Thermal conductive spacer and thermal conductive composition

Abstract

To provide a thermal conductive spacer and so on which can keep high thermal conductivity, even when it is repeatedly exposed to high temperature and low temperature.SOLUTION: A thermal conductive spacer includes a thermosetting resin and a thermal conductive filler. When cycles are repeated three times in each of which cycles a temperature is increased from -20°C to 150°C at a rate of temperature increase 5°C / min and decreased from 150°C to -20°C at a rate of temperature decrease -5°C / min, a storage elastic modulus G'up is defined at 25°C in the temperature increase process in the third cycle, and a storage elastic modulus G'down is defined at 25°C in the temperature decrease process in the third cycle. A ratio G'down / G'up of the storage elastic modulus G'down to the storage elastic modulus G'up is 3.0 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thermally conductive spacer and a thermally conductive composition. [Background technology]

[0002] As heat-generating electronic components, such as central processing units (CPUs) in personal computers, become smaller and more powerful, the amount of heat generated per unit area by these components has become extremely large. This amount of heat can reach approximately 20 times that of an iron. To prevent these heat-generating electronic components from breaking down over the long term, they must be cooled. Metal heat sinks and housings are used for cooling. However, when a heat-generating electronic component is placed directly in contact with a heat sink, microscopic air exists at the interface, which can impede heat conduction. Therefore, to efficiently transfer heat, a thermally conductive material is often placed between the heat-generating electronic component and the heat sink.

[0003] Examples of thermally conductive materials include thermally conductive spacers, which are made by filling a thermosetting resin with a thermally conductive filler and molding it into a sheet, and thermally conductive grease, which is made by filling a fluid resin with a thermally conductive filler and can be spread or made into a thin film.

[0004] To date, thermally conductive spacers (see Patent Document 1) have been developed that have improved flexibility in addition to thermal conductivity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2023 / 162928 Summary of the Invention [Problem to be solved by the invention]

[0006] The thermally conductive spacer can be used by being placed between a heat generating element and a heat sink. When the heat generating element is a heat generating electronic component such as a central processing unit (CPU) of a personal computer, the thermally conductive spacer is repeatedly exposed to high and low temperatures.

[0007] Therefore, an object of the present invention is to provide a thermally conductive spacer and a thermally conductive composition that can maintain high thermal conductivity even when repeatedly exposed to high and low temperatures. [Means for solving the problem]

[0008] As a result of intensive research to achieve the above object, the inventors discovered that the above problem can be solved by a thermally conductive spacer that has low hysteresis loss in storage modulus when repeatedly exposed to high and low temperatures, and thus completed the present invention.

[0009] That is, the present invention is as follows. [1] a thermosetting resin and a thermally conductive filler; When the cycle of heating from -20°C to 150°C at a heating rate of 5°C / min and then cooling from 150°C to -20°C at a cooling rate of -5°C / min is repeated three times, the ratio G'down / G'up of the storage modulus at 25°C during the heating process of the third cycle to the storage modulus at 25°C during the cooling process is 3.0 or less. Thermally conductive spacer. [2] the maximum value G'max of the storage modulus during the temperature increase process and the temperature decrease process of the third cycle is 50 to 700 kPa; [1] The thermally conductive spacer according to the present invention. [3] Thermal conductivity measured in accordance with ASTM D5470 is 2.5 W / m·K or greater. [1] or [2]. The thermally conductive spacer according to [1] or [2]. [4] When the temperature is increased from -40°C to 150°C within 5 minutes, held for 30 minutes, and then decreased from 150°C to -40°C within 5 minutes and held for 30 minutes, this cycle is repeated for 500 hours, and the increase in thermal resistance is 10% or less. The thermally conductive spacer according to any one of [1] to [3]. [5] The thermosetting resin includes an addition-curing silicone resin. The thermally conductive spacer according to any one of [1] to [4]. [6] Asker C hardness is 1 to 35. The thermally conductive spacer according to any one of [1] to [5]. [7] [1] to [6], for producing the thermally conductive spacer according to any one of [1] to [6], Thermally conductive compositions. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a thermally conductive spacer and a thermally conductive composition that can maintain high thermal conductivity even when repeatedly exposed to high and low temperatures. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram showing the relationship between storage modulus G′ and temperature T. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail. However, the present invention is not limited to the following embodiment, and various modifications are possible without departing from the gist of the present invention.

[0013] 1.Thermal conductive spacer The thermally conductive spacer of this embodiment contains a thermosetting resin and a thermally conductive filler, and when the cycle of heating from -20°C to 150°C at a heating rate of 5°C / min and then cooling from 150°C to -20°C at a cooling rate of -5°C / min is repeated three times, the ratio G'down / G'up of the storage modulus at 25°C during the heating process of the third cycle to the storage modulus at 25°C during the cooling process is 3.0 or less.

[0014] The inventors have found that even thermally conductive spacers with high initial thermal conductivity may experience a decrease in thermal conductivity over time. Further investigations have revealed that the decrease in thermal conductivity is significant when used in contact with a heating element that repeatedly generates heat intermittently. Because the volume of a heating element changes with temperature, when the heating element repeatedly generates heat intermittently, the compressive force that the thermally conductive spacer receives from the heating element fluctuates intermittently. If the thermally conductive spacer cannot keep up with the volume change associated with the temperature change of the heating element, the thermally conductive spacer may be excessively compressed or gaps may form, resulting in a decrease in thermal conductivity at the interface.

[0015] Therefore, in order to provide a thermally conductive spacer that maintains high thermal conductivity even when repeatedly exposed to high and low temperatures, it is considered necessary to make the thermally conductive spacer capable of changing shape in response to volumetric changes associated with temperature changes in the heating element. The thermally conductive spacer of this embodiment ensures that it can follow volumetric changes associated with temperature changes in the heating element by reducing hysteresis loss in high and low temperature cycles (hereinafter simply referred to as "heat cycles"). More specifically, the ratio G'down / G'up, between the storage modulus G'up at 25°C during the temperature rise process and the storage modulus G'down at 25°C during the temperature fall process, is set to a predetermined range in a given heat cycle, thereby ensuring that it can follow volumetric changes associated with temperature changes in the heating element.

