Thermally conductive molded body

Abstract

A thermally conductive molded body according to the present invention comprises a polymer matrix and a thermally conductive filler, and is characterized in that the relationship between the gel fraction a (mass%) of the thermally conductive molded body and the content b (vol%) of the polymer matrix satisfies both formula (1) and formula (2).　Formula (1): a>1.25×b-4.1 Formula (2): a<2.87×b-33 According to the present invention, it is possible to provide a thermally conductive molded body having excellent thermal conductivity and moldability.

Description

Thermally conductive molded body

[0001] The present invention relates to a thermally conductive molded article.

[0002] In electronic devices such as computers, automobile parts, and mobile phones, heat sinks and other heat dissipators are commonly used to dissipate heat generated by heat-generating elements such as semiconductor devices and mechanical parts. It is known that thermally conductive materials such as thermally conductive sheets and greases are placed between the heat generating elements and the heat dissipating elements to improve the efficiency of heat transfer to the heat dissipating elements.

[0003] Although some heat sinks and heating elements have flat surfaces, in recent years, as device structures have become more complex, many of them have shapes with unevenness or irregularities in some areas. Therefore, thermally conductive materials are required to be molded into three-dimensional shapes that can conform to the complex shapes of heat sinks and heating elements.

[0004] Patent Document 1 discloses an invention relating to a three-dimensional thermally conductive molded body that includes a thermally conductive material and a silicone-based material, and describes that the three-dimensional thermally conductive molded body can ensure sufficient gap filling and contact area without applying excessive stress to heat dissipation components such as heat sinks.

[0005] Patent Document 2 discloses an invention relating to a thermally conductive holder molded from a thermally conductive composition containing a silicone rubber material and a thermally conductive filler, which is capable of imparting excellent thermal conductivity and is easy to install. The thermally conductive composition contains 40 to 70 volume % of the thermally conductive filler relative to the total volume of the silicone rubber material and the thermally conductive filler, and 35 to 100 volume % of magnesium oxide with an average particle size of 5 μm or less relative to the total volume of the thermally conductive filler. The thermally conductive composition has a hardness (Type A durometer) of 20 to 70 after curing.

[0006] Japanese Patent No. 7053484 Japanese Patent Laid-Open No. 2005-56837

[0007] Thermally conductive molded articles having a three-dimensional shape require high thermal conductivity and excellent moldability. That is, when molding a thermally conductive molded article using a mold or the like, the desired three-dimensional shape may not be obtained due to breakage or partial residue remaining in the mold during production, and this needs to be prevented. Techniques for imparting excellent thermal conductivity include increasing the amount of thermally conductive filler and improving the gap filling and contact area with the heating element. However, increasing the amount of thermally conductive filler reduces the crosslink density within the molded article, making it brittle and resulting in poor moldability. Furthermore, flexibility is necessary for improving gap filling and contact area, but if the molded article is too flexible, it becomes difficult to maintain its shape and handleability deteriorates. Thus, improved thermal conductivity and moldability generally have a trade-off relationship. The thermally conductive molded articles described in Patent Documents 1 and 2 above left room for improvement in terms of achieving both excellent moldability and thermal conductivity when molded from a thermally conductive composition.

[0008] The present invention has been made in view of the above points, and an object of the present invention is to provide a thermally conductive molded article having excellent thermal conductivity, which is molded from a thermally conductive composition having excellent moldability.

[0009] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by providing a thermally conductive molded body containing a polymer matrix and a thermally conductive filler, where the gel fraction a of the thermally conductive molded body and the content b of the polymer matrix satisfy a predetermined relationship, and have completed the present invention. The present invention provides the following [1] to

[10] .

[0010] [1] A thermally conductive molded body comprising a polymer matrix and a thermally conductive filler, wherein the relationship between the gel fraction a (mass%) of the thermally conductive molded body and the content b (volume%) of the polymer matrix satisfies both of the following formulas (1) and (2): a > 1.25 × b - 4.1 Formula (1) a < 2.87 × b - 33 Formula (2) (Method for measuring gel fraction) (1) Approximately 2 g of the thermally conductive molded body is immersed in 40 g of an organic solvent capable of dissolving resin components other than the gel fraction for one day, and then the organic solvent-insoluble portion of the thermally conductive molded body is collected and dried, and the gel fraction is calculated using the following formula (3): Gel fraction = 100 × X / Y Equation (3) In equation (3), X = (dry mass of organic solvent insoluble matter - (mass of thermally conductive molded body before immersion × (1 - ratio of polymer matrix mass when the mass of the thermally conductive molded body is set to 1))) Y = (mass of thermally conductive molded body before immersion × ratio of polymer matrix mass when the mass of the thermally conductive molded body is set to 1) [2] A thermally conductive molded body comprising a polymer matrix and a thermally conductive filler, wherein the relationship between the gel fraction a (mass %) of the thermally conductive molded body and the content b (volume %) of the polymer matrix satisfies both of the following equations (1) and (2-2): a>1.25×b-4.1 Equation (1) a<4.50×b-97 Equation (2-2) (Method for Measuring Gel Fraction) (1) Approximately 2 g of a thermally conductive molded body is immersed in 40 g of an organic solvent capable of dissolving resin components other than the gel fraction for one day, and then the organic solvent-insoluble portion of the thermally conductive molded body is collected and dried, and the gel fraction is calculated using the following equation (3). Gel fraction = 100 x X / Y Equation (3) In equation (3), X = (dry mass of organic solvent insoluble matter - (mass of thermally conductive molded body before immersion x (1 - ratio of polymer matrix mass when the mass of the thermally conductive molded body is set to 1))) Y = (mass of thermally conductive molded body before immersion x ratio of polymer matrix mass when the mass of the thermally conductive molded body is set to 1) [3] The thermally conductive molded body according to [1] or [2] above, wherein the thermally conductive molded body has a three-dimensional surface having a surface area of ​​1.46 x A or more relative to a projected area A in at least one direction. [4] The thermally conductive molded body according to any of [1] to [3] above, wherein the polymer matrix content is 17.5 to 50% by volume.[5] The thermally conductive molded article according to any one of [1] to [4] above, wherein the content of the thermally conductive filler is 50 to 82.5% by volume. [6] The thermally conductive molded article according to any one of [1] to [5] above, wherein the polymer matrix is ​​a cured product of an organopolysiloxane. [7] The thermally conductive molded article according to any one of [1] to [6] above, wherein the polymer matrix is ​​a cured product of an addition reaction type organopolysiloxane. [8] The thermally conductive molded article according to any one of [1] to [7] above, wherein the thermally conductive filler comprises at least one selected from the group consisting of aluminum oxide and aluminum hydroxide. [9] The thermally conductive molded article according to any one of [1] to [8] above, wherein the E hardness is 3 to 90.

[10] The thermally conductive molded article according to any one of [1] to [9] above, wherein the thermal conductivity is 1 W / mK or more.

[0011] According to the present invention, it is possible to provide a thermally conductive molded article having excellent thermal conductivity and moldability.

[0012] 1 is a diagram showing the relationship between formula (1) and formula (2), FIG. 2 is a diagram showing the relationship between formula (1) and formula (2-2), and FIG. 3 is a diagram explaining formability evaluation.

[0013] [Thermal conductive molded body] The thermal conductive molded body of the present invention comprises a polymer matrix and a thermal conductive filler, and the relationship between the gel fraction a of the thermal conductive molded body and the content b of the polymer matrix satisfies both of the following formulas (1) and (2): a > 1.25 × b - 4.1 formula (1) a < 2.87 × b - 33 formula (2) Note that the unit of the gel fraction a is mass %, and the unit of the content b of the polymer matrix is ​​volume %.

[0014] If one or both of the above formulas (1) and (2) are not satisfied, moldability will be poor when the thermally conductive composition is molded into a three-dimensional shape using a mold or the like to form a thermally conductive molded body. The inventors have found, through numerous experiments, that satisfying both the above formulas (1) and (2) improves moldability. When the gel fraction is small and formulas (1) and (2) are not satisfied, the crosslinking of the polymer matrix becomes sparse, making it difficult to maintain the shape while retaining the thermally conductive filler, and thus reducing moldability. On the other hand, when the gel fraction is large and formulas (1) and (2) are not satisfied, although the crosslinking density of the polymer matrix is ​​dense, a large amount of thermally conductive filler is added in order to improve thermal conductivity. This results in poor toughness, making the molded body more likely to chip when demolded, and reducing moldability.

