WO2024024604A1

WO2024024604A1 - Highly pure spinel particles and production method therefor

Info

Publication number: WO2024024604A1
Application number: PCT/JP2023/026500
Authority: WO
Inventors: 隆一清岡; 高見新川; 浩児大道
Original assignee: Dic株式会社
Priority date: 2022-07-28
Filing date: 2023-07-20
Publication date: 2024-02-01
Also published as: TW202406847A; JPWO2024024604A1

Abstract

The purpose of the present invention is to provide: a highly pure metal composite oxide having excellent thermal conductivity and dielectric characteristics; and a method for efficiently producing said metal composite oxide. Specifically, the present invention is characterized by the use of spinel particles including at least magnesium atoms, aluminum atoms, and oxygen atoms, wherein the quantity of atoms other than said atoms is less than 0.27 at% and/or the number of calcium atoms relative to the sum of the number of magnesium atoms and aluminum atoms is less than 0.02 at%.

Description

High purity spinel particles and their manufacturing method

The present invention relates to high purity spinel particles and a method for producing the same.

Spinel particles are composite oxides of metal elements represented by MgAl ₂ O ₄ and have _the general formula AB ₂ It is used in applications such as protective films, fluorescent emitters, catalyst carriers, adsorbents, photocatalysts, and heat-resistant insulating materials. Among them, research is being conducted as a heat dissipation filler because of its excellent thermal conductivity (Patent Documents 1 and 2).

On the other hand, in recent years, the speed and capacity of information communication has rapidly increased, and communication infrastructure using millimeter wave electromagnetic waves, such as fifth generation communication systems (5G) and even sixth generation mobile communication systems (6G), is attracting attention. ing. As a result, in order to reduce transmission loss in printed circuit boards and the like of power-system high-frequency devices, heat dissipation fillers with excellent dielectric properties (low dielectric constant, low dielectric loss tangent) are being sought.

On the other hand, Patent Document 1 discloses spinel particles containing magnesium atoms, aluminum atoms, oxygen atoms, and molybdenum, and having a crystallite diameter of 220 nm or more in the [111] plane. It is described that the obtained particles have a significantly large crystallite size on the [111] plane, and as a result, have excellent thermal conductivity.

Further, Patent Document 2 describes a spinel structure mainly composed of MgAl ₂ O ₄ or ZnAl ₂ O ₄ obtained by firing a raw material containing at least an alumina-based compound and a compound of magnesium or zinc as its main components. Disclosed. Specifically, with a focus on chemical resistance, thermally conductive composite oxides are listed that have an absolute value of mass change rate of 2% or less in chemical resistance tests against hydrochloric acid, sulfuric acid, nitric acid, and sodium hydroxide. has been done.

International Publication No. 2017/221372 JP2016-135841A

All of the documents focused on thermal conductivity or thermal conductivity and chemical resistance, and did not examine dielectric properties. In addition, the inventors believe that in order to obtain low dielectric properties in molded products, it is important to make the shape of spinel particles spherical and improve the filling property when mixed with resin, but spherical spinel particles The production method is still subject to consideration.

The present invention was made in view of the above circumstances, and provides high purity spinel particles having both high thermal conductivity and low dielectric properties, and a method for producing the same.

As a result of extensive research to achieve the above object, the present inventors found that spinel particles obtained by firing fine particles of a highly pure magnesium compound and an aluminum compound have high purity and thermal conductivity. The present inventors have discovered that this material has excellent dielectric properties and dielectric properties, and have completed the present invention.

That is, the present invention includes the following aspects.
(1) Spinel particles containing at least a magnesium atom, an aluminum atom, and an oxygen atom,
A spinel particle in which the amount of atoms other than the above atoms is less than 0.27 at.%.
(2) Spinel particles containing at least a magnesium atom, an aluminum atom, and an oxygen atom,
Spinel particles in which the number of calcium atoms is less than 0.02 atomic % based on the sum of the numbers of magnesium atoms and aluminum atoms.
(3) The spinel particles according to (1) or (2) above, having an average particle diameter of 75 μm or less.
(4) The spinel particle according to any one of (1) to (3) above, having a dielectric loss tangent of less than 1.0×10 ⁻³ at 1 GHz.
(5) A resin composition comprising the spinel particles according to any one of (1) to (4) above and a resin.
(6) A molded article of the resin composition according to (5) above.
(7) A method for producing spinel particles by mixing and firing an aluminum-based compound and a magnesium-based compound, the method comprising:
The magnesium-based compound is fine particles with an average particle size of less than 4 μm,
A method for producing spinel particles, wherein the amount of impurities contained in the magnesium-based compound is less than 1.0 atomic %.
(8) A method for producing spinel particles by mixing and firing an aluminum-based compound and a magnesium-based compound, the method comprising:
The magnesium-based compound is fine particles with an average particle size of less than 4 μm,
A method for producing spinel particles, wherein the calcium atomic weight contained in the magnesium-based compound is 0.6 at % or less.
(9) The manufacturing method according to (7) or (8) above, wherein the aluminum-based compound has a spherical or true spherical shape.

According to the present invention, compared to conventional spinel particles, the spinel particles are highly purified and have excellent both thermal conductivity and dielectric properties. In addition, the spinel particles of the present invention can be easily obtained by mixing and firing fine particles of a highly pure magnesium compound and an aluminum compound, resulting in high productivity and excellent practicality. .

1 is a SEM image of spinel particles of Example 1. 3 is a SEM image of spinel particles of Example 3. 3 is a SEM image of spinel particles of Example 4. 3 is a SEM image of spinel particles of Comparative Example 3.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated in detail.
<Spinel particles>
One embodiment of the spinel particle of the present invention is a spinel particle containing at least a magnesium atom, an aluminum atom, and an oxygen atom, wherein the amount of atoms other than the above atoms is 0 with respect to the number of atoms of the spinel particle. It is characterized by being less than .27 atomic %.

One embodiment of the spinel particles of the present invention is a spinel particle containing at least a magnesium atom, an aluminum atom, and an oxygen atom, wherein the number of calcium atoms is greater than the sum of the numbers of magnesium atoms and aluminum atoms. , less than 0.02 atomic %.

