resin sheet

Abstract

A resin sheet comprising a styrene-based thermoplastic elastomer, a plate-shaped filler, and a connecting filler, wherein the Type A durometer hardness of the resin sheet, measured in accordance with JIS K 6253-3, is 40 or less.

Description

[Technical Field]

[0001] This invention relates to a resin sheet. This application claims priority based on Japanese Patent Application No. 2024-177259, filed in Japan on October 9, 2024, and Japanese Patent Application No. 2025-092472, filed in Japan on June 3, 2025, and the contents thereof are incorporated herein by reference. [Background technology]

[0002] The central processing unit (CPU) is one of the representative devices that make up a computer. The amount of heat generated by the CPU increases dramatically when the computer is in operation. In recent years, with the increasing performance, miniaturization, and weight reduction of electronic devices, the density of semiconductor packages has increased, the integration of LSIs has increased, and the processing speed has increased, making countermeasures against the heat generated in electronic devices extremely important.

[0003] In typical electronic devices, a heat spreader is attached to the CPU, which is placed on a circuit board, via a thermal interface material (TIM), and this heat spreader is positioned in contact with a heat sink. As a result, in electronic devices, the heat generated by the CPU is conducted to the heat spreader via the TIM, and then the heat is further conducted in the planar direction by this plate-shaped heat spreader, and the heat is dissipated to the outside of the electronic device via the heat sink.

[0004] Traditionally, the reasons for employing such a heat dissipation structure for CPUs are as follows: Heat spreaders are made of metal or graphite, and while they have high thermal conductivity in the planar direction and high heat dissipation, they do not conform to the object being cooled (CPU), their contact with the object being cooled (CPU) is insufficient, and they do not have insulating properties. On the other hand, TIMs have a certain degree of conformability to the object being cooled (CPU), good contact, and insulating properties, but their thermal conductivity is insufficient. Therefore, by using these (heat spreaders and TIMs) in combination and adopting the heat dissipation structure described above, these shortcomings are compensated for. However, in conventional electronic devices, as long as TIM is a mandatory component, the heat dissipation structure is limited, and the configuration of the electronic device is also limited.

[0005] A novel resin sheet is disclosed that can solve these problems and constitute a new heat dissipation structure with high heat dissipation effect. This resin sheet contains a thermoplastic resin, a plate-shaped filler, and a connecting filler, wherein the average particle size of the connecting filler is 2 μm or less. Because this resin sheet contains the plate-shaped filler and the connecting filler, it has high thermal conductivity and high heat dissipation in both the direction parallel to its surface and in the thickness direction. Furthermore, because this resin sheet contains a thermoplastic resin, it has high flexibility when heated. By covering, and preferably embedding, a heat-generating element such as a CPU with a resin sheet having these characteristics, a new heat dissipation structure can be constructed in various electronic devices, and a high effect in suppressing heat generation in various electronic devices can be obtained (see Patent Document 1). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2024-45039 [Overview of the project] [Problems that the invention aims to solve]

[0007] The resin sheet disclosed in Patent Document 1 possesses both heat dissipation and conformability, and unlike heat dissipation structures that require a heat spreader and TIM, it is extremely useful because it allows components to be embedded and heat to be dissipated in any direction, thus enabling the construction of a new heat dissipation structure using only the resin sheet.

[0008] On the other hand, using only the aforementioned resin sheet may result in insufficient heat dissipation. In this case, a greater heat dissipation effect can be obtained by using other components in combination with the resin sheet, such as a heat sink, metal plate, heat pipe, or vapor chamber. However, when connecting these other parts to the resin sheet disclosed in Patent Document 1 at room temperature, the rigidity of the resin sheet sometimes resulted in inconsistent screw-fastened component fitting or difficulty in connecting other parts. Furthermore, when removing (peeling off) the embedded resin sheet from the object at room temperature, the rigidity of the resin sheet posed a risk of damaging the components. Moreover, when embedding components with the resin sheet, pressing the resin sheet too hard before the temperature had risen sufficiently could apply excessive force to the components at near room temperature, potentially causing them to break.

[0009] Up to this point, I've used the CPU as an example, but the same principle applies to other devices that have similar heat-generating components.

[0010] The present invention aims to provide a resin sheet having heat dissipation and conformability, good connectivity with other parts at room temperature, and resistance to damage to parts during embedding and peeling at room temperature. [Means for solving the problem]

[0011] To solve the above problems, the present invention adopts the following configuration. [1] A resin sheet comprising a styrene-based thermoplastic elastomer, a plate-shaped filler, and a connecting filler, wherein the Type A durometer hardness of the resin sheet, measured in accordance with JIS K 6253-3, is 40 or less. [2] The resin sheet according to [1], wherein the resin sheet further comprises a plasticizer. [3] The resin sheet according to [1] or [2], wherein the resin sheet further comprises an amorphous poly-αolefin. [4] The resin sheet according to [1] or [2], wherein the total content ratio of the plate-shaped filler and the connecting filler to the total volume of the resin sheet is 55% by volume or less.

[0012] [5] The resin sheet according to any one of [1] to [4], wherein the relative permittivity of the resin sheet at a frequency of 10 GHz, as measured in accordance with the TM0m0 mode cavity resonator perturbation method, is 4 or less. [6] The resin sheet according to any one of [1] to [5], wherein the dielectric loss tangent of the resin sheet at a frequency of 10 GHz, measured in accordance with the TM0m0 mode cavity resonator perturbation method, is 0.01 or less. [7] The density of the resin sheet measured in accordance with JIS K 7112:1999 is 2 g / cm³ 3 The resin sheet described in any one of the following items [1] to [6]. [8] The resin sheet described in any one of items [1] to [7], wherein the dielectric breakdown voltage of the resin sheet measured in accordance with JIS C 2110-1 is 20 kV / mm or more.

[0013] [9] The resin sheet according to any one of [1] to [8], wherein the plate-shaped filler is made of boron nitride.

[10] The resin sheet according to any one of [1] to [9], wherein the connecting filler comprises either magnesium hydroxide or aluminum hydroxide, or both.

[11] The resin sheet according to [2], wherein the plate-shaped filler is made of boron nitride, and the connecting filler is made of either magnesium hydroxide or aluminum hydroxide or both.

[12] The resin sheet according to any one of [1] to

[11] , wherein the ratio of the content of the connecting filler to the content of the plate-shaped filler is 60 to 200% by volume.

[13] The resin sheet according to any one of [1] to

[12] , wherein the average particle diameter of the plate-like filler is 5 μm or more.

Advantages of the Invention

[0014] According to the present invention, there is provided a resin sheet having heat dissipation properties and followability, having good connectivity with other components at room temperature, and being such that components are hardly damaged during embedding and peeling at room temperature.

Brief Description of the Drawings

[0015] [Figure 1] It is a cross-sectional view schematically showing a resin sheet according to an embodiment of the present invention. [Figure 2A] It is a cross-sectional view for schematically explaining an example of a method of using a resin sheet according to an embodiment of the present invention. [Figure 2B] It is a cross-sectional view for schematically explaining an example of a method of using a resin sheet according to an embodiment of the present invention. [Figure 2C] It is a cross-sectional view for schematically explaining an example of a method of using a resin sheet according to an embodiment of the present invention.

Mode for Carrying Out the Invention

[0016] <<Resin Sheet>> The resin sheet according to an embodiment of the present invention includes a styrene-based thermoplastic elastomer, a plate-like filler, and a connecting filler, and the type A durometer hardness of the resin sheet measured in accordance with JIS K 6253-3 is 40 or less. The resin sheet of this embodiment contains the plate-shaped filler and the connecting filler, and therefore, even with a small filler content, it has high thermal conductivity and high heat dissipation in both the direction parallel to its surface and in the thickness direction. Furthermore, the resin sheet of this embodiment contains a styrene-based thermoplastic elastomer, which gives it high flexibility and conformability to the object to which it is applied. In particular, because the Type A durometer hardness is 40 or less, the resin sheet of this embodiment has high flexibility at room temperature, good connectivity with other parts at room temperature, and also good embedding properties for parts and good peelability from parts at room temperature, making parts less likely to be damaged when embedded and when peeled from parts at room temperature. By covering, and preferably embedding, heat-generating components such as CPUs (central processing units) with the aforementioned resin sheet having these properties, a high level of heat suppression can be obtained in various electronic devices. Furthermore, it is not limited to CPUs; a heat dissipation structure can be constructed for other devices equipped with heat-generating components similar to CPUs, and a high level of heat suppression can be obtained. At any desired timing, good connectivity with other components is maintained at room temperature, and components are less likely to be damaged during embedding and when peeling at room temperature. In this specification, the term "direction parallel to the surface" may be used to refer to a direction parallel to the surface, not only in the case of resin sheets.

[0017] The aforementioned resin sheet has insulating properties.

[0018] Figure 1 is a schematic cross-sectional view showing the resin sheet of this embodiment. The resin sheet 1 shown here contains a styrene-based thermoplastic elastomer, a plate-shaped filler, and a connecting filler. However, these components are not shown in Figure 1. The Type A durometer hardness of the resin sheet 1 is 40 or less. The thermal conductivity of resin sheet 1 is in the surface direction D of resin sheet 1. S And, the thickness direction D of the resin sheet 1 T It is high in both of these aspects.

[0019] Both the surface 1a and the other surface 1b of the resin sheet 1 are planar. However, in this embodiment, the shapes of both surfaces (one surface and the other surface) of the resin sheet are not limited to this, and may be curved or uneven, for example, and can be set as appropriate depending on the purpose.

[0020] When using the resin sheet 1, either one or both of the two surfaces 1a and 1b of the resin sheet 1 become the application surface (mounting surface) of the resin sheet 1 to the object to which it is applied.

[0021] <Styrene-based thermoplastic elastomer> The resin sheet, by containing the styrene-based thermoplastic elastomer, can maintain a sheet-like shape and possesses appropriate flexibility, as well as conformability and adhesion to the object to which it is applied.

[0022] Examples of the styrene-based thermoplastic elastomer include copolymers having structural units derived from styrene and structural units derived from conjugated diene compounds other than styrene; and hydrogenated products of the copolymer. More specifically, examples of styrene-based thermoplastic elastomers include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene-styrene block copolymer (SEBS), and styrene-ethylene-propylene-styrene block copolymer (SEPS).

[0023] In a styrene-based thermoplastic elastomer, the ratio of the amount of constituent units derived from styrene (parts by mass) to the total amount of constituent units (parts by mass) (sometimes referred to as "styrene content" in this specification) is preferably 20 to 50% by mass, and may be, for example, 20 to 40% by mass and 30 to 50% by mass. When the ratio (styrene content) is above the lower limit, the heat resistance of the resin sheet is increased. When the ratio is below the upper limit, the conformability and adhesion of the resin sheet to the object to which it is applied are increased.

