Inorganic powder and resin composition with the same

Abstract

To provide inorganic powder including MgTiO3, which is excellent in dielectric properties and also in dispersibility into a resin, and a resin composition using the same.SOLUTION: There is provided inorganic powder including MgTiO3. An average circularity of inorganic particles included in the inorganic powder is 0.80 or more. A value of (D90-D10) / D50 in a volume-basis particle size distribution of the inorganic powder obtained by measurement with a laser diffraction / scattering particle size distribution method is more than 1.2. The D50 is preferably 1.0 to 4.5 μm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an inorganic powder and a resin composition using the same. [Background technology]

[0002] In recent years, with the increase in the volume of information traffic in the communications field, the use of high-frequency signals has become widespread in electronic devices and communications equipment. However, the application of high-frequency signals to such devices has also led to the problem of increased transmission loss of circuit signals. In particular, there is a demand for ceramic fillers with lower dielectric loss tangents used in AiPs (Antenna in Package: AiP) for RF (Radio Frequency: RF) modules.

[0003] Furthermore, as related electronic materials and components become more highly functional, further miniaturization of antenna devices is also required. Communication devices can be made even smaller if the relative dielectric constant of the antenna material incorporated therein is increased. Therefore, ceramic fillers used in AiPs and the like for RF modules are required to be materials that can achieve a high dielectric constant and a low dielectric loss tangent (for example, Patent Document 1, etc.).

[0004] Perovskite-type complex metal oxides are primarily complex metal oxides represented by the formula ABO3. Powders containing such perovskite-type complex metal oxides have a relatively high dielectric constant, and are therefore expected to be used as ceramic fillers for next-generation electronic devices. Titanium-based complex metal oxides, such as barium titanate and strontium titanate, are expected to be used as electronic materials because they exhibit excellent electrical properties, including dielectric, pyroelectric, and piezoelectric properties.

[0005] Since ceramic fillers are often used by filling them into resins, it is desirable to improve their fillability and dispersibility in resins to stabilize their dielectric properties. Patent Document 2 proposes perovskite-type composite metal oxide particles that are excellent in basic performance such as refractive index and dielectric constant, and also have excellent dispersibility in organic compounds such as matrix resins and solvents. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-27386 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-186250 [Patent Document 3] Patent No. 4155750 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-246203 Summary of the Invention [Problem to be solved by the invention]

[0007] Conventional proposals regarding perovskite-type composite metal oxide particles, such as those in Patent Document 2, mainly relate to powders containing barium titanate or powders containing strontium titanate, and no consideration has been given to powders containing magnesium titanate (MgTiO). Magnesium titanate has a relatively high dielectric constant, making it suitable for use in high-frequency devices. However, there is little known inorganic powder containing MgTiO3 that also has excellent dielectric properties and dispersibility in resins.

[0008] An object of the present disclosure is to provide an inorganic powder containing MgTiO3, which has excellent dielectric properties and excellent dispersibility in resin, and a resin composition using the same. [Means for solving the problem]

[0009] As a result of extensive investigations, the present inventors have found that the above-mentioned problems can be solved by an inorganic powder containing MgTiO3, in which the inorganic particles contained in the inorganic powder have an average circularity of 0.80 or more, and the (D90-D10) / D50 ratio in the volume-based particle size distribution of the inorganic powder, as measured by a laser diffraction / scattering particle size distribution method, exceeds 1.2, and have thus completed the present invention. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide an inorganic powder containing MgTiO3, which has excellent dielectric properties and excellent dispersibility in resin, and a resin composition using the same. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a scanning electron microscope photograph showing one embodiment of the inorganic powder of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of the present disclosure will be described in detail below. However, the scope of the present disclosure is not limited to the embodiment described herein, and various modifications can be made without departing from the spirit of the present disclosure. Each aspect disclosed herein can be combined with any other feature disclosed herein. Furthermore, when multiple upper and lower limits are described for a particular parameter, any of these upper and lower limits can be combined to form a suitable numerical range. Furthermore, the lower and / or upper limits of a numerical range described in this disclosure are numerical values ​​within that range and may be replaced with numerical values ​​shown in the examples. An expression such as "1 to 10" indicating a numerical range means "1 or more and 10 or less." If a specific description described for one embodiment also applies to other embodiments, that description may be omitted in other embodiments.

[0013] The configurations and combinations thereof in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible as appropriate within the scope of the gist of the present disclosure. The present disclosure is not limited to the embodiments. Each feature disclosed herein may be combined with any other feature disclosed herein. In this specification, the term "powder" refers to an aggregate of a plurality of particles.

[0014] [Inorganic powder] The inorganic powder according to this embodiment is an inorganic powder containing MgTiO, wherein the inorganic particles contained in the inorganic powder have an average circularity of 0.80 or more, and the (D90-D10) / D50 ratio in the volume-based particle size distribution of the inorganic powder measured by a laser diffraction / scattering particle size distribution method is greater than 1.2. The inorganic powder according to this embodiment has excellent dielectric properties and good dispersibility in resins. One of the effects of the inorganic powder according to the present embodiment is that it can achieve a lower dielectric tangent while maintaining a high dielectric constant. Another effect is that even when the inorganic powder is highly filled in a resin, the viscosity does not increase easily, and processability and workability do not decrease easily.

