摘要 |
Hidden entries are provided on a receptor sheet by applying the desired intelligence to the sheet with a chemical densensitizing agent capable of preventing the formation of a visible image on the receptor sheet when the sheet is contacted with a mark-producing agent. The resulting visible image is provided in the form of a negative wherein the background of the visible image is provided by the mark-forming agent, while the foreground of the visible image is the densensitized portion of the sheet. The mark-forming system comprises a chromogenic composition which is applied to the surface of the receptor sheet adjacent the desensitized portion thereof. The coreactant for the chromogen may either be present on the receptor sheet prior to providing the hidden image thereon by means of a chemical desensitizer, or may be admixed with the chromogen prior to application thereof to the surface of the sheet.
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