WO2023112928A1

WO2023112928A1 - Spherical crystalline silica particles, method for producing same, and resin composite composition and resin composite containing same

Info

Publication number: WO2023112928A1
Application number: PCT/JP2022/045912
Authority: WO
Inventors: 一彦楠; 睦人田中; 竜太郎沼尾; 良介坂下
Original assignee: 日鉄ケミカル＆マテリアル株式会社
Priority date: 2021-12-13
Filing date: 2022-12-13
Publication date: 2023-06-22
Also published as: TW202337826A

Abstract

The purpose of the present invention is to provide: spherical crystal particles having a low lithium content and a high quartz crystallization rate; a method for producing same; and a resin composite composition and resin composite that contain said spherical crystalline silica particles.　These spherical crystalline silica particles have a circularity of 0.80 or more, an average particle diameter (D50) of 1.0-100.0 μm, contain lithium at a quantity of no more than/less than 0.05 mass% in terms of oxide and contain calcium at a quantity of 0.10 mass% to less than 1.00 mass% in terms of oxide, and in which 50.0% or more of the particles as a whole is crystalline silica and 90.0% or more of the crystalline silica is quartz. Also provided is a method for producing same.

Description

Spherical crystalline silica particles, method for producing the same, and resin composite composition and resin composite containing the same

The present invention provides spherical crystalline silica particles, particularly spherical crystalline silica particles having a low lithium content and a high quartz crystallinity, a method for producing the same, and a resin composite composition and a resin containing the spherical crystalline silica particles. Relating to complexes.

Silica particles are used as fillers for resins, for example, as fillers for encapsulants for semiconductor devices. Regarding the shape of the silica particles, if the shape is angular, the fluidity, dispersibility and filling properties in the resin will deteriorate. In order to improve these, spherical silica particles are widely used.

Thermal spraying is generally used as a method for manufacturing spherical silica. In thermal spraying, the particles are melted by passing them through a high temperature region such as a flame, and the shape of the particles becomes spherical due to surface tension. The fused and spherical particles are recovered by being conveyed by an air stream so as not to fuse with each other, but the particles after thermal spraying are rapidly cooled. Because it is quenched from the molten state, silica has an amorphous structure with few crystals, resulting in glassy particles commonly referred to as fused silica.

Because the spherical silica obtained by thermal spraying is amorphous, its coefficient of thermal expansion and thermal conductivity are low. These physical properties are considered to be equivalent to the coefficient of thermal expansion of quartz glass, which has an amorphous structure without a crystal structure. The rate is 1.4 W/mK.

Spherical silica particles, which are generally used for sealing materials, etc., are amorphous and have a low coefficient of thermal expansion. Therefore, it has the effect of lowering the coefficient of thermal expansion of the mixture (resin composition) when mixed with a resin. Thereby, the coefficient of thermal expansion of the resin composition can be brought close to that of the semiconductor element. Moreover, when the resin composition is used as a sealing material or the like, it is possible to suppress deformation that occurs during heating or cooling during the curing process of the resin. However, the thermal conductivity of amorphous silica is not very high. On the other hand, as the amount of heat generated increases as the performance of semiconductors increases, it is required to release the generated heat more efficiently. Therefore, there is a need for spherical silica particles with higher thermal conductivity.

Compared to amorphous silica, crystalline silica has a regular and dense structure, so it has high thermal conductivity. Crystal structures of silica include cristobalite, quartz, and tridymite, and silica having these crystal structures is known to have a higher coefficient of thermal expansion and thermal conductivity than amorphous silica. In particular, quartz has a denser crystal structure than other crystals, so it has a high thermal conductivity of 12.8 W/mK, and spherical silica particles containing a large amount of quartz are thought to provide a high thermal conductivity.

Various studies have been made so far on means for obtaining crystalline silica particles.

In Patent Document 1, a Zn compound is added to an amorphous silica gel produced by a sol-gel method, and heat treatment is performed at 900 to 1100 ° C. to obtain SiO ₂ as a main component, a Zn compound, and a main crystal phase. A porous powder made of quartz is obtained. Note that the heat treatment is performed in the atmosphere or the like, and no particular pressure is applied. Moreover, the content ratio of the crystalline phase is not disclosed.

In Patent Document 2, the crystal phase is 90% by mass or more of the whole, the quartz crystal is 70% by mass or more of the whole, and contains 0.4 to 5% by mass of lithium in terms of oxide and / or calcium. It discloses spherical crystalline silica particles containing 1 to 5% by mass in terms of oxide. The spherical crystalline silica particles are obtained by heat-treating the raw material powder at 800 to 1300° C. and cooling it. Note that the heat treatment is performed in an electric furnace, a gas furnace, or the like, and no particular pressure is applied.

Patent Document 3 relates to spherical crystalline silica particles, the ratio of the crystalline silica phase in the spherical crystalline silica particles is 40.0% or more, and the quartz occupies the crystalline silica phase. The ratio is 80.0% by mass or more, lithium is contained in an amount of 0.02% by mass or more and less than 0.40% by mass in terms of oxide, and calcium is contained in an amount of 0.004% by mass or more and 1.0% by mass in terms of oxide. % included. The spherical crystalline silica particles are obtained by heat-treating the raw material powder at 850 to 1150°C. Note that the heat treatment can be performed in an inert gas atmosphere such as nitrogen or argon. Moreover, the atmospheric pressure is preferably atmospheric pressure because a large amount of heat treatment is performed industrially, and no particular pressure is applied.

Patent Document 4 relates to a dental cured product, and the spherical crystal controlled powder contained in the dental cured product has a silicon dioxide content of 97% by mass or more and 100% by mass, and has an amorphous portion and a crystalline portion are mixed. The ratio of the amorphous portion to the crystalline portion is controlled by heat-treating the amorphous raw material powder at 600°C to 1700°C. Note that no particular pressure is applied in the heat treatment. Patent Document 4 describes that pressure may be applied during curing, but does not describe specific pressure. Also, the type and content of the crystalline are not specified.

Patent Document 5 discloses a spherical silica filler powder containing 80% by mass or more of a keatite phase. Keatite is not a common crystalline phase such as quartz or cristobalite, but is mainly synthesized under high temperature, high pressure and high water vapor pressure. In Patent Document 5, spherical amorphous silica particles and a lithium compound are mixed without applying any particular pressure, and the mixture is heated at 650 to 725° C. for 3 to 20 hours to obtain the spherical silica filler powder. It has gained.

Japanese Unexamined Patent Application Publication No. 2002-20111 WO2018/186308 WO2021/235530 Japanese Patent No. 5616672 JP 2019-52051 A

Semiconductor products are required to efficiently dissipate the generated heat. In particular, in order to cope with the increase in the amount of heat generated due to the higher performance, there is a demand for a material with high thermal conductivity that allows heat to escape more easily to peripheral members such as sealing materials for semiconductors. For this reason, spherical crystalline silica, which has high thermal conductivity and provides a high filling rate, is useful as a filler used in sealing materials and the like. Silica has various crystal forms, and quartz is particularly preferable because of its high thermal conductivity.

As a method for obtaining spherical crystalline silica, a method is disclosed in which an element for promoting crystallization is added to amorphous spherical silica, heat-treated at a high temperature, and crystallized. However, in general, additive elements may affect the properties of spherical crystalline silica. In particular, when used as a semiconductor encapsulating filler, there is concern that alkali metals may impair the reliability of electronic devices. Therefore, spherical crystalline silica is required to further reduce lithium.

In addition, from the viewpoint of improving thermal conductivity, spherical crystalline silica is required to have a crystalline content of a certain level or more. This is because if the amorphous content is high, the thermal conductivity becomes close to that of amorphous silica, and the thermal conductivity may not be sufficiently improved. In addition, it is also required that the main crystalline type be specified. The properties of thermal conductivity differ depending on the type of crystalline material. Therefore, when a plurality of crystalline types are mixed, the thermal conductivity fluctuates, and the desired thermal conductivity may not be obtained.

Patent Documents 1 and 4 do not specify the crystalline content or the type of crystalline. Moreover, although the powder for silica filler of Patent Document 5 discloses that the content of the keatite phase is 80% by mass, the content of the crystal phase in the powder is unknown. Therefore, these prior art techniques may not provide sufficient thermal conductivity.

In the spherical crystalline silica particles of Patent Document 2, the crystal phase accounts for 90% by mass or more of the whole, and the quartz crystal accounts for 70% by mass or more of the whole, so sufficient thermal conductivity can be expected. However, it contains 0.4 to 5% by mass of lithium in terms of oxide. Further, the spherical crystalline silica particles of Patent Document 3 contain calcium of 0.004% by mass or more and less than 1.0% by mass in terms of oxide, so that lithium is contained in an amount of 0.02% by mass or more and 0.40% by mass in terms of oxide. It is reduced to less than % by mass. However, it is desirable to further reduce lithium.

