JP7015888B2 - Spherical silica powder - Google Patents

Description

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

In recent years, with the increase in the amount of information communication in the communication field, the utilization of high frequency bands is spreading in electronic devices and communication devices. High frequencies are characterized by wideband, straightness, transparency, etc., and in particular, the GHz band having a frequency of ¹⁰⁹ or more is actively used. For example, in the automobile field, high frequencies of 76 to 79 GHz and 24 GHz are used in millimeter-wave radars and quasi-millimeter-wave radars installed for the purpose of collision prevention, respectively, and it is expected that they will become more widespread in the future. Will be done.

With the application of the high frequency band, there is a problem that the transmission loss of the circuit signal becomes large. The transmission loss is roughly classified into a conductor loss due to the skin effect of wiring and a dielectric loss due to the characteristics of the dielectric material of the insulator constituting an electric / electronic component such as a substrate. Since the dielectric loss is proportional to the first power of the frequency, the 1/2 power of the dielectric constant of the insulator, and the first power of the dielectric loss tangent, both the dielectric constant and the dielectric loss tangent are low for the materials used for the device for the high frequency band. Is required.

Polymer materials used for insulator materials generally have a low dielectric constant, but often have a high dielectric loss tangent. On the other hand, many ceramic materials have the opposite characteristics, and in order to achieve both of these characteristics, a ceramic filler-filled polymer material has been studied (for example, Patent Document 1).

The dielectric properties of the ceramic material in the GHz band are known, for example, in Non-Patent Document 1 and the like, but all of them are the properties of a sintered substrate. Silica (SiO ₂ ) has a small dielectric constant (3.7), a quality coefficient index Qf (the reciprocal of the dielectric loss tangent multiplied by the measurement frequency) of about 120,000, and a filler having a low dielectric constant and a dielectric loss tangent. It is a promising material for. Further, in order to facilitate compounding in the resin, it is preferable that the filler shape is closer to a spherical shape, but spherical silica can be easily synthesized (for example, Patent Document 2) and has already been used in many applications. .. Therefore, it is expected to be widely used in high frequency band dielectric devices and the like.

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

As a method for reducing the adsorbed water and polar functional groups on the surface of the filler particles, for example, in Non-Patent Document 2, a method of surface treatment with a silane coupling agent has been studied, but the dielectric loss tangent is almost reduced at 1 to 10 MHz. The effect of the millimeter wave band is not specified.

Japanese Unexamined Patent Publication No. 2014-24916 Japanese Unexamined Patent Publication No. 58-138740

International Materials Reviews vol.60 No. 70 Supplementary data (2015). IEEE Transitions on Dielectrics and Electrical Insulation Vol. 17, No. 6 (2010).

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

(1) When the temperature is raised from 25 ° C. to 30 ° C./min to 1000 ° C., the number of water molecules desorbed at 500 ° C. to 1000 ° C. is 0.01 mmol / g or less, and the specific surface area is 1 to 30 m. Spherical silica powder characterized by being ² / g.
(2) In the spherical silica powder before surface treatment, the peak intensity of the silica powder with a wave number of 3735 cm ^-1 to 3755 cm ^-1 measured by the diffuse reflection FT-IR method is A, and the peak intensity of the wave number is 3660 cm ^-1 to 3680 cm ^-1 . The spherical silica powder according to (1), wherein the B / A is 3.0 or less when the strength is B.
(3) The spherical silica powder according to (1) or (2), which is subjected to high-temperature heat treatment in an inert atmosphere or high-temperature heat treatment in a reducing reaction field.
(4) The spherical silica powder according to any one of (1) to (3), which has an average circularity of 0.85 or more.
(5) The spherical silica powder according to any one of (1) to (4), which is surface-treated with a surface treatment agent.
(6) The spherical silica powder according to any one of (1) to (5), which is used by blending in a resin.

According to the present invention, it is possible to provide a resin material, for example, a spherical silica powder capable of lowering the dielectric loss tangent of a substrate or the like.

Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments.
The silica powder of the present invention has 0.01 mmol / g or less of water molecules desorbed at 500 ° C. to 1000 ° C. when the temperature is raised from 25 ° C. to 30 ° C./min to 1000 ° C. The amount of desorbed water can be measured using, for example, a heated desorbed gas analyzer (TDS), and the temperature is raised from 25 ° C. to 30 ° C./min to obtain a mass chromatogram (m / z =). The number of _H2O desorbed molecules is calculated from the area value in the range of 500 ° C. to 1000 ° C. in 18). The number of desorbed molecules is preferably 0.008 mmol / g or less, and the lower limit is not particularly specified, but in reality, it is 0.0001 mmol / g or more.

