Method for manufacturing a ceramic product

Abstract

To provide a ceramic product having sufficient chemical resistance and capable of suppressing breakage of ornamental films during cleaning.SOLUTION: A ceramic product having ornamental films that include noble metal elements and matrix-forming elements is provided. The matrix-forming elements of the ceramic product include at least rare earth elements. The ceramic product of the present disclosure has a mass concentration CN of noble metal elements obtained in FESEM-EDS analysis intended for surfaces of the ornamental films of 11% or over and 70% or under, a ratio of mass concentration CR of the rare earth elements to mass concentration CN of the noble metal elements, (CR / CN), of 0.01 or over and 0.18 or under. The ornamental films of the ceramic product have alkali resistance and acid resistance both at a high level, thus have sufficient chemical resistance, so that breakage of the ornamental films during cleaning can be suppressed.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to ceramic products. Specifically, it relates to ceramic products having a decorative film containing noble metal elements and matrix-forming elements. Note that this application claims priority based on Japanese Patent Application No. 2021-140391 filed on August 30, 2021, and the entire contents of that application are incorporated herein by reference.

Background Art

[0002] On the surface of ceramic products such as ceramics, glassware, and enamelware, a decorative film containing noble metal elements may be formed to give an elegant or luxurious impression. This type of decorative film is formed by performing a firing process after applying a decorative composition containing predetermined components to the surface of the ceramic product. As an example of such a decorative composition, a metal resinate (an organic compound of a metal) containing noble metal elements and matrix-forming elements can be mentioned. When such a decorative composition is fired, a decorative film including an amorphous region and a noble metal region is formed. In this amorphous region, an amorphous matrix (typically a glass matrix) having oxides of predetermined metal elements and metalloid elements (matrix-forming elements) as a skeleton is formed.

[0003] Among this type of ceramic products, there are those (such as tableware, etc.) that are assumed to be heated in a microwave oven. If the decorative film of this ceramic product contains a large amount of noble metal, there is a risk that a spark may occur due to high-frequency electromagnetic waves (for example, about 2.45 GHz) and the decorative film may be damaged. For this reason, in recent years, microwave-compatible ceramic products with a reduced noble metal content in the decorative film have been proposed. An example of a decorative composition (top-coating paste) for forming this type of decorative film is disclosed in Patent Document 1. In the top-coating paste described in Patent Document 1, the content of the noble metal powder is adjusted to be 20% by weight or more and less than 50% by weight, and the particle size of the noble metal powder is adjusted to be 0.4 μm or more and 2 μm or less. When such a top-coating paste is fired, a noble metal layer dispersed in a polka dot pattern is formed on the surface of an insulating article (substrate).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in recent years, the development of a technology that can appropriately prevent damage (such as peeling and cracking) of the decorative film when cleaning ceramic products has been desired. Specifically, since the amorphous region of the decorative film has poor chemical resistance, it may be damaged when cleaning in a high-temperature environment using a strong alkaline detergent (for example, cleaning by an automatic dishwashing machine) or when immersed in an acidic detergent for a long period of time. In particular, the decorative film of a ceramic product compatible with a microwave oven has lost the continuity of the noble metal region, and the amorphous region is likely to be exposed, so the above-described damage during cleaning tends to occur more easily.

[0007] In order to solve the above problems, the present inventor considered incorporating rare earth elements into the amorphous region of the decorative film. Specifically, it is known that by causing rare earth elements to exist in an amorphous matrix, the alkali resistance of an amorphous material such as glass can be improved (see Non-Patent Document 1). It is considered that such an alkali resistance improvement effect is caused by the fact that the network structure is tightened when rare earth elements with high oxygen affinity are doped into the amorphous matrix, suppressing the intrusion of alkali ions. In addition, rare earth oxides are considered to have an effect of suppressing alkali erosion because they remain and form a film even after other components elute due to exposure to an alkaline agent. However, in the ceramic product having the above configuration, there were cases where a decorative film having sufficient alkali resistance could not be formed despite containing rare earth elements in the amorphous region.

[0008] The present invention has been made in view of the above circumstances, and an object thereof is to provide a ceramic product having sufficient chemical resistance and capable of suppressing damage to the decorative film during washing.

Means for Solving the Problems

[0009] As a result of various studies conducted by the present inventor to solve the above problems, it was discovered that the decorative film of the ceramic product having the above configuration contains noble metal elements and thus is more likely to have reduced alkali resistance than ordinary amorphous materials. Specifically, noble metal elements are added to the decorative film of the ceramic product to produce excellent aesthetics. However, since this type of noble metal element has a strong catalytic action, it may promote a decrease in alkali resistance due to hydrolysis of the amorphous matrix. On the other hand, a decorative film to which a large amount of rare earth elements are added to compensate for the alkali resistance reduced by the noble metal element may have a significant decrease in acid resistance. That is, in order to improve the overall chemical resistance of the decorative film of the ceramic product, the ratio (C N / C R ) of the mass concentration C R of the noble metal element to the mass concentration C N of the rare earth element needs to be appropriately controlled.

[0010] The technology disclosed herein has been made based on the above findings. The technology disclosed herein provides a ceramic product having a decorative film containing a precious metal element and a matrix-forming element. The matrix-forming element of the ceramic product contains at least a rare earth element. The ceramic product disclosed herein has a mass concentration C of the precious metal element obtained by FESEM-EDS analysis of the surface of the decorative film. N is 11% or more and 70% or less, and the mass concentration of the precious metal element C N Mass concentration of rare earth elements C R The ratio of (C R / C N ) is greater than or equal to 0.01 and less than or equal to 0.18.

[0011] The ceramic product disclosed herein has a mass concentration of precious metal elements C N Mass concentration of rare earth elements C R The ratio of (C R / C N ) is 0.01 or more. This allows the presence of a certain amount of rare earth elements, which are a factor in improving alkali resistance, in contrast to the presence of precious metal elements, which are a factor in reducing alkali resistance, so that the alkali resistance of the decorative film can be maintained within a suitable range. R / C N The upper limit of the rare earth element content is set to 0.18 or less. This makes it possible to suppress the deterioration of acid resistance caused by the presence of a large amount of rare earth element.

[0012] In addition, as a result of experiments conducted by the inventors, the mass concentration C N It has been confirmed that if the mass concentration C of the precious metal element is too low, the chemical resistance (especially the acid resistance) of the decorative film is reduced. NIf it becomes too much, it has been confirmed that the gloss of the decorative film is greatly reduced and the aesthetics of the ceramic product are impaired. Considering these points, in the ceramic product disclosed herein, the mass concentration C of the noble metal element in the FESEM-EDS analysis targeting the surface of the decorative film N is controlled to be 11% or more and 70% or less.

