Method for manufacturing a resin composition layer

Abstract

To provide a manufacturing method of a resin composition layer made of a resin composition containing an aggregated inorganic filler and a thermosetting resin.SOLUTION: A method of manufacturing a resin composition layer has the steps of: (a) press processing a carrier film and a sheet formed using the resin composition on the carrier film under the conditions of press temperature of 0°C or higher and 110°C or lower, and press pressure of 40 MPa or more and 1000 MPa or less; and (b) press processing the sheet subjected to the step (a), under the conditions of press temperature of 70°C or higher and 250°C or lower, and press pressure of 3 MPa or more and 100 MPa or less, to obtain the resin composition layer.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a resin composition layer, a resin composition layer obtained by the manufacturing method, and a composite molded body including the resin composition layer. The resin composition layer and the composite molded body obtained by the method for manufacturing the resin composition layer of the present invention can be suitably used, for example, as a heat dissipation material for power semiconductor devices.

Background Art

[0002] Regarding heat dissipation sheets having good thermal conductivity and excellent insulation properties, many studies have been conducted. In particular, attempts have been continuously made to mix fillers into resins to obtain heat dissipation resin sheets that satisfy high levels of thermal conductivity and insulation properties. As fillers contained in the heat dissipation resin sheets, various oxides and nitrides are used, and many studies have also been conducted on their particle sizes, particle size distributions, and the like.

[0003] Conventionally, the use of hexagonal boron nitride as a filler contained in a heat dissipation sheet has been studied. Hexagonal boron nitride is generally a thin plate-like crystal, and its thermal conductivity in the plane direction of the thin plate is high, but the thermal conductivity in the thickness direction of the thin plate is low. Therefore, when thin plate-like boron nitride is blended into a heat dissipation sheet, the boron nitride is oriented parallel to the sheet surface when forming the sheet, and sufficient thermal conductivity cannot be obtained in the thickness direction of the sheet.

[0004] There is an aggregated boron nitride filler as a material for increasing the thermal conductivity in the thickness direction of the sheet. By using the aggregated boron nitride filler, the thermal conductivity in the thickness direction of the sheet can be improved.

[0005] As an aggregated boron nitride filler, an aggregated boron nitride filler with a cardhouse structure has been developed (see, for example, Patent Document 1). Furthermore, an aggregated boron nitride filler with a cardhouse structure that has a relatively large average particle size and does not collapse easily even when pressure is applied has been developed (see, for example, Patent Document 2). Because the cardhouse structure of the aggregated boron nitride filler ensures a heat conduction path, incorporating it into a heat dissipation sheet results in excellent heat conductivity in the thickness direction of the sheet. Aggregated boron nitride fillers are composed of aggregated boron nitride particles without the use of a separate binder. Therefore, even when external forces are applied during sheet formation, the cardhouse structure does not easily collapse, maintaining the heat conduction path and allowing heat to be dissipated in the thickness direction of the sheet, thus achieving excellent thermal conductivity (see, for example, Patent Document 3). As a molding method to increase the thermal conductivity in the thickness direction of a sheet, a method is known in which the thermal conductivity is increased by bringing the aggregated boron nitride fillers within the sheet into surface contact with each other (see, for example, Patent Document 4).

[0006] Patent documents 1 to 4 describe forming a layer of resin composition containing agglomerated boron nitride by applying a thermosetting resin composition containing agglomerated boron nitride filler to a substrate and then heating and pressurizing it. However, detailed studies on the pressing conditions and pressing process have not been conducted.

[0007] Patent Document 5 describes drying a coating layer of a resin composition containing boron nitride filler and alumina, then heating and pressurizing it to bond the layers together to obtain a resin sheet in the B-stage state, and sandwiching the B-stage resin sheet between copper foils to obtain a cured resin sheet laminate in the C-stage state with copper foil on both sides. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 5679083 [Patent Document 2] Japanese Patent Publication No. 2016-135730 [Patent Document 3] International Publication No. 2015 / 119198 [Patent Document 4] International Publication No. 2019 / 189746 [Patent Document 5] Japanese Patent Publication No. 2016-79304 [Overview of the project] [Problems that the invention aims to solve]

[0009] The aggregated boron nitride fillers disclosed in Patent Documents 1 to 3 may have fine voids remaining between the fillers, and further improvement in insulation properties is necessary. Patent Document 4 does not consider the handling characteristics of the sheet, and improvement in handling characteristics is required for larger surface areas.

[0010] In Patent Document 5, the press pressure at the B stage is low in order to obtain sheet fluidity, resulting in voids remaining in the sheet and a low dielectric strength. In Patent Document 5, the remaining voids make the sheet brittle, and further improvements in handling are necessary for large-area applications.

[0011] The present invention aims to provide a method for manufacturing a resin composition layer formed using a resin composition containing aggregated inorganic fillers and a thermosetting resin, which improves the handling properties of the sheet formed using the resin composition, reduces damage and defects to the film due to handling, and improves the voltage resistance, adhesion, and heat resistance of the resin composition layer. [Means for solving the problem]

[0012] The inventors have found that the above problems can be solved by going through a specific pressing process in a method for producing a resin composition layer containing an aggregated inorganic filler and a thermosetting resin. The gist of this invention is as follows:

[0013] [1] A method for manufacturing a resin composition layer comprising a resin composition containing an aggregated inorganic filler and a thermosetting resin, the method for manufacturing a resin composition layer having the following steps (a) and (b). (a) A step of pressing a carrier film and a sheet formed using the resin composition on the carrier film under conditions where the pressing temperature is 0°C or higher and 110°C or lower, and the pressing pressure is 40 MPa or higher and 1000 MPa or lower (b) A step of pressing the sheet obtained in step (a) under conditions where the pressing temperature is 70°C or higher and 250°C or lower, and the pressing pressure is 3 MPa or higher and 100 MPa or lower to obtain a resin composition layer

[0014] [2] The method for manufacturing a resin composition layer according to [1], wherein the reaction rate of the thermosetting resin in the sheet after step (a) obtained by the following method (referred to as "reaction rate (A)") is less than 50%. <Method for measuring and calculating reaction rate (A)> (a) For the sheets before and after step (a), it is calculated by the following formula from the calorific value of the exothermic peak obtained when the temperature is raised from 40°C to 250°C at 10°C / min by differential scanning calorimetry (DSC). Reaction rate (A) (%) = (1 - ((calorific value after step (a)) / (calorific value before step (a)))) × 100

[0015] [3] In the method for manufacturing a resin composition layer according to [1] or [2], when the pressing temperature in step (b) is Tb (°C) and the pressing temperature in step (a) is Ta (°C), Tb > Ta and 30°C ≤ Tb - Ta ≤ 220°C.

[0016] [4] The method for manufacturing a resin composition layer according to any one of [1] to [3], wherein the reaction rate of the thermosetting resin in the sheet after step (b) obtained by the following method (referred to as "reaction rate (B)") is 60% or higher. <Method for measuring and calculating reaction rate (B)> (a) For the sheets before step (a) and after step (b), it is calculated by the following formula from the calorific value of the exothermic peak obtained when the temperature is raised from 40°C to 250°C at 10°C / min by differential scanning calorimetry (DSC). Reaction rate (B) (%) = (1 - (heat generation amount after step (b) / heat generation amount before step (a))) × 100

[0017] [5] When the press pressure in the said step (b) is Pb (MPa) and the press pressure in the said step (a) is Pa (MPa), Pa > Pb and Pa / Pb is 1.5 or more and 50 or less, The manufacturing method of the resin composition layer in any one of [1] - [4].

[0018] [6] When the film thickness after the said step (b) is Fb and the film thickness after the said step (a) is Fa, Fb / Fa is 0.7 or more and 1.2 or less, The manufacturing method of the resin composition layer in any one of [1] - [5].

[0019] [7] The press treatment in the said step (a) is a flat press treatment, The manufacturing method of the resin composition layer in any one of [1] - [6].

[0020] [8] The press treatment in the said step (a) is a roll press treatment, The manufacturing method of the resin composition layer in any one of [1] - [6].

[0021] [9] The press treatment in the said step (a) is a hydrostatic press treatment, The manufacturing method of the resin composition layer in any one of [1] - [6].

[0022]

[10] The thermosetting resin contains an epoxy compound, The manufacturing method of the resin composition layer in any one of [1] - [9].

[0023]

[11] The thermosetting resin contains an epoxy compound having a weight average molecular weight of 10,000 or more and an epoxy compound having a weight average molecular weight of 600 or less, The manufacturing method of the resin composition layer in

[10] .

[0024]

[12] The thermosetting resin contains an epoxy compound having a weight average molecular weight of 600 or less and containing three or more epoxy groups in one molecule, The manufacturing method of the resin composition layer in

[10] or

[11] .

[0025]

[13] A method for producing a resin composition layer according to any one of [1] to

[12] , wherein the aggregated inorganic filler comprises an aggregated boron nitride filler.

[0026]

[14] A method for producing a resin composition layer according to

[13] , wherein the aggregated inorganic filler comprises an aggregated boron nitride filler having a cardhouse structure.

[0027]

[15] A resin composition layer obtained by the manufacturing method described in any of [1] to

[14] .

[0028] A composite molded article having a resin composition layer and a metal part as described in

[16]

[15] .

