Zirconia composite sintered body

Abstract

The present invention provides a zirconia composite sintered body having excellent mechanical processability in a state of a sintered body and having excellent stability in expression of reddish and brownish colors. The present invention pertains to a zirconia composite sintered body comprising: zirconia; a stabilizer capable of suppressing phase transition of the zirconia; Nb2O5 and / or Ta2O5; and Cr.

Description

Zirconia composite sintered body

[0001] The present invention relates to a zirconia composite sintered body. More specifically, the present invention relates to a zirconia composite sintered body that has excellent machinability in a sintered state and excellent stability in reddish-brown color development.

[0002] Traditionally, metals have been commonly used for dental products (e.g., prosthetics such as veneers, dental crowns, crowns, and dental implants). However, metals have the drawback of being unaesthetic, and metal elution can cause allergies. Therefore, to solve the problems associated with the use of metals, ceramic materials such as aluminum oxide (alumina) and zirconium oxide (zirconia) have been used in dental products instead of metals. Zirconia sintered bodies, in particular, are excellent in aesthetics and strength, and demand for them is increasing, especially due to the recent decline in prices.

[0003] To improve the aesthetics of the oral cavity, it is necessary to make the appearance of dental products similar to that of natural teeth. However, it can be difficult to reproduce the same appearance as natural teeth, particularly the transparency, gloss (luster), and color tone, using a zirconia sintered body itself. Therefore, instead of exposing the zirconia sintered body, a veneer crown is used in which a ceramic material called porcelain is baked onto the exposed surface of a frame (substrate) formed from a zirconia sintered body, thereby reproducing the same appearance as natural teeth. Such dental products are called porcelain-fused-to-zirconia crowns (PFZ).

[0004] Furthermore, since the zirconia sintered body has high hardness after being completely sintered, it is almost impossible to process it with a dental processing machine. For example, if a cubic zirconia sintered body is machined to obtain a zirconia sintered body having a shape that matches the shape of a patient's teeth, the metal processing tool will be worn out significantly and it will take an enormous amount of time to produce even just one dental prosthesis.

[0005] For these reasons, when using a zirconia sintered body for dental material applications, a zirconia sintered body is usually not fully sintered, but is instead produced by processing a calcined body in a semi-sintered state that is easy to process into the shape of the desired dental prosthesis, and then further sintering it to produce a sintered body processed into the shape of the intended dental prosthesis (e.g., Patent Document 1, etc.). After that, the sintered body having the shape of the dental prosthesis is subjected to slight adjustment processing so that it fits comfortably in the patient's oral cavity when placed in the dental clinic. Therefore, the treatment period from the start of treatment to the completion of treatment, including visits to the dental clinic, often requires more than one month.

[0006] If the zirconia sintered body could be machined to a large extent, the treatment period from the start to the completion of treatment could be significantly shortened. From this perspective, zirconia sintered bodies have been proposed that have excellent machinability in the sintered body state and can be machined into the desired shape of a dental prosthesis from a prismatic or disc-shaped mill blank (for example, Patent Documents 2 and 3).

[0007] Patent Document 2 discloses a processable zirconia, which is a sintered body formed to contain a tetragonal zirconia composite powder containing 79.8 to 92 mol% ZrO2, 4.5 to 10.2 mol% YO3, 3.5 to 7.5 mol% Nb2O5 or 5.5 to 10.0 mol% Ta2O5, and a TiO2 nanopowder whose mass ratio to the zirconia composite powder is more than 0 mass% and 2.5 mass% or less, and a method for producing the same. Patent Document 3 discloses a method for producing a processable zirconia composite sintered body, which includes the steps of producing a compact using a raw material composition containing 78 to 95 mol% ZrO2, 2.5 to 10 mol% Y2O3, 2 to 8 mol% Nb2O5 and / or 3 to 10 mol% Ta2O5, and in which the ZrO2 has a predominant crystal system of a monoclinic system, and sintering the compact.

[0008] International Publication No. 2019 / 131782 Japanese Patent Application Laid-Open No. 2015-127294 International Publication No. 2021 / 132644

[0009] However, when a dark shade with a reddish-brown color is produced by adding NiO to a zirconia sintered body containing NbO or TaO, which has machinability in the sintered state, the inventors have found that, depending on the firing conditions, the reddish-brown color cannot be achieved and the resulting color tone is different from the intended color tone, or the color tone varies greatly, making the product unusable. As described above, the inventors have discovered that, unlike zirconia sintered bodies that do not contain NbO or TaO, it is difficult to achieve the intended color tone in some shades while maintaining excellent machinability in the sintered state. Specifically, the inventors have discovered a new problem in which the reddish-brown color required to reproduce dark dental colors is unstable in zirconia sintered bodies containing NbO or TaO.

[0010] An object of the present invention is to provide a zirconia composite sintered body that has excellent machinability in the sintered state and excellent stability in reddish-brown color development.

[0011] As a result of extensive research to solve the above problems, the present inventors have found that the problems can be solved by adding Cr to a zirconia composite sintered body containing NbO and / or TaO. Based on this finding, they have conducted further research and have completed the present invention.

[0012] That is, the present invention includes the following: [1] A zirconia composite sintered body containing zirconia, a stabilizer capable of suppressing a phase transition of zirconia, Nb2O5 and / or Ta2O5, and Cr. [2] The zirconia composite sintered body according to [1], in which the Cr content calculated as Cr2O3 is more than 0 mass% and 0.1 mass% or less, relative to 100 mass% of the total of zirconia, the stabilizer capable of suppressing a phase transition of zirconia, Nb2O5, and Ta2O5. [3] The zirconia composite sintered body according to [1] or [2], wherein, in a total of 100 mol% of zirconia, a stabilizer capable of suppressing a phase transition of zirconia, Nb2O5, and Ta2O5, the zirconia content is 78 mol% to 97.5 mol%; the stabilizer content is 1 mol% to 12 mol%; and the Nb2O5 and / or Ta2O5 content is 1 mol% to 9 mol%. [4] The zirconia composite sintered body according to any of [1] to [3], wherein the NiO content is less than 0.01 mass% relative to a total of 100 mass% of zirconia, a stabilizer capable of suppressing a phase transition of zirconia, Nb2O5, and Ta2O5. [5] The zirconia composite sintered body according to any of [1] to [4], further containing elements or ions derived from a capping agent. [6] The zirconia composite sintered body according to [5], wherein the content of the element or ion derived from the capping agent is more than 0 mol% and not more than 5 mol% relative to the total 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5. [7] The zirconia composite sintered body according to [5] or [6], wherein the element or ion derived from the capping agent is an element or ion thereof belonging to Periods 2 to 7 of the periodic table and having a first ionization energy smaller than that of Group 18 elements of the same period, and / or an element or ion thereof having a high electron affinity. [8] The zirconia composite sintered body according to [5] or [6], wherein the element or ion derived from the capping agent includes at least one element or ion thereof selected from the group consisting of Cu, Ag, Li, Na, K, Rb, Cs, Fr, At, I, Br, Cl, and F. [9] The zirconia composite sintered body according to [5] or [6], wherein the element or ion derived from the capping agent contains at least one element or ion thereof selected from the group consisting of Li, Na, K, Rb, Cs, and Fr.

[10] The zirconia composite sintered body according to any one of [3] to [9], wherein the ratio A / B is 0.9 or more and 3 or less, where A is the content of the stabilizer and B is the total content of Nb2O5 and Ta2O5 by mol%.

[11] The zirconia composite sintered body according to any one of [3] to

[10] , wherein the stabilizer contains Y2O3 and / or CeO2.

[12] The zirconia composite sintered body according to any one of [3] to

[11] , further comprising a zirconia toughener, wherein the content of the zirconia toughener is more than 0 mass% and 6.0 mass% or less, relative to 100 mass% of the total of zirconia, the stabilizer, Nb2O5, and Ta2O5.

[13] The zirconia composite sintered body according to

[12] , wherein the zirconia toughener contains TiO2 and / or Al2O3.

[14] The zirconia composite sintered body according to

[13] , wherein the zirconia strengthening agent contains TiO2 and the TiO2 content is 0.6 mass% or more and 4.5 mass% or less.

[15] The zirconia composite sintered body according to any one of [1] to

[14] , wherein the zirconia composite sintered body has an average crystal grain size of 0.5 to 5.0 μm.

[0013] According to the present invention, there is provided a zirconia composite sintered body having excellent machinability in a sintered state and excellent stability in reddish-brown coloring. The zirconia composite sintered body of the present invention is useful for intraoral applications such as dentistry, and is particularly useful as a dental material for dental prostheses and the like intended for dental treatment applications.

[0014] The zirconia composite sintered body of the present invention contains zirconia, a stabilizer capable of suppressing the phase transition of zirconia, NbO and / or TaO, and Cr. The raw material for the Cr contained in the zirconia composite sintered body of the present invention is not particularly limited as long as the effects of the present invention are achieved, but it is preferable to use CrO, which is commonly used as a pigment.

[0015] As used herein, the term "green body" refers to a body that has not yet reached either a semi-sintered state (calcined state) or a sintered state. In other words, a green body is distinguished from a calcined body and a sintered body in that it is a green body formed by molding and then unsintered. As used herein, a "zirconia composite calcined body" refers to a body in a semi-sintered state in which the raw material powders, such as zirconia, are necked (adhered) and are not completely sintered. As used herein, a "zirconia composite sintered body" refers to a body in a sintered state in which the raw material powders, such as zirconia, are completely sintered. In a zirconia composite sintered body, the raw material powders, such as zirconia, solidify or dissolve with each other through sintering, increasing the relative density and promoting densification. As used herein, "zirconia" refers to zirconium(IV) oxide (ZrO), containing a trace amount (0.5% by mass to 3% by mass) of HfO relative to the amount of ZrO. Because HfO2 is difficult to separate, terms such as "zirconia" and "zirconia powder" refer to both ZrO2 and HfO2. Therefore, in this specification, "zirconia content" refers to the total content of ZrO2 and HfO2. Furthermore, "zirconia powder" also includes powder in which a stabilizer is dissolved in zirconia. In this specification, "in the atmosphere" refers to standard atmospheric pressure (1 atm). In this specification, "zirconia strengthener" refers to a component that improves the mechanical strength of a zirconia composite sintered compact. In this specification, the content (mass%) of the zirconia strengthener is the external addition rate relative to the total of zirconia, the stabilizer, Nb2O5, and Ta2O5 (100 mass%). In this specification, the content of each component in a zirconia composite sintered compact can be calculated from the amount of raw material charged. In this specification, machining includes cutting and grinding. The mechanical processing may be either wet processing or dry processing, and is not particularly limited. In this specification, the upper and lower limits of the numerical ranges (temperature range, content of each component, abundance rate of crystalline system, values ​​calculated from components, etc., and each physical property, etc.) can be appropriately combined.

