Zirconia sintered body

Abstract

To provide at least any of a laminate which has changes in texture derived from zirconia, especially, changes in translucent feel, and is suitable for a dental prosthetic component, a precursor thereof, or a manufacturing method thereof.SOLUTION: Provided herein is a sintered body having a laminated structure of two or more zirconia layers including zirconia, containing a stabilizer. These zirconia layers include at least a first zirconia layer including zirconia with the stabilizer content of 4 mol% or more and a second zirconia layer including zirconia with a different stabilizer content from the zirconia included in the first zirconia layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to compositions having layers of zirconia laminated thereto, and further to zirconia laminates. [Background technology]

[0002] Zirconia (ZrO2) sintered bodies are manufactured by molding and sintering raw material powders that mainly contain zirconia. The raw material powders undergo thermal shrinkage and densification through heat treatments such as sintering and calcination, but their behavior during heat treatment varies depending on the characteristics of the raw material powders, especially their composition.

[0003] Zirconia accounts for the majority of the raw material powder. Nevertheless, even when raw material powders differ only by less than 0.1% by mass in additive content, the thermal shrinkage behavior of the two powders differs significantly. When a molded body formed by laminating raw material powders with such slight differences in composition is heat-treated, defects such as partial peeling of layers or distortion occur. The above-mentioned defects occur even when the same zirconia is used and additives are added. In order to heat-treat a molded body without these defects, special adjustments and treatments have been required (for example, Patent Documents 1 and 2).

[0004] Patent Document 1 discloses that by adjusting the composition and thermal shrinkage behavior of raw material powder by coating with a dopant and then molding the powder, a sintered body without distortion and consisting of laminates with different color tones can be obtained. Also, Patent Document 2 discloses that by applying vibrations that form a boundary layer where the powders in the upper and lower layers are mixed and then molding the laminate, a sintered body consisting of laminates with layers that have different colorant contents and change in color can be obtained. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2016-527017 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-218389 Summary of the Invention [Problem to be solved by the invention]

[0006] The laminates disclosed in Patent Documents 1 and 2 have a very small compositional difference of less than 0.5% by mass in the content of additives between layers. Furthermore, because the zirconia that accounts for the majority of the raw material powder has the same composition, these laminates also have the same texture, which is primarily due to the translucency of zirconia. Therefore, they have a different texture compared to natural teeth, which have a texture due to variations in translucency.

[0007] An object of the present disclosure is to provide at least one of a laminate having a change in texture, particularly a change in translucency, derived from zirconia and suitable as a dental prosthetic component, a precursor thereof, or a method for producing either or both. [Means for solving the problem]

[0008] The inventors focused on the compact before heat treatment, i.e., the state after molding of the raw material powder. As a result, they confirmed that the state of distortion generated at the time of molding in a compact formed from raw material powders with different zirconia stabilizer contents is significantly different from that in a compact formed from raw material powders with different additive contents. They also confirmed that such distortion significantly affects the state of the calcined body and sintered body after heat treatment. Furthermore, they found that by controlling the state of the compact, the above-mentioned problems are less likely to occur even when a laminate formed from raw material powders with different zirconia stabilizer contents is heat-treated.

[0009] That is, the gist of the present disclosure is as follows. [1] A structure in which two or more zirconia layers containing zirconia containing a stabilizer are laminated, and at least a first zirconia layer containing zirconia having a stabilizer content of 4 mol% or more; a second zirconia layer containing zirconia having a different stabilizer content from that of the zirconia contained in the first zirconia layer; A sintered body comprising: [2] The sintered body according to the above [1], wherein the stabilizer content of the stabilizer-containing zirconia contained in the second zirconia layer is 1.5 mol % or more and 7.0 mol % or less. [3] The sintered body according to the above [1] or [2], wherein the stabilizer content of the stabilizer-containing zirconia contained in the second zirconia layer is 5.0 mol % or more and 7.0 mol % or less. [4] The sintered body according to any one of [1] to [3] above, wherein the stabilizer content of the stabilizer-containing zirconia contained in the first zirconia layer is 4.0 mol % or more and 6.0 mol % or less. [5] The sintered body according to any one of [1] to [4] above, wherein the difference between the stabilizer content of the first zirconia layer and the stabilizer content of the second zirconia layer is 0.2 mol % or more. [6] The sintered body according to any one of the above [1] to [5], wherein the stabilizer is one or more selected from the group consisting of yttria (Y2O3), calcia (CaO), magnesia (MgO) and ceria (CeO2). [7] The sintered body according to any one of [1] to [6] above, wherein at least one of the zirconia layers contains alumina. [8] The sintered body according to any one of [1] to [7] above, which has a warpage of 1.0 mm or less as measured using a thickness gauge in accordance with JIS B 7524:2008. [9] Density measured according to JIS R 1634 is 5.7 g / cm 3 More than 6.3g / cm 3 The sintered body according to any one of the above [1] to [8], which is:

[10] The sintered body according to any one of [1] to [9] above, which has a zirconia layer having a total light transmittance of 30% or more and 50% or less for light with a wavelength of 600 nm when the sample thickness is 1.0 mm.

[11] The sintered body according to any one of [1] to

[10] above, which has a three-point bending strength of 500 MPa or more as measured by a method according to JIS R 1601.

[12] A structure in which two or more powder composition layers made of a powder composition containing zirconia containing a stabilizer and a binder are laminated, and at least a first powder composition layer including zirconia having a stabilizer content of 4 mol% or more and a binder; a second powder composition layer containing zirconia having a stabilizer content different from that of the zirconia contained in the first powder composition layer, and a binder; Equipped with sintering a molded body having a binder content difference of more than 0.01% by mass between the first powder composition layer and the second powder composition layer at 1200°C or higher and 1600°C or lower.

[13] A powder composition having a structure in which two or more powder composition layers each comprising a powder composition containing zirconia containing a stabilizer and a binder are laminated, and at least a first powder composition layer including zirconia having a stabilizer content of 4 mol% or more and a binder; a second powder composition layer containing zirconia having a stabilizer content different from that of the zirconia contained in the first powder composition layer, and a binder; Equipped with A step of calcining the molded body, in which the difference in binder content between the first powder composition layer and the second powder composition layer is more than 0.01% by mass, at 800°C or higher and lower than 1200°C to obtain a calcined body; and The method for producing a sintered body according to any one of [1] to

[11] above, characterized by comprising a step of sintering the calcined body at 1200°C or higher and 1600°C or lower.

[14] The method according to the above

[12] or

[13] , wherein the warpage of the molded product measured using a thickness gauge conforming to JIS B 7524:2008 is 1.0 mm or less.

[15] The manufacturing method according to any one of

[12] to

[14] above, wherein the binder is one or more selected from the group consisting of polyvinyl alcohol, polyvinyl butyrate, wax, and acrylic resin.

[16] The manufacturing method according to any one of

[12] to

[15] above, wherein the powder composition contained in the powder composition layer is a powder in a granulated state.

[17] The density of the molded body is 2.4 g / cm 3 More than 3.7g / cm 3 The manufacturing method according to any one of the above

[12] to

[16] , which is as follows:

[18] A dental material comprising the sintered body according to any one of [1] to

[11] above. [Effects of the Invention]

[0010] The present disclosure can provide a laminate having a change in texture, particularly a change in translucency, derived from zirconia and suitable as a dental prosthetic component, a precursor thereof, or a method for producing either of them. [Brief explanation of the drawings]

[0011] [Figure 1] Schematic diagram showing the cross section of a sintered body with a structure in which two zirconia layers are stacked [Figure 2] Schematic diagram showing the cross section of a sintered body with a structure in which three zirconia layers are stacked [Figure 3] Schematic diagram showing how to measure warpage [Figure 4] Schematic diagram showing the three-point bending strength measurement method [Figure 5] Schematic diagram showing zirconia with a necking structure DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, the sintered body of the present disclosure will be described with reference to an example of an embodiment.

[0013] This embodiment has a structure in which two or more zirconia layers containing zirconia containing a stabilizer are laminated, and at least a first zirconia layer containing zirconia having a stabilizer content of 4 mol% or more; a second zirconia layer containing zirconia having a different stabilizer content from that of the zirconia contained in the first zirconia layer; The sintered body is characterized by comprising:

[0014] The sintered body of this embodiment is a composition having a multilayer structure, that is, a laminate, and is a laminate made of a sintered structure. In this embodiment, the sintered structure is a structure made of zirconia in the later stage of sintering.

[0015] The sintered body of this embodiment has a zirconia layer (hereinafter simply referred to as "zirconia layer") containing zirconia containing a stabilizer. The zirconia layer is made of zirconia crystal particles containing a stabilizer. Therefore, the sintered body of this embodiment can also be considered as a laminate having two or more zirconia-containing layers made of zirconia crystal particles containing a stabilizer.

[0016] Fig. 1 is a schematic diagram showing an example of the structure of the sintered body of this embodiment, and shows a cross section of a sintered body (100) having a structure in which two zirconia layers containing zirconia containing a stabilizer are stacked. In Fig. 1, the direction in which the layers are stacked (hereinafter also referred to as the "stacking direction") is shown in the Y-axis direction, and the direction in which each layer extends (hereinafter also referred to as the "horizontal direction") is shown in the X-axis direction.

[0017] The sintered body (100) is shown as a sintered body having a structure in which a first zirconia layer (hereinafter also referred to as the "first layer") (11) containing zirconia with a stabilizer content of 4 mol% or more among zirconia layers and a second zirconia layer (hereinafter also referred to as the "second layer") (12) containing zirconia with a stabilizer content different from that of the zirconia contained in the first zirconia layer, and the first layer (11) and the second layer (12) are adjacently stacked. The stacked structure of zirconia layers containing zirconia with different stabilizer contents allows the sintered body to become a laminated body in which changes in texture, particularly changes in translucency, can be visually recognized. Note that the sintered body (100) shows a state in which the first layer and the second layer are in contact with each other via an interface. However, the sintered body of this embodiment may be stacked without a visible interface, and the interface between the layers is not limited to a linear one.

[0018] In the sintered body (100), the first and second layers have approximately the same thickness. However, in the sintered body of this embodiment, the thickness of each layer (hereinafter also referred to as "layer thickness") may be different, and either the first or second layer may be thick. For example, the thicknesses of the first and second layers may satisfy the following relationship, and further, the thickness of the zirconia layer with a high stabilizer content may be thicker than the thickness of the zirconia layer with a low stabilizer content. The layer thickness may be 1 mm or more and 20 mm or less, further 2 mm or more and 15 mm or less, or further 3 mm or more and 10 mm or less.

[0019] D high ≧D low , preferably 2 x D low ≧D high ≧D low However, D high is the thickness of the zirconia layer with high stabilizer content, and D low is the thickness of the zirconia layer with a low stabilizer content.

[0020] The shape of the sintered body of this embodiment may be any shape, including at least one selected from the group consisting of spherical, elliptical, discoid, cylindrical, cubic, rectangular, and polyhedral shapes, shapes suitable for dental materials, including dental prosthetic materials such as crowns, bridges, onlays, and onlays, and any other shape depending on the intended use. Note that in this embodiment, the term "spherical" may include shapes similar to a true sphere other than a true sphere, such as an approximately spherical shape, and the term "polyhedral" may include shapes similar to a polyhedron, such as an approximately polyhedral shape, in addition to a polyhedron.

