Sheet-shaped resin composition

Abstract

Provided is a sheet-shaped resin composition having both good handleability and good low-temperature storage stability. This sheet-shaped resin composition contains an epoxy resin, a curing agent, and inorganic particles. In a time-melt viscosity curve obtainable from dynamic viscoelasticity measurement performed under a heating condition in which the temperature is increased from 25°C to 135°C at a temperature increase rate of 0.93°C / s, the temperature is then increased from 135°C to 140°C at a temperature increase rate of 0.03°C / s, and thereafter is maintained at 140°C, the slope of a straight line connecting a point A indicating the viscosity at a heating time of 10 minutes and a point B indicating the viscosity at a heating time of 15 minutes is 1000-7000 Pa·s / min.

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 even after encapsulation, potentially leading to reduced encapsulation performance and deterioration of appearance. Therefore, it is desirable for sheet-like resin compositions to be resistant to cracking when flexed (this is 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 curing agent, and inorganic particles, wherein in a time-melt viscosity curve obtained from dynamic viscoelasticity measurements performed under heating conditions of increasing temperature from 25°C to 135°C at a rate of 0.93°C / second, from 135°C to 140°C at a rate of 0.03°C / second, and then holding at 140°C, the slope of the line connecting point A, which represents the viscosity at a heating time of 10 minutes, and point B, which represents the viscosity at a heating time of 15 minutes, is 1000 Pa·s / min or more and 7000 Pa·s / min or less.

[0009] Aspect 2 of the present invention is a sheet-like resin composition according to aspect 1, wherein the viscosity at point A is 5200 Pa·s or more.

[0010] Aspect 3 of the present invention is a sheet-like resin composition according to aspect 1 or 2, wherein the minimum melt viscosity in the time-melt viscosity curve is 15 Pa·seconds or less.

[0011] Aspect 4 of the present invention is a sheet-like resin composition according to any one of aspects 1 to 3, wherein, in the time-melt viscosity curve, the slope of the straight line connecting point C, which indicates the viscosity at the time when the temperature reaches 35°C, and point D, which indicates the lowest melt viscosity, is -1100 Pa·s / min or more and -300 Pa·s / min or less.

[0012] Aspect 5 of the present invention is a sheet-like resin composition according to any one of aspects 1 to 4, 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.

[0013] Aspect 6 of the present invention is a sheet-like resin composition according to aspect 5, wherein the curing accelerator comprises one or more selected from the group consisting of phosphorus-based curing accelerators and imidazole-based curing accelerators.

[0014] Embodiment 7 of the present invention is a sheet-like resin composition according to any one of Embodiments 1 to 6, wherein the curing agent comprises a phenolic curing agent.

[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, further comprising a solvent, wherein the content of the solvent is 0.10% by mass or more and 5.0% by mass or less.

[0018] Embodiment 11 of the present invention is a sheet-like resin composition according to any one of Embodiments 1 to 10, having a thickness of 0.10 mm or more and 1.00 mm or less.

[0019] 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.

[0020] This image shows an example of a time-melt viscosity curve (solid line) obtained from dynamic viscoelasticity measurement, and a graph (dashed line) showing the heating conditions during dynamic viscoelasticity measurement. It also shows an example of a photograph of the surface of a sheet-like resin composition that developed surface defects after long-term storage at low temperatures.

[0021] 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 by keeping the slope α1 of the line connecting the point at a heating time of 10 minutes (referred to as "point A") and the point at a heating time of 15 minutes (referred to as "point B") within a certain range in the time-melt viscosity curve obtained from dynamic viscoelasticity measurements of the sheet-like resin composition under predetermined heating conditions, a sheet-like resin composition with both good handling properties and low-temperature storage stability can be obtained, thus completing the present invention.

[0022] The slope α1 of the line connecting point A and point B has the same meaning as the rate of change in viscosity between heating times of 10 minutes and 15 minutes (= change in viscosity (Pa·seconds) / 5 minutes). A large slope α1 indicates a large change in viscosity (increase in viscosity) between heating times of 10 minutes and 15 minutes, indicating that the hardening of the sheet-like resin composition is progressing rapidly during this period. On the other hand, a small slope α1 indicates a small change in viscosity (increase in viscosity) between heating times of 10 minutes and 15 minutes, indicating that the hardening of the sheet-like resin composition is not progressing much, or not progressing at all, during this period.