[0016] The reason why the zirconia composite sintered body of the present invention has excellent machinability in the sintered state and excellent stability of the reddish-brown coloring is not clear, but it is thought to be as follows: The excellent machinability in the sintered state is presumably achieved by improving fracture toughness (IF method) by adding at least one of Nb2O5 and Ta2O5 to zirconia to which a conventional stabilizer has been added, and by minimizing hardness by coarsening the microstructure. Regarding the excellent stability of the reddish-brown coloring, it has been known that Cr2O3 is a pigment that develops a grayish-green color. However, in the case of a zirconia composite sintered body containing Nb2O5 and / or Ta2O5, the valence of Cr and the crystal structure of the zirconia composite sintered body containing Cr change in relation to Nb2O5 and / or Ta2O5 compared to a case where Nb2O5 and / or Ta2O5 is not contained, and as a result, a reddish-brown coloring is exhibited, and it is thought that this can bring about stability that allows stable coloring without variation in the reddish-brown coloring.

[0017] In the zirconia composite sintered body of the present invention, the Cr content calculated as Cr2O3 is preferably more than 0 mass%, more preferably 0.0001 mass% or more, even more preferably 0.001 mass% or more, and particularly preferably 0.002 mass% or more, relative to 100 mass% of the total of zirconia, the stabilizer capable of suppressing the phase transition of zirconia, Nb2O5, and Ta2O5, from the viewpoint of excellent stability of the reddish-brown coloring. Also, the Cr content calculated as Cr2O3 is preferably 0.1 mass% or less, more preferably 0.09 mass% or less, even more preferably 0.08 mass% or less, and particularly preferably 0.05 mass% or less, relative to 100 mass% of the total of zirconia, the stabilizer capable of suppressing the phase transition of zirconia, Nb2O5, and Ta2O5, from the viewpoint of excellent stability of the reddish-brown coloring.

[0018] Furthermore, in the zirconia composite sintered body of the present invention, in order to achieve excellent stability in the reddish-brown color development, the NiO content is preferably less than 0.01 mass%, more preferably less than 0.008 mass%, even more preferably less than 0.0001 mass%, and particularly preferably 0 mass%, relative to 100 mass% of the total of zirconia, the stabilizer capable of suppressing the phase transition of zirconia, NbO, and TaO.

[0019] In the zirconia composite sintered body of the present invention, the zirconia content is preferably 78 mol% to 97.5 mol% based on a total of 100 mol% of zirconia, a stabilizer capable of suppressing the phase transition of zirconia, NbO, and TaO, and from the viewpoint of superior translucency and strength, it is more preferably 79 mol% to 96 mol%, even more preferably 80 mol% to 94 mol%, and particularly preferably 81 mol% to 93 mol%. By using the zirconia content within this range, the zirconia composite sintered body has excellent translucency, and by combining it with a colorant or by forming it into a processed body similar to a dental prosthesis obtained by machining, and then building up a porcelain containing a colorant on the processed body and firing it, it is possible to finally obtain a dental prosthesis having aesthetic properties similar to the color tone of natural teeth.

[0020] Examples of stabilizers capable of suppressing the phase transition of zirconia (hereinafter also simply referred to as "stabilizers") include calcium oxide (CaO), magnesium oxide (MgO), yttrium oxide (YO), cerium oxide (CeO), scandium oxide (ScO), lanthanum oxide (LaO), erbium oxide (ErO), praseodymium oxide (PrO, PrO), and the like. 11 Examples of the stabilizer include oxides such as samarium oxide (SmO), europium oxide (EuO), thulium oxide (TmO), gallium oxide (GaO), indium oxide (InO), and ytterbium oxide (YbO), and from the viewpoints of superior effects of the present invention and particularly superior aesthetics, YO (yttria) and / or CeO are preferred. The stabilizers may be used alone or in combination of two or more.

[0021] In the zirconia composite sintered body of the present invention, the content of the stabilizer is preferably 1 mol% to 12 mol% inclusive, based on a total of 100 mol% of zirconia, the stabilizer, NbO, and TaO, and more preferably 2 mol% to 10 mol% inclusive from the viewpoint of easily obtaining sufficient machinability. From the viewpoint of more excellent translucency and strength, the content of the stabilizer is further preferably 3 mol% to 8.0 mol% inclusive, even more preferably 3.5 mol% to 7.5 mol% inclusive, particularly preferably 3.8 mol% to 7.0 mol% inclusive, and most preferably 4.0 mol% to 6.5 mol% inclusive. By using the stabilizer in this range, the zirconia composite sintered body has excellent translucency, and by combining it with a colorant or forming it into a processed body similar to a dental prosthesis obtained by machining, and then depositing a porcelain containing a colorant on the processed body and firing it, a dental prosthesis having aesthetic properties similar to the desired color tone of natural teeth can be finally obtained. In one preferred embodiment, the stabilizer capable of suppressing the phase transition of zirconia contains Y2O3 and / or CeO2, and the total content of Y2O3 and CeO2 is 2 mol% to 10 mol%. In another preferred embodiment, the stabilizer capable of suppressing the phase transition of zirconia contains Y2O3, and the total content of Y2O3 is 2 mol% to 10 mol%. In any embodiment herein, the contents of Y2O3 and CeO2 can be changed as appropriate within the ranges described herein. For example, in order to achieve better translucency and strength, the total content of Y2O3 and CeO2 may be 2.5 mol% to 10 mol% or 3 mol% to 9 mol%. As described above, when the stabilizer content is within the above range and has excellent translucency, a dental prosthesis having aesthetic properties close to the intended color tone of natural teeth can be obtained as the final dental prosthesis.

[0022] In the zirconia composite sintered body of the present invention, the content of Nb2O5 or Ta2O5 is preferably 1 mol% to 9 mol% and more preferably 1.5 mol% to 8.5 mol% based on a total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5. From the viewpoint of superior machinability, it is even more preferable that it be 2.5 mol% to 8 mol% and particularly preferably 3 mol% to 7 mol%. If the Nb2O5 or Ta2O5 content is less than 1 mol%, sufficient machinability is difficult to obtain. Furthermore, if the Nb2O or Ta2O5 content exceeds 9 mol%, chipping occurs in the resulting zirconia composite sintered body, making it difficult to obtain sufficient physical properties. Furthermore, in a preferred embodiment, in terms of superior machinability, it is preferable that the total content of NbO and TaO in the zirconia composite sintered body of the present invention be within the above-mentioned range of each content (e.g., 1 mol% or more and 9 mol% or less).

[0023] Furthermore, when the content of the stabilizer is A mol % and the total content of Nb2O5 and Ta2O5 is B mol %, the ratio A / B is preferably 0.9 or more and 3 or less, and more preferably 0.95 or more and 2 or less, from the viewpoint of superior machinability, and is even more preferably 1 or more and 1.6 or less, from the viewpoint of imparting superior machinability, suppressing wear of the processing tool, and further increasing the number of dental prostheses obtainable by continuous processing using one processing tool.

[0024] Furthermore, one preferred embodiment is a zirconia composite sintered body formed to contain tetragonal composite zirconia containing 79.8 to 92 mol% zirconia, 4.5 to 10.2 mol% Y2O3, and 3.5 to 7.5 mol% Nb2O5 or 5.5 to 10.0 mol% Ta2O5; TiO2 having a mass ratio relative to the composite zirconia of more than 0 mass% and not more than 2.5 mass%; and Cr2O3 having a mass ratio relative to the composite zirconia of more than 0 mass% and not more than 0.1 mass%.

[0025] In another preferred embodiment, the zirconia composite sintered body includes zirconia, the stabilizer, Nb2O5 and / or Ta2O5, and Cr, wherein, in a total of 100 mol% of the zirconia, the stabilizer, Nb2O5, and Ta2O5, the zirconia content is 78 mol% to 97.5 mol%, the stabilizer content is 1 mol% to 12 mol%, and the Nb2O5 and / or Ta2O5 content is 1 mol% to 9 mol%. In the zirconia composite sintered body, the Cr content calculated as Cr2O3 is preferably more than 0 mass% to 0.1 mass% relative to a total of 100 mass% of the zirconia, the stabilizer capable of suppressing the phase transition of zirconia, Nb2O5, and Ta2O5. Moreover, the zirconia composite sintered body may be a zirconia composite sintered body that does not contain elements or ions derived from a capping agent described later, or a zirconia composite sintered body that does not contain elements or ions derived from a capping agent described later and further contains a zirconia strengthening agent described later.

[0026] In addition, the zirconia composite sintered body of the present invention preferably further contains elements or ions derived from a capping agent, since this provides superior machinability in the sintered body state.

[0027] In another preferred embodiment, the zirconia composite sintered body includes zirconia, a stabilizer, Nb2O5 and / or Ta2O5, and Cr, wherein, in a total of 100 mol% of the zirconia, the stabilizer, Nb2O5, and Ta2O5, the zirconia content is 78 mol% to 97.5 mol%, the stabilizer content is 1 mol% to 12 mol%, and the Nb2O5 and / or Ta2O5 content is 1 mol% to 9 mol%, and the zirconia composite sintered body further includes an element or ion derived from a capping agent. In the zirconia composite sintered body, the Cr content calculated as Cr2O3 is preferably more than 0 mass% to 0.1 mass% relative to a total of 100 mass% of the zirconia, the stabilizer capable of suppressing the phase transition of zirconia, Nb2O5, and Ta2O5.

[0028] In this specification, the term "capping element or ion" refers to an element or ion derived from a capping agent that caps the ends of bonds in a zirconia composite sintered body made of a zirconia composite oxide containing NbO and / or TaO, thereby weakening the strength (hereinafter also referred to as "grain boundary strength") of the crystal interface (hereinafter also referred to as "grain boundary"). The capping agent can cap a portion of the grain boundary. "Capping" refers to the presence of a target element or ion (capping element or ion) at the grain boundary by bonding to the bonds of the zirconia composite oxide in place of the metal element. It is presumed that the presence of the capping element or ion at the grain boundary in the form of a +1-valent cation or a -1-valent anion causes electrostatic repulsion between the capped cations or anions, thereby weakening the grain boundary strength.

[0029] The contents of each Cr component in the zirconia composite sintered body, calculated as zirconia, stabilizer, NbO, TaO, and CrO, can also be measured by, for example, inductively coupled plasma (ICP) emission spectroscopy, X-ray fluorescence analysis, etc. The content (mol%) of the element or ion derived from the capping agent is the external addition rate relative to the total of zirconia, the stabilizer, NbO, and TaO, which is 100 mol%. Therefore, the content of the element or ion derived from the capping agent in the zirconia composite sintered body can be calculated by converting the amount (mass) of the raw material charged when added into mol%.

[0030] In the zirconia composite sintered body containing a capping element or ion, the presence of the capping element or ion at the grain boundary is presumably such that the capping element or ion acts in a direction that makes it easier for the grains to peel off by reducing the grain boundary strength in the form of a +1-valent cation or a -1-valent anion, making it easier to cut, and improving the machinability of the sintered body.

