Heat conducting sheet

Abstract

Provided is a highly reliable heat conducting sheet that has a low interfacial thermal resistance with a member in contact therewith when a high surface pressure is applied thereto. A heat conducting sheet 1 according to the present invention comprises a plurality of heat conducting portions 10 and bonding portions 20 that are made of a flexible material and that bond the heat conducting portions together, characterized in that: the heat conducting sheet 1 has void portions 2 in which the heat conducting portions 10 and the bonding portions 20 are not present; the proportion of the entire heat conducting sheet 1 occupied by the void portions 2 is 5 vol% or more and 65 vol% or less; and if the thickness of the heat conducting sheet 1 in a natural state is T1 [mm], the thickness of the heat conducting sheet 1 in a state in which the heat conducting sheet 1 in a natural state is being pressed with a surface pressure of 3.0 MPa in the thickness direction is T2 [mm], and the thickness when 5 minutes have elapsed after unloading is T3 [mm], the relationship 30 ≤ [(T1-T2) / T1] × 100 ≤ 75 and the relationship 2 ≤ [(T1-T3) / T1] × 100 ≤ 21 are satisfied.

Description

Thermal conductive sheet

[0001] This invention relates to a thermal conductive sheet.

[0002] In recent years, heat dissipation measures for heat-generating components in electronic devices, vehicle headlights, and automotive batteries have become an urgent necessity. For example, the miniaturization and high integration of electronic components such as central processing units in computers, image processing processors, SoCs in smartphones, DSPs and microcontrollers in embedded devices, semiconductor elements such as transistors, and light-emitting elements such as light-emitting diodes, electroluminescent devices, and liquid crystals have led to a tendency for greater heat generation. The reduced lifespan and malfunctions of devices and systems due to the heat generated by these electronic components are becoming a problem, and the demand for heat dissipation measures for electronic components is increasing year by year.

[0003] To address the high temperature of such heat-generating components, forced cooling using air-cooling fans is employed, as well as heat dissipation components such as metal heat fins and Peltier elements. These heat dissipation components have traditionally been coated with grease at the interface where they thermally connect to the heat source, to prevent the formation of an insulating air layer at the interface. However, general-purpose grease does not have high thermal conductivity. Therefore, diamond grease, which contains dispersed diamonds with relatively high thermal conductivity, is also used (see, for example, Patent Document 1).

[0004] However, diamond grease is expensive. Furthermore, even when using diamond grease, achieving sufficient thermal conductivity was difficult.

[0005] Furthermore, when a thermal conductive sheet is placed between a high-temperature component and a heat-dissipating component in an electronic component as described above, it may be placed in a compressed state under pressure. This improves the adhesion of the thermal conductive sheet to the high-temperature component and the heat-dissipating component, thereby lowering the interfacial thermal resistance and increasing the effective thermal conductivity.

[0006] In particular, in recent years, there has been a demand to apply higher pressure to thermal conductive sheets in order to improve their adhesion and lower their interfacial thermal resistance.

[0007] However, conventional thermal conductive sheets had a problem in that, under high pressure, the internal structure of the thermal conductive sheet would be irreversibly destroyed, resulting in an increased interfacial thermal resistance. Furthermore, when the thermal conductive sheet was pressed, it would deform excessively, and the protruding portion could come into contact with exposed wiring or electronic components, for example, making it prone to electrical short circuits and thus reducing reliability.

[0008] If the thermal conductive sheet is made of a relatively hard material, it will deform less even when pressed, and the problem of short circuits caused by protruding parts as described above will be prevented. However, it will be difficult to ensure that the thermal conductive sheet has sufficiently good adhesion to the high-temperature component and the heat dissipation component.

[0009] Special table 2017-530220 publication

[0010] The object of the present invention is to provide a heat conductive sheet that exhibits low interfacial thermal resistance between the sheet and the contacting member when high surface pressure is applied, and has excellent reliability.

[0011] The heat conductive sheet of the present invention is a heat conductive sheet comprising a plurality of heat conductive parts and a joint made of a flexible material that joins each of the heat conductive parts, wherein it has voids where the heat conductive parts and the joints are not present, the proportion of the voids to the entire heat conductive sheet is 5% by volume or more and 65% by volume or less, and when the thickness of the heat conductive sheet in its natural state is T1 [mm], the thickness when the heat conductive sheet in its natural state is pressed with a surface pressure of 3.0 MPa in the thickness direction of the heat conductive sheet is T2 [mm], and the thickness after 5 minutes have elapsed since unloading is T3 [mm], the relationship 30 ≤ [(T1 - T2) / T1] × 100 ≤ 75 and the relationship 2 ≤ [(T1 - T3) / T1] × 100 ≤ 21 are satisfied.

[0012] In this invention, the heat conductive sheet preferably has a thickness of 0.15 mm or more and 20 mm or less in its natural state.

[0013] In the present invention, it is preferable that at least a portion of the plurality of heat conducting portions are provided continuously inside the heat conducting sheet and are exposed on both main surfaces of the heat conducting sheet.

[0014] In the present invention, at least a portion of the plurality of heat conduction portions is a through heat conduction portion that is continuously provided inside the heat conduction sheet and exposed on both main surfaces of the heat conduction sheet, and it is preferable that the angle θ between the direction normal to the main surface and the direction of extension of the through heat conduction portion in the thickness direction of the heat conduction sheet is 0° or more and 45° or less.

[0015] In the present invention, it is preferable that the proportion of the heat conductive portion in the heat conductive sheet is 15% by volume or more and 80% by volume or less.

[0016] In the present invention, it is preferable that the proportion of the joint portion in the heat conductive sheet is 15% by volume or more and 70% by volume or less.

[0017] In the present invention, when the proportion of the heat conductive portion in the heat conductive sheet is VC [volume %], the proportion of the joint portion in the heat conductive sheet is VJ [volume %], and the proportion of the void portion in the heat conductive sheet is VV [volume %], it is preferable that the relationship 25 ≤ [(VJ + VV) / (VC + VJ + VV)] × 100 ≤ 90 is satisfied.

[0018] In the present invention, it is preferable that the heat conducting portion is made of a material containing graphite.

[0019] In the present invention, it is preferable that the heat conduction portion is composed of substantially a single component.

[0020] In this invention, the density of the thermal conductive sheet before it is pressed is 0.25 g / cm³. ３ 2.5g / cm or more ３ The following is preferable:

[0021] According to the present invention, it is possible to provide a heat conductive sheet that exhibits low interfacial thermal resistance between the sheet and the contacting member when high surface pressure is applied, and has excellent reliability.

[0022] This is a schematic perspective view showing an example of the heat conductive sheet of the present invention. This is a schematic side view showing the heat conductive sheet in its natural state. This is a schematic plan view showing the heat conductive sheet in its natural state. This is a schematic side view showing the heat conductive sheet pressed from the direction normal to the main surface of the heat conductive sheet. This is a schematic plan view showing the heat conductive sheet pressed from the direction normal to the main surface of the heat conductive sheet. This is a schematic side view showing the state of the heat conductive sheet 5 minutes after unloading. This is a schematic plan view showing the state of the heat conductive sheet 5 minutes after unloading. This is a first conceptual diagram of an example of the resin material constituting the joint. This is a second conceptual diagram of an example of the resin material constituting the joint. This is a schematic cross-sectional view showing a heat conductive part forming member composed of flake graphite. This is a schematic diagram showing an example of an apparatus used in the joint forming composition attachment process and the winding process. This is a schematic diagram showing the cut body obtained in the cutting process. This is a schematic diagram showing the state in which the cut body is pressed to increase the flatness of the cut body. This diagram schematically shows the cutting process. This diagram schematically shows the slicing process.

[0023] Preferred embodiments of the present invention will be described in detail below.

[0024] [1] Thermal Conductive Sheet First, the thermal conductive sheet of the present invention will be described.

[0025] Figure 1 is a schematic perspective view showing an example of the heat conductive sheet of the present invention. Figure 2A is a schematic side view showing the heat conductive sheet in its natural state, and Figure 2B is a plan view thereof. Figure 3A is a schematic side view showing the heat conductive sheet pressed from the direction normal to the main surface of the heat conductive sheet, and Figure 3B is a plan view thereof. Figure 4A is a schematic side view showing the state of the heat conductive sheet 5 minutes after unloading, and Figure 4B is a plan view thereof. Figures 5A and 5B are conceptual diagrams of an example of the resin material constituting the joint, respectively. Figure 5A shows the state of the resin material before stress in the direction of the arrow is applied, and Figure 5B shows the state of the resin material after stress in the direction of the arrow is applied.

[0026] In the following explanation, the direction from left to right in Figure 1 is referred to as the x-direction, the direction from back to front in Figure 1 is referred to as the y-direction, and the direction from bottom to top in Figure 1 is referred to as the z-direction.

[0027] Furthermore, in this specification, "natural state" refers to a state in which no external forces other than gravity are applied, and in particular, a state in which there is no history of external forces other than gravity being applied within the last 24 hours. It is also preferable that there is no history of stress application of 0.1 MPa or more after the manufacture of the thermal conductive sheet.

[0028] Furthermore, in the drawings referenced in this specification, some parts may be shown reduced or enlarged in order to make the relationships between each component easier to understand, and the size ratios between each component shown in the drawings do not represent the actual size ratios between each component.

[0029] Furthermore, unless otherwise specified, the measurements and processes described herein shall be performed at 20°C.

[0030] As will be described in detail later, the thermal conductive sheet 1 has excellent thermal conductivity in a predetermined direction, particularly in the thickness direction when pressed in the thickness direction, and is used, for example, by bringing the component to be cooled into contact with the thermal conductive sheet 1.

[0031] As shown in Figure 1, the thermal conductive sheet 1 comprises a plurality of thermal conductive parts 10 and a joint part 20 made of a flexible material that joins each thermal conductive part 10. The thermal conductive sheet 1 has voids 2 where the thermal conductive parts 10 and joint parts 20 are not present. The proportion of the thermal conductive sheet 1 occupied by the voids 2 (the proportion of the voids 2 in its natural state) is between 5% and 65% by volume.

[0032] Furthermore, when the thickness of the heat conductive sheet 1 in its natural state is T1 [mm] (see Figures 2A and 2B), the thickness of the heat conductive sheet 1 in its natural state is T2 [mm] (see Figures 3A and 3B) when it is pressed with a surface pressure of 3.0 MPa in the thickness direction of the heat conductive sheet 1, and the thickness after 5 minutes have elapsed since unloading is T3 [mm] (see Figures 4A and 4B), the following relationships are satisfied: 30 ≤ [(T1 - T2) / T1] × 100 ≤ 75 and 2 ≤ [(T1 - T3) / T1] × 100 ≤ 21.

[0033] In other words, the displacement rate of the thickness of the heat conduction sheet 1 when pressed at a surface pressure of 3.0 MPa with respect to the thickness of the heat conduction sheet 1 in the natural state is 30% or more and 80% or less, and after the pressing, when 5 minutes have elapsed since the load was removed, the displacement rate with respect to the thickness of the heat conduction sheet 1 in the natural state is 2% or more and 21% or less.

[0034] By satisfying such a relationship, when a high surface pressure is applied, the heat conduction sheet 1 has a low interfacial thermal resistance with the contacting member, and can have excellent substantial thermal conductivity in the thickness direction of the heat conduction sheet 1, and excessive deformation is prevented, and it has excellent shape restoration when the load is removed, etc., and has excellent reliability.

[0035] It is considered that such an effect is obtained for the following reasons. That is, due to the presence of voids, a large displacement amount can be obtained, and the interfacial thermal resistance with the contacting member can be lowered. On the other hand, due to the wide elastic range of the joint portion and the repulsion of the heat conduction portion, excessive deformation can be prevented.

