Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-05-09
2004-03-30
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031750, C106S031280, C106S031900, C283S072000
Reexamination Certificate
active
06712894
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of producing an image which is visually distinct from its reproductions. This method comprises the steps of formulating an ink composition comprising a liquid vehicle and at least one modified pigment and applying this ink composition to a substrate. The present invention also relates to methods of determining the authenticity of an image and verifying the date of creation of an image.
2. Description of the Related Art
Recent advances in color copying and printing have put increasing importance on developing new methods to prevent forgery of security documents such as banknotes. While there have been many techniques developed, one area of increasing interest is in identifying printing inks that can be used to create images that cannot be readily reproduced by a color copier or printer.
There have been several approaches to formulating an ink for creating a printed image that is visually distinct from its reproduction. For example, U.S. Pat. Nos. 5,059,245, 5,569,535, and 4,434,010 describe the use of stacked thin film platelets or flakes. Images produced with these pigments exhibit angular metamerism—that is, their color changes depending on the angle in which they are viewed. These pigments have been incorporated into security inks used, for example, in paper currency. These pigments have also been incorporated into plastics applications (see, for example, PCT Publication WO 00/24580).
U.S. Pat. No. 6,013,307 discloses a printing ink that contains a single dye or mixture of at least two dyes which is formulated in order to create the greatest possible metamerism between the formulated ink and a reference ink on the basis of two defined types of illumination. The original image is described as having visually clearly identifiable differences compared to its copy.
Another approach used to produce security documents has been to produce an image that contains a material which cannot be seen by the naked eye but which can be made visible under specific conditions. For example, U.S. Pat. Nos. 5,324,567, 5,718,754, and 5,853,464 disclose the use of Raman active compounds. U.S. Pat. Nos. 5,944,881 and 5,980,593 describe fluorescent materials that can be used in a security ink. Also, U.S. Pat. No. 4,504,084 discloses a document containing an information marking comprised of a first color which is at least partially opaque or visible in infrared light and a second color, which conceals the first color in the visible spectrum, but is invisible to infrared light.
Inks which change upon chemical exposure have also been used for security documents. For example, U.S. Pat. Nos. 5,720,801, 5,498,283, and 5,304,587 disclose ink compositions which are invisible when printed and develop a color upon exposure to bleach. Thus, attempts to alter a document printed with an image from these inks using bleach would be readily apparent.
While these efforts afford printed images which are difficult to reproduce, advances in color copiers and color printers continue to be made. Therefore, a need remains to provide a method of producing images, particularly for security documents, which cannot be easily reproduced and which are visually distinct from their reproductions.
SUMMARY OF THE INVENTION
The present invention relates to a method of producing an image which is visually different from reproductions produced therefrom, which comprises the steps of formulating an ink composition comprising a liquid vehicle and at least one modified pigment having attached at least one organic group and applying the ink composition to a substrate. In one embodiment, the ink composition is an ink jet ink composition.
The present invention further relates to a method of determining the authenticity of an image comprising the steps of (1) measuring the reflectance property of a subject image, (2) measuring the reflectance property of an authentic image, and (3) comparing the results, wherein the authentic image is produced from an ink composition which comprises at least one modified pigment having attached at least one organic group.
The present invention further relates to a method of determining the authenticity of an image comprising the steps of (1) measuring the elemental composition of a subject image, (2) measuring the elemental composition of an authentic image, and (3) comparing the results, wherein the authentic image is produced from an ink composition which comprises at least one modified pigment having attached at least one organic group.
The present invention further relates to a method of verifying the date of creation of an image comprising the steps of (1) measuring the elemental composition of a subject image, (2) measuring the elemental composition of an image created on a known date, and (3) comparing the results, wherein the image created on a known date is produced from an ink composition which comprises at least one modified pigment having attached at least one organic group.
The present invention further relates to a security document comprising a substrate and an image which is visually different from reproductions produced therefrom, wherein the image is produced from an ink composition which comprises at least one modified pigment having attached at least one organic group.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present invention, as claimed.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a method of producing an image which is visually distinct from its reproductions which comprises the steps of formulating an ink composition and applying the ink composition to a substrate. The ink composition comprises a liquid vehicle and at least one modified pigment having attached at least one organic group. In one preferred embodiment, the ink composition used in the method of the present invention is an ink jet ink composition.
Ink compositions can be categorized into various classifications. These include, for example, printing inks, ultraviolet cure inks, ball-point pen inks, and stamp pad or marking inks. Security inks represent a specific class of ink compositions. In general, a security ink is one that produces an image that is difficult, if not impossible, to reproduce. Thus, forgeries or reproductions become readily apparent when compared to an original.
In general, an ink composition consists of a vehicle which functions as a carrier and a colorant such as a dye or pigment. Additives and/or cosolvents can be incorporated in order to adjust the ink to attain the desired performance.
The vehicle for the ink compositions used in the method of the present invention may be either an aqueous or a non-aqueous vehicle. Preferably, the vehicle is an aqueous vehicle and the ink composition is an aqueous ink composition. The ink composition used in the method of the present invention is preferably an ink jet ink composition.
Suitable additives may also be incorporated into these ink compositions to impart a number of desired properties while maintaining the stability of the compositions. For example, surfactants may be added to further enhance the colloidal stability of the composition. Other additives are well known in the art and include humectants, biocides, binders, drying accelerators, penetrants, and the like. The amount of a particular additive will vary depending on a variety of factors but are generally present in an amount ranging between 0% and 40%.
Additionally, ink compositions may also incorporate dyes to modify color balance and adjust optical density. Such dyes include food dyes, FD&C dyes, derivatives of phthalocyanine tetrasulfonic acids, including copper phthalocyanine derivates, tetra sodium salts, tetra ammonium salts, tetra potassium salts, tetra lithium salts, and the like.
The ink compositions used in the method of the present invention include at least one modified pigment having attached at least one organic
Cabot Corporation
Faison Veronica F.
Klemanski Helene
LandOfFree
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