Truly spherical conductive particle, and slurry and resin composition containing same

Abstract

Regarding conductive particles added to and mixed with a resin material, provided are truly spherical conductive particles in which the shape and specific surface area of the particles are controlled in order to suppress a viscosity increase after mixing with the resin material. The truly spherical conductive particles each have a conductive layer on the surface of an inorganic oxide particle, wherein (1) the true sphericity of the inorganic oxide particles is 0.80 or more, (2) a quotient Qs of (the specific surface area of the truly spherical conductive particles) / (the specific surface area of the inorganic oxide particles) is 1.0-2.0, and (3) the conductive layer is tin oxide containing fluorine. The powder resistance value of the truly spherical conductive particles is 1-100000 Ω·cm.

Description

Spherical conductive particles, and slurries and resin compositions containing them.

[0001] The present invention relates to spherical conductive particles, and slurries and resin compositions containing them, and more particularly to spherical conductive particles in which a conductive coating is formed on the surface of inorganic material particles, and slurries and resin compositions containing them.

[0002] Spherical particles, for example, can be added to and mixed into resin materials as fillers to enhance the strength of molded resin products. In this case, the spherical particles are made conductive for the purpose of preventing static electricity in the molded resin products.

[0003] Therefore, the following particles have been proposed. Specifically, a powder having a coating layer of tin dioxide containing one of the elements tungsten, niobium, tantalum, antimony, fluorine, and phosphorus on the surface of white inorganic pigment particles (Patent Document 1), a white conductive powder having a conductive layer of tin oxide on the surface of white inorganic powder, wherein the ratio of (specific surface area of ​​white conductive powder) to (specific surface area of ​​white inorganic powder) is 2.0 to 5.0 and the powder volume resistivity is 100 to 100,000 Ω·cm (Patent Document 2), and white particles having a coating layer containing tin oxide formed on the surface of core particles, with a crystallite size of tin oxide of 70 to 200 Å, and the coating layer being made of tin oxide without doping elements (Patent Document 3).

[0004] The particles disclosed in the listed patent documents impart conductivity to the particle surface. However, when adding conductive particles to a resin material, the viscosity after mixing with the resin material is important for good kneading. In recent years, when considering the addition of conductive particles to resin materials used in three-dimensional molding devices such as 3D printers, good fluidity and suppression of viscosity increase are important. Generally, when particulate matter is mixed and kneaded into a resin material, the viscosity increases. The shape of the particles and the specific surface area greatly influence viscosity. In the particles disclosed in the listed patent documents, the shape of the central particle (core particle) and the resulting conductive particles are not specified. Furthermore, there is no clear description of the specific surface area, and even if there were a description of the specific surface area, conductive particles are not suitable for high-density filling of resin materials.

[0005] Japanese Patent Publication No. 2003-146505, Japanese Patent Publication No. 2011-054508, Japanese Patent Publication No. 2012-203312

[0006] The present invention has been made in view of the above points, and provides spherical conductive particles whose shape and specific surface area are controlled in order to suppress the increase in viscosity after mixing with a resin material, and a slurry and resin composition containing the same spherical conductive particles.

[0007] In other words, the embodiment is a spherical conductive particle having a conductive layer on the surface of the following inorganic oxide particles, characterized in that (1) the sphericity of the inorganic oxide particles is 0.80 or more, (2) the quotient Qs of (specific surface area of ​​the spherical conductive particle) / (specific surface area of ​​the inorganic oxide particle) is 1.0 to 2.0, and (3) the conductive layer is tin oxide containing fluorine.

[0008] Furthermore, the powder resistance of the perfectly spherical conductive particles may be set to 1 to 100,000 Ω·cm.

[0009] Furthermore, in the case of perfectly spherical conductive particles, the quotient Qt of (thickness of the conductive layer) / (particle diameter of the inorganic oxide particles) may be 0.01 to 0.10.

[0010] Furthermore, in spherical conductive particles, the conductive layer may be provided with a surface treatment derived from at least one silane compound or an organic compound having an organosilazane.

[0011] Furthermore, a slurry having spherical conductive particles and an organic solvent that disperses the spherical conductive particles may be prepared.

[0012] Furthermore, a resin composition having spherical conductive particles and a resin material that disperses the spherical conductive particles may be prepared.