[0029]

[17] A method for producing a composite molded article having a resin composition layer and a metal part, wherein the resin composition layer is formed by a method for producing a resin composition layer described in any of [1] to

[14] . [Effects of the Invention]

[0030] According to the present invention, when manufacturing a resin composition layer containing aggregated inorganic filler and thermosetting resin, the handling properties of the sheet formed using the resin composition can be improved by going through a specific pressing process, reducing damage and defects to the film due to handling, and improving the dielectric strength, adhesion, and heat resistance of the resulting resin composition layer. Furthermore, a reduction in thermal resistance at the interface can be expected due to the improved adhesion. [Modes for carrying out the invention]

[0031] The embodiments of the present invention will be described in detail below. The present invention is not limited to the embodiments described below, and can be implemented in various ways within the scope of its gist.

[0032] [Method for manufacturing a resin composition layer] The present invention relates to a method for producing a resin composition layer comprising a resin composition containing an aggregated inorganic filler and a thermosetting resin, and comprises the following steps (a) and (b). (a) A process of pressing a carrier film and a sheet formed on the carrier film using the resin composition, under conditions of a press temperature of 0°C to 110°C and a press pressure of 40 MPa to 1000 MPa. (b) A process to obtain a resin composition layer by pressing the sheet obtained in step (a) at a press temperature of 70°C to 250°C and a press pressure of 3 MPa to 100 MPa.

[0033] In the following, the resin composition layer produced by the method for producing the resin composition layer of the present invention may be referred to as the "resin composition layer of the present invention." Furthermore, the resin composition containing an aggregated inorganic filler and a thermosetting resin for forming the resin composition layer of the present invention may be referred to as the "resin composition of the present invention." In the present invention, "sheet" refers to a film-like material formed on a carrier film using the resin composition of the present invention, and is distinguished from a resin composition layer of the present invention obtained by curing this sheet.

[0034] The method for producing the resin composition layer of the present invention may include other steps in addition to the above steps (a) and (b). For example, there may be other steps between steps (a) and (b). For example, it may include a drying step, a smoothing step, a lamination step, and so on.

[0035] In the method for manufacturing the resin composition layer of the present invention, a sheet formed on a carrier film is subjected to a pressing process to become the resin composition layer of the present invention. Depending on the application and manufacturing process, the resin composition layer of the present invention may be used for various purposes as it is formed on the carrier film, or it may be separated from the carrier film and used for various purposes as a standalone resin composition layer. The resin composition layer of the present invention may be covered with a protective sheet or the like. One preferred embodiment is a composite molded article having a metal portion on one or both sides of the resin composition layer of the present invention. The resin composition of the present invention may contain other components in addition to the aggregated inorganic filler and thermosetting resin.

[0036] [Resin composition] The resin composition of the present invention will be described below.

[0037] <Agglomerated inorganic filler> The resin composition of the present invention contains aggregated inorganic fillers. The resin composition of the present invention preferably contains a large amount of aggregated inorganic fillers in order to improve the thermal conductivity and control the coefficient of linear expansion of the manufactured resin composition layer. The presence of aggregated inorganic fillers tends to result in higher thermal conductivity because the aggregated inorganic fillers deform upon contact with each other during steps (a) and (b) described below, and the surface contact creates more thermal conduction paths. The aggregation morphology of the aggregated inorganic fillers can be confirmed by scanning electron microscopy (SEM). The resin composition of the present invention may contain, in addition to aggregated inorganic fillers, unaggregated inorganic fillers and organic fillers.

[0038] Examples of aggregated inorganic fillers include those with electrical insulating properties, and fillers composed of at least one type of particle selected from the group consisting of metal carbides, metal oxides, and metal nitrides. Examples of metal carbides include silicon carbide, titanium carbide, and tungsten carbide. Examples of metal oxides include magnesium oxide, aluminum oxide, silicon oxide, calcium oxide, zinc oxide, yttrium oxide, zirconium oxide, cerium oxide, ytterbium oxide, and SiAlON (ceramics composed of silicon, aluminum, oxygen, and nitrogen). Examples of metal nitrides include boron nitride, aluminum nitride, and silicon nitride.

[0039] For power semiconductor applications, insulation is required, so aggregated inorganic fillers have a volume resistivity of 1 × 10⁻⁶. 12 Ω·cm or larger, especially 1 × 10⁻⁶ 13 It is preferable that the material consists of an inorganic compound with excellent insulating properties of Ω·cm or higher. Among these, oxides and nitrides are preferred because they provide sufficient electrical insulation to the formed resin composition layer.

[0040] More specifically, such aggregated inorganic fillers include alumina (Al2O3, volume resistivity 1 × 10⁻⁶). 14 Ω·cm), aluminum nitride (AlN, volume resistivity > 1 × 10⁻¹⁰ 14 Ω·cm), Boron nitride (BN), Volume resistivity 1 × 10⁻⁶ 14 Ω·cm), silicon nitride (Si3N4, volume resistivity > 1 × 10⁻⁶) 14 (Ω·cm), silica (SiO2, volume resistivity > 1 × 10⁻⁶) 14 Examples include Ω·cm). Among the aggregated inorganic fillers, alumina, aluminum nitride, boron nitride, and silica are preferred, with alumina and boron nitride being particularly preferred.

[0041] The aggregated inorganic filler may be surface-treated with a surface treatment agent. Any known surface treatment agent can be used.

[0042] The aggregated inorganic filler may be used alone, or two or more types may be mixed in any combination and ratio.

[0043] There are no particular restrictions on the method or degree of aggregation of the aggregated inorganic filler used in the present invention, but it is preferable to use the following aggregated boron nitride filler as the aggregated inorganic filler. The following aggregated boron nitride filler may be used in combination with a filler of a different shape and type than the aggregated boron nitride filler.

[0044] <Agglomerated boron nitride filler> Boron nitride has high thermal conductivity but is flaky. It exhibits high thermal conductivity in the plane direction of the flakes, but low thermal conductivity in the direction perpendicular to the plane. To improve handling, it is preferable to use aggregated particles formed by collecting flakes and agglomerating them into a spherical shape. In the case of aggregated boron nitride fillers that are stacked like cabbage, it is preferable to align them in the plane direction and to orient the radial direction of the aggregated particles toward the direction with good thermal conductivity. It is even more preferable that the aggregated boron nitride fillers have a cardhouse structure.

[0045] The "cardhouse structure" is described, for example, in Ceramics 43 No. 2 (published by the Ceramic Society of Japan in 2008), and is a structure in which plate-like particles are not oriented and are stacked in a complex manner. More specifically, an aggregated boron nitride filler having a cardhouse structure is an aggregate of primary boron nitride particles in which the planar portion and end portion of the primary particles are in contact, forming, for example, a T-shaped aggregate.

[0046] In the present invention, a cohesive boron nitride filler having the above-described cardhouse structure is particularly preferred. By using a cohesive boron nitride filler having a cardhouse structure, the thermal conductivity can be further increased.

[0047] The new Mohs hardness of the aggregated boron nitride filler is not particularly limited, but 5 or less is preferred. There is no particular lower limit to the new Mohs hardness of the aggregated boron nitride filler, but for example, it is 1 or more. A new Mohs hardness of 5 or less makes it easier for particles dispersed in the resin composition to make surface contact, forming heat conduction paths between particles and tending to improve the heat conductivity of the resulting resin composition layer.

[0048] The volume-average particle diameter of the aggregated boron nitride filler is not particularly limited, but is preferably 10 μm or more, and more preferably 15 μm or more. The volume-average particle diameter of the aggregated boron nitride filler is preferably 100 μm or less, and more preferably 90 μm or less. When the volume-average particle diameter is 10 μm or more, the number of particles in the resin composition and resin composition layer of the present invention is relatively small, so the number of interparticle interfaces is small, which reduces thermal resistance and may result in a resin composition layer with high thermal conductivity. When the volume-average particle diameter is below the above upper limit, the surface smoothness of the formed resin composition layer tends to be excellent.

[0049] The volume-average particle size of aggregated boron nitride filler refers to the particle size at which the cumulative volume reaches 50% when a cumulative curve is drawn with the volume of the powder being measured set to 100%. Measurement methods include a wet measurement method in which aggregated particles are dispersed in a pure water medium containing sodium hexametaphosphate as a dispersion stabilizer, and measured using a laser diffraction / scattering particle size distribution analyzer, and a dry measurement method using Malvern's "Morphologi". The same applies to the volume-average particle size of other aggregated inorganic fillers and non-aggregated inorganic fillers.

[0050] <Fracture strength of aggregated inorganic fillers> The fracture strength of the agglomerated inorganic filler is not particularly limited, but is preferably 300 MPa or less, more preferably 100 MPa or less, even more preferably 50 MPa or less, even more preferably 20 MPa or less, particularly preferably 15 MPa or less, and most preferably 10 MPa or less. When the fracture strength is below the above upper limit, the agglomerated structure of the agglomerated inorganic filler deforms when pressed, making it easier for the agglomerated inorganic fillers to come into surface contact with each other. The lower limit of the fracture strength of the aggregated inorganic filler is not particularly limited, but from the standpoint of ease of handling, it is preferably 2.5 MPa or higher, more preferably 3 MPa or higher, even more preferably 3.5 MPa or higher, and especially preferably 4 MPa or higher.

