Zirconia shaped body, zirconia calcined body and zirconia sintered body, and method for producing the same

Abstract

The present invention provides a zirconia sintered body, a zirconia formed body and a zirconia calcined body each having both excellent mechanical strength and light transmittance, and a method for producing the same. The present invention relates to a zirconia formed body comprising zirconia particles, a polyol and a binder, the zirconia particles comprising 2.0 to 9.0 mol% of yttria relative to the total moles of zirconia and yttria, and having an average primary particle diameter of 60 nm or less, the polyol and the binder satisfying the following relational expression, X1 < Y1 < X2 < Y2 ≤ 500°C (in the expression, the description of the omitted symbol is omitted).

Description

Technical Field

[0001] This invention relates to zirconia molded bodies, etc. More specifically, this invention relates to zirconia sintered bodies, zirconia molded bodies, and zirconia pre-sintered bodies with excellent mechanical strength and light transmittance, and methods for manufacturing the same, wherein the zirconia molded body comprises a binder capable of providing such zirconia sintered bodies and has a thickness of 10 mm or more. Background Technology

[0002] In recent years, sintered zirconia containing yttrium oxide has been used in dental materials such as dental repairs. These dental repairs are mostly manufactured by pressing zirconia particles or forming them using a slurry or composition containing zirconia particles to create a zirconia molded body with a desired shape, such as a disc or prism. This molded body is then pre-fired to create a pre-fired body (blank), which is then cut (ground) into the shape of the target dental repair and further sintered.

[0003] It has been confirmed to date that linear light transmittance is improved by making the crystal grain size of the zirconia sintered body small and uniform (see, for example, Patent Document 1). Hot isostatic pressing (HIP) is required to achieve small and uniform crystal grain size in the zirconia sintered body. However, the HIP apparatus used for this process is a specialized device classified as a high-pressure gas manufacturing equipment; therefore, it is difficult to say that a zirconia sintered body with high linear light transmittance can be easily obtained.

[0004] Therefore, a zirconia sintered body with excellent mechanical strength and light transmittance without the use of a HIP device has also been proposed, as well as a zirconia shaped body and a zirconia pre-sintered body that can obtain such a zirconia sintered body (Patent Document 2).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2008-214168

[0008] Patent Document 2: International Publication No. 2020 / 179876 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] Furthermore, in order to obtain the desired zirconia molded body, especially a zirconia molded body with a thickness of 10 mm or more, a binder needs to be added to maintain the shape. The more the amount of binder added, the better the shape retention will be. However, the inventors have found through research that if the amount of binder added increases, the light transmittance will decrease significantly due to the amount of binder.

[0011] Therefore, when using a zirconia molded body containing a binder and the binder being of a thickness of 10 mm or more, a sintered body with excellent mechanical strength and light transmittance cannot be obtained as the resulting zirconia sintered body.

[0012] The object of this invention is to provide zirconia sintered bodies, zirconia shaped bodies, and zirconia pre-sintered bodies with excellent mechanical strength and light transmittance, as well as methods for manufacturing the same, wherein the zirconia shaped body is capable of providing such zirconia sintered bodies and contains a binder of an amount contemplated to have a thickness of 10 mm or more. Furthermore, another object of this invention is to provide methods for manufacturing zirconia sintered bodies with excellent mechanical strength and light transmittance that can be easily manufactured without the use of a HIP (High-Intensity Interchange) device, as well as zirconia shaped bodies and zirconia pre-sintered bodies capable of providing such zirconia sintered bodies.

[0013] Solution for solving the problem

[0014] To achieve the aforementioned objectives, the inventors conducted repeated and in-depth research, and discovered that in a zirconia molded body containing a polyol, a binder, and zirconia particles comprising 2.0 to 9.0 mol% yttrium relative to the total molar percentage of zirconia and yttrium oxide, with an average primary particle size of 60 nm or less, the aforementioned problems can be solved by focusing on the combustion start-up temperature and combustion end-up temperature of the polyol and binder, when they satisfy a specific relationship. Furthermore, it was found that this zirconia sintered body is particularly suitable as a dental material, such as a dental repair, and is extremely useful not only as a dental repair for the cervical region of teeth but also as a dental repair for the occlusal surface of molars or the incisal edge of anterior teeth. Based on these insights, the inventors conducted further repeated research, thereby completing the present invention.

[0015] That is, the present invention includes the following technical solutions.

[0016] [1] A zirconia molded body comprising zirconia particles, a polyol, and a binder.

[0017] The zirconium oxide particles contain 2.0–9.0 mol% yttrium oxide relative to the total molar percentage of zirconium oxide and yttrium oxide, and have an average primary particle size of less than 60 nm.

[0018] The aforementioned polyol and the aforementioned binder satisfy the following relationship.

[0019] X1 <Y1<X2<Y2≤500℃

[0020] (In the formula, X1 represents the combustion start temperature of the polyol; X2 represents the combustion end temperature of the polyol; Y1 represents the combustion start temperature of the binder; Y2 represents the combustion end temperature of the binder; X1 and Y1 represent the temperatures at which a 0.5% weight loss is observed, with the weight before heating measured by thermogravimetric analysis set to 100%; X2 and Y2 represent the temperatures at which a 99.5% weight loss is observed.)

[0021] [2] The zirconia molded body according to [1] has a thickness of 10 mm or more.

[0022] [3] The zirconia molded body according to [1] or [2], wherein the combustion start temperature (X1) of the aforementioned polyol is above 50°C.

[0023] [4] The zirconia molded body according to any one of [1] to [3], wherein the thickness is 1.5 mm, ΔL * (WB) is 5 or higher.

[0024] [5] The zirconia molded body according to any one of [1] to [4], wherein the crystal grain size after sintering at atmospheric pressure and 900 to 1200 °C is less than 180 nm.

[0025] [6] The zirconia molded body according to any one of [1] to [5], wherein the three-point bending strength after sintering at atmospheric pressure and at 900 to 1200°C is 500 MPa or more.

[0026] [7] The zirconia molded body according to any one of [1] to [6], wherein the transmittance of light with a wavelength of 700 nm when the thickness is 0.5 mm after sintering at atmospheric pressure and 900 to 1200 °C is 40% or more.

[0027] [8] A zirconia molded body according to any one of [1] to [7], wherein the linear light transmittance is 1% or more when the thickness is 1.0 mm after sintering at atmospheric pressure and 900 to 1200 °C.

[0028] [9] The zirconia molded body according to any one of [1] to [8], wherein the 28.5 μm after sintering at atmospheric pressure and 900 to 1200 °C 2 The number of holes with a diameter of 50 nm or more per unit cross-sectional area is less than 10.

[0029]

[10] The zirconia molded body according to any one of [1] to [9], wherein the ΔL is 1.5 mm thick after pre-firing at 200 to 800 °C. * (WB) is 5 or higher.

[0030]

[11] A zirconia pre-sintered body comprising 2.0 to 9.0 mol% yttrium oxide relative to the total molar amount of zirconia and yttrium oxide, wherein the thickness of the zirconia pre-sintered body is 1.5 mm and the ΔL is... * With a WB value of 5 or higher, the 28.5μm thickness after sintering at 900–1200℃ 2 The number of holes with a diameter of 50nm or more per unit cross-sectional area is less than 10, and the thickness is more than 10mm.

[0031]

[12] A method for manufacturing a zirconia pre-fired body, comprising: a step of pre-firing a zirconia shaped body as described in any one of [1] to

[10] at 200 to 800°C.

[0032]

[13] A zirconia sintered body containing 2.0–9.0 mol% yttrium oxide relative to the total molar amount of zirconia and yttrium oxide, 28.5 μm 2 The number of holes with a diameter of 50nm or more per unit cross-sectional area is less than 10, and the thickness is more than 10mm.

[0033]

[14] A method for manufacturing a zirconia sintered body, comprising: a step of sintering a zirconia shaped body as described in any one of [1] to

[10] or a zirconia pre-sintered body as described in

[11] at atmospheric pressure and at 900 to 1200°C.

[0034] Invention Effects

[0035] According to the present invention, zirconia sintered bodies, zirconia shaped bodies, and zirconia pre-sintered bodies with excellent mechanical strength and light transmittance, as well as methods for manufacturing the same, are provided. The zirconia shaped bodies are capable of providing such zirconia sintered bodies and contain a binder of an amount contemplated to be 10 mm or more in thickness. Furthermore, according to the present invention, zirconia sintered bodies with excellent mechanical strength and light transmittance, zirconia shaped bodies, and zirconia pre-sintered bodies capable of providing such zirconia sintered bodies can be easily manufactured without the use of a HIP (High-Intensity Interchange) apparatus, and methods for manufacturing them are also provided. Detailed Implementation

[0036] In this invention, "zirconia molded body" refers to a shaped body obtained by using zirconia in various forms, such as powder, granules, paste, and slurry, as the main raw material, and shaping it through methods such as pressure molding, injection molding, and photoforming, without progressing to a pre-sintered or sintered state. That is, the zirconia molded body is distinguished from pre-sintered and sintered zirconia bodies in that it is not fired after being shaped.

[0037] In this invention, "zirconia pre-sintered body" refers to the precursor (intermediate product) of zirconia sintered body, which is the state in which zirconia particles (powder) are not completely sintered (pre-sintered state).

[0038] In this invention, "zirconia sintered body" refers to a substance in which zirconia particles (powder) have progressed to the sintered state.

[0039] It should be noted that the upper and lower limits of the numerical ranges (content of each component, X1, Y1, X2, Y2 and the values ​​calculated from them, temperature range, various physical properties, etc.) in this specification can be appropriately combined.

[0040] The zirconia particles, shaped zirconia bodies, pre-sintered zirconia bodies, or sintered zirconia bodies of the present invention contain zirconia and a stabilizer capable of inhibiting the zirconia phase transformation. This stabilizer preferably forms partially stabilized zirconia. Examples of such stabilizers include, for instance, calcium oxide (CaO), magnesium oxide (MgO), yttrium oxide (Y₂O₃), cerium oxide (CeO₂), scandium oxide (Sc₂O₃), niobium oxide (Nb₂O₅), lanthanum oxide (La₂O₃), erbium oxide (Er₂O₃), and praseodymium oxide (Pr₂O₃, Pr₆O₃). 11 Oxides such as samarium oxide (Sm₂O₃), europium oxide (Eu₂O₃), and thulium oxide (Tm₂O₃) are preferred, with yttrium oxide being the most suitable. The content of the stabilizer in the zirconia pre-sintered body and sintered body of the present invention can be determined by, for example, inductively coupled plasma (ICP) luminescence spectrophotometry or fluorescence X-ray diffraction analysis. In the zirconia pre-sintered body and sintered body of the present invention, the content of this stabilizer, unless otherwise specified as for yttrium oxide, is preferably 0.1 to 18 mol% relative to the total molar amount of zirconia and stabilizer, more preferably 1 to 15 mol%, and even more preferably 1.5 to 10 mol%.

[0041] Hereinafter, various suitable embodiments of the present invention will be described using the case where the aforementioned stabilizer is yttrium oxide (Y₂O₃) as an example. Solutions obtained by understanding yttrium oxide as any of the aforementioned stabilizers other than yttrium oxide are also included in the present invention.

[0042] The zirconia molded body of the present invention comprises zirconia particles, a polyol and a binder, wherein the zirconia particles contain 2.0 to 9.0 mol% yttrium oxide relative to the total molar amount of zirconia and yttrium oxide, and the average primary particle size is less than 60 nm, and the aforementioned polyol and the aforementioned binder satisfy the following relationship.

[0043] X1 <Y1<X2<Y2≤500℃

[0044] (In the formula, X1 represents the combustion start temperature of the polyol; X2 represents the combustion end temperature of the polyol; Y1 represents the combustion start temperature of the binder; Y2 represents the combustion end temperature of the binder; X1 and Y1 represent the temperatures at which a 0.5% weight loss is observed, with the weight before heating measured by thermogravimetric analysis set to 100%; X2 and Y2 represent the temperatures at which a 99.5% weight loss is observed.)

[0045] By using the aforementioned zirconia molded body, even a zirconia molded body containing a binder (and thus a zirconia molded body with a thickness of 10 mm or more) can be obtained, resulting in a zirconia sintered body with excellent mechanical strength and light transmittance.

[0046] Furthermore, as a suitable embodiment of the present invention, a zirconia pre-sintered body comprising 2.0 to 9.0 mol% yttrium oxide relative to the total molar amount of zirconia and yttrium oxide, wherein the thickness of the zirconia pre-sintered body is 1.5 mm, and ΔL is... * The zirconia pre-sintered body has a (WB) value of 5 or higher, and after sintering at 900–1200°C, the number of pores with a diameter of 50 nm or higher is less than 10, and the thickness is 10 mm or higher. By using the aforementioned zirconia pre-sintered body, it is also possible to obtain a zirconia sintered body with excellent mechanical strength and light transmittance.

[0047] In this invention, "zirconia" refers to zirconia containing yttrium oxide. Furthermore, in this invention, the "yttrium oxide content" in zirconia particles, shaped zirconia bodies, pre-sintered zirconia bodies, or sintered zirconia bodies refers to the ratio (mol%) of the number of moles of yttrium oxide to the total number of moles of zirconia and yttrium oxide. The yttrium oxide content in the shaped zirconia bodies, pre-sintered bodies, and sintered bodies of this invention can be determined by, for example, inductively coupled plasma (ICP) luminescence spectrophotometry or fluorescence X-ray analysis.

[0048] [Zirconium oxide sintered body]

[0049] 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% yttrium oxide relative to the total molar percentage of zirconia and yttrium oxide, and the zirconia sintered body has a thickness of 28.5 μm. 2 The number of holes with a diameter of 50 nm or more per unit cross-sectional area is 10 or less, and the thickness is 10 mm or more. The thickness of the zirconia sintered body is preferably 12 mm or more, more preferably 15 mm or more. The shape of the zirconia sintered body with a thickness of 10 mm or more is not particularly limited, and it can be blocky (cubic parallelepiped), etc. It should be noted that the following description does not limit the present invention.

[0050] The zirconia sintered body of the present invention may contain a fluorescent agent. The zirconia sintered body exhibits fluorescence by containing a fluorescent agent. The type of fluorescent agent is not particularly limited; one or more fluorescent agents capable of emitting fluorescence using light of any wavelength may be used. Examples of such fluorescent agents include those containing a metal element. Examples of such metal elements include, for example, Ga, Bi, Ce, Nd, Sm, Eu, Gd, Tb, Dy, and Tm. The fluorescent agent may contain only one of these metal elements or may contain two or more. Among these metal elements, Ga, Bi, Eu, Gd, and Tm are preferred from the perspective of more significantly exerting the effects of the present invention, and Bi and Eu are more preferred. Examples of fluorescent agents used in manufacturing the zirconia sintered body of the present invention include, for example, oxides, hydroxides, acetates, and nitrates of the aforementioned metal elements. Alternatively, fluorescent agents can be Y₂SiO₅:Ce, Y₂SiO₅:Tb, (Y,Gd,Eu)BO₃, Y₂O₃:Eu, YAG:Ce, ZnGa₂O₄:Zn, BaMgAl 10 O 17 Eu et al.

