Sheet-shaped resin composition

Abstract

Provided is a sheet-shaped resin composition that exhibits both good handling properties and good low-temperature storage stability.　The sheet-shaped resin composition contains an epoxy resin, a phenolic curing agent, inorganic particles, and a solvent, and satisfies formula (1). (1): 15.6 ≤ S × M ≤ 75.0. In formula (1), S is the solvent content (mass%), and, in the molecular weight distribution curve obtained by GPC measurement of the sheet-shaped resin composition, M is the area ratio (%) for the range for which the molecular weight as polystyrene is at least 120 and not more than 600 where the total peak area is 100%.

Description

Sheet-like resin composition

[0001] This disclosure relates to a sheet-like resin composition.

[0002] IC chips incorporated into electronic components are protected by a encapsulation material containing resin and filler, ensuring their reliability. This encapsulation material may generally contain inorganic particles and resin, as described in Patent Document 1.

[0003] Japanese Patent Publication No. 2021-145117

[0004] The sheet-like resin composition is manufactured by applying a liquid resin composition containing epoxy resin, inorganic particles, a solvent, and a curing agent to a substrate, and then removing a portion of the solvent. When the obtained sheet-like resin composition is heated and pressurized in contact with an object to be sealed, such as an IC chip, the epoxy resin constituting the sheet-like resin composition softens and covers the IC chip, and then the epoxy resin reacts with the curing agent and hardens, forming a sealing member that seals the IC chip.

[0005] Because sheet-like resin compositions are flexible, they may flex during the manufacturing of long sheets or when they come into contact with IC chips during the IC chip encapsulation process. When they flex, cracks may form in the sheet-like resin composition, and these crack marks may remain after encapsulation, potentially leading to reduced encapsulation performance and poor appearance. Furthermore, if the surface tackiness of the sheet-like resin composition is excessively high, it can cause defects during transport, such as the sheets sticking to each other or to transport equipment. Therefore, it is desirable for sheet-like resin compositions to be less prone to cracking when flexed and to have low surface tackiness (referred to as having "good handling properties").

[0006] Furthermore, the reaction between the epoxy resin and the curing agent in sheet-like resin compositions begins immediately after manufacturing. To slow down the reaction, sheet-like resin compositions are sometimes stored in a low-temperature environment (e.g., -20°C) from the time of manufacture until use. It has been found that when sheet-like resin compositions are stored at low temperatures for a long period of time, dendritic patterns (referred to as "dendritic defects") appear on the surface of the sheet-like resin composition, resulting in an appearance defect. It is preferable that sheet-like resin compositions are less prone to developing dendritic defects even when stored at low temperatures (referred to as "low-temperature storage stability").

[0007] Therefore, the object of one embodiment of the present invention is to provide a sheet-like resin composition that has good handling properties and low-temperature storage stability.

[0008] One aspect of the present invention is a sheet-like resin composition comprising an epoxy resin, a phenolic curing agent, inorganic particles, and a solvent, satisfying the following formula (1): 15.6 ≤ S × M ≤ 75.0 ... (1) where S is the content (mass%) of the solvent, and M is the area percentage (%) of the range in which the polystyrene-equivalent molecular weight is between 120 and 600, when the total peak area is set to 100% in the molecular weight distribution curve obtained by GPC measurement of the sheet-like resin composition.

[0009] Aspect 2 of the present invention is the sheet-like resin composition according to Aspect 1, wherein the solvent content is 0.10% by mass or more and 5.00% by mass or less.

[0010] Aspect 3 of the present invention is a sheet-like resin composition according to aspect 1 or 2, wherein the area ratio M is 15.0% or more and 85.0% or less.

[0011] Aspect 4 of the present invention is a sheet-like resin composition according to any one of aspects 1 to 3, which further satisfies the following formula (2): 10.0 ≤ S ２ ×M １／２ ×T １／２ ≤300 ... (2) Here, T is the thickness (μm) of the sheet-like resin composition.

[0012] Embodiment 5 of the present invention is a sheet-like resin composition according to any one of Embodiments 1 to 4, wherein the solvent comprises one or more selected from the group consisting of ketone-based solvents and ester-based solvents.

[0013] Aspect 6 of the present invention is a sheet-like resin composition according to any one of aspects 1 to 5, further comprising a curing accelerator, wherein the content of the curing accelerator in 100% by mass of the solid content of the sheet-like resin composition is 0.01% by mass or more and 1.00% by mass or less.

[0014] Aspect 7 of the present invention is a sheet-like resin composition according to aspect 6, wherein the curing accelerator comprises one or more selected from the group consisting of phosphorus-based curing accelerators and imidazole-based curing accelerators.

[0015] Embodiment 8 of the present invention is a sheet-like resin composition according to any one of embodiments 1 to 7, wherein the inorganic particles are one or more selected from the group consisting of alumina particles and silica particles.

[0016] Aspect 9 of the present invention is a sheet-like resin composition according to any one of aspects 1 to 8, wherein the content of inorganic particles in 100% by mass of the solid content of the sheet-like resin composition is 40% by mass or more and 99% by mass or less.

[0017] Embodiment 10 of the present invention is a sheet-like resin composition according to any one of Embodiments 1 to 9, wherein the thickness T is 100 μm or more and 1000 μm or less.

[0018] According to one embodiment of the present invention, a sheet-like resin composition can be provided that exhibits both good handling properties and low-temperature storage stability.

[0019] This is an example of a photograph of the surface of a sheet-like resin composition that has developed surface defects after long-term storage at low temperatures.

[0020] The inventors diligently conducted research to provide a sheet-like resin composition that exhibits both good handling properties and low-temperature storage stability. As a result, they discovered for the first time that when the solvent content and the low molecular weight component content (such as epoxy resin monomers) in the sheet-like resin composition satisfy the relationship of a specific formula (1), both good handling properties and low-temperature storage stability can be achieved, thus completing the present invention.

[0021] The inventors have for the first time discovered that, regarding low-temperature storage stability, when a sheet-like resin composition containing inorganic particles is stored at a low temperature (e.g., -20°C) for a long period, the sheet-like resin composition develops appearance defects (dendritic defects) as shown in Figure 1, which are thought to be caused by phase separation. When appearance defects occur, problems may arise when printing on the surface of the cured product after sealing with the sheet-like resin composition using a laser. Note that if the sheet-like resin composition is black due to a coloring agent, for example, the dendritic defects can be observed as white areas. It is thought that the dendritic defects are caused by the localized precipitation and / or recrystallization of some of the monomer components and curing agent components of the epoxy resin that were dissolved in the solvent due to the long-term storage of the sheet-like resin composition at low temperatures. Although the details are unclear, it is thought that the higher the solvent content in the sheet-like resin composition, the greater the amount of epoxy resin monomer components and curing agent components that precipitate / recrystallize due to low-temperature storage, resulting in dendritic defects of a visible size and number.

[0022] The following describes in detail a sheet-like resin composition according to one embodiment of the present invention.

[0023] [Sheet-like resin composition] A sheet-like resin composition according to one embodiment of the present invention comprises an epoxy resin, a phenolic curing agent, inorganic particles, and a solvent, and satisfies the following formula (1): 15.6 ≤ S × M ≤ 75.0 ... (1) Here, S is the content (mass%) of the solvent, and M is the area ratio (%) of the range in which the polystyrene-equivalent molecular weight is between 120 and 600, when the total peak area is set to 100% in the molecular weight distribution curve obtained by GPC measurement of the sheet-like resin composition.

[0024] In formula (1), the product (S×M) of the content S of the solvent contained in the sheet-shaped resin composition and the content of a component having a polystyrene-equivalent molecular weight of 120 or more and 600 or less (which may be referred to as a "low molecular weight component") (which may be referred to as the "area ratio M of the low molecular weight component") is within a predetermined range. When the relationship of formula (1) is satisfied, both the handling property and the low-temperature storage stability of the sheet-shaped resin composition can be improved. Although the reason is not clear, when the sheet-shaped resin composition satisfies formula (1), a high molecular weight component of the resin contained in the sheet-shaped resin composition is likely to be present appropriately, and precipitation and / or recrystallization of monomer components and curing agent components of the epoxy resin dissolved in the solvent, which cause poor appearance, are less likely to occur. Therefore, it is considered that both the handling property and the low-temperature storage stability are improved. Here, the "high molecular weight component" refers to a component having a polystyrene-equivalent molecular weight exceeding 600.