[0015] <Volumetric particle size distribution> The volume-based particle size distribution of the inorganic powder according to this embodiment can be measured by the following method. Measurement is carried out using a laser diffraction / scattering particle size distribution analyzer (e.g., Beckman Coulter, Inc., product name "LS 13 320"). First, 50 cm 31 g of pure water and 0.1 g of inorganic powder are added and dispersed for 1 minute at 50% power using an ultrasonic homogenizer (e.g., Microtec Unition Co., Ltd., product name "Smurt NR-50M" (homogenizer tip: NS-50M-MT 3 mm φ)) at 50% power. The dispersed inorganic powder dispersion is added dropwise to a laser diffraction / scattering particle size analyzer. 30 seconds after the specified amount is added, the particle size distribution is measured. Note that the refractive index of the inorganic powder is set to 2.31 and the specific gravity to 3.85, while the refractive index of water is set to 1.33 and the specific gravity to 1.00. The volumetric particle size distribution is calculated from the light intensity distribution data of the diffracted / scattered light of the inorganic powder detected by the sensor in the laser diffraction / scattering particle size analyzer. D10, D50, and D90 are calculated from the particle sizes corresponding to cumulative values ​​of 10% (D10), 50% (D50), and 90% (D90) in the measured volumetric particle size distribution. Based on the obtained D10, D50, and D90, "(D90-D10) / D50" (hereinafter sometimes referred to as "span value") is calculated. The span value of the inorganic powder according to this embodiment is the average value of span values ​​calculated by performing the above-mentioned volumetric particle size distribution measurement method with N=3.

[0016] In the volumetric particle size distribution measured by a laser diffraction / scattering particle size distribution method, the span value calculated from D10, D50, and D90 is considered to be narrower as the value approaches 0. The inorganic powder according to this embodiment has a (D90-D10) / D50 ratio of greater than 1.2, resulting in a somewhat broad particle size distribution. That is, the inorganic powder according to this embodiment contains a mixture of fine particles and somewhat coarse particles, resulting in a large span value. The present inventors have discovered that inorganic powders containing MgTiO3 and having the above-described span value exhibit excellent dielectric properties. In particular, they have found that they can achieve both a high dielectric constant and a low dielectric loss tangent. Furthermore, because the inorganic particles contained in the inorganic powder have an average circularity of 0.80 or more, they also exhibit excellent dispersibility in matrix resins.

[0017] The span value of the inorganic powder is greater than 1.2, preferably 1.5 or greater, more preferably 1.8 or greater, and even more preferably 2.0 or greater. The upper limit of the span value is not particularly limited as long as it is within a range that does not impair the effects of the present disclosure. However, since it is preferable to limit the particle size range for use in the same application, from this viewpoint, the upper limit of the span value is preferably 5.0 or less, more preferably 4.0 or less, even more preferably 3.0 or less, and particularly preferably 2.5 or less. In a preferred embodiment, the span value of the inorganic powder is greater than 1.2 and 5.0 or less, and can be any preferred numerical range within that range, or a range that combines the above-mentioned preferred lower and upper limits.

[0018] The inorganic powder having a span value of more than 1.2 according to this embodiment may be prepared by a manufacturing method including spheroidizing a raw inorganic powder (raw powder), or may be prepared by mixing two or more inorganic powders containing inorganic particles having an average circularity of 0.80 or more and having different average particle diameters (D50). From the viewpoint of easily controlling the span value and average circularity in this embodiment, it is preferable to employ a manufacturing method including spheroidizing the raw powder. When employing the manufacturing method including spheroidizing, it is preferable to use a raw powder having a specific span value (preferably a span value of 1.2 or less). The manufacturing method of the inorganic powder according to this embodiment will be described later.

[0019] In one embodiment, the D50 of the inorganic powder is preferably 1.0 to 4.5 μm, more preferably 1.5 to 3.0 μm, and even more preferably 1.8 to 2.8 μm. When the D50 is within the above range, the span value is likely to exceed 1.2. In addition, the effect of improving dispersibility within the compound is likely to be obtained.

[0020] In one embodiment, the D90 of the inorganic powder is preferably 2.5 to 15.0 μm, more preferably 3.0 to 11.0 μm, and even more preferably 4.5 to 10 μm. If the D90 is within the above range, the span value is likely to exceed 1.2. In addition, the effect of improving dispersibility within the compound is likely to be obtained.

[0021] The D10 of the inorganic powder is not particularly limited as long as it is within a range that does not impair the effects of the present disclosure. From the viewpoint that the span value is likely to exceed 1.2, the D10 may be 0.5 μm or more, 0.6 μm or more, 0.8 μm or more, or 0.9 μm or more.

[0022] <Crystal phase> The inorganic powder according to this embodiment contains MgTiO3. In this disclosure, "the inorganic powder contains MgTiO3" means that, when the crystalline phase of the inorganic particles constituting the inorganic powder is identified and quantified, the inorganic particles contain inorganic particles that contain the MgTiO3 phase as the main phase. Furthermore, "contains as the main phase" means that the proportion of the MgTiO3 phase relative to the total crystalline phase in the inorganic particles is greater than 50 mass%. The crystalline phase of the inorganic particles can be identified and quantified by XRD-WPPF analysis of any inorganic particles in the inorganic powder. (Identification and quantification of crystalline phases) As a measuring device, a horizontal sample multipurpose X-ray diffractometer (for example, manufactured by Rigaku Corporation, product name: RINT-UltimaIV-N) is used, and the X-ray diffraction pattern of any inorganic particle in the inorganic powder is measured under the following measurement conditions. X-ray source:CuKα Tube voltage: 40kV Tube current: 40mA Scan speed: 10.0° / min 2θ scan range: 10°~80° Furthermore, the crystalline phase of the inorganic particles is identified and quantitatively analyzed by WPPF analysis of the obtained X-ray diffraction pattern. Specifically, data analysis software (e.g., Rigaku, product name: Integrated Powder X-ray Software PDXL2) is used. The proportion (mass%) of the MgTiO3 phase can be calculated using the ICDD card (number: 01-079-0831).