In view of the above situation, the present invention provides spherical crystal particles having a low lithium content and a high quartz crystallinity, a method for producing the same, and a resin composite composition and a resin composite containing the spherical crystalline silica particles. intended to provide

The present inventors obtained the following ideas as a result of earnest studies for solving the above problems.
Crystallization into quartz is promoted by adding calcium to amorphous silica particles and heat-treating them. That is, calcium is a crystallization promoting element for quartz. However, crystallization to quartz occurs only in the vicinity where calcium is present. That is, the effect of calcification by adding calcium is local or limited.
In addition, when heat treatment crystallizes amorphous silica particles, crystallization to cristobalite generally also occurs. Therefore, crystallization to cristobalite rather than quartz proceeds within the range where the effect of calcium addition does not reach, typically inside amorphous silica particles. Calcium needs to thermally diffuse within the particles in order to promote the quartification of the entire amorphous silica particles, but the diffusion coefficient of calcium in the amorphous silica is small.
As a result, the quartz crystallinity is low with calcium addition alone. This is particularly noticeable in the case of large-sized silica particles (typically, D50: 10 μm or more). This is because the larger the diameter of the silica particles, the lower the specific surface area and the contact area with calcium.
Thus, there is a limit to improving the crystallinity of quartz only by adding calcium.
On the other hand, it is known that the crystallization of amorphous silica is affected by pressure, but there are few reports on detailed investigations.
Therefore, the inventors of the present patent conducted crystallization experiments by varying the type and amount of additive added to amorphous silica particles and the atmospheric pressure during heat treatment. In particular, the atmospheric pressure was varied up to a high pressure range using a hot isostatic pressing (HIP) apparatus for high-pressure and high-temperature processing. As a result, the inventors have found that silica with a high quartz crystallinity can be obtained even if the amount of lithium element added is reduced to a substantially non-added level.

The gist of the present invention is as follows.
[1]
Circularity is 0.80 or more, average particle size (D50) is 1.0 μm or more and 100.0 μm or less, lithium is 0.05% by mass or less in terms of oxide, and calcium is 0.10 in terms of oxide. Spherical crystalline silica particles containing less than ~1.00% by mass, 50.0% or more of the whole being crystalline silica, and 90.0% or more of said crystalline silica being quartz.
[2]
The spherical crystalline silica particles according to [1], containing 0.02% by mass or less of lithium in terms of oxide.
[3]
The spherical crystalline silica particles according to [1] or [2], wherein cristobalite accounts for 5.0% or less of the whole.
[4]
The spherical crystalline silica particles according to any one of [1] to [3], containing 90 to 9000 ppm of aluminum.
[5]
The spherical crystalline silica particles according to any one of [1] to [4], having an average particle diameter (D50) of 10.0 μm or more.
[6]
A raw material powder preparation step of mixing spherical amorphous silica particles with a calcium raw material or mixing a calcium raw material and lithium compound particles to obtain a raw material powder;
The raw material powder obtained in the raw material powder preparation step is heat-treated at a temperature of 1125° C. or higher and 1300° C. or lower and a pressure of 125 MPa or higher using a hot isostatic pressing apparatus for 1 hour or longer to obtain spherical crystals. a heat treatment step to produce fine silica particles;
including
In the spherical crystalline silica particles generated in the heat treatment step, calcium is 0.10 to 1.00% by mass in terms of oxide, and lithium is 0.05% by mass or less in terms of oxide. like,
Adjusting the mixing ratio of the calcium raw material or the calcium raw material and the lithium compound particles in the raw material powder adjusting step,
A method for producing spherical crystalline silica particles.
[7]
A resin composite composition characterized by containing the spherical crystalline silica particles according to any one of [1] to [5] in a resin.
[8]
A resin composite obtained by curing the resin composite composition described in [7].

According to the present invention, there are provided spherical crystal particles with a low lithium content and a high quartz crystallinity, a method for producing the same, and a resin composite composition and a resin composite containing the spherical crystalline silica particles.

The spherical crystalline silica particles of the present invention are
Circularity of 0.80 or more,
The average particle diameter (D50) is 1.0 μm or more and 100.0 μm or less,
Contains 0.05% by mass or less of lithium in terms of oxide,
Contains less than 0.10 to less than 1.00% by mass of calcium in terms of oxide,
50.0% or more of the whole is crystalline silica, and 90.0% or more of the crystalline silica is quartz. Each specific item will be explained below.

The spherical crystalline silica particles of the present invention are spherical, and the means for making them spherical is not particularly limited, and means such as pulverization and polishing may be used. In particular, thermal spraying before crystallization is highly productive and enables spheroidization at low cost. Spherical silica particles have high fluidity, dispersibility, and filling properties when used as a filler for a semiconductor encapsulant, and can also suppress abrasion of encapsulant-producing equipment.

(Circularity: 0.80 or more)
More specifically, the spherical crystalline silica particles of the present invention may have an average circularity of 0.80 or more, preferably 0.85, and more preferably 0.90 or more. Circularity can be measured by a commercially available flow-type particle image analyzer. A perfect circle is obtained when the degree of circularity is 1. In other words, the closer the circularity is to 1, the closer to a perfect circle. The average circularity is calculated as the average value of circularities measured for 100 or more particles. If the average circularity is less than 0.80, when used as a filler for a semiconductor encapsulating material, the fluidity, dispersibility, and filling properties are not sufficient, and the wear of the encapsulating material-producing equipment is accelerated. may be
Although the upper limit of the circularity may be 1.0, it is practically difficult to achieve a circularity of 1.0, and if it is to be achieved, the manufacturing and management costs will increase. The upper limit of circularity may be set to 0.98, preferably 0.95, depending on the application.

　In order to achieve the above average circularity, it is possible to adjust the circularity of the amorphous spherical silica particles (particles before crystallization) that are the starting material. If it is a thermal spraying means, the silica powder can be easily formed into particles with a high degree of circularity. Moreover, the average circularity of the spherical crystalline silica particles of the present invention hardly decreases before and after the heat treatment for crystallization. This is because the spherical crystalline silica particles of the present invention are crystalline at 1125 to 1300° C., and the circularity hardly decreases in this temperature range. In addition, amorphous silica particles may be bonded together by fusion or sintering at about 1125 to 1300 ° C., but the spherical crystalline silica particles of the present invention are crystalline (already (because it is not amorphous), bonding by fusion bonding or sintering at about 1125 to 1300° C. is sufficiently suppressed. Although the degree of circularity is reduced by bonding, the spherical crystalline silica particles of the present invention are sufficiently inhibited from being bonded to each other, so that the average degree of circularity hardly decreases. Therefore, the spherical crystalline silica particles of the present invention can improve fluidity, dispersibility, and filling properties when used as a filler for a semiconductor sealing material.

(Average particle size (D50): 1.0 μm or more and 100.0 μm or less)
The spherical crystalline silica particles of the present invention have an average particle size (D50) of 1.0 to 100.0 μm, and may be 10.0 μm or more. If the average particle size exceeds 100.0 μm, the particle size becomes too large when used as a filler for a semiconductor encapsulant, etc., and gate clogging and mold wear tend to occur. If the particle size is less than 1.0 μm, the particles become too small, and the viscosity of the resin composition in which the silica particles and the resin are mixed may be excessively increased, making it impossible to fill a large amount. The average particle size here can be obtained by particle size distribution measurement by a wet laser diffraction method (laser diffraction scattering method).
The average particle size referred to here is called a median diameter, and the particle size distribution is measured by a laser diffraction method, and the particle size at which the cumulative particle size frequency is 50% is defined as the average particle size (D50).

The above particle size range can be achieved by adjusting the particle size of the raw amorphous spherical silica particles (particles before crystallization). If it is thermal spraying means, the particle size can be easily adjusted. In other words, the average particle size of the spherical crystalline silica particles of the present invention hardly changes before and after the heat treatment for crystallization. Amorphous silica particles may be softened even at about 1125 to 1300° C. and may be bonded by fusion or sintering, but the spherical crystalline silica particles of the present invention are crystalline, Since it does not soften like an amorphous material, bonding by fusion or sintering at about 1125 to 1300° C. is sufficiently suppressed. In particular, bonding between particles due to fusion or sintering is more likely to occur as the surface area ratio of the particles increases, that is, as the particle size decreases. However, since the spherical crystalline silica particles of the present invention are crystalline, even if the average particle size is 1.0 μm, they are not bound by fusion or sintering, and are less likely to agglomerate. Therefore, the spherical crystalline silica particles of the present invention can improve fluidity, dispersibility, and filling properties when used as a filler for semiconductor sealing materials.
In addition, the temperature at which the particles are fused or sintered varies depending on the particle size of the raw material amorphous spherical silica, the type of additive component, and the amount added. It is desirable to carry out the heat treatment at an appropriate temperature at which fusion or sintering does not occur depending on the components and added components.

