Article comprising an at least partially porcelain substrate, a decorative element and a thermal expansion gradient buffer and method for making such an article

Abstract

The present application relates to an article (1) comprising a substrate (2) and a decoration (3), wherein the decoration (3) comprises a ceramic colorant (7) and a glaze (8), wherein the substrate (2) has a first thermal expansion coefficient, and the ceramic colorant (7) has a second thermal expansion coefficient, wherein the first thermal expansion coefficient is smaller than the second thermal expansion coefficient, and the article (1) is characterized in that the article further comprises a thermal expansion gradient buffer (4) at least partially disposed between the substrate (2) and the ceramic colorant (7), wherein the thermal expansion gradient buffer (4) has a third thermal expansion coefficient, wherein the third thermal expansion coefficient is between the first thermal expansion coefficient and the second thermal expansion coefficient. The present application also relates to a method for manufacturing such an article (1).

Description

Technical Field

[0001] The present invention relates to an article, in particular in the field of tableware (such as plates, cups, salad bowls, etc.), comprising a base at least partially made of ceramic, and more particularly of porcelain, and a decorative element.

[0002] The invention also relates to a method of making such an article. Background Art

[0003] Articles comprising a substrate and a decoration are known, in particular in the field of tableware, in particular tableware of the type of plates, cups, salad bowls and the like.

[0004] Such substrates are, for example, partially ceramic and more particularly porcelain and are conventionally coated with enamel.

[0005] The decoration usually comprises a glaze and a ceramic colorant, such as a ceramic pigment comprising, for example, a metal oxide, mixed with a fritte.

[0006] Ceramic pigments generally include elements such as lead (Pb), cadmium (Cd), cobalt (Co), chromium (Cr), nickel (Ni), arsenic (As), manganese (Mn), aluminum (Al), barium (Ba), iron (Fe), and gold (Au).

[0007] The glaze of the decorative article is particularly configured to form a diffusion barrier making it possible to limit the extraction of the elements contained in the ceramic colorant into foods and / or liquids that come into contact with the article during use of the article.

[0008] To this end, the glaze is traditionally formed from a mixture of oxides, nitrates, carbonates or composite oxides, including, for example, titanium oxide (TiO2), calcium oxide (CaO), magnesium oxide (MgO), boron oxide (B2O3), silicon dioxide (SiO2), aluminum oxide (Al2O3), potassium oxide (K2O), sodium oxide (Na2O), zinc oxide (ZnO), zirconium oxide (ZrO2), barium oxide (BaO) or bismuth oxide (Bi2O3).

[0009] Despite the presence of this glaze, it has been found that a portion of the elements contained in the ceramic color are released during use of the article. Summary of the invention

[0010] The present invention aims at providing an article, in particular in the field of tableware (such as plates, cups, salad bowls, etc.), comprising an at least partially ceramic, and more particularly porcelain, substrate and a decoration, wherein the extraction of elements of the decoration is reduced.

[0011] Thus, in a first aspect, the invention relates to an article comprising an at least partially porcelain substrate and a decoration comprising at least one ceramic colorant and a glaze, the substrate having a thermal expansion coefficient known as a first thermal expansion coefficient, the ceramic colorant having a thermal expansion coefficient known as a second thermal expansion coefficient, the first thermal expansion coefficient being less than the second thermal expansion coefficient, the article being characterized in that it also comprises a thermal expansion gradient buffer at least partially placed between the substrate and the ceramic colorant, the thermal expansion gradient buffer having a thermal expansion coefficient known as a third thermal expansion coefficient, which is between the first thermal expansion coefficient and the second thermal expansion coefficient, the thermal expansion gradient buffer and the decoration being configured to limit the appearance of cracks in at least the glaze.

[0012] The thermal expansion gradient buffer has a thermal expansion coefficient greater than that of the substrate and less than that of the ceramic colorant. Such a thermal expansion gradient buffer thus makes it possible to reduce the thermal expansion coefficient gradient in the article and thus reduce the thermomechanical stresses between the substrate and the decoration. The thermomechanical stresses cause cracks to appear in the decoration, more particularly in the diffusion barrier formed by the glaze.

[0013] This thermal expansion gradient buffer thus contributes to limiting degradation of the glaze of the decoration and in particular limiting the risk of cracks appearing, or at least limiting the size of cracks, ie in particular in terms of width and / or depth.

[0014] Furthermore, the thermal expansion gradient buffer helps to reduce the risk of tressaillage of the trim.

[0015] Even more surprisingly, it has been shown that the thermal expansion gradient buffer also results in a reduced release of elements contained in the at least one ceramic colorant during food contact experiments.

[0016] In particular, it has been shown that the elements contained in the at least one ceramic colorant are released from the article through cracks that can be formed in the decoration. These cracks thus form diffusion paths for the elements of the ceramic colorant towards the food or liquid placed on the decoration.

[0017] The thermal expansion gradient buffer helps limit the appearance of cracks (in number and / or size) in the glaze and has also been shown to help limit the diffusion of elements contained in the ceramic colorant into food or liquids placed on the decorative article.

