GB2217258A

GB2217258A - A security document with a warning pattern and a method for the preparation thereof

Info

Publication number: GB2217258A
Application number: GB8906710A
Authority: GB
Inventors: Erkki Gronholm; Seppo Koistinen
Original assignee: SUOMEN PANKIN SETELIPAINO
Current assignee: SUOMEN PANKIN SETELIPAINO
Priority date: 1988-03-24
Filing date: 1989-03-23
Publication date: 1989-10-25
Anticipated expiration: 2009-03-23
Also published as: FI80405C; FI881424A; GB2217258B; FI80405B; FI881424A0; GB8906710D0

Abstract

The invention relates to a security arrangement for a printed product, a security, a document, or the like, which prevents the precise copying of the original product by identifying the copy as non-authentic, and which comprises a protective area 4, 11 and a warning word 1, 10, each printed with a specific line technique which is parallel in relation to the other such that the warning word in the original product is not distinguishable from the protective area to the unaided eye, but that the properties of a copying machine or a scanner cause the protective area and the warning word to copy in ways different from each other, whereby a difference in the degree of blackness or in tone is produced between them, bringing out the warning word in the copy. Furthermore, the invention relates to a method for producing the line pattern of the protective area and the line pattern of the warning word described above and for combining these line patterns into one line pattern image so that, at the outline between the protective area and the letters of the warning word, there is formed according to a specific line technique a transition area 12, where the higher-frequency and the lower-frequency line rulings interlock and where the density range gradually changes. <IMAGE>

Description

A security document with a warning pattern & Hand a method for the preparation thereof The invention relates to a security arrangement for printed products, documents, or the like, an arrangement which prevents the precise copying of the original valuable product by identifying the copy as non-authentic and which comprises a protective area printed with a pattern and a seoul rity word printed with a pattern in such a manner that in the original product the security word is not distingufshl able from the protective area to the unaided eye, but the properties of a copying machine or a scanner make the protective area and rhe security word to copy in ways deviating from each other, whereby a difference in blackness or tone is produced between them, bringing out the security word in the copy. The invention also relates to n method for producing the line pattern of the protective area and the line pattern of the security word, of the type described, and for combining these line patterns into one line pattern film in such a way that, at the outline between the protective area and the security word, there is produced a fading area, where the higher-frequency and the lower-frequency line pattern rulings interlock and where the density range changes gradually from the density range of the protective area to the density range of the security word.

Printed products, documents or the like of the above type, protected with a security word, have been in use for a long time in a number of different variants. In aiming at forming in a printed product a warning word which in the original is not distinguishable to the unaided eye but in a copy is immediately visible, it is in general possible to use either a dot screen or a line screen. There are a number of variants of each of these, and these two principal groups are discussed below separately.

Various applications of the dot screen are disclosed, for example, in the publications US-4,31O,l8O, US-4,579,370, US-4,351,347, and US-4,341,404. All of these publications disclose a protective area and a security word having different dot frequencies, line frequencies, and halftone percentages and density ranges, as compared with each other. The purpose is that in the original document the area of the warning word will not be distinguishable to the unaided eye from the protective area but that the denser screen area will be, as compared with the general standard of copying machines, within the resolution capability, whereas the less dense screen area is beyond the resolution capability, in which case the coarser and the finer screen will be copied at different degrees of darkness.However, dot screens have the crucial disadvantage that, with present-day technology, when using digital color copying machines and scanners, a potential counterfeiter need not even try to copy the original; having examined one original he may screen a scanner or the like of the type in general use to produce a dot screen film fully corresponding to the original 3y using the film it is possible to make a printing base onto which "original" counterfeit documents can be printed. This is also the reason why, for example, all stock exchanges in the world demand absolutely that securities must in no case be prepared using the direct screen technique.

There are also a number of different implementations of the line screen alternative. The publication G3-2-040,224 discloses a system based on the line screen, in which the screens of the protective area and the security word are similar but at an angle to each other. This system is no longer usable, since present-day copying machines are able to reproduce screen rulings in different directions very well in the same manner. This situation is not improved even if an attempt is made to select special inks, as in the publications 2 026 945 and G3-2 167 010.In addition to the difference in orientation and the metallic irk, the last-rnentidned publication uses in the protective area and the security word, instead of conventional screens, line patterns of different line frequencies in order to ensure that the different areas are copied differently owing to the frequency difference, as in the dot screen systems. The purpose of the irregular line pattern is to mislead the examiner of the original document by forming in the product a pattern different from that of the security word.The greatest disadvantage of the prior-art line patterns and line screen patterns is that even in the original document the security word is always distinguishable to the unaided eye, at least to some degree, in which case the authenticity of the document is not unambiguous from the vIewpoint of the person examining it. Present-day copying machines are also capable of quite credibly imitating even special inks, such as metallic inks, and so the authenticity of a document cannot be verified unambiguously even in this manner.

