Thermally conductive sheet and method for manufacturing the thermally conductive sheet

Abstract

To provide a heat-conductive sheet excellent in thermal conductivity in a thickness direction by setting filler in high orientation, while being low density.SOLUTION: A heat-conductive sheet includes heat-conductive filler (B) containing at least one kind of carbon and boron nitride in a polymer matrix (A). In the heat-conductive sheet, a coefficient of thermal conductivity in a thickness direction is 15 W / m K or more. A degree of orientation of a longitudinal direction of the heat-conductive filler oriented is 1.0 or more with regard to the thickness direction of the heat-conductive sheet.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thermally conductive sheet and a method for manufacturing the thermally conductive sheet. [Background technology]

[0002] In recent years, as electronic devices have become more powerful, the density and packaging of semiconductor elements have increased. This has led to an increase in the amount of heat generated by the electronic components that make up electronic devices, making efficient heat dissipation important. To address this issue, heat dissipators such as heat sinks are commonly used to dissipate the heat generated by heat-generating elements. It is known that a heat dissipation sheet is placed between the heat-generating element and the heat dissipating element to improve heat transfer efficiency.

[0003] In particular, the computerization of automobiles has been remarkable, and the number of electronic components mounted has increased, leading to an increased demand for heat dissipation materials. Heat dissipation materials come in sheet and grease types, but the sheet type is often preferred due to its ease of mounting. Furthermore, with autonomous driving as a backdrop, further improvements in thermal conductivity are required for such heat dissipation materials. Generally, to achieve high thermal conductivity, it is necessary to increase the filling rate of the filler dispersed within the polymer, which tends to result in a high specific gravity exceeding 2.0, but this poses a problem when promoting weight reduction to improve the fuel efficiency of gasoline vehicles and the electric power efficiency of electric vehicles.

[0004] For example, Patent Document 1 proposes a method for producing a thermally conductive resin sheet, which includes at least a curing step of extruding a thermally conductive composition containing a polymer, an anisotropic filler, and a bulking agent using an extruder, and curing the extrusion to obtain a cured product, and a cutting step of cutting the cured product to a predetermined thickness in a direction perpendicular to the extrusion direction using an ultrasonic cutter.

[0005] Furthermore, for example, Patent Document 2 also proposes a method for manufacturing a thermally conductive sheet, in which a magnetic field is applied to a thermally conductive composition containing a polymer, an anisotropic filler, and a bulking agent to orient the anisotropic thermally conductive filler, form a bulk compact, and slice the compact to a desired sheet thickness.

[0006] Furthermore, for example, Patent Document 3 also proposes a method for manufacturing a thermally conductive sheet, in which a thermally conductive composition containing a polymer, an anisotropic filler, and a bulking agent is rolled, pressed, extruded, or coated to a thickness of 20 times or less the average major axis of the anisotropic filler to produce an oriented primary sheet, and the laminated molded body is then sliced.

[0007] However, no specific specific gravity is given in Patent Documents 1 to 3. Therefore, it has been desired to obtain a thermally conductive sheet with a low specific gravity. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-023335 [Patent Document 2] Japanese Patent Application Publication No. 2019-186555 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-126614 Summary of the Invention [Problem to be solved by the invention]

[0009] That is, an object of the present invention is to provide a thermally conductive sheet that has excellent thermal conductivity in the thickness direction and a low specific gravity by highly orienting the filler. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides a thermally conductive sheet containing a thermally conductive filler (B) including at least one of carbon and boron nitride in a polymer matrix (A), wherein the thermal conductivity of the thermally conductive sheet in the thickness direction is 15 W / m·K or more, and the degree of orientation of the major axis of the thermally conductive filler in the thickness direction of the thermally conductive sheet is 1.0 or more.

[0011] Such a thermally conductive sheet can take advantage of the anisotropy of the thermally conductive filler to achieve high thermal conductivity with a low loading and low specific gravity. Furthermore, carbon and boron nitride are known to have low specific gravity among thermally conductive fillers, making them ideal for achieving low specific gravity.

[0012] It is also preferable that the specific gravity of the thermally conductive sheet is less than 2.0.

[0013] Such a material is preferable as a thermally conductive sheet.

[0014] The content of the component (B) in the thermally conductive sheet is preferably 50 to 90% by mass.

[0015] Such a thermally conductive sheet is advantageous in achieving both high thermal conductivity and low specific gravity.

[0016] The component (A) is preferably a curable polymer composition containing at least one selected from organopolysiloxane, polyurethane, polyacrylate, perfluoropolyether elastomer, unsaturated polyester resin, polyamide resin, epoxy resin, and phenolic resin.

[0017] If component (A) is such, the filling properties of component (B) will be good.

[0018] The component (B) preferably has a fibrous, scaly, plate-like, flat, needle-like, or whisker-like shape.

[0019] Such a thermally conductive filler is easy to align when it is oriented.

[0020] The aspect ratio of the component (B) is preferably 2 or more.

[0021] When such a thermally conductive filler is oriented in the longitudinal direction, the number of times that heat transfers between the fillers is reduced, resulting in improved thermal conductivity of the filler in the longitudinal direction.

[0022] The present invention also provides a method for producing the thermally conductive sheet, comprising: (I-1) a preparation step of preparing a filler-containing resin composition containing the polymer matrix (A) and the thermally conductive filler (B); (I-2) a filling step of filling the filler-containing resin composition into a mold; (I-3) a vibration step of ultrasonically vibrating the mold to degas and align the filler; (I-4) a heating step of obtaining a filler-containing semi-cured resin composition in the form of strings from the filler-containing resin composition by heating; (I-5) a molding step of arranging the filler-containing string-shaped semi-cured resin composition in the longitudinal direction, heating and pressurizing the composition, and obtaining a filler-containing molded body; (I-6) a slicing step of slicing the filler-containing molded body to obtain a thermally conductive sheet; The present invention provides a method for producing a thermally conductive sheet, comprising:

[0023] The present invention also provides a method for producing the thermally conductive sheet, comprising: (II-1) a preparation step of preparing a filler-containing resin composition containing the polymer matrix (A) and the thermally conductive filler (B); (II-2) a coating step of coating the filler-containing resin composition onto a film separator in one direction to a uniform thickness; (II-3) a heating step of obtaining a filler-containing sheet-shaped semi-cured resin composition from the filler-containing resin composition by heating; (II-4) a cutting step of peeling the filler-containing sheet-shaped semi-cured resin composition from the film separator and cutting it to fit the size of a mold used in a molding step; (II-5) a molding step of arranging cut pieces of the filler-containing sheet-like semi-cured resin composition in the coating direction, heating and pressurizing the cut pieces, and obtaining a filler-containing molded body; (II-6) a slicing step of slicing the filler-containing molded body to obtain a thermally conductive sheet; The present invention provides a method for producing a thermally conductive sheet, comprising:

[0024] By any of these methods, the thermally conductive sheet of the present invention exhibiting good thermal conductivity can be produced.

[0025] Furthermore, it is preferable that the filler-containing resin composition contains an organic solvent.

