Resin composition, insulating resin cured product, laminate, and circuit board

Abstract

A resin composition containing a thermosetting resin, an inorganic filler, and an inorganic ion scavenger, wherein: the inorganic filler includes first particles, which are particles having a scaly shape, and second particles, which are aggregates of particles having a scaly shape; the first particle content is 1-60 vol% with respect to the total amount of the first particles and the second particles; and the inorganic ion scavenger content is 0.1-50 mass% with respect to the entire amount of the thermosetting resin.

Description

Resin composition, insulating resin cured body, laminate, and circuit board

[0001] The present invention relates to a resin composition, a cured insulating resin, a laminate, and a circuit board that are suitable for use in producing an insulating layer of a circuit board (metal-based circuit board).

[0002] A variety of circuit boards have been put to practical use as circuit boards for mounting electronic and electrical components such as semiconductor elements to form hybrid integrated circuits. Circuit boards are classified based on the board material, such as resin circuit boards, ceramic circuit boards, and metal-based circuit boards.

[0003] Resin circuit boards are inexpensive, but due to the low thermal conductivity of the substrate, they are limited to applications requiring relatively low power. Ceramic circuit boards, due to the high electrical insulation and heat resistance characteristics of ceramics, are suitable for applications requiring relatively high power, but have the disadvantage of being expensive. On the other hand, metal-based circuit boards have properties intermediate between the two, and are suitable for general-purpose applications requiring relatively high power, such as refrigerator inverters, commercial air conditioner inverters, power supplies for industrial robots, and automotive power supplies.

[0004] For example, Patent Document 1 discloses a method for obtaining a circuit board having excellent stress relaxation properties, heat resistance, moisture resistance, and heat dissipation properties by using a composition for circuit boards containing, as essential components, a specific epoxy resin, a curing agent, and an inorganic filler.

[0005] Japanese Patent Application Laid-Open No. 2008-266533

[0006] If ceramic circuit boards could be replaced with metal-based circuit boards, productivity could be expected to improve. Ceramic circuit boards also have the problem of prone to solder cracks on the board during heat cycles, but replacing them with metal-based circuit boards is expected to prevent solder cracks from occurring. Meanwhile, because ceramic circuits are suited to applications requiring relatively large amounts of power, replacing ceramic circuit boards with metal-based circuit boards requires improved insulation reliability against the application of high DC voltages (particularly insulation reliability under high-temperature conditions).

[0007] Therefore, an object of the present invention is to provide a resin composition capable of forming an insulating layer having excellent insulating reliability against application of a high DC voltage under high temperature (150° C.) conditions, a cured insulating resin product obtained by curing the resin composition, and a laminate and a circuit board using the cured insulating resin product.

[0008] The present invention includes the following [1] to

[13] . [1] A resin composition containing a thermosetting resin, an inorganic filler, and an inorganic ion scaly filler, wherein the inorganic filler comprises first particles that are scaly particles and second particles that are agglomerates of the scaly particles, the content of the first particles is 1% by volume or more and 60% by volume or less with respect to the total content of the first particles and the second particles, and the content of the inorganic ion scaly filler is 0.1 to 50% by mass with respect to the total amount of the thermosetting resin. [2] The resin composition according to [1], wherein the average aspect ratio of the first particles is 1 to 200, and the average aspect ratio of the second particles is 1 to 2. [3] The resin composition according to [1] or [2], wherein the first particles are boron nitride particles, and in X-ray diffraction measurement, the ratio I(002) / I(100) of the peak intensity I(002) of the (002) plane to the peak intensity I(100) of the (100) plane is 50 to 1000, and the second particles are boron nitride particles, and in X-ray diffraction measurement, the ratio I(002) / I(100) of the peak intensity I(002) of the (002) plane to the peak intensity I(100) of the (100) plane is 1 to 20. [4] The resin composition according to any one of [1] to [3], wherein the ratio of the average particle size of the first particles to the average particle size of the second particles is 1.5 to 20. [5] The resin composition according to any one of [1] to [4], wherein the ratio of the average aspect ratio of the first particles to the average aspect ratio of the second particles is 0.01 to 0.8. [6] The resin composition according to any one of [1] to [5], wherein the inorganic filler has a thermal conductivity of 20 W / m K or more. [7] The resin composition according to any one of [1] to [6], wherein the content of the inorganic filler is 30 to 70 volume % relative to the total volume of the resin composition. [8] The resin composition according to any one of [1] to [7], wherein the inorganic ion scavenger contains both an anion exchanger and a cation exchanger, or both ion exchangers. [9] The resin composition according to any one of [1] to [8], wherein the inorganic ion scavenger contains at least one element selected from the group consisting of Al, Mg, Bi, Zr, Sb, and Zn.

[10] The resin composition according to any one of [1] to [9], wherein the inorganic ion scavenger comprises at least one selected from the group consisting of Bi, Zr, Sb, and Zn.

[11] The resin composition according to any one of [1] to

[10] , wherein the resin composition has a peak in the range of 2θ=11 to 15° in X-ray diffraction measurement.

[12] The resin composition according to any one of [1] to

[11] , wherein the thermosetting resin is an epoxy resin.

[13] The resin composition according to any one of [1] to

[12] , further comprising a copolymer, wherein the copolymer has (meth)acrylic monomer units A having an anionic group, (meth)acrylic monomer units B having a cationic group, and (meth)acrylic monomer units C other than the (meth)acrylic monomer units A and the (meth)acrylic monomer units B.

[14] A cured insulating resin product, which is a cured product of the resin composition according to any one of [1] to

[13] .

[15] A laminate comprising a first metal layer, an insulating layer disposed on one surface of the first metal layer, and a second metal layer disposed on the surface of the insulating layer opposite to the first metal layer, wherein the insulating layer is the cured insulating resin product according to

[14] .

[16] A circuit board comprising a metal layer, an insulating layer disposed on one surface of the metal layer, and a metal circuit portion disposed on the surface of the insulating layer opposite to the metal layer, wherein the insulating layer is the cured insulating resin product according to

[14] .

[0009] The present invention provides a resin composition capable of forming an insulating layer having excellent insulating reliability against application of a high DC voltage under high temperature (150° C.) conditions. The present invention also provides a cured insulating resin product that is a cured product of the resin composition, and a laminate and a circuit board that use the cured insulating resin product.

[0010] 1A and 1B are cross-sectional views showing an embodiment of a laminate and an embodiment of a circuit board.

[0011] Preferred embodiments of the present invention will be described in detail below.

[0012] One embodiment of the present invention is a resin composition containing a thermosetting resin, an inorganic filler, and an inorganic ion scavenger.

[0013] Examples of thermosetting resins include silicone resins, epoxy resins, phenolic resins, cyanate resins, melamine resins, urea resins, thermosetting polyimide resins, and unsaturated polyester resins. The thermosetting resin may include an epoxy resin. The thermosetting resins may be used alone or in combination of two or more.

[0014] The content of the thermosetting resin may be 10% by mass or more, 20% by mass or more, or 25% by mass or more, relative to the total mass of the resin composition, from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature (150°C) conditions. The content of the thermosetting resin may be 50% by mass or less, 40% by mass or less, or 30% by mass or less, relative to the total mass of the resin composition, from the viewpoint of improving thermal conductivity. From these viewpoints, the content of the thermosetting resin may be 10 to 50% by mass, relative to the total mass of the resin composition.

[0015] The resin composition contains an inorganic filler. The inorganic filler may be, for example, a known inorganic filler used in applications requiring insulation and thermal conductivity (excluding those corresponding to inorganic ion scavengers described below). The inorganic filler may contain, for example, one or more selected from the group consisting of aluminum oxide (alumina), silicon oxide, silicon nitride, boron nitride, aluminum nitride, and magnesium oxide. From the viewpoint of further improving insulation reliability in a high-humidity environment, the inorganic filler may contain one or more selected from the group consisting of aluminum oxide, silicon oxide, silicon nitride, boron nitride, and aluminum nitride, or may contain one or more selected from the group consisting of aluminum oxide, boron nitride, and aluminum nitride.

[0016] The inorganic filler includes first particles, which are scaly particles, and second particles, which are agglomerates of the scaly particles. The inorganic filler may also include particles (third particles) that do not fall under the category of the first particles or the second particles. The content of the first particles is 1% by volume or more and 60% by volume or less of the total content of the first particles and the second particles.

