Glass or glass-ceramic article, method for the production thereof and ink

Abstract

To provide a glass product or a glass ceramic product having a coating, and to provide a method for producing the glass ceramic product.SOLUTION: The invention relates to a glass or glass ceramic article comprising a substrate (102) made of glass or glass ceramic, wherein the substrate (102) has on at least one side, on at least part of its surface, a substantially pigment-free coating (104), wherein the coating (104) has an at least partially molten glass flow, wherein the surface (114) of the coating has a root mean square height Sq of at least 0.1 μm and at most 2.5 μ m, and wherein the coating (104) has a core height Sk of at least 1.0 μm to at most 10 μm. Furthermore, the invention relates to a method and an ink for producing such a glass or glass-ceramic article.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to glass or glass-ceramic articles having a coating, as well as methods for making such glass-ceramic articles and inks for making glass or glass-ceramic articles.

[0002] Conventional technology A wide variety of applications for glass and glass-ceramic products are known from the prior art, with perhaps the most widespread application, particularly for plate-shaped glass-ceramic products, being their use as cooking surfaces.

[0003] In this case, glass-ceramic cooking surfaces are often provided with functional coatings on the upper surface that perform various functions. The prior art, for example, EP 2964854, discloses coatings that protect such glass-ceramic cooking surfaces from scratches by means of a layer applied to a substrate made of AlSiN. Furthermore, coatings are also known that specifically prevent fingerprints from smearing the cooking surface. WO 2023 / 099833, for example, is cited here.

[0004] Recently, there have been approaches that not only avoid scratches on the surface of a substrate but also prevent the occurrence of fingerprints or general cooking surface stains. Again, EP 4077231 A1 is cited as an example. This document discloses a glass-ceramic article obtained by a method comprising a heat treatment to ceramize a glass suitable for forming a glass ceramic and a chemical treatment of the glass surface before and / or after the heat treatment to ceramize, where the chemical surface treatment is carried out so that the surface has an arithmetic mean roughness value of 2 μm to 7 μm after the heat treatment. The chemical treatment of the surface specifically describes the use of an acid solution based on hydrofluoric acid.

[0005] Hydrofluoric acid is indeed known to be used in etching glasses and glass ceramics, but it has a number of drawbacks. One is the relatively long time required to etch the glass or glass ceramic until the aforementioned roughness is achieved. Another is that hydrofluoric acid is a very difficult substance to handle, and many safety measures must be taken into account to ensure the protection of the environment and of people working with hydrofluoric acid.

[0006] Against this background, there is a need in the prior art for a solution that allows glass or glass-ceramic articles to be produced at the lowest possible cost, both in terms of time and in terms of work safety, whose surfaces are not sensitive to scratches and which also largely avoid the appearance of fingerprints and other stains.

[0007] Disclosure of the Invention The above challenges are The solution is provided for a glass or glass-ceramic product having the features of claim 1. The solution is provided for a corresponding manufacturing method and for the ink used therein in claims 17 and 20. Advantageous configurations are the subject of the respective dependent claims.

[0008] In a first aspect, the present invention relates to a glass or glass-ceramic product having a substrate made of glass or glass-ceramic, the substrate bearing on at least one side, on at least a portion of its surface, a substantially pigment-free coating, the coating comprising an at least partially molten glass flow, preferably containing boron, the surface of the coating having a root-mean-square height Sq of at least 0.1 μm and at most 2.5 μm, and the coating having a core height Sk of at least 1.0 μm and at most 10 μm.

[0009] The term "substantially pigment-free" in this case means that the coating contains less than 1% by weight of pigment, i.e., at least 99% by weight of glass stream. "Pigment" in this case is understood to be particles that change the transmission properties of the coating compared to a coating that consists exclusively of glass stream. In particular, such pigment particles can cause the color of the coating or a reduced transmittance of the coating.

[0010] An "at least partially molten" glass flow is one in which, in a glass flow, i.e., a given amount of glass particles having a defined size distribution, at least some of the particles have melted and resolidified, and therefore no longer exist as particles of the shape and size originally present in the glass flow. This molten content of the particles firmly bonds the particles of the glass flow to form a layer. At the same time, the molten portions of the glass particles also serve to create a bond to the substrate. Here, the unmelted portions of the glass particles do not create a completely flat surface, as would be expected in a completely molten glass flow. Rather, the partial melting of the glass particles creates a defined surface roughness in the coating.

[0011] The surface roughness of the glass or glass-ceramic article according to the invention is expressed here by the root mean square height Sq of the surface, which in this case is at least 0.1 μm and at most 2.5 μm. In this case, the root mean square height of the surface of the coating is defined as follows:

number

[0012] Another parameter describing the properties of the coating according to the invention is the core height Sk of the surface of the coating. The core height in this case refers to the height of the area within the surface material fraction of the coating, where 100% of the equivalent line of the surface material fraction (also called the equivalent line) is omitted. This area is also called the core surface. Here, this surface material fraction (also called the "planar material fraction") represents how much the coating material fraction in the observed surface area is reduced in relation to the height area of ​​the surface of the coating. Thus, effectively, for each height within the surface of the coating, a surface material fraction above this height is allocated. Correspondingly, in the graphic representation of the above curve, the vertical axis shows the height within the surface of the coating, while the horizontal axis shows the material fraction allocated to the area above this height in %.

[0013] Here, the equivalence is the secant of the curve of surface material proportion with the smallest possible slope (or minimum gradient), and the intersections of this minimum slope with the curve of surface material proportion have a 40% interval on the abscissa. In this way, by extrapolating the abscissa values ​​to 0% and 100% equivalence, the corresponding ordinate values ​​can be calculated, where the core height is the interval between the ordinate values. A small core height therefore means a very compact and therefore resistant coating, since most of the surface material is concentrated in a small area. In this case, the core height Sk of the coating can be, in particular, 1.5 μm to 9 μm, 1.5 μm to 8 μm, 1.5 μm to 7 μm, 2 μm to 6 μm, or particularly preferably 2 μm to 5 μm.