[0051] The content of fluorescent agent in the zirconia sintered body is not particularly limited and can be appropriately adjusted according to the type of fluorescent agent or the intended use of the zirconia sintered body. From the viewpoint of being preferably used as a dental repair material, the content 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, based on the conversion of the metal element oxide contained in the fluorescent agent to 100% by mass of zirconia contained in the zirconia sintered body. In addition, it is preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less. By making this content above the lower limit, the fluorescence is not inferior even compared to natural human teeth. Furthermore, by making this content below the upper limit, the reduction in light transmittance and mechanical strength can be suppressed.

[0052] The zirconia sintered body of the present invention may contain a colorant. The zirconia sintered body is colored by containing a colorant. The type of colorant is not particularly limited; known pigments commonly used for coloring ceramics, known dental liquid colorants, etc., can be used. Examples of colorants include colorants containing metallic elements; specifically, oxides, composite oxides, or salts of metallic elements such as iron, vanadium, praseodymium, arsenic, chromium, nickel, and manganese can be used. Alternatively, commercially available colorants can be used, for example, Prettau Colour Liquid manufactured by Zirkonzahn Corporation. The zirconia sintered body may contain one colorant or two or more colorants.

[0053] The content of colorant in zirconia sintered body is not particularly limited and can be appropriately adjusted according to the type of colorant and the intended use of zirconia sintered body. From the viewpoint of being preferably used as a dental repair material, the content 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 sintered body, calculated based on the oxide content of the metal element contained in the colorant. In addition, it is preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and can be 0.1% by mass or less, and further preferably 0.05% by mass or less.

[0054] According to the present invention, a zirconia sintered body with excellent linear light transmittance can be obtained. To adjust the light transmittance of this zirconia sintered body, the zirconia sintered body of the present invention may contain a light transmittance modifier. Specific examples of light transmittance modifiers include, for instance, alumina, titanium dioxide, silica, zircon, lithium silicate, and lithium disilicate. The zirconia sintered body may contain one type of light transmittance modifier, or it may contain two or more types of light transmittance modifiers.

[0055] The content of the light transmittance modifier in the zirconia sintered body is not particularly limited, and can be appropriately adjusted according to the type of light transmittance modifier and the intended use of the zirconia sintered body. From the viewpoint of being preferably used as a dental repair material, it is preferably 0.1% by mass or less relative to 100% by mass of zirconia contained in the zirconia sintered body.

[0056] The zirconia sintered body of the present invention contains 2.0 to 9.0 mol% yttrium oxide relative to the total molar percentage of zirconia and yttrium oxide. When the yttrium oxide content in the zirconia sintered body is less than 2.0 mol%, sufficient light transmittance is not obtained. Furthermore, when the yttrium oxide content in the zirconia sintered body exceeds 9.0 mol%, the mechanical strength decreases. From the perspective of obtaining a zirconia sintered body with superior light transmittance and mechanical strength, the yttrium oxide content in the zirconia sintered body is preferably 3.0 mol% or more, more preferably 3.5 mol% or more, even more preferably 4.0 mol% or more, and preferably 8.0 mol% or less, more preferably 7.5 mol% or less, and even more preferably 7.0 mol% or less.

[0057] The grain size of the zirconia sintered body of the present invention is preferably 180 nm or less. If the grain size exceeds 180 nm, sufficient light transmittance may not be obtained. From the perspective of obtaining a zirconia sintered body with superior light transmittance, the grain size is preferably 140 nm or less, more preferably 120 nm or less, even more preferably 110 nm or less, and can be 100 nm or less. The lower limit of the grain size is not particularly limited; for example, the grain size can be set to 50 nm or more, and further to 70 nm or more. It should be noted that the grain size of the zirconia sintered body can be determined by taking a field-release scanning electron microscope (FE-SEM) image of the cross-section of the zirconia sintered body, selecting 100 arbitrary particles within the image, and averaging their respective circular equivalent diameters (the diameter of a circle of the same area).

[0058] The zirconia sintered body of the present invention exhibits excellent mechanical strength. The three-point flexural strength of the zirconia sintered body of the present invention is preferably 500 MPa or more, more preferably 600 MPa or more, further preferably 650 MPa or more, particularly preferably 700 MPa or more, and most preferably 800 MPa or more. By giving the zirconia sintered body of the present invention this three-point flexural strength, it is possible to suppress breakage in the oral cavity when used, for example, as a dental restoration. There is no particular upper limit to this three-point flexural strength; for example, it can be set to 1500 MPa or less, and further, to 1000 MPa or less. It should be noted that the three-point flexural strength of the zirconia sintered body can be measured according to ISO 6872:2015.

[0059] The zirconia sintered body of the present invention exhibits excellent light transmittance. The transmittance of 700 nm light at a thickness of 0.5 mm is preferably 40% or more, more preferably 45% or more, and can be 46% or more, 48% or more, 50% or more, and further, 52% or more. By keeping this transmittance within the aforementioned range, it is easy to meet the light transmittance requirements for the cut end when used, for example, as a dental restoration. There is no particular upper limit to this transmittance; for example, it can be set to 60% or less, and further, to 57% or less. It should be noted that the transmittance of 700 nm light at a thickness of 0.5 mm of the zirconia sintered body can be measured using a spectrophotometer. For example, a spectrophotometer (Hitachi High-Tech Scientific Co., Ltd., "Hitachi Spectrophotometer U-3900H") can be used, where light emitted from a light source is transmitted and scattered towards the sample, and the measurement is performed using an integrating sphere. In this measurement, the transmittance can be measured first in the wavelength region of 300–750 nm, and then the correlation transmittance of light at a wavelength of 700 nm can be calculated. As the sample used for the measurement, a disc-shaped zirconia sintered body with a diameter of 15 mm and a thickness of 0.5 mm, obtained by mirror polishing both sides, can be used.

[0060] The zirconia sintered body of the present invention exhibits excellent linear light transmittance. The linear light transmittance of the zirconia sintered body of the present invention when its thickness is 1.0 mm is preferably 1% or more, more preferably 3% or more, further preferably 5% or more, particularly preferably 7% or more, and further preferably 10% or more. By keeping this linear light transmittance within the aforementioned range, it is easy to meet the light transmittance requirements for the cut end when used, for example, as a dental repair material. There is no particular upper limit to this linear light transmittance; for example, it can be set to 60% or less, and further preferably 50% or less. It should be noted that the linear light transmittance of the zirconia sintered body when its thickness is 1.0 mm can be measured using a turbidimeter, such as a turbidimeter (manufactured by Nippon Denshoku Kogyo Co., Ltd., "Haze Meter NDH4000"), by transmitting and scattering light emitted from a light source towards the sample and measuring it using an integrating sphere. In this measurement, linear light transmittance is preferably measured according to ISO 13468-1:1996 and JIS K 7361-1:1997, and haze is preferably measured according to ISO 14782-1:1999 and JIS K 7136:2000. The sample used for the measurement can be a disc-shaped zirconia sintered body with a diameter of 15 mm and a thickness of 1.0 mm, obtained by mirror polishing both sides.

[0061] The zirconia sintered body of the present invention contains 28.5 μm 2The number of pores with a diameter of 50 nm or more per unit cross-sectional area is 10 or less, preferably 8 or less, and more preferably 6 or less. When the number of pores with a diameter of 50 nm or more exceeds 10, it may lead to a decrease in the mechanical strength and light transmittance of the zirconia sintered body when forming a blocky zirconia sintered body with a desired thickness. The zirconia sintered body of the present invention contains 28.5 μm... 2 The number of apertures with a diameter greater than 50 nm per unit cross-sectional area is set as follows: For 10 fields of view, each 28.5 μm... 2 Field-release scanning electron microscope (FE-SEM) images of the cross-section of zirconia sintered bodies were obtained. For each hole in the image, the equivalent diameter of the circle (the diameter of a circle of the same area) was calculated. The number of holes with a diameter greater than 50 nm was calculated in each image. The arithmetic mean of the calculated number of holes was obtained by summing 10 images and dividing the sum by 10.

[0062] The method for manufacturing the zirconia sintered body of the present invention is characterized by using a zirconia molded body described later in this invention. The preferred method for manufacturing the zirconia sintered body includes a step of sintering the zirconia molded body at atmospheric pressure and 900–1200°C. Alternatively, a zirconia pre-sintered body described later in this invention can be used, preferably a method including a step of sintering the zirconia pre-sintered body at atmospheric pressure and 900–1200°C. This manufacturing method allows for the easy manufacture of the zirconia sintered body of the present invention, which exhibits excellent mechanical strength, light transmittance, and linear light transmittance.

[0063] [Zirconium oxide molded body]

[0064] The zirconia molded body of the present invention comprises zirconia particles, a polyol and a binder, wherein the zirconia particles contain 2.0 to 9.0 mol% yttrium oxide relative to the total molar amount of zirconia and yttrium oxide, and the average primary particle size is less than 60 nm, and the aforementioned polyol and the aforementioned binder satisfy the following relationship.

[0065] X1 <Y1<X2<Y2≤500℃

[0066] (In the formula, X1 represents the combustion start temperature of the polyol; X2 represents the combustion end temperature of the polyol; Y1 represents the combustion start temperature of the binder; Y2 represents the combustion end temperature of the binder; X1 and Y1 represent the temperatures at which a 0.5% weight loss is observed, with the weight before heating measured by thermogravimetric analysis set to 100%; X2 and Y2 represent the temperatures at which a 99.5% weight loss is observed.)

[0067] By using the aforementioned zirconia molded body, even a zirconia molded body containing a binder (and thus a zirconia molded body with a thickness of 10 mm or more) can be obtained, resulting in a zirconia sintered body with excellent mechanical strength, light transmittance, and linear light transmittance. Furthermore, both the formability of the molded body and the light transmittance of the sintered body can be achieved.

[0068] The zirconia molded body of the present invention has high light transmittance, and can be used to manufacture zirconia sintered bodies and zirconia pre-sintered bodies with high linear light transmittance. The zirconia pre-sintered body can be used to manufacture zirconia sintered bodies with high linear light transmittance. Specifically, the ΔL of the zirconia molded body of the present invention when its thickness is 1.5 mm... * (WB) is preferably 5 or more, more preferably 8 or more, even more preferably 10 or more, and further preferably 11 or more, 12 or more. By making this ΔL * (WB) is within the range described above, thus, when combined with a polyol and binder satisfying the aforementioned formula, a zirconia sintered body with high linear light transmittance can be obtained during sintering at atmospheric pressure. This ΔL * There is no specific upper limit for (WB); for example, it can be set below 30, and further below 25. It should be noted that ΔL is defined as follows when the thickness of the zirconia molded body is 1.5 mm. * (WB) can be measured using a spectrophotometer, such as a KONICA MINOLTA JAPAN "CM-3610A". In this measurement, an F11 light source is used, and the result can be determined by measuring the reflected light. A disc-shaped zirconia specimen with a diameter of 20 mm and a thickness of 1.5 mm can be used as the sample. ΔL * (WB) refers to the lightness (L) against a white background. * ) and brightness (L) against a black background * The difference is 1.5 mm in thickness. Specifically, it refers to the difference between the L-shaped surface under a white background of a 1.5 mm thick zirconia molded body. * Value and L against a black background * The difference in value. L * The value is L * a * b * The L value of chromaticity (color space) in the color system (JIS Z 8781-4:2013) * Value. White background refers to the white portion of the occlusion test paper described in Section 1, Part 4 of JIS K 5600-4-1:1999, and black background refers to the black portion of the aforementioned occlusion test paper.

[0069] When the zirconia sintered body contains a fluorescent agent, a zirconia molded body containing a fluorescent agent can be suitably listed 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 according to the content of the fluorescent agent in the obtained zirconia sintered body, etc. The specific content of the fluorescent agent contained in the zirconia molded body, relative to 100% by mass of zirconia contained in the zirconia molded body, calculated according to the oxide of the metal element contained in the fluorescent agent, is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, further preferably 0.01% by mass or more, and preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.1% by mass or less.

[0070] When the zirconia sintered body contains a colorant, a zirconia molded body containing a colorant can be suitably listed as a raw material before sintering. The content of the colorant in the zirconia molded body containing the colorant can be appropriately adjusted according to the content of the colorant in the obtained zirconia sintered body, etc. The specific content of the colorant contained in the zirconia molded body, relative to 100% by mass of zirconia contained in the zirconia molded body, calculated according to the oxide of the metal element contained in the colorant, is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, further preferably 0.01% by mass or more, and preferably 5% by mass or less, more preferably 1% by mass or less, further preferably 0.5% by mass or less, can be 0.1% by mass or less, and can be 0.05% by mass or less.

[0071] When the zirconia sintered body contains a light transmittance modifier, a zirconia molded body containing the light transmittance modifier can be suitably listed as a raw material before sintering. The content of the light transmittance modifier in the zirconia molded body can be appropriately adjusted according to the content of the light transmittance modifier in the obtained zirconia sintered body. The specific content of the light transmittance modifier contained in the zirconia molded body is preferably 0.1% by mass or less relative to 100% by mass of zirconia contained in the zirconia molded body.

[0072] The yttrium oxide content in the zirconia molded body of the present invention is only required to be in the range of 2.0 to 9.0 mol% relative to the total molar number of zirconia and yttrium oxide, and to be the same as the yttrium oxide content in the obtained zirconia sintered body. Specifically, the yttrium oxide content in the zirconia molded body is 2.0 mol% or more, preferably 3.0 mol% or more, more preferably 3.5 mol% or more, even more preferably 4.0 mol% or more, and preferably 8.0 mol% or less, more preferably 7.5 mol% or less, and even more preferably 7.0 mol% or less.

[0073] 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, from the perspective of obtaining a dense zirconia sintered body, the density is preferably 3.0 g / cm³. 3 The above, more preferably 3.2 g / cm³ 3 The above is further optimized to be 3.4 g / cm³. 3 That's all. There is no specific upper limit to this density; for example, it could be set to 6.0 g / cm³. 3 Therefore, it can be set to 5.8 g / cm³. 3 the following.

[0074] The shape of the zirconia molded body of the present invention is not particularly limited, and can be made into a desired shape according to the application. However, considering the processability when obtaining a zirconia pre-sintered body for use as a blank for manufacturing dental materials such as dental repairs, a disc shape or a prism shape (cubic parallelepiped, etc.) is preferred. It should be noted that, as described later, in the manufacture of the zirconia molded body, if a photoforming method or the like is used, the zirconia molded body can be given a shape corresponding to the desired shape of the final zirconia sintered body, and the present invention also includes zirconia molded bodies with such desired shapes. In addition, the zirconia molded body can be a single-layer structure or a multi-layer structure. By making a multi-layer structure, the final zirconia sintered body can be made into a multi-layer structure, and its physical properties such as light transmittance can be locally modified.

