Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2002-04-10
2004-12-07
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031430, C106S031580, C106S031750, C106S031860, C106S031640
Reexamination Certificate
active
06827769
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention provides ink compositions for ink jet printing (ink jet inks), which are highly effective for simultaneously imparting visible and fluorescent images. In the preferred forms, both a dark, visible image and a complementary fluorescent image will be visually discernable as well as machine readable to enable efficient hand and automated processing or handling of the objects printed. The invention achieves these results through the development of ink formulations that moderate the typically occurring phenomenon of quenching while possessing the physical properties necessary for an ink jet ink.
It is generally known to employ automated detectors which are responsive to images with high reflective contrast in the visible region of the spectrum for the machine processing of various types of information-bearing tickets, tags, labels, postage indicia and similar security markings. It is further known to employ automated detectors that are responsive to fluorescent emissions of security markings resulting from excitation at a shorter wavelength such as ultraviolet (UV) excitation. In the postage meter art, for example, mail pieces carrying postage indicia printed with fluorescent ink enhance machine processing. In the United States and Canada automatic equipment correctly faces or orients individual mail pieces by detecting red-fluorescence of postal indicia attached to mail pieces. Postal Service facing equipment employs a simple detector to locate the fluorescence. While useful, detectors of this type do not verify that the fluorescence and the indicium image are physically coincident.
Generally, a fluorescent material fluoresces in a defined region of the spectrum upon exposure to a shorter wavelength excitation light such as UV light. As used herein, the term “fluorescent security marking”, refers to such an image. Desirably, the marking will be “red-fluorescent”, which term is used herein to refer to fluorescence in the red region of the spectrum as opposed to indicating the visible color of the ink. The shift in wavelength between the incident excitation light and the fluorescent emission clearly distinguishes fluorescence from direct reflection. Fluorescent security markings are effectively applied to detection of forged documents, such as tickets, securities, identification cards, security papers, and the like. The difficulty of copying the fluorescence of security markings deters copying and provides forensic evidence of counterfeits. Among the applications of these security markings are detection of articles, production marking, and automatic article identification. Intensity of the fluorescence is important to the success of these applications. Unfortunately, application of inks by ink jet printing so limits the physical properties of the inks that the normal tendency of the colorants in the ink to quench any fluorescence presents a major technical challenge.
The prior art has provided inks for rotary and other letter press postage meters to imprint indicia on envelopes with platens using ink impregnated into foam or other porous media. Red-fluorescent, colored inks have been made for letterpress meters and include red, blue, green and black inks. For example, U.S. Pat. Nos. 2,681,317, 2,763,785, 3,230,221, 3,560,238, 3,928,226 and 4,015,131 disclose red-fluorescent inks for this purpose. These inks, in general, have non-aqueous, solvent-based vehicle systems with low vapor pressures. Typically, they will have a high solids concentration, a high viscosity, a high boiling temperature and a low surface tension.
Unfortunately, letterpress technology lacks the ability of digital printing to print variable information, and the inks are not useful in ink jet printers, which require stable solutions or dispersions with small particle sizes, low viscosity and a specified surface tension. Special inks must be produced before the many advantages of ink jet printing technology can be realized. They must be low in viscosity and have specific surface tension properties to function properly. Beyond that, they must provide high image contrast at low solids concentrations. The viscosity of the liquid ink jet inks is typically from 1.5 to 15 centipoise (cps) in current piezoelectric ink jet printers and about 1 to 5 cps in thermal ink jet printers. A desirable range of surface tension of ink jet printer inks is between 30 to 50 dynes/cm.
These criteria have deterred the development of some fluorescent ink jet inks, but have not permitted any to date that are visually-dark and give high print contrast. A number of red-colored aqueous red-fluorescent inks are disclosed in U.S. Pat. No. 5,681,381 and U.S. Pat. No. 6,176,908, and those inks fulfill United States Postal Service (USPS) requirements for franking while being compatible with use in an ink jet printer. These inks are also stable for extended periods of time. They are based on water, co-solvent and penetrant solutions of water-soluble fluorescent toners. In order to achieve fluorescence with the required fluorescent signal, e.g., phosphor meter unit (PMU), these inks are designed with an optical density lower than that normally required for machine recognition at all wavelengths. These ink formulations are, however, limited in their utilities due to their color and their inapplicability to be black or other dark inks.
Postage indicia and franking machines have been developed to make use of digital printing and especially ink jet printing. They have utilized both dark, high-contrast inks and fluorescent inks separately, but no single dark, high-contrast, fluorescent ink has been available. For example, red and purple-colored, red-fluorescent indicia have been printed with variable data using digital printers. Digitally printed indicia provide significant advantages over letterpress indicia. Ink jet printing enables printing indicia with high-density, variable information. Pitney Bowes' PostPerfect® meter produces a red-colored red-fluorescent indicium with variable data by thermal transfer printing while the Personal Post Office™ system produces red-colored, red-fluorescent indicia by ink jet printing. The USPS “Information-Based Indicia Program” (IBIP) allows the use of a black machine-readable indicia. The Post Office equipment typically orients mail pieces bearing IBIP indicia using a facing identification mark (FIM) or by fluorescent tags added to the indicia. However, because there is no fluorescent black ink available for ink jet printing and using an FIM printed at the edge of an envelope is difficult, the IBIP use is limited.
Postal services utilize machine-readable variable information for a variety of value-added services, for cryptographic authentication of the indicium and for obtaining marketing information. Compared to letterpress technology, digital printers can provide print quality and contrast that do not decrease with the number of prints. The images can be printed at high resolution, with high quality and at high speeds by direct, non-impact print engines. These inks have additional advantages for security markings since they may include penetrating solvents that cause the selective penetration of colorant into the paper. This penetration provides rubbing and scratch resistance to the security markings. Unfortunately, the use of ink jet printing for postage franking is restricted, to some extent, by the present lack of inks functional with ink jet technology that are simultaneously suitable for franking and machine-readability.
Information contained in printed indicia is useful for security and marketing purposes, as well as for processing the mail. In particular, the IBIP contains high-density variable cryptographically protected information in a two-dimensional bar code. To capture this information, postal scanning equipment must efficiently detect and read the information-based indicium. Postal indicia must display sufficient contrast in reflection to enable machine-readability, regardless of the substrate. However, available red-fluorescent inks tend to exhibit low c
Auslander Judith D.
Bernard Richard A
Bell Mark L.
Chaclas Angelo N.
Faison Veronica F.
Malandra, Jr. Charles R.
PItney Bowes Inc.
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