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

Abstract

A resin composition which contains a thermosetting resin, an inorganic filler and an inorganic ion scavenger, and wherein the inorganic filler contains a first particle group having a peak in the range of 0.1 [mu] m to 15 [mu] m (inclusive) on a particle size distribution curve and a second particle group having a peak in the range of more than 15 [mu] m to 300 [mu] m (inclusive) on a particle size distribution curve, the content of the first particle group is from 1% by volume to 60% by volume (inclusive) with respect to the total content of the first particle group and the second particle group, and the content of the inorganic ion scavenger is from 0.1% by mass to 50% by mass with respect to the total amount of the thermosetting resin.

Description

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

[0001] This invention relates to a resin composition, an insulating resin cured body, a laminate, and a circuit board suitable for manufacturing an insulating layer for a circuit board (metal substrate circuit board). Background Technology

[0002] As circuit boards used to mount electronic and electrical components, such as semiconductor elements, to form hybrid integrated circuits, various types of circuit boards are now in practical use. Based on the substrate material, circuit boards are classified into resin circuit boards, ceramic circuit boards, metal-based circuit boards, etc.

[0003] While resin circuit boards are inexpensive, their low thermal conductivity limits their application to those requiring relatively low power. Ceramic circuit boards, due to the high electrical insulation and heat resistance of ceramics, are suitable for applications requiring higher power, but they are expensive. On the other hand, metal-based circuit boards offer a compromise between the two, making them suitable for general-purpose applications requiring higher power, such as inverters for refrigerators, commercial air conditioners, industrial robotic arms, and automotive power supplies.

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

[0005] Prior art literature, patent literature, patent literature 1: Japanese Patent Application Publication No. 2008-266533 Summary of the Invention

[0006] The problem this invention aims to solve is that replacing ceramic circuit boards with metal-based circuit boards could lead to increased productivity. Furthermore, ceramic circuit boards suffer from the technical problem of solder cracking during thermal cycling; however, replacing them with metal-based circuit boards could suppress this solder cracking. On the other hand, ceramic circuits are suitable for applications requiring high power output; therefore, when replacing ceramic circuit boards with metal-based circuit boards, the metal-based circuit boards must exhibit improved insulation reliability under high DC voltage application (especially at high temperatures).

[0007] Therefore, the object of the present invention is to provide a resin composition capable of forming an insulating layer with excellent insulation reliability under DC high voltage application at high temperatures (150°C). Furthermore, the object of the present invention is to provide an insulating resin cured body as a cured body of the resin composition, a laminate using the insulating resin cured body, and a circuit board.

[0008] The technical means for solving the problem include the following [1] to

[16] .

[0009] [1] A resin composition comprising a thermosetting resin, an inorganic filler and an inorganic ion scavenger, wherein the inorganic filler comprises a first particle group having a peak in the range of 0.1 μm or more and 15 μm or less on a particle size distribution curve, and a second particle group having a peak in the range of more than 15 μm and 300 μm or less on the particle size distribution curve, wherein the content of the first particle group is more than 1% by volume and less than 60% by volume relative to the total content of the first particle group and the second particle group, and the content of the inorganic ion scavenger is 0.1 to 50% by mass relative to the total amount of the thermosetting resin.

[0010] [2] According to the resin composition described in [1], the first particle group contains first particles with an aspect ratio of 1 to 200, and the second particle group contains second particles with an aspect ratio of 1 to 2.

[0011] [3] According to the resin composition described in [1] or [2], on the particle size distribution curve, the difference between the position of the peak of the first particle group and the position of the peak of the second particle group is more than 10 μm and less than 200 μm.

[0012] [4] In any one of the resin compositions according to [1] to [3], the content of the first particle group is 5% by volume or more and 30% by volume or less relative to the total content of the first particle group and the second particle group.

[0013] [5] According to any one of [1] to [4], the first particle group contains a first boron nitride particle, and the ratio of the peak intensity I(002) of the (002) plane to the peak intensity I(100) of the (100) plane in the X-ray diffraction measurement of the first boron nitride particle, I(002) / I(100) is 50 to 1000; the second particle group contains a second boron nitride particle, and the ratio of the peak intensity I(002) of the (002) plane to the peak intensity I(100) of the (100) plane in the X-ray diffraction measurement of the second boron nitride particle, I(002) / I(100) is 1 to 20.

[0014] [6] The inorganic filler material has a thermal conductivity of 20 W / m·K or higher in the resin composition according to any one of [1] to [5].

[0015] [7] The content of the inorganic filler material in the resin composition according to any one of [1] to [6] is 30 to 70% of the total volume of the resin composition.

[0016] [8] The resin composition according to any one of [1] to [7], wherein the inorganic ion scavenger comprises both anion exchangers and cation exchangers, or comprises zwitterionic exchangers.

[0017] [9] The resin composition according to any one of [1] to [8], wherein the inorganic ion scavenger contains at least one selected from the group consisting of Al, Mg, Bi, Zr, Sb and Zn.

[0018]

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

[0019]

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

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

[0020]

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

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

[0021]

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

[12] further comprises a copolymer containing: a (meth)acrylic monomer unit A having an anionic group, a (meth)acrylic monomer unit B having a cationic group, and a (meth)acrylic monomer unit C other than (meth)acrylic monomer unit A and (meth)acrylic monomer unit B.

[0022]

[14] An insulating resin cured body, which is a cured body of the resin composition described in any one of [1] to

[13] .

[0023]

[15] A laminate comprising: a first metal layer, an insulating layer disposed on a side of the first metal layer, and a second metal layer disposed on a side of the insulating layer opposite to the first metal layer, wherein the insulating layer is an insulating resin cured body as described in

[14] .

[0024]

[16] A circuit board comprising: a metal layer, an insulating layer disposed on one side of the metal layer, and a metal circuit portion disposed on the opposite side of the insulating layer, wherein the insulating layer is an insulating resin cured body as described in

[14] .

[0025] The invention provides a resin composition capable of forming an insulating layer with excellent insulation reliability under DC high voltage application at high temperatures (150°C). Furthermore, the invention provides an insulating resin cured body as a cured body of the resin composition, a laminate using the insulating resin cured body, and a circuit board. Attached Figure Description

[0026] Figure 1 is a cross-sectional view showing one embodiment of the laminate.

[0027] Figure 2 is a cross-sectional view showing one embodiment of the circuit board. Detailed Implementation

[0028] The preferred embodiments of the present invention will now be described in detail.

[0029] One embodiment of the present invention is a resin composition containing a thermosetting resin, an inorganic filler, and an inorganic ion scavenger.

[0030] Examples of thermosetting resins include, for example, silicone resins, epoxy resins, phenolic resins, cyanate ester resins, melamine resins, urea resins, thermosetting polyimide resins, and unsaturated polyester resins. Thermosetting resins may include epoxy resins. Thermosetting resins can be used alone or in combination of two or more.

[0031] From the viewpoint of readily obtaining a resin composition capable of forming an insulating layer with superior insulation reliability for DC high voltage applied at high temperatures (150°C), the content of thermosetting resin relative to the total mass of the resin composition can be 10% by mass or more, 20% by mass or more, or 25% by mass or more. From the viewpoint of improving thermal conductivity, the content of thermosetting resin relative to the total mass of the resin composition can be 50% by mass or less, 40% by mass or less, or 30% by mass or less. From these viewpoints, the content of thermosetting resin relative to the total mass of the resin composition can be 10 to 50% by mass.

[0032] The resin composition contains an inorganic filler. The inorganic filler can be, for example, a known inorganic filler used in applications requiring insulation and thermal conductivity (excluding materials belonging to the category of inorganic ion scavengers described later). The inorganic filler can, for example, comprise one or more selected from the group consisting of alumina, silicon oxide, silicon nitride, boron nitride, aluminum nitride, and magnesium oxide. From the viewpoint of superior insulation reliability in high humidity environments, it can comprise one or more selected from the group consisting of alumina, silicon oxide, silicon nitride, boron nitride, and aluminum nitride.

[0033] The inorganic filler material contains a first particle group with peaks in the range of 0.1 μm to 15 μm on the particle size distribution curve, and a second particle group with peaks in the range of more than 15 μm to 300 μm on the particle size distribution curve. The inorganic filler material may also contain particles that do not belong to the first or second particle groups (a third particle group). Furthermore, the content of the first particle group relative to the combined content of the first and second particle groups is 1% to 60% by volume. In addition, in this specification, having a peak within a specific range on the particle size distribution curve means that the peak apex is located within that specific range.

