JP7100867B2 - Manufacturing method of ceramic molded body and ceramic molded body - Google Patents

Description

The present invention relates to a method for manufacturing a ceramic molded body for manufacturing a ceramic molded body by a laminated molding method and a ceramic molded body manufactured by the manufacturing method.

Conventionally, a three-dimensional laminated modeling technique (Adaptive Manufacturing, hereinafter also referred to as AM) is a technique for modeling a three-dimensional complex shape from three-dimensional CAD data by additional manufacturing. AM is shifting from using mainly prototypes such as shape confirmation to direct digital manufacturing (DMM) that uses the modeled body as a member of the final product, and the materials that can be used as members are also metal materials and supermarkets. Development of various materials such as engineering plastics is in progress. On the other hand, regarding ceramics, there are few dedicated modeling devices, and there are very few cases of 3D commercialization in Japan. Since ceramics are a difficult-to-cut material that is hard and brittle compared to metal materials, there has been a demand for a final shape and near-net shape that do not require processing for some time, and there are great expectations for ceramics AM.

Various types of AM for ceramics have been proposed, such as a stereolithography method, a powder bed melt bonding method, and a material extrusion method. Patent Document 1 shows ceramics molding by a powder bed melt-bonding method (powder bed method), and is obtained by a step of dispersing ceramic fine particles in a liquid thermosetting resin or the like and a step of the dispersion step. A modeling material used for three-dimensional modeling, comprising a step of curing the mixture and a step of crushing the cured product obtained in the curing step into particles having a larger particle size than the ceramic fine particles to obtain a modeling material. The manufacturing method of is shown. However, the technique described in Patent Document 1 simultaneously performs laminated molding and direct sintering to obtain a molded block body, and direct sintering molding in AM of ceramics is a powder bed melt bonding method in metal laminated molding. Since it is the same idea, it is a construction method expected in the future, but ceramics are vitrified when melt-bonded at high temperature, and the original characteristics of ceramics cannot be exhibited, and because granules and powders of several tens of microns are used, they are high-definition. It was difficult to model.

Further, in the method of manufacturing a three-dimensional ceramic member by using the material extrusion method, when the adhesion strength between the laminated layers is weak, or when the layers (z direction) or the lateral direction (xy direction) are defective. May occur. For this reason, there is a possibility that the mechanical strength of the three-dimensional laminated member becomes significantly smaller than the required strength, and that breakage occurs between the layers formed in the laminated layer. ..

On the other hand, the stereolithography method is known as a method capable of high-definition modeling. Stereolithography is roughly divided into top surface irradiation (free liquid level method) and bottom surface irradiation (regulated liquid level method) according to the light irradiation direction, and laser point exposure scanning type and projector (DLP) depending on the light irradiation method. It can be divided into formula surface exposure types. Among these, the bottom surface irradiation type DLP stereolithography method irradiates light from the bottom surface through a transparent sheet or the like, has a flat exposed surface, and does not require a complicated squeezing mechanism, so that the device tends to be simple. By projecting image data layer by layer and stacking them, it is possible to produce a modeled object quickly and inexpensively.

As ceramics molding by stereolithography, Patent Document 2 describes (A) ceramic particles having a number average particle size of 0.01 to 0.5 μm by electron microscopy, and (B) a compound having a polymerizable functional group. (C) By using a photocurable liquid composition having a photocurable liquid composition containing a photopolymerization initiator, the ceramic filling ratio in the mixture of the ceramic powder or the like and the binder composition can be determined. A method for producing a three-dimensional shape object, which can exhibit good fluidity and photocurability even when the amount is increased and can easily form a desired three-dimensional shape object by a photolamination modeling method, is disclosed. However, Patent Document 2 basically relates to ceramics molding by a laser point exposure scanning type, does not show details of the influence of irradiation conditions on molding accuracy, and is a defect of the molded sintered body. And strength characteristics are not shown.

Further, in Patent Document 3, an ultraviolet polymerizable property is imparted to the particles by bonding a polymerizable unsaturated group to the ceramic particles, and an optical method is used in the layer of the ultraviolet curable resin composition containing the particles. Disclosed is a technique for obtaining a fine three-dimensional shape by condensing ultraviolet rays and moving the condensing position three-dimensionally to cure an arbitrary position. Further, in Patent Document 3, if extremely fine ceramic particles having a particle size of 70 nm or less are used, the transmittance of ultraviolet rays is high and the scattering of light can be suppressed, so that finer and more complicated modeling becomes possible. Is also shown. As described above, Patent Document 3 shows that fine and complicated modeling is possible by using extremely fine ceramic particles having high transmittance of ultraviolet rays and capable of suppressing light scattering. In order to obtain a dense sintered body, an impregnation step of the fluid ceramic material is required after molding. In this step, the fluid ceramic material is deposited on the surface of the molded body and penetrates sufficiently evenly into the inside. In addition, there is a risk that this method will not be used, and in this method, a micro model of 1 to 1000 μm order is basically produced, and it is not suitable for producing a model of several millimeters to several centimeters or more.

JP-A-2018-69549 Japanese Unexamined Patent Publication No. 2006-257323 Japanese Unexamined Patent Publication No. 2006-76822

The bottom-illuminated DLP-type stereolithography, which is a type of stereolithography, can produce high-definition ceramic moldings, but in ceramics molding utilizing this method, various moldings derived from the molding method are used. Defects are inherent and may therefore reduce mechanical properties as compared to conventional methods such as injection molding. There are the following three specific modeling defects that can be assumed.
(1) Delamination due to insufficient bonding of laminated interfaces due to the presence of factors that inhibit adhesion at the interface.
(2) End face step due to irradiation energy difference in each stacking pitch (3) End face step due to projector resolution (pixels)

No method has been reported for efficiently and optimally improving all of these problems in the bottom-illuminated DLP stereolithography method. Unless these problems are overcome, a ceramic model having sufficient mechanical properties cannot be obtained, and high-quality DDM of ceramics cannot be achieved.