The silica powder of the present invention has a peak intensity of 3735 cm ^-1 to 3755 cm ^-1 wave number of the silica powder measured by the diffuse reflection FT-IR method in the spherical silica powder before surface treatment, and has a wave number of 3660 cm ^-1 to 3680 cm. When the peak intensity of ^-1 is B, B / A is 3.0 or less. It is generally known that the peak with a wave number of 3735 cm ^-1 to 3755 cm ^-1 is an isolated silanol group, and the peak with a wave number of 3660 cm ^-1 to 3680 cm ^-1 is a hydrogen-bonded silanol group. In the present invention, paying attention to the hydrogen-bonding silanol group strength, when the B / A is 3.0 or less, the dielectric loss tangent of the resin composition can be sufficiently reduced.

The spherical silica powder of the present invention has a specific surface area of 1 to 30 m ² / g. If the specific surface area is larger than 30 m ² / g, it becomes difficult to mix in the resin, and if it is less than 1 m ² / g, the dielectric loss tangent reduction treatment effect becomes small.

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

The density of the spherical silica powder of the present invention is preferably 1.8 to 2.4 g / cm ³ . When the density is smaller than 1.8, a large amount of voids are contained in the particles, which makes kneading in the resin difficult. If the density is higher than 2.4, the crystal structure of silica contains α-quartz, cristobalite, etc., and there may be a concern about the influence on physical properties such as an increase in thermal expansion rate.

As the raw material silica powder of the present invention, any spherical silica powder having an average circularity of 0.85 or more and a specific surface area of 1 to 30 m ² / g can be preferably used. Examples of the method for producing spherical silica powder as a raw material include a powder melting method in which a spheroidal silica powder is spheroidized by passing through a high temperature range having a temperature higher than the melting point.

The spherical silica powder of the present invention can be produced by heat-treating the raw material silica powder in a high-temperature heat treatment or an electric furnace which is a reducing reaction field while flowing the powder in an inert atmosphere. The temperature and time may be such that the number of water molecules desorbed at 500 ° C. to 1000 ° C. is 0.01 mmol / g or less when the temperature is raised from 25 ° C. to 1000 ° C. under the condition of 30 ° C./min, and the raw material silica is used. Although it depends on the specific surface area of the powder, for example, the powder may be treated in a rotary kiln at 700 to 1000 ° C. for 1 to 24 hours while flowing in a rotary kiln, and then naturally allowed to cool in a furnace. .. The electric furnace, which is a reducing reaction field, is, for example, a carbon furnace in which the furnace material is carbon, and when the furnace material is other than carbon, firing is performed in an atmosphere in which several% hydrogen is added. It can be manufactured by cooling to 200 ° C. or lower, drying it in a vacuum dryer, and then collecting it in 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 after production, for example, even if stored in high humidity for one month, for example, in a 40 ° C.-90% RH environment, the adsorbed water and polar functionality on the surface of the particles affect the increase in the dielectric loss tangent of the spherical silica. It can be expected that the base amount will not change.

The production method may include a step of classifying the powder so as to obtain a desired specific surface area and average particle size. If the heating temperature is 1000 ° C. or lower, the specific surface area and average particle size do not change before and after heating. Therefore, the classification step is performed before heating, and after adjusting to the desired specific surface area and average particle size, heating is performed. It is desirable to process.

By surface-treating the obtained powder with a surface treatment agent, the surface polar groups can be further reduced and the dielectric loss tangent can be reduced. In addition, it can be expected to improve the compatibility with the resin interface and the adhesion. The surface treatment agent is preferably one that is compatible with the resin type to be added and one in which polar functional groups are unlikely to remain after surface treatment. For example, γ-glycidoxypropyltriethoxysilane and β- (3,4-epoxy). Cyclohexyl) Epoxysilane such as ethyltrimethoxysilane, aminopropyltriethoxysilane, aminosilane such as N-phenylaminopropyltrimethoxysilane, vinylsilane such as vinyltrimethoxysilane, acrylicsilane such as acryloxytrimethoxysilane, hexamethyldi Examples thereof include silane such as silane. The amount of the treating agent having a large amount of polar functional groups such as aminosilane and acrylic silane is preferably as small as possible, and is, for example, 1 part by mass or less with respect to 100 parts by mass of the spherical silica powder. After surface treatment, it is desirable to collect it again in a moisture-proof aluminum bag.