[0023] The proportion of the MgTiO3 phase relative to the total crystalline phase of the inorganic particles, as calculated by XRD-WPPF analysis, is greater than 50% by mass, preferably greater than 60% by mass, and more preferably greater than 75% by mass. The upper limit of the MgTiO3 phase is not particularly limited as long as it does not impair the effects of the present disclosure, but in one embodiment, it may be less than 99% by mass or less than 95% by mass. The proportion of the MgTiO3 phase relative to the total crystalline phase of the inorganic particles may be any preferred range between greater than 50% by mass and less than 99% by mass, or a range that combines the above-mentioned preferred lower and upper limits.

[0024] The inorganic powder preferably contains inorganic particles containing a crystalline phase other than the MgTiO3 phase. In one embodiment, the inorganic powder may contain inorganic particles containing more than 50 mass% of the MgTiO3 phase and one or more phases of a composite oxide composed of Mg—Ti—O. More preferably, the composite oxide composed of Mg—Ti—O is MgTi2O4 and / or MgTi2O5. In one embodiment, the proportion of the MgTiO3 phase relative to all crystalline phases in the inorganic particles may be 75% by mass or more, and the proportion of one or more phases of the composite oxide comprising Mg-Ti-O may be 25% by mass or less. Alternatively, in one embodiment, the proportion of the MgTiO3 phase relative to all crystalline phases in the inorganic particles may be 75 to 95% by mass, and the proportion of one or more phases of the composite oxide comprising Mg-Ti-O may be 5 to 25% by mass, or the proportion of the MgTiO3 phase relative to all crystalline phases may be 80 to 95% by mass, and the proportion of one or more phases of the composite oxide comprising Mg-Ti-O may be 5 to 20% by mass. The inclusion of inorganic particles containing such a crystalline phase facilitates achieving a lower dielectric tangent while maintaining a high dielectric constant, although the reason for this is not clear.

[0025] The MgTiO3 phase of the inorganic particles constituting the inorganic powder according to this embodiment has a larger crystallite diameter than the crystalline phase of perovskite-type composite metal oxides such as strontium titanate (SrTiO3) and barium titanate (BaTiO3). In one embodiment, the crystallite diameter of the MgTiO3 phase in the inorganic particles calculated by XRD may be greater than 10 nm, may be 15 to 200 nm, or may be 40 nm or more and less than 60 nm.

[0026] <Average circularity> The inorganic particles contained in the inorganic powder according to this embodiment have an average circularity of 0.80 or more. The inorganic powder according to this embodiment is an aggregate of inorganic particles having an average circularity of 0.80 or more. By including inorganic particles having an average circularity of 0.80 or more and having the above span value, the inorganic powder can achieve a lower dielectric tangent while maintaining a high dielectric constant. In addition, dispersibility in resins is improved. The average circularity is preferably 0.81 or more, more preferably 0.82 or more. The average circularity is the average value of the circularities calculated from the projected area (S) and projected perimeter (L) of the inorganic particles constituting the inorganic powder using the following method. (Method for measuring average circularity) An arbitrary amount of inorganic powder is fixed with carbon tape and then coated with osmium. Then, the inorganic powder is photographed at a magnification of 3,000 to 30,000 times using a scanning electron microscope (e.g., JEOL Ltd., product name "JSM-7001F SHL"). Then, an image analyzer (e.g., Nippon Roper Co., Ltd., product name "Image-Pro Premier Ver. 9.3") is used to calculate the projected area (S) and projected perimeter (L) of each inorganic particle constituting the inorganic powder, and then the circularity is calculated using the following formula (2). The circularity of any 200 inorganic particles is calculated, and the average value is used as the average circularity of the inorganic particles. Circularity = 4πS / L 2 ···(2)

[0027] According to the studies of the present inventors, it has been found that the dielectric constant of a powder obtained by spheroidizing perovskite-type composite metal oxide particles to improve dispersibility in resin can be significantly lower than that of the raw material powder. For example, in the case of a powder containing calcium titanate, the dielectric constant of the powder after spheroidization can be reduced to approximately one-sixth of the dielectric constant before spheroidization. In other words, it has been found that while the fillability of a powder containing a perovskite-type composite metal oxide in resin is improved by spheroidization, the dielectric constant can be significantly lower than that before spheroidization. The present inventors conducted research into magnesium titanate-based inorganic powders that can achieve a high dielectric constant and a lower dielectric loss tangent while also exhibiting good dispersibility in resins. As a result, they discovered that an inorganic powder containing MgTiO3 and inorganic particles with a specific average circularity can be obtained by controlling the particle size distribution of the inorganic powder so that the span value in the volumetric particle size distribution exceeds a certain value. This results in an inorganic powder that maintains a dielectric constant comparable to that of the raw powder (powder before spheroidization) while achieving a lower dielectric loss tangent, and that also exhibits good dispersibility in resins. While the exact reason why the inorganic powder according to this embodiment exhibits the above-mentioned effects is unclear, one possible reason is believed to be that the spherical inorganic particles contained in the inorganic powder form a densely packed structure in the compound, contributing to good dielectric properties and dispersibility. In this specification, "spherical particles" refers to particles whose projections (including three-dimensional and plan views) are nearly circular when observed under a microscope or the like.

