METHOD FOR PRODUCING A COMPOSITE PANE HAVING POLARISATION-SELECTIVE COATING

Abstract

A method for producing a composite pane suitable as a projection surface of a projection assembly, wherein (a) a polarisation-selective coating is provided on a carrier film; (b) the polarisation-selective coating is transferred from the carrier film onto a laminating film, by (i) arranging the carrier film and the laminating film areally one atop the other with the coating positioned therebetween to form a film stack, (ii) treating the film stack for at least 2 hours at a pressure of at least 8 bar and a temperature of 80 C. to 120 C. in an autoclave, and (iii) peeling the carrier film off the laminating film, with the coating remaining on the laminating film; (c) the laminating film is arranged areally between a first pane and a second pane; and (d) the first pane is laminated with the second pane via the laminating film to form the composite pane.

Claims

1. A method for producing a composite pane that is suitable as a projection surface of a projection assembly, the method comprising: (a) providing a polarisation-selective coating on a carrier film; (b) transferring the polarisation-selective coating from the carrier film onto a laminating film, by (i) arranging the carrier film and the laminating film areally one atop the other with the polarisation-selective coating positioned therebetween to form a film stack, (ii) treating the film stack for at least 2 hours at a pressure of at least 8 bar and a temperature of 80 C. to 120 C. in an autoclave, and (iii) peeling the carrier film off the laminating film, with the polarisation-selective coating remaining on the laminating film; (c) areally arranging the laminating film between a first pane and a second pane; and (d) laminating the first pane with the second pane via the laminating film to form the composite pane.

2. The method according to claim 1, wherein the polarisation-selective coating (5) includes liquid crystals.

3. The method according to claim 1, wherein the carrier film includes polyethylene terephthalate (PET).

4. The method according to claim 1, wherein the laminating film contains polyvinyl butyral (PVB), ethylene vinylacetate (EVA), polyurethane (PU), or mixtures or copolymers or derivatives thereof.

5. The method according to claim 1, wherein the laminating film has one surface with lower roughness and one surface with higher roughness, and wherein in step (i), the surface with lower roughness is turned toward the carrier film.

6. The method according to claim 1, wherein in step (ii), the film stack is arranged between two pressing plates.

7. The method according to claim 1, wherein in step (iii), the temperature of the film stack is from 30 C. to 65 C.

8. The method according to claim 1, wherein the polarisation-selective coating is arranged in direct contact with the first or second pane.

9. The method according to claim 1, wherein the first pane and/or the second pane has a masking print that conceals side edges of the polarisation-selective coating after lamination.

10. The method according to claim 1, wherein the composite pane is a windshield and the polarisation-selective coating substantially covers the central field of vision B per ECE-R43.

11. The method according to claim 1, wherein the composite pane is a windshield and the polarisation-selective coating is arranged outside the central field of vision B per ECE-R43.

12. The method according to claim 1, wherein in step (d), the lamination is carried out in an autoclave at a temperature of less than 130 C.

13. The method according to claim 1, wherein the polarisation-selective coating is arranged in the composite pane such that its reflectance for p-polarised radiation is maximised.

14. A method for producing a projection assembly, comprising: (a) producing a composite pane according to the method according to claim 1; (b) arranging a projector such that the polarisation-selective coating can be irradiated.

15. The method according to claim 14, wherein the projector irradiates the polarisation-selective coating with p-polarised radiation.

16. The method according to claim 2, wherein the liquid crystals are in a cholesteric phase.

17. The method according to claim 4, wherein the laminating film contains polyvinyl butyral (PVB).

18. The method according to claim 12, wherein in step (d), the temperature is at most 100 C.

Description

[0048] They depict:

[0049] FIG. 1 a cross-section through the carrier film and the laminating film during the transfer of the polarisation-selective coating from the carrier film onto the laminating film,

[0050] FIG. 2 a cross-section through a composite pane produced according to the invention,

[0051] FIG. 3 a cross-section through a projection assembly produced according to the invention,

[0052] FIG. 4 a plan view of an embodiment of the composite pane produced according to the invention,

[0053] FIG. 5 a plan view of another embodiment of the composite pane produced according to the invention, and

[0054] FIG. 6 a flowchart of an embodiment of the method for producing a composite pane according to the invention.

