PANE HAVING AN ELECTRICALLY CONDUCTIVE COATING, WITH REDUCED VISIBILITY OF FINGERPRINTS

Abstract

A pane having an electrically conductive coating, includes a substrate and an electrically conductive coating on an exposed surface of the substrate, which coating includes at least one electrically conductive layer, wherein the pane has a local minimum of reflectance (RL) in the range from 310 nm to 360 nm and a local maximum of reflectance (RL) in the range from 400 nm to 460 nm.

Claims

1. Pane having an electrically conductive coating, comprising a substrate and an electrically conductive coating on an exposed surface of the substrate, which electrically conductive coating, starting from the substrate, at least comprises a blocking layer against alkali diffusion having a refractive index of at least 1.9, a dielectric lower antireflection layer having a refractive index of 1.3 to 1.8, an electrically conductive layer, a dielectric barrier layer for regulating oxygen diffusion having a refractive index of at least 1.9, and a dielectric upper antireflection layer having a refractive index of 1.3 to 1.8, wherein the pane has a local minimum of reflectance (R.sub.L) in the range from 310 nm to 360 nm and a local maximum of reflectance (R.sub.L) in the range from 400 nm to 460 nm.

2. The pane according to claim 1, wherein the electrically conductive layer contains a transparent conductive oxide.

3. The pane according to claim 1, wherein the electrically conductive layer has a thickness of 50 nm to 150 nm.

4. The pane according to claim 1, wherein the lower antireflection layer and/or the upper antireflection layer contains at least one oxide.

5. The pane according to claim 1, wherein the lower antireflection layer has a thickness of 5 nm to 50 nm, and wherein the upper antireflection layer has a thickness of 10 nm to 100 nm .

6. The pane according to claim 1, wherein the upper antireflection layer is the uppermost layer of the coating.

7. The pane according to claim 1, wherein the barrier layer has a refractive index of 1.9 to 2.5.

8. The pane according to claim 1, wherein the barrier layer contains a metal, a nitride, or a carbide.

9. The pane according to claim 1, wherein the barrier layer has a thickness of 5 nm to 20 nm.

10. The pane according to claim 1, wherein the blocking layer has a refractive index of 1.9 to 2.5.

11. The pane according to claim 1, wherein the blocking layer contains silicon nitride, which is optionally aluminum-doped, zirconium-doped, titanium-doped, or boron-doped silicon nitride.

12. The pane according to claim 1, wherein the blocking layer has a thickness of 10 nm to 50 nm.

13. Method for producing a pane having an electrically conductive coating, comprising: (a) applying an electrically conductive coating on an exposed surface of a substrate, which electrically conductive coating, starting from the substrate, at least comprises a blocking layer against alkali diffusion having a refractive index of at least 1.9, a dielectric lower antireflection layer having a refractive index of 1.3 to 1.8, an electrically conductive layer, a dielectric barrier layer for regulating oxygen diffusion having a refractive index of at least 1.9, and a dielectric upper antireflection layer having a refractive index of 1.3 to 1.8; and (b) subjecting the substrate with the coating to a temperature treatment at at least 100 C., whereafter the pane has a local minimum of reflectance (R.sub.L) in the range from 310 nm to 360 nm and a local maximum of reflectance (R.sub.L) in the range from 400 nm to 460 nm.

14. A method comprising utilizing a pane according to claim 1 in buildings, in electrical or electronic equipment, or in means of transportation for travel on land, in the air, or on water or as a capacitive or resistive sensor for tactile applications.

15. The pane according to claim 2, wherein the transparent conductive oxide is indium tin oxide (ITO).

16. The pane according to claim 3, wherein the electrically conductive layer has a thickness of 60 nm to 100 nm.

17. The pane according to claim 4, wherein the at least one oxide is silicon oxide, which is optionally aluminum-doped, zirconium-doped, titanium-doped, or boron-doped.

18. The pane according to claim 5, wherein the lower antireflection layer has a thickness of 10 nm to 30 nm and wherein the upper antireflection layer has a thickness of 30 nm to 70 nm.

