Zirconia green body, zirconia calcined body, zirconia sintered body, and methods respectively for producing these products

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

Zirconia molded body, zirconia calcined body, zirconia sintered body, and methods for producing them

[0001] The present invention relates to a zirconia molded body, etc. More specifically, the present invention relates to a zirconia sintered body having both excellent mechanical strength and translucency, a zirconia molded body containing a binder capable of providing such a zirconia sintered body and having a thickness of 10 mm or more, a zirconia calcined body, and methods for producing the same.

[0002] In recent years, zirconia sintered bodies containing yttria have been used as dental materials for dental prostheses, etc. These dental prostheses are often produced by forming a zirconia molded body having a desired shape, such as a disk or a prism, by press-molding zirconia particles or by molding using a slurry or composition containing zirconia particles, and then calcining this to form a calcined body (mill blank), which is then cut (milled) into the shape of the desired dental prosthesis and then sintered.

[0003] It has been confirmed that the in-line light transmittance of a zirconia sintered body can be improved by making the crystal grain size small and uniform (see, for example, Patent Document 1). In order to make the crystal grain size of a zirconia sintered body small and uniform, a hot isostatic pressing (HIP) process is required. However, the HIP apparatus used in the HIP process is a special device classified as high-pressure gas production equipment, so it is difficult to say that a zirconia sintered body with high in-line light transmittance can be easily obtained.

[0004] Therefore, a zirconia sintered body having excellent mechanical strength and translucency without using a HIP apparatus, a zirconia molded body from which such a zirconia sintered body can be obtained, and a zirconia calcined body have also been proposed (Patent Document 2).

[0005] JP 2008-214168 A International Publication No. 2020 / 179876

[0006] Furthermore, 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 to maintain the shape. The shape retention improves as the amount of binder added increases, but the inventors' investigations have revealed that an increase in the amount of binder added results in a significant decrease in translucency due to the binder amount.

[0007] Therefore, when a zirconia molded body containing a binder in an amount intended for a thickness of 10 mm or more is used, the resulting zirconia sintered body has not been excellent in both mechanical strength and translucency.

[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 containing a binder in an amount sufficient to provide such a zirconia sintered body having a thickness of 10 mm or more, a zirconia calcined body, and methods for producing these. Another object of the present invention is to provide a zirconia sintered body having both excellent mechanical strength and translucency, and a zirconia molded body and a zirconia calcined body capable of providing such a zirconia sintered body, without using a HIP apparatus, and methods for producing these.

[0009] As a result of extensive research to achieve the above-mentioned object, the present inventors have found that in a zirconia molded body containing zirconia particles having an average primary particle size of 60 nm or less, containing yttria in an amount of 2.0 to 9.0 mol% relative to the total moles of zirconium oxide and yttria, a polyol, and a binder, the above-mentioned problems can be solved by focusing on the combustion start and end temperatures of the polyol and the binder, and finding that these temperatures satisfy a specific relationship. Furthermore, the present inventors have found that such a zirconia sintered body is particularly suitable as a dental material for dental prostheses, and is particularly useful not only for dental prostheses used in the cervical region of teeth, but also for dental prostheses used on the occlusal surfaces of molars or the incisal ends of anterior teeth. Based on these findings, the present inventors have conducted further research and completed the present invention.

[0010] That is, the present invention encompasses the following inventions: [1] A zirconia molded body comprising zirconia particles containing yttria in an amount of 2.0 to 9.0 mol % relative to the total moles of zirconium oxide and yttria and having an average primary particle size 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°C (wherein 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, and X2 and Y2 represent the temperatures at which a 99.5% weight loss is observed, assuming that the weight before heating measured by thermogravimetry is 100%). [2] The zirconia molded body according to [1], having a thickness of 10 mm or more. [3] The zirconia molded body according to [1] or [2], wherein the polyol has a combustion initiation temperature (X1) of 50° C. or higher. [4] ΔL at a thickness of 1.5 mm ＊ The zirconia molded body according to any one of [1] to [3], wherein (W-B) is 5 or more. [5] The zirconia molded body according to any one of [1] to [4], wherein the crystal grain size after sintering at 900 to 1200°C under normal pressure is 180 nm or less. [6] The zirconia molded body 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] The zirconia molded body 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] The zirconia molded body 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] The zirconia molded body according to any one of [1] to [7], wherein the linear light transmittance at a thickness of 28.5 μm after sintering at 900 to 1200°C under normal pressure. ２

[10] The zirconia molded body according to any one of [1] to [8], wherein the number of pores having a diameter of 50 nm or more per cross-sectional area is 10 or less. ＊

[11] The zirconia molded body according to any one of [1] to [9], wherein (W−B) is 5 or more.

[12] The zirconia molded body 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 ΔL ＊ (W−B) is 5 or more, and after sintering at 900 to 1200°C, the thickness is 28.5 μm ２

[12] A method for producing a zirconia calcined body, comprising a step of calcining the zirconia molded body according to any one of [1] to

[10] at 200 to 800°C.

[13] A zirconia calcined body 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 a thickness of 28.5 μm. ２

[14] A zirconia sintered body, the number of pores having a diameter of 50 nm or more per cross-sectional area of ​​which is 10 or less, and the thickness of which is 10 mm or more.

[14] A method for producing a zirconia sintered body, the method comprising a step of sintering the zirconia molded body according to any one of [1] to

[10] or the zirconia calcined body according to

[11] at 900 to 1200°C under normal pressure.

[0011] According to the present invention, it is possible to provide a zirconia sintered body having both excellent mechanical strength and translucency, a zirconia molded body and a zirconia calcined body which can provide such a zirconia sintered body and contain a binder in an amount intended for a thickness of 10 mm or more, and methods for producing these. Furthermore, it is possible to provide a zirconia sintered body having both excellent mechanical strength and translucency, and a method for easily producing a zirconia molded body and a zirconia calcined body which can provide such a zirconia sintered body without using a HIP apparatus.

[0012] The term "zirconia molded body" as used herein refers to a product obtained by press molding, injection molding, stereolithography, or the like using zirconia in various forms, such as powder, granules, paste, or slurry, as the main raw material, and which has not yet reached a calcined or sintered state. That is, the zirconia molded body is distinguished from a zirconia calcined body and a zirconia sintered body in that the zirconia molded body is a green body formed by molding and then unsintered. The term "zirconia calcined body" as used herein refers to a precursor (intermediate product) of a zirconia sintered body, in which the zirconia particles (powder) are not completely sintered (calcined state). The term "zirconia sintered body" as used herein refers to a product in which the zirconia particles (powder) have reached a sintered state. In this specification, the upper and lower limits of the numerical ranges (contents of each component, X1, Y1, X2, Y2 and values ​​calculated from these, temperature ranges, each physical property, etc.) can be combined as appropriate.

[0013] The zirconia particles, zirconia molded body, zirconia calcined body, or zirconia sintered body of the present invention contain zirconium oxide and a stabilizer capable of suppressing the phase transition of zirconium oxide. The stabilizer is preferably one capable of forming partially stabilized zirconia. Examples of the stabilizer include calcium oxide (CaO), magnesium oxide (MgO), and yttrium oxide (Y ２ O ３ ), cerium oxide (CeO ２ ), scandium oxide (Sc ２ O ３ ), niobium oxide (Nb ２ O ５ ), lanthanum oxide (La ２ O ３ ), erbium oxide (Er ２ O ３ ), praseodymium oxide (Pr ２ O ３ , Pr ６ O １１ ), samarium oxide (Sm ２ O ３ ), europium oxide (Eu ２ O ３ ) and thulium oxide (Tm ２ O ３), with yttria being preferred. The stabilizer content in the zirconia calcined body and sintered body thereof of the present invention can be measured, for example, by inductively coupled plasma (ICP) emission spectroscopy, X-ray fluorescence analysis, or the like. In the zirconia calcined body and sintered body thereof of the present invention, the stabilizer content 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 in the case of yttria.

[0014] Hereinafter, the stabilizer is referred to as yttria (Y ２ O ３ The preferred embodiments of the present invention will be described below taking as an example the case where yttria is replaced with the above-mentioned stabilizer other than yttria.

[0015] The zirconia molded body of the present invention contains zirconia particles having an average primary particle size of 60 nm or less, a polyol, and a binder, the 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 the average primary particle size of 60 nm or less, and the polyol and the binder satisfy the following relational formula: X1<Y1<X2<Y2≦500°C (wherein 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, and X2 and Y2 represent the temperatures at which a 99.5% weight loss is observed, assuming that the weight before heating measured by thermogravimetry is 100%).) By using the zirconia molded body, it is possible to obtain a zirconia sintered body that is excellent in both mechanical strength and translucency, despite being a zirconia molded body containing a binder (and further, a zirconia molded body having a thickness of 10 mm or more).

[0016] In a preferred embodiment of the present invention, yttria is contained in an amount of 2.0 to 9.0 mol % relative to the total mole number of zirconium oxide and yttria, and ΔL ＊Examples of suitable zirconia calcined bodies include those having a (W-B) of 5 or more, having 10 or less pores with a diameter of 50 nm or more after sintering at 900 to 1200°C, and having a thickness of 10 mm or more. Using such a zirconia calcined body also makes it possible to obtain a zirconia sintered body with excellent mechanical strength and translucency. In the present invention, "zirconia" refers to zirconium oxide containing yttrium oxide. Furthermore, in the present invention, the "yttria content" in the zirconia particles, zirconia molded body, zirconia calcined body, or zirconia sintered body refers to the ratio (mol %) of the number of moles of yttrium oxide to the total number of moles of zirconium oxide and yttrium oxide. The yttria content in the zirconia molded body, calcined body, and sintered body thereof of the present invention can be measured, for example, by inductively coupled plasma (ICP) emission spectroscopy, X-ray fluorescence analysis, or the like.

[0017] [Zirconia Sintered Body] Hereinafter, as an embodiment of the present invention, a zirconia sintered body will be described first. The zirconia sintered body of the present invention contains 2.0 to 9.0 mol % of yttria relative to the total number of moles of zirconium oxide and yttria, and has a particle size 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 having a thickness of 10 mm or more is not particularly limited, and may be a block shape (rectangular parallelepiped shape), etc. Note that the following description does not limit the present invention.

