Security Document System And Method

Abstract

Illegal or unauthorized reproduction of classified or copyrighted indicia by a variety of convenience office copiers operating in different energy ranges is inhibited. This indicia is pressure-transferred from a typewriter ribbon or carbon-like sheet, or printed directly, with an ink of one color onto a masking background of another color provided on an opaque substrate. The ink is light reflective to those convenience office copiers, like the Xerox 2400, that operate predominantly in the blue spectral region, and also to those thermographic copiers, like the 3M Thermofax copiers, that operate in the infrared spectral range, so that these copiers will not see the indicia. The ink is at least partially light absorptive to those copiers, like the currently marketed IBM Copier, that operate predominantly in the green or blue-green spectral region; hence, as to these copiers, the indicia will be indistinguishable from the camouflaging background, which is light absorptive to a greater degree than the ink throughout the operating ranges of all copiers of the aforementioned types. The novel combination of ink and background herein disclosed also provides legible but significantly deteriorated reproduction of such indicia by most broad spectrum white-light copiers and zinc-oxide coated paper copiers.

Description

This invention relates to a security document system for, and method of, inhibiting illegal or unauthorized reproduction of classified or copyrighted information by a wide variety of convenience copiers. The invention relates more particularly to a document system or set and method that provides legible indicia on a master but provides illegible or significantly deteriorated copies of such indicia when attempts are made to reproduce it by any of a wide variety of conventional office copiers.

BACKGROUND OF THE INVENTION

It is, of course, well known that indicia in certain blue colors is not reproducible on some electrostatic copiers; that indicia in green colors is not reproducible on others; and that indicia in red colors is not reproducible on thermographic copiers. It has heretofore been proposed to suppress reproduction of certain indicia by writing or printing it in an ink that is reflective in that specific energy range in which a particular convenience copier or class of copiers operates; e.g., print such indicia in a blue ink to preclude its reproduction by an electrostatic copier that operates predominantly in the blue region of the spectrum. However, this approach would not preclude legible reproduction of such indicia in electrostatic copiers operating in the green or blue-green region of the spectrum. Another approach to prevent reproduction in electrostatic copiers is to print the indicia in black ink on a dark red background. These approaches have never proved commercially practical because they preclude copying only by copiers operating in a specific narrow energy range and/or because the documents ae not acceptable from a human factors standpoint.

With so many different brands and classes of convenience office copiers now on the market and so readily accessible in offices and libraries, there is a need for a simple security document system and method that will provide legible indicia on a master in a form acceptable from a human factors standpoint but preclude or impair legible or acceptable reproduction of such indicia by a variety of brands and classes of such copiers.

SUMMARY OF THE INVENTION

Applicants have discovered that these objectives can be achieved by formulating an ink from a pigment of a color having a high reflectance across the operating energy ranges of at least one class of copiers but somewhat light absorptive across the operating energy range of at least one other class of copiers. The classified or copyrighted indicia is then printed with said ink on a masking background provided on an opaque master. This background is of another color that absorbs light within the operating energy ranges of both such classes of office copiers. The copiers of the first-mentioned class or classes fail to see the ink because of its reflectance, and the copiers of such other classes fail to distinguish the ink from the camouflaging background. In still other classes of office copiers, including most broad spectrum white-light copiers and electrostatic copiers using zinc-oxide coated paper, the particular blue ink in which the classified indicia is printed and the masking background ink herein disclosed when used in combination have been found to provide reproductions of the classified indicia which, though legible, are of considerably impaired quality.

Other objects and advantages will become apparent from the following more detailed description of the invention and from the accompanying drawings wherein:

FIG. 1 is a diagram depicting the operating energy levels for three distinct classes of commercially available convenience office copiers that peak at different wavelengths, and the reflectance characteristics of applicants' distinctive ink and background relative thereto;

FIG. 2 is a diagrammatic showing of the process by which the masking background is prepared; and

FIG. 3 is an enlarged fragmentary view of applicants' distinctive masking background.

DESCRIPTION

Referring now to FIG. 1, curve A depicts the approximate operating energy range of one class of electrostatic convenience copiers that operates predominantly in the blue region of the electromagnetic spectrum with a peak operating energy of about 482 to 507 m.mu. (millimicrons); this class includes the commercially available copiers known as the Xerox 2400, 660, 720, 914, 3600 I, and 3600 III. Curve B depicts the approximate operating energy range of another class of electrostatic copiers that operates predominantly in the blue-green to green region of the spectrum with a peak operating energy of about 495 to 545 m.mu. that somewhat overlaps the peak energies of the first class; this class includes the commercially available copier known as the IBM Copier. Curve C depicts the approximate operating energy range of still another class of copiers, namely thermographic copiers, that employ infrared light sources and depend upon the absorption of infrared radiation for the production of legible copy; this class includes the 3M Thermofax copiers. These curves A, B, C express the operating energy at approximate percentages of the peak operating energy at various wavelengths as measured in millimicrons.

