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

Abstract

A transparent, colorless lithium-aluminosilicate 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: Li2O 3.0-4.5, Na2O 0-1.5, K2O 0-1.5, SigmaNa2O+K2O 0.2-2.0, MgO 0-2.0, CaO 0-1.5, SrO 0-1.5, BaO 0-2.5, ZnO 0-2.5, B2O3 0-1.0, Al2O3 19-25, SiO2 55-69, TiO2 1-3, ZrO2 1-2.5, SnO2 0-0.4, SigmaSnO2+TiO2<3, P2O5 0-3.0, Nd2O3 0.01-0.4, CoO 0.0-0.004.

Description

Technical field [0001] The present invention relates to a transparent glass-ceramic plate having a high-temperature type quartz mixed crystal as the dominant crystal phase. The transparent glass-ceramic plate experiences high thermal stress in operation and has an opaque colored high-temperature stability on the entire surface or locally Bottom coating. Background technique [0002] The 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, such as a crimped, curved or arched plate. The board may be rectangular or circular, or may also have other contours. These glass ceramic plates have a very low thermal expansion coefficient between room temperature and 700°C, usually α 70 / 200 <1.5·10 -6 / K and therefore has high temperature resistance and temperature gradient resistance. They are used in transparent form, for example, as fireproof glass, fireplace window panels and cooking count...

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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