[0017] When the inorganic filler contains first particles that are scaly particles and second particles that are agglomerates of the scaly particles, and the content of the first particles is 1% by volume or more and 60% by volume or less relative to the total content of the first particles and the second particles, a resin composition capable of forming an insulating layer having excellent insulating reliability against application of high DC voltage under high temperature (150°C) conditions is easily obtained. The inventors speculate that the reason for this is as follows. That is, when the inorganic filler contains multiple particles with different shapes, the filling ability of the inorganic filler is improved, making it easier to restrict the migration of ions that affect the insulating properties. Furthermore, the presence of a certain amount of second particles with relatively complex shapes makes it easier to sufficiently restrict the migration of ions that affect the insulating properties. It is speculated that these factors restrict the migration of ions in the resin composition and make it easier for the ions to be captured by the inorganic ion scavenger, thereby improving the insulating properties of the insulating layer formed from the resin composition. However, the mechanism of the present invention is not limited to the above reasons.

[0018] The first particles and the second particles may each contain the same component or different components. The first particles and the second particles may each have the same composition. For example, the first particles and the second particles may each be boron nitride particles. The second particles may be agglomerated particles of the first particles, or may be agglomerated particles of scaly particles different from the first particles. In this specification, agglomerated particles refer to particles in which multiple particles are in contact with each other to form a mass.

[0019] The particle diameter of the first particles may be 50 μm or less, 30 μm or less, 15 μm or less, 10 μm or less, or 8 μm or less from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature (150°C) conditions, and from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature and high humidity (85°C, 85% RH) conditions. From the same viewpoint, it may be 0.1 μm or more, 1 μm or more, 3 μm or more, or 5 μm or more. The particle diameter of the first particles can be obtained by embedding the first particles in a resin, preparing a sample for cross-sectional observation by mechanical polishing and ion milling, depositing gold plating on the sample, and then measuring the maximum length of the particles when observing the particles at 10,000x magnification using a scanning electron microscope (SEM). From these viewpoints, the particle diameter of the first particles may be 0.1 to 50 μm.

[0020] The average particle diameter of the first particles may be 50 μm or less, 30 μm or less, 15 μm or less, 10 μm or less, or 8 μm or less from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature (150°C) conditions, and from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature and high humidity (85°C, 85% RH) conditions. From the same viewpoint, it may be 0.1 μm or more, 1 μm or more, 3 μm or more, or 5 μm or more. The average particle diameter of the first particles is obtained by measuring the maximum length of each of 10 first particles in one field of view during SEM observation in the above-mentioned method for measuring the particle diameter of the first particles and averaging the results. From these viewpoints, the average particle diameter of the first particles may be 0.1 to 50 μm.

[0021] The aspect ratio of the first particles may be 1 to 200, 5 to 200, 10 to 200, or 50 to 150, from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature (150°C) conditions, and from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature and high humidity (85°C, 85% RH) conditions. The aspect ratio of the first particles is obtained by measuring the maximum length of the first particles and the maximum length in a direction perpendicular to the direction of the maximum length in the method for measuring the particle diameter of the first particles described above, and dividing the maximum length by the maximum length in the direction perpendicular to the direction of the maximum length. When the first particles are scaly particles, the aspect ratio of the first particles is obtained by measuring the maximum length and maximum thickness (maximum length in the thickness direction) of the first particles in the method for measuring the particle diameter of the first particles described above, and dividing the maximum length by the maximum thickness.

[0022] From the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature (150°C) conditions, and from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature and high humidity (85°C, 85% RH) conditions, the average aspect ratio of the first particles may be 1 to 200, 5 to 200, 10 to 200, or 50 to 150. The average aspect ratio of the first particles can be obtained by measuring the maximum length and the maximum length in the direction perpendicular to the direction of the maximum length of each of 10 first particles in one field of view during SEM observation in the method for measuring the particle diameter of the first particles described above, and dividing the maximum length by the maximum length in the direction perpendicular to the direction of the maximum length. When the first particles are scaly particles, the average aspect ratio of the first particles can be obtained by measuring the maximum length and maximum thickness of each of 10 first particles in one field of view during SEM observation, dividing the maximum length by the maximum thickness, and averaging the results in the above-described method for measuring the particle diameter of the first particles.

[0023] When the first particles include boron nitride particles (first boron nitride particles), the ratio I(002) / I(100) of the peak intensity I(002) of the (002) plane to the peak intensity I(100) of the (100) plane in X-ray diffraction measurement of the first boron nitride particles may be 50 to 1000, 60 to 800, 70 to 600, 80 to 400, or 90 to 200.

[0024] The particle diameter of the second particles may be larger than the particle diameter of the first particles, and may be greater than 8 μm, greater than 10 μm, greater than 15 μm, greater than 30 μm, or greater than 50 μm. The particle diameter of the second particles may be 500 μm or less, 300 μm or less, 200 μm or less, 150 μm or less, or 100 μm or less. The particle diameter of the second particles is obtained by embedding the second particles in resin, preparing a sample for cross-sectional observation by mechanical polishing and ion milling, depositing gold plating on the sample, and then measuring the maximum length of the particles when observing the particles at 1,000x magnification using a scanning electron microscope (SEM). From these perspectives, the particle diameter of the second particles may be greater than 8 μm and less than 500 μm.

[0025] The average particle size of the second particles may be larger than the average particle size of the first particles, and may be greater than 8 μm, greater than 10 μm, greater than 15 μm, greater than 30 μm, or greater than 50 μm. The average particle size of the second particles may be 500 μm or less, 300 μm or less, 200 μm or less, 150 μm or less, or 100 μm or less. The average particle size of the second particles can be measured using a laser diffraction / scattering & dynamic image analysis particle size distribution / particle shape measuring device. From these perspectives, the average particle size of the second particles may be greater than 8 μm and less than 500 μm.

[0026] The aspect ratio of the second particles may be 1 to 5, 1 to 4, 1 to 3, or 1 to 2. The aspect ratio of the second particles can be obtained by measuring the maximum length of the second particles and the maximum length in a direction perpendicular to the direction of the maximum length in the method for measuring the particle diameter of the second particles described above, and dividing the maximum length by the maximum length in the direction perpendicular to the direction of the maximum length.

[0027] The average aspect ratio of the second particles may be 1 to 5, 1 to 4, 1 to 3, or 1 to 2. The average aspect ratio of the second particles can be measured using a laser diffraction / scattering & dynamic image analysis type particle size distribution / particle shape measuring device.

[0028] When the second particles include boron nitride particles (second boron nitride particles), the ratio I(002) / I(100) of the peak intensity I(002) of the (002) plane to the peak intensity I(100) of the (100) plane in X-ray diffraction measurement of the second boron nitride particles may be 1 to 20, 1 to 15, 1 to 10, 1 to 5, 1.1 to 4, 1.2 to 3, or 1.2 to 2.

[0029] The ratio of the average particle size of the first particles to the average particle size of the second particles (average particle size of the second particles / average particle size of the first particles) may be 1.5 or more, 2 or more, 3 or more, 4 or more, or 5 or more from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulation reliability against application of a high DC voltage under high temperature (150 ° C) conditions, and from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulation reliability against application of a high DC voltage under high temperature and high humidity (85 ° C, 85% RH) conditions, and from the same viewpoint, it may be 20 or less, 15 or less, 10 or less, 8 or less, or 6 or less. The ratio of the average particle size of the first particles to the average particle size of the second particles may be 1.5 or more and 20 or less, or 3 or more and 10 or less.

[0030] The ratio of the average aspect ratio of the first particles to the average aspect ratio of the second particles (average aspect ratio of the second particles / average aspect ratio of the first particles) may be 0.01 or more, 0.05 or more, 0.1 or more, 0.15 or more, or 0.18 or more from the viewpoint that it is easy to obtain a resin composition capable of forming an insulating layer having superior insulation reliability against application of high DC voltage under high temperature (150 ° C) conditions, and from the viewpoint that it is easy to obtain a resin composition capable of forming an insulating layer having superior insulation reliability against application of high DC voltage under high temperature and high humidity (85 ° C, 85% RH) conditions, and from the same viewpoint, it may be 0.8 or less, 0.6 or less, 0.4 or less, 0.3 or less, or 0.2 or less. The ratio of the average aspect ratio of the first particles to the average aspect ratio of the second particles may be 0.01 or more and 0.8 or 0.1 or more and 0.4 or less.

