EP1602782B1 - Fibrous web containing a part of a security film, and process for making the same - Google Patents

Description

The present invention relates to a sheet of fibrous material having a segment of plastic film at least partially embedded in the fibrous material, and a method of inserting a segment of plastic film into a fibrous material.

BACKGROUND OF THE INVENTION

For securing documents made from a sheet of fibrous material, it is known to insert in the sheet during its manufacture a wire or a security tape having a composition different from that of the fibrous material to achieve, at less by transparency, a contrast with all the fibrous material forming the document. In particular, it is known to introduce a plastic wire or ribbon into a paper made from cellulose fibers suspended in a liquid. In order for the suspended fibers to settle properly on the safety tape when dewatering the paper, the maximum width of the tape is limited to about 3 mm.

Moreover, in order to increase security, it is known to make on the security tape inscriptions in the form of a metallic or colored deposit, according to a text or a pattern making it possible to ensure the authentication of the ribbon and thereafter even an authentication of the document. However, the small width of the security ribbon makes it difficult to read the authentication elements.

In order to increase the width of the security tape while allowing a suitable insertion thereof into the paper, it has been proposed in the document WO 03/085193 inserting into the paper during its manufacture a segment of the plastic film comprising a visible identification area on at least one face of the sheet, the segment being perforated outside the identification area to allow fibers to nest in the perforations. However, the presence of an identification zone of dimensions large enough to be visible tends to reduce the porosity of the ribbon and thus makes it difficult to insert this ribbon during the manufacture of the paper.

The state of the art is also illustrated by the documents EP 0 860 298 , GB 19963 .

OBJECT OF THE INVENTION

An object of the invention is to provide a sheet of fibrous material having a segment of film suitably embedded in the fibrous material independently of the means used for identification.

SUMMARY OF THE INVENTION

In order to achieve this object, a sheet of fibrous material having a plastic film segment having perforations distributed over a perforated portion of the film segment covered by the fibrous material is provided according to the invention so that fibers are embedded in the perforations, characterized in that the perforated portion has perforations of different sizes distributed so that the perforated portion has a substantially homogeneous porosity.

Thus, it ensures a recovery by a homogeneous layer of fibrous material while allowing authentication by an analysis of the distribution of perforations.

According to another aspect of the invention, this relates to a method for inserting a segment of plastic film into a sheet of fibrous material, this method comprising a step of forming at least one fibrous layer on a sheet of fibrous material. porous form from a fiber bath suspended in a liquid, and a step of inserting, in the sheet of fibrous material in progress, a film segment having a perforated portion to be covered by the fibrous and compact material perforations having dimensions the perforations during a flow of the liquid through the perforations, characterized in that the perforations have different sizes and are distributed in the perforated portion so that it has a substantially homogeneous porosity, close to the porosity of the shape porous.

Thus, in the perforated portion, the film segment does not affect the flow rate of the liquid carrying the suspended fibers so that the covering of the perforated portion of the film segment by the fibers is homogeneous.

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 est une vue partielle très agrandie en coupe selon la ligne I-I des figures 2 et 3 d'une feuille de matière fibreuse équipée d'un segment de film selon l'invention,
• la figure 2 est une vue en coupe selon la ligne II-II de la figure 1,
• la figure 3 est une vue en coupe selon une ligne III-III de la figure 1,
• la figure 4 est une vue analogue à celle de la figure 1 illustrant une variante de réalisation des perforations dans le segment de film,
• la figure 5 est une vue en coupe schématique d'une cuve de formation d'une feuille de matière fibreuse conformément au procédé de l'invention.

Other characteristics and advantages of the invention will appear on reading the description which follows with reference to the attached figures among which:

• the figure 1 is a partial view greatly enlarged in section along line II of Figures 2 and 3 a sheet of fibrous material equipped with a film segment according to the invention,
• the figure 2 is a sectional view along line II-II of the figure 1 ,
• the figure 3 is a sectional view along a line III-III of the figure 1 ,
• the figure 4 is a view similar to that of the figure 1 illustrating an alternative embodiment of the perforations in the film segment,
• the figure 5 is a schematic sectional view of a forming tank of a sheet of fibrous material according to the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the figures, the sheet of fibrous material 1 according to the invention comprises a segment of film, here a ribbon 2, embedded in the fibrous material with the exception of a window 3.

In the illustrated embodiment, the ribbon 2 is cut from a plastic film 4, for example a transparent polyester film, beforehand coated on at least one face (here on each side) in zones 5 (only one of which is shown on the figure 1 ) with metal layers 6, deposited for example by screen printing using a screen configured to make a reserve delimiting the window 3 and to produce in the window a metallized pattern 7, here reproducing the letters BdF. The film 4 and the metal layers 6 are further perforated outside the window 3 in a series of perforations distributed so that the perforated portion has a substantially homogeneous porosity and preferably at least equal to a porosity of a shape used for the realization of the sheet of fibrous material as will be seen later.