[0013] In addition, the "mass concentration" in this specification is the relative mass of any metal element (or metalloid element) when the "total mass of metal elements and metalloid elements" obtained by performing FESEM-EDS (field emission scanning electron microscope - energy dispersive X-ray analysis) on the surface of the decorative film is set to 100%. The measurement procedure for such "mass concentration" is as follows. First, the surface (typically a flat surface) of the decorative film is observed using a field emission scanning electron microscope (FESEM) equipped with an energy dispersive X-ray analysis (EDS) device. Then, after adjusting the observation position so that the decorative film appears in the entire field of view at a magnification of 5000 times (field of view: 25.5 μm × 19.2 μm), a qualitative analysis chart of metal elements and metalloid elements is obtained using the EDS device. Then, metal elements and metalloid elements are specified in the obtained qualitative analysis chart, and the relative concentration of the desired element is calculated based on a predetermined quantitative correction method (for example, the standardless method). Thereby, the mass concentration of the desired element can be obtained. In the FESEM-EDS analysis targeting the surface of the decorative film, since elements located at a depth of several hundred nm to about 1000 nm from the surface of the decorative film are detected, the constituent elements of the layer (substrate or coating layer) located below the decorative film may be reflected in the measurement results. That is, the "mass concentration" in this specification means the "mass concentration of any element detected in the FESEM-EDS analysis targeting the surface of the decorative film", not the "mass concentration of any element contained in the decorative film". It has been confirmed by the experiments of the inventor that by satisfying the above conditions for the mass concentration of a predetermined element in the FESEM-EDS analysis targeting the surface of the decorative film, a ceramic product having sufficient chemical resistance and capable of suppressing damage to the decorative film during cleaning can be obtained.

[0014] In a preferred embodiment of the ceramic product disclosed herein, the matrix-forming element further contains at least one of the first elements consisting of Zr, Ti, and Co. These first elements can contribute to improving the chemical resistance of the decorative film.

[0015] Also, in the embodiment where the first element is included in the decorative film, the mass concentration C of the rare earth element obtained in the FESEM-EDS analysis of the surface of the decorative film R with respect to the mass concentration C of the first element 1 The ratio (C 1 / C R ) is preferably 3 or less. As described above, the first element can contribute to improving the chemical resistance of the decorative film. However, if the mass concentration C of the first element 1 becomes too high, the mass concentration C of the rare earth element R will be insufficient, so there is a risk that the alkali resistance will instead decrease. From this perspective, in this embodiment, the upper limit value of the above C 1 / C R is restricted.

[0016] In a preferred embodiment of the ceramic product disclosed herein, the decorative film contains at least one selected from the group consisting of Pt, Au, Pd, Rh, Ir, and Ag as noble metal elements. These noble metal elements can contribute to the formation of a decorative film with excellent aesthetics.

[0017] In a preferred embodiment of the ceramic product disclosed herein, the ratio (C N of the mass concentration C of Pt to the mass concentration C of the noble metal element Pt is 0.75 or more. Platinum (Pt) exhibits particularly excellent color development among the above noble metal elements, so it can be suitably used for the formation of a decorative film with excellent aesthetics. However, since Pt has a stronger catalytic action than other noble metal elements (such as Au, etc.), it is particularly likely to promote the hydrolysis of the amorphous matrix. However, in the technology disclosed herein, as described above, the ratio (C Pt / C N ) of the mass concentration C of the noble metal element to the mass concentration C of the rare earth element N with respect to R is R / CN ) is properly controlled, so that even when the main component of the noble metal element is Pt, a decorative film having sufficient alkali resistance can be formed.

[0018] In a preferred embodiment of the ceramic product disclosed herein, the decorative film contains at least one selected from the group consisting of Y, Sm, La, Ce, Pr, Nd, and Dy as rare earth elements. By containing these rare earth elements, a decrease in alkali resistance due to the noble metal element can be particularly preferably suppressed.

[0019] In a preferred embodiment of the ceramic product disclosed herein, the matrix-forming element further contains at least one of the second elements consisting of Si, Al, K, Na, Mg, Ca, Ga, Ba, and Bi. Thereby, an appropriate amorphous matrix can be constructed for the decorative film.

[0020] In a preferred embodiment of the ceramic product disclosed herein, the decorative film includes a noble metal region containing a noble metal element as a main component and an amorphous region containing a matrix-forming element as a main component, and a plurality of noble metal regions are scattered in the amorphous region. Thereby, each noble metal region can be insulated by the amorphous region, so that damage to the decorative film due to sparks during use of a microwave oven can be prevented. Note that, for the microwave oven-compatible ceramic product having the above configuration, since the exposure amount of the amorphous region is large, the chemical resistance of the decorative film is likely to decrease. However, according to the technology disclosed herein, a decorative film having sufficient chemical resistance can be formed even for this type of microwave oven-compatible ceramic product.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0022] Hereinafter, preferred embodiments of the technology disclosed herein will be described. Matters other than those specifically mentioned in this specification and necessary for implementation (for example, detailed preparation means of decorative compositions, manufacturing procedures of ceramic products, etc.) can be understood based on the technical content taught by this specification and the general common technical knowledge of those skilled in the art in this field. The content of the technology disclosed here can be implemented based on the content disclosed in this specification and the common technical knowledge in this field. Note that the notation "A to B" indicating a range in this specification means A or more and B or less. Therefore, it includes cases where it exceeds A and is less than B.

[0023] <Ceramic product> Hereinafter, an embodiment of the ceramic product disclosed herein will be described. FIG. 1 is a diagram schematically showing the cross-sectional structure of the ceramic product according to this embodiment. As shown in FIG. 1, this ceramic product 1 includes a base material 10, a coat layer 20, and a decorative film 30. Hereinafter, each will be specifically described.

[0024] 1. Base material The base material 10 is a molded body mainly composed of ceramics. Examples of the ceramics for such a base material 10 include silica, alumina, zirconia, ceria, yttria, boria, magnesia, calcia, and the like. Note that the thickness, shape, color, hardness, etc. of the base material 10 can be appropriately changed according to the use of the ceramic product 1, and since it does not limit the technology disclosed here, detailed description is omitted.

[0025] 2. Coat layer The coating layer 20 is a layer mainly composed of an amorphous material (typically glass), and is formed on the surface of the base material 10 for improving the aesthetics (especially gloss) and protecting the base material 10. This coating layer 20 is formed, for example, by applying a glaze to the surface of the base material 10 and then firing it. Such a glaze is a chemical containing metal elements and metalloid elements that become oxides and form an amorphous matrix when fired. This glaze may contain the same elements as those contained in the amorphous region 34 of the decorative film 30, or may contain different elements.

[0026] Note that the composition of the coating layer 20 is not particularly limited as long as it does not significantly inhibit the effects of the technology disclosed herein, and conventionally known components that can be used for the protective layer of a ceramic base material can be appropriately selected. As an example, the coating layer 20 can have Si, Al, Fe, Mg, Na, Zn, K, Ca, Sn, etc. as substantial constituent elements. And these constituent elements can construct an amorphous matrix in the form of oxides. That is, the coating layer 20 can have an amorphous matrix containing silicon oxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), iron oxide (Fe 2 O 3 ), magnesium oxide (MgO), sodium oxide (Na 2 O), zinc oxide (ZnO), potassium oxide (K 2 O), calcium oxide (CaO), tin oxide (SnO 2 ), etc. Note that since the abundance ratios of the above-described respective elements in the coating layer 20 do not limit the technology disclosed herein, detailed description thereof is omitted.

[0027] 3. Decorative film As shown in FIG. 1, the ceramic product 1 according to the present embodiment has a decorative film 30. Such a decorative film 30 is formed on the surface of the coat layer 20. Although not shown, the decorative film 30 is formed to exhibit a desired pattern (including characters and pictures) in a plan view for the purpose of improving the aesthetic appearance of the ceramic product 1. Further, this decorative film 30 contains a noble metal element and a matrix forming element, which will be described later. Typically, the decorative film 30 includes a noble metal region 32 and an amorphous region 34.

