Method of making high-reflection mirrors

Details Method of making high-reflection mirrors Method of making high-reflection mirrors

2000-08-28

2001-08-14

Shafer, Ricky D. (Department: 2872)

Optical: systems and elements

Having significant infrared or ultraviolet property

Multilayer filter or multilayer reflector

C359S584000, C359S585000, C359S589000, C359S883000, C359S900000

Reexamination Certificate

active

06275332

ABSTRACT:

FIELD AND BACKGROUND OF THE INVENTION
The present invention relates, in general, to a high-reflection silver containing mirror and specifically, to an environmentally stable silver containing mirror having very high reflection values over a wide spectral range.
Silver is a material with excellent optical properties. It is used inter alia In the protection of highly, reflecting mirrors and, in particular, for the production of elements for regulating solar energy transmission such as architectural glass coatings, heat protection layers, automobile windows and the like. The use of silver as an optical thin-film material is extensively described for example in the publication “Thin-film Optical Filters”, H. A. Macleod, Adam Hilger Ltd., Second Edition. Unfortunately, silver has poor environmental compatibility, since it is, on the one hand, relatively soft and consequently can readily be mechanically damaged and, on the other hand, an impairment of optical properties occurs due to corrosion if the silver mirror is exposed without protection against the environment or specific media. Silver sulfides, for example, are formed.
For this reason silver layers are frequently packed in layer systems wherein the material selected for the remaining layers is determined, on the one hand, by the desired optical properties such as spectral properties as well as the other hand by the necessity of increasing the resistance of the silver layer relative % environmental influences. A consideration of the nucleation properties of silver on these materials is also of significance, however.
Oxides, zinc sulfide, nitrides or metals are frequently used in order to pack silver. In particular, oxides are used due to their optical properties and their resistance and also because of their hardness. Applying the oxide layer, however, can already cause a degradation of the silver which is the reason why, in prior art, measures tome been suggested in order to avoid this problem.
For example DR-OS-33 07 661 suggests first covering the silver layer with a further metal layer comprising aluminum, titanium, tantalum, chromium, manganese or zirconium, onto which further metal layers; and lastly art oxide layer are disposed, comprising indium oxide, tin oxide or a mixed oxide thereof. DE-OS-35 43 178 suggests a multilayer covering wherein the silver layer, in turn, is covered by a further metal layer comprising tantalum, tungsten, nickel or iron, which further metal layer, in turn, is covered by an oxide layer, wherein SnO, SiO
2
, Al
2
O
3
, Ta
2
O
5
or ZrO
2
are suggested as the oxide layers.
In analogous manner U.S. Pat. No. 3,682,528 suggests covering the silver layer with a thin nickel layer, should further layers be applied.
According to another variant, DE 33 27 256 suggests applying at least one hypostoichiometric oxide layer on the silver, comprising, for example, titanium oxide or titanium nitride or a mixture thereof.
DE-A-33 29 504 suggests covering the silver layer with a dielectric layer wherein the material composition in the region of the transition areas, changes gradually and continuously. Titanium oxide is mentioned, for example, as such a dielectric layer.
Lastly, the U.S. Pat. No. 5,510,173 describes substantially transparent copper and silver plus noble metal coatings. Their ability to withstand corrosive environments is improved by over-coating the metal layers with a double coating of dielectric. The first coating is made up of dielectric based on indium and/or zinc, the second coating is made up of dielectric based on indium and tin.
SUMMARY OF THE INVENTION
The task of the present invention resides in suggesting an environmentally stable silver containing mirror having very high reflection values over a very large special range.
According to the invention a high-reflection silver mirror of this type is suggested comprising at least one silver containing layer disposed on a substrate, which layer is covered by a zinc sulfide layer, characterized in that between the a silver containing layer and zinc sulfide layer, at least one barrier or intermediate layer is disposed.
A high-reflection silver mirror comprises at least one silver containing layer to be disposed an a substrate, which is covered by a zinc sulfide layer, wherein, as an essential feature of the invention, at least one intermediate layer or a barrier layer is placed between the silver containing layer and the zinc sulfide layer. This barrier layer comprises a dielectric material.
The at least one silver containing, layer to be disposed on a substrate is either made up predominantly of silver or of silver, including up to approximately 20 weight % of copper. In addition, this at least silver containing layer may include-minor amounts of gold, platinum or palladium in addition to the adding of copper.
Materials for or the barrier or intermediate layer include oxides of the elements silicon, aluminum, magnesium, of groups VIb, Vb, and IVb, as well as scandium yttrium, calcium, strontium, zinc, iron, indium, tin, cerium, holmium as well as oxides of mixtures or alloys of these elements (in particular indium tin oxide); and further oxinitrides of the elements Tin Ta, Zr, Si, Hf, and Al, as well as fluorides of the elements magnesium, barium, strontium, calcium, the rare earths and lead.
According to a preferred embodiment magnesium fluoride is used for production of the barrier car intermediate layer, wherein the layer thickness can be determined by the desired optical function in general is <1 &mgr;m, but preferably <100 nm
According to a further embodiment it is also possible to provide two barrier or intermediate layers, wherein the one barrier or late layer is an oxide and the other is a fluoride.
According to the invention it is also essential to provide, between the substrate and the silver containing layer, at least one further intermediate layer, wherein this layer again is mainly a protective layer. This further ate layer can comprise for example zinc sulfide. For particular applications it may be necessary that, in addition to this layer, further layers must be placed between the substrate and the silver containing layer, be that in order to increase further the reflection (application of optical correction layers, for example with so-called rear-surface mirrors) or for the purpose of applying adhesion enhancing layers.
Very high reflection values were measured on environmentally stable silver containing mirrors, deflection mirrors for angles of incidence of 45° produced according to the invention, cover a very large spectral range such as for example in the range from 400 nm to 12,500 nm. The reflection values are greater than 95%. In the wave range from 420 nm to 580 nm and fax wavelengths>1,200 nm, even reflection values≧98% were measured. In the range form 2,500 nm to 12,500 nm and from 20,000 nm to 50,000 nm even reflection values>98.5% are obtained. These values apply for non-polarized light.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawing and descriptive matter in which preferred embodiments of the invention are illustrated.


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patent: 4312570 (1982-01-01), Southwell
patent: 4379622 (1983-04-01), Fischer et al.
patent: 4413877 (1983-11-01), Suzuki et al.
patent: 4799745 (1989-01-01), Meyer et al.
patent: 5548440 (1996-08-01), Hohenegger et al.
patent: 5751474 (1998-05-01), Hohenegger et al.
patent: 6128126 (2000-10-01), Hohenegger et al.

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