Silica powder

Abstract

This invention provides a silica powder with excellent viscosity and sedimentation properties when blended into resins. [Solution] The silica powder of the present invention satisfies the following conditions: when the sedimentation velocity measured according to a predetermined procedure is V (mm / h) and the viscosity measured according to a predetermined procedure is η (Pa·s), V and η satisfy η < -720V + 850.

Description

[Technical Field]

[0001] This invention relates to silica powder. [Background technology]

[0002] Various developments have been made regarding spherical silica. As an example of this type of technology, the technology described in Patent Document 1 is known. Patent Document 1 describes that molten spherical silica having the same particle size distribution as the raw material can be obtained by injecting silicate raw material powder into a flame and melting it. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2000-191317 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, as a result of our investigation, we found that in resin compositions containing silica powder, low viscosity and non-settling properties exhibit a trade-off relationship. [Means for solving the problem]

[0005] The inventors, through further investigation, discovered that by using the fact that the settling velocity and resin viscosity satisfy a predetermined relationship when silica powder is blended into a resin as an indicator, the trade-off characteristics between low viscosity and non-settling properties can be improved in a resin composition containing silica powder, thereby improving the practical viscosity and settling properties, and thus completing the present invention.

[0006] According to one aspect of the present invention, the following silica powder is provided. 1. Silica powder, A silica powder in which, when the sedimentation velocity measured according to the following procedure is V (mm / h) and the viscosity measured according to the following procedure is η (Pa·s), V and η satisfy η < -720V + 850. (Procedure for measuring sedimentation velocity) Area 2cm 2 An epoxy resin is filled into the inside of a cylindrical container, 15 g of the silica powder is placed at the interface of the epoxy resin layer, and after being held at 25°C for 18 hours, the deepest position of the silica powder that has settled from the interface of the layer into the interior is measured. The settling velocity is calculated by [deepest position (mm)] / [holding time (h)]. (Viscosity measurement procedure) The silica powder is mixed with liquid bisphenol F type epoxy at 25°C to obtain the above-mentioned evaluation resin sample. The viscosity (Pa·s) of the obtained evaluation resin sample is measured using a rheometer at 25°C and a shear rate of 1 [1 / s]. 2. The silica powder described in 1. Silica powder having V between 0.2 and 1.0, and / or η between 50 and 300. 3. Silica powder as described in 1. or 2., The specific surface area measured by the BET single-point method using nitrogen gas adsorption is 1.6 m². 2 / g or more 4.4m 2 Silica powder with a weight of less than / g. 4. A silica powder described in any one of items 1 to 3, In the volume-based cumulative distribution of particle size measured by laser diffraction scattering, the particle size at the point where the cumulative volume from the smallest particle side reaches 50% is defined as D. 50 In that case, D 50 Silica powder with a particle size between 15 μm and 35 μm. 5. A silica powder described in any one of items 1 to 4, Silica powder in which, in the volume-based cumulative distribution of particle size measured by laser diffraction scattering, the cumulative volume at a particle size of 1 μm is 1.6% or more. 6. The silica powder according to any one of 1. to 5., The silica powder, wherein the frequency of the maximum peak in the volume-based frequency distribution of the particle diameter measured by the laser diffraction scattering method is 14.0% or more. 7. The silica powder according to any one of 1. to 6., The silica powder according to 1. or 2., In the volume-based frequency distribution of the particle diameter measured by the laser diffraction scattering method, the frequency of particles having a particle diameter of 1 μm or less is 0.5% or more, and / or the frequency of particles having a particle diameter exceeding 64 μm and not exceeding 96 μm is 11.0% or less. 8. The silica powder according to any one of 1. to 7., The silica powder having an average sphericity of 0.85 or more.

Advantages of the Invention

[0007] According to the present invention, there is provided a silica powder having excellent viscosity characteristics and sedimentation characteristics when blended with a resin.

Brief Description of the Drawings

[0008] [Figure 1] It is a diagram showing the relationship between the viscosity and the sedimentation rate of the silica powder in Examples and Comparative Examples.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same components are denoted by the same reference numerals, and the description will be omitted as appropriate. The drawings are schematic and do not match the actual dimensional ratios.

[0010] The outline of the silica powder of the present embodiment will be described.

