Durable sputtered films of metal alloy oxides.

DESCRIPTION

The present invention relates in general to the technique of cathodic sublimation of films of metabolic oxides, and more particularly to the technique of cathode magnetic sublimation of films of multiple layers of metal and metal oxide oxide layers.

U.S. Pat. A-4,094,763 of Gillery et al. describes the production of transparent electroconductive articles by cathodic sublimation of metals such as tin and indium on refractory substrates such as glass, at a temperature above 204 ° C in a low-pressure atmosphere containing a controlled amount of oxygen.

U.S. Pat. Gillery's A-4,113,599 teaches a cathodic sublimation technique for the reactive deposition of indium oxide, in which the oxygen flow rate is adjusted to maintain a constant discharge current, while the argon flow rate is adjusted to maintain constant pressure in the cathode sublimation chamber.

U.S. Pat. Chapin A-4,166,018 discloses a cathodic sublimation apparatus in which a magnetic field adjacent to a flat cathode sublimation surface is formed, the field comprising arcuate flow lines on a closed mesh erosion region in the sublimation surface Cathodic

U.S. Pat. Gillery's A-4,201,649 discloses a method for manufacturing thin films of low resistance indium oxides by first depositing a very thin primary layer (primer) of low temperature indium oxide before heating the substrate to deposit the main thickness of the Conductive layer of indium oxide by cathode sublimation at topically high cathode sublimation temperatures.

U.S. Pat. Groth's A-4,327,967 discloses a thermo-reflective panel that has a neutral neutral appearance and comprises a glass sheet, an interference film having a refractive index greater than 2 on the glass surface, a gold film thermoreflector on the interference film and a neutralization film of chromium, iron, nickel, titanium or their alloys on the gold film.

U.S. Pat. A-4,349,425 of Miyake et al. It describes the reactive cathode sublimation of cadmium-stannous alloys in argon-oxogen mixtures to form stannous cadmium-oxide films that have low electrical resistance and high optical transparency.

U.S. Pat. Hart's A-4,462,883 describes a low emissivity coating produced by cathodic sublimation of a layer of silver, a small amount of metal other than silver and an antireflection layer of metalic oxide on a transparent substrate such as glass. The antireflection layer may be stannous oxide, titanium oxide, zinc oxide, indium oxide, bismuth oxide or zirconium oxide.

The US Reissue No. 27,473 of Mauer describes a transparent multilayer article comprising a thin layer of copper sandwiched between two layers of transparent material such as various metals, titanium oxide, lead oxide or bismuth oxide.

DE A-10 88198 describes a method for producing electrically conductive transparent coatings on glass sheets. The first layer is an adhesive layer of a metalic oxide, a metalic sulphide, a metalic sulfate or other metalic compound. A first conductive film of gold, silver, copper, iron or metal is deposited on the primary layer. A second layer of metal oxide adhesion is deposited on the first metal film and on it a second conductive metal layer is deposited, selected from chromium, nickel or an alloy of metals. If desired, a protective final coating can be deposited, selected from SiO2, alumina, magnesium fluoride or other useful material.

EP-A-35 906 refers to a selectively light-transmitting stratified structure having a transparent substrate, for example glass or a polymer and a plurality of coatings deposited thereon. The first layer on the substrate has a high refractive index and is selected from ZnS or a metalic oxide of the metals Ti, In, Zn, Sn, Y, Er, Zr, Ce, Ta and Hf. The second layer is a film that contains silver. In said film a third layer of a material selected from Ti, Zr, In, Si, C and Ni is provided. The fourth layer is also in a layer similar to the first layer. A transparent final layer seems to improve the surface hardness and strength of the structure selected from SiO2 or organic polymers.

EP-A-104 870 describes low emissivity coatings on transparent substrates of glass or plastic material. The first layer is an antireflector layer of tin oxide, titanium oxide, indium oxide, bismuth oxide or zirconium oxide. A layer of silver is deposited on it. An additional film of a layer of metal oxide similar to the first layer is deposited on the silver layer.