[0031] The inorganic filler may have multiple peaks in the particle size distribution curve. The inorganic filler may include, for example, a first particle group having a peak in the range of 0.1 μm to 15 μm in the particle size distribution curve, and a second particle group having a peak in the range of more than 15 μm to 300 μm in the particle size distribution curve. In this specification, having a peak in a specific range in the particle size distribution curve means that the peak top is present within a specific range.

[0032] The first particle group may have a single peak or multiple peaks in the range of 0.1 μm to 15 μm in a particle size distribution curve, and the second particle group may have a single peak or multiple peaks in the range of more than 15 μm to 300 μm in a particle size distribution curve.

[0033] The first particle group may have a peak in the range of 0.1 μm or more, 0.5 μm or more, 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, or 5 μm or more in the particle size distribution curve from the viewpoint that it is easy to obtain a resin composition capable of forming an insulating layer having superior insulating reliability against application of high DC voltage under high temperature (150 ° C) conditions, and from the viewpoint that it is easy to obtain a resin composition capable of forming an insulating layer having superior insulating reliability against application of high DC voltage under high temperature and high humidity (85 ° C, 85% RH) conditions, and from the same viewpoint, it may have a peak in the range of 15 μm or less, 12 μm or less, 10 μm or less, 9 μm or less, 8 μm or less, or 7 μm or less. From these viewpoints, the first particle group may have a peak in the range of 0.1 to 15 μm.

[0034] The second particle group, from the viewpoint that it is easy to obtain a resin composition capable of forming an insulating layer having superior insulating reliability against application of high DC voltage under high temperature (150 ° C) conditions, and from the viewpoint that it is easy to obtain a resin composition capable of forming an insulating layer having superior insulating reliability against application of high DC voltage under high temperature and high humidity (85 ° C, 85% RH) conditions, in the particle size distribution curve, it may have a peak in the range of more than 15 μm, more than 20 μm, more than 25 μm, more than 30 μm, more than 35 μm, or more than 40 μm, and from the same viewpoint, it may have a peak in the range of 300 μm or less, 250 μm or less, 200 μm or less, 150 μm or less, 100 μm or less, 80 μm or less, 60 μm or less, or 50 μm or less. From these viewpoints, the second particle group may have a peak in the range of more than 15 μm and less than 300 μm.

[0035] In the particle size distribution curve, the difference between the peak position (particle diameter) of the first particle group and the peak position (particle diameter) of the second particle group ((peak position of the second particle group) - (peak position of the first particle group)) is 10 μm or more, 20 μm or more, or 30 μm or more from the viewpoint that a resin composition capable of forming an insulating layer having superior insulation reliability against DC high voltage application under high temperature (150 ° C) conditions is easily obtained, and from the viewpoint that a resin composition capable of forming an insulating layer having superior insulation reliability against DC high voltage application under high temperature and high humidity (85 ° C, 85% RH) conditions is easily obtained, and from the same viewpoint, it may be 200 μm or less, 150 μm or less, 100 μm or less, or 50 μm or less. The difference between the peak position of the first particle group and the peak position of the second particle group may be 10 μm or more and 200 μm or less, or 20 μm or more and 100 μm or less.

[0036] The thermal conductivity of the inorganic filler may be 20 W / m K or more, 50 W / m K or more, 100 W / m K or more, or 150 W / m K or more, and may be 3500 W / m K or less, 2000 W / m K or less, 1500 W / m K or less, 600 W / m K or less, 300 W / m K or less, or 200 W / m K or less. The thermal conductivity of the first particles may be within the above range, and the thermal conductivity of the second particles may be within the above range.

[0037] The content of the first particles may be 2% by volume or more, 3% by volume or more, 5% by volume or more, 8% by volume or more, or 10% by volume or more, based on the total content of the first particles and the second particles, from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature (150 ° C) conditions, and from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature and high humidity (85 ° C, 85% RH) conditions. From the same viewpoint, it may be 50% by volume or less, 40% by volume or less, 30% by volume or less, 20% by volume or less, or 15% by volume or less. The content of the first particles may be 1% by volume or more and 50% by volume or less, 3% by volume or more and 30% by volume or less, 3% by volume or more and 30% by volume or less, or 5% by volume or more and 20% by volume or less, based on the total content of the first particles and the second particles.

[0038] The content of the second particles may be 50% by volume or more, 60% by volume or more, 70% by volume or more, 80% by volume or more, or 85% by volume or more, based on the total content of the first particles and the second particles, from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of high DC voltage under high temperature (150 ° C) conditions, and from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of high DC voltage under high temperature and high humidity (85 ° C, 85% RH) conditions. From the same viewpoint, it may be 99% by volume or less, 97% by volume or less, 95% by volume or less, 92% by volume or less, or 90% by volume or less. The content of the second particles may be 50% by volume or more, 60% by volume or more, 97% by volume or less, or 70% by volume or more, based on the total content of the first particles and the second particles.

[0039] The total content of the first particles and the second particles may be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more, relative to the total mass of the inorganic filler, from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability when a high DC voltage is applied under high temperature (150°C) conditions, and from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability when a high DC voltage is applied under high temperature and high humidity (85°C, 85% RH) conditions.

[0040] The total content of the first particles and the second particles may be 50% by volume or more, 60% by volume or more, 70% by volume or more, 80% by volume or more, 90% by volume or more, or 95% by volume or more, relative to the total volume of the inorganic filler, from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability when a high DC voltage is applied under high temperature (150°C) conditions, and from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability when a high DC voltage is applied under high temperature and high humidity (85°C, 85% RH) conditions.

[0041] The content of the inorganic filler may be 30% by mass or more, 40% by mass or more, 50% by mass or more, or 60% by mass or more, relative to the total mass of the resin composition, from the viewpoint of improving thermal conductivity. The content of the inorganic filler may be 80% by mass or less, 75% by mass or less, 70% by mass or less, or 65% by mass or less, relative to the total mass of the resin composition, from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulation reliability against application of high DC voltage under high temperature (150 ° C) conditions, and preferably 65% ​​by mass or less, from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulation reliability against application of high DC voltage under high temperature and high humidity (85 ° C, 85% RH) conditions. From these viewpoints, the content of the inorganic filler may be 30 to 80% by mass, relative to the total mass of the resin composition.

[0042] The content of the inorganic filler may be 20% by volume or more, 30% by volume or more, 40% by volume or more, 45% by volume or more, or 50% by volume or more, relative to the total volume of the resin composition, from the viewpoint of improving thermal conductivity. The content of the inorganic filler may be 80% by volume or less, 70% by volume or less, 60% by volume or less, 55% by volume or less, or 50% by volume or less, relative to the total volume of the resin composition, from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulation reliability against the application of high DC voltage under high temperature (150 ° C) conditions. From the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulation reliability against the application of high DC voltage under high temperature and high humidity (85 ° C, 85% RH) conditions, it is preferably 55% by volume or less. The content of the inorganic filler may be 20 to 80% by volume or 30 to 70% by volume, relative to the total volume of the resin composition. From these viewpoints, the content of the inorganic filler may be 30 to 80% by volume, relative to the total volume of the resin composition.

[0043] An inorganic ion scavenger is an inorganic material that has the function of capturing at least one of cations and anions (having ion-capturing properties). In this specification, "ion-capturing properties" refers to the property of adsorbing the ions to be captured onto the surface of the inorganic material, or the property of introducing the ions to be captured into the structure of the inorganic material by ion exchange between the ions in the structure of the inorganic material and the ions to be captured. Examples of ions to be captured by the inorganic ion scavenger include cations such as Na ions, Cu ions, and Ag ions; and anions such as Cl ions and Br ions.

[0044] The inorganic ion scavenger may contain, for example, at least one selected from the group consisting of Al, Mg, Bi, Zr, Sb, and Zn. From the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature (150°C) conditions, the inorganic ion scavenger may contain at least one selected from the group consisting of Al, Mg, Bi, Zr, Sb, and Zn. From the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature and high humidity (85°C, 85% RH) conditions, the inorganic ion scavenger may contain, for example, an oxide, an acid chloride, or a hydrate thereof containing at least one of these metal elements. The inorganic ion scavenger may contain two or more of these metal elements.

[0045] Examples of inorganic ion trapping agents include anion exchangers that trap anions, cation exchangers that trap cations, and amphoteric ion exchangers that trap both anions and cations. The inorganic ion trapping agents may be used singly or in combination of two or more. For example, amphoteric ion exchangers may be a mixture of anion exchangers and cation exchangers. From the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having excellent insulating reliability against application of a high DC voltage under high-temperature and high-humidity conditions (85°C, 85% RH), the inorganic ion trapping agent may contain both anion exchangers and cation exchangers, or both ion exchangers.