[0013] The spherical conductive particles of the present invention are spherical conductive particles having a conductive layer on the surface of inorganic oxide particles, wherein (1) the sphericity of the inorganic oxide particles is 0.80 or higher, (2) the quotient Qs of (specific surface area of ​​spherical conductive particles) / (specific surface area of ​​inorganic oxide particles) is 1.0 to 2.0, and (3) the conductive layer is tin oxide containing fluorine. As a result, the spherical conductive particles can be made to have a particle shape close to a perfect sphere, the specific surface area is controlled, and the increase in viscosity after mixing with resin material is suppressed. Furthermore, the increase in viscosity can also be suppressed in slurries and resin compositions.

[0014] This is an SEM image of Example 1. This is a TEM image of the spherical conductive particles of Example 1. This is a TEM image of the surface portion of the spherical conductive particles of Example 1.

[0015] As described above, the spherical conductive particles of the embodiment are primarily used as fillers, added to and mixed (kneaded) into known resin materials and homogeneously dispersed within them. Various molding methods, such as press molding and extrusion molding, are used to process the resin materials. Furthermore, their addition to resin materials used in 3D printing devices is also envisioned. To ensure the strength of the finished resin molded product and to prevent static electricity, the spherical conductive particles are homogeneously dispersed within the resin material, so it is necessary to suppress viscosity increase as much as possible. Also, considering the extrusion from the nozzle of a 3D printer, viscosity increase can lead to resin clogging, so it is necessary to suppress viscosity increase as much as possible from the standpoint of fluidity.

[0016] Existing resins can be used as resin materials, including, for example, polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyamide (PA), polyurethane (PU), and various other resins such as fluororesins, urea resins, phenolic resins, epoxy resins, acrylic resins, and silicone resins.

[0017] The truly spherical conductive particles of the embodiment are prepared by providing inorganic oxide particles as a base material, and a conductive layer is formed on the surface of the inorganic oxide particles. Figure 1 is an SEM photograph of a plurality of truly spherical conductive particles according to the embodiment (Example 1), and it can be seen that the particles are uniformly spherical. Figure 2 is a TEM photograph showing a cross-section of one truly spherical conductive particle according to the embodiment (Example 1), and Figure 3 is a further enlarged TEM photograph showing the cross-section. Observation with such an electron microscope confirms that a conductive layer is formed on the surface of the spherical inorganic oxide particles. The black regions in Figure 2 and Figure 3 are the conductive layers. The inorganic oxide particles are silicon oxide (silica; SiO ２ ) or aluminum oxide (alumina; Al ２ O ３ ). Details of silicon oxide and aluminum oxide will be described below.

[0018] The conductive layer of the truly spherical conductive particles is formed of tin oxide containing fluorine. Specifically, it is a tin fluoride such as tin fluoride (stannous fluoride, tin(II) fluoride, SnF ２ ). Heating during the production of the truly spherical conductive particles causes halogens such as fluorine to desorb, making it easy for tin to remain. As a result, tin in a metallic state is generated, which improves the conductivity of the truly spherical conductive particles. In addition to tin, metals such as silver and antimony may also be used. Furthermore, halogen compounds other than fluorine may be used for ionic bonding.

[0019] After preparation as truly spherical conductive particles, the conductive layer includes a surface-treated portion derived from at least one of an organic compound having a silane compound or an organosilazane. The surface-treated portion modifies functional groups.

[0020] (Inorganic oxide particles) Silicon oxide (silica; SiO ２ ) and aluminum oxide (alumina; Al ２ O ３ ) Regarding the particle size of the inorganic oxide particles, D measured by laser diffraction particle size distribution measurement ５０ (median diameter) is 0.01 µm or more and 5 µm or less. Examples of the lower limit of D ５０ include 0.01 µm, 0.05 µm, 0.1 µm, and 0.2 µm, and examples of the upper limit include 5.0 µm, 4.0 µm, 3.0 µm, and 2.0 µm. Any combination of these upper and lower limits is permissible.

[0021] D ５０ This value was measured by laser diffraction particle size distribution measurement, and represents the particle size that accounts for 50% of the volume, starting from the smallest particle size. １００ The particle sizes range from smallest to largest, representing 100% of the total particle size. Note that D ５０ , D １００ The value is calculated as a numerical value within the measurement limit range of laser diffraction particle size distribution measurement, and in reality, there are coarse particles and minute particles that cannot be detected by laser diffraction particle size distribution measurement. Therefore, D １００ There is no contradiction in the existence of particles with a particle size larger than the value of .

