Platinum solution for silver decoration and its uses

Abstract

According to the present disclosure, there is provided a feature for realizing a silver-colored ornament that is lustrous and has excellent coloration, without producing sparks due to heating performed using a microwave oven. A platinum liquid disclosed in this feature is used for applying silver-colored decoration to a ceramic substrate and includes at least Pt, Si, and Bi. The platinum liquid is characterized by having, in terms of a mass ratio where the total of Si and metallic elements included in the platinum liquid is deemed to be 100 wt%, a composition that includes: 50-99 wt% of Pt; 0-25.5 wt% in total of Au, Rh, Pd, and Ag (where Rh constitutes 0-8.5 wt%); 11 wt% or less of Si; 10 wt% or less of Bi; 0-5 wt% of Al; and 0-15 wt% of other metallic elements.

Description

[Technical Field]

[0001] This invention relates to a platinum solution for silver-colored decoration. More specifically, it relates to a platinum solution containing Pt that exhibits a silvery hue, and a ceramic product comprising a fired body of such platinum solution. This application claims priority to Japanese Patent Application No. 2021-061387, filed on March 31, 2021, and the entire contents of that application are incorporated herein by reference. [Background technology]

[0002] Some ceramic products, such as porcelain, glass, and tiles, have gold or silver decorations on their surfaces to give them an elegant or luxurious appearance. Some of these ceramic products are intended to be heated in a microwave oven (for example, tableware). Therefore, it is desirable that the decorative parts do not spark when exposed to high-frequency electromagnetic waves (for example, around 2.45 GHz) emitted by a microwave oven. Examples of technologies for realizing such decorative parts are disclosed in Patent Documents 1 and 2. For example, Patent Document 2 discloses a technology for a platinum decorative part that does not spark even when exposed to high-frequency electromagnetic waves emitted by a microwave oven and exhibits a matte platinum color. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent No. 2854813 [Patent Document 2] Japanese Patent Application Publication No. 2001-130985 [Overview of the Initiative]

[0004] Incidentally, there is a desire for decorative parts that do not spark when heated in a microwave oven, have a glossy finish, and exhibit a good silver color. Such decorative parts can result in ceramic products that give an even more elegant or luxurious impression.

[0005] Therefore, the present invention has been made in view of the above circumstances, and its main objective is to provide a platinum liquid that does not spark when heated in a microwave oven, has a glossy finish, and produces a silver-colored decorative part with good color development. Another objective is to provide a ceramic product equipped with a fired body of such platinum liquid.

[0006] To achieve the above objective, the platinum solution disclosed herein is a platinum solution used for silvering ceramic substrates, and contains at least Pt, Si, and Bi, with the following composition in a weight ratio where the total of the metal elements contained in the platinum solution and Si is 100 wt%: Pt 50wt%~99wt%, Total of Au, Rh, Pd, and Ag: 0 wt% to 25.5 wt%, (However, Rh is 0 wt% to 8.5 wt%) Si 11wt% or less, Bi 10wt% or less, Al 0wt%~5wt%, Other metallic elements 0 wt% ~ 15 wt% It is characterized by having the following features.

[0007] This platinum solution, due to its high Pt content, can produce a lustrous, well-colored silver decorative part (ornament). Furthermore, the inclusion of Si and Bi, which become glass components after firing, reduces the conductivity of the fired body, preventing sparking during microwave heating.

[0008] In a preferred embodiment of the platinum solution disclosed herein, in the above weight ratio, the total of the above Pt, Au, Rh, Pd, and Ag is 70 wt% or more and 99 wt% or less. According to such a configuration, since the composition ratio of the noble metal elements is high, a silver-colored decorative part with better color development is realized.

[0009] Also, in a preferred embodiment of the platinum solution disclosed herein, in the above weight ratio, Si > Bi. As a result, since the softening point of the glass component becomes high, in the fired body of the platinum solution, it is possible to suppress the uneven distribution of the glass component in the gravitational direction. As a result, the glass component is likely to be disposed between the noble metal particles, and the conductivity of the fired body can be further reduced.