[0014] The values ​​of the coatings according to the invention in terms of root mean square height and core height reveal that the coatings according to the invention combine, on the one hand, a relatively rough or matte surface with, at the same time, a very compact nature of the coating. Thus, the coatings according to the invention are characterized by good properties in terms of avoiding fingerprints and other stains, as well as high resistance to scratches and abrasion of the coating. Here, the coatings contain only ingredients that are not of concern in terms of health and can be produced by simple and low-cost methods.

[0015] The glass particles in the glass stream of the coating can be particles made of boron-containing glass. In this case, the use of a boron-containing glass stream has advantages, particularly with regard to the thermal shock resistance of the coating, and also improves the adhesion of the coating, especially when the substrate is a glass ceramic. Furthermore, when a boron-containing glass stream is used, the coating can be fired when the substrate is ceramicized, i.e., when the glass substrate is converted into a glass ceramic substrate. In this way, a step in the production of the product, namely, a separate firing of the coating (so-called secondary sintering), can be avoided.

[0016] The matte finish of the coating described above is manifested by the fact that, according to one embodiment, the coating has a gloss value of at most 25 measured at an angle of 60°, which also makes it possible to avoid the occurrence of visible impurities in the coating, particularly in the form of fingerprints, which are more visible on a glossy surface.

[0017] Two important and unique parameters of the coating according to the invention have already been discussed above, but the coating according to the invention also differs crucially from coatings known in the prior art with respect to another surface parameter.

[0018] Thus, according to one embodiment, the coating is further configured to have a slope Ssk greater than 0. Here, a measure of the slope (also called skewness) of a surface provides information on whether the surface tends to be described as having grooves or valleys, or as having peaks. In the case of a surface with a slope greater than 0, i.e., a grooved surface, by definition, the frequency of regions protruding above the average height in the surface height distribution is smaller than the proportion of regions below the average height. Since this case can only occur if the regions below the average height are rarer than the regions above the average height, but their height (or depth) is clearly significant, this means that the surface can be described by valleys and grooves rather than protruding peaks.

[0019] In this case, mathematically, the slope can be calculated by summing the cubes of all height values ​​and dividing the surface of the coating by the cube of the root mean square height Sq:

number

[0020] In this case, a slope greater than 0, i.e., a surface with grooves rather than peaks, has the advantage that the grooves are significantly more resistant than protruding peaks. Here, to reduce the depth of the grooves in the coating, significantly more material must be removed than by grinding the peaks. As a result, a surface slope greater than 0 is associated with a higher robustness of the surface properties, since the surface structure is less strongly affected, for example, by abrasive cleaning processes.

[0021] According to another embodiment, the surface of the coating is further configured to have a kurtosis Sku of >3, particularly preferably >3 and <8, where the kurtosis of the surface describes the sharpness of the surface profile and is calculated as follows:

number

[0022] Here, a kurtosis value of Sku>3 indicates a surface that tends to be jagged rather than rounded. In this case, a surface with a jagged rather than rounded type of surface structure has the advantage that, for example, when a touch-sensitive operating element is operated, only a smaller contact area occurs between the surface of the coating and the operator's finger. This effectively prevents fingerprints and the like from becoming visible, since they are located on the very narrow peaks of the surface structure.

[0023] In this case, according to another embodiment, the coating has a thickness of 2 μm to 10 μm. The coating thickness is selected so that sufficient stability of the coating is ensured, while at the same time the transmission properties of the substrate are affected as little as possible by the coating. Furthermore, structures arranged below the coating are thus more easily recognizable. Preferably, the coating thickness is at least 3 μm, particularly preferably at least 4 μm. Furthermore, the coating thickness is preferably at most 9 μm, particularly preferably at most 8 μm, and very particularly preferably at most 7 μm.

[0024] In yet another embodiment, a colored decorative layer is arranged at least partially between the substrate and the coating. In this case, the colored decorative layer is preferably applied directly to the substrate. The decorative layer can be, for example, a cooking zone indicator, especially when a glass or glass-ceramic product, which can be produced by inkjet printing or screen printing, is used as a cooking surface. By arranging the decorative layer below the coating, the decorative layer is protected from abrasion, for example, caused by cleaning the glass or glass-ceramic product. At the same time, due to the low coating thickness and the absence of pigments in the coating, the visibility of the decorative layer and, in particular, its edge sharpness are only slightly impaired. Here, the decorative layer can essentially be fired together with the coating, which simplifies the production of the glass or glass-ceramic product.

[0025] In this case, according to a preferred embodiment, the contour of the deco layer arranged below the coating is configured so that, in a plan view of the deco perpendicularly through the coating, the contour has a root-mean-square roughness Rq of at most 20 μm, preferably at most 15 μm, in a direction parallel to the surface of the substrate. In this case, the contour of the deco layer indicates the extent of the transition between the area of ​​the substrate surface covered by the deco layer and the area of ​​the substrate surface that is substantially exposed from the deco layer. In this case, "substantially exposed" is understood to mean an area in which the thickness of the deco layer and therefore the color effect of the deco is at least 10% and at most 25% of the maximum color effect of the deco. In this case, the extent of the contour is considered to be similar to the extent of the height profile of a surface, so that known parameters for describing surface properties can be used to describe the extent of the contour. This makes it possible to indicate, inter alia, the root mean square roughness Rq of the contour line extension, which essentially provides information on the magnitude of the mean square value of all the ordinate values ​​z(x) of the contour line at each different point x along the measurement section of length l, where the value Rq is calculated as follows:

number

[0026] Thus, the value Rq effectively represents the sharpness of the deco contours when viewed through the structured coating. In this case, the smaller the value Rq, the sharper the deco contours. This is particularly advantageous, since even the finest deco elements can be recognized virtually unmistakably through the structured coating.

[0027] According to another preferred embodiment, the glass or glass-ceramic article is covered with a coating in a first subregion and has a deco layer not covered with a coating in a second subregion, wherein the root-mean-square roughness Rq of the contour of the deco layer in the first subregion differs from the root-mean-square roughness Rq of the contour of the deco layer in the second subregion by at most 10%, preferably at most 5%.

[0028] Alternatively, however, the deco can be applied onto the coating, which can facilitate the production of the glass or glass-ceramic article: for example, a matte coating can be applied over a large area by screen printing, and then the deco can be applied in a separate step to the glass or glass-ceramic article thus prepared.