[0036] On the contrary, satisfactory results cannot be obtained if the above conditions are not satisfied. For example, if the heat conduction sheet does not have a void portion, it cannot absorb the deformation when the heat conduction sheet is pressed, so the amount of protrusion when the heat conduction sheet is pressed increases, and the protruded portion is likely to contact an unfavorable site, etc., leading to a decrease in reliability.

[0037] Also, even if it has a void portion, if the ratio is less than the lower limit value, it cannot sufficiently absorb the deformation when the heat conduction sheet is pressed, and cannot sufficiently reduce the amount of protrusion when the heat conduction sheet is pressed, and the reliability of the heat conduction sheet cannot be made sufficiently excellent.

[0038] Further, if the ratio of the void portion exceeds the upper limit value, the interfacial thermal resistance with the contacting member when a high surface pressure is applied cannot be made sufficiently low. Also,the shape restoring force of the heat conduction sheet is significantly reduced, and the durability of the heat conduction sheet is significantly lowered.

[0039] Further, in the thickness direction of the heat conduction sheet, if the thickness displacement rate when pressed at a surface pressure of 3.0 MPa, that is, the value of [(T1 - T2) / T1]×100 is less than the lower limit value, the interfacial thermal resistance cannot be sufficiently reduced.

[0040] Further, in the thickness direction of the heat conduction sheet, if the thickness displacement rate when pressed at a surface pressure of 3.0 MPa, that is, the value of [(T1 - T2) / T1]×100 exceeds the upper limit value, compatibility with the resilience cannot be achieved.

[0041] Further, when the displacement rate of the thickness, that is, the value of [(T1 - T3) / T1]×100 at the time when 5 minutes have elapsed after releasing the pressing at a surface pressure of 3.0 MPa is less than the lower limit value, there is no change in the structure, and the contact with the contact surface does not improve due to minute changes, resulting in the problem that the interfacial thermal resistance does not decrease.

[0042] Further, when the displacement rate in the thickness direction, that is, the value of [(T1 - T3) / T1]×100 at the time when 5 minutes have elapsed after releasing the pressing at a surface pressure of 3.0 MPa exceeds the upper limit value, the performance cannot be satisfied in long-term use, and the reliability of the heat conduction sheet deteriorates.

[0043] Incidentally, the pressing time from the start of pressing at a surface pressure of 3.0 MPa in the thickness direction of the heat conduction sheet 1 until the measurement of the thickness T2, and the time from the start of pressing at a surface pressure of 3.0 MPa in the thickness direction of the heat conduction sheet 1 until releasing the pressure are not particularly limited, but can be 5 seconds or more and 30 seconds or less, and particularly can be 10 seconds.

[0044] Further, in FIGS. 2A, 2B, 3A, 3B, 4A, and 4B, the display of the heat conduction portion 10, the joint portion 20, and the void portion 2 of the heat conduction sheet 1 is omitted. Also, for the pressing of the heat conduction sheet 1, a predetermined pressing jig, for example, two flat plates are used, but in FIGS. 3A and 3B, their display is also omitted.

[0045] Further, regarding the measurement described in this specification, when pressing the heat conduction sheet in the thickness direction, even in the pressing state, it is pressed by the flat surface of a pressing member larger than the size of the heat conduction sheet to be measured, more specifically, the area when viewed in plan.

[0046] Furthermore, if the main surface (the surface normal to the thickness direction) of the heat conductive sheet 1 to be measured is a 20 mm x 20 mm square or a size encompassing such a square, the measurement of the thickness and thickness displacement rate in each state may be performed with the size and shape adjusted so that the main surface is a 20 mm x 20 mm square.

[0047] As described above, the proportion of voids 2 to the entire thermal conductive sheet 1 is 5% to 65% by volume, but is preferably 5% to 50% by volume, more preferably 6% to 40% by volume, and even more preferably 7% to 32% by volume. This allows the effects of the present invention described above to be exhibited more significantly.

[0048] Furthermore, the thickness displacement rate [%] when the thermal conductive sheet is pressed in the thickness direction with a surface pressure of 3.0 MPa, i.e., the value of [(T1-T2) / T1] × 100, is 30 or more and 75 or less, but preferably 35 or more and 73 or less, more preferably 40 or more and 73 or less, and even more preferably 45 or more and 70 or less. This allows the effects of the present invention described above to be exhibited more significantly.

[0049] Furthermore, the thickness displacement rate, i.e., the value of [(T1-T3) / T1] × 100, after 5 minutes have elapsed since the surface pressure of 3.0 MPa was removed from the heat conductive sheet 1 as described above, is between 2 and 21, but is preferably between 2 and 18, more preferably between 2 and 15, and even more preferably between 2 and 12. This allows the effects of the present invention described above to be exhibited more significantly.

[0050] In the thermal conductive sheet 1, for example, the values ​​of [(T1-T2) / T1]×100 and [(T1-T3) / T1]×100 can be suitably adjusted by appropriately adjusting the proportion of thermal conductive parts 10, the proportion of joint parts 20, and the proportion and distribution of void parts 2 in the thermal conductive sheet 1, or by adjusting the flexibility of the joint parts 20, in other words, the material and degree of hardening of the joint parts 20.

[0051] [1-1] General shape of the thermal conductive sheet The thermal conductive sheet 1 is in the form of a sheet overall.

[0052] Thus, the sheet-like thermal conductive sheet 1 can be suitably positioned in the narrow space between multiple members (e.g., a high-temperature member and a heat-dissipating member) when used in conjunction with these multiple members, which is advantageous in effectively preventing the thickening and enlargement of devices and equipment comprising these multiple members. Furthermore, the entire thermal conductive sheet 1 can be suitably curved, allowing for, for example, a small volume of the thermal conductive sheet 1 while achieving particularly excellent thermal conductivity when applied to flat surfaces or surfaces with relatively small curvature. Here, "flat surface" includes surfaces with minute irregularities. Moreover, even if the member to which the thermal conductive sheet 1 is applied has irregularities on its surface, the thermal conductive sheet 1 and the member to which the thermal conductive sheet 1 is applied can be more suitably brought into close contact at a microscopic level across the entire surface to which the thermal conductive sheet 1 is applied. In other words, the contact between the member to which the thermal conductive sheet 1 is applied and the thermal conductive sheet 1 in minute regions becomes superior. For this reason, for example, the heat dissipation can be improved when the member to which the thermal conductive sheet 1 is applied is a heat-generating member.

[0053] The thickness of the heat conductive sheet 1 in its natural state, i.e., the length shown as T1 in Figure 2, is preferably 0.15 mm or more and 20 mm or less, more preferably 0.20 mm or more and 10 mm or less, and even more preferably 0.25 mm or more and 5 mm or less.

[0054] This allows the sheet-like heat conductive sheet 1 to conform more effectively to the surface shape of the component to which it is applied, and the aforementioned effects are more pronounced.

[0055] The planar shape of the heat conductive sheet 1 in its natural state is not particularly limited and may be any shape, but examples include rectangles, circles, ellipses, polygons other than quadrilaterals, etc. Furthermore, the corners of the heat conductive sheet 1 may be chamfered.

[0056] In the figures referenced herein, the interface between the heat conduction part 10 and the joint part 20 is clearly shown. However, the interface between the heat conduction part 10 and the joint part 20 may be unclear, for example, if a part of the heat conduction part 10 penetrates the joint part 20.

[0057] [1-2] The multiple heat conduction sections 10 are the parts that mainly contribute to the overall heat conductivity of the heat conduction sheet 1, and in particular to the heat conductivity in the thickness direction of the heat conduction sheet 1.

[0058] As shown in Figure 1, it is preferable that at least a portion of the plurality of heat conduction portions 10 are through-heat conduction portions 10c that are continuously provided inside the heat conduction sheet 1, particularly in the thickness direction of the heat conduction sheet 1, and are exposed on both main surfaces of the heat conduction sheet 1.

[0059] This makes it possible to improve the effective thermal conductivity of the thermal conductive sheet 1 in the thickness direction.

[0060] When at least a portion of the multiple heat conduction sections 10 is a through-heat conduction section 10c, the angle θ between the direction normal to the main surface of the heat conduction sheet 1 and the direction of extension of the through-heat conduction section 10c in the thickness direction of the heat conduction sheet 1 is preferably 0° or more and 45° or less, more preferably 0° or more and 40° or less, and even more preferably 0° or more and 35° or less.

[0061] As a result, when the heat conductive sheet 1 is compressed in the thickness direction, surface pressure is more easily applied to the heat conductive sheet 1, thereby improving the adhesion between the heat conductive sheet 1 and the member to which the heat conductive sheet 1 is applied. In addition, the adhesion between the heat conductive portion 10 and the joint portion 20 when pressure is applied to the heat conductive sheet 1 in the thickness direction can be improved, thereby improving the effective thermal conductivity of the heat conductive sheet 1.

[0062] The heat conduction section 10 is not particularly limited as long as it has thermal conductivity, but examples of materials that make up the heat conduction section 10 include ceramic materials such as aluminum nitride, boron nitride, silicon nitride, silicon carbide, and alumina, carbon materials such as graphite and carbon fiber, and metallic materials such as copper and aluminum. However, it is preferable that it is made of a carbon material, and more preferably that it is made of a material containing graphite.

[0063] This makes it possible to improve the effective thermal conductivity between the component to which the thermal conductive sheet 1 is applied and the thermal conductive sheet 1, while suppressing the manufacturing cost of the thermal conductive sheet 1.

[0064] [1-2-1] Carbon materials In particular, if the heat conduction part 10 is formed from a heat conduction part forming member 10' containing a carbon material such as graphite or carbon fiber, in addition to the effects described above, the following effects can be obtained. That is, the flexibility and suppleness of the heat conduction sheet 1 can be made even better, for example, the restoring force when the heat conduction sheet 1 is bent, as well as the cushioning effect due to the internal voids and the improvement of contact due to appropriate deformation when the heat conduction sheet 1 comes into contact with the member to which it is applied can be made even better. In particular, these effects are more pronounced when graphite is used as the carbon material.

[0065] [1-2-2] Metal Material Furthermore, if the heat conduction part 10 is formed by a heat conduction part forming member 10' made of a metal material, in addition to the effects described above, the following effects can be obtained. That is, the dust generation of the heat conduction sheet 1 can be further reduced due to the strength of the bonding force inside the metal material. Also, even when a relatively large load is applied to the heat conduction sheet 1, irreversible deformation of the heat conduction sheet 1, such as collapse of the heat conduction sheet 1 due to buckling, can be prevented more effectively.

[0066] Examples of metal materials constituting the heat conduction section 10 include various elemental metals and alloys, and one or more selected from these can be used in combination. However, it is preferable that the material contains one or more selected from the group consisting of Al, Cu, Ag, Au, Mg, and Zn. This makes the heat conduction of the heat conduction section 10 even more excellent.

[0067] Examples of alloys containing the aforementioned metallic elements include duralumin, which is an aluminum alloy containing Al, Cu, and Mg.

[0068] [1-2-3] Other conditions: Preferably, the heat conduction portion 10 is composed of substantially a single component. This makes the heat conduction of the heat conduction portion 10 even better. It is also generally advantageous in reducing the manufacturing cost of the heat conduction sheet 1.

[0069] Furthermore, "substantially composed of a single component" means that the proportion of the main component in the target area is 95% by weight or more. Preferably, the proportion of the main component is 97% by weight or more, and more preferably 99% by weight or more.

[0070] However, if the heat conduction section 10 contains a gas such as air, the gas content shall be disregarded. Furthermore, if the heat conduction section 10 is made of a metallic material, an oxide film of the metal constituting the heat conduction section 10, such as a passivation film, may be formed on its surface. Even if such an oxide film is formed, it shall be treated as being "substantially composed of a single component." The same applies to the heat conduction section forming member 10', which will be described in detail later.

