# US 2014/0150500 A1 · Process for producing a highly transparent impact-resistant glass ceramic

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- Number: US 2014/0150500 A1
- Document ID: US20140150500A1
- Status: Published application
- Kind: A1
- Application number: 13/705,577
- Filed: 2012-12-05
- Published: 2014-06-05
- Earliest claimed: 2012-12-05
- Assignees: Schott AG
- Inventors: Thilo Zachau; Friedrich Siebers; Ulrich Schiffner; Kurt Schaupert
- Web page: https://patentgrep.com/patent/US20140150500A1

## CPC

- C03C 10/0027: {containing SiO2, Al2O3, Li2O as main constituents}
- B32B 17/10045: {with at least one intermediate layer consisting of a glass sheet}
- B32B 17/10119: {having a composition deviating from the basic composition of soda-lime glass, e.g. borosilicate}
- B32B 17/10761: {containing vinyl acetal}
- C03C 3/085: containing an oxide of a divalent metal
- F41H 5/0407: {Transparent bullet-proof laminates}{informative reference: layered products essentially comprising glass in general B32B17/06, e.g. B32B17/10009; manufacture or composition of glass, e.g. joining glass to glass C03; permanent multiple-glazing windows, e.g. with spacing therebetween, E06B3/66}
- B32B 2333/12: Polymers of methacrylic acid esters, e.g. PMMA, i.e. polymethylmethacrylate
- C03C: CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- F41H: ARMOUR; ARMOURED TURRETS; ARMOURED OR ARMED VEHICLES; MEANS OF ATTACK OR DEFENCE, e.g. CAMOUFLAGE, IN GENERAL

## 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.

## Claims

### Claim 1

A process for producing a transparent plate, said process comprising the following steps:
a) preparing a green glass body comprising glass of a Li2O—Al2O—SiO2 system; and
b) using a ceramization program, said ceramization program comprising
heating the green glass body, for the purpose of nucleation, to a nucleation temperature of 750±20° C. and holding said nucleation temperature for 20±15 minutes,
further heating of the green glass body, for the purpose of ceramization, to a ceramization temperature of 900±20° C. and holding said ceramization temperature for 20±15 minutes, and
cooling to room temperature;
wherein said transparent plate is a lithium aluminosilicate glass ceramic with a composition, expressed in wt. %, comprising:
Li2O
3.0-4.5
Al2O3
18.0-24.0
SiO2
55.0-70.0
TiO2
0.01-2.3
ZrO2
0.01-2.0
Σ TiO2 + ZrO2
0.5-4.3
SnO2
0-0.2
MgO
0-0.8
Fe2O3
40-200 ppm
As2O3
0.3-0.9.

### Claim 2 (depends on 1)

The process according to claim 1, wherein said 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.

### Claim 3 (depends on 2)

The process according to claim 2, wherein said thermal expansion coefficient (CTE) is from −0.05×10−6/K to −0.10×106/K at 30 to 700° C.

### Claim 4 (depends on 1)

The process according to claim 1, where said composition comprises from 40 to 130 ppm of said Fe2O3.

### Claim 5 (depends on 1)

The process according to claim 1, wherein said composition further comprises, in wt. %:
BaO
0-3
Na2O
0-1.5
ZnO
0-2.5.

### Claim 6 (depends on 1)

The process according to claim 1, wherein the transparent plate has a brightness value for transmitted normal light observed at an angle of 2° of ≧80 for a plate thickness of 4 mm.