[0021] The sintered body of this embodiment may have any size, for example, a length of 10 mm to 120 mm, a width of 12 mm to 120 mm, and a height of 6 mm to 40 mm. The thickness of the sintered body of this embodiment in the stacking direction, i.e., the height of the sintered body, may be any size, for example, 4 mm to 40 mm, or even 5 mm to 30 mm.

[0022] In the sintered body of this embodiment, the first layer and the second layer are preferably stacked adjacent to each other. Furthermore, the first layer and the second layer are preferably located at the bottom in the stacking direction (hereinafter also referred to as the "bottom layer") or the top in the stacking direction (hereinafter also referred to as the "top layer"), respectively. Preferably, one of the first layer or the second layer is located at the bottom layer, and the other of the first layer or the second layer is located at the top layer.

[0023] The sintered body of this embodiment may have a structure in which two or more zirconia layers containing zirconia containing a stabilizer are laminated, and may have a structure in which three or more, or even four or more zirconia layers are laminated. By increasing the number of layers, the sintered body becomes a laminate in which subtle changes in texture can be visually recognized. In order to achieve a texture more similar to that of natural teeth, the sintered body of this embodiment may have a structure in which two to ten zirconia layers are laminated, or even two to five zirconia layers, or even two to four zirconia layers are laminated, for example.

[0024] The zirconia layer other than the first and second layers (hereinafter also referred to as the "third layer") may be any zirconia layer containing zirconia containing a stabilizer whose content is equal to or greater than the minimum value and equal to or less than the maximum value of the stabilizer content of the zirconia contained in the first and second layers. The sintered body of this embodiment may include multiple third layers.

[0025] The third layers may be stacked in any order, but a structure in which the third layer is sandwiched between the first and second layers is preferred. When multiple third layers (the first third layer is also referred to as the "third layer," and the second and subsequent third layers are also referred to as the "fourth layer," "fifth layer," etc.) are provided, the sintered body of this embodiment preferably has a structure in which the zirconia layers are stacked so that the change in the stabilizer content in the stacking direction is constant, i.e., increases (or decreases). In this embodiment, the structure in which the third layer is sandwiched between the first and second layers means a structure in which the third layer is located between the first and second layers in the stacking direction, and is not limited to a structure in which the third layer is stacked directly adjacent to both the first and second layers. In this embodiment, the terms "first," "second," "third," etc." are numbers assigned for convenience of explanation and do not represent a permutation or stacking state, such as a stacking order.

[0026] 2 is a schematic diagram showing another example of the structure of the sintered body of this embodiment, and is a schematic diagram showing a cross section of a sintered body (200) having a structure in which three zirconia layers are stacked. The sintered body (200) has a structure in which a third layer (23) is stacked in addition to a first layer (21) and a second layer (22), and the third layer (23) is sandwiched between the first layer (21) and the second layer (22).

[0027] When multiple zirconia layers such as a fourth layer and a fifth layer are included, the zirconia layers are preferably stacked so that the stabilizer content varies uniformly in the stacking direction, thereby forming a gradation of translucency in the stacking direction.

[0028] The sintered body of this embodiment preferably has a warpage (hereinafter simply referred to as "warpage") of 1.0 mm or less as measured using a thickness gauge in accordance with JIS B 7524:2008. A sintered body having a structure with two or more zirconia layers will warp in the stacking direction (or the opposite direction to the stacking direction) due to sintering. When such a sintered body is placed on a horizontal plate, a gap is formed between the sintered body and the horizontal plate.

[0029] The warpage in this embodiment is a value measured using a thickness gauge (hereinafter simply referred to as "gauge") conforming to JIS B 7524:2008. The warpage of the sintered body of this embodiment is preferably 0.3 mm or less, more preferably 0.2 mm or less, even more preferably 0.1 mm or less, and even more preferably 0.05 mm or less. It is preferable that the sintered body has no warpage (warpage of 0 mm), but the sintered body of this embodiment may have warpage that cannot be measured with a gauge (warpage of 0 mm or more). For example, the sintered body of this embodiment has a warpage of more than 0 mm, and even 0.01 mm or more. The warpage is preferably 0.06 mm or less, more preferably 0.05 mm or less, or even below the measurement limit (less than 0.03 mm).

[0030] Warpage can be measured by measuring the maximum thickness of a gauge that can be inserted into a gap formed when the sintered body is placed so that its convex portion is in contact with a horizontal plate. FIG. 3 is a schematic diagram showing a method for measuring warpage. The sintered body (300) shows a cross section of a disk-shaped sample, and shows a sintered body warped in the stacking direction (Y-axis direction). For ease of explanation, FIG. 3 exaggerates the warpage of the sintered body (300). As shown in FIG. 3, when measuring warpage, the sintered body (300) is placed so that its convex portion is in contact with the horizontal plate (31). This forms a gap between the surface where the sintered body (300) and the horizontal plate (31) come into contact (hereinafter also referred to as the "bottom surface") and the horizontal plate (31). A gauge is inserted into the gap, and the maximum thickness of the gauge that can be inserted is used to measure warpage. In FIG. 3, gauge 32A is positioned below the bottom surface of sintered compact 300 and can be inserted into the gap, while gauge 32B is not positioned below the bottom surface of sintered compact 300 and cannot be inserted into the gap. Gauges 32A and 32B in FIG. 3 differ in thickness by one step (e.g., 0.01 mm), and the warpage of sintered compact 300 is the thickness of gauge 32A. For ease of explanation, FIG. 3 shows both gauges 32A and 32B inserted, but warpage can be measured by inserting gauges into the gap in order of thickness (e.g., after measurement using gauge 32A, remove it and then measure using thicker gauge 32B).

[0031] The sintered body of this embodiment preferably has a warpage (hereinafter also referred to as "deformation amount") relative to the dimensions of the sintered body of 1.0 or less, more preferably 0.5 or less, more preferably 0.2 or less, and even more preferably 0.15 or less. The deformation amount can be, for example, 0 or more, further 0.01 or more, or further 0.05 or more.

[0032] The amount of deformation can be calculated using the following formula: Deformation amount = (warpage: mm) / (sintered body dimensions: mm) x 100

[0033] The dimensions of the sintered body are the size of the sintered body in a direction perpendicular to the direction of warpage. Since the sintered body (300) in FIG. 3 is warped in the stacking direction (Y-axis direction), the dimension of the sintered body (300) is the size (33) of the sintered body in the horizontal direction (X-axis direction) perpendicular to the stacking direction. The dimensions can be measured using a known measurement method such as a vernier caliper or a micrometer. For example, in the case of a disk-shaped or cylindrical laminate, the diameter of the top end and the diameter of the bottom end can be measured at four points using a vernier caliper, the average of the diameters of the top end and bottom end can be calculated, and the average of the calculated values ​​can be used as the dimension of the laminate.

[0034] In this embodiment, the amount of warping and deformation is preferably measured using a disk-shaped sample as the measurement sample, and more preferably measured using a disk-shaped sample with a diameter of 5 mm or more and 120 mm or less.

[0035] The sintered body of this embodiment is composed of a zirconia layer containing zirconia containing a stabilizer. The zirconia layer is a layer mainly composed of zirconia, and the zirconia contains a stabilizer (hereinafter also referred to as "stabilizer-containing zirconia"). The sintered body and zirconia layer of this embodiment may contain not only stabilizer-containing zirconia but also inevitable impurities such as hafnia (HfO2), but preferably do not contain impurities. Examples of impurities include silica (SiO2) and titania (TiO2), and the sintered body of this embodiment can be substantially free of silica or titania.

[0036] In the sintered body of the present embodiment, the zirconia is preferably zirconia obtained by heat-treating a zirconia sol and then sintering the zirconia, more preferably zirconia obtained by heat-treating a zirconia sol obtained by hydrolysis of a zirconium compound and then sintering the zirconia, and even more preferably zirconia obtained by heat-treating a zirconia sol obtained by hydrolysis of zirconium oxychloride and then sintering the zirconia.

[0037] The zirconia contained in the zirconia layer is sintered zirconia, that is, zirconia crystal particles.

[0038] The stabilizer may be any stabilizer that suppresses the phase transition of zirconia. The stabilizer is preferably one or more selected from the group consisting of yttria (YO), calcia (CaO), magnesia (MgO), and ceria (CeO), and more preferably yttria. The stabilizer is contained in the zirconia and dissolved in the zirconia. The sintered body of this embodiment preferably does not contain undissolved stabilizers, i.e., does not contain stabilizers that are not dissolved in the zirconia. In this embodiment, "does not contain undissolved stabilizers" means that no XRD peaks attributable to the stabilizer are detected in the XRD measurement and XRD pattern analysis described below. The presence of undissolved stabilizers is acceptable as long as no XRD peaks attributable to the stabilizer are detected. The stabilizer content of the stabilizer-containing zirconia contained in the first layer (hereinafter also referred to as the "stabilizer content of the first layer") is 4 mol% or more, preferably 4.1 mol% or more, and more preferably 4.2 mol% or more. The stabilizer content of the first layer is 6.0 mol% or less, further 5.8 mol% or less, further 5.5 mol% or less, or even 5.0 mol% or less.The stabilizer content of the first layer is, for example, 4 mol% to 6.0 mol%, further 4 mol% to less than 5.0 mol%.

[0039] The content of the stabilizer in the stabilizer-containing zirconia contained in the second layer (hereinafter also referred to as the "stabilizer content of the second layer") may be different from the stabilizer content of the first layer, but it is preferable that the stabilizer content of the second layer is higher than that of the first layer. In other words, it is preferable that the sintered body of this embodiment does not include a zirconia layer in which the content of the zirconia stabilizer is less than 4 mol%. This makes it easier to obtain a sintered body that exhibits a translucent appearance closer to that of natural teeth.

[0040] The stabilizer content of the second layer may be 1.5 mol% or more, further 2.0 mol% or more, or even 3.0 mol% or more, but is preferably 4.0 mol% or more, more preferably greater than 4.0 mol%, even more preferably 4.5 mol% or more, even more preferably 5.0 mol% or more, and even more preferably greater than 5.0 mol%. The stabilizer content of the second layer may be 7.0 mol% or less, further 6.5 mol% or less, even further 6.0 mol% or less, or even 5.8 mol% or less. By having different stabilizer contents in the first and second layers and the stabilizer contents of both layers within this range, the sintered body is more likely to exhibit a texture that can be visually recognized as being similar to that of natural teeth. The stabilizer content of the second layer may be from 1.5 mol% to 7.0 mol%, further from 3.0 mol% to 6.5 mol%, further from 5.0 mol% to 6.5 mol%, or further from more than 5.0 mol% to 6.5 mol%.

