Pane with thermal radiation reflecting coating

Abstract

The present invention relates to a pane with thermal radiation reflecting coating, comprising a substrate (1) and at least one thermal radiation reflecting coating (2) on at least one of the surfaces of the substrate (1), wherein the coating (2), proceeding from the substrate (1), comprises at least one lower dielectric layer (3), one functional layer (4) that contains at least one transparent, electrically conductive oxide, and one upper dielectric layer (5), and wherein at least one darkening layer (10) is arranged below the lower dielectric layer (3), between the lower dielectric layer (3) and the functional layer (4), between the functional layer (4) and the upper dielectric layer (5), and/or above the upper dielectric layer (5), and wherein the darkening layer (10) contains at least one metal, one metal nitride, and/or one metal carbide with a melting point greater than 1900 C. and a specific electrical resistivity less than 500 ohm*cm.

Claims

1. A pane with a thermal radiation reflecting coating, the pane comprising a substrate and at least one thermal radiation reflecting coating on at least one of the surfaces of the substrate, wherein: the thermal radiation reflecting coating comprises, in order proceeding from the substrate one lower dielectric layer having a thickness from 5 nm to 200 nm and comprising silicon oxide, silicon nitride, zinc oxide, tin oxide, mixed tin zinc oxide, zirconium oxide, hafnium oxide tantalum oxide, tungsten oxide, niobium oxide, or titanium oxide, one functional layer having a thickness from 100 to 150 nm and comprising indium tin oxide, a darkening layer having a thickness from 10 to 30 nm and comprising a metal nitride having a melting point greater than 1900 C. and a specific electrical resistivity less than 500 ohm*cm, and one upper dielectric layer having a thickness from 5 nm to 200 nm and comprises silicon oxide, silicon nitride, zinc oxide, tin oxide, mixed tin zinc oxide, zirconium oxide, hafnium oxide, tantalum oxide, tungsten oxide, niobium oxide, or titanium oxide.

2. The pane of claim 1, which has transmittance in the visible spectral range of less than 25%.

3. The pane of claim 1, wherein: the substrate has transmittance in the visible spectral range of less than 15% and the pane with the thermal radiation reflecting coating has transmittance of less than 10%.

4. The pane of claim 1, wherein the thickness of the darkening layer is from 5 nm to 20 nm.

5. The pane of claim 1, wherein the metal nitride of the darkening layer is selected from the groups IV B, V B, and VI B of the periodic system.

6. The pane of claim 1, wherein a melting point of the metal nitride is greater than 2200 C.

7. The pane of claim 1, wherein the upper dielectric layer comprises silicon oxide or silicon nitride.

8. The pane of claim 1, wherein the lower dielectric layer comprises silicon oxide or silicon nitride.

9. The pane of claim 1, wherein the thermal radiation reflecting coating further comprises an antireflection layer, which is arranged above the upper dielectric layer.

10. The pane of claim 1, wherein the thermal radiation reflecting coating further comprises as its uppermost layer a cover layer, which comprises at least one oxide.

11. The pane of claim 1, wherein: the substrate is bonded to a cover pane via at least one thermoplastic intermediate layer to form a composite pane; and the coating is arranged on the surface of the substrate facing away from the cover pane.

12. The pane of claim 1, which is employed as a pane or a component of a pane in a building or in a means of transportation for travel on land, in the air, or on water.

13. The pane of claim 1, wherein: the lower dielectric layer comprises silicon oxide; the darkening layer comprises a titanium nitride; and the upper dielectric layer comprises silicon oxide.

14. The pane of claim 1, wherein the coating further comprises a second darkening layer between the functional layer and the upper dielectric, wherein the second darkening layer has a thickness from 2 to 50 nm and comprises at least one metal, one metal nitride, one metal carbide, or a mixture thereof, with a melting point greater than 1900 C. and a specific electrical resistivity less than 500 ohm*cm.

