Resin composition and method for producing sheet using the resin composition

Abstract

To improve compatibility between a ceramic powder and a binder component in a resin composition.SOLUTION: There is provided a resin composition comprising a ceramic powder and a binder component. The binder component contains a component (A) which is a urethane (meth)acrylate and a component (B) which is a (meth)acrylate monomer. The component(A) and the component (B) are liquid at normal temperature. The resin composition comprises at least 5 mass% or more of the component (B) when the total of the component (A) and the component (B) is defined as 100 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a resin composition and a method for producing a sheet using the resin composition. [Background technology]

[0002] Power semiconductor elements (so-called power devices) have become indispensable for the efficient use of electrical energy. Demand is also increasing for lighting semiconductor elements (so-called high-power LED devices) used in energy-saving, long-life, high-brightness, and power LED lamps. The use of power devices and high-power LED devices requires technology for dissipating the generated heat to the surroundings. As shown in the following Patent Documents 1 to 5, active research and development is being conducted in this field.

[0003] The resin composition for thermally conductive materials disclosed in Japanese Patent No. 3875664 contains a liquid resin whose essential components are a (meth)acrylic polymer (A), a polymerizable monomer (B), and a plasticizer (C), and an inorganic filler having a thermal conductivity of 20 W / m·K or higher. The plasticizer (C) exhibits a weight loss of 10% by mass or less when maintained at 130°C for 168 hours. The inorganic filler is contained in an amount of 50 to 1500 parts by mass per 100 parts by mass of the liquid resin. The hardness of the cured product of the liquid resin is 5 to 70. The publication states that this composition not only has excellent thermal conductivity, but also makes it possible to efficiently obtain a cured product that has good moldability and flexibility for a thermally conductive sheet.

[0004] The resin composition for heat dissipation materials disclosed in Japanese Patent No. 4652916 is a resin composition that can be made into a heat dissipation material by blending an inorganic thermally conductive filler (excluding magnetic materials and carbon fibers) and then radically polymerizing and curing it. This resin composition contains, as essential components, a (meth)acrylic polymer with a hydroxyl value of 5 mgKOH / g or more and a radically polymerizable monomer. The publication states that this composition can provide a heat dissipation material with high thermal conductivity and can also improve the hardness, strength, and other properties of the heat dissipation material.

[0005] Japanese Patent No. 4344192 discloses a resin composition for heat dissipation materials that contains a liquid resin containing a trimellitic acid-based plasticizer and an acrylic copolymer as essential components. The resin composition further contains a crosslinker having an isocyanate group and an inorganic filler selected from aluminum oxide, boron nitride, and aluminum nitride. The publication states that this composition efficiently produces a cured product that can be used to produce a heat dissipation sheet that not only has excellent thermal conductivity but also good moldability and flexibility.

[0006] The green sheet disclosed in JP 2022-57233 A contains a nitride ceramic powder, a water-soluble resin binder, and a water-soluble plasticizer. The water-soluble resin binder has a glass transition temperature of 50°C or lower. The water-soluble plasticizer has a number-average molecular weight of 300 or higher and 1500 or lower. The publication states that this configuration can improve the formability, strength, and stability over time of the green sheet.

[0007] The green sheet disclosed in JP 2022-97775 A is described as containing a nitride ceramic powder, a water-soluble resin binder, and a plasticizer. The water-soluble resin binder in the green sheet is an acrylic resin having a glass transition point of 30°C or less. The publication also describes that this configuration makes it possible to produce a green sheet containing dense nitride ceramic powder. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 3875664 [Patent Document 2] Patent No. 4652916 [Patent Document 3] Patent No. 4344192 [Patent Document 4] Japanese Patent Publication No. 2022-57233 [Patent Document 5] Japanese Patent Publication No. 2022-97775 Summary of the Invention [Problem to be solved by the invention]

[0009] The present inventors are interested in improving the compatibility between the ceramic powder and the binder component in the resin composition. [Means for solving the problem]

[0010] The resin composition disclosed herein contains a ceramic powder and a binder component. The binder component contains component (A), which is a urethane (meth)acrylate, and component (B), which is a (meth)acrylate monomer. Components (A) and (B) are liquid at room temperature. When the total of components (A) and (B) is taken as 100 mass%, the resin composition contains at least 5 mass% of component (B). This configuration can improve the compatibility between the ceramic powder and the binder component in the resin composition.

[0011] In a preferred embodiment, the resin composition disclosed herein is a solvent-free system, which can more effectively achieve the above-mentioned effects, more effectively suppress the occurrence of defects in the production of a cured product of the resin composition, and more effectively realize the functions of the ceramic powder in the cured product.

