EP0687324B1 - Security paper comprising localised areas with reduced thickness and opacity, and method for making same - Google Patents

Abstract

A method for making a paper sheet comprising at least one region which is thinner than the rest of the sheet. According to the method, a first paper layer (3) is formed on a wire in a first wet end of a paper-making machine, a second paper layer (5) is formed on a wire in a second wet end of the paper-making machine, one of the two paper layers has a number of localised thinner regions (8) so that the thickness (e2) of said paper layers in said regions is up to 50 % less than the thickness (et) of the rest of the sheet, and the two layers are joined together and dried. The resulting paper may be used in banknotes or cheques.

Description

A sheet of security paper having areas localized with reduced thickness and opacity and more particularly a banknote paper or security paper with zones significant thickness and reduced opacity, at specific locations, these areas being watermarks.

The invention preferably relates to a sheet of paper comprising at least an area with a uniform average opacity at least 40% lower per compared to the opacity of the rest of the sheet.

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

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

We also know chemical processes of partial transparency, that is to say at specific locations. These processes use compositions based on grease or mineral or vegetable oil which are filed by printing. However, it is difficult to print on these areas transparentized using current standard printing techniques (offset, intaglio, heliography, etc.).

Furthermore, it is known to make differences in thickness and density in paper, in particular by the watermark technique used to secure bank note papers, identity documents or official and valuable documents. These watermarks are obtained during the manufacture of the sheet of paper by round shapes comprising intaglio and / or relief imprints or with watermarks comprising intaglio and / or relief drawings associated with a flat table (Fourdrinier machine). We then obtain an image which, when we look at the sheet of paper in transmission, appears to be clear, if the roller watermark has an embossed design, either dark, if the roller watermark has a hollow design. The light areas are due to the fact that the thickness of the sheet and the density of the fibers are lower than sheet thickness and fiber density in areas where there is no has not been imprinted by the watermark roller. On the contrary, dark areas are due to the fact that the sheet thickness and fiber density are more important.

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 print and even with very precise identification of the watermarks, it is difficult to obtain a good match.

European patent application No. 388,090, filed March 9, has been described 1990 by DE LA RUE COMPANY PLC. security paper with zones of reduced opacity, in specific and well-located places, the areas allowing to see by transmission, with the naked eye, impressions carried on the side opposite to the side on which we look at the paper. The areas can for example be made as a watermark using processes by round shape or by watermark rollers.

However, in this patent application, we do not describe how we obtain industrially these areas.

Industrially, it is relatively easy to manufacture paper comprising areas of reduced thickness and therefore clear, obtained by the watermark technique, when the area of these areas is less than 0.4 cm ² . On the other hand, if it is wished to obtain zones whose surface is greater than 0.4 cm ² , by the technique of the watermark the person skilled in the art encounters technical problems.

The first problem is: To make a watermark, the man in the profession knows that you can emboss the canvas in a round shape using a punch. For example, if you want a clear circular area, emboss the canvas with a circular punch. However, using such a method, one does not get a clear area of constant opacity. In fact, we have noticed that fibers tend to deposit more large quantity near the center of the embossed part only at the edges and therefore the center of the watermark appears much less clear than the edges. If we use a roller watermark which has raised asperities, we get the same phenomenon.

A second problem which arises is that when one wants zones of reduced thickness and therefore clear having an area of more than 0.4 cm ² , one does not obtain a clear zone.

We also know various ways to avoid forgery of checks. So we can add in or to check paper chemical compounds which react with acids, bases or erasers. However, we are always looking for new means against forgery.

There has been described in the European patent application filed on November 18, 1992 by the applicant and published on June 30, 1993 under the number EP-A-549 384, a method of manufacturing a sheet of paper comprising at least one zone having a thickness reduced 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, possibly arranged on a round shape, an aqueous dispersion containing at least cellulosic fibers, by draining the water to form the sheet, with or without the presence of a watermark roller, 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 relative to water dripping in areas with no 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 can also be such that said area has an average opacity less than 40% of the opacity of the rest of leaf.

Such a method therefore makes it possible to obtain zones of reduced opacity. However, we are looking further reduce the opacity of the areas.