[0034] Inorganic filler materials contain a first group of particles with peaks in the range of 0.1 μm to 15 μm on the particle size distribution curve, and a second group of particles with peaks in the range of more than 15 μm to 300 μm on the particle size distribution curve. The content of the first group of particles is 1% to 60% by volume relative to the total content of the first and second groups. Therefore, it is easy to obtain a resin composition capable of forming an insulating layer with excellent insulation reliability under DC high voltage application at high temperatures (150°C). The inventors speculate that, by containing multiple particles (particle groups) of different particle sizes, the filling capacity of the inorganic filler material is increased, making it easier to restrict the movement of ions that affect insulation. Furthermore, since the second group of particles with larger particle sizes exists at a certain level, it is easy to restrict the movement of ions that affect insulation. Therefore, it is speculated that since the movement of ions is restricted in the resin composition, and these ions can be easily captured by an inorganic ion scavenger, the insulation of the insulating layer formed by the resin composition is increased. However, the mechanism of the present invention is not limited to the above reasons.

[0035] The particle size distribution and particle shape analysis device (e.g., Microtrac SYNC-3L) can be used to determine the particle size distribution curve of inorganic fillers. More specific determination methods are described in the examples described later.

[0036] The first particle swarm may have a single peak or multiple peaks in the particle size distribution curve within the range of 0.1 μm to 15 μm. The second particle swarm may have a single peak or multiple peaks in the particle size distribution curve within the range of more than 15 μm to 300 μm.

[0037] From the viewpoint that it is easy to obtain a resin composition capable of forming an insulating layer with superior insulation reliability for DC high voltage application 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 with superior insulation reliability for DC high voltage application under high temperature and high humidity (85°C, 85%RH) conditions, the first particle group may have peaks in the range of 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 on the particle size distribution curve. From the same viewpoint, it may also have peaks in the range of 12 μm or less, 10 μm or less, 9 μm or less, 8 μm or less, or 7 μm or less.

[0038] From the viewpoint that it is easy to obtain resin compositions capable of forming insulating layers with superior insulation reliability for DC high voltage application under high temperature (150°C) conditions, and from the viewpoint that it is easy to obtain resin compositions capable of forming insulating layers with superior insulation reliability for DC high voltage application under high temperature and high humidity (85°C, 85%RH) conditions, the second particle group can have peaks in the range of 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, or 40 μm or more on the particle size distribution curve. From the same viewpoint, it can also have peaks in the range of 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.

[0039] From the viewpoint that it is easy to obtain resin compositions capable of forming insulating layers with superior insulation reliability for DC high voltage application under high temperature (150°C) conditions, and from the viewpoint that it is easy to obtain resin compositions capable of forming insulating layers with superior insulation reliability for DC high voltage application under high temperature and high humidity (85°C, 85%RH) conditions, the difference between the position (particle size) of the peak of the first particle group and the position (particle size) of the peak of the second particle group on the particle size distribution curve ((position of the peak of the second particle group) - (position of the peak of the first particle group)) can be 10 μm or more, 20 μm or more, or 30 μm or more. From the same viewpoint, it can also be 200 μm or less, 150 μm or less, 100 μm or less, or 50 μm or less. The difference between the position of the peak of the first particle group and the position of the peak of the second particle group can be 10 μm or more and 200 μm or less, or 20 μm or more and 100 μm or less.

[0040] The particles in the first particle group (the first particle) and the particles in the second particle group (the second particle) can each contain the same composition or different compositions. The particles in the first particle group (the first particle) and the particles in the second particle group (the second particle) can each have the same composition. For example, the first particle and the second particle can each be boron nitride particles.

[0041] Examples of the shape of the first particle include: flake-like, spherical, and polygonal shapes. From the viewpoint of easily obtaining a resin composition capable of forming an insulating layer with superior insulation reliability for DC high voltage application under high temperature (150°C) conditions, the first particle can be a flake-like particle.

[0042] From the viewpoint that resin compositions capable of forming insulating layers with superior insulation reliability for DC high-voltage application under high-temperature (150°C) conditions are readily available, and from the viewpoint that resin compositions capable of forming insulating layers with superior insulation reliability for DC high-voltage application under high-temperature and high-humidity (85°C, 85%RH) conditions are readily available, the particle size of the first particle can be 15 μm or less, 10 μm or less, or 8 μm or less. Similarly, from the same viewpoint, it can also be 0.1 μm or more, 1 μm or more, 3 μm or more, or 5 μm or more. A sample for cross-sectional observation is prepared by embedding the first particle in resin, followed by machine grinding and ion milling. This sample is then subjected to vapor gold deposition, and the maximum length of the particle when observed at 10,000x magnification is measured using a scanning electron microscope (SEM), thereby obtaining the particle size of the first particle. From these viewpoints, the particle size of the first particle can be 0.1 to 15 μm.

[0043] From the viewpoint that resin compositions capable of forming insulating layers with superior insulation reliability for DC high-voltage application under high-temperature (150°C) conditions are readily available, and from the viewpoint that resin compositions capable of forming insulating layers with superior insulation reliability for DC high-voltage application under high-temperature and high-humidity (85°C, 85%RH) conditions are readily available, the average particle size of the first particle group (multiple first particles) can be 15 μm or less, 10 μm or less, or 8 μm or less. Similarly, from the same viewpoint, it can also be 0.1 μm or more, 1 μm or more, 3 μm or more, or 5 μm or more. The average particle size of the first particle group (multiple first particles) can be obtained by measuring the maximum length of each of 10 first particles within one field of view when observed using SEM, and then averaging them. From these viewpoints, the average particle size of the first particles can be 0.1 to 15 μm.

[0044] From the viewpoint that resin compositions capable of forming insulating layers with superior insulation reliability for DC high voltage application under high temperature (150°C) conditions are readily available, and from the viewpoint that resin compositions capable of forming insulating layers with superior insulation reliability for DC high voltage application under high temperature and high humidity (85°C, 85%RH) conditions are readily available, the aspect ratio of the first particle can be 1–200, 5–200, 10–200, or 50–150. The aspect ratio of the first particle can be obtained by measuring the maximum length of the first particle and the maximum length in the direction perpendicular to the direction with the maximum length in the above-described method for measuring the particle size, and then dividing the maximum length by the maximum length in the direction perpendicular to the direction with the maximum length. If the first particle is a scaly particle, the aspect ratio of the first particle can be obtained by measuring the maximum length and the maximum thickness (maximum length in the thickness direction) of the first particle in the above-described method for measuring the particle size, and then dividing the maximum length by the maximum thickness.

[0045] From the viewpoint that resin compositions capable of forming insulating layers with superior insulation reliability for DC high voltage application under high temperature (150°C) conditions are readily available, and from the viewpoint that resin compositions capable of forming insulating layers with superior insulation reliability for DC high voltage application under high temperature and high humidity (85°C, 85%RH) conditions, the average aspect ratio of the first particle group (multiple first particles) can be 1–200, 5–200, 10–200, or 50–150. The average aspect ratio of the first particles can be obtained by measuring the maximum length of each of the 10 first particles within one field of view when observed using SEM, as well as the maximum length perpendicular to the direction with the maximum length, and then dividing the maximum length by the maximum length perpendicular to the direction with the maximum length. In the case where the first particle is a scale-like particle, the average aspect ratio of the first particle group (multiple first particles) can be obtained by measuring the maximum length and maximum thickness of each of the 10 first particles in one field of view when observing with SEM in the above-mentioned method for measuring the particle size of the first particle, and dividing the maximum length by the maximum thickness.

[0046] When the first particle group contains boron nitride particles (first boron nitride particles), the ratio of the peak intensity I(002) of the (002) plane to the peak intensity I(100) of the (100) plane in the X-ray diffraction measurement of the first boron nitride particles, I(002) / I(100), can be 50-1000, 60-800, 70-600, 80-400 or 90-200.

[0047] Examples of the shape of the second particle include: scaly, spherical, and polygonal shapes. The second particle can be an aggregate of multiple particles or an aggregate of scaly particles. From the viewpoint of easily providing a resin composition capable of forming an insulating layer with superior insulation reliability under DC high voltage application at high temperatures (150°C), the second particle can be an aggregate of scaly particles. The second particle can be an aggregate of the first particle or an aggregate of particles different from the first particle. In this specification, an aggregated particle refers to a blocky particle formed by the contact of multiple particles.