[0012] Another preferred embodiment of the resin composition disclosed herein contains 45% by mass or more and 95% by mass or less of component (A) and 5% by mass or more and 55% by mass or less of component (B), where the total of component (A) and component (B) is taken as 100% by mass. This configuration further improves the compatibility between the ceramic powder and the binder component, thereby achieving appropriate hardness in the molded product and the cured product.

[0013] In another preferred embodiment of the resin composition disclosed herein, the glass transition temperatures of component (A) and component (B) are both equal to or lower than 0° C. This configuration allows the effects of the technology disclosed herein to be more effectively achieved.

[0014] In another preferred embodiment of the resin composition disclosed herein, the ceramic powder is a powder containing at least one nitride compound selected from aluminum nitride, boron nitride, and silicon nitride. The effects of the technology disclosed herein can be particularly preferably achieved in an embodiment in which the ceramic powder contains a nitride compound.

[0015] In another preferred embodiment, the resin composition disclosed herein is used to form a heat-dissipating material, which has excellent thermal conductivity.

[0016] The technology disclosed herein provides a method for producing a sheet. The method includes molding a resin composition into a sheet and heat treating the sheet-shaped molded product of the resin composition. This method improves the moldability of the sheet.

[0017] According to the technology disclosed herein, a method for manufacturing a heat dissipating material is provided. This manufacturing method includes the method for manufacturing the sheet described above. With this configuration, an excellent heat dissipating material can be manufactured. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram of a rolling mill 5. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the technology disclosed herein will be described. It should be noted that matters other than those specifically mentioned in this specification that are necessary for implementing the technology disclosed herein can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The technology disclosed herein can be implemented based on the contents disclosed in this specification and the technical common sense in the relevant field. In this specification, the notation "P to Q" indicating a numerical range includes "P or more and Q or less," "more than P but less than Q," "more than P but Q or less," and "P or more and less than Q."

[0020] <Resin composition> The resin composition disclosed herein contains, for example, a ceramic powder and a binder component. The resin composition disclosed herein is, for example, a mixture of a ceramic powder, a binder component, and optional additive components. The resin composition (mixture) disclosed herein is cured, for example, by molding into a predetermined shape and then heat-treating the mixture to polymerize the binder component. As used herein, the term "resin composition" refers to a mixture of a ceramic powder, a binder component, and optional additive components in an uncured state, regardless of whether the mixture has been molded into a predetermined shape. As used herein, the term "molded product" refers to a resin composition in an uncured state molded into a predetermined shape. As used herein, the term "cured product" refers to a resin composition that has been subjected to a curing treatment (e.g., heat treatment). As used herein, the term "sheet-like" is used to describe the shape of a molded product and the shape of a cured product. As used herein, the term "sheet" refers to a sheet-like cured product.

[0021] The ceramic powder is, for example, a component that imparts functionality to the cured product. The type of ceramic powder is not particularly limited, and may be appropriately selected depending on the functionality desired for the cured product. Examples of ceramics that make up the ceramic powder include metal oxides such as alumina, ceria, zirconia, and titania; semi-metal oxides such as silica; metal nitrides such as aluminum nitride; and semi-metal nitrides such as boron nitride and silicon nitride. The ceramic powder may contain one type of ceramic alone, or may contain two or more types of ceramics.

[0022] When the resin composition is used to form a heat-dissipating material, the ceramic powder is preferably a powder containing a nitride compound such as aluminum nitride, boron nitride, or silicon nitride. These nitride compounds have long been known to have low compatibility with binder components, for example. Therefore, the effects of the technology disclosed herein can be more effectively achieved when the ceramic powder is composed of a nitride compound. When the resin composition is used to form a heat-dissipating material, the content of the nitride compound is, for example, 10% by mass or more, preferably 15% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more, based on the total ceramic powder being 100% by mass. This can further improve the thermal conductivity (heat dissipation) of the cured product. On the other hand, from the viewpoint of achieving favorable compatibility between the ceramic powder and the binder component and achieving an appropriate dispersion of the ceramic powder in the cured product, the content of the nitride compound is, for example, 50% by mass or less, preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less.

[0023] The shape of the ceramic powder is not particularly limited, and may be, for example, spherical (including nearly spherical), scaly, fibrous, plate-like, irregular, agglomerated powder, granular, or the like.

[0024] The average particle diameter of the ceramic powder is not particularly limited, but is generally 0.01 μm to 50 μm. From the viewpoint of imparting a predetermined function (for example, heat dissipation) to the cured product, the average particle diameter is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more. On the other hand, from the viewpoint of sheet processability, the average particle diameter is, for example, 45 μm or less, preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less. In this specification, the term "average particle diameter" refers to the particle diameter ("D") corresponding to the cumulative 50% from the fine particle side in the volume-based particle size distribution measured by particle size distribution measurement based on the laser diffraction / light scattering method. 50 Also called "diameter."