In addition, the process requires a transformation of the paper machine, namely that one combines with the watermarked canvas, or with the watermark roller, or with the round shape, pieces flexible. These parts must be fixed in specific places and therefore require a additional handling. In addition, the area is 30% less thick than the thickness of the rest of the sheet.

Document EP-A-0 229 645 describes a process for manufacturing a sheet of security with a security thread. It consists of forming a first layer of paper and a second layer of paper, to introduce a security element between these two layers, to combine these two layers. One of the layers has local regions whose thickness is 0 to 30% of the total thickness of the sheet of paper. Such a safety sheet makes it possible to obtain a sheet comprising a more or less apparent security thread on the surface.

We also know banknotes which consist of sheets of material transparent synthetic on which two-sided printing is performed, printing being such that it leaves a completely transparent area. On this transparent area we carry a hologram. Such plastic tickets, however, have some drawbacks. They are not very resistant to handling and traffic because the impression can be fragile on the plastic. This is why we prefer paper tickets, but we want to at the same time make the area as transparent as possible. However, according to the method described in the document EP-A-549 384, the area obtained is certainly of reduced thickness and reduced opacity, but we want an even lower opacity area.

Consequently, another object of the invention is to provide an area in the paper which is practically transparent or translucent, without piercing the paper in this area.

Another goal is to make a practically transparent or translucent area in the paper, this area can be printed and / or can receive a hologram or any other distinctive or security mark.

This zone must therefore be strong enough to support the carry of a security.

An object of the invention is therefore to provide zones of reduced thickness compared to the rest of the sheet without the need to use associated flexible parts.

Another object of the invention is to provide zones having a much smaller thickness. reduced than 40% compared to the rest of the sheet.

To this end, the invention relates to a sheet of paper comprising at least one zone of reduced thickness and opacity having an area of more than 0.4 cm ² , characterized in that said sheet is a sheet comprising a structure twin-jet consisting of a first layer of paper comprising at least one zone whose thickness is zero and of a second layer of paper of substantially constant thickness, the two layers being directly joined.

The sheet according to the invention may comprise in part of the zone reduced opacity a hologram, an iridescent coating, an impression using conventional inks or inks containing colored pigments, fluorescent, luminescent pigments, photochromic, piezooptic compounds, piezochromes.

The second throw can be partially or completely transparentized. In case the second roll is fully transparent, this jet can be obtained using the tracing paper, namely from a suspension of very strong cellulose fibers refined, to obtain transparency. In case the second roll is partially transparent, it is chemically transparent in a zone which comes in correspondence with the zero thickness zone of the first jet.

• on forme une première couche de papier sur une toile d'une première partie humide d'une machine à papier,
• on forme une seconde couche de papier sur une toile d'une seconde partie humide d'une machine à papier,
• la première couche de papier présentant au moins une région locale d'épaisseur nulle
• on réunit directement les deux couches et on les sèche,

ladite région d'épaisseur plus faible de la feuille ayant une opacité moyenne uniforme et une superficie d'au moins 0,4 cm².The invention further relates to a method for manufacturing a sheet of paper comprising at least one region having a reduced thickness and opacity compared to the rest of the sheet, in which:

• 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,
• the first layer of paper having at least one local region of zero thickness
• the two layers are brought together directly and dried,

said region of smaller thickness of the sheet having a uniform average opacity and an area of at least 0.4 cm ² .

Although the layers of paper are made on paper canvases separated, we obtain a sheet of paper that is no longer possible to separate due to the quick coupling of these layers and their drying in common. The sheet of paper does not differ from a sheet of paper made on a single canvas.

The process is such that regions of zero thickness are made by embossed regions in relief on the mechanical fabric, from which it follows that the deposition of fibers in these regions is totally prohibited.

Preferably at least one of the layers of the paper is produced by a machine with round shape.

The thinner regions of the paper sheet are formed under form of a simple geometric pattern, in particular in the form of regions flat approximately rectangular, round or elliptical or any other form.

La figure 1 montre un dispositif pouvant servir à la fabrication de papier de sécurité selon l'invention.

Les figures 2, 3 et 5 montrent en coupe divers papiers qui ne sont pas couverts par les revendications.

Les figures 4 et 6 montrent en coupe des papiers selon l'invention.

La figure 7 montre un papier pour chèques obtenu selon l'invention.

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.