The spinel particles are spinel particles containing at least a magnesium atom, an aluminum atom, and an oxygen atom, and the amount of other atoms is less than 0.27 atom%, more preferably less than 0.2 atom%, and 0. Particularly preferred is less than .1 atomic %. When it is less than the above upper limit, the resulting spinel particles have excellent dielectric properties, which is preferable.

The spinel particles are spinel particles containing at least a magnesium atom, an aluminum atom, and an oxygen atom, and the number of calcium atoms is less than 0.02 at% with respect to the sum of the numbers of magnesium atoms and aluminum atoms, and 0.01 It is more preferably less than atomic %, particularly preferably less than 0.005 atomic %. When it is less than the above upper limit, the resulting spinel particles have excellent dielectric properties, which is preferable.

The average particle diameter of the spinel particles is preferably 75 μm or less, more preferably 35 μm or less, and particularly preferably 10 μm or less. It is preferable that the particle size is below the above-mentioned particle size because when it is mixed with a resin and processed into a sheet or the like, the surface of the processed product does not become uneven.

In this specification, the "average particle diameter" of spinel particles refers to a particle size distribution system using laser diffraction scattering, such as a laser diffraction scattering particle size distribution analyzer MT3300EXII (manufactured by Microtrac Bell Co., Ltd.). The measured value is indicated by D50.

In addition, the above-mentioned average particle diameter is the longest diameter determined from the particle image of the primary particle of the spinel particle in a two-dimensional image taken with a scanning electron microscope (SEM). (the longest distance when an individual particle is sandwiched between two parallel line segments) may be used, and the obtained value is almost equivalent to the measured value obtained by the above method. shows.
The spinel particles to be measured are at least 50 spinel particles randomly selected from among those whose outlines can be identified as a whole.

The dielectric constant of the spinel particles is preferably 20 or less, more preferably 15 or less, and particularly preferably 10 or less. If it is within the above range, power consumption, that is, heat generation, and noise can be suppressed when the resin composition is prepared, so it is preferable.

The dielectric loss tangent of the spinel particles at 1 GHz is preferably 1.0×10 ⁻³ or less, more preferably 8.0×10 ⁻⁴ or less, and 5.0×10 ⁻⁴ or less. It is particularly preferable. If it is within the above range, power consumption, that is, heat generation, and noise can be suppressed when the resin composition is prepared, so it is preferable.

Examples of the shape of spinel particles include polyhedral, spherical, true spherical, elliptical, cylindrical, polygonal columnar, needle-like, rod-like, plate-like, disk-like, flaky, and scaly shapes. Among these, a spherical shape is preferable because it increases the filling property when mixed with resin, and a true spherical shape lowers the viscosity of the mixture, increases the filling rate, and tends to form a close-packed structure, so it is especially preferable. preferable.

When spinel particles having a spherical shape are included, preferably 50% or more of the particles have a spherical shape based on mass or number, more preferably 80% or more of the particles have a spherical shape, and 90% or more of the particles have a spherical shape. It is further preferred that the above particles have a spherical shape.

Note that if the shape is spherical or true spherical, it will be packed densely to easily avoid contact and fixation with other particles during molding of the resin composition. Further, due to the shape described above, the fractal dimension of the particle contour is reduced, and the void ratio when filled is suppressed. As a result, a close-packed structure provides excellent thermal conductivity and dielectric properties.

In this specification, the shape is determined visually from a scanning electron microscope (SEM) image, but it can also be determined by calculating circularity. For example, the circularity may be 0.7 or more, 0.75 or more, or 0.8 or more. The above-mentioned "circularity" can be calculated from "4 x π x area/circumference^2", and the area and circumference can be determined by observation using a scanning electron microscope (SEM). can.

The crystal structure of the spinel particles has MgAl ₂ O ₄ having a spinel type crystal structure. The spinel particles of this embodiment, which will be described later, mainly have a spinel crystal structure, but may contain impurity phases to the extent that they do not adversely affect the dielectric loss tangent.

<Content of each atom>
(magnesium atom)
The content of magnesium atoms in spinel particles is not particularly limited, but when the structural formula of spinel particles is represented by Mg _x Al _y O _z , x is preferably in the range of 0.8 to 1.2, and 0 More preferably, it is in the range of .9 to 1.1. In addition, in this specification, the content of magnesium atoms in spinel particles shall be the value measured by X-ray fluorescence elemental analysis (XRF).

(aluminum atom)
The content of aluminum atoms in spinel particles is not particularly limited, but when the structural formula of spinel particles is represented by Mg _x Al _y O _z , y is preferably in the range of 1.8 to 2.2, and 1 More preferably, it is in the range of .9 to 2.1. In addition, in this specification, the content of aluminum atoms in spinel particles shall be the value measured by X-ray fluorescence elemental analysis (XRF).

(oxygen atom)
The content of oxygen atoms in spinel particles is not particularly limited, but when the structural formula of spinel particles is represented by Mg _x Al _y O _z , z must be in the range of (x + y + 1.2) to (x + y + 0.8). is preferable, and a range of (x+y+1.1) to (x+y+0.9) is more preferable.

(Other atoms)
Other atoms are those present in the raw materials or unavoidably mixed into the spinel particles during the manufacturing process, are essentially unnecessary, and mean impurities that affect the characteristics of the spinel particles.

Other atoms in the spinel particles include, but are not particularly limited to, silicon, iron, potassium, sodium, calcium, and the like. These impurities may be contained alone or in combination of two or more types, but the content thereof is preferably less than 0.27 atomic % based on the atoms of the spinel particles. If it is within the above range, it is assumed that scattering of phonons (lattice vibrations) due to impurities is suppressed, and thereby the spinel particles have excellent dielectric properties. For the content of other atoms in the spinel, values measured by X-ray fluorescence elemental analysis (XRF) are used.

In the spinel particles, the number of impurity calcium atoms is preferably less than 0.02 at % based on the sum of the numbers of magnesium and aluminum atoms. Within the above range, it is estimated that scattering of phonons (lattice vibrations) due to impurities caused by calcium atoms substituted by magnesium atoms is suppressed, and the dielectric loss tangent of the spinel particles is excellent. As for the content of calcium atoms in the spinel particles, a value measured by X-ray fluorescence elemental analysis (XRF) is used.

