DE69017242T2 - Bow with safety device. - Google Patents

Description

The invention relates to a sheet with a safety device and a method for manufacturing such a sheet.

In the field of security documents, such as banknotes and the like, there is a continuing need to incorporate security devices that prevent such security documents from being counterfeited using the ever-improving printing equipment available on the market.

Examples of security devices used to date include complex patterns printed on the document, optical devices such as diffraction gratings, holograms and the like.

For certain types of translucent paper, a security feature was developed many years ago in which an image is presented (usually by printing) on both sides of the paper. In one embodiment, hereinafter referred to as a "see-through feature", complementary images are provided on each side of the sheet in precise registration with respect to one another, so that when the sheet is held up to the light, the image on the back fits precisely into spaces with the image on the front, sometimes with an unprinted uniform peripheral border. For example, each image may contain a series of black circles, with the circles on one side of the sheet fitting into the spaces between the circles on the other side. These images are normally printed using special lithographic presses which enable the front and back to be printed simultaneously in one press run. The tolerances of the design elements are usually a fraction of a millimetre, so that any deviation caused by printing both sides in a counterfeit in separate press runs can be quickly noticed. By printing both sides simultaneously, out-of-register printing due to changes in the dimensions of the sheet caused by changes in moisture content or heating and the like is avoided.

A second feature based on the same principle is referred to hereinafter as the "print-through" feature. In this feature, an image is printed in register on one side of the sheet and its inversion on the other side of the sheet so that when the sheet is held up to the light, the image on one side of the sheet substantially covers the image on the other side. The appearance of the image should not appear to be altered due to a lack of registration. However, it is possible to print the two images in different colors which may exhibit rainbow printing effects.

An example of a through-print feature is described in GB 315 528 A. For both the through-print and the through-print feature, there are four types of visual inspection: viewing the first image in reflected light, viewing the other side of the sheet in reflected light, viewing the composite image in transmitted light from the one side, with the image on that side predominating, and finally viewing the composite image from the other side of the sheet, with the image on that side predominating. When viewing the see-through features under fluoroscopy, the image on the opposite side of the sheet will appear in register in a genuine document. When viewing the print-through features under fluoroscopy, the image on the other side of the sheet will not be visible in a genuine document, but a slight lack of registration will show that the document is a forgery.

The printed images are generally graphic drawings, although alphanumeric characters may be used which appear identical in mirror reflection. The images may be printed with the same ink on both sides of the image, giving the impression that the ink has penetrated through the document, or the colors may be different. The print-through feature image on one side of the sheet may have two different printed portions on at least one side of the sheet, which may be printed in different colors. Alternatively, the image may be printed in continuously changing color, as in rainbow security printing processes.

Often, security document designers combine several individual see-through features to produce composite representations with these characteristics. Sometimes see-through and print-through features are combined to produce an overall composite representation feature that covers a large part of the banknote, for example up to 25%.

To date, these see-through and print-through security features have been most successfully applied to banknotes with a relatively low basis weight and have been restricted to white or nearly white paper. The heavier paper grades often found in harder currencies are too opaque to apply these features effectively. Similarly, coloured paper grades are too opaque to allow easy verification of these features.

WO 83/00766 A describes a security document, for example an identification card, with an anti-counterfeiting device in the form of a fused laminate which is very difficult to delaminate in order to gain access to the internal printing.

CA 1 116 851 A describes a process for the surface treatment of paper webs, in which a part of a web is sanded off.

According to one aspect of the present invention there is provided a sheet comprising a paper base material on which a security imprint is or will be provided and a security device comprising a see-through or print-through feature provided on the base material, characterized in that the feature is provided in an area of the base material which has a substantially uniform light transmittance and is more light transmitting than a major portion of the remainder of the base material prior to the formation of the security imprint.