[0048] The particle size of the second particle can also be larger than that of the first particle, exceeding 15 μm, 30 μm, or 50 μm. The particle size of the second particle can be less than 300 μm, 200 μm, 150 μm, or 100 μm. A sample for cross-sectional observation is prepared by embedding the second particle in resin, followed by machine grinding and ion polishing. After depositing a gold coating on the sample, the maximum length of the particle when observed at 1000x magnification is measured using a scanning electron microscope (SEM), thus obtaining the particle size of the second particle. Based on these considerations, the particle size of the second particle can exceed 15 μm but be less than 300 μm.

[0049] The average particle size of the second particle swarm (multiple second particles) can also be larger than the average particle size of the first particle, exceeding 15 μm, 30 μm, or 50 μm. The average particle size of the second particle swarm (multiple second particles) can be less than 300 μm, less than 200 μm, less than 150 μm, or less than 100 μm. The average particle size of the second particle swarm (multiple second particles) can be determined using a laser diffraction, scattering, and dynamic image analysis-based particle size distribution and shape measurement device. From these perspectives, the average particle size of the second particles can exceed 15 μm and be less than 300 μm.

[0050] The aspect ratio of the second particle can be 1–5, 1–4, 1–3, or 1–2. The aspect ratio of the second particle can be obtained by measuring the maximum length of the second particle and the maximum length perpendicular to the direction with the maximum length in the above-described method for measuring the particle size, and then dividing the maximum length by the maximum length perpendicular to the direction with the maximum length.

[0051] The average aspect ratio of the second particle swarm (multiple second particles) can be 1–5, 1–4, 1–3, or 1–2. The average aspect ratio of the second particle swarm (multiple second particles) can be determined using a laser diffraction, scattering, and dynamic image analysis-based particle size distribution and shape measurement device.

[0052] When the second particle group contains boron nitride particles (second boron nitride particles), the ratio of the peak intensity I(002) of the (002) plane to the peak intensity I(100) of the (100) plane in the X-ray diffraction measurement of the second boron nitride particles, I(002) / I(100), can be 1-20, 1-15, 1-10, 1-5, 1.1-4, 1.2-3 or 1.2-2.

[0053] From the viewpoint that it is easy to obtain a resin composition capable of forming an insulating layer with superior insulation reliability for DC high voltage application 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 with superior insulation reliability for DC high voltage application under high temperature and high humidity (85°C, 85%RH) conditions, the ratio of the average particle size of the first particle to the average particle size of the second particle (average particle size of the second particle / average particle size of the first particle) can be 1.5 or more, 2 or more, 3 or more, 4 or more, or 5 or more. From the same viewpoint, it can also 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 particle to the average particle size of the second particle can be 1.5 or more and 20 or less, or 3 or more and 10 or less.

[0054] From the viewpoint that it is easy to obtain a resin composition capable of forming an insulating layer with superior insulation reliability for DC high voltage application 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 with superior insulation reliability for DC high voltage application under high temperature and high humidity (85°C, 85%RH) conditions, the ratio of the average aspect ratio of the first particle to the average aspect ratio of the second particle (average aspect ratio of the second particle / average aspect ratio of the first particle) can be 0.01 or more, 0.05 or more, 0.1 or more, 0.15 or more, or 0.18 or more. From the same viewpoint, it can also 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 particle to the average aspect ratio of the second particle can be 0.01 or more and 0.8 or less, or 0.1 or more and 0.4 or less.

[0055] The thermal conductivity of the inorganic filler material can be above 20 W / m·K, above 50 W / m·K, above 100 W / m·K, or above 150 W / m·K, and below 3500 W / m·K, below 2000 W / m·K, below 1500 W / m·K, below 600 W / m·K, below 300 W / m·K, or below 200 W / m·K. The thermal conductivity of the first particle can be within the above range, and the thermal conductivity of the second particle can be within the above range.

[0056] From the viewpoint that it is easy to obtain a resin composition capable of forming an insulating layer with superior insulation reliability for DC high voltage application 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 with superior insulation reliability for DC high voltage application under high temperature and high humidity (85°C, 85%RH) conditions, the content of the first particle group relative to the total content of the first particle group and the second particle group can be 2 vol% or more, 3 vol% or more, 5 vol% or more, 8 vol% or more, or 10 vol% or more. From the same viewpoint, it can also be 50 vol% or less, 40 vol% or less, 30 vol% or less, 20 vol% or less, or 15 vol% or less. The content of the first particle relative to the total content of the first particle and the second particle can be 1 vol% or more and 50 vol% or less, 3 vol% or more and 30 vol% or less, 5 vol% or more and 30 vol% or less, or 5 vol% or more and 20 vol% or less. In this specification, the content of the first particle group relative to the total content of the first particle group and the second particle group refers to the cumulative frequency of 0.1 to 15 μm on the particle size distribution curve when the cumulative frequency of 0.1 to 300 μm is 100%.

[0057] From the viewpoint that resin compositions capable of forming insulating layers with superior insulation reliability for DC high voltage application under high temperature (150°C) conditions are readily available, and from the viewpoint that resin compositions capable of forming insulating layers with superior insulation reliability for DC high voltage application under high temperature and high humidity (85°C, 85%RH) conditions are readily available, the content of the second particle group relative to the total content of the first and second particle groups can 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. Similarly, from the same viewpoint, it can 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 particle relative to the total content of the first and second particles can be 50% by volume or more and 99% by volume or less, 60% by volume or more and 97% by volume or less, or 70% by volume or more and 95% by volume or less. In this specification, the content of the second particle group relative to the total content of the first particle group and the second particle group refers to the cumulative frequency of 15 to 300 μm when the cumulative frequency of 0.1 to 300 μm is 100% on the particle size distribution curve.

[0058] From the viewpoint that it is easy to obtain a resin composition capable of forming an insulating layer with superior insulation reliability for DC high voltage application 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 with superior insulation reliability for DC high voltage application under high temperature and high humidity (85°C, 85%RH) conditions, the total content of the first particle and the second particle relative to the total mass of the inorganic filler material can be 50% by mass or more, 60% by mass or more, 70% by mass, 80% by mass or more, 90% by mass or more, or 95% by mass or more, and can substantially be 100% by mass.

[0059] From the viewpoint that it is easy to obtain a resin composition capable of forming an insulating layer with superior insulation reliability for DC high voltage application 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 with superior insulation reliability for DC high voltage application under high temperature and high humidity (85°C, 85%RH) conditions, the total content of the first particle and the second particle relative to the total volume of the inorganic filler material can be 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more, and can substantially be 100% by volume.

[0060] From the viewpoint of improving thermal conductivity, the content of inorganic filler material relative to the total mass of the resin composition can be 30% by mass or more, 40% by mass or more, 50% by mass or more, or 60% by mass or more. From the viewpoint of easily obtaining a resin composition capable of forming an insulating layer with superior insulation reliability for DC high voltage application under high temperature (150°C) conditions, the content of inorganic filler material relative to the total mass of the resin composition can be 80% by mass or less, 75% by mass or less, 70% by mass or less, or 65% by mass or less; from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer with superior insulation reliability for DC high voltage application under high temperature and high humidity (85°C, 85%RH) conditions, 65% by mass or less is preferred. From these viewpoints, the content of inorganic filler material relative to the total mass of the resin composition can be 30 to 80% by mass.

[0061] From the viewpoint of improving thermal conductivity, the content of inorganic filler material relative to the total volume of the resin composition can 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. From the viewpoint of easily obtaining a resin composition capable of forming an insulating layer with superior insulation reliability for DC high voltage application under high temperature (150°C) conditions, the content of inorganic filler material relative to the total volume of the resin composition can 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; from the viewpoint of easily obtaining a resin composition capable of forming an insulating layer with superior insulation reliability for DC high voltage application under high temperature and high humidity (85°C, 85%RH) conditions, 55% by volume or less is preferred. The content of inorganic filler material relative to the total volume of the resin composition can be 20 to 80% by volume or 30 to 70% by volume.