[0023] Regarding low-temperature storage stability, the inventors have for the first time discovered that when a sheet-like resin composition containing inorganic particles is stored at a low temperature (e.g., -20°C) for a long period of time, the sheet-like resin composition develops appearance defects (dendritic defects) as shown in Figure 2, 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, for example, a coloring agent, the dendritic defects can be observed as white areas. It is thought that the dendritic defects occur when the sheet-like resin composition is stored at a low temperature for a long period of time, due to the localized precipitation and / or recrystallization of some of the low molecular weight components, such as monomer components and curing agent components of the epoxy resin contained in the sheet-like resin composition. Although the details are unclear, it is thought that if the viscosity change during the heating time of 10 to 15 minutes is appropriate, the generation of low molecular weight components, which are one of the causes of dendritic defects, becomes less likely, or phase separation of low molecular weight components becomes less likely, thus suppressing the occurrence of dendritic defects. Furthermore, it is believed that the low molecular weight components mainly consist of monomers and oligomers of epoxy resins and curing agents, as well as low molecular weight impurities.

[0024] The following describes in detail a sheet-like resin composition according to one embodiment of the present invention.

[0025] [Sheet-like Resin Composition] A sheet-like resin composition according to one embodiment of the present invention comprises an epoxy resin, a curing agent, and inorganic particles. The solid line in Figure 1 is an example of a time-melt viscosity curve graph obtained from dynamic viscoelasticity measurement of the sheet-like resin composition according to this disclosure, where the horizontal axis is heating time (minutes) and the vertical axis (logarithmic axis on the left) is viscosity (Pa·seconds). The viscosity characteristics of the sheet-like resin composition can be determined from the time-melt viscosity curve. This time-melt viscosity curve shows the change in viscosity over time at measurement temperatures of 25°C to 140°C under the above heating conditions. The dashed line in Figure 1 is a graph showing the heating conditions during dynamic viscoelasticity measurement, where the horizontal axis is heating time (minutes) and the vertical axis (linear axis on the right) is temperature (°C). The measurement temperature range is 25°C to 140°C.

[0026] As described above, the heating conditions (the dashed line graph in Figure 1) are as follows: the heating rate from 25°C to 135°C is 0.93°C / second, the heating rate from 135°C to 140°C is 0.03°C / second, and once 140°C is reached, the temperature is maintained at that temperature (140°C). The heating time required to reach 135°C from 25°C is approximately 2 minutes, and the heating time required to reach 140°C from 135°C is approximately 2 minutes and 45 seconds.

[0027] In general dynamic viscoelasticity measurements, measurements are performed at a relatively slow heating rate (e.g., 0.5 to 5°C / min = 0.008 to 0.08°C / second) to improve measurement accuracy. However, when sealing is performed by compression molding, for example, the sheet-like resin composition is placed on a mold heated from room temperature to a high temperature (e.g., 140°C), resulting in rapid heating. Therefore, in order to understand the viscoelastic properties of the sheet-like resin composition in the sealing process, the inventors performed dynamic viscoelasticity measurements under rapid heating conditions close to the sealing conditions. The heating conditions described above are those obtained when the device used for dynamic viscoelasticity measurement (Anton Paar modular compact rheometer MCR302e) was heated from room temperature (25°C) to 140°C at its maximum heating rate, and then held at 140°C.

[0028] The inventors of the present invention have advanced their study by using the slope α1 obtained from the time-melt viscosity curve of the sheet-like resin composition as an index for the curability of the epoxy resin contained in the sheet-like resin composition (this is referred to as the "reactivity of the sheet-like resin composition"). As a result, they have found that a sheet-like resin composition with a slope α1 of 1000 Pa·s / min or more and 7000 Pa·s / min or less has good handling properties and low-temperature storage stability.

[0029] When the slope α1 is 7000 Pa·s / min or less, the reactivity of the sheet-like resin composition does not become too high, and the curing reaction of the sheet-like resin composition during storage can be suppressed from proceeding and becoming brittle. Therefore, the handling properties of the sheet-like resin composition can be improved. In addition, since the rapid reaction is suppressed, the reactivity within the sheet-like resin composition tends to become uniform. As a result, it is less likely to generate low-molecular-weight components or cause phase separation of low-molecular-weight components, so the low-temperature storage stability is also likely to be improved. When the slope α1 is 1000 Pa·s / min or more, since the sheet-like resin composition has a certain degree of reactivity, phase separation of low-molecular-weight components during low-temperature storage is less likely to occur, and the generation of dendritic defects is suppressed. Therefore, it is easy to improve the low-temperature storage stability.