[0029] In this case, the combination of the deco layer and the coating has, according to another embodiment, a thickness of at most 15 μm, preferably a thickness of at most 12 μm, particularly preferably a thickness of at most 10 μm.

[0030] It has already been mentioned up to this point that the coating is applied to at least a portion of the surface of the substrate. This means that the coating can have voids throughout, for example, to provide areas where a display can be placed. In other words, the voids in the coating, i.e., the surface areas where the coating is not applied, can improve the display visibility compared to a full-surface coating. However, according to another embodiment, the coating is configured to be applied to the entire surface of one side of the substrate, which can simplify the production of the glass or glass-ceramic product.

[0031] It has already been mentioned above that the glass stream is preferably formed containing boron. In this case, according to a further preferred embodiment, the glass stream has the following oxide-based composition: SiO275-85 Al2O30.1-5 B2O310-15 Na2O 1-5 K2O 0.1-1.5 It is configured to have the following weight percent.

[0032] Glass streams of this composition are particularly suitable for firing the coating during the ceramicization of the substrate, which offers significant advantages for the production of glass or glass-ceramic products according to the invention. In this case, the glass streams used can consist of a mixture of different types of glass. By mixing different types of glass, for example, the physical properties of the glass stream can be adapted to the given requirements for the production of the coating.

[0033] However, such mixed glass streams may have compositions different from those mentioned above. Thus, such glass streams may have, for example, the following oxide-based compositions: SiO250-65 B2O314-20 Al2O313-20 Li2O 2.0-4.0 MgO 1.0-2.5 CaO 1.5-2.5 SrO 1.5-3.0 ZnO 1.5-3.0 ZrO20.5-1.5 in weight percent.

[0034] When specifically selecting a glass stream or a mixture of various glass streams for producing a coating, many material parameters of the glass stream can affect the properties of the resulting coating. This is advantageous for the thermal stability of the coating, for example, if the thermal expansion coefficient of the glass stream and thus the coating differs only slightly from that of the substrate. The surface properties of the coating can also be adjusted by selecting a material with a suitable softening point. In this case, it is advantageous to select the softening point relative to the firing temperature of the coating so that the particles of the glass stream are only partially melted during firing of the coating in the context of ceramicization of the substrate, thereby achieving the desired rough surface properties.

[0035] In this case, according to another embodiment, the substrate is plate-shaped and has a thickness of 2 mm to 6 mm, preferably 3 mm to 5 mm, particularly preferably 4 mm. A "plate-shaped" substrate in this case means a substrate whose length and width are at least one order of magnitude greater than its thickness. In particular, the glass or glass-ceramic product may be a cooktop.

[0036] In this case, various materials can be used as the substrate.

[0037] Thus, according to one embodiment, the substrate has a transmittance τ of more than 80%, preferably more than 85%. vis transparent, with a saturation of less than 10, especially less than 8 * where saturation c * is defined as follows:

number

[0038] Here, the oxide-based composition of such a substrate may be, for example, as follows: SiO264-68 Al2O319-23 Li2O 3.2-4.2 MgO 0.2-1.0 Na2O+K2O 0.1-1.5 BaO 0-1.5 CaO+SrO 0-1.5 ZnO 1-2.5 TiO21.6-2.6 ZrO21.2-2.0 SnO20-0.5 Nd2O30.005-0.15 Fe2O30.001-0.03 It can be selected in weight percent.

[0039] Alternatively, according to another embodiment, the substrate is bulk-colored and has a transmittance τ of less than 10%. visを In this case, "bulk-colored" is understood to mean a substrate that does not receive its color from a coating, but rather contains elements that contribute to the color of the material itself. Such bulk coloring can be caused, for example, by elements such as chromium, vanadium, or molybdenum that are mixed into the glass composition. For example, the substrate here may have the following oxide-based composition: Li2O 3.0-4.2 Na2O+K2O 0.2-1.5 MgO 0-1.5 CaO+SrO+BaO 0-4 ZnO 0-2 B2O30-2 Al2O319-23 SiO260-69 TiO22.5-4 ZrO20.5-2 P2O50-3 SnO20.1-<0.6 TiO2+ZrO2+SnO23.8-6 V2O50.01-0.06 Fe2O30.03-0.2 in weight percent.

[0040] In another alternative embodiment, the substrate further comprises a transmittance τ of 2% to 25%. vis Translucent or with a transmittance of 0.1% to 2% vis In particular, the substrate may be a glass ceramic having the composition described above for the transparent substrate, where the substrate may have a high volume fraction of keatite in the crystalline phase. In the case of an opaque substrate, it is furthermore possible to use a glass ceramic having a composition similar to that described above for the transparent substrate, where the substrate may have a high volume fraction of keatite in the crystalline phase. In this case, the opaque substrate may further have a composition similar to that described above for the transparent substrate, where the composition is similar to that described above for the transparent * =85~97, a * =-1.5~0.5 and b * Alternatively, in the case of a translucent substrate, the color of the substrate at a transmittance of 2% to 10% may be L * =72~93, a * =-5.5~0, b * Alternatively, the color of the substrate at a transmittance of 10% to 25% may be L * =60~82, L * =-7.5~-2, b * =-19 to -4.5.

[0041] In particular, when the glass or glass-ceramic product according to the invention is used as a cooking surface, according to another embodiment, the substrate is made of LAS glass ceramic, i.e., lithium-aluminum-silicate glass ceramic, which has a very low coefficient of thermal expansion and is very resistant to temperature changes, making it particularly well suited to the thermal requirements of the cooking surface.

[0042] In this case, in another embodiment, the substrate is further configured to have at least one cavity. In particular, such a cavity may be an opening in the substrate, which allows a range hood (also called a downdraft) to be integrated into the cooking surface when the substrate is used as a cooking surface. In this case, the coating on the substrate preferably extends to the edge of the cavity, so that the coated area smoothly transitions into the cavity. Such a cavity in the substrate can be formed by a number of methods, including, in particular, drilling, milling, and water jet cutting.