[0062] Inorganic ion scavengers are inorganic materials that possess the function of scavenging at least one of cations and anions (having ion-scavenging properties). In this specification, "ion-scavenging property" refers to the property of adsorbing target ions onto the surface of an inorganic material, or the property of introducing target ions into the structure of an inorganic material through ion exchange between ions within the inorganic material and the target ions. Examples of target ions for inorganic ion scavengers include: cations such as Na ions, Cu ions, and Ag ions; and anions such as Cl ions and Br ions.

[0063] The inorganic ion scavenger may contain at least one element selected from the group consisting of Al, Mg, Bi, Zr, Sb, and Zn. From the viewpoint of readily obtaining a resin composition capable of forming an insulating layer with superior insulation reliability under DC high voltage application at high temperatures (150°C), it may contain at least one element selected from the group consisting of Al, Mg, Bi, Zr, Sb, and Zn. From the viewpoint of readily obtaining a resin composition capable of forming an insulating layer with superior insulation reliability under DC high voltage application at high temperatures and high humidity (85°C, 85%RH), it may contain at least one element selected from the group consisting of Bi, Zr, Sb, and Zn. The inorganic ion scavenger may be, for example, an oxide containing at least one of these metal elements, an acyl chloride, or a hydrate thereof. The inorganic ion scavenger may also contain two or more of these metal elements.

[0064] Examples of inorganic ion scavengers include anion exchangers that scavenge anions, cation exchangers that scavenge cations, and zwitterionic exchangers that scavenge both anions and cations. Inorganic ion scavengers can be used alone or in combination of two or more; for example, a zwitterionic exchanger can be a mixture of anion exchangers and cation exchangers.

[0065] From the viewpoint that it is easy to obtain resin compositions capable of forming an insulating layer with excellent insulation reliability for DC high voltage application under high temperature and high humidity (85°C, 85%RH) conditions, inorganic ion scavengers may contain both anion exchangers and cation exchangers, or contain zwitterions.

[0066] Examples of anion exchangers include inorganic materials containing at least one element selected from the group consisting of Al, Mg, Bi, Zr, and Zn. Specific examples of anion exchangers 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 Toa Synthetic Co., Ltd.).

[0067] Examples of cation exchangers include inorganic materials containing at least one of the following groups: Zr, Sn, and Ti. Specific examples of cation exchangers include IXE-100 (Zr-based), IXE-200 (Sn-based), IXE-300 (Sb-based), and IXE-400 (Ti-based) (all manufactured by Toa Synthetic Co., Ltd.).

[0068] Examples of zwitterionic exchangers include inorganic materials containing at least one element selected from the group consisting of Al, Mg, Bi, Zr, and Sb. Specific examples of zwitterionic 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 Toa Synthetic Co., Ltd.).

[0069] Inorganic ion scavengers can be in powder form. When in powder form, the average particle size of the inorganic ion scavenger can be ≥0.05 μm, ≥0.1 μm, ≥0.15 μm, ≥0.2 μm, ≥0.3 μm, ≥0.4 μm, or ≥0.5 μm, and can also be <10 μm, <5 μm, <3 μm, <2 μm, <1.5 μm, or <1 μm. The average particle size of the inorganic ion scavenger can range from 0.05 to 10 μm. The average particle size of the inorganic ion scavenger can be determined by laser diffraction and scattering.

[0070] The content of an inorganic ion scavenger containing at least one of the group consisting of Al, Mg, Bi, Zr, Sb, and Zn may be 80% by mass or more, 90% by mass or more, or 95% by mass or more relative to the total mass of the inorganic ion scavenger. The content of an inorganic ion scavenger containing at least one of the group consisting of Al, Mg, Bi, Zr, Sb, and Zn may substantially be 100% by mass relative to the total mass of the inorganic ion scavenger.

[0071] The content of inorganic ion scavenger is 0.1 to 50% by mass relative to the total amount of thermosetting resin.

[0072] From the viewpoint that it is easy to obtain a resin composition capable of forming an insulating layer with superior insulation reliability for DC high voltage application 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 with superior insulation reliability for DC high voltage application under high temperature and high humidity (85°C, 85%RH) conditions, the content of the inorganic ion scavenger relative to the total amount of the thermosetting resin can 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 it can 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.

[0073] From the viewpoint that it is easy to obtain a resin composition capable of forming an insulating layer with superior insulation reliability for DC high voltage application 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 with superior insulation reliability for DC high voltage application under high temperature and high humidity (85°C, 85%RH) conditions, the content of the inorganic ion scavenger relative to the total mass of the resin composition can 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, and can also 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 relative to the total mass of the resin composition can also be 0.05 to 30% by mass.

[0074] From the viewpoint of readily obtaining resin compositions capable of forming insulating layers with superior insulation reliability for DC high-voltage application under high-temperature (150°C) conditions, and from the viewpoint of readily obtaining resin compositions capable of forming insulating layers with superior insulation reliability for DC high-voltage application under high-temperature and high-humidity (85°C, 85%RH) conditions, the mass ratio of the inorganic ion scavenger to the copolymer (content of inorganic ion scavenger based on mass / content of copolymer based on mass) can be 0.005 or more, 0.01 or more, or 0.05 or more, and can also be 1000 or less, 100 or less, or 50 or less. The mass ratio of the inorganic ion scavenger to the copolymer can 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 can also be from 0.001 to 10000.

[0075] The resin composition may further contain a dispersant for dispersing the inorganic filler. The dispersant may be a copolymer comprising a (meth)acrylic monomer unit A (hereinafter also referred to as "Unit A," and the monomer providing Unit A is also referred to as "Monomer A"); a (meth)acrylic monomer unit B (hereinafter also referred to as "Unit B," and the monomer providing Unit B is also referred to as "Monomer B"); and a (meth)acrylic monomer unit C (hereinafter also referred to as "Unit C," and the monomer providing Unit C is also referred to as "Monomer C") other than (meth)acrylic monomer unit A and (meth)acrylic monomer unit B. Furthermore, the copolymer may also contain a (meth)acrylic monomer unit (Unit X) having both anionic and cationic groups. In this case, Unit X is considered to be a unit belonging to both Unit A and Unit B. In other words, the copolymer having Unit X is considered to be a copolymer having both Unit A and Unit B.

[0076] In this specification, "monomer" refers to a monomer having a polymerizable group before polymerization. "Monomer unit" refers to a structural unit derived from the monomer that constitutes the copolymer. "(Meth)acrylic monomer" refers to a monomer having a (meth)acryloyl group. "(Meth)acrylic monomer" refers to acrylic monomers and their corresponding methacrylic monomers; similar expressions such as "(meth)acryloyl group" have the same meaning.

[0077] The copolymer has one or more units A, B, and C. The copolymer can be a random copolymer or a block copolymer. Monomer A, monomer B, and monomer C can 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), preferably a monofunctional (meth)acrylic monomer.

[0078] The anionic group of unit A is, for example, one or more selected from the group consisting of carboxyl, phosphate, phenolic hydroxyl, and sulfonic acid groups. From the viewpoint of further improving the dispersibility of the inorganic filler material, the anionic group is preferably one or more selected from the group consisting of carboxyl, phosphate, and phenolic hydroxyl groups.

[0079] From the viewpoint of further improving the dispersibility of inorganic filler materials, unit A preferably also has an electron-withdrawing group bonded to an anionic group. The electron-withdrawing group has the function of stabilizing the anion of the anionic group. Examples of electron-withdrawing groups include halogen groups (also called halogenated groups). Examples of anionic groups to which the electron-withdrawing group is bonded include groups with a halogen group bonded to the α-carbon atom of the carboxyl group.

[0080] Unit A may not have an electron-donating group that bonds to an anionic group. Electron-donating groups can sometimes destabilize the anionic group. Examples of electron-donating groups include the methyl group.

[0081] Examples of monomer A include acrylic acid, methacrylic acid, propyl methacrylate (acid phosphoryloxy) acrylate, acid phosphoryloxy polyoxyethylene glycol monomethacrylate, acid phosphoryloxy polyoxypropylene glycol monomethacrylate, phosphate-modified epoxy acrylate, acid 2-acryloyloxy ethyl phosphate, acid 2-methacryloyloxy ethyl phosphate, 4-hydroxyphenyl acrylate, 4-hydroxyphenyl methacrylate, 2-methacryloyloxy ethyl succinate, and 2-acrylamido-2-methylpropanesulfonic acid. From the viewpoint of further improving the dispersibility of the inorganic filler material, monomer A is preferably selected from one or more of the group consisting of acrylic acid, 2-methacryloyloxy ethyl phosphate, 4-hydroxyphenyl methacrylate, and 2-acrylamido-2-methylpropanesulfonic acid, and more preferably acrylic acid.

