GB2040224A

GB2040224A - Security documents

Info

Publication number: GB2040224A
Application number: GB7931791A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-01-23
Filing date: 1979-09-13
Publication date: 1980-08-28
Also published as: AU5109979A; NL7907996A; SE7909041L

Abstract

A document bearing a reproduction- resistant security pattern comprises (1) an image including at least one plurality of parallel spaced-apart lines oriented in a first direction and (2) a background including at least one other plurality of parallel spaced-apart lines oriented in a second direction different from the first direction. The line thickness, line spacing and relative contrast between the lines and spaces are substantially the same for both the image and background. Consequently the artwork appears as a uniform tint and the image merges with the background when viewed on the original document with the naked eye, but becomes discernible when reproduced with a line by line electrophotographic copier of, e.g. the rotary type. Image/background line set pairs may be arranged at a variety of angles to the document axes to defeat any attempt to defeat the security pattern by feeding the document slant wise through a copier. <IMAGE>

Description

SPECIFICATION Document security The present invention relates to the manufacture of documents and more particularly to an improved technique of printing documents so as to inhibit the unauthorized reproduction of those documents.

Documents of value, such as money, checks, bonds, stocks, lottery tickets, etc. are frequently made with intricate designs, logo, lettering etc. so as to inhibit the unauthorized reproduction of the documents. However, with the increased use and improvements in electrostatic reproduction processes, exact reproduction can be easily accomplished; sometimes making it difficult to discern with the naked eye, the original from the duplicate. This problem is even more acute where the documents are processed by computers which are not necessarily equipped to detect such unauthorized duplications. Although many of these documents are now printed in color, the state of the art of color electrostatic reproduction has made it now imperative to develop techniques to easily discern original documents from duplicates.

Accordingly, an object of the present invention is to provide an improved method of printing documents so as to inhibit the unauthorized reproduction of the documents.

The method of the present invention takes advantage of the fact that when a copy is processed in many electrostatic copy machines of the type employing a rotating drum, such as the Model 6500 manufactured by Xerox Corporation of Stamford, Connecticut, the thickness of lines oriented in one principal direction, i.e., parallel to the axis of the drum, tends to slightly increase with respect to the thickness of lines oriented in the other direction perpendicular thereto; a phenomenon believed to be caused by the effect of heat on the toner material of the copy machine.

Accordingly, a more specific object of the present invention is to provide an improved technique for printing documents with a relatively undiscernable artwork image which when reproduced by such an electrostatic copy machine will become discernable.

These and other objects are achieved by an improved method of printing documents and the articles produced thereby. The method comprises printing the documents with an artwork, the latter being made from at least two groups of lines. The term "line" as used herein shall mean a component having an elongated dimension (herein referred to as its "length") and a short dimension (herein referred to as its "thickness") in a perpendicular direction to its length. The artwork includes (1 ) an image comprising at least one plurality of equally spaced-apart parallel lines having their length oriented substantially in a first direction and (2) a background comprising at least one other plurality of equally spaced-apart parallel lines having their length oriented substantially in a second direction different from the first direction.The lines of the artwork are such that the image is essentially undiscernable in the original but clearly discernable when reproduced in accordance with an electrostatic reproduction process of the type where the thickness of lines oriented in one direction is modified with respect to the thickness of lines in the other direction.

Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises the processes involving the several steps and the relation and order of one or more of such steps with respect to each of the others, and the products possessing the features, properties and relation of elements which are exemplified in the following detailed disclosure and the scope of the application all of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the present invention, reference should be had to the following detailed description taken in connection with the accompanying drawing wherein: Figure 1 shows an enlarged view of a typical printed artwork pattern made in accordance with the present invention which artwork can be applied to any original document; Figure 2 shows an example of an artwork printed on an original document, when the document is reproduced on an electrostatic copier of the type described; and Figure 3 shows an enlarged view of a typical printed artwork utilizing the artwork pattern of Figure 1.

In accordance with the present invention, each article or document, typically in sheet form, printed in accordance with the present invention is provided with an artwork, such as the one generally designated 10 in Figure 1. The artwork preferably comprises a first plurality of parallel, equally spaced-apart lines 12, shown in Figure 1 as oriented generally in a vertical direction, so as to form a background to an image 14. The latter is formed by a second plurality of parallel, equally spaced-apart lines 16 oriented generally in a horizontal diection. The lines 12 and 16 are preferably disposed relative to one another so as not to intersect or overlap.The technique, of using mutually perpendicular lines to print letters is shown in a slur guage printed by GATFTechnical Services Report published by Graphics Arts Tech Foundation, 4615 Forbes Avenue, Pittsburgh, Pennsylvania 15213. The slur gauge, used in off-set form color printing, provides a guide, to the printer, to indicate if the press or ink need adjusting, whether the sheets are slipping during the printing process, whether the blanket is too tight, whether the ink is too thick, etc.

