JP6672766B2 - Zirconia sintered body and its use - Google Patents

Description

  The present invention relates to a zirconia sintered body in which zirconia having different colors is joined by sintering. More specifically, the present invention relates to a zirconia sintered body in which zirconia having different colors is joined by sintering, in which one zirconia forms a pattern on the other zirconia.

  The zirconia sintered body can be a high-grade member because it has a glossiness in addition to high toughness and high strength. Therefore, the zirconia sintered body is used as various members such as high-grade watch parts and decorative articles. The color tone of the zirconia sintered body is a single color though it is a member exhibiting a high quality feeling. In addition, zirconia with different colors usually has different sintering behavior. Therefore, when zirconia having different color tones is sintered at the same time, cracks, cracks, strains, and the like occur, and a zirconia sintered body having no defect could not be obtained. Therefore, it was not possible to obtain a zirconia sintered body having two or more different color tones and a member made of the same.

  In order to make a member having two or more different colors using a zirconia sintered body, a combination of a zirconia sintered body and a material other than the zirconia sintered body having a different color tone from the zirconia sintered body is combined. Such members have been studied (for example, Patent Documents 1 and 2). However, these members differ greatly in texture between materials. Therefore, the obtained member has a design property different from the design property of the member made only of ceramics, and particularly impairs the high-grade feeling peculiar to the zirconia sintered body.

  Further, a ceramic joined body in which two or more ceramics are joined via an intermediate layer such as an adhesive has been conventionally known. However, the ceramic joined body is likely to be broken starting from the intermediate layer. Therefore, in a zirconia sintered body characterized by high toughness and high strength, it is not preferable to form a joined body with an intermediate layer interposed.

  On the other hand, Patent Document 3 reports a zirconia sintered body obtained by sintering two zirconia molded bodies having different color tones. Patent Document 3 discloses a zirconia sintered body obtained by sintering a molded body of zirconia powder containing FeCrNi spinel and a molded body of zirconia powder containing CoAl.

JP 2011-191321 A Patent No. 4370361 JP-A-08-081255

  The sintered body disclosed in Patent Document 3 is made of a zirconia sintered body, and there is no difference in texture between members. However, the sintered body has a visible "color transition zone" between zirconia sintered bodies having different color tones. Such a color transition band is visually recognized as “color blur”. The border between the zirconia sintered bodies becomes unclear due to color bleeding. As a result, a portion where the zirconia sintered body is in contact with the zirconia sintered body, in particular, a pattern formed by one of the zirconia sintered bodies becomes unclear. Such an unclear pattern gives an impression that the quality of the zirconia sintered body is further impaired.

  Patent Literature 3 discloses a zirconia sintered body having no color transition zone. However, the zirconia sintered body has a gap at a boundary between the zirconia sintered bodies because sintering has not sufficiently progressed. That is, in the zirconia sintered body having no color transition zone in Patent Literature 3, the color did not migrate due to the gap. The gap is visually recognized as a color tone different from any of the zirconia sintered bodies, and deteriorates the aesthetics of the member. In addition, the gap existing at the boundary between the zirconia sintered bodies is a starting point of the destruction. Therefore, such a zirconia sintered body has remarkably low mechanical strength and is easily broken as a member.

  Furthermore, the sintered body disclosed in Patent Literature 3 needs to have a large pattern so that color bleeding and gaps do not affect the aesthetics of the member, and thus cannot be a sintered body having a fine pattern. .

The present invention solves these problems, and is a zirconia sintered body having two or more different color tones, which has an aesthetic appearance that gives a sense of quality and has sufficient strength to be used as a member. An object is to provide a sintered body. In particular, the present invention is a multicolor zirconia sintered body composed of a zirconia sintered body exhibiting any of pink, orange, lavender and other light colors, and a zirconia sintered body exhibiting a blue color. Another object of the present invention is to provide a zirconia sintered body that has a sufficient strength for use as a member.

  The present inventors are zirconia sintered bodies having two or more different color tones, particularly zirconia sintered bodies having two or more different tones, wherein one zirconia is formed as a pattern on the surface of the other zirconia. The zirconia sintered body was studied.

  As a result, they have found that a zirconia sintered body having two or more different colors can be obtained by simultaneously sintering a zirconia molded body containing a spinel oxide and a zirconia molded body containing other than a spinel oxide. . Furthermore, such a zirconia sintered body has found that the zirconia sintered body and the zirconia sintered body form a grain boundary as a joining surface thereof, and that the interface has no color blur and no gap, The present invention has been completed.

  That is, the present invention relates to a zirconia sintered body including a first zirconia sintered body and a second zirconia sintered body, wherein the first zirconia sintered body is made of Ce, Pr, Nd, Eu, Tb, Ho. , A zirconia sintered body containing at least one lanthanoid selected from the group consisting of Er, Yb and Gd, wherein the second zirconia sintered body contains a spinel oxide containing cobalt and aluminum. Zirconia sintered body characterized in that the first zirconia sintered body and the second zirconia sintered body form a grain boundary, and the grain boundary does not have a gap and color blur. ,.

  Hereinafter, the zirconia sintered body of the present invention will be described.

  The zirconia sintered body of the present invention is a zirconia sintered body including a first zirconia sintered body and a second zirconia sintered body (hereinafter, also referred to as “multicolored zirconia sintered body”). The first zirconia sintered body (hereinafter, also referred to as "light-colored sintered body") and the second zirconia sintered body (hereinafter, also referred to as "dark-colored sintered body") have different zirconia colors. It is a sintered body. The multicolored zirconia sintered body of the present invention includes a dark-colored sintered body containing spinel oxide as a coloring material, and a light-colored sintered body containing other than spinel oxide as a coloring agent, preferably substantially. By being composed of the dark-colored sintered body and the light-colored sintered body, it is possible to obtain a member made of only the zirconia sintered body for the first time and having a high-quality aesthetic.

  In the multicolor zirconia sintered body of the present invention, the light-colored sintered body and the dark-colored sintered body form a grain boundary, and the two sintered bodies are joined together. Furthermore, the light-colored sintered body and the dark-colored sintered body have grain boundaries (hereinafter, also referred to as “interfaces”) formed by sintering. By sintering the interface, the interface becomes a bonding surface having no defects such as cracks and strains. Thereby, the interface does not become a starting point of the destruction. Therefore, the multicolored zirconia sintered body of the present invention can be used as a member requiring the original strength of the zirconia sintered body.

  By sintering the light-colored sintered body and the dark-colored sintered body, they become one continuous zirconia sintered body. Therefore, the multicolor zirconia sintered body of the present invention has a structure in which crystal grains of a light-colored sintered body are sintered with each other, and a structure in which crystal grains of a dark-colored sintered body are sintered with each other. And a crystal structure of a sintered body of a dark-colored sintered body.

  Therefore, the multicolor zirconia sintered body of the present invention is different from a zirconia composite or a zirconia bonded body not having such a particle structure. The zirconia composite or the zirconia joined body has only a structure in which crystal particles of a light-colored sintered body are sintered and a structure in which crystal particles of a dark-colored sintered body are sintered. Examples of the zirconia composite include a zirconia composite obtained by separately sintering a light-colored sintered body and a dark-colored sintered body and then combining them. Examples of the zirconia joined body include a zirconia joined body in which a light-colored sintered body and a dark-colored sintered body are integrated via an adhesive layer and other intermediate layers. Further, even when the zirconia composite or the zirconia bonded body is subjected to the HIP treatment, a particle structure having a crystal particle structure obtained by sintering crystal particles of a dark-colored sintered body is not included. The HIP treatment only removes the open pores contained in each of the light-colored sintered body and the dark-colored sintered body, and the densification of each sintered body proceeds. This is because sintering cannot be performed. As described above, even if the zirconia composite or the like is subjected to the HIP processing, only the physical fitting due to the shrinkage of each sintered body is increased.

