Method for obtaining a laminated curved glazing

Abstract

A method for obtaining a laminated curved glazing, particularly for a motor vehicle windscreen or roof. The method includes the deposition (b) of an enamel layer on a stack of thin layers deposited on a first glass sheet as well as the deposition (c), at least on the enamel layer, of refractory particles based on oxides, of metals or carbides, at least one dimension of which is larger than 30 ?m. The stack of thin layers is completely dissolved by the enamel layer at the end of a bending procedure (d) carried out before laminating (e) the first glass sheet with an additional glass sheet by a lamination interlayer.

Claims

1. A method for obtaining a laminated curved glazing, comprising: a. providing a first glass sheet, coated on at least part of one of the faces thereof with a stack of thin layers, b. a step of depositing, on part of the surface of the stack of thin layers, an enamel layer, c. a step of depositing, at least on said enamel layer, refractory particles based on oxides, carbides or metals, at least one dimension of which is greater than or equal to 30 ?m, d. a step of simultaneously bending the first glass sheet and an additional glass sheet, with the enamel layer facing said additional glass sheet, e. a step of laminating said first glass sheet with the additional glass sheet by a lamination interlayer, such that the enamel layer is facing said interlayer, said method further comprising a step of pre-firing the enamel layer during which the stack of thin layers located under the enamel layer is at least partially dissolved by said enamel layer, said pre-firing step being either a step b1 performed between step b and step c or a step c1 carried out between step c and step d, the stack of thin layers located under the enamel layer being completely dissolved by said enamel layer at least by the end of step d, wherein the refractory particles are deposited in a mixture with infrared radiation absorbent elements.

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 at least one functional layer is an electrically conductive functional layer that is a metal layer or a layer of a transparent conductive oxide.

4. The method according to claim 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.

5. 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.

6. The method according to claim 1, wherein the refractory particles are based on oxides selected from simple metal oxides and complex oxides, high-melting glass or glass-ceramic frits, or inorganic pigments.

7. Method according to claim 6, wherein the simple metal oxides include aluminum, titanium or zirconium oxide, and the complex oxides include silicates.

8. The method according to claim 1, wherein the refractory particles have at least one dimension greater than or equal to 40 ?m.

9. The method according to claim 8, wherein the at least one dimension is greater than or equal to 60 ?m.

10. The method according to claim 1, wherein the refractory particles are elongated, and have a length/diameter ratio greater than 3.

11. The method according to claim 1, wherein an amount of particles having at least one dimension greater than or equal to 30 ?m is at least 0.1 g/m.sup.2.

12. The method according to claim 1, wherein the refractory particles are deposited on the enamel layer and on areas of the first glass sheet near the enamel layer.

13. The method according to claim 1, comprising between step b and step c, or between step b1 and step c, a step b2 of depositing, solely on the enamel layer, an adhesion layer capable of fixing the refractory particles onto the enamel layer.

14. The method according to claim 13, further comprising, after step c and before step d, a step c2 of removing refractory particles other than those fixed by the adhesion layer.

15. The method according to claim 1, further comprising, between step d and step e a step d1 of removing the refractory particles.

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

17. 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.

18. A laminated curved glazing capable of being obtained by the method of claim 1.

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

20. The method according to claim 1, wherein the infrared radiation absorbent elements include a resin, pigments or carbon black.

Description

EXAMPLES

(1) The following exemplary embodiments illustrate the invention in a non-limiting manner, in connection with FIGS. 1 to 4, wherein:

(2) FIG. 1 schematically illustrates one embodiment of the method according to the invention.

(3) FIG. 2 schematically illustrates another embodiment of the method according to the invention.

(4) FIG. 3 schematically illustrates another embodiment of the method according to the invention.

(5) FIG. 4 schematically illustrates another embodiment of the method according to the invention.

(6) These figures show a schematic cross-section of a portion of the glass sheets and the elements deposited on the glass sheets near the periphery thereof. The various elements are obviously not represented to scale, so that they can be visualized.

(7) 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).

(8) In the embodiment of FIGS. 1 and 3, 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.

(9) In the embodiment shown in FIG. 1, refractory particles 16 are then deposited on the enamel layer 14 and on the stack 12 (step c).

(10) 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 d). 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.

(11) In step e, 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. The particles 16 were previously removed in a step d1 not shown.

(12) The embodiment of FIG. 2 differs from that of FIG. 1 in that the pre-firing step (step c1) is performed after step c of depositing the refractory particles 16, and before step d of bending.