[0022] D ５０ The value is silicon dioxide (silica; SiO ２ ) and aluminum oxide (alumina; Al ２ O ３ The inorganic oxide particles are controlled through their manufacturing conditions. In addition, they are adjusted by classification and the addition of particle materials with other particle size distributions. For the classification operation, centrifugation such as a cyclone is preferably used. The added particle materials are also subjected to classification.

[0023] The specific surface area of ​​inorganic oxide particles of silicon dioxide and aluminum oxide is 0.1 m². ２ / g or more 300m ２ It is less than or equal to / g. The lower limit of the specific surface area is 0.1m². ２ / g, 0.30m ２ / g, 0.5m ２ An example given is approximately / g, with an upper limit of 300m ２ / g, 250m ２ / g, 20m ２ A value of approximately / g is used as an example. The specific surface area is a value measured by the BET method using nitrogen. A smaller specific surface area is preferable because it reduces the viscosity when used in slurry compositions, etc. The method for controlling the specific surface area is not particularly limited, and can be adjusted by performing the synthesis of inorganic oxide particles under conditions that reduce the amount of fine powder, or by controlling the residence time in the classifier to be longer when performing classification to reduce the amount of fine powder.

[0024] (Method for producing inorganic silicon oxide particles) The method for producing inorganic silicon oxide particles of the embodiment comprises a manufacturing step, a classification step, and other steps as necessary. The manufacturing step is a step of producing inorganic silicon oxide particles by burning raw material particle material. The inorganic oxide particles produced have a volume average particle size of 0.1 μm or more and 5 μm or less.

[0025] The manufacturing process is a method for producing perfectly spherical oxide nanoparticles using the deflagration phenomenon of metal powder, known as the VMC method (Vaporized Metal Combustion Method). The inorganic oxide particles of silicon oxide produced by the VMC method have high sphericity, are dense, and have excellent electrical properties. Metallic silicon is used as the raw material for the particles. The VMC method involves burning a combustible agent (such as hydrocarbon gas) with a burner in an oxygen-containing atmosphere to form a chemical flame as a high-temperature atmosphere. A quantity of the raw material for the particles is then added to this chemical flame in an amount sufficient to form a dust cloud, causing deflagration and obtaining a spherical silica composition. A high-temperature atmosphere of 2000°C or higher is desirable.

[0026] The VMC method works as follows: First, a container is filled with a gas containing oxygen, which is the reaction gas, and a chemical flame is formed in this reaction gas. Next, the raw material particles are introduced into this chemical flame to form a dust cloud. The chemical flame then imparts thermal energy to the surface of the raw material particles, raising the surface temperature of the metals that make up the raw material particles, and vapors of the metals contained in the raw material particles spread into the surroundings. These vapors react with the oxygen gas and ignite, producing a flame. The heat generated by this flame further promotes the vaporization of the raw material particles, and the resulting vapors and oxygen gas mix, causing a chain reaction of ignition and propagation. Therefore, the smaller the particle size of the raw material particles, the larger the specific surface area and the higher the reactivity, thus reducing the amount of energy that can be introduced.

[0027] Furthermore, in addition to the preparation of silicon oxide inorganic oxide particles by the aforementioned VMC method, silicon oxide inorganic oxide particles can also be prepared by a flame fusion method or the like. In the preparation of silicon oxide inorganic oxide particles by the flame fusion method, crystalline silica as the raw material used is pulverized to, for example, 5 µm or less, and granulation or the like is performed according to the target particle size. Alternatively, heating exceeding 1000°C is performed, for example, to gasify the moisture in the voids contained in the crystalline silica, thereby reducing the voids.

[0028] As such chain ignition progresses, the raw material particle material itself is also broken and scattered, promoting flame propagation. After combustion, the generated gas is naturally cooled, thereby forming a cloud of the metal contained in the raw material particle material. The obtained silicon oxide inorganic oxide particles are collected by a bag filter, an electrostatic precipitator, or the like.