[0018] The zirconia sintered body of the present invention may contain a fluorescent agent. The zirconia sintered body has fluorescence due to the inclusion of a fluorescent agent. There are no particular limitations on the type of fluorescent agent, and one or more types that can emit fluorescence with light of any wavelength can be used. Such fluorescent agents include those containing metal elements. Examples of such metal elements include Ga, Bi, Ce, Nd, Sm, Eu, Gd, Tb, Dy, and Tm. The fluorescent agent may contain one of these metal elements alone or two or more types. Among these metal elements, Ga, Bi, Eu, Gd, and Tm are preferred, and Bi and Eu are more preferred, as they more significantly exhibit the effects of the present invention. Examples of fluorescent agents used in producing the zirconia sintered body of the present invention include oxides, hydroxides, acetates, and nitrates of the above metal elements. The fluorescent agent may also be Y. ２ SiO ５ : Ce, Y ２ SiO ５ :Tb, (Y, Gd, Eu)BO ３ , Y ２ O ３ :Eu, YAG:Ce, ZnGa ２ O ４ :Zn, BaMgAl １０ O １７ :Eu, etc.

[0019] The content of the fluorescent agent in the zirconia sintered body is not particularly limited and can be adjusted appropriately depending on the type of fluorescent agent or the application of the zirconia sintered body, but from the viewpoint of favorable use as a dental prosthesis, the content of the fluorescent agent, calculated as the oxide of the metal element contained in the fluorescent agent, relative to 100% by mass of zirconia contained in the zirconia sintered 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 preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less. When the content is equal to or higher than the lower limit, the fluorescence is not inferior to that of human natural teeth, and when the content is equal to or lower than the upper limit, a decrease in translucency and mechanical strength can be suppressed.

[0020] The zirconia sintered body of the present invention may contain a colorant. The zirconia sintered body becomes a colored zirconia sintered body by containing a colorant. The type of colorant is not particularly limited, and known pigments commonly used for coloring ceramics, known dental liquid colorants, etc. may be used. Examples of colorants include those containing metal elements, such as oxides containing metal elements such as iron, vanadium, praseodymium, erbium, chromium, nickel, and manganese, composite oxides thereof, or salts thereof. Commercially available colorants may also be used, such as Prettau Colour Liquid manufactured by Zirkonzahn. The zirconia sintered body may contain one type of colorant or two or more types of colorants.

[0021] The content of the colorant in the zirconia sintered body is not particularly limited, and can be adjusted as appropriate depending on the type of colorant and the application of the zirconia sintered body, etc. However, from the viewpoint of favorable use as a dental prosthesis, the content of the colorant, calculated as the oxide of the metal element contained in the colorant, relative to 100% by mass of zirconia contained in the zirconia sintered body, is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, and even more preferably 0.01% by mass or more, and is preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, and may be 0.1% by mass or less, or even 0.05% by mass or less.

[0022] According to the present invention, a zirconia sintered body having excellent in-line light transmittance can be obtained. To adjust the translucency of the zirconia sintered body, the zirconia sintered body of the present invention may contain a translucency adjuster. Specific examples of the translucency adjuster include aluminum oxide, titanium oxide, silicon dioxide, zircon, lithium silicate, and lithium disilicate. The zirconia sintered body may contain one type of translucency adjuster, or may contain two or more types of translucency adjusters.

[0023] The content of the light-transmitting adjuster in the zirconia sintered body is not particularly limited, and can be appropriately adjusted depending on the type of light-transmitting adjuster and the application of the zirconia sintered body. However, from the viewpoint of favorable use as a dental prosthesis, the content is preferably 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 2.0 to 9.0 mol% of yttria relative to the total moles of zirconium oxide and yttria. If the yttria content in the zirconia sintered body is less than 2.0 mol%, sufficient translucency 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 translucency 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, and even more preferably 4.0 mol% or more, and is preferably 8.0 mol% or less, more preferably 7.5 mol% or less, and even more preferably 7.0 mol% or less.

[0025] The crystal grain size of the zirconia sintered body of the present invention is preferably 180 nm or less. If the crystal grain size exceeds 180 nm, sufficient translucency may not be obtained. Since a zirconia sintered body with better translucency can be obtained, the crystal 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 on the crystal grain size, but the crystal grain size can be, for example, 50 nm or more, or even 70 nm or more. The crystal grain size of the zirconia sintered body can be determined by taking a field emission scanning electron microscope (FE-SEM) photograph of the cross section of the zirconia sintered body, arbitrarily selecting 100 particles from the photographed image, and calculating the average value of the circle-equivalent diameters (diameters of perfect circles with the same area) of the particles.

[0026] The zirconia sintered body of the present invention has 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. When the zirconia sintered body of the present invention has such a three-point bending strength, it 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 the three-point bending strength can be, for example, 1500 MPa or less, or 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 has excellent translucency. The zirconia sintered body of the present invention preferably has a transmittance of 40% or more, more preferably 45% or more, and may be 46% or more, 48% or more, 50% or more, or even 52% or more at a thickness of 0.5 mm, for light having a wavelength of 700 nm. Having the transmittance within the above range makes it easier to satisfy the translucency required for the incisal edge when used, for example, as a dental prosthesis. While there is no particular upper limit to the transmittance, the transmittance can be, for example, 60% or less, or even 57% or less. The transmittance of light having a wavelength 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 Spectrophotometer U-3900H, manufactured by Hitachi High-Technologies Corporation) can be used to transmit and scatter light generated from a light source through a sample, and the measurement can be performed using an integrating sphere. In this measurement, the transmittance may be measured in the wavelength region of 300 to 750 nm first, and then the transmittance for light with a wavelength of 700 nm may be determined. As a sample used for the measurement, a disk-shaped zirconia sintered body having a diameter of 15 mm and a thickness of 0.5 mm and having both sides mirror-polished can be used.

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

[0029] The 28.5 μm diameter contained in the zirconia sintered body of the present invention ２ The number of pores with a diameter of 50 nm or more per 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, when a block-shaped zirconia sintered body having a desired thickness is formed, the mechanical strength and translucency of the zirconia sintered body may be reduced. ２ The number of pores with a diameter of 50 nm or more per cross-sectional area is 28.5 μm ２Ten field-emission scanning electron microscope (FE-SEM) photographs of the cross section of the zirconia sintered body were taken, and the circle-equivalent diameters of the pores in the photographed images (the diameter of a perfect circle with the same area) were determined. Of these, the number of pores with a diameter of 50 nm or more was calculated in each photographed image. The calculated numbers for the 10 photographed images were summed up and divided by 10 to obtain an arithmetic mean value.

[0030] The method for producing a zirconia sintered body of the present invention is characterized by using the zirconia molded body of the present invention described below. The method for producing a zirconia sintered body preferably includes a step of sintering the zirconia molded body at 900 to 1200°C under normal pressure. The zirconia calcined body of the present invention described below may also be used, and a preferred method includes a step of sintering the zirconia calcined body at 900 to 1200°C under normal pressure. By using such a production method, a zirconia sintered body of the present invention having excellent mechanical strength and translucency and excellent in-line light transmittance can be easily produced.

[0031] [Zirconia Molded Body] The zirconia molded body of the present invention comprises zirconia particles containing 2.0 to 9.0 mol % of yttria relative to the total number of moles of zirconium oxide and yttria and having an average primary particle size 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°C (wherein 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, and X2 and Y2 represent the temperatures at which a 99.5% weight loss is observed, assuming that the weight before heating measured by thermogravimetry is 100%).) By using the zirconia molded body, it is possible to obtain a zirconia sintered body that is excellent in both mechanical strength and translucency and in in-line light transmittance, despite being a zirconia molded body containing a binder (and further, a zirconia molded body having a thickness of 10 mm or more). Furthermore, it is possible to achieve both the moldability of the molded body and the translucency of the sintered body.

[0032] The zirconia molded body of the present invention has high translucency, and from such a zirconia molded body, it is possible to produce a zirconia sintered body with high in-line light transmittance and a zirconia calcined body from which a zirconia sintered body with high in-line light transmittance can be produced. Specifically, the zirconia molded body of the present invention has a ΔL ＊ (W−B) is preferably 5 or more, more preferably 8 or more, even more preferably 10 or more, and may further be 11 or more, or 12 or more. ＊ When (W−B) is within the above range, a zirconia sintered body with high in-line light transmittance can be obtained when sintered under normal pressure in combination with a polyol and a binder that satisfy the above formula. ＊ There is no particular upper limit to (W−B), but it can be set to, for example, 30 or less, or even 25 or less. ＊ (W-B) can be measured using a spectrophotometer, for example, a spectrophotometer ("CM-3610A" manufactured by Konica Minolta Japan, Inc.). In this measurement, F11 is used as a light source, and the value can be obtained by measuring reflected light. A disk-shaped zirconia molded body having a diameter of 20 mm and a thickness of 1.5 mm can be used as a sample for the measurement. ΔL ＊ (W-B) is the brightness on a white background (L ＊ ) and brightness on a black background (L ＊ Specifically, the difference between the L and the white background of a zirconia molded body having a thickness of 1.5 mm is ＊ value and L on a black background ＊ It means the difference between the values. ＊ The value is L ＊ a ＊ b ＊ L of chromaticity (color space) in the color system (JIS Z 8781-4:2013) ＊ The white background refers to the white portion of the hiding power test paper described in JIS K 5600-4-1:1999, Part 4, Section 1, and the black background refers to the black portion of the hiding power test paper.

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

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

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

[0036] The content of yttria contained in the zirconia molded body of the present invention may be within 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 content of yttria in the resulting zirconia sintered body. The specific content of yttria in the zirconia molded body is 2.0 mol% or more, preferably 3.0 mol% or more, more preferably 3.5 mol% or more, and even more preferably 4.0 mol% or more, and is preferably 8.0 mol% or less, more preferably 7.5 mol% or less, and even more preferably 7.0 mol% or less.

[0037] The density of the zirconia molded body of the present invention is not particularly limited, and varies depending on the manufacturing method of the zirconia molded body, etc. However, since a dense zirconia sintered body can be obtained, the density is preferably 3.0 g / cm ３ It is preferable that the density is 3.2 g / cm or more. ３ More preferably, it is 3.4 g / cm or more. ３ There is no particular upper limit to the density, but it is preferably 6.0 g / cm3 or more. ３ Further, 5.8 g / cm ３ It can be as follows:

[0038] The shape of the zirconia molded body of the present invention is not particularly limited and can be any desired shape depending on the application. However, considering the ease of handling when obtaining a zirconia calcined body to be used as a mill blank for producing dental materials such as dental prostheses, a disk shape, a prism shape (e.g., a rectangular parallelepiped shape), etc. are preferred. As will be described later, in the production of a zirconia molded body, a shape corresponding to the desired shape of the zirconia sintered body to be finally obtained can be imparted to the zirconia molded body by employing a stereolithography method or the like. The present invention also encompasses zirconia molded bodies having such desired shapes. Furthermore, the zirconia molded body may have a single-layer structure or a multilayer structure. By adopting a multilayer structure, the finally obtained zirconia sintered body can have a multilayer structure, and its physical properties, such as translucency, can be locally changed.