[0051] <Elastic modulus of aggregated inorganic fillers> The elastic modulus of the agglomerated inorganic filler is not particularly limited, but is preferably 10 MPa or higher, more preferably 20 MPa or higher, even more preferably 30 MPa or higher, even more preferably 48 MPa or higher, particularly preferably 50 MPa or higher, and most preferably 55 MPa or higher. If the elastic modulus is above the above lower limit, the agglomerated inorganic filler tends to deform plastically in the direction of the press pressure, suppressing the collapse of the agglomerated structure. The upper limit of the elastic modulus of the aggregated inorganic filler is not particularly limited, but from the standpoint of easily obtaining sufficient deformation, it is preferably 5 GPa or less, more preferably 2 GPa or less, even more preferably 1.5 GPa or less, even more preferably 1 GPa or less, particularly preferably 500 MPa or less, especially preferably 300 MPa or less, and most preferably 250 MPa or less.

[0052] When the elastic modulus of the aggregated inorganic filler is within the above range, it tends to maintain its spherical shape during pressing. When the fracture strength of the aggregated inorganic filler is within the above range, the parts in contact with each other tend to deform, and surface contact becomes easier. As a result, while maintaining the high thermal conductivity inside the aggregated inorganic filler, the contact thermal resistance at the interface between the aggregated inorganic fillers and the interface between the metal part described later and the resin composition layer of the present invention can be reduced, thereby improving the overall thermal conductivity.

[0053] The fracture strength and elastic modulus of the agglomerated inorganic filler can be measured after removing the resin from the resin composition layer by firing, in order to prevent the agglomerated inorganic filler from degrading, if the agglomerated inorganic filler is present in the resin composition layer.

[0054] <Content of aggregated inorganic fillers> The content of aggregated inorganic filler in the resin composition layer of the present invention is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 45% by mass or more, and particularly preferably 50% by mass or more, based on 100% by mass of the resin composition layer. Furthermore, it is preferably 99% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and particularly preferably 80% by mass or less. The combination of upper and lower limits for the content of aggregated inorganic fillers in the resin composition layer of the present invention is not particularly limited, but it is preferably 30% by mass or more and 99% by mass or less, more preferably 40% by mass or more and 90% by mass or less, and particularly preferably 50% by mass or more and 80% by mass or less.

[0055] Accordingly, the content of aggregated inorganic filler in the resin composition of the present invention is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 45% by mass or more, particularly preferably 50% by mass or more, preferably 99% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and particularly preferably 80% by mass or less. The combination of upper and lower limits for the content of aggregated inorganic fillers in the resin composition layer of the present invention is not particularly limited, but it is preferably 30% by mass or more and 99% by mass or less, more preferably 40% by mass or more and 90% by mass or less, and particularly preferably 50% by mass or more and 80% by mass or less. Here, the solid content in the resin composition refers to the total amount of all components in the resin composition other than the solvent.

[0056] When the content of aggregated inorganic fillers is above the lower limit, it tends to be possible to fully obtain the effects of improved thermal conductivity and control of the coefficient of linear expansion due to the inclusion of aggregated inorganic fillers. When the content of aggregated inorganic fillers is below the upper limit, voids in the resin composition layer can be reduced, and it tends to improve insulation and interfacial adhesion in composite molded articles.

[0057] <Other non-aggregated inorganic fillers> In this invention, in addition to the aggregated inorganic filler, other non-aggregated inorganic fillers may be used in combination. There are no restrictions on the shape of the non-aggregated inorganic filler, and examples include spherical, whisker-like, fibrous, and plate-like forms. Other non-aggregated inorganic fillers may include flaky boron nitride primary particles, and are not limited to their shape. Other non-aggregated inorganic fillers may be used individually or mixed in any combination and ratio of two or more types.

[0058] <Spherical filler> As a non-aggregated inorganic filler used in addition to agglomerated inorganic fillers, spherical fillers are preferably used.

[0059] The thermal conductivity of the spherical filler is not particularly limited, but is 1 W / m·K or more, preferably 10 W / m·K or more, more preferably 15 W / m·K or more, and even more preferably 20 W / m·K or more, for example 20 to 30 W / m·K. The spherical filler is preferably one with a new Mohs hardness of 3.1 or higher, for example, 5 to 10. By using such spherical fillers in combination with the aforementioned aggregated inorganic fillers, the adhesion strength to metal and heat dissipation properties of the resulting resin composition layer can be enhanced.

[0060] Here, "spherical" simply means something that is generally recognized as being spherical. For example, an object with an average circularity of 0.4 or higher may be considered spherical, or an object with an average circularity of 0.6 or higher may be considered spherical. The upper limit of the average circularity is usually 1. Circularity can be measured by image processing of the projected image. For example, circularity can be measured using Sysmex's FPIA series.

[0061] The spherical filler is preferably at least one selected from the group consisting of alumina, synthetic magnesite, crystalline silica, aluminum nitride, silicon nitride, silicon carbide, zinc oxide, and magnesium oxide. The use of these preferred spherical fillers can further enhance the heat dissipation properties of the resulting resin composition layer.

[0062] The volume-average particle diameter of the spherical filler is preferably within the range of 0.5 μm or more and 40 μm or less. A volume-average particle diameter of 0.5 μm or more allows the resin and filler to flow easily during heat molding, which is thought to enhance the interfacial adhesion in the composite molded article of the present invention, as described later. A volume-average particle diameter of 40 μm or less makes it easier to maintain the dielectric breakdown properties of the resin composition layer.

[0063] <Content of other non-aggregated inorganic fillers> When other non-aggregated inorganic fillers are used in combination with the aggregated inorganic filler, the content ratio of the aggregated inorganic filler to other non-aggregated inorganic fillers in the resin composition and the resin composition layer of the present invention is not particularly limited, but is preferably 99:1 to 1:99 by mass ratio, and more preferably 95:5 to 9:91.

[0064] For reasons similar to those for the content of aggregated boron nitride filler in the resin composition layer of the present invention, the total content of aggregated inorganic filler and other non-aggregated inorganic filler in the resin composition layer of the present invention is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 45% by mass or more, and particularly preferably 50% by mass or more, while on the other hand, it is preferably 99% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and particularly preferably 80% by mass or less.

[0065] Accordingly, the total content of aggregated inorganic fillers and other non-aggregated inorganic fillers in the resin composition of the present invention is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 45% by mass or more, and particularly preferably 50% by mass or more, while it is preferably 99% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and particularly preferably 80% by mass or less.

[0066] When the total content of aggregated inorganic fillers and other non-aggregated inorganic fillers is above the lower limit, it tends to be possible to obtain sufficient improvements in thermal conductivity and control of the coefficient of linear expansion due to the inclusion of inorganic fillers. When the total content of aggregated inorganic fillers and other non-aggregated inorganic fillers is below the upper limit, voids can be reduced, and insulation and interfacial adhesion in composite molded articles tend to improve.

[0067] <Other Organic Fillers> The resin composition and resin composition layer of the present invention may contain organic fillers in addition to aggregated inorganic fillers. In the present invention, an organic filler is a component that does not contain epoxy groups, does not fall under the definition of a thermosetting catalyst, and is a solid at room temperature composed of organic components. Examples of organic fillers include natural products such as wood flour, modified cellulose, starch, various organic pigments, thermoplastic resins, and thermosetting resins. Specific examples include acrylic resin particles, nylon resin particles, polyester resin particles, polystyrene resin particles, and silicone resin particles.

[0068] The inclusion of organic fillers can impart appropriate elongation to the resin composition, alleviate stress, and suppress crack formation during temperature cycling tests.

[0069] The upper limit of the average particle diameter of the organic filler is preferably 100 μm or less, and more preferably 50 μm or less. By keeping the average particle diameter below the above upper limit, a decrease in thermal conductivity can be suppressed, and resin composition layers of various thicknesses can be created. The average particle diameter of the organic filler is also the volume-average particle diameter obtained from the volume-average particle size distribution measurement results measured by a laser diffraction particle size distribution analyzer.

[0070] Organic fillers may be used individually or mixed in any combination and ratio of two or more types.

[0071] <Thermosetting resin> The thermosetting resin included in the resin composition of the present invention is not particularly limited, as long as it can be cured in the presence of a curing agent or curing catalyst to obtain a cured product.

[0072] Examples of thermosetting resins include epoxy resins, phenolic resins, polycarbonate resins, unsaturated polyester resins, cyanate resins, maleimide resins, urethane resins, melamine resins, and urea resins. Among these, epoxy resins are preferred from the viewpoint of viscosity, heat resistance, hygroscopicity, and ease of handling. Examples of epoxy resins include epoxy group-containing silicon compounds, aliphatic epoxy resins, bisphenol A or F type epoxy resins, novolac type epoxy resins, alicyclic epoxy resins, glycidyl ether type epoxy resins, glycidyl ester type epoxy resins, glycidylamine type epoxy resins, polyfunctional epoxy resins, and polymeric epoxy resins.

[0073] <Epoxy resin> Epoxy resins are a general term for compounds that have one or more oxirane rings (epoxy groups) in their molecule. The oxirane ring (epoxy group) contained in the epoxy resin may be either an alicyclic epoxy group or a glycidyl group, but a glycidyl group is preferable from the viewpoint of reaction rate or heat resistance.

