WO2021100876A1 - Zirconia composition, zirconia calcined body, and zirconia sintered body, and production method therefor - Google Patents

Abstract

The present invention provides: a zirconia composition from which a zirconia sintered body having high shielding properties and favorable color development can be produced while shortening the firing time when producing a zirconia sintered body; and a calcined body. The present invention is a zirconia composition which contains a zirconia powder and a stabilizer capable of suppressing the phase transition of the zirconia powder, and which satisfies all of the following (1) to (3): (1) the zirconia powder includes zirconia particles having an average particle diameter of 0.17-0.4 μm (exclusive of 0.17); (2) at least a part of the stabilizer is not solid-soluted in zirconia; and (3) in a case where the composition is fired at 1,300-1,600ºC, the ratio (C^*(30)/C^*(120)) of the saturation C^*(30) of a sintered body when held for 30 minutes at the above temperature to the saturation C^*(120) of the sintered body when held for 120 minutes at the above temperature is at least 0.4.

Description

Zirconia composition, zirconia calcined body and zirconia sintered body, and method for producing them.

The present disclosure relates to compositions primarily containing zirconia (zirconium oxide (IV); ZrO _2). The present disclosure also relates to a calcined body and a sintered body of zirconia. Furthermore, the present disclosure relates to a method for producing a zirconia composition, a calcined body and a sintered body.

Zirconia is a compound in which a phase transition occurs between a plurality of crystal systems. Therefore, yttria (yttrium _oxide; Y 2 _{O 3)} a stabilizing agent phase transition is suppressed by a solid solution in the zirconia partially stabilized zirconia, such as (PSZ; Partially-Stabilized Zirconia) and fully stabilized zirconia various fields It is used in. For example, Patent Document 1 discloses a partially stabilized zirconia sintered body for use in dental materials.

The translucent zirconia sintered body described in Patent Document 1 is produced by sintering a press-molded zirconia powder under the conditions of 1450 ° C., a heating rate of 300 ° C./hr, and a holding time of 2 hours. The zirconia powder contains 2 to 4 mol% yttria and 0.1 to 0.2 wt% alumina, has a BET specific surface area of 5 to 15 m ² / g, and has an average particle size of 0.3 to 0. It is 7 μm.

Japanese Unexamined Patent Publication No. 2009-269812

As one form of use of zirconia as a dental material, a tooth serving as an abutment is formed by cutting a caries-affected part, and a zirconia crown processed to fit the abutment tooth is used by coalescing. There is a use. When the abutment tooth is discolored due to a lesion or coloring due to lifestyle, the zirconia crown is required to have a certain degree of low translucency (high shielding property) in order to shield the discolored abutment tooth. , The zirconia described in Patent Document 1 has insufficient shielding property.

Further, since the zirconia sintered body obtained by sintering zirconia particles (powder) usually has high strength, it is not easy to directly machine the zirconia sintered body into a desired shape. Therefore, in the molding of the zirconia sintered body, a press-molded body of zirconia powder (including a molded body subjected to CIP (Cold Isostatic Pressing) treatment) is fired at a temperature that does not lead to sintering ( It may be performed in a calcined body that has been blocked by (hereinafter referred to as "temporary firing"). In this case, the block body of the zirconia calcined body is formed into a desired shape by cutting or the like, and the molded calcined body is fired at a temperature higher than the sinterable temperature to prepare a zirconia sintered body having a desired shape. To do. In particular, as a dental material, a zirconia sintered body containing a colorant is produced so as to have a color close to that of natural teeth.

When the zirconia powder press-molded product is fired, it shrinks depending on the firing temperature. For example, a press-molded body shrinks about 1% when it becomes a calcined body by firing, and shrinks about 20% when it becomes a sintered body. Therefore, in consideration of these shrinkage rates, the calcined body is molded to be larger than the size of the sintered body, which is the final target product. For example, the size of the molded calcined body was calculated by subtracting the shrinkage rate from the press-molded body to the calcined body from the shrinkage rate from the powder press-molded body to the sintered body. Determined based on the coefficient.

Therefore, when a plurality of press-molded bodies are fired in one firing furnace to produce a plurality of calcined bodies (block bodies), the shrinkage rate from the press-molded body to the calcined body among the plurality of products. However, there is a demand for a zirconia composition that is not easily affected by the temperature difference (temperature unevenness) that occurs in the firing furnace during the production of the calcined body.

Further, in the method for producing a zirconia sintered body described in Patent Document 1, the holding time at the maximum firing temperature is 2 hours. Such long-term firing lowers production efficiency and increases energy costs. Also, for example, when making a dental prosthesis from a zirconia sintered body, the patient cannot be treated with the prosthesis on the day of the examination and another day to be treated with the prosthesis. I have to go to the hospital again. On the other hand, in the zirconia powder as described in Patent Document 1, if the holding time at the maximum firing temperature is shortened, the zirconia powder becomes cloudy and the color development deteriorates.

Therefore, there is a demand for a zirconia composition and a calcined product capable of producing a zirconia sintered body having high shielding properties and good color development while shortening the firing time when producing the zirconia sintered body. ing.

As a result of intensive research to solve the above problems, the present inventors have a specific crystal system, have an average particle size of specific zirconia particles, and develop a specific saturation at the time of firing. We have found that the above problems can be solved by using a zirconia composition, and based on this finding, we proceeded with research and completed the present invention.

That is, the present invention includes the following.
[1] A zirconia composition containing a zirconia powder and a stabilizer capable of suppressing the phase transition of the zirconia powder, and satisfying all of the following (1) to (3).
(1) The zirconia powder contains zirconia particles having an average particle size of more than 0.17 μm and 0.4 μm or less.
(2) At least a part of the stabilizer is not dissolved in zirconia.
(3) When the composition was fired at 1300 to 1600 ° C., the saturation C ^* (30) of the sintered body when held at the temperature for 30 minutes and the sintered body when held at the temperature for 120 minutes. The ratio C ^* (30) / C ^* (120) of saturation C ^* (120) is 0.4 or more.
[2] The zirconia composition according to [1], wherein the zirconia crystal system has a monoclinic crystal system of 55% or more.
[3] The zirconia composition according to [1] or [2], wherein the stabilizer is yttria.
[4] The zirconia composition according to [3], which contains 3 to 7.5 mol% of yttria with respect to the total mol of zirconia and yttria.
[5] The zirconia composition according to [3] or [4], wherein the yttria peak is present in the X-ray diffraction pattern.
Prevalence f _y yttria that is not dissolved in the calculated zirconia based on [6] The following equation (i) is not less than 1%, [3] to zirconia composition according to any one of [5] ..

(However, I _y (111) indicates the peak intensity of the yttria (111) plane near 2θ = 29 ° in the X-ray diffraction pattern by CuKα rays.
I _m (111) and _I m (11-1) shows a peak intensity of (111) plane of the monoclinic zirconia in the X-ray diffraction pattern and (11-1) plane,
I _t (111) indicates the peak intensity of the (111) plane of tetragonal zirconia in the X-ray diffraction pattern,
I _c (111) indicates the peak intensity of cubic (111) plane of the zirconia in the X-ray diffraction pattern. )
[7] The zirconia composition according to [6], _{wherein the fy is 15% or less.}
[8] The zirconia composition according to any one of [1] to [7], ^{wherein the saturation C *} (30) of the sintered body when held at the temperature for 30 minutes is 3 or more.
[9] The zirconia composition according to any one of [1] to [8], wherein the translucency of the sintered body obtained by firing at a maximum firing temperature of 1300 to 1600 ° C. satisfies the following formula.
ΔL ^* (WB) ≤11
(In the formula, ΔL ^* (WB) is the ^{value obtained by subtracting the second L *} value from the first L ^* value, and the first L ^* value is the value of the sintered body having a thickness of 1.2 mm. a L ^* value measured in the white background, the second L ^* values are L ^* value background was measured in the black of the same sintered body was measured first L ^* values, L ^{* values,} L ^* a * ^{b *} color system (JIS Z 8781-4: 2013) is a ^{L *} value of chromaticity (color space) in).
^{[10] Ratio ΔL *} (30) / ΔL ^{* of translucency ΔL *} (30) when held at the temperature for 30 minutes ^{and translucency ΔL *} (120) when held at the temperature for 120 minutes. The zirconia composition according to [9], wherein (120) is 0.88 or more.
[11] A method for producing a zirconia calcined body, which is produced by using the zirconia composition according to any one of [1] to [10].
[12] The method for producing a zirconia calcined product according to [11], which comprises firing a press-molded product composed of the zirconia composition according to any one of [1] to [10] at 800 to 1200 ° C.
[13] A first molded product is obtained by molding a zirconia composition containing the zirconia powder according to any one of [1] to [10] and a stabilizer capable of suppressing the phase transition of the zirconia powder. The first molding process to produce
A calcining step of firing the first molded product at a temperature at which the zirconia particles do not sinter.
The method for producing a zirconia calcined product according to [11] or [12], which comprises.
[14] The method for producing a zirconia calcined product according to [13], wherein in the calcining step, the first molded product is fired at 800 to 1200 ° C.
[15] Prior to the first molding step, the mixture of the zirconia powder and the stabilizer is pulverized so that the zirconia powder contains the average particle size of the zirconia particles of more than 0.17 μm and 0.4 μm or less. The method for producing a zirconia calcined product according to [13] or [14], further comprising a pulverization step for obtaining a zirconia composition.
[16] The method for producing a zirconia calcined product according to any one of [13] to [15], further comprising a drying step of spray-drying the zirconia composition into granules before the first molding step.
[17] The method for producing a zirconia calcined body according to any one of [11] to [16], wherein the density of the zirconia calcined body is 2.7 to 4.0 g / cm ^3.
[18] The method for producing a zirconia calcined product according to any one of [11] to [17], wherein the bending strength of the zirconia calcined product measured in accordance with ISO6782: 2015 is 15 to 70 MPa.
[19] A first molding step of molding the zirconia composition according to any one of [1] to [10] to prepare a first molded product.
A sintering step of firing the first molded product at a temperature above which it can be sintered, and
A method for producing a zirconia sintered body, including.
[20] Prior to the sintering step, a calcining step of firing the first molded body at a temperature at which zirconia particles do not reach sintering is further included to prepare a zirconia calcined body. The method for producing a zirconia sintered body according to [19], wherein the zirconia calcined body is fired as a first molded body.
[21] Prior to the sintering step, a second molding step of molding the zirconia calcined body to prepare a second molded body is further included.
The method for producing a zirconia sintered body according to [20], wherein the second molded body is fired in the sintering step.
[22] The method for producing a zirconia sintered body according to any one of [19] to [21], wherein the holding time at the maximum firing temperature is 1 hour or less in the sintering step.