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

[0040] The zirconia molded body of the present invention preferably has a crystal grain size of 180 nm or less after sintering at 900 to 1200°C for 2 hours under normal pressure (after being made into a zirconia sintered body). This makes it possible to easily produce a zirconia sintered body of the present invention with excellent translucency. Because a zirconia sintered body with better translucency can be obtained, the crystal grain size is more preferably 140 nm or less, even more preferably 120 nm or less, particularly preferably 110 nm or less, and may even be 100 nm or less. There is no particular lower limit to the crystal grain size, but the crystal grain size can be, for example, 50 nm or more, or even 70 nm or more. The method for measuring the crystal grain size is as described above in the explanation of the crystal grain size in the zirconia sintered body.

[0041] The zirconia molded 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 being made into a zirconia sintered body). This makes it possible to easily produce a zirconia sintered body of the present invention with excellent mechanical strength. Because a zirconia sintered body with excellent 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, or even 1000 MPa or less. The method for measuring the three-point bending strength is as described above in the description of the three-point bending strength of a zirconia sintered body.

[0042] The zirconia molded body of the present invention preferably has a transmittance of 40% or more at a 700 nm wavelength at a thickness of 0.5 mm after sintering at 900°C to 1200°C under normal pressure (after being converted into a zirconia sintered body). This allows for easy production of a zirconia sintered body of the present invention with excellent translucency. Because a zirconia sintered body with better translucency 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, or even 57% or less. The method for measuring the transmittance is as described above for the transmittance of 700 nm wavelength light at a thickness of 0.5 mm through a zirconia sintered body.

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

[0044] In a preferred embodiment of the present invention, the thickness of the sintered product is 28.5 μm after sintering at 900 to 1200° C. under atmospheric pressure. ２ An example of such a zirconia molded body is one in which the number of pores having a diameter of 50 nm or more per cross-sectional area is 10 or less. The preferred range and measuring method for the number of pores are the same as those for the zirconia sintered body.

[0045] [Method for producing zirconia molded body] The method for producing the zirconia molded body of the present invention is not particularly limited as long as it achieves the effects of the present invention, but since it can easily produce the zirconia sintered body of the present invention that is excellent in both translucency and mechanical strength, it is preferable that the method include a molding step of molding zirconia particles, a polyol, and a binder to obtain the zirconia molded body. The combination of the polyol and the binder is not particularly limited as long as it satisfies the above-mentioned relationship, and specific materials are as described below.

[0046] The yttria content of the zirconia particles used is preferably the same as the yttria content of the resulting zirconia molded body, and in turn the zirconia calcined body and sintered body. The specific yttria content of the zirconia particles is 2.0 mol% or more, preferably 3.0 mol% or more, more preferably 3.5 mol% or more, and even more preferably 4.0 mol% or more, and is 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 size of 60 nm or less. In addition to the average primary particle size of 60 nm or less, the zirconia particles preferably have a particle size exceeding 100 nm in an amount of 0.5 mass% or less relative to the total amount of zirconia particles. This allows the zirconia molded body of the present invention, and in turn the zirconia calcined body and zirconia sintered body of the present invention, to be easily obtained. From the viewpoint of ease of production of the zirconia molded body of the present invention, and in turn the zirconia calcined body and zirconia sintered body of the present invention, the average primary particle size of the zirconia particles is preferably 50 nm or less, more preferably 30 nm or less, and even more preferably 20 nm or less, and may be 10 nm or less, and is preferably 1 nm or more, and more preferably 5 nm or more. From the viewpoints of ease of production of the zirconia molded body of the present invention, and in turn the zirconia calcined body and zirconia sintered body of the present invention, and ease of obtaining the desired linear light transmittance, the content of zirconia particles having a particle size exceeding 100 nm is more preferably 0.3 mass% or less, even more preferably 0.1 mass% or less, and may even be 0.05 mass% or less. The average primary particle size of zirconia particles can be determined, for example, by photographing zirconia particles (primary particles) with a transmission electron microscope (TEM), measuring the particle size (maximum diameter) of each of 100 randomly selected particles on the obtained image, and calculating the average value of these particle sizes. The content of zirconia particles having a particle size exceeding 100 nm can be measured on a volume basis by dispersing the zirconia particles in methanol and using a laser diffraction / scattering particle size distribution analyzer (LA-950, manufactured by Horiba, Ltd.).

[0048] The method for preparing zirconia particles is not particularly limited, and examples thereof include a breakdown process in which coarse particles are pulverized into fine particles, a building-up process in which atoms or ions are synthesized through a nucleation and growth process, etc. Of these, the building-up process is preferred for obtaining high-purity fine zirconia particles.

[0049] The breakdown process can be carried out by pulverizing the powder using, for example, a ball mill or a bead mill. In this case, it is preferable to use a fine-sized pulverizing medium, for example, 100 μm or less. In addition, it is preferable to use a pulverizing medium having a desired ΔL ＊ In order to obtain a desired (W-B) and linear light transmittance, it is preferable to classify the resulting zirconia particles after pulverizing the coarse particles. For classification, known methods and devices can be used, such as a porous membrane (e.g., a membrane filter having a pore size of 100 nm) or a classification device (a wet classification device, a dry classification device).

[0050] On the other hand, examples of the build-up process include a gas-phase pyrolysis method in which an oxide is precipitated by thermally decomposing an oxyacid salt of a metal ion or an organometallic compound while vaporizing it; a gas-phase reaction method in which synthesis is carried out by a gas-phase chemical reaction between a gas of a metal compound with a high vapor pressure and a reactive gas; an evaporation concentration method in which a raw material is heated and vaporized, and then rapidly cooled in an inert gas at a predetermined pressure to condense the vapor into fine particles; a melt method in which a molten liquid is cooled into small droplets and solidified to form a powder; a solvent evaporation method in which a solvent is evaporated to increase the concentration in the liquid to a supersaturated state, and then precipitates; and a precipitation method in which the solute concentration is supersaturated by reaction with a precipitant or hydrolysis, and a poorly soluble compound such as an oxide or hydroxide is precipitated through a nucleation-growth process.

[0051] Precipitation methods are further classified into homogeneous precipitation methods, in which a precipitant is produced in a solution by a chemical reaction, eliminating local non-uniformities in the precipitant concentration; coprecipitation methods, in which multiple metal ions coexisting in a solution are simultaneously precipitated by adding a precipitant; hydrolysis methods, in which an oxide or hydroxide is obtained by hydrolysis from a metal salt solution or an alcohol solution of a metal alkoxide or the like; and solvothermal synthesis methods, in which an oxide or hydroxide is obtained from a high-temperature, high-pressure fluid. Solvothermal synthesis methods are further classified into hydrothermal synthesis methods, in which water is used as a solvent, and supercritical synthesis methods, in which water or a supercritical fluid such as carbon dioxide is used as a solvent.

[0052] In any build-up process, it is preferable to increase the precipitation rate to obtain finer zirconia particles. ＊In order to obtain a desired (W-B) and in-line light transmittance, it is preferable to classify the obtained zirconia particles. For classification, known methods and devices can be used, such as a porous membrane (e.g., a membrane filter having a pore size of 100 nm) and a classification device (a wet classification device, a dry classification device).

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

[0054] In order to adjust the yttria content of the zirconia particles to the above range, yttria can be blended during the production process of the zirconia particles, for example, by dissolving yttria in the zirconia particles. Examples of the yttrium source that can be used include nitrates, acetates, chlorides, and alkoxides. Specifically, yttrium chloride, yttrium acetate, and yttrium nitrate can be used.

[0055] The zirconia particles may be surface-treated in advance, if necessary, with a known surface treatment agent such as an organic compound having an acidic group; a fatty acid amide such as saturated fatty acid amide, unsaturated fatty acid amide, saturated fatty acid bisamide, or unsaturated fatty acid bisamide; or an organometallic compound such as a silane coupling agent (organosilicon compound), an organotitanium compound, an organozirconium compound, or an organoaluminum compound. Surface-treating the zirconia particles can adjust the miscibility with a liquid when preparing a powder containing zirconia particles and a fluorescent agent using a slurry containing a liquid whose dispersion medium has a surface tension of 50 mN / m or less at 25°C, as described below, or can adjust the miscibility between the zirconia particles and a polymerizable monomer when producing a zirconia molded body by a method including a step of polymerizing a composition containing zirconia particles, a fluorescent agent, and a polymerizable monomer, as described below. Among the above surface treatment agents, organic compounds having an acidic group are preferred because they have excellent miscibility with liquids having a surface tension of 50 mN / m or less at 25°C and can improve the chemical bonding between the zirconia particles and the polymerizable monomer, thereby improving the mechanical strength of the resulting zirconia molded article.

[0056] Examples of organic compounds having an acidic group 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, phosphoric acid group-containing organic compounds having at least one phosphoric acid group and carboxylic acid group-containing organic compounds having at least one carboxylic acid group are preferred, and phosphoric acid group-containing organic compounds are more preferred. The zirconia particles may be surface-treated with one type of surface treatment agent, or may be surface-treated with two or more types of surface treatment agents. When the zirconia particles are surface-treated with two or more types of surface treatment agents, the resulting surface treatment layer may be a surface treatment layer of a mixture of two or more types of surface treatment agents, or may be a surface treatment layer with a multi-layer structure in which multiple surface treatment layers are stacked.