[0074] The epoxy resin used in the present invention may be an aromatic oxirane ring (epoxy group) containing compound. Specific examples include bisphenol-type epoxy resins obtained by glycidly fermenting bisphenols such as bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetramethylbisphenol A, tetramethylbisphenol F, tetramethylbisphenol AD, tetramethylbisphenol S, and tetrafluorobisphenol A; biphenyl-type epoxy resins; epoxy resins obtained by glycidly fermenting divalent phenols such as dihydroxynaphthalene and 9,9-bis(4-hydroxyphenyl)fluorene; epoxy resins obtained by glycidly fermenting trisphenols such as 1,1,1-tris(4-hydroxyphenyl)methane; epoxy resins obtained by glycidly fermenting tetrakisphenols such as 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane; and novolac-type epoxy resins obtained by glycidly fermenting novolacs such as phenol novolac, cresol novolac, bisphenol A, novolac, and brominated bisphenol A novolac.

[0075] The epoxy resin included in the resin composition of the present invention is not particularly limited, but it is preferable to include one or more selected from the following: various bisphenol-type epoxy resins obtained by glycidly modifying bisphenols such as bisphenol A type epoxy resin and bisphenol F type epoxy resin; various biphenyl-type epoxy resins obtained by glycidly modifying biphenyls, aliphatic epoxy resins, epoxy resins obtained by glycidly modifying aromatic compounds having multiple hydroxyl groups such as dihydroxynaphthalene and 9,9-bis(4-hydroxyphenyl)fluorene; epoxy resins obtained by glycidly modifying trisphenols such as 1,1,1-tris(4-hydroxyphenyl)methane, epoxy resins obtained by glycidly modifying tetrakisphenols such as 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane; novolac-type epoxy resins obtained by glycidly modifying novolacs such as phenol novolac, cresol novolac, bisphenol A novolac, and brominated bisphenol A novolac; and silicone-containing epoxy resins.

[0076] The epoxy resin used in this invention may be one type, or a combination of multiple types of epoxy resins may be used.

[0077] The molecular weight of the epoxy resin used in this invention is not particularly limited. From the viewpoint of film-forming properties, low moisture absorption, and flexibility, the epoxy resin used in the present invention preferably contains a high molecular weight epoxy resin. Specifically, the high molecular weight epoxy resin is preferably an epoxy resin with a weight-average molecular weight of 10,000 or more, and more preferably an epoxy resin with a weight-average molecular weight of 15,000 or more. The high molecular weight epoxy resin is preferably an epoxy resin with a weight-average molecular weight of 200,000 or less, and more preferably 180,000 or less.

[0078] High molecular weight epoxy resins are preferably more hydrophobic, and specifically, a higher epoxy equivalent weight of the epoxy component is preferable. Specifically, an epoxy equivalent weight of 5,000 g / equivalent or more is preferred, 7,000 g / equivalent or more is more preferred, while 100,000 g / equivalent or less is preferred.

[0079] From the viewpoint of increasing the storage modulus of the resin composition layer of the present invention, it is preferable that the epoxy resin used in the present invention contains an epoxy resin with a weight-average molecular weight of 600 or less, and particularly 550 or less. The lower limit of the weight-average molecular weight of this epoxy resin is not particularly limited, but is usually 100 or more.

[0080] The epoxy resin used in the present invention, having a weight-average molecular weight of 600 or less, is preferably an epoxy resin having two or more epoxy groups per molecule. It is even more preferable to include a polyfunctional epoxy resin having three or more epoxy groups per molecule and having a weight-average molecular weight of 600 or less, as described later. The epoxy resin with a weight-average molecular weight of 600 or less may be a combination of a polyfunctional epoxy resin having three or more epoxy groups per molecule and an epoxy resin having two or fewer epoxy groups per molecule.

[0081] The thermosetting resin in the resin composition of the present invention preferably contains an epoxy resin with a weight-average molecular weight of 10,000 or more and an epoxy resin with a weight-average molecular weight of 600 or less, from the viewpoint of film-forming properties, coatability, and heat resistance after curing.

[0082] The weight-average molecular weight of epoxy resin is the polystyrene equivalent value measured by gel permeation chromatography. The epoxy equivalent of epoxy resin is defined as "the weight of epoxy resin containing one equivalent of epoxy groups" and can be measured in accordance with JIS K7236.

[0083] (Polyfunctional epoxy resin with a molecular weight of 600 or less) The resin composition of the present invention is a thermosetting resin with a molecular weight of 600 or less and contains epoxy groups per molecule. It is more preferable to include a polyfunctional epoxy resin having three or more of the following properties.

[0084] From the viewpoint of increasing the storage modulus of the resin composition layer of the present invention, and particularly increasing the storage modulus at high temperatures which is important in cases of high heat generation such as power semiconductors, epoxy resins having three or more oxirane rings (epoxy groups) in the molecule are preferred, and epoxy resins having four or more oxirane rings (epoxy groups) in the molecule are even more preferred. Having multiple oxirane rings (epoxy groups), especially glycidyl groups, in the molecule improves the crosslinking density of the formed resin composition layer, resulting in higher strength. As a result, when internal stress occurs in the resin composition layer during a moisture absorption reflow test, the resin composition layer maintains its shape without deforming or breaking, thereby suppressing the generation of voids and other air pockets in the resin composition layer.

[0085] From the viewpoint of increasing the storage modulus of the resin composition layer, the molecular weight of the polyfunctional epoxy resin is preferably 600 or less, and more preferably 550 or less. The lower limit of the molecular weight of the polyfunctional epoxy resin is not particularly limited, but is usually 100 or more.

[0086] By adding a polyfunctional epoxy resin, it is possible to introduce highly polar oxirane rings (epoxy groups) at high density. This increases the effects of physical interactions such as van der Waals forces and hydrogen bonds, thereby improving the adhesion between the metal part and the resin composition layer in the composite molded article described later. By adding a polyfunctional epoxy resin, the storage modulus of the resin composition layer after heat curing can be increased. As a result, the cured resin composition penetrates into the irregularities of the metal part to which it is adhered, exhibiting a strong anchoring effect and improving the adhesion between the metal part and the resin composition layer.

[0087] Specifically, a polyfunctional epoxy resin having three or more epoxy groups is preferred. Examples of polyfunctional epoxy resins that can be used include jER630 from Mitsubishi Chemical Corporation, the ELM-434 series and ELM-100 series from Sumitomo Chemical Corporation, EX321L, EX-411, and EX-512 from Nagase ChemteX Corporation, and BATG and PETG from Showa Denko Corporation.

[0088] A single type of polyfunctional epoxy resin may be used, or two or more types may be used in combination.

[0089] <Content of thermosetting resin> In the resin composition layer of the present invention, it is preferable that the main component of the resin components, excluding the inorganic filler, is a thermosetting resin, and it is particularly preferable that it contains an epoxy resin. Here, the main component refers to the component that is present in the largest quantity.

[0090] The resin composition layer of the present invention preferably contains 5 to 90% by mass, particularly 10 to 60% by mass, of thermosetting resin in 100% by mass of the resin composition layer. Therefore, the proportion of thermosetting resin in 100% by mass of solids in the resin composition of the present invention is preferably 5 to 90% by mass, particularly 10 to 60% by mass. If the content of thermosetting resin is above the lower limit, moldability is good, and if it is below the upper limit, the content of other components can be ensured, and thermal conductivity can be improved.

[0091] The content of thermosetting resin in the resin components excluding the inorganic filler in the resin composition layer of the present invention is not particularly limited, but is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, and particularly preferably 45% by mass or more. Accordingly, the content of thermosetting resin in the solid content excluding the inorganic filler in the resin composition of the present invention is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, and particularly preferably 45% by mass or more. The upper limit for the content of thermosetting resin in the resin components excluding the inorganic filler is 100% by mass, and all components other than the inorganic filler may be thermosetting resins. When the proportion of thermosetting resin falls within the above range, it tends to result in low hygroscopicity, high modulus of elasticity, and high toughness, while also facilitating reaction control, leading to high reflow resistance, high reliability in cycle testing, and high thermal conductivity.

[0092] The content of the aforementioned preferred epoxy resin, a high molecular weight epoxy resin with a weight-average molecular weight of 10,000 or more, in the resin composition layer of the present invention and in the resin component of the resin composition of the present invention is preferably 5% by mass or more, more preferably 10% by mass or more, and on the other hand, preferably 90% by mass or less. The content of epoxy resin with a weight-average molecular weight of 600 or less in the resin composition layer of the present invention and in the resin components of the present invention is preferably 5% by mass or more, more preferably 10% by mass or more, and on the other hand, preferably 90% by mass or less. The ratio of high molecular weight epoxy resin with a weight-average molecular weight of 10,000 or more to epoxy resin with a weight-average molecular weight of 600 or less is preferably 1:18 to 18:1 by mass. When the content of high molecular weight epoxy resin is above the lower limit, the film-forming properties of the resin composition of the present invention tend to improve, and when it is below the upper limit, the strength of the resin composition layer of the present invention can be made excellent.

[0093] <Other ingredients> The resin composition and resin composition layer of the present invention may contain components other than agglomerated inorganic fillers and thermosetting resins. Examples of other components include, in addition to the non-aggregated inorganic fillers and organic fillers mentioned above, surface treatment agents such as curing catalysts, curing agents, and silane coupling agents, insulating carbon components such as reducing agents, viscosity modifiers, dispersants, thixotropic agents, flame retardants, colorants, organic solvents, thermoplastic resins, and the like.

