Silica powder, resin composition, and substrate

Abstract

To provide silica powder which has low frequency dependence of dielectric dissipation factor in a high frequency band.SOLUTION: Silica powder is kneaded at a ratio of 30 vol.% into a polypropylene resin to obtain a test composition which is then formed into a shape of a sheet having a thickness of 0.35 mm to 0.45 mm. The sheet, when measured for dielectric dissipation factor by a resonator method, has the ratio tanδ91 / tanδ10 between the dielectric dissipation factor tanδ10 measured at a frequency of 10 GHz and the dielectric dissipation factor tanδ91 measured at a frequency of 91 GHz of 1.6 or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to silica powder, a resin composition, and a substrate.

Background Art

[0002] A resin composition filled with silica powder is widely used in applications such as substrates, semiconductor encapsulation, and insulating layers of printed wiring boards. In recent years, with the improvement of performance and high-speed communication of electronic devices and information terminals, it has become necessary to control the dielectric tangent of resin compositions in order to control the dielectric properties of substrates, semiconductor encapsulants, insulating layer materials, etc. As one means for reducing the dielectric tangent of the resin composition, it is conceivable to control the dielectric tangent of the filled silica powder, and various studies have been conducted.

[0003] For example, Patent Document 1 aims to provide silica powder with a very small dielectric tangent and a resin composition containing the same, and discloses low-dielectric silica powder having a dielectric tangent of 0.0005 or less measured at a frequency of 10 GHz.

[0004] For example, Patent Document 2 aims to provide silica powder having a sufficiently small dielectric tangent and excellent miscibility with a resin composition, and discloses silica powder having a dielectric tangent of 0.020 or less measured at a frequency of 1 GHz.

[0005] Patent Documents 1 and 2 describe that the dielectric tangent of silica powder can be reduced by reducing the silanol groups (Si-OH) on the surface of the silica powder. Means for reducing silanol groups include heat-treating the silica powder, surface-treating it, controlling the particle size and specific surface area, etc.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] In recent years, with the development of communication technologies such as beyond 5G and 6G, in resin compositions used for substrate applications, semiconductor encapsulation applications, insulating layer applications of printed wiring boards, etc., dielectric properties in high-frequency bands of several tens of GHz and above have also begun to be emphasized. When the frequency bands used in this way cover a wide range, if the dielectric properties change depending on the frequency, the device design becomes complicated. Therefore, it is preferable that the behavior of the dielectric properties does not change significantly over a wide range of frequencies.

[0008] However, as described above, silica powder with a low dielectric tangent below 10 GHz is known, but it cannot be said that the behavior of the dielectric properties in high-frequency bands of several tens of GHz and above has been sufficiently studied. In particular, generally, the dielectric tangent of silica powder has frequency dependence, and as the frequency increases, the dielectric tangent also increases. However, it cannot be said that studies have focused on the frequency dependence in high-frequency bands of several tens of GHz and above. In fact, for existing silica powders such as Excella SE-8 (manufactured by Tokuyama) produced by the flame fusion method and having few surface silanol groups, and Sansil SP-10M (manufactured by Tokuyama) with surface treatment and few surface silanol groups, when evaluating the dielectric properties in the high-frequency band, as shown in the reference example of this application, the dielectric tangent at 91 GHz is about twice the value of the dielectric tangent at 10 GHz, and the frequency dependence of the dielectric tangent is relatively large.

[0009] The present invention has been made in view of such circumstances, and an object thereof is to provide silica powder having a small frequency dependence of the dielectric tangent in a high-frequency band. [Means for Solving the Problems]

[0010] As a result of intensive studies to solve the above problems, the present inventors have succeeded in obtaining silica powder having a small difference between the dielectric tangent measured at a frequency of 10 GHz and the dielectric tangent measured at a frequency of 91 GHz as compared with existing silica powder.