According to the present disclosure, it is possible to produce a zirconia sintered body having high shielding properties and good color development while shortening the production time of the sintered body. As a result, the production efficiency of the product can be increased and the energy cost can be reduced. When the zirconia sintered body is applied to a dental prosthesis, the time burden on the patient can be reduced. Further, according to the present disclosure, since it has excellent shielding properties, it is possible to shield the color of the discolored abutment tooth, and the zirconia sintered body is used for dental treatment of a patient having the abutment tooth discolored due to a lesion or lifestyle. It can be suitably applied as a prosthesis.

It is important that the zirconia composition of the present disclosure contains a zirconia powder and a stabilizer capable of suppressing the phase transition of the zirconia powder, and satisfies all of the following (1) to (3).
(1) The zirconia powder contains zirconia particles having an average particle size of more than 0.17 μm and 0.4 μm or less.
(2) At least a part of the stabilizer is not dissolved in zirconia.
(3) When the composition was fired at 1300 to 1600 ° C., the saturation C * (30) of the sintered body when held at the temperature for 30 minutes and the sintered body when held at the temperature for 120 minutes The ratio C * (30) / C * (120) of the saturation C * (120) is 0.4 or more.

First, the zirconia composition of the present disclosure will be described. The zirconia composition in the present disclosure can be a precursor (intermediate product) of a zirconia sintered body and a calcined product.

The zirconia composition of the present disclosure contains a zirconia powder and a stabilizer capable of suppressing the phase transition of zirconia. The stabilizer is preferably one capable of forming partially stabilized zirconia. As the stabilizer, for example, calcium oxide (CaO), magnesium oxide (MgO), yttria (yttrium _oxide; Y _{2 O} 3), cerium oxide _(CeO 2), scandium oxide _{(Sc 2 O} 3), lanthanum oxide ( La ₂ O ₃ ), Elbium Oxide (Er ₂ O ₃ ), Placeodym Oxide (Pr ₆ O ₁₁ ), Samalium Oxide (Sm ₂ O ₃ ), Europium Oxide (Eu ₂ O ₃ ) and Thurium Oxide (Tm ₂ O ₃ ) Oxides such as. The content of the stabilizer in the zirconia composition, calcined body and sintered body can be measured by, for example, inductively coupled plasma (ICP) emission spectroscopic analysis, fluorescent X-ray analysis and the like.

^{In the zirconia composition of the present disclosure, from the viewpoint of the saturation C *} of the zirconia sintered body when fired for a short time, the stabilizer exists so that at least a part of the zirconia crystals is monoclinic. It is important that at least some of the stabilizers are not dissolved in zirconia. It can be confirmed by, for example, an X-ray diffraction (XRD) pattern that a part of the stabilizer is not dissolved in zirconia. When a peak derived from the stabilizer is confirmed in the XRD pattern of the zirconia composition, it means that the stabilizer that is not dissolved in zirconia is present in the zirconia composition. When the entire amount of the stabilizer is dissolved, basically no peak derived from the stabilizer is confirmed in the XRD pattern. However, depending on the conditions such as the crystal state of the stabilizer, the stabilizer may not be dissolved in zirconia even when the peak of the stabilizer does not exist in the XRD pattern. If the predominant crystal system of zirconia is tetragonal and / or cubic and there are no stabilizer peaks in the XRD pattern, then most, essentially all, of the stabilizer will be zirconia. It is considered that it is solidly dissolved.

From the viewpoint of the strength and shielding property of the zirconia sintered body prepared from the zirconia composition of the present disclosure, it is preferable that the stabilizer is yttria. The yttria content is preferably 3 mol% or more with respect to the total mol of zirconia and yttria, and when combined with zirconia powder having a predetermined average particle size, the discolored abutment tooth color is sufficiently obtained. From the viewpoint of being able to shield and having more excellent shielding property, it is more preferably 3.3 mol% or more, and further preferably 3.5 mol% or more. When the yttria content is 3 mol% or more, the phase transformation of the zirconia sintered body can be suppressed. The yttria content is preferably 7.5 mol% or less, more preferably 7 mol% or less, still more preferably 6.5 mol% or less, based on the total mol of zirconia and yttria. , 6 mol% or less is particularly preferable. When the yttria content is 7.5 mol% or less, the decrease in strength of the zirconia sintered body can be suppressed.

Prevalence f _y yttria that is not solid solution in the zirconia in the zirconia compositions of the present disclosure (referred to as "undissolved yttria" hereinafter) can be calculated based on the following equation (i). Prevalence f _y undissolved yttria, preferably greater than 0%, more preferably 1% or more, more preferably 2% or more, and still further preferably 3% or more. The preferable upper limit of the existence ratio f _y undissolved yttria is dependent on the content of yttria in zirconia composition. When the content of yttria is less than 7.5 mol% relative to the total mol of zirconia and yttria, from the viewpoint of short firing, _{f y} can be 15% or less. For example, when the content of yttria is not more than 3.5 mol% or more 4.5 mol%, _{f y} may be 7% or less. When the yttria content is more than 4.5 mol% and 6 mol% or less, _fy can be 10% or less. When the content of yttria is not more than 6 mol% ultra 7.5 mol%, _{f y} may be a 11% or less.

In the above mathematical formula (i), I _y (111) indicates the peak intensity of the yttria (111) plane near 2θ = 29 ° in the XRD pattern by CuKα rays. I _m (111) and _I m (11-1) shows a peak intensity of zirconia monoclinic (111) plane and (11-1) plane. I _t (111) indicates the peak intensity of the (111) plane of tetragonal zirconia. I _c (111) indicates the peak intensity of the (111) plane of the cubic system of zirconia.

The above formula (i) can also be applied to the calculation of the abundance of stabilizers other than yttria in unsolid solution by substituting another peak instead of _{I y (111).}

The main crystal system of zirconia in the zirconia composition of the present disclosure is preferably a monoclinic system. In the present disclosure, "the main crystal system is a monoclinic system" means XRD by CuKα ray with respect to the total amount of all crystal systems (monoclinic system, square system and cubic system) in zirconia. is calculated by the following equation (ii) based on the peak, the ratio f _m of monoclinic zirconia refers to those accounts for 55% or more. The meaning of each symbol in the mathematical formula (ii) is the same as that in the mathematical formula (i). In zirconia compositions of the present invention, it is preferred that the ratio f _m of monoclinic zirconia is at least 55%, more preferably 60% or more, more preferably 70% or more, 80 % Or more is even more preferable, 90% or more is particularly preferable, and 95% or more is most preferable. The main crystal system in the zirconia composition may contribute to raising the shifting temperature and shortening the firing time.

