GLASS-CERAMIC ARTICLE

Abstract

The present invention relates to a glass-ceramic article comprising at least one substrate, such as a plate, made of glass-ceramic, said substrate being coated in at least one area with at least one enamel coating such that: 1) the enamel has a gloss at 60° of less than 40, 2) the coverage rate of said enamel in said area coated with said coating is 40 to 80%, 3) said enamel comprises pigments in the form of mica and/or aluminum oxide and/or silica particles coated with metal oxides or combinations of metal oxides, 4) said enamel has a roughness Ra greater than or equal to 0.4 μm, 5) said enamel has a roughness Rt greater than 4 μm.

Claims

1. A glass-ceramic article, comprising: at least one substrate made of glass-ceramic, wherein said substrate is coated in at least one area with at least one enamel coating such that: 1) said enamel has a gloss at 60° of less than 40; 2) the coverage rate of said enamel in said area coated with said coating is 40 to 80%; 3) said enamel comprises pigments in the form of mica and/or aluminum oxide and/or silica particles coated with metal oxides or combinations of metal oxides; 4) said enamel has a roughness Ra greater than or equal to 0.4 μm; and 5) said enamel has a roughness Rt greater than 4 μm.

2. The glass-ceramic article as claimed in claim 1, wherein said substrate is based on a glass-ceramic having intrinsically a light transmittance LT under illuminant D65 of less than 40% and an optical transmittance between 0.5 and 3% for a wavelength of 625 nm.

3. The glass-ceramic article as claimed in claim 1, wherein the area coated with said enamel coating is at least 5 cm by 5 cm.

4. The glass-ceramic article as claimed in claim 1, wherein the profile or pattern of said enamel coating is random and isotropic.

5. The glass-ceramic article as claimed in claim 1, wherein the roughness Ra is from 0.4 to 0.7 μm.

6. The glass-ceramic article as claimed in claim 5, wherein the roughness Rt is comprised between 4 and 8 μm.

7. The glass-ceramic article as claimed in claim 1, wherein said enamel comprises a proportion of B.sub.2O.sub.3 less than or equal to 25% by weight.

8. The glass-ceramic article as claimed in claim 1, wherein a thickness of said coating is between 1.5 μm and 3.5 μm.

9. The glass-ceramic article as claimed in claim 1, wherein said enamel coating is devoid of hydrophobic character and devoid of oleophobic character.

10. The glass-ceramic article as claimed in claim 1, wherein said area is coated with said enamel coating without preliminary treatment of said area.

11. The glass-ceramic article as claimed in claim 1, wherein said article or said substrate is a cooktop or a worktop or a central island or a console.

12. A process for manufacturing a glass-ceramic article as claimed in claim 1, the process comprising: applying at least one enamel coating such that: 1) said enamel has a gloss at 60° of less than 40; 2) the coverage rate of said enamel in said area coated with said coating is 40 to 80%; 3) said enamel comprises pigments in the form of mica and/or aluminum oxide and/or silica particles coated with metal oxides or combinations of metal oxides; 4) said enamel has a roughness Ra greater than or equal to 0.4 μm; and 5) said enamel has a roughness Rt greater than 4 μm; either on at least part of a glass substrate and then performing ceramization of the glass substrate thus coated, or on at least part of a glass-ceramic substrate and then firing the enamel.

13. The glass-ceramic article as claimed in claim 1, wherein the area coated with said enamel coating is at least 10 cm by 10 cm.

14. The glass-ceramic article as claimed in claim 1, wherein the area coated with said enamel coating is at least 20 cm by 20 cm.

15. The glass-ceramic article as claimed in claim 1, wherein said enamel comprises a proportion of B.sub.2O.sub.3 less than or equal to 20% by weight.

16. The glass-ceramic article as claimed in claim 1, wherein said enamel comprises a proportion of B.sub.2O.sub.3 less than or equal to 15% by weight.

17. The glass-ceramic article as claimed in claim 1, wherein said area coated with said enamel coating is not primarily coated with a primer.

Description

[0059] The following examples illustrate but do not limit the present invention.

[0060] In these examples, 10 cm by 10 cm plaques of the same substrate made of a translucent black glass-ceramic, marketed as KeraBlack+ by Eurokera, were used, these plaques having a smooth top side and a bottom side with pins and a thickness of 4 mm, these plaques being coated according to the examples of different enamel coatings to be compared, the enamel coatings having been deposited by screen-printing on the green glass substrate to afford the translucent black glass-ceramic, and then said green

[0061] glass substrate having been ceramized to afford the glass-ceramic.

[0062] Several impressions were then made on the enamel-coated areas and on the glass-ceramic as a reference. The following scoring was used, the higher the number the more visible the print, the highest score (4) being that of the reference (uncoated glass-ceramic): 0 corresponded to the absence of visible fingerprints, 1 corresponded to a print that is barely discernable, 2 corresponded to a print that could be made out by closer observation, 3 corresponded to a print that could be seen immediately but was less pronounced than that on the glass-ceramic, and 4 corresponded to a fingerprint identical to that on the glass-ceramic. These scores were attributed for each comparison by a 5-person panel, under the same conditions at each evaluation, per series of roughly 10 samples per enamel, at an angle of 60° to normal, on the same day of the application of the finger (unless otherwise stated), the scores attributed by the different people being then compared and averaged.

