A MULTILAYER COATING

Abstract

The present disclosure describes a multilayer coating, comprising at least one metal oxide layer; and a composite layer provided on said metal oxide layer, said composite layer comprising at least one metal layer disposed between at least two barrier layers, and wherein said barrier layers are substantially impermeable to oxygen. The multilayer coating may be useful as transparent heat reflectors on glass, plastic, and on low temperature processing transparent substrate for energy saving application.

Claims

1-12. (canceled)

13. A multilayer coating, comprising: a. at least one metal oxide layer; and, b. a composite layer provided on said metal oxide layer, said composite layer comprising at least one metal layer disposed between at least two barrier layers, and wherein said barrier layers are substantially impermeable to oxygen; and, c. wherein the thickness of the metal layer is in the range of 15 nm to 30 nm.

14. The multilayer coating according to claim 13, wherein the barrier layer is an oxide of an element selected from Group 4, Group 11, Group 12, Group 13 or Group 14 of the Periodic Table of Elements.

15. ; The multilayer coating according to claim 14, wherein the element of the oxide is selected from the group consisting of aluminium, zinc, silicon, titanium and mixtures thereof.

16. The multilayer coating according to claim 13, wherein the barrier layer is aluminium oxide,

17. The multilayer coating according to claim 13, wherein the thickness of the barrier layer is in the range of 1 nm to 5 nm.

18. The multilayer coating according to claim 13, wherein the metal layer comprises a metal selected from Group 11, Group 12 or Group 13 of the Periodic Table of Elements.

19. The muiltilayer coating according to claim 18, wherein the metal is selected from the group consisting of copper, gold, silver, aluminium, zinc and mixtures thereof.

20. The multilayer coating according to claim 13, wherein the metal oxide layer is an oxide of a transition metal selected from the group consisting of zirconium, tantalum, niobium, titanium, hafnium, tin, tungsten, molybdenum and mixtures thereof.

21. The multilayer coating according to claim 13, wherein the thickness of the metal oxide layer is in the range of 40 nm to 100 nm.

22. A method of preparing a multilayer coating, the method comprising: a. providing a metal layer, wherein the thickness of the metal layer is in the range of 15 nm to 30 nm; b. depositing a barrier layer on the metal layer, wherein the barrier layer is substantially impermeable to oxygen; c. depositing a transition metal oxide layer on the metal layer covered with the barrier layer.

23. A method of using a multilayer coating as a transparent heat reflector coating on glass, plastic and other low temperature processing transparent substrates, wherein the multilayer coating comprises: a. at least one metal oxide layer; and, b. a composite layer provided on said metal oxide layer, said composite layer comprising at least one metal layer disposed between at least two barrier layers, and wherein said barrier layers are substantially impermeable to oxygen; and, c. wherein the thickness of the metal layer is in the range of 15 nm to 30 nm.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0042] The accompanying drawings illustrate a disclosed embodiment and serves to explain the principles of the disclosed embodiments. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition of the limits of the invention.

[0043] FIG. 1

[0044] [FIG. 1] refers to a schematic diagram of a Cu and ZrO.sub.2 based multilayer coating on glass substrate as described in Example 1.

[0045] FIG. 2

[0046] [FIG. 2] refers to the UV-vis spectra of the heat reflector of FIG. 1 after thermal treatment at different temperatures for 1 minute with the thickness of Cu and ZrO.sub.2 being 20 nm and 40 nm respectively, in which (a) refers to the full spectra taken from 300 nm to 2300 nm and (b) is an enlargement of the full spectra wherein the wavelength is from 300 nm to 900 nm.

[0047] FIG. 3

[0048] [FIG. 3] refers to the transmission spectra of the heat reflector of FIG. 1 after thermal treatment at different temperatures for 1 minute with the thickness of Cu and ZrO.sub.2 being 30 nm and 80 nm respectively in which (a) refers to the full spectra taken from 300 nm to 2300 nm and (b) is an enlargement of the full spectra wherein the wavelength is from 300 nm to 900 nm.

[0049] FIG. 4

[0050] [FIG. 4] refers to a schematic diagram of a Cu and ZrO.sub.2 based heat reflector on a glass substrate with an Al.sub.2O.sub.3 oxygen diffusion barrier as discussed in Example 2.

[0051] FIG. 5

[0052] [FIG. 5] refers to the transmission spectra of the heat reflector of FIG. 4 after thermal treatment at different temperatures for 1 minute with the thickness of Cu, ZrO.sub.2 and Al.sub.2O.sub.3 being 20 nm, 40 nm and 2 nm respectively.

[0053] FIG. 6

[0054] [FIG. 6] refers to the transmission spectra of a ZrO.sub.2/Cu/ZrO.sub.2 multilayer coating immediately after coating deposition, after 6 months of the coating deposition, and after thermal treatment at 100 C. for 6 hours with the thickness of Cu and ZrO.sub.2 being 40 nm and 20 nm respectively in which (a) refers to the full spectra taken from 300 nm to 2300 nm and (b) is an enlargement of the full spectra wherein the wavelength is from 300 nm to 900 nm.

