Insulating heat diffusion sheet and manufacturing method thereof

Abstract

An insulating thermal diffusion sheet that has thermal conductivity while maintaining insulating properties, and a manufacturing method thereof are provided. This insulating thermal diffusion sheet is configured from a paper sheet containing binder fibers and 80-95 wt% boron nitride, wherein the insulation volume resistivity is 3.0×1013Ω·cm or greater, the thermal conductivity is 8 W / m·K or greater in the in-plane direction and 0.5 W / m·K or greater in the thickness direction. By means of this configuration, it is possible to achieve excellent heat dissipation properties while maintaining electrical insulation properties.

Description

[Technical Field]

[0001] The present invention relates to an insulating thermal diffusion sheet and a method for producing the same. [Background technology]

[0002] Thermal diffusion sheets and heat dissipation sheets for promoting heat dissipation from heat-generating bodies are used in a variety of applications. For example, in automotive and stationary power supply devices that stack multiple secondary battery cells to achieve high output and capacity, it is known that the secondary battery cells generate heat during charging and discharging. To improve the heat dissipation of such secondary battery cells, a thermal diffusion sheet is attached to the outer can of the battery cell. To improve heat dissipation with a thermal diffusion sheet, high thermal conductivity is required. In addition to secondary battery cells, electronic components such as power transistors, CPUs, and SoCs, as well as light-emitting elements such as LEDs and LDs, are also heat-generating bodies and therefore require heat dissipation properties.

[0003] However, materials with high thermal conductivity, such as metals, generally also have high electrical conductivity, making them unsuitable for applications requiring insulation. In particular, secondary battery cells often have metal exterior cans, which have an electrical potential, so they require insulation to prevent unintended short circuits. Similarly, short circuits must be avoided in electronic components. For this reason, insulation has traditionally been achieved by using a thermal diffusion sheet between insulating sheets such as resin sheets or paper.

[0004] However, while such insulating sheets do not conduct electricity, they often also do not conduct heat, and so even if a thermal diffusion sheet is used to improve heat dissipation, the insulating sheet forms a heat insulating layer, impairing thermal conduction. In this way, increasing thermal conductivity leads to a loss of insulation, and vice versa, so it has traditionally been difficult to improve heat dissipation while maintaining insulation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-135371 [Patent Document 2] Japanese Patent Publication No. 2020-105505 [Patent Document 3] Patent No. 6755421 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide an insulating thermal diffusion sheet that exhibits thermal conductivity while maintaining insulation properties, and a method for manufacturing the same.

[0007] The insulating thermal diffusion sheet according to the first embodiment of the present invention is made of a paper sheet containing 80 to 95% by weight of boron nitride and binder fibers, and has an insulation resistance volume ratio of 3.0 × 10 13 The thermal conductivity is 8 W / m K or more in the surface direction and 0.5 W / m K or more in the thickness direction. This configuration makes it possible to achieve excellent heat dissipation while maintaining electrical insulation.

[0008] Furthermore, in the insulating thermal diffusion sheet according to the second embodiment of the present invention, in the above embodiment, the dielectric strength against AC voltage is 10 kV / mm or more.

[0009] Furthermore, in any of the above-mentioned embodiments, the insulating thermal diffusion sheet according to a third aspect of the present invention has a dielectric strength against a DC voltage of 13 kV / mm or more.

[0010] Furthermore, in any one of the above-mentioned embodiments, the insulating thermal diffusion sheet according to a fourth embodiment of the present invention has a static friction coefficient of 0.15 to 0.18.

[0011] Furthermore, in any one of the above-mentioned embodiments, the insulating thermal diffusion sheet according to a fifth embodiment of the present invention has a dynamic friction coefficient of 0.10 to 0.12.

[0012] Furthermore, in the insulating thermal diffusion sheet according to a sixth aspect of the present invention, in any one of the above aspects, the binder fibers are at least one of synthetic fibers and fine fibrous organic fibers.

[0013] Furthermore, in the insulating thermal diffusion sheet according to a seventh aspect of the present invention, in any one of the above aspects, the synthetic fibers contain aramid pulp and PPS fibers.