[0071] In Figure 1, the thickness of the heat conduction portion 10, indicated by t10, is preferably 5 μm or more and 500 μm or less, and more preferably 20 μm or more and 150 μm or less. This allows the effects of the present invention described above to be exhibited more significantly.

[0072] The proportion of the heat conductive portion 10 in the heat conductive sheet 1 (proportion in the natural state; the same applies hereinafter) is preferably 15% by volume or more and 80% by volume or less, more preferably 20% by volume or more and 75% by volume or less, even more preferably 25% by volume or more and 70% by volume or less, and most preferably 30% by volume or more and 65% by volume or less.

[0073] This makes it possible to ensure that the proportion of the heat conductive portion 10 within the heat conductive sheet 1 is sufficiently high, while also making the overall flexibility of the heat conductive sheet 1 more excellent, thereby more reliably and significantly demonstrating the effects of the present invention described above.

[0074] [1-3] Joint The joint 20 is positioned between a plurality of heat conduction parts 10 to join the heat conduction parts 10 together, and is composed of a flexible resin material 21. The resin material 21 is a cured product of a curable resin material 21', which will be described later.

[0075] By including a flexible resin material 21 in the joint portion 20, the thermal conductive sheet 1 exhibits excellent shape conformability to the surface shape of the member to which the thermal conductive sheet 1 is applied, such as a heat-generating member or a heat-dissipating member.

[0076] Furthermore, by including a flexible resin material 21 in the joint portion 20, it is possible to effectively prevent the heat conductive sheet 1 from being damaged when it deforms.

[0077] [1-3-1] The resin material 21 constituting the resin material joint 20 is not particularly limited as long as it is flexible, and examples include flexible epoxy resin, rubber resin, urethane resin, silicone resin, fluororesin, acrylic resin, thermoplastic elastomer, etc. However, as shown in Figures 5A and 5B, the resin material 21 preferably includes a polyrotaxane 50 having a cyclic molecule 51, a first polymer 52 having a linear molecular structure that encloses the cyclic molecule 51 in a skewer-like manner, and sealing groups 53 provided near both ends of the first polymer 52, and a second polymer 60, wherein the polyrotaxane 50 and the second polymer 60 are bonded via the cyclic molecule 51.

[0078] This makes it possible to improve the bonding strength between the heat conductive portion 10 and the joint portion 20 of the heat conductive sheet 1, and also to more effectively suppress irreversible deformation of the heat conductive sheet 1 even when it is repeatedly pressed with a relatively large force or when it is pressed with a relatively large force for a long period of time, thereby improving the durability of the heat conductive sheet 1. In addition, the flexibility and heat resistance of the heat conductive sheet 1 can be made particularly excellent.

[0079] In particular, when a stress in the direction of the arrow is applied to the resin material 21 in the state shown in Figure 5A, the resin material 21 can take the form shown in Figure 5B. That is, in the resin material 21, the cyclic molecule 51 is movable along the first polymer 52, that is, the first polymer 52 is movable within the cyclic molecule 51, so that deformation stress can be efficiently absorbed within the resin material 21. Therefore, even when a large external force such as a torsional deformation force is applied, the joint 20 is not destroyed, and the joint between the heat conduction parts 10 is not destroyed, which is effectively prevented.

[0080] The resin material 21 containing polyrotaxane 50 and a second polymer 60 will be described in detail below.

[0081] The cyclic molecule 51 constituting the polyrotaxane 50 may be movable along the first polymer 52, but is preferably a substituted cyclodextrin molecule, and is particularly preferably selected from the group consisting of α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, and their derivatives.

[0082] At least a portion of the cyclic molecules 51 in the polyrotaxane 50 are bonded to at least a portion of the second polymer 60, as described above.

[0083] Examples of functional groups (functional groups that bond with the second polymer 60) that the cyclic molecule 51 may have include -OH groups, -NH2 groups, -COOH groups, epoxy groups, vinyl groups, thiol groups, and photocrosslinking groups. Examples of photocrosslinking groups include cinnamic acid, coumarin, chalcone, anthracene, styrylpyridine, styrylpyridinium salts, and styrylquinolium salts.

[0084] When the amount of cyclic molecule 51 that is encapsulated in the first polymer 52 in a skewer-like manner is defined as 1, the amount of cyclic molecule 51 encapsulated in the first polymer 52 in a skewer-like manner is preferably 0.001 or more and 0.6 or less, more preferably 0.01 or more and 0.5 or less, and even more preferably 0.05 or more and 0.4 or less. Two or more different types of cyclic molecules 51 may be used.

[0085] The first polymer 52 constituting the polyrotaxane 50 may be, for example, cellulosic resins such as polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, polyacrylamide, polyethylene oxide, polyethylene glycol, polypropylene glycol, polyvinyl acetal resins, polyvinyl methyl ether, polyamine, polyethyleneimine, casein, gelatin, starch, etc. and / or copolymers thereof, polyolefin resins such as copolymer resins with polyethylene, polypropylene, and other olefin monomers, polyester resins, polyvinyl chloride resins, polystyrene resins such as polystyrene and acrylonitrile-styrene copolymer resins, polymethyl methacrylate Examples include acrylic resins such as (meth)acrylic acid ester copolymers and acrylonitrile-methyl acrylate copolymer resins, polycarbonate resins, polyurethane resins, vinyl chloride-vinyl acetate copolymer resins, polyvinyl butyral resins, and their derivatives or modified forms; polyamides such as polyisobutylene, polytetrahydrofuran, polyaniline, acrylonitrile-butadiene-styrene copolymers, nylon, polyimides, polyisoprene, polydienes such as polybutadiene, polysiloxanes such as polydimethylsiloxane, polysulfones, polyimines, polyacetic anhydride, polyureas, polysulfides, polyphosphozenes, polyketones, polyphenylenes, polyhaloolefins, and their derivatives, with polyethylene glycol being particularly preferred.

[0086] The weight-average molecular weight of the first polymer 52 is preferably 10,000 or more, more preferably 20,000 or more, and even more preferably 35,000 or more. Two or more different types of the first polymer 52 may be used.

[0087] The combination of the cyclic molecule 51 and the first polymer 52 is preferably such that the cyclic molecule 51 is an α-cyclodextrin which may be substituted, and the first polymer 52 is polyethylene glycol.

[0088] The suffocating group 53 constituting the polyrotaxane 50 is not particularly limited as long as it has the function of preventing the cyclic molecule 51 from being removed from the first polymer 52. Examples include dinitrophenyl groups, cyclodextrins, adamantane groups, trityl groups, fluoresceins, pyrenes, substituted benzenes (substituents include alkyl, alkyloxy, hydroxy, halogen, cyano, sulfonyl, carboxyl, amino, phenyl, etc. There may be one or more substituents), substituted polynuclear aromatics, steroids, etc.

[0089] Substituents that constitute substituted benzenes and substituted polynuclear aromatics include alkyl, alkyloxy, hydroxy, halogen, cyano, sulfonyl, carboxyl, amino, and phenyl groups. One or more substituents may be present. In addition, two or more different suffocating groups 53 may be used.

[0090] In the resin material 21, at least some of the polyrotaxane 50 are bonded to the second polymer 60 via a cyclic molecule 51. However, the resin material 21 may also contain polyrotaxane 50 that is not bonded to the second polymer 60, or polyrotaxane 50 that are bonded to each other.

[0091] The second polymer 60 is bonded to the polyrotaxane 50 via a cyclic molecule 51. Examples of functional groups that the second polymer 60 has to bond to the cyclic molecule 51 include -OH groups, -NH2 groups, -COOH groups, epoxy groups, vinyl groups, thiol groups, and photocrosslinking groups. Examples of photocrosslinking groups include cinnamic acid, coumarin, chalcone, anthracene, styrylpyridine, styrylpyridinium salt, and styrylquinolium salt.

[0092] The second polymer 60 may include, for example, cellulosic resins such as polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, polyacrylamide, polyethylene oxide, polyethylene glycol, polypropylene glycol, polyvinyl acetal resins, polyvinyl methyl ether, polyamine, polyethyleneimine, casein, gelatin, starch, etc. and / or copolymers thereof, polyolefin resins such as copolymer resins with polyethylene, polypropylene, and other olefin monomers, polyester resins, polyvinyl chloride resins, polystyrene resins such as polystyrene and acrylonitrile-styrene copolymer resins, polymethyl methacrylate, and Examples include acrylic resins such as (meth)acrylic acid ester copolymers and acrylonitrile-methyl acrylate copolymer resins, polycarbonate resins, polyurethane resins, vinyl chloride-vinyl acetate copolymer resins, polyvinyl butyral resins, and derivatives or modified versions thereof, polyamides such as polyisobutylene, polytetrahydrofuran, polyaniline, acrylonitrile-butadiene-styrene copolymers, polyimides, polyisoprene, polybutadiene and other polydienes, polysiloxanes such as polydimethylsiloxane, polysulfones, polyimines, polyanhydrides, polyureas, polysulfides, polyphosphazenes, polyketones, polyphenylenes, and polyhaloolefins, which have the aforementioned functional groups as their backbone.

[0093] Furthermore, the second polymer 60 and the cyclic molecule 51 may be chemically bonded together by a crosslinking agent.

[0094] The molecular weight of the crosslinking agent is preferably less than 2000, more preferably less than 1000, even more preferably less than 600, and most preferably less than 400.

[0095] Examples of crosslinking agents include cyanuryl chloride, trimethoyl chloride, terephthaloyl chloride, epichlorohydrin, dibromobenzene, glutaraldehyde, phenylenediisocyanate, trilein diisocyanate, divinyl sulfone, 1,1'-carbonyldiimidazole, and alkoxysilanes. Two or more different crosslinking agents may also be used.

[0096] Furthermore, the second polymer 60 may be a homopolymer or a copolymer. In the resin material 21, at least a portion of the second polymer 60 is bonded to the polyrotaxane 50 via the cyclic molecule 51, but the resin material 21 may also contain second polymer 60 that is not bonded to the polyrotaxane 50, or the second polymers 60 may be bonded to each other. In addition, two or more different types of second polymer 60 may be used.

[0097] Preferably, the ratio of the polyrotaxane 50 content to the second polymer 60 content in the resin material 21 is 1 / 1000 or more by weight.

[0098] [1-3-2] Other components The joint portion 20 may contain components other than resin material.

[0099] Examples of such components include metal particles, ceramic particles, resin fibers, spacers, plasticizers, colorants, antioxidants, UV absorbers, light stabilizers, softeners, modifiers, rust inhibitors, fillers, electromagnetic wave absorbers such as ferrite, surface lubricants, corrosion inhibitors, heat stabilizers, lubricants, primers, antistatic agents, crosslinking agents, catalysts, leveling agents, thickeners, dispersants, anti-aging agents, flame retardants, hydrolysis inhibitors, and corrosion inhibitors.

[0100] If the joint portion 20 contains metal particles, the following effects can be obtained. That is, as mentioned above, the part that mainly contributes to the thermal conductivity of the thermal conductive sheet 1 is the thermal conductive portion 10, but since metal particles generally have higher thermal conductivity than the resin material 21 that constitutes the joint portion 20, the inclusion of metal particles in the joint portion 20 can improve the thermal conductivity of the joint portion 20, and further improve the thermal conductivity of the thermal conductive sheet 1 as a whole.

[0101] In particular, when adjacent heat conduction sections 10 are connected by one or more metal particles contained in the joint 20, these metal particles form a "thermal path" that thermally connects the heat conduction sections 10, further improving the overall thermal conductivity of the heat conduction sheet 1.