It is an object of the present invention to provide a method for producing a high-definition ceramic molded product having a three-dimensional complex shape by improving the above-mentioned modeling defects in a bottom-illuminated DLP-type stereolithography method, and providing a ceramic molded product produced by the method. It is supposed to be.

The present invention has been made to solve the above problems. That is, a main object of the present invention is to provide a technique capable of increasing the mechanical strength of a ceramic molded product manufactured by a three-dimensional laminated molding method.

（上記式において、σ _f は脆性材料の破壊強度、Ｙは微小クラックの形状因子、ｃは前記臨界亀裂長さ、Ｋ _ＩＣ は臨界応力拡大係数である。）
セラミックス成形体の製造方法。
（２）前記造形工程において、各層を鉛直方向に対して斜め方向に積層させる場合に、前記端面段差が臨界亀裂長さよりも小さくなる照射単位面積で照射光の照射範囲を制御しながら、各層を積層造形することを特徴とする、上記（１）に記載のセラミックス成形体の製造方法。
（３）前記造形工程において、積層ピッチに対して１／５以下の平均粒子径を有するセラミックス粉末を、光硬化性樹脂に１０体積％以上８０体積％以下添加した光硬化性セラミックススラリーを使用して造形することを特徴とする、上記（１）または（２）に記載のセラミックス成形体の製造方法。
（４）前記造形工程において使用する光硬化性セラミックススラリーの粘度が３００ｍＰａ・ｓ～５０００ｍＰａ・ｓであることを特徴とする、上記（１）ないし（３）のいずれかに記載のセラミックス成形体の製造方法。
（５）前記造形工程において、積層ピッチに応じて特定される必要最小照射エネルギーの１．２～３．０倍の照射エネルギーの照射光を照射して造形を行うことを特徴とする、上記（１）ないし（４）のいずれかに記載のセラミックス成形体。
（６）前記造形工程において、照射光の照射エネルギーを一定としながら照射強度を低くすることで硬化深さが低下し始める照射強度を基準照射強度とした場合に、照射光の照射強度を前記基準照射強度の４０～２００％の強度にして造形を行うことを特徴とする、上記（１）ないし（５）のいずれかに記載のセラミックス成形体。
（７）焼結後のセラミックス成形体において、積層界面剥離が生じておらず、かつ、寸法誤差が５％以内である、上記（１）ないし（６）のいずれかに記載のセラミックス成形体の製造方法。
The gist of the present invention is the method for producing a ceramic molded product according to the following (1) to (7).
(1) In the method for manufacturing a ceramic molded body by a bottom-illuminated DLP-type stereolithography method .
A molding process in which the end face step of the ceramic molded body after sintering is set to be smaller than the critical crack length and each layer is laminated at the laminated pitch , and the molded ceramic molded body is fired at normal pressure. A method for manufacturing a ceramic molded body, which comprises a step and the critical crack length is determined based on the following formula .

(In the above equation, σ _f is the fracture strength of the brittle material, Y is the shape factor of the microcracks, c is the critical crack length, and KIC _is the critical stress intensity factor.)
A method for manufacturing a ceramic molded product.
(2) In the modeling step, when each layer is laminated in an oblique direction with respect to the vertical direction, each layer is controlled while controlling the irradiation range with an irradiation unit area in which the end face step is smaller than the critical crack length. The method for manufacturing a ceramic molded body according to (1) above, which comprises laminating molding.
(3) In the molding step, a photocurable ceramic slurry obtained by adding 10% by volume or more and 80% by volume or less of ceramic powder having an average particle diameter of 1/5 or less with respect to the stacking pitch to a photocurable resin is used. The method for producing a ceramic molded product according to (1) or (2) above, which is characterized by molding.
(4) The ceramic molded product according to any one of (1) to (3) above, wherein the photocurable ceramic slurry used in the molding step has a viscosity of 300 mPa · s to 5000 mPa · s. Production method.
(5) The above-mentioned (5), which is characterized in that, in the modeling step, irradiation light with an irradiation energy of 1.2 to 3.0 times the required minimum irradiation energy specified according to the stacking pitch is irradiated to perform modeling. The ceramic molded body according to any one of 1) to (4).
(6) In the modeling step, when the irradiation intensity at which the curing depth begins to decrease by lowering the irradiation intensity while keeping the irradiation energy of the irradiation light constant is set as the reference irradiation intensity, the irradiation intensity of the irradiation light is used as the reference. The ceramic molded body according to any one of (1) to (5) above, wherein the molding is performed with an intensity of 40 to 200% of the irradiation intensity.
(7) The ceramic molded product according to any one of (1) to (6) above, wherein the laminated interface peeling does not occur and the dimensional error is within 5% in the ceramic molded body after sintering. Production method.

（上記式において、σ _f は脆性材料の破壊強度、Ｙは微小クラックの形状因子、ｃは前記臨界亀裂長さ、Ｋ _ＩＣ は臨界応力拡大係数である。）
（９）焼成後の前記端面段差が臨界亀裂長さよりも小さいことを特徴とする、上記（８）に記載のセラミックス成形体。
（１０）焼結後に積層界面剥離が生じておらず、かつ、寸法誤差が５％以内である、上記（８）または（９）に記載のセラミックス成形体。 Further, the gist of the present invention is the ceramic molded body of the following (8) to (10).
(8) A ceramic molded body molded by a bottom-illuminated DLP-type stereolithography method , in which each layer is laminated at a stacking pitch in which the step on the end face of the ceramic molded body after firing is smaller than the critical crack length . , The critical crack length can be obtained based on the following formula, a ceramic molded product.