[0014] Furthermore, in an eighth aspect of the present invention, in any one of the above aspects, the insulating thermal diffusion sheet is characterized in that the fine fibrous organic fibers contain fine fibrous cellulose.

[0015] Furthermore, in the insulating thermal diffusion sheet according to a ninth embodiment of the present invention, in any one of the above-mentioned embodiments, the papermaking sheet does not contain graphite.

[0016] Furthermore, in a tenth aspect of the present invention, in any one of the above-mentioned aspects, the electrically insulating thermal diffusion sheet is such that the papermaking sheet is a wet-laid papermaking sheet.

[0017] Furthermore, in an eleventh aspect of the present invention, in any one of the above aspects, the electrically insulating thermal diffusion sheet is such that the paper sheet is subjected to a heat and pressure treatment. With this configuration, high density is achieved by the heat and pressure treatment.

[0018] Furthermore, in a twelfth aspect of the present invention, in any one of the above-mentioned aspects, the insulating thermal diffusion sheet is such that the thickness of the paper sheet is 0.3 mm or less.

[0019] Furthermore, a method for producing an insulating thermal diffusion sheet according to a thirteenth aspect of the present invention includes the steps of forming a sheet by wet papermaking using 80 to 95% by weight of boron nitride and binder fibers, and subjecting the sheet to a heat-pressure treatment. This allows the sheet to exhibit excellent heat dissipation properties while maintaining electrical insulation. Furthermore, the heat-pressure treatment achieves high densification.

[0020] Furthermore, in the method for producing an electrically insulating thermal diffusion sheet according to a fourteenth aspect of the present invention, in any one of the above aspects, the binder fibers are at least one of synthetic fibers and fine fibrous organic fibers.

[0021] Furthermore, in the method for producing an insulating thermal diffusion sheet according to a fifteenth aspect of the present invention, in any one of the above aspects, the insulation resistance volume ratio is 3.0×10 13 The material has a surface resistance of 8 W / m K or more and a thermal conductivity of 0.5 W / m K or more in the thickness direction, which allows it to exhibit excellent heat dissipation while maintaining electrical insulation.

[0022] Furthermore, in the method for producing an insulating thermal diffusion sheet according to a sixteenth aspect of the present invention, in any one of the above aspects, the dielectric strength against AC voltage is 10 kV / mm or more.

[0023] Furthermore, in the method for producing an insulating thermal diffusion sheet according to a seventeenth aspect of the present invention, in any one of the above aspects, the dielectric strength against a DC voltage is 13 kV / mm or more.

[0024] Furthermore, in the method for producing an electrically insulating thermal diffusion sheet according to an eighteenth embodiment of the present invention, in any one of the above embodiments, the static friction coefficient is 0.15 to 0.18.

[0025] Furthermore, in the method for producing an electrically insulating thermal diffusion sheet according to a nineteenth embodiment of the present invention, in any one of the above embodiments, the coefficient of dynamic friction is 0.10 to 0.12.

[0026] Furthermore, in the method for producing an electrically insulating thermal diffusion sheet according to a twentieth embodiment of the present invention, in any one of the above embodiments, the sheet contains aramid pulp and PET fibers.

[0027] Furthermore, the method for manufacturing an insulating thermal diffusion sheet according to the 21st embodiment of the present invention is, in any of the above embodiments, that the binder fibers are fine fibrous organic fibers, and the fine fibrous organic fibers are fine fibrous cellulose.

[0028] Furthermore, in the method for producing an electrically insulating thermal diffusion sheet according to a 22nd embodiment of the present invention, in any one of the above-mentioned embodiments, the sheet does not contain graphite. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is an exploded perspective view showing a power supply device according to a first embodiment of the present invention. [Figure 2] 1 is a schematic cross-sectional view of a thermal diffusion sheet according to a first embodiment. [Figure 3] FIG. 4 is a cross-sectional view showing an insulating thermal diffusion sheet according to a second embodiment. [Figure 4] FIG. 10 is a cross-sectional view showing how an insulating thermal diffusion sheet according to a third embodiment is obtained. [Figure 5] 1 is a schematic diagram illustrating the configuration of a manufacturing apparatus for manufacturing a thermal radiation sheet according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] Embodiments of the present invention will be described below with reference to the drawings. However, the embodiments described below are merely examples for embodying the technical concept of the present invention, and the present invention is not limited thereto. Furthermore, this specification in no way specifies the components set forth in the claims as components of the embodiments. The dimensions, materials, shapes, and relative positions of components described in the embodiments are not intended to limit the scope of the present invention, and are merely illustrative unless otherwise specified. The size and relative positions of components shown in the drawings may be exaggerated for clarity. Furthermore, in the following description, the same names and symbols indicate identical or similar components, and detailed descriptions will be omitted as appropriate. Furthermore, the elements constituting the present invention may be configured with the same components, so that one component serves multiple functions, or conversely, the functions of one component may be shared among multiple components. [Embodiment 1]