[0102] Furthermore, by including metal particles made of a metal material with electromagnetic shielding properties, the thermal conductive sheet 1 can also be given an electromagnetic shielding function.

[0103] The metal particles preferably consist of one or more selected from the group consisting of Fe, Ag, Pt, Cu, Sn, Al, and Ni, and more preferably contain Fe.

[0104] The shape of the metal particles is not particularly limited, but a spherical shape is preferred, and a perfectly spherical shape is more preferred. This makes the effects described above more pronounced.

[0105] More specifically, the shape coefficient SF-2 of the metal particles is preferably 100 to 150, more preferably 100 to 125, and even more preferably 100 to 120.

[0106] The shape factor SF-2 is obtained by squaring the projected perimeter of a particle, dividing that value by the projected area of ​​the particle, dividing the result by 4π, and then multiplying by 100. The closer the particle's shape is to a sphere, the closer the value will be to 100.

[0107] The shape factor SF-2 can be determined, for example, by the following measurement: For example, by observation using FE-SEM, the projected area S [μm²] of 100 metal particles can be determined. ２ The shape coefficient SF-2 is determined by calculating the shape coefficient L [μm] and the projected perimeter L. The average value of the shape coefficient SF-2 for each metal particle is then adopted as the shape coefficient SF-2 for the metal particle. SF-2 = ((L ２ / S) / 4π)×100

[0108] The average particle size of the metal particles is not particularly limited, but is preferably 0.01 μm to 10 μm, and more preferably 0.1 μm to 3.0 μm. This can further enhance the effects described above.

[0109] In this specification, the average particle size refers to the particle size at which the cumulative total from the smallest diameter side reaches 50% in the weight-based particle size distribution measured by a laser diffraction particle size distribution analyzer.

[0110] Iron particles are preferred as the metal particles. For example, Fe(CO) ５ Examples include iron particles produced by thermal decomposition.

[0111] Such iron particles are of very high purity, form a perfect sphere as described above, and have a very fine average particle size, which allows them to exhibit the effects described above in a particularly pronounced manner.

[0112] If metal particles are included in the joint 20, the metal particle content in the joint 20 (content in its natural state) is preferably 1% by volume or more and 50% by volume or less, and more preferably 10% by volume or more and 30% by volume or less.

[0113] This makes it possible to achieve a good balance between the effects of including the resin material 21 and the effects of including the metal particles, as described above.

[0114] If the joint 20 contains ceramic particles, the structure of the joint 20 can be stabilized and made uniform, and the proportion and size of voids in the joint 20 can also be stabilized. As a result, undesirable variations in the properties of each part of the thermal conductive sheet 1 can be prevented more effectively.

[0115] Various ceramics can be used as constituent materials for ceramic particles, but when using ceramic materials such as nitride-based ceramics such as aluminum nitride, boron nitride, and silicon nitride, carbide-based ceramics such as silicon carbide, and oxide-based ceramics such as alumina, the overall thermal conductivity of the thermal conductive sheet 1 can be further improved. In particular, when adjacent thermal conductive parts 10 are connected by one or more ceramic particles contained in the joint 20, these ceramic particles become "thermal paths" that thermally connect the thermal conductive parts 10, further improving the overall thermal conductivity of the thermal conductive sheet 1.

[0116] If the joint 20 contains the aforementioned metal particles in addition to ceramic particles, the heat path may be formed of ceramic particles and metal particles.

[0117] Furthermore, the ceramic particles may be composed of silica. This allows for the stabilization and homogenization of the structure of the joint 20, as described above, while suppressing the production cost of the thermal conductive sheet 1.

[0118] The shape of the ceramic particles is not particularly limited, but a spherical shape is preferred, and a perfectly spherical shape is more preferred. This makes the effects described above more pronounced.

[0119] The average particle size of the ceramic particles is not particularly limited, but is preferably 5 μm to 200 μm, more preferably 10 μm to 100 μm, and even more preferably 20 μm to 70 μm. This can further enhance the effects described above.

[0120] When ceramic particles are included in the joint 20, the content of ceramic particles in the joint 20 (content in its natural state) is preferably 1% by volume or more and 50% by volume or less, and more preferably 10% by volume or more and 30% by volume or less.

[0121] This makes it possible to achieve a good balance between the effects of including the resin material 21 and the effects of including ceramic particles, as described above.

[0122] If the joint portion 20 contains resin fibers, it is possible to more effectively prevent the heat conductive sheet 1 from sagging and deforming even when the heat conductive sheet 1 is used under pressure for a long period of time. This also makes it possible to more effectively prevent the problem of decreased adhesion between the heat conductive sheet 1 and the member in contact with it, and an increase in thermal resistance, due to a decrease in surface pressure on the member in contact with the heat conductive sheet 1 over time.

[0123] The thickness of the resin fibers contained in the joint 20 is preferably 1.0 μm to 30 μm, more preferably 2.0 μm to 25 μm, even more preferably 3.0 μm to 20 μm, and most preferably 4.0 μm to 15 μm. This allows the aforementioned effects to be exhibited more significantly.

[0124] The resin fiber can be composed mainly of a resin material. Examples of resin materials that make up the resin fiber include polyethylene, polyolefins such as polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides, ethylene vinyl acetate resin, and polyvinyl alcohol. However, the resin fiber is preferably composed of polyester, and more preferably of polyethylene terephthalate.

[0125] This makes it possible to improve the strength of the resin fibers themselves, allowing the effects of including resin fibers in the joint 20 as described above to be more effectively exhibited, as well as improving the adhesion between the resin fibers and the resin material 21, thereby improving the durability and reliability of the heat conductive sheet 1.

[0126] The resin fiber only needs to be present as at least one fiber in the joint 20, but it is preferable that it be present as multiple fibers. This allows the aforementioned effects to be exhibited more significantly.

[0127] Furthermore, each resin fiber may be included in the joint 20 in an independent state, or multiple resin fibers may be included in an intertwined state. More specifically, the resin fibers may be made of a fibrous base material such as woven fabric or nonwoven fabric.

[0128] If the joint portion 20 includes a fibrous base material, undesirable variations in the thickness of the joint portion 20 can be suitably suppressed. Furthermore, a void portion 2 can be suitably formed between the resin material 21 constituting the joint portion 20 and the fibrous base material. In addition, during the manufacturing of the thermal conductive sheet 1, it is possible to effectively prevent the resin material 21 constituting the joint portion 20 from protruding from the edges. As a result, the problem of the joint portion 20 preferentially contacting the member to which the thermal conductive sheet 1 is applied, thereby hindering contact at the thermal conductive portion 10, can be effectively prevented, and the substantial thermal conductivity of the thermal conductive sheet 1 when it is pressed in the thickness direction can be more reliably improved.

[0129] In particular, because the resin fibers are included as a nonwoven fabric in the joint 20, the resin fibers can be distributed more uniformly within the joint 20, effectively suppressing undesirable compositional variations, and the aforementioned effects are exhibited more significantly.

[0130] If the joint portion 20 includes a fibrous substrate, the thickness of the fibrous substrate is preferably 3 μm or more and 300 μm or less, and more preferably 5 μm or more and 100 μm or less.

[0131] If resin fibers are included in the joint 20, the resin fiber content in the joint 20 (natural content) is preferably 2% by volume or more and 70% by volume or less, more preferably 4% by volume or more and 50% by volume or less, and even more preferably 6% by volume or more and 30% by volume or less.

[0132] This makes it possible to more clearly demonstrate the effects of including the aforementioned resin fibers, and to ensure a sufficient content of the resin material 21 in the joint 20, thereby making the bonding strength of the heat conducting portion 10 by the joint 20 sufficiently excellent.

[0133] When resin fibers are included in the joint 20, if the content of resin material 21 in the joint 20 (content in its natural state) is X1 [volume %] and the content of resin fibers in the joint 20 (content in its natural state) is X2 [volume %], it is preferable that the relationship 0.04 ≤ X2 / X1 ≤ 10.0 is satisfied, more preferably that 0.07 ≤ X2 / X1 ≤ 5.0 is satisfied, and even more preferably that 0.10 ≤ X2 / X1 ≤ 3.0 is satisfied. This allows the aforementioned effects to be exhibited more significantly.

[0134] However, the content of components other than resin material, metal particles, ceramic particles, and resin fibers in the joint 20 is preferably 5% by weight or less, more preferably 3% by weight or less, and even more preferably 1% by weight or less.

[0135] If the joint 20 includes a spacer, undesirable variations in the thickness of the joint 20 can be effectively suppressed. Furthermore, a gap 2 can be effectively formed between the resin material 21 constituting the joint 20 and the spacer. This effect is particularly pronounced when the spacer has the size and shape described later. In addition, it is possible to effectively prevent the resin material 21 constituting the joint 20 from protruding from the edges during the manufacturing of the heat conductive sheet 1. As a result, the problem of the joint 20 preferentially contacting the member to which the heat conductive sheet 1 is applied, thereby hindering contact at the heat conductive portion 10, can be effectively prevented, and the effective thermal conductivity of the heat conductive sheet 1 when it is pressed in the thickness direction can be made more reliably superior.

[0136] The spacer may be ellipsoidal, cylindrical, prismatic, or needle-shaped, but it is preferably spherical, and more preferably perfectly spherical.

[0137] This makes it possible to more effectively suppress undesirable variations in the thickness of the joint 20. In addition, it is possible to more effectively form a gap 2 between the resin material 21 constituting the joint 20 and the spacer.

[0138] When the spacer is spherical, especially perfectly spherical, the shape coefficient SF-2 of the spacer is preferably 100 to 150, more preferably 100 to 125, and even more preferably 100 to 120. This allows the aforementioned effects to be exhibited more significantly.

[0139] When the spacer is spherical, especially perfectly spherical, the average particle size of the spacer is not particularly limited, but is preferably 0.1 μm or more and 100 μm or less, and more preferably 1 μm or more and 50 μm or less. This allows the aforementioned effects to be exhibited more significantly.

[0140] The spacer may be made of any material, such as metal, ceramic, or glass, but it is preferable that it be made of a resin material.

[0141] This improves the adhesion between the spacer and the resin material 21, thereby improving the durability and reliability of the thermal conductive sheet 1.

[0142] Examples of resin materials that make up the spacer include polyester resins such as polyethylene terephthalate, acrylic resins, polyolefin resins such as polyvinyl chloride, polystyrene, polyethylene, and polypropylene, phenolic resins (including Bakelite), and fluororesins. One or more of these can be selected and used in combination. Among these, acrylic resins, phenolic resins (including Bakelite), and fluororesins are excellent in terms of heat resistance. Acrylic resins are also particularly excellent in terms of softness during processing.

[0143] If the joint portion 20 includes a spacer, the spacer content in the joint portion 20 is preferably 0.1 volume% or more and 20 volume% or less, and more preferably 0.5 volume% or more and 10 volume% or less.

[0144] Furthermore, the joint portion 20 may also include a fibrous substrate containing fibers made of materials other than the resin fibers described above. In this case as well, the same effects as those obtained with the fibrous substrate containing resin fibers described above can be obtained. Examples of constituent materials for the fibers that make up such a fibrous substrate (a fibrous substrate containing fibers made of materials other than resin fibers) include glass, cellulose, synthetic rubber, and the like.

[0145] [1-3-3] Other conditions In Figure 1, the thickness of the joint portion 20 indicated by t20 is preferably 1 μm or more and 2000 μm or less, more preferably 2 μm or more and 1500 μm or less, and even more preferably 3 μm or more and 1000 μm or less. This allows the effects of the present invention described above to be exhibited more significantly.

[0146] The proportion of the joint portion 20 in the thermal conductive sheet 1 (proportion in the natural state; the same applies hereinafter) is preferably 15% to 70% by volume, more preferably 20% to 65% by volume, even more preferably 25% to 60% by volume, and most preferably 30% to 60% by volume.