[0030] The slope α1 is preferably 1500 Pa·s / min or more, more preferably 2000 Pa·s / min or more, still more preferably 2500 Pa·s / min or more, even more preferably 3000 Pa·s / min or more, particularly preferably 3600 Pa·s / min or more, and preferably 6800 Pa·s / min or less, more preferably 6500 Pa·s / min or less, particularly preferably 6000 Pa·s / min or less.

[0031] The procedure for determining the slope α1 is as follows: First, the sheet-like resin composition is stored at -20°C for one week, and then left at room temperature for 24 hours. After that, it is cut to the specified dimensions (10 mm x 10 mm) to prepare the sample for measurement. The sample for measurement is set in a dynamic viscoelasticity measuring device (Anton Paar modular compact rheometer MCR302e), and using an 8 mm parallel plate, the temperature is increased from 25°C to 135°C at 0.93°C / second, and then from 135°C to 140°C at 0.03°C / second. Once 140°C is reached, it is held at that temperature. While heating under these heating conditions, measurements are taken at a frequency of 1 Hz, strain of 0.05%, normal force of 1 N, and a measurement frequency of 5 points per second. From the obtained dynamic viscoelasticity measurement results, a time-melt viscosity curve is plotted with heating time (minutes) on the horizontal axis and viscosity (Pa·seconds) on the vertical axis.

[0032] In the obtained time-melt viscosity curve, let point A be the point that shows the viscosity (referred to as "v3 (Pa·seconds)") at a heating time of 10 minutes (referred to as "heating time t3 (minutes)"). Also, let point B be the point that shows the viscosity (referred to as "v4 (Pa·seconds)") at a heating time of 15 minutes (referred to as "heating time t4 (minutes)"). Then, draw a straight line passing through points A and B and find the slope α1 of that line. Note that the slope α1 can be found from the following equation (1): α1 (Pa·seconds / minute) = (v4 - v3) / (t4 - t3) ... (1) Here, since t3 = 10 minutes and t4 = 15 minutes, (t4 - t3) = 5 minutes. Substituting this into equation (1), it can be transformed into the following equation (1)': α1 (Pa·seconds / minute) = (v4 - v3) / 5 ... (1)'

[0033] In one embodiment of the present invention, the viscosity v3 at point A is preferably 5200 Pa·s or more. Thereby, the low-temperature storage stability of the sheet-like resin composition can be more effectively improved. The viscosity v3 is more preferably 5500 Pa·s or more, still more preferably 6000 Pa·s or more, particularly preferably 7000 Pa·s or more, preferably 300000 Pa·s or less, more preferably 200000 Pa·s or less, still more preferably 150000 Pa·s or less, particularly preferably 130000 Pa·s or less, and may be, for example, 110000 Pa·s or less, or 100000 Pa·s or less. When the viscosity v3 at point A is within the above range, a sheet-like resin composition excellent in low-temperature storage stability and sealing properties can be easily obtained. In addition, since it is easy to control the inclination α1 within a desired range, a sheet-like resin composition having both good handling properties and low-temperature storage stability can be easily obtained.

[0034] In one embodiment of the present invention, the viscosity v4 at point B is preferably 8000 Pa·s or more. Thereby, the low-temperature storage stability of the sheet-like resin composition can be more effectively improved. The viscosity v4 is more preferably 10000 Pa·s or more, still more preferably 20000 Pa·s or more, particularly preferably 25000 Pa·s or more, more preferably 350000 Pa·s or less, still more preferably 300000 Pa·s or less, even more preferably 200000 Pa·s or less, particularly preferably 150000 Pa·s or less, and may be, for example, 120000 Pa·s or less. When the viscosity v4 at point B is within the above range, a sheet-like resin composition excellent in low-temperature storage stability and sealing properties can be easily obtained. In addition, since it is easy to control the inclination α1 within a desired range, a sheet-like resin composition having both good handling properties and low-temperature storage stability can be easily obtained.