In addition, in the spinel particles of the present invention, either the content of impurities (silicon, iron, potassium, sodium, calcium, etc.) or the number of calcium atoms relative to the sum of the numbers of magnesium and aluminum atoms is within the above range. It is sufficient if both conditions are satisfied. In addition, it is particularly preferable that both of them are within the above-mentioned ranges, since spinel particles having better dielectric properties can be obtained.

<Method for manufacturing spinel particles>
The method for producing spinel particles includes a step of firing a mixture containing a magnesium-based compound and an aluminum-based compound.

[Mixing process]
The mixing step is a step of mixing a magnesium-based compound and an aluminum-based compound to obtain a mixture. At this time, the mixing state of the magnesium-based compound and the aluminum-based compound is not particularly limited. When mixing the two, simple mixing methods such as putting the raw materials in a bag or the like and shaking them to mix the powder, mechanical mixing using a grinder or mixer, mixing using a mortar, etc. are performed. . At this time, the resulting mixture may be in either a dry state or a wet state, but it is preferably in a dry state from the viewpoint of cost.

In the mixing step, the mixing ratio of the magnesium-based compound and the aluminum-based compound is not particularly limited, but the molar ratio of the aluminum element of the aluminum-based compound to the magnesium element of the magnesium-based compound (aluminum element/magnesium element) is 1. It is preferable to mix so that it becomes 8 or more and 2.2 or less, and it is more preferable to mix so that it becomes 1.9 or more and 2.1 or less.
The contents of the mixture will be explained below.

(Magnesium-based compound)
Examples of the magnesium compound include, but are not particularly limited to, metal magnesium, magnesium derivatives, magnesium oxoacid salts, magnesium organic salts, and hydrates thereof. Examples of magnesium derivatives include magnesium oxide, magnesium hydroxide, magnesium peroxide, magnesium fluoride, magnesium chloride, magnesium bromide, magnesium iodide, magnesium hydride, magnesium diboride, magnesium nitride, and magnesium sulfide. It will be done. Examples of magnesium oxoacid salts include magnesium carbonate, calcium magnesium carbonate, magnesium nitrate, magnesium sulfate, magnesium sulfite, magnesium perchlorate, trimagnesium phosphate, magnesium permanganate, and magnesium phosphate. Examples of magnesium organic salts include magnesium acetate, magnesium citrate, magnesium malate, magnesium glutamate, magnesium benzoate, magnesium stearate, magnesium acrylate, magnesium methacrylate, magnesium gluconate, magnesium naphthenate, magnesium salicylate, and lactic acid. Examples include magnesium, magnesium monoperoxyphthalate, and the like. Note that these magnesium compounds may be used alone or in combination of two or more.

Among these, magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium acetate, magnesium nitrate, or magnesium sulfate are preferable, and magnesium oxide, magnesium hydroxide, magnesium nitrate, or magnesium acetate is more preferable.

The volume-based average particle diameter D50 in the laser diffraction particle size distribution measurement of magnesium-based compounds is determined by using particles with a smaller particle diameter within the range of no agglomeration. particles can be obtained. The average particle diameter D50 is 0.01 μm or more and less than 4 μm, more preferably 0.1 μm or more and 2 μm or less, even more preferably 0.5 μm or more and 2 μm or less, and particularly preferably 0.5 μm or more and 1.5 μm or less. When it is at least the above lower limit, it is possible to suppress particles from agglomerating during mixing. When it is less than the above upper limit, magnesium atoms can diffuse and enter the aluminum-based compound particles without destroying the shape of the aluminum-based compound, and it is possible to grow well-shaped particles.

The magnesium-based compound may be a commercially available product or may be prepared by yourself. When preparing the magnesium-based compound yourself, the reactivity for spinel particle production can be adjusted. For example, magnesium hydroxide with a small particle size can be obtained by neutralizing an acidic aqueous solution of magnesium ions with a base. Since the obtained magnesium hydroxide having a small particle size has high reactivity, the crystallite size of spinel particles obtained using this tends to be large.

Commercially available or prepared magnesium compounds may contain impurities such as silicon, iron, potassium, sodium, calcium, phosphorus, sulfur, and chlorine. The total amount of these impurities is preferably less than 1.0 at% and 0.5 at% or less based on magnesium when the value measured by X-ray fluorescence elemental analysis (XRF) is converted to the number of atoms. It is more preferable that it is, and even more preferable that it is 0.3 atom % or less.

The atomic weight of calcium contained in the magnesium-based compound of commercially available products or prepared products is preferably 0.6 atomic % or less, more preferably 0.4 atomic % or less, and 0.3 atomic % or less. It is even more preferable.

(aluminum compound)
Examples of aluminum-based compounds include, but are not limited to, metal aluminum, aluminum derivatives such as alumina (aluminum oxide), aluminum hydroxide, aluminum sulfide, aluminum nitride, aluminum fluoride, aluminum chloride, aluminum bromide, and aluminum iodide; sulfuric acid. Aluminum, aluminum oxoarates such as sodium aluminum sulfate, potassium aluminum sulfate, ammonium aluminum sulfate, aluminum nitrate, aluminum perchlorate, aluminum aluminate, aluminum silicate, aluminum phosphate; aluminum acetate, aluminum lactate, aluminum laurate, stearin Aluminum organic salts such as aluminum acid and aluminum oxalate; alkoxyaluminums such as aluminum propoxide and aluminum butoxide; aluminum-magnesium-containing compounds such as magnesium aluminate, hydrotalcite, and magnesium aluminum isopropoxide; and hydrates thereof etc. Among these, it is preferable to use aluminum oxide, aluminum hydroxide, aluminum chloride, aluminum sulfate, aluminum nitrate, and hydrates thereof, and it is more preferable to use aluminum oxide and aluminum hydroxide.
In addition, the above-mentioned aluminum-based compounds may be used alone or in combination of two or more types.

The volume-based average particle diameter D50 in the laser diffraction particle size distribution measurement of aluminum-based compounds is determined by using particles with a smaller particle diameter within the range of no agglomeration, which improves reactivity during firing and improves purity without impurity phases. It is preferable that spinel particles with high viscosity can be obtained. Since the particle size of the aluminum raw material is correlated with the particle size of the spinel particles to be obtained, it is appropriately selected depending on the desired particle size of the spinel particles. The average particle diameter D50 of the aluminum compound is 0.01 μm or more and 70 μm or less, preferably 0.1 μm or more and 30 μm or less, more preferably 0.1 μm or more and 15 μm or less, and most preferably 0.5 μm or more and 10 μm or less.