  The interface in the present invention can be confirmed from an electron image obtained by observation with an electron microscope such as a scanning electron microscope (hereinafter, referred to as “SEM”) or observation with an optical microscope. That is, the light-colored sintered body and the dark-colored sintered body have different color tones. Therefore, in the observation with an optical microscope, the interface can be confirmed by the portion where the color tone changes. Further, the light-colored sintered body and the dark-colored sintered body contain different coloring components. Since the electronic image has a different color tone due to the difference in the coloring components, the interface can be confirmed by a portion where the color tone changes in the electronic image.

  FIG. 1 is a diagram showing an example of a backscattered electron image obtained by SEM observation of the multicolor zirconia sintered body of the present invention. In FIG. 1, the region (1) is a light-colored sintered body, and the region (2) is a dark-colored sintered body. From FIG. 1, it is possible to confirm the interface (3), which is the boundary between the regions (1) and (2), from the difference in the color tone in the reflected electron image (for example, the dotted circle in FIG. 1).

  In the multicolor zirconia sintered body of the present invention, a light-colored sintered body and a dark-colored sintered body are joined by sintering. Further, either the light-colored sintered body or the dark-colored sintered body has one zirconia sintered body having a concave portion, and the other zirconia sintered body has a convex portion, and the concave portion and the convex portion are combined. Thus, it is preferable that the light-colored sintered body and the dark-colored sintered body are laminated and joined. Such a combination of the zirconia sintered bodies can form a pattern on the surface of the multicolor zirconia sintered body of the present invention as a pattern having no steps or gaps.

  In the multicolor zirconia sintered body of the present invention, the light-colored sintered body and the dark-colored sintered body have an interface, and the interface has no gap. Thereby, the multicolored zirconia sintered body of the present invention exhibits an aesthetic created only from the zirconia sintered body, and the multicolored zirconia sintered body of the present invention can be used as a member that gives a higher-grade impression. it can. In addition, since there is no gap at the interface, breakage starting from the interface is less likely to occur, so that the original mechanical properties of the zirconia sintered body are not impaired.

  In the present invention, the gap is a gap formed at and near an interface that is a bonding surface between the light-colored sintered body and the dark-colored sintered body, and is obtained by optical microscope observation or SEM observation at a magnification of 500 times or less. It can be confirmed by an electronic image of at least one of a secondary electron image and a reflected electron image (hereinafter, these are collectively simply referred to as “electronic images”).

  It is preferable that the multicolor zirconia sintered body of the present invention does not contain fine voids such as voids that can be confirmed by a secondary electron image or a reflected electron image obtained by SEM observation at a magnification of more than 500 times. However, when the multicolored zirconia sintered body of the present invention is used as various members, it is observed in an electron image obtained by SEM observation at a magnification of more than 500 times or transmission electron microscope (hereinafter referred to as “TEM”). May be provided. Such fine voids do not practically affect the aesthetics of the member.

  In FIG. 1, the interface (3), which is the boundary between the regions (1) and (2), can be confirmed from the difference in the color tone in the backscattered electron image (for example, the dotted circle in FIG. 1). Furthermore, the interface confirmed in FIG. 1 is a continuous interface, and no void is found in the interface. On the other hand, FIG. 2 is a diagram showing a backscattered electron image obtained by observing a multicolored zirconia sintered body having a gap at the interface with a SEM at a magnification of 500 times. In FIG. 2, (1) is a light-colored sintered body, and (2) is a dark-colored sintered body. The interface between the two was not a continuously formed interface, but was a partially formed interface (in FIG. 2, a dotted circle). Furthermore, it can be confirmed that a part of the interface has peeled off and a gap has been formed (arrow portion in FIG. 2).

  In the multicolor zirconia sintered body of the present invention, the light-colored sintered body and the dark-colored sintered body have an interface, and the interface has no color blur. Thereby, the boundary between the light-colored sintered body and the dark-colored sintered body becomes clear, so that the multicolored zirconia sintered body of the present invention can be a member having a clear pattern. Furthermore, the pattern formed by one of the zirconia sintered bodies can be a fine pattern.

  The color blur is a portion exhibiting a color tone in which the color tone of the light-colored sintered body and the color tone of the dark-colored sintered body are mixed, and is observed visually or by an optical microscope. Further, the color bleeding at the interface refers to an area including a color tone of the other zirconia sintered body and a region near the interface, which is observed in one of the light-colored sintered body and the dark-colored sintered body. Hereinafter, also referred to as a “transition region”), which is visually observed or observed with an optical microscope. In the present invention, an interface including the color tone of the dark-colored sintered body and a region near the interface, which are observed in the light-colored sintered body, particularly mean those observed visually or by an optical microscope. The presence or absence of color bleeding at the interface can be confirmed visually or by observing the multicolored zirconia sintered body with, for example, an optical microscope with a magnification of 10 to 100 times.

  FIG. 3 is an optical micrograph showing an example of a multicolor zirconia sintered body having color blur. In FIG. 3, the area (1) is a light-colored sintered body, and the area (2) is a dark-colored sintered body. 3, the boundary between the regions (1) and (2) is blurred and the vicinity of the interface is unclear (for example, a broken-line square in FIG. 3). In such a multicolor zirconia sintered body, color blur near the interface can be confirmed.

  The multicolor zirconia sintered body of the present invention may have a transition region that cannot be observed visually or with an optical microscope. The transition region that cannot be visually observed or observed with an optical microscope does not substantially affect the aesthetics when the multicolored zirconia sintered body of the present invention is used as various members.

  As a transition region that cannot be visually observed or observed with an optical microscope, it is a region of one of the zirconia sintered bodies of the light-colored sintered body and the dark-colored sintered body, and the other includes the coloring component contained in one of the zirconia sintered bodies. Of the zirconia sintered body.

  If the color component contained in the transition area is 3% by weight or less, further 2.5% by weight or less, or 2% by weight or less, color bleeding does not occur. Here, the presence or absence of the transition region and the content of the deposition component are all obtained by quantitative point analysis (hereinafter referred to as “EPMA analysis”) of the region of the light-colored sintered body at a certain distance from the interface with the electron beam microanalyzer. These are the presence or absence and the weight ratio of the coloring component to the weight of the element.

  FIG. 4 is a schematic diagram showing the measurement of the transition region by EPMA analysis. In FIG. 4, (1) is a region of a light-colored sintered body, (2) is a region of a dark-colored sintered body, and (3) is an interface. Further, (4) is a region of the light-colored sintered body at a certain distance from the interface, and (5) is a circle having a diameter of 10 μm formed around the (4) region. In the EPMA analysis, all the elements contained in (5) are analyzed, and when a coloring component is contained, the region becomes a transition region. In the present invention, EPMA analysis is performed on a plurality of regions (regions corresponding to (4) in FIG. 4) at different distances from the interface, and a region containing a coloring component corresponding to the maximum distance from the interface is determined in the sample. The transition region of each coloring component was used.

  The transition region is a region corresponding to the maximum distance from the interface containing the coloring component, and a region within 200 μm from the interface, further, a region within 150 μm, or even a region within 100 μm. The region of the light-colored sintered body within 200 μm, the region of the light-colored sintered body of 150 μm or less, and the region of the light-colored sintered body within 100 μm can be mentioned.

  When the transition region has the above range and the amount of the coloring agent, the multicolored zirconia sintered body of the present invention does not have color bleeding on aesthetics when used as a member.

  Examples of the coloring component contained in the transition region include metal elements constituting the spinel oxide contained in the dark-colored sintered body, and further include at least one of iron (Fe) and cobalt (Co). it can.

