Printing – Embossing or penetrating – Processes
Patent
1997-06-16
1999-01-26
Burr, Edgar
Printing
Embossing or penetrating
Processes
101 25, 101 27, 101488, B31F 107, B44C 124
Patent
active
058627502
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for impressing directly on paper holograms, kinetic holograms, diffraction patterns or microengravings producing other optical effects.
In order to permanently transfer optical microengravings (i.e. microengravings of the above-mentioned type) from a type plate to paper sheets it is usually necessary to provide a pretreatment of the paper consisting of a coating of the paper with a film of a material (such as PVC, polyester, polypropylene, polythene, coating, etc.) suitable to receive and permanently retain the microengravings present (in low relief and/or high relief) on the plate.
In fact, it is usually excluded that it is possible to transfer directly said microengravings onto common paper (i.e. not pre-treated as above) due both to the deformability (at micrometric level) of paper in time and to the surface micro-roughness usually found in paper sheets, caused by the fibrous structure of paper, which roughness is not compatible with the degree of resolution of the microengravings to be transferred, which can range from about 120 lines/mm to about 5000 lines/mm.
The present invention is aimed at overcoming said prejudice on the impossibility of impressing microengravings on common untreated paper by providing a method for impressing microengravings on common paper, which not only is simpler and cheaper than the conventional methods for impressing microengravings on a pre-treated paper substrate but also gives further advantages such as making available: type of microengravings; writing paper and printing paper (for offset, copperplate, typographic, serigraphic, rotogravure, xerographic, etc., printing); protected from forgery or guaranteed for originality.
According to the method of the present invention for impressing directly on paper holograms, kinetic holograms, diffraction patterns or microengravings producing other optical effects, the impression of said microengravings is achieved by means of an embossing process wherein the paper is passed between a pair of embossing cylinders, namely an embossing cylinder, carrying said microengravings, and a counterthrust cylinder, said process being carried out, after humidification of the paper, at a temperature and a pressure on the paper passing between said cylinders respectively within the ranges of 90.degree.-220.degree. C. and 20-120 kg/mm.sup.2, preferably 130.degree.-170.degree. C. and 40-100 kg/mm.sup.2.
The characteristics of the invention will be apparent from the following description and from the annexed drawings which illustrate non-limiting examples of embodiments, whose figures show:
FIG. 1: a machine for embossing paper in reels according to the present method;
FIG. 2: an enlarged detail of FIG.1 relating to the paper humidifier;
FIG. 3: a machine for embossing paper in sheets according to the present method.
FIG. 1 shows an example of a machine for embossing paper in reels according to the present invention.
The structural and functional characteristics of the machine follow those of a conventional embossing machine with substantial differences regarding the conditions (temperature and pressure) under which the embossing process is carried out and regarding the presence of a paper humidifier upstream from the embossing group consisting of the embossing cylinder and the relevant counterthrust cylinder.
In FIG. 1, the meaning of the various members is the following: pre-heating the paper strip. cooling the paper strip. respectively in order to assure the friction driving of the paper strip by rollers 8 and 9. shifting their axis so as to keep the passing strip in conditions of proper tension. on its cylindrical surface the matrix of the microengravings to be impressed on the paper (the microengravings may be engraved directly on the embossing cylinder or on a thin type plate fixed onto the cylinder), and of an idle counterthrust cylinder 18 exerting on cylinder 17 an adequate pressure. gas and capable of shifting vertically for moving closer/farther with respect to the passing strip in order to adjust
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Database WPI, Week 9442, Derwent Publications Ltd., GB AN 94-338829 & JP, A, 06 264 400 (Tokushi Seishi KK), 20 Sep. 1994.
Burr Edgar
Grohusky Leslie
Oranmay Investments B.V.
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