scattering of the graphite powder, and since the surface has a certain viscosity, the mountability is excellent, and the thermal conductivity is high in the in-plane. The heat dissipation characteristics in the direction and the vertical direction are excellent.

[Embodiment]

[Best Mode for Carrying Out the Invention]

[thermally conductive sheet]

The thermally conductive sheet of the present invention is a thermosoftening polyoxyxylene resin which is substantially solid at room temperature (25 ° C ± 5 ° C) or a thermally conductive filler is dispersed in the thermal softening layer by a graphite sheet having porosity. A thermosoftening polyoxyxylene resin formulation formed by a polyoxyxylene resin is impregnated with a thermosoftening polyoxyxylene resin or a thermosoftening polyoxymethylene resin compound in which a thermally conductive filler is dispersed. The hollow portion of the graphite sheet is formed.

Here, the term "thermal softening property" means heat (usually 40 ° C or more). In the case of thermal softening, low viscosity, or melting, it is possible to have a "thermal softening property" when the surface is fluidized by heat softening, low viscosity, or melting.

[graphite sheet]

The graphite flakes can be used as long as they have porosity. In this case, the porosity (% by volume) is 30 to 80 vol%, and particularly preferably 40 to 70 vol%. Further, the porosity is usually obtained by a gas substitution method or a liquid weighing method.

For the graphite sheet, for example, a graphite sheet produced by a method in which a polymer film is thermally decomposed and graphitized can be used, and a commercially available product can be used. Commercially available products include, for example, MACFOIL (made by Japan Matex Co., Ltd.: trade name) and PGS graphite sheet (made by Panasonic Co., Ltd.: trade name).

The thickness of the graphite flakes is preferably in the range of 3 to 250 μm, more preferably 5 to 160 μm, still more preferably in the range of 10 to 130 μm. When it is less than 3 μm, there is a case where the strength is insufficient, and there is damage due to brittleness. When it exceeds 250 μm, it is very brittle, and a small amount of bending pressure graphite sheet may be broken to cause cracks or breakage. Moreover, when it is too thick, the flexibility of the heat conductive sheet may be impaired, and the adhesion to the electronic component may be impaired, and the thermal conductivity in the vertical direction may be lowered on the sheet surface.

Further, the thickness of the thermally conductive sheet which is impregnated with the thermosoftening polyoxynoxy resin which is substantially solid at room temperature and filled in the pore portion of the graphite sheet is about the same as the thickness of the graphite sheet before impregnation and filling. Degree (usually It is preferably about ±3 to 12%, particularly about ±5 to 8%, and preferably from 3 to 280 μm, particularly from 5 to 180 μm, and more preferably from about 10 to 150 μm.

[Heat softening silicone resin]

The thermosoftening polyphthalocyanine resin obtained by dispersing the thermosoftening polyoxyxylene resin or the thermally conductive filler used in the present invention is substantially solid at room temperature (25 ° C ± 5 ° C) (that is, without self The fluid non-liquid material is in a temperature range of usually 40 ° C or more and the maximum temperature of the heat generation of the heat generating component (that is, 40 to 120 ° C, particularly 40 to 90 ° C). It can be soft-softened, low-viscosity or melted and can be fluidized at least on the contact surface with the heat-generating electronic component.

In the present invention, the softening point (or melting point) of the above-mentioned thermosoftening polyoxymethylene resin is preferably 40 to 120 ° C, more preferably 45 to 100 ° C. When the temperature is below 40 ° C, the ambient temperature is high, the flowability of the formed body is clearly exhibited, and the operation becomes difficult; when it exceeds 120 ° C, the forming is difficult due to the high temperature of the soft softening temperature. . However, the softening point is determined by the drop ball test method (that is, in the falling ball viscometer, when the resin is heated, when the falling ball is completely sunk into the resin, the temperature at this time is set as the softening point. ) and so on.

The thermosoftening polyoxymethylene resin formulation in which the thermosetting polyoxyxylene resin or the thermally conductive filler to be used in the thermally conductive sheet of the present invention is dispersed is not particularly limited as long as it satisfies the above conditions. The above thermal softening property and the composition of the polyoxyxylene resin are important factors.