[0055] FIG. 7

[0056] [FIG. 7] refers to the transmission spectra of a ZrO.sub.2/Al.sub.2O.sub.3/Cu/Al.sub.2O.sub.3/ZrO.sub.2 multilayer coating immediately after coating deposition, after 6 months of the coating deposition, and after thermal treatment at 100 C. for 6 hours with the thickness of Cu, Al.sub.2O.sub.3 and ZrO.sub.2 being 40 nm, 2 nm and 20 nm respectively in which (a) refers to the full spectra taken from 300 nm to 2300 nm and (b) is an enlargement of the full spectra wherein the wavelength is from 300 nm to 900 nm.

EXAMPLES

[0057] Non-limiting examples of the invention will be further described in greater detail by reference to specific examples, which should not be construed as in any way limiting the scope of the invention.

Example 1: Cu and ZrO.SUB.2 .Based Multilayer Coating

[0058] A multilayer coating having two symmetrical metal oxide layers with identical thickness on and below a metal layer has been proposed to maximize the visible transmittance of the multilayer coating. In this example, the metal oxide layers were made from zirconium oxide and the metal layer was a copper layer. By changing the thickness of Cu and ZrO.sub.2 layer, visible transmittance and heat reflecting properties of the multilayer coating (hereby termed as a heat reflector coating or heat reflector) can be tuned. A schematic diagram of the structure of such a Cu and ZrO.sub.2 based heat reflector is seen in FIG. 1.

[0059] For example, a multilayer coating of ZrO.sub.2/Cu/ZrO.sub.2 thin film was deposited using sputter deposition technique at room temperature. Pure copper (purity of 99.99% purchased from Kurt J. Lesker Company, USA) and stoichiometric ZrO.sub.2 targets (purity of 99.99% purchased from Kurt J. Lesker Company, USA) were used to sputter the ZrO.sub.2/Cu/ZrO.sub.2 multilayer thin film on glass or any transparent substrate. The deposition of the multilayers was performed sequentially without breaking the vacuum. The RF power was maintained at 150 W to sputter the ZrO.sub.2 until the required thickness is obtained and the DC power was held at 100 W to deposit the copper metal layer. Argon gas flow rate was kept constant at 25 sccm and the deposition was done at a working pressure of 3.3 mTorr. To improve the metal oxide quality of the multilayer coating, annealing was done at different temperatures in nitrogen ambient for 1 minute with heating and cooling rate of 10 C./sec by using rapid thermal processing (RTP) system, Jet First 150 (Jipelec). The sputtering power and the working pressure can be adjusted to improve the performance of the coating. FIG. 2 provides the UV-Vis spectra (transmission) of the above heat reflector after thermal treatment at different temperatures for 1 minute wherein the thickness of Cu and ZrO.sub.2 was 20 nm and 40 nm respectively. FIG. 2(a) provides the full spectra taken from 300 nm to 2300 nm while FIG. 2(b) is an enlargement of the full spectra wherein the wavelength is from 300 nm to 900 nm. The spectra compare the transparency of glass when it is coated with the ZrO.sub.2/Cu/ZrO.sub.2 multilayer coating and when it is not.

[0060] FIG. 3 provides the UV-Vis spectra (transmission) of the heat reflector after thermal treatment at different temperatures for 1 minute wherein the thickness of Cu and ZrO.sub.2 as 30 nm and 80 nm respectively. FIG. 3(a) provides the full spectra taken from 300 nm to 2300 nm and FIG. 3(b) is an enlargement of the full spectra wherein the wavelength is from 300 nm to 900 nm. The spectra compare the transparency of glass when it is coated with the ZrO.sub.2/Cu/ZrO.sub.2 multilayer coating and when it is not.

[0061] The spectra in FIG. 2(a), FIG. 2(b), FIG. 3(a) and FIG. 3(b) indicate that by changing the thickness of Cu and ZrO.sub.2 in the heat reflector, the visible transmittance and heat reflecting property can be altered. As can be seen from the figures, as the thickness of the zirconium oxide layer increases, the transmittance of the heat reflector decreases, leading to an inverse relationship between the thickness of the zirconium oxide layer and the transmittance of the heat reflector.

Example 2: Cu, Al.SUB.2.O.SUB.3 .and ZrO.SUB.2 .Based Multilayer Coating

[0062] In this example, the multilayer coating comprise two metal oxide layers made from zirconium oxide, a metal layer such as a copper layer and two barrier layers made from aluminium oxide that were disposed between the metal layer and the respective metal oxide layers. The aluminium oxide layer functioned as an oxygen diffusion barrier layer to enhance the visible transmission durability of transparent heat reflector (THR) without sacrificing heat reflection.

[0063] Here, the thickness of the aluminium oxide was about 2 nm to 3 nm and may be used to block oxygen diffusion through the heat reflector such that an interfacial layer (that may be formed in conventional heat reflectors when a metal oxide layer is deposited directly onto a metal layer) between the copper layer and the zirconium oxide layer is substantially minimised or eliminated. Hence, the problems associated with conventional heat reflectors may be overcome by adding a barrier layer between the two layers. The barrier layer may aid in reducing the corrosion of the metal layer or metal oxide layer or both.