[0018] Thus, the limitation of these diffusion paths helps to reduce the precipitation of these elements.

[0019] In a specific example, the third coefficient of thermal expansion (ie, the coefficient of thermal expansion of the thermal expansion gradient buffer) is between the first coefficient of thermal expansion and the coefficient of thermal expansion of the decoration.

[0020] In this case, the coefficients of thermal expansion are each measured between 100° C. and 300° C.

[0021] Preferred features of the articles of the present invention which are particularly simple, convenient and economical are given below, which features can be used individually or in combination.

[0022] In an exemplary embodiment, the at least one ceramic colorant is located between the substrate and the glaze, in particular between the thermal expansion gradient buffer and the glaze.

[0023] Thus, preferably, the glaze covers the at least one ceramic colorant.

[0024] In another exemplary embodiment, the substrate is provided with an enamel at least partially disposed between the porcelain and the thermal expansion gradient buffer.

[0025] In a specific exemplary embodiment, the first thermal expansion coefficient of the substrate is 3.0x10 -6 K -1 Up to 6.0x10 -6 K -1 , preferably 3.5x10 -6 K -1 Up to 5.0x10 -6 K -1 .

[0026] In an exemplary embodiment, the second thermal expansion coefficient of the ceramic colorant is 5.0x10 -6 K -1 to 11.0x10 -6 K -1 .

[0027] In one exemplary embodiment, the third thermal expansion coefficient is 4.5x10 -6 K -1 Up to 7.0x10 -6 K -1 , even 5.0x10 -6 K -1 Up to 6.5x10 -6 K -1 .

[0028] In a favorable exemplary embodiment, the at least one ceramic colorant comprises a mixture of glass frit and pigment and comprises at least one element selected from the group consisting of lead (Pb), cadmium (Ca), aluminum (Al), cobalt (Co), barium (Ba), chromium (Cr), nickel (Ni), arsenic (As), manganese (Mn), iron (Fe), gold (Au), silver (Ag), vanadium (V), titanium (Ti) and copper (Cu).

[0029] In an exemplary embodiment, the thermal expansion gradient buffer comprises (content expressed as mass percentage, expressed as "% by weight"):

[0030] - 10-30% by weight of boron oxide (B2O3);

[0031] - 20-70% by weight of silicon oxide (SiO2);

[0032] - 1-10% by weight of aluminum oxide (Al2O3);

[0033] - 0-3% by weight of titanium oxide (TiO2);

[0034] - 0-3% by weight of calcium oxide (CaO);

[0035] - 0-2% by weight of manganese oxide (MgO);

[0036] - 0-8% by weight of potassium oxide (K2O);

[0037] - 0-8% by weight of sodium oxide (Na2O);

[0038] - 0-8% by weight of zinc oxide (ZnO);

[0039] - 0-8% by weight of zirconium oxide (ZrO2);

[0040] - 0-5% by weight of barium oxide (BaO) and

[0041] - 0-5% by weight of bismuth oxide (Bi2O3).

[0042] Preferably, the sum of these contents equals 100% by weight.

[0043] In an exemplary embodiment, the glaze comprises (content expressed as mass percentage, expressed as "% by weight"):

[0044] - 10-30% by weight of boron oxide (B2O3);

[0045] - 20-70% by weight of silicon oxide (SiO2);

[0046] - 1-10% by weight of aluminum oxide (Al2O3);

[0047] - 0-3% by weight of titanium oxide (TiO2);

[0048] - 0-3% by weight of calcium oxide (CaO);

[0049] - 0-2% by weight of manganese oxide (MgO);

[0050] - 0-8% by weight of potassium oxide (K2O);

[0051] - 0-8% by weight of sodium oxide (Na2O);

[0052] - 0-8% by weight of zinc oxide (ZnO);

[0053] - 0-8% by weight of zirconium oxide (ZrO2);

[0054] - 0-5% by weight of barium oxide (BaO); and

[0055] - 0-5% by weight of bismuth oxide (Bi2O3).

[0056] Preferably, the sum of these contents equals 100% by weight.

[0057] According to a preferred example, the content of at least one of the oxides of the glaze is different from the content of the oxide of the thermal expansion gradient buffer.

[0058] In an exemplary embodiment, the content of silicon oxide (SiO 2 ) in the thermal expansion gradient buffer is less than the content of silicon oxide (SiO 2 ) in the glaze.

[0059] In an exemplary embodiment, the content of boron oxide (B2O3) in the thermal expansion gradient buffer is greater than the content of boron oxide (B2O3) in the glaze.

[0060] In an exemplary embodiment, the content of aluminum oxide (Al2O3) in the thermal expansion gradient buffer is greater than the content of aluminum oxide (Al2O3) in the glaze.

[0061] For example, the substrate has a thickness of 1 mm to 10 mm.

[0062] For example, the thermal expansion gradient buffer has a thickness of 1 μm to 20 μm, preferably 1 μm to 10 μm, or even 3 μm to 8 μm.

[0063] For example, the thermal expansion gradient buffer and the decoration have a thickness of 10 μm to 25 μm.