In order to obtain the average particle diameter D50, the raw material aluminum compound may be ground by using a grinder or the like. In addition, from the viewpoint of the particle shape of the aluminum-based compound described later and the shape of the obtained spinel particles, it is more preferable to use an aluminum-based compound that does not require pulverization for particle size adjustment as the raw material.

The shape of the aluminum-based compound may be polyhedral, spherical, true spherical, elliptical, cylindrical, polygonal columnar, needle-like, rod-like, plate-like, disk-like, flaky, or scaly; From the viewpoint of the shape of the obtained spinel particles, it is more preferable that the spinel particles are spherical or truly spherical. According to the manufacturing method of this embodiment, since magnesium atoms diffuse and enter into the aluminum compound particles, it is possible to grow the aluminum compound as a raw material without losing its shape during particle growth. It becomes possible to easily control the shape of the spinel particles.

The crystal structure of the aluminum-based compound is not particularly limited, and may be a single phase or a mixed phase. Note that when the crystal structure is a mixed phase, the aluminum-based compound often has a true spherical shape.

[Firing process]
Spinel particles can be obtained by firing the mixture at a high temperature in a firing furnace.

The firing temperature is not particularly limited as long as the desired spinel particles can be obtained, but it is preferably 1100 to 1600°C, more preferably 1200 to 1500°C, and particularly preferably 1300 to 1400°C. It is preferable that the firing temperature is 1100° C. or higher because it suppresses unreacted raw materials, while it is preferable that the firing temperature is 1600° C. or lower because it allows the use of a general-purpose firing furnace and is suitable for mass production.

The firing time is not particularly limited, but is preferably 1 to 20 hours, more preferably 5 to 10 hours. It is preferable that the firing time is 1 hour or more because highly crystalline spinel particles can be obtained. On the other hand, it is preferable that the firing time is 20 hours or less because manufacturing costs can be reduced.

The firing atmosphere may be an air atmosphere, an inert gas atmosphere such as nitrogen gas or argon gas, an oxygen atmosphere, an ammonia gas atmosphere, or a carbon dioxide atmosphere. . At this time, an air atmosphere is preferable from the viewpoint of manufacturing costs.

The pressure during firing is not particularly limited either, and may be under normal pressure, increased pressure, or reduced pressure, but from the viewpoint of manufacturing costs, it is preferable to carry out under normal pressure.

The heating means is not particularly limited, but it is preferable to use a firing furnace. Firing furnaces that can be used in this case include box furnaces, tunnel furnaces, roller hearth furnaces, rotary kilns, muffle furnaces, and the like.

Compared to manufacturing methods such as the general flame method, in the above manufacturing method, magnesium atoms do not diffuse through the surface or grain boundaries during particle growth, but instead use the diffusion route within the aluminum compound particles. As a result, it is assumed that particle growth is possible while maintaining the shape of the raw material aluminum-based compound.
Further, the manufacturing method of the present invention is a manufacturing method with excellent productivity because it does not require pretreatment such as adsorbing magnesium atoms onto the surface of the aluminum compound.

[Cooling process]
The cooling step is a step in which spinel particles that have grown as crystals in the firing step are cooled and crystallized into particles.

The cooling rate is also not particularly limited, but it is preferably 1 to 1000°C/hour, more preferably 5 to 500°C/hour, and even more preferably 100 to 500°C/hour. It is preferable that the cooling rate is 1° C./hour or more because the manufacturing time can be shortened. On the other hand, it is preferable that the cooling rate is 1000° C./hour or less because the firing container is less likely to crack due to heat shock and can be used for a long time.
The cooling method is not particularly limited, and may be natural cooling or a cooling device may be used.

The manufacturing method of the present invention may include a post-treatment step. The post-treatment step is a step of removing additives and the like. The post-treatment step may be performed after the above-mentioned firing step, after the above-mentioned cooling step, or after the firing step and the cooling step. Further, if necessary, the process may be repeated two or more times.

Post-treatment methods include washing and high temperature treatment. These can be done in combination.
The cleaning method is not particularly limited, but it can be removed by, for example, cleaning with water, ammonia aqueous solution, sodium hydroxide aqueous solution, acidic aqueous solution, or the like.
Examples of the high-temperature treatment include a method of raising the temperature above the sublimation point or boiling point of the additive.

[Crushing process]
The spinel particles obtained by firing may aggregate and may not satisfy the particle size range suitable for the present invention. In this case, if necessary, the particles may be pulverized to satisfy the particle size range suitable for the present invention.

The pulverization method is not particularly limited, and conventionally known pulverization methods such as a ball mill, jaw crusher, jet mill, disk mill, spectromill, grinder, mixer mill, etc. can be applied.

[Classification process]
Spinel particles can also be subjected to classification treatment in order to adjust the average particle diameter and improve the fluidity of the powder, or to suppress an increase in viscosity when added to a binder for forming a matrix. "Classification processing" refers to an operation of dividing particles into groups according to their size.

The classification method may be either wet or dry, but from the viewpoint of productivity, dry classification is preferable. In addition to classification using a sieve, dry classification includes wind classification that uses the difference between centrifugal force and fluid drag, but from the perspective of classification accuracy, wind classification is preferable, and air classifiers that use the Coanda effect, This can be carried out using a classifier such as a swirling airflow classifier, a forced vortex centrifugal classifier, or a semi-free vortex centrifugal classifier.

The above-mentioned pulverization process and classification process can be performed at any necessary stage, including before and after the organic compound layer forming process described below. For example, the average particle diameter of the obtained particles can be adjusted by whether or not these pulverization and classification are performed and by selecting the conditions thereof.

<Resin composition>
According to one aspect of the invention, a composition is provided that includes spinel particles and a resin. At this time, the composition may further contain a curing agent, a curing catalyst, a viscosity modifier, a plasticizer, etc., if necessary.

(spinel particles)
As the spinel particles, those explained in the above "spinel particles" can be used, so the explanation will be omitted here.