According to a second aspect of the present invention, there is proposed a method for producing a sheet with a security device, in which a paper base material is produced on which a security imprint is or will be provided, wherein the Base material has a region which has a substantially uniform light transmittance and is more light transmitting than the greater part of the remainder of the base material prior to application of the security imprint, and in which a see-through or print-through feature is formed in said region.

We have proposed a new type of sheet in which a security device with a see-through or print-through feature can be provided even if most of the base material is largely opaque to light.

The invention is particularly applicable to colored or relatively heavy security paper substrates or base materials which have a high absorbency and where see-through and print-through features have been found to be inadequate. These features have therefore been previously limited to lighter weight white paper. However, according to the invention, the benefits of these features can be applied to previously unacceptable substrates. This makes the invention particularly suitable for security documents which are in common use, for example banknotes. However, the invention is applicable to a wide variety of paper base sheet substrate materials, for example paper, including rag paper, paper-plastic laminates and plastic coated paper. However, often the sheet will contain rag paper which has been provided with a security print to form a banknote.

Normally, the radiation used to capture the images is in the visible range.

The security device according to the invention can be used with all suitable documents provided with a security imprint on both sides, for example banknotes, cheques, including bank and traveler's cheques, and passports, bonds, certificates, tickets, passes, plastic cards (for example financial cards, bank cards, credit cards, debit cards, guarantee cards, service authorization cards), integrated circuits comprising cards, identity cards and permit documents.

The transparency of such documents can be measured automatically when the document is presented for machine processing, for example when sorting banknotes.

Preferably, the features substantially fill the region of uniform transparency, although a planar peripheral region may be provided.

As previously mentioned, the images printed in the area may be similar to those conventionally used to represent see-through or stencil features. In addition, these features may be modified so that, instead of an overall uniformly toned impression, the images may be made of interlocking geometric arrangements. These arrangements include parallel spaced line patterns, for example, those in which the spaces and lines are of equal width, so that when the composition is viewed by transillumination, the lines alternately overlap to give the impression of a continuous figure. Concentric circles or other curvilinear shapes may also be used. Another alternative is an interlocking or nested pattern of perpendicular lines, in which where the width of the lines and their spacing are equal, which when illuminated give the impression of an overlapping pattern of squares with either no overlap, a single overlap or a double overlap. Poor registration gives the impression of a noticeable change. Another alternative, described in DE 32 08 204 C1, is a periodic line or dot pattern, which in a counterfeit produces a moiré pattern.

The images can be printed in one color or in multiple colors or in a combination of the two.

As the printing ink, lithographic inks, including colored ink, white ink, black ink, metallic ink, optically variable ink (for example, those forming optical thin film interference filters) and the like can be used. Thermochromatic inks, photochromatic inks, fluorescent and phosphorescent inks that are visible can also be used. The printing inks can be used in rainbow printing.

The images can also be printed using white or colourless substances that are difficult to detect with the eye but can be detected by machine scanning, for example X-ray absorbing dyes. When such a process is used, the security feature will only be visible on an X-ray photograph.

Preferably, the formation of the base material comprises the manufacture of the base material such that the weight per unit area of the material in the region of uniform transparency is less than the weight per unit area in most of the rest of the base material. Preferably this is achieved by using a watermark forming process, for example by using forming or screen rolling processes, but which results in substantially no change in the radiolucency in the area.

Alternatively, for relatively thin sheets, the greater part of the base material can be made substantially more opaque than the area to be imaged by using dies or the like. In a further alternative, this reduction in transparency can be achieved by non-electrodeposition of metals, as taught in JP 63 219694 A (Dai Nippon Printing KK), in which the metal is deposited within the paper without discoloration.

For a die-formed watermarked white paper having an average relative light transmittance of 1.00 in its non-watermarked areas, the planar area in which the security device is provided preferably has a relative light transmittance of 1.05 to 1.25, preferably 1.10 to 1.20. The shadow areas of graphic watermarks in these watermarked paper grades may range from 0.95 to 0.65, preferably 0.90 to 0.80. A specific example of a die-formed watermarked (prior to printing) paper grade had a relative light transmittance of 1.00 in its non-watermarked areas, a maximum relative light transmittance of 1.17 in its light areas, and a minimum of 0.85 in the shadow areas of the graphic watermark.