[0043] According to another embodiment, the illumination source positioned 0.5 mm below the glass or glass-ceramic substrate generates a halo of at most 1.2, preferably at most 1.15, for a substrate thickness of 4 mm. Even more preferably, the illumination source positioned 1.75 mm below the glass or glass-ceramic substrate generates a halo of at most 1.4, preferably at most 1.3, for a substrate thickness of 4 mm. In this case, the aforementioned spacing refers to the distance between the upper surface of the illumination source and the lower surface of the substrate. "Halo" is understood in this case to be a measure of the distortion of the perception of the illumination source when passing through the substrate and the coating disposed thereon.

[0044] For this purpose, the illumination source intensity profile recorded by the camera in the absence of the glass or glass ceramic product is compared with the intensity profile recorded by the same camera and the same camera arrangement through the glass or glass ceramic product when the distance between the illumination source and the underside of the substrate is specified. In this case, the underside of the substrate is preferably smooth, so that only minimal scattering occurs on the underside of the substrate. To evaluate the scattering behavior, the half-widths of the intensity profiles measured with and without a substrate above the illumination source are compared, and the halo value is obtained by dividing the half-width when the substrate is present by the half-width when the substrate is absent. Thus, if the value is 1, the substrate with a coating placed above the illumination source does not affect the measured intensity distribution. In contrast, if the value is greater than 1, the scattering behavior of the coated substrate is confirmed.

[0045] In another aspect, the present invention provides a method for producing the glass-ceramic article described above, comprising the steps of: a. preparing a substrate made of glass; b. applying a layer of ink comprising a glass flow and a printing medium onto at least one partial area of ​​the surface of the substrate, wherein the application is preferably performed by screen printing; c. ceramifying the coated substrate; The present invention relates to a method, comprising:

[0046] Thus, in the present method, in common method step c, not only is the substrate cerammed, i.e., converted from glass to glass ceramic, but the coating is also fired, which makes it possible to avoid a separate step of firing the coating, thereby significantly simplifying the production of glass or glass-ceramic products.

[0047] Here, during the ceramification of the coated substrate, for example, a. Heat from room temperature to 680°C within 23 minutes; b. Increase the temperature from 680°C to 800°C within 19 minutes; c. Increase the temperature from 800°C to 918°C (maximum temperature) within 24 minutes; d. Hold maximum temperature for 10 minutes; e. Cool to 800°C within 20 minutes; f. Rapidly cool to room temperature in less than 150 minutes; It can be proceeded as follows.

[0048] Instead, ceramicization, a. Rapid heating from room temperature to 740°C in 20-26 minutes, especially 24 minutes: b. Increase the temperature from 740°C to 825°C in 12 to 18 minutes, especially 14 minutes; c. Increase the temperature from 825°C to 930°C (maximum temperature) in 4 to 8 minutes, especially in 6 minutes; d. Hold the maximum temperature for 4-8 minutes, especially 6 minutes; e. Cooling to 800°C within 8-16 minutes, especially within 10 minutes; f. Rapidly cool to room temperature; It may be done like this.

[0049] In another embodiment, the coating is applied by screen printing, using a screen having a screen thickness of 140-31 to 54-64 mm. A screen having a screen thickness of 77-55 mm has proven particularly advantageous. The screen can be configured to have areas where the glass flow is not transmitted to the substrate, allowing for simple implementation of voids in the coating. In particular, a screen that creates a microstructure in the coating can also be used, so that the area coverage of the coating, i.e., the ratio of the area of ​​the coated area to the area of ​​the uncoated area of ​​the substrate, is less than 100%. This allows for the formation of a pattern in the coating that further reduces the visibility of scratches or impurities on the surface. The area coverage is preferably no less than 80%.

[0050] According to another embodiment, it is further provided that a deco layer is applied to the substrate before the application of the coating to the substrate, and that the coating is then applied at least partially onto the deco layer. The deco layer here can be applied to the substrate in particular by inkjet printing. However, it can alternatively be provided that the deco layer is applied after method step b, i.e., arranged on the coating.

[0051] It has already been mentioned above that the substrate can have a cavity for integrating, for example, a range hood. In this case, such a cavity is preferably introduced into the substrate before the substrate is coated. In this case, the coating can then be applied to the substrate up to the edge of the cavity, so that the coating is not damaged by the cavity manufacturing process. However, the cavity can also be formed in an already coated substrate after ceramization.

[0052] In another aspect, the present invention is an ink for producing the glass or glass-ceramic product described above, wherein the ink comprises a boron-containing glass flow and a print medium, wherein the glass flow has a D of greater than 1 μm. 10 Particle size and D less than 20 μm 90 Particle size, preferably D less than 15 μm 90 The ink has a particle size. The printing medium is particularly a medium containing dipropylene glycol monomethyl ether as a solvent, which is advantageous in particular with regard to its biocompatibility. Alternatively, a pressure medium based on naphtha as a solvent may be used.

[0053] In this case, the glass stream is preferably particles made of borosilicate glass, the glass preferably having the following oxide-based composition: SiO275-85 Al2O30.1-5 B2O310-15 Na2O 1-5 K2O 0.1-1.5 in weight percent.

[0054] According to another embodiment, in this case the ratio of glass flow in the ink to print medium is between 10:15 and 10:5, which has a particularly advantageous effect on the printing properties of the ink.

[0055] The invention will now be explained in more detail with reference to the drawings, in which, however, the invention is not limited thereto, and in which the same reference numerals represent the same or similar elements. [Brief explanation of the drawings]

[0056] [Figure 1] 1A-1C are schematic diagrams illustrating various embodiments of exemplary glass or glass-ceramic products. [Figure 2] FIG. 1 is a schematic diagram illustrating an exemplary method for making an exemplary glass-ceramic article. [Figure 3] FIG. 1 shows the surface profile of a matte surface as a comparative example. [Figure 4] 1 is a histogram illustrating an exemplary particle size distribution of a glass stream for producing a coating. [Figure 5] FIG. 5 is a perspective view showing the surface profile of a coating produced by the glass flow of FIG. 4. [Figure 6] FIG. 6 shows the surface profile along a line within the surface shown in FIG. 5. [Figure 7] 10 is a histogram illustrating another exemplary particle size distribution of a glass stream for producing a coating. [Figure 8] FIG. 8 is a perspective view showing the surface profile of a coating produced by the glass flow of FIG. 7. [Figure 9] FIG. 9 shows the surface profile along a line within the surface shown in FIG. 8. [Figure 10] 1 is a top view of an exemplary glass-ceramic article and the outline of a deco layer derived therefrom, showing a deco disposed below a coating. FIG. [Figure 11]1 is a top view of an exemplary glass-ceramic article and the outline of a deco layer derived therefrom, showing a deco disposed below a coating. FIG. [Figure 12] FIG. 1 illustrates an exemplary measurement structure for determining halo values.

