Marking
Number of patents in Portfolio can not be more than 2000
United States of America Patent
Stats
-
Feb 12, 1991
Issued Date -
N/A
app pub date -
Jan 11, 1990
filing date -
Feb 13, 1987
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A marking comprises a layer, preferably of film-forming material, which contains a photochromic compound. The photochromic compound is capable of changing color when exposed to uv light, but can be converted to a permanently non-photochromic compound, preferably by overexposure to uv light. An image is formed in the layer by converting the photochromic compound to a permanently non-photochromic compound in one or more selected areas. When the layer is subsequently viewed under uv light a colorless image of non-photochromic compound can be seen on a background of colored photochromic compound.
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