[0046] The anion exchanger may be an inorganic material containing at least one selected from the group consisting of Al, Mg, Bi, Zr, and Zn. Specific examples of the anion exchanger include IXE-500 (Bi-based), IXE-530 (Bi-based), IXE-550 (Bi-based), IXE-700 (Mg, Al-based), IXE-700F (Mg, Al-based), IXE-770 (Mg, Al-based), IXE-770D (Mg, Al-based), IXE-702 (Al-based), IXE-800 (Zr-based), and IXE-1000 (Zn-based) (all manufactured by Toagosei Co., Ltd.).

[0047] The cation exchanger may be an inorganic material containing at least one selected from the group consisting of Zr, Sn, and Ti. Specific examples of the cation exchanger include IXE-100 (Zr-based), IXE-200 (Sn-based), IXE-300 (Sb-based), and IXE-400 (Ti-based) (all manufactured by Toagosei Co., Ltd.).

[0048] The ion exchangers include inorganic materials containing at least one selected from the group consisting of Al, Mg, Bi, Zr, and Sb. Specific examples of the ion exchangers include IXE-1320 (Mg, Al-based), IXE-600 (Sb, Bi-based), IXE-633 (Bi-based), IXE-680 (Bi-based), IXE-6107 (Zr, Bi-based), IXE-6136 (Zr, Bi-based), IXEPLAS-A1 (Zr, Mg, Al-based), IXEPLAS-A2 (Zr, Mg, Al-based), and IXEPLAS-B1 (Zr, Bi-based) (all manufactured by Toagosei Co., Ltd.).

[0049] The inorganic ion scavenger may be in powder form. When the inorganic ion scavenger is in powder form, the average particle size of the inorganic ion scavenger may be 0.05 μm or more, 0.1 μm or more, 0.15 μm or more, 0.2 μm or more, 0.3 μm or more, 0.4 μm or more, or 0.5 μm or more, and may be 10 μm or less, 5 μm or less, 3 μm or less, 2 μm or less, 1.5 μm or less, or 1 μm or less. The average particle size of the inorganic ion scavenger may be 0.05 to 10 μm. The average particle size of the inorganic ion scavenger can be measured by a laser diffraction / scattering method.

[0050] The content of the inorganic ion scavenger containing at least one selected from the group consisting of Al, Mg, Bi, Zr, Sb, and Zn may be 80 mass% or more, 90 mass% or more, or 95 mass% or more, based on the total mass of the inorganic ion scavenger. The content of the inorganic ion scavenger containing at least one selected from the group consisting of Al, Mg, Bi, Zr, Sb, and Zn may be substantially 100 mass% based on the total mass of the inorganic ion scavenger.

[0051] The content of the inorganic ion scavenger is 0.1 to 50% by mass relative to the total amount of the thermosetting resin. From the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature (150°C) conditions and from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature and high humidity (85°C, 85% RH) conditions, the content of the inorganic ion scavenger may be 0.3% by mass or more, 0.5% by mass or more, 1% by mass or more, 3% by mass or more, 5% by mass or more, 8% by mass or more, or 10% by mass or more, or may be 40% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, or 15% by mass or less, relative to the total amount of the thermosetting resin.

[0052] From the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature (150°C) conditions, and from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature and high humidity (85°C, 85% RH) conditions, the content of the inorganic ion scavenger may be 0.05% by mass or more, 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 1.2% by mass or more, or 1.4% by mass or more, relative to the total mass of the resin composition, and may be 30% by mass or less, 20% by mass or less, 15% by mass or less, 10% by mass or less, 8% by mass or less, 6% by mass or less, or 4% by mass or less. From these viewpoints, the content of the inorganic ion scavenger may be 0.05 to 30% by mass, relative to the total mass of the resin composition.

[0053] The mass ratio of the inorganic ion scavenger to the copolymer (the content by mass of the inorganic ion scavenger / the content by mass of the copolymer) may be 0.005 or more, 0.01 or more, or 0.05 or more, and may be 1,000 or less, 100 or less, or 50 or less, from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature (150°C) conditions, and from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer having superior insulating reliability against application of a high DC voltage under high temperature and high humidity (85°C, 85% RH) conditions. The mass ratio of the inorganic ion scavenger to the copolymer may be 25 or less, 10 or less, 5 or less, or 3 or less. The mass ratio of the inorganic ion scavenger to the copolymer may be 0.001 to 10,000.

[0054] The resin composition may further contain a dispersant for dispersing the inorganic filler. The dispersant may be a copolymer having (meth)acrylic monomer units A having an anionic group (hereinafter also referred to as "units A," and the monomer that provides units A is also referred to as "monomer A"), (meth)acrylic monomer units B having a cationic group (hereinafter also referred to as "units B," and the monomer that provides units B is also referred to as "monomer B"), and (meth)acrylic monomer units C other than (meth)acrylic monomer units A and (meth)acrylic monomer units B (hereinafter also referred to as "units C," and the monomer that provides units C is also referred to as "monomer C"). The copolymer may also have a (meth)acrylic monomer unit (unit X) having both an anionic group and a cationic group. In this case, unit X is considered to correspond to both unit A and unit B. In other words, a copolymer having unit X is considered to have both unit A and unit B.

[0055] In this specification, "monomer" means a monomer having a polymerizable group before polymerization. "Monomer unit" means a structural unit derived from the monomer and constituting a copolymer. "(Meth)acrylic monomer" means a monomer having a (meth)acryloyl group. "(Meth)acrylic monomer" means an acrylic monomer and its corresponding methacrylic monomer, and similar expressions such as "(meth)acryloyl group" have the same meaning.

[0056] The copolymer has one or more types of each of unit A, unit B, and unit C. The copolymer may be a random copolymer or a block copolymer. Monomer A, monomer B, and monomer C may each be a monomer having one (meth)acryloyl group (monofunctional (meth)acrylic monomer) or a monomer having two or more (meth)acryloyl groups (polyfunctional (meth)acrylic monomer), and is preferably a monofunctional (meth)acrylic monomer.

[0057] The anionic group contained in the unit A is, for example, one or more selected from the group consisting of a carboxyl group, a phosphoric acid group, a phenolic hydroxy group, and a sulfonic acid group. From the viewpoint of further improving the dispersibility of the inorganic filler, the anionic group is preferably one or more selected from the group consisting of a carboxyl group, a phosphoric acid group, and a phenolic hydroxy group.

[0058] From the viewpoint of further improving the dispersibility of the inorganic filler, the unit A preferably further has an electron-withdrawing group bonded to the anionic group. The electron-withdrawing group has the effect of stabilizing the anion of the anionic group. Examples of the electron-withdrawing group include a halogen group (also called a halogeno group). Examples of the anionic group bonded to an electron-withdrawing group include a group in which a halogen group is bonded to the carbon atom at the α-position of a carboxyl group.

[0059] The unit A may not have an electron-donating group attached to the anionic group. The electron-donating group may destabilize the anion of the anionic group. Examples of the electron-donating group include a methyl group.

[0060] Examples of monomer A include acrylic acid, methacrylic acid, acid phosphooxypropyl methacrylate, acid phosphooxypolyoxyethylene glycol monomethacrylate, acid phosphooxypolyoxypropylene glycol monomethacrylate, phosphoric acid-modified epoxy acrylate, 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, 4-hydroxyphenyl acrylate, 4-hydroxyphenyl methacrylate, 2-methacryloyloxyethyl succinic acid, 2-acrylamido-2-methylpropanesulfonic acid, etc. From the viewpoint of further improving the dispersibility of the inorganic filler, monomer A is preferably one or more selected from the group consisting of acrylic acid, 2-methacryloyloxyethyl phosphate, 4-hydroxyphenyl methacrylate, and 2-acrylamido-2-methylpropanesulfonic acid, and more preferably acrylic acid.

[0061] The cationic group contained in the unit B is, for example, one or more selected from the group consisting of a primary amino group, a secondary amino group, a tertiary amino group, and a quaternary ammonium salt group. From the viewpoint of further improving the dispersibility of the inorganic filler, the cationic group is preferably a tertiary amino group.