[0041] The sintered body of this embodiment preferably comprises at least a first zirconia layer and a zirconia layer containing zirconia with a stabilizer content of 5 mol% or more, and more preferably a first zirconia layer and a zirconia layer containing zirconia with a stabilizer content of more than 5 mol%. In another embodiment, the sintered body of this embodiment preferably has a stabilizer content of 4.0 mol% to 5.1 mol% in the first layer and a stabilizer content of 4.5 mol% to 6.0 mol% in the second layer, and more preferably has a stabilizer content of 4.0 mol% to 5.0 mol% in the first layer and a stabilizer content of more than 5.0 mol% to 6.0 mol% in the second layer.

[0042] The content of the stabilizer in the stabilizer-containing zirconia contained in the third layer (hereinafter also referred to as the "stabilizer content in the third layer") is equal to or greater than the minimum value and equal to or less than the maximum value of the content of the stabilizer in the zirconia contained in the first layer and the second layer, and preferably is greater than the minimum value and less than the maximum value of the content of the stabilizer in the zirconia contained in the first layer and the second layer. The stabilizer content in the third layer can be, for example, 1.5 mol% to 7.0 mol%, further 3.0 mol% to 6.5 mol%, or even 4.0 mol% to 6.0 mol%. When the content of the stabilizer in the zirconia contained in the first layer is 4.0 mol% and the content of the stabilizer in the zirconia contained in the second layer is 6.0 mol%, the content of the stabilizer in the zirconia in the third layer can be 4.0 mol% to 6.0 mol%, preferably greater than 4.0 mol% and less than 6.0 mol%. In addition, when the stabilizer content of the third layer is the same as that of the first or second layer, the zirconia layer having the same stabilizer content as that of the third layer and located at the top or bottom can be regarded as the first or second layer.

[0043] The difference between the stabilizer content of the first layer and the stabilizer content of the second layer is preferably 0.2 mol% or more, more preferably 0.5 mol% or more, even more preferably 0.7 mol% or more, even more preferably 1.0 mol% or more, and even more preferably 1.2 mol% or more. The greater the difference in stabilizer content, the greater the difference in translucency between the zirconia layers tends to be, but warping may also increase. If the difference between the stabilizer content of the first layer and the stabilizer content of the second layer is less than 2.5 mol%, or even 2.0 mol% or less, the translucency of the sintered body is likely to be equivalent to that of natural teeth. It is more preferable that the difference between the stabilizer content of the first layer and the stabilizer content of the second layer is 0.7 mol% or more but less than 2.5 mol%, and that warping is 0.5 mm or less.

[0044] The sintered body of this embodiment preferably has a structure in which the difference in the stabilizer content between adjacently stacked zirconia layers is 0.5 mol% or more and 3.0 mol% or less, further 1.0 mol% or more and 2.5 mol% or less, and further 1.2 mol% or more and 2.0 mol% or less.

[0045] The stabilizer content of the sintered body of this embodiment (stabilizer content of the entire sintered body) is optional, but is preferably, for example, more than 1.5 mol% and less than 7.0 mol%, further 2.5 mol% to 6.5 mol%, further 3.0 mol% to 6.0 mol%, further 3.5 mol% to 5.8 mol%, further 4.1 mol% to 5.5 mol%, and more preferably 4.7 mol% to 5.3 mol%. The stabilizer content of the sintered body is calculated using the following formula and varies depending on the thickness of each zirconia layer. Stabilizer content of sintered body = (thickness of first layer / height of sintered body) × stabilizer content of first layer + (thickness of second layer / height of sintered body) x stabilizer content of second layer +··· + (thickness of nth layer / height of sintered body) × stabilizer content of nth layer

[0046] Since the stabilizer content of the first layer is 4 mol% or more, for example, if the stabilizer content of the second layer exceeds 4.0 mol%, the stabilizer content of the sintered body having two zirconia layers with equal layer thickness will exceed 4.0 mol%.

[0047] In the sintered body of this embodiment, it is preferable that the stabilizer content of the first layer is 4.0 mol% or more and 5.0 mol% or less, the stabilizer content of the second layer is more than 5.0 mol% and 6.0 mol% or less, and the difference between the stabilizer content of the first layer and the stabilizer content of the second layer is 0.7 mol% or more and 1.8 mol% or less; it is more preferable that the yttria content of the first layer is 4.0 mol% or more and 5.0 mol% or less, the yttria content of the second layer is more than 5.0 mol% and 6.0 mol% or less, and the difference between the yttria content of the first layer and the yttria content of the second layer is 0.7 mol% or more and 1.8 mol% or less.

[0048] In this embodiment, the content of the stabilizer is the molar ratio of the stabilizer to the total of zirconia and the stabilizer, and when the stabilizer is yttria (Y2O3), it can be calculated as {Y2O3 / (ZrO2+Y2O3)}×100 (mol%).

[0049] The sintered body of this embodiment may contain alumina, and preferably at least one zirconia layer contains alumina. The alumina content of the sintered body of this embodiment, expressed as a ratio of the weight of alumina to the weight of the sintered body, may be 0% by mass or more, and may be 0% by mass or more and 0.15% by mass or less, further 0% by mass or more and 0.10% by mass or less, or even 0% by mass or more and 0.07% by mass or less. When alumina is contained, the alumina content may be more than 0% by mass and 0.15% by mass or less, preferably 0.005% by mass or more and 0.10% by mass or less, and more preferably 0.01% by mass or more and 0.70% by mass or less.

[0050] The alumina content of each zirconia layer may be within the same range as described above. The alumina content of each zirconia layer may affect the thermal shrinkage behavior during the calcination stage. The alumina content of each zirconia layer is arbitrary, and although the alumina contents of the zirconia layers may differ, it is preferable that the alumina contents are equal. When the alumina contents of the zirconia layers differ, the difference in alumina content between adjacent zirconia layers may be greater than 0% by mass and less than 1.0% by mass, greater than 0% by mass and less than 0.5% by mass, greater than 0% by mass and less than 0.03% by mass, or even 0.005% by mass to 0.01% by mass. For example, in the case of a zirconia layer made of zirconia containing alumina (Al2O3) and stabilized with yttria (YO3), the alumina content can be calculated as {Al2O3 / (ZrO2 + YO3 + Al2O3)} × 100 (mass%).

[0051] The sintered body and each zirconia layer of this embodiment may not contain a colorant. On the other hand, in order to obtain a desired color, the sintered body of this embodiment may contain an element (hereinafter also referred to as a "colorant") that has the function of coloring zirconia. The colorant may be any element that has the function of coloring zirconia, and may further be an element that has the function of coloring zirconia and has the function of suppressing phase transition. Specific examples of colorants include at least one of transition metal elements and lanthanoid rare earth elements, preferably at least one selected from the group consisting of iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), praseodymium (Pr), neodymium (Nd), europium (Eu), gadolinium (Gd), terbium (Tb), erbium (Er), and ytterbium (Yb), more preferably at least one selected from the group consisting of iron, cobalt, manganese, praseodymium, gadolinium, terbium, and erbium, and even more preferably at least one selected from the group consisting of iron, cobalt, and erbium.

[0052] The content of the colorant, expressed as the mass ratio of each colorant converted to oxide relative to the mass of each zirconia layer, can be, for example, 0 mass % or more and 0.3 mass % or less, preferably 0 mass % or more and 0.2 mass % or less.

[0053] The colorant contained in the sintered body of this embodiment may be in any state, and examples thereof include at least one of an oxide state and a state in which the colorant is solid-dissolved in zirconia.

[0054] When two or more zirconia layers contain a colorant, the content and type of the colorant may differ between the zirconia layers.

[0055] The sintered body of this embodiment preferably includes at least a zirconia layer containing zirconia having at least one of a tetragonal (T phase) and a cubic (C phase) crystal phase, more preferably includes at least a zirconia layer containing zirconia having a tetragonal crystal phase as the main phase, and even more preferably includes a zirconia layer containing zirconia having a tetragonal crystal phase as the main phase and a zirconia layer containing zirconia having a cubic crystal phase as the main phase. Note that the "main phase" in this embodiment refers to the crystal phase with the highest abundance (proportion of peak integrated intensity) among the zirconia crystal phases. The abundance can be determined from the XRD pattern of the sintered body surface.

[0056] The following conditions can be exemplified as conditions for measuring the XRD pattern of the surface of the sintered body. Radiation source: CuKα radiation (λ=1.541862Å) Measurement mode: Step scan Scan condition: 0.000278° per second Measurement range: 2θ=10-140° Irradiation width: constant (10mm)

[0057] The obtained XRD pattern can be subjected to Rietveld analysis to determine the ratio of tetragonal and cubic crystals (the ratio of integrated peak intensities), and the crystalline phase with the highest ratio can be determined as the main phase. Measurement of the XRD pattern and Rietveld analysis can be performed using a general-purpose powder X-ray diffractometer (e.g., X'pert PRO MPD, manufactured by Spectris) and analysis software (e.g., RIETAN-2000).

[0058] The sintered body of this embodiment has a density of 5.7 g / cm as measured by a method conforming to JIS R 1634. 3 More than 6.3g / cm 3 Preferably 5.9 g / cm or less 3 More than 6.1g / cm 3 The following can be given as examples: A density in this range corresponds to a relative density of 99% or more, and is a density that results in a so-called dense sintered body with practical strength.

[0059] The sintered body of this embodiment preferably includes at least a translucent zirconia layer, and more preferably has a zirconia layer having a total light transmittance (hereinafter simply referred to as "total light transmittance") of 30% to 50%, more preferably 32% to 45%, even more preferably 35% to 42% for light with a wavelength of 600 nm at a sample thickness of 1.0 mm.

[0060] In the sintered body of this embodiment, the difference in total light transmittance between adjacently stacked zirconia layers is preferably 1% or more and 10% or less, and more preferably 1.5% or more and 5% or less.

[0061] The total light transmittance of the sintered body of this embodiment is preferably 30% to 50%, more preferably 32% to 45%, even more preferably 35% to 42%. The total light transmittance of the sintered body of this embodiment can be measured by cutting out any part of the sintered body horizontally and processing it to a sample thickness of 1 mm.

[0062] Total luminous transmittance can be measured by a method conforming to JIS K 7361, using light with a wavelength of 600 nm as incident light, and can be calculated as the transmittance value obtained by adding up the diffuse transmittance and linear transmittance for that incident light. A sample having a thickness of 1 mm and a surface roughness (Ra) of ≦0.02 μm is used as the measurement specimen, and a general spectrophotometer (e.g., V-650, manufactured by JASCO Corporation) is used to irradiate the sample with light with a wavelength of 600 nm, and the transmitted light is collected using an integrating sphere to measure the transmittance (diffuse transmittance and linear transmittance) of the sample, which can be used as the total luminous transmittance.

[0063] The sintered body of this embodiment preferably has a three-point bending strength of 500 MPa or more, more preferably 550 MPa or more, and even more preferably 600 MPa or more, measured by a method in accordance with JIS R 1601. The three-point bending strength can be, for example, less than 1100 MPa, or even 1000 MPa or less.

