Not Applicable
Not Applicable
Not Applicable
This invention relates to authentication patterns formed by UV inks and in particular patterns produced by using two or more inks which respond to illumination at differing spectral frequencies.
Ultra-Violet marking for identification or authentication has been in use for many years. Examples are UV hand-stamps, patterns formed by UV inks on Identification documents such as drivers licenses and passports, and patterns formed by UV inks on currency or tickets. The technology to view these patterns has, to date, primarily been Fluorescent or Mercury Vapor Backlighting. The manufacturers of UV reactive Inks and Dyes have tailored their products to the frequency of operation of the backlight devices. Many Inks and Dyes are in either the 365 nm, 380 nm or 395 nm optical frequency range. UV light sources are typically very High Q devices, as shown in
The inventors have developed a multi-spectral UV illuminator, described in co-pending application Ser. No. 12/011,795, which is incorporated in its entirety by reference. This device is shown in
The invention is a method of marking documents, including printing an authentication pattern on the document using a first UV ink responsive at a first spectral frequency, and printing at least one of a second authentication pattern or an addition to the first pattern in at least one second UV ink responsive at a second spectral frequency. The illumination of the document by a UV source capable of emitting at at least the first and second spectral frequencies is required to authenticate the document.
In one embodiment at least a part of the patterns overlap whereby the first UV ink shows as a first color, the second shows as a second color and overlap area shows as a third color when illuminated by both spectral frequencies
In a preferred embodiment, the patterns are adapted to produce an animation when illuminated by the spectral frequencies sequentially.
The invention will be better understood by referring to the following figures.
With a convenient multi-spectral source, multiple ink types with different spectral response can be printed on single documents. This enables an array of options. In the general case, a pattern of some sort is printed with one ink with its spectral response, and either a second pattern or an overlapping pattern is printed with another ink with a different spectral response. Depending on the type of illuminator available, more than two inks may be used as well. The patterns are so configured that without illuminating at more than one UV frequency, the expected results will not show, thereby requiring the multi-spectral illumination to authenticate the document. Thus a document becomes much harder to counterfeit, requiring both knowledge of and availability of the differing inks. Because it takes multiple UV frequencies to detect the full image of the pattern, unless the counterfeiter has the specialized illuminator they may never even know of all the elements of the security markings.
Several specific examples of the invention are shown, with the understanding that other approaches within the scope of the broad invention will occur to one skilled in the art.
As shown in