FIG. 1 shows a device which can be used for manufacturing security paper according to the invention.

Figures 2, 3 and 5 show in section various papers which are not covered by the claims.

Figures 4 and 6 show in section papers according to the invention.

Figure 7 shows a check paper obtained according to the invention.

Figure 1 shows a device that can be used to make a paper according to the invention. The device essentially corresponds to usual commercial papers, which include at least two wet parts separated. The preferred embodiment shown here consists of a combination of two round-shaped wet parts 1 and 2 of a so-called double round paper. In the wet part 1, a first strip of paper 3, which is directed towards the second wet part 2 by hanging below the taker felt 4. In the second installation 2 we make a second strip of paper 5. The two strips of paper are gathered at the roller 6 and are then dried.

It is preferable to use two layers of paper for the production round-shaped installations. But it is also possible to carry out the two layers of paper in flat table installations, or use for making the two layers of paper a combination of an installation with a flat table and a round-shaped installation.

In Figures 2 and 3, there is shown a paper which is not covered by the claims. This sheet 7 is formed of a first strip 3 and a second strip 5. The strip 5 comprises clear watermarks 8 obtained for example by an embossing in relief of the canvas of the round shape 5. These clear watermarks have a depth e ₁ . The total thickness e _t of the sheet 7 is the sum of the thicknesses e ₃ of the strip 3 and e ₆ of the strip 5. The thickness e ₂ of the sheet 7 opposite the watermarks 8 is less than the total thickness and _t . In Figure 2, we have ₁ = 1/3 e _t = 33.3% e _t .

In Figure 3, we have ₁ = 1/2 e _t = 50% e _t .

In FIG. 4, the region 8 is such that the strip 5 has a hole.

The reduction in thickness is therefore approximately 33% in the first case and 50% in the second case. The sheet of Figure 3 therefore has a reduced opacity much lower than the opacity of the sheet of Figure 2, in the region 8 and this for a total thickness e _t substantially equal.

By adjusting the thickness e ₃ and e ₅ of the strips 3 and 5, as well as the depth e ₁ of the watermarks 8, it is possible to obtain the reduced opacities and thicknesses that are desired.

The sheet shown in Figure 5 is made according to the technique of monojet. This sheet is obtained by the process described in the request. EP-A-549 384 and is not covered by the claims of this European patent.

The sheet 11 comprises zones 12, 12 a , 12 b , of thickness e ₁ and zones 13, 13 a , of thickness e ₂ not zero. Zones 13, 13 a have a density of fibers much lower than the density of zones 12, 12 a , 12 b . Each zone 13, 13 has undergone an additional transparency. This transparentization is carried out chemically according to this embodiment. Preferably, the transparentization is carried out using a transparentization composition described in the European patent of the applicant EP-91 341. The additional transparentization is carried out after drying of the sheet, at the end of the machine.

12 % d'une résine de condensation cétone - aldéhyde modifiée

23 % d'une résine hexaméthoxyméthylmélaminée

4 % d'alcool éthylique

17 % d'alcool butylique

28 % de dibutylphtalate

16 % de produits isopar affiniqués.

This composition can for example consist of:

12% of a modified ketone - aldehyde condensing resin

23% of a hexamethoxymethyl melamine resin

4% ethyl alcohol

17% butyl alcohol

28% dibutylphthalate

16% refined isopar products.

This composition is applied for example by printing using an engraved printing cylinder, the cylinder engravings corresponding to the areas 13, 13 a to be transparentized.

FIG. 6 represents in section a sheet 14 obtained according to the technique of "bijet" shown in Figure 1.

The sheet 14 shown in Figure 6 is formed of a first strip 16 and a second strip 17. The strip 17 is such that it has zones 18 of zero thickness. The strip 16 can be transparentized or not in the zones next to zones 18.

Zero thickness areas are made by embossing the canvas with the round shape 5, sufficiently so that at the level of the embossings, there is no deposition of cellulose fibers.

If we make the two layers of paper in flat table installations, the strip 16 can be a tracing paper obtained by a deep refining of cellulose fibers.