For a dandy roll watermarked white paper, the relative light transmittance in the flat area, which is preferred, is similar to that of a die watermarked white paper. A specific example of a dandy roll watermarked paper had a relative light transmittance of 1.00, a maximum relative light transmittance of 1.17 in the light areas and a minimum of 0.89 in the shadow areas of the graphic watermark.

The change in light transmittance in the watermark-free areas before printing is normally in the range of 2%.

It is to be understood that the term "watermarked paper" is intended to mean only that the area in which the security device is provided has been produced by applying a watermarking process, although the area designed to support the images has a substantially uniform transparency.

Preferably, however, the sheet has a conventional (i.e. graphic) watermark in addition to this area. This graphic watermark should be separate from the area comprising the security device and may be formed in any conventional manner, typically the same as that used to produce the security device area, but additionally providing a change in the light transmittance of the paper. For example, a die-formed mark may be provided which is a three-dimensional image formed within the paper body during the manufacturing process. It consists of a small-scale, controlled change in the weight of the paper, which allows more or less light to pass through the paper, creating areas of light and shadow that form the graphic watermark.

Typically, the area containing the security device is 0.4 to 5 cm² in area, and although it is generally separate from other graphic watermark features, it could form part of a larger composite watermark. Areas larger than 5 cm² are undesirable unless there is a compromise in the strength of the document.

Generally, the reduction in opacity (not being transparent) of the area containing the security device is up to about 40% of the average opacity of the sheet. This figure can be higher, i.e. the contrast between the general background areas of the sheet and the security device area can be greater if the base material itself is colored.

The method of printing the transparency or tracing features is normally double offset printing, although double dry offset printing and double gravure printing may also be used. To achieve accurate registration, the image portion on one side of the sheet is printed at the same time as its counterpart on the other side of the sheet. The two image portions are therefore printed during one printing operation and not separately, even during the same pass through the printing press. The combination of lithography and gravure does not normally give sufficient registration to be practical.

The planar watermarked area for the application of these features must have a uniform light transmittance across the area of the feature in which it is to be formed. The conventional method of forming watermarks in banknotes and similar security paper requires many careful changes in light transmittance to represent the graphic watermark. In conventional watermarks, the areas of high light transmittance are generally too small to provide see-through and print-through features. In some cases, the area containing the see-through and print-through feature is separate from a conventional graphic watermark. In other cases, it may be adjacent to or contained within it.

Typically, the area intended for the see-through or tracing feature contains the feature entirely, leaving a marginal area free to allow for a change in registration between the area and the feature. However, this is not essential. For example, a large conventional see-through or tracing feature may contain a feature of the invention. The area containing that feature fits within the conventional feature, but sufficiently defines the print to be viewed in combination with the area. The overall effect of a localized inventive feature contained within a larger area of a see-through and/or tracing print is to create a bright area.

A security document, such as a banknote, may contain a selection of see-through and print-through features, and individual design elements may contain parts of both.

When the security device area is made more transparent to radiation using a watermarking process, it should be taken into account that the watermarking process will result in poorer registration than with a two-sided precision register lithographic print. In this regard, the area contained in the security device will normally be made larger than the images themselves, for example by 3 mm in each direction. The registration of the security device area and the images therefore need not be as precise as between the images themselves.

Another advantage of using the watermark formation process is that it is more difficult to counterfeit when this process is combined with precision double-sided lithographic printing.

The final registration between the images on both sides of the sheet should be within a tolerance of 0.1 mm.

If the flat area is formed by locally changing the basis weight of the paper, it is advisable that this area of lower weight does not extend beyond the edge of the sheet containing the security device in order not to reduce the strength of the document.