[0015] FIG. 1 illustrates the case where both formula (1) and formula (2) are satisfied. That is, by adjusting the polymer matrix content b and gel fraction a to fall within the region between the lines a = 1.25 × b - 4.1 and a = 2.87 × b - 33 (the region indicated by the vertical arrows in FIG. 1), moldability is improved. The polymer matrix content b at the intersection of formula (1) and formula (2) is approximately 17.8% by volume. Therefore, in order to satisfy both formula (1) and formula (2), the polymer matrix content must be 17.8% by volume or more.

[0016] As can be seen from FIG. 1 , the higher the polymer matrix content, the wider the gel fraction range required to obtain a thermally conductive molded body with good moldability. That is, when the polymer matrix content is high, the gel fraction range can be widened, allowing for greater design freedom. On the other hand, when the polymer matrix content is low, the gel fraction range required to obtain a thermally conductive molded body with good moldability is narrowed. That is, when the polymer matrix content is low, the gel fraction range required to obtain a thermally conductive molded body with good moldability is narrowed, and the gel fraction must be carefully adjusted. From the perspective of obtaining a thermally conductive molded body with excellent thermal conductivity, it is preferable to lower the polymer matrix content (i.e., increase the content of the thermally conductive filler). By applying the present invention, even in a region with a low polymer matrix content where it is generally difficult to achieve good moldability, a thermally conductive molded body with excellent moldability can be obtained by setting the gel fraction within a predetermined range.

[0017] From this viewpoint, it is preferable that the formulas (1) and (2) are satisfied when the polymer matrix content is in the range of 17.5 vol% to 50 vol%, more preferably in the range of 20 vol% to 50 vol%, and even more preferably in the range of 30 vol% to 40 vol%.

[0018] A thermally conductive molded body according to another aspect of the present invention includes a polymer matrix and a thermally conductive filler, and the relationship between the gel fraction a of the thermally conductive molded body and the content b of the polymer matrix satisfies both of the following formulas (1) and (2-2): a>1.25×b-4.1 formula (1) a<4.50×b-97 formula (2-2) Note that the unit of the gel fraction a is mass%, and the unit of the content b of the polymer matrix is ​​volume%.

[0019] When both of the above formulas (1) and (2-2) are satisfied, the thermally conductive composition exhibits good moldability when it is molded into a three-dimensional shape into a thermally conductive molded article using a mold, etc. As a result of numerous experiments, the present inventors have found that satisfying both of the above formulas (1) and (2-2) results in good moldability.

[0020] FIG. 2 illustrates the case where both formula (1) and formula (2-2) are satisfied. That is, by adjusting the polymer matrix content b and gel fraction a to fall within the region between the lines a = 1.25 × b - 4.1 and a = 4.50 × b - 97 (the region indicated by the vertical arrows in FIG. 2), moldability is improved. The polymer matrix content b at the intersection of formula (1) and formula (2-2) is approximately 28.6% by volume. Therefore, in order to satisfy both formula (1) and formula (2-2), the polymer matrix content must be 28.6% by volume or more.

[0021] As can be seen from Figure 2, the higher the polymer matrix content, the wider the gel fraction range required to obtain a thermally conductive molded body with good moldability. That is, when the polymer matrix content is high, the gel fraction range can be widened, allowing for greater design freedom. On the other hand, when the polymer matrix content is low, the gel fraction range required to obtain a thermally conductive molded body with good moldability becomes narrower. That is, when the polymer matrix content is low, the gel fraction range required to obtain a thermally conductive molded body with good moldability is narrower, and the gel fraction must be carefully adjusted.

[0022] From the viewpoint of obtaining a thermally conductive molded body with excellent thermal conductivity, it is preferable to reduce the polymer matrix content (i.e., increase the content of the thermally conductive filler). By applying the present invention, even in a region where the polymer matrix content is low, where it is generally difficult to improve moldability, it is possible to obtain a thermally conductive molded body with excellent moldability by setting the gel fraction within a predetermined range.

[0023] From this viewpoint, the content of the polymer matrix in the thermally conductive molded body is preferably 17.5% by volume or more and 50% by volume or less, more preferably 20% by volume or more and 50% by volume or less, even more preferably 30% by volume or more and 40% by volume or less, and even more preferably 30% by volume or more and 35% by volume or less, when the thermally conductive molded body is taken as 100% by volume.

[0024] Furthermore, the content of the thermally conductive filler in the thermally conductive molded body is preferably 50% by volume or more and 82.5% by volume or less, and more preferably 50% by volume or more and 70% by volume or less, when the thermally conductive molded body is taken as 100% by volume. When the content of the thermally conductive filler is 50% by volume or more, a certain level of thermal conductivity can be imparted to the thermally conductive molded body. By setting the content of the thermally conductive filler to 70% by volume or less, the thermally conductive filler can be properly dispersed in the polymer matrix. Furthermore, it is possible to prevent the viscosity of the thermally conductive composition from becoming unnecessarily high. The volume-based content of the thermally conductive filler is more preferably 60% by volume or more and 70% by volume or less, and even more preferably 65% ​​by volume or more and 70% by volume or less.

[0025] The gel fraction of the thermally conductive molded body can be adjusted by adjusting the content of the polymer matrix, the crosslink density of the polymer matrix, and the like. For example, increasing the content of the polymer matrix can increase the gel fraction. Furthermore, increasing the crosslink density of the polymer matrix can increase the gel fraction. When the polymer matrix is ​​a cured product of an addition reaction type organopolysiloxane, the gel fraction can be adjusted by adjusting the ratio (H / Vi) of the base agent and curing agent of the addition reaction type organopolysiloxane. For example, the gel fraction can be increased by bringing H / Vi closer to 1. The gel fraction can also be adjusted by the type of thermally conductive filler, for example, by the type (chain length, etc.) of the surface treatment agent used to surface treat the thermally conductive filler.

[0026] The gel fraction of the thermally conductive molded body is not particularly limited as long as it is within a range that satisfies the above formulas (1) and (2), but is, for example, 35 to 85% by mass, and preferably 40 to 70% by mass.

[0027] The gel fraction is measured by the following method. (Method of Measuring Gel Fraction) Approximately 2 g of a thermally conductive molded body is immersed for one day in 40 g of an organic solvent capable of dissolving resin components other than the gel fraction, and then the organic solvent-insoluble portion of the thermally conductive molded body is collected and dried, and the gel fraction is calculated using the following formula (3): Gel fraction = 100 x X / Y Formula (3) In formula (3), X = (dry mass of organic solvent-insoluble portion - (mass of thermally conductive molded body before immersion x (1 - ratio of polymer matrix mass when the mass of the thermally conductive molded body is taken as 1))) Y = (mass of thermally conductive molded body before immersion x ratio of polymer matrix mass when the mass of the thermally conductive molded body is taken as 1)

[0028] X corresponds to the mass obtained by subtracting the mass of the thermally conductive filler contained in the organic solvent insoluble matter from the dry mass of the organic solvent insoluble matter, and Y corresponds to the mass of the polymer matrix in the thermally conductive molded body before immersion.

[0029] The organic solvent is not particularly limited as long as it can dissolve resin components other than the gel component, but when the polymer matrix of the thermally conductive molded body is a silicone matrix, toluene is preferably used.

[0030] <Three-dimensional shape> The thermally conductive molded article of the present invention may be in the form of a sheet or plate, but preferably has a three-dimensional shape. That is, in order to improve the ability of the thermally conductive molded article of the present invention to conform to a heat generating body or a heat dissipating body having a complex shape, it is preferable that the thermally conductive molded article of the present invention is not in the form of a sheet or plate with a flat surface, but for example, in the case of a plate-shaped molded article, one or both surfaces are formed with steps, protrusions, irregularities, grooves, etc., to have a non-flat shape.

[0031] The thermally conductive molded article of the present invention preferably has a three-dimensional surface whose surface area in at least one direction is preferably 1.20 A or more, more preferably 1.46 A or more, and even more preferably 2.10 A or more, where A is the projected area observed in at least one direction. In the present invention, by satisfying the above-mentioned formulas (1) and (2), the thermally conductive molded article having the above-mentioned three-dimensional surface can be formed with good moldability.

[0032] <Polymer Matrix> The polymer matrix is ​​a polymer compound such as elastomer or rubber, and is preferably formed by curing a liquid resin component consisting of a mixture of a base resin and a curing agent. The resin component may be, for example, a mixture of uncrosslinked rubber and a crosslinking agent, or a mixture of a monomer, prepolymer, etc. and a curing agent. The curing reaction may be room temperature curing or heat curing. Examples of polymer matrices that can be used include silicone matrices, epoxy matrices, urethane matrices, phenol matrices, unsaturated polyester matrices, polyimide matrices, acrylic matrices, polyamide matrices, polyether matrices, polybutadiene matrices, polyisopropylene matrices, polyisobutylene matrices, ethylene-propylene-diene matrices, natural rubber matrices, silyl-modified polyether matrices, and combinations thereof. Among polymer matrices, silicone matrices are particularly preferred.