[0010] In another aspect, a ceramic product is provided by the technology disclosed herein. This ceramic product is characterized by comprising a fired body of the platinum solution disclosed herein. Such a fired body does not spark when heated by a microwave oven, has a luster, and exhibits a silver color with good color development.

[0011] Also, the ceramic product disclosed herein is a ceramic product having a decorative part, the above decorative part contains a noble metal component, and in a weight ratio with the total of the noble metal elements contained in the above noble metal component being 100 wt%, has the following composition: Pt 70 wt% ~ 100 wt%, Total of Au, Rh, Pd, and Ag 0 wt% ~ 30 wt% (however, Rh 0 wt% ~ 10 wt%, and Au 0 wt% ~ 18 wt%) It has. Further, the sheet resistance value of the above decorative part is 1×10 8 Ω / □ or more. Thereby, a ceramic product having a decorative part that does not spark when heated by a microwave oven, has a luster, and exhibits a silver color with good color development is realized.

[0012] In a preferred embodiment of the ceramic product disclosed herein, the decorative portion is in the form of a film, and the average film thickness is 20 nm or more and 300 nm or less. Thereby, a decorative portion presenting a silver color with better color development is realized.

[0013] In a preferred embodiment of the ceramic product disclosed herein, the 8° gloss value of the decorative portion is 560 or more. Thereby, a decorative portion with particularly good gloss is realized.

[0014] Moreover, the ceramic product disclosed herein is preferably configured as tableware. Since the decorative portion does not spark due to heating by a microwave oven, it can be tableware provided with a silver-colored decorative portion that can be heated in a microwave oven.

Brief Description of the Drawings

[0015] [Figure 1] FIG. 1 is a cross-sectional FE-SEM image showing the cross-section of the fired film of the platinum solution of Example 14.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, preferred embodiments of the technology disclosed herein will be described. In addition, matters other than those specifically mentioned in this specification and necessary for implementation (for example, the manufacturing method of the ceramic substrate to be decorated, etc.) can be understood based on the technical content taught in this specification and the general technical common sense 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 technical common sense in this field. In addition, the notation "A to B" indicating a range in this specification means A or more and B or less. Therefore, it includes the case of exceeding A and being less than B.

[0017] The platinum solution disclosed herein contains metallic elements, including noble metal elements. The noble metal elements include at least platinum (Pt), and the metallic elements other than Pt include at least bismuth (Bi). In addition, it contains at least silicon (Si). The various components that the platinum solution disclosed herein may contain are described below.

[0018] Precious metal elements are components that contribute to the color of the calcined body of the platinum solution (hereinafter also referred to as the "calcined film" or "decorative part"). The platinum solution disclosed herein contains platinum (Pt) as the main precious metal element. It may also contain gold (Au), rhodium (Rh), palladium (Pd), and silver (Ag). It may also contain ruthenium (Ru), iridium (Ir), and osmium (Os).

[0019] Platinum (Pt) is the component that gives the sintered body of the platinum solution a lustrous silvery hue. Pt is the main component among the noble metal elements contained in the platinum solution (i.e., Pt accounts for 50 wt% or more of the noble metal elements contained in the platinum solution). Furthermore, Pt is the main component of the platinum solution disclosed herein. For example, Pt is included in the platinum solution as a constituent element of Pt resinate. Pt resinate has the property of forming Pt particles with a larger particle size than other noble metal elements upon sintering. Therefore, Pt particles are less likely to sinter than other noble metal elements. As a result, in the sintered body of the platinum solution, Pt particles tend to be separated from each other, thus suppressing conductivity. Consequently, the platinum solution disclosed herein can produce a sintered body that does not spark when heated in a microwave oven, even when the content of components that reduce conductivity in the sintered body (e.g., glass components such as Si and Bi) is low.