[0062] From the viewpoint of further improving the dispersibility of the inorganic filler, the unit B preferably further has an electron-donating group bonded to the cationic group. The electron-donating group has the effect of stabilizing the cation of the cationic group. An example of the electron-donating group is a methyl group. An example of the cationic group bonded to an electron-donating group is a group in which a methyl group is bonded to the carbon atom at the α-position of an amino group.

[0063] The unit B may not have an electron-withdrawing group bonded to the cationic group. The electron-withdrawing group may destabilize the cation of the cationic group. Examples of the electron-withdrawing group include a carboxyl group.

[0064] Examples of monomer B include 1-aminoethyl acrylate, 1-aminopropyl acrylate, 1-aminoethyl methacrylate, 1-aminopropyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, t-butylaminoethyl (meth)acrylate, dimethylaminoethyl methacrylate quaternary salt, 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, 2,2,6,6-tetramethyl-4-piperidyl methacrylate, dimethylaminoethyl acrylate benzyl chloride quaternary salt, etc. From the viewpoint of further improving the dispersibility of the inorganic filler, monomer B is preferably one or more selected from the group consisting of 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate and 2,2,6,6-tetramethyl-4-piperidyl methacrylate, more preferably 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate.

[0065] The unit C is a (meth)acrylic monomer that does not contain either a cationic group or an anionic group. The unit C may have an amphipathic group, a hydrophobic group, or a hydrophilic group in addition to the (meth)acryloyl group. Examples of the amphipathic group include an oxyalkylene group. Examples of the hydrophobic group include a siloxane group and a hydrocarbon group. Examples of the hydrophilic group include a phosphate ester group. Note that the hydrocarbon group referred to here does not include a methyl group that constitutes a methacryloyl group (the same applies hereinafter to the hydrocarbon group in the unit C).

[0066] From the viewpoint of affinity or compatibility between the copolymer and the resin when the resin composition further contains a resin, the unit C has one or more groups selected from the group consisting of an oxyalkylene group, a siloxane group, and a hydrocarbon group, and more preferably has one or more groups selected from the group consisting of a siloxane group and a hydrocarbon group.

[0067] Examples of the (meth)acrylic monomer having an oxyalkylene group include ethoxycarbonylmethyl (meth)acrylate, phenol ethylene oxide-modified (meth)acrylate, phenol (ethylene oxide 2 mol modified) (meth)acrylate, phenol (ethylene oxide 4 mol modified) (meth)acrylate, paracumylphenol ethylene oxide-modified (meth)acrylate, nonylphenol ethylene oxide-modified (meth)acrylate, nonylphenol (ethylene oxide 4 mol modified) (meth)acrylate, nonylphenol (ethylene oxide 8 mol modified) (meth)acrylate, nonylphenol (propylene oxide 2.5 mol modified) acrylate, 2-ethylhexylcarbitol (meth)acrylate, ethylene oxide-modified phthalic acid (meth)acrylate, ethylene oxide-modified succinic acid (meth)acrylate, and tetrahydrofurfuryl (meth)acrylate.

[0068] Examples of (meth)acrylic monomers having a siloxane group include α-butyl-ω-(3-methacryloxypropyl)polydimethylsiloxane. Examples of (meth)acrylic monomers having a hydrocarbon group include methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, isooctyl(meth)acrylate, isodecyl(meth)acrylate, lauryl(meth)acrylate, stearyl(meth)acrylate, phenyl(meth)acrylate, cyclohexyl(meth)acrylate, dicyclopentanyl(meth)acrylate, dicyclopentenyl(meth)acrylate, dicyclopentenyloxyethyl(meth)acrylate, isobornyl(meth)acrylate, and methoxylated cyclodecatriene(meth)acrylate.

[0069] Examples of the (meth)acrylic monomer having a phosphate group include (meth)acryloyloxyethyl dialkyl phosphate.

[0070] In addition to the above, the monomer C may also be, for example, a (meth)acrylic monomer having a hydroxy group. Examples of the (meth)acrylic monomer having a hydroxy group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth)acrylate.

[0071] Monomer C may be, for example, a (meth)acrylic monomer having an amide bond. Examples of the (meth)acrylic monomer having an amide bond include N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, diacetone(meth)acrylamide, and acryloylmorpholine.

[0072] Monomer C may be, for example, a polyfunctional (meth)acrylic monomer. Examples of the polyfunctional (meth)acrylic monomer include 1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexadiol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, 2-ethyl-2-butyl-propanediol (meth)acrylate, neopentyl glycol-modified trimethylolpropane di(meth)acrylate, stearic acid-modified pentaerythritol di(meth)acrylate, 2-(1,2-cyclohexacarboximide)ethyl (meth)acrylate, hexanediol di(meth)acrylate, and polyfunctional (meth)acrylates having a bisphenol structure.

[0073] The content of unit A may be 0.03 mol% or more, 0.1 mol% or more, 0.5 mol% or more, 1 mol% or more, 2 mol% or more, 3 mol% or more, 4 mol% or more, or 5 mol% or more, relative to 100 mol% of the total of unit A, unit B, and unit C (in other words, the total of all monomer units contained in the copolymer; the same applies below), and may be 70 mol% or less, 60 mol% or less, 50 mol% or less, 40 mol% or less, 30 mol% or less, 20 mol% or less, 15 mol% or less, 10 mol% or less, or 5 mol% or less. When the content of unit A is 0.03 mol% or more, the dispersibility of the inorganic filler tends to be further improved. When the content of unit A is 70 mol% or less, the viscosity of the resin composition tends to be further reduced, and the handleability of the resin composition tends to be further improved.

[0074] The content of unit B may be 0.02 mol% or more, 0.05 mol% or more, 0.07 mol% or more, or 0.1 mol% or more, relative to 100 mol% of the total of unit A, unit B, and unit C, and may be 20 mol% or less, 10 mol% or less, 5 mol% or less, 3 mol% or less, 1 mol% or less, 0.5 mol% or less, or 0.1 mol% or less. When the content of unit B is 0.02 mol% or more, the affinity of the copolymer to inorganic fillers tends to be better. When the content of unit B is 20 mol% or less, the viscosity of the resin composition tends to be further reduced, and the handleability of the resin composition tends to be further improved.

[0075] The content of unit C may be 10 mol% or more, 20 mol% or more, 30 mol% or more, 40 mol% or more, 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, 92 mol% or more, or 94 mol% or more, and 99.8 mol% or less, 99 mol% or less, 98 mol% or less, 97 mol% or less, 96 mol% or less, or 95 mol% or less, relative to the total 100 mol% of unit A, unit B, and unit C. When the content of unit C is 10 mol% or more, the viscosity of the resin composition tends to be further reduced, and the handleability of the resin composition tends to be further improved. When the content of unit C is 99.8 mol% or less, the affinity of the copolymer to the inorganic filler tends to be better.

[0076] The total content of units A and units B may be 0.05 mol% or more, 0.2 mol% or more, 1 mol% or more, 2 mol% or more, 3 mol% or more, 4 mol% or more, or 5 mol% or more, relative to the total of units A, units B, and units C (100 mol%), and may be 90 mol% or less, 80 mol% or less, 70 mol% or less, 60 mol% or less, 50 mol% or less, 40 mol% or less, 30 mol% or less, 20 mol% or less, 10 mol% or less, 8 mol% or less, or 6 mol% or less. When the total content of units A and units B is 0.05 mol% or more, the dispersibility of the inorganic filler tends to be further improved. When the total content of units A and units B is 90 mol% or less, the handleability of the resin composition tends to be further improved.

[0077] The molar ratio of units A to units B (units A / units B) may be 0.01 or more, 0.9 or more, 1 or more, 5 or more, 10 or more, 20 or more, 30 or more, 40 or more, or 50 or more, or may be 200 or less, 150 or less, 100 or less, 90 or less, 80 or less, 70 or less, 60 or less, 50 or less, 40 or less, 30 or less, 20 or less, 15 or less, or 10 or less. When the molar ratio of units A to units B is within the above range, the dispersibility of the inorganic filler tends to be further improved.

[0078] The weight-average molecular weight of the copolymer may be 1,000 or more, 5,000 or more, 7,000 or more, 10,000 or more, 20,000 or more, 30,000 or more, 40,000 or more, or 50,000 or more, or 1,000,000 or less, 500,000 or less, 300,000 or less, 100,000 or less, 90,000 or less, 80,000 or less, 70,000 or less, or 60,000 or less. By having a weight-average molecular weight of 1,000 or more, the dispersibility of the inorganic filler can be maintained and an increase in hardness of the resin composition can be suppressed even when the resin composition is stored in a high-temperature environment for a long period of time. In addition, the shape retention of the resin composition is improved, and the resin composition is prevented from slipping or dripping when applied to an inclined or vertical surface. When the weight-average molecular weight of the copolymer is 1,000,000 or less, the viscosity of the resin composition is further reduced, and the handleability of the resin composition tends to be further improved. The weight-average molecular weight of the copolymer is determined as a weight-average molecular weight converted into standard polystyrene using a GPC (gel permeation chromatography) method.