[0029] The VMC method utilizes the principle of dust explosion. According to the VMC method, a large amount of silicon oxide inorganic oxide particles can be obtained instantaneously. The obtained silicon oxide inorganic oxide particles have a substantially spherical shape. It is possible to adjust the particle size distribution of the obtained silicon oxide inorganic oxide particles by adjusting the particle size, input amount, flame temperature, etc. of the raw material particle material to be input. Further, as the raw material particle material, even if it is metallic silicon alone, silica (quartz) can also be added.

[0030] The raw material particle material is dispersed in a carrier and then fed into a flame to be combusted. The feeding rate of the raw material particle material into the flame is not particularly limited. As the carrier, gases such as nitrogen, argon and air, and liquids such as water and alcohol can be selected. There is no particular limitation on the method of dispersion, and when dispersed in a liquid, it is preferable to spray it in the form of mist into the flame before feeding. For example, it is preferable that the content of the raw material particle material is about 10% to 80% based on the total volume.

[0031] As the flame, a flame in an oxidizing atmosphere is employed. Examples thereof include a flame obtained by burning a combustible gas such as LPG, ammonia, or hydrogen in an atmosphere containing excess oxygen. Thermal plasma is also included in flames. The raw material particulate material charged into the flame is vaporized by combustion, and is quenched to form raw material silica particles made of silica. The obtained raw material silica particles are collected by a bag filter or the like.

[0032] The classification step is a step of classifying the content of the silicon oxide inorganic oxide particles until the particle size distribution falls within the above-mentioned upper limit or lower limit. Classification operations include centrifugation in a gas or a solvent, separation by specific gravity in a liquid, and a method using a dry or wet sieve. The classification is repeated until the target particle size distribution is achieved by one or more classification operations.

[0033] (Method for Producing Aluminum Oxide Inorganic Oxide Particles) In producing the aluminum oxide inorganic oxide particles of the embodiment, a typical production method for each component is presented. The method comprises a production step, a classification step, and other steps that are employed as necessary.

[0034] Various crystalline alumina (aluminum oxide) is used as the raw material particulate material, and a particulate material having an average particle size larger than the average particle size (volume average particle size) of the finally prepared aluminum oxide inorganic oxide particles is employed as the crude raw material particulate material. Then, raw material particulate material having a required volume average particle size can be obtained by a pulverization operation. For example, after pulverizing the crude raw material particulate material, the particle size distribution is adjusted. In addition, instead of or in addition to adjusting the particle size distribution after pulverization, the particle size distribution is adjusted before pulverization. For controlling the particle size distribution, it is preferable to remove particles having a small particle diameter.

[0035] The crude raw material particle is preferably manufactured by the VMC method (deflagration process) described in the above-mentioned method for producing inorganic oxide particles of silicon oxide. The spherical inorganic composition of alumina produced by the VMC method has high sphericity, is dense, and has excellent electrical properties. Metallic aluminum is used as the raw material particle. The VMC method is a method in which a combustible agent (such as hydrocarbon gas) is burned with a burner in an oxygen-containing atmosphere to form a chemical flame as a high-temperature atmosphere, and the raw material particle is introduced into this chemical flame in an amount sufficient to form a dust cloud, causing deflagration to obtain particulate oxide. An atmosphere of 2000°C or higher is desirable as the high-temperature atmosphere.

[0036] When alumina is produced using the VMC method, a mixture of large-particle material and small-particle material is obtained. Therefore, the fraction with larger particle sizes is classified and used as the crude raw material.

[0037] The grinding method is not particularly limited, and general grinding methods such as jet mills, ball mills, and vibrating ball mills can be used. Jet mills are particularly preferred because they contain fewer impurities originating from the media used for grinding, and also have high grinding efficiency on the micrometer order. The particle material produced by the VMC method has high circularity and may contain a certain amount of fine particles with a particle size smaller than 1 μm in its particle size distribution.

[0038] The inorganic oxide particles of aluminum oxide produced by the VMC method are either used as is or classified. Since the metals constituting the raw material for the VMC method are easier to purify than their metal oxides, it is easy to achieve high purity in the raw material particles obtained through the VMC method.

[0039] In addition to the preparation of inorganic aluminum oxide particles by the VMC method described above, inorganic aluminum oxide particles can also be prepared by methods such as flame melting. In the preparation of inorganic aluminum oxide particles by flame melting, the alumina used as the raw material is crushed to, for example, 5 μm or less, and granulation or the like is performed according to the desired particle size. Alternatively, for example, heating to over 1000°C is performed, which promotes the separation and gasification of water contained in the crystal, and the voids tend to decrease.