[0020] In a weight ratio where the total amount of metal elements in the platinum solution and Si is 100 wt%, the proportion of Pt is 50 wt% or more, may be 60 wt% or more, and may be 70 wt% or more. This results in a sintered body that is glossy and exhibits a good silver color. On the other hand, if the proportion of Pt is too high, the number of Pt particles in the sintered platinum solution becomes excessively large. Because the particle size of Pt particles is large, unevenness with differences in height occurs on the surface of the sintered platinum solution, which may impair the gloss. Therefore, in the above weight ratio, the proportion of Pt is appropriate to be 99 wt% or less, preferably 98 wt% or less, more preferably 90 wt% or less, and even more preferably 85 wt% or less.

[0021] Gold (Au) is an ingredient that adjusts the silvery hue in the platinum solution sintered body. The platinum solution disclosed herein may or may not contain Au. When Au is included, the proportion of Au is, for example, 0.1 wt% or more, preferably 3 wt% or more, and may be 4 wt% or more, in the weight ratio where the total of the metal elements in the platinum solution and Si is 100 wt%. This makes it possible to achieve a sintered body that exhibits a good silvery color. On the other hand, the proportion of Au may be, for example, 20 wt% or less, preferably 15 wt% or less, preferably 10 wt% or less, and may be 8.5% or less. According to the technology disclosed herein, even with the proportion of Au in such a range, it is possible to achieve a sintered body that exhibits a good silvery color. Furthermore, since Au is expensive among precious metals, costs can be reduced by not including Au or by limiting the amount of Au to such a range.

[0022] Rhodium (Rh) is a component that can suppress the increase in particle size of Pt particles produced by firing and increase the number of Pt particles with an appropriate particle size. This improves the strength of the fired body and improves the color development of the fired body. The platinum solution disclosed herein may or may not contain Rh. When Rh is included, the proportion of Rh is, for example, 0.1 wt% or more, and preferably 0.4 wt% or more, in the weight ratio where the total of the metal elements in the platinum solution and Si is 100 wt%. On the other hand, if the proportion of Rh is too high, the particle size of the Pt particles may become excessively small. As a result, the Pt particles become easier to sinter with each other, so that Pt is arranged continuously in the fired body and the conductivity may increase. This is undesirable because it may cause sparking when the fired body is heated in a microwave oven. Therefore, the proportion of Rh is appropriately 8.5 wt% or less, may be 6 wt% or less, may be 1.2 wt% or less, and may even be 1 wt% or less.

[0023] Palladium (Pd) is a component that exhibits a silvery hue and can be used to adjust the color of the calcined platinum solution. The platinum solution disclosed herein may or may not contain Pd. When Pd is included, the proportion of Pd is, for example, 0.1 wt% or more, and preferably 1 wt% or more, in a weight ratio where the total of the metal elements in the platinum solution and Si is 100 wt%. This results in good silvery coloration of the calcined platinum solution. Furthermore, since Pd is more expensive than Pt, from the viewpoint of cost reduction, the proportion of Pd is, for example, preferably 10 wt% or less, and more preferably 8.5 wt% or less.

[0024] Silver (Ag) is a component that exhibits a silvery hue and can be used to adjust the color of the calcined platinum solution. The platinum solution disclosed herein may or may not contain Ag. When Ag is included, the proportion of Ag may be, for example, 0.1 wt% or more, or 1 wt% or more, in a weight ratio where the total of the metal elements in the platinum solution and Si is 100 wt%. Furthermore, since Ag readily tarnishes, a high proportion of Ag may result in a darkened color. For this reason, the proportion of Ag should be, for example, 10 wt% or less.

[0025] The proportion of the precious metal elements disclosed herein is preferably 70 wt% or more, more preferably 75 wt% or more, and even more preferably 80 wt% or more, based on a weight ratio where the total of the metal elements and Si contained in the platinum solution is 100 wt%. This increases the proportion of the precious metal component in the calcined body of the platinum solution, resulting in good color development of the calcined body. Furthermore, since the platinum solution disclosed herein contains Si and Bi, the proportion of the precious metal elements may be, for example, 99 wt% or less, 95 wt% or less, or 90 wt% or less.