[0025] From the viewpoint of appropriately imparting the desired function to the cured product, when the entire resin composition is taken as 100% by mass, the content of the ceramic powder is generally 70% by mass or more, for example 75% by mass or more, preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more. From the viewpoint of facilitating molding the resin composition into a desired shape, when the entire resin composition is taken as 100% by mass, the content of the ceramic powder is generally 99% by mass or less, preferably 98% by mass or less, more preferably 97% by mass or less, and even more preferably 96% by mass or less.

[0026] The binder component is, for example, a component that has the function of binding particles constituting a ceramic powder together. The compatibility between the ceramic powder and the binder component can be an important factor, for example, in properly molding a resin composition and obtaining a cured product that is less susceptible to damage. The present inventors have investigated the composition of the resin composition, including the binder component, in order to improve the compatibility between the ceramic powder and the binder component in the resin composition, thereby enabling the resin composition to be properly molded without causing damage or the like when molded into a predetermined shape, and to prevent damage or the like from occurring in the cured product and ensure that it functions properly.

[0027] The binder components herein include component (A) and component (B). Component (A) is a urethane (meth)acrylate. Component (A) is a component that imparts, for example, appropriate hardness and appropriate softness to the resin composition and the cured product. In this specification, "urethane (meth)acrylate" refers to a compound containing a urethane bond (-NH-C(=O)-O-) and a (meth)acryloyl group in one molecule. In this specification, the term "(meth)acryloyl group" encompasses both a "methacryloyl group (-C(=O)-C(CH3)=CH2)" and an "acryloyl group ((-C(=O)-CH=CH2)." In this specification, the term "(meth)acrylate" encompasses both "methacrylate" and "acrylate." Therefore, the urethane (meth)acrylate of component (A) may be either a urethane acrylate or a urethane methacrylate.

[0028] The urethane (meth)acrylate, which is component (A), is liquid at room temperature (25°C). This facilitates compatibility between the ceramic powder and the binder component during preparation of the resin composition, and maintains this compatibility. From this perspective, the glass transition temperature of component (A) is generally 10°C or lower, for example, 0°C or lower is preferable, -5°C or lower is preferable, -10°C or lower is more preferable, -15°C or lower is even more preferable, -20°C or lower is even more preferable, and -25°C or lower is particularly preferable. On the other hand, from the perspective of imparting appropriate hardness to the resin composition and the cured product, the glass transition temperature of component (A) is, for example, -60°C or higher, preferably -55°C or higher, and more preferably -50°C or higher.

[0029] Although not particularly limited, the weight-average molecular weight of component (A) is generally 100 to 25,000. The weight-average molecular weight of component (A) is, for example, 200 or more, or 500 or more, preferably 750 or more, and more preferably 1,000 or more. On the other hand, the weight-average molecular weight of component (A) is, for example, 20,000 or less, preferably 17,500 or less, and more preferably 15,000 or less. The weight-average molecular weight of component (A) can be, for example, measured by gel permeation chromatography (GPC) and converted using a standard polystyrene calibration curve to obtain a weight-average molecular weight. Alternatively, a nominal value published by a manufacturer or the like may be used.

[0030] Component (A) is preferably a urethane (meth)acrylate having one to three functional groups in one molecule. This can impart appropriate softness to the resin composition and the cured product. From the viewpoint of more effectively realizing this effect, component (A) is preferably a monofunctional or bifunctional urethane (meth)acrylate, and more preferably a bifunctional urethane (meth)acrylate.

[0031] The urethane (meth)acrylate of component (A) is, for example, a compound obtained by reacting a polyisocyanate with a (meth)acrylate having a hydroxyl group, a compound obtained by reacting a (meth)acrylate having an isocyanate group with a polyol, or a compound obtained by reacting a polyisocyanate with a polyol.

[0032] The polyisocyanate is not particularly limited, but examples thereof include isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), hydrogenated MDI, polymeric MDI, 1,5-naphthalene diisocyanate, norbornane diisocyanate, tolidine diisocyanate, xylylene diisocyanate (XDI), hydrogenated XDI, lysine diisocyanate, triphenylmethane triisocyanate, tris(isocyanatophenyl)thiophosphate, tetramethylxylylene diisocyanate, 1,6,11-undecane triisocyanate, etc. As the polyisocyanate, one of the above-mentioned compounds may be used alone, or two or more may be used in combination.

