METHOD FOR OBTAINING A LAMINATED CURVED GLAZING

Abstract

A method for obtaining a laminated curved glazing, includes a. providing a first glass sheet, covered on at least part of one of its faces with a stack of thin layers, b. depositing, on a part of a surface of the stack of thin layers, a layer of enamel, the deposition being carried out by screen-printing an enamel composition including refractory particles having a diameter of at least 20 m in a proportion by volume of at least 0.5%, but no particles having a diameter greater than 80 m, c. bending the first glass sheet, the stack of thin layers located under the enamel layer being completely dissolved by the enamel layer at least at the end of the bending, and then d. laminating the first glass sheet with an additional glass sheet with an lamination interlayer, so that the enamel layer faces the interlayer.

Claims

1. A method for obtaining a laminated curved glazing, comprising the following successive steps: a. providing a first glass sheet, covered on at least part of one of its faces with a stack of thin layers, b. depositing, on a part of a surface of the stack of thin layers, a layer of enamel, the deposition being carried out by screen-printing an enamel composition comprising refractory particles having a diameter of at least 20 m in a proportion by volume of at least 0.5%, but no particles having a diameter greater than 80 m, c. bending the first glass sheet, the stack of thin layers located under the enamel layer being completely dissolved by said enamel layer at least at the end of the step of bending, and then d. laminating said first glass sheet with an additional glass sheet with an lamination interlayer, so that the enamel layer faces said interlayer.

2. The method according to claim 1, wherein the stack of thin layers comprises at least one functional layer.

3. The method according to claim 2, wherein the electrically conductive functional layer is a metal layers and a layers of a transparent conductive oxide.

4. The method according to claim 1, wherein after step d, the enamel layer is opaque, has a black hue, and forms a strip at the periphery of the first glass sheet.

5. The method according to claim 1, wherein the refractory particles are based on metal oxides or metals.

6. The method according to claim 5, wherein the metal oxides are simple oxides or complex oxides.

7. The method according to claim 6, wherein the refractory particles are zirconia-based.

8. The method according to claim 1, wherein the refractory particles are black.

9. The method according to claim 1, wherein an average sphericity of the refractory particles is greater than 0.60.

10. The method according to claim 1, wherein the deposition of the enamel layer is carried out by screen printing using a screen printing screen having an aperture size of at least 40 m.

11. The method according to claim 1, wherein: the method comprises between step b) and step c) a step b1) of pre-firing the enamel layer during which the thin layer stack located under the enamel layer is at least partially dissolved by said enamel layer, and in step c) the first glass sheet and the additional glass sheet are curved together with the enamel layer facing said additional glass sheet.

12. The method according to claim 1, wherein the additional glass sheet has a thickness of between 0.5 and 1.2 mm.

13. The method according to claim 1, wherein the additional glass sheet carries, on the face opposite the face facing the lamination interlayer, an additional stack of thin layers.

14. A laminated curved glazing, in particular for a windscreen or roof of a motor vehicle, obtainable by the method of claim 1, comprising a first glass sheet coated on at least part of one of its faces with a stack of thin layers, said first glass sheet being coated on part of its surface with an enamel layer comprising refractory particles having a diameter of at least 20 m in a proportion by volume of at least 0.5%, said first glass sheet being laminated with an additional glass sheet with an lamination interlayer, said enamel layer facing said lamination interlayer.

15. An enamel composition for carrying out the method according to claim 8, comprising a zinc bismuth borosilicate-based glass frit, at least one pigment and at least 0.5% by volume of black refractory particles having a diameter of at least 20 m, but not comprising particles having a diameter greater than 80 m.

16. The method according to claim 1, wherein the laminated curved glazing is a windscreen or roof of a motor vehicle.

17. The method according to claim 2, wherein the at least one functional layer is an electrically conductive functional layer.

18. The method according to 3, wherein the metal layer is a silver or niobium layer and the layer of a transparent conductive oxide is a layer of indium tin oxide, doped tin oxide, or doped zinc oxide.

19. The method according to claim 6, wherein the simple oxides are aluminum oxide, titanium oxide or zirconium oxide and the complex oxides are high-melting glass frits or inorganic pigments.

20. The method according to claim 9, wherein an average sphericity of the refractory particles is greater than 0.70.

Description

EXAMPLES

[0096] The example embodiments which follow illustrate the invention in a non-limiting manner, in connection with FIG. 1.

