Silicon nitride powder, boron nitride powder, aluminum nitride powder, method for producing nitride powder, three-dimensional modeling composition, modeled object, sintered body, and method for producing modeled object

Abstract

To provide a silicon nitride powder that enables improvement of the modeling speed of a three-dimensional modeled object.SOLUTION: The silicon nitride powder of the present invention has a diffuse reflectance of 57% or more with respect to light of a wavelength of 405 nm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to silicon nitride powder, boron nitride powder, aluminum nitride powder, a method for producing nitride powders, a composition for three-dimensional modeling, a shaped object, a sintered body, a method for producing a shaped object, and a method for producing a sintered body. More specifically, the present invention relates to silicon nitride powder, boron nitride powder, aluminum nitride powder, a method for producing nitride powder, a composition for three-dimensional modeling containing silicon nitride powder, a method for producing a composition for three-dimensional modeling, a shaped object comprising a hardened body of a composition for three-dimensional modeling, a sintered body of the shaped object, a method for producing a shaped object, and a method for producing a sintered body. [Background technology]

[0002] 2. Description of the Related Art Conventionally, one known method for producing a three-dimensional object is to laminate a pattern shape using a material for three-dimensional modeling. Also known is so-called stereolithography, in which a material formed into a three-dimensional shape by lamination or the like is cured by irradiating it with electromagnetic waves such as ultraviolet light. Examples of stereolithography methods include the SLA (Stereo Lithography Apparatus) method, in which a photocurable composition is irradiated with spot-shaped ultraviolet laser light to obtain a three-dimensional object, and the DLP (Digital Light Processing) method, in which a photocurable composition is irradiated with planar light to obtain a three-dimensional object.

[0003] For example, the particles described in Patent Document 1 (JP 2023-90120 A) are known to be used as raw materials for photocuring additive manufacturing objects. Patent Document 1 discloses the use of filler particles comprising black inorganic particles such as carbon as conductive particles and a white inorganic substance such as gadolinium-doped ceria particles that coat the surfaces of the black inorganic particles. Patent Document 1 discloses that black inorganic particles absorb light from a light source, making it impossible to uniformly photocur the entire molded object. However, Patent Document 1 discloses that providing a white inorganic substance on the surfaces of the black inorganic particles produces a powder for additive manufacturing suitable for manufacturing additive manufacturing objects using stereolithography. Furthermore, Patent Document 2 (JP 2017-119363 A) discloses a technology that uses a powder that is a blend of ceramic powder and resin powder in a three-dimensional modeling apparatus to increase the initial strength of a three-dimensional model. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-90120 [Patent Document 2] Japanese Patent Application Publication No. 2017-119363 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, three-dimensional objects have been attracting increasing attention. However, the techniques described in Patent Documents 1 and 2 do not specifically consider the formability of three-dimensional objects when nitride powder is used as a raw material for the object. The reason for this is thought to be that conventional nitride powders tend to absorb light, which can lead to insufficient photocuring. Therefore, the present inventors focused on the issue of increasing the forming speed when nitride powder is used as a raw material for the three-dimensional object. [Means for solving the problem]

[0006] As a result of intensive research to solve the problems, the inventors discovered that the manufacturing speed of three-dimensional objects can be effectively increased by using the diffuse reflectance of silicon nitride powder, boron nitride powder, and aluminum nitride powder at a specific wavelength as an index, and by using silicon nitride powder, boron nitride powder, and aluminum nitride powder having a predetermined diffuse reflectance, and thus completed the first invention. Furthermore, as a result of intensive research into solving the problem, the inventor discovered that the speed at which three-dimensional objects are produced can be effectively increased by subjecting nitride powder to a specific heat treatment, and thus completed the second invention.

[0007] According to the present invention, there are provided the following silicon nitride powder, boron nitride powder, and aluminum nitride powder, as well as methods for producing nitride powders and techniques relating thereto.

[0008] [1] Silicon nitride powder with a diffuse reflectance of 57% or more for light with a wavelength of 405 nm. [2] Silicon nitride powder with a diffuse reflectance of 54% or more for light with a wavelength of 355 nm. [3] Silicon nitride powder with a diffuse reflectance of 50.5% or more for light with a wavelength of 300 nm. [4] Silicon nitride powder with a diffuse reflectance of 40.7% or more for light with a wavelength of 250 nm. [5] The silicon nitride powder according to any one of [1] to [4], which is used as a raw material for stereolithography. [6] The silicon nitride powder according to any one of [1] to [5], which is used as a raw material for additive manufacturing. [7] The silicon nitride powder according to any one of [1] to [6], A silicon nitride powder having an internal oxygen content of 0.3 mass % or less. [8] The silicon nitride powder according to any one of [1] to [7], Specific surface area is 0.1m 2 / g or more, 20m 2 / g or less silicon nitride powder. [9] The silicon nitride powder according to any one of [1] to [8], Silicon nitride powder with a β ratio of 70% or more.

[10] The silicon nitride powder according to any one of [1] to [8], Silicon nitride powder with an alpha rate of 70% or more.

[11] A composition for three-dimensional modeling, comprising the silicon nitride powder according to any one of [1] to

[10] .

[12] A modeled object made from the composition for three-dimensional modeling according to

[11] .

[13] A sintered compact of the shaped product described in

[12] .

[14] A method for producing a shaped object according to

[12] , comprising: A method for manufacturing a three-dimensional object, comprising the step of forming a predetermined pattern shape using the composition for three-dimensional modeling to obtain a three-dimensional object.

[15] A method for manufacturing a shaped object according to

[12] , comprising: The method for producing a three-dimensional object includes irradiating the composition for three-dimensional object with electromagnetic waves or electron beams to cure the composition, thereby obtaining the three-dimensional object.

[16] A step of preparing a nitride powder material containing one or more compounds selected from a group III compound, a group IV compound, and a group V compound; heat-treating the nitride powder material at 400°C or higher and 2500°C or lower to obtain nitride powder; Including, In the step of obtaining the nitride powder, the nitride powder material is put into a furnace and heating is started, the internal pressure of the furnace is set to 50 Pa or less at temperatures below 100°C, and gas is introduced at temperatures above 100°C, the flow rate of the gas introduced into the furnace is set to A (L / min), and the volume of the furnace is set to B (m 3 ) and adjust the ratio A / B so that A / B>5.

[17] A method for producing a nitride powder according to

[16] , The method for producing nitride powder, wherein the gas introduction temperature during the heat treatment is 400°C or higher.

[18] A method for producing a nitride powder according to

[17] , The method for producing a nitride powder, wherein the nitride powder is one or more particles selected from silicon nitride particles, aluminum nitride particles, and boron nitride particles.

[19] Boron nitride powder with a diffuse reflectance of 93% or more for light with a wavelength of 355 nm.

[20] Aluminum nitride powder with a diffuse reflectance of 74% or more for light with a wavelength of 405 nm. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide silicon nitride powder, boron nitride powder, and aluminum nitride powder that can improve the speed of manufacturing three-dimensional objects, as well as methods for manufacturing nitride powders and techniques related thereto. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing an example of a chart obtained by oxygen / nitrogen analysis of silicon nitride. [Figure 2] FIG. 1 is a diagram showing a schematic configuration of a UV irradiation test in an example. [Figure 3] FIG. 1 is a graph showing the relationship between the diffuse reflectance (%) and the treatment temperature (° C.) of the silicon nitride powders of Examples 1-6 of the first and second examples. [Figure 4] FIG. 1 is a graph showing the relationship between the diffuse reflectance (%) at 405 nm and the thickness (relative value) of the hardened region of the silicon nitride powders of Examples 1-12 and Comparative Examples 1-3 of the first embodiment. [Figure 5] FIG. 1 is a graph showing the relationship between the diffuse reflectance (%) at 355 nm and the thickness (relative value) of the hardened region of the silicon nitride powders of Examples 1-12 and Comparative Examples 1-3 of the first embodiment. [Figure 6] FIG. 2 is a graph showing the relationship between diffuse reflectance (%) and wavelength (nm) for silicon nitride powders of Examples 1 to 6 of the first and second examples and Comparative Example 1. [Figure 7] FIG. 1 is a graph showing the relationship between diffuse reflectance (%) and wavelength (nm) for silicon nitride powders of Examples 7-12 of the first embodiment. [Figure 8] 1 is a graph showing the relationship between the frequency (volume %) and particle size (μm) of silicon nitride powders of Examples 1 to 6 of the first and second examples and Comparative Example 1. FIG. [Figure 9] FIG. 1 is a graph showing the relationship between the frequency (volume %) and particle size (μm) of silicon nitride powders of Examples 7-12 of the first embodiment. [Figure 10] FIG. 2 is a diagram showing X-ray diffraction patterns of silicon nitride powders of Examples 1 to 6 of the first and second examples and Comparative Example 1. [Figure 11] FIG. 11 is an enlarged view of FIG. [Figure 12] FIG. 1 shows X-ray diffraction patterns of silicon nitride powders of Examples 7-12 of the first embodiment. [Figure 13] FIG. 13 is an enlarged view of FIG. [Figure 14] FIG. 10 is a graph showing the relationship between the diffuse reflectance (%) at 405 nm and the thickness (mm) of the hardened region of the silicon nitride powders of Examples 1-6 and Comparative Examples 1-3 of the second example. [Figure 15] FIG. 10 is a graph showing the relationship between the diffuse reflectance (%) at 355 nm and the thickness (mm) of the hardened region of the silicon nitride powders of Examples 1-6 and Comparative Examples 1-3 of the second example. [Figure 16] FIG. 10 is a graph showing the relationship between the diffuse reflectance (%) and the treatment temperature (° C.) of the boron nitride powders of the examples and comparative examples of the second example. [Figure 17] FIG. 10 is a graph showing the relationship between the diffuse reflectance (%) at 405 nm and the thickness (mm) of the hardened region of the boron nitride powders of the examples and comparative examples of the second example. [Figure 18] FIG. 10 is a graph showing the relationship between the diffuse reflectance (%) at 355 nm and the thickness (mm) of the hardened region of the boron nitride powders of the examples and comparative examples of the second embodiment. [Figure 19] FIG. 10 is a graph showing the relationship between diffuse reflectance (%) and wavelength (nm) of boron nitride powders of each example and comparative example of the second embodiment. [Figure 20] FIG. 10 is a graph showing the relationship between the frequency (volume %) and particle size (μm) of boron nitride powder in each example and comparative example of the second example. [Figure 21] FIG. 10 is a diagram showing X-ray diffraction patterns of boron nitride powders of the example and comparative example of the second example. [Figure 22] FIG. 10 is a diagram showing X-ray diffraction patterns of boron nitride powders of the example and comparative example of the second example. [Figure 23] FIG. 10 is a graph showing the relationship between the diffuse reflectance (%) and the treatment temperature (° C.) of the aluminum nitride powders of the examples and comparative examples of the second embodiment. [Figure 24] FIG. 10 is a graph showing the relationship between the diffuse reflectance (%) at 405 nm and the thickness (mm) of the hardened region of the aluminum nitride powders of the examples and comparative examples of the second example. [Figure 25]FIG. 10 is a graph showing the relationship between the diffuse reflectance (%) at 355 nm and the thickness (mm) of the hardened region of the aluminum nitride powders of the examples and comparative examples of the second embodiment. [Figure 26] FIG. 10 is a graph showing the relationship between the diffuse reflectance (%) and wavelength (nm) of the aluminum nitride powders of the examples and comparative examples of the second embodiment. [Figure 27] FIG. 10 is a graph showing the relationship between the frequency (volume %) and particle size (μm) of aluminum nitride powder in each example and comparative example of the second embodiment. [Figure 28] FIG. 10 is a diagram showing X-ray diffraction patterns of aluminum nitride powders of each of the examples of the second embodiment and the comparative example. [Figure 29] FIG. 10 is a diagram showing X-ray diffraction patterns of aluminum nitride powders of each of the examples of the second embodiment and the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail.

[0012] In this specification, the expression "a to b" in the description of a numerical range means from a to b, unless otherwise specified. For example, "1 to 5 mass%" means "1 mass% to 5 mass%." Furthermore, the lower limit and upper limit of a numerical range can be arbitrarily combined with the lower limit and upper limit of another numerical range.

[0013] Unless otherwise specified, each of the components and materials exemplified in this specification may be used alone or in combination of two or more.

[0014] The gas content (vol %) in this specification is a value under standard conditions (0° C., 1 atm).

[0015] 1. Manufacturing method of nitride powder (A) The method for producing the nitride powder (A) of this embodiment is as follows: A step (step 1) of preparing a nitride powder material (a) containing one or more compounds selected from group III compounds, group IV compounds, and group V compounds; and a step (step 2) of heat-treating the nitride powder material (a) at 400°C or higher and 2500°C or lower to obtain nitride powder (A), In the step of obtaining nitride powder (A), the nitride powder material (a) is put into a furnace and heating is started, the internal pressure of the furnace is set to 50 Pa or less at temperatures below 100°C, and gas is introduced at temperatures above 100°C, the flow rate of the gas introduced into the furnace is set to A (L / min), and the volume of the furnace is set to B (m 3 ) and adjust it so that A / B>5. That is, by controlling the temperature and pressure under specified conditions and subjecting nitride powder material (a) to heat treatment at 400°C or higher and 2500°C or lower, it is possible to obtain nitride powder (A) that can improve the speed at which three-dimensional objects can be fabricated. Although the details of why this happens are not clear, it is speculated that the heat treatment changes the surface condition of nitride powder (A), making it more likely to reflect light, thereby improving the speed of stereolithography.

[0016] In this embodiment, the nitride powder (A) is preferably one or more types selected from silicon nitride particles, aluminum nitride particles, and boron nitride particles. Each step will be described in detail below.

[0017] (Step 1) Step of preparing nitride powder material (a) First, the nitride powder material (a) is a powder containing nitride, and is a raw material for the nitride powder (A). The nitride powder material (a) may be a commercially available product or one prepared by reaction, such as silicon nitride powders such as "9FWS" manufactured by Denka and "E10" manufactured by Ube Industries, aluminum nitride powders such as "E Grade" manufactured by Tokuyama, and boron nitride particles such as "SP-2" manufactured by Denka.

[0018] The preparation of the nitride powder material (a) by reaction will be described below.

[0019] <Preparation of silicon nitride powder material> First, silicon powder and other raw material powders are filled into a container. When the oxygen concentration of the silicon powder is high, for example, the amount of oxygen bonded to the silicon powder can be reduced using a pretreatment liquid containing hydrofluoric acid. In this case, the method may further include a pretreatment step of pretreating the silicon powder with a pretreatment liquid containing hydrofluoric acid to obtain silicon powder with an oxygen concentration of 0.4 mass%. The pretreatment liquid may contain hydrofluoric acid. The pretreatment liquid may be, for example, a mixed acid with an acid such as hydrochloric acid, or may consist solely of hydrofluoric acid. The temperature of the pretreatment liquid in the pretreatment step may be, for example, 40 to 80°C. The contact time between the pretreatment liquid and the silicon powder may be, for example, 1 to 10 hours.