[0011] The silica powder of the present embodiment is When the sedimentation velocity measured according to the following procedure is V (mm / h) and the viscosity measured according to the following procedure is η (Pa·s), V and η satisfy the condition η < -720V + 850. (Procedure for measuring sedimentation velocity) Area 2cm 2 An epoxy resin is filled into a cylindrical container, 15 g of the silica powder is placed at the interface of the epoxy resin layer, and after being held at 25°C for 18 hours, the deepest position of the silica powder that has settled from the layer interface into the interior is measured. The settling velocity is calculated by [deepest position (mm)] / [holding time (h)]. (Viscosity measurement procedure) The silica powder is mixed with liquid bisphenol F type epoxy to obtain the above-mentioned evaluation resin sample. The viscosity (Pa·s) of the obtained evaluation resin sample is measured using a rheometer at 25°C and a shear rate of 1 [1 / s].

[0012] For example, it is preferable that V is between 0.2 and 1.0, and / or that η is between 50 and 300. In this case, the lower limit of V is preferably 0.3 or higher, more preferably 0.4 or higher. The upper limit of V is preferably 0.9 or lower, more preferably 0.85 or lower. On the other hand, the lower limit of η is preferably 70 or higher, more preferably 90 or higher. The upper limit of η is preferably 280 or lower, more preferably 250 or lower.

[0013] Generally, the relationship between particle size and viscosity or sedimentation velocity is considered to be as follows: As the particle size of silica powder increases, the viscosity of the resin composition containing the silica powder decreases, and conversely, as the particle size decreases, the viscosity tends to increase. According to Stokes' equation, if the particle size of silica powder is large, the settling velocity of the silica powder in the resin composition increases, and conversely, if the particle size is small, the settling velocity decreases. In other words, when using general silica powder and varying its particle size, plotting the viscosity of the resin composition on the vertical axis and the sedimentation velocity of the silica powder in the resin composition on the horizontal axis resulted in a straight line showing the trade-off between viscosity and sedimentation velocity, or a distribution above such a straight line, because the sedimentation velocity increased as the viscosity decreased.

[0014] According to our findings, by combining coarse powder with relatively large particle sizes and fine powder with relatively small particle sizes, and appropriately controlling the particle size and particle size distribution of the silica powder, we have found that the above-mentioned trade-off characteristics can be improved, and a silica powder can be realized that has the characteristics of being distributed below the trade-off line where the vertical axis is viscosity and the horizontal axis is sedimentation velocity. Although the detailed mechanism is not clear, it is presumed that by controlling the amount of coarse and fine powder added and the particle size of the coarse powder based on the volume-based frequency distribution of particle size, the viscosity of the resin composition containing the silica powder can be reduced while reducing the overall particle size of the silica powder, thereby improving the trade-off characteristics of high viscosity and non-settling properties.

[0015] The composition of the silica powder in this embodiment will be described in detail below.

[0016] <Silica powder> Silica powder can be any powder that contains silica (SiO2) as its main component. The term "main component" means that, by mass, silica (SiO2) is present in the total amount of silica powder, for example, 50% or more, preferably 80% or more, and more preferably 90% or more. While high purity is preferable for silica powder, the presence of impurities that inevitably occur during the raw material and manufacturing process is acceptable.

[0017] Silica powder may contain either amorphous or crystalline silica, or both. The amorphous content of the silica powder is, for example, 95.0% or more, preferably 97.0% or more, and more preferably 99.0% or more.

[0018] The amorphous ratio of the silica powder is measured from the intensity ratio of specific diffraction peaks by performing X-ray diffraction analysis in the range of 2θ of CuKα ray from 26° to 27.5° using a powder X-ray diffractometer (for example, the product name "Model MiniFlex" manufactured by Rigaku Corporation). In the case of silica powder, crystalline silica has a main peak at 26.7°, but amorphous silica has no peak. When amorphous silica and crystalline silica are mixed, a peak height of 26.7° corresponding to the proportion of crystalline silica is obtained. Then, from the ratio of the X-ray intensity of the sample to the X-ray intensity of the crystalline silica standard sample, the mixed ratio of crystalline silica (X-ray diffraction intensity of the sample / X-ray diffraction intensity of crystalline silica) is calculated, and the amorphous ratio (%) can be calculated from the formula, amorphous ratio (%) = (1 - mixed ratio of crystalline silica) × 100.