[0147] This makes it possible to ensure that the proportion of the heat conductive portion 10 within the heat conductive sheet 1 is sufficiently high, while also making the overall flexibility of the heat conductive sheet 1 more excellent, thereby more reliably and significantly demonstrating the effects of the present invention described above.

[0148] [1-4] Void Void 2 is a portion of the heat conductive sheet 1 where the heat conductive portion 10 and the joint portion 20 are not present. The void 2 usually contains air or gases such as gas generated when the resin material 21 constituting the joint portion 20 hardens.

[0149] The presence of voids 2 in the thermal conductive sheet 1 allows the voids 2 to act as a cushion when the thermal conductive sheet 1 is pressed, absorbing the deformation of the thermal conductive sheet 1 when pressed, particularly the deformation of the joint portion 20, thereby suppressing excessive deformation. Furthermore, it becomes possible to impart appropriate flexibility to the thermal conductive sheet 1, allowing it to be suitably adjusted to satisfy the above-mentioned conditions regarding the thickness displacement rate.

[0150] In the heat conductive sheet 1, the void portion 2 is provided at least in a portion adjacent to the joint portion 20.

[0151] When the proportion of the heat conductive portion 10 in the heat conductive sheet 1 is VC [volume %], the proportion of the joint portion 20 in the heat conductive sheet 1 is VJ [volume %], and the proportion of the void portion 2 in the heat conductive sheet 1 is VV [volume %], it is preferable that the relationship 25 ≤ [(VJ + VV) / (VC + VJ + VV)] × 100 ≤ 90 is satisfied, more preferably that the relationship 25 ≤ [(VJ + VV) / (VC + VJ + VV)] × 100 ≤ 85 is satisfied, even more preferably that 31 ≤ [(VJ + VV) / (VC + VJ + VV)] × 100 ≤ 80 is satisfied, and most preferably that 37 ≤ [(VJ + VV) / (VC + VJ + VV)] × 100 ≤ 75 is satisfied. This allows the effects of the present invention described above to be exhibited more significantly.

[0152] [1-5] Other conditions The heat conductive sheet 1 of the present invention preferably satisfies the following conditions. That is, it is preferable that the amount of thickness displacement (T1-T2) when the heat conductive sheet 1 in its natural state is pressed in the thickness direction with a surface pressure of 3.0 MPa is 0.15 mm or more and 0.4 mm or less, and that the amount of thickness displacement (T1-T3) after 5 minutes have elapsed since unloading is 0.01 mm or more and 0.105 mm or less.

[0153] By satisfying this relationship, the thermal conductive sheet 1 exhibits lower interfacial thermal resistance and greater reliability when high surface pressure is applied to the contacting material.

[0154] As described above, with respect to the heat-conducting sheet 1 in its natural state, the amount of displacement in thickness (T1 - T2) in the state of being pressed at a surface pressure of 3.0 MPa in the thickness direction thereof is preferably 0.15 mm or more and 0.4 mm or less, more preferably 0.175 mm or more and 0.39 mm or less, still more preferably 0.2 mm or more and 0.39 mm or less, and most preferably 0.225 mm or more and 0.375 mm or less. Thereby, the effects of the present invention described above are more remarkably exhibited.

[0155] As described above, the amount of displacement in the thickness direction (T1 - T3) at the time when 5 minutes have elapsed after unloading is preferably 0.01 mm or more and 0.105 mm or less, more preferably 0.01 mm or more and 0.09 mm or less, still more preferably 0.01 mm or more and 0.075 mm or less, and most preferably 0.01 mm or more and 0.06 mm or less. Thereby, the effects of the present invention described above are more remarkably exhibited.

[0156] The density of the heat-conducting sheet 1 in the state before setting it to the above-described pressing state (the state of being pressed at a surface pressure of 3.0 MPa in the thickness direction of the heat-conducting sheet 1) (natural state) is preferably 0.25 g / cm ３ or more and 2.5 g / cm ３ or less, and more preferably 0.9 g / cm ３ or more and 2.0 g / cm ３ or less.

[0157] The density of aluminum, which is often used in conventional heat conductors, for example, heat dissipation members such as heat sinks, is about 2.7 g / cm ３ .

[0158] By using the materials as described above as the materials constituting the heat conduction part 10 and the joining part 20 in the heat-conducting sheet 1, the density as a whole can be made lower than that of conventional heat conductors.

[0159] Thereby, the heat-conducting sheet 1 can be made particularly lightweight. And when the heat-conducting sheet 1 is mounted on an electronic device or the like, it does not prevent the weight reduction of the electronic device or the like. That is, the electronic device or the like can be made lighter.

[0160] When the thermal conductive sheet 1 is pressed in the thickness direction with a surface pressure of 3.0 MPa, the measured value of the thermal conductivity in the thickness direction of the thermal conductive sheet 1 is preferably 50 W / (m·K) or more, more preferably 70 W / (m·K) or more and 1200 W / (m·K) or more and still preferably 100 W / (m·K) or more and 800 W / (m·K) or less.

[0161] This improves the adhesion between the heat conductive sheet 1 and the member to which it is applied when pressed, keeping the interfacial thermal resistance low and making the effective thermal conductivity particularly high.

[0162] Here, the measured value of thermal conductivity can be determined, for example, by a method conforming to the US standard ASTM D5470.

[0163] Furthermore, the measured value of thermal conductivity can also be determined, for example, by measurement using a thermal diffusivity / thermal conductivity measuring device (ai-Phase Mobile M3 series, manufactured by i-Phase Corporation). The temperature during measurement can be set to 50°C.

[0164] In this embodiment, the measured value of the thermal conductivity is taken using a sample whose shape has been adjusted so that the surface pressed against the thermal conductive sheet 1 is a 20 mm x 20 mm square.

[0165] The pressure applied in the thickness direction when using the thermal conductive sheet 1 is not particularly limited, but is preferably 1.0 MPa or more and 6.0 MPa or less, more preferably 1.5 MPa or more and 5.0 MPa or less, and even more preferably 2.0 MPa or more and 4.0 MPa or less.

[0166] This makes it possible to lower the interfacial thermal resistance between the thermal conductive sheet 1 and the member in contact with the thermal conductive sheet 1, thereby improving the effective thermal conductivity of the thermal conductive sheet 1 in the thickness direction. In particular, with conventional thermal conductive sheets, when used under relatively high pressure as described above, the internal structure of the thermal conductive sheet is irreversibly destroyed, and problems such as an increase in interfacial thermal resistance tend to occur. However, the present invention can suitably prevent the occurrence of such problems. That is, when the pressure applied to the thickness direction of the thermal conductive sheet 1 during use is within the above range, the effects of the present invention are exhibited more significantly.

[0167] [2] Method for Manufacturing a Thermal Conductive Sheet Next, the method for manufacturing a thermal conductive sheet according to the present invention will be described. Figure 6 is a schematic cross-sectional view showing a thermal conductive part forming member composed of flake graphite. Figure 7 is a schematic diagram showing an example of an apparatus used in the joint forming composition attachment step and the winding step. Figure 8 is a schematic diagram showing a cut body obtained in the cutting step. Figure 9 is a schematic diagram showing a state in which the cut body is pressed to increase its flatness. Figure 10 is a schematic diagram showing the cutting step. Figure 11 is a schematic diagram showing the slicing step. Note that in Figure 11, the void portion 2 of the thermal conductive sheet 1 is not shown.

[0168] A method for manufacturing the heat conductive sheet 1 includes, for example, a winding step in which a joint-forming composition 20', which is a composition containing a curable resin material 21', is applied, and a heat conductive part-forming member 10' used for forming the heat conductive part 10 is wound around the circumferential surface of a winding roll R2 to obtain a cylindrical winding body 30; an incision step in which the winding body 30 is cut open in a direction not perpendicular to the axial direction of the roll to obtain an incision body 40; a curing step in which the curable resin material 21' contained in the incision body 40 is cured to form a joint 20 and obtain a heat conductive body 1'; and a slicing step in which the heat conductive body 1' is sliced ​​into a sheet to obtain the heat conductive sheet 1.

[0169] By winding the heat conduction part forming member 10', to which the joint-forming composition 20' has been applied, around the circumferential surface of a roll, the heat conduction sheet 1 can be manufactured more efficiently than, for example, when using a single sheet of raw material. Furthermore, by curing the curable resin material 21' after cutting the wound body 30, it can be cut in a softer state compared to the joint 20 containing the resin material 21. As a result, the strain generated by winding can be effectively corrected, and when creating a cut body 40 that is flatter than the wound body 30, peeling or a decrease in adhesion between the heat conduction part forming member 10', which corresponds to the heat conduction part 10, and the joint-forming composition 20', which corresponds to the joint 20, can be effectively prevented. As a result, the final heat conductive sheet 1 is made free of strain, and peeling, reduced adhesion, breakage of the joint 20, and failure of the joint between the heat conductive parts 10 are effectively prevented, resulting in a strong bond between the heat conductive parts 10 and the joint 20.

[0170] Furthermore, the method for manufacturing a heat conductive sheet may include, for example, a step of applying a joint-forming composition 20' to a heat conductive part-forming member 10' prior to the winding step.

[0171] [2-1] The heat conduction member 10' used in the step of attaching the heat conduction member forming composition is to become the heat conduction member 10 in the heat conduction sheet 1.

[0172] As the heat conduction part forming member 10', a member made of the same material as the heat conduction part 10 to be formed is usually used. That is, it is preferable that the heat conduction part forming member 10' satisfies the same conditions as described in [1-2] above.

[0173] The heat conduction portion forming member 10' is preferably composed of substantially a single component. This makes it possible to further improve the thermal conductivity of the formed heat conduction portion 10. In addition, it is generally advantageous in suppressing the manufacturing cost of the heat conduction sheet 1.

[0174] The shape of the heat conduction member 10' is not particularly limited, but a sheet material can be suitably used as the heat conduction member 10'.

[0175] By using a sheet material containing graphite as the heat conduction part forming member 10', the effective thermal conductivity between the member in contact with the heat conduction sheet 1 and the heat conduction sheet 1 can be improved while suppressing the manufacturing cost of the heat conduction sheet 1. Furthermore, the flexibility and suppleness of the heat conduction sheet 1 can be improved, for example, the restorative force when the heat conduction sheet 1 is bent, the cushioning effect due to internal voids, and the improved contact effect due to appropriate deformation when in contact with an overheated area can be improved. Hereinafter, the sheet material containing graphite will also be referred to as "graphite sheet material".

[0176] Furthermore, by using a sheet material made of a metal as the heat conduction part forming member 10', the effective thermal conductivity between the member in contact with the heat conduction sheet 1 and the heat conduction sheet 1 can be improved while suppressing the manufacturing cost of the heat conduction sheet 1. In addition, the dust generation of the heat conduction sheet 1 can be further reduced due to the strong bonding force within the metal material. Moreover, even when a relatively large load is applied to the heat conduction sheet 1, irreversible deformation of the heat conduction sheet 1, such as collapse due to buckling, can be more effectively prevented. Hereinafter, the sheet material made of a metal will also be referred to as "metal sheet material".

[0177] [2-1-1] Graphite Sheet Material As a graphite sheet material, in addition to graphite, materials containing components other than graphite, such as binders and resin fibers, may be used, but it is preferable that the material is substantially composed of only graphite, that is, substantially composed of a single component. Such a graphite sheet material can be manufactured, for example, by compressing powdered graphite into a sheet.

[0178] The graphite is preferably flaky graphite. This allows the flaky graphite to be suitably oriented in the in-plane direction of the heat conduction section 10, resulting in particularly excellent in-plane thermal conductivity of the heat conduction section 10.