According to a third aspect of the invention, there is proposed a security-printable paper base material having an area of sufficient size to accommodate a see-through or print-through security feature and having a substantially uniform light transmittance which is greater than that of the greater part of the remainder of the base material prior to formation of the security imprint, wherein the area of substantially uniform light transmission was created during manufacture of the base material and has a basis weight which is less than that of the greater part of the remainder of the base material.

For example, the base material may comprise banknote paper and, separate from the transparent area, contain one or more security threads, a graphic watermark, security fibers and (metal) plates.

The base material may comprise a sheet having at least twelve such regions and preferably forms a roll having at least a thousand such regions.

Some examples of banknotes according to the invention are described below using the drawings. They show:

Fig. 1 a side of a banknote with a watermark area and an area with uniform light transmission,

Fig. 2 is a picture of a combination of a transparent and a print-through device,

Fig. 3 the other picture of the device according to Fig. 2,

Fig. 4 shows the appearance of the device according to Figs. 2 and 3 when viewed against transmitted light,

Fig. 5 the device according to Figs. 2 to 4 on the banknote according to Fig. 1,

Fig. 6 another banknote with a printing device and the

Fig. 7A and 7B each show a cross section through a partially printed banknote and a graphical representation of the light transmittance along the cross section.

Fig. 1 shows a banknote 1 with a conventional graphic watermark 2 shown in outline and an area 3 with uniform light transmission.

Fig. 2 shows the front view of the part of a combined see-through and print-through device (not shown in Fig. 1) which is printed on the front of the banknote 1 in area 3 and in which the black areas are printed areas. This consists of an outline of a figurine 4, a background shading 5 and an overall perimeter line 6A. It is completely contained in the area 3 of uniform light transmission (not shown in Fig. 2).

Fig. 3 represents the view of the other part of the device, printed on the back of the banknote 1 and seen from this perspective. It is similarly included in the area 3 of uniform light transmission (not shown in Fig. 3). It consists of a solid figurine 7, which may be printed in rainbow colors, on an unprinted background 8 and is delimited by a perimeter line 6B with the same dimensions as those of Fig. 2.

Fig. 4 shows the front view of the device when viewed against the light. The assembled device is arranged in the region 3 of uniform light transmission (not shown in Fig. 4).

The figurine is shown in such precise register that it fits into the outline of the part printed on the front and is surrounded by a uniform unprinted border 9. This represents the see-through feature.

The circumferential lines 6A and 6B of the two impressions forming the device are printed in such precise register that they lie exactly one above the other so that they form a circumferential line 10 having exactly the same dimensions as the circumferential lines 6A and 6B. This forms the print-through feature. When the device is viewed in translucent light, it is not apparent to the viewer that the line 6B lies behind the line 6A.

Fig. 5 illustrates the relative position of the device in the finished banknote when viewed in transmitted light.

Fig. 6 shows a similar device 11 seen from the front in transparent light. This device 11 is a pure printing device, the elements of which are assembled in a similar way to the previous example, but which are printed in full register on both sides of the paper. In this case, the mirror image of the design 11, which is shown in Fig. 6 as being on the front of the banknote, is printed in full register on the back.

Fig. 7A shows the banknote 1 with the area 3 of uniform light transmission in which a figurine 12 similar to the figurine 7 is printed. On the banknote 1 another fully distinguished figurine 13 is printed elsewhere in the larger part of the sheet printed. The light transmittance through the partially printed document is characterized by four values A to D as shown in Fig. 7B. The value A is the light transmittance of the major part of the sheet; the value B is the light transmittance in the region 3 of uniform light transmittance; the value C represents the light transmittance in the region provided with the figurine 13; and the value D represents the light transmittance in the part of the region 3 of uniform light transmittance provided with the solid figurine 12.