[0031] The capping element or ion becomes a +1-valent cation or a -1-valent anion at the grain boundary of the zirconia composite sintered body and bonds with a bond possessed by the zirconia composite oxide. This bond causes electrostatic repulsion between the cations or anions, weakening the grain boundary strength while maintaining the strength and translucency properties of the particles constituting the zirconia composite sintered body, and acting to improve the machinability of the sintered body. For example, a +1-valent cation may bond with the other bond of an oxygen atom bonded to a metal element (e.g., Zr, Hf, Y, Nb, or Ta) contained in the zirconia composite oxide in place of the metal element. Alternatively, a -1-valent anion may bond to an OH2 bonded to a metal element (e.g., Zr, Hf, Y, Nb, or Ta) contained in the zirconia composite oxide. + Furthermore, a form in which a −1-valent anion is bonded to a cation derived from a metal element (for example, Zr, Hf, Y, Nb, or Ta) contained in the zirconia-based composite oxide and bonded to another metal element is also conceivable.

[0032] Furthermore, since Nb2O5 and / or Ta2O5 act to coarsen the microstructure and reduce hardness in the zirconia composite sintered body, the capping element or ion and Nb2O5 and / or Ta2O5 act together to improve machinability. Therefore, the capping element or ion and Nb2O5 and / or Ta2O5 act together to further enhance excellent machinability while maintaining the strength required for artificial teeth, thereby shortening the machining time and suppressing wear of the machining tool, thereby increasing the number of dental prostheses that can be obtained by continuous machining using a single machining tool.

[0033] In the zirconia composite sintered body of the present invention, the capping element or ion further improves the machinability and acts as a free cutting aid as described above, without significantly impairing the strength and translucency.

[0034] The content of the capping element or ion contained in the zirconia composite sintered body used in the present invention is preferably more than 0 mol% and not more than 5 mol%, and from the viewpoint of being more excellent in machinability and being able to further increase the number of dental prostheses that can be continuously machined with one machining tool, it is more preferably 0.05 mol% or more and 3 mol% or less, even more preferably 0.06 mol% or more and 2.5 mol% or less, particularly preferably 0.07 mol% or more and 1.0 mol% or less, and most preferably 0.08 mol% or more and 0.34 mol% or less. Furthermore, when the capping element or ion contained in the zirconia composite sintered body used in the present invention is a Group 17 element or ion, the content is more preferably 0.2 mol% or more and 5 mol% or less, even more preferably 0.3 mol% or more and 4 mol% or less, particularly preferably 0.4 mol% or more and 3.5 mol% or less, and most preferably 0.5 mol% or more and 3.0 mol% or less, in terms of superior machinability and the ability to further increase the number of dental prostheses that can be continuously machined with one machining tool.

[0035] As mentioned above, the presence of capping elements or ions at the grain boundaries results in +1 cations or -1 anions, which can provide suitable interactions between the charged sites at the grain boundaries and the adsorption sites.

[0036] The capping element or ion is preferably an element or ion thereof belonging to Periods 2 to 7 of the periodic table and having a smaller first ionization energy than Group 18 elements of the same period, an element or ion thereof having a high electron affinity, nitrate ion, hypochlorite ion, chlorite ion, chlorate ion, perchlorate ion, bromate ion, permanganate ion, metaborate ion, or cyanide ion. A preferred embodiment includes a zirconia composite sintered body in which the element or ion thereof derived from the capping agent is an element or ion thereof belonging to Periods 2 to 7 of the periodic table and having a smaller first ionization energy than Group 18 elements of the same period, and / or an element or ion thereof having a high electron affinity.

[0037] Suitable examples of elements belonging to Periods 2 to 7 of the periodic table and having a first ionization energy smaller than that of Group 18 elements in the same period include Cu, Ag, Li, Na, K, Rb, Cs, and Fr, from the viewpoints of easier formation of +1-valent cations and superior machinability.

[0038] As elements with high electron affinity, Group 17 elements are preferred, since −1-valent anions are more easily obtained and machinability is superior. Preferred Group 17 elements are At, I, Br, Cl, and F.

[0039] The first ionization energy is the energy required to remove one electron from a neutral atom and ionize it. This can be the same as the first ionization energy described in "Schreiber-Atkins Inorganic Chemistry (Vol. 1), 4th Edition, Part I, Fundamentals, 1. Atomic Structure." The first ionization energy can be converted to units of "KJ / mol" using the unit "eV" described in "Schreiber-Atkins Inorganic Chemistry (Vol. 1), 4th Edition, Appendix 2," where 1 eV = 96.485 KJ / mol. The first ionization energy can also be determined using photoelectron yield spectroscopy (PYS). Electron affinity (EA) is the energy released when an electron is added to a neutral atom. Electron affinity can be measured by the difference in the energy gap from the ionization potential. The ionization potential is defined as the energy difference between the highest-energy occupied orbital of a compound's molecules and the vacuum level, and its value is measured using ultraviolet photoelectron spectroscopy. The first ionization energy and electron affinity may be determined using data stored in the NIST Chemistry WebBook (https: / / webbook.nist.gov / chemistry / ) (select "Ionization Energy" or "Electron Affinity" from "Ion energetics properties"). The first ionization energy and electron affinity are sufficient if they allow comparison of the likelihood of an element becoming a +1-valent cation or a -1-valent anion with other elements to be compared, and therefore the measurement methods described above can be used as appropriate.

[0040] Specific examples of capping elements include Cu, Ag, Li, Na, K, Rb, Cs, Fr, At, I, Br, Cl, and F. From the viewpoint of further improving machinability, Cu, Ag, Li, Na, K, Rb, Cs, Fr, I, Br, Cl, and F are preferred, and Li, Na, K, Rb, Cs, and Fr are more preferred. In a preferred embodiment, there is mentioned a zirconia composite sintered body comprising zirconia, a stabilizer, NbO and / or TaO, Cr, and an element or ion derived from a capping agent, wherein the element derived from the capping agent comprises at least one element selected from the group consisting of Cu, Ag, Li, Na, K, Rb, Cs, Fr, At, I, Br, Cl, and F, and the ion of the element is at least one +1-valent cation or −1-valent anion selected from the group consisting of Cu, Ag, Li, Na, K, Rb, Cs, Fr, I, Br, Cl, and F. In another preferred embodiment, there is mentioned a zirconia composite sintered body wherein the element or ion derived from the capping agent comprises at least one element or ion thereof selected from the group consisting of Ag, Li, Na, K, Rb, Cs, Fr, At, I, Br, Cl, and F. The capping elements or ions may be used alone or in combination of two or more.

[0041] In the zirconia composite sintered body containing elements or ions derived from a capping agent, the zirconia content, the type and content of the stabilizer, and the A / B ratio (A: stabilizer content, B: total content of NbO and TaO) can be appropriately changed, as described above.

[0042] As described above, the capping element or ions and NbO and / or TaO act together, so the effect of the stabilizer is not impaired, and the stabilizer is not particularly limited, and the effects of the present invention can be achieved. Another preferred embodiment is a zirconia composite sintered body containing zirconia, a stabilizer capable of suppressing the phase transition of zirconia, NbO and / or TaO, Cr, and a capping element or ions, wherein the stabilizer contains YO, and the YO content is 2 mol% or more and 10 mol% or less.

[0043] In the zirconia composite sintered body containing the capping element or ions, the content of NbO or TaO is preferably 1 mol% to 9 mol%, more preferably 1.5 mol% to 8.5 mol%, based on a total of 100 mol% of zirconia, the stabilizer, NbO, and TaO. In order to achieve superior machinability through cooperation with the capping element or ions, the content of NbO or TaO is even more preferably 2.5 mol% to 8 mol%, and particularly preferably 3 mol% to 7 mol%. If the NbO or TaO content is less than 1 mol%, sufficient machinability is difficult to obtain. Furthermore, if the NbO or TaO content exceeds 9 mol%, chipping and other defects occur in the resulting zirconia composite sintered body, making it difficult to obtain sufficient physical properties. Furthermore, in a preferred embodiment, in terms of better machinability, it is preferable that the total content of NbO and TaO in the zirconia composite sintered body containing the capping element or ions is within the above-mentioned respective content ranges (e.g., 1 mol% or more and 9 mol% or less).

[0044] As described above, NbO and TaO act to coarsen the microstructure and reduce hardness, and act together with the capping element or ion to impart excellent machinability. In addition, they maximize the sintered density through interaction with other components (e.g., TiO, AlO) added to the zirconia composite sintered compact and application of HIP, thereby ensuring the aesthetics of natural teeth in the resulting zirconia composite sintered compact (preferably a dental material for dental prostheses, etc.).

[0045] The content of each of the above-mentioned components, zirconia, stabilizer, NbO, and TaO, is a percentage relative to a total of 100 mol% of zirconia, stabilizer, NbO, and TaO, and the total of zirconia, stabilizer, NbO, and TaO does not exceed 100 mol%. For example, if the raw material composition contains NbO but does not contain TaO, the content of each of the components, zirconia, stabilizer, and NbO means a content percentage relative to a total of 100 mol% of zirconia, stabilizer, and NbO.

[0046] Furthermore, when the content of the stabilizer is A mol % and the total content of Nb2O5 and Ta2O5 is B mol %, the ratio A / B is preferably 0.9 or more and 3 or less, and more preferably 0.95 or more and 2 or less, from the viewpoint of superior machinability, and is even more preferably 1 or more and 1.6 or less, from the viewpoint of enhancing the effect of the capping element or ion and Nb2O5 and / or Ta2O5 acting together, imparting superior machinability, suppressing wear of the processing tool, and further increasing the number of dental prostheses obtained by continuous processing using one processing tool.

[0047] In a preferred embodiment of the present invention, the composition comprises zirconia, a stabilizer capable of suppressing a phase transition of zirconia, Nb2O5 and / or Ta2O5, and Cr, wherein, in a total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5, the content of Z zirconia is 78 mol% or more and 97.5 mol% or less, the content of the stabilizer is 1 mol% or more and 12 mol% or less, the content of Nb2O5 and / or Ta2O5 is 1 mol% or more and 9 mol% or less, and further comprises a capping element or ion, the stabilizer comprises Y2O3 and / or CeO2, and the content of the capping element or ion is more than 0 mol% and 5 mol% or less, relative to a total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5, The zirconia composite sintered body may have a Cr content calculated as Cr2O3 of more than 0 mass% and 0.1 mass% or less relative to 100 mass% of the total of zirconia, the stabilizer, Nb2O5, and Ta2O5, and the A / B ratio is 0.9 or more and 3 or less, where A mol% is the content of the stabilizer and B mol% is the total content of Nb2O5 and Ta2O5.

[0048] Other zirconia composite sintered bodies usable in the present invention include zirconia composite sintered bodies containing zirconia, a stabilizer capable of suppressing the phase transition of zirconia, NbO and / or TaO, Cr, a capping element or ion, and a zirconia strengthener. In a zirconia composite sintered body containing zirconia, a stabilizer capable of suppressing the phase transition of zirconia, NbO and / or TaO, and Cr, the zirconia strengthener acts together with the capping element or ion to improve the strength of the sintered body.

[0049] In the case of a zirconia composite sintered body containing a zirconia strengthener, as described above, the zirconia content, the type and content of the stabilizer, the NbO and / or TaO content, the Cr content calculated as CrO, the type and content of the capping element or ion, and the A / B ratio can be appropriately changed.