[0026] By adding an organic solvent, the viscosity of the filler-containing resin composition decreases, which improves the filling property and also makes it easier to align the component (B), thereby improving the degree of orientation. [Effects of the Invention]

[0027] According to the present invention, by highly orienting the thermally conductive filler, it is possible to obtain a thermally conductive sheet that has excellent thermal conductivity in the thickness direction and a low specific gravity. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 2 is a schematic view showing an example of a mold used in a filling step. [Figure 2] FIG. 2 is a schematic diagram showing the cross-sectional structure of FIG. [Figure 3] FIG. 2 is a schematic view showing an example of a mold used in a molding process. [Figure 4] FIG. 1 is a schematic diagram showing a mold for molding a typical 2 mm sheet. [Figure 5] 1 is an SEM image of the surface of a thermally conductive sheet 1 of Example 1. [Figure 6]1 shows the results of X-ray diffraction on the surface of the thermally conductive sheet 1 of Example 1. [Figure 7] 1 is an SEM image of the surface of a thermally conductive sheet 2 of Example 2. [Figure 8] 1 shows the results of X-ray diffraction on the surface of a thermally conductive sheet 2 of Example 2. [Figure 9] 1 is an SEM image of the surface of a thermally conductive sheet 3 of Example 3. [Figure 10] 1 shows the results of X-ray diffraction on the surface of the thermally conductive sheet 3 of Example 3. [Figure 11] 1 is an SEM image of the surface of a thermally conductive sheet 4 of Example 4. [Figure 12] 1 shows the results of X-ray diffraction on the surface of the thermally conductive sheet 4 of Example 4. [Figure 13] 1 is an SEM image of the surface of a thermally conductive sheet 5 of Example 5. [Figure 14] 1 shows the results of X-ray diffraction on the surface of the thermally conductive sheet 5 of Example 5. [Figure 15] 1 is an SEM image of the surface of a thermally conductive sheet 6 of Example 6. [Figure 16] 1 shows the results of X-ray diffraction on the surface of a thermally conductive sheet 6 of Example 6. [Figure 17] 1 is an SEM image of the surface of a thermally conductive sheet 7 of Comparative Example 1. [Figure 18] 1 shows the results of X-ray diffraction on the surface of a thermally conductive sheet 7 of Comparative Example 1. [Figure 19] 10 is an SEM image of the surface of a thermally conductive sheet 8 of Comparative Example 2. [Figure 20] 1 shows the results of X-ray diffraction on the surface of a thermally conductive sheet 8 of Comparative Example 2. [Figure 21] 10 is an SEM image of the surface of a thermally conductive sheet 9 of Comparative Example 3. [Figure 22] 1 shows the results of X-ray diffraction on the surface of a thermally conductive sheet 9 of Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0029] As described above, there has been a demand for a thermally conductive sheet that has excellent thermal conductivity and a low specific gravity.

[0030] As a result of extensive research to solve the above problems, the present inventors discovered that a thermal conductivity of 15 W / m K or more can be achieved in a thermally conductive sheet in which anisotropic thermally conductive fillers are oriented with a certain degree of orientation, with the major axis oriented in the thickness direction, and this discovery led to the completion of the present invention.

[0031] That is, the present invention provides a thermally conductive sheet containing a thermally conductive filler (B) including at least one of carbon and boron nitride in a polymer matrix (A), wherein the thermal conductivity of the thermally conductive sheet in the thickness direction is 15 W / m·K or more, and the degree of orientation of the major axis of the thermally conductive filler in the thickness direction of the thermally conductive sheet is 1.0 or more.

[0032] In the present invention, the degree of orientation refers to a value calculated from peak intensity measured under the following conditions.

[0033] [Orientation degree] (Measuring equipment) BRUKER JAPAN Tabletop Powder X-ray Diffractometer “D2 PHASER 2nd Generation” (Measurement conditions) Sample size: 12.7mmΦ Scan range: 20-90° Step size: 0.024° Sample rotation: 10 rpm Voltage: 30KV Current: 10mA The degree of orientation is calculated from the peak intensity of the measurement results as follows: Orientation degree = {sum of vertical counts + (sum of diagonal counts / 2)} / horizontal counts Vertical count 2θ=41.0~43.0°(100 faces), 2θ=76.5~78.5°(110 faces) Diagonal count 2θ=43.5~45.5°(101 faces), 2θ=81.5~83.5°(112 faces) Horizontal count 2θ=25.5~27.5°(002 surface)

[0034] The present invention will be described in detail below.

[0035] [Thermal conductive sheet] The thermally conductive sheet of the present invention is obtained by molding a filler-containing resin composition containing a thermally conductive filler containing at least one of carbon and boron nitride in a polymer matrix by the method described below.

[0036] [Filler-containing resin composition] The filler-containing resin composition is a resin composition containing (A) a polymer matrix and (B) a thermally conductive filler.

[0037] [(A) Polymer matrix] The polymer matrix, which is component (A) of the present invention, is not particularly limited, but in terms of the filling ability of component (B), it is preferably one or more curable polymer compositions selected from organopolysiloxane, polyurethane, polyacrylate, perfluoropolyether elastomer, unsaturated polyester resin, polyamide resin, epoxy resin, and phenolic resin, more preferably an organopolysiloxane, perfluoropolyether elastomer, polyurethane, or polyacrylate, which have excellent flexibility, and even more preferably an organopolysiloxane or perfluoropolyether elastomer, which have excellent heat resistance and cold resistance.

[0038] [Curable polymer composition] Therefore, component (A) is preferably a curable organopolysiloxane composition or a curable perfluoropolyether elastomer composition.

[0039] [Curable organopolysiloxane composition] The curable organopolysiloxane composition will now be described in detail.

[0040] Examples of curable organopolysiloxane compositions include thermosetting organopolysiloxane compositions, moisture-curing organopolysiloxane compositions, and electron beam-curing silicone resins. Examples of thermosetting silicone resins include addition-curing organopolysiloxane compositions and peroxide-curing organopolysiloxane compositions. Among these, addition-curing organopolysiloxane compositions are preferred, and the following (A-1) to (A-3) are also preferred: (A-1) an alkenyl group-containing organopolysiloxane, (A-2) organohydrogenpolysiloxane, (A-3) Platinum group metal curing catalyst An addition-curable organopolysiloxane composition containing the formula (I) is more preferred.

[0041] [(A-1) Alkenyl Group-Containing Organopolysiloxane] The alkenyl-containing organopolysiloxane, component (A-1), is an organopolysiloxane having two or more silicon-bonded alkenyl groups per molecule, and serves as the base component of the filler-containing resin composition of the present invention (which produces a thermally conductive silicone cured product). While the main chain typically consists essentially of repeating diorganosiloxane units, this may include a branched structure as part of the molecular structure, or may be cyclic. However, linear diorganopolysiloxanes are preferred from the standpoint of physical properties such as the mechanical strength of the cured product.

[0042] Examples of the alkenyl group include those typically having about 2 to 8 carbon atoms, such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, and cyclohexenyl groups, and among these, lower alkenyl groups such as vinyl and allyl are preferred, with vinyl being particularly preferred. Note that, although it is preferable for two or more alkenyl groups to be present in the molecule, it is preferable for them to be bonded only to silicon atoms at the molecular chain terminals in order to improve the flexibility of the resulting cured product.

[0043] The functional groups other than the alkenyl group are monovalent hydrocarbon groups, such as alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl; aryl groups such as phenyl, tolyl, xylyl, naphthyl, and biphenylyl; and aralkyl groups such as benzyl, phenylethyl, phenylpropyl, and methylbenzyl. Among these, those having 1 to 10 carbon atoms, and particularly those having 1 to 6 carbon atoms, are preferred, and alkyl groups having 1 to 3 carbon atoms, such as methyl, ethyl, propyl, and 3,3,3-trifluoropropyl, and phenyl are more preferred. Furthermore, the functional groups other than the alkenyl groups bonded to the silicon atom do not necessarily have to be the same.

[0044] The kinematic viscosity of this organopolysiloxane at 25°C is usually preferably 10 to 100,000 mm 2 / s, particularly preferably 5,000 to 100,000 mm 2 / s. The viscosity is in the range of 10mm 2 / s or more, the resulting resin composition has good storage stability, and 2 If the viscosity is 1 / s or less, the extensibility of the resulting resin composition will not be impaired.

[0045] In this specification, the kinematic viscosity is a value measured at 25°C using a Cannon-Fenske viscometer according to JIS Z 8803:2011.

[0046] The organopolysiloxane of component (A-1) may be used either alone, or in combination of two or more different viscosities.