[0075] From a processability point of view, the biaxial bending strength of the zirconia molded article of the present invention is preferably in the range of 2 to 10 MPa, and more preferably in the range of 5 to 8 MPa. It should be noted that the biaxial bending strength of the zirconia molded article can be measured according to JIS T 6526:2018.

[0076] The zirconia shaped body of the present invention, after sintering at atmospheric pressure and 900–1200°C for 2 hours (after forming a zirconia sintered body), preferably has a grain size of 180 nm or less. This allows for the easy manufacture of the zirconia sintered body of the present invention with excellent light transmittance. From the perspective of obtaining a zirconia sintered body with even better light transmittance, this grain size is more preferably 140 nm or less, further preferably 120 nm or less, particularly preferably 110 nm or less, and can be 100 nm or less. The lower limit of this grain size is not particularly limited; for example, it can be set to 50 nm or more, and further preferably 70 nm or more. It should be noted that the method for measuring this grain size is as described above as an explanation of the grain size of the zirconia sintered body.

[0077] The three-point flexural strength of the zirconia molded body of the present invention, after sintering at atmospheric pressure and 900–1200°C (after forming a zirconia sintered body), is preferably 500 MPa or more. This allows for the easy manufacture of the zirconia sintered body of the present invention with excellent mechanical strength. From the perspective of obtaining zirconia sintered bodies with even better mechanical strength, this three-point flexural strength is more preferably 600 MPa or more, further preferably 650 MPa or more, particularly preferably 700 MPa or more, and most preferably 800 MPa or more. There is no particular limitation on the upper limit of this three-point flexural strength; for example, it can be set to 1500 MPa or less, and further preferably 1000 MPa or less. It should be noted that the method for measuring this three-point flexural strength is as described above as an explanation of the three-point flexural strength of the zirconia sintered body.

[0078] The transmittance of the zirconia shaped body of the present invention, after sintering at ambient pressure and 900°C to 1200°C (after forming a zirconia sintered body), when its thickness is 0.5 mm, at a wavelength of 700 nm, is preferably 40% or more. Therefore, it is possible to easily manufacture the zirconia sintered body of the present invention with excellent light transmittance. From the perspective of obtaining a zirconia sintered body with even better light transmittance, this transmittance is more preferably 45% or more, further preferably 46% or more, particularly preferably 48% or more, most preferably 50% or more, and further preferably 52% or more. There is no particular limitation on the upper limit of this transmittance; for example, it can be set to 60% or less, and further preferably 57% or less. It should be noted that the method for measuring this transmittance is as described above in the explanation of the transmittance of light at a wavelength of 700 nm when the thickness of the zirconia sintered body is 0.5 mm.

[0079] The linear light transmittance of the zirconia molded body of the present invention, after sintering at atmospheric pressure and 900°C to 1200°C (after forming a zirconia sintered body), when its thickness is 1.0 mm, is preferably 1% or more, more preferably 3% or more, further preferably 5% or more, particularly preferably 7% or more, and even more than 10%. By keeping this linear light transmittance within the range described above, it is easy to meet the light transmittance requirements for the cut ends when used, for example, as a dental repair. There is no particular upper limit to this linear light transmittance; for example, it can be set to 60% or less, and even more preferably 50% or less. It should be noted that the method for measuring this linear light transmittance is as described above regarding the linear light transmittance when the thickness of the zirconia sintered body is 1.0 mm.

[0080] Furthermore, as a suitable embodiment of the present invention, a zirconia molded body with a diameter of 28.5 μm after sintering at atmospheric pressure and 900–1200 °C can be cited. 2The number of pores with a diameter greater than 50 nm per unit cross-sectional area is less than 10. The suitable range and determination method for the number of pores are the same as those for zirconia sintered bodies.

[0081] [Method for manufacturing zirconia molded bodies]

[0082] The method for manufacturing the zirconia molded body of the present invention is not particularly limited as long as the effects of the present invention are achieved. From the perspective of easily obtaining the zirconia sintered body of the present invention with excellent light transmittance and mechanical strength, a method having a forming step of forming zirconia particles, a polyol, and a binder to obtain the zirconia molded body is preferred. There is no particular limitation as long as the combination of the polyol and the binder satisfies the aforementioned relationship, and specific materials are described below.

[0083] The yttrium oxide content in the zirconia particles used is preferably the same as the yttrium oxide content in the resulting zirconia molded body, and subsequently the zirconia pre-sintered body and the zirconia sintered body. Specifically, the yttrium oxide content in the zirconia particles is 2.0 mol% or more, preferably 3.0 mol% or more, more preferably 3.5 mol% or more, even more preferably 4.0 mol% or more, and preferably 8.0 mol% or less, more preferably 7.5 mol% or less, and even more preferably 7.0 mol% or less.

[0084] The average primary particle size of the zirconia particles used is 60 nm or less. Based on the average primary particle size of 60 nm or less, the percentage of zirconia particles with a diameter exceeding 100 nm relative to the total amount of zirconia particles is preferably 0.5% by mass or less. This allows for the easy acquisition of the zirconia molded body, and further, the zirconia pre-sintered body and zirconia sintered body of the present invention. From the viewpoint of ease of manufacturing of the zirconia molded body, and further, the zirconia pre-sintered 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, even more preferably 20 nm or less, and can be 10 nm or less. Furthermore, it is preferably 1 nm or more, and more preferably 5 nm or more. From the viewpoint of ease of manufacturing of the zirconia molded body, and further, the zirconia pre-sintered body and zirconia sintered body of the present invention, and ease of obtaining the desired linear light transmittance, the percentage of zirconia particles with a diameter exceeding 100 nm is more preferably 0.3% by mass or less, even more preferably 0.1% by mass or less, and can be 0.05% by mass or less. It should be noted that the average primary particle size of zirconia particles can be calculated as follows: For example, by taking photographs of the zirconia particles (primary particles) using a transmission electron microscope (TEM), the particle size (maximum diameter) of any 100 particles in the resulting image is measured, and the average value is calculated. The content of zirconia particles with a particle size exceeding 100 nm can be determined by dispersing the zirconia particles in methanol and measuring the particle size distribution using a laser diffraction / scattering particle size distribution measuring device (Horiba Manufacturing Co., Ltd., LA-950) according to a volume basis.

[0085] There are no particular limitations on the preparation method of zirconia particles. For example, a break-down process can be used to pulverize coarse particles into micronized particles; or a building-up process can be used to synthesize particles from atoms and / or ions through nucleation and growth. Among these methods, a building-up process is preferred in order to obtain high-purity and fine zirconia particles.

[0086] The crushing process can be carried out by pulverizing, for example, using a ball mill or bead mill. In this case, it is preferable to use pulverizing media with very small particle sizes, for example, pulverizing media with a particle size of 100 μm or less. Furthermore, from the perspective of obtaining the desired ΔL... * From the perspective of (WB) and linear light transmittance, it is preferable to classify the resulting zirconia particles after crushing the coarse particles. Classification can be performed using known methods and apparatus, such as porous membranes (membrane filters with pore sizes of 100 nm, etc.) and classification devices (wet classification devices, dry classification devices), etc.

[0087] On the other hand, as construction processes, examples include: gas-phase thermal decomposition method, which involves vaporizing and thermally decomposing oxoacid salts or organometallic compounds with high vapor pressure metal ions to precipitate oxides; gas-phase reaction method, which synthesizes by gas-phase chemical reaction of gaseous metal compounds with high vapor pressure and reaction gases; evaporation concentration method, which involves heating raw materials to vaporize them and then rapidly cooling them in an inert gas at a specified pressure to condense the vapor into particulate particles; melt method, which involves forming molten liquid into small droplets and cooling and solidifying them to form powder; solvent evaporation method, which involves evaporating the solvent to increase the concentration in the liquid, creating a supersaturated state, and precipitating the oxides or hydroxides; and precipitation method, which involves reacting with a precipitant, hydrolyzing the solute to create a supersaturated state, and then undergoing a nucleation-growth process to precipitate insoluble compounds such as oxides or hydroxides.

[0088] Precipitation methods can be further subdivided into: homogeneous precipitation methods, which generate precipitants in solutions through chemical reactions to eliminate local unevenness in precipitant concentration; coprecipitation methods, which simultaneously precipitate multiple metal ions coexisting in a liquid by adding precipitants; hydrolysis methods, which obtain oxides or hydroxides from metal salt solutions, metal alkoxides, and other alcohol solutions through hydrolysis; and solvothermal synthesis methods, which obtain oxides or hydroxides from high-temperature and high-pressure fluids. Solvothermal synthesis methods can be further subdivided into: hydrothermal synthesis methods using water as a solvent; and supercritical synthesis methods using water or supercritical fluids such as carbon dioxide as solvents.

[0089] Regarding any fabrication process, accelerating the precipitation rate is preferred to obtain finer zirconia particles. Furthermore, achieving the desired ΔL... * From the perspective of (WB) and linear light transmittance, it is preferable to classify the obtained zirconia particles. Classification can be carried out using known methods and apparatus, such as porous membranes (membrane filters with pore sizes of 100 nm, etc.) and classification devices (wet classification devices, dry classification devices), etc.

[0090] As a zirconium source in the construction process, nitrates, acetates, chlorides, alkoxides, etc. can be used. Specifically, zirconium dichloride, zirconium acetate, zirconium oxynitrate, etc. can be used.

[0091] Furthermore, in order to achieve the yttrium oxide content within the aforementioned range in the zirconia particles, yttrium oxide can be incorporated into the zirconia particle manufacturing process. For example, yttrium oxide can be dissolved in the zirconia particles. As a yttrium source, nitrates, acetates, chlorides, alkoxides, etc., can be used; specifically, yttrium chloride, yttrium acetate, yttrium nitrate, etc., can be used.

[0092] Zirconia particles can be pre-treated with known surface treatment agents such as organic compounds with acidic groups; fatty acid amides such as saturated fatty acid amides, unsaturated fatty acid amides, saturated fatty acid diamides, and unsaturated fatty acid diamides; and organometallic compounds such as silane coupling agents (organosilicon compounds), organotitanium compounds, organozirconium compounds, and organoaluminum compounds. If the zirconia particles are surface-treated, when preparing a powder containing zirconia particles and a fluorescent agent using a slurry containing a liquid with a surface tension of 50 mN / m or less at 25°C, as described later, the miscibility with this liquid can be adjusted. Furthermore, when manufacturing zirconia molded articles by a method that involves polymerizing a composition containing zirconia particles, a fluorescent agent, and a polymerizable monomer, as described later, the miscibility between the zirconia particles and the polymerizable monomer can be adjusted. Among the aforementioned surface treatment agents, organic compounds with acidic groups are preferred, based on their excellent miscibility with liquids with a surface tension of 50 mN / m or less at 25°C and their ability to improve the chemical bonding between zirconia particles and polymerizable monomers, thereby increasing the mechanical strength of the resulting zirconia molded articles.

[0093] Examples of organic compounds having acidic groups include organic compounds having at least one phosphate group, carboxylic acid group, pyrophosphate group, thiophosphate group, phosphonic acid group, sulfonic acid group, etc. Among these, organic compounds containing phosphate groups having at least one phosphate group and organic compounds containing carboxylic acid groups having at least one carboxylic acid group are preferred, and organic compounds containing phosphate groups are more preferred. Zirconia particles can be surface treated with one surface treatment agent or with two or more surface treatment agents. When zirconia particles are surface treated with two or more surface treatment agents, the resulting surface treatment layer can be a mixture of two or more surface treatment agents or a multilayer structure surface treatment layer with multiple surface treatment layers stacked on top of each other.

[0094] Examples of organic compounds containing phosphate groups include, for instance, 2-ethylhexyl phosphate, stearyl phosphate, 2-(meth)acryloyloxyethyl phosphate, 3-(meth)acryloyloxypropyl phosphate, 4-(meth)acryloyloxybutyl phosphate, 5-(meth)acryloyloxypentyl phosphate, 6-(meth)acryloyloxyhexyl phosphate, 7-(meth)acryloyloxyheptyl phosphate, 8-(meth)acryloyloxyoctyl phosphate, 9-(meth)acryloyloxynonyl phosphate, 10-(meth)acryloyloxydecyl phosphate, 11-(meth)acryloyloxyundecyl phosphate, 12-(meth)acryloyloxydodecyl phosphate, and 16-(meth)acryloyloxyhexadecyl phosphate. Alkyl esters, dihydrogen 20-(meth)acryloyloxyeicosyl ester, hydrogen bis[2-(meth)acryloyloxyethyl] ester, hydrogen bis[4-(meth)acryloyloxybutyl] ester, hydrogen bis[6-(meth)acryloyloxyhexyl] ester, hydrogen bis[8-(meth)acryloyloxyoctyl] ester, hydrogen bis[9-(meth)acryloyloxynonyl] ester, hydrogen bis[10-(meth)acryloyloxydecyl] ester, dihydrogen 1,3-di(meth)acryloyloxypropyl ester, hydrogen 2-(meth)acryloyloxyethylphenyl ester, hydrogen 2-(meth)acryloyloxyethyl-2-bromoethyl ester, hydrogen bis[2-(meth)acryloyloxy-(1-hydroxymethyl)ethyl] ester, and their acyl chlorides, alkali metal salts, ammonium salts, etc.

[0095] Examples of organic compounds containing carboxylic acid groups include succinic acid, oxalic acid, octanoic acid, capric acid, stearic acid, polyacrylic acid, 4-methyloctanoic acid, neodecanoic acid, neopentanoic acid, 2,2-dimethylbutyric acid, 3,3-dimethylbutyric acid, 2,2-dimethylpentanoic acid, 2,2-diethylbutyric acid, 3,3-diethylbutyric acid, cycloalkyl acids, cyclohexanedicarboxylic acid, (meth)acrylic acid, N-(meth)acryloylglycine, N-(meth)acryloylaspartic acid, O-(meth)acryloyltyrosine, N-(meth)acryloyltyrosine, and N-(meth)acryloyl-p-amino... N-(meth)acryloyl-o-aminobenzoic acid, p-vinylbenzoic acid, 2-(meth)acryloyloxybenzoic acid, 3-(meth)acryloyloxybenzoic acid, 4-(meth)acryloyloxybenzoic acid, N-(meth)acryloyl-5-aminosalicylic acid, N-(meth)acryloyl-4-aminosalicylic acid, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl maleate, 2-(2-(2-methoxyethoxy)ethoxy)acetic acid (commonly known as " MEEAA), 2-(2-methoxyethoxy)acetic acid (commonly known as "MEAA"), mono[2-(2-methoxyethoxy)ethyl] succinate, mono[2-(2-methoxyethoxy)ethyl] maleate, mono[2-(2-methoxyethoxy)ethyl] glutarate, malonic acid, glutaric acid, 6-(meth)acryloyloxyhexane-1,1-dicarboxylic acid, 9-(meth)acryloyloxynonane-1,1-dicarboxylic acid, 10-(meth)acryloyloxydecane-1,1-dicarboxylic acid, 11-(meth)acryloyloxyundecane-1,1- Dicarboxylic acids, 12-(meth)acryloyloxydodecane-1,1-dicarboxylic acid, 13-(meth)acryloyloxytetane-1,1-dicarboxylic acid, trimellitic acid 4-(meth)acryloyloxyethyl ester, trimellitic acid 4-(meth)acryloyloxybutyl ester, trimellitic acid 4-(meth)acryloyloxyhexyl ester, trimellitic acid 4-(meth)acryloyloxydecyl ester, 2-(meth)acryloyloxyethyl-3'-(meth)acryloyloxy-2'-(3,4-dicarboxybenzoyloxy)propyl succinate, and their anhydrides, acyl halides, alkali metal salts, ammonium salts, etc.

