Zirconia molded bodies, zirconia calcined bodies, and zirconia sintered bodies, and methods for manufacturing the same.

Abstract

The present invention provides: a zirconia sintered body which has both of excellent mechanical strength and excellent light transmissiveness; a zirconia green body which can provide the zirconia sintered body and contains a binder in such an amount that a thickness of 10 mm or more is intended; a zirconia calcined body; and methods respectively for producing the zirconia sintered body, the zirconia green body and the zirconia calcined body. The present invention relates to a zirconia green body which comprises zirconia particles containing yttria in an amount of 2.0 to 9.0 mol% relative to the total number of moles of zirconium oxide and yttria and having an average primary particle diameter of 60 nm or less, a polyol, and a binder, in which the polyol and the binder satisfy a relational formula.　X1<Y1<X2<Y2≤500°C (wherein the explanation about the symbols is left out).

Description

[Technical Field]

[0001] The present invention relates to zirconia molded articles and the like. More specifically, the present invention relates to a zirconia sintered article having excellent mechanical strength and light transmittance, a zirconia molded article containing a binder capable of giving such a zirconia sintered article and having a thickness of 10 mm or more, a calcined zirconia article, and methods for manufacturing these. [Background technology]

[0002] Zirconia sintered bodies containing yttria have recently been used in dental materials such as dental prostheses. These dental prostheses are often manufactured by first forming a zirconia molded body in a desired shape, such as a disc or prismatic shape, by press-molding zirconia particles or by using a slurry or composition containing zirconia particles. This molded body is then calcined to form a calcined body (mill blank), which is then milled into the shape of the intended dental prosthesis, and finally sintered.

[0003] To date, it has been confirmed that reducing the grain size and uniformity of zirconia sintered bodies improves the linear light transmittance (see, for example, Patent Document 1). Reducing the grain size and uniformity of zirconia sintered bodies requires hot isostatic pressing (HIP) treatment. However, since the HIP equipment used for HIP treatment is a special device classified as high-pressure gas manufacturing equipment, it is difficult to say that zirconia sintered bodies with high linear light transmittance can be easily obtained.

[0004] Therefore, zirconia sintered bodies with excellent mechanical strength and light transmittance without the use of a HIP device, zirconia molded bodies that can obtain such zirconia sintered bodies, and zirconia calcined bodies have also been proposed (Patent Document 2). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-214168 [Patent Document 2] International Publication No. 2020 / 179876 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] In addition, in order to obtain a desired zirconia molded body, particularly a zirconia molded body having a thickness of 10 mm or more, it is necessary to add a binder for shape retention. The shape retention improves as the amount of the binder added increases. However, as a result of the inventors' studies, it has become clear that when the amount of the binder added increases, the translucency significantly decreases due to the amount of the binder.

[0007] Therefore, when a zirconia molded body containing an amount of binder assumed to have a thickness of 10 mm or more is used, a zirconia sintered body having both excellent mechanical strength and translucency has not been obtained.

[0008] An object of the present invention is to provide a zirconia sintered body having both excellent mechanical strength and translucency, a zirconia molded body capable of providing such a zirconia sintered body and containing an amount of binder assumed to have a thickness of 10 mm or more, and a zirconia green compact, and methods for producing them. Another object of the present invention is to provide methods for producing a zirconia sintered body having both excellent mechanical strength and translucency, a zirconia molded body and a zirconia green compact capable of providing such a zirconia sintered body, without using a HIP apparatus, and which can be simply produced. [Means for Solving the Problems]

[0009] The inventors, through diligent research to achieve the above objectives, have found that the above problems can be solved in a zirconia molded body containing zirconia particles with an average primary particle diameter of 60 nm or less, containing yttria in an amount of 2.0 to 9.0 mol% relative to the total number of moles of zirconium oxide and yttria, a polyol, and a binder, by focusing on the combustion start temperature and combustion end temperature of the polyol and binder, and finding that these satisfy a specific relationship. Furthermore, they have found that such a zirconia sintered body is particularly suitable as a dental material such as dental prostheses, and is extremely useful not only as a dental prosthesis used in the cervical area of ​​the tooth, but also as a dental prosthesis used in the occlusal surface of molars or the incisal edge of anterior teeth. Based on these findings, the inventors have conducted further research and completed the present invention.

[0010] In other words, the present invention encompasses the following inventions. [1] Zirconia particles containing yttria in an amount of 2.0 to 9.0 mol% relative to the total number of moles of zirconium oxide and yttria, and having an average primary particle diameter of 60 nm or less, It contains a polyol and a binder. A zirconia molded article wherein the polyol and the binder satisfy the following relationship. X1 <Y1<X2<Y2≦500℃ (In the formula, X1 represents the combustion start temperature of the polyol, X2 represents the combustion end temperature of the polyol, Y1 represents the combustion start temperature of the binder, Y2 represents the combustion end temperature of the binder, X1 and Y1 represent the temperatures at which a 0.5% weight loss is observed, with the weight before heating measured by thermogravimetric analysis being 100%, and X2 and Y2 represent the temperatures at which a 99.5% weight loss is observed.) [2] The zirconia molded article described in [1], having a thickness of 10 mm or more. [3] The zirconia molded article according to [1] or [2], wherein the combustion start temperature (X1) of the polyol is 50°C or higher. [4] ΔL at a thickness of 1.5 mm * A zirconia molded article according to any of [1] to [3], wherein the (WB) is 5 or greater. [5] A zirconia molded article according to any one of [1] to [4], wherein the grain size after sintering at 900 to 1200°C under normal pressure is 180 nm or less. [6] A zirconia molded article according to any one of [1] to [5], wherein the three-point bending strength after sintering at 900 to 1200°C under normal pressure is 500 MPa or more. [7] A zirconia molded article according to any one of [1] to [6], wherein the transmittance of light with a wavelength of 700 nm at a thickness of 0.5 mm after sintering at 900 to 1200 °C under normal pressure is 40% or more. [8] A zirconia molded article according to any one of [1] to [7], wherein the linear light transmittance at a thickness of 1.0 mm after sintering at 900 to 1200°C under normal pressure is 1% or more. [9] 28.5 μm after sintering at 900-1200°C under normal pressure. 2 A zirconia molded article according to any one of [1] to [8], wherein the number of pores with a diameter of 50 nm or more per unit cross-sectional area is 10 or less.

[10] ΔL at a thickness of 1.5 mm after calcination at 200-800°C * A zirconia molded article according to any of [1] to [9], wherein the (WB) is 5 or greater.

[11] Contains yttria in an amount of 2.0 to 9.0 mol% relative to the total number of moles of zirconium oxide and yttria, and ΔL at a thickness of 1.5 mm. * (WB) is 5 or higher, and the 28.5 μm after sintering at 900-1200°C 2 A calcined zirconia body having 10 or fewer pores with a diameter of 50 nm or more per unit cross-sectional area, and a thickness of 10 mm or more. A method for producing a calcined zirconia body, comprising the step of calcining a zirconia molded body described in any of

[12] [1] to

[10] at 200 to 800°C.

[13] Contains yttria in an amount of 2.0 to 9.0 mol% relative to the total number of moles of zirconium oxide and yttria, and is 28.5 μm 2 A zirconia sintered body having 10 or fewer pores with a diameter of 50 nm or more per unit cross-sectional area, and a thickness of 10 mm or more. A method for producing a zirconia sintered body, comprising the step of sintering a zirconia molded body described in any of [1] to

[10] or a zirconia calcined body described in

[11] at 900 to 1200°C under normal pressure. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a zirconia sintered body with excellent mechanical strength and light transmittance, a zirconia molded body and a zirconia calcined body containing an amount of binder that is expected to give such a zirconia sintered body and a thickness of 10 mm or more, and a method for manufacturing these. Furthermore, according to the present invention, it is possible to provide a method for manufacturing a zirconia sintered body with excellent mechanical strength and light transmittance, a zirconia molded body and a zirconia calcined body that can give such a zirconia sintered body, in a simple manner without using a HIP (High-Intensity Pressurization) apparatus. [Modes for carrying out the invention]

[0012] In this invention, "zirconia molded body" refers to a body formed using zirconia in various forms such as powder, granules, paste, or slurry as the main raw material, by press molding, injection molding, stereolithography, etc., and which has not reached either a calcined or sintered state. In other words, a zirconia molded body is distinguished from a calcined zirconia body and a sintered zirconia body by being uncalcined after being formed by molding. In this invention, "calcined zirconia body" refers to a precursor (intermediate product) of a sintered zirconia body, in which the zirconia particles (powder) are not completely sintered (calcined state). In this invention, "zirconia sintered body" refers to a state in which zirconia particles (powder) have reached a sintered state. In this specification, the upper and lower limits of the numerical ranges (content of each component, X1, Y1, X2, Y2 and the values ​​calculated therefrom, temperature range, physical properties, etc.) can be combined as appropriate.

[0013] The present invention provides zirconia particles, zirconia molded articles, zirconia calcined articles, or zirconia sintered articles, which contain zirconium oxide and a stabilizer capable of suppressing the phase transition of zirconium oxide. The stabilizer is preferably capable of forming partially stabilized zirconia. Examples of the stabilizer include calcium oxide (CaO), magnesium oxide (MgO), yttrium oxide (Y2O3), cerium oxide (CeO2), scandium oxide (Sc2O3), niobium oxide (Nb2O5), lanthanum oxide (La2O3), erbium oxide (Er2O3), and praseodymium oxide (Pr2O3, Pr6O). 11 Examples of oxides include samarium oxide (Sm2O3), europium oxide (Eu2O3), and thulium oxide (Tm2O3), with yttria being preferred. The content of the stabilizer in the zirconia calcined body and its sintered body of the present invention can be measured, for example, by inductively coupled plasma (ICP) emission spectroscopy, X-ray fluorescence analysis, etc. In the zirconia calcined body and its sintered body of the present invention, the content of the stabilizer is preferably 0.1 to 18 mol%, more preferably 1 to 15 mol%, and even more preferably 1.5 to 10 mol%, based on the total moles of zirconia and stabilizer, unless otherwise specified, such as yttria.

[0014] The following describes preferred embodiments of the present invention, using the case where the stabilizer is yttria (Y2O3) as an example. The present invention also includes cases where yttria is replaced with a stabilizer other than yttria.

[0015] The zirconia molded article of the present invention comprises zirconia particles containing yttria in an amount of 2.0 to 9.0 mol% relative to the total number of moles of zirconium oxide and yttria, and having an average primary particle diameter of 60 nm or less, a polyol, and a binder, wherein the polyol and the binder satisfy the following relationship. X1 <Y1<X2<Y2≦500℃ (In the formula, X1 represents the combustion start temperature of the polyol, X2 represents the combustion end temperature of the polyol, Y1 represents the combustion start temperature of the binder, Y2 represents the combustion end temperature of the binder, X1 and Y1 represent the temperatures at which a 0.5% weight loss is observed, with the weight before heating measured by thermogravimetric analysis being 100%, and X2 and Y2 represent the temperatures at which a 99.5% weight loss is observed.) By using the aforementioned zirconia molded body, it is possible to obtain a zirconia sintered body that has excellent mechanical strength and light transmittance, even though it is a zirconia molded body containing a binder (and even a zirconia molded body with a thickness of 10 mm or more).

[0016] Furthermore, in one preferred embodiment of the present invention, yttria is contained in an amount of 2.0 to 9.0 mol% relative to the total number of moles of zirconium oxide and yttria, and the ΔL at a thickness of 1.5 mm is * Examples of calcined zirconia bodies include those with a WB of 5 or higher, a number of pores with a diameter of 50 nm or more after sintering at 900-1200°C of 10 or less, and a thickness of 10 mm or more. By using the calcined zirconia body, a sintered zirconia body with excellent mechanical strength and light transmittance can also be obtained. In this invention, "zirconia" means zirconium oxide containing yttrium oxide. Furthermore, in this invention, "yttria content" in zirconia particles, zirconia molded bodies, zirconia calcined bodies, or zirconia sintered bodies means the ratio (mol%) of moles of yttrium oxide to the total number of moles of zirconium oxide and yttrium oxide. The yttria content in the zirconia molded bodies, calcined bodies, and sintered bodies of this invention can be measured, for example, by inductively coupled plasma (ICP) emission spectroscopy, X-ray fluorescence analysis, etc.

[0017] [Zirconia sintered body] Hereinafter, an embodiment of the present invention will be described, firstly, as a zirconia sintered body. The zirconia sintered body of the present invention contains yttria in an amount of 2.0 to 9.0 mol% relative to the total number of moles of zirconium oxide and yttria, and has a thickness of 28.5 μm.2 The number of pores with a diameter of 50 nm or more per cross-sectional area is 10 or less, and the thickness is 10 mm or more. The thickness of the zirconia sintered body is preferably 12 mm or more, more preferably 15 mm or more. The shape of the zirconia sintered body with a thickness of 10 mm or more is not particularly limited, and it may be a block shape (rectangular parallelepiped shape) or the like. The following description does not limit the present invention.

[0018] The zirconia sintered body of the present invention may contain a fluorescent agent. When the zirconia sintered body contains a fluorescent agent, it has fluorescence. There is no particular limitation on the type of the fluorescent agent, and one or more of those capable of emitting fluorescence with light of any wavelength can be used. Examples of such fluorescent agents include those containing a metal element. Examples of the metal element include Ga, Bi, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Tm, etc. The fluorescent agent may contain one of these metal elements alone, or may contain two or more of them. Among these metal elements, Ga, Bi, Eu, and Tm are preferred, and Bi and Eu are more preferred because the effects of the present invention are more显著. Examples of the fluorescent agent used when manufacturing the zirconia sintered body of the present invention include oxides, hydroxides, acetates, nitrates, etc. of the above metal elements. The fluorescent agent may also be Y2SiO5:Ce, Y2SiO5:Tb, (Y,Gd,Eu)BO3, Y2O3:Eu, YAG:Ce, ZnGa2O4:Zn, BaMgAl 10 O 17 :Eu or the like.

[0019] There are no particular restrictions on the content of the fluorescent agent in the zirconia sintered body, and it can be adjusted as appropriate depending on the type of fluorescent agent or the intended use of the zirconia sintered body. However, from the viewpoint of suitability for use as a dental prosthesis, it is preferable that the content of the fluorescent agent, in terms of oxides of the metal elements contained in it, be 0.001% by mass or more, more preferably 0.005% by mass or more, even more preferably 0.01% by mass or more, and even more preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less, based on 100% by mass of zirconia contained in the zirconia sintered body. By having a content above the lower limit, the fluorescence is not inferior to that of natural human teeth, and by having a content below the upper limit, a decrease in light transmittance and mechanical strength can be suppressed.

