FR2503890A1 - Multi-colour anti-copying system for e.g. xerographic copier - uses pre-selected background and image colours for colouring original document to prevent copying - Google Patents

Abstract

The system provides a multi-colour anti-copying system in which different parts of an image or text on the original document are printed in different colours on a background of a third colour, the colours being so selected that one part of the image or text drops out in the resultant copy on a first group of copying machines while another part of the image or text drops out in the resultant copy on a second group of copying machines. The system utilises the various colour responses of the different photoconductor materials mentioned above for inhibiting or preventing the reproduction of intelligible copy. For example, printing a blue, light green or yellow-green image on a yellow background will inhibit satisfactory reproduction of copies on machines using those photoreceptors which respond well to yellow, but which respond weakly to blue or green. In attempting to copy such a coloured original, the background colour on the original will 'print up' in the copy and thus will be strong or dense while the image colour will 'print down' and thus will be faded. The resultant copy will therefore lack contrast, making it unreadable or unintelligible.

Description

 Multi-color anti-copy system for xerographic and electrostatic copying machines.

 The present invention relates to anti-copy systems in which the original documents are produced in colors chosen so as to prevent or prevent intelligible reproduction on xerographic and / or electrostatic copying machines.

 Owing to the accessibility of xerographic and electrostatic copying machines in offices, the ease of use and the low reproduction costs, there has been a widespread unauthorized and non-discriminatory copying of documents in recent years. The problem of unauthorized copying of copyrighted documents such as musical scores and texts is particularly important since it violates the legal rights of authors and publishers. Representative lessons regarding this problem in relation to the state of the technique can be found in the US patents 3,852,088, 3,887,742, 3,603,681, 3,807,852, 3,713,861, 3,671,451, 776,470, 776,515, 17,473 dated January 2, 1957, 4,025,673, 3,597,082, 3,977,785, 1,692,405, Swiss Patent 109,040, French Patent 809,379, British Patents 402,028, 411,178 and 198,364.

 Most of the solutions proposed in the aforementioned patents provide for the use of a special form of document which is intended to prevent or prevent readable reproduction. Such solutions are generally unsatisfactory since they favor only one very narrow type or range of reproduction machines or photoreceptors over others and are expensive or both. Thus, no optimal solution has been found to prevent copying economically on most different types of reproduction machines. Most normal paper copying machines use one of the four photoconductive or photoreceptor with different mixes of color sensitizers. Such photoconductive materials are the selenium used in some of the Xerox machines, zinc oxide, as used in Royal or Royfax machines, cadmium sulfide used in Saxon machines and organic materials (polyvinylcarbazole) used in IBM machines. None of the color document anti-copy systems is capable of adequately preventing the production of intelligible copies of any of the four classes of photoconductive materials mentioned above.

 During the development of the present invention it has been discovered that the different types of photoconductors mentioned above respond in varying degrees to selected colors and that the set or responses of the spectral system of the different reproduction machines using such Photoconductive materials each depend on the spectral response of the photoreceptor and the photoconductor itself associated with the distribution of spectral energy from the light source of the reproducing apparatus. In addition, it has been discovered that there is a certain relationship between the spectral responses of the system of the reproducing apparatuses using the various photoconductors mentioned above.

For example, reproduction machines equipped with a type of photoconductor or photoreceptor are capable of recognizing blue and thus copying it strongly, while at the same time iras do not recognize yellow and do not copy yellow. Furthermore, copying machines using other types of photoconductors mentioned above are capable of copying yellow very well but not blue at all. The multi-color anti-copy system of the present invention is intended to use the different color responses of the different photoconductors mentioned above in order to erase or prevent the reproduction of an intelligible copy. For example, by printing a blue, light green or yellow-green image on a yellow background, we will satisfactorily inhibit the reproduction of copies on machines using photoreceptors which respond well to yellow and which respond weakly to blue and green. When trying to copy such an original to multiple colors
the background color of the original will stand out during copying and will be very intense or dense while the color of the image will not stand out and, therefore, will be washed out. The resulting copy will lack contrast making it unreadable and unintelligible.

 With the aim of avoiding copying with a larger group of copying machines in an economical manner, using different photoconductive materials, the present invention aims at a color-coded anti-copying system in which the different parts of the image or text from the original are printed in two different colors on a background in a third color. For example, the background color of the original can be advantageously selected to match on most copying machines. An image color is chosen to stand out less on a certain number of copying machines while it stands out other copying machines and the other image color is chosen to have an opposite effect to the first color of the image mentioned above, that is to say which stands out on some copiers when it does not appear on other copy machines.

