GLASS-CERAMIC ARTICLE

Abstract

The present invention relates to an article, especially a cooktop or a furniture element, comprising at least one substrate, such as a plate, made of glass-ceramic, said substrate being coated in at least one zone with a paint comprising at least: 1) a silicone resin comprising methyl and phenyl groups, 2) one or more lamellar inorganic fillers with a thickness of less than 2 μm and with lateral dimensions, for at least 80% by weight of said fillers, of between 10 μm and 65 μm, including at least: 2a) mica(s), and 2b) talc and/or one or more carbonates, 3) one or more black pigments.

The present invention also relates to a process for obtaining said article.

Claims

1. An article, comprising at least one substrate made of glass-ceramic, said substrate being coated in at least one zone with a paint comprising at least: 1) a silicone resin comprising methyl and phenyl groups; 2) one or more lamellar inorganic fillers with a thickness of less than 2 μm and with lateral dimensions, for at least 80% by weight of said fillers, of between 10 μm and 65 μm, including at least: 2a) mica(s), and 2b) talc and/or one or more carbonates; and 3) one or more black pigments.

2. The article as claimed in claim 1, wherein the silicone resin(s) of said paint are devoid of one or more functional groups selected from the group consisting of: halogen, epoxy, polyester, alkenyl, vinyl, allyl, alkynyl, mercapto, thiol, and acrylic.

3. The article as claimed in claim 1, wherein said paint comprises, as silicone resins, at least 75% by weight of the silicone resin(s) comprising methyl and phenyl groups, with respect to the total weight of silicone resins present, and wherein said paint is devoid of silicone resins of alkyd type and/or of epoxy type and/or of polyester type and/or of methyl type.

4. The article as claimed in claim 1, wherein a content of silicone resin(s) is between 20% and 50% by weight of said paint.

5. The article as claimed in claim 1, wherein a content of said lamellar fillers is from 5% to 20% by weight with respect to said paint.

6. The article as claimed in claim 1, wherein a content of pigment(s) is of between 10% and 30% by weight of the paint, and wherein at least 50% of the particles of pigments exhibit a size of less than 1 μm.

7. The article as claimed in claim 1, wherein a thickness of the paint coating is between 20 and 40 μm.

8. The article as claimed in claim 1, wherein the paint coating exhibits a lightness L* of less than 5.

9. A process for the manufacture of the article as claimed in claim 1, the process comprising: coating a glass-ceramic substrate in at least one zone with a paint comprising at least: 1) a silicone resin comprising methyl and phenyl groups; 2) one or more lamellar inorganic fillers with a thickness of less than 2 μm and with lateral dimensions, for at least 80% by weight of said fillers, of between 10 μm and 65 μm, including at least: 2a) mica(s), and 2b) talc and/or one or more carbonates; and 3) one or more black pigment(s).

10. The process as claimed in claim 9, wherein the paint is applied by screen printing to the glass-ceramic substrate, and is fired at temperatures between 350 and 480° C. for from 40 to 60 min.

11. The article as claimed in claim 1, wherein the article is a cooktop or a furniture element.

12. The article as claimed in claim 1, wherein the silicone resin(s) are at least one selected from the group consisting of polyphenylmethylsiloxane resin(s) and polydiphenyldimethylsiloxane resin(s).

13. The article as claimed in claim 1, wherein said paint comprises, as silicone resins, at least 80% by weight of the silicone resin(s) comprising methyl and phenyl groups, with respect to the total weight of silicone resins present, and wherein said paint is devoid of silicone resins of alkyd type and/or of epoxy type and/or of polyester type and/or of methyl type.

14. The article as claimed in claim 1, wherein a content of said lamellar fillers is from 8% to 20% by weight with respect to said paint.

15. The article as claimed in claim 1, wherein a content of said lamellar fillers is from 1% to 10% by volume, with respect to said paint.

16. The article as claimed in claim 5, wherein a content of talc/carbonate(s) is between 5% and 15% by weight of the paint and a content of mica(s) is between 3% and 12% by weight of the paint.

17. The article as claimed in claim 6, wherein at least 75% of the particles of pigments exhibit a size of less than 1 μm.

