Method for manufacturing a green body, and method for manufacturing a three-dimensional object.

Abstract

To provide a manufacturing method of a three-dimensional molded product from which a ceramic sintered body having high precision and high density can be obtained.SOLUTION: A manufacturing method of three-dimensional molded products is a method of molding a three-dimensional molded product using primary particles containing at least a ceramic material, the manufacturing method including: a forming step of forming a layer with the primary particles and secondary particles including binding resin; and an adding step of adding a liquid that dissolves the binding resin to the layer formed in the forming step, where a central particle diameter of the primary particles is 5 μm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention Method for manufacturing a green body, and Methods for manufacturing three-dimensional objects In the law Regarding [Background technology]

[0002] Recently, resin powders for fabricating complex and fine three-dimensional objects have been known, such as the one described in Patent Document 1. However, even when fabricating using the resin powder described in Patent Document 1, it has been difficult to obtain high-precision and high-density ceramic sintered bodies. [Overview of the project] [Problems that the invention aims to solve]

[0003] The present invention aims to provide a method for manufacturing three-dimensional objects that can produce highly accurate and high-density ceramic sintered bodies. [Means for solving the problem]

[0004] The present invention provides a method for manufacturing a green body as a means for solving the aforementioned problems, a method for forming a green body using primary particles containing a ceramic material, comprising: a forming step of forming a layer with the primary particles and secondary particles containing a binder resin; and a provisioning step of applying a liquid that dissolves the binder resin to the layer formed in the forming step, wherein the forming step and the provisioning step are repeated, the primary particles contained in the secondary particles are coated with the binder resin, the secondary particles contain 40% by mass or less of the binder resin, and the central particle size of the secondary particles is 100nm or more The particle size is 50 μm or less, the liquid contains inorganic particles, the water content is less than 5% by mass relative to the liquid, and the central particle size of the inorganic particles is primary particle Smaller than the central particle size. [Effects of the Invention]

[0005] According to the present invention, it is possible to provide a method for manufacturing a three-dimensional object that can obtain a highly accurate and high-density ceramic sintered body. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is a conceptual diagram showing an example of a method for manufacturing a three-dimensional object. [Figure 2] Figure 2 is a flowchart showing an example of the processing flow in a method for manufacturing three-dimensional objects. [Figure 3] Figure 3 is a functional block diagram showing an example of a manufacturing apparatus for three-dimensional objects. [Figure 4A] Figure 4A is a schematic diagram illustrating an example of a method for manufacturing a three-dimensional object (Part 1). [Figure 4B] Figure 4B is a schematic diagram illustrating an example of a method for manufacturing a three-dimensional object (part 2). [Figure 4C] Figure 4C is a schematic diagram illustrating an example of a method for manufacturing a three-dimensional object (part 3). [Figure 4D] Figure 4D is a schematic diagram illustrating an example of a method for manufacturing a three-dimensional object (part 4). [Figure 4E] Figure 4E is a schematic diagram illustrating an example of a method for manufacturing a three-dimensional object (Part 5). [Figure 4F] Figure 4F is a schematic diagram illustrating an example of a method for manufacturing a three-dimensional object (part 6). [Modes for carrying out the invention]

[0007] (Method for manufacturing three-dimensional objects and apparatus for manufacturing three-dimensional objects) The present invention relates to a method for manufacturing a three-dimensional object using primary particles containing at least a ceramic material, comprising a forming step of forming a layer with primary particles and secondary particles containing a binder resin, and a applying step of applying a liquid that dissolves the binder resin to the layer formed in the forming step, wherein the central particle size of the primary particles is 5 μm or less, and further includes other steps as necessary.

[0008] The manufacturing apparatus for a three-dimensional shaped object of the present invention is an apparatus for shaping a three-dimensional shaped object using primary particles containing at least a ceramic material, and includes a forming means for forming a layer with secondary particles including the primary particles and a binder resin, and an applying means for applying a liquid for dissolving the binder resin to the layer formed by the forming means. The center particle size of the primary particles is 5 μm or less, and further includes other means as necessary.

[0009] The manufacturing method for a three-dimensional shaped object of the present invention can be preferably implemented by the manufacturing apparatus for a three-dimensional shaped object of the present invention. The forming step can be performed by the forming means, the applying step can be performed by the applying means, and other steps can be performed by other means.

[0010] According to the present invention, ceramic primary particles with a small particle size in the nano order are granulated using a binder resin to form secondary particles, and a powder layer is formed using these secondary particles. A liquid for dissolving the binder resin is applied to the surface of this powder layer to return the secondary particles to primary particles, and by promoting densification, a high-density green body can be produced. As a result, the generation of internal defects in the green body can be suppressed, a high-strength sintered body can be obtained, and cracks and deformations in heat treatment processes such as debinding and sintering can be suppressed, so that a ceramic sintered body with high shape accuracy can be obtained. Also, according to the present invention, even for a shape having a thickness of several centimeters, it is possible to obtain a high-density ceramic sintered body without generating deformation, cracks, etc.