The impurities of alkali metals such as Na, Li or K and metal elements such as Fe contained in the spherical silica powder of the present invention are preferably as small as possible from the viewpoint of reducing the dielectric loss tangent. Other impurities should be reduced as much as possible.

As a method for preserving the spherical silica powder with reduced dielectric tangents of the present invention, the water permeability under condition B (temperature 40 ° C.-relative humidity 90%) of JIS Z 0208-1976 is 0.1 (g / m ^2.24h ). It is preferable to store in the following moisture-proof bag, for example, a moisture-proof aluminum bag or a PET / AL / PE laminated bag.

A mixed powder can be obtained by blending and mixing the spherical silica powder of the present invention with another powder having a different specific surface area, average particle size, and composition. By using the mixed powder, the dielectric constant, the dielectric loss tangent, the coefficient of thermal expansion, the thermal conductivity, the filling ratio, and the like when blended in the resin can be more easily adjusted.

The spherical silica powder and the mixed powder of the present invention are used, for example, by blending them in a resin. Examples of the resin used in the present invention include polyamides such as polyethylene, polypropylene, epoxy resin, silicone resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyimide, polyamideimide, and polyetherimide. Polybutylene terephthalate, polyester such as polyethylene terephthalate, polyphenylene sulfide, total aromatic polyester, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber / styrene) resin, AES (acrylonitrile) -Ethyl, propylene, diene rubber-styrene) resin and the like can be mentioned.

The spherical silica powder and the mixed powder of the present invention can be blended with a known low-dielectric resin used for this application, particularly when used as a substrate material or an insulating material for high frequency. Specifically, it is blended in the following resins, crosslinked and cured as necessary, and used. As such a resin, for example, one or more selected from hydrocarbon-based elastomers, polyphenylene ethers, and aromatic polyene-based resins can be used. Among these, hydrocarbon-based elastomers or polyphenylene ethers are preferable. The mass ratio of the spherical silica powder and the mixed powder to these resins is arbitrary, but is preferably in the range of 5:95 to 80:20, more preferably in the range of 5:95 to 70:30.

<Hydrocarbon elastomer>
Among the hydrocarbon-based elastomers, conjugated diene-based polymers are preferable. Among the conjugated diene-based polymers, 1,2-polybutadiene is preferable. The hydrocarbon-based elastomer that can be suitably used may have a number average molecular weight of 1000 or more, preferably 10,000 or more. Examples of hydrocarbon-based elastomers include ethylene-based and propylene-based elastomers, conjugated diene-based polymers and aromatic vinyl compounds-conjugated diene-based block copolymers or random copolymers, and hydrides thereof (hydrogenated. The one or more elastomers selected from the thing) can be mentioned. Examples of the ethylene-based elastomer include ethylene-α-olefin copolymers such as ethylene-octene copolymer and ethylene-1-hexene copolymer, EPR, and EPDM. Examples of the propylene-based elastomer include propylene-α-olefin copolymers such as atactic polypropylene, polypropylene with low stereoregularity, and propylene-1-butene copolymer.

<Conjugated diene polymer>
Examples of the conjugated diene polymer include polybutadiene and 1,2-polybutadiene. Examples of the aromatic vinyl compound-conjugated diene-based block copolymer or random copolymer, and hydrogenated products thereof (hydrogenates) include SBS, SIS, SEBS, SEPS, SEEPS, and SEEBS. The 1,2-polybutadiene that can be suitably used can be obtained, for example, as a product of JSR Corporation, or can be obtained from Nippon Soda Corporation under the product names of liquid polybutadiene: product names B-1000, 2000 and 3000. Further, as a copolymer containing a 1,2-polybutadiene structure that can be preferably used, "Ricon 100" manufactured by TOTAL CRAY VALLEY can be exemplified.

