Decoration for glass-ceramic articles containing talc

Abstract

The present invention relates to an enamel composition for glass-ceramic articles containing glass and talc. According to a second aspect, the present invention relates to a method of producing said composition, which comprises mixing a frit of glass and talc and optionally comminuting the resulting mixture. The present invention also relates to a glass-ceramic article having at least one substrate, such as a glass-ceramic plate, at least partially coated with an enamel composition according to the present invention. Finally, the present invention also relates to a method of producing said glass-ceramic article, which comprises providing a glass-ceramic substrate, printing an enamel composition according to the present invention thereon, and ceramifying the assembly of the substrate and the enamel.

Description

Technical Field

[0001] The present invention relates to the field of glass ceramics. More precisely, it relates to glass ceramic articles which are intended, in particular, to cover a heating element or to receive a heating element and / or to function as a furniture surface, optionally in combination with a heating element. Examples of such articles include cooktops, oven doors, fireplace inserts, firewalls, or central islands for the kitchen or the dining room.

Background Art

[0002] A glass ceramic article is defined as an article based on a substrate of glass ceramic material, such as a glass-ceramic plate, etc., which may be provided with accessories or additional decorative or functional elements. The article may refer to the substrate only or to the substrate with additional equipment. For example, the article may refer to a cooktop equipped with a control panel and / or a heating element.

[0003] There are several commonly used glass ceramic articles, in particular glass ceramic cooktops, which have proven to be very popular among household retailers, home appliance manufacturers, and end-users. This success is explained, in particular, by the attractive appearance of such cooktops and by their ease of cleaning.

[0004] Glass ceramic was originally glass, known as precursor glass, mother glass, or raw glass, and its specific chemical composition enables crystallization to be induced by an appropriate heat treatment known as ceramization. This particular, partially crystallized structure gives glass ceramic its unique properties.

[0005] At present, there are various types of glass-ceramics, and each of their variations results from major research and numerous tests, considering that it is very difficult to make changes to these plates and / or the methods of obtaining them without the risk of unfavorably affecting the desired properties.

[0006] In particular, for use as a cooking hob, a glass-ceramic hob generally needs to be low enough to cover at least part of the heating element that is below in the stationary state, and high enough for the user to visually detect the heating element in operation for safety purposes, depending on the type of heating, and have a transmittance in the visible wavelength range. A glass-ceramic hob needs to have a high transmittance in the infrared wavelength range, especially in the case of a radiant hob. Also, it needs to have sufficient mechanical strength in the application field of such a hob. In particular, to be suitable for use as a hob, a glass-ceramic hob needs to have good resistance to the pressure and impact specified in EN 60335-2-6.

[0007] The most common glass-ceramic hobs are dark in color, especially black or brown or orange-tinted brown. These are generally decorated on the top with enamel to demarcate the cooking zone and function keys and protect the glass-ceramic from abrasion and damage. The use of black enamel is particularly attractive because it provides a low-contrast appearance in the case of a black glass-ceramic hob.

[0008] Enamel is usually a mineral layer formed by firing an enamel composition containing glass frit and pigments.

[0009] As a result, enamel has much higher heat resistance, abrasion resistance (abrasive resistance), peeling resistance, and chemical resistance than conventional decorative elements such as paints, etc., making it possible to use them for glass-ceramic articles, especially hobs.

[0010] However, enamel pigments based on commercially available black pigments, such as spinel CoCrFeNi or CuCr, etc., result in a brownish hue. Further, in the case of pattern decoration, these enamels are likely to show streaks after the plate is wiped with a dry cloth. These drawbacks are particularly prominent in enamels made from DEC146 glass frit, as described in French Patent Application Publication No. 2 701 473.

[0011] Furthermore, the accumulation of food deposits on enamel glass ceramics can cause the enamel to peel off due to temperature, particularly in the case of enamels made from DEC146 glass frit, and more particularly enamels made from IB2 glass frit, as described in French Patent Application Publication No. 2 701 473.

[0012] French Patent Application Publication No. 2 457 312 describes self-cleaning coating compositions, particularly for the inner walls of ovens, which contain an oxidation catalyst, a polymerization inhibitor for oil and grease, and a binder. The action of the oxidation catalyst enables self-cleaning by the volatile oxidation of oil and grease on the oven walls. According to this document, the polymerization inhibitor for oil and grease makes it possible to lower the temperature at which self-cleaning occurs. Talc is one of these polymerization inhibitors. However, this document does not consider any specific aspects related to the use of talc in glass-ceramic plate enamels, such as the required mechanical properties or aesthetic considerations, particularly those related to color.

