Composition for decoration and ceramic product

Abstract

Disclosed is a composition for decoration that is for use in decorating ceramic bases in silver color, which comprises noble metal elements and a matrix-forming element. The noble metal elements comprise a first element, which comprises Pt, a second element, which comprises Rh, and a third element, which comprises Pd and / or Ir. The matrix-forming element includes Bi. If the sum of the noble metal elements and the matrix-forming element is taken as 100 mol%, the content of the noble metal elements is 80 mol% or more and the total content of the second element and the third element is 6-60 mol%.

Description

Decorative compositions and ceramic products

[0001] The present invention relates to a decorative composition and a ceramic product. This application claims priority to Japanese Patent Application No. 2023-103893, filed on June 26, 2023, the entire contents of which are incorporated herein by reference.

[0002] Gold- or silver-colored decorative portions are sometimes formed on the surfaces of ceramic products such as china, glassware, and enamelware to impart an elegant or luxurious impression. Such decorative portions are formed, for example, by applying a composition containing a metal organic compound, such as a metal resinate, to the surface of the ceramic product and firing it. For example, Patent Documents 1 to 3 disclose examples of compositions for forming such decorative portions on ceramics and the like. Patent Document 1 discloses a composition containing 75% or more gold (Au) to form a decorative white gold alloy. Patent Document 2 discloses a composition containing platinum (Pt), palladium (Pd), gold (Au), and bismuth (Bi) as essential components to form a microwave-safe platinum-colored decorative portion.

[0003] Japanese Patent Application Laid-Open No. 2008-214718 Japanese Patent Application Laid-Open No. 2001-130985 Japanese Patent Application Laid-Open No. 01-000179

[0004] In recent years, the price of gold has tended to rise, and studies have been conducted to switch from compositions with a high gold content to compositions with higher platinum or silver content than conventional compositions. However, the inventors have found that compositions with a higher platinum content than conventional compositions cause the silver color to darken and lose luster in the decorative portion after firing.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and its main object is to provide a silver decorative part having excellent color development and gloss, and a decorative composition for realizing the silver decorative part.

[0006] To achieve the above object, the decorative composition disclosed herein is a decorative composition for use in silver-coloring a ceramic substrate, and includes a precious metal element and a matrix-forming element. The precious metal element includes a first element consisting of Pt, a second element consisting of Rh, and a third element that is at least one selected from the group consisting of Pd and Ir. The matrix-forming element includes Bi. In this case, the molar ratio of the precious metal element is 80 mol % or more, and the total of the second element and the third element is 6 mol % or more and 60 mol % or less, where the sum of the precious metal element and the matrix-forming element is 100 mol %.

[0007] When a composition containing Pt, Rh, Pd, and Ir is fired, the Rh, Pd, and Ir adhere to the Pt particles as oxides during firing, suppressing the aggregation of the Pt particles. This prevents the Pt particles from becoming coarse during firing. Furthermore, because the Pt particles do not aggregate, the Pt particles are uniformly distributed in the fired film (silver decorative portion) of the composition. Therefore, the above-mentioned configuration can provide a decorative composition that realizes a silver decorative portion with excellent color development and luster.

[0008] In a preferred embodiment of the decorative composition disclosed herein, the ratio of the total molar fraction of the second element and the third element to the molar fraction of the first element ((second element + third element) / first element) is 0.1 or more and 1 or less. This configuration provides a decorative composition that realizes a silver decorative portion with more suitable color development and luster.

[0009] In a preferred embodiment of the decorative composition disclosed herein, the Pt content is 50 mol % or more and 80 mol % or less in the molar ratio described above, which allows for more suitable color development in the silver decorative portion.

[0010] In a preferred embodiment of the decorative composition disclosed herein, the Rh content is 3 mol % or more and 10 mol % or less in the above molar ratio, which allows the effects of the technology disclosed herein to be exhibited more stably.

[0011] In a preferred embodiment of the decorative composition disclosed herein, the Pd content is 10 mol % or more and 35 mol % or less in the above molar ratio, which allows the decorative composition to produce a silver decorative portion with a more suitable luster.

[0012] In a preferred embodiment of the decorative composition disclosed herein, the precious metal element further includes a fourth element, and the fourth element is at least one element selected from the group consisting of Au, Ag, Ru, and Os. In another preferred embodiment of the decorative composition disclosed herein, the content of the fourth element in the molar ratio is 18.5 mol% or less. This configuration allows the effects of the technology disclosed herein to be optimally exhibited, providing a silver decorative part with excellent color development and luster.

[0013] In another aspect, there is provided a ceramic product disclosed herein. The ceramic product disclosed herein comprises a ceramic substrate and a silver decorative portion disposed on the ceramic substrate and made of a fired body of the decorative composition disclosed herein. The silver decorative portion has an 8° gloss value of 750 or more when measured by the SCI method, and a lightness L of the silver decorative portion when measured by the SCE method. ＊ The value divided by (8° gloss value / lightness L ＊ ) is 20 or more. According to this configuration, it is possible to provide a ceramic product having a silver decorative portion with excellent color development and luster.

[0014] Fig. 1 is an FE-SEM observation image (10,000x magnification) of the silver decorative portion according to Example 1. Fig. 2 is an FE-SEM observation image (10,000x magnification) of the silver decorative portion according to Comparative Example 2.