The double coloring of the image or text can be arranged so that alternate paragraphs of the text are printed in two different colors. With the three-color system, the resulting copy tends to eliminate part of the paragraphs on one group of copiers and part of the paragraphs on another group of copiers.

Rather than using a two-color system in which one color stands out and the other does not stand out on printing, the present invention also aims at a color anti-copy system in which the two colors are chosen to stand out approximately. the same level of density on the copy on certain photoreceptors so as to eliminate the contrast with the background on the copy and make it unintelligible.

 With the above in mind, the general object of the present invention is therefore to provide a multi-color anti-copy system and a method for economically copying documents on a large number of xerographic and copy machines. electrostatic using different photoconductive materials.

 Another object of the invention is to provide an anti-copy method of coloring an original document with a contrasting image and background colors which, in combination, prevent or prevent intelligible reproduction of office copiers such as machines xerographic copy.

 Another important object of the invention is a novel multi-color anti-copying system or a method in which the different parts of an image of a text of an original document are printed in different colors on a background of a third color, the colors being chosen so that part of the text image is removed from the resulting copy on a first group of copying machines while the other part of the text image is removed from the resulting copy for a second group of copy machines.

 Other objects of the invention will appear on reading the description which follows, in relation to the appended drawing.

 The single figure in the drawing is a graph containing a family of responses or sensitivity curves showing the relative spectral responses for various popular copying machines currently used commercially.

 The terms "image" and "graphic information" are used interchangeably to include words, letters, numbers, graphics, drawings, illustrations, or any indicia that may be printed on a sheet of paper or other material.

The term "original" or more specifically "original document" is used in the present description to designate any document which can be copied, whether it is a true original or a color copy or a reproduction thereof. The expression "dominant wavelength" applied to colors signifies the value of the maximum reflectance of a determined color.

We will only consider copying machines producing non-colored copies; such uncoloured copies comprising shades of gray, white or close to white and black or close to black.

 Referring to the drawing, the illustrated graph contains four spectral system responses or peat of sensitivity 10, 11, 12 and 13 for different copying machines usually in the trade.

 Each of the curves 10 to 13 is a representation of the wavelengths of reflected light expressed in nanometers (i.e. the light reflected from the original intended to be copied) with respect to the relative density of l impression of the reproduction (image or background) of the copy. Relative density is therefore a measure of the relative reflectance of light from the original for a given wavelength.

 As it is, the relative density for curves 10 to 13 represents the responses of the relative spectral systems of the copying machines associated with curves 10 to 13 for a range of wavelengths or regions ranging from approximately 400 nanometers to 700 nanometers. . The colors associated with the different bands or regions with wavelengths between 400 and 700 nanometers are shown at the top of the graph.

For convenience, the dominant wavelengths or maximum reflections for most colors are shown in Table I below:
TABLE I
Color Dominant wavelength
(nm)
Purple 410
Blue 465
Green 530
Yellow-green 555
Yellow 580
Orange 615
Red 690
The response curve 10 is that of the Xerox 4000 copier having a selenium-tellurium alloy as photoreceptor, the response curve II and that of the IBM II copier having as polyvinylcarbazole photoreceptor, the response curve 12 is that of the Xerox 3100 copier having a selenium photoreceptor and the response curve 13 is that of the Kodak Ektaprint 150 copier having an organic photoreceptor.

Each of these curves shows a variation in relative density and therefore relative reflectance over the wavelength range mentioned above. The response curve of the relative spectral system illustrated in the drawing for each of the copying machines mentioned above has been determined experimentally and represents a combination essentially of two responses, in particular the relative spectral response of the photoconductive material used in the imaging machine. copy and distribution of the spectral energy relative to the outputs of the light source used in the copy machine.

 By analyzing the system responses, we can observe that the maximum reflectance (max) for the Xerox 4000, Kodak and IBM copiers (curves 11 to 13) is very close to a wavelength of about 580 nanometers which is the wavelength region of yellow. At maximum reflectance, the density of the impression of the reproduction, that is to say the density of the impression of the copy, will be at a minimum.

 As a result, IBM II, Kodak 150 and Xerox 4000 copiers will tend not to bring out the yellow, making the copy print very bland and clear.

 The maximum reflectance of the Xerox 3100 copier is in the region of 482 nanometers to 507 nanometers (blue-green).