[0013] French Patent Application Publication No. 2,858,974 addresses the problem of the discoloration of enamels based on black pigments to brown. According to this document, this color development is due to zinc oxide present in the flux reacting chemically with the surface of commercially available black pigments during firing. To solve this problem, this document proposes the use of enamels based on colorless frit and black pigments coated with glass in a weight ratio of 0% to 10%. However, the drawback of this solution is that it requires special processing techniques, makes the manufacturing method of the enamel relatively complex, and generates additional costs.

[0014] There is still a need for an easily available enamel composition for glass-ceramic articles that colors black and has satisfactory mechanical properties. In particular, it is required that the resulting enamel does not leave prominent marks when in contact with, for example, a fingernail or a dry cloth during use and reduces peeling to enable cleaning of food deposits.

Summary of the Invention

Problems to be Solved by the Invention

[0015] The object of the present invention is to provide such an enamel composition to meet these needs. As can be seen from this specification, the inventors have demonstrated that incorporating talc into the enamel composition makes it possible to obtain a black enamel that does not leave prominent marks during use and provides improved resistance to damage.

Means for Solving the Problems

[0016] The present invention is very surprising from a tribology perspective because, for example, in contrast to the pigments commonly used in enamels, the hardness of talc is very low.

[0017] Talc also has the advantage of being an abundant and inexpensive raw material.

[0018] This solution can be easily transferred to existing enamel formulations because it does not require significant changes in the enamel manufacturing process and is not accompanied by a significant increase in cost.

[0019] Thus, according to a first aspect, the present invention relates to an enamel composition for a glass-ceramic article comprising glass and talc.

[0020] The enamel composition can refer to both the enamel before firing and after firing. Thus, in the enamel composition according to the present invention, the term "glass" refers to glass frit before firing and to a glass matrix obtained by melting the glass frit after firing. The enamel according to the present invention is typically obtained by firing at a temperature above 850 °C, preferably above 900 °C.

[0021] Other features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings showing exemplary embodiments thereof and are not of a limiting nature. In the figures:

Brief Description of the Drawings

[0022]

Figure 1

[0023]

Figure 2

[0024]

Figure 3

[0025]

Figure 4

Mode for Carrying Out the Invention

[0026] Description of Embodiments of the Invention

[0027] In a particular embodiment, the enamel composition according to the present invention comprises a glass frit and talc. According to this embodiment, the composition according to the present invention may further comprise an organic medium.

[0028] The organic medium enables setting a viscosity desirable for application to a substrate and enables bonding to the substrate. This medium is selected to ensure good suspension of the (frit and talc) particles and must be consumed at least by the time of baking of the enamel, and may be any medium or organic binder conventionally used in conventional enamel compositions, and in particular may include solvents, diluents, oils such as pine oil and other oils, resins such as acrylic resins, petroleum fractions, film-forming substances such as cellulose substances.

[0029] In particular, the organic medium suitable for the present invention may contain at least one compound selected from glycols and pine oil. Preferably, the organic medium contains at least one glycol such as 2-(2-butoxyethoxy)ethanol or 2-butoxyethanol.

[0030] The proportion of the medium in the composition in a state ready for deposition may be 40% to 60% by weight of the above composition, preferably 45% to 55% by weight. Therefore, the enamel composition before being deposited on the glass-ceramic substrate is generally in the form of a stable liquid-solid mixture, is paste-like and viscous, and has a viscosity suitable for the deposition method, particularly suitable for screen printing.

[0031] In another embodiment, the enamel composition according to the present invention contains a vitreous matrix and talc.

[0032] The composition according to the present invention may contain talc in a proportion in the range of 5% to 40% by weight, particularly 7% to 35% by weight, preferably 10% to 30% by weight, based on the total weight of the enamel.

[0033] The composition according to the present invention may contain a pigment of less than 1% by weight, for example less than 0.5% by weight, particularly less than 0.1% by weight, based on the total weight of the enamel, and preferably the enamel does not contain a pigment.