[0011] That is, in the present invention, when a test composition obtained by kneading silica powder into a polypropylene resin at a ratio of 30% by volume is formed into a sheet having a thickness of 0.35 mm to 0.45 mm and the sheet dielectric tangent is measured by the resonator method, the dielectric tangent tanδ measured at a frequency of 10 GHz 10 and the dielectric tangent tanδ measured at a frequency of 91 GHz 91 and the ratio tanδ 91 / tanδ 10 is 1.6 or less. The silica powder is preferably such that when a test composition obtained by kneading it into a polypropylene resin at a ratio of 30% by volume is formed into a sheet having a thickness of 0.35 mm to 0.45 mm and the relative permittivity of the sheet is measured by the resonator method, the relative permittivity measured at a frequency of 10 GHz is 3.0 or less. Also, the median diameter D50 is preferably 0.05 to 10 μm, and the specific surface area is preferably 0.5 to 50 m 2 / g. As a form of the present invention, a resin composition containing the silica powder and a resin, and further, a substrate containing the resin composition or a cured product thereof can be mentioned.

Advantages of the Invention

[0012] The silica powder of the present invention makes it possible to provide a resin composition having a small frequency dependence of the dielectric tangent in the 10 to 91 GHz band. By using such a resin composition for substrate applications, semiconductor encapsulation applications, and insulating layer applications, the behavior of dielectric characteristics becomes stable at a wide range of frequencies, and the design of communication devices and the like becomes easier than before.

Modes for Carrying Out the Invention

[0013] The silica powder of the present invention is obtained by kneading the silica powder into a polypropylene resin at a ratio of 30% by volume, forming a test composition into a sheet with a thickness of 0.35 mm to 0.45 mm, and measuring the dielectric tangent of the sheet by the resonator method. When the dielectric tangent tanδ measured at a frequency of 10 GHz 10 and the dielectric tangent tanδ measured at a frequency of 91 GHz 91 The ratio tanδ of 91 / tanδ 10 is 1.6 or less.

[0014] The dielectric tangent is a numerical value representing the degree of loss of electrical energy. The larger this value, the greater the energy loss and the greater the transmission loss. In silica powder, generally, the dielectric tangent has a frequency dependence that is affected by the frequency of the applied current, and the dielectric tangent increases as the frequency increases.

[0015] On the other hand, the silica powder of the present invention has a ratio tanδ of the dielectric tangent tanδ measured at a frequency of 10 GHz 10 and the dielectric tangent tanδ measured at a frequency of 91 GHz 91 The ratio tanδ of 91 / tanδ 10 is 1.6 or less, and the frequency dependence is small. Due to this characteristic, the resin composition using the silica of the present invention can exhibit stable behavior at a wide range of frequencies from several GHz to several tens of GHz. tanδ 91 / tanδ 10 is preferably 1.4 or less, and more preferably 1.2 or less. tanδ 91 / tanδ 10 The lower limit value of is not particularly limited, but generally, the dielectric tangent increases as the frequency increases as described above, and is usually 1.0 or more.

[0016] The silica powder has a dielectric tangent tanδ measured at a frequency of 28 GHz 28 , a dielectric tangent tanδ measured at a frequency of 35 GHz 35 , a dielectric tangent tanδ measured at a frequency of 56 GHz 56 , a dielectric tangent tanδ measured at a frequency of 74 GHz 74Regarding this, it is preferable that the difference between the dielectric tangents is small, and the difference between the dielectric tangent and tanδ 10 and tanδ 91 is small. That is, tanδ 74 / tanδ 10 , tanδ 56 / tanδ 10 , tanδ 35 / tanδ 10 , tanδ 28 / tanδ 10 , tanδ 91 / tanδ 28 , tanδ 56 / tanδ 28 , tanδ 35 / tanδ 28 , tanδ 91 / tanδ 35 , tanδ 74 / tanδ 35 , tanδ 56 / tanδ 35 , tanδ 91 / tanδ 56 and tanδ 74 / tanδ 56 are preferably 1.6 or less, more preferably 1.4 or less, even more preferably 1.2 or less, and generally 1.0 or more. Due to this characteristic, the resin composition using the silica of the present invention is likely to exhibit stable behavior over a wide range of frequencies.