[0028] The noble metal region 32 is a region containing the noble metal elements described below as the main components. This noble metal region 32 mainly contributes to the coloring of the decorative film 30. In this specification, the "noble metal region containing noble metal elements as the main components" refers to the region with the highest luminance at the peak of the histogram obtained by image analysis of the cross-section of the ceramic product. In such image analysis, first, the ceramic product is cut along the thickness direction of the decorative film, and after fixing the cut surface by resin embedding treatment, it is polished by ion milling. Next, while the sample stage is fixed with carbon tape so that the polished surface faces upward, it is coated using an osmium plasma coater (manufactured by Nippon Laser & Electronics Co., Ltd.: OPC80N) to produce a measurement sample with the cut surface coated with osmium. In the osmium coating, the discharge voltage is 1.2 kV, the degree of vacuum is 6 - 8 Pa, and the coating time is 10 seconds. Next, using a field emission scanning electron microscope (manufactured by Hitachi High-Tech Corporation: SU8230), a secondary electron image of the cut surface of the decorative film is acquired. In the acquisition of the secondary electron image, the acceleration voltage is 2.0 kV, the emission current is 10 ± 0.5 μA, and the magnification is 50,000 - 100,000 times. Next, for the acquired secondary electron image, noise removal is performed using image processing software image J (ver. 1.53e) with a Gaussian filter set to sigma = 2 - 5. In this specification, the region where the luminance value in the image after this noise removal is 125 or more is regarded as the "noble metal region containing noble metal elements as the main components". When the luminance value of the image after the above noise removal is plotted on the horizontal axis and the count number is plotted on the vertical axis to form a histogram, four peaks with different luminances are confirmed (see Figure 2). And these four peaks correspond to four regions, namely, the embedding resin, the base material, the amorphous region, and the noble metal region, in ascending order of luminance, and the region with the highest luminance corresponds to the noble metal region. The threshold value (luminance of 125 or more in Figure 2) for determining whether it is the above noble metal region is set based on such histogram analysis.

[0029] On the one hand, the amorphous region 34 is a region that contributes to the fixing and protection of the noble metal region 32. An amorphous matrix with the oxide of the matrix-forming element as the backbone is formed in this amorphous region 34. In this specification, the "matrix-forming element" is a concept that includes metal elements and metalloid elements capable of constructing an amorphous matrix in the state of an oxide. Further, the "amorphous matrix" refers to a structure in which amorphous oxides (oxides with an amorphous structure) of predetermined metal elements and metalloid elements form the backbone, and various metal elements (or metalloid elements) exist in the backbone in the form of oxides or cations. An example of a material (amorphous material) having such an amorphous matrix is glass. The "amorphous region containing the matrix-forming element as the main component" in this specification is the region where the second highest brightness is confirmed in the image analysis of the cross-section of the above-described ceramic product.

[0030] Also, the decorative film 30 is not limited to a layer composed only of the noble metal region 32 and the amorphous region 34 as shown in FIG. 1. For example, particles (crystalline particles) mainly composed of a crystalline metal oxide may be dispersed in the amorphous region 34. Even when the decorative film 30 containing such crystalline particles is formed, the effects of the technology disclosed herein (improvement in chemical resistance) can be appropriately exhibited.

[0031] The thickness T of the decorative film 30 is preferably 30 nm or more and 250 nm or less. While the ceramic product 1 formed with such a thin decorative film 30 can achieve excellent aesthetics at low cost, the decorative film 30 is very likely to peel off, and even a slight peeling of the decorative film 30 may significantly impair the aesthetics. However, according to the technology disclosed herein, the chemical resistance of the decorative film 30 can be improved, and peeling of the decorative film 30 due to exposure to chemicals (such as detergents) can be suppressed. That is, the technology disclosed herein can be particularly preferably applied to the ceramic product 1 having a thin decorative film 30. Note that the "thickness T of the decorative film" in this specification refers to the distance from the surface 30a of the decorative film 30 to the deepest position where the noble metal region 32 exists, as shown in FIG. 1. When the coating layer 20 mainly composed of an amorphous material exists between the base material 10 and the decorative film 30 as in the present embodiment, a clear boundary may not occur between the decorative film 30 (amorphous region 34) and the coating layer 20. For this reason, in this specification, for convenience, the portion where the noble metal region 32 exists is regarded as the decorative film 30.

[0032] In the ceramic product 1 shown in FIG. 1, a plurality of noble metal regions 32 are scattered in the amorphous region 34. As a result, since each noble metal region 32 is insulated by the amorphous region 34, it is possible to appropriately prevent a spark from occurring when using a microwave oven. On the other hand, this type of microwave oven-compatible ceramic product has a large exposed amount of the amorphous region, so the chemical resistance of the decorative film is likely to decrease. However, the ceramic product 1 according to the present embodiment has a decorative film 30 with excellent chemical resistance despite being a microwave oven-compatible ceramic product. Hereinafter, the composition of the decorative film 30 that realizes such excellent chemical resistance will be described.

[0033] (1) Noble metal element The noble metal element is a component that contributes to the coloring of the decorative film 30. As described above, the noble metal element is the main component of the noble metal region 32. However, the position where the noble metal element exists within the decorative film 30 is not a limiting factor for the technology disclosed herein. That is, depending on the manufacturing conditions, a part of the noble metal element may be mixed into the amorphous region 34. Examples of this noble metal element include platinum (Pt), gold (Au), palladium (Pd), rhodium (Rh), iridium (Ir), silver (Ag), ruthenium (Ru), osmium (Os), and the like.

[0034] Here, the ceramic product 1 according to the present embodiment has a first feature that the mass concentration C of the noble metal element in the FESEM-EDS analysis targeting the surface 30a of the decorative film 30 N is controlled to be 11% or more and 70% or less. As a result, a significant decrease in chemical resistance (especially acid resistance) is suppressed, and a decorative film 30 with excellent aesthetics can be formed. Specifically, the mass concentration C of the noble metal element in the FESEM-EDS analysis targeting the surface 30a of the decorative film 30 N When it decreases, it has been experimentally confirmed that while the decrease in alkali resistance due to the catalytic action of the noble metal element is less likely to occur, the acid resistance of the decorative film 30 is likely to decrease. In contrast, in the present embodiment, by setting the mass concentration C of the noble metal element N to 11% or more, a significant decrease in acid resistance is prevented. From the viewpoint of forming a decorative film 30 having more excellent acid resistance, the mass concentration C of the noble metal element N is preferably 11.5% or more, more preferably 12% or more, further preferably 12.5% or more, and particularly preferably 13% or more. Also, when the amount of the noble metal element contained in the decorative film 30 decreases, there is a possibility that the aesthetics of the ceramic product 1 may deteriorate due to the decrease in the coloring component. However, it has also been confirmed that when the mass concentration C of the noble metal element in the FESEM-EDS analysis targeting the surface 30a of the decorative film 30 N is 11% or more, a decorative film 30 with suitable coloring can be formed.

[0035] On the other hand, the mass concentration C of the noble metal element NIf it becomes too much, it has been confirmed that the gloss of the decorative film 30 decreases and the appearance of the ceramic product 1 is impaired. This is presumably because in a decorative film with an excessive abundance of noble metal elements, the particle size of the noble metal particles becomes too large due to over-sintering, causing cloudiness in the decorative film. From this perspective, in the present embodiment, the mass concentration C of the noble metal element N is controlled to be 70% or less. From the viewpoint of obtaining a ceramic product 1 with more excellent appearance, the mass concentration C of the noble metal element N is preferably 69.5% or less, more preferably 69% or less, still more preferably 68.5% or less, and particularly preferably 68% or less.