In particular, as a thermosoftening polyoxyxene resin, it is impregnated with a graphite flake (ie, a thermosoftening polyoxyxylene resin or a thermally conductive filler is a dispersed thermosoftening polyoxyl resin formulation). The thermally conductive sheet formed by the structure in which the pores of the graphite sheet are filled must be substantially solid at room temperature, and thus contains, for example, a trifunctional sesquiterpene represented by RSiO _3/2 of a branched structural unit. a silsesquioxane structural unit (hereinafter referred to as T unit) and/or a tetrafunctional structural unit (hereinafter referred to as Q unit) represented by SiO ₂ as a main component (for example, 40 mol% or more, particularly 50 mol) The polysiloxane resin (so-called silicone resin) of the copolymer of the three-dimensional network structure of % or more is preferably exemplified by T units and/or Q units, and difunctional oxime represented by R ₂ SiO. The polyoxymethylene resin having a three-dimensional network structure of a copolymer of a siloxane structural unit (hereinafter referred to as D unit) is preferably exemplified by copolymerization with a D unit and/or a Q unit. was, to the end of R ₃ SiO _1/2 monofunctional silane-group (the Siloxy) represented by the structure Copolymers bit three-dimensional network structure (hereinafter, referred to as M units) obtained by blocking (i.e., containing T units and / or Q units, M units and copolymers containing more D units) and the like.

Here, the above R is preferably independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 8 carbon atoms which may have a carbonyl group other than the aryl group. Specific examples of R include, for example, a hydrogen atom; an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group or a hexyl group; a cycloalkyl group such as a cyclopentyl group or a cyclohexyl group; a vinyl group and an allyl group; An alkenyl group such as an acryl group, an isopropenyl group or a butenyl group; or a fluorenyl group such as an acryloyl group or a methacryl group. From the viewpoint of easiness of obtaining raw materials, a hydrogen atom, a methyl group, an ethyl group, or a vinyl group can be suitably used as R.

Further, as the thermosoftening polyoxyxene resin to be used in the present invention, one or two or more kinds of polyoxynoxy resin copolymers having a generally three-dimensional network structure containing the above-mentioned branched structural unit may be used, and D may be further added. The main chain of the unit as a main component (usually 80 mol% or more, preferably 90 mol% or more) is substantially composed of a repeating structure of D units, and the end of the molecular chain is terminated by M units (or not An organic polyoxane (for example, a polyoxyxane or a polyoxynized rubber) which is linearly branched (or may have a small number of T units or Q units). It is used as a mixture with the aforementioned three-dimensional network copolymer containing a branched structural unit.

Among these, as the thermosoftening polyoxyxene resin used in the present invention, a polyfluorene oxide resin having a T unit and a D unit (M unit is optional) and a T-unit polyfluorene oxide resin are contained by rotation. A polyoxyxylene resin composition in which a viscosity at 25 ° C measured by a viscometer is 100 Pa ‧ or more of a combination of a polyoxygenated oil or a polyoxynized raw rubber is preferred. The polyoxyxene resin may be terminated at the end by R ₃ SiO _1/2 (M unit).

When the composition of the thermosoftening polyoxyxene resin is more specifically described, the thermosoftening polyphthalocyanine resin usually has a three-dimensional network structure including a T unit and/or a Q unit as a main component, and is only M unit. Design with T units, or only M units and Q units. However, in order to improve the toughness at the time of solid form (to improve the impregnation of the thermosoftening polyoxyphthalocene resin or the thermally conductive filler into the dispersed thermosoftening polyoxymethylene resin formulation, the void portion of the graphite sheet is filled. The brittleness of the formed thermally conductive sheet to prevent breakage during handling, etc., is particularly effective in introducing T units, and it is preferable to use them in units of D. Here, as the T unit The substituent (R) is preferably a methyl group or a phenyl group, and the substituent (R) as a D unit is preferably a methyl group, a phenyl group or a vinyl group. Further, the composition ratio (Mohr ratio) of the T unit and the D unit is preferably 10:90 to 90:10, and particularly preferably 20:80 to 80:20.