[0020] The zirconia sintered body of the present invention may contain a coloring agent. By containing a coloring agent, the zirconia sintered body becomes a colored zirconia sintered body. There are no particular restrictions on the type of coloring agent; known pigments commonly used to color ceramics, known dental liquid coloring agents, etc., can be used. Examples of coloring agents include those containing metal elements, specifically oxides containing metal elements such as iron, vanadium, praseodymium, erbium, chromium, nickel, and manganese, composite oxides thereof, or salts thereof. Commercially available coloring agents can also be used; for example, Prettau Colour Liquid manufactured by Zirkonzahn can be used. The zirconia sintered body may contain one type of coloring agent, or it may contain two or more types of coloring agents.

[0021] There are no particular restrictions on the content of colorants in the zirconia sintered body, and it can be adjusted as appropriate depending on the type of colorant and the intended use of the zirconia sintered body. However, from the viewpoint of suitability for use as a dental prosthesis, it is preferable that the amount of metal element oxides contained in the colorant is 0.001% by mass or more, more preferably 0.005% by mass or more, even more preferably 0.01% by mass or more, and also preferable that it be 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, even more preferably 0.1% by mass or less, and even more preferably 0.05% by mass or less, based on 100% by mass of zirconia contained in the zirconia sintered body.

[0022] According to the present invention, a zirconia sintered body with excellent linear light transmittance can be obtained. To adjust the light transmittance of the zirconia sintered body, the zirconia sintered body of the present invention may contain a light transmittance adjusting agent. Specific examples of light transmittance adjusting agents include aluminum oxide, titanium oxide, silicon dioxide, zircon, lithium silicate, and lithium disilicate. The zirconia sintered body may contain one type of light transmittance adjusting agent, or it may contain two or more types of light transmittance adjusting agents.

[0023] There are no particular restrictions on the content of the translucency modifier in the zirconia sintered body, and it can be adjusted as appropriate depending on the type of translucency modifier and the intended use of the zirconia sintered body. However, from the viewpoint of being suitable for use as a dental prosthesis, it is preferable that the content is 0.1% by mass or less relative to 100% by mass of zirconia contained in the zirconia sintered body.

[0024] The zirconia sintered body of the present invention contains yttria in an amount of 2.0 to 9.0 mol% relative to the total number of moles of zirconium oxide and yttria. If the yttria content in the zirconia sintered body is less than 2.0 mol%, sufficient light transmission cannot be obtained. Furthermore, if the yttria content in the zirconia sintered body exceeds 9.0 mol%, the mechanical strength decreases. Since a zirconia sintered body with superior light transmission and mechanical strength can be obtained, the yttria content in the zirconia sintered body is preferably 3.0 mol% or more, more preferably 3.5 mol% or more, even more preferably 4.0 mol% or more, preferably 8.0 mol% or less, more preferably 7.5 mol% or less, and even more preferably 7.0 mol% or less.

[0025] In the zirconia sintered body of the present invention, the grain size is preferably 180 nm or less. If the grain size exceeds 180 nm, sufficient light transmission may not be obtained. Since a zirconia sintered body with superior light transmission can be obtained, the grain size is preferably 140 nm or less, more preferably 120 nm or less, even more preferably 110 nm or less, and may be 100 nm or less. There is no particular lower limit to the grain size, but the grain size can be, for example, 50 nm or more, and even 70 nm or more. The grain size in the zirconia sintered body can be determined by taking a field emission scanning electron microscope (FE-SEM) image of the cross-section of the zirconia sintered body, selecting 100 arbitrary particles from the image, and taking the average value of the equivalent circle diameter (diameter of a true circle with the same area) of each particle.

[0026] The zirconia sintered body of the present invention exhibits excellent mechanical strength. The three-point bending strength of the zirconia sintered body of the present invention is preferably 500 MPa or more, more preferably 600 MPa or more, even more preferably 650 MPa or more, particularly preferably 700 MPa or more, and most preferably 800 MPa or more. Having such a three-point bending strength in the zirconia sintered body of the present invention can suppress fracture in the oral cavity when used, for example, as a dental prosthesis. There is no particular upper limit to the three-point bending strength, but it can be, for example, 1500 MPa or less, and even 1000 MPa or less. The three-point bending strength of the zirconia sintered body can be measured in accordance with ISO 6872:2015.

[0027] The zirconia sintered body of the present invention exhibits excellent light transmittance. Preferably, the zirconia sintered body of the present invention has a transmittance of 40% or more, more preferably 45% or more, and may also be 46% or more, 48% or more, 50% or more, or even 52% or more, at a thickness of 0.5 mm. Having this transmittance within the above range makes it easier to satisfy the required light transmittance at the incisal edge, for example, when used as a dental prosthesis. There is no particular upper limit to this transmittance, but it can be, for example, 60% or less, or even 57% or less. The transmittance of 700 nm at a thickness of 0.5 mm of the zirconia sintered body can be measured using a spectrophotometer. For example, a spectrophotometer (Hitachi High-Technologies Corporation, "Hitachi Spectrophotometer U-3900H") can be used to transmit and scatter light generated from a light source through the sample, and measure it using an integrating sphere. In this measurement, the transmittance may be measured first in the wavelength range of 300 to 750 nm, and then the transmittance for light at a wavelength of 700 nm may be determined. As the sample used for the measurement, a disc-shaped zirconia sintered body with a diameter of 15 mm and a thickness of 0.5 mm, with both sides mirror-polished, can be used.

[0028] The zirconia sintered body of the present invention exhibits excellent linear light transmittance. Preferably, the linear light transmittance of the zirconia sintered body of the present invention at a thickness of 1.0 mm is 1% or more, more preferably 3% or more, even more preferably 5% or more, particularly preferably 7% or more, and may even be 10% or more. Having the linear light transmittance within this range makes it easier to satisfy the required light transmittance at the incisal edge, for example, when used as a dental prosthesis. There is no particular upper limit to the linear light transmittance, but it can be, for example, 60% or less, and even 50% or less. The linear light transmittance at a thickness of 1.0 mm of the zirconia sintered body can be measured using a turbidimeter. For example, a turbidimeter (Haze Meter NDH4000, manufactured by Nippon Denshoku Industries Ltd.) can be used to transmit and scatter light generated from a light source through the sample, and the transmittance can be measured using an integrating sphere. In this measurement, linear light transmittance is preferably measured in accordance with ISO 13468-1:1996 and JIS K 7361-1:1997, and haze is preferably measured in accordance with ISO 14782-1:1999 and JIS K 7136:2000. As the sample used for measurement, a disc-shaped zirconia sintered body with a diameter of 15 mm and a thickness of 1.0 mm, with both sides mirror-polished, can be used.

[0029] The zirconia sintered body of the present invention contains 28.5 μm 2 The number of pores (holes) with a diameter of 50 nm or more per unit cross-sectional area is 10 or less, preferably 8 or less, and more preferably 6 or less. If the number of pores with a diameter of 50 nm or more exceeds 10, it may lead to a decrease in the mechanical strength and light transmittance of the zirconia sintered body when it is made into a block-shaped zirconia sintered body with a desired thickness. The zirconia sintered body of the present invention contains 28.5 μm 2 The number of pores with a diameter of 50 nm or more per unit cross-sectional area is 28.5 μm. 2Ten field-emission scanning electron microscope (FE-SEM) images were taken of the cross-section of the zirconia sintered body. The equivalent diameter of each pore in the images was determined, and the number of pores with a diameter of 50 nm or more was calculated for each image. The calculated number was then summed for all 10 images and divided by 10 to obtain the arithmetic mean.

[0030] The method for manufacturing a zirconia sintered body of the present invention is characterized by using a zirconia molded body of the present invention, as described later. The preferred method for manufacturing a zirconia sintered body includes a step of sintering the zirconia molded body at 900 to 1200°C under normal pressure. Alternatively, a calcined zirconia body of the present invention, as described later, may be used, and the preferred method includes a step of sintering the calcined zirconia body at 900 to 1200°C under normal pressure. By such a manufacturing method, a zirconia sintered body of the present invention, which has excellent mechanical strength and light transmittance and excellent linear light transmittance, can be easily manufactured.

[0031] [Zirconia molded material] The zirconia molded article of the present invention comprises zirconia particles containing yttria in an amount of 2.0 to 9.0 mol% relative to the total number of moles of zirconium oxide and yttria, and having an average primary particle diameter of 60 nm or less, a polyol, and a binder, wherein the polyol and the binder satisfy the following relationship. X1 <Y1<X2<Y2≦500℃ (In the formula, X1 represents the combustion start temperature of the polyol, X2 represents the combustion end temperature of the polyol, Y1 represents the combustion start temperature of the binder, Y2 represents the combustion end temperature of the binder, X1 and Y1 represent the temperatures at which a 0.5% weight loss is observed, with the weight before heating measured by thermogravimetric analysis being 100%, and X2 and Y2 represent the temperatures at which a 99.5% weight loss is observed.) By using the aforementioned zirconia molded body, it is possible to obtain a zirconia sintered body that has excellent mechanical strength and light transmittance, as well as excellent linear light transmittance, even though it is a zirconia molded body containing a binder (and even a zirconia molded body with a thickness of 10 mm or more). Furthermore, it becomes possible to achieve both the moldability of the molded body and the light transmittance of the sintered body.

[0032] The zirconia molded body of the present invention has high light transmittance, and a zirconia sintered body with high linear light transmittance and a zirconia calcined body capable of producing a zirconia sintered body with high linear light transmittance can be produced from such a zirconia molded body. Specifically, the zirconia molded body of the present invention has a ΔL at a thickness of 1.5 mm. * (WB) is preferably 5 or more, more preferably 8 or more, even more preferably 10 or more, and may be 11 or more, or 12 or more. * As (WB) falls within the above range, when combined with a polyol and binder that satisfy the above formula, a zirconia sintered body with high linear light transmittance can be obtained when sintered under normal pressure. * There is no particular upper limit on (WB), but it can be, for example, 30 or less, or even 25 or less. Note that ΔL at a thickness of 1.5 mm in a zirconia molded body. * (WB) can be measured using a spectrophotometer, for example, a spectrophotometer (Konica Minolta Japan, "CM-3610A") can be used. In this measurement, an F11 light source is used, and the value can be determined by measuring the reflected light. A disc-shaped zirconia molded body with a diameter of 20 mm and a thickness of 1.5 mm can be used as the sample for measurement. ΔL * (WB) is the brightness (L) on a white background. * ) and brightness (L) on a black background * This refers to the difference between ) and L on a white background of a 1.5mm thick zirconia molded body. * The value and L on a black background * It means the difference in values. L * The value is L * a * b * Chromaticity (color space) L in the color system (JIS Z 8781-4:2013) * This is the value. White background refers to the white area of ​​the opacity test paper described in JIS K 5600-4-1:1999 Part 4 Section 1, and black background refers to the black area of ​​the same opacity test paper.

[0033] When a zirconia sintered body contains a fluorescent agent, a zirconia molded body containing the fluorescent agent is preferably used as the raw material before sintering. The content of the fluorescent agent in the zirconia molded body containing the fluorescent agent can be appropriately adjusted according to the content of the fluorescent agent in the resulting zirconia sintered body. The specific content of the fluorescent agent in the zirconia molded body is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, even more preferably 0.01% by mass or more, and even more preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less, based on 100% by mass of zirconia contained in the zirconia molded body, in terms of the oxide of the metal element contained in the fluorescent agent.

[0034] When a zirconia sintered body contains a coloring agent, a zirconia molded body containing the coloring agent is preferably used as the raw material before sintering. The coloring agent content in the zirconia molded body containing the coloring agent can be appropriately adjusted according to the coloring agent content in the resulting zirconia sintered body. The specific coloring agent content in the zirconia molded body is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, even more preferably 0.01% by mass or more, and also preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, even more preferably 0.1% by mass or less, and may even be 0.05% by mass or less, based on 100% by mass of zirconia contained in the zirconia molded body.

[0035] When a zirconia sintered body contains a translucency modifier, a zirconia molded body containing the translucency modifier is preferably used as the raw material before sintering. The content of the translucency modifier in the zirconia molded body containing the translucency modifier can be appropriately adjusted according to the content of the translucency modifier in the resulting zirconia sintered body. Preferably, the specific content of the translucency modifier in the zirconia molded body is 0.1% by mass or less relative to 100% by mass of zirconia contained in the zirconia molded body.

[0036] The yttria content in the zirconia molded article of the present invention may be in the range of 2.0 to 9.0 mol% relative to the total number of moles of zirconium oxide and yttria, and may be the same as the yttria content in the resulting zirconia sintered body. The specific yttria content in the zirconia molded article is 2.0 mol% or more, preferably 3.0 mol% or more, more preferably 3.5 mol% or more, even more preferably 4.0 mol% or more, and also preferably 8.0 mol% or less, more preferably 7.5 mol% or less, and even more preferably 7.0 mol% or less.

[0037] There are no particular limitations on the density of the zirconia molded body of the present invention, and it will vary depending on the manufacturing method of the zirconia molded body, but since a dense zirconia sintered body can be obtained, the density is 3.0 g / cm³. 3 Preferably, it is 3.2 g / cm³ or more. 3 It is more preferable that the amount be greater than or equal to 3.4 g / cm³. 3 It is even more preferable that the density be greater than or equal to the above. There is no particular upper limit to the density, but for example, 6.0 g / cm³ 3 Furthermore, 5.8 g / cm³ 3 The following is possible:

[0038] There are no particular restrictions on the shape of the zirconia molded body of the present invention, and it can be made into any desired shape depending on the application. However, considering the ease of handling when obtaining a calcined zirconia body to be used as a mill blank for manufacturing dental materials such as dental prostheses, disc-shaped, prismatic (rectangular parallelepiped, etc.) bodies are preferred. As will be described later, if a stereolithography method or the like is used in the manufacturing of the zirconia molded body, it is possible to impart a shape to the zirconia molded body that corresponds to the desired shape of the final zirconia sintered body. The present invention also includes zirconia molded bodies having such desired shapes. Furthermore, the zirconia molded body may have a single-layer structure or a multi-layer structure. By using a multi-layer structure, the final zirconia sintered body can have a multi-layer structure, and its physical properties such as light transmittance can be locally altered.

