阅读说明：本技术 球状二氧化硅粉末 (Spherical silica powder ) 是由 冈部拓人 深泽元晴 于 2020-01-30 设计创作，主要内容包括：本发明提供一种介电损耗角正切低的球状二氧化硅粉末。更详细而言,本发明提供一种球状二氧化硅粉末,其配合于树脂而成型为片状后,由通过空腔谐振器法在频率35～40GHz的条件下测定的该片材的介电损耗角正切计算的球状二氧化硅粉末的介电损耗角正切中,将介电损耗角正切降低处理前的球状二氧化硅粉末的介电损耗角正切设为A,将介电损耗角正切降低处理后的球状二氧化硅粉末的介电损耗角正切设为B时,B/A为0.70以下,介电损耗角正切降低处理后的球状二氧化硅粉末的比表面积为1～30m～(2)/g。(The invention provides a sphere with low dielectric loss tangentSilicon dioxide powder. More specifically, the present invention provides a spherical silica powder which is blended with a resin, molded into a sheet, and then molded into a sheet, wherein in the dielectric tangent of the spherical silica powder calculated from the dielectric tangent of the sheet measured by the cavity resonator method at a frequency of 35 to 40GHz, the B/A is 0.70 or less, and the specific surface area of the spherical silica powder after the dielectric tangent reduction treatment is 1 to 30m, where A represents the dielectric tangent of the spherical silica powder before the dielectric tangent reduction treatment and B represents the dielectric tangent of the spherical silica powder after the dielectric tangent reduction treatment 2 /g。)

1. A spherical silica powder which is molded into a sheet by blending with a resin, and which is then molded into a sheet, wherein in the dielectric loss tangent of the spherical silica powder calculated using the following formula (I) from tan δ c, which is the dielectric loss tangent of the sheet measured by the resonator method at a frequency of 35 to 40GHz, when Tan δ fA, which is the dielectric loss tangent of the spherical silica powder before the dielectric loss tangent reduction treatment, is A and Tan δ fB, which is the dielectric loss tangent of the spherical silica powder after the dielectric loss tangent reduction treatment, is B, B/A is 0.70 or less, and the spherical silica powder after the dielectric loss tangent reduction treatment has a specific surface area of 1 to 30m²/g，

Mathematical formula 1

log (tan δ c) ═ Vf · log (tan δ f) + (1-Vf) · log (tan δ r) · · formula (I)

Wherein the symbols in formula (I) have the following meanings,

vf; the volume fraction of spherical silica powder in the sheet,

tan δ r; the dielectric loss tangent of a resin sheet, which is not compounded with a filler.

2. The spherical silica particles according to claim 1, wherein the dielectric loss tangent reduction treatment comprises subjecting the raw spherical silica powder to a heating treatment at a temperature of 500 to 1100 ℃ for a predetermined time such that the heating temperature x the heating time is 1000 to 26400 ℃ · h, the heating temperature being in ° c, and the heating time being in h, that is, hours.

3. The spherical silica powder according to claim 1 or 2, wherein the average circularity is 0.85 or more.

4. The spherical silica powder according to any one of claims 1 to 3, which is surface-treated with a surface-treating agent.

5. According to claim 1 to 4Any of the spherical silica powders having a moisture permeability of 0.1g/m under the condition B of JIS Z0208-²The moisture-proof bag was stored for 24 hours or less, and the condition B of JIS Z0208-1976 was a temperature of 40 ℃ and a relative humidity of 90%.

6. A resin sheet comprising the spherical silica powder according to any one of claims 1 to 5.

7. A storage method comprising subjecting the spherical silica powder described in any one of claims 1 to 4 to a moisture permeability of 0.1g/m under the condition B of JIS Z0208-²And 24 hours or less, under the condition B of JIS Z0208-1976, the temperature is 40 ℃ and the relative humidity is 90%.

Technical Field

The present invention relates to a spherical silica powder having a low dielectric loss tangent.

