Method for the production of a thermally conductive film

Abstract

Method for producing a thermally conductive film (10), comprising: a first step of forming a film or block by pressing and / or rolling a mixture of a binder resin (14) and a first thermally conductive filler (15) with shape anisotropy, which has a plate shape and a main surface thereof or a needle shape and a longitudinal direction thereof, such that the first thermally conductive filler (15) is oriented in a direction of the main surface of the film or block; a second step of hardening the binder resin (14) and then cutting the film or block in one direction of thickness to obtain mold filler pieces (12) such that the first thermally conductive filler (15) in each of them is oriented in the thickness direction of the corresponding mold filler pieces (12); and a third step of mixing the mold-filler pieces (12), a matrix resin (11) and a second thermally conductive filler (13), forming the mixture into a foil mold using pressure rollers, and then hardening the matrix resin (11); wherein the thermally conductive film (10) contains the first thermally conductive filler (15) with its main surface aligned in a thickness direction of the thermally conductive film (10), if the first thermally conductive filler (15) has a plate shape; or else wherein the thermally conductive film (10) contains the first thermally conductive filler (15) with its longitudinal direction aligned in the thickness direction of the thermally conductive film (10), if the first thermally conductive filler (15) has a needle shape, and wherein the matrix resin (11) and the binder resin (14) can be cured by an addition reaction using a platinum group metal catalyst, and wherein the second thermally conductive filler (13) consists of inorganic particles, and the inorganic particles are coated with an R(CH3) a Si(OR') 3-a expressed alkoxysilane compound are surface-treated, wherein R represents a substituted or unsubstituted organic group with 1 to 20 carbon atoms, R' represents an alkyl group with 1 to 4 carbon atoms, and a is 0 or 1.

Description

Technical field

[0001] The present invention relates to a method for producing a thermally conductive film for use in thermally conductive components such as electronic components. In particular, the invention relates to a method for producing a thermally conductive film comprising a shaped filler. State of the art

[0002] Semiconductors used in computers (CPUs), transistors, light-emitting diodes (LEDs), etc., generate heat during operation, and this heat can impair the performance of the electronic components they contain. For this reason, a heat-dissipating component is attached to a heat-generating component, such as a CPU, in these electronic components. The heat-dissipating component is often made of metal. Therefore, the adhesion of the heat-dissipating component to the heat-generating component is enhanced by inserting a plate-like or gel-like thermally conductive film between the heat-dissipating component and the heat-generating component, thus improving heat transfer between them.Patent document 1 discloses the preparation of a mixture of an epoxy resin and hexagonal boron nitride particles, comprising both coarse and fine particles, and roller pressing of the mixture to form a film in which the particles are oriented in a specific direction. Patent document 2 discloses a method for producing a film (i.e., a laminating and separating method). The method comprises the following steps: mixing a poly(meth)acrylic ester resin with plate-like boron nitride particles; using the mixture to form a film such that the plate-like boron nitride particles are oriented parallel to the surface direction of the film; laminating a plurality of the films; and separating the laminated body in the direction of thickness, thereby providing a film in which the plate-like boron nitride particles are arranged in the direction of the sheet thickness.Patent document 3 discloses an orientation of the fillers by centrifugal forming and pressing. Patent document 4 discloses a method for producing a thermally conductive film in which several layers of an organic resin with a thermally conductive filler embedded therein are stacked and then cut in the stacking direction to form the thermally conductive film. State of the art patent documents Patent Document 1: JP 2011-090868 A Patent Document 2: JP 5454300 B2 Patent Document 3: JP 2017-037833 A Patent Document 4: JP 2014-067926 A Disclosure of the invention; Problem to be solved by the invention

[0003] However, there is a need to further improve the thermal conductivity of a thermally conductive film.

[0004] The present invention discloses a method for producing a thermally conductive film. methods for problem solving

[0005] A thermally conductive film produced according to the present invention comprises a matrix resin, mold filler pieces containing a first thermally conductive filler with shape anisotropy, and a second thermally conductive filler. The mold filler pieces contain a binder resin and the first thermally conductive filler. The first thermally conductive filler is oriented in the direction of the thickness of each mold filler piece. The first thermally conductive filler is also oriented in the direction of the thickness of the thermally conductive film, if present in the thermally conductive film.

[0006] A method for producing a thermally conductive film of the present invention provides the thermally conductive film of the present invention. The method comprises the following: a first step of forming a film or block by pressure processing a mixture of a binder resin and a first thermally conductive filler having shape anisotropy, such that the first thermally conductive filler is oriented in the direction of the main surface of the film or block; a second step of curing the binder resin and then cutting the film or block in a direction of thickness to obtain shape-filler pieces in which the first thermally conductive filler is oriented in the direction of the thickness of the shape-filler piece; and a third step of mixing the shape-filler pieces, a matrix resin, and a second thermally conductive filler, forming the mixture into a film mold, and then curing the matrix resin. Effects of the invention

[0007] The thermally conductive film of the present invention comprises the matrix resin, the mold filler pieces containing the first thermally conductive filler with shape anisotropy, and the second thermally conductive filler. The mold filler pieces contain the binder resin and the first thermally conductive filler. The first thermally conductive filler is oriented in the direction of the thickness of each mold filler piece. The first thermally conductive filler is also oriented in the direction of the thickness of the thermally conductive film, if present in the thermally conductive film. In this way, the thermally conductive film can exhibit high thermal conductivity in the direction of its thickness.