[0011] Here, the following is used as the definition of terms in the present invention. In the present invention, "three-dimensional shaping" refers to the process until the production of the green body before the debinding process. "Green body" in the present invention refers to an object composed of ceramics, a binder resin, and a solvent, which is formed by repeating the forming process and the applying process. "Three-dimensional shaped object" in the present invention mainly refers to a member after all processes are completed, indicating a state where debinding and sintering are completed.

[0012] The manufacturing method of the three-dimensional object of the present invention includes a forming step and an applying step, and further includes other steps as required. By repeating the forming step and the applying step a predetermined number of times, it becomes possible to obtain a homogeneous and highly accurate green body. The manufacturing apparatus of the three-dimensional object of the present invention has a forming means and an applying means, and further has other means as required.

[0013] <Forming step and forming means> The forming step is a step of forming a layer with secondary particles containing primary particles and a binding resin, and is carried out by a forming means. The forming step is carried out using secondary particles containing at least primary particles and a binding resin, and is a step of forming a powder layer, and may also be referred to as a "powder layer forming step".

[0014] - Primary particles - The main component of the primary particles in the present invention is ceramics. Ceramics means a sintered body obtained by heat-treating and sintering inorganic substances. Here, the main component means that the ceramics in the primary particles contain more than 50% by mass, and the content of the ceramics in the primary particles is preferably 80% by mass or more, and more preferably 90% by mass or more. Examples of the raw materials for ceramics include glass, metal oxides, metal carbides, metal nitrides, and the like.

[0015] Examples of glass include silica glass (quartz glass), soda lime silica glass, and the like. Examples of metal oxides include zirconia, alumina, mullite (aluminosilicate mineral), and the like. Examples of metal carbides include silicon carbide, tungsten carbide, and the like. Examples of metal nitrides include silicon nitride, aluminum nitride, and the like. Ceramics may be used individually or in combination of two or more types. Among these, zirconia, alumina, mullite (aluminosilicate mineral), tungsten carbide, silicon carbide, silicon nitride, and aluminum nitride are preferred from the viewpoint of maintaining high strength.

[0016] The central particle size of the primary particles is 5 μm or less, preferably 1 μm or less, and more preferably 500 nm or less. The lower limit of the central particle size of the primary particles is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 50 nm or more. When the central particle size of the primary particles is 5 μm or less, a high-density green material with fewer internal defects can be produced. The central particle size of primary particles is synonymous with the cumulative 50% volume particle diameter based on the volume-based particle size distribution, and can be measured using, for example, a laser diffraction / scattering particle size analyzer (LA-300, manufactured by Horiba, Ltd.). A powder for three-dimensional modeling is manufactured by creating secondary particles from primary particles. Because primary particles have a small particle size, they have low fluidity and are difficult to handle; processing them into secondary particles makes them easier to handle.

[0017] There are no particular restrictions on the method for producing secondary particles, and a suitable method can be selected depending on the purpose. For example, a method of mixing a binder resin with primary particles according to a known method can be used. There are no particular restrictions on the method of granulating primary particles with a binder resin, and any known granulation method can be appropriately selected. Examples include the rolling flow method, spray drying method, agitation granulation method, dipping method, and kneader coating method. Furthermore, these granulation methods can be carried out using various commercially available coating and granulation devices.

[0018] The secondary particles used in three-dimensional modeling contain a binding resin. The binding resin is used, for example, to bind primary particles together.

[0019] -Binding resin- The binding resin contained in the secondary particles contributes, for example, to the binding between primary particles, and to re-binding surrounding ceramic particles after dissolving during liquid dropping. There are no particular restrictions on the type of binder resin, and it can be appropriately selected according to the purpose. Examples include acrylic, maleic acid, silicone, butyral, polyester, polyvinyl acetate, vinyl chloride / vinyl acetate copolymer, polyethylene, polypropylene, polyacetal, ethylene / vinyl acetate copolymer, ethylene / (meth)acrylic acid copolymer, α-olefin / maleic anhydride copolymer, esterified α-olefin / maleic anhydride copolymer, polystyrene, poly(meth)acrylic acid ester, α-olefin / maleic anhydride / vinyl group-containing monomer copolymer, styrene / maleic anhydride copolymer, styrene / (meth)acrylic acid ester copolymer, polyamide, epoxy resin, xylene resin, ketone resin, petroleum resin, rosin or its derivatives, coumarone indene resin, terpene resin, polyurethane resin, styrene / butadiene rubber, polyvinyl butyral, nitrile rubber, acrylic rubber, synthetic rubber such as ethylene / propylene rubber, and nitrocellulose. These may be used individually or in combination of two or more types.