(Lithium content: 0.05% by mass or less in terms of oxide)
The spherical crystalline silica particles of the present invention contain 0.05% by mass or less of lithium in terms of oxide based on the total mass of the spherical crystalline silica particles. Lithium is one of alkali metals, and alkali metals may impair the reliability of electronic devices. Therefore, the lower the lithium content of the silica particles, the more reliable the electronic device using the silica particles as a filler. In this respect, the lithium content is preferably as low as possible, and may be 0.03% by mass or less or less, 0.02% by mass or less or less, or 0.01% by mass or less or less in terms of oxide. Moreover, the lower limit of the lithium content is not limited, and may be zero. Lithium in the present invention is not limited to being positively added, and may be an impurity contained in the raw material such as amorphous silica particles. Moreover, in order to adjust the lithium content, lithium or a lithium compound may be mixed with the raw material such as amorphous silica particles. The form of the lithium compound to be added is not particularly limited, and may be an oxide, carbonate, hydroxide, nitrate, or the like.
In general, lithium can exist in the form of oxides, carbonates, hydroxides, nitrates, etc., or composite oxides with silica within silica particles with enhanced crystallization, and substantially The part is present in oxide form. Therefore, unless otherwise specified, in the present invention, the lithium content is calculated in terms of oxide. Specifically, the content of lithium is obtained by measuring by ICP mass spectrometry (ICP-MS) and converting it to oxide.

(Calcium content: 0.10% by mass or more and less than 1.00% by mass in terms of oxide)
The spherical crystalline silica particles of the present invention contain 0.10% by mass or more and less than 1.00% by mass of calcium in terms of oxide based on the total mass of the spherical crystalline silica particles. Calcium promotes crystallization of amorphous silica by heating with amorphous silica. If the calcium content is less than 0.10% by mass, crystallization may not be promoted sufficiently. The higher the calcium content, the higher the effect of promoting crystallization. From that point of view, the calcium content may be 0.20% by mass or more. However, if the calcium content is 1.00% by mass or more and the amorphous silica is heated, the calcium and silica react with each other to easily form a silicic acid compound such as Ca ₂ (SiO ₄ ). In particular, under high pressure, the possibility of this is further increased. Such compounds are likely to be generated in the outer periphery of silica particles, and the shape of the particles is deformed to reduce the circularity of the particles. There is a risk of reducing fluidity when mixed with resin. Therefore, the upper limit of the calcium content is less than 1.00% by mass, preferably less than or equal to 0.90% by mass, and more preferably less than or equal to 0.80% by mass.
To adjust the calcium content, calcium or a calcium compound may be mixed with the raw material, such as amorphous silica particles. The form of the calcium compound to be added is not particularly limited, and may be an oxide, carbonate, hydroxide, nitrate, or the like. Silica stone, which is the raw material for amorphous silica particles, often contains calcium compounds as impurities. can be adjusted to the preferred range described above.
In general, calcium can be present in the form of oxides, carbonates, hydroxides, nitrates, etc., or composite oxides with silica within silica particles with accelerated crystallization, and can be substantially large. The part is present in oxide form. Therefore, unless otherwise specified, in the present invention, the calcium content is calculated in terms of oxide. Specifically, the content of calcium is obtained by measuring by ICP mass spectrometry (ICP-MS) and converting it to oxide.

(aluminum)
In one aspect of the present invention, the spherical crystalline silica particles may contain 90 to 9000 ppm of aluminum in terms of metallic aluminum based on the total mass of the spherical crystalline silica particles.
When calcium is used to promote crystallization of amorphous silica particles, it preferably contains 90 to 9000 ppm of aluminum in terms of metallic aluminum. Without being bound by any particular theory, aluminum acts as a crystal nucleating agent during heat treatment, and can have the effect of producing more quartz crystals when used with calcium. However, when aluminum is less than 90 ppm in terms of metal aluminum, a sufficient effect of promoting crystallization cannot be obtained. In addition, if the amount of aluminum exceeds 9000 ppm in terms of metal aluminum, a composite oxide of calcium, aluminum, and silicon contained in silica is likely to be formed. cristobalite is likely to be generated by increasing the That is, excess aluminum may reduce the production of quartz crystals. Based on the above, the aluminum content may be set to 100 ppm or more and may be set to 8200 ppm or less.
In order to adjust the aluminum content, aluminum or an aluminum compound may be mixed with the raw material amorphous silica particles or the like. As an aluminum compound, aluminum oxide, aluminum hydroxide, or the like may be used. Silica stone, which is the raw material for amorphous silica particles, often contains aluminum compounds as impurities. can be adjusted to the preferred range described above.
Also, the content of aluminum is obtained by measurement by ICP mass spectrometry (ICP-MS).

Furthermore, in one aspect of the present invention, the spherical crystalline silica particles may contain metal impurities within a range that does not affect the degree of crystallinity. Typical metal impurities include alkali metals (potassium, sodium, etc.), alkaline earth metals (magnesium, barium, etc.), and the like.

(Crystalline silica: 50.0% or more of spherical crystalline silica particles)
In the spherical crystalline silica particles of the present invention, 50.0% or more of the whole is crystalline silica. Here, the whole refers to the whole spherical crystalline silica particles.
If the crystalline silica is less than 50.0%, the proportion of amorphous silica will be 50.0% or more. Since the thermal conductivity of amorphous silica is as low as 1.4 W/mK, if 50.0% or more of amorphous silica is contained, the thermal conductivity of silica particles may be lowered. The higher the proportion of crystalline silica, the higher the thermal conductivity, which is preferable. Therefore, the proportion of crystalline silica may be 60.0% or more, preferably 70.0% or more, more preferably 80.0% or more, and still more preferably It may be 90.0% or more. The upper limit of the proportion of crystalline silica is not particularly limited and may be adjusted depending on the application, typically the desired thermal conductivity. Therefore, the upper limit of the proportion of crystalline silica may be 100%, 95% or less, 90% or less, 85% or less, or 80% or less. may
The crystalline phase and amorphous content can be quantitatively analyzed by X-ray diffraction. Quantitative analysis by X-ray diffraction can be performed without using a standard sample by using an analysis method such as the Rietveld method.
More specifically, the ratio of crystalline silica to the total spherical crystalline silica particles (hereinafter sometimes referred to as "crystallinity") is obtained by X-ray diffraction, the integration of the amorphous peak and the crystalline peak The area is obtained, and the ratio of the crystalline area is defined as the crystallization rate. That is, the crystallinity ratio is calculated as follows: integrated area of crystalline peak/(integrated area of amorphous peak + integrated area of crystalline peak).

(Quartz: 90.0% or more of crystalline silica)
In the spherical crystalline silica particles of the present invention, 90.0% or more of the crystalline silica is quartz. Quartz has a thermal conductivity of 12.8 W/mK, which is much higher than the 1.4 W/mK thermal conductivity of amorphous silica. Therefore, in the spherical crystalline silica particles of the present invention, 50.0% or more of the entire particle is crystalline silica, and 90.0% or more of the crystalline silica is quartz crystal, so that desirable high thermal conductivity is obtained. be able to.
Crystalline silica may include cristobalite, tridymite and other crystalline forms as crystalline phases other than quartz. Both crystals have a thermal conductivity of about 10 W/mK, which is lower than the 12.8 W/mK of quartz, but higher than that of amorphous silica.
However, when the content of quartz is less than 90.0%, in other words, when the content of cristobalite, tridymite, etc. is 10.0% or more, a phase transition from α-cristobalite to β-cristobalite or α-tridymite → β1-tridymite → A phase transition to β2 tridymite occurs, and the volume expansion associated with the phase transition may cause voids between the resin and silica particles when mixed with a resin and cause cracks. Therefore, it is important to reduce the content of cristobalite and tridymite by replacing 90.0% or more of the crystalline silica with quartz. In this respect, it is preferable that the content of cristobalite, tridymite, etc. is as low as possible. Therefore, in one aspect of the present invention, the content of cristobalite and/or tridymite may be 5.0% or less of the total spherical crystalline silica particles.
The content of quartz, cristobalite, tridymite, and other crystals, as well as the crystalline phase and amorphous content, can be quantitatively analyzed by X-ray diffraction. Quantitative analysis by X-ray diffraction can be performed without using a standard sample by using an analysis method such as the Rietveld method.
More specifically, the ratio of each crystal to crystalline silica is obtained from the ratio of the areas of the crystals obtained by obtaining the integrated area of the peak of each crystal by X-ray diffraction. As an example, the ratio of quartz crystals = integrated area of quartz peak / (integrated area of quartz peak + integrated area of cristobalite peak + integrated area of tridymite peak + integrated area of peaks of other crystal forms) Calculate as

