EP0690939A1

EP0690939A1 - Security paper having a transparent zone of substantially zero opacity

Info

Publication number: EP0690939A1
Application number: EP94926263A
Authority: EP
Inventors: Pierre Doublet; Jean-Paul Menez
Original assignee: ArjoWiggins SAS
Current assignee: ArjoWiggins Security SAS
Priority date: 1993-09-28
Filing date: 1994-09-01
Publication date: 1996-01-10
Anticipated expiration: 2014-09-01
Also published as: ES2141837T3; WO1995009274A1; EP0690939B1; DE69422029T2; DE69422029D1

Abstract

A sheet of security paper (1) comprising transparent or translucid zones of substantially zero opacity consists of at least one layer of paper having at least one zone (3, 3a^-, 3b^-) of zero thickness and at least one strip (4) of transparent or translucid material enveloped in the layer of paper so that the strip of transparent material lies opposite the zone of zero thickness. Application to papers for banknotes and cheques.

Description

SECURITY PAPER WITH A SUBSTANTIALLY ZERO TRANSPARENT AREA

The invention relates to a sheet of paper comprising at least one transparent zone of substantially zero opacity having an area of at least 0.2 cm ² .

In the present description, "paper" means any sheet obtained by the wet process using a suspension of natural cellulose fibers and / or synthetic fibers which may contain various fillers and various additives commonly used in stationery.

Papers which are transparentized are already known in the prior art. These papers are for example made transparent by chemical compositions (see in particular French patent n ° 82 05124, filed on March 15, 1982 by A-RJOMARI-PRIOUX). These papers are made transparent over their entire surface and are intended for applications for industrial design, reproduction of plans, etc.

Chemical processes of partial transparency are also known, that is to say at specific locations. These methods use compositions based on grease or mineral or vegetable oil which are deposited by printing. However, it is difficult to print on these transparent areas using current conventional printing techniques (offset, intaglio, gravure, etc.).

Furthermore, it is known to make differences in thickness and density in the paper, in particular by the watermark technique used to secure papers for banknotes, identity documents or official and valuable documents. These watermarks are obtained during the manufacture of the sheet of paper by round shapes comprising hollow and / or relief imprints or by means of watermark rollers comprising hollow and / or relief drawings associated with a flat table. (Fourdrinier machine). One then obtains an image which, when looking at the sheet of paper in transmission, appears either clear, if the watermark roll has a line drawing-or dark, if the watermark roll has a hollow pattern. The light areas are due to the fact that the sheet thickness and the fiber density are lower than the sheet thickness and the fiber density in the areas where there was no imprint by the watermark roll. On the contrary, the dark areas are due to the fact that the thickness of the sheet and the density of the fibers are greater.

Such watermarks have clear parts which generally have areas of a few mm ² and the variation in opacity between the light part of the watermark and the non-watermarked paper is small. If you want to print on the light areas of these watermarks, it is very difficult to match the light areas and the printing and even with very precise identification of the watermarks, it is difficult to obtain a good match.

We have described in European patent application No. 388,090, filed March 9, 1990 by DE LA RUE COMPANY PLC. a security paper comprising zones of reduced opacity, at determined and well-localized locations, the zones making it possible to see by transmission, with the naked eye, prints carried on the face opposite to the face on which we are looking at the paper . The zones can, for example, be produced in the form of a watermark by using methods of round shape or with watermark rollers.

There has been described in the European patent application filed by the Applicant No. EP-A-549 384 and published on June 30, 1993, a method of manufacturing a sheet of paper comprising at least one zone having a reduced thickness compared to the thickness of the rest of the sheet, and having an area of at least 0.4 cm ² , by placing on an embossed or unembossed canvas, optionally arranged on a round shape, an aqueous dispersion containing at least cellulosic fibers, draining the water to form the sheet, with or without the presence of a watermark roll, while drying. Flexible parts are used which are combined with the watermarked canvas, the watermark roller or the round shape, so that the dripping of water during the formation of the sheet in the areas of the flexible parts is reduced by compared to water dripping in areas without flexible parts.

The sheet of paper obtained according to this process is such that the zone having a reduced thickness has a thickness less than 40% of the thickness of the rest of the sheet. The sheet may also be such that said zone has an average opacity less than 40% of the opacity of the rest of the sheet. We have described in the French patent application filed by the applicant, March 2, 1993, No. 93 02373, another method of manufacturing a sheet of paper comprising at least one region having a reduced thickness compared to the thickness from the rest of the sheet, characterized in that:

a first layer of paper is formed on a canvas of a first wet part of a paper machine,

- a second layer of paper is formed on a canvas of a second wet part of a paper machine, - one of the two layers of paper having at least local regions of smaller thickness, so that the thickness of the two layers of paper in said regions is up to 80% relative to the thickness of the rest of the sheet,

- the two layers are combined and dried.