[0096] In addition, as an organic compound having at least one acidic group other than the above, such as a pyrophosphate group, a thiophosphate group, a phosphonic acid group, or a sulfonic acid group, compounds described, for example, in International Publication No. 2012 / 042911 can be used.

[0097] Examples of saturated fatty acid amides include palmitamide, stearamide, and behenamide. Examples of unsaturated fatty acid amides include oleamide and erucamide. Examples of saturated fatty acid diamides include ethylene bispalmitamide, ethylene bisstearamide, and hexamethylene bisstearamide. Examples of unsaturated fatty acid diamides include ethylene dioleamide, hexamethylene dioleamide, and N,N'-diolenyl sebacate amide.

[0098] As silane coupling agents (organosilicon compounds), examples include R 1 n SiX 4-n The compounds shown are, etc. (where R is a compound). 1 X is a substituted or unsubstituted hydrocarbon group with 1 to 12 carbon atoms, X is an alkoxy, hydroxyl, halogen, or hydrogen atom with 1 to 4 carbon atoms, and n is an integer from 0 to 3, wherein multiple R are present. 1 When X and X are involved, either the same or different can be chosen.

[0099] Specific examples of silane coupling agents (organosilicon compounds) include, for example, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, and 3,3,3-trifluoropropyltrimethylsilane. oxysilanes, methyl-3,3,3-trifluoropropyldimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-epoxypropoxypropyltrimethoxysilane, γ-epoxypropoxypropylmethyldiethoxysilane, γ-epoxypropoxypropyltriethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, γ-methacryloyloxypropylmethyldiethoxysilane, N-(β-aminoethyl)γ-aminopropylmethyldimethoxysilane, N-(β-aminoethyl)γ-aminopropyltrimethoxysilane, 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 silanes include trimethylbromosilane, diethylsilane, vinyltriacetoxysilane, ω-(meth)acryloyloxyalkyltrimethoxysilane [the number of carbon atoms between (meth)acryloyloxy and the silicon atom: 3 to 12, e.g., γ-methacryloyloxypropyltrimethoxysilane], and ω-(meth)acryloyloxyalkyltriethoxysilane [the number of carbon atoms between (meth)acryloyloxy and the silicon atom: 3 to 12, e.g., γ-methacryloyloxypropyltriethoxysilane]. It should be noted that in this specification, the term "(meth)acryloyl" is used to include both methacryloyl and acryloyl groups.

[0100] Among these, silane coupling agents having functional groups are preferred, and more preferably ω-(meth)acryloyloxyalkyltrimethoxysilane [number of carbon atoms between (meth)acryloyloxy and silicon atoms: 3 to 12], ω-(meth)acryloyloxyalkyltriethoxysilane [number of carbon atoms between (meth)acryloyloxy and silicon atoms: 3 to 12], vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, and γ-epoxypropoxypropyltrimethoxysilane.

[0101] Examples of organotitanium compounds include tetramethyl titanate, tetraisopropyl titanate, tetrabutyl titanate, tetrabutyl titanate dimer, and tetra(2-ethylhexyl) titanate.

[0102] Examples of the organozirconium compound include zirconium isopropoxide, zirconium n-butoxide, zirconium acetylacetonate, zirconium oxychloride, and the like.

[0103] Examples of the organoaluminum compound include aluminum acetylacetonate, an aluminum chelate compound of an organic acid, and the like.

[0104] The specific method of the surface treatment is not particularly limited, and a known method can be adopted. For example, a method of spray-adding the above surface treatment agent while vigorously stirring the zirconia particles; a method of removing the solvent after dispersing or dissolving the zirconia particles and the above surface treatment agent in a suitable solvent. The solvent can be a dispersion medium containing a liquid having a surface tension of 50 mN / m or less at 25°C as described later. In addition, after dispersing or dissolving the zirconia particles and the above surface treatment agent, refluxing or high-temperature and high-pressure treatment (autoclave treatment, etc.) can be performed.

[0105] Regarding the polyol and the binder used in the present invention, when the ignition start temperature (X1) of the polyol, the ignition end temperature (X2) of the polyol, the ignition start temperature (Y1) of the binder, and the ignition end temperature (Y2) of the binder are denoted, the relational expression of X1 < Y1 < X2 < Y2 ≤ 500°C is satisfied. It can be considered that by selecting substances satisfying the foregoing relationship and combining them, a path for the binder to be burned and removed during sintering is created inside the zirconia formed body, and the binder is easily removed during sintering. In particular, when the average primary particle diameter of the zirconia particles contained in the zirconia formed body is 60 nm or less, there is a tendency that due to the fine particle diameter, particles are joined to each other (necking phenomenon) during heating, the voids between particles are filled, and the binder cannot be completely removed by heating. By combining and using a polyol and a binder satisfying the above relational expression, the polyol can play a role of forming a path for the binder to be burned and removed during sintering inside the zirconia formed body, and the binder can be completely removed. Thus, although there is a specific problem that the binder is difficult to be burned and removed when the zirconia formed body contains a binder in an amount assumed to have a thickness of 10 mm or more, the problems of the zirconia formed body containing a binder are solved, and the mechanical strength and light transmittance of the sintered zirconia sintered body are both excellent. In addition, the linear light transmittance of such a zirconia sintered body is also excellent.

[0106] The ignition start temperature (X1) of the polyol, the ignition end temperature (X2) of the polyol, the ignition start temperature (Y1) of the binder, and the ignition end temperature (Y2) of the binder can be measured by thermogravimetric measurement (TG). In the present invention, the weight before heating is set to 100%, the temperature at which a weight loss of 0.5% is observed is denoted as X1 and Y1, and the temperature at which a weight loss of 99.5% is observed is denoted as X2 and Y2. The measurement conditions of the thermogravimetric measurement (TG) are as described in the following examples.

[0107] As the polyol used in this invention, examples such as diols and triols can be used. 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 glycerol, 1,2,3-butanediol, and 1,2,4-butanediol. Other polyols include polyglycerol and sugars. A single polyol can be used, or two or more can be used in combination. Regarding the binder, by selecting a polyol and binder that satisfy the aforementioned relationship and combining them in the zirconia molded body, the number of pores generated in the zirconia pre-sintered body and zirconia sintered body obtained during the sintering of the binder-containing zirconia molded body can be reduced, resulting in a zirconia sintered body with excellent mechanical strength and light transmittance, and possessing the desired shape and thickness. Therefore, as long as the polyols are selected in a manner that satisfies the aforementioned relationship, there is no particular limitation on the type of polyols, and the aforementioned effects of the present invention can be achieved.

[0108] Examples of adhesives used in this invention include polyvinyl alcohol, methylcellulose, carboxymethylcellulose, acrylic adhesives, wax adhesives, polyvinyl butyral, polymethyl methacrylate, and ethylcellulose. One type of adhesive may be used alone, or two or more may be used in combination. For the same reasons as with the aforementioned polyols, the type of adhesive is not particularly limited as long as it is selected in a manner that satisfies the aforementioned relationship, and the aforementioned effects of this invention can be achieved.

[0109] X1 is preferably 50°C or higher, more preferably 70°C or higher, and even more preferably 90°C or higher. Furthermore, X1 is preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower. When X1 is 50°C or higher, the outflow of polyol from the zirconia molded body is easily controlled, and the shape retention of the zirconia molded body is excellent. Furthermore, when X1 is 300°C or lower, the bonding of zirconia particles is not hindered, and the desired physical properties are easily obtained.

[0110] Y2 is below 500°C, preferably below 480°C, more preferably below 460°C, and even more preferably below 440°C. When Y2 exceeds 500°C, the bonded zirconia particles cannot withstand the pressure of the gas generated by the combustion of the binder, and the zirconia pre-sintered body may be destroyed.

[0111] In the zirconia molded body of the present invention, the polyol is burned off before the binder during sintering. Therefore, a path for the binder to be burned off is created inside the zirconia molded body. The binder is burned off before necking occurs. From the above 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.

[0112] In the zirconia molded body of the present invention, the polyol is burned off before the binder during sintering. Therefore, a path for the binder to be burned off is created inside the zirconia molded body. The binder is burned off before necking occurs. From the above 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.

[0113] The content of polyol in the zirconia molded body of the present invention (the content relative to 100% by mass of zirconia (the content calculated according to the oxide conversion of the metal element)) 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, and is further preferably 1.5% by mass or less from the viewpoint of having better light transmittance of the resulting zirconia sintered body. Furthermore, the content of polyol 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 it with a binder within the aforementioned range of polyol content, the number of pores generated in the zirconia sintered body can be reduced even when a zirconia molded body with a thickness of 10 mm or more is produced. In the present invention, the content of polyol and binder is the external addition rate, which refers to the mass relative to 100% by mass of zirconia (zirconia containing yttrium oxide).

[0114] The content of the binder in the zirconia molded body of the present invention (the content relative to 100% by mass of zirconia (the content calculated according to the oxide conversion of the metal element)) is not particularly limited, but is preferably less than 10% by mass relative to 100% by mass of zirconia, more preferably 5% by mass or less, and even more preferably 3% by mass or less. Furthermore, the content of the binder 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 aforementioned content range, the number of pores generated in the zirconia sintered body can be reduced even when a zirconia molded body with a thickness of 10 mm or more is produced.

[0115] The mixing ratio (mass ratio) of binder and polyol in the zirconia molded body of the present invention is not particularly limited, but preferably binder:polyol = 10:1 to 1:10, more preferably 5:1 to 1:5. From the viewpoint that the light transmittance of the resulting zirconia sintered body is better, it is further preferably 3:1 to 1:4, and particularly preferably 2.5:1 to 1.1:1.

[0116] As a suitable embodiment, a zirconia molded article can be cited, comprising zirconia particles, a polyol, and a binder, wherein the zirconia particles contain 2.0 to 9.0 mol% yttrium oxide relative to the total molar percentage of zirconia and yttrium oxide, and have an average primary particle size of 60 nm or less.

[0117] The binder content relative to 100% by mass of zirconium oxide is 0.05% by mass or more.

[0118] The polyol content relative to 100% by mass of zirconium oxide is 0.01% by mass or more.

[0119] The aforementioned polyol and the aforementioned binder satisfy the following relationship:

[0120] X1 <Y1<X2<Y2≤500℃

[0121] (The symbols in the formula are explained as described above.)

[0122] In the aforementioned suitable embodiments, the content of the polyol is preferably less than or equal to the content of the binder, more preferably less than or equal to the content of the binder, and even more preferably more than or equal to 0.1% by mass less than the content of the binder. The content of the binder, the content of the polyol, the zirconium oxide particles, etc., can be appropriately set within the ranges described in this specification. For example, relative to 100% by mass of zirconium oxide, the content of the binder can be set to 0.2% by mass or more, or 7% by mass or less.

[0123] As a suitable embodiment of the present invention, a zirconia molded body with a thickness of 10 mm or more can be cited. 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 with a thickness of 10 mm or more is not particularly limited, and it can be block-shaped (cubic parallelepiped), etc.

[0124] In this invention, when manufacturing a zirconia shaped body by means of a forming process that forms zirconia particles, the type of forming process is not particularly limited. From the perspective of being able to easily obtain the zirconia shaped body of this invention, and further the zirconia pre-fired body and zirconia sintered body of this invention, the forming process is preferably at least any one of the following processes.

[0125] (i) A process of casting a slurry containing zirconium oxide particles;

[0126] (ii) The process of gel casting a slurry containing zirconium oxide particles;

[0127] (iii) A process of pressing powder containing zirconium oxide particles into shape;

[0128] (iv) A process for molding a composition comprising zirconium oxide particles and resin; and

[0129] (v) A process of polymerizing a composition containing zirconium oxide particles and polymerizable monomers.

[0130] Slurry containing zirconium oxide particles

[0131] There are no particular limitations on the preparation method of the slurry containing zirconium oxide particles. For example, it can be a slurry obtained by the above-mentioned crushing and forming process, or it can be a commercially available slurry.

[0132] When manufacturing the zirconia molded body containing a binder and a polyol according to the present invention, it is preferable to mix the binder and the polyol separately in a liquid state such as a solution or dispersion with the slurry containing zirconia particles. Furthermore, when the zirconia molded body, and consequently the zirconia pre-sintered body and the zirconia sintered body, contain a colorant and / or a light transmittance modifier, such a colorant and / or light transmittance modifier can be included in the slurry containing zirconia particles and a fluorescent agent. In this case, the colorant and / or light transmittance modifier are preferably mixed separately in a liquid state such as a solution or dispersion with the slurry containing zirconia particles.

[0133] • Powder containing zirconium oxide particles

[0134] The method for preparing the powder containing zirconia particles is not particularly limited. However, from the perspective of obtaining a more uniform zirconia sintered body with excellent physical properties, it is preferable to obtain it by drying the aforementioned slurry containing zirconia particles. The slurry provided for drying may further contain fluorescent agents and / or colorants and / or light transmittance modifiers.

[0135] The drying method is not particularly limited and can include, for example, spray drying, supercritical drying, freeze drying, hot air drying, and vacuum drying. Among these, spray drying, supercritical drying, and freeze drying are preferred, especially those that can suppress particle aggregation during drying and produce a denser zirconia sintered body. Spray drying is even more preferred, and spray drying is still the most preferred.

[0136] The slurry containing zirconia particles supplied for drying can be a slurry in which water is the dispersion medium. From the perspective of being able to suppress the aggregation of particles during drying and to obtain a denser zirconia sintered body, a slurry in which an organic solvent or other dispersion medium other than water is preferred.

[0137] Examples of organic solvents include, for instance, 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, glycerol, and other alcohols; acetone, methyl ethyl ketone, and other ketones; tetrahydrofuran, diethyl ether, diisopropyl ether, 1,4-dioxane, dimethoxyethane, and other ethers (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)); ethyl acetate, butyl acetate, and other esters; hexane, toluene, and other hydrocarbons; chloroform, carbon tetrachloride, and other halogenated hydrocarbons. These organic solvents can be used individually or in combination of two or more. Among these, considering both safety to organisms and ease of removal, the organic solvent is preferably a water-soluble organic solvent, and more preferably ethanol, 2-propanol, 2-methyl-2-propanol, 2-ethoxyethanol, 2-(2-ethoxyethoxy)ethanol, propylene glycol monomethyl ether acetate, acetone, and tetrahydrofuran.