15. A method for producing a pane with a thermal radiation reflecting coating, the method comprising applying at least (a) one lower dielectric layer having a thickness from 5 nm to 200 nm and comprising silicon oxide, silicon nitride, zinc oxide, tin oxide, mixed tin zinc oxide, zirconium oxide, hafnium oxide, tantalum oxide, tungsten oxide, niobium oxide, or titanium oxide, (b) one functional layer having a thickness from 100 to 150 nm and comprising indium tin oxide, (c) a darkening layer having a thickness from 10 to 30 nm and comprising a metal nitride having a melting point greater than 1900 C. and a specific electrical resistivity less than 500 ohm*cm, and (d) one upper dielectric layer having, a thickness from 5 nm to 200 nm and comprises silicon oxide, silicon nitride, zinc oxide, tin oxide, mixed tin zinc oxide, zirconium oxide, hafnium oxide, tantalum oxide, tungsten oxide, niobium oxide, or titanium oxide in succession on a substrate.

16. The method of claim 15, wherein the substrate with the coating is heated to a temperature of at least 200 C.

Description

(1) The invention is explained in detail in the following with reference to drawings and exemplary embodiments. The drawings are schematic representations and not true to scale. The drawings in no way restrict the invention.

(2) They depict:

(3) FIG. 1 a cross-section through an embodiment of the pane according to the invention with thermal radiation reflecting coating,

(4) FIG. 2 a cross-section through another embodiment of the pane according to the invention with thermal radiation reflecting coating,

(5) FIG. 3 a cross-section through another embodiment of the pane according to the invention with thermal radiation reflecting coating,

(6) FIG. 4 a cross-section through another embodiment of the pane according to the invention with thermal radiation reflecting coating,

(7) FIG. 5 a cross-section through a composite pane including a pane according to the invention,

(8) FIG. 6 a detailed flow chart of an embodiment of the method according to the invention.

(9) FIG. 1 depicts a cross-section through an embodiment of the pane according to the invention with the substrate 1 and the thermal radiation reflecting coating 2 (also called low-E-coating). The substrate 1 contains soda lime glass and has a thickness of 2.9 mm. The coating 2 comprises a lower dielectric layer 3, a functional layer 4, a darkening layer 10, and an upper functional layer 5. The layers are arranged in the order indicated with increasing distance from the substrate 1.

(10) The functional layer 4 is made of indium tin oxide (ITO) and has a thickness of roughly 100 nm. The lower dielectric layer 3 and the upper dielectric layer 5 can be configured in a manner known per se to the person skilled in the art and can, for example, be made of silicon oxide (SiO.sub.2) or silicon nitride (Si.sub.3N.sub.4) and have a thickness of roughly 100 nm.

(11) The darkening layer 10 is made of titanium nitride (TiN.sub.x) and has a thickness of roughly 20 nm. The darkening layer 10 effects a reduction in the transmittance of the coating 2 in the visible spectral range.

(12) The darkening layer 10 can, alternatively, also be arranged between the lower dielectric layer 3 and the functional layer 4, or between the substrate 1 and the lower dielectric layer 3. The coating 2 can, alternatively, also have a plurality of darkening layers 10.

(13) By means of the darkening layer 10, the light transmittance of the coating 2 is reduced. If the substrate 1 is tinted, the light transmittance through the coating 2 is further reduced. Consequently, it is possible to realize very dark panes, for example, with transmittance in the visible spectral range of less than 10%. Panes with such low transmittance are difficult to produce by means of a tinted substrate alone because glasses with such with such heavy tinting are typically not available commercially. In contrast to a coating with a transmittance-reducing functional layer (based, for example, on nickel, chromium, zirconium, tantalum, or niobium) on a clear substrate, production-related layer defects of the coating 2 according to the invention on a tinted substrate 1 have a lower contrast. Consequently, layer defects are less disturbingly noticeable to the observer. These are major advantages of the present invention.

(14) FIG. 2 depicts a cross-section through another embodiment of the pane according to the invention with the substrate 1 and the thermal radiation reflecting coating 2. The substrate 1 is configured as in FIG. 1. The coating 2 comprises a lower dielectric layer 3, a darkening layer 10, a functional layer 4, an upper functional layer 5, and an antireflection layer 6. The layers are arranged in the order indicated with increasing distance from the substrate 1.

