Plate comprising glass or glass ceramic, method for the production thereof and use thereof

Abstract

The invention relates generally to plates comprising glass or glass-ceramic, in particular those which are at least partially covered with a coating, a method for producing such plates and their use.

Description

Area of ​​Experience

[0001] The invention relates generally to plates comprising glass or glass ceramic, in particular those which are at least partially covered with a coating, a method for producing such plates and their use.

[0002] In particular, the invention relates to a plate comprising a glass or a glass ceramic, in particular a lithium aluminum silicate glass or a lithium aluminum silicate glass ceramic, which comprises a coating.

[0003] Coated glass or glass-ceramic plates have long been known and have been used for many years, for example, as cover plates for cooking appliances (also called "cooktops" or "cooking surfaces"). Such plates are typically provided with at least one coating. Examples include plates comprising a volume-colored substrate, on which so-called cooking zone markings are applied on the side facing the user (also referred to as the "top" or "front"). The printing of logos is also known. Furthermore, plates comprising a non-volume-colored substrate, on which a so-called "underside coating" is applied, are also known. Depending on the precise design of such a plate, different coatings can be combined on different sides of such a plate.

[0004] Printing processes are generally used as the application method of choice. Screen printing is the state-of-the-art in this field, allowing for high throughput in the production of printed plates. However, the disadvantage is that these plates must always be printed the same way, and different processing steps are required for different printing inks.

[0005] Inkjet printing has therefore become increasingly popular as an alternative. This process allows for more flexibility in the production of such plates. For example, smaller batch sizes are now possible.

[0006] In practice, however, for reasons that are still unclear, it has been shown that the print quality in screen printing is generally better than in inkjet printing.

[0007] European patent application EP 3 346 876 A1 describes large-format worktops for a kitchen block with a minimum area of ​​0.7 m² and a flatness of less than 0.1% of the substrate diagonal. However, the quality of the printing is not discussed here. Inkjet printing is not mentioned either. Nor is the surface roughness of this worktop, which is relevant for the quality of inkjet printing, discussed.

[0008] The US patent application US 2019 / 128534 A2 describes a glass-ceramic worktop for kitchen furniture with a low flatness of less than 0.1% based on the diagonal. However, the print quality or inkjet printing are not mentioned here either. Nor is the surface roughness of this worktop, which is relevant for the quality of inkjet printing, discussed.

[0009] Japanese patent application JP 2015 / 176753 A describes polished surfaces of cooktops used as hobs. However, this application does not address the quality of the applied decoration, but rather focuses on the reflectivity of the surfaces or their gloss, and on the visual impression of the underside print.

[0010] No prior art document addresses the improvement of the print image, especially in contactless printing, such as inkjet printing.

[0011] There is therefore a need for glass or glass-ceramic plates which have a good print image in a contactless printing process, such as inkjet printing, as well as for a process for their production. Task of Experience

[0012] The object of the invention is to provide panels comprising a substrate made of glass or glass-ceramic and at least one coating that at least partially mitigate the problems of the prior art. Accordingly, there is also a need for a method for producing such panels. Summary of Experience

[0013] The object of the invention is achieved by the subject matter of the independent claims. Preferred and specific embodiments can be found in the dependent claims as well as in the description and drawings of the present disclosure.

[0014] The disclosure therefore relates to a plate comprising glass or glass ceramic with two opposing side surfaces and a circumferential edge surface, wherein the flatness of the plate is less than or equal to 0.1% of a lateral dimension and at least one side in at least one region has an average surface roughness R z,average of less than 0.5 µm with a standard deviation of the surface roughness, σ Rz of less than 0.1 µm, further comprising a coating which is arranged on at least two different sub-regions of the at least one region of the at least one side of the plate, wherein the at least two sub-regions are spaced at least 3 cm from one another and wherein the raggedness of the coating in the two sub-regions differs from one another by a maximum of 10%.

[0015] Such a design has a number of advantages.

[0016] The simultaneous good flatness and roughness of the plate enables excellent print quality of the coating, for example, in an inkjet printing process. The excellent print quality is particularly evident in the so-called "raggedness" of the corresponding coating. Raggedness can preferably be determined according to a method according to ISO 24790.

[0017] Raggedness is a measure of the image quality of a printed image and describes, for example, the so-called edge sharpness. The method for determining raggedness is described below in Figs. 1 explained in detail.

[0018] The flatness of the plate is less than or equal to 0.1% of a lateral dimension, preferably the largest lateral dimension, of the plate. For example, according to one embodiment, the corresponding lateral dimension of the plate can be the diagonal of a rectangular plate. The diagonal is generally understood here as the surface diagonal of the plate, i.e., the diagonal of one of the main surfaces (or sides) of the plate.

[0019] In the context of the present disclosure, a lateral dimension is generally understood to mean one of the length dimensions of the plate. In the context of the present application, a plate is generally understood to be a body whose dimensions in two spatial directions of a Cartesian coordinate system are at least one order of magnitude larger than in the third spatial direction perpendicular to these first two spatial directions. In other words, the thickness of a plate is at least one order of magnitude smaller than its length and width. The length and width of the plate determine the main surfaces (in contrast to the circumferential edge surfaces, which only make up a small proportion of the total surface area of ​​the plate) for a generally rectangular plate. A lateral dimension in the sense of the present disclosure is, however, in particular the surface diagonal, which in the context of the present application is also referred to as the diagonal.This is the largest lateral dimension of a generally rectangular plate. In the case of a non-rectangular plate, for example, the diameter can be used instead of the length, width, or diagonal and referred to as the corresponding lateral dimension.

[0020] Advantageously, the average surface roughness R z,average and the standard deviation of the surface roughness, σ Rz , are determined by measuring the roughness R z at nine points on the plate, each spaced at least 5 cm apart, preferably at least 10 cm apart, and particularly preferably at least 15 cm apart, and determining the arithmetic mean and standard deviation from these nine measured values. Particularly preferably, R z is determined by measuring a line profile with a stylus and evaluating the results in accordance with ISO 4827.