<Polyphenylene ether>
As the polyphenylene ether, a commercially available known polyphenylene ether can be used. The number average molecular weight of the polyphenylene ether is arbitrary, and the number average molecular weight is preferably 10,000 or less, most preferably 5,000 or less in consideration of the molding processability of the compound. The number average molecular weight may be preferably 500 or more. Further, in the case of addition for the purpose of curing the formulation, it is preferable that the molecular end is modified, and / or it is preferable that a plurality of functional groups are contained in one molecule. Examples of the functional group include an allyl group, a vinyl group, an epoxy group and the like. As the functional group, a radically polymerizable functional group is preferable. As the radically polymerizable functional group, a vinyl group is preferable. As the vinyl group, a (meth) acrylic group or an aromatic vinyl group is preferable. Further, bifunctional polyphenylene ethers in which both ends of the molecular chain are modified with radically polymerizable functional groups are particularly preferable. As such a polyphenylene ether, SABIC's Noryl ™ SA9000 or Mitsubishi Gas Chemical Company's bifunctional polyphenylene ether oligomer (OPE-2St) can be used.

<Aromatic polyene resin>
The aromatic polyene-based resin includes a divinylbenzene-based reactive multi-branched copolymer (PDV) manufactured by Nittetsu Chemical & Materials Co., Ltd. For such PDV, for example, the document "Synthesis of polyfunctional aromatic vinyl copolymer and development of new IPN type low dielectric loss material using it" (Honest Kawabe et al., Journal of Electronics Packaging Society p125, Vol. 12 No. 2 (2009)). Further, examples of the aromatic polyene-based resin include the aromatic polyene polymer resin having the above-mentioned aromatic polyene monomer as a main constituent unit.

The spherical silica powder and the mixed powder of the present invention can be crosslinked and cured by using the following crosslinking materials and curing agents together with these resins. As the cross-linking material, various maleimides, bismaleimides, maleic anhydride, glycidyl (meth) acrylate, glycidyl (meth) acrylate, triallyl isocyanurate, tri (meth) acrylic isocyanurate, trimethylolpropane tri (meth). Examples include acrylate. Maleimides and bismaleimides that can be used in the present invention are described in, for example, International Publication No. 2016/114287, and can be purchased from, for example, Daiwa Kasei Kogyo Co., Ltd. These maleimide group-containing compounds may be used as polyaminobismaleimide compounds from the viewpoints of solubility in an organic solvent, high frequency characteristics, high adhesiveness to a conductor, moldability of a prepreg, and the like. The polyaminobismaleimide compound is obtained, for example, by carrying out a Michael addition reaction between a compound having two maleimide groups at the terminal and an aromatic diamine compound having two primary amino groups in the molecule. When high cross-linking efficiency is to be obtained with a small amount of addition, it is preferable to use a cross-linking material having a polyfunctional group of two or more functional groups, such as bismaleimides, triallyl isocyanurate (TAIC), and trimethylolpropane tri (meth). An acrylate can be exemplified. The amount of the cross-linking material may be in the range of 0.1 to 30 parts by mass, preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the resin.

<Curing agent>
As the curing agent to be used, a known curing agent that can be conventionally used for polymerization or curing of aromatic polyenes and aromatic vinyl compounds may be used. Examples of such a curing agent include a radical polymerization initiator, a cationic polymerization initiator, and an anionic polymerization initiator, and a radical polymerization initiator can be preferably used. Preferred are organic peroxide-based (peroxide), azo-based polymerization initiators, and the like, which can be freely selected depending on the intended use and conditions. Catalogs containing organic peroxides can be found on the NOF website, for example.
https://www.nof.co.jp/business/chemical/product01a.html
https://www.nof.co.jp/business/chemical/product01b.html
https://www.nof.co.jp/business/chemical/product01c.html
It is possible to download from. Organic peroxides are also listed in the catalogs of Wako Pure Chemical Industries, Ltd. and Tokyo Chemical Industry Co., Ltd. The curing agent used in the present invention is available from these companies. Further, a known photopolymerization initiator using light, ultraviolet rays, or radiation can also be used as a curing agent. Examples of the curing agent using the photopolymerization initiator include a photoradical polymerization initiator, a photocationic polymerization initiator, and a photoanionic polymerization initiator. Such a photopolymerization initiator can be obtained from, for example, Tokyo Chemical Industry Co., Ltd. Furthermore, it can be cured by radiation or the electron beam itself. Further, it is also possible to carry out cross-linking and curing by thermal polymerization of the contained raw materials without containing a curing agent. The amount of the curing agent used is not particularly limited, but generally 0.01 to 10 parts by mass is preferable with respect to 100 parts by mass of the resin (preferably excluding the curing agent and the solvent). When a curing agent such as a peroxide-based or azo-based polymerization initiator is used, the curing treatment is performed at an appropriate temperature and time in consideration of its half-life. The conditions in this case are arbitrary according to the curing agent, but generally, a temperature range of about 50 ° C. to 180 ° C. is suitable.