[0024] The weight-average molecular weight (Mw) of the styrene-based thermoplastic elastomer is preferably between 100,000 and 500,000. In this specification, the weight-average molecular weight is a value obtained from the polystyrene equivalent value measured by gel permeation chromatography (GPC).

[0025] The styrene-based thermoplastic elastomer contained in the resin sheet may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0026] In the resin sheet, the ratio of the styrene-based thermoplastic elastomer content (parts by mass) to the total mass (parts by mass) of the resin sheet ([styrene-based thermoplastic elastomer content (parts by mass) of the resin sheet] / [total mass (parts by mass) of the resin sheet] × 100) is preferably 5 to 60% by mass, and may be, for example, 5 to 40% by mass, 5 to 30% by mass, or 5 to 20% by mass. If the ratio is above the lower limit, the effect obtained by the resin sheet containing the styrene-based thermoplastic elastomer will be higher. If the ratio is below the upper limit, the effect obtained by the resin sheet containing components other than the styrene-based thermoplastic elastomer will be higher. The aforementioned ratio is typically the same as the ratio of the styrene-based thermoplastic elastomer content (parts by mass) to the total content (parts by mass) of components that do not vaporize at room temperature in the resin composition described later ([Styrene-based thermoplastic elastomer content (parts by mass) in the resin composition] / [Total content (parts by mass) of components that do not vaporize at room temperature in the resin composition] × 100). The relationship between the content of any component contained in the resin sheet and the content of the said component in the resin composition for forming the resin sheet is the same not only for styrene-based thermoplastic elastomers but also for components other than styrene-based thermoplastic elastomers, as will be described later.

[0027] In this specification, "room temperature" means a temperature that is neither cooled nor heated, i.e., a normal temperature, such as 15-25°C.

[0028] <Sheet-shaped filler> The resin sheet has improved heat dissipation due to the inclusion of the plate-shaped filler. The plate-shaped filler in the resin sheet tends to be oriented in the same direction as the surface direction of the resin sheet, or in a direction close to the surface direction of the resin sheet. As a result, the thermal conductivity of the resin sheet in that surface direction becomes particularly high, and the heat dissipation in that surface direction becomes high. For example, if a filler other than a plate-shaped filler is used, such as a polyhedral filler or a card-house-shaped filler (a filler in which plate-shaped fillers aggregate to form secondary particles), the heat dissipation of the resin sheet in its planar direction will be reduced. Furthermore, card-house-shaped fillers significantly reduce the flexibility of the resin sheet when heated.

[0029] The aspect ratio of the plate-like filler ([particle diameter of plate-like filler] / [thickness of plate-like filler]) is preferably 10 to 100, and may be, for example, 10 to 45, 40 to 70, or 65 to 100. Having the aspect ratio of the plate-like filler within this range enhances the effects obtained by the resin sheet containing the plate-like filler.

[0030] As the particle size of the plate-shaped filler, for example, the maximum length of the line segment connecting two different points on the outer circumference of the plate-shaped filler can be adopted. As the thickness of the plate-like filler, for example, the maximum distance between the main surfaces of the plate-like filler can be used. As the aspect ratio of the plate-shaped filler, for example, the average of the aspect ratios of 50 randomly selected plate-shaped fillers can be adopted. The length of the line segment connecting two different points on the outer circumference of the plate-shaped filler described above, and the distance between the main surfaces, may be the length of the line segment and the distance between the main surfaces in the imaging data of the plate-shaped filler, respectively.

[0031] The average particle diameter of the plate-shaped filler is preferably 5 μm or more, and may be, for example, 6.5 μm or more, or 8 μm or more. When the average particle diameter of the plate-shaped filler is above the lower limit, the effects obtained by using the plate-shaped filler are further enhanced. There is no particular upper limit to the average particle size of plate-shaped fillers. For example, plate-shaped fillers with an average particle size of 15 μm or less are more readily available. In one embodiment, the average particle size of the plate-shaped filler may be, for example, 5 to 15 μm, 6.5 to 15 μm, and 8 to 15 μm. However, these are just examples of average particle sizes for plate-shaped fillers.

[0032] In this specification, not only in the case of plate-shaped fillers, but unless otherwise specified, "average particle diameter" refers to the particle diameter at 50% accumulation of particles (D50) when the particle size distribution of the particles is measured on a volume basis by laser diffraction particle size distribution measurement.

[0033] The thermal conductivity of the plate-shaped filler may be, for example, 5 W / m·K or higher, 10 W / m·K or higher, 25 W / m·K or higher, and 40 W / m·K or higher. The upper limit of the thermal conductivity of the plate-shaped filler is not particularly limited. For example, plate-shaped fillers with a thermal conductivity of 400 W / m·K or less are readily available. The thermal conductivity of the plate-shaped filler may be, for example, 100 W / m·K or less. In one embodiment, the thermal conductivity of the plate-shaped filler may be, for example, 5-400 W / m·K, 10-400 W / m·K, 25-400 W / m·K, and 40-400 W / m·K, or 5-100 W / m·K, 10-100 W / m·K, 25-100 W / m·K, and 40-100 W / m·K. However, these are just examples of the thermal conductivity of the plate-shaped filler.

[0034] The thermal conductivity of fillers, not limited to plate-shaped fillers, can be measured, for example, by fabricating a sintered body of the filler and measuring it using a known thermal conductivity measuring device such as the laser flash method or the hot disk method, or by measuring it using a thermal property microscope or the like.

[0035] In order to more easily lower the dielectric constant of the resin sheet described later, the dielectric constant of the plate-shaped filler is preferably 5.5 or less, and more preferably 4.5 or less. On the other hand, the lower limit of the relative permittivity of the plate-shaped filler is not particularly limited. For example, plate-shaped fillers with a relative permittivity of 3.5 or higher are easier to prepare or obtain.

[0036] Examples of materials for the plate-shaped filler include metal nitrides such as boron nitride (BN) and metal oxides such as aluminum oxide (Al2O3).

[0037] The plate-shaped filler contained in the resin sheet may be of one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0038] The plate-shaped filler is preferably made of boron nitride or aluminum oxide (i.e., it is either a boron nitride filler or an aluminum oxide filler). A resin sheet containing such a plate-shaped filler has high heat dissipation properties, better fluidity when heated, and better conformability to the object to which the resin sheet is applied. For example, when covering a heating element with the resin sheet, the heating element can be easily covered with the resin sheet.

[0039] The plate-shaped filler is more preferably made of boron nitride (BN) (i.e., a boron nitride filler). In addition to having the above-mentioned desirable properties, a resin sheet containing such a plate-shaped filler has even more desirable properties, as described later, because its dielectric constant is lower.

[0040] In the resin sheet, the ratio of the content (volume) of the plate-shaped filler to the total volume (volume) of the resin sheet ([content (volume) of the plate-shaped filler in the resin sheet] / [total volume (volume) of the resin sheet] × 100) is preferably within a numerical range that satisfies the ratio of the content of the connecting filler to the content of the plate-shaped filler described later. For example, it is preferably 5 vol% or more, and may be 10 vol% or more, or 15 vol% or more. When the ratio is equal to or above the lower limit, the effect obtained by using the plate-shaped filler is further enhanced. In the resin sheet, the ratio of the content (volume) of the plate-shaped filler to the total volume (volume) of the resin sheet may be 35 volume% or less, for example, 30 volume% or less, or 25 volume% or less. By keeping the ratio below the upper limit, the effects obtained by using fillers other than plate-shaped fillers, such as the linked fillers, are further enhanced. In one embodiment, the percentage may be, for example, 5-35% by volume, 10-35% by volume, and 15-35% by volume; or 5-30% by volume, 10-30% by volume, and 15-30% by volume; or 5-25% by volume, 10-25% by volume, and 15-25% by volume. However, these are just examples of the percentages.

[0041] <Connecting Filler> The resin sheet has enhanced heat dissipation due to the inclusion of the connecting filler. The connecting filler is widely distributed in both the planar and thickness directions of the resin sheet, and as will be described later, the size of the connecting filler is small. Therefore, the connecting filler maintains contact with the plate-shaped filler in both the planar and thickness directions of the resin sheet, thereby connecting the plate-shaped fillers to each other through itself. As a result, the thermal conductivity of the resin sheet is increased in both the planar and thickness directions, and the heat dissipation is enhanced.

[0042] The average particle size of the connecting filler may be 2 μm or less. This enhances the effect of the plate-shaped fillers being connected by the connecting filler. To further enhance this effect, the average particle size of the linked filler may be 1.7 μm or less, 1.5 μm or less, or for example, 1.2 μm or less, and 0.9 μm or less. The lower limit of the average particle diameter of the linked filler is not particularly limited. For example, linked fillers with an average particle diameter of 0.5 μm or more are more readily available, and using such linked fillers makes it easier to improve the heat dissipation of the resin sheet. In one embodiment, the average particle size of the linked filler may be, for example, 0.5 to 2 μm, 0.5 to 1.7 μm, 0.5 to 1.5 μm, 0.5 to 1.2 μm, and 0.5 to 0.9 μm. However, these are just examples of the average particle size of the linked filler.

[0043] The shape of the connecting filler is not particularly limited, but it is preferably flat, and more preferably plate-shaped. Having a flat surface, and especially being plate-shaped, of the connecting filler increases the contact area between the connecting filler and the plate-shaped filler. As described above, since the surface direction of the plate-shaped filler tends to be the same as, or close to, the surface direction of the resin sheet, even if the connecting filler has a flat surface, the contact area between the connecting filler and the plate-shaped filler tends to decrease as the overall shape of the connecting filler deviates from plate-shaped. However, sufficient contact between the connecting filler and the plate-shaped filler is maintained by keeping the average particle diameter of the connecting filler at 2 μm or less.

[0044] The linking filler is preferably non-aggregated (not aggregated). The lower the content of aggregated linking filler in the resin sheet, the better the fluidity of the resin sheet when heated, and the higher its conformability to the object to which the resin sheet is applied. For example, when covering a heating element with the resin sheet, the heating element can be easily covered with the resin sheet.

