JP2014141388A - Colored light-transmitting zirconia sintered compact and use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a colored light-transmitting zirconia sintered compact which has a high sintered compact density, high strength, color appearance extremely close to that of a tooth and excellent light transmissibility, and can be used as a dental material, particularly as a mill blank or an orthodontic bracket.SOLUTION: A colored light-transmitting zirconia sintered compact comprises: 2 to 4 mol% of yttria, 0.02 to 0.8 mol% of ErO; an iron compound in an amount of 20 ppm or more and less than 2000 ppm in terms of FeO; 0.005 wt% or more; less than 0.2 wt% of AlO; and a remainder comprising zirconia, and has a brightness value L, a value a, and a value b, which are chromatic parameters as defined in accordance with JIS-Z8729, and are 55 to 75, 0 to 10 and 0 to 30, respectively, a relative density of 99.80% or more, and a total light transmittance of 18 to 40% inclusive as measured at a sample thickness of 1 mm using a D65 light source. A colored light-transmitting zirconia sintered compact comprises: 2 to 4 mol% of yttria; less than 0.01 wt.% of cobalt oxide in terms of CoO; an iron compound in an amount of 20 ppm or more and less than 2000 ppm in terms of FeO, 0.005 wt% or more; less than 0.2 wt% of AlO; and a remainder comprising zirconia, and has a brightness value L, a value a, and a value b, which are chromatic parameters as defined in accordance with JIS-Z8729, and are 50 to 75, -1 to 10 and 0 to 30, respectively, a relative density of 99.80% or more, and a total light transmittance of 18 to 40% inclusive as measured at a sample thickness of 1 mm using a D65 light source.

Description

  The present invention relates to a colored zirconia sintered body having a high density and strength of a sintered body, a color tone very close to that of a tooth, and excellent in translucency. This colored translucent zirconia sintered body is particularly used in dental applications, and is further suitable for use as a mill blank such as a denture material or an orthodontic bracket.

Zirconia sintered body in which a small amount of Y ₂ O ₃ (yttria) is used as a stabilizer is a high strength and high toughness. Therefore, mechanical structural materials such as cutting tools, dies, nozzles and bearings, dental materials, etc. It is widely used as a biomaterial. In recent years, high-strength zirconia sintered bodies have come to be used for dental materials, but in order to bring the color tone closer to that of natural teeth, so far, other materials have been laminated on the surface of the zirconia sintered body, It was used after adjusting aesthetics. However, as zirconia sintered bodies are used in the dental field, there is an increasing demand for zirconia sintered bodies that can be used as they are for dental materials without laminating other materials.

In order to use a zirconia sintered body as it is for a dental material, both translucency and coloring (color appearance) are required. So far, zirconia sintered bodies having an ivory color close to natural teeth have been disclosed (see, for example, Patent Document 1). In this patent document, it is essential to add Pr ₆ O ₁₁ and ZnO to the sintered body, and there is no description of translucency.

Further, a zirconia sintered body having a translucent sintered body density of 99.8% in a composition of ₃ mol% Y ₂ O ₃ and 0.25 wt% Al ₂ O ₃ (alumina) is disclosed (for example, a patent References 2 and 3). However, the sintered body disclosed therein does not contain a colorant, and there has been no zirconia sintered body that has been colored and has high translucency.

  Patent Document 4 discloses a translucent zirconia sintered body colored yellow by adding Fe. Although a color tone similar to natural teeth can be obtained by giving a yellow color tone, redness and blackness are insufficient, and it was possible to use it by stacking other materials on the surface to approximate the color tone of natural teeth As it was, the color difference from the natural teeth could not be used greatly.

JP-A-4-280864 JP 2008-50247 A WO2009 / 125793 WO2013 / 018728

  The present invention eliminates the problems in the conventional methods as described above, and provides a colored zirconia sintered body having a high sintered body density and strength and excellent translucency, particularly such a zirconia sintered body. Can be produced by atmospheric pressure sintering.

  The present inventors have found that when the kind and content of the colorant of the zirconia sintered body are adjusted, a zirconia sintered body having both coloring and translucency equivalent to the color sample of natural teeth can be obtained. The invention has been completed. Examples of natural tooth color tone samples include VITA's shade guide “VITAPAN (registered trademark)” and Matsukaze's “vintage halo NCC shade guide”.

That is, the present invention is, 2～4Mol% yttria, 0.02～0.8Mol% of _{Er 2 O 3, Fe 2 O} 3 iron compounds less than 20~2000ppm in translation and less than 0.005～0.2Wt% by weight of _Al 2 _{O 3,} the balance being a zirconia sintered body is a zirconia, JIS-Z8729 lightness ^L which is a color parameter defined ^* within 55 to 75, ^{a *} is 0, ^{b *} 0 A colored translucent zirconia sintered body characterized by having a relative density of 99.80% or more and a total light transmittance of 18% to 40% with a D65 light source at a sample thickness of 1 mm. and 2～4Mol% yttria, cobalt oxide of less than 0.01 wt% in terms of CoO, iron oxide less than 20~2000ppm in terms _{of Fe} 2 _{O 3,} less than 0.005~0.2wt% Al It is a zirconia sintered body containing ₂ O ₃ and the balance being zirconia, the lightness L ^{* of} color parameters specified in JIS-Z8729 is 50 to 75, a ^* is −1 to 10, and b ^* is 0 to 0. The colored translucent zirconia sintered body is characterized in that it has a relative density of 99.80% or more and a total light transmittance by a D65 light source at a sample thickness of 1 mm is 18% or more and 40% or less. .

