EP0687326B1 - Security sheet comprising security elements for preventing duplication, and being recognisable in transmitted and reflected light, and method for making same - Google Patents

Abstract

A security sheet comprising at least one discontinuous security element (2) on the sheet surface (S). One portion (3) of the security element (2) is located on the surface of the sheet and the complementary portion (4) of the security element is located within said sheet. The security element (2) comprises at least one light-reflecting or light-diffracting surface. The sheet may be used as banknote paper.

Description

It is known in security documents such as banknote papers, checks, passports, to introduce security features. These security elements can be security wires which are small strips of plastic, metal which are incorporated in the sheet of paper during its manufacture. These wires are identifiable in light transmitted.

There have been described in EP-A-59056 and EP-A-229645 methods for incorporating a security thread in the paper so that it comes out in certain places from the mass of the paper. These methods are advantageous when the wire has metallic reflection properties and is therefore brilliant. Such reflective threads cannot be reproduced by photocopying. To the place of the reflective surface of the wire, it appears only a dark spot, which allows to distinguish the original from the copy.

However, it is possible to later produce a reflective surface on the copy by applying a metallic varnish.

EP-A-377167 describes security papers comprising threads of security located at least at one point on the surface of the paper, having deviating structures light, for example holograms.

Document US-4,437,935 describes a water-soluble support comprising dichroic elements. When this support is introduced during papermaking, only the dichroic elements remain, the support dissolving. The dichroic elements are at inside the paper.

Thus, it is known in the prior art to produce security paper comprising openings through which security elements are visible in reflection. These elements   may be visible in transmission as a dark longitudinal line.

However, as mentioned above, when photocopying such paper safety, we can reproduce by a dark line the wire and we can reproduce by a varnish a reflective or fluorescent surface.

The invention aims to provide a security document avoiding the drawbacks mentioned above.

The invention therefore relates to a security sheet according to one of claims 1 to 5 and a method of manufacturing such a sheet according to one of claims 6 to 9.

Thus, in reflected light, we see a security element having a certain shape and in transmitted light, the visible security element has a different shape.

The security element may for example comprise at least one metal surface reflective, or a light-scattering surface or an iridescent, or dichroic surface or may include a hologram or an opaque coating of liquid crystals.

The sheet is such that it has on one side at least one window whose total area is less than the total area of the security element.

The method of manufacturing a security document according to the invention is such that we introduce during the manufacture of the sheet by the papermaking process, a security thread consisting of a ribbon bearing visible marks in reflected light, for example metallic marks, iridescent, dichroic, holograms, marks consisting of coatings liquid crystals.

The tape can be water soluble. For example, it can be polyvinyl alcohol (PVA) or more generally it is a water-soluble ester. The tape can also be a tape   support made beforehand so as to be integrated and invisible in the finished sheet. This strip can be obtained by papermaking from a fibrous composition of fibers cellulose and water-soluble ester fibers, for example PVA.

The tape is then introduced during the manufacture of the security sheet, so that the marks appear on the surface of the paper, but only for part, the part complementary to the mark being inside the paper. We can for example introduce the ribbon according to the methods described in documents EP-A-59056 and EP-A-70172 or is formed a twin-jet with thicknesses less than where the marks will appear, as in document EP-A-229645.

When carrying out these methods, windows will be made in the paper so that these windows have an area smaller than the area of the marks made on the ribbon.

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

Figure 1 is a top view of a security sheet according to the invention, this sheet being view in transmitted light.

Figure 2 is a top view of a sheet according to Figure 1, the sheet being seen in light thoughtful.

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

Figure 4 is a plan view of a ribbon used to make the sheet according to the invention.

FIG. 5 is a view of a round-shaped paper machine for carrying out the method according to the invention.

In Figure 1, there is shown a security sheet 1 according to the invention.  

The sheet 1 comprises at least one discontinuous security element 2 located at a point of the leaf area S. The security element 2 is located partly on the surface of the sheet 1. In Figures 1 and 2, part 3 of the element located on the surface of the sheet is a rectangle. The complementary part 4 of the element 2 which is located inside the sheet is the part 4 formed by the total surface of the security element minus part 3.

The security element 2 has a star shape in FIG. 1. When the sheet 1 is viewed in reflected light, we only see the rectangle and when the sheet is seen in transmitted light, namely when the sheet is seen in transparency, we see the security element 2 in its together, that is to say in the star form.

Preferably, the security element is a metallic print or a hologram, or a iridescent layer or a dichroic element.

So, when an infringer wants to photocopy security sheet 1, it will appear gray area in place of the rectangle.

If the counterfeiter manages to deposit a metallic or iridescent or other varnish in the rectangle, it will be even more difficult for him to reproduce the complementary part 4 of element 2, this part inside the sheet.

In FIG. 3, it can be seen that the total length L of the security element 2 is greater than the length l of the window 5 produced in the sheet 1.

The ribbon 6 shown in FIG. 4 is a ribbon which can be soluble in water, for example example an ester and more particularly a polyvinyl alcohol.

Ribbon 6 can also be a ribbon obtained by the papermaking process using a mixture of fibers cellulose and water-soluble matter, such as PVA, the respective amounts of cellulose and PVA fibers being regulated by those skilled in the art so that when the ribbon 6 is introduced into sheet 1, this ribbon is invisible.  