(Production method)
The spherical crystalline silica particles of the present invention can be produced by a method including the following steps. That is, the production method of the present invention is
A raw material powder preparation step of mixing spherical amorphous silica particles with a calcium raw material or mixing a calcium raw material and lithium compound particles to obtain a raw material powder;
The raw material powder obtained in the raw material powder preparation step is heat-treated at a temperature of 1125° C. or higher and 1300° C. or lower and a pressure of 125 MPa or higher using a hot isostatic pressing apparatus for 1 hour or longer to obtain spherical crystals. a heat treatment step to produce fine silica particles;
including
In the spherical crystalline silica particles generated in the heat treatment step, calcium is 0.10 to 1.00% by mass in terms of oxide, and lithium is 0.05% by mass or less in terms of oxide. like,
Adjusting the mixing ratio of the calcium raw material or the calcium raw material and the lithium compound particles in the raw material powder adjusting step,
A method for producing spherical crystalline silica particles.

(Spherical amorphous silica particles)
The raw material spherical amorphous silica particles can be produced by a method such as thermal spraying. For example, in the thermal spraying method, by passing silica powder pulverized to a desired particle size through a flame, the particles are melted and the shape of the particles becomes spherical due to surface tension.

The particles after thermal spraying may be quenched so that the particles that have been melted and sphericalized by thermal spraying do not fuse with each other. In that case, since the molten state is rapidly cooled, the spherical silica particles do not have a crystal structure but have an amorphous structure. Since the spherical silica particles are thermally sprayed, they may be non-porous. Non-porous spherical silica particles are expected to be dense and have high thermal conductivity.

The spherical amorphous silica particles can be made to have an average circularity of 0.80 or more by thermal spraying or the like. Since the maximum temperature of the subsequent heat treatment for crystallization is about 1300° C., the circularity of the spherical silica particles hardly changes. Circularity may change due to adhesion during the process from amorphous silica particles to crystalline silica particles. Silica particles can be obtained. That is, when amorphous silica particles having a circularity of 0.80 or more are used, crystalline silica particles obtained by heat treatment also have a circularity of 0.80 or more. Pulverization can be carried out with a general mixer or mill such as a tumbling ball mill, rocking mixer, bead mill, or the like. If the circularity changes due to heat treatment, the rate of change in circularity can be confirmed in a preliminary test or preliminary survey, and the circularity of the spherical amorphous silica particles before heat treatment can be adjusted based on the confirmation results. . Then, if it is a thermal spraying means, it is possible to easily obtain spherical amorphous silica particles having a high average circularity. Therefore, according to the method of the present invention, spherical crystalline silica particles having a circularity of 0.8 or more can be easily obtained. Of course, if spherical amorphous silica particles with an average circularity of less than 0.80 are used, spherical crystalline silica particles with an average circularity of less than 0.80 can be obtained by the method of the present invention.

The spherical amorphous silica particles obtained by thermal spraying or the like may have an average particle size (D50) of 1.0 to 100.0 μm, or may be 10.0 μm or more. Since the maximum temperature of the subsequent heating and cooling steps for crystallization is about 1300° C., the particle size of the spherical silica particles hardly changes. The average particle diameter D50 may change due to adhesion in the process from amorphous silica particles to crystalline silica particles, but if crushed, the average particle diameter is almost the same as that of the original amorphous silica particles. of crystalline silica particles can be obtained. That is, if amorphous silica particles with a D50 of 1.0 μm or more and 100 μm or less are used, crystalline silica particles obtained by heat treatment also have a D50 of 1.0 μm or more and 100 μm or less. Due to the heat treatment, the silica powder may be lightly adhered, but by performing the crushing treatment, it becomes a powder having the same average particle size as the original. Pulverization can be carried out with a general mixer or mill such as a tumbling ball mill, rocking mixer, bead mill, or the like. If the average particle size (D50) changes due to heat treatment, the change rate of the average particle size (D50) is confirmed in a preliminary test or preliminary survey, and based on the confirmation results, the spherical amorphous silica particles before heat treatment. The average particle size (D50) can be adjusted. Then, the particle size of the spherical amorphous silica particles can be easily adjusted by thermal spraying means. Therefore, the method of the present invention can easily produce spherical crystalline silica particles having an average particle size (D50) of 1.0 to 100.0 μm. In addition, spherical crystalline silica particles having an average particle size (D50) of 10.0 μm or more can be easily realized. Of course, if spherical amorphous silica particles with an average particle size (D50) of less than 1.0 μm are used, the process of the present invention will yield spherical crystalline silica particles with an average particle size (D50) of less than 1.0 μm. be able to. Moreover, when spherical amorphous silica particles having an average particle diameter (D50) of 10.0 μm or more are used, spherical crystalline silica particles having an average particle diameter (D50) of 10.0 μm or more can be obtained by the method of the present invention. can be done. Furthermore, if spherical amorphous silica particles having an average particle size (D50) of more than 100.0 μm are used, the method of the present invention can obtain spherical crystalline silica particles having an average particle size (D50) of more than 100.0 μm. can be done.

Also, the silica powder may be prepared so that the silica powder before thermal spraying contains 90 to 9000 ppm of aluminum. While not wishing to be bound by any particular theory, it is believed that aluminum acts as a crystal nucleator during heat treatment. Through the thermal spraying process (melting) the aluminum is evenly dispersed in the silica particles. It is thought that aluminum acts as a crystal nucleating agent during the subsequent heat treatment process, and because it is evenly dispersed in the silica particles, the crystals grow evenly at a lower temperature and in a shorter time than before. Realized.
In addition, alumina obtained by oxidizing aluminum can be expected to have the effect of enhancing the chemical durability (acid resistance, etc.) of silica particles. If the aluminum content is less than 90 ppm, the effect of promoting crystallization and the effect of improving chemical durability may not be sufficient. On the other hand, aluminum or alumina is also known to have the effect of lowering the melting point of silica. For example, the melting point of alumina-silica glass is lower than that of pure silica glass. Therefore, when the content of aluminum exceeds 9000 ppm, the melting point of the silica particles is lowered, and the silica particles are likely to bond together by fusion or sintering during heat treatment. If the bonding between the particles progresses, the fluidity, dispersibility and filling properties are insufficient when used as a filler for a semiconductor encapsulant, and wear of encapsulant production equipment is accelerated. In addition, semiconductor encapsulants generally require high purity, and it may not be appropriate to add 9000 ppm or more of aluminum.
In addition, the presence of aluminum has the effect of promoting crystallization when amorphous silica particles are mixed with calcium and crystallized.
Also, the content of aluminum can be measured by ICP mass spectrometry (ICP-MS).
The content of aluminum remains almost unchanged during the heat treatment stage for crystallization. Moreover, the mass of the silica particles before and after the heat treatment hardly changes. Therefore, by using spherical silica particles containing 90 to 9000 ppm of aluminum, the effect of promoting crystallization can be obtained. If the aluminum content changes due to heat treatment, the rate of change in the aluminum content is confirmed in a preliminary test or survey, and based on the confirmation results, the aluminum content of the spherical amorphous silica particles before heat treatment may be adjusted.

In addition, the silica powder before thermal spraying may contain metal impurities within a range that does not affect crystallization. Typical metal impurities include alkali metals (potassium, sodium, etc.), alkaline earth metals (magnesium, barium, etc.), and the like.

(Calcium raw material)
As a calcium raw material, _CaCO3, which is a carbonate, or Ca(OH) ₂ , which is a hydroxide, may be used. CaCO ₃ and Ca(OH) ₂ are chemically more stable than CaO, which is an oxide, and are relatively easy to handle because of their low safety hazards. When CaCO ₃ or Ca(OH) ₂ is used, Ca(OH) ₂ decomposes into CaO at a lower temperature of 580° C. compared to 825° C. of CaCO ₃ . Therefore, the use of Ca(OH) ₂ is considered to be CaO at a low temperature with the effect of promoting crystallization, and it is possible to obtain the effect of crystallization into quartz, which is a low-temperature crystal of silica. .

