WO1991017283A1

WO1991017283A1 - A vacuum deposited dark coating on a substrate

Info

Publication number: WO1991017283A1
Application number: PCT/US1991/002974
Authority: WO
Inventors: Chong T. Wan; Douglas L. Chambers; Guy T. Susi
Original assignee: Xytorr Corporation
Priority date: 1990-05-01
Filing date: 1991-04-30
Publication date: 1991-11-14
Also published as: EP0548084A4; CA2081912A1; EP0548084A1

Abstract

The present invention is an improved method for applying a dark coating (16), such as for a border, to a substrate (11) such as glass, plastic, or other transparent article. The method incorporates the use of metal carbides, oxides and nitrides, deposited on the substrate (11) by using a vacuum vapor deposition process such as a sputtering process. Other vacuum vapor deposition processes such as cathodic arc or ion plating may be used to apply the coating (16). The coating (16) of this invention is applied at much lower temperatures than silk screened ceramic paints and the coating (16) is less thick than applied ceramic type paints. The coating (16) can be applied so that it appears in many different colors.

Description

A VACUUM DEPOSITED DARK COATING ON A SUBSTRATE

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates generally to vacuum vapor deposition processes and coatings for primarily glass or plastic substrates, and more particularly, to a dark coating which provides a decorative and/or functional border or band on glass, plastic or other transparent article for automotive winήnwR an windshields including glass roofs, aircraft windows and windshields, architectural applications, computer screens, display panels, glass freezer doors, microwave oven glass doors, home or office skylights, mirrors, marine vehicle windows, framed glass as well as many other similar applications.

Dark coatings on substrates have been used for strictly decorative, aesthetic purposes as well as for performing a useful function. For example, in automobile windshields there has been a relatively recent advancement of electrically heating the windshields to defrost, de-ice or defog them. One manner of doing this has been to place bus bars near the top and bottom of a windshield for supplying an electrical power across a transparent conductive coating which is applied on the vision portion of the windshield and is in contact with the electrical conducting bus bars. To conceal from view, the bus bars which may not be aesthetically pleasing, a dark or near opaque coating is applied to a border area of the windshield. The coating is usually black but could be many other darker shades such as gray, blue, magenta, bronze, brown and golden. There are many other uses for this dark border coating such as: to conceal electric wires, antenna conductors and other assemblies that appear behind glass, or just for aesthetic purposes.

U.S. Patent No. 4,684,388 to Boaz (incorporated by reference herein) discloses a method for forming a glass sheet with a UV-base ceramic paint l-hprsnn. Γ.PT-RITΠr paint- compositions are generally well-known in the art. These paints usually include a mixture of metal oxides which act as a coloring agent. Such ceramic paint compositions include a low melting point glass frit. This frit bonds the mixture of metal oxides to the glass sheet and insures that the mixture remains bonded after the glass sheet has been cooled to room temperature.

In some processes, the metal oxide frits and enamels are heated to a temperature in a range up to 1300°F. A zinc metal powder is mixed with stannous oxide and the aforementioned materials to form a liquid type paint which can be silkscreen printed. Ceramic base paints also contain volatiles which must be driven off. Non-reactive metal oxides are used such as chrome, cobalt, nickel, manganese, iron, and copper. Such mixtures are commonly known as black oxide powders. Other mixtures of oxides may be used in order to get different colors which is well-known in the art. Boaz uses the addition of the stannous oxide powder to the zinc metal powder to prevent sticking of the paint to a forming die. In Boaz the forming die is what comes in contact with the glass and paint during the application of the paint to the glass.

There are several disadvantages to the above mentioned ceramic paint applications. One disadvantage is that the paint and frit use volatile solvents with coloring pigments. Another disadvantage is that prior coatings have been thick (.001 to .003 inches). Also, high temperature firing causes stress and weakness in the glass. Another disadvantage is that the paint may tend to stick to another glass in contact, with the forming die and other fixtures used in this method. Yet another disadvantage is that previous application processes have not been easily integrated into the window lamination process such as for automobile and aircraft glass.