[0028] <Specific surface area> In one embodiment, the specific surface area of ​​the inorganic powder is 0.3 to 4.5 m 2 / g is preferred, and 0.5 to 3.5m 2 / g is more preferable, and 1.0 to 3.0m 2 / g is even more preferable. When the specific surface area is within the above range and the average circularity is satisfied, the dispersibility of the inorganic powder in the resin is likely to be improved. In addition, the dielectric properties are likely to be good. The specific surface area of ​​the inorganic powder can be measured by the BET single-point method using a fully automatic specific surface area measuring device.

[0029] <Average particle density> In one embodiment, the average particle density of the inorganic powder is 3.0 to 4.5 g / cm 3 is preferred, and 3.2 to 4.2 g / cm 3 More preferably, 3.6 to 4.0 g / cm 3 When the average particle density is within the above range, the number of voids in the inorganic powder tends to be small, making it easier to achieve a high dielectric constant. The average particle density of the inorganic powder can be measured by the following method. (Method for measuring average particle density) 5.0 g of inorganic powder is placed in a measurement sample cell, and the average particle density is measured by the gas (helium) substitution method using a dry density meter (for example, Shimadzu Corporation, product name "Accupyk II 1340").

[0030] <Shear viscosity> In one embodiment, the shear viscosity of the inorganic powder measured under the following condition (I) is preferably 3,000 Pa·s or less, more preferably 2,500 Pa·s or less, and even more preferably 2,000 Pa·s or less. <Condition (I)> The shear viscosity of a resin composition consisting of 60% by volume of bisphenol A liquid epoxy resin (epoxy equivalent: 184 to 194) and 40% by volume of the inorganic powder is measured using a rheometer at a shear rate of 1.0 / s, plate shape: circular flat plate (10 mmφ), sample thickness: 1 mm, and temperature: 25±1°C.

[0031] <Dielectric constant> In one embodiment, the dielectric constant (εr f ) is preferably 15 to 35, more preferably 20 to 35, and even more preferably 22 to 35. The inorganic powder according to this embodiment can achieve a high dielectric constant comparable to that of bulk MgTiO3. <Condition (II)> Polyethylene resin (density: 0.92 g / cm 3 The dielectric constant (εr c) is measured using a split cylinder resonator at a measurement frequency of 40 GHz, a temperature of 20°C, and a humidity of 60% RH. f ) is calculated using the following formula (1). log(εr c )=V f log(εr f )+(1-V f )·log(εr r ) (1) (In formula (1), εr c , εr f , εr r represent the dielectric constants of the resin composition, inorganic powder, and polyethylene resin, respectively, and V f represents the content (vol %) of inorganic powder in the resin composition.

[0032] <Dielectric loss tangent> In one embodiment, the dielectric loss tangent (tanδ) of the inorganic powder calculated using a sheet of the same resin composition as in the condition (II) is f ) is 3.0 × 10 -3 Less than 2.5 x 10 is preferable. -3 Less than 1.5 x 10 is preferable. -3 The following is more preferable. f ) can be calculated using the following formula (3): tanδ c =V f tanδ f +(1-V f )·tanδ r (3) (In formula (3), V f represents the content (vol %) of inorganic powder in the resin composition, and tanδ c represents the dielectric tangent of the resin composition, and tanδ r represents the dielectric loss tangent of polyethylene resin.)

[0033] In one embodiment, the inorganic powder may contain inorganic particles that have been surface-treated with a treatment agent having a hydrophobic functional group, such as vinylsilane or hexamethyldisilazane (HMDS). Surface treatment can reduce polar functional groups on the inorganic particle surface, making it easier to achieve a lower dielectric tangent. Whether or not the inorganic powder contains surface-treated inorganic particles can be confirmed by analyzing the inorganic powder using, for example, IR, TG-DTA, mass spectrometry, or the like.

[0034] [Method of manufacturing inorganic powder] The inorganic powder according to this embodiment can be produced by a method including a spheroidizing treatment of a raw material powder (step (i)). Hereinafter, one embodiment of the method for producing an inorganic powder including step (i) will be described.

[0035] <Process (i)> Step (i) is a step of spheroidizing the raw material powder. "Spheroidization" includes spheroidizing inorganic particles (raw material particles) contained in the raw material powder to improve their circularity. In step (i), the raw material powder is preferably spheroidized by a powder melting method. The powder melting method is a method of spheroidizing raw material particles under high-temperature conditions above the melting point (e.g., by introducing the raw material particles into a flame, plasma, electric furnace, gas furnace, etc.). For example, methods such as those described in Patent Documents 3 and 4 can be employed. The melting atmosphere is not particularly limited, but spheroidization in an environment with a high oxygen partial pressure is desirable to easily prevent reduction of the raw material particles. For example, spheroidization can be performed in a flame using LPG / O2 gas. The flame temperature can be, for example, 1900°C. Alternatively, the spheroidization can be performed using a slurry in which the raw material powder is dispersed in water, alcohol, or the like.