[0055] FIG. 1 depicts cross-sections at three points in time during the transfer of a polarisation-selective coating 5 from a carrier film 4 onto a laminating film 3. The polarisation-selective coating 5 includes, for example, liquid crystals in a cholesteric phase and was commercially acquired applied on a carrier film 4 made of PET (thickness 100 m). Since the PET film is very stiff and has no hot melt adhesive properties relative to the glass surfaces at typical lamination temperatures, it cannot be used as an intermediate layer of a composite pane. In order to produce a composite pane of high optical quality, it is, consequently, necessary to transfer the coating 5 onto a laminating film 3, for example, a PVB film with a thickness of 0.76 mm.

[0056] In the initial state, the carrier film 4 provided with the coating 5 and the uncoated laminating film 3 are present (Part a). The carrier film 4 and the laminating film 3 are arranged one atop another with the coating 5 areally positioned therebetween to form a film stack, pressed against one another by means of a first pressing plate 21 and a second pressing plate 22 and treated in an autoclave (Part b). The films 4, 3, already trimmed to their final shape, have, for example, dimensions of approx. 1.1 m1.7 m. Suitable processing parameters in the autoclave are a pressure of 12 bar, a temperature of 100 C., and a treatment duration of 2.5 hours. The film stack is then removed from the autoclave and allowed to cool to a temperature of, for example, 40 C. Then, the carrier film 4 is carefully peeled off starting from one corner and the coating 5 remains on the laminating film 3 (Part c). As is customary for PVB films, the laminating film 3 has one surface II with higher roughness and one surface I with lower roughness. The coating 5 is applied on the surface I, as a result of which better adhesion is achieved.

[0057] FIG. 2 depicts a cross-section of a composite pane 10 produced according to the invention. It comprises a first pane 1 made of soda lime glass with a thickness of, for example, 2.1 mm and a second pane 2 made of soda lime glass with a thickness of, for example, 1.6 mm, that are bonded to one another via a laminating film 3 provided with the polarisation-selective coating 5. The coating 5 is directed toward the second pane 2. The surface of the first pane 1 facing the laminating film 3 as well as the surface of the second pane 2 facing away from the laminating film 3 are provided with a surrounding, peripheral masking print 6, as is common for window panes for vehicles. The masking print 6 conceals the side edges of the coating 5.

[0058] FIG. 3 depicts a cross-section of the composite pane 10 of FIG. 2 as a projection surface of a projection assembly. The composite pane 10 is the windshield of a motor vehicle. The first pane 1 is, in this case, the outer pane; the second pane 2, the inner pane. It is irradiated by a projector P with p-polarised radiation at an angle of approx. 65. The p-polarised radiation is hardly reflected by the surface of the panes 1, 2, but is very efficiently reflected by the polarisation-selective coating 5. This creates a projection that an observer O, for example, the driver of the vehicle can perceive.

[0059] FIG. 4 depicts a plan view of an embodiment of the composite pane 10 produced according to the invention. The composite pane 10 is the windshield of a motor vehicle and has a field of vision B per ECE-R43. It is provided with the polarisation-selective coating 5 over its full surface, minus a surrounding edge region with a width of a few centimeters. Consequently, the coating 5 completely covers the field of vision B. The side edges of the coating 5 are concealed by the masking print 6. This embodiment is particularly suitable as a projection surface for a contact-analog augmented reality HUD. Projections can be produced on the entire pane and the environment can be included in the display. It is thus possible, for example, to project an arrow such that it apparently lies on a traffic lane and marks this for the driver.

[0060] FIG. 5 depicts a plan view of another embodiment of the composite pane 10 produced according to the invention. The composite pane 10 is likewise the windshield of a motor vehicle and has a field of vision B per ECE-R43. Only a relatively small region of the composite pane 10 is provided with the polarisation-selective coating 5, which region is located completely outside the field of vision B. Any data desired by the observer can be displayed there. An additional masking print 6 can be arranged outside the field of vision B to conceal the side edges of the coating B.

[0061] FIG. 6 depicts a flowchart of an exemplary embodiment of the method for producing a composite pane according to the invention.

LIST OF REFERENCE CHARACTERS

[0062] (10) composite pane [0063] (1) first pane [0064] (2) second pane [0065] (3) laminating film [0066] (4) carrier film [0067] (5) polarisation-selective coating [0068] (6) masking print [0069] (20) autoclave [0070] (21) first pressing plate [0071] (22) second pressing plate [0072] (I) surface of the laminating film 3 with lower roughness [0073] (II) surface of the laminating film 3 with higher roughness [0074] (P) projector [0075] (O) observer/vehicle driver [0076] (B) central field of vision of the composite pane 10