  Hereinafter, the colored translucent zirconia sintered body of the present invention will be described in more detail.

The colored translucent zirconia sintered body of the present invention comprises 2 to 4 mol% yttria, 0.02 to 0.8 mol% Er ₂ O ₃ , an iron compound of less than 20 to 2000 ppm in terms of Fe ₂ O ₃ , and 0. A zirconia sintered body containing 005 to less than 0.2 wt% of Al ₂ O ₃ and the balance being zirconia, the lightness L ^{* of the} color parameter defined in JIS-Z8729 is 55 to 75, and a ^* is 0 -10, b ^* is 0-30, the relative density is 99.80% or more, and the total light transmittance with a D65 light source at a sample thickness of 1 mm is 18% or more and 40% or less. It is a ligated body (zirconia sintered body A).

  The colored translucent zirconia sintered body A of the present invention contains 2 to 4 mol% yttria as a stabilizer. If the stabilizer is less than 2 mol%, the strength is lowered and the crystal phase becomes unstable. On the other hand, if it exceeds 4 mol%, the strength of the sintered body will be reduced.

  The yttria contained in the zirconia sintered body A is not particularly limited as long as it becomes yttria after sintering, and there is no particular limitation on the yttrium compound used before sintering. For example, soluble compounds such as yttrium chloride and yttrium nitrate Insoluble compounds such as yttrium oxide can be mentioned. The yttrium compound is preferably added to the zirconia sol and dissolved.

Although the colored translucent zirconia sintered body A of the present invention contains a colorant, Er ₂ O ₃ and an iron compound that color zirconia are essential as elements constituting the colorant. The Er ₂ O ₃ content is preferably 0.02 to 0.8 mol%, more preferably 0.05 to 0.7 mol%. The content of the iron compound calculated _{as Fe} 2 _{O 3} less than 20ppm than 2000 ppm, still in terms _{of Fe} 2 _{O 3} at 100ppm or more, preferably less than 1500 ppm.

The Er ₂ O ₃ contained in the zirconia sintered body A only needs to be Er ₂ O ₃ after sintering, and the erbium compound used before sintering is not particularly limited. For example, erbium chloride, erbium nitrate And insoluble compounds such as erbium oxide. The erbium compound is preferably added to the zirconia sol and dissolved. The reason is that if an erbium compound is added during pulverization of the zirconia powder, the particles locally grow abnormally, resulting in a sintered body having a low sintered density or a low strength.

  If the erbium compound is uniformly dissolved, it may be contained as a stabilizer together with the yttrium compound. A zirconia powder stabilized only with an erbium compound may be mixed with a zirconia powder stabilized with another yttrium compound. In the case of a zirconia powder stabilized only with an erbium compound, a zirconia powder containing 2 to 4 mol% of an erbium compound is preferable, and the content of the erbium compound is 0.8 mol% by mixing with a zirconia powder stabilized with another yttrium compound. It is sufficient to make it less than.

  The iron compound to be used is not particularly limited, and examples thereof include soluble compounds such as iron chloride and iron nitrate, and insoluble compounds such as iron oxide and iron oxide hydroxide. When using an insoluble compound, an iron compound having an average particle size of 1 μm or less is preferably added and dispersed and mixed when the zirconia powder is pulverized. The reason for this is that if the insoluble iron compound is added at other times and only stirred and mixed, spots will occur in the sintered body due to the presence of agglomerates, resulting in uneven color tone, or a low-strength sintered body. Because it becomes.

The colored translucent zirconia sintered body A of the present invention further contains Al ₂ O ₃ (alumina). By including alumina, the hydrothermal deterioration resistance of the zirconia sintered body is improved. The content of alumina is preferably 0.005 to less than 0.2 wt%, and more preferably 0.005 wt% or more and 0.15 wt% or less.

  When the alumina content of the colored translucent zirconia sintered body A of the present invention is 0.2 wt% or more, it is difficult to increase the density, and light diffusion occurs due to the presence of alumina particles in the sintered body. Therefore, it becomes difficult to obtain translucency, and if it is less than 0.005 wt%, the hydrothermal deterioration resistance property may be deteriorated and the color tone of the sintered body may be decolored.

The colored translucent zirconia sintered body A of the present invention has lightness L ^* of 55 to 75, a ^* of 0 to 10, and b ^* of 0 to 30 as defined in JIS-Z8729. If the lightness L ^* , a ^* value, and b ^* value are out of the range, it is difficult to obtain a color tone closer to the teeth. In terms of aesthetics, preferable L ^* values are 50 to 75, a ^* values are 0 to 7, and b ^* values are 10 to 27.

  The relative density of the colored translucent zirconia sintered body A of the present invention is 99.80% or more, preferably 99.89% or more, and more preferably 99.95% or more. If the relative density is less than 99.80%, the translucency tends to be low, and the sintered body is inferior in aesthetics as a dental material.

The colored translucent zirconia sintered body A of the present invention has a translucency of 18% to 40% in total light transmittance at a thickness of 1.0 mm. In a colored zirconia sintered body having a dark color tone and a low value of lightness L ^* , the value of the total light transmittance is lowered, and the translucent feeling of the colored zirconia sintered body having a high sintered body density obtained in the present invention is The lightness L ^* is high, and it has the same translucency even when compared with a sintered body having a high sintered body density, and has an aesthetics equivalent to that of natural teeth.