[0020] The central particle size of the secondary particles is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 50 μm or less, more preferably 40 μm or less, and particularly preferably 30 μm or less. The lower limit of the central particle size of the secondary particles is preferably 100 nm or more, more preferably 500 nm or more, and particularly preferably 1 μm or more. The central particle size of secondary particles is synonymous with the cumulative 50% volume particle diameter based on the volume-based particle size distribution, and can be measured using, for example, a laser diffraction / scattering particle size analyzer (LA-300, manufactured by Horiba, Ltd.). There are no particular restrictions on the binder resin content in the secondary particles, and it can be appropriately selected depending on the purpose. However, from the viewpoint of preventing cracking, defect formation, and deformation of the three-dimensional molded object, it is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, and particularly preferably 35% by mass or less. Furthermore, the lower limit of the binder resin content is preferably 1% by mass or more, and more preferably 3% by mass or more. Furthermore, secondary particles must not be subjected to heat treatment such as sintering.

[0021] There are no particular limitations on the method for forming the powder layer, and it can be appropriately selected depending on the purpose. Examples include a method using a known counter rotation mechanism (counter roller) used in the selective laser sintering method described in Japanese Patent Publication No. 3607300, a method of spreading the powder into a thin layer using components such as brushes, rollers, and blades, a method of spreading the powder into a thin layer by pressing the surface of the powder with a pressing member, and a method using a known powder additive manufacturing apparatus.

[0022] When forming a powder layer on a support using a counter-rotating mechanism (counter roller), brush or blade, pressing member, etc., for example, the powder layer is formed by placing the secondary particles on a support that is positioned to move up and down while sliding along the inner wall of an outer frame (sometimes referred to as a "mold," "hollow cylinder," or "cylindrical structure") within the outer frame, using a counter-rotating mechanism, brush, brush or blade, pressing member, etc. In this case, if a support that can move up and down within the outer frame is used, it is preferable to position the support slightly below the upper end opening of the outer frame (by the thickness of the powder layer) and place the powder on the support.

[0023] Furthermore, the powder layer can be formed automatically and easily using a known powder bed fusion apparatus. A powder bed fusion apparatus generally comprises a recoater for stacking secondary particles, a movable supply tank for supplying secondary particles onto a support, and a movable molding tank for forming and stacking layers of secondary particles. In this powder bed fusion apparatus, the surface of the supply tank can be raised slightly above the surface of the molding tank by raising the supply tank, lowering the molding tank, or both. Therefore, this powder bed fusion apparatus can form a powder layer by stacking secondary particles using the recoater from the supply tank side, and the powder layer can be stacked by repeatedly moving the recoater.

[0024] There are no particular restrictions on the average thickness of the powder layer, and it can be appropriately selected depending on the purpose. However, the average thickness per layer is preferably 10 μm to 200 μm, and more preferably 30 μm to 100 μm.

[0025] <Granting process and granting means> The application step involves applying a liquid that dissolves the binder resin to the layer formed in the forming step, and this is carried out by an application means. In the application process, the binder resin contained in the secondary particles is dissolved, converting them into primary particles. The primary particles then fill the voids formed between the secondary particles. As a result, the areas to which the liquid is applied are fixed by the binder resin, and the areas to which the liquid is applied become homogenized due to the breakdown of the shape of the secondary particles. This reduces the amount of voids and unsolidified areas in the areas to which the liquid is applied. Furthermore, the edges of the areas to which the liquid is applied can be reduced in the planar direction, which originates from the secondary particles, enabling highly accurate molding.

[0026] The application process is not particularly limited as long as it involves applying a liquid that dissolves the binder resin contained in the secondary particles to a predetermined area, and can be appropriately selected according to the purpose. Methods for applying liquid to a predetermined area include, for example, a dispenser method, a spray method, and an inkjet method. Among these methods, the dispenser method offers excellent droplet quantity control but has a limited coating area. The spray method allows for easy formation of fine particles, offers a wide coating area and excellent coating performance, but suffers from poor droplet quantity control and the scattering of secondary particles due to the spray flow. For this reason, the inkjet method is particularly preferred. Compared to the spray method, the inkjet method has the advantage of better droplet quantity control and a larger coating area compared to the dispenser method, and is preferred because it can form complex three-dimensional shapes accurately and efficiently. In the case of the inkjet method, the application means has a nozzle capable of applying liquid to a predetermined area by the inkjet method. A nozzle (discharge head) from a known inkjet printer can be suitably used as the nozzle, and an inkjet printer can also be suitably used as the application means. A suitable example of an inkjet printer is the Ricoh SG7100. Inkjet printers are preferable because they can dispense a large amount of liquid at once from the head and have a wide coating area, thus enabling high-speed coating.

[0027] <<Liquid>> As for the liquid, there are no particular restrictions as long as it can dissolve the binder resin of the secondary particles, and it can be appropriately selected according to the purpose. The liquid preferably contains a solvent, a resin, and inorganic particles, and may further contain other components as needed.