[0036] In addition, platinum (Pt) exhibits particularly excellent color development among the above-described noble metal elements, and thus is suitable for forming a decorative film 30 with excellent appearance. For example, the ceramic product 1 corresponding to a microwave oven as in the present embodiment has a problem that the decorative film 30 tends to look dark because the continuity of the noble metal region 32 is lost. However, by using Pt as the main component of the noble metal element, even in the ceramic product 1 corresponding to a microwave oven, a decorative film 30 with excellent color development can be formed. On the other hand, since Pt has a stronger catalytic action than other noble metal elements (e.g., Au, etc.), it particularly easily promotes a decrease in alkali resistance due to hydrolysis of the amorphous matrix. However, in the ceramic product 1 according to the present embodiment, the ratio of C R / C N described later is controlled within an appropriate range so as to compensate for the decrease in alkali resistance of the decorative film 30 due to the noble metal element (Pt). Therefore, according to the present embodiment, even when Pt is used as the main component of the noble metal element, a decorative film 30 having sufficient alkali resistance and excellent color development can be formed. Note that "including Pt as the main component of the noble metal element" in the present specification means the ratio (C N of the mass concentration C of Pt to the mass concentration C of all noble metal elements confirmed by FESEM-EDS analysis targeting the surface of the decorative film Pt (C Pt / C N ) is 0.75 or more (preferably 0.85 or more, more preferably 0.95 or more).

[0037] (2) Matrix-forming element As described above, the matrix-forming element is a metal element or a metalloid element that can construct an amorphous matrix in the state of an oxide. However, similar to the above noble metal elements, the position where the matrix-forming element exists in the decorative film 30 does not limit the technology disclosed herein. That is, depending on the manufacturing conditions, a part of the element that can be regarded as a matrix-forming element may be mixed into the noble metal region 32. Examples of this matrix-forming element include Al, Ti, Zr, Si, Bi, Sm, Y, La, Ce, Pr, Nd, Sm, Dy, Sn, Zn, Be, Mg, Ca, Sr, Ba, Li, Na, K, Rb, B, V, Fe, Cu, P, Sc, Pm, Eu, Gd, Tb, Ho, Er, Tm, Yb, Lu, Ni, In, Co, Cr, etc. Among the above-mentioned noble metal elements, there are also elements (such as Ag) that are partially oxidized in the firing process to form an amorphous matrix. However, in this specification, for the sake of convenience, the elements listed in the above (1) noble metal elements are not regarded as matrix-forming elements. That is, the "mass concentration C of the matrix-forming element" in this specification M refers to the mass concentration of elements excluding noble metal elements among metal elements and metalloid elements that can form an amorphous matrix.

[0038] Although it does not limit the technology disclosed herein, the mass concentration C of the matrix-forming element in the FESEM-EDS analysis targeting the surface 30a of the decorative film 30 M is preferably 20% or more, more preferably 22.5% or more, further preferably 25% or more, and particularly preferably 27.5% or more. Thereby, a decorative film 30 having a sufficient amorphous region 34 and exhibiting excellent gloss can be formed. On the other hand, the mass concentration C of the above matrix-forming element M is preferably 50% or less, more preferably 47.5% or less, and particularly preferably 45% or less. Thereby, a noble metal region 32 of a certain level or more can be ensured, and a decorative film 30 excellent in color development can be formed.

[0039] Next, the elements that can be included in the decorative film 30 as matrix-forming elements will be specifically described.

[0040] (a) Rare earth elements First, the decorative film 30 in the present embodiment contains at least rare earth elements as matrix-forming elements. The rare earth elements can be selected without particular limitation from scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu). Since these rare earth elements have a high oxygen affinity, they can tighten the network structure by being doped into the amorphous matrix. Further, the rare earth oxide remains and forms a film even after other components are eluted by the exposure to an alkaline agent. Thereby, it is possible to suppress the intrusion of alkali into the amorphous region 34 and damage to the decorative film 30. Among the above-mentioned rare earth elements, Y, Sm, La, Ce, Pr, Nd, and Dy can appropriately improve the alkali resistance of the decorative film 30. In particular, Sm, La, Ce, Pr, Nd, and Dy can sufficiently improve the alkali resistance with a relatively small amount.

[0041] Here, the ceramic product 1 according to the present embodiment has a second feature that in the FESEM-EDS analysis of the surface 30a of the decorative film 30, the ratio (C N of the mass concentration C of the rare earth element to the mass concentration C of the noble metal element R (C R / C N ) is configured to be 0.01 or more and 0.18 or less. First, the decorative film 30 in which the above C R / C N is 0.01 or more contains a certain amount or more of rare earth elements, which are factors for improving alkali resistance, with respect to noble metal elements, which are factors for reducing alkali resistance. Therefore, the alkali resistance can be maintained within a suitable range. From the viewpoint of realizing a decorative film 30 having more excellent alkali resistance, the above CR / C N is preferably 0.012 or more, more preferably 0.014 or more, still more preferably 0.016 or more, and particularly preferably 0.018 or more. On the other hand, the decorative film 30 containing excessive rare earth elements may significantly reduce the acid resistance. Considering such a decrease in acid resistance, in the ceramic product 1 according to the present embodiment, the above C R / C N is defined to have an upper limit value of 0.18 or less. From the viewpoint of realizing a decorative film 30 having more excellent acid resistance, the above C R / C N is preferably 0.17 or less, more preferably 0.16 or less, and still more preferably 0.15 or less. In the technology disclosed herein, the mass concentration C N of the noble metal element satisfies 11% or more and 70% or less, and the above C R / C N only needs to satisfy 0.01 or more and 0.18 or less, and the mass concentration C R itself of the rare earth element is not particularly limited. For example, the mass concentration C R of the rare earth element in the FESEM-EDS analysis targeting the surface 30a of the decorative film 30 may be 0.3% or more, 0.4% or more, or 0.5% or more. On the other hand, the upper limit value of the mass concentration C R of the rare earth element may be 7.5% or less, 6.0% or less, or 5.5% or less.

[0042] (b) First element Further, the decorative film 30 preferably contains at least one of the first elements composed of zirconium (Zr), titanium (Ti), and cobalt (Co). These first elements can contribute to further improving the chemical resistance of the decorative film 30. Although there is no intention to limit the technology disclosed herein, the reason for obtaining such an effect is presumed as follows. First, Zr exists in the amorphous matrix in the state of zirconium oxide (ZrO 2 ), and Ti exists in the amorphous matrix in the state of titanium oxide (TiO 2 ). These ZrO 2 and TiO 2can be combined with the framework of the amorphous matrix (e.g., silicate glass) as an ion that modifies the network structure. And ZrO 2 and TiO 2 have very high chemical resistance as single materials, so they remain after other components are eluted due to exposure to alkaline agents to form a film, contributing to the improvement of the chemical resistance of the decorative film 30. On the other hand, Co exists in the amorphous matrix in the state of cobalt oxide (at least one of CoO, Co 3 O 4 , Co 2 O 3 ). This cobalt oxide can also be combined with the framework of the amorphous matrix as an ion that modifies the network structure. And cobalt oxide can contribute to the improvement of the chemical resistance of the decorative film 30 by strengthening the adhesion between the noble metal region 32 and the amorphous region 34.

