Documents containing information invisible to the naked eye
US4504084A · kind A · utility
115Cited by
11References
4Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | Jan 30, 1984 |
| Grant date | Mar 12, 1985 |
| Priority date | — |
| Expiry date | Jan 30, 2004 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S283/901
- WIPO fieldOther consumer goods
- WIPO sectorOther fields
Abstract
A document is disclosed, which contains information invisible to the naked eye, but which information can be made visible by a simple method. Said information is represented by markings on the document, which markings comprise a first color at least partially opaque to at least part of the invisible light spectrum, and a second color which serves to conceal said first color in the visible spectrum, but which second color is itself transparent to said part of the invisible light spectrum.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.