Printed matter – Having revealable concealed information – fraud preventer or... – And electrically conductive material
Patent
1982-08-24
1985-08-20
Corbin, John K.
Printed matter
Having revealable concealed information, fraud preventer or...
And electrically conductive material
350331R, 350334, 353122, 356 71, 428 1, G02F 1133, G03B 2100, G06K 974, C09K 334
Patent
active
045360146
DESCRIPTION:
BRIEF SUMMARY
The use of credit cards is very widespread. Unfortunately, besides their advantages, the traditional credit cards also have serious disadvantages; in the case of lost or stolen cards the owners are not protected against illegal use. This causes irritation and worry to the owner and financial loss both to the owner and to the issuing bank.
On the traditional credit cards the identification marks (code numbers, signature, etc.) are visible and, therefore can be easily forged. To prevent this happening various methods have been devised which make unauthorized use difficult or near impossible. Some of these methods have been based on invisible markings. However, in the majority of cases these methods do not give the required protection (e.g. the markings readily can be made visible with equipment available in most households) or are only suitable for simple designs. The presently available methods which may give greater protection are often very complicated, difficult to produce, can be used only once and are expensive. Hence their limited use.
The object of the present invention is to provide means to ensure the necessary protection, against misuse of identity documents such as credit cards, security passes and the like, by making invisable even the most complicated designs, which cannot readily be made visible domestically, and which are at the same time cheap, simple and available for unlimited use.
According to a first aspect of the present invention, there is provided an identifiable article, comprising an element bearing markings, and a mask permanently overlying said markings and normally opaque so as to obscure said markings from view, the mask being of a material which, upon the application of a suitable electric field, changes from an opaque state to an at least translucent state whereby the said markings can be viewed. It is preferred that in said translucent state, the mask is transparent.
Usually, but not necessarily, the identifiable article of the invention is an identity document such as credit card, identification card, security pass or the like. The invention has especial application to identity documents in the form of flat laminated cards.
The marked element may be opaque, in which case the markings are viewed by reflection. Alternatively, the marked element may be at least translucent, preferably transparent, for viewing of the markings either by reflection or by transmission.
The change of the mark from its opaque state to its translucent state preferably is obtained by the use in the mask of a blocking material which causes a rotation of the axis of polarized light, and which undergoes a change of polarization when energised by the electric field. In such a case, the article of the invention preferably includes polarizing screen means for the purpose of obtaining cut-off when the angles of polarization are not appropriate.
In a preferred form the blocking material is a liquid-crystal substance as used in liquid-crystal displays. These substances are organic compounds with rod-like molecules. Their state depends on their composition and temperature; being liquified at high temperature, but before reaching a certain temperature (usually 80.degree.-90.degree. C.) the liquid has a definite crystalline structure. At these temperatures, these compounds also display certain specific optical and electrical properties (mesomorphic phase) which make their use as blocking material feasible.
The mesomorphic liquid-crystals used as blocking material can be classified into three groups, namely nematic, smectic and cholesteric liquid-crystals
Nematic liquid crystals consist of long, threadlike or rod-like molecules. The compounds behave differently in an electric field and in a neutral field according to the angle between the molecular axis and the electric moment. In the liquid-crystalline state the molecular axes are parallel to each other. Typical nematic compounds include p-ethoxybenzylidene-p-aminobenzonitrile (PEBAB), ansylidene-p-aminophenylacetate (APAPA), and p-anoxyanisole.
Smectic liquid-cry
REFERENCES:
patent: 3674338 (1970-08-01), Cartmell et al.
patent: 3787110 (1974-01-01), Berreman
patent: 4105313 (1978-08-01), Altman
patent: 4171864 (1979-10-01), Jung
patent: 4175775 (1979-11-01), Kruegle
patent: 4189353 (1980-02-01), Harriman
patent: 4410887 (1983-10-01), Stolov et al.
Electronic Applications Bulletin, vol. 35, No. 3, May 1978, "Liquid Crystal Displays"-Part 1, pp. 136 to 144, see Chapter Twisted Neumatic, p. 139.
Boutaleb Aboubekr
Boutaleb Lucy A.
Kerekess Tibor T.
Corbin John K.
Lewis David
Securicard Systems Limited
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