One or even two layers of paper can be produced without problem so as to be locally very thin, at least one of the layers of paper in a region being reduced locally so that the overall thickness of the two layers is sufficiently reduced to get good transparency.

The sheets of paper obtained by the methods described in the preceding documents are used either so as to see transparently the impressions carried on the face opposite to the face on which the paper is viewed, the latter face also comprising impressions which are complementary at first impressions. Sheets of paper can also be used to prevent scratching of inscriptions on the reduced thickness region.

Banknotes are also known which consist of sheets of transparent synthetic material on which a two-sided printing is carried out, the printing being such that it leaves a completely transparent area. On this transparent area, a hologram is reported. Such plastic tickets have some drawbacks, however, they are not very resistant to handling and circulation because the print can be fragile on the plastic. This is why we prefer paper tickets, but at the same time we want to make the area as transparent as possible. However, according to the method described in the EP-A-549 384, the area obtained is certainly of reduced thickness and reduced opacity, but we want an area of even lower opacity. According to document FR 93 02373, a sheet of paper with an even lower opacity area is obtained. But this opacity is still very far from a substantially zero opacity. We therefore thought of further reducing the thickness of the zones of reduced opacity. But in this case, we make holes in the paper. Consequently, a problem which arises is to produce a practically transparent area in the paper, without piercing the paper in this area.

Another problem which arises is to produce in the paper a practically transparent zone, this zone which can be printed and / or which can receive a hologram or any other distinctive or security mark.

This zone must therefore be strong enough to support the carrying of a safety mark.

There has been described in patent application WO 94/00225 filed by the applicant on March 1, 1994, a sheet of security paper comprising at least one zone of reduced opacity, that is to say a zone having medium opacity uniform at least about 40% less than the opacity of the rest of the sheet, the area having an area of at least 0.4 cm ² and the area having reduced opacity due to the reduction in its thickness compared to the thickness of the rest of the sheet and the fact that it has undergone additional transparency.

The sheet according to this request can comprise, in a part of the reduced opacity zone, a hologram, an iridescent coating, a printing using conventional inks or inks containing colored pigments, fluorescent pigments, luminescent pigments, photochromic compounds. , piezooptics, piezochromes.

The sheet of paper can be a monojet sheet, that is to say a sheet comprising an area whose thickness is not zero, the residual thickness being chemically transparentized.

The sheet of paper can be a bijet sheet, that is to say that it consists of a first jet comprising an area whose thickness is zero, and a second jet partially or completely transparentized. In the case where the second jet is completely transparent, this jet can be obtained according to the tracing paper technique, namely from a suspension of very refined cellulose fibers, to obtain transparency. In the case where the second jet is partially transparent, it is chemically transparent in an area which comes into correspondence with the zone of zero thickness of the first jet.

Such a sheet of paper has a transparent area in transmitted light, this area having a large surface area. If a layer, for example an iridescent layer, is deposited on the transparent zone, this layer only partially covering the transparent zone, there will be an additional visual effect. In addition, such a sheet will be very difficult to reproduce by color photocopier because the iridescent area will not be reproduced by copying and the transparent area will be opaque after copying.

However, there is still a desire to improve the transparency of the zones. However, because transparency is obtained, on the one hand by reducing the thickness of the sheet and / or by decreasing the density of the cellulose fibers, and, on the other hand by chemical transparency, fails to achieve sufficient transparency to avoid counterfeiting. Indeed, if one does not deposit on the transparent area obtained according to this document, another security element such as an iridescent layer, or a hologram, the counterfeiter may attempt, after having reproduced the ticket by color photocopy, to transparent the area made opaque by copy.

Document GB-A-1 604 463 describes a security paper which comprises a thin security element, namely a narrow strip or a wire, wrapped in a sheet of paper. Such a wire is at most 1 to 1.5 mm wide. The paper is a paper formed from a layer and it can have holes on one side or on both sides. Because the wire has a small width, the holes have a small area. Thus, if a metallic or plastic wire is used, because of the small width of the wire and the small area of the holes, it will be difficult to print the wire by prints visible to the naked eye.