[0020] In addition to silicon powder, the raw material powder may optionally contain a fluoride containing Li, Na, K, Mg, Ca, Sr, or Ba as a constituent element to promote nitridation. However, from the viewpoint of reducing the fluorine content of the silicon nitride powder, the content of the fluoride per 100 parts by mass of silicon powder is preferably 0.5 parts by mass or less, more preferably 0.3 parts by mass or less. From the viewpoint of sufficiently reducing the fluorine content of the silicon nitride powder, the raw material powder does not need to contain fluoride. If necessary, the silicon powder may be pretreated with an acid to reduce impurities in the silicon powder.

[0021] The container can be made of a material that does not change in quality up to a temperature of 1500°C in an inert atmosphere, and specifically, for example, alumina, boron nitride, or carbon can be used. The structure of the container is not particularly limited, and for example, a container that can form a storage space for storing raw material powder can be used. From the viewpoint of handleability, the container may include a container body having a recess and a lid that covers the recess in the body. The amount of raw material powder to be filled is adjusted as appropriate, but is, for example, 0.7 to 1.6 g / cm 3 It may also be possible to use the following.

[0022] The raw material powder packed in the container is then fired in an atmosphere containing nitrogen gas to obtain a fired product containing silicon nitride. The firing can nitride the silicon powder contained in the raw material powder. The concentration of nitrogen gas in the atmosphere during firing may be 90% by volume or more, 95% by volume or more, or 97% by volume or more.

[0023] The firing atmosphere may contain nitrogen gas and other gases different from nitrogen gas. Examples of other gases include argon gas and hydrogen gas. The addition of argon gas can adjust the reaction rate of the nitriding reaction. The addition of hydrogen gas reduces oxides such as SiO2 contained in the raw material powder, making it easier to produce a nitride powder (A) with high purity. From this viewpoint, the hydrogen gas content in the firing atmosphere may be 1% by volume or more, or may be 2% by volume or more. On the other hand, from the viewpoint of promoting nitriding of the silicon powder, the hydrogen gas content in the firing atmosphere may be 5% by volume or less. An example of the hydrogen gas content in the firing atmosphere is 1 to 5% by volume.

[0024] The firing temperature may be, for example, 1100 to 1450° C. or 1200 to 1400° C. The firing time may be, for example, 30 to 100 hours. Furthermore, the firing process may include multiple stages in which the firing temperature ranges are different from one another.

[0025] Furthermore, the obtained fired product may be pulverized. The pulverization may be carried out in multiple stages, including coarse pulverization and fine pulverization. The pulverization may be carried out wet using, for example, a ball mill. When the specific surface area of ​​the fired product is 8.0 to 15.0 m, 2 It may be ground to a concentration of 1 / g. The time for the pulverization treatment (pulverization time) in the ball mill pulverization step may be 5 to 15 hours, or 8 to 12 hours, which makes it possible to sufficiently finely disintegrate aggregated particles while preventing excessive pulverization.

[0026] The pulverized product obtained in the ball mill pulverization step may be further pulverized in a vibration mill pulverization step. The ball filling rate in the container in the vibration mill pulverization step may be 50 to 80 volume % or 60 to 75 volume %. The pulverization time in the vibration mill pulverization step (pulverization time) may be 8 to 20 hours or 12 to 17 hours.

[0027] Furthermore, classification may be carried out to adjust the particle size of the pulverized material.

[0028] <Preparation of boron nitride powder material> In order to effectively obtain hexagonal boron nitride powder as one of the boron nitride powder materials, first, an oxygen-containing calcium compound, an oxygen-containing boron compound, and a carbon source are mixed as follows.

[0029] (oxygen-containing calcium compounds) The oxygen-containing calcium compound forms a composite oxide with the oxygen-containing boron compound, which serves as a grain growth catalyst for boron nitride particles. Examples of oxygen-containing calcium compounds include calcium carbonate, calcium bicarbonate, calcium hydroxide, calcium oxide, calcium nitrate, calcium sulfate, calcium phosphate, and calcium oxalate. Of these, oxygen-containing calcium compounds are preferably used. Examples of oxygen-containing calcium compounds that can be used include calcium carbonate, calcium bicarbonate, calcium hydroxide, calcium oxide, calcium nitrate, calcium sulfate, calcium phosphate, and calcium oxalate. Two or more of these compounds can also be used in combination. Of these, calcium oxide and calcium carbonate are preferably used. Two or more of the oxygen-containing calcium compounds can also be used in combination. The average particle size of the oxygen-containing calcium compound is preferably 0.01 to 200 μm, more preferably 0.05 to 120 μm, and particularly preferably 0.1 to 80 μm.

[0030] (carbon source) The carbon source acts as a reducing agent, and it is preferable to use one containing a specific amount of sulfur in order to ensure that sulfur contributes to the reaction. As the carbon source, a petroleum-derived carbon source that already contains sulfur is preferred. Although the sulfur can be added as elemental sulfur separately from the carbon source, it is preferable that the sulfur be in close proximity to the carbon source. In this case, it is preferable to premix the sulfur and the carbon source in advance, for example, using a ball mill. If the premixing is omitted, not only will the sulfur volatilize violently during the reaction, requiring the addition of a large amount, but there is also a risk of sulfur scattering into the exhaust system of the reactor, causing blockage. The concentration of sulfur contained in the carbon source is 1000 to 10000 ppm, preferably 1500 to 8000 ppm, and more preferably 2000 to 6000 ppm. The carbon source is preferably amorphous carbon, which has high reactivity, and carbon black is particularly preferred because it is industrially quality controlled.The average particle size of the carbon source is preferably 0.01 to 3 μm, more preferably 0.02 to 2 μm, and particularly preferably 0.05 to 1 μm.

[0031] (Preparation of raw materials) The reduction-nitridation reaction is carried out by supplying a carbon source and nitrogen, and in order to effectively obtain the desired hexagonal boron nitride powder, the ratio of B contained in the oxygen-containing boron compound and composite oxide to C contained in the carbon source, calculated as B / C (element ratio), is 0.75 to 0.85, preferably 0.77 to 0.83.

[0032] To effectively obtain the desired hexagonal boron nitride powder, the oxygen-containing calcium compound is mixed in a ratio of 10 to 15 parts by mass, calculated as CaO, for 100 parts by mass of the total amount of the oxygen-containing boron compound and the carbon source (calculated as B2O3 and C).

[0033] In the method for producing a boron nitride powder material, the form in which the mixture containing the above-mentioned raw materials is supplied to the reaction is not particularly limited; it may be in powder form or may be formed into granules. To mix the raw materials, a common mixer such as a vibration mill, bead mill, ball mill, Henschel mixer, drum mixer, vibration agitator, or V-shaped mixer can be used. For granulation, a binder can be used as needed, and known methods such as extrusion granulation, rolling granulation, and compactor granulation can be used. In this case, the size of the granules is preferably about 5 to 10 mm.

[0034] (reduction nitridation) In the method for producing a boron nitride powder material, the nitrogen source can be supplied to the reaction system by known means. For example, the most preferred method is to circulate nitrogen gas through the reaction system of the reactor illustrated below. The nitrogen source to be used is not limited to the nitrogen gas described above, and any gas capable of nitriding in the reduction-nitridation reaction can be used. Specifically, ammonia gas can be used in addition to the nitrogen gas described above. A mixed gas obtained by mixing nitrogen gas or ammonia gas with a non-oxidizing gas such as hydrogen, argon, or helium can also be used.

[0035] To obtain hexagonal boron nitride powder, it is important to heat the reaction at 1450-1550°C for at least 4 hours and at 1650-2100°C for at least 2 hours. That is, heating for at least 4 hours in the temperature range of 1450-1550°C, where the reduction-nitridation reaction begins, facilitates layering of the hexagonal crystal planes, enabling the highly selective production of hexagonal boron nitride particles with a high amount of NH groups on the particle edge faces and a low aspect ratio. Temperatures below 1450°C are undesirably slow, while temperatures above 1550°C are undesirably too fast. Furthermore, temperatures less than 4 hours are undesirable due to the insufficient reaction time. Furthermore, to obtain highly crystalline hexagonal boron nitride particles, the maximum heating temperature for the reduction-nitridation reaction is 1650-2100°C, preferably 1700-2100°C, and more preferably 1800-2000°C, for at least 2 hours.

[0036] The method for producing hexagonal boron nitride powder can be carried out using a known reaction apparatus capable of controlling the reaction atmosphere, such as an atmosphere-controlled high-temperature furnace in which heat treatment is performed by high-frequency induction heating or heater heating, or a batch furnace or a continuous furnace such as a pusher-type tunnel furnace or a vertical reactor.

[0037] (acid washing) The reaction product obtained by the above-mentioned reduction nitridation contains impurities such as a composite oxide of boron oxide and calcium oxide in addition to the hexagonal boron nitride powder, so it is preferable to wash it with an acid. The acid washing method is not particularly limited, and known methods can be used without limitation. For example, the by-product-containing boron nitride obtained after the nitriding treatment is crushed and placed in a container, and dilute hydrochloric acid (10 to 20% by mass HCl) is added in an amount 5 to 10 times the amount of the impurity-containing hexagonal boron nitride powder, and the mixture is allowed to contact for at least 4 hours. In addition to hydrochloric acid, other acids such as nitric acid, sulfuric acid, and acetic acid can also be used in the acid washing. After the acid washing, the product is washed with pure water to remove any remaining acid. One method for washing the product is to filter the acid used in the acid washing, disperse the acid-washed boron nitride in pure water in an amount equal to the amount of acid used, and then filter again.

[0038] (Dry) The conditions for drying the hydrous aggregates after the acid washing and water washing are preferably, for example, drying in the air or under reduced pressure at 50 to 250° C. The drying time is not particularly specified, but it is preferable to dry until the moisture content approaches 0%.

[0039] (classification) The dried boron nitride powder may be subjected to rough crushing, removal of coarse particles using a sieve or the like, and removal of fine particles using air classification or the like, as required.

[0040] <Preparation of aluminum nitride powder material> Aluminum nitride powder material can be obtained by heat treating boehmite powder in a non-oxidizing atmosphere containing ammonia (NH3) or by mixing it with a carbon-containing substance.

[0041] Examples of the ammonia (NH3)-containing non-oxidizing atmosphere include an ammonia (NH3) gas atmosphere, or an ammonia (NH3) and nitrogen (N2) mixed gas atmosphere having an ammonia (NH3) content of 70% by volume or more but less than 100% by volume, with the remainder being nitrogen (N2). In the case of an ammonia (NH3) and nitrogen (N2) mixed gas, the ammonia (NH3) content is preferably 75 to 95% by volume. The heat treatment temperature for promoting the AlN production reaction can be 1200 to 1600°C, and more preferably 1300 to 1550°C.

[0042] The heat treatment can be carried out by placing the raw material powder in a furnace with an air-tight structure, maintaining the furnace atmosphere in a predetermined ammonia-containing non-oxidizing atmosphere, and raising the temperature of the powder in the furnace to the predetermined range. The pressure in the furnace may be atmospheric pressure. During the heat treatment, in order to maintain the atmospheric gas composition in the furnace within a constant range, it is desirable to pass an externally supplied ammonia-containing gas through the furnace and expose the powder to the gas flow. The powder is desirably placed in the furnace in as thin a state as possible so that individual particles can easily come into contact with the atmospheric gas components. For example, if the powder is deposited on a tray and the tray is placed in the furnace, the thickness of the powder deposited on the tray is preferably 5 mm or less.

[0043] The above heat treatment time is sufficient to convert all of the raw material boehmite powder placed in the furnace into aluminum nitride (AlN). The required firing time varies depending on the specific surface area of ​​the raw material powder, the heating temperature, the atmospheric gas composition, and the deposition state of the powder placed in the furnace. For example, if the BET specific surface area is 180 to 300 m, 2 When boehmite powder of about 1 / g is heated to 1200 to 1600°C in a non-oxidizing atmosphere with an ammonia (NH3) content of 70 to 100% by volume, an appropriate heating time can usually be set within the range of 2 to 10 hours, more preferably within the range of 4 to 8 hours. The obtained aluminum nitride powder may be subjected to rough crushing, removal of coarse particles by sieving or the like, and removal of fine particles by air classification or the like, as required.

[0044] By the above-described procedure, the nitride powder material (a) is prepared.

[0045] (Step 2) Heat treatment Next, the nitride powder material (a) is heat-treated at 400°C or higher and 2500°C or lower. Specifically, the nitride powder material (a) is heat-treated at 400°C or higher and 2500°C or lower while controlling the atmosphere, packing density, and pressure in the pot. This improves the surface reflectivity of the resulting nitride powder (A). This is thought to be because controlling the atmosphere, packing density, pressure, temperature, and pot material makes it easier to reduce defects caused by nitrogen vacancies and oxygen intrusion and solid solution, thereby reducing excess light absorption. Alternatively, the heat treatment may be initiated after the nitride powder material (a) is filled into the pot at room temperature. Heating is initiated from room temperature and continued while evacuating to 400°C or higher, preferably 800°C or higher, thereby expelling moisture adsorbed on the nitride powder (A) and moisture desorbed from water of crystallization (OH groups) from the furnace. Subsequent gas introduction reduces impurities such as moisture in the atmosphere, enabling efficient removal of defects in the nitride powder (A). The heat treatment temperature is 400 to 2500°C, preferably 1000 to 2300°C, and more preferably 1500 to 2000°C. The heat treatment temperature is preferably 1650°C to 2000°C, more preferably 1700°C to 2000°C, from the viewpoint of reducing the internal oxygen content, and is preferably 1500°C to 1800°C, more preferably 1500°C to 1700°C, from the viewpoint of reducing nitrogen defects and improving surface reflectivity, etc. The heat treatment temperature may also be set depending on the type of nitride. For example, in the case of silicon nitride, the temperature is preferably 1600°C to 1800°C, in the case of boron nitride, the temperature is preferably 1600°C to 1800°C, and in the case of aluminum nitride, the temperature is preferably 1400°C to 1600°C. By setting the heat treatment temperature at or above the lower limit, surface reflectivity and the like can be increased, and the molding speed can be improved. On the other hand, by setting the heat treatment temperature at or below the upper limit, good surface reflectivity and the like can be obtained while improving the moldability of the nitride powder (A). Furthermore, the heat treatment may be performed by holding the temperature during the temperature rise, or by adjusting the temperature rise rate or cooling rate. The temperature held during the temperature rise is preferably 600°C, 800°C, 1000°C, 1200°C, 1400°C, or a temperature around the above. The holding time is preferably 2 hours, 6 hours, 12 hours, 36 hours, or a temperature around the above. The temperature rise rate may be 10°C / min or less, 1°C / min or less, or 0.1°C / min or less. The cooling rate may be 0.1°C / min or more, 1°C / min or more, 10°C / min or more, or 100°C / min or more. It is preferable to start the heat treatment at a temperature of 50°C or below. Furthermore, it is desirable that the pot material has as low a density as possible, since this makes it easier to expel unwanted components from inside the pot.