[0064] For example, the at least one ceramic colorant, ie one ceramic colorant or all ceramic colorants if a plurality of ceramic colorants are present, has a thickness of 2 μm to 250 μm, preferably 5 μm to 50 μm.

[0065] For example, the glaze has a thickness of 1 to 20 μm, preferably 1 to 10 μm, or even 3 to 8 μm.

[0066] In a second aspect, the present invention is also directed to a method for manufacturing an article as described above, comprising:

[0067] - a step of providing a substrate at least partially made of porcelain;

[0068] - A step of providing a decorative object comprising at least one ceramic colorant and a glaze;

[0069] - a step of providing a thermal expansion gradient buffer; and

[0070] - a step of assembling the substrate, the decoration and the thermal expansion gradient buffer, the thermal expansion gradient buffer being at least partially interposed between the substrate and the ceramic colorant,

[0071] The substrate has a coefficient of thermal expansion referred to as a first coefficient of thermal expansion,

[0072] The ceramic colorant has a coefficient of thermal expansion referred to as a second coefficient of thermal expansion, the first coefficient of thermal expansion being smaller than the second coefficient of thermal expansion,

[0073] The thermal expansion gradient buffer has a thermal expansion coefficient called a third thermal expansion coefficient, which is between the first thermal expansion coefficient and the second thermal expansion coefficient.

[0074] The thermal expansion gradient buffer and the decorator are configured to limit the occurrence of cracks in at least the glaze.

[0075] This method thus enables an article as described above to be easily manufactured.

[0076] In a specific exemplary embodiment, the method comprises the sub-step of firing the substrate at a temperature of 1380°C to 1400°C, for a duration of, for example, 20-24 hours.

[0077] In another specific exemplary embodiment, the manufacturing method further comprises a step of forming a substrate, which step comprises a sub-step of providing the porcelain and a sub-step of enameling the porcelain, which step precedes the step of providing the substrate.

[0078] Optionally, the method comprises the sub-step of firing the porcelain at a temperature of 950°C to 1000°C.

[0079] It is then covered with an enamel consisting, for example, of a mixture of silicon dioxide, feldspar and kaolin.

[0080] In yet another specific exemplary embodiment, the manufacturing method further comprises a step of forming a decorative object, the step comprising at least one sub-step of assembling the glaze and the at least one ceramic colorant.

[0081] This step precedes the step of providing the decorations.

[0082] Optionally, the step of forming the decoration further comprises a sub-step of assembling the thermal expansion gradient buffer with the glaze and the ceramic colorant.

[0083] For example, the sub-step of assembling at least the glaze and the ceramic color, even together with the thermal expansion gradient buffer, is performed by chromolithographie.

[0084] For example, the chromolithography process comprises the steps of providing a paper support; applying to the paper support at least one first fabric comprising at least one hollow area, i.e., for example, a cutout, representing a first pattern; and applying a first paste to the paper support through the cutout of the first fabric.

[0085] Thus, the first fabric forms a first stencil.

[0086] The chromolithography process then comprises, if necessary, a step of removing the first fabric; a drying step; then a step of applying a second fabric to a paper support previously coated with the first paste, the second fabric comprising at least one cutout pattern or hollowed-out area representing a second pattern; and then a step of applying the second paste to the paper support (coated with the first paste) through the cutout pattern of the second fabric.

[0087] Optionally, if necessary, the same operation is applied to the third paste, and so on. This process may be repeated for all color pastes required for the final pattern. Due to the complexity of some patterns, a large number of color pastes may be applied. For example, 14 different fabrics using 14 different color pastes, or even more.

[0088] The final paste is preferably a paste comprising the glaze, which is deposited evenly on the colorant layer.

[0089] For example, the first paste comprises the at least one ceramic colorant and the last paste comprises the glaze.

[0090] Or for example, a first paste comprises the thermal expansion gradient buffer, a second paste comprises the at least one ceramic colorant, and a third paste comprises the glaze.

[0091] Optionally, the manufacturing method further comprises the step of applying an acrylic type polymer coating (top layer) on the glaze layer.

[0092] Such a polymer coating is applied as the last layer to the glaze in order to provide a thickness sufficient to operate on the whole of the layer applied to the substrate.

[0093] However, this polymer coating is consumed during the firing of the article and is therefore not detectable in the final product.

[0094] Preferably, the method comprises a step of drying the paper and at least one paste layer applied thereto. For example there is drying between the layers, which enables evaporation of the solvent present in the respective paste.

[0095] Then, once dry, the (coated) paper is placed in a water bath.

[0096] The "chromo" (ie the entirety of the dried polymer / paste layer) comes off and can be manipulated.

[0097] The color planographic print is placed on the substrate such as a porcelain product, and the water is drained to adhere the color planographic print to the substrate and properly condition it.

[0098] Thus, in one particular exemplary embodiment, the method includes an oven drying step.

[0099] The article is then placed, for example, in a heating tunnel at 700-900° C. for 2 hours (temperature gradient).

[0100] The polymer (acrylic) is consumed and the assembly formed by the frit, glaze and buffer melts and adheres to the surface of the substrate.