[0015] Preferred embodiments of the technology disclosed herein are described below. Matters other than those specifically mentioned in this specification that are necessary for implementation (e.g., a method for manufacturing a ceramic substrate to be decorated) can be understood based on the technical content taught by this specification and the general technical common sense of a person skilled in the art. The technology disclosed herein can be implemented based on the content disclosed in this specification and the general technical common sense of a person skilled in the art. In this specification, the notation "A to B" indicating a range means A or more and B or less.

[0016] <Decorative Composition> The decorative composition disclosed herein (hereinafter sometimes simply referred to as the "composition") is used to form a silver decorative portion on a ceramic substrate. The decorative composition disclosed herein contains a precious metal element and a matrix-forming element. The precious metal element includes at least Pt, Rh, and at least one of Pd and Ir. The matrix-forming element includes at least Bi. The content of the precious metal element is 80 mol % or more, and the total of Rh, Pd, and Ir is 6 mol % to 60 mol %, based on a molar ratio of the total of the precious metal element and the matrix-forming element being 100 mol %. By firing this decorative composition, a silver decorative portion with good color development and luster can be formed on the ceramic substrate.

[0017] The reason for this effect is not particularly limited, but is speculated to be as follows: Platinum (Pt) is more prone to over-sintering than other precious metal elements, such as gold (Au) or silver (Ag), and Pt particles tend to aggregate. Over-sintering of Pt particles can result in unevenness on the surface of the silver decorative portion, which can impair gloss. Furthermore, Pt is a component that particularly contributes to the coloring of the silver decorative portion. Therefore, if excessive grain growth of Pt particles occurs in the fired product (silver decorative portion) of the decorative composition, or if over-sintering occurs, color development and gloss may be reduced in areas with few Pt particles. Therefore, the decorative composition disclosed herein contains Rh as an essential constituent element in addition to Pt. Furthermore, in addition to Pt and Rh, it contains either one of Pd and Ir, or both. According to the inventors' research, when Rh, Pd, and Ir are fired together with Pt, the Rh, Pd, and Ir adhere to the Pt particles as oxides during firing, suppressing the aggregation of the Pt particles. This prevents the Pt particles from becoming coarse during firing. Furthermore, because the Pt particles do not aggregate, the Pt particles are uniformly distributed in the silver decorative portion. This improves the color development and gloss of the silver decorative portion.

[0018] As described above, the decorative composition disclosed herein contains at least a precious metal element and a matrix-forming element. Hereinafter, various components that may be contained in the decorative composition disclosed herein will be specifically described.

[0019] Precious metal elements are components that contribute to the coloring of the fired decorative composition (hereinafter simply referred to as the "silver decorative portion"). Examples of precious metal elements include gold (Au), silver (Ag), platinum (Pt), rhodium (Rh), iridium (Ir), palladium (Pd), ruthenium (Ru), and osmium (Os). The decorative composition disclosed herein contains at least a first element, a second element, and a third element as precious metal elements. The first element is platinum (Pt). The second element is rhodium (Rh). The third element (third element group) is at least one element selected from the group consisting of palladium (Pd) and iridium (Ir). That is, the decorative composition disclosed herein contains Pt and Rh as essential components. Furthermore, the decorative composition disclosed herein contains, in addition to Pt and Rh, either Pd or Ir, or both. This makes it possible to provide a decorative composition that realizes a silver decorative portion with good color development and luster. The precious metal element may be contained in the decorative composition, for example, in the form of a metal resinate (an organic metal compound). However, the state of the precious metal element in the decorative composition is not limited to the metal resinate described above, and may be a complex, a polymer, or metal particles.

[0020] The decorative composition disclosed herein has a molar ratio of precious metal elements of at least 80 mol % or more, where the sum of the precious metal elements and matrix-forming elements contained in the decorative composition is 100 mol % (hereinafter simply referred to as the "molar ratio of the decorative composition"). The molar ratio of the precious metal elements in the decorative composition is preferably 83 mol % or more, more preferably 84 mol % or more, and may even be 90 mol % or more. Furthermore, because the decorative composition disclosed herein contains a matrix-forming element, the molar ratio of the precious metal elements in the decorative composition is preferably 98 mol % or less, more preferably 97 mol % or less, and may even be 96 mol % or less. By ensuring that the content of the precious metal elements is within the above range, the proportion of the precious metal components in the decorative composition is sufficiently ensured, resulting in a silver decorative part with good color development and luster.

[0021] Platinum (Pt) is a component that imparts a lustrous silver-like color tone to the silver decorative portion. Furthermore, Pt is relatively cheaper than Au, Pd, etc., making it advantageous from a cost perspective. The decorative composition disclosed herein contains Pt as an essential component. Pt is preferably included in the decorative composition, for example, as a constituent element of Pt resinate. The Pt content is preferably 35 mol% or more, more preferably 39 mol% or more, and even more preferably 50 mol% or more, based on a molar ratio of 100 mol% of the total of the precious metal elements and matrix-forming elements contained in the decorative composition. This allows for favorable improvement of the gloss value (glossiness) of the silver decorative portion. If the Pt content in the decorative composition is too high, the effect of Rh, Pd, and Ir in suppressing over-sintering may not be fully exerted, potentially impairing the color development and gloss of the silver decorative portion. From this viewpoint, the content of Pt element in the decorative composition is preferably, for example, 90 mol % or less, more preferably 85 mol % or less, and even more preferably 80 mol % or less. The content of each element in the decorative composition can be measured, for example, by ICP emission spectrometry.