[0064] FIG. 4 is a schematic diagram showing the measurement of the three-point bending strength of a sintered body (400) consisting of two zirconia layers. The sintered body (400) is shown as a sintered body having a structure in which two zirconia layers of different thicknesses are stacked. In FIG. 4, the X-axis direction represents the stacking direction, and the Y-axis direction represents the horizontal direction. The measurement sample used for the three-point bending strength measurement is a rectangular parallelepiped sintered body prepared with the width and thickness in the stacking direction and the length in the horizontal direction. The dimensions of the measurement sample are 4 mm wide, 3 mm thick, and 45 mm long. As shown in FIG. 4, the three-point bending strength can be measured by applying a load (41) perpendicular to the length of the measurement sample (400). The measurement sample can be positioned so that the load (41) is applied to the center of the support distance (42). The support distance is 30 mm.

[0065] The sintered body of this embodiment can be used for known zirconia applications such as structural materials and optical materials, but can also be suitably used as a dental material for dentures, such as crowns and bridges, and can be a dental material containing the sintered body of this embodiment.

[0066] Next, a method for producing the sintered body of this embodiment will be described.

[0067] The manufacturing method of this embodiment is as follows: The powder composition has a structure in which two or more powder composition layers each comprising a powder composition containing zirconia containing a stabilizer and a binder are laminated, and at least a first powder composition layer including zirconia having a stabilizer content of 4 mol% or more and a binder; Zirconia having a different content of stabilizer from the zirconia contained in the first powder composition layer; a second powder composition layer comprising a binder; and Equipped with and sintering a molded body, in which the difference in binder content between the first powder composition layer and the second powder composition layer exceeds 0.01 mass %, at 1200°C or higher and 1600°C or lower.

[0068] Another manufacturing method of this embodiment is as follows: The powder composition has a structure in which two or more powder composition layers each comprising a powder composition containing zirconia containing a stabilizer and a binder are laminated, and at least a first powder composition layer including zirconia having a stabilizer content of 4 mol% or more and a binder; a second powder composition layer containing zirconia having a stabilizer content different from that of the zirconia contained in the first powder composition layer, and a binder; Equipped with A step of calcining the molded body, in which the difference in binder content between the first powder composition layer and the second powder composition layer is more than 0.01% by mass, at 800°C or higher and lower than 1200°C to obtain a calcined body; and and sintering the calcined body at a temperature of 1200°C or higher and 1600°C or lower.

[0069] Further, another manufacturing method of the present embodiment is as follows: The zirconia composition layer has a structure in which two or more zirconia composition layers containing a stabilizer and zirconia having a necking structure are laminated, and the zirconia composition layer has at least a first zirconia composition layer containing zirconia having a stabilizer content of 4 mol% or more; a second zirconia composition layer containing zirconia having a different stabilizer content from that of the zirconia contained in the first zirconia composition layer; and sintering the calcined body comprising the above at 1200°C or higher and 1600°C or lower.

[0070] The molded body to be subjected to the manufacturing method of this embodiment is: The powder composition has a structure in which two or more powder composition layers each comprising a powder composition containing zirconia containing a stabilizer and a binder are laminated, and at least a first powder composition layer including zirconia having a stabilizer content of 4 mol% or more and a binder; a second powder composition layer containing zirconia having a stabilizer content different from that of the zirconia contained in the first powder composition layer, and a binder; Equipped with The molded article has a difference in binder content between the first powder composition layer and the second powder composition layer of more than 0.01% by mass.

[0071] It is known that a powder composition containing a binder improves the cohesive strength of zirconia and suppresses the occurrence of defects during molding, such as cracks and chips. To ensure uniform strength of the resulting molded body, it is usually necessary to uniformly adjust the binder content in the powder composition used to prepare the molded body. In contrast, the molded body of this embodiment is thought to not only improve the strength of the molded body, but also to perform a different function from conventional methods: suppressing stress generation between stacked layers by varying the binder content between layers. As a result, deformation during molding is suppressed, and molded bodies made of laminates of powder compositions containing zirconia with different stabilizer contents can be heat-treated without excessive defects.

[0072] The molded body used in the manufacturing method of this embodiment will be described below in terms of the main differences from the sintered body described above.

[0073] The molded body to be subjected to the manufacturing method of this embodiment is: The powder composition has a structure in which two or more powder composition layers each comprising a powder composition containing zirconia containing a stabilizer and a binder are laminated, and at least a first powder composition layer including zirconia having a stabilizer content of 4 mol% or more and a binder; a second powder composition layer containing zirconia having a stabilizer content different from that of the zirconia contained in the first powder composition layer, and a binder; Equipped with The molded article has a difference in binder content between the first powder composition layer and the second powder composition layer of more than 0.01% by mass.

[0074] The compact is a composition having a multilayer structure, i.e., a laminate made of a powder composition, and can be used as a precursor for a calcined body or a sintered body.

[0075] Instead of having a zirconia layer, the molded body has a powder composition layer (hereinafter also referred to as a "powder layer") made of a powder composition containing zirconia containing a stabilizer and a binder, and has a structure equivalent to the laminated structure shown in Figure 1 or Figure 2. Therefore, the molded body can also be considered as a laminated body having two or more layers containing zirconia powder containing a stabilizer and a binder.

[0076] The molded article preferably has a warpage of 1.0 mm or less, more preferably 0.3 mm or less, even more preferably 0.1 mm or less, and even more preferably 0.05 mm or less. The molded article preferably has no warpage (warpage of 0 mm), but may have warpage that cannot be measured with a gauge (warpage of 0 mm or more). The molded article may have a warpage of more than 0 mm, or even 0.01 mm or more. The warpage is preferably 0.06 mm or less, more preferably 0.05 mm or less, or even below the measurement limit (less than 0.03 mm).

[0077] The deformation amount of the molded article is preferably 1.0 or less, more preferably 0.5 or less, more preferably 0.2 or less, and even more preferably 0.15 or less. The deformation amount can be, for example, 0 or more, further 0.01 or more, or further 0.05 or more.

[0078] The zirconia contained in the powder layer is preferably zirconia obtained by heat-treating a zirconia sol, more preferably zirconia obtained by hydrolysis of a zirconium compound and heat-treated, and even more preferably zirconia obtained by hydrolysis of zirconium oxychloride and heat-treated.

[0079] The zirconia contained in the powder layer is preferably zirconia powder, and the average particle size of the zirconia powder is preferably 0.3 μm or more and 0.7 μm or less, and more preferably 0.4 μm or more and 0.5 μm or less.

[0080] The binder contained in the powder layer is preferably a binder that vaporizes at 1200°C or less, more preferably an organic binder, and even more preferably an organic binder that has fluidity at room temperature (e.g., 10°C to 30°C). The binder may not contain a plasticizer or a release agent. The organic binder is at least one selected from the group consisting of polyvinyl alcohol, polyvinyl butyrate, wax, and acrylic resin, preferably at least one of polyvinyl alcohol and acrylic resin, and more preferably an acrylic resin. In this embodiment, the acrylic resin is a polymer containing at least one of an acrylic acid ester or a methacrylic acid ester. The acrylic resin contained in the powder composition may be any resin that is used as a binder for ceramics. Specific examples of the acrylic resin include at least one selected from the group consisting of polyacrylic acid, polymethacrylic acid, acrylic acid copolymers, and methacrylic acid copolymers, and derivatives thereof.

[0081] The stabilizer content of the stabilizer-containing zirconia contained in the first powder layer (hereinafter also referred to as the "first powder layer"), the stabilizer content of the stabilizer-containing zirconia contained in the second powder layer (hereinafter also referred to as the "second powder layer"), and the stabilizer content of the stabilizer-containing zirconia contained in the third powder layer (hereinafter also referred to as the "third powder layer") may be the same as the stabilizer content of the first layer, the second layer, and the third layer, respectively.

[0082] The content of the stabilizer in the compact and each powder layer is arbitrary, provided that it is the same as that in the sintered body of the present embodiment described above.

[0083] From the viewpoint of suppressing defects during molding, the binder content of each powder layer is preferably 1.5% by mass or more, more preferably 1.5% by mass or more and 8.0% by mass or less, even more preferably 2.0% by mass or more and 6.0% by mass or less, and even more preferably 2.5% by mass or more and 5.5% by mass or less.

[0084] In the molded body, the difference in binder content between the first powder layer and the second powder layer (hereinafter also referred to as "binder amount difference") is preferably more than 0.01% by mass and 0.03% by mass or more. In this way, the molded body has different binder contents between the first powder layer and the second powder layer. This suppresses stress generation during molding. From the viewpoint of suppressing stress generation, the binder amount difference may be more than 0.01% by mass and 5% by mass or less, or even 0.03% by mass or more and 3.5% by mass or less, preferably 0.04% by mass or more and 3% by mass or less, more preferably 0.05% by mass or more and 2% by mass or less, even more preferably 0.06% by mass or more and 1.5% by mass or less, and even more preferably 0.07% by mass or more and 1% by mass or less. In another embodiment, the difference in binder amount is greater than 0.01% by mass and not more than 3% by mass, further 0.03% by mass or more and not more than 2% by mass, further 0.1% by mass or more and not more than 1.2% by mass, further 0.12% by mass or more and not more than 1% by mass, or further 0.13% by mass or more and not more than 0.5% by mass.

[0085] The binder content is the weight ratio of the binder to the weight of the powder composition in the powder layer excluding the binder ({binder / (powder composition-binder)} x 100). When producing the powder composition, the total mass of the components of the powder composition other than the binder (e.g., stabilizer, zirconia, and alumina converted into oxides) is determined, and then the weight ratio of the desired binder relative to this is determined to produce the powder composition.

[0086] In order to prevent warpage of the compact, it is preferable to adjust the binder content of each powder layer according to the stabilizer content of the adjacent powder layer. The second powder layer has a higher content of stabilizer and binder than the first powder layer; The second powder layer has a lower content of stabilizer and binder than the first powder layer; The second powder layer has a higher stabilizer content and a lower binder content than the first powder layer; and For example, the second powder layer may have a lower stabilizer content and a higher binder content than the first powder layer; the second powder layer has a higher stabilizer content and a lower binder content than the first powder layer; or It is preferable that the second powder layer has a lower stabilizer content and a higher binder content than the first powder layer. The first powder layer and the second powder layer may have different stabilizer and binder contents, but a large difference in binder content is preferable because warpage of the molded body tends to be suppressed. It is also preferable that one of the first and second powder layers has a lower stabilizer content and a higher binder content than the other powder layer.

[0087] In addition, in adjacently stacked powder layers, one powder layer containing zirconia with a low stabilizer content preferably has a higher binder content than the other powder layer. Furthermore, when adjacently stacked powder layers are used and the zirconia contained in one powder layer is a mixture of two or more zirconias with different stabilizer contents, it is preferable that the one powder layer containing zirconia with a low stabilizer content has a lower binder content than the other powder layer.

[0088] From the viewpoint of operability, the powder composition contained in the powder layer is preferably a powder in a granulated state of zirconia powder and a binder (hereinafter also referred to as "granulated powder"), and more preferably a granulated powder (hereinafter also referred to as "powder granules") granulated into granules by spray drying or the like.

[0089] The particle size of the granulated powder is optional, but the average agglomeration size can be 1 μm or more and 150 μm or less, preferably 1 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less, and even more preferably 5 μm or more and 30 μm or less. In another embodiment, the average agglomeration size can be 20 μm or more and 50 μm or less.