(lithium compound particles)
Li ₂ CO ₃ , which is a carbonate, may be used as the lithium compound particles. Li ₂ CO ₃ is relatively easy to handle when mixed with water because of its low solubility and low safety hazards. Also, Li ₂ CO ₃ melts at 710° C., but it is thought that it reacts with SiO ₂ at a temperature below the melting point and is incorporated into the SiO ₂ particles. By incorporating Li into SiO ₂ at such a low temperature, an effect of promoting crystallization at a low temperature is expected. On the other hand, lithium is one of alkali metals, and alkali metals may impair the reliability of electronic devices. Therefore, lithium compound particles do not have to be actively added, and are optionally mixed with spherical amorphous silica particles. Moreover, the lithium contained in the spherical crystalline silica particles after the heat treatment may be derived from impurities contained in the raw material amorphous silica particles or the like.

(Raw material powder adjustment process)
In the raw material powder preparation step, the spherical amorphous silica particles are mixed with the calcium raw material, or the calcium raw material and the lithium compound particles are mixed to obtain the raw material powder.

The calcium raw material and lithium compound particles to be mixed with the spherical amorphous silica particles are not particularly limited in form when added, such as oxides, carbonates, hydroxides, and nitrates. It can be added in the form of powder, aqueous solution, or the like, as long as it can be uniformly mixed with the amorphous spherical silica particles. The method of mixing is not particularly limited as long as each raw material is uniformly dispersed and mixed in the mixture. Mixing may be performed by a powder mixer. The mixing brings the calcium source material and the lithium compound particles into contact with at least a portion of the spherical amorphous silica, and the subsequent heat treatment step promotes crystallization of the spherical amorphous silica, particularly crystallization into quartz.

Here, in the spherical crystalline silica particles generated in the heat treatment step, calcium is 0.10 to 1.00% by mass in terms of oxide, and lithium is 0.05% by mass or less in terms of oxide. , the mixing ratio of the calcium raw material, or the calcium raw material and the lithium compound particles is adjusted. In addition, the said mass % makes the total mass of a spherical crystalline silica particle 100 mass %. The mass ratio of the raw material powder obtained by this mixing is generally the same even in the subsequent heat treatment stage for crystallization. However, since the total amount of the mixed calcium raw material and lithium compound particles may not be contained in the spherical crystalline silica particles after heat treatment, the mixing ratio is adjusted in consideration of the yield. Typically, when there is a difference in the composition of the raw material powder and the spherical crystalline silica particles, the difference in composition is confirmed in a preliminary test or preliminary investigation, and based on the confirmation result, the calcium raw material in the raw material powder before heat treatment, Alternatively, the mixing ratio of the calcium raw material and the lithium compound particles can be adjusted. Note that these adjustments may not be made depending on the results of prior confirmation. As a specific example, the loss of lithium and calcium under the heat treatment conditions for crystallization may be found in advance by testing under the same conditions, and the operation may be performed under those conditions. Therefore, by using the raw material powder, the lithium content and calcium content in the spherical crystalline silica particles of the present invention can be obtained.

(Heat treatment process)
The raw material powder obtained by mixing is heat-treated at 1125° C. or higher and 1300° C. or lower at an atmospheric pressure of 125 MPa or higher using a hot isostatic pressing apparatus for 1 hour or longer. In the heat treatment step, the calcium raw material and/or lithium compound particles contained in the raw material powder diffuse into the spherical amorphous silica particles, thereby promoting the crystallization of the spherical amorphous silica particles into quartz.

The heat treatment temperature is 1125° C. or higher and 1300° C. or lower.
If the temperature is lower than 1125°C, crystallization of amorphous silica is not sufficiently promoted, and spherical crystalline silica particles containing 50.0% or more of crystalline silica may not be obtained. In addition, when the temperature exceeds 1300° C., crystallization of amorphous silica is sufficiently promoted, but the resulting crystalline silica may contain a large amount of cristobalite in addition to quartz. That is, it may not be possible to obtain spherical crystalline silica particles in which 90.0% or more of the crystalline silica is quartz. The rate of temperature rise to the heat treatment temperature is not particularly limited, but if the rate of temperature rise is too slow, productivity may decrease, and if the rate of temperature rise is too fast, excessive equipment performance will be required. , 2° C./min to 20° C./min.

The atmospheric pressure is 125 MPa or higher. Crystallization of amorphous silica is sufficiently promoted by appropriate heat treatment, but crystalline silica obtained at a low atmospheric pressure may contain a large amount of cristobalite in addition to quartz. That is, when the pressure is less than 125 MPa, spherical crystalline silica particles in which 90.0% or more of the crystalline silica is quartz may not be obtained. It is believed that the higher the pressure, the more the formation of quartz is promoted, and the atmospheric pressure may be 147 MPa or higher. Although the upper limit of the pressure is not particularly limited, there is a limit of capability depending on the device, and typically it may be about 200 MPa or 196 MPa.

The heat treatment time is 1 hour or longer.
If the heat treatment time is less than 1 hour, crystallization of amorphous silica is not sufficiently promoted, and spherical crystalline silica particles containing 50.0% or more of crystalline silica may not be obtained. In general, longer heat treatment times promote crystallization. On the other hand, crystal forms other than quartz, such as cristobalite, may occur. Therefore, the heat treatment time can be appropriately adjusted so as to obtain the desired crystallinity and silica ratio. Therefore, the upper limit of the heat treatment time is not particularly limited, but it may be 24 hours or less, 20 hours or less, 16 hours or less, or 12 hours or less in consideration of productivity or the like.

In the present invention, heat treatment is performed using a hot isostatic pressing device. The hot isostatic pressing apparatus is a pressure treatment apparatus that pressurizes using the synergistic effect of pressure and temperature. It is possible to simultaneously apply pressure to the object to be treated.

Although not wishing to be bound by any particular theory, the following is believed to be the reason why the heat treatment at high temperature and high pressure yields spherical crystalline silica particles with a high silicification ratio.
It is known that heat treatment of amorphous silica under normal pressure (not under high pressure) promotes crystallization of amorphous silica. Furthermore, by mixing the amorphous silica with the calcium raw material, the calcium contained in the calcium raw material promotes crystallization, particularly quartification. However, the effect of calcium is limited to the points in contact with the amorphous silica particles. Therefore, crystallization (quartzification) inside the amorphous silica particles is less likely to be promoted, while cristobalite formation may be promoted inside the amorphous silica particles due to the influence of heat treatment (temperature). In other words, it is difficult to obtain spherical crystal grains with a high quartz crystallinity. According to the present invention, heat treatment under a pressure of 125 MPa or higher facilitates thermal diffusion of calcium into the amorphous silica particles, promoting crystallization (quartzization) even inside the amorphous silica particles. be. As a result, it is believed that spherical crystalline silica particles having a high silicification rate are obtained.
In general, the larger the grain size of the particles, the smaller the specific surface area and the thermal diffusion of calcium is not promoted, making it difficult to obtain spherical crystalline silica particles with a high silicification rate. According to the present invention, even with such particles having a large particle size, typically having an average particle size (D50) of 10.0 μm or more, a high silica ratio can be obtained.

(Use of spherical crystalline silica particles)
According to one aspect of the present invention, a composite composition of the finally obtained spherical crystalline silica particles and a resin, and further a resin composite obtained by curing the resin composite composition can be produced. The composition and the like of the resin composite composition will be described in more detail below.

By using a slurry composition containing spherical crystalline silica particles and a resin, it is possible to obtain a resin composite composition such as a semiconductor encapsulating material (especially a solid encapsulating material) and an interlayer insulating film. Further, by curing these resin composite compositions, it is possible to obtain resin composites such as sealing materials (cured bodies) and substrates for semiconductor packages.

When producing the resin composite composition, for example, in addition to the spherical crystalline silica particles and the resin, a curing agent, a curing accelerator, a flame retardant, a silane coupling agent, etc. are blended as necessary, and kneading or the like is performed. Composite in a way. Then, it is molded into a pellet shape, a film shape, or the like according to the application.

Furthermore, when producing a resin composite by curing the resin composite composition, for example, the resin composite composition is melted by applying heat, processed into a shape according to the application, and subjected to a higher heat than during melting. and let it harden completely. In this case, a known method such as a transfer molding method can be used.