  For example, in the light-colored sintered body included in the multicolored zirconia sintered body of the present invention, the transition region is a region within 100 μm from the interface, and iron is contained in the region in an amount of 1% by weight or less, further 0.6% by weight or less. Or even 0.3% by weight or less, but the region beyond the transition region does not contain iron. In this case, the iron transfer region is a region within 100 μm from the interface.

  Further, the light-colored sintered body contained in the multicolored zirconia sintered body of the present invention has a cobalt content of 0.5% by weight or less, more preferably 0.3% by weight, in a region within 100 μm from the interface, and further in a region within 50 μm. It can be mentioned that cobalt is not contained in a region including the following and further than 100 μm from the interface. In this case, the transition region of cobalt is within 50 μm from the interface. However, when the area within 50 μm does not substantially contain cobalt (0% by weight), the area does not have a cobalt migration area or is at least an area closer to the interface than 50 μm from the interface.

  In the multicolor zirconia sintered body of the present invention, it is preferable that any one of the light-colored sintered body and the dark-colored sintered body has a pattern formed on the surface of the other zirconia sintered body. . The multicolor zirconia sintered body of the present invention can form a finer pattern than in the past. Accordingly, it is possible to provide a multicolored zirconia sintered body which not only has a higher design property but also is a member used in a wider range of applications.

  In the present invention, a pattern is formed on a part of one of a light-colored sintered body and a dark-colored sintered body, and is a diagram, a graphic, or a combination of the other zirconia sintered bodies. It is. Specific diagrams include linear shapes such as solid lines, broken lines, and wavy lines, numbers and characters, and figures such as geometric shapes such as round shapes and polyhedral shapes.

  In the multicolor zirconia sintered body of the present invention, the pattern of the light-colored sintered body may be formed on the surface of the dark-colored sintered body, while the pattern of the dark-colored sintered body may be formed on the surface of the light-colored sintered body. It may be formed.

The multicolor zirconia sintered body of the present invention can form a pattern having the size obtained by a conventional multicolor zirconia sintered body. In addition, the multicolor zirconia sintered body of the present invention can form a clear pattern even in a finer range than before. The pattern is, for example, an area of 1 cm ² or less, further an area of 1 mm ² or less, or even an area of 0.5 mm ² or less, or an area of 0.05 mm ² or less, or even an area of 0.005 mm ² or less. If it is a region, it can be clearly formed. Further, as the pattern of the multicolored zirconia sintered body of the present invention, for example, a diagram consisting of a line having a thickness of about 150 μm, a diagram or figure with an interval of about 150 μm, a diameter of 1 mm or less, and a diameter of 0.1 mm or less. Figures of 5 mm or less can be mentioned.

  The shape of the multicolor zirconia sintered body of the present invention and the shape of the pattern possessed by the multicolor zirconia sintered body are arbitrary. For example, examples of the shape and the pattern of the multicolor zirconia sintered body of the present invention are shown in FIGS.

  For example, FIG. 5 is a schematic view of a multicolor zirconia sintered body having a shape of a bezel ring for a timepiece and having the surface of the bezel ring. The left figure is a front view, the middle figure is a side view, and the right figure is a rear view. In the front view, the surface of the bezel ring is made of a dark-colored sintered body ((2) in the left diagram of FIG. 5), and a pattern of Arabic numerals made of a light-colored sintered body is formed on the surface ((1) in the left diagram of FIG. )). The side surface is that the multicolor zirconia sintered body is such that a dark-colored sintered body having a concave portion having the same shape as the Arabic numeral is laminated on a light-colored sintered body having a convex portion having the Arabic numeral shape. (FIG. 5 middle diagram). Further, the light-colored sintered body has a ring shape having a hollow portion, and the light-colored sintered body and the dark-colored sintered body are laminated (FIG. 5, right diagram).

  Also, for example, FIG. 6 is a schematic diagram of a multicolor zirconia sintered body having the shape of a timepiece dial. The left figure is a front view, and the right figure is a rear view. In FIG. 6, the sintered body has a disk-like shape, and the surface is a dark-colored sintered body. A diagram of a portion corresponding to each time from 1 o'clock to 12 o'clock of an analog timepiece and a light-colored sinter having a shape of Arabic numeral 3, 6, 9 and 12 on the surface of the sintered body Has a body. The light-colored sintered body has a disk shape, and a light-colored sintered body and a dark-colored sintered body are laminated (the right figure in FIG. 6).

  7 to 10 are schematic diagrams showing a multicolor zirconia sintered body having a bracelet shape, a housing shape, a mobile phone cover shape, and a disk shape, respectively.

  Since the light-colored sintered body and the dark-colored sintered body are joined by sintering, the multicolored zirconia sintered body of the present invention has a high density. The relative density of the multicolored zirconia sintered body of the present invention is 99.5% or more, and more preferably 99.7% or more. When the relative density is 99.5% or more, not only there is no gap at the interface, but also the number of defects in portions other than the interface is reduced. Thereby, the mechanical strength of the multicolor zirconia sintered body of the present invention tends to be higher.

  The zirconia composite and the zirconia joined body are obtained by combining different zirconia sintered bodies after sintering. Therefore, even if the relative densities of the zirconia sintered bodies constituting these are respectively 99.5% or more, the relative densities of the zirconia composite and the zirconia joined body do not become 99.5% or more.

  In the present invention, the relative density of the multicolor zirconia sintered body can be obtained from the following equation (1).

Relative density (%) = Measured density of multicolored zirconia sintered body (g / cm ³ ) / theoretical density of multicolored zirconia sintered body (g / cm ³ ) × 100 (1)

  The measured density (sintered body density) of the multicolored zirconia sintered body can be determined by the Archimedes method.

  Further, the theoretical density of the multicolored zirconia sintered body can be calculated from the following formula based on each density and volume ratio of the light-colored sintered body and the dark-colored sintered body.

                M = (Ma · X + Mb · Y) / (X + Y) (1 ′)

In the above formula, M is the theoretical density of the multicolored zirconia sintered body (g / cm ³ ), Ma is the theoretical density of the light-colored sintered body (g / cm ³ ), and Mb is the theoretical density of the dark-colored sintered body (g). / Cm ³ ), X is the volume ratio of the light-colored sintered body to the volume of the multicolored zirconia sintered body, and Y is the volume ratio of the dark-colored sintered body to the volume of the multicolored zirconia sintered body.

  In the formula (1 '), Ma and Mb differ depending on the composition of the light-colored sintered body and the dark-colored sintered body. Ma and Mb may be determined from the theoretical densities of the compounds constituting each sintered body and the weight ratio of these compounds. Examples of the theoretical density of the compound constituting each sintered body include the following.

Black zirconia: 6.05 g / cm ³
3 mol% yttria-containing zirconia: 6.09 g / cm ³
Aluminum oxide: 3.98 g / cm ³
Aluminum cobalt oxide spinel: 4.42 g / cm ³
Iron oxide: 5.24 g / cm ³

  In the formula (1 ′), X is a volume ratio obtained by multiplying Ma by a weight ratio of the light-colored sintered body to the weight of the multicolored zirconia sintered body, and Y is a dark color to the weight of the multicolored zirconia sintered body. It is a volume ratio obtained by multiplying the weight ratio of the sintered body by Mb.

  The light-colored sintered body and the dark-colored sintered body are 2 mol% or more and 6 mol% or less, further 2.5 mol% or more and 4 mol% or less, or 2.5 mol% or more and 3.5 mol% or less, or even 2.8 mol%. % Or more and 3.2 mol% or less of a stabilizer. By containing the stabilizer in the above range, these zirconia sintered bodies become zirconia sintered bodies having a tetragonal crystal structure. This results in a sintered body having high mechanical strength.

  Examples of the stabilizer include at least one selected from the group consisting of yttria, calcia, magnesia, and scandia, and further include yttria.

