United States Patent  [li] Patent Number: 4,963,012
Tracy et al.  Date of Patent: Oct. 16,1990
 PASSIVATION COATING FOR FLEXIBLE SUBSTRATE MIRRORS
 Inventors: C. Edwin Tracy; David K. Benson,
both of Golden, Colo.
 Assignee: The United States of America as represented by the United States Department of Energy, Washington, D.C.
 Appl. No.: 259,634
 Filed: Oct. 19,1988
Related U.S. Application Data
 Continuation-in-part of Ser. No. 873,069, Jun. 4, 1986, Pat No. 4,780,372, which is a continuation of Ser. No. 632,742, Jul. 20, 1984, abandoned.
 Int. CI.5 G02B 5/08; G02B 7/18
 U.S. a 350/641; 350/164;
 Field of Search 350/641, 642, 582, 164-166,
350/320; 428/428, 434, 460-463
 References Cited
U.S. PATENT DOCUMENTS
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Primary Examiner—Bruce Y. Arnold
Assistant Examiner—Thong Nguyen
Attorney, Agent, or Firm—Kenneth Richardson; John
M. Albrecht; William R. Moser
A protective diffusion barrier for metalized mirror structures is provided by a layer or coating of silicon nitride which is a very dense, transparent, dielectric material that is impervious to water, alkali, and other impurities and corrosive substances that typically attack the metal layers of mirrors and cause degradation of the mirrors' reflectivity. The silicon nitride layer can be deposited on the substrate before metal deposition thereon to stabilize the metal/substrate interface, and it can be deposited over the metal to encapsulate it and protect the metal from corrosion or other degradation. Mirrors coated with silicon nitride according to this invention can also be used as front surface mirrors. Also, the silver or other reflective metal layer on mirrors comprising thin, lightweight, flexible substrates of metal or polymer sheets coated with glassy layers can be protected with silicon nitride according to this invention.
25 Claims, 6 Drawing Sheets