[0179] More specifically, when flake graphite is compressed into a sheet, the flake graphite FG is oriented in the in-plane direction of the sheet, as shown in Figure 6. That is, the thickness direction of the flake graphite FG is suitably oriented along the thickness direction of the sheet. When used as a thermal conductive sheet 1, the thermal conductivity of the thermal conductive portion 10 in the in-plane direction can be made particularly excellent.

[0180] Graphite sheet material is preferably manufactured by a method comprising, for example, a pressurizing step of pressurizing flaky graphite to form it into a sheet, a drying step of drying the sheet-shaped graphite, and a heating and pressing step of heating and pressing (hot pressing) the sheet-shaped graphite.

[0181] In the pressurization process, graphite is compressed and formed into a sheet. The pressurization process can preferably be carried out at a temperature of, for example, 10°C to 35°C. The press pressure at this time can be, for example, 1 MPa to 30 MPa.

[0182] In the drying process, the graphite, which has been formed into a sheet, is subjected to a drying treatment. This removes excess moisture and other volatile components, improving handling. It also improves the shape stability and strength of the graphite sheet material.

[0183] The drying process can be carried out by reduced pressure, heating, or natural drying. When heating is used, the heating temperature can be between 40°C and 100°C.

[0184] In the heating and pressurizing process, the sheet-shaped graphite is subjected to heating and pressurizing treatment in the thickness direction of the sheet. This allows for a more favorable orientation of the flaky graphite. Furthermore, the stability of the shape and strength of the graphite sheet material are improved.

[0185] The heating temperature in the heating and pressing process can be, for example, between 100°C and 400°C. This more effectively prevents moisture, binders, etc., from unintentionally remaining in the final graphite sheet material. The pressing pressure in the heating and pressing process can be, for example, between 10 MPa and 40 MPa.

[0186] Furthermore, regarding density, the density is relatively high near the surface of the graphite sheet material, while the density is relatively low inside the graphite sheet material.

[0187] The overall density of the graphite sheet material is 0.3 g / cm³. ３ 2.1g / cm or more ３ Preferably, it is 0.7 g / cm³. ３ 2.1g / cm or more ３ The following is more preferable. This makes it possible to reduce the weight of the thermal conductive sheet 1 while making the thermal conductive sheet material itself particularly excellent in terms of thermal conductivity and strength in the planar direction.

[0188] [2-1-2] Metal Sheet Material As a metal sheet material, in addition to the metal material, a material other than the metal material, such as a binder or resin fiber, may be used, but it is preferable that it is substantially composed only of the metal material, that is, substantially composed of a single component. As a metal sheet material, for example, a metal foil obtained by rolling a metal material into a sheet can be preferably used.

[0189] [2-2] Composition for forming joints The composition for forming joints used in the bonding step is to form a joint 20 on the heat conductive sheet 1 and is a composition containing a curable resin material 21'.

[0190] The curable resin material 21' is not particularly limited as long as the resin material 21 obtained by curing the curable resin material 21' is flexible, and the precursor of the aforementioned resin material 21, for example, an uncured product or a semi-cured product, can be used. This will provide the same effects as described above.

[0191] Furthermore, it is preferable that the curable resin material 21' generates gas during the curing process described later. This allows for the suitable formation of voids 2 within the heat conductive sheet 1.

[0192] [2-3] Joint-forming composition application process: In the joint-forming composition application process, a joint-forming composition 20' containing a curable resin material 21' is applied to at least one surface of the heat-conducting member 10'.

[0193] Methods for applying the joint-forming composition 20' to the surface of the heat-conducting member 10' include, for example, applying it using a bar coater, roll coater, reverse roll coater, gravure coater, die coater, kiss coater, rod coater, dip coater, or spray coater.

[0194] This allows the bonding composition 20' to be continuously and appropriately applied to the surface of the heat conduction member 10', which is advantageous in improving the reliability and productivity of the manufactured heat conduction sheet 1.

[0195] The joint-forming composition 20' may be applied to only one side of the heat-conducting member 10', or it may be applied to both sides.

[0196] This process can be carried out, for example, using the apparatus shown in Figure 7. More specifically, a raw material roll R1 is prepared by winding a pre-fabricated heat conduction part forming member 10' into a roll shape. Then, one end of the heat conduction part forming member 10' is pulled out from the raw material roll R1, and the joint forming composition 20' is applied to one side of the heat conduction part forming member 10' using a kiss coater M10.

[0197] The Kiss Coater M10 is a device that applies coating to a sheet using one or more rolls, and is capable of applying coating only to the area where the coating roll M11 is in contact with the sheet.

[0198] The Kiss Coater M10 comprises a coating roll M11 that is rotated in the direction of the arrow by a motor (not shown), a liquid receiving pan M12 that holds the joint-forming composition 20', and a squeegee M13 that maintains a constant film thickness of the joint-forming composition 20' on the surface of the coating roll M11 by bringing its tip into contact with the surface of the coating roll M11. Approximately the lower half of the coating roll M11 is immersed in the joint-forming composition 20' in the liquid receiving pan M12. The heat conduction-forming member 10' is guided and conveyed by guide rolls M14, M14, so that it comes into contact with the upper surface of the coating roll M11 when the joint-forming composition 20' is applied. As a result, when the coating roll M11 rotates, the joint-forming composition 20' in the liquid receiving pan M12 is drawn up by the coating roll M11, adjusted to a predetermined amount by the squeegee M13, and then applied to the surface of the heat conduction-forming member 10'. The joint-forming composition 20' is supplied to the liquid receiving pan M12 by a pump from a supply tank (not shown), and the height of the joint-forming composition 20' in the liquid receiving pan M12 is controlled to be kept constant.

[0199] By using the Kiss Coater M10, the heat conduction part forming member 10' can be coated with the joint forming composition 20' without immersing it in the composition. Therefore, in the coating process, a constant amount of the joint forming composition 20' can be efficiently applied continuously.

[0200] In the step of applying the joint-forming composition, it is preferable to include air bubbles between the heat-conducting member 10' and the joint-forming composition 20'. This allows for the formation of a suitable void 2 between the heat-conducting portion 10 and the joint portion 20 after the resin material 21 has cured.

[0201] Methods for incorporating air bubbles between the heat conduction part forming member 10' and the joint forming composition 20' include, for example, adjusting the surface shape of the heat conduction part forming member 10', the viscosity of the joint forming composition 20', and the wettability of the heat conduction part forming member 10'.

[0202] Furthermore, after applying the joint-forming composition 20' to the heat-conducting member 10', the gas generated during the curing reaction can be used to form bubbles (formation of voids 2).

[0203] This process is preferably carried out using a heated joint-forming composition 20' such that its viscosity is lower than its viscosity at room temperature (20°C).

[0204] As a result, after the completion of this process, for example in the winding process, the joint-forming composition 20' applied to the heat-conducting member 10' is cooled, and the viscosity of the joint-forming composition 20' can be made lower than the viscosity in this process. Consequently, it is possible to more effectively prevent the joint-forming composition 20' applied to the heat-conducting member 10' from unintentionally flowing out in processes after the joint-forming composition application process.

[0205] The heating temperature of the joint-forming composition 20' in this process is not particularly limited, but it is preferable to set it so that the viscosity of the joint-forming composition 20' satisfies the following conditions.

[0206] When applying the joint-forming composition 20' to the heat-conducting member 10', the viscosity of the joint-forming composition 20' is preferably 500 mPa·s or more and 50,000 mPa·s or less, and more preferably 2,000 mPa·s or more and 40,000 mPa·s or less.

[0207] This allows the joint-forming composition 20' to be more effectively applied to the heat-conducting member 10' with a predetermined thickness.

[0208] The viscosity of the joint-forming composition 20' can be determined by measurement in accordance with JIS Z8803:2011.

[0209] Furthermore, for example, in this process, multiple types of joint-forming compositions 20' may be used, or a material containing only some of the components of the aforementioned joint-forming composition 20' and a material containing other components may be used separately in combination.

[0210] [2-4] Winding process In the winding process, the heat conduction part forming member 10' to which the joint forming composition 20' has been applied is wound around the circumferential surface of the winding roll R2 to obtain a cylindrical winding body 30.

[0211] The wound body 30 obtained in this manner has a structure in which portions composed of heat conduction portion forming member 10' and portions composed of joint portion forming composition 20' are alternately arranged from the center toward the outer circumference.

[0212] In Figure 7, the heat conduction forming member 10' is shown being transported guided by guide rolls M14, M14. However, the heat conduction forming member 10' may also be transported by guide rolls other than guide rolls M14, M14 (not shown), and the transport direction may be changed by the guide rolls as needed.

[0213] In the illustrated configuration, the heat conduction member 10' to which the joint-forming composition 20' is applied is wound around the circumferential surface of a winding roll R2 with a circular cross-section. However, the configuration is not limited to this, and it may be wound around the circumferential surface of a roll with an elliptical, polygonal, or track-shaped cross-section.

[0214] Furthermore, in the winding process, a resin fiber sheet (woven fabric, nonwoven fabric, etc.) as a fibrous base material containing resin fibers may be wound onto the winding roll R2 together with the heat conduction part forming member 10' described above.

[0215] In this case, the resin fiber sheet may be coated with the joint-forming composition 20' in the same manner as described above, or it may not be coated with the joint-forming composition 20'.

[0216] When using a resin fiber sheet to which the joint-forming composition 20' has been applied, the heat-conducting member 10' may be one to which the joint-forming composition 20' has been applied as described above, or one to which the joint-forming composition 20' has not been applied. In other words, in the joint-forming composition application step, the joint-forming composition 20' may be applied to the resin fiber sheet instead of the heat-conducting member 10'. Furthermore, when using a resin fiber sheet, it may be used with an adhesive applied to at least a part of its surface.

[0217] By using a resin fiber sheet in the manufacture of the heat conductive sheet 1 (heat conductor 1'), the resin fibers can be suitably oriented in the in-plane direction of the joint 20. This allows for more uniform dispersion of the resin fibers and a more uniform overlapping state of the resin fibers. As a result, the tensile strength of the joint 20 is improved, and the thickness of the joint 20 can be made more uniform.

[0218] When using a resin fiber sheet, the thickness of the resin fiber sheet is preferably 3 μm or more and 300 μm or less, and more preferably 5 μm or more and 100 μm or less.

[0219] [2-5] Cutting process In the cutting process, the wound body 30 is cut open in a direction not perpendicular to the axial direction of the winding roll R2 to obtain a cut body 40.

[0220] By cutting the wound body 30 before the curing process in which the curable resin material 21' is cured, it can be cut in a softer state compared to the joint 20 containing the resin material 21 (cured product of the curable resin material 21').

[0221] In this process, an incision is made in the stacking direction of the winding body 30, in a direction not perpendicular to the axial direction of the cylindrical winding roll R2, and extending from one end to the other in the axial direction of the winding roll R2. The winding body 30 is then removed from the winding roll R2 while being opened at the incision, resulting in a cut body 40.

[0222] The direction in which the winding body 30 is cut open is not particularly limited, as long as it is not perpendicular to the axial direction of the winding roll R2. For example, it may be in a direction substantially parallel to the axial direction of the winding roll R2, or it may be in a direction oblique to the axial direction of the roll. Furthermore, the winding body 30 may have portions that are cut open in different directions. For example, it may have portions that are cut open in a direction substantially parallel to the axial direction of the winding roll R2 and portions that are cut open in a direction oblique to the axial direction of the roll.

[0223] The method for cutting the coiled body 30 is not particularly limited, but examples include using a band saw, saw, cutter, trimming cutter, laser, ultrasonic cutter, water cutter, etc.

[0224] [2-6] Curing process In the curing process, the curable resin material 21' contained in the joint-forming composition 20' is cured in the cut body 40.