(In the above equation, σ _f is the fracture strength of the brittle material, Y is the shape factor of the microcracks, c is the critical crack length, and KIC _is the critical stress intensity factor.)
(9) The ceramic molded product according to (8) above, wherein the step on the end face after firing is smaller than the critical crack length.
(10) The ceramic molded product according to (8) or (9) above, wherein the laminated interface is not peeled off after sintering and the dimensional error is within 5%.

To create a high-value-added high-definition ceramic molded body that has mechanical properties comparable to those of conventional construction methods, with less interfacial peeling and end face steps of the modeled body, and has a three-dimensional complex shape unique to AM. Is possible.

It is a block diagram of the 3D laminated modeling machine which concerns on this embodiment. It is a figure for demonstrating the outline of the 3D laminated modeling technique. It is a figure for demonstrating the irradiation energy of the irradiation light in this embodiment. It is a figure for demonstrating the end face step of a ceramic molded body in the case of laminating molding in the vertical direction. It is a figure for demonstrating the end face step of a ceramic molded body in the case of laminating molding in an oblique direction.

<< 3D laminated modeling machine >>
Hereinafter, embodiments of the ceramic molded product according to the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a three-dimensional laminated molding machine 1 for molding a ceramic molded body according to the present embodiment. Further, FIG. 2 is a diagram for explaining the outline of the three-dimensional laminated molding technique.

As shown in FIG. 1, the three-dimensional laminated modeling machine 1 has a control device 10 and a projector 20 that irradiates irradiation light such as ultraviolet light, and light is directed to the irradiation destination of the irradiation light emitted by the projector 20. A transparent resin tray 30 for filling a curable ceramic slurry (a mixture of a photocurable resin liquid and a ceramic powder) is arranged.

In the present embodiment, CAD data of the completed form of the ceramic molded body is input to the control device 10, and the control device 10 creates slice data of the ceramic molded body. Then, as shown in FIG. 2, the control device 10 irradiates the projector 20 with irradiation light based on the created slice data, and cures the photocurable ceramic slurry layer by layer to form a ceramic molded body. Perform additional manufacturing.

"projector"
In order to cure the photocurable ceramic slurry, the projector 20 irradiates the transparent resin tray 30 filled with the photocurable ceramic slurry with irradiation light such as ultraviolet rays. Here, if the irradiation energy of the irradiation light of the projector 20 is not sufficient, there is a problem that interface peeling occurs at the laminated interface of the ceramic model. On the other hand, if the irradiation energy of the irradiation light of the projector 20 is excessively increased, the photocurable ceramics slurry contains a large amount of ceramic particles having different refractive indexes, so that light scattering becomes large and the cured portion is covered. There is also a problem that distortion may occur or swelling may occur, an error may occur from the assumed dimensions, and high-definition modeling cannot be performed.

上記式（１）において、Ｃｄは硬化深さ（μｍ）、Ｅは照射エネルギー（ｍＪ／ｃｍ^２）、Ｅｃは臨界照射エネルギー（ｍＪ／ｃｍ^２）、Ｄｐは光硬化感度（μｍ）を意味する。ここで、図３は、本実施形態における照射光の照射エネルギーを説明するための図であり、所望の積層ピッチに対する必要最小照射エネルギー（Ｅ_１）と、本実施形態で照射される照射エネルギー範囲とを例示している。たとえば、図３に示す例において、積層ピッチ（硬化深さ）を１００μｍとした場合、必要最小照射エネルギーは約１５ｍＪ／ｃｍ^２となり、本実施形態における照射光の照射エネルギーの範囲（必要最小照射エネルギーの１．２～３．０倍の範囲）は、おおよそ１８～４５ｍＪ／ｃｍ^２の範囲となる。 《Irradiated light》
In consideration of such a problem, the projector 20 according to the present embodiment has 1.2 to 3.0 times, preferably 1.5 to 2 times the required minimum irradiation energy (E ₁ ) according to the stacking pitch of the ceramics. The irradiation energy of the irradiation light to be irradiated is set so as to be in the range of 5.5 times. Here, the required minimum irradiation energy according to the stacking pitch is, for example, a single-layer curing test by light irradiation with a light source wavelength of 405 nm, and the relationship between the irradiation energy and the curing depth is obtained by using the Beer-Lambert law of the following equation. be able to.

In the above formula (1), Cd means the curing depth (μm), E means the irradiation energy (mJ / cm ² ), Ec means the critical irradiation energy (mJ / cm ² ), and Dp means the photocuring sensitivity (μm). .. Here, FIG. 3 is a diagram for explaining the irradiation energy of the irradiation light in the present embodiment, and is the minimum required irradiation energy (E ₁ ) for a desired stacking pitch and the irradiation energy range irradiated in the present embodiment. Is illustrated. For example, in the example shown in FIG. 3, when the stacking pitch (curing depth) is 100 μm, the required minimum irradiation energy is about 15 mJ / cm ² , and the range of irradiation energy of the irradiation light in the present embodiment (required minimum irradiation energy). The range (1.2 to 3.0 times the range of 1.2 to 3.0 times) is approximately 18 to 45 mJ / cm ² .