For a color in such a wavelength region, the Xerox copier will not bring out the color but to a lesser degree if compared to other copiers at their maximum reflectance.

 The responses of the spectral system represented in the drawing are not indicative of the proportions of the copying machines which bring out the yellow; on the contrary it has been found that most of the copiers currently used tend to bring out the yellow.

 Thus, according to an implementation of a two-color system of the invention, the paper to be printed for the document is printed or produced by applying a colored image such as text printed on a background having a contrasting color. Advantageously, yellow is chosen for the background and has a dominant reflected light wavelength (a maximum reflectance value) of approximately 580 nanometers. A suitable ink to print this yellow background is Day-Glo Arc Yellow 5-77-16, lithography ink manufactured by Coates Brothers, Zinc. of Ldsaner, Norton, England.

The color of the image is chosen so as to have a dominant reflected light wavelength which is less than that of the yellow background. In this embodiment, the color image is preferably turquoise having a dominant reflected light wavelength between 465 nanometers and 530 nanometers. Such a selection of the background and the colors of the image makes it possible to obtain a high degree of visual contrast on the original intended to be read. An ink suitable for printing the color image is called ink
Permanent Turquoise LR19 manufactured by the company mentioned above (Coates Brothers, Inc.).

 When a document with such a turquoise image printed on a yellow background (about 580 nanometers) is copied by a Xerox 3100 copier or on other copying machines with similar answers, the yellow background will stand out while the image will be turned down on the resulting copy.

In other words, the density of the reproduction print resulting from the yellow background will be relatively high while the density of reproduction print resulting from the turquoise image will be relatively low. More specifically, the density of the printing of the background on the resulting copy will be considerably greater and stronger than the density of the printing of the image on the copy as shown by curve 11. On the resulting copy, the image will disappear or be washed out in the darker background and will be only slightly discernible on the copy. Thus, by the combination of effects which bring out and which do not bring out the background and the image respectively, the contrast on the copy is reduced enough to inhibit or prevent the production of readable or intelligible copies.

 To avoid reproduction by a larger number of copying machines, the different parts or portions of the image are printed or produced by another process in two different colors on a background of a third color, the third color or background. being the yellow described above for the 2-color system. The two colors of the image are chosen so that one has a dominant wavelength higher than the dominant wavelength of the yellow background while the other has a dominant wavelength which is less to that of the yellow background.

The color of the image having the highest dominant wavelength is advantageously red-orange having a dominant reflected wavelength of approximately 625 nm. A suitable tank to print this orange red color image on the yellow background of the original is
Day Glow Fine Orange 55-77-14, lithographic ink produced by Coates Brothers.

 The color of the image with the shorter wavelength can be in the spectrum range from light green of dominant reflected wavelength of about 550 nm to yellow-green of dominant wavelength from about 555 to about 565 nm. Preferably, the color of the image having a dominant wavelength of about 560 to 565 nm is used. An example of a work suitable for the yellow-green image is the Pates Green LS13 from Coates Brothers.

 For books or other materials in the form of text and comprising several paragraphs, it is advantageous to print the successive paragraphs in different image colors, in particular in red-orange and yellow-green. Considering a page of a text having four paragraphs for example, the first and third paragraphs can be printed in red-orange and the second and fourth paragraphs can be printed in yellow-green. Naturally, the alternate coloring of the paragraphs can be reversed by using yellow-green to print the first paragraphs and red-orange to print the other paragraphs. Basically, half of the text on a particular page or sheet can be printed in red-orange and the rest of the text on the same page will be printed in yellow-green. alternating in two different image colors on a yellow background follows.

TEXT OFFERED ON YELLOW PAPER
Paragraph I - Printed in red-orange
The systematic arrangement of parallels and
meridians of a flat or flat surface constitutes
the framework on which we build a map.

Paragraph II - Printed in yellow-green
By projecting the grid of the earth on a cylinder
tangent, we can make a series of parallels and
meridians at right angles to each other.

Paragraph III - Printed in red-orange
The scale of a map is related to the
surface it represents. She is usually
determined by measuring the distance between two
localities indicated on the map and establishing the
relationship with the distance between the two points on the
menu.

Paragraph IV - Printed in yellow-green
On maps of the world where the scale varies greatly
from one latitude to another, we use a scale
variable graphics.

 When this sample of colored text in three colors is copied to a Xerox 3100 machine, the red-orange paragraphs will stand out in relation to the print density of the yellow background, but the yellow-green paragraphs will not stand out compared to the background print density.