  The colored translucent zirconia sintered body A of the present invention preferably further has a crystal grain size of 0.35 to 0.50 μm. If the crystal grain size is less than 0.35 μm, there are many fine pores between grains, and the relative density may not reach 99.8%. On the other hand, when the crystal grain size exceeds 0.50 μm, the hydrothermal deterioration of the sintered body proceeds remarkably and the sintered body is destroyed, which may not be preferable.

  In the colored translucent zirconia sintered body A of the present invention, there are no abnormally grown crystal particles (abnormally grown particles), and the sintered body is constituted by crystal particles having a uniform particle diameter. Abnormally grown particles are particles having a size of 5 times or more of the average particle diameter, and are easily generated mainly by segregation of the stabilizer, and are low because the crystal phase of the particles is cubic. It tends to cause strength.

  The colored translucent zirconia sintered body A of the present invention preferably includes a tetragonal crystal phase, and preferably a tetragonal single phase. This tends to increase the mechanical strength. The colored translucent zirconia sintered body A of the present invention preferably has a three-point bending strength of 1000 MPa to 1200 MPa. Further preferred strength is 1100 MPa or more.

  The colored translucent zirconia sintered body A of the present invention preferably has a monoclinic phase transition depth of 15 μm or less after being immersed in hot water at 140 ° C. for 24 hours. When the monoclinic phase transition depth exceeds 15 μm, hydrothermal deterioration of the sintered body proceeds and the sintered body is destroyed. A more preferable monoclinic phase transition depth is 10 μm or less. Here, the transition depth of the monoclinic phase can be observed by cutting the sintered body and observing the cross section with a scanning electron microscope (SEM).

  The colored zirconia sintered body A of the present invention may contain a compound that dissolves in zirconia in order to finely adjust the color tone. Examples of the compound that dissolves in zirconia include, for example, Group 3a (Group 3), Group 5a (Group 5), Group 6a (Group 6), Group 7a (Group 6), Group 7a (Group 7), Group 8 One or more oxides of (Group 8 to Group 10) and Group 3b (Group 13) can be raised (in parentheses are display methods by the International Union of Pure Applied Sciences (IUPAC)).

Also, colored translucent zirconia sintered body of the present invention, 2～4Mol% yttria, cobalt oxide of less than 0.01 wt% in terms of CoO, iron oxide less than 20~2000ppm in terms _{of Fe} 2 _{O 3,} 0. A zirconia sintered body containing 005 to less than 0.2 wt% of Al ₂ O ₃ and the balance being zirconia, the lightness L ^{* of the} color parameter defined in JIS-Z8729 is 50 to 75, and a ^* is − 1 to 10, colored translucent zirconia having a b ^* of 0 to 30, a relative density of 99.80% or more, and a total light transmittance of 18% to 40% by a D65 light source at a sample thickness of 1 mm. It is a sintered body (zirconia sintered body B).

Here, the same yttrium, Fe ₂ O ₃ , and Al ₂ O ₃ as those of the zirconia sintered body A can be used.

  The zirconia sintered body B contains cobalt oxide of less than 0.01 wt% in terms of CoO.

  The cobalt oxide contained in the zirconia sintered body B is not particularly limited as long as it becomes cobalt oxide after sintering, and is not particularly limited as a cobalt compound used before sintering, for example, soluble such as cobalt chloride and cobalt nitrate. Examples thereof include insoluble compounds such as compounds and cobalt oxide. When using an insoluble compound, it is preferable to add and disperse a cobalt compound having an average particle size of 1 μm or less when the zirconia powder is pulverized. The reason is the same as that of the iron compound.

In the colored translucent zirconia sintered body B of the present invention, the lightness L ^{* of the} color parameters specified in JIS-Z8729 is 50 to 75, a ^* is -1 to 10, and b ^* is 0 to 30. If the lightness L ^* , a ^* value, and b ^* value are out of the range, it is difficult to obtain a color tone closer to the teeth. In terms of aesthetics, the preferred L ^* value is 50 to 75, the a ^* value is −1 to 7, and the b ^* value is 10 to 27.

Further, the relationship between the a ^* value and the b ^* value is preferably the following relationship.
a ^* > 0.0123b ^* 2-0.0598b ^* -2.9088
The relative density of the colored translucent zirconia sintered body B of the present invention is 99.80% or more, preferably 99.89% or more, and more preferably 99.95% or more. If the relative density is less than 99.80%, the translucency tends to be low, and the sintered body is inferior in aesthetics as a dental material.

The colored translucent zirconia sintered body B of the present invention has a translucency with a total light transmittance of 18% or more and 40% or less at a thickness of 1.0 mm. In a colored zirconia sintered body having a dark color tone and a low value of lightness L ^* , the value of the total light transmittance is lowered, and the translucent feeling of the colored zirconia sintered body having a high sintered body density obtained in the present invention is The lightness L ^* is high, and it has the same translucency even when compared with a sintered body having a high sintered body density, and has an aesthetics equivalent to that of natural teeth.

  The colored translucent zirconia sintered body B of the present invention preferably further has a crystal grain size of 0.35 to 0.50 μm. If the crystal grain size is less than 0.35 μm, there are many fine pores between grains, and the relative density may not reach 99.8%. On the other hand, when the crystal grain size exceeds 0.50 μm, the hydrothermal deterioration of the sintered body proceeds remarkably and the sintered body is destroyed, which may not be preferable.