[0057] Examples of the phosphoric acid group-containing organic compound 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, 7-(meth)acryloyloxyhexyl dihydrogen phosphate, 8-(meth)acryloyloxyhexyl dihydrogen phosphate, 9-(meth)acryloyloxyhexyl dihydrogen phosphate, 10-(meth)acryloyloxyhexyl dihydrogen phosphate, 11-(meth)acryloyloxyhexyl dihydrogen phosphate, 12-(meth)acryloyloxyhexyl dihydrogen phosphate, 13-(meth)acryloyloxyhexyl dihydrogen phosphate, 14-(meth)acryloyloxyhexyl dihydrogen phosphate, 15-(meth)acryloyloxyhexyl dihydrogen phosphate, 16-(meth)acryloyloxyhexyl dihydrogen phosphate, 17-(meth)acryloyloxyhexyl dihydrogen phosphate, 18-(meth)acryloyloxyhexyl dihydrogen phosphate, 19-(meth)acryloyloxyhexyl dihydrogen phosphate, 20-(meth)acryloyloxyhexyl dihydrogen phosphate, 21-(meth)acryloyloxyhexyl dihydrogen phosphate, 22-(meth)acryloyloxyhexyl dihydrogen phosphate, 23-(meth)acryloyloxyhexyl dihydrogen phosphate, 24-(meth)acryloyloxyhexyl dihydrogen phosphate, 25-(meth)acryloyloxyhexyl dihydrogen phosphate, 26-(meth)acryloyloxyhex ) 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)acryloyloxydodecyl dihydrogen phosphate, 16-(meth)acryloyloxyhexadecyl dihydrogen phosphate, 20-(meth)acryloyloxyicosyl 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 bis[2-(meth)acryloyloxydecyl]hydrogenphosphate, 1,3-di(meth)acryloyloxypropyl dihydrogenphosphate, 2-(meth)acryloyloxyethylphenylhydrogenphosphate, 2-(meth)acryloyloxyethyl-2-bromoethylhydrogenphosphate, bis[2-(meth)acryloyloxy-(1-hydroxymethyl)ethyl]hydrogenphosphate, and acid chlorides, alkali metal salts, and ammonium salts thereof.

[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) Acryloyl tyrosine, N-(meth)acryloyl tyrosine, N-(meth)acryloyl-p-aminobenzoic acid, N-(meth)acryloyl-o-aminobenzoic acid, p-vinyl benzoic 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 benzoate 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"), succinic acid mono[2-(2-methoxyethoxy)ethyl]ester, maleic acid mono[2-(2-methoxyethoxy)ethyl]ester, glutaric acid mono[2-(2 -methoxyethoxy)ethyl] ester, 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, 11-(meth)acryloyloxyundecane-1,1-dicarboxylic acid, 12-(meth)acryloyloxydodecane-1,1-dicarboxylic acid, 13-(meth)acryloyloxytridecane-1,Examples of suitable carboxylic acids include 1-dicarboxylic acids, 4-(meth)acryloyloxyethyl trimellitate, 4-(meth)acryloyloxybutyl trimellitate, 4-(meth)acryloyloxyhexyl trimellitate, 4-(meth)acryloyloxydecyl trimellitate, 2-(meth)acryloyloxyethyl-3'-(meth)acryloyloxy-2'-(3,4-dicarboxybenzoyloxy)propyl succinate, and acid anhydrides, acid halides, alkali metal salts, and ammonium salts thereof.

[0059] Furthermore, as organic compounds having at least one acidic group other than those described above, such as a pyrophosphate group, a thiophosphate group, a phosphonate group, or a sulfone group, those described in, for example, WO 2012 / 042911 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'-dioleylsebacic acid amide.

[0061] Examples of silane coupling agents (organosilicon compounds) include R １ ｎ Six ４－ｎ (wherein R １ is a substituted or unsubstituted hydrocarbon group having 1 to 12 carbon atoms, X is an alkoxy group having 1 to 4 carbon atoms, a hydroxy group, a halogen atom, or a hydrogen atom, and n is an integer of 0 to 3, provided that R １ and when there are a plurality of X's, they may be the same or different).

[0062] Specific examples of silane coupling agents (organic silicon compounds) include methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(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) N-(β-aminoethyl)γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, trimethylsilanol, methyltrichlorosilane, methyldichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, vinyltrichlorosilane Examples of such alkylsilanes include silane, 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 a functional group are preferred, and ω-(meth)acryloyloxyalkyltrimethoxysilane [number of carbon atoms between the (meth)acryloyloxy group and the silicon atom: 3 to 12], ω-(meth)acryloyloxyalkyltriethoxysilane [number of carbon atoms between the (meth)acryloyloxy group and the silicon atom: 3 to 12], vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, and γ-glycidoxypropyltrimethoxysilane are more preferred.

[0064] Examples of the organic titanium compound include tetramethyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, and tetra(2-ethylhexyl) titanate.

[0065] Examples of the organic zirconium compound include zirconium isopropoxide, zirconium n-butoxide, zirconium acetylacetonate, and zirconyl acetate.

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

[0067] The specific method for surface treatment is not particularly limited, and any known method can be used. For example, a method in which the surface treatment agent is sprayed onto the zirconia particles while vigorously stirring them, or a method in which the zirconia particles and the surface treatment agent are dispersed or dissolved in a suitable solvent and then the solvent is removed, can be used. The solvent may be a dispersion medium containing a liquid having a surface tension of 50 mN / m or less at 25°C, as described below. Furthermore, after dispersing or dissolving the zirconia particles and the surface treatment agent, reflux or high-temperature, high-pressure treatment (such as autoclave treatment) may be performed.

[0068] The polyol and binder used in the present invention satisfy the relationship X1 < Y1 < X2 < Y2 ≦ 500°C, where X1 is the combustion start temperature of the polyol, X2 is the combustion end temperature of the polyol, Y1 is the combustion start temperature of the binder, and Y2 is the combustion end temperature of the binder. By selecting and combining those that satisfy this relationship, it is believed that the polyol creates a route within the zirconia molded body through which the binder burns off during sintering, making it easier for the binder to be removed during sintering. In particular, when the average primary particle size of zirconia particles contained in the zirconia molded body is 60 nm or less, the particles tend to bond together during heating (necking phenomenon) due to the fine particle size, filling the voids between the particles and preventing the binder from being completely removed by heating. However, by using a combination of a polyol and binder that satisfies the above relationship, the polyol serves to form a route within the zirconia molded body through which the binder burns off during sintering, allowing the binder to be completely removed. This solves the problem inherent in binder-containing zirconia molded bodies, which is that the binder is less likely to burn out when the zirconia molded body contains a binder in an amount corresponding to a thickness of 10 mm or more, and the zirconia sintered body after sintering has excellent mechanical strength and translucency. Furthermore, such a zirconia sintered body also has excellent in-line light transmittance.

[0069] The polyol combustion initiation temperature (X1), polyol combustion end temperature (X2), binder combustion initiation temperature (Y1), and binder combustion end temperature (Y2) can be measured by thermogravimetry (TG). In the present invention, the weight before heating is taken as 100%, and the temperatures at which a 0.5% weight loss is observed are taken as X1 and Y1, and the temperatures at which a 99.5% weight loss is observed are taken as X2 and Y2. The measurement conditions for thermogravimetry (TG) are as described in the Examples below.

[0070] Examples of polyols that can be used in the present invention include 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. Examples of other polyols that can be used include polyglycerin and sugar. One polyol may be used alone, or two or more polyols may be used in combination. By selecting and combining a polyol and a binder that satisfy the above relationship in relation to the binder and incorporating them into a zirconia molded body, the number of pores that will be generated in the zirconia calcined body and sintered body obtained when the binder-containing zirconia molded body is sintered can be reduced, and a zirconia sintered body with excellent mechanical strength and translucency and a desired shape and thickness can be obtained. Therefore, the type of polyol is not particularly limited as long as it is selected so as to satisfy the above-mentioned relational expression, and the above-mentioned effects of the present invention can be achieved.

[0071] Examples of binders used in the present invention include polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, acrylic binders, wax-based binders, polyvinyl butyral, polymethyl methacrylate, and ethyl cellulose. One binder may be used alone, or two or more binders may be used in combination. For the same reasons as for the polyols described above, the type of binder is not particularly limited as long as it is selected to satisfy the above-described relationship, and the effects of the present invention 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. 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, it is easy to control the outflow of polyol from the zirconia molded body, and the shape retention of the zirconia molded body is excellent. Furthermore, when X1 is 300° C. or lower, bonding between zirconia particles is not inhibited, and desired physical properties are easily obtained.

[0073] Y2 is 500° C. or less, preferably 480° C. or less, more preferably 460° C. or less, and even more preferably 440° C. or less. If Y2 exceeds 500° C., the bound 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 be destroyed.

[0074] In the zirconia molded body of the present invention, the polyol burns out before the binder during sintering, thereby creating a route for the binder to burn out inside the zirconia molded body, and the binder burns out before necking occurs. From this viewpoint, 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 body of the present invention, the polyol burns out before the binder during sintering, thereby creating a route for the binder to burn out inside the zirconia molded body, and the binder burns out before necking occurs. From this viewpoint, 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 (content relative to 100% by mass of zirconia (content in terms of metal element oxides)) in the zirconia molded body of the present invention is not particularly limited, but is preferably 8% by mass or less, more preferably 4% by mass or less, relative to 100% by mass of zirconia. Since the resulting zirconia sintered body has better translucency, it is even more preferably 1.5% by mass or less. 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-mentioned polyol content range, the number of pores generated in the zirconia sintered body can be reduced even when the zirconia molded body has a thickness of 10 mm or more. In the present invention, the polyol and binder contents are external addition rates, and refer to mass % relative to 100% by mass of zirconia (zirconium oxide containing yttrium oxide).

[0077] The binder content (content relative to 100% by mass of zirconia (content in terms of metal element oxide)) in the zirconia molded body of the present invention 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. 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 above-mentioned binder content range, the number of pores generated in the zirconia sintered body can be reduced, even when a zirconia molded body having a thickness of 10 mm or more is obtained.

[0078] The blending ratio (mass ratio) of the binder to the polyol in the zirconia molded body of the present invention is not particularly limited, but is preferably binder:polyol=10:1 to 1:10, more preferably 5:1 to 1:5, and from the viewpoint that the resulting zirconia sintered body has better translucency, is further preferably 3:1 to 1:4, and particularly preferably 2.5:1 to 1.1:1.

[0079] A preferred embodiment includes a zirconia molded body comprising: zirconia particles containing 2.0 to 9.0 mol% yttria relative to the total 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 binder content relative to 100 mass% of zirconia is 0.05 mass% or more; the polyol content relative to 100 mass% of zirconia is 0.01 mass% or more; and the polyol and the binder satisfy the following relationship: X1<Y1<X2<Y2≦500°C (wherein the symbols are as defined above). In the preferred embodiment, the polyol content is preferably equal to or less than the binder content, more preferably lower than the binder content, and even more preferably at least 0.1 mass% lower than the binder content. The binder content, polyol content, zirconia particles, etc. can be set as appropriate within the ranges described herein. For example, the content of the binder may be 0.2 mass % or more and 7 mass % or less relative to 100 mass % of zirconia.