[0045] The thermal conductivity of the connecting filler may be, for example, 5 W / m·K or higher, 10 W / m·K or higher, 25 W / m·K or higher, and 40 W / m·K or higher. The upper limit of the thermal conductivity of the connecting filler is not particularly limited. For example, connecting fillers with a thermal conductivity of 400 W / m·K or less are more readily available. The thermal conductivity of the connecting filler may be, for example, 100 W / m·K or less, or 20 W / m·K or less. In one embodiment, the thermal conductivity of the connecting filler may be, for example, 5-400 W / m·K, 10-400 W / m·K, 25-400 W / m·K, and 40-400 W / m·K; or 5-100 W / m·K, 10-100 W / m·K, 25-100 W / m·K, and 40-100 W / m·K; or 5-20 W / m·K and 10-20 W / m·K. However, these are just examples of the thermal conductivity of the connecting filler.

[0046] Examples of materials for the connecting filler include metal hydroxides such as magnesium hydroxide (Mg(OH)2) and aluminum hydroxide (Al(OH)3).

[0047] The connecting filler may or may not have its surface treated with a surface treatment agent. By using a surface-treated connecting filler, for example, the affinity between the connecting filler and a resin such as a styrene-based thermoplastic elastomer (e.g., a thermoplastic resin) is improved, and the fluidity of the resin sheet is improved, thereby increasing the conformability and adhesion of the resin sheet to the object to which it is applied. Examples of surface treatments for coupling fillers include surface treatment with fatty acids or organosilicon compounds (silane coupling agents).

[0048] The connecting filler contained in the resin sheet may be of one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0049] The aforementioned connecting filler is preferably composed of either magnesium hydroxide or aluminum hydroxide, or both (i.e., it is either a magnesium hydroxide filler, an aluminum hydroxide filler, or a mixture of magnesium hydroxide filler and aluminum hydroxide filler). Since magnesium hydroxide and aluminum hydroxide are also flame retardants, a resin sheet containing such a connecting filler will have high heat dissipation and high flame retardancy.

[0050] The flame-retardant resin sheet, such as the resin sheet containing either or both of magnesium hydroxide filler and aluminum hydroxide filler, can, for example, meet the UL94 standard (vertical combustion test) grades V-0, V-1, or V-2.

[0051] When the connecting fillers are magnesium hydroxide filler and aluminum hydroxide filler, the volume ratio of [magnesium hydroxide filler content (parts by volume)] to [aluminum hydroxide filler content (parts by volume)] in the resin sheet is preferably 90:10 to 10:90, for example, it may be any of 75:25 to 10:90 and 60:40 to 10:90, or any of 90:10 to 25:75 and 90:10 to 40:60, or any of 75:25 to 25:75, 75:25 to 40:60, 60:40 to 25:75, and 60:40 to 40:60. For example, if the shape of the aluminum hydroxide filler is irregular, the processability of the resin sheet may deteriorate. In such cases, in order to better balance the flame retardancy and processability of the resin sheet, the volume ratio is preferably 60:40 to 40:60.

[0052] To impart flame retardancy to a resin sheet, it is preferable to match the decomposition temperature of the organic components contained in the resin sheet (e.g., styrene-based thermoplastic elastomer, plasticizer, etc.) with the decomposition temperature of the metal hydroxide (magnesium hydroxide, aluminum hydroxide, etc.) (creating a region where these decomposition temperatures overlap). By matching these decomposition temperatures, water is generated by the decomposition of the metal hydroxide at the same time as the generation of combustible decomposition gases, thereby suppressing the combustion of the resin sheet and imparting flame retardancy to the resin sheet.

[0053] In the aforementioned resin sheet, the ratio of the content of the connecting filler (in volume parts) to the total volume (in volume parts) of the resin sheet ([Content of the connecting filler (in volume parts) of the resin sheet] / [Total volume (in volume parts) of the resin sheet] × 100) is preferably within a numerical range that satisfies the ratio of the content of the connecting filler to the content of the plate-shaped filler described later. For example, it is preferably 10 vol% or more, and may be 15 vol% or more, or 20 vol% or more. When the ratio is equal to or above the lower limit, the effect obtained by using the connecting filler is further enhanced. In the resin sheet, the ratio of the content (volume) of the connecting filler to the total volume (volume) of the resin sheet may be 45 vol% or less, for example, 40 vol% or less, or 35 vol% or less. By keeping the ratio below the upper limit, the effects obtained by using fillers other than the connecting filler, such as the plate-shaped filler, become more pronounced. In one embodiment, the percentage may be, for example, 10-45% by volume, 15-45% by volume, and 20-45% by volume; or 10-40% by volume, 15-40% by volume, and 20-40% by volume; or 10-35% by volume, 15-35% by volume, and 20-35% by volume. However, these are just examples of the percentages.

[0054] In the resin sheet, the ratio of the content (volume) of the binding filler to the content (volume) of the plate-shaped filler ([content (volume) of the binding filler in the resin sheet] / [content (volume) of the plate-shaped filler in the resin sheet] × 100) is preferably 60 volume% or more, and may be, for example, 80 volume% or more, 100 volume% or more, or 120 volume% or more. When the ratio is above the lower limit, the effect obtained by using the binding filler is further enhanced. In the resin sheet, the ratio of the content of the binding filler to the content of the plate-shaped filler is preferably 200 volume% or less, and may be, for example, 185 volume% or less, 170 volume% or less, or 155 volume% or less. By keeping the ratio below the upper limit, the effects obtained by using fillers other than binding fillers, such as the plate-shaped filler, are further enhanced. In one embodiment, the percentage is preferably 60 to 200 volume%, and may be any of 80 to 200 volume%, 100 to 200 volume%, and 120 to 200 volume%, or any of 60 to 185 volume%, 80 to 185 volume%, 100 to 185 volume%, and 120 to 185 volume%, or any of 60 to 170 volume%, 80 to 170 volume%, 100 to 170 volume%, and 120 to 170 volume%, or any of 60 to 155 volume%, 80 to 155 volume%, and 100 to 155 volume%. However, these are just examples of the percentages.

[0055] In the resin sheet, the ratio of the total content (volume) of the plate-shaped filler and the connecting filler to the total volume (volume) of the resin sheet may be 55 vol% or less, 50 vol% or less, or for example, 40 vol% or less, or 30 vol% or less. When the ratio is below the upper limit, the conformability and adhesion of the resin sheet to the object to which it is applied are further improved. In the resin sheet, the ratio of the total content (volume) of the plate-shaped filler and the connecting filler to the total volume (volume) of the resin sheet is preferably 15% by volume or more, and may be, for example, 25% by volume or more, or 35% by volume or more. When the ratio is above the lower limit, the effects obtained by using the plate-shaped filler and the connecting filler are further enhanced. In one embodiment, the aforementioned percentage may be 15-50% by volume, 15-40% by volume, or 15-30% by volume or less, or 25-50% by volume, or 25-40% by volume, or 35-50% by volume. However, these are merely examples of the aforementioned percentages.

[0056] <Plasticizer> Preferably, the resin sheet further contains a plasticizer. The plasticizer is a component for improving the flexibility of the resin sheet, and by including a plasticizer in the resin sheet, the Type A durometer hardness of the resin sheet, as described later, can be reduced more easily.

[0057] Examples of the aforementioned plasticizers include mineral oil; hydrocarbons such as aromatic hydrocarbons, paraffinic hydrocarbons (also known as paraffinic oils), and naphthenic hydrocarbons (also known as naphthenic oils); carboxylic acid esters such as bis(2-ethylhexyl) phthalate (DOP) and dibutyl phthalate (DBP); tackifiers (tackifying resins) such as terpene resins, aromatically modified terpene resins, terpene phenol resins, styrene resins, hydrogenated terpene phenol resins, hydrogenated terpene resins, and hydrogenated styrene resins.

[0058] When the plasticizer is an oligomer or polymer having structural units derived from styrene, the effect of improving the flexibility of the resin sheet may be even greater. Examples of plasticizers having structural units derived from styrene include tackifiers such as aromatically modified terpene resins, styrene resins, and hydrogenated styrene resins.

[0059] A resin composition containing aluminum hydroxide filler, described later, for forming a resin sheet containing aluminum hydroxide filler as a binding filler, may have a higher viscosity and reduced handling properties than a resin composition without aluminum hydroxide filler. Furthermore, if the shape of the aluminum hydroxide filler is irregular, the resin sheet containing aluminum hydroxide filler may have lower processability than a resin sheet without aluminum hydroxide filler. In contrast, the resin composition containing aluminum hydroxide filler, further containing the aforementioned tackifier, has a lower viscosity and improved processability of the resin sheet. Furthermore, the lower hardness of the resin sheet makes it softer, which also improves its ability to embed parts.

[0060] The plasticizer contained in the resin sheet may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0061] When a plasticizer is used, the content of the plasticizer in the resin sheet is preferably 200 to 600 parts by mass per 100 parts by mass of styrene-based thermoplastic elastomer, and may be, for example, 200 to 400 parts by mass, 300 to 500 parts by mass, or 400 to 600 parts by mass. When the content of the plasticizer is above the lower limit, the effect obtained by using the plasticizer is enhanced. When the content of the plasticizer is below the upper limit, excessive use of the plasticizer is suppressed, and for example, the resin sheet can maintain its sheet shape more stably.

[0062] In the resin sheet containing a tackifier, the ratio of the tackifier content (volume) to the total volume (volume) of the resin sheet is preferably 3 to 25 vol% or more, for example, it may be 3 to 20 vol% and 3 to 15 vol%, or 7 to 25 vol% and 11 to 25 vol%, or 7 to 20 vol% and 11 to 15 vol%. When the ratio is above the lower limit, the effect obtained by using the tackifier is increased. When the ratio is below the upper limit, excessive use of the tackifier is suppressed, and for example, the resin sheet can maintain its sheet shape more stably.

[0063] <Amorphous polyalphaolefin> The resin sheet may further contain amorphous poly-α-olefin (sometimes referred to as "APAO" in this specification). APAO is a thermoplastic olefin resin and is a component for improving the room-temperature plastic deformability of the resin sheet. APAO has a linear block copolymer structure and possesses plasticizer-like properties similar to synthetic oils and plastic deformability that reduces the return to its original shape after deformation. Furthermore, by including APAO in the resin sheet, the type A durometer hardness of the resin sheet, as described later, can be reduced more easily.

[0064] In this specification, "room temperature plastic deformability" means that a material can be easily plastically deformed at room temperature and has excellent shape retention properties.

[0065] APAO is more preferably an APAO having a structural unit derived from propylene, and even more preferably an APAO having a structural unit derived from propylene and a structural unit derived from ethylene, or an APAO having a structural unit derived from propylene and a structural unit derived from 1-butene. For example, it may be an APAO (amorphous propylene-ethylene-1-butene ternary copolymer) having a structural unit derived from propylene, a structural unit derived from ethylene, and a structural unit derived from 1-butene. By including a structural unit derived from 1-butene, it is possible to make it softer and lower the hardness at room temperature.