EP-A-183 052, which is a document according to Art. 54 (3) EPC, describes a transparent non-metallic substrate with several coatings on top. The first layer is an oxyxide reaction product of a metal alloy comprising zinc and tin. A transparent film of an oxide reaction product of a metal alloy comprising zinc and tin is deposited on the metal film. An additional primary layer may be deposited on the first metal oxide film and a second primary layer may be deposited on said metal film. A protective metal coating may be present, for example, from iron or nickel alloys such as stainless steel or Inconel.

In order to improve the energy efficiency of double window units, it is desirable to provide a coating on one of the glass surfaces that increases the insulating capacity of the unit by reducing the radioactive heat transfer. The coating must therefore have a low emissivity in the longi2 range

015 525 tud of infrared wave of the radiation spectrum. For practical reasons, the coating must have a high transmittance in the visible wavelength range. For esthetic reasons, the coating should have a low luminous reflectance and preferably be essentially colorless.

The high transmittance and low emissivity coatings as described above generally comprise a thin metal layer, for infrared reflectance and low emissivity, sandwiched between dielectric layers of metal oxides to reduce visible reflectance. These multilayer films are produced topically by cathodic sublimation, especially magnetron cathode sublimation. The metallic layer may be gold or copper, but it is usually silver. The layers of metal oxide described in the prior art include stannous oxide, indium oxide, titanium oxide, bismuth oxide, zinc oxide, zirconium oxide and lead oxide. In some cases, these oxides incorporate small amounts of other metals, such as manganese in bismuth oxide, indium in tin oxide and vice versa, to overcome certain disadvantages such as poor durability or marginal emissivity. However, all these metalic oxides have some deficiency.

Although the coating can be maintained on an inner surface of a double-window unit in use, where it is protected from environmental elements and agents that caused its deterioration, a durable effective coating capable of resisting handling, packaging, washing is particularly desirable. and other manufacturing procedures encountered between manufacturing and installation. These properties are sought in the metabolic oxide. However, in addition to the hardness that provides mechanical durability, inertia that provides chemical durability, and good adhesion to the glass and the metabolic layer, the metalic oxide must also have the following properties.

The methanol oxide must have a reasonably high refractive index, preferably greater than 2.0, to reduce the reflection of the metabolic layer and thus improve the transmittance of the coated product. Metallic oxide must also have a minimum absorption to maximize the transmittance of the coated product. For commercial reasons, the metabolic oxide should be reasonably priced, have a relatively rapid deposition rate due to magnetroonic cathode sublimation and be non-toxic.

Perhaps the most important requirements, and the most difficult to satisfy, of the metal oxidic film, refer to its interaction with the metalic film. The metal oxyxide film must have low porosity, to protect the underlying metal film from agents external, and low diffusivity for the metal in order to maintain the integrity of the separated layers. Finally, and above all, the metal oxide must provide a good nucleation surface to deposit the metal layer, so that a continuous metal film with a minimum resistance and maximum transmittance can be deposited. The characteristics of continuous and discontinuous silver films are described in the

U.S. Patent A-4,462,884 of Gillery et al.

Of the multilayer films of general-purpose metaol oxide, those comprising zinc oxide and bismuth oxide are insufficiently durable, the oxides being soluble in acidic and alkaline agents, the film of the multilayer layers being degraded by fingerprints and destroyed in tests with salt, sulfur dioxide and moisture. Indium oxide, preferably impurified with tin, is more durable and protective of an underlying metal layer; however, the Indian sublimates cathodically slowly and is relatively expensive. Tin oxide, which can be impurified with indium or antimony, is also more durable and protective of an underlying metabolic layer, but does not provide a suitable surface for the nucleation of the silver film, producing high electrical resistance and low transmittance. The characteristics of a methanoxide film that produce an appropriate nucleation of a subsequently deposited silver film have not been established; however, experimentation has been widely practiced by scores with the metabolic oxides described above.