[0019] The shape of the silica powder may be any of spherical, crushed, needle-like, flaky, etc., but spherical is preferred.

[0020] The average sphericity of the silica powder is, for example, 0.85 or more, preferably 0.90 or more, and more preferably 0.95 or more. Thereby, when the silica powder is mixed with the resin, a decrease in fluidity can be more suppressed.

[0021] The average sphericity of the silica powder is measured as follows. Particle images taken with a stereomicroscope (for example, the model "SMZ-10 type" manufactured by Nikon Corporation), a scanning electron microscope, etc. are imported into an image analyzer (for example, manufactured by Nippon Avionics Co., Ltd., etc.). The projected area (A) and the perimeter (PM) of the particles are measured from the photograph. Assuming the area of a perfect circle corresponding to the perimeter (PM) as (B), the circularity of the particle can be expressed as A / B. Therefore, assuming a perfect circle having the same perimeter as the perimeter (PM) of the sample particles, PM = 2πr, B = πr 2 So, B = π × (PM / 2π) 2 And the sphericity of each particle can be calculated as sphericity = A / B = A × 4π / (PM) 2 and can be calculated as such. The roundness of 200 arbitrary particles obtained in this way was determined, and the average value was taken as the average sphericity.

[0022] The upper limit of the specific surface area of ​​silica powder is, for example, 4.4 m². 2 Less than or equal to / g, preferably 4.0m 2 / g or less, more preferably 3.0m 2 It is less than / g. This suppresses the increase in viscosity in the low shear region when compounded with resin. The lower limit of the specific surface area mentioned above is, for example, 1.2 m². 2 / g or more, preferably 1.5m 2 / g or more, more preferably 1.7m 2 It is 1 / g or more. This allows for better suppression of the increase in sedimentation velocity when mixed with resin.

[0023] The specific surface area of ​​silica powder can be measured by the BET single-point method using nitrogen gas adsorption. Specifically, using a specific surface area analyzer (Anton Paar, instrument name: NOVA 800 BET), nitrogen gas is transported as the adsorption gas by a vacuum pump, and 0.1 to 5.0 g of the sample is dried and degassed at 300°C for 30 minutes before measurement.

[0024] In the volume-based cumulative distribution of particle size of silica powder, the particle size at the point where the cumulative volume from the smallest particles reaches 50% is defined as D. 50 Let's assume that. D 50 The lower limit is, for example, 15 μm or more, preferably 16 μm or more, and more preferably 17 μm or more. This improves the fluidity during resin filling. D 50 The upper limit is, for example, 35 μm or less, preferably 32 μm or less, and more preferably 30 μm or less. Keeping it below the upper limit improves the particle settling velocity.

[0025] In the volume-based cumulative distribution of particle size of silica powder, the lower limit of the cumulative volume at a particle size of 1 μm is, for example, 1.6% or more, preferably 1.7% or more. This improves the particle sedimentation velocity. The upper limit of the cumulative volume for a particle size of 1 μm is, for example, 7% or less, preferably 6% or less, and more preferably 5% or less. Keeping it below this upper limit improves the fluidity during resin filling.

[0026] In the volume-based cumulative distribution of particle size of silica powder, the lower limit of the cumulative volume for a particle size of 48 μm is, for example, 63% or more, preferably 65% ​​or more, and more preferably 68%. This improves the particle settling velocity. The upper limit of the cumulative volume for a particle size of 48 μm is, for example, 75% or less, preferably 74% or less, and more preferably 73% or less. Keeping it below this upper limit improves the fluidity during resin filling.

[0027] The lower limit of the frequency of the maximum peak in the volume-based frequency distribution of silica powder particle size is, for example, 14.0% or more, preferably 15.0% or more, and more preferably 17.0% or more. This improves the fluidity during resin filling. The upper limit of the frequency of the maximum peak mentioned above is not particularly limited, but it may be 35% or less, 25% or less, or 22% or less.

[0028] Furthermore, in the volume-based frequency distribution of silica powder, the number of peaks showing a frequency maximum within the range of 1 μm to 96 μm may be one or multiple peaks. If silica powder has multiple peaks, the peak with the highest frequency is defined as the "maximum peak." Furthermore, in the volume-based frequency distribution, among the multiple peaks, the lower limit of the particle size difference between the largest and smallest particle sizes may be, for example, 30 μm or more, 40 μm or more, or 60 μm or more, while the upper limit may be 100 μm or less, 90 μm or less, or 80 μm or less.

