Radiation imagery chemistry: process – composition – or product th – Dye image from radiation sensitive dye or dye former by dry... – Multiple image formation – multiple image exposure – or...
Patent
1999-02-25
2000-08-22
McPherson, John
Radiation imagery chemistry: process, composition, or product th
Dye image from radiation sensitive dye or dye former by dry...
Multiple image formation, multiple image exposure, or...
430292, 430337, 430338, 430945, 430962, 235488, G03C 556, B41M 314, B41M 528
Patent
active
061070106
DESCRIPTION:
BRIEF SUMMARY
The invention relates to the area of printing and deals in particular with printing a visible thermoplastic or thermosetting polymerized layer of a portable data medium.
The term "printing" in the present invention must be considered in the broad sense as being a technique in which an action is applied to an object in such a way as to leave a visible mark on this object. The portable data medium can be any data medium. However, it is in particular a standard data medium in the smart card format to which reference will be made in the description hereinbelow.
Smart cards and, in general, memory cards have a thermoplastic or thermosetting card body formed of one or more layers. Two faces of this body are visible. These faces show a drawing, a logo, a photographic reproduction, and often written information printed serially according to various known methods.
Certain printing methods involve simply classical ink deposition. Other methods, which are generally more rapid and precise, involve lasers.
The latter known methods include methods in which a colored ink is heat-transferred by a laser from a heat-resistant transfer film applied to one face of the polymerized card body. With different films or different segments of one and the same film having inks of different colors, a card body is obtained that exhibits a color design according to the path of the laser radiation on the film or films. However, such methods, known as indirect methods, require the intermediary of a film from which the inks diffuse and are accordingly slow. Moreover, since the laser radiation diameter applied to the film or films must be sufficient for the inks to be transferred to the surface and/or into the body of the card and, moreover, the colored inks that were not initially present in the card body are likely to diffuse in this body, the definition of the design obtained is poor.
In other known methods, using a YAG laser adjusted to emit infrared electromagnetic radiation, a given zone of a top layer of a multilayer card body is removed to reveal a sublayer of the body whose color is different from that of the top layer. With several superimposed layers of different colors, it is possible to obtain a multicolored card body whose design is defined by directed scanning of the laser radiation. However, ablation of all the layers or sublayers covering a sublayer to obtain a given color of a given area of this sublayer in theory requires several laser passes, which prolongs the time taken by the methods. Moreover, product is wasted and the surface of the printed card body does not stay intact because it has differences in relief. Hence it is not always possible to apply a perfectly flat, transparent, protective film to the card body.
Still other methods propose either evaporation of particular areas of the card body surface, or foaming these areas. This evaporation or foaming is induced by the heat produced by laser radiation. Evaporation leaves a hole and can reveal a colored sublayer of the card body. Foaming changes the nature of the card body surface which for example exhibits differences in refractive index which generate the designs. In general these methods are slow, and both definition and contrast of the design are poor. In addition, as before, the surface of the card body does not remain intact.
Finally, so-called bleaching methods propose directed, selective destruction of pigments or other color molecules contained in a layer of the card body by a laser whose radiation is emitted in the visible range. The color appears negatively. Thus, to cause a given color to appear, two laser irradiations are necessary. For example, to cause blue to appear at the surface of a black layer of a card body that contains blue, red, and yellow pigments, two laser radiations are necessary, one destroying the red pigments, and the other, the yellow pigments. If white is to be obtained, the black layer of the card body is irradiated with three laser radiations of different wavelengths. These methods are slow because obtaining one color at a given
REFERENCES:
patent: 3615454 (1971-10-01), Cescomi
patent: 5330686 (1994-07-01), Smith et al.
Corniglion Isabelle
Gellis Armand
Guguelmetti Robert
Leriche Christian
Morgavi Paul
Gemplus S.C.A.
McPherson John
Plottel Roland
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