[0022] Among precious metal elements, Pt is a component that particularly exhibits a lustrous silver-like hue. By incorporating a large amount of Pt, a silver decorative portion with even better color development and luster can be provided. From this perspective, Pt is preferably the major component among the precious metal elements contained in the decorative composition (i.e., Pt accounts for 50 mol% or more of the precious metal elements contained in the decorative composition). When the total amount of precious metal elements contained in the decorative composition is taken as 100 mol%, Pt is, for example, 50 mol% or more, preferably 57 mol% or more, or even 60 mol% or more, or even 70 mol% or more. As described above, the decorative composition disclosed herein contains, in addition to Pt, Rh, Pd, Ir, etc., as precious metal elements in order to improve color development and luster. Therefore, when the total amount of precious metal elements contained in the decorative composition is taken as 100 mol%, Pt is preferably, for example, 94 mol% or less, and more preferably 92.5 mol% or less.

[0023] Rhodium (Rh), palladium (Pd), and iridium (Ir) are components that effectively suppress the increase in particle size of Pt particles that occurs during firing and can increase the number of Pt particles with appropriate particle sizes. This improves the strength of the silver decorative portion and achieves a silver decorative portion with good color development. Rh, in particular, effectively suppresses the increase in particle size of Pt particles. For this reason, the decorative composition disclosed herein contains Rh as an essential component. Furthermore, the decorative composition disclosed herein contains Pd and / or Ir in addition to Pt and Rh.

[0024] In the decorative composition disclosed herein, the total molar ratio of the second and third elements (i.e., the total of Rh, Pd, and Ir) is 6 mol% or more and 60 mol% or less, where the total of the precious metal elements and matrix-forming elements contained in the decorative composition is 100 mol%. In the molar ratio of the decorative composition, the total of the second and third elements is preferably 6 mol% or more, more preferably 10 mol% or more, even more preferably 17 mol% or more, and may even be 20 mol% or more. This achieves the above-mentioned effects, favorably improving the color development and gloss of the silver decorative portion. Rh, Pd, and Ir tend to have slightly lower gloss than Pt and exhibit a dull silver color. Furthermore, if the decorative composition contains excessive amounts of Rh, Pd, or Ir, Pt particles may become excessively small, which may result in areas of the silver decorative portion with few (or no) Pt particles. Therefore, excessive content of Rh, Pd, or Ir is undesirable from the viewpoint of color development. Furthermore, since Rh, Pd, and Ir are expensive, it may also be disadvantageous from the viewpoint of cost. From these viewpoints, the total content of the second element and the third element is preferably 60 mol% or less, more preferably 50 mol% or less, and even more preferably 46 mol% or less, and may be 40 mol% or less, or even 30 mol% or less.

[0025] The respective contents of Rh, Pd, and Ir in the decorative composition are not particularly limited, as long as the total of Rh, Pd, and Ir is adjusted to satisfy the above-mentioned range. The content of Rh element is preferably 1 mol% or more, more preferably 2 mol% or more, even more preferably 3 mol% or more, and particularly preferably 3.9 mol% or more, in terms of the molar ratio of the decorative composition. If Rh is contained in the decorative composition in excess, the Pt particles may become excessively small. From this perspective, the content of Rh element is preferably 10 mol% or less, more preferably 8 mol% or less, and may even be 5 mol% or less, in terms of the molar ratio of the decorative composition.

[0026] The decorative composition disclosed herein may or may not contain Pd. When the decorative composition contains Pd, the Pd content is preferably 1 mol% or more, more preferably 5 mol% or more, even more preferably 10 mol% or more, and particularly preferably 12 mol% or more, based on the molar ratio of the decorative composition. When the decorative composition contains more Pd than Pt, the gloss value tends to be lower. From this perspective, the Pd content is preferably 45 mol% or less, more preferably 40 mol% or less, even more preferably 35 mol% or less, and particularly preferably 25 mol% or less, based on the molar ratio of the decorative composition.

[0027] The decorative composition disclosed herein may or may not contain Ir. When the decorative composition contains Ir, the Ir content is preferably 1 mol% or more, more preferably 1.5 mol% or more, and even more preferably 2 mol% or more, based on the molar ratio of the decorative composition. Furthermore, the Ir content is preferably 5 mol% or less, more preferably 4 mol% or less, even more preferably 3 mol% or less, and particularly preferably 2.6 mol% or less, based on the molar ratio of the decorative composition.

[0028] As described above, by including Rh, Pd, and Ir in addition to Pt, over-sintering of Pt is effectively suppressed, improving the color development and gloss of the silver decorative portion. For example, by appropriately adjusting the molar fraction ratio of Pt to (Rh + Pd + Ir), the above-mentioned effects are further enhanced, and the gloss value of the silver decorative portion tends to be further improved. Although not particularly limited, the ratio of the total molar fraction of the second element and the third element to the molar fraction of the first element ((second element + third element) / first element) is preferably 0.08 or more, more preferably 0.1 or more, and particularly preferably 0.3 or more. If the total molar fraction of Rh, Pd, and Ir is too high relative to the molar fraction of Pt, the gloss value of the silver decorative portion tends to be low. From this viewpoint, the ratio of the total molar fraction of the second element and the third element to the molar fraction of the first element ((second element + third element) / first element) is preferably 1.2 or less, more preferably 1 or less, and even more preferably 0.5 or less.

[0029] The decorative composition disclosed herein may contain a fourth element as a precious metal element other than the elements described above, such as gold (Au), silver (Ag), ruthenium (Ru), or osmium (Os).

