Ceramic printing ink, in particular for inkjet printing, for producing coating on glass ceramic, and coated glass ceramic panel

Abstract

To provide a ceramic printing ink that is suitable for application using an inkjet printing process, and a glass ceramic panel comprising a coating.SOLUTION: The invention relates to a glass ceramic panel (1) which comprises a coating produced or producible from a printing ink. The coating (2) comprises at least one glassy phase and pigment particles, and the weight percentage of the pigment particles in the coating (2) is at least 5 wt.% and less than 40 wt.%. The pigment particles are dispersed in the glassy phase. The coating (2) preferably has a porosity of less than 5 vol.%, further preferably of less than 1 vol.%, yet further preferably of less than 0.5 vol.%, and most preferably of less than 0.1 vol.%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates generally to a ceramic printing ink, in particular suitable for application by inkjet printing methods, particularly preferably for producing coatings on glass ceramics. A further aspect of the invention relates to a glass ceramic plate comprising a coating produced or producible with the printing ink.

[0002] Background of the Invention Ceramic printing inks are used in a variety of applications, and it is also known in principle to apply such printing inks to glass ceramics, for example glass ceramic plates with a low coefficient of thermal expansion.

[0003] Generally, such ceramic printing inks can be applied in a wide variety of ways, usually by screen printing, although other methods are also possible, such as inkjet printing.

[0004] For production reasons, it may be preferable to apply such ceramic inks by screen printing, since this allows for the efficient production of large quantities of printed material. Furthermore, when producing printed glass-ceramic plates, it may be preferable not to apply the printing ink to glass-ceramics that have already been ceramized. Instead, it is common to print on a precursor product that has not yet been ceramized, known as "green glass," and then bake the ceramic printing ink during ceramization. This is known as the first bake.

[0005] In principle, however, it is also possible to print on already ceramized glass-ceramic products, such as glass-ceramic plates, and then bake the ink in a so-called "second bake." This would require two bakes, which is certainly not desirable from a manufacturing technology point of view. However, such a second bake can be advantageous, for example, for product individualization.

[0006] However, in addition to the application and baking problems of such ceramic printing inks, further demands are placed on the coatings and printed plates obtained with these printing inks.

[0007] For example, such printing inks may contain pigments, i.e. may be designed as opaque or at least partially opaque coatings, in particular when the corresponding product is a glass ceramic plate, which is used, for example, as a cook plate, and such coatings are used for indicating or marking functional areas, such as cooking zones or display areas.

[0008] Since such coatings may be subjected to significant loads, such as thermal and abrasive loads, in part during daily use, it is further required that the resulting coating has sufficient adhesive strength.

[0009] Furthermore, it is known that such printing inks or coatings obtained therewith can impair the strength of the printed substrate.

[0010] Therefore, various demands are placed on printing inks for glass-ceramic plates: they not only need to be suitable for a specific application method and high temperatures, but also must provide sufficient adhesion strength and scratch resistance of the coating, or resistance of the coating to mechanical and / or abrasive attack on the substrate in general, without significantly reducing the mechanical strength of the substrate.

[0011] To address this issue, various solutions have been proposed.

[0012] US Patent Application Publication No. 2016 / 0244356 describes a glass-ceramic article that is at least partially coated with an enamel coating, the coating containing only a small amount of pigment, less than 5% by weight.

[0013] US Patent Application Publication No. 2012 / 0263957 describes an enamel composition that includes at least 40% and up to 65% by weight of pigment.

[0014] US Patent Application Publication No. 2007 / 0031603 describes a digital inkjet printer for printing on glass, without providing any details about the composition of the printing ink.

[0015] U.S. Patent Application Publication No. 2020 / 0283333 describes a coated glass or glass-ceramic substrate with high heat resistance, high strength, and low thermal expansion. The coating contains closed pores with dimensions of 0.1 μm to 30 μm and thicknesses of 1.5 μm to 50 μm.

[0016] US Patent Application Publication No. 2016 / 0340232 describes a glass melt for producing an opaque coating and a coated glass substrate having the coating. The glass melt contains at least one pigment. The glassy component of the described glass melt has a thermal expansion coefficient of 4.7×10 -6 / K.

[0017] WO 2016 / 008848 describes ceramic inkjet inks for low expansion glasses and / or low expansion glass ceramics.

[0018] US Patent Application Publication No. 2008 / 0139375 describes a glass ceramic plate having a black decorative ink, the glass melt of which is formed to be black, and the decorative ink further contains 0 to 10 wt % of a black pigment.

[0019] US Patent Application Publication No. 2007 / 0191206 describes a glass or glass-ceramic object that can be subjected to high thermal loads, which is decorated with a coating containing fused silicate and effect pigments based on SiO2 flakes. The document does not mention the thermal expansion coefficient of the coating. The layer is applied by screen printing.

[0020] US Patent Application Publication No. 2008 / 0214379 also describes decorated glass-ceramic or vitreous components that can withstand high thermal loads. The decoration is achieved with a metallic paint containing effect pigments and fused silicates. The effect pigments are based on synthetic flakes of Al2O3.

[0021] US Patent No. 6,525,300 describes a coated glass-ceramic plate, in which the coating is a glass-based coating, which has a thermal expansion coefficient significantly different from that of the low-stretch glass-ceramic.