[0035] In one embodiment of the present invention, it is preferable that the minimum melt viscosity in the time-melt viscosity curve is 15 Pa·seconds or less. The minimum melt viscosity affects the fluidity when the sheet-like resin composition is heated and pressurized to seal it. By setting the minimum melt viscosity to 15 Pa·seconds or less, the fluidity during sealing can be improved, and a sheet-like resin composition with excellent sealing properties can be obtained. Note that "minimum melt viscosity" refers to the lowest viscosity in the time-melt viscosity curve, which is the viscosity at point D in the time-melt viscosity curve shown in Figure 1. The minimum melt viscosity is v2 (Pa·seconds), and the heating time to reach the minimum melt viscosity is t2 (minutes).

[0036] The minimum melt viscosity v2 is more preferably 13 Pa·seconds or less, even more preferably 12 Pa·seconds or less, and particularly preferably 10 Pa·seconds or less. The lower limit of the minimum melt viscosity v2 is not particularly limited, but may be, for example, 0.1 Pa·seconds or more, 0.3 Pa·seconds or more, or 0.5 Pa·seconds or more. When the minimum melt viscosity v2 is within the above range, the sealing properties of the sheet-like resin composition can be improved, and the tackiness of the surface of the sheet-like resin composition can be reduced, thus improving the operability during the manufacturing and sealing of the sheet-like resin composition.

[0037] The heating time t2 at which the minimum melt viscosity is reached is preferably 3.0 minutes or less, more preferably 2.8 minutes or less, even more preferably 2.5 minutes or less, preferably 1.2 minutes or more, and more preferably 1.5 minutes or more, from the viewpoint of improving the operability when sealing the sheet-like resin composition.

[0038] In one embodiment of the present invention, it is preferable that the slope α2 of the straight line passing through point C, which represents the viscosity at the time when the heating temperature reaches 35°C, and point D, which represents the minimum melt viscosity v2, is between -1100 Pa·s / min and -300 Pa·s / min. When the slope α2 is within the above range, it becomes easier to improve both handling properties and low-temperature storage stability. Furthermore, the slope α2 is an indicator of the initial behavior when the sheet-like resin composition is heated and pressurized, that is, the behavior of the sheet-like resin composition as it softens. When the slope α2 is within the above range, the sheet-like resin composition softens appropriately during heating and pressurizing in the sealing process, thus enabling good sealing performance.

[0039] The inclination α2 is preferably -1080 Pa·s / min or more, more preferably -1050 Pa·s / min or more, preferably -350 Pa·s / min or less, more preferably -400 Pa·s / min or less, and particularly preferably -450 Pa·s / min or less.

[0040] The procedure for determining the slope α2 is as follows: Create a time-melt viscosity curve using the method described in "Procedure for determining the slope α1". Also, from the graph showing the heating conditions (the dashed line graph in Figure 1), identify the heating time t1 at which the heating temperature reaches 35°C. In the time-melt viscosity curve, let point C be the point that shows the viscosity at heating time t1 (this is called "v1 (Pa·seconds)"). Also, in the time-melt viscosity curve, let point D be the point at which the minimum melt viscosity v2 occurs, and let t2 be the heating time at point D. Then, draw a straight line passing through points C and D, and find the slope α2 of that line. Note that the slope α2 can be calculated from the following equation (2): α2 (Pa·seconds / minute) = (v2 - v1) / (t2 - t1) ... (2)

[0041] In one embodiment of the present invention, the viscosity v1 at point C is preferably 50 Pa·s or more, more preferably 100 Pa·s or more, even more preferably 200 Pa·s or more, even more preferably 400 Pa·s or more, and may be, for example, 500 Pa·s or more, or 550 Pa·s or more, preferably 4500 Pa·s or less, more preferably 3000 Pa·s or less, even more preferably 2500 Pa·s or less, even more preferably 2000 Pa·s or less, and may be, for example, 1840 Pa·s or less. The heating time t1 at point C is determined according to the heating conditions and is not particularly limited. In the case of the above heating conditions, it is 0.25 minutes.

