Transparent glass ceramic plate having opaque colored bottom coating on whole or part of its surface

Abstract

A colorless, transparent glass ceramic plate with high-quartz mixed crystals as the prevailing crystal phase, which is provided on one side with an opaque, colored, temperature-stable coating over the entire surface or over the entire surface to a large extent, is described, which has a content of Nd2O3 of 40 to 4000 ppm, a Yellowness Index of less than 10% with a 4 mm glass (ceramic) layer thickness, and a variegation of colors of the glass or the glass ceramic in the CIELAB color system of C* of less than 5. The glass ceramic plate preferably has a composition (in % by weight based on oxide) of: 3.0-4.5 of Li2O, 0-1.5 of Na2O, 0-1.5 of K2O, 0.2-2.0 of SigmaNa2O+K2O, 0-2.0 of MgO, 0-1.5 of CaO, 0-1.5 of SrO, 0-2.5 of BaO, 0-2.5 of ZnO, 0-1.0 of B2O3, 19-25 of Al2O3, 55-69 of SiO2, 1-3 of TiO2, 1-2.5 of ZrO2, 0-0.4 of SnO2, SigmaSnO2+TiO2<3, 0-3.0 of P2O5, 0.01-0.4 of Nd2O3, 0.0-0.004 of CoO.

Description

technical field [0001] The invention relates to transparent glass-ceramic plates with high-temperature quartz mixed crystals as the predominant crystalline phase, which are subjected to high thermal stresses in operation and have an opaque colored high-temperature stable over the entire surface or locally Underside coating. Background technique [0002] A glass-ceramic plate within the scope of the present invention is understood not only as a flat plate, but also as a three-dimensionally twisted plate, for example a beaded, curved or arched plate. The plates can be rectangular or circular or can also have other contours. These glass-ceramic plates have a very low coefficient of thermal expansion between room temperature and 700°C, typically α 70 / 200 <1.5·10 -6 / K and thus have high temperature resistance and resistance to temperature gradients. In transparent form they are used, for example, as fire-resistant glass, fireplace shutters and cooking tops. [0003] Hobs...

AI Technical Summary

Problems solved by technology

Glass-ceramic also enters among these cullets, which causes the following problem, namely because Li 2 O-Al 2 o 3 -SiO 2 Glass-ceramics prepared from glass systems have relatively high melting temperatures and therefore very negatively affect soda-lime glasses (Kalk-Natron- ) remelting and forming

The risk is that the high melting point Li 2 O-Al 2 o 3 -SiO 2 Glass forms non-melting residues in soda-lime glass. This leads in favorable cases to visually recognizable residues in soda-lime glass products, and in unfavorable cases to Li 2 O-Al 2 o 3 -SiO 2 Glass residues and clogging of channels or nozzles during the forming process and thus complete interruption of soda-lime glass production

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