[0043] However, if the mass concentration C 1 of the first element in the FESEM-EDS analysis of the surface 30a of the decorative film 30 becomes too high, the mass concentration C R of the rare earth element will relatively decrease. Therefore, it may be difficult to form the decorative film 30 with excellent alkali resistance that satisfies the above C R / C N condition. From this perspective, the ratio (C R / C 1 ) of the mass concentration C 1 / C R ) of the first element to the mass concentration C R / C N of the rare earth element is preferably 3 or less, more preferably 2.9 or less, further preferably 2.8 or less, and particularly preferably 2.7 or less. On the other hand, if the decorative film 30 in this embodiment satisfies the above C 1 / C R condition, it can exhibit a certain level of chemical resistance even without the first element. Therefore, the lower limit value of the above C 1 / C R is not particularly limited, and C 1 / C R may be 0. However, when appropriately exerting the effect of improving chemical resistance by the first element, C 1 / C RIt is preferable to contain the first element so that it is 0.1 or more (more preferably 0.2 or more, still more preferably 0.3 or more, particularly preferably 0.4 or more).

[0044] Incidentally, the mass concentration C of the first element 1 itself is not particularly limited. However, from the viewpoint of more appropriately exerting the effect of improving chemical resistance by the first element, the mass concentration C of the first element 1 is preferably 0.01% or more, more preferably 0.02% or more, and particularly preferably 0.03% or more. On the other hand, from the viewpoint of preventing a relative decrease in the mass concentration C of the rare earth element due to excessive addition of the first element, the mass concentration C of the first element R is preferably 5% or less, more preferably 4% or less, still more preferably 3% or less, and particularly preferably 2% or less. 1

[0045] (c) Second element Next, the matrix-forming element may contain a metal element or a metalloid element other than the rare earth element and the first element as long as it can form an appropriate amorphous matrix in the amorphous region 34. In this specification, such a matrix-forming element other than the rare earth element and the first element is referred to as the "second element". Hereinafter, as an example of such a second element, Si, Al, and Bi will be described.

[0046] First, Si can constitute the skeleton of the amorphous matrix in the amorphous region 34 in the state of silicon oxide (SiO 2 ). Although not limiting the technology disclosed herein, the mass concentration C of Si in the FESEM-EDS analysis targeting the surface 30a of the decorative film 30 Si is preferably 10% or more, more preferably 15% or more, still more preferably 17.5% or more, and particularly preferably 20% or more. Thereby, a strong amorphous matrix having an appropriate skeleton can be formed. On the other hand, from the viewpoint of ensuring other elements (rare earth elements, the first element, etc.) sufficiently, the upper limit of the mass concentration C of the above Si Si is preferably 60% or less, more preferably 59.5% or less, still more preferably 59% or less, and particularly preferably 58.5% or less. ​

[0047] Next, part of the Al forms a composite oxide with other elements (such as Si, rare earth elements, etc.), which can contribute to the improvement of the chemical resistance of the decorative film 30. Although not limiting the technology disclosed herein, from the perspective of obtaining a decorative film 30 with more excellent chemical resistance, the mass concentration C of Al in the FESEM-EDS analysis targeting the surface 30a of the decorative film 30 Al is preferably 1% or more, more preferably 1.5% or more, still more preferably 2% or more, and particularly preferably 2.5% or more. On the other hand, from the perspective of ensuring a sufficient abundance of rare earth elements, the first element, etc., the mass concentration C of the above-mentioned Al Al has an upper limit that is preferably 15% or less, more preferably 14% or less, still more preferably 13.5% or less, and particularly preferably 13% or less.

[0048] Also, Bi forms part of the skeleton of the amorphous matrix in the amorphous region 34 in the state of bismuth oxide (Bi 2 O 3 ). Such Bi 2 O 3 has the effect of softening the amorphous material, so it can contribute to the improvement of the fixing property of the decorative film 30 in the ceramic product 1. In particular, when the decorative film 30 is formed on the surface of the coating layer 20 as in this embodiment, Bi 2 O 3 diffuses toward the coating layer 20 side, and higher fixing property can be obtained. Bi can contribute to preventing the peeling of the decorative film 30 by such an action of improving the fixing property. From the perspective of more preferably exerting the fixing property improvement effect by Bi, the mass concentration C of Bi in the FESEM-EDS analysis targeting the surface 30a of the decorative film 30 Bi is preferably 0.01% or more, more preferably 0.015% or more, and particularly preferably 0.05% or more. On the other hand, from the perspective of ensuring a sufficient abundance of rare earth elements, the first element, etc., the mass concentration C of the above-mentioned Bi Bi is preferably 5% or less, more preferably 4.7% or less, still more preferably 4.5% or less, and particularly preferably 4% or less.

[0049] Note that the above description is not intended to limit the second element to Si, Al, and Bi. Since the impact on the effects of the technology disclosed herein is small, a detailed description is omitted. Examples of the second element other than Si, Al, and Bi include Sn, Zn, Be, Mg, Ca, Sr, Ba, Li, Na, K, Rb, B, V, Fe, Cu, P, Ni, Cr, etc. The mass concentration C of the second element in the FESEM-EDS analysis of the surface 30a of the decorative film 30 2 is preferably 88% or less, more preferably 80% or less, still more preferably 75% or less, and particularly preferably 70% or less. This can prevent the relative decrease in the mass concentration of elements (such as rare earth elements and the first element) that significantly affect the chemical resistance of the decorative film 30. On the other hand, the lower limit of the mass concentration C of the above second element 2 is not particularly limited and may be 20% or more, 25% or more, or 30% or more.

[0050] (3) Non-metallic elements In addition, the decorative film 30 of the ceramic product 1 according to the present embodiment may contain non-metallic elements in addition to noble metal elements and metal elements that form the matrix. For example, as described above, since the matrix-forming element exists in the amorphous region 34 in the form of an oxide, oxygen (O) may be present in the decorative film 30. Also, although details will be described later, various organic materials are added to the decorative composition (paint), which is the precursor of the decorative film 30. The fired decorative film 30 may contain non-metallic elements derived from such organic materials. Examples of this type of non-metallic element include carbon (C), sulfur (S), nitrogen (N), phosphorus (P), etc.

[0051] <Method for manufacturing a ceramic product> Next, an example of a method for manufacturing the ceramic product 1 according to the present embodiment will be described. Note that the ceramic product disclosed herein is not limited to those manufactured by the following manufacturing method.

[0052] When manufacturing the ceramic product 1 according to this embodiment, first, a desired base material 10 is prepared. For example, the base material 10 can be produced by molding and firing a base material material kneaded with a predetermined ceramic component. Also, the base material 10 with the coating layer 20 as shown in FIG. 1 can be produced by applying a glaze to the surface of the fired base material 10 and then firing it again. However, this step is not particularly limited as long as the base material 10 can be prepared. For example, a separately produced base material 10 may be purchased and prepared.

[0053] Next, in the manufacture of the ceramic product 1 according to this embodiment, a decorative film 30 is formed on the base material 10. In the formation of this decorative film 30, a decorative composition (paint) containing a predetermined component is used to draw a desired pattern on the surface of the base material 10, and then a firing process is carried out. In the firing process in this step, it is preferable to set the firing temperature in the range of 700°C to 1000°C. Thereby, the components of the decorative composition can be appropriately sintered to form the decorative film 30.