[0039] From the viewpoint of handling ease, the zirconia molded article of the present invention preferably has a biaxial bending strength in the range of 2 to 10 MPa, and more preferably in the range of 5 to 8 MPa. The biaxial bending strength of the zirconia molded article can be measured in accordance with JIS T 6526:2018.

[0040] The zirconia molded article of the present invention preferably has a grain size of 180 nm or less after sintering at 900 to 1200°C for 2 hours under normal pressure (after becoming a zirconia sintered article). This makes it easy to manufacture the zirconia sintered article of the present invention which has excellent light transmittance. Since a zirconia sintered article with excellent light transmittance can be obtained, the grain size is more preferably 140 nm or less, even more preferably 120 nm or less, particularly preferably 110 nm or less, and may also be 100 nm or less. There is no particular limit to the lower limit of the grain size, but the grain size can be, for example, 50 nm or more, and even 70 nm or more. The method for measuring the grain size is as described above in the explanation of the grain size in the zirconia sintered article.

[0041] The zirconia molded article of the present invention preferably has a three-point bending strength of 500 MPa or more after sintering at 900 to 1200°C under normal pressure (after becoming a zirconia sintered article). This makes it possible to easily manufacture the zirconia sintered article of the present invention which has excellent mechanical strength. Since a zirconia sintered article with superior mechanical strength can be obtained, the three-point bending strength is more preferably 600 MPa or more, even more preferably 650 MPa or more, particularly preferably 700 MPa or more, and most preferably 800 MPa or more. There is no particular upper limit to the three-point bending strength, but the three-point bending strength can be, for example, 1500 MPa or less, and even 1000 MPa or less. The method for measuring the three-point bending strength is as described above in the explanation of the three-point bending strength in the zirconia sintered article.

[0042] The zirconia molded body of the present invention preferably has a transmittance of 40% or more of light at a wavelength of 700 nm at a thickness of 0.5 mm after sintering at 900°C to 1200°C under normal pressure (after becoming a zirconia sintered body). This makes it possible to easily manufacture the zirconia sintered body of the present invention which has excellent light transmittance. Since a zirconia sintered body with excellent light transmittance can be obtained, the transmittance is more preferably 45% or more, even more preferably 46% or more, particularly preferably 48% or more, most preferably 50% or more, and may even be 52% or more. There is no particular upper limit to the transmittance, but the transmittance can be, for example, 60% or less, and even 57% or less. The method for measuring the transmittance is as described above in the explanation of the transmittance of light at a wavelength of 700 nm at a thickness of 0.5 mm in the zirconia sintered body.

[0043] The zirconia molded body of the present invention preferably has a linear light transmittance of 1% or more, more preferably 3% or more, even more preferably 5% or more, particularly preferably 7% or more, and may even be 10% or more, after being sintered at 900°C to 1200°C under normal pressure (after becoming a zirconia sintered body) at a thickness of 1.0 mm. Having the linear light transmittance within the above range makes it easier to satisfy the required light transmittance at the incisal edge, for example, when used as a dental prosthesis. There is no particular upper limit to the linear light transmittance, but it can be, for example, 60% or less, and even 50% or less. The method for measuring the linear light transmittance is as described above in the explanation of the linear light transmittance at a thickness of 1.0 mm in the zirconia sintered body.

[0044] Furthermore, in one preferred embodiment of the present invention, a 28.5 μm material is obtained after sintering at 900 to 1200°C under normal pressure. 2 A zirconia molded body is one in which the number of pores with a diameter of 50 nm or more per unit cross-sectional area is 10 or less. The preferred range and measurement method for the number of pores are the same as for zirconia sintered bodies.

[0045] [Method for manufacturing zirconia molded articles] The method for producing the zirconia molded article of the present invention is not particularly limited as long as it achieves the effects of the present invention. However, since the zirconia sintered article of the present invention, which has excellent light transmittance and mechanical strength, can be easily obtained, it is preferable that the method includes a molding step of molding zirconia particles, a polyol, and a binder to obtain the zirconia molded article. The combination of the polyol and the binder is not particularly limited as long as it satisfies the above relationship, and specific materials are as described later.

[0046] The yttria content in the zirconia particles used is preferably the same as the yttria content in the resulting zirconia molded article, and consequently the zirconia calcined article and zirconia sintered article. The specific yttria content in the zirconia particles is preferably 2.0 mol% or more, more preferably 3.0 mol% or more, more preferably 3.5 mol% or more, even more preferably 4.0 mol% or more, and also preferably 8.0 mol% or less, more preferably 7.5 mol% or less, and even more preferably 7.0 mol% or less.

[0047] The zirconia particles used have an average primary particle diameter of 60 nm or less. In addition to having an average primary particle diameter of 60 nm or less, it is preferable that the amount of zirconia particles having a particle size greater than 100 nm is 0.5% by mass or less relative to the total amount of zirconia particles. This makes it easy to obtain the zirconia molded article, and by extension, the zirconia calcined article and zirconia sintered article of the present invention. From the viewpoint of ease of manufacturing the zirconia molded article, and by extension, the zirconia calcined article and zirconia sintered article of the present invention, the average primary particle diameter of the zirconia particles is preferably 50 nm or less, more preferably 30 nm or less, even more preferably 20 nm or less, may be 10 nm or less, and also preferably 1 nm or more, and more preferably 5 nm or more. From the viewpoint of ease of manufacturing the zirconia molded article, and by extension the zirconia calcined article and zirconia sintered article of the present invention, and the ease of obtaining the desired linear light transmittance, it is more preferable that the amount of zirconia particles having a particle size greater than 100 nm be 0.3% by mass or less, even more preferable that be 0.1% by mass or less, and may be 0.05% by mass or less. The average primary particle diameter of the zirconia particles can be determined, for example, by photographing the zirconia particles (primary particles) with a transmission electron microscope (TEM), measuring the particle diameter (maximum diameter) of any 100 particles on the obtained image, and taking the average value of these measurements. The content of zirconia particles having a particle size greater than 100 nm can be measured by volume using a laser diffraction / scattering particle size distribution analyzer (LA-950, manufactured by Horiba, Ltd.) after dispersing the zirconia particles in methanol.

[0048] There are no particular restrictions on the method for preparing zirconia particles. For example, a breakdown process in which coarse particles are crushed into fine powder, or a building-up process in which particles are synthesized from atoms or ions through nucleation and growth processes can be employed. Of these, the building-up process is preferred for obtaining high-purity, fine zirconia particles.

[0049] The breakdown process can be carried out, for example, by grinding using a ball mill or bead mill. In this case, it is preferable to use fine-sized grinding media, for example, grinding media of 100 μm or less. Also, the desired ΔL * It is preferable to classify the zirconia particles after crushing the coarse particles, in order to obtain the (WB) and linear light transmittance. Known methods and apparatus can be used for classification, such as porous membranes (membrane filters with a pore size of 100 nm, etc.) and classification apparatuses (wet classifiers, dry classifiers, etc.).

[0050] On the other hand, building-up processes include, for example, gas-phase thermal decomposition, in which oxides are precipitated by thermal decomposition while vaporizing metal ion oxysate salts or organometallic compounds with high vapor pressure; gas-phase reaction, in which synthesis is carried out by a gas-phase chemical reaction between a gas of a metal compound with high vapor pressure and a reaction gas; evaporation and concentration, in which raw materials are heated and vaporized, and the vapor is condensed into fine particles by rapid cooling in an inert gas at a predetermined pressure; melt, in which the melt is cooled and solidified into small droplets to form a powder; solvent evaporation, in which the solvent is evaporated to increase the concentration in the liquid and precipitate the product in a supersaturated state; and precipitation, in which the solute concentration is made supersaturated by reaction with a precipitating agent or hydrolysis, and poorly soluble compounds such as oxides or hydroxides are precipitated through a nucleation-growth process.

[0051] Precipitation methods are further subdivided into homogeneous precipitation methods, which generate a precipitant in solution through a chemical reaction to eliminate local heterogeneity in the concentration of the precipitant; coprecipitation methods, which simultaneously precipitate multiple metal ions coexisting in a solution by adding a precipitant; hydrolysis methods, which obtain oxides or hydroxides from metal salt solutions, metal alkoxides, or other alcohol solutions by hydrolysis; and solvothermal synthesis methods, which obtain oxides or hydroxides from high-temperature, high-pressure fluids. Sorvothermal synthesis methods are further subdivided into hydrothermal synthesis methods, which use water as the solvent, and supercritical synthesis methods, which use water or supercritical fluids such as carbon dioxide as the solvent.

[0052] In any building process, it is preferable to increase the deposition rate to obtain finer zirconia particles. Also, the desired ΔL* It is preferable to classify the obtained zirconia particles in order to obtain the (WB) and linear light transmittance. Known methods and apparatus can be used for classification, for example, porous membranes (such as membrane filters with a pore size of 100 nm) and classification apparatuses (wet classifiers, dry classifiers).

[0053] As a zirconium source in the building process, for example, nitrates, acetates, chlorides, and alkoxides can be used. Specifically, zirconium oxychloride, zirconium acetate, and zirconyl nitrate can be used.

[0054] Furthermore, in order to ensure that the yttria content in the zirconia particles is within the above range, yttria can be added during the manufacturing process of the zirconia particles. For example, yttria may be solid-dissolved in the zirconia particles. As a yttrium source, for example, nitrates, acetates, chlorides, alkoxides, etc., can be used. Specifically, yttrium chloride, yttrium acetate, yttrium nitrate, etc., can be used.

[0055] Zirconia particles may be pre-treated with known surface treatment agents as needed, such as organic compounds having acidic groups; fatty acid amides such as saturated fatty acid amides, unsaturated fatty acid amides, saturated fatty acid bisamides, and unsaturated fatty acid bisamides; and organometallic compounds such as silane coupling agents (organosilicon compounds), organotitanium compounds, organozirconium compounds, and organoaluminum compounds. Surface treatment of zirconia particles can adjust their miscibility with liquids when preparing a powder containing zirconia particles and a fluorescent agent using a slurry containing a liquid with a surface tension of 50 mN / m or less at 25°C as the dispersion medium, as described later, or when producing a zirconia molded article by a method that includes a step of polymerizing a composition containing zirconia particles, a fluorescent agent, and a polymerizable monomer, as described later. Among the surface treatment agents mentioned above, organic compounds having acidic groups are preferred because they exhibit excellent miscibility with liquids having a surface tension of 50 mN / m or less at 25°C, and can improve the mechanical strength of zirconia molded articles obtained by enhancing the chemical bonding between zirconia particles and polymerizable monomers.

[0056] Examples of organic compounds having acidic groups include organic compounds having at least one acidic group such as a phosphoric acid group, a carboxylic acid group, a pyrophosphate group, a thiophosphate group, a phosphonic acid group, or a sulfonic acid group. Among these, organic compounds containing at least one phosphoric acid group and organic compounds containing at least one carboxylic acid group are preferred, and organic compounds containing phosphoric acid groups are more preferred. Zirconia particles may be surface-treated with one surface treatment agent or with two or more surface treatment agents. When zirconia particles are surface-treated with two or more surface treatment agents, the resulting surface treatment layer may be a surface treatment layer of a mixture of the two or more surface treatment agents, or it may be a surface treatment layer with a multilayer structure in which multiple surface treatment layers are laminated.

[0057] Examples of phosphate-containing organic compounds include 2-ethylhexyl acid phosphate, stearyl acid phosphate, 2-(meth)acryloyloxyethyl dihydrogen phosphate, 3-(meth)acryloyloxypropyl dihydrogen phosphate, 4-(meth)acryloyloxybutyl dihydrogen phosphate, 5-(meth)acryloyloxypentyl dihydrogen phosphate, 6-(meth)acryloyloxyhexyl dihydrogen phosphate, and 7-(meth) ) Acryloyloxyheptyl dihydrogen phosphate, 8-(meth)acryloyloxyoctyl dihydrogen phosphate, 9-(meth)acryloyloxynonyl dihydrogen phosphate, 10-(meth)acryloyloxydecyl dihydrogen phosphate, 11-(meth)acryloyloxyundecyl dihydrogen phosphate, 12-(meth)acryloyloxidedecyl dihydrogen phosphate, 16-(meth)acryloyloxyhexadecyl dihydrogen 20-(meth)acryloyloxycosyl dihydrogen phosphate, bis[2-(meth)acryloyloxyethyl]hydrogen phosphate, bis[4-(meth)acryloyloxybutyl]hydrogen phosphate, bis[6-(meth)acryloyloxyhexyl]hydrogen phosphate, bis[8-(meth)acryloyloxyoctyl]hydrogen phosphate, bis[9-(meth)acryloyloxynonyl]hydrogen phosphate, bis[10 Examples include -(meth)acryloyloxydecyl]hydrogen phosphate, 1,3-di(meth)acryloyloxypropyl dihydrogen phosphate, 2-(meth)acryloyloxyethylphenyl hydrogen phosphate, 2-(meth)acryloyloxyethyl-2-bromoethyl hydrogen phosphate, bis[2-(meth)acryloyloxy-(1-hydroxymethyl)ethyl]hydrogen phosphate, and their acid chlorides, alkali metal salts, ammonium salts, etc.

[0058] Examples of carboxylic acid group-containing organic compounds include succinic acid, oxalic acid, octanoic acid, decanoic acid, stearic acid, polyacrylic acid, 4-methyloctanoic acid, neodecanoic acid, pivalic acid, 2,2-dimethylbutyric acid, 3,3-dimethylbutyric acid, 2,2-dimethylvaleric acid, 2,2-diethylbutyric acid, 3,3-diethylbutyric acid, naphthenic acid, cyclohexanedicarboxylic acid, (meth)acrylic acid, N-(meth)acryloylglycine, N-(meth)acryloylaspartic acid, O-(meth)acryloyltyrosine, N-(meth)acryloyltyrosine, N-(meth)acryloyl 2-p-aminobenzoic acid, N-(meth)acryloyl-o-aminobenzoic acid, p-vinylbenzoic acid, 2-(meth)acryloyloxybenzoic acid, 3-(meth)acryloyloxybenzoic acid, 4-(meth)acryloyloxybenzoic acid, N-(meth)acryloyl-5-aminosalicylic acid, N-(meth)acryloyl-4-aminosalicylic acid, 2-(meth)acryloyloxyethyl hydrogen succinate, 2-(meth)acryloyloxyethyl hydrogen phthalate, 2-(meth)acryloyloxyethyl hydrogen maleate, 2-( 2-(2-methoxyethoxy)ethoxy)acetic acid (commonly known as "MEEAA"), 2-(2-methoxyethoxy)acetic acid (commonly known as "MEAA"), mono[2-(2-methoxyethoxy)ethyl] succinate, mono[2-(2-methoxyethoxy)ethyl] maleate, mono[2-(2-methoxyethoxy)ethyl] glutarate, malonic acid, glutaric acid, 6-(meth)acryloyloxyhexane-1,1-dicarboxylic acid, 9-(meth)acryloyloxynonane-1,1-dicarboxylic acid, 10-(meth)acryloyloxydecane-1,1-dicarboxylic acid Rubonic acid, 11-(meth)acryloyloxyundecane-1,1-dicarboxylic acid, 12-(meth)acryloyloxidedodecane-1,1-dicarboxylic acid, 13-(meth)acryloyloxytridecane-1,1-dicarboxylic acid, 4-(meth)acryloyloxyethyl trimellitate, 4-(meth)acryloyloxybutyl trimellitate, 4-(meth)acryloyloxyhexyl trimellitate, 4-(meth)acryloyloxydecyl trimellitate, 2-(meth)acryloyloxyethyl-3'-(meth)acryloyloxy-2'-(3,Examples include 4-dicarboxybenzoyloxy)propyl succinate, and their acid anhydrides, acid halides, alkali metal salts, and ammonium salts.