[0057] FIG. 1 shows schematic diagrams of various embodiments of an exemplary glass or glass-ceramic product 100. Here, FIG. 1a) shows the simplest case, in which a coating 104 is applied directly to the surface 106 of a plate-shaped substrate 102 made of glass or glass ceramic. The coating has a rough surface 114 with a root-mean-square height Sq in the range of 0.1 μm to 2.5 μm and a core height Sk of 1.5 μm to 10 μm, giving the coating 104 a matte appearance. In this case, no additional coating, particularly a deco, is initially provided between the coating 104 and the substrate 102. The substrate 102 is preferably a lithium-aluminum-silicate glass ceramic (LAS glass ceramic), which, due to its generally low coefficient of thermal expansion, is particularly well suited for use as a cooking surface. The substrate 102 may be a transparent, translucent, or opaque material. Furthermore, the substrate 102 may be substantially colorless or bulk-colored.

[0058] Here, in the illustrated embodiment, a coating 104 is applied to the top surface of the substrate 102, which faces the user when the product 100 is used as a cooking surface, and on which, for example, cooking utensils are placed. In all configurations of Figure 1, even if a separate coating is not shown on the bottom surface 116 of the substrate 102, such an additional bottom coating is not essentially excluded. Rather, particularly in the case of a transparent substrate 102, it may be advantageous to use a bottom coating that is as opaque as possible in addition to the top coating 104, for example, to hide electronic components located below the substrate 102.

[0059] The dimensions of the elements shown in Figure 1 are greatly simplified for reasons of clarity of illustration and are not drawn to scale, particularly in relation to one another. Thus, the preferred thickness of substrate 102 is, for example, 4 mm, while coating 104 preferably has a thickness in the range of only 2 to 10 μm. Similarly, the length extent of substrate 102 is shown merely by way of example; typically, the thickness of substrate 102 is at least an order of magnitude smaller than its length.

[0060] 1b) shows another embodiment of the glass or glass-ceramic product 100, in which a further coating 108 as a deco is applied to the surface 106 of the substrate 102. Here, the deco 108 is completely covered by the coating 104 in the illustrated embodiment and is therefore protected from external influences. In this case, the high edge sharpness of the deco 108 remains guaranteed by applying the deco 108 directly to the generally very smooth surface 106 of the substrate 102, while the rough surface 114 of the coating 104 gives the glass or glass-ceramic product 100 an overall matte appearance. Here, the deco 108 may be, for example, a cooking zone indicator, a manufacturer's logo, or other markings. In addition to the configuration shown here in which the deco 108 is completely covered by the coating 104, configurations in which the deco 108 is only partially covered by the coating 104, i.e., in which there are areas of the deco 108 exposed, are also possible within the scope of the present invention.

[0061] Although the coating 104 is depicted in FIGS. 1A and 1B as a coating covering the entire surface 106 of the substrate 102, it is also possible that the coating 104 extends over only a portion of the surface 106 of the substrate 102, and thus there are regions in which the coating 104 does not have voids. This is the case shown in FIG. 1C. In the illustrated embodiment based on the embodiment of FIG. 1B, the coating 104 has a void 110 in the center of the figure, in which the surface 106 of the substrate 102 is exposed. Such voids 110 can be taken into account during the production of the coating 104, for example by appropriately masking the substrate 102 or by appropriately designing a screen for applying the coating 104 by screen printing, so that corresponding regions are formed as voids on the surface 106 of the substrate 102.

[0062] Such a gap 110 can be particularly advantageous if a display device 112, for example in the form of a seven-segment display or a full-color display, is arranged below the substrate 102. Image reproduction of such a display device 112 would be distorted when passing through the coating 104 due to its rough surface, although this can be avoided by a corresponding gap in the coating 104.

[0063] 2 shows an example method for producing an example glass-ceramic product 100. Here, in a first method step 200, a substrate 102 made of glass is provided, which can already be cut to the dimensions desired for the final product. Furthermore, a pretreatment of the surface 106 of the substrate 102 to be coated can also be carried out here, for example by polishing the surface 106 to prepare the surface 106 as smooth as possible.

[0064] Next, in a second method step 202, an ink containing a glass flow and a print medium is applied onto at least a portion of the surface 106 of the substrate 102. In this case, the glass flow has a D of more than 1 μm. 10Particle size and D less than 20 μm 90 Particle size, preferably D less than 15 μm 90 Preferably, the ink has particles of this size. To apply the ink to the surface 106 of the substrate 102, any printing method suitable for processing glass flows with the above-mentioned particle size can be used. However, the application of the ink by a screen printing method is particularly preferred. This method has the advantage that, on the one hand, large coatings can be produced at low cost, and, on the other hand, areas in the coating 104 can be formed as voids by appropriately configuring the screen used. In this way, for example, structures such as those described above with reference to FIG. 1c) can be formed.

[0065] The screens used for screen printing can be selected here in principle to suit the printing medium and glass flow used, although it has been found to be particularly advantageous to use a 140-31 strength screen when using a naphtha-based pressure medium as the solvent.

[0066] In a third method step 204, the printed substrate 102 is then cerammed. For this purpose, for example, and by way of example only and not by way of limitation, the following ceramming program may be used: a. Rapid heating from room temperature to 680°C in less than 23 minutes; b. Increase the temperature from 680°C to 800°C within 19 minutes; c. Increase the temperature from 800°C to 918°C (maximum temperature) within 24 minutes; d. Hold maximum temperature for 10 minutes; e. Cool to 800°C within 20 minutes; f. Rapid cooling to room temperature in less than 150 minutes; can be used.