[0034] Thus, the enamel composition can be simplified according to the present invention because a black enamel can be obtained by simply mixing a glass frit and talc without adding a pigment. However, the production of conventional black enamel may require the use of additional pigments in addition to black pigments to complement the color tone of a specific shade.

[0035] The enamel composition according to the present invention can be obtained from a mixture of a glass frit and talc with a D90 of less than 20 μm, particularly less than 15 μm, preferably less than 10 μm.

[0036] That is, in this case, 90% of the particles constituting the mixture of the glass frit and talc have a diameter of less than 20 μm, particularly less than 15 μm, preferably less than 10 μm.

[0037] As shown in the following examples, the inventors observed that the decrease in the diameter of the particles, i.e., the particle size, constituting the above mixture improves the effect of the present invention. Thus, an enamel composition containing glass frit and talc with a fine particle size as described in the previous paragraph can achieve an enamel with a relatively dark enamel color and relatively less susceptibility to marking than an equivalent enamel composition having a relatively large particle size.

[0038] Furthermore, such a fine particle size also makes it possible to achieve higher enamel abrasion resistance than the enamel abrasion resistance observed for equivalent enamel compositions having a relatively large particle size.

[0039] In a specific embodiment of the present invention, the composition according to the present invention contains glass having the following composition. SiO2: 35 - 50%, B2O3: 23 - 30%, Al2O3: 10 - 22%, Li2O: 1 - 3%, Na2O: 0 - 3%, K2O: 2 - 5%, Li2O + Na2O + K2O: less than 8%, CaO: 1 - 5%, CaO + MgO + ZnO + BaO + SrO: less than 7%, TiO2: 0 - 2%, ZrO2: 0 - 5%, The ratios are expressed as weight percentages based on the total weight of the glass.

[0040] Such a glass composition corresponds to a glass frit known as "DEC146" and is described in French Patent Application Publication No. 2 701 473. For the enamel composition according to the present invention containing the above glass composition, among the effects of the above invention, the addition of talc particularly improves the traceability resistance of the enamel.

[0041] According to this embodiment, the glass is 60×10 -7 K -1 Hereinafter, particularly 56×10-7 K -1 It may have the following coefficient of thermal expansion.

[0042] According to this embodiment, the glass may have a softening point T exceeding 650 °C, particularly exceeding 680 °C. L It may have.

[0043] According to this embodiment, the composition according to the present invention may contain talc in a proportion in the range of 15% to 40% by weight, particularly 17% to 35% by weight, preferably 20% to 30% by weight, based on the total weight of the enamel.

[0044] In another embodiment, the enamel composition contains a glass having the following composition, and the proportion is expressed as a weight percentage based on the total weight of the glass. SiO2 45% - 60%, preferably 50% - 58%, Al2O3 12% - 22%, preferably 15% - 19%, B2O3 12% - 22%, preferably 15% - 19%, Li2O 0% - 5%, preferably more than 0% - 5%, Na2O 0% - 2%, K2O more than 2%, CaO 0% - 4%, preferably 0% - 2%, MgO 0% - 4%, preferably more than 0% - 4%, ZnO 0% - 4%, preferably more than 0% - 4%, BaO 0% - 4%, preferably more than 0% - 4%, ZrO2 0% - 4%, particularly 0% - 2%, preferably more than 0% - 2%, TiO2 0% - 1%, preferably 0% - 0.5%, The total proportion of the oxides, CaO + MgO + BaO + SrO + ZnO, is further 10% or less, preferably 2% - 8%.

[0045] Such a glass composition corresponds to a glass frit known as "IB2" and is described in French Patent Application Publication No. 3,012,130. For the enamel composition according to the present invention containing the above-described glass composition, among the effects of the present invention described above, the addition of talc particularly improves the peel resistance of the enamel.

[0046] According to this embodiment, the composition according to the present invention may contain talc in a proportion of 5% to 30% by weight, particularly 7% to 20% by weight, and preferably, the enamel contains talc in a proportion of 10% to 20% by weight based on the total weight of the enamel.

[0047] According to a second aspect, the present invention relates to a method for obtaining an enamel composition according to the present invention, which includes mixing a glass frit and talc, and optionally rubbing and crushing the obtained mixture for a time ranging from 5 minutes to 1 hour, particularly from 15 minutes to 45 minutes, preferably from 20 minutes to 40 minutes.