[0026] Bismuth (Bi) is a component that improves the adhesive strength between the platinum solution-fired body and the ceramic substrate to which the firing body is applied (coated). Furthermore, Bi is a glass component that becomes an oxide after firing and can reduce the conductivity of the platinum solution-fired body. In a weight ratio where the total amount of metal elements and Si in the platinum solution is 100 wt%, the proportion of Bi in the platinum solution disclosed herein is preferably 0.4 wt% or more, and may be, for example, 1 wt% or more. Within this range, the conductivity of the platinum solution-fired body can be suitably reduced, and the adhesive strength between the firing body and the ceramic substrate can be suitably improved. However, if the proportion of Bi is high, the luster and color of the platinum solution-fired body may be impaired. Therefore, the proportion of Bi may be, for example, 10 wt% or less, or even 8 wt% or less.

[0027] Silicon (Si) is a glass component that forms an oxide after firing and can reduce the conductivity of the platinum solution-fired body. Si can also improve the strength of the fired body. In a weight ratio where the total of metal elements in the platinum solution and Si is 100 wt%, the proportion of Si is preferably 0.5 wt% or more, may be 1 wt% or more, or may be 2 wt% or more. This allows for a suitable reduction in the conductivity of the platinum solution-fired body. However, if the proportion of Si is high, the luster of the platinum solution-fired body may be impaired. Therefore, the proportion of Si may be, for example, 11 wt% or less, or 10 wt% or less.

[0028] Furthermore, in the platinum solution disclosed herein, from the viewpoint of further reducing the conductivity of the fired body, it is preferable that the proportion of Si in the platinum solution is higher than the proportion of Bi by weight (Si > Bi). Si is a component that raises the softening point of the glass formed after firing. Therefore, if Si > Bi, the uneven distribution of glass components to the bottom of the precious metal particles due to gravity during the firing of the platinum solution is suppressed. As a result, the glass components are more reliably positioned between the precious metal particles in the fired body of the platinum solution, thus further reducing the conductivity.

[0029] Aluminum (Al) is a glass component that becomes an oxide after firing and can reduce the conductivity of the fired platinum solution body. Furthermore, Al can improve the strength of the fired body. The platinum solution disclosed herein may or may not contain Al. If Al is included, a high Al content may impair the luster and color of the fired body. Therefore, in a weight ratio where the total of the metal elements in the platinum solution and Si is 100 wt%, the proportion of Al should be, for example, 5 wt% or less, and generally 4 wt% or less.

[0030] The platinum solution disclosed herein may contain other metallic elements besides those mentioned above, to the extent that it does not impair the effects of the disclosed technology. Examples of such metallic elements include zirconium (Zr), yttrium (Y), samarium (Sm), titanium (Ti), calcium (Ca), barium (Ba), chromium (Cr), and tin (Sn). When other metals are included, the proportion of other metals is typically 15 wt% or less, preferably 10 wt% or less, and may be, for example, 5 wt% or less, in a weight ratio where the total of the metallic elements in the platinum solution and Si is 100 wt%. Furthermore, the platinum solution may not contain other metals.

[0031] The metal elements and Si contained in the platinum solution disclosed herein are, for example, included as resinates. As metal resinates, one or more organometallic compounds that have the metal element as a constituent element can be used without particular limitation for each metal element contained in the platinum solution. Similarly, one or more organo-Si compounds that have Si as a constituent element can be used without particular limitation for Si resinates. Examples of organic compounds contained in organometallic compounds and organo-Si compounds include high-carbon (e.g., 8 or more carbon atoms) carboxylic acids such as octic acid (2-ethylhexanoic acid), abietic acid, naphthenic acid, stearic acid, oleic acid, linolenic acid, and neodecanoic acid; sulfonic acids; resin acids contained in rosin, etc.; resin sulfide balsams containing essential oil components such as turpentine oil and lavender oil; alkyl mercaptides (alkylthiolates), aryl mercaptides (arylthiolates), mercaptocarboxylic acid esters, alkoxides, etc.