[0046] Furthermore, pressure may be applied during the heat treatment, preferably under a pressure of 0.001 to 100 MPaG, more preferably under a pressure of 0.005 to 10 MPaG, and even more preferably under a pressure of 0.020 to 1 MPaG. By setting the pressure during the heat treatment to be equal to or higher than the lower limit, it becomes easier to increase the surface reflectivity, etc. On the other hand, by setting the pressure during the heat treatment to be equal to or higher than the upper limit, it becomes easier to obtain good surface reflectivity, etc., while also improving the moldability of the nitride powder (A). For example, it is preferable that the heat treatment is carried out in a vacuum of 100 Pa or less from the start of heating until the temperature reaches 800°C, and then in a gas atmosphere at 800°C or higher.

[0047] Furthermore, the heat treatment is preferably carried out in an inert gas, a reducing gas, or under vacuum, i.e., by introducing a predetermined gas into a furnace. Examples of inert gases include rare gas elements such as helium, neon, and argon, as well as nitrogen gas, etc. Examples of reducing gases include chlorine gas, hydrogen sulfide gas, ammonia gas, sulfur oxide gas, hydrogen gas, and nitrogen oxide gas, etc.

[0048] In this embodiment, the nitride powder material (a) is put into a furnace and heating is started, the internal pressure of the furnace is set to 50 Pa or less at temperatures below 100°C, and gas is introduced at temperatures above 100°C, the flow rate of the gas introduced into the furnace is set to A (L / min), and the volume of the furnace is set to B (m 3 ), the ratio is adjusted so that A / B>5. By setting A / B>5, the gas generated from the nitride powder (A) can be efficiently discharged outside the furnace, reducing impurities in the atmosphere and efficiently removing defects in the nitride powder (A). (Gas flow rate (L / min)) ÷ (Furnace volume (m 3 ))(A / B) is preferably 10 or more, and more preferably 20 or more. It is also preferable to discharge the gas so that the pressure inside the furnace is kept constant. That is, from the start of heating until the temperature reaches at least 100°C, it is preferable to keep the internal pressure in the furnace at 50 Pa or less by vacuum treatment, and the internal pressure in the furnace after reaching 100°C may be 50 Pa or less or may exceed 50 Pa. Furthermore, as long as the temperature is 100°C or higher, gas may be introduced at any time; for example, the gas introduction temperature may be 400°C or higher, and gas may be introduced once 1000°C is reached. In addition, it is preferable to start the heat treatment at a temperature of 50° C. or less.

[0049] The heat treatment is preferably carried out by filling the nitride powder material (a) into a container. Examples of the container include ceramics such as boron nitride and silicon nitride, and metals such as tungsten and molybdenum. The pot (container) for containing the nitride powder (A) is preferably made of boron nitride, which has a relatively low density, in order to efficiently volatilize the gas generated from the nitride powder (A). The amount of the nitride powder material (a) to be filled is adjusted appropriately, but for example, the bulk density is set to 0.3 to 1.6 g / cm 3 It can also be 1.14 g / cm 3 It is preferable to do the following: By setting the amount of nitride powder (A) packed in the pot (container) to the above upper limit or less, gas generated from the nitride powder (A) can be efficiently volatilized outside the pot (container).

[0050] The resulting nitride powder (A) may also be pulverized. The pulverization may be carried out in multiple stages, including coarse pulverization and fine pulverization. The pulverization may be carried out wet using, for example, a ball mill. When the specific surface area of ​​the fired product is 3.0 to 15.0 m, 2 It may be ground to a concentration of 1 / g. The time for the pulverization treatment (pulverization time) in the ball mill pulverization step may be 5 to 100 hours, or 8 to 12 hours, which makes it possible to sufficiently finely disintegrate aggregated particles while preventing excessive pulverization.

[0051] The pulverized product obtained in the ball mill pulverization step may be further pulverized in a vibration mill pulverization step. The ball filling rate in the container in the vibration mill pulverization step may be 50 to 80 volume % or 60 to 75 volume %. The pulverization time in the vibration mill pulverization step (pulverization time) may be 8 to 20 hours or 12 to 17 hours.

[0052] Furthermore, in order to adjust the particle size of the pulverized material, classification may be carried out using a sieve, for example, a sieve with openings of 20 to 350 μm.

[0053] When using a wet ball mill or wet jet mill, a filtration or drying process may be performed. Filtration may be performed by vacuuming to separate the solvent, or by applying gas or mechanical pressure to the slurry to push the solvent out of the filter paper or filter. Natural drying, heat drying, or vacuum and heat drying may also be used. Before drying, the nitride powder may be allowed to settle using centrifugal force, and the supernatant may be removed before drying. Alternatively, an acid or alkali may be used to adjust the isoelectric point and promote sedimentation, and the supernatant may be removed before drying.

[0054] The obtained nitride powder (A) may be subjected to rough crushing, removal of coarse particles by sieving or the like, and removal of fine particles by air classification or the like, if necessary.

[0055] By such a production method, the nitride powder (A) of this embodiment can be obtained.

[0056] 2. Nitride powder (A) Next, the nitride powder (A) will be described in detail. The nitride powder (A) is a particle group containing primary particles of nitride. The nitride powder (A) may further contain agglomerated particles (secondary particles) formed by agglomeration of the primary particles of nitride. The purity of the nitride in the nitride powder (A) may be 98% by mass or more, or may be 99% by mass or more. When the nitride is silicon nitride, the primary particles and aggregated particles in the nitride powder (A) may have an oxide such as silicon dioxide on their surfaces. That is, the surfaces may be partially or entirely covered with a coating layer. However, it is preferable that the coating layer is one other than a Y-Si-ON composite film. The thickness of the coating layer may be less than 1 nm.

[0057] The nitride powder (A) is preferably one or more selected from silicon nitride particles, aluminum nitride particles, and boron nitride particles, and more preferably contains silicon nitride particles, which have higher thermal conductivity than other oxides and other substances, and can be easily molded. Among these, boron nitride particles are preferred in terms of obtaining high thermal conductivity. Furthermore, aluminum nitride particles are preferred in terms of obtaining higher thermal conductivity than silicon nitride and of obtaining a sintered product with higher mechanical strength than boron nitride. Silicon nitride particles are preferred in terms of obtaining a sintered product with higher mechanical strength than boron nitride. Furthermore, silicon nitride particles are preferably used in terms of having a lower specific gravity than alumina or metals and having higher chemical resistance and moisture resistance than metals.

[0058] (particle size) The nitride powder (A) of this embodiment preferably has a particle size at 90% of the cumulative total (D90) of 1 to 200 μm, more preferably 1 to 100 μm, and even more preferably 1 to 50 μm, as determined from the volume-based particle size distribution measured with a particle size distribution measuring device using a laser diffraction / scattering method for primary particles. The nitride powder (A) of this embodiment preferably has a particle size at 50% of the cumulative total (D50) of 0.1 to 60 μm, more preferably 0.2 to 30 μm, and even more preferably 0.5 to 15 μm, as determined from the volume-based particle size distribution measured with a particle size distribution analyzer using a laser diffraction / scattering method for primary particles. The nitride powder (A) of this embodiment preferably has a particle size (D10) at 10% cumulative volume determined from the volume-based particle size distribution measured with a particle size distribution analyzer using a laser diffraction / scattering method for primary particles of 0.1 to 10 μm, more preferably 0.2 to 8 μm or less, and even more preferably 0.3 to 5 μm. By setting the particle size within the above numerical range, it becomes easier to improve the modeling speed. Furthermore, by setting the particle size at or above the above lower limit, it becomes possible to control the viscosity low when mixed with resin, and set the viscosity to facilitate additive manufacturing. Furthermore, by setting the particle size at or below the above upper limit, it becomes possible to reduce the surface roughness during sintering. The particle size can be controlled by adjusting classification and pulverization conditions.

[0059] (specific surface area) The nitride powder (A) of this embodiment has a specific surface area of ​​0.1 to 20 m 2 / g, and 0.2 to 10m 2 / g is more preferable, and 0.5 to 8m 2 / g is even more preferable. By setting the specific surface area to be equal to or greater than the above lower limit, sintering becomes easier. On the other hand, by setting the specific surface area to be equal to or less than the above upper limit, the frequency with which irradiated light hits the nitride powder (A) during stereolithography decreases, the probability that irradiated light is absorbed by the nitride powder (A) decreases, the curing speed of the photocurable resin increases, and the modeling speed becomes easier to improve. Furthermore, by setting the specific surface area to be equal to or less than the above upper limit, the viscosity does not increase too much when the nitride powder (A) is mixed with a resin, making it easier to layer the nitride powder (A). The specific surface area, BET specific surface area, can be measured by the BET single-point method using nitrogen gas in accordance with JIS Z 8803:2013.

[0060] The specific surface area is controlled by the manufacturing conditions of the nitride powder (A), and can be controlled to a low value by promoting sintering and particle growth through heat treatment, or to a high value by pulverizing using jet milling or ball milling. It can also be controlled to a low value by removing fine powder through classification, or to a high value by removing coarse powder. By controlling the specific surface area low, the viscosity can be controlled low when mixed with resin, making it possible to set a viscosity that is easy to use in additive manufacturing.

[0061] (Application) The nitride powder (A) of this embodiment can be suitably used for various applications. For example, when used as a raw material for three-dimensional modeling, a modeled object having excellent mechanical properties can be obtained. Examples of three-dimensional modeling include at least one method selected from additive manufacturing and photolithography.

[0062] <Silicon nitride powder> The silicon nitride powder will be described in detail below. The silicon nitride powder is a particle group containing primary particles of silicon nitride. The silicon nitride powder may further contain agglomerated particles (secondary particles) formed by agglomeration of the primary particles of silicon nitride. The primary particles and aggregated particles in the silicon nitride powder may have an oxide such as silicon dioxide on their surfaces. The purity of silicon nitride in the silicon nitride powder may be 98% by mass or more, or may be 99% by mass or more.

[0063] (diffuse reflectance) The silicon nitride powder of this embodiment has a diffuse reflectance of 57% or more for light with a wavelength of 405 nm, more preferably 58% or more, more preferably 60% or more, more preferably 70% or more, and even more preferably 75% or more. In one embodiment, the diffuse reflectance may be 80% or more, or even 90% or more. This allows electromagnetic waves irradiated onto the silicon nitride powder to be efficiently reflected and diffused around the silicon nitride powder. As a result, when the silicon nitride powder is used as a material for stereolithography, the curability of the material can be improved, and the modeling speed can be increased. The upper limit of the diffuse reflectance of silicon nitride powder for light with a wavelength of 405 nm is not particularly limited, but may be, for example, 100% or less, or 99% or less. In addition, light with a wavelength of 405 nm is widely used as an LED or laser for photopolymerization, and acts efficiently on photopolymerization initiators in UV-curable resins, allowing them to be cured efficiently through polymerization caused by the generation of radicals.

[0064] The silicon nitride powder of this embodiment has a diffuse reflectance of 54% or more for light with a wavelength of 355 nm, preferably 57% or more, more preferably 66% or more, and even more preferably 70% or more. In one embodiment, the diffuse reflectance may be 80% or more, or even 90% or more. This allows electromagnetic waves irradiated onto the silicon nitride powder to be efficiently reflected and diffused around the silicon nitride powder. As a result, when the silicon nitride powder is used as a material for stereolithography, the curability of the material can be improved, and the modeling speed can be increased. The upper limit of the diffuse reflectance of silicon nitride powder for light with a wavelength of 355 nm is not particularly limited, but may be, for example, 100% or less, or 99% or less. Furthermore, because light with a wavelength of 355 nm is a short wavelength, it has more energy than light with a wavelength of 405 nm, and is widely used in LEDs and lasers for stereolithography. It acts efficiently as a photopolymerization initiator for ultraviolet-curing resins, and can be cured efficiently through polymerization caused by the generation of radicals.

[0065] The silicon nitride powder of this embodiment has a diffuse reflectance of 50.5% or more for light with a wavelength of 300 nm, preferably 51% or more, more preferably 57% or more, and even more preferably 67% or more. In one embodiment, the diffuse reflectance may be 80% or more, or even 90% or more. This allows electromagnetic waves irradiated onto the silicon nitride powder to be efficiently reflected and diffused around the silicon nitride powder. As a result, when the silicon nitride powder is used as a material for stereolithography, the curability of the material can be improved, and the modeling speed can be increased. The upper limit of the diffuse reflectance of silicon nitride powder for light with a wavelength of 300 nm is not particularly limited, but may be, for example, 100% or less, or 99% or less. Furthermore, because light with a wavelength of 300 nm is a short wavelength, it has more energy than light with a wavelength of 405 nm, and acts efficiently on the photopolymerization initiator of ultraviolet curing resins, allowing for efficient curing through polymerization caused by the generation of radicals, etc.

[0066] The silicon nitride powder of this embodiment has a diffuse reflectance of 40.7% or more for light with a wavelength of 250 nm, preferably 43% or more, more preferably 46% or more, more preferably 49% or more, and even more preferably 52% or more. In one embodiment, the diffuse reflectance may be 70% or more, 80% or more, or even 90% or more. This allows electromagnetic waves irradiated onto the silicon nitride powder to be efficiently reflected and diffused around the silicon nitride powder. As a result, when the silicon nitride powder is used as a material for stereolithography, the curability of the material can be improved, and the modeling speed can be increased. The upper limit of the diffuse reflectance of silicon nitride powder for light with a wavelength of 250 nm is not particularly limited, but may be, for example, 100% or less, or 99% or less. Furthermore, because light with a wavelength of 250 nm is a short wavelength, it has more energy than light with a wavelength of 405 nm, and acts efficiently on the photopolymerization initiator of ultraviolet curing resins, allowing for efficient curing through polymerization caused by the generation of radicals, etc.

[0067] The diffuse reflectance of the silicon nitride powder can be measured using an ultraviolet-visible spectrophotometer equipped with an integrating sphere device.

[0068] Silicon nitride powder having the above-mentioned diffuse reflectance can be realized by using the manufacturing method described below. For example, it is possible to select the raw material of the silicon nitride powder, or to use a conventional silicon nitride powder as the raw material and subject it to a predetermined heat treatment. However, the manufacturing method of the silicon nitride powder of this embodiment is not limited to this.

[0069] (particle size) The silicon nitride powder of this embodiment preferably has a particle size at 90% of the cumulative particle diameter (D90) of 1 to 200 μm, more preferably 1 to 100 μm or less, and even more preferably 1 to 50 μm, as determined from the volume-based particle size distribution measured with a particle size distribution analyzer using a laser diffraction / scattering method for primary particles. The silicon nitride powder of this embodiment preferably has a particle size at 50% of the cumulative particle size (D50) of 0.1 to 60 μm, more preferably 0.2 to 30 μm, and even more preferably 0.5 to 15 μm, as determined from the volume-based particle size distribution measured with a particle size distribution analyzer using a laser diffraction / scattering method for primary particles. The silicon nitride powder of this embodiment preferably has a particle size (D10) at 10% cumulative volume determined from the volume-based particle size distribution measured with a particle size distribution analyzer using a laser diffraction / scattering method for primary particles of 0.1 to 10 μm, more preferably 0.2 to 8 μm or less, and even more preferably 0.3 to 5 μm. By setting the particle size within the above numerical range, it becomes easier to improve the modeling speed. Furthermore, by setting the particle size at or above the above lower limit, it becomes possible to control the viscosity low when mixed with resin, and set the viscosity to facilitate additive manufacturing. Furthermore, by setting the particle size at or below the above upper limit, it becomes possible to reduce the surface roughness during sintering. The particle size can be controlled by adjusting classification and pulverization conditions.