19. The pane according to claim 8, wherein the barrier layer contains silicon nitride or silicon carbide.

20. The pane according to claim 9, wherein the barrier layer has a thickness of 7 nm to 12 nm.

21. The pane according to claim 12, wherein the blocking layer has a thickness of 20 nm to 40 nm.

22. The method according to claim 14, wherein the pane is a window pane, a building window pane or a roof panel, a side window, a rear window, a windshield of a vehicle, a touch screen or a touch panel.

Description

[0056] In the following, the invention is explained in detail with reference to drawings and exemplary embodiments. The drawings are a schematic representation and are not to scale. The drawings in no way restrict the invention.

[0057] They depict:

[0058] FIG. 1 a cross-section through an embodiment of the pane according to the invention having a heatable coating,

[0059] FIG. 2 a flowchart of an embodiment of the method according to the invention,

[0060] FIG. 3 a diagram of reflectance R.sub.L as a function of wavelength for two examples to according to the invention and two comparative examples, and

[0061] FIG. 4 simulation results of the relative reflectance as a function of the thickness of an oil film deposited on the on the coating 2 for the examples and comparative examples of FIG. 3.

[0062] FIG. 1 depicts a cross-section through an embodiment of the pane according to the invention with the substrate 1 and the electrically conductive coating 2. The substrate 1 is, for example, a glass pane made of tinted soda lime glass and has a thickness of 2.1 mm. The coating 2 is a thermal radiation reflecting coating (low-E coating). The pane is intended, for example, as a roof panel of a motor vehicle. Roof panels are typically implemented as composite glass panes, wherein the substrate 1 is joined by its surface facing away from the coating 2 to an outer pane (not shown) via a thermoplastic film. The substrate 1 forms the inner pane of the composite glass, wherein the coating 2 is applied on the exposed interior-side surface that can be touched directly by the vehicle occupants. As a result, fingerprints can accumulate on the coating 2. The optical properties of the coating 2 are optimized such that fingerprints are less highly visible than with conventional coatings. This is accomplished according to the invention in that the coating is designed such that the pane has a local minimum of reflectance R.sub.L in the range from 320 nm to 350 nm and a local maximum of reflectance R.sub.L in the range from 400 nm to 460 nm. Surprisingly, fingerprints are less noticeable under this condition.

[0063] The coating 2 is a sequence of thin layers, comprising, starting from the substrate 1, the following individual layers: a blocking layer 7 against alkali diffusion, a lower antireflection layer 3, an electrically conductive layer 4, a barrier layer 5 for regulating the oxygen diffusion layer 5, and an upper antireflection layer 6. The materials and layer thicknesses are summarized in Table 1. The individual layers of the coating 2 were deposited by magnetron-enhanced cathodic sputtering.

TABLE-US-00001 TABLE 1 Reference Thick- Layer No. Material ness Upper antireflection layer 6 2 SiO.sub.2:Al 50 nm Barrier layer 5 Si.sub.3N.sub.4:Al 9 nm Electrically conductive layer 4 ITO 70 nm Lower antireflection layer 3 SiO.sub.2:Al 17 nm Blocking layer 7 Si.sub.3N.sub.4:Al 30 nm Substrate 1 Soda lime glass 2.1 mm

[0064] FIG. 2 shows a flowchart of an exemplary embodiment of the production method according to the invention.

[0065] lo FIG. 3 shows diagrams of the reflectance R.sub.L for four examples according to the invention and three comparative examples. The materials and layer thicknesses of the coating 2 of examples 1-4 are summarized in Table 2; those of the comparative examples 1-3, in Table 3. In the examples 1-4, the pane comprised a substrate 1 of tinted soda lime glass with light transmittance T.sub.L of approx. 25% and the coating 2, which, starting from the substrate 1, was constructed from a blocking layer 7, a lower antireflection layer 3, an electrically conductive layer 4, a barrier layer 5, and an upper antireflection layer 6. The layers were formed from the same materials, with the coatings 2 of the examples 1-4 differing in the layer thicknesses. However, for the examples 1-4 according to the invention, the coating 2 was, in contrast to the comparative examples, in each case adjusted such that the pane had a local minimum of reflectance R.sub.L in the range from 320 nm to 350 nm and a local maximum of reflectance R.sub.L in the range from 400 nm to 460 nm, as can be seen in the figure. All panes had been subjected to a temperature treatment at approx. 650 C. within a glass bending process.