[0016] This will be explained in more detail using Figure 1. Figure 1 is a schematic diagram showing the relationship between the storage modulus G' and temperature when the storage modulus G' of a thermally conductive spacer is measured while undergoing a heat cycle. As shown in Figure 1, the storage modulus G' during the temperature decrease process is higher than the storage modulus G' during the temperature increase process, and the area of ​​the region enclosed by curve C corresponds to the hysteresis loss. When the hysteresis loss is large, it becomes difficult for the thermally conductive spacer to follow the volume change that accompanies the temperature change of the heating element, and as a result, it is thought that the thermal conductivity via the thermally conductive spacer decreases.

[0017] In the thermally conductive spacer of this embodiment, realizing low hysteresis loss is defined by the ratio G'down / G'up, which is the ratio of the storage modulus G'up at 25°C during the temperature rise process to the storage modulus G'down at 25°C during the temperature fall process. In this way, realizing low hysteresis loss in the thermally conductive spacer allows it to follow the volumetric changes that accompany temperature changes in the heating element, and maintain high thermal conductivity even when repeatedly exposed to high and low temperatures. Hereinafter, the ability to maintain high thermal conductivity even when repeatedly exposed to high and low temperatures is referred to as the "reliability" of the thermally conductive spacer.

[0018] 1.1.Physical properties of thermally conductive spacers 1.1.1.Storage modulus In this embodiment, low hysteresis loss is expressed by the ratio G'down / G'up. Specifically, when a cycle of heating from -20°C to 150°C at a heating rate of 5°C / min and then cooling from 150°C to -20°C at a cooling rate of -5°C / min is repeated three times, the ratio G'down / G'up of the storage modulus at 25°C during the heating process to the storage modulus at 25°C during the cooling process in the third cycle is 3.0 or less.

[0019] As described above, by setting the ratio G'down / G'up to 3.0 or less, low hysteresis loss can be reliably achieved and the decrease in thermal conductivity due to heat cycles can be reliably suppressed.

[0020] Therefore, the ratio G'down / G'up is preferably 2.8 or less, 2.5 or less, 2.0 or less, or 1.8 or less. The lower limit of the ratio G'down / G'up is not particularly limited, and the ratio G'down / G'up may be, for example, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.1 or more, or 1.2 or more.

[0021] The storage modulus G'down at 25°C during the temperature drop is not particularly limited, but is preferably 20 to 300 kPa, 30 to 280 kPa, 35 to 270 kPa, 40 to 260 kPa, 50 to 250 kPa, or 60 to 200 kPa. Within the above range, the G'down value may be 80 kPa or more, 100 kPa or more, 150 kPa or more, or 180 kPa or more, 100 kPa or less, or 80 kPa or less.

[0022] The storage modulus G'up at 25°C during the temperature rise process is not particularly limited, but is preferably 10 to 280 kPa, 20 to 250 kPa, 25 to 240 kPa, 30 to 220 kPa, 35 to 200 kPa, or 40 to 180 kPa. Within the above range, the G'up value may be 47 kPa or more, 80 kPa or more, or 100 kPa or more, or 130 kPa or less, 100 kPa or less, 50 kPa or less, or 47 kPa or less.

[0023] The difference between the storage modulus G'down and G'up (G'down-G'up) is not particularly limited, but is preferably -30 to 100 kPa, -20 to 80 kPa, -10 to 70 kPa, 0 to 60 kPa, or 10 to 50 kPa.

[0024] By ensuring that the storage modulus G'down and G'up values, as well as the ratio and difference between them, are within the above ranges, low hysteresis loss can be more reliably achieved, and the reliability of the thermally conductive spacer tends to be further improved.

[0025] In this embodiment, the maximum value G'max of the storage modulus during the temperature increase and decrease steps of the third cycle is preferably 50 to 700 kPa, 60 to 500 kPa, 70 to 400 kPa, 80 to 300 kPa, or 100 to 250 kPa. When the maximum value G'max of the storage modulus is within the above range, the repulsive force of the thermally conductive spacer falls within an appropriate range, and physical impact on the heat generating element and heat dissipating element tends to be alleviated.

[0026] The heat cycle begins at room temperature, and is heated to 150°C and then cooled to -20°C. The cycle of heating from -20°C to 150°C and cooling from 150°C to -20°C is then repeated. In this embodiment, the thermal history previously applied to the thermally conductive spacer is kept constant, and the storage modulus during the heating and cooling processes of the third cycle is used to evaluate the thermal behavior under stable conditions. Furthermore, from the perspective of more appropriately evaluating low hysteresis loss, the storage modulus at 25°C, which is approximately the midpoint between -20°C and 150°C, is used.

[0027] The storage modulus is measured by compressing the thermally conductive spacer by 15% from its initial thickness and then performing dynamic viscoelasticity measurement with a rheometer in a compression mode at a strain of 0.5% and a frequency of 1.0 Hz. More specifically, the storage modulus can be measured by the method described in the Examples.

[0028] The values ​​of the storage moduli G'down and G'up, and the ratio and difference between them, can be adjusted to fall within the above ranges by, for example, adjusting the composition or manufacturing method of the thermally conductive spacer, such as by changing the type of thermosetting resin or by adjusting the temperature and time of aging after curing the thermosetting resin in the manufacturing method of the thermally conductive spacer described below.

[0029] 1.1.2.Asker C hardness The thermally conductive spacer can be disposed between the heat generating element and the heat dissipating element so that the thermally conductive spacer is compressed. Therefore, from the viewpoint of mitigating physical impact on the heat generating element and the heat dissipating element, it is preferable that the flexibility of the thermally conductive spacer, in other words, its hardness, be within a certain range.

[0030] Therefore, the Asker C hardness of the thermally conductive spacer is preferably 1-35, 3-20, or 5-15.

[0031] The Asker C hardness of the thermally conductive spacer can be measured at 25°C using an Asker C type spring hardness tester conforming to SRIS0101, and more specifically, can be measured by the method described in the examples.