(13) The embodiments of FIGS. 3 and 4 add a step b2 of depositing an adhesive layer 18 as well as a step c2 of removing refractory particles 16 other than those fixed onto the enamel layer 14. Thus, in step c, the particles 16 deposited on the enamel layer 14 are fixed onto the enamel layer 14, and in step d of bending, only the particles 16 fixed onto the enamel layer 14 are present.

(14) The embodiment of FIG. 4 differs from that of FIG. 3 in that the pre-firing step (step c1) is performed after step c of depositing the refractory particles 16, and before step d of bending.

Example 1

(15) The method carried out by Example 1 corresponds to the embodiment of FIG. 1.

(16) Glass sheets 2.1 mm thick, coated beforehand by cathode sputtering of a stack of thin layers comprising two 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.

(17) After drying (150? C., 1 to 2 minutes) and then pre-firing at 630? C., particles were dispersed over the entire surface of the first glass sheet, including the pre-fired enamel layer.

(18) These particles were based on magnesium silicate, obtained by grinding fibers marketed under the reference Isofrax? 1260C. The particles obtained were less than 50 ?m in diameter and at least 1 mm in length.

(19) 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. After washing to remove refractory particles, the two glass sheets were laminated together with a PVB interlayer.

(20) 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 below 5 is considered acceptable. The bonding was evaluated qualitatively by visual observation.

(21) The value of L* was less than 4.8 for a bending temperature above 628? C., and 3.6 for a bending temperature of 651? C. No bonding was observed up to a bending temperature of 651? C.

Example 2

(22) The method carried out by Example 2 corresponds to the embodiment of FIG. 3.

(23) In step b2, a resin (Ferro 80-007 medium) was deposited by screen-printed onto the enamel layer, with a wet thickness of 10 to 15 ?m. The resulting adhesive layer was then dried at about 150? C. for 1-2 minutes to remove the solvent. Refractory particles not attached to the enamel by the adhesive layer were then air-blown away. The other steps were performed in the same way as for Example 1.

(24) The same results in terms of aesthetics and lack of bonding as in Example 1 were obtained. On the other hand, no scratches were observed on the stack of thin films, unlike in Example 1.

Example 3

(25) The method carried out by Example 3 corresponds to the embodiment of FIG. 4. The only difference from Example 2 was the order of the steps, as the particles were deposited on a dried enamel layer, with the pre-firing performed just prior to bending.

(26) The same results in terms of aesthetics and lack of bonding as in Example 2 were obtained. Likewise, no scratches were observed on the stack of thin films, unlike in Example 1.

Comparative Example C1

(27) In this example, and compared to Example 1, the deposition of refractory particles has been replaced by the screen printing of a 25 ?m bismuth enamel with non-stick properties.

(28) However, bonding was observed, and in addition the value of L* was greater than 5 for all the bending temperatures studied.

Comparative Example C2

(29) In this example, and compared to Example 1, the deposition of refractory particles has been replaced by the deposition of black pigments with a size smaller than 20 ?m.

(30) Though no bonding was observed, the L* value was at least 12.4 (value observed for a bending temperature of 650? C.).

Comparative Example C3

(31) In this example, and compared to Example 1, the deposition of refractory particles has been replaced by the deposition of white pigments with a size smaller than 20 ?m.

(32) Though no bonding was observed, the L* value was at least 20.

Comparative Example C4

(33) In this example, and compared to Example 1, the deposition of refractory particles has been replaced by the screen printing of a silica sol-gel layer (Product TLU0059 from Ferro).

(34) The aesthetics were satisfactory (L*<5, particularly 3.3 for a bending temperature of 654? C.), but bonding was observed.

Comparative Example C5

(35) In this example, and compared to Example 1, the deposition of refractory particles has been replaced by deposition by screen-printing of an alkali silicate based solution additionally comprising black pigments.

(36) The L* value was 16 for a bending temperature of 650? C., and a transfer of the silicate layer to the additional glass sheet was observed.

Comparative Example C6

(37) In this example, and compared to Example 1, the deposition of refractory particles has been replaced by the silk-screen deposition of a 25 ?m bismuth enamel, marketed under the reference 14316 by the company Ferro, known for its non-stick properties. In contrast to Example C1, a second pre-firing treatment was performed after this enamel was deposited.

(38) However, bonding was observed, and in addition the L* value was 8.9 for a bending temperature of 650? C.