[0082] The cationic group of unit B is, for example, one or more selected from the group consisting of primary amine, secondary amine, tertiary amine, and quaternary ammonium salt groups. From the viewpoint of further improving the dispersibility of the inorganic filler material, the cationic group is preferably a tertiary amine.

[0083] From the viewpoint of further improving the dispersibility of the inorganic filler material, unit B preferably also has an electron-donating group bonded to a cationic group. The electron-donating group has the effect of stabilizing the cation of the cationic group. For example, a methyl group can be cited as an electron-donating group. For example, a group to which the electron-donating group is bonded can be a group with a methyl group bonded to the α-carbon atom of an amino group.

[0084] Unit B may not have an electron-withdrawing group that bonds to a cationic group. Electron-withdrawing groups can sometimes destabilize the cation of a cationic group. Examples of electron-withdrawing groups include carboxyl groups.

[0085] Examples of monomer B include, for instance, 1-aminoethyl acrylate, 1-aminopropyl acrylate, 1-aminoethyl methacrylate, 1-aminopropyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, tert-butylaminoethyl (meth)acrylate, dimethylaminoethyl methacrylate quaternary salt, 1,2,2,6,6-pentamethyl-4-piperidinyl methacrylate, 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, and benzyl chloride quaternary salt of dimethylaminoethyl acrylate. From the viewpoint of further improving the dispersibility of the inorganic filler material, monomer B is preferably selected from one or more of the group consisting of 1,2,2,6,6-pentamethyl-4-piperidinyl methacrylate and 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, and more preferably 1,2,2,6,6-pentamethyl-4-piperidinyl methacrylate.

[0086] Unit C is a (meth)acrylic acid monomer that does not contain either a cationic or anionic group. Unit C may have an amphiphilic, hydrophobic, or hydrophilic group in addition to a (meth)acryloyl group. Examples of amphiphilic groups include, for example, an alkenyl oxide group. Examples of hydrophobic groups include, for example, siloxane groups and hydrocarbon groups. Examples of hydrophilic groups include, for example, a phosphate ester group. Furthermore, the hydrocarbon group referred to herein does not include the methyl group that constitutes the methacryloyl group (the same applies to hydrocarbon groups in Unit C below).

[0087] From the viewpoint of the affinity or compatibility between the copolymer and the resin when the resin composition also contains resin, unit C has one or more selected from the group consisting of oxidized alkenyl groups, siloxane groups and hydrocarbon groups, and more preferably has one or more selected from the group consisting of siloxane groups and hydrocarbon groups.

[0088] Examples of (meth)acrylate monomers having an oxidized alkenyl group include, for example, ethoxycarbonyl methyl methacrylate, phenol ethylene oxide modified (meth)acrylate, phenol (ethylene oxide 2 moles modified) (meth)acrylate, phenol (ethylene oxide 4 moles modified) (meth)acrylate, p-cumylphenol ethylene oxide modified (meth)acrylate, nonylphenol ethylene oxide modified (meth)acrylate, nonylphenol (ethylene oxide 4 moles modified) (meth)acrylate, nonylphenol (ethylene oxide 8 moles modified) (meth)acrylate, nonylphenol (propylene oxide 2.5 moles modified) acrylate, 2-ethylhexylcarbitol (meth)acrylate, ethylene oxide modified phthalic acid (meth)acrylate, ethylene oxide modified succinic acid (meth)acrylate, and tetrahydrofurfuryl (meth)acrylate.

[0089] Examples of (meth)acrylic monomers having a siloxane group include, for example, α-butyl-ω-(3-methacryloyloxypropyl)polydimethylsiloxane. Examples of (meth)acrylic monomers having a hydrocarbon group include, for example, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, isodecanyl methacrylate, lauryl methacrylate, stearyl methacrylate, phenyl methacrylate, cyclohexyl methacrylate, dicyclopentyl methacrylate, dicyclopentenyl methacrylate, dicyclopentenyloxyethyl methacrylate, isobornyl methacrylate, and methoxylated cyclodecadiene (meth)acrylate.

[0090] Examples of (meth)acrylic monomers having phosphate ester groups include (meth)acryloyloxyethyl dialkyl phosphate.

[0091] Regarding monomer C, in addition to the monomers mentioned above, it can also be, for example, a (meth)acrylic monomer having a hydroxyl group. Examples of (meth)acrylic monomers having a hydroxyl group include, for example, 2-hydroxyethyl (meth)acrylic acid, 2-hydroxypropyl (meth)acrylic acid, 3-hydroxypropyl (meth)acrylic acid, 4-hydroxybutyl (meth)acrylic acid, 2-hydroxy-3-phenoxypropyl (meth)acrylic acid, and 3-chloro-2-hydroxypropyl (meth)acrylic acid.

[0092] Monomer C can be, for example, a (meth)acrylic acid monomer having an amide bond. Examples of (meth)acrylic acid monomers having an amide bond include N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, diacetone (meth)acrylamide, and acryloylmorpholine.

[0093] Monomer C can also be, for example, a multifunctional (meth)acrylate monomer. Examples of multifunctional (meth)acrylate monomers include 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dicyclopentyl 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-cyclohexanedicarboximide)ethyl (meth)acrylate, hexanediol di(meth)acrylate, and multifunctional (meth)acrylates having a bisphenol structure.

[0094] The content of unit A, relative to the total of units A, B, and C (in other words, the total number of all monomer units in the copolymer; the same applies below), per 100 mol%, can 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; and can 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. By making the content of unit A 0.03 mol% or more, there is a tendency to further improve the dispersibility of the inorganic filler. By making the content of unit A 70 mol% or less, there is a tendency to further reduce the viscosity of the resin composition and further improve the workability of the resin composition.

[0095] The content of unit B, relative to the total 100 mol% of units A, B, and C, can be 0.02 mol% or more, 0.05 mol% or more, 0.07 mol% or more, or 0.1 mol% or more, and can 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. By making the content of unit B 0.02 mol% or more, there is a tendency for the affinity between the copolymer and the inorganic filler to become better. By making the content of unit B 20 mol% or less, there is a tendency for the viscosity of the resin composition to be further reduced and the workability of the resin composition to be further improved.

[0096] The content of unit C, relative to the total 100 mol% of units A, B, and C, can 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 can be 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. By making the content of unit C 10 mol% or more, there is a tendency to further reduce the viscosity of the resin composition and further improve the workability of the resin composition. By making the content of unit C 99.8 mol% or less, there is a tendency to improve the affinity between the copolymer and the inorganic filler.

[0097] The total content of unit A and unit B, relative to 100 mol% of the total content of units A, B, and C, can 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, and can 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. By making the total content of unit A and unit B 0.05 mol% or more, there is a tendency to further improve the dispersibility of the inorganic filler. By making the total content of unit A and unit B 90 mol% or less, there is a tendency to further improve the workability of the resin composition.

[0098] The molar ratio of unit A to unit B (unit A / unit B) can 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, and can 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. By keeping the molar ratio of unit A to unit B within the above ranges, there is a tendency to further improve the dispersibility of the inorganic filler material.

[0099] The weight-average molecular weight of the copolymer can 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 less than 1,000,000, less than 500,000, less than 300,000, less than 100,000, less than 90,000, less than 80,000, less than 70,000, or less than 60,000. By making the weight-average molecular weight of the copolymer 1,000 or more, the dispersibility of the inorganic filler can be maintained even when the resin composition is stored at high temperatures for a long time, and the increase in hardness of the resin composition can be suppressed. Furthermore, the shape retention of the resin composition is improved, and the offset and sagging of the resin composition are suppressed when coated on inclined or vertical surfaces. By reducing the weight-average molecular weight of the copolymer to below 1,000,000, there is a tendency to further reduce the viscosity of the resin composition and further improve its workability. The weight-average molecular weight of the copolymer is determined using GPC (gel permeation chromatography) as a conversion to standard polystyrene.

[0100] The copolymer can be obtained by polymerizing monomers A, B, and C using known polymerization methods. Examples of polymerization methods include free radical polymerization and anionic polymerization. Free radical polymerization is preferred.