[0028] -solvent- There are no particular restrictions on the solvent, and it can be appropriately selected depending on the purpose. Examples include water, alcohols with 2 to 7 carbon atoms, ketones with 3 to 8 carbon atoms, cyclic ethers, and polyethers. These may be used individually or in combination of two or more.

[0029] Examples of alcohols with 2 to 7 carbon atoms include ethyl alcohol, isopropanol, and n-butanol. Examples of ketones having 3 to 8 carbon atoms include acetone and ethyl methyl ketone. Examples of cyclic ethers include tetrahydrofuran. Examples of polyethers include dimethoxyethanol and dimethoxydiethylene glycol.

[0030] There are no particular restrictions on the solvent content in the liquid; it can be appropriately selected depending on the purpose. Furthermore, if the liquid contains resin, the solvent content in the liquid is preferably 60% by mass or more and 95% by mass or less, and more preferably 70% by mass or more and 90% by mass or less. If the liquid does not contain resin, the solvent content in the liquid is preferably 50% by mass or more and 99% by mass or less, and more preferably 70% by mass or more and 90% by mass or less. A low water content in the liquid is preferable. The water content in the liquid is preferably less than 45% by mass, and preferably less than 5% by mass.

[0031] -resin- There are no particular restrictions on the resin used, and it can be appropriately selected depending on the purpose. Examples include acrylic, maleic acid, silicone, butyral, polyester, polyvinyl acetate, vinyl chloride / vinyl acetate copolymer, polyethylene, polypropylene, polyacetal, ethylene / vinyl acetate copolymer, ethylene / (meth)acrylic acid copolymer, α-olefin / maleic anhydride copolymer, esterified α-olefin / maleic anhydride copolymer, polystyrene, poly(meth)acrylic acid ester, α-olefin / maleic anhydride / vinyl group-containing monomer copolymer, styrene / maleic anhydride copolymer, styrene / (meth)acrylic acid ester copolymer, polyamide, epoxy resin, xylene resin, ketone resin, petroleum resin, rosin or its derivatives, coumarone indene resin, terpene resin, polyurethane resin, styrene / butadiene rubber, polyvinyl butyral, nitrile rubber, acrylic rubber, synthetic rubber such as ethylene / propylene rubber, and nitrocellulose. These may be used individually or in combination of two or more. Furthermore, the resin may be a polymer compound of an organic or organometallic substance with low hydrophilicity.

[0032] There are no particular restrictions on the resin content in the liquid, and it can be appropriately selected depending on the purpose. However, from the viewpoint of controlling the viscosity of the liquid within a predetermined range, 5% by mass or more and 40% by mass or less is preferred, and 10% by mass or more and 30% by mass or less is more preferred.

[0033] -Inorganic particles- The liquid preferably contains inorganic particles with a medium particle size that does not clog the nozzle. When the liquid contains inorganic particles, the inorganic particles are positioned in the gaps between the powder particles in a given area when the liquid is applied to that area. As a result, the density of the resulting three-dimensional object is improved.

[0034] The material of the inorganic particles is preferably the same as the material of the raw materials for the ceramics, and more preferably zirconia, alumina, mullite (aluminosilicate mineral), tungsten carbide, silicon carbide, silicon nitride, or aluminum nitride.

[0035] The central particle size of the inorganic particles is not particularly limited as long as it is smaller than the central particle size of the ceramic raw material, and can be appropriately selected according to the purpose, but it is preferably 0.05 μm or more and 0.5 μm or less. The central particle size of inorganic particles is synonymous with the cumulative 50% volume particle diameter based on the volume-based particle size distribution, and can be measured using, for example, a laser diffraction / scattering particle size analyzer (LA-300, manufactured by Horiba, Ltd.). There are no particular restrictions on the inorganic particle content, and it can be appropriately selected depending on the purpose, but it is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, relative to the total volume of the liquid. The upper limit of the inorganic particle content is preferably 60% by mass or less, and more preferably 50% by mass or less.

[0036] -Other ingredients- Other ingredients are not particularly limited and can be selected as appropriate depending on the purpose, such as dispersants and surfactants.

[0037] <Other processes> Other processes are not particularly limited and can be selected as appropriate depending on the purpose, such as heat treatment processes. Heat treatment processes include drying, degreasing, and sintering. While heat treatment can be performed according to the material, the resulting green body generally has a distinctive shape, and therefore, pressurization is often not used to prevent its collapse. In particular, in sintering, pressurized sintering (hot pressing) is often performed to improve sintering density, but in this invention, this is not used, and atmospheric pressure sintering is basically assumed. In this invention, a method for manufacturing a three-dimensional object made of ceramics is used, in which the raw materials of the three-dimensional object are temporarily bonded together before the object is obtained. In this case, even if resin is used for bonding, for example, only a small amount of resin is needed, resulting in less volume shrinkage after sintering. As a result, cracking during sintering can be prevented even when fabricating large structural members, making it possible to fabricate models with dimensions that are practical for use as structural members.