The compositions such as the various resins, cross-linking materials, and / or curing agents used when the spherical silica powder and mixed powder of the present invention are used as a substrate material or an insulating material for high frequency, and the cured product thereof are described below, for example. It is described in the patent of. Japanese Patent Application Laid-Open No. 8-208856, Japanese Patent Application Laid-Open No. 2017-75270, Japanese Patent Application Laid-Open No. 2009-167268, Japanese Patent Application Laid-Open No. 2011-678713, Japanese Patent Application Laid-Open No. 2018-1315119, Japanese Patent Application Laid-Open No. 2016-534549, Japanese Patent Application Laid-Open No. 2017-573352 Gazette, WO2016-175325 International Pamphlet, WO2016-175326 International Pamphlet.

The ratio of the spherical silica powder and the mixed powder in the resin is appropriately selected according to the physical properties such as the target dielectric constant and the dielectric loss tangent. For example, the amount of the resin used is appropriately selected in the range of 10 to 10000 parts by mass with respect to 100 parts by mass of the spherical silica powder. Assuming that the density of the resin is 1.2 g / cm ³ , the volume ratio of the resin is appropriately selected in the range of 1.8 to 94.3%.

By blending the spherical silica powder of the present embodiment in the resin, the dielectric loss tangent of the resin sheet after the powder blending can be lowered. Further, the resin sheet containing the spherical silica powder of the present embodiment has a low viscosity, so that it has good fluidity and excellent moldability.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the Examples.

[Raw material silica powder 1]
Spherical silica (manufactured by Denka Co., Ltd .: FB-5D, specific surface area 2.3 m ² / g) was evaluated as it was without heat treatment in the same manner as in Example 1 described later. The evaluation results are shown in Table 1. The dielectric loss tangent of the resin sheet of the raw material silica powder 1 is 8.0 × 10 ^-4 when polyethylene (PE) is used as the resin, and 6.1 × 10 ^-4 when polypropylene (PP) is used. there were.

[Raw material silica powder 2]
Spherical silica (manufactured by Denka: SFP-30M, specific surface area of 6.0 m ² / g) was evaluated as it was without heat treatment in the same manner as in Example 1 described later. The evaluation results are shown in Table 1. The dielectric loss tangent of the resin sheet (PE) of the raw material silica powder 2 was 1.4 × 10 ^-3 .

[Example 1]
As the raw material silica, 50 g of the raw material silica powder 1 (manufactured by Denka: FB-5D, specific surface area 2.3 m ² / g) is placed in a quartz glass cylindrical container, and the cylindrical container is filled in a mulite rotary kiln, and nitrogen is used. In the atmosphere, the rotary kiln was heat-treated at a temperature of 900 ° C. for 2 hours. After the heat treatment, the inside of the furnace was cooled to 200 ° C. or lower, and dried in a vacuum dryer (in an environment of less than 120 ° C.-133 Pa) for 24 hours. It was stored in a stand pack of an aluminum pack (PET / AL / PE laminated bag: manufactured by Japan) until just before various evaluations. The evaluation results are shown in Table 2. The dielectric loss tangent of the resin sheet (PE) was 4.7 × 10 ^-4 .

[Examples 2 and 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 2. The evaluation results are shown in Table 2.

[Example 4]
As the raw material silica, 50 g of the raw material silica powder 1 (manufactured by Denka: FB-5D, specific surface area 2.3 m ² / g) is placed in a quartz glass cylindrical container, and the cylindrical container is filled in a mulite rotary kiln, and nitrogen is used. In the atmosphere, the rotary kiln was heat-treated at a temperature of 900 ° C. for 2 hours. After the heat treatment, the inside of the furnace was cooled to 200 ° C. or lower, and dried in a vacuum dryer (in an environment of less than 120 ° C.-133 Pa) for 24 hours. To 100 parts by mass of the recovered sample, 1 part by mass of hexamethyldisilazane (SZ-31; HMDS, manufactured by Shinetsu Silicone Co., Ltd.) was added as a surface treatment agent. The added powder is mixed with a vibration mixer manufactured by Resodyn, dried in a vacuum dryer (in an environment of less than 120 ° C.-133 Pa) for 24 hours, and stored in an aluminum pack in the same manner as in Example 1 until just before various evaluations. did. The evaluation was carried out in the same manner as in Example 1. The evaluation results are shown in Table 2.