For example, when manufacturing semiconductor-related materials such as package substrates and interlayer insulating films, as the resin used in the resin composite composition, known resins can be applied, but it is preferable to adopt epoxy resin. Epoxy resins are not particularly limited, but for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, naphthalene type epoxy resin, phenoxy type epoxy resin, etc. can be used. One of these may be used alone, or two or more of them having different molecular weights may be used in combination. Among these, epoxy resins having two or more epoxy groups in one molecule are preferable from the viewpoint of curability, heat resistance, and the like. Specifically, biphenyl-type epoxy resins, phenol novolac-type epoxy resins, ortho-cresol novolak-type epoxy resins, epoxidized novolac resins of phenols and aldehydes, glycidyl ethers such as bisphenol A, bisphenol F and bisphenol S, Glycidyl ester acid epoxy resins, linear aliphatic epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, alkyl-modified polyfunctionals obtained by the reaction of polybasic acids such as phthalic acid and dimer acid with epochlorhydrin Epoxy resins, β-naphthol novolak type epoxy resins, 1,6-dihydroxynaphthalene type epoxy resins, 2,7-dihydroxynaphthalene type epoxy resins, bishydroxybiphenyl type epoxy resins, bromine etc. for imparting flame retardancy Epoxy resin into which halogen is introduced. Among these epoxy resins having two or more epoxy groups in one molecule, bisphenol A type epoxy resins are particularly preferred.

In addition, resins other than epoxy resins can also be used for applications other than composite materials for semiconductor encapsulants, such as prepregs for printed circuit boards and resin composite compositions such as various engineering plastics. Specifically, in addition to epoxy resins, polyamides such as silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyimides, polyamideimides, and polyetherimides; polybutylene terephthalate, polyethylene terephthalate, etc. polyester; polyphenylene sulfide, aromatic polyester, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber/styrene) resin, AES (acrylonitrile/ethylene/propylene/diene rubber-styrene ) resins.

As the curing agent used in the resin composite composition, a known curing agent may be used to cure the resin, and for example, a phenol-based curing agent may be used. Phenol novolak resins, alkylphenol novolak resins, polyvinylphenols, and the like can be used as the phenol-based curing agent either singly or in combination of two or more.

As for the compounding amount of the phenolic curing agent, the equivalent ratio to the epoxy resin (phenolic hydroxyl group equivalent/epoxy group equivalent) is preferably 0.1 or more and less than 1.0. As a result, there is no residual unreacted phenolic curing agent, and the moisture absorption and heat resistance is improved.

The amount of the spherical crystalline silica particles of the present invention added to the resin composite composition is preferably large from the viewpoint of heat resistance and coefficient of thermal expansion, but is usually 70% by mass or more and 95% by mass or less, preferably 80% by mass. % or more and 95 mass % or less, more preferably 85 mass % or more and 95 mass % or less. This is because if the amount of the spherical crystalline silica particles is too small, it is difficult to obtain the effects of improving the strength of the sealing material and suppressing thermal expansion. This is because, regardless of the surface treatment, segregation due to agglomeration of spherical crystalline silica particles tends to occur in the composite material, and the viscosity of the composite material becomes too high, making it difficult to use as a sealing material.

As for the silane coupling agent, a known coupling agent may be used, but one having an epoxy-based functional group is preferable.

The present invention will be explained through the following examples and comparative examples. However, the present invention should not be construed as being limited to the following examples.

(Examples 1 to 4)
Amorphous silica particles were prepared by thermal spraying. In thermal spraying, a powder obtained by mixing 0.80% by mass of calcium in terms of oxide with respect to the total mass of the mass of crushed silica and the mass of calcium in terms of oxide was used as a raw material. The spherical amorphous silica particles (average particle diameter d50: 27.8 μm, circularity 0.92) are filled in a BN (boron nitride) container and subjected to hot isostatic pressing by Kobe Steel, Ltd. (Hot Isostatic Pressing: HIP) apparatus, nitrogen gas was used as a pressure medium, and heat treatment was performed under isostatic pressure. The holding temperature is Example 1 (1150 ° C.), Example 2 (1200 ° C.), Example 3 (1250 ° C.), Example 4 (1300 ° C.), Example 1 is 12 hours, Example 2 and Example 3 was held for 8 hours, and Example 4 was held for 1 hour. The temperature increase rate was about 600°C/hour. The nitrogen gas holding pressure under the holding temperature was 196 MPa.

(Examples 5 to 17)
The amorphous spherical silica powder used in Examples 1 to 4 was used. Lithium carbonate powder was mixed with the amorphous spherical silica. With respect to the total mass of the mass of the spherical amorphous silica and the mass of lithium in terms of oxide, the lithium carbonate particles were 0.01 mass% in terms of oxide (Examples 5 to 8) and 0.02 mass. % (Example 9), 0.03% by mass (Examples 10 to 13), and 0.05% by mass (Examples 14 to 17) were mixed. The mixed powder was filled in a BN container and heat-treated under isostatic pressure in a HIP apparatus using nitrogen gas as a pressure medium. The holding temperature was 1125°C (Example 14), 1150°C (Example 15), 1200°C (Example 5, Example 6, Example 9, Example 10, Example 11, Example 16), 1250°C. (Example 7, Example 12, Example 17) and 1300°C (Example 8, Example 13). The holding time was 1 hour (Example 5, Example 8, Example 9, Example 10, Example 13, Example 17), 8 hours (Example 6, Example 7, Example 11, Example 12). , Example 14, Example 15, and Example 16). The temperature increase rate was about 600°C/hour. The nitrogen gas holding pressure under the holding temperature was 196 MPa.

(Example 18)
The amorphous spherical silica powder used in Examples 1 to 4 was used. The amorphous spherical silica powder was filled in a BN container and heat-treated under isotropic pressure with a HIP apparatus using nitrogen gas as a pressure medium. The holding temperature was 1250° C., the holding time was 8 hours, and the heating rate was about 600° C./hour. The nitrogen gas holding pressure under the holding temperature was 147 MPa.

(Example 19, Example 20)
The amorphous spherical silica powder used in Examples 1 to 4 was used. Lithium carbonate powder was mixed with the amorphous spherical silica powder. Lithium carbonate particles were mixed in an amount of 0.01% by mass in terms of oxide with respect to the total mass of the mass of spherical amorphous silica and the mass of lithium in terms of oxide. The mixed powder was filled in a BN container and heat-treated under isostatic pressure in a HIP apparatus using nitrogen gas as a pressure medium. The holding temperature was 1250° C., the holding time was 8 hours, and the heating rate was about 600° C./hour. The nitrogen gas holding pressure under the holding temperature was 147 MPa (Example 19) and 125 MPa (Example 20).

(Examples 21 to 31)
Amorphous silica particles were prepared by thermal spraying. Calcium hydroxide particles and lithium carbonate particles were mixed with the spherical amorphous silica particles (average particle diameter d50: 30.2 μm, circularity 0.91). With respect to the total mass of the mass of spherical amorphous silica, the mass of calcium converted to oxide, and the mass of lithium converted to oxide, 0.20% by mass of calcium hydroxide particles in terms of oxide, and lithium carbonate particles in terms of oxide In conversion, no addition (Example 21), 0.01% by mass (Examples 22 to 24), 0.03% by mass (Example 25), 0.05% by mass (Examples 26 to 31 ) were mixed. The mixed powder was filled in a BN container and heat-treated at a high isostatic pressure with a HIP apparatus using nitrogen gas as a pressure medium. The holding temperature was 1250°C, the holding time was 8 hours (Example 21, Example 23, Example 25, Example 29, and Example 31), the holding temperature was 1150°C, the holding time was 12 hours (Example 22). ), the holding temperature is 1300°C, the holding time is 1 hour (Examples 24 and 30), the holding temperature is 1125°C, the holding time is 12 hours (Example 26), the holding temperature is 1200°C, the holding time is 8 The time (Examples 27 and 28) and the rate of temperature increase were about 600°C/h. The nitrogen gas holding pressure under the holding temperature was 196 MPa (Examples 21 to 27, 29 and 30), 147 MPa (Example 31) and 125 MPa (Example 28).

(Examples 32 to 40)
Amorphous silica particles were prepared by thermal spraying. Calcium hydroxide particles and lithium carbonate particles were mixed with the spherical amorphous silica particles (average particle diameter d50: 2.20 μm, circularity 0.93). With respect to the total mass of the mass of spherical amorphous silica, the mass of calcium converted to oxide, and the mass of lithium converted to oxide, 0.90% by mass of calcium hydroxide particles in terms of oxide, and lithium carbonate particles in terms of oxide In conversion, no addition (Examples 32 to 35), 0.01% by mass (Example 36), 0.03% by mass (Example 37), 0.05% by mass (Examples 38 and 39 , Example 40) were mixed. The mixed powder was filled in a BN container and heat-treated at a high isostatic pressure with a HIP apparatus using nitrogen gas as a pressure medium. The holding temperature was 1125°C and the holding time was 12 hours (Example 38), the holding temperature was 1150°C and the holding time was 12 hours (Example 32), the holding temperature was 1200°C and the holding time was 8 hours (Example 33), the holding temperature is 1250°C, the holding time is 8 hours (Examples 34, 36, 37, 39, and 40), the holding temperature is 1300°C, the holding time is 1 hour (Example 35), and the rate of temperature increase was about 600° C./hour. The nitrogen gas holding pressure under the holding temperature was 196 MPa (Example 32, Examples 34 to 39), 147 MPa (Example 40), and 125 MPa (Example 33).