[0070] (specific surface area) The silicon nitride powder of this embodiment has a specific surface area of ​​0.1 to 20 m 2 / g, and 0.2 to 10m 2 / g is more preferable, and 0.5 to 8m 2 / g is even more preferable. By setting the specific surface area to be equal to or greater than the above-mentioned lower limit, sintering becomes easier. On the other hand, by setting the specific surface area to be equal to or less than the above-mentioned upper limit, the frequency with which irradiated light hits the silicon nitride during stereolithography decreases, the probability that irradiated light is absorbed by the silicon nitride decreases, the curing speed of the photocurable resin increases, and the modeling speed becomes easier to improve. Furthermore, by setting the specific surface area to be equal to or less than the above-mentioned upper limit, the viscosity does not increase too much when the silicon nitride is mixed with the resin, making it easier to laminate. The specific surface area, BET specific surface area, can be measured by the BET single-point method using nitrogen gas in accordance with JIS Z 8803:2013.

[0071] The specific surface area is controlled by the manufacturing conditions of the silicon nitride powder. For example, it can be controlled to a low value by promoting sintering and particle growth through heat treatment, or to a high value by pulverizing using jet milling or ball milling. It can also be controlled to a low value by removing fine powder through classification, or to a high value by removing coarse powder. By controlling the specific surface area low, the viscosity when mixed with resin can be controlled low, making it possible to set a viscosity that is easy to use in additive manufacturing.

[0072] (surface oxygen amount, internal oxygen amount) The silicon nitride powder of this embodiment preferably has an internal oxygen content of 0.3 mass% or less. Internal oxygen is likely to exist as oxygen defects, which are likely to cause light absorption, so it is believed that a lower internal oxygen content increases the diffuse reflectance. This allows for a significant increase in diffuse reflectance.

[0073] The amount of surface oxygen can be measured using an oxygen / nitrogen analyzer. Specifically, silicon nitride powder is heated from 20°C to 2000°C in a helium atmosphere, and as the temperature rises, oxygen is detected first, followed by silicon nitride. When the temperature is first raised, oxygen bound to the surface of the silicon nitride powder is desorbed and detected. The amount of surface oxygen can be determined by quantifying the amount of oxygen desorbed from the detected silicon nitride. After that, when the silicon nitride begins to decompose, silicon nitride is detected and oxygen inside the silicon nitride powder is desorbed. The amount of internal oxygen can be determined by quantifying the amount of oxygen desorbed after silicon nitride is detected. For example, Figure 1 shows an example of a chart obtained by oxygen / nitrogen analysis of silicon nitride. The peak intensity on the vertical axis indicates the intensity of the detected oxygen. The time (seconds) on the horizontal axis indicates the elapsed time from the start of the temperature rise. As shown in Figure 1, Peak 1 is the surface oxygen peak, and Peak 2 is the internal oxygen peak. Peak 3 is the nitrogen peak. Line 4 shows the temperature rise line. Peak 1 and Peak 2 are separated by temperature T1, where nitrogen begins to be generated. Temperature T1 is the temperature at which detection of Peak 3 begins, and is usually between 1350 and 1500°C. The temperature at which detection of Peak 1 begins (the temperature at the left end of Peak 1) is, for example, 750 to 1200°C. The temperature at which detection of Peak 2 ends (the temperature at the right end of Peak 2) is, for example, 1600 to 1800°C. The amount of internal oxygen and the amount of surface oxygen can be calculated based on the calibration curve from the integrated values ​​(areas) of Peaks 1 and 2. In Figure 1, the left end of Peak 3 (temperature T1) coincides with the deepest points of the valleys of Peaks 1 and 2, but these do not have to coincide completely. However, normally, temperature T1 (the left end of Peak 3) will be located between the temperatures at which the tops of Peak 1 and Peak 2 are detected.

[0074] The surface and internal oxygen contents can generally be reduced by raising the heat treatment temperature to 1400°C or higher during the silicon nitride powder manufacturing process. The specific surface area increases when silicon nitride powder is pulverized, and an oxide layer forms on the surface as it reacts with moisture in the air, so the surface oxygen content increases by controlling the particle size to a small size.

[0075] (α rate, β rate) Silicon nitride has two main crystalline structures: α-phase and β-phase, and the higher the α-fraction, the greater the α-phase content. The α-phase is easily densified and produces high-strength sintered bodies. On the other hand, the β-phase tends to be more difficult to densify than the α-phase, but because it is a columnar crystal, it tends to have improved fracture toughness. The α-fraction and β-fraction of silicon nitride can be adjusted by the manufacturing method.

[0076] For the silicon nitride powder having a high α ratio in this embodiment, the α ratio (proportion of α phase) of the silicon nitride powder is preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, still more preferably 90% or more, and even more preferably 95% or more, in order to obtain a sintered body having high diffuse reflectance and good strength.

[0077] For the silicon nitride powder having a high α ratio in this embodiment, the β ratio (proportion of β phase) of the silicon nitride powder is preferably 10% or more, more preferably 15% or more, even more preferably 20% or more, and even more preferably 25% or more, in order to obtain a high diffuse reflectance while also obtaining appropriate toughness.

[0078] For the silicon nitride powder having a high β ratio in this embodiment, the β ratio (proportion of β phase) of the silicon nitride powder is preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, still more preferably 90% or more, and even more preferably 95% or more, in order to obtain a sintered body having high diffuse reflectance and good fracture toughness.

[0079] For the silicon nitride powder having a high β ratio in this embodiment, the α ratio (proportion of α phase) of the silicon nitride powder is preferably 10% or more, more preferably 15% or more, even more preferably 20% or more, and even more preferably 25% or more, in order to obtain a high diffuse reflectance while also obtaining a moderate strength.

[0080] The α-proportion of silicon nitride powder can be determined based on the diffraction intensity of X-ray diffraction. For example, if the heating temperature is increased, the β-phase is generated, and the α-proportion of silicon nitride powder tends to decrease.

[0081] (Application) The silicon nitride powder of this embodiment can be suitably used for various applications. For example, when used as a raw material for three-dimensional modeling, a model with excellent mechanical properties can be obtained. Three-dimensional modeling can be performed by at least one method selected from additive manufacturing and stereolithography.

[0082] [Manufacturing method] Next, an example of a method for producing the silicon nitride powder of this embodiment will be described. The method for producing silicon nitride powder of this embodiment includes: A step of preparing a silicon nitride powder material (step 1); and a step (step 2) of heat treating the silicon nitride powder material at 500°C or higher and 2500°C or lower. In other words, by subjecting silicon nitride powder material to heat treatment at 500°C or higher and 2500°C or lower, it is possible to obtain silicon nitride powder that satisfies at least one of the following: a diffuse reflectance of 57% or higher for light with a wavelength of 405 nm, a diffuse reflectance of 54% or higher for light with a wavelength of 355 nm, a diffuse reflectance of 50.5% or higher for light with a wavelength of 300 nm, or a diffuse reflectance of 40.7% or higher for light with a wavelength of 250 nm. Each step will be described in detail below.

[0083] (Step 1) A step of preparing silicon nitride powder material First, the raw material of the silicon nitride powder material is a powder containing silicon powder. The silicon powder may be a commercially available product or one prepared by reaction, such as "9FWS" manufactured by Denka Co., Ltd. or "E10" manufactured by Ube Industries, Ltd.

[0084] The following describes the case where silicon nitride powder material is prepared by reaction. First, silicon powder and other raw material powders are filled into a container. When the oxygen concentration of the silicon powder is high, for example, the amount of oxygen bonded to the silicon powder can be reduced using a pretreatment liquid containing hydrofluoric acid. In this case, the method may further include a pretreatment step of pretreating the silicon powder with a pretreatment liquid containing hydrofluoric acid to obtain silicon powder with an oxygen concentration of 0.4 mass%. The pretreatment liquid may contain hydrofluoric acid. The pretreatment liquid may be, for example, a mixed acid with an acid such as hydrochloric acid, or may consist solely of hydrofluoric acid. The temperature of the pretreatment liquid in the pretreatment step may be, for example, 40 to 80°C. The contact time between the pretreatment liquid and the silicon powder may be, for example, 1 to 10 hours.

[0085] In addition to silicon powder, the raw material powder may optionally contain a fluoride containing Li, Na, K, Mg, Ca, Sr, or Ba as a constituent element to promote nitridation. However, from the viewpoint of reducing the fluorine content of the silicon nitride powder, the content of the fluoride per 100 parts by mass of silicon powder is preferably 0.5 parts by mass or less, more preferably 0.3 parts by mass or less. From the viewpoint of sufficiently reducing the fluorine content of the silicon nitride powder, the raw material powder does not need to contain fluoride. If necessary, the silicon powder may be pretreated with an acid to reduce impurities in the silicon powder.

[0086] The container can be made of a material that does not change in quality up to a temperature of 1500°C in an inert atmosphere, and specifically, for example, alumina, boron nitride, or carbon can be used. The structure of the container is not particularly limited, and for example, a container that can form a storage space for storing raw material powder can be used. From the viewpoint of handleability, the container may include a container body having a recess and a lid that covers the recess in the body. The amount of raw material powder to be filled is adjusted as appropriate, but is, for example, 0.7 to 1.6 g / cm 3 It may also be possible to use the following.

[0087] The raw material powder packed in the container is then fired in an atmosphere containing nitrogen gas to obtain a fired product containing silicon nitride. The firing can nitride the silicon powder contained in the raw material powder. The concentration of nitrogen gas in the atmosphere during firing may be 90% by volume or more, 95% by volume or more, or 97% by volume or more.

[0088] The firing atmosphere may contain nitrogen gas and other gases different from nitrogen gas. Examples of other gases include argon gas and hydrogen gas. The addition of argon gas can adjust the reaction rate of the nitriding reaction. The addition of hydrogen gas reduces oxides such as SiO2 contained in the raw material powder, allowing the production of silicon nitride powder with high purity. From this viewpoint, the hydrogen gas content in the firing atmosphere may be 1% by volume or more, or may be 2% by volume or more. On the other hand, from the viewpoint of promoting nitriding of the silicon powder, the hydrogen gas content in the firing atmosphere may be 5% by volume or less. An example of the hydrogen gas content in the firing atmosphere is 1 to 5% by volume.

[0089] The firing temperature may be, for example, 1100 to 1450° C. or 1200 to 1400° C. The firing time may be, for example, 30 to 100 hours. Furthermore, the firing process may include multiple stages in which the firing temperature ranges are different from one another.

[0090] Furthermore, the obtained fired product may be pulverized. The pulverization may be carried out in multiple stages, including coarse pulverization and fine pulverization. The pulverization may be carried out wet using, for example, a ball mill. When the specific surface area of ​​the fired product is 8.0 to 15.0 m, 2 It may be ground to a concentration of 1 / g. The time for the pulverization treatment (pulverization time) in the ball mill pulverization step may be 5 to 15 hours, or 8 to 12 hours, which makes it possible to sufficiently finely disintegrate aggregated particles while preventing excessive pulverization.

[0091] The pulverized product obtained in the ball mill pulverization step may be further pulverized in a vibration mill pulverization step. The ball filling rate in the container in the vibration mill pulverization step may be 50 to 80 volume % or 60 to 75 volume %. The pulverization time in the vibration mill pulverization step (pulverization time) may be 8 to 20 hours or 12 to 17 hours.

[0092] Furthermore, classification may be carried out to adjust the particle size of the pulverized material.

[0093] The silicon nitride powder material is prepared by the above-described procedure.

[0094] (Step 2) Heat treatment Next, the silicon nitride powder is heat-treated at 400°C or higher and 2500°C or lower. Specifically, the silicon nitride powder material is heat-treated at 400°C or higher and 2500°C or lower while controlling the atmosphere, packing density, and pressure in the pot. This improves the diffuse reflectance of the silicon nitride powder. It is believed that controlling the atmosphere, packing density, pressure, and temperature in the pot reduces defects caused by nitrogen vacancies and oxygen intrusion and solid solution, thereby reducing excess light absorption. Heating from room temperature to 100°C or higher, preferably 400°C or higher, and more preferably 800°C or higher while evacuating the furnace removes moisture adsorbed on the silicon nitride powder and moisture desorbed from water of crystallization (OH groups). Gas is then introduced, reducing impurities such as moisture in the atmosphere and enabling efficient removal of defects in the silicon nitride powder. The heat treatment temperature is 400 to 2500°C, preferably 1000 to 2300°C, and more preferably 1500 to 2000°C. The heat treatment temperature is preferably 1650°C to 2000°C, more preferably 1700°C to 2000°C, from the viewpoint of reducing the amount of internal oxygen, and is preferably 1500°C to 1800°C, more preferably 1500°C to 1700°C, from the viewpoint of reducing nitrogen defects and increasing the diffuse reflectance. By setting the heat treatment temperature at or above the lower limit, the diffuse reflectance can be increased and the molding speed can be improved. On the other hand, by setting the heat treatment temperature at or below the upper limit, good diffuse reflectance can be obtained while improving the moldability of the silicon nitride powder. Furthermore, the heat treatment may be held during the temperature rise, or the temperature rise rate or cooling rate may be adjusted. The temperature held during the temperature rise is preferably 600°C, 800°C, 1000°C, 1200°C, 1400°C, or temperatures around these. Furthermore, the holding time is preferably 2 hours, 6 hours, 12 hours, 36 hours, or around these. Furthermore, the temperature rise rate may be 10°C / min or less, 1°C / min or less, or 0.1°C / min or less. Furthermore, the cooling rate may be 0.1°C / min or more, 1°C / min or more, 10°C / min or more, or 100°C / min or more. It is preferable to start the heat treatment at a temperature of 50°C or below.

[0095] Furthermore, pressure may be applied during the heat treatment, preferably under a pressure of 0.001 to 100 MPaG, more preferably under a pressure of 0.005 to 10 MPaG, and even more preferably under a pressure of 0.020 to 1 MPaG. By setting the pressure during heat treatment to be equal to or greater than the lower limit, the diffuse reflectance can be increased, while by setting the pressure during heat treatment to be equal to or greater than the upper limit, the formability of the silicon nitride powder can be improved while still obtaining a good diffuse reflectance. For example, it is preferable that the heat treatment is carried out in a vacuum of 100 Pa or less from the start of heating until the temperature reaches 800°C, and then in a gas atmosphere at 800°C or higher.

[0096] Furthermore, the heat treatment is preferably carried out in an inert gas, a reducing gas, or under vacuum, i.e., by introducing a predetermined gas into a furnace. Examples of inert gases include rare gas elements such as helium, neon, and argon, as well as nitrogen gas, etc. Examples of reducing gases include chlorine gas, hydrogen sulfide gas, ammonia gas, sulfur oxide gas, hydrogen gas, and nitrogen oxide gas, etc. The flow rate of the gas introduced into the furnace relative to the volume of the furnace is A (L / min), and the volume of the furnace is B (m 3 ), by setting A / B > 5, the gas generated from the silicon nitride powder (A) can be efficiently discharged outside the furnace, reducing impurities in the atmosphere and efficiently removing defects in the silicon nitride powder (A). (Gas flow rate (L / min)) ÷ (Furnace volume (m 3 ))(A / B) is preferably 10 or more, and more preferably 20 or more. It is also preferable to discharge the gas so that the pressure inside the furnace is kept constant.

