WO2012013809A1

WO2012013809A1 - Porous fabric for producing a security paper, methods for producing such a fabric, and watermarked paper created by such a fabric

Info

Publication number: WO2012013809A1
Application number: PCT/EP2011/063154
Authority: WO
Inventors: Michel Blanc; Férédéric BEAUCHET
Original assignee: Banque De France
Priority date: 2010-07-30
Filing date: 2011-07-29
Publication date: 2012-02-02
Also published as: FR2963363A1; EP2598691A1; FR2963363B1

Abstract

The invention relates to a porous fabric for producing a security paper. According to the invention, the fabric comprises at least one region having a non-null permeability that is different from that of the rest of the fabric and can create, on a surface of the security paper, a part having an opacity different from an extensive part of the security paper. The invention also relates to methods for producing such a fabric. The invention further relates to a watermarked paper produced using said fabric.

Description

Porous canvas for the manufacture of a security paper, methods of manufacturing such a canvas and watermarked paper created by such a canvas.

The invention relates to a porous web for the production of security paper, methods of manufacturing such a web and watermark paper created by such a web.

By security paper is meant here a paper that can not be easily falsified and that can be used for example for the manufacture of banknotes, identity documents, secure packaging, writing paper and, in general, any article based on paper or cardboard which one wishes to provide protection vis-à-vis the counterfeit.

By current portion of a security paper, here will be understood a base of the security paper on which will be created security elements such as watermarks.

BACKGROUND OF THE INVENTION

A security paper is made of organic fibers and / or synthetic fibers. Various methods, requiring the use of a porous cloth, make it possible to manufacture such a paper. Referring to Figure 1, a first method of manufacture is to scroll through a bath of fibrous solution 1 a round shape 2, which is surrounded by a porous fabric 3, and report a strip 8 near the round shape 2. A liquid portion of the fibrous solution will infiltrate pores of the porous fabric 3, causing the fibers to agglutinate on the surface of said web, and then transfer the fibrous mass of the web to the web 8. With reference to FIG. 2, a layer of fibrous solution 5 can also be scrolled on a flat table 4. A roll 6, surrounded by a porous cloth 7, then drains the solution layer 5 in order to promote the agglutination of the fibers. fibers between them. In both cases, the agglutination of the fibers forms a security paper 10.

It is known to protect a security paper by incorporating a watermark. A watermark is generally obtained by embossing or molding the security paper during the manufacture of the latter.

It is thus known from EP 1 122 360 and EP 1 252 389, to provide the porous fabric with a network of masks in relief. Each mask locally limits the accumulation of fibers on the surface of the porous web during the formation of the security paper. Thus, the security paper has lighter areas, having a lower fiber concentration, than a running portion of the security paper. It is thus possible to reproduce a watermark on the security paper by alternating at least one light area and the darker running part of the security paper.

However, masks are elements in relief of the porous fabric and therefore tend to wear out quickly. It is possible to reinforce the masks to limit their wear, but this makes the manufacture of the masks network more complex.

It is also known from EP 1 252 389 to directly make the network of masks in the thickness of the fabric by sealing locally the pores of said fabric so as to create a zone of zero permeability.

Although no mask comes in relief from the canvas, the canvas only creates portions of the same opacity on the security paper. In particular, the canvas does not create an opacity area darker than the current portion of the security paper.

OBJECT OF THE INVENTION

An object of the invention is to provide a porous fabric for the manufacture of a security paper which allows the printing of a watermark of varying opacity levels on said paper without resorting to a network of masks.

BRIEF DESCRIPTION OF THE INVENTION

In order to achieve this goal, a porous fabric is proposed for the manufacture of a security paper. According to the invention, the porous fabric comprises at least one zone which is of non-zero permeability different from that of the remainder of the porous fabric and which is capable of creating on a surface of the security paper a portion of opacity different from a current part of the security paper.

By modifying the permeability of the fabric, it is thus possible to reduce but also to increase the accumulation of fibers on certain areas of the porous fabric during the manufacture of the security paper. Areas darker than the current portion of the security paper can be created and also areas of varying opacity levels. By alternating the zones of different opacities and the current part of the security paper, it is possible to integrate watermarks of variable opacity levels with the security paper.

Another advantage of the invention is that areas of opacity different from the current portion of the large security paper can be created.

The invention also relates to a watermark paper created by such a fabric. According to a particular embodiment, the watermarked paper has portions of opacity different from a current portion of the paper which form a barcode at least one dimension. Advantageously, the watermark created on the current portion of the security paper by means of the fabric is then much thinner than a watermark which would have been created as in the prior art. It is thus possible to create watermarks in the form of 1D, 2D or 3D barcodes which will contain a greater quantity of information by unit of surface that bar codes created as in the prior art.

