METHOD FOR MANUFACTURING THIN GLASS

Abstract

The invention relates to a process for manufacturing flat glass, comprising the following successive steps: (a) applying a layer of a glass frit to a glass textile, the glass of the frit and of the textile having essentially the same composition, (b) heating the glass textile bearing the layer of glass frit to a temperature T>T.sub.L20 C., T.sub.L being the Littleton temperature of the glass frit, for a sufficient length of time to convert the layer of frit into an enamel layer of the same composition as the glass textile, and (c) cooling the glass textile impregnated with the enamel or bearing an enamel layer, obtained in step (b), so as to obtain a glass sheet.

It also relates to a glass sheet capable of being obtained by this process.

Claims

1. A process for manufacturing flat glass, the process comprising: (a) applying a layer of a glass frit comprising a glass powder to a glass textile, the glass of the glass powder and of the glass textile having essentially the same composition, (b) heating the glass textile bearing the layer of glass frit to a temperature T>T.sub.L20 C., wherein T.sub.L is the Littleton temperature of the glass powder, thereby converting the layer of frit into an enamel layer of the same composition as the glass textile and thereby obtaining a glass textile impregnated with the enamel or bearing an enamel layer, and (c) cooling the resulting glass textile impregnated with the enamel or bearing an enamel layer, thereby obtaining a glass sheet.

2. The process of claim 1, wherein the applying (a) is carried out by screen printing, spiral rod coating, coating with a doctor blade or a bar coater, roll coating, or slot coating.

3. The process of claim 1, wherein the heating temperature T is at least equal to T.sub.L.

4. The process of claim 1, wherein the heating (b) comprises, throughout the heating, subjecting the glass textile to a tensile force in at least one direction in the plane of the glass textile, and wherein the process further comprises maintaining the tensile force during the cooling (c) at least until the glass sheet has stiffened.

5. The process of claim 1, wherein the glass textile has a weight per unit area of between 30 and 500 g/m.sup.2.

6. The process of claim 1, wherein the amount of glass powder applied from 100 to 2000 g/m.sup.2.

7. The process of claim 1, wherein the glass textile has apertures with an average equivalent diameter smaller than 1 mm.

8. The process of claim 1, wherein the glass textile is a woven having a number of warp threads and/or a number of weft threads of between 3 and 100/cm.

9. The process of claim 1, wherein the glass textile is a nonwoven.

10. The process of claim 1, wherein the hot glass textile impregnated with the enamel or bearing an enamel layer obtained in the heating (b) does not make contact with any solids or liquids before cooling to a temperature at least 50 C. lower than T.sub.L.

11. A glass sheet obtained by the process of claim 1.

12. The glass sheet as claimed in claim 11, having a thickness of between 50 m and 1000 m.

13. The glass sheet of claim 11, wherein the structure of the glass textile is visible to the naked eye.

14. The process of claim 1, wherein the glass frit comprises from 50 to 90% by weight of a glass powder, and from 10 to 50% by weight of an organic polymer dissolved in a solvent.

15. The process of claim 14, wherein the heating (b) comprises: heating the glass textile bearing the layer of glass frit at a first temperature of from 100 C. to 200 C., thereby evaporating the solvent, heating the resulting glass textile bearing the layer of glass frit at a second temperature of from 350 to 450 C., thereby eliminating the organic polymer, and heating the resulting glass textile bearing the layer of glass frit at a third temperature T higher than the second temperature and higher than T.sub.L20 C., thereby melting the glass powder.

16. The process of claim 1, wherein the heating (b) does not comprise devitrification.

17. The process of claim 1, wherein the heating temperature T is between T.sub.L20 C. and T.sub.L+20 C.

Description

EXAMPLE 1

[0046] A mat of E glass is coated with a glass paste consisting of a dispersion of E-glass powder of particle size smaller than 63 m in an organic solvent, using a bar coater.

[0047] The composition of the glass of the textile and of the frit used for this example is the following:

TABLE-US-00001 oxide SiO.sub.2 Al.sub.2O.sub.3 CaO MgO SrO B.sub.2O.sub.3 Na.sub.2O K.sub.2O TiO.sub.2 F Fe.sub.2O.sub.3 SO.sub.3 wt % 54.75 14.4 22.5 0.5 0.15 5.75 0.35 0.5 0.35 0.4 0.3 0.01

[0048] The glass textile is a glass mat formed from 166 warp threads (68 den) per 10 cm and 124 weft threads per 10 cm. Its weight per unit area is 205 g/m.sup.2 and its thickness about 170 m.

[0049] After coating, the coated textile is dried for 30 minutes at 120 C. The thickness of the dried film is 400 m. The textile is then fixed to a refractory frame and annealed in an oven at 860 C. for 40 minutes. After cooling to room temperature, the film shown in FIG. 1 is obtained. Its final thickness is 200 m. The surface preserves the imprint of the initial texture of the textile and weakly scatters light. The film forms a gas-tight barrier.

[0050] FIG. 2 is a cross-sectional view taken by electron microscopy of the textile after coating and before baking: the grains of the coating and the fibers of the textile are distinctly visible.

[0051] FIG. 3, also a cross-sectional view obtained by electron microscopy, shows the structure of the film obtained after baking. It is no longer possible to see the fibers and the grains. The result is a film that is impermeable to gas, containing a few rare closed pores.

Example 2

[0052] Example 1 is repeated, with the same type of E-glass textile and the same E-glass frit, the only difference being that the sample is of larger size (about 150 cm.sup.2 instead of 20 cm.sup.2 for example 1). After coating, and drying of the coated textile for 30 minutes at 120 C., the bake is carried out for 20 minutes at 870 C. in an oven.

[0053] FIG. 4 shows the solidified film obtained.