[0067] Alternatively, ceramicization may be performed by: a. Heating from room temperature to 740°C in 0-26 minutes, especially 24 minutes; b. Increase the temperature from 740°C to 825°C in 12 to 18 minutes, especially 14 minutes; c. Increase the temperature from 825°C to 930°C (maximum temperature) in 4 to 8 minutes, especially in 6 minutes; d. Maintain maximum temperature for 4 to 8 minutes, especially 6 minutes; e. Cooling to 800°C within 8-16 minutes, especially within 10 minutes; f. Cool to room temperature; It can be executed as follows.

[0068] In this case, during the ceramization of the substrate 102, after a nucleation phase in which crystal nuclei are formed within the substrate 102, a further temperature increase stimulates controlled crystal growth, thereby converting the glass substrate 102 into a glass-ceramic with defined mechanical and optical properties. Due to the high temperature during ceramization, the glass flow present on the surface 106 of the substrate 102 also partially melts, while the pressure medium of the ink evaporates substantially without residue. The molten glass flow then bonds to the glass substrate 102, resulting in a coating 104 on the surface 106 of the substrate 102 that is highly robust and substantially insensitive to mechanical loads. The unmelted parts of the glass flow now form a non-planar structure on the surface 114 of the coating 104, which results in the surface parameters according to the invention.

[0069] 3a) shows a schematic diagram of a surface height profile for illustrating the surface parameters according to the invention. Here, the surface height z(x) above the zero line for each different point along the measurement section (x-axis) within the surface is expressed in μm. The zero line is located at the height at which the sum of the deviations of the local elevations of the surface from the zero line along the measurement section is zero. In the two-dimensional case shown here, only the surface parameters already mentioned above have been selected for the purpose of illustration. However, the surface parameters used to describe the article according to the invention are actually calculated from a consideration of the entire surface, i.e., a three-dimensional representation of the surface, and not along individual lines within the surface.

[0070] Starting from the zero line shown in Figure 3a), all local deviations of the surface from the zero line z(x) are squared, summed and divided by the length of the measurement section to determine the root mean square height Sq of the surface. The square root is then derived from this result. In this way, information is effectively obtained about how much the surface deviates from the zero line on average, i.e., how rough the surface is. The higher this value, the rougher the surface.

[0071] To determine the core height Sk, first, for each height y on the vertical axis, it is determined which portion of the surface is higher than the observed y value. This percentage is then designated the surface material percentage M on the horizontal axis. For example, for the surface in FIG. 3a), a surface material percentage value of 0% is calculated at a height of 8 μm, since the surface does not deviate from the zero line by more than 8 μm. For a height of 6 μm, a small percentage of the surface that deviates from the zero line by more than +6 μm is already calculated. By definition, a percentage of 50% is assigned to the ordinate value 0 μm in the illustrated case, since the zero line divides exactly equal portions of the surface. However, a different zero line can also be selected as a reference point. For a value of -10 μm, a value of more than 95% is already calculated for the surface material percentage M, but above an ordinate value of approximately -13 μm, 100% of the surface exceeds this value.

[0072] An exemplary distribution 300 of this type is shown in FIG. 3b. To determine the core height Sk from the distribution, the equivalence of the distribution 300 of face material proportions is determined in a first step. For this purpose, the area in which 40% of the face material proportion ΔM is omitted is shifted along the vertical axis until a region is found in which the secant of the end point of the area ΔM of the curve 300 has the smallest possible slope in the distribution of face material proportions. This is shown in FIG. 3b for three different areas ΔM, each with a width of 40%. For the first area ΔM1, corresponding points s11 and s12 are marked, which correspond to the area ΔM1 on the curve 300 of face material proportions. From these intersection points s11 and s12, the secant 301 of the curve 300 of the face material component for the first area ΔM1 results. Similarly, for the second region ΔM2, a secant 302 is calculated from the intersection points s21 and s22, and further, for the third region ΔM3, a secant 303 is calculated from the intersection points s31 and s32.

[0073] Here, the average curve 302 of the illustrated curves 301, 302, and 303 has the smallest slope that can be found. The curve 302 with the smallest slope calculated according to the method described above is also called the equivalence. To determine the core height Sk, the equivalence is calculated at the intersection of the surface fractions 0% (intersection with the horizontal axis) and 100% (intersection S 100 ) is extrapolated to The core height Sk is then determined from the intersections of the equivalence with the 0% and 100% surface fractions, as the distance between these intersections along the horizontal axis. In this case, a small core height is synonymous with a high material density on the surface, which also contributes to the surface's robustness against mechanical loads. For example, the core height Sk of the surface shown in Figure 3a) is 12.7 μm.

[0074] Another important parameter for describing the surface of a coating is the surface slope (Ssk). As already explained, skewness indicates whether the surface can be described as being more crested (positive slope) or more grooved (negative slope). This is equivalent to the question of whether the surface slope from the zero line tends more frequently towards the positive or negative regions. That is, if more positions along the measurement section are found with positive ordinate values, the slope Ssk will also be positive; if more positions along the measurement section are found with negative ordinate values, the slope Ssk will also be negative. In this case, two surfaces with the same value for the root-mean-square height Sq can have completely different slope values. This is because the calculation of the surface heights squared to determine the value Sq does not take into account the issue of slope direction, as the slope above or below the average surface height. For example, the surface in FIG. 3a) has a slope Sk of -0.33, ie it tends to be more inclined than the grooved surface.

[0075] A comparable statistical observation of surface characteristics allows for another surface parameter, kurtosis Sku, to be considered here. In this case, kurtosis is calculated by normalizing the sum of the fourth powers of the local heights of the surface z(x) over the measurement interval and dividing it by the root mean square height Sq. This effectively considers the frequency of occurrence of a particular value z along the measurement interval, regardless of its sign. For a value Sku=3, the different values ​​of surface height are normally distributed around the zero line. For values ​​of Sku less than 3, the surface tends to have a rather circular structure; for values ​​Sku greater than 3, the surface tends to have a rather jagged structure. In this case, the surface shown in FIG. 3a) has a kurtosis Sku of 2.77, i.e., a rather rounded and chamfered surface structure.

[0076] Below, two examples are given to explain how coatings having the above-mentioned claimed properties can be produced.

[0077] In this regard, Figure 4 discloses an exemplary particle size distribution histogram of a glass stream for producing a coating, where the particles of the glass stream have the following composition on an oxide basis: SiO281 B2O313 Al2O32 Na2O 3.5 K2O 0.5 in weight percent.