The zirconia composition of the present disclosure contains zirconia powder. In the present disclosure, the powder may be an aggregate of granules. Granules are aggregates of primary particles and / or secondary particles in which primary particles are aggregated.

The "primary particle" in the present disclosure means a spherical particle having the smallest unit. For example, primary particles refer to spheres that appear to be in a separable state without being bonded to each other in an electron microscope (for example, a scanning electron microscope). The "secondary particles" referred to in the present disclosure refer to particles in a state in which particles that look like primary particles in an electron microscope are aggregated. The secondary particles also include agglomerates in which the primary particles are crushably attached, and agglomerates in which the primary particles are inseparably fused to form a single particle. In the electron microscope image, the secondary particles are often not spherical and have a distorted shape.

It is preferable that the particles constituting the granules are mainly primary particles. For example, in the visual confirmation of an electron microscope image, the number of primary particles is preferably larger than the number of secondary particles. For example, in the visual confirmation of the electron microscope image, among the primary particles (including the primary particles constituting the secondary particles), preferably 50% or more, more preferably 70% or more, still more preferably 80% or more of the primary particles. , It is a particle that does not constitute a secondary particle. Since the secondary particles usually have an irregular shape, the larger the number of secondary particles, the lower the circularity of the granules described later.

The average particle size of the zirconia particles in the present disclosure is important to exceed 0.17 μm, preferably 0.18 μm or more, preferably 0.19 μm or more when measured by the laser diffraction / scattering type particle size distribution measuring method. Is more preferable. Since the zirconia powder contains zirconia particles having an average particle size of more than 0.17 μm, the shielding property is excellent. Further, when the zirconia powder contains only zirconia particles having an average particle size of 0.17 μm or less, the shielding property becomes insufficient. Further, it is important that the average particle size is 0.40 μm or less, preferably 0.35 μm or less, and more preferably 0.30 μm or less. If it exceeds 0.40 μm, the strength may be insufficient. The "average particle size of zirconia particles" in the present disclosure is a particle size measured without distinguishing between primary particles and secondary particles. In one preferred embodiment, "average particle size of zirconia particles" means primary particles. In another preferred embodiment, "average particle size of zirconia particles" means secondary particles. When the zirconia powder is granules, it refers to the average particle size of the particles constituting the granules. The laser diffraction / scattering method uses, for example, a laser diffraction type particle size distribution measuring device (“SALD-2300” manufactured by Shimadzu Corporation, etc.) and ethanol or a 0.2% sodium hexametaphosphate aqueous solution as a dispersion medium on a volume basis. Can be measured.

The BET specific surface area of the zirconia powder in the present disclosure ^{is preferably 7.0 m 2} / g or more, and more preferably 7.5 m ² / g or more when measured in accordance with JIS Z 8830 (2013). It is preferably 8 m ² / g or more, and more preferably 8 m 2 / g or more. If it is less than 7.0 m ² / g, it is difficult to sinter, or even if it can be sintered, the sintered body becomes cloudy. The BET specific surface area is ^{preferably 30 m 2} / g or less, ^{more preferably 25 m 2} / g or less, and even more preferably 20 m ² / g or less. If it exceeds 30 m ² / g, the speed change temperature described later becomes high, and it becomes easily affected by the temperature unevenness in the firing furnace. Further, if the firing time for sintering is shortened, the color development of the sintered body deteriorates. The BET specific surface area referred to here is a specific surface area measured without distinguishing between primary particles and secondary particles.

Of the zirconia powders in the zirconia composition of the present disclosure, 50% or more, preferably 70% or more, more preferably 80% or more, still more preferably 90% or more of the zirconia powder can take the granular form.

In the embodiment in which the average particle size of the zirconia particles is the primary particles, the average particle size of the granules (secondary particles) in the zirconia composition of the present disclosure is preferably 10 μm or more, more preferably 12 μm or more. It is more preferably 14 μm or more. If the average particle size of the granules is less than 10 μm, air may be entrained when the granules are placed in a mold, deaeration may be insufficient during molding, and a uniform and dense molded product may not be produced. In addition, granules may be ejected from the gap during molding to produce a molded product that does not meet a predetermined required amount. The average particle size of the granules is preferably 200 μm or less, more preferably 190 μm or less, further preferably 180 μm or less, further preferably 150 μm or less, and particularly preferably 100 μm or less. preferable. If the average particle size of the granules exceeds 200 μm, cavities are likely to be formed inside the granules. In addition, gaps are likely to occur when the granules are placed in the mold. Due to these phenomena, deaeration may be insufficient during molding, and a dense molded product may not be produced. In addition, shrinkage becomes large during molding, and there is a possibility that a molded body having a desired size cannot be manufactured. In the present disclosure, the average particle size of the granules is preferably measured by a method that does not destroy the granules. The average particle size of the granules can be measured by, for example, a dry sieving method or a wet sieving method. The dry sieving method can be measured according to the sieving test method described in JIS Z 8815: 1994, and manual sieving and mechanical sieving can be used, and mechanical sieving is preferable. As the sieve used in the sieving method, the sieve described in JIS Z 8801-1: 2019 test sieve can be used. As the measuring device used in the sieving method, for example, a low-tap type sieving shaker or a sonic vibration type sieving measuring device can be used for measurement. Examples of the low-tap type sieve shaker include "RPS-105M" manufactured by Seishin Enterprise Co., Ltd. Examples of the sonic vibration type sieving measuring instrument include "Robot Shifter RPS-01" and "Robot Shifter RPS-02" manufactured by Seishin Enterprise Co., Ltd.

It is preferable that the zirconia composition of the present disclosure has a high degree of sphericity of the granules. By increasing the sphericity of the granules, it is possible to cause mixing at the interface between the layers when zirconia powders with different compositions are laminated. Further, when zirconia powder is filled in a mold to prepare a molded product, even if the average particle size is the same, the higher the sphericity, the higher the packing density. The strength of the sintered body can be increased by filling a specific mold (mold or the like) with zirconia powder or zirconia granules and increasing the packing density, which is the density of the molded product formed into a specific shape by pressure. Further, even when the mold has corners, the filling property of the granules in the corners can be improved. The sphericity of the granules can be represented by, for example, the circularity based on the projected image, the angle of repose, the light bulk density, the heavy bulk density, and the like.

The average circularity based on the projected image of the granules in the zirconia composition of the present disclosure is preferably 0.81 or more, more preferably 0.85 or more, still more preferably 0.90 or more. It is even more preferably 0.95 or more. The circularity can be calculated as the ratio of the perimeter of a circle equal to the area of the granules to the perimeter of the granules in the projected image. That is, the circularity can be calculated from the following formula. The average circularity is preferably the average value of the circularity of 10,000 or more granules.
Circularity = (circumferential length of a circle equal to the area of the granule (circumference)) / perimeter of the granule

The angle of repose of the zirconia composition of the present disclosure is preferably 35 ° or less, more preferably 32 ° or less, further preferably 28 ° or less, still more preferably 26 ° or less. , 24 ° or less is particularly preferable. The angle of repose can be measured in accordance with JIS R 9301-2-2: 1999.

The light bulk density of the zirconia composition of the present disclosure ^{is preferably 1.0 g / cm 3} or more, more preferably 1.1 g / cm ³ or more, and 1.2 g / cm ³ or more. It is more preferably 1.3 g / cm ³ or more, and particularly preferably 1.3 g / cm 3. Light bulk density can be measured in accordance with JIS R9301-2-3: 1999.

The heavy bulk density of the zirconia composition of the present disclosure ^{is preferably 1.3 g / cm 3} or more, more preferably 1.4 g / cm ³ or more, and 1.5 g / cm ³ or more. Is even more preferable. The heavy bulk density can be measured according to JIS R 9301-2-3: 1999.

The zirconia composition of the present disclosure may contain additives other than the zirconia powder and the stabilizer. Additives include, for example, colorants (including pigments, composite pigments and fluorescent agents), binders, dispersants, defoamers, alumina (Al ₂ O ₃ ), titanium oxide (TIO ₂ ), silica (SiO ₂ ). And so on. As the additive, one kind may be used alone, or two or more kinds may be used in combination. The content of these additives can be appropriately set in consideration of the desired saturation C ^*.

The colorant is selected from the group of, for example, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Y, Zr, Sn, Sb, Bi, Ce, Pr, Sm, Eu, Gd, Tb and Er. Examples thereof include oxides of at least one element (specifically, NiO, Cr ₂ O _3, etc.). Examples of the composite pigment include (Zr, V) O ₂ , Fe (Fe, Cr) ₂ O ₄ , (Ni, Co, Fe) (Fe, Cr) ₂ O ₄ · ZrSiO ₄ , (Co, Zn) Al. composite oxides such as ₂ O _4. Examples of the fluorescent agent include Y ₂ SiO ₅ : Ce, Y ₂ SiO ₅ : Tb, (Y, Gd, Eu) BO ₃ , Y ₂ O ₃ : Eu, YAG: Ce, ZnGa ₂ O ₄ : Zn, BaMgAl. ₁₀ O ₁₇ : Eu and the like can be mentioned.