For reference purposes and to a different ordinate scale, curve D is included to depict the approximate reflectance characteristics of the conventional uncoated white-bond copy papers normally used with electrostatic copiers of the types depicted in curves A, B. Curve E is included to depict the approximate reflectance of a typical black ink. Curve F depicts the relative reflectance of applicants' distinctive bright blue ink, hereinbelow described, for printing the classified indicia; whereas curve G depicts the relative reflectance of the ink in applicants' distinctive masking background. These curves D, E, F, G show reflectance characteristics in percentage, referenced against manganese oxide as 100% as measured by a Beckman DK-2A Spectroreflectometer, at various wavelengths as measured in millimicrons.

According to a feature of the invention, applicants' bright blue ink is a non-light absorptive (i.e.. reflective) to electrostatic copiers having operating energy peaks within the blue spectral region and to thermographic copiers; hence, indicia imprinted in such ink will not be "seen" by such copiers. However, such ink is sufficiently light absorptive to copiers having operating energy peaks within the green and blue-green regions that it will be "seen" by such copiers; but these copiers will fail to distinguish the indicia printed in said ink from a distinctive camouflaging background that is not objectionable from a human factors standpoint. This masking or camouflaging background preferably is of a color, such as hereinafter disclosed, the absorbs light to a greater degree than the blue ink in all classes of copiers operating predominantly in the blue, green, blue-green or infrared regions. Thus, to all these copiers, the background is similar to black. However, the reasons for the background are (a) to mask the indicia that would otherwise legibly reproduce in those copiers operating predominantly in the blue-green to green region, and (b) provide deteriorated, though legible, reproduction of the indicia in broad spectrum white-light copiers, such as the Xerox 4000 and 7000, and zinc-oxide coated paper copiers, such as the Bruning 2000.

Applicants' distinctive blue ink and masking background and the basis for their characteristics will now be described in greater detail.

From curve F it will be noted that applicants' blue ink is highly reflective to the copiers depicted by curve A which operate predominantly in the blue region of the spectrum. However, said ink is sufficiently light absorptive to the copiers depicted in curve B which operate in the green to blue-green region of the spectrum that it will be visible, although faintly, to said copiers. It will also be noted from curve F that applicants' blue ink is highly reflective to those thermographic copiers depicted by curve C that operate in the infrared region of the spectrum. Accordingly, such thermographic copiers will not "see" the ink (even though of a bright blue hue).

From curve G, it will be noted that the masking background is very absorptive (i.e., exhibits low reflectance) through the visible region of the spectrum, including the blue, blue-green, and green regions. Although the background is somewhat less absorptive in the infrared region, a comparison of curves G and F shows that the background is nevertheless more absorptive than the blue ink in said region. The background is somewhat absorptive, although to a lesser degree than the blue ink, in the wavelengths between the green and infrared regions. Since both the blue ink and background are absorptive enough, however, to be reproduced by the broad spectrum white-light copiers and zinc-oxide coated paper copiers, the background will have a partial (though incomplete) masking effect to insure the deteriorated quality of reproductions in copiers of these two types.

OPERATION

In actual tests, applicants' novel masking background was applied to paper substrate masters of various colors and weights. However, the background is preferably applied to white bond paper of high brightness, such as commercially available OCR-grade paper. More specifically, the masking background was prepared by a process comprising the following steps:

1. A predetermined format ##SPC1##

was typed onto 20-pound bond white paper.

2. The typed format was then photographed on high contrast film in conventional manner to produce a negative.

3. A composite master negative was then made, as shown in FIG. 2, by

a. placing a 25% fine mezzo tint over the negative of the typed format;

b. placing a 25% coarse mezzo tint under the negative of the typed format;

c. laying the tint-negative-tint sandwich on a high quality duplicating film with the coarse tint adjacent said film; and

d. producing, by contact exposure, a composite master negative of a background masking pattern comprised of a plurality of letters or other symbols each defined by a series of discontinuous screened portions as shown in FIG. 3.