[0048] "Rubbing and crushing" particularly means crushing by rubbing using a mill or a micro grinder, particularly in an alcoholic medium. Examples of such a micro grinder include those sold under the reference number "Mill PE075" by Netzsch.

[0049] Rubbing and crushing makes it possible to reduce the mixture of glass frit and talc particles of a known particle size, and particularly makes it possible to obtain a D90 of less than 20 μm, particularly less than 15 μm, preferably less than 10 μm.

[0050] According to a third aspect, the present invention relates to a glass-ceramic article, which includes at least one substrate, such as a glass-ceramic plate, etc., and the above substrate is at least partially coated with the enamel composition according to the present invention.

[0051] The substrate is generally a plate and is particularly intended for the following: · To be used together with at least one light source and / or heating element, in particular to cover or receive these, or, · To be used as a surface of furniture or an insertion opening of a fireplace.

[0052] The base material generally has a shape selected from the following: rectangular, in particular square, circular, and elliptical. It generally has the following characteristics: · A surface facing the user at the usage position, known as the visible surface or outer surface, which may correspond to the upper surface at the usage position, · A second surface facing the side opposite to the outer surface, known as the inner surface, which is generally hidden at the usage position, for example, a surface in a furniture frame or cabinet, and which may correspond to the lower surface at the usage position, and, · An edge or thickness.

[0053] The upper or outer surface is generally flat, but locally may have at least one convex region, and / or at least one concave region, and / or at least one opening, and / or a chamfered edge. Such shape changes may constitute continuous changes in the plate.

[0054] The lower or inner surface may also be flat and smooth, or may be provided in a teardrop shape.

[0055] The thickness of the glass-ceramic base material is generally at least 2 mm, in particular at least 2.5 mm, and advantageously less than 15 mm, in particular 3 - 15 mm, in particular 3 - 8 mm or 3 - 6 mm.

[0056] The base material may be based on any glass-ceramic, advantageously having a coefficient of thermal expansion (CTE) of zero or approximately zero, in particular less than 30×10 -7 K -1 in absolute value at 20°C to 700°C, in particular less than 15×10 -7 K -1 in absolute value, or even less than 5×10 at 20°C to 700°C-7 K -1 has a lower coefficient of thermal expansion (CTE) than

[0057] In particular, a black or brown substrate is used and, in combination with a light source arranged below, it is possible to cover any underlying elements while displaying a light-emitting zone or a decoration. In particular, it may be based on a black glass-ceramic containing crystals of the β-quartz structure in the residual glass phase, the absolute value of its coefficient of thermal expansion being advantageously 15×10 -7 K -1 below, or even 5×10 -7 K -1 below, such as, for example, a glass-ceramic plate sold under the name Kerablack+ by Eurokera.

[0058] It is in particular an arsenic-added glass-ceramic having a composition as described in European Patent No. 0437228 or US Patent No. 5070045 or French Patent Application Publication No. 2657079, or a tin-added glass-ceramic containing arsenic oxide as described in International Publication No. 2012 / 156444, preferably a tin-added glass-ceramic having an arsenic oxide content of less than 0.1%, or even a sulfide-added glass-ceramic as described in International Publication No. 2008 / 053110, etc.

[0059] Optionally, the substrate may be coated with other functional and / or decorative coatings or layers, in particular in regions other than those coated with the enamel according to the invention, such as, for example, a normal pattern based on another enamel or an opacifying paint layer on another part of the substrate, or at least one functional layer, such as a scratch-resistant layer, a sputter-resistant layer, an opacifying layer, etc. may be deposited.

[0060] The article according to the invention may further have at least one light source and / or at least one heating element selected from a radiation element or a halogen element, an atmospheric gas burner, and induction heating means, in relation to or in combination with the substrate.

[0061] The light source may be incorporated into or coupled to, for example, at least one display unit structure, an electronic control panel having touch sensitivity control and a digital screen. Advantageously, those light sources are formed by a display consisting of light-emitting diodes spaced apart to some extent, and the diodes are optionally associated with at least one optical guide.

[0062] Also, the article according to the invention can be combined with at least one additional functional element, such as a frame, a connector, a cable, or a control element.

[0063] In particular, the article according to the invention has good heat resistance suitable for the use of various types of heaters, and in particular does not cause the maintenance, scratching, or wear problems as pointed out above when compared with glass-ceramic articles containing typical enamels.