[0059] Furthermore, as organic compounds having at least one acidic group other than those mentioned above, such as a pyrophosphate group, thiophosphate group, phosphonic acid group, or sulfonic acid group, those described in International Publication No. 2012 / 042911, for example, can be used.

[0060] Examples of saturated fatty acid amides include palmitic acid amide, stearic acid amide, and behenic acid amide. Examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Examples of saturated fatty acid bisamides include ethylene bispalmitic acid amide, ethylene bisstearic acid amide, and hexamethylene bisstearic acid amide. Examples of unsaturated fatty acid bisamides include ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, and N,N'-dioleylsebacinic acid amide.

[0061] Examples of silane coupling agents (organosilicon compounds) include R 1 n SiX 4-n Examples include compounds represented by the formula (where R 1 X is a substituted or unsubstituted hydrocarbon group having 1 to 12 carbon atoms, X is an alkoxy group, hydroxyl group, halogen atom, or hydrogen atom having 1 to 4 carbon atoms, and n is an integer from 0 to 3, where R 1 (And if there are multiple X's, they may be the same or different.)

[0062] Specific examples of silane coupling agents (organosilicon compounds) include, for example, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, vinyltrimethoxysilane, vinyltrith(β-methoxyethoxy)silane, and 3,3,3-trifluoropropyltrimethoxysilane. , Methyl-3,3,3-trifluoropropyldimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, γ-methacryloyloxypropylmethyldiethoxysilane, N-(β-aminoethyl)γ-aminopropylmethyldimethoxysilane, N-(β-aminoethyl (L)γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, trimethylsilanol, methyltrichlorosilane, methyldichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, vinyltrichloro Examples include silanes, trimethylbromosilane, diethylsilane, vinyltriacetoxysilane, ω-(meth)acryloyloxyalkyltrimethoxysilane [number of carbon atoms between the (meth)acryloyloxy group and the silicon atom: 3 to 12, e.g., γ-methacryloyloxypropyltrimethoxysilane], and ω-(meth)acryloyloxyalkyltriethoxysilane [number of carbon atoms between the (meth)acryloyloxy group and the silicon atom: 3 to 12, e.g., γ-methacryloyloxypropyltriethoxysilane]. In this specification, the term "(meth)acryloyl" is used to encompass both methacryloyl and acryloyl.

[0063] Among these, silane coupling agents having functional groups are preferred, with ω-(meth)acryloyloxyalkyltrimethoxysilane [number of carbon atoms between (meth)acryloyloxy group and silicon atom: 3 to 12], ω-(meth)acryloyloxyalkyltriethoxysilane [number of carbon atoms between (meth)acryloyloxy group and silicon atom: 3 to 12], vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, and γ-glycidoxypropyltrimethoxysilane being more preferred.

[0064] Examples of organotitanium compounds include tetramethyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, and tetra(2-ethylhexyl) titanate.

[0065] Examples of organozirconium compounds include zirconium isopropoxide, zirconium n-butoxide, zirconium acetylacetonate, and zirconyl acetate.

[0066] Examples of organoaluminum compounds include aluminum acetylacetonate and aluminum organic acid salt chelate compounds.

[0067] There are no particular restrictions on the specific method of surface treatment, and known methods can be employed. For example, a method of spraying the above-mentioned surface treatment agent while vigorously stirring the zirconia particles can be employed, or a method of dispersing or dissolving the zirconia particles and the above-mentioned surface treatment agent in a suitable solvent and then removing the solvent can be employed. The solvent may be a dispersion medium containing a liquid with a surface tension of 50 mN / m or less at 25°C, as described later. Alternatively, after dispersing or dissolving the zirconia particles and the above-mentioned surface treatment agent, reflux or high-temperature and high-pressure treatment (such as autoclaving) may be performed.

[0068] Regarding the polyol and the binder used in the present invention, when the combustion start temperature (X1) of the polyol, the combustion end temperature (X2) of the polyol, the combustion start temperature (Y1) of the binder, and the combustion end temperature (Y2) of the binder are considered, the relational expression of X1 < Y1 < X2 < Y2 ≦ 500°C is satisfied. By selecting and combining those that satisfy the above relationship, it is considered that the polyol creates a route through which the binder burns out inside the zirconia molded body during sintering, and the binder becomes easier to escape during sintering. In particular, when the average primary particle diameter of the zirconia particles contained in the zirconia molded body is 60 nm or less, due to the fine particle diameter, the particles join together (necking phenomenon) during heating, the voids between the particles are filled, and there is a tendency that the binder cannot escape by heating. However, by using a combination of a polyol and a binder that satisfy the above relational expression, the polyol plays a role of forming a route through which the binder burns out inside the zirconia molded body during sintering, and the binder can escape. As a result, even when the zirconia molded body contains an amount of binder assuming a thickness of 10 mm or more, and there is a specific problem that the binder is difficult to burn out, the problems of the zirconia molded body containing the binder are solved, and the zirconia sintered body after sintering has excellent mechanical strength and translucency. Further, such a zirconia sintered body also has excellent linear light transmittance.

[0069] The combustion start temperature (X1) of the polyol, the combustion end temperature (X2) of the polyol, the combustion start temperature (Y1) of the binder, and the combustion end temperature (Y2) of the binder can be measured by thermogravimetric measurement (TG). In the present invention, taking the weight before heating as 100%, the temperature at which a 0.5% weight loss is observed is taken as X1 and Y1, and the temperature at which a 99.5% weight loss is observed is taken as X2 and Y2. The measurement conditions of the thermogravimetric measurement (TG) are as described in the examples described later.

[0070] Polyols used in the present invention include, for example, diols and triols. Examples of diols include ethylene glycol, propylene glycol, diethylene glycol, 3-methyl-1,5-pentanediol, 2-methylpentane-2,4-diol, 3-methyl-1,3-butanediol, and polyethylene glycol. Examples of triols include glycerin, 1,2,3-butanediol, and 1,2,4-butanediol. Other polyols that can be used include, for example, polyglycerin and sugars. A single polyol may be used alone, or two or more may be used in combination. By selecting and combining a polyol that satisfies the above relationship with the binder and a binder and incorporating them into a zirconia molded body, the number of pores that occur in the calcined zirconia and sintered zirconia obtained when the zirconia molded body containing the binder is sintered can be reduced, and a zirconia sintered body with excellent mechanical strength and light transmittance and a desired shape and thickness can be obtained. Therefore, the type of polyol is not particularly limited as long as it is selected to satisfy the above relation, and the effects of the present invention described above can be achieved.

[0071] Examples of binders used in the present invention include polyvinyl alcohol, methylcellulose, carboxymethylcellulose, acrylic binders, wax binders, polyvinyl butyral, polymethyl methacrylate, and ethylcellulose. The binder may be used alone or in combination of two or more types. For the same reasons as with the polyols described above, the type of binder is not particularly limited as long as it satisfies the above-mentioned relational equation, and the effects of the present invention described above can be achieved.

[0072] X1 is preferably 50°C or higher, more preferably 70°C or higher, and even more preferably 90°C or higher. Furthermore, X1 is preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower. When X1 is 50°C or higher, the outflow of polyol from the zirconia molded article is easily controlled, and the shape retention of the zirconia molded article is excellent. Also, when X1 is 300°C or lower, the bonding between zirconia particles is not inhibited, and the desired physical properties are easily obtained.

[0073] Y2 is 500°C or lower, preferably 480°C or lower, more preferably 460°C or lower, and even more preferably 440°C or lower. If Y2 exceeds 500°C, the bonded zirconia particles may not be able to withstand the pressure of the gas generated by the combustion of the binder, and the zirconia calcined body may break.

[0074] In the zirconia molded article of the present invention, the polyol burns out before the binder during sintering, creating a path for the binder to burn out inside the zirconia molded article. Since the binder burns out before necking occurs, Y1 > X1, and Y1-X1 is preferably 5°C or higher, more preferably 15°C or higher, and even more preferably 30°C or higher.

[0075] In the zirconia molded article of the present invention, the polyol burns out before the binder during sintering, creating a path for the binder to burn out inside the zirconia molded article. Since the binder burns out before necking occurs, Y2 > X2, and Y2-X2 is preferably 30°C or higher, more preferably 40°C or higher, and even more preferably 45°C or higher.

[0076] The polyol content in the zirconia molded article of the present invention (content relative to 100% by mass of zirconia (content in terms of oxide of metal elements)) is not particularly limited, but is preferably 8% by mass or less, more preferably 4% by mass or less, and even more preferably 1.5% by mass or less, as the resulting zirconia sintered body has better light transmittance. Furthermore, the polyol content is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more. By combining the polyol with a binder within the above range of polyol content, the number of pores formed in the zirconia sintered body can be reduced even when the zirconia molded article has a thickness of 10 mm or more. In the present invention, the polyol and binder content are external addition rates and mean mass percent relative to 100% by mass of zirconia (zirconium oxide containing yttrium oxide).

[0077] The binder content in the zirconia molded article of the present invention (content relative to 100% by mass of zirconia (content in terms of oxide of metal elements)) is not particularly limited, but is preferably less than 10% by mass, more preferably 5% by mass or less, and even more preferably 3% by mass or less, relative to 100% by mass of zirconia. Furthermore, the binder content is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more. By combining the binder with a polyol within the range of the above binder content, the number of pores generated in the zirconia sintered body can be reduced even when the zirconia molded article has a thickness of 10 mm or more.

[0078] The mixing ratio (mass ratio) of the binder to the polyol in the zirconia molded article of the present invention is not particularly limited, but a binder:polyol ratio of 10:1 to 1:10 is preferred, 5:1 to 1:5 is more preferred, 3:1 to 1:4 is even more preferred, and 2.5:1 to 1.1:1 is particularly preferred, as the resulting zirconia sintered article has better light transmittance.

[0079] One preferred embodiment is a zirconia particle containing yttria in an amount of 2.0 to 9.0 mol% relative to the total number of moles of zirconium oxide and yttria, and having an average primary particle diameter of 60 nm or less. It contains a polyol and a binder. The binder content relative to 100% by mass of zirconia is 0.05% by mass or more. The polyol content relative to 100% by mass of zirconia is 0.01% by mass or more. The relationship between the polyol and the binder is given by the following equation X1 <Y1<X2<Y2≦500℃ (The symbols in the formula are explained above.) Examples of zirconia molded articles that satisfy the above conditions are provided. In the above preferred embodiments, the polyol content is preferably less than or equal to the binder content, more preferably lower than the binder content, and even more preferably 0.1% by mass or more lower than the binder content. The binder content, polyol content, zirconia particles, etc., can be appropriately set within the range described herein. For example, the binder content may be 0.2% by mass or more, or 7% by mass or less, based on 100% by mass of zirconia.

[0080] A preferred embodiment of the present invention is a zirconia molded article having a thickness of 10 mm or more. The thickness of the zirconia molded article is preferably 12 mm or more, and more preferably 15 mm or more. The shape of the zirconia molded article having a thickness of 10 mm or more is not particularly limited and may be block-shaped (rectangular parallelepiped-shaped), etc.

[0081] In the present invention, there are no particular restrictions on the type of molding step used when manufacturing a zirconia molded body by a method that includes a molding step for shaping zirconia particles. However, since the zirconia molded body of the present invention, and by extension the zirconia calcined body and zirconia sintered body of the present invention, can be easily obtained, the molding step is suitable. (i) A step of slip casting a slurry containing zirconia particles; (ii) A step of gel casting a slurry containing zirconia particles; (iii) A process of press-molding a powder containing zirconia particles; (iv) A step of molding a composition containing zirconia particles and resin; and (v) A step of polymerizing a composition containing zirconia particles and polymerizable monomers; It is preferable that it be at least one of the following.

[0082] • Slurry containing zirconia particles There are no particular restrictions on the method for preparing the slurry containing zirconia particles; for example, it may be obtained through the breakdown process or building-up process described above, or it may be a commercially available product.

[0083] When producing a zirconia molded article containing the binder and polyol of the present invention, it is preferable to mix the binder and polyol, respectively, in a liquid state such as a solution or dispersion with a slurry containing zirconia particles. Furthermore, when a coloring agent and / or a light transmittance modifier is to be included in the zirconia molded article, and consequently in the calcined zirconia article and sintered zirconia article, such a coloring agent and / or light transmittance modifier may be included in the slurry containing zirconia particles and a fluorescent agent. In this case, it is preferable to mix the coloring agent and / or light transmittance modifier, respectively, in a liquid state such as a solution or dispersion with the slurry containing zirconia particles.

[0084] • Powder containing zirconia particles There are no particular restrictions on the method for preparing the powder containing zirconia particles, but it is preferable to obtain it by drying a slurry containing the zirconia particles described above, as this allows for obtaining a more uniform and superiorly physical zirconia sintered body. The slurry subjected to drying may further contain a fluorescent agent and / or a coloring agent and / or a light transmittance modifier.

[0085] There are no particular restrictions on the drying method, and for example, spray drying, supercritical drying, freeze drying, hot air drying, and vacuum drying can be used. Of these, spray drying, supercritical drying, and freeze drying are preferred, spray drying and supercritical drying are more preferred, and spray drying is even more preferred, as they can suppress the aggregation of particles during drying and yield a denser zirconia sintered body.

[0086] The slurry containing zirconia particles subjected to drying may be a slurry in which the dispersion medium is water, but it is preferable to use a slurry in which the dispersion medium is not water, such as an organic solvent, because it is possible to suppress the aggregation of particles during drying and obtain a denser zirconia sintered body.