In addition to what has been described above, it is poss#- ble, taking copying machines having different properties into account, to use in the same security word and/or protective area a number of screen areas of different densities or types, as in the publication US-4,5S2,346, in order that the copying machine in each given case will, on the basis of its resolution capability, copy at some point of screen density the less dense screen but not the finer screen. This is, in fact, a method independent of those described above, since it can always be used to supplement the actual screen alternative.

One further method for disguising the security word so that it cannot be distinguished in the original is to use camouflaging printing which will mislead the examiner so that the original warning word will not be easily observed. Such camouflaging printing is disclosed in publications US4,227,720 a#d'US-41420,l75. In the latter publication, the method of which is based on the dot screen, an endeavor has also been made to disguise the letters by using somewhat rounded and indefinite letter shapes.The use of camouflag- ing printing and shapes of letters constitutes a technique independent of all of the above methods, and they can be used to supplement any of the other methods described above, None of the methods described above for forming a protective area and a warning word will provide proper protection against the counterfeiting of documents and securities.

If it is desired to protect a valuable product absolutely and surely against counterfeiting, it must fulfill all of the requirements listed below: First, it must be possible by visual estimate to recognize the authenticity of the product at the handling stage, and it must not provide alternatives for the examiner; the authenticity of the product must be immediately observable without any additional tools. This means that the security word in the document must not be observable to the unaided eye even if the person examining the document knows to look for it.

Second, changes of tone are not sufficient at the handling stage to reveal a copy, since an authentic original is not always immediately available for comparison.

Third, neither the protective area nor the security word must consist of a dot screen or other screen which can be produced by generally used scanning screen equipment. Z.e., the "screen" must be of the line pattern type.

Fourth., the warning or securIty word must reliably copy in a different manner than the protective area in order that a sufficient difference of darkness or color be produced between them so that the security word is immediately readable in the copied product identifying the copy as nonw authentic.

No method according to the state of the art fulfills all of these requirements.

The object of the invention is thus to fulfill all of the requirements presented above, in which case the security word in the original publication cannot be distinguished from the protective area, products imitating the original document cannot be printed, and the security word is absolutely and clearly revealed when the document is copied. To implement this, the security arrangement according to the inventIon is characterized in what is disclosed in the characterizing clause of Claim 1, and the method for producing a line-pattern film containing the protective area and the security word is characterized in what is defined in the characterizing clause of Claim 9.

It can be regarded as the most important advantage of the invention that the security word is very well hidden in the protective area, whereupon it is very difficult to detect even by a person knowing the location of the word, that the line pattern structure of the protective area and the security word according to the invention is very difficult to produce using the equipment in general use, in which case it will be difficult to produce counterfeits based on printing technology, and that, in the process of copying, the security word is brought out clearly and unambiguously, thereby canceling the said copy# It is a further advantage that the bringing out of the security word is independent of the direction of copying, and therefore reliable.It is a further advantage that the protective area and the secu- rity word can in most cases be printed using a relatively light color, which enables such paper to be used generally as a writing base, for example, normal typewritten text distinguishing from it well owing to sufficient contrast, but that, in copying, the security word is, however, brought out reliably.

The invention is described below in detail, with reference to the accompany ng drawings.

Figure 1A depicts a part of a warning word containing a positive letter image, in which the line pattern has been used in its basic form, Figure iS depicts a protective area containing a negative letter image corresponding to Figure 1A, in which the line pattern according to the invention has been used in its basic form, Figure 1C depicts Figures 1A and 1B combined in accordance with the invention, Figure 2 depicts the line pattern highly enlarged to depict the border zone between the letter of the warning word and the protective area, Figure 3 depicts an alternative line pattern according to the invention, Figure 4 is a schematic representation of the arrangement of the method according to the invention.

Figure 1A depicts a representation of one letter of a warning word, highly enlarged as compared with the natural size. This positive letter image is in this case made up of a straight line pattern 1. The letter has been shaped according to the invention so as to have rounded corners both at its outer corners 2 and its inner corners 3. Figure 1B depicts a protective area having a negative letter image, corresponding to the letter of Figure 1A. The protective area or the base pattern is in this case also made up of a rectilinear line pattern 4, which has in this case a lower frequency than the line pattern 1 of the warning word.