[0040] By utilizing the principle of dust explosion in the VMC method, a large amount of inorganic aluminum oxide particles can be obtained instantaneously. The resulting inorganic aluminum oxide particles have a nearly spherical shape. By adjusting the particle size of the raw material particles, the amount of material added, the flame temperature, etc., it is possible to adjust the particle size distribution of the resulting inorganic aluminum oxide particles.

[0041] The raw material particles are burned by being introduced into the flame while dispersed in a carrier. The rate at which the raw material particles are introduced into the flame is not particularly limited. As the carrier, gases such as nitrogen, argon, and air, or liquids such as water and alcohol can be selected. There are no particular limitations on how the material is dispersed, but when dispersed in a liquid, it is preferable to introduce it into the flame by spraying it in a mist. For example, it is preferable that the raw material particles make up about 10% to 80% of the total volume.

[0042] An oxidizing atmosphere flame is used as the combustion chamber. For example, this includes a flame created by burning flammable gases such as LPG, ammonia, and hydrogen in an atmosphere containing an excess of oxygen. Thermal plasma is also included in the flame. The raw material particles introduced into the flame vaporize through combustion and are rapidly cooled to become raw alumina particles. The obtained raw alumina particles are recovered using a bag filter or the like.

[0043] The classification process involves classifying the aluminum oxide to a particle size distribution that meets the upper or lower limits mentioned above, based on the content of inorganic oxide particles. Classification methods include centrifugation in a gas or solvent, separation by specific gravity in a liquid, and dry or wet sieving. The classification process is repeated until the desired particle size distribution is achieved in a single operation.

[0044] In the spherical conductive particles of the embodiment, preferably, the conductive layer on the surface of the inorganic oxide particles comprises a surface treatment derived from at least one silane compound or an organic compound having an organosilazane. The silane compound and silazane compound are not particularly limited, and surface treatment is performed by selecting a silane compound or silazane compound having an appropriate functional group as needed. Surface treatment is performed by a combination of two or more types selected from the silane compound and silazane compound.

[0045] When forming the surface treatment area, the amount of surface treatment agent, such as a silane compound or an organic compound having an organosilazane, is not particularly limited. For example, when using a substance that reacts with the surface of particles, such as a silane compound or silazane compound, as the surface treatment agent, an amount that reacts to 100%, 75%, 50%, 25%, etc., based on the amount of OH groups present on the surface of the particles to be treated, can be selected. Furthermore, an excess amount exceeding 100% (120%, 150%, etc.) can also be selected. In that case, unreacted surface treatment agent will remain on the surface of the particles. The silane compound is not particularly limited and can be a compound having a phenyl group, alkyl group, vinyl group, methacrylic group, epoxy group, phenylamino group, amino group, styryl group, etc.

[0046] The spherical conductive particles of the embodiment further have the following characteristics. The inorganic oxide particles that make up the majority of the spherical conductive particles are core particles, and the sphericity of these inorganic oxide particles is 0.80 or higher, preferably 0.90 or higher, and more preferably 0.96 or higher. Sphericity is the ratio between the long axis and the short axis of a particle, and if it is a perfect sphere, the long axis and short axis coincide and the ratio is 1.0. Therefore, the closer the sphericity value is to 1.0, the closer it is to a perfect sphere. The sphericity is calculated from the area and perimeter of the observed spherical conductive particles using the formula "(sphericity) = {4π × (area) ÷ (perimeter)²}". Since the spherical conductive particles of the embodiment are mainly used for mixing with resin materials, the inorganic oxide particles that make up the majority of the spherical conductive particles are finished to be as spherical as possible in order to ensure good mixing and suppress viscosity increase.

[0047] In the spherical conductive particles of the embodiment, when the specific surface area of ​​the spherical conductive particles is divided by the specific surface area of ​​the inorganic oxide particles, the quotient (Qs) is in the range of 1.0 to 2.0. The specific surface area of ​​the spherical conductive particles is the outermost surface of the particle, and is therefore inevitably larger than the specific surface area of ​​the inorganic oxide particles on the inside. However, considering good mixing with the resin material and suppression of viscosity increase, it is preferable to control the specific surface area of ​​the spherical conductive particles so that it does not become too large. This is because an increase in specific surface area increases resistance during mixing, leading to an increase in viscosity. Therefore, the range of Qs is defined by the relative relationship between the specific surface area of ​​the spherical conductive particles and the specific surface area of ​​the inorganic oxide particles. Qs is in the range of 1.0 to 2.0, preferably 1.3 to 1.9.