[0030] The decorative composition disclosed herein may or may not contain a fourth element. For example, if the decorative composition contains a fourth element, the content of the fourth element is preferably 18.5 mol% or less, or may be 16 mol% or less, or may be 10 mol% or less, or may be 5 mol% or less, based on the molar ratio of the decorative composition. Specifically, if the decorative composition contains Au, the content of the Au element is preferably 0.5 mol% to 18.5 mol%, and more preferably 1 mol% to 18.3 mol%. Furthermore, if the decorative composition contains Ag, the content of the Ag element is preferably 0.5 mol% to 16 mol%, and more preferably 1 mol% to 15.5 mol%. By including Au or Ag in the decorative composition, the silver color of the silver decorative portion is favorably adjusted, tending to increase the gloss value. However, as mentioned above, Au and Ag are not essential components of the decorative composition disclosed herein, and may not be included in the decorative composition.

[0031] The matrix-forming element is a component that improves the adhesion of the silver decorative portion to the ceramic substrate. In this specification, the term "matrix-forming element" encompasses metal elements and metalloid elements that can form an amorphous matrix in the oxide state in the fired body (silver decorative portion) of the decorative composition. Furthermore, the term "amorphous matrix" refers to a structure in which amorphous oxides (oxides with an amorphous structure) of specific metal elements and metalloid elements form a skeleton, and various metal elements (or metalloid elements) exist within the skeleton as oxides or in the form of cations. An example of a material having an amorphous matrix (amorphous material) is glass. Examples of such matrix-forming elements include Si, Bi, Zr, Ti, Al, Ni, Cr, 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, In, and Co. Among the above-mentioned noble metal elements, some elements (e.g., Ag) may become amorphous oxides during firing and form part of the amorphous matrix. However, for the sake of convenience, the elements listed above as noble metal elements are not considered to be matrix-forming elements in this specification. Similarly to the noble metal elements, the form of the matrix-forming components in the decorative composition is not particularly limited and may take the form of metal resinates (organic metal compounds), complexes, polymers, fine particles (glass frit), and the like.

[0032] The decorative composition disclosed herein contains at least bismuth (Bi) as a matrix-forming element. Bi is a component that forms the framework of the amorphous matrix after firing and can improve adhesion to the substrate. The inclusion of Bi improves adhesion, thereby effectively preventing peeling of the silver decorative portion when exposed to, for example, alkaline chemicals.

[0033] The content of Bi element is preferably 2.5 mol% or more, more preferably 3 mol% or more, and even 6 mol% or more, based on 100 mol% of the total of the precious metal elements and matrix-forming elements contained in the decorative composition. This allows the aforementioned effect of improving adhesion to the substrate to be favorably achieved. On the other hand, if the content of Bi in the decorative composition is too high, the content of precious metal elements will relatively decrease, which may impair the color development and gloss of the silver decorative portion. From this perspective, the content of Bi element is preferably 20 mol% or less, more preferably 15.5 mol% or less, and even more preferably 15.2 mol% or less, based on the molar ratio of the decorative composition.

[0034] The decorative composition disclosed herein may contain metal elements or metalloid elements other than Bi as matrix-forming elements, as long as the effects of the technology disclosed herein are not impaired. Examples of such other elements include silicon (Si), yttrium (Y), zirconium (Zr), samarium (Sm), calcium (Ca), barium (Ba), chromium (Cr), and tin (Sn). When the entire conductive composition is taken as 100 mol %, the content of the other elements may be, for example, 5 mol % or less, 3 mol % or less, or 1.6 mol % or less. The other elements may not be present.

[0035] The elements that may be contained in the decorative composition disclosed herein have been described above. In addition to the components described above, the decorative composition disclosed herein preferably contains various other components in consideration of factors such as adhesion to the substrate surface and formability of the silver decorative portion. Below, other components that may be contained in the decorative composition disclosed herein are described. However, the other components described below can be any conventionally known components that may be used in decorative compositions, without any particular restrictions, as long as they do not significantly impede the effects of the technology disclosed herein. In other words, the decorative composition disclosed herein can appropriately change the components other than the essential elements described above depending on its intended use.

[0036] First, as described above, the decorative composition disclosed herein may contain both a noble metal element and a matrix-forming element in the form of a metal resinate. In this case, the decorative composition contains an organic compound for forming the metal resinate. Any conventionally known resin material that can be used to form a metal resinate can be used as the organic compound, without particular limitation. Examples of such resin materials include carboxylic acids with a high carbon number (e.g., 8 or more carbon atoms), such as octylic acid (2-ethylhexanoic acid), abietic acid, naphthenic acid, stearic acid, oleic acid, linolenic acid, and neodecanoic acid; sulfonic acids; resin acids contained in rosin; resin sulfur balsams containing essential oil components such as turpentine oil and lavender oil; alkyl mercaptides (alkylthiolates); aryl mercaptides (arylthiolates); mercaptocarboxylic acid esters; and alkoxides.

[0037] In addition, in decorative compositions containing both a noble metal element and a matrix-forming element in the form of a metal resinate, an organic solvent that disperses or dissolves the metal resinate is preferably used. Such organic solvents can be any of those conventionally used in resinate pastes or liquid gold solutions, without any particular restrictions. Examples of organic solvents 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, dihydrocarvone, dibromomethane, dimethyl sulfoxide, dimethylformamide, nitrobenzene, pyrrolidone, propylene glycol monophenyl ether, pulegone, benzyl acetate, benzyl alcohol, benzaldehyde, turpentine oil, and lavender oil. These organic solvents may be used alone or in combination. Metal resinates are commercially available as resinate pastes, for example, and such resinate pastes may be used as they are.

