Coating processes – Fraud or tamper detecting
Reexamination Certificate
2002-01-08
2003-09-09
Beck, Shrive P. (Department: 1762)
Coating processes
Fraud or tamper detecting
C427S256000, C427S288000, C106S031320, C106S031640, C106S031940, C252S586000
Reexamination Certificate
active
06616964
ABSTRACT:
The invention relates to a method for protecting the authenticity of an object by applying a photochromic ink to the object.
Safety applications for protecting the authenticity of documents or objects comprise the use of suitable security features or authentication labels. The use of photochromic materials for safety applications has been described, for example, in U.S. Pat. No. 4,927,180. In the known examples, the photochromic identification feature is made visible by using UV light. However, the identification feature used is as such detectable only with difficulty, if at all, so that there is a danger of the user not noticing the absence of the identification feature. Due to the use of UV light, the eyes of the authenticity checker require suitable protection. The use of UV light for identifying the security feature can therefore be regarded as disadvantageous. U.S. Pat. No. 5,807,625 describes a similar prior art. Here too, UV light is used for visualizing the security feature.
Organic photochromic materials which said documents disclose have a typical switching cycle number of 10
4
-10
5
. This limits the number of possible checking processes for identifying the security feature. Using said security features for automated test processes such as, for example, in automated telling machines or access control devices is therefore possible only with limitations, if at all.
It is furthermore desirable to be able to identify a particular batch of a label preparation and thus, for example when the preparations prepared for security purposes have been lost or illegally removed, to be able to determine the particular origin. The security features disclosed in said documents of the prior art cannot be used for applications of this kind.
In addition, conventional photochromic materials have the disadvantage of one of their two switching states having no noticeable inherent coloration.
It is an object of the invention to provide an optically detectable security feature for which both the bleaching process and the extinction process can be carried out using light of the visible wavelength range. In this manner it would be possible to induce a color change using inexpensive and universally available light sources, for example light-emitting diodes. Even with the light of a simple lamp, a test would then be possible and be detectable with the naked eye. Furthermore, it would be desirable to provide a security feature which has a switching cycle number of greater than 10
4
-10
5
.
Another object is to provide a multiplicity of structurally similar photochromic materials which differ in their coloration and/or their color change.
While the security features known from the prior art, owing to the small technical effort necessary for verifying them, can be defined as low-level security features, another object is to provide additionally high-level security features the verification of which is technically demanding and thus impossible for an unskilled person.
WO 98/06084 discloses the use of nucleic acid molecules, in particular DNA molecules, which can be detected by suitable amplification reactions such as, for example, the PCR reaction by means of specific primers, as invisible high-level security feature.
According to the present invention, a material, namely bacteriorhodopsin (BR), in which a low-level security feature such as, for example, photochromism can be combined with a high-level security feature which, for example, allows identification of individual batches has been successfully found and this material has been successfully used for labeling and authenticating objects.
A method according to the invention for protecting the authenticity of objects by using a bacteriorhodopsin-containing ink is provided, with preferred developments of said methods being described in the claims.
According to the invention, the abovementioned objects are achieved by a method for protecting the authenticity of an object by applying a photochromic ink to the object, which comprises using a photochromic ink which contains as photochromic portion at least one bacteriorhodopsin variant which when illuminated with light of the visible wavelength range undergoes a visually detectable reversible change of state, in particular color change, utilizable as low-level security feature for an authenticity check, and which ink has in addition to the low-level security feature one or more visually undetectable high-level security features which is/are detectable only by instrumental analysis.
The present invention thus relates to the use of a photochromic ink in a method for protecting the authenticity of an object. The ink to be used according to the invention contains at least one bacteriorhodopsin variant as photochromic portion. Such a BR variant provides both a visually detectable low-level security feature for the purpose of an authenticity check and inherently an additional high-level security feature which is detectable only by means of instrumental analysis.
Photochromism means a light-induced reversible change of state (in particular color change) of a substance, during which the color (absorption spectrum) of the starting substance changes. It is then possible for the reverse reaction to be started, for example, by light of a different wavelength or by heat. By using according to the invention a bacteriorhodopsin variant which undergoes a change of state when illuminated with light of the visible wavelength range as photochromic portion, illumination with UV light is not required according to the invention. As a result, it is possible to dispense with the disadvantages connected with the use of UV light, in particular the equipment requirements and protective measures connected therewith.
The bacteriorhodopsin variants used according to the invention are preferably those in which both and particularly preferably all switching states are colored.
One aspect of the invention therefore comprises a method for protecting the authenticity of objects, in which method a photochromic preparation in the form of an ink containing bacteriorhodopsin and/or a bacteriorhodopsin variant as the photochromic portion is applied to the object, illumination of this photochromic preparation with light of the visible wavelength range leading to a change of state, in particular color change, which is detectable for the purpose of an authenticity check. The detectable change of state, in particular color change, is preferably reversible, the bacteriorhodopsin variants used according to the invention having in particular a switching cycle number (i.e. a color change for checking purposes) >10
5
, more preferably >10
6
and particularly preferably >10
7
. As a result, a repeated security verification of the authenticity-protected object within the framework of routine measures is possible on the basis of the low-level security feature. If the change of state is made irreversible, for example by destroying the photochromically active part of the bacteriorhodopsin, the low-level security feature can be canceled or rendered invalid.
The authenticity check is preferably carried out by illuminating the photochromic ink with visible light in order to bleach the bacteriorhodopsin, and the photochromic ink is then illuminated with light of a second wavelength range, in order to revert the bacteriorhodopsin photochemically to the initial state, or thermal relaxation to the unbleached state takes place. It is possible to observe the change in the optical properties during the bleaching and/or extinction process with the naked eye or using an optical instrument.
The term “low-level security feature” denotes a feature whose presence or absence can be verified by unskilled persons without technical aids in a simple manner or with low technical complexity.
The term “high-level security feature” on the other hand, denotes a feature when it is impossible for the unskilled person to detect its presence or absence and which can commonly be verified only by specialists under high technical complexity.
Low-level security features are the
Hampp Norbert
Seitz Arne
Beck Shrive P.
Hampp Norbert
Jolley Kirsten Crockford
Sutherland & Asbill & Brennan LLP
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