[0064] According to a fourth aspect, the invention relates to a method for obtaining a glass-ceramic article according to the invention, which comprises: a. providing a glass-ceramic substrate, b. printing, in particular screen-printing, the enamel composition according to the invention on the substrate, and c. ceramizing the assembly of the substrate and the enamel. In particular, the ceramizing step comprises heating the assembly of the substrate and the enamel at a temperature of 650 °C to 830 °C, preferably for 5 minutes to 90 minutes, and then at a temperature of 850 °C to 1100 °C, preferably for 5 minutes to 30 minutes.

[0065] The production of glass-ceramic plates is generally carried out as follows: Glass of a composition selected to form the glass-ceramic is melted in a melting furnace, and the molten glass is rolled into a standard ribbon or sheet by passing it between rolling rolls, and the glass ribbon is cut into the desired dimensions. The plates cut in this manner are decorated with decorations based on enamels applied by screen printing or enamel spraying, and then ceramized in a known manner. The ceramization consists of firing the plate according to a selected heat profile to convert the glass into a polycrystalline material called glass-ceramic, which has a thermal expansion coefficient of zero or close to zero and can withstand thermal shocks up to 700 °C. The ceramization generally includes a step of raising the temperature step by step, for example, raising it to a "nucleation plateau" temperature of 650 °C to 830 °C and maintaining it for 5 minutes to 90 minutes. Then, the temperature is raised again to allow the crystals to grow, raising it to a so-called "crystal growth plateau" temperature, for example, 850 °C to 1100 °C, preferably 900 °C to 1000 °C in the case of milky white and opaque glass-ceramics, and maintaining it for, for example, 5 minutes to 30 minutes. Finally, the plate is rapidly cooled to room temperature.

[0066] Optionally, this process includes cutting operations, such as those using a water jet or mechanical scoring using a scoring wheel, followed by shaping operations, such as polishing or chamfering. Preferably, this cutting operation is performed before ceramization.

[0067] The enamel is deposited on the glass-ceramic substrate before ceramization. This deposition is carried out by printing, such as digital printing or screen printing.

[0068] The screen printing method involves, in particular using a squeegee, depositing a paste-like liquid onto a glass sheet through the mesh of a screen printing screen. The gaps in the screen are blocked in the portions corresponding to the zones of the glass sheet that are not to be coated, so that the paste can only pass through the screen within the zone to be printed, according to a predefined design. Thus, the selective blocking of the gaps is carried out according to the negative of the design to be printed.

[0069] This selective blocking is generally carried out by applying a photocrosslinkable resin onto the screen and then irradiating the portions of the screen to be blocked with ultraviolet light.

[0070] Selective exposure is achieved, for example, by an LED that emits ultraviolet light, which is computer-controlled to block the screen mesh so as to match a selected image file.

[0071] The mesh of the screen is selected according to the viscosity and surface tension of the paste, and the desired thickness of the layer obtained as a result of the deposition by screen printing.

[0072] The following examples are representative of the invention described above, but are not limited thereto.

Example

[0073] The following examples show the results obtained by comparing the glass-ceramic articles and enamels according to the present invention (Examples 1 to 8) with reference examples (Comparative Examples 1 to 4) including glass-ceramic articles and enamels of different prior arts. The compositions of the enamels contained therein are shown in detail in Tables 1 and 2 below, and the content of each compound is expressed in weight percentage based on the total weight of the enamel. The enamels were tested for two different types of frit: one is DEC146 described in French Patent Application Publication No. 2,701,473, and the other is IB2 described in French Patent Application Publication No. 3,012,130. For IB2, two different glass frit particle sizes were tested.

[0074]

Table 1

[0075]

Table 2

[0076] Also, Tables 1 and 2 show some parameters specific to the obtained enamels, and the details are shown below.

[0077] For each example, a mixture of glass frit and pigment or talc is prepared. And if desired, this mixture is ground using a attrition micro grinder (Netzsch's "Mill PE075") in an alcoholic medium containing zirconium oxide beads with a diameter of 1 mm (refer to Netzsch's "Zetabeads Plus").

[0078] And the particle size of the obtained mixture is measured using a Malvern reference "Mastersizer 3000" laser particle size analyzer, regardless of whether it is ground or not.