Background

In recent years, with an increase in the amount of information communication in the communication field, the use of high-frequency bands in electronic devices, communication devices, and the like has been expanding. The high frequency has the characteristics of wide frequency band, linear propagation property, permeability and the like, and the frequency is particularly 10⁹The use of the above GHz band is prevalent. For example, in the automotive field, millimeter wave radars and quasi-millimeter wave radars mounted for the purpose of preventing collision use high frequencies of 76 to 79GHz and 24GHz, respectively, and are expected to become more popular in the future.

With the application of the high frequency band, a problem arises that transmission loss of a circuit signal becomes large. The transmission loss includes approximately a conductor loss due to a skin effect of a wiring and a dielectric loss due to a characteristic of a dielectric material of an insulator constituting an electric and electronic component such as a substrate. The dielectric loss is proportional to the frequency to the power of 1, the dielectric constant of an insulator to the power of 1/2, and the dielectric loss tangent to the power of 1, and therefore, materials used in devices for high frequency bands are required to have low dielectric constants and low dielectric loss tangents.

The polymeric materials used in insulator materials are generally mostly low in dielectric constant but high in dielectric loss tangent. On the other hand, ceramic materials often have properties opposite to those of ceramic materials, and a polymer material filled with a ceramic filler has been studied in order to achieve both properties (patent document 1).

Dielectric properties of ceramic materials in the GHz band are known from, for example, non-patent document 1, but all of them are properties of a sintered substrate. Silicon dioxide (SiO)₂) The dielectric constant (2) is small (3.7), and the quality factor index Qf (the value obtained by multiplying the reciprocal of the dielectric loss tangent by the measurement frequency) is about 12 ten thousand, and is expected as a material for a filler having a low dielectric constant and a low dielectric loss tangent. In addition, in order to facilitate the incorporation into the resin, the filler is more preferably shaped to be closer to a spherical shape, and spherical silica can be easily synthesized (for example, patent document 2), and has been used in many applications. Therefore, it is expected to be widely used for high-frequency band dielectric devices and the like.

However, there is a problem that a large amount of polar functional groups such as water and silanol groups are adsorbed on the surface of the spherical silica particles, and in particular, the dielectric loss tangent is deteriorated more than the characteristics as a sintered substrate.

As a method for reducing water and polar functional groups adsorbed on the surface of filler particles, for example, a method of surface treatment with a silane coupling agent is studied in non-patent document 2, but the dielectric loss tangent at 1 to 10MHz is hardly lowered, the effect is insufficient, and the effect of the GHz band is not clearly described.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2014-24916

Patent document 2: japanese laid-open patent publication No. 58-138740

Non-patent document

Non-patent document 1 International Materials Reviews vol.60 No.70supplement data (2015).

Non-patent document 2 IEEE Transactions on Dielectrics and electric Insulation Vol.17, No.6 (2010).

Disclosure of Invention

The present invention provides a spherical silica powder having a low dielectric loss tangent.

(1) A spherical silica powder which is molded into a sheet by blending with a resin and then resonatedThe dielectric loss tangent (tan δ c) of the sheet measured under the condition of the frequency of 35 to 40GHz is calculated by using the following formula (I) in the dielectric loss tangent of the spherical silica powder, when the dielectric loss tangent (tan δ fA) of the spherical silica powder before the dielectric loss tangent reduction treatment is defined as A and the dielectric loss tangent (tan δ fB) of the spherical silica powder after the dielectric loss tangent reduction treatment is defined as B, the B/A is 0.70 or less, and the specific surface area of the spherical silica powder after the dielectric loss tangent reduction treatment is 1 to 30m²/g。

[ mathematical formula 1]

log (tan δ c) ═ Vf · log (tan δ f) + (l-Vf) · log (tan δ r) · · formula (I)

Wherein the symbols in formula (I) have the following meanings.

Vf; volume fraction of spherical silica powder in sheet

tan δ r; dielectric loss tangent of resin sheet (without filler)

(2) The spherical silica particles according to (1), wherein the dielectric loss tangent reduction treatment comprises subjecting the raw spherical silica powder to a heating treatment at a temperature of 500 to 1100 ℃ for a predetermined time such that the heating temperature (. degree. C.). times.the heating time (h) is 1000 to 26400 (. degree. C. h).