  The light-colored sintered body contained in the multicolored zirconia sintered body of the present invention is a lanthanoid of one or more of the group consisting of Ce, Pr, Nd, Eu, Tb, Ho, Er, Yb and Gd. Zirconia sintered body containing a light-colored lanthanoid). Thereby, the light-colored sintered body becomes a zirconia sintered body having a lighter color tone than the dark-colored sintered body containing the spinel oxide.

The color of the light-colored sintered body may be a desired color tone. For example, the value of L ^{* in} the L ^* a ^* b ^* color system may be 20 or more higher than that of the dark-colored sintered body. Further, L ^* a ^* b ^* color system L ^* of the light-colored sintered body may be 55 or more.

  In the present invention, the light-colored sintered body is a light-colored zirconia sintered body other than the white zirconia sintered body. The light-colored sintered body is at least one selected from the group consisting of Ce, Pr, Nd, Eu, Tb, Ho, Er, Yb, and Gd, and further, any one selected from the group consisting of Er, Pr, and Nd. It is preferable to contain one or more. As a result, the light-colored sintered body has a lighter tone than the dark-colored sintered body and has a lighter color tone than white. The light-colored sintered body contains, for example, a pink zirconia sintered body by containing erbium (Er), an orange zirconia sintered body by containing praseodymium (Pr), and neodymium (Nd). Thus, a lavender-colored zirconia sintered body is obtained.

  The content of the light-colored lanthanoid only needs to include the amount of solid solution in the zirconia of the light-colored sintered body. Further, the light-colored lanthanoid is 0.1% by weight or more and 6% by weight based on the weight of the light-colored sintered body. % Or less, more preferably from 0.3% by weight to 3.5% by weight.

  The light-colored sintered body may include alumina in addition to the light-colored lanthanoid. In this case, the alumina contained in the light-colored sintered body is 0.5% by weight or less, more preferably 0.3% by weight or less, and further preferably 0.25% by weight or less based on the zirconia of the light-colored sintered body. In the case of a light-colored sintered body exhibiting a light color other than white, if this contains more than 0.5% by weight of alumina, the color becomes too light.

When the light-colored sintered body exhibits a pink color, the coloration is L ^* = 65 or more and 85 or less, a ^* = 0 or more and 15 or less, and b ^* = − 10 or more and 0 or less, and L ^* = It is preferable that it is 70 or more and 85 or less, a ^{* is} 2 or more and 12 or less, and b ^{* is} -8 or more and -0.5 or less.

When the light-colored sintered body exhibits an orange color, the coloration is L ^* = 55 to 80, a ^* = 0 to 20 and b ^* = 30 to 65, and L ^* = 60. It is preferable that it is not less than 75, not more than a ^* = 3 and not more than 18, and b ^* = 35 and not more than 65.

When the light-colored sintered body exhibits a lavender color, the coloration must be L ^* = 55 to 80, a ^* = 3 to 15 and b ^* = − 15 to −3, and further L ^*. = 60 or more and 80 or less, a ^* = 5 or more and 15 or less, and b ^* =-11 or more and -5 or less.

  The dark-colored sintered body contained in the multicolored zirconia sintered body of the present invention is a zirconia sintered body containing a spinel oxide containing cobalt and aluminum (hereinafter, also simply referred to as “spinel oxide”). By containing the spinel oxide, a zirconia sintered body having a darker color tone than the light color sintered body is obtained.

The color development of the dark-colored sintered body includes, for example, that the value of L ^* is 20 or more lower than that of the light-colored sintered body. Further, it can be exemplified that L ^{* of} the dark-colored sintered body is less than 55.

  In the present invention, the dark sintered body is a blue zirconia sintered body. The spinel oxide contained in the dark-colored sintered body is a spinel oxide containing cobalt and aluminum. Thereby, the dark-colored sintered body becomes a zirconia sintered body exhibiting a blue color.

  The content of the spinel oxide containing cobalt and aluminum is 0.25% by weight or more and 13% by weight or less, more preferably 1% by weight or more and 10% by weight or less as the weight of the spinel oxide based on the weight of the dark-colored sintered body. Is preferably 3% by weight or more and 5% by weight or less. By containing the spinel oxide in this range, the color tone of the sintered body becomes clearer blue.

A preferred spinel oxide is CoAl ₂ O ₄ .

Furthermore, when the spinel oxide is a spinel oxide containing cobalt and aluminum, the dark-colored sintered body contains a spinel oxide containing cobalt and aluminum, and a transition metal oxide, and further contains iron oxide ( Fe ₂ O ₃ ). Thereby, the deep-colored sintered body exhibits a deeper blue color. The content of the transition metal oxide may be 0.1% by weight or more and 2% by weight or less based on the weight of the dark-colored sintered body so as to give a blue color.

By containing the above spinel oxide, the color of the dark-colored sintered body is L ^* = 20 or more and 60 or less, a ^* =-20 or more and 20 or less, and b ^* =-70 or more and -20 or less. L ^* = 30 or more and 40 or less, a ^* = − 20 or more and 15 or less, and b ^* = − 70 or more and −40 or less, and L ^* = 30 or more and 35 or less, a ^* = It is preferable that it is 0 or more and 15 or less, and b ^* =-65 or more and -60 or less. When L ^* a ^* b ^* is within this range, the dark-colored sintered body is not reddish, and becomes a blue-colored zirconia sintered body having a true blue color. Thereby, a blue zirconia sintered body having a higher quality can be obtained.

  Next, a method for producing the multicolor zirconia sintered body of the present invention will be described.

  The multicolor zirconia sintered body of the present invention is a zirconia powder containing one or more lanthanoids selected from the group consisting of Ce, Pr, Nd, Eu, Tb, Ho, Er, Yb and Gd, or cobalt. A primary molding step of molding any one of the zirconia powders containing zirconia powder containing spinel oxide containing aluminum and obtaining a primary molded body, and forming the other zirconia powder on the primary molded body at a molding temperature equal to or lower than the primary molding step. A secondary molding step of molding to obtain a secondary molded body, a sintering step of firing the secondary molded body at 1300 ° C. or higher to obtain a pre-sintered body, and a step of firing the pre-sintered body at 1250 ° C. to 1650 ° C. And hot isostatic pressing at 100 MPa or more and 250 MPa or less.

  In the primary molding step, a primary molded body is obtained. The primary compact is a zirconia powder containing at least one lanthanoid (light-colored lanthanoid) selected from the group consisting of Ce, Pr, Nd, Eu, Tb, Ho, Er, Yb, and Gd (hereinafter, referred to as “light-colored powder”). ) Or a zirconia powder containing spinel oxide (hereinafter also referred to as a “dark colored powder”). (Hereinafter, also referred to as a “dark-colored molded product”).

  The molding method in the primary molding step is optional. Examples of the molding method include any one or more of the group consisting of press molding, cold isostatic pressing, casting, sheet molding, and injection molding. Since a molded article having an arbitrary shape is easily obtained, it is preferable that the molding method is at least one of cast molding and injection molding. Further, since a molded article having a more complicated and fine shape can be easily obtained, the molding method is more preferably injection molding.

  In the secondary molding step, a molded body is formed by molding the other powder on the primary molded body made of either the light-colored molded article or the dark-colored molded article. Thereby, a molded article in which the primary molded article and the secondary molded article are joined is obtained.

  The molding temperature in the secondary molding step (hereinafter, also referred to as “secondary molding temperature”) is equal to or lower than the molding temperature in the primary molding step (hereinafter, also referred to as “primary molding temperature”). When the secondary molding temperature is higher than the primary molding temperature, distortion or collapse of the shape of the primary molded body during secondary molding tends to occur. In this case, a secondary molded body including a fine shape of the primary molded body such as a convex portion in a distorted state is obtained. When such a secondary molded body is sintered, the resulting multicolored zirconia sintered body becomes a sintered body having color blur due to shape distortion.

