Paper for secret documents with security marks and the method of its manufacture.
Patent. 2705107 France, IPC D21H 21/48. — Published. 11/18/94.
Paper for secret documents with security marks and the method of its manufacture.
There are various methods of protecting secret documents and securities, such as banknotes, bank checks, passports, etc., from counterfeiting by including certain security elements in them (for example, metal or plastic threads or strips included in the paper on which these documents are printed). These elements are identified in transmitted light.
Methods for incorporating such elements into paper are described, for example, in French patent applications EP-A-59056 and EP-A-229645. They proposed using metal threads with reflective properties as security elements. These reflective threads prevent documents from being copied, as dark stripes appear on the copies.
Patent application EP-A-377167 describes a method for incorporating threads into paper for classified documents, which are located at certain points on the surface of the paper and whose structure deflects light. These could be, for example, holograms recorded on a very thin aluminum film and applied to the paper using the transfer method. However, when printing text on such paper, for example using the offset method, particles of the aluminum film stick to the printing matrices, which degrades the quality of the printed text. To avoid this effect, it was proposed to first print the text and then apply the holograms.
The present invention aims to eliminate the above-mentioned drawbacks and inconveniences. For this purpose, it is proposed to use paper containing at least one security element at a certain point on its surface, covered with a protective film. This element may have a surface that reflects or scatters light. Preferably, this element contains a hologram.
It is recommended to protect the hologram with a thin plastic film or colorless varnish to improve the quality of printing.
In the process of manufacturing paper for secret documents, a security tape is included in it, carrying at least one security element covered with a security film. This tape may be plastic and transparent, soluble in water, for example, obtained from polyvinyl alcohol or, more generally, from polyester. It may be manufactured separately, for example, from synthetic fibers and included in the paper pulp so that it becomes invisible in the finished paper. In this case, the security element is located at the level of the paper surface and is supported by a tape.
An example of the production of paper for secret documents with security elements in the form of holograms in the shape of a symmetrical star is given.