Marks 7 which are obtained by depositing on the entire surface of the ribbon of a metal such as aluminum, and printing of a varnish insoluble in soda, this printing corresponding to the marks 7 that one wishes to achieve. Then we remove aluminum unprotected using sodium hydroxide. You can also print marks 7 using metallic ink or varnish containing iridescent pigments. We can also deposit and bring together dichroic elements. You can also make marks 7 in the form holograms. Marks 7 can also be printed using fluorescent ink. Finally, marks 7 can be produced in the form of bar codes for printing lines metallic or magnetic / metallic lines.

The method of introducing the wire can be done as shown in Figure 5. A machine paper basket comprising an aqueous suspension 8 of cellulose fibers, binders and possibly other compounds usually used to form a sheet of paper.

A round shape 9 consists of a grid in the form of a cylinder. The composition is deposited on the grid when it rotates in the direction of arrow F1. Sheet 1 is formed on the cylinder and is pulled by the roller 10 and is transferred to a felt 11 to be then dried.

A ribbon 6 is introduced which is guided by a roller 12 so that the fibers do not settle over a certain length 1 to form the windows 5. The ribbon 6 has marks 7. The distance d between the marks is adjusted 7, as well as the distance between the windows 5 by locating the tape 6 relative to the sheet 1 and by the running speeds of the tape 6 and the sheet 1. The windows are produced by embossing carried out on the grid of the round shape 9. These windows 5 are in fact watermarks. The shape of the embossings (not shown in Figure 5) depends on the desired shape of the windows.

Of course, the sheet according to the invention can be produced by a double jet process.  

Example 1

A sheet is produced by papermaking from a fibrous composition containing 40 parts cellulose fibers refined to 45 degrees Schopper and 60 parts of PVA fibers and possibly conventional adjuvants used in stationery.

The sheet is dried at a temperature lower than that of thermosolubilization of fibers PVA used, i.e. at a temperature below 60 ° C.

On the sheet thus obtained, marks are deposited in the form of holograms. We cut the sheet of ribbon 3cm wide and the ribbon is wound up.

On a round-shaped paper machine, the fabric of which is embossed to form windows rectangular in the paper, introduce the ribbon as described for figure 5.

The size of the windows is adjusted by means of the embossing so as to be smaller than the size brands. Similarly the distance between the windows is adjusted so that the marks coincide with the windows. The speeds of the round shape and the unwinding of the ribbon are similarly adjusted to make the windows and the marks coincide.

The dissolution of PVA fibers leads to a transparency of the paper sheet but this transparency is compensated for by the cellulose fibers of the ribbon.

This produces a sheet of paper with windows through which you can see the holograms with the naked eye and this by reflection.

If we look at the sheet by transparency, the marks will appear to have a shape distinct from the shape of the windows. The ribbon supporting the marks will not appear in transparency.

Such a sheet is not reproducible by photocopy and moreover it is recognizable by the naked eye by the user.  

Example 2

Vacuum deposition on a sheet of transparent plastic, namely polyester a layer of aluminum. We print marks on aluminum with a varnish resistant to soda. The unprotected aluminum is dissolved using a sodium hydroxide solution.

The sheet is cut in the form of a ribbon which is introduced between two jets of wet paper one of which has windows obtained by embossing the canvas of the round shape. We then press the two jets of paper and dry. As in example 1, by adjusting the dimensions of windows and marks, their respective distances and respective speeds jets and tape, we get a finished sheet that has windows through which can see the reflective aluminum surface with the naked eye by reflection and by transparency marks of different shape from the shape of the windows.

Claims (9)

1. Security sheet which includes at least one discontinuous security element(2) lying in a region of the surface (S) of the sheet, a single part (3) of which security element lies at the surface of the sheet, the complementary part (4) of the security element lying inside the sheet, the said complementary part being visible in transmitted light and invisible in reflected light, the said complementary part (4) having a shape other than a rectangle and distinct from the shape of the said surface part (3).
2. Sheet according to Claim 1, characterized in that the security element (2) includes at least one surface which deflects or defracts light.
3. Sheet according to Claim 2, characterized in that the security element (2) includes at least one metallic, iridescent or dichroic surface or one hologram.
4. Sheet according to one of the preceding claims, characterized in that it includes, on one face and in line with each security element (2), a window (5), the total area of which is less than the total area of the security element (2).
5. Sheet according to Claim 4, characterized in that the total length (L) of the security element (2) is greater than the length (l) of the window (5) produced in the sheet (1).
6. Process for manufacturing a sheet according to either of Claims 4 and 5, in which, during manufacture of the sheet by a papermaking process, a tape (6) bearing at least one security element (2) of shape other than a rectangle is introduced, a window (5) associated with each security element (2) and having a smaller area is produced, the shapes of a security element and of the associated window being distinct, and the rate of introduction of the tape (6) is adjusted so that each window is superposed on a security element.
7. Process according to Claim 6, characterized in that the tape (6) is obtained from a transparent plastic sheet, on which sheet security elements (2) are deposited and fastened, and the sheet is cut into strips.
8. Process according to Claim 6, characterized in that the tape (6) is obtained from a sheet obtained by a papermaking process from cellulose fibres and from water-soluble fibres, on which sheet security elements (2) are deposited and fastened, and the sheet is cut into strips.
9. Process according to Claim 6, characterized in that the strip (6) is obtained from a water-soluble sheet, on which sheet security elements (2) are deposited and fastened, and the sheet is cut into strips.