[0064] The thin film Al.sub.2O.sub.3 layer can be deposited onto the copper layer by sputtering using an Al.sub.2O.sub.3 target of purity 99.99% purchased from Kurt J. Lesker Company. It is also possible to deposit a thin film of aluminium metal onto the copper layer and then allowing that aluminium thin film to oxidise. FIG. 4 is a schematic diagram of the heat reflector of this example showing the various layers, in which the copper layer is between two layers of aluminium oxide, which is in turn sandwiched between two layers of zirconium oxide.

[0065] Visible transmittance increased by about 8% with no change in the heat reflection property of the heat reflector (data not shown). In addition, as the thin film Al.sub.2O.sub.3 provided a uniform surface on the copper layer, the growth of the zirconium oxide layer (or layers) was homogeneous. In this manner, the stability of the heat reflecting properties of the heat reflector can be maintained for a longer duration.

[0066] FIG. 5 provides the UV-Vis spectra (transmission) of the heat reflector after thermal treatment at different temperatures for 1 minute wherein the thickness of Cu, ZrO.sub.2 and Al.sub.2O.sub.3 is 20 nm, 40 nm and 2 nm respectively. FIG. 5 provides the full spectra taken from 300 nm to 2300 nm. The spectra compare the transparency of glass when it is coated with the ZrO.sub.2/Al.sub.2O.sub.3/Cu/Al.sub.2O.sub.3/ZrO.sub.2 multilayer coating and when it is not.

Example 3: Stability of a Cu and ZrO.SUB.2 .Based Multilayer Coating

[0067] The optical characteristics of the ZrO.sub.2/Cu/ZrO.sub.2 multilayer coating (from Example 1) were analysed using UV-Vis spectrometry immediately and after 6 months of fabrication. Furthermore, the optical characteristics of the multilayer coating after thermal treatment at 100 C. for 6 hours in the atmosphere were analysed using UV-Vis spectrometry.

[0068] FIG. 6 provides the UV-Vis spectra (transmission) of the ZrO.sub.2/Cu/ZrO.sub.2 multilayer coating immediately after coating deposition, after 6 months of the coating deposition, and after thermal treatment at about 100 C. for 6 hours, wherein the thickness of Cu and ZrO.sub.2 was 40 nm and 20 nm respectively. FIG. 6(a) provides the full spectra taken from 300 nm to 2300 nm and FIG. 6(b) is an enlargement of the full spectra wherein the wavelength is from 300 nm to 900 nm. The spectra compare the transparency of glass when it is coated with the ZrO.sub.2/Cu/ZrO.sub.2 multilayer coating and when it is not.

[0069] The results in FIG. 6(a) and FIG. 6(b) thus show that there is no change in the optical properties (UV-Vis transmission and infrared reflection), indicating that the ZrO.sub.2/Cu/ZrO.sub.2 multilayer coating is robust and ambient stable.

Example 4: Stability of a Cu, Al.SUB.2.O.SUB.3 .and ZrO.SUB.2 .Based Heat Reflector

[0070] The optical characteristics of the ZrO.sub.2/Al.sub.2O.sub.3/Cu/Al.sub.2O.sub.3/ZrO.sub.2 multilayer coating (from Example 2) were analysed using UV-Vis spectrometry immediately and after 6 months of fabrication. Furthermore, the multilayer coating after thermal treatment at about 100 C. for 6 hours in the atmosphere was analysed using UV-Vis spectrometry.

[0071] FIG. 7 provides the UV-Vis spectra (transmission) of the ZrO.sub.2/Al.sub.2O.sub.3/Cu/Al.sub.2O.sub.3/ZrO.sub.2 multilayer coating immediately after coating deposition, after 6 months of the coating deposition, and after thermal treatment at about 100 C. for 6 hours, wherein the thickness of Cu, Al.sub.2O.sub.3 and ZrO.sub.2 was 40 nm, 2 nm and 20 nm respectively. FIG. 7(a) provides the full spectra taken from 300 nm to 2300 nm and FIG. 7(b) is an enlargement of the full spectra wherein the wavelength is from 300 nm to 900 nm. The spectra compare the transparency of glass when it is coated with the ZrO.sub.2/Al.sub.2O.sub.3/Cu/Al.sub.2O.sub.3/ZrO.sub.2 multilayer coating and when it is not.

[0072] The results in FIG. 7(a) and FIG. 7(b) thus show that there is no change in the optical properties (UV-Vis transmission and infrared reflection), indicating the ZrO.sub.2/Al.sub.2O.sub.3/Cu/Al.sub.2O.sub.3/ZrO.sub.2 multilayer coating is robust and ambient stable.

INDUSTRIAL APPLICABILITY

[0073] In the present disclosure, the multilayer coating may be useful as transparent heat reflectors on glass, plastic, and on low temperature processing transparent substrate for energy saving application. Hence, the multilayer coating may be used on windows on buildings or automobiles, or on screens on electronic devices, as well as devices that require anti-scratch and wear resistance properties, leading to multiple applications in the construction, automobile or electronic industries.

[0074] It will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.