[0038] The weight ratio of the solvent that can be contained in the decorative composition is not particularly limited, as the preferred range varies depending on the application method of the decorative composition, and can be adjusted as appropriate. For example, the solvent content in the decorative composition may be approximately 10 wt% to 50 wt%. For example, when applying by inkjet, the solvent content in the decorative composition is preferably, for example, 10 wt% to 50 wt%. For another example, when applying by brush, the solvent content in the decorative composition is preferably, for example, 10 wt% to 30 wt%.

[0039] The viscosity of the decorative composition is not particularly limited and can be adjusted as needed depending on the application method of the decorative composition. The viscosity of the decorative composition may be, for example, about 10 mPa·s to 500 mPa·s. The viscosity of the decorative composition can be adjusted as needed by adjusting the amount of solvent or adding resin balsam, for example.

[0040] The decorative composition disclosed herein may additionally contain other components as appropriate, provided that the effects of the technology disclosed herein are not significantly impaired. Examples of additional components include organic binders, protective materials, surfactants, dispersants, thickeners, pH adjusters, preservatives, antifoaming agents, plasticizers, stabilizers, and antioxidants.

[0041] The decorative composition disclosed herein can be produced, for example, by mixing materials containing desired metal elements in a predetermined ratio so as to contain at least a precious metal component and a matrix-forming component. As mentioned above, the form of the precious metal component and matrix-forming component contained in the decorative composition disclosed herein is not limited to metal resinates, but may also be complexes, polymers, or fine particles. When the precious metal component and matrix-forming component are in a form other than metal resinates, it is preferable to appropriately change the solvent and additional components described above depending on the form of the precious metal component and matrix-forming component. For example, when the precious metal component and matrix-forming component are contained in a form that is insoluble in a solvent, such as fine particles, it is preferable to select a solvent that can appropriately disperse the fine particles and to add a dispersant or other additional component.

[0042] <Ceramic Product> One embodiment of the ceramic product disclosed herein will now be described. The ceramic product disclosed herein has a silver decorative portion containing a precious metal component. For example, the silver decorative portion may be provided on a substrate primarily composed of ceramic. Alternatively, for example, the substrate primarily composed of ceramic may have a coating layer primarily composed of an amorphous material (typically glass) and a silver decorative portion. Such a ceramic product can be suitably produced by applying the decorative composition described above to a ceramic substrate and firing it.

[0043] (1) Substrate The substrate is a molded body mainly composed of ceramics (for example, a molded body having a ceramic content of 50 mass % or more). Examples of ceramics constituting such a substrate include silica (SiO ２ ), alumina (Al ２ O ３ ), zirconia (ZrO ２ ), magnesia (MgO), titania (TiO ２ ), ceria (CeO ２ ), yttria (Y ２ O ３ ) and the like. The thickness, shape, hardness, color, etc. of the substrate can be changed as appropriate depending on the application of the ceramic product, and detailed explanations will be omitted as they do not limit the technology disclosed herein. Note that the chemical formula shown in parentheses after the above substance name indicates a representative composition of the substance, and is not intended to limit the composition of the actual ceramic to that chemical formula.

[0044] (2) Coating Layer The coating layer is a layer mainly composed of an amorphous material (e.g., glass) (e.g., a layer containing 50% or more by mass of amorphous material). Such a coating layer can be formed on the surface of the substrate for purposes such as protecting the substrate. Note that the coating layer is not essential and can be omitted in other forms. Such a coating layer is formed, for example, by applying a glaze to the surface of the substrate and then firing it. Here, the glaze is a chemical agent containing metallic and semi-metallic elements that become oxides upon firing and form an amorphous matrix. This glaze may contain the same elements as those contained in the amorphous region of the silver decorative portion, or it may contain different elements.

[0045] The composition of the coating layer is not particularly limited as long as it does not significantly impair the effects of the technology disclosed herein, and conventionally known components that can be used to protect ceramic substrates can be appropriately selected. As an example, the coating layer may contain Si, Al, Fe, Mg, Na, Zn, K, Ca, Sn, etc. These elements can form a matrix in the form of amorphous oxide. That is, the coating layer may contain silicon oxide (SiO ２ ), aluminum oxide (Al ２ O ３ ), iron oxide (Fe ２ O ３ ), magnesium oxide (MgO), potassium oxide (Na ２ O), zinc oxide (ZnO), potassium oxide (K ２ O), calcium oxide (CaO), tin oxide (SnO ２ ) and the like. The abundance ratio of each element in the coating layer does not limit the technology disclosed herein, and therefore a detailed description thereof will be omitted.

[0046] (3) Silver Decorative Portion The ceramic product disclosed herein has a silver decorative portion. The silver decorative portion can be formed on the surface of the substrate or the surface of the coating layer. The silver decorative portion of the ceramic product disclosed herein contains a precious metal component. The precious metal component can include precious metal particles. For example, the precious metal component may be composed of precious metal particles. Such a silver decorative portion has an 8° gloss value of 750 or more when measured by the SCI method, and a lightness L of 750 or more when the 8° gloss value is measured by the CE method. ＊ The value divided by (8° gloss value / lightness L ＊ ) is 20 or more. That is, the silver decorative portion disclosed herein is a decorative portion that is shiny and exhibits a silver color with good color development.