[0048] Furthermore, the quotient (Qt) obtained by dividing the thickness of the conductive layer by the particle diameter of the inorganic oxide particles is in the range of 0.01 to 0.20. The conductive layer only needs to be sufficient to allow the spherical conductive particles to exhibit conductivity. If the conductive layer is developed too much, it will lead to a decrease in the sphericity of the particles, coupling between particles, an increase in resistance and viscosity when mixed with the resin material. Therefore, Qt is in the range of 0.01 to 0.20, preferably 0.01 to 0.15.

[0049] The conductivity of spherical conductive particles is evaluated as a powder resistance value, based on the aggregated state of the spherical conductive particles. A low powder resistance value ensures good conductivity and is effective in preventing static electricity in resin products. In the embodiments described later, the powder resistance value is measured after drying and pressurization at 20 kN. Therefore, the powder resistance value is in the range of 1 to 100,000 Ω·cm, preferably 1 to 10,000 Ω·cm, and more preferably 1 to 5,000 Ω·cm.

[0050] (Slurry Composition) The spherical conductive particles of the embodiment can be processed into a suitable slurry. The slurry is a composition prepared by mixing the above-mentioned spherical conductive particles with a liquid dispersion medium (solvent, resin material precursor, etc.). The mixing ratio of the spherical conductive particles to the dispersion medium is not particularly limited. In addition to the resin material precursor mentioned above, the dispersion medium can be methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), hexane, isopropanol, or other alcohols.

[0051] (Resin Composition) The spherical conductive particles of the embodiment are a composition prepared by dispersing the above-mentioned spherical conductive particles in a resin material (including a resin material precursor). The mixing ratio of the spherical conductive particles to the resin material is not particularly limited. The resin material can be any suitable material, and examples include polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyamide (PA), polyurethane (PU), and various other resins such as fluororesins, urea resins, phenolic resins, epoxy resins, acrylic resins, and silicone resins. Alternatively, a resin material precursor before curing may also be used.

[0052] The spherical conductive particles of the embodiment were prepared and subjected to measurement based on the following. The measurement results for each example and comparative example are shown in Tables 1 and 2.

[0053] (Particle size, sphericity) For each of the inorganic oxide particles (core material) and spherical conductive particles, images observed with a scanning electron microscope (SEM) were analyzed on a computer using image analysis software ("ImageJ," National Institutes of Health, USA (NIH)). Photographs were taken so that approximately 100 particles were observed on the SEM. The sphericity was calculated from the area and perimeter of the particles observed in the photographs using the formula: (Sphericity) = {4π × (Area) ÷ (Perimeter)²}. The sphericity of all particles (approximately 100) in the photographs was calculated, and the sphericity of the measured examples and comparative examples was determined by the simple average (arithmetic mean). Similarly, the particle size of the measured examples and comparative examples was determined by the simple average (arithmetic mean) of the diameters of all particles (approximately 100) in the photographs.

[0054] (Specific Surface Area / BET Method) 1.0 g of each sample from the examples and comparative examples was weighed and placed in a measurement cell. After pretreatment, the BET specific surface area value was measured by nitrogen adsorption. An automatic specific surface area and pore distribution analyzer: TriStar®-II 3020 (manufactured by Shimadzu Corporation) was used for the measurement. The pretreatment conditions were as follows: Degassing temperature: 200°C Degassing time: 30 minutes Cooling time: 4 minutes

[0055] (Fluorine Content) The fluorine content in the conductive layer of each example and comparative example sample was measured by X-ray photoelectron spectroscopy. An X-ray photoelectron spectrometer, PHI5000 VersaProbe (manufactured by ULVAC-FI, Inc.), was used for the measurement. The measurement conditions were as follows: Primary X-ray source: Al Kα rays 1.4 keV Measurement diameter: 200 μm Detection angle: 45°

[0056] (Powder Resistance Value) For each example and comparative example, the samples were dried in air at 120°C for 2 hours. After drying, predetermined amounts of the samples were weighed into evaluation compression containers and pressurized at 20 kN. The powder resistance value of the pellets of the pressurized samples was measured using a powder resistance meter (MCP-PD51, manufactured by Nitto Seikou Analytech Co., Ltd.).