[0054] The decorative composition used in this embodiment is a paste-like composition containing a noble metal element and a matrix-forming element. In addition, the forms of the noble metal element and the matrix-forming element in this decorative composition are not particularly limited. For example, the noble metal element and the matrix-forming element can take forms such as metal resinates, complexes, polymers, and solids (fine particles). The details of the noble metal element and the matrix-forming element contained in the decorative composition are omitted because they would be redundant explanations.

[0055] In addition, when the firing treatment in this step is carried out, the decorative composition may be mixed with a part of the components of the base layer (base material 10 or coating layer 20) to which the decorative composition is applied. Therefore, the decorative film 30 after the firing treatment contains not only the elements derived from the decorative composition but also the elements derived from the base layer. Furthermore, the degree to which the components of the base layer are mixed into the decorative film can vary depending not only on the components of the decorative composition and the base layer but also on the firing conditions (firing temperature, firing time, etc.). Therefore, when manufacturing the ceramic product disclosed herein, it is preferable to appropriately change various conditions such as the composition of the decorative composition, the composition of the base layer, and the firing conditions, and to appropriately conduct preliminary tests to examine the conditions under which a ceramic product with a desired configuration is formed.

[0056] In addition, it is preferable that various components are added to the decorative composition in consideration of the adhesion to the base material surface and the formability, etc., in addition to the noble metal element and the matrix-forming element. Such additives can be used without particular limitation as conventionally known components that can be used in the decorative composition as long as they do not significantly interfere with the effects of the technology disclosed herein. For example, when each of the noble metal element and the matrix-forming element is contained in the state of a metal resinate, an organic compound for forming the metal resinate is added to the decorative composition. Such an organic compound can be used without particular limitation as a conventionally known resin material that can be used for the production of the metal resinate. Examples of such resin materials include carboxylic acids having a high number of carbon atoms (for example, 8 or more carbon atoms) such as octylic acid (2-ethylhexanoic acid), abietic acid, naphthenic acid, stearic acid, oleic acid, linolenic acid, neodecanoic acid; sulfonic acid; resin acids contained in rosin, etc.; resin sulfide balsams containing essential oil components such as turpentine oil and lavender oil, alkyl mercaptides (alkyl thiolates), aryl mercaptides (aryl thiolates), mercaptocarboxylic acid esters, alkoxides, etc.

[0057] When each of the noble metal element and the matrix forming element is contained in the state of a metal resinate, it is preferable that an organic solvent for dispersing or dissolving the metal resinate is used. As such a solvent, those conventionally used in resinate pastes and those used in gold water solutions can be used without particular limitation. For example, 1,4-dioxane, 1,8-cineole, 2-pyrrolidone, 2-phenylethanol, N-methyl-2-pyrrolidone, p-tolualdehyde, benzyl benzoate, butyl benzoate, eugenol, caprolactone, geraniol, methyl salicylate, cyclohexanone, cyclohexanol, cyclopentyl methyl ether, citronellal, di(2-chloroethyl) ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, dihydrocarboxylic acid, dibromomethane, dimethyl sulfoxide, dimethylformamide, nitrobenzene, pyrrolidone, propylene glycol monophenyl ether, pregone, benzyl acetate, benzyl alcohol, benzaldehyde, turpentine oil, lavender oil, etc. can be mentioned. In addition, these organic solvents may be used alone or in combination of two or more. Since the metal resinate is, for example, commercially available as a resinate paste, such a resinate paste may be used as it is.

[0058] Also, the decorative composition may contain other additional components as long as the effects of the technology disclosed herein are not significantly impaired. Examples of such additional components include, for example, organic binders, protective materials, surfactants, thickeners, pH adjusters, preservatives, defoamers, plasticizers, stabilizers, antioxidants, etc.

[0059] <Other embodiments> Above, one embodiment of the technology disclosed herein has been described. Note that the ceramic product 1 according to the above-described embodiment is an example to which the technology disclosed herein is applied, and does not limit the technology disclosed herein.

[0060] For example, as shown in FIG. 1, the ceramic product 1 according to the above-described embodiment includes a coating layer 20 between a base material 10 and a decorative film 30. However, in the ceramic product disclosed herein, the coating layer 20 is not an essential component. That is, the decorative film may be directly formed on the surface of the ceramic base material. According to the technology disclosed herein, even in a ceramic product in which a decorative film is directly formed on the surface of the base material, a decorative film having sufficient chemical resistance can be formed. Further, as another example of the ceramic product, a mat layer in which predetermined metal oxide particles (for example, zircon particles) are dispersed is formed between the base material and the decorative film, and the gloss of the decorative film is intentionally reduced. Furthermore, as another example of the ceramic product, a paint layer is formed between the base material and the coating layer to form a three-dimensional decorative film. The technology disclosed herein can be applied to these configurations of ceramic products without particular limitation.

[0061] Also, as shown in FIG. 1, the ceramic product 1 according to the above-described embodiment is a ceramic product corresponding to a microwave oven in which a plurality of noble metal regions 32 are scattered in an amorphous region 34. However, according to the technology disclosed herein, it can also contribute to the realization of a decorative film having excellent chemical resistance in ceramic products other than those corresponding to microwave ovens. However, in the ceramic product 1 corresponding to a microwave oven as shown in FIG. 1, since the exposure amount of the amorphous region 32 is very large, the phenomenon of promoting the hydrolysis of the amorphous matrix due to the catalytic action of the noble metal element is likely to appear in the form of a significant decrease in the alkali resistance of the decorative film 30. Since the technology disclosed herein can appropriately suppress the decrease in alkali resistance due to this noble metal element, it can be particularly preferably applied to ceramic products corresponding to microwave ovens.

[0062] [Test Example] Hereinafter, test examples related to the technology disclosed herein will be described, but it is not intended to limit the technology disclosed herein to such test examples.

[0063] A. First Test In this test, ceramic products (Examples 1 to 23) prepared using 23 types of decorative compositions with different compositions were prepared, and the performance (acid resistance, alkali resistance, gloss of the decorative film) of the ceramic products of each example was examined.

[0064] 1. Preparation of Samples <Fabrication of Ceramic Products> In this test, first, a white porcelain flat plate with a coating layer (length: 15 mm, width: 15 mm) was prepared. Then, a decorative composition containing a noble metal element and a matrix-forming element was applied to the entire surface of one side of this white porcelain flat plate. For the application of this decorative composition, a spin coater (Opticoat MS-A-150) manufactured by Mikasa Co., Ltd. was used, and the spin conditions were adjusted so that the film thickness of the decorative film after firing was within the range of 30 nm to 250 nm. Then, the white porcelain flat plate with the decorative composition applied was dried on a hot plate at 60 °C for 1 hour and then fired at 800 °C for 10 minutes. Thereby, a ceramic product with a decorative film formed on the surface was prepared. The coating layer formed on the white porcelain flat plate is a glaze fired at 1200 °C with the following composition.