The U.S. Patent Application Serial No. 665,680, filed on October 29, 1984 by FH Gillery, provides a new film composition of a metal oxide alloy, as well as a new multi-layer film of metal oxide and metal alloy alloys layers as a high transmittance and low emissivity coating.

The object of the present invention is to improve the duration of multilayer films, especially multilayer films comprising metal oxides layers and / or metal alloys and metal layers such as silver, by an outer protective layer of a resistant material particularly funny.

This object is achieved by an article of high transmittance and low emissivity, which comprises: a) a transparent non-metallic substrate;

b) a first transparent antireffective film comprising a metalic oxide deposited on a surface of said substrate; c) a transparent infrared reflective metal film deposited after said first anti-reflective metalic oxide film; d) a second transparent anti-reflective film comprising a deposited metal oxide after said infrared reflective metal film; and e) an overcoat of protective oxyxide deposited after said second anti-reflective metalic oxide film, characterized in that the anti-reflective metalic oxide films comprise an oxide reaction product of an alloy comprising zinc and tin.

A film composition preferably comprising an oxide of a metal or of a metal alloy is preferably deposited by cathode sublimation, preferably magnetronic cathode sublimation. An anticóatodo is prepared comprising the desired metal elements or metal alloy. The anti-cathode is then sublimated cathodically into a reactive atmosphere, which preferably contains oxygen,

015 525 in order to deposit a film of metal oxide or metal alloy on a surface of a substrate.

An oxide of a preferred metabolic alloy followed by the present invention is an oxide of an alloy comprising zinc and tin. A zinc / tin alloy oxide film can be deposited according to the present invention by cathode sublimation, preferably magnetically increased. The cathodic sublimation is also a preferred method for depositing high transmittance and low emissivity films according to the present invention. Such films topically comprise multiple layers, preferably a highly reflective metal layer such as gold or silver sandwiched between layers of anti-reflective metal oxides of an oxide of a zinc alloy and stanne which preferably comprises zinc stannate.

Although various metal alloys can be sublimated cathodematically to form oxides films of metal alloys, in order to produce a preferred multilayer film of high transmittance and low emissivity in accordance with the present invention, tin and zinc alloys are preferred. A particularly preferred alloy comprises zinc and tin, preferably in proportions of 10 to 90 percent zinc and 90 to 10 percent tin. A preferred zinc / tin alloy ranges from 30 to 60 percent zinc, preferably having a zinc / tin ratio of 40:60 to 60:40. An interval, the preferred maos, is 46:54 to 50:50 by weight of tin to zinc. A reactively sublimated zinc / stannous alloy cathode in an oxidizing atmosphere produces the deposition of a layer of methanoxide comprising zinc, stanne and oxygen, preferably comprising zinc stannate, Zn2SnO4.

In a conventional magnetronic cathodic sublimation procedure, a substrate is placed inside a facing chamber in relation to a coatode having an objective surface of the material to sublimate cathodically. Preferred substrates according to the present invention include glass, ceramic products and plastics that are not adversely affected by the operating conditions of the coating process.

The cathode can be of any conventional design, preferably an elongated rectangular design, connected to a source of electrical potential, and preferably used in combination with a magnetic field to improve the process of sublimation cathode. At least one surface of the anticóatodo comprises a metal alloy such as zinc / stannous that sublimates cathodesically in a reactive atmosphere to form a film of metalic alloy oxide. The anode is preferably a set designed and symmetrically located as taught in US Pat. A-4,478,702 of Gillery et al.

In a preferred embodiment of the present invention, a multilayer film is deposited by cathode sublimation to form a coating of high transmittance and low emissivity. In addition to the metal alloy alloy cathode, at least one other cathode surface comprises a metal to be sublimated cathodically to form a reflective metal layer. At least one surface of the additional anticoratode comprises the metal to be deposited as the primary layer. A durable multi-layer coating is produced as follows, which has a reflective metal film in combination with an anti-reflective metal alloy oxide film, using primary layers to improve the adhesion between the metal and metal oxide films.