Examples of the binder include an organic binder. For example, acrylic binders, paraffin binders, fatty acid binders, polyvinyl alcohol binders and the like can be mentioned.

The zirconia composition of the present disclosure may be in a dry state, may be in a state containing a liquid, or may be in a state of being contained in a liquid. For example, the zirconia composition can be in the form of powder, paste, slurry or the like. Further, the zirconia composition may be a molded product having a predetermined shape (hereinafter referred to as "first molded product").

Density of the first molded body is preferably at 2.75 g / cm ³ or more, more preferably 2.80 g / cm ³ or more, still more preferably 2.85 g / cm ³ or more, more preferably more that it is 2.90 g / cm ³ or more, particularly preferably 3.00 g / cm ³ or more. The density can be calculated as, for example, (mass of the first molded product) / (volume of the first molded product).

In the present disclosure, the degree of color development of the zirconia sintered body ^{can be represented by the saturation C *} , and the zirconia composition of the present invention has a saturation C ^* of 3 or more when fired at 1300 to 1600 ° C. Is preferable, 5 or more is more preferable, and 7 or more is further preferable. ^{The saturation C *} in the present invention is ^{the C *} value of the chromaticity (color space) in the L ^* a ^* b ^* color system (JIS Z 8781-4: 2013), and is a zirconia firing having a thickness of 1.2 mm. It can be calculated by using the formula (iii) from ^{the a *} value and b ^* value measured with the background of the boiled sample black. ^{It is preferable that the saturation C *} when firing at at least one temperature in the range of 1300 to 1600 ° C. satisfies the above range.
C ^* = {(a ^* ) ² + (b ^* ) ² } ^(1/2) (iii)

Regarding the method for preparing the sample, first, the zirconia composition (for example, granules) is press-molded so that the thickness of the zirconia sintered body is 1.2 mm, followed by CIP molding, for example, a disk having a diameter of 19 mm. A shaped molded product can be produced. Next, the molded product can be fired under predetermined firing conditions to prepare a sample zirconia sintered body having a thickness of 1.2 mm. For the measurement of a ^* value and b ^* value, after applying the contact liquid to the surface of the sample, analyze with a color difference meter (for example, dental color measuring device "Crystal Eye CE100-DC / JP" (manufactured by Olympus Corporation)). ^{The a *} value and b ^* value of a black background can be measured using the soft "Crystal Eye" (manufactured by Olympus Corporation). The black background means the black part of the concealment rate test paper described in JIS K 5600-4-1: 1999, Part 4, Section 1. As the contact liquid, for example, one having a refractive index nD measured at a measurement wavelength of 589 nm (sodium D line) and having a refractive index of 1.60 can be used.

The zirconia composition of the present invention shows good color development even when fired for a short time, and a zirconia sintered body ^{showing a desired saturation C * can be obtained.} As an index for determining whether or not firing is possible in a short time, the ^{ratio of C *} at each holding time x and y = C ^* (x) / C ^* (y) (x≤y unit: minutes) can be calculated. .. When the zirconia composition of the present invention is fired at a maximum firing temperature of 1300 to 1600 ° C., the saturation C ^* (30) of the sintered body when held at the above temperature for 30 minutes and the saturation C * (30) when held at the above temperature for 120 minutes ^{It is important that the ratio C *} (30) / C ^* (120) of the saturation C ^* (120) of the sintered body is 0.4 or more, preferably 0.6 or more, and 0.8 The above is more preferable, 0.9 or more is further preferable, and 0.93 or more is particularly preferable. When C ^* (30) / C ^* (120) is less than 0.4, the color development during short-time firing is poor, and the desired saturation C ^* cannot be obtained. In the range of 1300 to 1600 ° C., ^{it is important that the saturation ratio C *} (30) / C ^* (120) when firing at at least one specific temperature satisfies the above range.

When measuring the saturation C ^{* of the} present disclosure, instead of using a sample in which the zirconia composition as described above is calcined at a temperature in the range of 1300 to 1600 ° C. and directly sintered. A sample that has passed through the baked state, for example, a sample of a zirconia sintered body that is first fired at a temperature in the range of 800 to 1200 ° C. to obtain a zirconia calcined product and then fired at a temperature in the range of 1300 to 1600 ° C. You may use it.

One of the advantages of the zirconia composition of the present invention will be described below. In general, the shrinkage rate from the press-molded zirconia to the sintered body is not constant with respect to the firing temperature, and the shrinkage rate is low up to a certain temperature, but the shrinkage rate is high at the certain temperature. The temperature at which the contraction speed changes is referred to as "shift temperature" in the present disclosure. According to the zirconia composition of the present disclosure, the shifting temperature can be set to 1050 ° C. or higher, preferably 1100 ° C. or higher.

When a plurality of press-molded bodies are simultaneously fired in one firing furnace as one lot to produce a plurality of calcined bodies (block bodies), the shrinkage rate to the calcined body is achieved between the plurality of press-molded bodies. It is preferable that the variation of is small. If the shrinkage rate varies widely, when the calcined product is molded, the same coefficient is applied to the lot to determine the dimensions of the molded product, and zirconia sintering does not have the desired dimensions. The body is obtained. This point is particularly problematic in the case of products such as dental prostheses that require a high degree of dimensional accuracy. Therefore, a block body whose shrinkage rate is out of the permissible range in one lot cannot be used as a product, and the yield is lowered.

According to the zirconia composition of the present disclosure, the variation in the shrinkage rate in one lot can be reduced with respect to the firing temperature (for example, about 1000 ° C.) for producing the block body of the zirconia calcined body. Usually, the maximum firing temperature for producing a zirconia calcined body (hereinafter referred to as "temporary calcining temperature") is close to the shifting temperature. Normally, at the calcining temperature, a temperature difference (temperature unevenness) of about 20 to 50 ° C. occurs in the firing furnace. Therefore, when the shifting temperature is near the calcining temperature, the lot of the composition is strongly affected by this temperature unevenness. That is, in one lot, the shrinkage rate is significantly different between the zirconia calcined body in the place where the temperature is low and the zirconia calcined product in the place where the temperature is high. Since the zirconia calcined product whose shrinkage rate is out of the allowable range cannot be produced as a product, the yield is lowered. On the other hand, according to the zirconia composition of the present disclosure, the shifting temperature can be raised and the difference between the shifting temperature and the calcining temperature can be reduced. Therefore, in one lot, the difference in shrinkage between the zirconia calcined body in the low temperature portion and the zirconia calcined product in the high temperature portion can be reduced. As a result, it is possible to reduce the amount of zirconia calcined material whose shrinkage rate is out of the permissible range and increase the yield. In addition, the number of products that can be fired at one time can be increased, and the production efficiency can be improved.

Specifically, when a press-molded body of a zirconia composition is fired at 800 ° C. or higher and 1000 ° C. or lower to prepare a calcined body, the shrinkage rate from the press-molded body to the calcined body is unidirectional. It is preferably 1% or less with respect to the dimension of. Further, when the press-molded body of the zirconia composition is fired at 1200 ° C. or lower higher than 1000 ° C. to prepare a zirconia calcined body, the shrinkage rate from the press-molded body to the calcined body is unidirectional. It is preferably 5% or less with respect to the size. However, in the press-molded article referred to here, for example, a molded article obtained by press-molding zirconia powder at a predetermined pressure (for example, 300 kg / cm ² ) is further subjected to CIP treatment (for example, 1700 kg / cm ² ). It is a thing.

Furthermore, according to the zirconia composition of the present disclosure and the zirconia calcined product produced from the zirconia composition, it is possible to produce a final product (zirconia sintered body) with high dimensional accuracy regardless of any block body in one lot. it can. The zirconia composition and the zirconia calcined product of the present disclosure are particularly useful for producing products (for example, dental products) that require a high degree of dimensional accuracy.

The zirconia composition and the zirconia calcined product of the present disclosure have further advantages. According to the zirconia composition and the zirconia calcined product of the present disclosure, the firing time for producing the zirconia sintered body can be shortened without lowering the strength of the produced zirconia sintered body. In particular, the holding time at the maximum firing temperature for producing the zirconia sintered body can be shortened (short-time firing). As a result, the production efficiency can be increased and the manufacturing cost can be reduced. When firing for a short time, the mooring time for holding the zirconia composition or the zirconia calcined body in the firing furnace is preferably 60 minutes or less at the maximum firing temperature. In addition, when the zirconia composition and zirconia calcined body of the present disclosure are applied to a dental product, the time from determining the dimensions of the dental product to be used for treatment until the dental product can be treated. Can be shortened, and the time burden on the patient can be reduced.