[0087] Examples of organic solvents include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, 2-methoxyethanol, 2-ethoxyethanol, 2-(2-ethoxyethoxy)ethanol, diethylene glycol monobutyl ether, and glycerin; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran, diethyl ether, diisopropyl ether, 1,4-dioxane, and dimethoxyethane (including modified ethers such as propylene glycol monomethyl ether acetate (commonly known as "PGMEA") (preferably ether-modified ethers and / or ester-modified ethers, more preferably ether-modified alkylene glycols and / or ester-modified alkylene glycols)); esters such as ethyl acetate and butyl acetate; hydrocarbons such as hexane and toluene; and halogenated hydrocarbons such as chloroform and carbon tetrachloride. These organic solvents may be used individually or in combination of two or more. Among these, considering both safety for living organisms and ease of removal, the organic solvent is preferably a water-soluble organic solvent. Specifically, ethanol, 2-propanol, 2-methyl-2-propanol, 2-ethoxyethanol, 2-(2-ethoxyethoxy)ethanol, propylene glycol monomethyl ether acetate, acetone, and tetrahydrofuran are more preferred.

[0088] Furthermore, especially when spray drying is employed, it is preferable that the dispersion medium of the slurry containing zirconia particles and a fluorescent agent subjected to drying contains a liquid with a surface tension of 50 mN / m or less at 25°C, as this suppresses the aggregation of particles during drying and allows for the production of a denser zirconia sintered body. From this viewpoint, the surface tension of the above liquid is preferably 40 mN / m or less, and more preferably 30 mN / m or less.

[0089] The surface tension at 25°C can be determined using values ​​found, for example, in the Handbook of Chemistry and Physics. For liquids not listed therein, the values ​​found in International Publication No. 2014 / 126034 can be used. For liquids not listed in either of these, the surface tension can be determined by known measurement methods, such as the ring method or the Wilhelmy method. It is preferable to measure the surface tension at 25°C using the "CBVP-Z" automatic surface tension meter manufactured by Kyowa Interface Science Co., Ltd., or the "SIGMA702" manufactured by KSV Instruments Ltd.

[0090] As the liquid, an organic solvent having the above surface tension can be used. As the organic solvent, any of the above-mentioned ones having the above surface tension can be used, but at least one selected from the group consisting of methanol, ethanol, 2-methoxyethanol, 1,4-dioxane, 2-ethoxyethanol and 2-(2-ethoxyethoxy)ethanol is preferred, and at least one selected from the group consisting of methanol, ethanol, 2-ethoxyethanol and 2-(2-ethoxyethoxy)ethanol is more preferred, as it can suppress the aggregation of particles during drying and allow for the production of a denser zirconia sintered body.

[0091] The content of the above liquid in the dispersion medium is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more, because it can suppress the aggregation of particles during drying and allow for the production of a denser zirconia sintered body.

[0092] Slurries containing dispersion media other than water can be obtained by substituting the dispersion media in a slurry where the dispersion media is water. There are no particular restrictions on the method of substituting the dispersion media; for example, a method can be employed in which a dispersion media other than water (such as an organic solvent) is added to a slurry where the dispersion media is water, and then the water is removed by distillation. In the distillation of water, some or all of the dispersion media other than water may be removed together. The addition of the dispersion media other than water and the distillation of water may be repeated multiple times. Alternatively, a method can be employed in which a dispersion media other than water is added to a slurry where the dispersion media is water, and then the dispersed phase is precipitated. Furthermore, in a slurry where the dispersion media is water, the dispersion media may be replaced with a specific organic solvent, and then further replaced with another organic solvent. While fluorescent agents may be added after replacing the dispersion medium, it is preferable to add them before replacing the dispersion medium, as this allows for the production of a more uniform zirconia sintered body with superior physical properties. Similarly, when adding colorants and / or light transmittance modifiers to the slurry, they may be added after replacing the dispersion medium, but it is preferable to add them before replacing the dispersion medium, as this allows for the production of a more uniform zirconia sintered body with superior physical properties.

[0093] The slurry containing zirconia particles used for drying may have undergone dispersion treatment using heat or pressure, such as reflux treatment or hydrothermal treatment. Alternatively, the slurry containing zirconia particles used in the drying process may have undergone mechanical dispersion treatment using a roll mill, colloid mill, high-pressure jet disperser, ultrasonic disperser, vibrating mill, planetary mill, bead mill, etc. One of the above treatments may be used, or two or more may be used.

[0094] The slurry containing zirconia particles subjected to drying may further contain one or more other components besides the binder and polyol, such as dispersants, emulsifiers, defoamers, pH adjusters, and lubricants. By including such other components (especially dispersants and defoamers) in addition to the binder, it may be possible to suppress the aggregation of particles during drying and obtain a denser zirconia sintered body.

[0095] Examples of dispersants include ammonium polycarboxylate (such as triammonium citrate), ammonium polyacrylate, acrylic copolymer resin, acrylic ester copolymer, polyacrylic acid, bentonite, carboxymethylcellulose, anionic surfactants (such as polyoxyethylene alkyl ether phosphates like polyoxyethylene lauryl ether phosphate), nonionic surfactants, oleic glycerides, amine surfactants, and oligosaccharide alcohols.

[0096] Examples of emulsifiers include alkyl ethers, phenyl ethers, sorbitan derivatives, and ammonium salts.

[0097] Examples of defoaming agents include alcohol, polyether, polyethylene glycol, silicone, and wax.

[0098] Examples of pH adjusting agents include ammonia, ammonium salts (including ammonium hydroxide such as tetramethylammonium hydroxide), alkali metal salts, and alkaline earth metal salts.

[0099] Examples of lubricants include polyoxyethylene alkylate ethers and waxes.

[0100] The moisture content in the slurry containing zirconia particles subjected to drying is preferably 3% by mass or less, more preferably 1% by mass or less, and even more preferably 0.1% by mass or less, as this suppresses the aggregation of particles during drying and allows for the production of a denser zirconia sintered body. This moisture content can be measured using a Karl Fischer moisture meter.

[0101] There are no particular restrictions on the drying conditions in each of the above drying methods, and known drying conditions can be used as appropriate. When using an organic solvent as the dispersion medium, it is preferable to dry in the presence of a non-flammable gas, and more preferably in the presence of nitrogen, in order to reduce the risk of explosion during drying.

[0102] There are no particular restrictions on the supercritical fluid used in supercritical drying; for example, water or carbon dioxide can be used. However, carbon dioxide is preferred as the supercritical fluid because it can suppress the aggregation of particles, resulting in a denser zirconia sintered body.

[0103] • Composition containing zirconia particles and resin There are no particular restrictions on the method for preparing the composition containing zirconia particles and resin; for example, it can be obtained by mixing the above-mentioned powder containing zirconia particles with the resin.

[0104] • Composition containing zirconia particles and polymerizable monomers There are no particular restrictions on the method for preparing the composition containing zirconia particles and polymerizable monomers; for example, it can be obtained by mixing the powder containing the zirconia particles and the polymerizable monomers.

[0105] (i) Slip casting When manufacturing a zirconia molded body by a method that includes a step of slip casting a slurry containing zirconia particles, there are no particular restrictions on the specific slip casting method. For example, a method can be employed in which the slurry containing zirconia particles is poured into a mold and then dried.

[0106] The content of the dispersion medium in the slurry containing the zirconia particles used is preferably 80% by mass or less, more preferably 50% by mass or less, and even more preferably 20% by mass or less, as this facilitates pouring the slurry into the mold, prevents excessive drying time, and increases the number of times the mold can be used.

[0107] While the slurry can be poured into the mold under atmospheric pressure, it is preferable to do so under pressurized conditions from the viewpoint of production efficiency. There are no particular restrictions on the type of mold used in slip casting; for example, porous molds made of gypsum, resin, ceramics, etc., can be used. Porous molds made of resin or ceramics are superior in terms of durability.

[0108] The slurry containing the zirconia particles used for slip casting may further contain one or more of the following components in addition to the binder and polyol: dispersants, emulsifiers, defoamers, pH adjusters, lubricants, etc.

[0109] (ii) Gel casting In a method for producing a zirconia molded article that includes a step of gel casting a slurry containing zirconia particles, there are no particular restrictions on the specific method of gel casting. For example, a method can be employed in which a slurry containing zirconia particles and a fluorescent agent is gelled in a mold to obtain a shaped wet article, and then dried.

[0110] The content of the dispersion medium in the slurry containing the zirconia particles used is preferably 80% by mass or less, more preferably 50% by mass or less, and even more preferably 20% by mass or less, in order to prevent the drying process from taking an excessive amount of time and to suppress the occurrence of cracks during drying.

[0111] The above gelation may be carried out, for example, by adding a gelling agent, or by adding a polymerizable monomer and then polymerizing it. There are no particular restrictions on the type of mold used; for example, porous molds made of gypsum, resin, ceramics, etc., or non-porous molds made of metal, resin, etc., can be used.

[0112] There are no restrictions on the type of gelling agent; for example, a water-soluble gelling agent can be used, and specifically, agarose, gelatin, etc., are preferably used. One type of gelling agent may be used alone, or two or more types may be used in combination. From the viewpoint of suppressing crack generation during sintering, the amount of gelling agent used is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less, based on the mass of the slurry after the gelling agent has been added.

[0113] Furthermore, there are no particular restrictions on the type of polymerizable monomer. Examples include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, propylene glycol mono(meth)acrylate, glycerol mono(meth)acrylate, erythritol mono(meth)acrylate, N-methylol (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, and N,N-bis(2-hydroxyethyl)(meth)acrylamide. A single polymerizable monomer may be used alone, or two or more may be used in combination.

[0114] From the viewpoint of suppressing crack formation during sintering, the amount of polymerizable monomer used is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less, based on the mass of the slurry after the polymerizable monomer has been added.

[0115] When gelation is performed by polymerization of polymerizable monomers, it is preferable to use a polymerization initiator. There are no particular restrictions on the type of polymerization initiator, but photopolymerization initiators are particularly preferred. As a photopolymerization initiator, one can be appropriately selected from those used in general industry, and among these, photopolymerization initiators used in dental applications are preferred.

[0116] Specific examples of photopolymerization initiators include (bis)acylphosphine oxides (including salts), thioxanthones (including salts such as quaternary ammonium salts), ketals, α-diketones, coumarins, anthraquinones, benzoin alkyl ether compounds, and α-aminoketone compounds. One photopolymerization initiator may be used alone, or two or more may be used in combination. Among these photopolymerization initiators, it is preferable to use at least one selected from the group consisting of (bis)acylphosphine oxides and α-diketones. This allows polymerization (gelation) to be carried out in both the ultraviolet region (including the near-ultraviolet region) and the visible light region, and in particular, polymerization (gelation) can be carried out sufficiently regardless of the light source used, such as lasers such as Ar lasers and He-Cd lasers; or lighting such as halogen lamps, xenon lamps, metal halide lamps, light-emitting diodes (LEDs), mercury lamps, and fluorescent lamps.

[0117] Among the (bis)acylphosphine oxides listed above, examples of acylphosphine oxides include 2,4,6-trimethylbenzoyldiphenylphosphine oxide (commonly known as "TPO"), 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylmethoxyphenylphosphine oxide, 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide, 2,3,5,6-tetramethylbenzoyldiphenylphosphine oxide, benzoyldi(2,6-dimethylphenyl)phosphonate, sodium salt of 2,4,6-trimethylbenzoylphenylphosphine oxide, potassium salt of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and ammonium salt of 2,4,6-trimethylbenzoyldiphenylphosphine oxide.

[0118] Among the above (bis)acylphosphine oxides, examples of bisacylphosphine oxides include bis(2,6-dichlorobenzoyl)phenylphosphine oxide, bis(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide, bis(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide, bis(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and bis(2,3,6-trimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide. Furthermore, compounds described in Japanese Patent Publication No. 2000-159621 can also be used.

[0119] Among these (bis)acylphosphine oxides, the sodium salts of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylmethoxyphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and 2,4,6-trimethylbenzoylphenylphosphine oxide are preferred.

[0120] Examples of α-diketones include diacetyl, benzyl, camphorquinone, 2,3-pentadione, 2,3-octadione, 9,10-phenanthrenequinone, 4,4'-oxybenzyl, and acenaphthenequinone. Among these, camphorquinone is particularly preferred when using a light source in the visible light region.

[0121] The slurry containing the zirconia particles used for gel casting may, like the slurry used for slip casting, further contain one or more of the above-mentioned components, such as dispersants, emulsifiers, defoamers, pH adjusters, and lubricants, in addition to the binder and polyol.

[0122] There are no particular restrictions on the drying method used to dry the formed wet material. Examples include natural drying, hot air drying, vacuum drying, dielectric heating drying, induction heating drying, and constant temperature and humidity drying. One of these methods may be used, or two or more may be used. Among these, natural drying, dielectric heating drying, induction heating drying, and constant temperature and humidity drying are preferred because they can suppress the occurrence of cracks during drying.

[0123] (iii) press forming In a method for producing a zirconia molded body that includes a step of press molding a powder containing zirconia particles, there are no particular restrictions on the specific method of press molding, and it can be carried out using a known press molding machine. Specific press molding methods include, for example, uniaxial pressing. Furthermore, in order to increase the density of the resulting zirconia molded body, it is preferable to further apply cold isostatic pressing (CIP) treatment after uniaxial pressing.

[0124] The powder containing the zirconia particles used in press molding may further contain one or more of the following components in addition to the binder and polyol: dispersants, emulsifiers, defoamers, pH adjusters, lubricants, etc. These components may be added when preparing the powder.

[0125] (iv) Molding of resin-containing compositions When manufacturing a zirconia molded article by a method that includes a step of molding a composition containing zirconia particles and resin, there are no particular restrictions on the specific method for molding the composition; for example, injection molding, casting, and extrusion molding can be used. Alternatively, the composition may be fabricated using fused deposition modeling (FDM), inkjet printing, powder / binder deposition modeling, or other additive manufacturing methods (3D printing, etc.). Among these molding methods, injection molding and casting are preferred, with injection molding being more preferred.

[0126] There are no particular restrictions on the type of resin mentioned above, and any resin that can be used as a molding raw material is preferably used. Specific examples of such resins include, for example, paraffin wax, polyvinyl alcohol, polyethylene, polypropylene, ethylene vinyl acetate copolymer, polystyrene, atactic polypropylene, methacrylic resin, and fatty acids such as stearic acid. These resins may be used individually or in combination of two or more types.