[0047] The glossiness of the silver decorative part can be evaluated by the 8° gloss value measured by the SCI method (hereinafter simply referred to as "8° gloss value"). Here, "8° gloss value" is a value indicating glossiness, and the higher the 8° gloss value, the glossier and more lustrous the silver decorative part. The 8° gloss value can be measured using a spectrophotometer (such as the CM-700d or CM-600d manufactured by Konica Minolta Sensing Co., Ltd.) designed to approximate a 60° gloss meter based on JIS Z 8741:1997. The SCI (Specular Components Include) method is a measurement method that includes specular reflection.

[0048] The color development of the silver decorative part is measured by the SCE method. ＊ (Hereafter, simply "Lightness L ＊ The brightness can be evaluated by the L value based on JIS Z 8781:2013. ＊ a ＊ b ＊ In the color system, it is a value that indicates the degree of whiteness, and lightness L ＊ The higher the value, the whiter the color. ＊Measurement of colorimeter (colorimeter) can be performed using a spectrophotometer conforming to JIS Z 8722:2009 (for example, the CM-700d or CM-600d manufactured by Konica Minolta Sensing, Inc.). The SCE (Specular Components Exclude) method is a method in which specular reflected light is removed and only diffuse reflected light is measured, and is also called the diffuse reflectance measurement method. With the SCE method, the measured values ​​vary depending on the surface condition even for the same color, and measurement results can be obtained that are close to those obtained when the color is recognized visually.

[0049] The silver decorative portion of a ceramic product can be produced by applying the decorative composition described above to the surface of a ceramic substrate (or coating layer) and firing it. In the silver decorative portion where the Pt particles are oversintered during firing, the 8° gloss value is low and the lightness L ＊ The 8° gloss value is low and the lightness L ＊ When the silver decorative portion has too high a gloss value, the silver luster is not felt sufficiently by the naked eye and it looks cloudy. ＊ It has been found that by evaluating the silver decorative portion based on both of the above indices, a silver decorative portion that is free from cloudiness when visually observed and has a good sense of luster and color development can be realized.

[0050] Specifically, the silver decorative portion of the ceramic product disclosed herein has an 8° gloss value of 750 or more, and the 8° gloss value is less than the brightness L ＊ The value divided by (8° gloss value / lightness L ＊ ) is 20 or more. The higher the 8° gloss value, the more lustrous the silver tends to be. The 8° gloss value of the silver decorative portion is 750 or more, preferably 800 or more, may be 900 or more, may be 990 or more, or may be 1000 or more. The 8° gloss value is calculated by the lightness L ＊ The value divided by (8° gloss value / lightness L ＊ ) tends to be better in silver color development as this value increases. ＊is 20 or more, preferably 24 or more, more preferably 50 or more, may be 60 or more, or may be 70 or more. ＊ By satisfying the above range, a silver decorative part that has both color development and luster can be realized.

[0051] Lightness L ＊ is not particularly limited as long as it is adjusted to satisfy the above value. ＊ is preferably 10 or more, and may be 15 or more. ＊ If the lightness L is too high, the silver tends to be whitish and cloudy. ＊ is preferably 50 or less, more preferably 35 or less, even more preferably 30 or less, and particularly preferably 22 or less. For example, the lightness L ＊ is preferably 10 or more and 22 or less.

[0052] In order for the silver decorative portion to have a suitable silver color, L based on JIS Z 8781:2013 ＊ a ＊ b ＊ Chromaticity a in the color system ＊ and chromaticity b ＊ It is preferable that the chromaticity a is adjusted to a value that is neither too high nor too low. ＊ and chromaticity b ＊ indicates the color direction, and +a ＊ is the red direction, -a ＊ is the green direction, +b ＊ is the yellow direction, -b ＊ indicates the blue direction. ＊ and chromaticity b ＊ The measurement of chromaticity a can be performed using a spectrophotometer conforming to JIS Z 8722:2009. Although not particularly limited, the chromaticity a measured by the SCE method can be ＊ (Hereinafter, simply "chromaticity a ＊ ") is preferably, for example, -5 or more and 5 or less, and more preferably -1 or more and 1 or less. In addition, the chromaticity b ＊(Hereinafter, simply "chromaticity b ＊ ") is, for example, preferably -10 or more and 10 or less, and more preferably -5 or more and 5 or less.

[0053] Although not particularly limited, the ceramic product disclosed herein has suitable alkali resistance. Specifically, the ceramic product disclosed herein has alkali resistance to the extent that 30% or more of the silver decorative portion remains even after immersion in a boiling (100°C) 0.5 wt% Na2CO3 aqueous solution (approximately 3 L) for 0.5 hours, rinsing with water, and rubbing with zircon paper 10 times. This makes it possible to realize a ceramic product that can withstand cleaning in an automatic dishwasher using an alkaline detergent, for example.

[0054] The silver decorative portion is typically formed in the form of a film on the surface of the substrate (or coating layer) of the ceramic product. The average thickness of the silver decorative portion is not particularly limited, but is preferably 20 nm to 300 nm, and more preferably 50 nm to 150 nm. A silver decorative portion having such an average thickness will achieve a good silver color without the color of the ceramic substrate showing through. The average thickness of such a silver decorative portion can be appropriately adjusted, for example, by the application method.

[0055] <Method for manufacturing ceramic product> Next, an example of a method for manufacturing the ceramic product disclosed herein will be described. Note that the ceramic product disclosed herein is not limited to those manufactured by the following manufacturing method.

[0056] When manufacturing the ceramic product according to this embodiment, first, a desired substrate is prepared. For example, the substrate can be prepared by molding and firing a substrate material in which a predetermined ceramic material is kneaded. Alternatively, a substrate with a coating layer can be prepared by applying a glaze to the surface of the fired substrate and then firing it again. However, such a process is not particularly limited as long as the substrate can be prepared. For example, a separately prepared substrate may be purchased and prepared.