[0033] Examples of (meth)acrylates having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 1,4-cyclohexanedimethanol mono(meth)acrylate. Alternatively, mono(meth)acrylates of dihydric alcohols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and polyethylene glycol; mono(meth)acrylates or di(meth)acrylates of trihydric alcohols such as trimethylolethane, trimethylolpropane, and glycerin; and epoxy (meth)acrylates such as bisphenol A-type epoxy (meth)acrylate. As the (meth)acrylate having a hydroxyl group, one of the above-mentioned compounds may be used alone, or two or more may be used in combination.

[0034] Examples of the (meth)acrylate having an isocyanate group include 2-(meth)acryloyloxyethyl isocyanate, 1,1-bis(acryloyloxymethyl)ethyl isocyanate, etc. As the (meth)acrylate having an isocyanate group, one of the above-mentioned compounds may be used alone, or two of them may be used in combination.

[0035] Examples of polyols include ethylene glycol, propylene glycol, glycerin, sorbitol, trimethylolpropane, carbonate diol, polyether diol, polyester diol, polycaprolactone diol, etc. As the polyol, one of the above compounds may be used alone, or two or more may be used in combination.

[0036] The urethane (meth)acrylate of component (A) may be an aliphatic urethane (meth)acrylate or an aromatic urethane (meth)acrylate as long as it has the above-mentioned characteristics. The urethane (meth)acrylate of component (A) may be a single type or a combination of two or more types.

[0037] To achieve the effects of the technology disclosed herein, it is preferable to use a solvent-free urethane (meth)acrylate as component (A). Examples of commercially available urethane (meth)acrylates that can be preferably used as component (A) include "KRM9276," "KRM9465," "EBECRYL230," "EBECRYL270," "KRM8296," and "EBECRYL210" manufactured by Daicel-Allnex Corporation.

[0038] Component (B) is, for example, a (meth)acrylate monomer. Component (B) is, for example, a component that prevents the viscosity of the binder component from becoming too high and reduces the hardness of the binder component. The (meth)acrylate of component (B) may be an acrylate monomer or a methacrylate monomer.

[0039] The (meth)acrylate monomer of component (B) is liquid at room temperature (25°C). This allows component (B), for example, to improve the compatibility between the entire binder component and the ceramic powder, allowing the ceramic powder to better exhibit its functions in the cured product. From this perspective, the glass transition temperature of component (B) is generally 10°C or lower, for example, 0°C or lower is preferable, -5°C or lower is preferable, -10°C or lower is more preferable, -15°C or lower is even more preferable, and -20°C or lower is particularly preferable. On the other hand, from the perspective of imparting appropriate hardness to the resin composition and the cured product, the glass transition temperature of component (B) is, for example, -60°C or higher, preferably -55°C or higher, and more preferably -50°C or higher.

[0040] Although not particularly limited, the weight-average molecular weight of component (B) is generally 50 to 2000. The weight-average molecular weight of component (B) is, for example, 100 or more, or 200 or more, preferably 300 or more, and more preferably 400 or more. On the other hand, the weight-average molecular weight of component (B) is, for example, 1500 or less, preferably 1000 or less, and more preferably 800 or less. The weight-average molecular weight of component (B) can be, for example, measured by gel permeation chromatography (GPC) and converted using a standard polystyrene calibration curve to obtain a weight-average molecular weight. Alternatively, a nominal value published by a manufacturer or the like may be used.

[0041] Component (B) is preferably a (meth)acrylate monomer having one or three functional groups in one molecule. This can impart appropriate softness to the resin composition and molded article. From the viewpoint of more effectively realizing this effect, component (B) is preferably a monofunctional (meth)acrylate monomer or a bifunctional (meth)acrylate monomer, and more preferably a bifunctional (meth)acrylate monomer.

[0042] Preferred examples of monofunctional (meth)acrylate monomers include phenoxydiethylene glycol acrylate and phenoxyethyl acrylate. Preferred examples of bifunctional (meth)acrylates include polyethylene glycol diacrylate (e.g., PEG400 diacrylate and PEG600 diacrylate). To achieve the effects of the technology disclosed herein, it is preferable to use a solventless (meth)acrylate monomer as component (B). Commercially available (meth)acrylate monomers that can be preferably used as component (B) include, for example, "EBECRYL110," "EBECRYL114," "PEG400DA," and "EBECRYL11" manufactured by Daicel-Allnex Corporation.

[0043] The resin composition contains 5% by mass or more of component (B) when the total of components (A) and (B) is taken as 100% by mass. The greater the content of component (B), the better the compatibility between the ceramic powder and the binder component, thereby achieving an appropriate hardness in the molded body and the cured product. From this perspective, when the total of components (A) and (B) is taken as 100% by mass, the content of component (B) is preferably 6% by mass or more. From the same perspective, when the total of components (A) and (B) is taken as 100% by mass, the content of component (B) is, for example, 60% by mass or less, and preferably 55% by mass or less. Note that when the total of components (A) and (B) is taken as 100% by mass, the resin composition may contain, for example, 45% to 95% by mass of component (A).