[0025] S×M is preferably 15.8 or more, more preferably 16.0 or more, preferably 70.0 or less, more preferably 65.0 or less, still more preferably 60.0 or less, and particularly preferably 50.0 or less, and the handling property and the low-temperature storage stability of the sheet-shaped resin composition can be further improved.

[0026] (Content S of the solvent) The content S of the solvent contained in the sheet-shaped resin composition is preferably 0.10% by mass or more and 5.00% by mass or less. Thereby, the handling property and the low-temperature storage stability of the sheet-shaped resin composition can be further improved. When the content S of the solvent is 0.10% by mass or more, the sheet-shaped resin composition is likely to become flexible and the handling property is likely to be improved. When the content S of the solvent is 5.00% by mass or less, the tackiness on the surface of the sheet-shaped resin composition can be reduced, the handling property is likely to be improved, and precipitation and / or recrystallization of the low molecular weight component in the sheet-shaped resin composition during low-temperature storage can be easily suppressed. Therefore, the occurrence of poor appearance (tree-like defects) can be easily suppressed. Here, the "content S of the solvent" is the content of the solvent determined with the mass of the sheet-shaped resin composition before heating as 100% by mass.

[0027] The content S of the solvent is more preferably 0.20% by mass or more, still more preferably 0.30% by mass or more, even more preferably 0.40% by mass or more, particularly preferably 0.50% by mass or more, more preferably 4.0% by mass or less, still more preferably 3.0% by mass or less, even more preferably 2.4% by mass or less, particularly preferably 2.0% by mass or less, and particularly even more preferably 1.0% by mass or less. When the content S of the solvent is within the above range, the handling property and the low-temperature storage stability of the sheet-shaped resin composition can be more effectively improved.

[0028] Furthermore, when the content S of the solvent is within the above range, the fluidity during heating and pressurization is good, and the aggregation and sedimentation of the inorganic particles can be suppressed, so that the sealing property of the sheet-shaped resin composition can also be enhanced.

[0029] The content S of the solvent contained in the sheet-shaped resin composition is determined from the mass change of the sheet-shaped resin composition before and after heating. Specifically, a sample of the sheet-shaped resin composition having a predetermined size (for example, 4 cm square) is prepared, and the mass X1 (g) of the sample before heating is measured. Next, using a full-exhaust oven, the sample is heated at 150°C for 10 minutes to evaporate the solvent contained in the sheet-shaped resin composition. Then, it is left to stand at room temperature for 5 minutes to return to room temperature, and the mass X2 (g) of the sample after heating is measured. The content (mass%) of the solvent is obtained by dividing the mass difference (X1 - X2) obtained by subtracting the mass X2 (g) of the sample after heating from the mass X1 (g) of the sample before heating by the mass X1 (g) of the sample before heating (see the following formula (3)). Content of solvent (mass%) = (X1 - X2) / X1 × 100... (3)

[0030] (Area ratio M of low molecular weight components) The area ratio M (%) of low molecular weight components contained in the sheet-like resin composition is preferably 15.0% or more and 85.0% or less, which can further improve the handling properties and low-temperature storage stability of the sheet-like resin composition. When the area ratio M of low molecular weight components is 15.0% or more, it is easier to suppress the reaction between the epoxy resin and the curing agent in the sheet-like resin composition, which can lead to an excessive amount of high molecular weight components, thus improving handling properties. When the area ratio M of low molecular weight components is 85.0% or less, it is possible to suppress an excessive amount of low molecular weight components in the sheet-like resin composition, which can cause dendritic defects, and it is easier to suppress the precipitation and / or recrystallization of low molecular weight components in the sheet-like resin composition during low-temperature storage, thus making it easier to suppress the occurrence of appearance defects (dendritic defects).

[0031] Furthermore, sheet-like resin compositions with a high area ratio M of low molecular weight components can be said to contain a large amount of monomer components that are highly crystalline and have low solvent solubility. As a result, these sheet-like resin compositions are prone to surface defects (dendritic defects) during low-temperature storage, resulting in not only low low-temperature storage stability but also reduced flexibility and handling properties. On the other hand, sheet-like resin compositions with a low area ratio M of low molecular weight components can be said to contain a large amount of high molecular weight components. Since high molecular weight components are more flexible than monomer components, the sheet-like resin composition becomes more flexible and has good handling properties.

[0032] The area percentage M of low molecular weight components is more preferably 16.0% or more, even more preferably 20.0% or more, even more preferably 25.0% or more, particularly preferably 30.0% or more, particularly more preferably more than 30.1%, more preferably 84.0% or less, and even more preferably 82.0% or less. When the area percentage M of low molecular weight components is within the above range, the handling properties and low-temperature storage stability of the sheet-like resin composition can be more effectively improved. The low molecular weight components are thought to mainly include monomers and oligomers of epoxy resins and curing agents, and low molecular weight impurities.

[0033] The method for measuring the area ratio M of low molecular weight components is as follows: Prepare a sheet-like resin composition for measurement, pre-treat the sheet-like resin composition according to the following procedure, and then perform gel permeation chromatography (GPC) measurement under the following measurement conditions.

[0034] - The pre-treated sheet-like resin composition is dissolved in tetrahydrofuran (THF) with 0.1% by mass of toluene added as an internal standard to obtain a 0.1% by mass solution, which is then filtered through a 0.45 μm filter to be used as the measurement solution. - Measurement conditions Column: TSKgel G4000HXL (7.8 mm I.D. × 300 mm × 1 tube), TSKgel G2000HXL (7.8 mm I.D. × 300 mm × 1 tube) Eluent: THF Flow rate: 1.0 mL / min Detector: UV detector UV-8320 Detection wavelength: 254 nm Column temperature: 40°C Injection volume: 10 μL Molecular weight standard: Standard polystyrene

[0035] From the molecular weight distribution curve obtained in the gel permeation chromatography analysis described above, the area percentage M (%) of the range where the polystyrene-equivalent molecular weight is between 120 and 600 is calculated, with the total peak area of ​​the molecular weight distribution curve being set to 100%. The relative retention time (Rrt) of each peak is calculated as (retention time of peak) ÷ (retention time of toluene) × 20.8.

[0036] The sheet-like resin composition is further preferably satisfied with the following formula (2): 10.0 ≤ S ２ ×M １／２ ×T １／２ ≤300 ... (2) Here, T is the thickness (μm) of the sheet-like resin composition. Note that S and M in formula (2) are the same as S and M in formula (1) above. That is, S is the solvent content (mass%), and M is the area percentage (%) of the range in which the polystyrene-equivalent molecular weight is between 120 and 600, when the total peak area is set to 100% in the molecular weight distribution curve obtained by GPC measurement of the sheet-like resin composition.

[0037] When the sheet-like resin composition satisfies the above formula (2), handling properties and low-temperature storage stability are more easily improved. ２ ×M １／２×T １／２ is preferably 12.0 or more, more preferably 15.0 or more, still more preferably 18.0 or more, preferably 200 or less, more preferably 150 or less, still more preferably 138 or less, even more preferably 120 or less, and particularly preferably 100 or less.

[0038] The "sheet-like resin composition" in the present disclosure is a sheet-like resin composition containing an epoxy resin, a phenolic curing agent, inorganic particles, and a solvent, which has fluidity when heated and pressurized, and includes an uncured sheet-like resin composition (also referred to as a "sheet-like resin composition in the A stage"). For example, after a liquid resin composition containing a solvent is applied in a sheet form onto a substrate or the like, a part of the solvent is removed by evaporation or the like to obtain an uncured (A stage) sheet-like resin composition.