[0036] (Raw material powder) The raw material powder is preferably an inorganic powder containing MgTiO3, and is selected from the viewpoint of easily controlling the span value of the raw material powder after spheroidization to be greater than 1.2. When the spheroidization is performed by a powder fusion method, the average circularity of the raw material powder is not particularly limited. That is, the raw material powder may be an inorganic powder containing raw material particles having a specific average circularity, or a pulverized product as described below. The proportion of the MgTiO3 phase in the raw material particles is not particularly limited as long as the effects of the present disclosure are achieved. From the viewpoint of easily controlling the proportion of the MgTiO3 phase in the inorganic particles contained in the finally obtained inorganic powder within the above-mentioned preferred range, the proportion of the MgTiO3 phase relative to all crystalline phases in the raw material particles may be more than 50 mass% and not more than 100 mass%, or may be 60 to 98 mass%, or may be 75 to 98 mass%.

[0037] The span value of the raw material powder is preferably 1.2 or less, more preferably 1.0 or less. Furthermore, it is preferable to select an inorganic powder having a smaller D50 than the inorganic powder (D50 (μm) of raw material powder < D50 (μm) of inorganic powder). In one embodiment, the D50 of the raw material powder is preferably 0.5 μm or more and less than 1.2 μm, more preferably 0.8 to 1.1 μm. The span value of the raw material powder can be measured using the same method as for the inorganic powder.

[0038] The inorganic powder according to this embodiment can suppress the decrease in dielectric constant due to the spheroidization treatment by making the span value exceed a certain value. In other words, the difference in dielectric constant between the raw material powder and the inorganic powder finally obtained is small. Therefore, it is desirable to select an inorganic powder with a relatively high dielectric constant as the raw material powder. In one embodiment, the dielectric constant of the raw material powder may be 15 to 50, 24 to 50, or 25 to 40. The dielectric constant may also be 15 to 35. The dielectric constant of the raw material powder can be measured under the above condition (I).

[0039] The method for preparing the raw material powder is not particularly limited. For example, a pulverized product obtained by a method such as pulverizing bulk magnesium titanate obtained by a solid phase method may be used as the raw material powder.

[0040] The raw material powder contains impurities such as alkali metal elements such as Li, Na, and K, and metal elements such as Fe, as well as Cl, from the viewpoint of reducing the dielectric loss tangent and ensuring the reliability of electronic materials. - , Br - It is preferable that the content of anions such as these is low. Specifically, it is preferable that the total amount of these impurities and anions in the raw material powder is 0.01 mass % or less.

[0041] <Process (ii)> The production method according to this embodiment may include a step (ii) of heat-treating the spheroidized raw material powder after step (i). When the production method according to this embodiment includes steps (i) and (ii), the raw material powder spheroidized in step (i) will be referred to as "spheroidized powder" for convenience.

[0042] When step (ii) is performed, the heating temperature is preferably 1250°C or lower, more preferably 1150°C or lower, and even more preferably 600 to 1000°C. Heat-treating the spheroidized powder at such a heating temperature makes it possible to adjust the crystallinity of the inorganic particles constituting the spheroidized powder (e.g., the proportion of one or more phases selected from the MgTi2O4 phase and the MgTi2O5 phase in the inorganic particles contained in the final inorganic powder tends to be higher), and the amount of impurities tends to be reduced. Furthermore, the shear viscosity measured under the above condition (I) tends to be 3,000 Pa s or lower. From the viewpoint of adjusting the shear viscosity, it is desirable that the heating temperature in step (ii) does not exceed 1250°C.

[0043] As the heating device, for example, an electric furnace or a gas furnace can be used. Step (ii) is preferably carried out in the atmosphere. The heating time is preferably 1 to 24 hours, more preferably 1 to 12 hours. If the heating time is 1 to 24 hours, productivity tends to be good.

[0044] In one embodiment, from the viewpoint of easily obtaining an inorganic powder having a span value of more than 1.2, it is preferable not to perform step (ii). In that case, step (i) may be to spheroidize the raw material powder to prepare the inorganic powder according to this embodiment. By spheroidizing the raw material powder using the above-mentioned preferred method, an inorganic powder containing fine particles and coarse particles is obtained. The inclusion of such particles makes it easier for the span value to exceed 1.2, and as a result, it becomes easier to obtain an inorganic powder with excellent dielectric properties.

[0045] The inorganic powder according to this embodiment can be prepared by a production method including the aforementioned step (i) (or, if necessary, a production method including steps (i) and (ii)). After step (i) (or step (ii)), the powder obtained may be in the form of aggregates. Therefore, a crushing treatment may be performed, if necessary. When crushing is performed, it is preferable to control the span value so that it exceeds 1.2. Examples of such a method include crushing using an agate mortar, ball mill, vibration mill, jet mill, wet jet mill, etc. Crushing may be performed dry, or wet by mixing with a liquid such as water or alcohol. In wet crushing, inorganic powder can be obtained by drying after crushing. The drying method is not particularly limited, and examples thereof include heat drying, vacuum drying, freeze drying, and supercritical carbon dioxide drying.

[0046] Furthermore, from the viewpoint of easily obtaining an inorganic powder having a span value of more than 1.2, the production method according to this embodiment preferably does not include classifying the obtained inorganic powder. Examples of classification methods include classification using a sieve, as well as liquid cyclone and air classification, but it is preferable not to perform these.

[0047] In one embodiment, the method may include surface treating the inorganic powder with a surface treatment agent and washing the inorganic powder to reduce impurities (such as the above-mentioned anions) in the inorganic powder.