(3) The spherical silica powder according to (1) or (2), wherein the average circularity is 0.85 or more.

(4) The spherical silica powder according to any one of (1) to (3), which is surface-treated with a surface-treating agent.

(5) The spherical silica powder according to any one of (1) to (4), which has a moisture permeability of 0.1 (g/m) under condition B (temperature 40 ℃ to relative humidity 90%) of JIS Z0208-²24h) in a moisture-proof bag.

(6) A resin sheet comprising the spherical silica powder according to any one of (1) to (5).

(7) A storage method comprising subjecting the spherical silica powder described in any one of (1) to (4) to the conditions of JIS Z0208-The moisture permeability of B (temperature 40-relative humidity 90%) is 0.1 (g/m)²24h) in a moisture-proof bag.

According to the present invention, it is possible to provide spherical silica powder capable of reducing the dielectric loss tangent of a resin material such as a substrate.

Detailed Description

Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments.

The spherical silica powder of the present invention is a raw material spherical silica powder before the dielectric loss tangent reduction treatment_A) A is the dielectric loss tangent (tan. delta.f) of the spherical silica powder having been subjected to the dielectric loss tangent reduction treatment_B) When B is used, the ratio B/A is 0.70 or less, preferably 0.60 or less, and more preferably 0.40 or less. If B/A is more than 0.70, the effect of lowering the dielectric loss tangent at the time of resin compounding becomes small. The smaller the B/A ratio, the greater the effect of lowering the dielectric loss tangent at the time of resin compounding. The lower limit of B/A is not particularly limited, but is actually 0.01 or more.

The tan δ f in the present invention is a value calculated from a value (tan δ c) measured by a cavity resonator method under a condition of a frequency of 35GHz after being blended with a resin and molded into a sheet shape, according to the composite rule of the following formula (I). The resin is not particularly limited as long as it can measure the dielectric constant and the dielectric loss tangent, and Polyethylene (PE) and polypropylene (PP) are used in the present invention.

[ mathematical formula 2]

log (tan δ c) ═ Vf · log (tan δ f) + (1-Vf) · log (tan δ r) · · formula (I)

Wherein the symbols in formula (I) have the following meanings.

Vf; volume fraction of spherical silica powder in sheet

tan δ r; dielectric loss tangent of resin sheet (without filler)

The dielectric loss tangent (tan. delta. c) of the resin sheet was measured by blending the raw spherical silica powder before the dielectric loss tangent reduction treatment with the resin_a) A is the dielectric loss tangent (tan δ c) of a resin sheet measured by blending the resin with spherical silica powder having been subjected to dielectric loss tangent reduction treatment_b) The reduction rate (%) of the dielectric loss tangent of the resin sheet itself was determined from formula (II).

[ mathematical formula 3]

{1- (b/a) } x 100. formula (II)

The specific surface area of the spherical silica powder of the present invention is 1 to 30m²(ii) in terms of/g. The specific surface area is more than 30m²At the time of the reaction,/g, the incorporation in the resin becomes difficult, and less than 1m²At the time of/g, the effect of dielectric loss tangent reduction treatment is small.

The spherical silica powder of the present invention has an average circularity of 0.85 or more, preferably 0.90 or more. If the average circularity is less than 0.85, the viscosity increases and the fluidity decreases when the resin is mixed, and the processability and the filling property deteriorate.

The density of the spherical silica powder of the present invention is preferably 1.8 to 2.4g/cm³. If the density is less than 1.8, a large number of voids are contained in the particles, and kneading in the resin becomes difficult. If the density is more than 2.4, α -quartz, cristobalite, etc. are contained in the crystal structure of silica, and there is a concern that the physical properties are affected by, for example, an increase in thermal expansion coefficient.

The spherical silica powder used as a raw material of the spherical silica powder having been subjected to dielectric loss tangent reduction treatment of the present invention has an average circularity of 0.85 or more and a specific surface area of 1 to 30m²The spherical silica powder per gram can be suitably used. As a method for producing the spherical silica powder as a raw material, for example, a powder melting method of passing the spherical silica powder through a high temperature range of a temperature equal to or higher than the melting point to be spheroidized is exemplified.