[0057] Next, in the production of the ceramic product disclosed herein, a silver decorative portion is formed on the substrate (or coating layer). This silver decorative portion can be formed by applying (applying) the decorative composition described above to the surface of the substrate or coating layer, followed by firing at a predetermined temperature. A suitable example of the firing process in this step is the use of the decorative composition disclosed herein for "overglaze painting," which involves decorating a substrate with a coating layer after a glaze has been applied. In overglaze painting, the decorative composition is applied to the surface of the glaze, followed by firing at a medium temperature of approximately 700°C to 1000°C. The decorative composition disclosed herein can also be used for "underglaze painting," which involves decorating a bisque-fired base (ceramic substrate). In underglaze painting, the decorative composition is applied to the base, followed by firing at a high temperature of approximately 1200°C to 1400°C. Examples of methods for applying the decorative composition include brush painting, screen printing, and inkjet printing.

[0058] In this manner, a ceramic product having a glossy, silver-colored decorative portion with good color development can be realized. Furthermore, a decorative composition that can suitably form such a silver-colored decorative portion can also be realized. As mentioned above, "ceramic products" include pottery, porcelain, earthenware, stoneware, glass, etc., and specific products include, for example, tableware, decorative utensils, various tiles, sanitary ware, roofing tiles, bricks, clay pipes, and ceramic pipes. In particular, the technology disclosed herein can suitably produce tableware having a glossy, clear, and silver-colored decorative portion with good color development. <Test Examples> Test examples related to the technology disclosed herein are described below, but it is not intended that the technology disclosed herein be limited to these test examples.

[0059] 1. Preparation of Decorative Compositions In this test, raw materials for precious metal elements and matrix-forming elements were mixed to obtain the compositions shown in Table 1. Each value in Table 1 represents the content (mol %) of each element when the total of the precious metal elements and matrix-forming elements contained in the decorative composition is taken as 100 mol %. Specifically, the various raw materials were mixed in an ointment jar and mixed for 2 minutes at 1800 rpm using a mixer manufactured by Thinky Corporation (product name: Rotating and Revolution Awatori Rentaro). In this manner, decorative compositions for Examples 1 to 10, Comparative Examples 1 and 2, and Reference Example 1 were prepared. The viscosities of the decorative compositions were 10 to 15 mPa·s. The raw materials for each element used are listed below. Pt: Pt resinate (platinum resin sulfide balsam) Rh: Rh resinate (rhodium resin sulfide balsam) Pd: Pd resinate (palladium resin sulfide balsam) Ir: Ir resinate (iridium resin sulfide balsam) Au: Au resinate (gold resin sulfide balsam) Ag: Ag resinate (silver resin sulfate) Bi: Bi resinate (bismuth resinate) Si: Si resinate (silicon resinate) Zr: Zr resinate (zirconium resinate) Sm: Sm resinate (samarium resinate)

[0060] (2) Application of Decorative Composition and Firing A white porcelain plate (length: 15 mm, width: 15 mm) with a coating layer (glaze) applied to its surface was prepared as a ceramic substrate, and the decorative composition prepared above (any of Examples 1 to 10, Comparative Examples 1 and 2, or Reference Example 1) was applied (sprayed) to the entire surface of one side of the white porcelain plate. The thickness of the silver decorative portion after firing was adjusted to 30 to 200 nm. A spin coater (Opticoat MS-A-150) manufactured by Mikasa Co., Ltd. was used to apply the decorative composition. The spin coater was set to spin conditions of 1000 rpm to 5000 rpm for 10 seconds. The white porcelain 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. As a result, white porcelain flat plates of Examples 1 to 10, Comparative Examples 1 and 2, and Reference Example 1 were obtained, each having a silver decorative portion formed on the surface of the ceramic substrate.

[0061] (3) Evaluation of gloss and color development The 8° gloss value and L ＊ Value, a ＊ value, b ＊ The 8° gloss value was measured using a spectrophotometer (CM-700d, manufactured by Konica Minolta Sensing Co., Ltd.) in accordance with JIS Z 8722:2009. The 8° gloss value was measured using the SCI method, and the L ＊ Value, a ＊ value, b ＊ The values ​​were measured by the SCE method. ＊ From, 8° gloss value / lightness L ＊ The 8° gloss value was calculated as follows: ＊ The silver decorative portion having a value of 20 or more was evaluated as having good luster and color development. The results are shown in Table 1.

[0062] (4) FESEM Observation FE-SEM observation was performed on the white porcelain plate on which the silver decorative portion was formed. FE-SEM observation images (magnification: 10,000 times) of the surface of the silver decorative portion were obtained using an FE-SEM (manufactured by Hitachi High-Technologies Corporation: SU8230). The acceleration voltage used to obtain the FE-SEM observation images was 10.0 kV, and the emission current was 10±0.5 μA. As an example, FE-SEM observation images of Example 1 and Comparative Example 2 are shown in Figures 1 and 2.

[0063]

[0064] As shown in Table 1, in Examples 1 to 10 and Reference Example 1, which mainly contained Au, the 8° gloss value was 750 or more and the 8° gloss value / lightness L ＊ It can be seen that the value is 20 or more. The decorative compositions of Examples 1 to 10 contain Pt, and the total of Rh, Pd, and Ir is 6 mol% or more and 60 mol% or less, relative to the total of the precious metal elements and matrix-forming elements being 100 mol%, so it is presumed that the effect of Pt in suppressing over-sintering is suitably exerted, resulting in improved color development and gloss. In other words, by using the decorative composition disclosed herein, it is possible to achieve color development and gloss that are equal to or better than those of silver decorative parts using a composition mainly composed of Au.