[0032] The platinum solution disclosed herein preferably contains a solvent for dispersing or dissolving metal resinates and / or Si resinates. Such solvents can be those conventionally used in resinate pastes or water-gold solutions, without any particular limitations. Examples include 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, dihydrocarbone, dibromomethane, dimethyl sulfoxide, dimethylformamide, nitrobenzene, pyrrolidone, propylene glycol monophenyl ether, pulegone, benzyl acetate, benzyl alcohol, benzaldehyde, turpentine oil, and lavender oil. One or more solvents may be used. Since resinates are commercially available as, for example, resinate pastes, such resinate pastes may be used as is.

[0033] The weight ratio of the solvent that can be included in the platinum solution is not particularly limited, as the optimal range varies depending on the application method of the platinum solution, and can be adjusted as appropriate. For example, if the total platinum solution is 100 wt%, the proportion of the solvent should be approximately 10 wt% to 50 wt%. As an example, when applying by inkjet, it is preferable to have a ratio of 10 wt% to 50 wt%. As another example, when applying by brush, it is preferable to have a ratio of 10 wt% to 30 wt%.

[0034] The viscosity of the platinum solution can be adjusted as appropriate depending on the application method and is not particularly limited. For example, the viscosity of the platinum solution should be around 10 mPa·s to 500 mPa·s. The viscosity of the platinum solution can be adjusted as appropriate by changing the amount of solvent or adding resin balsam.

[0035] The platinum solution disclosed herein may optionally contain other components, provided that they do not significantly impair the effects of the technology disclosed herein. Examples of additional components include organic binders, protective agents, surfactants, dispersants, thickeners, pH adjusters, preservatives, defoamers, plasticizers, stabilizers, and antioxidants.

[0036] The platinum solution disclosed herein can be produced, for example, by mixing a material containing a desired metal element and a material containing Si in a predetermined ratio, such that the mixture contains at least Pt, Si, and Bi. Typically, a metal resinate is used as the material containing the metal element, but metal complexes or metal nanoparticles may also be used, as long as the effects of the disclosed technology are achieved. Typically, a Si resinate is used as the material containing Si, but glass components such as Si and Bi may be included as glass particles, as long as the effects of the disclosed technology are achieved. The mixing method may follow any conventional method used for decorative water-gold solutions and is not particularly limited. Furthermore, the method for producing the platinum solution is not limited thereto.

[0037] The platinum solution disclosed herein can be used to decorate the surface of a ceramic substrate as an object to be decorated. The decoration can be carried out by applying the platinum solution to the surface of the ceramic substrate and then firing it at a predetermined temperature. A preferred example is the use of the platinum solution disclosed herein in "overglaze painting," which is the decoration of a substrate after it has been glazed. In overglaze painting, it is preferable to apply the platinum solution to the surface of the glaze and then fire it at a medium temperature of about 700°C to 1000°C. The platinum solution disclosed herein can also be used in "underglaze painting," which is the decoration of a bisque-fired ceramic substrate. In underglaze painting, it is preferable to apply the platinum solution to the ceramic substrate and then fire it at a high temperature of, for example, about 1200°C to 1400°C. Examples of methods for applying the platinum solution include brush painting, screen printing, and inkjet printing.

[0038] As described above, ceramic products can be obtained that do not spark when heated in a microwave oven, have a glossy finish, and feature a silver decorative part with good color development. The term "ceramic products" as used herein includes pottery, porcelain, earthenware, stone tools, and glass. Specific examples of such products include tableware, decorative items, various tiles, sanitary ware, roof tiles, bricks, clay pipes, and ceramic pipes. In particular, the technology disclosed herein allows for the suitable realization of microwave-safe tableware with a silver decorative part.