[0039] The substrate is preferably in the form of a film, and a general polymer film can be used. Examples of the polymer film include polyolefin films such as polyethylene films and polypropylene films, vinyl films such as polyvinyl chloride films, polyester films such as polyethylene terephthalate films, polycarbonate films, acetyl cellulose films, and tetrafluoroethylene films. The thickness of the substrate is not particularly limited, but from the viewpoint of excellent workability and drying properties, 20 to 200 μm is preferable.

[0040] (Filling ratio of inorganic particles) The ratio of inorganic particles in 100% by mass of the solid content of the sheet-like resin composition (which may be referred to as the "filling ratio of inorganic particles") is preferably 40% by mass or more, and the thermal conductivity of the sealing member obtained by curing the sheet-like resin composition can be made sufficiently high. The lower limit of the filling ratio of inorganic particles is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, and particularly preferably 80% by mass or more. By setting the filling ratio of inorganic particles to be not less than the above lower limit value, the thermal conductivity of the sealing member can be further increased.

[0041] The upper limit of the inorganic particle filling rate is preferably 99% by mass or less, which allows for the creation of a sheet-like resin composition with good sealing properties. The inorganic particle filling rate is preferably 95% by mass or less, more preferably 92% by mass or less, even more preferably 90% by mass or less, and even more preferably 88% by mass or less. By setting the inorganic particle filling rate to or below the above upper limit, the sealing properties of the sheet-like resin composition can be further improved.

[0042] In this disclosure, the solid content of a sheet-like resin composition refers to the solid content remaining after heating the sheet-like resin composition at 150°C for 10 minutes, excluding components that evaporate or volatilize upon heating, such as solvents. Even components that are liquid at 25°C are included in the solid content if they remain in the sheet-like resin composition after heating.

[0043] The packing density of inorganic particles can be determined, for example, by the following method. First, the sheet-like resin composition is heated to remove volatile components such as solvents, and then the mass of the sheet-like resin composition (corresponding to the mass of "solids") is measured. Next, epoxy resin and other components contained in the sheet-like resin composition are removed, for example, by dissolving them in an organic solvent or by thermal decomposition by heating to a temperature of 500°C or higher, thereby separating only the inorganic particles from the sheet-like resin composition, and the mass of these inorganic particles is measured. The packing density of inorganic particles can then be calculated using these measurement results. Alternatively, the packing density of inorganic particles can also be calculated from the amount of sheet-like resin composition used.

[0044] (Thickness T of the sheet-like resin composition) The thickness T of the sheet-like resin composition is preferably 100 μm or more and 1000 μm or less (0.10 mm or more and 1.00 mm or less). If the thickness is 100 μm (0.10 mm) or more, it is possible to suppress the partial exposure of the IC chip and the occurrence of irregularities on the surface when encapsulating the IC chip. If the thickness is 1000 μm (1.00 mm) or less, the heating time required for sufficient curing can be shortened, and a sheet-like resin composition in which inorganic particles are uniformly dispersed can be obtained.

[0045] The thickness T of the sheet-like resin composition is preferably 130 μm or more, more preferably 150 μm or more, even more preferably 200 μm or more, particularly preferably more than 200 μm, preferably 900 μm or less, more preferably 700 μm or less, even more preferably 500 μm or less, even more preferably 400 μm or less, and particularly preferably 350 μm or less. When the thickness of the sheet-like resin composition is within the above range, the handling properties and low-temperature storage stability of the sheet-like resin composition are more easily improved. In addition, when the sheet-like resin composition is heated and pressurized during sealing, the inorganic particles (especially particles with small particle sizes) and epoxy resin flow more uniformly, and voids are less likely to occur after sealing and curing. Furthermore, when the sheet-like resin composition is stored in the atmosphere, aggregation and sedimentation of inorganic particles (especially particles with small particle sizes) caused by evaporation of solvent from the surface are less likely to occur, and the sealing properties are more easily maintained over a long period of time.

[0046] The thickness T of the sheet-like resin composition can be measured, for example, using a micrometer (Mitutoyo Corporation, PMU150-25MX). For example, in the case of a sheet-like resin composition on a PET substrate, the total thickness of the PET substrate and the sheet-like resin composition, and the thickness of the PET substrate can be measured separately, and the thickness can be calculated by subtracting the thickness of the PET substrate from the total thickness. It is preferable to measure the thickness T at three or more locations and obtain the average value. Specifically, it can be obtained, for example, by the method described in the examples.

[0047] Next, the inorganic particles, epoxy resin, phenolic curing agent, and solvent that constitute the sheet-like resin composition will be described in detail.

[0048] [Inorganic Particles] The inorganic particles according to this embodiment have the following characteristics.

[0049] As inorganic particles, ceramic particles consisting of silica, alumina, aluminum nitride, boron nitride, silicon nitride, silicon carbide, etc. are preferred. Since ceramics have high thermal conductivity, using ceramic particles can improve the heat dissipation performance of the sealing member formed from the sheet-like resin composition. Furthermore, when insulating ceramic particles are used as inorganic particles, short circuits of the sealed IC chip and the like can be suppressed. For this reason, the inorganic particles are more preferably insulating ceramic particles, and more specifically, one or more selected from the group consisting of alumina particles and silica particles are more preferable. Among these, alumina particles are particularly preferred from the viewpoint of thermal conductivity.

[0050] (Average roundness of inorganic particles) From the viewpoint of fluidity with epoxy resin, the inorganic particles are preferably spherical particles, and their average roundness is preferably 0.80 or higher, more preferably 0.90 or higher, even more preferably 0.93 or higher, and usually 1.00 or lower, preferably 0.99 or lower, and more preferably 0.98 or lower. When the average roundness of the inorganic particles is within the above range, it is easier to increase the inorganic filling rate, sedimentation in the sheet-like resin composition is less likely to occur, and dispersibility is improved, so that appearance defects are less likely to occur and good sealing performance can be achieved. In particular, when the thickness of the sheet-like resin composition is within the above range, the inorganic particles (especially particles with small particle diameters) and the epoxy resin flow uniformly when heated and pressurized, and voids are less likely to occur after curing. In addition, when the average roundness of the inorganic particles is high, the kneadability with epoxy resin is also good, which has the effect of increasing the fluidity of the liquid resin composition after kneading and making it easier to mold into a sheet.

[0051] Roundness (SPHT) can be analyzed in accordance with ISO 9276-6. SPHT = 4πA / P ２The average roundness of inorganic particles is determined from the following equation. In the equation, A is the measured area of ​​the projected particle image, and P is the measured perimeter of the particle projection image. The average roundness of inorganic particles is measured using a measuring device based on the principle of dynamic image analysis in accordance with ISO 13322-2 (for example, CAMSIZER X2 (manufactured by VERDER Scientific)). The measurement of the average roundness of inorganic particles in a sheet-like resin composition can be performed by removing the epoxy resin etc. contained in the sheet-like resin composition by dissolving it with an organic solvent, heating it to a temperature of 500°C or higher to cause thermal decomposition, etc., separating only the inorganic particles, and using those inorganic particles.

[0052] Another method for determining the average roundness of inorganic particles is to use image analysis. For a sheet-like resin composition, cross-sectional observation can be performed using a scanning electron microscope (SEM), and all inorganic particles contained within a predetermined observation area (e.g., 200 μm × 200 μm) can be image-analyzed. Based on the measurement results of their roundness, the average roundness can be calculated.

[0053] (Particle size of inorganic particles) The inorganic particles have a particle size D50 of 50% of the cumulative particle size distribution from the finest particle side based on volume, for example, 10 μm or less. Normally, if the particle size of inorganic particles is small, aggregation occurs and they tend to settle in the sheet-like resin composition, which tends to worsen the sealing performance of the sheet-like resin composition. However, in the sheet-like resin composition of this disclosure, good sealing performance can be achieved even if the particle size D50 of the inorganic particles is 10 μm or less. The D50 of the inorganic particles in this disclosure is preferably less than 6.0 μm, more preferably 5.0 μm or less, even more preferably 3.0 μm or less, preferably 0.5 μm or more, more preferably 0.7 μm or more, even more preferably 1.0 μm or more, and particularly preferably 1.5 μm or more. When the D50 of the inorganic particles in this disclosure is within the above range, good dispersibility in the epoxy resin can be achieved, making it easier to prevent defects in the appearance of the sheet-like resin composition and further improving sealing performance.