[0022] EP 0 978 493 describes a lead- and cadmium-free glass composition that can decorate glasses and glass ceramics, and a method for producing glass ceramics coated with said glass composition.

[0023] US Pat. No. 6,043,171 describes lead- and cadmium-free glass compositions for glazing, enameling and decorating glass or glass-ceramics.

[0024] DE 4201286 describes the use of lead- and cadmium-free glass compositions for glazing, enameling and decorating, as well as said compositions.

[0025] DE 19512847 A1 describes lead- and cadmium-free glass compositions for use in glazes and enamels. The glazes and enamels are suitable for coating glass. Glass ceramics as substrate materials are not addressed.

[0026] US Patent No. 6,187,429 describes a decorative ceramic color layer applied to a glass or glass-ceramic substrate, and describes the addition of fillers, such as mica, to the ceramic coating to improve adhesion strength.

[0027] US Patent No. 5,747,395 describes a cobalt-containing glass composition for producing a coating, which is itself colored blue by the cobalt contained in the glass.

[0028] US Patent Application Publication No. 2021 / 0115281 describes mineral inks for inkjet printing.

[0029] US Patent Application Publication No. 2010 / 0273631 describes a reinforced glass-ceramic article and an enamel suitable for coating the article, which can be done without adding pigments to the enamel and is intended to introduce stress into the surface of the glass-ceramic article.

[0030] WO 2016 / 110724 describes a glass frit composition and a ceramic inkjet printing ink containing the glass frit. The coating is particularly suitable for coating glass as a substrate material.

[0031] WO 2020 / 043929 describes a ceramic ink for digital inkjet printing and a method for producing the same. This printing ink is intended in particular for use with glass as a substrate material.

[0032] US Patent Application Publication No. 2009 / 0214840 describes inks for producing etching effects by printing on ceramic surfaces, especially glass surfaces.

[0033] WO 2015 / 003736 describes ceramic inkjet inks, especially for printing on glass substrates.

[0034] US Patent Application Publication No. 2016 / 0264455 describes a substrate with a glass-based acoustically optimized coating, which may consist of or contain glass or glass ceramic.

[0035] US Patent Application Publication No. 2013 / 0273320 describes coated glass or glass-ceramic substrates with tactile properties, which are provided by structuring particles in the coating.

[0036] US Patent Application Publication No. 2006 / 0189470 describes lead- and cadmium-free glasses for glazing, enameling, or decorating glasses and glass ceramics, which allow for high bending strength of the coated substrates.

[0037] EP 3372569 describes an enamel composition and a method for producing an enamelled glass-ceramic article, the enamel composition having a very high pigment content of more than 50% by weight.

[0038] EP 1 870 383 describes an alkali- and cadmium-free glass frit and its use for producing ceramic inks.

[0039] DE 102016216442 A1 describes a coated substrate with a decoration having an optimized coefficient of friction. The decoration is glass-based. Furthermore, the patent document relates to a method for producing such a decoration and its use.

[0040] DE 102005040588 describes the use of lead- and cadmium-free glasses and methods for glazing, enameling and decorating so-called lithium aluminosilicate glass ceramics.

[0041] German Patent Application No. 102004002766 describes a glass-ceramic plate having at least one matte-treated area and a method for producing the same, in which a pigment-free glass melt is applied during the matte treatment.

[0042] None of the aforementioned publications in the prior art describe ceramic printing inks that are suitable for inkjet printing and whose individual components are adapted to one another in that, during inkjet printing, the glass particles of the printing ink and the pigments used in the printing ink match each other in terms of their thermal expansion coefficients.Moreover, most of the prior art publications are concerned with printing methods such as screen printing and the so-called first bake for producing glass-based coatings on glass-ceramics.

[0043] There is therefore a need for ceramic printing inks, in particular for application by inkjet printing methods, particularly preferably for producing coatings on glass ceramics, which can be used flexibly, in particular can be baked, also by secondary baking, and which ensure sufficient strength of the coated glass ceramic articles, and which also have sufficient adhesion strength and resistance to mechanical loads.

[0044] Problem to be solved by the invention It is an object of the present invention to provide a ceramic printing ink which at least partially overcomes or alleviates the problems of the prior art outlined above.

[0045] Summary of the Invention This problem is solved by the subject matter of the independent claims. Preferred specific embodiments are set out in the dependent claims, the description and the drawings according to the present disclosure.

[0046] The present disclosure therefore relates to a ceramic printing ink, in particular for application by inkjet printing, particularly preferably for producing coatings on glass ceramics, which comprises at least one vitreous material comprising glass particles and at least one pigment comprising pigment particles, wherein the ratio of the total weight of the glass particles contained in the printing ink to the total weight of the pigment particles contained in the printing ink is at least 1.5 and less than 19.

[0047] Generally, in the present disclosure, printing inks for application by inkjet printing methods are understood to mean printing inks that can be printed with conventional inkjet printers, in particular for ceramic printing inks. In particular, in the present disclosure, this is understood to mean printing inks, in particular ceramic printing inks, having properties within the following parameter ranges: [Table 1]

[0048] It should be noted that inkjet printing requires consideration of various parameters and properties of the printing medium, such as viscosity, surface tension, and density, not just individually but also in their interactions. For example, this can be achieved by using the so-called Z value, which is the reciprocal of the Ohnesorge number.