[0066] The glass transition temperature of APAO is preferably -50°C to -10°C, more preferably -50°C to -20°C, and even more preferably -50°C to -30°C. If the glass transition temperature of APAO is above the lower limit, the handling properties of the resin sheet can be further improved. If the glass transition temperature of APAO is below the upper limit, the room-temperature plastic deformability of the resin sheet can be further improved.

[0067] The penetration depth, measured in accordance with APAO's ASTM D-1321, is preferably 10 to 50, more preferably 20 to 50, and even more preferably 20 to 40. If the penetration of APAO is above the lower limit, the room-temperature plastic deformability of the resin sheet can be further improved. If the penetration of APAO is below the upper limit, the handling of the resin sheet can be further improved.

[0068] The melt viscosity at 190°C, measured in accordance with APAO's ASTM D-3236, is preferably between 1,000 cps and 150,000 cps (1 Pa·s and 150 Pa·s), more preferably between 1,000 cps and 50,000 cps (1 Pa·s and 50 Pa·s), and even more preferably between 3,000 cps and 30,000 cps (3 Pa·s and 30 Pa·s). If the melt viscosity of APAO is above the lower limit, the handling properties of the resin sheet can be further improved. If the melt viscosity of APAO is below the upper limit, the room-temperature plastic deformability of the resin sheet can be further improved.

[0069] The elongation at break, measured according to APAO's ASTM D-638 and D-412 standards, is preferably 20% to 1000%, more preferably 100% to 1000%, and even more preferably 500% to 1000%. If the elongation at break of APAO is above the lower limit, the plastic deformability of the resin sheet at room temperature can be further improved. If the elongation at break of APAO is below the upper limit, the handling of the resin sheet can be further improved.

[0070] The APAO contained in the resin sheet may be of one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0071] When APAO is used, the APAO content in the resin sheet is preferably 5 to 500 parts by mass per 100 parts by mass of styrene-based thermoplastic elastomer, and may be, for example, 10 to 300 parts by mass, 20 to 200 parts by mass, or 30 to 100 parts by mass. When the APAO content is above the lower limit, the effects obtained by using APAO are enhanced. When the APAO content is below the upper limit, excessive use of APAO is suppressed, and for example, the resin sheet can maintain its sheet shape more stably.

[0072] When APAO is used, the ratio of APAO content (volume) to the total volume (volume) of the resin sheet is preferably 1 to 20 vol%, and may be, for example, 2 to 15 vol%, 2 to 10 vol%, or 2 to 7 vol%. When the aforementioned ratio is above the aforementioned lower limit, the effects obtained by using APAO become greater. When the aforementioned ratio is below the aforementioned upper limit, excessive use of APAO is suppressed, and for example, the resin sheet can maintain its sheet shape more stably.

[0073] <Other ingredients> The resin sheet may or may not contain other components that do not fall under any of the following categories: the styrene-based thermoplastic elastomer, the plate-like filler, the connecting filler, the plasticizer, and the APAO, as long as they do not impair the effects of the present invention. The aforementioned other components can be arbitrarily selected depending on the purpose and are not particularly limited.

[0074] The other components contained in the resin sheet may consist of only one type or two or more types. If there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0075] Examples of the other components mentioned above include additives known in the field. Examples of the aforementioned additives include antioxidants, antistatic agents, viscosity reducers, viscosity thickeners, infrared absorbers, ultraviolet absorbers, and antiblocking agents. In particular, by including an antioxidant in the resin sheet, discoloration caused by the tackifier can be further suppressed.

[0076] In the resin sheet, the ratio of the total content (parts by mass) of the styrene-based thermoplastic elastomer, the plate-shaped filler, the connecting filler, the plasticizer, and the APAO (([Content of styrene-based thermoplastic elastomer in the resin sheet (parts by mass)] + [Content of plate-shaped filler in the resin sheet (parts by mass)] + [Content of connecting filler in the resin sheet (parts by mass)] + [Content of plasticizer in the resin sheet (parts by mass)] + [Content of APAO in the resin sheet (parts by mass)]) / [Total mass (parts by mass) of the resin sheet] × 100) is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, 95% by mass or more, 97% by mass or more, or 99% by mass or more. When the ratio is above the lower limit, the heat dissipation of the resin sheet, flexibility when heated, connectivity with parts at room temperature, embedding ability of parts, and peelability from parts at room temperature are all improved in a well-balanced manner. On the other hand, the aforementioned ratio is 100% by mass or less. Here, if the resin sheet does not contain plasticizers, the plasticizer content of the resin sheet is 0 parts by mass.

[0077] The thickness of the resin sheet is preferably 100 μm or more, and may be, for example, 600 μm or more, 1200 μm or more, or 1800 μm or more. A thickness of the resin sheet greater than or equal to the lower limit improves the heat dissipation performance of the resin sheet. On the other hand, the thickness of the resin sheet may be 3000 μm or less, and may be, for example, 2200 μm or less, or 1400 μm or less. When the thickness of the resin sheet is below the upper limit, the flexibility of the resin sheet when heated, and the component connectivity and peelability at room temperature are further improved. In one embodiment, the thickness of the resin sheet may be, for example, 100 to 3000 μm, 600 to 3000 μm, 1200 to 3000 μm, and 1800 to 3000 μm, or 100 to 2200 μm and 100 to 1400 μm or less. However, these are just examples of resin sheet thicknesses. The thickness of the resin sheet is preferably adjusted according to the thickness of the object to which the resin sheet is applied, as will be described later. The thickness of the aforementioned resin sheet can be measured using a micrometer.

[0078] <Mixture containing styrene-based thermoplastic elastomer and plasticizer (Mixture (X))> When a plasticizer is used, a mixture containing a styrene-based thermoplastic elastomer and a plasticizer (sometimes referred to as "mixture (X)" in this specification) may be used. Mixtures containing both a styrene-based thermoplastic elastomer and a plasticizer as main components are commercially available, and in this embodiment, such a mixture can be used as mixture (X) containing the above-mentioned styrene-based thermoplastic elastomer, the above-mentioned plasticizer, and, if necessary, other components.

[0079] The mixture (X) is preferably in a solid state at room temperature and pressure. The density of the solid mixture (X) measured in accordance with JIS K 7112:1999 was 0.8 to 0.95 g / cm³. 3 Preferably, it is 0.83 to 0.92 g / cm³. 3 That's fine. The tensile strength of the solid mixture (X), as measured in accordance with JIS K 6251:2017, is preferably 0.8 to 2.5 MPa, and may be, for example, 1 to 2.3 MPa. The elongation at break of the solid mixture (X), measured in accordance with JIS K 6251:2017, is preferably 1100 to 1330%, and may be, for example, 1150 to 1280%. The melt flow rate of the solid mixture (X), measured in accordance with JIS K 7210-1:2014 or ASTM D 1238, is preferably 7 to 10 g / 10 min, and may be, for example, 7.5 to 9.5 g / 10 min. The hardness of the solid mixture (X) measured in accordance with JIS K 6253-3:2012, preferably a Type E durometer hardness of 0 to 20, and for example, it may be 0 to 15. The hardness of the solid mixture (X), measured according to JIS K 6253-3:2012, is preferably 0 to 20, and may be, for example, 0 to 15.

[0080] The plasticizer in mixture (X) is preferably a plasticizer other than a tackifier (for example, the mineral oil, hydrocarbon, carboxylic acid ester, etc.).

[0081] In mixture (X), the ratio of the total content (parts by mass) of the styrene-based thermoplastic elastomer and the plasticizer to the total mass (parts by mass) of mixture (X) is preferably 60 to 100% by mass, and may be, for example, 60 to 80% by mass, 70 to 90% by mass, or 80 to 100% by mass. When the ratio is above the lower limit, the effect obtained by using the styrene-based thermoplastic elastomer and the plasticizer is further enhanced.

[0082] In mixture (X), the ratio of the content of styrene-based thermoplastic elastomer (parts by mass) to the total content (parts by mass) of styrene-based thermoplastic elastomer and plasticizer is preferably 10 to 50% by mass, for example, it may be 10 to 30% by mass, 20 to 40% by mass, or 30 to 50% by mass. When the ratio is above the lower limit, excessive use of plasticizer is suppressed, and for example, the resin sheet can maintain a more stable sheet shape. When the ratio is below the upper limit, the effect obtained by using the plasticizer is further enhanced.

[0083] <Characteristics of resin sheets> [Room temperature plastic deformability] When a resin sheet is placed on a circuit board with protrusions at room temperature (24°C), and the resin sheet is hand-pressed against the circuit board for 1 minute to embed the resin sheet into the circuit board, and the resin sheet is peeled off the circuit board and left at room temperature for about 3 hours, and the thickness of the recess on the side of the resin sheet that is attached to the circuit surface is measured, the embedding deformation rate of the side of the resin sheet that is attached to the circuit surface, calculated by the following formula, is preferably 30% or more. As a result, the resin sheet has good room-temperature plastic deformability. [Deformation rate of the resin sheet's adhesive surface on the circuit board (%)] = ([Original thickness of the resin sheet] - [Thickness of the recess on the resin sheet's adhesive surface]) / [Height of the convex part of the circuit board] × 100

[0084] In terms of achieving the above-mentioned effects, it is more preferable that the embedding deformation rate of the surface of the resin sheet attached to the circuit surface be 30% or more, and may be, for example, 40% or more, 50% or more, or 80% or more. On the other hand, the embedding deformation rate of the resin sheet's adhesive surface to the circuit surface is less than 100%, and within this range, there is no particular upper limit. By having the embedding deformation rate equal to or greater than the lower limit, the pressure (pressing force) required to maintain the embedded state within the device into which the component is incorporated can be further reduced, thereby reducing the burden on the device, especially the warping of the substrate.

[0085] The degree of embedded deformation of the resin sheet's adhesive surface to the circuit board can be adjusted, for example, by adjusting the type and content of the components in the resin sheet, and the thickness of the resin sheet. In particular, the degree of embedded deformation of the resin sheet's adhesive surface to the circuit board can be adjusted more easily by adjusting the type of APAO, its content in the resin sheet, and the thickness of the resin sheet.

[0086] [Type A Durometer Hardness] The Type A durometer hardness of the resin sheet, measured in accordance with JIS K 6253-3, is 40 or less. As a result, the resin sheet has good connectivity with other parts at room temperature, as well as good embedding properties for parts (objects to be cooled) and good peelability from parts at room temperature. Parts are less likely to be damaged during embedding and peeling from parts at room temperature, and no deformation is observed in the parts.