[0008] The method for producing the thermally conductive film of the present invention comprises the following: mixing the mold-filler pieces, in which the first thermally conductive filler is oriented in the direction of thickness, the matrix resin, and the second thermally conductive filler; forming the mixture into a film mold; and then curing the matrix resin. In this way, a large-format thermally conductive film can be produced without the use of, for example, magnetic field alignment methods or lamination and separation processes. Therefore, the manufacturing method of the present invention can efficiently and reasonably produce the thermally conductive film with high thermal conductivity properties. Brief description of the drawings Fig. Figure 1 is a schematic cross-sectional view of a thermally conductive film of an embodiment of the present invention. Fig.2A is a photograph (100x) of a side view of a mold filler piece in Example 1 and Fig. 2B is a photograph (100x) of a top view of the mold filler piece. Fig. Figures 3A to 3C are schematic diagrams illustrating an example of a method for producing a mold-filler piece of the present invention. Description of the invention

[0009] The present invention relates to a thermally conductive film comprising a matrix resin, mold filler pieces containing a first thermally conductive filler with shape anisotropy, and a second thermally conductive filler. The mold filler pieces contain a binder resin and the first thermally conductive filler. The first thermally conductive filler is oriented in the direction of the thickness of each mold filler piece. The first thermally conductive filler is also oriented in the direction of the thickness of the thermally conductive film, if present in the thermally conductive film. In this way, the thermally conductive film can exhibit high thermal conductivity properties. The thermally conductive filler is also referred to as thermally conductive particles.

[0010] The first thermally conductive filler with shape anisotropy is preferably a filler with at least one shape selected from a plate and a needle. The plate shape is also referred to as a flat shape, a plate shape, etc. The needle shape is also referred to as a rod shape, a fiber shape, etc. The fillers having these shapes are likely to be oriented in a predetermined direction. Particularly in the preparation process of a shape-filler piece, when the shape-anisotropic filler is present in the film or block, the main surface of the plate-like filler tends to be oriented in the plane direction of the main surface of the film or block, e.g., it tends to be arranged substantially parallel to the main surface of the film or block. Furthermore, the longitudinal direction of a needle-like filler tends to be oriented in the plane direction of the main surface of the film or block, e.g.,It tends to be oriented essentially parallel to the main surface of the film or block. The film or block is then cut in the direction of its thickness (which is the direction corresponding to the shortest side of the film or block), for example, along the line perpendicular to the longitudinal direction of the main surface of the film or block. This results in mold filler pieces. Consequently, the sheet-like filler in the plane of a mold filler piece, which is orthogonal to the cutting surface and also orthogonal to the main surface of the film or block (i.e., other than the main surface of the film or block), is likely oriented in the direction of the thickness of the mold filler piece (which is the direction corresponding to the shortest side of the film or block), e.g.,The longitudinal direction of the plate-like filler is likely to be substantially the same as the direction of the thickness of the molded filler piece. Furthermore, the needle-like filler is likely oriented in the direction of the thickness of the molded filler piece; for example, the longitudinal direction of the needle-like filler is likely to be substantially the same as the direction of the thickness of the molded filler piece. The first thermally conductive filler with shape anisotropy is preferably formed from at least one compound selected from boron nitride and aluminum oxide. The filler containing these components has high thermal conductivity properties as well as high electrical insulation properties.

[0011] The matrix resin and the binder resin are preferably of the same or different types of thermosetting resin. This is because thermosetting resins offer high heat resistance and high dimensional stability. Examples of thermosetting resins include silicone polymer, epoxy resin, acrylic resin, urethane resin, polyimide resin, polyester resin, and phenolic resin. Among these, silicone polymer is suitable for both the matrix resin and the binder resin.

[0012] Preferably, the mold-filler pieces are further selected from a spherical thermally conductive filler and an irregularly shaped filler. These fillers can fill the gaps between particles of the anisotropic first thermally conductive filler in the individual mold-filler pieces, thus further improving the thermal conductivity properties.

[0013] The second thermally conductive filler is preferably selected from a spherical thermally conductive filler and an irregularly shaped filler. In this way, the second thermally conductive filler can fill the gaps between the shaped filler pieces in the thermally conductive film, thereby increasing the thermal conductivity properties of the thermally conductive film.

[0014] The higher the thermal conductivity of the thermally conductive film, the better. For example, the thermal conductivity is preferably 1.5 W / m*K or more, more preferably 2.0 W / m*K or more, and most preferably 11 W / m*K or more.