[0029] In the volume-based frequency distribution of particle size of silica powder, the frequency of particles with a particle size of 1 μm or less may be, for example, 0.5% or more, and / or the frequency of particles with a particle size greater than 64 μm and less than or equal to 96 μm may be, for example, 11.0% or less. The lower limit of the frequency of particles with a particle diameter of 1 μm or less is, for example, 0.5% or more, preferably 0.6% or more, and more preferably 0.7% or more. This improves the fluidity during resin filling. The upper limit of the frequency of particles with a particle diameter of 1 μm or less is not particularly limited, but may be 2.0% or less. Furthermore, the upper limit for the frequency of particles with a particle diameter greater than 64 μm and less than or equal to 96 μm is, for example, 11.0% or less, preferably 10.5% or less, and more preferably 10% or less. Keeping the frequency below this upper limit improves the particle sedimentation velocity. The lower limit of the frequency of particles with a diameter greater than 64 μm and less than or equal to 96 μm is not particularly limited, but it may be 7.5% or more.

[0030] The volume-based frequency distribution and volume-based cumulative distribution of particle size of silica powder are values ​​based on particle size measurement using the wet laser diffraction scattering method. For example, the Coulter LS13 320 particle size analyzer can be used for measurement. For measurement, water is used as the solvent, and as a pretreatment, dispersion treatment can be performed using a homogenizer at a power of 500W for 120 seconds or more. Furthermore, the PIDS (Polarization Intensity Differential Scattering) concentration should be adjusted to 45-55%. A refractive index of 1.33 is used for water, and the refractive index of the powder material should be considered. For example, amorphous silica is measured with a refractive index of 1.50.

[0031] In this embodiment, the sedimentation rate and viscosity when compounded with the resin can be controlled by appropriately selecting, for example, the raw material components of the silica powder and the method for producing the silica powder. Among these, for example, combining the adjustment of the amount of fine powder added and the adjustment of the particle size of the added powder based on the volume-based frequency distribution of particle size can be cited as elements for setting the sedimentation rate and viscosity when compounded with the resin to a desired numerical range.

[0032] <Method for producing silica powder> As an example of the manufacturing method of this embodiment, silica powder can be obtained by classifying raw silica powder produced by a dry process. Furthermore, classification can be carried out by mixing or classifying appropriate amounts of silica powder with different particle size configurations. Industrially, classification using a classifier such as a sieve or a precision air classifier is preferable, and the classification operation is preferably performed using a dry method. By dry classifying raw silica powder produced by a dry method, aggregation of the silica powder can be suppressed and handling properties can be improved compared to using raw silica powder produced by a wet method and / or wet classification.

[0033] Next, the resin composition of this embodiment will be described. The silica powder of this embodiment, when incorporated into a resin composition, can be suitably used as a resin material. The resin composition includes, in addition to the silica powder of this embodiment, a resin and known resin additives.

[0034] Silica powder may be used alone in the resin composition, or it may be used in mixture with other fillers. The resin composition may contain 10 to 99% by mass of silica powder, or 10 to 99% by mass of a mixed inorganic powder containing silica powder and other fillers. In addition, the content of other fillers in the mixed inorganic powder may be, for example, 0 to 99% by mass or 1 to 50% by mass, relative to 100% by mass of silica powder. In this specification, unless otherwise specified, "~" indicates that it includes both the upper and lower limits.

[0035] Other fillers include, for example, silica other than the silica powder of this embodiment, alumina, titania, silicon nitride, aluminum nitride, silicon carbide, talc, calcium carbonate, and the like. Other fillers used typically have an average particle size of around 5 to 100 μm, and there are no particular restrictions on their particle size composition or shape.

[0036] Examples of the above-mentioned resins include epoxy resins, silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyimides, polyamide-imides, polyetherimides and other polyamides, polyesters such as polybutylene terephthalate and polyethylene terephthalate, polyphenylene sulfide, fully aromatic polyesters, polysulfones, liquid crystal polymers, polyethersulfones, polycarbonates, maleimide-modified resins, ABS resins, AAS (acrylonitrile-acrylic rubber-styrene) resins, and AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins. These may be used individually or in combination of two or more types.