However, an object of the invention is to provide a sheet of security paper comprising transparent, printable areas whose area is greater than 0.2 cm ² . But such a sheet poses technical problems. Indeed, it is necessary to introduce a ribbon or a strip whose width is greater than 5 mm and preferably 20 mm. However, during the manufacture of the sheet of paper, a sheet is formed from an aqueous suspension of cellulose fibers, drained and dried. Between the wet part and the dry part, the sheet of paper undergoes an elongation. This elongation can be done in the machine direction and / or in the cross direction. It can be around 3%.

Consequently, a problem is to introduce the wide band, without it turning or twisting and without it breaking.

Document EP-A-0 059 056 describes the introduction of a wire into a sheet of paper so that the wire is visible on one or both sides of the sheet.

Again, this is a single layer paper, or monojet paper, and the wire is narrow.

The object of the present invention is therefore to provide a sheet of security paper comprising at least one transparent or translucent printable zone, this zone having a substantially zero opacity and having an area of at least 0.2 cm ² . The sheet consists of two layers of paper, the first layer comprising at least one zone of zero thickness and the second layer comprising at least one zone of zero thickness, each zone of the first layer being exactly opposite each zone of the second layer, of at least one strip of transparent or translucent printable material coated in the layer of paper so that the strip of transparent material is facing the zone (s) of zero thickness, the width L of the transparent strip being greater than the width 1 of the largest of the zones to avoid a discontinuity of the sheet.

An essential characteristic of the invention is that the strip of transparent material is such that its elongation in the longitudinal and transverse directions is compatible with the elongation of the sheet of paper, running direction and transverse direction during its manufacture.

According to one embodiment of the invention, the strip of transparent material is a strip of synthetic material, for example polyester. According to another embodiment, the strip of synthetic material is completely coated in the sheet of paper in the places which are not opposite the zones of zero thickness. The strip of transparent material has a width of at least 5 mm and preferably 20 mm

But it is also possible to produce the sheet of paper so that the strip is alternately coated in the sheet of paper in places which are not opposite the zones of zero thickness and appears on the surface thereof. Finally, the strip of synthetic material may include metallic prints, magnetic prints, holograms and any other security element.

The invention further relates to a method of manufacturing the sheet according to the invention.

The process is such that a first layer of paper is made on a round shape from an aqueous suspension of cellulose fibers, a second layer of paper is made on a second round shape, areas of zero thickness being made respectively on the first and second layers, by means of embossing fabrics of round shapes, said round shapes being perfectly synchronized so that the zones of zero thickness of the first layer come perfectly opposite the zones of zero thickness of the second layer, a strip of transparent material is introduced between the layers, the two layers are combined and dried.

The following description with reference to the accompanying drawings by way of nonlimiting examples will make it possible to understand how the invention can be put into practice.

Figure 1 is a sectional view of a sheet of security paper according to the invention.

Figure 2 is another embodiment of the sheet according to the invention.

Figure 3 is a top view of a sheet according to the invention.

Figure 4 is a schematic view of a device for producing the sheet according to the invention.

The sheet 1 shown in Figure 1 consists of a layer 2 of paper which has zones 3, 3a, 3b, of zero thickness and a strip 4 of transparent or translucent material partially coated in the layer 2 of paper. The strip 4 is opposite the zones of zero thickness 3, 3a, 3b, as can be seen in FIG. 3. The sheet 1 of paper further comprises a second layer 5 of paper which has zones 6, 6a, 6b, of zero thickness.

Zones 3, 3a, 3b are respectively opposite zones 6, 6a, 6b.

Thus, if we look at the sheet according to FIG. 1, in transparency according to arrow F, we will see a completely transparent zone, this zone being formed by the zones of zero thickness and by the transparent strip. The transparent strip 4 can for example be a polyester strip.

This strip is 20 mm wide and the zones have a maximum width of 17 mm.

Indeed, the strip can zizagrate more or less 3 mm compared to the zone of zero thickness.

If the area is a circle, its radius will therefore be 8.50 mm and its area approximately 2.26 cm ² .

It is therefore understood that a particularly difficult problem to solve is to make an area 3 of a layer 2 coincide exactly with an area 6 of the layer 5.

In Figure 2, there is shown another embodiment of the sheet according to the invention. The layer 7 of paper comprises zones 9, 9a, of zero thickness, the layer 8 of paper comprises zones 10, 10a, 10b, of zero thickness, only the zones 9, 9a being opposite zones 10, 10b . Thus, part of the zero thickness areas of the first layer 7 is located opposite the zero thickness areas of the second layer 8 of paper. By transparency, where the zones 9, 10 and 9a, 10b are opposite, the observer will see transparent zones 11, 12 (see FIG. 3), the strip 4 of synthetic material being invisible outside the transparent zones 11 , 12, because completely coated in the sheet of paper.