[0042] In this disclosure, "sheet-like resin composition" refers to a sheet-like resin composition containing an epoxy resin, a curing agent, and inorganic particles, which is fluid when heated and pressurized, and includes an uncured sheet-like resin composition (also referred to as a "Stage A" sheet-like resin composition). For example, an uncured (Stage A) sheet-like resin composition can be obtained by applying a liquid resin composition containing a solvent to a substrate in a sheet-like manner, and then removing a portion of the solvent by evaporation or the like. The sheet-like resin composition may contain a solvent. The time-melt viscosity curve of the above-described sheet-like resin composition changes depending on the components contained in the sheet-like resin composition and their content, and the curability of the sheet-like resin composition can be controlled, for example, by the type and blending ratio of the curing agent contained in the sheet-like resin composition, the melting point of the contained components, etc.

[0043] The substrate is preferably in the form of a film, and a general polymer film can be used. Examples of polymer films include polyethylene film, polyolefin films such as polypropylene film, vinyl films such as polyvinyl chloride film, polyester films such as polyethylene terephthalate film, polycarbonate film, acetylcellulose film, and tetrafluoroethylene film. The thickness of the substrate is not particularly limited, but from the viewpoint of excellent workability and drying properties, 20 to 200 μm is preferred.

[0044] (Inorganic particle filling rate) The proportion of inorganic particles in 100% by mass of the solid content of the sheet-like resin composition (sometimes referred to as the "inorganic particle filling rate") is preferably 40% by mass or more, which allows the thermal conductivity of the sealing member obtained by curing the sheet-like resin composition to be sufficiently high. The lower limit of the inorganic particle filling rate is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 80% by mass or more. By setting the inorganic particle filling rate to or above the above lower limit, the thermal conductivity of the sealing member can be further increased.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] (Thickness of the sheet-like resin composition) The thickness of the sheet-like resin composition is preferably 0.10 mm or more and 1.00 mm or less. If the thickness is 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 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.

[0049] The thickness of the sheet-like resin composition is preferably 0.13 mm or more, more preferably 0.15 mm or more, even more preferably 0.20 mm or more, particularly preferably more than 0.20 mm, preferably 0.90 mm or less, more preferably 0.70 mm or less, even more preferably 0.50 mm or less, even more preferably 0.40 mm or less, and particularly preferably 0.35 mm 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. Furthermore, when the sheet-like resin composition is heated and pressurized during sealing, the inorganic particles (especially particles with small particle sizes) and the epoxy resin flow more uniformly, and voids are less likely to occur after sealing and curing. In addition, 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.

[0050] The thickness of the sheet-like resin composition can be measured, for example, using a micrometer (Mitutoyo Corporation, PMU150-25MX). If the sheet-like resin composition is 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 at three or more locations and obtain the average value. Specifically, it can be determined, for example, by the method described in the examples.

[0051] Next, the inorganic particles, epoxy resin, and curing agent constituting the sheet-like resin composition, as well as any optionally included solvents, will be described in detail.

[0052] [Inorganic Particles] The inorganic particles according to this embodiment have the following characteristics.

[0053] 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.

[0054] (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.

[0055] 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.

[0056] 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.

[0057] (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, 6.0 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.

[0058] The particle diameter D50 of the inorganic particles can be determined, for example, by measuring the particle size distribution of the inorganic particles by the laser diffraction method using "Microtrac MT3300EXII" manufactured by Microtrac Bell Corporation as a laser particle size distribution measuring device. The measurement of the particle diameter of the inorganic particles in the sheet-like resin composition can be carried out by removing the epoxy resin or the like contained in the sheet-like resin composition, for example, by dissolving it with an organic solvent or the like, heating it to a temperature of 500 °C or higher to thermally decompose it, separating only the inorganic particles, and using the inorganic particles.

[0059] (BET specific surface area of inorganic particles) The BET specific surface area of the inorganic particles measured by the nitrogen adsorption method is preferably 0.2 m ２ / g or more and 10 m ２ / g or less, more preferably 0.2 m ２ / g or more and 5.0 m ２ / g or less, still more preferably 0.3 m ２ / g or more and 3.0 m ２ / g or less, even more preferably 0.35 m ２ / g or more and 1.0 m ２ / g or less. When the BET specific surface area of the inorganic particles is within the above range, it is easy to prevent the occurrence of appearance defects of the sheet-like resin composition, and the fluidity can be enhanced, so that the sealing property of the obtained sheet-like resin composition becomes good. Also, from the viewpoint of enhancing the handling property of the sheet-like resin composition, the BET specific surface area of the above inorganic particles may be 0.35 m ２ / g or more and 0.98 m ２ / g or less.

