Optical impression of a PDLC vehicle pane through a combination of dark inner and outer stacks

Abstract

A vehicle pane, includes successively a) an outer glass pane, b) at least one laminated layer, c) a PDLC layer, including a polymer matrix, in which liquid crystal droplets are embedded, and in each case an electrically conductive layer on both sides of the polymer matrix, d) at least one laminated layer, and e) an inner glass pane. The TL(inside) is in the range from 5 to 46% and the TL(outside) is in the range from 20 to 73% and the TL(outside) is greater than or equal to TL(inside), wherein the TL(inside) is the light transmittance of an inner stack that is formed by the inner glass pane and the layers between the PDLC layer and the inner glass pane, and TL(outside) is the light transmittance of an outer stack that is formed by the outer glass pane and the layers between the PDLC layer and the outer glass pane.

Claims

1. A vehicle pane, comprising, in this order a) an outer glass pane, b) one or a plurality of laminated layers, c) a PDLC layer, comprising a polymer matrix, in which liquid crystal droplets are embedded, and in each case an electrically conductive layer on both sides of the polymer matrix, d) one or a plurality of laminated layers, and e) an inner glass pane, wherein a TL(inside) is in the range from 5 to 46% and a TL(outside) is in the range from 20 to 73% and the TL(outside) is greater than or equal to the TL(inside), wherein TL(inside) is the light transmittance of an inner stack that is formed by the inner glass pane and the layers between the PDLC layer and the inner glass pane, and the TL(outside) is the light transmittance of an outer stack that is formed by the outer glass pane and the layers between the PDLC layer and the outer glass pane, and wherein the ratio TL(outside)/TL(inside) is in the range from 3 to 2.

2. The vehicle pane according to claim 1, wherein TL(inside) is in the range from 7 to 28% and/or TL(outside) is in the range from 24 to 40%.

3. The vehicle pane according to claim 1, wherein a protective layer is in each case arranged on both sides of the PDLC layer.

4. The vehicle pane according to claim 3, wherein the protective layer is a polyethylene terephthalate layer.

5. The vehicle pane according to claim 1, wherein at least two laminated layers are included between the outer glass pane and the PDLC layer, and an IR-reflective layer composed of a carrier layer and an IR-reflective coating situated thereon is arranged between the two laminated layers.

6. The vehicle pane according to claim 5, wherein the carrier layer is preferably a polyethylene terephthalate layer.

7. The vehicle pane according to claim 1, wherein the inner glass pane and/or the outer glass pane has a low-E coating.

8. The vehicle pane according to claim 7, wherein only the inner glass pane has a low-E coating.

9. The vehicle pane according to claim 1, wherein the laminated layers contain polyvinyl butyral, ethylene vinyl acetate, polyurethane, and/or mixtures thereof.

10. The vehicle pane according to claim 1, wherein at least one of the laminated layers is a tinted laminated layer.

11. The vehicle pane according to claim 10, wherein the tinted laminated layer is a gray laminated layer.

12. The vehicle pane according to claim 1, wherein the inner glass pane and/or the outer glass pane are selected from tinted glass panes.

13. The vehicle pane according to claim 12, wherein the tinted glass pane is a gray or dark gray glass pane.

14. The vehicle pane according to claim 1, wherein the inner glass pane is a tinted glass pane and the outer glass pane is a clear glass pane, or the inner glass pane is a tinted glass pane and the outer glass pane is a tinted glass pane.

15. The vehicle pane according to claim 1, wherein a light transmittance TL(total) of the entire vehicle pane in the switched-on mode is less than or equal to 30%.

16. The vehicle pane according to claim 1, wherein the vehicle pane is a motor vehicle pane.

17. The vehicle pane according to claim 1, wherein the vehicle pane is a sliding roof panel, a glass roof, a rear window, a rear side window, or a front side window, in a motor vehicle.

18. A vehicle, including a vehicle pane according to claim 1, wherein the vehicle is a motor vehicle.

Description

(1) The invention is explained in the following and in the attached drawings. They depict:

(2) FIG. 1 a schematic representation of a vehicle pane according to the invention with a PDLC layer in cross-section;

(3) FIG. 2a-b a schematic representation of a vehicle pane with a PDLC layer in cross-section in the cloudy or opaque mode (switched-off mode, FIG. 2a) and in the transparent mode (switched-on mode, FIG. 2b);

(4) FIG. 3 a schematic representation of another vehicle pane according to the invention with a PDLC layer in cross-section;

(5) FIG. 4 a schematic exploded view of another vehicle pane according to the invention with a PDLC layer.