It is to be understood that the format may be typed onto any photographically acceptable surface or substrate in lieu of the 20-pound bond white paper. Also the predetermined format preferably should cover the entire area to be protected, and should not comprise identical letters or symbols in adjacent lateral or vertical relation; i.e., each letter or symbol used should not be repeated in close proximity to a similar letter or symbol. The composite master negative is created by conventional exposure control methods that will insure exact dot-for-dot reproduction; e.g., by use of gray scales, star targets, dot form scales, and resolution line guides.

The mezzo tints used were those commercially available from Direct Image Corp., Monterey Park, Calif. The duplicating film used was that designated as MRK 471 CRW-4 sold by E.I. du Pont de Nemours and Co., Inc.

The master composite negative created in the manner just described was then used to prepare a lithographic plate in conventional manner. Of course, if preferred, the negative may be used to prepare other types of printing plates (e.g., relief printing plates) suitable for the particular printing process to be employed.

As earlier noted, the color of the masking background is critical in that it must absorb light to a greater degree than the pigment in all copiers operating predominantly in blue-green to green region. By considerable experimentation, it was found that printing a master on a lithographic press with a masking background of an ink having a color identified as "PMS 456" of the Pantone Matching System and having intensity characteristics preferably like those shown in curve G of FIG. 1 best insured illegibility of copies from copiers operating in the blue-green to green region while affording good human factors acceptability. The Pantone Matching System developed by Pantone Press, Inc. expresses colors in a certified matching system that is well known as a standard to those skilled in the art. This system, in which all constituents are expressed in parts by weight, defines the PMS 456 ink formulation as:

One Part Warm Red

One Part Reflex Blue

Fourteen Parts Yellow

One Part Black

The confidential or copyrighted indicia which is not to be machine copied was printed on the masking background by applicants' blue ink, which was specially formulated to match the spectrally blind region of the Xerox 2400 copier. (This blind region is substantially identical for the Xerox 660, 720, 914, 2400, 3600 I and 3600 II electrostatic copiers; and hence it is to be understood that unless otherwise specifically stated, the characteristics described with respect to the Xerox 2400 copier are deemed to apply with equal force to these other specifically identified Xerox copiers.) The blue ink employed in the formulation preferably has spectral characteristics similar to those shown in curve F of FIG. 1. Preferred pigments for use in applicants' distinctive blue ink are those of the phthalocyanine blue type which exhibit a broad reflectance curve in the blue region in which the Xerox 2400 copiers operate.

Very satisfactory results were obtained with the following ink formulation applied by a lithographic press, all constituents being expressed in terms of percent by weight:

0.4% Phthalocyanine Blue Pigment

88.3% Opague Mixing White (VanSon 46402-S)

10.9% 100-s grinding Base (Lawter Chemical Company)

.4% Thixcin R White Powder (Baker Castor Oil Company)

It will, of course, be understood that other workable formulations can readily be made to suit the particular application and printing process used; however, the phthalocyanine blue pigment is the important ingredient.

It will now be apparent that the function of the masking background is primarily to expand the range of nonlegible copy to copiers, like the IBM Copier, that operate predominantly in the blue-green to green region of the spectrum. The background pattern serves to camouflage the indicia overprinted in the special blue ink, for a legible copy of such indicia would be reproduced by the IBM Copier in the absence of such a background. The background pattern is a stronger competitor for toner than the indicia overprinted in the blue ink, thus helping to provide illegible copy when such ink and background are concurrently employed. The blue ink, when used in conjunction with the background pattern illustrated above and to enlarged scale in FIG. 3, affords a high degree of acceptance from a human factors standpoint, while at the same time assuring against reproduction of legible copies of the classified indicia on both the Xerox 2400 type and the IBM type electrostatic copiers and on thermographic copiers.

In the tests above described, the "nonreproducible" classified indicia was printed in a lithographic press over a masking background that had previously been printed on a paper substrate in a lithographic press. It is to be understood, however, that this indicia can be applied by a number of other media; i.e., from a typewriter ribbon impregnated with a suitable formulation containing this special blue pigment, from a separate transfer sheet (in the nature of carbon paper) coated with a suitable formulation including such pigment, by a toner containing such pigment and used in electrostatic copiers, or by a hand-manipulated pen or pencil having an ink or lead embodying such pigment. Hence, the term "medium" as employed in the claims is intended to be broadly construed to embrace any means, such as an ink or the other means just specified, for carrying the pigment and/or applying it as legible indicia to the masking background. Moreover, it is to be understood that, if preferred, the masking background may take forms or employ formulations other than those herein specifically disclosed or be applied by different printing or screening techniques, so long as the color is maintained at or close to that known as PMS 456.