Further, even if it is a polyoxyxene resin synthesized by only M units and T units, or a polyfluorene oxide resin synthesized only by M units and Q units, the mixing is mainly composed of T units. A high-viscosity polyoxygenated oil composed of a repeating structure of D units (end of M unit) (for example, a viscosity at a temperature of 25 ° C or more measured by a rotary viscometer of 1,000 Pa ‧ or more) or a raw rubbery polyoxygen The compound can improve the brittleness of the thermally conductive sheet obtained by impregnating the thermally softened polyoxyxylene resin or the thermally conductive filler into the dispersed thermosoftening polyoxymethylene resin formulation and filling the pores of the graphite sheet. Further, it is possible to prevent the grease from flowing out when a thermal shock is applied (the voids due to the separation of the graphite flakes from the base helium oxide and the outflow of the base helium oxide). Therefore, when a polyfluorene oxide resin having a T-unit but not a D-unit three-dimensional network structure is used, a high-viscosity polyoxygenated oil or a polyoxynized raw rubber containing D unit as a main component is added to the polyoxyxene resin. The compound is preferred.

Therefore, if the polyfluorene oxide resin having a softening point or a melting point higher than room temperature is contained in the T unit but does not contain the D unit, the high-viscosity polyoxygenated oil containing the D unit as a main component is added for the above reasons. Or polyoxynized rubber can be used as an excellent material for handling. In this case, with respect to 100 parts by mass of the polyoxyxene resin having a softening point or a melting point higher than room temperature, the addition of a high-viscosity polysulfonated oil or a raw rubber-like polyoxane compound having a D unit as a main component is added. The amount is 1~100 mass parts, especially set to 2 to 10 parts by mass. When the amount is less than 1 part by mass, the possibility of occurrence of the outflow of the ointment is large, and when it exceeds 100 parts by mass, the thermal resistance is increased and the thermal conductivity is lowered.

As described above, in order to reduce the viscosity (which is large in temperature dependence), it is preferred that the polyoxyxylene resin be used in a relatively low molecular weight. The molecular weight of the thermosoftening polydecane resin is from 500 to 10,000, particularly preferably from 1,000 to 6,000.

In addition, the molecular weight can be usually determined by gel permeation chromatography using toluene or the like as a developing solvent, and the number average molecular weight in terms of polystyrene.

Further, the thermosoftening polyphthalocene resin to be used in the present invention is suitable for imparting strength and viscosity to the thermally conductive sheet used in the present invention, and a single viscosity polymer or the like can be used, but if the mixed viscosity is When two or more types of polymers are used in combination, it is advantageous to obtain a sheet having excellent balance between strength and viscosity, and it is advantageous to use two or more kinds of polymers having different viscosities.

Specific examples of the thermosoftening polyphthalocyanine resin to be used in the present invention include a difunctional oxirane structural unit (D unit) and a trifunctional sesquiterpene alkane structural unit (T unit). The specific composition of the polyoxyl resin.

D ¹ _m T _p D ² _n

(here, D ¹ represents a dimethyl decane unit (ie, (CH ₃ ) ₂ SiO), and T represents a phenyl sesquioxane unit (ie, (C ₆ H ₅ ) SiO _3/2). ), D ² represents a methyl vinyl siloxane unit (ie, (CH ₃ )(CH ₂ =CH) SiO), and the composition ratio is related to (m+n)/p (mole ratio)=0.25 to 4.0. , again, (m+n)/m (mole ratio) = range of 1.0 to 4.0).

Further, for example, the following includes a monofunctional decyloxy structural unit (M unit), a difunctional siloxane structural unit (D unit), and a trifunctional sesquiterpene structural unit (T unit). The composition of polyoxyn resin.

M _l D ¹ _m T _p D ² _n

(here, M system represents a trimethyloxetane unit (i.e., (CH ₃ ) ₃ SiO _1/2 ), and D ¹ , T, and D ² are the same as described above, and the composition ratio is related to (m+n)/ p (möer ratio) = 0.25 ~ 4.0, again, (m + n) / m (mole ratio) = 1.0 ~ 4.0, and, l / (m + n) (mr ratio) = 0.001 ~ 0.1 range ).

Further, for example, the following polyoxane having a specific composition including a monofunctional nonalkoxy structural unit (M unit), a difunctional siloxane structural unit (D unit), and a tetrafunctional structural unit (Q unit) may be mentioned. Resin.

