METHOD FOR OBTAINING A CURVED LAMINATED GLAZING UNIT

Abstract

A method for obtaining a curved laminated glazing unit, includes applying an enamel coating to a part of a first face of a first glass sheet so as to create at least one enameled zone and at least one unenameled zone, applying a sacrificial layer to a part, called the sacrificial zone, of a first face of a second glass sheet, simultaneously bending the first and second glass sheets, the sacrificial zone being disposed at least in line with at least one part of an enameled zone, removing the sacrificial layer, either during the bending or after the bending step, and laminating the first and second glass sheets by a thermoplastic interlayer.

Claims

1. A method for obtaining a curved laminated glazing unit possessing a concave side and a convex side, said glazing unit comprising a glass sheet, forming an internal glass sheet, disposed to the concave side of the glazing unit and bonded adhesively by a thermoplastic interlayer with another glass sheet, forming an external glass sheet, disposed to the convex side of the glazing unit, said method comprising: applying an enamel coating to a part of a first face of a first glass sheet so as to create at least one enameled zone and at least one unenameled zone, applying a sacrificial layer to a part of a first face of a second glass sheet, said part of the first face of the second glass sheet forming a sacrificial zone, simultaneously bending the first and second glass sheets, the first and second glass sheets being disposed during bending so that one of the first and second glass sheets is disposed on the other one of the first and second glass sheets, the respective first faces of each of the first and second glass sheets are oriented toward the concave side of the glazing unit, and the sacrificial zone is disposed at least in line with at least one part of an enameled zone, removing said sacrificial layer, either during bending or after the bending step, laminating the first and second glass sheets with a thermoplastic interlayer.

2. The method as claimed in claim 1, wherein the internal glass sheet is the first glass sheet.

3. The method as claimed in claim 1, wherein the external glass sheet is the first glass sheet.

4. The method as claimed in claim 1, wherein the enameled zone takes the form of a peripheral strip.

5. The method as claimed in claim 1, wherein the enamel coating is applied from a fluid enamel composition comprising a glass frit, pigments, and an organic medium.

6. The method as claimed in claim 1, wherein the sacrificial zone is disposed in line with a camera zone.

7. The method as claimed in claim 1, wherein the sacrificial layer is applied by screen printing, digital printing, by pad printing or by roll coating, curtain coating or spray coating.

8. The method as claimed in claim 1, wherein the sacrificial layer absorbs a part of the infrared radiation.

9. The method as claimed in claim 8, wherein the sacrificial layer comprises pigments.

10. The method as claimed in claim 1, wherein the sacrificial layer comprises a resin and refractory mineral compounds, the sacrificial layer being removed after the bending step.

11. The method as claimed in claim 1, wherein the sacrificial layer comprises a resin and combustible mineral compounds, the sacrificial layer being removed simultaneously with the bending.

12. The method as claimed in claim 1, further comprising, before the bending step, a prebaked treatment of the enamel.

13. The method as claimed in claim 1, wherein the glazing unit is an automotive windshield.

14. The method as claimed in claim 1, wherein at least one sensor is disposed on the internal glass sheet opposite an unenameled zone surrounded by a part of the enameled zone.

15. The method as claimed in claim 14, wherein said at least one sensor is a camera.

16. The method as claimed in claim 9, wherein the pigments are black pigments, or carbon black pigments.

17. The method as claimed in claim 10, wherein the sacrificial layer is removed by washing and/or brushing.

18. The method as claimed in claim 15, wherein said camera is a visible and/or infrared camera.

19. method as claimed in claim 15, wherein the camera is a thermal camera or a Lidar.

Description

[0075] The exemplary embodiment which follows demonstrates the advantages of the invention.

[0076] A first glass sheet was coated by screen printing, over half of its first face, with a black enamel coating. A second glass sheet was then disposed on top of the first glass sheet, the two sheets then being heat treated by being placed in an oven heated to a temperature of 710° C. for a duration of 180 seconds. The change in the temperature of the glass (measured by thermocouples situated on the first glass sheet) in the enameled zone (T1) and in the unenameled zone (T2) were measured.

[0077] In test 1A, the first face of the second glass sheet (turned upward during the heat treatment) was coated beforehand by screen printing with a composition consisting of an organic medium and black mineral pigments based on oxides of copper (37% by mass), of iron (17% by mass) and of manganese (46% by mass). The wet thickness was 15 μm. In this example, the heat treatment enabled the sacrificial layer to be removed by combustion of the resin, leaving the pigments on the surface of the second glass sheet, which were subsequently removed by washing.

[0078] In test 1B (comparative), no sacrificial layer was applied.

[0079] FIG. 2 presents the temperature difference T1-T2 as a function of the temperature T1.

[0080] The results show that the sacrificial layer on the second glass sheet enables a sharp reduction in the temperature difference at high temperature between the enameled and unenameled zones, the difference being 10° C. at most as an absolute value in the case of example 1A, while possibly being up to more than 35° C. in the absence of a sacrificial layer.