[0048] Another example of a method for producing the inorganic powder according to this embodiment is a method that includes mixing two or more inorganic powders (including MgTiO) having different average particle sizes (D50). The mixing may include, for example, mixing an inorganic powder (A) having a D50 of 1.0 to 1.2 μm with an inorganic powder (B) having a D50 of 3.0 to 3.5 μm to obtain an inorganic powder having a span value of more than 1.2. The method for mixing two or more inorganic powders is not particularly limited, and for example, a shaking mixer, a bead mill, or the like can be used. The production method may also include surface treatment and washing the inorganic powder after mixing.

[0049] [Application] As described above, the inorganic powder according to this embodiment has excellent dielectric properties and excellent dispersibility in resins. Therefore, it can be suitably used as a filler for filling resins. In particular, the inorganic powder according to this embodiment can be suitably used as a ceramic filler for high-frequency band (e.g., GHz band) devices.

[0050] [Resin composition] The resin composition according to this embodiment contains the inorganic powder described above and at least one resin selected from thermoplastic resins and thermosetting resins. The content of the inorganic powder in the resin composition is not particularly limited and can be adjusted appropriately depending on the purpose. The inorganic powder according to this embodiment does not deteriorate in processability or workability even when highly filled in the resin, so the amount of powder blended in the resin composition can be adjusted to obtain the desired dielectric properties. For example, when used as a substrate material for high frequency bands or an insulating material, the powder may be blended in a range of 1 to 80 mass % relative to the total mass of the resin composition, more preferably in a range of 10 to 70 mass %.

[0051] <Resin> The resin composition according to the present embodiment includes at least one resin selected from thermoplastic resins and thermosetting resins. More specifically, examples of the resin include polyolefin-based resins such as polyethylene resins and polypropylene resins; epoxy-based resins; silicone-based resins; phenol-based resins; melamine-based resins; urea-based resins; unsaturated polyester-based resins; fluorine-based resins; polyamide-based resins such as polyimide resins, polyamideimide resins, and polyetherimide resins; polyester-based resins such as polybutylene terephthalate resins and polyethylene terephthalate resins; polyphenylene sulfide-based resins; wholly aromatic polyester-based resins; polysulfone-based resins; liquid crystal resins; polyethersulfone-based resins; polycarbonate-based resins; maleimide-based resins; ABS (acrylonitrile-butadiene-styrene)-based resins; AAS (acrylonitrile-acrylic rubber-styrene)-based resins; AES (acrylonitrile-ethylene-propylene-diene rubber-styrene)-based resins; hydrocarbon elastomer resins; polyphenylene ether-based resins; and aromatic polyene-based resins. These may be used alone or in combination of two or more.

[0052] The resin composition according to this embodiment may contain a curing agent, a curing accelerator, a release agent, a coupling agent, a colorant, a flame retardant, an ion scavenger, etc., within the range that does not impair the effects of the present invention.

[0053] <Method of manufacturing resin composition> The method for producing the resin composition is not particularly limited, and the resin composition can be produced by stirring, dissolving, mixing, and dispersing predetermined amounts of each material. The apparatus for mixing, stirring, dispersing, etc., of these mixtures is not particularly limited, and examples that can be used include a mortar and pestle machine equipped with a stirring and heating device, a three-roll mill, a ball mill, and a planetary mixer. These apparatuses may also be used in appropriate combination.

[0054] [Application] As described above, the resin composition containing the inorganic powder according to this embodiment can achieve a high dielectric constant and a low dielectric loss tangent. Furthermore, the resin composition containing the inorganic powder according to this embodiment has low viscosity, and therefore is excellent in processability and workability. In a preferred embodiment, the resin composition can be used as a resin material for AiP (AiP) for RF modules.

[0055] Another embodiment of the present disclosure is a method for further reducing the dielectric loss tangent while maintaining the dielectric constant of the raw material powder by spheroidizing a raw material powder containing MgTiO3 so that the raw material particles have an average circularity of 0.80 or more and a span value of the raw material powder exceeding 1.2. The span value is preferably greater than 1.2 and equal to or less than 5.0.

[0056] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of the present disclosure are set forth below. [1] An inorganic powder containing MgTiO3, the inorganic particles contained in the inorganic powder have an average circularity of 0.80 or more; The inorganic powder has a volume-based particle size distribution (D90-D10) / D50 ratio of more than 1.2 as measured by a laser diffraction / scattering particle size distribution method. [2] The inorganic powder according to [1], wherein the D50 is 1.0 to 4.5 μm. [3] The inorganic powder according to [1] or [2], wherein the D90 is 2.5 to 15.0 μm. [4] Specific surface area (BET) is 0.3 to 4.5 m 2 / g of the inorganic powder according to any one of [1] to [3]. [5] The inorganic powder according to any one of [1] to [4], which has a shear viscosity measured under the following condition (I) of 3,000 Pa·s or less. <Condition (I)> The shear viscosity of a resin composition consisting of 60% by volume of bisphenol A liquid epoxy resin (epoxy equivalent: 184 to 194) and 40% by volume of the inorganic powder is measured using a rheometer at a shear rate of 1.0 / s, plate shape: circular flat plate (10 mmφ), sample thickness: 1 mm, and temperature: 25±1°C. [6] The dielectric constant (εr f ) is 15 to 35. The inorganic powder according to any one of [1] to [5]. <Condition (II)> The dielectric constant (εr c ) is measured using a split cylinder resonator at a measurement frequency of 40 GHz, a temperature of 20°C, and a humidity of 60% RH. f ) is calculated using the following formula (1). log(εr c )=V f log(εr f )+(1-V f )·log(εr r ) (1) (In formula (1), εr c , εr f , and εr r represent the dielectric constants of the resin composition, the inorganic powder, and the polyethylene resin, respectively, and V f represents the content (vol %) of the inorganic powder in the resin composition. [7] The inorganic powder according to any one of [1] to [6], wherein the inorganic powder contains inorganic particles containing an MgTiO3 phase as a main phase, and the proportion of the MgTiO3 phase to all crystalline phases in the inorganic particles is 75 mass% or more. [8] The inorganic powder according to any one of [1] to [7], which is used for filling in resin. [9] A resin composition comprising the inorganic powder according to any one of [1] to [8] and at least one resin selected from a thermoplastic resin and a thermosetting resin. [Example]