[0047] [(A-2) Organohydrogenpolysiloxane] The organohydrogenpolysiloxane of component (A-2) is an organohydrogenpolysiloxane having an average of at least two, preferably 2 to 100, hydrogen atoms directly bonded to silicon atoms (hydrosilyl groups) per molecule, and functions as a crosslinker for component (A-1). Specifically, the hydrosilyl groups in component (A-2) and the alkenyl groups in component (A-1) undergo addition via a hydrosilylation reaction promoted by the platinum group metal curing catalyst of component (A-3), described below, to form a three-dimensional network structure with a crosslinked structure. Note that if the number of hydrosilyl groups is less than two, the composition will not cure.

[0048] The organohydrogenpolysiloxane used is one represented by the following average structural formula (1), but is not limited thereto. [ka] (In the formula, R is independently a hydrogen atom or a monovalent hydrocarbon group containing no aliphatic unsaturated bonds, and 2 or more, preferably 2 to 100, and more preferably 2 to 10, hydrogen atoms are present in one molecule, and e is an integer of 1 or more, preferably an integer of 10 to 200.)

[0049] In the general formula (1), examples of the monovalent hydrocarbon group R containing no aliphatic unsaturated bonds other than hydrogen atoms include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl; aryl groups such as phenyl, tolyl, xylyl, naphthyl, and biphenylyl; and aralkyl groups such as benzyl, phenylethyl, phenylpropyl, and methylbenzyl. Among these, groups having 1 to 10 carbon atoms, and particularly 1 to 6 carbon atoms, are preferred, and alkyl groups having 1 to 3 carbon atoms, such as methyl, ethyl, propyl, and 3,3,3-trifluoropropyl, and phenyl are more preferred. Furthermore, R does not necessarily have to be all the same.

[0050] The amount of component (A-2) added is, for example, an amount such that the hydrosilyl groups derived from component (A-2) are 0.1 to 5.0 moles per mole of alkenyl groups derived from component (A-1), preferably 0.3 to 2.0 moles, and more preferably 0.5 to 1.5 moles. When the amount of hydrosilyl groups derived from component (A-2) is 0.1 mole or more per mole of alkenyl groups derived from component (A-1), sufficient curing occurs, and the strength of the cured product is sufficient to retain its shape as a molded product, so that it is not difficult to handle due to insufficient strength. When the amount is 5.0 moles or less, the flexibility of the cured product is good, and it does not become brittle.

[0051] [(A-3) Platinum group metal curing catalyst] The platinum group metal curing catalyst of component (A-3) is a catalyst for promoting the addition reaction between the alkenyl groups derived from component (A-1) and the hydrosilyl groups derived from component (A-2), and examples thereof include catalysts well known for use in hydrosilylation reactions. Specific examples include platinum group metals such as platinum (including platinum black), rhodium, and palladium; platinum chlorides such as HPtCl·nH2O, HPtCl·nH2O, NaHPtCl·nH2O, KHPtCl·nH2O, NaPtCl·nH2O, KPtCl·nH2O, PtCl·nH2O, PtCl·nH2O, PtCl2, and NaHPtCl·nH2O (wherein n is an integer of 0 to 6, preferably 0 or 6); chloroplatinic acid and chloroplatinic acid salts; and alcohol-modified chloroplatinic acid (see U.S. Pat. No. 3,220,972, specification and claims). document), complexes of chloroplatinic acid and olefins (see U.S. Pat. Nos. 3,159,601, 3,159,662, and 3,775,452), platinum black, platinum group metals such as palladium supported on a support such as alumina, silica, or carbon, rhodium-olefin complexes, chlorotris(triphenylphosphine)rhodium (Wilkinson's catalyst), complexes of platinum chloride, chloroplatinic acid, or chloroplatinate with vinyl group-containing siloxanes, particularly vinyl group-containing cyclic siloxanes, and the like.

[0052] The amount of component (A-3) used may be an effective amount, preferably 0.1 to 2,000 ppm, more preferably 50 to 1,000 ppm, calculated as the mass of platinum group metal element relative to component (A-1). At 0.1 ppm or more, sufficient catalytic activity is obtained, and at 2,000 ppm or less, the effect of promoting the addition reaction is sufficient and costs can be reduced.

[0053] [Curable perfluoropolyether elastomer composition] Another preferred embodiment, the curable perfluoropolyether elastomer composition, will also be specifically described.

[0054] Examples of curable perfluoropolyether elastomer compositions include thermosetting perfluoropolyether elastomer compositions, moisture-curing perfluoropolyether elastomer compositions, and electron beam-curing perfluoropolyether elastomers. Examples of thermosetting perfluoropolyether elastomers include addition-curing perfluoropolyether elastomer compositions and peroxide-curing perfluoropolyether elastomer compositions. Among these, addition-curing perfluoropolyether elastomer compositions are preferred, and the following (A-4) to (A-6) are also preferred. (A-4) alkenyl group-containing perfluoropolyether compound, (A-5) fluorine-containing organohydrogenpolysiloxane, (A-6) Platinum group metal curing catalyst An addition-curable perfluoropolyether elastomer composition containing the formula (I) is more preferred.

[0055] [(A-4) Alkenyl group-containing perfluoropolyether compound] The alkenyl group-containing perfluoropolyether compound (A-4) is a perfluoropolyether compound having two or more alkenyl groups in one molecule, and serves as the main component of the filler-containing resin composition of the present invention (which provides a thermally conductive perfluoropolyether cured product). Usually, the main chain portion is basically composed of a repetition of perfluoropolyether units (perfluorooxyalkylene units).

[0056] Among them, the following general formula (2) CH2=CH-(X) z -Rf 1 -(X') z -CH=CH2(2) wherein X is a group of the formula: -CH2-, -CH2O-, -CH2OCH2- or -Y-NR 1 -CO- (wherein Y is a group of the formula: -CH2- or a group of the formula: [ka] is a divalent group represented by R 1 is a hydrogen atom or a monovalent hydrocarbon group; X' is a group of the formula: -CH2-, -CH2O-, -CH2OCH2- or -CO-NR 1 -Y'- (wherein Y' is a group of the formula: -CH2- or [ka] is a divalent group represented by R 1 is the same as above.) is a divalent group represented by Rf 1 is represented by the following general formula (i): -C t F 2t [OCF2CF(CF3)] p OCF2(CF2) r CF2O[CF(CF3)CF2O] q C t’ F 2t’ -(i) (In the formula, p and q are integers of 1 to 150, and the average of the sum of p and q is 2 to 200. Yeswherein r is an integer of 0 to 6, and t and t' are 2 or 3), or a compound represented by the following general formula (ii): -C t F 2t [OCF2CF(CF3)] u (OCF2) v OC t’ F 2t’ -(ii) (wherein u is an integer of 1 to 200, v is an integer of 1 to 50, and t and t' are the same as above) Yes (It is.) and z is independently 0 or 1.

[0057] Rf 1 The lower limit of the degree of polymerization (p+q) or (u+v) of the divalent perfluoropolyether group represented by the formula (I) is not particularly limited as long as it is an integer of 2 or more. However, it is preferable that the lower limit be an integer of 2 or more, which has low contamination and low residual properties. Ruta Therefore, it is preferably 30 or more, and particularly preferably 80 or more.

[0058] R 1 When is a monovalent hydrocarbon group, examples thereof include monovalent hydrocarbon groups having 1 to 20 carbon atoms, and specific examples thereof include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, cyclohexyl, octyl, and decyl; alkenyl groups such as vinyl and allyl; aryl groups such as phenyl, tolyl, and naphthyl; and aralkyl groups such as benzyl and phenylethyl.