On the copy, therefore, the reproduction of the red-orange paragraphs will have a print density which is higher than that of the yellow background, but the reproduction of the yellow-green paragraphs may have a print density which is less important than that resulting for the yellow background.

 It follows that the red-orange paragraphs will be readable on the copy while the yellow-green paragraphs will disappear or be erased in the more dense and dirty background of the copy so as to make any other paragraph illegible and unintelligible and not not allow actual transmission of text information.

 When the text sample is colored in the above three colors and is used in copy machines such as Xerox 4000, IBM II or Kodak 150, the background will be very clear on the copy and the red-orange paragraphs will stand out strongly by compared to this background. The yellow-green paragraphs, however, will stand out only slightly relative to the density of the background print on the copy so that the density or print of the yellow-green paragraphs is relatively light and pale on the copy. On the copy, therefore, the contrast between the background and the reproduction of the yellow-green paragraphs will be very low, making the reproduction difficult to read.

 When the text sample in the above three colors is copied to different copying machines using a zinc oxide photoconductor, the yellow background and the yellow-green paragraphs will be reproduced or will stand out strongly on the copy while the paragraphs red-orange will be reproduced very pale, so that an intelligible contrast is lost between the reproduction of the red-orange paragraphs and the reproduction of the yellow background.

 It is obvious from the above that the three color copying system described above will make it possible to economically avoid copying using a greater number of different types of office copy machine. comparative title with realizations in two colors.

The effectiveness of the three-color anti-copy system to allow the absence of reproduction of a large number of office copying machines does not only lie in the selection of colors, but also in the selection of the material intended for be printed in color. Thus, portions of the image which are printed in two different colors are chosen in such a way that non-reproduction or partial unintelligible reproduction and not of the whole image nevertheless makes the image total at least generally if not totally incomprehensible. Taking into account the example above, for example the parts of the reproduced text which will still be intelligible on the copy are not sufficient to give the reader the full meaning of this text.

According to another two-color implementation of the invention, the contrasting background and the colors of the image are chosen so that they bring out approximately the same relative density of printing on copying machines such as Kodak. Ektaprint 150, IBM II and
Xerox 4000. In this embodiment, the background color of the original is a background having a dominant wavelength or a maximum frequency value of approximately 650 nm and the color of the image of the original is a color having a dominant wavelength or a maximum reflectance value of about 450 nanometers. In general, a turquoise or cyan image on a red or magenta background meets these requirements of dominant wavelength.
Inks suitable for color image are manufactured by the aforementioned company, Coates Brocher s and include these permanent inks Turquoise LRl9
Cyan LR41, and offset inks such as Process Cyan MR39 and Turquoise MR37. Suitable inks or background colors are sold by Howard Smith Papers, Ltd. and include pink, cherry and salmon.

 It will be noted from the drawing that the dominant wavelength of 650 nm for the background color is considerably higher than the wavelength band containing the maximum reflectance values for the response curves 10, 11 and 13, and is located in the region where curves 10, 11 and 12 are practically flat (i.e. zero slope) or are close to a flat configuration. The dominant wavelength of 450 nm for the image color is considerably lower than the narrow wavelength band containing the maximum reflectance values for curves 10, 11 and 13.

At this lower part of the illustrated spectrum, the wavelength of 450 nm is located in the region where the curves 10, 11 and 13 are practically flat or are close to a flat configuration on the lower side of the inflection. more importantly for each of the response curves 10, 11 and 13, the two densities of 450 nm and 650 nm are very close to each other and are for practical purposes approximately equal.

 When using such a combination of image and background colors on the original, the print density of the image and background reproduction should be approximately equal on the copy when the original is reproduced on copiers such as Kodak 150, IBM II and Xerox 4000 as well as in other copiers with similar response systems.

The contrast will therefore be lost or greatly reduced on the copy so as to make the image unreadable or unintelligible.

 For Xerox 3100 copiers or other copiers with response systems similar to curve 11, it should be noted that the print density at approximately 650 nm is significantly greater than the print density a or approximately 450 nm. By using an image color having the dominant wavelength lower than about 450 nm and a background having the dominant wavelength approximately 650 nm, the image will be lost in the background on the copy made at from a Xerox 3100 machine or copiers with a response system similar to curve 11. As a result, the above color combination will prevent reproduction on such copying machines.