[0101] The polymerization initiators used in free radical polymerization can be thermal polymerization initiators or photopolymerization initiators. Examples of thermal polymerization initiators include azo compounds such as azobisisobutyronitrile (AIBN); and organic peroxides such as benzoyl peroxide, tert-butyl hydroperoxide, and di-tert-butyl peroxide. Examples of photopolymerization initiators include benzoin derivatives. Polymerization initiators can also be known polymerization initiators used in living radical polymerization, such as ATRP and RAFT.

[0102] Polymerization conditions can be adjusted appropriately depending on the type of monomer and polymerization initiator. When the copolymer is a random copolymer, the monomers can be pre-mixed and polymerized. When the copolymer is a block copolymer, the monomers can be added sequentially to the polymerization system.

[0103] The copolymer content can be 0.01 to 10 parts by weight relative to 100 parts by weight of the inorganic filler. By keeping the copolymer content within this range, it is easy to obtain a resin composition capable of forming an insulating layer with superior insulation reliability for DC high voltage application under high temperature (150°C) conditions. The copolymer content relative to 100 parts by weight can be 0.05 parts by weight or more, 0.1 parts by weight or more, 0.5 parts by weight or more, 1 part by weight or more, 2 parts by weight or more, 3 parts by weight or more, or 4 parts by weight or more, and can be 9 parts by weight or less, 8 parts by weight or less, 7 parts by weight or less, 6 parts by weight or less, 5 parts by weight or less, or 4 parts by weight or less.

[0104] The content of the copolymer relative to the total mass of the resin composition can be more than 0.1% by mass, more than 0.5% by mass, more than 1% by mass, more than 2% by mass, or more than 2.5% by mass, or less than 10% by mass, less than 8% by mass, less than 6% by mass, less than 5% by mass, less than 4% by mass, or less than 3% by mass.

[0105] The resin composition may also contain a curing agent for curing the thermosetting resin. The curing agent is appropriately selected depending on the type of thermosetting resin. For example, amine resins, anhydride resins, and phenolic resins can be cited as curing agents when the thermosetting resin is an epoxy resin. The curing agent can be used alone or in combination of two or more.

[0106] The content of the curing agent relative to the total mass of the resin composition can be more than 1% by mass or more than 3% by mass, or less than 10% by mass or less than 5% by mass.

[0107] The resin composition may also contain other components. Examples of other components include, for instance, curing accelerators, coupling agents, leveling agents, antioxidants, defoamers, wetting agents, dispersants, and stabilizers.

[0108] The resin composition is obtained by mixing a thermosetting resin, an inorganic filler, and an inorganic ion trap (as well as dispersants, curing agents, and other components as needed). Mixing can be carried out using, for example, a planetary mixer, a universal mixer, a kneader, or a hybrid mixer.

[0109] The resin composition may exhibit peaks in the range of 2θ = 11 to 15° in X-ray diffraction measurements. The peak positions in X-ray diffraction measurements of the resin composition can be confirmed, for example, by preparing a cured body of the resin composition and performing X-ray diffraction measurements on the cured body. The resin composition may exhibit peaks at positions of 2θ = 11.5 to 14.5° or 11.8 to 14° in X-ray diffraction measurements.

[0110] The resin composition described above can be prepared by mixing thermosetting resin, inorganic filler, inorganic ion scavenger, and other components as needed. The resin composition can be prepared by mixing a powder (containing a first particle group and a second particle group) that has a peak in the particle size distribution curve of 0.1 μm or more and 15 μm or less, and a peak in the particle size distribution curve of more than 15 μm or less and 300 μm or less, with components other than the inorganic filler; or it can be prepared by separately preparing powders with peaks in the particle size distribution curve of 0.1 μm or more and 15 μm or less, and powders with peaks in the particle size distribution curve of more than 15 μm or less and 300 μm or less, and then mixing these powders with components other than the inorganic filler.

[0111] The resin composition described above can be cured and used, for example. That is, one embodiment of the present invention is a cured body (insulating resin cured body) of the above-described resin composition. The cured body can be in a semi-cured state (stage B) or in a fully cured state (stage C).

[0112] A cured body can be obtained, for example, by heat-treating the above-described resin composition to cure it. The heat treatment conditions (heating temperature, heating time, etc.) can be appropriately set according to the type of resin and curing agent, the desired curing state, etc. The heat treatment can be carried out in one stage or in two stages.

[0113] The cured body can be, for example, in sheet form. A sheet-like cured body can be obtained, for example, by coating the above-described resin composition onto a substrate and heating (and, if necessary, pressurizing). The sheet-like cured body can be a B-stage sheet in a semi-cured state or a C-stage sheet in a fully cured state.

[0114] The above-described resin composition and its cured form can be suitably used to form an insulating layer for a metal substrate. That is, the above-described resin composition and its cured form can also be referred to as a resin composition for a metal substrate and a cured form for a metal substrate, respectively.

[0115] Figure 1 is a schematic cross-sectional view illustrating one embodiment of the laminate. As shown in Figure 1, one embodiment of the laminate 10A includes: a first metal layer 1A; an insulating layer (cured form of the resin composition described above) 2 disposed on one side of the first metal layer; and a second metal layer 3A disposed on the side of the insulating layer 2 opposite to 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 remain electrically insulated from each other.

[0116] Examples of metallic materials constituting the first metal layer 1A include aluminum, aluminum alloys, copper, copper alloys, iron, and stainless steel. The first metal layer 1A can be composed of one metallic material or two or more metallic materials. The first metal layer 1A can be a single-layer structure or a multi-layer structure.

[0117] Examples of metallic materials constituting the second metal layer 3A include copper, aluminum, and nickel. The second metal layer 3A can be composed of one metallic material or two or more metallic materials. The second metal layer 3A can be a single-layer structure or a multi-layer structure. In Figure 1, the second metal layer 3A is disposed on approximately the entire surface of the insulating layer 2, but the second metal layer may also be disposed on only a portion of the insulating layer 2.

[0118] The thickness of the first metal layer 1A can be, for example, 0.5 mm or more, or 3 mm or less. The thickness of the insulating layer 2 can be, for example, 50 μm or more, or 300 μm or less. The thickness of the second metal layer 3A can be, for example, 5 μm or more, or 1 mm or less.

[0119] Figure 2 is a schematic cross-sectional view showing one embodiment of the circuit board. As shown in Figure 2, one embodiment of the circuit board 10B includes: a metal layer 1B; an insulating layer (a cured form of the resin composition described above) 2 disposed on one side of the metal layer 1B; and a metal circuit portion 3B disposed on the side 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 that has been processed (e.g., etched) into a predetermined pattern.

[0120] The metal material constituting metal layer 1B can be the same as the metal material constituting the first metal layer 1A described above. Similarly, the metal material constituting the metal circuit section 3B can be the same as the metal material constituting the second metal layer 3A described above.

[0121] The thickness of the metal layer 1B can be, for example, 0.5 mm or more, or 3 mm or less. The thickness of the insulating layer 2 can be, for example, 50 μm or more, or 300 μm or less. The thickness of the metal circuit portion 3B can be, for example, 5 μm or more, or 1 mm or less.

[0122] [Examples] Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to these examples.

[0123] <Synthesis of Copolymers> The following shows the monomers used in the synthesis of copolymers in the examples.

[0124] (A) Acrylic acid monomer with an anionic group (manufactured by Toa Synthetic Co., Ltd.) (B) 1,2,2,6,6-pentamethyl-4-piperidinium methacrylate ("ADEKA STABLA-82" manufactured by ADEKA Co., Ltd.) (C) Benzyl methacrylate ("LIGHT ESTER BZ" manufactured by Kyoei Chemical Co., Ltd.) First, 100 parts by weight of a (meth)acrylic acid monomer containing 5 mol% acrylic acid, 0.1 mol% 1,2,2,6,6-pentamethyl-4-piperidinium methacrylate, and 94.9 mol% benzyl methacrylate are added to an autoclave equipped with a stirrer. Next, 0.5 parts by mass of azobisisobutyronitrile (manufactured by Tokyo Chemical Co., Ltd.) as an initiator (relative to 100 parts by mass of the total (meth)acrylic acid monomers) and 1000 parts by mass of a mixed solution of toluene (reagent grade) and 2-propanol (reagent grade) as a solvent (toluene:2-propanol = 7:3 (volume ratio)) were added, and the autoclave was purged with nitrogen. Then, free radical polymerization was carried out in an oil bath at 65°C for 20 hours. After polymerization, the mixture was degassed at 120°C under reduced pressure for 1 hour to obtain the copolymer.