TABLE-US-00002 TABLE 2 Thickness Layer Material Example 1 Example 2 Example 3 Example 4 6 SiO.sub.2 50 nm 55 nm 50 nm 50 nm 5 Si.sub.3N.sub.4 9 nm 9 nm 9 nm 9 nm 4 ITO 70 nm 80 nm 70 nm 120 nm 3 SiO.sub.2 17 nm 10 nm 30 nm 15 nm 7 Si.sub.3N.sub.4 30 nm 25 nm 20 nm 10 nm 1 Glass 2.1 mm 2.1 mm 2.1 mm 2.1 mm

TABLE-US-00003 TABLE 3 Thickness Layer Material Comp. Ex, 1 Comp. Ex, 2 Comp. Ex, 3 TiO.sub.2 5 nm 6 SiO.sub.2 70 nm 70 nm 50 nm 5 Si.sub.3N.sub.4 9 nm 9 nm 9 nm 4 ITO 70 nm 80 nm 70 nm 3 SIO.sub.2 30 nm 30 nm 17 nm 7 Si.sub.3N.sub.4 30 nm 1 Glass 2.1 mm 2.1 mm 2.1 mm

[0066] The comparative examples 1 and 2 basically differed from the examples according to the invention through the absence of the blocking layer 7, resulting in significant changes in the reflection spectrum, such that the local extrema did not occur according to the invention. In the comparative example 3, yet another layer TiO.sub.2 was applied above the upper antireflection layer 6, as it is used, for example, as a photocatalytic layer in self-cleaning coatings. The upper antireflection layer 6 was, consequently, not the uppermost layer of the coating 2.

[0067] In contrast to the examples 1-4 according to the invention, the local extrema of the reflectance R.sub.L with the comparative examples 1-3 were not positioned in the spectrum according to the invention. The occurrence of the local extrema is summarized in Table 4. The values of reflectance R.sub.L presented were determined through simulations using CODE software.

TABLE-US-00004 TABLE 4 Minimum R.sub.L Maximum R.sub.L Ex. 1 335 nm 420 nm Ex. 2 335 nm 425 nm Ex. 3 345 nm 450 nm Ex. 4 335 nm 450 nm Comp. Ex. 1 <300 nm 350 nm Comp. Ex. 2 305 nm 370 nm Comp. Ex. 3 375 nm 425 nm

[0068] To take into account the influence of a fingerprint, the simulations were expanded by an oil film (refractive index 1.58) on the coating 2. The relative reflectance for the examples and comparative examples was then calculated as a quotient (reflectance of the pane with oil film)/(reflectance of the pane without oil film). The result is presented in FIG. 4 as a function of the thickness of the oil film.

[0069] In the examples 1 and 2 according to the invention, the relative reflectance for thin oil films up to approx. 20 nm is approx. 1; i.e., the reflectance is hardly changed by the oil film. With thicker oil films, the reflectance increases slowly to a value of approx. 2.5 with an oil film of 100 nm. In the examples 3 and 4, the relative reflectance decreases slightly at the beginning and increases just as slowly starting at approx. 30 nm oil film thickness.

[0070] In the comparative examples 1 and 2, a significantly different behavior is seen. Already with thin oil films, the reflection changes significantly and the relative reflectance initially decreases sharply. It then also increases starting at an oil film thickness of approx. 20 nm, but significantly more sharply than in the examples according to the invention. In the case of comparative example 3, a much sharper increase of the relative reflectance can already be seen with very thin oil films.

[0071] From the examples and comparative examples, it can clearly be seen that the presence of an oil film results, in the case of the coatings 2 according to the invention, in a significantly less pronounced change in the reflectance than in the case of coatings not according to the invention. Fingerprints, which are essentially fat deposits and are optically quite similar to an oil film, are thus significantly less visible due to the lower contrast. The fact that the visibility of fingerprints can be reduced by simply optimizing the optical properties of the coating was unexpected and surprising for the person skilled in the art.