[0033] In the thermally conductive molded body, when the polymer matrix is ​​a silicone matrix, the silicone matrix is ​​preferably a cured product of an organopolysiloxane, and is preferably formed from a resin component containing the organopolysiloxane. Furthermore, the thermally conductive molded body is preferably formed from a thermally conductive composition containing the resin component and a thermally conductive filler. The resin component preferably contains an organopolysiloxane.

[0034] The polymer matrix is ​​preferably a cured product of an addition reaction type organopolysiloxane. The addition reaction type organopolysiloxane preferably contains an alkenyl group-containing organopolysiloxane and a hydrosilyl group-containing organopolysiloxane. Furthermore, the thermally conductive molded article may contain a thermally conductive filler and other components (such as additives) in addition to the silicone matrix, as described in the thermally conductive composition described below.

[0035] The alkenyl group-containing organopolysiloxane is an organopolysiloxane having an alkenyl group, and the alkenyl group may be present in a side chain, at a terminal, or at both a side chain and a terminal. The alkenyl group-containing organopolysiloxane may be used alone or in combination of two or more. When an organopolysiloxane having an alkenyl group in a side chain (side-chain alkenyl group-containing organopolysiloxane) is used, the gel fraction is more likely to be increased even when the ratio (H / Vi) of hydrosilyl groups contained in the resin component to alkenyl groups contained in the resin component is the same.

[0036] When an organopolysiloxane containing side chain alkenyl groups is used, the crosslinking points in the formed polymer matrix approach a state in which they are uniformly dispersed, and the molecular weight of the crosslinking points becomes relatively large, thereby suppressing local increases in hardness and imparting flexibility to the crosslinking points, which was difficult to achieve with conventional structures. The organopolysiloxane containing side chain alkenyl groups may be linear or branched, or may be a mixture of linear and branched groups, but linear groups are preferred. The alkenyl groups contained in the side chains mean that they are contained at positions other than the ends of the molecular chains of the polysiloxane structure. Furthermore, the organopolysiloxane containing side chain alkenyl groups may have alkenyl groups at the ends in addition to the side chains, but it is preferred that the alkenyl groups be contained only in the side chains.

[0037] The side-chain alkenyl group-containing organopolysiloxane is preferably liquid at 25°C. The viscosity of the side-chain alkenyl group-containing organopolysiloxane at 25°C is preferably 50,000 mPas or less, more preferably 10,000 mPas or less, and even more preferably 3,000 mPas or less. By setting the viscosity of the side-chain alkenyl group-containing organopolysiloxane to the upper limit or less, it is possible to prevent a decrease in reactivity and a high viscosity of the thermally conductive composition. Furthermore, the viscosity of the side-chain alkenyl group-containing organopolysiloxane at 25°C is preferably 50 mPas or more, more preferably 100 mPas or more, and even more preferably 200 mPas or more. By setting the viscosity of the side-chain alkenyl group-containing organopolysiloxane to the above-mentioned lower limit or more, it is possible to prevent an increase in crosslink density and to easily reduce the hardness after curing. In addition, it prevents the reactivity from becoming too rapid, making it easier for the addition reaction to proceed appropriately. The viscosity is measured using a Brookfield B-type viscometer in accordance with JIS K7117-1. The spindle in the Brookfield B-type viscometer should be appropriately selected so that the torque is 10 to 80%.

[0038] The alkenyl group-containing organopolysiloxane may have one or more alkenyl groups, but preferably has two or more alkenyl groups. As described below, the weight average molecular weight (g / mol) is Mw, and the alkenyl group concentration (μmol / g) is C. The average number of alkenyl groups per molecule is Mw×C×10 －６ It can be calculated by the formula: The average value of the number of alkenyl groups calculated in this way is preferably 2 or more, more preferably 2.2 or more, and even more preferably 2.4 or more. By making the average number of alkenyl groups 2 or more, a crosslinked structure can be appropriately introduced, and it becomes easier to further reduce compression set while maintaining good hardness, thermal conductivity, etc. Furthermore, the average value of the number of alkenyl groups may be, for example, 5 or less, but is preferably 4 or less, more preferably 3.5 or less, and even more preferably 3 or less.

[0039] The weight-average molecular weight (Mw) of the alkenyl group-containing organopolysiloxane is preferably 5,000 to 100,000, more preferably 10,000 to 50,000, and even more preferably 15,000 to 35,000. By setting the weight-average molecular weight of the alkenyl group-containing organopolysiloxane to the upper limit or less, it is possible to prevent a decrease in reactivity and a high viscosity of the thermally conductive composition. Furthermore, by setting the weight-average molecular weight of the alkenyl group-containing organopolysiloxane to the lower limit or more, it is possible to prevent an increase in crosslink density and ensure flexibility after curing. Furthermore, it is possible to prevent excessively rapid reactivity and facilitate the appropriate progression of the addition reaction. The weight-average molecular weight can be measured by gel permeation chromatography (GPC).

[0040] The functional group concentration of the alkenyl group-containing organopolysiloxane is preferably 1 μmol / g or more and 5000 μmol / g or less. When the functional group concentration is 1 μmol / g or more, the amount of alkenyl groups is at least a certain level, allowing for the formation of an appropriate crosslinked structure. On the other hand, when the functional group concentration is 5000 μmol / g or less, an increase in crosslink density is prevented, making it easier to ensure flexibility after curing. The functional group concentration of the alkenyl group-containing organopolysiloxane is more preferably 20 μmol / g or more and 1000 μmol / g or less, and even more preferably 50 μmol / g or more and 400 μmol / g or less. The functional group concentration (μmol / g) refers to the concentration of alkenyl groups in the alkenyl group-containing organopolysiloxane, and is typically the vinyl group concentration. The functional group concentration can be a value calculated from the integral ratio of 1H-NMR spectra measured using an NMR measurement device.

[0041] The alkenyl group in the alkenyl group-containing organopolysiloxane is not particularly limited, but examples include those having 2 to 8 carbon atoms, such as vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, and octenyl. Of these, vinyl is preferred from the standpoints of ease of synthesis and reactivity. The double bond in the alkenyl group may be provided at the terminal of the alkenyl group. The alkenyl group may be an alkenyl group directly bonded to a silicon atom. Examples of residual groups bonded to silicon atoms other than the alkenyl group include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl; aryl groups such as phenyl; and aralkyl groups such as 2-phenylethyl and 2-phenylpropyl. Specific examples also include substituted hydrocarbon groups such as chloromethyl and 3,3,3-trifluoropropyl. Of these, hydrocarbon groups are preferred, with methyl being more preferred from the standpoint of ease of synthesis. Of the remaining groups bonded to silicon atoms, preferably 80 mol % or more are methyl groups, more preferably 90 mol % or more are methyl groups, and even more preferably 100 mol % are methyl groups. Note that the alkenyl group-containing organopolysiloxane preferably does not have hydrogen atoms as residual groups bonded to silicon atoms, i.e., the alkenyl group-containing organopolysiloxane preferably does not contain hydrosilyl groups.

[0042] The content of the alkenyl group-containing organopolysiloxane is not particularly limited and may be appropriately selected so that the H / Vi ratio described below can be adjusted within the desired range. However, the content is preferably 25% by mass or more and 95% by mass or less, and more preferably 30% by mass or more and 90% by mass or less, based on the total amount of organopolysiloxane contained in the thermally conductive composition for forming the thermally conductive molded body.

[0043] (Hydrosilyl Group-Containing Organopolysiloxane) As described above, the resin component contains a hydrosilyl group-containing organopolysiloxane. By containing the hydrosilyl group-containing organopolysiloxane, the thermally conductive composition undergoes an addition reaction between the hydrosilyl group-containing organopolysiloxane and the alkenyl group-containing organopolysiloxane to extend the chain, thereby forming a cured product with appropriate hardness. It is preferable that the hydrosilyl group-containing organopolysiloxane has at least two or more functional hydrosilyl groups. By containing two or more functional hydrosilyl groups, the thermally conductive composition can be appropriately cured and a crosslinked structure can be introduced into the cured product.

[0044] The hydrosilyl group-containing organopolysiloxane may be linear or branched, may contain a cyclic structure, or may be a mixture of two or more of these, but preferably contains a linear hydrosilyl group-containing organopolysiloxane. The linear or branched hydrosilyl group-containing organopolysiloxane may contain hydrosilyl groups at either the terminal or side chain of the molecular chain of the polysiloxane structure, or may contain hydrosilyl groups at both the terminal and side chain, but preferably contains hydrosilyl groups at at least the terminal, and more preferably contains two hydrosilyl groups at each of the terminals of the molecular chain of the polysiloxane structure. The number of functional groups (the number of hydrosilyl groups per molecule) of the linear or branched hydrosilyl group-containing organopolysiloxane is preferably 2 to 25, more preferably 3 to 20. The hydrosilyl group-containing organopolysiloxane should be liquid at 25°C.