[0038] The green body, formed by repeating the formation and application processes, is embedded in the powder when the three-dimensional molding is completed. At that stage, the green material contains a large amount of solvent, resulting in low strength and poor handling properties, so drying is necessary. Drying can also be performed layer by layer using an infrared heater or the like after the forming and imparting processes. There are no particular restrictions on the drying method, and any known method can be used. However, it is necessary to select a method that does not cause cracking or deformation depending on the type of solvent. For example, if ethanol is used as the solvent, it is preferable to dry at 50°C for 24 hours.

[0039] There are no particular restrictions on the degreasing method, and any well-known method can be used. For example, when kaolin is used as the primary particle, degreasing can be suitably achieved by heat treatment at 500°C for 3 hours under a nitrogen-purged environment, but the method is not limited to this.

[0040] There are no particular restrictions on the sintering method, and well-known methods can be used, but in order to maximize the effects of the present invention, it is preferable to perform sintering under atmospheric pressure. The atmosphere, heat treatment temperature, and heat treatment time need to be adjusted depending on the material. For example, when alumina is used as the primary particle, heat treatment at 1,550°C for 3 hours under an argon atmosphere is preferable. Increasing the heat treatment temperature can increase the density, but this also has disadvantages such as a decrease in strength due to the formation of coarse particles and deformation, so optimization of the conditions is necessary. As for the sintering method, for example, in the case of graphite type, an electric current sintering method such as pulsed current heating can be suitably used, but it is not limited to this.

[0041] (3D model) The three-dimensional object of the present invention is manufactured by the method for manufacturing the three-dimensional object of the present invention, or by the apparatus for manufacturing the three-dimensional object of the present invention.

[0042] There are no particular restrictions on the use of three-dimensional objects; they can be appropriately selected according to the purpose. For example, they are suitable for use in meters and control panels of automobiles, office automation equipment, electrical and electronic equipment, cameras, various parts, daily necessities, prototypes, and more.

[0043] Here, using drawings, an example of a method for manufacturing a three-dimensional object and an example of a manufacturing apparatus for a three-dimensional object according to the present invention will be explained.

[0044] Figure 1 is a conceptual diagram of the manufacturing process for three-dimensional objects. Figure 1 illustrates a three-dimensional object manufacturing apparatus 100 and a computer 103. The three-dimensional object manufacturing apparatus 100 has a molding unit 101 and a post-processing unit 102. In the manufacturing of three-dimensional objects, 3D data of the object is sent from the computer 103 to the molding unit 101, where the molding unit 101 performs molding based on the 3D data. Subsequently, post-processing such as heat treatment is performed in the post-processing unit 102 to complete the three-dimensional object.

[0045] This document describes a method for manufacturing three-dimensional objects and an example of a manufacturing apparatus for such objects. Figure 2 is a flowchart showing an example of the processing flow in the manufacturing method of a three-dimensional object. The processing flow in the manufacturing method of the three-dimensional object of the present invention shown in Figure 2 will be explained below with reference to Figures 3 and 4A to 4F. Figure 3 is a functional block diagram showing an example of a manufacturing apparatus for three-dimensional objects. The three-dimensional object manufacturing apparatus 100 shown in Figure 3 has a molding section 101 and a post-processing section 102. The molding section 101 has a forming means 1 and a coating means 2. The post-processing section 102 has a heat treatment means 3. Figures 4A to 4F are schematic diagrams illustrating an example of a method for manufacturing three-dimensional objects.

[0046] In step S1, when the user inputs the number of repetitions to the three-dimensional object manufacturing device 100, the process moves to S2.

[0047] In step S2, when the user inputs k=0 to the three-dimensional object manufacturing device 100, the process moves to S3.

[0048] In step S3, once the manufacturing apparatus 100 for the three-dimensional object has completed the forming process, the process moves on to S4. Before the formation process, secondary particles are granulated using primary particles containing ceramic material and a binder resin (see Figure 4A). In the forming process, a powder layer is formed from primary particles containing ceramic material and secondary particles containing a binder resin. The forming process can be carried out, for example, using a forming means. The forming mechanism includes, for example, a supply-side powder storage tank 52 for storing secondary particles 51, a molding-side powder storage tank 54 for forming a powder layer, and a leveling mechanism 55, as shown in Figure 4B. The supply-side powder storage tank 52 has a vertically movable stage 50. The molding-side powder storage tank 54 has a vertically movable stage 53. As the roller, which acts as the leveling mechanism 55, moves from the supply-side powder storage tank 52 to the molding-side powder storage tank 54, the secondary particles 51 in the supply-side powder storage tank 52 move to the molding-side powder storage tank 54, and a powder layer 56 consisting of the secondary particles 51 is formed on the stage 53 (see Figure 4C).