[0050] In a zirconia composite sintered body containing a zirconia toughener, the content of the zirconia toughener is preferably more than 0 mass% and not more than 6.0 mass%, relative to a total of 100 mass% of zirconia, a stabilizer capable of suppressing the phase transition of zirconia, NbO, and TaO. In view of the fact that the zirconia toughener acts as a unit when combined with a capping element or ion and provides superior strength, the content of the zirconia toughener is more preferably 0.01 mass% or more and not more than 5.5 mass%, and even more preferably 0.5 mass% or more and not more than 5.0 mass%.

[0051] Examples of the zirconia reinforcing agent include TiO2, Al2O3, etc. The zirconia reinforcing agent may be used alone or in combination of two or more.

[0052] Another example of the zirconia composite sintered body used in the present invention is a zirconia composite sintered body in which the zirconia strengthening agent contains TiO2 and the TiO2 content is 0.6 mass % or more and 4.5 mass % or less.

[0053] Another zirconia composite sintered body used in the present invention contains zirconia, a stabilizer capable of suppressing the phase transition of zirconia, Nb2O5 and / or Ta2O5, and Cr, and in which, in a total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5, the zirconia content is 78 mol% or more and 97.5 mol% or less, the stabilizer content is 1 mol% or more and 12 mol% or less, the Nb2O5 and / or Ta2O5 content is 1 mol% or more and 9 mol% or less, and further contains a capping element or ion, the stabilizer contains Y2O3 and / or CeO2, the zirconia reinforcer contains TiO2 and the TiO2 content is 0.6 to 4.5 mass%, The zirconia composite sintered body may have a content of the capping element or ion that is more than 0 mol % and not more than 5 mol % relative to a total of 100 mol % of zirconia, the stabilizer, Nb2O5, and Ta2O5, a content of Cr calculated as Cr2O3 that is more than 0 mass % and not more than 0.1 mass % relative to a total of 100 mass % of zirconia, the stabilizer, Nb2O5, and Ta2O5, and an A / B ratio of 0.9 to 3, where A mol % is the content of the stabilizer and B mol % is the total content of Nb2O5 and Ta2O5.

[0054] The average crystal grain size of the zirconia composite sintered body used in the present invention is preferably 0.5 to 5.0 μm, more preferably 0.5 to 4.5 μm, and even more preferably 0.7 to 4.0 μm, from the viewpoint of superior machinability, strength, and translucency. The average crystal grain size can be measured, for example, by the following method. First, an image of the surface of a pellet-shaped zirconia composite sintered body is obtained using a scanning electron microscope (product name "VE-9800", manufactured by Keyence Corporation). The grain boundaries of each crystal grain are recorded in the obtained image, and the average crystal grain size is calculated by image analysis. The average crystal grain size is measured using image analysis software (product name "Image-Pro Plus", manufactured by Hakuto Co., Ltd.). The captured SEM image is binarized, the brightness range is adjusted so that the grain boundaries are clearly visible, and the particles are recognized from the field of view (area). The crystal grain size obtained using Image-Pro Plus is the average length of the line segments connecting the outlines of the crystal grains passing through the center of gravity, measured at intervals of two degrees from the center of gravity. The arithmetic mean value of the crystal grain size of all particles not on the edge of the image in the SEM photographs (three fields of view) of each Example and Comparative Example is used as the average crystal grain size (by number) in the sintered body. "Particles not on the edge of the image" refers to particles that do not fit within the outline of the SEM photograph (particles whose outlines are interrupted at the top, bottom, left, and right boundaries). The crystal grain size of all particles not on the edge of the image can be determined by selecting the option to exclude all particles on boundary lines in Image-Pro Plus. The average crystal grain size can be measured by adjusting the number of particles so that the number of particles in one field of view of the SEM photograph is approximately 50 or 100, using the method described in the Examples.

[0055] The density of the zirconia composite sintered body according to the present invention is set to 5.5 g / cm because the higher the density, the fewer the internal voids, the less light scattering occurs, the better the translucency and the better the strength. 3 It is preferable that the density is 5.7 g / cm or more. 3 More preferably, it is 5.9 g / cm or more. 3It is more preferable that the zirconia composite sintered body is substantially free of voids. The density of the composite sintered body can be calculated by dividing the mass of the composite sintered body by the volume of the composite sintered body.

[0056] As described above, the zirconia composite sintered body used in the present invention can be the workable zirconia described in Patent Document 2, and the workable zirconia can be produced in accordance with the production method described in Patent Document 2.

[0057] A method for producing a zirconia composite sintered body of the present invention when the zirconia composite sintered body contains a capping element or ions will be described below.

[0058] Examples of methods for producing a zirconia composite sintered body containing a capping element or ion include a method for producing a zirconia composite sintered body, the method comprising the steps of: preparing a green body using a raw material composition containing zirconia, a stabilizer capable of suppressing the phase transition of zirconia, NbO and / or TaO, CrO, and a capping agent; and sintering the green body. The raw material composition may, for example, be one in which, relative to 100 mol% in total of zirconia, the stabilizer, NbO, and TaO, the zirconia content is 78 mol% or more and 97.5 mol% or less, the stabilizer content is 1 mol% or more and 12 mol% or less, the NbO and / or TaO content is 1 mol% or more and 9 mol% or less, and the CrO content is more than 0 mass% and 0.1 mass% or less, relative to 100 mass% in total of zirconia, the stabilizer, NbO, and TaO, and further contains a capping agent.

[0059] The raw material composition for the zirconia composite sintered body includes, for example, zirconia, a stabilizer capable of suppressing the phase transition of zirconia, NbO and / or TaO, CrO, and a capping agent. The raw material composition for the zirconia composite sintered body may be in a dry state, or may contain or be contained in a liquid. The raw material composition may be in the form of, for example, powder, granules, agglomerates, paste, slurry, etc.

[0060] The raw material composition contains a capping agent so that the resulting zirconia composite sintered body contains a capping element or ion. The capping agent is not particularly limited as long as it is a compound that can become a monovalent ion (a +1-valent cation or a -1-valent anion) in a solvent containing water, and examples thereof include hydroxides, salts, halides (fluorides, chlorides, bromides, iodides), cyanides, etc. that contain an element or ion derived from the capping agent. Each of the capping agents may be used alone, or two or more may be used in combination.

[0061] Examples of hydroxides containing capping elements or ions include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, francium hydroxide, etc. Examples of salts containing capping elements or ions include carbonates, bicarbonates, nitrates, hypochlorites, chlorites, chlorates, perchlorates, bromates, permanganates, metaborates, sulfide salts, and cyanide salts.

[0062] Examples of carbonates containing capping elements or ions include lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, francium carbonate, cesium carbonate, etc. Examples of bicarbonates containing capping elements or ions include lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, rubidium bicarbonate, francium bicarbonate, cesium bicarbonate, etc. Examples of nitrates containing capping elements or ions include calcium nitrate, strontium nitrate, iron (II) nitrate, iron (III) nitrate, cobalt (II) nitrate, magnesium nitrate, gallium nitrate, yttrium (III) nitrate, lanthanum (III) nitrate, praseodymium nitrate, neodymium (III) nitrate, manganese (II) nitrate, europium nitrate, copper (II) nitrate, thorium nitrate, aluminum nitrate, nickel (II) nitrate, titanium (IV) nitrate, zirconium nitrate, zirconium oxynitrate (IV) hydrate (ZrO(NO3)2.xH2O), cerium (III) nitrate, tin nitrate, bismuth (III) nitrate, scandium (III) nitrate, indium (III) nitrate, and hafnium (IV) nitrate. Examples of hypochlorites containing capping elements or ions include sodium hypochlorite and calcium hypochlorite. Examples of chlorites containing capping elements or ions include sodium chlorite, potassium chlorite, lithium chlorite, calcium chlorite, magnesium chlorite, barium chlorite, copper(II) chlorite, copper(III) chlorite, silver chlorite, and nickel chlorite. Examples of chlorates containing capping elements or ions include calcium chlorate, barium chlorate, cobalt chlorate, nickel chlorate, magnesium chlorate, zinc chlorate, and copper chlorate. Examples of perchlorates containing capping elements or ions include iron(III) perchlorate, barium perchlorate, calcium perchlorate, cobalt perchlorate, nickel perchlorate, magnesium perchlorate, beryllium perchlorate, aluminum perchlorate, and cerium perchlorate. Examples of bromates containing capping elements or ions include neodymium bromate, lanthanum bromate, and praseodymium bromate.Examples of permanganates containing capping elements or ions include calcium permanganate (VII), potassium permanganate (VII), and sodium permanganate (VII). Examples of metaborates containing capping elements or ions include sodium metaborate and barium metaborate. Examples of sulfide salts containing capping elements or ions include copper (I) sulfide. Examples of cyanide salts containing capping elements or ions include barium cyanide, sodium cyanide, potassium cyanide, and calcium cyanide.

[0063] Examples of fluorides containing capping elements or ions include lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, cesium fluoride, francium fluoride, beryllium fluoride, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, scandium (III) fluoride, yttrium (III) fluoride, lanthanum (III) fluoride, cerium (III) fluoride, and fluorides Examples of the fluoride include neodymium (III), titanium (III) fluoride, titanium (IV) fluoride, zirconium (IV) fluoride, hafnium (IV) fluoride, tantalum (V) fluoride, manganese (II) fluoride, manganese (III) fluoride, iron (II) fluoride, iron (III) fluoride, copper (II) fluoride, zinc (II) fluoride, aluminum fluoride, bismuth (III) fluoride, indium (III) fluoride, and tin (II) fluoride.

[0064] Examples of chlorides containing capping elements or ions include zirconium oxychloride, lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride, francium chloride, beryllium chloride, magnesium chloride, calcium chloride, strontium chloride, barium chloride, scandium (III) chloride, yttrium (III) chloride, lanthanum (III) chloride, cerium (III) chloride, praseodymium chloride, neodymium (III) chloride, samarium chloride, europium chloride, titanium (III) chloride, titanium (IV) chloride, zirconium (IV) chloride, hafnium (IV) chloride, tantalum (V) chloride, manganese chloride, iron (II) chloride, iron (III) chloride, cobalt (II) chloride, nickel (II) chloride, copper (I) chloride, copper (II) chloride, zinc (II) chloride, aluminum chloride, gallium chloride, bismuth (III) chloride, indium (I) chloride, indium (III) chloride, and tin (II) chloride.

[0065] Examples of bromides containing capping elements or ions include lithium bromide, sodium bromide, potassium bromide, rubidium bromide, cesium bromide, francium bromide, beryllium bromide, magnesium bromide, calcium bromide, strontium bromide, barium bromide, scandium(III) bromide, yttrium(III) bromide, cerium(III) bromide, neodymium(III) bromide, titanium(IV) bromide, zirconium(IV) bromide, tantalum(V) bromide, manganese(II) bromide, iron(II) bromide, iron(III) bromide, cobalt(II) bromide, nickel(II) bromide, copper(I) bromide, copper(II) bromide, zinc(II) bromide, bismuth(III) bromide, vanadium(III) bromide, indium(III) bromide, and tin bromide.