The light transmission measurements were made with the light source on the same side as the solid figurines 12 and 13 and the light detection on the side facing away from the figurines. The contrast between the print and the paper when the print is viewed through the paper can be expressed by these four values. The contrast P, which represents the print contrast for the solid figurine 13 printed on the larger part of the sheet, can be defined as value A minus value C. Similarly, the contrast T, which represents the print contrast for the solid figurine 12 printed in the region 3 of greater light transmission, can be defined as value B minus value D. The increase in contrast represented by the increase in contrast T over contrast P is therefore a measure of the improvement in clarity of a see-through feature of the invention.

example 1

A white paper sheet of approximately 85 g/m² was produced on a laboratory sheet former. An area or surface of greater light transmission was formed during the production of the sheet. The sheet was coated with a suitable solid image printed in black in the area of greater light transmission and elsewhere on the greater part of the sheet. Light transmission measurements, calculated from the reading of a light transmission densitometer, gave the characteristic values mentioned A = 31.4%, B = 74.1%, C = 1.8% and D = 3.7%. This gives contrast P = 29.6% and contrast T = 43.4%, an improvement of 13.8% in print contrast.

Example 2

A white paper sheet of approximately 95 g/m² was prepared and printed as in Example 1. The light transmission values were A = 25.7%, B = 41.2%, C = 7.8% and D = 11.6%. The relevant print contrast values are therefore P = 17.9% and T = 29.6%, an improvement in print contrast of 11.7%.

Example 3

A pink sheet of paper of about 95 g/m² was prepared and printed as in Example 1. The characteristic light transmission values were: A = 12.9%, B = 30.9%, C = 3.5% and D = 7.2%, giving print contrasts P = 9.4% and T = 23.7%, an improvement of 14.3%.

Claims (18)

1. Sheet (1) with a paper base material on which a security imprint is or will be provided, and a security device with a transparent or print-through feature provided on the base material, characterized in that the feature is provided in an area (3) of the base material which has a largely uniform light transmittance and is more light transmitting than a larger part of the rest of the base material before the formation of the security imprint. 2. A sheet according to claim 1, wherein the feature is printed using a white or colorless substance which is detectable by machine scanning. 3. A sheet according to claim 1 or claim 2 with a graphic watermark which is separated from the area (3) containing the security device. 4. A sheet according to any preceding claim, wherein the area comprising the security device has an area of between 0.4 and 5 cm². 5. A sheet according to any preceding claim, wherein the area having the security device has a reduced opacity compared to the remainder of the sheet in the absence of applied ink of up to 40% of the average opacity of the sheet. 6. Sheet according to one of the preceding claims, in which the base material is provided with a security imprint. 7. A sheet according to any preceding claim, wherein the feature is printed on the base material. 8. A method of making a sheet with a security device comprising the steps of preparing a paper base material having a security imprint thereon, the base material having a region having a substantially uniform light transmittance and being more light transmitting than the greater part of the remainder of the base material prior to the application of the security imprint, and forming a see-through or print-through feature in said region. 9. A method according to claim 8, in which the production of the base material is effected in such a way that the basis weight of the base material in the region of uniform light transmission is smaller than the basis weight in the larger part of the remaining base material. 10. A method according to claim 8 or claim 9, wherein the feature is printed on the base material. 11. A method according to any one of claims 8 to 10, wherein the region is formed using a watermarking process. 12. Security printable paper base material having an area of sufficient size to accommodate a see-through or print-through security feature and having substantially uniform light transmission greater than that of the majority of the remainder of the base material prior to the formation of the security imprint, the area of substantially uniform light transmission being created during manufacture of the base material and having a basis weight less than that of the majority of the remainder of the base material. 13. Material according to claim 12, which comprises banknote paper. 14. Material according to claim 12 or claim 13, which comprises at least one security thread, a watermark, security fibers and planchettes (metal plates). 15. Material according to one of claims 12 to 14, in which the region has an area between 0.4 and 5 cm². 16. Material according to one of claims 12 to 15, which has at least twelve such regions. 17. A roll of paper material according to claim 16, having at least a thousand such regions. 18. A sheet with a security device according to any one of claims 1 to 7, which is made from a paper material according to any one of claims 12 to 17.