[0127] The composition containing the zirconia particles and resin described above may further contain one or more other components, in addition to the binder and polyol, such as dispersants, emulsifiers, defoamers, pH adjusters, and lubricants as described above.

[0128] (v) Polymerization of compositions containing polymerizable monomers By polymerizing a composition containing zirconia particles and polymerizable monomers, the polymerizable monomers in the composition polymerize and the composition can be cured. When manufacturing a zirconia molded body by a method having such polymerization steps, there are no particular restrictions on the specific method, and for example, (a) a method of polymerizing a composition containing zirconia particles and polymerizable monomers in a mold; (b) a stereolithography (SLA) method using a composition containing zirconia particles and polymerizable monomers can be employed. Among these, the stereolithography method (b) is preferred. With the stereolithography method, the desired shape corresponding to the final zirconia sintered body can be imparted to the zirconia molded body at the time of manufacturing. For this reason, the stereolithography method may be particularly suitable when the zirconia sintered body of the present invention is used as a dental material such as a dental prosthesis.

[0129] There are no particular restrictions on the type of polymerizable monomer in the composition containing the zirconia particles and polymerizable monomers described above. It may be any monofunctional polymerizable monomer such as monofunctional (meth)acrylate or monofunctional (meth)acrylamide, or any polyfunctional polymerizable monomer such as a bifunctional aromatic compound, a bifunctional aliphatic compound, or a trifunctional or higher-functioning compound. One polymerizable monomer may be used alone, or two or more may be used. Among these, it is particularly preferable to use a polyfunctional polymerizable monomer when employing a photopolymerization method.

[0130] Examples of monofunctional (meth)acrylates include hydroxyl group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, propylene glycol mono(meth)acrylate, glycerol mono(meth)acrylate, and erythritol mono(meth)acrylate; methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and sec-butyl (meth)acrylate. Examples include alkyl(meth)acrylates such as acrylate, t-butyl(meth)acrylate, isobutyl(meth)acrylate, n-hexyl(meth)acrylate, lauryl(meth)acrylate, cetyl(meth)acrylate, and stearyl(meth)acrylate; alicyclic(meth)acrylates such as cyclohexyl(meth)acrylate and isobornyl(meth)acrylate; aromatic group-containing(meth)acrylates such as benzyl(meth)acrylate and phenyl(meth)acrylate; and(meth)acrylates having functional groups such as 2,3-dibromopropyl(meth)acrylate, 3-(meth)acryloyloxypropyltrimethoxysilane, and 11-(meth)acryloyloxyundecyltrimethoxysilane.

[0131] Examples of monofunctional (meth)acrylamides include (meth)acrylamide, N-(meth)acryloylmorpholine, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-di-n-propyl(meth)acrylamide, N,N-di-n-butyl(meth)acrylamide, N,N-di-n-hexyl(meth)acrylamide, N,N-di-n-octyl(meth)acrylamide, N,N-di-2-ethylhexyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, and N,N-bis(2-hydroxyethyl)(meth)acrylamide.

[0132] Among these monofunctional polymerizable monomers, (meth)acrylamide is preferred due to its excellent polymerizability, and N-(meth)acryloylmorpholine, N,N-dimethyl(meth)acrylamide, and N,N-diethyl(meth)acrylamide are more preferred.

[0133] Examples of bifunctional aromatic compounds include 2,2-bis((meth)acryloyloxyphenyl)propane, 2,2-bis[4-(3-(meth)acryloyloxy-2-hydroxypropoxy)phenyl]propane, 2,2-bis[4-(3-methacryloyloxy-2-hydroxypropoxy)phenyl]propane (commonly known as "Bis-GMA"), 2,2-bis(4-(meth)acryloyloxyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxypolyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxydiethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxytetraethoxyphenyl)propane, and 2,2-bis(4-(meth)acryloyloxypentaethoxyphenyl)propane. Examples include 2,2-bis(4-(meth)acryloyloxydipropoxyphenyl)propane, 2-(4-(meth)acryloyloxydiethoxyphenyl)-2-(4-(meth)acryloyloxyethoxyphenyl)propane, 2-(4-(meth)acryloyloxydiethoxyphenyl)-2-(4-(meth)acryloyloxytriethoxyphenyl)propane, 2-(4-(meth)acryloyloxydipropoxyphenyl)-2-(4-(meth)acryloyloxytriethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxypropoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxyisopropoxyphenyl)propane, and 1,4-bis(2-(meth)acryloyloxyethyl)pyromellitate. Among these, 2,2-bis[4-(3-methacryloyloxy-2-hydroxypropoxy)phenyl]propane (commonly known as "Bis-GMA") and 2,2-bis(4-(meth)acryloyloxypolyethoxyphenyl)propane are preferred due to their excellent polymerizability and the mechanical strength of the resulting zirconia molded articles. Among 2,2-bis(4-(meth)acryloyloxypolyethoxyphenyl)propane, 2,2-bis(4-methacryloyloxypolyethoxyphenyl)propane (a compound with an average number of added ethoxy groups of 2.6 (commonly known as "D-2.6E")) is preferred.

[0134] Examples of bifunctional aliphatic compounds include glycerol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4- Examples include butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 2-ethyl-1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,2-bis(3-methacryloyloxy-2-hydroxypropoxy)ethane, and 2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl) dimethacrylate (commonly known as "UDMA"). Among these, triethylene glycol dimethacrylate (commonly known as "TEGDMA") and 2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl) dimethacrylate are preferred due to their excellent polymerizability and the mechanical strength of the resulting zirconia molded articles.

[0135] Examples of compounds with three or more functionalities include trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolmethane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, N,N-(2,2,4-trimethylhexamethylene)bis[2-(aminocarboxy)propane-1,3-diol]tetra(meth)acrylate, and 1,7-diacryloyloxy-2,2,6,6-tetra(meth)acryloyloxymethyl-4-oxaheptane. Among these, N,N-(2,2,4-trimethylhexamethylene)bis[2-(aminocarboxy)propane-1,3-diol]tetramethacrylate and 1,7-diacryloyloxy-2,2,6,6-tetraacryloyloxymethyl-4-oxaheptane are preferred due to their excellent polymerizability and the mechanical strength of the resulting zirconia molded articles.

[0136] In either method (a) or (b) above, polymerization of the composition is preferably carried out using a polymerization initiator, and the composition is preferably further comprising a polymerization initiator. There are no particular restrictions on the type of polymerization initiator, but photopolymerization initiators are particularly preferred. As the photopolymerization initiator, it can be appropriately selected from photopolymerization initiators used in general industry, and among these, photopolymerization initiators used in dental applications are preferred. Specific examples of photopolymerization initiators are the same as those described above in the explanation of gel casting, and therefore, redundant explanations are omitted here.

[0137] The composition containing the zirconia particles and polymerizable monomer described above may further contain one or more other components, in addition to the binder and polyol, such as dispersants, emulsifiers, defoamers, pH adjusters, and lubricants as described above.

[0138] When manufacturing a zirconia molded article by photopolymerization using a composition containing zirconia particles and polymerizable monomers, there are no particular restrictions on the specific method of photopolymerization, and known methods can be appropriately employed for photopolymerization. For example, a method can be employed in which a target zirconia molded article is obtained by sequentially forming each layer having the desired shape by photopolymerizing a liquid composition with ultraviolet light, a laser, etc., using a photopolymerization apparatus.

[0139] When obtaining a zirconia molded article by stereolithography, the content of zirconia particles in the composition containing zirconia particles and polymerizable monomers is preferably as high as possible from the viewpoint of subsequent sinterability. Specifically, the content of zirconia particles in the composition is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and particularly preferably 50% by mass or more. On the other hand, in stereolithography, due to the principle of additive manufacturing, it is preferable that the viscosity of the composition be within a certain range. Therefore, the content of zirconia particles in the above composition is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, and particularly preferably 60% by mass or less. Adjusting the viscosity of the composition is particularly important when performing a controlled liquid level method in which layers are cured by irradiating light from below the container through the bottom surface of the container to sequentially form a zirconia molded body layer by layer. This is to raise the cured layer by one layer and allow the composition for forming the next layer to flow smoothly between the lower surface of the cured layer and the bottom surface of the container.

[0140] The specific viscosity of the above composition is preferably 20,000 mPa·s or less, more preferably 10,000 mPa·s or less, even more preferably 5,000 mPa·s or less, and preferably 100 mPa·s or more, as measured at 25°C. In this composition, the viscosity tends to increase as the zirconia particle content increases. Therefore, it is preferable to appropriately adjust the balance between the zirconia particle content and viscosity in the above composition, taking into account the balance between the speed of stereolithography and the accuracy of the resulting zirconia molded product, in accordance with the performance of the stereolithography apparatus used. The viscosity can be measured using an E-type viscometer.

[0141] In the method for producing a zirconia molded article of the present invention, in order to further improve the density of the zirconia molded article, the zirconia molded article may be subjected to a humidification treatment followed by a CIP treatment. When press molding is performed, the powder containing zirconia particles may be subjected to a humidification treatment before press molding. The method of humidification can be any known method without any limitations, and may be sprayed with water using a spray bottle or treated using a constant humidity chamber or a constant temperature and humidity chamber. The amount of moisture increase due to the humidification treatment depends on the particle size of the zirconia particles contained, but is preferably more than 2% by mass, more preferably more than 3% by mass, even more preferably more than 4% by mass, particularly preferably more than 5% by mass, and also preferably 15% by mass or less, more preferably 13% by mass or less, and even more preferably 11% by mass or less. The increase in moisture content due to the humidification process can be calculated as a percentage by subtracting the mass of the powder and molded body before humidification from the mass of the wet powder (powder after humidification) and molded body, and then dividing this result by the mass of the powder and molded body before humidification.

[0142] [Zirconia calcined body] Another embodiment of the present invention involves a material containing yttria in an amount of 2.0 to 9.0 mol% relative to the total number of moles of zirconium oxide and yttria, with a ΔL of 1.5 mm thickness. *(WB) is 5 or higher, and the 28.5 μm after sintering at 900-1200°C 2 A calcined zirconia body is provided in which the number of pores with a diameter of 50 nm or more per unit cross-sectional area is 10 or less, and the thickness is 10 mm or more. By using the calcined zirconia body, a sintered zirconia body can be obtained that has excellent mechanical strength and light transmittance, and excellent linear light transmittance. ΔL * The definition of (WB) is the same as for the zirconia molded body. The method for measuring the number of pores with a diameter of 50 nm or more is as described above in the explanation of the number of pores with a diameter of 50 nm or more in the zirconia sintered body. The thickness of the zirconia calcined body is preferably 12 mm or more, and more preferably 15 mm or more. The shape of the zirconia calcined body with a thickness of 10 mm or more is not particularly limited and may be block-shaped (rectangular parallelepiped), etc.

[0143] When the zirconia sintered body of the present invention contains a fluorescent agent, a zirconia calcined body containing a fluorescent agent is preferably used as the raw material before sintering. The content of the fluorescent agent in the zirconia calcined body containing a fluorescent agent can be appropriately adjusted according to the content of the fluorescent agent in the resulting zirconia sintered body. The specific content of the fluorescent agent contained in the zirconia calcined body is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, even more preferably 0.01% by mass or more, and also preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less, based on 100% by mass of zirconia contained in the zirconia calcined body, in terms of the oxide of the metal element contained in the fluorescent agent.

[0144] When a zirconia sintered body contains a coloring agent, a zirconia calcined body containing the coloring agent is preferably used as the raw material before sintering. The coloring agent content in the zirconia calcined body can be appropriately adjusted according to the coloring agent content in the resulting zirconia sintered body. The specific coloring agent content in the zirconia calcined body is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, even more preferably 0.01% by mass or more, and also preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, even more preferably 0.1% by mass or less, and may even be 0.05% by mass or less, based on 100% by mass of zirconia contained in the zirconia calcined body.

[0145] When a zirconia sintered body contains a translucency modifier, a zirconia calcined body containing the translucency modifier is preferably used as the raw material before sintering. The content of the translucency modifier in the zirconia calcined body containing the translucency modifier can be appropriately adjusted according to the content of the translucency modifier in the resulting zirconia sintered body. Preferably, the specific content of the translucency modifier in the zirconia calcined body is 0.1% by mass or less relative to 100% by mass of zirconia contained in the zirconia calcined body.

[0146] The yttria content in the zirconia calcined body of the present invention may be in the range of 2.0 to 9.0 mol%, and may be the same as the yttria content in the resulting zirconia sintered body. The specific yttria content in the zirconia calcined body is 2.0 mol% or more, preferably 3.0 mol% or more, more preferably 3.5 mol% or more, even more preferably 4.0 mol% or more, and also preferably 8.0 mol% or less, more preferably 7.5 mol% or less, and even more preferably 7.0 mol% or less.

[0147] There are no particular limitations on the density of the calcined zirconia body of the present invention, and it varies depending on the manufacturing method of the zirconia molded body used in its production, but it is generally between 3.0 and 6.0 g / m². 3 It is preferably within the range of 3.2 to 5.8 g / m 3 It is more preferable that it be within the range.

[0148] There are no particular restrictions on the shape of the zirconia calcined body of the present invention, and it can be made into any desired shape depending on the application. However, considering ease of handling when used as a mill blank for manufacturing dental materials such as dental prostheses, disc-shaped, prismatic (rectangular parallelepiped, etc.) shapes are preferred. As will be described later, the zirconia calcined body can be made into any desired shape depending on the application by cutting (milling) before it is made into a zirconia sintered body, and the present invention also includes zirconia calcined bodies having such a desired shape after cutting (milling). Furthermore, the zirconia calcined body may have a single-layer structure or a multi-layer structure. By making it a multi-layer structure, the final zirconia sintered body can have a multi-layer structure, and its physical properties such as light transmittance can be locally changed.

[0149] The three-point bending strength of the zirconia calcined body of the present invention is preferably in the range of 10 to 70 MPa, and more preferably in the range of 20 to 60 MPa, from the viewpoint of being able to maintain the shape of the workpiece when processed using a cutting machine and also being able to perform the cutting itself easily. The three-point bending strength of the zirconia calcined body can be measured using a universal testing machine with a span length (distance between supports) of 30 mm and a crosshead speed of 0.5 mm / min for a test piece measuring 5 mm × 40 mm × 10 mm.