[0065] [Composition of Glaze for Forming Coating Layer] SiO 2 : 70.8 wt% Al 2 O 3 : 16.39 wt% Fe 2 O 3 : 0.11 wt% CaO: 4.2 wt% MgO: 3.99 wt% K 2 O: 3.36 wt% Na 2 O: 0.63 wt% ZnO: 0.53 wt%

[0066] And in this test, in each of Examples 1 to 23, the composition of the paint (decorative composition) for forming the decorative film was varied. In the preparation of the decorative composition, various raw materials were blended in an ointment pot, and using a stirrer manufactured by Shinki Co., Ltd. (product name: Rotating and Revolving Mixing Taro), mixing was carried out at a rotational speed of 1800 rpm for 2 minutes. Then, each decorative composition was appropriately diluted so that the viscosity would be in the range of 10 mPa·s to 15 mPa·s. The composition of the decorative composition used in each of Examples 1 to 23 is shown in Table 1. Each element shown in Table 1 was added to the decorative composition in the following forms.

[0067] [Forms of Each Element in the Decorative Composition] Ag: Ag resinate (silver resinate) Au: Au resinate (gold resin sulfide balsam) Pt: Pt resinate (platinum resin sulfide balsam) Rh: Rh resinate (rhodium resin sulfide balsam) Al: Al resinate (aluminum resinate) and aluminum complex Ti: Ti resinate (titanium resinate) and titanium complex Co: Co resinate (cobalt resinate) Si: Si resinate (silicon resinate) Bi: Bi resinate (bismuth resinate) Sm: Sm resinate (samarium resinate) Y: Y resinate (yttrium resinate) La: La resinate (lanthanum resinate) Ce: Ce resinate (cerium resinate) Pr: Pr resinate (praseodymium resinate) Nd: Nd resinate (neodymium resinate) Dy: Dy resinate (dysprosium resinate)

[0068]

Table 1

[0069] 2. Evaluation Test <Measurement of Mass Concentration> Test pieces cut from the ceramic products of Examples 1 to 23 were fixed to the sample stage with carbon tape so that the decorative film faced upward, and coating was performed using an osmium plasma coater (manufactured by Nippon Laser & Electronics Co., Ltd.: OPC80N). As a result, a measurement sample in which the surface of the decorative film was coated with osmium was prepared. In the coating, the discharge voltage was 1.2 kV, the degree of vacuum was 6 to 8 Pa, and the coating time was 10 seconds.

[0070] Next, using a field emission scanning electron microscope (manufactured by Hitachi High-Tech Corporation: SU8230) and an energy dispersive X-ray analyzer (detector manufactured by Horiba, Ltd.: X-Max80, software: EMAX ENERGY version 2.04), qualitative analysis charts of each element on the surface of the decorative film of the measurement sample of each example were obtained. In this test, K lines were used for the analysis of C, O, Na, Mg, Al, Si, K, Ca, Ti, Zn, Ga, and Co. Also, L lines were used for the analysis of Ba, Y, La, Ce, Pr, Nd, Sm, Dy, Pt, Au, and Rh, and M lines were used for the analysis of Bi. Then, based on such qualitative analysis charts, the mass concentration of each element was measured. The mass concentration of each element was calculated by automatic calculation (standardless method) by designating only metal elements and semi-metal elements as target elements in the "quantitative analysis" mode of the EMAX software. The detailed measurement conditions in the above FESEM-EDS analysis are as follows.

[0071] [Detection Conditions] Magnification: 5000 times Accelerating Voltage: 15.0 kV Emission Current: 10 μA Extraction Voltage: 4.2 kV Probe Current Setting: High Condenser Lens 1: 4.0 Working Distance: 15.0 ± 0.5 mm

[0072] [Qualitative Analysis Conditions] Spectrum Collection Time: 60 seconds Process time: 4 Spectral range: 0 - 20 keV Number of channels: 2k

[0073] And in this test, based on the qualitative analysis chart obtained under the above conditions, the mass concentration (%) of each element with respect to the total number of atoms (100%) on the surface of the decorative film was calculated. The calculation results are shown in Table 2.

[0074]

Table 2

[0075] Also, in this test, based on the measured mass concentration of each element, the "mass concentration C of noble metal elements N ", the "ratio (C of the mass concentration C of rare earth elements with respect to the mass concentration C of noble metal elements N R / C R N )", the "ratio (C of the mass concentration C of the first element with respect to the mass concentration C of rare earth elements R 1 / C 1 R )", and the "ratio (C of the mass concentration C of Pt with respect to the mass concentration C of noble metal elements N Pt / C Pt N )" were calculated. The respective calculation results are shown in Table 3.

[0076] <Acid resistance evaluation> A 4 wt% acetic acid aqueous solution was maintained at room temperature (23 - 25 °C), and the test piece was immersed in the acetic acid aqueous solution for 24 hours. Then, the test piece taken out from the acetic acid aqueous solution was washed with water, and a rubbing test of rubbing back and forth 10 times with zircon paper was carried out to observe whether there was damage to the decorative film. And in this test, a sample with 30% or more of the decorative film remaining was regarded as having sufficient acid resistance (○). The evaluation results are shown in Table 3.

[0077] <Alkali resistance evaluation> In this test, a 0.5 wt% Na heated to 100 °C until boiling2 CO 3 The test pieces of each example were immersed in an aqueous solution (3 L) for 30 minutes. Then, the immersed test pieces were washed with water, and a rubbing test was carried out by rubbing back and forth 10 times with zircon paper to observe whether there was damage to the decorative film. In this test, the immersion time was extended in 30-minute units, and the maximum immersion time with 30% or more of the decorative film remaining was regarded as the "durability time (h)". The durability time of each example is shown in Table 3.

[0078] <Gloss Evaluation> Using a spectrophotometer, the gloss value of the decorative part of each example was measured. Specifically, a spectrophotometer (CM-700d) manufactured by Konica Minolta Sensing Inc. was used to measure the L*, a*, b* values and the gloss value representing the 8° glossiness in the SCI and SCE modes. In this evaluation, a decorative part with a gloss value of 500 or more was evaluated as having a suitable gloss. The gloss values of each example are shown in Table 3.

[0079]

Table 3

[0080] As described above, in Examples 1 to 17, decorative films with excellent acid resistance, alkali resistance and gloss value were formed. However, in Examples 22 and 23, most of the decorative film peeled off only by being immersed in an alkaline solution for a short time of 30 minutes. From this, it was found that in order to sufficiently ensure the alkali resistance of the decorative film, it is necessary to ensure a certain level of C R / C N On the other hand, in Example 19 where C R / C N was too high, it was confirmed that the decorative film was easily peeled off by immersion in an acid solution. From this, since rare earth elements have the effect of reducing the acid resistance of the decorative film, in order to obtain a ceramic product with excellent comprehensive chemical resistance, it was found that it is necessary to control C R / C N below a certain level. Also, in Example 18, C R / C NDespite being controlled within an appropriate range, the acid resistance had significantly decreased. From this, it was found that in order to obtain appropriate chemical resistance (acid resistance), it was necessary to ensure that the mass concentration C of the noble metal element N was maintained at a certain level or higher. Furthermore, in Examples 25 and 26, the gloss values were both significantly decreased. From this, it was found that in order to obtain a ceramic product with a predetermined aesthetic appearance, it was necessary to control the mass concentration C of the noble metal element N to a certain level or lower.

[0081] B. Second Test In this test, ceramic products were produced (Examples 24 to 29) using a decorative composition with the same composition for six types of substrates having different base layers. Then, for the ceramic products of each example, acid resistance, alkali resistance, and the gloss of the decorative film were evaluated in the same manner as in the first test.