[0087] In terms of achieving the above-mentioned effects, the Type A durometer hardness of the resin sheet is preferably 38 or less, and may be, for example, 36 or less, 34 or less, or 32 or less. On the other hand, the lower limit of the Type A durometer hardness of the resin sheet is not particularly limited. For example, a resin sheet with a Type A durometer hardness of 10 or higher has a high effect in suppressing deformation at room temperature and is easy to handle. In one embodiment, the Type A durometer hardness of the resin sheet may be, for example, 10-40, 10-38, 10-36, 10-34, and 10-32. However, these are just examples of Type A durometer hardness of the resin sheet.

[0088] The Type A durometer hardness of the resin sheet can be adjusted, for example, by adjusting the type and content of the components contained in the resin sheet, and the thickness of the resin sheet. In particular, the Type A durometer hardness can be adjusted more easily by adjusting the type of styrene-based thermoplastic elastomer and its content in the resin sheet; the type of plasticizer and its content in the resin sheet; and the thickness of the resin sheet.

[0089] [Thermal conductivity in the planar direction] The thermal conductivity of the resin sheet in the planar direction is preferably 1.5 W / m·K or higher, more preferably 2 W / m·K or higher, and may be, for example, 2.5 W / m·K or higher. The resin sheet having a thermal conductivity equal to or greater than the lower limit has high heat dissipation in its planar direction. The upper limit of the thermal conductivity of the resin sheet in the planar direction is not particularly limited. For example, a resin sheet with a thermal conductivity of 15 W / m·K or less can be manufactured more easily. The thermal conductivity may be, for example, 7 W / m·K or less. In one embodiment, the thermal conductivity of the resin sheet in the planar direction may be, for example, 1.5 to 15 W / m·K, 2 to 15 W / m·K, and 2.5 to 15 W / m·K, or 1.5 to 7 W / m·K, 2 to 7 W / m·K, and 2.5 to 7 W / m·K. However, these are just examples of thermal conductivity. In addition to the case of the aforementioned resin sheet, the thermal conductivity in the planar direction of the resin sheet is, more specifically, the thermal conductivity of the resin sheet in a direction parallel to one or the other surface of the resin sheet.

[0090] The thermal conductivity of a resin sheet in the planar direction can be measured by the hot disk method, for example, in accordance with ISO 22007-2. For example, the thermal conductivity can be measured using a hot disk method thermophysical property measuring device manufactured by Kyoto Electronics Manufacturing Co., Ltd. (e.g., "TPS 2500 S", "TPS 500 S", etc.).

[0091] The thermal conductivity of the resin sheet in the planar direction can be adjusted, for example, by adjusting the type of styrene-based thermoplastic elastomer and its content in the resin sheet; the type of plate-shaped filler and its content in the resin sheet; the type of connecting filler and its content in the resin sheet; the thickness of the resin sheet, etc.

[0092] [relative permittivity] The relative permittivity of the resin sheet at a frequency of 10 GHz, measured in accordance with the TM0m0 mode cavity resonator perturbation method, is preferably 4 or less, and may be, for example, 3.75 or less, 3.65 or less, or 3.55 or less. The resin sheet having a relative permittivity at a frequency of 10 GHz that is below the upper limit is particularly suitable for covering and mounting a heating element on a circuit board, for example, because it has high insulating properties and is highly effective in suppressing the generation of electrical signal noise in circuits within the object being cooled by the resin sheet. The lower limit of the relative permittivity at a frequency of 10 GHz is not particularly limited. For example, a resin sheet having a relative permittivity of 1 or more at a frequency of 10 GHz can be manufactured more easily. In one embodiment, the relative permittivity at a frequency of 10 GHz may be, for example, 1 to 4, 1 to 3.75, 1 to 3.65, and 1 to 3.55. However, these are just examples of the relative permittivity at a frequency of 10 GHz. The relative permittivity at a frequency of 10 GHz is preferably measured under normal temperature conditions (for example, under a temperature of 23°C).

[0093] The relative permittivity of the resin sheet at a frequency of 1 GHz, measured in accordance with the TM0m0 mode cavity resonator perturbation method, is preferably 4 or less, and may be, for example, 3.9 or less and 3.8 or less. The resin sheet having a relative permittivity at a frequency of 1 GHz that is below the upper limit is particularly suitable for covering and mounting a heating element on a circuit board, as it has high insulating properties and, for example, is highly effective in suppressing the generation of electrical signal noise in a circuit within the object to be cooled by the resin sheet. The lower limit of the relative permittivity at a frequency of 1 GHz is not particularly limited. For example, a resin sheet having a relative permittivity of 1 or more at a frequency of 1 GHz can be manufactured more easily. In one embodiment, the relative permittivity at a frequency of 1 GHz may be, for example, 1 to 4, 1 to 3.9, and 1 to 3.8. However, these are just examples of the relative permittivity at a frequency of 1 GHz. The relative permittivity at a frequency of 1 GHz is preferably measured under normal temperature conditions (for example, under a temperature of 23°C).

[0094] The relative permittivity of the resin sheet can be adjusted regardless of frequency by adjusting the type and amount of components contained in the resin sheet.

[0095] [Dielectric Loss Tangent] The dielectric loss tangent of the resin sheet at a frequency of 10 GHz, measured in accordance with the TM0m0 mode cavity resonator perturbation method, is preferably 0.01 or less, and may be, for example, 0.007 or less, 0.004 or less, or 0.001 or less. The resin sheet having a dielectric loss tangent in this range at a frequency of 10 GHz has high radio wave transparency and is suitable for constructing electronic equipment equipped with an antenna. The lower limit of the dielectric loss tangent at a frequency of 10 GHz is not particularly limited. For example, a resin sheet having a dielectric loss tangent of 0.0005 or more at a frequency of 10 GHz can be manufactured more easily. In one embodiment, the dielectric loss tangent at a frequency of 10 GHz may be, for example, 0.0005 to 0.01, 0.0005 to 0.007, 0.0005 to 0.004, and 0.0005 to 0.001. However, these are just examples of the dielectric loss tangent at a frequency of 10 GHz. The dielectric loss tangent at a frequency of 10 GHz is preferably measured under normal temperature conditions (for example, 23°C).

[0096] The dielectric loss tangent of the resin sheet at a frequency of 1 GHz, measured in accordance with the TM0m0 mode cavity resonator perturbation method, is preferably 0.01 or less, and may be, for example, 0.007 or less, 0.004 or less, or 0.001 or less. A resin sheet having a dielectric loss tangent in this range at a frequency of 1 GHz has high radio wave transparency and is suitable for constructing electronic equipment equipped with an antenna. The lower limit of the dielectric loss tangent at a frequency of 1 GHz is not particularly limited. For example, a resin sheet having a dielectric loss tangent of 0.0005 or more at a frequency of 1 GHz can be manufactured more easily. In one embodiment, the dielectric loss tangent at a frequency of 1 GHz may be, for example, 0.0005 to 0.01, 0.0005 to 0.007, 0.0005 to 0.004, and 0.0005 to 0.001. However, these are just examples of the dielectric loss tangent at a frequency of 1 GHz. The dielectric loss tangent at a frequency of 1 GHz is preferably measured under normal temperature conditions (for example, at a temperature of 23°C).

[0097] The dielectric loss tangent of the resin sheet can be adjusted by adjusting the types and contents of the components contained in the resin sheet regardless of the frequency.

[0098] In the resin sheet, it is preferable that both the relative permittivity at a frequency of 10 GHz and the relative permittivity at a frequency of 1 GHz are within the above numerical ranges. In the resin sheet, it is preferable that both the dielectric loss tangent at a frequency of 10 GHz and the dielectric loss tangent at a frequency of 1 GHz are within the above numerical ranges. In the resin sheet, it is more preferable that all of the relative permittivity at a frequency of 10 GHz, the relative permittivity at a frequency of 1 GHz, the dielectric loss tangent at a frequency of 10 GHz, and the dielectric loss tangent at a frequency of 1 GHz are within the above numerical ranges.

[0099] [Density] The density of the resin sheet measured in accordance with JIS K 7112:1999 is preferably 2 g / cm 3 or less, for example, it may be 1.7 g / cm 3 or less. Various electronic devices configured by mounting such a resin sheet are suitable for use in, for example, constituting portable electronic devices because, in addition to suppressing heat generation, they are lightweight. The lower limit value of the density of the resin sheet is not particularly limited. For example, the resin sheet having a density of 1 g / cm 3 or more can be more easily realized. In one embodiment, the density of the resin sheet is, for example, 1 to 2 g / cm 3 , and it may be either 1 to 1.7 g / cm 3 . However, these are examples of the density of the resin sheet. The density of the resin sheet can be adjusted, for example, by adjusting the types and contents of the components contained in the resin sheet.

[0100] The resin sheet may be irradiated with an electron beam. In that case, it is preferable that the resin sheet is irradiated with an electron beam under conditions of an absorbed dose of 20 to 300 kGy. The acceleration voltage for electron beam irradiation is preferably 100 to 300 kV. By irradiating the aforementioned resin sheet with an electron beam, the resin sheet is partially crosslinked, improving the heat resistance of the resin sheet, its connectivity with components at room temperature, and its peelability from components at room temperature.

[0101] [Dielectric breakdown voltage] The dielectric breakdown voltage of the resin sheet, measured in accordance with JIS C 2110-1, is preferably 20kV / mm or higher, more preferably 30kV / mm or higher, and even more preferably 40kV / mm or higher. Dielectric breakdown refers to the phenomenon where an insulator is subjected to a voltage exceeding its limit, causing its electrical resistance to drop sharply and resulting in a current flow. Insulators cannot withstand all voltages, and exceeding the allowable voltage can cause dielectric breakdown, potentially leading to unexpected current flow in areas that should be insulated. Therefore, designing products with dielectric breakdown in mind is necessary to enhance product safety, and a higher dielectric breakdown voltage allows for greater product safety. Furthermore, a higher dielectric breakdown voltage also allows for thinner products. The upper limit of the dielectric breakdown voltage of the resin sheet is not particularly limited. For example, a resin sheet having a dielectric breakdown voltage of 50 kV / mm or less can be more easily realized. In one embodiment, the dielectric breakdown voltage of the resin sheet may be, for example, 10 to 50 kV / mm and 30 to 50 kV / mm. However, these are just examples of the dielectric breakdown voltage of the resin sheet. The dielectric breakdown voltage of the resin sheet can be adjusted, for example, by adjusting the type and content of the components contained in the resin sheet.