[0097] For example, silicon nitride powder material is put into a furnace and heating is started, and the internal pressure of the furnace is set to 50 Pa or less at temperatures below 100°C, and gas is introduced at temperatures above 100°C, and the flow rate (L / min) of the gas introduced into the furnace is set to the volume (m 3 ) is preferably adjusted to 5 or more. That is, from the start of heating until the temperature reaches at least 100°C, it is preferable to keep the internal pressure in the furnace at 50 Pa or less by vacuum treatment, and the internal pressure in the furnace after reaching 100°C may be 50 Pa or less or may exceed 50 Pa. Furthermore, as long as the temperature is 100°C or higher, gas may be introduced at any time; for example, gas may be introduced once the temperature reaches 1000°C. In addition, it is preferable to start the heat treatment at a temperature of 50° C. or less.

[0098] The heat treatment is preferably carried out by filling a container with the silicon nitride powder material. Examples of containers include ceramics such as boron nitride and silicon nitride, and metals such as tungsten and molybdenum. The pot (container) for containing the silicon nitride powder is preferably made of boron nitride, which has a relatively low density, in order to efficiently volatilize the gas generated from the silicon nitride powder. For example, a pot (container) with a density of 1.8 g / cm 3 Preferably, the density is 1.6 g / cm or less. 3 The following is more preferred: The amount of silicon nitride powder material (a) to be filled is adjusted appropriately, but for example, the bulk density is adjusted to 0.3 to 1.6 g / cm 3 It can also be 1.14 g / cm 3 By setting the amount of silicon nitride powder filled in the pot (container) to the above upper limit or less, gas generated from the silicon nitride powder can be efficiently volatilized outside the pot (container).

[0099] The resulting silicon nitride powder may be pulverized. The pulverization may be carried out in multiple stages, including coarse pulverization and fine pulverization. The pulverization may be carried out wet using, for example, a ball mill. The balls may be made of aluminum oxide, zirconium oxide, silicon nitride, etc. The specific surface area of ​​the fired material is 3.0 to 15.0 m 2 It may be ground to a concentration of 1 / g. In one embodiment, the time for the pulverization treatment (pulverization time) in the ball mill pulverization step may be 5 to 100 hours. The pulverization time may be 5 to 15 hours, or 8 to 12 hours. This allows the agglomerated particles to be sufficiently fine while preventing excessive pulverization.

[0100] The pulverized product obtained in the ball mill pulverization step may be further pulverized in a vibration mill pulverization step. The ball filling rate in the container in the vibration mill pulverization step may be 50 to 80 volume % or 60 to 75 volume %. The pulverization time in the vibration mill pulverization step (pulverization time) may be 8 to 20 hours or 12 to 17 hours.

[0101] Furthermore, in order to adjust the particle size of the pulverized material, classification may be carried out using a sieve, for example, a sieve with openings of 20 to 350 μm.

[0102] When using a wet ball mill or wet jet mill, a filtration or drying process may be performed. Filtration may be performed by vacuuming to separate the solvent, or by applying gas or mechanical pressure to the slurry to push the solvent out of the filter paper or filter. Natural drying, heat drying, or vacuum and heat drying may also be used. Before drying, the silicon nitride powder may be allowed to settle using centrifugal force, and the supernatant may be removed before drying. Alternatively, an acid or alkali may be used to adjust the isoelectric point and promote sedimentation, and the supernatant may be removed before drying.

[0103] The silicon nitride powder thus obtained may be subjected to rough crushing, removal of coarse particles by sieving or the like, and removal of fine particles by air classification or the like, as required.

[0104] The silicon nitride powder of this embodiment can be obtained by such a production method.

[0105] <Boron nitride powder> The boron nitride powder is a particle group containing primary particles of boron nitride. The boron nitride powder may further contain agglomerated particles (secondary particles) formed by agglomeration of the primary particles of boron nitride.

[0106] (diffuse reflectance) The boron nitride powder of this embodiment has a diffuse reflectance of 93% or more for light with a wavelength of 355 nm, preferably 95% or more, more preferably 97% or more, and even more preferably 99% or more. This allows electromagnetic waves irradiated onto the boron nitride powder to be efficiently reflected and diffused around the boron nitride powder. As a result, when the boron nitride powder is used as a material for stereolithography, the curability of the material can be improved, and the modeling speed can be increased. The upper limit of the diffuse reflectance of the boron nitride powder for light with a wavelength of 355 nm is not particularly limited, but may be, for example, 100% or less. Furthermore, because light with a wavelength of 355 nm is a short wavelength, it has more energy than light with a wavelength of 405 nm, and acts efficiently on the photopolymerization initiator of ultraviolet curing resins, allowing for efficient curing through polymerization caused by the generation of radicals, etc.

[0107] Boron nitride powder having the above-described diffuse reflectance can be realized by using the manufacturing method described below. For example, the method may involve selecting the raw material of the boron nitride powder, or using conventional boron nitride powder as the raw material and subjecting it to a predetermined heat treatment. However, the manufacturing method of the boron nitride powder of this embodiment is not limited to this.

[0108] <Aluminum nitride> The aluminum nitride powder is a particle group containing primary particles of aluminum nitride. The aluminum nitride powder may further contain agglomerated particles (secondary particles) formed by agglomeration of the primary particles of aluminum nitride.

[0109] (diffuse reflectance) The aluminum nitride powder of this embodiment has a diffuse reflectance of 74% or more for light with a wavelength of 405 nm, preferably 77% or more, more preferably 80% or more, and even more preferably 90% or more. This allows electromagnetic waves irradiated onto the aluminum nitride powder to be efficiently reflected and diffused around the aluminum nitride powder. As a result, when the aluminum nitride powder is used as a material for stereolithography, the curability of the material can be improved, and the modeling speed can be increased. The upper limit of the diffuse reflectance of the aluminum nitride powder for light with a wavelength of 405 nm is not particularly limited, but may be, for example, 100% or less, or 99% or less. In addition, light with a wavelength of 405 nm is widely used as an LED or laser for photopolymerization, and acts efficiently on photopolymerization initiators in UV-curable resins, allowing them to be cured efficiently through polymerization caused by the generation of radicals.

[0110] Aluminum nitride powder having the above-described diffuse reflectance can be realized by using the manufacturing method described below. For example, it is possible to select the raw material of the aluminum nitride powder, or to use a conventional aluminum nitride powder as the raw material and subject it to a predetermined heat treatment. However, the manufacturing method of the aluminum nitride powder of this embodiment is not limited to this.

[0111] 3. Composition for three-dimensional modeling The composition for three-dimensional modeling of this embodiment contains the nitride powder (A) described above, which can improve the modeling speed using the composition for three-dimensional modeling. The composition for three-dimensional modeling may be in a powder form or a paste form. In particular, the composition for three-dimensional modeling is preferably in a powder form. In other words, the composition for three-dimensional modeling is preferably in the form of particles.

[0112] Next, the components contained in the composition for three-dimensional formation will be described. The composition for three-dimensional modeling may be a mixture of the nitride powder (A) and other powders, and may further contain a curable resin as described below.

[0113] (Nitride powder (A)) The content of the nitride powder (A) in the total amount of the composition for three-dimensional modeling can be adjusted appropriately depending on the application. For example, when a photocurable resin is used, the content of the nitride powder (A) is preferably 5 to 100% by mass, more preferably 40 to 60% by mass, in order to obtain good photocurability. Furthermore, when a photocurable resin is not used, the content of the nitride powder (A) in the total amount of the composition for three-dimensional modeling may be 90% by mass or more, 99% by mass or more, or even 100% by mass. This reduces the work required to remove the resin residue. The nitride powder (A) of this embodiment may be a mixture of a powder with a small particle size obtained by pulverization or the like and a powder with a large particle size. By using a portion of the nitride powder (A) with a small particle size, sintering during three-dimensional molding can be more easily promoted.

[0114] (curable resin) The composition for three-dimensional modeling of this embodiment may contain a curable resin. This provides appropriate viscosity, making it easier to form complex or dense patterns with high precision. Furthermore, since the curable resin is subsequently burned off by firing, the sintered body of the model can have high strength.

[0115] The curable resin may be one or more selected from photocurable resins, thermosetting resins, and photo- and thermosetting resins. Specifically, known resins such as acrylic resins and epoxy resins can be used, with acrylic resins being preferred. For example, when a photocurable resin is included, the content of the photocurable resin is relatively preferably 10 to 90 mass %, more preferably 20 to 80 mass %, more preferably 30 to 70 mass %, and even more preferably 40 to 60 mass %, relative to the total amount of the composition for three-dimensional modeling.

[0116] (others) In addition, the composition for three-dimensional modeling may contain known additives, such as the powder (B) other than the nitride powder (A) (silicon nitride powder), adhesives, bonding resins, thermosetting resins, dispersants, photopolymerization initiators, ultraviolet absorbers, pigments, and slurries. Impurities may also be included.

[0117] (Powder (B)) The powder (B) other than the nitride powder (A) may be either an inorganic or organic powder, and examples thereof include inorganic powders such as conventionally known nitride powder (A), metal particles, and ceramic particles; and organic powders.

[0118] The powder (B) may also be a so-called sintering aid. The nitride powder (A) of this embodiment becomes a dense sintered body by being sintered together with the sintering aid. As the sintering aid, for example, those listed in JP 2002-029849 A can be used, and specific examples include one or more compounds selected from Al, Y, lanthanoid elements (rare earth elements), Li, Mg, Ca, Ti, Zr, and Hf, as well as oxides, nitrides, oxynitrides, fluorides, and carbonates thereof.

[0119] More specifically, the conventionally known nitride powder (A) as powder (B) is intended to be one that has not been previously heat-treated at 400°C or higher and 2500°C or lower. For example, the composition for three-dimensional modeling of this embodiment may contain a mixture containing the conventionally known nitride powder (A) in addition to the nitride powder (A) of this embodiment. Since the conventionally known nitride powder (A) has not been previously heat-treated at 400°C or higher and 2500°C or lower, the inclusion of the conventionally known nitride powder (A) can promote sintering after three-dimensional modeling. Furthermore, from the viewpoint of promoting sintering, it is preferable that the conventionally known nitride powder (A) has a small particle size and a large specific surface area.

[0120] Powder (B) may be a metal powder. For example, by using metallic silicon, the metallic silicon is nitrided by heating in nitrogen, and reactive sintering proceeds, making it possible to obtain a dense sintered body.

[0121] Furthermore, when powder (B) contains the above-described conventionally known silicon nitride powder, the silicon nitride powder specifically refers to a silicon nitride powder whose diffuse reflectance does not satisfy a predetermined value and which has not been previously heat-treated at 1500°C or higher and 2500°C or lower. That is, the silicon nitride powder does not satisfy any of the following: a diffuse reflectance of 57% or higher for light with a wavelength of 405 nm, a diffuse reflectance of 54% or higher for light with a wavelength of 355 nm, a diffuse reflectance of 50.5% or higher for light with a wavelength of 300 nm, and a diffuse reflectance of 40.7% or higher for light with a wavelength of 250 nm. For example, the composition for three-dimensional modeling of this embodiment may contain a mixture containing a conventionally known silicon nitride powder in addition to the silicon nitride powder of this embodiment. Because the conventionally known silicon nitride powder has not been previously heat-treated at 1500°C or higher and 2500°C or lower, the inclusion of the conventionally known silicon nitride powder can promote sintering after three-dimensional modeling. Furthermore, from the viewpoint of promoting sintering, the conventionally known silicon nitride powder preferably has a small particle size and a large specific surface area.

[0122] Furthermore, examples of the ceramic particles used as powder (B) include powders of glass such as silica glass (quartz glass) and soda-lime silica glass; metal oxides such as zirconia, alumina, and mullite (aluminosilicate minerals); metal carbides such as silicon carbide and tungsten carbide; and metal nitrides such as aluminum nitride.

[0123] When the composition for three-dimensional modeling contains the above powder (B), the content of the nitride powder (A) relative to the total amount of powder is relatively preferably 40 mass% or more, preferably 60 mass% or more, more preferably 80 mass% or more, even more preferably 95 mass% or more, particularly preferably 99.9 mass% or more, and most preferably 100 mass%. For example, the conventionally known nitride powder (A) may be contained in an amount of 5 to 50 mass% of the total amount of powder, preferably 30 mass% or more in order to obtain good curability, and more preferably 40 mass% or more in order to obtain good curability. In some cases, the raw material of nitride powder (A) may be mixed with a part of powder (B) and heat-treated before use, which promotes the reaction between the raw material of nitride powder (A) and powder (B), and then pulverizes the mixture and uses it as a composition for three-dimensional modeling, thereby improving sinterability and the like.

[0124] (glue) The adhesive (such as a binding resin or a thermosetting resin) is preferably used when the three-dimensional modeling composition does not contain a curable resin. That is, the nitride powder (A) can be shaped using the adhesive (such as a binding resin or a thermosetting resin). Specifically, for example, the nitride powder (A) may be applied, and then the process of spraying the adhesive (such as a binding resin or a thermosetting resin) may be repeated to stack the nitride powder (A) and shape it. As the adhesive (such as a binding resin or a thermosetting resin), any known adhesive for three-dimensional modeling compositions can be used.

[0125] (viscosity) The viscosity (25° C.) of the composition for three-dimensional modeling is preferably 100 Pa·s to 150,000 Pa·s in terms of ejection properties and pattern shape formability. The viscosity can be measured using a rheometer ("MCR-300" manufactured by Nippon SiberHegner KK) under the following conditions. Conditions: Plate shape: 25 mm diameter, sample thickness: 1 mm, temperature: 25 ± 1 °C, shear rate: 0.1 s -1

[0126] 4. Modeled objects The object of the present embodiment is made of a three-dimensional modeling composition and is obtained by forming a predetermined pattern shape using the above-mentioned composition for three-dimensional modeling. Because the object of the present embodiment uses the above-mentioned composition for three-dimensional modeling, it has an excellent modeling speed and good productivity. The method for producing the shaped object is not particularly limited, and any known method can be used, but it is preferable to select an appropriate method depending on the composition and application of the composition for three-dimensional modeling.

[0127] For example, the method for manufacturing a shaped object preferably includes the steps of forming a predetermined pattern shape using the above-described composition for three-dimensional modeling, and curing the composition for three-dimensional modeling to obtain a cured body.

[0128] The curing method is preferably determined depending on the composition and application of the composition for three-dimensional modeling. For example, when the composition for three-dimensional modeling contains a photocurable resin or a photo- and thermosetting resin, it is preferable to cure the resin by irradiating it with electromagnetic waves or electron beams. Examples of electromagnetic waves include ultraviolet rays, visible light, infrared rays, and microwaves. Among these, ultraviolet rays are preferred. Furthermore, when the composition for three-dimensional modeling contains a thermosetting resin, it may be cured by heating. The three-dimensional modeling composition may also be cured by drying. Alternatively, an adhesive (such as a bonding resin or a thermosetting resin) may be locally applied to the composition for three-dimensional modeling, and the composition may be cured using a modeling method (binder jet type).