[0066] Examples of iodides containing capping elements or ions include lithium iodide, sodium iodide, potassium iodide, rubidium iodide, cesium iodide, francium iodide, beryllium iodide, calcium iodide, magnesium iodide, strontium iodide, barium iodide, scandium (III) iodide, yttrium (III) iodide, lanthanum (III) iodide, cerium (III) iodide, neodymium (III) iodide, and iodides. Examples of iodides include titanium(IV), zirconium(IV) iodide, hafnium(IV) iodide, tantalum(V) iodide, manganese(II) iodide, iron(II), iron(III), cobalt(II), nickel(II), copper(I), zinc(II), aluminum, vanadium(II), bismuth(III), indium(III), tin(II), and tin(IV) iodides.

[0067] Regarding zirconia, commercially available zirconia powder can be used. Examples of commercially available zirconia powder include zirconia powder (trade name "Zpex (registered trademark)" (Y2O3 content: 3 mol%), "Zpex (registered trademark) 4" (Y2O3 content: 4 mol%), and "Zpex (registered trademark) Smile (registered trademark)" (YO content: 5.5 mol%), "TZ-3Y" (YO content: 3 mol%), "TZ-3YS" (YO content: 3 mol%), "TZ-4YS" (YO content: 4 mol%), "TZ-6Y" (YO content: 6 mol%), "TZ-6YS" (YO content: 6 mol%), "TZ-8YS" (YO content: 8 mol%), "TZ-10YS" (YO content: 10 mol%), and "TZ-3Y-E" (YO content: 3 mol%) Examples include "TZ-3YS-E" (YO content: 3 mol%), "TZ-3YB-E" (YO content: 3 mol%), "TZ-3YSB-E" (YO content: 3 mol%), "TZ-3YB" (YO content: 3 mol%), "TZ-3YSB" (YO content: 3 mol%), "TZ-3Y20AB" (YO content: 3 mol%), "TZ-8YSB" (YO content: 8 mol%), and "TZ-0" (YO content: 0 mol%); all manufactured by Tosoh Corporation. The commercially available zirconia powder also contains HfO. Commercially available products containing YO may also be used. As the zirconia powder, a zirconia powder in which Y2O3 is uniformly dispersed and solid-solved, such as the commercially available TZ series (product names including "TZ"), can also be used in the raw material composition of the present invention.

[0068] There are no particular limitations on the method for producing the zirconia powder, and known methods such as a breakdown process in which coarse particles are pulverized into fine powder, or a building-up process in which zirconia is synthesized from atoms or ions through a nucleation and growth process can be used.

[0069] The type of zirconia powder in the raw material composition is not particularly limited. When the zirconia powder contains zirconia but no stabilizer, or when the stabilizer content is increased as needed, stabilizer particles can be added separately. The stabilizer particles are not particularly limited as long as they can adjust the stabilizer content in the zirconia composite sintered body to the above-mentioned predetermined range. For example, a commercially available product may be used as the stabilizer particles, or a commercially available powder may be crushed using a known crushing and mixing device (such as a ball mill) before use.

[0070] The stabilizer may be either a stabilizer that is not solid-dissolved in zirconia or a stabilizer that is solid-dissolved in zirconia. In a preferred embodiment, a method for producing a zirconia composite sintered body includes a stabilizer (preferably YO) that is not solid-dissolved in zirconia in the raw material composition, because this is one factor that makes it easy to obtain the desired zirconia composite sintered body. The fact that the stabilizer includes one that is not solid-dissolved in zirconia can be confirmed, for example, by an X-ray diffraction (XRD) pattern.

[0071] When a peak attributable to the stabilizer is confirmed in the XRD pattern of the raw material composition or the molded body, it means that the stabilizer is present in the raw material composition or the molded body without being solid-dissolved in zirconia. When the entire amount of the stabilizer is solid-dissolved in zirconia, basically, no peak attributable to the stabilizer is confirmed in the XRD pattern. However, depending on conditions such as the crystalline state of the stabilizer, even if no stabilizer peak is present in the XRD pattern, the stabilizer may not be solid-dissolved in zirconia.

[0072] A case where the stabilizer contains a stabilizer that is not solid-dissolved in zirconia will be described below, taking as an example a case where the stabilizer is yttria.

[0073] In the raw material composition or the molded body of the present invention, the abundance rate f of yttria that is not dissolved in zirconia (hereinafter sometimes referred to as "undissolved yttria") is ycan be calculated based on the following formula (1): y =I 29 / (I 28 +I 29 +I 30 )×100 (1) (where f y represents the proportion (%) of undissolved yttria, and in the XRD measurement, I 28 represents the integrated intensity of the peak at around 2θ = 28° where the main peak of the monoclinic system appears, and I 29 represents the area intensity of the peak at 2θ=29° where the main peak of yttria appears, and I 30 represents the area intensity of the peak near 2θ = 30° where the main peak of the tetragonal or cubic crystal system appears.)

[0074] When a stabilizer other than yttria is used in combination, I 29 By substituting the peak of another stabilizer in place of yttria, the formula can also be applied to calculate the undissolved fraction of stabilizers other than yttria.

[0075] Undissolved yttria abundance f y From the viewpoint that the desired zirconia composite sintered body can be easily obtained, the abundance ratio f of undissolved yttria is preferably greater than 0%, more preferably 1% or more, even more preferably 2% or more, and particularly preferably 3% or more. y The upper limit may be, for example, 25% or less, but preferably depends on the content of yttria in the raw material composition or the compact.

[0076] For example, when the content of yttria in the raw material composition or the molded article of the present invention is 3 mol % or more and 8 mol % or less, the following applies: When the content of yttria is 3 mol % or more and less than 4.5 mol %, f y When the yttria content is 4.5 mol % or more and less than 5.8 mol %, f y When the content of yttria is 5.8 mol % or more and 8 mol % or less, f y can be 25% or less.

[0077] For example, when the content of yttria is 3 mol% or more and less than 4.5 mol%, f y is preferably 2% or more, more preferably 3% or more, even more preferably 4% or more, and particularly preferably 5% or more. When the yttria content is 4.5 mol% or more and less than 5.8 mol%, f y is preferably 3% or more, more preferably 4% or more, even more preferably 5% or more, even more preferably 6% or more, and particularly preferably 7% or more. When the yttria content is 5.8 mol% or more and 8 mol% or less, f y is preferably 4% or more, more preferably 5% or more, even more preferably 6% or more, even more preferably 7% or more, and particularly preferably 8% or more.

[0078] In the raw material composition or molded article of the present invention, the stabilizer does not have to be entirely dissolved in zirconia. In the present invention, the term "solid solution of the stabilizer" means, for example, that elements (atoms) contained in the stabilizer are dissolved in zirconia.

[0079] The NbO and / or TaO added to the raw material composition of the present invention is not particularly limited as long as the content of NbO and / or TaO contained in the zirconia composite sintered body can be adjusted to the above-mentioned predetermined range (e.g., 1 mol% to 9 mol%). The NbO and / or TaO are not particularly limited, and for example, commercially available products may be used, or the powder of the commercially available product may be crushed in a known crushing and mixing device (e.g., a ball mill) before use.

[0080] The process for preparing the raw material composition includes, for example, wet mixing the raw materials of the raw material composition in a solvent containing water to obtain the raw material composition. The raw materials of the raw material composition are zirconia, the stabilizer, at least one of NbO and TaO, and CrO. If the resulting zirconia composite sintered body contains a capping element or ion, it further contains a capping agent (e.g., a compound that can become a monovalent ion in a solvent containing water). Furthermore, the raw materials of the raw material composition may contain other components (such as a zirconia strengthening agent) as necessary.

[0081] The method for wet-mixing the raw materials in a solvent containing water is not particularly limited. For example, the raw materials may be wet-pulverized and mixed in a known pulverizing and mixing device (such as a ball mill) to form a slurry, and then the slurry may be dried and granulated to prepare a granular raw material composition.

[0082] In the wet mixing step, additives such as a binder, a plasticizer, a dispersant, an emulsifier, an antifoaming agent, a pH adjuster, a lubricant, etc. may be further contained. Each of the additives may be used alone or in combination of two or more.

[0083] The binder may be added to a slurry obtained by adding a primary powder consisting of a mixture of zirconia, Y2O3, Nb2O5 and / or Ta2O5, Cr2O3, and a capping agent to water, and then milling the slurry.

[0084] The binder is not particularly limited, and known binders can be used, such as polyvinyl alcohol binders, acrylic binders, wax binders (paraffin wax, etc.), methyl cellulose, carboxymethyl cellulose, polyvinyl butyral, polymethyl methacrylate, ethyl cellulose, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polystyrene, atactic polypropylene, and methacrylic resins.

[0085] Examples of the plasticizer include polyethylene glycol, glycerin, propylene glycol, and dibutyl phthalate.

[0086] Examples of dispersants include ammonium polycarboxylate (e.g., triammonium citrate), ammonium polyacrylate, acrylic copolymer resin, acrylic acid ester copolymer, polyacrylic acid, bentonite, carboxymethyl cellulose, anionic surfactants (e.g., polyoxyethylene alkyl ether phosphate esters such as polyoxyethylene lauryl ether phosphate esters), nonionic surfactants, olein glyceride, amine salt surfactants, oligosaccharide alcohols, and stearic acid.

[0087] Examples of emulsifiers include alkyl ethers, phenyl ethers, and sorbitan derivatives.

[0088] Examples of the antifoaming agent include alcohol, polyether, silicone, and wax.

[0089] Examples of pH adjusters include ammonia and ammonium salts (including ammonium hydroxides such as tetramethylammonium hydroxide).

[0090] Examples of the lubricant include polyoxyethylene alkyl ether and wax.

[0091] The solvent used in the wet mixing is not particularly limited as long as it contains water, and an organic solvent, a mixed solvent of water and an organic solvent, or water alone may be used. Examples of the organic solvent include ketone solvents such as acetone and ethyl methyl ketone; and alcohol solvents such as ethanol, 1-propanol, 2-propanol, 2-methyl-2-propanol, glycerin, diglycerin, polyglycerin, propylene glycol, dipropylene glycol, polypropylene glycol, ethylene glycol, diethylene glycol, polyethylene glycol, polyethylene glycol monomethyl ether, 1,2-pentanediol, 1,2-hexanediol, and 1,2-octanediol.

[0092] The raw material composition of the zirconia composite sintered body used in the present invention may contain ZrO2, YO3, Nb2O5, Ta2O5, Cr2O3, a capping agent, and, if necessary, other components in addition to the zirconia reinforcement, as long as the effects of the present invention are achieved. Examples of such other components include colorants (pigments and composite pigments), fluorescent agents, and SiO2. Each of the other components may be used alone, or two or more may be used in combination.

[0093] Examples of the pigment include an oxide of at least one element selected from the group consisting of V, Mn, Fe, Co, Ni, Zn, Y, Zr, Sn, Sb, Bi, Ce, Pr, Sm, Eu, Gd, Tb, and Er (specifically, NiO, etc.), and an oxide of at least one element selected from the group consisting of V, Mn, Fe, Co, Ni, Zn, Y, Zr, Sn, Sb, Bi, Ce, Pr, Sm, Eu, Gd, and Tb is preferred, and an oxide of at least one element selected from the group consisting of V, Mn, Fe, Co, Ni, Zn, Y, Zr, Sn, Sb, Bi, Ce, Sm, Eu, Gd, and Tb is more preferred. However, YO and CeO may be excluded from the pigment.