[0138] Furthermore, especially when spray drying is employed, it is preferable that the dispersion medium for the slurry containing zirconia particles and fluorescent agent supplied for drying contains a liquid with a surface tension of 50 mN / m or less at 25°C. This helps to suppress particle aggregation during drying, resulting in a denser zirconia sintered body. From this perspective, the surface tension of the liquid is preferably 40 mN / m or less, and more preferably 30 mN / m or less.

[0139] The surface tension at 25°C can be determined using values ​​described, for example, in the Handbook of Chemistry and Physics. For liquids not described therein, values ​​described in International Publication No. 2014 / 126034 can be used. For liquids not described in either of these publications, known measurement methods can be used, such as the ring method or the Wilhelmy method. The surface tension at 25°C is preferably measured using an automatic surface tension meter, the "CBVP-Z" manufactured by Kyowa Interface Science Co., Ltd., or the "SIGMA702" manufactured by KSV INSTRUMENTS LTD.

[0140] As the liquid described above, an organic solvent having the aforementioned surface tension can be used. The organic solvent can be one of the solvents described above that has the aforementioned surface tension, preferably selected from at least one of methanol, ethanol, 2-methoxyethanol, 1,4-dioxane, 2-ethoxyethanol, and 2-(2-ethoxyethoxy)ethanol, more preferably selected from at least one of methanol, ethanol, 2-ethoxyethanol, and 2-(2-ethoxyethoxy)ethanol, based on the principle that it can suppress particle aggregation during drying and obtain a denser zirconia sintered body.

[0141] From the perspective that it can suppress the aggregation of particles during drying and obtain a denser zirconia sintered body, the content of the above-mentioned liquid in the dispersion medium is preferably 50% by mass or more, more preferably 80% by mass or more, further preferably 95% by mass or more, and particularly preferably 99% by mass or more.

[0142] Slurries containing a dispersion medium other than water can be obtained by replacing the dispersion medium in a slurry containing water. The method of displacement is not particularly limited; for example, adding a dispersion medium other than water (such as an organic solvent) to a slurry containing water and then removing the water by distillation can be employed. During water distillation, some or all of the dispersion medium other than water can be removed together. This addition of the dispersion medium other than water and the distillation removal of water can be repeated multiple times. Alternatively, a method can be used where a dispersion medium other than water is added to a slurry containing water, followed by precipitation of the dispersed phase. Furthermore, for slurries containing water, after replacing the dispersion medium with a specific organic solvent, further displacement can be performed using another organic solvent.

[0143] It should be noted that while fluorescent agents can be added after the dispersion medium has been replaced, it is preferable to add them before the dispersion medium has been replaced, in order to obtain a more uniform zirconia sintered body with superior physical properties. Similarly, when the slurry contains colorants and / or light transmittance modifiers, they can be added after the dispersion medium has been replaced, but it is preferable to add them before the dispersion medium has been replaced, in order to obtain a more uniform zirconia sintered body with superior physical properties.

[0144] The slurry containing zirconium oxide particles supplied for drying can undergo heat- and pressure-based dispersion treatments such as reflux treatment and hydrothermal treatment. Alternatively, the slurry containing zirconium oxide particles supplied for the drying process can be mechanically dispersed using roller mills, colloid mills, high-pressure jet dispersers, ultrasonic dispersers, vibratory mills, planetary mills, bead mills, etc. Only one of the above treatments may be used, or two or more may be employed.

[0145] In addition to binders and polyols, the slurry containing zirconia particles supplied for drying may further contain one or more of the following components: dispersants, emulsifiers, defoamers, pH adjusters, lubricants, etc. By including these other components (especially dispersants, defoamers, etc.) in addition to binders, it is sometimes possible to inhibit the aggregation of particles during drying, thereby obtaining a denser zirconia sintered body.

[0146] Examples of dispersants include ammonium polycarboxylate (such as triammonium citrate), ammonium polyacrylate, acrylic copolymer resins, acrylate copolymers, polyacrylic acid, bentonite, carboxymethyl cellulose, anionic surfactants (such as polyoxyethylene lauryl ether phosphate and polyoxyethylene alkyl ether phosphate), nonionic surfactants, glyceryl oleate, amine surfactants, and oligosaccharide alcohols.

[0147] Examples of emulsifiers include alkyl ethers, phenyl ethers, sorbitol derivatives, and ammonium salts.

[0148] Examples of defoaming agents include alcohols, polyethers, polyethylene glycols, silicones, and waxes.

[0149] Examples of pH adjusters include ammonia, ammonium salts (including ammonium hydroxide such as tetramethylammonium hydroxide), alkali metal salts, and alkaline earth metal salts.

[0150] Examples of lubricants include polyoxyethylene alkyl ethers and waxes.

[0151] From the perspective of suppressing particle aggregation during drying and obtaining a denser zirconia sintered body, the water content in the slurry containing zirconia particles supplied for drying is preferably 3% by mass or less, more preferably 1% by mass or less, and even more preferably 0.1% by mass or less. This water content can be measured using a Karl Fischer moisture meter.

[0152] The drying conditions in the above-described drying methods are not particularly limited, and known drying conditions can be appropriately adopted. It should be noted that when using organic solvents 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.

[0153] There are no particular limitations on the supercritical fluid used in supercritical drying; for example, water or carbon dioxide can be used. However, carbon dioxide is preferred as it can suppress particle aggregation and produce a denser zirconia sintered body.

[0154] • Compositions comprising zirconium oxide particles and resin

[0155] The method for preparing the composition containing zirconium oxide particles and resin is not particularly limited, and it can be obtained, for example, by mixing the powder containing zirconium oxide particles described above with resin.

[0156] Compositions comprising zirconium oxide particles and polymerizable monomers

[0157] The method for preparing the composition containing zirconium oxide particles and polymerizable monomers is not particularly limited, and it can be obtained, for example, by mixing the powder containing zirconium oxide particles described above with polymerizable monomers.

[0158] (i) casting

[0159] When a zirconia molded body is manufactured by means of a process of casting a slurry containing zirconia particles, the specific casting method is not particularly limited, and a method such as flowing the slurry containing zirconia particles into a mold and then drying it can be used.

[0160] Based on the considerations that the slurry can easily flow into the mold, prevent drying from taking a long time, and increase the number of times the mold can be used, the content of the dispersion medium in the slurry containing zirconium oxide particles is preferably 80% by mass or less, more preferably 50% by mass or less, and even more preferably 20% by mass or less.

[0161] The slurry can be poured into the mold under normal pressure, but from a production efficiency point of view, it is preferable to do so under pressure. There are no particular limitations on the type of mold used for flow casting; for example, porous molds made of plaster, resin, or ceramic can be used. Porous molds made of resin or ceramic offer excellent durability.

[0162] In addition to binders and polyols, the slurry containing zirconia particles used in casting may further contain one or more of the following components: dispersants, emulsifiers, defoamers, pH adjusters, lubricants, etc.

[0163] (ii) Gel filling

[0164] When manufacturing a zirconia molded body by means of a process of gel casting a slurry containing zirconia particles, the specific method of gel casting is not particularly limited. For example, a method can be used to gel the slurry containing zirconia particles and a fluorescent agent in a mold, shape it to obtain a wet body, and then dry it.

[0165] From the perspective of preventing excessive drying time and suppressing cracks during drying, the content of the dispersion medium in the slurry containing zirconium oxide particles is preferably 80% by mass or less, more preferably 50% by mass or less, and even more preferably 20% by mass or less.

[0166] The aforementioned gelation can be achieved, for example, by adding a gelling agent, or by polymerizing the product after adding a polymerizable monomer. There are no particular limitations on the type of mold used; for example, porous molds made of plaster, resin, ceramic, etc., or non-porous molds made of metal, resin, etc., can be used.

[0167] There is no limitation on the type of gelling agent; for example, water-soluble gelling agents can be used. Specifically, agarose, gelatin, etc., are preferred. A single gelling agent can be used, or two or more can be used in combination. From the viewpoint of suppressing cracks 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, depending on the mass of the slurry after mixing the gelling agent.

[0168] Furthermore, there are no particular limitations on the types of polymerizable monomers, and examples include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, propylene glycol mono(meth)acrylate, glycerol mono(meth)acrylate, erythritol mono(meth)acrylate, N-hydroxymethyl (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, and N,N-bis(2-hydroxyethyl)(meth)acrylamide. A single polymerizable monomer can be used, or two or more monomers can be used in combination.

[0169] From the viewpoint of suppressing 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 mixing the polymerizable monomer.

[0170] In the case of gelation by polymerization of polymerizable monomers, polymerization is preferably carried out using a polymerization initiator. The type of polymerization initiator is not particularly limited, but photopolymerization initiators are particularly preferred. As a photopolymerization initiator, it is appropriate to select and use from those commonly used in industry, with photopolymerization initiators used in dental applications being preferred.

[0171] Specific examples of photopolymerization initiators include (bis)acylphosphine oxides (including salts), thioxanthones (including quaternary ammonium salts), ketals, α-diketones, coumarins, anthraquinones, benzoin alkyl ethers, and α-aminoketone compounds. A single photopolymerization initiator can be used, or two or more can be used in combination. Among these photopolymerization initiators, at least one selected from (bis)acylphosphine oxides and α-diketones is preferred. This allows polymerization (gelation) to occur in both the ultraviolet (including near-ultraviolet) and visible light regions. In particular, polymerization (gelation) can be sufficiently achieved even when using any light source, such as Ar lasers, He-Cd lasers, halogen lamps, xenon lamps, metal halide lamps, light-emitting diodes (LEDs), mercury lamps, and fluorescent lamps.

[0172] Among the aforementioned (bis)acylphosphine oxides, examples of acylphosphine oxides include 2,4,6-trimethylbenzoyl diphenylphosphine oxide (commonly known as "TPO"), 2,6-dimethoxybenzoyl diphenylphosphine oxide, 2,6-dichlorobenzoyl diphenylphosphine oxide, 2,4,6-trimethylbenzoyl methoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyl ethoxyphenylphosphine oxide, 2,3,5,6-tetramethylbenzoyl diphenylphosphine oxide, benzoyl di(2,6-dimethylphenyl)phosphonate, sodium salt of 2,4,6-trimethylbenzoyl phenylphosphine oxide, potassium salt of 2,4,6-trimethylbenzoyl diphenylphosphine oxide, and ammonium salt of 2,4,6-trimethylbenzoyl diphenylphosphine oxide.

[0173] Among the aforementioned (bis)acylphosphine oxides, examples of 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 are included. Furthermore, compounds described in Japanese Patent Application Publication No. 2000-159621 may also be used.

[0174] Among these (bis)acylphosphine oxides, sodium salts of 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 2,4,6-trimethylbenzoyl methoxyphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and 2,4,6-trimethylbenzoyl phenylphosphine oxide are preferred.

[0175] Examples of α-diketones include diacetyl, biphenylyl, camphorquinone, 2,3-pentanedione, 2,3-octanedione, 9,10-phenanthroquinone, 4,4'-oxybiphenylyl, and acenaphthoquinone. Among these, camphorquinone is preferred, especially when using light sources in the visible light region.

[0176] The slurry containing zirconia particles used in gel casting, like the slurry used in flow casting, may further contain one or more of the following components, in addition to binders and polyols: dispersants, emulsifiers, defoamers, pH adjusters, lubricants, etc.

[0177] There are no particular limitations on the drying method used to dry the shaped wet body. Examples include natural drying, hot air drying, vacuum drying, dielectric heating drying, induction heating drying, and constant temperature and humidity drying. One or more of these methods can be used. Among these, natural drying, dielectric heating drying, induction heating drying, and constant temperature and humidity drying are preferred to prevent cracking during drying.

[0178] (iii) Pressure forming

[0179] When manufacturing zirconia molded articles by means of a process involving the pressure forming of powder containing zirconia particles, the specific method of pressure forming is not particularly limited, and a known pressure forming machine can be used. Examples of specific pressure forming methods include uniaxial pressure forming. Furthermore, to increase the density of the resulting zirconia molded article, it is preferable to further perform cold isostatic pressing (CIP) treatment after uniaxial pressure forming.

[0180] The powder containing zirconia particles used in pressure molding may further contain one or more of the following components, in addition to binders and polyols: dispersants, emulsifiers, defoamers, pH adjusters, lubricants, etc. These components may be mixed during powder preparation.

[0181] (iv) Molding of compositions containing resins

[0182] When manufacturing a zirconia molded body using a method that includes a process of molding a composition comprising zirconia particles and resin, the specific method used for molding the composition is not particularly limited, and can be, for example, injection molding, casting molding, extrusion molding, etc. Alternatively, methods for molding the composition using hot melt dispersive molding (FDM), inkjet printing, powder / binder lamination, and other lamination molding methods (3D printing, etc.) can be used. Among these molding methods, injection molding and casting molding are preferred, with injection molding being more preferred.

[0183] The type of resin is not particularly limited, but resins that can be used as molding raw materials are preferred. Specific examples of such resins include, for instance, alkane waxes, polyvinyl alcohol, polyethylene, polypropylene, ethylene vinyl acetate copolymer, polystyrene, atactic polypropylene, methacrylic resins, and fatty acids such as stearic acid. One of these resins may be used alone, or two or more may be used in combination.

[0184] The composition comprising zirconium oxide particles and resin may further include, in addition to binders and polyols, one or more of the following other components: dispersants, emulsifiers, defoamers, pH adjusters, lubricants, etc.

[0185] (v) Polymerization of compositions containing polymerizable monomers

[0186] By polymerizing a composition containing zirconia particles and polymerizable monomers, the polymerizable monomers in the composition can be polymerized and the composition can be cured. When manufacturing a zirconia molded body using this polymerization process, the specific method is not particularly limited, and methods such as (a) polymerizing the composition containing zirconia particles and polymerizable monomers in a mold; and (b) photolithography (stereolithography; SLA) using the composition containing zirconia particles and polymerizable monomers can be employed. Of these, photolithography (b) is preferred. According to photolithography, a shape corresponding to the desired shape in the final zirconia sintered body can be imparted at the time of manufacturing the zirconia molded body. Therefore, photolithography is sometimes suitable, especially when the zirconia sintered body of the present invention is used as a dental material such as dental repairs.

[0187] The type of polymerizable monomer in the above-mentioned composition containing zirconium oxide particles and polymerizable monomers is not particularly limited, and can be any of the following: monofunctional (meth)acrylates, monofunctional (meth)acrylamides, etc.; and polyfunctional polymerizable monomers such as difunctional aromatic compounds, difunctional aliphatic compounds, and trifunctional or higher compounds. One type of polymerizable monomer can be used alone, or two or more types can be used. Among these, polyfunctional polymerizable monomers are preferred, especially in cases where photoforming methods are employed.

[0188] Examples of monofunctional (meth)acrylates include 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, erythritol mono(meth)acrylate, and other (meth)acrylates containing hydroxyl groups; methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, etc. Alkyl methacrylates such as tert-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, cetyl methacrylate, and stearyl methacrylate; alicyclic methacrylates such as cyclohexyl methacrylate and isobornyl methacrylate; methacrylates containing aromatic groups such as benzyl methacrylate and phenyl methacrylate; and methacrylates with functional groups such as 2,3-dibromopropyl methacrylate, 3-(meth)acryloyloxypropyltrimethoxysilane, and 11-(meth)acryloyloxyundecyltrimethoxysilane.