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

[0081] In the present invention, when a zirconia molded body is produced by a method having a molding step of molding zirconia particles, the type of the molding step is not particularly limited. However, since the zirconia molded body of the present invention, and further the zirconia calcined body and zirconia sintered body of the present invention can be easily obtained, the molding step is preferably at least one of: (i) a step of slip-casting a slurry containing zirconia particles; (ii) a step of gel-casting a slurry containing zirconia particles; (iii) a step of press-molding a powder containing zirconia particles; (iv) a step of molding a composition containing zirconia particles and a resin; and (v) a step of polymerizing a composition containing zirconia particles and a polymerizable monomer.

[0082] Slurry Containing Zirconia Particles There is no particular limitation on the method for preparing the slurry containing zirconia particles. For example, the slurry may be one obtained through the breakdown process or building-up process described above, or may be a commercially available product.

[0083] When preparing a zirconia molded body containing the binder and polyol of the present invention, it is preferable to mix the binder and polyol in a liquid state, such as a solution or dispersion, with a slurry containing zirconia particles. Furthermore, when a colorant and / or a translucency modifier are to be added to the zirconia molded body, and in turn to the zirconia calcined body and zirconia sintered body, the colorant and / or the translucency modifier may be added to the slurry containing zirconia particles and a fluorescent agent. In this case, it is preferable to mix the colorant and / or the translucency modifier with the slurry containing zirconia particles in a liquid state, such as a solution or dispersion.

[0084] Powder containing zirconia particles The method for preparing the powder containing zirconia particles is not particularly limited, and it is preferable to obtain the powder by drying the above-mentioned slurry containing zirconia particles, since this allows for the production of a more uniform zirconia sintered body with excellent physical properties. The slurry to be dried here may further contain a fluorescent agent and / or a colorant and / or a translucency adjuster.

[0085] The drying method is not particularly limited, and can be, for example, spray drying, supercritical drying, freeze drying, hot air drying, reduced pressure drying, etc. Among these, any of spray drying, supercritical drying, and freeze drying is preferred, any of spray drying and supercritical drying is more preferred, and spray drying is even more preferred, because it can suppress aggregation of particles during drying and thereby obtain a denser zirconia sintered body.

[0086] The slurry containing zirconia particles to be dried may be a slurry in which the dispersion medium is water, but it is preferable that the slurry be a slurry in which the dispersion medium is other than water, such as an organic solvent, because this can suppress aggregation of particles during drying and allow a denser zirconia sintered body to be obtained.

[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 alone or in combination of two or more. Among these, taking into consideration both safety to living organisms and ease of removal, the organic solvent is preferably a water-soluble organic solvent, and 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, particularly when spray drying is employed, it is preferable that the dispersion medium of the slurry containing zirconia particles and a fluorescent agent to be dried contains a liquid having a surface tension of 50 mN / m or less at 25° C., since this can suppress aggregation of particles during drying and allow for the production of a denser zirconia sintered body. From this viewpoint, the surface tension of the 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, for example, from the values ​​described in the Handbook of Chemistry and Physics. For liquids not described therein, the values ​​described in WO 2014 / 126034 can be used. For liquids not described in any of these publications, the surface tension can be determined by known measurement methods, such as the hanging ring method or the Wilhelmy method. The surface tension at 25°C is preferably measured using an automatic surface tensiometer "CBVP-Z" manufactured by Kyowa Interface Science Co., Ltd. or a "SIGMA 702" manufactured by KSV INSTRUMENTS LTD.

[0090] As the liquid, an organic solvent having the above-mentioned surface tension can be used. As the organic solvent, any of the above-mentioned organic solvents having the above-mentioned 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, because it can suppress aggregation of particles during drying and thereby produce a denser zirconia sintered body.

[0091] The content of the 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 this makes it possible to suppress aggregation of particles during drying and to obtain a denser zirconia sintered body.

[0092] A slurry containing a dispersion medium other than water can be obtained by replacing the dispersion medium in a slurry containing water. The method for replacing the dispersion medium is not particularly limited. For example, a method of adding a dispersion medium other than water (such as an organic solvent) to a slurry containing water and then evaporating the water can be employed. When evaporating the water, part or all of the dispersion medium other than water may be removed. The addition of the dispersion medium other than water and the removal of the water may be repeated multiple times. A method of adding a dispersion medium other than water to a slurry containing water and then precipitating the dispersoids can also be employed. Furthermore, for a slurry containing water, the dispersion medium may be replaced with a specific organic solvent, and then further replaced with another organic solvent. The fluorescent agent may be added after replacing the dispersion medium, but it is preferable to add it before replacing the dispersion medium, as this allows for the production of a more uniform zirconia sintered body with excellent physical properties. Similarly, when a colorant and / or a light-transmittance adjuster is to be contained in the slurry, they may be added after the dispersion medium is replaced. However, it is preferable to add them before the dispersion medium is replaced, since this allows a more uniform zirconia sintered body having excellent physical properties to be obtained.

[0093] The slurry containing zirconia particles to be dried may be one that has been subjected to a dispersion treatment using heat or pressure, such as reflux treatment or hydrothermal treatment. Furthermore, the slurry containing zirconia particles to be dried may be one that has been subjected to a mechanical dispersion treatment using a roll mill, colloid mill, high-pressure jet disperser, ultrasonic disperser, vibration mill, planetary mill, bead mill, etc. Only one of the above-mentioned treatments may be employed, or two or more of them may be employed.

[0094] The slurry containing zirconia particles to be dried may further contain, in addition to the binder and polyol, one or more of other components such as a dispersant, an emulsifier, an antifoaming agent, a pH adjuster, a lubricant, etc. By containing such other components (particularly a dispersant, an antifoaming agent, etc.) in addition to the binder, it may be possible to suppress aggregation of particles during drying, and to obtain a denser zirconia sintered body.

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

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

[0097] Examples of the antifoaming agent include alcohol, polyether, polyethylene glycol, silicone, and wax.

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

[0099] Examples of the lubricant include polyoxyethylene alkylate ether and wax.

[0100] The water content of the slurry containing zirconia particles to be dried is preferably 3% by mass or less, more preferably 1% by mass or less, and even more preferably 0.1% by mass or less, because this can suppress aggregation of particles during drying and enable the production of a denser zirconia sintered body. The water content can be measured using a Karl Fischer moisture meter.

[0101] The drying conditions in each of the above drying methods are not particularly limited, and known drying conditions can be appropriately adopted. When an organic solvent is used as the dispersion medium, in order to reduce the risk of explosion during drying, it is preferable to carry out drying in the presence of a non-flammable gas, and more preferably in the presence of nitrogen.

[0102] The supercritical fluid used in supercritical drying is not particularly limited, and for example, water, carbon dioxide, etc. can be used. However, it is preferable that the supercritical fluid is carbon dioxide, since this can suppress aggregation of particles and thereby produce a denser zirconia sintered body.

[0103] Composition Containing Zirconia Particles and Resin There are no particular limitations on the method for preparing the composition containing zirconia particles and a resin. For example, the composition can be obtained by mixing the powder containing the zirconia particles with a resin.

[0104] Composition containing zirconia particles and a polymerizable monomer The method for preparing the composition containing zirconia particles and a polymerizable monomer is not particularly limited, and the composition can be obtained, for example, by mixing the powder containing the zirconia particles with the polymerizable monomer.

[0105] (i) Slip Casting When a zirconia molded body is produced by a method including a step of slip-casting a slurry containing zirconia particles, the specific method of slip-casting is not particularly limited. For example, a method can be employed in which a slurry containing zirconia particles is poured into a mold and then dried.

[0106] The content of the dispersion medium in the slurry containing zirconia particles to be used is preferably 80% by mass or less, more preferably 50% by mass or less, and even more preferably 20% by mass or less, because this allows the slurry to be easily poured into a mold, prevents a long drying time from being required, and enables the mold to be used more frequently.

[0107] The slurry may be poured into the mold under normal pressure, but from the viewpoint of production efficiency, it is preferable to pour the slurry under pressurized conditions. There are no particular limitations on the type of mold used in slip casting, and for example, porous molds made of gypsum, resin, ceramics, etc. can be used. Porous molds made of resin or ceramics are excellent in terms of durability.

[0108] The zirconia particle-containing slurry used in slip casting may further contain, in addition to the binder and polyol, one or more of the above-mentioned other components such as a dispersant, an emulsifier, an antifoaming agent, a pH adjuster, and a lubricant.

[0109] (ii) Gel Casting When a zirconia molded body is produced by a method including a step of gel-casting a slurry containing zirconia particles, the specific method of gel-casting is not particularly limited. For example, a method can be employed in which a shaped wet body is obtained by gelling a slurry containing zirconia particles and a fluorescent agent in a mold, and then the obtained wet body is dried.

[0110] The content of the dispersion medium in the slurry containing zirconia particles to be used is preferably 80% by mass or less, more preferably 50% by mass or less, and even more preferably 20% by mass or less, because this can prevent drying from taking a long time and can also suppress the occurrence of cracks during drying.

[0111] The 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 limitations on the type of mold used, and for example, a porous mold made of gypsum, resin, ceramics, etc., or a non-porous mold made of metal, resin, etc., can be used.

[0112] There is no limitation on the type of gelling agent, and for example, a water-soluble gelling agent can be used, and specifically, agarose, gelatin, etc. can be preferably used. One gelling agent may be used alone, or two or more gelling agents may be used in combination. From the viewpoint of suppressing cracking 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 is blended.

[0113] The type of polymerizable monomer is not particularly limited, and examples thereof 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, N,N-bis(2-hydroxyethyl) (meth)acrylamide, etc. One type of polymerizable monomer may be used alone, or two or more types may be used in combination.

[0114] From the viewpoint of suppressing the occurrence of cracks 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 blended.

[0115] When gelation is carried out by polymerization of a polymerizable monomer, the polymerization is preferably carried out using a polymerization initiator. There are no particular restrictions on the type of polymerization initiator, but a photopolymerization initiator is particularly preferred. The photopolymerization initiator can be appropriately selected from photopolymerization initiators used in general industry, and photopolymerization initiators used in dental applications are particularly preferred.

[0116] Specific examples of the photopolymerization initiator 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 occur in both the ultraviolet (including near-ultraviolet) and visible light regions, and in particular, polymerization (gelation) can be sufficiently performed using any light source, such as a laser (e.g., Ar laser, He—Cd laser), or lighting (e.g., halogen lamp, xenon lamp, metal halide lamp, light-emitting diode (LED), mercury lamp, or fluorescent lamp.