[0079] The copolymer can be obtained by polymerizing the monomer A, the monomer B, and the monomer C by a known polymerization method. Examples of the polymerization method include radical polymerization and anionic polymerization. The polymerization method is preferably radical polymerization.

[0080] The polymerization initiator used in radical polymerization may be a thermal polymerization initiator or a photopolymerization initiator. Examples of thermal polymerization initiators include azo compounds such as azobisisobutyronitrile; and organic peroxides such as benzoyl peroxide, tert-butyl hydroperoxide, and di-tert-butyl peroxide. Examples of photopolymerization initiators include benzoin derivatives. The polymerization initiator may be a known polymerization initiator used in living radical polymerization such as ATRP or RAFT.

[0081] The polymerization conditions can be appropriately adjusted depending on the type of monomer, polymerization initiator, etc. When the copolymer is a random copolymer, the monomers may be mixed in advance and polymerized. When the copolymer is a block copolymer, the monomers may be added sequentially to the polymerization system.

[0082] The content of the copolymer may be 0.01 to 10 parts by mass relative to 100 parts by mass of the inorganic filler. Having the content of the copolymer within this range makes it easier to obtain a resin composition capable of forming an insulating layer having superior insulating reliability against application of high DC voltage under high temperature (150°C) conditions. The content of the copolymer may be 0.05 parts by mass or more, 0.1 parts by mass or more, 0.5 parts by mass or more, 1 part by mass or more, 2 parts by mass or more, 3 parts by mass or more, or 4 parts by mass or more relative to 100 parts by mass of the inorganic filler, or may be 9 parts by mass or less, 8 parts by mass or less, 7 parts by mass or less, 6 parts by mass or less, 5 parts by mass or less, or 4 parts by mass or less.

[0083] The content of the copolymer may be 0.1 mass% or more, 0.5 mass% or more, 1 mass% or more, 2 mass% or more, or 2.5 mass% or more, relative to the total mass of the resin composition, and may be 10 mass% or less, 8 mass% or less, 6 mass% or less, 5 mass% or less, 4 mass% or less, or 3 mass% or less.

[0084] The resin composition may further contain a curing agent that cures the thermosetting resin. The curing agent is appropriately selected depending on the type of thermosetting resin. For example, when the thermosetting resin is an epoxy resin, examples of the curing agent include amine-based resins, acid anhydride-based resins, and phenol-based resins. The curing agent may be used alone or in combination of two or more.

[0085] The content of the curing agent may be 1% by mass or more, or 3% by mass or more, and may be 10% by mass or less, or 5% by mass or less, relative to the total mass of the resin composition.

[0086] The resin composition may further contain other components, such as a curing accelerator, a coupling agent, a leveling agent, an antioxidant, an antifoaming agent, a wetting agent, a dispersant, and a stabilizer.

[0087] The resin composition can be obtained by mixing a thermosetting resin, an inorganic filler, and an inorganic ion scavenger (and optionally a dispersant, a curing agent, and other components) using, for example, a planetary mixer, a universal mixer, a kneader, a hybrid mixer, or the like.

[0088] The resin composition may have a peak in the range of 2θ=11 to 15° in X-ray diffraction measurement. The peak position in X-ray diffraction measurement of the resin composition can be confirmed, for example, by preparing a cured product of the resin composition and performing X-ray diffraction measurement on the cured product. The resin composition may have a peak at a position of 2θ=11.5 to 14.5 or 11.8 to 14 in X-ray diffraction measurement.

[0089] The resin composition described above can be prepared by mixing a thermosetting resin, an inorganic filler, an inorganic ion scavenger, and, if necessary, other components. The resin composition may be prepared by mixing a powder containing at least scaly particles (first particles) and agglomerates of the scaly particles (second particles) as the inorganic filler with components other than the inorganic filler, or by preparing a powder containing the first particles and a powder containing the second particles, and then mixing these powders with components other than the inorganic filler.

[0090] The resin composition can be used after being cured, for example. That is, one embodiment of the present invention is a cured product (insulating resin cured product) of the above-mentioned resin composition. The cured product may be in a semi-cured state (B stage) or a completely cured state (C stage).

[0091] The cured product can be obtained, for example, by heat-treating the resin composition described above to cure it. The heat-treatment conditions (heating temperature, heating time, etc.) are appropriately set depending on the types of resin and curing agent, the desired cured state, etc. The heat treatment may be performed in one step or two steps.

[0092] The cured product may be, for example, in the form of a sheet. A sheet-like cured product can be obtained, for example, by applying the resin composition described above to a substrate and heating (and applying pressure as necessary). The sheet-like cured product may be a B-stage sheet in a semi-cured state or a C-stage sheet in a fully cured state.

[0093] The resin composition and its cured product are suitable for use in forming an insulating layer of a metal base substrate. That is, the resin composition and its cured product can be referred to as a resin composition for metal base substrates and a cured product for metal base substrates, respectively.

[0094] Fig. 1 is a schematic cross-sectional view showing one embodiment of a laminate. As shown in Fig. 1, a laminate 10A according to one embodiment includes a first metal layer 1A, an insulating layer (a cured product of the resin composition described above) 2 disposed on one surface of the first metal layer, and a second metal layer 3A disposed on the surface of the insulating layer 2 opposite the first metal layer. In this laminate 10A, the first metal layer 1A and the second metal layer 3A are separated by the insulating layer 2 and are electrically insulated from each other.

[0095] Examples of metal materials constituting the first metal layer 1A include aluminum, aluminum alloys, copper, copper alloys, iron, and stainless steel. The first metal layer 1A may be composed of one type of metal material, or may be composed of two or more types of metal materials. The first metal layer 1A may have a single-layer structure or a multi-layer structure.

[0096] Examples of metal materials constituting the second metal layer 3A include copper, aluminum, and nickel. The second metal layer 3A may be composed of one metal material or two or more metal materials. The second metal layer 3A may have a single-layer structure or a multi-layer structure. In FIG. 1, the second metal layer 3A is disposed on substantially the entire surface of the insulating layer 2, but the second metal layer may be disposed on only a portion of the insulating layer 2.

[0097] The thickness of the first metal layer 1A may be, for example, 0.5 mm or more and 3 mm or less. The thickness of the insulating layer 2 may be, for example, 50 μm or more and 300 μm or less. The thickness of the second metal layer 3A may be, for example, 5 μm or more and 1 mm or less.

[0098] Fig. 2 is a schematic cross-sectional view showing one embodiment of a circuit board. As shown in Fig. 2, a circuit board 10B according to one embodiment includes a metal layer 1B, an insulating layer (a cured product of the resin composition described above) 2 disposed on one surface of the metal layer 1B, and a metal circuit portion 3B disposed on the surface of the insulating layer 2 opposite to the metal layer 1B. In this circuit board 10B, the metal circuit portion 3B is, for example, a circuit processed (e.g., etched) into a predetermined pattern.

[0099] Examples of the metal material constituting the metal layer 1B include the same metal material as that constituting the first metal layer 1A. Examples of the metal material constituting the metal circuit portion 3B include the same metal material as that constituting the second metal layer 3A.

[0100] The thickness of the metal layer 1B may be, for example, 0.5 mm or more and 3 mm or less. The thickness of the insulating layer 2 may be, for example, 50 μm or more and 300 μm or less. The thickness of the metal circuit portion 3B may be, for example, 5 μm or more and 1 mm or less.

[0101] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0102] <Synthesis of Copolymer> The monomers used in the synthesis of the copolymers of the examples are as follows: ((Meth)acrylic monomer A having an anionic group) Acrylic acid (manufactured by Toagosei Co., Ltd.) ((Meth)acrylic monomer B having a cationic group) 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate ("ADEKA STAB LA-82" manufactured by ADEKA Corporation) ((Meth)acrylic monomer C) Benzyl methacrylate ("Light Ester BZ" manufactured by Kyoeisha Chemical Co., Ltd.)

