Use of encapsulated ink for enhancing postage meter security

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BACKGROUND OF THE INVENTION

Throughout the existence of the postage meter, consistent efforts have been made to render the postage meters secure, and prevent the unauthorized printing of postage. By unauthorized printing of postage is meant the printing of a postage indicia on a mail piece without the sender of the mail accounting for the postage. Throughout the years, postage meters have generally used physical security, such as secure housings and non accessible connections. Despite such physical security, conventional postage meter imprints are subject to counterfeiting through the use of readily available fluorescent postage meter inks with rubber stamps or other printing dies. In addition, various digital printers, such as bubble jet printers and drop on demand ink jet printers, can be used to create an authentic appearing, fraudulent postage meter imprint.

It would be advantageous, and substantially reduce the opportunity of fraudulent postage indicia printing, to have a scheme whereby physical characteristics are imparted to the postage indicia that provide an indication of a genuine postage meter impression. In addition, it would be advantageous if such a scheme had the advantage of occurring at the time of printing of the genuine postage imprint without the possibility of an alteration thereafter.

SUMMARY OF THE INVENTION

A scheme has been devised whereby postage meter imprints are rendered difficult to counterfeit. This is accomplished by use of a fluorescent quenching substance that will react with a portion of the fluorescent ink, such as red fluorescent, that prints the postage meter impression during the printing of the same. This is accomplished by the use of encapsulated fluorescent quenching dyes that are blended with the red fluorescent ink. A portion of the encapsulated materials are ruptured during the printing of the postage meter impression at a designated location of the postage indicia. As a consequence, the postage indicia will have a fluorescent peak at two locations. The first location is that of the unquenched fluorescent ink and the second location is that of the quenched fluorescent ink. The encapsulated materials can be ruptured either physically or through the application of heat or vibration.

BRIEF DESCRIPTION OF THE DRAWING

In the following figures, the same reference numbers are used to indicate like parts.

FIG. 1 is a cross sectional view of the printing portion of a postage meter that embodies the principals of this invention;

FIG. 2 is similar to FIG. 1, showing alternative embodiments;

FIG. 3 is a postage meter impression printed in accordance with the instant invention;

FIG. 4 is a chemical structure of a preferred reflectance quenching dye; and

FIG. 5 is a graph illustrating the shift in spectral response and percent reflectance.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference now to FIG. 1, the printing station of a postage meter is shown generally at 10, and includes a printhead 12a having rows of print dies 14 extending therefrom. A selected portion of the print dies 16a extend from the printhead 12a with a somewhat greater length than the other print dies 14. The printhead 12a is attached to the postage meter by conventional means (not shown).

Spaced relative to and facing the printhead 12a is a platen 18 which is shown supporting a mail piece 20 thereon. The platen 18 is supported by a rack 22 whose teeth engage the teeth of a pinion 24. The pinion 24 is mounted on the output shaft of a stepper motor 26 for rotation therewith to impart reciprocal motion to the rack 22 as indicated by the arrow. An ink pad 28 is operative to be driven into contact with the dies 14, 16a by means (not shown) to transfer ink to the dies. Although the invention is described with use of an ink pad, it will be appreciated that ink rollers can be used equally as well. Mechanisms for accomplishing the movement of the ink pad 28 are well known, see for example U.S. Pat. No. 5,269,220. The pad 28 will have a fluorescent ink, preferably red fluorescent ink, blended with an encapsulated fluorescent quenching material. Fluorescent inks used in postage meters are well known, see, for example U.S. Pat. Nos. 3,928,226; 4,014,131 and 5,114,478. The techniques used to encapsulate the fluorescent quenching material are known as microencapsulation. Encapsulation techniques are well known and have been used for decades in the production of carbonless paper. An example of a microencapsulation process involves using the combination of an emulsion of polymerized vinyl, monomers in an aqueous medium containing an emulsifier and a water soluble initiator. Reference can be had to U.S. Pat. Nos. 2,730,456, 3,788,994 and 4,016,099 for examples of different types of microencapsulation techniques.

An example of a dye that can be encapsulated is Acid Blue No. 9 which is soluble in water and can therefore be used in the aqueous solution. Other examples are phthalocyanine dyes with aromatic donor groups, CI Food Blue 2, CI Acid Blue 9 and CI Pigment Blue 24. The resins used to encapsulate the dyes have to match the triggering mechanism, i.e., rupture by the defined mechanical, thermal or vibration energy. Examples of resins that can be used are styrene divinyl benzene, polystyrene and polystyrene copolymers.

The printhead 12a will operate in a normal manner for printing a postage impression upon the mail piece 20. This is accomplished by the rack 22 moving reciprocally in order to bring about printing contact between the printhead 12a and the mail piece 20. Upon completion of such printing operation, the platen 18 will be lowered by the rack 22 and the ink pad 28 will be driven across the printhead 12a to deposit ink on the dies 14, 16a and then withdrawn.