[0125] The polymerization rate relative to 100% monomer input was analyzed by gas chromatography, and the result was over 98%. This suggests that the ratio of monomer units in the copolymer is similar to the monomer input ratio.

[0126] The weight-average molecular weight of the obtained copolymer was determined using GPC (gel permeation chromatography) in the form of weight-average molecular weight converted to standard polystyrene. Furthermore, the determination conditions are as follows.

[0127] High-efficiency GPC apparatus: HLC-8020 chromatographic column manufactured by Tosoh Corporation: 1 TSK guardcolumn MP (×L) 6.0mm ID×4.0cm and 2 TSK-GELMULTIPOREHXL-M 7.8mm ID×30.0cm (theoretical plate number is 16,000), a total of 3 columns (theoretical plate number as a whole is 32,000). Developing solvent: tetrahydrofuran. Detector: RI (differential refractive index meter). <Preparation of resin composition> (Example 1) 27.9 parts by weight of naphthalene-type epoxy resin HP-4032D (manufactured by DIC Corporation) as a thermosetting resin and 3.5 parts by weight of phenolic varnish 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. A resin composition was prepared by stirring and mixing resin containing a curing agent, 12.9 parts by weight (10 vol%) of boron nitride filler (thermal conductivity 150 W / m·K) as an inorganic filler, 2.6 parts by weight (4 phr) of copolymer, 1.3 parts by weight (4.5 phr) of inorganic ion scavenger 1 (zwitterionic exchanger (Zr, Mg, Al-based, average particle size 0.2 μm, manufactured by Toa Synthetic Co., Ltd.) as an inorganic ion scavenger, and 0.2 parts by weight of 1B2PZ (manufactured by Shikoku Chemical Industry Co., Ltd.) as a curing accelerator for 15 minutes. The inorganic filler material is a powder composed of a first particle group (average particle size: 10.1 μm, average aspect ratio: 7.5, peak intensity ratio I(002) / I(100): 126.4) which essentially contains only scaly boron nitride particles and a second particle group (average particle size: 50.9 μm, average aspect ratio: 1.46, peak intensity ratio I(002) / I(100): 6.8) which essentially contains only scaly boron nitride particles. On the particle size distribution curve, the first particle group has a peak at 6.6 μm and the second particle group has a peak at 43.5 μm. The content of the first particle group (the cumulative frequency of 0.1–15 μm when the cumulative frequency of 0.1–300 μm is 100% on the particle size distribution curve) is 11.8% by volume, and the content of the second particle group (the cumulative frequency of 15–300 μm when the cumulative frequency of 0.1–300 μm is 100% on the particle size distribution curve) is 88.2% by volume.

[0128] <Preparation of Cured Body> The obtained resin composition was coated onto a polyethylene terephthalate (PET) film with a thickness of 0.20 mm after curing, and then heated and dried at 100°C for 50 minutes to produce a semi-cured cured body (a sheet in the B stage state).

[0129] <Fabrication of Metal Substrate Circuit Board> The cured body (B-stage sheet) is peeled off from the PET film and placed on the rough surface of a metal plate (2.0 mm thick copper plate). A rough surface of a metal foil (0.5 mm thick copper foil) is placed on top of the cured body. While applying a surface pressure of 10 MPa using a press, it is heated and cured at 180°C for 410 minutes.

[0130] Next, after masking the designated locations with a photoresist, the copper foil was etched using a sulfuric acid-hydrogen peroxide mixture as the etching solution. After removing the photoresist, the substrate was cleaned and dried, thus obtaining a metal-based circuit board with circular electrodes (copper foil) with a diameter of 20 mm.

[0131] (Example 2) Except for using inorganic ion scavenger 2 (zwitterion (Zr, Bi-based), average particle size 0.4 μm, manufactured by Toa Synthetic Co., Ltd.) as inorganic ion scavenger, a resin composition, a cured body, and a metal substrate circuit board were prepared using the same method as in Example 1.

[0132] (Example 3) Except for using inorganic ion scavenger 3 (anion exchanger (Mg, Al type), average particle size 1.5 μm, manufactured by Toa Synthetic Co., Ltd.) as inorganic ion scavenger, a resin composition, a cured body, and a metal substrate circuit board were prepared using the same method as in Example 1.

[0133] (Example 4) Except for using inorganic ion scavenger 4 (anion exchanger (Bi-based), average particle size 1.5 μm, manufactured by Toa Synthetic Co., Ltd.) as inorganic ion scavenger, a resin composition, a cured body, and a metal substrate circuit board were prepared using the same method as in Example 1.

[0134] (Example 5) Except for using inorganic ion scavenger 5 (anion exchanger (Zr-based), average particle size 1.0 μm, manufactured by Toa Synthetic Co., Ltd.) as inorganic ion scavenger, a resin composition, a cured body, and a metal substrate circuit board were prepared using the same method as in Example 1.

[0135] (Example 6) Except for using inorganic ion scavenger 6 (zwitterion (Sb, Bi-based), average particle size 1.0 μm, manufactured by Toa Synthetic Co., Ltd.) as inorganic ion scavenger, a resin composition, a cured body, and a metal substrate circuit board were prepared using the same method as in Example 1.

[0136] (Example 7) Except for using inorganic ion scavenger 6 (zwitterion (Zr, Bi-based), average particle size 1.5 μm, manufactured by Toa Synthetic Co., Ltd.) as inorganic ion scavenger, a resin composition, a cured body, and a metal substrate circuit board were prepared using the same method as in Example 1.

[0137] (Example 8) Except for using a first particle group consisting of essentially only scaly boron nitride particles (average particle size: 10.1 μm, average aspect ratio: 7.5, peak intensity ratio I(002) / I(100): 126.4) and a second particle group consisting of essentially only scaly boron nitride particles (average particle size: 50.9 μm, average aspect ratio: 1.46, peak intensity ratio I(002) / I(100): 6.8), the first particle group has a peak at 6.6 μm on the particle size distribution curve and the second particle group has a peak at 4 μm. Aside from using a powder having a peak at 3.5 μm, containing 6.3 vol% of the first particle group (cumulative frequency of 0.1–15 μm when the cumulative frequency of 0.1–300 μm is 100% on the particle size distribution curve) and 93.7 vol% of the second particle group (cumulative frequency of 15–300 μm when the cumulative frequency of 0.1–300 μm is 100% on the particle size distribution curve) as an inorganic filler, a resin composition, a cured body, and a metal substrate circuit board were prepared using the same method as in Example 1.

[0138] (Example 9) Except for using a first particle group consisting of essentially only scaly boron nitride particles (average particle size: 10.1 μm, average aspect ratio: 7.5, peak intensity ratio I(002) / I(100): 126.4) and a second particle group consisting of essentially only scaly boron nitride particles (average particle size: 50.9 μm, average aspect ratio: 1.46, peak intensity ratio I(002) / I(100): 6.8), the first particle group has a peak at 6.6 μm on the particle size distribution curve and the second particle group has a peak at 4 μm. Aside from using a powder with a peak at 3.5 μm, containing 55.3 vol% of the first particle group (cumulative frequency of 0.1–15 μm when the cumulative frequency of 0.1–300 μm is 100% on the particle size distribution curve) and 44.7 vol% of the second particle group (cumulative frequency of 15–300 μm when the cumulative frequency of 0.1–300 μm is 100% on the particle size distribution curve) as an inorganic filler, a resin composition, a cured body, and a metal substrate circuit board were prepared using the same method as in Example 1.

[0139] (Example 10) Except that the amount of inorganic ion scavenger was set to 0.14 parts by mass (0.5 phr), a resin composition, a cured body, and a metal substrate circuit board were prepared using the same method as in Example 1.

[0140] (Example 11) Except that the amount of inorganic ion scavenger was set to 0.42 parts by mass (1.5 phr), the resin composition, cured body and metal substrate circuit board were prepared using the same method as in Example 1.

[0141] (Example 12) Except that the amount of inorganic ion scavenger was set to 1.8 parts by mass (6 phr), the resin composition, cured body and metal substrate circuit board were prepared using the same method as in Example 1.