[0079] Then, the mixture is screen-printed onto the Kerablack+ mother glass of Eurokera S.N.C. and fired in a ceramic cycle at 930 °C.

[0080] The colorimetric parameters L * , a * , b * defined in the CIE colorimetric system are evaluated by a known method using a Byk-Gardner Color Guide 45 / 0 colorimeter by reflectance colorimetry.

[0081] Also, all the colorimetric data of Examples 1 to 4 according to the present invention, and Comparative Examples 1 and 2, all containing DEC146 glass frit, are shown in the colorimetric diagram of FIG. 1.

[0082] Comparative Examples 1 and 2 containing black pigment and blue pigment both show a brown colorimetric tendency, that is, the a * coordinate is greater than 0.7, and particularly significant in Comparative Example 2.

[0083] Examples 1 to 4 containing the same glass frit as Comparative Examples 1 and 2 and no pigment hardly change between 0 and -0.3 based on the amount of talc and their particle size, and have less brown hue than the enamels of Comparative Examples 1 and 2, with an a * coordinate.

[0084] Similarly, the b * coordinates of Examples 1 to 4 according to the present invention are stable, at -3.53 for Example 1 and -4.04 for Example 2, and abrasion is considered to cause a slight shift in the colorimetric value towards the blue hue.

[0085] Finally, abrasion affects the brightness of the enamel. Specifically, when comparing Example 1 and 2, or Example 3 and 4, a decrease in the L * coordinate is observed when abrasion is performed. This effect is particularly significant in Example 4, which has an 80 / 20 frit / talc ratio.

[0086] Therefore, the enamel composition according to the invention makes it possible to obtain a satisfactory dark color shade, in particular when D90 is 10 μm or less and / or the content of talc relative to the total weight of the enamel is 20% by weight.

[0087] Regarding the enamel compositions containing IB2 glass frit, Comparative Examples 3 and 4 made from 100% IB2 glass frit have a neutral black hue. Examples 5 and 6 - 8 have the advantage that their colorimetric values are very close to those of the reference compositions without talc, i.e., Comparative Examples 3 and 4.

[0088] Tables 3 and 4 below show the tests carried out on each of the compositions presented above.

[0089]

Table 3

[0090]

Table 4

[0091] The measured values of the total roughness Rt and the average roughness Ra are obtained for an evaluation length of 4 mm at 5 locations on a 5 cm square planar area screen - printed on a 9×9 cm substrate in accordance with ISO 97 standard using a Mitutoyo Sj - 400 surface roughness measuring instrument.

[0092] The gloss measurement at 60° is carried out in accordance with ISO 2813 using a Byk - Gardner Spectro - Guide 45 / 0 gloss colorimeter. These measurement results are expressed in gloss units (GU). The higher the gloss value, the glossier the observed sample. Conversely, a relatively low value indicates that the sample is dull.

[0093] Generally, a decrease in particle size in talc - based enamels leads to an increase in gloss and a decrease in roughness.

[0094] The samples were also subjected to a "fingernail scratch" test, which was performed on an enamel plate that completely covered the glass-ceramic substrate. This test involves moving the fingernail of the index finger over a distance of 5 cm. Then, a score of 0 - 4 is assigned to the sample based on the marks left on the enamel. A score of 0 indicates no marks on the enamel, while a score of 4 indicates very prominent marks on the enamel. Figure 2 shows photographs of representative samples with scores of 0, 2, and 4. A score of 0 or 1 meets the consumer's expectations in terms of the ease with which the enamel picks up marks, such as those from a dishcloth. Figure 3 shows the results obtained for Examples 1 - 4 according to the present invention.

[0095] Therefore, Comparative Examples 1 and 2 of the enamel have an evaluation of 2, which is considered unsatisfactory, while the talc-based enamels of Examples 1 - 4, which contain the same glass frit, are found to have a relatively low evaluation of 1 or even 0 in the case of the enamel (Examples 2 and 4) where the mixture of frit and talc has been subjected to abrasion. The presence of talc in these enamels means that they exhibit relatively excellent performance in terms of markability.

[0096] Regarding the enamels containing IB2 glass frit, those of Comparative Examples 3 and 4 already have satisfactory evaluations. Therefore, it should be noted that the addition of talc makes it possible to maintain satisfactory markability.