[0032] The Asker C hardness can be adjusted to fall within the above range by, for example, adjusting the composition of the thermally conductive spacer, such as by changing the type of thermosetting resin or adjusting the content of the thermally conductive filler.

[0033] 1.1.3.Heat Conduction Properties The thermally conductive spacer of this embodiment is suitable for use as a thermally conductive heat dissipation material. Therefore, it is preferable that the thermal conductivity of the thermally conductive spacer be high. Specifically, the thermal conductivity measured in accordance with ASTM D5470 is preferably 2.5 W / m·K or more, 3.0 W / m·K or more, 3.5 W / m·K or more, 4.0 W / m·K or more, or 5.0 W / m·K or more. While the upper limit of the thermal conductivity measured in accordance with ASTM D5470 is not particularly limited, the thermal conductivity may be, for example, 10 W / m·K or less, 8.0 W / m·K or less, or 7.0 W / m·K or less.

[0034] The thermal conductivity of the thermally conductive spacer is measured in accordance with ASTM D5470 under a condition of 30% compression, and more specifically, can be measured by the method described in the examples.

[0035] In order to set the thermal conductivity within the above range, for example, the type and content of the thermally conductive filler may be adjusted.

[0036] The thermally conductive spacer of this embodiment can maintain high thermal conductivity even when repeatedly exposed to high and low temperatures. Therefore, when the cycle of increasing the temperature from -40°C to 150°C within 5 minutes, maintaining the temperature for 30 minutes, and decreasing the temperature from 150°C to -40°C within 5 minutes and maintaining the temperature for 30 minutes is repeated for 500 hours, the rate of increase in thermal resistance is preferably 10% or less, 9% or less, 8% or less, or 6% or less. The lower limit of the rate of increase in thermal resistance is not particularly limited, but the rate of increase in thermal resistance may be, for example, 0% or more, 1% or more, or 3% or more.

[0037] The thermal resistance of the thermally conductive spacer can be measured by placing the spacer on a measuring jig with a smooth copper surface, leaving it to stand for one day, and then measuring it, more specifically, by the method described in the Examples. The rate of increase in thermal resistance can be calculated by measuring the thermal resistance of the thermally conductive spacer before the above cycles and then measuring the thermal resistance of the thermally conductive spacer after the above cycles.

[0038] 1.2. Composition of the thermally conductive spacer The thermally conductive spacer of this embodiment contains a thermosetting resin and a thermally conductive filler, and may contain a surfactant, a curing catalyst, or other components as necessary. The thermally conductive spacer preferably contains the thermosetting resin in a cured state, but some uncured thermosetting resin may remain.

[0039] 1.2.1.Thermosetting resin The thermosetting resin is not particularly limited, but examples thereof include silicone resin, epoxy resin, acrylic resin, urethane resin, and phenol resin. Among these, silicone resin is preferred from the viewpoint of improving heat resistance and flexibility. The thermosetting resin may be used alone or in combination of two or more.

[0040] The thermosetting resin preferably contains an addition-curable silicone resin that cures by an addition reaction. The addition-curable silicone resin is not particularly limited, but examples thereof include polyorganosiloxanes having alkenyl groups and polyorganosiloxanes having hydrosilyl groups. The alkenyl group contained in the polyorganosiloxane is preferably a vinyl group. The thermally conductive spacer may contain a commercially available thermosetting silicone resin and / or a cured product thereof.

[0041] From the viewpoint of increasing the thermal conductivity of the thermally conductive spacer, the thermosetting resin particularly preferably contains a vinyl-modified organopolysiloxane A having a vinyl group and a hydrosilyl-modified organopolysiloxane B having a hydrosilyl group. In the thermally conductive spacer, the vinyl-modified organopolysiloxane A and the hydrosilyl-modified organopolysiloxane B are preferably contained in a state in which they are crosslinked (i.e., cured) by addition reaction, but unreacted vinyl-modified organopolysiloxane A and / or hydrosilyl-modified organopolysiloxane B may also be contained.

[0042] 1.2.1.1. Vinyl-modified organopolysiloxane A Vinyl-modified organopolysiloxane A (hereinafter simply referred to as "organopolysiloxane A") is an organopolysiloxane having at least one vinyl group. Organopolysiloxane A may have a vinyl group on a side chain and / or at a terminal. Such organopolysiloxane has a structural unit represented by the following formula (a-1) or a terminal structure represented by formula (a-2). Organopolysiloxane A may have, for example, at least one of the structural unit represented by formula (a-1) and the terminal structure represented by formula (a-2), and a structural unit represented by formula (a-3).

[0043] [ka]

[0044] In formulas (a-1), (a-2), and (a-3), R represents any monovalent hydrocarbon group that may have a substituent. Examples of such monovalent hydrocarbon groups include, but are not limited to, alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl; cycloalkyl groups such as cyclopentyl and cyclohexyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, 2-phenylethyl, and 2-phenylpropyl; and groups having a substituent in these groups. Examples of substituents that the monovalent hydrocarbon groups may have include halogen atoms, particularly fluorine and chlorine atoms.

[0045] The organopolysiloxane A may be used alone or in combination of two or more. There is no particular upper limit on the number of vinyl groups in the organopolysiloxane A, and the number of vinyl groups may be, for example, 1.0 to 4.0 or 2.0 to 3.0 on average per molecule. The average number of vinyl groups per molecule of the organopolysiloxane A may be 2.0.

[0046] The average number of vinyl groups per molecule of organopolysiloxane A can be measured by NMR. Specifically, for example, measurement can be performed using an ECP-300NMR manufactured by JEOL Corporation, dissolving organopolysiloxane A in deuterated chloroform as a deuterated solvent. The average number of vinyl groups per molecule can be calculated by dividing the measurement result obtained in this manner by the average molecular weight of organopolysiloxane A.

[0047] The organopolysiloxane A preferably contains an organopolysiloxane having vinyl groups at both ends. The use of such an organopolysiloxane allows for adjustment of the crosslink density. As a result, the hysteresis loss of the thermally conductive spacer can be reduced, which tends to further improve the reliability of the thermally conductive spacer.