The spherical silica powder having been subjected to dielectric loss tangent reduction treatment of the present invention can be produced by subjecting a raw spherical silica powder to high-temperature heat treatment. Can be manufactured as follows: spherical silica powder as a raw material is treated with hot air or an electric furnace at a temperature of 500 to 1100 ℃ for a predetermined time (for example, about 1 to 52 hours) at a heating temperature (DEG C) x heating time (h) of 1000 to 26400 (DEG C.h), preferably for a predetermined time (for example, about 2 to 35 hours) at 1800 to 17600 (DEG C.h), and after naturally cooling in the electric furnace, the spherical silica powder is recovered at 110 to 300 ℃, cooled to 25 ℃ in an environment having a humidity of 40% RH or less, stored at 15 to 25 ℃, and recovered with a moisture-proof aluminum bag.

By the above-mentioned production method, the adsorbed water and polar functional groups on the surface of the spherical silica particles can be reduced without changing the powder characteristics such as the specific surface area. Even if the particles are stored under high humidity for 1 month, for example, after production, it is expected that the amount of adsorbed water and polar functional groups on the surface of the particles will not change to such an extent as to affect the increase in the dielectric loss tangent (tan δ f) of the spherical silica.

The production method may include a step of classifying the powder so as to obtain a desired specific surface area and average particle diameter. Since the specific surface area and the average particle diameter do not change before and after heating as long as the heating temperature is 500 to 1100 ℃, it is preferable that the classification step is performed before heating, and after the specific surface area and the average particle diameter are adjusted to a desired value, the heat treatment is performed.

The obtained powder is subjected to surface treatment with a surface treatment agent, whereby the surface polar groups can be further reduced and the dielectric loss tangent can be lowered. The surface treatment agent is preferably one in which a polar functional group is less likely to remain after the surface treatment, and examples thereof include hexamethyldisilazane. After the surface treatment, it is preferably recycled again by means of a moisture-proof aluminum bag.

As a method for storing the spherical silica powder having a reduced dielectric loss tangent of the present invention, it is preferable to use a spherical silica powder having a moisture permeability of 0.1 (g/m) under condition B (temperature 40 ℃ to relative humidity 90%) of JIS Z0208-1976²24h) below, for example, a moisture-proof aluminum bag or a PET/AL/PE laminated bag.

The spherical silica powder of the present invention can be mixed with other powders having different specific surface areas, average particle diameters, and compositions to obtain a mixed powder. By using the mixed powder, the dielectric constant, dielectric loss tangent, thermal expansion coefficient, thermal conductivity, filling ratio, and the like when the powder is blended in a resin can be more easily adjusted.

The spherical silica powder and the mixed powder of the present invention are used by being mixed with a resin, for example. Examples of the resin used in the present invention include polyethylene, polypropylene, epoxy resins, silicone resins, phenol resins, melamine resins, urea resins, unsaturated polyesters, fluorine resins, polyimides, polyamides such as polyamideimides and polyetherimides, polyesters such as polybutylene terephthalate and polyethylene terephthalate, polyphenylene sulfide, wholly aromatic polyesters, polysulfones, liquid crystal polymers, polyether sulfones, polycarbonates, maleimide-modified resins, ABS resins, AAS (acrylonitrile-acrylic rubber-styrene) resins, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins, and the like. The spherical silica powder and the mixed powder of the present invention are particularly preferably used by blending with Polyethylene (PE) or polypropylene (PP).

The ratio of the spherical silica powder to the mixed powder in the resin is appropriately selected depending on the properties such as the dielectric constant and the dielectric loss tangent. For example, the amount of the resin to be used is appropriately selected within a range of 10 to 10000 parts by mass per 100 parts by mass of the spherical silica powder. If the density of the resin is set to 1.2g/cm³The volume ratio of the resin is suitably selected within the range of 1.8 to 94.3%.

By blending the spherical silica powder of the present embodiment into a resin, the dielectric loss tangent of the resin sheet after the powder blending can be reduced. Further, the resin sheet containing the spherical silica powder of the present embodiment has good flowability and excellent moldability due to its low viscosity.