Further, in the present embodiment, the irradiation intensity of the irradiation light is also adjusted. The photocurable ceramics slurry is a mixture of photocurable resin and ceramic particles having different refractive indexes, and the degree of light scattering changes depending on the irradiation intensity, which is considered to have a great influence on the dimensional control of the ceramic molded body. Be done. Specifically, by reducing the irradiation intensity, light scattering can be suppressed, and modeling with excellent dimensional control becomes possible. On the other hand, if the irradiation intensity is excessively reduced, the desired curing depth may not be obtained even if the irradiation energy is set to the required minimum irradiation energy according to the stacking pitch. Therefore, in the projector 20 according to the present embodiment, the irradiation intensity of the irradiation light is set to 40 to 200%, preferably 60 to 150% of the reference irradiation intensity at which the desired modeling depth can be formed. If the irradiation intensity is lower than 40%, interface peeling occurs and the modeling time becomes enormous. On the other hand, if the irradiation intensity is higher than 200%, light scattering becomes strong and dimensional control becomes difficult. The reference irradiation intensity is the irradiation intensity at which the curing depth begins to decrease when the irradiation intensity is reduced at the irradiation intensity at which the irradiation energy is constant and a certain curing depth can be obtained. To say.

《Photo-curable ceramic slurry》
In the present embodiment, the ceramic molded body is formed by curing the photocurable ceramics slurry, which is a mixture of the photocurable resin and the ceramic powder, with the irradiation light irradiated by the projector 20. The photocurable ceramic slurry can be adjusted as follows. First, the particle size of the ceramic powder used needs to be sufficiently small with respect to the set stacking pitch. If the size is larger than the stacking pitch or close to the stacking pitch, it becomes difficult to perform sufficient curing bonding, resulting in insufficient stacking or stacking defects. Therefore, it is preferable to use a ceramic powder having an average particle size of 1/5 or less, preferably 1/10 or less with respect to the stacking pitch. Further, if the content of the ceramic powder added to the photocurable resin is less than 10% by volume, the shrinkage rate after firing becomes large, which not only causes cracks but also makes it difficult to obtain a dense body. On the other hand, if it is higher than 80% by volume, it is difficult to prepare a ceramic slurry having fluidity. Therefore, the ceramic powder contained in the photocurable ceramic slurry is preferably 10% by volume or more and 80% by volume or less, preferably 20% by volume or more and 60% by volume or less. Further, if the viscosity of the photocurable ceramic slurry is excessively high, tensile stress acts on the interface when the laminated model is lifted for each layer, which causes interface peeling. On the other hand, if the viscosity of the photocurable ceramic slurry is excessively lowered, the ceramic particles are separated. Therefore, in the present embodiment, the viscosity coefficient of the photocurable ceramic slurry is adjusted to 300 to 5000 mPa · s, preferably 500 to 3000 mPa · s.

《Stacking pitch》
Next, the stacking pitch of the ceramic molded product according to the present embodiment will be described. Here, FIG. 4 (A) is a photograph of an electron microscope showing an end face step of a ceramic molded body formed with a lamination pitch of 150 μm, and FIG. 4 (B) is an end face of a ceramic molded body formed with a lamination pitch of 25 μm. It is a photograph of an electron microscope showing a step. As shown in FIGS. 4A and 4B, in the additive manufacturing method, when each layer is formed so as to be laminated, an end face step is formed on the end face (side surface, surface in the stacking direction) of the ceramic molded body. Will end up. If the end face step is large, the strength in the direction parallel to the laminated interface may be significantly reduced at the laminated interface. As shown in FIGS. 4 (A) and 4 (B), the size of the end face step depends on the size of the stacking pitch. For example, as shown in FIG. 4 (A), the stacking pitch is formed at 150 μm. In this case, the end face step is about 70 μm, and as shown in FIG. 4B, when the stacking pitch is 25 μm, the end face step is about 10 μm. As described above, when the end face step is large, the strength in the direction parallel to the laminated interface is remarkably lowered. Therefore, by reducing the stacking pitch, the end face step can be reduced and the strength of the ceramics can be increased. However, if the stacking pitch is made excessively small, the time required for forming the ceramics becomes enormous, and the stability of the photocurable ceramic slurry is impaired. Therefore, in the present embodiment, based on the fracture mechanics, the stacking pitch is set so that the step on the end face is smaller than the critical crack length of the fracture source originally possessed by the ceramic to be molded.

なお、上記式２において、σ_fは脆性材料の破壊強度、Ｙは微小クラックの形状因子、ｃは臨界亀裂長さ（破壊源の大きさ）、Ｋ_ＩＣは臨界応力拡大係数（破壊靭性値）である。たとえば、アルミナの破壊強度を４００ＭＰａ、破壊靭性値を３ＭＰａ・ｍ^１／２とすると、臨界亀裂長さは約１７μｍとなり、このサイズよりも端面段差を小さくすることで積層界面と平行方向の強度低下を防ぐことが出来る。また、ムライトおよび部分安定化ジルコニアの臨界亀裂長さは、同様にそれぞれ約３０μｍ、１２μｍであり、これらサイズより端面段差を小さくすることが必要である。 Here, the critical crack length c of the ceramics can be expressed by the following equation 2.

In Equation 2 above, σ _f is the fracture strength of the brittle material, Y is the shape factor of the microcracks, c is the critical crack length (the size of the fracture source), and _KIC is the critical stress intensity factor (fracture toughness value). Is. For example, if the fracture strength of alumina is 400 MPa and the fracture toughness value is 3 MPa · m ^1/2 , the critical crack length is about 17 μm, and by making the end face step smaller than this size, the strength in the direction parallel to the laminated interface decreases. Can be prevented. The critical crack lengths of mullite and partially stabilized zirconia are also about 30 μm and 12 μm, respectively, and it is necessary to make the end face step smaller than these sizes.