[0049] This is defined as follows:

number

[0050] The Weber number (abbreviated as We) is defined as follows:

number

[0051] where η is the viscosity (Pas) at shear rates above 1000 / s, σ is the surface tension (N / m), and ρ is the density (kg / m 3 ), d is the characteristic length (nozzle diameter) (m), and v is the droplet velocity (m / s).

[0052] Z and We are correlated with each other through the Reynolds number. The viscosity index is an index that indicates how Newtonian a fluid is and how easily its viscosity changes during printing. This is determined by determining the viscosity curve at the printing temperature (usually 10°C to 40°C, preferably around 25°C).

[0053] The glass particles have an equivalent diameter d ranging from at least 0.5 μm to a maximum of 5 μm. 90 , preferably in the range of at least 0.5 μm to a maximum of 5 μm. 97 , particularly preferably in the range of at least 0.5 μm to a maximum of 2.5 μm. 97 It has.

[0054] The effective coefficient of linear thermal expansion α obtained for the glass particles and pigment particles contained in the printing ink 20-300,eff is 6.5 x 10 -6 / K~11×10 -6 / K range.

[0055] The effective linear thermal expansion coefficient α obtained 20-300,eff The preferred upper limit of -6 / K, particularly preferably 9.5 × 10 -6 / K, very particularly preferably up to 9 × 10 -6 / K, or even 9×10 -6 / K.

[0056] Preferably, the effective linear thermal expansion coefficient α20-300,eff is calculated according to the following formula: α 20-300,eff =Σ(weight fraction of glassy material i × α 20-300,ガラス質材料i ) + Σ(weight ratio of pigment z × α 20-300,顔料z )

[0057] The percentages by weight are each relative to the total weight of the solids of the printing ink (ie the solids content of the printing ink), ie this total weight includes all vitreous materials and pigments.

[0058] According to one embodiment, the ceramic printing ink is designed to be lead-free, i.e., apart from impurities for technical reasons, the ceramic printing ink and correspondingly the coating on the glass-ceramic plate contains the component PbO in a content of at most 500 ppm by weight, preferably at most 200 ppm by weight.

[0059] According to a further embodiment, the printing ink does not comprise a swelling agent. In the present disclosure, a swelling agent is understood to be an agent that decomposes at elevated temperature to form a fluid phase, e.g., an agent that releases a gas. Such swelling agents are also sometimes called foaming agents. The ceramic printing ink according to the present disclosure, as mentioned above, preferably does not comprise such a swelling agent.

[0060] Such a printing ink design is highly advantageous.

[0061] In this case, the printing ink is in ceramic form. In the present application, ceramic ink is understood to mean an ink with an inorganic structure, i.e., an ink that contains at least 95% by weight of inorganic components in the fired state. In particular, such ceramic inks can be in glass-based form, for example as so-called enamel paints.

[0062] By forming the ink of the present disclosure as a printing ink, it is possible to apply the printing ink laterally structured, i.e., for example, in a pattern, which in particular allows for marking of the substrate.

[0063] The printing ink is preferably designed for inkjet printing.Another advantage of this method is that it is not necessary to prepare a printing plate, such as a screen for so-called screen printing.Since the printing image can be digitally defined in advance, this method is particularly advantageous for small-scale production and individualization of products.

[0064] The printing ink according to the present disclosure comprises at least one glassy material. In this disclosure, a glassy material is understood to mean an amorphous, inorganic, non-metallic material obtained or obtainable by a melting process. Since the glassy material contains glass particles, it is preferably in powder form. Furthermore, the printing ink comprises at least one pigment containing pigment particles. In this disclosure, a pigment is understood to mean a colorant, particularly a ceramic colorant. In this disclosure, a ceramic colorant is an inorganic, preferably inorganic, non-metallic pigment. For example, spinel pigments are suitable as pigments in this application, but TiO2 or Fe2O3 are also suitable. Such ceramic colorants can withstand baking conditions such as those encountered during baking of ceramic inks, and can also be exposed to high operational temperatures during use of the coated product, e.g., glass ceramic, without decomposition of the pigment. Since the pigment contains pigment particles, it is also preferably in powder form.

[0065] Furthermore, it is possible, and sometimes preferred, for a ceramic printing ink to contain more than one glassy material and more than one pigment.

[0066] The present disclosure further provides that the ratio of the total weight of glass particles contained in the printing ink to the total weight of pigment particles contained in the printing ink is at least 1.5 and less than 19. This corresponds to a proportion of glass particles relative to the weight of glass and pigment particles contained in the printing ink of at least 60% by weight and at most 95% by weight. Preferably, this proportion of glass particles may be at least 80% by weight and at most 90% by weight.

[0067] This is highly advantageous because it ensures sufficient mechanical durability of the resulting coating on a substrate, such as a glass-ceramic plate. This is because the glassy material, or materials as the case may be, acts as a binder, providing sufficient bonding between the substrate and the pigment particles. However, a high proportion of the glassy material or materials has the disadvantage of potentially affecting the strength of the coated substrate. Therefore, the proportion of the glassy component, or materials as the case may be, should not be too high and is preferably limited to a maximum of 95% by weight, preferably a maximum of 90% by weight, based on the total weight of the glassy material or materials and the pigment. This also ensures that the coating still has sufficient opacity or visibility, which can be important for safety reasons, for example, when the ceramic printing ink according to the present disclosure is intended for marking technical areas such as operating areas. This can be particularly important, for example, when coating glass-ceramic plates used as cooking surfaces or cooktops with the printing ink.