[0060] The BET specific surface area is measured in accordance with JIS-Z8830 (2013). When the inorganic particles are contained in the sheet-like resin composition, the epoxy resin or the like contained in the sheet-like resin composition is removed, for example, by dissolving it with an organic solvent or the like, heating it to a temperature of 500 °C or higher to thermally decompose the resin, separating only the inorganic particles, and the specific surface area can be measured using the inorganic particles.

[0061] 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.

[0062] 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)

[0063] 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.

[0064] In chemical formula (A), Y is a monovalent organic group. Y is preferably a C1-C20 alkyl group which may have a vinyl group, epoxy group, phenyl group, styryl group, methacrylic group, acrylic group, amino group, ureido group, mercapto group, isocyanate group, etc. at its terminus. Part of the carbon skeleton may be substituted with -O-, -NH-, -S-, -CO-, -COO- as long as they are not adjacent. Among these, an unsubstituted C1-C20 alkyl group having a vinyl group, a phenyl group, or an epoxy group is more preferred. An unsubstituted C1-C20 alkyl group is even more preferred. This improves the compatibility between inorganic particles and epoxy resin and suppresses the occurrence of appearance defects.

[0065] 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.

[0066] Silane coupling agents include those represented by the above chemical formula (A), as well as tetraalkoxysilanes, silazane compounds, and the like.

[0067] 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.

[0068] 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 mass ratio is above the lower limit, the surface modification properties of the inorganic particles improve, and the compatibility with the epoxy resin tends to improve. When the 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.

[0069] [Epoxy Resin] In this embodiment, the sheet-like resin composition contains an epoxy resin. The epoxy resin may be included alone or in combination of 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.

[0070] 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.

[0071] [Curing Agent] Any curing agent capable of controlling the inclinations α1 and α2 within the above range is acceptable for the sheet-like resin composition, and known curing agents can be used. From the viewpoint of easily controlling the reactivity with epoxy resin, phenolic curing agents and amine-based curing agents are preferred. Phenolic curing agents are more preferred from the viewpoint of further suppressing the reaction rate between the curing agent and epoxy resin in a low-temperature environment, and producing a sheet-like resin composition particularly suitable for long-term storage at low temperatures.

[0072] The phenolic curing agent (phenolic resin curing agent) contained 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] [Solvent] The sheet-like resin composition according to one embodiment of the present invention preferably contains a solvent. This makes the sheet-like resin composition more fluid and can be easily deformed to conform to the fine structure of the IC chip and substrate, making it easier to seal the dense structure without gaps. The solvent has, for example, a molecular weight of 500 or less, a boiling point of 250°C or less, and is liquid in the range of -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.

[0078] 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.

[0079] 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).

[0080] The solvent content in the sheet-like resin composition is preferably 0.10% by mass or more and 5.00% by mass or less. This further improves the handling properties and low-temperature storage stability of the sheet-like resin composition. When the solvent content is 0.10% by mass or more, the sheet-like resin composition tends to become more flexible, improving handling properties. When the solvent content is 5.00% by mass or less, the tackiness of the surface of the sheet-like resin composition can be reduced, improving handling properties, and phase separation in the sheet-like resin composition during low-temperature storage can be suppressed, thus suppressing the occurrence of appearance defects (dendritic defects). Here, "solvent content" refers to the solvent content calculated with the mass of the sheet-like resin composition before heating set to 100% by mass.

[0081] The solvent content is more preferably 0.20% by mass or more, even 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 4.00% by mass or less, even more preferably 3.00% by mass or less, even more preferably 2.40% by mass or less, particularly preferably 2.00% by mass or less, and particularly preferably 1.50% by mass or less. When the solvent content is within the above range, the handling properties and low-temperature storage stability of the sheet-like resin composition can be more effectively improved.

[0082] Furthermore, when the solvent content is within the above range, the fluidity during heating and pressurization is good, and the aggregation and sedimentation of inorganic particles can be suppressed, thereby improving the sealing properties of the sheet-like resin composition.