A clean glass substrate is placed in a coating chamber in which the vacuum is made, preferably at less than 1.33x10^-2 Pa (10^-4torr), more preferably less than 2.66x10^-3Pa (2 x 10^-5 torr). A selective atmosphere of inert gases and reagents, preferably argon and oxygen, is established in the chamber, up to a pressure between 6.65 x 10^-2 Pay10Pa (5x10^-4 y10² torr). A coatode having an anti-cathode surface of zinc / tin metal alloy is actuated on the surface of the substrate to be coated. The metal of the anti-cathode is sublimated cathodically, reacting with the chamber's atmosphere to deposit a layer of zinc alloy / stannous oxide oxide coating on the glass surface.

After depositing the initial layer of zinc alloy / tin alloy, the vacuum is made in the coating chamber, and an inert atmosphere such as pure argoon is established at a pressure between 6.65 x 10^-2 Pay10Pa (5x10^-4 and 10^-2 torr). A coatode that has an anticóatode surface of a metal such as copper is cathodically sublimated to deposit a primary layer on the oxide layer of zinc / stan alloy. A coatode having a surface of silver anticóatodo is then sublimated cathodically to deposit a reflective layer of silver metal on the primary layer that improves the adhesion of the silver film to the underlying film of methoal oxide. A metal such as copper is then deposited on the reflective silver layer to improve the adhesion between the silver film and the subsequently deposited superimposed metal oxide film. Finally, a second primary layer is deposited under essentially the same conditions used to deposit the first layer of zinc alloy / tin alloy.

In the most preferred embodiments of the present invention, a protective overcoat is deposited on the final metal oxide film. The protective overcoating is preferably deposited cathodically sublimed onto the film of metal oxide a layer. Preferred metals for protective overcoating include iron-nickel alloys, such as stainless steel or Inconel. Titanium is a preferred overcoating due to its high transmittance.

Following the present invention, the chemical resistance of a multilayer film is further enhanced by depositing a protective coating comprising titanium oxide on the multilayer film. Preferably, the titanium oxide protective coating is deposited cathodically sublimating at a rate of 4

015 525 relatively high position and low pressure, preferably around 3.99 x 10^-1 Pa (3 millitorr). A protective coating comprising titanium oxide can be formed by sublimating titanium in an atmosphere with sufficient oxygen to directly deposit titanium oxide. In an alternative embodiment of the present invention, a protective coating comprising titanium oxide cathodely sublimating titanium can be formed in an inert atmosphere to deposit a titanium-containing film that subsequently oxidizes to titanium oxide by exposure to an oxidizing atmosphere such as air .

The present invention will be further understood from the description of a specific example that follows. In the example, reference is made to the zinc alloy / stannous oxide oxide film as zinc stannate, although the composition of the film does not need to be precisely Zn2SnO4.

Example

A multi-layered film is deposited on a glass substrate of sodium-solchoic solid to produce a coated product of high transmittance and low emissivity. A stationary cathode measuring 12.7 by 43.2 centimeters comprises a cathode sublimation surface of zinc / tin alloy consisting of 52.4 percent by weight of zinc and 47.6 percent of tin. A substrate of sodicocaolic silica glass is placed in the coating chamber, in which the vacuum is made until a pressure of 5.32 x 10 is established^-1 Pa (4 millitorr) in a 50/50 argon / oxygen atmosphere. The catode is sublimated in a magnetic field with a power of 1.7 kilowatts while the glass is transported past the cathodic sublimation surface with a speed of 2.8 meters per minute. A zinc stannate film is deposited on the glass surface. Three passes produce a film thickness of 34x10^-3 μm (340 Angstroms), producing a 83 percent decrease in glass for the glass substrate coated with zinc stannate. A stationary cathode is then sublimated cathodically with a copper anticatode to produce a primary layer of copper on zinc stannate, reducing the transmittance to approximately 80.6 percent. Subsequently, a silver layer is deposited on the primary layer of sublimed copper, a silver antipode in an argon gas atmosphere at a pressure of 5.32 x 10^-1 Pa (4 millitorr). By passing the substrate under the silver anti-iodine at the same speed, two passes are necessary to deposit ten micrograms of silver per square centimeter, corresponding to a film thickness of approximately 9x10^-3μm (90 Angstroms), decreasing the transmittance of the coated substrate to approximately