[0015] The method for producing the thermally conductive film of the present invention comprises the following steps: (1) a first step of forming a film or block by pressure processing a mixture (I) of the binder resin and the first thermally conductive filler with shape anisotropy, such that the first thermally conductive filler is oriented towards the main surface of the film or block; (2) a second step of curing the binder resin and then cutting the film or block in a direction of thickness to obtain mold filler pieces in which the first thermally conductive filler is oriented in the direction of the thickness of the mold filler piece; and (3) a third step of mixing the mold filler pieces, the matrix resin and the second thermally conductive filler, forming the mixture (II) into a foil mold, and then hardening the matrix resin.

[0016] In the manufacturing process of the thermally conductive film according to the present invention, a large-format thermally conductive film can be produced even without the use of, for example, magnetic field alignment methods or lamination and separation processes, due to the presence of the mold filler pieces. Therefore, the manufacturing process of the present invention can efficiently and reasonably produce the thermally conductive film with high thermal conductivity properties. In this case, large format (large area) means 100 mm or more in length and 100 mm or more in width, and preferably 300 mm or more in length and 400 mm or more in width. The thickness of the thermally conductive film can be the same as that of a conventional thermally conductive film and is preferably, for example, 0.3 mm or more and 5.0 mm or less.

[0017] The printing process for the mixture (I) from the first step is selected from presses and rollers.

[0018] In the third step, the forming of the mixture (II) into a film-like material is preferably carried out by presses or rollers, particularly when forming a large-format (wide surface) film. Furthermore, continuous forming is specifically carried out by pressure rollers.

[0019] The binder resin and the matrix resin can be cured by an addition reaction using a platinum metal catalyst. A suitable process can be chosen to allow these resins to be thermally cured at the end and to provide electrically stable thermal conductivity or volumetric resistivity properties.

[0020] If a silicone polymer is chosen as the binding resin for the mold filler pieces, it is desirable that the mixture (I) in the first step contains the following components a to c (where component c is one of components c1 and c2): (Component a) 100 parts by weight polyorganosiloxane (Component b) 50 to 2500 parts by weight of the first thermally conductive filler based on 100 parts by weight of component a (Component c) (Component c1) Platinum metal catalyst (Component c2) 0.01 to 5 parts by weight organic Peroxide based on 100 parts by weight of component a

[0021] If a silicone polymer is chosen as the binding resin for the mold filler pieces, it is even more desirable that the mixture (I) in the first step contains the following components a to d (where component c is one of components c1 and c2), with regard to improving the thermal conductivity properties: (Component a) 100 parts by weight polyorganosiloxane (Component b) 50 to 2500 parts by weight of the first thermally conductive filler based on 100 parts by weight of component a (Component c) (Component c1) Platinum metal catalyst (Component c2) 0.01 to 5 parts by weight organic Peroxide based on 100 parts by weight of component a (Component d) 10 to 500 parts by weight of a spherical thermally conductive filler or an irregularly shaped filler, based on 100 parts by weight of component a

[0022] If a silicone polymer is chosen as the matrix resin for the thermally conductive film, it is even more desirable that the mixture (II) in the third step contains the following components A to D (where component D is one of components D1 and D2): (Component A) 100 parts by weight polyorganosiloxane (Component B) 50 to 2500 parts by weight of mold filler pieces based on 100 parts by weight of Component A (Component C) 50 to 2500 parts by weight of the second thermally conductive filler based on 100 parts by weight of component A (Component D) (Component D1) Platinum metal catalyst (Component D2) 0.01 to 5 parts by weight organic Peroxide based on 100 parts by weight of component A

[0023] The silicone polymer can be either an addition-curable silicone polymer or a silicone polymer curable by organic peroxides.

[0024] If the silicone polymer is an addition-curable silicone polymer, the polyorganosiloxane, which constitutes the binder and matrix resin, contains a polymer base component and a crosslinking binder component, described later, and is usually stored separately in solution A and solution B. For example, solution A and solution B contain the polymer base component. Solution A further contains a curing catalyst, such as a platinum metal catalyst. Solution B further contains the crosslinking binder component. The polyorganosiloxane is commercially available in this state.

[0025] If the silicone polymer is an organic peroxide-curable silicone polymer, the polyorganosiloxane comprising the binder and matrix resins preferably has at least two silicon-atom-bonded alkenyl groups per molecule. Examples of alkenyl groups include vinyl, allyl, and propenyl groups. Organic groups other than the alkenyl group of the polyorganosiloxane include the following alkenyl groups, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, and dodecyl groups; aryl groups, such as phenyl and tolyl groups; aralkyl groups, such as β-phenylethyl groups; and halogen-substituted alkyl groups, such as 3,3,3-trifluoropropyl and 3-chloropropyl groups.

[0026] Polyorganosiloxanes can have a small number of hydroxyl groups, for example, at the end of the molecular chain. The molecular structure of polyorganosiloxanes can be linear, branched linear, ring-shaped, or network-like. Two or more types of polyorganosiloxanes may be used in combination.