When the warning word of Figure 1A and the protective area of Figure 1B are combined, the result is Figure lC, which corresponds, highly enlarged, to the line pattern film from which the final printing plate will be made.

The essential characteristics of the invention are clearly visible in Figure lC. In this case the line frequency of the line pattern 1 of the warning word is double the fre quency of the line pattern 4 of the protective area, and the line patterns are in alignment in relation to each other and evenly distributed. In this case every second line 5 of the warning word is a continuation of a line 7 of the protective area, and every second line 5 of the warning word is half-way between lines 7 of the protective area. By this arrangement it is ensured that the outlines of the letters of the warning word in the original document will not be visible to the unaided eye.

The density ranges of the line pattern 1 of the warning word and the line pattern 4 of the protective area must be selected so that the area of the line pattern of the warning word will seem exactly as dark as the area of the line pattern of the protective area. For physiological reasons the density ranges of the line pattern 1 and the line pattern 4 are in general not mutually exactly the same.

In order to ensure the copying of the warning word in, for example, a lighter tone than the copying of the protective area, the line frequency in the line pattern of the warning word must be selected sufficiently high, so that the re solution capability of copying machines or scanners will not be sufficient to distinguish an individual line 5 from the lighter base 6.Purthermore, if the density range formed by the darker linen 5 of the line powtt=-n is St- lected so as to be sufficiently low, typically 10-25 %, the warning word will be copied substantially in the color of the paper base, since the copying machine or the scanning device will in this case distinguish only the base color, The line frequency of the line pattern of the protective area, for fts part, is selected to be so low that with a density range corresponding to the density range of the warning word the thickness of the dark lines 7 will be sufficient, so that any copying machine or scanning device will distinguish these lines from the base color 8.With this combination, the line pattern of the warning word will not copy, whereas in the protective area the line pattern will copy, resulting in the warning word being visible and identifying the paper in question as a copy and as void.

According to the invention, it is, of course, possible to reverse the frequencies of the line pattern 1 of the warning word and the line pattern 4 of the protective area, in which case, during copying, the line pattern of the protective area will not copy but the line pattern of the warning word will copy, whereupon the warning word will again be clearly readable on the paper and will cancel it. The density range formed by the line pattern ink can be shifted closer to one of the extreme values, i.e, within the range 75-90 %, as a result of which the warning word will be copied as an even dark surface as compared with the prea cisely copying protective-area line pattern in a case in which the line pattern of the warning word is of a higher frequency than the line pattern of the protective area. The same density range change can also be made when the line pattern frequencies of the warning word and the protective area are the reverse as compared with that described above.

In any case, the density ranges must deviate substantially from 50 %, since otherwise there will be a risk that everything is copied according to the average, as medium dark, in which case the warning word will no longer be readable unambiguously enough in the copy.

Since the frequencies of the line patterns must be such that, as seen by the unaided eye, even a lower-frequency line pattern will not come out, at least not very strongly, since otherwise the warning word is distinguishable already in the original owing to the great line frequency difference, and that simultaneously the width of the line of the higher-frequency line pattern must be sufficiently small and the line frequency sufficiently high to be below the resolution capability of copying machines or other similar devices, the following embodiment, preferred at the moment, has been arrived at. In this, in the area of the lower frequency line pattern #aLt##LL ###ia lirrafrequency is approximately 25-30 lines/cm, preferably approximately 30 lines/cm, and the width of the line is approximately 0.06-0.11 mm, preferably approximately 0.09 mm.In the area of the higher- frequency line pattern the line frequency is precisely double, i.e., depending on the line frequency of the lowerfrequency line pattern, 50170 lines/cm, preferably approximately 60 lines/cm, and the line width is 0.02-0.04 mm and preferably approximately 0.03 mm. In this case the density range is within 10-30 %.

