Glass-ceramic article and enamel for the coating thereof
A glass-ceramic article is at least partly coated with at least one layer of enamel, including a glass frit. The frit includes, expressed by weight, SiO 2 , 45-60%; Al 2 O 3 , 12-22%; B 2 O 3 , 12-22%; Li 2 O, 0-5%; Na 2 O, 0-2%; K 2 O, >2%; CaO, 0-4%; MgO, 0-4%; ZnO, 0-4%; BaO, 0-4%; ZrO 2 , 0-4%; and TiO 2 , 0-1%. The sum of oxides CaO+MgO+BaO+SrO+ZnO is at most 10%, preferably from 2 to 8%. A process can be used to obtain the article.
1. A glass-ceramic article, at least partly coated with at least one layer of an enamel formed from a glass frit having the following composition, the proportions being expressed as weight percentages:
SiO 2 45-60%,
Al 2 O 3 12-22%,
B 2 O 3 12-22%,
Li 2 O 0-5%,
Na 2 O 0-2%
K 2 O >2%
CaO 0-4%,
MgO 0-4%,
ZnO 0-4%,
BaO 0-4%,
ZrO 2 0-4%,
TiO 2 0-1%,
the sum of the oxides CaO + MgO + BaO + SrO + ZnO moreover being less than or equal to 10%,
wherein the enamel provides an appearance that is merged with the glass-ceramic article on which it is coated or a contrast with respect to the remainder of the article depending on an angle of observation.
2. The glass-ceramic article as claimed in claim 1 , wherein the enamel comprises a pigment content of less than 5% by weight.
3. The glass-ceramic article of claim 1 , wherein the difference between the refractive index of the enamel and that of the glass-ceramic is less than 0.05.
4. The glass-ceramic article of claim 1 , having a softening point of less than 800° C.
5. The glass-ceramic article of claim 1 , wherein the difference between the lightness of the enamel and that of the glass-ceramic is less than 1.
6. The glass-ceramic article of claim 1 , wherein the brightness B of the enamel is greater than 50.
7. The glass-ceramic article of claim 1 , wherein the particle size distribution of the frit, and of optional pigments, in powder form is such that at least 90% by weight of the particles forming the powder have a diameter of less than 15 μm.
8. The glass-ceramic article of claim 1 , wherein the thickness of the enamel layer is from 2 μm to 4 μm.
9. The glass-ceramic article of claim 1 , wherein the article is formed from a glass-ceramic comprising less than 0.2% by weight of arsenic oxides.
10. The glass-ceramic article as claimed in claim 1 , wherein the enamel is devoid of pigment.
11. The glass-ceramic article of claim 1 , wherein the difference between the refractive index of the enamel and that of the glass-ceramic is less than 0.02.
12. The glass-ceramic article of claim 1 , wherein the brightness B of the enamel is greater than 60.
13. The glass-ceramic article of claim 1 , wherein the particle size distribution of the frit, and of the optional pigments, in powder form is such that at least 90% by weight of the particles forming the powder have a diameter of less than 4 μm.
14. The glass-ceramic article as claimed in claim 1 , wherein:
the difference between the lightness of the enamel and that of the glass-ceramic is less than 1;
the difference between the refractive index of the enamel and that of the glass-ceramic is less than 0.02;
the particle size distribution of the frit, and of optional pigments, in powder form is such that at least 90% by weight of the particles forming the powder have a diameter of 9-14 μm.
15. The glass-ceramic article of claim 14 , wherein the article is formed from a glass-ceramic comprising less than 0.2% by weight of arsenic oxides.
16. The glass-ceramic article of claim 14 , wherein the enamel is devoid of pigment.
17. The glass-ceramic article of claim 15 , wherein the enamel is devoid of pigment.