M _l D ¹ _m Q _q D ² _n

(here, the Q system indicates SiO _4/2 , M, D ¹ , and D ² are the same as described above, and the composition ratio is related to (m + n) / q (mole ratio) = 0.25 to 4.0, and again, (m + n) / m (mole ratio) = 1.0 ~ 4.0, again, l / (m + n) (mole ratio) = range of 0.001 ~ 0.1).

These may be used alone or in combination of two or more.

[thermally conductive filler]

Further, in the present invention, the amount of the thermosoftening polyoxyl resin is also in the range of not inhibiting the fluidization of the contact surface with the heat generating electronic component. A thermally conductive filler can be added or dispersed to be used as a thermosoftening polyoxymethylene resin formulation.

As the thermally conductive filler, a conventional material generally used as a thermally conductive filler in such a use can be used, and is not particularly limited. Metals such as copper, silver, aluminum, etc.; metal oxides such as aluminum oxide, cerium oxide, magnesium oxide, aluminum hydroxide, zinc oxide; aluminum nitride, tantalum nitride, tantalum carbide, boron nitride, etc. Ceramics; artificial diamonds, etc. Among these, relatively easy to obtain and relatively inexpensive, alumina and cerium oxide are preferred.

The thermal conductive filler has an average particle diameter of 0.5 to 100 μm, preferably 1 to 50 μm, particularly preferably 1 to 10 μm. When the average particle diameter is too large, the contact area with the polyoxymethylene resin is small, and the oil-resistant paste flowability is deteriorated; when it is too small, it is difficult to mix with the polyoxymethylene resin. Further, the average particle diameter can be obtained by, for example, a laser light diffraction method as a cumulative weight average diameter (or intermediate diameter, d50) in the particle size distribution test.

The amount of the thermally conductive filler is not within the range of the fluidization of the contact surface with the heat-generating electronic component, and specifically, the thermal conductive filling is performed with respect to 100 parts by mass of the thermosoftening polyoxynoxy resin. The dosage of the agent is preferably from 1 to 100 parts by mass, particularly preferably from 10 to 50 parts by mass.

[Modulation of Thermosoftening Polyoxymethylene Resin Formulation]

A thermosoftening polyoxymethylene resin formulation by using the above-mentioned thermosoftening polydecane resin and a thermally conductive filler by using a planetary mixer 80~160°C, especially mixed with 100~150°C for 0.5~5 hours, especially for 1~3 hours.

[solvent]

In the case of producing the heat conductive sheet of the present invention, as a solvent used for improving workability, for example, toluene, xylene, hexane, heptane or the like is preferable, and toluene and xylene are preferable. The solvent is used in an amount of from 1 to 50 parts by mass, particularly preferably from 3 to 20 parts by mass, per 100 parts by mass of the thermosoftening polydecane resin. When the amount of the solvent used is too large, it takes a lot of time to remove the solvent, and when it is too small, the workability cannot be improved.

[Manufacture of thermal conductive sheet]

Next, a method of producing a thermally conductive sheet according to the present invention will be described.

A typical production method of the thermally conductive sheet of the present invention is as follows, as long as the thermosoftening polyoxymethylene resin composition is dispersed in a solvent-diluted thermosoftening polysiloxane resin or a thermally conductive filler. The method of impregnating the graphite flakes and then drying them is not limited thereto.

As an example of the production method, the following method is used.

(1) The thermosoftening polyoxyphthalocene resin or the thermally conductive filler is diluted with a solvent, and the diluted thermosetting polyoxymethylene resin is diluted with a solvent to prepare an impregnation liquid.

(2) The graphite flakes are immersed in the impregnation liquid.

(3) Volatilizing to remove the solvent.

Further, as another manufacturing method, specifically, a graphite sheet is supplied onto the polymer film which has been subjected to release treatment using a coating device, and the thermosoftening polyoxynoxy resin or the thermally conductive filler is diluted with a solvent to be dispersed. The thermosoftening polyoxymethylene resin formulation is used as an impregnation liquid, and after applying the impregnation liquid, the solvent is volatilized and removed by a heating furnace to produce a thermally conductive sheet. At this time, in order to allow the thermosoftening polyoxyphthalocene resin or the thermally conductive filler to be dispersed, the thermosoftening polyoxymethylene resin formulation can be satisfactorily impregnated into the internal space of the graphite sheet, and pressure can be applied.