[0027] The molecular weight of the polyorganosiloxane is not specifically limited, and the polyorganosiloxane can be in any form, including, for example, a low-viscosity liquid and a high-viscosity raw rubber. Preferably, the polyorganosiloxane has a viscosity of 100 mPa*s or more at 25°C to form a rubber-like elastic body upon curing. It is even more preferred that the polyorganosiloxane is in the form of a raw rubber with a polystyrene-like average molecular weight of 200,000 to 700,000, as measured by gel permeation chromatography (GPC). [Binder resin, matrix resin]

[0028] Next, each component of the binding resin and the matrix resin will be described. (1) Polymer base component

[0029] The polymer base component is preferably a polyorganosiloxane with two or more alkenyl groups bonded to silicon atoms per molecule. In the polyorganosiloxane, two alkenyl groups, preferably with 2 to 8 carbon atoms, and more preferably with 2 to 6 carbon atoms (such as vinyl or allyl groups), are bonded to the silicon atoms per molecule. The viscosity of the polyorganosiloxane is preferably 10 to 1,000,000 mPa*s and more preferably 100 to 1,000,000 mPa*s at 25°C with respect to processability and hardness.

[0030] Specifically, a polyorganosiloxane expressed by the following formula (chemical formula 1) is used. This polyorganosiloxane has, on average, two or more alkenyl groups per molecule, in which the alkenyl groups are bonded to silicon atoms at the ends of the molecular chain. The polyorganosiloxane expressed by the general formula (1) is a linear polyorganosiloxane, both ends of which are blocked by triorganosiloxy groups. The linear polyorganosiloxane may contain a small amount of branched structures (trifunctional siloxane units) within the molecular chain.

[0031] In the general formula (chemical formula 1), R represents 1 substituted or unsubstituted monovalent hydrocarbon groups that are identical or different and have no aliphatic, unsaturated bonds, R 2represents alkenyl groups that are the same or different, and k represents 0 or a natural number.

[0032] Monovalent hydrocarbon groups have, for example, 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms. Specific examples of monovalent hydrocarbon groups include the following: alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl groups; aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl groups; and substituted forms of these groups in which some or all of the hydrogen atoms have been substituted by halogen atoms (fluorine, bromine, chlorine, etc.) or cyano groups, including halogen-substituted alkyl groups such as chloromethyl, chloropropyl, bromoethyl, and trifluoropropyl groups, and cyanoethyl groups. The alkenyl groups that are from R 2The alkenyl groups represented, for example, have 2 to 6 carbon atoms, preferably 2 to 3 carbon atoms. Certain examples of alkenyl groups include vinyl, allyl, propenyl, isopropenyl, butenyl, isobutenyl, hexenyl, and cyclohexenyl groups. The vinyl group is particularly preferred. In the general formula (chemical formula 1), k is typically 0 or a natural number satisfying 5 ≤ k ≤ 10000, more preferably 10 ≤ k ≤ 2000, and most preferably 0 ≤ k ≤ 1200.

[0033] Component a and component A can also contain a polyorganosiloxane with three or more, typically 3 to 30 and preferably 3 to 20, alkenyl groups bonded to silicon atoms per molecule. The alkenyl groups have 2 to 8 carbon atoms and preferably 2 to 6 carbon atoms and can be, for example, vinyl or allyl groups. The molecular structure can be linear, ring-shaped, branched, or a three-dimensional network structure. The polyorganosiloxane is preferably a linear polyorganosiloxane in which the main chain is composed of repeating diorganosiloxane units and both ends of the molecular chain are blocked with triorganosiloxy groups. The viscosity of the linear polyorganosiloxane is preferably 10 to 1,000,000 mPa*s, and more preferably 100 to 100,000 mPa*s at 25°C.

[0034] Each of the alkenyl groups can be bonded to any part of the molecule. For example, the alkenyl groups can be bonded either to a silicon atom at the end of the molecular chain or to a silicon atom that is not at the end (but in the middle) of the molecular chain. In particular, a linear polyorganosiloxane, expressed by the following formula (chemical formula 2), is preferred. The linear polyorganosiloxane has 1 to 3 alkenyl groups on each of the silicon atoms at both ends of the molecular chain. In this case, however, if the total number of alkenyl groups bonded to the silicon atoms at both ends of the molecular chain is less than 3, at least one alkenyl group is bonded to a silicon atom that is not at the end (but in the middle) of the molecular chain (e.g., as a substituent in the diorganosiloxane unit). As described above, the viscosity of the linear polyorganosiloxane is preferably 10 to 1,000,000 mPa*s at 25°C with respect to processability and hardness.Furthermore, the polyorganosiloxane can contain a small amount of branched structures (trifunctional siloxane units) in the molecular chain.

[0035] In the general formula (chemical formula 2), R represents 3 substituted or unsubstituted monovalent hydrocarbon groups, which are the same or different and at least one of them is an alkenyl group, R 4 represents substituted or unsubstituted monovalent hydrocarbon groups that are identical or different and have no aliphatic, unsaturated bonds, R 5 R represents alkenyl groups, and 1 and m represent 0 or a natural number. The monovalent hydrocarbon groups represented by R 3The monovalent hydrocarbon groups represented preferably have 1 to 10 carbon atoms, and more preferably 1 to 6 carbon atoms. Certain examples of monovalent hydrocarbon groups include the following: alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl groups; aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl groups; alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl, and octenyl groups; and substituted forms of these groups in which some or all of the hydrogen atoms have been substituted by halogen atoms (fluorine, bromine, chlorine, etc.) or cyano groups, including halogen-substituted alkyl groups such as chloromethyl, chloropropyl, bromoethyl and trifluoropropyl groups and cyanoethyl groups.