 To further broaden the different types of copiers that we want to prevent from copying the three-color schemes described above, the background color ink is advantageously printed in different shades such as 30% of a structure in dotted, 60% of a dotted structure, finally 100% of solid. Such prints can be printed on white paper. The percentages in dotted structure mean the proportion of the sum of the dotted areas in relation to the total area containing the dotted lines. The advantage of using shades is that the chosen color reproduces more strongly than black, thereby increasing the density of the background on the copy compared with the original, which results in a significant decrease between the background that stands out and the image that is folded down.

 For each of the coloring systems described above, the original document (such as white paper) can be prepared by first printing a colored background for the paper and the color image on the colored background.

 Other embodiments of the invention can also be carried out without departing from the essential characteristic spirit of these. The implementations described above are therefore considered only as illustrative and in no way restrictive and the invention includes all the modifications which are covered by the definitions and the range of equivalences.

Claims (16)

 1. Anti-copying process for preparing an original document bearing an image so as to prevent or prevent an intelligible reproduction of the image of the original document by means of xerographic and electrostatic copying machines, characterized in that it consists applying a yellow background to this document, first printing a preselected part of the image on said background in a first preselected color having a dominant wavelength which is higher than that of the yellow background and printing the remainder of said image in a second preselected color having a dominant wavelength which is less than that of the yellow background.  2. Anti-copying process for the preparation of an original paper document bearing an image so as to prevent or prevent the intelligible reproduction of the image on the original document by means of a xerographic and electrostatic copying machine, characterized in that '' it consists in applying a yellow background to said document, in printing a first preselected portion of said image on said background in a first preselected color having a dominant length which is higher than that of the yellow background and in printing a second preselected part of said image in a second preselected color having a dominant wavelength which is less than that of the yellow background, said first and second preselected parts being chosen so as to avoid an intelligible reproduction of either one or the other said first and second portions so that the image as a whole is at least generally incomprehensible.  3. Anti-copy method according to claim 1 or 2, characterized in that said first color is red orange.  4. Anti-copy method according to claim 1 or 2, characterized in that said second color is yellow-green.  5. Anti-copy method according to claim 1 or 2, characterized in that said second color has a dominant wavelength in a range between 550 nanometers - and about 565 nanometers.  6. Anti-copy method according to claiml su 2, characterized in that said first color is red orange having a dominant wavelength of approximately 625 nanometers and in which the second color is yellow green having a wavelength dominant in a range between 555 nanometers and around 565 nanometers.  7. Anti-copy method according to claim 6, characterized by the fact that said yellow background has a dominant wavelength of about 580 nanometers.  8. Anti-copy method according to claim 1 or 2, characterized in that said image is a readable text having several paragraphs, a first preselected group of said paragraphs being printed in said first color and a second preselected group of said paragraphs being printed in the second color.  9. Anti-copy method according to claim 1 or 2, characterized in that said image is a text having several paragraphs, alternating paragraphs of the text being printed respectively in said first and second colors.  10. Anti-copy method according to claim 8 or 9, characterized in that said first color is red-orange having a dominant dVonde length of about 625 nanometers in which said second color is yellow-green having a length d dominant wave in a range between ~ 555 and 565 nanometers.  11. Anti-copy method according to claim 8 or 9, characterized in that said first color is red-orange having a dominant wavelength of approximately 625 nanometers, and in which the second color is yellow-green having a color dominant wave in the range of 555 to about 565 manometers and in which said yellow background has a dominant wavelength of about 580 nanometers.  12. Anti-copy method according to claim 8 or 9, characterized in that said first color is red-orange and in which the second color is yellowgreen.  13. Anti-copy system according to claiml or 2, characterized in that the background is in a yellow tint.  14. Anti-copying method according to claim 1 or 2, characterized in that said selection of the first and second colors on said yellow background is carried out so as to allow non-reproduction effectively on a first and second type of copying machines and to which each of the copying machines of the first type has a maximum reflectance Xmax at a wavelength which is situated or which is close to the dominant wavelength of said yellow background and which is higher than the wavelength at which occurs the maximum reflectance for each copying machine of said second type; said first and second colors being chosen so that the wavelength where the maximum reflectance of said first and second types of copying machines occurs is closer to the dominant wavelength of said second color than to the dominant length of said first color.  15. Anti-copy method according to claim 14, characterized in that the dominant wavelength of said second color between the region of the wavelength where there is the maximum reflectance for said first type of copying machine is the wavelength region where the maximum reflectance occurs for said second type of copying machine.  16. Anti-copying method according to claim 14, characterized in that said second color has a dominant wavelength in the range between approximately 550 manometers and approximately 565 manometers.