[0117] Among the (bis)acylphosphine oxides, examples of the 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] Of the (bis)acylphosphine oxides, examples of the 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 JP-A No. 2000-159621 can also be used.

[0119] Among these (bis)acylphosphine oxides, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylmethoxyphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and sodium salts of 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, acenaphthenequinone, etc. Among these, camphorquinone is preferred, particularly when a light source in the visible light region is used.

[0121] The zirconia particle-containing slurry used in gel casting may also contain, in addition to the binder and polyol, one or more of the above-mentioned other components such as a dispersant, an emulsifier, an antifoaming agent, a pH adjuster, and a lubricant, as in the case of a slurry used in slip casting.

[0122] The drying method for drying the shaped wet body is not particularly limited, and examples thereof include natural drying, hot air drying, vacuum drying, dielectric heating drying, induction heating drying, and constant temperature and humidity drying. These may be used alone or in combination. 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 Molding When a zirconia molded body is produced by a method including a step of press-molding a powder containing zirconia particles, the specific method of press molding is not particularly limited, and the press molding can be carried out using a known press molding machine. Specific examples of the press molding method include uniaxial pressing. Furthermore, in order to increase the density of the resulting zirconia molded body, it is preferable to further perform cold isostatic pressing (CIP) treatment after uniaxial pressing.

[0124] The powder containing the zirconia particles used for press molding may further contain, in addition to the binder and polyol, one or more of the above-mentioned other components such as a dispersant, an emulsifier, an antifoaming agent, a pH adjuster, a lubricant, etc. These components may be blended when preparing the powder.

[0125] (iv) Molding of a Resin-Containing Composition When a zirconia molded body is produced by a method including a step of molding a composition containing zirconia particles and a resin, the specific method for molding the composition is not particularly limited, and for example, injection molding, cast molding, extrusion molding, etc. can be used. Alternatively, a method of molding the composition by fusion dynamic molding (FDM), an inkjet method, a powder / binder lamination method, or other additive manufacturing methods (e.g., 3D printing) may also be used. Among these molding methods, injection molding and cast molding are preferred, and injection molding is more preferred.

[0126] The type of the resin is not particularly limited, and those that can be used as raw materials for molding can be preferably used. Specific examples of the resin include 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 alone or in combination of two or more.

[0127] The composition containing the zirconia particles and the resin may further contain, in addition to the binder and the polyol, one or more of the above-mentioned other components such as a dispersant, an emulsifier, an antifoaming agent, a pH adjuster, and a lubricant.

[0128] (v) Polymerization of a composition containing a polymerizable monomer. Polymerizing a composition containing zirconia particles and a polymerizable monomer polymerizes the polymerizable monomer in the composition, thereby hardening the composition. When producing a zirconia molded body using a method including this polymerization step, the specific method is not particularly limited. For example, (a) a method of polymerizing a composition containing zirconia particles and a polymerizable monomer in a mold; or (b) a stereolithography (SLA) method using a composition containing zirconia particles and a polymerizable monomer can be employed. Among these, the stereolithography method (b) is preferred. The stereolithography method allows the zirconia molded body to be given a shape corresponding to the desired shape of the final zirconia sintered body at the time of production. Therefore, the stereolithography method may be particularly suitable when the zirconia sintered body of the present invention is used as a dental material for dental prostheses, etc.

[0129] The type of polymerizable monomer in the composition containing the zirconia particles and the polymerizable monomer is not particularly limited, and may be any of monofunctional polymerizable monomers such as monofunctional (meth)acrylates and monofunctional (meth)acrylamides, and polyfunctional polymerizable monomers such as bifunctional aromatic compounds, bifunctional aliphatic compounds, and trifunctional or higher functional compounds. One type of polymerizable monomer may be used alone, or two or more types may be used. Among these, it is preferable to use a polyfunctional polymerizable monomer, especially when a stereolithography method is employed.

[0130] Examples of monofunctional (meth)acrylates include (meth)acrylates having a hydroxyl group 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. 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 a functional group 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 because of its excellent polymerizability, and N-(meth)acryloylmorpholine, N,N-dimethyl(meth)acrylamide, and N,N-diethyl(meth)acrylamide are more preferred.

[0133] Examples of the bifunctional aromatic compound 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. 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, 1,4-bis(2-(meth)acryloyloxyethyl)pyromellitate, and the like. 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 because of their excellent polymerizability and the mechanical strength of the resulting zirconia molded article. Of the 2,2-bis(4-(meth)acryloyloxypolyethoxyphenyl)propanes, 2,2-bis(4-methacryloyloxypolyethoxyphenyl)propane (a compound having an average number of moles of ethoxy groups added of 2.6 (commonly known as "D-2.6E")) is preferred.

[0134] Examples of the 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 of suitable zirconia diacrylates 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 because of their excellent polymerizability and the mechanical strength of the resulting zirconia molded article.

[0135] Examples of tri- or higher functional compounds 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 in terms of excellent polymerizability and the mechanical strength of the resulting zirconia molded article.

[0136] In both of the above methods (a) and (b), the polymerization of the composition is preferably carried out using a polymerization initiator, and the composition preferably further contains a polymerization initiator. There are no particular limitations on the type of polymerization initiator, but a photopolymerization initiator is particularly preferred. The photopolymerization initiator can be appropriately selected from photopolymerization initiators used in general industry, and photopolymerization initiators used in dental applications are particularly preferred. Specific examples of photopolymerization initiators are the same as those described above in the explanation of gel casting, and a duplicated explanation will be omitted here.

[0137] The composition containing the zirconia particles and the polymerizable monomer may further contain, in addition to the binder and the polyol, one or more of the above-mentioned other components such as a dispersant, an emulsifier, an antifoaming agent, a pH adjuster, and a lubricant.

[0138] When a zirconia molded body is produced by stereolithography using a composition containing zirconia particles and a polymerizable monomer, the specific method of stereolithography is not particularly limited, and any known method can be appropriately employed for stereolithography. For example, a method can be employed in which a liquid composition is photopolymerized using an optical shaping device with ultraviolet light, a laser, or the like to sequentially form layers having the desired shape, thereby obtaining the desired zirconia molded body.

[0139] When obtaining a zirconia molded body by stereolithography, the content of zirconia particles in a composition containing zirconia particles and a polymerizable monomer is preferably as high as possible from the viewpoint of subsequent sintering properties. 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 layered molding, it is preferable that the viscosity of the composition be within a certain range. Therefore, the content of zirconia particles in the 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 can be particularly important when a controlled liquid level method is carried out in which a zirconia molded body is formed one layer at a time by curing layers by irradiating light from below a container through the bottom surface of the container, in order to raise the cured layer by one layer and allow the composition for forming the next layer to smoothly flow between the underside of the cured layer and the bottom surface of the container.

[0140] The specific viscosity of the composition at 25°C 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. Since the viscosity of the composition tends to increase as the zirconia particle content increases, it is preferable to appropriately adjust the balance between the zirconia particle content and viscosity of the composition in accordance with the performance of the stereolithography device used, taking into account the balance between the stereolithography speed and the precision of the resulting zirconia molded body. The viscosity can be measured using an E-type viscometer.

[0141] In the method for producing a zirconia molded body of the present invention, in order to further improve the density of the zirconia molded body, the zirconia molded body may be subjected to a humidification treatment followed by a CIP treatment. When press molding is performed, a powder containing zirconia particles may be humidified before press molding, and then the press molding may be performed. The humidification method may be any known method without any limitations, and may involve spraying water with a spray bottle or using a hygrostat or thermo-hygrostat. The amount of moisture increase due to the humidification treatment depends on the particle size of the zirconia particles contained, but is preferably greater than 2% by mass, more preferably greater than 3% by mass, even more preferably greater than 4% by mass, and particularly preferably greater than 5% by mass, relative to the mass of the powder before humidification (powder before humidification treatment) and the molded body. It is also preferably 15% by mass or less, more preferably 13% by mass or less, and even more preferably 11% by mass or less. The amount of moisture increase due to the humidification treatment can be calculated as a percentage by subtracting the mass of the pre-humidifying powder and the compact from the mass of the moistened powder (powder after the humidification treatment) and the compact, and dividing the result by the mass of the pre-humidifying powder and the compact.

[0142] [Zirconia Calcined Body] In another embodiment of the present invention, yttria is contained in an amount of 2.0 to 9.0 mol % based on the total mole number of zirconium oxide and yttria, and ΔL ＊ (W−B) is 5 or more, and after sintering at 900 to 1200°C, the thickness is 28.5 μm ２An example of such a calcined zirconia body is one having 10 or less pores with a diameter of 50 nm or more per cross-sectional area and a thickness of 10 mm or more. By using such a calcined zirconia body, it is possible to obtain a zirconia sintered body that is excellent in both mechanical strength and translucency and in in-line light transmittance. ＊ The definition of (W-B) is the same as that of 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, 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 a block shape (rectangular parallelepiped shape), etc.

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

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

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

[0146] The yttria content in the zirconia calcined body of the present invention may be within 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, and even more preferably 4.0 mol% or more, and is preferably 8.0 mol% or less, more preferably 7.5 mol% or less, and even more preferably 7.0 mol% or less.

[0147] The density of the zirconia calcined body of the present invention is not particularly limited, and varies depending on the method for producing the zirconia molded body used for its production, but is preferably 3.0 to 6.0 g / m ３It is preferable that the range is 3.2 to 5.8 g / m ３ It is more preferable that the range is within the range of

[0148] The shape of the zirconia calcined body of the present invention is not particularly limited and can be any desired shape depending on the application. However, considering the ease of handling when used as a mill blank for producing dental materials such as dental prostheses, a disk shape, a prism shape (e.g., a rectangular parallelepiped shape), or the like is preferred. As will be described later, the zirconia calcined body can be cut (milled) to a desired shape depending on the application before being made into a zirconia sintered body. The present invention also encompasses zirconia calcined bodies having such a desired shape after cutting (milling). Furthermore, the zirconia calcined body may have either a single-layer structure or a multilayer structure. By forming the zirconia calcined body into a multilayer structure, the final zirconia sintered body can be made into a multilayer structure, allowing for localized changes in its physical properties, such as translucency.

[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 viewpoints of being able to maintain the shape of the workpiece during processing using a cutting machine, and also being able to easily perform the cutting itself. The three-point bending strength of the zirconia calcined body can be measured using a universal testing machine on a test piece of 5 mm × 40 mm × 10 mm under conditions of a span length (distance between supports) of 30 mm and a crosshead speed of 0.5 mm / min.