[0078] To form the glass stream, the glass melted according to the above composition was crushed, in this case by wet crushing with water. The glass stream thus formed had a particle size distribution D of 1.37 μm. 10 , 17.02 μm D 90 and D of 24.10 μm 99 It has the following characteristics.

[0079] The glass flow thus formed was then mixed with a screen printing medium based on dipropylene glycol monomethyl ether (DPM) as the solvent in a compatibility ratio (ratio of glass flow to screen printing medium) of 10:6. The ink thus formed was then applied by screen printing onto a ceramizable glass substrate using a screen with a screen strength of 140-31 and fired according to the ceramization program described above.

[0080] In this case, in addition to the glass streams mentioned above, other glass streams can be mixed in order to adapt the coating in its properties to the substrate used, with the following compositions being given as examples: SiO254.3 B2O316.7 Al2O316.6 Li2O3.1 MgO 1.7 CaO 2.0 SrO2.3 ZnO 2.2 ZrO21.1 A glass flow of 1000 .mu.m can be used.

[0081] Such glass flows differ from the previously mentioned glass flows, for example, in their softening temperatures and thermal expansion coefficients, and so by mixing these glass flows it is possible to tailor the mechanical and thermal properties of the resulting coating.

[0082] In this case, FIG. 5 shows that the surface profile of the coating thus obtained is approximately 1 mm 2 A perspective view of a local section over an area of ​​1.21 μm is shown. The resulting surface has a root mean square height Sq of 1.21 μm, a core height Sk of 3.1 μm, a slope Ssk of 0.01, and a kurtosis Sku of 3.05. Furthermore, the surface has a mean arithmetic height Sa of 0.96 μm.

[0083] In this case, the average arithmetic height Sa is calculated from the coating area A and coating height z as follows:

number

[0084] Additionally, FIG. 6 illustrates a diagram of the surface profile along a line within the surface shown in FIG.

[0085] 7 shows another histogram of an exemplary particle size distribution of a glass stream for producing a coating for an exemplary glass-ceramic article. In this case, the glass stream is made of the same material as the glass stream described above in connection with FIG. 4. In the case of FIG. 7, the glass is again ground by wet grinding, which results in the particle size distribution shown. In this case, D 10 is 1.15 μm, and D 90 is 14.72 μm, and D 99 The glass flow thus obtained was mixed with a naphtha-based screen printing medium in a 10:12 compatibility ratio and applied to the surface of a substrate using a 77-55 strength screen, similar to the example in Figure 4, and fired to ceramize the substrate.

[0086] Figure 8 shows the surface profile of the coating obtained in this way, with a thickness of about 1 mm 2 A perspective view of a local section over an area of ​​1.6 μm is shown. The resulting surface has a root mean square height Sq of 1.6 μm, a core height Sk of 3.9 μm, a slope Ssk of 0.045, and a kurtosis Sku of 3.46. Furthermore, the surface has a mean arithmetic height Sa of 1.25 μm.

[0087] Additionally, FIG. 9 illustrates a representation of the surface profile along a line within the surface shown in FIG.

[0088] 10a) shows a monochrome view of an exemplary glass-ceramic product with a colored deco layer disposed beneath the coating. Such imaging can be performed, for example, by optical microscopy. The grain structure of the coating weakens or abrades the otherwise sufficiently uniform deco layer, particularly the normally very sharp deco contour line 404 that marks the transition between the deco area 402 and the undecoated substrate 400.

[0089] To describe the characteristics of the contour 404, a simple means can be used to first extract the specific extent of the contour 404 from the diagram in Fig. 11 a). To do this, a gray value between 0 and 100 can be set, with limits between 0% and 100% set as a value of, for example, 20, instead of the color effect of the deco. In the diagram in Fig. 11 a), all measurement points with a gray value above or below the defined limit are assigned the gray value 0, while all measurement points with a gray value of 20 are assigned the value 100. In this case, not only the discrete limits but also the range of limits that can be assumed for the contour can be determined, for example, all gray values ​​between 15 and 20.

[0090] The result of this calculation is shown diagrammatically in Fig. 11b) for the upper half of the part shown in Fig. 11a). As can be seen in Fig. 11b), by using a limit for the grey value of the measurement points, spots in the deco, which are sometimes caused by optical distortions due to the structured coating, are also interpreted as contours. These points can be manually removed from the display, or an area in which contours should be observed can be specified so that points outside this area are no longer taken into account.

[0091] In this way, a discrete contour line can be calculated, as illustrated in FIG. 11 a). Due to the optical distortion caused by the structured coating placed above the deco layer, when considering the contour line in an xz graph, there may be a point on the x-axis and two different points on the z-axis located on the contour line. In FIG. 11, this is the case, for example, for point x1, because this point x1 cannot be assigned a unique z value that lies on the contour line, since a line parallel to the z-axis and passing through point x1 intersects the contour line at two points.

[0092] However, to determine the mean square value of all ordinate values ​​of the contour, a curve is required in which each value x is assigned only one value z(x), and therefore the curve must be transformed into a correspondingly adapted curve in a separate step. This can be done by assigning to each point x, which can be assigned several ordinate values ​​z(x), the maximum value z(x) on the contour. This is illustrated in FIG. 11 b). Conversely, it is also possible to assign to each point x the minimum ordinate value z(x) on the contour, as shown in FIG. 11 c).

[0093] In this case, the root mean square roughness Rq, which is the root mean square roughness, can be determined from the contours obtained in this way. In this case, it is also possible to determine the value Rq for each of the two contours shown in Figure 11b) and Figure 11c) and to assume the average of these two values ​​as the actual value of the contour. In this way, it is possible to describe how the sharp contours of the deco are distorted by the structured coating applied to the deco.

[0094] In addition to the aforementioned value Rq, other parameters characterizing the contour line extension, which are known from the analysis of the surface properties, can also be determined. For example, the two-dimensional parameters Sa, Ssk, and Sku described above with respect to the properties of the surface 114 of the coating 104 of the exemplary glass or glass-ceramic product 100, can also be calculated in one-dimensional form, i.e., as Ra, Rsk, and Rku, respectively, relating to the contour line extension. In this case, the arithmetic mean roughness value Ra of the contour line is preferably at most 15 μm, while the skewness Rsk preferably has a value less than 0. Furthermore, the kurtosis Rku of the contour line is preferably greater than 3.