It can also be provided that the strip of paper can be located in certain places on the surface of at least one layer, as shown at 13 in FIGS. 2 and 3. The strip will then be visible by reflection.

If security elements are placed on the strip 4 at the places provided to be on the surface of the wire, these security elements will then be seen with the naked eye. It is also possible to place security elements on the strip 4 at the places where the zones of zero thickness will not be in correspondence.

Thus, in FIGS. 2 and 3, there is shown a strip 4, layers 7 and 8 and security elements 14, 15 such that the sheet has both transparent zones 11, 12, security elements 14, 15 visible either on one side of the sheet of paper or on the other side. We can alternate according to the desired criteria, the transparent zones, the parts on the surface with or without security element.

The transparent zone (11, 12) can also include deferred security elements.

Of course, the width L of the transparent strip 4 must be greater than the width 1 of the largest of the transparent zones to avoid a discontinuity in the sheet 1.

Finally, the security elements can be any, for example prints using conventional inks or inks containing colored pigments, fluorescent pigments, luminescent pigments, photochromic, piezooptic, piezochromic compounds.

The sheet 1 can be manufactured with a device which essentially corresponds to the usual commercial paper machines, which comprise at least two separate wet parts. The device shown in FIG. 4 consists of a combination of two wet parts with a round shape 16 and 17 of a paper machine called a double round shape. In the wet part of the form 16 a first layer of paper 2 is produced, which is directed towards the wet part of the form 17 while being suspended below the pick-up felt. In the second wet part of the form 17 a second layer of paper 5 is produced. Between the layers 2 and 5, a strip of transparent material is introduced. The two layers of paper are joined at the level of the roller 18 and are then dried.

The zones of zero thickness are produced by embossing fabrics of round shapes (16, 17), these embossments being sufficiently thick to completely prevent the deposition of fibers in certain places. According to the invention, two exactly identical round shapes are preferably used and they are synchronized by mechanical coupling of their rotating shaft. This synchronism is achieved by a mechanical coupling well known according to the technique.

Preferably, for the rehsation of the two layers of paper, two installations with a round shape are used. However, it is also possible to make the two layers of paper in flat table installations, or use for the rehsation of the two layers of paper a combination of a flat table installation and a round form installation. It is then necessary to synchronize the installations so that the zones of zero thickness of one layer come opposite the zones of zero thickness of the other layer.

Claims

1. Sheet of security paper comprising at least one transparent or translucent zone of substantially zero opacity, with an area of at least 0.2 cm ² , characterized in that the sheet (1) consists of two layers of paper (2, 5), the first layer (2) comprising at least one zone (3, 3a, 3b) of zero thickness and the second layer (5) comprising at least one zone (6, 6a, 6b) d '' zero thickness, each zone (3, 3a, 3b) of the first layer being exactly opposite each zone (6, 6a, 6b) of the second layer, at least one strip (4) of transparent or translucent material printable coated in the layer (2, 5) of paper so that the strip (4) of transparent material is facing the zone (s) (3, 3a, 3b) of zero thickness, the width L of the transparent strip (4) being greater than the width 1 of the largest of the zones to avoid a discontinuity in the sheet (1).

2. Sheet according to any one of the preceding claims, characterized in that the strip (4) of transparent material is a strip at least 5 mm wide, preferably 20 mm wide.

3. Sheet according to one of claims 1 and 2, characterized in that the strip of transparent material is such that its elongation is compatible with the elongation of the sheet of paper during its formation.

4. Sheet according to any one of the preceding claims, characterized in that the strip (4) of synthetic material is completely coated in the sheet of paper in places which are not opposite the zones of zero thickness.

5. Sheet according to any one of the preceding claims, characterized in that the strip (4) is alternately coated in the sheet (1) of paper in places which are not opposite areas of zero thickness and appears (13) on the surface thereof.

6. Sheet according to any one of the preceding claims, characterized in that the strip of transparent material may include metallic prints, magnetic prints, holograms, iridescent pigments and any other security element.

7. A method of manufacturing a sheet according to any one of the preceding claims, characterized in that a first layer (1) of paper is produced on a round shape (16) from an aqueous suspension of fibers of cellulose, a second layer (2) of paper is produced on a second round shape (17), zones of zero thickness being sheathed respectively on the first and the second layer (1, 2), by means of embossing fabrics of round shapes, said round shapes (16, 17) being perfectly synchronized so that the zones of zero thickness of the first layer come perfectly opposite the zones of zero thickness of the second layer, the layers are introduced between the layers (2 , 5) a strip (4) of transparent material, the two layers (1, 2) are combined and dried.