Figure 2 depicts one further specific characteristic of the invention, consisting of the fact that in the border zone between the higher-frequency line pattern 1 and the lowerfrequency line pattern 4, where the lines of the line patterns are parallel, there is formed a fading area 9, where the lines of the higher-frequency and the lower-frequency line pattern interlock. Furthermore, as in this fading area 9 the density range of the line pattern 1 is arranged to change gradually to the density range of the line pattern 4, which is accomplished, for example, by narrowing the ends of the lines extending into the line-fading area 9 so as to correspond to the density-range change, any letter outline effects possibly increasing detectability can be eliminated effectively.In practice, the most advantageous size of the fading area 9, i.e. its length in the direction of the ruling, depends on the line frequencies of the line patterns, the density range, the darkness of the colors used, and the letter size. There are no theoretical limits for the size of the fading area; in principle it may be of any size, provided that the correct change of density range in the fading area is accomnlished. Thus the limitina factor will be the line-pattern p-#oducing technique, which sets as a limit for the width of the fading area in the direction of the line pattern lines a value which is close to the above-mentioned line widths. At present, 0.02-0.05 mm, or approximately 0.03 mm, is regarded as the preferred width of the fading area.

For the sake of simplicity, line patterns consisting of straight lines have been discussed above. In order to make the making of printed counterfeits imitating the original even more difficult, it is possible to use line pattern. in which the lines are sur.ved or wave-like or otherwise irreg- ularly ly sheped.The lines of the L#L# patterns ularly sheped. The lines patterns 10 end 11 may O and 11 may also be curved within the border zone between them and within the fading area 12 included in this zone, provided that they are, in accordance with the invention, parallel and in register. One such alternative is shown in Figure 3.

The width of the border zone, i.e. the zone in which the lines of the different line patterns are parallel, may be differentially small or of the size of the fading area, as in Figure 3, or of the size of the whole letter image, as in Figures 1C and 2.

Figure 4 shows a preferred method for producing a line pattern combination of the type described above. In it, a first line imagig film 13, corresponding to Figure IA, which contains a positive letter image, and a second line imaging film 14, corresponding to Figure 1B, which contains a negative letter image, have been superimposed and placed in register on top of a photosensitive film 16. This pack of films has been placed on a rotating base 17. The films 13 and 14 have been made, starting from the desired warning word image, otherwise by using the normal optical screen technique, except that the line pattern used is a ruling of the desired type and that in the letters of films 13 and 14 the lines of the line patterns are in register in the area of the outlines of the letters in the manner described above.At this stage, the outlines of the positive and the negative letter image are congruent. When so desired, it is further possible to use in the film pack a separating membrane 15 between the films 13 and 14 and the photosensitive film 16. When the photosensitive film 16 is exposed by using a source 20 of light located at a relatively great distance and offset from the rotation axis 18 of the base t whilo the EX60 17 ic rotating, p fading arca 1X produced on the photosensitive film 16 at the border be tween the line pattern areas.

In the arrangement described, the width of the fading area 9 and the change in the density range within this area can be adjusted to the desired values by changing the angle K of the rotation axis is to the straight line drawn from the source of light to the center 19 of rotation, and by changing the thickness of the separating membrane 15. In general, the value of the angle K is within 10.300. Preferably it is approximately 200, when the line frequencies and line widths are in accordance with the above example, when the films 13 and 14 are placed with the emulsion sides against each other, in which case their distance from the photo sensitive film 16 will be the thickness of the film background, and when the height of the letters is approximately 4-5 mm.

The invention is not limited to the alternatives described above; the structure of the line patterns may vary within the scope defined in the claims, For example, the ratio of the line frequency of the line pattern of the protective area to that of the security word may be even some other integer than two. It may be, for example, three or four.

When areas having the shape of the letter but different line frequencies are used one inside the other in the letters of the warning word, the line frequencies of any two adjacent areas must, in accordance with the invention, be multiples of one another, Thus it is possible to form zones of alternating line frequency or zones according to a noncontinuous series. The following number series illustrate some of the numerous alternatives of zone combinations, the numbers indicating the line frequency in each zone as compared with the lowest frequency used: 1-2-4-8; 1-2-1-2; 1- 2 37 2-1-3-6s 1-3-1-2; etc.

In addition to the line structure according to the invention, a printed product may be provided with any other additional patterns known Per se, such as camouflaging printing, several letter images one inside the other, having different line patterns or the same line pattern at different points, or by some other printing.

Claims

1. A security arrangement for a printed article, for preventing precise copying of the original valuable article by identifying the copy as non-authentic, comprising:- a protective area printed with a line pattern and a security word printed with a line pattern, the protective area and security word being printed with different line frequencies and having their density ranges selected so that in the original article the security word is not distinguishable from the protective area to the unaided eye, but that the properties of a copying machine or a scanner cause the protective area and the security word to copy in manners which are different from each other whereby a difference in blackness or tone is produced between them to bring out the security word in the copy, wherein the lines in said line patterns of the protective area and security word are parallel at least in the border zone between the outline of the letters and the protective zone, and wherein in the border zone between the protective area and the outline of the image of the security word there is a transition zone in which the higher-frequency line pattern and the lower-frequency line pattern interlock.