As earlier noted, the blue ink herein disclosed when used in conjunction with the masking background above described produced legible, but hard to read, copy on most so-called broad spectrum white-light copiers, such as the Xerox 4000 and 7000 electrostatic copiers; it also produced poor quality copies in the electrostatic copiers, such as the Bruning 2000, employing zinc-oxide coated paper.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be apparent that the foregoing and other changes may be made in the security document system and method without departing from the spirit, scope and teaching of the present invention. Accordingly, the system and method herein disclosed are to be considered merely as illustrative, and the scope of the invention is to be limited only as specified in the claims.

Claims

What is claimed is:

1. The method of precluding generation of legible copies of human readable indicia from a master by any one of a plurality of convenience office copiers having different operating energy ranges, comprising the steps of

providing an ink of a color that is highly reflective across the operating energy range of at least one group of copiers including electrostatic copiers operating predominantly in the blue region of the spectrum and thermographic copiers operating in the infrared region of the spectrum, but which ink is at least partially absorptive within different operating energy ranges of another group of copiers including electrostatic copiers operating predominantly in the green to blue-green regions of the spectrum,

providing on the master a background of another color that absorbs light within such different operating energy ranges and masks the ink color which would be legible in the blue-green to green regions, and

printing the human readable indicia over said background with said ink,

whereby said copiers of said one group will fail to reproduce the indicia printed in said ink because of its reflectance and said other group of copiers will reproduce illegible indicia printed in said ink and masked by said background.

2. The method according to claim 1, wherein the masking background comprises a predetermined format of a plurality of different contiguous symbols, no identical two of which are directly adjacent each other, and each of which symbols is defined by screened discontinuities.

3. The method according to claim 1, wherein the ink includes a bright blue pigment of the phthalocyanine blue type.

4. The method according to claim 1, wherein the ink consists, by weight, essentially of 0.4% phthalocyanine blue pigment, 88.3% opaque mixing white, 10.9% grinding base and 0.4% white powder.

5. The method according to claim 1, wherein the background is printed on a white bond paper master of high brightness and in an ink having a color substantially identical with that known as PMS 456.

6. A security document system comprising, in combination,

a medium carrying a pressure-transferrable visible ink or the like of a color that exhibits high reflectance when indicia printed therewith is sought to be reproduced in one class of convenience office copiers including electrostatic copiers that operate predominantly within the blue region of the spectrum but is at least partially absorptive when such indicia is sought to be reproduced in a different class of convenience office copiers including electrostatic copiers that operate predominantly within the green to blue-green region of the spectrum, and

an opaque substrate having on at least one surface a visible masking background of another color, said surface adapted to be printed over by a typewriter or the like with legible indicia from said medium,

said other color being one which absorbs light when the background formed thereof is reproduced thereby to inhibit reproduction of said legible indicia by any copiers operating in any of said energy ranges, inasmuch as said one class of copiers will fail to reproduce the indicia printed with said ink because of its reflectance and said different class of copiers will reproduce illegible indicia printed in said ink and masked by said background.

7. A system according to claim 6, wherein the indicia is in an ink comprising a bright phthalocyanine blue pigment, and the background is essentially of a color identified as PMS 456.

8. A security document system comprising

a substrate providing a surface of high brightness with a masking background applied thereto which is of a color substantially identical with that known as PMS 456, and

a medium for apply over the background visible indicia in a formulation comprising a bright blue phthalocyanine pigment.

9. A system according to claim 6, wherein said background is sufficiently light absorptive in electrostatic copiers of the broad spectrum white-light type and those using zinc-oxide coated copy papers to provide legible, but poor quality, copies of said indicia in such copiers.

10. The method of precluding generation of legible copies of human readable indicia from a master by any one of a plurality of classes of electrostatic office copiers having different operating energy ranges, comprising the steps of

providing an ink of a color that is highly reflective across the operating energy range of electrostatic copiers of one class operating predominantly in one region of the spectrum, but which ink is at least partially absorptive within the different operating energy range of another class of electrostatic copiers operating predominantly in another region of the spectrum,

providing on the master a background of another color that absorbs light within said different operating energy range and masks the ink color which would be legible in said other region, and

printing the human readable indicia over said background with said ink,

whereby said electrostatic copiers of said one class will fail to reproduce the indicia printed in said ink because of its reflectance and said electrostatic copiers of the other class will reproduce illegible indicia printed in said ink and masked by said background.