[0090] In this embodiment, the average agglomerate diameter is the diameter corresponding to 50% of the cumulative total in the measurement of the volume particle size distribution. The volume particle size distribution is a value that can be measured using a general-purpose device (e.g., MT3100II, manufactured by Microtrac-Bell), and is the volume diameter of particles that are approximately spherical.

[0091] More preferably, the molded body includes at least a powder layer containing zirconia having a tetragonal or cubic crystal as the main phase.

[0092] The compact has a density of 2.4 g / cm 3 More than 3.7g / cm 3 Preferably, it is 3.1 g / cm or less. 3 More than 3.5g / cm 3 The density in this range corresponds to a relative density of 40% to 60%.

[0093] The density of the molded body can be determined from the weight obtained by weighing and the volume obtained by measuring the dimensions.

[0094] The molded body and each powder layer are opaque and have a total light transmittance of 0%, but when measurement error is taken into consideration, the total light transmittance can be, for example, 0% or more and 0.2% or less.

[0095] The molded body only needs to have a strength sufficient to prevent cracking or chipping when subjected to calcination or sintering.

[0096] A compact is obtained by layering powder compositions and molding them. Each powder composition is obtained by mixing zirconia powder and a binder in a desired ratio using a known method. Forming is preferably pressure molding. For example, a powder composition having a composition corresponding to the bottom layer is filled into a mold to form the bottom layer. Then, a powder composition having a composition corresponding to the layer adjacent to the bottom layer is filled on top of the bottom layer. To obtain a compact having a structure in which three or more powder layers are layered, a similar operation can be repeated to layer the necessary powder compositions. After filling with a powder composition having a composition corresponding to the top layer, a preform is obtained by uniaxial pressing at an appropriate pressure, and this is then subjected to cold isostatic pressing (hereinafter also referred to as "CIP") to obtain a compact. During layering, vibration to form a mixed layer between the layers, such as vibration using a vibrator, is not required. Uniaxial pressing is preferably performed after filling with a powder composition having a composition corresponding to the top layer; it is preferable not to apply pressure before filling with a powder composition having a composition corresponding to the top layer.

[0097] The molding pressure of the uniaxial pressing is preferably 15 MPa or more and 200 MPa or less, and more preferably 18 MPa or more and 100 MPa or less. In the uniaxial pressing, warpage of the molded body tends to be suppressed as the molding pressure increases. The molding pressure of the CIP treatment can be 98 MPa or more and 392 MPa or less.

[0098] The calcined body used in the manufacturing method of this embodiment will be described below in terms of the main differences from the sintered body described above.

[0099] The calcined body to be used in the manufacturing method of this embodiment is: The zirconia composition layer contains a stabilizer and has a structure in which two or more zirconia composition layers containing zirconia having a necking structure are laminated, and the zirconia composition layer has at least a first zirconia composition layer containing zirconia having a stabilizer content of 4 mol% or more; a second zirconia composition layer containing zirconia having a different stabilizer content from that of the zirconia contained in the first zirconia composition layer; The calcined body comprises:

[0100] The calcined body is a composition having a multilayer structure, i.e., a laminate, and is a laminate consisting of a structure having a necking structure, i.e., calcined particles. The calcined body can be processed as necessary and used as a precursor of a sintered body, and is also called a pre-sintered body or a semi-sintered body.

[0101] The necking structure is a structure possessed by zirconia heat-treated below the sintering temperature, and is a structure in which zirconia particles are chemically adhered to one another. As shown in FIG. 5, the zirconia (51) contained in the zirconia composition layer of the calcined body is a structure in which the particle shape of zirconia in the powder composition can be partially confirmed. In this embodiment, the structure having the necking structure is a structure consisting of zirconia in the early stage of sintering. This is different from the sintered structure, i.e., a structure consisting of zirconia crystal particles in the later stage of sintering. Therefore, the calcined body of this embodiment can also be considered a laminate having two or more zirconia-containing layers consisting of zirconia particles having a necking structure of zirconia containing a stabilizer.

[0102] The calcined body has a zirconia composition layer (hereinafter also referred to as "composition layer") containing a stabilizer and zirconia having a necking structure, instead of having a zirconia layer, and has a structure equivalent to the layered structure shown in FIG. 1 or FIG. 2.

[0103] The calcined body preferably has a warpage of 1.0 mm or less, more preferably 0.3 mm or less, even more preferably 0.2 mm or less, even more preferably 0.1 mm or less, and even more preferably 0.05 mm or less. The calcined body preferably has no warpage (warpage of 0 mm), but may have a warpage that cannot be measured with a gauge (warpage of 0 mm or more). The calcined body may have a warpage of more than 0 mm, and even 0.01 mm or more, for example. The warpage is preferably 0.06 mm or less, even 0.05 mm or less, or even below the measurement limit (less than 0.03 mm).

[0104] The calcined body preferably has a deformation amount of 1.0 or less, more preferably 0.5 or less, more preferably 0.2 or less, and even more preferably 0.15 or less. The deformation amount can be, for example, 0 or more, further 0.01 or more, or further 0.05 or more.

[0105] The zirconia contained in the calcined body is preferably in a state where zirconia obtained by heat-treating a zirconia sol has been heat-treated at a temperature lower than the sintering temperature, more preferably in a state where zirconia obtained by heat-treating a zirconia sol obtained by hydrolysis of a zirconium compound has been heat-treated at a temperature lower than the sintering temperature, and even more preferably in a state where zirconia obtained by heat-treating a zirconia sol obtained by hydrolysis of zirconium oxychloride has been heat-treated at a temperature lower than the sintering temperature.

[0106] The content of the stabilizer in the stabilizer-containing zirconia contained in the first composition layer (hereinafter also referred to as the "first composition layer"), the content of the stabilizer in the stabilizer-containing zirconia contained in the second composition layer (hereinafter also referred to as the "second composition layer"), and the content of the stabilizer in the stabilizer-containing zirconia contained in the third composition layer (hereinafter also referred to as the "third composition layer") may be the same as the stabilizer contents in the first layer, second layer, and third layer, respectively.

[0107] The content of the stabilizer in the calcined body and each composition layer is arbitrary, provided that it is the same as that in the sintered body of the present embodiment described above.

[0108] The calcined body more preferably includes at least a zirconia composition layer containing zirconia having a tetragonal or cubic crystal as a main phase.

[0109] The calcined body has a density of 2.4 g / cm 3 More than 3.7g / cm 3 Preferably, it is 3.1 g / cm or less. 3 More than 3.5g / cm 3 The following can be given as an example. A density in this range corresponds to a relative density of 40% to 60%. The calcined body may be any laminate having strength suitable for processing such as CAD / CAM processing.

[0110] The density of the calcined body is determined from the weight determined by weighing and the volume determined by measuring the dimensions.

[0111] The calcined body and each composition layer are opaque and have a total light transmittance of 0%, but when measurement error is taken into consideration, the total light transmittance can be, for example, 0% or more and 0.2% or less.

[0112] The calcined body only needs to have a strength that is such that defects are unlikely to occur during processing such as CAD / CAM or cutting.

[0113] The compact is converted into a calcined body by treating the compact at a temperature lower than the sintering temperature. Known calcination methods and conditions can be used.

[0114] The holding temperature during calcination (hereinafter also referred to as "calcination temperature") is 800°C or higher and 1200°C or lower, preferably 900°C or higher and 1150°C or lower, and more preferably 950°C or higher and 1100°C or lower.

[0115] The holding time at the calcination temperature (hereinafter also referred to as "calcination time") is preferably 0.5 hours or more and 5 hours or less, more preferably 0.5 hours or more and 3 hours or less.

[0116] The atmosphere in the calcination step (hereinafter also referred to as "calcination atmosphere") is preferably an atmosphere other than a reducing atmosphere, more preferably at least either an oxygen atmosphere or an air atmosphere, and even more preferably an air atmosphere.

[0117] In the manufacturing method of this embodiment, either a compact or a calcined body (hereinafter, these are also collectively referred to as "compact, etc.") is treated at a temperature higher than 1200°C and not higher than 1600°C. This converts the compact, etc. into a sintered body. Prior to sintering, the compact, etc. may be processed into any shape.

[0118] Known methods can be used for the sintering method and sintering conditions. Examples of the sintering method include at least one selected from the group consisting of atmospheric sintering, HIP treatment, SPS, and vacuum sintering. As this is a commonly used industrial sintering method, atmospheric sintering is preferred, and atmospheric sintering in an air atmosphere is more preferred. The sintering method is preferably atmospheric sintering alone, and more preferably, pressure sintering is not performed after atmospheric sintering. This allows the sintered body to be obtained as an atmospheric sintered body. In this embodiment, atmospheric sintering is a method in which the sintered body is sintered simply by heating without applying an external force to the sintered body during sintering.

[0119] The holding temperature during sintering (hereinafter also referred to as "sintering temperature") is 1200°C or higher and 1600°C or lower, preferably 1300°C or higher and 1580°C or lower, more preferably 1400°C or higher and 1560°C or lower, even more preferably 1430°C or higher and 1560°C or lower, and even more preferably 1480°C or higher and 1560°C or lower. In another embodiment, the sintering temperature is 1450°C or higher and 1650°C or lower, preferably 1500°C or higher and 1650°C or lower, and more preferably 1500°C or higher and 1650°C or lower.

[0120] The rate of temperature rise up to the sintering temperature is 50°C / hour or more and 800°C / hour or less, preferably 100°C / hour or more and 800°C / hour or less, more preferably 150°C / hour or more and 800°C / hour or less, and even more preferably 150°C / hour or more and 700°C / hour or less.

[0121] The holding time at the sintering temperature (hereinafter also referred to as "sintering time") varies depending on the sintering temperature, but is preferably 1 hour or more and 5 hours or less, more preferably 1 hour or more and 3 hours or less, and even more preferably 1 hour or more and 2 hours or less.

[0122] The sintering atmosphere (hereinafter also referred to as "sintering atmosphere") is preferably an atmosphere other than a reducing atmosphere, more preferably at least one of an oxygen atmosphere and an air atmosphere, and even more preferably an air atmosphere. The air atmosphere is, for example, composed mainly of nitrogen and oxygen, with an oxygen concentration of about 18 to 23% by volume.

[0123] A preferred sintering condition in the sintering step is atmospheric sintering in an air atmosphere. [Example]

[0124] The sintered body of this embodiment will be described below using examples, but the present invention is not limited to these examples. (density measurement) The densities of the compacts and calcined bodies were calculated from the weights measured by gravimetry and the volumes measured by dimensional measurements. Dimensional measurements were performed using disk-shaped samples, with the top diameter, bottom diameter, and thickness measured at four points using a vernier caliper, and the average thickness and the average diameter of the top and bottom ends were measured. The density of the sintered body was measured by a method in accordance with JIS R 1634.

