Stock material or miscellaneous articles – Composite
Patent
1996-09-11
1999-07-27
Jones, Deborah
Stock material or miscellaneous articles
Composite
428 418, 428195, 428323, 428337, 428405, 428500, 428688, 156219, 156220, 156269, B32B 900
Patent
active
059287888
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a single- or multilayer data carrier, such as an identity card, bank card or the like, which has at least one plastic layer.
Data carriers like identity cards, credit cards, bank cards, passport personalization pages, telephone cards and the like have attained great significance in daily life and will continue to grow in importance. Their spread and the number of cards in circulation have risen steeply in recent years. High-grade cards, which are used for example in the security area or in areas requiring high mechanical resistance, are usually made of several layers. A core layer printed on one or both sides is chiefly covered by two transparent cover layers.
BACKGROUND OF THE INVENTION
Of card materials to be selected for use, in particular PVC has proven useful. DE 30 48 736 A1 discloses for example a single-layer identity card of PVC dyed white with titanium dioxide. However, PVC is also preferably used in cards which consist of several layers. This material can be processed into foils which offer considerable advantages over other foil materials as the starting material for the individual layers. The individual layers can thus be laminated, i.e. interconnected under pressure and heat. Additives which influence or determine certain properties of the PVC foil can be incorporated very well in the material. For example one can produce both transparent layers and opaque layers. Furthermore this plastic can be mixed with pigments and other usual additives so that the material properties can be adjusted within wide limits, e.g. color, radiation absorption behavior and the like.
Multilayer identity cards of PVC have also been proposed which consist for example of a printed opaque card core and two transparent cover foils (DE 30 29 939 A1). Since all layers consist of the same plastic material they can be connected into a card laminate in a simple way.
However, PVC itself has the decisive drawback in terms of environmental acceptability that it can hardly be recycled. Disposal of the plastic furthermore causes considerable difficulties since hydrochloric acid arises during combustion and ultimate disposal of PVC. Furthermore PVC readily becomes brittle at low temperatures so that the card breaks easily.
To improve the mechanical properties and temperature stability of PVC cards, on the one hand, and reduce the quantity of PVC used, on the other, one has proposed producing high-grade cards from several layers of different materials.
EP 430 282 A2 thus discloses a card wherein the PVC cover layers and the PVC core layer of the card are each separated by a layer of thermoplastic polyurethane (TPU) so that the mechanical properties are improved. The PVC layers in such cards can also be replaced by other plastics, such as polyethylene or polycarbonate, without adversely affecting the mechanical properties of the card.
A drawback of such multilayer cards, however, is that the different plastics in the card compound can hardly be separated again on a large scale for recycling processes. At the end of the service life of the card only the crushed card laminate, i.e. a mixture of the plastics used, can be further treated in the recycling process, so that the card compound can only be processed into inferior plastic articles which cannot meet any high requirements with regard to color and mechanical properties.
SUMMARY OF THE INVENTION
The problem of the invention is to propose a data carrier, and a method for producing it, which has favorable mechanical, optical and thermal properties while being readily recyclable and disposable in environmentally acceptable fashion.
This problem is solved by the features stated in the main claim.
The basic idea of the invention is to use a thermally nonrecrystallizing polyester instead of the PVC used up to now for data carriers. This material is characterized by not losing its transparency during thermal processing, on the one hand, and easily being dyed by the addition of dyes or pigments, on the other. Single- or multilaver data carriers of thermally
REFERENCES:
patent: 4370293 (1983-01-01), Petersen-Hoj
patent: 4522670 (1985-06-01), Caines
patent: 5187496 (1993-02-01), Yu
Database WPI, Section Ch, Week 9425, Derwent Publications Ltd., London, GB,; Class A32, AN 94-205789.
Bahta Abraham
Giesecke & Devrient GmbH
Jones Deborah
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