PROCESS FOR MANUFACTURING A GLASS SUBSTRATE EQUIPPED WITH PRINTED PATTERNS AND A PROTECTIVE UNDERLAYER FOR ONE-WAY VISION

Abstract

The present invention relates to a process for manufacturing a one-way vision glass pane comprising one or more separate enamel patterns composed of a number of exactly aligned layers, characterized in that:

a) at least one protective layer based on oxides, having a thickness greater than or equal to 10 nm, is deposited on the glass substrate,
b) at least two layers of different compositions are deposited on the protective layer, the composition of one containing at least one mineral pigment and being free of glass frit, the composition of the other being an enamel containing at least one glass frit and at least one mineral pigment having a color different from that of the layer free of glass frit, the layer free of glass frit being deposited over all or some of the surface of the pane and the layer of enamel being deposited by screen printing in the shape of the desired pattern(s),
c) the pane coated with said layers is heated at a temperature sufficient to fire the enamel, and
d) the pigments not fixed by the enamel that are located outside of the pattern(s) are removed, the particles of pigment(s) and the particles of glass frit(s) having a similar size, in particular a particle size distribution such that 50% of the particles have a size of less than 7 m.

Claims

1. A process for manufacturing a one-way vision glass pane comprising one or more separate enamel patterns which comprise a number of exactly aligned layers, the process comprising: (a) depositing at least one protective layer based on an oxide and having a thickness greater than or equal to 10 nm on a glass substrate, (b) depositing at least two layers of different compositions on the at least one protective layer, the at least two layers comprising a layer that comprises at least one mineral pigment which layer is free of glass frit, the at least two layers further comprising a layer that comprises an enamel that comprises at least one glass frit and at least one mineral pigment having a color different from that of the layer free of glass frit, wherein the layer free of glass frit is deposited over all or some of a surface of the pane and the layer of enamel is deposited by screen printing in a shape of a desired pattern, thereby obtaining a pane coated with at least three layers, (c) heating the pane coated with said at least three layers at a temperature sufficient to fire the enamel, and (d) removing a portion of pigments not fixed by the enamel located outside of the pattern, thereby obtaining the one-way vision glass pane comprising one or more separate enamel patterns which comprise a number of exactly aligned layers, wherein particles of the pigments and particles of the at least one glass frit have a similar size.

2. The process of claim 1, wherein the layer free of glass frit is deposited on the protective layer over a thickness of between 4 and 15 m, then the layer of enamel is deposited by screen printing over a thickness of between 10 and 100 .m.

3. The process of claim 1, wherein the layer of enamel is deposited on the protective layer over a thickness of between 10 and 100 m, then the layer free of glass frit is deposited over a thickness of between 4 and 30 m.

4. The process of claim 1, wherein the protective layer deposited in the depositing (a) is a layer of silicon oxide or of titanium oxide.

5. The process of claim 4, wherein the protective layer is a layer of silicon oxide deposited by magnetron sputtering.

6. The process of claim 1, wherein the thickness of the at least one protective layer is between 10 and 150 nm.

7. The process of claim 1, wherein the depositing (a) comprises depositing two successive protective layers of different nature and thickness.

8. The process of claim 1, wherein the at least one mineral pigment in the layer free of glass frit is capable of imparting a black color after drying.

9. The process of claim 8, wherein the at least one pigment in the layer free of glass frit is based on chromium, iron, manganese, copper and/or cobalt, optionally as an oxide and/or sulfide.

10. The process of claim 1, wherein the glass frit is free of lead oxide PbO.

11. The process of claim 10, wherein the glass frit is a borosilicate based on bismuth oxide Bi.sub.2O.sub.3 and/or zinc oxide ZnO.

12. The process of claim 10, wherein the glass frit has a content of 35 to 75 wt % of SiO.sub.2 and 20 to 40 wt % of Bi.sub.2O.sub.3 and optionally 25 to 30 wt % of ZnO.

13. The process of claim 11, wherein the glass frit comprising Bi.sub.2O.sub.3 if present has a softening point of from 550 to 580 C., and/or the frit comprising ZnO if present has a softening point below 600 C.

14. The process of claim 1, wherein the at least one mineral pigment of the enamel layer has a different color from the at least one mineral pigment in the layer free of glass frit.

15. The process of claim 14, wherein the at least one mineral pigment of the enamel layer is capable of imparting a white color after drying.

16. The process of claim 14, wherein the at least one mineral pigment in the enamel layer has a color other than white.

17. The process of claim 1, wherein a proportion of pigments in the composition of the enamel is from 5 to 25 wt %.

18. The process of claim 1, wherein pigment particles and particles of the at least one glass frit have a particle size distribution such that 50% of the particles have a size of less than 7 m.