[0125] (Warp and deformation amount) The disk-shaped compact, calcined body, or sintered body was used as a measurement sample, and the amount of deformation of each was calculated using the following formula. Deformation amount = (warpage: mm) / (dimension: mm) x 100 Warpage was measured using the measurement method shown in Figure 3. The specimen was placed so that its protrusion was in contact with the horizontal plate. A thickness gauge (product name: 75A19, manufactured by Nagai Gauge Manufacturing Co., Ltd.) conforming to JIS B 7524:2008 was inserted into the gap formed between the horizontal plate and the bottom surface to measure the warpage. The gauge, placed parallel to the horizontal plate, was inserted into the gap formed between the horizontal plate and the bottom surface of the specimen, and the maximum gauge thickness that could be inserted into the gap was measured. This gauge thickness was taken as the warpage. Warpage was measured using a single gauge or a combination of gauges in 0.01 mm increments starting from a gauge thickness of 0.03 mm. The dimensions of the measurement sample were measured by using a vernier caliper to measure the diameter of the upper end and the diameter of the lower end at four points each, and the average value of the diameters of the upper and lower ends was calculated.

[0126] (Total light transmittance) The total light transmittance was measured using a spectrophotometer (device name: V-650, manufactured by JASCO Corporation) according to a method in accordance with JIS K 7361. A disk-shaped sample was used for the measurement. Prior to the measurement, both sides of the sample were polished to a thickness of 1 mm and a surface roughness (Ra) of 0.02 μm or less. Light with wavelengths of 220 to 850 nm was transmitted through the sample and collected using an integrating sphere to measure the transmittance at each wavelength, and the transmittance at a wavelength of 600 nm was taken as the total light transmittance.

[0127] (three-point bending strength) The three-point bending strength was measured according to JIS R 1601. The measurement sample was a columnar shape with a width of 4 mm, a thickness of 3 mm, and a length of 45 mm, with the length measured in the stacking direction. The measurement was performed with a support distance of 30 mm and a load applied horizontally to the measurement sample. (Average aggregate diameter) The average agglomerate diameter was measured by placing the powder granule sample into a Microtrac particle size distribution analyzer (device name: MT3100II, manufactured by Microtrac-Bell). The particle size at which the cumulative volume reached 50% was taken as the average agglomerate size.

[0128] (crystalline phase) The crystalline phase of the laminate sample was measured by XRD measurement under the following conditions: A general XRD device (device name: X'pert PRO MPD, manufactured by Spectris) was used as the measuring device. Radiation source: CuKα radiation (λ=1.541862Å) Measurement mode: Step scan Scan condition: 0.000278° per second Measurement range: 2θ=10-140° Irradiation width: constant (10mm) The obtained XRD patterns were subjected to Rietveld analysis using analysis software (RIETAN-2000) to determine the ratio of tetragonal and cubic crystals (ratio of integrated peak intensities), and the crystal phase with the highest ratio was determined as the main phase.

[0129] Synthesis Example 1 (Synthesis of zirconia powder) (Zirconia powder A1) A hydrated zirconia sol was obtained by hydrolysis of an aqueous zirconium oxychloride solution. Yttrium chloride was added to the hydrated zirconia sol so that the yttria concentration became 5.5 mol%, and then the sol was dried at 180°C. The dried zirconia sol was fired at 1160°C for 2 hours, washed with distilled water, and dried in air at 110°C. α-alumina was mixed with the dried powder to obtain a mixed powder, and distilled water was added to the mixed powder to obtain a slurry, which was then processed in a ball mill for 22 hours. After the ball milling, an acrylic acid binder (acrylic resin) was added to the slurry as a binding agent so that the weight ratio of the binder to the weight of the mixed powder in the slurry was 3.13 mass%. The mixed slurry was spray-dried at 180°C to obtain powder granules containing 3.13 mass% of the acrylic acid binder (acrylic resin), 0.05 mass% of alumina, and the remainder being 5.5 mol% yttria-containing zirconia, with an average agglomerate diameter of 45 μm.

[0130] (Zirconia powder A2) Powder granules containing 3.5 mass% of an acrylic acid-based binder, 0.05 mass% of alumina, and the remainder being 5.5 mol% yttria-containing zirconia, and having an average agglomerate diameter of 44 μm were obtained in the same manner as for zirconia powder A1, except that an acrylic acid-based binder was added to and mixed with the slurry so that the weight ratio of the binder to the slurry weight was 3.5% by mass. (Zirconia powder A3) Powder granules containing 4.0 mass% of an acrylic acid-based binder, 0.05 mass% of alumina, and the remainder being 5.5 mol% yttria-containing zirconia, and having an average agglomerate diameter of 46 μm were obtained in the same manner as for zirconia powder A1, except that an acrylic acid-based binder was added to and mixed with the slurry so that the weight ratio of the binder to the slurry weight was 4.0 mass%. (Zirconia powder A4) Powder granules containing 5.0 mass% of an acrylic acid-based binder, 0.05 mass% of alumina, and the remainder being 5.5 mol% yttria-containing zirconia, and having an average agglomerate diameter of 46 μm were obtained in the same manner as for zirconia powder A1, except that an acrylic acid-based binder was added to and mixed with the slurry so that the weight ratio of the binder to the slurry weight was 5.0 mass%. (Zirconia powder A5) Powder granules containing 6.0 mass% of an acrylic acid-based binder, 0.05 mass% of alumina, and the remainder being 5.5 mol% yttria-containing zirconia, and having an average agglomerate diameter of 45 μm were obtained in the same manner as for zirconia powder A1, except that an acrylic acid-based binder was added to and mixed with the slurry so that the weight ratio of the binder to the slurry weight was 6.0 mass%. (Zirconia powder A6) Powder granules containing 3.05 mass% of an acrylic acid-based binder and 0.05 mass% of alumina, with the remainder being 5.2 mol% yttria-containing zirconia, and having an average agglomerate diameter of 43 μm were obtained in the same manner as for zirconia powder A1, except that yttrium chloride was added to the hydrated zirconia sol so that the yttria concentration was 5.2 mol%, and an acrylic acid-based binder was added to the slurry and mixed so that the weight ratio of the binder to the slurry weight was 3.05 mass%. (Zirconia powder A7) Powder granules containing 3.08 mass% of an acrylic acid-based binder and 0.05 mass% of alumina, with the remainder being 5.8 mol% yttria-containing zirconia, and having an average agglomerate diameter of 44 μm were obtained in the same manner as for zirconia powder A1, except that yttrium chloride was added to the hydrated zirconia sol so that the yttria concentration was 5.80 mol%, and an acrylic acid-based binder was added to the slurry and mixed so that the weight ratio of the binder to the slurry weight was 3.08 mass%.

[0131] (Zirconia powder B1) A dried powder was obtained in the same manner as for zirconia powder A1, and this was mixed with α-alumina and distilled water to form a slurry. This was then treated in a ball mill for 22 hours to obtain a slurry containing a powder containing 0.05 mass% alumina and the remainder being 5.5 mol% yttria-containing zirconia. In addition, a dried powder was obtained in the same manner as for zirconia powder A1, except that yttrium chloride was added to the hydrated zirconia sol so that the yttria concentration was 3.0 mol %, and this was mixed with α-alumina and distilled water to form a slurry, which was then treated in a ball mill for 22 hours to obtain a slurry containing a powder containing 0.05 mass % alumina and the remainder being 3.0 mol % yttria-containing zirconia. The two slurries were mixed to obtain a slurry containing 0.05% by mass of alumina and 4.0 mol% yttria-containing zirconia powder, and then an acrylic acid-based binder was added to the slurry and mixed so that the weight ratio of the binder to the slurry weight was 3.05% by mass. The mixed slurry was spray-dried at 180°C to obtain powder granules containing 3.05% by mass of the acrylic acid-based binder and 0.05% by mass of alumina, with the remainder being 4.0 mol% yttria-containing zirconia, and having an average agglomeration diameter of 43 μm.

[0132] (Zirconia powder B2) Powder granules containing 3.08 mass% of an acrylic acid-based binder and 0.05 mass% of alumina, with the remainder being 4.0 mol% yttria-containing zirconia, and having an average agglomerate diameter of 46 μm, were obtained in the same manner as for zirconia powder B1, except that a slurry containing a powder containing 0.05 mass% of alumina and the remainder being 5.5 mol% yttria-containing zirconia was mixed with a slurry containing a powder containing 0.05 mass% of alumina and the remainder being 2.5 mol% yttria-containing zirconia, and an acrylic acid-based binder was added to the slurry and mixed so that the weight ratio of the binder to the slurry weight was 3.08 mass%. (Zirconia powder B3) Powder granules containing 2.0 mass% of an acrylic acid-based binder and 0.05 mass% of alumina, with the remainder being 4.15 mol% yttria-containing zirconia, and having an average agglomerate diameter of 45 μm, were obtained in the same manner as zirconia powder B1, except that a slurry containing a powder containing 0.05 mass% of alumina and the remainder being 5.5 mol% yttria-containing zirconia was mixed with a slurry containing a powder containing 0.05 mass% of alumina and the remainder being 2.5 mol% yttria-containing zirconia, and an acrylic acid-based binder was added to the slurry and mixed so that the weight ratio of the binder to the slurry weight was 2.0 mass%. (Zirconia powder B4) Powder granules containing 3.06 mass% of an acrylic acid-based binder and 0.05 mass% of alumina, with the remainder being 4.5 mol% yttria-containing zirconia, and having an average agglomeration diameter of 45 μm were obtained in the same manner as for zirconia powder B1, except that the mixing ratio of the two slurries was changed so that the yttria content was 4.5 mol% and that an acrylic acid-based binder was added to and mixed with the slurry so that the weight ratio of the binder to the slurry weight was 3.06 mass%.