[0057] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following description.

[0058] [Example 1 and Comparative Example 1] A raw material powder (inorganic powder; manufactured by Kyoritsu Material Co., Ltd., product name "MT-1H") was subjected to a spheroidizing treatment by a powder fusion method to obtain an inorganic powder. The span value, average circularity, average particle density, specific surface area, shear viscosity, dielectric constant, and dielectric loss tangent of the obtained inorganic powder were measured by the following methods. In addition, the crystalline phase of any inorganic particles in the inorganic powder was identified and quantified. Similar measurements were also performed on the raw material powder (Comparative Example 1). The results are shown in Table 1.

[0059] <Volumetric particle size distribution> Measurements were carried out using a laser diffraction / scattering particle size distribution analyzer (manufactured by Beckman Coulter, Inc., product name "LS 13 320"). First, 50 cm 3 100g of pure water and 0.1g of inorganic powder were added and dispersed for 1 minute at 50% power using an ultrasonic homogenizer (Microtec Unition Co., Ltd., product name "Smurt NR-50M" (homogenizer tip: NS-50M-MT 3mmφ)) at 50% power. The dispersed inorganic powder dispersion was added dropwise to a laser diffraction / scattering particle size analyzer. 30 seconds after the specified amount was added, the particle size distribution was measured. Note that the refractive index of the inorganic powder was set to 2.31 and the specific gravity to 3.85, while the refractive index of water was set to 1.33 and the specific gravity to 1.00. The volumetric particle size distribution was calculated from the light intensity distribution data of the diffracted / scattered light of the inorganic powder detected by the sensor in the laser diffraction / scattering particle size analyzer. D10, D50, and D90 were calculated from the particle sizes corresponding to cumulative values ​​of 10% (D10), 50% (D50), and 90% (D90) in the measured volumetric particle size distribution. Based on the obtained D10, D50, and D90, "(D90-D10) / D50" (hereinafter sometimes referred to as "span value") was calculated. The span value was the average value of span values ​​calculated by performing the above-mentioned measurement method for volumetric particle size distribution with N=3.

[0060] <Crystal phase> Using a horizontal sample multipurpose X-ray diffractometer (Rigaku Corporation, product name: RINT-UltimaIV-N), the X-ray diffraction pattern of any inorganic particle in the inorganic powder was measured under the following measurement conditions. X-ray source:CuKα Tube voltage: 40kV Tube current: 40mA Scan speed: 10.0° / min 2θ scan range: 10°~80° In addition, the crystalline phases of the inorganic particles were identified and quantitatively analyzed by WPPF analysis of the obtained X-ray diffraction patterns (using data analysis software, Rigaku, product name "Integrated Powder X-ray Software PDXL2"). The proportion of the MgTiO3 phase (mass%) was calculated using ICDD card (number: 01-079-0831). The proportion of the MgTi2O4 phase was calculated using ICDD card (number: 01-072-6967), and the proportion of the MgTi2O5 phase was calculated using ICDD card (number: 01-079-0833).

[0061] <Average circularity> An arbitrary amount of inorganic powder was fixed to a sample stage with carbon tape and then coated with osmium. The inorganic powder was then photographed at 3,000-30,000x magnification using a scanning electron microscope (JEOL Ltd., product name "JSM-7001F SHL"), and the captured images with a resolution of 1280 x 1024 pixels were imported into a computer. The images were then analyzed using an image analyzer (Nippon Roper Co., Ltd., product name "Image-Pro Premier Ver. 9.3") to calculate the projected area (S) and projected perimeter (L) of each inorganic particle constituting the inorganic powder, and the circularity was calculated using the following formula (2). The circularity of 200 randomly selected inorganic particles was calculated, and the average value was used as the average circularity of the inorganic particles. Circularity = 4πS / L 2 ···(2)

[0062] <Average particle density> 5.0 g of inorganic powder was placed in a measurement sample cell, and the average particle density was measured by the gas (helium) substitution method using a dry density meter (Shimadzu Corporation, product name "Accupyk II 1340").

[0063] <Specific surface area> 2 g of inorganic powder was filled into a measurement cell, and the specific surface area was measured using a Mountech Macsorb HM model-1201 fully automatic specific surface area measurement device (BET single-point method). Degassing conditions before measurement were 200°C for 10 minutes. Nitrogen was used as the adsorption gas.