[0036] The monovalent hydrocarbon groups that are formed by R 4 The hydrocarbon groups represented preferably have 1 to 10 carbon atoms, and more preferably 1 to 6 carbon atoms. The monovalent hydrocarbon groups can be the same as the specific examples of R. 1 , but do not contain alkenyl groups.

[0037] The alkenyl groups that are from R 5 They are represented, for example, by having 2 to 6 carbon atoms, and preferably 2 to 3 carbon atoms. Certain examples of alkenyl groups are the same as those of R. 2 in the general formula (1), and the vinyl group is preferred.

[0038] In the general formula (chemical formula 2), 1 and m are typically 0 or a natural number satisfying 0 ≤ 1 + m ≤ 10000, more preferably 5 ≤ 1 + m ≤ 2000, and most preferably 10 ≤ 1 + m ≤ 1200. Furthermore, 1 and m are integers satisfying 0 < 1 / (1 + m) ≤ 0.2 and more preferably 0.0011 ≤ 1 / (1 + m) ≤ 0.1. (2) Crosslinking binding component

[0039] The crosslinking binder component of component a and component A is preferably an organohydrogen polysiloxane. The addition reaction (hydrosilylation) between SiH groups in the crosslinking binder component and alkenyl groups in the polymer base component of component A produces a cured product. Any organohydrogen polysiloxane having two or more hydrogen atoms bonded to silicon atoms (i.e., SiH groups) per molecule can be used. The molecular structure of the organohydrogen polysiloxane can be linear, ring-shaped, branched, or three-dimensional. The number of silicon atoms in a molecule (i.e., the degree of polymerization) is preferably 2 to 1000, more preferably about 2 to 300.

[0040] The positions of the silicon atoms to which the hydrogen atoms are bonded are not particularly limited. The silicon atoms can be located either at the ends or not at the ends (but in the middle) of the molecular chain. The organic groups bonded to the silicon atoms that are not hydrogen atoms can be, for example, substituted or unsubstituted monovalent hydrocarbon groups that lack aliphatic, unsaturated bonds, which are the same as those of R. 1 from the general formula (1).

[0041] The organohydrogen polysiloxane can have a structure that is expressed by the following general formula (chemical formula 3).

[0042] In the formula, R can be 6L represents an integer from 0 to 1000, and preferably 0 to 300, and M represents an integer from 0 to 200. L represents an integer from 0 to 1000, and preferably 0 to 300, and M represents an integer from 0 to 200. (3) catalyst component

[0043] Component c1 of the binder resin and component D1 of the matrix resin can be a platinum metal catalyst for use in a hydrosilylation reaction.

[0044] Examples of platinum metal catalysts include platinum-based, palladium-based, and rhodium-based catalysts. Platinum-based catalysts include, for example, platinum black, platinum chloride, chloroplatinic acids, a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and olefin or vinylsiloxane, and platinum bis(acetoacetate).

[0045] The platinum group metal catalyst can be added in an amount necessary to harden the polyorganosiloxane, which is component a or component A, and preferably in an amount capable of sufficiently hardening the polyorganosiloxane. The amount of the platinum group metal catalyst can be appropriately adjusted to the desired degree of hardness or the like. The platinum group metal catalyst is normally contained in the silicone polymer (e.g., a two-part, room-temperature curable silicone polymer) used in the manufacture of the thermally conductive film of the present invention. Furthermore, an additional platinum group metal catalyst can be mixed with the silicone polymer in the manufacture of the thermally conductive film of the present invention to sufficiently harden component a or component A. The amount of the platinum group metal catalyst is preferably 0.0.1 to 1000 ppm, expressed in weight of metal atoms, with respect to the polyorganosiloxane component.

[0046] The “amount capable of sufficiently hardening the polyorganosiloxane” means that the quantity is large enough for the hardened product to be able to have an Asker C hardness of 5 or more.

[0047] Component c2 of the binder resin and component D2 of the matrix resin are organic peroxides and form radicals when heated, causing crosslinking reactions of component a and component A, respectively. Examples of organic peroxides include: acyl peroxides such as benzoyl peroxide and bis(p-methylbenzoyl) peroxide; alkyl peroxides such as di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl cumyl peroxide, and dicumyl peroxide; and ester-based organic peroxides such as tert-butyl perbenzoate. The amounts of component c2 of the binder resin and component D2 of the matrix resin are preferably 0.01 to 5 parts by weight, and more preferably 0.1 to 4 parts by weight, respectively, with respect to 100 parts by weight of component a and 100 parts by weight of component A. Second thermally conductive filler