[0068] The glass-ceramic plate according to the invention can be used in a variety of applications.

[0069] In one embodiment, the glass ceramic plate can be used as a cook plate in a cooking appliance.

[0070] In a further embodiment, the glass ceramic plate can be used to cover the user interface of an operating panel for the control of at least one household appliance, in particular a cooking appliance, oven, refrigerator or hood.

[0071] In a further development of this embodiment, the control panel can be designed to control multiple household appliances, for example for the cooking appliance, the oven and the hood. The hood can also be integrated into the cooking appliance together with a corresponding glass-ceramic cooktop in the form of a so-called downdraft hood. In this case, the glass-ceramic plate can be provided with a recess into which the downdraft hood can be inserted.

[0072] In a further embodiment, the glass ceramic plate can be designed as a cover for a hood, in particular a downdraft hood. In particular, in modular cooking systems, the downdraft hood can be designed as an independent module without cooking functionality. However, such a module must also meet the very high requirements for thermal and chemical resistance typical of glass ceramics, since it is suitable for use in combination with a module with cooking functionality. Furthermore, such a module can be equipped with a user interface for controlling the downdraft exhaust system.

[0073] In a further embodiment, the glass ceramic plate can be designed as the hood's exterior. This embodiment can be particularly aesthetically pleasing if the cooking area of ​​the cooking appliance and the hood's exterior have the same glass ceramic plate. This embodiment is particularly advantageous if the hood has a user interface located behind the glass ceramic plate for controlling the hood or a user interface for controlling the hood and the cooking appliance together.

[0074] In ovens, especially pyrolysis ovens, glass ceramic sheets can be used as part of the door glazing.

[0075] In a further embodiment, the glass-ceramic plate can be used as a worktop in kitchen fixtures, in particular in kitchen cabinets, kitchen systems or countertops.

[0076] In a further embodiment, the glass ceramic plate can be used as a splash protection panel for a kitchen. The glass ceramic plate can be used, for example, in the form of a plate as a back wall of a kitchen, instead of a contamination protection panel. The glass ceramic plate can also be provided as a separate splash protection panel for a kitchen island. Such splash protection panels can be permanently installed or designed to be retractable. Retractable splash protection panels can be extended to function as splash protection when operating the cooking appliance. After the cooking process is completed, they can be lowered, for example, on the cooking appliance or worktop. In this case, it can be particularly aesthetically pleasing if both the cooktop and the splash protection panel of the cooking appliance comprise a glass ceramic plate according to the present invention. Furthermore, the kitchen worktop can also comprise the same glass ceramic plate.

[0077] Kitchen splash protection panels are constantly exposed to hot liquids such as salt water and vegetable or animal fats and oils during cooking and are regularly cleaned with chemical cleaners. The glass-ceramic plate according to the present invention is particularly suitable for use as a kitchen splash protection panel due to its high thermal and chemical stability.

[0078] In a further embodiment, the glass ceramic plate can be used to cover a user interface or as a worktop in laboratory equipment, particularly a heating plate, oven, balance, or laboratory fixture, particularly an exhaust vent, cabinet, or table.

[0079] In further embodiments, the glass ceramic panes can be used as sight glasses in fireplaces, as sight glasses in combustion chambers and other high-temperature process chambers, as fire protection glazing, as part of the housing of portable electronic devices, in particular mobile phones and tablet computers, as covers for infrared heaters or gas burners, in particular gas grills, as screens or as covers for induction charging stations, for example in the operating area or center console of motor vehicles, for example in the motor vehicle sector.

[0080] The glass ceramic plates have excellent heat and chemical resistance and can therefore be used in indoor and outdoor fireplaces, which can be ignited, for example, by gas, wood or pellets.

[0081] The high temperature process chamber may be, for example, a vacuum coating apparatus.

[0082] The glass particles have an equivalent diameter d ranging from at least 0.5 μm to a maximum of 5 μm. 90 , preferably in the range of at least 0.5 μm to a maximum of 5 μm. 97 , particularly preferably in the range of at least 0.5 μm to a maximum of 2.5 μm. 97 The existence of such extremely fine particles is advantageous because they can be printed well in inkjet printing without clogging the printhead. Here, the equivalent diameter is understood to be the diameter of a sphere having the same volume as the particle, based on the volume of the particle. This is therefore the diameter of a so-called volume-equivalent sphere.

[0083] Such a design with a corresponding equivalent diameter is highly advantageous, since it allows for easy achievement of dense layers, especially when the equivalent diameter of the pigment particles used and contained in the ceramic printing ink is taken into account accordingly. It is therefore also possible to obtain very smooth layers, which allows for easy cleaning of the coating. This is particularly important when dealing with coatings on glass-ceramic plates used as cooking surfaces or cooktops. Furthermore, smaller particles allow for more uniform melting of the particles, which also reduces baking temperatures and times.

[0084] As a result, the effective linear thermal expansion coefficient α for the glass particles and pigment particles contained in the printing ink 20-300,eff is 6.5 x 10 -6 / K~11×10 -6 / K. In this way, sufficient strength of the substrate coated with such a printing ink and also of the glass-ceramic substrate can still be ensured.