[0017] Also, tanδ 10 , tanδ 28 , tanδ 35 , tanδ 56 , tanδ 74 , tanδ 91 are preferably 0.005 or less, more preferably 0.004 or less, and even more preferably 0.003 or less. By being within the above range, the transmission loss at each frequency can be reduced. tanδ 10 , tanδ 28 , tanδ 35 , tanδ 56 , tanδ 74 , tanδ 91The lower limit is not particularly limited, but generally it is 0.0001 or more.

[0018] The silica powder is obtained by kneading the silica powder into a polypropylene resin at a ratio of 30% by volume, forming a test composition into a sheet with a thickness of 0.35 mm to 0.45 mm, and measuring the relative permittivity εr at a frequency of 10 GHz by the resonator method. 10 is preferably 3.0 or less, and more preferably 2.7 or less. Similarly, the relative permittivity εr measured at a frequency of 28 GHz 28 , the relative permittivity εr measured at a frequency of 35 GHz 35 , the relative permittivity εr measured at a frequency of 56 GHz 56 , the relative permittivity εr measured at a frequency of 74 GHz 74 , the relative permittivity εr measured at a frequency of 91 GHz 91 also preferably is 3.0 or less, and more preferably 2.7 or less. By the relative permittivity at each frequency being within the above range, it becomes easy to reduce the transmission loss at each frequency. εr 10 , εr 28 , εr 35 , εr 56 , εr 74 , εr 91 The lower limit is not particularly limited, but generally it is 2.0 or more.

[0019] The relative permittivity and dielectric loss tangent in the present invention are measured using an evaluation sample formed into a sheet with a thickness of 0.35 to 0.45 mm from a test composition obtained by kneading silica powder into a polypropylene resin at a ratio of 30% by volume. As the polypropylene resin, for example, Novatec PP MA3 manufactured by Japan Polypropylene Corporation can be used. When kneading the silica powder into the polypropylene resin, a kneading device may be used. Measure the silica powder and the polypropylene resin so that the silica powder accounts for 30% by volume of the whole, and put them into the heated mixing part of the kneading device and knead them to obtain a test composition. Specifically, use a Labo Plastomill 3S150 manufactured by Toyo Seiki Seisakusho Co., Ltd. as the kneading device. After heating the mixing part to 200°C, put a predetermined amount of polypropylene into the mixing part and dissolve it, then put a predetermined amount of silica powder into the mixing part, and knead at 200°C for 10 minutes at a rotation speed of 30 rpm to obtain a test composition. Next, the test composition is pressed for 2 minutes under the conditions of 2 tons and 180°C and then pressed for 2 minutes under the conditions of 2 tons and 40°C using a SUS mold with a thickness of 0.4 mm, and formed into a sheet with a thickness of 0.35 mm to 0.45 mm, whereby an evaluation sample can be obtained.

[0020] The measurement of the relative permittivity and dielectric loss tangent in the present invention is performed by the resonance method. Specifically, a resonator adjusted to a predetermined frequency is connected to a network analyzer, and an evaluation sample is set in the resonator for measurement, whereby the relative permittivity and dielectric loss tangent can be calculated. The measurement is carried out in a thermo-hygrostat chamber at a temperature of 25°C and a humidity of 50%RH. When setting the evaluation sample in the resonator during the measurement, the frequency of the resonator may change slightly due to the influence of the evaluation sample. However, the measurement frequency in this application shall mean the frequency of the resonator before setting the evaluation sample. For example, "measurement at a frequency of 10 GHz" means that the frequency of the resonator before setting the evaluation sample is 10 GHz, and "measurement at a frequency of 91 GHz" means that the frequency of the resonator before setting the evaluation sample is 91 GHz. The frequency of the resonator is strongly affected by the thickness of the evaluation sample. However, by adjusting the thickness of the evaluation sample to a constant range of 0.35 mm to 0.45 mm, the influence can be minimized.