2. A security arrangement according to claim 1, wherein within said transition zone the lines of the line patterns of the security word and the protective area are evenly distributed in relation to each other, and there is a line of the higher-frequency line pattern in alignment with each line of the lower-frequency line pattern, and wherein within this transition zone the density range of each line frequency area gradually changes into that of the other.

3. A security arrangement according to claim 1 or 2, wherein the line frequency of the line pattern of the security word is a multiple of the line frequency of the protective area, or the line frequency of the line pattern of the protective area is a multiple of the line frequency of the security word.

4. A security arrangement according to claim 2 or 3, wherein the interlocking of the higher-frequency and the lower-frequency line patterns in the transition zone is, in the longitudinal direction of the line pattern lines, substantially within range of magnitude of the line thicknesses of the line patterns at this point.

5. A security arrangement according to any of the preceding claims wherein, within the area of the lowerfrequency line pattern, the width of the line is greater than within the area of the high-frequency line pattern, and the density ranges differ substantially from 50%.

6. An arrangement according to any of claims 2 to 5, wherein within the area of the lower-frequency line pattern the line frequency is 25-35 1/cm, and the line width is 0.07-0.11 mm, wherein within the area of the higher-frequency line pattern the line frequency is respectively 50-70 1/cm, and the line width is 0.02-0.04 mm, the density ranges being 10-30%, and wherein the magnitude of the interlocking in the fading area in the direction of the line pattern lines is substantially 0.020.05 mm.

7. An arrangement according to claim 6, wherein within the area of the lower-frequency line pattern the line frequency is substantially 30 1/cm, and the line width substantially 0.09 mm, wherein within the area of the higher-frequency line pattern the line frequency is substantially 60 1/cm, and the line width is substantially 0.03 mm, and wherein the density ranges are 10-20%.

8. A security arrangement according to any one of the preceding claims, wherein the images of the security word have been designed so as to be rounded at their inner and outer corners so that the radii of the rounding are at maximum the magnitude of the distance between the lines in the lower-frequency line pattern, and so that the shortest line length appearing at the edge of a letter of the security word is at maximum approximately the magnitude of the distance between the lines in the lower-frequency line pattern.

9. A security arrangement according to any one of the preceding claims, wherein each letter of the security word has areas, one inside another and substantially corresponding to the shape of the letter, in which areas the line frequency of the line pattern of one of the areas, either the inner or the outer one, is a multiple of the line frequency of the line pattern of the other said area of the letter of the security word.

10. A security system according to any one of claims 3 to 9, wherein the ratio between the line frequency of the security word and that of parts of the security word of the protective area is an integer other than two, and wherein the lines in the security word and in the protective area are parallel only in the border zone between them.

11. A method of making the line pattern of the protective area and the line pattern of the security word according to any one of claims 1 to 10 into one line pattern film so that there is formed at the outline between the protective area and the letters of the security word a transition zone where the higher-frequency and the lowerfrequency line pattern rulings interlock and where the density range changes gradually from the density range of the protective area into the density range of the security word, wherein a first line pattern film, containing the positive image and a second line pattern film containing the respective negative letter image, the outlines of the letters in the first film and the second film being congruent and the letters forming a security word, are placed one over the other in register on a rotating base and on top of a photosensitive film to form a pack; wherein the photosensitive film is exposed through this pack while the base is rotating; and wherein the exposure is by means of a source of light which is located far from the base and is offset from the rotation axis of the rotation base.

12. A method according to claim 11, wherein said first and second line pattern films åre placed one over the other on said rotating base on top of not only a photosensitive film but also intermediate membranes.

13. A method according to claim 11 or 12, wherein the width of the transition zone is adjusted by means of the distance of the source of light from the base and by means of the offset of the source of light from the rotation axis of the base and by means of the distance of the first and second films in the pack from the photosensitive film.

14. A method according to claim 13, wherein the angle of the rotation axis to the straight line drawn from the source of light to the rotation centre of the base is 10-30 .

15. A method according to claim 14, wherein said angle is substantially 20 .

16. A security arrangement for a printed article, substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

17. A method of masking the line pattern of a security arrangement for a printed document, substantially as hereinbefore described with reference to the accompanying drawings.