Here, the thermosoftening polyoxynoxy resin or the thermally conductive filler is an impregnation amount or a coating amount of the dispersed thermosoftening polyoxymethylene resin formulation, relative to the pore volume in the graphite sheet (ie, the graphite sheet The product of the volume and the porosity is 50 to 200 vol% in terms of the thermosoftening polyoxyl resin, and preferably about 95 to 120 vol%. When the amount of the impregnation or the amount of coating is too small, the adhesion is impaired, and when it is too large, the outflow of the ointment may occur.

The molding conditions are not particularly limited as long as they can sufficiently volatilize and remove the solvent to be used. The heating conditions of the heating furnace vary depending on the type of the solvent, but in order to avoid generation of bubbles, it is preferably 50 to 200 ° C, more preferably 60 to 180 ° C. Further, in order to maintain the surface of the thermal conductive sheet with heat softening, low viscosity or meltability, the upper surface (coated or impregnated with a liquid thermosoftening polyoxyxylene resin or a thermally conductive filler is a dispersed heat softening) The surface of the polyoxymethylene resin formulation is also preferably in contact with the polymer film which has been subjected to release treatment.

The thermally conductive sheet of the present invention obtained in such a manner, The thermal conductivity of the in-plane direction (that is, the horizontal or parallel direction to the sheet surface) measured by a thermal conductivity testing device such as the Bethel Corporation under the trade name Thermowave Analyzer is 100 W/m ‧ K or more. 200~2,000W/m‧K, especially 500~2,000W/m‧K is preferred. When the above thermal conductivity is less than 100 W/m‧K, the heat dissipation characteristics are insufficient. In addition, the thermal conductivity in the in-plane direction of the thermally conductive sheet of the present invention can be achieved by using a graphite sheet having high crystallinity or the like.

Further, in the thermal conductive sheet of the present invention, the thermal resistance in the vertical direction of the sheet surface is 0.5 cm ² ‧ K/W or less, and 0.02 to 0.3 cm ² ‧ K/W as measured according to ASTM D 5470 It is better. When the above thermal resistance exceeds 0.5 cm ² ‧ K/W, the heat dissipation characteristics are insufficient. Further, the thermal resistance of the surface of the thermally conductive sheet of the present invention in the direction perpendicular to the surface is set to the above value, and it is a composition of a thermosoftening polyoxyxylene resin or a thermosoftening polyoxymethylene resin which can be substantially solid at room temperature. It can be achieved by impregnating the void portion of the filled graphite sheet.

[Examples]

Hereinafter, the present invention will be specifically described by showing examples and comparative examples, but the present invention is not limited to the following examples. Further, the molecular weight is represented by a polystyrene-equivalent number average molecular weight obtained by gel permeation chromatography analysis using toluene as a developing solvent. Further, the softening point is represented by a test value obtained by dropping a ball type viscometer.

[Examples 1 to 3, Comparative Examples 1 to 3]

First, the polyfluorene oxide component and the graphite flakes used to form the thermally conductive sheet of the present invention are as follows.

<Polyoxygen component>

‧Ingredient (A): Thermosoftening polydecane resin (polyoxane component (A-1))

A polyoxonane resin having a three-dimensional network structure represented by the following composition formula (number average molecular weight: about 2,000, softening point: 48 ° C)

D ¹ ₂₅ T ₅₅ D ² ₂₀

Wherein D ¹ represents a dimethyloxane unit (ie, (CH ₃ ) ₂ SiO), and T represents a phenyl siloxane unit (ie, (C ₆ H ₅ )SiO _3/2 ), D ² represents a methyl vinyl siloxane unit (ie, (CH ₃ )(CH ₂ =CH)SiO)].

‧Ingredient (B): Polyoxygenated oil (for comparison) (polyoxygenated component (B-1)) KF-96 (trade name, linear dimethyl polyoxyalkylene manufactured by Shin-Etsu Chemical Co., Ltd.) , dynamic viscosity 500mm ² / s (25 ° C)).