《Projector resolution》
When each layer is laminated in an oblique direction with respect to the vertical direction in the case of laminating a ceramic molded body, as shown in FIG. 5, an end face step different from the end face step derived from the stacking pitch is generated. It is considered that this step is caused by the resolution (size of 1 pixel) of the irradiation surface of the projector 20 in addition to the stacking pitch. That is, the DLP stereolithography is surface exposure, and the smallest unit irradiation surface on which the projector 20 irradiates the irradiation light can be considered as the resolution of the projector 20. For example, in the example shown in FIG. 5, in order to form the layer B, irradiation is performed on the irradiation surface a and the irradiation surface b of the irradiation surface of the projector 20, but when the layer A is formed, the irradiation surface b is used. Irradiation is not performed, but irradiation is performed on the irradiation surface a. As shown in FIG. 5, when the ceramic molded body is formed with an inclination with respect to the laminating direction in this way, an end face step is generated. Here, the size of the end face step depends on the stacking pitch and the resolution of the irradiation surface (minimum unit area of the irradiation surface). That is, in order to reduce the size of the step on the end face, the stacking pitch may be reduced and the resolution of the irradiation surface of the projector 20 may be reduced. However, the harmful effects of making the stacking pitch excessively small are as described above, and the higher the resolution of the irradiation surface of the projector 20, the more expensive the device becomes and the less versatile it becomes. Therefore, when modeling the ceramic molded body in the diagonal direction with respect to the vertical direction, the ceramic molded body is modeled using a device that can obtain the resolution of the irradiated surface in which the end face step in the inclined direction is smaller than the critical crack length. By doing so, it is possible to effectively prevent a decrease in the strength of the ceramic molded bodies laminated in the diagonal direction.

(Examples 1 to 11)
Next, examples of the present invention are shown in Table 1 below. As shown in Table 1 below, alumina powder (purity 99.99%, average particle size 0.61 μm) was used as the ceramic powder in Examples 1 to 4, and Murite powder (average particle size 1) was used in Examples 5 to 8. .2 μm) was used, and in Examples 9 to 11, 3 molY-zirconia powder (average particle size 0.64 μm) was used. Further, in Examples 1 to 11, as the photocurable resin, a radical polymerization type acrylic base monomer, a monofunctional diluted monomer, a polymerization initiator and the like were added in appropriate amounts. This photocurable resin had a refractive index of 1.49, a viscosity measured by a viscometer (manufactured by Toki Sangyo Co., Ltd., R115 type) at a shear rate of 3.06 s ^-1 and a temperature of 25 ° C., and was 48 mPa · s. .. The photocuring characteristics of the photocurable resin were that the critical irradiation energy (Ec) was 4.3 mJ / cm ² and the photocuring sensitivity (Dp) was 183 μm.

In this example, the ceramic powders of Examples 1 to 11 and the photocurable resin are mixed, and the modified polymer containing a carboxyl group as a dispersant is added in an amount of 0.3 to 2.0 wt% with respect to the ceramic powder. The above amount was added and dissolved. Further, in Examples 1 to 3, 5 to 11, the solid content concentration of the ceramic powder is 35 vol%, and in Example 4, the solid content concentration of the ceramic powder is 40 vol%. It was mixed with a sex resin. Then, a photocurable ceramic slurry was prepared by mixing and stirring using a planetary stirrer (Mazellster KK-250S manufactured by Kurabo Industries).

The viscosity of the prepared photocurable ceramic slurry was 728 mPa · s in Examples 1 to 3 (alumina powder 35 vol%), 3392 mPa · s in Example 4 (alumina powder 40 vol%), and Examples 5 to 8 (mullite powder 35 vol%). %) Was 568 mPa · s, and in Examples 9 to 11 (zirconia powder 35 vol%), it was 1216 mPa · s (sliding speed 3.06 s ^-1 , temperature 25 ° C.).

The ceramic molded body was molded using a bottom-illuminated DLP-type stereolithography apparatus (ML-48, manufactured by Muto Kogyo Co., Ltd.) in which the wavelength of the light source was 405 nm. The shape of the ceramic molded body was a rectangular cuboid of about 2.5 × 2.5 × 10 mm, and the shape was formed so that the longitudinal direction was parallel to the z-axis direction.

Further, in the molding of the ceramic molded body, as shown in Table 1 above, the stacking pitch was set to 20 μm in Example 9, 25 μm in Examples 1 to 5, 10 and 11, and 50 μm in Examples 6 to 8. Further, as shown in Table 1 above, in Examples 1 to 11, the irradiation intensity of the projector 20 was 0.27 to 0.84 W / cm ² , and the relative irradiation intensity with respect to the reference irradiation intensity was 45 to 162%. did. Further, in Examples 1 to 11, the irradiation energy (irradiation intensity × irradiation time) is adjusted to 5.08 to 22.38 mJ / cm ² by changing the irradiation time, and the relative irradiation energy with respect to the required minimum irradiation energy is 150. It was set to ~ 300%.

The molded ceramic molded body was degreased in a nitrogen atmosphere at 650 ° C. and fired in an atmospheric atmosphere at a heating rate of 1 ° C./min for 1 hour. The firing temperatures were 1700 ° C. for Examples 1 to 4 (containing alumina powder), 1650 ° C. for Examples 5 to 8 (containing mullite powder), and 1500 ° C. for Examples 9 to 11 (containing zirconia). did. The step on the end face of the ceramic molded product after firing was evaluated using FE-SEM (JSM-7001F manufactured by JEOL Ltd.).