[0021] The median diameter D50 of the silica powder of the present invention, as measured by the laser diffraction method, is preferably 0.05 to 10 μm, more preferably 0.1 to 6.0 μm. Also, the specific surface area measured by the nitrogen adsorption method is preferably 0.5 to 50 m 2 / g, more preferably 1.0 to 40 m 2 / g. When the median diameter D50 is less than 0.05 μm, the flow characteristics of the resin composition deteriorate and the processability decreases, which is not preferable. When the median diameter D50 exceeds 10 μm and is large, when used as a material for a semiconductor package where miniaturization progresses, the permeability into the gaps deteriorates. Similarly, when the specific surface area exceeds 50 m 2 / g and is large, the flow characteristics of the resin composition deteriorate and the processability decreases, which is not preferable. When the specific surface area is less than 0.5 m 2 / g, when used as a material for a semiconductor package where miniaturization progresses, the permeability into the gaps deteriorates.

[0022] The silica powder of the present invention preferably has a surface silanol group amount of 5 per nm 2 or less, and more preferably 3 per nm 2 or less. By reducing the surface silanol groups, it becomes easier to lower the dielectric tangent and relative permittivity. The amount of surface silanol groups can be measured by the method described in WO2018 / 096876.

[0023] The silica powder of the present invention can be obtained by performing a surface stabilization treatment in a nitrogen atmosphere after silica synthesis. Although the reason is not clear, it is presumed that the surface state of the silica powder affects the dielectric properties, and by performing the surface stabilization treatment, its behavior can be controlled. As described above, by reducing the surface silanol groups of the silica powder, the dielectric tangent and relative permittivity can be made low. However, simply having a small amount of silanol groups alone cannot sufficiently reduce the frequency dependence of the dielectric tangent and relative permittivity. By synthesizing silica with a small amount of silanol groups and performing a surface stabilization treatment on this, it is possible to obtain silica powder with a low dielectric tangent and relative permittivity, and furthermore, with a small frequency dependence of these.

[0024] The production of silica powder (hereinafter sometimes referred to as "crude silica powder") before the surface stabilization treatment can use known methods. For example, it can be carried out by a flame fusion method or a sol-gel method.

[0025] As the flame melting method, for example, a method of supplying raw material silica, quartz, an organic silane compound, etc. into a flame obtained by mixing a gaseous or liquid fuel with a supporting combustion gas such as oxygen or air and burning it with a burner to melt and generate spherical silica (flame melted silica) can be mentioned. There are methods disclosed in WO2020 / 175160, JP-A-2004-002059, etc. Such a flame melting method can be mentioned as a preferable method because silica is generated in a high-temperature flame and the surface silanol groups of the silica powder can be reduced, and the relative dielectric constant and dielectric tangent can be lowered. As the raw material silica and quartz, known silica and quartz can be used without particular limitation. As the organic silane compound, for example, cyclic siloxanes such as octamethylcyclotetrasiloxane, chain siloxanes such as hexamethyldisiloxane, alkoxysilanes such as tetramethoxysilane, and chlorosilanes such as tetrachlorosilane can be used. The flame is preferably a hydrogen-oxygen flame, and it is preferably carried out under flame temperature conditions exceeding the melting point of silica. The flame melted silica may be used as it is as a crude silica powder, or may be used as a crude silica powder after classification or firing of the flame melted silica.

[0026] The sol-gel method is a method of supplying silicon alkoxide into a reaction medium composed of water and an organic solvent containing a hydrolysis catalyst, hydrolyzing and polycondensing it to generate a silica sol, gelling this, and then taking out the generated solid content and drying it to obtain a sol-gel silica powder. The conditions of the sol-gel method can be used without any limitation using known conditions. For example, the method disclosed in WO2018 / 096876 can be mentioned. After drying, classification may be further carried out. Since the sol-gel silica powder obtained by the sol-gel method has many silanol groups on the particle surface and it is difficult to control them, it is necessary to use it as a crude silica powder after firing.

[0027] The firing can be carried out, for example, in an air atmosphere by holding at the target temperature for 0.5 to 48 hours, particularly 2 to 24 hours. The target temperature (firing temperature) can be 300 to 1300 °C, preferably 600 to 1200 °C.

