GB652858A - Colored mirrors - Google Patents

Abstract

652,858. Reflective surfaces. LIBBEYOWENS-FORD GLASS CO. July 29, 1946, No. 22543. Convention date, Feb. 11. [Class 97 (i)] A mirror giving a coloured reflected image by light interference comprises a support carrying a plurality of thin transparent superimposed layers of different substances each layer having a thickness not greater than 9#/4N when # is the wavelength of minimum reflection from the mirror and N is the refractive index, and an opaque speculary reflective backing on the layers having a different refractive index than the layer in contact therewith and reflecting incident light back through the superimposed layers. The. layers may be deposited chemically or by thermal evaporation in vacuo. Fig. 10 shows a support 1, which need not be transparent bearing an opaque silver reflective layer 3, two interference layers 12, 13 of zinc sulphide and silica respectively and a lacquer protective layer 15. Alternatively the mirror layer 3 may be in the place of the layer 15 and be of silver, copper, aluminium or gold. Thus the following examples are described : glass coated with interference layers, in order, of copper and magnesium fluoride, copper-silica, silvermagnesium fluoride, aluminium-silica, chromium-magnesium fluoride, all backed by a reflective layer of silver ; copper and magnesium fluoride or magnesium fluoride and copper, aluminium and silica or silica and aluminium, all backed by silver, copper, aluminium or gold. Alternatively, glass may have on one side an opaque reflective layer of silver and on the other layers of lead sulphide and silica. An all-metal coating comprises copper-aluminium or aluminium copper backed by silver or copper. Multiple layers may be used. Thus glass may be coated alternately with layers of copper and silica, the mirror being finally backed with silver or copper. Synthetic plastics may be used as supports and many examples of suitable backing materials are given such as magnesium, iron, nickel, rhodium, cobalt, iridium, indium, antimony, molybdenum, palladium, cadmium and lead sulphide. Other suitable substances for the interference layers include stibnite, molybdenite, pyrite, silicon, antimony, calcium or lithium fluoride, oxides of lead, magnesium, silver, aluminium, arsenic, tin, titanium, and iron, copper sulphide lead selenide, chlorides of silver, sodium and lead. Specifications 624,846, 632,570, 652,851 and 652,859 are referred to.