[0039] The silver decorative portion of the ceramic product obtained as described above is a fired body of the platinum solution disclosed herein, which contains at least Pt, Si, and Bi. Such a decorative portion is glossy and exhibits a good silver color. Furthermore, because such a decorative portion is insulating, sparks are prevented from being generated when heated in a microwave oven. In addition, because it is insulating, the temperature rise of the decorative portion can be suppressed, thereby preventing cracking of the decorative portion that may occur due to heating. In this specification, "insulating" means that the sheet resistance value is 1 × 10⁻⁶. 8 This means that the resistance is greater than or equal to Ω / □. The sheet resistance can be measured, for example, by the four-probe method.

[0040] The precious metal components contained in the decorative parts of the ceramic products disclosed herein consist of the precious metal elements contained in the platinum solution disclosed herein. That is, the proportion of precious metal elements in the decorative parts reflects the proportion of precious metal elements in the platinum solution. When the total amount of precious metal elements in the precious metal components is 100 wt%, the decorative parts have the following composition: Pt 70wt%~100wt%, Total of Au, Rh, Pd, and Ag: 0 wt% to 30 wt% (However, Rh 0wt%~10wt%, and Au 0wt%~18wt%) It is preferable that the material has the following properties. This results in a glossy, well-colored silver decorative part. Furthermore, with this configuration, a well-colored silver decorative part can be achieved even if it does not contain Au, or if the amount of Au is low, such as 18 wt% or less. The composition ratio of metal elements and Si included in the decorative part may be the composition ratio of the platinum solution used, but inorganic components derived from ceramic products (e.g., glaze) may also be mixed in.

[0041] The proportion of Pt in the decorative part to the total amount of precious metal elements contained in the decorative part is generally 70 wt% or more, for example, 80 wt% or more, 85 wt% or more, 90 wt% or more, 95 wt% or more, and even 100 wt%. According to the technology disclosed herein, even with a Pt proportion within this range, a decorative part can be realized that does not spark when heated in a microwave oven, has a glossy finish, and exhibits a good silver color.

[0042] Furthermore, the decorative part may or may not contain Au, Rh, Pd, and Ag. When these precious metal elements are included in the decorative part, the proportions contained in the platinum solution disclosed herein are reflected. For example, when the total amount of precious metal elements is 100 wt%, the proportion of Au may be, for example, 20 wt% or less, 18 wt% or less, 15 wt% or less, or 10 wt% or less. The proportion of Rh may be, for example, 10 wt% or less, 7 wt% or less, or 1.5 wt% or less. The proportion of Pd may be, for example, 10 wt% or less, or 7 wt% or less. The proportion of Ag may be, for example, 12 wt% or less. According to the technology disclosed herein, even when Au, Rh, Pd, and Ag are not included, or when they are included in low proportions as described above, a decorative part exhibiting a lustrous, well-colored silver finish can be realized.

[0043] The color tones of the decorative parts of the ceramic products disclosed herein are based on JIS Z8729 (2004) L * a * b* The L in the color system * value, a * value and b * value can be indicated. Here, the L * value, a * value and b * value is the value of SCI (Specular Component Include) including specularly reflected light.

[0044] L * value is an index indicating lightness. The L of the decorative part * value is preferably 60 or more, and may be, for example, 61 or more, 62 or more, 65 or more. Further, the L * value of the decorative part is more preferably 68 or more, even more preferably 69 or more, and particularly preferably 70 or more. Thereby, a bright color tone can be realized. On the other hand, when the L * value is too high, it exhibits a color close to white. Therefore, the L * value of the decorative part is preferably, for example, 80 or less, more preferably 78 or less, and may be, for example, 77 or less.

[0045] a * value and b * value are indices indicating chromaticity (hue and chroma). More specifically, the +a * value indicates the red direction, and the -a * value indicates the green direction. The +b * value indicates the yellow direction, and the -b * value indicates the blue direction. Therefore, for the decorative part to exhibit a silver color, the a * value and b * value are preferably not too high and not too low. The a * value is, for example, -20 or more and 20 or less, preferably -10 or more and 10 or less, and more preferably -5 or more and 5 or less. On the other hand, the b * value is, for example, -20 or more and 20 or less, may be -15 or more and 15 or less, and may be -10 or more and 10 or less.