[0048] The weight average molecular weight of the vinyl-modified organopolysiloxane A is preferably 1,000 to 100,000, or may be 1,500 to 75,000, or 2,500 to 50,000. In this specification, the weight average molecular weight of each component can be determined by GPC (gel permeation chromatography).

[0049] The vinyl group equivalent of the vinyl-modified organopolysiloxane A is preferably 0.1 to 1.0 mol / kg, or may be 0.15 to 0.8 mol / kg, or 0.2 to 0.6 mol / kg.

[0050] The content of organopolysiloxane A is preferably 60 to 99.5% by weight, or 80 to 95.0% by weight, based on the total of all components other than thermally conductive filler D. When the content of vinyl-modified organopolysiloxane A is within the above range, the hysteresis loss of the thermally conductive spacer can be reduced, and the reliability of the thermally conductive spacer tends to be further improved.

[0051] 1.2.1.2. Hydrosilyl-modified organopolysiloxane B Hydrosilyl-modified organopolysiloxane B (hereinafter simply referred to as "organopolysiloxane B") is an organopolysiloxane having at least two hydrosilyl groups. Organopolysiloxane B may have hydrosilyl groups on side chains and / or at terminals. Such organopolysiloxanes have a structural unit represented by the following formula (b-1) or a terminal structure represented by formula (b-2). Organopolysiloxane B may have, for example, at least one of the structural unit represented by formula (b-1) and the terminal structure represented by formula (b-2), and a structural unit represented by formula (b-3).

[0052] [ka]

[0053] In formulas (b-1), (b-2), and (b-3), R represents any monovalent hydrocarbon group which may have a substituent. That is, in organopolysiloxane B, any monovalent hydrocarbon group which may have a substituent is bonded to a side chain of the siloxane skeleton. Examples of such monovalent hydrocarbon groups include the same monovalent hydrocarbon groups that may be contained in vinyl-modified organopolysiloxane A.

[0054] The organopolysiloxane B may be used alone or in combination of two or more. For example, the organopolysiloxane B may be a hydrosilyl-modified organopolysiloxane B having a hydrosilyl group in a side chain. x It is preferable that the organopolysiloxane further contains a hydrosilyl-modified organopolysiloxane having hydrosilyl groups at both ends.

[0055] Organopolysiloxane B x has at least two hydrogen atoms in the side chains of the organopolysiloxane skeleton, and the hydrogen atoms and silicon atoms form hydrosilyl groups. x may further have hydrosilyl groups at both ends of the organopolysiloxane skeleton, but preferably does not have hydrosilyl groups at both ends. In that case, organopolysiloxane B x Preferably, each of the two terminals has three alkyl groups. Examples of such alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl groups, with methyl being preferred.

[0056] The number of hydrosilyl groups in organopolysiloxane B is preferably more than 2.0, 2.5 or more, or 3.0 or more on average per molecule. There is no particular upper limit to the number of hydrosilyl groups in organopolysiloxane B, and the number of hydrosilyl groups per molecule may be, for example, 8.0 or less, 6.0 or less, or 5.0 or less on average.

[0057] The average number of hydrosilyl groups per molecule of organopolysiloxane B can be measured by NMR. Specifically, for example, measurement can be performed using an ECP-300NMR manufactured by JEOL Corporation, dissolving organopolysiloxane B in deuterated chloroform as a deuterated solvent. The average number of hydrosilyl groups per molecule can be calculated by dividing the measurement result thus obtained by the average molecular weight of organopolysiloxane B.

[0058] The weight average molecular weight of the hydrosilyl-modified organopolysiloxane B is preferably 100 to 10,000, or may be 150 to 7,500, or 250 to 5,000. The hydrosilyl group equivalent of the hydrosilyl-modified organopolysiloxane B is preferably 1.0 to 10 mol / kg, or may be 1.2 to 8.0 mol / kg, or 1.5 to 6.0 mol / kg.

[0059] The content of organopolysiloxane B is preferably 0.5 to 30% by weight, 1.0 to 20% by weight, 3.0 to 15% by weight, or 5.0 to 10% by weight, based on the total of all components other than thermally conductive filler D. When the content of organopolysiloxane B is within the above range, the hysteresis loss of the thermally conductive spacer can be reduced, and the reliability of the thermally conductive spacer tends to be further improved.

[0060] 1.2.2. Surfactant C The surfactant C may be a component that improves the wettability of the thermally conductive filler D with the thermosetting resin. From the viewpoint of further improving the wettability of the thermally conductive filler, the surfactant preferably has at least one of an anionic group, a cationic group, and a group having a siloxane skeleton.

[0061] The anionic group is not particularly limited, but examples thereof include a carboxy group, a phosphate group, a phenolic hydroxy group, and a sulfonic acid group. Among these, the anionic group is preferably at least one selected from the group consisting of a carboxy group, a phosphate group, and a phenolic hydroxy group, and is preferably a carboxy group.

[0062] The cationic group is not particularly limited, but examples thereof include a primary amino group, a secondary amino group, a tertiary amino group, and a quaternary ammonium cationic group. Of these, the anionic group is preferably a tertiary amino group.

[0063] The group having a siloxane skeleton is not particularly limited, but examples thereof include groups having an organopolysiloxane skeleton, and among these, the group having a siloxane skeleton is preferably a group having a polydimethylsiloxane skeleton.

[0064] The weight-average molecular weight of the surfactant C is, for example, 20,000 to 150,000, 30,000 to 120,000, or 40,000 to 100,000. When the weight-average molecular weight of the surfactant is within the above range, the dispersibility of the thermally conductive filler D tends to be further improved.

[0065] The surfactant C may be a component that improves the wettability of the thermally conductive filler D with the vinyl-modified organopolysiloxane A and / or the hydrosilyl-modified organopolysiloxane B. From the viewpoint of further improving the wettability of the thermally conductive filler, the surfactant is preferably a copolymer having at least two of an anionic group, a cationic group, and a group having a siloxane skeleton.

[0066] The anionic group is not particularly limited, but examples thereof include a carboxy group, a phosphate group, a phenolic hydroxy group, and a sulfonic acid group. Among these, the anionic group is preferably at least one selected from the group consisting of a carboxy group, a phosphate group, and a phenolic hydroxy group, and is preferably a carboxy group.