[0021] This flatness is advantageous because it enables a homogeneous application of the coating during printing, thus enabling even small and fine structures to be printed with high quality. Furthermore, it is also advantageous because it can increase the installability of a panel. It has also been shown that such an arrangement can improve the visibility of displays. A uniform surface with only the smallest possible thickness variations in the panel minimizes differences in brightness in the display. This is particularly advantageous for volume-dyed materials, where thickness variations are exponentially influenced by the transmission properties.

[0022] This can advantageously be combined with the plate not only being very smooth, i.e., not very rough, and flat on at least one side, but also with the two side surfaces being arranged parallel to one another. Therefore, according to one embodiment, it can also preferably be provided that the side surfaces are arranged parallel to one another. An arrangement is understood to be parallel if the normal angles to the side surfaces enclose an angle of no more than 5°, preferably no more than 2°, and most preferably, within the scope of usual manufacturing and measurement tolerances, of 0°.

[0023] If one side of the plate is studded, the area resulting from the stud tips is used to determine the normal angle.

[0024] The inventors also assume that this approach will also improve the processing of the board in general. The improved flatness and roughness also improve the dimensional stability of the boards. This also makes them easier to handle and, for example, allows for better bonding.

[0025] According to one embodiment, the plate can have a thickness between 2 mm and 6 mm. This is particularly advantageous for use as a cover plate in a cooking appliance, as it allows for a good compromise between the smallest possible thickness, which is advantageous for the initial cooking behavior, and sufficient plate strength, which is absolutely necessary for such an application and which increases with the plate thickness.

[0026] In general, the flatness and roughness of the plate according to the disclosure are advantageous for all coating types and processes. However, this is particularly advantageous for inkjet printing coatings.

[0027] Flatness determines the minimum distance to the print head in non-contact inkjet printing. It has been shown that, especially for contactless printing processes, the distance between the print head and the substrate to be printed is very important for a good print image. With a flatness of more than 0.1%, there can be a height difference of up to 600 µm (for example, with a diagonal of 60 cm). This means that the distance between the print head and the substrate is not sufficient for the drop to actually break off and fully form after exiting the print head. This can be very critical, especially with small distances between the print head and substrate, such as just 1 mm. It would theoretically be possible to correct this by inline determination of the distance between the plate and print head, by adjusting the height of the print head depending on the measured distance.However, this would require a great deal of mechanical effort. However, this can be cleverly circumvented by the deliberate use of flat and smooth substrates.

[0028] The low flatness enables the defined deposition of droplets. This leads to better print control and reproducible droplet deposition. This also enables improved print image resolution.

[0029] Especially in inkjet printing, it has proven crucial that the distance between the substrate and the print head is precisely maintained. Only then can the droplet shape of the printing ink or printing ink be optimally formed. It is therefore important to maintain a minimum distance between the print head and the substrate, which can be approximately 1.5 mm. Depending on the printing press, however, smaller distances, such as 1 mm, are also possible. If the minimum distance is not met, the droplet shape cannot be optimally formed, at least approximately spherical.

[0030] However, if the distance between the print head and the substrate is too large, the droplet may be deflected, causing it to land on the substrate instead of where it was intended, and / or so-called satellites may form. This leads to reduced edge sharpness and, in some cases, even holes in the print image.

[0031] Both of these conditions result in a choppy and blurry print image. This is particularly problematic when different print images are applied between areas of a substrate, and the print images are printed with varying degrees of sharpness at different points on the plate due to a lack of flatness and roughness.

[0032] According to one embodiment, the coating comprises a glass flux and / or is formed as an enamel. The coating is preferably formed as a coating comprising a glass flux and / or as an enamel and comprising at least one pigment. Particularly preferably, the at least one pigment does not comprise any pigment particles with a primary grain size, determined as the d 50 value of the equivalent diameter, of more than 1.0 µm, and very particularly preferably does not comprise any pigment particles with a primary grain size, determined as the d 90 value of the equivalent diameter, of more than 2.5 µm.

[0033] Such a design is particularly advantageous because coatings comprising glass flux or enamel coatings are particularly thermally stable and also adhere well to glassy surfaces, such as glass or glass-ceramic surfaces. For example, such coatings can be designed to form a so-called "melting reaction zone," so that the coating or the glass flux encompassed by the coating and the substrate material form an intimate bond during firing. In this way, such coatings are also designed to be used, for example, as surface decoration on so-called cooking surfaces.Such surface decorations, which are used, for example, to print logos or to mark cooking zones, must withstand the sometimes very harsh cleaning conditions (with a so-called glass field scraper) as well as the operating conditions (abrasion, for example, due to the moving of cookware, sometimes under heat stress).

[0034] In the context of the present disclosure, coatings comprising a glass flux are understood to mean coatings that have at least one vitreous component, for example, made from a paste comprising a glass powder. In the context of the present disclosure, such coatings are also referred to as "enamel," especially when the glass flux at least partially melts during firing.

[0035] In principle, it is possible for the coating applied to the substrate to comprise only a glass flux. In this case, it can also be understood or referred to as a "glaze." However, it is generally possible and may even be preferred for the coating to comprise at least one pigment in addition to a glass flux, or to be formed as an enamel comprising at least one pigment. This increases the visibility of a marking, which can, for example, increase the user safety of a cooking appliance equipped with such a plate. Furthermore, depending on the type of pigment, the mechanical resistance of the coating can also be increased, for example, if a particularly abrasion-resistant pigment is used.

[0036] Suitable glass fluxes can, for example, have a composition based on SiO 2 and B 2 O 3 or on Bi 2 O 3 and SiO 2. "Based on" means that these components constitute at least 50 wt.% of the composition.