  In the colored translucent zirconia sintered body B of the present invention, there are no abnormally grown crystal particles (abnormally grown particles), and the sintered body is composed of crystal particles having a uniform particle diameter. Abnormally grown particles are particles having a size of 5 times or more of the average particle diameter, and are easily generated mainly by segregation of the stabilizer, and are low because the crystal phase of the particles is cubic. It tends to cause strength.

  The colored translucent zirconia sintered body B of the present invention preferably has a tetragonal crystal phase, and preferably a tetragonal single phase. This tends to increase the mechanical strength. The colored translucent zirconia sintered body B of the present invention preferably has a three-point bending strength of 1000 MPa or more. Further preferred strength is 1100 MPa or more.

  The colored translucent zirconia sintered body B of the present invention preferably has a monoclinic phase transition depth of 15 μm or less after being immersed in hot water at 140 ° C. for 24 hours. When the monoclinic phase transition depth exceeds 15 μm, hydrothermal deterioration of the sintered body proceeds and the sintered body is destroyed. A more preferable monoclinic phase transition depth is 10 μm or less. Here, the transition depth of the monoclinic phase can be observed by cutting the sintered body and observing the cross section with a scanning electron microscope (SEM).

The colored translucent zirconia sintered body B of the present invention may contain 0.02 to 0.8 mol% of Er ₂ O ₃ . As the Er ₂ O ₃ , the same zirconia sintered body A can be used.

  The colored zirconia sintered body B of the present invention may contain a compound that dissolves in zirconia in order to finely adjust the color tone. Examples of the compound that dissolves in zirconia include, for example, Group 3a (Group 3), Group 5a (Group 5), Group 6a (Group 6), Group 7a (Group 6), Group 7a (Group 7), Group 8 One or more oxides of (Group 8 to Group 10) and Group 3b (Group 13) can be raised (in parentheses are display methods by the International Union of Pure Applied Sciences (IUPAC)).

  Next, a method for producing the colored translucent zirconia sintered bodies A and B of the present invention will be described.

The zirconia powder used for the production of the colored translucent zirconia sintered bodies A and B of the present invention preferably has a BET specific surface area in the range of 10 to 15 m ² / g. When the zirconia powder has a BET specific surface area of less than 10 m ² / g, it may be difficult to sinter at low temperatures, and when it exceeds 15 m ² / g, the agglomeration force between particles may be significant. There is. In particular, the BET specific surface area is preferably in the range of 11 to 14 m ² / g.

  The zirconia powder preferably has an average particle size in the range of 0.4 to 0.7 μm. If the average particle size of the zirconia powder is smaller than 0.4 μm, the fine particles that increase the cohesiveness of the powder may increase and may be difficult to mold, while if larger than 0.7 μm, hard aggregated particles are included. Since the number of coarse grains increases, it may be difficult to mold, and the coarse grains may impair sintering densification, which may result in poor sinterability. A preferred average particle size is 0.4 to 0.6 μm. Moreover, it is preferable that the maximum particle diameter of a zirconia powder is 2.0 micrometers or less, More preferably, it is 1.5 micrometers or less.

The zirconia powder has a sintering shrinkage rate (Δρ / ΔT: g / cm ³ · ° C.) of 70% to 90% relative density in atmospheric pressure sintering at a heating rate of 300 ° C./hour in the atmosphere (hereinafter, It is preferable that the “sintering shrinkage rate” is 0.012 or more and 0.016 or less. Sintering shrinkage speed is an index of sinterability of zirconia powder. When the sintering shrinkage rate is within this range, the zirconia powder is excellent in sinterability. The sintering shrinkage rate is a measured value when the relative density is 70% or more. Therefore, the sintering shrinkage rate is not affected by the variation in the density of the molded body. Further, the sintering shrinkage rate at a relative density of 70% to 90% is constant. Thus, since the sintering shrinkage rate is a linear function of temperature and relative density, an accurate sintering shrinkage rate can be obtained without using a special approximate calculation process.

  The zirconia powder may be obtained by, for example, drying, calcining, and pulverizing a hydrated zirconia sol obtained by hydrolysis of a zirconium salt aqueous solution. The zirconia powder may be obtained by adding an alkali metal hydroxide and / or alkaline earth to the zirconium salt aqueous solution. After adding the metal hydroxide, hydrated zirconia sol obtained by hydrolysis until the reaction rate reaches 98% or more is added with yttrium as a raw material for the stabilizer, and if necessary, erbium is added and dried. Also good.

  Zirconium salts used for the production of the hydrated zirconia sol include zirconium oxychloride, zirconyl nitrate, zirconium chloride, zirconium sulfate and the like, and in addition, a mixture of zirconium hydroxide and acid may be used. Examples of the alkali metal hydroxide and / or alkaline earth metal hydroxide added to the zirconium salt aqueous solution include hydroxides such as lithium, sodium, potassium, magnesium, and calcium. The hydroxide is preferably added as an aqueous solution.

  A zirconia powder can be obtained by calcining the dried powder of the hydrated zirconia sol obtained above at a temperature of 1000 to 1200 ° C. When the calcination temperature is outside this range, the zirconia fine powder obtained under the following pulverization conditions of the present invention becomes remarkably strong or coarse particles containing hard agglomerated particles increase, and the average particle size becomes 0. It is outside the range of 4 to 0.7 μm, and it may be difficult to obtain zirconia powder. The calcining temperature is particularly preferably from 1050 to 1150 ° C.