[0049] In step S4, once the manufacturing apparatus 100 for the three-dimensional object has completed the application process, the process moves on to S5. In the application step, a liquid that dissolves the binder resin is applied to the powder layer formed in the forming step, dissolving the binder resin contained in the secondary particles and converting the secondary particles into primary particles. The application step is performed, for example, using an application means. An application means is, for example, an inkjet head 57, as shown in Figure 4D. Using the inkjet head 57, the liquid 58 that dissolves the binder resin is applied to a predetermined area of ​​the powder layer 56. Then, as shown in Figure 4E, the binder resin contained in the secondary particles is dissolved and converted into primary particles, filling the voids formed between the secondary particles with primary particles. As a result, the area to which the liquid was applied is fixed by the binder resin, and the area to which the liquid was applied is homogenized as the shape of the secondary particles is disrupted, reducing the amount of voids and unsolidified areas in the area to which the liquid was applied.

[0050] In step S5, if we set k+1=k, we proceed to S6.

[0051] In step S6, if k is less than the number of iterations, the process moves to S3; if k is greater than or equal to the number of iterations, the process moves to S7. The forming process and the application process are repeated until the desired number of layers is reached. In this way, a layered structure is obtained on the stage 53. By drying this, a green body 59 as shown in Figure 4F is obtained.

[0052] In step S7, the manufacturing apparatus 100 for the three-dimensional object completes the process by performing a heat treatment step. In the heat treatment step, the dried green body is heated. The heat treatment step is performed using, for example, a heat treatment means 3. Examples of heat treatment means 3 include a heating device. In the heat treatment step, for example, the decomposition and removal of the resin and the sintering of the green body can be performed in one step. As a result, a sintered body is obtained by sintering the raw materials of ceramics. [Examples]

[0053] The following describes embodiments of the present invention, but the present invention is not limited in any way to these embodiments.

[0054] (Examples 1-14) The three-dimensional object was manufactured according to the flowchart shown in Figure 2 and the manufacturing method for the three-dimensional object shown in Figures 4A to 4F.

[0055] The powder used was prepared using the materials shown in Table 1 below, as described below. <Preparation of primary and secondary particles> First, raw material particles (primary particles; fine particles of kaolin, titanium dioxide, or alumina) with a predetermined central particle size, as shown in Table 1, and a binder resin (polyvinyl butyral (PVB)) were mixed together in a solvent (ethanol) and thoroughly dispersed to prepare a slurry. Next, the obtained slurry was granulated into droplets using a spray granulator and a drying sintering furnace, and then dried. Secondary particles with the central particle sizes shown in Table 1 were obtained by classification as needed. Next, the secondary particles were sintered. The secondary particles have a three-dimensional structure in which fine primary particles are bonded to each other, creating gaps, and are roughly spherical in shape. The size of the primary particles in these samples varied considerably, corresponding to the central particle size of the raw material particles. The central particle sizes of the primary and secondary particles were measured as follows. The results are shown in Table 1.

[0056] -Measurement of central particle size of primary and secondary particles- The central particle size of primary and secondary particles was measured using a laser diffraction / scattering particle size analyzer (LA-300, manufactured by Horiba, Ltd.), and the cumulative 50% particle size (D) is based on the volume-based particle size distribution. 50 )

[0057] <Liquid for dissolving the binder resin> Ethyl acetate was used as the main solvent, SN Dispersant 5468 from Sannopco was used as a dispersant, and inorganic particles as shown in Table 2 were added as needed. These were then stirred for 24 hours and used as the solution.

[0058] <Sculpture> The 3D printing was performed using a binder jet 3D printer (Desktopmetal), specifically a simplified prototype machine that had been modified to be partially solvent-compatible. The layer spacing was set to 100 μm. The printed model was a cube measuring 10 mm × 10 mm × 10 mm. A liquid that dissolves the binder resin was applied to the desired area. The amount of liquid applied was set to 600 dpi.

[0059] <Degreasing and Sintering> Degreasing and sintering were performed using an electric furnace, with the temperature raised at 5°C / min to predetermined temperatures between 1,100°C and 1,500°C, held for 2 hours each, and then cooled in the furnace.

[0060] [Table 1]

[0061] [Table 2]

[0062] Details of each material in Tables 1 and 2 are as follows:

[0063] -Primary particles- *Kaolin 1: HYDRITE r manufactured by Hayashi Kasei Co., Ltd., central particle size (D 50 ) = 5 μm *Kaolin 2: Hydrite SB 100 manufactured by Hayashi Chemical Co., Ltd., median particle size (D 50 ) = 1 μm *Kaolin 3: Eckalite 1, manufactured by Hayashi Chemical Co., Ltd., central particle size (D 50 ) = 500nm *Titanium dioxide 1: ST-01 manufactured by Ishihara Sangyo Co., Ltd., central particle size (D 50 ) = 10nm *Titanium dioxide 2: Custom-made ST series product manufactured by Ishihara Sangyo Co., Ltd., central particle size (D 50 ) = 50nm *Alumina 1: Sumitomo Chemical Co., Ltd. AA series, median particle size (D 50 ) = 5 μm *Alumina 2: AA series manufactured by Sumitomo Chemical Co., Ltd., median particle size (D 50 ) = 500 nm