[0037] Examples of glass fluxes based on SiO 2 and B 2 O 3 are given below.

[0038] Two examples of suitable glass fluxes based on Bi 2 O 3 and SiO 2 are listed in the following table. Component Eq.-% Eq.-% SiO 19,9 16,1 B 2 O 3 12,2 9,6 Al 2 O 3 0,6 0,5 Na 2 O 5,3 4,3 K 2 O 0,14 0,17 ZnO 3,9 10,2 TiO 2,6 5,9 ZrO 3,3 2,6 SnO 0,12 5,6 Bi 2 O 3 50 42 HfO 0,07 0,05 Density [g / cm 3< 4,49 4,75 α 20–300 [ppm / K] 8,15 8,11 T g [°C] 487 495 E w [°C] 599 581 V to [°C] 830 889

[0039] A pigment is understood here to be a coloring agent comprising solid particles. In particular, the pigment according to the present disclosure can be configured as a ceramic coloring agent. "Ceramic" is understood in the context of the present disclosure to mean inorganic, non-metallic substances. This is advantageous because ceramic coloring agents have high temperature resistance, which is particularly necessary for the applications addressed here.

[0040] It may also be advantageous if the primary grain size of the pigment particles, i.e., the particles encompassed by the color body, is limited accordingly, as explained above. This is advantageous for coating by inkjet printing without clogging the nozzles. Furthermore, the use of fine pigment particles also simplifies the printing of fine structures and can therefore be used particularly advantageously here, because the high flatness and planarity of the plate according to the present disclosure allows such fine structures to be reproduced particularly well.

[0041] In particular, it is also possible for the plate to be designed as a plate with smooth surfaces on both sides, which means that neither side of the plate is dimpled. Plates with smooth surfaces on both sides can be particularly advantageous when high-resolution displays are to be arranged underneath the plate. The low roughness and the low roughness of the plate are particularly well suited for such a design and can therefore also be easily combined with a high-resolution display.

[0042] Alternatively, particularly in cases where particularly high plate strength is required or advantageous, one side of the plate can be smooth and the opposite side dimpled, with the coating being arranged on the smooth side of the plate. In this case, the dimpled side of the plate is formed as the underside. The dimpled structure can at least somewhat mitigate the impact of any mechanical damage to the glassy or glass-ceramic material on the plate's strength. This also makes handling the plate easier.

[0043] According to one embodiment, the plate comprises a glass ceramic, wherein the glass ceramic preferably comprises at least one of the following features: the glass ceramic is volume-colored, the glass ceramic does not comprise a glassy surface zone on at least one side.

[0044] A design of the plate in such a way that it comprises glass ceramic is particularly advantageous because glass ceramic, in particular a so-called lithium aluminum silicate glass ceramic, has a high strength and a low thermal expansion and thus also a sufficient temperature difference resistance to be able to be used particularly advantageously in cooking appliances.

[0045] Suitable glass-ceramics can be produced using various refining agents. For example, glass-ceramics refined with As2O3, Sb2O3, SnO2, CeO2, or combinations thereof are suitable.

[0046] For example, glass ceramics with the following composition in wt% on an oxide basis are suitable: Component 1 2 3 4 Reach Al 2 O 3 21,23 21,35 21,30 20,47 20-23 As 2 O 3 0,59 0,00 0,01 0,00 0-1 BaO 1,65 1,57 1,70 1,71 1-2 CaO 0,23 0,32 0,39 0,32 0-1 CeO 0,00 0,00 0,22 0,22 0-0,5 Cr 2 O 3 0 0 0 0 0-0,1 CoO 0 0 0 0 0-0,1 Fe 2 O 3 0,11 0,09 0,10 0,07 0,01-0,3 K 2 O 0,14 0,12 0,14 0,24 0-1 The 2 O 3,65 3,90 3,94 3,62 3,0-4,5 MgO 0,43 0,67 0,58 0,58 0-1 MnO 0,02 0,02 0,00 0,14 0-0,5 MoOs 0 0 0 0 0-0,4 Na 2 O 0,66 0,66 0,68 0,44 0-1 Nd 2 O 3 0 0 0 0 0-0,5 NiO 0 0 0 0 0-0,5 P 2 O 5 0,87 0,78 0,95 1,18 0-3 Sb 2 O 3 0,00 0,00 0,00 0,07 0-0,2 SiO 64,43 64,33 63,80 64,35 60-68 SnO 0,02 0,24 0,23 0,18 0-0,6 TiO 2,95 3,03 3,11 3,09 2-4 V 2 O 5 0,21 0,03 0,03 0,03 0-0,4 ZnO 1,19 1,25 1,23 1,61 0,5-3 ZrO 1,58 1,60 1,54 1,52 0,5 - 3

[0047] Such glass ceramics may also contain up to 2 wt.% of other components, particularly in the form of impurities.

[0048] It may be advantageous for the glass ceramic to be volume-tinted. This is advantageous because the glass ceramic itself is sufficiently opaque to shade components of a cooking appliance located behind the plate—especially without the need for a masking layer on the side facing or away from the user.

[0049] According to a further embodiment, the plate comprises a glass ceramic, wherein the plate does not have a glassy surface zone on at least one side. It has been shown that a particularly flat and only slightly rough surface on at least one side can be achieved in this way. This can be achieved in particular if at least one side of the plate is ground and polished.

[0050] According to a further preferred embodiment of the plate, it has improved character surround area haze. This value describes the number of defects or satellites of the drop of printing ink around the deposited drop or the printed image. This value is improved in the plate according to the present disclosure, particularly due to the low roughness and high flatness of the plate. In this way, the drops can be deposited evenly in a contactless process, and deflection of the drop is also much less likely.