Subsequently, it is preferable to wet-grind the calcined powder obtained above using zirconia balls in an average particle size range of 0.4 to 0.7 μm. By pulverizing the calcined powder calcined at the calcining temperature so that the average particle size becomes 0.4 to 0.7 μm, a zirconia powder having a BET specific surface area of 10 to 15 m ² / g is obtained. It is done. In addition, the crystallite diameter at this time is 25 to 40 nm, and after calcination, the zirconia powder having a tetragonal phase of approximately 100% becomes a zirconia powder having a monoclinic phase of 30 to 50%.

  When aluminum is used for the production of the colored translucent zirconia sintered body of the present invention, examples of the raw material compound include alumina, hydrated alumina, alumina sol, aluminum hydroxide, aluminum chloride, aluminum nitrate, aluminum sulfate and the like. Can do. It is preferable to use an insoluble compound as well as the colored element compound.

  In order to obtain a sintered body having a desired color tone, a zirconia powder stabilized with yttria and erbia may be prepared by adjusting a colored zirconia powder to which a necessary amount of iron compound and cobalt compound is added as a colorant. It is also possible to prepare several kinds of zirconia powders containing the respective colorants in advance and mix several kinds of colored zirconia powders so as to obtain a desired composition to change the colorant composition.

For example, zirconia powder stabilized with 3 mol% yttria is produced (powder 1). Separately, zirconia powder stabilized with 3.2 mol% of elvia is produced (powder 2). Further, a powder obtained by adding 1500 ppm of an iron compound in terms of Fe ₂ O ₃ to a zirconia powder stabilized with 3 mol% of yttria and a powder in which 0.05 wt% of a cobalt compound in terms of CoO are added (powder 3, 4). The powders 1 to 4 contain 0.005 to less than 0.2 wt% alumina. By mixing these four kinds of powders until they are uniform and blending the contents of Er ₂ O ₃ , Fe ₂ O ₃ , and CoO as colorants to the desired concentration, a sintered body is obtained, A colored sintered body having the same color tone as that obtained by sintering a colored zirconia powder obtained by adding a necessary amount of an iron compound or a cobalt compound as a colorant to a zirconia powder stabilized with Elvia is obtained.

  The shade guide “VITAPAN (registered trademark)” of VITA, which is a color tone sample of natural teeth, has 16 color tone samples, but all color tones can be reproduced by adjusting the mixing ratio of the above four types of powders. .

  At this time, by finely adjusting the four types of powder physical properties (for example, BET specific surface area) and matching the sintering shrinkage rate, which is an index of sinterability, as much as possible, without reducing the density of the obtained sintered body, A high-density sintered body is obtained, and the translucency is not impaired.

  As the zirconia powder, spray granulated powder granules are preferably used, and spray granulated powder containing an organic binder may be used.

When the zirconia powder is made into a slurry and spray-dried, the fluidity when forming the molded body is high, and bubbles are hardly generated in the sintered body. It is preferable that the granule has a particle size of 30 to 80 μm and a light bulk density of 1.10 to 1.40 g / cm ³ .

  When a binder is used in the granule, examples of the binder include commonly used binders such as polyvinyl alcohol, polyvinyl butyrate, wax, acrylic, etc. Among them, carboxyl groups or derivatives thereof (for example, salts, particularly Acrylic materials having an ammonium salt or the like are preferred. Examples of the acrylic binder include polyacrylic acid, polymethacrylic acid, acrylic acid copolymer, methacrylic acid copolymer, and derivatives thereof. The amount of the binder added is preferably 0.5 to 10% by weight, particularly preferably 1 to 5% by weight, based on the ceramic powder in the ceramic powder slurry.

  In order to obtain the colored translucent zirconia sintered bodies A and B of the present invention, the zirconia powder is molded to a relative density of about 50 ± 5% by ordinary press molding (hydrostatic press (CIP treatment if necessary)). It is preferable to sinter as a body.

  The colored translucent zirconia sintered bodies A and B of the present invention are preferably produced by sintering at 1350 to 1450 ° C., particularly 1400 ° C. under normal pressure.

  When the sintering temperature is less than 1350 ° C., the relative density may not reach 99.80%. When the sintering temperature exceeds 1450 ° C., the hydrothermal deterioration of the sintered body proceeds remarkably, and the sintered body tends to break. May arise.

  The colored translucent zirconia sintered bodies A and B of the present invention are obtained by atmospheric pressure sintering, but the sintering atmosphere is not particularly limited unless it is a reducing atmosphere, and may be an oxygen atmosphere or sintering in the air. It is particularly preferable to sinter in the atmosphere.

  The colored translucent zirconia sintered body of the present invention exhibits a color tone close to teeth, high density, high strength, and excellent translucency, so that the zirconia sintered body used in dental applications, specifically, Is excellent as a sintered body used as a mill blank for orthodontic materials, orthodontic brackets, etc. The powder for the colored translucent zirconia sintered body of the present invention is a pressure such as HIP even under normal pressure sintering. A colored translucent zirconia sintered body having the above-described characteristics can be produced even by sintering.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples at all.

  In the examples, the average particle diameter of the zirconia fine powder was measured using a Microtrac particle size distribution meter (manufactured by Honeywell, model: 9320-HRA). As pretreatment conditions for the sample, the powder was suspended in distilled water and dispersed using an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, model: US-150T) for 3 minutes.

  The raw material powder was molded by a mold press at a pressure of 19.6 MPa, and the preform was put in a rubber mold and subjected to cold isostatic pressing (CIP) at a pressure of 196 MPa to obtain a molded body. The obtained molded body was sintered at a predetermined temperature (holding time 2 hours).