Note that the spinel particles may be further surface-treated by the method described below. By surface treatment it is possible to further improve the thermal conductivity of spinel particles.
For example, surface-treated spinel particles can be produced from the spinel particles obtained as described above by attaching a surface treatment layer containing an organic compound to at least a portion of the spinel particle surface.

By attaching the surface treatment layer to at least a portion of the surface of the untreated spinel particles, the wettability with the resin contained in the resin composition is improved, and the adhesion with the spinel particles is improved. Therefore, the formation of voids that tend to occur on the surface of spinel particles is suppressed, and the loss in thermal conductivity is reduced, so that, for example, the thermal conductivity of molded products of the resin composition can be improved. Such technical effects are produced by the fact that a surface treatment layer based on a surface treatment agent based on an organic compound or a cured product thereof is attached to a part of the surface of the spinel particles. If the surface treatment agent is removed from the spinel particles by subsequent firing or the like, it will not be possible to develop the surface treatment agent.

Furthermore, when multiple types of spinel particles are used, spinel particles having a surface treatment layer can be used as one or more of the multiple types.

Specifically, the untreated spinel particles were mixed with a surface treatment agent capable of forming a surface treatment layer containing an organic compound, and the surface treatment agent was attached to at least a portion of the surface of the untreated spinel particles. Afterwards, surface-treated spinel particles can be manufactured by performing drying, curing, etc., for example.

If the surface treatment agent itself is an organic compound that does not have reactivity but has adsorptive properties, or if it is a solution or dispersion in which the surface treatment agent is dissolved or dispersed in a liquid medium, it may be possible to promote adsorption or If the surface treatment agent is a reactive organic compound, the above-mentioned surface treatment layer can be formed by curing based on the reactive groups of the compound. Can be done. Note that when the surface treatment agent is applied to the entire surface of untreated spinel particles, the untreated spinel particles are covered with the surface treatment layer.

The surface treatment agent is preferably a nonpolar silane compound. If it is nonpolar, it does not have a polar substituent, so deterioration of dielectric properties can be suppressed. A polar substituent refers to a group capable of hydrogen bonding or an ionic dissociative group. Such polar substituents include, but are not particularly limited to, -OH, -COOH, -COOM, -NH ₃ , -NR ₄ ⁺ A ^- , -CONH ₂ and the like. Here, M is a cation such as an alkali metal, an alkaline earth metal, or a quaternary ammonium salt, R is H or a hydrocarbon group having 8 or less carbon atoms, and A is an anion such as a halogen atom.

The surface treatment agent may be treated by any known and commonly used method, such as a spraying method using a fluid nozzle, stirring with shear force, a dry method using a ball mill or mixer, or a wet method using an aqueous or organic solvent system. law may be adopted. It is desirable that the surface treatment using shear force be carried out to such an extent that the filler will not be destroyed.

Furthermore, the internal temperature of the surface treatment agent in the dry method or the drying or curing temperature after treatment in the wet method is appropriately determined in a range where thermal decomposition does not occur depending on the type of the surface treatment agent. For example, it is desirable to heat at a temperature of 80 to 230°C.

The amount of nonvolatile content or cured product of the surface treatment agent in the surface treatment layer for untreated spinel particles is not particularly limited, but the amount of nonvolatile content or cured product of the surface treatment agent per 100 parts by mass of untreated spinel particles is It is preferable that the amount of the cured product be 0.01 to 10 parts from the viewpoint of improving functions such as thermal conductivity.

Whether unknown spinel particles correspond to the surface-treated spinel particles of the present invention can be determined by, for example, immersing or boiling the unknown spinel particles in a solvent that dissolves the nonvolatile content or cured product of the surface treatment agent. Infrared absorption analysis (IR) and atomic absorption spectrometry reveal that the extracted liquid and the spinel particle surface itself have a chemical structure corresponding to the surface treatment agent itself and its cured product, and the presence of silicon atoms, titanium atoms, or phosphorus atoms. You can check whether it can be observed with (AAS).

(resin)
The resin is not particularly limited, and examples thereof include thermoplastic resins, thermosetting resins, and the like.

The thermoplastic resin is not particularly limited, and known and commonly used resins used for molding materials and the like can be used. Specifically, for example, polyethylene resin, polypropylene resin, polymethyl methacrylate resin, polyvinyl acetate resin, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, polyvinyl chloride resin, polystyrene resin, polyacrylonitrile resin. , polyamide resin. Polycarbonate resin, polyacetal resin, polyethylene terephthalate resin, polyphenylene oxide resin, polyphenylene sulfide resin, polysulfone resin, polyether sulfone resin, polyether ether ketone resin, polyallyl sulfone resin, thermoplastic polyimide resin, thermoplastic urethane resin, polyamino bismaleimide Resin, polyamideimide resin, polyetherimide resin, bismaleimide triazine resin, polymethylpentene resin, fluorinated resin, liquid crystal polymer, olefin-vinyl alcohol copolymer, ionomer resin, polyarylate resin, acrylonitrile-ethylene-styrene copolymer Examples include acrylonitrile-butadiene-styrene copolymers, acrylonitrile-butadiene-styrene copolymers, and acrylonitrile-styrene copolymers.

The thermosetting resin is a resin that has the property of becoming substantially insoluble and infusible when cured by means such as heating, radiation, or a catalyst, and is generally used as a molding material, etc. Known and commonly used resins can be used. Specifically, for example, phenol resin, epoxy resin, urea resin, resin having a triazine ring, (meth)acrylic resin, vinyl resin, unsaturated polyester resin, bismaleimide resin, polyurethane resin, diallyl phthalate resin, silicone resin, Examples include resins having a benzoxazine ring and cyanate ester resins. Examples of the phenol resin include novolac type phenol resin, resol type phenol resin, and the like. Examples of the novolak type phenolic resin include phenol novolak resin, cresol novolak resin, and the like. Examples of the resol type phenolic resin include unmodified resol phenol resin, oil-modified resol phenol resin, and the like. Examples of the oil used for oil modification include tung oil, linseed oil, and walnut oil. Examples of the epoxy resin include bisphenol-type epoxy resins, fatty chain-modified bisphenol-type epoxy resins, novolak-type epoxy resins, biphenyl-type epoxy resins, and polyalkylene glycol-type epoxy resins. Examples of the bisphenol type epoxy resin include bisphenol A epoxy resin, bisphenol F epoxy resin, and the like. Examples of the novolac type epoxy resin include novolac epoxy resin, cresol novolac epoxy resin, and the like. Examples of the resin having a triazine ring include melamine resin. Examples of vinyl resins include vinyl ester resins.