[0031] The insulating thermal diffusion sheet according to an embodiment of the present invention can be used in applications requiring not only thermal conductivity but also electrical insulation. For example, it can be used as a buffer sheet interposed between a heat-generating element requiring insulation and a heat sink or other heat dissipation sheet attached directly to the heat-generating element to dissipate heat. As an example, the exploded perspective view of FIG. 1 shows an example of a power supply device using multiple stacked secondary battery cells. The power supply device 100 shown in this figure is used as an on-board power supply for driving the motor that turns the wheels of electric vehicles and hybrid vehicles. Furthermore, power supply devices are not limited to automobiles; they can also be used as power sources for electric vehicles such as electric buses, trains, and electric carts, as backup power sources for factories and base stations, and even as home storage batteries. Furthermore, the insulating thermal diffusion sheet according to an embodiment of the present invention can be used for a variety of applications, not just power supplies, such as for dissipating heat from heat-generating elements. For example, the insulating heat diffusion sheet according to the embodiment of the present invention can be used for heat dissipation and insulation in the power supply devices described above and the motors of electric vehicles, railways, and other vehicles driven by the power supply devices.

[0032] The power supply device 100 shown in FIG. 1 includes multiple secondary battery cells 20 and an insulating heat diffusion sheet 10 interposed between the secondary battery cells 20. The secondary battery cells 20 have outer cans 21 in a rectangular cylindrical shape with a bottom, and multiple cells are stacked with their main surfaces facing each other. For example, the stacking is performed by covering both end faces of a battery stack 25 formed by stacking the secondary battery cells 20 with end plates 30 and fastening the end plates 30 together with fastening members. The battery stack 25 is also fixed onto a base plate 40 as needed. The base plate 40 can function as a cooling plate, for example, by circulating a refrigerant inside.

[0033] Each secondary battery cell 20 houses an electrode body inside an outer can 21, and the open end is sealed with a sealing plate 22. In FIG. 1 , the sealing plate 22, which is located on the top surface of the outer can 21, is provided with a pair of electrodes 23 and an explosion-proof valve 24. The multiple secondary battery cells 20 are electrically connected to each other in series and / or parallel by connecting the electrodes 23 with bus bars. The explosion-proof valve 24 is a component that opens when it detects an increase in the internal pressure of the outer can 21, and discharges high-pressure gas from inside the outer can 21. Each explosion-proof valve 24 is connected to a gas duct for guiding high-pressure gas to the outside as necessary. (Insulating heat diffusion sheet 10)

[0034] An insulating heat diffusion sheet 10 is interposed between adjacent secondary battery cells 20. The insulating heat diffusion sheet 10 is also called a spacer or separator, and insulates the exterior cans 21 between adjacent secondary battery cells 20 to prevent short-circuiting.

[0035] 1 illustrates a configuration in which a battery stack 25, which is made up of multiple stacked secondary battery cells 20, dissipates heat from the bottom using an insulating heat diffusion sheet 10. However, the present invention is not limited to this configuration, and heat radiation sheets may be placed on the side or end surfaces of the battery stack, for example. Furthermore, the number of secondary battery cells making up the battery stack is not limited to three, and may be four or more, or two or less.

[0036] A cross-sectional view of an insulating thermal diffusion sheet 10 is shown in FIG. 2. The insulating thermal diffusion sheet 10 shown in this figure is made of a paper sheet containing 80 to 95% by weight of boron nitride (BN) and binder fibers. Hexagonal boron nitride, which has high thermal conductivity, is preferably used as BN. It is also known that BN can be classified into flaky, spherical, etc. depending on its morphology and exists as an aggregate of these. In the present invention, it is preferable to contain BN with two or more particle sizes from the viewpoints of entanglement with the binder fibers and packing efficiency.