[0044] In addition to components (A) and (B), the binder component may also contain an optional component (C) as long as the effects of the technology disclosed herein are achieved. The optional component (C) is, for example, a resin that does not fall into either component (A) or component (B). When the entire binder component is taken as 100% by mass, the content of components (A) and (B) is, for example, 90% by mass or more, preferably 95% by mass or more, more preferably 97% by mass or more, even more preferably 99% by mass or more, and particularly preferably 99.5% by mass or more. The closer to 100% by mass, the better.

[0045] The resin composition contains a binder component in an amount of approximately 0.5% by mass or more, when the entire composition is taken as 100% by mass. From the viewpoint of adequately binding the ceramic particles constituting the ceramic powder together, the content ratio of the binder component relative to the entire resin composition is, for example, 1% by mass or more, and preferably 3% by mass or more. From the viewpoint of better realizing the functionality of the ceramic powder in the cured product of the resin composition, the content ratio of the binder component relative to the entire resin composition is, for example, 10% by mass or less, preferably 8% by mass or less, and more preferably 6% by mass or less.

[0046] In addition to the ceramic powder and binder component, the resin composition may contain any additive component as needed. Any additives conventionally known for this type of application may be used as the additive component without particular limitation. Examples of such additives include plasticizers, dispersants (preferably anionic dispersants), polymerization initiators, release agents, antifoaming agents, antioxidants, and thickeners.

[0047] As described above, the resin composition disclosed herein contains a ceramic powder and a binder component. The binder component contains component (A), which is a urethane (meth)acrylate, and component (B), which is a (meth)acrylate monomer. Components (A) and (B) are liquid at room temperature. When the total of components (A) and (B) is 100% by mass, the resin composition contains at least 5% by mass of component (B).

[0048] The resin composition disclosed herein contains a binder component consisting of component (A) which is a urethane (meth)acrylate and component (B) which is a (meth)acrylate monomer. This allows, for example, the physical properties of the binder component (e.g., viscosity, hardness, etc.) to be adjusted favorably, thereby achieving appropriate hardness and softness in the resin composition and the cured product. The fact that both components (B) are liquid at room temperature facilitates compatibility between the ceramic powder and the binder component during the preparation of the resin composition, maintains their good compatibility, and allows the ceramic powder to function appropriately in the cured product. By including at least 5% by mass of component (B) when the total of components (A) and (B) is 100% by mass, the binder component can achieve physical properties that are compatible with the ceramic powder. This improves the compatibility between the ceramic powder and the binder component in the resin composition disclosed herein.

[0049] From the viewpoint of achieving the effects of the technology disclosed herein, the resin composition is preferably solvent-free. The resin composition does not contain, for example, an organic solvent. Depending on the type of ceramic constituting the ceramic powder, wettability by organic solvents may be low. When using such ceramic powder, making the resin composition solvent-free can improve the compatibility between the ceramic powder and the binder component, thereby increasing the dispersibility of the ceramic powder in the resin composition and the cured product. Therefore, making the resin composition solvent-free can suppress the occurrence of defects during the production of a cured product, and the functionality of the ceramic powder in the cured product can be better realized. Furthermore, when the resin composition is solvent-free, for example, even when a curing treatment (e.g., heat treatment) of a molded product is performed, the organic solvent does not volatilize from the molded product. Therefore, for example, the generation of bubbles in the cured product due to heat treatment can be suppressed, and ultimately, damage to the cured product is less likely to occur. Note that the resin composition may contain an organic solvent as long as the effects of the technology disclosed herein can be achieved. The content of the organic solvent can be appropriately set so as to appropriately achieve the effects of the technology disclosed herein.

[0050] The resin composition may be used, for example, to form a heat-dissipating material. Examples of heat-dissipating materials include heat-dissipating sheets. The heat-dissipating sheet is a sheet-like member interposed between a heat-generating component (e.g., a power device) and a heat-dissipating component (e.g., a heat-dissipating fin, a heat sink, a heat-dissipating plate, etc.). Alternatively, the heat-dissipating sheet may be used in place of the heat-dissipating component. In this case, the resin composition may contain, for example, a powder containing the nitride compound described above as the ceramic powder. In the resin composition, the binder component is composed of component (A) and component (B) in a predetermined content ratio, thereby improving the compatibility of the binder component with the nitride compound. This improves the dispersibility of the ceramic powder in the resin composition, which in turn improves the thermal conductivity of the cured product.