[0057] (Example 1) SiO as inorganic oxide particles (core material) ２ Five parts by mass of spherical particles (particle size 0.5 μm, sphericity 0.99) are dispersed in 3200 parts by mass of ion-exchanged water, and tin fluoride (SnF) is added thereto. ２ 2.8 parts by mass of ) were added, the temperature was raised to 40°C, and the mixture was stirred for 10 hours. After stirring, the solids were washed with deionized water and dried at 120°C for 3 hours. The dried powder was calcined in an electric furnace at 400°C for 2 hours. In this way, the spherical conductive particles of Example 1 were produced.

[0058] The spherical conductive particles obtained in Example 1 had a sphericity of 0.95 and a specific surface area of ​​11.5 m². ２The values ​​were / g. The quotient (Qs) obtained by dividing the "specific surface area of ​​spherical conductive particles" by the "specific surface area of ​​inorganic oxide particles" was 1.9, and the powder volume resistivity was 850 Ω·cm. The thickness of the conductive layer derived from tin fluoride was 0.017 μm. The quotient (Qt) obtained by dividing the "thickness of the conductive layer" by the "particle diameter of inorganic oxide particles" was 0.03.

[0059] (Example 2) The amount of tin fluoride added in Example 1 was changed to 6.5 parts by mass, and otherwise the same procedure as in Example 1 was used to produce spherical conductive particles of Example 2.

[0060] (Example 3) In Example 1 described above, inorganic oxide particles are SiO ２ The spherical particles of Example 3 were prepared by changing the particle size to 0.1 μm (particle size, sphericity 0.98) and changing the amount of tin fluoride added to 2.0 parts by mass, with the rest of the procedure being the same as in Example 1.

[0061] (Example 4) In Example 1 described above, inorganic oxide particles are SiO ２ The spherical particles of Example 4 were prepared by changing the particle size to 2.0 μm (particle size, sphericity 0.99) and changing the amount of tin fluoride added to 1.6 parts by mass, while otherwise performing the same procedure as in Example 1.

[0062] (Example 5) In Example 1 described above, the inorganic oxide particles were changed to spherical alumina particles (particle size 0.2 μm, sphericity 0.98), and the amount of tin fluoride added was changed to 2.0 parts by mass. The other operations were the same as in Example 1 to produce the spherical conductive particles of Example 5.

[0063] (Comparative Example 1) In the above-described Example 1, the amount of tin fluoride added was changed to 1.4 parts by mass. Otherwise, the spherical conductive particles of Comparative Example 1 were prepared using the same procedure as in Example 1.

[0064] (Comparative Example 2) In the above-described Example 1, the amount of tin fluoride added was changed to 13.0 parts by mass. The spherical conductive particles of Comparative Example 2 were prepared using the same procedure as in Example 1.

[0065] (Comparative Example 3) The same procedure as in Example 1 was followed, but the firing in an electric furnace after drying was omitted. In this way, perfectly spherical conductive particles of Comparative Example 3 were produced.

[0066] (Example 6) 3-methacryloxypropyltrimethoxysilane was added to the spherical conductive particles of Example 1 and mixed in a mixer, and a surface treatment was performed to produce spherical conductive particles with the surface treatment of Example 6.

[0067] (Example 7) The spherical conductive particles of Example 1 were added to a liquid epoxy resin to a filler concentration of 50% by weight and mixed using a rotary-orbiting stirrer to prepare the resin composition containing the spherical conductive particles of Example 7. After mixing, further kneading was performed using a three-roller system, and the kinematic viscosity was measured using a rheometer (ARES-G2, TA Instruments Inc.). The kinematic viscosity was measured as the viscosity (Pa·s) when the flow rate was 0.1 cm, 1.0 cm, and 10 cm per second.

[0068] (Example 8) In Example 8, the spherical conductive particles of Example 1 were replaced with the spherical conductive particles of Example 6, and the kinematic viscosity was measured in the same manner as in Example 7.

[0069] (Comparative Example 4) In Comparative Example 4, the spherical conductive particles of Example 1 were replaced with the spherical conductive particles of Comparative Example 1, and the kinematic viscosity was measured in the same manner as in Example 7.