[0054] The particle size D50 of inorganic particles can be determined, for example, by measuring the particle size distribution of inorganic particles using the laser diffraction method with a Microtrac MT3300EXII laser particle size distribution analyzer manufactured by Microtrac Bell Co., Ltd. The particle size measurement of inorganic particles in a sheet-like resin composition can be performed by removing the epoxy resin and other components contained in the sheet-like resin composition, for example by dissolving them with an organic solvent or by thermal decomposition by heating them to a temperature of 500°C or higher, separating only the inorganic particles, and then using those inorganic particles.

[0055] (BET specific surface area of ​​inorganic particles) The BET specific surface area of ​​inorganic particles measured by the nitrogen adsorption method is preferably 0.2 m². ２ / g or more 10m ２ It is less than or equal to / g, and more preferably 0.2m ２ / g or more 5.0m ２ / g or less, more preferably 0.3m ２ / g or more 3.0m ２ / g or less, more preferably 0.35m ２ / g or more 1.0m ２ It is less than or equal to / g. When the BET specific surface area of ​​the inorganic particles is within the above range, it is easier to prevent defects in the appearance of the sheet-like resin composition and the fluidity can be improved, resulting in good sealing properties of the resulting sheet-like resin composition. Furthermore, from the viewpoint of improving the handling properties of the sheet-like resin composition, the BET specific surface area of ​​the inorganic particles is 0.35 m². ２ / g or more, 0.98m ２ It may be less than / g.

[0056] The BET specific surface area is measured in accordance with JIS-Z8830 (2013). If inorganic particles are present in the sheet-like resin composition, the epoxy resin and other components in the composition can be removed by dissolving them in an organic solvent, heating them to a temperature of 500°C or higher to thermally decompose the resin, and the inorganic particles can be separated. The specific surface area can then be measured using these inorganic particles.

[0057] The inorganic particles may be surface-treated with a silane coupling agent. This can improve the compatibility between the inorganic particles and the epoxy resin. The silane coupling agent may be one or more types.

[0058] Known silane coupling agents can be used. In one embodiment of the present invention, the silane coupling agent may be represented by the following chemical formula (A): X ３－ｎ Me ｎ -Si-Y...(A) (wherein Me is a methyl group, X is a hydrolyzable group, Y is a monovalent organic group, and n is 0, 1, or 2)

[0059] In chemical formula (A), X (hydrolyzable group) can be, for example, a methoxy group (CH ３ O-), ethoxy group (CH ３ CH ２ O-), propoxy group (CH ３ CH ２ CH ２ O-), isopropoxy group ((CH ３ ) ２ CHO-), chloro group, or 2-methoxyethoxy group (CH ３ OCH ２ CH ２ Examples include O-). n is preferably 0 or 1, and more preferably 0.

[0060] In chemical formula (A), Y is a monovalent organic group. Y is preferably a C1-C20 alkyl group which may have vinyl, epoxy, phenyl, styryl, methacrylic, acrylic, amino, ureido, mercapto, isocyanate, etc., at its terminals. Part of the carbon skeleton may be substituted with -O-, -NH-, -S-, -CO-, -COO- as long as they are not adjacent. Among these, unsubstituted C1-C20 alkyl groups having vinyl, phenyl, or epoxy groups are more preferred. Unsubstituted C1-C20 alkyl groups are particularly preferred. This improves the compatibility between inorganic particles and epoxy resin and suppresses the occurrence of appearance defects.

[0061] In chemical formula (A), Y is preferably a linear alkyl group having 1 to 20 carbon atoms, more preferably 2 or more carbon atoms, and even more preferably 5 or more carbon atoms. This makes it easier to obtain the effect of suppressing aggregation between inorganic particles due to steric hindrance of the silane coupling agent.

[0062] Silane coupling agents include those represented by the above chemical formula (A), as well as tetraalkoxysilanes, silazane compounds, and the like.

[0063] Examples of silane coupling agents include: tetraalkoxysilanes such as tetramethoxysilane; long-chain alkylalkoxysilanes such as decyltrimethoxysilane (the number of carbon atoms in the alkyl group is, for example, 5 to 16, preferably 8 to 12); alkenyl group-containing silane coupling agents such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltrichlorosilane, and 7-octenyltrimethoxysilane (especially vinyl group-containing silane coupling agents); epoxy group-containing silane coupling agents such as 8-glycidoxyoctyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropylethoxysilane; mercapto group- or polysulfide-containing silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and bis(triethoxysilylpropyl)tetrasulfide; amino group-containing silane coupling agents such as 3-aminopropyltriethoxysilane, N-2(aminoethyl)3-aminopropylmethyldimethoxysilane, N-2(aminoethyl)3-aminopropyltrimethoxysilane, N-2(aminoethyl)3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-ditylidene)propylamine, and hydrochloride salts of N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane; aromatic alkoxysilanes having aromatic hydrocarbon groups with 6 to 10 carbon atoms, such as N-phenyl-3-aminopropyltrimethoxysilane, phenyltrimethoxysilane, 2-phenylethyltrimethoxysilane, and 2,2-diphenylethyltrimethoxysilane; silazane compounds such as hexamethyldisilazane; styryl group-containing silane coupling agents such as p-styryltrimethoxysilane; Silane coupling agents containing (meth)acryloyl groups, such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane;Silane coupling agents containing ureido groups, such as 3-ureidopropyltriethoxysilane; chloroalkylalkoxysilanes, such as 3-chloropropyltrimethoxysilane; and silane coupling agents containing isocyanate groups, such as 3-isocyanatetopropyltriethoxysilane, can be used.

[0064] The mass ratio of the inorganic particles (g) to the silane coupling agent (g) in the sheet-like resin composition is preferably 1:0.0005 to 1:0.03, more preferably 1:0.001 to 1:0.02, and even more preferably 1:0.0015 to 1:0.01. This makes it easier to further improve the compatibility between the inorganic particles and the epoxy resin. When the above mass ratio is above the lower limit, the surface modification properties of the inorganic particles tend to improve, and the compatibility with the epoxy resin tends to improve. When the above mass ratio is below the upper limit, the self-condensation of hydrolyzable groups remaining without bonding to the surface of the inorganic particles is suppressed, thereby suppressing aggregation of the inorganic particles. This makes it easier to further improve the compatibility between the inorganic particles and the epoxy resin. Furthermore, it becomes easier to obtain a sheet-like resin composition with a good appearance.

[0065] [Epoxy Resin] In this embodiment, the sheet-like resin composition contains an epoxy resin. The epoxy resin may be a single type or two or more types. Examples of epoxy resins include bisphenol A type epoxy resin, bisphenol AP type epoxy resin, bisphenol AF type epoxy resin, bisphenol B type epoxy resin, bisphenol BP type epoxy resin, bisphenol C type epoxy resin, bisphenol E type epoxy resin, bisphenol F type epoxy resin, bisphenol G type epoxy resin, bisphenol M type epoxy resin, bisphenol S type epoxy resin, bisphenol P type epoxy resin, bisphenol PH type epoxy resin, bisphenol TMC type epoxy resin, bisphenol Z type epoxy resin, bisphenol S type epoxy resin such as hexanediol bisphenol S diglycidyl ether, novolacphenol type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, bixylenol type epoxy resin such as bixylenol diglycidyl ether, hydrogenated bisphenol A type epoxy resin such as hydrogenated bisphenol A glycidyl ether, and their dibasic acid modified diglycidyl ether type epoxy resins, aliphatic epoxy resins, and phenylcyclohexyl type epoxy resins. Preferred epoxy resins include phenylcyclohexyl epoxy resins, naphthalene epoxy resins, biphenyl epoxy resins, bisphenol A epoxy resins, and bisphenol F epoxy resins. Furthermore, from the viewpoint of thermal conductivity, epoxy resins having mesogenic groups (sometimes referred to as mesogenic epoxy resins) are more preferred among these, and even more preferred are epoxy resins having mesogenic groups that exhibit a phase transition temperature in the temperature range of 100°C to 200°C during sealing and exhibit liquid crystalline properties.The total amount of phenylcyclohexyl epoxy resin, naphthalene epoxy resin, phenol epoxy resin, biphenyl epoxy resin, bisphenol A epoxy resin, and bisphenol F epoxy resin in 100% by mass of epoxy resin is preferably 95 to 100% by mass, more preferably 98 to 100% by mass, and even more preferably 100% by mass, and among these, it is preferable that the amount of epoxy resin having a mesogenic group satisfies the above range.

