# US 2014/0193627 A1 · Reinforced glass-ceramic article and enamel suitable for the coating thereof

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- Number: US 2014/0193627 A1
- Document ID: US20140193627A1
- Status: Published application
- Kind: A1
- Application number: 14/152,230
- Filed: 2014-01-10
- Published: 2014-07-10
- Earliest claimed: 2008-01-18
- Assignees: Eurokera S.N.C.
- Applicants: Eurokera S.N.C.
- Inventors: Stephanie Pelletier; Marie-Helene Chopinet; Caroline Faillat; Marie-Helene Rouillon; Pablo Vilato
- Web page: https://patentgrep.com/patent/US20140193627A1

## CPC

- C03C 8/04: containing zinc
- C03C 3/085: containing an oxide of a divalent metal
- C03C 8/02: Frit compositions, i.e. in a powdered or comminuted form
- C03C 10/0027: {containing SiO2, Al2O3, Li2O as main constituents}
- C03C 17/04: by fritting glass powder
- Y10T 428/315: Surface modified glass [e.g., tempered, strengthened, etc.]
- 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
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

The present invention relates to 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: SiO2 50-66% MgO 3-8% Na2O 7-15% K2O 0-3% Li2O 0-12% CaO 0-10% BaO 0-15% Al2O3 0-3% ZrO2 0-3% ZnO 0-5% B2O3 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 Na2O+K2O+Li2O moreover being between 7 and 20%. The invention also relates to the reinforced glass-ceramics obtained.

## Claims

### Claim 1

(canceled)

### Claim 2

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.

### Claim 3 (depends on 2)

The reinforced glass-ceramic article of claim 2, 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:
SiO2
50-66%;
MgO
3-8%;
Na2O
7-15%;
K2O
0-3%;
Li2O
0-12%;
CaO
0-10%;
BaO
0-15%;
Al2O3
0-3%;
ZrO2
0-3%;
ZnO
0-5%; and
B2O3
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, Na2O+K2O+Li2O, is between 7 and 20%.

### Claim 4 (depends on 3)

The reinforced glass-ceramic article of claim 3, wherein the glass frit comprises less than 2% of alumina Al2O3.

### Claim 5 (depends on 2)

The reinforced glass-ceramic article of claim 2, wherein the article is at least partly coated with a layer of opacifying paint, an enamel, or a mixture thereof.

### Claim 6 (depends on 2)

The reinforced glass-ceramic article of claim 2, having a scale factor, obtained according to the Weibull model, after a bending test, of at least 130 MPa.

### Claim 7 (depends on 2)

The reinforced glass-ceramic article of claim 2, wherein the article is at least partly coated with at least one layer of a crystalline enamel.

### Claim 8 (depends on 2)

The reinforced glass-ceramic article of claim 2, wherein a crack formed during a shock is oriented parallel to the surface.

### Claim 9 (depends on 2)

The reinforced glass-ceramic article of claim 2, which is a 3-mm thick glass-ceramic plate.

### Claim 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.

### Claim 11 (depends on 10)

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.

### Claim 12 (depends on 10)

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

### Claim 13 (depends on 12)

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:
SiO2
50-66%;
MgO
3-8%;
Na2O
7-15%;
K2O
0-3%;
Li2O
0-12%;
CaO
0-10%;
BaO
0-15%;
Al2O3
0-3%;
ZrO2
0-3%;
ZnO
0-5%; and
B2O3
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, Na2O+K2O+Li2O, is between 7 and 20%.

### Claim 14 (depends on 13)

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.

### Claim 15 (depends on 14)

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.

### Claim 16 (depends on 2)

A device for baking or for maintaining at high temperature, comprising a reinforced glass-ceramic article of claim 2 and at least one heating element.