Vapor deposition processes are also well known in the art but until now have been used primarily for applying transparent conductive coatings for heated windshields. For example, U.S. Patent No. 4,861,669 to Gillery (incorporated by reference herein) describes one such process called sputtering. However, vapor deposition processes have not been used for applying dark coatings for various reasons. One reason is that it is difficult to get the dark coating to adhere to a substrate when the coating is applied using this process. Without adhesion the coating may peel off with time.^' The present invention discloses a way to use a vapor deposition process to apply dark coatings and to get the coatings to adhere to the substrate. Other reasons may be difficulty with, obtaining a dark color using a vapor deposition process or, masking areas of the substrate not to be coated for placing in a vacuum chamber.

Thus it is an object of the present invention to provide a transparent substrate where a dark coating is applied at a low temperature and is significantly thinner than conventional ceramic paints or frits* Further objects are to provide fewer production steps (the old way requires: mix paint, silk screen, fire at high temperature) in the manufacture of such coated substrates and to provide an improvement in function and different physical characteristics from a paint band. One of the advantages of the present invention is its relatively low temperature process which results in less thermal stress induced in the substrate.

Therefore, the present invention provides a coating or film of ceramic carbonitrides, metal oxides, metal nitrides or combinations thereof, deposited by using anyone of three vapor deposition processes known as sputtering, cathodic arc, or ion plating. The coating is applied upon a selected substrate to the thickness necessary to control light transmission and reflectance. Typically, an opaque coating of 500 Angstroms to 5,000 Angstroms or more is deposited to form an obscured band that light cannot pass through. The coating may be continuous or segmented or even applied in a particular pattern. In some applications, thinner coatings may be desired in which partial light may be transmitted. Oxynitride mixtures are used to change color and light transmission. The foregoing and other objects and advantages will become more apparent when viewed in light of the accompanying drawings and following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a perspective view of an automobile windshield having the coating of the present invention; and FIGURE 2 is a cross-sectional view taken along the section line 2-2 in FIGURE 1.

DESCRIPTION OF PREFERRED EMBODIMENTS) Referring to FIGURE 1, there is shown a typical automobile windshield 10 comprising a glass panel 11. (It should be noted that this is just one use for the subject invention which could be used on glass, plastic, or transparent substrates of many kinds in many different applications.) The glass panel 11 may have electrical bus bars (not shown) at a top portion 12 and bottom portion 14 of the windshield. These bus bars may be used to transfer electrical current across the windshield, through a conductive coating, to heat, defrost, defog or de-ice the windshield. To make the windshield more aesthetically pleasing, a dark coating 16 may be applied in a band shape around the border or on other portions or segments of the glass 11 to conceal the bus bars or other assorted components.

As shown in FIGURE 2, a windshield 10 panel 11 may typically- contain multiple layers. Starting from outside the • automobile, there is a first surface 18 on a first outside layer 20 of glass. Inside the first layer 20 of glass is a second surface 22 which lies between the first layer 20 of glass and a layer of plastic 24. Inside the layer of plastic 24 s a third surfβce 26 which lies between the l3^*"-er of plastic 24 and a second inner layer 28 of glass. Lastly, there is the inside surface 30 of the glass which is inside the automobile. The coating band 16 or border of the present invention is preferably applied to the second surface 22 or the third surface 26. However, it is also feasible to apply the coating to the fourth, inside surface 30 of the second glass layer 28. In case of a single monolithic glass sheet or window the coating band would preferably be applied to the inner surface of the glass or window.