[0095] FIG. 13 shows an exemplary measurement setup for measuring the halo value of an exemplary glass or glass-ceramic product 100. In this case, a holder 504 is arranged on a vibration-damping base 502 in a darkroom 500. An illumination source 506 having a light-emitting means, e.g., a white seven-segment display, is arranged on the holder 504. Similarly, an object 508 to be inspected, particularly a plate-shaped substrate, can be placed on the illumination source. A spacer piece arranged between the object 508 and the illumination source 506 creates a defined distance between the light-emitting means and the underside of the object 508. Above the object 508, above the illumination source 506 or the light-emitting means used, a camera 512 with an objective lens 514 focused on the surface of the light-emitting means is arranged vertically. In this case, the camera 512 may be arranged above the illumination source 506, e.g., approximately 30 cm to 35 cm.

[0096] To determine the halo value, a zero measurement is then carried out in the absence of article 508 and a measurement in the presence of article 508, during which the image of the light-emitting means is respectively imaged in grey scale. From the images thus obtained and in particular the extent of the intensity distribution in a cross section transverse to the recorded image that can be calculated therefrom, the halo value can then be calculated as described above.

[0097] The surface parameters Sq, Sk, Ssk, Sku and Sa used and described herein are also described, for example, in DIN EN ISO 25178-2:2023-09.

[0098] Although the present invention has been described based on the preferred embodiments, it is not limited to these and can be modified in various ways. [Explanation of symbols]

[0099] 100 Glass or glass-ceramic products 102 Base material 104 Coating 106 Top surface of substrate 108 Deco 110 Vacant Space 112 Display device 114 Coating Surface 116 Bottom surface of substrate 300 Surface Material Distribution 301 Secant 302 Equivalence 303 Secant

Claims

1. A glass or glass-ceramic product having a substrate made of glass or glass ceramic, the substrate having, on at least one side, a substantially pigment-free coating on at least a portion of its surface; the coating having an at least partially molten glass flow; the surface of the coating has a root mean square height Sq of at least 0.1 μm and at most 2.5 μm; the coating has a core height Sk of at least 1.0 μm and up to 10 μm; Glass or glass-ceramic products.

2. 10. The glass or glass-ceramic article of claim 1, wherein the coating has a gloss value of at most 25 at a 60° viewing angle.

3. 3. The glass or glass-ceramic article according to claim 1, wherein the coating has a slope Ssk > 0.

4. 4. The glass or glass-ceramic product according to claim 1, wherein the coating has a kurtosis Sku>3.

5. The glass or glass-ceramic article according to any one of claims 1 to 4, wherein the coating has a thickness of from 2 μm to 10 μm.

6. 6. The glass or glass-ceramic product according to claim 1, wherein an at least partially colored deco layer is arranged between the substrate and the coating.

7. 7. The glass or glass-ceramic product of claim 6, wherein a contour of the deco layer located below the coating has a root-mean-square roughness value Rq of at most 20 μm in a direction parallel to the surface of the substrate in a plan view looking perpendicularly at the deco through the coating.

8. 8. The glass or glass-ceramic product according to claim 6 or 7, wherein the combination of the deco layer and the coating has a thickness of at most 15 μm.

9. 9. The glass or glass-ceramic article according to claim 1, wherein the coating is applied over the entire surface of one side of the substrate.

10. The glass stream has the following oxide-based composition: Yes ２ 75-85 Al ２ O ３ 0.1-5 B ２ O ３ 10-15 Na ２ O1-5 K ２ O 0.1-1.5 % by weight of the glass or glass-ceramic product.

11. 11. The glass or glass-ceramic product according to claim 1, wherein the substrate is plate-shaped and has a thickness of 2 mm to 6 mm, preferably 3 mm to 5 mm, particularly preferably 4 mm.

12. The substrate has a transmittance τ of more than 80% ｖｉｓ and has a chroma c of less than 10. ＊ , especially chroma c less than 8 ＊ 12. The glass or glass-ceramic article according to claim 1, wherein the glass or glass-ceramic article has a viscosity of 1000 MPa or less.

13. The substrate is bulk-colored and has a transmittance τ of 2% to 10%. ｖｉｓ 12. The glass or glass-ceramic article according to claim 1, wherein the glass or glass-ceramic article has a viscosity of 1000 MPa or less.

14. The substrate has a transmittance τ of 2% to 25% ｖｉｓ or translucent with a transmittance τ of 0.1% to 2% ｖｉｓ 12. The glass or glass-ceramic article according to claim 1, which is opaque at 1000 .mu.m.

15. 15. The glass or glass-ceramic product according to any one of claims 1 to 14, wherein the substrate consists of an LAS glass ceramic.

16. 16. The glass or glass-ceramic product according to claim 1, wherein an illumination source positioned 0.5 mm below the glass or glass-ceramic product generates a halo of at most 1.2 when the substrate has a thickness of 4 mm.

17. 17. A method for producing a glass-ceramic product according to any one of claims 1 to 16, comprising the steps of: a. preparing a substrate made of glass; b. applying a layer of ink comprising a glass flow and a print medium to at least one partial area of ​​the surface of the substrate, wherein the application is preferably performed by screen printing; c. ceramifying the coated substrate; A method comprising:

18. 18. The method of claim 17, wherein the application of the coating is performed by screen printing, and a screen having a screen strength of 140-31 to 54-64 is used for the screen printing.

19. 19. The method of claim 17 or 18, wherein prior to application of the coating to the substrate, a deco layer is applied onto the substrate, and then the coating is applied at least partially onto the deco layer.

20. 17. An ink for producing a glass or glass-ceramic product according to any one of claims 1 to 16, comprising: The ink comprises a boron-containing glass stream and a print medium, wherein: The glass flow has a D of more than 1 μm １０ Particle size and D less than 20 μm ９０ Particle size, preferably D less than 15 μm ９０ having a particle size, ink.

21. 21. The ink of claim 20, wherein the ratio of glass flow to print medium in the ink is from 10:15 to 10:5.

Images