[0059] [(A-5) Fluorine-containing organohydrogenpolysiloxane] The fluorine-containing organohydrogenpolysiloxane (A-5) acts as a crosslinking agent or chain extender for the above-mentioned component (A-4). For this purpose, the above-mentioned fluorine-containing organohydrogenpolysiloxane has two or more, preferably three or more, hydrogen atoms bonded to silicon atoms (i.e., hydrosilyl groups) per molecule. The component (A-5) can be used singly or in combination of two or more.

[0060] From the viewpoints of compatibility with component (A-4), dispersibility, etc., the fluorine-containing organohydrogenpolysiloxane preferably has one or more groups selected from perfluoroalkyl groups, perfluoroalkylene groups, perfluorooxyalkyl groups, and perfluorooxyalkylene groups in each molecule. Examples of these perfluoro groups include those represented by the following general formula: Perfluoroalkyl groups: C g F 2g+1 - (In the formula, g is an integer of 1 to 20, preferably 2 to 10.) Perfluoroalkylene groups: -C g F 2g - (wherein g is the same as above.) Perfluorooxyalkyl groups: [ka] (wherein f is an integer of 2 to 200, preferably 2 to 100, and h is an integer of 1 to 3. be .) Perfluorooxyalkylene groups: [ka] (wherein i and j are integers of 1 or more, and the average of i+j is 2 to 200, preferably 2 to 100) Yes (It is.) -(CF2CF2O) k (CF2O) L CF2- (wherein k and L are each an integer of 1 or more, and the average of k+L is 2 to 200, preferably Kuha 2 to 100.)

[0061] In addition, divalent linkages connecting these perfluoroalkyl groups, perfluorooxyalkyl groups, perfluoroalkylene groups, or perfluorooxyalkylene groups to silicon atoms are also useful. group is an alkylene group, an arylene group, or a combination thereof, or an aryl group attached to these groups. Teru The bond may be an amide bond, a carbonyl bond, or the like. For example, -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2OCH2-, -CH2CH2CH2-NH-CO-, -CH2CH2CH2-N(Ph)-CO-, -CH2CH2CH2-N(CH3)-CO-, -CH2CH2CH2-O-CO-, -Ph'-N(CH3)-CO- (Ph represents a phenyl group, and Ph' represents a phenylene group) and the like, each having 2 to 12 carbon atoms.

[0062] In the fluorine-containing organohydrogenpolysiloxane of component (A-5), examples of the monovalent fluorine-containing substituent, i.e., the monovalent substituent bonded to a silicon atom other than an organic group containing a perfluoroalkyl group or a perfluorooxyalkyl group, include unsubstituted hydrocarbon groups such as hydrocarbon groups having 1 to 20 carbon atoms, e.g., alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, cyclohexyl, octyl, and decyl; alkenyl groups such as vinyl and allyl; aryl groups such as phenyl, tolyl, and naphthyl; and aralkyl groups such as benzyl and phenylethyl. Also included are substituted hydrocarbon groups in which at least a portion of the hydrogen atoms of these hydrocarbon groups have been substituted with chlorine atoms or the like, such as chloromethyl, chloropropyl, and cyanoethyl.

[0063] The fluorine-containing organohydrogenpolysiloxane of component (A-5) may be cyclic, linear, three-dimensional network, or a combination thereof. The number of silicon atoms in this fluorine-containing organohydrogenpolysiloxane is not particularly limited, but is usually about 3 to 60, and preferably about 4 to 30.

[0064] The molecular weight of the fluorine-containing organohydrogenpolysiloxane of component (A-5) is preferably in the range of 750 to 3,000, and more preferably 800 to 2,400.

[0065] The amount of component (A-5) added is an effective amount required to cure component (A-4) and obtain a cured product with the required rubber elasticity. In particular, the amount is such that 0.5 to 5.0 moles, preferably 1.0 to 2.0 moles, of hydrosilyl groups in component (A-5) are supplied per mole of the total alkenyl groups in component (A-4) in the composition. A sufficient amount ensures a sufficient degree of crosslinking; if the amount is not too high, chain extension is not prioritized, resulting in sufficient curing, no foaming during curing, and no deterioration in the heat resistance of the resulting cured film.

[0066] [(A-6) Platinum group metal curing catalyst] The platinum group metal curing catalyst of component (A-6) is a catalyst for promoting the addition reaction between the alkenyl group derived from component (A-4) and the hydrosilyl group derived from component (A-5), and examples thereof include catalysts well known for use in hydrosilylation reactions.Specific examples include the same curing catalysts as those exemplified for component (A-3) above.

[0067] The amount of component (A-6) used may be an amount effective as a catalyst, for example, 0.1 to 500 ppm (by mass) of platinum group metals relative to component (A-4) is preferably blended.

[0068] [(B) Thermally conductive filler] The thermally conductive filler, component (B) of the present invention, is selected from thermally conductive fillers containing at least one of carbon and boron nitride.

[0069] The shape of the thermally conductive filler is not particularly limited, and examples thereof include spherical, elliptical, plate-like, scaly, fibrous, flat, needle-like, crushed, whisker-like, etc. In order to provide thermal conductivity to a molded article with oriented filler, anisotropic thermally conductive fillers such as fibrous, scaly, plate-like, flat, needle-like, and whisker-like shapes are preferred. Fibrous shapes are more preferred.

[0070] The size of the thermally conductive filler may be appropriately selected as needed and is not particularly limited, but is preferably a filler with an aspect ratio (average major axis length / average minor axis length) of 2 or more, more preferably 5 or more. The upper limit is not particularly limited, but can be, for example, 500 or less.

[0071] Such a thermally conductive filler is preferable because, when the filler is oriented in the longitudinal direction, the number of times heat transfers between the fillers is reduced, resulting in an improvement in the thermal conductivity of the filler in the longitudinal direction.

[0072] When the thermally conductive filler has anisotropy, its average major axis length and average minor axis length can be measured using a scanning electron microscope (SEM), and the aspect ratio can be calculated from these values. For example, the aspect ratio of carbon fibers is the value of "average fiber length / average fiber diameter" of the carbon fibers.

[0073] When the thermally conductive filler has a non-anisotropic shape, such as a spherical shape, its average particle size is the volume-based average particle size (median diameter) of the particle size distribution measured by a laser diffraction scattering method (JIS R1629:1997) (for example, it can be the value of the volume-based cumulative average particle size (50% diameter in cumulative fraction) measured using a Microtrac MT3300EX particle size analyzer manufactured by Microtrac Bell Co., Ltd.).

[0074] The thermally conductive filler may be used in combination with fillers of different shapes and sizes as required.

[0075] The content of the component (B) in the thermally conductive sheet of the present invention is preferably 50 to 90 mass %, more preferably 55 to 85 mass %, which is preferable because the thermally conductive filler in the thermally conductive sheet of the present invention is oriented to increase thermal conductivity.

[0076] [Other ingredients] The filler-containing resin composition may further contain, as needed, components such as solvents, thixotropy-imparting agents, dispersants, curing agents, curing accelerators, retarders, slight tackifiers, plasticizers, flame retardants, antioxidants, stabilizers, and colorants.

[0077] The filler-containing resin composition may also contain a filler other than the component (B). Specific examples include silica and titanium oxide. The amount of the filler to be added is not particularly limited, but is preferably 0 to 60 parts by mass, and more preferably 0 to 40 parts by mass, per 100 parts by mass of the component (A).

[0078] [Method for producing filler-containing resin composition] The filler-containing resin composition can be produced by mixing the polymer matrix, the thermally conductive filler, and, if necessary, the other components using a mixer or the like.

[0079] [Method for manufacturing thermally conductive sheets] The method for producing the thermally conductive sheet of the present invention includes the steps of molding and curing the filler-containing resin composition, and examples thereof include the following methods.