[0045] The hydrosilyl group-containing organopolysiloxane may contain a hydrosilyl group-containing organopolysiloxane having a cyclic structure, but the content thereof may be small, for example, from 0.01% by mass to 1% by mass, preferably from 0.03% by mass to 0.5% by mass in the resin component. However, the hydrosilyl group-containing organopolysiloxane having a cyclic structure should have a high functional group concentration (i.e., hydrosilyl group concentration). Specifically, it is sufficient to use one having a functional group concentration of about 1000 μmol / g to 20000 μmol / g, preferably from 2000 μmol / g to 10000 μmol / g.

[0046] In the hydrosilyl group-containing organopolysiloxane, examples of residual groups bonded to silicon atoms other than hydrosilyl groups include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl; aryl groups such as phenyl; and aralkyl groups such as 2-phenylethyl and 2-phenylpropyl. Specific examples also include substituted hydrocarbon groups such as chloromethyl and 3,3,3-trifluoropropyl. Of these, methyl groups are preferred from the standpoint of ease of synthesis. Furthermore, of the residual groups bonded to silicon atoms, preferably 80 mol % or more are methyl groups, more preferably 90 mol % or more are methyl groups, and even more preferably 100 mol % are methyl groups. It is preferable that the hydrosilyl group-containing organopolysiloxane does not have alkenyl groups as residual groups bonded to silicon atoms; that is, the hydrosilyl group-containing organopolysiloxane does not contain alkenyl groups. The hydrosilyl group-containing organopolysiloxanes may be used alone or in combination of two or more.

[0047] The weight-average molecular weight (Mw) of the hydrosilyl group-containing organopolysiloxane is preferably 3,000 to 50,000, more preferably 5,000 to 20,000, and even more preferably 10,000 to 15,000. By setting the weight-average molecular weight of the hydrosilyl group-containing organopolysiloxane to the upper limit or less, it is possible to prevent a decrease in reactivity and a high viscosity of the thermally conductive composition. Furthermore, by setting the weight-average molecular weight of the hydrosilyl group-containing organopolysiloxane to the lower limit or more, it is possible to prevent an increase in crosslink density and ensure flexibility after curing.

[0048] The content of the hydrosilyl group-containing organopolysiloxane is not particularly limited and may be appropriately selected so that, for example, the H / Vi ratio described below can be adjusted to fall within a desired range. However, the content is preferably from 4 to 74% by mass, more preferably from 9 to 69% by mass, based on the total amount of organopolysiloxane contained in the thermally conductive composition.

[0049] The content of the alkenyl group-containing organopolysiloxane and the content of the hydrosilyl group-containing organopolysiloxane are such that the ratio (H / Vi) of the hydrosilyl groups contained in the resin component to the alkenyl groups contained in the resin component is, on a molar basis, preferably 0.3 to 1.5, more preferably 0.4 to 1.0. Adjusting the content within such a range makes it easier to satisfy formulas (1) and (2), thereby making it easier to obtain a thermally conductive molded article with excellent moldability. H / Vi can be calculated from the hydrosilyl group concentration, alkenyl group concentration, and content of each component of each component. The hydrosilyl group concentration and alkenyl group concentration of each component can be calculated from the integral ratio of 1H-NMR spectra measured using an NMR measurement device.

[0050] (Other Resin Components) The thermally conductive composition may contain organopolysiloxanes other than hydrosilyl group-containing organopolysiloxanes and alkenyl group-containing organopolysiloxanes (also referred to as other organopolysiloxanes). Specific examples include silicone oils, organopolysiloxanes having at least one alkoxy group (alkoxy group-containing organopolysiloxanes), organopolysiloxanes having at least one hydroxyl group (hydroxyl group-containing organopolysiloxanes), and organopolysiloxanes having a group with an aromatic structure such as pyrene or perylene, preferably a polycyclic aromatic structure (aromatic group-containing organopolysiloxane).

[0051] Examples of silicone oils include straight silicone oils such as dimethyl silicone oil and phenylmethyl silicone oil, as well as non-reactive modified silicone oils in which a non-reactive organic group is introduced into a main chain having a polysiloxane structure, a side chain bonded to the main chain, or the end of the main chain.The non-reactive organic group is an organic group that does not have an addition reaction group.Examples of non-reactive modified silicone oils include polyether-modified silicone oil, aralkyl-modified silicone oil, fluoroalkyl-modified silicone oil, long-chain alkyl-modified silicone oil, higher fatty acid ester-modified silicone oil, higher fatty acid amide-modified silicone oil, and phenyl-modified silicone oil.Among the above, straight silicone oil is preferred as the silicone oil, and among straight silicone oils, dimethyl silicone oil is more preferred.The silicone oil may be used alone or in combination of two or more.

[0052] The alkoxy group-containing organopolysiloxane may be linear or branched, or may be a mixture of linear and branched, but is preferably linear. Furthermore, the alkoxy group-containing organopolysiloxane may be an organopolysiloxane having at least one alkoxy group, but an organopolysiloxane having at least one alkoxy group at the molecular chain terminal of the polysiloxane structure is preferred, and an organopolysiloxane having at least one alkoxy group at only one terminal is more preferred. The alkoxy group-containing organopolysiloxane, having an alkoxy group, particularly an alkoxy group at the terminal, is likely to react or interact with functional groups present on the surface of the thermally conductive filler, and the polysiloxane structure, combined with the fact that it reduces the friction of the filler, making it easier to reduce the viscosity of the thermally conductive composition.

[0053] The alkoxy group-containing organopolysiloxane preferably has a group represented by the following formula (4), and the group represented by formula (4) is preferably bonded to Si constituting the polysiloxane structure via a linking group: —SiR １ ａ (OR ２ ３－ａ ) (4) (Note that in formula (4), R １ , R ２ are each independently a hydrocarbon group, preferably an alkyl group. １ , R ２ The number of carbon atoms in R is, for example, 1 to 8, preferably 1 to 4, and more preferably 1 or 2. １ , R ２Preferred specific examples of the formula (4) are a methyl group and an ethyl group. a is an integer of 0 to 2, preferably 0 or 1, and more preferably 0. The linking group connecting the group represented by formula (4) to Si is either an oxygen atom, a divalent hydrocarbon group, or an ester structure, with a divalent hydrocarbon group being preferred. Examples of divalent hydrocarbon groups include those having approximately 1 to 8 carbon atoms, such as a methylene group, an ethylene group, a propylene group, a butylene group, and a methylethylene group, with an ethylene group being preferred. The alkoxy-containing organopolysiloxane has a siloxane skeleton (—Si—O—), and the number of repeating units, n, of the siloxane skeleton is, for example, 10 to 320, preferably 20 to 280, and more preferably 25 to 230.

[0054] The hydroxyl-containing organopolysiloxane may have only one hydroxyl group, or two or more hydroxyl groups. While the upper limit of the number of hydroxyl groups is not particularly limited, it is preferably six or fewer hydroxyl groups, and more preferably three or fewer hydroxyl groups. The hydroxyl-containing organopolysiloxane, due to its hydroxyl groups, is more likely to react or interact with functional groups on the surface of the thermally conductive filler, thereby improving the dispersibility of the thermally conductive filler and reducing the viscosity of the composition. The number of hydroxyl groups in the hydroxyl-containing organopolysiloxane may be one, and an organopolysiloxane having a hydroxyl group at one end of the main chain is preferred. The hydroxyl group may be directly bonded to the end of the organopolysiloxane chain, but is preferably bonded via a linking group. One hydroxyl group may be bonded to one Si via a linking group, or multiple (e.g., two or three) hydroxyl groups may be bonded to one Si via a linking group. The linking group is a hydrocarbon group which may contain an ester bond, an amide bond, an ether bond, an oxime ester bond (-C=N-O-C(=O)-), or the like, and is preferably a hydrocarbon group having an ether bond. The number of carbon atoms in the linking group is about 1 to 20, preferably 2 to 15, and more preferably 3 to 10. The organopolysiloxane having hydroxyl groups of the present invention has a siloxane skeleton (-Si-O-), and the number of repeating units, n, of the siloxane skeleton is preferably 11 or more and 350 or less, more preferably 20 or more and 300 or less, and even more preferably 50 or more and 270 or less.