[0051] The present disclosure also relates to a method for producing a plate comprising a glass or a glass-ceramic, in particular a plate according to an embodiment of the present disclosure. The method comprises the steps: Providing a plate comprising a glass or a glass ceramic. In particular, the plate can comprise a lithium aluminum silicate glass or a lithium aluminum silicate glass ceramic. The plate preferably has a thickness between 2 mm and 6 mm. The plate is in particular plate-shaped, i.e., with two opposing, preferably parallel, side surfaces and a circumferential edge surface.Sanding at least one side of the plate, polishing at least one side of the plate, preferably the side that was previously sanded, printing at least one side of the plate, preferably the side that was previously sanded and / or polished, on at least two different partial regions of the at least one region of the at least one side of the plate, such that a coating is arranged in these at least two different partial regions, wherein the at least two partial regions are spaced apart from one another by at least 3 cm, preferably at least 9 cm and particularly preferably at least 15 cm. The printing can preferably be carried out using a contactless printing process, preferably using inkjet printing. Baking the coating. .

[0052] Firing can be performed using a variety of known methods. For example, firing can be performed in a furnace, particularly a furnace for thermal tempering of glass or for ceramizing glass ceramics. Tunnel furnaces can also be used for this purpose. Firing temperatures can be above 650 °C, above 700 °C, or even above 750 °C.

[0053] In addition, optical processes such as laser irradiation, in particular using CO2 lasers, flash lamps ("photonic flash sintering") or short-wave infrared radiation (KIR emitters) can also be used.

[0054] The process according to embodiments can also be carried out, for example, by printing on so-called green glass. This is then converted into a glass-ceramic during firing (so-called primary firing).

[0055] However, it may be preferable to print on a glass ceramic. This can already have been ground and polished before ceramization. However, it is also possible, and may even be preferable, to carry out the grinding and polishing steps after conversion to glass ceramic. This can be advantageous because it enables the plate to have a high level of dimensional accuracy. Due to the temperatures required, ceramization can result in dimensional changes in the glass ceramic (e.g. shrinkage), which could reduce the high surface quality and the advantageous flatness of the plate. It is also possible that the surface roughness increases during ceramization due to oxidizing impurities and / or the adaptation of the softening glass body to the base plate.This can be avoided by grinding and polishing the plate's good surface properties after ceramization. In this case, the coating is then fired in a so-called secondary firing, which allows for lower temperatures than those used for the primary firing.

[0056] According to one embodiment of the method, the coating comprises a glass flux and / or is formed as an enamel. Preferably, the coating comprises a glass flux or is formed as an enamel and further comprises at least one pigment, wherein the at least one pigment particularly preferably does not comprise pigment particles with a primary grain size, determined as the d 50 value of the equivalent diameter, of more than 1.0 µm, and very particularly preferably does not comprise pigment particles with a primary grain size, determined as the d 90 value of the equivalent diameter, of more than 2.5 µm.

[0057] According to one embodiment, the plate comprises a glass, in particular a green glass, and the firing of the coating takes place during a ceramization step in which the glass is converted into a glass-ceramic.

[0058] According to a further preferred embodiment, the plate comprises a glass ceramic, and the firing of the coating takes place in a secondary firing.

[0059] The present disclosure also relates to a plate comprising glass or glass ceramic, preferably according to embodiments of the present disclosure, produced or producible in a method according to an embodiment.

[0060] The present disclosure also relates to the use of a plate according to embodiments and / or produced using a method according to an embodiment as a cooking surface. Within the scope of the present disclosure, a cooking surface is understood to mean a plate used as a cover plate in a cooking appliance. Such a cooking surface can also be referred to synonymously as a hotplate. Within the scope of the present disclosure, a cooking appliance is understood to mean an appliance for preparing food by heating, in particular a so-called hob on which cookware is placed. Examples

[0061] In the following, the invention is further explained using examples and comparative examples. Example 1

[0062] A volume-colored, ceramized glass-ceramic material (600* 600 mm 2< ) was subjected to a two-stage removal process.

[0063] The first step was a rough grinding operation using a rotating pad (d = 15 cm) impregnated with a CeO2 suspension. The d50 value of the abrasive grains was between 2 and 2.5 µm. The process was continued until the flatness of the plate was less than 0.1% of the plate's diagonal—in this case, less than 600 µm.

[0064] After reaching the target flatness value, the initial roughness was reduced by local heating using a CO 2 laser with a spatial wavelength range of 100 µm until a roughness of Rz,mean of less than 0.5 µm was achieved.

[0065] The polished surface was printed with a secondary firing flux using an inkjet printer. The ink was fired for 45 minutes at a maximum temperature of 750°C.

[0066] The print or printed image subsequently shows a very slight variation in print quality across the plate (raggedness for lines with a width of 300 µm at 22.26 µm).

[0067] The composition of the plate can be found in the following table: Component Eq.-% The 2 O 3,74 Al 2 O 3 21,29 SiO 65,21 TiO 3,64 ZrO 0,90 SnO 0,28 As 2 O 3 Cr 2 O 3 0,0035 P 2 O 5 0,052 MnO 0,021 Na 2 O 0,56 K 2 O 0,41 MgO 0,31 CaO 0,44 BaO 1,31 ZnO 1,58 V 2 O 5 0,0026 MoOs 0,046 Fe 2 O 3 0,089 α 50-700 α 20-700 0,14 ∗< 10 -6< / K α 25-700

[0068] The composition of the glass flux can be found in the following table: Component Eq.-% SiO 47,5 B 2 O 3 19 Al 2 O 3 2 The 2 O 4 Na 2 O 7,5 K 2 O 4 CaO 1 BaO 2 ZnO 8,75 TiO 3,8 Sb 2 O 3 0,2

[0069] The ink used for printing was composed as follows: Glasfluss 1 2.98 Eq.-% Black Pigment CuCr 2 O 4 1.05 Eq.-% White pigment TiO 0.87 Wt.-% Dipropylenglycolmethylether 62.71 Wt.-% Additive 1 2.09 Gew.-% Additive 2 0.30 Eq.-%

[0070] Additive 1 is poly(oxy-1,2-ethanediyl) α-methyl-ω-phosphate. Additive 2 is polyether-modified polymethylsiloxane.