In the illustrated embodiment, the film comprises a series of holes 8 having a diameter of about 500 microns spaced a distance of 1000 microns and regularly distributed except for one part of the window 3 and other part of an area 9 delimited by a mixed line in which a pattern is formed using perforations 10 of smaller diameter and closer to each other, here the letters BdF made according to perforations having a diameter of 150 μm spaced from 300 μm. It will be noted in the figure that apart from the pattern produced by the perforations 10, the film may also comprise perforations 8 interposed so that the porosity of the ribbon is homogeneous in the zone 9 without disturbing the recognition of the pattern formed by the perforations 10. In the embodiment of the figure 4 the perforations 16 are elongated. Like the perforations 8 or 10, the perforations 16 pass through the film 4 and the metal layers 6. In the illustrated embodiment, the perforations 16 are in the form of rectilinear or curvilinear slits, or have complex shapes for constituting a pattern. By way of example, the perforation 16 constituting the central part of the F has a shape In the illustrated example, the perforations 16 have a width e equal to 150 μm and a length L equal to 1500 μm.

The incorporation of the ribbon 2 into the sheet of fibrous material is carried out in a manner known per se by using a paper machine comprising a porous shape 11 comprising sealed pads 12 having the dimensions of the windows 3. The porous shape 11 is immersed in a liquid bath 13 comprising fibers in suspension so as to produce a first fibrous layer 14 in contact with the porous shape 11 and a second fibrous layer 15 covering the ribbon 2 with the exception of the locations of the windows 3. It should be noted in this regard that in line with the ribbon 2 the liquid passes through the perforations 8 and 10 and thereby causes fibers that interlock in the perforations and thus perform an anchoring of the ribbon 2 in the sheet of fibrous material.

Of course, the invention is not limited to the illustrated embodiment and variants can be made without departing from the scope of the invention as defined by the claims.

In particular, although the invention has been illustrated by providing in the ribbon 2 of the transparent windows 3 not covered by the fibers during the formation of the sheet of paper, it is possible to provide a ribbon 2 perforated over its entire surface and totally embedded. in the fibrous mass or visible on the surface of it by outcropping.

Although in the embodiment illustrated on the figure 1 the perforations are circular and are made in only two dimensions, it is possible to provide patterns using perforations of different shapes and sizes, the size of the perforations being preferably between 100 μm and 1000 μm and the perforations being spaced a distance preferably between 200 microns and 2000 microns so as to allow fiber interweaving in the perforations and to obtain a porosity equivalent to that of the shape 11 while retaining the ribbon 2 sufficient mechanical strength. In the case of perforations in the shape of slits as the perforations 16, the smallest dimension is preferably between 100 .mu.m and 1000 μ m while the largest dimension is preferably comprised between 1000 microns and 5000 microns, the perforations being such previously spaced a distance preferably between 200 microns and 2000 microns.

Although in the illustrated embodiment the perforations 10 have been arranged to produce a pattern directly recognizable by transparency, it is possible to produce by means of the perforations an encoding as described in the patent. FR 2 843 072 in the name of the Banque de France.

Although the film 4 has been described as a partially transparent, fully transparent plastic film, it may also be colored while being transparent, translucent or opaque or fluorescent, or may include diffractive or holographic images. The film may be incorporated in the sheet of fibrous material in the form of point segments, for example in the form of stamps serving, if necessary, to support other security elements such as electronic chips. In the latter case, the stamp carrying an electronic chip is preferably deposited on a first wet fibrous layer after complete formation thereof and before the deposition of a second fibrous layer, the interweaving of fibers in the perforations occurring during final pressing of the two fibrous layers against each other.

Claims (7)

1. Sheet of fibrous material (1) including a segment of plastic material film (2) including perforations (8, 10) distributed over a perforated portion of the film segment covered by the fibrous material so that fibres interlink with the perforations (8, 10), characterised in that the perforated portion includes perforations of different sizes distributed so that the perforated portion has a substantially homogeneous porosity.
2. Sheet of fibrous material according to claim 1, characterised in that at least some of the perforations (10) form a recognizable pattern.
3. Sheet of fibrous material according to claim 1, characterised in that the perforations (8, 10) have a size between 100 µm and 1000 µm and are spaced apart by a distance between 200 µm and 2000 µm.
4. Sheet of fibrous material according to claim 1, characterised in that some of the perforations (16) are of elongate shape.
5. Sheet of fibrous material according to claim 4, characterised in that the perforations (16) of elongate shape have a minimum dimension between 100 µm and 1000 µm and a maximum dimension between 1000 µm and 5000 µm and are spaced apart by a distance between 200 µm and 2000 µm.
6. Sheet of fibrous material according to claim 1, characterised in that the film segment (2) includes metallized areas on at least one side and in that the perforations (8, 10) extend through said metallized areas.
7. Method of inserting a segment of plastic material film (2) into a sheet of fibrous material (1), including a step of forming at least one fibrous layer (14) on a porous former from a bath (13) of fibres in suspension in a liquid and a step of inserting in the sheet of fibrous material being made a film segment (2) including a perforated portion intended to be covered by the fibrous material and including perforations (8, 10) having dimensions sufficient to enable fibres to interlink with the perforations when the liquid flows through the perforations, characterised in that the perforations are different sizes and are distributed in the perforated portion so that the latter has a substantially uniform porosity similar to the porosity of the porous former (11).

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