[0066] The amount of epoxy resin (total amount if multiple types are included) in 100% by mass of the solid content of the sheet-like resin composition layer is preferably 5% by mass or more and 20% by mass or less, more preferably 7% by mass or more and 18% by mass or less, and even more preferably 8% by mass or more and 16% by mass or less.

[0067] [Phenol-based curing agent] By using a phenol-based curing agent (phenol resin-based curing agent) as the curing agent for sheet-like resin compositions, the reaction rate between the curing agent and the epoxy resin in low-temperature environments can be further suppressed. By using a phenol-based curing agent, sheet-like resin compositions suitable for long-term storage at low temperatures can be manufactured.

[0068] The phenolic curing agent included in the sheet-like resin composition is not particularly limited, but a phenolic resin having two or more phenolic groups in one molecule that are reactive with the glycidyl groups of the epoxy resin is preferred. One type of phenolic curing agent may be used alone, or two or more types may be used in combination. Known phenolic curing agents can be used, and commercially available products can be used.

[0069] Suitable phenolic resins as phenolic curing agents include, for example, resins obtained by condensing or co-condensing phenols such as phenol, cresol, xylenol, resorcinol, catechol, bisphenol A and bisphenol F, naphthols such as α-naphthol, β-naphthol and dihydroxynaphthalene, and aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde and salicylaldehyde under an acidic catalyst; biphenyl skeleton phenolic resins; paraxylylene-modified phenolic resins; metaxylylene / paraxylylene-modified phenolic resins; melamine-modified phenolic resins; terpene-modified phenolic resins; dicyclopentadiene-modified phenolic resins; cyclopentadiene-modified phenolic resins; polycyclic aromatic ring-modified phenolic resins; novolac-type phenolic resins; phenol aralkyl resins; allylphenolic resins; and xylylene-modified naphthol resins. In particular, phenols such as bisphenol A and bisphenol F, biphenyl skeleton-type phenol resins, novolac-type phenol resins, phenol aralkyl resins, or allylphenol resins are preferred, and the use of novolac-type phenol resins, phenol aralkyl resins, or allylphenol resins is more preferred. Examples of novolac-type phenol resins include phenol novolac, catechol novolac, resorcinol novolac, o-cresol novolac, m-cresol novolac, and p-cresol novolac.

[0070] Examples of commercially available phenolic resins include Phenolite LF2882, Phenolite LF2822, Phenolite TD-2090, Phenolite TD-2131, Phenolite TD-2149, Phenolite VH-4150, and Phenolite VH4170 from DIC Corporation; PAPS-PN from Asahi Organic Chemicals Co., Ltd.; XLC-LL and XLC-4L from Mitsui Chemicals, Inc.; SN-100, SN-180, SN-300, SN-395, and SN-400 from Nippon Steel & Sumitomo Metal Chemicals, Ltd.; TrisP-HAP, TrisP-PA, TriP-PHBA, CyRS-PRD4, and MTPC from Honshu Chemical Industry Co., Ltd.; MEHC-7851 from Meiwa Chemicals, Inc.; and LVA from Gun-ei Chemical Industry Co., Ltd.

[0071] The equivalent ratio (phenolic hydroxyl group / glycidyl group (molar ratio)) of the phenolic resin curing agent to the epoxy resin is preferably 0.3 to 1.5, more preferably 0.4 to 1.0, and even more preferably 0.5 to 1.0, from the viewpoint of excellent curability, adhesion, and storage stability of the sheet-like resin composition. When the equivalent ratio is within the above range, the sealing properties and adhesive strength of the sheet-like resin composition tend to improve, the water absorption rate is kept low, and the insulation reliability tends to improve further.

[0072] In one embodiment of the present invention, the content of the phenolic curing agent in the sheet-like resin composition is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 7% by mass or less, and particularly preferably 6% by mass or less, based on 100% by mass of the solid content of the sheet-like resin composition. When the content of the phenolic curing agent is within the above range, a sheet-like resin composition suitable for long-term storage at low temperatures can be produced.

[0073] [Solvent] As described above, the sheet-like resin composition according to one embodiment of the present invention always contains a solvent. Because the sheet-like resin composition of this disclosure contains a solvent, it is easily fluid, can be easily deformed to conform to the fine structure of IC chips and substrates, and can seal dense structures without gaps. In one embodiment of the present invention, the solvent has a molecular weight of 500 or less, a boiling point of 250°C or less, and is liquid from -40°C to 30°C. The boiling point of the solvent is preferably 200°C or less, more preferably 180°C or less, even more preferably 160°C or less, preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher. When the boiling point of the solvent is within the above range, the reaction between the epoxy resin and the phenolic curing agent can be suppressed and effectively removed during drying when the sheet-like resin composition is formed into a sheet, and the sheet-like resin composition can be stored at low temperatures for a long period of time.

[0074] Any known solvent can be used, and it is not limited to any solvent that can dissolve epoxy resin. Examples include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, amine-based solvents, amide-based solvents, halogen-based solvents, hydrocarbon-based solvents, and nitrile-based solvents. From the viewpoint of being a good solvent for epoxy resin and having excellent coatability of the resulting resin composition, it is preferable that the resin composition contains one or more solvents selected from the group consisting of ketone-based solvents and ester-based solvents.

[0075] Examples of ketone-based solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone. Examples of ester-based solvents include methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, n-propyl acetate, amine acetate, and sec-butyl acetate. Preferably, the solvent includes one or more selected from the group consisting of methyl ethyl ketone, cyclopentanone, and cyclohexanone. These solvents are liquid at the storage temperature of the sheet-like resin composition (-20°C).

[0076] [Other Additives] The sheet-like resin composition may, if necessary, contain known additives such as plasticizers, curing accelerators, coupling agents, fillers, pigments, flame retardants, antioxidants, surfactants, compatibilizers, weathering agents, antiblocking agents, antistatic agents, leveling agents, and mold release agents, either alone or in combination of two or more, as long as they do not impair the effects of the invention.

[0077] In one embodiment of the present invention, the sheet-like resin composition may further contain a curing accelerator. The curing accelerator may be included alone or in combination of two or more types. The curing accelerator may include one or more curing accelerators selected from the group consisting of phosphorus-based curing accelerators and imidazole-based curing accelerators. Examples of phosphorus-based curing accelerators include triphenylphosphine (TPP). Examples of imidazole-based curing accelerators include 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole, and commercially available products include "Cureazole® 2E4MZ-CN" and "Cureazole® 2PHZ-PW" manufactured by Shikoku Chemicals, Inc. Phosphorus-based and imidazole-based curing accelerators make it easier to control the area ratio M of low molecular weight components within a predetermined range, and can more effectively improve the handling properties and low-temperature storage stability of the sheet-like resin composition.

[0078] In one embodiment of the present invention, the content of the curing accelerator in the sheet-like resin composition (total amount if multiple types are included) is preferably 0.01% by mass or more and 1.00% by mass or less, based on 100% by mass of the solid content of the sheet-like resin composition. The content of the curing accelerator is more preferably 0.05% by mass or more, even more preferably 0.10% by mass or more, preferably 0.80% by mass or less, and even more preferably 0.50% by mass or less, based on 100% by mass of the solid content of the sheet-like resin composition. When the content of the curing accelerator in the sheet-like resin composition is within the above range, it is easier to control the reaction between the sheet-like resin composition and the curing agent, and it is easier to adjust the area ratio M of the low molecular weight component to a predetermined range, thereby more effectively improving the handling properties and low-temperature storage stability of the sheet-like resin composition.