[0101] Thus, in a particular exemplary embodiment, the method comprises the step of firing the article at a temperature between 700°C and 900°C, for example at about 880°C.

[0102] The duration of this calcination step is, for example, 1 h30 to 2 h30, preferably about two hours.

[0103] In a specific exemplary embodiment, the calcining step includes ramping to 880° C. in about ten minutes, then heating for 1 h30 to 2 h, and then cooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0104] The invention according to an exemplary embodiment will be better understood and its advantages will better appear by reading the following detailed description given in an illustrative and non-limiting manner with reference to the accompanying drawings, in which:

[0105] [ Figure 1 ] Figure 1 A cross section of an article according to an exemplary embodiment of the present invention is schematically shown, comprising a substrate, a decoration, and a thermal expansion gradient buffer.

[0106] [ Figure 2 ] Figure 2 A cross section of an article according to another exemplary embodiment of the present invention is schematically shown, which includes a decoration formed of ceramic color and glaze, a thermal expansion gradient buffer, and a substrate formed of porcelain and enamel.

[0107] [ Figure 3 ] Figure 3 Schematically shows an exemplary embodiment of the present invention. Figure 1 The steps of the method for manufacturing the product.

[0108] [ Figure 4 ] Figure 4 Schematically shows another exemplary embodiment of the present invention. Figure 1 The steps of the method for manufacturing the product.

[0109] [ Figure 5 ] Figure 5 This is a scanning electron microscope image of a cross section of a product without a thermal expansion gradient buffer.

[0110] [ Figure 6 ] Figure 6 is a scanning electron microscope image of a cross section of an article according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0111] Figure 1 A cross section of an article 1 according to an exemplary embodiment of the invention is schematically shown, for example a cross section through the thickness of the article.

[0112] The product 1 is, for example, a plate, a bowl, a salad bowl, etc.

[0113] The article 1 mainly comprises a substrate 2 and a decoration 3 .

[0114] The substrate 2 comprises at least one ceramic, for example porcelain.

[0115] Such a substrate 2 has a coefficient of thermal expansion which is referred to herein as the first coefficient of thermal expansion.

[0116] The first thermal expansion coefficient is 3.0x10 -6 K -1Up to 6.0x10 -6 K -1 .

[0117] The substrate has a thickness of, for example, 1 mm to 10 mm.

[0118] The decoration 3 represents a coating applied to the substrate.

[0119] According to the present invention, the article 1 further comprises a thermal expansion gradient buffer 4 .

[0120] The thermal expansion gradient buffer 4 is, for example, at least partially interposed between the substrate 2 and the decoration 3 .

[0121] This thermal expansion gradient buffer 4 has a thermal expansion coefficient which is referred to as the third thermal expansion coefficient.

[0122] This third coefficient of thermal expansion is greater than the first coefficient of thermal expansion of the substrate 2 and, according to an exemplary embodiment of the present invention, is less than the coefficient of thermal expansion of the decoration 3 .

[0123] Thus, for example, the third thermal expansion coefficient is 4.5x10 -6 K -1 Up to 7.0x10 -6 K -1 , even 5.0x10 -6 K -1 Up to 6.5x10 -6 K -1 .

[0124] The thickness of the thermal expansion gradient buffer 4 is 1 μm to 20 μm, preferably 1 μm to 10 μm, or even 3 μm to 8 μm.

[0125] The thermal expansion gradient buffer 4, for example, comprises (the content is expressed as mass percentage, expressed as "% by weight"):

[0126] - 10-30% by weight of boron oxide (B2O3);

[0127] - 20-70% by weight of silicon oxide (SiO2);

[0128] - 1-10% by weight of aluminum oxide (Al2O3);

[0129] - 0-3% by weight of titanium oxide (TiO2);

[0130] - 0-3% by weight of calcium oxide (CaO);

[0131] - 0-2% by weight of manganese oxide (MgO);

[0132] - 0-8% by weight of potassium oxide (K2O);

[0133] - 0-8% by weight of sodium oxide (Na2O);

[0134] - 0-8% by weight of zinc oxide (ZnO);

[0135] - 0-8% by weight of zirconium oxide (ZrO2);

[0136] - 0-5% by weight of barium oxide (BaO) and

[0137] - 0-5% by weight of bismuth oxide (Bi2O3).

[0138] The composition can be adapted by a person skilled in the art to obtain an expansion coefficient value within a target range.

[0139] The thermal expansion gradient buffer 4 having the third thermal expansion coefficient makes it possible to reduce the thermal expansion coefficient gradient between, for example, the substrate 2 and the decoration, and thus reduce the thermomechanical stresses exerted between the substrate 2 and the decoration 3 .

[0140] exist Figure 2 In the exemplary embodiment of FIG. 8 , the decoration 3 comprises at least one ceramic colorant 7 and a glaze 8 .

[0141] The at least one ceramic colorant 7 is configured to provide a specific color to the decorative object depending on its composition.

[0142] The ceramic colorant 7 includes, for example, ceramic pigments and / or metal oxides mixed with glass frit.