[0080] [Method for manufacturing thermally conductive sheets (I)] An example of a method for producing the thermally conductive sheet of the present invention is as follows: (I-1) a preparation step of preparing a filler-containing resin composition containing the polymer matrix (A) and the thermally conductive filler (B); (I-2) a filling step of filling the filler-containing resin composition into a mold; (I-3) a vibration step of ultrasonically vibrating the mold to degas and align the filler; (I-4) a heating step of obtaining a filler-containing string-like semi-cured resin composition from the filler-containing resin composition by heating; (I-5) a molding step of arranging the filler-containing string-shaped semi-cured resin composition in the longitudinal direction, heating and pressurizing the composition, and obtaining a filler-containing molded body; (I-6) a slicing step of slicing the filler-containing molded body to obtain a thermally conductive sheet; Therefore, there is a method for obtaining a thermally conductive sheet that has excellent thermal conductivity in the thickness direction and a low specific gravity by increasing the amount of filler.

[0081] Each of the above steps will be described in detail below.

[0082] Preparation process (I-1) In this step, a filler-containing resin composition containing the polymer matrix (A) and the thermally conductive filler (B) is prepared according to the method for producing the filler-containing resin composition.

[0083] Filling process (I-2) The prepared filler-containing resin composition is filled into a mold.

[0084] (Mold used in the filling process) The mold used in the above filling process has a width of 5.0 mm or less, a depth of width length + 1.0 mm or more, and a length of 10.0 mm or more, and has one or more grooves whose bottom shape is not particularly limited, but examples include V-shaped, semicircular, wavy, and flat shapes.

[0085] (Filling method) In the filling step, a specified amount of the filler-containing resin composition may be filled into the mold groove, or a large amount of the filler-containing resin composition may be filled and then the unnecessary portion may be scraped off with a squeegee or the like.

[0086] Adding a solvent (organic solvent) to the filler-containing resin composition is preferable because it reduces the viscosity of the filler-containing resin composition and improves the filling ability. Furthermore, when degassing and settling the thermally conductive filler in the subsequent vibration step, the long axis direction of the thermally conductive filler is more likely to be aligned along the long axis direction of the filler-containing string-like semi-cured resin composition.

[0087] Vibration process (I-3) The vibration step is performed by ultrasonically vibrating the mold to degas and align the thermally conductive filler. In order to obtain a filler-containing semi-cured resin composition in the form of strings in the subsequent heating step, the mold is ultrasonically vibrated to degas and precipitate and orient the filler, aligning the filler in the long axis direction of the filler-containing semi-cured resin composition in the long axis direction.

[0088] Heating process (I-4) The heating step is a step of heating the filler-containing resin composition to obtain the filler-containing string-like semi-cured resin composition. If the filler-containing resin composition contains a solvent, the heating step also includes a step of volatilizing the solvent by heating.

[0089] Molding process (I-5) The obtained filler-containing semi-cured resin composition in the form of strings is aligned in the longitudinal direction and heated and pressed to obtain a filler-containing molded article.

[0090] (Molds used in the molding process) The mold can have a concave shape with inner dimensions of 10.0 mm or more in width, 10.0 mm or more in length, and 10.0 mm or more in depth, and can have a lower mold with a flat bottom and an upper mold that is 0.01 to 0.2 mm shorter in width and length than the inner dimensions of the lower mold. There are no particular restrictions on the height of the upper mold, but it must be high enough to be able to pressurize the upper mold.

[0091] (Filling method) The filler-containing, string-like semi-cured resin composition obtained in the heating step is filled into the lower die of a metal mold as follows. (i) The mold is lined up so that the longitudinal direction is parallel to the X-axis direction, and then stacked and filled in the Z-axis direction. (ii) The mold is lined up so that the longitudinal direction is parallel to the Y-axis direction, and then stacked and filled in the Z-axis direction. In this way, a molded body in which the anisotropic filler or the like is oriented can be obtained more preferably and efficiently. The number of times of stacking in the Z-axis direction is preferably 2 or more, and more preferably 5 to 3,000.

[0092] (Molding method) In the molding step, the lower mold is pressed in the Z-axis direction by the upper mold and heated to completely harden the filler-containing string-shaped resin composition, thereby obtaining a filler-containing molded body.

[0093] As a method of applying pressure, it is preferable to gradually increase pressure from atmospheric pressure until the desired pressure is reached.

[0094] The pressure applied to the mold is appropriately selected depending on the desired shape and hardness of the filler-containing string-like resin composition, but is preferably 0.1 to 20.0 MPa, more preferably 0.5 to 5.0 MPa.

[0095] The temperature at which the mold is pressed is preferably from -10 to 40°C, more preferably from 0 to 30°C.

[0096] The curing conditions for the filler-containing resin composition in the form of strings are optimized depending on the type of resin in the filler-containing resin composition in the form of strings, etc. For example, the following conditions are preferred for the curing conditions for a filler-containing molded body obtained from a filler-containing resin composition in the form of strings using a silicone resin.

[0097] The curing temperature is preferably 50 to 200° C., more preferably 100 to 150° C. The curing time is preferably 1 minute to 24 hours, more preferably 5 minutes to 1 hour.

[0098] Slicing process (I-6) The slicing step is a step of slicing the filler-containing molded body obtained in the molding step to obtain a thermally conductive sheet of a desired thickness. Specifically, the slicing step is carried out through the following steps (i) or (ii): (i) The mold is aligned so that the longitudinal direction is parallel to the X-axis direction, and then stacked in the Z-axis direction. The filled filler-containing molded body is then parallel to the YZ plane. (ii) The mold is aligned so that the longitudinal direction is parallel to the Y-axis direction, and then stacked in the Z-axis direction. The filled molded body is then parallel to the XZ plane. By slicing the molded body to a desired thickness, a thermally conductive sheet in which the longitudinal direction of the anisotropic filler is oriented in the thickness direction can be obtained.

[0099] [Method for manufacturing thermally conductive sheets (II)] Furthermore, as a method for producing the thermally conductive sheet of the present invention that is different from the above-mentioned production method, (II-1) a preparation step of preparing a filler-containing resin composition containing the polymer matrix (A) and the thermally conductive filler (B); (II-2) a coating step of coating the filler-containing resin composition onto a film separator in one direction to a uniform thickness; (II-3) a heating step of obtaining a filler-containing sheet-shaped semi-cured resin composition from the filler-containing resin composition by heating; (II-4) a cutting step of peeling the filler-containing sheet-shaped semi-cured resin composition from the film separator and cutting it to fit the size of a mold used in a molding step; (II-5) a molding step of arranging cut pieces of the filler-containing sheet-like semi-cured resin composition in the coating direction and heating and pressurizing them to obtain a filler-containing molded body; (II-6) a slicing step of slicing the filler-containing molded body to obtain a thermally conductive sheet; There is a method for obtaining a thermally conductive sheet that has excellent thermal conductivity in the thickness direction and a low specific gravity by highly orienting the filler.

[0100] Each of the above steps will be described in detail below.

[0101] Preparation process (II-1) In this step, a filler-containing resin composition containing the polymer matrix (A) and the thermally conductive filler (B) is prepared according to the method for producing the filler-containing resin composition.

[0102] Coating process (II-2) The prepared filler-containing resin composition is applied in one direction onto a film separator so as to have a uniform thickness.

[0103] By using a Baker-type film applicator or the like to apply the filler-containing sheet-like semi-cured resin composition in one direction to a uniform thickness onto a film separator that can peel the filler-containing sheet-like semi-cured resin composition from the filler-containing resin composition in the subsequent heating step, the filler can be aligned so that its long axis direction is parallel to the application direction of the filler-containing sheet-like semi-cured resin composition.

[0104] Heating process (II-3) The heating step is a step of heating the filler-containing resin composition to obtain the filler-containing sheet-shaped semi-cured resin composition. If the filler-containing resin composition contains a solvent, the heating step also includes a step of volatilizing the solvent by heating.

