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Method for making electrochromic films having improved etch resistance

  • US 4,233,339 A
  • Filed: 10/23/1978
  • Issued: 11/11/1980
  • Est. Priority Date: 10/23/1978
  • Status: Expired due to Term
First Claim
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1. A method for improving the resistance of electrochromic material to the degrading effects, such as etching, resulting from contact with electrolyte means associated with electrochromic displays, comprising the steps of:

  • (a) forming an amorphous, water-bearing film of electrochromic material of selected thickness, said film having electrochromic properties suitable for display purposes but having a free surface susceptible to etching by said electrolyte means;

    (b) subjecting the film to a heat treatment at a selected high temperature at least equivalent to the crystallization temperature of said electrochromic material for a selected short time of sufficient duration so as to cause crystallization through at least the free surface portion of the film thickness but of insufficient duration to cause substantial loss of water from said film,whereby crystallization of at least said free surface portion substantially increases resistance of the film to etching while retention of water in the film preserves the electrochromic properties for display purposes.

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