[0048] The second thermally conductive filler (component C) is preferably added in an amount of 100 to 2500 parts by weight of component A. The addition of the second thermally conductive filler can maintain a high thermal conductivity of the thermally conductive film. The thermally conductive filler preferably consists of at least one of the following: aluminum oxide, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, and silicon oxide. The thermally conductive filler can have various shapes, such as spherical, platelet-shaped, or polyhedral. If aluminum oxide is used, α-aluminum oxide with a purity of 99.5% by weight is preferred. The specific surface area of ​​the second thermally conductive filler is preferably 0.06 to 10 m². 2 / g. The specific surface area is a BET specific surface area and is measured according to JISE 1626. The average particle size of the second thermally conductive filler is D50 (mean diameter) in a particle size distribution measured by a laser diffraction scattering method. The method can use, for example, a LA-950 S2 laser diffraction / scattering particle size distribution analyzer manufactured by HORIBA Ltd.

[0049] The second thermally conductive filler preferably contains at least two types of inorganic particles with different average particle sizes. This is because small-sized thermally conductive inorganic particles can fill the gaps between larger-sized inorganic particles, providing almost the densest packing and improving the thermal conductivity properties.

[0050] According to the invention, the inorganic particles are surface-treated with a silane compound or its partial hydrolysate. The silane compound is oxidized by R(CH3) a Si(OR') 3-a expressed where R represents a substituted or unsubstituted organic group with 1 to 20 carbon atoms, R' represents an alkyl group with 1 to 4 carbon atoms, and a is 0 or 1. Examples of an alkoxysilane compound (hereafter referred to simply as "silane") expressed by R(CH3) a Si(OR') 3-a, where R represents a substituted or unsubstituted organic group with 1 to 20 carbon atoms, R' represents an alkyl group with 1 to 4 carbon atoms, and a is 0 or 1, the following are included: methyltrimethoxysilane; ethyltrimethoxysilane; propyltrimethoxysilane; butyltrimethoxysilane; pentyltrimethoxysilane; hexyltrimethoxysilane; hexyltriethoxysilane; octyltrimethoxysilane; octyltriethoxysilane; decyltrimethoxysilane; decyltriethoxysilane; dodecyltrimethoxysilane; dodecyltriethoxysilane; hexadecyltrimethoxysilane; hexadecyltriethoxysilane; octadecyltrimethoxysilane; and octadecyltriethoxysilane. These silane compounds can be used individually or in combination of two or more. The alkoxysilane and the one-terminated silanolsiloxane can be used together as surface treatment agents. In this case, the surface treatment can include adsorption in addition to a covalent bond.The quantity of particles with a particle size of 2 µm or more is preferably 50% by mass or more in relation to 100% by mass of the total number of particles. [Other components]

[0051] The mixture (II) may contain components other than those listed above, if required. For example, the mixture (II) may contain an inorganic pigment such as colcothar and alkyltrialkoxysilane, e.g., for use in the surface treatment of the filler. The material used for the surface treatment of the filler may, for example, be a silicone containing an alkoxy group.

[0052] Fig.Figure 1 is a schematic cross-sectional view of a thermally conductive film of an embodiment of the present invention. A thermally conductive film 10 comprises a matrix resin 11, mold filler pieces 12 containing a first thermally conductive filler with shape anisotropy, and a second thermally conductive filler 13. The mold filler pieces 12 contain a binder resin 14 and the first thermally conductive filler 15. The first thermally conductive filler 15 is oriented in the direction of the thickness of each of the mold filler pieces 12. The first thermally conductive filler 15 is also oriented in the direction of the thickness of the thermally conductive film 10, if present in the thermally conductive film 10.

[0053] Fig. Figures 3A to 3C are schematic diagrams illustrating a method for producing the mold-filler pieces 12 in an embodiment of the present invention. First, as shown in Fig.As shown in Figure 3A, a film is produced by pressure processing a mixture (I) of the binder resin 14 and the first thermally conductive filler 15 with shape anisotropy such that the first thermally conductive filler 15 is oriented towards the main surface of the film or block (first step).

[0054] The binding resin 14 is then cured, resulting in a foil-like shaped body 16 with a thickness a. Next, the foil-like shaped body 16 is cut in the direction of its thickness, e.g., along the dotted line in Fig.3A, to obtain the shaped filler pieces 12. In this case, assuming that the film-like shaped body 16 has a thickness a and a width c (where c>a, since the shaped body 16 has the shape of a film), the relationship between the thickness a and a section width b is defined as a>b. Due to the relationship a>b, the first thermally conductive filler 15 is likely to be oriented in the direction of the thickness of the thermally conductive film if the shaped filler pieces 12 are present in the thermally conductive film 10. Fig. 3B is a perspective view of a shape-filler piece 12, which is obtained by cutting the foil-like shaped body 16. Fig. 3C is a side view (i.e., ab view) of the mold filler piece 12. In this way the mold filler pieces 12 are procured.

[0055] The foil-like shaped body 16 can break when cut. In such a case, the width c of the shape-filler piece need not be maintained. As in Fig. As shown in Figure 3B, under the claim that the shape-filler piece in the form of a rectangular parallelepiped has a thickness b (corresponding to the “cutting width b”, as will be described later), a side a corresponding to the thickness a of the foil-like shaped body 16 and a side d which is the remaining side, the foil-like shaped body 16 can be cut such that the width c becomes narrower, as long as the shape-filler piece thus obtained has a shape which satisfies d≥a>b or a≥d>b.