  In a general molding method having a primary molding and a secondary molding, in particular, a casting molding or an injection molding having a primary molding and a secondary molding, the temperature of the primary molded body increases due to heat at the time of the secondary molding. Thereby, the temperature of the secondary forming step increases. Therefore, when the molding temperature is not controlled in the primary molding and the secondary molding, the secondary molding temperature usually exceeds the primary molding temperature. On the other hand, the secondary molding temperature in the present invention is equal to or lower than the primary molding temperature, and is lower than the primary molding temperature. When the secondary molding temperature is equal to or lower than the primary molding temperature, that is, when the primary molding temperature is equal to or higher than the secondary molding temperature, the flow of the pattern and the color bleeding due to the flow do not occur. By sintering the thus obtained secondary molded body, a multicolored zirconia sintered body having no gaps and no color blur at the interface can be obtained. The flow of the pattern means that the shape of the primary molded body, such as a convex portion of the primary molded body, is deformed by molding of the secondary molded body.

  In the secondary molding step, as the difference between the primary molding temperature and the secondary molding temperature increases, a secondary molded body that does not include a distorted shape is more easily obtained. The primary molding temperature is 3 ° C. or more, more preferably 5 ° C. or more, furthermore 10 ° C. or more, furthermore 20 ° C. or more, or even 30 ° C. or more than the secondary molding temperature. However, in the production method of the present invention, the secondary molding temperature is lower than the primary molding temperature, and the difference is 3 to 30 ° C, more preferably 3 to 20 ° C, furthermore 3 to 10 ° C, or even more. Even if it is as small as 5 to 10 ° C., a secondary molded body that does not include a distorted shape can be obtained with good reproducibility.

  The primary molding temperature and the secondary molding temperature may be controlled by the temperature of the mold (hereinafter, also referred to as “mold”) of the molded body. That is, in the molding step, the temperature of the mold for the primary molding is raised to the temperature of the mold for the secondary molding, more than 3 ° C., or even 5 ° C. or more, furthermore 10 ° C. or more, or even 20 ° C. or more. Further, by setting the temperature to 30 ° C. or more, the secondary molding temperature can be set to the primary molding temperature or less.

  The molding method in the secondary molding step is at least one of the group consisting of press molding, cold isostatic pressing, cast molding, sheet molding and injection molding, provided that the primary molding temperature and the secondary molding temperature satisfy the above relationship. Any molding method may be used. Since a molded article having an arbitrary shape is easily obtained, it is preferable that the molding method is at least one of cast molding and injection molding. Further, since a molded article having a more complicated and fine shape can be easily obtained with good reproducibility, the molding in the secondary molding step is more preferably injection molding.

  The injection pressure in the injection molding may be, for example, 50 MPa or more and 150 MPa or less, and more preferably 70 MPa or more and 130 MPa or less.

  The light-colored powder to be subjected to the primary molding step, the secondary molding step, or both steps (hereinafter, also referred to as a “molding step”) is a zirconia powder containing a light-colored lanthanoid powder, and a light-colored lanthanoid powder and a zirconia powder. Any mixed powder may be used.

The light-colored powder preferably has a BET specific surface area of 7 to ²⁰ m ² / g, more preferably 7.5 to 15 m ² / g. By setting the BET specific surface area in this range, the light-colored molded product tends to have the same sintering behavior as the dark-colored molded product containing the spinel oxide.

  Examples of the zirconia powder include a zirconia powder containing 3 mol% of yttria.

  If the light powder contains alumina, the alumina needs to be less than the light lanthanoid. Alumina contained in the light-colored powder may be 0.5% by weight or less, more preferably 0.3% by weight or less, or even 0.25% by weight or less based on zirconia in the light-colored powder.

  The content of the light-colored lanthanoid may be from 0.1% by weight to 6% by weight, and more preferably from 0.3% by weight to 3.5% by weight, based on the weight of the light-colored powder.

  The mixing method is arbitrary as long as these powders and zirconia powder are uniformly mixed. The mixing method is preferably wet mixing, more preferably a ball mill or a bead mill. As a specific mixing method, mixing with a ball mill for 24 hours or more can be mentioned.

  The dark-colored powder to be subjected to the molding step is zirconia powder containing spinel oxide, and may be a mixed powder of spinel oxide powder and zirconia powder.

The weight of the spinel oxide powder may be from 2% by weight to 6% by weight, and more preferably from 2% by weight to 4% by weight, based on the weight of the dark-colored powder. Further, the dark powder has a BET specific surface area of 4 to 10 m ² / g.

  Examples of the zirconia powder include a zirconia powder containing 3 mol% of yttria.

When the dark powder contains a spinel oxide powder containing cobalt and aluminum, and further contains CoAl ₂ O ₄ powder, the weight of the spinel oxide relative to the weight of the dark powder is 0.25% by weight or more and 13% by weight or less. It is preferably from 1% by weight to 10% by weight, and more preferably from 3% by weight to 5% by weight.

  Further, in addition to the spinel oxide powder, a transition metal oxide powder and further an iron oxide powder may be contained. The content of the transition metal oxide powder is 0.1% by weight or more and 2% by weight or less based on the weight of the dark-colored powder.

  In the molding step, it is preferable that at least one of the light-colored powder and the dark-colored powder contains an organic binder in order to improve the fluidity of the powder.

  When an organic binder is contained, the content of the organic binder in each zirconia powder is 25 to 65% by volume, and more preferably 35 to 60% by volume.

  Examples of the organic binder include at least one selected from the group consisting of an acrylic resin, a polyolefin resin, a wax, and a plasticizer.

  The mixing method is optional as long as the zirconia powder and the organic binder can be uniformly mixed. Examples of the mixing method include heat kneading and wet mixing.

  It is preferable that the light-colored molded product and the dark-colored molded product have the same sintering shrinkage strength. Thereby, distortion due to the difference in the amount of shrinkage does not occur, and the formed body can be sintered in a state where both are more firmly joined.

  In the firing step, the secondary formed body is fired to temporarily sinter it to obtain a preliminary sintered body.

  In the firing step, the firing temperature is 1300 ° C. or higher, and more preferably 1350 ° C. or higher. If the firing temperature is lower than 1300 ° C., the sintered body will not be densified in the HIP process. The firing temperature does not need to be higher than necessary, and may be 1300 ° C to 1550 ° C, more preferably 1350 ° C to 1500 ° C, or even 1350 ° C to 1450 ° C.

  The firing atmosphere may be any of the air, an inert atmosphere, or a vacuum, preferably at least one of the air and an inert atmosphere, and more preferably the air. Any combination of the above firing temperature and firing atmosphere can be applied. The firing step is preferably normal pressure sintering, which is a method of sintering by simply heating the molded body without applying external force.

  The firing time varies depending on the firing temperature, but is preferably 1 hour or more, more preferably 2 hours or more. When the firing time is one hour or more, removal of the gap is promoted in the firing step. On the other hand, the firing time may be 5 hours or less, and more preferably, 3 hours or less.

  In the case where a molded body is produced from zirconia powder containing an organic binder, a degreasing treatment is performed before the firing treatment to remove the organic binder from the molded body.

  The firing temperature in the degreasing treatment may be 400 ° C. or more and 600 ° C. or less. The degreasing atmosphere may be any atmosphere selected from the group consisting of air, an inert gas atmosphere, and an oxidizing gas atmosphere.

  In the manufacturing method of the present invention, the pre-sintered body is subjected to HIP processing. Thereby, while the color bleeding at the interface is suppressed, the elimination of the gap at the interface is promoted, and the preliminary sintered body is sintered to obtain the multicolored zirconia sintered body of the present invention.