(15) The lower dielectric layer 3 is an adhesive layer made of aluminum-doped silicon dioxide (SiO.sub.2:Al) and has a thickness of roughly 30 nm. The functional layer 4 is made of indium tin oxide (ITO) and has a thickness of roughly 120 nm. The upper dielectric layer 5 is a barrier layer for regulating oxygen diffusion during a temperature treatment of the pane. The barrier layer 5 is made of aluminum-doped silicon nitride (Si.sub.3N.sub.4:Al) and has a thickness of roughly 10 nm. The antireflection layer 6 is made of aluminum-doped silicon dioxide (SiO.sub.2:Al) and has a thickness of roughly 40 nm.

(16) The darkening layer 10 between the lower dielectric layer 3 and the functional layer 4 is made of titanium nitride (TiN.sub.x) and has a thickness of roughly 20 nm. The darkening layer 10 effects a reduction in the transmittance of the coating 2 in the visible spectral range.

(17) The darkening layer 10 can, alternatively, also be applied in a different position, for example, between the functional layer 4 and the upper dielectric layer 5, between the upper dielectric layer 5 and the antireflection layer 6, or between the substrate 1 and the lower dielectric layer 3. The coating 2 can, alternatively, also have a plurality of darkening layers 10.

(18) FIG. 3 depicts a cross-section through another embodiment of the pane according to the invention with the substrate 1 and the thermal radiation reflecting coating 2. The coating 2 comprises, as in FIG. 2, a lower dielectric layer 3 (adhesive layer), a functional layer 4, an upper dielectric layer 5 (barrier layer), and an antireflection layer 6. The layers 3, 4, 5, and 6 are configured as in FIG. 2. The coating 2 moreover includes a cover layer 7 above the antireflection layer 6. The cover layer 7 contains, for example, Ta.sub.2O.sub.5 or TiO.sub.2 and has a thickness of 10 nm. The cover layer advantageously protects the coating 2 against mechanical damage, in particular against scratching.

(19) The coating 2 further includes three darkening layers 10. The first darkening layer 10 is arranged between the substrate 1 and the lower dielectric layer 3. The second darkening layer 10 is arranged between the lower dielectric layer 3 and the functional layer 4. The third darkening layer 10 is arranged between the functional layer 4 and the upper dielectric layer 5. The darkening layers 10 are made of TiN.sub.x and have thicknesses between 10 nm and 15 nm. By means of three darkening layers 10 according to the invention 10, the light transmittance is more greatly reduced than by a single darkening layer 10, without the advantageous optical properties being lost as a result of an excessively thick darkening layer 10.

(20) FIG. 4 depicts a cross-section through a pane according to the invention with thermal radiation reflecting coating 2. The pane is intended as a side window of a motor vehicle. The substrate 1 has a thickness of 3.15 mm. The substrate 1 is made of tinted soda lime glass and has transmittance of roughly 14% in the visible spectral range. The pane is thermally prestressed and bent, as is customary for side windows in the automotive sector.

(21) The coating 2 is applied on the interior-side surface of the substrate 1. There, the advantageous effect of the coating 2 on the thermal comfort in the interior of the vehicle is particularly pronounced. The coating 2 reflects part of the sunlight incident via the pane, in particular in the infrared range. The thermal radiation emitted from the warm pane in the direction of the vehicle interior is, moreover, at least partially suppressed as a result of the low emissivity of the coating 2. Thus, the interior is less strongly heated in the summer. In the winter, the thermal radiation emanating from the interior is reflected. Consequently, the cold pane acts less strongly as an uncomfortable heat sink. Moreover, the necessary heating performance of the climate control system can be reduced, which results in significant energy savings.

(22) The coating 2 is preferably applied on the flat substrate 1 before the bending of the substrate 1. Coating a flat substrate is technically significantly simpler than coating a curved substrate. The substrate 1 is then typically heated to a temperature from 500 C. to 700 C., for example, 640 C. On the one hand, the temperature treatment is necessary to bend the substrate 1. On the other hand, the emissivity of the coating 2 is regularly improved by the temperature treatment. The upper dielectric layer 5 implemented as a barrier layer influences the extent of oxidation of the functional layer 4 during the temperature treatment. The oxygen content of the functional layer 4 is sufficiently low after the temperature treatment that the coating 2 can be subjected to a bending process. An excessively high oxygen content would result in damage to the functional layer 4 during bending. On the other hand, the oxygen content of the functional layer 4 is sufficiently high after the temperature treatment for low emissivity.