[0133] (Zirconia powder C1) A hydrated zirconia sol was obtained by hydrolysis of an aqueous zirconium oxychloride solution. Yttrium chloride was added to the hydrated zirconia sol so that the yttria concentration became 4.05 mol%, and then the sol was dried at 180°C. The dried zirconia sol was fired at 1160°C for 2 hours, washed with distilled water, and dried in air at 110°C. α-alumina was mixed with the dried powder to obtain a mixed powder, and distilled water was added to the mixed powder to obtain a slurry, which was then processed in a ball mill for 22 hours. After the ball milling, an acrylic acid-based binder was added to the slurry so that the weight ratio of the binder to the weight of the mixed powder in the slurry was 3.30 mass%. The mixed slurry was spray-dried at 180°C to obtain powder granules containing 3.30 mass% of the acrylic acid-based binder, 0.05 mass% of alumina, and the remainder being 4.05 mol% yttria-containing zirconia, with an average agglomerate diameter of 43 μm. (Zirconia powder C2) Powder granules containing 3.20 mass% of an acrylic acid-based binder and 0.05 mass% of alumina, with the remainder being 4.10 mol% yttria-containing zirconia, and having an average agglomerate diameter of 46 μm were obtained in the same manner as for zirconia powder C1, except that yttrium chloride was added to the hydrated zirconia sol so that the yttria concentration was 4.10 mol%, and an acrylic acid-based binder was added to the slurry and mixed so that the weight ratio of the binder to the slurry weight was 3.20 mass%. (Zirconia powder C3) Powder granules containing 3.29 mass% of an acrylic acid-based binder and 0.05 mass% of alumina, with the remainder being 4.25 mol% yttria-containing zirconia, and having an average agglomerate diameter of 44 μm were obtained in the same manner as for zirconia powder C1, except that yttrium chloride was added to the hydrated zirconia sol so that the yttria concentration was 4.25 mol%, and an acrylic acid-based binder was added to the slurry and mixed so that the weight ratio of the binder to the slurry weight was 3.29 mass%. (Zirconia powder C4) Powder granules were obtained in the same manner as for zirconia powder C1, except that yttrium chloride was added to the hydrated zirconia sol so that the yttria concentration was 4.00 mol%, α-alumina was not used, and an acrylic acid-based binder was added to the slurry and mixed so that the weight ratio of the binder to the slurry weight was 3.50 mass%. The powder granules were composed of 3.50 mass% of the acrylic acid-based binder and the remainder was 4.00 mol% yttria-containing zirconia, and had an average agglomeration diameter of 44 μm. (Zirconia powder C5) Powder granules containing 3.50 mass% of an acrylic acid-based binder and 0.05 mass% of alumina, with the remainder being 4.00 mol% yttria-containing zirconia, and having an average agglomerate diameter of 46 μm were obtained in the same manner as for zirconia powder C1, except that yttrium chloride was added to the hydrated zirconia sol so that the yttria concentration was 4.00 mol%, and an acrylic acid-based binder was added to the slurry and mixed so that the weight ratio of the binder to the slurry weight was 3.50 mass%. (Zirconia powder C6) Powder granules containing 3.50 mass% of an acrylic acid-based binder and 0.10 mass% of alumina, with the remainder being 4.00 mol% yttria-containing zirconia, and having an average agglomerate diameter of 45 μm, were obtained in the same manner as for zirconia powder C1, except that yttrium chloride was added to the hydrated zirconia sol so that the yttria concentration was 4.00 mol%, α-alumina was mixed in so that the alumina content was 0.10 mass%, and an acrylic acid-based binder was added to the slurry and mixed so that the weight ratio of the binder to the slurry weight was 3.50 mass%.

[0134] Example 1 (Molded body) A mold with an inner diameter of 48 mm was filled with 25 g of zirconia powder A1, and the mold was then tapped to form the first powder layer. The same amount of zirconia powder B1 was filled on top of the first powder layer, and the mold was then tapped to form the second powder layer, which was then subjected to uniaxial press molding at a pressure of 49 MPa. This was then subjected to CIP processing at a pressure of 196 MPa to obtain a two-layer laminate, which was used as the molded body of this example. The stabilizer content of the first powder layer was 5.5 mol% and the stabilizer content of the second powder layer was 4.0 mol%, with a difference in yttria content between the layers of 1.50 mol% and a difference in binder content (binder amount difference) of 0.08 mass%. The warpage of the molded body was 0.06 mm, and the deformation amount was 0.12.

[0135] (calcined body) The compact was calcined at a temperature increase rate of 20° C. / hour, at a calcination temperature of 1000° C. for a calcination time of 2 hours to obtain a laminate, which was used as the calcined body of this example. The calcined body had a warp of 0.06 mm and a deformation amount of 0.12 mm.

[0136] (sintered body) The calcined body was sintered at a temperature increase rate of 100°C / hour, a sintering temperature of 1500°C, and a sintering time of 2 hours to obtain a laminate, which was used as the sintered body of this example.

[0137] The warpage of the sintered body was 0.06 mm, the amount of deformation was 0.15, and the stabilizer content of the sintered body was 4.75 mol %.

[0138] Example 2 A laminate was obtained in the same manner as in Example 1, except that zirconia powder A2 and zirconia powder B2 were used instead of zirconia powder A1 and zirconia powder B1, and this was used as the molded body of this Example. The stabilizer content of the first powder layer was 5.5 mol % and the stabilizer content of the second powder layer was 4.0 mol %, the difference in yttria content between the layers was 1.50 mol %, and the difference in binder content was 0.42 mass %.

[0139] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used.

[0140] The warpage was 0.04 mm for the green body, 0.05 mm for the calcined body, and 0.04 mm for the sintered body, and the deformation amount was 0.08 for the green body, 0.10 for the calcined body, and 0.10 for the sintered body.

[0141] Example 3 A laminate was obtained in the same manner as in Example 1, except that zirconia powder A4 and zirconia powder B2 were used instead of zirconia powder A1 and zirconia powder B1, respectively, and this was used as the molded body of this example. The stabilizer content of the first powder layer was 5.5 mol % and the stabilizer content of the second powder layer was 4.0 mol %, the difference in yttria content between the layers was 1.50 mol %, and the difference in binder content was 1.92 mass %.

[0142] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used.

[0143] The warpage of the green body was below the measurement limit (less than 0.03 mm), the calcined body was 0.04 mm, and the sintered body was below the measurement limit (less than 0.03 mm). The deformation amount of the calcined body was 0.09.

[0144] Example 4 A laminate was obtained in the same manner as in Example 1, except that zirconia powder A5 and zirconia powder B2 were used instead of zirconia powder A1 and zirconia powder B1, respectively, and this was used as the molded body of this example. The stabilizer content of the first powder layer was 5.5 mol % and the stabilizer content of the second powder layer was 4.0 mol %, the difference in yttria content between the layers was 1.50 mol %, and the difference in binder content was 2.92 mass %.

[0145] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used.

[0146] The warpage was 0.04 mm for the green body, 0.03 mm for the calcined body, and less than the measurement limit (less than 0.03 mm) for the sintered body, and the deformation amount was 0.08 for the green body and 0.06 for the calcined body.

[0147] From Examples 1 to 4, it was confirmed that when the difference in yttria content was 1.50 mol%, warping of the calcined body tended to be suppressed as the difference in binder amount increased, and that when the difference in binder amount was 0.5 mass% or more, warping in the sintered body state was below the measurement limit.

[0148] Example 5 A laminate was obtained in the same manner as in Example 1, except that zirconia powder B3 was used instead of zirconia powder B1, and this was used as the molded body of this Example. The stabilizer content of the first powder layer was 5.5 mol % and the stabilizer content of the second powder layer was 4.15 mol %, the difference in yttria content between the layers was 1.35 mol %, and the difference in binder content was 1.13 mass %.

[0149] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used.

[0150] The warpage was 0.04 mm for the green body, 0.03 mm for the calcined body, and 0.03 mm for the sintered body, and the deformation amount was 0.08 for the green body, 0.06 for the calcined body, and 0.08 for the sintered body.

[0151] Example 6 A laminate was obtained in the same manner as in Example 1, except that zirconia powder B4 was used instead of zirconia powder B1, and this was used as the molded body of this Example. The stabilizer content of the first powder layer was 5.5 mol %, and the stabilizer content of the second powder layer was 4.5 mol %, the difference in yttria content between the layers was 1.0 mol %, and the difference in binder content was 0.07 mass %.

[0152] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used.

[0153] The warpage was 0.05 mm for the green body, 0.05 mm for the calcined body, and 0.05 mm for the sintered body, and the deformation amount was 0.10 for the green body, 0.10 for the calcined body, and 0.13 for the sintered body. The stabilizer content of the sintered body was 5.0 mol%.

[0154] Example 7 A laminate was obtained in the same manner as in Example 1, except that zirconia powder A3 and zirconia powder B4 were used instead of zirconia powder A1 and zirconia powder B1, respectively, and this was used as the molded body of this example. The stabilizer content of the first powder layer was 5.5 mol % and the stabilizer content of the second powder layer was 4.5 mol %, the difference in yttria content between the layers was 1.0 mol %, and the difference in binder content was 0.94 mass %.

[0155] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used.

[0156] The warpage was 0.04 mm for the green body, 0.04 mm for the calcined body, and 0.03 mm for the sintered body, and the deformation amount was 0.08 mm for the green body, 0.08 mm for the calcined body, and 0.08 mm for the sintered body.

[0157] Example 8 A laminate was obtained in the same manner as in Example 1, except that zirconia powder C1 was used instead of zirconia powder B1, and this was used as the molded body of this Example. The stabilizer content of the first powder layer was 5.5 mol % and the stabilizer content of the second powder layer was 4.05 mol %, the difference in yttria content between the layers was 1.45 mol %, and the difference in binder content was 0.2 mass %.

[0158] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used.

[0159] The warpage of the green body, the calcined body and the sintered body was below the measurement limit (less than 0.03 mm).

[0160] Example 9 A laminate was obtained in the same manner as in Example 1, except that zirconia powder C2 was used instead of zirconia powder B1, and this was used as the molded body of this Example. The stabilizer content of the first powder layer was 5.5 mol % and the stabilizer content of the second powder layer was 4.1 mol %, the difference in yttria content between the layers was 1.4 mol %, and the difference in binder content was 0.1 mass %.

[0161] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used. The stabilizer content of the sintered body was 4.8 mol%.

[0162] The warpage was 0.03 mm for the green body, 0.03 mm for the calcined body, and 0.04 mm for the sintered body, and the deformation amount was 0.06 for the green body, 0.06 for the calcined body, and 0.10 for the sintered body.

[0163] Example 10 A laminate was obtained in the same manner as in Example 1, except that zirconia powder C3 was used instead of zirconia powder B1, and this was used as the molded body of this Example. The stabilizer content of the first powder layer was 5.5 mol % and the stabilizer content of the second powder layer was 4.25 mol %, the difference in yttria content between the layers was 1.25 mol %, and the difference in binder content was 0.19 mass %.

[0164] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used.

[0165] The warpage of the green body was below the measurement limit (less than 0.03 mm), that of the calcined body was 0.03 mm, and that of the sintered body was 0.03 mm. The deformation amount of the calcined body was 0.06 and that of the sintered body was 0.08.

[0166] The density of the compact is 3.28 g / cm 3 and the calcined body was 3.22 g / cm 3 The density of the sintered body is 6.06 g / cm 3 It was.

[0167] Example 11 A laminate was obtained in the same manner as in Example 10 except that the pressure in the uniaxial press molding was 19.6 MPa, and this was used as the molded body of this example.

[0168] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used.

[0169] The warpage of the compact was below the measurement limit (less than 0.03 mm), that of the calcined body was 0.03 mm, and that of the sintered body was 0.05 mm. The deformation amount of the calcined body was 0.07, and that of the sintered body was 0.14.

[0170] The density of the compact is 3.25 g / cm 3 and the calcined body was 3.19 g / cm 3 The density of the sintered body is 6.06 g / cm 3 It was.

[0171] Example 12 A laminate was obtained in the same manner as in Example 10 except that the pressure in the uniaxial press molding was 98 MPa, and this was used as the molded body of this example.

[0172] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used.

[0173] The warpage of the green body, the calcined body and the sintered body was below the measurement limit (less than 0.03 mm).

[0174] The density of the compact is 3.35 g / cm 3 and the calcined body was 3.29 g / cm 3 The density of the sintered body is 6.06 g / cm 3 It was.

[0175] Examples 10 to 12 show that increasing the pressure of the uniaxial press molding tends to improve the density of the compact and the calcined body, and also tends to suppress warpage when the compact is made into a calcined body or a sintered body.