Next, an example of the method for producing the zirconia composition of the present disclosure will be described.

First, the zirconia powder and the stabilizer are mixed at a predetermined ratio to prepare a mixture (mixing step). For example, when the stabilizer is yttria, the mixing ratio can be the same as the yttria content in the zirconia composition described above. The mixing may be carried out dry or wet. The zirconia composition of the present disclosure can be produced by pulverizing the mixture until it reaches the average particle size of the above-mentioned zirconia particles and, if necessary, the BET specific surface area of the zirconia powder (first pulverization). Process). The mixing step and the first crushing step can be performed in the same step. The pulverization can be carried out using a ball mill after dispersing the mixture in a solvent such as water. In the method for producing the zirconia composition, when the steps after the calcination step described later are not performed, the zirconia powder has an average particle size of more than 0.17 μm and 0.4 μm due to the increase in the shifting temperature and / or the short-time firing. It comprises the step of grinding the mixture so as to include the following zirconia particles. The average particle size can be measured by the laser diffraction / scattering type particle size distribution measuring method as described above. After the mixing step and / or the first pulverization step, the zirconia composition may be dried by spray drying with a spray dryer or the like to form the zirconia composition into the granule form as described above (first drying step). .. Thereby, the zirconia composition according to the present invention can be produced.

The following steps can be arbitrarily carried out according to the purpose of use of the zirconia composition. For example, after any of the steps described above, the mixture and / or the zirconia composition can be fired (ie, calcined) at a temperature at which the zirconia particles do not sinter (firing (temporary firing) step). The firing conditions are preferably such that the main crystal system of zirconia when cooled after firing does not become a tetragonal system or a cubic system as described above. Further, the firing conditions are preferably such that at least a part of the stabilizer does not dissolve in zirconia. For example, the firing temperature is preferably 700 ° C. or higher, more preferably 800 ° C. or higher. The firing temperature is preferably 1200 ° C. or lower, more preferably 1100 ° C. or lower, further preferably 1000 ° C. or lower, further preferably 980 ° C. or lower, and 950 ° C. or lower. It is particularly preferable to have. Firing can be performed in the atmosphere. By performing the calcining step, a part of the stabilizer is dissolved in zirconia, the stabilizer can be easily dissolved in the subsequent sintering step, and the properties of the zirconia sintered body are improved. It is thought that it can be done.

After any of the steps described above, the zirconia composition can be dispersed in a solvent such as water to prepare a slurry, and additives such as a binder and a colorant can be added to the zirconia composition (addition step). ). After the addition step, the zirconia composition can be pulverized to the average particle size of the zirconia particles described above, and if necessary, to the BET specific surface area of the zirconia powder described above (second pulverization step). The addition step and the second pulverization step can be performed in the same step. The second crushing step can be performed in the same manner as the first crushing step. After the addition step and / or the second pulverization step, the zirconia composition may be dried by spray drying with a spray dryer or the like to form the zirconia composition into the granule form as described above (second drying step). ..

As described above, the zirconia composition can also be molded into a first molded product (first molding step). The molding method is not limited to a specific method, and a suitable method can be appropriately selected depending on the intended purpose. For example, the zirconia composition can be molded by a molding method such as press molding, injection molding, or stereolithography to obtain a first molded body. Moreover, you may perform multi-step molding. For example, the zirconia composition may be press-molded and then further subjected to CIP treatment.

In order to obtain the desired saturation C ^* , the above-mentioned additives such as binder and colorant can be appropriately added in each step.

According to the production method, the zirconia composition of the present invention can be produced. Suitable methods for producing a zirconia composition include the above-mentioned production method capable of producing a zirconia composition capable of producing a zirconia composition having a high shifting temperature and / or a shortening of firing time for sintering. Shortening the baking time, the adjustment or selection of prevalence f _y undissolved yttria described above, it can be adjusted by selection of the average particle diameter of the zirconia powder.

Using the zirconia composition of the present disclosure, a zirconia calcined body can be suitably produced. Further, a zirconia sintered body can be suitably prepared by using the zirconia composition of the present disclosure or a zirconia calcined product prepared from the zirconia composition. Hereinafter, a specific description will be given.

First, the zirconia calcined body of the present disclosure will be described. The calcined product in the present disclosure can be a precursor (intermediate product) of a zirconia sintered body. In the present disclosure, the zirconia calcined product may be, for example, a zirconia particle (powder) blocked in a state where it is not completely sintered. The density of the zirconia calcined product of the present disclosure ^{is preferably 2.7 g / cm 3} or more. Moreover, it said seal degree is preferably not more than 4.0 g / cm ^3, more preferably 3.8 g / cm ³ or less, further preferably 3.6 g / cm ³ or less. When the density of the zirconia calcined body is within the range, the molding process can be easily performed. The density can be calculated as, for example, (mass of calcined body) / (volume of calcined body). The density of the zirconia calcined body is determined by filling the zirconia granules in a specific mold (mold, etc.) and heating the molded product, which has been shaped into a specific shape by pressure, at a temperature at which the binder can be removed to remove the binder, and then yttria. It means the density of the calcined body obtained by heating at a temperature at which it melts moderately and necking (fixation) is formed moderately. The temperature at which the binder can be removed is not particularly limited as long as the binder can remove the binder, and may be 150 to 500 ° C. The temperature at which yttria dissolves moderately and necking (fixation) forms moderately is not particularly limited, but may be 800 to 1050 ° C.

The preferable range of the content of the stabilizer in the zirconia calcined product of the present disclosure is the same as the content of the zirconia composition described above. From the viewpoint of strength and translucency after sintering, the stabilizer is preferably yttria.

In the zirconia calcined product of the present disclosure, the stabilizer is present so that at least a part of the zirconia crystals is monoclinic, that is, at least a part of the stabilizer is dissolved in zirconia. It is preferable not to. The abundance of the stabilizer in the zirconia calcined body in an unsolid solution depends on the firing temperature at the time of preparing the zirconia calcined body, but is usually less than or equal to the abundance in the zirconia composition before the preparation of the zirconia calcined body. It is possible that there is. Prevalence f _y undissolved yttria in zirconia calcined body can be calculated based on the equation (i). A preferred range of prevalence f _y undissolved yttria in zirconia calcined body is the same as f _y of the above-described zirconia composition.

The crystal system of zirconia in the zirconia calcined body of the present disclosure depends on the firing temperature at the time of preparing the zirconia calcined body, but is usually less than or equal to the ratio of the monoclinic system in the zirconia composition before the preparation of the zirconia calcined body. It is possible that there is. Ratio f _m of monoclinic in zirconia calcined body is monoclinic system, is preferably tetragonal and 60% or more with respect to the total amount of cubic, more preferably 70% or more , 80% or more, more preferably 90% or more, and particularly preferably 95% or more.

The bending strength of the zirconia calcined product of the present disclosure measured in accordance with ISO6782: 2015 is preferably 15 MPa or more in order to secure the strength that enables mechanical processing. Further, the bending strength is preferably 70 MPa or less, and more preferably 60 MPa or less in order to facilitate mechanical processing.

The zirconia calcined product of the present disclosure can similarly contain the additives as described above for the zirconia composition.

The zirconia calcined body of the present disclosure may be a molded body having a predetermined shape (hereinafter referred to as "second molded body"). For example, the zirconia calcined body can have a disc shape, a rectangular parallelepiped shape, and a dental product shape (for example, a crown shape). Dental products (for example, crown-shaped prostheses) obtained by processing a calcined zirconia disc with a CAD / CAM (Computer-Aided Design / Computer-Aided Manufacturing) system are also included in the calcined body.

The zirconia calcined product of the present disclosure is produced so that the fluctuation of the shrinkage rate from the zirconia composition becomes small as described above. As a result, according to the zirconia calcined body of the present disclosure, the shrinkage rate from the calcined body to the sintered body can be made equal, and a zirconia sintered body having high dimensional accuracy can be produced.

According to the zirconia calcined product of the present disclosure, as described above, a zirconia sintered body having high translucency can be produced even by firing for a short time. That is, the zirconia calcined product of the present disclosure has the above-mentioned advantages regarding short-time firing.

Next, an example of the method for producing the zirconia calcined body of the present disclosure will be described.