[0189] 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.

[0190] Among these monofunctional polymerizable monomers, from the viewpoint of excellent polymerizability, (meth)acrylamide is preferred, and N-(meth)acryloylmorpholine, N,N-dimethyl(meth)acrylamide, and N,N-diethyl(meth)acrylamide are more preferred.

[0191] Examples of difunctional aromatic compounds include 2,2-bis((meth)acryloyloxyphenyl)propane, 2,2-bis[4-(3-(meth)acryloyloxy-2-hydroxypropoxy)phenyl]propane, 2,2-bis[4-(3-methacryloyloxy-2-hydroxypropoxy)phenyl]propane (commonly known as "Bis-GMA"), 2,2-bis(4-(meth)acryloyloxyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxypolyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxydiethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxytetraethoxyphenyl)propane, and 2,2-bis(4-(meth)acryloyloxypentaethoxy)propane. 2,2-Bis(4-(methyl)acryloyloxydipropoxyphenyl)propane, 2-(4-(methyl)acryloyloxydiethoxyphenyl)-2-(4-(methyl)acryloyloxyethoxyphenyl)propane, 2-(4-(methyl)acryloyloxydiethoxyphenyl)-2-(4-(methyl)acryloyloxytriethoxyphenyl)propane, 2-(4-(methyl)acryloyloxydipropoxyphenyl)-2-(4-(methyl)acryloyloxytriethoxyphenyl)propane, 2,2-bis(4-(methyl)acryloyloxypropoxyphenyl)propane, 2,2-bis(4-(methyl)acryloyloxyisopropoxyphenyl)propane, 1,4-bis(2-(methyl)acryloyloxyethyl)phenyltrimethylolpropane, etc. Among these, from the viewpoint of excellent polymerizability and mechanical strength of the resulting zirconia molded articles, 2,2-bis[4-(3-methacryloyloxy-2-hydroxypropoxy)phenyl]propane (commonly referred to as "Bis-GMA") and 2,2-bis(4-(meth)acryloyloxypolyethoxyphenyl)propane are preferred. Among 2,2-bis(4-(meth)acryloyloxypolyethoxyphenyl)propane, 2,2-bis(4-methacryloyloxypolyethoxyphenyl)propane (a compound with an average molar number of ethoxy addition of 2.6 (commonly referred to as "D-2.6E")) is preferred.

[0192] Examples of difunctional aliphatic compounds include glycerol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, propylene glycol dimethacrylate, butanediol dimethacrylate, neopentyl glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 2-ethyl-1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, 1,2-bis(3-methacryloyloxy-2-hydroxypropoxy)ethane, and 2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl)dimethacrylate (commonly known as "UDMA"). Among these, from the viewpoint of excellent polymerizability and mechanical strength of the resulting zirconia molded articles, triethylene glycol dimethacrylate (commonly known as "TEGDMA") and 2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl) dimethacrylate are preferred.

[0193] Examples of compounds with trifunctionality or higher 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-(aminocarboxyl)propane-1,3-diol]tetra(meth)acrylate, and 1,7-diacetoxy-2,2,6,6-tetra(meth)acryloxymethyl-4-oxaheptane. Among these, from the viewpoint of excellent polymerizability and mechanical strength of the resulting zirconia molded articles, N,N-(2,2,4-trimethylhexamethylene)bis[2-(aminocarboxyl)propane-1,3-diol]tetramethacrylate and 1,7-diacetoxy-2,2,6,6-tetracetoxymethyl-4-oxaheptane are preferred.

[0194] In either of the methods described in (a) and (b) above, polymerization of the composition is preferably carried out using a polymerization initiator, and the composition preferably further comprises a polymerization initiator. The type of polymerization initiator is not particularly limited, but photopolymerization initiators are particularly preferred. As a photopolymerization initiator, it is appropriate to select and use from those commonly used in industry, with photopolymerization initiators used in dental applications being preferred. Specific examples of photopolymerization initiators are the same as those described above in the instructions for gel casting, and are omitted here for repetition.

[0195] The composition comprising zirconium oxide particles and polymerizable monomers may further include, in addition to binders and polyols, one or more of the following other components: dispersants, emulsifiers, defoamers, pH adjusters, lubricants, etc.

[0196] When manufacturing zirconia molded bodies using a photoforming method that employs a composition comprising zirconia particles and polymerizable monomers, the specific method of photoforming is not particularly limited, and known methods can be appropriately employed. For example, the following method can be used: by using a photoforming device, photopolymerizing a liquid composition using ultraviolet light, laser, or the like, thereby sequentially forming layers with the desired shape, thus obtaining the desired zirconia molded body.

[0197] When obtaining zirconia molded bodies by photoforming, from the viewpoint of subsequent sintering, the content of zirconia particles in the composition comprising zirconia particles and polymerizable monomers is preferably as high as possible. Specifically, the content of zirconia particles in the composition is preferably 20% by mass or more, more preferably 30% by mass or more, further preferably 40% by mass or more, and particularly preferably 50% by mass or more. On the other hand, in photoforming, based on its layering principle, the viscosity of the composition is preferably within a certain specified range. Therefore, the content of zirconia particles in the above composition is preferably 90% by mass or less, more preferably 80% by mass or less, further preferably 70% by mass or less, and particularly preferably 60% by mass or less. In the case of implementing a restricted liquid surface method to sequentially form zirconia molded bodies layer by layer by curing the layers through light irradiating the bottom surface of the container from the lower side, the viscosity adjustment of the composition sometimes becomes particularly important in order to ensure that the cured layer rises by only one layer and flows smoothly between the lower surface of the cured layer and the bottom surface of the container to form the next layer.

[0198] Regarding the specific viscosity of the above composition, measured at 25°C, it 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 more preferably 100 mPa·s or more. In this composition, there is a tendency for the viscosity to increase as the content of zirconia particles increases. Therefore, it is preferable to appropriately adjust the balance between the zirconia particle content and viscosity in the above composition, taking into account factors such as the performance of the photoforming apparatus used and the balance between the photoforming speed and the accuracy of the resulting zirconia molded body. It should be noted that this viscosity can be measured using an E-mold viscometer.

[0199] In the method for manufacturing the zirconia molded article of the present invention, in order to further increase the density of the zirconia molded article, a CIP treatment can be performed after humidifying the zirconia molded article. In the case of pressure molding, the powder containing zirconia particles can be humidified before pressure molding, and then pressure molding can be performed. The humidification method can be any known method without any limitation; water can be sprayed or applied using a humidifier or a constant temperature and humidity device. The increase in moisture content due to the humidification treatment depends on the particle size of the contained zirconia particles, etc., and is preferably more than 2% by mass, more preferably more than 3% by mass, further preferably more than 4% by mass, particularly preferably more than 5% by mass, and preferably 15% by mass or less, more preferably 13% by mass or less, and even more preferably 11% by mass or less, relative to the mass of the powder before humidification (powder before humidification) and the molded article. It should be noted that the increase in moisture based on the humidification treatment can be calculated as follows: subtract the mass of the powder and the molded body before humidification from the mass of the humidified powder (powder after humidification treatment) and the molded body, and then divide the resulting value by the mass of the powder and the molded body before humidification to obtain the percentage.

[0200] [Zirconium oxide pre-sintered body]

[0201] As another embodiment of the present invention, a zirconia pre-sintered body is provided, which contains 2.0 to 9.0 mol% yttrium oxide relative to the total molar percentage of zirconia and yttrium oxide, wherein the zirconia pre-sintered body has a ΔL of 1.5 mm thickness. * With a WB value of 5 or higher, the 28.5μm thickness after sintering at 900–1200℃ 2 The number of pores with a diameter of 50 nm or more per unit cross-sectional area is less than 10, and the thickness is more than 10 mm. By using the aforementioned zirconia pre-sintered body, a zirconia sintered body with excellent mechanical strength, light transmittance, and linear light transmittance can be obtained. ΔL * The definition of (WB) is the same as that of the zirconia shaped body. It should be noted that the method for determining the number of pores with a diameter of 50 nm or more is as described above as an explanation of the number of pores with a diameter of 50 nm or more in a zirconia sintered body. The thickness of the zirconia pre-sintered body is preferably 12 mm or more, more preferably 15 mm or more. The shape of the zirconia pre-sintered body with a thickness of 10 mm or more is not particularly limited and can be blocky (cubic parallelepiped), etc.

[0202] When the zirconia sintered body of the present invention contains a fluorescent agent, a zirconia pre-sintered body containing a fluorescent agent can be suitably listed as a raw material before sintering. The content of the fluorescent agent in the zirconia pre-sintered body containing the fluorescent agent can be appropriately adjusted according to the content of the fluorescent agent in the obtained zirconia sintered body, etc. The specific content of the fluorescent agent contained in the zirconia pre-sintered body, relative to 100% by mass of zirconia contained in the zirconia pre-sintered body, calculated according to the oxide of the metal element contained in the fluorescent agent, is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, further preferably 0.01% by mass or more, and preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.1% by mass or less.

[0203] When the zirconia sintered body contains a colorant, a zirconia pre-sintered body containing a colorant can be suitably listed as a raw material before sintering. The content of the colorant in the zirconia pre-sintered body containing the colorant can be appropriately adjusted according to the content of the colorant in the obtained zirconia sintered body, etc. The specific content of the colorant contained in the zirconia pre-sintered body, relative to 100% by mass of zirconia contained in the zirconia pre-sintered body, calculated according to the oxide of the metal element contained in the colorant, is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, further preferably 0.01% by mass or more, and preferably 5% by mass or less, more preferably 1% by mass or less, further preferably 0.5% by mass or less, can be 0.1% by mass or less, and can even be 0.05% by mass or less.

[0204] When the zirconia sintered body contains a light transmittance modifier, a zirconia pre-sintered body containing the light transmittance modifier can be suitably listed as a raw material before sintering. The content of the light transmittance modifier in the zirconia pre-sintered body can be appropriately adjusted according to the content of the light transmittance modifier in the resulting zirconia sintered body. The specific content of the light transmittance modifier contained in the zirconia pre-sintered body is preferably 0.1% by mass or less relative to 100% by mass of zirconia contained in the zirconia pre-sintered body.

[0205] The yttrium oxide content in the zirconia pre-sintered body of the present invention is only required to be in the range of 2.0 to 9.0 mol% and the same as the yttrium oxide content in the obtained zirconia sintered body. Specifically, the yttrium oxide content in the zirconia pre-sintered body is 2.0 mol% or more, preferably 3.0 mol% or more, more preferably 3.5 mol% or more, even more preferably 4.0 mol% or more, and preferably 8.0 mol% or less, more preferably 7.5 mol% or less, even more preferably 7.0 mol% or less.

[0206] The density of the zirconia pre-fired body of the present invention is not particularly limited, and varies depending on the manufacturing method of the zirconia shaped body used in its manufacture, but is preferably 3.0 to 6.0 g / m³. 3 Within the range of 3.2–5.8 g / m, it is more preferably within the range of 3.2–5.8 g / m 3 Within the range.

[0207] The shape of the zirconia pre-fired body of the present invention is not particularly limited, and can be made into a desired shape according to the application. Considering its processability when used as a blank for manufacturing dental materials such as dental repairs, a disc-shaped or prismatic (cubic parallelepiped, etc.) shape is preferred. It should be noted that, as described later, the zirconia pre-fired body can be cut (ground) to form a desired shape suitable for the application before being made into a zirconia sintered body. The present invention also includes a zirconia pre-fired body having this desired shape after cutting (grinding). Furthermore, the zirconia pre-fired body can be a single-layer structure or a multi-layer structure. By forming a multi-layer structure, the final zirconia sintered body can be made into a multi-layer structure, and its physical properties such as light transmittance can be locally modified.

[0208] From the viewpoint of maintaining the shape of the workpiece during machining and easily cutting itself, the three-point bending strength of the zirconia pre-sintered body of the present invention is preferably in the range of 10 to 70 MPa, more preferably in the range of 20 to 60 MPa. It should be noted that the three-point bending strength of the zirconia pre-sintered body can be measured as follows: for a 5 mm × 40 mm × 10 mm test piece, a universal testing machine is used, with a span length (distance between support points) of 30 mm and a crosshead speed of 0.5 mm / min.

[0209] The crystal grain size of the zirconia pre-sintered body of the present invention, after sintering at atmospheric pressure and 900–1200°C for 2 hours (after forming the zirconia sintered body), is preferably 180 nm or less. This allows for the easy manufacture of the zirconia sintered body of the present invention with excellent light transmittance. From the perspective of obtaining a zirconia sintered body with even better light transmittance, this crystal grain size is more preferably 140 nm or less, further preferably 120 nm or less, particularly preferably 115 nm or less, and can be 110 nm or less. The lower limit of this crystal grain size is not particularly limited; for example, it can be set to 50 nm or more, and further preferably 100 nm or more. It should be noted that the method for measuring this crystal grain size is as described above as an explanation of the crystal grain size in the zirconia sintered body.

[0210] The ΔL of the zirconia pre-sintered body of the present invention at a thickness of 1.5 mm * (WB) is 5 or more, preferably 7 or more, and further preferably 10 or more. By making this ΔL *(WB) Within the aforementioned range, when sintering is performed under normal pressure, a zirconia sintered body with high linear light transmittance can be obtained. This ΔL * There is no specific upper limit for (WB); for example, it can be set below 30, and further below 25. It should be noted that ΔL is calculated for a zirconia pre-sintered body with a thickness of 1.5 mm. * (WB) Except for changing the test specimen from the zirconia molded body to the zirconia pre-burnt body, the same method as for the zirconia molded body can be used for the test.

[0211] The three-point flexural strength of the zirconia pre-sintered body of the present invention, after sintering at atmospheric pressure and 900–1200°C (after forming a zirconia sintered body), is preferably 500 MPa or more. This allows for the easy manufacture of the zirconia sintered body of the present invention with excellent mechanical strength. From the perspective of obtaining zirconia sintered bodies with even better mechanical strength, this three-point flexural strength is more preferably 600 MPa or more, further preferably 650 MPa or more, particularly preferably 700 MPa or more, and most preferably 800 MPa or more. There is no particular limitation on the upper limit of this three-point flexural strength; for example, it can be set to 1500 MPa or less, and further preferably 1000 MPa or less. It should be noted that the method for measuring this three-point flexural strength is as described above as an explanation of the three-point flexural strength in zirconia sintered bodies.