[0051] According to the technology disclosed herein, a method for manufacturing a sheet is disclosed. In this embodiment, the method for manufacturing a sheet includes a preparing step, a mixing step, a molding step, and a heating step. The preparing step is, for example, a step of preparing raw materials for a resin composition. In this step, for example, a ceramic powder, a binder component, and, if necessary, additives are prepared. The characteristics of each component are as described above. Here, as the binder component, it is preferable to prepare a solvent-free component (A) and a solvent-free component (B). When an optional component (C) is included as the binder component, it is preferable that component (C) is also solvent-free.

[0052] The mixing step is, for example, a step of mixing the raw materials prepared in the preparation step. This results in a clay-like resin composition. In this embodiment, in this step, the raw materials are stirred and mixed using a commercially available mixer. The stirring and mixing is preferably performed at room temperature, for example, from the viewpoint of suppressing reaction of the binder component in this step. The stirring time, stirring speed, etc. are not particularly limited and can be set appropriately.

[0053] The molding step is, for example, a step of molding the resin composition obtained by carrying out the mixing step into a sheet. FIG. 1 is a schematic diagram of a rolling apparatus 5. FIG. 1 schematically shows one embodiment of manufacturing a molded body 100 using the rolling apparatus 5. As shown in FIG. 1, the rolling apparatus 5 has a storage tank 1, a feeder 1b, and a pair of rolls 2. The storage tank 1 is, for example, a portion for storing the resin composition 10. In this embodiment, the storage tank 1 is disposed at the top of the rolling apparatus 5. The feeder 1b is, for example, a portion for feeding the resin composition 10 from the storage tank 1 toward the rolls 2. In the embodiment shown in FIG. 1, the feeder 1b is disposed at the bottom of the storage tank 1. The pair of rolls 2 is, for example, a portion for roll-molding the resin composition 10 into a sheet. In this embodiment, the pair of rolls 2 is disposed below the feeder 1b so that their rotation axes are parallel to each other.

[0054] In the molding process, first, as shown in FIG. 1, the resin composition 10 obtained in the mixing process is charged into a storage tank 1 of a rolling device 5. The resin composition 10 charged into the storage tank 1 is discharged to the outside through a feeder 1b at the bottom. The discharged resin composition 10 is supplied between a pair of rolls 2. The rolls 2 rotate at a predetermined rotation speed in the direction of the arrow in FIG. 1, thereby compressing the supplied resin composition 10. The temperature of the pair of rolls 2 at this time is preferably a temperature at which the binder component does not react, for example. The temperature can be set appropriately depending on, for example, the glass transition temperature of the binder component. The rotation speed of the rolls 2 can be set appropriately. In this process, the resin composition 10 is molded into a sheet, and a sheet-like molded product 100 is produced.

[0055] The heating step is, for example, a step of subjecting the molded body 100 obtained in the molding step to a heat treatment. This causes the components (A) and (B) to copolymerize, curing the molded body 100 and producing a cured product (a sheet, which is the object of production by this production method). In this embodiment, in the heating step, the molded body 100 is heated in a temperature range of 100°C to 120°C for 5 minutes to 2 hours. There are no particular limitations on the means for heating the molded body 100, and a conventionally known heater such as an oven can be used.

[0056] As described above, the sheet manufacturing method disclosed herein includes forming a resin composition into a sheet and heat treating the sheet-shaped molded product of the resin composition. As described above, since the compatibility between the ceramic powder and the binder component in the resin composition is improved, the moldability of the sheet can be improved.

[0057] The above-described manufacturing method may be employed, for example, in a method for manufacturing a thermally conductive material. That is, the manufacturing method for a thermally conductive material disclosed herein may include the above-described method for manufacturing a sheet. When manufacturing a thermally conductive material, a ceramic powder containing a nitride compound may be used. By including the above-described method for manufacturing a sheet, the use of organic solvents can be reduced or eliminated. This allows the use of components that are not compatible with the ceramic powder to be reduced, and the compatibility between the ceramic powder and the binder component to be improved. This improves the formability of a sheet containing an acrylic resin, and ultimately allows the production of a thermally conductive material with high thermal conductivity and excellent heat dissipation properties.

[0058] In the above-described sheet manufacturing method, a rolling machine having a pair of rolls is used to mold the resin composition into a sheet. However, the manufacturing method is not limited to this. For example, the manufacturing method may involve applying the resin composition to a release-treated substrate by a doctor blade method to form a coating film, and then pressing the coating film to a predetermined thickness to form a sheet. Thereafter, the sheet-shaped molded product of the resin composition is subjected to a heat treatment to produce the sheet to be manufactured.

[0059] Next, test examples relating to the technology disclosed herein will be described. Note that the test examples shown below are not intended to limit the technology disclosed herein. In the following description, unless otherwise specified, "%" is based on mass.