[0085] At the same time, this also makes it possible to use a glass material, such as a glass melt, that can be used under the conditions of the second firing.

[0086] Effective linear thermal expansion coefficient α 20-300,eff is preferably given by the following formula: α 20-300,eff =Σ(weight fraction of glassy material i × α 20-300,ガラス質材料i ) + Σ(weight ratio of pigment z × α 20-300,顔料z )

[0087] In other words, this means multiplying the weight proportion of the glassy material or pigment relative to the total weight, which is the sum of the weights of the glassy material, or the glassy material and the pigment, or the pigment, respectively, by the corresponding coefficient of linear thermal expansion, whereby, according to this preferred embodiment, the effective (or obtained) coefficient of linear thermal expansion of the printing ink is then determined as the sum of these products.

[0088] This embodiment provides a ceramic printing ink that allows for the adaptation of the linear thermal expansion coefficient resulting from the solid components of the printing ink, i.e., one or more glassy materials or one or more pigments. This makes it easy to adjust the resulting or effective linear thermal expansion coefficient of the printing ink already during the ink development phase. For example, in this way, it is possible to select a glassy material specifically for a given pigment and / or to adjust the ratios of the individual materials that influence the effective linear thermal expansion coefficient of the printing ink to one another in order to achieve, for example, a specific color or other advantageous properties, such as a specific film hardness.

[0089] The term "glassy component of the printing ink" is understood here to mean, in particular, that the glassy material can be or is in the form of a glass melt or glass frit. The glassy material can be added to the printing ink as a glass frit or glass melt. However, it is also possible to add the individual components of the glassy material as constituents or in the form of precursor products, so that the glassy material is only formed during baking.

[0090] According to one embodiment, the glass particles are at least 5×10 -6 / K and up to 11 x 10 -6 / K linear thermal expansion coefficient α 20-300 This is advantageous, since it allows for example to obtain a printing ink that can form a layer with good adhesion on a glass-ceramic substrate. On the other hand, these are also glassy materials, which can usually also be fired by the so-called second firing, and therefore melt at low firing temperatures.

[0091] Thus, according to one embodiment, it is provided that the printing ink is bakeable at temperatures below 830°C, preferably below 750°C and advantageously at least 500°C.

[0092] A baking temperature that is too high is not only disadvantageous from an economical standpoint, but also from a manufacturing technology standpoint, since too high a baking temperature can, for example, further ceramicize or deform the glass-ceramic product, which can lead to a failure to meet the product specifications. Therefore, the baking temperature should not be too high, and is preferably not more than 830°C, preferably not more than 750°C. On the other hand, a minimum baking temperature of at least 500°C is preferred, since this ensures a good intimate bond between the glassy material and the substrate, and preferably also between the individual components of the ceramic printing ink itself.

[0093] According to a further embodiment, the pigment particles contained in the printing ink have an equivalent diameter d of at least 0.5 μm and up to 5 μm. 90 It is advantageous that the pigment particles used are not too large, because they do not print well and may cause nozzle clogging, especially in inkjet printing. However, to ensure sufficient hiding power and color strength, it is also undesirable for the particles to be too small. Therefore, the d of the pigment particles based on the equivalent diameter 90 is at most 5 μm but is advantageously at least 0.5 μm.

[0094] According to yet another embodiment, the glass particles have a softening point of 500° C. to 800° C. Preferably, the softening point of the glass particles is 500° C. to 700° C. This ensures sufficient coating of the pigment particles even at a relatively low temperature, i.e., during the secondary baking.

[0095] According to yet another embodiment, the glass particles comprise or consist of a glass containing at least 15% and at most 72% by weight of SiO. SiO is known as a glass-forming component and can also provide glass with sufficient chemical resistance. Therefore, it is desirable for the SiO content of the glass to be at least 15% by weight. However, because SiO also increases the melt viscosity and melting temperature, it is desirable for the vitreous material to have a moderate SiO content, and therefore, a maximum of 72% by weight is preferred.

[0096] According to a further embodiment, the glass particles comprise or consist of glass containing NaO, preferably with a NaO content of at least 0.5% by weight, particularly preferably at most 11% by weight. NaO is known as a glass component and acts as a network modifier and lowers the melting temperature. Therefore, the glass particles or vitreous material can comprise or consist of glass containing NaO as a component. It can be advantageous if the NaO content of the glass is at least 0.5% by weight. However, it is desirable that the NaO content of the glass is not too high, as too high a content can reduce the chemical resistance of the glass. This also leads to an increase in the thermal expansion coefficient. Therefore, it has been found to be advantageous overall for the NaO content of the glass particles or vitreous material to be not too high. Preferably, this content is no more than 11% by weight.

[0097] A further aspect of the present disclosure relates to a glass-ceramic plate comprising a coating. Preferably, the coating is produced, or at least is producible, by a printing ink according to one embodiment. The coating comprises at least one glassy phase and pigment particles, the weight percentage of which in the coating is at least 5% by weight and less than 40% by weight. The pigment particles are dispersed within the glassy phase.