[0105] Cutting process (II-4) In the cutting step, the filler-containing sheet-shaped semi-cured resin composition obtained in the heating step is peeled from the film separator and cut to fit the size of a mold to be used in the molding step. By cutting the size to a width and length that are -0.3 to -1.0 mm smaller than the inner dimensions of the mold, the filler-containing sheet-shaped semi-cured resin composition can be easily filled in the subsequent molding step.

[0106] Molding process (II-5) The obtained filler-containing sheet-like semi-cured resin compositions are arranged so that the coating flow direction is parallel, and heated and pressed to obtain a filler-containing molded article.

[0107] (Molds used in the molding process) This is the same as the molding step (I-5) above.

[0108] (Filling method) The filler-containing semi-cured resin composition sheet obtained in the cutting step is filled into the lower die of a mold as follows. (i) The materials are aligned in a mold so that the coating flow direction is parallel to the X-axis direction, and then stacked and filled in the Z-axis direction. (ii) The mold is lined up so that the coating flow direction is parallel to the Y-axis direction, and then stacked and filled in the Z-axis direction. In this way, a molded body in which the anisotropic filler or the like is oriented can be obtained more preferably and efficiently. The number of times of stacking in the Z-axis direction is preferably 2 or more, and more preferably 5 to 3,000.

[0109] (Molding method) In the molding step, the lower mold is pressed in the Z-axis direction by the upper mold and heated to completely cure the filler-containing sheet-shaped resin composition, thereby obtaining a filler-containing molded body.

[0110] As a method of applying pressure, it is preferable to gradually increase pressure from atmospheric pressure until the desired pressure is reached.

[0111] The pressure applied to the mold is appropriately selected depending on the desired shape and hardness of the filler-containing sheet-shaped resin composition, but is preferably 0.1 to 20.0 MPa, more preferably 0.5 to 5.0 MPa.

[0112] The temperature at which the mold is pressed is preferably from -10 to 40°C, more preferably from 0 to 30°C.

[0113] The curing conditions for the filler-containing sheet-shaped resin composition are optimized depending on the type of resin in the filler-containing sheet-shaped resin composition, etc. For example, the following conditions are preferred for curing a filler-containing molded article obtained from a filler-containing sheet-shaped resin composition using a silicone resin.

[0114] The curing temperature is preferably 50 to 200° C., more preferably 100 to 150° C. The curing time is preferably 1 minute to 24 hours, more preferably 5 minutes to 1 hour.

[0115] Slicing process (II-6) The slicing step is a step of slicing the molded body obtained in the molding step to obtain a thermally conductive sheet of a desired thickness. Specifically, the slicing step involves the following steps (i) and (ii): (i) The mold is aligned so that the coating flow direction is parallel to the X-axis direction, and then stacked in the Z-axis direction. The filled molded body is parallel to the YZ plane. (ii) The mold is aligned so that the coating flow direction is parallel to the Y-axis direction, and stacked in the Z-axis direction. The filled molded body is parallel to the XZ plane. By slicing the molded body to a desired thickness, a thermally conductive sheet in which the longitudinal direction of the anisotropic filler is oriented in the thickness direction can be obtained.

[0116] [Thermal conductive sheet] The thermally conductive sheet of the present invention has a thermal conductivity in the thickness direction of 15 W / m K or more, and the degree of orientation of the long axis of the thermally conductive filler contained in the thermally conductive sheet in the thickness direction of the thermally conductive sheet is 1.0 or more. The maximum thermal conductivity of conventional thermally conductive sheets with a high loading of thermally conductive filler is about 13 W / m K, but the thermally conductive sheet of the present invention exceeds this.

[0117] If the degree of orientation is 1.0 or less, it is not possible to provide the thermal conductive sheet with a good thermal conductivity of 15 W / m·K or more. The method for measuring the degree of orientation is as described above.

[0118] The thermal conductivity can be measured in accordance with JIS R 1611:2010 using a laser flash method (LFA 447 Nanoflash, manufactured by Netzsch GmbH).

[0119] Furthermore, the thermally conductive sheet of the present invention has a low specific gravity, preferably less than 2.0. The specific gravity value can be determined by measuring the specific gravity at 25°C in accordance with JIS K 6249:2003.

[0120] Such a thermally conductive sheet of the present invention has excellent thermal conductivity in the thickness direction and a low specific gravity. [Example]

[0121] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these. The kinematic viscosity is the value measured at 25°C using a Cannon-Fenske viscometer according to JIS Z 8803:2011, the average fiber length, average fiber diameter, and aspect ratio were determined by SEM measurement, and the average particle size is the cumulative average particle size (median diameter) on a volume basis measured using a Microtrac MT3300EXII particle size analyzer manufactured by Microtrac Bell Corporation.

[0122] <Filler-containing organopolysiloxane composition A> Filler-containing organopolysiloxane composition A (specific gravity 1.3) was obtained by mixing 38.2 mass% of an addition reaction type organopolysiloxane composition (specific gravity 1.0), 22.6 mass% of carbon fiber (average fiber length 50 μm, average fiber diameter 10 μm, aspect ratio 5, specific gravity 2.2), 22.6 mass% of carbon fiber (average fiber length 250 μm, average fiber diameter 10 μm, aspect ratio 25, specific gravity 2.2), and 16.6 mass% of toluene (specific gravity 0.9).

[0123] The components of the addition reaction type organopolysiloxane composition are the following (A-1) to (A-3).

[0124] Component (A-1) Organopolysiloxane represented by the following formula: 97.1% by mass [ka] In the above formula, n is the kinematic viscosity at 25°C in units of 30,000 mm 2 / s.

[0125] Ingredient (A-2) Organohydrogenpolysiloxane represented by the following formula: 2.2% by mass [ka] In the above formula, o=27 and p=3, each of which is the average degree of polymerization.

[0126] Ingredient (A-3) 5% chloroplatinic acid 2-ethylhexanol solution: 0.7% by mass

[0127] <Filler-containing organopolysiloxane composition B> Filler-containing organopolysiloxane composition B (specific gravity 1.3) was obtained by mixing 31.1 mass% of an addition reaction type organopolysiloxane composition (specific gravity 1.0), 23.6 mass% of carbon fiber (average fiber length 50 μm, average fiber diameter 10 μm, aspect ratio 5, specific gravity 2.2), 23.6 mass% of carbon fiber (average fiber length 250 μm, average fiber diameter 10 μm, aspect ratio 25, specific gravity 2.2), and 21.7 mass% of toluene (specific gravity 0.9).

[0128] <Filler-containing organopolysiloxane composition C> Filler-containing organopolysiloxane composition C (specific gravity 1.3) was obtained by mixing 23.5 mass% of an addition reaction type organopolysiloxane composition (specific gravity 1.0), 24.6 mass% of carbon fiber (average fiber length 50 μm, average fiber diameter 10 μm, aspect ratio 5, specific gravity 2.2), 24.6 mass% of carbon fiber (average fiber length 250 μm, average fiber diameter 10 μm, aspect ratio 25, specific gravity 2.2), and 27.3 mass% of toluene (specific gravity 0.9).

[0129] <Filler-containing organopolysiloxane composition D> 18.5% by mass of addition reaction type organopolysiloxane composition (specific gravity 1.0), 64.9% by mass of flaky boron nitride (average particle size 30 μm, aspect ratio 30, specific gravity 2.2) ,toThen, 16.7 mass % of toluene (specific gravity 0.9) was mixed to obtain a filler-containing organopolysiloxane composition D (specific gravity 1.5).

