Reinforced glass-ceramic article and enamel suitable for the coating thereof

Patent metadata

Field	Value
Publication number	US-8986841-B2
Application number	US-201414152230-A
Country	US
Kind code	B2
Filing date	Jan 10, 2014
Priority date	Jan 18, 2008
Publication date	Mar 24, 2015
Grant date	Mar 24, 2015

Abstract

A process for reinforcing a glass-ceramic article, into which a maximum tension is introduced beneath the surface of the glass-ceramic, advantageously in proximity to said surface. The invention also relates to an enamel that can be used for this reinforcement, this enamel being formed from a glass frit having the following composition, the proportions being expressed as weight percentages:
SiO 2 50-66% MgO 3-8% Na 2 O  7-15% K 2 O 0-3% Li 2 O  0-12% CaO  0-10% BaO  0-15% Al 2 O 3 0-3% ZrO 2 0-3% ZnO 0-5% B 2 O 3 0-8%
the sum of the alkaline-earth metal oxides CaO+BaO moreover being between 8 and 15%, and the sum of the alkali metal oxides Na 2 O+K 2 O+Li 2 O moreover being between 7 and 20%. The reinforced glass-ceramics obtained by the process.

First claim

The invention claimed is:

1. A reinforced glass-ceramic article, reinforced over at least one region of at least one face, wherein the glass-ceramic has a tensile stress of at least 1.2 MPa at a depth of at least 50 μm, beneath its surface, in at least said region or face.

2. The reinforced glass-ceramic article of claim 1 , wherein the article is at least partly coated with at least one layer of an enamel formed from a glass frit comprising, as weight percentages:

SiO 2
50-66%;

MgO
 3-8%;

Na 2 O
 7-15%;

K 2 O
 0-3%;

Li 2 O
 0-12%;

CaO
 0-10%;

BaO
 0-15%;

Al 2 O 3
 0-3%;

ZrO 2
 0-3%;

ZnO
 0-5%; and

B 2 O 3
 0-8%;

wherein the sum of the alkaline-earth metal oxides, CaO+BaO, is between 8 and 15%, and the sum of the alkali metal oxides, Na 2 O+K 2 O+Li 2 O, is between 7 and 20%.

3. The reinforced glass-ceramic article of claim 2 , wherein the glass frit comprises less than 2% of alumina Al 2 O 3 .

4. The reinforced glass-ceramic article of claim 1 , wherein the article is at least partly coated with a layer of opacifying paint, an enamel, or a mixture thereof.

5. The reinforced glass-ceramic article of claim 1 , having a scale factor, obtained according to the Weibull model, after a bending test, of at least 130 MPa.

6. The reinforced glass-ceramic article of claim 1 , wherein the article is at least partly coated with at least one layer of a crystalline enamel.

7. The reinforced glass-ceramic article of claim 1 , wherein a crack formed during a shock is oriented parallel to the surface.

8. The reinforced glass-ceramic article of claim 1 , which is a 3-mm thick glass-ceramic plate.

9. A device for baking or for maintaining at high temperature, comprising a reinforced glass-ceramic article of claim 1 and at least one heating element.

10. A process for reinforcing a glass-ceramic article, the process comprising:
introducing a maximum tension beneath a surface of a glass-ceramic in proximity to said surface, wherein introducing comprises treating the glass-ceramic so as to have a tensile stress of at least 1.2 MPa at a depth of at least 50 μM beneath the glass-ceramic surface.

11. The process of claim 10 , wherein introducing comprises treating the glass-ceramic so as to have a tensile stress of at least 1.2 MPa at a depth of at least 50 μm, and at most 25% of the thickness of the glass-ceramic relative to the surface of the glass-ceramic, in at least one region of the glass-ceramic.

12. A process for manufacturing a reinforced glass-ceramic article, comprising the reinforcing of claim 10 .

13. The process of claim 12 , wherein the introducing of a maximum tension in the glass-ceramic is carried out using an enamel composition formed from a glass frit comprising, as weight percentages:

SiO 2
50-66%;

MgO
 3-8%;

Na 2 O
 7-15%;

K 2 O
 0-3%;

Li 2 O
 0-12%;

CaO
 0-10%;

BaO
 0-15%;

Al 2 O 3
 0-3%;

ZrO 2
 0-3%;

ZnO
 0-5%; and

B 2 O 3
 0-8%;

wherein the sum of the alkaline-earth metal oxides, CaO+BaO, is between 8 and 15%, and the sum of the alkali metal oxides, Na 2 O+K 2 O+Li 2 O, is between 7 and 20%.

14. The process of claim 13 , comprising applying the enamel composition to a precursor glass article before ceramization, and baking said composition during a ceramization cycle and/or applying said composition to the glass-ceramic article after ceramization, and baking said composition.

15. The process of claim 14 , wherein the baking of the enamel after ceramization is carried out at a temperature located in the crystallization zone and/or at a temperature of the order of 250° C. to 300° C. higher with respect to the dilatometric softening temperature of the enamel.

Assignees

• Pelletier Stephanie
• Chopinet Marie-Helene
• Faillat Caroline
• Rouillon Marie-Helene
• Vilato Pablo
• Eurokera

Inventors

• Pelletier Stephanie
• Chopinet Marie-Helene
• Faillat Caroline
• Rouillon Marie-Helene
• Vilato Pablo

Classifications

• C03C8/02 Primary

  Frit compositions, i.e. in a powdered or comminuted form · CPC title

• C03C8/04 Primary

  containing zinc · CPC title

• C03C17/04

  by fritting glass powder · CPC title

• C03C3/085 Primary

  containing an oxide of a divalent metal · CPC title

• C03C10/0027

  containing SiO2, Al2O3, Li2O as main constituents · CPC title