(Comparative Examples 1 to 9)
The amorphous spherical silica powder used in Examples 1 to 4 was used. This silica powder was not mixed with lithium carbonate powder (Comparative Examples 1, 2, and 7), and the powder was mixed with lithium carbonate powder (Comparative Examples 3 to 6, and Comparative Example 8). , Comparative Example 9) were prepared. In the mixing of lithium carbonate, 0.01% by mass of lithium carbonate particles in terms of oxide with respect to the total mass of the mass of the spherical amorphous silica and the mass of lithium in terms of oxide (Comparative Example 3, Comparative Example 5, Comparative Example 8) and 0.05% by mass (Comparative Example 4, Comparative Example 6, Comparative Example 9) were mixed. The powder not mixed with lithium carbonate powder and the powder mixed with lithium carbonate powder were filled in a BN container, and heat-treated under isostatic pressure in a HIP apparatus using nitrogen gas as a pressure medium. The holding temperature was 1100° C. (Comparative Example 1, Comparative Example 3, Comparative Example 4, Comparative Example 7) and 1350° C. (Comparative Example 2, Comparative Example 5, Comparative Example 6, Comparative Example 8, Comparative Example 9). The holding time was 12 hours (Comparative Examples 1, 3, 4, 7) and 1 hour (Comparative Examples 2, 5, 6, 8, 9). The temperature increase rate was about 600°C/hour. The nitrogen gas holding pressure under the holding temperature was 196 MPa (Comparative Examples 1 to 6) and 147 MPa (Comparative Examples 7 to 9).

(Comparative Examples 10 to 13)
The amorphous spherical silica powder used in Examples 1 to 4 was used. A powder (Comparative Example 10) in which lithium carbonate powder was not mixed with this silica powder and a powder in which lithium carbonate powder was mixed (Comparative Examples 11 to 13) were prepared. In the mixing of lithium carbonate, 0.01% by mass of lithium carbonate particles in terms of oxide with respect to the total mass of the mass of the spherical amorphous silica and the mass of lithium in terms of oxide (Comparative Example 11). 03% by mass (Comparative Example 12) and 0.05% by mass (Comparative Example 13) were mixed. The powder not mixed with lithium carbonate powder and the powder mixed with lithium carbonate powder were filled in a BN container, and subjected to heat treatment at high isostatic pressure in a HIP apparatus using nitrogen gas as a pressure medium. The holding temperature was 1250°C. The holding time was 8 hours (Comparative Examples 10 to 12) and 1 hour (Comparative Example 13). The temperature increase rate was about 600°C/hour. The nitrogen gas holding pressure under the holding temperature was 118 MPa (Comparative Examples 10 to 13).

(Comparative Example 14, Comparative Example 15)
The amorphous spherical silica powder used in Examples 1 to 4 was used. A powder (Comparative Example 14) in which lithium carbonate powder was not mixed with this silica powder and a powder in which lithium carbonate powder was mixed (Comparative Example 15) were prepared. In the mixing of lithium carbonate, 0.05% by mass of lithium carbonate particles in terms of oxide was mixed with respect to the total mass of the mass of the spherical amorphous silica and the mass of lithium in terms of oxide. Powder not mixed with lithium carbonate powder and powder mixed with lithium carbonate powder were filled in an alumina container and heat-treated in an atmospheric atmosphere (atmospheric pressure) using an electric furnace SUPER-BURN (manufactured by Motoyama Co., Ltd.). . The temperature was raised to 1250° C. at a rate of 600° C./hour and held for 8 hours (Comparative Example 14) and 1 hour (Comparative Example 15). After that, it was cooled to room temperature at a cooling rate of about 100° C./hour.

(Comparative Examples 16 to 18)
The amorphous spherical silica powder used in Examples 21 to 31 was used. A powder was prepared by mixing only calcium hydroxide particles with the spherical amorphous silica particles (average particle size d50: 30.2 μm). 0.20% by mass of calcium in terms of oxide was mixed with respect to the total mass of the mass of spherical amorphous silica and the mass of calcium in terms of oxide. The mixed powder was filled in a BN container, and heat-treated under isostatic pressure in a HIP apparatus using nitrogen gas as a pressure medium. The holding temperature was 1100° C. (Comparative Example 16), 1350° C. (Comparative Example 17), and 1250° C. (Comparative Example 18). The holding time was 12 hours (Comparative Example 16), 1 hour (Comparative Example 17), and 8 hours (Comparative Example 18). The temperature increase rate was about 600°C/hour. The nitrogen gas holding pressure under the holding temperature was 196 MPa (Comparative Examples 16 and 17) and 118 MPa (Comparative Example 18).

(Comparative Examples 19 to 22)
The amorphous spherical silica powder used in Examples 21 to 31 was used. Powders were prepared by mixing both calcium hydroxide particles and lithium carbonate particles (Comparative Examples 19 to 22) with the spherical amorphous silica particles (average particle size d50: 30.2 μm). In the case of a powder in which only calcium hydroxide particles are mixed with amorphous silica particles, a predetermined amount of calcium in terms of oxide is added to the total mass of the mass of spherical amorphous silica and the mass of calcium in terms of oxide. were mixed. On the other hand, in the powder obtained by mixing both calcium hydroxide particles and lithium carbonate particles with spherical amorphous silica particles, the mass of spherical amorphous silica and calcium are converted to oxides, and lithium is converted to oxides. With respect to the total mass of the mass obtained, the calcium hydroxide particles are 0.20% by mass in terms of calcium oxide, and the lithium carbonate particles are 0.01% by mass in terms of lithium oxide (Comparative Example 19, Comparative Example 21) and 0.05% by mass (Examples 20 and 22). The mixed powder was filled in a BN container, and heat-treated under isostatic pressure in a HIP apparatus using nitrogen gas as a pressure medium. The holding temperature was 1100° C. (Comparative Examples 19 and 20) and 1350° C. (Comparative Examples 21 and 22), and the holding time was 12 hours (Comparative Examples 19 and 20) and 1 hour (Comparative Example 21). , Comparative Example 22). The temperature increase rate was about 600°C/hour. The nitrogen gas holding pressure under the holding temperature was 196 MPa.

(Comparative Examples 23 to 25)
The amorphous spherical silica particles used in Examples 32-40 were used. A powder was prepared by mixing only calcium hydroxide particles with the spherical amorphous silica particles (average particle size d50: 2.2 μm). 0.90% by mass of calcium in terms of oxide was mixed with respect to the total mass of the mass of spherical amorphous silica and the mass of calcium in terms of oxide. The mixed powder was filled in a BN container, and heat-treated under isostatic pressure in a HIP apparatus using nitrogen gas as a pressure medium. The holding temperature was 1100° C. (Comparative Example 23), 1350° C. (Comparative Example 24) and 1250° C. (Comparative Example 25), and the holding time was 12 hours (Comparative Example 23), 1 hour (Comparative Example 24) and 8 hours. (Comparative Example 25). The temperature increase rate was about 600°C/hour. The nitrogen gas holding pressure under the holding temperature was 196 MPa (Comparative Examples 23 and 24) and 118 MPa (Comparative Example 25).

(Comparative Examples 26 to 29)
The amorphous spherical silica particles used in Examples 32-40 were used. A powder was prepared by mixing both calcium hydroxide particles and lithium carbonate particles with the spherical amorphous silica particles (average particle size d50: 2.2 μm). With respect to the total mass of the mass of spherical amorphous silica, the mass of calcium converted to oxide, and the mass of lithium converted to oxide, calcium hydroxide particles are added in an amount of 0.90% by mass in terms of calcium oxide, and lithium carbonate particles were mixed so that lithium was 0.01% by mass (Comparative Examples 26 and 28) and 0.05% by mass (Examples 27 and 29) in terms of oxide. The mixed powder was filled in a BN container, and heat-treated under isostatic pressure in a HIP apparatus using nitrogen gas as a pressure medium. The holding temperature was 1100° C. (Comparative Examples 26 and 27) and 1350° C. (Comparative Examples 28 and 29), and the holding time was 12 hours (Comparative Examples 26 and 27) and 1 hour (Comparative Example 28). , Comparative Example 29). The temperature increase rate was about 600°C/hour. The nitrogen gas holding pressure under the holding temperature was 196 MPa.

The silica particles obtained in Examples and Comparative Examples are shown in Tables 1 and 2, respectively.