Because these multiple layers 20, 24, 28 of the windshield 10 are sandwiched together during the manufacturing of the windshield 10, it is important to keep the thickness of any applied coatings 16 to a minimum to avoid having undue stress imposed on the glass. Since a dark coating 16 is usually not applied across the entire surface of the glass 11, but typically at the edges, when the layers 20, 24, 28 are compressed together, they will tend to bow at the edges if the coating 16 is too thick. This may induce critical stresses. By sputtering the coating 16 onto the glass 11, the coating 16 can be applied in a much thinner layer than previous ceramic type paints applied with high temperature firing.

In order to obtain good adhesion of the coating to the substrate, the substrate must be washed. First it is washed with a warm water detergent wash. Then it is rinsed with water followed by rinsing again with deionized water. The substrate is then dried with warm air blown over it. The substrate is then placed in a vacuum chamber and heated or glow discharge cleaned by ionic bombardment in a wet gas as is known in the glass cleaning art. The coating is then applied immediately.

The coating may be applied in a DC reactive vacuum sputtering apparatus which uses an ion sputtering method with a shield or mask to protect selected uncoated areas of the glass. This low temperature process allows a very thin, durable coating with no curing required. This translates into less stress in the glass. The coating can be altered to appear black, gray, magenta, golden, brown, bronze, and blue as well as other darker shades. The sputtering process is compatible with the window lamination process currently in use by most windshield manufacturers. Because sputtering does not require high temperatures, or silk screening the application of the coating of the present invention can be accomplished faster by using fewer process steps.

The metal rich coating of the present invention may be comprised of a chromium oxide-nitride or oxynitride. Other metal compounds may also be used, such as: oxides, nitrides, carbides, and oxynitrides of base metals chromium, aluminum, titanium, molybdenum, tantalum, tungsten, stainless steel, niobium, and zirconium, and their alloys.

The dark color of the coating is obtained by regulating reactive gases which interact with the metal and its compound in the vacuum chamber. The reactive gases are nitrogen, oxygen, and ater vapor₌ The sputtering process also uses argon gas which is non-reactive. Atmospheric air has the three reactive gases which make it suitable for this process. The relative amounts of the. reactive gases mixed with the argon in a metal rich environment are varied to develop different colors. Generally, as the percentage of reactive gases are increased and the thickness of the coating remains the same the color of the coating will lighten (the light transmittance will increase) .

It is thought that the improved dark coating and method of the present invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form and construction of the components thereof without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form herein before described being merely a preferred or exemplary embodiment thereof.

Claims

What is claimed is:

1. A method of applying a dark coating to a portion of a transparent substrate said dark coating substantially preventing the transmittance therethrough of light in the wavelengths visible to the human eye, whereby the dark coating is capable of substantially concealing from view a thing behind the portion of said substrate to which the dark coating is applied, said method comprising the steps of:

^1^ ^ i i " a trans-^parent substrate;

(2) selecting a portion of said substrate to define a predetermined area on which the dark coating is to be applied;

(3) selecting a metal compound capable of application to the substrate by a vacuum vapor deposition process from the group consisting of ceramic carbonitrides, metal oxides, and metal nitrides; and

(4) applying said selected metal compound in a metal rich monolithic layer to the selected portion of said substrate by a vacuum vapor deposition process.