[0102] <Example of a resin sheet> A preferred resin sheet of this embodiment is a resin sheet comprising a styrene-based thermoplastic elastomer, a plate-shaped filler, a linking filler, a plasticizer, and APAO, The hardness of the resin sheet, measured in accordance with JIS K 6253-3, is 40 or less. The aforementioned plate-shaped filler is made of boron nitride, Examples include resin sheets in which the connecting filler consists of either magnesium hydroxide or aluminum hydroxide, or both. In such resin sheets, it is preferable that the plasticizer is one or more selected from the group consisting of mineral oil, hydrocarbons, carboxylic acid esters, and tackifiers.

[0103] A more preferred example of the resin sheet of this embodiment is a resin sheet comprising a styrene-based thermoplastic elastomer, a plate-shaped filler, a linking filler, a plasticizer, and APAO, The hardness of the resin sheet, measured in accordance with JIS K 6253-3, is 40 or less. The aforementioned plate-shaped filler is made of boron nitride, The aforementioned connecting filler consists of either magnesium hydroxide or aluminum hydroxide, or both. In the resin sheet, the ratio of the total content of the plate-shaped filler and the linked filler to the total volume of the resin sheet is 55% by volume or less, or 50% by volume or less. A resin sheet is provided in which the ratio of the content of the connecting filler to the content of the plate-shaped filler is 60 to 200% by volume. In such resin sheets, it is particularly preferable that the average particle size of the plate-shaped filler is 5 μm or more. In such resin sheets, it is preferable that the plasticizer is one or more selected from the group consisting of mineral oil, hydrocarbons, carboxylic acid esters, and tackifiers.

[0104] A more preferred example of the resin sheet of this embodiment is a resin sheet comprising a styrene-based thermoplastic elastomer, a plate-shaped filler, a linking filler, a plasticizer, and APAO, The hardness of the resin sheet, measured in accordance with JIS K 6253-3, is 40 or less. The aforementioned plate-shaped filler is made of boron nitride, The aforementioned connecting filler consists of either magnesium hydroxide or aluminum hydroxide, or both. The relative permittivity of the resin sheet at a frequency of 10 GHz, measured according to the TM0m0 mode cavity resonator perturbation method, is 4 or less. The dielectric loss tangent of the resin sheet at a frequency of 10 GHz, measured according to the TM0m0 mode cavity resonator perturbation method, is 0.01 or less. The density of the resin sheet, measured in accordance with JIS K 7112:1999, is 2 g / cm³. 3 The following are examples of resin sheets. In such resin sheets, it is particularly preferable that the thermal conductivity in the planar direction is 1.5 W / m·K or higher.

[0105] <<Resin composition and method for producing the same>> The resin sheet of this embodiment can be manufactured, for example, by using a resin composition comprising the styrene-based thermoplastic elastomer, the plate-shaped filler, the connecting filler, the plasticizer if necessary, APAO if necessary, and the other components if necessary.

[0106] The aforementioned resin composition may or may not contain a solvent in addition to the components described above. The resin composition containing a solvent may have improved handling properties. In this specification, unless otherwise specified, the term "solvent" refers not only to components capable of dissolving solutes in solution, but also to components that act as a dispersion medium in a dispersion.

[0107] The solvent is preferably an organic solvent, and more preferably an organic solvent that can be removed by vaporization when the resin composition is heated.

[0108] The solvent content of the resin composition can be arbitrarily selected depending on the purpose and is not particularly limited.

[0109] The resin composition may be manufactured by adjusting the types and amounts of the constituent components so that the resin sheet contains the desired components (constituent materials) in the desired amounts. For example, the ratio of the amounts of components that do not vaporize at room temperature in the resin composition is usually the same as the ratio of the amounts of those components in the resin sheet.

[0110] The resin composition can be produced by blending the styrene-based thermoplastic elastomer, the plate-like filler, the connecting filler, the plasticizer if necessary, APAO if necessary, the other components if necessary, and the solvent if necessary. The order in which each component is added during formulation is not particularly limited, and two or more components may be added simultaneously. When a plasticizer is used, instead of separately formulating the styrene-based thermoplastic elastomer and the plasticizer, the mixture (X) may be formulated. When the mixture (X) is formulated, a plasticizer may be further formulated separately from the mixture (X), or it may not be formulated at all. The method of mixing each component during formulation is not particularly limited and can be appropriately selected from known methods. The temperature and time during the addition and mixing of each component are not particularly limited, as long as the individual components do not deteriorate, and can be adjusted as appropriate.

[0111] The resin composition may be, for example, a compound obtained by kneading the styrene-based thermoplastic elastomer, the plate-like filler, the connecting filler, the plasticizer if necessary, APAO if necessary, and the other components if necessary.

[0112] <<Method for manufacturing resin sheets>> The resin sheet can be manufactured, for example, by molding the resin composition. The resin composition can be molded by known methods. For example, when molding under vacuum conditions, the resin composition can be molded by vacuum heating press. For example, when extrusion molding, the resin composition can be molded by methods such as the feed block method or the co-extrusion T-die method such as the multi-manifold method. In this embodiment, a resin composition containing a plasticizer can also be extruded.

[0113] For example, the conditions for molding the resin composition under vacuum conditions are as follows: In other words, the molding temperature (pressure temperature) of the resin composition may be higher than the melting point of the styrene-based thermoplastic elastomer, or it may be equal to or lower than a temperature 75°C higher than the melting point of the styrene-based thermoplastic elastomer. Alternatively, for example, if pseudo-crosslinking by the styrene skeleton of a styrene-based thermoplastic elastomer occurs at around 125°C, the molding temperature (pressure temperature) of the resin composition may be 120°C or higher. The pressure applied during molding of the resin composition is preferably 3 to 20 MPa. The molding time (pressure time) for the resin composition is preferably 0.5 to 10 minutes. The molding of the resin composition is preferably carried out under reduced pressure, and more preferably under vacuum conditions such as a pressure of 0.05 MPa or less.

[0114] For example, when the resin composition is extruded, the temperature at that time (extrusion temperature) may be 120 to 220°C. If the resin composition contains a flame retardant, the extrusion molding temperature of the resin composition is preferably lower than the decomposition temperature of the flame retardant. If the resin composition contains aluminum hydroxide as the flame retardant, the extrusion molding temperature of the resin composition is preferably 120 to 200°C.

[0115] <<How to use resin sheets>> The resin sheet can be applied, for example, to a heat-generating element such as a CPU placed on a circuit board in an electronic device, thereby enabling heat dissipation from the heat-generating element. The resin sheet can be easily peeled off from the object being cooled at any time at room temperature. The method of using the aforementioned resin sheet will be described below.

[0116] Figure 2 is a schematic cross-sectional view illustrating an example of how to use the resin sheet of this embodiment. Here, we will explain how to use the resin sheet 1 shown in Figure 1 as an example.

[0117] When using the resin sheet 1, first, as shown in Figure 2A, the other side 1b of the resin sheet 1 is placed on the circuit board 9 with the other side 1b facing the heating element 8 located on the circuit board 9. In this case, it is preferable to place a first pressing means 7 on one side 1a of the resin sheet 1 for attaching the resin sheet 1 to the circuit board 9 and the heating element 8 by applying pressure to the resin sheet 1. Similarly, it is preferable to place a second pressing means 6 on the side of the circuit board 9 opposite to the circuit surface 9a (in other words, the back side) for attaching the resin sheet 1 to the circuit board 9 and the heating element 8 by applying pressure to the circuit board 9.

[0118] The first pressurizing means 7 is not particularly limited as long as it can pressurize the resin sheet 1, and the second pressurizing means 6 is not particularly limited as long as it can pressurize the circuit board 9. Pressurizing the resin sheet 1 by the first pressurizing means 7 and pressurizing the circuit board 9 by the second pressurizing means 6 may be done simultaneously. For example, the first pressurizing means 7 and the second pressurizing means 6 may be the housing of an electronic device that includes the circuit board 9 and the heating element 8. Either pressurizing the resin sheet 1 by the first pressurizing means 7 or pressurizing the circuit board 9 by the second pressurizing means 6 may be omitted.

[0119] The resin sheet 1 or the circuit board 9 may be pressurized after preheating (heating) the resin sheet 1, or it may be done without preheating the resin sheet 1.

[0120] The preheating temperature of the resin sheet 1 is preferably such that the flexibility of the resin sheet 1 is sufficiently high, and is preferably between 70 and 150°C. A preheating temperature above the lower limit further increases the flexibility of the resin sheet 1. A preheating temperature below the upper limit avoids excessive preheating. At this stage, the resin sheet 1 does not need to be in contact with the heating element 8. The resin sheet 1 can be preheated, for example, by heating either one or both of the first pressurizing means 7 and the second pressurizing means 6, or by heating means other than these pressurizing means.

[0121] Next, the heated resin sheet 1 is pressed against the circuit board 9 (heating element 8) to attach the resin sheet 1 to the circuit board 9 (more specifically, the circuit surface 9a of the circuit board 9) and the heating element 8, as shown in Figure 2B. At this time, the resin sheet 1 can be pressed using either or both of the first pressing means 7 and the second pressing means 6.

[0122] The pressure applied to the resin sheet 1 is preferably 0.1 to 1 MPa, and the pressurizing time is preferably 10 to 60 seconds. When the pressurizing pressure or pressurizing time is above the lower limit, the adhesion between the resin sheet 1 and the heating element 8, and the adhesion between the resin sheet 1 and the circuit board 9 are improved. When the pressurizing pressure or pressurizing time is below the upper limit, excessive pressurization is avoided, and deformation of the heating element 8, for example, is suppressed.

[0123] Because the resin sheet 1 has sufficiently high flexibility and conformability when heated, at this stage, the resin sheet 1 (more specifically, the other surface 1b of the resin sheet 1) is in close contact with the upper surface 8a and side surface 8c of the heating element 8, as well as the circuit surface 9a of the circuit board 9. Therefore, the heat dissipation effect of the resin sheet 1 on the heating element 8 and the circuit board 9 is sufficiently high. In addition, the resin sheet 1 maintains good connectivity between the heating element 8 and other components even at room temperature.