[0055] In the alkoxy group-containing organopolysiloxanes and hydroxy group-containing organopolysiloxanes, the specific explanation of the residual groups bonded to silicon atoms is the same as that for the alkenyl group-containing organopolysiloxanes, and therefore will not be repeated. Furthermore, the alkoxy group-containing organopolysiloxanes, hydroxy group-containing organopolysiloxanes, and aromatic group-containing organopolysiloxanes are preferably organopolysiloxanes that are liquid at 25°C.

[0056] The content of other organopolysiloxanes in the resin component is not particularly limited, but is, for example, from 0.1% by mass to 12% by mass, and preferably from 0.5% by mass to 10% by mass.

[0057] Furthermore, the thermally conductive composition may contain a resin component other than the organopolysiloxane as long as the effects of the present invention are achieved. However, the organopolysiloxane may be the main component of the resin component. Specifically, the content of the organopolysiloxane may be, for example, 70% by mass or more and 100% by mass or less, preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 100% by mass, based on the total resin component. In other words, it is preferable that the resin component does not contain any resin component other than the organopolysiloxane.

[0058] The content of the resin component in the thermally conductive composition is preferably 30% by volume or more and 50% by volume or less. That is, the content of the polymer matrix in the thermally conductive molded body is preferably 30% by volume or more and 50% by volume or less. When the content is 30% by volume or more, the thermally conductive filler can be properly held by the polymer matrix after curing. Furthermore, when the content is 50% by volume or less, it becomes easier to incorporate components other than the polymer matrix, such as a thermally conductive filler, into the thermally conductive molded body. Incorporating a large amount of thermally conductive filler makes it easier to improve thermal conductivity. The content of the resin component in the thermally conductive composition (i.e., the content of the polymer matrix in the thermally conductive molded body) is more preferably 30% by volume or more and 40% by volume or less, and even more preferably 30% by volume or more and 35% by volume or less.

[0059] [Thermal Conductive Filler] Examples of thermally conductive fillers include metals, metal oxides, metal nitrides, metal hydroxides, carbon materials, oxides other than metals, nitrides, carbides, and organic fibers. The thermally conductive filler may be spherical or in the form of an irregular powder. Examples of metals in the thermally conductive filler include aluminum, copper, and nickel. Examples of metal oxides include aluminum oxide (e.g., alumina), magnesium oxide, and zinc oxide. Examples of metal nitrides include aluminum nitride. Examples of metal hydroxides include aluminum hydroxide. Examples of carbon materials include spherical graphite and diamond. Examples of oxides, nitrides, and carbides other than metals include quartz, boron nitride, and silicon carbide. Examples of organic fibers include polyparaphenylene benzoxazole fibers. Among these, metal oxides, metal nitrides, metal hydroxides, and carbon materials are preferred as thermally conductive fillers from the viewpoint of improving thermal conductivity, and metal oxides or metal hydroxides are more preferred. Specifically, the thermally conductive filler is preferably aluminum oxide, aluminum hydroxide, or boron nitride, more preferably aluminum oxide or aluminum hydroxide, and more preferably at least one selected from the group consisting of aluminum oxide and aluminum hydroxide. Among these, aluminum oxide is preferred from the viewpoint of improving the heat dissipation properties of the thermally conductive molded body, and aluminum hydroxide is preferred when it is desired to improve flame retardancy or when the specific gravity of the inorganic filler is reduced to reduce the weight of the thermally conductive resin composition. These thermally conductive fillers may be used alone or in combination of two or more.

[0060] The average particle size of the thermally conductive filler is not particularly limited, but is preferably 0.1 to 200 μm, more preferably 0.3 to 100 μm, and even more preferably 0.5 to 70 μm. It is preferable to use two or more types of thermally conductive filler with different average particle sizes in combination, and it is preferable to use a small-particle size thermally conductive filler with an average particle size of 0.1 μm to 5 μm inclusive in combination with a large-particle size thermally conductive filler with an average particle size of more than 5 μm and 200 μm inclusive in combination. Another preferable embodiment of the large-particle size thermally conductive filler is to use a first large-particle size thermally conductive filler with an average particle size of more than 5 μm and 20 μm inclusive in combination with a second large-particle size thermally conductive filler with an average particle size of more than 20 μm and 200 μm inclusive in combination. The average particle size of the thermally conductive filler is D50, which can be calculated by observing the thermally conductive filler under a microscope and using the major axis as the diameter. More specifically, it means the particle size corresponding to a cumulative frequency of 50% when the major axis of at least 500 random particles is measured using, for example, an electron microscope or optical microscope. Specifically, it can be determined from a particle size distribution curve using a thermally conductive filler as a sample, with the horizontal axis representing particle size and the vertical axis representing cumulative frequency. The particle size distribution curve is a numerical particle size distribution curve obtained by sequentially accumulating the particle sizes of thermally conductive fillers starting from the smallest particle size. Note that the particle size can be determined by measuring the major axis, and for example, in the case of fibrous materials described below, the length in the major axis direction can be measured.

[0061] The thermally conductive filler may be surface-treated with a surface treatment agent such as a silane coupling agent. The surface-treated thermally conductive filler can be obtained by mixing the surface treatment agent with the thermally conductive filler. Furthermore, from the viewpoint of facilitating the surface treatment during mixing, it is preferable to use a wet treatment method, a dry treatment method, or the like. In the wet treatment method, for example, the thermally conductive filler is added to a solution in which the surface treatment agent is dispersed or dissolved, and mixed, followed by heat treatment to bond or adhere the surface treatment agent to the surface of the thermally conductive filler. The dry treatment method is a surface treatment method that does not use a solution. Specifically, the thermally conductive filler and the surface treatment agent are mixed and stirred in a mixer or the like, followed by heat treatment to bond or adhere the surface treatment agent to the surface of the thermally conductive filler.

[0062] Examples of surface treatment agents include silane coupling agents and fatty acids. As the silane coupling agent, known agents can be used without particular limitation, and examples thereof include dimethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, n-decyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, and 3-phenylaminopropyltrimethoxysilane. Other examples include alkenyltriethoxysilanes having an alkenyl group with approximately 8 to 18 carbon atoms, such as octenyltrimethoxysilane. Furthermore, the fatty acid may be a fatty acid that is liquid at room temperature (25°C), or a fatty acid that is solid at room temperature. Liquid fatty acids include saturated fatty acids such as butyric acid, valeric acid, caproic acid, heptanoic acid, caprylic acid, and pelargonic acid, and unsaturated fatty acids such as myristoleic acid, palmitoleic acid, ricinoleic acid, oleic acid, linoleic acid, and linolenic acid. Solid fatty acids include saturated fatty acids with approximately 10 to 24 carbon atoms, such as capric acid, palmitic acid, and stearic acid, and unsaturated fatty acids such as crotonic acid and sorbic acid. Among these, stearic acid is preferred. Surface treatment agents may be used alone or in combination. Surface treatment with a surface treatment agent such as a silane coupling agent may also be performed using an integral blending method. Therefore, a surface treatment agent such as a silane coupling agent may be incorporated into the resin component, and the thermally conductive filler may be surface-treated with the silane coupling agent or fatty acid incorporated into the resin component.

[0063] (Other Additives) The thermally conductive composition for forming the thermally conductive molded article of the present invention may contain various additives, such as curing catalysts, reaction control agents, dispersants, flame retardants, plasticizers, antioxidants, colorants, surface treatment agents, and thixotropy-imparting agents.

[0064] Among the above, it is preferable that the thermally conductive composition contains a curing catalyst. The curing catalyst may be any catalyst that promotes the addition reaction between the alkenyl group-containing organopolysiloxane and the hydrosilyl group-containing polysiloxane. By including a curing catalyst in the thermally conductive composition, the curing and crosslinking of the thermally conductive composition can be appropriately promoted. Examples of curing catalysts include platinum group curing catalysts. Examples of platinum group curing catalysts include, but are not limited to, chloroplatinic acid, complex compounds of chloroplatinic acid with olefins, vinylsiloxanes, or acetylene compounds, and the like. The content of the platinum group curing catalyst in the thermally conductive composition is not particularly limited as long as it is contained in an amount that promotes the addition reaction, but is, for example, 0.0001 to 1 part by mass, preferably 0.001 to 0.5 parts by mass, per 100 parts by mass of the organopolysiloxane contained in the thermally conductive composition.