[Example 5]
Heat treatment and evaluation were carried out in the same manner as in Example 4 except that vinyltrimethoxysilane (KBM-1003; vinyl manufactured by Shinetsu Silicone Co., Ltd.) was used as the surface treatment agent. The evaluation results are shown in Table 2.

[Example 6]
Heat treatment and evaluation were carried out in the same manner as in Example 1 except that the raw material silica was the raw material silica powder 2 (manufactured by Denka Co., Ltd .: SFP-30M, specific surface area 6.0 m ² / g). The evaluation results are shown in Table 2.

[Example 7]
Heat treatment and evaluation were carried out in the same manner as in Example 1 except that polypropylene powder was used in the evaluation of the dielectric property. The evaluation results are shown in Table 2.

[Example 8]
As raw material silica, 50 g of raw material silica powder 1 (manufactured by Denka: FB-5D, specific surface area 2.3 m ² / g), an alumina crucible, high mulch (carbon furnace) manufactured by Fuji Denpa Kogyo, electric furnace in a nitrogen atmosphere. Internal temperature 1000 ° C.-4 hours heat treatment. After the heat treatment, the inside of the furnace was cooled to 200 ° C. or lower, and dried in a vacuum dryer (in an environment of less than 120 ° C.-133 Pa) for 24 hours. It was stored in a stand pack of an aluminum pack (PET / AL / PE laminated bag: manufactured by Japan) until just before various evaluations. The evaluation results are shown in Table 2.

[Example 9]
Heat treatment and evaluation were performed in the same manner as in Example 8 except that the raw material silica was the raw material silica powder 2 (manufactured by Denka: SFP-30M, specific surface area 6.0 m ² / g) and the heating temperature and atmosphere were as shown in Table 2. Was done. The evaluation results are shown in Table 2.

[Example 10]
The heat treatment and evaluation were carried out in the same manner as in Example 9 except that the heat treatment temperature, time and atmosphere were as shown in Table 2. The evaluation results are shown in Table 2.

[Comparative Examples 1 to 4]
The heat treatment and evaluation were carried out in the same manner as in Example 1 except that the heat treatment temperature, time, raw material silica powder, and atmosphere were as shown in Table 3. The evaluation results are shown in Table 3.

The characteristics of each sample were evaluated by the following method. The evaluation results are shown in Tables 1 to 3.

[Average circularity]
After fixing the powder to the sample table with carbon tape, osmium coating is applied, and an image with a magnification of 500 to 50,000 times and a resolution of 1280 x 1024 pixels taken with a scanning electron microscope (JSM-7001F SHL manufactured by JEOL Ltd.) is transferred to a personal computer. I took it in. Using an image analysis device (Image-Pro Premier Ver. 9.3, manufactured by Nippon Roper Co., Ltd.), the projected area (S) of the particles (powder particles) and the projected peripheral length (L) of the particles were calculated for this image. Then, the circularity was calculated from the following equation (1). When the raw material silica was FB-5D, the circularity was calculated for 1 to 10 μm, and when the raw material silica was SFP-30M, the circularity was calculated for 200 arbitrary particles of 0.2 to 1 μm, and the average value was taken as the average circularity.
Circularity = 4πS / L ² ... Equation (1)

[density]
1.2 g of the powder was placed in a sample cell for measurement, and measured by a gas (helium) substitution method using a dry densitometer (“Accupic II 1340” manufactured by Shimadzu Corporation).

[Specific surface area]
The measurement cell was filled with 1 g of a sample, and the specific surface area was measured by a Maxorb HM model-1201 fully automatic specific surface area measuring device (BET one-point method) manufactured by Muntech. The degassing condition before the measurement was 200 ° C. for 10 minutes. The adsorbed gas was nitrogen.