[0028] For the production of the silica powder of the present invention, it is important to perform a surface stabilization treatment on the crude silica powder in a nitrogen atmosphere. The surface stabilization treatment may be carried out by allowing the crude silica powder to stand in a nitrogen atmosphere at 10 to 50 °C for 12 hours or more. If the crude silica powder is stored in air after production, it becomes impossible to obtain the silica powder of the present invention even if the surface stabilization treatment is performed. Therefore, the surface stabilization treatment needs to be started within 12 hours from the time when the production of the crude silica powder is completed. Here, the time when the production of the crude silica powder is completed refers to the time when the surface silanol groups of the silica particles have decreased. In the case of the flame fusion method, it refers to the time when silica is generated in a high-temperature flame, and in the case of the sol-gel method, it refers to the time when firing is completed (the time when the temperature in the firing furnace becomes less than 300 °C). However, even in the flame fusion method, when the above-mentioned firing is performed, the time when the firing is completed is regarded as the time when the production of the crude silica powder is completed. As long as the surface stabilization treatment is started within 12 hours from the time when the production of the crude silica powder is completed, there is no problem even if its completion exceeds 12 hours from the time when the production of the crude silica powder is completed.

[0029] The silica powder of the present invention may be silica powder that has not been surface-treated with a surface treatment agent, or may be surface-treated silica powder that has been surface-treated with a surface treatment agent such as a silane coupling agent. By surface-treating with a silane coupling agent, it becomes easy to enhance the affinity with a resin or to reduce the silanol groups on the surface to lower the dielectric tangent and relative permittivity. Known substances can be used as the silane coupling agent. For example, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, n-butyltrimethoxysilane, i-butyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, i-butyltriethoxysilane, decyltriethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane and other alkoxysilanes; hexamethyldisilazane, hexaethyldisilazane, hexapropyldisilazane, hexabutyldisilazane, hexapentyldisilazane, hexahyexyldisilazane, hexaphenyldisilazane, divinyltetramethyldisilazane, dimethyltetravinyldisilazane and other disilazanes; etc. can be exemplified.

[0030] When the silica powder of the present invention is a surface-treated silica powder, surface treatment is performed before the surface stabilization treatment. As the method of this surface treatment, a known method can be adopted without particular limitation, and it may be performed by any method of dry surface treatment or wet surface treatment. Dry surface treatment is a method by dry mixing without using a large amount of solvent when mixing the raw material powder and the surface treatment agent. For example, a method of gasifying the surface treatment agent and mixing it with the raw material powder, a method of spraying or dropping the liquid surface treatment agent and mixing it with the raw material powder, a method of diluting the surface treatment agent with a small amount of organic solvent to increase the liquid amount, and further spraying or dropping it, etc. can be mentioned. Further, wet surface treatment is a method through a solvent when mixing the raw material powder and the surface treatment agent. For example, a method of removing the solvent by drying or the like after mixing the raw material powder, the surface treatment agent, and the solvent can be mentioned. When performing surface treatment, the time when the surface treatment is completed is set as the time when the production of the above-mentioned crude silica powder is completed. Specifically, in the case of dry surface treatment, it is the time when the mixing of the raw material powder and the surface treatment agent is completed, and in the case of wet surface treatment, it is the time when the treatment of removing the solvent is completed (for example, when removing the solvent by reduced pressure or heating, it is the time when the reduced pressure or heating is stopped), which is set as the time when the surface treatment is completed.

[0031] The use of the silica powder of the present invention is not particularly limited, but it can be used as a filler for filling a resin with the silica powder of the present invention. When the silica powder of the present invention is used as a filler, a resin composition containing the silica powder of the present invention and a resin can be obtained. And, compared with the case of using other silica powders, the resin composition has less frequency dependence in the high-frequency region, so it can be suitably used for applications where dielectric properties are important, such as substrate applications, semiconductor encapsulation applications, and insulation layer applications of printed wiring boards and package substrates. Among these applications, it is particularly preferably used as a material for substrates such as printed wiring boards and package substrates, and a substrate containing the resin composition or its cured product can be cited as a preferred example.