[0065] [One-component or Two-component Thermally Conductive Composition] The thermally conductive composition of the present invention may be a one-component or a two-component composition comprising a first component and a second component. A two-component composition is obtained by mixing the first component and the second component at the time of use. In the case of a two-component composition, the components of the thermally conductive composition may be appropriately divided into the first component and the second component. For example, in a two-component thermally conductive composition, the first component may contain an alkenyl group-containing organopolysiloxane and a curing catalyst, but may not contain a hydrosilyl group-containing organopolysiloxane. In this case, the second component may contain a hydrosilyl group-containing organopolysiloxane but may not contain a curing catalyst. The second component may also contain an alkenyl group-containing organopolysiloxane. It is preferable that at least one of the first and second parts contains a thermally conductive filler, but it is preferable that both the first and second parts contain a thermally conductive filler. It is also preferable that other organopolysiloxanes, other resin components, and additives are appropriately distributed between the first and second parts.

[0066] A one-component thermally conductive composition can be obtained by appropriately mixing the components that make up the thermally conductive composition. A two-component thermally conductive composition can be obtained by mixing the components that make up the first and second components to prepare the first and second components, respectively, and then mixing the first and second components. The method for mixing the first and second components to obtain the thermally conductive composition is not limited, and can be, for example, a static mixer, a mixer with stirring blades, a vibration mixer, or a planetary mixer.

[0067] [Physical Properties of Thermally Conductive Molded Product] (E Hardness) The E hardness of the thermally conductive molded product of the present invention is preferably 3 or more and 90 or less. When the E hardness is 90 or less, the hardness of the thermally conductive molded product is not too high, and it can be used as a thermally conductive molded product having a three-dimensional shape. Furthermore, by setting the E hardness to 3 or more, it is possible to prevent the hardness from being lowered more than necessary. The E hardness is preferably 70 or less, more preferably 50 or less, and even more preferably 30 or less. When the thermally conductive molded product has such a low E hardness, the thermally conductive molded product has high flexibility and improves its ability to conform to heating elements, etc. Furthermore, it is easier to compress, improving handleability. In other words, the molded product of the present invention having a low E hardness has excellent handleability, thermal conductivity, and moldability. The E hardness is more preferably 5 or more, and even more preferably 10 or more, from the viewpoint of preventing excessive flexibility and ensuring a certain degree of moldability. The E hardness is the type E hardness specified in JIS K6253.

[0068] (OO Hardness) The OO hardness of the thermally conductive molded article of the present invention is not particularly limited, but is preferably 15 or more, more preferably 20 or more, even more preferably 30 or more, and is preferably 80 or less, more preferably 75 or less, even more preferably 70 or less, and even more preferably 60 or less. The type OO hardness is measured by the method specified in ASTM D2240.

[0069] (Thermal conductivity) The thermal conductivity of the thermally conductive molded body of the present invention is preferably 1.0 W / (m K) or more. When the thermal conductivity of the thermally conductive molded body is 1.0 W / (m K) or more, the heat dissipation properties can be improved, and the heat dissipation properties required for a thermally conductive molded body having a three-dimensional shape can be appropriately ensured. From the viewpoint of further improving heat dissipation, the thermal conductivity is more preferably 1.5 W / (m K) or more, and even more preferably 2.0 W / (m K) or more. The upper limit of the thermal conductivity is not particularly limited, but in practice, it is, for example, 30 W / (m K) or less, and more preferably 10 W / (m K) or less.

[0070] (Flame Retardancy) The flame retardancy of the thermally conductive molded article of the present invention is preferably V-1 or higher according to the UL94 standard, and more preferably V-0. Flame retardancy of V-1 can be achieved by incorporating a predetermined amount or more of a thermally conductive filler into the silicone matrix, but flame retardancy of V-0 can also be achieved by using a thermally conductive filler that can impart flame retardancy, such as aluminum hydroxide.

[0071] [Method for manufacturing a thermally conductive molded body] The thermally conductive molded body can be obtained by curing a thermally conductive composition. The thermally conductive molded body of the present invention is preferably obtained by pouring the thermally conductive composition into a mold such as a die and molding it into a thermally conductive molded body having a three-dimensional shape that matches the shape of the mold. As described above, the thermally conductive molded body of the present invention satisfies formulas (1) and (2), and therefore has excellent moldability. The method for molding the thermally conductive composition into a thermally conductive molded body having a three-dimensional shape is not particularly limited, but examples thereof include compression molding, injection molding, and transfer molding. The shape of the thermally conductive molded body having a three-dimensional shape is not particularly limited, but it may have a shape that matches the shape of the heat sink or heat generator to be used, and may have appropriate recesses or protrusions. The curing conditions for curing the thermosetting composition are not particularly limited, but can be, for example, heated at 80°C to 200°C for 30 seconds to 30 minutes, and preferably heated at 100°C to 160°C for 1 minute to 15 minutes. Typically, the curing time is 125°C for 8 minutes. After curing into the three-dimensional shape, secondary curing can be performed. For example, secondary curing can be performed by heating at 150°C or higher and 200°C or lower for 24 hours or less. Preferably, secondary curing can be performed at 120°C to 180°C for 1 to 6 hours.

[0072] However, the thermally conductive molded body does not necessarily have to be a thermally conductive molded body having a three-dimensional shape; it may be a block-shaped thermally conductive molded body or a sheet-shaped thermally conductive molded body. Block-shaped or sheet-shaped thermally conductive molded bodies can also be produced by curing the thermally conductive composition under the above-mentioned curing conditions. After curing, the thermally conductive composition may be sliced ​​into a sheet. Furthermore, when the thermally conductive molded body contains an anisotropic filler, the anisotropic filler may be oriented in one direction. Examples of anisotropic fillers include fibrous materials and scaly materials, with scaly materials being preferred. Anisotropic fillers have a high aspect ratio, specifically, an aspect ratio of greater than 2. Orienting the anisotropic filler in one direction facilitates improving the thermal conductivity of the thermally conductive molded body in one direction. For example, in the case of a sheet-shaped thermally conductive molded body, it is preferable to orient the anisotropic filler in the thickness direction as described above in order to increase the thermal conductivity in the thickness direction.

[0073] Hereinafter, a manufacturing method for orienting an anisotropic filler will be described using as an example a method for obtaining a sheet-shaped thermally conductive molded body in which the anisotropic filler is oriented in the thickness direction. The manufacturing method for a thermally conductive molded body according to one embodiment comprises the following steps (A) and (B): Step (A): A step of obtaining an oriented molded body in which the anisotropic filler is oriented along one direction; Step (B): A step of cutting the oriented molded body into sheets to obtain a sheet-shaped molded body.

[0074] Each step will be described in more detail below. [Step (A)] In step (A), an oriented molded body is formed from the thermally conductive composition. The thermally conductive composition may be cured to form the oriented molded body. The oriented molded body has the anisotropic filler oriented along one direction, which is the thickness direction of the thermally conductive sheet. More specifically, the oriented molded body can be obtained by a magnetic field orientation method, a flow orientation method, or the like.

[0075] (Magnetic Field Orientation Method) In the magnetic field orientation method, a thermally conductive composition is injected into a molding die such as a metal mold, placed in a magnetic field, and the anisotropic filler is oriented along the magnetic field. The thermally conductive composition is then cured to obtain an oriented molded body. The oriented molded body is preferably block-shaped. A release film may be placed inside the molding die at the portion where the molding die comes into contact with the mixed composition. The release film may be, for example, a resin film with good releasability or a resin film with one side treated with a release agent. The use of a release film makes it easier to release the oriented molded body from the mold. The curing of the thermally conductive composition in the magnetic field orientation method is preferably carried out under the curing conditions described above.

[0076] The viscosity of the thermally conductive composition used in the magnetic field orientation manufacturing method is preferably 10 to 300 Pa·s in order to achieve magnetic field orientation. By setting the viscosity at 10 Pa·s or higher, the fillers are less likely to settle. Furthermore, by setting the viscosity at 300 Pa·s or less, the fluidity is improved, the anisotropic fillers are properly oriented in the magnetic field, and problems such as excessive time required for orientation do not occur. The viscosity is measured using a rotational viscometer (Brookfield viscometer DV-E, spindle SC4-14) at 25°C and a rotation speed of 10 rpm. However, when using fillers that are less likely to settle or when combining additives such as anti-settling agents, the viscosity of the thermally conductive composition may be less than 10 Pa·s.

[0077] In the magnetic field orientation method, magnetic field generating sources for applying magnetic field lines include superconducting magnets, permanent magnets, electromagnets, etc., but superconducting magnets are preferred because they can generate a magnetic field with a high magnetic flux density. The magnetic flux density of the magnetic field generated from these magnetic field generating sources is preferably 1 to 30 Tesla. If the magnetic flux density is 1 Tesla or higher, it becomes possible to easily orient the anisotropic filler. Furthermore, if the magnetic flux density is 30 Tesla or lower, practical production becomes possible.