[0130] <Filler-containing organopolysiloxane composition E> Filler-containing organopolysiloxane composition E (specific gravity 1.4) was obtained by mixing 45.8 mass% of an addition reaction type organopolysiloxane composition (specific gravity 1.0), 27.1 mass% of carbon fiber (average fiber length 50 μm, average fiber diameter 10 μm, aspect ratio 5, specific gravity 2.2), and 27.1 mass% of carbon fiber (average fiber length 250 μm, average fiber diameter 10 μm, aspect ratio 25, specific gravity 2.2). (Filler-containing organopolysiloxane composition A without toluene)

[0131] <Filler-containing organopolysiloxane composition F> Filler-containing organopolysiloxane composition F (specific gravity 1.7) was obtained by mixing 22.1 mass% of an addition reaction type organopolysiloxane composition (specific gravity 1.0) and 77.9 mass% of flaky boron nitride (average particle size 30 μm, aspect ratio 30, specific gravity 2.2). (Filler-containing organopolysiloxane composition D without toluene)

[0132] <Mold> The molds used in the examples and comparative examples will be described below with reference to the drawings. Fig. 1 shows a mold used in the filling step of the present invention, Fig. 2 shows a cross section of the mold used in the filling step, and Fig. 3 shows a mold used in the molding step.

[0133] Example 1 We prepared a mold for the filling process with a groove having a width of 1.5 mm, length of 50.0 mm, and depth of 2.5 mm and a semicircular bottom shape; a lower mold for the molding process with inner dimensions of width 33.0 mm (X-axis), length 52.0 mm (Y-axis), and depth 50.0 mm (Z-axis); and an upper mold for the molding process with width 32.9 mm, length 51.9 mm, and height 40.0 mm.

[0134] The above filler-containing organopolysiloxane composition A was filled into the mold used in the above filling step so that it overflowed from the grooves, and the overflowed portion was scraped off with a squeegee.

[0135] The mold used in the filling step filled with the filler-containing organopolysiloxane composition A was vibrated for 30 minutes in a Sharp tabletop ultrasonic cleaner UT-106 under conditions of a water temperature of 25°C, a frequency of 37 kHz, and an output of 100%, and then dried at 80°C for 2 minutes to obtain a filler-containing string-shaped resin composition A. Furthermore, the filler-containing string-shaped resin composition A was filled into the lower mold 2 of the mold used in the molding step so that it was arranged in the Y-axis direction, forming 21 rows in the X-axis direction and 40 columns in the Z-axis direction, and the upper mold 1 used in the molding step was pressed in the Z-axis direction with a hydraulic press to a depth of 1.0 m. P Under pressure at a, 120℃ × 30 minutes The cured product, which was the filler-containing molded body, was then heated for a short time to obtain a filler-containing molded body 1. The cured product, which was the filler-containing molded body, was sliced ​​parallel to the XZ plane with a cutter knife to obtain a 2 mm-thick thermally conductive sheet 1. An SEM image of the surface of the thermally conductive sheet 1 is shown in FIG. 5, and the results of X-ray diffraction are shown in FIG. 6.

[0136] <Example 2> The filler-containing organopolysiloxane composition was changed to the filler-containing organopolysiloxane composition B, and a thermally conductive sheet 2 was obtained by the same production method as in Example 1. An SEM image of the surface of the thermally conductive sheet 2 is shown in Figure 7, and the X-ray diffraction results are shown in Figure 8.

[0137] Example 3 The filler-containing organopolysiloxane composition was changed to the filler-containing organopolysiloxane composition C, and a thermally conductive sheet 3 was obtained by the same production method as in Example 1. An SEM image of the surface of the thermally conductive sheet 3 is shown in Figure 9, and the X-ray diffraction results are shown in Figure 10.

[0138] Example 4 The filler-containing organopolysiloxane composition A was applied to a fluorine-surface-treated film separator using a Baker-type film applicator, and after drying at 80°C for 10 minutes, a 500-550µm-thick filler-containing sheet-like resin composition A was obtained. The filler-containing sheet-like resin composition A was then cut into pieces 32.5mm wide and 51.5mm long, and 80 pieces were stacked and loaded into the lower die of the mold used in the molding step. The upper die used in the molding step was then pressed 1.0mm in the Z-axis direction using a hydraulic press. P Under pressure at a, 120℃ × 30 minutes The mixture was heated for a short time to obtain a filler-containing molded body 4.

[0139] The cured filler-containing molded product was sliced ​​parallel to the XZ plane with a cutter knife to obtain a 2 mm-thick thermally conductive sheet 4. An SEM image of the surface of thermally conductive sheet 4 is shown in FIG. 11, and the X-ray diffraction results are shown in FIG. 12.

[0140] <Example 5> The filler-containing organopolysiloxane composition was changed to the filler-containing organopolysiloxane composition D, and a thermally conductive sheet 5 was obtained by the same production method as in Example 1. An SEM image of the surface of the thermally conductive sheet 5 is shown in FIG. 13, and the X-ray diffraction results are shown in FIG.

[0141] Example 6 We prepared a mold for the filling process with a width of 2.7 mm, length of 50.0 mm, depth of 2.5 mm, and a groove with a semicircular bottom shape; a lower mold for the molding process with inner dimensions of width 33.0 mm (X-axis), length 52.0 mm (Y-axis), and depth 50.0 mm (Z-axis); and an upper mold for the molding process with width 32.9 mm, length 51.9 mm, and height 40.0 mm.

[0142] The above filler-containing organopolysiloxane composition A was filled into the mold used in the above filling step so that it overflowed from the grooves, and the overflowed portion was scraped off with a squeegee.

[0143] The mold used in the filling step filled with the filler-containing organopolysiloxane composition A was vibrated for 30 minutes in a Sharp tabletop ultrasonic cleaner UT-106 under conditions of a water temperature of 25°C, a frequency of 37 kHz, and an output of 100%, and then dried at 80°C for 2 minutes to obtain a filler-containing string-shaped resin composition A. Furthermore, the filler-containing string-shaped resin composition A was filled into the lower mold 2 of the mold used in the molding step so that it was arranged in the Y-axis direction, in 12 rows in the X-axis direction, and in 40 rows in the Z-axis direction, and the upper mold 1 used in the molding step was pressed in the Z-axis direction with a hydraulic press to a depth of 1.0 m. P Under pressure at a, 120℃ × 30 minutes The cured product, which was the filler-containing molded body, was then heated for a short time to obtain a filler-containing molded body 6. The cured product, which was the filler-containing molded body, was sliced ​​parallel to the XZ plane with a cutter knife to obtain a 2 mm-thick thermally conductive sheet 6. An SEM image of the surface of the thermally conductive sheet 6 is shown in FIG. 15, and the results of X-ray diffraction are shown in FIG. 16.

[0144] <Comparative Example 1> A mold was prepared with a lower recess of 50 mm wide, 50 mm long, and 2.0 mm high as shown in Figure 4. Mixture E was filled into lower mold 4 of the mold, and a pressure of 10 MPa was applied from above upper mold 3 using a hydraulic press. The mixed composition was cured by heating and curing at 110°C for 30 minutes, yielding a thermally conductive sheet 7 with a thickness of 2 mm.

[0145] FIG. 17 shows an SEM image of the surface of a sheet obtained by slicing the thermally conductive sheet 7 in the thickness direction, and FIG. 18 shows the results of X-ray diffraction.

[0146] <Comparative Example 2> The filler-containing organopolysiloxane composition was changed to the filler-containing organopolysiloxane composition F, and a thermally conductive sheet 8 was obtained by the same production method as in Comparative Example 1. An SEM image of the surface of the thermally conductive sheet 7 is shown in FIG. 19, and the X-ray diffraction results are shown in FIG. 20.

[0147] <Comparative Example 3> We prepared a mold for the filling process with a width of 3.5 mm, length of 50.0 mm, depth of 2.5 mm and a semicircular groove at the bottom, a lower mold for the molding process with inner dimensions of width 33.0 mm (X-axis), length 52.0 mm (Y-axis) and depth 50.0 mm (Z-axis), and an upper mold for the molding process with width 32.9 mm, length 51.9 mm and height 40.0 mm.