18. The article as claimed in claim 6, wherein at least 80% of the particles of pigments exhibit a size of less than 1 μm.

19. The process as claimed in claim 10, wherein the screen-printing screen employed has a number of yarns per cm of between 32 and 43 yarns per cm.

Description

[0033] In a preferred embodiment according to the invention, the paint according to the invention exhibits the following composition (or comprises the following constituents within the boundaries defined below, limits included), the proportions being expressed as percentages by weight (with respect to the total weight of the ready-for-deposition paint composition): [0034] silicone resin(s) of methyl/phenyl type: 20-50%, preferably 28-40%, [0035] black pigment(s): 10-30%, preferably 18-25%, [0036] lamellar filler(s) based on mica(s) and on talc and/or carbonate(s): 5-20%, preferably 10-20%, indeed even 15-20%, [0037] dispersing agent(s) and air-release agent(s): 1-10%, preferably 2-5%, [0038] solvent(s): 25-45%, preferably 28-45%.

[0039] The paint coating, once solid, is formed mainly of the abovementioned silicone resin(s), fillers and pigments. The paint before deposition is generally provided in the form of a stable liquid/solid mixture of pasty consistency, the viscosity at deposition of the paint preferentially being between 1000 and 3000 mPa.Math.s, especially between 1300 and 1800 mPa.Math.s.

[0040] The paint can be formed directly by mixing its constituents in the required proportions, the viscosity being adjusted, if appropriate, by the addition of the solvent.

[0041] The thickness of the final paint coating (once dry) is preferentially between 20 and 40 μm, in particular between 25 and 35 μm.

[0042] The solution according to the present invention makes it possible to obtain, in a simple and economical way, without a complex operation (the paint layer being in particular advantageously and simply deposited by screen printing), in a lasting fashion and with great flexibility, the products desired according to the invention. The coating obtained (after drying/firing) is especially deep black and is characterized in particular by an unusually low lightness L*, of less than 5 (the lightness of the existing paints for the applications targeted generally being at least 12), the lightness L* being a component defined in the CIE colorimetric system and being evaluated in a known way, using in particular a Byk-Gardner Color Guide 45/0 colorimeter (colorimetry in reflection), on the upper face of the substrate (the substrate used for the measurement of lightness of the paint being a transparent glass-ceramic substrate with a thickness of 4 mm intrinsically having a light transmission TL (integrated in the visible wavelength range) of 85-90% and placed on an opaque white background) using the D65 illuminant (the sample being illuminated under an angle of 45° and observed under an angle of 0°). Furthermore, the paint exhibits a good resistance to the normal thermomechanical stresses of glass-ceramics, no discoloration or delamination being observed, in particular in the case of temperature variations of up to 500° C. The paint composition can be used in any zone of the glass-ceramic substrate, even when these zones are subjected to high temperatures and/or to strong illumination. Good adhesion of the paint to the substrate is also observed, this paint additionally exhibiting a good scratch resistance, in particular a resistance to the 2B pencil according to the standard ISO 15184 and a resistance of at least 1N according to the standard ISO 1518-1.

[0043] If appropriate, the substrate can comprise one or more additional coatings, in particular localized coatings (for example an enamel on the upper face in order to form logos or simple patterns). Advantageously, the paint as selected coats the substrate according to the invention without the necessity for an overlayer or underlayer.

[0044] The article according to the invention can also comprise at least one or more light sources and/or one or more heating elements (such as one or more induction heating means) placed on the lower face of the substrate. The source(s) can be integrated in/coupled to one or more structure(s) of display device(s) type (for example “7-segment” light-emitting diodes), to a touch-sensitive digital-display electronic control panel, to an LCD screen, and the like. The light sources are advantageously formed by light-emitting diodes which are more or less spaced out.

[0045] The article according to the invention can comprise, if appropriate, other elements; for example, in the case of a cooking module or of a cooktop, the article can be provided with (or combined with) additional functional or decorative element(s) (frame, connector(s), cable(s), control element(s)), and the like.