The above resins may be used alone or in combination of two or more. At this time, two or more types of thermoplastic resins may be used, two or more types of thermosetting resins may be used, and one or more types of thermoplastic resins and one or more types of thermosetting resins may be used. good.

(hardening agent)
The curing agent is not particularly limited, and any known curing agent may be used. Specific examples of the curing agent include amine compounds, amide compounds, acid anhydride compounds, phenol compounds, etc.

Examples of the amine compounds include diaminodiphenylmethane, diethylenetriamine, triethylenetetramine, diaminodiphenylsulfone, isophoronediamine, imidazole, BF ^3- amine complex, and guanidine derivatives.

Examples of the amide compound include dicyandiamide, a polyamide resin synthesized from a dimer of linolenic acid, and ethylenediamine, and the like.

Examples of the acid anhydride compounds include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, Examples include methylhexahydrophthalic anhydride.

Examples of the phenolic compounds include phenol novolak resin, cresol novolak resin, aromatic hydrocarbon formaldehyde resin-modified phenol resin, dicyclopentadiene phenol addition type resin, phenol aralkyl resin (Zyrock resin), and resorcin novolac resin. Polyhydric phenol novolac resins synthesized from polyhydric hydroxy compounds and formaldehyde, naphthol aralkyl resins, trimethylolmethane resins, tetraphenylolethane resins, naphthol novolac resins, naphthol-phenol cocondensed novolak resins, naphthol-cresol cocondensed novolak resins , biphenyl-modified phenolic resin (a polyhydric phenol compound with a phenol nucleus linked by a bismethylene group), biphenyl-modified naphthol resin (a polyhydric naphthol compound with a phenol nucleus linked by a bismethylene group), aminotriazine-modified phenol resin (melamine, benzoguanamine) Polyhydric phenol compounds such as polyhydric phenol compounds in which the phenol nucleus is linked with phenol, etc.), alkoxy group-containing aromatic ring-modified novolac resins (polyhydric phenol compound in which the phenol nucleus and the alkoxy group-containing aromatic ring are linked with formaldehyde), etc. Can be mentioned.

The above curing agents may be used alone or in combination of two or more.

(hardening accelerator)
The curing accelerator has a function of accelerating curing when curing the resin composition.
The curing accelerator is not particularly limited, and examples thereof include phosphorus compounds, tertiary amines, imidazole, organic acid metal salts, Lewis acids, and amine complex salts.
The above-mentioned curing accelerators may be used alone or in combination of two or more.

The curing catalyst has the function of advancing the curing reaction of a compound having a polymerizable functional group instead of the curing agent.
The curing catalyst is not particularly limited, and known and commonly used thermal polymerization initiators and active energy ray polymerization initiators can be used.
Note that the curing catalyst may be used alone or in combination of two or more types.

(viscosity modifier)
The viscosity modifier has the function of adjusting the viscosity of the resin composition.
The viscosity modifier is not particularly limited, and for example, organic polymers, polymer particles, inorganic particles, etc. can be used.
The above-mentioned viscosity modifiers may be used alone or in combination of two or more.

(Plasticizer)
Plasticizers have the function of improving processability, flexibility, and weather resistance of thermoplastic synthetic resins.
The plasticizer is not particularly limited, and for example, phthalate ester, adipate ester, phosphate ester, trimellitate ester, polyester, polyolefin, polysiloxane, etc. can be used.
The above-mentioned plasticizers may be used alone or in combination of two or more.

[mixture]
The resin composition of the present invention can be obtained by mixing spinel particles, a resin, and, if necessary, other compounds. There is no particular limitation on the mixing method, and the mixing may be carried out by any known and commonly used method.
When the resin is a thermosetting resin, a general method for mixing the thermosetting resin and spinel particles is to mix a predetermined amount of the thermosetting resin, spinel particles, and other ingredients as necessary. A method of obtaining a liquid composition having fluidity by thoroughly mixing the ingredients using a mixer or the like and then kneading the mixture using a triple roll or the like can be mentioned. In addition, as a method for mixing the thermosetting resin and spinel particles in another embodiment, a predetermined amount of the thermosetting resin, spinel particles, and other components as necessary are sufficiently mixed using a mixer or the like. Afterwards, the mixture may be melt-kneaded using a mixing roll, an extruder, etc., and then cooled to obtain a solid composition. Regarding the mixing state, when a curing agent, a catalyst, etc. are blended, it is sufficient that the curable resin and the blend thereof are sufficiently uniformly mixed, but it is more preferable that the spinel particles are also uniformly dispersed and mixed.

The content of spinel particles is preferably 5% by volume or more and 95% by volume or less, more preferably 20% by volume or more and 90% by volume or less, and 30% by volume, based on the volume of the resin composition. Particularly preferred is 80% by volume or more. When the content of spinel particles is at least the above lower limit, the resin composition can be provided with more excellent thermal conductivity and dielectric properties. On the other hand, when the content of spinel particles is below the above upper limit, the resin composition has excellent fluidity and can be easily molded.

When the resin is a thermoplastic resin, a general method for mixing the thermoplastic resin with spinel particles, etc. is to mix the thermoplastic resin, spinel particles, and other components as necessary, for example, in a tumbler, Henschel mixer, etc. Examples include a method of pre-mixing using various mixers, and then melt-kneading with a mixer such as a Banbury mixer, a roll, a Brabender, a single-screw kneading extruder, a twin-screw kneading extruder, a kneader, or a mixing roll. Note that the melt-kneading temperature is not particularly limited, but is usually in the range of 100°C or higher and 320°C or lower.
A coupling agent may be externally added to the resin composition because it can further improve the fluidity of the resin composition and the filling properties with fillers such as spinel particles. In addition, by externally adding a coupling agent, the adhesion between the resin and spinel particles can be further enhanced, the interfacial thermal resistance between the resin and spinel particles can be reduced, and the thermal conductivity of the resin composition can be improved. .

Examples of the coupling agent include organic silane compounds.