[0225] As shown in Figure 8, when the wound body 30 is cut open to form the cut body 40, the cut body 40 is usually in a curved state. If the curable resin material 21' is cured before the wound body 30 is cut open, attempting to improve the flatness of the curved cut body 40 will result in strain caused by the difference in curvature between the inner and outer circumferences of the cut body 40, which can easily lead to delamination or reduced adhesion between the heat conduction part 10 and the joint part 20, fracture of the joint part 20, and fracture of the joint between the heat conduction parts 10. In contrast, by applying the curable resin material 21' to the cut body 40, which has been cut open to improve its flatness, the occurrence of the above problems can be effectively prevented.

[0226] This process can be carried out, for example, by curing the curable resin material 21' while the inner and outer circumferential sides of the incised body 40 are in contact with a flat surface.

[0227] More specifically, as shown in Figure 9, for example, the cut section 40 can be sandwiched between two flat plates 90 and pressure can be applied to improve the flatness of the heat conduction section 10 and the joint section 20, thereby curing the curable resin material 21' to form the resin material 21.

[0228] The pressure at this time is not particularly limited, but it is preferably greater than 0 MPa and less than or equal to 100 MPa, and more preferably between 10 MPa and 50 MPa.

[0229] If the pressure is below the lower limit, it may become difficult to sufficiently improve the flatness of the heat conduction portion 10 and the joint portion 20. On the other hand, if the pressure exceeds the upper limit, significant leakage of the curable resin material 21' from between adjacent heat conduction portion forming members 10' may occur, making it difficult to form a joint portion 20 of the desired thickness.

[0230] Furthermore, by performing the hardening process while pressing the cut section 40, peeling or a decrease in adhesion between the heat conductive section 10 and the joint section 20, the destruction of the joint section 20, and the destruction of the joint between the heat conductive sections 10 can be more effectively prevented, thereby improving the durability of the heat conductive sheet 1.

[0231] Through the process described above, a heat conductor 1' is obtained. The heat conductor 1' itself has excellent thermal conductivity in a direction nonparallel to the lamination direction of the heat conduction portion 10 and the joint portion 20 (for example, a direction approximately perpendicular to the lamination direction of the heat conduction portion 10 and the joint portion 20), but it is processed into a heat conductive sheet 1 through a slicing process as described later.

[0232] [2-7] Cutting Process The heat conductor 1' obtained through the hardening process may be cut to a desired size and shape by a cutting process. More specifically, for example, a rectangular parallelepiped heat conductor 1' with length L1 can be obtained by cutting along the cutting lines A-A' and B-B' in Figure 10.

[0233] By performing a cutting process, for example, the storage and transportation of the heat conductor 1' can be carried out more efficiently.

[0234] The shape of the heat conductor 1' obtained in the cutting process is not particularly limited, but can be, for example, a block shape such as a rectangular parallelepiped.

[0235] Furthermore, if the heat conductor 1' is cut into a sheet shape in this process, the slicing process described later can be omitted, and the desired heat conductive sheet 1 can be obtained. In other words, if the heat conductor 1' is cut into a sheet shape in this process, this process (cutting process) can be said to be the slicing process.

[0236] The cutting method is not particularly limited, but examples include using a cutter, trimming cutter, laser, ultrasonic cutter, water cutter, etc.

[0237] The cutting direction may be approximately parallel to the stacking direction (the thickness direction of the cut body 40), or it may be oblique to the stacking direction (the thickness direction of the cut body 40). Figure 10 shows how the cut body 40 is cut approximately parallel to the stacking direction.

[0238] [2-8] Slicing process In the slicing process, the heat conductor 1' is sliced ​​into a sheet to obtain a heat conductive sheet 1. In particular, it is preferable to carry out this process so that the heat conductive portion 10 and the joint portion 20 are exposed on both main surfaces of the obtained heat conductive sheet.

[0239] In the configuration shown in Figure 11, a heat conductive sheet 1 with a thickness T1 is obtained by slicing along the cutting lines C-C' and D-D'.

[0240] Here, even if the thickness T1 of the heat conductive sheet 1 to be manufactured is relatively small, the curable resin material 21' becomes a resin material 21 with higher shape stability after the curing process, so the heat conductor 1' can be easily sliced.

[0241] While there are no particular limitations on the slicing method, examples include using a cutter, trimming cutter, laser, ultrasonic cutter, water cutter, etc.

[0242] The surface of the thermal conductive sheet 1, particularly the main surface, may be polished. This allows for a suitable adjustment of the surface roughness of the thermal conductive sheet 1.

[0243] Such polishing treatment may also be applied to the heat conductor 1' described above.

[0244] In its natural state, the surface roughness Ra of the thermal conductive sheet 1 is preferably 0.1 μm or more and 80 μm or less, more preferably 0.1 μm or more and 30 μm or less, and even more preferably 0.1 μm or more and 10 μm or less.

[0245] This allows the heat conductive sheet 1 to conform more favorably to the surface shape of the member to which it is applied, thereby improving the effective heat conductivity between the member and the heat conductive sheet 1.

[0246] The surface roughness Ra of the thermal conductive sheet 1 can be measured, for example, by a method conforming to JIS B 0601-2013.

[0247] [3] Usage of the thermal conductive sheet Next, the usage of the thermal conductive sheet 1 will be explained.

[0248] The thermal conductive sheet 1 can be used, for example, as various heat dissipation members, a heat transfer member that comes into contact with a high-temperature member and a heat dissipation member to transfer heat from the high-temperature member to the heat dissipation member and efficiently dissipate heat from the heat dissipation member, or a heat transfer member that comes into contact with an object to be heated and a high-temperature member that is at a higher temperature than the object to be heated, to transfer thermal energy from the high-temperature member to the object to be heated and efficiently heat the object to be heated.

[0249] The following explanation will primarily focus on the case where the thermal conductive sheet 1 is used in contact with at least a portion of the surface of the high-temperature component which is a heat-generating element.

[0250] High-temperature components are not particularly limited as long as they become hotter than the surrounding atmosphere. Examples include various electronic and electrical components, more specifically, central processing units (CPUs) of computers, graphics processing units (GPUs), power devices, FPGAs, ASICs, SoCs for smartphones, DSPs and microcontrollers for embedded devices, semiconductor elements such as transistors, light-emitting elements such as laser diodes, light-emitting diodes (LEDs) and electroluminescent devices, liquid crystals, image sensors such as CCDs and image sensors (e.g., 8K), switching regulators, motor coils, and printer heads. High-temperature components may also include relays, batteries, transformers, power supply units, bearings, electron guns, vacuum tubes, and high-frequency oscillators. Furthermore, high-temperature components may include tubes or containers containing a high-temperature fluid.

[0251] In particular, power devices are examples of high-temperature components to which the thermal conductive sheet of the present invention is applied. The thermal conductive sheet is used in a state where it is pressed against the power device with a relatively high surface pressure, for example, about 1 MPa to 3 MPa. Furthermore, a higher thermal conductivity is required for the thermal conductive sheet applied to a power device. For these reasons, the effects of the present invention are more pronounced when the thermal conductive sheet is applied to a power device.

[0252] As for the high-temperature component, it is preferable that its maximum surface temperature is 40°C or higher and 250°C or lower, more preferably 50°C or higher and 200°C or lower, and even more preferably 60°C or higher and 180°C or lower.

[0253] When the thermal conductive sheet 1 is applied to such a high-temperature component, it can conduct and dissipate heat more effectively, and the effects of the present invention are more pronounced.

[0254] The thermal conductive sheet of the present invention described above can also be applied to electronic devices. Such electronic devices include, for example, electronic components and the thermal conductive sheet of the present invention as a heat dissipation member or a heat transfer member as described above.

[0255] Examples of electronic devices to which the heat conductive sheet of the present invention is applied include small electronic devices.

[0256] Examples of small electronic devices include notebook computers, tablet devices, mobile communication devices, mobile phones, smartphones, portable music players, portable radios, portable televisions, digital cameras, video cameras, portable game consoles, e-readers, and portable medical devices.

[0257] Such electronic devices are equipped with thermal conductive sheets that offer excellent thermal conductivity, allowing for more efficient heat dissipation from heat-generating electronic components. This effectively reduces the risk of reduced device and system lifespan and malfunctions. Furthermore, the thermal conductive sheets are designed to resist excessive deformation when pressed, preventing failures caused by short circuits in the wiring of electronic components, for example, thus further enhancing the reliability of the electronic devices.

[0258] Preferred embodiments of the present invention have been described above, but the present invention is not limited thereto.

[0259] For example, in a method for manufacturing a heat conductive sheet, in addition to the steps described above, other steps (such as pre-treatment steps, intermediate treatment steps, and post-treatment steps) may be further included.

[0260] Furthermore, in the method for manufacturing a heat conductive sheet, at least some of the steps described above may be rearranged.

[0261] Furthermore, the thermal conductive sheet of the present invention is a thermal conductive sheet comprising a plurality of thermal conductive parts and a joint made of a flexible material that joins each of the thermal conductive parts, wherein it has voids where the thermal conductive parts and the joints are not present, and the proportion of the voids to the entire thermal conductive sheet is 5% by volume or more and 65% by volume or less, and when the thickness of the thermal conductive sheet in its natural state is T1 [mm], the thickness when the thermal conductive sheet in its natural state is pressed with a surface pressure of 3.0 MPa in the thickness direction of the thermal conductive sheet is T2 [mm], and the thickness after 5 minutes have elapsed since unloading is T3 [mm], the relationship 30 ≤ [(T1 - T2) / T1] × 100 ≤ 75 and 2 ≤ [(T1 - T3) / T1] × 100 ≤ 21 is satisfied, it may be manufactured by any method.

[0262] More specifically, the embodiments described above primarily focused on the case where a heat conductive sheet is manufactured using a method comprising a winding step, a cutting step, a hardening step, and a slicing step. However, the heat conductive sheet of the present invention may also be manufactured by, for example, laminating single-sheet heat conductive part-forming members to which a joint-forming composition is attached to form a laminate, and by a method that does not involve a cutting step (a method that does not include a winding step and a cutting step).

[0263] Furthermore, while the above explanation primarily focused on cases where the heat conduction portion and joint portion constituting the heat conduction sheet are planar, at least a portion of the heat conduction portion and joint portion constituting the heat conduction sheet may be non-planar, for example, curved or bent surfaces.

[0264] Furthermore, the thermal conductive sheet may have a structure other than the thermal conductive portion, joint portion, and void portion described above.

[0265] Furthermore, the heat conductor according to the present invention described above (a heat conductor that is not in the form of a sheet), that is, a heat conductor in which the proportion of voids in the entire heat conductor is 5% by volume or more and 65% by volume or less, and when a heat conductive sheet is cut out from the heat conductor, the thickness of the heat conductive sheet in its natural state is T1 [mm], the thickness when the heat conductive sheet in its natural state is pressed with a surface pressure of 3.0 MPa in the thickness direction of the heat conductive sheet is T2 [mm], and the thickness after 5 minutes have elapsed since unloading is T3 [mm], then the heat conductor that satisfies the relationships 30 ≤ [(T1 - T2) / T1] × 100 ≤ 75 and 2 ≤ [(T1 - T3) / T1] × 100 ≤ 21 may be used in a shape other than a sheet.

[0266] The present invention will be described in detail below based on examples and comparative examples, but the present invention is not limited to these. Unless otherwise specified, the treatments were performed at 20°C.

[0267] [4] Manufacturing of Thermal Conductive Sheets The thermal conductive sheets of each example and each comparative example were manufactured as follows: (Example 1) First, a thermal conductive sheet, a nonwoven fabric made of resin fibers, and a joint forming composition were prepared as thermal conductive material.

[0268] For the heat conduction sheet, we prepared a commercially available graphite sheet material with holes formed in it.