[0072] Additional examples according to the invention (Ex. 6-12) and comparative examples (Comp. Ex. 4-12) are presented in Table 5. In each case, the thicknesses of the individual layers are indicated, from left to right starting from the substrate 1 (tinted soda lime glass). The spectral position of the local extrema of the reflectance R.sub.L is summarized in Table 6. All panes were again subjected to a temperature treatment at approx. 650 C. in a glass bending process.

TABLE-US-00005 TABLE 5 Layer 1 7 3 4 5 6 Material Glass Si.sub.3N.sub.4 SiO.sub.2 ITO Si.sub.3N.sub.4 SiO.sub.2 TiO.sub.2 Ex. 6 2.1 mm 30 nm 30 nm 75 nm 9 nm 30 nm Ex. 7 2.1 mm 40 nm 10 nm 70 nm 9 nm 50 nm Ex. 8 2.1 mm 15 nm 20 nm 90 nm 9 nm 50 nm Ex. 9 2.1 mm 20 nm 15 nm 100 nm 9 nm 45 nm Ex. 10 2.1 mm 25 nm 20 nm 60 nm 9 nm 50 nm Ex, 11 2.1 mm 25 nm 25 nm 50 nm 9 nm 60 nm Ex. 12 2.1 mm 20 nm 10 nm 70 nm 9 nm 70 nm Comp. 2.1 mm 20 nm 10 nm 70 nm 9 nm 70 nm 5 nm Ex. 4 Comp. 2.1 mm 30 nm 70 nm 9 nm 50 nm Ex. 5 Comp. 2.1 mm 0 nm 30 nm 70 nm 9 nm 50 nm 5 nm Ex. 6 Comp. 2.1 mm 20 nm 15 nm 100 nm 9 nm 45 nm 5 nm Ex. 7 Comp. 2.1 mm 30 nm 100 nm 9 nm 55 nm Ex. 8 Comp. 2.1 mm 10 nm 15 nm 120 nm 9 nm 50 nm 5 nm Ex. 9 Comp. 2.1 mm 30 nm 120 nm 9 nm 75 nm Ex. 10 Comp, 2.1 mm 25 nm 20 nm 60 nm 9 nm 50 nm 5 nm Ex. 11 Comp. 2.1 mm 30 nm 50 nm 9 nm 50 nm Ex. 12

TABLE-US-00006 TABLE 6 Minimum R.sub.L Maximum R.sub.L Ex. 6 330 nm 425 nm Ex. 7 330 nm 415 nm Ex. 8 340 nm 450 nm Ex. 9 345 nm 455 nm Ex. 10 320 nm 400 nm Ex. 11 345 nm 410 nm Ex. 12 355 nm 430 nm Comp. Ex. 4 385 nm 455 nm Comp. Ex. 5 385 nm 610 nm Comp. Ex. 6 300 nm 370 nm Comp. Ex. 7 385 nm 500 nm Comp. Ex. 8 310 nm 375 nm Comp. Ex. 9 390 nm 490 nm Comp. Ex. 10 380 nm 460 nm Comp. Ex. 11 365 nm 455 nm Comp. Ex. 12 350 nm 560 nm

[0073] In reality, fingerprints have a wide range of thicknesses, including even those with layer thicknesses greater than 1 m. In the case of such thick deposits, the effects of interference optics no longer play a decisive role such that visibility can no longer be significantly influenced by the optical properties of the coating 2. However, for the majority of fingerprints in the range up to approx. 100 nanometers, visibility can be significantly reduced. This significantly improves the overall impression of the pane.

LIST OF REFERENCE CHARACTERS

[0074] (1) substrate

[0075] (2) heatable coating

[0076] (3) lower antireflection layer

[0077] (4) electrically conductive layer

[0078] (5) barrier layer for regulating oxygen diffusion

[0079] (6) upper antireflection layer

[0080] (7) blocking layer against alkali diffusion

[0081] R.sub.L reflectance (per DIN EN410)