[0032] The resin of the resin composition may be a thermoplastic resin or a thermosetting resin. Examples include epoxy resin, phenolic resin, melamine resin, urea resin, unsaturated polyester resin, acrylic resin, methacrylic resin, silicone resin, fluororesin, polyphenylene ether, LCP, etc. The resin may have a polymerizable functional group, and may be used as a cured product obtained by polymerizing and curing a resin composition comprising the silica powder of the present invention and a resin having a polymerizable functional group. The blending amount of the silica powder of the present invention in the resin composition is not particularly limited and may be appropriately adjusted according to the application. For example, the blending amount of the silica powder can be 1 to 900 parts by mass, preferably 30 to 800 parts by mass, based on 100 parts by mass of the resin. When the resin composition is used as a material for a substrate, the resin is preferably an epoxy resin, polyphenylene ether, or LCP. Also, it is preferable to contain 10 to 400 parts by mass, more preferably 30 to 250 parts by mass, of silica powder based on 100 parts by mass of the resin.

[0033] The resin composition may contain, as other components, for example, other fillers other than silica, flame retardants, rubber particles, thickeners, defoamers, leveling agents, adhesion improvers, antioxidants, ultraviolet degradation preventives, and colorants.

[0034] Examples of the material for a substrate comprising the resin composition include build-up films and prepregs. Also, examples of the material for a substrate containing the resin composition include a copper-clad laminate in which the resin composition and copper are laminated.

Examples

[0035] Hereinafter, examples will be described to specifically explain the present invention, but the present invention is not limited to these examples. The measurements of each item in the examples and comparative examples were measured by the following methods.

[0036] <Measurement of median diameter D50> For a sample in which silica powder was dispersed in a solvent at a concentration of 0.2% by mass and dispersed by ultrasonic irradiation at about 40 W for 10 minutes, the particle size distribution was measured using a laser diffraction scattering type particle size distribution analyzer (manufactured by Beckman Coulter, Inc.: LS13 320). In the obtained volume frequency distribution of particle sizes (particle size distribution), the volume frequency was accumulated from the smaller particle sizes, and the particle size at which the cumulative value became 50% was defined as the median diameter D50. In the case of silica powder not surface-treated with a silane coupling agent, water was used as the solvent, and in the case of surface-treated silica powder surface-treated with a silane coupling agent, ethanol was used as the solvent.

[0037] <Measurement of BET specific surface area> The BET specific surface area was determined by the BET method (nitrogen adsorption single point method) using a rapid surface area measuring device (manufactured by Shibata Scientific Co., Ltd.: SA-1000). For the measurement, 2 g of the powder sample was used, and the sample that had been previously dried at 100 °C for 1 hour in a nitrogen gas flow was used.

[0038] <Measurement of relative permittivity and dielectric loss tangent> Polypropylene resin (manufactured by Nippon Polypropylene Corporation: Novatec PP MA3) and silica powder were each weighed so that the silica powder accounted for 30% by volume of the whole, and were put into the mixing section heated to 200 °C of a kneading device (manufactured by Toyo Seiki Seisakusho, Ltd.: Laboplastmill 3S150). Then, kneading was carried out at 200 °C for 10 minutes at a rotational speed of 30 prm to obtain a test composition. Next, the test composition was pressed at 2 tons and 180 °C for 2 minutes using a SUS mold with a thickness of 0.4 mm, and then pressed at 2 tons and 40 °C for 2 minutes to obtain a sheet-shaped molded body with a thickness of 0.35 mm to 0.45 mm. Thereafter, the molded body was cut according to the size of the resonator used according to the frequency to obtain an evaluation sample.

[0039] The measurement of dielectric properties was carried out by connecting a split cylinder resonator with a predetermined frequency to a network analyzer (N5290A for measurements at 10 GHz and 28 GHz, HP8510 for measurements at 35 GHz, HP8757 for measurements at 56 GHz, 74 GHz and 91 GHz), setting the evaluation sample in the resonator, performing measurements in the TE011 mode, and obtaining the relative permittivity and dielectric loss tangent from the obtained results. The measurements were carried out in a thermo-hygrostat environment chamber at a temperature of 25 °C and a humidity of 50% RH.