Examples of the organic silane compound include methyltrimethoxysilane, dimethyldimethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, iso-propyltrimethoxysilane, and iso-propyltrimethoxysilane. - Alkyltrimethoxysilanes in which the alkyl group has 1 to 22 carbon atoms, such as propyltriethoxysilane, pentyltrimethoxysilane, hexyltrimethoxysilane, and octenyltrimethoxysilane; 3,3,3-trifluoropropyltri Methoxysilane; Alkyltrichlorosilanes in which the alkyl group has 1 to 22 carbon atoms such as tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane; phenyltrimethoxysilane, phenyltriethoxysilane, p- Chloromethylphenyltrimethoxysilane, p-chloromethylphenyltriethoxysilane; γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane , glycidoxyoctyltrimethoxysilane; γ-aminopropyltriethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxy Aminosilanes such as silane, γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane; Mercaptosilanes such as 3-mercaptopropyltrimethoxysilane; p-styryltrimethoxysilane, vinyltrichlorosilane, vinyltris(β- Vinyl silanes such as methoxyethoxy) silane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and methacryloxyoctyltrimethoxysilane; Examples include silane. In addition, the said organic silane compound may be contained independently and may contain 2 or more types.

The amount of the coupling agent added is not particularly limited, but it is preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.1% by mass or more and 3% by mass or less, based on the mass of the resin. preferable.

<Application>
According to one embodiment of the present invention, the resin composition of the present invention is used for a low dielectric heat dissipation material.
Generally, as a thermally conductive material, aluminum oxide is often used from the viewpoint of cost, and other materials such as boron nitride, aluminum nitride, magnesium oxide, and magnesium carbonate have also been used. However, these materials, for example, aluminum oxide does not have sufficient dielectric properties, boron nitride has anisotropy derived from its crystal structure, and therefore uniform dielectric properties cannot be obtained in the resin composition. Magnesium oxide and magnesium carbonate have low water resistance and therefore do not have sufficient dielectric properties. Therefore, a material that has both thermal conductivity and dielectric properties has not been found.

On the other hand, the spinel particles of the present invention have an unprecedentedly high purity and therefore have both excellent thermal conductivity and dielectric properties, and the resin composition containing the spinel particles has a low purity. Suitable for use in dielectric heat dissipation materials. Further, when the shape of the spinel particles of the present invention is spherical or true spherical, anisotropy is reduced and it becomes possible to obtain uniform dielectric properties in the resin composition, so that it is particularly suitable for use as a low dielectric material.

Since the resin composition of the present invention has excellent thermal conductivity and dielectric properties, it can be used as a base material/substrate for single-layer or multilayer printed circuit boards, flexible printed circuit boards, and the like. It can also be suitably used as an insulating material for wiring, especially for high-frequency signal wiring, such as cover lays, solder resists, build-up materials, interlayer insulating materials, bonding sheets, interlayer adhesives, and bump sheets for flip chip bonders. Can be done.

In addition, spinel particles can be used for jewelry, catalyst carriers, adsorbents, photocatalysts, optical materials, phosphors, heat-resistant insulating materials, substrates, sensors, etc.

According to one embodiment of the present invention, a molded article formed by molding the above-mentioned resin composition is provided. Since the spinel particles of the present invention contained in the molded article have excellent thermal conductivity and dielectric properties, the molded article is preferably used as a low dielectric heat dissipation member. As a result, the heat dissipation function of the device can be improved, which not only contributes to making the device smaller and lighter and has higher performance, but also contributes to higher communication functions in high-frequency circuits.

Hereinafter, the present invention will be explained in more detail based on Examples, but this description is not intended to limit the present invention. In the examples, values are expressed in terms of the number of atoms unless otherwise specified.

(Analysis of the amount of elements contained in the raw material magnesium compound)
Composition analysis was performed using a fluorescent X-ray analyzer Supermini 200 (manufactured by Rigaku Co., Ltd.) using about 5 g of a magnesium-based compound.
Using the XRF analysis results, the amount of impurities was calculated from the molar ratio (number of atoms) for elements other than oxygen. That is, the amount of impurities (atomic %)=(number of atoms other than Mg)/(number of atoms of Mg)×100.
Similarly, Ca impurity amount (atomic %)=(number of Ca atoms)/(number of Mg atoms)×100.

(Synthesis of spinel particles)
<Example 1>
70 g of alumina particles (manufactured by Denka, DAW-05, spherical, average particle size 6.4 μm) and magnesium hydroxide (Kisuma 5Q-S, manufactured by Kyowa Chemical Co., Ltd., average particle size 0.66 μm, Ca impurity amount not detected, total (impurity amount: 0.13 atomic %) was mixed in an absolute mill (manufactured by Osaka Chemical Co., Ltd.) to obtain a mixture. The obtained mixture was placed in a crucible, heated to 1300°C at 5°C/min in a ceramic electric furnace, and held at 1300°C for 10 hours to perform firing. Thereafter, the temperature was lowered to room temperature at a rate of 5° C./min, and the crucible was taken out to obtain about 90 g of white powder.

<Example 2>
The same procedure as in Example 1 was carried out except that the firing temperature was changed to 1400°C.

<Example 3>
The procedure was the same as in Example 1, except that the magnesium hydroxide was changed to Magseyz I went.

<Example 4>
The procedure was carried out in the same manner as in Example 1, except that the magnesium hydroxide was changed to MAGSTAR #5 manufactured by Tateho Industries (average particle size 0.99 μm, Ca impurity amount 0.28 at%, total impurity amount 0.7 at%). Ta.

<Example 5>
The same procedure as in Example 1 was carried out except that the alumina particles were changed to DAW-03 manufactured by Denka (spherical, average particle diameter 4.9 μm).

<Example 6>
The same procedure as in Example 1 was carried out except that the alumina particles were changed to DAW-01 (spherical, average particle diameter 1.9 μm) manufactured by Denka.

<Comparative example 1>
70 g of alumina particles (manufactured by Denka, DAW-05, spherical, average particle size 6.4 μm) and magnesium oxide (Kyowa Mag MF-150, manufactured by Kyowa Chemical Co., Ltd., average particle size 0.71 μm, Ca impurity content 0.64 atomic %) 27.67 g (total impurity amount: 1.7 at%) were mixed in an absolute mill (manufactured by Osaka Chemical Co., Ltd.) to obtain a mixture. The obtained mixture was placed in a crucible, heated to 1300°C at 5°C/min in a ceramic electric furnace, and held at 1300°C for 10 hours to perform firing. Thereafter, the temperature was lowered to room temperature at a rate of 5° C./min, and the crucible was taken out to obtain about 90 g of white powder.