[0212] The transmittance of light with a wavelength of 700 nm when the thickness of the zirconia pre-sintered body of the present invention is 0.5 mm after sintering at atmospheric pressure and 900–1200 °C (after forming a zirconia sintered body) is preferably 40% or more. Therefore, it is easy to manufacture the zirconia sintered body of the present invention with excellent light transmittance. From the perspective of obtaining a zirconia sintered body with even better light transmittance, this transmittance is more preferably 45% or more, further preferably 46% or more, particularly preferably 48% or more, most preferably 50% or more, and further preferably 52% or more. There is no particular limitation on the upper limit of this transmittance; for example, it can be set to 60% or less, and further preferably 57% or less. It should be noted that the method for measuring this transmittance is as described above in the explanation of the transmittance of light with a wavelength of 700 nm when the thickness of the zirconia sintered body is 0.5 mm.

[0213] The linear light transmittance of the zirconia pre-sintered body of the present invention, after sintering at atmospheric pressure and 900–1200°C (to form a zirconia sintered body), when its thickness is 1.0 mm, is preferably 1% or more, more preferably 3% or more, further preferably 5% or more, particularly preferably 7% or more, and even more than 10%. By keeping this linear light transmittance within the aforementioned range, it is easy to meet the light transmittance requirements for the cut ends when used, for example, as a dental repair. There is no particular upper limit to this linear light transmittance; for example, it can be set to 60% or less, and even more preferably 50% or less. It should be noted that the method for measuring this linear light transmittance is as described above regarding the linear light transmittance when the thickness of the zirconia sintered body is 1.0 mm.

[0214] [Method for manufacturing zirconia pre-sintered body]

[0215] The method for manufacturing a zirconia pre-sintered body according to the present invention is characterized by, for example, using a zirconia molded body of the present invention. The method for manufacturing a zirconia pre-sintered body preferably includes a step of pre-sintering the zirconia molded body at 200 to 800°C. The method for manufacturing a zirconia pre-sintered body according to the present invention may include a step of machining the zirconia molded body of the present invention, and then pre-sintering the machined zirconia molded body. The machining method is not particularly limited, and known apparatus (e.g., known grinding apparatus) and methods can be used. From the viewpoint of easily obtaining the desired zirconia pre-sintered body, the pre-sintering temperature is preferably 200°C or higher, more preferably 250°C or higher, further preferably 300°C or higher, and preferably 800°C or lower, more preferably 700°C or lower, and further preferably 600°C or lower. By setting the pre-sintering temperature to the lower limit or above, the generation of organic residue can be effectively suppressed. Furthermore, by setting the pre-sintering temperature to the upper limit or below, over-sintering that makes machining (grinding) difficult can be prevented.

[0216] The heating rate during pre-firing 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, even more preferably 0.5°C / min or more, and preferably 50°C / min or less, more preferably 30°C / min or less, even more preferably 20°C / min or less. By keeping the heating rate at or above the above lower limit, productivity is improved. In addition, by keeping the heating rate at or below the above upper limit, the volume difference between the inside and outside of the zirconia molded body and the zirconia pre-firing body can be suppressed. Furthermore, in the case where the zirconia molded body contains organic matter, the rapid decomposition of the organic matter can be suppressed, and cracking and damage can be suppressed.

[0217] The pre-firing time for the zirconia molded body of the present invention is not particularly limited. However, from the perspective of being able to obtain the zirconia pre-fired body as a target with good productivity and stability, the pre-firing time is preferably 0.5 hours or more, more preferably 1 hour or more, even more preferably 2 hours or more, and preferably 10 hours or less, more preferably 8 hours or less, and even more preferably 6 hours or less.

[0218] The pre-firing in this invention can be carried out using a pre-firing furnace. There is no particular limitation on the type of pre-firing furnace; for example, electric furnaces and degreasing furnaces commonly used in industry can be used.

[0219] The zirconia pre-sintered body of the present invention can be cut (ground) to form a desired shape suitable for its intended use before being made into a zirconia sintered body. In particular, the zirconia sintered body of the present invention, despite containing a fluorescent agent, exhibits excellent light transmittance and mechanical strength, and is therefore particularly suitable as a dental material such as a dental restoration. To obtain a zirconia sintered body for use in such applications, the zirconia pre-sintered body can be cut (ground) in a manner that produces a corresponding shape. The cutting (grinding) method is not particularly limited, and can be performed using, for example, a known grinding apparatus.

[0220] [Method for manufacturing zirconia sintered bodies]

[0221] As described above, the zirconia sintered body of the present invention can be manufactured by sintering the zirconia shaped body of the present invention under normal pressure. Alternatively, it can be manufactured by sintering the zirconia pre-sintered body of the present invention under normal pressure.

[0222] In both the sintering of the zirconia molded body and the sintering of the zirconia pre-sintered body of the present invention, from the viewpoint of easily obtaining the desired zirconia sintered body, the sintering temperature is preferably 900°C or higher, more preferably 1000°C or higher, even more preferably 1050°C or higher, and preferably 1200°C or lower, more preferably 1150°C or lower, and even more preferably 1120°C or lower. By setting the sintering temperature to the lower limit or above, sintering can be performed sufficiently, and a dense sintered body can be easily obtained. Furthermore, by setting the sintering temperature to the upper limit or below, a zirconia sintered body with a crystal grain size within the suitable range of the present invention can be easily obtained, and the deactivation of the fluorescent agent can be suppressed.

[0223] When sintering the zirconia molded body of the present invention and the zirconia pre-sintered body of the present invention, the sintering time is not particularly limited. From the perspective of being able to obtain the zirconia sintered body as a target with good productivity and stability, the sintering time is preferably 5 minutes or more, more preferably 15 minutes or more, further preferably 30 minutes or more, and preferably 6 hours or less, more preferably 4 hours or less, and further preferably 2 hours or less.

[0224] The sintering in this invention can be performed using a sintering furnace. There is no particular limitation on the type of sintering furnace; for example, electric furnaces and degreasing furnaces commonly used in industry can be used. Especially in applications involving dental materials, in addition to conventional dental zirconia sintering furnaces, dental porcelain furnaces with lower sintering temperatures can also be used.

[0225] The zirconia sintered body of the present invention can be easily manufactured even without HIP treatment. By performing HIP treatment after sintering under the above-mentioned atmospheric pressure, the light transmittance and mechanical strength can be further improved.

[0226] [Applications of Zirconia Sintered Bodies]

[0227] The applications of the zirconia sintered body of the present invention are not particularly limited. The zirconia sintered body of the present invention exhibits excellent light transmittance and mechanical strength, as well as excellent linear light transmittance. Therefore, it is particularly suitable as a dental material, such as a dental repair. It is extremely useful not only as a dental repair for use at the neck of teeth, but also as a dental repair for use on the occlusal surface of molars and the incisal end of anterior teeth. The zirconia sintered body of the present invention is particularly preferred for use as a dental repair for the incisal end of anterior teeth.

[0228] Example

[0229] The present invention will now be described in detail with reference to examples and comparative examples, but the present invention is not limited to these examples, etc. It should be noted that the methods for measuring each physical property are as follows.

[0230] (1) Average primary particle size of zirconium oxide particles

[0231] For the zirconium oxide particles in the zirconium oxide slurry, a transmission electron microscope (TEM) was used to take pictures. The particle size (maximum diameter) of any 100 particles was measured on the obtained image, and their average value was taken as the average primary particle size of the zirconium oxide particles.

[0232] (2) The proportion of particles with a diameter exceeding 100 nm

[0233] Zirconia particles in the zirconia slurry were dispersed in methanol and measured using a laser diffraction / scattering particle size distribution measuring device (Horiba Manufacturing Co., Ltd., LA-950) according to volume.

[0234] (3) Crystal grain size

[0235] The grain size in the zirconia sintered body is determined as follows: a field-release scanning electron microscope (FE-SEM) image of the cross-section of the zirconia sintered body is taken, and 100 arbitrary particles in the image are selected and the grain size is determined as the average of their respective circular equivalent diameters (the diameter of a circle of the same area).

[0236] (4) Three-point bending strength

[0237] The three-point bending strength of zirconia sintered bodies was determined according to ISO 6872:2015. Under the conditions of a distance of 30 mm between support points, a test piece size of 40 mm × 4 mm × 3 mm, and a crosshead speed of 0.5 mm / min, the test was conducted with n = 10, and the average value was calculated.

[0238] The test piece was obtained by the following operation: the powder containing zirconia particles obtained in the process of the example was shaped into square rods of 40mm×6mm×5mm by uniaxial pressing, and they were subjected to cold isostatic pressing (CIP) treatment (pressure of 170MPa) to increase the density and obtain zirconia shaped bodies. After firing, the surface was polished.

[0239] (5) Light transmittance (wavelength 700nm, 0.5mm thickness)

[0240] The transmittance of 700 nm light at a thickness of 0.5 mm in a zirconia sintered body was determined as follows: A spectrophotometer (Hitachi High-Tech Scientific Co., Ltd., "Hitachi Spectrophotometer U-3900H") was used. Light emitted from the light source was transmitted and scattered through the sample, and the measurement was performed using an integrating sphere. In this measurement, the transmittance was first measured in the wavelength region of 300–750 nm, and then the relevant transmittance at a wavelength of 700 nm was calculated. For the measurement, a disc-shaped zirconia sintered body with a diameter of 15 mm and a thickness of 0.5 mm, obtained by mirror polishing, was used as the sample. Measurements were performed with n=3 samples, and the average value was calculated.

[0241] (6) Linear light transmittance (1.0 mm thickness)

[0242] The linear light transmittance of a 1.0 mm thick zirconia sintered body was determined as follows: A turbidimeter (Nippon Denshoku Kogyo Co., Ltd., "Haze Meter NDH4000") was used to transmit and scatter light emitted from a light source onto the sample, and the measurement was performed using an integrating sphere. In this measurement, linear light transmittance was measured according to ISO 13468-1:1996 and JIS K 7361-1:1997, and haze was measured according to ISO 14782-1:1999 and JIS K 7136:2000, thereby determining the linear light transmittance. For the measurement, a 15 mm diameter × 1.0 mm thick disc-shaped zirconia sintered body, obtained by mirror polishing, was used as the sample. Measurements were performed with n = 3 samples, and the average value was calculated.

[0243] (7) 28.5μm 2 The number of holes with a diameter of 50 nm or larger per unit cross-sectional area

[0244] 28.5μm 2 The number of holes with a diameter greater than 50 nm per unit cross-sectional area was set as follows: using sintered zirconia bodies obtained by sintering bulk zirconia, 28.5 μm images were captured in 10 fields of view. 2 Field-release scanning electron microscope (FE-SEM) images of the cross-section of the zirconia sintered body were used to determine the equivalent circular diameter (diameter of a circle of equal area) of each hole within the image. The number of holes with a diameter greater than 50 nm was calculated in each image. The arithmetic mean of the calculated number was obtained by summing 10 images and dividing by 10. The number of holes with a diameter greater than 50 nm is presented in Tables 3-6 below.

[0245] (8) Appearance of zirconia sintered body

[0246] The appearance (color) of zirconia sintered bodies is evaluated visually.

[0247] (9) Fluorescence of zirconia sintered bodies

[0248] Regarding the fluorescence of zirconia sintered bodies, the presence or absence of fluorescence under UV light is evaluated visually.

[0249] (10) ΔL of zirconia molded body and zirconia pre-sintered body * (WB)

[0250] ΔL when the thickness of the zirconia shaped body and the zirconia pre-sintered body is 1.5 mm *(WB) measurements were performed using a spectrophotometer (KONICA MINOLTA JAPAN, "CM-3610A"). In this measurement, an F11 light source was used, and the result was determined by measuring the reflected light. Disc-shaped zirconia molded bodies and pre-sintered bodies, each 20 mm in diameter and 1.5 mm thick, obtained by mirror polishing, were used as samples. Measurements were performed with n = 3 samples, and the average value was calculated.

[0251] (11) Combustion start temperature and combustion end temperature of polyols and binders

[0252] For the polyols and binders used in the examples and comparative examples, the combustion onset temperature and combustion end temperature were measured using a thermal analysis apparatus manufactured by Rigaku Corporation (“Trade Name: Thermo plus EVO2”, Differential Calorimetry-Thermogravimetric Analysis Apparatus “TG-DTA8122”, Analysis Software: Thermo plus EVO ver2.086, Sample Pot: Platinum, Measurement Atmosphere: Air (100cc / min), Heating Rate: 10.0℃ / min, Sampling Interval: 1.0 sec). The types of polyols and binders used, along with the measurement results of their combustion onset and combustion end temperatures, are shown in Tables 1 and 2.

[0253] [Table 1]

[0254]

[0255] (X1 represents the temperature at which a 0.5% weight loss was observed when the weight before heating was set to 100%; X2 represents the temperature at which a 99.5% weight loss was observed.)

[0256] [Table 2]

[0257]

[0258] (Y1 represents the temperature at which a 0.5% weight loss was observed when the weight before heating was set to 100%; Y2 represents the temperature at which a 99.5% weight loss was observed.)

[0259] [Example 1]

[0260] Prepare 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 an aqueous solution containing 1.9 mol / L sodium hydroxide.

[0261] 1.0L of pure water is injected into the sedimentation tank, and then the above-mentioned mixed aqueous solution and sodium hydroxide aqueous solution are injected simultaneously to cause zirconium oxychloride and yttrium chloride to co-precipitate, thus obtaining a slurry.

[0262] After filtration and washing, 22.2 g of acetic acid was added to the slurry, and the mixture was subjected to hydrothermal treatment at 200°C for 3 hours. The resulting slurry was then centrifuged using a membrane filter with a pore size of 100 nm. Pure water was added to achieve a solids concentration (concentration of zirconium oxide dissolved in yttrium oxide) of 5.0% by mass, resulting in a zirconium oxide slurry after the removal of coarse particles. The zirconium oxide slurry contained zirconium oxide particles with an average primary particle size of 17 nm, and zirconium oxide particles with a diameter greater than 100 nm accounted for 0.33% by mass.

[0263] Nine volumes of isopropanol were added to the zirconia slurry, and the mixture was added to a centrifuge tube and thoroughly mixed. The mixture was centrifuged at 4000 rpm for 10 minutes. After confirming the sedimentation of the white residue, the supernatant was removed, and isopropanol was added again and thoroughly mixed. The mixture was centrifuged at 4000 rpm for 10 minutes. After confirming the sedimentation of the white residue, the supernatant was removed, and methanol was added to make it equal in volume to the zirconia slurry used. The mixture was then thoroughly mixed to obtain a methanol-displaced slurry. The residual moisture content of the methanol-displaced slurry was determined using a Karl Fischer moisture meter and was found to be 0.08% by mass.

[0264] Add 1% by mass of glycerol relative to 100% by mass of zirconium oxide and 2% by mass of acrylic binder "KFE-124" relative to 100% by mass of zirconium oxide to the obtained slurry, and then perform ultrasonic dispersion at 40 kHz for 1 hour to obtain a slurry containing additives.