[0124] Next, if it becomes necessary to peel and remove the resin sheet 1 that is applied to the heating element 8 and the circuit board 9 from the heating element 8 and the circuit board 9, the resin sheet 1 can be peeled off at room temperature. At this time, because the resin sheet 1 has high peelability at room temperature, the resin sheet 1 can be easily peeled off from the heating element 8 and the circuit board 9 without having to strictly adjust the peeling operation to avoid damaging the heating element 8 and the circuit board 9 during peeling, and the resin sheet 1 is easy to handle. As a result, as shown in Figure 2C, the heating element 8 and the circuit board 9 can be returned to the same state as before the resin sheet 1 was attached, without damaging them. The resin sheet 1 can also be easily peeled off from the pressurizing means 7. Because the resin sheet 1 has high embedding capacity for the heating element 8, the shape of the heating element 8 is clearly reflected on the other surface 1b of the resin sheet 1. The peeled resin sheet 1 can be reused to manufacture a new resin sheet. [Examples]

[0125] The present invention will be described in more detail below with reference to specific examples. However, the present invention is not limited in any way to the examples shown below. The raw materials and components used in the examples and comparative examples are shown below.

[0126] [Mixture containing styrene-based thermoplastic elastomer and plasticizer] Mixture (X1): A mixture of styrene-based thermoplastic elastomer (a1) and plasticizer (s1) (Kuraray Plastics Co., Ltd. "Erneston® JS150NS"). Mixture (X2): A mixture of styrene-based thermoplastic elastomer (a2) and plasticizer (s2) (Aron Kasei Co., Ltd. "Elastomer AR-SC-0"). The hardness of the aforementioned mixture (X1) on a Type E durometer measured in accordance with JIS K 6253-3:2012 was 14, and its density measured in accordance with JIS K 7112:1999 was 0.89 g / cm³. 3The tensile strength measured in accordance with JIS K 6251:2017 (Dumbbell-shaped No. 3, tensile speed 500 mm / min) was 2.0 MPa, the elongation at break was 1250%, and the melt flow rate measured in accordance with JIS K 7210-1:2014 was 9.0 g / 10 min. The hardness of the aforementioned mixture (X2) is 0 according to JIS K 6253-3:2012 on a Type A durometer, and its density is 0.86 g / cm³ according to JIS K 7112:1999. 3 The tensile strength measured in accordance with JIS K 6251:2017 is 1.3 MPa, the elongation at break (elongation rate) is 1180%, and the melt flow rate (125℃ × 21.2N) measured in accordance with ASTM D 1238 is 8 g / 10 min.

[0127] [Thermoplastic resin] Thermoplastic resin (a3): Ethylene-vinyl acetate copolymer (EVA) (Mitsui Dow Polychemicals "EVAflex® EV150", melting point approximately 60°C, MFR 30g / 10min, density 0.96g / cm³) 3 , vinyl acetate content 33% by mass) The MFR of the aforementioned EVA was measured in accordance with JIS K7210:1999, under a temperature of 190°C and with a load of 2.16 kg applied.

[0128] [APAO] APAO(a4): Amorphous propylene-ethylene-1-butene ternary copolymer (Rextack "RT5250P"; amorphous poly-alpha-olefin; glass transition temperature -37℃; penetration 22; melt viscosity at 190℃ 25,000 cps (25 Pa·s); elongation at break 737%)

[0129] [Sheet-shaped filler] Plate-shaped filler (b1): Plate-shaped boron nitride filler (Tokuyama Corporation "K03", average particle size 9 μm, density 2.3 g / cm³) 3 (Thermal conductivity 60 W / m·K, aspect ratio 30, relative permittivity 4) [Connecting filler] Linked filler (c1): Magnesium hydroxide filler surface-treated with higher fatty acids (Kyowa Chemical Industry Co., Ltd.'s "KISUMA® 5B," magnesium hydroxide content 95% by mass or more, higher fatty acid content 5% by mass or less, average particle size 0.83 μm, thermal conductivity 8 W / m·K) Linked filler (c2): Magnesium hydroxide filler (Kyowa Chemical Industry Co., Ltd. "KISUMA® 8", average particle size 1.38 μm, thermal conductivity 8 W / m·K) Linked filler (c3): Aluminum hydroxide filler (Sumitomo Chemical Co., Ltd. "C-301N", central particle size 1.5 μm, thermal conductivity 20 W / m·K)

[0130] [Plasticizer] Plasticizer (s3): Aromatic modified terpene resin (Yasuhara Chemical Co., Ltd. "YS Resin TO105", tackifier)

[0131] [Antioxidant] Antioxidant (d1): Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (hindered phenol antioxidant, "Irganox 1010" manufactured by BASF Japan)

[0132] [Example 1] <<Manufacturing of resin sheets>> A pelletized resin composition was prepared by melt-kneading a mixture (X1) (800g), a plate-shaped filler (b1) (800g), a linked filler (c1) (120g), and a linked filler (c2) (1080g) using a twin-screw extruder. Furthermore, the obtained resin composition was fed into an extruder and melt-extruded using a T-die to obtain a single-layer resin sheet (thickness 1000 μm).

[0133] <<Evaluation of resin sheets>> <Evaluation of component connectivity of resin sheets at room temperature> A circuit board measuring 30mm x 68mm and 1mm thick, with four components measuring 8mm x 13mm and 1mm high connected to it, was prepared as the target object for application of the resin sheet. The circuit board was placed on a hot plate heated to 120°C with the circuit surface (in other words, the connection surface of the components) facing upwards. Two of the resin sheets (1000 μm thick) obtained above were then placed on top of it, covering the entire circuit surface with these resin sheets. Next, a separately prepared hot plate heated to 120°C was brought into contact with the upper surface of the resin sheet, and this state was maintained for 10 to 30 seconds to preheat (heat) the resin sheet. Then, the preheated resin sheet was pressed against the circuit board using the hot plate heated to 120°C, thereby attaching the resin sheet to the circuit surface of the circuit board and obtaining a laminate. The thickness of the laminate (the total thickness of the resin sheet and the circuit board) was set to 3 mm.

[0134] Next, two polycarbonate substrates measuring 50mm x 50mm and 10mm thick were prepared, each adjusted so that its four corners could be fastened with M3 bolts with a 30mm shank length. The laminate, cooled to room temperature, was sandwiched between these polycarbonate substrates, and at room temperature, each of the four M3 bolts was tightened gradually using a 10cN·m torque wrench until it could no longer be turned, ensuring that no bolts were tightened unevenly, thereby pressing the polycarbonate substrates against the resin sheet in the laminate. After leaving the polycarbonate substrate in this state for one hour, the connection between the resin sheet in the laminate and the polycarbonate substrate corresponding to the component was visually observed from the top surface of the polycarbonate substrate, and the component connectivity of the resin sheet at room temperature was evaluated according to the following criteria. The results are shown in Table 1. [Evaluation Criteria] A: In over 80% of the area where the polycarbonate substrate is pressed against the resin sheet, the polycarbonate substrate and the resin sheet are connected without any gaps, demonstrating particularly excellent component connectivity of the resin sheet at room temperature. B: In the area where the polycarbonate substrate is pressed against the resin sheet, the polycarbonate substrate and the resin sheet are connected without any gaps in between 50% and less than 80% of the area, indicating excellent component connectivity of the resin sheet at room temperature. C: In the area where the polycarbonate substrate is pressed against the resin sheet, more than 50% of the area is a void, meaning that the polycarbonate substrate and the resin sheet are not connected, resulting in poor component connectivity of the resin sheet at room temperature.

[0135] <Evaluation of the peelability of resin sheets at room temperature> After evaluating the component connectivity of the resin sheet as described above, the polycarbonate substrate was removed from the laminate, and the laminate was taken out. Next, at room temperature, the resin sheet was peeled off from the circuit board by lifting it from its edge, and the ease of peeling at this time was evaluated according to the following criteria for peelability of the resin sheet at room temperature. The results are shown in Table 1. [Evaluation Criteria] A: The resin sheet is soft, allowing for easy removal from components on the circuit surface, and the resin sheet exhibits excellent peelability at room temperature. B: The resin sheet is somewhat hard, and it can be peeled off from the components on the circuit surface, although not easily. The peelability of the resin sheet at room temperature is inferior to that of A. C: The resin sheet is hard, making it difficult to peel it from components on the circuit surface, and the peelability of the resin sheet at room temperature is poor.

[0136] <Evaluation of the embeddability of resin sheets> After evaluating the peelability of the resin sheet at room temperature as described above, the adhesive surface of the peeled resin sheet was visually inspected, and the embedding ability of the resin sheet to components on the circuit surface was evaluated according to the following criteria. The results are shown in Table 1. [Evaluation Criteria] A: The shape of all components on the circuit surface is clearly reflected on the adhesive surface of the resin sheet, resulting in excellent embedding properties for the resin sheet. B: The surface of the resin sheet that is attached to the circuit surface does not clearly reflect the shape of at least some of the components on the circuit surface, resulting in poor embedding of the resin sheet.

[0137] <Evaluation of the room-temperature plastic deformability of resin sheets> A circuit board measuring 30mm x 62mm and 1mm thick, with four components measuring 8mm x 13mm and 1mm high connected to it, was prepared as the target object for application of the resin sheet. The circuit board was placed on a board at room temperature (24°C) with the circuit surface (in other words, the connection surface of the components) facing upwards. The resin sheet (2000 μm thick) obtained above was then placed on top of the circuit board, and the entire circuit surface was covered with these resin sheets. Next, a hand press with metal plates on the top and bottom was prepared. A 44.6mm thick sponge-like cushion rubber sheet with a Shore A hardness of 16 was placed on the bottom metal plate, and the hand press was adjusted so that there was no gap between the top surface of the sponge-like cushion rubber sheet and the top metal plate of the hand press when the hand press was fully closed. Next, the hand press was opened, and the previously constructed circuit board, with the resin sheet placed on top of the sponge-like cushion rubber sheet, was placed on top of it. The upper and lower metal plates were then completely closed with the hand press and pressure was applied for 1 minute to adhere the resin sheet to the circuit surface of the circuit board, thereby obtaining a laminate. The thickness of the laminate (the total thickness of the resin sheet and the circuit board) was set to 3 mm.

[0138] Next, the resin sheet was peeled off from the circuit board by starting from its edge and left at room temperature for about 3 hours.

[0139] Furthermore, the thickness of the recessed area on the adhesive surface of the resin sheet after peeling was measured, and the embedding deformation rate (embedded shape retention rate) from the original thickness was measured. The embedding deformation rate was then calculated according to the following formula. [Deformation rate of the resin sheet's adhesive surface on the circuit board (%)] = ([Original thickness of the resin sheet] - [Thickness of the recess on the resin sheet's adhesive surface]) / [Height of the convex part of the circuit board] × 100 The room-temperature plastic deformability of resin sheets relative to components on a circuit surface was evaluated according to the following criteria. The results are shown in Table 1. [Evaluation Criteria] A: The degree of embedded deformation of the resin sheet's adhesive surface to the circuit board is 50% or more. B: The degree of embedded deformation of the resin sheet's adhesive surface on the circuit board is less than 50%.

