Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2000-05-09
2004-09-07
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031150, C106S031600, C106S031270, C462S903000, C283S072000, C283S092000
Reexamination Certificate
active
06786954
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to processes for authenticating objects, ink sets and ink compositions used in such processes, and objects formed using such ink sets and ink compositions. The present invention also relates to an ink which can be used for labeling an object (for example, a document or other object) with identifying markings which can be rapidly verified as authentic and which are highly resistant to counterfeiting. In particular, the present invention relates to inks, for security documents, which can be used with low cost and available (“off-the-shelf”) technology for hardware, for verifying authenticity, and to methods of printing using such inks and methods of verifying authentication of objects containing markings of such inks.
Widespread availability of inexpensive document scanners and color inkjet printers has created a severe problem, in that they have facilitated the creation of counterfeit documents in areas ranging from financial papers, access control documents, official identification documents, trademarked consumer goods, industrial component certifications, currency and entertainment event tickets.
Traditional government and corporate anti-counterfeiting technology has utilized techniques for discouraging copying based on restricting access to crucial raw materials such as special papers or inks, and by using printing techniques that require machines so costly that few can afford to acquire the necessary printing hardware. Such techniques include use of optical variable devices, such as holograms, embossed diffraction gratings, thin film interference coatings, laser images, etc.; special inks including ultraviolet, fluorescent, infrared, liquid crystal, magnetic, photochromic, thermochromic, optically variable, metallic and thermochromic color shifting inks, etc.; special substrates such as security papers, metallic threads, watermarks, embedded security strips, etc.; and exotic printing techniques such as laser engraving, intaglio printing, microprinting, continuous color shift printing, spatially periodic printed structures, see-through patterns (dual-sided printing), screen-angle modulation for periodic structure, etc. The intent behind these methods is to make the replication of the original document impossible without access to highly expensive printing hardware, or the authorization to purchase restricted raw materials such as special papers and inks. Most of these security labeling techniques rely upon the appearance of the object viewer whose visual examination of the object is the criterian used for its acceptance as a legitimate document.
These techniques are currently being compromised due to the availability of low-cost sophisticated color printers, image scanners and image processing software designed for use with personal computers. In addition, increasing sophistication in the commercial graphics arts fields has resulted in techniques used to produce objects such as embossed holograms, kinetigrams and diffractive color changing objects becoming public knowledge. Counterfeit credit cards and software certification labels having forged holograms have already been produced. Formerly exotic printing materials such as color-changing paint are being introduced commercially into areas as mundane as automotive painting. Human-verified visual security features in general are being rendered less effective with time, by the increasing ability to utilize commercial and consumer quality graphics hardware to make reproductions that while often not identical are rendered close enough to the original to pass a retail transaction inspection. Another reason for the failure of certain economic denial-of-resources based anti-counterfeiting technologies is that the profits in some areas of brand-named goods forgery is lucrative enough for counterfeiters to justify matching the expenditures of the legitimate printer of anti-counterfeiting labels. Another disadvantage is that these techniques of combating counterfeiting tend to restrict the printing of secure documents to those printed by large governments and wealthy corporations.
One attempt to counter this trend has been to introduce machine-readable security features into the protected documents. Some of the techniques include embedded magnetic strips, magnetic inks, periodic printed patterns that produce a Moirè pattern when viewed by electronic vision equipment, and recently data embedded in high resolution embossed patterns similar in format to CDROMs.
However, magnetic strips have been shown to be vulnerable to forgery with low-cost hardware. Embedded silicon chips are not physically useable for most paper-based documents. Optical card technology is suitable for mechanically stiff protected objects such as credit cards that can be fed into appropriate readers, but like smart chips is not physically compatible with the majority of documents requiring forgery protection. Printed bar codes are vulnerable to being duplicated by inkjet printers.
U.S. Pat. No. 3,928,226 to McDonough, et al. discloses an ink composition which can be provided for machine-readable tickets, tags, labels, postal imprints and the like, having (1) a visible color, that is, a color under ordinary mixed light frequencies, and (2) a fluorescent radiation color which, when irradiated with. ultraviolet life, for example, fluoresces preferably in the red wavelength of about 5800 Å to 6200 Å. The ink imprint may be read visually and then read by a fluorescent machine reader which is set to pick up the fluorescent wavelength of the ink. Thus, this technique checks two different properties of a same ink.
U.S. Pat. No. 5,289,527 to Ligas, et al. discloses a method for authenticating articles, using a mixture of at least two photochromic compounds, the activated spectra having different absorption maxima. This patent discloses that by using combinations of photochromic compounds having instrumentally identifiable different activated spectra and preferably also other identifiable different photochromic properties, a verifying instrument can be used to identify the individual photochromic compounds used in the display data and thereby authenticate the article. This patent also discloses that basing authentication on different activated spectra and other defined characteristic photochromic properties of at least two photochromic compounds enables a large number of combinations and permutations which may be used to authenticate an article, increasing substantially the difficulty of copying the total system and thereby facilitating identification of counterfeit articles.
When using a mixture of coloring agents (for example, a mixture of dyes or a mixture of pigments), in one instance the spectral responses of the mixture of components containing the plurality of pigments and/or dyes are linearly additive (e.g., linear mixing of the spectra, or linearly additively combining of the spectral responses). This can be seen in
FIGS. 1
a-
1
c
. Using fluorescence as an example, suppose that as shown in
FIG. 1
a
a first pigment gives the fluorescent spectrum
1
, and a second pigment gives the fluorescent spectrum
3
shown in
FIG. 1
b
. If there is one-half as much of the first pigment as compared to the second pigment in a mixture formed from the first and second pigments, then the total fluorescent spectrum of the mixture will be that shown in
FIG. 1
c
, having intensities
5
and
7
, where the spectral response of the mixture is a linearly additive combining of the spectral responses of each pigment. If there is one-tenth as much of the first pigment as compared to the second pigment in the mixture, then such mixture will have a total fluorescent spectrum as shown in
FIG. 1
d
with intensity maxima
9
and
11
, where the spectra of the two pigments are linearly additive.
Linear mixing can provide a great variety of spectral patterns; however, where a well-equipped and determined counterfeiter has acquired knowledge of the set of inks used on a particular document, and also has a reader for reading su
Lee Eric R.
Perl Martin L.
Antonelli Terry Stout & Kraus LLP
Bell Mark L.
Faison Veronica F.
The Board of Trustees of the Leland Stanford Junior University
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