Examples

The present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples.

[ raw silica powder 1]

Spherical silica (manufactured by Denka corporation: FB-5D, specific surface area 2.4 m)²/g) was subjected to heat treatment and evaluated in the same manner as in example 1 described later. Will evaluate the knotThe results are shown in Table 1. The powder reduced dielectric loss tangent (tan. delta.f) of the raw material silica powder 1 which had not been subjected to the dielectric loss tangent reduction treatment_A) In the case of using Polyethylene (PE) as the resin, the resin content is 2.9X 10^-3In the case of polypropylene (PP), the ratio is 3.0X 10^-3。

[ raw silica powder 2]

Spherical silica (manufactured by Denka corporation: SFP-30M, specific surface area 6.0M)²/g) was subjected to heat treatment and evaluated in the same manner as in example 1 described later. The evaluation results are shown in table 1. The powder reduced dielectric loss tangent (tan. delta.f) of the raw material silica powder 2 which had not been subjected to the dielectric loss tangent reduction treatment_A) Is 1.2X 10^-2。

[ raw silica powder 3]

Asymmetric spherical silica (manufactured by Denka Co., Ltd.: UFP-30, specific surface area 30 m)²/g) was subjected to heat treatment and evaluated in the same manner as in example 1 described later. The evaluation results are shown in table 1. The powder reduced dielectric loss tangent (tan. delta.f) of the raw material silica powder 3 which had not been subjected to the dielectric loss tangent reduction treatment_A) Is 5.0X 10^-2。

[ raw silica powder 4]

Asymmetric spherical silica (manufactured by Denka corporation: FB-40R, specific surface area 0.4 m)²/g) was subjected to heat treatment and evaluated in the same manner as in example 1 described later. The evaluation results are shown in table 1. The powder reduced dielectric loss tangent (tan. delta.f) of the raw material silica powder 4 which had not been subjected to the dielectric loss tangent reduction treatment_A) Is 3.7 multiplied by 10^-4。

[ example 1]

A raw material, namely, silica powder 1 (manufactured by Denka Co., Ltd.: FB-5D, specific surface area 2.4 m)²/g)15g of silica as a raw material was charged in an alumina crucible and heat-treated at a temperature of 1000 ℃ in an electric furnace for 4 hours. After the heat treatment, the mixture was cooled to 200 ℃ in a furnace, cooled to room temperature in a desiccator (23 ℃ to 10% RH), and packaged in aluminum (PET/AL/PE laminate bag: manufactured by Japan K.K.)Manufactured) was stored in a stand-up package (スタンドパック) until various evaluations. The evaluation results are shown in table 2. The powder reduced dielectric loss tangent (tan. delta.f) of the spherical silica powder after heat treatment, which was measured by a 36GHz cavity resonator (Samtec Co., Ltd.)_B) Is 7.6X 10^-4Powder reduced dielectric loss tangent (tan. delta.f) of raw material silica powder 1_A) Is 2.9 multiplied by 10^-3Therefore, B/A is 0.26.

[ examples 2 to 5]

The heat treatment and evaluation were carried out in the same manner as in example 1 except that the heat treatment temperature and time were as shown in table 2. The evaluation results are shown in table 2.

[ example 6]

15g of a raw material silica powder 1 (manufactured by Denka Co., Ltd.: FB-5D, specific surface area 2.4 m)²/g) silica as a raw material was filled in an alumina crucible and heat-treated at a temperature of 1000 ℃ in an electric furnace for 4 hours. After the heat treatment, the reaction mixture was cooled to 200 ℃ in a furnace, cooled to room temperature in a desiccator (23 ℃ to 10% RH), and 1 part by mass of hexamethyldisilazane (SZ-31, HMDS, Shinetsu Silicone Co.) was added to 100 parts by mass of the collected sample. The added powders were mixed with a vibration mixer made by Resodyn corporation and dried for 200 to 4 hours, and stored in an aluminum package until various evaluations as in example 1. Evaluation was performed in the same manner as in example 1. The evaluation results are shown in table 2.