[0143] The ceramic pigment 7 generally contains at least one element selected from the group consisting of lead (Pb), cadmium (Ca), aluminum (Al), cobalt (Co), barium (Ba), chromium (Cr), nickel (Ni), arsenic (As), manganese (Mn), iron (Fe), gold (Au), and silver (Ag).

[0144] For example, cobalt oxide in ceramic colors typically provides a blue coloration.

[0145] Typically, the article comprises a plurality of ceramic colourants 7 to produce a multi-coloured decoration.

[0146] The total thickness of the at least one ceramic colorant 7 or, if a plurality of ceramic colorants are present, the total thickness of all ceramic colorants is preferably 2 μm to 250 μm, preferably 5 μm to 50 μm.

[0147] The glaze 8 of the decoration 3 is notably configured to form a diffusion barrier making it possible to limit the precipitation of the elements contained in the ceramic color or colors 7 .

[0148] The glaze 8 preferably has a thickness of 1 μm to 20 μm, preferably 1 μm to 10 μm, or even 3 μm to 8 μm.

[0149] Glaze 8 contains, for example (content is expressed as mass percentage, expressed as "% by weight"):

[0150] - 10-30% by weight of boron oxide (B2O3);

[0151] - 20-70% by weight of silicon oxide (SiO2);

[0152] - 1-10% by weight of aluminum oxide (Al2O3);

[0153] - 0-3% by weight of titanium oxide (TiO2);

[0154] - 0-3% by weight of calcium oxide (CaO);

[0155] - 0-2% by weight of manganese oxide (MgO);

[0156] - 0-8% by weight of potassium oxide (K2O);

[0157] - 0-8% by weight of sodium oxide (Na2O);

[0158] - 0-8% by weight of zinc oxide (ZnO);

[0159] - 0-8% by weight of zirconium oxide (ZrO2);

[0160] - 0-5% by weight of barium oxide (BaO); and

[0161] - 0-5% by weight of bismuth oxide (Bi2O3).

[0162] Preferably, the content of at least one of the oxides of the glaze is different from the content of the oxide of the thermal expansion gradient buffer.

[0163] In particular, the content of silicon oxide (SiO 2 ) in the thermal expansion gradient buffer 4 is less than the content of silicon oxide (SiO 2 ) in the glaze 8 .

[0164] The content of boron oxide (B 2 O 3 ) in the thermal expansion gradient buffer 4 is greater than the content of boron oxide (B 2 O 3 ) in the glaze 8 .

[0165] The content of aluminum oxide (Al 2 O 3 ) in the thermal expansion gradient buffer 4 is greater than the content of aluminum oxide (Al 2 O 3 ) in the glaze 8 .

[0166] In an exemplary embodiment that is not shown, the at least one ceramic colorant 7 and the glaze 8 are at least partially mixed.

[0167] In a specific exemplary embodiment, Figure 2As schematically shown, the at least one ceramic colorant 7 is at least partially disposed between the thermal expansion gradient buffer 4 and the glaze 8 .

[0168] Thermomechanical stresses partly cause cracks to appear in the decoration 3 and more particularly in the diffusion barrier formed by the glaze 8 of the decoration 3 .

[0169] Thus, the thermal expansion gradient buffer 4 helps to limit degradation in at least the glaze 8 of the decoration 3 and therefore the risk of cracks appearing, or at least the size of cracks, ie in particular in terms of their width and / or their depth.

[0170] By reducing cracks, the thermal expansion gradient buffer 4 acts in synergy with the glaze 8 to help limit the release of elements contained in the at least one ceramic color 7 that occurs via these cracks.

[0171] Furthermore, the thermal expansion gradient buffer 4 makes it possible to limit cracking of the decoration 3 .

[0172] In such Figure 2 In the exemplary embodiment of the article 1 shown, the substrate 2 comprises porcelain 6 which is also provided with an enamel 5 .

[0173] Porcelain 6 traditionally comprises a mixture of quartz, kaolin and feldspar.

[0174] The enamel 5 of the substrate 2 contains, for example, various minerals such as silicon dioxide, kaolin and feldspar.

[0175] In this exemplary embodiment, the enamel 5 is at least partially interposed between the porcelain 6 and the thermal expansion gradient buffer 4 .

[0176] In practice, the porcelain 6 and the enamel 5 of the substrate 2 are usually at least partially mixed.

[0177] In an exemplary embodiment, the enamel 5 and the thermal expansion gradient buffer 4 are at least partially mixed.

[0178] In order to manufacture the product 1 as described above, Figure 3 and Figure 4 A method according to an exemplary embodiment of the present invention is schematically shown in FIG.