[0071] Using this printing ink, a resulting effective linear thermal expansion coefficient, α 20-300, eff , based on the glass particles and pigment particles contained in the printing ink, of 9.15 * 10 -6< / K is achieved. Example 2:

[0072] A volume-colored, ceramized glass-ceramic material (600* 600 mm 2< ) was subjected to a two-stage removal process.

[0073] The first step was a rough grinding operation using a rotating pad (d = 15 cm) impregnated with a CeO2 suspension. The d50 value of the abrasive grains was between 2 and 2.5 µm. The process was continued until the flatness of the plate was less than 0.1% of the plate's diagonal—in this case, less than 600 µm.

[0074] After reaching the target flatness value, further material was removed using ion beam figuring (IBF) until a roughness of RZ,average of less than 0.5 µm was achieved.

[0075] The polished surface was printed with a secondary firing flux using an inkjet printer. The ink was fired for 45 minutes at a maximum temperature of 750°C.

[0076] The print or printed image subsequently showed very little variation in print quality across the plate (raggedness for lines with a width of 300 µm at 29.04 µm).

[0077] The composition of the glass-ceramic material used can be found in the following table: Component Eq.-% The 2 O 3,74 Al 2 O 3 21,29 SiO 65,21 TiO 3,64 ZrO 0,90 SnO 0,28 As 2 O 3 Cr 2 O 3 0,0035 P 2 O 5 0,052 MnO 0,021 Na 2 O 0,56 K 2 O 0,41 MgO 0,31 CaO 0,44 BaO 1,31 ZnO 1,58 V 2 O 5 0,0026 MoOs 0,046 Fe 2 O 3 0,089 α 50-700 α 20-700 0,14 α 25-700

[0078] The composition of the glass flux used can be found in the following table: Component Eq.-% SiO 47,5 B 2 O 3 19 Al 2 O 3 2 The 2 O 4 Na 2 O 7,5 K 2 O 4 CaO 1 BaO 2 ZnO 8,75 TiO 3,8 Sb 2 O 3 0,2

[0079] The printing ink / ink used was composed as follows: Glasfluss 1 2.98 Eq.-% Black Pigment CuCr 2 O 4 1.05 Eq.-% White pigment TiO 0.87 Wt.-% Dipropylenglycolmethylether 62.71 Wt.-% Additive 1 2.09 Gew.-% Additive 2 0.30 Eq.-%

[0080] Additive 1 is poly(oxy-1,2-ethanediyl) α-methyl-ω-phosphate. Additive 2 is polyether-modified polymethylsiloxane. This results in an effective linear thermal expansion coefficient, α 20-300, eff , based on the glass particles and pigment particles contained in the printing ink, of 9.15 * 10 -6 < / K.

[0081] Example 3:

[0082] A green glass material (600 ∗< 600 mm 2< ) was subjected to a two-stage removal process.

[0083] The first step was a rough grinding operation using a rotating pad (d = 15 cm) impregnated with a CeO2 suspension. The d50 value of the abrasive grains was between 2 and 2.5 µm. The process was continued until the flatness of the plate was less than 0.1% of the plate's diagonal—in this case, less than 600 µm.

[0084] After reaching the target flatness value, the initial roughness was reduced by local heating using a CO 2 laser with a spatial wavelength range of 100 µm until a roughness of RZ,average of less than 0.5 µm was achieved.

[0085] The polished surface was printed with a secondary firing flux using an inkjet printer. The ink was fired for 45 minutes at a maximum temperature of 750°C.

[0086] The print or printed image subsequently shows a very slight variation in print quality across the plate (raggedness for lines with a width of 300 µm for lines at 23.02 µm).

[0087] After printing, the substrate with the print was subjected to a ceramization process and converted into a glass ceramic. Comparison example 1

[0088] Comparative Example 1 exhibits good flatness combined with poor, i.e., high, roughness. This leads to a significantly altered raggedness of the printed image, as shown below.

[0089] A volume-colored, ceramized glass-ceramic material (600* 600 mm 2< ) was subjected to a single-step removal process.

[0090] This step involved coarse grinding with a rotating pad (d = 15 cm) impregnated with a CeO2 suspension. The d50 value of the abrasive grains was between 2 and 2.5 µm. The process was continued until the flatness of the plate was less than 0.1% of the diagonal—in this case, less than 600 µm.

[0091] After reaching the target flatness, no further polishing was performed. The roughness (RZ,medium) was 0.7 µm.

[0092] The polished surface was printed with a secondary firing flux using an inkjet printer. The ink was fired for 45 minutes at a maximum temperature of 750°C.

[0093] The print or printed image then shows a deviation in print quality across the plate (raggedness in lines with a width of 300 µm at 45.3 µm).

[0094] The composition of the plate can be found in the following table: Component Eq.-% The 2 O 3,74 Al 2 O 3 21,29 SiO 65,21 TiO 3,64 ZrO 0,90 SnO 0,28 As 2 O 3 Cr 2 O 3 0,0035 P 2 O 5 0,052 MnO 0,021 Na 2 O 0,56 K 2 O 0,41 MgO 0,31 CaO 0,44 BaO 1,31 ZnO 1,58 V 2 O 5 0,0026 MoOs 0,046 Fe 2 O 3 0,089 α 50-700 α 20-700 0,14 ∗< 10 -6< / K α 25-700

[0095] The composition of the glass flux can be found in the following table: Component Eq.-% SiO 47,5 B 2 O 3 19 Al 2 O 3 2 The 2 O 4 Na 2 O 7,5 K 2 O 4 CaO 1 BaO 2 ZnO 8,75 TiO 3,8 Sb 2 O 3 0,2

[0096] The ink used for printing was composed as follows: Glasfluss 1 2.98 Eq.-% Black Pigment CuCr 2 O 4 1.05 Eq.-% White pigment TiO 0.87 Wt.-% Dipropylenglycolmethylether 62.71 Wt.-% Additive 1 2.09 Gew.-% Additive 2 0.30 Eq.-%

[0097] Additive 1 is poly(oxy-1,2-ethanediyl) α-methyl-ω-phosphate. Additive 2 is polyether-modified polymethylsiloxane.