[0129] Alternatively, sintered layers may be stacked and molded by repeatedly applying the composition for three-dimensional modeling and sintering the nitride powder (A). In this case, the curing step can be omitted. Sintering is performed in the same manner as for the sintered body described below.

[0130] Furthermore, the method for forming the predetermined pattern shape is not particularly limited and any known method can be used, but it is preferable to repeatedly apply or coat the composition for three-dimensional modeling to form layers and then laminate the layers. The composition for three-dimensional modeling may be in any form of powder, paste, liquid, or gas.

[0131] 5. Sintered body The sintered body of this embodiment is obtained by sintering a shaped object. The method for producing a sintered body includes a step of sintering the shaped object obtained by the method for producing a shaped object at 1500 to 2500°C. This sinters the nitride powder (A), resulting in excellent strength. Furthermore, when the composition for three-dimensional modeling contains a curable resin, a debinding treatment is carried out at about 400 to 800°C before sintering to remove the resin component.

[0132] <Application> The nitride powder (A) of this embodiment can be suitably used for sputtering targets and in the production of electronic devices such as MEMS, SAW filters, and BAW filters. High purity (low levels of impurities other than the target substance) is important for sputtering targets and electronic devices such as MEMS, SAW filters, and BAW filters. The heat treatment of this embodiment reduces the amount of components volatilized during the heat treatment. Furthermore, particle growth during the heat treatment reduces the proportion of adsorbed substances and oxide layers present on the nitride surface relative to the total volume of the nitride, thereby reducing the proportion of adsorbed substances and oxide layers relative to the total volume of the nitride, thereby increasing the purity of the nitride. Furthermore, during the heat treatment, heterogeneous phases and dissolved elements present inside the nitride, such as dissolved oxygen impurities and metal impurities of other elements, are expelled from the nitride and volatilized and removed, thereby increasing the purity of the nitride. For example, the powder can also be used for sputtering targets containing Si3N4 or the nitrides listed above.

[0133] <Reference form> A reference embodiment of this embodiment is shown below.

[0134] An example of a first reference mode of this embodiment will be described below. [1] Silicon nitride powder with a diffuse reflectance of 57% or more for light with a wavelength of 405 nm. [2] Silicon nitride powder with a diffuse reflectance of 54% or more for light with a wavelength of 355 nm. [3] Silicon nitride powder with a diffuse reflectance of 50.5% or more for light with a wavelength of 300 nm. [4] Silicon nitride powder with a diffuse reflectance of 40.7% or more for light with a wavelength of 250 nm. [5] The silicon nitride powder according to any one of [1] to [4], which is used as a raw material for three-dimensional modeling. [6] The silicon nitride powder according to any one of [1] to [4], which is used as a raw material for stereolithography. [7] The silicon nitride powder according to any one of [1] to [4], which is used as a raw material for additive manufacturing. [8] The silicon nitride powder according to any one of [1] to [7], Silicon nitride powder having a particle size at 50% of the cumulative size (D50) of 0.1 to 60 μm, as determined by the volume-based particle size distribution measured with a particle size distribution analyzer using a laser diffraction / scattering method for silicon nitride primary particles. [9] The silicon nitride powder according to any one of [1] to [8], A silicon nitride powder having an internal oxygen content of 0.3 mass % or less.

[10] The silicon nitride powder according to any one of [1] to [9], Specific surface area is 0.1 to 20m 2 / g of silicon nitride powder.

[11] A composition for three-dimensional modeling, comprising the silicon nitride powder according to any one of [1] to

[10] .

[12] The composition for three-dimensional object formation according to any one of [1] to

[10] , A composition for three-dimensional modeling, wherein the content of the silicon nitride powder is 30 mass% or more based on the total amount of the powder.

[13] A method for producing a composition for three-dimensional object formation according to

[11] or

[12] , mixing the silicon nitride powder with a powder other than the silicon nitride powder; A method for producing a composition for three-dimensional modeling, wherein the content of the silicon nitride powder is 30 mass% or more based on the total amount of the powder.

[14] A modeled object made from the composition for three-dimensional modeling according to any one of

[11] to

[13] .

[15] A sintered compact of the shaped product described in

[14] .

[16] A method for manufacturing a shaped object according to

[14] , comprising: A method for manufacturing a three-dimensional object, comprising the step of forming a predetermined pattern shape using the composition for three-dimensional modeling to obtain a three-dimensional object.

[17] A method for producing a shaped object according to

[16] , and hardening the composition for three-dimensional modeling in the predetermined pattern shape to obtain the model.

[18] A method for producing a shaped object according to

[16] or

[17] , The method for producing a three-dimensional object includes irradiating the composition for three-dimensional object with electromagnetic waves or electron beams to cure the composition, thereby obtaining the three-dimensional object.

[19] A method for manufacturing a shaped object according to any one of

[16] to

[18] , The method for manufacturing a shaped object includes repeatedly applying or coating and laminating the composition for three-dimensional modeling to form the predetermined pattern shape.

[20] A method for manufacturing a shaped object according to any one of

[16] to

[19] , A method for manufacturing a shaped object, further comprising the step of processing the shaped object.

[21] A method for manufacturing a shaped object according to any one of

[16] to

[20] , A method for producing a sintered body, comprising a step of sintering silicon nitride powder at 1500°C or higher and 2500°C or lower.

[22] The silicon nitride powder according to any one of [1] to

[10] , which is used for a sputtering target.

[23] The silicon nitride powder according to any one of [1] to

[10] , which is used for producing MEMS.

[24] The silicon nitride powder according to any one of [1] to

[10] , which is used to prepare a SAW filter or a BAW filter.

[25] The silicon nitride powder according to any one of [1] to

[10] , which is used to fabricate an electronic device.

[0135] An example of a second reference mode of this embodiment will be described below. [1] A step of preparing a nitride powder material (a) containing one or more compounds selected from group III compounds, group IV compounds, and group V compounds; a step of heat-treating the nitride powder material (a) at 400°C or higher and 2500°C or lower to obtain nitride powder (A); Including, In the step of obtaining the nitride powder (A), the nitride powder material (a) is put into a furnace and heating is started, the internal pressure of the furnace is set to 50 Pa or less at temperatures below 100°C, and gas is introduced at temperatures above 100°C, the flow rate of the gas introduced into the furnace is set to A (L / min), and the volume of the furnace is set to B (m 3 ) so that A / B>5. [2] A method for producing the nitride powder (A) according to [1], wherein the gas introduction temperature during the heat treatment is 400°C or higher. [3] A method for producing the nitride powder (A) according to [1], wherein the gas introduction temperature during the heat treatment is 800°C or higher. [4] The method for producing the nitride powder (A) according to [1], wherein the flow rate of the gas introduced into the furnace during the heat treatment is A (L / min), and the volume of the furnace is B (m 3 ) and adjust the ratio A / B so that A / B>10. [5] A method for producing the nitride powder (A) according to any one of [1] to [4], The method for producing nitride powder (A), wherein the heat treatment is started at a temperature of 50°C or lower. [6] A method for producing the nitride powder (A) according to [1] or [5], The method for producing nitride powder (A) comprises discharging the gas so that the pressure inside the furnace is constant. [7] A method for producing the nitride powder (A) according to any one of [1] to [6], A method for producing nitride powder (A), wherein the nitride powder (A) is used in additive manufacturing. [8] A method for producing the nitride powder (A) according to any one of [1] to [7], A method for producing a nitride powder (A), wherein the nitride powder (A) is used in a resin composition for optical molding. [9] A method for producing a nitride powder (A) according to any one of [1] to [8], wherein the heat treatment is performed under a pressure of 0.001 to 100 MPaG, a method for producing a nitride powder (A).

[10] A method for producing a nitride powder (A) according to any one of [1] to [9], wherein the heat treatment is performed in an inert gas, a reducing gas, or under vacuum, a method for producing a nitride powder (A).

[11] A method for producing a nitride powder (A) according to any one of [1] to

[10] , wherein the nitride powder (A) is one or more selected from silicon nitride particles, aluminum nitride particles, and boron nitride particles, a method for producing a nitride powder (A).

[12] A method for producing a nitride powder (A) according to any one of [1] to

[11] , wherein the heat treatment is performed by filling a container with a nitride powder material (a) so that the bulk density of the nitride powder (A) is 1.14 g / cm 3 the following, a method for producing a nitride powder (A).

[13] A method for producing a nitride powder (A) according to any one of [1] to

[12] , wherein the nitride powder (A) contains primary particles, and the particle size (D50) at cumulative 50% obtained from the volume-based particle size distribution measured by a particle size distribution measuring device using the laser diffraction / scattering method of the primary particles is 0.5 to 60 μm, a method for producing a nitride powder (A).

[14] A method for producing a nitride powder (A) according to any one of [1] to

[13] , wherein the specific surface area of the nitride powder (A) is 0.1 to 20 m 2 / g, a method for producing a nitride powder (A).

[15] A method for producing a molded object using a three-dimensional lamination molding composition or a resin composition for optical molding containing the nitride powder (A) obtained by the method for producing a nitride powder (A) according to any one of [1] to

[14] , A method for manufacturing a shaped object, comprising a step of forming a predetermined pattern shape using the composition for three-dimensional additive manufacturing or the resin composition for stereolithography to obtain a shaped object.

[16] A method for producing a shaped object according to

[15] , a method for producing a shaped object, the shaped object being obtained by curing the three-dimensional additive manufacturing composition or the stereolithography resin composition having the predetermined pattern shape.

[17] A method for producing a shaped object according to

[15] or

[16] , A method for producing a shaped object, comprising irradiating the composition for three-dimensional additive manufacturing or the resin composition for stereolithography with electromagnetic waves or electron beams to cure the composition, thereby obtaining the shaped object.

[18] A method for manufacturing a shaped object according to any one of

[15] to

[17] , A method for manufacturing a shaped object, comprising repeatedly applying or coating and laminating the composition for three-dimensional additive manufacturing or the resin composition for stereolithography to form the predetermined pattern shape.

[19] A method for manufacturing a shaped object according to any one of

[15] to

[18] , A method for manufacturing a shaped object, further comprising the step of processing the shaped object.

[20] A method for manufacturing a shaped object according to any one of

[15] to

[19] , A method for producing a sintered body, comprising a step of sintering nitride powder (A) at 1500°C or higher and 2500°C or lower.

[21] A method for producing the nitride powder (A) according to any one of [1] to

[14] , A method for producing nitride powder (A), wherein the nitride powder (A) is used for a sputtering target, or for producing a MEMS, a SAW filter, a BAW filter, or an electronic device.

[0136] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations can also be adopted. [Example]

[0137] Next, the present invention will be described in detail with reference to examples, but the content of the present invention is not limited to the examples.

[0138] <<First Example>> (1) Measurement of diffuse reflectance The diffuse reflectance was measured using an ultraviolet-visible spectrophotometer (V-650) manufactured by JASCO Corporation equipped with an integrating sphere device (ISV-722). Baseline correction was performed using a standard reflector (Spectralon), and a solid sample holder filled with silicon nitride powder (a quartz cell filled with silicon nitride powder and tapped 20 times) was set in place, and diffuse reflectance was measured in the wavelength range of 220 to 850 nm. The measurement parameters were set as follows: response: Medium, bandwidth: 2.0 nm, scan speed: 200 nm / min, data acquisition interval: 0.5 nm, scan mode: Continuous, control settings: Baseline correction, switching wavelength: 340 nm, light source: "Automatic," and filter switching: "Stop scan." The diffuse reflectance (%) was measured at 250 nm, 300 nm, 355 nm, 405 nm, 500 nm, 600 nm, 700 nm and 800 nm.

[0139] (2) Measurement of particle size The particle size of the silicon nitride powder was measured using a Microtrac MT3300EXII (Microtrac Bell Corporation), a particle size measuring device that uses the laser diffraction and scattering method, in accordance with the method described in JIS Z 8825:2013, "Particle size analysis - Laser diffraction and scattering method." The measurement procedure was as follows: first, 60 mg of silicon nitride powder was weighed into a 500 mL container. This was mixed with 2 mL of a 20% aqueous solution of sodium hexametaphosphate as a dispersant and 200 g of water. Next, the powder was mixed and dispersed for 3 minutes using an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, trade name: US-300) to obtain a measurement sample. The particle size of this measurement sample was measured using the MT3300EII. Pure water was used as the solvent for the Microtrac circulator. This pure water was used to adjust the concentration of silicon nitride powder in the measurement sample. From the particle size distribution of the obtained silicon nitride, the particle sizes (units: μm) were calculated as follows: D50, D10, which is the particle size at 10% of the cumulative volume from the small particle size side, D50, which is the particle size at 50% of the cumulative volume from the small particle size side, D90, which is the particle size at 90% of the cumulative volume from the small particle size side, D99, which is the same as above, and D100, which is the particle size at 100% of the cumulative volume from the small particle size side.

[0140] (3) Measurement of specific surface area The BET specific surface area V of silicon nitride was measured by the BET single-point method using nitrogen gas in accordance with JIS Z 8803:2013 "Method for measuring the specific surface area of ​​powders (solids) by gas adsorption."

[0141] (4) Measurement of total oxygen and nitrogen content Oxygen and nitrogen were measured using an oxygen and nitrogen analyzer (EMGA-920 (HORIBA)).

[0142] (5) Measurement of surface and internal oxygen content The oxygen and nitrogen contents of silicon nitride were analyzed using an oxygen / nitrogen analyzer (EMGA-920 (HORIBA)). 0.01 g of the measurement sample was heated from 20°C to 2000°C at a heating rate of 8°C / sec in a helium gas atmosphere. The surface oxygen content was determined by quantifying the amount of oxygen after oxygen was first detected during the heating process. After that, when the temperature reached approximately 1400°C, nitrogen was detected, and the internal oxygen content was determined by quantifying the amount of oxygen after nitrogen detection.

[0143] (6) Measurement of impurity content The impurity content of silicon nitride powder was measured using the following procedure. A sample solution was prepared by dissolving the powder using a pressurized acid decomposition method. The resulting sample solution was subjected to quantitative elemental analysis using an ICP optical emission spectrometer (manufactured by Rigaku Corporation, product name: CIROS-120). The carbon and sulfur contents were measured using a CS-444LS spectrometer manufactured by LECO.

[0144] (7) Measurement of alpha and beta rates The α ratio of the silicon nitride powder was measured by the following procedure. X-ray diffraction of silicon nitride powder was performed using CuKα radiation using an X-ray diffractometer (manufactured by Bruker, device name: D8 ADVANCE). Crystal parameter analysis was performed using the RIETVELD method using peak analysis software TOPAS, and the α-phase proportion, β-phase proportion, and lattice constant were calculated. For the comparative example and Examples 1 to 6, measurements were performed at a tube voltage of 45 kV and a tube current of 360 mA, and for Examples 7 to 12, measurements were performed at a tube voltage of 40 kV and a tube current of 40 mA.