[0063] For the first comparisons, an enamel of the following composition was used: Al.sub.2O.sub.3: 12.5-13.4%; Li.sub.2O+Na.sub.2O+K.sub.2O: 3.8-5.9%; B.sub.2O.sub.3: 18-19.8%, CaO+BaO+MgO: 1.7-2.3%, ZrO.sub.2: 1.4-2%, mixture of mica particles coated with TiO.sub.2, of mica particles coated with Fe.sub.2O.sub.3, and of mica particles coated with a combination TiO.sub.2—Fe.sub.2O.sub.3—SnO.sub.2 (pigments with metallic effect): 30%, the rest (to 100% by weight) being silica SiO.sub.2, this enamel having a gloss (flat) of 26.3, a roughness Ra of 0.5 μm, and a roughness Rt of 4.5 μm, and being tested with different coverage rates, in a 2.5 μm thick coating. The coverage rates tested were respectively: 10%, 36%, 42%, 46%, 48%, 58%, 59%, 60%, 72%, 74%, 78%, 80% and 100%. Scores (averages) below 1 down to 0 were given for rates 42 to 80%, with the lowest scores and with the least dispersion being observed for rates ranging from 55 to 78%, with an optimum at 60%.

[0064] The enamel was then compared, at the same thickness (2.5 μm) and with an 80% coverage rate for each enamel tested, with a metallized enamel not in accordance with the invention having a gloss (flat) of 66, a roughness Ra of 0.2 μm, and a roughness Rt of 2.8 μm, of composition selected from the following composition: Al.sub.2O.sub.3: 15.2-16.2%; Li.sub.2O+Na.sub.2O+K.sub.2O: 4.6-7.1%; B.sub.2O.sub.3: 21.8-24.1%, CaO+BaO+MgO: 2-2.8%, ZrO.sub.2: 1.7-2.5%, Xirallic F60-25 pigments marketed by Merck (pigments with metallic effect): 15%, the rest (to 100% by weight) being silica SiO.sub.2. The average score obtained was of the order of 2.

[0065] The enamel was then compared, at an 80% coverage rate and the same thickness as before, with a non-metallized enamel not in accordance with the invention having a gloss (flat) of 15.7, a roughness Ra of 0.3 μm, and a roughness Rt of 4.4 μm, of composition selected from the following composition: Al.sub.2O.sub.3: 5.4-6.5%; Li.sub.2O+Na.sub.2O+K.sub.2O: 4.8-7.4%; B.sub.2O.sub.3: 3.6-5.4%, CaO+BaO+MgO: 17-20.3%, ZrO.sub.2: 1-1.7%, ZnO: 5.9-7.4%, mixture of particles of TiO.sub.2, of Fe.sub.2O.sub.3, of Fe—Cr—Co—Ni oxides, and of Al—Co oxides (pigments without metallic effect): 15%, the rest (to 100% by weight) being silica SiO.sub.2. The average score obtained was of the order of 2.

[0066] The enamel was then compared, at an 80% coverage rate and the same thickness as before, with another metallized enamel according to the invention having a gloss (flat) of 38.4, a roughness Ra of 0.6 μm, and a roughness Rt of 4.6 μm, of composition selected from the following composition: Al.sub.2O.sub.3: 12.5-13.4%; Li.sub.2O+Na.sub.2O+K.sub.2O: 3.8-5.9%; B.sub.2O.sub.3: 18.0-19.8%, CaO+BaO+MgO: 1.7-2.3%, ZrO.sub.2: 1.4-2%, Colorstream F10-00 pigments marketed by Merck (pigments with metallic effect): 30%, the rest (to 100% by weight) being silica SiO.sub.2. The average score obtained was of the order of 0.

[0067] The enamel was then compared, at an 80% coverage rate and the same thickness as before, with another metallized enamel according to the invention having a gloss (flat) of 37.6, a roughness Ra of 0.4 μm, and a roughness Rt of 6 μm, of composition selected from the following composition: Al.sub.2O.sub.3: 14.3-15.3%; Li.sub.2O+Na.sub.2O+K.sub.2O: 4.3-6.7%; B.sub.2O.sub.3: 20.5-22.7%, CaO+BaO+MgO: 1.9-2.6%, ZrO.sub.2: 1.6-2.3%, mixture of mica particles coated with TiO.sub.2, of mica particles coated with Fe.sub.2O.sub.3, and of mica particles coated with a combination TiO.sub.2—Fe.sub.2O.sub.3—SnO.sub.2 (pigments with metallic effect): 20%, the rest (to 100% by weight) being silica SiO.sub.2. The average score obtained was of the order of 0.

[0068] The enamel was then compared, at an 80% coverage rate and the same thickness as before, with a metallized enamel not in accordance with the invention having a gloss (flat) of 80, a roughness Ra of 0.2 μm, and a roughness Rt of 2.5 μm, of composition selected from the following composition: Al.sub.2O.sub.3: 16.1-17.2%; Li.sub.2O+Na.sub.2O+K.sub.2O: 4.9-7.6%; B.sub.2O.sub.3: 23.1-25.5%, CaO+BaO+MgO: 2.2-3%, ZrO.sub.2: 1.8-2.6%, Xirallic T60-10 pigments marketed by Merck (pigments with metallic effect): 10%, the rest (to 100% by weight) being silica SiO.sub.2. The average score obtained was between 1 and 2.

[0069] The enamel coatings meeting the conditions according to the invention have shown anti-fingerprint properties as opposed to other coatings not meeting these conditions. Furthermore, there were no significant differences in scoring noted when the tests were performed 7 or 14 days after application of the fingers.

[0070] In addition, the substrate and the coatings obtained showed no delamination after a thermal shock of 620° C. and showed no degradation of appearance after 100 h at 580° C.

[0071] The articles according to the invention can in particular be used with advantage to make a new range of cooktops for stoves or hotplates or a new range of worktables, consoles, credenzas, central islands, etc.