  In the HIP treatment, the HIP temperature may be 1200 ° C. or higher, further 1250 ° C. or higher, further 1300 ° C. or higher, and further 1350 ° C. or higher. As the densification progresses, the HIP temperature does not need to be set higher than necessary. The HIP temperature may be 1650 ° C. or lower, and further 1450 ° C. or lower.

  The HIP pressure is 50 MPa or more, more preferably 100 MPa or more, or even 140 MPa or more. In the HIP processing using a normal HIP processing apparatus, the HIP pressure becomes 250 MPa or less, and further, 180 MPa or less.

  The atmosphere for the HIP treatment may be an inert atmosphere, and may include at least one of a nitrogen atmosphere and an argon atmosphere, and is preferably an argon atmosphere. The above-mentioned HIP temperature, HIP pressure and atmosphere, and the upper and lower limits thereof can be any combination.

  According to the production method of the present invention, a multicolor zirconia sintered body having no color blur and no gap at the interface can be obtained.

  Furthermore, the production method of the present invention includes at least one of a processing step and a polishing step (hereinafter, also referred to as a “post-treatment step”) for making the obtained multicolored zirconia sintered body into various members. You may go out.

  In the processing step, the multicolor zirconia sintered body obtained by the HIP processing is processed into a desired shape. Any processing method can be used. The processing method may be a general cutting method, and examples thereof include one or more of the group consisting of lathe processing, surface grinding, R grinding, and NC processing (numerical control machining).

  In the polishing step, the multicolored zirconia sintered body obtained by the HIP process or a processed product thereof is polished. As a result, the gloss can be further enhanced, and the sense of quality of the multicolor zirconia sintered body of the present invention is further emphasized. The polishing method is optional, and examples thereof include at least one of barrel polishing and R polishing.

  In the production method of the present invention, any combination of the above conditions may be used in the primary molding step, the secondary molding step, the firing step, the HIP treatment step, and the post-treatment step.

  According to the present invention, there is provided a zirconia sintered body having two or more different color tones, which has an aesthetic appearance exhibiting a sense of quality and has sufficient strength to be used as a member. it can. Further, according to the present invention, it is possible to provide a zirconia sintered body having two or more different color tones and having no color blur or a gap between the zirconia sintered bodies.

  Further, according to the present invention, it is possible to provide a member having a high-class feeling.

Backscattered electron image of pink / blue zirconia sintered body of Example 1 (scale in the figure is 50 μm) Backscattered electron image of a multicolored zirconia sintered body with a gap at the interface (scale in the figure is 50 μm) Optical micrograph of multicolored zirconia sintered body with color blur (scale in the figure is 50 μm) Schematic diagram showing measurement of transition area by quantitative point analysis of EPMA Schematic diagram showing an example of a watch bezel ring made of the multicolored zirconia sintered body of the present invention. Schematic diagram showing an example of a timepiece dial made of the multicolored zirconia sintered body of the present invention. Schematic diagram showing an example of a bracelet made of the multicolored zirconia sintered body of the present invention Schematic diagram showing an example of a housing made of the multicolored zirconia sintered body of the present invention. Schematic diagram showing an example of a cover for a mobile phone made of the multicolored zirconia sintered body of the present invention. Schematic view showing an example of a disc-shaped sintered body made of the multicolored zirconia sintered body of the present invention Overview of pink / blue zirconia sintered body of Example 3 (A) Optical microscope photograph and (b) SEM photograph (scale in the figure is 20 μm) of the interface of the ceramic molded article of Comparative Example 1. SEM photograph of the interface of the ceramic molded article of Comparative Example 2 (scale in the figure is 20 μm) Optical micrograph of the interface having a gap between the ceramic shaped articles of Comparative Example 3 Optical micrograph of the interface with color bleeding of the ceramic shaped article of Comparative Example 3

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited to these.
(Sintered body density and relative density)
The measured density (sintered body density) of the multicolored zirconia sintered body was measured by the Archimedes method. The relative density of the multicolor zirconia sintered body was determined from the obtained measured density and theoretical density. The theoretical density of the multicolor zirconia sintered body was calculated from the equation (1 ′). The calculated theoretical densities of the multicolor zirconia sintered bodies of the example and the comparative example are shown in Table 2.
(Specific surface area)
The BET specific surface area by nitrogen adsorption was measured and defined as the specific surface area of the powder sample. A general specific surface area measuring device (manufactured by QUANTA CHROME) was used for the measurement.
(Observation by optical microscope)
The interface of the sintered body sample was observed using an optical microscope (device name: MM-800, manufactured by Nikon) or a three-lens zoom stereo microscope (device name: AR-372ZH, manufactured by Arm System Co., Ltd.). In the optical microscope observation, the presence or absence of a gap at the interface and the presence or absence of color blur were observed.
(SEM observation)
The interface of the sintered body sample was observed using SEM (apparatus name: JSM-5400, manufactured by JEOL). In the SEM observation, the magnification was set to 500 times, and the presence or absence of a gap at the interface was observed.

(Elemental quantitative analysis by EPMA)
Using a wavelength dispersive electron beam microanalyzer (EPMA) (apparatus name: EPMA1610, manufactured by Shimadzu Corporation), point analysis of the sintered body sample near the interface of the light-colored sintered body was performed. The measurement conditions are as follows.
Acceleration voltage: 15KV
Irradiation current: 100 nA
Analysis range: φ10 μm
The measurement is performed at a distance of 30 μm, 50 μm, 100 μm, 130 μm, 170 μm, and 200 μm of the light-colored sintered body from the interface. Area.

(Color tone by L ^* a ^* b ^* color system)
According to JISZ8722, the color tone of the sintered body sample was measured. A general color difference meter (device name: Color Analyzer TC-1800MK-II, manufactured by Tokyo Denshoku Co., Ltd.) was used for the measurement. The measurement conditions are as follows.
Light source: D65 light source
Viewing angle: 2 °
As the sintered body sample, a disc-shaped one having a thickness of 1 mm and a diameter of 20 mm and having both surfaces polished was used.
(Mechanical strength test)
As the mechanical strength of a multicolor zirconia sintered body sample. The impact strength was measured by a hard ball drop test according to ISO14368-3. That is, a multicolor zirconia sintered body sample was placed on a SUS plate. Thereafter, an iron ball having a weight of 16 g was dropped from a height of 5 cm from the multicolored zirconia sintered body sample near the interface between the light-colored sintered body and the dark-colored sintered body, and cracks of the multicolored zirconia sintered body were obtained. The presence or absence of cracks, cracks and other destructions was confirmed. Thereafter, the same measurement was performed with the iron ball drop start position (hereinafter, also referred to as a “falling ball position”) raised at 5 cm intervals. The impact strength of the sample of the multicolored zirconia sintered body was defined as the falling ball position (cm) at which destruction was confirmed in the multicolored zirconia sintered body.

Example 1
A pink / blue zirconia sintered body composed of a pink zirconia sintered body and a blue zirconia sintered body was produced.

(Preparation of pink zirconia raw material)
The BET specific surface area is 8 m ² / g, and 3 mol% containing 0.25 wt% alumina so that the weight of erbium is 2 wt% based on the total weight of yttria and zirconia in the 3 mol% yttria stabilized zirconia powder. Erbium oxide powder (trade name: Erbium oxide, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to yttria stabilized zirconia powder (trade name: TZ-3YSE, manufactured by Tosoh Corporation).
After the addition, using a zirconia ball having a diameter of 10 mm, these powders were mixed in a ball mill for 24 hours in an ethanol solvent. The powder after mixing was dried to obtain a pink zirconia powder.
An acrylic binder was mixed with the obtained pink zirconia powder, and this was used as a pink zirconia raw material. The content of the pink zirconia powder in the pink zirconia raw material was 45% by volume.