[0037] The binder fiber may be synthetic fiber or fine organic fiber. The synthetic fiber may be any known fibrous binder, specifically, pulp fiber such as polyolefin, PVA, PAN, PPS, PET, or aramid, or composite fiber of two or more components. Among these, aramid pulp and PET fiber are preferred in terms of heat resistance, electrical insulation, etc.

[0038] Furthermore, organic fibers with a fiber diameter of less than 1 μm are preferably used as the fine fibrous organic fibers. The fiber diameter here refers to the average value of 10 randomly selected fiber diameters measured using a scanning electron microscope (SEM) after freeze-drying a fiber sample. Specific examples of such fine fibrous materials include ultrafine fibers such as nylon and PET that have been split or dissolved after composite spinning, and fine fibrous cellulose obtained by highly beating cellulose fibers such as wood pulp and rayon. Among these, the inclusion of fine fibrous cellulose is preferred. Untreated BN has low hydrophilicity and tends to aggregate or float in papermaking slurry, but the addition of fine fibrous cellulose disperses it. This allows the BN to be uniformly dispersed in the papermaking sheet, resulting in a highly uniform insulating thermal diffusion sheet. While the reason for this has not been determined, it is presumed to be due to the amphiphilic nature of the surfaces of the fine fibers.

[0039] However, the papermaking sheet does not contain graphite, which allows it to exhibit insulating properties.

[0040] The papermaking sheet is preferably a wet-laid papermaking sheet. It is also preferable to subject the papermaking sheet to a heat and pressure treatment, which allows for high density. Furthermore, the thickness of the sheet is preferably 0.3 mm or less.

[0041] The insulating heat diffusion sheet 10 has an insulation resistance volume ratio of 3.0×10 13 It is preferable that the surface resistance is 8 W / m K or more and the thickness resistance is 0.5 W / m K or more. This configuration makes it possible to achieve excellent heat dissipation while maintaining electrical insulation.

[0042] The insulating thermal diffusion sheet 10 preferably has a dielectric strength against AC voltage of 10 kV / mm or more, and a dielectric strength against DC voltage of 13 kV / mm or more. The insulating thermal diffusion sheet 10 also preferably has a static friction coefficient of 0.15 to 0.18, and a dynamic friction coefficient of 0.10 to 0.12. [Embodiments 2 and 3]

[0043] While the example in FIG. 2 shows an example in which the insulating thermal diffusion sheet is formed from a single layer of sheet, the present invention is not limited to this configuration, and the insulating thermal diffusion sheet may be formed from multiple layers of sheets. For example, the insulating thermal diffusion sheet 20 may be formed from a laminated sheet in which multiple sheets are stacked, as in the insulating thermal diffusion sheet 20 according to embodiment 2 shown in FIG. 3. Alternatively, the insulating thermal diffusion sheet 30 may be obtained by slicing a laminate SS in which multiple sheets are stacked in a direction intersecting the stacking direction, as in the insulating thermal diffusion sheet 30 according to embodiment 3 shown in FIG. 4. In the example in FIG. 4, the insulating thermal diffusion sheet 30 is obtained by cutting in a direction perpendicular to the sheet stacking direction, as indicated by the dashed dotted line, but it may also be cut at an angle relative to the perpendicular direction. (Method for manufacturing an insulating heat diffusion sheet)

[0044] The insulating thermal diffusion sheet is manufactured by wet-processing a sheet containing 80 to 95% by weight of boron nitride and binder fibers, and then subjecting the sheet to a heat-press treatment. Here, the manufacturing method for the insulating thermal diffusion sheet will be described with reference to FIG. 5. FIG. 5 shows a schematic configuration diagram of a manufacturing apparatus 1000 for manufacturing an insulating thermal diffusion sheet 10. The manufacturing apparatus 1000 shown in FIG. 5 includes a papermaking machine 1 that forms a sheet from a papermaking slurry, a dryer 3 that dries the papermaking sheet 9 formed by the papermaking machine 1, and a press 2 that heat-presses the dried papermaking sheet 9 to a predetermined thickness. As shown in this figure, the insulating thermal diffusion sheet is manufactured through a papermaking process in which a papermaking slurry in which BN powder and fibers are suspended in a dispersion liquid is wet-processed to form a sheet-shaped papermaking sheet 9, and a pressing process in which the papermaking sheet 9 obtained in the papermaking process is heat-pressed to a predetermined thickness. (Paper making process)