[0067] The cationic group is not particularly limited, but examples thereof include a primary amino group, a secondary amino group, a tertiary amino group, and a quaternary ammonium cationic group. Of these, the anionic group is preferably a tertiary amino group.

[0068] The group having a siloxane skeleton is not particularly limited, and examples thereof include groups consisting of an organopolysiloxane skeleton. Among these, the group having a siloxane skeleton is preferably a group consisting of a polydimethylsiloxane skeleton. Examples of the siloxane skeleton include organopolysiloxane skeletons such as dialkylpolysiloxane, diphenylpolysiloxane, and alkylphenylpolysiloxane. The alkyl group contained in the siloxane skeleton is not particularly limited, and examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. The phenyl group contained in the siloxane skeleton is not particularly limited, and examples thereof include a phenyl group and a benzyl group.

[0069] The surfactant C is, for example, a copolymer having a (meth)acrylic monomer unit α (monomer unit α) having a carboxy group, a (meth)acrylic monomer unit β (monomer unit β) having a tertiary amino group, and a (meth)acrylic monomer unit γ (monomer unit γ) having a siloxane skeleton. The use of such a copolymer tends to improve the dispersibility of the thermally conductive filler D and reduce the viscosity of the first and second agents. Note that "monomer" refers to a monomer having a polymerizable unsaturated bond before polymerization, and "monomer unit" refers to a repeating unit that constitutes part of the copolymer after polymerization and is derived from a specific monomer. Furthermore, (meth)acrylic includes acrylic and methacrylic, and (meth)acrylic monomers include (meth)acrylate and (meth)acrylamide.

[0070] In the copolymer, the monomer units α, β, and γ may be contained randomly or in blocks. In the surfactant, it is preferred that at least the monomer units α and γ are contained as a random copolymer. When the monomer units α and γ are contained as a random copolymer, the viscosity of the first agent tends to be further reduced.

[0071] The monomer unit α is not particularly limited, but examples thereof include acrylic acid, methacrylic acid, 2-acryloyloxyethyl succinic acid, 2-methacryloyloxyethyl succinic acid, etc. Among these, acrylic acid and 2-methacryloyloxyethyl succinic acid are preferred, and acrylic acid is more preferred. The monomer unit α may be used alone or in combination of two or more types.

[0072] The content of the monomer unit α is, for example, 0.05 to 20 parts by weight, preferably 0.08 to 6.0 parts by weight, 0.1 to 5.0 parts by weight, 0.3 to 4.0 parts by weight, or 0.5 to 3.0 parts by weight, relative to 100 parts by weight of the total of the monomer units α, β, and γ. Within the above range, the content of the monomer unit α may be 0.7 parts by weight or more, or 2.0 parts by weight or less.

[0073] The monomer unit β is not particularly limited, but examples thereof include dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate. Among these, dimethylaminoethyl methacrylate and 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate are preferred, and 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate is more preferred. The monomer unit β may be used alone or in combination of two or more types.

[0074] The content of the monomer unit β is, for example, 0.02 to 4.0 parts by weight, preferably 0.05 to 4.0 parts by weight, 0.07 to 3.0 parts by weight, 0.8 to 2.0 parts by weight, or 0.1 to 1.0 part by weight, relative to 100 parts by weight of the total of the monomer units α, β, and γ. Within the above range, the content of the monomer unit β may be 0.3 part by weight or more, or 0.8 part by weight or less.

[0075] The number average molecular weight of the monomer unit γ is preferably 1,500 to 50,000, more preferably 3,000 to 30,000, and even more preferably 4,000 to 20,000.

[0076] The content of the monomer unit γ is, for example, 70.0 to 99.9 parts by weight, preferably 80.0 to 99.5 parts by weight, 90.0 to 99.0 parts by weight, 93.0 to 98.8 parts by weight, or 96.0 to 98.7 parts by weight, relative to 100 parts by weight of the total of the monomer units α, β, and γ.

[0077] The content of surfactant C is preferably 0.5 to 30% by weight, 1.0 to 20% by weight, 1.5 to 15% by weight, or 2.0 to 10% by weight, based on the total amount of components other than thermally conductive filler D. When the content of surfactant C is within the above range, the dispersibility of thermally conductive filler D tends to be further improved.

[0078] 1.2.3.Thermal Conductive Filler D The thermally conductive filler D is a filler having thermal conductivity. The thermal conductivity of the thermally conductive filler D is not particularly limited, but is, for example, 10 W / m·K or more. Examples of such thermally conductive fillers D are not particularly limited, but include aluminum oxide (hereinafter also referred to as "alumina"), aluminum nitride, silica (particularly crystalline silica), boron nitride, silicon nitride, silicon oxide, zinc oxide, aluminum hydroxide, metallic aluminum, magnesium oxide, diamond, carbon, indium, gallium, copper, silver, iron, nickel, gold, tin, metallic silicon, and the like.

[0079] The thermally conductive filler D preferably contains one or more selected from the group consisting of boron nitride, aluminum nitride, aluminum oxide, silicon nitride, silicon oxide, magnesium oxide, metallic aluminum, and zinc oxide, more preferably contains one or more selected from the group consisting of aluminum oxide, magnesium oxide, aluminum nitride, and metallic aluminum, and even more preferably contains aluminum oxide. This is because the thermally conductive filler has high thermal conductivity, high insulating properties, and is inexpensive. The thermally conductive filler D may be used alone or in combination of two or more.

[0080] The average particle size of the thermally conductive filler D is preferably 0.05 to 120 μm, more preferably 0.1 to 100 μm. When the average particle size of the thermally conductive filler D is within the above range, the dispersibility and filling property of the thermally conductive filler D tend to be further improved.

[0081] Furthermore, fillers with different average particle sizes may be mixed and used as the thermally conductive filler D. As the thermally conductive filler D, it is preferable to use a combination of two or more of the following: thermally conductive filler (D-1) having an average particle size of 30 to 100 μm, thermally conductive filler (D-2) having an average particle size of 10 to 25 μm, thermally conductive filler (D-3) having an average particle size of 1.2 to 8.0 μm, and thermally conductive filler (D-4) having an average particle size of 0.05 to 1.0 μm, and it is more preferable to use a combination of three or more or all of these.