[0094] Examples of the composite pigment include (Zr, V)O2 and (Co, Zn)Al2O4.

[0095] Examples of the fluorescent agent include Y2SiO5:Ce, Y2SiO5:Tb, (Y, Gd, Eu)BO3, Y2O3:Eu, YAG:Ce, ZnGa2O4:Zn, and BaMgAl. 10 O 17 : Eu, etc.

[0096] Next, the obtained raw material composition is molded to produce a molded body. The molding method is not particularly limited, and known methods (for example, press molding) can be used.

[0097] When a zirconia molded body is produced by a method including a step of press-molding a raw material composition, the specific method of press-molding is not particularly limited, and the press-molding can be carried out using a known press-molding machine. Specific examples of the press-molding method include uniaxial pressing.

[0098] The pressing pressure is set to an optimum value depending on the size, open porosity, biaxial bending strength, and particle size of the raw material powder of the target compact, and is usually 5 MPa to 1000 MPa. By increasing the pressing pressure during molding in the above-mentioned production method, the pores of the obtained compact are more fully filled, the open porosity can be set lower, and the density of the compact can be increased. Furthermore, in order to increase the density of the obtained zirconia compact, a cold isostatic pressing (CIP) treatment may be further performed after uniaxial pressing.

[0099] Next, the obtained compact is sintered to obtain a zirconia composite sintered body. The sintering temperature (maximum sintering temperature) at which the compact is sintered to obtain the zirconia composite sintered body is, for example, preferably 1300°C or higher, more preferably 1350°C or higher, even more preferably 1400°C or higher, even more preferably 1450°C or higher, and particularly preferably 1500°C or higher. The sintering temperature is, for example, preferably 1680°C or lower, more preferably 1650°C or lower, and even more preferably 1600°C or lower. The method for producing the zirconia composite sintered body used in the present invention preferably includes a step of sintering the compact at a maximum sintering temperature of 1300 to 1680°C. The maximum sintering temperature is preferably a temperature in the atmosphere.

[0100] The holding time (holding time) at the maximum sintering temperature varies depending on the temperature, but is preferably 30 hours or less, more preferably 20 hours or less, even more preferably 10 hours or less, even more preferably 5 hours or less, particularly preferably 3 hours or less, and most preferably 2 hours or less. Furthermore, the holding time can be 25 minutes or less, 20 minutes or less, or 15 minutes or less. The holding time is preferably 1 minute or more, more preferably 5 minutes or more, and even more preferably 10 minutes or more. According to the manufacturing method of the present invention, a zirconia composite sintered body with excellent bending strength and machinability can be produced depending on the content of the stabilizer, Nb2O5, and / or Ta2O5. Furthermore, the sintering time may be shortened as long as the effects of the present invention are obtained. By shortening the sintering time, production efficiency can be improved and energy costs can be reduced.

[0101] In the method for producing a zirconia composite sintered body, the temperature rise rate during sintering of the compact is not particularly limited, but is preferably 0.1°C / min or more, more preferably 0.2°C / min or more, and even more preferably 0.5°C / min or more. The temperature rise rate is preferably 50°C / min or less, more preferably 30°C / min or less, and even more preferably 20°C / min or less. By setting the temperature rise rate at or above the lower limit, productivity is improved.

[0102] A common dental zirconia firing furnace can be used in the step of sintering the green body. Commercially available dental zirconia firing furnaces may be used. Examples of commercially available dental zirconia firing furnaces include Noritake Katana (registered trademark) F-1, F-1N, F-2, and F-2N (all manufactured by SK Medical Electronics Co., Ltd.).

[0103] Furthermore, the step of sintering the compact preferably includes a step of hot isostatic pressing (HIP) treatment in addition to sintering at the maximum sintering temperature. The HIP treatment can further improve the translucency and strength of the zirconia composite sintered body.

[0104] Hereinafter, the sintered body obtained by sintering at the maximum sintering temperature will be referred to as a "primary sintered body," and the sintered body after HIP treatment will be referred to as a "HIP-treated sintered body."

[0105] The HIP treatment can be carried out using a known hot isostatic press (HIP) device.

[0106] The temperature of the HIP treatment is not particularly limited, but is preferably 1200° C. or higher, more preferably 1300° C. or higher, and even more preferably 1400° C. or higher, because a dense zirconia composite sintered body with high strength can be obtained. The temperature of the HIP treatment is also preferably 1700° C. or lower, more preferably 1650° C. or lower, and even more preferably 1600° C. or lower.

[0107] In the method for producing the zirconia composite sintered body, when the primary sintered body is subjected to the HIP treatment, the pressure of the HIP treatment is not particularly limited, but is preferably 100 MPa or more, more preferably 125 MPa or more, and even more preferably 130 MPa or more, because a dense sintered body with high strength can be obtained. The upper limit of the pressure of the HIP treatment is not particularly limited, but can be, for example, 400 MPa or less, 300 MPa or less, or even 200 MPa or less.

[0108] In the method for producing the zirconia composite sintered body, when the primary sintered body is subjected to HIP treatment, the temperature rise rate is not particularly limited, but is preferably 0.1°C / min or more, more preferably 0.2°C / min or more, and even more preferably 0.5°C / min or more. The temperature rise rate is preferably 50°C / min or less, more preferably 30°C / min or less, and even more preferably 20°C / min or less. By setting the temperature rise rate at or above the lower limit, productivity is improved.

[0109] In the method for producing a zirconia composite sintered body used in the present invention, when the primary sintered body is subjected to HIP treatment, the HIP treatment time is not particularly limited, and since a dense zirconia composite sintered body with high strength can be obtained, the HIP treatment time is preferably 5 minutes or more, more preferably 10 minutes or more, and even more preferably 30 minutes or more. Moreover, the HIP treatment time is preferably 10 hours or less, more preferably 6 hours or less, and even more preferably 3 hours or less.

[0110] In the method for producing the zirconia composite sintered body, when the primary sintered body is subjected to HIP treatment, the pressure medium is not particularly limited, and from the viewpoint of low influence on zirconia, at least one pressure medium selected from the group consisting of oxygen gas, oxygen mixed gas, air, and inert gas (e.g., nitrogen gas, argon gas, etc.) can be selected as the pressure medium. When the primary sintered body is HIP treated in an oxygen mixed gas atmosphere, the oxygen concentration is not particularly limited, but can be, for example, more than 0% to 20% or less. When an oxygen mixed gas is used, at least one inert gas (e.g., nitrogen gas, argon gas, etc.) can be selected as the gas other than oxygen.

[0111] In the method for producing the zirconia composite sintered body, if the HIP treatment is performed in a reducing atmosphere, such as using an inert gas, black discoloration may occur due to oxygen defects. In this case, to remove the black discoloration, it is preferable to include a heat treatment step (hereinafter also referred to as "tempering treatment") in air or an oxygen-rich atmosphere at 1650°C or less after the HIP treatment step. From the viewpoint of efficient heat treatment, it is more preferable to perform the heat treatment in an oxygen-rich atmosphere. In this specification, "oxygen-rich atmosphere" means that the oxygen concentration is higher than that of air. The oxygen-rich atmosphere is not particularly limited as long as the oxygen concentration is more than 21% and less than or equal to 100%, and can be appropriately selected from this range. For example, the oxygen concentration may be 100%.

[0112] The zirconia composite sintered body used in the present invention is not particularly limited as long as it exhibits the effects of the present invention, and may be a primary sintered body, a HIP-treated sintered body, or a sintered body after tempering. A preferred embodiment is a zirconia composite sintered body that is a sintered body after tempering.

[0113] The temperature of the heat treatment in the air or in an oxygen-excess atmosphere can be appropriately changed depending on the aesthetics of the zirconia composite sintered body (e.g., the shade of a dental prosthesis). In a preferred embodiment, the temperature of the heat treatment in the air or in an oxygen-excess atmosphere is preferably 1650°C or less, more preferably 1600°C or less, and even more preferably 1550°C or less, from the viewpoint of the aesthetics of the zirconia composite sintered body. In another preferred embodiment, the temperature of the heat treatment in the air or in an oxygen-excess atmosphere is preferably 1400°C or less, more preferably 1300°C or less, and even more preferably 1200°C or less, from the viewpoint of the aesthetics of the zirconia composite sintered body. Furthermore, in any embodiment, the temperature of the heat treatment is preferably 500°C or more, more preferably 600°C or more, and even more preferably 700°C or more.

[0114] A general dental zirconia firing furnace can be used for the tempering treatment. Commercially available dental zirconia firing furnaces may be used. Examples of commercially available dental zirconia firing furnaces include Noritake Katana (registered trademark) F-1, F-1N, and F-2 (all manufactured by SK Medical Electronics Co., Ltd.).

[0115] The zirconia composite sintered body used in the present invention has excellent machinability despite being a sintered body, so there is no need to machine a semi-sintered calcined body in the form of a mill blank and then sinter it to form a sintered body. On the other hand, a method for producing a zirconia composite sintered body may also be a method in which a molded body obtained using the raw material composition is calcined to produce a semi-sintered calcined body, and the unprocessed calcined body is then machined to form a sintered body.

[0116] Another example of a method for producing a zirconia composite sintered body is a method for producing a zirconia composite sintered body, which includes the steps of: preparing a molded body from the raw material composition; calcining the obtained molded body to obtain a zirconia composite calcined body (calcining step); and sintering the zirconia composite calcined body.

[0117] In order to ensure blocking, the firing temperature (calcination temperature) in the calcination step is, for example, preferably 800°C or higher, more preferably 900°C or higher, and even more preferably 950°C or higher. The calcination temperature is, for example, preferably 1200°C or lower, more preferably 1150°C or lower, and even more preferably 1100°C or lower. The calcination temperature is preferably, for example, 800°C to 1200°C. At such a calcination temperature, it is believed that the dissolution of the stabilizer does not progress significantly in the calcination step.

[0118] The density of the zirconia composite calcined body is 2.7 g / cm 3 The density of the zirconia composite calcined body is preferably 4.0 g / cm 3 Preferably, 3.8 g / cm or less 3 More preferably, 3.6 g / cm 3 The following is more preferable. When the density is within this range, processing can be easily performed. The density of the composite calcined body can be calculated, for example, by dividing the mass of the composite calcined body by the volume of the composite calcined body.

[0119] The three-point bending strength of the zirconia composite calcined body is preferably 15 to 70 MPa, more preferably 18 to 60 MPa, and even more preferably 20 to 50 MPa. The bending strength can be measured using a test piece measuring 5 mm thick, 10 mm wide, and 50 mm long, in accordance with ISO 6872:2015, except for the size of the test piece. The test piece's face and C-face (the surface where the corners of the test piece are chamfered at a 45° angle) are surface-finished in the longitudinal direction with 600-grit sandpaper. The test piece is positioned so that the widest surface faces vertically (the load direction). In the bending test, the span is 30 mm, and the crosshead speed is 1.0 mm / min.