[0140] <Measurement of Durometer Hardness of Type A Resin Sheets> The Type A durometer hardness of the resin sheets obtained above was measured in accordance with JIS K 6253-3. The results are shown in Table 1.

[0141] <Measurement of thermal conductivity in the planar direction of a resin sheet> The thermal conductivity of the resin sheets obtained above was measured in the planar direction using a hot disk method thermophysical property measurement device (Kyoto Electronics Manufacturing Co., Ltd. "TPS 500 S") in accordance with ISO 22007-2. Two resin sheets were placed between insulating materials, and a 7mm diameter sensor was inserted between these resin sheets to measure the thermal conductivity of the resin sheets. The results are shown in Table 1.

[0142] <Measurement of relative permittivity and dielectric loss tangent of resin sheets> At room temperature, test specimens of a predetermined size were cut from the resin sheet obtained above. The relative permittivity at 1 GHz and 10 GHz, and the dielectric loss tangent at 1 GHz and 10 GHz were measured for these specimens in accordance with the TM0m0 mode cavity resonator perturbation method. The results are shown in Table 1.

[0143] <Measuring the density of a resin sheet> The density of the resin sheet obtained above was measured in accordance with JIS K 7112:1999. The results are shown in Table 1.

[0144] <Measurement of dielectric breakdown voltage of resin sheet> In accordance with JIS C 2110-1, the dielectric breakdown voltage of the resin sheet (50 mm square, 1000 μm thick) obtained above was measured. From this, the dielectric breakdown strength per unit thickness was determined, and the results are shown in Table 1.

[0145] <<Manufacturing and evaluation of resin sheets>> [Example 2] Except for using mixture (X2) (800g) instead of mixture (X1) (800g), a single-layer resin sheet (thickness 1000 μm) was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0146] [Example 3] A pelletized resin composition was prepared by melt-kneading a mixture (X1) (600g), a plate-shaped filler (b1) (800g), a linked filler (c1) (120g), a linked filler (c2) (480g), a linked filler (c3) (600g), and a plasticizer (s3) (200g) using a twin-screw extruder. Subsequently, a single-layer resin sheet (thickness 1000 μm; thickness 2000 μm for evaluation of room-temperature plastic deformability) was manufactured and evaluated in the same manner as in Example 1, except that this resin composition was used. The results are shown in Table 1.

[0147] [Example 4] A pelletized resin composition was prepared by melt-kneading a mixture (X1) (450g), APAO (a4) (95g), plate-shaped filler (b1) (800g), linking filler (c1) (120g), linking filler (c2) (480g), linking filler (c3) (600g), plasticizer (s3) (195g), and antioxidant (d1) (5g) using a twin-screw extruder. Subsequently, a single-layer resin sheet (thickness 1000 μm; thickness 2000 μm for evaluation of room-temperature plastic deformability) was manufactured and evaluated in the same manner as in Example 1, except that this resin composition was used. The results are shown in Table 1.

[0148] [Comparative Example 1] A pelletized resin composition was prepared by melt-kneading thermoplastic resin (a3) ​​(500g), plate-shaped filler (b1) (250g), linked filler (c1) (75g), and linked filler (c2) (675g) using a twin-screw extruder. Furthermore, the obtained resin composition was sandwiched between a pair of hot plates and molded by vacuum heating and pressing at a pressure of 15 MPa for 1 minute while heating at 120°C under vacuum conditions of 0.02 MPa or less, thereby obtaining a single-layer resin sheet (thickness 1500 μm). The obtained resin sheets were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0149] In Tables 1 and 2, "Content of plate-shaped filler (volume %)" refers to the ratio of the content (volume parts) of plate-shaped filler to the total volume (volume parts) of the resin sheet. Similarly, "bonding filler content (volume %)" refers to the ratio of the bonding filler content (volume parts) to the total volume (volume parts) of the resin sheet. "The ratio of the content of linked fillers to the content of plate-shaped fillers (volume %)" refers to the ratio of the content of linked fillers (volume portion) to the content of plate-shaped fillers (volume portion) in a resin sheet.

[0150] [Table 1]

[0151] [Table 2]

[0152] As is clear from the results above, in Examples 1 to 4, the component connectivity and peelability of the resin sheets, as well as the embedding properties of the resin sheets, were high at room temperature. In Examples 1 to 4, the Type A durometer hardness of the resin sheet was 38 or less (30 to 38). Furthermore, visual inspection of the circuit surface after peeling off the resin sheet revealed no damage or deformation to any of the components on the circuit surface. This indicates that component damage was suppressed during the embedding of the resin sheet and during peeling at room temperature. This result is consistent with the high embeddability of the resin sheet and its peelability at room temperature. The resin sheets of Examples 1 to 4 contained a styrene-based thermoplastic elastomer.

[0153] Furthermore, in Examples 1 to 4, the thermal conductivity of the resin sheet in the planar direction was 3 W / m·K, indicating high thermal conductivity in the planar direction of the resin sheet. The resin sheets of Examples 1 to 4 contained, in addition to the styrene-based thermoplastic elastomer, plate-shaped fillers and connecting fillers.

[0154] In the resin sheets of Examples 1 to 4, the ratio of the total content of plate-shaped fillers and linked fillers to the total volume of the resin sheet was 50.9% by volume or less (47.8 to 50.9% by volume), and the ratio of the content of linked fillers to the content of plate-shaped fillers was 146.9 to 148.7% by volume. In the resin sheets of Examples 1 to 4, the average particle size of the plate-shaped filler was 9 μm.

[0155] The relative permittivity of the resin sheets in Examples 1 to 4 satisfied the condition of being 4 or less in both cases of 1 GHz and 10 GHz frequencies. The dielectric loss tangent of the resin sheets in Examples 1 to 4 satisfied the condition of being 0.01 or less in both the 1 GHz and 10 GHz cases. The density of the resin sheets in Examples 1-4 is 2 g / cm³. 3 The following conditions were met: In other words, the resin sheets of Examples 1 to 4 also exhibited excellent properties other than those mentioned above, such as component connectivity, release properties, and thermal conductivity.

[0156] The resin sheet of Example 3 is obtained by replacing a portion of the magnesium hydroxide filler with aluminum hydroxide filler in the resin sheet of Example 1, and further replacing a portion of the mixture (X1) with a plasticizer (s3). The resin sheet of Example 3, containing aluminum hydroxide filler, exhibited improved flame retardancy compared to the resin sheets of Examples 1 and 2, and was confirmed to meet UL94 Vertical Combustion Test Grade V-2. Although the resin sheet of Example 3 contained aluminum hydroxide filler, unlike the resin sheets of Examples 1 and 2, it also contained a plasticizer (s3) and possessed the same flexibility, component connectivity, embedding ability, and release properties as the resin sheets of Examples 1 and 2.

[0157] The resin sheet of Example 4 is the same as the resin sheet of Example 3, but with a portion of the mixture (X1) replaced by APAO (a4) and an antioxidant (e1). The resin sheet of Example 4 had the same flexibility, component connectivity, embedding ability, and peelability as the resin sheets of Examples 1 to 3. The resin sheet of Example 4, by containing APAO(a4), was found to have improved room-temperature plastic deformability compared to the resin sheet of Example 3.

[0158] In contrast, in Comparative Example 1, the component connectivity of the resin sheet at room temperature was inferior to that of Examples 1 to 4. In Comparative Example 1, the Type A durometer hardness of the resin sheet was 87. The resin sheet in Comparative Example 1 did not contain a styrene-based thermoplastic elastomer.

[0159] Visual inspection of the circuit surface after peeling off the resin sheet revealed no damage or deformation to any components on the circuit surface. This indicates that component damage was suppressed during the embedding of the resin sheet and during peeling at room temperature. This result is consistent with the finding that the embedding properties of the resin sheet and the peeling properties of the resin sheet at room temperature were not inferior. [Industrial applicability]

[0160] The present invention, assuming that it will be peeled off after use, can be used to cool the CPU or other heat-generating elements in electronic devices equipped with a CPU, and other devices equipped with heat-generating elements similar to those of a CPU. [Explanation of Symbols]

[0161] 1. Resin sheet 1a One side of the resin sheet 1b The other side of the resin sheet 7 Pressurization means 8. Heating element 8a Top surface of the heating element 8c Side of the heating element 9 Circuit board 9a Circuit side of the circuit board D S Surface direction of the resin sheet D T Thickness direction of the resin sheet

Claims

1. It is a resin sheet, The aforementioned resin sheet comprises a styrene-based thermoplastic elastomer, a plate-shaped filler, and a connecting filler. A resin sheet having a Type A durometer hardness of 40 or less, as measured in accordance with JIS K 6253-3.

2. The resin sheet according to claim 1, wherein the resin sheet further contains a plasticizer.

3. The resin sheet according to claim 1 or 2, wherein the resin sheet further comprises amorphous poly-αolefin.

4. The resin sheet according to claim 1 or 2, wherein the ratio of the total content of the plate-shaped filler and the connecting filler to the total volume of the resin sheet is 55% by volume or less.

5. The resin sheet according to claim 1 or 2, wherein the relative permittivity of the resin sheet at a frequency of 10 GHz, as measured in accordance with the TM0m0 mode cavity resonator perturbation method, is 4 or less.

6. The resin sheet according to claim 1 or 2, wherein the dielectric loss tangent of the resin sheet at a frequency of 10 GHz, measured in accordance with the TM0m0 mode cavity resonator perturbation method, is 0.01 or less.

7. The density of the resin sheet, measured in accordance with JIS K 7112:1999, is 2 g / cm³. ３ The resin sheet according to claim 1 or 2, which is as follows:

8. The resin sheet according to claim 1 or 2, wherein the dielectric breakdown voltage of the resin sheet, measured in accordance with JIS C 2110-1, is 20 kV / mm or more.

9. The resin sheet according to claim 1 or 2, wherein the plate-shaped filler is made of boron nitride.

10. The resin sheet according to claim 1 or 2, wherein the connecting filler consists of either magnesium hydroxide or aluminum hydroxide, or both.

11. The aforementioned plate-shaped filler is made of boron nitride, The resin sheet according to claim 2, wherein the connecting filler consists of either magnesium hydroxide or aluminum hydroxide, or both.

12. The resin sheet according to claim 1 or 2, wherein the ratio of the content of the connecting filler to the content of the plate-shaped filler is 60 to 200% by volume.

13. The resin sheet according to claim 1 or 2, wherein the average particle size of the plate-shaped filler is 5 μm or more.

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