‧Ingredient (C): Thermosoftening polyoxymethylene resin formulation (polyoxygenated component (C-1))

Thermosoftening polyoxymethylene resin formulation obtained by the following method

Using a 5 L frame mixer (trade name: 5-L Planetary Mixer, manufactured by Inoue Seisakusho Co., Ltd.), 100 parts by mass of the above polyfluorene oxide component (A-1) and thermal conductivity filling were mixed at 120 °C. Agent (average particle size 5.3μm Alumina powder) 20 parts by mass for 1 hour to obtain a target thermosoftening polyoxymethylene resin formulation.

<graphite sheet>

‧Ingredient (D): Graphite flakes

(D-1): Graphite sheet MACFOIL (manufactured by Japan Matex Co., Ltd., porosity: about 45 vol%, thickness: 130 μm)

(D-2): PGS graphite sheet (made by Panasonic), porosity: about 45 vol%, thickness: 100 μm

[Manufacture of thermal conductive sheet]

The graphite flakes are supplied onto the demolded polymer film, and the liquid thermosoftening polyoxyxylene resin or the thermosoftening polyoxymethylene resin compound coated with toluene and used for improving workability is coated by a blade coater. On the graphite sheet, the solvent was volatilized and removed by a heating furnace at a coating speed of 2 m/min and a heating condition of 100 ° C, and then heat-pressed by another release-treated polymer film to form a thermally conductive sheet. The composition and thickness of the thermally conductive sheet are shown in Table 1. Further, the amount of toluene used for dilution is 14 parts by mass based on 100 parts by mass of the above-mentioned thermosoftening polydecane resin, and the diluted liquid thermosoftening polyoxyxylene resin or thermosoftening polyoxyl resin formulation is diluted. Among them, the coating and impregnation amount of the graphite sheet of the thermosoftening polyoxyxylene resin or the thermosoftening polyoxynoxy resin compound after removing the solvent (toluene) are relative to the pore volume in the graphite sheet (graphite) The volume of the sheet × the porosity was about 100 vol%, and coating and impregnation were carried out.

[Evaluation method]

Each of the obtained thermally conductive sheets and graphite sheets (D-1) and (D-2) was tested and tested for the following characteristics, and the results of the evaluation are shown in Table 1.

[The thermal conductivity of thermal conductive sheets]

The thermal conductivity of the thermal conductive sheet in both the thickness direction and the in-plane direction was tested using a trade name Thermowave Analyzer manufactured by Bethel.

As a test principle of the thermal conductivity in the thickness direction of the thermal conductive sheet, pulsed laser light is irradiated onto the surface of the sample, and by testing the specific heat, the thermal diffusivity, and the thermal conductivity as the product of the specific heat, the thermal diffusivity, and the density of the test piece. And can be calculated.

As a test principle of the thermal conductivity in the in-plane direction of the thermal conductive sheet, periodic heating is performed from one point of one surface of the thermal conductive sheet, and when the temperature is measured from the opposite surface, the temperature measurement position is moved and the unit of each distance is obtained. The phase difference is obtained to obtain the thermal diffusivity in the in-plane direction, and the thermal diffusivity is calculated from the thermal diffusivity.

[Ointment outflow]

The test pieces were clamped between two standard aluminum plates, and the load was applied at a compression load of 410 kPa, and then placed in an oven, and the temperature was repeated at 0 ° C / 30 minutes. A temperature cycle of 125 ° C / 30 minutes was cycled for 500 cycles. After the test, the presence or absence of the outflow of the polyoxon component was visually observed.

Evaluation A: Polyoxane component did not flow out

Evaluation B: The polyoxane component has an outflow

[brittleness (strength)]

The presence or absence of breakage of the thermally conductive sheet when the blade was cut in the crack direction was evaluated.

Evaluation A: Unbroken

Evaluation B: Damaged

As is clear from Table 1, each of the examples has high thermal conductivity and excellent heat dissipation performance, and is excellent in oil-resistant paste effluent or brittleness (strength).