[0094] <Curing catalyst> The resin composition of the present invention may contain a curing catalyst (thermosetting catalyst) to adjust the curing speed and the physical properties of the cured product.

[0095] The curing catalyst is not particularly limited, but is appropriately selected depending on the type of thermosetting resin and other components used. Specific examples of curing catalysts include linear or cyclic tertiary amines, organophosphorus compounds, quaternary phosphonium salts, or diazabicycloalkenes such as organic acid salts. Organometallic compounds, quaternary ammonium salts, or metal halides can also be used as curing catalysts. Examples of organometallic compounds include zinc octyolate, tin octyolate or aluminum acetylacetone complexes, gallium acetylacetone complexes, and imidazoles. Imidazoles are particularly preferred from the viewpoint of heat resistance and stability. These may be used individually or in combination of two or more types.

[0096] The curing catalyst is preferably present in an amount of 0.1 to 10% by mass, and particularly 0.1 to 5% by mass, of 100% by mass of the resin composition of the present invention, excluding the solvent and inorganic filler. If the content of the curing catalyst is above the lower limit, the curing reaction can be sufficiently promoted and cured well. If the content of the curing catalyst is below the upper limit, the curing rate will not be too fast, and therefore, the storage stability of the resin composition of the present invention can be improved.

[0097] When the curing catalyst is solid, its average particle size is not particularly limited, but the average particle size of at least one curing catalyst is preferably 15 μm or less, and more preferably 10 μm or less. Having an average particle size below the above upper limit improves the solubility of the curing catalyst in the resin component, tends to improve the reaction rate, and also tends to increase the elastic modulus of the formed resin composition layer, thereby raising the glass transition temperature. Furthermore, it tends to improve the dispersibility of the curing catalyst, thereby improving the storage stability of the resin composition of the present invention. The lower limit of the average particle size of the curing catalyst is not particularly limited.

[0098] <Hardening agent> The resin composition of the present invention may contain a curing agent. The curing agent is not particularly limited, but examples include phenolic resins, aliphatic amines, aromatic amines, modified amines, polyamide resins, imidazoles, polymercaptans, polysulfides, acid anhydrides, carboxylic acid-containing compounds, and dicyandiamides.

[0099] Of these, for example, phenolic resins, acid anhydrides having an aromatic or alicyclic skeleton, or aqueous additives of said acid anhydrides or modified products of said acid anhydrides are preferred. The use of these preferred curing agents tends to yield a resin composition layer with an excellent balance of heat resistance, moisture resistance, and electrical properties. The curing agent may be used alone or in combination of two or more types.

[0100] The phenolic resin used as a curing agent is not particularly limited. Specific examples of phenolic resins include phenol novolac, o-cresol novolac, p-cresol novolac, t-butylphenol novolac, dicyclopentadiene cresol, poly-p-vinylphenol, bisphenol A type novolac, xylylene-modified novolac, decalin-modified novolac, poly(di-o-hydroxyphenyl)methane, poly(di-m-hydroxyphenyl)methane, or poly(di-p-hydroxyphenyl)methane. In particular, for further improvement of the flexibility and flame retardancy of the resin composition, and for improvement of the mechanical properties and heat resistance of the resin composition layer, novolac-type phenolic resins having a rigid main chain skeleton or phenolic resins having a triazine skeleton are preferred. For improvement of the flexibility of the resin composition of the present invention and the toughness of the resin composition layer of the present invention, phenolic resins having allyl groups are preferred.

[0101] Commercially available phenolic resins include MEH-8005, MEH-8000H, and NEH-8015 (all manufactured by Meiwa Kasei Co., Ltd.), YLH903 (manufactured by Mitsubishi Chemical Corporation), LA-7052, LA-7054, LA-7751, LA-1356, and LA-3018-50P (all manufactured by Dainippon Ink & Chemicals Inc.), as well as PSM6200, PS6313, and PS6492 (manufactured by Gun-ei Chemical Industry Co., Ltd.).

[0102] The acid anhydride having an aromatic skeleton, the aqueous additive of the acid anhydride, or the modified product of the acid anhydride used as a curing agent is not particularly limited. Specific examples include SMA resin EF30 and SMA resin EF60 (both manufactured by Sartomer Japan), ODPA-M and PEPA (both manufactured by Manac), Ricajit MTA-10, Ricajit TMTA, Ricajit TMEG-200, Ricajit TMEG-500, Ricajit TMEG-S, Ricajit TH, Ricajit MH-700, Ricajit MT-500, Ricajit DSDA and Ricajit TDA-100 (all manufactured by Shin Nippon Rika), EPICLON B4400 and EPICLON B570 (all manufactured by Dainippon Ink and Chemicals).

[0103] The acid anhydride having an alicyclic skeleton, the aqueous additive of the acid anhydride, or the modified acid anhydride is preferably an acid anhydride having a polyalicyclic skeleton, the aqueous additive of the acid anhydride, or the modified acid anhydride, or an acid anhydride having an alicyclic skeleton obtained by an addition reaction between a terpene compound and maleic anhydride, the aqueous additive of the acid anhydride, or the modified acid anhydride. Specific examples include Ricasit HNA and Ricasit HNA-100 (both manufactured by Shin-Nippon Rika Co., Ltd.), and Epicure YH306 and Epicure YH309 (both manufactured by Mitsubishi Chemical Corporation).

[0104] The curing agent is preferably present in an amount of 0 to 70% by mass, particularly 0 to 55% by mass, of 100% by mass of the resin composition of the present invention, excluding the solvent and inorganic filler. If the curing agent content is above the lower limit, sufficient curing performance can be obtained. If the curing agent content is below the upper limit, the reaction proceeds effectively, improving the crosslinking density, increasing strength, and further improving film-forming properties.

[0105] When the thermosetting resin is an epoxy resin, the content of the reactive groups in the curing agent is not particularly limited, but may be 0 equivalents relative to the amount of epoxy groups in the thermosetting resin, preferably 0.05 equivalents or more, more preferably 0.1 equivalents or more, and even more preferably 0.15 equivalents or more. The content of the reactive groups in the curing agent is preferably 2 equivalents or less, and more preferably 1.2 equivalents or less, relative to the amount of epoxy groups in the thermosetting resin. When the amount of reactive groups of the curing agent relative to the amount of epoxy groups in the thermosetting resin is above the lower limit, the reduction in curing rate is suppressed, epoxy groups are less likely to remain, and there is a tendency to obtain an improvement in the strength of the formed resin composition layer and an effect of suppressing moisture absorption. When the amount of reactive groups of the curing agent relative to the epoxy groups is below the upper limit, there is a tendency for the elastic modulus of the formed resin composition layer to be higher.

[0106] <Dispersant> The resin composition of the present invention may contain a dispersant. The inclusion of a dispersant makes it possible to form a uniform resin composition layer, which may improve the thermal conductivity and dielectric breakdown properties of the resulting resin composition layer.

[0107] The dispersant preferably has a functional group containing hydrogen atoms that have hydrogen bonding properties. By having a functional group containing hydrogen atoms that have hydrogen bonding properties in the dispersant, the thermal conductivity and dielectric breakdown properties of the formed resin composition layer can be further enhanced. Examples of the functional group containing hydrogen atoms that have hydrogen bonding properties include a carboxyl group (pKa=4), a phosphate group (pKa=7), or a phenol group (pKa=10).

[0108] The pKa of the functional group containing hydrogen atoms with hydrogen bonding properties is preferably in the range of 2 to 10, and more preferably in the range of 3 to 9. When the pKa is 2 or higher, the acidity of the dispersant is within an appropriate range, which may suppress the reaction of the epoxy resin in the thermosetting resin component. Therefore, when the molded product is stored in an uncured state, the storage stability tends to improve. When the pKa is 10 or lower, the dispersant function is fully performed, and the thermal conductivity and dielectric breakdown properties of the formed resin composition layer tend to be sufficiently enhanced.

[0109] The functional group containing hydrogen atoms that have hydrogen bonding properties is preferably a carboxyl group or a phosphate group. In this case, the thermal conductivity and dielectric breakdown properties of the formed resin composition layer can be further enhanced.

[0110] Examples of dispersants include polyester carboxylic acids, polyether carboxylic acids, polyacrylic carboxylic acids, aliphatic carboxylic acids, polysiloxane carboxylic acids, polyester phosphoric acids, polyether phosphoric acids, polyacrylic phosphoric acids, aliphatic phosphoric acids, polysiloxane phosphoric acids, polyester phenols, polyether phenols, polyacrylic phenols, and polysiloxane phenols. A single dispersant may be used, or two or more may be used in combination.

[0111] <Thermoplastic resin> The resin composition of the present invention may contain a thermoplastic resin. The inclusion of a thermoplastic resin may impart appropriate elongation to the formed resin composition layer, relieve the resulting stress, and suppress the occurrence of cracks during temperature cycling tests.