<Comparative example 2>
Comparative Example 1 was carried out in the same manner as Comparative Example 1 except that the firing temperature was changed to 1400°C.

<Comparative example 3>
Comparative Example 1 was carried out in the same manner as in Comparative Example 1, except that the magnesium hydroxide was changed to MAGSTAR #20 manufactured by Kamishima Chemical Industry Co., Ltd. (average particle diameter 4 μm, Ca impurity amount 0.29 at%, total impurity amount 0.29 at%). Ta.

[Evaluation method]
The obtained spinel particles were measured and evaluated according to the following method.

(Measurement of dielectric properties)
The spinel particles obtained in the Examples and Comparative Examples were used as a test piece and filled into an EM Lab Cavity Resonator CP-001-PW, and measured using a Keysight Network Analyzer P9373A to determine the dielectric constant and dielectric loss tangent at 1 GHz. It was measured.

(Average particle size)
A small amount of the spinel particle powder obtained in Examples and Comparative Examples was placed in a beaker, 50 mL of 0.5% sodium hexametaphosphate aqueous solution was added, and then the mixture was heated for 2 minutes using an ultrasonic homogenizer Sonifier 450D (manufactured by BRANSON). A sample for measurement was prepared by dispersion treatment. The volume accumulation standard D50 of this measurement sample was measured using a laser diffraction scattering particle size distribution analyzer MT3300EXII (manufactured by Microtrac Bell Co., Ltd.).

(Analysis of the amount of elements contained in spinel particles)
Composition analysis was performed using a fluorescent X-ray analyzer Supermini 200 (manufactured by Rigaku Co., Ltd.) using about 5 g of the prepared sample.
Using the XRF analysis results, the amount of impurities was calculated from the molar ratio (number of atoms) for elements other than oxygen. That is, the amount of impurities (atomic %)=(number of atoms other than Al/Mg)/(number of Al atoms+number of Mg atoms)×100. The ratio of Al and Mg was determined by the ratio of the number of atoms using the same method.
Similarly, Ca impurity amount (atomic %)=(number of Ca atoms)/(number of Al atoms+number of Mg atoms)×100.

The crystal phase was measured using a Rigaku X-ray diffractometer Ultima IV (40 kV, 40 mA, CuKα ray). The spinel particles of Examples and Comparative Examples had MgAl ₂ O ₄ with a spinel crystal structure, and no other impurity phases were observed.

The results of each of the above evaluations are shown in Table 1. "N.D." is an abbreviation for "not detected" and represents non-detection.

From Comparative Example 3, it was found that if a magnesium compound with a large particle size was used, the mechanism of diffusion of the magnesium source into aluminum would be disrupted, resulting in an amorphous shape, so it was necessary to use a fine particle magnesium compound. .

(Preparation of resin composition)
<Example 7>
30.7 g of DIC-PPS LR100G (X-1, polyphenylene sulfide resin manufactured by DIC Corporation, density 1.35 g/cm3) as a thermoplastic resin and 69.3 g of spinel particles obtained in Example 1 were uniformly dried. After blending, they were melt-kneaded using a resin melt-kneading device Labo Plastomill at a kneading temperature of 300° C. and a rotation speed of 80 rpm to obtain a polyphenylene sulfide resin composition having a particle content of 40% by volume. The filler content (volume %) in the resin composition was calculated from the density of the thermoplastic resin and the density of the thermally conductive filler.

(Method for measuring thermal conductivity of thermoplastic resin composition)
The obtained resin composition was injection molded using a tabletop injection molding machine (Injection Molding IM 12 manufactured by Xplore) at a cylinder temperature of 320°C and a mold temperature of 140°C to produce a test piece with a diameter of 10 mm and a thickness of 0.2 mm. did. The thermal conductivity was measured at 25° C. using a thermal conductivity measuring device (LFA467 HyperFlash, manufactured by NETZSCH).

(Examples 8-9, Comparative Example 4)
A polyphenylene sulfide resin composition having a filler content of 40% by volume was prepared in the same manner as in Example 7, and its thermal conductivity was measured. Note that the fillers used are as shown in Table 2.
In Comparative Example 4, DAW-05 (manufactured by Denka Co., Ltd., spherical alumina) was used as a filler.

The resin composition containing spinel particles of this embodiment has higher thermal conductivity than resin compositions containing alumina, which generally has high thermal conductivity, and has both high thermal conductivity and low dielectric loss tangent. It can be said that we have achieved a spinel particle that has the following properties.

Claims

A spinel particle containing at least a magnesium atom, an aluminum atom, and an oxygen atom,
A spinel particle in which the amount of atoms other than the above atoms is less than 0.27 at.%.
A spinel particle containing at least a magnesium atom, an aluminum atom, and an oxygen atom,
Spinel particles in which the number of calcium atoms is less than 0.02 atomic % based on the sum of the numbers of magnesium atoms and aluminum atoms.
The spinel particles according to claim 1 or 2, having an average particle diameter of 75 μm or less.
The spinel particles according to claim 1 or 2, having a dielectric loss tangent of less than 1.0×10 −3 at 1 GHz.
A resin composition comprising the spinel particles according to claim 1 or 2 and a resin.
A molded article of the resin composition according to claim 5.
A method for producing spinel particles by mixing and firing an aluminum-based compound and a magnesium-based compound, the method comprising:
The magnesium-based compound is fine particles with an average particle size of less than 4 μm,
A method for producing spinel particles, wherein the amount of impurities contained in the magnesium-based compound is less than 1.0 atomic %.
A method for producing spinel particles by mixing and firing an aluminum-based compound and a magnesium-based compound, the method comprising:
The magnesium-based compound is fine particles with an average particle size of less than 4 μm,
A method for producing spinel particles, wherein the calcium atomic weight contained in the magnesium-based compound is 0.6 at % or less.
The manufacturing method according to claim 7 or 8, wherein the aluminum-based compound has a spherical or true spherical shape.