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

[0151] The zirconia calcined body of the present invention has a ΔL ＊ (W−B) is 5 or more, preferably 7 or more, and may further be 10 or more. ＊ When (W−B) is within the above range, a zirconia sintered body with high in-line light transmittance can be obtained when sintered under normal pressure. ＊ There is no particular upper limit to (W−B), but it can be set to, for example, 30 or less, or even 25 or less. ＊ (WB) can be measured in the same manner as for the zirconia molded body, except that the measurement sample is changed from the measurement on the zirconia molded body to the measurement on the zirconia calcined body.

[0152] The zirconia calcined 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 being made into a zirconia sintered body). This makes it possible to easily produce a zirconia sintered body of the present invention with excellent mechanical strength. Because a zirconia sintered body with better 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, or even 1000 MPa or less. The method for measuring the three-point bending strength is as described above in the description of the three-point bending strength of a zirconia sintered body.

[0153] The zirconia calcined body of the present invention preferably has a transmittance of 40% or more at a wavelength of 700 nm at a thickness of 0.5 mm after sintering at 900 to 1200°C under normal pressure (after being made into a zirconia sintered body). This allows for easy production of a zirconia sintered body of the present invention with excellent translucency. Because a zirconia sintered body with better translucency 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, or even 57% or less. The method for measuring the transmittance is as described above for the transmittance of light with a wavelength of 700 nm at a thickness of 0.5 mm through a zirconia sintered body.

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

[0155] [Method for Producing Zirconia Calcined Body] The method for producing a zirconia calcined body of the present invention is characterized by using the zirconia molded body of the present invention. The method for producing a zirconia calcined body of the present invention preferably includes a step of calcining the zirconia molded body at 200 to 800°C. The method for producing a zirconia calcined body of the present invention may also include a step of cutting the zirconia molded body of the present invention, and calcining the cut zirconia molded body. The cutting method is not particularly limited, and known devices (e.g., known milling devices) and methods can be used. From the viewpoint of easily obtaining the desired zirconia calcined body, the calcination temperature is preferably 200°C or higher, more preferably 250°C or higher, and even more preferably 300°C or higher, and is preferably 800°C or lower, more preferably 700°C or lower, and even more preferably 600°C or lower. By maintaining the calcination temperature at or above the lower limit, generation of organic residues can be effectively suppressed. Furthermore, by setting the calcination temperature to the above upper limit or less, it is possible to prevent excessive sintering from occurring, making cutting (milling) with a cutting machine difficult.

[0156] The heating rate during calcination of the zirconia molded body of the present invention is not particularly limited, but is preferably 0.1°C / min or more, more preferably 0.2°C / min or more, and even more preferably 0.5°C / min or more, and is preferably 50°C / min or less, more preferably 30°C / min or less, and even more preferably 20°C / min or less. Having a heating rate equal to or greater than the above-mentioned lower limit improves productivity. Furthermore, having a heating rate equal to or less than the above-mentioned upper limit can suppress the difference in volume between the interior and exterior of the zirconia molded body or zirconia calcined body, and, if the zirconia molded body contains an organic substance, can suppress rapid decomposition of the organic substance, thereby suppressing cracking and fracture.

[0157] There are no particular limitations on the calcination time when the zirconia molded body of the present invention is calcined. However, in order to enable the desired calcined zirconia body to be obtained efficiently and stably with good productivity, the calcination time is preferably 0.5 hours or more, more preferably 1 hour or more, and even more preferably 2 hours or more, and is preferably 10 hours or less, more preferably 8 hours or less, and even more preferably 6 hours or less.

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

[0159] The zirconia calcined body of the present invention can be cut (milled) to a desired shape depending on the intended use before being made into a zirconia sintered body. In particular, the zirconia sintered body of the present invention is particularly suitable as a dental material for dental prostheses and the like because it has both excellent translucency and mechanical strength despite containing a fluorescent agent. To obtain a zirconia sintered body for such an application, the zirconia calcined body can be cut (milled) to a shape corresponding to the intended use. There are no particular limitations on the method of cutting (milling), and it can be carried out using, for example, a known milling device.

[0160] [Method for Producing Zirconia Sintered Body] As described above, the zirconia sintered body of the present invention can be produced by sintering the zirconia molded body of the present invention under normal pressure, and can also be produced by sintering the zirconia calcined body of the present invention under normal pressure.

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

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

[0163] The sintering in the present invention can be carried out using a sintering furnace. There are no particular limitations on the type of sintering furnace, and for example, electric furnaces and degreasing furnaces 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 produced without HIP treatment, but by performing HIP treatment after the above-mentioned sintering under normal pressure, it is possible to further improve the translucency and mechanical strength.

[0165] [Uses of Zirconia Sintered Body] There are no particular limitations on the uses of the zirconia sintered body of the present invention, but the zirconia sintered body of the present invention is particularly suitable as a dental material for dental prostheses and the like because it has excellent translucency and mechanical strength and excellent in-line light transmittance, and is particularly useful not only as a dental prosthesis used in the cervical region of teeth, but also as a dental prosthesis used on the occlusal surfaces of molars and the incisal edges of anterior teeth. The zirconia sintered body of the present invention is preferably used as a dental prosthesis used in the incisal edges of anterior teeth.

[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, etc. The methods for measuring each physical property are as follows.

[0167] (1) Average Primary Particle Diameter of Zirconia Particles The zirconia particles in the zirconia slurry were photographed using a transmission electron microscope (TEM), and the particle diameters (maximum diameters) of 100 randomly selected particles were measured on the obtained image. The average value of these was taken as the average primary particle diameter of the zirconia particles.

[0168] (2) Proportion of Particles Having a Particle Size Exceeding 100 nm Zirconia particles in the zirconia slurry were dispersed in methanol, and the particle size distribution was measured on a volume basis using a laser diffraction / scattering particle size distribution analyzer (LA-950, manufactured by Horiba, Ltd.).

[0169] (3) Crystal grain size The crystal grain size of the zirconia sintered body was determined by taking a field emission scanning electron microscope (FE-SEM) photograph of the cross section of the zirconia sintered body, arbitrarily selecting 100 particles in the photographed image, and calculating the average value of the circle equivalent diameters (diameters of perfect circles having the same area).

[0170] (4) Three-Point Bending Strength The three-point bending strength of the zirconia sintered body was measured in accordance with ISO 6872:2015, and the average value was calculated under the conditions of a support distance of 30 mm, a test piece size of 40 mm × 4 mm × 3 mm, and a crosshead speed of 0.5 mm / min, n = 10. This test piece was prepared by molding the powder containing zirconia particles obtained in the course of the examples into a square rod of 40 mm × 6 mm × 5 mm using a uniaxial press, and then subjecting these to cold isostatic pressing (CIP) treatment (pressure 170 MPa) to increase the density to obtain a zirconia molded body, which was then fired and surface polished.

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

[0172] (6) Linear Light Transmittance (1.0 mm Thickness) The linear light transmittance of the zirconia sintered body at a thickness of 1.0 mm was measured using a turbidity meter (manufactured by Nippon Denshoku Industries Co., Ltd., "Haze Meter NDH4000"), with light generated from a light source being transmitted through and scattered by the sample, and an integrating sphere. In this measurement, the linear light transmittance was measured in accordance with ISO 13468-1:1996 and JIS K 7361-1:1997, and the haze was measured in accordance with ISO 14782-1:1999 and JIS K 7136:2000 to measure the linear light transmittance. For the measurement, a disk-shaped zirconia sintered body having a diameter of 15 mm and a thickness of 1.0 mm obtained by mirror polishing a disk-shaped zirconia sintered body was used as a 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 cross-sectional area 28.5 μm ２The number of pores with a diameter of 50 nm or more per cross-sectional area was measured using a zirconia sintered body obtained by sintering a block-shaped zirconia compact. ２ Ten field-emission scanning electron microscope (FE-SEM) photographs of the cross section of the zirconia sintered body were taken, the circle-equivalent diameter of each pore in the photographed images (the diameter of a perfect circle with the same area) was determined, and the number of pores with a diameter of 50 nm or more was calculated for each photographed image. The calculated numbers for the 10 photographed images were added together and divided by 10 to obtain an arithmetic mean value. In Tables 3 to 6 below, this is referred to as the "number of pores with a size of 50 nm or more."

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

[0175] (9) Fluorescence of Zirconia Sintered Body The fluorescence of the zirconia sintered body was evaluated by visually observing the presence or absence of fluorescence under UV light.

[0176] (10) ΔL of zirconia compact and zirconia calcined body ＊ (W-B) ΔL at a thickness of 1.5 mm of the zirconia molded body and the zirconia calcined body ＊ (W-B) was measured using a spectrophotometer ("CM-3610A" manufactured by Konica Minolta Japan, Inc.). In this measurement, F11 was used as a light source, and the color was determined by measuring reflected light. For the measurement, a disk-shaped zirconia molded body and a zirconia calcined body, each having a diameter of 20 mm and a thickness of 1.5 mm, were obtained by mirror-polishing a disk-shaped zirconia molded body and a calcined body, respectively, and the average value was determined for n = 3 measurements.

[0177] (11) Combustion initiation temperature and combustion end temperature of polyol and binder The combustion initiation temperature and combustion end temperature of each of the polyols and binders used in the examples and comparative examples were measured using a thermal analyzer manufactured by Rigaku Corporation ("Trade name: Thermo plus EVO2", differential thermal - thermogravimetric simultaneous measurement device "TG-DTA8122", analysis software: Thermo plus EVO ver. 2.086, sample pan: platinum, measurement atmosphere: air (100 cc / min), heating rate: 10.0 ° C. / min, sampling interval: 1.0 second). The types of polyols and binders used and the measurement results of the combustion initiation temperature and combustion end temperature are shown in Tables 1 and 2.

[0178]

[0179]

[0180] Example 1: 1.0 L of a mixed aqueous solution containing 0.62 mol / L zirconium oxychloride and 0.038 mol / L yttrium chloride, and 0.5 L of a 1.9 mol / L sodium hydroxide aqueous solution were prepared. 1.0 L of pure water was poured into a precipitation tank, and the mixed aqueous solution and sodium hydroxide aqueous solution were simultaneously poured to co-precipitate zirconium oxychloride and yttrium chloride to obtain a slurry. After filtering and washing, 22.2 g of acetic acid was added to the slurry, which was then hydrothermally treated at 200°C for 3 hours. The resulting slurry was centrifuged through a membrane filter with a pore size of 100 nm, and pure water was added to obtain a solids concentration (the concentration of zirconia in which yttria is solid-dissolved) of 5.0% by mass. A zirconia slurry was obtained from which coarse particles had been removed. 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 having a particle size of 100 nm or greater was present.