[0112] Any thermoplastic resin that is generally known can be used. Specifically, examples of thermoplastic resins include polyethylene, polypropylene, polystyrene, polyvinyl chloride, (meth)acrylic resin, vinyl polymers such as ethylene-vinyl acetate copolymer and ethylene-vinyl alcohol copolymer, polylactic acid resin, polyesters such as polyethylene terephthalate and polybutylene terephthalate, nylon, polyamides such as polyamidoamine, polyvinyl acetal resins such as polyvinyl acetal, polyvinyl benzal and polyvinyl butyral resin, ionomer resin, polyphenylene ether, polyphenylene sulfide, polycarbonate, polyether ether ketone, polyacetal, ABS resin, LCP (liquid crystal polymer), fluororesin, urethane resin, silicone resin, various elastomers, and modified products of these resins.

[0113] The thermoplastic resin may be homogeneous within the resin phase of the formed resin composition layer, or it may undergo phase separation, allowing its shape to be recognized. If it undergoes phase separation, the thermoplastic resin in the resin composition layer may be particulate or fibrous. The thermoplastic resin may also be included as the organic filler described above.

[0114] <Organic solvents> The resin composition of the present invention may contain an organic solvent to improve the coatability in the coating process described later.

[0115] Examples of organic solvents that may be contained in the resin composition of the present invention include methyl ethyl ketone, cyclohexanone, propylene glycol monomethyl ether acetate, butyl acetate, isobutyl acetate, and propylene glycol monomethyl ether. Organic solvents may be used individually or in combination of two or more types.

[0116] When the resin composition of the present invention contains an organic solvent, it is preferable from the viewpoint of coatability in the coating process that the content of the organic solvent is such that the solid content (total of components other than the solvent) in the resin composition of the present invention is 10% by mass or more, particularly 40% by mass or more, and 90% by mass or less, particularly 80% by mass or less.

[0117] <Method for producing resin compositions> The resin composition of the present invention can be obtained by uniformly mixing an aggregated inorganic filler, a thermosetting resin, and other components added as needed, by stirring or kneading. For mixing, general kneading equipment such as a mixer, kneader, single-screw or twin-screw kneader can be used. Heating may be used during mixing as needed.

[0118] The mixing order of each component is arbitrary as long as there are no particular problems such as reactions or precipitate formation. For example, one method is to prepare a resin solution by mixing and dissolving the thermosetting resin component in an organic solvent (e.g., methyl ethyl ketone), and then add a mixture of aggregated inorganic filler and other components to the resulting resin solution and mix.

[0119] [Method for manufacturing a resin composition layer] The present invention provides a method for producing a resin composition layer comprising steps (a) and (b). The following are possible reasons why the manufacturing method of the present invention provides improved handling, voltage resistance, adhesion, and heat resistance.

[0120] (a) In step (a), a pressing process is performed at a specific pressing pressure and pressing temperature. This pressing process is performed at a temperature lower than the curing temperature of the thermosetting resin contained in the resin composition of the present invention, making it possible to press while suppressing the reaction rate of the thermosetting resin. As a result, the thermosetting resin can more easily penetrate the voids derived from the aggregated inorganic filler, thereby reducing the number of voids. The brittleness of the resin composition layer obtained by the penetration of the resin into the voids derived from the aggregated inorganic filler is reduced, and handling properties are improved. Furthermore, the sheet that has gone through process (a) is subjected to press treatment in process (b) at a specific press pressure and press temperature. By performing the specific press treatment in process (b) while suppressing the reaction rate of the thermosetting resin after process (a), adhesion can be improved, and by allowing the reaction after process (b) to proceed sufficiently, the dielectric strength and heat resistance can be improved. Furthermore, by using a higher pressing temperature in step (b) than in step (a), the fluidity of the thermosetting resin before curing is increased, further reducing voids. By going through steps (a) and (b), a resin composition layer with improved voltage resistance, adhesion, and heat resistance can be obtained.

[0121] <(a) Process> (a) The step involves pressing a sheet on which a layer of the resin composition of the present invention has been formed on a carrier film, under conditions of a press temperature of 0°C or more and 110°C or less, and a press pressure of 40 MPa or more and 1000 MPa or less.

[0122] (a) In step (a), a sheet is formed on a carrier film using the resin composition of the present invention, and the sheet with the carrier film is subjected to press treatment under specific conditions. By performing step (a) on the sheet with the carrier film under specific conditions, the sheet handling performance up to step (b) can be improved.

[0123] The method for forming a sheet using the resin composition of the present invention is not particularly limited, but one method is to form it by a coating process. In this case, the resin composition of the present invention may contain an organic solvent to improve coatability.

[0124] There are no particular limitations on the method of applying the resin composition of the present invention, but for example, a dip method, spin coating method, spray coating method, blade method, or any other method can be employed. For application, coating equipment such as a spin coater, slit coater, die coater, or blade coater can be used. These devices make it possible to uniformly form a sheet (coating film) of a predetermined thickness on a carrier film.

[0125] The carrier film used is not particularly limited, but it is desirable that it does not dissolve in the resin composition of the present invention and that it deforms little at the press temperature and press pressure in step (a). Examples include olefin films, polyester films such as PET (polyethylene terephthalate), polyimide films, and copper materials.

[0126] When a sheet is formed using the resin composition of the present invention containing an organic solvent, it is preferable to remove the solvent by a drying process or the like before pressing in step (a). The sheet before pressing in step (a) preferably has a solid content concentration of 95% by mass or more, and more preferably 98% by mass or more.

[0127] The drying process is not particularly limited, but is usually performed at a temperature of 10 to 150°C, preferably 25 to 120°C, and more preferably 30 to 110°C. When the drying temperature is below the upper limit mentioned above, the hardening of the thermosetting resin in the sheet is suppressed, and the resin tends to flow more easily in the subsequent pressing process, making it easier to remove voids. When the drying temperature is above the lower limit mentioned above, organic solvents can be effectively removed.

[0128] When drying at temperatures below 80°C, the drying time is typically 5 minutes to 10 days, preferably 10 minutes to 3 days, more preferably 20 minutes to 1 day, and particularly preferably 30 minutes to 4 hours. When drying at temperatures above 80°C, the drying time is preferably 1 minute or more, preferably 30 minutes or less, more preferably 20 minutes or less, even more preferably 15 minutes or less, and particularly preferably 10 minutes or less. A drying time above the lower limit tends to sufficiently remove organic solvents and suppress the formation of voids in the sheet by residual solvents. A drying time below the upper limit tends to improve productivity and reduce manufacturing costs.

[0129] (a) The pressing temperature in step (a) is 0°C or higher and 110°C or lower, preferably 3°C or higher and 100°C or lower, more preferably less than 100°C, and even more preferably 95°C or lower. This temperature range tends to suppress the reaction rate of the thermosetting resin in step (a), resulting in a sheet with good handling properties.

[0130] (a) The pressing pressure in the process is 40 MPa to 1000 MPa, preferably 45 MPa or more, more preferably 50 MPa or more, preferably 900 MPa or less, more preferably 700 MPa or less, and even more preferably 500 MPa or less. This pressure range tends to reduce voids and yield a resin composition layer with good thermal conductivity.

[0131] (a) The time for the pressing process in step (a) is not particularly limited, but is preferably 1 minute or more, more preferably 3 minutes or more, preferably within 5 hours, and more preferably within 2 hours. When the pressing time falls within the above range, sheets with good handling properties and adhesion to metal parts tend to be obtained.

[0132] (a) The reaction rate of the thermosetting resin contained in the sheet after the process (hereinafter sometimes referred to as "reaction rate (A)") is not particularly limited, but is preferably less than 50%. The reaction rate (A) is more preferably 40% or less, even more preferably 30% or less, and particularly preferably 20% or less. When the reaction rate (A) of the thermosetting resin is below the above upper limit, a sheet with good handling and adhesion properties tends to be obtained. The reaction rate (A) of the thermosetting resin in the sheet is calculated using the following formula from the amount of heat generated at the exothermic peak obtained when the sheet is heated from 40°C to 250°C at a rate of 10°C / min by differential scanning calorimetry (DSC) of the sheet before and after the (a) process. Reaction rate (A) (%) = (1 - ((amount of heat generated after step (a) / (amount of heat generated before step (a))) × 100

[0133] (a) The film thickness (Fa) of the sheet after the process is not particularly limited, but is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, preferably 1000 μm or less, and more preferably 800 μm or less. When the film thickness (Fa) of the sheet is above the lower limit, insulating properties tend to be obtained, and when it is below the upper limit, thermal resistance tends to be reduced. The film thickness of the sheet can be measured using a contact-type or non-contact-type film thickness gauge. (b) The same applies to the film thickness (Fb) of the resin composition layer after the process.

[0134] (a) The pressing process in step (a) is not particularly limited, but flat plate pressing, roll pressing, and hydrostatic pressing are preferred.

[0135] The specific configuration of the flat plate press machine for press processing is not particularly limited, and examples include a pair of parallel flat plates (press plates) on which a mirror-polished hard chrome plating layer is disposed on the surface, a pressure control means for controlling the pressing pressure by the press plates, and a heating means for heating the press plates to a predetermined temperature, wherein a sheet is sandwiched between the pair of press plates and pressed from both sides while heating to a predetermined temperature. (a) In the process, by performing flat plate press processing with a highly smooth press plate surface, the surface of the sheet becomes easier to smooth, and the adhesion between the formed resin composition layer and the metal part tends to improve.