[0045] The papermaking process produces a papersheet 9 through a raw material preparation process in which a papermaking slurry containing BN is prepared, and a slurry supplying process in which the papermaking slurry prepared in the raw material preparation process is dispersed on the papermaking surface 4A of the mesh conveyor 4. In the raw material preparation process, a papermaking slurry with an adjusted BN content is prepared. This papermaking slurry is dispersed sequentially on the mesh conveyor 4 in the papermaking tank 5 to produce paper. In the slurry supplying process, the papermaking slurry is dispersed on the moving mesh conveyor 4 to form a layer, thereby forming the papersheet 9. In this way, the papersheet 9 is produced. In the above papermaking process, a known wet papermaking machine can be used to produce the papersheet 9 by the wet method, but a mesh conveyor arranged in an inclined position is preferably used because it provides good fiber dispersion and makes it easy to adjust the orientation. (drying process)

[0046] The paper sheet 9 produced in the papermaking process is moved to a dryer 3 as shown in Figure 5 and dried. The dryer 3 shown in the figure is a drum-type dryer that dries the paper sheet 9 transported along the outer periphery of a drum 7 with hot air. The dryer 3 shown in the figure is equipped with multiple drums 7, and is configured to supply hot air of 120 to 130°C emitted from the outer periphery of each drum 7 to the paper sheet 9, thereby drying the paper sheet 9 passing through the dryer 3. However, the dryer is not limited to a drum-type dryer, and other dryers that can dry paper sheets can also be used. (pressing process)

[0047] The paper sheet 9 dried in the drying process is transferred to a press machine 2 and heat-pressed. The press machine 2 shown in FIG. 5 has a pair of rollers 8 arranged horizontally one above the other, and heat-presses the paper sheet 9 by passing it between the pair of rollers 8. The paper sheet 9 passing between the pair of rollers 8 is heated to a predetermined temperature and pressurized to a predetermined thickness. The press machine 2 shown in FIG. 5 has a pair of rollers 8 with a diameter of 30 to 100 cm arranged facing each other in a parallel position. The paper sheet 9 passing between the rollers 8 is heated to a temperature of 100 to 250°C and pressed with a pressure of 100 to 700 kg / cm. In this pressing process, the paper sheet 9 is pressed to a thickness of 50 μm to 500 μm, preferably 50 μm to 300 μm, and more preferably 70 μm to 230 μm, to form an insulating thermal diffusion sheet 10. The insulating thermal diffusion sheet 10 manufactured in a continuous, long sheet form is wound into a roll and shipped.

[0048] The manufacturing apparatus shown in Figure 5 has a papermaking machine 1, a dryer 3, and a press 2 arranged in a straight line, and is configured to manufacture electrically insulating thermal diffusion sheets 10 on a single line. However, the manufacturing apparatus can also be configured to wind up the paper sheet dried in the dryer into a roll and then heat press it in a press on a separate line. This method allows the movement speed of the manufacturing line for paper sheets manufactured in the papermaking and drying processes to be different from the movement speed of the manufacturing line for heat radiation sheets manufactured by heat pressing in a press on a separate line.

[0049] As the pressing device, known devices such as a double belt press and a flat plate press can be used in addition to the roller press shown in Fig. 5. These pressing steps may be carried out alone or multiple times using the same or different types of devices in combination. [Example]

[0050] The insulating thermal diffusion sheet 10 according to Example 1 of the present invention was manufactured by the following steps. [Paper making process] (Raw material adjustment process)