[0046] The present invention also relates to the process for the manufacture of the articles according to the invention, in which the glass-ceramic substrate is coated with regard to at least one zone with a paint as selected above.

[0047] For the record, the manufacture of glass-ceramic plates is generally carried out as follows: the glass with the composition chosen in order to form the glass-ceramic is melted in a melting furnace, the molten glass is then rolled to give a standard ribbon or sheet by causing the molten glass to pass between rolling rolls and the glass ribbon is cut to the desired dimensions. The plates, thus cut, are subsequently ceramized in a way known per se, the ceramization consisting in firing the plates according to the thermal profile chosen in order to convert the glass into the polycrystalline material known as “glass-ceramic”, the coefficient of expansion of which is zero or virtually zero and which withstands a thermal shock which can range up to 700° C. The ceramization generally comprises a stage in which the temperature is gradually raised up to the nucleation range, generally located in the vicinity of the range of transformation of the glass, a stage of passing through the nucleation interval in several minutes, a further gradual rise in the temperature up to the temperature of the ceramization stationary phase, the maintenance of the temperature of the ceramization stationary phase for several minutes and then a rapid cooling down to ambient temperature.

[0048] The paint selected according to the invention is preferentially applied (in one or more layers, preferably one layer), rapidly and simply, by screen printing (in the form in particular of solid tone(s), with, if appropriate, clear spaces in the display zone) on the glass-ceramic substrate (this deposition being carried out after the optional ceramization of the substrate), advantageously on the lower face of said substrate, in the appropriate zones (with regard to the radiant zone(s), for example).

[0049] Preferably, the screen-printing screen used, composed, for example, of fabrics of polyester or polyamide yarns, is chosen so as to exhibit a number of yarns per cm of between 32 and 43 yarns per cm, thus making it possible to obtain a particularly appropriate thickness and definition of the paint coating.

[0050] The paint, once deposited, is dried (for example a few minutes at 160° C.) and fired (off-line) on the ceramized substrate, at temperatures of between 350 and 480° C. for from 40 to 60 min approximately, the final paint coating obtained forming a layer based on polymers.

[0051] If appropriate, the process also comprises a cutting operation (generally before ceramization), for example using a jet of water, mechanical marking using a cutting wheel, and the like, followed by a shaping operation (grinding, beveling, and the like).

[0052] A better understanding of the present invention and its advantages will be obtained on reading the comparative examples which follow, given solely by way of illustration and without limitation, the glass-ceramic substrate used being a transparent substrate as defined in the document EP 0 437 228.

[0053] Example 1 according to the invention:

[0054] The paint used is prepared by mixing: [0055] 30% by weight of silicone resin of methyl/phenyl type sold under the reference RSN-0249 by Dow Corning, [0056] 20% by weight of black pigments based on iron and manganese oxide, the size distribution of which is less than 0.5 μm, these pigments being sold under the reference PBk 26.77494 by Kremer, [0057] 10% by weight of fillers in the form of (particles of) lamellar micas with a thickness of less than 2 μm, these fillers/mica(s) exhibiting a D80 of 15 μm and being sold under the reference Ronaflair Mica M by Merck, [0058] 8% by weight of (fillers in the form of) talc sold by Imerys, these talc particles being of lamellar shape and with a thickness of less than 2 μm and exhibiting a D80 of 30 μ, [0059] 1% by weight of dispersant of reference Disperbyk 103 from Byk, [0060] 1% by weight of air-release agent of reference Byketol OK from Byk, [0061] 30% by weight of solvent of naphtha type sold under the reference Solvesso 100 by Exxon.

[0062] The paint is subsequently applied by screen printing with a mesh of reference 32 (32 yarns per cm) to the substrate and then dried at 160° C. for 4 minutes. It is subsequently fired using a heat treatment from 350° C. to 450° C. for 45 minutes.