[0037] Resin compositions can be manufactured, for example, by blending raw material components in predetermined ratios using a blender or Henschel mixer, then kneading them using a heated roll, kneader, single-screw or twin-screw extruder, cooling, and then grinding the mixture.

[0038] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. [Examples]

[0039] The present invention will be described in detail below with reference to examples, but the present invention is not limited in any way to the descriptions of these examples.

[0040] <Manufacturing of silica powder> Silica powder was produced by mixing at least two types of raw silica particles A to F, having average particle sizes of 50 μm, 40 μm, 10 μm, 5 μm, 0.5 μm, and 0.2 μm, in predetermined mixing ratios, so as to achieve the particle size distribution and specific surface area shown in Table 1.

[0041] <Specific surface area> The specific surface area of ​​silica powder was measured using the BET 1-point method with nitrogen gas adsorption. Specifically, using a specific surface area analyzer (Anton Paar, model name: NOVA 800 BET), nitrogen gas was transported by a vacuum pump, and 0.1 to 5.0 g of the sample was dried and degassed at 300°C for 30 minutes before measurement.

[0042] <Particle size> The volume-based frequency distribution and volume-based cumulative distribution of silica powder particle size were determined using a wet laser diffraction scattering method with a particle size distribution analyzer (Microtrac-Bell MT-3300). Water was used as the solvent for the measurements. A refractive index of 1.33 was used for water, and the refractive index of the powder material was considered. For example, amorphous silica was measured with a refractive index of 1.50. In each distribution, the particle size (μm) intervals were set to 1, 1.5, 2, 3, 4, 6, 8, 12, 16, 24, 32, 48, 64, 96, 128, and 192 μm. In the obtained volume-based frequency distribution, the number of particle size frequency peaks within the range of 1 μm to 96 μm was two or more in Examples 1 to 3 and Comparative Examples 1 to 3. The frequency (%) of the maximum particle size peak, the difference (μm) between the particle size of the maximum frequency peak and the particle size of the minimum frequency peak, the frequency of 1 μm or less, and the frequency of 64 μm to 96 μm are shown in Table 1, respectively. Based on the obtained volume-based cumulative distribution, the particle size (D) at which the cumulative value from the small particle size side becomes X% X The cumulative volume (%) for particle size 1 μm and the cumulative volume (%) for particle size 48 μm are shown in Table 1.

[0043] <Average sphericity> The average sphericity of silica powder was measured by capturing particle images using a stereomicroscope (e.g., Nikon's SMZ-10 model) or scanning electron microscope, and then inputting the images into an image analysis device (e.g., one manufactured by Japan Avionics Co., Ltd.) as follows: The projected area (A) and perimeter (PM) of the particle were measured from the photograph. If (B) is the area of ​​a perfect circle corresponding to the perimeter (PM), then the roundness of the particle can be expressed as A / B. Therefore, assuming a perfect circle with the same perimeter (PM) as the sample particle, PM = 2πr and B = πr 2 Therefore, B = π × (PM / 2π) 2 Therefore, the sphericity of each particle is given by: Sphericity = A / B = A × 4π / (PM) 2 It can be calculated as follows. The roundness of 200 arbitrary particles obtained in this way was determined, and the average value was taken as the average sphericity. The average sphericity of the silica powders in Examples 1 to 3 was confirmed to be 0.85 or higher in all cases.

[0044] [Table 1]

[0045] The following items were evaluated for the obtained silica powder.

[0046] <Settling velocity> Area 2cm 2 An epoxy resin was filled into a cylindrical container, and 15 g of the silica powder was placed at the interface of the epoxy resin layer. The container was then held at 25°C for 18 hours. After that, the deepest position of the silica powder that had settled inside the epoxy resin layer was measured. Based on the obtained results, the settling velocity was calculated based on [deepest position (mm)] / [holding time (h)]. The results are shown in Table 1.

[0047] <Viscosity> A resin sample (evaluation resin sample) was obtained by mixing 20% ​​by mass of the obtained silica powder with 80% by mass of liquid epoxy resin (Mitsubishi Chemical Corporation, bisphenol F type resin, JER807). The viscosity (Pa·s) of the obtained resin samples was measured at 25°C and a shear rate of 1 [1 / s] using a rheometer (Anton Paar, Model Modular Compact Rheometer MCR 102) equipped with a conical cone (3 degrees). The results are shown in Table 1.