FIG. 2 shows an alternative embodiment to that shown in FIG. 1. The dies 14 are all of the same height, but one of the dies 16b has a heating element 32 in connection therewith with a lead 34 extending therefrom and connected to a source of power, (not shown), for the purpose of applying power to the heating element. Alternatively the lead 34 can be connected to an ultrasonic vibration generating coil 32.

With reference to FIG. 3, a postage indicia printed on a mail piece 20 is shown generally at 38 having a logo 40, a postage block 42, a date circle 44 and a postage meter number 46. This postage indicia 38 will have been printed either by the printhead 12a or 12b. The postage meter number is shown with a dotted frame 46 to indicate the postage meter number will emit a different wavelength when exposed to ultra-violet light as will be discussed hereinafter.

With reference to FIG. 4, a chemical structure is shown for a preferred fluorescent quenching dye. This fluorescent quenching dye will be encapsulated so as to be released when the capsule is ruptured. This fluorescent quenching dye will cause a bathomatic shift of the reflectance of the ink dye upon contact. For the purpose of this teaching, a spectral sensitive dye is defined as those dyes having a chemical structure that yields an absorption spectra that overlaps with the emission spectra of the primary dye and has a high extinction coefficient, 1.times.10.sup.2 liters/mol cm and a narrow band width 50 nm.

In operation, a red fluorescent ink and encapsulated fluorescent quenching dye mixture is deposited on the dies 14, 16a, and the printhead 12a is moved into printing engagement with a mail piece 20 supported by the platen 18. The dies 14, 16a will be made of a material such as hard rubber, so that the encapsulated portion of the inks will not be ruptured by the dies 14. On the other hand, the die 16a exerts a greater pressure upon the ink because of its extended height. As a result of this greater pressure, the encapsulated substances will be ruptured and that portion of the printhead 12a that has raised dyes 16a will have the fluorescent quenching substance released. In the preferred embodiment of the invention, the postage meter number imprint 46 will be that portion that is printed by raised dies 16a. Because the encapsulated substance is ruptured, the fluorescent quenching dye mixes with the fluorescent ink. As a result, the postage meter number 46 portion of the indicia 38 will have a different reflectance than the other portions of the indicia due to the bathomatic shift. By inspecting the indicia through use of a source of ultraviolet light and spectrophotometer, one can look for the different peaks of reflectance to determine if a bathomatic shift has occurred. A genuine postage meter impression will have two such peaks, because of the quenching effect on a portion of the indicia; whereas, one that does not have the characteristics of rupturing the encapsulated fluorescent quenching substance will have a single peak. The imprint with only red fluorescent dye will not have a peak at the location where one would be present for a quenched fluorescence.

With reference to FIG. 2, once more the printhead 12b will have ink deposited thereon by application from the ink pad 28, but the die 16b will be heated to a higher temperature relative to the other dies 14. Because of this increased temperature, the encapsulating resin will be melted and the fluorescent quenching dye will be allowed to react with the fluorescent ink with the same results achieved in connection with FIG. 1. Alternatively, the die 16b could emit ultrasonic vibration that will cause the encapsulated materials to rupture.

With reference to FIG. 4, an example is shown of a chemical formula of a preferred fluorescent quenching dye that can be used in the instant invention. This compound is a condensed o-formybenzensulfonic acid with a-(N-ethylanilino)-m-toluensulfanic which has been oxidized with the product formed into ammonium sodium salt.

With reference to FIG. 5, a graph shows a red fluorescent ink plot 54, a fluorescent ink plot 56 that has been quenched with a spectral sensitive dye, such as CI acid Blue 9, and another plot 58 of a fluorescent ink that has been quenched with a second spectral sensitive dye, C.I. Pigment Blue 24. It will be noted that there is a first shift of the reflectance peak from approximately. 490 nm to 460 nm using one spectral sensitive dye and to 440 nm using the second spectral sensitive dye and also another shift from approximately 590 nm to approximately 700 nm using either of the spectral sensitive dyes. By exposing the logo 38 and the meter number block to ultra violet light, two different reflectances will be observed.

The advantage of the instant invention is that measures are taken at the time of indicia printing to provide a way of determining whether the printing of a meter impression is genuine. Once the printing occurs, the characteristics of the inks cannot be altered to allow one to be able to obtain shifts in the peaks of reflectance. This provides a convenient and easy method for the postal service to determine that the postage meter impression is genuine.

The above embodiment have been given by way of illustration only, and other embodiments of the instant invention will be apparent to those skilled in the art from consideration of the detailed description. Accordingly, limitations on the instant invention are to be found only in the claims.

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