As shown in Table 1 above, in Examples 1 to 11, no peeling of the laminated interface was observed in the ceramic molded product. Further, in Examples 1 to 11, the dimensional error after firing was also within 5%. Further, in Examples 1 to 11, the step on the end face after firing was smaller than the critical crack length, and it was possible to effectively prevent the strength decrease in the direction parallel to the laminated interface. As described above, in Examples 1 to 11, the irradiation intensity of the projector 20 is set in the range of 40 to 200% of the reference irradiation intensity, and the irradiation energy of the projector 20 is set to 120 to 300% of the minimum required irradiation energy for each stacking pitch. Furthermore, by laminating and modeling each layer at a laminating pitch where the step on the end face after firing is smaller than the critical crack length, there is no peeling of the laminated interface even after firing, the dimensional error is within 5%, and the end face. It was possible to form a ceramic molded body with a step smaller than the critical crack length and high strength.

(Comparative Examples 1 to 11)
Next, Comparative Examples 1 to 11 will be described. As shown in Table 2 below, alumina powder (purity 99.99%, average particle size 0.61 μm) was used as the ceramic powder in Comparative Examples 1 to 6, and Murite powder (average particle size 1) was used in Comparative Examples 7 to 9. .2 μm) was used, and in Comparative Examples 10 and 11, 3 molY-zirconia powder (average particle size 0.64 μm) was used. Further, in Comparative Examples 1 to 11, the same photocurable resins as those in Examples 1 to 11 were used.

Further, in Comparative Examples 1 to 6, the ceramic molded product is formed by using the photocurable ceramic slurry containing alumina powder as in Examples 1 to 4, but unlike Examples 1 to 4, in Comparative Example 3. In Comparative Examples 4 to 6, the stacking pitch was set to 50 μm, and the stacking pitch was set to 100 μm to form a ceramic molded body. Similarly, in Comparative Examples 7 to 9, the ceramic molded product was formed by using the photocurable ceramic slurry containing the mullite powder as in Examples 5 to 8, but unlike Examples 5 to 8, the comparison was made. In Example 9, a ceramic molded body was formed with a lamination pitch of 100 μm. Further, in Comparative Examples 10 and 11, the ceramic molded product was formed by using the photocurable ceramic slurry containing the zirconia powder as in Examples 9 to 11, but unlike Examples 9 to 11, in Comparative Example 11. A ceramic molded body was formed with a stacking pitch of 50 μm.

Further, in Comparative Examples 1 to 3, 7 and 10, the relative irradiation intensities with respect to the reference irradiation intensity were set to 278%, 30%, 321%, 213% and 215%, and the relative intensities of Examples 1 to 11 were 40 to 200%. A ceramic molded body was formed outside the range. Further, in Comparative Examples 1, 6, 8 and 9, the relative irradiation energy with respect to the required minimum irradiation energy was set to 301%, 100%, 100% and 481%, which was 120 to 300% of the relative irradiation energy in Examples 1 to 11. The ceramic molded body was molded outside the range.

As a result, as shown in Table 2 above, in Comparative Examples 1, 3, 6, 7, 9, and 10, the dimensional error of the ceramic molded product was 5% or more. Further, in Comparative Examples 2, 6 and 8, peeling of the laminated interface was observed in the ceramic molded product. Further, in Comparative Examples 4, 5 and 11, the irradiation conditions of the projector 20 are appropriate, but the stacking pitch is set to be larger than that of Examples 1 to 11, and the step on the end face of the ceramic molded body after sintering is critical. It became larger than the crack length. As described above, in Comparative Examples 1 to 11, the irradiation intensity of the projector 20 is outside the range of 40 to 200% of the reference irradiation intensity, the irradiation energy is outside the range of 120 to 300% of the minimum required irradiation energy for each stacking pitch, or. By setting the end face step after firing to be larger than the stacking pitch where the end face step is smaller than the critical crack length, interface peeling is observed, the dimensional error exceeds 5%, and the end face step becomes larger than the critical crack length. It was found that the strength may be significantly reduced.

As Example 12, a ceramic molded body was manufactured under the following conditions. That is, as the ceramic powder, alumina powder (purity 99.99%, average particle diameter 0.61 μm) was used. Further, as a sintering aid, 500 ppm of magnesium oxide powder (purity 99.98%, average particle diameter 0.05 μm) was added to the alumina powder. Further, as the photocurable resin, the same ones used in Examples 1 to 11 and Comparative Examples 1 to 11 described above were used. Then, the alumina powder and the photocurable resin are mixed so that the solid content concentration of the ceramic powder is 35 vol%, and 0.3 wt% of the modified polymer containing a carboxyl group as a dispersant is added to the alumina powder. Then, the mixture was mixed and stirred using a planetary stirrer (Mazelstar KK-250S manufactured by Kurabou) to prepare a photocurable ceramic slurry. The viscosity of the prepared photocurable ceramic slurry was 936 mPa · s at a shear rate of 3.06 s ^-1 and a temperature of 25 ° C.

Further, in Example 12, a ceramic molded body was molded as follows. That is, two rectangular cuboids having a size of about 2.5 × 2.5 × 30 mm were formed using a bottom-illuminated DLP-type stereolithography apparatus (ML-48 manufactured by Muto Kogyo Co., Ltd.) having a light source wavelength of 405 nm. Specifically, one in which the longitudinal direction of the rectangular cuboid is the interface direction (direction parallel to the laminated interface) and the other in which the rectangular cuboid is in the laminated direction (direction perpendicular to the laminated interface) are modeled. Further, in the molding of the ceramic molded body, the stacking pitch is 25 μm, the irradiation intensity is 0.89 mW / cm ² (relative irradiation intensity with respect to the standard irradiation intensity is 148%), and the irradiation energy is 6.2 mJ / cm ² (minimum required). The relative irradiation energy with respect to the irradiation energy was set to 200%).