(6) FIG. 1 depicts schematically a vehicle pane according to the invention in cross-section with an outer glass pane 1, a laminated layer 2, a PDLC layer 4, a laminated layer 6, and an inner glass pane 7. The PDLC layer 4 is formed from two electrically conductive layers 3 and 5 and a polymer matrix 9 arranged therebetween, in which liquid crystal droplets 8 are embedded. The laminated layers 2 and 6 can be formed in each case from a PVB film. The electrically conductive layers 3, 5 of the PDLC layer can be transparent ITO coatings. In the vehicle pane depicted, TL(inside) is in the range from 5 to 46%, TL(outside) is in the range from 20 to 73%, and TL(outside) is greater than or equal to TL(inside).

(7) FIGS. 2a and 2b depict the mode of operation of the PDLC technology on a vehicle pane per FIG. 1. The pane is connected to a voltage source V via the two electrically conductive layers 3 and 5. Using a switch S/S′, the circuit can be closed (ON-mode, S′) and opened (OFF-mode, S). In the ON-mode (switched-on or transparent mode), an electrical field is applied, the liquid crystals 8 align themselves in an orderly manner, and incident light 10 is hardly scattered, yielding a transparent PDLC layer (FIG. 2b). When the electric current is switched off (switched-off or opaque mode), the electric crystals 8 are aligned randomly such that incident light 10 is scattered 10′ and the PDLC layer and the pane become opaque or nontransparent (FIG. 2a).

(8) FIG. 3 depicts schematically another vehicle pane according to the invention in cross-section with an outer glass pane 1, a laminated layer 2, a protective layer 11 for the PDLC layer, a PDLC layer 4, a protective layer 12 for the PDLC layer, a laminated layer 6, and an inner glass pane 7. The laminated layers 2 and 6 can, in each case, be formed from a PVB film. The protective layers 11 and 12 can, in each case, be formed from a PET film. The electrically conductive layers 3, 5 of the PDLC layer can be transparent ITO coatings. In the vehicle pane depicted, TL(inside) is in the range from 5 to 46%, TL(outside) is in the range from 20 to 73%, and TL(outside) is greater than or equal to TL(inside).

(9) FIG. 4 depicts a schematic exploded view of another vehicle pane according to the invention in cross-section with the following layers in this order: Outer glass pane 1 with a thickness of 2.1 mm made of clear glass, laminated layer 2 with a thickness of 0.38 mm made of clear PVB, IR-reflective layer 13 made of a PET film, with IR-reflective coating laminated layer 2 with a thickness of 0.38 mm made of gray PVB, protective layer 11 for the PDLC layer PDLC layer 4, incorporated with a frame 14 made of PVB, thickness PDLC layer+protective layers 11 and 12: 0.44 mm, protective layer 12 for the PDLC layer, laminated layer 6 with a thickness of 0.38 mm made of clear PVB, inner glass pane 7 with a thickness of 2.1 mm made of gray glass with low-E coating.

(10) In the vehicle pane depicted, TL(inside) is in the range from 5 to 46%, TL(outside) is in the range from 20 to 73%, and TL(outside) is greater than or equal to TL(inside).

EXAMPLES

(11) Seven vehicle panes A-G according to the invention and, as a reference, two vehicle panes H and I not according to the invention were investigated with regard to optical properties. In all examples, the same PDLC film was used together with two PET protective films arranged thereon. The components of the vehicle panes are listed below, with the order of the information corresponding to the structure from the outside (outer glass pane) to the inside (inner glass pane):

(12) Vehicle pane A (2× VG10)

(13) Dark gray glass/clear PVB/PDLC/clear PVB/dark gray glass

(14) Vehicle pane B (2× VG10, Comfortsky®)

(15) Dark gray glass/clear PVB/PDLC/clear PVB/dark gray glass+low-E coating (Comfortsky®)

(16) Vehicle pane C (PET IRR)

(17) Clear glass/clear PVB/PET with IR-reflective coating/gray PVB/PET protective layer/PDLC/PET protective layer/clear PVB/dark gray glass

(18) Vehicle pane D (PET IRR HPS)

(19) Clear glass/clear PVB/PET with highly IR-reflective coating/gray PVB/PET protective layer/PDLC/PET protective layer/clear PVB/dark gray glass

(20) Vehicle pane E (HPS+2× dark)

(21) Clear glass/clear PVB/PET with highly IR-reflective coating/gray PVB/PET protective layer/PDLC/PET protective layer/gray PVB/dark gray glass

(22) Vehicle pane F (HPS, 2× d, Comfortsky®)