As the color tone of the sintered body, the color parameters L ^* , a ^* , b ^* defined in JIS-Z8729 were measured. Since the sintered body has translucency, the thickness of the sintered body was standardized to 2.8 mm for the measurement of color tone, and the mirror-polished surface was measured.

  The density of the sintered body was measured by the Archimedes method.

  The total light transmittance of the sintered body was measured with a light source D65 in accordance with JIS K7361 using a turbidimeter (Nippon Denshoku Industries Co., Ltd., model: NDH2000). The sample used was a disc-shaped one having a thickness of 1 mm obtained by polishing the sintered body on both sides.

  The crystal grain size of the sintered body was measured by a planimetric method using a scanning electron microscope (JEM Co., Ltd., model: JSM-6390LV) by thermally etching the mirror-polished sintered body. Calculated. Specifically, when a circle is drawn on a microscope image, a circle is drawn such that the sum of the number of particles nc in the circle and the number of particles Ni applied to the circumference is at least 100 to 150, or 100 In the case of an image less than 1, a plurality of circles are drawn using images of several fields so that the total number of particles (nc + Ni) is at least 100 to 150, and an average crystal grain size is obtained by a planimetric method. It was.

  The strength of the sintered body was evaluated by a three-point bending measurement method in accordance with JIS R1601.

  Hydrothermal deterioration characteristics were evaluated by mirror-polishing one side of the obtained sintered body and immersing it in hot water at 140 ° C. for 24 hours, and determining the transition depth of the monoclinic phase produced.

  The transition depth refers to cutting the immersed sintered body and observing the cross section with a scanning electron microscope (SEM) (manufactured by JEOL Ltd., model: JSM-6390LV). This was determined by observing the coarse depth.

  The “average particle size” related to the zirconia powder in the present invention is a particle having a median value (median diameter; particle size corresponding to 50% of the cumulative curve) of the cumulative particle size distribution expressed by volume. Is the diameter of a sphere having the same volume as that measured by a particle size distribution measuring apparatus using a laser diffraction method.

“Stabilizer concentration” refers to a value expressed as mole% of the ratio of stabilizer / (ZrO ₂ + stabilizer).

“Additive content” refers to a value expressed as a weight% ratio of additive / (ZrO ₂ + stabilizer + additive). Here, the additive is a value converted to an oxide.

The “relative density” is a value expressed by converting the ratio ρ measured by the Archimedes method and the density ρ ₀ of the HIP sintered body into a ratio (%) of (ρ / ρ ₀ ) × 100. .

Examples 1-8
(Synthesis of 0.05 wt% alumina and 3.0 mol% yttria-containing zirconia granule powder)
Yttria was added to the zirconium oxychloride aqueous solution to adjust the Y ₂ O ₃ concentration to 3.0 mol%, and then the hydrated zirconia sol obtained by hydrolysis was dried and calcined at a calcining temperature of 1100 ° C. for 2 hours.

  The obtained calcined powder was washed with water, and α-alumina was added to a slurry having an alumina content of 0.05 wt% and distilled water to give a zirconia concentration of 45 wt%. This slurry was pulverized for 24 hours with a vibration mill using zirconia balls having a diameter of 3 mm.

The average particle diameter of the obtained slurry was 0.41 μm, and the maximum particle diameter was ≦ 1.5 μm. The dried zirconia powder had a BET specific surface area of 13 m ² / g, a crystallite diameter of 33 nm, and a dry powder M phase ratio of 40%. 3 wt% of an organic binder was added to the obtained slurry, and spray drying was performed to obtain zirconia granule powder having an average granule diameter of 50 μm.
(Synthesis of 0.05 wt% alumina, 3.0 mol% yttria, 1500 ppm iron oxide-containing zirconia granule powder)
Also, yttria was added to the zirconium oxychloride aqueous solution to adjust the Y ₂ O ₃ concentration to 3.0 mol%, and then the hydrated zirconia sol obtained by hydrolysis was dried and calcined at a calcining temperature of 1100 ° C. for 2 hours. .

After the obtained calcined powder was washed with water, α-alumina was added at 0.05 wt% in terms of alumina, iron oxide hydroxide was added at 1500 ppm in terms of Fe ₂ O ₃ , and distilled water was added to add a zirconia concentration of 45 wt%. Slurry. This slurry was pulverized for 24 hours with a vibration mill using zirconia balls having a diameter of 3 mm.

The average particle size of the obtained slurry was 0.42 μm, and the maximum particle size was ≦ 1.5 μm. The dried zirconia powder had a BET specific surface area of 13 m ² / g, a crystallite diameter of 33 nm, and a dry powder M phase ratio of 42%. 3 wt% of an organic binder was added to the obtained slurry, and spray drying was performed to obtain zirconia granule powder having an average granule diameter of 48 μm.
(Synthesis of 0.05 wt% alumina and 3.2 mol% erbia-containing zirconia granule powder)
Further, erbia was added to the zirconium oxychloride aqueous solution to adjust the Er ₂ O ₃ concentration to 3.2 mol%, and then the hydrated zirconia sol obtained by hydrolysis was dried and calcined at a calcining temperature of 1100 ° C. for 2 hours. .

  The obtained calcined powder was washed with water, and α-alumina was added to a slurry having an alumina content of 0.05 wt% and distilled water to give a zirconia concentration of 45 wt%. This slurry was pulverized for 24 hours with a vibration mill using zirconia balls having a diameter of 3 mm.