[0082] The average particle size of thermally conductive fillers can be measured using, for example, a Shimadzu SALD-20 laser diffraction particle size analyzer. The evaluation sample is prepared by adding 50 ml of pure water and 5 g of the thermally conductive filler powder to a glass beaker, stirring with a spatula, and then dispersing in an ultrasonic cleaner for 10 minutes. The dispersed thermally conductive filler powder solution is then added dropwise to the sampler using a dropper. Measurements can be performed once the absorbance has stabilized. The laser diffraction particle size analyzer calculates the particle size distribution from the light intensity distribution data of the diffraction / scattering holes detected by the sensor. The average particle size is calculated by multiplying the measured particle size value by the relative particle amount (difference %) and dividing by the total relative particle amount (100%). The average particle size is the average diameter of the particles and can be calculated as the cumulative weight average D50 (median diameter).

[0083] In this case, the content of the thermally conductive filler (D-1) is preferably 30 to 70% by weight or 40 to 60% by weight based on the total amount of the thermally conductive filler D. The content of the thermally conductive filler (D-2) relative to the total amount of the thermally conductive filler D is preferably 0 to 30% by weight, 5 to 30% by weight, or 10 to 20% by weight. The content of the thermally conductive filler (D-3) is preferably 5 to 30% by weight or 10 to 20% by weight based on the total amount of the thermally conductive filler D. The content of the thermally conductive filler (D-4) is preferably 0 to 30% by weight, 5 to 30% by weight, or 8 to 15% by weight based on the total amount of the thermally conductive filler D. By using the thermally conductive filler D as described above, the dispersibility and packing property of the thermally conductive filler D tend to be further improved.

[0084] The content of the thermally conductive filler D is preferably 300 to 2500 parts by weight, 400 to 2000 parts by weight, or 500 to 1800 parts by weight per 100 parts by weight of the content of components other than the thermally conductive filler D. When the content of the thermally conductive filler D is within the above range, the thermal conductivity of the thermally conductive spacer tends to be further improved and the hysteresis loss tends to be reduced. As a result, the reliability of the thermally conductive spacer tends to be further improved.

[0085] 1.2.4.Curing catalyst E The curing catalyst E is not particularly limited as long as it catalyzes the curing reaction of the thermosetting resin. When the thermosetting resin contains a vinyl-modified organopolysiloxane A and a hydrosilyl-modified organopolysiloxane B, it is sufficient that it catalyzes the addition reaction between them. Examples of such curing catalysts E include platinum compound catalysts, rhodium compound catalysts, and palladium compound catalysts. Among these, platinum compound catalysts are preferred.

[0086] The platinum compound catalyst is not particularly limited, but examples thereof include simple platinum, platinum compounds, and platinum-supported inorganic powders. The platinum compound is not particularly limited, but examples thereof include chloroplatinic acid, platinum-olefin complexes, platinum-alcohol complexes, and platinum coordination compounds. The platinum-supported inorganic powder is not particularly limited, but examples thereof include platinum-supported alumina powder, platinum-supported silica powder, and platinum-supported carbon powder. The curing catalyst E may be used alone or in combination of two or more types.

[0087] The content of the curing catalyst E is preferably 0.05 to 10 parts by weight, 0.1 to 5.0 parts by weight, or 0.3 to 3.0 parts by weight, relative to 100 parts by weight of the content of the components other than the thermally conductive filler D.

[0088] 1.2.5.Other Ingredients In addition to the above components, the thermally conductive spacer may contain additives such as a cure retarder, a colorant, a silane coupling agent, a viscosity modifier, etc., as needed.

[0089] The curing retarder is not particularly limited as long as it is a component that retards the curing reaction of the thermosetting resin. For example, when the thermosetting resin contains a vinyl-modified organopolysiloxane A and a hydrosilyl-modified organopolysiloxane B, an alkenyl alcohol such as 1-ethynyl-1-cyclohexanol can be used as the curing retarder. When the thermally conductive spacer contains a curing retarder, the content of the curing retarder is preferably 0.001 to 1.0 part by weight, more preferably 0.01 to 0.1 part by weight, per 100 parts by weight of the content of the components other than the thermally conductive filler D.

[0090] Examples of the silane coupling agent include epoxy-based silane coupling agents such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and 3-glycidoxypropylmethyldimethoxysilane; (meth)acrylic acid-modified silane coupling agents such as 3-methacryloxypropylmethyldimethoxysilane and 3-methacryloxytrimethoxysilane; and amino-based silane coupling agents such as N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane.

[0091] Examples of viscosity modifiers include polysiloxanes other than vinyl-modified organopolysiloxane A and hydrosilyl-modified organopolysiloxane B, synthetic rubber latex, urethane resin, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, polyvinyl alcohol, polyethylene oxide, and dibenzylidene sorbitol.

[0092] When the thermally conductive spacer contains additives such as colorants, silane coupling agents, and viscosity modifiers, the content of the additives is, for example, 0.001 to 0.2 parts by weight per 100 parts by weight of the content of components other than the thermally conductive filler D.

[0093] 2.Applications The thermally conductive spacer of this embodiment can be suitably used as a thermally conductive heat dissipating material disposed between a heat generating body such as an electronic component and a heat dissipating body such as a heat sink.

[0094] Examples of electronic components include, but are not limited to, heat-generating electronic components such as motors, battery packs, circuit boards mounted on in-vehicle power supply systems, power transistors, microprocessors, etc. Examples of heat sinks include, but are not limited to, housings, particularly metal housings.

[0095] 3. Manufacturing method The thermally conductive spacer of this embodiment can be produced by curing a thermally conductive composition containing a thermosetting resin and a thermally conductive filler. The thermally conductive spacer of this embodiment may include, for example, a step of mixing the components to obtain a thermally conductive composition (hereinafter referred to as a "mixing step"), a step of applying the thermally conductive composition to a substrate (hereinafter referred to as an "application step"), and a step of curing the thermally conductive composition applied to the substrate (hereinafter referred to as a "curing step").