(Preparation of blue zirconia raw material)
3 mol% yttria-stabilized zirconia having a BET specific surface area of 8 m ² / g such that the weight of spinel oxide (the weight of spinel) with respect to the total weight of yttria and zirconia in the 3 mol% yttria-stabilized zirconia powder is 3 wt%. To a powder (trade name: TZ-3Y, manufactured by Tosoh Corporation), a spinel oxide powder (trade name: aluminum cobalt oxide, manufactured by Wako Pure Chemical Industries, Ltd.) containing cobalt and aluminum was added.
After the addition, using a zirconia ball having a diameter of 10 mm, these powders were mixed in a ball mill for 24 hours in an ethanol solvent. The powder after mixing was dried to obtain a blue zirconia powder.
An acrylic binder was mixed with the obtained blue zirconia powder, and this was used as a blue zirconia raw material. The content of the blue zirconia powder in the blue zirconia raw material was 45% by volume.

(Preparation of molded body)
The pink zirconia raw material was subjected to injection molding to obtain a bezel ring-shaped pink zirconia molded article having a convex portion. The injection molding pressure was 100 MPa.
Next, a blue zirconia raw material was injection-molded on the obtained pink zirconia molded body. The injection molding pressure was 100 MPa, and the temperature of the mold was 5 ° C. lower than the injection molding temperature of the pink zirconia raw material. As a result, a molded article in which the blue zirconia molded article was laminated on the pink zirconia molded article and which were joined to each other was obtained.
The obtained molded body was subjected to a degreasing treatment in the atmosphere at a temperature rising rate of 2.0 ° C./h, a degreasing temperature of 450 ° C., and a degreasing time of 4 hours.

(Firing and HIP processing)
The pre-sintered body was obtained by firing the molded body after the degreasing treatment in the air at a heating rate of 100 ° C./h, a firing temperature of 1450 ° C., and a sintering time of 2 hours.
The obtained pre-sintered body was placed in an alumina container, and then subjected to HIP treatment under an atmosphere of argon gas having a purity of 99.9% at a HIP temperature of 1400 ° C., a HIP pressure of 150 MPa, and a holding time of 1 hour. A HIP-treated product was obtained. The HIP-treated body was used as the white / blue zirconia sintered body of this example. Table 1 shows the manufacturing conditions of this example, and Table 2 shows the evaluation results.
In the obtained pink / blue zirconia sintered body, the volume ratio of the pink / blue zirconia sintered body was 41:59, and the relative density of the pink / blue zirconia sintered body was 99.9. %Met.

(Material processing)
The surface of the pink / blue zirconia sintered body of the present example on the side of the blue zirconia sintered body was processed until the convex portions of the pink zirconia sintered body were clearly confirmed. Thus, the pink / blue zirconia sintered body of the present example was formed into a bezel ring having a pattern of the pink zirconia sintered body on the surface of the blue zirconia sintered body. The bezel ring after the surface processing was polished to obtain a bezel ring made of the pink / blue zirconia sintered body of the present example and having a strong glossiness.
The bezel ring had a surface made of a blue zirconia sintered body, and had a pattern made of a pink zirconia sintered body on the surface.
Further, the interface of the bezel ring was visually confirmed. As a result, it was confirmed that the pink color of the interface was not blurred and the interface had no color blur.
Further, the interface of the bezel ring was observed with an optical microscope and SEM observation. FIG. 1 shows a backscattered electron image obtained by SEM observation. It was confirmed that pink zirconia and blue zirconia were sintered to form an interface, that no gap was formed at the interface, and that there was no bonding layer (the dotted circle in FIG. 1).
Further, a mechanical strength test of the obtained bezel ring was performed. No cracks or cracks occurred when the iron ball was dropped from a height of 85 cm. From this, it was confirmed that the pink / blue zirconia sintered body of the present example had an impact strength of 85 cm or more and high strength.

Example 2
An orange / blue zirconia sintered body composed of an orange zirconia sintered body and a blue zirconia sintered body was produced.
That is, a 3 mol% yttria-stabilized zirconia powder having a BET specific surface area of 8 m ² / g and containing 0.25 wt% of alumina (trade name: TZ-3YSE, Tosoh Co., Ltd.) so that the praseodymium weight becomes 3 wt%. Praseodymium oxide powder (trade name: praseodymium oxide, manufactured by Shin-Etsu Chemical Co., Ltd.).
After the addition, using a zirconia ball having a diameter of 10 mm, these powders were mixed in a ball mill for 24 hours in an ethanol solvent. The powder after mixing was dried to obtain an orange zirconia powder.

Except for using the orange zirconia powder in place of the pink zirconia powder, molding, firing and HIPing were performed in the same manner as in Example 1 to obtain an orange / blue zirconia sintered body of the present example. . Table 1 shows the manufacturing conditions of this example, and Table 2 shows the evaluation results.
The obtained orange / blue zirconia sintered body had a volume ratio of the orange / blue zirconia sintered body of 41:59, and the relative density of the orange / blue zirconia sintered body was 99.8. %Met.

Next, the obtained orange / blue zirconia sintered body is processed and polished in the same manner as in Example 1, and is made of the orange / blue zirconia sintered body of this example, and has a strong glossiness. Got a bezel ring.
The bezel ring had a surface made of a blue zirconia sintered body, and had a pattern made of an orange zirconia sintered body on the surface.
The interface of the bezel ring was visually confirmed. As a result, it was confirmed that the orange color of the interface was not blurred and the interface had no color blur.
Further, the interface of the bezel ring was observed with an optical microscope and SEM observation. As a result, the orange zirconia and the blue zirconia are sintered to form an interface, and although the interface has a curvature, no gap is formed at the interface, and a gap is formed at the interface. It could be confirmed that there was no bonding layer and that there was no bonding layer.
Further, a mechanical strength test of the obtained bezel ring was performed. No cracks or cracks occurred when the iron ball was dropped from a height of 85 cm. From this, it was confirmed that the orange / blue zirconia sintered body of the present example had an impact strength of 85 cm or more and high strength.

Example 3
A disk-shaped pink / blue zirconia sintered body composed of a pink zirconia sintered body and a blue zirconia sintered body was produced.
(Preparation of raw materials)
Pink zirconia powder obtained by the same method as in Example 1 was used as a pink zirconia raw material, and blue zirconia powder obtained by the same method as in Example 1 was used as a pink zirconia raw material.
(Preparation of molded body)
A pink primary zirconia raw material was uniaxially pressed at room temperature to obtain a convex primary molded body. The obtained primary compact was filled with blue zirconia powder, and the primary compact and the blue zirconia powder were simultaneously subjected to uniaxial press molding. A secondary compact was obtained by subjecting the compact after uniaxial pressing to cold isostatic pressing (CIP). The pressure for the CIP treatment was set to 200 MPa, and the molding temperature was set to room temperature or lower.
(Firing and HIP processing)
A pink / blue zirconia sintered body of this example was obtained in the same manner as in Example 1 except that the obtained secondary molded body was used.

(Material processing)
The surface of the pink / blue zirconia sintered body of the present example on the side of the blue zirconia sintered body was processed until the convex portions of the pink zirconia sintered body were clearly confirmed. As a result, the pink / blue zirconia sintered body of this example was made into a disc-shaped zirconia sintered body having a pattern of the pink zirconia sintered body on the surface of the blue zirconia sintered body. The disc-shaped zirconia sintered body after the surface processing was polished to obtain a disc-shaped zirconia sintered body composed of the pink / blue zirconia sintered body of the present example and having a strong glossiness. FIG. 11 shows a photograph of the obtained disk-shaped zirconia sintered body. The disc-shaped zirconia sintered body had a diameter of 16 mm, a thickness of 2.5 mm, and a pattern width of 3 mm.
The disc-shaped zirconia sintered body had a surface made of a blue zirconia sintered body, and had a pattern made of a pink zirconia sintered body on the surface.
The interface of the disc-shaped zirconia sintered body was visually confirmed. As a result, it was confirmed that the pink color of the interface was not blurred and the interface had no color blur.
Further, the interface of the disc-shaped zirconia sintered body was observed with an optical microscope and SEM observation. As a result, it was confirmed that pink zirconia and blue zirconia were sintered to form an interface, that no gap was formed at the interface, and that there was no bonding layer.