[ example 7]

The raw material silica was used as a raw material silica powder 2 (manufactured by Denka: SFP-30M, specific surface area: 6.0M)²(g), the heat treatment and evaluation were performed in the same manner as in example 1 except for the above. The evaluation results are shown in table 2.

[ example 8]

The raw material silica was used as a raw material silica powder 3 (manufactured by Denka Co., Ltd.: UFP-30, specific surface area 30 m)²(g), the heat treatment and evaluation were performed in the same manner as in example 1 except for the above. The evaluation results are shown in table 2.

[ example 9]

The heat treatment and evaluation were carried out in the same manner as in example 1 except that polypropylene powder was used for evaluation of the dielectric properties. The evaluation results are shown in table 2.

[ comparative examples 1 to 3]

The heat treatment and evaluation were carried out in the same manner as in example 1 except that the heat treatment temperature and time were as shown in table 3. The evaluation results are shown in table 3.

Comparative example 4

The raw material silica was used as a raw material silica powder 4 (manufactured by Denka corporation: FB-40R, specific surface area 0.4 m)²Except for the fact that the amount of the carbon black was changed, heat treatment and evaluation were carried out in the same manner as in example 1. The evaluation results are shown in table 3.

Comparative example 5

The heating treatment and evaluation were carried out in the same manner as in example 1 except that the polypropylene powder was used for the evaluation of the dielectric properties and the temperature in the electric furnace was set to 200 ℃ and the heating time was set to 8 hours. The evaluation results are shown in table 3.

[ example 10]

After the spherical silica powder after the heat treatment of example 7 was packed in the same aluminum package { PET/AL/PE laminated bag: production manufactured by Nippon corporation: a moisture permeability of 0.1 or less (g/m)²24h), the resultant was put into a high-temperature and high-humidity chamber adjusted to 40 to 75% RH, and the dielectric characteristics were evaluated 3 months later. The evaluation results are shown in table 4.

[ example 11]

After the spherical silica powder after the heat treatment of example 7 was put into a PE bag with a zipper { UNI-PACK0.08 type: production manufactured by Nippon corporation: moisture permeability of 15.2 (g/m)²24h), the resultant was put into a high-temperature and high-humidity chamber adjusted to 40 to 75% RH, and the dielectric characteristics were evaluated 3 months later. The evaluation results are shown in table 4.

The properties of each sample were evaluated in the following manner. The evaluation results are shown in tables 1 to 5.

[ evaluation of dielectric Properties ]

The spherical silica and Polyethylene (PE) powder (FLO-THENE UF-20S, manufactured by Sumitomo Seiko Co., Ltd.) or polypropylene (PP) powder (FLOBLEN QB200, manufactured by Sumitomo Seiko) were measured so that the loading of the spherical silica after the heat treatment was 40 vol%, and they were mixed by a vibration mixer, manufactured by Resodyn (acceleration 60g, treatment time 2 minutes). The obtained mixed powder was measured in predetermined volume parts (thickness: about 0.3mm), placed in a gold frame having a diameter of 3cm, and formed into a sheet by a hot press (model IMC-1674-A, manufactured by Kogyo Co., Ltd.) at 140 ℃ for 10MPa for 15 minutes in the case of PE and at 190 ℃ for 10MPa for 60 minutes in the case of PP, to prepare an evaluation sample. The thickness of the sheet of the evaluation sample is about 0.3mm, and the shape and size of the sheet are about 1 to 3cm square, although the evaluation result is not affected as long as the sheet can be mounted on a measuring instrument.

The dielectric characteristics were measured by connecting a 36GHz cavity resonator (manufactured by Samtec Co., Ltd.) to a vector network analyzer (85107, manufactured by Keysight Technology Co., Ltd.), mounting a sample (1.5cm square and 0.3mm thick) so as to close a hole having a diameter of 10mm provided in the resonator, and measuring the resonance frequency (f0) and the unloaded Q value (Qu). The sample was rotated for each measurement, and the measurement was repeated 5 times in the same manner, and the average of f0 and Qu obtained was taken as a measurement value. The dielectric constant was calculated from f0 by using analytical software (Samtec software), and the dielectric loss tangent (tan. delta.c) was calculated from Qu. The measurement temperature was 20 ℃ and the humidity was 60% RH.