[0181] Isopropanol was added in an amount 9 times the volume of the zirconia slurry, and the mixture was placed in a centrifuge tube, thoroughly mixed, and centrifuged at 4000 rpm for 10 minutes. After confirming the precipitation of white matter, the supernatant was removed, and isopropanol was added again, thoroughly mixed, and centrifuged at 4000 rpm for 10 minutes. After confirming the precipitation of white matter, the supernatant was removed, and methanol was added to the mixture to make it the same volume as the zirconia slurry used, and further mixed thoroughly to obtain a methanol-substituted slurry. The residual moisture content of this methanol-substituted slurry was measured using a Karl Fischer moisture meter and was found to be 0.08% by mass. Glycerin was added to the obtained slurry in an amount of 1% by mass relative to 100% by mass of zirconia, and the acrylic binder "KFE-124" was added in an amount of 2% by mass relative to 100% by mass of zirconia. The mixture was subjected to ultrasonic dispersion at 40 kHz for 1 hour to obtain an additive-containing slurry. The obtained additive-containing slurry was supercritically dried using a supercritical drying apparatus according to the following procedure. That is, the additive-containing slurry was placed in a pressure vessel, the pressure vessel was connected to a supercritical carbon dioxide extraction apparatus, and no pressure leakage was confirmed. The pressure vessel and preheating tube were then immersed in a water bath heated to 60 ° C., heated to 80 ° C., pressurized to 25 MPa, and allowed to stand for 10 minutes for stabilization. Next, carbon dioxide and methanol as an entrainer were introduced under specified 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 of introduction of carbon dioxide alone, the introduction of methanol was stopped, and the introduction of carbon dioxide alone was continued. After 2 hours of introduction of carbon dioxide alone, the carbon dioxide flow was stopped, and the pressure was gradually reduced from 25 MPa over about 20 minutes while maintaining the temperature at 80 ° C., and returned to normal pressure. The pressure vessel was removed from the water bath and cooled to room temperature, opened, and the treated sample was recovered to obtain a powder containing zirconia particles.

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

[0183] Furthermore, the block-shaped zirconia calcined body was milled using a milling machine ("Katana (registered trademark) H-18", manufactured by Kuraray Noritake Dental Co., Ltd.) to cut zirconia calcined bodies having a single crown shape for a maxillary central incisor and a single crown shape for a mandibular first molar, and these were sintered at 1100°C for 2 hours under normal pressure to obtain dental prostheses having a crown shape.

[0184] Comparative Example 1: Glycerin was added to the methanol-substituted slurry prepared in Example 1 at 1% by mass relative to 100% by mass of zirconia, and ultrasonic dispersion was performed at 40 kHz for 1 hour to obtain an additive-containing slurry. A powder containing zirconia particles, plate-shaped and disk-shaped zirconia compacts, calcined zirconia compacts, and sintered zirconia compacts were obtained in the same manner as in Example 1, except that the above slurry was used as the additive-containing slurry. The obtained sintered zirconia compacts were white. The measurement results are shown in Table 3. The block-shaped zirconia compacts were destroyed when the pressure was released from the uniaxial press, indicating insufficient mechanical strength. Therefore, it was not possible to produce block-shaped calcined zirconia compacts or block-shaped zirconia sintered compacts.

[0185] [Comparative Example 2] A powder containing zirconia particles, a plate-shaped and disk-shaped zirconia molded body, a calcined zirconia body, and a zirconia sintered body were obtained in the same manner as in Comparative Example 1, except that the amount of glycerin used in Comparative Example 1 was changed to 2% by mass relative to 100% by mass of zirconia. The obtained zirconia sintered body was white. The results of each measurement are shown in Table 3. Note that the block-shaped zirconia molded body was destroyed when the pressure was released from the uniaxial press, and had insufficient mechanical strength.

[0186] Comparative Example 3 An acrylic binder "KFE-124" was added to the methanol-substituted slurry prepared in Example 1 in an amount of 2% by mass relative to 100% by mass of zirconia, and the mixture was subjected to ultrasonic dispersion at 40 kHz for 1 hour to obtain an additive-containing slurry. A powder containing zirconia particles, a plate-shaped, disk-shaped, or block-shaped zirconia molded body, a zirconia calcined body, and a zirconia sintered body were obtained in the same manner as in Example 1, except that the above slurry was used as the additive-containing slurry. The obtained zirconia sintered body was white. The measurement results are shown in Table 3.

[0187] [Comparative Example 4] A powder containing zirconia particles, a plate-shaped, disk-shaped, and block-shaped zirconia molded body, a zirconia calcined body, and a zirconia sintered body were obtained in the same manner as in Example 1, except that the polyol was changed to dipentaerythritol. The obtained zirconia sintered body was white. The measurement results are shown in Table 3.

[0188]

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

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

[0191] [Example 4] A dilute nitric acid solution of bismuth nitrate was added to the zirconia slurry prepared in Example 2 (average primary particle size: 18 nm, zirconia particles having a particle size of 100 nm or more: 0.35 mass %). The dilute nitric acid solution of bismuth nitrate was added to the zirconia slurry (average primary particle size: 18 nm, zirconia particles having a particle size of 100 nm or more: 0.35 mass %). ２ O ３The polyol and binder were added so that the content was 0.02 mass % in terms of the total mass of the zirconia particles and the fluorescent agent to prepare a slurry containing the zirconia particles and the fluorescent agent. An additive-containing slurry containing a polyol and a binder was prepared in the same manner as in Example 1, except that the slurry obtained above was used. Then, powder containing zirconia particles, plate-shaped, disk-shaped, and block-shaped zirconia compacts, zirconia calcined bodies, and zirconia sintered bodies were obtained in the same manner as in Example 1. The obtained zirconia sintered bodies were white and had fluorescence. The measurement results are shown in Table 4.

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

[0193]

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

[0195] [Example 7] Powder containing zirconia particles, plate-shaped, disk-shaped, and block-shaped zirconia molded bodies, zirconia calcined bodies, and zirconia sintered bodies were obtained in the same manner as in Example 2, except that propylene glycol was used as the polyol. The obtained zirconia sintered bodies were white. The measurement results are shown in Table 5.

[0196] Example 8 A powder containing zirconia particles, a plate-shaped, disk-shaped, and block-shaped zirconia molded body, a calcined zirconia body, and a sintered zirconia body were obtained in the same manner as in Example 2, except that polyglycerin #310 was used as the polyol and "KFA-440" was used as the binder. The obtained sintered zirconia bodies were white. The measurement results are shown in Table 5.

[0197]

[0198] Example 9 A powder containing zirconia particles, a plate-shaped, disk-shaped, and block-shaped zirconia molded body, a calcined zirconia body, and a sintered zirconia body were obtained in the same manner as in Example 2, except that an acrylic binder "KFA-440" was used as the binder. The obtained sintered zirconia bodies were white. The measurement results are shown in Table 6.

[0199] Example 10: A powder containing zirconia particles, a plate-shaped, disk-shaped, and block-shaped zirconia molded body, a zirconia calcined body, and a zirconia sintered body were obtained in the same manner as in Example 2, except that an acrylic binder "Orikox KC-700" was used as the binder. The obtained zirconia sintered body was white. The measurement results are shown in Table 6.

[0200] [Example 11] Powder containing zirconia particles, plate-shaped, disk-shaped, and block-shaped zirconia molded bodies, zirconia calcined bodies, and zirconia sintered bodies were obtained in the same manner as in Example 2, except that an acrylic binder "Orikox KC-500" was used as the binder. The obtained zirconia sintered bodies were white. The measurement results are shown in Table 6.

[0201] [Example 12] Powder containing zirconia particles, plate-shaped, disk-shaped, and block-shaped zirconia molded bodies, zirconia calcined bodies, and zirconia sintered bodies were obtained in the same manner as in Example 1, except that the polyol content was 2 mass%. The obtained zirconia sintered bodies were white. The measurement results are shown in Table 6.

[0202]

Claims

1. Zirconia particles containing yttria in an amount of 2.0 to 9.0 mol % based on the total mole number of zirconium oxide and yttria and having an average primary particle size of 60 nm or less; A polyol and a binder, The zirconia molded body, wherein the polyol and the binder satisfy the following relational formula: 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, and X2 and Y2 represent the temperatures at which a 99.5% weight loss is observed, with the weight before heating measured by thermogravimetry being 100%).)

2. 2. The zirconia molded body according to claim 1, having a thickness of 10 mm or more.

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

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

5. The zirconia molded body according to claim 1 or 2, having a crystal grain size of 180 nm or less after sintering at 900 to 1200° C. under normal pressure.

6. 3. The zirconia molded body according to claim 1, having a three-point bending strength of 500 MPa or more after sintering at 900 to 1200° C. under normal pressure.

7. 3. The zirconia molded body according to claim 1, which has a transmittance of 40% or more for light with a wavelength of 700 nm at a thickness of 0.5 mm after sintering at 900 to 1200° C. under normal pressure.

8. 3. The zirconia molded body according to claim 1, which has a linear light transmittance of 1% or more at a thickness of 1.0 mm after sintering at 900 to 1200° C. under normal pressure.

9. 28.5μm after sintering at 900-1200℃ under normal pressure 2 3. The zirconia molded body according to claim 1, wherein the number of pores having a diameter of 50 nm or more per cross-sectional area is 10 or less.

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

11. The yttria content is 2.0 to 9.0 mol% based on the total mole number of zirconium oxide and yttria, and ΔL ＊ (W−B) is 5 or more, and after sintering at 900 to 1200° C., the thickness is 28.5 μm 2 The calcined zirconia body has a thickness of 10 mm or more and a number of pores having a diameter of 50 nm or more per cross-sectional area of ​​10 or less.

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

13. The content of yttria is 2.0 to 9.0 mol% based on the total mole number of zirconium oxide and yttria, and the thickness is 28.5 μm. 2 The number of pores having a diameter of 50 nm or more per cross-sectional area is 10 or less, and the thickness is 10 mm or more.

14. A method for producing a zirconia sintered body, comprising a step of sintering the zirconia molded body according to claim 1 or 2, or the zirconia calcined body according to claim 11, at normal pressure at 900 to 1200 ° C.