[0103] First, 100 parts by mass of (meth)acrylic monomers consisting of 5 mol% acrylic acid, 0.1 mol% 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, and 94.9 mol% benzyl methacrylate were added to an autoclave equipped with a stirrer. Next, 0.5 parts by mass (relative to 100 parts by mass of the total (meth)acrylic monomers) of azobisisobutyronitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) as an initiator and 1,000 parts by mass of a mixed solution of toluene (special reagent grade) and 2-propanol (special reagent grade) (toluene:2-propanol = 7:3 (volume ratio)) as a solvent were added, and the atmosphere inside the autoclave was replaced with nitrogen. Thereafter, the autoclave was heated in an oil bath at 65°C for 20 hours to carry out radical polymerization. After completion of polymerization, the mixture was degassed under reduced pressure at 120°C for 1 hour to obtain a copolymer.

[0104] The polymerization rate relative to 100% of the charged amount of monomer was analyzed by gas chromatography and found to be 98% or more. From this, it was estimated that the ratio of each monomer unit in the copolymer was approximately the same as the charged ratio of the monomer.

[0105] The weight-average molecular weight of the obtained copolymer was determined as a weight-average molecular weight converted to standard polystyrene using a GPC (gel permeation chromatography) method. The measurement conditions were as follows. High-speed GPC apparatus: "HLC-8020" manufactured by Tosoh Corporation Column: One "TSK guard column MP (xL)" manufactured by Tosoh Corporation, 6.0 mm ID x 4.0 cm, and two "TSK-GELMULTIPORE HXL-M" manufactured by Tosoh Corporation, 7.8 mm ID x 30.0 cm (theoretical plate number: 16,000), for a total of three (total theoretical plate number: 32,000) Developing solvent: tetrahydrofuran Detector: RI (differential refractometer)

[0106] <Preparation of Resin Composition> (Example 1) 27.9 parts by mass of naphthalene-type epoxy resin HP-4032D (manufactured by DIC Corporation) as a thermosetting resin and 3.5 parts by mass of phenol novolac resin VH-4150 (manufactured by DIC Corporation) as a curing agent were stirred at 170°C to dissolve the curing agent in the thermosetting resin. The resin in which the curing agent was dissolved, 12.9 parts by mass (10% by volume) of boron nitride filler (thermal conductivity 150 W / m K) as an inorganic filler, 2.6 parts by mass (4 phf) of a copolymer, 1.3 parts by mass (4.5 phr) of Inorganic Ion Trap 1 (a dual ion exchanger (Zr, Mg, Al-based), average particle size 0.2 μm, manufactured by Toagosei Co., Ltd.) as an inorganic ion trapping agent, and 0.2 parts by mass of 1B2PZ (manufactured by Shikoku Chemicals Corporation) as a curing accelerator were stirred and mixed in a planetary mixer for 15 minutes to prepare a resin composition. The inorganic filler was a powder consisting of 11.8% by volume of scaly boron nitride particles (first particles, average particle size: 10.1 μm, average aspect ratio: 7.5, peak intensity ratio I(002) / I(100): 126.4) and 88.2% by volume of agglomerated particles of scaly boron nitride particles (second particles, average particle size: 50.9 μm, average aspect ratio: 1.46, peak intensity ratio I(002) / I(100): 6.8), and had peaks at 6.6 μm and 43.5 μm in a particle size distribution curve.

[0107] <Preparation of Cured Product> The obtained resin composition was applied to a polyethylene terephthalate (PET) film having a thickness of 0.038 mm so that the thickness after curing would be 0.20 mm, and the applied resin composition was dried by heating at 100°C for 50 minutes, thereby preparing a semi-cured product (a sheet in a B-stage state).

[0108] <Preparation of Metal Base Circuit Board> The prepared cured product (sheet in a B-stage state) was peeled from the PET film and placed on the roughened surface of a metal plate (copper plate with a thickness of 2.0 mm). The roughened surface of metal foil (copper foil with a thickness of 0.5 mm) was then placed on top of the cured product, and the resulting mixture was heated and cured at 180°C for 410 minutes while applying a surface pressure of 10 MPa using a press.

[0109] Next, after masking predetermined positions with an etching resist, the copper foil was etched using a sulfuric acid-hydrogen peroxide mixed solution as an etching solution. The etching resist was removed, and the substrate was washed and dried to obtain a metal base circuit board having a circular electrode (copper foil) with a diameter of 20 mm.

[0110] (Example 2) A resin composition, a cured product, and a metal base circuit board were prepared in the same manner as in Example 1, except that inorganic ion scavenger 2 (a dual ion exchanger (Zr, Bi-based), average particle size 0.4 μm, manufactured by Toagosei Co., Ltd.) was used as the inorganic ion scavenger.

[0111] (Example 3) A resin composition, a cured product, and a metal base circuit board were prepared in the same manner as in Example 1, except that inorganic ion scavenger 3 (anion exchanger (Mg, Al-based), average particle size 1.5 μm, manufactured by Toagosei Co., Ltd.) was used as the inorganic ion scavenger.

[0112] (Example 4) A resin composition, a cured body, and a metal base circuit board were prepared in the same manner as in Example 1, except that inorganic ion scavenger 4 (anion exchanger (Bi-based), average particle size 1.5 μm, manufactured by Toagosei Co., Ltd.) was used as the inorganic ion scavenger.

[0113] (Example 5) A resin composition, a cured body, and a metal base circuit board were prepared in the same manner as in Example 1, except that inorganic ion scavenger 5 (cation exchanger (Zr-based), average particle size 1.0 μm, manufactured by Toagosei Co., Ltd.) was used as the inorganic ion scavenger.

[0114] (Example 6) A resin composition, a cured product, and a metal base circuit board were prepared in the same manner as in Example 1, except that inorganic ion scavenger 6 (a dual ion exchanger (Sb, Bi-based), average particle size 1.0 μm, manufactured by Toagosei Co., Ltd.) was used as the inorganic ion scavenger.

[0115] (Example 7) A resin composition, a cured product, and a metal base circuit board were prepared in the same manner as in Example 1, except that Inorganic Ion Scavenger 6 (a dual ion exchanger (Zr, Bi-based), average particle size 1.5 μm, manufactured by Toagosei Co., Ltd.) was used as the inorganic ion scavenger.

[0116] Example 8 A resin composition, a cured product, and a metal base circuit board were prepared in the same manner as in Example 1, except that the inorganic filler used was a powder consisting of 6.3 volume % scaly boron nitride particles (first particles, average particle diameter: 10.1 μm, average aspect ratio: 7.5, peak intensity ratio I(002) / I(100): 126.4) and 93.7 volume % agglomerated particles of scaly boron nitride particles (second particles, average particle diameter: 50.9 μm, average aspect ratio: 1.46, peak intensity ratio I(002) / I(100): 6.8), and the powder had peaks at 6.6 μm and 43.5 μm in its particle size distribution curve.

[0117] (Example 9) A resin composition, a cured body, and a metal base circuit board were prepared in the same manner as in Example 1, except that the inorganic filler used was a powder consisting of 55.3 volume % scaly boron nitride particles (first particles, average particle diameter: 10.1 μm, average aspect ratio: 7.5, peak intensity ratio I(002) / I(100): 126.4) and 44.7 volume % agglomerated particles of scaly boron nitride particles (second particles, average particle diameter: 50.9 μm, average aspect ratio: 1.46, peak intensity ratio I(002) / I(100): 6.8), and the powder had peaks at 6.6 μm and 43.5 μm in its particle size distribution curve.

[0118] Example 10 A resin composition, a cured product, and a metal base circuit board were prepared in the same manner as in Example 1, except that the amount of the inorganic ion scavenger was changed to 0.14 parts by mass (0.5 phr).

[0119] Example 11 A resin composition, a cured product, and a metal base circuit board were prepared in the same manner as in Example 1, except that the amount of the inorganic ion scavenger was changed to 0.42 parts by mass (1.5 phr).

[0120] Example 12 A resin composition, a cured product, and a metal base circuit board were prepared in the same manner as in Example 1, except that the amount of the inorganic ion scavenger was changed to 1.8 parts by mass (6 phr).

[0121] Example 13 A resin composition, a cured product, and a metal base circuit board were prepared in the same manner as in Example 1, except that the amount of the inorganic ion scavenger was changed to 2.8 parts by mass (10 phr).

[0122] Example 14 A resin composition, a cured product, and a metal base circuit board were prepared in the same manner as in Example 1, except that the amount of the inorganic ion scavenger was changed to 5.6 parts by mass (20 phr).