[0078] (Flow Orientation Method) In the flow orientation method, a thermally conductive composition is first prepared as described above, and then a shear force is applied to the thermally conductive composition to produce a preliminary sheet in which the anisotropic filler is oriented in the plane direction. A plurality of these sheets are then stacked to produce a laminate block, which serves as an oriented molded article. The thermally conductive composition used in the flow orientation method has a relatively high viscosity so that a shear force is applied when stretched into a sheet. Specifically, the viscosity is preferably 3 to 500 Pa·s. The thermally conductive composition may be diluted by adding an appropriate solvent. Furthermore, the thermally conductive composition can be flattened and stretched into a sheet by applying a shear force, thereby orienting the anisotropic filler in the shear direction. For example, the thermally conductive composition can be formed into a sheet by applying a coating applicator such as a bar coater or doctor blade, or by extrusion molding or nozzle discharge, and then drying or semi-curing the thermally conductive composition as necessary. The thickness of the preliminary sheet is preferably about 50 to 5000 μm. In the preliminary sheet, the anisotropic filler is oriented in one direction along the surface direction of the sheet.

[0079] Next, multiple preliminary sheets are stacked on top of each other so that they have the same orientation direction, and the mixed composition is cured as needed by heating, ultraviolet irradiation, etc., while the preliminary sheets are adhered to each other by hot pressing, etc. to form a laminated block, which can be used as an oriented molded body.

[0080] [Step (B)] In step (B), the oriented molded body obtained in step (A) is cut perpendicular to the orientation direction of the anisotropic filler by slicing or the like to obtain a sheet-like molded body. Slicing can be performed, for example, using a shear blade or a laser. Cutting the sheet-like molded body by slicing or the like may result in a portion of the anisotropic filler being exposed from the matrix at each cut surface. The sheet-like molded body obtained by slicing in step (B) may be further heated, or the sheet-like molded body may be secondary-cured by heating. Furthermore, if a coupling agent is blended into the thermally conductive composition, the sheet-like molded body may be heated to volatilize some or all of the coupling agent. The sheet-like molded body may be heated, for example, at 100 to 200°C, preferably 120 to 180°C, for example, for 30 minutes to 24 hours, preferably 1 to 6 hours.

[0081] The sheet-like molded article obtained through the above step (B) may be used as a thermally conductive molded article as is, or the surface may be polished, etc. By polishing, the surface condition of the sheet-like molded article becomes better, and the thermal conductivity can be further improved.

[0082] The method for obtaining a sheet-shaped thermally conductive molded body in which the anisotropic filler is oriented in the thickness direction is not limited to the above, and for example, step (B) may be omitted. Specifically, in the magnetic field orientation method, step (B) can be omitted by producing a sheet-shaped oriented molded body instead of producing a block-shaped oriented molded body in step (A). Step (B) may also be omitted when obtaining a block-shaped thermally conductive molded body, etc. Furthermore, when obtaining a thermally conductive molded body in which the anisotropic filler is oriented in one direction along the surface direction, part of step (A) and step (B) may be omitted, and the preliminary sheet obtained by the flow orientation method may be used as a sheet-shaped thermally conductive molded body.

[0083] <Uses of Thermally Conductive Members> The thermally conductive molded article of the present invention may be used for various electronic components, for example, by being disposed between a heat generating element and a heat sink. The thermally conductive molded article may be interposed between the heat generating element and the heat sink, and the heat generated by the heat generating element may be transferred to the heat sink by thermal conduction, and then dissipated from the heat sink. Examples of the heat generating element include, but are not limited to, various electronic components such as CPUs, LEDs, coils, and lithium ion batteries, as well as wiring through which large currents flow. Examples of the heat sink include heat sinks, heat pumps, and metal housings for electronic devices. A Peltier element may be disposed instead of the heat sink, and the heat sink may be disposed on peripheral components such as bus bars, copper wires, and connectors around the heat generating element rather than being disposed directly on the heat generating element. The thermally conductive molded article of the present invention is preferably a thermally conductive molded article having a three-dimensional shape as described above. However, by having a three-dimensional shape corresponding to the shape of the heat generating element or heat sink, adhesion and conformability to the heat generating element or heat sink can be further improved.

[0084] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0085] In this example, the evaluation was carried out by the following method.

[0086] [Gel Fraction] Approximately 2 g of a thermally conductive molded body was immersed in 40 g of toluene for one day, and then the toluene-insoluble portion of the thermally conductive molded body was collected and dried using a rotary evaporator under a vacuum of -100 kPa at 50°C for two hours. The dry mass was measured and the gel fraction was calculated using the following formula (3): Gel fraction = 100 x X / Y Formula (3) In formula (3), X = (dry mass of toluene-insoluble portion - (mass of thermally conductive molded body before immersion x (1 - ratio of silicone matrix mass when the mass of the thermally conductive molded body is taken as 1))) Y = (mass of thermally conductive molded body before immersion x ratio of silicone matrix mass when the mass of the thermally conductive molded body is taken as 1)

[0087] [E Hardness] The Type E hardness of the thermally conductive molded body was measured according to Japanese Industrial Standard JIS K 6253. Specifically, the Type E hardness was measured for the thermally conductive molded body prepared in each Example and Comparative Example using a Type E durometer. The measurement was performed using a sample cut from the thermally conductive molded body to a length of 15 mm, a width of 15 mm, and a thickness of 10 mm.

[0088] [0000 Hardness] The hardness of the thermally conductive molded articles prepared in each Example and Comparative Example was measured using a type 0000 durometer in accordance with ASTM D2240-05. The measurement was performed using a sample cut from the thermally conductive molded article to a length of 15 mm, a width of 15 mm, and a thickness of 10 mm.

[0089] [Flame Retardancy UL94] "Flame retardancy" was evaluated by the flame test (UL94) established by Underwriters Laboratories Inc. of the United States. The thermally conductive molded body of each experimental example and comparative example was cut to the size of a test specimen (127 mm long x 12.7 mm wide x 2 mm thick). The test specimen was held in a fixing clamp so that the longitudinal direction of the test specimen was vertical. The specimen was then exposed to a burner flame for 10 seconds, and then removed from the flame to record the burning time of each test specimen. Furthermore, the time the flame was maintained after the second exposure (glowing time) and the presence or absence of dripping material that ignited the absorbent cotton placed below the test specimen were recorded. The above procedure was performed five times for each test specimen. Then, based on the criteria shown in Table 1 below, a pass / fail rating of "V-0" or "V-1" was determined. In this flame retardancy rating, "V-0" indicates higher flame retardancy than "V-1."

[0090]

[0091] [Thermal Conductivity] The thermal conductivity (W / m·K) of the thermally conductive molded article was measured by a method in accordance with ASTM D5470-06.

[0092] <Components used in producing thermally conductive molded body> Organopolysiloxane 1: organopolysiloxane having vinyl groups only on the side chains (weight average molecular weight 22,500, vinyl group concentration 128 μmol / g, viscosity at 23°C 700 mPa·s) Organopolysiloxane 2: organopolysiloxane having vinyl groups on both ends (weight average molecular weight 17,700, vinyl group concentration 140 μmol / g) Organopolysiloxane 3: organopolysiloxane having vinyl groups on both ends (weight average molecular weight 25,400, vinyl group concentration 105 μmol / g)

[0093] Organopolysiloxane 4: an organopolysiloxane having vinyl groups at both ends (weight average molecular weight 17,100, vinyl group concentration 135 μmol / g); Organopolysiloxane 5: a mixture of an organopolysiloxane having vinyl groups at both ends and an organopolysiloxane having hydrosilyl groups at both ends and in the side chain (weight average molecular weight 15,700, vinyl concentration 66 μmol / g, hydrosilyl group concentration 638 μmol / g); Organopolysiloxane 6: a mixture of an organopolysiloxane having vinyl groups at both ends and an organopolysiloxane having hydrosilyl groups at both ends and in the side chain (weight average molecular weight 23,300, vinyl concentration 31 μmol / g, hydrosilyl group concentration 82 μmol / g).

[0094] Organopolysiloxane 7: a mixture of an organopolysiloxane having vinyl groups at both ends and an organopolysiloxane having hydrosilyl groups at both ends and in a side chain (weight average molecular weight 20,100, vinyl concentration 125 μmol / g, hydrosilyl group concentration 103 μmol / g) Organopolysiloxane 8: a mixture of an organopolysiloxane having vinyl groups at the side chain and an organopolysiloxane having hydrosilyl groups (weight average molecular weight 15,100, vinyl concentration 59 μmol / g, hydrosilyl group concentration 550 μmol / g) Organopolysiloxane 9: a cyclic organopolysiloxane having hydrosilyl groups (hydrosilyl group concentration 4,415 μmol / g) Organopolysiloxane 10: Organopolysiloxane having hydrosilyl groups (weight average molecular weight 20,489, hydrosilyl group concentration 1,160 μmol / g) * Organopolysiloxane 1 and Organopolysiloxane 2 contain a catalytic amount of platinum catalyst.