[0048] Figure 1 shows a graph plotting the values ​​for each example and comparative example listed in Table 1, with sedimentation velocity (V) on the horizontal axis (X-coordinate) and viscosity (η) on the vertical axis (Y-coordinate). In Figure 1, the trade-off function (straight line) represented by Y(η) = -720X(V) + 850 is shown as a dotted line. All comparative examples 1-3 are plotted in the upper right of the trade-off function, and all examples 1-3 are plotted in the lower left. Comparative Examples 1-3, shown in Figure 1, confirm a trade-off relationship where decreasing viscosity increases the settling velocity, while increasing viscosity decreases the settling velocity. In contrast, the silica powders of Examples 1-3 plot below the function showing the trade-off, confirming that the above trade-off relationship can be improved.

[0049] (Evaluation of viscosity properties) For the resin samples obtained using the <viscosity> method, the viscosity (Pa·s) at 60 [1 / s] was measured, and the thixotropy index was calculated using [viscosity at 60 [1 / s] / viscosity at [1 / s]]. The thixotropic indices of Examples 1-3 were higher than those of Comparative Examples 1 and 2, confirming their superiority in terms of fluidity.

[0050] (Evaluation of sedimentation characteristics) The resin samples obtained with the above viscosity were kneaded, and the true density of the resulting kneaded material was measured. When the degree of dispersion of the true density of multiple samples was calculated using the standard deviation, the degree of dispersion of the true density of Examples 1 to 3 showed a smaller value than that of Comparative Examples 2 and 3, confirming superior uniformity of dispersion in the resin.

[0051] From the results above, it was found that when the silica powders of Examples 1 to 3 are incorporated into the resin, the viscosity and sedimentation properties can be improved in practical terms compared to Comparative Examples 1 to 3.

Claims

1. Silica powder, A silica powder in which, when the sedimentation velocity measured according to the following procedure is V (mm / h) and the viscosity measured according to the following procedure is η (Pa·s), V and η satisfy η < -720V + 850. (Procedure for measuring sedimentation velocity) Area 2 cm ２ An epoxy resin is filled into the inside of a cylindrical container, 15 g of the silica powder is placed at the interface of the epoxy resin layer, and after being held at 25°C for 18 hours, the deepest position of the silica powder that has settled from the interface of the layer into the interior is measured. The settling velocity is calculated by [the deepest position (mm)] / [holding time (h)]. (Viscosity measurement procedure) The silica powder is mixed with liquid bisphenol F type epoxy to obtain the above-mentioned evaluation resin sample. The viscosity (Pa·s) of the obtained evaluation resin sample is measured using a rheometer at 25°C and a shear rate of 1 [1 / s].

2. The silica powder according to claim 1, Silica powder having V between 0.2 and 1.0, and / or η between 50 and 300.

3. A silica powder according to claim 1 or 2, The specific surface area measured by the BET one-point method using nitrogen gas adsorption is 1.6 m². ２ / g or more 4.4m ２ Silica powder with a weight of less than / g.

4. A silica powder according to claim 1 or 2, In the volume-based cumulative distribution of particle size measured by laser diffraction scattering, the particle size at the point where the cumulative volume from the smallest particle side reaches 50% is defined as D. ５０ In that case, D ５０ Silica powder having a particle size of 15 μm or more and 35 μm or less.

5. A silica powder according to claim 1 or 2, Silica powder in which, in the volume-based cumulative distribution of particle size measured by laser diffraction scattering, the cumulative volume at a particle size of 1 μm is 1.6% or more.

6. A silica powder according to claim 1 or 2, Silica powder in which the frequency of the maximum peak in the volume-based frequency distribution of particle size, measured by laser diffraction scattering, is 14.0% or higher.

7. A silica powder according to claim 1 or 2, In the volume-based frequency distribution of particle size measured by laser diffraction scattering, The frequency of particles with a particle diameter of 1 μm or less is 0.5% or more, and / or Silica powder in which the frequency of particles with a particle size greater than 64 μm and less than or equal to 96 μm is 11.0% or less.

8. A silica powder according to claim 1 or 2, Silica powder with an average sphericity of 0.85 or higher.

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