[0136] By performing a roll press process, the sheet surface can be smoothed in step (a), which tends to improve productivity. The specific configuration of the roll press machine is not particularly limited, and various types of roll press machines can be used, such as a type with a pair of nip rolls or a multi-stage nip roll type. An example of a roll press machine is an apparatus that includes a preheating roll (which may or may not be necessary), at least a pair of nip rolls, and preferably a heating means for heating the nip rolls, and is configured to pressurize and smooth the surface of a sheet by sandwiching the sheet between the pair of nip rolls and pressing it from both sides.

[0137] Hydrostatic pressing enables high-pressure pressing over large areas, which tends to reduce unevenness in sheet pressing. Hydrostatic pressing also allows for simultaneous processing of multiple sheets, leading to improved productivity. The specific configuration of a hydrostatic press is not particularly limited. For example, it may include a pressure vessel filled with a liquid such as oil or water, a pressurizing cylinder for pressurizing the liquid, control means for controlling the pressure applied to the liquid, and heating means for heating the liquid to a predetermined temperature. More specifically, an example is a device configured such that a sheet with a carrier film is vacuum-packed and immersed in the liquid such as oil or water of the hydrostatic press, and then hydrostatic pressing is performed so that the sheet is pressed with uniform pressure and the surface of the sheet is smoothed.

[0138] <(b) Process> (b) is a process in which the sheet that has gone through process (a) is pressed at a press temperature of 70°C to 250°C and a press pressure of 3 MPa to 100 MPa to obtain a resin composition layer.

[0139] (b) The method of pressing in step (b) is not particularly limited and can be done by, for example, a flat plate press.

[0140] (b) Step (b) involves providing the sheet that has undergone step (a), and the sheet alone, a laminate of carrier film / sheet / metal part, a laminate of metal part / sheet, etc., may be press-treated. The manufacturing method of the present invention is a method with excellent adhesion and is suitable for a manufacturing method that press-treats a laminate including a metal part and a sheet.

[0141] (b) The pressing temperature in step is 70°C to 250°C, preferably 75°C or higher, more preferably 80°C or higher, preferably 240°C or lower, more preferably 230°C or lower, and even more preferably 220°C or lower. This temperature range tends to yield a resin composition layer with high elastic modulus, adhesion, and heat resistance.

[0142] (b) The pressing pressure in the process is 3 MPa to 100 MPa, preferably 3.5 MPa or higher, and more preferably 4 MPa or higher. This pressure range tends to yield a resin composition layer with excellent dielectric strength, thermal conductivity, and adhesion.

[0143] (b) The time for the pressing process is not particularly limited, but is preferably 5 minutes or more, more preferably 10 minutes or more, and preferably within 24 hours. The pressing time is preferably such that the reaction rate (B) of the thermosetting resin, as described later, becomes 60% or more.

[0144] (b) The reaction rate of the thermosetting resin contained in the sheet after the process (hereinafter sometimes referred to as "reaction rate (B)") is not particularly limited, but is preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, and especially preferably 80% or more. The upper limit of reaction rate (B) is not particularly limited, but is 100%. When the reaction rate (B) of the thermosetting resin is within the above range, sufficient curing proceeds, and a resin composition layer with excellent heat resistance and adhesion tends to be obtained. The reaction rate (B) of the thermosetting resin in the sheet is calculated using the following formula from the amount of heat generated by the exothermic peak obtained when the sheet is heated from 40°C to 250°C at a rate of 10°C / min by differential scanning calorimetry (DSC) of the sheet before process (a) and after process (b). Reaction rate (B) (%) = (1 - ((B) heat generation / (A) heat generation before process (a))) × 100

[0145] (b) The thickness of the resin composition layer after the process (Fb) is not particularly limited, but is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, preferably 1000 μm or less, and more preferably 800 μm or less. When the thickness of the resin composition layer (Fb) is above the lower limit, insulating properties tend to be obtained, and when it is below the upper limit, thermal resistance tends to be reduced.

[0146] <(a) combination of process (b)> The pressing conditions for steps (a) and (b), and the film thickness of the sheet and resin composition layer are not particularly limited as long as they are within the above range, but the following combinations are particularly preferred.

[0147] If the press temperature in step (b) is Tb (°C) and the press temperature in step (a) is Ta (°C), then Tb > Ta and 30℃ ≤ Tb - Ta ≤ 220℃ It is preferable that this be the case. Tb-Ta is preferably 30°C or higher, more preferably 40°C or higher, preferably 220°C or lower, more preferably 200°C or lower, and even more preferably 180°C or lower. Having Tb-Ta within the above range tends to allow for a balance between sheet handling and adhesion of the resin composition layer.

[0148] If the press pressure in step (b) is Pb (MPa) and the press pressure in step (a) is Pa (MPa), then Pa > Pb, and Pa / Pb is between 1.5 and 50. It is preferable that this be the case. The Pa / Pb ratio is preferably 1.5 or higher, more preferably 1.8 or higher, even more preferably 2 or higher, preferably 50 or lower, more preferably 45 or lower, and even more preferably 40 or lower. Having a Pa / Pb ratio within this range reduces voids within the resin composition layer and appropriately maintains the shape of the aggregated inorganic fillers, resulting in a resin composition layer with excellent dielectric strength and thermal conductivity.

[0149] The thickness of the resin composition layer and the sheet is preferably such that the ratio (Fb / Fa) is 0.7 or more and 1.2 or less, where Fb is the thickness of the resin composition layer after step (b) and Fa is the thickness of the sheet after step (a). Fb / Fa is preferably 0.7 or higher, more preferably 0.8 or higher, even more preferably 0.85 or higher, preferably 1.2 or lower, and more preferably 1.1 or lower. When Fb / Fa is within the above range, it indicates that (a) voids in the sheet are efficiently reduced after the process, and (b) the change in film thickness before and after the process is small, which tends to result in a resin composition layer with excellent dielectric strength and thermal conductivity.

[0150] In the present invention, it is particularly preferable that, as step (a), a sheet is formed on a carrier film using the resin composition of the present invention, and the carrier film is pressed together, and as step (b), the laminate including the metal part and the sheet is pressed together with the sheet that has gone through step (a) in contact with the metal part.

[0151] [Thermal conductivity and dielectric strength of the resin composition layer] The thermal conductivity and dielectric strength of the resin composition layer of the present invention are not particularly limited, but the thermal conductivity is preferably 8 W / mK or higher, more preferably 9 W / mK or higher, and even more preferably 10 W / mK or higher. The dielectric strength of the resin composition layer of the present invention is preferably 30 kV / mm or higher, more preferably 35 kV / mm or higher, and particularly preferably 40 kV / mm or higher. The method for measuring thermal conductivity and dielectric strength in the present invention is not particularly limited, but the method shown in the following examples is one example.

[0152] [Composite molded body] The composite molded article of the present invention is formed by laminating and integrating a resin composition layer of the present invention with a metal part. The metal part may be provided on only one surface of the resin composition layer of the present invention, or on two or more surfaces. For example, the resin composition layer may have a metal part on only one surface, or it may have metal parts on both surfaces. Furthermore, the metal part may be patterned.

[0153] Such a composite molded article of the present invention can be manufactured, for example, by using a metal part as a base material (carrier film), forming the resin composition of the present invention in a sheet shape on this base material, and performing the pressing steps (a) and (b) described above. A composite molded article having metal parts on both sides can also be obtained by layering it with another metal plate during step (b).

[0154] Furthermore, the composite molded article of the present invention can also be manufactured by (a) peeling off a sheet-like resin composition formed on a substrate (carrier film) separate from the metal part from the carrier film after step (a), placing it on top of a metal member that will become the metal part, and performing the pressing in step (b).

[0155] In this case, the sheet-like resin composition of the present invention can be peeled off the carrier film after step (a) in the same manner as described above, except that it is applied to a carrier film such as PET which may have been treated with a release agent. The sheet-like resin composition can then be placed on another metal plate or sandwiched between two metal plates and integrated by pressing in step (b).

[0156] As the metal plate, a metal plate with a thickness of approximately 10 μm to 10 cm made of copper, aluminum, nickel-plated metal, etc., can be used. The surface of the metal plate may be physically roughened or chemically treated with a surface treatment agent. From the viewpoint of adhesion between the resin composition layer and the metal plate, these treatments are more preferable.

[0157] [Semiconductor devices] The composite molded body of the present invention can be used as a semiconductor device. In particular, it can be effectively used in power semiconductor devices that enable high output and high density by operating at high temperatures. [Examples]

[0158] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples unless it exceeds the essence of the invention. The various conditions and evaluation result values ​​in the following embodiments represent preferred ranges for the present invention, similar to the preferred ranges in the embodiments of the present invention. The preferred ranges for the present invention can be determined by considering the preferred ranges in the embodiments described above and the ranges shown by the values ​​in the following embodiments or combinations of values ​​from the embodiments.

[0159] [raw materials] The raw materials used in the examples and comparative examples are as follows:

[0160] <Thermosetting resin> Resin component 1: Epoxy resin manufactured in accordance with the epoxy resin manufacturing method disclosed in the examples of Japanese Patent Publication No. 2006-176658. Weight-average molecular weight in polystyrene equivalent: 30,000 Epoxy equivalent: 9,000 g / equivalent Resin component 2: Bisphenol A type liquid epoxy resin. Weight-average molecular weight: 600 or less. Resin component 3: Biphenyl-type solid epoxy resin. Weight-average molecular weight: 600 or less. Resin component 4: Non-aromatic polyfunctional epoxy resin containing a structure with four or more glycidyl groups per molecule. Weight-average molecular weight: 600 or less.