The average particle size of the obtained slurry was 0.42 μm, and the maximum particle size was ≦ 1.5 μm. The dried zirconia powder had a BET specific surface area of 12 m ² / g, a crystallite diameter of 34 nm, and a dry powder M phase ratio of 39%. 3 wt% of an organic binder was added to the obtained slurry, and spray drying was performed to obtain zirconia granule powder having an average granule diameter of 45 μm.

The above three kinds of powders are mixed in an arbitrary ratio in a plastic bottle to obtain a Y ₂ O ₃ concentration of 2.85 to 2.92 mol%, an Er ₂ O ₃ concentration of 0.08 to 0.17 mol%, and an oxidized hydroxide. A mixed powder of 200 to 1430 ppm of iron in terms of Fe ₂ O ₃ was obtained.

  The obtained mixed powder is molded by a uniaxial press (19.6 MPa) and then molded by CIP (196 MPa), and sintered under the conditions of a sintering temperature of 1400 ° C. or 1450 ° C., a heating rate of 600 ° C./hr, and a holding time of 2 hours. (Normal pressure sintering) to produce a colored translucent zirconia sintered body.

Examples 9-12
In Examples 9 to 12, a colored transmissive zirconia sintered body was manufactured by further subjecting the zirconia sintered body obtained by normal pressure sintering at 1450 ° C. to HIP treatment at a processing temperature of 1400 ° C. and a pressure of 150 MPa. .

  There was almost no change in the relative density and total light transmittance of the colored translucent zirconia sintered body before and after the HIP treatment. Thereby, it turned out that the colored translucent zirconia sintered compact of this invention is a sintered compact which has a characteristic equivalent to a HIP process, without performing a HIP process.

Comparative Examples 1-3
The above-mentioned two kinds of powders not containing Er ₂ O ₃ are mixed in an arbitrary ratio in a plastic bottle, and the Y ₂ O ₃ concentration is 3.0 mol%, and iron oxide hydroxide is 200 or 450 ppm in terms of Fe ₂ O _3. Of mixed powder was obtained.

  The obtained granular powder is molded with a uniaxial press (19.6 MPa) and then molded with CIP (196 MPa) and sintered under conditions of a sintering temperature of 1400 ° C. or 1450 ° C., a heating rate of 600 ° C./hr, and a holding time of 2 hours. (Normal pressure sintering) to produce a colored translucent zirconia sintered body.

It was found that in the colored translucent zirconia sintered body containing no Er ₂ O ₃ , the a ^* value decreases and the reddish color fades, so that the color tone of natural teeth cannot be obtained.

Examples 13-16
The above three kinds of powders are mixed in an arbitrary ratio in a plastic bottle so that the Y ₂ O ₃ concentration is 2.40 to 2.70 mol% and the Er ₂ O ₃ concentration is 0.33 to 0.66 mol%. A colored translucent zirconia sintered body was produced in the same manner as in Examples 1 to 8, except for the above.

Examples 17-20
In Examples 17 to 20, a colored translucent zirconia sintered body was manufactured by further subjecting the zirconia sintered body obtained by normal pressure sintering at 1450 ° C. to HIP treatment at a processing temperature of 1400 ° C. and a pressure of 150 MPa. .

In Examples 1 to 12 and Comparative Examples 1 to 3, the amount of yttria, the amount of Er ₂ O _{3, the} amount of Fe added as Fe ₂ O ₃ , the composition of the amount of alumina added, the sintering temperature, and the actually measured density of the obtained zirconia sintered body , Relative density, total light transmittance with D65 light source, lightness L ^* value, a ^* value, b ^* value, intensity, crystal grain size, color grain size specified in JIS-Z8729, 24 in 140 ° C. hot water The monoclinic transition depth after soaking for hours is shown in Table 1 below, and the same numerical values of Examples 13 to 20 are shown in Table 2 below.

Examples 21-41
(Synthesis of 0.05 wt% alumina, 360 ppm cobalt oxide, 3.0 mol% yttria-containing zirconia granule powder)
Yttria was added to the zirconium oxychloride aqueous solution to adjust the yttria concentration to 3.0 mol%, and then the hydrated zirconia sol obtained by hydrolysis was dried and calcined at a calcining temperature of 1100 ° C. for 2 hours.

  The obtained calcined powder was washed with water, and α-alumina was added to a slurry having an alumina content of 0.05 wt%, cobalt oxide in terms of CoO was 360 ppm, and distilled water was added to form a slurry having a zirconia concentration of 45 wt%. This slurry was pulverized for 24 hours with a vibration mill using zirconia balls having a diameter of 3 mm.

The average particle diameter of the obtained slurry was 0.41 μm, and the maximum particle diameter was ≦ 1.5 μm. The BET specific surface area of the dried zirconia powder was 13 m ² / g, the crystallite diameter was 32 nm, and the M phase ratio of the dried powder was 43%. 3 wt% of an organic binder was added to the obtained slurry, and spray drying was performed to obtain zirconia granule powder having an average granule diameter of 47 μm.

  The above powder and the three kinds of powders prepared in Examples 1 to 8 were mixed in a plastic bottle so as to have the composition shown in Table 3 to obtain a mixed powder.

  The obtained granular powder is molded by a uniaxial press (19.6 MPa) and then molded by CIP (196 MPa) and sintered under conditions of a sintering temperature of 1450 ° C., a heating rate of 600 ° C./hr and a holding time of 2 hours (normally Pressure sintering) A colored translucent zirconia sintered body was produced.