[0179] like Figure 3 As shown, the method for manufacturing the product 1 mainly includes:

[0180] - a step 12 of providing a substrate 2 at least partially made of porcelain 6, the substrate having a coefficient of thermal expansion referred to as a first coefficient of thermal expansion;

[0181] - a step 13 of providing a decorative object 3 comprising at least one ceramic colorant 7 and a glaze 8;

[0182] - step 14 of providing a thermal expansion gradient buffer 4; and

[0183] - a step 15 of assembling the substrate 2, the decorative object 3 and the thermal expansion gradient buffer 4, the thermal expansion gradient buffer 4 being at least partially disposed between the substrate 2 and the ceramic colorant 7;

[0184] The substrate has a coefficient of thermal expansion referred to as a first coefficient of thermal expansion,

[0185] The ceramic colorant 7 has a thermal expansion coefficient called a second thermal expansion coefficient, the first thermal expansion coefficient is smaller than the second thermal expansion coefficient,

[0186] The thermal expansion gradient buffer 4 has a thermal expansion coefficient called a third thermal expansion coefficient, which is between the first thermal expansion coefficient and the second thermal expansion coefficient.

[0187] The thermal expansion gradient buffer 4 and the decoration 3 are configured to limit the appearance of cracks in at least the glaze 8 .

[0188] Thus, the thermal expansion gradient buffer 4 and the decoration 3 are configured to limit the appearance of at least cracks in the glaze 8, or at least limit the size of cracks.

[0189] The steps of providing a substrate, providing a decoration and providing a thermal expansion gradient buffer may be performed sequentially or simultaneously.

[0190] Figure 4 Schematically shows a method for implementing Figure 3 Various helpful options for the method.

[0191] For example, the method of manufacturing the article 1 includes a step 22 of forming the substrate 2 .

[0192] This step 22 of forming a substrate may include the sub-steps of providing porcelain and enameling the porcelain with enamel.

[0193] This step 22 of forming a substrate typically precedes the step 12 of providing a substrate 2 .

[0194] The substrate 2 may be coated with a thermal expansion gradient buffer 4 .

[0195] In a particular case, the step 22 of forming the substrate will then include the sub-step of assembling the enameled porcelain and the thermal expansion gradient buffer 4 together.

[0196] The method for manufacturing the article 1 may further comprise a step 23 of forming the decoration 3 .

[0197] This step 23 typically precedes the step 13 of providing the decoration 3 .

[0198] For example, said step 23 of forming the decoration 3 comprises a sub-step 33 of assembling the glaze 8 and the at least one ceramic colorant 7 .

[0199] According to an advantageous embodiment, the step 23 of forming the decoration 3 comprises a sub-step of assembling the glaze 8 and at least one ceramic colorant 7 with the thermal expansion gradient buffer 4 .

[0200] The step 15 of assembling the substrate 2 , the decoration 3 and the thermal expansion gradient buffer 4 comprises, for example, one or more sub-steps 25 of firing the substrate 2 , the decoration 3 and the thermal expansion gradient buffer 4 .

[0201] For example, the sub-step for firing the substrate 2 has a firing temperature of 1380° C. to 1400° C. and a duration of 20 to 24 hours.

[0202] For example, the firing temperature of the sub-step for firing the decoration 3 is 700°C to 900°C.

[0203] For example, the sub-step for firing the thermal expansion gradient buffer 4 assembled with the substrate 2 and / or the decorative object 3 has a firing temperature of 700-900°C.

[0204] Figure 5 and Figure 6 Backscattered electron photographs showing cross-sections of articles with and without thermal expansion gradient buffers (preferential chemical contrast).

[0205] The product under consideration here is a plate.

[0206] Figure 6 The ceramic product 1 comprises: a base 2 made of porcelain 6 covered with enamel 5, a thermal expansion gradient buffer 4, and a decoration 3 comprising a ceramic colorant 7 and a glaze 8.

[0207] This is, for example, Limoges porcelain.

[0208] For example, the porcelain 6 here contains kaolin, feldspar and quartz.

[0209] More particularly, the porcelain comprises approximately 50% kaolin, 25% feldspar and 25% quartz.

[0210] The porcelain 6 is first fired at, for example, 950°C to 1000°C.

[0211] It is then covered with an enamel consisting, for example, of a mixture of silica, feldspar and kaolin, and the substrate is then fired at 1380°C to 1400°C.

[0212] This substrate is used as a decorative support.

[0213] The decoration operation is carried out, for example, by ceramic chromolithography.

[0214] Here, the color lithography is printed layer by layer by screen printing through a fabric on a paper support.

[0215] For example, a first fabric comprising at least one hollowed-out area representing a desired first pattern is applied to the paper support and the paste is spread on the first fabric. Thus, the paste contacts the paper only in the perforated area.

[0216] A similar operation is repeated using at least one second fabric comprising at least one cutout representing the desired second pattern, which is then applied to the paper support already covered in places with the first colorant, and another paste is then spread on the second fabric.

[0217] Here, the ceramic chromolithography is applied to the thermal expansion gradient buffer 4, at least one of the ceramic colorants 7 and the glaze 8. It thus comprises at least three stages for at least three pastes.

[0218] The thermal expansion gradient buffer is achieved by a mixture of 50% glass frit and 50% acrylic binder, which forms the first paste.

[0219] A layer of this first paste containing the thermal expansion gradient buffer is printed onto a paper support by screen printing.

[0220] The screen printing fabric used to apply the first paste containing the thermal expansion gradient buffer is adapted so that after firing, the thickness of the thermal expansion gradient buffer is 3 μm to 8 μm.