(23) The coating 2 is configured as in FIG. 2. The light transmittance through the pane is further reduced by the darkening layer 10. The pane with the coating 2 thus has transmittance in the visible spectral range of less than 10%. Such dark (rear) side windows can be desirable for thermal and/or aesthetic reasons. The darkening layer 10 according to the invention is suitable due to its corrosion and oxidation resistance to withstand the temperature treatment and the bending process undamaged.

(24) FIG. 5 depicts a cross-section through a pane according to the invention with thermal radiation reflecting coating 2 as part of a composite pane. The substrate 1 is bonded to a cover pane 8 via a thermoplastic intermediate layer 9. The composite pane is intended as a roof panel for a motor vehicle. The composite pane is curved as is customary for panes in the automotive sector. In the installed position of the composite pane, the cover pane 8 faces the outside environment and the substrate 1 faces the vehicle interior. The interior-side surface of the substrate 1, which faces away from the cover pane 8 and the thermoplastic intermediate layer 9, is provided with the coating 2 according to the invention. The substrate 1 and the cover pane 8 are made of soda lime glass and have, in each case, a thickness of 2.1 mm. The thermoplastic intermediate layer 9 contains polyvinyl butyral (PVB) and has a thickness of 0.76 mm.

(25) The substrate 1, the cover pane 8, and the thermoplastic intermediate layer 9 are tinted. By means of the coating 2, the light transmittance is further reduced. Thus, very dark composite panes can be realized.

(26) FIG. 6 depicts a flowchart of an exemplary embodiment of the method according to the invention for producing a pane with thermal radiation reflecting coating 2.

EXAMPLES

(27) Panes with thermal radiation reflecting coating 2 were produced according to the invention. The precise layer sequence with the materials used and layer thicknesses of Examples 1 to 8 are presented in Table 2 and Table 3. The substrate 1 was made of tinted soda lime glass and had transmittance in the visible spectral range of 25%. The darkening layers 10 contained titanium nitride. Titanium nitride has (based on a solid) a melting point of 2950 C. and specific electrical resistivity of 20 ohm*cm. The examples differ in terms of the number and the thickness as well as the position of the darkening layers 10.

(28) In all examples, the substrate 1 was initially flat and was provided with the coating 2 according to the invention by means of cathodic sputtering. The substrate 1 with the coating 2 was then subjected for 10 minutes to a temperature treatment at 640 C., bent in the process, and provided with a radius of curvature of roughly 30 cm.

(29) TABLE-US-00002 TABLE 2 Reference Thickness Character Material Example 1 Example 2 Example 3 Example 4 2 6 SiO.sub.2:Al 70 nm 70 nm 70 nm 70 nm 10 TiN.sub.x 5 Si.sub.3N.sub.4:Al 20 nm 20 nm 20 nm 20 nm 10 TiN.sub.x 5 nm 10 nm 10 nm 4 ITO 120 nm 120 nm 120 nm 120 nm 10 TiN.sub.x 5 nm 10 nm 10 nm 3 SiO.sub.2:Al 35 nm 35 nm 35 nm 35 nm 1 Glass 2.1 mm 2.1 mm 2.1 mm 2.1 mm

(30) TABLE-US-00003 TABLE 3 Reference Thickness Character Material Example 5 Example 6 Example 7 Example 8 2 6 SiO.sub.2:Al 70 nm 70 nm 70 nm 70 nm 10 TiN.sub.x 20 nm 5 Si.sub.3N.sub.4:Al 20 nm 20 nm 20 nm 20 nm 10 TiN.sub.x 20 nm 20 nm 30 nm 4 ITO 120 nm 120 nm 120 nm 120 nm 10 TiN.sub.x 20 nm 3 SiO.sub.2:Al 35 nm 35 nm 35 nm 35 nm 1 Glass 2.1 mm 2.1 mm 2.1 mm 2.1 mm

(31) The observations on the test panes are summarized in Table 6. R.sub.square is the sheet resistance of the coating 2. T.sub.L indicates the transmittance of the panes for visible light. R.sub.L indicates the reflectivity of the panes for visible light. A.sub.L indicates the absorption of the panes for visible light. The optical condition of the coating is influenced, in particular, by clouding (haze) as well as cracks.