[0064] -Binder resin- *PVB (polyvinyl butyral, manufactured by Sekisui Chemical Co., Ltd., Esrec B) *Acrylic resin (manufactured by Daisheng Fine Chemical Co., Ltd., acrylic polyol)

[0065] -Inorganic particles- *Mullite 1: Custom-made KM series by Kyoritsu Materials Co., Ltd., median particle size (D 50 ) = 1 μm *Mullite 2: Custom-made KM series by Kyoritsu Materials Co., Ltd., median particle size (D 50 ) = 500 nm *Alumina A: AKP series manufactured by Sumitomo Chemical Co., Ltd., median particle size (D 50 ) = 1 μm *Alumina B: AKP series manufactured by Sumitomo Chemical Co., Ltd., median particle size (D 50 ) = 50 nm

[0066] (Comparative Examples 1 - 6) As shown in Table 3, shaping was performed using a general binder jet method by repeatedly applying a liquid (pure water) in which polyvinyl alcohol (PVA) was added as a binder resin to a commercially available ceramic material (alumina or kaolin). Inorganic particles were added to the liquid (pure water) in which polyvinyl alcohol (PVA) was added as a binder resin as shown in Table 3 as necessary. Note that in Comparative Examples 1 - 6, since commercially available products were used as the ceramic material, secondary particles were not formed (primary particles).

[0067]

Table 3

[0068] Details of each material in Table 3 are as follows.

[0069] -Powder (primary particles)- *Alumina 1: Sumitomo Chemical Co., Ltd. AA series, median particle size (D 50 ) = 5 μm *Alumina 3: AA series manufactured by Sumitomo Chemical Co., Ltd., central particle size (D 50 ) = 50 μm *Alumina 4: AA series manufactured by Sumitomo Chemical Co., Ltd., central particle size (D 50 ) = 20 μm *Alumina 5: AA series manufactured by Sumitomo Chemical Co., Ltd., central particle size (D 50 ) = 1 μm *Kaolin 4: Hydrite SB 100S manufactured by Hayashi Chemical Co., Ltd., granulated in-house, median particle size (D 50 ) = 20 μm

[0070] -Binding resin- *PVA: Cellball manufactured by Sekisui Chemical Co., Ltd.

[0071] -Inorganic particles- *Alumina B: AKP series manufactured by Sumitomo Chemical Co., Ltd., median particle size (D 50 ) = 50nm

[0072] Next, the characteristics of each resulting three-dimensional object were evaluated as follows. The results are shown in Table 4.

[0073] <Condition evaluation of three-dimensional objects after degreasing and sintering> During the degreasing and sintering processes, each resulting three-dimensional object was observed for abnormal deformation, cracking, etc., and evaluated according to the following criteria. [Evaluation Criteria] ○: No abnormal deformation such as distortion. △: Although difficult to discern visually, distortion or other deformation has occurred as a result of measurements such as length measurement. ×: Clear deformation or cracking is visible to the naked eye.

[0074] <Arithmetic mean surface roughness Ra> As an indicator for evaluating the accuracy of each obtained three-dimensional object, the surface roughness of the three-dimensional object was measured. For the surface of each three-dimensional object, the arithmetic mean surface roughness Ra was calculated in accordance with JIS B0601:2001 and evaluated according to the following criteria. [Evaluation Criteria] ◎: Arithmetic mean surface roughness Ra is 30 μm or less ○: Arithmetic mean surface roughness Ra is greater than 30 μm and 80 μm or less. △: Arithmetic mean surface roughness Ra is greater than 80 μm and less than or equal to 100 μm. ×: Arithmetic mean surface roughness Ra is greater than 100 μm

[0075] <Porosity> To evaluate the finish of each resulting three-dimensional object, the porosity of the object was measured. The Archimedes method using a balance was employed to measure the porosity. Specifically, the weight of the solid was measured in air (A), then its weight was measured again in a displacement solution (water) (B), and the porosity was calculated using the following formula: [(B)-(A)] / (A)×100, and evaluated according to the following criteria. [Evaluation Criteria] ◎: Porosity of 1% or less ○: Porosity greater than 1% and less than or equal to 10% △: Porosity greater than 10% and less than or equal to 20% ×: Porosity greater than 20%

[0076] [Table 4] *In Comparative Example 6 in Table 4, the arithmetic mean surface roughness "-" and porosity "-" indicate that measurement was not possible.