[0221] Subsequently, at least one ceramic colorant 7 is also applied to the fabric in the form of at least one second paste. The ceramic colorant 7 is then only in (indirect) contact with the paper support according to the openwork decorative pattern in the corresponding fabric.

[0222] The second paste contains the pigments of the ceramic colorant 7 and the glass frit on the one hand and an acrylic binder on the other hand.

[0223] The ratio between pigment and glass frit on the one hand and acrylic binder on the other hand is, for example, approximately 57:43.

[0224] Typically, the acrylic binder is consumed during heating.

[0225] The second paste is applied, for example, in one layer.

[0226] The second ceramic colorant is then applied from a third paste in the same manner.

[0227] The total thickness of the ceramic colorant after firing is then, for example, 5 μm to 50 μm, or even 10 μm to 25 μm.

[0228] If the decoration includes multiple colorants, each colorant can be applied in the same manner as described above.

[0229] Optionally, at least one of the ceramic colorants 7 contains cobalt element.

[0230] Possibly, a plurality of colorants each containing cobalt can be applied, for example to generate a blue gradient.

[0231] Then, a layer of a fourth paste comprising a glaze and a mixture of 50% of glass frit and 50% of an acrylic binder is printed by screen printing to achieve a glaze thickness of preferably 3 to 8 μm after firing.

[0232] Also, typically, acrylic adhesives are consumed during the heating process.

[0233] For example, a layer of a fourth paste comprising a glaze is applied over the layer comprising ceramic color and thermal expansion gradient buffer.

[0234] Finally, an optional final layer (top layer) of, for example, an acrylic polymer is printed over the glaze.

[0235] After drying, a ceramic chromolithographie is obtained.

[0236] The ceramic chromolithographic print is then immersed in water to release it from the paper support and then positioned and applied to the enameled substrate.

[0237] Any water that may be present between the surface of the enameled substrate and the ceramic chromolithographic print is then driven off with the aid of, for example, a flexible glue.

[0238] The article was dried in an oven and then fired at 880°C for about two hours.

[0239] After firing, the thermal expansion gradient buffer and the decoration have a thickness of 10 μm to 25 μm.

[0240] Thus, in this example:

[0241] -The thermal expansion coefficient of the thermal expansion gradient buffer is equal to 6.1x10 -6 K -1 ;

[0242] -The thermal expansion coefficient of the first ceramic pigment is equal to 6.3x10 -6 K -1 ;

[0243] -The thermal expansion coefficient of the second ceramic pigment is equal to 7.3x10 -6K -1 ;

[0244] -The thermal expansion coefficient of the glaze is 5.4x10 -6 K -1 ;

[0245] - The thermal expansion coefficient of the plate's porcelain 6 is equal to 4.6x10 -6 K -1 ;

[0246] -The thermal expansion coefficient of enamel 5 is 4.5x10 -6 K -1 .

[0247] In this case, the coefficients of thermal expansion are each measured at 100° C. to 300° C.

[0248] Figure 5 The product corresponds to the above Figure 6 products, but without thermal expansion gradient buffers.

[0249] Figure 5 and Figure 6 It is shown that the ceramic colorant 7 is placed directly between the substrate 2 and the glaze 8 without a thermal expansion gradient buffer.

[0250] In the presence of the thermal expansion gradient buffer 4 , the ceramic colorant 7 is placed between the thermal expansion gradient buffer 4 and the glaze 8 .

[0251] In other words, the thermal expansion gradient buffer 4 is located on the substrate 2 , between the substrate 2 and the ceramic pigment 7 .

[0252] In order to reveal the benefits of the invention in terms of elemental leaching during use of the article 1 , specific migration tests of elements in contact with food were carried out according to standard NF EN 1388-1 on the above-mentioned article with and without thermal expansion gradient buffer.

[0253] In the example shown here, the element being tracked is cobalt.

[0254] The specific migration value of cobalt (in ppb: <<particle per bilion>>) was measured by ICP-MS after three 24-hour contact times in 4% (v / v) acetic acid at 22° C. (+ / −2° C.).

[0255] This testing showed that with the thermal expansion gradient buffer 4, 31 ppb was measured for cobalt, while in the absence of the thermal expansion gradient buffer, 461 ppb was measured for cobalt.

[0256] The presence of a thermal expansion gradient buffer can reduce cobalt precipitation by nearly fifteen times.

Claims

1. An article comprising a substrate (2) at least partially made of porcelain (6) and a decoration (3), the decoration (3) comprising at least one ceramic colorant (7) and a glaze (8), the substrate (2) having a thermal expansion coefficient referred to as a first thermal expansion coefficient, the ceramic colorant (7) having a thermal expansion coefficient referred to as a second thermal expansion coefficient, the first thermal expansion coefficient being smaller than the second thermal expansion coefficient, the article (1) being characterized in that the article further comprises a thermal expansion gradient buffer (4) at least partially disposed between the substrate (2) and the ceramic colorant (7), the thermal expansion gradient buffer (4) having a thermal expansion coefficient referred to as a third thermal expansion coefficient, the third thermal expansion coefficient being between the first thermal expansion coefficient and the second thermal expansion coefficient, the thermal expansion gradient buffer (4) and the decoration (3) being configured to limit the occurrence of cracks in at least the glaze (8); The third thermal expansion coefficient is between the first thermal expansion coefficient and the thermal expansion coefficient of the decoration; These coefficients of thermal expansion are each measured between 100°C and 300°C; and The at least one ceramic colorant (7) is located between the substrate (2) and the glaze (8).