The molded ceramic molded body was degreased in a nitrogen atmosphere at 650 ° C., and firing was performed in an atmospheric atmosphere at a heating rate of 1 ° C./min and 1700 ° C. for 1 hour. The step on the end face of the molded sintered body after firing was evaluated using FE-SEM (JSM-7001F manufactured by JEOL Ltd.). The density of the sintered body was measured by the Archimedes method using water as a medium, and the bending strength was evaluated by a three-point bending test (n = 9 to 10) according to JIS.

As a result, the dimensional error of the ceramic molded product after firing was 3.2%, which was within 5%. In addition, no interfacial delamination was observed at the laminated interface. Furthermore, it was also found that the relative density of the three-dimensional laminated molding member after firing was about 96%, and it was almost densified.

Further, the bending strength when a load in the stacking direction is applied to the sintered body of the ceramic molded body formed so that the longitudinal direction is the interface direction is 400 MPa, and the fracture toughness value is 2.9 MPa · ml ^/. It became ² . When the critical crack length was calculated from these values, the critical crack length was about 16 μm. Next, when the step on the end face of the ceramic molded body after firing was measured so that the longitudinal direction was the stacking direction, the average was 9.9 μm and the maximum was 11.9 μm. It became smaller than the length of 16 μm. Further, the bending strength when a load in the interface direction is applied to the sintered body of the ceramic molded body molded so that the longitudinal direction is the laminating direction is 356 MPa, and the molding is performed so that the longitudinal direction is the interface direction. Although the strength was lower than that of the sintered body of the ceramic molded body, it was possible to produce a molded sintered body in which sufficient strength was maintained and the influence on the strength of the end face step was suppressed.

Further, as Comparative Example 12, a photocurable ceramic slurry was prepared in the same manner as in Example 12, and a rectangular cuboid having a size of about 2.5 × 2.5 × 30 mm was prepared by the same method as in Example 12, and the longitudinal direction of the rectangular cuboid was changed. The one that is in the interface direction (direction parallel to the stacking interface) and the one that is in the stacking direction are modeled. However, in Comparative Example 12, unlike Example 12, the ceramic molded body was molded with a stacking pitch of 100 μm.

In the ceramic molded product of Comparative Example 12, no interfacial delamination was observed at the laminated interface as in Example 12, and the relative density of the sintered body was about 97%, which was almost densified. On the other hand, in Comparative Example 12, the dimensional error was 9.2%, which was 5% or more. Here, the bending strength when a load in the stacking direction is applied to the sintered body of the ceramic molded body formed so that the longitudinal direction is the interface direction is 391 MPa, and the fracture toughness value is 2.9 MPa · m. Since it was ^{l / 2} , the critical crack length was calculated to be about 17 μm. Next, when the end face step of the sintered body of the ceramic molded body molded so that the longitudinal direction was the laminating direction was measured, the average was 45.7 μm and the maximum was 51.2 μm. The step on the end face of was larger than the critical crack length of 17 μm. Further, the bending strength when a load in the interface direction is applied to the sintered body of the ceramic molded body molded so that the longitudinal direction is the laminating direction is 211 MPa, and the molding is formed so that the longitudinal direction is the interface direction. The strength was greatly reduced as compared with the ceramic molded body.

Further, in Example 13, mullite powder (average particle size 1.2 μm) was used as the ceramic powder. As the photocurable resin, the same one as in Example 12 was used. Then, in Example 13, the alumina powder and the photocurable resin are mixed so that the solid content concentration of the ceramic powder is 35 vol%, and a carboxyl group-containing modified polymer as a dispersant is added to the alumina powder. After adding 0.8 wt%, the mixture was mixed and stirred using a planetary stirrer (Mazelstar KK-250S manufactured by Kurabou) to prepare a photocurable ceramic slurry. The viscosity of the prepared photocurable ceramic slurry was 568 mPa · s at a shear rate of 3.06 s ^-1 and a temperature of 25 ° C.

Further, in Example 13, the ceramic molded body is a rectangular cuboid having a size of about 2.5 × 2.5 × 30 mm as in Example 12, and the longitudinal direction of the rectangular cuboid is the stacking direction (z-axis direction) (implementation). Example 13-1) and a rectangular cuboid whose longitudinal direction is the interface direction (y-axis direction) and tilted at 45 ° with respect to the stacking direction (z-axis direction) (Example 13-2) are modeled, respectively. did. Further, in the molding of the ceramic molded body, the stacking pitch is 25 μm, the irradiation intensity is 0.78 mW / cm ² (relative irradiation intensity with respect to the standard irradiation intensity is 100%), and the irradiation energy is 5.1 mJ / cm ² (minimum required). The relative irradiation energy with respect to the irradiation energy was set to 200%).

The ceramic molded body was degreased in a nitrogen atmosphere at 650 ° C., and firing was performed in an atmospheric atmosphere at a heating rate of 1 ° C./min and holding at 1650 ° C. for 1 hour. The step on the end face of the molded sintered body after firing was evaluated using FE-SEM (JSM-7001F manufactured by JEOL Ltd.).

In the ceramic molded body (Example 13-1) in which the longitudinal direction of the rectangular cuboid is the laminating direction, the evaluation was as follows. That is, the dimensional error of the ceramic molded product after firing was 2.9%, which was within 5%. In addition, no interfacial delamination was observed at the laminated interface. Further, the end face step was a maximum of 8 μm, which was smaller than the critical crack length of 30 μm.