The zirconia calcined product of the present disclosure is produced by firing (that is, calcining) the press-molded product (first molded product) produced in the first molding step at a temperature at which the zirconia particles do not reach sintering. Can be done (temporary firing process). That is, as a method for producing the zirconia calcined product of the present disclosure, a production method including a calcining step of firing the first molded product at a temperature at which the zirconia particles do not reach sintering can be mentioned. The manufacturing method may include a first molding step of molding a zirconia composition to prepare a first molded product. The first molding step is as described above for the zirconia composition. The firing temperature is preferably, for example, 800 ° C. or higher, more preferably 900 ° C. or higher, and even more preferably 950 ° C. or higher in order to ensure blocking. Further, the firing temperature is preferably, for example, 1200 ° C. or lower, more preferably 1150 ° C. or lower, and further preferably 1100 ° C. or lower in order to improve the dimensional accuracy. In particular, in the calcining step, it is preferable to fire a press-molded product (first molded product) made of the zirconia composition of the present disclosure at 800 to 1200 ° C. to prepare a zirconia calcined product.

In the method for producing the zirconia calcined product of the present disclosure, before the first molding step, the zirconia powder is mixed with the zirconia powder so that the average particle size of the zirconia particles is more than 0.17 μm and 0.4 μm or less. A pulverization step of pulverizing the mixture with the stabilizer to obtain a zirconia composition may be further included. The crushing step is the same as the first crushing step. Further, the method for producing the zirconia calcined product of the present disclosure may further include a second pulverization step in addition to the first pulverization step or in place of the first pulverization step. The second pulverization step is as described above.

Further, the method for producing the zirconia calcined product of the present disclosure may further include a drying step of atomizing the zirconia composition into granules before the first molding step. The drying step is the same as the first drying step. Further, the method for producing the zirconia calcined product of the present disclosure may further include a second drying step in addition to or in place of the first drying step. The second drying step is as described above.

The zirconia calcined body of the present disclosure can be molded before the sintering step described later to produce a second molded body (second molding step). The molding method is not limited to a specific method, and a suitable method can be appropriately selected depending on the intended purpose. For example, a second molded body can be produced by cutting a zirconia disc, which is also a zirconia calcined body, into the shape of a dental product (for example, a crown-shaped prosthesis) with a CAD / CAM system.

According to the production method, the zirconia calcined product of the present disclosure can be produced. A suitable method for producing a zirconia calcined product is a method capable of producing a zirconia calcined product having a small fluctuation in shrinkage rate and / or producing a zirconia calcined product that can be fired for a short time. Can be mentioned. Fluctuations in the shrinkage rate can be suppressed by adjusting the shifting temperature, selecting the main crystal system of zirconia, and the like. Short firing, the adjustment or selection of prevalence f _y undissolved yttria described above, it can be adjusted by selection of the average particle diameter of the zirconia powder.

Next, the zirconia sintered body of the present disclosure will be described. The sintered body in the present disclosure can be said to be, for example, a zirconia particle (powder) that has reached a sintered state. The relative density of the zirconia sintered body of the present disclosure is preferably 99.5% or more. The relative density can be calculated as the ratio of the measured density measured by the Archimedes method to the theoretical density. The relative density is the density d1 of a sintered body obtained by firing the molded product at a high temperature in a molded product obtained by filling a specific mold with zirconia particles or granules and forming a specific shape by pressure, theoretically (including voids inside). No) It means the value divided by the zirconia density d2.

The zirconia sintered body of the present disclosure includes not only a sintered body obtained by sintering molded zirconia particles under normal pressure or non-pressurization, but also HIP (Hot Isostatic Pressing) treatment or the like. It also includes sintered bodies that have been densified by high-temperature pressurization.

The preferable range of the content of the stabilizer in the zirconia sintered body of the present disclosure is the same as the content in the zirconia composition and / or the zirconia calcined body described above. Also, the crystal system of the zirconia in the zirconia sintered body of the present disclosure, the ratio f _m of monoclinic system, monoclinic system, it is 10% or less of the total amount of the tetragonal and cubic It is preferably 5% or less, and more preferably not substantially contained (0%).

Regarding the solid solution ratio of the stabilizer in the zirconia sintered body of the present disclosure, it is preferable that 95% or more of the contained stabilizer is solid-solved in zirconia, and substantially all the stabilizers are dissolved. Is more preferably dissolved. If the stabilizing agent is yttria, prevalence f _y undissolved yttria is preferably 5% or less, more preferably 1% or less, and is a solid solution substantially all the (0%) is more preferable.

^{The translucency (ΔL *} (WB)) of the zirconia sintered body of the present disclosure is preferably 11 or less, more preferably 9 or less, from the viewpoint of shielding the color of the discolored abutment tooth. , 7 or less is more preferable. The term translucent and ([Delta] L ^* (W-B)) ^is, L ^* a * ^{b *} color system (JIS Z 8781-4: 2013) for ^{L *} values of chromaticity (color space) in thickness The background of the 1.2 mm sample (sintered body) is white, the L ^* value measured is the first L ^* value, and ^{for the same sample for which the first L *} value is measured, the background of the sample is black. ^{The L *} value measured in the above is used as the second L ^* value, and the value obtained by subtracting ^{the second L *} value from the first L ^{* value.} Regarding the method for preparing a sample, first, a zirconia composition (for example, granules) is press-molded so that the thickness of the sintered body is 1.2 mm, and then CIP molding is carried out to form a disk having a diameter of, for example, 19 mm. Can be produced. Next, the molded product can be fired under predetermined firing conditions to prepare a sintered body having a thickness of 1.2 mm as a sample. For the measurement of L ^* value, after applying the contact liquid to the surface of the sample, a color difference meter (for example, dental color measuring device "Crystal Eye CE100-DC / JP" (manufactured by Olympus Corporation), analysis software "Crystal Eye" (Manufactured by Olympus Corporation)) can be used to measure ^{the L * value of a black background and a white background.} The white background means the white part of the hiding rate test paper described in JIS K 5600-4-1: 1999, Part 4, Section 1, and the black background means the black part of the hiding rate test paper. As the contact liquid, for example, one having a refractive index nD measured at a measurement wavelength of 589 nm (sodium D line) and having a refractive index of 1.60 can be used.

Regarding the translucency of the zirconia sintered body of the present disclosure, the translucency of the sintered body fired by holding the maximum firing temperature in the range of 1300 to 1600 ° C. for 30 minutes (measured value on the white background). And the difference between the measured values on a black background, hereinafter ^{also referred to as “ΔL *} (30)”), and the sintered body that was fired by holding it at the same temperature as the maximum firing temperature of ^{ΔL * (30) for 120 minutes. The ratio ΔL *} (30) / ΔL ^* (120) to the translucency (difference between the measured value on the white background and the measured value on the black background, hereinafter ^{also referred to as “ΔL *} (120)”) is 0. It is preferably .88 or more, and is suitably used as a dental prosthesis in the dental treatment of patients who have good color development while having high shielding properties and have abutment teeth that are discolored due to lesions and lifestyle. From the point of view, 0.90 or more is more preferable, and 0.95 or more is further preferable.

The zirconia sintered body of the present disclosure can similarly contain the additives as described above for the zirconia composition.

The zirconia sintered body of the present disclosure may be a molded body having a predetermined shape (hereinafter referred to as "third molded body"). For example, the sintered body can have a disc shape, a rectangular parallelepiped shape, and a dental product shape (for example, a crown shape).

From the viewpoint of achieving good color development, the zirconia sintered body of the present disclosure ^{preferably has a saturation C *} of 3 or more, more preferably 5 or more, and even more preferably 7 or more. ^{The definition of saturation C *} and the method for measuring the saturation C * are as described above for the zirconia composition, but the firing temperature and firing time for evaluating ^{the saturation C * of the zirconia sintered body are particularly limited.} Not done.

Next, an example of the method for producing the zirconia sintered body of the present disclosure will be described.

The zirconia sintered body of the present disclosure refers to the temperature at which the zirconia particles of the zirconia composition (including the first molded body) and / or the zirconia calcined body (including the second molded body) of the present disclosure are sintered. It can be produced by firing at (sinterable temperature) or higher (sintering step). One embodiment includes a method for producing a zirconia sintered body, which comprises a sintering step of firing the first molded body at a temperature above which it can be sintered. The manufacturing method may include a first molding step of molding a zirconia composition to prepare a first molded product. The first molding step is as described above for the zirconia composition. The sinterable temperature is, for example, preferably 1400 ° C. or higher, more preferably 1450 ° C. or higher. The sinterable temperature is, for example, preferably 1650 ° C. or lower, and more preferably 1600 ° C. or lower. The maximum firing temperature in the sintering step is preferably 1400 ° C. or higher, more preferably 1450 ° C. or higher. The maximum firing temperature including the sinterable temperature is preferably 1650 ° C. or lower, and more preferably 1600 ° C. or lower. The rate of temperature rise and temperature decrease is preferably 300 ° C./min or less. Prior to the sintering step, a calcining step of firing the first molded product at a temperature at which the zirconia particles do not reach sintering may be further included to prepare a zirconia calcined product. The calcination step is as described above in the method for producing the zirconia calcination body. Further, the method for producing the zirconia sintered body may further include a second molding step of molding the zirconia calcined body to produce a second molded body before the sintering step. When the second molding step is included, a method for producing a zirconia sintered body in which the second molded body is fired as the zirconia calcined body in the sintering step can be mentioned.