[0269] The graphite sheet material used in this embodiment had a thickness of 80 μm, and the flake-like graphite was oriented along the thickness direction of the graphite sheet material. Near the surface of the graphite sheet material, the flake-like graphite was densely compressed, and there were a relatively large number of voids near the center of the thickness direction of the graphite sheet material. However, there were no voids penetrating the thickness direction of the graphite sheet material. The density of the graphite sheet material was 1.5 g / cm³. ３ Furthermore, the in-plane thermal conductivity of the graphite sheet material at 20°C, measured by the transient hot-wire method in accordance with JIS R2616-2000, was 250 W / (m·K).

[0270] The holes in the graphite sheet material were formed as follows: A roll body, on which multiple protrusions corresponding to holes were formed in a staggered arrangement, was pressed against the surface of the graphite sheet material, thereby forming multiple holes in the graphite sheet material. The holes formed in this way were circular in shape with a diameter of 200 μm and penetrated the graphite sheet material in the thickness direction. The distance between the centers of adjacent holes was 700 μm.

[0271] Furthermore, as a nonwoven fabric composed of polyethylene terephthalate fibers as resin fibers, the polyethylene terephthalate fiber thickness is 7 μm, the thickness is 40 μm, and the basis weight is 12 g / cm². ２ I prepared something with those conditions.

[0272] In this embodiment, a solvent-free, one-component elastomer fabric called Celmu Elastomer was used as the joint-forming composition.

[0273] The celm elastomer used as a bonding composition in this embodiment comprises a polyrotaxane having a cyclic molecule, a first polymer having a linear molecular structure that encloses the cyclic molecule in a skewer-like manner, and sealing groups provided near both ends of the first polymer, and a second polymer, wherein the polyrotaxane and the second polymer are bonded via the cyclic molecule.

[0274] Next, in addition to the configuration shown in Figure 7, the apparatus further includes a resin fiber sheet supply means (nonwoven fabric supply means) (not shown) for supplying a resin fiber sheet (nonwoven fabric), and is configured to wind the resin fiber sheet (nonwoven fabric) on a winding roll while it is superimposed on a graphite sheet to which the bonding composition has been applied. Using a kiss coater, the bonding composition was applied to one side of the heat conduction part forming sheet, and then the heat conduction part forming sheet to which the bonding composition has been applied was superimposed on the resin fiber sheet (nonwoven fabric) and wound on a winding roll with a diameter of 20 cm at a speed of 2 m / min to obtain a wound body.

[0275] When the bonding composition was applied to the heat conduction sheet, the bonding composition penetrated into the holes and also into the voids located near the center of the heat conduction sheet in the thickness direction.

[0276] In the heat conductor obtained as described above, when observed from the stacking direction between the heat conducting portion and the junction, the pores in multiple heat conducting portions were arranged so that they did not overlap.

[0277] Next, a cutter was used to make an incision parallel to the axial direction of the winding roll, cutting open the wound body and removing it from the winding roll to obtain a cut section. The obtained cut section was curved in its natural state, but the curvature of the inner surface of the cut section, i.e., the surface that was in contact with the winding roll, was smaller than when it was in contact with the winding roll, and the cut section was flatter than the wound body.

[0278] Next, the resulting incised body was sandwiched between two flat plates and pressed with 20 MPa. At this time, the entire portion corresponding to the outer surface of the wound body was in contact with one flat plate, and the entire portion corresponding to the inner surface of the wound body was in contact with the other flat plate.

[0279] Next, with the cut body pressed down, a heat treatment was performed at 160°C for 8 hours to cure the curable resin material constituting the joint-forming composition, thereby obtaining a heat conductor. Even after the pressure was released, the two surfaces of the heat conductor obtained in this way that had been in contact with the flat plate were both flat surfaces, and these surfaces were parallel.

[0280] Next, the thermal conductor was cut to a thickness of 0.3 mm along the stacking direction, and then cut into a 20 mm square shape to obtain a thermal conductive sheet as shown in Figure 1. That is, the obtained thermal conductive sheet had a thickness T1 (thickness T1 in its natural state) of 0.3 mm and was a square shape with sides of 20 mm.

[0281] The heat-conducting sheet obtained in this manner, as shown in Figure 1, had multiple heat-conducting sections and joint sections arranged alternately, with the heat-conducting sections and joint sections exposed on both main surfaces. The heat-conducting sections were composed of flaky graphite, and the joint sections were composed of a flexible resin material. In other words, the multiple heat-conducting sections of the heat-conducting sheet were continuously provided inside the sheet and were through-heat-conducting sections exposed on both main surfaces of the heat-conducting sheet. The angle θ between the normal direction of these main surfaces and the direction of extension of the through-heat-conducting sections in the thickness direction of the heat-conducting sheet was 3°. Furthermore, in the heat-conducting sections, the graphite was oriented so that its thickness direction was aligned with the thickness direction of the heat-conducting section.

[0282] In the thermal conductive sheet, the thickness of the thermal conductive portion obtained by the thermal conductive portion forming sheet was 80 μm, and the thickness of the joint portion composed of resin material was 40 μm. The proportion of the thermal conductive portion to the thermal conductive sheet was 63 volume%, and the proportion of the joint portion was 29 volume%. The density of the thermal conductive sheet was 1.32 g / cm³. The joint portion contained polyethylene terephthalate fibers as resin fibers along with a cured product of a curable resin material.

[0283] (Examples 2-6, Comparative Examples 1-4) A thermal conductive sheet was manufactured in the same manner as in Example 1, except that the conditions were adjusted to have the configuration shown in Table 1.

[0284] Table 1 summarizes the configuration of the thermal conductive sheets for each of the above embodiments and comparative examples.

[0285]

[0286] [5] Measurement and Evaluation The following measurements and evaluations were performed on the thermal conductive sheets of each of the above examples and comparative examples.

[0287] [5-1] Compression and Recovery Rate Using an autograph (Shimadzu Corporation, AG-50kNG), the thickness T1 in its natural state, the thickness T2 when the heat conductive sheet in its natural state was pressed with a surface pressure of 3.0 MPa, and the thickness T3 5 minutes after unloading were determined for each of the above examples and comparative examples. From these measured values, the compression rate [(T1-T2) / T1] × 100 [%] and the recovery rate [(T1-T3) / T1] × 100 [%] of the heat conductive sheet were determined. The pressing rate when pressing the heat conductive sheet in its natural state with a surface pressure of 3.0 MPa was 0.5 mm / min.

[0288] For the transient method of calculating thermal conductivity, the thermal conductive sheet was shaped into a 10 mm x 10 mm square. The thermal diffusivity measured using a thermal diffusivity / thermal conductivity measuring device (ai-Phase Mobile M3 series, manufactured by i-Phase Corporation) was then multiplied by the separately measured density and specific heat to calculate the thermal conductivity.

[0289] [5-2] Thermal conductivity under pressure The thermal conductive sheets of each of the above examples and comparative examples were shaped into 10 mm x 10 mm squares, and then pressed in the thickness direction of the thermal conductive sheet at 3.0 MPa. The thermal conductivity in the thickness direction was determined by a method in accordance with the US standard ASTM D5470. During measurement, the heating heater was adjusted so that the temperature of the upper and lower surfaces of the thermal conductive sheet was 50°C.

[0290] [5-3] Area change rate For each of the above examples and comparative examples, the area of ​​the heat conductive sheet when viewed from above in its natural state is S0 [cm²]. ２ ], the heat conductive sheet in its natural state is pressed from the top side at 3.0 MPa for 5 minutes, and the area of ​​the heat conductive sheet when viewed from above after unloading is S1 [cm²]. ２ The area change rate [%] was calculated as [(S1 - S0) / S0] × 100 when ] was set to ]. The thermal conductive sheet was pressed using an Autograph (Shimadzu Corporation, AG-50kNG) under the condition of a measurement speed (pressure speed) of 0.5 mm / min.

[0291] These results are shown in Table 2.

[0292]

[0293] As is clear from Table 2, the thermal conductive sheets in each embodiment, i.e., the thermal conductive sheets according to the present invention, all exhibited low interfacial thermal resistance with the contacting member when high surface pressure was applied, and were highly reliable. In contrast, satisfactory results were not obtained in each comparative example.

[0294] 1...Heat conductive sheet, 1'...Heat conductor, 2...Void, 10...Heat conductive part, 10c...Through heat conductive part, 10'...Metal for forming heat conductive part, 20...Joint, 20'...Composition for forming joint, 21...Resin material, 21'...Curable resin material, 30...Wound body, 40...Cut body, 50...Polyrotaxane, 51...Cylindrical molecule, 52...First polymer, 53...Sealing group, 60...Second polymer, 90...flat plate, A-A'...cutting line, B-B'...cutting line, C-C'...cutting line, D-D'...cutting line, FG...flaky graphite, L1...length, M10...kiss coater, M11...coating roll, M12...liquid receiving pan, M13...squeegee, M14...guide roll, R1...raw material roll, R2...winding roll, T1...thickness, T2...thickness, T3...thickness, t10...thickness, t20...thickness

Claims

1. A thermal conductive sheet comprising a plurality of thermal conductive parts and a joint made of a flexible material that joins each of the thermal conductive parts, wherein the sheet has voids where the thermal conductive parts and the joints are not present, the proportion of the voids to the entire thermal conductive sheet is 5% by volume or more and 65% by volume or less, and when the thickness of the thermal conductive sheet in its natural state is T1 [mm], the thickness when the thermal conductive sheet in its natural state is pressed with a surface pressure of 3.0 MPa in the thickness direction of the thermal conductive sheet is T2 [mm], and the thickness after 5 minutes have elapsed since unloading is T3 [mm], the relationship 30 ≤ [(T1 - T2) / T1] × 100 ≤ 75 and the relationship 2 ≤ [(T1 - T3) / T1] × 100 ≤ 21 is satisfied.

2. The thermal conductive sheet according to claim 1, wherein the thickness in its natural state is 0.15 mm or more and 20 mm or less.

3. The heat conductive sheet according to claim 1 or 2, wherein at least a portion of the plurality of heat conductive parts are provided continuously inside the heat conductive sheet and are exposed on both main surfaces of the heat conductive sheet.

4. The heat conductive sheet according to claim 1 or 2, wherein at least a portion of the plurality of heat conductive portions are provided continuously inside the heat conductive sheet and are through heat conductive portions exposed on both main surfaces of the heat conductive sheet, and the angle θ between the direction normal to the main surface and the direction of extension of the through heat conductive portion in the thickness direction of the heat conductive sheet is 0° or more and 45° or less.

5. The thermal conductive sheet according to claim 1 or 2, wherein the proportion of the thermal conductive portion in the thermal conductive sheet is 15% by volume or more and 80% by volume or less.

6. The thermal conductive sheet according to claim 1 or 2, wherein the proportion of the joint portion in the thermal conductive sheet is 15% by volume or more and 70% by volume or less.

7. The thermal conductive sheet according to claim 1 or 2, wherein when VC [volume %] is the proportion of the thermal conductive portion in the thermal conductive sheet, VJ [volume %] is the proportion of the joint portion in the thermal conductive sheet, and VV [volume %] is the proportion of the void portion in the thermal conductive sheet, the relationship 25 ≤ [(VJ + VV) / (VC + VJ + VV)] × 100 ≤ 90 is satisfied.

8. The heat conductive sheet according to claim 1 or 2, wherein the heat conductive portion is made of a material containing graphite.

9. The thermal conductive sheet according to claim 1 or 2, wherein the thermal conductive portion is composed of substantially a single component.

10. The density of the thermal conductive sheet in the state before being pressed is 0.25 g / cm³. ３ 2.5g / cm or more ３ The thermal conductive sheet according to claim 1 or 2, which is as follows:

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