From the tan δ c thus obtained, the dielectric loss tangent (tan δ f) in terms of filler (silica powder) was calculated according to the following formula (I).

[ mathematical formula 4]

log (tan δ c) ═ Vf · log (tan δ f) + (l-Vf) · log (tan δ r) · · formula (I)

Wherein the symbols in formula (I) have the following meanings.

Vf; volume fraction of spherical silica powder in sheet

tan δ r; dielectric loss tangent of resin sheet (without filler)

The dielectric loss tangents (tan. delta. r) of the PE resin sheet and PP resin sheet without a compounding filler were 3.4X 10, respectively^-4And 2.1X 10^-4。

The dielectric characteristics of only the raw material silica powder 1 were evaluated in the same manner as a 40GHz split cylindrical resonator (manufactured by kanto electronic application developer) and a balanced type circular plate resonator (manufactured by Keysight corporation). The samples used for the dielectric property evaluation were prepared in the same manner as in the measurement of the 36GHz cavity resonator.

As a method for evaluating dielectric properties using a 40GHz split cylindrical resonator, a sample (3 cm in diameter and 0.2mm in thickness) was mounted on the resonator, and the resonance frequency (f0) and the unloaded Q value (Qu) were measured. The sample was rotated for each measurement, and the measurement was repeated 5 times in the same manner, and the average of f0 and Qu obtained was taken as a measurement value. The dielectric constant was calculated from f0 by using analytical software, and the dielectric loss tangent (tan δ c) was calculated from Qu. The measurement temperature was 26 ℃ and the humidity was 60% RH.

As a method for evaluating dielectric characteristics of a balanced type disk resonator, 2 identical samples (diameter 3cm, thickness 0.5mm) were prepared, mounted in the resonator with a copper foil interposed therebetween, and the resonance frequency (f0) and the unloaded Q value (Qu) of the peak appearing at 35 to 40GHz were measured. The dielectric constant was calculated from f0 by using analytical software, and the dielectric loss tangent (tan δ c) was calculated from Qu. The measurement temperature was 25 ℃ and the humidity was 50% RH.

The values of the dielectric constant and the dielectric loss tangent of the resin sheet measured by the 3 measurement methods are shown in Table 5.

[ specific surface area ]

The measuring cell was filled with 1g of a sample, and the specific surface area was measured by a MacsorbHM model-1201 full-automatic specific surface area measuring apparatus (BET one-point method) manufactured by Mountech. The degassing conditions before the measurement were 200 to 10 minutes. The adsorbed gas is nitrogen.

[ average roundness ]

The powder was fixed to a sample stage with a carbon tape, and then osmium was applied, and an image of 500 to 50000 times magnification and 1280 × 1024 pixels resolution, which were obtained by scanning electron microscopy (JSM-7001F SHL, manufactured by Japan Electron Ltd.), was read into a computer. The projected area (S) of the particles (powder particles) and the projected perimeter (L) of the particles were calculated using an Image analyzer (Image-Pro Premier ver.9.3, manufactured by Japan rope corporation), and then the circularity was calculated from the following formula (III). The circularity was calculated for any 200 particles, and the average value thereof was taken as the average circularity.

[ math figure 5]

Roundness of 4 pi S/L²The formula (III)

[ Density ]

1.2g of the powder was charged into a sample cell for measurement, and measured by a gas (helium) displacement method using a dry densitometer ("AccuPyc II 1340" manufactured by Shimadzu corporation).

[ Table 1]

[ Table 2]

[ Table 3]

[ Table 4]

[ Table 5]

The resin sheets containing the spherical silica powders of examples 1 to 11 had a dielectric loss tangent that was suppressed to be lower than that of the resin sheets containing the spherical silica powders of comparative examples 1 to 5.

Industrial applicability

When the spherical silica powder of the present invention is filled in a resin material, it can be used as a filler that can reduce the dielectric loss tangent of a base material.