[0098] Effective linear thermal expansion coefficient α 20-300,eff is preferably given by the following formula: α 20-300,eff =Σ(weight fraction of glassy material i × α 20-300,ガラス質材料i ) + Σ(weight ratio of pigment z × α 20-300,顔料z )

[0099] Preferably, the coating has a porosity of less than 5% by volume, particularly preferably less than 1% by volume, very particularly preferably less than 0.5% by volume, and most preferably less than 0.1% by volume. In other words, the coating preferably has a low porosity. It can be particularly advantageous if the pore volume of the coating is not only small, as described above, but also if the pores have a small equivalent diameter, particularly an equivalent diameter of up to 200 nm, preferably less than 100 nm. Such coatings with only low porosity, preferably only small, particularly closed pores, can result in particularly dense, scratch-resistant coatings with high adhesion strength. Furthermore, such coatings typically have higher abrasion resistance and better chemical resistance, especially compared to coatings with open pores on the surface. This is because impurities and particles accumulate in the open pores, which can not only cause problems during cleaning but also promote further deterioration of the coating. This is advantageously avoided in the glass-ceramic plate according to the embodiment by the low porosity, preferably the pores being purely closed. "Dense" here means (usually g / cm 3 is understood to mean not only the mass density (denoted by ρ) but also the property of the coating to act as a barrier to the penetration of fluids. The fewer the pores, and in particular the fewer the open pores, the better the coating will resist the penetration of fluids, such as water or water vapor.

[0100] The formation of pores in the coating can be advantageously investigated by evaluating scanning electron microscope images. Here, the magnification is advantageously selected so that a 10 μm cross section is visible. In such an image, even very small pores can be sufficiently well visible. The porosity can then be assessed by statistically examining the pore-free and pore-containing parts of the scanning electron microscope image. Preferably, in such a cross section, corresponding to a magnification of 10,000 times, the coating contains at most one pore per 10 μm × 10 mm area.

[0101] In general, the effective coefficient of linear thermal expansion α 20-300,eff is 6.5 x 10 -6 / K~11×10 -6 / K range. This is also advantageous, especially when combined with the design of a coating with a very low porosity, since this allows a dense, strong coating to be achieved on the glass-ceramic plate without significantly impairing the strength of the coated glass-ceramic plate.

[0102] In this application, pores are understood to mean empty spaces in a coating, which may be open or closed. Pores can generally be produced in coatings, especially glass-based or particulate coatings, such as pigmented coatings, by targeted pore formation, for example, with so-called blowing agents, which decompose during baking to form gases that create voids in the coating. However, pores can also arise not from intentional production but from air bubbles present in the liquid coating agent or in the film formed on the substrate after application of such a coating agent. Such pores can also arise from gaps between particulate components, for example, due to incomplete particle melting or incomplete encapsulation of the pigment or pigment particles.

[0103] It can therefore be particularly advantageous if one or more glassy materials of the printing ink forming the coating are designed to ensure as complete a melting as possible at the aforementioned baking temperature when the coating produced by the printing ink is baked onto a substrate. For this purpose, it can also be particularly useful if the glass particles of the glassy material have a relatively small particle size, preferably within the limits mentioned for the printing ink according to the embodiment. It can also be preferable if the particle size distribution is fairly narrow, i.e., preferably with only slight deviations in particle size around the average value, since this ensures a uniform melting behavior. In this way, incompletely melting larger particles can be largely avoided or at least minimized, which has a favorable effect on the porosity, i.e., in particular, fewer and, in that case, only small pores are obtained. This can be achieved, in particular, by skillfully adjusting the composition of the glassy material and, therefore, the composition of the glassy phase of the coating. However, it can also be advantageously achieved by ensuring that the pigment content of the coating is not excessively high. This is because, during melting (which forms the glassy phase of the coating), the glassy material can surround the pigment particles as completely as possible, resulting in only a few pores and, in particular, only a few open pores.

[0104] According to one embodiment, the glassy phase, i.e. the glassy phase of the coating, has a glassy phase of at least 5×10 -6 / K and preferably up to 11×10 -6 / K linear thermal expansion coefficient α 20-300 This is preferred, since it allows an overall coating with a relatively low expansion to be obtained, which does not excessively reduce the strength of the glass-ceramic plate provided with such a coating. In particular, this embodiment can therefore also be advantageously combined with the embodiment of the glass-ceramic plate in which the coating has only a very low porosity, as explained above.

[0105] According to a further embodiment, the glassy phase of the coating has a softening point between 500°C and 800°C, preferably between 500°C and 750°C.

[0106] It should be noted here that, in general, the glassy phase originates from or is formed by one or more glassy materials of the printing ink and is usually present as a homogeneous phase, and therefore the linear thermal expansion coefficient of the glassy materials contained in the printing ink may differ from that of the glassy phase of the coating.

[0107] However, if the printing ink contains only one glassy material, the glassy phase of the coating coincides with the glassy material and the coefficient of linear thermal expansion of the glassy material coincides with the coefficient of linear thermal expansion of the glassy phase of the coating, subject to errors due to measurement technique.

[0108] According to yet another embodiment, the pigment particles contained in the coating have an equivalent diameter d of at least 0.5 μm and at most 5 μm. 90 As mentioned above, this has the advantage that the coating can be applied by inkjet printing. Furthermore, it is designed so that during the baking process, in which one or more glassy materials of the printing ink melt to form the glassy phase of the coating, the pigment particles are well and as completely surrounded as possible by the glassy phase. Furthermore, in this way, good processability and good hiding power of the coating are guaranteed.