Further, in the ceramic molded body (Example 13-2) in which the longitudinal direction of the rectangular cuboid is the interface direction (y-axis direction) and is inclined at 45 ° with respect to the stacking direction (z-axis direction), in addition to the stacking pitch. An end face step was generated due to the resolution of the irradiation surface of the projector 20, but the size of the step was about 20 to 30 μm, which was smaller than the critical crack length of 30 μm. In the present embodiment, by increasing the resolution of the irradiation surface of the projector 20 to 40 μm, the step on the end face derived from the projector can be made smaller than the critical crack length, and the decrease in strength due to the modeling direction can be prevented.

As described above, in the ceramic molded body according to the present embodiment, since each layer is laminated at a predetermined stacking pitch in which the end face step of the ceramic molded body after firing is smaller than the critical crack length, the end face step is critical. It becomes smaller than the crack length, and it is possible to form a ceramic molded body having high strength in terms of fracture mechanics. Further, in the ceramic molded body according to the present embodiment, the ceramic powder having an average particle diameter of 1/5 or less, preferably 1/10 or less with respect to the stacking pitch is added to the photocurable resin in an amount of 10% by volume or more and 80 volumes. % Or less, preferably 20% by volume or more and 60% by volume or less, is used for molding to produce a ceramic molded body having no peeling of the laminated interface after firing and having little dimensional error. can do. Further, by setting the viscosity of the photocurable ceramic slurry to 300 mPa · s to 5000 mPa · s, it is possible to prevent peeling of the laminated interface and prevent separation of ceramic particles. Further, in the ceramic molded body according to the present embodiment, irradiation light having an irradiation energy of 1.2 to 3.0 times the required minimum irradiation energy set according to the stacking pitch is irradiated, and the irradiation intensity of the irradiation light is increased. By irradiating with an intensity of 40 to 200% of the reference irradiation intensity, it is possible to prevent peeling of the laminated interface and reduce the dimensional error to 5% or less in the ceramic molded body after firing.

Further, in the ceramic molded body according to the present embodiment, even when each layer is laminated in an oblique direction with respect to the vertical direction, the end face step is laminated with an irradiation unit area of irradiation light in which the end face step is smaller than the critical crack length. The end face step formed according to the resolution of the irradiation light can be made smaller than the critical crack length, and the decrease in intensity can be prevented.

Although the preferred embodiment of the present invention has been described above, the technical scope of the present invention is not limited to the description of the above embodiment. Various changes and improvements can be added to the above-described embodiments, and those in which such changes or improvements have been made are also included in the technical scope of the present invention.

10 ... Control device 20 ... Projector 30 ... Transparent resin tray

Claims (10)

Bottom-illuminated DLP-type stereolithography In the method of manufacturing a ceramic molded product by
Lamination pitch at which the step on the end face of the ceramic molded product after sintering is smaller than the critical crack lengthAnd the stacking pitchModeling process of laminating each layer inWhen,
A firing process in which the molded ceramic molded body is fired at normal pressure, Havedeath,
The critical crack length is obtained based on the following equation. A method for manufacturing a ceramic molded product.

(In the above equation, σ _f Is the fracture strength of the brittle material, Y is the shape factor of the microcracks, c is the critical crack length, and K _IC Is the critical stress intensity factor. ) In the modeling process, when each layer is laminated in an oblique direction with respect to the vertical direction, each layer is laminated while controlling the irradiation range of the irradiation light with an irradiation unit area where the end face step is smaller than the critical crack length. The method for manufacturing a ceramic molded body according to claim 1, wherein the ceramic molded body is molded. In the molding step, a photocurable ceramic slurry obtained by adding 10% by volume or more and 80% by volume or less of ceramic powder having an average particle size of 1/5 or less with respect to the lamination pitch to a photocurable resin is used for molding. The method for producing a ceramic molded product according to claim 1 or 2, wherein the ceramic molded body is characterized in that. The method for producing a ceramic molded product according to any one of claims 1 to 3, wherein the photocurable ceramic slurry used in the molding step has a viscosity of 300 mPa · s to 5000 mPa · s. Claims 1 to 4 are characterized in that in the modeling step, modeling is performed by irradiating irradiation light having an irradiation energy of 1.2 to 3.0 times the required minimum irradiation energy specified according to the stacking pitch. The method for manufacturing a ceramic molded body according to any one of the above. In the modeling step, when the irradiation intensity at which the curing depth begins to decrease by lowering the irradiation intensity while keeping the irradiation energy of the irradiation light constant is set as the reference irradiation intensity, the irradiation intensity of the irradiation light is defined as the reference irradiation intensity. The method for producing a ceramic molded body according to any one of claims 1 to 5, wherein the molding is performed with a strength of 40 to 200%. The method for manufacturing a ceramic molded body according to any one of claims 1 to 6, wherein the laminated interface peeling does not occur in the ceramic molded body after sintering, and the dimensional error is within 5%. Bottom-illuminated DLP-type stereolithography Each layer is laminated at a stacking pitch in which the step on the end face of the ceramic molded body after firing is smaller than the critical crack length.Ori
The critical crack length can be obtained based on the following equation., Ceramic molded body.

(In the above equation, σ _f Is the fracture strength of the brittle material, Y is the shape factor of the microcracks, c is the critical crack length, and K _IC Is the critical stress intensity factor. ) The ceramic molded product according to claim 8, wherein the step on the end face after firing is smaller than the critical crack length. The ceramic molded product according to claim 8 or 9, wherein the laminated interface is not peeled off after sintering and the dimensional error is within 5%.

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