  The “relative density” after Example 21 was determined from the following equation (1) from the theoretical density ρ0 and the measured density ρ. The actual density was determined by the Archimedes method.

Relative density (%) = (ρ / ρ0) × 100 (1)
The theoretical density ρx, ρy, ρz of the sintered body in each composition used for mixing was obtained from the following formula from the density and concentration of the added oxide.
Theoretical density ρx = 100 / [(0.05 / ρAl) + (99.95 / ρZr)] of 0.05 wt% alumina / 3.0 mol% yttria-containing zirconia sintered body
= 6.0940 g / cm ³
Theoretical density ρy = 100 / [(0.05 / ρAl) + (0.15 / ρFe) + (99.80 / ρZr) of 0.05 wt% alumina, 3.0 mol% yttria, 1500 ppm iron oxide-containing zirconia sintered body ]]
= 6.0925 g / cm ³
Theoretical density ρz = 100 / [(0.05 / ρAl) + (0.036 / ρCo) + (99.914 // 0.05 wt% alumina, 360 ppm cobalt oxide, 3.0 mol% yttria-containing zirconia sintered body ρZr)]
= 6.0941 g / cm ³
still,
ρAl: theoretical density of alumina; 3.99 g / cm ³
ρFe: Theoretical density of Fe2O3; 5.24 g / cm ³
ρCo: CoO theoretical density; 6.40 g / cm ³
ρZr: Theoretical density of zirconia containing 3.0 mol% yttria; 6.0956 g / cm ³
It was.

The theoretical density of the 0.05 wt% alumina / 3.2 mol% erbia-containing zirconia sintered body was a HIP sintered body density of 6.336 g / cm ³ .
The theoretical density ρ0 was determined from the following equation (2) from the theoretical density of each sintered body and the blending ratio thereof.

ρ0 = 100 / [(x / ρx) + (y / ρy) + (z / ρz) + (100−x−yz) /6.336] (2)
x: Mixing ratio of 0.05 wt% alumina / 3.0 mol% yttria-containing zirconia; wt%
y: Mixing ratio of 0.05 wt% alumina, 1500 ppm iron oxide containing, 3.0 mol% yttria containing zirconia; wt%
z: Mixing ratio of 0.05 wt% alumina, 360 ppm cobalt oxide, 3.0 mol% yttria-containing zirconia; wt%
Compositions in Examples 21 to 32, sintering temperature, measured density of the obtained zirconia sintered body, relative density, total light transmittance with a D65 light source, lightness L ^* value of a color parameter defined in JIS-Z8729, Table 3 below shows the a ^* value, b ^* value, strength, crystal grain size, and monoclinic transition depth after immersion in hot water at 140 ° C. for 24 hours.

  As is clear from this table, the colored translucent zirconia sintered bodies of Examples 1 to 20 have a high relative density of 99.80% or higher and a total light transmittance of 18% or higher with a D65 light source. It is a very excellent colored translucent zirconia sintered body and is expected to be used as a dental material such as a mill blank and an orthodontic bracket.

  The colored translucent zirconia sintered body of the present application has high sintered body density and strength, has a color appearance very close to the color tone of the teeth, and is excellent in translucency, so that the zirconia sintered body used particularly in dental applications. Furthermore, it is suitable for use as a mill blank such as a denture material or an orthodontic bracket.

Claims (8)

2～4Mol% yttria, the 0.02～0.8Mol% of _{Er 2 O 3, Fe 2 O} 3 of iron compound and less than 0.005～0.2Wt% less than 20~2000ppm in terms _Al 2 _{O 3} A zirconia sintered body containing the remainder being zirconia, the lightness L ^{* of the} color parameters specified in JIS-Z8729 is 55 to 75, a ^* is 0 to 10, b ^* is 0 to 30, A colored translucent zirconia sintered body having a density of 99.80% or more and a total light transmittance of 18% to 40% by a D65 light source at a sample thickness of 1 mm. Wherein 2～4Mol% yttria, cobalt oxide of less than 0.01 wt% in terms of CoO, iron oxide less than 20~2000ppm in terms _{of Fe} 2 _{O 3,} the _Al 2 _{O 3} less than 0.005～0.2Wt%, The balance is a zirconia sintered body having zirconia as the balance, the lightness L ^{* of} color parameters specified in JIS-Z8729 is 50 to 75, a ^* is -1 to 10, b ^* is 0 to 30, and the relative density 99.80% or more, and the total light transmittance with a D65 light source at a sample thickness of 1 mm is 18% or more and 40% or less. The colored translucent zirconia sintered body according to claim _2, further comprising 0.02 to 0.8 mol% of Er ₂ O ₃ . The colored translucent zirconia sintered body according to claim 2 or 3, wherein the lightness L ^* , a ^* , b ^{* of} the color parameters defined in JIS-Z8729 is in the following range.
L ^* is 50 to 75
a ^* is -1 to 7
b ^* is 10 to 27
a ^* > 0.0123b ^* 2-0.0598b ^* -2.9088   The colored translucent zirconia sintered body according to claim 1, wherein the crystal grain size is 0.35 to 0.50 μm.   6. The colored translucent zirconia sintered body according to claim 1, wherein the monoclinic phase has a transition depth of 0 to 15 μm after being immersed in 140 ° C. hot water for 24 hours. body.   The colored translucent zirconia sintered body according to any one of claims 1 to 6, having a three-point bending strength of 1000 MPa or more.   A dental material comprising the colored translucent zirconia sintered body according to any one of claims 1 to 7.