In the sintering step, the holding time at the sinterable temperature (particularly, the maximum firing temperature) is preferably less than 120 minutes, and the dentistry has high shielding properties and good color development while shortening the firing time. From the viewpoint that a product for use can be produced, it is more preferably 90 minutes or less, further preferably 75 minutes or less, further preferably 60 minutes or less, and particularly preferably 45 minutes or less. It is preferably 30 minutes or less, and most preferably 30 minutes or less. The holding time is preferably 1 minute or longer, more preferably 5 minutes or longer, and even more preferably 10 minutes or longer. According to the method for producing a zirconia sintered body of the present disclosure, it is possible to suppress a decrease in the translucency of the produced zirconia sintered body even with such a firing time. Further, by shortening the firing time, it is possible to increase the production efficiency and reduce the energy cost.

The zirconia sintered body of the present disclosure can be molded to produce a third molded body (third molding step). The molding method is not limited to a specific method, and a suitable method can be appropriately selected depending on the intended purpose. For example, a zirconia block, which is also a zirconia sintered body, can be cut into the shape of a dental product (for example, a crown-shaped prosthesis) by a CAD / CAM system to produce a third molded body.

The zirconia sintered body of the present disclosure can be suitably used as a dental product. The zirconia sintered body can have, for example, a crown shape. The dental product in the present disclosure may further include a porcelain material laminated on the zirconia sintered body. The porcelain material can be, for example, ceramics such as a glass material. Dental products include, for example, dental prostheses (eg, ceramic frames, full cantour crowns), orthodontic products (eg, orthodontic brackets), dental implant products (eg, dental implant abutments). ).

Next, the manufacturing method of the dental product in the present disclosure will be described. Dental products can be prepared by sintering the zirconia composition of the present disclosure (including the first molded product) and / or the zirconia calcined product (including the second molded product) having a predetermined shape. it can. The dental product can also be produced by cutting the zirconia sintered body of the present disclosure (including a third molded body).

When the dental product in the present disclosure has a porcelain material, for example, a step of applying a slurry containing the porcelain material on the zirconia sintered body and a zirconia sintered body coated with the porcelain material are fired and sintered. It can be produced by the process of baking porcelain on the body. The temperature and time for baking the porcelain can be set as appropriate.

According to the zirconia composition, the zirconia calcined product, and / or the zirconia sintered body of the present disclosure, a dental product with high dimensional accuracy can be obtained, and / or has high shielding property and good color development. Dental products can be produced in a short time.

The examples of the present disclosure will be described below, but the present invention is not limited to the following examples.

[Preparation of zirconia composition]
(Examples 1 to 3)
First, a mixture was prepared by combining yttria with 100% monoclinic zirconium oxide powder so that the content of yttria with respect to the total mol of zirconia and yttria is as shown in Table 1 (mixing step). .. Next, this mixture was added to water to prepare a slurry, which was wet-ground with a ball mill until the average particle size (primary particles) of the zirconia particles became 0.20 μm. Next, a binder was added to the pulverized slurry and then dried with a spray dryer to prepare a zirconia composition. Next, nickel (II) oxide (NiO) was wet-ground with a ball mill until the average particle size became 0.20 μm in the same manner as described above, and dried with a spray dryer to prepare NiO powder. NiO powder was added to the above-mentioned zirconia composition at a ratio of 0.02% by mass, and the mixture was sufficiently mixed to obtain the zirconia composition according to Examples 1 to 3. The average particle size can be measured by a laser diffraction type particle size distribution measuring device (SALD-2300: manufactured by Shimadzu Corporation) on a volume basis using a 0.2% sodium hexametaphosphate aqueous solution as a dispersion medium. ..

(Comparative Examples 1 to 3)
As a comparative example, a commercially available partially stabilized zirconia powder was used. The zirconia composition according to Comparative Example 1 was prepared by adding 0.02% by mass of the NiO powder prepared in Examples 1 to 3 to TZ-3YSB-E manufactured by Tosoh Corporation and thoroughly mixing them. Similarly, the zirconia composition according to Comparative Example 2 was prepared by adding 0.02% by mass of the above-mentioned NiO powder to Zpex manufactured by Tosoh Corporation and mixing them sufficiently, and the zirconia composition according to Comparative Example 3 was prepared. 0.02% by mass of the above-mentioned NiO powder was added to Zpex Smile manufactured by Tosoh Corporation and mixed thoroughly.

(Example 4)
The NiO powder prepared in Examples 1 to 3 after adding the zirconia composition of Comparative Example 1 in addition to the zirconia composition containing the monoclinic zirconium oxide powder and yttria prepared in the same manner as in Example 1. Was added in an amount of 0.02% by mass and sufficiently mixed to obtain a zirconia composition according to Example 4. The zirconia composition has a lower proportion of monoclinic crystals than in Examples 1 to 3. In Table 1, since the average particle size of the zirconia particles contained in the zirconia composition according to Comparative Example 1 could not be measured, the relevant portion is indicated by “NA”.

(Comparative Example 4)
The zirconia composition according to Comparative Example 4 was prepared in the same manner as in Example 1 except that the zirconia composition before adding the NiO powder was pulverized so that the average particle size of the zirconia particles after pulverization was 0.12 μm. did.

(Comparative Example 5)
The zirconia composition according to Comparative Example 5 was prepared in the same manner as in Example 1 except that the zirconia composition before adding the NiO powder was pulverized so that the average particle size of the zirconia particles after pulverization was 0.50 μm. did.

[Confirmation of the abundance of undissolved yttria and the proportion of zirconia crystals]
Performed XRD measurement for zirconia compositions according to Examples and Comparative Examples, the f _y indicating the existence ratio of undissolved yttria, was calculated based on the equation (i). Further, the f _m that indicates the percentage of monoclinic in zirconia was calculated based on the equation (ii). The results are shown in Table 1.

[Measurement of translucency and color development with respect to firing time]
A zirconia sintered body was prepared using the zirconia composition of the present disclosure, and the relationship between translucency and color development with respect to the holding time (baking time) at the firing temperature was investigated. First, the zirconia compositions according to Examples and Comparative Examples were press-molded at a pressure of ^{300 kg / cm 2} so as to obtain a zirconia sintered body having a thickness of 1.2 mm. Next, the press molded product ^{was further subjected to CIP treatment at 1700 kg / cm 2} to prepare the first molded product described above. The first molded product was fired at 1000 ° C. for 2 hours to prepare a zirconia calcined product. The maximum firing temperature was set to 1550 ° C., the holding time at the maximum firing temperature was 120 minutes, and the obtained zirconia calcined product was fired to prepare a zirconia sintered body. Next, with respect to the zirconia calcined body produced by the same method, the maximum firing temperature was set to 1550 ° C., and the holding time at the maximum firing temperature was changed to 30 minutes to prepare a zirconia sintered body. Using the obtained zirconia sintered body as a sample, the translucency and saturation C ^* were measured by the method described later. The results are shown in Table 1.

For translucency, color difference meter (dental color measuring device "Crystal Eye CE100-DC / JP" (7band LED lighting, 45 ° incident diffuse reflection type, manufactured by Olympus Co., Ltd.), analysis software "Crystal Eye" (Olympus Co., Ltd.) Ltd.)) was measured using ^a, L ^* a * ^{b *} color system (JIS Z 8781-4: 2013) in was calculated using the ^{L *} values of chromaticity (color space). ^{The L *} value measured with the background of the sintered body sample being white is defined as the first L ^* value, and ^{the same sample measured with the first L *} value is measured with the sample background black ^. The value was defined as the second L ^* value, and the value ΔL ^{* (WB) obtained by subtracting the second L *} value from the first L ^* value was defined as a numerical value indicating translucency (n = 1). A contact liquid having a refractive index of 1.60 was applied to the measurement surface of the sample. The white background means the white part of the hiding rate test paper described in JIS K 5600-4-1: 1999, Part 4, Section 1, and the black background means the black part of the hiding rate test paper.

Saturation C ^* is a color difference meter (dental color measuring device "Crystal Eye CE100-DC / JP" (7band LED lighting, 45 ° incident diffuse reflection type, manufactured by Olympus Corporation), analysis software "Crystal Eye" (Olympus Corporation) ^{Using the a *} value and b ^* value on a black background measured using (manufactured by the company)), each sample was calculated from the above mathematical formula (iii) (n = 1). A contact liquid having a refractive index of 1.60 was applied to the measurement surface of the sample.