[0109] According to another embodiment, the coating has a thickness of 1 μm to 4 μm, preferably 1.5 μm to 3.5 μm. This thickness ensures sufficient resistance of the coating to mechanical attack without excessively reducing the mechanical strength of the glass-ceramic plate. Therefore, this thickness allows for the successful production of coatings with a small pore volume, as described above.

[0110] In particular, such coatings according to the embodiments are therefore also suitable for glass-ceramic plates which contain or consist of glass-ceramics with a low coefficient of thermal expansion, such as so-called LAS glass-ceramics. According to one embodiment, the glass-ceramic of the glass-ceramic plate has a linear thermal expansion coefficient α in the range of 20 °C to 700 °C. GK,20-700 is 3 x 10 -6 / K, preferably less than 2 × 10 -6 / K. Such glass ceramics can be used in particular for glass ceramic plates that are exposed to high thermal loads during operation, for example as cooking surfaces or fireplace viewing windows.

[0111] The glass ceramic plate according to the present disclosure may have a thickness of 1 mm to 10 mm, preferably 2 mm to 7 mm, particularly preferably 3 mm to 5 mm.

[0112] Pigments suitable for printing inks according to the present disclosure may include, in particular, oxide-based materials, such as spinel-based pigments, i.e., pigments of the general formula AB2O4 with different dopants. Suitable oxide-based pigments have a density of about 6.5 x 10 -6 / K~Approx. 14×10 -6 The material may have a linear thermal expansion coefficient α of 1 / K. [Brief explanation of the drawings]

[0113] [Figure 1] 1 shows, diagrammatically and not to scale, a glass-ceramic plate 1 according to an embodiment comprising a coating 2. The coating 2 can in particular be obtained by a ceramic ink according to an embodiment of the present disclosure.

[0114] Example Some examples of printing ink compositions according to the present disclosure are given in the table below, where each component shown is a solid component, i.e. other fluid components such as solvents are not taken into account.

[0115] In the table, the percentages shown are based on the total solid weight of the printing ink. In each case, "α" is the coefficient of linear thermal expansion determined in the temperature range of 20°C to 300°C. The effective coefficient of linear thermal expansion α 20-300,eff is also shown, which is here α eff The linear thermal expansion coefficients are 10 -6 It is shown in units of / K.

[0116] [Table 2]

[0117] The melts used in the above table are listed in the table below. The linear thermal expansion coefficients were again determined in the temperature range 20°C to 300°C and are given in the range 10 -6 / K. Density is expressed in g / cm 3 It is expressed in units of T g is the glass transition temperature, Ew is the softening temperature, and Va is the processing point. These temperatures are shown in °C. The composition of the glass melt is shown in wt% on an oxide basis.

[0118] [Table 3]

[0119] The ceramic printing ink according to the present invention can be used for various glass-ceramic sheets. The composition of the glass-ceramic is not particularly limited, and in principle, both volume-colored and non-volume-colored glass-ceramics can be used. Furthermore, the ceramic printing ink according to the present invention can be applied to transparent glass-ceramics as well as opaque or translucent glass-ceramics.

[0120] The following table lists exemplary compositions of known glass ceramics from the prior art, which in principle can be coated with the ceramic printing ink according to the present disclosure. Such suitable glass ceramics are known, for example, from the following publications: WO 2010 / 040443, EP 3450411, WO 2019 / 121742, CN 111072276, WO 2010 / 137000, DE 202021103464, or CN 104609733.

[0121] [Table 4]

[0122] Glass ceramics 1, 2, and 8-10 are formed translucently, while glass ceramics 3-7 are formed transparently.

[0123] [Table 5]

[0124] Glass ceramics 11 to 16 are transparent and volume-colored. Glass ceramic 16 has a thickness of 4 mm and a light transmittance of 2.8%.

[0125] Glass ceramics 1 to 16 can be particularly plate-shaped, preferably having a thickness of 3.5 to 4.5 mm. These plates can have polished or rolled surfaces. Furthermore, these plates, especially when the surface is not polished, can have a glassy zone on the surface. Furthermore, even if there is no glassy zone, an unpolished surface can also be present. The glass ceramics can have protrusions on one side, especially the side opposite the printed surface, to increase their breaking strength.

[0126] An example of a ceramic printing ink according to the present disclosure is shown below: Glass frit 32.98% by weight Black pigment CuCr2O4 1.05% by weight White pigment TiO2 0.87% by weight Dipropylene glycol methyl ether 62.71% by weight Additive 1 2.09 wt% Additive 2 0.30% by weight

[0127] Additive 1 is poly(oxy-1,2-ethanediyl), α-methyl-ω-phosphate. Additive 2 is polyether-modified polymethylsiloxane. The resulting printing ink has an effective linear thermal expansion coefficient α of 0.05 for the glass particles and pigment particles. 20-300,eff is 9.15 x 10 -6 / K.

[0128] This ceramic printing ink was used to coat an already ceramized glass-ceramic plate by inkjet printing. 2 The coating was printed on a smooth, double-sided 11-type glass ceramic plate and then baked. The weight percentage of pigment particles in the coating was 5.5%. The porosity was less than 5% by volume.