The measurement method for each item in Tables 1 and 2 will be described.

(Constituent phase ratio)
The existence ratio of amorphous and crystalline silica in the silica particles obtained by the heat treatment, the type of crystalline silica, and the ratio thereof were determined by XRD. In the present invention, an X-ray diffractometer "D2 PHASER" (manufactured by Bruker) was used. Quantitative analysis of the crystal phase by the Riedveld method was performed using crystal structure analysis software "TOPAS" (manufactured by Bruker).
When the spherical crystalline silica particles are composed of amorphous and crystalline silica, the existence ratio of amorphous and crystalline silica, the type of crystalline silica, and the ratio are determined by the integrated intensity of the crystalline peak in XRD measurement. From the sum (Ic) and the integrated intensity (Ia) of the amorphous halo portion, the ratio of the crystalline phase can be obtained by calculation according to the following formula. More specifically, the proportion of the crystalline silica phase contained in the spherical crystalline silica particles can be determined.
X (crystal phase ratio) = Ic / (Ic + Ia) × 100 (%)
In the present invention, XRD measurements were performed in the range of 2Θ=10° to 90°. The crystalline phase ratio was obtained from the sum of the crystalline peak intensities appearing in the 2Θ measurement range and the integrated intensity of the halo portion caused by the broad amorphous matter appearing around 2Θ=22°.
Furthermore, the quantitative analysis of the crystal phase by the Reedveld method was performed without using a standard sample.

(Circularity)
Circularity was determined by a flow particle image analysis method. In the present invention, a flow type particle image analyzer "FPIA-3000" (manufactured by Spectris) was used.

(Average particle size)
The average particle size (D50) of the spherical quartz particles was measured by a laser diffraction/scattering particle size distribution measurement method.

(impurity amount or additive amount)
The content of impurities or additive elements such as lithium and calcium in the spherical silica particles of the present invention was measured by ICP mass spectrometry (ICP-MS). Specifically, it was measured using ICP-MS (“7700X” manufactured by Agilent) in accordance with JIS-K0133. An aqueous solution in which silica particles were completely dissolved with hydrofluoric acid was used as a sample. Here, the impurity element content contained in the silica particles was defined as the impurity element content in the silica solution. A standard curve was prepared using a reagent-only base solution.

(Regarding impurities in amorphous spherical silica particles)
The zinc content of the spherical amorphous silica particles produced by the thermal spraying method in Examples and Comparative Examples is less than 1.0 ppm in terms of metal content, and the total amount of alkali metals (Li, K and Na) is It was 22 to 38 ppm in terms of metal. The amorphous spherical silica described in Examples 1 to 18 and Comparative Examples 1 to 15 in which calcium was added during thermal spraying contains 7931 ppm of calcium, but Examples 19 to 28 and Comparative Example 16. The total amount of alkaline earth metals (Ca+Mg+Ba) in the amorphous spherical silica used in Comparative Example 27 was 11 to 32 ppm, and the amount of aluminum metal was 97 to 8230 ppm.

(Regarding Examples and Comparative Examples)
In the examples according to the present invention, the lithium content is 0.05% by mass or less in terms of oxide, and the calcium content is in the range of 0.10% by mass or more and less than 1.0% by mass in terms of oxide. Spherical crystalline silica particles were obtained in which 50% or more of the mass of the whole was crystalline silica, and 90.0% or more of the crystalline silica was quartz. The particles of the examples according to the invention had a circularity of 0.86 to 0.92. As for the average particle size, three types of amorphous spherical silica having average particle sizes of 27.8 μm, 30.2 μm and 2.20 μm were used as raw materials in the examples according to the present invention. The average particle size of the silica particles of the present invention using a raw material having an average particle size of 27.8 μm was 27.8 μm to 30.2 μm. In addition, the average particle size of the silica of the present invention using a raw material having an average particle size of 30.2 μm was 32.3 μm to 33.8 μm. Furthermore, the average particle size of the silica particles of the present invention using a raw material having an average particle size of 2.2 μm was 2.3 μm to 2.6 μm.

(About heat treatment temperature)
Comparing Examples 1 to 20 with Comparative Examples 1 to 9, the lithium content is 0.05 mass% or less in terms of oxide, and the calcium content is 0.10 mass in terms of oxide. When the isotropic pressure of the atmosphere gas is 125 to 196 MPa and the heat treatment temperature is from 1125 ° C. to 1300 ° C. or less using raw materials that are less than 1.0% by mass, 50% or more of the whole is crystalline silica. , and 90% or more of the crystalline silica is quartz.

(Regarding the type of amorphous spherical silica used as raw material)
When comparing Examples 21 to 31 (using amorphous spherical silica having an average particle size of 30.2 μm as a raw material) with Comparative Examples 16, 17, and 19 to 22, further (average Compared with Examples 32 to 40 and Comparative Examples 23, 24, and 26 to 29, in which amorphous spherical silica having a particle size of 2.20 μm was used as a raw material, the lithium content was oxidized. It is 0.05% by mass or less in terms of substance, the calcium content is 0.10% by mass or more and less than 1.0% by mass in terms of oxide, and even when using raw materials with different average particle diameters, the atmospheric gas Only when the isotropic pressure is 125 MPa or more and the heat treatment temperature is from 1125° C. to 1300° C. or less, 50% or more of the whole is crystalline silica, and 90% or more of the crystalline silica is quartz.

(Regarding isotropic pressure of atmosphere gas)
Comparing Example 3, Example 7, Example 12, Example 17 to Example 20 with Comparative Example 10 to Comparative Example 15, the isotropic pressure of the atmosphere gas was 125 MPa or more even at the same heat treatment holding temperature of 1250 ° C. 50% or more of the whole is crystalline silica, and 90% or more of the crystalline silica is quartz. It can be seen that when the isotropic pressure of the atmosphere is less than 125 MPa, the appearance of cristobalite increases and the proportion of quartz in the crystalline silica falls below 90%. It can be seen that the isotropic pressure of the atmosphere gas must be 125 MPa or more and the heat treatment temperature must be 125° C. to 1300° C. or less.
Examples 21 to 31 and Comparative Example 18 (using amorphous spherical silica having an average particle size of 30.2 μm as a raw material), and Comparative Example 18 (using amorphous spherical silica having an average particle size of 2.20 μm as a raw material) ) When Examples 32 to 40 and Comparative Example 25 are compared, the lithium content is less than 0.05% by mass in terms of oxide, and the calcium content is 0.10 mass or more in terms of oxide. It can be seen that even when raw materials with less than 0% by mass and different average particle diameters are used, the appearance of cristobalite increases when the isotropic pressure of the atmosphere is less than 125 MPa, and the proportion of quartz in crystalline silica falls below 90%. . It can be seen that the isotropic pressure of the atmosphere gas must be 125 MPa or more and the heat treatment temperature must be 1125° C. to 1300° C. or less.

Claims

Circularity is 0.80 or more, average particle size (D50) is 1.0 μm or more and 100.0 μm or less, lithium is 0.05% by mass or less in terms of oxide, and calcium is 0.10 in terms of oxide. Spherical crystalline silica particles containing less than ~1.00% by mass, 50.0% or more of the whole being crystalline silica, and 90.0% or more of said crystalline silica being quartz.
The spherical crystalline silica particles according to claim 1, containing 0.02% by mass or less of lithium in terms of oxide.
The spherical crystalline silica particles according to claim 1 or 2, wherein cristobalite accounts for 5.0% or less of the whole.
The spherical crystalline silica particles according to any one of claims 1 to 3, containing 90 to 9000 ppm of aluminum.
The spherical crystalline silica particles according to any one of claims 1 to 4, having an average particle size (D50) of 10.0 μm or more.
A raw material powder preparation step of mixing spherical amorphous silica particles with a calcium raw material or mixing a calcium raw material and lithium compound particles to obtain a raw material powder;
The raw material powder obtained in the raw material powder preparation step is heat-treated at a temperature of 1125° C. or higher and 1300° C. or lower and a pressure of 125 MPa or higher using a hot isostatic pressing apparatus for 1 hour or longer to obtain spherical crystals. a heat treatment step to produce fine silica particles;
including
In the spherical crystalline silica particles generated in the heat treatment step, calcium is 0.10 to 1.00% by mass in terms of oxide, and lithium is 0.05% by mass or less in terms of oxide. like,
Adjusting the mixing ratio of the calcium raw material or the calcium raw material and the lithium compound particles in the raw material powder adjusting step,
A method for producing spherical crystalline silica particles.
A resin composite composition comprising the spherical crystalline silica particles according to any one of claims 1 to 5 in a resin.
A resin composite obtained by curing the resin composite composition according to claim 7.