Patent Application
20070281139
The present invention relates to a chemically sensitive security ink, and the use of such ink on secure documents. The security ink, when exposed to a solvent, changes color, or changes between a colored and colorless state. This change in color or opaqueness can provide an indication of tampering with a document, or can be used to authenticate a document. The ink has the advantage of being reactive with a wide variety of solvents—polar, nonpolar, aliphatic, aromatic, oxygenated, and halogenated. Further, the ink can be used on documents that will subsequently be processed through laser printers.
The invention also contemplates printing a solvent sensitive ink over a message on a security document in order to mask or to obscure the message. The message is preferably printed in a solvent resistant ink. The message remains hidden until the masking ink is exposed to solvent and its color removed. The solvent sensitive ink of the present invention is preferred as the masking ink, but other solvent sensitive inks are also contemplated. An exemplary use in this fashion is on security documents, such as certificates of title, bank checks, currency, birth certificates, negotiable documents, gift certificates, college transcripts, and the like. The message could be used to indicate an attempt to alter the security document through the use of the solvent. Other uses for the hidden message arrangement, including authentication, will also be apparent.
In one version of the security document, having a hidden message, if the security document has a background printed as pantograph, the message is preferably printed in the same ink as the pantograph. Pantographs are typically printed by wet offset, lithography, or rotogravure printing processes, and are typically printed with inks that are relatively impervious to solvents once completely cured or dried. The message portion of the document may be in narrative form, such as for example, “If you can read this message, this document has been compromised.” Alternately the message may simply be “Tamper-Alert!,” “VOID,” or a graphic of some sort. The message may be printed anywhere on the security document, including its front and rear surfaces. Preferably, the masking ink and message ink are the same color.
The preferred masking ink utilizes a non-drying vehicle such that it remains open to being sensitive to solvents. The ink may also bleed through to the opposite side of the paper, creating feature that is difficult to duplicate if an attempt is made to replicate the form with a copier or scanner. While non-drying, the ink is compatible for use on documents being processed through laser printers.
The security documents preferably contain multiple security features to thwart criminal attempts at altering or duplicating the form. Using more features results in more robust fraud protection. Such features may include any combination feature, such as a void pantograph for anti-copy protection, thermochromic ink for validation or authentication purposes, laid lines to prevent cut and paste fraud, solvent sensitive coatings, printings, or speckles that go from colorless to color upon attacks from solvents, water marks, security threads, colored paper fibers, high resolution borders, microprinting, and any other of a large number of security features that are known in the art.
The chemically reactive security ink of the present invention may also be used apart from obscuring a hidden message. For example, it may be used as a bleeding numbering ink. It may be used for printing lines or borders around certain fields of a security document such as the payee field, convenience amount field, written amount field, MICR account field, or other fields of a bank check.
This novel chemically reactive security ink can be applied by wet offset lithography and letterpress to any document needing a security feature that makes it evident to even a casual observer that tampering using solvents to remove inks and toners has occurred. The most preferred method of printing this ink is dry offset printing or letterpress printing.
The chemical reactive ink of this invention reacts with a variety of solvents—polar, nonpolar, aromatic, aliphatic, halogenated, and oxygenated. A hidden message can be printed under the ink so that it is revealed if there is any tampering with the document using a solvent. The hidden message can be printed by any typical method, such as flexography, wet or dry lithography, or screen-printing. The message will be hidden best if the message is printed with an ink that has a color which matches that of the chemical reactive ink. The message can be printed as either a solid or a screen, varying from a 100% solid to a 1% screen. The chemical reactive ink can be printed in a pattern, such as Chinese characters or pseudorandom marble patterns, to hide the message effectively.
Other security techniques can be used with security document according to the present invention, providing cumulative security provisions. For example, other arrangements can be added for detecting the use of solvents. These arrangements include using paper that has one or several dyes as dry particles that will spread and create small stained dots when exposed to solvent. More than one dye is typically used to react with all types of solvents. Certain prior art inks may also be used, although they may not be as effective as desired, since if the forger is patient and washes the document with one or more solvents over an extended period of time, the stains from such inks can be completely removed.
Another type of solvent reactive ink is the chemical void ink. Chemical void inks react with solvent to go from colorless to colored, and are usually printed as a message such as “VOID.” Some void inks are reactive with bleach, producing a color image when exposed to bleach. Chemical void inks typically contain solid leuco dyes and solid activators. The active components are only soluble in polar and oxygenated solvents (e.g. alcohols, ketones, esters) and thus tampering with non-oxygenated solvents is not revealed.
The chemical reactive ink of the present invention has the advantage over security paper and void inks of the prior art that it reacts with a wide variety of solvents - polar, nonpolar, aliphatic, aromatic, oxygenated, and halogenated. When exposed to solvent, the ink color will disappear and a hidden message can be revealed that confirms tampering. As stated above, prior art chemical void inks may not reveal tampering with a non-oxygenated solvent, and some dyes within a security paper can be completely dissolved and washed away leaving no evidence of tampering. Some examples of solvents that effectively remove the color from the invention are: methanol, ethanol, isopropanol, hexyl carbitol, 1-pentanol, acetone, toluene, gasoline, isopropyl amine, 1-methyl-2-pyrrolidone, mineral spirits, S-limonene, orange oil, m-xylene, propylene glycol propyl ether, heptanes, caprolactone, chloroform, diethylene glycol monobutyl ether, phenyl ether, 3-methyl-2-butanone, 2-butanone, carbon tetrachloride, propylene glycol monomethyl ether acetate, oleic acid, dioctyl phthalate, 2-ethyl hexanoic acid, rubbing alcohol, and nail polish remover.