[0097] FIG. 1 schematically illustrates an embodiment of the method according to the invention. It shows a schematic cross-section of a portion of the glass sheets and the elements deposited on the glass sheets near their periphery. The various elements are obviously not represented to scale, so that they can be visualized.

[0098] The first glass sheet 10 coated with the thin film stack 12 is provided in step a, and then part of the stack 12 is coated with an enamel layer 14, in particular by screen printing (step b).

[0099] The assembly then undergoes a pre-firing (step b1), which in the illustrated case leads to a partial dissolution of the stack 12 by the enamel 14.

[0100] An additional glass sheet 20, herein provided with a further thin layer stack 22, is then placed on the first glass sheet 10, the assembly then being curved (step c). As the view shown is only from the end of the glass sheet, the curvature is not shown here. The diagram illustrates that, after bending, the enamel 14 has completely dissolved the underlying thin layer stack 12.

[0101] In step d, the first glass sheet 10 coated with the thin film stack 12 and the enamel layer 14 and the additional glass sheet 20 coated with the additional stack 22 are joined together with the aid of the laminating interlayer 30. The diagram shows each of the elements separately, in exploded view.

[0102] The method used in the examples corresponds to the embodiment shown in FIG. 1.

[0103] Glass sheets 2.1 mm thick, coated beforehand by cathode sputtering of a stack of thin layers comprising three silver layers protected by zinc oxide layers, silicon nitride layers and NiCr blockers, were coated by screen printing with enamel layers with a wet thickness of 25 m.

[0104] The enamel composition included large refractory oxide particles larger than 20 m.

[0105] Two types of particles were used: particles marked A in the table below, which are white and irregularly shaped, and particles marked B in the table below, which are zirconia-based, black, and more rounded in shape than the A particles. Particles B were black zirconia granules marketed under the name ColorYZe G Black by Saint-Gobain Zirpro, calcined at a temperature of 1300 C.

[0106] Particles B had the following chemical composition (by weight): ZrO.sub.2: 89.6%, Y.sub.2O.sub.3: 5.26%, Al.sub.2O.sub.3: 1.05%, black pigments: 4.1%. The particle size distribution by volume was as follows: D10=40 m, D50=49 m, D90=60 m.

[0107] Table 1 below shows the proportion by volume of these particles for each test, noted as % vol.

[0108] The enamel layer was deposited using a screen with a mesh aperture size of 71 m (screen 1) or 49 m (screen 2), depending on the example.

[0109] The enamel was then dried (150 C., 1 to 2 minutes) and pre-fired at approximately 650 C.-680 C.

[0110] After pairing with an additional glass sheet of soda-lime glass with a stack comprising an ITO layer on face 4, the assembly was curved at over 600 C. for 350 to 500 seconds.

[0111] After firing, the appearance, more particularly the black color viewed from face 1, was evaluated by measuring the lightness L* in reflection (illuminant D65, reference observer 10). A value less than or equal to 6.0, preferably less than 5.0, is considered acceptable. The haze (from face 1 of the glazing) and bonding were assessed qualitatively by visual observation.

[0112] For bonding, a scale of 0 to 5 was used, where a score of 0 means no defects, a score of 1 means limited enamel transfer in the corners, a score of 2 means enamel transfer in the corners and sides, a score of 3 means bonding in the corners, a score of 4 means bonding in the corners and sides, and a score of 5 means total bonding. A score higher than 3 is not acceptable.

TABLE-US-00001 TABLE 1 Part. % vol Screen Thickness (m) L* Haze Bonding C0 0 1 14.0 5.1 5 C1 A <0.5%.sup. 1 14.0 5.8 4 C2 A* 1 N/A 1 A 2% 1 14.0 4.6 + 1 2 A 2% 2 11.9 5.0 + 2 3 B 3% 1 14.0 4.5 0 4 B 3% 1 14.0 4.8 0

[0113] The comparative example C0 shows that the absence of large refractory particles results in complete bonding. In the case of comparative example C1, the addition of refractory particles, but in too small quantities, does not sufficiently reduce bonding. In the case of example C2, the presence of refractory particles larger than 80 m did not allow the enamel layer to be deposited by screen printing.

[0114] The addition of the refractory particles A (examples 1 and 2) reduces this bonding, especially as the proportion of coarse particles and the mesh aperture size of the screen printing screen are large, but generate a slight haze.

[0115] In the case of examples 3 and 4, the B particles, which are black and more spherical than the A particles, made it possible to achieve a lack of bonding while reducing the haze.