[0096] In the mixing step, the components including the thermosetting resin and the thermally conductive filler are mixed. For example, a mixer such as a roll mill, kneader, Banbury mixer, or line mixer is used for mixing. More specifically, for example, a universal mixer, a hybrid mixer, a Trimix (manufactured by Inoue Seisakusho), or a static mixer is used for kneading. In the mixing step, for example, the above components A to E are mixed with optional additives.

[0097] In the coating step, the thermally conductive composition obtained in the mixing step is coated onto a substrate and molded. The coating method is preferably a doctor blade method, but depending on the viscosity of the composition, extrusion, pressing, calendar roll, or other methods may also be used. Examples of substrates include metal plates and resin films such as PET films. Coating and molding are preferably performed so that the thickness of the thermally conductive spacer is 0.3 to 10 mm, or 0.5 to 5.0 mm.

[0098] In the curing step, the thermally conductive composition applied to the substrate is cured to form a thermally conductive spacer. The curing conditions may be adjusted depending on the type of thermosetting resin and the type of curing catalyst, but for example, the curing step may be a step of heating at 100 to 170°C for 5 to 60 minutes.

[0099] After the curing step, the cured thermally conductive composition may be used as a thermally conductive spacer as is. However, the manufacturing method of this embodiment preferably further includes a step of aging at a predetermined temperature after the curing step (hereinafter referred to as an "aging step"). By including the aging step, the physical properties of the thermally conductive spacer tend to be stabilized. As a result, the hysteresis loss tends to be further reduced, and the reliability of the thermally conductive spacer tends to be further improved.

[0100] The aging temperature in the aging step is preferably -10 to 20°C, -5 to 15°C, or 0 to 10°C. The aging time is preferably 5 to 80 hours, 10 to 50 hours, 12 to 48 hours, or 20 to 36 hours. Aging may be carried out in air or in an inert gas such as nitrogen or argon. Aging under such aging conditions tends to further reduce hysteresis loss and further improve the reliability of the thermally conductive spacer.

[0101] 4. Thermally conductive composition The thermally conductive composition of this embodiment is a composition for producing the thermally conductive spacer of this embodiment. As described in detail in the above section 3. Production method, the thermally conductive composition of this embodiment can be molded and cured to produce the thermally conductive spacer.

[0102] The thermally conductive composition of this embodiment may contain the above-mentioned components A to E in the above-mentioned amounts. The thermally conductive composition may further contain an additive such as a cure retarder in the above-mentioned amount. [Example]

[0103] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0104] 1. Manufacturing of thermally conductive spacers The components shown below were mixed according to the compounding ratio (parts by weight) shown in Table 1. The components were mixed using a hybrid mixer ARE-310 (trade name, manufactured by Thinky Corporation).

[0105] Vinyl-modified organopolysiloxane RH-Vi100E (manufactured by Runhe Chemical Industry Co., Ltd., trade name), organopolysiloxane modified with vinyl groups at both ends, average number of vinyl groups per molecule: 2, vinyl group equivalent: 0.39 mol / kg, weight-average molecular weight: 11,000

[0106] Hydrosilyl-modified organopolysiloxane RH-H33 (manufactured by Runhe Chemical Industry Co., Ltd., trade name), organopolysiloxane with trimethylsilyl end groups and hydrosilyl side chains, average number of hydrosilyl groups per molecule: 3 or more, hydrosilyl equivalent: 1.8 mol / kg, weight average molecular weight: 3000-4000

[0107] Surfactants Surfactants produced by the method described below

[0108] ·Curing catalyst Platinum complex polymethylvinylsiloxane solution (Blue Star Silicone, product name: Silicolyse Catalyst 12070)

[0109] ·Cure retarder PA90 (trade name, manufactured by Elkem), a mixture of 1-ethynyl-1-cyclohexanol, polyorganosiloxane, and filler (1-ethynyl-1-cyclohexanol concentration: 10% by mass)

[0110] Thermally conductive filler Denka Corporation, spherical alumina, average particle size: 90 μm, thermal conductivity 35 W / m·K DAW45S (product name, manufactured by Denka), spherical alumina, average particle size: 45 μm, thermal conductivity 35 W / m·K Denka Corporation, spherical alumina, average particle size: 20 μm, thermal conductivity 35 W / m·K DAW05 (product name, manufactured by Denka Co., Ltd.), spherical alumina, average particle size: 5 μm, thermal conductivity: 35 W / m·K AA-05 (product name, manufactured by Sumitomo Chemical Co., Ltd.), crystalline alumina, average particle size: 0.5 μm, thermal conductivity 35 W / m·K

[0111] Two-component addition-curing silicone SE1885 (product name, manufactured by Toray DOW Corning) (agents A and B), containing vinyl-modified organopolysiloxane and hydrosilyl-modified organopolysiloxane

[0112] The mixed composition was then applied to a PET film using a doctor blade. The amount of coating was adjusted so that the thickness of the cured thermally conductive spacer would be 1.0 mm. The composition was then cured by heating at 150°C for 60 minutes. In Example 3 and Comparative Example 2, the cured product obtained in the curing step was used as the thermally conductive spacer.

[0113] In Examples 1 and 2, the cured product obtained in the curing step was then further aged in the atmosphere at 5° C. for 24 hours to obtain a thermally conductive spacer.

[0114] In Comparative Example 1, a commercially available thermally conductive spacer (TGP8000, manufactured by Honeywell) was used.

[0115] The surfactant was synthesized as follows. First, 1.5 parts by weight of acrylic acid (manufactured by Toagosei Co., Ltd.), 0.5 parts by weight of 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate ("ADEKA STAB LA-82" manufactured by ADEKA Corporation), and 98.0 parts by weight of α-butyl-ω-(3-methacryloxypropyl)polydimethylsiloxane ("Silaplane FM-0725" manufactured by JNC Corporation, number average molecular weight 10,000) were added to an autoclave equipped with a stirrer. Next, 0.05 parts by weight of azobisisobutyronitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) was added as an initiator per 100 parts by weight of the total (meth)acrylic monomers, and 1,000 parts by weight of a mixed solution of toluene (special reagent grade) and isopropyl alcohol (special reagent grade) in a volume ratio of 7:3 was added as a solvent, and the atmosphere inside the autoclave was replaced with nitrogen. The autoclave was then heated in an oil bath at 65°C for 20 hours to carry out radical polymerization. After the polymerization was completed, the mixture was degassed under reduced pressure at 120°C for 1 hour to obtain a surfactant.