[0098] Using this printing ink, a resulting effective linear thermal expansion coefficient, α 20-300, eff , based on the glass particles and pigment particles contained in the printing ink, of 9.15 * 10 -6< / K is achieved. Comparison example 2

[0099] Comparative Example 2 exhibits poor flatness but good, i.e., low, roughness of the plate. This leads to poor raggedness of the printed image, as shown below.

[0100] A volume-colored, ceramized glass-ceramic material (600* 600 mm 2< ) was subjected to a one-step removal process.

[0101] No grinding was performed to achieve flatness. Flatness was 789 µm.

[0102] The plate was subjected to local heating using a CO 2 laser with a spatial wavelength range of 100 µm to reduce its initial roughness until a roughness of RZ,average of less than 0.5 µm was achieved.

[0103] The polished surface was printed using an inkjet printer with a secondary firing-capable flow. Due to the low flatness, the printhead distance had to be adjusted during printing to avoid damage to the printhead. This resulted in the droplets generated in the printhead having different path lengths to the substrate. The printing ink was fired using a 45-minute firing process at a maximum temperature of 750°C.

[0104] The print or printed image then shows a variation in print quality across the plate (raggedness in lines with a width of 300 µm at 62.8 µm).

[0105] The composition of the plate can be found in the following table: Component Eq.-% The 2 O 3,74 Al 2 O 3 21,29 SiO 65,21 TiO 3,64 ZrO 0,90 SnO 0,28 As 2 O 3 Cr 2 O 3 0,0035 P 2 O 5 0,052 MnO 0,021 Na 2 O 0,56 K 2 O 0,41 MgO 0,31 CaO 0,44 BaO 1,31 ZnO 1,58 V 2 O 5 0,0026 MoOs 0,046 Fe 2 O 3 0,089 α 50-700 α 20-700 0,14 * 10 -6< / K α 25-700

[0106] The composition of the glass flux can be found in the following table: Component Eq.-% SiO 47,5 B 2 O 3 19 Al 2 O 3 2 The 2 O 4 Na 2 O 7,5 K 2 O 4 CaO 1 BaO 2 ZnO 8,75 TiO 3,8 Sb 2 O 3 0,2

[0107] The ink used for printing was composed as follows: Glasfluss 1 2.98 Eq.-% Black Pigment CuCr 2 O 4 1.05 Eq.-% White pigment TiO 0.87 Wt.-% Dipropylenglycolmethylether 62.71 Wt.-% Additive 1 2.09 Gew.-% Additive 2 0.30 Eq.-%

[0108] Additive 1 is poly(oxy-1,2-ethanediyl) α-methyl-ω-phosphate. Additive 2 is polyether-modified polymethylsiloxane.

[0109] Using this printing ink, a resulting effective linear thermal expansion coefficient, α 20-300, eff , based on the glass particles and pigment particles contained in the printing ink, of 9.15 * 10 -6< / K is achieved. Description of Drawings

[0110] The invention is further explained below with reference to figures. Fig. 1 is a schematic illustration to explain the raggedness, Fig. 2 is a plan view of a schematic and not to scale plate according to an embodiment, and Figs. 3 and 4 are side views of schematic and not to scale plates according to embodiments.

[0111] In Figs. 1 The principle of raggedness and its determination are explained using three schematic representations a), b) and c).

[0112] In Figs. 1a) and Figs. 1b) two print images are shown, of which the one shown in Fig. 1a9 has only slight raggedness and the one in Figs. 1b ) a high degree of raggedness. "Raggedness" literally means "tornness" and can be understood as a measure of the quality of a printed image, especially its edge sharpness. High raggedness means low edge sharpness, and vice versa.

[0113] In Figs. 1a) and Figs. 1b ) enlargements of two "line prints" can be seen. In Figs. 1b ), the image with high "raggedness," the individual drops are still clearly visible in some cases, as they were unable to blend sufficiently to create a homogeneous print image. Edge sharpness is only slightly developed, and holes are occasionally visible in the print image.

[0114] In contrast, the representation in Figs. 1a ), in which the sharpness of the edges is obviously better - which in turn corresponds to a lower raggedness.

[0115] In Figs. 1c ) is shown schematically the enlarged print image of a "line". First, the area is selected which is significant in terms of line width 1, and both edges of the line are fitted with a straight line. These two straight lines, which represent the boundaries of the "ideal line", are shown in Figs. 1c ) are shown schematically as white lines on the black print image.

[0116] Based on these two lines, the standard deviation of the real boundaries of the printed image on both sides of the ideal line is then determined, as shown in Figs. 1c ) is shown schematically at point 2.

[0117] Raggedness is the arithmetic mean of the standard deviations on one side, here "left", and the other side, here "right".

[0118] According to one embodiment, the board is preferably designed such that the raggedness in the two sub-regions differs from each other by only 10% at most. Preferably, the ratio of the raggedness in one sub-region, R1, to the raggedness in the second sub-region, R2, i.e., the value R1 / R2, is between 0.5 and 2, preferably between 0.75 and 1.5, particularly preferably between 0.9 and 1.1.