[0046] The glossiness of the decorative part can be indicated by the 8° gloss value. Here, the "8° gloss value" refers to the value measured by a spectrophotometer designed to approximate a 60° gloss meter based on JIS Z8741 (1997) (for example, spectrophotometers CM-600d, CM-700d, etc., manufactured by Konica Minolta Sensing, Inc.). A higher 8° gloss value indicates greater gloss. The 8° gloss value of the decorative part of the ceramic product disclosed herein is, for example, 550 or higher, preferably 560 or higher, more preferably 600 or higher, more preferably 700 or higher, even more preferably 800 or higher, and particularly preferably 900 or higher. According to the technology disclosed herein, a ceramic product with a highly glossy decorative part can be realized.

[0047] The decorative portion is typically formed as a film on the surface of a ceramic substrate. The average film thickness of the decorative portion is not particularly limited, but is preferably between 20 nm and 300 nm, for example, it may be between 20 nm and 200 nm. With such an average film thickness, the reflected light from the surface of the decorative portion and the reflected light from the interface between the decorative portion and the ceramic substrate can interfere, resulting in better silver coloration. The average film thickness of the decorative portion can be appropriately adjusted by the coating method; for example, brush coating can achieve a thin film decorative portion with an average film thickness of about 20 nm or a decorative portion with a film thickness of 200 nm or more.

[0048] The following describes test examples relating to the technology disclosed herein, but it is not intended that the technology disclosed herein is limited to these test examples.

[0049] <Preparation of platinum solution> Metal elements and Si elements were mixed to achieve the compositions shown in Table 1 (percentages of elements by weight (wt%)). Specifically, the various raw materials were combined in an ointment jar and mixed for 2 minutes at a rotation speed of 1800 rpm using a stirrer manufactured by Thinky Co., Ltd. (product name: Jiten Koten Awatori Rentaro). Platinum solutions for Examples 1 to 21 were prepared in this manner. The percentage (wt%) of the noble metal elements relative to the total noble metals in the platinum solution for each example is shown in Table 2. The raw materials for the metal elements and Si elements used here are listed below. Pt: Pt resinate (platinum resin sulfide balsam) Au: Au resinate (gold resin sulfide balsam) Rh: Rh resinate (rhodium resin sulfide balsam) Pd:Pd resinate (palladium resin sulfide balsam) Ag:Ag resinate (silver resin salt) Si:Si resinate (silicone resin salt) Bi:Bi resinate (bismuth resin salt) Al:Al resinate (aluminum resin salt) and aluminum complexes Zr:Zr resinate (zirconium resin salt) Y: Y resinate (yttrium resin salt) Sm: Sm resinate (samarium resin salt)

[0050] [Table 1]

[0051] [Table 2]

[0052] <Platinum solution coating and firing> A white porcelain plate (15 mm long, 15 mm wide) with glaze applied to its surface was prepared, and the platinum solution prepared above was applied (coated) to the entire surface of one side of the white porcelain plate. A spin coater: Opticoat MS-A-150 manufactured by Mikasa Corporation was used for coating, and the spin conditions were set to 5000 rpm for 10 seconds. The coated white porcelain plate was dried on a hot plate at 60°C for 1 hour, and then fired at 800°C for 10 minutes. This resulted in white porcelain plates (Examples 1-21) with a fired platinum solution body (also called a "fired film" or "decorative part"). It was confirmed that a fired film with a thickness of approximately 20 nm to 200 nm could be obtained by coating under these conditions. This film thickness was confirmed by cross-sectional observation using FE-SEM (Hitachi High-Technologies Corporation, SU-8200). As a representative example, Figure 1 shows a cross-sectional FE-SEM image of the decorative part of the white porcelain plate of Example 14. Note that the white areas in the sintered film in the cross-sectional FE-SEM image of Figure 1 are the areas where noble metal particles are present.