[0065] On the other hand, as shown in Table 1, in Comparative Example 1 which did not contain Rh, Pd, or Ir, and in Comparative Example 2 in which the total of Rh, Pd, and Ir exceeded 60 mol%, the 8° gloss value and the 8° gloss value / lightness L ＊ It can be seen that the value is significantly lower. This is presumably because Comparative Example 1, which does not contain Rh, Pd, or Ir, does not exhibit the effect of suppressing Pt over-sintering. Also, in Comparative Example 2, in which the total of Rh, Pd, and Ir exceeds 60 mol%, it is presumed that this is because the Pt particles become excessively small and the color-developing factors of Rh, Pd, and Ir themselves become large.

[0066] As shown in Table 1, when the ratio of the total molar fraction of the second and third elements to the molar fraction of the first element ((second element + third element) / first element) is 0.1 or greater and 1 or less, the 8° gloss value is 900 or greater and the 8° gloss value / lightness L* is 59 or greater. In other words, by appropriately adjusting the total molar fraction of Rh, Pd, and Ir relative to the molar fraction of Pt, a silver decorative part with even better color development and gloss can be achieved.

[0067] Although specific examples of the technology disclosed herein have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0068] The technology disclosed herein includes the following items 1 to 8. The following items 1 to 8 are not limited to the above-described embodiment.

[0069] Item 1 relates to a decorative composition. The decorative composition in item 1 is a decorative composition used for silver-coloring a ceramic substrate, and includes a precious metal element and a matrix-forming element, wherein the precious metal element includes a first element consisting of Pt, a second element consisting of Rh, and a third element that is at least one selected from the group consisting of Pd and Ir, and the matrix-forming element includes Bi, wherein, in a molar ratio where the sum of the precious metal element and the matrix-forming element is 100 mol %, the content of the precious metal element is 80 mol % or more, and the sum of the second element and the third element is 6 mol % to 60 mol %.

[0070] Item 2 is the decorative composition according to item 1, wherein the ratio of the total molar fraction of the second element and the third element to the molar fraction of the first element ((second element + third element) / first element) is 0.1 or more and 1 or less.

[0071] Item 3 is the decorative composition according to item 2, wherein the Pt content is 50 mol % or more and 80 mol % or less in the molar ratio.

[0072] Item 4 is the decorative composition according to any one of items 1 to 3, wherein the content of Rh in the molar ratio is 3 mol % or more and 10 mol % or less.

[0073] Item 5 is the decorative composition according to any one of items 1 to 4, wherein the Pd content is 10 mol % or more and 35 mol % or less in the molar ratio.

[0074] Item 6 is the decorative composition according to any one of items 1 to 5, wherein the precious metal element further includes a fourth element, and the fourth element is at least one element selected from the group consisting of Au, Ag, Ru, and Os.

[0075] Item 7 is the decorative composition according to any one of items 1 to 6, wherein the content of the fourth element in the molar ratio is 18.5 mol % or less.

[0076] Item 8 relates to a ceramic product. The ceramic product in item 8 comprises a ceramic substrate, and a silver decorative part disposed on the ceramic substrate and made of a fired body of the decorative composition according to any one of items 1 to 7, wherein the silver decorative part has an 8° gloss value of 750 or more when measured by the SCI method, and a lightness L of the silver decorative part when measured by the SCE method. ＊ The value divided by (8° gloss value / lightness L ＊ ) is 20 or more.

Claims

1. A decorative composition used for silver decoration of a ceramic substrate, comprising a precious metal element and a matrix-forming element, wherein the precious metal element comprises a first element consisting of Pt, a second element consisting of Rh, and a third element being at least one selected from the group consisting of Pd and Ir, and the matrix-forming element comprises Bi, wherein, in a molar ratio where the sum of the precious metal element and the matrix-forming element is 100 mol %, the content of the precious metal element is 80 mol % or more, and the sum of the second element and the third element is 6 mol % or more and 60 mol % or less.

2. The decorative composition according to claim 1, wherein the ratio of the total molar fraction of the second element and the third element to the molar fraction of the first element ((second element + third element) / first element) is 0.1 or more and 1 or less.

3. The decorative composition according to claim 2, wherein the Pt content is 50 mol % or more and 80 mol % or less in said molar ratio.

4. The decorative composition according to claim 1 or 2, wherein the content of Rh in said molar ratio is 3 mol % or more and 10 mol % or less.

5. The decorative composition according to claim 1 or 2, wherein the Pd content in said molar ratio is 10 mol % or more and 35 mol % or less.

6. The decorative composition according to claim 1 or 2, wherein the precious metal element further comprises a fourth element, and the fourth element is at least one element selected from the group consisting of Au, Ag, Ru and Os.

7. The decorative composition according to claim 6, wherein the content of the fourth element in said molar ratio is 18.5 mol % or less.

8. A ceramic substrate; and a silver decorative part arranged on the ceramic substrate and made of a fired body of the decorative composition according to claim 1 or 2, wherein the silver decorative part has an 8° gloss value of 750 or more when measured by the SCI method, and a lightness L of the silver decorative part when the 8° gloss value is measured by the SCE method. ＊ The value divided by (8° gloss value / lightness L ＊ ) is 20 or more.

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