[0120] The step of sintering the zirconia composite calcined body can be carried out by the same method and under the same conditions (temperature, pressure, etc.) as those used in the step of sintering the molded body described above. Therefore, in the embodiment of the production method using the zirconia composite calcined body, the "molded body" can be read as the "calcined body."

[0121] The zirconia composite sintered body used in the present invention has excellent strength. The biaxial bending strength of the zirconia composite sintered body used in the present invention is preferably 300 MPa or more, more preferably 350 MPa or more, even more preferably 400 MPa or more, even more preferably 450 MPa or more, and particularly preferably 500 MPa or more. When the zirconia composite sintered body used in the present invention has such a biaxial bending strength, it can suppress intraoral fracture when used, for example, as a dental prosthesis. There is no particular upper limit to the biaxial bending strength, but the biaxial bending strength can be, for example, 1200 MPa or less, or even 1000 MPa or less. The biaxial bending strength of the zirconia composite sintered body can be measured in accordance with ISO 6872:2015.

[0122] ΔL * is the brightness (first L) of the same sample on a white background. * value) and lightness on a black background (second L * Specifically, the difference between the L * Value (JIS Z 8781-4:2013 Colorimetry - Part 4: CIE 1976 L * a * b * color space) and L on a black background * The white background refers to the white portion of the hiding power test paper described in JIS K 5600-4-1:1999 Part 4, Section 1, and the black background refers to the black portion of the hiding power test paper.

[0123] ΔL * There is no particular upper limit to the value, but it can be, for example, 25 or less, and from the viewpoint of aesthetics, even 20 or less.

[0124] In addition, ΔL when the zirconia composite sintered body has a diameter of 15 mm and a thickness of 1.2 mm * can be measured using a spectrophotometer, for example, a spectrophotometer (product name "CM-26d", di: 8°, de: 8° (diffuse illumination (integrating sphere) method, light reception in 8° direction), manufactured by Konica Minolta Japan, Inc.).

[0125] Another zirconia composite sintered body used in the present invention contains zirconia, a stabilizer capable of suppressing the phase transition of zirconia, Nb2O5 and / or Ta2O5, and Cr, and in which, in a total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5, the zirconia content is 73 to 97.5 mol%, the stabilizer content is 1 to 12 mol%, the Nb2O5 and / or Ta2O5 content is 1 mol% or more and 9 mol% or less, and further contains elements or ions derived from a capping agent as necessary, and the L measured on a sample with a thickness of 1.2 mm is * a * b * L on a white background in the color space * Values ​​are 40 to 90, a * Values ​​are 1.0 to 15, b * Examples of suitable zirconia composite sintered bodies include those having a value of 0 to 30.

[0126] The L measured on the 1.2 mm thick sample * a * b * L on a white background in the color space * Value, a * value, b * The method for measuring the values ​​is as described in the Examples below.

[0127] In the zirconia composite sintered body, the type of the stabilizer, the type of element or ion derived from the capping agent, and the zirconia content, the stabilizer content, the NbO and / or TaO content, the Cr content calculated as CrO, and the content of the element or ion derived from the capping agent are the same as those in the above-mentioned embodiment.

[0128] In the zirconia composite sintered body, L * The value is preferably 40 or more, more preferably 45 or more, even more preferably 48 or more, and particularly preferably 50 or more. *The value is preferably 90 or less, more preferably 85 or less, even more preferably 82 or less, and particularly preferably 80 or less.

[0129] In the zirconia composite sintered body, * The value is preferably 1.0 or more, more preferably 1.5 or more, even more preferably 2.0 or more, and particularly preferably 3.5 or more. * The value is preferably 15 or less, more preferably 12 or less, even more preferably 10 or less, and particularly preferably 9 or less. Since it can be appropriately selected depending on the target shade (A2, A3, etc.), the upper and lower limits can be appropriately combined within the above range. For example, * The value may be 1.0 or more and 10 or less.

[0130] In the zirconia composite sintered body, b * The value is preferably 0 or more, more preferably 2.0 or more, even more preferably 5.0 or more, and particularly preferably 10.0 or more. * The value is preferably 30 or less, more preferably 29 or less, even more preferably 28 or less, and particularly preferably 25 or less.

[0131] The zirconia composite sintered body may further contain a zirconia strengthening agent, the type and content of which may be the same as those in the above-described embodiment.

[0132] Furthermore, when the zirconia composite sintered body of the present invention contains zirconia, a stabilizer capable of suppressing the phase transition of zirconia, NbO and / or TaO, and Cr, but does not contain a capping element or ion, it can be produced in the same manner as the above-mentioned method for producing a zirconia composite sintered body when the zirconia composite sintered body contains a capping element or ion, except that the raw material composition does not contain a capping agent. Furthermore, the zirconia composite sintered body can also be produced in accordance with the production method disclosed in WO 2021 / 132644, depending on the content of each component and / or the crystal system of zirconia.

[0133] Dental prostheses manufactured using the zirconia composite sintered body used in the present invention include, for example, crown restorations such as inlays, onlays, veneers, crowns, core-integrated crowns, and bridges, as well as abutments, dental posts, dentures, denture bases, and implant components (fixtures and abutments). Machining is preferably performed using, for example, a commercially available dental CAD / CAM system. Examples of such CAD / CAM systems include the "CEREC System" manufactured by Dentsply Sirona Dental Systems Inc. and the "Katana (registered trademark) System" manufactured by Kuraray Noritake Dental Co., Ltd.

[0134] The zirconia composite sintered body used in the present invention can also be used for applications other than dental applications, and is particularly suitable for zirconia components requiring irregular or complex shapes and strength. Compared to sintered bodies produced solely by existing manufacturing methods (e.g., injection molding, CIP, slip casting, or 3D printing), the zirconia composite sintered body used in the present invention can be processed as is. Therefore, for example, it is economical when the desired zirconia component can be obtained in a short time. For complex-shaped components difficult to produce by conventional manufacturing methods, it is possible to obtain zirconia components that maintain high strength by eliminating the need to mechanically fit multiple components. Furthermore, since the sintered body can be processed as is, a sintering process is not required when dimensional precision is required, and uneven firing shrinkage is eliminated, resulting in highly accurate zirconia components. Specifically, it can be used as a method for producing jewelry, engine and interior components for mobility such as aircraft and automobiles, display panel frames, building components, electrical appliance components, household goods components, and toy parts. The zirconia component may also be fitted with a different material to form a composite component.

[0135] The present invention includes embodiments in which all or part of the above configurations are combined in various ways within the scope of the technical concept of the present invention, as long as the effects of the present invention are achieved.

[0136] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to these examples, and many modifications within the scope of the technical concept of the present invention are possible by those skilled in the art.

[0137] [Examples 1 to 11 and Comparative Examples 1 to 5] Measurement samples for each of the Examples and Comparative Examples were prepared through the steps of preparing a granular raw material composition, preparing a compact, and preparing a sintered body (preparing a primary sintered body, HIP treatment, and tempering treatment).

[0138] [Preparation of Granular Raw Material Compositions] To prepare the granular raw material compositions of each Example and Comparative Example, commercially available ZrO powder, YO powder, NbO powder, or TaO powder, coloring components (components such as CrO listed in Tables 1 and 2), and optionally a capping agent and TiO powder were mixed so that the content of each component in the sintered zirconia composite sintered body would be the composition listed in Tables 3 and 4. Water was added to prepare a slurry, which was then wet-pulverized and mixed in a ball mill until the average particle size was 0.13 μm or less. A binder was added to the pulverized slurry, which was then dried in a spray dryer to prepare a granular raw material composition (hereinafter also simply referred to as the "raw material composition"), which was used to produce the molded body described below. The average particle diameter is a value measured on a volume basis using a laser diffraction / scattering particle size distribution measuring device (Partica LA-950, manufactured by Horiba, Ltd.) by irradiating a slurry diluted with water with ultrasonic waves for 30 minutes and then applying ultrasonic waves.

[0139] [Preparation of Molded Body] For each Example and Comparative Example, pellet-shaped compacts and block-shaped compacts were prepared as follows to obtain sintered body samples for evaluating machinability, translucency, biaxial bending strength, and color tone. For pellet-shaped compacts, a cylindrical mold with a diameter of 19 mm was used, and the raw material composition was placed in the mold so that the thickness of the zirconia composite sintered body after sintering would be 1.2 mm. Next, the raw material composition was press-molded using a uniaxial press molding machine at a surface pressure of 200 MPa for 10 seconds to prepare a pellet-shaped compact.

[0140] For the block-shaped compact, the raw material composition was placed in a mold having an inner dimension of 19 mm × 18 mm so that the thickness of the zirconia composite sintered body after sintering would be 14.5 mm. Next, the raw material composition was press-molded using a uniaxial press molding machine at a surface pressure of 200 MPa for 90 seconds to produce a block-shaped compact.

[0141] [Preparation of primary sintered body] The pellet-shaped and block-shaped compacts obtained were held in the air for 2 hours at the maximum sintering temperature shown in Tables 1 and 2 using a sintering furnace "Noritake Katana (registered trademark) F-1" manufactured by SK Medical Electronics Co., Ltd., to obtain pellet-shaped and block-shaped zirconia composite sintered body (primary sintered body) samples. However, in Examples 9 to 11, the holding time at the maximum sintering temperature was changed to 50 hours.

[0142] [Preparation of HIP-treated sintered body] The obtained pellet-shaped and block-shaped zirconia composite sintered bodies (primary sintered bodies) were subjected to a HIP apparatus "O2-Dr. HIP" manufactured by Kobe Steel, Ltd., under an argon atmosphere at 150 MPa at the HIP treatment temperatures shown in Tables 1 and 2 for 2 hours, thereby obtaining pellet-shaped and block-shaped zirconia composite sintered body (HIP-treated sintered body) samples.

[0143] [Preparation of zirconia composite sintered body (tempered sintered body)] The obtained pellet-shaped and block-shaped zirconia composite sintered body (HIP-treated sintered body) was subjected to heating at 700°C for 60 hours in a Noritake Katana (registered trademark) F-1 firing furnace manufactured by SK Medical Electronics Co., Ltd., to obtain pellet-shaped and block-shaped zirconia composite sintered body (tempered sintered body) samples. The pellet-shaped samples had a diameter of 15 mm and a thickness of 1.2 mm, and the block-shaped samples had a width of 15.7 mm, a length of 16.5 mm, and a height of 14.5 mm.

[0144] [Evaluation of Workability of Zirconia Composite Sintered Body] Thirty samples of block-shaped zirconia composite sintered body (sintered body after tempering) of each Example and Comparative Example were prepared by attaching a metal jig to a surface of approximately 15.7 mm wide x 14.5 mm high, and processed into a general anterior tooth crown shape using the CEREC system "MC-XL" (manufactured by Dentsply Sirona). The processing program used the software "inLab (registered trademark) CAM version 20.0.1.203841", manufacturer: IVOCLAR VIVADENT, material name: IPS e. Max CAD, Production Method: Grinding, Block size: C16 were selected, and Step Bur 12 and Cylinder Pointed Bur 12S were used as machining tools.