[0161] <Agglomerated inorganic filler> Inorganic Filler 1: Boron nitride aggregates having a cardhouse structure, manufactured in accordance with the method for producing boron nitride aggregates disclosed in the examples of International Publication No. 2015 / 561028. New Mohs hardness scale: 2 Volume-average particle size: 45 μm

[0162] <Other fillers> Inorganic filler 2: Spherical alumina particles manufactured by Admatex Corporation. New Mohs hardness: 9 Volume-average particle size: 6.5 μm Thermal conductivity: 20-30 W / m·K

[0163] <Hardening agent> Hardener 1: MEH-8000H manufactured by Meiwa Kasei Co., Ltd. Phenolic resin-based curing agent

[0164] <Curing catalyst component> Curing catalyst 1: "Curesol 2E4MZ-A" manufactured by Shikoku Chemicals Co., Ltd. Curing catalyst 2: "Curesol 2PHZ-PW" manufactured by Shikoku Chemicals Co., Ltd.

[0165] [Measurement method] <Reaction rate of thermosetting resins> Differential scanning calorimetry (DSC) was performed on the sheets formed before and after each of the processes (a) and (b) (the resin composition layer after process (b)). The reaction rates were calculated from the heat generated by the exothermic peaks obtained when the temperature was increased from 40°C to 250°C at a rate of 10°C / min, using the following formula. (a) Reaction rate of process (A) (%) = (1 - ((a) amount of heat generated after process (a) / (a) amount of heat generated before process (a))) × 100 (b) Reaction rate of process (B) (%) = (1 - ((heat generation after process (b) / heat generation before process (a))) × 100

[0166] <Thermal conductivity in the thickness direction of the resin composition layer> Using a thermal resistance measuring device (manufactured by Mentor Graphics Co., Ltd., product name "T3ster"), the thermal resistance values ​​of resin composition layers of different thicknesses, manufactured under the same composition and conditions, were measured. The thermal conductivity was then determined from the slope of the graph plotting the thermal resistance values ​​against thickness.

[0167] <Withstand voltage of the resin composition layer> In an insulating oil, the voltage applied to the resin composition layer was increased by 500V every minute, and the voltage at which the resin composition layer broke was determined. The obtained breakdown voltage value was converted to the breakdown voltage per 1 mm of film thickness to obtain the withstand voltage (kV / mm).

[0168] <Seat handling performance test (mandrel test)> (a) After the process, the carrier film-attached sheets were subjected to a bending test at 24°C with the carrier film facing inward, in accordance with JIS K 5600-5-1. An 8 mm diameter mandrel was used to perform a 180° bending test, and sheets with cracks or peeling were marked with ×, while those without cracks or peeling were marked with ○.

[0169] [Example 1] Using a rotation-and-revolving stirring device, resin component 1, resin component 2, resin component 4, curing agent 1, curing catalyst 1, inorganic filler 1, and inorganic filler 2 were mixed in the mass ratios shown in Composition A of Table 1 below to obtain a mixture. In preparing this mixture, a slurry-like resin composition was prepared by using 18.5% each of methyl ethyl ketone and cyclohexanone so that the above mixture constituted 63% by mass (solid content concentration) of the coating slurry.

[0170] The obtained slurry-like resin composition was applied onto a PET film using the doctor blade method, and after heating and drying at 60°C for 120 minutes, (a) the PET film was pressed together with the composition using a flat plate press at 50°C and 147 MPa for 10 minutes to obtain a sheet with a thickness of 150 μm. The total content of methyl ethyl ketone and cyclohexanone in the sheet was 1% by mass or less (solid content concentration of 99% by mass or more). (a) The reaction rate (A) of the thermosetting resin in the sheet after the process was less than 10%.

[0171] (a) After laminating a copper substrate onto the sheet that had undergone step (a), curing was performed in step (b) at 175°C and 9.8 MPa for 30 minutes to obtain a resin composition layer. The thickness of the resin composition layer was 141 μm, and the ratio of the film thickness after step (b) to the film thickness after step (a) (Fb / Fa) was 0.94. The results of the sheet handling performance evaluation (mandrel test) are shown in Table 2A. (b) The reaction rate (B) of the thermosetting resin in the resin composition layer after the process was 90% or more, and the dielectric strength of the resin composition layer was 53 kV / mm.

[0172] The thermal conductivity of the resin composition layer of Example 1 was measured for the following samples, which had the same composition and had undergone the same (a) and (b) steps. (a) The sheet-like resin composition after step (a) was sandwiched between PET films, and (b) it was cured at a predetermined pressure and temperature in step (b) to obtain a resin composition layer. Furthermore, using a similar method, after removing the carrier film from the sheet after step (a), the samples, which were stacked two, three, and four times, were sandwiched between PET films, and then processed at a predetermined pressure / temperature in step (b) to obtain four types of resin composition layers with different thicknesses. The thermal conductivity of these resin composition layers was measured using the method described above and was found to be 15 W / mK. These results are summarized in Table 2A.

[0173] <Examples 2-6, Comparative Examples 1-7> Resin compositions were prepared according to the method of Example 1, using composition A or B as shown in Table 1, and then processed using the pressing conditions and methods shown in Tables 2A and 2B. The results are summarized in Tables 2A and 2B.

[0174] [Table 1]

[0175] [Table 2A]

[0176] [Table 2B]

[0177] Tables 2A and 2B show that, according to the present invention, a resin composition layer with good dielectric strength and thermal conductivity can be obtained by processing in steps (a) and (b) at predetermined pressure / temperature.

[0178] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications are possible without departing from the intent and scope of the invention. This application is based on Japanese Patent Application No. 2020-069766, filed on 8 April 2020, which is incorporated herein by reference in its entirety.

Claims

1. A method for producing a resin composition layer comprising an aggregated inorganic filler and a thermosetting resin, the method comprising the following steps (a) and (b). (a) A process of forming a sheet on a carrier film using the resin composition, and performing hydrostatic pressing on the carrier film together under the conditions of a press temperature of 3°C to 95°C, a press pressure of 40 MPa to 500 MPa, and a press processing time of 3 minutes to 2 hours. (b) A process to obtain a resin composition layer by performing a flat plate press on a laminate including the metal part and the sheet, with the sheet and metal part in contact after going through process (a), under the conditions of a press temperature of 70°C to 250°C, a press pressure of 3 MPa to 100 MPa, and a press processing time of 10 minutes to 24 hours.

2. A method for producing a resin composition layer according to claim 1, wherein the reaction rate of the thermosetting resin in the sheet after step (a), determined by the method described below (referred to as "reaction rate (A)") is less than 50%. <Method for measuring and calculating the response rate (A)> (a) For sheets before and after the process, the amount of heat generated is calculated from the exothermic peak obtained when the temperature is increased from 40°C to 250°C at a rate of 10°C / min by differential scanning calorimetry (DSC) using the following formula. Reaction rate (A) (%) = (1 - (heat generated after step (a) / heat generated before step (a))) × 100

3. A method for producing a resin composition layer according to claim 1 or 2, wherein, if the press temperature in step (b) is Tb (°C) and the press temperature in step (a) is Ta (°C), then Tb > Ta and 30°C ≤ Tb - Ta ≤ 220°C.

4. A method for producing a resin composition layer according to any one of claims 1 to 3, wherein the reaction rate of the thermosetting resin in the sheet after step (b) (referred to as "reaction rate (B)"), determined by the method described below, is 60% or more. <Method for measuring and calculating the response rate (B)> For the sheets before (a) the process and after (b) the process, the amount of heat generated at the exothermic peak obtained when the temperature is increased from 40°C to 250°C at a rate of 10°C / min by differential scanning calorimetry (DSC) is calculated using the following formula. Reaction rate (B) (%) = (1 - (heat generated after step (b) / heat generated before step (a))) × 100

5. A method for producing a resin composition layer according to any one of claims 1 to 4, wherein, if the press pressure in step (b) is Pb (MPa) and the press pressure in step (a) is Pa (MPa), then Pa > Pb and Pa / Pb is 1.5 or more and 50 or less.

6. A method for producing a resin composition layer according to any one of claims 1 to 5, wherein, if the film thickness after step (b) is Fb and the film thickness after step (a) is Fa, then Fb / Fa is 0.7 or more and 1.2 or less.

7. A method for producing a resin composition layer according to any one of claims 1 to 6, wherein the thermosetting resin contains an epoxy compound.

8. A method for producing a resin composition layer according to claim 7, wherein the thermosetting resin comprises an epoxy compound having a weight-average molecular weight of 10,000 or more and an epoxy compound having a weight-average molecular weight of 600 or less.

9. A method for producing a resin composition layer according to claim 7 or 8, wherein the thermosetting resin comprises an epoxy compound having a weight-average molecular weight of 600 or less and containing three or more epoxy groups in one molecule.

10. A method for producing a resin composition layer according to any one of claims 1 to 9, wherein the aggregated inorganic filler includes an aggregated boron nitride filler.

11. A method for producing a resin composition layer according to claim 10, wherein the aggregated inorganic filler includes an aggregated boron nitride filler having a cardhouse structure.

12. A method for producing a composite molded article having a resin composition layer and a metal part, wherein the resin composition layer is formed by the method for producing a resin composition layer described in any one of claims 1 to 11.

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