[0060] <Preparing urethane (meth)acrylate> As the urethane (meth)acrylate, the following urethane (meth)acrylates A to D were prepared. Urethane (meth)acrylate A: "KRM9465" from Daicel Allnex Co., Ltd. Urethane (meth)acrylate B: Daicel Allnex Corporation's "EBECRYL270" Urethane (meth)acrylate C: Daicel Allnex Corporation's "KRM2000" Urethane (meth)acrylate D: "EBECRYL4587" from Daicel Allnex Corporation

[0061] The physical properties (glass transition temperature (Tg), number of functional groups, viscosity, weight-average molecular weight, density) of urethane (meth)acrylates A to D are shown in the corresponding columns in Table 1. All physical properties shown in Table 1 are nominal values ​​disclosed by the distributor. A "-" in Table 1 indicates that no nominal value was disclosed. With regard to the viscosities shown in Table 1, the viscosities of urethane (meth)acrylates A to C are measured at 60°C. The viscosity of urethane (meth)acrylate D is measured at 23°C.

[0062] [Table 1]

[0063] <Preparing (meth)acrylate monomers> As the (meth)acrylate monomer, the following (meth)acrylate monomers A to E were prepared. (Meth)acrylate monomer A: "EBECRYL11" from Daicel Allnex Corporation (Meth)acrylate monomer B: "PEG400DA" from Daicel Allnex Corporation (Meth)acrylate monomer C: "EBECRYL150" from Daicel Allnex Corporation (Meth)acrylate monomer D: "EBECRYL160S" from Daicel Allnex Corporation (Meth)acrylate monomer E: "EBECRYL40" from Daicel Allnex Corporation

[0064] The physical properties (glass transition temperature (Tg), number of functional groups, viscosity, weight average molecular weight, and density) of (meth)acrylate monomers A to E are shown in the corresponding columns in Table 2. All of the physical properties shown in Table 2 are nominal values ​​disclosed by the distributors. All of the viscosities of the (meth)acrylate monomers shown in Table 2 are measured at 25°C.

[0065] [Table 2]

[0066] [Preparation of resin composition] --Example 1-- As ceramic powders, aluminum nitride powder (Tokuyama Corporation) and alumina powder were prepared. The aluminum nitride powder was amorphous and had an average particle diameter of 5 μm. The alumina powder was spherical and had an average particle diameter of 1 μm. As binder components, urethane (meth)acrylate A and (meth)acrylate monomer A were prepared. In addition, a plasticizer, a dispersant, and a thermal polymerization initiator were prepared. When the entire resin composition was taken as 100%, the total of the organic components was 5%, the aluminum nitride powder was 30%, and the alumina powder was 65%. When the entire binder components were taken as 100%, component (A) was 57%, and component (B) was 43%. Here, the organic components refer to the components of the resin components excluding the ceramic powder.

[0067] The prepared materials were charged into an automatic revolving mixer and mixed to prepare a clay-like resin composition. The clay-like resin composition was then formed into a sheet using a rolling mill. The sheet-like molded product was then heat-treated. The heat treatment was carried out for 10 minutes in an oven set at 110°C. This heat treatment caused copolymerization of component (A) and component (B), resulting in the curing of the sheet-like molded product. This resulted in the sheet of this example.

[0068] -Example 2 to Example 15- Regarding the binder components, the urethane (meth)acrylate and (meth)acrylate monomer shown in Table 3 were blended in the content ratios shown in Table 3. Other than that, the sheets of each example were produced using the same materials and procedures as in Example 1. The alphabets in the "Type" column of Table 3 correspond to the alphabets of urethane (meth)acrylates A to D or (meth)acrylate monomers A to D.

[0069] [Evaluation of sheet formability] The formability of each example sheet was evaluated. First, a portion of each example sheet was fixed tightly to the surface of a test stand, and the fixed portion was bent against the surface of the test stand using a metal rod with a diameter of 10 mm as a base point. Next, the example sheets that did not suffer damage (cracks, etc.) were further bent. The appearance of each example sheet when bent was evaluated using the following three-point scale. The results are shown in the corresponding column in Table 3. "Excellent": Excellent sheet formability. Even when the sheet was wrapped around the metal rod and bent by 90 degrees or more from the surface of the test stand, the sheet did not break. "○": Good sheet formability. The sheet was not damaged when the metal rod was wrapped around it and bent 90 degrees from the surface of the test stand, but was damaged when bent more than 90 degrees. "X": Poor sheet formability. The sheet broke from the surface of the test bench until it was wrapped around the metal rod and bent 90 degrees.