The chemical reactive ink of the present invention is comprised of two parts. The first part is a solvent soluble dye. Any solvent dye can be incorporated into the invention. Such dyes can be from any of the chemical families of solvent dyes, such as azo, xanthene, anthraquinone, triarylmethane, azine, thiazine, phathalocynine, and metal complexes of the same. The most effective solvent dye is soluble in a wide variety of solvents. The preferred dye for this invention is from the anthraquinone family, specifically solvent blue 35 [1,4-bis(butylamine)anthraquinone]. Examples of other dyes that can be used, however, are: solvent black 3, solvent black 5, solvent red 23, solvent red 132, solvent red 8, solvent red 49, solvent red 89, solvent red 122, solvent blue 4, solvent blue 5, solvent blue 35, solvent blue 44, solvent blue 45, solvent blue 59, solvent blue 97, solvent violet 9, and solvent violet 8. The present invention is not to be considered to be limited to any specific dye, however. The concentration of dye in the ink can be from 0.1% to 20%, with the preferred range being 1% to 8%.
The second part is a non-drying vehicle or ink base. Although a drying vehicle (e.g., based on either an alkyd or linseed oil) or UV curable vehicle can be used, such vehicles tend to trap the dye in a crosslinked matrix which reduces the amount of dye that can be dissolved and leached out by the solvent. The preferred base consists of a blend of two or more of tall oil butyl ester, modified phenolic resin, silica, and calcium stearate. This base provides good printing qualities, solvency of the dye, and is non-drying. Other types and combinations of resins, oils, and modifiers may be equally effective. The level of resin can be from 10% to 60% of the non-dryiing vehicle or ink base by weight, with the preferred range being 32% to 45%. The oil level can be from 30% to 90% of the non-drying vehicle or ink base by weight, with the preferred range being 40% to 65%. Silica can be incorporated at 0% to 15% of the non-drying vehicle or ink base by weight, with the preferred level being 6% to 9%. The calcium stearate can be added at 0% to 6% of the non-drying vehicle or ink base by weight, with the preferred level being 1% to 3%.
When the ink has only the solvent dye as the colorant, the ink will go from colored to colorless when exposed to solvent.
A third component can be added to give a color change. The component can be another solvent dye that is soluble in a limited group of solvents, and thus it could be dissolved out of the ink with the blue or remain on the paper depending on the solvent. The component can also be a pigment that cannot be dissolved by solvents. A portion of the pigment can be washed away by a solvent that solubilizes the ink base while a portion of the pigment remains in the paper fibers, giving a visible tint to the printed area. If a hidden message is printed under this ink, the ink is selected such that the message is visible through the pigment color.
An optional addition to the ink of the present invention is a bleach reactive chemical to reveal evidence of exposure to bleach. One such chemical is Chlorostain OR (a guanidine derivative) from Bayer Corp.
Another variation of the invention is using a dye dispersion mixed into a flexographic ink base. The solvent dye is ground to a small particle size to act as a pigment in the water-based ink. However, the dye can still be dissolved and removed by a solvent. This allows printing by flexographic methods.
Examples of formulations include the following, where Formula 1 is the preferred formulation.
SPR 10 Resin is available from Akzo Nobel Resins, Woodstock, Conn. This is a maleated phenolic modified resin.
Sylfat 9012 is available from Arizona Chemical, Panama City, Fla. This is a tall oil fatty acid butyl ester.
Aerosil R972 is available from Degussa Corp., Ridgefield Park, N.J. This is a hydrophobic fumed silica.
Calcium stearate is available from Witco Corp.
Solvent Blue G (Solvent Blue 35) is available from Aakash Chemical, Glendale Heights, Ill.
Chlorostain RR is available from Bayer Corp., Pittsburg, Pa. This is Solvent Blue 97.
Chlorostain RR had lower solubility over the range of solvents as compared to Solvent Blue G.
Here, a solvent dye was incorporated into a conventional drying ink. The dye could be dissolved out of the ink immediately after printing but the amount of ink that could be removed after 24 hours was reduced due to oxidation of the ink vehicle.
After curing, the amount of dye that could be removed was greatly reduced.
Turning to the drawings, it will be seen that the chemically reactive ink can be printed over a hidden warning message virtually anywhere on the security document. It is particularly advantageous to use such ink and hidden warning messages in those areas of the document that are most likely to be the subject of attempted alteration.
Alternatively, the message may be printed in a pale ink as shown in
It will be appreciated that the hidden message may be printed on the substrate 10 in any of the areas 14, 16, 18, 20, and 22 that carry handwritten information, rather than adjacent these areas. This has the advantage of making it difficult to apply a solvent to the handwritten information without activating the masking ink. However, it has the disadvantage that the message could be partially obscured by the handwritten information. As a further alternative, the message may be printed around the periphery of one or more information areas 14, 16, 18, 20, and 22 on the security document, as shown in
Other aspects, objects, and advantages of the present invention can be obtained from a study of the drawings, the disclosure, and the appended claims.
This application claims the benefit of provisional patent application Ser. No. 60/810,086, filed Jun. 1, 2006, under 35 U.S.C. 119.
| Number | Date | Country | |
|---|---|---|---|
| 60810086 | Jun 2006 | US |