[0176] Example 13 A laminate was obtained in the same manner as in Example 10, except that a mold with an inner diameter of 110 mm was used and the pressure for uniaxial press molding was 98 MPa, and this was used as the molded body of this example.

[0177] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used.

[0178] The warpage of the green body, the calcined body and the sintered body was below the measurement limit (less than 0.03 mm).

[0179] From Examples 12 and 13, it can be seen that there is no difference (more accurately, no change) in the warpage of the compact, calcined body, and sintered body due to differences in the dimensions of the laminate.

[0180] The sintered bodies obtained in all Examples had a change in translucency between the top layer and the bottom layer, and exhibited a texture similar to that of natural teeth.

[0181] Example 14 A laminate was obtained in the same manner as in Example 1, except that a mold with an inner diameter of 110 mm was used, the uniaxial press molding pressure was 19.6 MPa, and zirconia powder C4 was used instead of zirconia powder B1, and this was used as the molded body of this example. The stabilizer content of the first powder layer was 5.5 mol% and the stabilizer content of the second powder layer was 4.0 mol%, the difference in yttria content between the layers was 1.5 mol%, and the difference in binder content was 0.4 mass%.

[0182] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used. The stabilizer content of the sintered body was 4.75 mol %.

[0183] The warpage was 0.05 mm for the green body, 0.11 mm for the calcined body, and less than the measurement limit (less than 0.03 mm) for the sintered body, and the deformation amount was 0.05 for the green body and 0.11 for the calcined body.

[0184] Example 15 A laminate was obtained in the same manner as in Example 1, except that a mold with an inner diameter of 110 mm was used, the uniaxial press molding pressure was 19.6 MPa, and zirconia powder C5 was used instead of zirconia powder B1, and this was used as the molded body of this example. The stabilizer content of the first powder layer was 5.5 mol% and the stabilizer content of the second powder layer was 4.0 mol%, the difference in yttria content between the layers was 1.5 mol%, and the difference in binder content was 0.37 mass%.

[0185] Except for using this molded body, a calcined body and a sintered body were obtained in the same manner as in Example 1. The stabilizer content of the sintered body was 4.75 mol %.

[0186] The warpage was 0.05 mm for the green body, 0.14 mm for the calcined body, and less than the measurement limit (less than 0.03 mm) for the sintered body, and the deformation amount was 0.05 for the green body and 0.11 for the calcined body.

[0187] Example 16 A laminate was obtained in the same manner as in Example 1, except that a mold with an inner diameter of 110 mm was used, the uniaxial press molding pressure was 19.6 MPa, and zirconia powder C6 was used instead of zirconia powder B1. This laminate was used as the molded body of this example. The stabilizer content of the first powder layer was 5.5 mol% and the stabilizer content of the second powder layer was 4.0 mol%, the difference in yttria content between the layers was 1.5 mol%, and the difference in binder content was 0.4 mass%. A calcined body and a sintered body were obtained in the same manner as in Example 1, except that this molded body was used. The stabilizer content of the sintered body was 4.75 mol%.

[0188] The warpage was 0.05 mm for the green body, 0.15 mm for the calcined body, and less than the measurement limit (less than 0.03 mm) for the sintered body, and the deformation amount was 0.05 for the green body and 0.15 for the calcined body.

[0189] From Examples 14 to 16, as the alumina content in the layer with a low stabilizer content decreased, the warpage of the calcined body decreased, but there was no change in the magnitude of warpage of the compacted body and sintered body.

[0190] Example 17 A laminate was obtained in the same manner as in Example 1, except that a mold with an inner diameter of 110 mm was used, the uniaxial press molding pressure was 98 MPa, and zirconia powders A7 and C5 were used instead of zirconia powders A1 and B1. The stabilizer content of the first powder layer was 5.8 mol%, the stabilizer content of the second powder layer was 4.0 mol%, the difference in yttria content between the layers was 1.8 mol%, and the difference in binder content was 0.42 mass%.

[0191] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used. The stabilizer content of the sintered body was 4.9 mol%.

[0192] The warpage of the calcined body was 0.04 mm, while the compacted body and the sintered body were below the measurement limit (less than 0.03 mm). The deformation amount of the calcined body was 0.03 mm.

[0193] Example 18 A laminate was obtained in the same manner as in Example 1, except that a mold with an inner diameter of 110 mm was used, the uniaxial press molding pressure was 98 MPa, and zirconia powders A6 and C5 were used instead of zirconia powders A1 and B1. The stabilizer content of the first powder layer was 5.2 mol%, the stabilizer content of the second powder layer was 4.0 mol%, the difference in yttria content between the layers was 1.2 mol%, and the difference in binder content was 0.45 mass%.

[0194] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used. The stabilizer content of the sintered body was 4.6 mol%.

[0195] The warpage of the green body, the calcined body and the sintered body was below the measurement limit (less than 0.03 mm).

[0196] Comparative Example 1 A mold with an inner diameter of 110 mm was filled with 25 g of zirconia powder containing 4.25 mol% yttria, and the mold was then tapped to form a first powder layer. The same amount of zirconia powder containing 4.25 mol% yttria was filled on top of the first powder layer, and the mold was then tapped to form a second powder layer, which was then subjected to uniaxial press molding at a pressure of 98 MPa. A CIP process was then performed at a pressure of 196 MPa to obtain a two-layer laminate, which was used as the molded body of this comparative example. The difference in yttria content between the layers was 0 mol%, and the difference in binder amount was 0 mass%.

[0197] A calcined body and a sintered body were produced in the same manner as in Example 1 except that the green body was used. In both cases, the warpage was below the measurement limit (<0.03 mm).

[0198] In the calcined body of this comparative example, in which the first and second layers had the same yttria content, no warping occurred, and the obtained sintered body had no change in translucency.

[0199] Comparative Example 2 A mold with an inner diameter of 110 mm was filled with 25 g of zirconia powder containing 0.094 mass% iron oxide and 0.0045 mass% cobalt oxide, with the remainder being 4 mol% yttria-containing zirconia. The mold was then tapped to form a first powder layer. The same amount of zirconia powder containing 4 mol% yttria was filled on top of the first powder layer, and the mold was tapped to form a second powder layer. This was then subjected to uniaxial press molding at a pressure of 98 MPa. A CIP process was then performed at a pressure of 196 MPa to obtain a two-layer laminate, which was used as the compact of this comparative example. The difference in yttria content between the layers was 0 mol%, and the difference in binder content was 0.02 mass%.

[0200] A calcined body was produced in the same manner as in Example 1 except that the compact was used, and the warpage was 0.67 mm.

[0201] In the calcined body of this comparative example, in which the first and second layers had the same yttria content but the colorant content differed by 0.139 mass %, significant warping occurred in the calcined body.

[0202] Reference example 1 Zirconia powder A1 was filled into a mold with an inner diameter of 48 mm, and then the mold was tapped and subjected to uniaxial press molding at a pressure of 49 MPa. After that, a CIP process was performed at a pressure of 196 MPa to obtain a green body.

[0203] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used.

[0204] The obtained sintered body contained 0.05% by mass of alumina and the remainder 5.5 mol% of yttria-containing zirconia, and its crystalline phase consisted of tetragonal and cubic crystals with a cubic main phase. The total light transmittance of the sintered body was 37.5%, and the three-point bending strength was 600 MPa.

[0205] Reference example 2 Zirconia powder B1 was filled into a mold with an inner diameter of 48 mm, and then the mold was tapped and subjected to uniaxial press molding at a pressure of 49 MPa. After that, a CIP treatment was performed at a pressure of 196 MPa to obtain a green body.

[0206] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used.

[0207] The resulting sintered body contained 0.05% by mass of alumina and the remainder 4.0 mol% of yttria-containing zirconia, and its crystalline phase consisted of tetragonal and cubic crystals with a tetragonal main phase. The total light transmittance of the sintered body was 36%, and the three-point bending strength was 1100 MPa.

[0208] Reference example 3 Zirconia powder B4 was filled into a mold with an inner diameter of 48 mm, and then the mold was tapped and uniaxial press molding was performed at a pressure of 49 MPa. After that, CIP processing was performed at a pressure of 196 MPa to obtain a green body.

[0209] A calcined body and a sintered body were obtained in the same manner as in Example 1, except that the green body was used.

[0210] The obtained sintered body contained 0.05 mass % alumina, with the remainder being 4.5 mol % yttria-containing zirconia, and had a total light transmittance of 37%. [Explanation of symbols]

[0211] 100, 200, 300, 400: Zirconia sintered body 11, 21: 1st layer 12, 22: 2nd layer 23:Third layer 32A, 32B: Thickness gauge 33: Size of sintered body 41: Load 42: Distance between supports 51: Zirconia with necking structure

Claims

1. It has a structure in which two or more zirconia layers containing zirconia containing a stabilizer are laminated, and at least a first zirconia layer containing zirconia having a stabilizer content of 4 mol% or more; a second zirconia layer containing zirconia having a stabilizer content different from that of the zirconia contained in the first zirconia layer; Equipped with A sintered body characterized by a warpage of 1.0 mm or less in the direction in which the layers are stacked, as measured using a thickness gauge in accordance with JIS B 7524:2008 (however, excluding a zirconia sintered body having a two-layer structure of zirconia containing 7.37 wt% Y2O3, 0.048 wt% Al2O3, 0.0091 wt% Fe, 0.0024 wt% Cr, 0.002 wt% Pr, 0.3981 wt% Er, and 0.1537 wt% La, and zirconia containing 9.25 wt% Y2O3, 0.048 wt% Al2O3, 0.028 wt% Fe, 0.0014 wt% Cr, and 0.2238 wt% Er).

2. 2. The sintered body according to claim 1, wherein the stabilizer content of the stabilizer-containing zirconia contained in the second zirconia layer is 1.5 mol % or more and 7.0 mol % or less.

3. 3. The sintered body according to claim 1, wherein the stabilizer content of the stabilizer-containing zirconia contained in the second zirconia layer is 5.0 mol % or more and 7.0 mol % or less.

4. 4. The sintered body according to claim 1, wherein the stabilizer content of the stabilizer-containing zirconia contained in the first zirconia layer is 4.0 mol % or more and 6.0 mol % or less.

5. 5. The sintered body according to claim 1, wherein the difference between the stabilizer content of the first zirconia layer and the stabilizer content of the second zirconia layer is 0.2 mol % or more.

6. The stabilizer is yttria (Y ２ O ３ ), calcia (CaO), magnesia (MgO) and ceria (CeO ２ 6. The sintered body according to claim 1, wherein the sintered body is one or more selected from the group consisting of:

7. The sintered body according to claim 1 , wherein at least one of the zirconia layers contains alumina.

8. The density measured according to JIS R 1634 is 5.7 g / cm ３ 6.3g / cm or more ３ The sintered body according to any one of claims 1 to 7, wherein:

9. 9. The sintered body according to claim 1, which has a zirconia layer having a total light transmittance of 30% or more and 50% or less for light with a wavelength of 600 nm when the sample is 1.0 mm thick.

10. 10. The sintered body according to claim 1, which has a three-point bending strength measured in accordance with JIS R 1601 of 500 MPa or more.

11. A dental material comprising the sintered body according to any one of claims 1 to 10.

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