[0129] Advantageously, the glass ceramic plate made of glass ceramic has a linear thermal expansion coefficient α in the range of 20 ° C to 700 ° C. GK,20-700 is -0.5 to 2 × 10 -6 / K, preferably 0 to 1 × 10 -6 / K, particularly preferably 0.1 to 0.5 × 10 -6 / K. [Explanation of symbols]

[0130] 1 glass ceramic plate 2. Coating

Claims

1. A ceramic printing ink, particularly for application by an inkjet printing method, particularly preferably for producing a coating on a glass ceramic, wherein the printing ink comprises at least one vitreous material containing glass particles and at least one pigment containing pigment particles, the ratio of the total weight of the glass particles contained in the printing ink to the total weight of the pigment particles contained in the printing ink is at least 1.5 and less than 19, The glass particles have an equivalent diameter d in the range of at least 0.5 μm to a maximum of 5 μm ９０ , preferably an equivalent diameter d in the range of at least 0.5 μm to a maximum of 5 μm ９７ , particularly preferably an equivalent diameter d in the range of at least 0.5 μm to a maximum of 2.5 μm ９７ and have The resulting coefficient of thermal expansion α of the effective line for the glass particles and the pigment particles contained in the printing ink ２０－３００，ｅｆｆ is in the range of 6.5 × 10 －６ / K to 11 × 10 －６ / K, Preferably, the effective linear thermal expansion coefficient α ２０－３００，ｅｆｆ is given by the following equation: α ２０－３００，ｅｆｆ = Σ (weight ratio of glassy material i × α ２０－３００，ガラス質材料ｉ ) + Σ (weight ratio of pigment z × α ２０－３００，顔料ｚ ) as determined herein, where the weight ratios are each relative to the total weight of the solids of the printing ink, i.e., the total weight includes all vitreous materials and pigments, printing ink.

2. The glass particles have a linear thermal expansion coefficient α of at least 5×10 －６ / K and at most 11×10 －６ / K, and contain glass, and the printing ink according to claim 1. ２０－３００ ​

3. The printing ink according to claim 1, which is capable of being fired at a temperature of 830 °C or lower, preferably 750 °C or lower and advantageously at least 500 °C.

4. The pigment particles contained in the printing ink have an equivalent diameter d of at least 0.5 μm to a maximum of 5 μm ９０ The printing ink according to claim 1, having the same.

5. The glass particles according to claim 1 have a softening point of 500 °C to 800 °C, preferably 500 °C to 750 °C.

6. The glass particles contain at least 15% by weight and at most 72% by weight of SiO ２ The printing ink according to claim 1, comprising glass containing such SiO or consisting of such glass.

7. The glass particles contain or consist of a glass containing Na ２ 2O, and the proportion of Na ２ 2O is preferably at least 0.5% by weight and particularly preferably at most 11% by weight. The printing ink according to claim 1.

8. A glass ceramic plate (1) comprising at least one coating (2), preferably a coating produced or producible by the printing ink according to any one of claims 1 to 7, wherein the coating (2) comprises a vitreous phase and pigment particles, the weight ratio of the pigment particles in the coating (2) is at least 5 wt% and less than 40 wt%, the pigment particles are dispersed within the vitreous phase, the coating (2) preferably has a porosity of less than 5% by volume, particularly preferably less than 1% by volume, very particularly preferably less than 0.5% by volume, most preferably less than 0.1% by volume, In the coating (2), the resulting coefficient of linear thermal expansion α ２０－３００，ｅｆｆ is in the range of 6.5×10 －６ / K to 11×10 －６ / K, and Preferably, the effective linear thermal expansion coefficient α ２０－３００，ｅｆｆ is given by the following formula: α ２０－３００，ｅｆｆ = Σ (weight ratio of glassy material i × α ２０－３００，ガラス質材料ｉ ) + Σ (weight ratio of pigment z × α ２０－３００，顔料ｚ ) as determined herein, glass ceramic plate (1).

9. The vitreous phase of the coating (2) has a linear thermal expansion coefficient α of at least 5×10 －６ / K and preferably at most 11×10 －６ / K, the glass-ceramic plate (1) according to claim 8. ２０－３００ ​

10. The vitreous phase of the coating (2) according to claim 8 has a softening point of 500 °C to 800 °C, preferably 500 °C to 750 °C.

11. The pigment particles contained in the coating (2) have an equivalent diameter d of at least 0.5 μm to a maximum of 5 μm ９０ The glass-ceramic plate (1) according to claim 8, having the same.

12. The coating (2) according to claim 8 has a thickness of 1 µm to 4 µm, preferably 1.5 µm to 3.5 µm.

13. In the glass ceramic, the linear thermal expansion coefficient α in the range of 20°C to 700°C ＧＫ，２０－７００ is -0.5 to 2×10 －６ / K, preferably 0 to 1×10 －６ / K, particularly preferably 0.1 to 0.5×10 －６ / K, The glass ceramic plate (1) according to claim 8

14. Use of the glass-ceramic plate (1) according to claim 8 in cooking appliances, ovens, kitchen accessories, kitchen splash panels, indoor heaters, in particular as an internal or external cladding, or as a viewing window, as an outdoor heater, in particular as an internal or external cladding, or as a viewing window, in grills, refrigerators, microwave ovens, hood covers or facades, mobile phones, tablets, motor vehicles, laboratory equipment, laboratory accessories, fire-resistant glazing, as a viewing window in high-temperature process chambers, in covers of infrared radiators, screens, advantageously in covers of user interfaces in control operation panels of at least one household appliance, or in covers of induction charging stations.

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