[0077] Examples of the present invention are as follows: <1> A method for creating a three-dimensional object using primary particles containing at least ceramic material, A forming step of forming a layer with the primary particles and secondary particles containing a binder resin, The process includes a step of applying a liquid that dissolves the binder resin to the layer formed in the forming step, This method for manufacturing a three-dimensional object is characterized in that the central particle size of the primary particles is 5 μm or less. <2> The central particle size of the primary particle is 0.01 μm or more and 1 μm or less, <1> This is a method for manufacturing three-dimensional objects as described above. <3> The liquid contains inorganic particles, <1> from <2> This is a method for manufacturing a three-dimensional object as described in any of the following. <4> The inorganic particles have a central particle size of 0.05 μm or more and 0.5 μm or less. <3> This is a method for manufacturing three-dimensional objects as described above. <5> The inorganic particles are contained in the liquid at a concentration of 20% by mass or more. <3> from <4> This is a method for manufacturing a three-dimensional object as described in any of the following. <6> The primary particles or inorganic particles include at least one selected from alumina, silicon nitride, mullite, zirconia, silicon carbide, tungsten carbide, and aluminum nitride. <3> from <5> This is a method for manufacturing a three-dimensional object as described in any of the following. <7> The central particle size of the secondary particle is 50 μm or less, <1> from <6> This is a method for manufacturing a three-dimensional object as described in any of the following. <8> The secondary particles contain 40% by mass or less of the binder resin, <7> This is a method for manufacturing three-dimensional objects as described above. <9> The aforementioned application step involves applying the liquid by an inkjet method. <1> from <8> This is a method for manufacturing a three-dimensional object as described in any of the following. <10> The process further includes a volatilization step of volatilizing the aforementioned liquid. <1> from <9> This is a method for manufacturing a three-dimensional object as described in any of the following. <11> A device for creating three-dimensional objects using primary particles containing at least ceramic material, Forming means for forming a layer with the primary particles and secondary particles containing a binder resin, A means for applying a liquid that dissolves the binder resin to the layer formed by the forming means, It has, This is a manufacturing apparatus for three-dimensional molded objects, characterized in that the central particle size of the primary particles is 5 μm or less. <12> The aforementioned <1> from <10> A method for manufacturing a three-dimensional object as described in any of the above, and the <11> This is a three-dimensional object characterized by being obtained by any of the three-dimensional object manufacturing apparatuses described above.

[0078] The aforementioned <1> from <10> A method for manufacturing a three-dimensional object as described in any of the above, <11> The apparatus for manufacturing three-dimensional objects as described above, and the <12> The three-dimensional model described herein can solve the problems of the past and achieve the objectives of the present invention. [Explanation of symbols]

[0079] 51 Secondary particles 52 Supply-side powder storage tank 53 stages 54 Powder storage tank on the molding side 55. Leveling mechanism (roller) 56 Powder layer 57 Inkjet heads 58 Liquid for dissolving the binder resin 59 Green body 100 Manufacturing equipment for three-dimensional objects 101 Modeling Department 102 Post-processing 103 Computer [Prior art documents] [Patent Documents]

[0080] [Patent Document 1] Patent No. 6520182

Claims

1. A method for fabricating a green body using primary particles containing ceramic material, A forming step of forming a layer with the primary particles and secondary particles containing a binder resin, The process includes a step of applying a liquid that dissolves the binder resin to the layer formed in the forming step, The forming step and the imparting step are repeated, The primary particles contained in the secondary particles are coated with the binder resin. The secondary particles contain 40% by mass or less of the binder resin. The central particle size of the secondary particles is 100 nm or more and 50 μm or less. The liquid is characterized by containing inorganic particles, having a water content of less than 5% by mass relative to the liquid, and the central particle size of the inorganic particles being smaller than the central particle size of the primary particles. A method for manufacturing a green body.

2. The method for producing a green body according to claim 1, wherein the central particle size of the primary particles is 5 μm or less.

3. The method for producing a green body according to any one of claims 1 to 2, wherein the inorganic particles have a central particle size of 0.05 μm or more and 0.5 μm or less.

4. The method for producing a green body according to any one of claims 1 to 3, wherein the inorganic particles are contained in the liquid in an amount of 20% by mass or more.

5. A method for producing a green body according to any one of claims 1 to 4, wherein the primary particles or inorganic particles include at least one selected from alumina, silicon nitride, mullite, zirconia, silicon carbide, tungsten carbide, and aluminum nitride.

6. The method for producing a green body according to any one of claims 1 to 5, wherein the application step involves applying the liquid by an inkjet method.

7. A method for producing a green substance according to any one of claims 1 to 6, further comprising a volatilization step of volatilizing the aforementioned liquid.

8. The method for producing a green body according to any one of claims 1 to 7, characterized in that the secondary particles are granulated from the primary particles and the binder resin.

9. A method for creating a three-dimensional object using a green body obtained by a method for manufacturing a green body according to any one of claims 1 to 8, A method for manufacturing a three-dimensional object, characterized by including a sintering step of sintering the aforementioned green body.

10. The method for manufacturing a three-dimensional object according to claim 9, characterized in that the sintering step is carried out under normal pressure.