[0123] Comparative Example 1 A resin composition, a cured product, and a metal base circuit board were prepared in the same manner as in Example 1, except that no inorganic ion scavenger was added.

[0124] Comparative Example 2 A resin composition, a cured product, and a metal base circuit board were prepared in the same manner as in Example 1, except that the amount of the inorganic ion scavenger was changed to 27.9 parts by mass (100 phr).

[0125] Comparative Example 3 A resin composition, a cured product, and a metal base circuit board were prepared in the same manner as in Example 1, except that the inorganic filler used was a powder consisting of 0.9% by volume of agglomerated particles of scaly boron nitride particles (first particles, average particle diameter: 50.9 μm, average aspect ratio: 1.46, peak intensity ratio I(002) / I(100): 6.8) and 99.1% by volume of agglomerated particles of scaly boron nitride particles (second particles, average particle diameter: 50.9 μm, average aspect ratio: 1.46, peak intensity ratio I(002) / I(100): 6.8), and the powder had peaks at 6.6 μm and 43.5 μm in its particle size distribution curve.

[0126] Comparative Example 4 A resin composition, a cured product, and a metal base circuit board were prepared in the same manner as in Example 1, except that the inorganic filler used was a powder consisting of 77.1% by volume of scaly boron nitride particles (first particles, average particle diameter: 10.1 μm, average aspect ratio: 7.5, peak intensity ratio I(002) / I(100): 126.4) and 22.9% by volume of agglomerated particles of scaly boron nitride particles (second particles, average particle diameter: 50.9 μm, average aspect ratio: 1.46, peak intensity ratio I(002) / I(100): 6.8), and the powder had peaks at 6.6 μm and 43.5 μm on its particle size distribution curve.

[0127] [Measurement of particle size distribution] The particle size distribution was measured under the following measurement conditions using a particle size distribution / particle shape analyzer (SYNC-3L S / N: H0153, manufactured by Microtrac). The particle size distribution was measured by replacing the circulation bath with an aqueous sodium hexametaphosphate solution, placing the sample in the circulation bath, and allowing it to stabilize before measuring. <Measurement conditions> Particle refractive index: 1.74 Particle shape: aspherical Solvent used: aqueous sodium hexametaphosphate solution Solvent refractive index: 1.333 Flow rate: 60% Measurement time: 10 seconds (wet)

[0128] [Measurement of Average Particle Size and Average Aspect Ratio] For scaly boron nitride particles, boron nitride particles were embedded in resin and mechanically polished and ion milled to prepare a sample for cross-sectional observation. The prepared sample was then gold-plated and vapor-deposited. The cross-section was observed at 10,000x magnification using a scanning electron microscope (SEM). The maximum length and maximum thickness of 10 boron nitride particles in one field of view were measured, and the average maximum length and the average maximum length / maximum thickness were calculated to calculate the average particle size and average aspect ratio. For agglomerated particles of scaly boron nitride particles, the particle size distribution was measured under the following measurement conditions using a particle size distribution / particle shape analyzer (SYNC-3L S / N: H0153, manufactured by Microtrac). The average particle size and average aspect ratio were measured by replacing the circulating bath with an aqueous sodium hexametaphosphate solution, placing the sample in the circulating bath, and allowing it to stabilize before measurement. <Measurement conditions> Particle refractive index: 1.74 Particle shape: non-spherical Solvent used: aqueous sodium hexametaphosphate Solvent refractive index: 1.333 Measurement time: 10 seconds (wet)

[0129] [XRD Peak Measurement] X-ray diffraction measurements were performed on the cured bodies prepared in each Example and Comparative Example using a Rigaku MiniFlex II X-ray diffractometer. The positions of the XRD peaks detected in the range of 2θ = 11 to 15° are shown in Tables 1 to 4. The peak intensity ratio (I(002) / I(100)) of the boron nitride particles was measured in the range of 2θ = 20 to 50°, and the intensity of the diffraction line near 2θ = 27° was defined as I(002) and the intensity of the diffraction line near 2θ = 41° was defined as I(100).

[0130] [Evaluation of reliability by high-temperature, high-voltage bias test (V-t)] The obtained metal base substrate was subjected to a high-temperature, high-voltage bias test (V-t), in which a DC voltage of 10 kV was applied between the metal foil and the metal plate in an environment of 150°C to measure the time until breakdown. The time until breakdown was defined as the time from the start of voltage application to the point at which the leakage current value measured with a voltage resistance tester reached 10 mA or more. The measurement results are shown in Tables 1 to 4.

[0131] [Evaluation of Reliability by High-Temperature, High-Humidity Bias Test (THB)] The obtained metal base substrate was subjected to a high-temperature, high-humidity bias test (THB) in which a DC voltage of 2.0 kV was applied between the metal foil and the metal plate in an environment of 85°C and 85% RH to measure the time until breakdown. The time until breakdown was defined as the time from the start of voltage application to the point at which the leakage current value measured with a voltage withstand tester reached 10 mA or more. The measurement results are shown in Tables 1 to 4. In the tables, "-" indicates that the measurement was not performed.

[0132]

[0133]

[0134]

[0135]

[0136] 1A...first metal layer, 1B...metal layer, 2...insulating layer, 3A...second metal layer, 3B...metal circuit portion, 10A...laminated body, 10B...circuit board.

Claims

1. A resin composition comprising a thermosetting resin, an inorganic filler, and an inorganic ion scaly filler, the inorganic filler comprising first particles which are scaly particles and second particles which are agglomerates of the scaly particles, the content of the first particles being 1 volume % or more and 60 volume % or less with respect to the total content of the first particles and the second particles, and the content of the inorganic ion scaly filler being 0.1 to 50 mass % with respect to the total amount of the thermosetting resin.

2. The resin composition according to claim 1, wherein the average aspect ratio of the first particles is 1 to 200, and the average aspect ratio of the second particles is 1 to 2.

3. The resin composition according to claim 1, wherein the first particles are boron nitride particles, and in X-ray diffraction measurement, the ratio I(002) / I(100) of the peak intensity I(002) of the (002) plane to the peak intensity I(100) of the (100) plane in X-ray diffraction measurement is 50 to 1000; and the second particles are boron nitride particles, and in X-ray diffraction measurement, the ratio I(002) / I(100) of the peak intensity I(002) of the (002) plane to the peak intensity I(100) of the (100) plane in X-ray diffraction measurement is 1 to 20.

4. The resin composition according to claim 1, wherein the ratio of the average particle size of the first particles to the average particle size of the second particles is 1.5 or more and 20 or less.

5. The resin composition according to claim 1, wherein the ratio of the average aspect ratio of the first particles to the average aspect ratio of the second particles is 0.01 or more and 0.8 or less.

6. The resin composition according to claim 1, wherein the thermal conductivity of the inorganic filler is 20 W / m·K or more.

7. The resin composition according to claim 1, wherein the content of said inorganic filler is 30 to 70% by volume based on the total volume of said resin composition.

8. The resin composition according to claim 1, wherein the inorganic ion scavenger comprises both an anion exchanger and a cation exchanger, or both ion exchangers.

9. The resin composition according to claim 1, wherein the inorganic ion scavenger contains at least one element selected from the group consisting of Al, Mg, Bi, Zr, Sb, and Zn.

10. The resin composition according to claim 1, wherein the inorganic ion scavenger contains at least one element selected from the group consisting of Bi, Zr, Sb, and Zn.

11. The resin composition according to claim 1, which has a peak in the range of 2θ=11 to 15° in X-ray diffraction measurement.

12. The resin composition according to claim 1, wherein the thermosetting resin is an epoxy resin.

13. The resin composition according to claim 1, further comprising a copolymer, the copolymer having (meth)acrylic monomer units A having an anionic group, (meth)acrylic monomer units B having a cationic group, and (meth)acrylic monomer units C other than (meth)acrylic monomer units A and (meth)acrylic monomer units B.

14. A cured insulating resin product, which is a cured product of the resin composition according to any one of claims 1 to 13.

15. A laminate comprising a first metal layer, an insulating layer disposed on one surface of the first metal layer, and a second metal layer disposed on a surface of the insulating layer opposite the first metal layer, wherein the insulating layer is the cured insulating resin body described in claim 14.

16. A circuit board comprising a metal layer, an insulating layer disposed on one surface of the metal layer, and a metal circuit portion disposed on the surface of the insulating layer opposite the metal layer, wherein the insulating layer is the cured insulating resin body described in claim 14.

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