The invention also relates to methods of manufacturing such a porous fabric.

BRIEF DESCRIPTION OF THE DRAWINGS

Figures 1 and 2 have already been invoked and schematically illustrate two devices for the manufacture of a security paper.

The invention will be better understood in the light of the following description of a particular non-limiting embodiment of the invention with reference to the attached figures among which:

FIG. 3 is a partial view of a porous fabric according to a first embodiment of the invention;

FIG. 4 is a partial view of a porous fabric according to another example of the first embodiment of the invention;

FIG. 5 is a partial view of a porous fabric according to a second embodiment of

The invention;

- Figure 6 is a partial view of a porous fabric according to another example of the second embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The porous fabric according to the invention can be used in known devices for manufacturing a security paper, such as the devices illustrated in FIGS.

2.

According to the invention, the porous fabric comprises at least one zone which is of non-zero permeability different from that of the rest of the porous fabric. If this zone has a greater permeability, when forming the security paper, a larger amount of fibrous solution will infiltrate into pores of this material. area then causing a greater accumulation of fibers on the surface of this area. As a result, the area will create a darker portion of the security paper than the current portion of the security paper. Conversely, if the zone has a lower permeability, it will create a portion lighter than said current portion.

Thus, by varying the position of said different permeability zones on the porous web, a watermark can be created on the security paper.

By playing locally on the permeability of the porous web, a wide range of different opacity portions can be created on the security paper.

In a preferred manner, the remainder of the porous fabric has a permeability substantially similar to a conventional canvas of the prior art.

According to a first embodiment, the zone has the same pore density per unit area as the rest of the porous web but the pores of the zone have different dimensions from those of the pores of the rest of the porous web. The permeability of this zone differs from that of the rest of the fabric: the larger the pores, the more the area will be permeable and the portion created by this area on the security paper will be dark (and vice versa).

With reference to FIG. 3, the porous fabric as a whole comprises, for example, pores in the form of vertical segments of a certain thickness. In some portions of the web, the pore thickness is varied to vary the permeability of said portions.

With this embodiment, for example, watermarks can be created on the security paper in the form of 1D barcodes.

FIG. 4 describes another example of such a fabric with pores of substantially circular shape. According to a second embodiment, the zone has a density of pores per unit area different from the rest of the fabric but the pores of the zone have dimensions identical to those of the pores of the rest of the fabric. The permeability of this zone differs from that of the rest of the fabric: the more porous the zone, the more permeable the zone will be, and the portion created by this zone on the security paper will be dark (and vice versa).

With reference to FIG. 5, the porous fabric as a whole comprises, for example, pores in a square shape. In some portions of the web, the pore density per unit area is decreased relative to the pore density per unit area of the remainder of the porous web. FIG. 6 illustrates another example of a porous fabric according to the second embodiment in which the pores are in the form of crosses.

Various methods make it possible to manufacture a porous fabric according to the invention. According to a first method, the porous fabric is obtained by electroplating. A matrix of conductive zones is created on a non-conductive cylinder covered with a conductive layer, by ultraviolet irradiation and / or laser etching. The cylinder is then immersed in an electrolytic bath. By electrodeposition, the porous web is then formed identically to the matrix: a lack of corresponding conductive layer a pore of the fabric and vice versa.

According to a second method, the fabric is obtained by micro-drilling a metal or polymer sheet by a laser, a high-pressure water jet micro-drilling to create pores in the sheet. It is thus possible to manufacture the desired porous fabric by adjusting the micro-drilling on one or more zones of the sheet, during the micro-drilling of the sheet, so that said zones are non-zero permeabilities different from that of the rest of the fabric once the micro-drilling completed.

Naturally, the invention is not limited to the mode of implementation described and variations can be made thereto without departing from the scope of the invention as defined by the claims.

In particular, although it has been said that a watermark in the form of a 1D barcode can be created on the security paper, 2D or 3D barcodes can also be created. It is recalled that a watermark created by the porous fabric according to the invention is much thinner than a watermark which would have been created as in the prior art. It is thus possible to create watermarks in the form of 1D, 2D or 3D barcodes which will contain a larger amount of information per unit area than barcodes created as in the prior art. According to a preferred embodiment, the porous fabric is arranged to create directly on the security paper a bar code said sensitive copy. A sensitive copy barcode is a barcode losing a certain amount of information between its initial state where it is in a digital version on a computer and its final version where it is integrated with the security paper. At the conclusion of the manufacture of the authentic paper, it is provided a measurement of the watermark degradation rate to allow subsequent detection of counterfeiting by comparing the rate of degradation of the watermark alleged infringing paper. Indeed, any reproduction of a genuine watermark paper leads to further degradation of the watermark on the copy, degradation all the more significant that the density of information is important on the authentic watermark. Said barcode is therefore difficult to reproduce. Advantageously, this type The bar code could only be realized in the prior art by printing methods.