[0070]

[0071]

[0072] (Results and Discussion) Figure 1 is an SEM image (magnification 500,000x) of multiple spherical conductive particles from Example 1, and all particles are uniformly spherical. Figure 2 is a TEM image (magnification 22,500x) showing a cross-section of one spherical conductive particle from the embodiment (Example 1), and Figure 3 is an enlargement of Figure 2, with the inorganic oxide particles (core material) in the lower left of the page (magnification 3,100,000x). A conductive layer is formed as black streaks on the surface of the inorganic oxide particles (core material). Because the inorganic oxide particles (core material) are spherical in shape that is very close to a perfect sphere, the resulting spherical conductive particles are also spherical in shape that is very close to a perfect sphere. By making the inorganic oxide particles spherical at the stage, the final completed particles can also be made spherical.

[0073] Table 1 shows that as the particle size of the inorganic oxide particles (core material) decreases, both the specific surface area of ​​the inorganic oxide particles and the specific surface area of ​​the spherical conductive particles increase. Simply using the specific surface area value results in significant fluctuations depending on the particle size. Therefore, by adopting "Qs" shown as "C / B" in Table 1, the fluctuations due to particle size are mitigated, and a relative relationship can be evaluated. Even particles with extremely different particle sizes, as in Examples 3 and 4, can be evaluated using Qs. In Comparative Example 1, the amount of tin fluoride added was insufficient, preventing uniform coating of the inorganic oxide particles' surfaces. This resulted in a sparse conductive layer, which is likely the cause of the increased specific surface area. Note that similarly good results were obtained when using alumina (Example 5) instead of silica for the inorganic oxide particles.

[0074] Comparative Example 2 is an example where tin fluoride was added in excess. Although the powder resistance value of the resulting spherical conductive particles was low, the sphericity decreased. Comparative Example 3 remained in the state of tin hydroxide because no firing was performed, and conductivity did not occur due to the influence of hydroxyl groups, which are factors that increase resistance, and the water that hydrogen-bonds to the hydroxyl groups.

[0075] From each example, even when using different particle sizes for the inorganic oxide particles (core material), it was possible to converge the sphericity and powder resistance values ​​to a suitable range by controlling "Qs" (indicated as "C / B") and "Qt" (indicated as "D / A"). Therefore, it is possible to provide spherical conductive particles of various particle sizes according to the application and purpose.

[0076] Table 2 shows that, comparing the resin composition using spherical conductive particles from Example 1 (Example 7) with the resin composition using spherical conductive particles from Example 6 (Example 8), the presence of a surface treatment on the surface of the spherical conductive particles reduces the kinematic viscosity. Furthermore, Comparative Example 4 shows that an increase in the specific surface area of ​​spherical conductive particles leads to an increase in kinematic viscosity and hinders the mixing process.

[0077] The spherical conductive particles of this embodiment, when added to and mixed with a resin material, provide an antistatic effect to resin molded products and suppress the increase in viscosity after mixing with the resin material, thereby contributing to improved productivity in resin molding. Furthermore, improved performance of slurries or resin compositions containing the spherical conductive particles is expected.

Claims

1. A spherical conductive particle having a conductive layer on the surface of the following inorganic oxide particles, characterized in that: (1) the sphericity of the inorganic oxide particles is 0.80 or more; (2) the quotient (Qs) of (specific surface area of ​​the spherical conductive particle) / (specific surface area of ​​the inorganic oxide particle) is 1.0 to 2.0; and (3) the conductive layer is tin oxide containing fluorine.

2. The spherical conductive particles according to claim 1, wherein the powder resistance value of the spherical conductive particles is 1 to 100,000 Ω·cm.

3. The spherical conductive particle according to claim 1, wherein the quotient (Qt) of (thickness of the conductive layer) / (particle diameter of the inorganic oxide particles) is 0.01 to 0.

10.

4. The spherical conductive particle according to claim 1, wherein the conductive layer comprises a surface treatment derived from at least one silane compound or an organic compound having an organosilazane.

5. A slurry characterized by comprising the spherical conductive particles described in claim 1 and an organic solvent for dispersing the spherical conductive particles.

6. A resin composition characterized by comprising the spherical conductive particles described in claim 1 and a resin material for dispersing the spherical conductive particles.

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