[0082] 1. Preparation of Samples <Production of Ceramic Products> In Examples 24 to 28, five types of white porcelain plates with different coating layers were prepared. In Example 29, a white porcelain plate with a matte layer in which Zr particles were dispersed was used on the surface. Then, by applying a decorative composition to the surface of each substrate and firing it, a ceramic product having a decorative film was produced. The decorative composition used in this test was the same as the decorative composition used in Example 6 of the first test. Also, the conditions regarding the application and firing treatment of the decorative composition were set to the same conditions as in the first test.

[0083] In Examples 24 to 29, since commercially available tableware was purchased and white porcelain plates were cut out and used, the composition of the chemicals (such as glaze) used for forming the base layer (coating layer or matte layer) was unknown. Therefore, in this test, elemental analysis by FESEM-EDS was performed on the surface of the white porcelain plate before forming the decorative film to examine the composition of the base layer. The results of the FESEM-EDS analysis are shown in Table 4.

[0084]

Table 4

[0085] 2. Evaluation Test In this test, following the same procedure as the above first test, (1) measurement of mass concentration, (2) acid resistance evaluation, (3) alkali resistance evaluation, and (4) gloss evaluation were carried out. The measurement results of the mass concentration are shown in Table 5, and the results of the acid resistance evaluation, alkali resistance evaluation, and gloss evaluation are shown in Table 6. In Example 29, since a matte layer for intentionally reducing the gloss of the decorative film was formed, the gloss value decreased to a state where it could not be measured. Therefore, in the column of the gloss value of Example 29 in Table 6, "-" indicating non-measurable was described.

[0086] Also, in this test, similar to the first test, based on the measurement results of the mass concentration, "mass concentration C of noble metal element N ", "ratio of the mass concentration C of rare earth element to the mass concentration C of noble metal element N (C R / C R )", "ratio of the mass concentration C of the first element to the mass concentration C of rare earth element N (C R / C 1 )", and "ratio of the mass concentration C of Pt to the mass concentration C of noble metal element 1 (C R / C N )" were calculated. These calculation results are shown in Table 6. Pt Pt N / N )" were calculated. These calculation results are shown in Table 6.

[0087]

Table 5

[0088]

Table 6

[0089] As described above, in Examples 24 to 29, although the decorative compositions of the same composition were used, the compositions of the decorative films after firing were different. This is presumably due to the fact that a part of the decorative composition and the base layer were mixed in the firing process and the constituent elements of the base layer were reflected in the FESEM-EDS analysis. However, in the FESEM-EDS analysis of the decorative film after firing, the mass concentration C N of the noble metal element is 11% or more and 70% or less, and the mass concentration C N of the rare earth element with respect to the noble metal element is C R If the ratio (C R / C N ) is 0.01 or more and 0.18 or less, it has been found that even when the decorative composition and the base layer are mixed, a ceramic product having sufficient chemical resistance can be produced.

[0090] C. Third Test In this test, five types of decorative compositions having different compositions from those of the first test were prepared, and ceramic products were produced using each of the decorative compositions (Examples 30 to 34). Then, the acid resistance, alkali resistance, and gloss of the decorative film of each example of the ceramic product were evaluated in the same manner as in the first and second tests.

[0091] 1. Preparation of Samples In this test, a white porcelain flat plate having a coat layer (glaze) of the same composition as that of the first test was prepared. Then, the decorative composition was applied to the entire surface of one side of this white porcelain flat plate. For the application of this decorative composition, a spin coater (Opticoat MS-A-150) manufactured by Mikasa Co., Ltd. was used, and the spin conditions were adjusted so that the film thickness of the decorative film after firing was within the range of 30 nm to 250 nm. Then, in this test, firing treatment was performed under the same conditions as in the first test except that the firing temperature was raised to 850°C. As a result, ceramic products having decorative films formed on their surfaces were produced (Examples 30 to 34). The compositions of the five types of decorative compositions used in this test are as shown in Table 7 below.

[0092]

Table 7

[0093] 2. Evaluation Test In this test, in accordance with the same procedures as in the above-mentioned first and second tests, (1) measurement of mass concentration, (2) acid resistance evaluation, (3) alkali resistance evaluation, and (4) gloss evaluation were carried out. The measurement results of the mass concentration are shown in Table 8, and the results of the acid resistance evaluation, alkali resistance evaluation, and gloss evaluation are shown in Table 9.

[0094] Also, in this test, similar to the first and second tests, based on the measurement results of the mass concentration, "mass concentration C of noble metal elements N ", "ratio of the mass concentration C of rare earth elements to the mass concentration C of noble metal elements N (C R / C R )", "ratio of the mass concentration C of the first element to the mass concentration C of rare earth elements N (C R / C 1 )", and "ratio of the mass concentration C of Pt to the mass concentration C of noble metal elements 1 (C R / C N )" were calculated. These calculation results are shown in Table 9. Pt Pt N

[0095]

Table 8

[0096]

Table 9

[0097] ​​As shown in Table 8, in this test, not only in Example 31 (see Table 7) where bismuth (Bi) was not added to the decorative composition, but also in all of Examples 30 to 34, the presence of bismuth (Bi) in the decorative film was not confirmed. This is presumably because the diffusion of Bi elements during firing was promoted by increasing the firing temperature, resulting in a Bi concentration below the detection limit. On the other hand, in each of Examples 30 to 34, a decorative film with excellent acid resistance, alkali resistance, and gloss value was formed. From this, it was found that if the mass concentration C N is in the range of 11% or more and 70% or less, and C R / C N is in the range of 0.01 or more and 0.18 or less, even if the Bi element has an extremely low concentration below the detection limit, a decorative film with excellent chemical resistance and aesthetic appeal can be formed.

[0098] The specific examples of the technology disclosed herein have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

Explanation of Reference Numerals

[0099] 1 Ceramic product 10 Substrate 20 Coat layer 30 Decorative film 32 Noble metal region 34 Amorphous region

Claims

A preparation step of preparing a substrate, A coating step of applying a decorative composition to the surface of the substrate, A firing step of forming a decorative film on the surface of the substrate by firing the substrate and the decorative composition, and comprising: The decorative composition contains a noble metal element and a matrix-forming element, The noble metal element contains at least platinum, The matrix-forming element contains at least a rare earth element, The content rate of the noble metal element with respect to the total amount of the decorative composition is 62 wt% or more and 87 wt% or less, The thickness of the decorative film after the firing step is 30 nm or more and 250 nm or less, and the ratio (CR / CN) of the mass concentration CR of the rare earth element to the mass concentration CN of the noble metal element obtained in the FESEM-EDS analysis of the surface of the decorative film is 0.01 or more and 0.18 or less. A method for manufacturing a ceramic product that controls the coating step and the firing step. The method for manufacturing a ceramic product according to claim 1, wherein the noble metal element further contains rhodium. The matrix-forming element further contains at least one of a first element composed of Zr, Ti, and Co, The ratio (C1 / CR) of the mass concentration C1 of the first element to the mass concentration CR of the rare earth element obtained in the FESEM-EDS analysis of the surface of the decorative film after the firing step is 0.4 or more and 3 or less. The method for manufacturing a ceramic product according to claim 1. The method for manufacturing a ceramic product according to claim 1, wherein the rare earth element is composed of at least one selected from the group consisting of Y, Sm, La, Pr, Nd, and Dy. The method for manufacturing a ceramic product according to claim 1, wherein a coating layer containing an amorphous material is formed on the surface of the substrate to which the decorative composition is applied. The method for manufacturing a ceramic product according to claim 1, wherein the firing temperature in the firing step is 700°C to 1000°C.

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