[0150] The zirconia calcined body of the present invention preferably has a grain size of 180 nm or less after sintering at 900 to 1200°C for 2 hours under normal pressure (after becoming a zirconia sintered body). This makes it easy to manufacture the zirconia sintered body of the present invention, which has excellent light transmittance. Since a zirconia sintered body with excellent light transmittance can be obtained, the grain size is more preferably 140 nm or less, even more preferably 120 nm or less, particularly preferably 115 nm or less, and may also be 110 nm or less. There is no particular limit to the lower limit of the grain size, but the grain size can be, for example, 50 nm or more, and even 100 nm or more. The method for measuring the grain size is as described above in the explanation of the grain size in the zirconia sintered body.

[0151] The zirconia calcined body of the present invention has a ΔL of 1.5 mm in thickness. * (WB) is 5 or greater, preferably 7 or greater, and may be 10 or greater. * As (WB) falls within the above range, a zirconia sintered body with high linear light transmittance can be obtained when sintered under normal pressure. * There is no particular upper limit on (WB), but it can be, for example, 30 or less, or even 25 or less. Note that ΔL at a thickness of 1.5 mm for zirconia calcined material. * (WB) can be measured in the same way as with zirconia molded bodies, except that the measurement sample is changed from zirconia molded bodies to zirconia calcined bodies.

[0152] The calcined zirconia body of the present invention preferably has a three-point bending strength of 500 MPa or more after sintering at 900 to 1200°C under normal pressure (after becoming a zirconia sintered body). This makes it possible to easily manufacture the zirconia sintered body of the present invention, which has excellent mechanical strength. A zirconia sintered body with superior mechanical strength is obtained, and therefore, the three-point bending strength is more preferably 600 MPa or more, even more preferably 650 MPa or more, particularly preferably 700 MPa or more, and most preferably 800 MPa or more. There is no particular upper limit to the three-point bending strength, but it can be, for example, 1500 MPa or less, and even 1000 MPa or less. The method for measuring the three-point bending strength is as described above in the explanation of the three-point bending strength in the zirconia sintered body.

[0153] The zirconia calcined body of the present invention preferably has a transmittance of 40% or more of light at a wavelength of 700 nm at a thickness of 0.5 mm after sintering at 900 to 1200°C under normal pressure (after becoming a zirconia sintered body). This makes it possible to easily manufacture the zirconia sintered body of the present invention which has excellent light transmittance. Since a zirconia sintered body with excellent light transmittance can be obtained, the transmittance is more preferably 45% or more, even more preferably 46% or more, particularly preferably 48% or more, most preferably 50% or more, and may even be 52% or more. There is no particular upper limit to the transmittance, but the transmittance can be, for example, 60% or less, and even 57% or less. The method for measuring the transmittance is as described above in the explanation of the transmittance of light at a wavelength of 700 nm at a thickness of 0.5 mm in the zirconia sintered body.

[0154] The zirconia calcined body of the present invention preferably has a linear light transmittance of 1% or more, more preferably 3% or more, even more preferably 5% or more, particularly preferably 7% or more, and may even be 10% or more, after sintering at 900 to 1200°C under normal pressure (after becoming a zirconia sintered body) at a thickness of 1.0 mm. Having the linear light transmittance within the above range makes it easier to satisfy the required light transmittance at the incisal edge, for example, when used as a dental prosthesis. There is no particular upper limit to the linear light transmittance, but it can be, for example, 60% or less, and even 50% or less. The method for measuring the linear light transmittance is as described above in the explanation of the linear light transmittance at a thickness of 1.0 mm in the zirconia sintered body.

[0155] [Method for manufacturing zirconia calcined bodies] The method for producing a calcined zirconia body of the present invention is characterized by using, for example, a zirconia molded body of the present invention. The method for producing a calcined zirconia body preferably includes a step of calcining the zirconia molded body at 200 to 800°C. The method for producing a calcined zirconia body of the present invention also includes a step of cutting the zirconia molded body of the present invention, and the cut zirconia molded body may be calcined. The cutting method is not particularly limited, and known apparatus (for example, known milling apparatus) and method can be used. The calcination temperature is preferably 200°C or higher, more preferably 250°C or higher, even more preferably 300°C or higher, and preferably 800°C or lower, more preferably 700°C or lower, and even more preferably 600°C or lower, from the viewpoint of easily obtaining the desired calcined zirconia body. By setting the calcination temperature above the lower limit, the generation of organic residue can be effectively suppressed. Furthermore, by setting the calcination temperature below the upper limit, it is possible to suppress excessive sintering that would make cutting (milling) with a cutting machine difficult.

[0156] There are no particular restrictions on the heating rate when calcining the zirconia molded body of the present invention, but it is preferably 0.1°C / min or more, more preferably 0.2°C / min or more, even more preferably 0.5°C / min or more, and also preferably 50°C / min or less, more preferably 30°C / min or less, and even more preferably 20°C / min or less. Productivity is improved when the heating rate is above the lower limit. Furthermore, when the heating rate is below the upper limit, the volume difference between the inside and outside of the zirconia molded body or calcined zirconia body can be suppressed, and if the zirconia molded body contains organic matter, the rapid decomposition of such organic matter can be suppressed, thereby suppressing cracks and fractures.

[0157] There are no particular restrictions on the calcination time when calcining the zirconia molded article of the present invention. However, in order to obtain the target zirconia calcined article efficiently and stably with good productivity, the calcination time is preferably 0.5 hours or more, more preferably 1 hour or more, even more preferably 2 hours or more, and also preferably 10 hours or less, more preferably 8 hours or less, and even more preferably 6 hours or less.

[0158] The calcination in this invention can be carried out using a calcination furnace. There are no particular restrictions on the type of calcination furnace; for example, electric furnaces and degreasing furnaces commonly used in general industry can be used.

[0159] The zirconia calcined body of the present invention can be shaped into a desired form according to its application by milling before being formed into a zirconia sintered body. In particular, the zirconia sintered body of the present invention is particularly suitable as a dental material such as dental prostheses because it has excellent light transmission and mechanical strength despite containing a fluorescent agent. To obtain a zirconia sintered body for such applications, the zirconia calcined body can be milled to the corresponding shape. There are no particular restrictions on the method of milling, and it can be done, for example, using a known milling apparatus.

[0160] [Method for manufacturing zirconia sintered bodies] As described above, the zirconia sintered body of the present invention can be manufactured by sintering the zirconia molded body of the present invention under atmospheric pressure, and can also be manufactured by sintering the calcined zirconia body of the present invention under atmospheric pressure.

[0161] In both cases—when sintering the zirconia molded body of the present invention and when sintering the calcined zirconia body of the present invention—the sintering temperature is preferably 900°C or higher, more preferably 1000°C or higher, even more preferably 1050°C or higher, preferably 1200°C or lower, more preferably 1150°C or lower, and even more preferably 1120°C or lower, from the viewpoint of easily obtaining the desired zirconia sintered body. By setting the sintering temperature above the lower limit, sintering can proceed sufficiently, and a dense sintered body can be easily obtained. Furthermore, by setting the sintering temperature below the upper limit, a zirconia sintered body with a crystal grain size within the preferred range of the present invention can be easily obtained, and the deactivation of the fluorescent agent can be suppressed.

[0162] In both cases of sintering the zirconia molded body of the present invention and sintering the calcined zirconia body of the present invention, there are no particular restrictions on the sintering time. However, in order to obtain the desired zirconia sintered body with good productivity, the sintering time is preferably 5 minutes or more, more preferably 15 minutes or more, even more preferably 30 minutes or more, and also preferably 6 hours or less, more preferably 4 hours or less, and even more preferably 2 hours or less.

[0163] The sintering in this invention can be carried out using a sintering furnace. There are no particular restrictions on the type of sintering furnace; for example, electric furnaces and degreasing furnaces commonly used in general industry can be used. In particular, when used for dental materials, in addition to conventional sintering furnaces for dental zirconia, dental porcelain furnaces with relatively low sintering temperatures can also be used.

[0164] The zirconia sintered body of the present invention can be easily manufactured without HIP treatment, but further improvements in light transmittance and mechanical strength are possible by performing HIP treatment after sintering under atmospheric pressure as described above.

[0165] [Applications of zirconia sintered bodies] While there are no particular limitations on the use of the zirconia sintered body of the present invention, it is particularly suitable as a dental material such as dental prostheses because it has excellent light transmittance and mechanical strength, as well as excellent linear light transmittance. In particular, it is extremely useful not only as a dental prosthesis used in the cervical region of the tooth, but also as a dental prosthesis used in the occlusal surface of molars and the incisal edge of anterior teeth. The zirconia sintered body of the present invention is especially preferable for use as a dental prosthesis used in the incisal edge of anterior teeth. [Examples]

[0166] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. The methods for measuring each physical property are as follows.

[0167] (1) Average primary particle diameter of zirconia particles Zirconia particles in a zirconia slurry were photographed using a transmission electron microscope (TEM). The particle diameter (maximum diameter) of 100 arbitrary particles was measured from the obtained images, and the average value of these measurements was defined as the average primary particle diameter of the zirconia particles.

[0168] (2) Percentage of particles with a particle size greater than 100 nm Zirconia particles in a zirconia slurry were dispersed in methanol and measured by volume using a laser diffraction / scattering particle size distribution analyzer (LA-950, Horiba, Ltd.).

[0169] (3) Crystal grain size The grain size of the zirconia sintered body was determined by taking a field emission scanning electron microscope (FE-SEM) image of the cross-section of the zirconia sintered body, selecting 100 arbitrary particles from the image, and calculating the average value of the equivalent circle diameter (diameter of a true circle with the same area) of each particle.

[0170] (4) Three-point bending strength The three-point bending strength of the zirconia sintered body was measured in accordance with ISO 6872:2015, with a support distance of 30 mm, specimen size of 40 mm × 4 mm × 3 mm, and a crosshead speed of 0.5 mm / min. The average value was calculated from n=10 measurements. This test specimen was obtained by forming a 40mm x 6mm x 5mm rectangular bar shape from a powder containing zirconia particles obtained in the process of the example using a uniaxial press, increasing the density by cold isostatic pressing (CIP) (pressure 170 MPa) to obtain a zirconia molded body, firing it, and then polishing the surface.

[0171] (5) Light transmittance (wavelength 700nm, 0.5mm thickness) The transmittance of 700 nm light at a thickness of 0.5 mm was measured using a spectrophotometer (Hitachi High-Technologies Corporation, "Hitachi Spectrophotometer U-3900H") by transmitting and scattering light generated from a light source through the sample and then measuring it using an integrating sphere. In this measurement, the transmittance was first measured in the wavelength range of 300 to 750 nm, and then the transmittance for 700 nm light was determined. For the measurement, a disc-shaped zirconia sintered body with a diameter of 15 mm and a thickness of 0.5 mm, obtained by mirror polishing a disc-shaped zirconia sintered body, was used as the sample, and the average value measured with n=3 was calculated.

[0172] (6)Linear light transmittance (1.0mm thickness) The linear light transmittance of a 1.0 mm thick zirconia sintered body was measured using a turbidimeter (Haze Meter NDH4000, manufactured by Nippon Denshoku Industries Ltd.), by transmitting and scattering light generated from a light source through the sample and then measuring it using an integrating sphere. In this measurement, linear light transmittance was measured according to ISO 13468-1:1996 and JIS K 7361-1:1997, and haze was measured according to ISO 14782-1:1999 and JIS K 7136:2000. For the measurement, a disc-shaped zirconia sintered body with a diameter of 15 mm and a thickness of 1.0 mm, obtained by mirror polishing a disc-shaped zirconia sintered body, was used as the sample, and the average value measured with n=3 was calculated.

[0173] (7) 28.5 μm 2 Number of pores with a diameter of 50 nm or more per unit cross-sectional area 28.5 μm 2 The number of pores with a diameter of 50 nm or more per unit cross-sectional area was calculated using a zirconia sintered body obtained by sintering a block-shaped zirconia molded body, at 28.5 μm. 2 Ten field-emission scanning electron microscope (FE-SEM) images were taken of the cross-section of the zirconia sintered body. The equivalent diameter of each pore in the images (the diameter of a true circle with the same area) was determined, and the number of pores with a diameter of 50 nm or larger was calculated for each image. The calculated number was then totaled for all 10 images and divided by 10 to obtain the arithmetic mean. In Tables 3-6 below, this is referred to as "number of pores with a diameter of 50 nm or larger".

[0174] (8) Appearance of the zirconia sintered body The appearance (color) of the zirconia sintered body was evaluated visually.

[0175] (9) Fluorescence of zirconia sintered bodies The fluorescence of zirconia sintered bodies was evaluated visually by checking for the presence or absence of fluorescence under UV light.

[0176] (10) ΔL of zirconia molded articles and calcined zirconia articles * (WB) ΔL at a thickness of 1.5 mm for zirconia molded articles and calcined zirconia articles * The white balance (WB) was measured using a spectrophotometer (Konica Minolta Japan, "CM-3610A"). In this measurement, an F11 light source was used, and the reflected light was measured to determine the WB. For the measurement, a disc-shaped zirconia molded body and a zirconia calcined body with a diameter of 20 mm and a thickness of 1.5 mm, obtained by mirror polishing a disc-shaped zirconia molded body and calcined body, were used as samples, and the average value measured with n=3 was calculated.

[0177] (11) Combustion start temperature and combustion end temperature of polyol and binder For the polyols and binders used in the examples and comparative examples, the combustion start temperature and combustion end temperature were measured using a thermal analyzer manufactured by Rigaku Corporation (product name: Thermo plus EVO2, differential thermal-thermogravimetric simultaneous measurement device TG-DTA8122, analysis software: Thermo plusEVO ver2.086, sample pan: platinum, measurement atmosphere: Air (100cc / min), heating rate: 10.0℃ / min, sampling interval: 1.0 second). The types of polyols and binders used, along with the measurement results for combustion start temperature and combustion end temperature, are shown in Tables 1 and 2.

[0178] [Table 1]

[0179] [Table 2]

[0180] [Example 1] A 1.0 L mixed aqueous solution containing 0.62 mol / L zirconium oxychloride and 0.038 mol / L yttrium chloride, and a 0.5 L aqueous solution of 1.9 mol / L sodium hydroxide were prepared. 1.0 L of pure water was poured into the sedimentation tank, and then the above mixed aqueous solution and sodium hydroxide aqueous solution were poured in simultaneously to coprecipitate zirconium oxychloride and yttrium chloride, thereby obtaining a slurry. After filtering and washing, 22.2 g of acetic acid was added to the slurry, and the slurry was hydrothermally treated at 200°C for 3 hours. The resulting slurry was centrifuged using a membrane filter with a pore size of 100 nm, and pure water was added to obtain a zirconia slurry from which coarse particles were removed, so that the solid content concentration (concentration of zirconia with yttria dissolved in it) was 5.0% by mass. The average primary particle size of the zirconia particles contained in this zirconia slurry was 17 nm, and 0.33% by mass of zirconia particles had a particle size of 100 nm or larger.