[0145] (8) Preparation of silicon nitride powder The silicon nitride powders obtained in the following Examples and Comparative Examples were subjected to the above measurements (1) to (7), and the results are shown in Tables 1 to 5 and FIGS.

[0146] <Examples 1 to 4> First, "9FWS" manufactured by Denka Company Ltd. was prepared as the raw silicon nitride powder material, and heat-treated under the test conditions shown in Table 1 to obtain silicon nitride powders of the examples and comparative examples. The conditions not listed in Table 1 are as follows: 200 g of silicon nitride powder material was weighed into a cylindrical boron nitride container with a lid (a molded product made by Denka Co., Ltd., mainly composed of boron nitride (product name: Denka Boron Nitride N-1), inner diameter: 10 cm, height: 10 cm). The weight of the silicon nitride powder material relative to the volume of the container was 0.5 g / cm. 3 The weight of the silicon nitride powder in the container was controlled as described above. If the weight of the silicon nitride powder material relative to the volume inside the container is too high, sintering of the silicon nitride material will proceed, which will hinder an increase in diffuse reflectance, so this was taken into consideration. Furthermore, if the weight of the silicon nitride powder relative to the volume inside the container is too high, the components volatilizing from the silicon nitride powder material will be less likely to leave the container, so the weight of the silicon nitride powder in the container was controlled as described above. The container was then placed in an electric furnace equipped with a carbon heater, and the pressure was evacuated to 6 Pa or less. While evacuating with a vacuum pump, the temperature was raised to 1000°C in a vacuum state. When the temperature was above 1000°C, nitrogen gas was introduced, and the temperature was raised to the temperature conditions in Table 1 under a nitrogen gas atmosphere (pressure: 0.025 MPaG) (heat treatment I). After the introduction of nitrogen gas, the gas flow rate (L / min) introduced into the furnace was divided by the furnace volume (m 3) was set to 33, and the introduction and discharge of gas was controlled to maintain a constant pressure. This was done to expel volatile components from the raw silicon nitride powder material outside the furnace and to prevent the silicon nitride powder material from being affected by the volatiles. After heating, the sample that had become loosely agglomerated in the container was placed in a mortar and crushed. After crushing, the sample was passed through a sieve with 250 μm openings to obtain a powdered sintered body (silicon nitride powder; Si3N4).

[0147] <Example 5> The same treatment as in Example 2 was carried out except that Ar gas was introduced during heat treatment I and treatment was carried out in an Ar gas atmosphere.

[0148] Example 6 The silicon nitride powder obtained in Example 4 was further pulverized in ethanol using a ball mill with ceramic balls of Φ5 mm, filtered, dried, and passed through a sieve with 250 μm openings.

[0149] Example 7 The same treatment as in Example 6 was carried out, except that a cylindrical boron nitride container with a lid (manufactured by Denka Corporation, boron nitride (product name: Denka Boron Nitride NB-1000)) was used during Heat Treatment I.

[0150] Example 8 The same treatment as in Example 4 was carried out, except that a cylindrical boron nitride container with a lid (manufactured by Denka Corporation, boron nitride (product name: Denka Boron Nitride NB-1000)) was used during Heat Treatment I.

[0151] Example 9 The same treatment as in Example 4 was carried out, except that "E10" manufactured by UBE was used as the silicon nitride powder material, which was the raw material.

[0152] Example 10 The same treatment as in Example 9 was carried out except that the treatment temperature in Heat Treatment I was changed to 1750°C.

[0153] Example 11 The silicon nitride powder obtained in Example 9 was further pulverized in ethanol using a ball mill with ceramic balls of Φ5 mm, filtered, dried, and passed through a sieve with 250 μm openings.

[0154] Example 12 The silicon nitride powder obtained in Example 10 was further pulverized in ethanol using a ball mill with ceramic balls of Φ5 mm, filtered, dried, and passed through a sieve with 250 μm openings.

[0155] <Comparative Example 1> The silicon nitride powder material (a) was used as is and the above measurements were carried out.

[0156] <Comparative Examples 2 and 3> During heat treatment I, a container filled with silicon nitride powder was placed in an electric furnace equipped with a carbon heater, and the furnace was evacuated to 6 Pa or less. Nitrogen gas was then introduced at room temperature, and the temperature was raised to the temperature shown in Table 1 under a nitrogen gas atmosphere (pressure: 0.025 MPaG). Heating was then carried out at the set temperature shown in Table 1. After introducing nitrogen gas, the gas flow rate (L / min) introduced into the furnace was divided by the furnace volume (m 3 ) was set to 4, and the introduction and discharge of gas was controlled to maintain a constant pressure, but the same treatments were carried out as in Examples 1 to 4. In Comparative Example 3, the same treatments as in Comparative Example 2 were carried out, except that the heat treatment was carried out in an Al2O3 container instead of a cylindrical boron nitride container with a lid.

[0157] (9) Evaluation The silicon nitride powders obtained in the above Examples and Comparative Examples were evaluated as follows, and the results are shown in Table 2. (curing speed 1) 1.0 g of the obtained silicon nitride powder and 2.5 g of photocurable resin (containing methacrylate monomer, product name Standard Photopolymer Resin Translucent, manufactured by ELEGOO, irradiated with light at 405 nm, viscosity (25°C) 150-200 mPa·s, ultraviolet-curable resin (transparent) used in resin 3D printers, used to evaluate the curing speed during stereolithography of silicon nitride powder) were stirred until homogeneous using a mixer (THINKY ARV-310, manufactured by Thinky Corporation) to produce a paste-like composition for three-dimensional modeling. A polyethylene terephthalate (PET) film (250 μm thick) and a silicone sheet (1 mm thick) were placed on a glass plate (5 mm thick), and a paste-like three-dimensional modeling composition was poured into a 13 mm square opening that had been pre-made in the silicone sheet.The top surface was scraped off with a spatula to prepare a sample.

[0158] FIG. 2 is a diagram showing a schematic configuration of the UV irradiation test. As shown in Figure 2, a frame-shaped boron nitride substrate 2 (15 mm thick) is placed on the top surface of a workbench 3, with a UV irradiator 1 installed on top. The prepared sample was placed on the top surface of the workbench 3 within the frame of the boron nitride substrate 2, and the composition for three-dimensional modeling was cured by UV irradiation (1.5 hours) using the UV irradiator 1. The UV irradiator 1 used was a "BOX-S3000" manufactured by Sanhayato Corporation. The cured product was then removed from the sample silicone sheet, and the thickness (depth) of the cured region near the center of the irradiated surface of the cured product was measured. The thicker (deeper) the cured region, the faster the modeling speed. The results are shown in Table 1. The thickness (depth) of the cured region near the center of the irradiated surface of the cured product was measured after cutting or splitting the cured product near the center.

[0159] (curing speed 2) In the evaluation of the curing rate 1 described above, the thickness of the silicone sheet was changed from 1 mm to 2 mm, and a paste-like three-dimensional modeling composition was poured into a 13 mm square opening previously provided in the silicone sheet, and the top surface was scraped off with a spatula to prepare a sample. Furthermore, evaluation was performed in the same manner as in the curing rate 1 described above, except that the UV irradiation time using UV irradiator 1 was changed from 1.5 hours to 23 minutes to cure the three-dimensional modeling composition, and the thickness (depth) of the cured area was measured. The relative value to the thickness of the three-dimensional modeling composition (2 mm thickness of the silicone sheet) was calculated. In addition, in curing speed 1, the entire three-dimensional modeling composition cured, making it impossible to evaluate the difference in curing speed between each three-dimensional modeling composition. Therefore, in curing speed 2, the thickness of the silicone sheet was increased and the UV exposure time was shortened to evaluate the difference in curing speed between each three-dimensional modeling composition.

[0160] In addition, for the silicon nitride powders obtained in each of the Examples and Comparative Examples, the results for each Example and Comparative Example were plotted on a graph with the diffuse reflectance (%) of (1) above on the vertical axis and each processing temperature (°C) in the manufacturing process of the silicon nitride powder on the horizontal axis, and are shown in Figure 3. Furthermore, the results of each example and comparative example were plotted on a graph with the diffuse reflectance (%) at 405 nm (1) on the horizontal axis and the thickness (relative value) of the cured region (cured portion) on the vertical axis, and are shown in Figure 4. Furthermore, the results of each Example and Comparative Example were plotted on a graph with the diffuse reflectance (%) at 355 nm (1) on the horizontal axis and the thickness (relative value) of the cured region (cured portion) on the vertical axis, and are shown in Figure 5. Furthermore, the results of each example and comparative example were plotted on a graph with the diffuse reflectance (%) of (1) above on the vertical axis and the wavelength (nm) of (1) above on the horizontal axis, and are shown in FIG.

[0161] [Table 1]

[0162] [Table 2]

[0163] [Table 3]

[0164] [Table 4]

[0165] [Table 5]

[0166] <<Second Example>> (1) Measurement of particle size [Silicon nitride, boron nitride] The particle size of the nitride powder (A) (silicon nitride, boron nitride) was measured using a Microtrac MT3300EXII (Microtrac Bell Corporation), a particle size measuring device that uses the laser diffraction and scattering method, in accordance with the method described in JIS Z 8825:2013, "Particle size analysis - Laser diffraction and scattering method." The measurement procedure was as follows: First, 60 mg of nitride powder (A) (silicon nitride, boron nitride) was weighed into a 500 mL container. A 20% aqueous solution of sodium hexametaphosphate (2 mL) and water (200 g) were mixed as a dispersant. Next, the mixture was mixed and dispersed for 3 minutes using an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, trade name: US-300) to obtain a measurement sample. The particle size of the measurement sample was measured using the MT3300EII. Pure water was used as the solvent for the circulator of the Microtrac. This pure water was used to adjust the concentration of nitride powder (A) (silicon nitride, boron nitride) in the measurement sample. From the particle size distribution of the obtained nitride powder (A) (silicon nitride, boron nitride), the particle sizes (unit: μm) of D10, which is the particle size at 10% of the cumulative volume from the small particle size side, D50, which is the particle size at 50% of the cumulative volume from the small particle size side, and D90, which is the particle size at 90% of the cumulative volume from the small particle size side were calculated.

[0167] [Aluminum nitride] The particle size of the nitride powder (A) (aluminum nitride) was measured using a Microtrac MT3300EXII (Microtrac Bell Corporation), a particle size measuring device using the laser diffraction / scattering method. The measurement procedure was as follows: 0.5 g of the nitride powder (A) (aluminum nitride) to be measured was added to 100 ml of an aqueous solution of ion-exchanged water mixed with 0.05 wt% sodium hexametaphosphate, and the mixture was dispersed for 3 minutes using an ultrasonic homogenizer, Ultrasonic Homogenizer US-150E (Nippon Seiki Seisakusho Co., Ltd.), at an amplitude of 100%, an oscillation frequency of 19.5 ± 1 kHz, a tip size of 20 φ, and an amplitude of 32 ± 2 μm. The tip was placed in the center of the solution and dispersed for 3 minutes, after which the particle size was measured using the MT3300EII. From the particle size distribution of the resulting nitride powder (A) (aluminum nitride), the particle sizes (units [μm]) of D10, which is the particle size at 10% of the cumulative volume from the small particle size side, D50, which is the particle size at 50% of the cumulative volume from the small particle size side, and D90, which is the particle size at 90% of the cumulative volume from the small particle size side were calculated.

[0168] (2) Measurement of specific surface area The BET specific surface area V of the nitride powder (A) was measured by the BET single-point method using nitrogen gas in accordance with JIS Z 8803:2013 "Method for measuring the specific surface area of ​​powders (solids) by gas adsorption."

[0169] (3) Measurement of total oxygen and nitrogen content Oxygen and nitrogen were measured using an oxygen and nitrogen analyzer (EMGA-920 (HORIBA)).

[0170] (4) Quantitative determination of crystalline phase X-ray diffraction of nitride powder (A) was performed using an X-ray diffractometer (Bruker, D8 ADVANCE, 18kW) with a LynxEye detector, a scanning speed of 0.017° / 0.5 sec, CuKa radiation, and a rotating sample stage. Quantitative analysis was performed using the Rietveld analysis software TOPAS.

[0171] (5) Measurement of impurity content The impurity contents of the nitride powder (A) were measured by the following procedure. The impurities were dissolved by the pressure acid decomposition method to prepare a sample solution. The obtained sample solution was subjected to quantitative elemental analysis using an ICP optical emission spectrometer (manufactured by Rigaku Corporation, product name: CIROS-120). The carbon and sulfur contents were measured using a CS-444LS manufactured by LECO.

[0172] (6) Measurement of diffuse reflectance The diffuse reflectance was measured using an ultraviolet-visible spectrophotometer (V-650) manufactured by JASCO Corporation equipped with an integrating sphere device (ISV-722). Baseline correction was performed using a standard reflector (Spectralon), and a solid sample holder filled with silicon nitride powder, boron nitride powder, or aluminum nitride powder (a quartz cell filled with silicon nitride powder and tapped 20 times) was set in place, and diffuse reflectance measurements were performed in the wavelength range of 220 to 850 nm. The measurement parameters were set as follows: medium response, 2.0 nm bandwidth, 200 nm / min scan speed, 0.5 nm data acquisition interval, continuous scan mode, baseline correction, 340 nm wavelength switching, automatic light source, and stop scan for filter switching. The diffuse reflectance (%) was measured at 250 nm, 300 nm, 355 nm, 405 nm, 500 nm, 600 nm, 700 nm and 800 nm.

[0173] (7) Preparation of nitride powder (A) (7-1) Silicon nitride powder The silicon nitride powders obtained in the following Examples and Comparative Examples were subjected to the above measurements (1) to (6), and the results are shown in Tables 6 to 8 and FIGS. The silicon nitride powders in Examples 1 to 6 of the first embodiment and Comparative Examples 1 to 3 are the same as the silicon nitride powders in Examples 1 to 6 and Comparative Examples 1 to 3 of the second embodiment.

[0174] <Examples 1 to 4> First, silicon nitride powder material ("9FWS" manufactured by Denka Co., Ltd.) was prepared as nitride powder material (a) and subjected to heat treatment under the test conditions shown in Table 6 to obtain silicon nitride powders of the examples and comparative examples. The conditions not listed in Table 6 are as follows: 200 g of silicon nitride powder material was weighed into a cylindrical boron nitride container with a lid (a molded product made by Denka Co., Ltd., primarily composed of boron nitride (product name: Denka Boron Nitride N-1), inner diameter: 10 cm, height: 10 cm). The weight of the silicon nitride powder material relative to the volume of the container was 0.5 g / cm. 3 The weight of the silicon nitride powder material in the container was controlled as described above. If the weight of the silicon nitride powder material relative to the volume in the container is too high, sintering of the silicon nitride powder material will proceed, which will hinder an increase in diffuse reflectance, so this was taken into consideration. Furthermore, if the weight of the silicon nitride powder relative to the volume in the container is too high, components volatilizing from the silicon nitride powder material will be less likely to escape from the container, so the weight of the silicon nitride powder material in the container was controlled as described above. The container was then placed in an electric furnace equipped with a carbon heater, and the pressure was evacuated to 6 Pa or less. While evacuating with a vacuum pump, the temperature was raised to 1000°C in a vacuum state. Once above 1000°C, nitrogen gas was introduced, and the temperature was raised to the temperature conditions in Table 6 under a nitrogen gas atmosphere (pressure: 0.025 MPaG), and heating was performed at the set temperature in Table 6 (heat treatment I). After the introduction of nitrogen gas, the flow rate of the gas introduced into the furnace was set to A (L / min), and the volume in the furnace was set to B (m 3 ), and A / B (gas flow rate (L / min) ÷ furnace volume (m 3 ) was set to 33, and the introduction and discharge of gas was controlled to maintain a constant pressure. This was done to expel volatile components from the raw silicon nitride powder material outside the furnace and to prevent the volatiles from affecting the silicon nitride powder (A). After heating, the sample that had become loosely agglomerated in the container was placed in a mortar and crushed. After crushing, the sample was passed through a sieve with 250 μm openings to obtain a powdered sintered body (silicon nitride powder (A); Si3N4).