[0095] Dimethyl silicone oil 1: Dimethyl silicone oil (viscosity 300 cs) Dimethyl silicone oil 2: Dimethyl silicone oil (viscosity 110 cs)

[0096] Dispersant: Hydroxy group-containing organopolysiloxane, number average molecular weight 5,000, hydroxyl group equivalent weight 2,500, compound having the following structure ・Reaction retarder

[0097] Aluminum hydroxide 1: Aluminum hydroxide (irregular shape, D50 = 10 μm) dry surface treated with 7-octenyltrimethoxysilane. Aluminum hydroxide 2: Aluminum hydroxide (irregular shape, D50 = 10 μm) dry surface treated with dimethyldimethoxysilane. Aluminum hydroxide 3: Aluminum hydroxide (irregular shape, D50 = 10 μm) dry surface treated with n-decyltrimethoxysilane. Aluminum hydroxide 4: Aluminum hydroxide (irregular shape, D50 = 54 μm). Aluminum hydroxide 5: Aluminum hydroxide (irregular shape, D50 = 54 μm) dry surface treated with dimethyldimethoxysilane. Aluminum hydroxide 6: Aluminum hydroxide (irregular shape, D50 = 1.0 μm) surface treated with stearic acid.

[0098] Aluminum oxide 1: Aluminum oxide (spherical, D50 = 41 μm) Aluminum oxide 2: Aluminum oxide (spherical, D50 = 41 μm), dry surface-treated with 7-octenyltrimethoxysilane Aluminum oxide 3: Aluminum oxide (spherical, D50 = 2.2 μm), dry surface-treated with dimethyldimethoxysilane Aluminum oxide 4: Aluminum oxide (spherical, D50 = 4.0 μm), dry surface-treated with dimethyldimethoxysilane Aluminum oxide 5: Aluminum oxide (irregular, D50 = 3.0 μm) Aluminum oxide 6: Aluminum oxide (polyhedral, D50 = 3.0 μm) Aluminum oxide 7: Aluminum oxide (polyhedral, D50 = 0.5 μm) Aluminum oxide 8: Aluminum oxide dry-treated with dimethyldimethoxysilane (polyhedral, D50 = 3.0 μm) Aluminum oxide 9: Aluminum oxide (spherical, D50 = 13 μm) Aluminum oxide 10: Aluminum oxide (spherical, D50=75 μm) Aluminum oxide 11: Aluminum oxide (plate-shaped, D50=4 μm)

[0099] - Coloring pigment: Iron tetraoxide (black pigment)

[0100] Thixotropic agent: AEROSIL COK84 (manufactured by Nippon Aerosil)

[0101] [Example 1] The components were mixed according to the formulation shown in Table 2 to obtain a thermally conductive composition. The following moldability evaluations were performed using this thermally conductive composition. <Moldability Evaluation> The moldability was evaluated when a thermally conductive molded body 10 having the shape shown in Figure 3 was molded using a mold. The lower view of Figure 3 is a cross-sectional view of the thermally conductive molded body 10, and the upper view of Figure 3 is a top view of the thermally conductive molded body. The thermally conductive molded body 10 shown in Figure 3 has a shape in which 16 trapezoidal cross-sectional protrusions 12 are arranged in a grid pattern on one side of a plate-shaped molded body 11. Note that the thermally conductive molded body has a three-dimensional surface in one direction with a surface area of ​​1.46 x A relative to the projected area A. (Evaluation Method) A mold corresponding to the shape of the thermally conductive molded body 10 in Figure 3 was prepared, and a PET film was attached to the surface of the upper mold side of the mold. The thermally conductive compositions of each Example and Comparative Example were introduced into the mold and molded at a molding temperature of 120°C for a molding time of 8 minutes. The upper mold provided with the PET film was pulled up and removed, and moldability was evaluated based on the number of protrusions 12 remaining on the mold according to the following criteria. Note that A indicates the best moldability, and D indicates the worst moldability. A: 14 to 16 B: 11 to 13 C: 8 to 10 D: Less than 8

[0102] Examples 2 to 18, Comparative Examples 1 to 19 The moldability of the thermally conductive compositions was evaluated in the same manner as in Example 1, except that the formulation was changed as shown in Tables 2 to 5.

[0103]

[0104]

[0105]

[0106]

[0107] The thermally conductive molded bodies produced in each of Examples 1 to 18 had a relationship between the polymer matrix content and gel fraction that satisfied formula (1) and formula (2). As a result, the thermally conductive molded bodies of each Example were rated "C" or higher in moldability, demonstrating excellent moldability. Furthermore, the thermally conductive molded bodies of each Example contained a certain amount of thermally conductive filler or more and exhibited excellent thermal conductivity. Furthermore, Examples 2, 4, 6 to 8, 12 to 13, and 15 were thermally conductive molded bodies with low E hardness (30 or less). Even with such low hardness, good moldability could be achieved by adjusting the gel fraction and polymer matrix content within a predetermined range. Furthermore, low hardness makes the molded bodies easier to compress and use, improving workability. In contrast, the thermally conductive molded bodies produced in each of the comparative examples did not satisfy formula (1) or formula (2). As a result, the moldability rating was rated "D," demonstrating poor moldability.

[0108] 10 Thermally conductive molded body 11 Plate-shaped molded body 12 Convex portion with trapezoidal cross section

Claims

1. A thermally conductive molded body comprising a polymer matrix and a thermally conductive filler, wherein the relationship between the gel fraction a (mass%) of the thermally conductive molded body and the content b (volume%) of the polymer matrix satisfies both of the following formulas (1) and (2): a > 1.25 × b - 4.1 Formula (1) a < 2.87 × b - 33 Formula (2) (Method for measuring gel fraction) (1) Approximately 2 g of the thermally conductive molded body is immersed in 40 g of an organic solvent capable of dissolving resin components other than the gel fraction for one day, and then the organic solvent-insoluble portion of the thermally conductive molded body is collected and dried, and the gel fraction is calculated using the following formula (3): Gel fraction = 100 x X / Y Equation (3) In equation (3), X = (dry mass of organic solvent insoluble matter - (mass of thermally conductive molded body before immersion x (1 - ratio of polymer matrix mass when the mass of the thermally conductive molded body is taken as 1))) Y = (mass of thermally conductive molded body before immersion x ratio of polymer matrix mass when the mass of the thermally conductive molded body is taken as 1) 2. A thermally conductive molded body comprising a polymer matrix and a thermally conductive filler, wherein the relationship between the gel fraction a (mass%) of the thermally conductive molded body and the content b (volume%) of the polymer matrix satisfies both of the following formulas (1) and (2-2): a > 1.25 × b - 4.1 Formula (1) a < 4.50 × b - 97 Formula (2-2) (Method for measuring gel fraction) (1) Approximately 2 g of the thermally conductive molded body is immersed in 40 g of an organic solvent capable of dissolving resin components other than the gel fraction for one day, and then the organic solvent-insoluble portion of the thermally conductive molded body is collected and dried, and the gel fraction is calculated using the following formula (3): Gel fraction = 100 x X / Y Equation (3) In equation (3), X = (dry mass of organic solvent insoluble matter - (mass of thermally conductive molded body before immersion x (1 - ratio of polymer matrix mass when the mass of the thermally conductive molded body is taken as 1))) Y = (mass of thermally conductive molded body before immersion x ratio of polymer matrix mass when the mass of the thermally conductive molded body is taken as 1) 3. The thermally conductive molded body according to claim 1 or 2, wherein the thermally conductive molded body has a three-dimensional surface with a surface area of ​​1.46 x A or more relative to a projected area A in at least one direction.

4. The thermally conductive molded body according to claim 1 or 2, wherein the content of the polymer matrix is ​​17.5 to 50% by volume.

5. The thermally conductive molded body according to claim 1 or 2, wherein the content of the thermally conductive filler is 50 to 82.5% by volume.

6. The thermally conductive molded body according to claim 1 or 2, wherein the polymer matrix is ​​a cured body of organopolysiloxane.

7. The thermally conductive molded body according to claim 1 or 2, wherein the polymer matrix is ​​a cured product of an addition reaction type organopolysiloxane.

8. The thermally conductive molded body according to claim 1 or 2, wherein the thermally conductive filler comprises at least one selected from the group consisting of aluminum oxide and aluminum hydroxide.

9. The thermally conductive molded article according to claim 1 or 2, having an E hardness of 3 to 90.

10. The thermally conductive molded body according to claim 1 or 2, having a thermal conductivity of 1 W / mK or more.

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