[0083] The solvent content in a sheet-like resin composition is determined from the change in mass of the sheet-like resin composition before and after heating. Specifically, a sample of the sheet-like resin composition of a predetermined size (e.g., 4 cm square) is prepared, and the mass X1 (g) of the sample before heating is measured. Next, the sample is heated at 150°C for 10 minutes using a fully exhausted oven to evaporate the solvent contained in the sheet-like resin composition. After that, it is left at room temperature for 5 minutes to return to room temperature, and the mass X2 (g) of the sample after heating is measured. The difference in mass (X1 - X2), obtained by subtracting the mass X2 (g) of the sample after heating from the mass X1 (g) of the sample before heating, is divided by the mass X1 (g) of the sample before heating to determine the solvent content (mass %) (see formula (3) below). Solvent content (mass %) = (X1 - X2) / X1 × 100 ... (3)

[0084] [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.

[0085] 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. Using phosphorus-based and imidazole-based curing accelerators makes it easier to control the reactivity of the sheet-like resin composition and more effectively improves the handling properties and low-temperature storage stability of the sheet-like resin composition.

[0086] In one embodiment of the present invention, the content of curing accelerators 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 curing accelerators 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, even more preferably 0.50% by mass or less, and may be, for example, 0.30% by mass or less, or 0.25% by mass or less, based on 100% by mass of the solid content of the sheet-like resin composition. When the content of curing accelerators in the sheet-like resin composition is within the above range, the reactivity of the sheet-like resin composition can be easily controlled, and the handling properties and low-temperature storage stability of the sheet-like resin composition can be more effectively improved.

[0087] [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 the solvent, thereby obtaining a sheet-like resin composition.

[0088] 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.

[0089] 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.

[0090] 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 in which the inclination α1 is within a desired range, 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.

[0091] 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 the evaporation of the solvent are easily controlled, and the slopes α1 and α2 can be easily adjusted to the desired 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.

[0092] 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 the viscoelasticity within the sheet-like resin composition uniform. 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, if the sheet-like resin composition contains a solvent, preventing the solvent content from decreasing too much.

[0093] [Method for Manufacturing Inorganic Particles] The method for manufacturing inorganic particles used in this embodiment will be explained using alumina particles as an example.

[0094] (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.

[0095] 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.

[0096] (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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] (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.

[0101] 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.

[0102] [Preparation of Inorganic Particles] The inorganic particles to be used in the examples and comparative examples were prepared as follows.

[0103] - 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] • 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.

[0109] • 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%.

[0110] Furthermore, the average roundness of alumina particle A, silica particle A, and silica particle B was 0.90 or higher for all of them.

[0111] (Measurement of average roundness) The average roundness of each inorganic particle was measured using a CAMSIZER X2 (manufactured by VERDER Scientific) based on the principle of dynamic image analysis in accordance with ISO 13322-2.

[0112] (Measurement of Specific Surface Area) The specific surface area of ​​each inorganic particle 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 particle. 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)

[0113] [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.

[0114] As shown in Table 1, the epoxy resins used were mesogenic epoxy resin (phenylcyclohexyl epoxy resin (ME); details will be described later), bisphenol A type epoxy resin (ADEKA Corporation, EP-4100HF), and bisphenol F type epoxy resin (Mitsubishi Chemical Corporation, jER YL983U).

[0115] 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.

[0116]

[0117] As shown in Table 1, the curing agents used were phenolic resin (TD-2131, manufactured by DIC Corporation, a novolac-type phenolic resin), allylphenolic resin (phenolic resin represented by the structural formula shown below), or 4,4-diaminodiphenylmethane (DDM) (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0118]

[0119] 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.

[0120] Methyl ethyl ketone (MEK) and cyclopentanone (CYP) were used as solvents.

[0121] (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.

[0122] (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.

[0123] (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 as shown in Table 4. 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 Example 1, 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.

[0124] The following tests were performed on the obtained sheet-like resin composition.

[0125] (i) Dynamic Viscoelasticity Measurement A 10 mm x 10 mm sample was cut from the PET substrate-attached sheet-like resin composition of the example and comparative example, along with the PET substrate, and the PET substrate was peeled off to prepare the sample for measurement. The sample for measurement was set in a dynamic viscoelasticity measuring device (Anton Paar modular compact rheometer MCR302e), and an 8 mm diameter parallel plate was used to raise the temperature from 25°C to 135°C at 0.93°C / second, and from 135°C to 140°C at 0.03°C / second, and after reaching 140°C it was held at that temperature. While heating under these heating conditions, measurements were taken at a frequency of 1 Hz, strain of 0.05%, normal force of 1 N, and a measurement frequency of 5 points per second. From the obtained dynamic viscoelasticity measurement results, a time-melt viscosity curve was plotted with the horizontal axis representing heating time (minutes) and the vertical axis representing viscosity (Pa·seconds).