[0119] Figs. 2is a schematic and not-to-scale representation of a plate 3 according to one embodiment. The plate 3 comprises a glass or a glass-ceramic. The glass can in particular be a lithium aluminum silicate glass; the glass-ceramic can be a lithium aluminum silicate glass-ceramic. The plate 3 preferably has a thickness between 2 mm and 6 mm. The plate has two opposing, preferably parallel, side surfaces, whereby in this case only the side surface 31 is visible, as well as the circumferential edge surface 33. The flatness of the plate 3 is less than or equal to 0.1% of a lateral dimension 5, which here is, for example, the diagonal of the rectangular plate 3. The lateral dimension 5 considered can preferably be the maximum lateral dimension of the plate 3; for example, the diameter of a circular plate 3.

[0120] On at least one side of the plate 3, here side 31, it has, in at least one area, here area 311, an average surface roughness R z,average of less than 0.5 µm with a standard deviation of the surface roughness, σ Rz, of less than 0.1 µm. Preferably, R z,average and the standard deviation of the surface roughness, σ Rz, are determined by measuring the roughness R z at nine points on the plate 3, each of which is spaced at least 5 cm, preferably at least 10 cm, and particularly preferably at least 15 cm apart, and determining the arithmetic mean and the standard deviation from these nine measured values, and wherein R z is particularly preferably determined by measuring a line profile with a stylus device and evaluating it in accordance with ISO 4827.

[0121] The roughness Rz is also called roughness depth and indicates the maximum height difference along a center line on a specified measuring distance.

[0122] Furthermore, the plate 3 comprises a coating 5, which is arranged on at least two different sub-regions 3101, 3102 of the region 311 of at least one side 31 of the plate 3. Here, for example, the coating 4 is designed as a cooking zone marker, specifically in the form of four rings applied to the side 31. The region 311 here comprises, for example, one of these cooking zone markers.

[0123] In principle, it is possible for the area 311 to encompass the entire area of ​​side 31. In particular, it is also possible for the sub-areas 3101 and 3102 of the area 311 to relate to different cooking zone markings.

[0124] The raggedness of coating 5 in the two sub-areas 3101 and 3102 differs by a maximum of 10%, with the raggedness preferably being determined according to ISO 24790.

[0125] Preferably, according to one embodiment, the coating 5 may be an inkjet printing coating.

[0126] The Figs. 3 shows a schematic and not to scale side view or a section of a plate 3 according to one embodiment. The plate 3 comprising a glass or a glass ceramic, in particular a lithium aluminum silicate glass or a lithium aluminum silicate glass ceramic, preferably has a thickness d which is between 2 mm and 6 mm. The thickness of the plate 3 is generally understood to be the distance between the two side surfaces 31, 32 of the plate 3. The two side surfaces 31, 32 of the plate 3 are opposite each other and are preferably, as in the illustration of the Figs. 3, arranged parallel to each other within the limits of measurement accuracy.

[0127] An arrangement is understood to be parallel if the normal angles to the side surfaces 31, 32 enclose an angle of no more than 5°, preferably of no more than 2° and most preferably of 0° within the scope of usual manufacturing and measuring tolerances.

[0128] If one side 31, 32 of the plate 3 is studded, the area resulting from the stud tips is used to determine the normal angle. This is shown schematically below using the Figs. 4 shown.

[0129] Further shown in Figs. 3 the circumferential edge surface 33 of the plate 3.

[0130] At least the side 31, on which in particular the coating 5 is also arranged, has in at least one region 311, as stated, only a low average roughness R z,average of less than 0.5 µm with a standard deviation of the surface roughness, σ Rz, of less than 0.1 µm.

[0131] Furthermore, the plate 3 comprises a coating 5, which is arranged on at least two different partial regions 3101, 3102 of the at least one region 311. The at least two partial regions 3101, 3102 are spaced apart by at least 3 cm, preferably at least 9 cm, and particularly preferably at least 15 cm, with the raggedness of the coating 5 in the two partial regions 3101, 3102 differing from one another by a maximum of 10%, with the raggedness preferably being determined according to ISO 24790.

[0132] It can be provided that side 32 is also designed as a very smooth and / or very flat surface. However, it is also possible and can even be preferred that only one side, here side 31, which faces the user or operator during operation of an appliance such as a so-called hob, has the particularly good roughness and flatness. In particular, it can be provided that the region 311 of side 31 of the plate 3 comprises the entire surface of side 31, in other words the entire side 31 is designed as a very smooth, flat surface. In this way, it is possible to achieve uniformly good print images on the entire side 31, in particular also in a contactless printing process such as inkjet printing.

[0133] In the event that the side 32 of the plate 3 opposite the side 31 configured as the upper side is not as smooth and flat as the side 31, it can be provided that the side 32 is, for example, dimpled. This can advantageously be combined, for example, with the plate 3 comprising a colored glass ceramic, since in this case the dimples are not disturbingly visible due to the inherent color of the glass ceramic encompassed by the plate 3. Such a design can be particularly advantageous when particularly good strength of the plate 3 is desired.

[0134] Figs. 4shows a schematic and not to scale side view of a plate 3 according to one embodiment. The plate 3 has a side 31 which has very good flatness and a very low average roughness, i.e. is very smooth. The side 31 is designed as the upper side, i.e. is intended to be facing the user during operational use of a device for which the plate 3 is used as a cover plate (for example for a so-called hob). On the side 31 of the plate 3, in the two partial regions 3101, 3102 of the region 311, which has at least good flatness and smoothness, the coating 4 is arranged, which can in particular have been applied by a contactless printing process, such as inkjet printing.For example, in general, without limitation to the example of the plate 3 specifically shown here, the coating 4 can be designed as a cooking zone marking, but also as a logo. In particular, the coating 4 can be designed as a glass flux-based coating or can comprise a glass flux or can be designed as an enamel, and it is furthermore possible and can even be preferred that the coating 4 is designed as a glass flux-based coating (or comprises a glass flux) or can be designed as an enamel and furthermore comprises at least one pigment, in particular a ceramic pigment. The at least one pigment preferably does not comprise any pigment particles with a primary grain size, determined as the d 50 value of the equivalent diameter, of more than 1.0 µm, very particularly preferably no pigment particles with a primary grain size, determined as the d 90 value of the equivalent diameter, of more than 2.5 µm.