[0056] The pressure processing of the mixture of the binder resin and the first thermally conductive filler can produce either a film or a block in the first step. In the case of the film, the block is cut to a width b to obtain the shape-filler pieces 12, and each of the shape-filler pieces has a shape that satisfies c ≥ a > b or a ≥ c > b. Due to the relationship c > a > b or a ≥ c > b, the first thermally conductive filler 15 is likely to be oriented in the direction of the thickness of the thermally conductive film if the shape-filler pieces 12 are present in the thermally conductive film. Examples

[0057] The present invention will be explained below using examples. However, the present invention is not limited to the following examples. <Wärmeleitfähigkeit>

[0058] A thermal resistance value (m) 2*K / W) was determined by a thermal resistance measurement method according to ASTM D5470. An approximate line graph was then created by plotting the measured thickness on the x-axis and the thermal resistance value on the y-axis. The reciprocal of the slope of this approximate line was determined as the thermal conductivity. (Example 1)<Form-Füllstoff-Stück> 1. Material components (1) Silicone component

[0059] A two-part, room-temperature curable silicone polymer containing a polyorganosiloxane was used as the silicone component in the amounts shown in Table 1. Solution A contained a polymer base component and a platinum metal catalyst. Solution B contained a polymer base component and an organohydrogen polysiloxane (crosslinking binder component). (2) Thermally conductive filler

[0060] A plate-like boron nitride filler (first thermally conductive filler) with a major axis of 700 µm and a minor axis of 50 µm, and a spherical aluminum oxide filler with an average particle size of 2 µm, were each used in amounts as shown in Table 1. The aluminum oxide filler was surface-treated with a silane adhesion promoter (triethoxysilane), thereby preventing a reduction in curing acceleration, which is the catalytic capability of the Pt catalyst. In the surface treatment, 1 part by weight of the silane adhesion promoter was added to 100 parts by weight of the aluminum oxide filler, and the mixture was stirred thoroughly. The stirred aluminum oxide filler was then spread evenly onto, for example, a tray and dried at 100°C for 2 hours. 2. Mixing and shaping

[0061] The silicone component and the thermally conductive filler were weighed and mixed in the quantities shown in Table 1 to form a fabric. Next, the fabric was sandwiched between PET films that had undergone a stress-relieving treatment and were rolled with rollers at a uniform speed to produce a film with a thickness of 3.0 mm (see Fig. 3A). The film was heated at 100°C for 15 minutes to cure the silicone polymer. Consequently, a film-like body was obtained in which the plate-like boron nitride filler (first thermally conductive filler) was oriented towards the main surface of the film-like body, i.e., the main surface of the plate-like boron nitride filler (first thermally conductive filler) was arranged essentially parallel to the main surface of the film-like body. [Table 1] Example 1 silicone component Solution A (parts by weight) 50 Solution B (parts by weight) 0,15 Plate-like boron nitride filler (first thermally conductive filler) (parts by weight) 50 Spherical aluminum oxide filler, average particle size: 2 µm (parts by weight) 100 3. Cutting the foil-shaped body

[0062] The foil-shaped body was cut with a cutter in the direction of the thickness (a) at average intervals of 0.5 mm (see Fig. 3A). In this way, mold filler pieces were obtained. Each of the mold filler pieces was in the shape of a rectangular parallelepiped with a length c of 5 mm, a width a of 3 mm and a thickness b of 0.5 mm (see Fig. 3B). Fig. Figure 2A shows a photograph (100x) of a side view (from the surface) of the mold filler piece. Fig. 2A was the plate-like boron nitride filler (first thermally conductive filler) oriented in the direction of the thickness b of the mold filler piece. Fig. Figure 2B shows a photograph (100x) of a top view (bc surface) of the mold filler piece. Fig. 2B considered the plane of the plate-like boron nitride filler (first thermally conductive filler). <Herstellung der wärmeleitfähigen Folie>

[0063] The mold filler pieces, a silicone component (a two-part, room-temperature curable silicone polymer) that would become a matrix resin upon curing, and a spherical aluminum oxide filler were weighed and mixed in the quantities shown in Table 2. The mixture was then formed into a film mold, and the resulting film was cured by heating at 100°C for 15 minutes. This yielded a thermally conductive film in which the plate-like boron nitride filler (the first thermally conductive filler) was oriented along the thickness of the thermally conductive film.In other words, in a cut surface that would have been seen if the thermally conductive film had been cut in the direction of its thickness, the longitudinal direction of the plate-like boron nitride filler (first thermally conductive filler) was oriented in the direction of the thickness of the thermally conductive film and was essentially the same as the direction of the thickness of the thermally conductive film.