[0175] <Example 5> The same treatment as in Example 2 was carried out except that Ar gas was introduced during heat treatment I and treatment was carried out in an Ar gas atmosphere.

[0176] Example 6 The silicon nitride powder (A) obtained in Example 4 was further pulverized in ethanol using a ball mill with ceramic balls of Φ5 mm, filtered, dried, and passed through a sieve with 250 μm openings.

[0177] <Comparative Example 1> The silicon nitride powder material (a) was used as is and the above measurements (1) to (6) were carried out.

[0178] <Comparative Examples 2 and 3> During heat treatment I, a container filled with silicon nitride powder was placed in an electric furnace equipped with a carbon heater, and the furnace was evacuated to 6 Pa or less. Nitrogen gas was then introduced at room temperature, and the temperature was raised to the temperature shown in Table 6 under a nitrogen gas atmosphere (pressure: 0.025 MPaG). Heating was then carried out at the set temperature shown in Table 6. After the introduction of nitrogen gas, the flow rate of the gas introduced into the furnace was set to A (L / min), and the volume inside the furnace was set to B (m 3 ), and A / B (gas flow rate (L / min) ÷ furnace volume (m 3 )) was set to 4, and the introduction and discharge of gas was controlled to maintain a constant pressure, but the same treatments were carried out as in Examples 1 to 4. In Comparative Example 3, the same treatments as in Comparative Example 2 were carried out, except that the heat treatment was carried out in an Al2O3 container instead of a cylindrical boron nitride container with a lid.

[0179] (7-2) Boron nitride powder The boron nitride powders obtained in the following Examples and Comparative Examples were subjected to the above measurements (1) to (6), and the results are shown in Tables 6 to 8 and FIGS.

[0180] <Examples 7 and 8> First, "SP-2" manufactured by Denka Company Ltd. was prepared as the raw material boron nitride powder, and heat treatment was carried out under the test conditions shown in Table 6 to obtain boron nitride powders of the examples and comparative examples. The conditions not listed in Table 6 are as follows: 200 g of boron nitride powder material was weighed into a cylindrical boron nitride container with a lid (a molded product made by Denka Co., Ltd., mainly composed of boron nitride (product name: Denka Boron Nitride N-1), inner diameter: 10 cm, height: 10 cm). The weight of the boron nitride powder material relative to the volume of the container was 0.5 g / cm. 3 The weight of the boron nitride powder material relative to the volume in the container was set to below 0.05. If the weight of the boron nitride powder material relative to the volume in the container is too high, sintering of the boron nitride powder material will proceed, which will hinder an increase in diffuse reflectance, so this was taken into consideration. Furthermore, if the weight of the nitride powder (A) relative to the volume in the container is too high, the components volatilizing from the boron nitride powder material will be less likely to escape from the container, so the weight of the nitride powder (A) in the container was controlled as above. The container was then placed in an electric furnace equipped with a carbon heater, and the pressure was evacuated to 6 Pa or less. While evacuating with a vacuum pump, the temperature was raised to 1000°C in a vacuum state. Once above 1000°C, nitrogen gas was introduced, and the temperature was raised to the temperature conditions in Table 6 under a nitrogen gas atmosphere (pressure: 0.025 MPaG), and heating was performed at the set temperature in Table 6 (heat treatment I). After introducing the nitrogen gas, the flow rate of the gas introduced into the furnace was set to A (L / min), and the volume in the furnace was set to B (m 3 ), and A / B (gas flow rate (L / min) ÷ furnace volume (m 3 ) was set to 33, and the introduction and discharge of gas was controlled to maintain a constant pressure. This was done to expel volatile components from the raw boron nitride powder material outside the furnace and to prevent the volatiles from affecting the boron nitride powder material. After heating, the sample that had become loosely agglomerated in the container was placed in a mortar and crushed. After crushing, the sample was passed through a sieve with 250 μm openings to obtain a powdered sintered body (boron nitride powder; BN).

[0181] <Examples 9 and 10> The same treatment as in Example 7 was carried out except that Ar gas was introduced during heat treatment I, treatment was carried out in an Ar gas atmosphere, and treatment temperatures were set at the temperatures shown in Table 6.

[0182] Example 11 The boron nitride powder obtained in Example 8 was further pulverized in ethanol using a ball mill with ceramic balls of Φ5 mm, filtered, dried, and passed through a sieve with 250 μm openings.

[0183] <Comparative Example 4> The boron nitride powder material was used as is to carry out the measurements (1) to (6) above.

[0184] <Comparative Example 5> During heat treatment I, a container filled with boron nitride powder was placed in an electric furnace equipped with a carbon heater, and the furnace was evacuated to 6 Pa or less. Ar gas was then introduced at room temperature, and the temperature was raised to the temperature shown in Table 6 under an Ar gas atmosphere (pressure: 0.025 MPaG). Heating was then carried out at the set temperature shown in Table 6. After the introduction of Ar gas, the flow rate of the gas introduced into the furnace was set to A (L / min), and the volume of the furnace was set to B (m 3 ), and A / B (gas flow rate (L / min) ÷ furnace volume (m 3 The same treatments as in Examples 7 to 10 were carried out except that the pressure was set to 4 and the introduction and discharge of gas was controlled so as to keep the pressure constant.

[0185] (7-3) Aluminum nitride powder The aluminum nitride powders obtained in the following Examples and Comparative Examples were subjected to the above measurements (1) to (6), and the results are shown in Tables 6 to 8 and FIGS.

[0186] <Examples 12 and 13> First, E grade aluminum nitride powder (manufactured by Tokuyama Corporation) was prepared as a raw material, and heat-treated under the test conditions shown in Table 6 to obtain each aluminum nitride powder. The conditions not listed in Table 6 are as follows: 200 g of aluminum nitride powder material was weighed into a cylindrical boron nitride container with a lid (a molded product made by Denka Co., Ltd., mainly composed of boron nitride (product name: Denka Boron Nitride N-1), inner diameter: 10 cm, height: 10 cm). The weight of the aluminum nitride powder material relative to the volume of the container was 0.5 g / cm. 3The weight of the aluminum nitride powder material relative to the volume in the container was set to below 0.05. If the weight of the aluminum nitride powder material relative to the volume in the container is too high, sintering of the aluminum nitride powder material will proceed, which will hinder an increase in diffuse reflectance, so this was taken into consideration. Furthermore, if the weight of the nitride powder (A) relative to the volume in the container is too high, the components volatilizing from the aluminum nitride powder material will be less likely to escape from the container, so the weight of the nitride powder (A) in the container was controlled as described above. Thereafter, the container was placed in an electric furnace equipped with a carbon heater, and the pressure was evacuated to 6 Pa or less. While evacuating with a vacuum pump, the temperature was raised to 1000°C in a vacuum state. When the temperature was above 1000°C, nitrogen gas was introduced, and the temperature was raised to the temperature conditions in Table 6 under a nitrogen gas atmosphere (pressure: 0.025 MPaG), and heating was performed at the set temperature in Table 6 (heat treatment I). After the nitrogen gas was introduced, the flow rate of the gas introduced into the furnace was set to A (L / min), and the volume in the furnace was set to B (m 3 ), and A / B (gas flow rate (L / min) ÷ furnace volume (m 3 ) was set to 33, and the introduction and discharge of gas was controlled to maintain a constant pressure. This was done to expel volatile components from the raw aluminum nitride powder material outside the furnace and to prevent the aluminum nitride powder material from being affected by the volatiles. After heating, the sample that had become loosely agglomerated in the container was placed in a mortar and crushed. After crushing, the sample was passed through a sieve with 250 μm openings to obtain a powdered sintered body (aluminum nitride powder; AlN).

[0187] Example 14 The same treatment as in Example 12 was carried out except that Ar gas was introduced during heat treatment I and treatment was carried out in an Ar gas atmosphere.

[0188] <Comparative Example 6> The aluminum nitride powder material was used as it was, and the above measurements (1) to (6) were carried out.

[0189] <Comparative Example 7> During heat treatment I, a container filled with aluminum nitride powder was placed in an electric furnace equipped with a carbon heater, and the furnace was evacuated to 6 Pa or less. Nitrogen gas was then introduced at room temperature, and the temperature was raised to the temperature shown in Table 6 under a nitrogen gas atmosphere (pressure: 0.025 MPaG). Heating was then carried out at the set temperature shown in Table 6. After the introduction of nitrogen gas, the flow rate of the gas introduced into the furnace was set to A (L / min), and the volume inside the furnace was set to B (m 3 ), and A / B (gas flow rate (L / min) ÷ furnace volume (m 3 The same treatments as in Examples 12 to 14 were carried out except that the temperature was set to 4 and the gas introduction and discharge were controlled so as to keep the pressure constant.

[0190] (8) Evaluation The silicon nitride powder, boron nitride powder, and aluminum nitride powder obtained in the above examples and comparative examples were evaluated as follows, and the results are shown in Table 7.

[0191] 0.5 g of the obtained nitride powder (A) was weighed out in the case of boron nitride, and 1.0 g in the case of silicon nitride or aluminum nitride, and 2.5 g of a photocurable resin (containing methacrylate monomer, product name Standard Photopolymer Resin Translucent, manufactured by ELEGOO, irradiated with light at 405 nm, viscosity (25°C) 150-200 mPa·s, UV-curable resin used in resin 3D printers was used to evaluate the curing speed of nitride powder (A) during stereolithography) was added and stirred until homogeneous using a mixer (THINKY ARV-310, manufactured by Thinky Corporation) to produce a paste-like composition for three-dimensional modeling. A polyethylene terephthalate (PET) film (250 μm thick) and a silicone sheet (1 mm thick) were placed on a glass plate (5 mm thick), and a paste-like three-dimensional modeling composition was poured into a 13 mm square opening that had been pre-made in the silicone sheet.The top surface was scraped off with a spatula to prepare a sample.

[0192] FIG. 2 is a diagram showing a schematic configuration of the UV irradiation test. As shown in FIG. 2, a frame-shaped boron nitride substrate 2 (15 mm thick) was placed on the top of a workbench 3, with a UV irradiator 1 installed on top. The prepared sample was placed on the top of the workbench 3 within the frame of the boron nitride substrate 2, and UV irradiation was performed using the UV irradiator 1 (1.5 hours for silicon nitride-based samples (Examples 1-6, Comparative Examples 1-3), 2 minutes for boron nitride-based samples (Examples 7-11, Comparative Examples 4 and 5), and 51 minutes for aluminum nitride-based samples (Examples 12-14, Comparative Examples 6 and 7)) to harden the three-dimensional modeling composition. The UV irradiator 1 used was a "BOX-S3000" manufactured by Sanhayato Corporation. The cured product was then removed from the sample silicone sheet, and the thickness (depth) of the cured region (cured part) near the center of the irradiated surface of the cured product was measured. The thicker (deeper) the cured region, the faster the modeling speed. The thickness (depth) of the cured region near the center of the irradiated surface of the cured product was measured after cutting or splitting the cured product near the center.

[0193] [Table 6]

[0194] [Table 7]

[0195] [Table 8]

[0196] This application claims priority based on Japanese Patent Application Nos. 2024-080743 and 2024-080746, filed May 17, 2024, the disclosures of which are incorporated herein in their entireties. [Explanation of symbols]

[0197] 1 UV irradiation machine 2. Boron nitride substrate 3 Workbench

Claims

1. Silicon nitride powder having a diffuse reflectance of 57% or more for light with a wavelength of 405 nm.

2. Silicon nitride powder having a diffuse reflectance of 54% or more for light with a wavelength of 355 nm.

3. A silicon nitride powder having a diffuse reflectance of 50.5% or more for light with a wavelength of 300 nm.

4. Silicon nitride powder having a diffuse reflectance of 40.7% or more for light with a wavelength of 250 nm.

5. 5. The silicon nitride powder according to claim 1, which is used as a raw material for stereolithography.

6. 5. The silicon nitride powder according to claim 1, which is used as a raw material for additive manufacturing.

7. 5. The silicon nitride powder according to claim 1, A silicon nitride powder having an internal oxygen content of 0.3 mass % or less.

8. 5. The silicon nitride powder according to claim 1, Specific surface area is 0.1m ２ / g or more, 20m ２ / g or less.

9. 5. The silicon nitride powder according to claim 1, Silicon nitride powder having a β ratio of 70% or more.

10. 5. The silicon nitride powder according to claim 1, Silicon nitride powder having an α ratio of 70% or more.

11. A composition for three-dimensional modeling, comprising the silicon nitride powder according to claim 1 .

12. A modeled object made from the composition for three-dimensional modeling according to claim 11.

13. A sintered compact of the shaped article according to claim 12.

14. The method for manufacturing a shaped object according to claim 12, A method for manufacturing a three-dimensional object, comprising the step of forming a predetermined pattern shape using the composition for three-dimensional modeling to obtain a three-dimensional object.

15. The method for manufacturing a shaped object according to claim 12, The method for producing a three-dimensional object includes irradiating the composition for three-dimensional object with electromagnetic waves or electron beams to cure the composition, thereby obtaining the three-dimensional object.

16. preparing a nitride powder material containing one or more compounds selected from the group consisting of group III compounds, group IV compounds, and group V compounds; heat-treating the nitride powder material at 400°C or higher and 2500°C or lower to obtain nitride powder; Including, In the step of obtaining the nitride powder, the nitride powder material is put into a furnace and heating is started, the internal pressure of the furnace is set to 50 Pa or less at temperatures below 100°C, and gas is introduced at temperatures above 100°C, the flow rate of the gas introduced into the furnace is set to A (L / min), and the volume of the furnace is set to B (m ３ ) and adjust the ratio A / B so that A / B>5.

17. 17. The method for producing a nitride powder according to claim 16, The method for producing nitride powder, wherein the gas introduction temperature during the heat treatment is 400°C or higher.

18. 18. The method for producing a nitride powder according to claim 17, The method for producing a nitride powder, wherein the nitride powder is one or more kinds selected from silicon nitride particles, aluminum nitride particles, and boron nitride particles.

19. Boron nitride powder having a diffuse reflectance of 93% or more for light with a wavelength of 355 nm.

20. Aluminum nitride powder having a diffuse reflectance of 74% or more for light with a wavelength of 405 nm.

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