[0079] [Method for Manufacturing Sheet-Like Resin Compositions] In one example of a method for manufacturing sheet-like resin compositions, first, epoxy resin, a phenolic curing agent, inorganic particles, and a solvent are mixed, and the resulting mixture is applied to a substrate. Then, the applied mixture is dried under specific drying conditions to remove part of the solvent, thereby obtaining a sheet-like resin composition.

[0080] Known phenolic curing agents can be used. If necessary, known additives such as plasticizers, curing accelerators, coupling agents, fillers, pigments, flame retardants, antioxidants, surfactants, compatibilizers, weathering agents, antiblocking agents, antistatic agents, leveling agents, and mold release agents may be added individually or in combination of two or more, as long as they do not impair the effects of the invention. In particular, it is preferable to add one or more curing accelerators selected from the group consisting of phosphorus-based curing accelerators and imidazole-based curing accelerators.

[0081] The mixing method is not particularly limited, and mills, mixers, stirring blades, etc., can be used. The method of applying the mixture is not particularly limited, but coating equipment such as comma coaters, lip coaters, roll coaters, gravure coaters, die coaters, and spin coaters can be used.

[0082] Drying is preferably carried out by heating, for example, with a heating temperature of 50 to 120°C and a heating time of 10 to 30 minutes. In this disclosure, from the viewpoint of facilitating the production of a sheet-like resin composition satisfying the above formula (1), it is preferable to carry out heating by a combination of multiple steps with different heating temperatures and heating times, and it is more preferable that the heating temperature increases and the heating time increases with each step. It is preferable that there are two heating steps, with the first step being a heating temperature of 50 to 70°C and a heating time of 7 to 12 minutes, and the second step being a heating temperature of 80 to 120°C and a heating time of 10 to 20 minutes. In one embodiment of the present invention, the first step is 65°C for 10 minutes, and the second step is 100°C for 15 minutes.

[0083] The heating rate in the drying process is preferably 20 to 40°C / min until the temperature is 10 to 20°C lower than the target drying temperature (final temperature reached). More preferably, the heating rate is 22 to 38°C / min, and even more preferably 25 to 35°C / min. When the heating rate is within the above range, the productivity of the sheet-type resin composition is excellent, the reactivity of the sheet-type resin composition and solvent evaporation can be easily controlled, and the solvent content S and the area ratio M of low molecular weight components can be adjusted to a preferred range. The drying method is not particularly limited and may be carried out by known methods. For example, drying by known dryers or hot plates can be used.

[0084] After the drying process, it is preferable to store the sheet-like resin composition for a while in a temperature environment of 0°C to 25°C, from the viewpoint of making it easier to uniformize the area ratio M of low molecular weight components and the solvent content S within the sheet-like resin composition. Storage in the above temperature environment is preferably 30 minutes to 5 hours, more preferably 1 hour to 2 hours. After storage in the above temperature environment, it is preferable to store the sheet-like resin composition in a low temperature environment (for example, -20°C), from the viewpoint of suppressing the reaction of the epoxy resin in the sheet-like resin composition and preventing the solvent content S from decreasing too much.

[0085] [Method for Manufacturing Inorganic Particles] The method for manufacturing inorganic particles used in this embodiment will be explained using alumina particles as an example.

[0086] (Alumina raw material) Alumina raw material is produced by known methods. Examples include the Bayer process, ammonium alum process, ammonium aluminum carbonate hydroxide process (AACH process), solvent extraction method, organoaluminum hydrolysis method (aluminum alkoxide process), CZ process, Bernoulli process, Chiroporous process, Bridgman process, EFG process, and other melt growth methods.

[0087] In the Bayer process, raw alumina can be produced by calcining aluminum hydroxide obtained from bauxite. Furthermore, the ammonium alum method, AACH method, solvent extraction method, and aluminum alkoxide method are preferable because they can produce high-purity raw alumina.

[0088] (Grinding of raw alumina) In order to easily obtain alumina particles of the desired size by the flame melting method, the raw alumina is ground to obtain alumina raw material powder for flame melting. The raw alumina can be ground using known methods such as a vibratory mill, bead mill, ball mill, or jet mill, and may be ground in either a dry or wet state.

[0089] In the above grinding process, a surface protectant may be used. The surface protectant not only protects the surface of the alumina raw material powder after grinding, but may also have the function of inactivating the surface of the alumina raw material powder. Because the surface protectant reduces aggregation of alumina raw material powders due to its surface inactivation function, it is suitable for obtaining alumina particles of a target particle size after flame melting using raw material alumina with a high BET specific surface area that is prone to aggregation. Suitable surface protectants include, for example, monohydric alcohols such as methanol, ethanol, 1-propanol, and 2-propanol; glycols such as ethylene glycol, polyethylene glycol, propylene glycol, and polypropylene glycol; amines such as triethanolamine; and higher fatty acids such as palmitic acid, stearic acid, and oleic acid. One of these surface protectants may be used alone, or two or more may be used in combination. Of these, glycols are preferred, and one or more of ethylene glycol, polyethylene glycol, propylene glycol, and polypropylene glycol are particularly preferred.

[0090] Polyethylene glycol and polypropylene glycol, which are preferably used as surface protective agents, do not have any particular restrictions on their molecular weight, but liquid forms with an average molecular weight of about 200 to 600 are preferred for ease of addition.

[0091] The amount of surface protective agent added is preferably 0.01 parts by mass or more when the raw material alumina is 100 parts by mass, in order to allow the surface protective agent to exert its full effect. However, if the amount of surface protective agent added is too large, the effect of the surface protective agent will saturate, so it is preferable to add 10 parts by mass or less. The amount of surface protective agent added is more preferably 0.05 to 8 parts by mass, and even more preferably 0.1 to 5 parts by mass.

[0092] (Flame Melting) The flame melting method is preferred as a method for producing alumina particles having a desired average roundness. The flame melting method is a method in which raw material alumina is sprayed into a flame, liquefied, and then cooled and solidified. In the flame melting method, the temperature of the flame melting furnace is preferably 1000°C or higher. In the flame melting method, the raw material supply rate can be adjusted as appropriate, but it is preferably 50 kg / hour or less, and more preferably 10 kg / hour or less. By setting the amount of thermal energy applied to the alumina particles within a predetermined range, it becomes easier to obtain alumina particles that satisfy the above-mentioned predetermined requirements.

[0093] The alumina particles after flame melting are collected by a cyclone or bag filter and classified as necessary. After classification, it is preferable to immerse the obtained alumina particles in an acidic solution such as hydrochloric acid. The surface of the alumina particles is modified, H ２ O ５５０－９００℃ The concentration can be adjusted to the desired value. Hydrochloric acid is preferred as the type of acidic solution to be used due to the ease of concentration adjustment. The concentration of the acidic solution is preferably 1 M to 12 M, more preferably 1 M to 10 M, and even more preferably 2 M to 5 M. The preferred mass ratio of alumina particles to acidic solution is alumina particles:acidic solution = 1:2 to 1:10. The preferred immersion time is 5 hours or more. The immersion time can be shortened by heating the acidic solution. The temperature of the heated acidic solution is, for example, 50 to 90°C. After immersion in the acidic solution, the alumina particles are washed and dried.

[0094] [Preparation of Inorganic Particles] The inorganic particles to be used in the examples and comparative examples were prepared as follows.

[0095] - Alumina particles A: As a raw material, high-purity metallic aluminum obtained by the method described in Japanese Patent Application Publication No. 2010-106329 was prepared. After obtaining aluminum hydroxide from metallic aluminum by the aluminum alkoxide method described in Japanese Patent Application Publication No. 2018-048060, the aluminum hydroxide was calcined to obtain the alumina raw material.