[0040] [Example 1] Flame-fused silica was obtained by the method described in Example 9 of WO2020 / 175160. The flame-fused silica was used as crude silica powder, and within 6 hours from the time when the flame-fused silica was obtained, the inside of the container was sufficiently replaced with nitrogen, and surface stabilization treatment was carried out by leaving it standing for 15 hours in a nitrogen atmosphere controlled at a temperature of 20 to 30 °C to obtain silica powder. The results of the evaluation of the obtained silica powder are shown in Tables 1 to 3.

[0041] [Example 2] Silica powder was obtained in the same manner as in Example 1 of the present application, except that the flame-fused silica was obtained by the method described in Comparative Example 2 of WO2020 / 175160. The results of the evaluation of the obtained silica powder are shown in Tables 1 to 3.

[0042] [Example 3] Silica powder was obtained in the same manner as in Example 1 of the present application, except that the flame-fused silica was obtained by the method described in Comparative Example 3 of WO2020 / 175160. The results of the evaluation of the obtained silica powder are shown in Tables 1 to 3.

[0043] [Example 4] Silica powder was obtained in the same manner as in Example 1 of the present application, except that the flame-fused silica was obtained by the method described in Example 6 of JP-A-2015-086120. The results of the evaluation of the obtained silica powder are shown in Tables 1 to 3.

[0044] [Example 5] Silica powder was obtained in the same manner as in Example 1 of the present application, except that the flame-fused silica was obtained by the method described in Example 1 of JP-A-2015-086120. The results of evaluating the obtained silica powder are shown in Tables 1 to 3.

[0045] [Example 6] Sol-gel silica was obtained by the method described in Example 1 of WO2018 / 096876. The sol-gel silica was used as crude silica powder, and surface stabilization treatment was carried out in the same manner as in Example 1 of the present application within 6 hours from the completion of firing to obtain silica powder. The results of evaluating the obtained silica powder are shown in Tables 1 to 3.

[0046] [Example 7] Silica powder was obtained in the same manner as in Example 6 of the present application, except that the sol-gel silica was obtained by the method described in Example 7 of WO2018 / 096876. The results of evaluating the obtained silica powder are shown in Tables 1 to 3.

[0047] [Example 8] The flame-fused silica obtained in Example 2 of the present application was dispersed in a mixed solvent of ethanol and isopropyl alcohol (mass ratio 7:2), and then HMDS (SZ-31 manufactured by Shin-Etsu Silicone) as a surface treatment agent was added at 200 μmol / g based on the amount of the flame-fused silica and stirred for 2 hours. Then, the solvent was removed under reduced pressure at 50°C, and then dried under reduced pressure at 100°C to perform surface treatment to obtain crude silica powder. The crude silica powder was subjected to surface stabilization treatment in the same manner as in Example 1 of the present application within 6 hours from the completion of the surface treatment to obtain silica powder. The results of evaluating the obtained silica powder are shown in Tables 1 to 3.

[0048] [Example 9] The flame-fused silica obtained in Example 5 of the present application was dispersed in a mixed solvent of ethanol and isopropyl alcohol (mass ratio 7:2). After that, HMDS (SZ-31 manufactured by Shin-Etsu Silicone) was added at 200 μmol / g based on the amount of flame-fused silica as a surface treatment agent and stirred for 2 hours. Then, the solvent was removed under reduced pressure at 50 °C, and then dried under reduced pressure at 100 °C to perform surface treatment, obtaining a crude silica powder. The crude silica powder was subjected to surface stabilization treatment in the same manner as in Example 1 of the present application within 6 hours from the time when the surface treatment was completed, obtaining a silica powder. The results of evaluating the obtained silica powder are shown in Tables 1 to 3.

[0049] [Example 10] Sol-gel silica was obtained by the method described in Example 6 of WO2018 / 096876. The sol-gel silica was used as a crude silica powder, and surface stabilization treatment was performed in the same manner as in Example 1 of the present application within 6 hours from the time when the firing was completed, obtaining a silica powder. The results of evaluating the obtained silica powder are shown in Tables 1 to 3.