On the other hand, in Comparative Example 1 and Comparative Example 2 in which the graphite sheets were simple, the brittleness (strength) was poor, and the breakage of the thermally conductive sheet when the blade was cut in the crack direction was remarkable.

Further, in Comparative Example 3 using polyoxygenated oil, the outflow of the polyoxo component (polyoxygenated oil) was observed in the ointment outflow test, and the brittleness (strength) was also observed. difference.

Claims (13)

A thermally conductive sheet characterized by impregnating and filling a hollow portion of a graphite sheet with a substantially solid thermosoftening polyoxymethylene resin at room temperature. The thermally conductive sheet of claim 1, wherein the thermosoftening polyoxynoxy resin contains a difunctional siloxane structural unit (D unit) and a trifunctional sesquiterpene structural unit (T unit). The thermally conductive sheet of claim 2, wherein the thermosoftening polyoxynoxy resin is represented by the following formula D ¹ _m T _p D ² _n (wherein D ¹ represents (CH ₃ ) ₂ SiO units, and T represents ( C ₆ H ₅ ) SiO _3/2 unit, D ² represents (CH ₃ )(CH ₂ =CH)SiO unit, m, p, n is a positive number, (m+n)/p (mole ratio)=0.25 ~4.0, (m + n) / m (mole ratio) = 1.0 ~ 4.0 range). The thermally conductive sheet of claim 1, wherein the thermosoftening polyoxynoxy resin contains a monofunctional decyloxy structural unit (M unit), a difunctional decane structural unit (D unit), and a trifunctional double Semi-oxane structural unit (T unit). The thermally conductive sheet of claim 4, wherein the thermosoftening polyoxynoxy resin is of the formula M _l D ¹ _m T _p D ² _n (wherein M represents (CH ₃ ) ₃ SiO _1/2 units, lines D ¹ represents (CH _{3) 2} SiO unit, T represents a line (C ₆ H ₅₎ SiO _3/2 unit, D ² are diagrams _{(CH 3) (CH 2 =} CH) SiO units, l, m, p, n is a positive number, (m + n) / p (mole ratio) = 0.25 ~ 4.0, (m + n) / m (mr ratio) = 1.0 ~ 4.0, l / (m + n) (mr ratio) = 0.001 to 0.1 range). The thermally conductive sheet according to claim 1, wherein the thermosoftening polyoxynoxy resin contains a monofunctional decyloxy structural unit (M unit), a difunctional siloxane structural unit (D unit), and a tetrafunctional structure. Unit (Q unit). The thermally conductive sheet of claim 6, wherein the thermosoftening polyoxynoxy resin is of the formula M _l D ¹ _m Q _q D ² _n (wherein M represents (CH ₃ ) ₃ SiO _1/2 units, D ¹ represents (CH ₃ ) ₂ SiO units, Q represents SiO _4/2 units, D ² represents (CH ₃ )(CH ₂ =CH)SiO units, and l, m, q, n are positive numbers, (m +n)/q (möer ratio)=0.25~4.0, (m+n)/m (möer ratio)=1.0~4.0, l/(m+n) (möer ratio)=0.001~0.1 range ) said. The thermally conductive sheet of claim 1, wherein the thermosoftening polyoxynoxy resin is composed of only M unit and T unit, or only M unit and Q unit, and the thermosoftening polyoxymethylene resin And use high viscosity polyoxygenated oil or raw rubbery polyoxynitride. The thermally conductive sheet according to any one of claims 1 to 8, wherein the thermally softening polysiloxane resin is further formulated and dispersed in a range that does not hinder the flow of the thermosoftening polyoxymethylene resin. Sex filler. The thermally conductive sheet according to claim 9, wherein the thermally conductive filler is added in an amount of from 1 to 100 parts by mass based on 100 parts by mass of the thermosoftening polydecane resin. The thermally conductive sheet according to any one of claims 1 to 8, wherein the softening point of the thermosoftening polyoxymethylene resin is 40 to 120 °C. The thermally conductive sheet according to any one of claims 1 to 8, wherein the thermosoftening polyoxymethylene resin has an average molecular weight of 500 to 10,000. The thermally conductive sheet according to any one of claims 1 to 8, wherein the thermal conductivity in the in-plane direction is 100 W/m‧K or more.