Process for producing a highly transparent impact-resistant glass ceramic

Abstract

The process for producing a transparent lithium aluminosilicate glass ceramic plate includes ceramicizing a green glass body of the Li2O—Al2O—SiO2 system using a ceramization program, which includes heating it, for the purpose of nucleation, to a temperature of 750° C.±20° C. and maintaining the temperature for 20±15 minutes, further heating the green glass body, for the purpose of ceramization, to a temperature of 900±20° C. and maintaining the to temperature for 20±15 minutes and then cooling to room temperature. The transparent plate has a thermal expansion coefficient (CTE) from −0.15×10−6 / K to +0.15×10−6 / K at 30 to 700° C. and a brightness value observed at an angle of 2° of ≧80 for a 4-mm thick plate for transmitted normal light.

Description

CROSS-REFERENCE[0001]This is a divisional of U.S. patent application Ser. No. 12 / 616,982, filed on Nov. 12, 2009, which claims priority of invention based on German Patent Application 10 2008 043 718.2 filed on Nov. 13, 2008 in Germany. The aforesaid German Patent Application contains subject matter described and claimed herein below.BACKGROUND OF THE INVENTION[0002]The inventions described herein comprise a transparent plate made of lithium aluminosilicate glass ceramic having a high transmission, a process for making same and also transparent plate laminates comprising at least one of the plates of the lithium aluminosilicate glass ceramic according to the invention and the use thereof as armored glass or in bullet-proof vests.[0003]Until now, the inherent color of transparent glass ceramics has been too strong. The reasons for the inherent color of transparent glass ceramics can vary. The constituents of the raw material mixtures for the melts contain the coloring element Fe as a...

AI Technical Summary

Benefits of technology

[0007]Another object of the present invention is to provide glass ceramic plates exhibiting high overall transmission for visible light. In particular, these glass ceramic plates show a high overall transmission for visible light which manifests itself in a high brightness value for transmitted standard light A under 2° observation) (YA / 2°).

[0069]The armored glass according to the invention ensures maximum energy absorption when a bullet strikes. This splinter-proof design preferably serves to protect the persons present in a motor vehicle or building provided with such an armored glass from being hit by flying glass splinters stemming from a glass pane hit by a bullet.

Problems solved by technology

Until now, the inherent color of transparent glass ceramics has been too strong.

The temperature- and pressure-controlled process of linking the individual layers and plastic materials to each other, in particular, is time-consuming and cost-intensive.

The many interfacial transitions between glass plates and plastic materials result in poor transmission characteristics which may lead to the formation of interference fringe patterns in the form of Newton fringes.

Also, the large amount of glass, namely the high number of glass plates in the known bullet-proof plates results in their exhibiting a very high weight per unit area.

The high weight per unit area leads to a significant construction cost for installation and vitrification.

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