70.3 percent A second primary layer of copper is sublimated cathoidically over the silver layer to improve the adhesion and protect the silver layer before depositing the final anti-reflective zinc stannate layer. Since the primary copper layers decrease the transmittance, their thicknesses are preferably minimal. The primary copper layers are deposited by cathodically sublimating a copper target with minimum argon power at a pressure of 5.32 x 10^-1 Pa (4 millitorr). The transmittance of the sample decreases to 68.3 percent after depositing the second primary layer of copper. Next, the zinc / tin alloy anticathode is cathodically sublimated in an oxidizing atmosphere to produce a zinc stannate film. Four passes at a speed of 2.8 meters per minute produces a film thickness of approximately 43 x 10^-3 μm (430 Angstroms), increasing the transmittance of the coated product from 68.3 to 83.2 percent. The multilayer coating has a surface resistance of 10 ohms per square and a slightly bluish reflectance of both sides, with a luminous reflectance of 5 percent of the coated face and 6 percent of the uncoated glass face. Finally, a stationary titanium catode measuring 12.7 by 43.4 centimeters is sublimated to 10 kilowatts in an atmoisphere that comprises equal volumes of argon and oxygen at a pressure of 3.99 x 10^-1 Pa (3 millitorr). Two passes of the substrate at a speed of 2.8 meters per minute are sufficient to deposit a 1.5 x 10 titanium oxygen coating^-3at 2x10^-3 μm (15 to 20 Angstroms) thick. The protective coating of titanium oxide does not significantly affect the strength and reflectance properties of the multilayer coating, and changes the non-mine transmittance of approximately one percent.

The improved duration of the coated article resulting from the improved adhesion between the metal and metal oxide films as a result of the primary layers of the present invention is readily demonstrated by a simple abrasion test consisting of cleaning the coated surface with a wet cloth. A surface coated with zinc / silver stannate / zinc stannate that does not have primary layers following the present invention increases the reflectance from about 6 percent to about 18 percent after several passes of a wet pan, indicating the elimination of Final zinc stannate and underlying silver layers. In contrast, prolonged vigorous rubbing with a wet cloth does not produce visible change in an article coated with zinc / copper / silver / copper / zinc stannate comprising the primary layers of the present invention.

Preferred titanium oxide protective coatings have thicknesses in the range of 1 x 10^-3 at 5x10^-3 μm (10 to 50 Angstroms). With a 2 x 10 titanium oxide protective coating^-3 µm (20 Angstroms) thick, the duration of a multilayer coating following this example increases from 2 hours to 22 hours in a salt solution to 21/2 percent at room temperature, and from 5 hours to a week in the Cleveland moisture test performed with a Cleveland Q Q-ADO Model Q Condensation Meter containing deionized water at approximately 66 ° C.

The above example is offered to illustrate the present invention. Various product and process modifications are included. By

015 525 example, other coating compositions are within the scope of the present invention. Depending on the proportions of zinc and tin when a zinc / tin alloy is cathodically sublimated, the coating may contain widely varying amounts of zinc oxide and tin oxide in addition to zinc stannate. The adhesion between a wide variety of metal and methanol oxide films can be improved by means of primary layers according to the present invention. Since the process does not require very high temperatures, substrates other than glass, such as various plastics, can be coated. An exploration coatode with a stationary substrate can be used. They can be varied over a wide range of process parameters such as pressure and gas concentration. The primary layers may comprise other metals, such as indium, or oxides such as copper oxides or indium oxide. Protective coatings of other chemically resistant materials can be deposited in the metal or oxide state.

015 525