[0181] Nine volumes of isopropanol were added to the zirconia slurry, and the mixture was placed in a centrifuge tube and thoroughly mixed. The mixture was then centrifuged at 4000 rpm for 10 minutes. After confirming the sedimentation of a white substance, the supernatant was removed, and isopropanol was added again and thoroughly mixed. The mixture was then centrifuged at 4000 rpm for 10 minutes. After confirming the sedimentation of a white substance, the supernatant was removed, and methanol was added to bring the volume to the same volume as the zirconia slurry used. The mixture was then thoroughly mixed to obtain a methanol-substituted slurry. The residual water content of this methanol-substituted slurry was measured using a Karl Fischer moisture meter and was found to be 0.08% by mass. To the obtained slurry, glycerin was added at a concentration of 1% by mass per 100% by mass of zirconia, and the acrylic binder "KFE-124" was added at a concentration of 2% by mass per 100% by mass of zirconia. The mixture was then ultrasonically dispersed at 40 kHz for 1 hour to obtain a slurry containing the additives. The obtained additive-containing slurry was supercritically dried using a supercritical drying apparatus according to the following procedure. Specifically, the additive-containing slurry was placed in a pressure vessel, the pressure vessel was connected to a supercritical carbon dioxide extractor, and it was confirmed that there was no pressure leakage. Then, the pressure vessel and preheating tube were immersed in a water bath heated to 60°C, the temperature was raised to 80°C, and the pressure was increased to 25 MPa, and it was left to stand for 10 minutes to stabilize. Next, carbon dioxide and methanol as an entrainer were introduced under predetermined conditions (temperature: 80°C, pressure: 25 MPa, carbon dioxide flow rate: 10 mL / min, entrainer (methanol) flow rate: 1.5 mL / min). After 2 hours, the methanol introduction was stopped, and the introduction of carbon dioxide alone was continued. After 2 hours of introduction of carbon dioxide alone, the supply of carbon dioxide was stopped, and the pressure was gradually reduced from 25 MPa over approximately 20 minutes while maintaining the temperature at 80°C, returning to atmospheric pressure. The pressure vessel was removed from the water bath and cooled to room temperature, opened, and the treated sample was collected to obtain a powder containing zirconia particles.

[0182] The obtained powder was molded using a uniaxial press into 20mm x 20mm x 5mm plates, 20mm diameter x 2.5mm thickness discs, and 20mm x 20mm x 15mm blocks. These were then subjected to cold isostatic pressing (CIP) (pressure 170 MPa) to increase their density and obtain zirconia molded bodies. These zirconia molded bodies were calcined at 500°C for 2 hours under atmospheric pressure to obtain calcined zirconia bodies. Furthermore, the calcined zirconia bodies other than the block-shaped ones were sintered at 1100°C for 2 hours under atmospheric pressure to obtain sintered zirconia bodies. The obtained sintered zirconia bodies were white. The measurement results are shown in Table 3.

[0183] Furthermore, using a milling device ("Katana® H-18", manufactured by Kuraray Noritake Dental Co., Ltd.), the above-mentioned block-shaped zirconia calcined bodies were cut into the shape of a single crown for the maxillary central incisor and a single crown for the mandibular first molar, respectively. These were then sintered at 1100°C for 2 hours under normal pressure to obtain dental prostheses in the shape of tooth crowns.

[0184] [Comparative Example 1] A slurry containing additives was obtained by adding glycerin at a concentration of 1% by mass per 100% by mass of zirconia to the methanol-substituted slurry prepared in Example 1 and ultrasonically dispersing it at 40 kHz for 1 hour. Except for using the above-mentioned slurry as the additive-containing slurry, powder containing zirconia particles, plate-shaped and disc-shaped zirconia molded bodies, zirconia calcined bodies, and zirconia sintered bodies were obtained in the same manner as in Example 1. The obtained zirconia sintered bodies were white. The measurement results are shown in Table 3. However, the block-shaped zirconia molded bodies broke when the pressure was released from the uniaxial press, indicating insufficient mechanical strength. Therefore, it was not possible to manufacture block-shaped zirconia calcined bodies and block-shaped zirconia sintered bodies.

[0185] [Comparative Example 2] Except for using 2% by mass of glycerin relative to 100% by mass of zirconia in Comparative Example 1, powder containing zirconia particles, plate-shaped and disc-shaped zirconia molded bodies, calcined zirconia bodies, and sintered zirconia bodies were obtained in the same manner as in Comparative Example 1. The obtained sintered zirconia bodies were white. The measurement results are shown in Table 3. Note that the block-shaped zirconia molded body broke when the pressure was released from the uniaxial press, indicating insufficient mechanical strength.

[0186] [Comparative Example 3] In Example 1, an acrylic binder "KFE-124" was added at a concentration of 2% by mass relative to 100% by mass of zirconia to the methanol-substituted slurry prepared, and the slurry containing the additive was obtained by ultrasonic dispersion at 40 kHz for 1 hour. Except for using the above-mentioned slurry as the additive-containing slurry, powder, plate-shaped, disc-shaped, and block-shaped zirconia molded bodies, calcined zirconia bodies, and sintered zirconia bodies containing zirconia particles were obtained by the same method as in Example 1. The obtained sintered zirconia bodies were white. The measurement results are shown in Table 3.

[0187] [Comparative Example 4] Except for replacing the polyol with dipentaerythritol, powder containing zirconia particles, plate-shaped, disc-shaped, and block-shaped zirconia molded bodies, calcined zirconia bodies, and sintered zirconia bodies were obtained using the same method as in Example 1. The obtained sintered zirconia bodies were white. The measurement results are shown in Table 3.

[0188] [Table 3]

[0189] [Example 2] The test was carried out in the same manner as in Example 1, except that 1.0 L of a mixed aqueous solution containing 0.62 mol / L of zirconium oxychloride and 0.066 mol / L of yttrium chloride was used. The average primary particle size of the zirconia particles contained in the zirconia slurry was 18 nm, and 0.35% by mass of zirconia particles had a particle size of 100 nm or larger. An additive-containing slurry containing a polyol and binder was prepared in the same manner as in Example 1, except that the slurry obtained above was used. Subsequently, powder containing zirconia particles, plate-shaped, disc-shaped, and block-shaped zirconia molded bodies, calcined zirconia bodies, and sintered zirconia bodies were obtained in the same manner as in Example 1. The obtained sintered zirconia bodies were white. The measurement results are shown in Table 4.

[0190] [Example 3] The test was carried out in the same manner as in Example 1, except that 1.0 L of a mixed aqueous solution containing 0.62 mol / L of zirconium oxychloride and 0.108 mol / L of yttrium chloride was used. The average primary particle size of the zirconia particles contained in the zirconia slurry was 17 nm, and 0.15% by mass of zirconia particles had a particle size of 100 nm or larger. An additive-containing slurry containing a polyol and binder was prepared in the same manner as in Example 1, except that the slurry obtained above was used. Subsequently, powder containing zirconia particles, plate-shaped, disc-shaped, and block-shaped zirconia molded bodies, calcined zirconia bodies, and sintered zirconia bodies were obtained in the same manner as in Example 1. The obtained sintered zirconia bodies were white. The measurement results are shown in Table 4.

[0191] [Example 4] To the zirconia slurry prepared in Example 2 (average primary particle diameter of 18 nm, with 0.35% by mass of zirconia particles having a particle size of 100 nm or larger), a dilute bismuth nitrate solution was added so that the content of bismuth oxide (Bi2O3) relative to 100% by mass of zirconia was 0.02% by mass, to obtain a slurry containing zirconia particles and a fluorescent agent. An additive-containing slurry containing a polyol and binder was prepared in the same manner as in Example 1, except that the slurry obtained above was used. Subsequently, powder containing zirconia particles, plate-shaped, disc-shaped, and block-shaped zirconia molded bodies, calcined zirconia bodies, and sintered zirconia bodies were obtained in the same manner as in Example 1. The obtained sintered zirconia bodies were white and fluorescent. The measurement results are shown in Table 4.

[0192] [Example 5] To the zirconia slurry prepared in Example 2 (average primary particle diameter of 18 nm, with 0.35% by mass of zirconia particles having a particle size of 100 nm or larger), an aqueous nickel(II) nitrate solution was added so that the nickel(II) oxide (NiO) content relative to 100% by mass of zirconia was 0.02% by mass, to obtain a slurry containing zirconia particles and a coloring agent. An additive-containing slurry containing a polyol and binder was prepared in the same manner as in Example 1, except that the slurry obtained above was used. Subsequently, powder containing zirconia particles, plate-shaped, disc-shaped, and block-shaped zirconia molded bodies, calcined zirconia bodies, and sintered zirconia bodies were obtained in the same manner as in Example 1. The obtained sintered zirconia bodies were colored red. The measurement results are shown in Table 4.

[0193] [Table 4]

[0194] [Example 6] Except for using polyethylene glycol "PEG-6000P" as the polyol and "KFA-440" as the binder, powder containing zirconia particles, plate-shaped, disc-shaped, and block-shaped zirconia molded bodies, calcined zirconia bodies, and sintered zirconia bodies were obtained in the same manner as in Example 2. The obtained sintered zirconia bodies were white. The measurement results are shown in Table 5.

[0195] [Example 7] Except for using propylene glycol as the polyol, powder containing zirconia particles, plate-shaped, disc-shaped, and block-shaped zirconia molded bodies, calcined zirconia bodies, and sintered zirconia bodies were obtained in the same manner as in Example 2. The obtained sintered zirconia bodies were white. The measurement results are shown in Table 5.

[0196] [Example 8] Except for using polyglycerin #310 as the polyol and KFA-440 as the binder, powder containing zirconia particles, plate-shaped, disc-shaped, and block-shaped zirconia molded bodies, calcined zirconia bodies, and sintered zirconia bodies were obtained in the same manner as in Example 2. The obtained sintered zirconia bodies were white. The measurement results are shown in Table 5.

[0197] [Table 5]

[0198] [Example 9] Except for using the acrylic binder "KFA-440" as the binder, powder, plate-shaped, disc-shaped, and block-shaped zirconia molded bodies, calcined zirconia bodies, and sintered zirconia bodies containing zirconia particles were obtained in the same manner as in Example 2. The obtained sintered zirconia bodies were white. The measurement results are shown in Table 6.

[0199] [Example 10] Except for using the acrylic binder "Oricox KC-700" as the binder, powder containing zirconia particles, plate-shaped, disc-shaped, and block-shaped zirconia molded bodies, calcined zirconia bodies, and sintered zirconia bodies were obtained in the same manner as in Example 2. The obtained sintered zirconia bodies were white. The measurement results are shown in Table 6.

[0200] [Example 11] Except for using the acrylic binder "Oricox KC-500" as the binder, powder containing zirconia particles, plate-shaped, disc-shaped, and block-shaped zirconia molded bodies, calcined zirconia bodies, and sintered zirconia bodies were obtained in the same manner as in Example 2. The obtained sintered zirconia bodies were white. The measurement results are shown in Table 6.

[0201] [Example 12] Except for using a polyol content of 2% by mass, the same method as in Example 1 was used to obtain powder containing zirconia particles, plate-shaped, disc-shaped, and block-shaped zirconia molded bodies, calcined zirconia bodies, and sintered zirconia bodies. The obtained sintered zirconia bodies were white. The measurement results are shown in Table 6.

[0202] [Table 6]

Claims

1. Zirconia particles containing yttria in an amount of 2.0 to 9.0 mol% relative to the total number of moles of zirconium oxide and yttria, and having an average primary particle diameter of 60 nm or less, It contains a polyol and a binder. The mixing ratio (mass ratio) of the binder and the polyol is binder:polyol = 10:1 to 1:

10. The binder content is 0.01% by mass or more and less than 10% by mass relative to 100% by mass of zirconia. The polyol content is 0.01% by mass or more and 8% by mass or less, relative to 100% by mass of zirconia. A zirconia molded article wherein the polyol and the binder satisfy the following relationship. X1<Y1<X2<Y2≦500℃ (In the formula, X1 represents the combustion start temperature of the polyol, X2 represents the combustion end temperature of the polyol, Y1 represents the combustion start temperature of the binder, Y2 represents the combustion end temperature of the binder, X1 and Y1 represent the temperatures at which a 0.5% weight loss is observed, with the weight before heating measured by thermogravimetric analysis being 100%, X2 and Y2 represent the temperatures at which a 99.5% weight loss is observed, and X1 is 200°C or less.)

2. A zirconia molded article according to claim 1, wherein the thickness is 10 mm or more.

3. The zirconia molded article according to claim 1 or 2, wherein the combustion initiation temperature (X1) of the polyol is 50°C or higher.

4. ΔL at a thickness of 1.5 mm ＊ A zirconia molded article according to claim 1 or 2, wherein (W-B) is 5 or more.

5. A zirconia molded article according to claim 1 or 2, wherein the crystal grain size after sintering at 900 to 1200°C under normal pressure is 180 nm or less.

6. A zirconia molded article according to claim 1 or 2, wherein the three-point bending strength after sintering at 900 to 1200°C under normal pressure is 500 MPa or more.

7. A zirconia molded article according to claim 1 or 2, wherein the transmittance of light at a wavelength of 700 nm at a thickness of 0.5 mm after sintering at 900 to 1200°C under normal pressure is 40% or more.

8. A zirconia molded article according to claim 1 or 2, wherein the linear light transmittance at a thickness of 1.0 mm after sintering at 900 to 1200°C under normal pressure is 1% or more.

9. 28.5 μm after sintering at 900-1200°C under normal pressure. 2 The zirconia molded article according to claim 1 or 2, wherein the number of pores with a diameter of 50 nm or more per unit cross-sectional area is 10 or less.

10. ΔL at a thickness of 1.5 mm after calcination at 200-800°C ＊ A zirconia molded article according to claim 1 or 2, wherein (W-B) is 5 or more.

11. A method for producing a calcined zirconia body, comprising the step of calcining the zirconia molded body according to claim 1 or 2 at 200 to 800°C.

12. A method for producing a zirconia sintered body, comprising the step of sintering the zirconia molded body according to claim 1 or 2 at 900 to 1200°C under normal pressure.

Images