The printed letters of the slur gauge form clearly discernable images in the original artwork. In accordance with the present invention the entire artwork is prepared and sufficiently reduced in the printing process so as to appear as a "tint".

More specifically, the original artwork is carefully prepared making sure that the lines 12 are of equal thickness, equally spaced and parallel to one another. Similarly, lines 16 are of equal thickness equally-spaced parallel to one another.

The thickness of lines 12 and 16 are all of equal thickness, of the same color and of equal spacing so that the "line density" (defined herein as the number of lines per linear inch) and the "tint value" or "tone" (defined herein as the relative surface area taken up by the lines relative to the entire surface area covered by the lines and spaces) is the same for both sets of lines.

Where the image 14 is composed of lettering or numbering, good results have been achieved where such lettering or numbering is substantially in block form so that the boundary edges defined by each letter (the boundary being defined by the upper and lower lines 16A and an imaginary line connecting adjacent terminal ends 20 of each line 16) are either parallel to lines 12 or lines 16.

Further, the ends 20 of the lines 16 should be spaced approximately one-half a space from adjacent line 12, and similarly ends 20 of lines 12 should be spaced approximately one-half a space from the boundary lines 16A, for best results.

Once the original artwork is completed it is reduced sufficiently to appear as a tint, making the contrast between lines 12 and 16 difficult to distinguish with the naked eye without a close and concentrated inspection. Typically, the artwork is reduced so that the line density of lines 12 and 16 is between 120-130 lines/inch with 128 lines/inch being preferred. The original artwork can be reduced in accordance with any known method. Preferably, the artwork is reduced using photographic techniques well known in the printing art. Typically, a reduction of twenty to thirty times is required although this would depend on the line density of the original artwork.

It will be appreciated that since the artwork appears as a tint it can be applied as an overprint, in accordance with well known printing techniques, on logo, numbers, indicia, etc. without interfering with their legibility. The tone of the overprint can easily be controlled by controlling the thickness of lines 12 and 16 relative to the spacing therebetween. When the artwork is used as an overprint, the tone or value of the tint is preferably 33 1/3% i.e., the thickness of the lines displaces 113 of the total surface area and the surface area of the spacings between the lines displaces 2/3's of the total surface area (stated in another way the lines are one-half the thickness of the spaces therebetween), although this tint value may vary depending upon the colour chosen.Further, the color or colors of the surface upon which the image is printed should be such that the edges of each of the lines defines with respect to the adjacent space, a substantial discontinuity in colour intensity or gray scale so that a contrast is provided for electrostatic reproduction.

When the particular document is made in accordance with the present invention, the artwork provided by the horizontal lines 16 is essentially indistinguishable from the vertical lines 12, without a careful and close inspection. However, duplicating the original document on an electrostatic copier of the type such as the Model 6500, results in lines 12 and 16 being reproduced at different thicknesses.

Specifically, the thickness of those lines oriented parallel to the axis of the drum, e.g. lines 12, will tend to increase relative to the thickness of those lines oriented perpendicular to the axis, e.g. lines 16. This is believed to be primarily due to the effect of the heat on the toner material in the copy machine. This change in the thickness of one set of lines produces a corresponding change in tint value so as to contrast between the two sets of lines, thereby enabling the image 14to be clearly distinguishable such as shown in Figure 2, where the image 14 is the word "copy".

It should be appreciated that image 14 is not limited to words, but can include logo, geometric designs, etc. Further, in order to prevent the unauthorized reproduction of a document printed with the artwork 10, whereby the document can be oriented during the reproduction process so that lines 12 and 16 are all oriented at 450 angles to the axis of the rotating drum of the copying machine so that the thickness of both sets of lines increases the same amount in the reproduction process, the document preferably is printed with a pluraility of artwork patterns, each oriented at a different angle so as to provide an assymmetrical design. More specifically, as shown in Figure 3, a plurality of the artworks 10 are prepared in a pattern so that the lines of one artwork are oriented at an angle with respect to lines of another artwork.As shown artwork 1 0A has its lines 12 and 16 oriented respectively in the relative vertical and horizontal direc tions. The artworks 1 10B, 10C, 10D and 10E are each prepared identically to artwork 10A and placed adjacent a different side of the artwork 1 OA. The lines 12 and 16 of each artwork 10B are perpendicularto each other but oriented at an acute angle to the corresponding lines 12 and 16 of artwork 10A. Lines 12 and 16 of artworks 10B, 10C, 10Dand 10Eare oriented with respect to lines 12 and 16 so that it is impossible to orient the artworks 10A, 10B, 10C, 10D and 1 0E so as to lie symmetrically with respect to the drum axis of a copy machine. Preferably lines 12 and 16 of artworks 10B, 10C, 10D and 10E are oriented at either 25", 35", 45" or 55" with respect to the lines 12 and 16 of artwork 1 0A although this can vary.