[0142] (Example 13) Except that the amount of inorganic ion scavenger was set to 2.8 parts by mass (10 phr), the resin composition, cured body and metal substrate circuit board were prepared using the same method as in Example 1.

[0143] (Example 14) Except that the amount of inorganic ion scavenger was set to 5.6 parts by mass (20 phr), the resin composition, cured body and metal substrate circuit board were prepared using the same method as in Example 1.

[0144] (Comparative Example 1) Except that no inorganic ion scavenger was added, a resin composition, a cured body, and a metal substrate circuit board were prepared using the same method as in Example 1.

[0145] (Comparative Example 2) Except that the amount of inorganic ion scavenger was set to 27.9 parts by mass (100 phr), the resin composition, cured body and metal substrate circuit board were prepared using the same method as in Example 1.

[0146] (Comparative Example 3) In addition to using aggregated particles composed of flake-like boron nitride particles (average particle size: 50.9 μm, average aspect ratio: 1.46, peak intensity ratio I(002) / I(100): 6.8) and a second particle group consisting of aggregated particles that essentially contain only flake-like boron nitride particles (average particle size: 50.9 μm, average aspect ratio: 1.46, peak intensity ratio I(002) / I(100): 6.8), the first particle group has a peak at 6.6 μm on the particle size distribution curve, and the second particle group has a peak at 43 μm. Aside from using a powder having a peak at the 0.5 μm position, a first particle group content (cumulative frequency of 0.1–15 μm when the cumulative frequency of 0.1–300 μm is 100% on the particle size distribution curve) of 0.9 vol% and a second particle group content (cumulative frequency of 15–300 μm when the cumulative frequency of 0.1–300 μm is 100% on the particle size distribution curve) of 99.1 vol% as an inorganic filler, a resin composition, a cured body, and a metal substrate circuit board were prepared using the same method as in Example 1.

[0147] (Comparative Example 4) Except for the first particle group (average particle size: 10.1 μm, average aspect ratio: 7.5, peak intensity ratio I(002) / I(100): 126.4) and the second particle group (average particle size: 50.9 μm, average aspect ratio: 1.46, peak intensity ratio I(002) / I(100): 6.8) which consist of aggregated particles that essentially contain only scaly boron nitride particles, the first particle group has a peak at 6.6 μm on the particle size distribution curve, and the second particle group has a peak at 6.6 μm on the particle size distribution curve. Aside from using a powder containing a peak at 43.5 μm, a first particle group (cumulative frequency of 0.1–15 μm when the cumulative frequency of 0.1–300 μm is 100% on the particle size distribution curve) with a content of 77.1 vol%, and a second particle group (cumulative frequency of 15–300 μm when the cumulative frequency of 0.1–300 μm is 100% on the particle size distribution curve) with a content of 22.9 vol%, a resin composition, a cured body, and a metal substrate circuit board were prepared using the same method as in Example 1.

[0148] [Determination of Particle Size Distribution] The particle size distribution was determined using a particle size distribution and particle shape analyzer (Microtrac, SYNC-3L S / N: H0153) under the following conditions. For the determination of particle size distribution, the circulating tank was purged with an aqueous solution of sodium hexametaphosphate, and the sample was placed in the circulating tank and allowed to stabilize before the determination was performed.

[0149] <Measurement Conditions> Particle Refractive Index: 1.74 Particle Shape: Non-spherical Solvent Used: Sodium Hexametaphosphate Aqueous Solution Solvent Refractive Index: 1.333 Flow Rate: 60% Measurement Time: 10 seconds (wet) [Determination of Average Particle Size and Average Aspect Ratio] For the first particle group, samples for cross-sectional observation were prepared by embedding particles in resin, followed by machine grinding and ion polishing. After depositing a gold coating on the prepared samples, the cross-section was observed using a scanning electron microscope (SEM) at 10,000x magnification. The maximum length and maximum thickness of 10 boron nitride particles in one field of view were measured. The average maximum length and the average maximum length / maximum thickness of each particle were calculated to determine the average particle size and average aspect ratio.

[0150] For the second particle group, the particle size distribution was determined using a particle size distribution and particle shape analyzer (Microtrac, SYNC-3L S / N: H0153) under the following conditions. For the determination of average particle size and average aspect ratio, the circulating tank was purged with an aqueous solution of sodium hexametaphosphate, and the sample was placed in the circulating tank and allowed to stabilize before measurement.

[0151] <Measurement Conditions> Particle refractive index: 1.74 Particle shape: Non-spherical Solvent used: Sodium hexametaphosphate aqueous solution Solvent refractive index: 1.333 Measurement time: 10 seconds (wet) [Measurement of XRD peaks] X-ray diffraction measurements were performed on the cured bodies prepared in each example and comparative example using a Rigaku MiniFlexII X-ray diffraction apparatus manufactured by Rigaku Corporation. The positions of the XRD peaks detected in the range of 2θ = 11 to 15° are shown in Tables 1 to 4. In addition, the peak intensity ratio (I(002) / I(100)) of boron nitride particles in the first and second particle groups was measured in the range of 2θ = 20 to 50°, and the intensity of the diffraction line near 2θ = 27° was set as I(002) and the intensity of the diffraction line near 2θ = 41° was set as I(100) for calculation.

[0152] [Reliability Evaluation Based on High Temperature and High Voltage Bias Test (Vt)] A high temperature and high voltage bias test (Vt) was conducted on the obtained metal substrate. The high temperature and high voltage bias test (Vt) was performed under test conditions where a DC voltage of 10kV was applied between the metal foil and the metal plate at 150°C, and the time until insulation breakdown was measured. The time until insulation breakdown was defined as the time from the start of voltage application until the leakage current value measured by a withstand voltage tester reached 10mA or more. The test results are shown in Tables 1-4.

[0153] [Reliability Evaluation Based on High Temperature and Humidity Bias Test (THB)] A high temperature and humidity bias test (THB) was performed on the obtained metal substrate. The THB test was conducted at 85°C and 85% RH, under conditions where a DC voltage of 2.0 kV was applied between the metal foil and metal plate, and the time until insulation breakdown was measured. The time until insulation breakdown was defined as the time from the start of voltage application until the leakage current value measured using a withstand voltage tester reached 10 mA or more. The test results are shown in Tables 1-4. In the tables, items marked with "-" indicate that no test was performed.

[0154] [Table 1] [Table 2] [Table 3] [Table 4] Symbol explanation: 1A... First metal layer, 1B... Metal layer, 2... Insulating layer, 3A... Second metal layer, 3B... Metal circuit section, 10A... Stacked body, 10B... Circuit board.

Claims

1. A resin composition comprising a thermosetting resin, an inorganic filler, and an inorganic ion scavenger; wherein the inorganic filler comprises a first particle group having a peak in the range of 0.1 μm to 15 μm on a particle size distribution curve, and a second particle group having a peak in the range of more than 15 μm to 300 μm on the particle size distribution curve; wherein the content of the first particle group is 1% by volume or more and 60% by volume or less relative to the total content of the first particle group and the second particle group; and wherein the content of the inorganic ion scavenger is 0.1% to 50% by mass relative to the total amount of the thermosetting resin.

2. The resin composition according to claim 1, wherein the first particle group contains first particles with an aspect ratio of 1 to 200, and the second particle group contains second particles with an aspect ratio of 1 to 2.

3. The resin composition according to claim 1, wherein on the particle size distribution curve, the difference between the position of the peak of the first particle group and the position of the peak of the second particle group is more than 10 μm and less than 200 μm.

4. The resin composition according to claim 1, wherein the content of the first particle group is 5% by volume or more and 30% by volume or less relative to the total content of the first particle group and the second particle group.

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

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

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

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

9. The resin composition according to claim 1, wherein the inorganic ion scavenger contains at least one 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 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 measurements.

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 containing: a (meth)acrylic monomer unit A having an anionic group, a (meth)acrylic monomer unit B having a cationic group, and a (meth)acrylic monomer unit C other than (meth)acrylic monomer unit A and (meth)acrylic monomer unit B.

14. An insulating resin cured body, which is a cured body 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 a side of the first metal layer, and a second metal layer disposed on a side of the insulating layer opposite to the first metal layer, wherein the insulating layer is an insulating resin cured body as described in claim 14.

16. A circuit board comprising: a metal layer, an insulating layer disposed on one side 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 an insulating resin cured body as described in claim 14.

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