19. The process of claim 14, wherein the at least one mineral pigment of the enamel layer comprises TiO.sub.2, Cr.sub.2O.sub.3, Co.sub.3O.sub.4, or Fe.sub.2O.sub.3.

Description

[0037] The invention is illustrated by means of the following nonlimiting examples and the attached figures in which:

[0038] FIG. 1 represents a PLANILUX float glass on which a black pigment has been deposited and which has undergone a firing at temperatures varying between 600 and 700 C.

[0039] FIG. 2 represents various PLANILUX float glass substrates on which a protective layer of silicon oxide has optionally been deposited with various thicknesses.

[0040] FIG. 3 represents a pattern printed on a PLANILUX float glass substrate with or without a protective layer.

[0041] FIG. 4 represents various PLANILUX float glass substrates on which a layer of silicon oxide has been deposited by various methods then coated with black pigments.

EXAMPLE 1

[0042] A chromium-free black pigment is deposited by the screen-printing process using a 150.27 screen (150 being the number of filaments/cm and 27 being the thickness in pm of the polyester filament forming the screen) on a PLANILUX glass substrate. The thickness deposited is 6 m: it is measured using a laser perthometer just after the screen-printing step and before the drying at 140 C. Next, this substrate covered with black pigment is fired in a gradient furnace at temperatures between 600 and 700 C., and then the fired glass is cleaned.

[0043] The photo of the substrate obtained after firing and cleaning is given in FIG. 1.

[0044] A color gradient is clearly observed that is linked to the migration of the pigment toward the substrate, which migration is larger or smaller depending on the temperature.

[0045] Equivalent tests were carried out on substrates coated with a protective layer based on silicon oxide deposited with a greater or lesser thickness. FIG. 2 is a photo in which four different samples were tested.

[0046] Sample A corresponds to that which was represented in FIG. 1, as explained above. Sample B corresponds to a PLANILUX glass substrate on which a layer of silica having a thickness of 20 nm was deposited by magnetron sputtering before depositing a black mineral pigment and carrying out a firing of the substrate thus prepared in a gradient furnace between 600 and 700 C. Sample C is identical to sample B except for the difference that the silica layer is thicker (around 25 nm). Sample D is identical to samples B and C except for the difference that the protective layer made of silica has a thickness of 70 nm. The step of depositing the black pigment is carried out under the same experimental conditions as those described above for sample A.

[0047] By comparing these various samples it is observed that the effect of the protective layer is significant: even for a thin silica layer, the gray tint decreases markedly and only appears more faintly for high firing temperatures. By increasing the thickness of the protective layer, the gray tint disappears completely even at a high firing temperature of the order of 700 C.

EXAMPLE 2

[0048] FIG. 3 represents a printed pattern according to the process of the present invention, with or without a protective layer made of silica.

[0049] A layer of black pigment was deposited by screen printing on two different substrates 2a and 2b; the substrate 2a corresponding to a clear glass pane and the substrate 2b corresponding to a clear glass pane on which a 25 nm layer of silica was deposited by magnetron sputtering.

[0050] The screen-printing screen used is a 150.27 screen (150 filaments/cm and filaments of 27 m). The mean thickness of the (wet) layer of black pigments deposited on the glass is equal to 6 m. The glasses were then introduced into a drying device equipped with infrared lamps operating at a temperature of the order of 145 to 155 C. in order to remove the organic medium.

[0051] The pattern representing the person visible in FIG. 3 was then deposited by screen printing also on the two glasses containing the black pigment. The enamel used is white and is composed of a frit based on bismuth oxide and pigment based on titanium oxide. After drying of the enamel at a temperature between 145 and 155 C., the glasses were fired at a uniform standard tempering temperature (around 655 C.).

[0052] The pigments that were not fixed were removed by brushing and washing in water. The tinting of the glass was prevented with the aid of the SiO.sub.2 protective layer previously deposited on one of the substrates.

EXAMPLE 3

[0053] A black mineral pigment was printed on various glasses coated with a layer containing SiO.sub.2; the process used being the same as in example 1.

[0054] The layers used were deposited by various processes (magnetron sputtering (A), chemical vapor deposition (B) CVD and also a combination of these two techniques (C)).

[0055] FIG. 4 represents the 3 types of layer-coated glasses on which the black pigment was deposited. The glasses were then washed and fired at a temperature of 650 C.

[0056] These various layer-coated glasses (having a layer containing SiO.sub.2) have indeed made it possible to prevent the migration of the black pigment to the surface of the glass.