2. The product according to claim 1, characterized in that The substrate (2) is provided with an enamel (5) which is at least partially disposed between the porcelain (6) and the thermal expansion gradient buffer (4).

3. The product according to any one of claims 1 or 2, characterized in that The first thermal expansion coefficient of the substrate (2) is 3.0x10 -6 K -1 Up to 6.0x10 -6 K -1 .

4. The product according to any one of claims 1 or 2, characterized in that The second thermal expansion coefficient of the ceramic colorant (7) is 5.0×10 -6 K -1 to 11.0x10 -6 K -1 .

5. The product according to any one of claims 1 or 2, wherein the third thermal expansion coefficient is 4.5x10 -6 K -1 Up to 7.0x10 -6 K -1 .

6. The product according to any one of claims 1 or 2, characterized in that The at least one ceramic pigment (7) contains at least one element selected from the group consisting of lead (Pb), cadmium (Ca), aluminum (Al), cobalt (Co), barium (Ba), chromium (Cr), nickel (Ni), arsenic (As), manganese (Mn), iron (Fe), gold (Au), and silver (Ag).

7. The product according to any one of claims 1 or 2, characterized in that The thermal expansion gradient buffer (4) comprises: - 10-30% by weight of boron oxide (B2O3); - 20-70% by weight of silicon oxide (SiO2); - 1-10% by weight of aluminum oxide (Al2O3); - 0-3% by weight of titanium oxide (TiO2); - 0-3% by weight of calcium oxide (CaO); - 0-2% by weight of manganese oxide (MgO); - 0-8% by weight of potassium oxide (K2O); - 0-8% by weight of sodium oxide (Na2O); - 0-8% by weight of zinc oxide (ZnO); - 0-8% by weight of zirconium oxide (ZrO2); - 0-5% by weight of barium oxide (BaO) and - 0-5% by weight of bismuth oxide (Bi2O3).

8. The product according to claim 7, characterized in that The glaze (8) comprises: - 10-30% by weight of boron oxide (B2O3); - 20-70% by weight of silicon oxide (SiO2); - 1-10% by weight of aluminum oxide (Al2O3); - 0-3% by weight of titanium oxide (TiO2); - 0-3% by weight of calcium oxide (CaO); - 0-2% by weight of manganese oxide (MgO); - 0-8% by weight of potassium oxide (K2O); - 0-8% by weight of sodium oxide (Na2O); - 0-8% by weight of zinc oxide (ZnO); - 0-8% by weight of zirconium oxide (ZrO2); - 0-5% by weight of barium oxide (BaO); and - 0-5% by weight of bismuth oxide (Bi2O3); The content of at least one of the oxides of the glaze is different from the content of the oxide of the thermal expansion gradient buffer.

9. The product according to claim 8, characterized in that The content of silicon oxide (SiO2) in the thermal expansion gradient buffer (4) is less than the content of silicon oxide (SiO2) in the glaze (8).

10. The product according to any one of claims 8 or 9, characterized in that The content of boron oxide (B2O3) in the thermal expansion gradient buffer (4) is greater than the content of boron oxide (B2O3) in the glaze (8).

11. The product according to any one of claims 8 or 9, characterized in that The content of aluminum oxide (Al2O3) in the thermal expansion gradient buffer (4) is greater than the content of aluminum oxide (Al2O3) in the glaze (8).

12. A method for manufacturing an article according to any one of claims 1 to 11, comprising: - a step (12) of providing a substrate (2) at least partially made of porcelain (6); - a step (13) of providing a decorative object (3) comprising at least one ceramic colorant (7) and a glaze (8); - a step (14) of providing a thermal expansion gradient buffer (4); and - a step (15) of assembling the substrate (2), the decorative element (3) and the thermal expansion gradient buffer (4), the thermal expansion gradient buffer (4) being at least partially disposed between the substrate (2) and the ceramic colorant (7), The substrate (2) has a coefficient of thermal expansion referred to as a first coefficient of thermal expansion, The ceramic colorant (7) has a thermal expansion coefficient called a second thermal expansion coefficient, the first thermal expansion coefficient is smaller than the second thermal expansion coefficient, The thermal expansion gradient buffer (4) has a thermal expansion coefficient called a third thermal expansion coefficient, which is between the first thermal expansion coefficient and the second thermal expansion coefficient. The thermal expansion gradient buffer (4) and the decoration (3) are configured to limit the occurrence of cracks in at least the glaze (8), The third thermal expansion coefficient is between the first thermal expansion coefficient and the thermal expansion coefficient of the decoration; These coefficients of thermal expansion are each measured between 100°C and 300°C; and The at least one ceramic colorant (7) is located between the substrate (2) and the glaze (8).

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