It should further be appreciated that printing the pattern of artworks 10 can be accomplished by any well known printing technique, such as offset or intaglio printing.

The above described process and articles produced thereby provide improved protection against unauthorized reproduction of valuable documents.

Claims

1. A method of printing a document so as to inhibit the unauthorized reproduction thereof comprising the steps of preparing an artwork so that it comprises an image including at least a first plurality of lines and a background to the image including at least a second plurality of lines and printing the artwork on the document so that the artwork appears as a tint and the image is relatively undiscernable to the naked eye, the image becoming discernable when the artwork is reproduced so that the thickness of the lines of one of the plurality changes relative to the thickness of the lines of the other of the plurality.

2. A method as claimed in claim 1, in which the step of preparing the artwork includes the steps of making the image with at least a first plurality of parallel, spaced-apart lines and the background of the image with a second plurality of parallel, spaced apart lines, wherein the first plurality of lines are oriented at an angle with respect to the second plurality.

3. A method as claimed in claim 2, in which the angle is 90".

4. A method as claimed in claim 2 or 3, in which the lines of the first plurality and the second plurality are of equal thickness and are each spaced an equal distance from the adjacent parallel lines.

5. A method as claimed in claim 4, in which the lines of the first plurality do not intersect with the lines of the second plurality.

6. A method as claimed in claim 5, in which the ends of the lines of the first plurality adjacent the lines of the second plurality, are each spaced from the adjacent line substantially one-half the distance between two lines of the second plurality.

7. A method as claimed in claim 2, in which the step of printing includes the step of reducing the artwork so that the line density of the lines of the first and second plurality is between about 120-130 lines/inch.

8. A method as claimed in claim 7, in which the line density is about 128 lines/inch.

9. A method as claimed in claim 7, in which the step of preparing the artwork includes the step of spacing the lines so that when the artwork is reduced the tint has a value of about 33 1/3%.

10. A method as claimed in claim 1, in which the step of printing includes the step of overprinting the artwork on the document.

11. A method as claimed in claim 1, in which a plurality of artworks is prepared in an assymmetrical pattern.

12. A method as claimed in claim 1, in which the first and second plurality of lines are perpendicular to one another and the pattern includes lines oriented at 25", 35", 45" and 55" to the first and second plurality.

13. A document made in accordance with the following steps, preparing an artwork so that it comprises an image including at least a first plurality of lines and a background to the image including at least a second plurality of lines and printing the artworkon the document so thatthe artwork appears as a tint and the image is relatively undiscernable to the naked eye, the image becoming discernable when the artwork is reproduced so that the thickness of the lines of one of the plurality changes relative to the thickness of the lines of the other of the plurality.

14. A document as claimed in claim 13, in which the step of preparing the artwork includes the steps of making the image with at least a first plurality of parallel, spaced-apart lines and the background of the image with a second plurality of parallel, spaced apart lines, wherein the first plurality of lines are oriented at an angle with respect to the second plurality.

15. A document as claimed in claim 14, in which the angle is 90".

16. A document as claimed in claim 14, in which the lines of the first plurality and the second plurality are of equal thickness and are each spaced an equal distance from the adjacent parallel lines.

17. A document as claimed in claim 16, in which lines of the first plurality do not intersect with the lines of the second plurality.

18. A document as claimed in claim 17, in which the ends of the lines of the first plurality adjacent the lines of the second plurality, are each spaced from the adjacent line substantially one-half the distance between two lines of the second plurality

19. A document as claimed in claim 18, in which the printing includes the step of reducing the artwork so that the line density of the lines of the first and second plurality is between about 120-130 lines/inch.

20. A document as claimed in claim 19, in which the line density is about 128 lines/inch.

21. A document as claimed in claim 19, in which the step of preparing the artwork includes the step of spacing the lines so that when the artwork is reduced the tint has a value of about 33 1/3%.

22. A document as claimed in claim 13, in which the step of printing includes the step of overprinting the artwork on the document.

23. A document as claimed in claim 22, in which a plurality of artworks is prepared in an assymmetrical pattern.

24. A document as claimed in claim 23, in which first and second plurality of lines are perpendicular to one another and the pattern includes lines oriented at 25", 35", 45", and 55" with respect to the first and second plurality.

25. An article printed so as to inhibit the unauthorized reproduction thereof, which comprises a sheet and an artwork including an image including a first plurality of lines and a background of the image including at least a second plurality of lines, the artwork being printed on the sheet and appearing as a tint and the image being relatively undiscernable to the naked eye, wherein the image becomes discernable when the artwork is reproduced so that the thickness of lines of one of the plurality changes relative to the thickness of lines of the other plurality.

26. An article printed so as to inhibit the unauthorized reproduction thereof, substantially as herein described with reference to and as illustrated in the accompanying drawings.

27. A method of printing a document so as to inhibit the unauthorized reproduction thereof substantially as herein described.