[B / A]
The integrated intensity ratio of B (hydrogen-binding silanol group) and A (isolated silanol group) is diffusely reflected in an atmospheric atmosphere using a Fourier transform infrared spectrophotometer (Frontier infrared spectroscope manufactured by PerkinElmer). Measurements by the method (resolution 8.0 cm ^-1 , integration count 32 times) were performed, and a baseline was drawn between 3800-2875 cm ^-1 from the obtained diffuse reflection spectrum, and 3735 cm ^-1 to 3755 cm ^-1 isolated silanol. The group peak intensity and the hydrogen-binding silanol group peak intensity of 3660 cm ^-1 to 3680 cm ^-1 were calculated, respectively, and the peak intensity ratio was determined.

[Amount of desorbed water]
Obtained by raising the temperature of the upper thermocouple from 25 ° C to 30 ° C / min to 1000 ° C in an atmospheric atmosphere using a temperature-raising desorption gas analyzer (EMD-WA1000S / W; TDS manufactured by Electronic Science). The number of _H2O desorbed molecules was calculated from the area value of the mass chromatogram (m / z = 18) in the range of 500 ° C. to 1000 ° C. The measurement was performed with the carbon sheet, the sample powder (10 mg), and the carbon sheet placed in this order on the quartz sample dish.

[Evaluation of dielectric properties]
Spherical silica powder and polyethylene (PE) powder (Frosen UF-20S manufactured by Sumitomo Seika Chemical Co., Ltd.) or polypropylene (PP) powder (Sumitomo Seika Chemical Co., Ltd.) so that the filling amount of the spherical silica powder after heat treatment is 40% by volume. Flowbren QB200 manufactured by Co., Ltd.) was weighed and mixed with a vibration mixer manufactured by Resodyn (acceleration 60 g, processing time 2 minutes). The obtained mixed powder is weighed in a predetermined volume (so that the thickness is 0.3 mm), placed in a metal frame with a diameter of 3 cm, and placed in a heat press machine (“IMC-1674-A type” manufactured by Imoto Seisakusho Co., Ltd.”. ) At 140 ° C., 10 MPa, 15 minutes for PE, and 190 ° C., 10 MPa, 60 minutes for PP, and used as an evaluation sample. The thickness of the sheet of the evaluation sample is 0.3 mm, and the shape and size are 1.5 cm square, although it does not affect the evaluation result if it can be mounted on the measuring instrument.

To measure the dielectric characteristics, a 36 GHz hollow resonator (manufactured by Samtec) is connected to a vector network analyzer (85107, manufactured by KeySight Technology), and a sample (1.5 cm square, thickness 0.3 mm) is provided in the resonator. The hole having a diameter of 10 mm was set to be closed, and the resonance frequency (f0) and the no-load 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 the obtained f0 and Qu was taken and used as the measured value. The permittivity was calculated from f0, and the dielectric loss tangent was calculated from Qu using analysis software (software manufactured by Samtec). The measured temperature was 20 ° C. and the humidity was 60% RH.
Further, the dielectric loss tangent of the resin sheet measured by blending the raw material spherical silica powders 1 and 2 with the resin is defined as a, and the dielectric loss tangent of the resin sheet measured by blending the spherical silica powders of Examples and Comparative Examples with the resin is defined as b. , The reduction rate (%) of the dielectric loss tangent of the resin sheet itself was obtained from the formula (2).
Reduction rate of dielectric loss tangent of the resin sheet itself (%) = {1- (b / a)} × 100 ... Equation (2)

The results show that the resin sheets containing the spherical silica powders of Examples 1 to 10 have a lower dielectric loss tangent than the resin sheets containing the spherical silica powders of Comparative Examples 1 to 4.

The spherical silica powder of the present invention can be used as a filler capable of lowering the dielectric loss tangent of the base material as compared with the conventional spherical silica when filled in a resin material.

Claims (3)

When the temperature is raised from 25 ° C to 30 ° C / min to 1000 ° C, the number of water molecules desorbed at 500 ° C to 1000 ° C is 0.010 mmol / g or less, and the specific surface area is 1 to 30 m ² /. g,
In the spherical silica powder before surface treatment, the peak intensity of the silica powder with a wave number of 3735 cm ^-1 to 3755 cm ^-1 measured by the diffuse reflection FT-IR method is A, and the peak intensity of a wave number of 3660 cm ^-1 to 3680 cm ^-1 is B. When, B / A is 3.0 or less,
A spherical silica powder having an average circularity of 0.85 or more. The spherical silica powder according to claim 1, wherein the surface is treated with a surface treatment agent. The spherical silica powder according to claim 1 or 2, wherein the spherical silica powder is blended in a resin and used.