[0135] Plate 3 is shown here in the schematic and not to scale illustration of Figs. 4 designed so that the side 32 of the plate 3 opposite side 31 is dimpled. The two opposite sides 31, 32 are designed here so that they are parallel to each other. To determine this, as shown schematically in Figs. 4 is shown, the normal angle to the two sides 31, 32 is determined, i.e. the angles n 31 and n 32 . In the case of a knobbed side 32, a surface 32a is used, in the schematic sectional view of the Figs. 4 represented as a dashed line, which is determined by the tips of the studs. The normal angle to this surface is then taken as the normal angle n 32 of side 32.

[0136] How to follow the schematic diagram in Fig. 4As can be seen, the normals to the two sides 31, 32 are parallel to each other within the measurement accuracy, so that the sides 31, 32 are also parallel to each other within the measurement accuracy. List of reference symbols

[0137] 1 Line width 2 Deviation from edge of the print image 3 plate 31, 32 Side surfaces of the plate 32a Determined area of ​​a studded plate or page 32 33 Circumferential edge surface 311 Area of ​​page 31 3101, 3102 Subsection of 311 4 Coating 5 lateral dimension of 3 n. 31 , n. 32 Normal angle at 31, 32

Claims

1. Plate comprising glass or glass ceramic, in particular a lithium aluminum silicate glass or a lithium aluminum silicate glass ceramic, preferably with a thickness between 2 mm and 6 mm, with two opposite, preferably parallel, side surfaces and a circumferential edge surface, wherein the flatness of the plate is less than or equal to 0.1% of a lateral dimension, for example a diagonal, of the plate and at least one side in at least one region has an average surface roughness R z,mittel of less than 0.5 µm with a standard deviation of the surface roughness, σ Rz of less than 0.1 µm, preferably R z,mittel and the standard deviation of the surface roughness, σ Rz , can be determined by the roughness R zat nine points on the plate, each of which is at least 5 cm, preferably at least 10 cm and particularly preferably at least 15 cm apart, and the arithmetic mean and the standard deviation are determined from these nine measured values, and wherein particularly preferably R z is determined by measuring a line profile with a stylus device and an evaluation according to ISO 4827, and further comprising a coating which is arranged on at least two different partial regions of the at least one region of the at least one side of the plate, wherein the at least two partial regions are spaced apart from one another by at least 3 cm, preferably at least 9 cm and particularly preferably at least 15 cm, and wherein the raggedness of the coating in the two partial regions differs from one another by a maximum of 10%, wherein the raggedness is preferably determined according to ISO 24790.

2. The plate of claim 1, wherein the coating is an inkjet printing coating.

3. Plate according to one of claims 1 or 2, wherein the coating comprises a glass flux and / or is designed as an enamel, preferably as a coating comprising a glass flux and / or as an enamel and comprising at least one pigment, wherein particularly preferably the at least one pigment does not comprise pigment particles with a primary grain size determined as d 50 -value of the equivalent diameter, of more than 1.0 µm, most preferably no pigment particles with a primary grain size, determined as d 90 -value of the equivalent diameter, of more than 2.5 µm.

4. Plate according to one of claims 1 to 3, wherein the plate is designed as a plate smooth on both sides, in particular in the form that no side of the plate is dimpled, or wherein the plate is designed in the form that one side is smooth and the opposite side is dimpled and wherein the coating is arranged on the smooth side of the plate.

5. Plate according to one of claims 1 to 4, wherein the plate comprises a glass ceramic, preferably having at least one of the following features: - the glass ceramic is volume-colored, - the glass ceramic does not comprise a glassy surface zone on at least one side.

6. A method for producing a plate comprising a glass or a glass ceramic, preferably a plate according to one of claims 1 to 5, comprising the steps: - providing a plate comprising a glass or a glass ceramic, in particular a lithium aluminum silicate glass or a lithium aluminum silicate glass ceramic, preferably with a thickness between 2 mm and 6 mm, with two opposing, preferably parallel, side surfaces and a circumferential edge surface, - grinding at least one side of the plate, - polishing at least one side of the plate, - printing at least one side of the plate on at least two different partial areas of the at least one area of ​​the at least one side of the plate, so that a coating is arranged in these at least two different partial areas, wherein the at least two partial areas are at least 3 cm,preferably at least 9 cm and particularly preferably at least 15 cm apart, preferably printing by means of a contactless printing process, preferably by means of inkjet printing, - baking the coating., 7. Method according to claim 6, characterized by at least one of the following features: - the coating comprises a glass flux and / or is designed as an enamel, preferably a coating comprising a glass flux and / or designed as an enamel and comprising at least one pigment, wherein particularly preferably the at least one pigment does not comprise pigment particles with a primary grain size determined as d 50 -value of the equivalent diameter, of more than 1.0 µm, most preferably no pigment particles with a primary grain size, determined as d 90-value of the equivalent diameter of more than 2.5 µm, - the plate comprises a glass, in particular a green glass, and the firing of the coating takes place during a ceramisation step in which the glass is converted into a glass-ceramic, - the plate comprises a glass-ceramic and the firing of the coating takes place in a secondary firing.

8. A plate comprising glass or glass-ceramic, preferably a plate according to any one of claims 1 to 5, manufactured or producible by a process according to any one of claims 6 or 7.

9. Use of a plate according to one of claims 1 to 5 or 8 and / or produced by a process according to one of claims 6 or 7 as a cooking surface.