[0064] The aluminum oxide filler was surface-treated with a silane adhesion promoter (triethoxysilane). In the surface treatment, 1 part by weight of the silane adhesion promoter was added to 100 parts by weight of the aluminum oxide filler, and the mixture was stirred thoroughly. The stirred aluminum oxide filler was then spread evenly onto, for example, a tray and dried at 100°C for 2 hours.

[0065] Fig.Figure 1 shows a schematic cross-sectional view of a thermally conductive film. Table 2 also shows the thermal conductivity and hardness of the thermally conductive film.

[0063] (Comparative example 1)

[0066] A thermally conductive film was produced as follows. Without using a mold filler piece, a silicone component, which would become a matrix resin upon curing, a first thermally conductive filler, and a second thermally conductive filler were weighed and mixed in the amounts shown in Table 2. The mixture was then formed into a film mold, and the resulting film was cured by heating at 100°C for 15 minutes. Table 2 also shows the thermal conductivity and hardness of the thermally conductive film of Comparative Example 1. [Table 2] Example 1 Comparative example 1 silicone component Solution A (parts by weight) 25 50 Solution B (parts by weight) 25 50 Mold filler pieces (parts by weight) 110 - Spherical aluminum oxide filler (second thermally conductive filler) average particle size: 2 µm (parts by weight) 90 100 Spherical aluminum oxide filler (second thermally conductive filler) average particle size: 35 µm (parts by weight) 100 100 Plate-like boron nitride filler (first thermally conductive filler) (parts by weight) - 50 thermal conductivity 2,08 1,07

[0067] Example 1 and Comparison Example 1 had the same weight ratio of resin component to thermally conductive filler. As can be seen from Table 2, the thermally conductive film from Example 1 contained the molded filler pieces in which the plate-like boron nitride filler was oriented in the direction of the thickness of the thermally conductive film, and thus had a higher thermal conductivity than the thermally conductive film of Comparison Example 1. Industrial applicability

[0068] The thermally conductive film of the present invention can be used to promote the heat dissipation from various heat-generating components to various heat-dissipating materials, e.g. as a thermally conductive film inserted between the heat-generating components, such as electronic components, and the heat-dissipating materials, such as metal. Description of reference symbols 1 Thermal conductivity measuring device 2 Sensor 3a, 3b Sample 4 Sensor tip 5 electrodes for applied current 6 Electrode for resistance value (temperature measuring electrode) 10 thermally conductive films 11 Matrix resin 12 pieces of form filler 13 second thermally conductive filler 14 Binding resin 15 first thermally conductive filler 16 molded bodies

Claims

[1] Method for producing a thermally conductive film (10), comprising: a first step of forming a film or block by pressing and / or rolling a mixture of a binder resin (14) and a first thermally conductive filler (15) with shape anisotropy, which has a plate shape and a main surface thereof or a needle shape and a longitudinal direction thereof, such that the first thermally conductive filler (15) is oriented in a direction of the main surface of the film or block; a second step of hardening the binder resin (14) and then cutting the film or block in one direction of thickness to obtain mold filler pieces (12) such that the first thermally conductive filler (15) in each of them is oriented in the thickness direction of the corresponding mold filler pieces (12); and a third step of mixing the mold-filler pieces (12), a matrix resin (11) and a second thermally conductive filler (13), forming the mixture into a foil mold using pressure rollers, and then hardening the matrix resin (11); wherein the thermally conductive film (10) contains the first thermally conductive filler (15) with its main surface aligned in a thickness direction of the thermally conductive film (10), if the first thermally conductive filler (15) has a plate shape; or else wherein the thermally conductive film (10) contains the first thermally conductive filler (15) with its longitudinal direction aligned in the thickness direction of the thermally conductive film (10), if the first thermally conductive filler (15) has a needle shape, and wherein the matrix resin (11) and the binder resin (14) can be cured by an addition reaction using a platinum group metal catalyst, and wherein the second thermally conductive filler (13) consists of inorganic particles, and the inorganic particles are coated with an R(CH3) a Si(OR') 3-a expressed alkoxysilane compound are surface-treated, wherein R represents a substituted or unsubstituted organic group with 1 to 20 carbon atoms, R' represents an alkyl group with 1 to 4 carbon atoms, and a is 0 or 1. [2] Method according to claim 1, wherein the first thermally conductive filler (15) with shape anisotropy consists of at least one selected from boron nitride and aluminium oxide. [3] Method according to claim 1 or 2, wherein the matrix resin (11) and the binder resin (14) are thermosetting resins of the same or different types. [4] Method of one of claims 1 to 3, wherein both the matrix resin (11) and the binder resin (14) are silicone polymers. [5] Method according to any one of claims 1 to 4, wherein the mold filler pieces (12) comprise spherical thermally conductive filler and / or irregularly shaped filler. [6] Method according to any one of claims 1 to 5, wherein the second thermally conductive filler (13) is selected from a spherical thermally conductive filler and an irregularly shaped filler. [7] Method according to any one of claims 1 to 6, wherein the thermal conductivity of the thermally conductive film (10) is 1.5 W / m·K or more. [8] Method according to any one of claims 1 to 7, wherein the second thermally conductive filler (13) contains at least two types of inorganic particles with different average particle sizes.

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