METHOD FOR OBTAINING GLAZINGS PROVIDED WITH ELECTROCONDUCTIVE PATTERNS

Abstract

A method for obtaining a glazing includes a glass sheet covered, on one of its faces with electroconductive patterns having in at least one area, a so-called extra thickness area, a greater thickness than in the other areas, the method including depositing by screenprinting a first electroconductive layer forming patterns on one side of the glass sheet, then depositing by a digital printing technique, in the or each extra thickness area, a second electroconductive layer on the first layer while the latter is still wet, then a heat treatment step to cure the first and the second layer.

Claims

1. A method for obtaining a glazing comprising a sheet of glass covered on a face thereof with electroconductive patterns having in at least one area, forming an so called extra thickness area, a greater thickness than in other areas of said face, said method comprising depositing by screenprinting a first electroconductive layer forming patterns on said face of said glass sheet, followed by depositing by a digital printing technique, in the at least one extra thickness area, a second electroconductive layer on the first electroconductive layer while the first electroconductive layer is still wet, then performing a heat treatment step to cure the first and second electroconductive layers.

2. The method according to claim 1, wherein the electroconductive patterns comprise electroconductive tracks located in at least one lateral portion and in a central portion of the glazing, with the extra thickness areas being located in said central portion and/or in at least one lateral portion.

3. The method according to claim 2, wherein the extra thickness areas are located in the central portion and in the lateral portions.

4. The method according to claim 1, comprising, before depositing the first electroconductive layer, a prior step of depositing by screenprinting a black enamel coating at an edge of the glass sheet, on which part of the electroconductive patterns is deposited.

5. The method according to claim 1, wherein the digital printing technique.

6. The method according to claim 1, wherein the electroconductive patterns are formed from a silver paste.

7. The method according to claim 1, that wherein the thickness of the electroconductive patterns in the at least one extra thickness areas is at least 8 μm after the curing heat treatment step.

8. The method according to claim 1, wherein a drying step is implemented between the step of depositing the second electroconductive layer and the curing heat treatment step.

9. The method according to claim 1, wherein the extra thickness area encompasses or corresponds to a soldering areas.

10. The method according to claim 9, further comprising an extra step of soldering at least one connector to at least one part of an extra thickness area.

11. The method according to claim 10, wherein the connector is metallic and the soldering is carried out using a tin-based, silver-based or copper-based soldering alloy.

12. A glazing obtained by the method according to claim 1, comprising said glass sheet covered with silver-based electroconductive patterns on said face and having in said at least one area, forming the extra thickness area, said greater thickness than in the other areas.

13. The glazing according to claim 12, wherein the thickness of the patterns in at least one extra thickness area is at least 8 μm.

14. The glazing according to claim 13, wherein the thickness of the patterns in areas other than the extra thickness area is 8 μm at most.

15. The glazing according to claim 12, which is a rear window of a motor vehicle, a side window of a motor vehicle or a windshield of a motor vehicle, with the electroconductive patterns notably being antennae, bus bars, alarm wires and/or heating wires, and the at least one extra thickness area encompassing or being a soldering area for connecting an antenna and/or a heating network and/or an alarm network.

16. The method according to claim 5, wherein the transfer printing is laser transfer.

17. The method according to claim 6, wherein the silver paste comprises in its wet state a maximum of 88% by weight of silver.

18. The method according to claim 7, wherein the thickness of the electroconductive patterns in the at least one extra thickness area is between 10 and 20 μm after the curing heat treatment step.

19. The method according to claim 10, wherein the at least one connector is soldered onto the soldering areas.

20. The method according to claim 11, wherein the connector is made of steel containing chrome.

Description

[0057] The following example embodiments, illustrated in FIG. 1, will serve to make the invention easier to understand.

[0058] FIG. 1 shows a glazing obtained according to the invention; in the example, a rear window of a motor vehicle.

[0059] The glazing 1 comprises a glass sheet 2 having a central portion A and two lateral portions C. In portions A and C, electroconductive patterns 4, 6, 8, 10, more specifically a network of 4 horizontal and vertical heating wires, were printed, connected in the lateral portions C to bus bars 8, an antenna 6, a soldering area for antenna buttons 10. In each lateral portion C, the bus bars 8 comprise a soldering area 12 for powering the heating network. The position of the soldering areas 12, in the low part of the bus bars 8, is represented in the FIGURE by the dotted lines.

[0060] The wires 4 and 6, and the bus bars 8 as well as the antenna button 10 were screenprinted with a silver paste (comprising 80% by weight of silver) on the glass sheet 2, to form a first layer whose wet thickness at the bus bars was 25 μm in the example (giving a thickness of 8 μm after curing). In a previous step, a coating of black enamel (not shown) was deposited by screenprinting on the edge of the glass sheet 2, in the form of a peripheral band. The electroconductive patterns 6, 8 and 10, were therefore deposited on this enamel coating.

[0061] In a second step, while the first layer was still wet, therefore with no intermediate drying step, a second layer was deposited by digital printing by means of laser transfer of a silver paste onto certain areas 10A, 12A of the first layer, shown by a darker color. Area 10A is an area corresponding to a soldering area for connecting antenna 6. Areas 12A are areas located on the bus bars 8 and encompass the soldering areas for connecting the heating network.

[0062] Therefore, the electroconductive patterns have a greater thickness in the extra thickness areas 10A and 12A than in the other areas, because they are composed of the superimposed first and second layers.

[0063] Here, the extra thickness areas 12A are wider than the soldering area 12 proper, and therefore “overflow” beyond this area, in order to prevent unwanted heating in the areas located in the vicinity of the soldering area. In another embodiment, the extra thickness areas 12A may correspond exactly to the soldering areas 12.

[0064] The glass sheet was then subject to bending heat treatment at a temperature of approximately 620° C., a step during which the curing of the first and second layers was also performed.

[0065] After curing, the thickness in the extra thickness areas 10A and 12A was typically of the order of 10 to 15 μm. In the other areas, the thickness was 8 μm.