[0070] [Measurement of thermal conductivity] The thermal conductivity (W / m K) of each sheet in the thickness direction was measured using a thermal conductivity measuring device (LFA 467 HyperFlash (registered trademark) (NETZSCH)) according to the device's manual. The results are shown in the relevant columns in Table 3. In this test example, examples with a thermal conductivity of 2 (W / m K) or more but less than 3 (W / m K) were evaluated as having "good thermal conductivity," and examples with a thermal conductivity of 3 (W / m K) or more were evaluated as having "excellent thermal conductivity."

[0071] [Asker C hardness measurement] The Asker C hardness of each example sheet was measured using an Asker C hardness tester according to the device manual. The results are shown in the corresponding column in Table 3. In this test example, examples with an Asker C hardness of 80 or less were considered to have passed.

[0072] [Table 3]

[0073] As shown in Table 1, the resin compositions of Examples 1 to 6 contain component (A), which is a urethane (meth)acrylate, and component (B), which is a (meth)acrylate monomer. Component (A) (here, urethane (meth)acrylate A or urethane (meth)acrylate B) and component (B) (here, (meth)acrylate monomer A or (meth)acrylate monomer B) are liquid at room temperature. When the total of components (A) and (B) is taken as 100%, the resin compositions contain at least 5 mass% of component (B). As can be seen from Table 1, the resin compositions of Examples 1 to 6 had appropriate hardness and also excellent or good sheet formability. This indicates that the resin compositions of Examples 1 to 6 have improved compatibility between the ceramic powder and the binder component.

[0074] The technology disclosed herein has been described above, but these are merely examples and do not limit the scope of the claims. Various modifications can be made to the technology disclosed herein without departing from the spirit of the technology.

[0075] The techniques disclosed herein include the techniques described in the following sections. Section 1: A resin composition comprising a ceramic powder and a binder component, The binder component includes a component (A) that is a urethane (meth)acrylate and a component (B) that is a (meth)acrylate monomer, The component (A) and the component (B) are liquid at room temperature, A resin composition containing at least 5% by mass or more of the component (B) when the total of the component (A) and the component (B) is 100% by mass. Section 2: Item 1. The resin composition according to item 1, which is a solventless type. Section 3: Item 3. The resin composition according to item 1 or 2, wherein the component (A) is contained in an amount of 45% by mass or more and 95% by mass or less, and the component (B) is contained in an amount of 5% by mass or more and 55% by mass or less, when the total amount of the component (A) and the component (B) is 100% by mass. Section 4: 4. The resin composition according to any one of items 1 to 3, wherein the glass transition temperature of the component (A) and the glass transition temperature of the component (B) are both 0° C. or lower. Section 5: 5. The resin composition according to any one of items 1 to 4, wherein the ceramic powder is a powder containing at least one nitride compound selected from aluminum nitride, boron nitride, and silicon nitride. Item 6: 6. The resin composition according to any one of items 1 to 5, which is used to form a heat dissipating material. Section 7: Item 7. Molding the resin composition according to any one of items 1 to 6 into a sheet; subjecting the sheet-shaped molded body of the resin composition to a heat treatment; A method for manufacturing a sheet, comprising: Section 8: Item 8. A method for producing a heat dissipating material, comprising the method for producing the heat dissipating material according to item 7. [Explanation of symbols]

[0076] 1. Storage tank 1b Feeder 2 rolls 5. Rolling equipment 10 Resin composition 100 Molded body

Claims

1. A resin composition comprising a ceramic powder and a binder component, The binder component includes a component (A) that is a urethane (meth)acrylate and a component (B) that is a (meth)acrylate monomer, The component (A) and the component (B) are liquid at room temperature, A resin composition comprising at least 5% by mass or more of the component (B) when the total of the component (A) and the component (B) is 100% by mass.

2. The resin composition according to claim 1, which is a solvent-free type.

3. 3. The resin composition according to claim 1, wherein the component (A) is contained in an amount of 45% by mass or more and 95% by mass or less, and the component (B) is contained in an amount of 5% by mass or more and 55% by mass or less, when the total amount of the component (A) and the component (B) is 100% by mass.

4. The resin composition according to claim 1 or 2, wherein the glass transition temperature of the component (A) and the glass transition temperature of the component (B) are both 0°C or lower.

5. 3. The resin composition according to claim 1, wherein the ceramic powder is a powder containing at least one nitride compound selected from the group consisting of aluminum nitride, boron nitride, and silicon nitride.

6. The resin composition according to claim 5 , which is used to form a heat dissipating material.

7. Molding the resin composition according to claim 1 or 2 into a sheet; subjecting the sheet-shaped molded body of the resin composition to a heat treatment; A method for manufacturing a sheet, comprising:

8. A method for producing a heat-dissipating material, comprising the method according to claim 7.

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