[0097] The above results also show that the talc content has little effect on the markability of the enamel, because similar results have been obtained for Examples 1 and 3 (20 wt% and 30 wt% talc respectively), Examples 2 and 4 (20 wt% and 30 wt% talc respectively), and Examples 6 and 8 (10 wt% and 20 wt% talc respectively) according to the present invention.

[0098] Furthermore, when observing by comparing Example 1 and 2, or Example 3 and 4 according to the present invention, the reduction in particle size by abrasion provides relatively excellent performance in terms of the traceability of the talc-containing enamel.

[0099] The peeling test simulates cleaning the charring of food stuck to a glass ceramic stove decorated with enamel. It is carried out on an induction-heated zone, which consists of placing a mixture of different foods (ground meat, cheese, sugar, eggs, milk, flour, tomato sauce, corn starch, salt, pepper) on the enamel in the heating zone and baking it for 10 minutes at an output corresponding to a hot spot of 420°C. The above hot spot is the average of the values measured using a thermocouple on the lower side of the frying pan and a thermal camera on the top after removing the frying pan from the glass ceramic article. This process is repeated 5 times. After the first and fifth cycles, the glass ceramic surface is cleaned using a scraper, a pad without abrasive, and a cleaning article for glass ceramic. Then, the degree of enamel peeling is observed, and a score is assigned to the sample from 0 (no peeling) to 5 (peeling over the entire tested surface).

[0100] Figure 4 shows the results of the peeling test for Comparative Example 3 and Example 5 according to the present invention.

[0101] When comparing as follows, · Examples 2 and 4 according to the present invention with Comparative Example 1, · Example 5 according to the present invention with Comparative Example 3, · Examples 7 and 8 according to the present invention with Comparative Example 4, The addition of talc to the glass frit in the enamel brings about an improvement in peeling resistance.

[0102] In particular, the peeling resistance of the IB2 glass frit-containing enamel shown in Comparative Examples 3 and 4 is significantly improved by the addition of talc, as observed in Examples 5, 7, and 8.

[0103] Also, the abrasion resistance of the enamel according to the present invention is tested according to two protocols reported as "Manual Test" and "Taber Test" in Table 5 below.

[0104]

Table 5

[0105] The enamel compositions of Examples 9 to 14 according to the present invention are obtained in the same manner as the compositions described above.

[0106] The mixture is screen printed onto Kerablack + mother glass from Eurokera S.N.C., and then fired by a ceramization cycle at 930 ° C. to obtain a glass-ceramic plate sample. Then, the thickness of the deposit is measured.

[0107] The protocol for the abrasion test is as follows: · Manual Test: 1 mL of an article of the VitroClen brand from Reckitt Benckiser is applied to a single point on the glass-ceramic sample to be tested. Then, cleaning is simulated by rubbing back and forth 100 times over a distance of 10 cm using a Scotch Brite Blue sponge and pad sold by 3M. After cleaning, the test surface is wiped with a cloth and glass cleaner, and then the enamel abrasion is evaluated by assigning a contrast score to the sample in the range of 0 to 5 relative to the original state of the enamel, where 0 refers to undamaged enamel, 1 refers to particularly excellent abrasion resistance, 2 refers to excellent abrasion resistance, 3 refers to acceptable enamel abrasion, 4 refers to poor abrasion resistance, and 5 refers to completely abraded enamel. · Taber Test: This test uses a linear abrasive wear tester sold by Taber, on which an 18 mm disc fitted with a white Veraclen Critical Cleaning PL WIP 74603 cloth sold by Chicopee is mounted. The abrasion tester is set to apply 5 N·cm to the disc. -2Set it to apply pressure so that it reciprocates (or cycles) at a speed of 60 cycles per minute over a 38.1 mm stroke. Apply 1 mL of VitroClen sold by Rekit Benki Za to a single point on the glass-ceramic sample to be tested. Then, operate the abrasion tester to cause 500 reciprocations. Wipe the test surface clean with a cloth and a glass cleaner, and then the operator evaluates the enamel wear by assigning a contrast score to the sample on a scale of 0 to 5 relative to the original state of the enamel, where 0 indicates non-damaged enamel, 1 indicates particularly excellent wear resistance, 2 indicates excellent wear resistance, 3 indicates acceptable enamel wear, 4 indicates poor wear resistance, and 5 indicates completely worn enamel.