[0063] Example 2 according to the invention:

[0064] The paint used is prepared by mixing: [0065] 30% by weight of silicone resin of methyl/phenyl type sold under the reference KR-282 by Shin-Etsu, [0066] 20% by weight of black pigments based on copper, chromium and manganese oxide, the size distribution of which is 0.6 μm, these pigments being sold under the reference 42-303B by Tomatec, [0067] 10% by weight of fillers in the form of particles of lamellar micas with a thickness of less than 2 μm and exhibiting a D80 of 60 μm, sold under the reference Iriodin 600 by Merck, [0068] 8% by weight of (fillers in the form of) talc sold by Imerys, these talc particles being of lamellar shape and with a thickness of less than 2 μm and exhibiting a D80 of 30 μm, [0069] 1% by weight of dispersant of reference Disperbyk 103 from Byk, [0070] 1% by weight of air-release agent of reference Byketol OK from Byk, [0071] 30% by weight of solvent of naphtha type sold under the reference Solvesso 100 by Exxon.

[0072] The paint is subsequently applied by screen printing with a mesh of reference 32 to the substrate and then dried at 160° C. for 4 minutes. It is subsequently fired using a heat treatment from 350° C. to 450° C. for 45 minutes.

[0073] Reference example 1 not in accordance with the invention:

[0074] The paint used is prepared by mixing: [0075] 35% by weight of silicone resin of methyl/phenyl type sold under the reference RSN-0249 by Dow Corning, [0076] 25% by weight of black pigments based on copper, chromium and manganese oxide, the size distribution of which is 0.6 μm, these pigments being sold under the reference 42-303B by Tomatec, [0077] 8% by weight of (fillers in the form of) talc sold by Imerys, these talc particles being of lamellar shape and with a thickness of less than 2 μm and exhibiting a D80 of 8 μm, [0078] 1% by weight of dispersant of reference Disperbyk 103 from Byk, [0079] 1% by weight of air-release agent of reference Byketol OK from Byk, [0080] 30% by weight of solvent of naphtha type sold under the reference Solvesso 100 by Exxon.

[0081] The paint is subsequently applied by screen printing with a mesh of reference 32 to the substrate and then dried at 160° C. for 4 minutes. It is subsequently fired using a heat treatment from 350° C. to 450° C. for 45 minutes.

[0082] Reference example 2 not in accordance with the invention:

[0083] The paint used is prepared by mixing: [0084] 35% by weight of silicone resin of methyl type sold under the reference KR-220L by Shin-Etsu, [0085] 20% by weight of black pigments of reference PBk 26.77494 sold by Kremer, based on iron and manganese oxide, the size distribution of which is less than 0.5 μm, [0086] 13% by weight of (fillers in the form of) talc sold by Imerys, these talc particles being of lamellar shape and with a thickness of less than 2 μm and exhibiting a D80 of 8 μm, [0087] 1% by weight of dispersant of reference Disperbyk 103 from Byk, [0088] 1% by weight of air-release agent of reference Byketol OK from Byk, [0089] 30% by weight of solvent of naphtha type sold under the reference Solvesso 100 by Exxon.

[0090] The paint is subsequently applied by screen printing with a mesh of reference 32 to the substrate and then dried at 160° C. for 4 minutes. It is subsequently fired using a heat treatment from 350° C. to 450° C. for 45 minutes.

[0091] A sample of each glass-ceramic provided with each paint is subsequently placed on a heating element. The temperature measured at the coating is 260° C. (corresponding to the temperature experienced by the coating during the cooking of food of sausages type). Several heating cycles of 15 minutes at 260° C., followed by cooling down to ambient temperature, are subsequently carried out (total duration of each cycle of 20 minutes).

[0092] It is observed that the paint in the examples according to the invention withstands at least 1500 heating cycles without splitting or exhibiting cracks or delaminating, whereas, in the reference comparative examples, the paint splits/exhibits cracks and delaminates after 100 cycles. Furthermore, the paint of the examples according to the invention is particularly black (with an L*<5) and adheres well to the glass-ceramic substrate, the scratch tests according to the standards ISO 15184 and ISO 1518-1 respectively giving a resistance to a 2B pencil and a resistance to a force of at least 1N.

[0093] The articles, in particular plates, according to the invention can in particular be used with advantage to produce a novel range of cooktops for kitchen ranges or cooking surfaces or a novel range of work tables, consoles, central islands, and the like.