Printed patterns 15 can be placed next to zones 18. It is also possible deposit layers of fluorescent pigments, layers or prints of iridescent pigments, metallic prints, holograms. We'll have then a sheet of paper with a transparent area in light transmitted, this area being of large surface. If we lay a layer, for example iridescent on the transparent area, this layer not covering only partially the transparent area, we will have a visual effect additional. In addition, such a sheet will be very difficult to reproduce by color photocopier because the iridescent area will not be reproduced by copy and the transparent area will be opaque after copying.

In Figure 7 there is shown a security paper, preferably a paper for checks, obtained according to the method according to the invention. This security paper 19 comprises at least one zone 20 whose thickness is less than the thickness from the rest of the sheet. So, if we write on field 20, the amount of check, in the event that a counterfeiter attempts to scratch this zone 20, he will pierce the security paper. Preferably, the zone 20 has a thickness 40% less than the thickness of the rest of the sheet.

Claims (16)

1. Sheet of security paper comprising at least one region (8, 20) of reduced thickness and opacity having an area of more than 0.4 cm², characterized in that the said sheet is a sheet comprising a two-ply structure consisting of a first ply (17) of paper comprising at least one region (18) whose thickness is zero and of a second ply (16) of paper of approximately constant thickness, the two plies being directly joined together.
2. Sheet of security paper according to Claim 1, characterized in that the thickness of the sheet in the regions of reduced thickness and opacity is up to 80% with respect to the thickness of the rest of the sheet.
3. Sheet of security paper comprising at least one region (8, 20) of reduced opacity according to Claim 1 or 2, characterized in that the said region has a reduced opacity because of the reduction in its thickness with respect to the thickness of the rest of the sheet and because the said second ply (16) has undergone an additional transparentization step.
4. Sheet according to Claim 1 or 3, characterized in that, in the region of reduced thickness and opacity, the sheet has a thickness at least 40% less than the thickness of the rest of the sheet.
5. Sheet according to any one of Claims 1 to 4, characterized in that it includes, in part of the region of reduced opacity, a security element (15), such as a hologram, an iridescent coating, or printing using conventional inks or inks containing colour pigments, fluorescent or luminescent pigments or photochromic, piezooptic or piezochromic compounds.
6. Sheet according to one of Claims 3 to 5, characterized in that the said second ply (16) is completely transparentized and obtained using the tracing-paper technique, starting from a suspension of highly refined cellulose fibres.
7. Sheet according to one of Claims 1 to 6, characterized in that the said second ply (16) is partially transparentized using a chemical technique in a region which will be in correspondence with the region (18) of zero thickness of the said first ply (17).
8. Process for manufacturing a sheet of paper comprising at least one region (8,20) having a reduced thickness and opacity with respect to the rest of the sheet, in which:

   a first ply (3) of paper is formed on a wire of a first wet end of a papermaking machine,

   a second ply (5) of paper is formed on a wire of a second wet end of a papermaking machine,

   the first ply of paper having at least one local region (18) of zero thickness,

   the two plies are joined together directly and dried,

   the said region (8, 20) of smaller thickness of the sheet having a uniform average opacity and an area of at least 0.4 cm².
9. Process according to Claim 8, characterized in that the said second ply (16) is completely transparentized and obtained using the tracing-paper technique, starting from a suspension of highly refined cellulose fibres.
10. Process according to Claim 8, characterized in that the said second ply (16) is partially transparentized by a chemical technique in a region which will come into correspondence with the region (18) of zero thickness of the said first ply.
11. Process according to one of Claims 8 to 10, characterized in that the thickness of the two plies of paper in the said local regions (8, 20) of smaller thickness is up to 80% with respect to the thickness of the rest of the sheet.
12. Process according to either of Claims 8 and 11, characterized in that the process is such that the regions (18) of zero thickness are produced by embossed regions in relief on a metal watermarking wire, from which it follows that the deposition of fibres in these regions is completely prevented.
13. Process according to one of Claims 8 to 12, characterized in that at least one of the two plies of paper is preferably produced by a cylinder-mould paper machine.
14. Process according to one of Claims 8 to 13, characterized in that the regions (8, 20) of thinner thickness of the sheet of paper are in the form of a simple geometrical pattern, particularly in the form of approximately rectangular, round or elliptical flat regions.
15. Application of a sheet according to one of Claims 1 to 7 as paper for bank-notes.
16. Application of a sheet according to one of Claims 1 to 7 as security paper.

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