[0126] The following data was obtained using the time-melt viscosity curve. The data values ​​are shown in Table 3. • [Point A] Point A is defined as the point on the time-melt viscosity curve that shows viscosity v3 (Pa·seconds) at heating time t3 (10 minutes), and the value of viscosity v3 was determined. • [Point B] Point B is defined as the point on the time-melt viscosity curve that shows viscosity v4 (Pa·seconds) at heating time t4 (15 minutes), and the value of viscosity v4 was determined. • [Point C] Point C is defined as the point on the time-melt viscosity curve that shows viscosity v1 (Pa·seconds) at heating time t1 (minutes) when the heating temperature reaches 35°C, and the value of viscosity v1 and heating time t1 were determined. • [Point D] Point D is defined as the point on the time-melt viscosity curve that shows the lowest melt viscosity v2 (Pa·seconds), and the value of the lowest melt viscosity v2 and the heating time t2 (minutes) at which the lowest melt viscosity v2 occurs were determined. - Slope α1: This is the slope α1 (Pa·s / min) of the line passing through point A and point B, and was calculated from the following equation (1): α1 (Pa·s / min) = (v4 - v3) / (t4 - t3) ... (1) - Slope α2: This is the slope α2 (Pa·s / min) of the line passing through point C and point D, and was calculated from the following equation (2): α2 (Pa·s / min) = (v2 - v1) / (t2 - t1) ... (2)

[0127] (ii) Thickness measurement of the sheet-like resin composition The thickness 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 taken as the thickness of the sheet-like resin composition (average thickness) and is shown in Table 3.

[0128] (iii) Measurement of Solvent Content The solvent content of the sheet-like resin composition was determined by the following measurement, and the results are 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 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 is given by equation (4) below. Solvent content (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)

[0129] (iv) Evaluation of Handling Properties A 2 cm × 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, and stored at -20°C for one week. After that, it was left at room temperature for 24 hours. Then, 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 pass, and evaluation C is fail.

[0130] (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.

[0131]

[0132]

[0133]

[0134]

[0135]

[0136]

[0137] 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 3.

Claims

1. A sheet-like resin composition comprising epoxy resin, a curing agent, and inorganic particles, wherein the time-melt viscosity curve obtained from dynamic viscoelasticity measurements performed under heating conditions of heating from 25°C to 135°C at a rate of 0.93°C / second, from 135°C to 140°C at a rate of 0.03°C / second, and then holding at 140°C, has a slope of 1000 Pa·s / min or more and 7000 Pa·s / min or less of the straight line connecting point A, which represents the viscosity at a heating time of 10 minutes, and point B, which represents the viscosity at a heating time of 15 minutes.

2. The sheet-like resin composition according to claim 1, wherein the viscosity at point A is 5200 Pa·s or more.

3. The sheet-like resin composition according to claim 1 or 2, wherein the minimum melt viscosity in the time-melt viscosity curve is 15 Pa·seconds or less.

4. The sheet-like resin composition according to claim 1 or 2, wherein, in the time-melt viscosity curve, the slope of the straight line connecting point C, which indicates the viscosity at the time when the temperature reaches 35°C, and point D, which indicates the lowest melt viscosity, is -1100 Pa·s / min or more and -300 Pa·s / min or less.

5. 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.

6. The sheet-like resin composition according to claim 5, wherein the curing accelerator comprises one or more selected from the group consisting of phosphorus-based curing accelerators and imidazole-based curing accelerators.

7. The sheet-like resin composition according to claim 1 or 2, wherein the curing agent comprises a phenolic curing agent.

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 the 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 1 or 2, further comprising a solvent, wherein the content of the solvent is 0.10% by mass or more and 5.0% by mass or less.

11. The sheet-like resin composition according to claim 1 or 2, wherein the thickness is 0.10 mm or more and 1.00 mm or less.

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