[0116] The polymerization rate relative to 100% of the monomer charge was analyzed by gas chromatography and found to be 98% or more. From this, it was estimated that the ratio of each monomer unit in the surfactant was approximately the same as the ratio of the monomer charge.

[0117] The weight-average molecular weight of the obtained surfactant was determined as a weight-average molecular weight converted into standard polystyrene using a GPC (gel permeation chromatography) method, and was found to be 85000. The measurement conditions were as follows: High-speed GPC equipment: Tosoh Corporation "HLC-8020" Columns: One Tosoh "TSK guardcolumn MP(xL)" 6.0 mm ID x 4.0 cm, and two Tosoh "TSK-GELMULTIPOREHXL-M" 7.8 mm ID x 30.0 cm (16,000 theoretical plates), for a total of three (total theoretical plate count: 32,000). Developing solvent: tetrahydrofuran Detector: RI (differential refractometer)

[0118] 2. Measurement and evaluation of physical properties (Measurement of storage modulus) Two 1.0 mm thick thermally conductive spacers were stacked and placed in a rheometer (Thermo Fisher Scientific, "MARS40"). The thermally conductive spacers were circular and 35 mm in diameter to match the plate shape of the rheometer. Dynamic viscoelasticity measurements were continuously performed while the sample was heat cycled under conditions of 0.5% strain and 1 Hz frequency, while being compressed 15% from the initial thickness (2.0 mm). The heat cycle began at room temperature, and the sample was heated to 150°C and then cooled to -20°C. The cycle was then repeated, with the temperature rising from -20°C to 150°C and then cooled from 150°C to -20°C. The heating rate was 5°C / min and the cooling rate was -5°C / min. The heat cycle was repeated seven times.

[0119] Table 1 shows the storage modulus G'up at 25°C during the heating process of the third cycle, the storage modulus G'down at 25°C during the heating process, and their ratio G'down / G'up, as well as the maximum storage modulus G'max during the heating process and the heating process of the third cycle.

[0120] (Asker C hardness measurement) The Asker C hardness was measured at 25°C in accordance with SRIS0101 using an "Asker Rubber Hardness Tester Type C" manufactured by Kobunshi Keiki Co., Ltd. Specifically, the thermally conductive spacer was punched out into 2 cm square pieces using a punching blade, and the Asker C hardness (Asker C Hardness 1) of 12 stacked pieces was measured. The results are shown in Table 1.

[0121] (Evaluation of thermal conductivity characteristics) Using a 1mm thick thermally conductive spacer cut into a 10mm x 10mm piece, thermal resistance was measured under a 30% compression condition using a resin material thermal resistance measuring device (manufactured by Hitachi Technology & Services Co., Ltd.) in accordance with ASTM D5470. Thermal resistance values ​​were measured for thermally conductive spacers of several thicknesses (1mm, 2mm), and the thickness vs. thermal resistance values ​​were plotted. The thermal conductivity was calculated from the slope of each point. The results are shown in Table 1.

[0122] The 1 mm thermally conductive spacer prepared using the above method was placed on a measurement jig with a smooth copper surface measuring 2 cm wide and 4 cm deep. It was then sandwiched between two jigs with copper surfaces of the same size, and any excess thermally conductive spacer was scraped off. The mixture was then adjusted to a width of 2 cm, a depth of 4 cm, and a thickness of 0.7 mm, and then screwed in place. After leaving this for one day, a heater was inserted into the top of the jig, and thermocouples were inserted into the top and bottom surfaces to measure the initial thermal resistance.

[0123] The cured product was subjected to a thermal shock test from -40°C to 150°C using a test jig, and the thermal resistance was then measured again. The holding time at -40°C and 150°C was 30 minutes, and the temperature increase and decrease from -40°C to 150°C and 150°C to -40°C were within 5 minutes. This test was carried out for 500 hours. Similar to the measurement of the initial value, a heater and thermocouple were inserted and the thermal resistance after the thermal shock test was measured. The increase (%) in thermal resistance before and after the heat cycle was calculated based on the thermal resistance before the heat cycle. The results are shown in Table 1. As shown in Table 1, all of the thermally conductive spacers of the examples maintained high thermal conductivity and were highly reliable, even when repeatedly exposed to high and low temperatures.

[0124] [Table 1]

Claims

1. a thermosetting resin and a thermally conductive filler; When a cycle of heating from -20°C to 150°C at a heating rate of 5°C / min and then cooling from 150°C to -20°C at a cooling rate of -5°C / min is repeated three times, the ratio G'down / G'up of the storage modulus at 25°C during the heating process of the third cycle to the storage modulus at 25°C during the cooling process is 3.0 or less. Thermally conductive spacer.

2. the maximum value G'max of the storage elastic modulus during the temperature increase process and the temperature decrease process of the third cycle is 50 to 700 kPa; The thermally conductive spacer according to claim 1 .

3. The thermal conductivity measured in accordance with ASTM D5470 is 2.5 W / m K or more. The thermally conductive spacer according to claim 1 .

4. When the cycle of increasing the temperature from -40°C to 150°C within 5 minutes, maintaining the temperature for 30 minutes, decreasing the temperature from 150°C to -40°C within 5 minutes, and maintaining the temperature for 30 minutes is repeated for 500 hours, the rate of increase in thermal resistance is 10% or less. The thermally conductive spacer according to claim 1 .

5. The thermosetting resin includes an addition-curing silicone resin. The thermally conductive spacer according to claim 1 .

6. Asker C hardness is 1 to 35. The thermally conductive spacer according to claim 1 .

7. For producing the thermally conductive spacer according to any one of claims 1 to 6, Thermally conductive compositions.

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