[0108] From the above tests, it is clear that the enamel composition according to the present invention containing 20% by weight of talc relative to the total weight of the enamel has particularly satisfactory wear resistance.

[0109] Furthermore, a comparison of the results of the Taber tests in Examples 13 and 14 shows that the smaller the particle size of the glass frit used, the relatively better the wear resistance of the resulting enamel.

Claims

1. Enamel compositions for glass-ceramic articles containing glass and talc.

2. The enamel composition according to claim 1, wherein the talc is present in a proportion of 5% to 40% by weight, particularly 7% to 35% by weight, preferably 10% to 30% by weight, based on the total weight of the enamel.

3. The enamel composition according to claim 1 or 2, comprising less than 1% by weight of pigment, for example less than 0.5% by weight, and particularly less than 0.1% by weight of pigment, with respect to the total weight of the enamel, preferably the enamel being pigment-free.

4. The enamel composition according to claim 1 or 2, wherein the enamel is obtained from a mixture of glass frit and talc, having a D90 of less than 20 μm, particularly less than 15 μm, and preferably less than 10 μm.

5. The glass in question has the following composition: Yes ２ :35~50%, B ２ O ３ :23~30%、 Al ２ O ３ :10~22%、 Li ２ O: 1~3%, Na ２ O:0~3%、 K ２ O: 2~5%, Li ２ O + Na ２ O + K ２ O: less than 8%, CaO: 1-5%, CaO + MgO + ZnO + BaO + SrO: Less than 7% TO ２ :0~2%、 ZrO ２ : 0-5%, The enamel composition according to claim 1 or 2, wherein the proportion is expressed as a weight percentage relative to the total weight of the glass.

6. The glass is 60 x 10 －７ K －１ The following, in particular, 56 x 10 －７ K －１ The enamel composition according to claim 5, having the following coefficient of thermal expansion.

7. The glass has a softening point T above 650°C, particularly above 680°C. Ｌ The enamel composition according to claim 5, having the following characteristics.

8. The enamel composition according to claim 5, comprising talc in a proportion of 15% to 40% by weight, particularly 17% to 35% by weight, preferably 20% to 30% by weight, based on the total weight of the enamel.

9. The glass in question has the following composition: SiO ２ 45% to 60%, preferably 50% to 58%, Al ２ O ３ 12% to 22%, preferably 15% to 19%, B ２ O ３ 12% to 22%, preferably 15% to 19%, Li ２ O 0% to 5%, preferably more than 0% to 5%, Na ２ O0%~2%、 K ２ O 2% over, CaO 0% to 4%, preferably 0% to 2%, MgO 0% to 4%, preferably more than 0% to 4%, ZnO 0% to 4%, preferably more than 0% to 4%, BaO 0% to 4%, preferably more than 0% to 4%, ZrO ２ 0% to 4%, particularly 0% to 2%, preferably more than 0% to 2%. TiO ２ The concentration is 0% to 1%, preferably 0% to 0.5%. Total proportion of oxides, CaO+MgO+BaO+SrO+ZnO, However, it is even less than 10%, preferably between 2% and 8%. The enamel composition according to claim 1 or 2, wherein the proportion is expressed as a weight percentage relative to the total weight of the glass.

10. The enamel composition according to claim 9, comprising talc in a proportion of 5% to 30% by weight, particularly 7% to 20% by weight, preferably the enamel comprising talc in a proportion of 10% to 20% by weight relative to the total weight of the enamel.

11. A method for obtaining the enamel composition according to claim 1 or 2, comprising mixing glass frit and talc, and optionally rubbing the resulting mixture for 5 minutes to 1 hour, particularly 15 minutes to 45 minutes, preferably 20 minutes to 40 minutes.

12. A glass-ceramic article having at least one substrate, for example, a glass-ceramic plate, wherein the substrate is at least partially coated with the enamel composition described in claim 1 or 2.

13. A method for obtaining the glass article described in claim 12, the following: a. To provide a glass ceramic substrate. b. Printing the enamel composition onto the substrate, particularly by screen printing, and c. Ceramicizing the assembly of the substrate and the enamel, In particular, the ceramicization step is a method comprising heating the assembly of the substrate and enamel at a temperature of 650°C to 830°C, preferably for 5 to 90 minutes, and then at a temperature of 850°C to 1100°C, preferably for 5 to 30 minutes.

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