(23) Clear glass/clear PVB/PET with highly IR-reflective coating/gray PVB/PET protective layer/PDLC/PET protective layer/gray PVB/dark gray glass+low-E (Comfortsky®)

(24) Vehicle pane G (2× PLC, 2× d)

(25) Clear glass/dark PVB/PET protective layer/PDLC/PET protective layer/dark PVB/clear glass (the dark PVB of the inner stack was darker than the dark PVB of the outer stack)

(26) Vehicle pane H (2× PLC, 1× d)

(27) Clear glass/dark PVB/PET protective layer/PDLC/PET protective layer/clear PVB/clear glass (this structure provides good thermal comfort)

(28) Vehicle pane I (2× PLC)

(29) Clear glass/clear PVB/PET protective layer/PDLC/PET protective layer/clear PVB/clear glass (standard structure for partition panels in motor vehicles)

(30) For the vehicle panes A to G and the reference panes H and I, the transmittance levels TL(total) in the switched-on mode (transparent mode of the PDLC layer), TL(outside), TL(inside) and the ratio TL(outside)/TL(inside) were determined. The results are listed in the following table

(31) TABLE-US-00001 TABLE TL(out- TL(total) TL(outside) TL(inside) side)/ No. Pane [%] [%] [%] TL(inside) A 2x VG10 7.4 28 28 1.0 B 2x VG10, 7.2 28 27.4 1.0 Comfortsky C PET IRR 6 22.9 8.7 2.6 D PET IRR HPS 6.1 23.2 8.7 2.7 E HPS, 2x dark 1.9 23.2 8.7 2.7 F HPS, 2x d, 1.9 23.2 8.5 2.7 Comfortsky G 2x PLC, 2x d 30 72.9 45.7 1.6 H* 2x PLC, 1x d 7.6 9.3 90.5 0.1 I* 2x PLC 74.4 90.8 90.8 1.0 *Reference panes

(32) Prior art roof panels have a haze <1% which is increased to <3% by the use of a dark PVB. Through the use of PDLC, an opaque light source that both illuminates the vehicle interior evenly and also prevents glare for the occupants is obtained. As soon as the white PDLC film is illuminated by a light source, such as the sun, the PDLC scatters it. When occupants look at this white scattered light, they get a low-quality “plastic” visual impression.

(33) When looking at the same PDLC film with the darker inner stack according to the invention and the same lighting conditions, a higher-quality discreetly gray impression was observed with the vehicle panes according to the invention in comparison to the reference panes H and I.

(34) Prior art PDLC films have, in the transparent state, a haze between 2% and 16%. Films with low haze are generally suitable for use in vehicles. The dark polymeric laminated layers also increase the haze value. Thus, a complete structure can have as much as 10% haze. In direct comparison with light-colored panes (e.g., with 70% TL as with reference pane I), there is thus greatly increased haze, but the product according to the invention still has a more optically attractive effect.

(35) Another difference arises when an external light source shines on the pane. With a prior art pane, the light is evenly scattered, specifically, for example, sunlight is scattered such that only a very small portion is deflected into the eye of the observer. This light interferes only slightly with vision toward the outside.

(36) With the use of a PDLC pane, sunlight is scattered depending on the direction. In principle, when one moves away from the direction of the light with the viewing angle, the intensity of the scattered light decreases. However, there is a colored “halo” that represents an intensity maximum in the viewing-angle-dependent scattered light profile. Following this colored phenomenon, an intensely white scattered light is seen that only weakens at very large angles.

(37) Looking at objects through PDLC panes with a customary structure is significantly disrupted, in this intensely white scattered light region, in particular. The intensity of the scattered light can exceed the light intensity of the object, as a result of which the white scattered light (white veil) outshines the colors of the object.

(38) With the glass structure according to the invention having a dark inner layer, the intensity of the scattered light is particularly reduced. The colors of the object can still be discerned while looking at it. Despite higher haze and possibly darker overall structure in the vehicle panes according to the invention, the object appears more clearly than with the reference panes H and I.

(39) With the vehicle panes according to the invention, the best overall optical impression or the greatest reduction of white haze and “plastic” impression was achieved with the panes A to F, and, in particular, with the panes C to F.

LIST OF REFERENCE CHARACTERS

(40) 1 outer glass pane 2 laminated layer 3 electrically conductive layer 4 PDLC layer 5 electrically conductive layer 6 laminated layer 7 inner glass pane 8 liquid crystal droplets 9 polymer matrix 10 incident light 10′ scattered light 11 protective layer 12 protective layer 13 IR-reflective layer 14 frame S switch (circuit open) S′ switch (circuit closed) V voltage source