Marking of articles with photochromic compounds
First Claim
1. A security device in the form of a label, document or card which incorporates a security mark or device which is partially or wholly invisible in light which does not contain a U.V. component, said device comprising:
- (a) a flexible substrate having printed thereon a mark or device in a clear, dried, reversibly photochromic ink film, said ink in its liquid state comprising a solution of from 1 to 5% of a photochromic compound in a solvent/resin medium and said photochromic compound being selected from fulgides, fulgimides, benzopyrans and naphthopyrans and said dried ink film being from 10 to 60 microns thick, and(b) a clear, superficial protective layer extending over said mark or device, which gives protection for the photochromic compound against degradation by atmospheric moisture and oxygen,whereby said photochromic compound is converted to a colored form on exposure to U.V. light within about 60 seconds and reverts to a pale or substantially colourless form within about 2 minutes in the absence of U.V. light.
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Accused Products
Abstract
A method of marking an article or substrate with a mark or device which is made visible or is enhanced on exposure to U.V. light which comprises printing onto the article or substrate a photochromic ink containing a photochromic compound which is reversibly converted to a colored form on exposure to U.V. light and reverts to a substantially colorless form in the absence of U.V. light and applying a superficial protective layer to said mark or device which protects the phototochromic compound against degradation by atmospheric moisture and oxygen. In addition the invention includes a security device in the form of a label, document or card which incorporates a mark or device which is partially or wholly invisible in light which does not contain a U.V. component, which comprises a substrate having printed thereon using a photochromic ink a mark or device and having a clear, superficial protective layer over said mark or device gives protection for the photochromic compound against degradation by atmospheric moisture and oxygen, said photochromic compound being converted to a colored form on exposure to U.V. light and reverting to a pale or substantially colorless form in the absence of U.V. light.
134 Citations
11 Claims
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1. A security device in the form of a label, document or card which incorporates a security mark or device which is partially or wholly invisible in light which does not contain a U.V. component, said device comprising:
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(a) a flexible substrate having printed thereon a mark or device in a clear, dried, reversibly photochromic ink film, said ink in its liquid state comprising a solution of from 1 to 5% of a photochromic compound in a solvent/resin medium and said photochromic compound being selected from fulgides, fulgimides, benzopyrans and naphthopyrans and said dried ink film being from 10 to 60 microns thick, and (b) a clear, superficial protective layer extending over said mark or device, which gives protection for the photochromic compound against degradation by atmospheric moisture and oxygen, whereby said photochromic compound is converted to a colored form on exposure to U.V. light within about 60 seconds and reverts to a pale or substantially colourless form within about 2 minutes in the absence of U.V. light. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of marking an article or substrate with a security or identification mark or device which is made visible or its visibility is enhanced on exposure to U.V. light, said method comprising the steps of:
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(a) printing onto the article or substrate a photochromic ink which comprises a solution in a clear ink, including a varnish or resin component and a solvent, of from 1 to 5% by weight of a photochromic compound selected from fulgides, fulgimides, benzopyrans and naphthopyrans, (b) drying the ink to form a clear, dried ink film which is reversibly converted to a colored form on exposure to U.V. light within about 60 seconds and reverts to a substantially colorless form within about 2 minutes in the presence of white light having substantially no U.V. component, and (c) applying over the resulting printed mark or device, a superficial, protective layer having reduced permeability to oxygen and water so as to protect the photochromic compound against degradation by atmospheric moisture and oxygen. - View Dependent Claims (8, 9, 10, 11)
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Specification