[0148] The above filler-containing organopolysiloxane composition A was filled into the mold used in the above filling step so that it overflowed from the grooves, and the overflowed portion was scraped off with a squeegee.

[0149] The mold used in the filling step filled with the filler-containing organopolysiloxane composition A was vibrated for 30 minutes in a Sharp tabletop ultrasonic cleaner UT-106 under conditions of a water temperature of 25°C, a frequency of 37 kHz, and an output of 100%, and then dried at 80°C for 2 minutes to obtain a filler-containing string-shaped resin composition A. Furthermore, the filler-containing string-shaped resin composition A was filled into the lower mold 2 of the mold used in the molding step so that it was arranged in the Y-axis direction, in 9 rows in the X-axis direction, and in 40 rows in the Z-axis direction, and the upper mold 1 used in the molding step was pressed in the Z-axis direction with a hydraulic press to a depth of 1.0 m. P Under pressure at a, 120℃ × 30 minutes The cured product, which was the filler-containing molded body, was then heated for a short time to obtain a filler-containing molded body 9. The cured product, which was the filler-containing molded body, was sliced ​​parallel to the XZ plane with a cutter knife to obtain a 2 mm-thick thermally conductive sheet 9. An SEM image of the surface of the thermally conductive sheet 9 is shown in FIG. 21, and the results of X-ray diffraction are shown in FIG. 22.

[0150] <Evaluation items> <Orientation degree> Each of the thermally conductive sheets obtained in the examples and comparative examples was punched out into a circle with a diameter of 12.7 mm, and this was used as a test piece. The resultant was analyzed by a tabletop powder X-ray diffractometer D2 PHASER 2nd Generation manufactured by BRUKER JAPAN under the following conditions: scan range: 20-90°, step size: 0.024°, sample rotation: 10 rpm, voltage: 30 KV, current: 10 mA Measurements were performed under the above conditions, and the results calculated from the peak intensities of the measurement results are shown in Table 1. The degree of orientation was defined as {sum of vertical counts + (sum of diagonal counts / 2)} / horizontal count. Vertical count 2θ=41.0~43.0°(100 faces), 2θ=76.5~78.5°(110 faces) Diagonal count 2θ=43.5~45.5°(101 faces), 2θ=81.5~83.5°(112 faces) Horizontal count 2θ=25.5~27.5°(002 surface)

[0151] <Thermal conductivity> Each thermally conductive sheet obtained in the examples and comparative examples was punched out into a circle with a diameter of 12.7 mm, and the thermal conductivity of each test piece was measured using a laser flash method (LFA 447 Nanoflash, manufactured by Netzsch GmbH) in accordance with JIS R 1611: 2010. The results are shown in Table 1.

[0152] <Specific gravity> The specific gravity of each of the thermally conductive sheets obtained in the examples and comparative examples was measured at 25° C. in accordance with JIS K 6249:2003. The results are shown in Table 1.

[0153] [Table 1]

[0154] Thermally conductive sheet Example 1, which has the same carbon fiber filler content of 54.2 mass%, has a degree of orientation of 5.16 and a thermal conductivity of 21.8 W / m·K, whereas Example 4 has a degree of orientation of 1.20 and a thermal conductivity of 17.2 W / m·K, and Example 6 has a degree of orientation of 1.08 and a thermal conductivity of 15.7 W / m·K. Furthermore, Comparative Example 1 has a degree of orientation of 0.05 and a thermal conductivity of 2.1 W / m·K, and Comparative Example 3 has a degree of orientation of 0.94 and a thermal conductivity of 14.7 W / m·K, which means that for the same filler content, a higher degree of orientation leads to higher thermal conductivity.

[0155] Furthermore, when comparing thermally conductive sheets with different carbon fiber filler mass percentages, Example 1 had 54.2 mass%, a degree of orientation of 5.16, and a thermal conductivity of 21.8 W / m·K, while Example 2 had 60.3 mass%, a degree of orientation of 4.40, and a thermal conductivity of 32.7 W / m·K, and Example 3 had 67.7 mass%, a degree of orientation of 5.43, and a thermal conductivity of 51.9 W / m·K.This means that for the same degree of orientation, a higher filler mass percentage results in higher thermal conductivity.

[0156] Furthermore, while the thermally conductive sheet of Example 5, which contains the same amount of boron nitride filler (77.9 mass%), has an orientation degree of 2.64 and a thermal conductivity of 16.2 W / m K, the thermally conductive sheet of Comparative Example 2 has an orientation degree of 0.08 and a thermal conductivity of only 1.3 W / m K. This means that for the same amount of filler, a higher orientation degree results in higher thermal conductivity.

[0157] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0158] 1...Upper mold of a mold used in a molding process, 2...Lower mold of a mold used in a molding process, 3...Upper mold of the mold used in the comparative example, 4...Lower mold of the mold used in the comparative example.

Claims

1. A thermally conductive sheet containing a thermally conductive filler (B) containing one or more of carbon and boron nitride in a polymer matrix (A), wherein the thermal conductivity of the thermally conductive sheet in the thickness direction is 15 W / m·K or more, the degree of orientation of the major axis of the thermally conductive filler in the thickness direction of the thermally conductive sheet is 1.0 or more, and the specific gravity of the thermally conductive sheet is less than 2.

0.

2. 2. The thermally conductive sheet according to claim 1, wherein the content of the component (B) in the thermally conductive sheet is 50 to 90 mass %.

3. 3. The thermally conductive sheet according to claim 1, wherein the component (A) is a curable polymer composition containing at least one selected from organopolysiloxane, polyurethane, polyacrylate, perfluoropolyether elastomer, unsaturated polyester resin, polyamide resin, epoxy resin, and phenolic resin.

4. 4. The thermally conductive sheet according to claim 1, wherein the component (B) has a shape of fiber, scale, plate, flat, needle, or whisker.

5. 5. The thermally conductive sheet according to claim 1, wherein the aspect ratio of the component (B) is 2 or more.

6. A method for producing the thermally conductive sheet according to any one of claims 1 to 5, (I-1) a preparation step of preparing a filler-containing resin composition containing the polymer matrix (A) and the thermally conductive filler (B); (I-2) a filling step of filling the filler-containing resin composition into a mold; (I-3) a vibration step of ultrasonically vibrating the mold to degas and align the filler; (I-4) a heating step of obtaining a filler-containing semi-cured resin composition in the form of strings from the filler-containing resin composition by heating; (I-5) a molding step of arranging the filler-containing string-shaped semi-cured resin composition in the longitudinal direction, heating and pressurizing it, and obtaining a filler-containing molded body; (I-6) a slicing step of slicing the filler-containing molded body to obtain a thermally conductive sheet; A method for producing a thermally conductive sheet, comprising:

7. A method for producing the thermally conductive sheet according to any one of claims 1 to 5, (II-1) a preparation step of preparing a filler-containing resin composition containing the polymer matrix (A) and the thermally conductive filler (B); (II-2) a coating step of coating the filler-containing resin composition onto a film separator in one direction to a uniform thickness; (II-3) a heating step of obtaining a filler-containing sheet-shaped semi-cured resin composition from the filler-containing resin composition by heating; (II-4) a cutting step of peeling the filler-containing sheet-shaped semi-cured resin composition from the film separator and cutting it to fit the size of a mold used in a molding step; (II-5) a molding step of arranging cut pieces of the filler-containing sheet-like semi-cured resin composition in the coating direction and heating and pressurizing them to obtain a filler-containing molded body; (II-6) a slicing step of slicing the filler-containing molded body to obtain a thermally conductive sheet; A method for producing a thermally conductive sheet, comprising:

8. 8. The method for producing a thermally conductive sheet according to claim 6, wherein the filler-containing resin composition further contains an organic solvent.

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