[0050] [Example 11] The sol-gel silica obtained in Example 7 of the present application was dispersed in a mixed solvent of ethanol and isopropyl alcohol (mass ratio 7:2). After that, HMDS (SZ-31 manufactured by Shin-Etsu Silicone) was added at 200 μmol / g based on the amount of flame-fused silica as a surface treatment agent and stirred for 2 hours. Then, the solvent was removed under reduced pressure at 50 °C, and then dried under reduced pressure at 100 °C to perform surface treatment, obtaining a crude silica powder. The crude silica powder was subjected to surface stabilization treatment in the same manner as in Example 1 of the present application within 6 hours from the time when the surface treatment was completed, obtaining a silica powder. The results of evaluating the obtained silica powder are shown in Tables 1 to 3.

[0051] [Comparative Example 1] The crude silica powder obtained in Example 2 of the present application was evaluated without performing surface stabilization treatment. The evaluation results are shown in Tables 1 to 3.

[0052] [Comparative Example 2] The crude silica powder obtained in Example 6 of the present application was evaluated without performing surface stabilization treatment. The evaluation results are shown in Tables 1 to 3.

[0053] [Comparative Example 3] The crude silica powder obtained in Example 8 of the present application was evaluated without performing a surface stabilization treatment. The evaluation results are shown in Tables 1 to 3.

[0054] [Comparative Example 4] The crude silica powder obtained in Example 10 of the present application was evaluated without performing a surface stabilization treatment. The evaluation results are shown in Tables 1 to 3.

[0055] [Reference Example 1] As a commercially available silica powder, Excellica SE-8 (manufactured by Tokuyama) was evaluated. Excellica SE-8 was manufactured by the flame fusion method and has not been surface-treated with a silane coupling agent. The evaluation results are shown in Tables 1 to 3.

[0056] [Reference Example 2] As a commercially available silica powder, Sansil SP-10M (manufactured by Tokuyama) was evaluated. Sansil SP-10M was manufactured by the sol-gel method and has been surface-treated with hexamethyldisilazane. The evaluation results are shown in Tables 1 to 3.

[0057]

Table 1

[0058]

Table 2

[0059]

Table 3

[0060] As shown in Table 1, the silica powders of Examples 1 to 11 subjected to the surface stabilization treatment had a tanδ 91 / tanδ 10 of 1.6 or less and a small frequency dependence of the dielectric tangent. On the other hand, the silica powder produced by the conventional production method without the surface stabilization treatment had a tanδ91 / tanδ 10 exceeded 1.6, and the frequency dependence of the dielectric tangent was large. Incidentally, all of the silica powders in the above Examples and Comparative Examples had a silanol group amount of 3 per nm 2 or less.

Claims

1. Silica powder, a test composition obtained by kneading the silica powder into a polypropylene resin at a ratio of 30% by volume is formed into a sheet having a thickness of 0.35 mm to 0.45 mm, and when the dielectric tangent of the sheet is measured by the resonator method, the dielectric tangent tanδ measured at a frequency of 10 GHz １０ and the dielectric tangent tanδ measured at a frequency of 91 GHz ９１ and the ratio tanδ ９１ / tanδ １０ is 1.6 or less, characterized silica powder.

2. a test composition obtained by kneading the silica powder into a polypropylene resin at a ratio of 30% by volume is formed into a sheet having a thickness of 0.35 mm to 0.45 mm, and when the relative dielectric constant of the sheet is measured by the resonator method, the relative dielectric constant measured at a frequency of 10 GHz is 3.0 or less, the silica powder according to claim 1.

3. The median diameter D50 measured by the laser diffraction method is 0.05 to 10 μm, and the specific surface area measured by the nitrogen adsorption method is 0.5 to 50 m ２ / g, the silica powder according to claim 1.

4. A resin composition comprising the silica powder according to any one of claims 1 to 3 and a resin.

5. A substrate comprising the resin composition according to claim 4 or a cured product thereof.

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