[0053] <Color development evaluation> Using a spectrophotometer, the L in SCI mode of the platinum solution fired body (decorative part) on the white porcelain plate was measured. * value, a * value, b * The L value and 8° gross value were measured. A Konica Minolta Sensing Co., Ltd. CM-700d spectrophotometer was used as the spectrophotometer. The L value was used as the standard for evaluating color development. * "〇" indicates that the value is 60 or higher and the 8° gross value is 510 or higher. * Values ​​less than 60 and / or 8° gross values ​​less than 510 are indicated as "×". The results are shown in Table 3.

[0054] <Spark Test> White porcelain plates (Examples 1-21) equipped with the platinum solution fired as described above were heated in a microwave oven (output: 1000W, electromagnetic wave: 2.45GHz) for 60 seconds. Those that did not produce sparks were marked with "○", and those that did produce sparks were marked with "×", and the results are shown in Table 3.

[0055] <Evaluation of conductivity> The sheet resistance (Ω / □) of the white porcelain plates (Examples 1-21) equipped with the platinum solution fired as described above was measured. The sheet resistance was measured using the four-probe method with a resistivity meter: Loresta GP MCP-T610 manufactured by Mitsubishi Chemical Analytec Corporation. The results are shown in Table 3.

[0056] [Table 3]

[0057] As shown in Table 3, Examples 1-3 had an 8° gloss value of less than 510, resulting in silver decorative parts with insufficient gloss. In particular, Example 3 had a lower sheet resistance value than the other examples, and sparks occurred when heated in a microwave oven. On the other hand, Examples 4-21 had an 8° gloss value of 560 or higher, and L * The values ​​were 60 or higher, and the material exhibited a glossy silver color with good color development. Furthermore, in examples 4-21, the sheet resistance values ​​were all 1 × 10⁻⁶. 8 The ratio was greater than Ω / □, and no sparks were generated even when heated in a microwave oven. This indicates that a platinum solution with a composition of 50 wt% to 99 wt% Pt, 0 wt% to 25.5 wt% total for Au, Rh, Pd, and Ag (however, Rh is 0 wt% to 8.5 wt%), 11 wt% or less Si, 10 wt% or less Bi, 0 wt% to 5 wt% Al, and 0 wt% to 15 wt% other metallic elements can achieve a silver decoration that does not spark when heated in a microwave oven, has a glossy finish, and exhibits good color development.

[0058] The specific examples of the technology disclosed herein have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples illustrated above.

Claims

1. A platinum solution used for silver-colored decoration of ceramic substrates, It contains at least Pt, Si, and Bi, In a weight ratio where the total amount of metal elements and Si contained in the platinum solution is 100 wt%, The following composition: Pt 50wt% to 99wt%, Total of Au, Rh, Pd, and Ag: 0 wt% to 25.5 wt% (However, Rh is between 0 wt% and 8.5 wt%) Si 11wt% or less, Bi 10wt% or less, Al 0wt%~5wt%, Other metallic elements: 0 wt% to 15 wt% A platinum solution containing [the following properties].

2. The platinum solution according to claim 1, wherein in the weight ratio, the total proportion of Pt, Au, Rh, Pd, and Ag is 70 wt% or more and 99 wt% or less.

3. The platinum solution according to claim 1 or 2, wherein in the weight ratio, Si > Bi.

4. A ceramic product comprising a platinum liquid firing body according to any one of claims 1 to 3.

5. A ceramic product having a decorative part, The aforementioned decorative part contains a precious metal component, In a weight ratio where the total amount of precious metal elements contained in the aforementioned precious metal component is 100 wt%, The following composition: Pt 70wt% to 100wt%, Total of Au, Rh, Pd, and Ag: 0 wt% to 30 wt% (However, Rh 0 wt% to 10 wt%, and Au 0 wt% to 18 wt%) It has, The sheet resistance value of the decorative part is 1 × 10 ８ Ω / □ or greater, The decorative portion is in the form of a film, with an average film thickness of 20 nm or more and 300 nm or less. Ceramic products.

6. The ceramic product according to claim 5, wherein the 8° gloss value of the decorative part is 560 or more.

7. A ceramic product according to claim 5 or 6, which constitutes tableware.

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