[0064] <Shear viscosity> (Condition (I)) The shear viscosity of a resin composition consisting of 60% by volume of bisphenol A liquid epoxy resin (epoxy equivalent: 184-194, manufactured by Mitsubishi Chemical Corporation, product name "JER828") and 40% by volume of inorganic powder was measured using a rheometer (manufactured by Anton-Paar, product name "MCR302") at a shear rate of 1.0 / s, plate shape: circular flat plate (10 mmφ), sample thickness: 1 mm, and temperature: 25±1°C.

[0065] <Evaluation of dielectric properties (dielectric constant and dielectric loss tangent)> (Condition (II)) Polyethylene resin (density: 0.92 g / cm 3 The dielectric constant (εr c ) was measured using a split cylinder resonator at a measurement frequency of 40 GHz, a temperature of 20°C, and a humidity of 60% RH. f ) was calculated using the following formula (1). log(εr c )=V f log(εr f )+(1-V f )·log(εr r ) (1) (In formula (1), εr c , εr f , εr r represent the dielectric constants of the resin composition, inorganic powder, and polyethylene resin, respectively, and V f represents the content (vol %) of inorganic powder in the resin composition.

[0066] In addition, using the same sheet as in the condition (II), the dielectric loss tangent was measured with a split cylinder resonator at a measurement frequency of 40 GHz, a temperature of 20°C, and a humidity of 60% RH. f ) was calculated using the following formula (3). tanδ c =V f tanδ f +(1-V f )·tanδ r (3) (In formula (3), V f represents the content (vol %) of inorganic powder in the resin composition, and tanδ c represents the dielectric tangent of the resin composition, and tanδ r represents the dielectric loss tangent of polyethylene resin.)

[0067] [Table 1]

[0068] In Table 1, the notation "-" in the proportion of the crystalline phase means that the component was not contained. Figure 1 shows a scanning electron microscope photograph of the inorganic powder of Example 1. As shown in Figure 1, the inorganic powder of Example 1 contained a mixture of fine and coarse inorganic particles. Table 1 also shows the evaluation results of the inorganic powder of Example 1 and the raw material powder of Comparative Example 1. As shown in Table 1, the inorganic powder of Example 1 achieved a lower dielectric tangent while maintaining a dielectric constant similar to that of Comparative Example 1 (raw material powder). It was also found that the shear viscosity was low at 1,480 Pa·s, and dispersibility in the resin was improved. The crystallite diameter of the MgTiO3 phase (lattice constants, a: 5.05 Å, b: 5.05 Å, c: 13.90 Å) of the inorganic particles contained in the inorganic powder of Example 1 was 46.8 nm. The crystallite diameter of the MgTiO3 phase (lattice constants, a: 5.05 Å, b: 5.05 Å, c: 13.90 Å) of the raw material particles contained in the raw material powder of Comparative Example 1 was 60.3 nm. From the above results, it was confirmed that the inorganic powder according to the present disclosure has excellent dielectric properties and also excellent dispersibility in resin. [Industrial Applicability]

[0069] The inorganic powder according to this embodiment has excellent dielectric properties and excellent dispersibility in resins. Such inorganic powders can be suitably used for resin filling. In one embodiment, the inorganic powder has industrial applicability as a ceramic filler for AiP (AiP) for RF modules.

Claims

1. MgTiO ３ An inorganic powder comprising: the inorganic particles contained in the inorganic powder have an average circularity of 0.80 or more; The inorganic powder has a volume-based particle size distribution (D90-D10) / D50 of more than 1.2 as measured by a laser diffraction / scattering particle size distribution method.

2. The inorganic powder according to claim 1, wherein the D50 is 1.0 to 4.5 μm.

3. The inorganic powder according to claim 1 or 2, wherein the D90 is 2.5 to 15.0 μm.

4. Specific surface area (BET) 0.3 to 4.5 m ２ The inorganic powder according to claim 1 or 2, wherein the solubility is 1 / g.

5. 3. The inorganic powder according to claim 1, which has a shear viscosity of 3,000 Pa·s or less as measured under the following condition (I): <Condition (I)> The shear viscosity of a resin composition consisting of 60% by volume of a bisphenol A liquid epoxy resin (epoxy equivalent: 184 to 194) and 40% by volume of the inorganic powder is measured using a rheometer at a shear rate of 1.0 / s, a circular flat plate shape (10 mmφ), a sample thickness of 1 mm, and a temperature of 25±1°C.

6. The dielectric constant (εr ｆ 3. The inorganic powder according to claim 1, wherein the molecular weight of the inorganic powder is 15 to 35. <Condition (II)> The dielectric constant (εr ｃ ) is measured using a split cylinder resonator at a measurement frequency of 40 GHz, a temperature of 20°C, and a humidity of 60% RH. ｆ ) is calculated using the following formula (1). log(εr ｃ )=V ｆ ・log(εr ｆ )+(1-V ｆ )・log(εr ｒ ) (1) (In formula (1), εr ｃ , εr ｆ , and εr ｒ represent the dielectric constants of the resin composition, the inorganic powder, and the polyethylene resin, respectively, and V ｆ represents the content (vol %) of the inorganic powder in the resin composition.

7. The inorganic powder is MgTiO ３ The inorganic particles contain a MgTiO phase as a main phase, and the ratio of the MgTiO phase to the total crystalline phase in the inorganic particles is ３ 3. The inorganic powder according to claim 1, wherein the proportion of the phase is 75% by mass or more.

8. The inorganic powder according to claim 1 or 2, which is used for filling in resin.

9. A resin composition comprising the inorganic powder according to claim 1 or 2 and at least one resin selected from thermoplastic resins and thermosetting resins.

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