[0051] BN powder, a mixture of aggregated BN with an average particle size of 200 μm and flake BN with an average particle size of 40 μm, is mixed with pulp-like para-aramid fiber (aramid pulp), PPS fiber, and PET fiber as binder fibers in a specified ratio. The mixed materials and water as a dispersion liquid are fed into a chest, where they are suspended and dispersed in the dispersion liquid to prepare a papermaking slurry of a specified concentration. Papermaking slurry: BN powder...80% by mass Aramid fiber...8% by mass PPS fiber...8% by mass PET fiber...4% by mass (Slurry supply process)

[0052] The papermaking slurry is supplied to a mesh conveyor 4 for wet papermaking. In this embodiment, the papermaking slurry is dispersed on the mesh conveyor 4 to form a papermaking sheet 9 having an overall thickness of 600 μm. [Pressing process]

[0053] The paper sheet 9 produced in the papermaking process is dried in a drying process, and then heat-pressed in a press to produce an insulating thermal diffusion sheet 10. In the drying process, the paper sheet 9 produced in the papermaking process is passed through a dryer 3 to dry it. The dryer dries the paper sheet 9 with hot air at 120 to 130°C using, for example, nine drums. In the pressing process, the paper sheet 9 is passed between a pair of rollers 8 with a diameter of 50 cm as a heat press device, and is heat-pressed at a pressure of 200 kg / cm while being heated to a temperature of 120°C. The heat press treatment also increases the density. This produces an insulating thermal diffusion sheet 10 with a thickness of approximately 250 μm. In this way, the insulating thermal diffusion sheet 10 is obtained. [Example]

[0054] An electrically insulating thermal diffusion sheet according to Example 2 was also produced in the same manner as in Example 1, except that the composition of the papermaking slurry was changed to 90% by weight of BN powder, 4% by weight of aramid pulp, 3% by weight of PPS fiber, and 3% by weight of PET fiber. [Comparative Example 1]

[0055] On the other hand, as Comparative Example 1, a thermal diffusion sheet was produced in the same manner as in Example 1, except that the composition of the papermaking slurry was 80% by weight of graphite, 7% by weight of aramid pulp, and 13% by weight of PET fiber. Comparative Example 2

[0056] As Comparative Example 2, a thermal diffusion sheet was produced in the same manner as in Example 1, except that the composition of the papermaking slurry was 90% by weight of graphite, 4.5% by weight of aramid pulp, 2.5% by weight of PPS fiber, and 3% by weight of PET fiber. (insulating)

[0057] The insulating properties of Examples 1 and 2 and Comparative Examples 1 and 2 obtained in this manner were measured. The measurement method for insulating volume resistivity was performed in accordance with JIS K6911 "General Testing Methods for Thermosetting Plastics" using a DKK-TOA Ultra-Super Insulation Meter SM-10E in an environment at 23°C. The measurement for dielectric strength (AC voltage) was performed in accordance with JIS C2110-1 "Solid Electrical Insulating Materials - Testing Methods for Dielectric Breakdown Strength - Part 1: Testing by Application of Power Frequency AC Voltage" using a Tokyo Seiden TW-5110ADL withstand voltage tester in an environment at 23°C. The measurement for dielectric strength (DC voltage) was performed in accordance with JIS C2110-2 "Solid Electrical Insulating Materials - Testing Methods for Dielectric Breakdown Strength - Part 2: Testing by Application of DC Voltage" using a Tokyo Seiden TW-5110ADL withstand voltage tester in an environment at 23°C. The voltage increase rate was 100 V / min for both AC and DC. (thermal conductivity)

[0058] Heat dissipation was measured for each of the samples of Examples 1 and 2 and Comparative Examples 1 and 2. Two samples were prepared for each sample, and the thickness, density, thermal conductivity in the perpendicular direction (sheet thickness direction), and thermal conductivity in the in-plane direction were measured. The measurement was performed using the laser flash method in accordance with JIS R 1611:2010. The measurement device used was an Xe flash analyzer LFA-447 Nanoflash. (Static and dynamic friction coefficients)

[0059] The static and dynamic friction coefficients were measured for each of the samples of Examples 1 and 2 and Comparative Examples 1 and 2. The measurement method was in accordance with the horizontal method of JIS P 8147:2010, in which the friction coefficient was measured when the measurement sample was slid across a stainless steel plate. The size of the measurement sample and weight was 60 x 100 mm, the weight mass was 1000 g, and the test speed was 100 mm / min. The measurement device used was a universal material testing machine manufactured by A&D Co., Ltd. The results are shown in Table 1. (Orientation of thermally conductive particles)