[0096] Next, using a jet mill grinder (horizontal jet mill grinder PJM-280SP manufactured by Nippon Pneumatic Mfg. Co., Ltd.), the raw material alumina was processed under the conditions of a supply rate of 30 kg / hour and a gauge pressure of 0.5 MPa at the air supply port during grinding, to obtain alumina raw material particles with an average particle diameter of approximately 2 μm for the secondary particles.

[0097] The obtained alumina raw material particles were introduced into a flame melting furnace and melted to obtain spherical alumina particles. The ambient temperature inside the flame melting furnace was set to 1250°C, and the raw material supply rate was set to 5 kg / hour. The obtained alumina particles were recovered using a cyclone and subjected to classification by cyclone classification to remove particles larger than 5 μm, thereby obtaining alumina particles (D50 = 2.3 μm). In this example, the D50 of the alumina particles was measured by laser diffraction using a Microtrac MT3300EXII laser particle size distribution analyzer manufactured by Microtrac-Bell Co., Ltd.

[0098] The obtained alumina particles were immersed in 2M hydrochloric acid. The mass ratio of alumina particles to hydrochloric acid was alumina particles:hydrochloric acid = 1:5, the hydrochloric acid temperature was 80°C, and the immersion time was 12 hours. After immersion in hydrochloric acid, the alumina particles were washed by immersing them in water multiple times. For this washing, the alumina particles and water were placed in a container, and all the water was replaced each time, repeating until the water used for washing became neutral. After washing was completed, the alumina particles were removed from the container and allowed to stand at 80°C for 6 hours to dry. The specific surface area of ​​the obtained alumina particles was 0.95 m². ２ The weight was / g, and the average roundness was 0.94.

[0099] A slurry was prepared by mixing 50 g of the obtained alumina particles with 20 g of isopropanol. To the prepared slurry, 0.5% by mass of the silane coupling agent KBM-3103 (manufactured by Shin-Etsu Chemical Co., Ltd.) relative to the alumina particles, and 0.02 g of formic acid were added, and the mixture was stirred for 30 minutes. Then, 0.2 g of 10% by mass aqueous ammonia was added, and the mixture was stirred for 60 minutes. The stirred slurry was heated at 120°C for 3 hours to remove the solvent, thereby obtaining silane-coupled alumina particles A. The obtained alumina particles A had a D50 of 2.3 μm and a specific surface area of ​​0.95 m².２ The weight was / g, and the average roundness was 0.94.

[0100] • Alumina particles B: Alumina particles manufactured by Denka Co., Ltd., DAW-01 (average particle size (D50): 1.9 μm, specific surface area: 1.0 m²) ２ Except for changing the concentration to / g, alumina particle B was obtained by silane coupling treatment in the same manner as alumina particle A.

[0101] • Silica particles A: AdmaFine SO-E5 manufactured by Admatex Co., Ltd. (average particle size (D50): 1.5 μm, specific surface area: 4.5 m²) ２ A slurry was prepared by mixing 50 g of ( / g) with 20 g of isopropanol. 0.5% by mass of KBM-403 (a silane coupling agent with epoxy groups, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to the prepared slurry, and the mixture was stirred at room temperature for 5 minutes using an evaporator. Then, the isopropanol was evaporated under reduced pressure. After leaving the silane-coupled silica particles at room temperature for 24 hours, silica particles A were obtained by further heating them at 120°C for 24 hours using a drying oven.

[0102] • Silica particles B: Silica particles are made using AdmaFine SO-E1 manufactured by Admatex Co., Ltd. (average particle diameter (D50): 0.3 μm, specific surface area: 10.0 m²). ２ Silica particles B were obtained in the same manner as silica particles A, except that the amount was changed to ( / g) and the amount of KBM-403 added was changed to 1.0 mass%.

[0103] Furthermore, the average roundness of alumina particle A, alumina particle B, silica particle A, and silica particle B was all 0.90 or higher.

[0104] (Measurement of average roundness) The average roundness of inorganic particles was measured using a CAMSIZER X2 (manufactured by VERDER Scientific) based on the principle of dynamic image analysis in accordance with ISO 13322-2.

[0105] (Measurement of Specific Surface Area) The specific surface area of ​​inorganic particles was measured as follows. A Shimadzu FlowSorb III 2310 was used as the specific surface area measuring device, and the nitrogen adsorption BET specific surface area obtained by the nitrogen adsorption single-point method according to the method specified in JIS-Z8830 (2013) was used as the specific surface area of ​​the inorganic particles. The measurement conditions were as follows: Carrier gas: Nitrogen / helium mixed gas filling Sample amount: 0.1 g Sample pretreatment conditions: Treatment at 200°C for 20 minutes Nitrogen adsorption temperature: Liquid nitrogen temperature (-196°C or below) Nitrogen desorption temperature: Room temperature (approximately 20°C)

[0106] [Preparation of Sheet-like Resin Compositions] Sheet-like resin compositions were prepared using the epoxy resin, curing agent, curing accelerator, and inorganic particles listed in Table 1, following the procedures (1) to (3) described below.

[0107] As shown in Table 1, the epoxy resins used were mesogenic epoxy resin (phenylcyclohexyl epoxy resin (ME); details will be described later), biphenyl epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER YX4000HK), bisphenol A epoxy resin (manufactured by ADEKA Corporation, EP-4100HF), and bisphenol F epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER YL983U).

[0108] Mesogenic epoxy resin (ME) is a prepolymer obtained by reacting Trans-4-{4-(2,3-epoxypropoxy)phenyl}cyclohexyl=4-(2,3-epoxypropoxy)benzoate (an epoxy resin represented by the structural formula below) with 6-hydroxy-2-naphthoic acid.

[0109]

[0110] As shown in Table 1, the curing agents used were phenolic resin (TD-2131, a novolac-type phenolic resin manufactured by DIC Corporation) or 4,4-diaminodiphenylmethane (DDM), manufactured by Tokyo Chemical Industry Co., Ltd.

[0111] As shown in Table 1, triphenylphosphine (TPP) (manufactured by Tokyo Chemical Industry Co., Ltd.) and Cureazole 2E4MZ-CN (manufactured by Shikoku Chemicals Co., Ltd.) were used as curing accelerators.

[0112] Methyl ethyl ketone (MEK) and cyclopentanone (CYP) were used as solvents.

[0113] (1) Preparation of varnish: The epoxy resin was dissolved in a mixed solvent of methyl ethyl ketone (MEK) and cyclopentanone (CYP) (mass ratio 3:1) to prepare a 40% by mass mixed solution. Furthermore, a curing agent and a curing accelerator were added in predetermined amounts (the mixing ratio is shown in Table 1) per 100% by mass of the mixed solution to prepare the varnish. The equivalent ratio of the phenolic resin curing agent to the epoxy resin was 1.0.

[0114] (2) Preparation of inorganic particle / varnish mixture Inorganic particles were added to the obtained varnish in the proportions shown in Table 1, and the mixture was kneaded at 2000 rpm for 60 seconds using a rotational mixer (manufactured by Sinky Co., Ltd.) to prepare the inorganic particle / varnish mixture.

[0115] (3) Film Forming and Drying The obtained inorganic particle / varnish mixture was applied to a PET substrate and, using an applicator, was formed into a film so that the thickness of the sheet-like resin composition after drying was the thickness T shown in Table 3. Then, it was heated under the conditions shown in Table 2 to evaporate the solvent and dry it. After that, it was left at room temperature (25°C) for 1 hour to form a sheet-like resin composition on the PET substrate (sheet-like resin composition with PET substrate). The drying conditions were carried out in the order of the first drying step, the second drying step, and the third drying step. Note that a horizontal line (-) in the table indicates that the drying step was not performed. In Examples 1 to 7 and Comparative Examples 1 and 3, the heating rate from 25°C to 55°C in the first drying step was 30°C / min, and the heating rate from 60°C to 80°C in the second drying step was 30°C / min. The above temperatures were determined by measuring the temperature of the PET substrate with a thermocouple.