In addition, the watermark can take any other appearance than a barcode: geometric pattern, portrait, landscape, text, letter ... The watermark can be indifferently different levels of opacity or the same level opacity.

The pores of the canvas can be of any shape: dash, square, round, star, line ...

Although here two embodiments of the porous fabric are proposed, it will of course be possible to produce a fabric according to the invention that mixes these two embodiments. Thus, at least one area of the fabric will have a pore density per unit area different from that of the rest of the fabric and the pores of the area will have dimensions different from those of the pores of the rest of the fabric. It will also be possible to make a fabric according to the invention by modifying only the shape of the pores. Thus, at least one area of the fabric will have a pore shape different from that of the pores of the rest of the fabric so that said area will have a non-zero permeability different from that of the rest of the fabric. It is also possible to make a fabric according to the invention by mixing the two embodiments described above with a modification of the shape of the pores. Thus, at least one zone of the fabric will have a pore density per unit area different from that of the rest of the fabric, the pores of the zone will have dimensions different from those of the pores of the rest of the fabric and the pores of the canvas will have pores of different shape from the pores of the rest of the canvas. It is also conceivable to combine a modification of the shape of the pores with only one of the two embodiments described above. In addition, although here it is said that the porous web can be created by electroplating or microdrilling, the canvas can be created differently. In particular, one can create said canvas from a conventional canvas of the prior art having a constant permeability. A third manufacturing method thus comprises the steps of:

- Blocking, by resin or molten metal, at least one area of a uniform permeability web;

- Rework the area so that the area has non-zero permeability different from that of the rest of the canvas.

The area is reworked eg micro ^¬ drilling.

Another manufacturing method is to cut portions of a web of uniform permeability and to directly patch the canvas with a non-zero permeable element different from that of the rest of the fabric.

Portions of different opacity can be arranged to form:

a code having a sufficient information density to prevent a reproduction of the code, from the watermarked paper, without degradation of information.

a figurative pattern with dots having a size at most equal to 1 mm and, preferably, less than about 200 μm.

Claims

1. Porous web for the manufacture of a security paper, characterized in that the fabric comprises at least one zone which is of non-zero permeability different from that of the rest of the fabric and which is capable of creating on a surface of the paper a portion of opacity different from a current portion of the security paper.

2. The porous fabric of claim 1, wherein the pores of the zone have different dimensions from those of the pores of the rest of the fabric.

The porous fabric of claim 1, wherein the area has a pore density per unit area different from the rest of the fabric.

The porous fabric of claim 1, wherein the pores of the zone have a shape different from the pores of the rest of the fabric.

A security paper obtained by means of a porous web according to claim 1 and wherein the area of the porous web has created a watermark, the watermark having portions of opacity different from that of a current portion of the paper.

The security paper of claim 5, wherein said portions are arranged to form a bar code of at least one dimension.

Security paper according to claim 5, wherein the portions are arranged to form a code having a sufficient information density to prevent code reproduction from the watermark paper without information degradation.

Security paper according to claim 5, wherein the portions are arranged to form a pattern figurative with points having a size at most equal to 1 mm and preferably less than 200μπι approximately.

A method of manufacturing a porous fabric as claimed in claim 1, including the step of dipping a matrix into an electrolytic bath for a porous web to be formed by electrodeposition on said matrix, the matrix being created so that the web porous formed by electroplating has at least one zone of non-zero permeability different from that of the rest of the fabric.

A method of manufacturing a porous fabric according to claim 1, comprising the simultaneous steps of:

- micro-piercing a leaf to create pores in the leaf;

- Adjusting the micro-drilling on at least one area of the sheet so that said area is of non-zero permeability different from that of the rest of the fabric once the micro-drilling completed.

11. A method of manufacturing a fabric according to claim 1, comprising the steps of:

- obstruct at least one zone of a porous web of uniform permeability;

12. A method of manufacturing a porous fabric according to claim 11, including the step of reworking the area by micro-drilling.

The method of manufacturing a porous fabric according to claim 1, comprising the steps of:

cutting at least one zone of a fabric of uniform permeability;

- patch the canvas with an element of non-zero permeability different from that of the rest of the canvas.