[0060] The orientation of the thermally conductive particles was measured for the samples of Examples 1 and 2 and Comparative Examples 1 and 2 using a horizontal goniometer on an X-ray diffraction apparatus RINT-Ultima III manufactured by Rigaku Corporation. The degree of orientation was calculated from the peak intensity ratio of the 002 and 100 planes of the thermally conductive particles in the obtained spectrum using the following formula. The larger this value, the more thermally conductive particles are oriented in the plane direction of the sample. (Degree of orientation) = (peak intensity of 002 plane) / (peak intensity of 100 plane) The results are shown in Table 1.

[0061] [Table 1]

[0062] As shown in Table 1, in Examples 1 and 2, the 13 It was confirmed that the insulation resistance volume fraction was excellent and that insulation properties were ensured. On the other hand, in Comparative Examples 1 and 2, because highly conductive graphite was used, the values ​​were below the lower limit of measurement and could not be measured. Furthermore, in terms of dielectric strength, all of Examples 1 and 2 achieved 10 kV / mm or more for AC voltage and 13 kV / mm or more for DC voltage. In contrast, in Comparative Examples 1 and 2, the values ​​were below the lower limit of measurement and could not be measured. From the above, it was confirmed that the insulating thermal diffusion sheets of Examples 1 and 2, which do not use graphite, exhibit insulation properties sufficient for practical use. (heat dissipation)

[0063] As shown in Table 1, Examples 1 and 2 all achieved thermal conductivities of 8 W / m·K or more in the plane direction and 0.5 W / m·K or more in the thickness direction. On the other hand, Comparative Examples 1 and 2 achieved higher thermal conductivities of 99.5 W / m·K or more in the plane direction and 1.8 W / m·K or more in the thickness direction. However, while this thermal conductivity is sufficient for practical use, the thermal diffusion sheet using graphite according to the comparative example is generally used in conjunction with an insulating sheet, resulting in poor thermal conductivity during actual use. Considering this point, the insulating thermal diffusion sheets according to Examples 1 and 2, which can provide insulation with a single sheet, combined with their thinness, can be used in space-saving applications where insulation is required.

[0064] As shown in Table 1, the static friction coefficients of Examples 1 and 2 were all 0.15 to 0.18 and the dynamic friction coefficients were 0.10 to 0.12, which were lower than those of Comparative Examples 1 and 2. By providing such slipperiness, the insulating thermal diffusion sheet can easily conform to deformations of the heat dissipation object that it comes into contact with, in other words, it is less likely to form gaps, thereby providing the advantage of being able to avoid insulation caused by the formation of voids. Furthermore, when used in locations where vibrations occur, such as in vehicles, maintaining good slipperiness at the contact interface is expected to effectively prevent damage to the thermal diffusion sheet or the shedding of thermally conductive particles or fibers. [Industrial Applicability]

[0065] The insulating thermal diffusion sheet and its manufacturing method of the present invention can be used as an insulating thermal diffusion sheet sandwiched between objects that repeatedly expand and contract, such as a heat-insulating spacer interposed between secondary battery cells or secondary battery cell modules, a buffer sheet interposed between an explosion-proof valve and a gas duct, or a heat insulating material to protect a drive circuit such as an ECU. [Explanation of symbols]

[0066] 1000...Heat radiation sheet manufacturing equipment 100...Power supply device 1…Paper machine 2...Press machine 3...Dryer 4...Mesh conveyor 4A…Paper side 5…Paper making tank 7...Drums 8...Roller 9...Paper sheet 10...Insulating heat diffusion sheet 12...Surface sheet 20...Secondary battery cell 21...Outer can 22...Sealing plate 23...Electrode 24...Explosion-proof valve 25...Battery stack 30...End plate 40...Foundation plate SS…Laminated body

Claims

1. 80 to 95 wt % of boron nitride; and a papermaking sheet containing binder fibers, Insulation resistance volume ratio: 3.0 x 10 13 Ω cm or more, An insulating heat diffusion sheet having a thermal conductivity of 8 W / m·K or more in the surface direction and 0.5 W / m·K or more in the thickness direction.

