Photocopying – Contact printing – Methods
Patent
1983-03-30
1985-12-10
Wintercorn, Richard A.
Photocopying
Contact printing
Methods
283 94, 355 52, 355 71, G03B 2702, G09F 302
Patent
active
045575967
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of producing screened picture themes in which the gray tones of a half-tone picture theme are reproduced by varying a basic screen structure.
The use of security line patterns such as guilloches has been known for some time, in particular for the production of security paper, identification cards and so on, as a means of preventing imitation or falsification of such data carriers. The picture theme to be protected and the security line pattern have been used up to now as separate elements. Swiss patent No. 477 066, for example, describes an identification card in which a photograph of the card owner provided in the card is protected against manipulation by being printed over with a guilloche.
Security printing can be relatively easily and cheaply produced according to this method since the security pattern is printed over the picture theme on a large area without any additional measures being involved. However, it has proved disadvantageous that color blending occurs in the areas in which the picture theme and the security lines are superimposed, thus disturbing the continuity of the color of the line.
When the picture theme and the line pattern have a monochrome design, or the picture theme is very dark, the security lines are either impossible or very difficult to recognize in the picture theme area. This kind of protection technique is therefore only used for security printing of simple quality.
It is customary to avoid such disadvantages, in particular in the printing of bank-notes, by inserting picture themes into recesses or windows in the background guilloche. The picture themes are generally carried out in high-quality steel intaglio printing which itself offers a high degree of protection in spite of the lack of a guilloche pattern over the picture theme. However, it is disadvantageous that the area reserved for the picture theme reduces the area which may be used for the background printing, thus greatly reducing the protection against forgery and falsification provided by a guilloche background pattern when the picture theme is relatively large. The existing security guidelines (stock exchange guidelines), which require, among other things, a percentual minimum area for the guilloche background, do not allow the use of picture themes covering the entire area for security paper bound to these guidelines.
A further method for the production of identification cards has become known which avoids some of the disadvantages of the above-mentioned method in which the security pattern is printed over the picture theme. By the newer method, photographs can be protected, even in their black areas, by clearly recognizable guilloche lines (see German Auslegeschrift No. 29 07 809).
In order to make the security pattern more recognizable, this publication proposed that the photo area be provided with a security pattern before being exposed, so that after exposure the exposed areas of the picture theme are interrupted by an unexposed security pattern and thus the lines of the guilloche pattern are just as recognizable as before.
In spite of the obvious advantages of this method, it involves the disadvantage that this technique can only be used in connection with picture themes which are applied by photographic means. It is not possible to exploit its advantages for other data carriers without using photographic measures.
In accordance with a novel method it has been proposed that security line patterns be integrated into picture themes on security paper or other data carriers. The printed picture theme is overlapped by a printed line pattern, the picture theme being interrupted by a negative contour matching the line pattern, and the line pattern being printed in congruently. Depending on the embodiment, the lines of the negative contour may be just as wide as the lines of the line pattern, or else wider so that the security lines are at a small distance from the picture theme on each side and thus run through the picture theme in the form of free lines, without touching it.
Th
REFERENCES:
patent: 2767093 (1956-10-01), Bilhoefer
patent: 2952080 (1950-09-01), Avakian et al.
patent: 2984030 (1961-05-01), Hannon
patent: 3610120 (1971-10-01), Morse et al.
patent: 3807852 (1974-04-01), Hoydic
patent: 4360548 (1982-11-01), Skees et al.
patent: 4459020 (1984-07-01), May et al.
May Stefan
Muller Hans
GAO Gesellschaft fur Automation und Organisation mbH
Wintercorn Richard A.
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