First, the zirconia composition will be described. In the zirconia composition composed of commercially available zirconia powder according to Comparative Examples 1 to 3, the crystal system of zirconia is basically a tetragonal system and / or a cubic system, and at most a monoclinic system. It was about 52%. Further, in the zirconia compositions according to Comparative Examples 1 to 3, the XRD peak of yttria was not confirmed. Therefore, it is considered that all yttria is dissolved in zirconia.

On the other hand, in Examples 1 to 3, the crystal system of zirconia was 100% monoclinic. In Example 4, since a part of the tetragonal partially stabilized zirconia composed of commercially available zirconia powder was added, about 76% was monoclinic. Further, in Examples 1 to 4 and Comparative Examples 4 and 5, yttria XRD peaks were observed. In Examples 1 and 4 and Comparative Examples 4 and 5 having a low yttria content, the _fy was 6% or less. Further, in Examples 2 to 3 in which the yttria content was as high as 5 to 6 mol%, _fy was in the range of more than 7% and 10% or less.

Next, the zirconia sintered body will be described. In Examples 1 to 4, the translucency is 11 or less, the saturation C ^* is 3 or more, and ^{the values of C *} (30) / C ^* (120) are also high, both when firing for 120 minutes and when firing for 30 minutes. Since it showed a high value of 0.97 or more, it was a result that the shielding property and the color development were sufficient even if it was fired for a short time. As a result, in dental treatment, it is possible to shield the discolored abutment tooth color when the abutment tooth is discolored due to a lesion or coloring due to lifestyle, etc., while obtaining good color development by firing for a short time. ..

On the other hand, in Comparative Examples 1 to 3, the translucency was 11 or less at the time of firing for 120 minutes and at the time of firing for 30 minutes, but the saturation C ^* was less than 3 at the time of firing at 30 minutes, and C ^* (30) / C. ^{* Since} the value of (120) also showed a low value of 0.40 or less, the desired color was not developed by firing for a short time.

In Comparative Example 4, the translucency was too high and the shielding property was insufficient. In addition, ^{the values of C *} (30) / C ^* (120) were also slightly lower than those of Examples 1 to 3, and the result was that the color development in short-time firing was also inferior.

In Comparative Example 5, a dense zirconia sintered body could not be produced during either 120-minute firing or 30-minute firing.

The zirconia compositions, zirconia calcined bodies and zirconia sintered bodies of the present disclosure, and methods for producing them are described in dental products such as dental prostheses, connecting parts for optical fibers such as ferrules and sleeves, and various tools (for example, grinding). It can be used for various purposes such as balls, grinding tools), various parts (for example, screws, bolts and nuts), various sensors, electronic parts, and decorative items (for example, watch bands). When the compositions, calcined and sintered bodies are used in dental materials, for example, copings, frameworks, crowns, crown bridges, abutments, implants, implant screws, implant fixtures, implant bridges, implant bars, brackets. , Prosthesis bed, inlay, onlay, orthodontic wire, laminated veneer, etc.

Claims (22)

1. A zirconia composition containing a zirconia powder and a stabilizer capable of suppressing the phase transition of the zirconia powder, and satisfying all of the following (1) to (3).
   (1) The zirconia powder contains zirconia particles having an average particle size of more than 0.17 μm and 0.4 μm or less.
   (2) At least a part of the stabilizer is not dissolved in zirconia.
   (3) When the composition was fired at 1300 to 1600 ° C., the saturation C ^* (30) of the sintered body when held at the temperature for 30 minutes and the sintered body when held at the temperature for 120 minutes. The ratio C ^* (30) / C ^* (120) of saturation C ^* (120) is 0.4 or more.
2. The zirconia composition according to claim 1, wherein the zirconia crystal system has a monoclinic crystal system of 55% or more.
3. The zirconia composition according to claim 1 or 2, wherein the stabilizer is yttria.
4. The zirconia composition according to claim 3, which contains 3 to 7.5 mol% of yttria with respect to the total mol of zirconia and yttria.
5. The zirconia composition according to claim 3 or 4, wherein the yttria peak is present in the X-ray diffraction pattern.
6. Prevalence f _y of the following formula (i) yttria which is not dissolved in the calculated zirconia based on is not less than 1%, the zirconia composition according to any one of claims 3-5.
   

   

   (However, I _y (111) indicates the peak intensity of the yttria (111) plane near 2θ = 29 ° in the X-ray diffraction pattern by CuKα rays.
   I _m (111) and _I m (11-1) shows a peak intensity of (111) plane of the monoclinic zirconia in the X-ray diffraction pattern and (11-1) plane,
   I _t (111) indicates the peak intensity of the (111) plane of tetragonal zirconia in the X-ray diffraction pattern,
   I _c (111) indicates the peak intensity of cubic (111) plane of the zirconia in the X-ray diffraction pattern. )
7. The zirconia composition according to claim 6, wherein the _{fy is 15% or less.}
8. The zirconia composition according to any one of claims 1 to 7, ^{wherein the saturation C *} (30) of the sintered body when held at the temperature for 30 minutes is 3 or more.
9. The zirconia composition according to any one of claims 1 to 8, wherein the translucency of the sintered body obtained by firing at a maximum firing temperature of 1300 to 1600 ° C. satisfies the following formula.
   ΔL ^* (WB) ≤11
   (In the formula, ΔL ^* (WB) is the ^{value obtained by subtracting the second L *} value from the first L ^* value, and the first L ^* value is the value of the sintered body having a thickness of 1.2 mm. a L ^* value measured in the white background, the second L ^* values are L ^* value background was measured in the black of the same sintered body was measured first L ^* values, L ^{* values,} L ^* a * ^{b *} color system (JIS Z 8781-4: 2013) is a ^{L *} value of chromaticity (color space) in).
10. ^{Ratio ΔL *} (30) / ΔL ^* (120) ^{of translucency ΔL *} (30) when held at the temperature for 30 minutes ^{and translucency ΔL *} (120) when held at the temperature for 120 minutes The zirconia composition according to claim 9, wherein the amount is 0.88 or more.
11. A method for producing a zirconia calcined body, which is produced by using the zirconia composition according to any one of claims 1 to 10.
12. The method for producing a zirconia calcined product according to claim 11, wherein the press-molded product made of the zirconia composition according to any one of claims 1 to 10 is fired at 800 to 1200 ° C. to produce the zirconia calcined product.
13. A zirconia composition containing the zirconia powder according to any one of claims 1 to 10 and a stabilizer capable of suppressing the phase transition of the zirconia powder is molded to prepare a first molded product. The first molding process and
    A calcining step of firing the first molded product at a temperature at which the zirconia particles do not sinter.
    The method for producing a zirconia calcined product according to claim 11 or 12, which comprises.
14. The method for producing a zirconia calcined product according to claim 13, wherein in the calcining step, the first molded product is fired at 800 to 1200 ° C.
15. Prior to the first molding step, the mixture of the zirconia powder and the stabilizer is pulverized so that the zirconia powder contains the average particle size of the zirconia particles of more than 0.17 μm and 0.4 μm or less to form a zirconia composition. The method for producing a zirconia calcined product according to claim 13 or 14, further comprising a pulverization step for obtaining a product.
16. The method for producing a zirconia calcined product according to any one of claims 13 to 15, further comprising a drying step of atomizing the zirconia composition into granules before the first molding step.
17. The method for producing a zirconia calcined product according to any one of claims 11 to 16, wherein the density of the zirconia calcined product is 2.7 to 4.0 g / cm ^3.
18. The method for producing a zirconia calcined product according to any one of claims 11 to 17, wherein the bending strength of the zirconia calcined product measured in accordance with ISO6782: 2015 is 15 to 70 MPa.
19. A first molding step of molding the zirconia composition according to any one of claims 1 to 10 to prepare a first molded product.
    A sintering step of firing the first molded product at a temperature above which it can be sintered, and a sintering step.
    A method for producing a zirconia sintered body, including.
20. Prior to the sintering step, a calcining step of calcining the first molded body at a temperature at which zirconia particles do not reach sintering is further included to prepare a zirconia calcined body. The method for producing a zirconia sintered body according to claim 19, wherein the zirconia calcined body is fired as a molded body.
21. Prior to the sintering step, a second molding step of molding the zirconia calcined body to prepare a second molded body is further included.
    The method for producing a zirconia sintered body according to claim 20, wherein in the sintering step, the second molded body is fired.
22. The method for producing a zirconia sintered body according to any one of claims 19 to 21, wherein the holding time at the maximum firing temperature is 1 hour or less in the sintering step.