2. The insulating thermal diffusion sheet according to claim 1, An insulating heat diffusion sheet having a dielectric strength against AC voltage of 10 kV / mm or more.

3. 3. The insulating thermal diffusion sheet according to claim 1 or 2, An insulating heat diffusion sheet having a dielectric strength against DC voltage of 13 kV / mm or more.

4. The insulating thermal diffusion sheet according to any one of claims 1 to 3, An insulating heat diffusion sheet having a static friction coefficient of 0.15 to 0.

18.

5. The insulating thermal diffusion sheet according to any one of claims 1 to 4, An insulating heat diffusion sheet having a dynamic friction coefficient of 0.10 to 0.

12.

6. The insulating thermal diffusion sheet according to any one of claims 1 to 5, The insulating heat diffusion sheet, wherein the binder fibers are at least one of synthetic fibers and fine organic fibers.

7. The insulating thermal diffusion sheet according to any one of claims 1 to 6, The insulating heat diffusion sheet, wherein the synthetic fibers include aramid pulp and PET fibers.

8. The insulating thermal diffusion sheet according to any one of claims 1 to 7, The insulating heat diffusion sheet, wherein the fine fibrous organic fibers are fine fibrous cellulose.

9. The insulating thermal diffusion sheet according to any one of claims 1 to 8, The insulating heat diffusion sheet, wherein the papermaking sheet does not contain graphite.

10. The insulating thermal diffusion sheet according to any one of claims 1 to 9, The insulating and thermal diffusion sheet is a wet-laid paper sheet.

11. The insulating thermal diffusion sheet according to any one of claims 1 to 10, The insulating and thermally diffusing sheet is obtained by subjecting the paper sheet to a heat and pressure treatment.

12. The insulating thermal diffusion sheet according to any one of claims 1 to 11, The insulating heat diffusion sheet has a thickness of 0.3 mm or less.

13. A method for manufacturing an insulating thermal diffusion sheet, comprising: forming a sheet by wet papermaking containing 80 to 95% by weight of boron nitride and binder fibers; a step of subjecting the sheet to heat and pressure treatment; A method for producing an insulating heat diffusion sheet comprising the steps of:

14. A method for producing an insulating thermal diffusion sheet according to claim 13, comprising the steps of: The method for producing an insulating thermal diffusion sheet, wherein the binder fiber is at least one of synthetic fiber and fine organic fiber.

15. A method for producing an insulating thermal diffusion sheet according to claim 13 or 14, comprising the steps of: Insulation resistance volume ratio: 3.0 x 10 13 Ω cm or more, A method for producing an insulating thermal diffusion sheet having a thermal conductivity of 8 W / m·K or more in the surface direction and 0.5 W / m·K or more in the thickness direction.

16. A method for producing the insulating thermal diffusion sheet according to any one of claims 13 to 14, comprising: An insulating heat diffusion sheet having a dielectric strength against AC voltage of 10 kV / mm or more.

17. A method for producing the insulating thermal diffusion sheet according to any one of claims 13 to 16, comprising: An insulating heat diffusion sheet having a dielectric strength against DC voltage of 13 kV / mm or more.

18. A method for producing the insulating thermal diffusion sheet according to any one of claims 13 to 17, comprising: A method for producing an insulating thermal diffusion sheet having a static friction coefficient of 0.15 to 0.

18.

19. A method for producing an insulating thermal diffusion sheet according to any one of claims 13 to 18, comprising: A method for producing an insulating thermal diffusion sheet having a dynamic friction coefficient of 0.10 to 0.

12.

20. A method for producing an insulating thermal diffusion sheet according to any one of claims 13 to 19, comprising: The method for producing the insulating thermal diffusion sheet comprises the aramid pulp and the PET fiber in the sheet state.

21. A method for producing an insulating thermal diffusion sheet according to any one of claims 13 to 20, comprising: the binder fibers are fine organic fibers, The method for producing an insulating thermal diffusion sheet, wherein the fine fibrous organic fibers are fine fibrous cellulose.

22. A method for producing the insulating thermal diffusion sheet according to any one of claims 13 to 21, A method for producing the insulating thermal diffusion sheet, which does not contain graphite in the sheet state.

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