[0116] The following tests were performed on the obtained sheet-like resin composition.

[0117] (i) Measurement of the thickness T of the sheet-like resin composition The thickness T of the sheet-like resin assembly was calculated by using a micrometer (Mitutoyo Corporation, PMU150-25MX) to measure the total thickness of the PET substrate and the sheet-like resin composition, and the thickness of the PET substrate, respectively, and subtracting the thickness of the PET substrate from the total thickness. Five arbitrary measurement points were selected, and the average value was calculated from the thickness of the sheet-like resin composition obtained at each measurement point using the above method. This average value was defined as the thickness (average thickness) T of the sheet-like resin composition and is shown in Table 3.

[0118] (ii) Measurement of Solvent Content S The solvent content S of the sheet-like resin composition was determined by the following measurement and is shown in Table 3. A 4 cm square sample was cut from each example and comparative example of the PET substrate-attached sheet-like resin composition, along with the PET substrate, and the mass W1 (g) of the sample (with PET substrate) was measured. Next, the sample was heated at 150°C for 10 minutes using a fully exhausted oven to evaporate all the solvent contained in the sample. After that, it was left at room temperature for 5 minutes to return to room temperature, and the mass W2 (g) of the heated sample (with PET substrate) was measured. The PET substrate was peeled off the heated sample, and the mass W3 (g) of the PET substrate was measured. The mass of the sample before and after heating was determined by subtracting W3 (g) from W1 (g) and W2 (g), respectively. The value obtained by subtracting the mass of the sample after heating (W2-W3) from the mass of the sample before heating (W1-W3) was taken as the mass of solvent contained in the sheet-like resin composition. The solvent content S was defined as the ratio of the mass of the solvent to the mass of the sample before heating. The formula for calculating the solvent content S is given by equation (4) below. Solvent content S (mass%) = {(W1 - W3) - (W2 - W3)} / (W1 - W3) × 100 ... (4) Substituting the mass of the sample before heating X1 (g) = W1 - W3 and the mass of the sample after heating X2 (g) = W2 - W3 into equation (4) above, we obtain the following equation (3). Solvent content S (mass%) = (X1 - X2) / X1 × 100 ... (3)

[0119] (iii) Area percentage M (%) of polystyrene equivalent molecular weight in the range of 120 to 600 From each example and comparative example, a 4 cm square sample was cut out together with the PET substrate from the PET substrate-attached sheet-like resin composition. Then, after peeling off the PET substrate, the sheet-like resin composition was pretreated according to the following procedure, and then gel permeation chromatography (GPC) measurement was performed using a high-speed GPC instrument HLC-6320GPC manufactured by Tosoh Corporation under the following measurement conditions.

[0120] - The pre-treated sheet-like resin composition was dissolved in tetrahydrofuran (THF) with 0.1% by mass of toluene added as an internal standard to obtain a 0.1% by mass solution, which was then filtered through a 0.45 μm filter to be used as the measurement solution. - Measurement conditions Column: TSKgel G4000HXL (7.8 mm I.D. × 300 mm × 1 tube), TSKgel G2000HXL (7.8 mm I.D. × 300 mm × 1 tube) Eluent: THF Flow rate: 1.0 mL / min Detector: UV detector UV-8320 Detection wavelength: 254 nm Column temperature: 40°C Injection volume: 10 μL Molecular weight standard: Standard polystyrene

[0121] From the molecular weight distribution curves obtained in the gel permeation chromatography analysis described above, the area percentage M (%) of the polystyrene-equivalent molecular weight in the range of 120 to 600 was determined, with the total peak area of ​​the molecular weight distribution curve set to 100%. The area percentage M of the sheet-like resin compositions of the examples and comparative examples is shown in Table 3. The relative retention time (Rrt) of each peak was calculated as (retention time of peak) ÷ (retention time of toluene) × 20.8.

[0122] In gel permeation chromatography analysis, it is known that ghost peaks may appear due to dissolved gases, impurities, and electrical noise in the sample. Under the measurement conditions described herein, ghost peaks were detected around 19-22 minutes relative retention time, assuming the sample injection time was 0 minutes. Therefore, peaks in the range of polystyrene-equivalent molecular weight between 0 and 120 were considered ghost peaks and excluded from the calculation range of area percentage M (%).

[0123] (iv) Evaluation of Handling Properties A 2 cm x 40 cm sample was cut from each of the PET substrate-attached sheet-like resin compositions of the Examples and Comparative Examples, along with the PET substrate. The samples were stored at -20°C for one week, and then left at room temperature for 24 hours. After that, at room temperature, the sheet-like resin composition was wrapped around a mandrel with an outer diameter of φ100 mm so that the surface of the sheet-like resin composition was in contact with it, and bent 90° over 1 to 2 seconds. The bent PET substrate-attached sheet-like resin composition was placed on a flat plate with the PET substrate side down, and the surface of the part that came into contact with the mandrel was observed with the naked eye. The PET substrate-attached sheet-like resin compositions obtained in the Examples and Comparative Examples were evaluated based on the evaluation criteria described in Table 5, and the evaluation results are shown in Table 4. Evaluations A and B are considered passing grades, and evaluations C and D are considered failing grades.

[0124] (v) Presence or absence of dendritic defects A 5 cm square sheet-like resin composition with a PET substrate (observation sample) was prepared and stored in a freezer at -20°C. One day and one week after the start of storage, the observation sample was removed from the freezer and both sides of the observation sample were visually inspected to check for the presence or absence of dendritic defects. If one or more dendritic defects were found, it was judged that "defects were found". Based on the evaluation criteria described in Table 6, the PET substrate-like sheet-like resin compositions (observation samples) obtained in the examples and comparative examples were evaluated, and the evaluation results are shown in Table 4. Evaluations A and B are considered pass, and evaluation C is considered fail.

[0125]

[0126]

[0127]

[0128]

[0129]

[0130]

[0131] The sheet-like resin compositions obtained in Examples 1 to 7 were found to have superior handling properties and low-temperature storage stability compared to the sheet-like resin compositions obtained in Comparative Examples 1 to 4.

Claims

1. A sheet-like resin composition comprising an epoxy resin, a phenolic curing agent, inorganic particles, and a solvent, satisfying the following formula (1): 15.6 ≤ S × M ≤ 75.0 ... (1) where S is the content (mass%) of the solvent, and M is the area percentage (%) of the range in which the polystyrene-equivalent molecular weight is between 120 and 600, when the total peak area is set to 100% in the molecular weight distribution curve obtained by GPC measurement of the sheet-like resin composition.

2. The sheet-like resin composition according to claim 1, wherein the solvent content is 0.10% by mass or more and 5.00% by mass or less.

3. The sheet-like resin composition according to claim 1, wherein the area ratio M is 15.0% or more and 85.0% or less.

4. Furthermore, the sheet-like resin composition according to claim 1 or 2, satisfying the following formula (2): 10.0 ≤ S ２ ×M １／２ ×T １／２ ≤300 ... (2) Here, T is the thickness (μm) of the sheet-like resin composition.

5. The sheet-like resin composition according to claim 1 or 2, wherein the solvent comprises one or more selected from the group consisting of ketone-based solvents and ester-based solvents.

6. The sheet-like resin composition according to claim 1 or 2, further comprising a curing accelerator, wherein the content of the curing accelerator in 100% by mass of the solid content of the sheet-like resin composition is 0.01% by mass or more and 1.00% by mass or less.

7. The sheet-like resin composition according to claim 6, wherein the curing accelerator comprises one or more selected from the group consisting of phosphorus-based curing accelerators and imidazole-based curing accelerators.

8. The sheet-like resin composition according to claim 1 or 2, wherein the inorganic particles are one or more selected from the group consisting of alumina particles and silica particles.

9. The sheet-like resin composition according to claim 1 or 2, wherein the content of inorganic particles in 100% by mass of the solid content of the sheet-like resin composition is 40% by mass or more and 99% by mass or less.

10. The sheet-like resin composition according to claim 4, wherein the thickness T is 100 μm or more and 1000 μm or less.

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