2. The method of Claim 1, wherein said vacuum vapor deposition process uses a sputtering process.

3. The method of Claim 1, wherein said metal compound is chromium oxynitride.

4. The method of Claim 1, wherein said metal compound is chromium oxide.

5. The method of Claim 1, wherein said metal compound is chromium carbide.

6. The method of Claim 1, wherein said metal compound is chromium nitride.

7. The method of Claim 1, wherein said metal compound is aluminum oxide.

8. The method of Claim 1, wherein said metal compound is aluminum nitride.

9. The method of Claim 1, wherein said metal compound is aluminum oxynitride.

10. The method of Claim 1, wherein said metal compound is titanium oxide.

11. The method of Claim 1, wherein said metal compound is titanium nitride.

12. The method of Claim 1, wherein said metal compound is titanium oxynitride.

13. The method of Claim 1, wherein said metal compound is molybdenum oxide.

14. The method of Claim 1, wherein said metal compound is molybdenum nitride.

15. The method of Claim 1, wherein said metal compound is molybdenum oxynitride.

16. The method of Claim 1, wherein said metal compound is tantalum oxide.

17. The method of Claim 1, wherein said metal compound is tantalum nitride.

18. The method of Claim 1, wherein said metal compound is tantalum oxynitride.

19. The method of Claim 1, wherein said metal compound is niobium oxide.

20. The method of Claim 1, wherein said metal compound is niobium nitride.

21. The method of Claim 1, wherein said metal compound is niobium oxynitride.

22. The method of Claim 1, wherein said metal compound is zirconium oxide.

23. The method of Claim 1, wherein said metal compound is zirconium nitride.

24. The method of Claim 1, wherein said metal compound is zirconium oxynitride.

25. The method of Claim 1, further compromising: masking another portion of said substrate which will remain uncoated.

26. The method of Claim 1, wherein said steps of applying said coating to said substrate require a maximum temperature of 250°F.

27. The method of Claim 1, wherein said substrate is glass.

28. The method of Claim 1, wherein said substrate is plastic.

29. The method of Claim 1, wherein said coating appears black in color.

30. The method of Claim 1, wherein said coating appears brown in color.

31. The method of Claim 1, wherein said coating appears golden in color.

32. The method of Claim 1, wherein said coating appears magenta in color.

33. The method of Claim 1, wherein said coating appears blue in color.

34. The method of Claim 1, wherein said coating appears gray in color.

^~\ ^~> . The method of Claim 1, wherein said coating appears bronze in color.

36. The method of Claim 1, wherein said coating comprises non-volatile ingredients.

37. The method of Claim 1, wherein said coating is between 500 and 5,000 Angstroms thick.

38. The method of Claim 1, wherein said coating is more than 5,000 Angstroms thick.

39. The method of Claim 1, wherein said metal compound is an alloy of any of the metals aluminum, chromium, titanium, molybdenum, tantalum, niobium, and zirconium, with at least one of the compounds oxide, nitride and carbide.

40. A method in accordance with Claim 1 for applying a black coating to an automobile windshield having bus bars placed thereon, said method comprising the steps of: selecting chromium oxynitride for said coating; applying said coating by a sputtering process to conceal from view said bus bars, said process requiring a maximum temperature of le'ss than 250°F.

41. A method of Claim 1 in which before the step of applying the selected metal compound, the substrate is treated by the steps of: washing the substrate with a detergent wash; rinsing said substrate with water; drying said substrate with warm blown air; and atomically cleaning said substrate in a vacuum system using a wet gas, glow discharge technique.

42. A method in accordance with Claim 1 for screening from view a thinq behind or within a portion of the transparent substrate provided by applying the dark coating to the portion selected of said substrate which portion includes a predetermined area within the line of sight of the thing intended to be concealed from view.

43. The method of Claim 42 in which the transparent substrate provided is a vehicle window and the thing intended to be concealed from view is a bus bar.

44. The method of Claim 43 in which the portion selected of the substrate is a border portion at the periphery of the window.

45. The method of Claim 44 in which the window is an automobile window or windshield.

46. The method of Claim 44 in which the window is an aircraft window or windshield.

47. The method of Claim 42 in which the transparent substrate provided is a computer screen.

48. A transparent substrate in accordance with Claim 1 including a dark coating applied in a thickness of a range from 2 micro-inches to 400 micro-inches to a portion thereof which allows negligible or no light transmittance in the wavelengths visible to the human eye and substantially conceals from view a thing which would otherwise be visible behind said coated portion if said coating had not been applied.

49. A substrate in accordance with Claim 48 in which the substrate is a laminate and the dark coating is applied to any one or more surfaces of the separate substrates forming the laminate.