[0265] The resulting slurry containing additives was subjected to supercritical drying using a supercritical drying apparatus, following these steps: The slurry containing additives was placed into a pressure vessel, which was then connected to a supercritical carbon dioxide extraction device, ensuring no pressure leaks. The pressure vessel and preheating tube were then immersed in a water bath heated to 60°C, the temperature was raised to 80°C, and the pressure was increased to 25 MPa. The mixture was allowed to stand for 10 minutes for stabilization. Next, under specified conditions (temperature: 80°C, pressure: 25 MPa, carbon dioxide flow rate: 10 mL / min, azeotropic agent (methanol) flow rate: 1.5 mL / min), carbon dioxide and methanol (as an azeotropic agent) were introduced. After 2 hours, the methanol introduction was stopped, and only carbon dioxide was continuously introduced. After 2 hours of carbon dioxide introduction alone, the carbon dioxide supply was stopped, and the pressure was slowly reduced from 25 MPa to atmospheric pressure over approximately 20 minutes while maintaining the temperature at 80°C. The pressure vessel was removed from the water bath and cooled to room temperature. The treated sample was then opened and recovered to obtain a powder containing zirconium oxide particles.

[0266] The obtained powder was shaped into plates (20mm × 20mm × 5mm), discs (20mm diameter × 2.5mm thickness), and blocks (20mm × 20mm × 15mm) using uniaxial pressure. These blocks were then subjected to cold isostatic pressing (CIP) (170MPa) to increase density and obtain zirconia shaped bodies. These zirconia shaped bodies were pre-fired at 500°C for 2 hours under normal pressure to obtain zirconia pre-fired bodies. Subsequently, the zirconia pre-fired bodies (excluding the blocks) were sintered at 1100°C for 2 hours under normal pressure to obtain zirconia sintered bodies. The resulting zirconia sintered bodies were white. The measurement results are shown in Table 3.

[0267] In addition, using a grinding device (“KATANA (registered trademark) H-18”, manufactured by Kuraray Noritake Dental Co., Ltd.), zirconia pre-fired bodies in the shape of a single crown for the maxillary central incisor and a single crown for the mandibular first molar were cut out, and they were sintered at 1100°C for 2 hours under normal pressure to obtain dental restorations in the shape of crowns.

[0268] [Comparative Example 1]

[0269] Glycerol at 1% by mass relative to 100% by mass of zirconium oxide was added to the methanol displacement slurry prepared in Example 1, and ultrasonic dispersion was performed at 40 kHz for 1 hour to obtain a slurry containing additives.

[0270] Using the above-described slurry as an additive-containing slurry, and except for the method described in Example 1, powder containing zirconia particles, plate-shaped and disc-shaped zirconia molded bodies, zirconia pre-sintered bodies, and zirconia sintered bodies were obtained. The resulting zirconia sintered bodies were white. The results of each measurement are shown in Table 3. It should be noted that the blocky zirconia molded bodies were destroyed during the pressure release stage after uniaxial pressurization, resulting in insufficient mechanical strength. Therefore, it was impossible to manufacture blocky zirconia pre-sintered bodies and blocky zirconia sintered bodies.

[0271] [Comparative Example 2]

[0272] The glycerol used in Comparative Example 1 was set to 2% by mass relative to 100% by mass of zirconium oxide. Otherwise, using the same method as in Comparative Example 1, powder containing zirconium oxide particles, plate-shaped and disc-shaped zirconia molded bodies, pre-sintered zirconium oxide bodies, and sintered zirconium oxide bodies were obtained. The resulting sintered zirconium oxide bodies were white. The results of each measurement are shown in Table 3. It should be noted that the block-shaped zirconium oxide molded bodies were destroyed during the pressure release phase after uniaxial pressurization, indicating insufficient mechanical strength.

[0273] [Comparative Example 3]

[0274] An acrylic binder, KFE-124, at 2% by mass relative to 100% by mass of zirconium oxide, was added to the methanol displacement slurry prepared in Example 1, and ultrasonically dispersed at 40 kHz for 1 hour to obtain a slurry containing the additive.

[0275] Using the above-described slurry as an additive-containing slurry, and otherwise using the same method as in Example 1, zirconia powder, plate-shaped, disc-shaped, block-shaped zirconia molded bodies, zirconia pre-sintered bodies, and zirconia sintered bodies containing zirconia particles were obtained. The resulting zirconia sintered bodies were white. The results of each measurement are shown in Table 3.

[0276] [Comparative Example 4]

[0277] The polyol was changed to dipentaerythritol. Otherwise, using the same method as in Example 1, zirconia powder, plate-shaped, disc-shaped, block-shaped zirconia molded bodies, zirconia pre-sintered bodies, and zirconia sintered bodies containing zirconia particles were obtained. The resulting zirconia sintered bodies were white. The results of each measurement are shown in Table 3.

[0278] [Table 3]

[0279]

[0280] (*1) Content relative to 100% by mass of zirconium oxide (content calculated as oxide of metal element)

[0281] (*2) The ratio of the number of moles of yttrium oxide to the total number of moles of zirconium oxide and yttrium oxide

[0282] [Example 2]

[0283] The experiment was conducted in the same manner 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 zirconium oxide slurry contained zirconium oxide particles with an average primary particle size of 18 nm, and zirconium oxide particles with a particle size of 100 nm or more accounted for 0.35% by mass.

[0284] Using the slurry obtained above, except for the method described in Example 1, an additive-containing slurry containing polyol and binder was prepared. Subsequently, using the same method as in Example 1, zirconia powder, plate-shaped, disc-shaped, block-shaped zirconia molded bodies, zirconia pre-sintered bodies, and zirconia sintered bodies containing zirconia particles were obtained. The resulting zirconia sintered bodies were white. The results of each measurement are shown in Table 4.

[0285] [Example 3]

[0286] The experiment was conducted in the same manner 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 zirconium oxide slurry contained zirconium oxide particles with an average primary particle size of 17 nm, and zirconium oxide particles with a particle size of 100 nm or more accounted for 0.15% by mass.

[0287] Using the slurry obtained above, except for the method described in Example 1, an additive-containing slurry containing polyol and binder was prepared. Subsequently, using the same method as in Example 1, zirconia powder, plate-shaped, disc-shaped, block-shaped zirconia molded bodies, zirconia pre-sintered bodies, and zirconia sintered bodies containing zirconia particles were obtained. The resulting zirconia sintered bodies were white. The results of each measurement are shown in Table 4.

[0288] [Example 4]

[0289] Compared to the zirconia slurry prepared in Example 2 (0.35% by mass of zirconia particles with an average primary particle size of 18 nm and a particle size of 100 nm or more), a dilute nitric acid solution containing bismuth nitrate was added to make a slurry containing zirconia particles and a fluorescent agent, with the content of bismuth oxide (Bi2O3) converted to 100% by mass of zirconia being 0.02% by mass.

[0290] Using the slurry obtained above, except for the method described in Example 1, an additive-containing slurry containing polyol and binder was prepared. Subsequently, using the same method as in Example 1, zirconia powder, plate-shaped, disc-shaped, block-shaped zirconia molded bodies, zirconia pre-sintered bodies, and zirconia sintered bodies containing zirconia particles were obtained. The resulting zirconia sintered bodies were white and fluorescent. The results of each measurement are shown in Table 4.

[0291] [Example 5]

[0292] Compared to the zirconia slurry prepared in Example 2 (0.35% by mass of zirconia particles with an average primary particle size of 18 nm and a particle size of 100 nm or more), an aqueous solution of nickel(II) nitrate was added in such a way that the content of nickel(II) oxide (NiO) relative to 100% by mass of zirconia was 0.02% by mass, thus preparing a slurry containing zirconia particles and a colorant.

[0293] Using the slurry obtained above, except for the method described in Example 1, an additive-containing slurry containing polyol and binder was prepared. Subsequently, also using the method described in Example 1, zirconia powder, plate-shaped, disc-shaped, block-shaped zirconia molded bodies, zirconia pre-sintered bodies, and zirconia sintered bodies containing zirconia particles were obtained. The resulting zirconia sintered bodies were colored red. The results of each measurement are shown in Table 4.

[0294] [Table 4]

[0295]

[0296]

[0297] (*1) Content relative to 100% by mass of zirconium oxide (content calculated as oxide of metal element)

[0298] (*2) The ratio of the number of moles of yttrium oxide to the total number of moles of zirconium oxide and yttrium oxide

[0299] [Example 6]

[0300] Polyethylene glycol "PEG-6000P" was used as the polyol, and "KFA-440" was used as the binder. Otherwise, using the same method as in Example 2, zirconia powder, plate-shaped, disc-shaped, and block-shaped zirconia molded bodies, zirconia pre-sintered bodies, and zirconia sintered bodies containing zirconia particles were obtained. The resulting zirconia sintered bodies were white. The results of each measurement are shown in Table 5.

[0301] [Example 7]

[0302] Propylene glycol was used as the polyol. Otherwise, using the same method as in Example 2, zirconia powder, plate-shaped, disc-shaped, block-shaped zirconia molded bodies, zirconia pre-sintered bodies, and zirconia sintered bodies containing zirconia particles were obtained. The resulting zirconia sintered bodies were white. The results of each measurement are shown in Table 5.

[0303] [Example 8]

[0304] Polyglycerol #310 was used as the polyol, and KFA-440 was used as the binder. Otherwise, using the same method as in Example 2, zirconia powder, plate-shaped, disc-shaped, block-shaped zirconia molded bodies, zirconia pre-sintered bodies, and zirconia sintered bodies containing zirconia particles were obtained. The resulting zirconia sintered bodies were white. The results of each measurement are shown in Table 5.

[0305] [Table 5]

[0306]

[0307]

[0308] (*1) Content relative to 100% by mass of zirconium oxide (content calculated as oxide of metal element)

[0309] (*2) The ratio of the number of moles of yttrium oxide to the total number of moles of zirconium oxide and yttrium oxide

[0310] [Example 9]

[0311] Acrylic binder "KFA-440" was used as the binder. Otherwise, using the same method as in Example 2, zirconia powder, plate-shaped, disc-shaped, block-shaped zirconia molded bodies, zirconia pre-sintered bodies, and zirconia sintered bodies containing zirconia particles were obtained. The resulting zirconia sintered bodies were white. The measurement results are shown in Table 6.

[0312] [Example 10]

[0313] Using the acrylic binder "OLYCOX KC-700" as the binder, and otherwise employing the same method as in Example 2, zirconia powder, plate-shaped, disc-shaped, block-shaped zirconia molded bodies, zirconia pre-sintered bodies, and zirconia sintered bodies containing zirconia particles were obtained. The resulting zirconia sintered bodies were white. The results of each measurement are shown in Table 6.

[0314] [Example 11]

[0315] Using the acrylic binder "OLYCOX KC-500" as the binder, and otherwise employing the same method as in Example 2, zirconia powder, plate-shaped, disc-shaped, block-shaped zirconia molded bodies, zirconia pre-sintered bodies, and zirconia sintered bodies containing zirconia particles were obtained. The resulting zirconia sintered bodies were white. The results of each measurement are shown in Table 6.

[0316] [Example 12]

[0317] The polyol content was set to 2% by mass. Otherwise, using the same method as in Example 1, zirconia powder, plate-shaped, disc-shaped, block-shaped zirconia molded bodies, zirconia pre-sintered bodies, and zirconia sintered bodies containing zirconia particles were obtained. The resulting zirconia sintered bodies were white. The results of each measurement are shown in Table 6.

[0318] [Table 6]

[0319]

[0320] (*1) Content relative to 100% by mass of zirconium oxide (content calculated as oxide of metal element)

[0321] (*2) The ratio of the number of moles of yttrium oxide to the total number of moles of zirconium oxide and yttrium oxide.

Claims

1. A zirconia molded body comprising zirconia particles, a polyol, and a binder. The zirconium oxide particles contain 2.0~9.0 mol% yttrium oxide relative to the total molar percentage of zirconium oxide and yttrium oxide, and have an average primary particle size of less than 60 nm. The polyol and the binder satisfy the following relationship: X1 <Y1<X2<Y2≤500℃ In the formula, X1 represents the combustion start temperature of the polyol, which is below 200℃; X2 represents the combustion end temperature of the polyol; Y1 represents the combustion start temperature of the binder; Y2 represents the combustion end temperature of the binder; X1 and Y1 represent the temperatures at which a 0.5% weight loss is observed, with the weight before heating measured by thermogravimetric analysis set to 100%; X2 and Y2 represent the temperatures at which a 99.5% weight loss is observed.

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

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

4. The zirconia molded body according to claim 1 or 2, wherein ΔL is 1.5 mm thick. * (WB) is 5 or higher, the ΔL * (WB) is the difference in brightness between a white background and a black background.

5. The zirconia molded article according to claim 1 or 2, wherein, The crystal grain size after sintering at atmospheric pressure and 900~1200℃ is less than 180nm.

6. The zirconia molded article according to claim 1 or 2, wherein, The three-point bending strength after sintering at normal pressure and 900~1200℃ is above 500MPa.

7. The zirconia molded article according to claim 1 or 2, wherein, The transmittance of light with a wavelength of 700nm when sintered at atmospheric pressure and 900~1200℃ is more than 40% when the thickness is 0.5mm.

8. The zirconia molded article according to claim 1 or 2, wherein, The linear light transmittance of a thickness of 1.0 mm after sintering at atmospheric pressure and 900~1200℃ is greater than 1%.

9. The zirconia molded article according to claim 1 or 2, wherein, The 28.5μm thickness after sintering at atmospheric pressure and 900~1200℃ 2 The number of holes with a diameter of 50 nm or more per unit cross-sectional area is less than 10.

10. The zirconia molded article according to claim 1 or 2, wherein, ΔL when the thickness is 1.5 mm after pre-firing at 200~800℃ * (WB) is 5 or higher, the ΔL * (WB) is the difference in brightness between a white background and a black background.

11. A zirconia pre-fired body, which is formed by pre-firing a zirconia shaped body according to any one of claims 1 to 10, comprising 2.0 to 9.0 mol% yttrium oxide relative to the total molar amount of zirconia and yttrium oxide, wherein the thickness of the zirconia pre-fired body is 1.5 mm. * With a WB value of 5 or higher, the 28.5μm thickness after sintering at 900~1200℃ 2 The number of holes with a diameter of 50 nm or more per unit cross-sectional area is less than 10, and the thickness is more than 10 mm. The ΔL * (WB) is the difference in brightness between a white background and a black background.

12. A method for manufacturing a zirconia pre-fired body, comprising: The process of pre-firing the zirconia molded body according to claim 1 or 2 at 200~800°C.

13. A zirconia sintered body, formed by sintering a zirconia shaped body according to any one of claims 1 to 10 or a zirconia pre-sintered body according to claim 11, comprising 2.0 to 9.0 mol% yttrium oxide relative to the total molar amount of zirconia and yttrium oxide, wherein the zirconia sintered body has a 28.5 μm diameter. 2 The number of holes with a diameter of 50nm or more per unit cross-sectional area is less than 10, and the thickness is more than 10mm.

14. A method for manufacturing the zirconia sintered body according to claim 13, comprising: The process of sintering the zirconia shaped body according to any one of claims 1 to 10 or the zirconia pre-sintered body according to claim 11 at atmospheric pressure and 900 to 1200°C.

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