[0145] [Machining Time] The machining times shown in Tables 3 and 4 are the time required to complete machining of the first sample using a new machining tool under the conditions described in the above [Evaluation of the Machinability of Zirconia Composite Sintered Body]. If an error occurred due to the load during machining or other reasons and the CEREC system "MC-XL" stopped midway through machining, a new machining tool was installed and machining was resumed. This operation was repeated until one sample was completely machined, and the time required was recorded as the machining time. In the evaluation of [Number of Machined Pieces] below, samples rated as "unmachinable" were unable to be machined into the crown shape of a front tooth using a single machining tool, and therefore the machining time was also rated as "unmachinable."

[0146] [Number of Pieces Machined] The number of pieces machined shown in Tables 3 and 4 refers to the number of pieces machined into a front tooth crown shape using a new set of machining tools under the conditions described in the above [Evaluation of Zirconia Composite Sintered Compacts Machinability] without changing the machining tools. A maximum of 30 samples were used for the test. If machining of up to 30 samples could be completed using one machining tool, no additional machining tests were conducted and the test was uniformly rated as "30 or more." Furthermore, if an error occurred due to a machining load or other reason, causing the MC-XL to stop mid-machining before completing machining of the first sample, the tool was replaced with a new one and machining resumed. This process was repeated until one sample was completely machined, and the number of pieces machined was calculated as the reciprocal of the number of machining tools used. The results are shown in Tables 3 and 4 below. Samples that could not be machined into a front tooth crown shape even using multiple machining tools were rated as "unmachinable."

[0147] [Evaluation of Translucency of Zirconia Composite Sintered Body] Using samples (diameter approximately 15 mm × thickness 1.2 mm) of pellet-shaped zirconia composite sintered bodies (sintered bodies after tempering treatment) of each Example and Comparative Example as they were, the translucency was evaluated by the following method (n = 3). As a measuring device, a spectrophotometer (product name "CM-26d", di: 8°, de: 8° (diffuse illumination (integrating sphere) method, light reception in 8° direction), manufactured by Konica Minolta Japan, Inc.) was used. First, the background (underlay) of the sample was set to white (the side opposite to the measuring device was set to white) and the L * a * b * Color system (JIS Z 8781-4:2013 Colorimetry - Part 4: CIE 1976 L * a * b * The L* value of the first L * Next, the first L * For the same sample for which the value was measured, the background (underlay) of the sample was black (the side opposite to the measuring device was black) and the L * a * b * Color system L * The value is measured and the second L * In the present invention, the first L * value and the second L *The difference between the first L * value to the second L * The value obtained by subtracting the value of ΔL * It is written as ΔL * If ΔL is high, the light transmittance is high. * A lower ΔL indicates lower light transmittance. For the black and white background (underlay) used in measuring chromaticity, the hiding power test paper used in measuring paints described in JIS K 5600-4-1:1999 was used. * The arithmetic mean values ​​of ΔL are shown in Tables 3 and 4. * A score of 1 or above was considered a pass.

[0148] [Strength Evaluation of Zirconia Composite Sintered Body] Using samples of the pellet-shaped zirconia composite sintered body (sintered body after tempering treatment) of each Example and Comparative Example as is, the biaxial bending strength was measured in accordance with ISO 6872:2015 using a universal testing machine "AGS-X" (manufactured by Shimadzu Corporation) at a crosshead speed of 1.0 mm / min (n=5). The arithmetic mean values ​​are shown as the measurement results in Tables 3 and 4. A strength of 300 MPa or more was considered acceptable.

[0149] [Evaluation of Color Tone of Zirconia Composite Sintered Body] Using samples (diameter approximately 15 mm × thickness 1.2 mm) of pellet-shaped zirconia composite sintered bodies (sintered bodies after tempering treatment) of each Example and Comparative Example as they were, the color tone was evaluated by the following method (n = 3). As a measuring device, a spectrophotometer (product name "CM-26d", di: 8°, de: 8° (diffuse illumination (integrating sphere) method, light reception in 8° direction), manufactured by Konica Minolta Japan Inc.) was used, and the background (underlay) of the sample was set to white (the side opposite to the measuring device was set to white) and the L * a * b * Color system (JIS Z 8781-4:2013 Colorimetry - Part 4: CIE 1976 L * a * b * Color space) L * , a * , and b *The white background (underlay) used in the measurement was the hiding power test paper used for measuring paints as described in JIS K 5600-4-1:1999. The suitability for use as a reddish-brown dental color is determined by visual evaluation, but the numerical criteria are as follows: * The results are shown in Tables 3 and 4.

[0150] [Evaluation of color development stability of zirconia composite sintered body] In each example and comparative example, the color data (L * 1. a * 1, b * 1), (L * 2. a * 2, b * 2), (L * 3. a * 3. b * 3), and the color difference ΔE between each sample * The color stability was evaluated by ΔE * is calculated using the following formulas (2) to (4), and the obtained ΔE * The case where all the values ​​were 2.7 or less was judged to be acceptable, and the case where even one value exceeded 2.7 was judged to be unacceptable because a uniform color tone could not be obtained. The results are shown in Tables 3 and 4. ΔE * 12 = {(L * 1-L * 2) 2 + (a * 1-a * 2) 2 +(b * 1-b * 2) 2} 1 / 2 (2) ΔE * 13 = {(L * 1-L * 3) 2 + (a * 1-a * 3) 2 +(b * 1-b * 3) 2} 1 / 2 (3) ΔE *23 = {(L * 2-L * 3) 2 + (a * 2-a * 3) 2 +(b * 2-b * 3) 2} 1 / 2 (4)

[0151] The content of each component of the sintered body in Tables 3 and 4 is a value calculated from the amount of raw material charged. The content (mol%) of a capping element or ion (e.g., Na) in Tables 3 and 4 is the external addition rate relative to the total of 100 mol% of zirconia (total of ZrO2 and HfO2), the stabilizer (yttria), Nb2O5, and Ta2O5. The content (mol%) of zirconia (total of ZrO2 and HfO2), the stabilizer, Nb2O5, and Ta2O5 in Tables 3 and 4 is the content of each component relative to the total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5. The content (mass%) of coloring components and TiO2 in Tables 3 and 4 is the external addition rate relative to the total of 100 mol% of zirconia, the stabilizer, Nb2O5, and Ta2O5. In Tables 3 and 4, "A / B" represents the ratio of A to B when the content of Y2O3 is A mol % and the total content of Nb2O5 and Ta2O5 is B mol %.

[0152]

[0153]

[0154]

[0155]

[0156] From the above results, the zirconia composite sintered bodies of Examples 1 to 8 had excellent machinability in the sintered state and excellent stability in the reddish-brown coloring. More specifically, Examples 1 to 3 and 6 to 8 exhibited stable reddish-brown coloring, and it is believed that adding other pigment components can favorably reproduce tooth crown colors (especially dark shades). Furthermore, in Examples 4 and 5, the tooth crown color of dark shades itself was favorably reproduced. It is believed that the coloring performance of Cr changed in relation to NbO and / or TaO, and stable reddish-brown coloring was achieved. Furthermore, Examples 9 and 10 exhibited stable reddish-brown coloring, and Example 11 favorably reproduced the tooth crown color of dark shades itself. In contrast, the zirconia composite sintered bodies of Comparative Examples 1, 2, and 5 could not be machined. Furthermore, the zirconia composite sintered body according to Comparative Example 3 did not produce a stable reddish-brown color, and the zirconia composite sintered body according to Comparative Example 4 did not produce the desired reddish-brown color (dark gray), and therefore could not be industrially produced as a product.

[0157] The zirconia composite sintered body used in the present invention has excellent machinability in the sintered state and excellent stability of reddish-brown coloring, and is particularly useful as a dental material for dental prostheses and other dental treatments.

Claims

1. A zirconia composite sintered body comprising zirconia, a stabilizer capable of suppressing the phase transition of zirconia, Nb₂O₅ and / or Ta₂O₅, and Cr.

2. The zirconia composite sintered body according to claim 1, wherein the content of Cr calculated as Cr₂O₃ is more than 0% by mass and 0.1% by mass or less with respect to 100% by mass in total of zirconia, a stabilizer capable of suppressing the phase transition of zirconia, Nb₂O₅ and Ta₂O₅.

3. In 100 mol% in total of zirconia, a stabilizer capable of suppressing the phase transition of zirconia, Nb₂O₅ and Ta₂O₅, - the content of zirconia is 78 mol% or more and 97.5 mol% or less, - the content of the stabilizer is 1 mol% or more and 12 mol% or less, - the content of Nb₂O₅ and / or Ta₂O₅ is 1 mol% or more and 9 mol% or less. The zirconia composite sintered body according to claim 1 or 2.

4. The zirconia composite sintered body according to claim 1 or 2, wherein the content of NiO is less than 0.01% by mass with respect to 100% by mass in total of zirconia, a stabilizer capable of suppressing the phase transition of zirconia, Nb₂O₅ and Ta₂O₅.

5. The zirconia composite sintered body according to claim 1 or 2, further comprising an element or ion derived from a capping agent.

6. The zirconia composite sintered body according to claim 5, wherein the content of the element or ion derived from the capping agent is more than 0 mol% and 5 mol% or less with respect to 100 mol% in total of zirconia, the stabilizer, Nb₂O₅, and Ta₂O₅.

7. The zirconia composite sintered body according to claim 5, wherein the element or ion derived from the capping agent belongs to the 2nd to 7th periods of the periodic table and is an element or its ion having a first ionization energy smaller than that of the element of Group 18 in the same period, and / or an element or its ion having a high electron affinity.

8. The zirconia composite sintered body according to claim 5, wherein the element or ion derived from the capping agent contains at least one element or its ion selected from the group consisting of Cu, Ag, Li, Na, K, Rb, Cs, Fr, At, I, Br, Cl, and F.

9. The zirconia composite sintered body according to claim 5, wherein the element or ion derived from the capping agent contains at least one element or its ion selected from the group consisting of Li, Na, K, Rb, Cs, and Fr.

10. The zirconia composite sintered body according to claim 3, wherein when the content of the stabilizer is Amol% and the total content of Nb2O5 and Ta2O5 is Bmol%, the ratio of A / B is 0.9 or more and 3 or less.

11. The zirconia composite sintered body according to claim 3, wherein the stabilizer contains Y2O3 and / or CeO2.

12. The zirconia composite sintered body according to claim 3, further comprising a zirconia strengthening agent, wherein the content of the zirconia strengthening agent is more than 0% by mass and 6.0% by mass or less based on the total 100% by mass of zirconia, the stabilizer, Nb2O5 and Ta2O5.

13. The zirconia composite sintered body according to claim 12, wherein the zirconia strengthening agent contains TiO2 and / or Al2O3.

14. The zirconia composite sintered body according to claim 13, wherein the zirconia strengthening agent contains TiO2, and the content of TiO2 is 0.6% by mass or more and 4.5% by mass or less.

15. The zirconia composite sintered body according to claim 1 or 2, wherein the average crystal grain size of the zirconia composite sintered body is 0.5 to 5.0 μm.

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