(32) By means of the coatings 2 according to the invention with the darkening layers 10, the transmittance of the pane is further reduced. The temperature treatment during the bending of the pane results in a reduction of sheet resistance and, thus, to reduced emissivity. The darkening layer 10 is not oxidized, which would result in a significant increase in the transmittance T.sub.L. The bending process also does not result in damaging of the coating such that the optical condition of the layer is good in all cases.

Comparative Examples

(33) The Comparative Examples differ from the Examples according to the invention by the thermal radiation reflecting coating 2. The coatings comprised, as in the Examples, the lower dielectric layer 3, the functional layer 4, the upper dielectric layer 5, and the antireflection layer 6. However, the coatings included no darkening layers 10 according to the invention. Instead, each coating had two layers made of a material that did not satisfy the requirements according to the invention for the darkening layer (cf. Table 5, in which the corresponding melting points T.sub.s and specific electrical conductivities are summarized).

(34) The precise layer sequences with the materials used and layer thicknesses of the Comparative Examples 1 to 3 are presented in Table 4. The observations on the test panes are summarized in Table 6.

(35) TABLE-US-00004 TABLE 4 Material (Thickness) Reference Comparative Comparative Comparative Character Example 1 Example 2 Example 3 6 SiO.sub.2:Al (70 nm) SiO.sub.2:Al (70 nm) SiO.sub.2:Al (70 nm) 5 Si.sub.3N.sub.4:Al (20 nm) Si.sub.3N.sub.4:Al (20 nm) Si.sub.3N.sub.4:Al (20 nm) NiCr (10 nm) Ti (10 nm) NiCrN (10 nm) 4 ITO (120 nm) ITO (120 nm) ITO (120 nm) NiCr (10 nm) Ti (10 nm) NiCrN (10 nm) 3 SiO.sub.2:Al (35 nm) SiO.sub.2:Al (35 nm) SiO.sub.2:Al (35 nm) 1 Glass (2.1 mm) Glass (2.1 mm) Glass (2.1 mm)

(36) TABLE-US-00005 TABLE 5 T.sub.S/ C. /cm NiCr 1400 100 Ti 1660 43

(37) TABLE-US-00006 TABLE 6 Before Temperature Treatment After Temperature Treatment and Bending R.sub.Square R.sub.Square Optical [Ohm/ T.sub.L [Ohm/ T.sub.L R.sub.L A.sub.L Condition of Square] [%] Square] [%] [%] [%] the Coating Example 1 56 20.0 16 22.8 3.6 73.6 good Example 2 55 15.7 17 18.8 2.8 78.4 good Example 3 53 20.8 16 22.5 1.5 76.0 good Example 4 53 19.7 16 22.2 4.9 72.9 good Example 5 48 16.7 19 18.8 5.2 76.0 good Example 6 50 11.2 18 13.2 1.7 85.1 good Example 7 28 13.4 16 15.8 0.6 83.6 good Example 8 47 15.6 21 18.9 0.8 80.3 good Comparative 35 5.9 12 6.9 5.4 87.7 unacceptable Example 1 Comparative 52 14.6 18 25.8 6.0 68.2 unacceptable Example 2 Comparative 44 6.7 25 6.6 9.8 83.6 unacceptable Example 3

(38) The darkening layers not according to the invention made of NiCr, Ti, or NiCrN are damaged by the temperature treatment with the bending process such that the optical condition of the coating was in all cases unacceptable for customers in the automotive sector. In addition, in particular the absorber layers made of Ti are not sufficiently oxidation resistant, so they have, after the temperature treatment, significantly increased transmittance T.sub.L.

(39) From Table 6, it is furthermore discernible that, in particular, transmittance can be influenced by the thickness of the darkening layers 10. This yields the preferred ranges for the thickness of the darkening layer 10.

(40) By means of the darkening layers 10 according to the invention, a reduction in the transmittance of the thermal radiation reflecting coating is achieved. The darkening layers 10 are sufficiently corrosion and oxidation resistant to withstand a temperature treatment and a bending process without damage. This result was unexpected and surprising for the person skilled in the art.

LIST OF REFERENCE CHARACTERS

(41) (1) substrate (2) thermal radiation reflecting coating (3) lower dielectric layer (4) functional layer (5) upper dielectric layer (6) antireflection layer (7) cover layer (8) cover pane (9) thermoplastic intermediate layer (10) darkening layer