Example 4
A disk-shaped orange / blue zirconia sintered body composed of an orange zirconia sintered body and a black zirconia sintered body was produced.
Molding, firing, and HIPing were performed in the same manner as in Example 3 except that the orange zirconia powder obtained in the same manner as in Example 2 was used as the orange zirconia raw material instead of the pink zirconia raw material. An orange / blue zirconia sintered body of the example was obtained. Further, the obtained orange / blue zirconia sintered body was processed in the same manner as in Example 3 to obtain a disk-shaped zirconia sintered body having a diameter of 16 mm, a thickness of 2.5 mm, and a pattern width of 3 mm. Was.
The disc-shaped zirconia sintered body had a surface made of a blue zirconia sintered body, and had a pattern made of an orange zirconia sintered body on the surface.
The interface of the disc-shaped zirconia sintered body was visually confirmed. As a result, it was confirmed that the orange color of the interface was not blurred and the interface had no color blur.
Further, the interface of the disc-shaped zirconia sintered body was observed with an optical microscope and SEM observation. As a result, it was confirmed that the orange zirconia and the blue zirconia were sintered to form an interface, that no gap was formed at the interface, and that there was no bonding layer.

Comparative Example 1
In accordance with the method described in Patent Document 3, a multicolor ceramic molded article was produced.
Two kinds of compositions were obtained by mixing 1000 g of a 3 mol% yttria-stabilized zirconia powder, a coloring material, and an acrylic binder. A composition using 20 g of FeCrNi spinel as a coloring material was used as a black zirconia raw material, and a composition using 14 g of CoAl as a coloring material was used as a blue zirconia raw material.
After the blue zirconia raw material was converted into a bezel ring-shaped blue zirconia molded body having a convex portion by injection molding, the black zirconia raw material was injection-molded on the blue zirconia molded body under a pressure of 100 MPa. In this way, a molded body in which the black zirconia molded body was laminated on the blue zirconia molded body and the two were joined was obtained.
After the obtained molded body was degreased, it was fired in the air at a heating rate of 100 ° C./h, at a firing temperature of 1500 ° C., and at a sintering time of 20 minutes to obtain a multicolor ceramic molded product of this comparative example. . The relative density of the obtained ceramic shaped article was 99.8%, and it was confirmed that the article had a high density.
The multicolor ceramic molded article of this comparative example was processed until an interface between the black zirconia sintered body and the blue zirconia sintered body was confirmed, and the interface was observed with an optical microscope and an SEM. FIG. 12A shows the observation result of the optical microscope. From FIG. 12A, it was confirmed that a gap was formed between the black zirconia sintered body and the blue zirconia sintered body (arrow portion in FIG. 12A). FIG. 12B shows a SEM observation diagram of the gap. It was confirmed that the gap had a width of 40 μm or more.

Comparative Example 2
A multicolor ceramic molded article of this comparative example was produced in the same manner as in Comparative Example 1 except that the firing time was set to 2 hours, and the interface between the black zirconia sintered body and the blue zirconia sintered body was confirmed by SEM. . FIG. 13 shows the results.
From FIG. 13, it was confirmed that a gap exceeding 40 μm was generated between the black zirconia sintered body and the blue zirconia sintered body. In addition, visual observation confirmed that the interface was blurred in blue and that the interface had color bleeding.

Comparative Example 3
A multicolor ceramic molded article of this comparative example was prepared in the same manner as in Comparative Example 1 except that the firing time was set to 4 hours, and an optical microscope photograph of an interface between a black zirconia sintered body and a blue zirconia sintered body was obtained. As shown in FIGS. From FIG. 14, it was confirmed that a gap was formed between the black zirconia sintered body and the blue zirconia sintered body (arrow portion in FIG. 14). Also, from FIG. 15, the interface was confirmed in the multicolor ceramic molded article of this comparative example, but it was confirmed that the interface itself had a width and color bleeding occurred (in FIG. 15, the dashed square portion). ). From this, it was confirmed that the ceramic modeled product of this comparative example had both gaps and color blur at the interface.
From the results of Comparative Examples 1 to 3, it was confirmed that a clear interface was formed by insufficient sintering under the control based on the firing time, and the interface became unclear due to color bleeding as sintering proceeded.

  The zirconia sintered body of the present invention can be widely used for watch parts, decorative articles, portable equipment parts, vehicle-mounted parts, high-grade daily parts, and the like. In particular, the zirconia sintered body of the present invention can be used for watch parts such as watch bands, bezels, dials, watch cases, broochs, tie pins, handbag fittings, bracelets and other decorative parts, portable electronic device housings, lighter cases, and cosmetics. It can be used for exterior parts such as cases, mobile phone cases and earphone housings, as well as daily necessities such as knives and cooking utensils, as well as logos of various products.

(1) Light-colored sintered body (2) Dark-colored sintered body (3) Interface (4) Area of light-colored sintered body at a certain distance from the interface (5) ..A 10-μm-diameter circle formed around a region of the light-colored sintered body at a certain distance from the interface

Claims (9)

A zirconia sintered body including a first zirconia sintered body and a second zirconia sintered body, wherein the first zirconia sintered body is made of Ce, Pr, Nd, Eu, Tb, Ho, Er, Yb and a zirconia sintered body containing any one or more lanthanides of the group consisting of gd, a zirconia sintered body which said second zirconia sintered body contains a spinel oxide containing cobalt and aluminum, the a spinel oxide is CoAl ₂ O _4, said first zirconia sintered body and the said second zirconia sintered body have a surface, of said first zirconia sintered body from the interface within 100μm include cobalt in the region, the cobalt is 0.5% by weight or less contained in the region, zirconia sintered body in which the interface is characterized in that no bleeding gap and color. The zirconia sintered body of one of the first zirconia sintered body and the second zirconia sintered body has a pattern formed on the surface of the other zirconia sintered body. 2. The zirconia sintered body according to 1. The zirconia sintered body according to claim 1, wherein the relative density is 99.5% or more. The lanthanoid of any one of the group consisting of Ce, Pr, Nd, Eu, Tb, Ho, Er, Yb and Gd is contained in an amount of 0.1% by weight or more and 6% by weight or less. The zirconia sintered body according to any one of claims 3 to 3 . The zirconia sintered body according to any one of claims 1 to 4 , wherein the first zirconia sintered body contains alumina. The zirconia sintered body according to claim 5 , wherein the first zirconia sintered body contains 0.5% by weight or less of alumina with respect to zirconia in the first zirconia sintered body. Zirconia powder containing one or more lanthanoids selected from the group consisting of Ce, Pr, Nd, Eu, Tb, Ho, Er, Yb and Gd, or zirconia containing spinel oxide containing cobalt and aluminum A primary molding step of molding either zirconia powder of the powder to obtain a primary molded body, a secondary molding of molding the other zirconia powder on the primary molded body at a molding temperature equal to or less than the primary molding step to obtain a secondary molded body A forming step, a sintering step of firing the secondary formed body at 1300 ° C. or more to obtain a pre-sintered body, and hot isostatic pressing the pre-sintered body at 1250 ° C. to 1650 ° C. and 100 MPa to 250 MPa. The method for producing a zirconia sintered body according to any one of claims 1 to 6 , comprising a HIP treatment step of treating. The method according to claim 7 , wherein the molding in the secondary molding step is injection molding. A member comprising the zirconia sintered body according to any one of claims 1 to 6 .

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