ES2261269T3 - SECURITY DOCUMENT ELABORATION PROCEDURE. - Google Patents

Abstract

The invention concerns a security document comprising a support consisting of a sheet of paper with fibrous texture, characterised in that the fibrous texture is impregnated over its entire thickness with a protective substance, such that said substance provides a coating for the fibres of the texture and covers the binding zones of said fibres, the pores of said support being hermetically closed by the coating.

Description

Document preparation procedure security.

The present invention relates to security or value documents. More precisely, the invention to be refers to a procedure that allows to elaborate some documents extremely robust fiduciaries, in order to preserve their qualities and their specificities (for example some elements of security associated with the document) and / or prolong its duration of use, particularly when they are subjected to an environment aggressive.

A particularly advantageous application of the invention, which will be developed by way of example in this text, It refers to banknotes.

However this example is not limiting, applying the invention in general to the realization of any sensitive document that includes marked ones recognizable intended to allow document authentication (banknote, check, any fiduciary document, of security or official, etc.), and susceptible to being damaged.

To allow authenticating certain documents sensitive, marked associated with documents are known, readable by an observer or by a machine. Sayings marked They thus constitute a security element of the document. exist numerous types of marking that can be deposited on the document surface, or integrated into its internal structure, the marking having physical properties (optical, electrical, magnetic ...), chemical, or any other nature (biological, ...) in a way that allows its recognition.

To ensure its element function of security, the marking must remain legible, that is, it must not be covered by dirt or other document degradation that hide it or be in turn altered.

Now, in the case of documents sensitive comprising said markings, and intended to be used in aggressive environments, the marked ones are liable to be thus illegible facts, which constitutes a inconvenient in terms of security.

For example, banknotes are manipulated and treated as usual objects, and suffer currently degraded and dirty.

Such degradations may compromise the reading the different authentication marks that can understand tickets or even make it impossible (in particular in the case of a rereading by machine); this constitutes a important limitation of ticket security and reduces its life span, since it is necessary for numerous Applications can authenticate tickets.

Traditional paper tickets and documents they may in this respect be poor. Given the importance Increasing security features on tickets - but also in numerous types of documents - this limitation It constitutes an important inconvenience.

To try to solve this problem, it is known to use a classic printing techniques to deposit a protective varnish on the surface of a bill of paper. See for example the document US-A-5660919.

But it is found that the effectiveness of said procedure is very limited and that although printing by varnish can be relatively effective against dirt, said protection resists badly to the mechanical wear of the bill. In in particular, in the case of banknotes that circulate in an environment wet, and the bill is not preserved from degradation, in particularly those caused by water (water projections, impurities deposited in the weft of the ticket by the humid air, ...)

You could also plan to make some bills whose structure itself was based on polymers, but the known procedures for printing, and more generally integrate safety markings, are poorly adapted to secured from said tickets and therefore lead to some documents whose security is mediocre.

The objective of the invention is to enable a document comprising at least one marking of authentication that constitutes a security element of the document, with the authentication mark (s) preserved of degradations and dirt so as to guarantee the Document security

In order to achieve this objective, the invention proposes a security document that includes a sheet holder of paper with fibrous weft, characterized in that the fibrous weft is impregnated throughout its thickness by a protective substance, of so that said substance covers the weft fibers and covers the areas of union of these fibers, the pores of said Support tightly plugged by the coating.

Preferred, but not limiting, aspects of the security document according to the invention are the following:

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 Protective substance It comprises an organic substance,

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 The organic substance is a silane, a fluorinated silane, a xylene-type polymer or another polymer,

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 Protective substance comprises an inorganic substance,

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 The inorganic substance is SiO 2, Si 3 N 4, TiO 2, ZnO or SnO 2,

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 The protective substance has been deposited on the paper sheet support by low evaporation empty.

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 The protective substance has been deposited on the paper sheet support by decomposition of a plasma on the surface of the support.

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 Plasma breakdown takes place under a pressure close to that of the vacuum,

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 The protective substance has been deposited on the paper sheet holder by chemical deposit in the vapor phase,

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 The protective substance has been deposited on the paper sheet support by impregnating the support for a low viscosity solution and then realization of an annealing stage that allows fixing the solution in the frame of support,

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 The equivalent thickness of coating is between 0.2 and 30 micrometers.

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 The equivalent thickness of coating is between 1 and 5 micrometers,

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 The protective substance is colored.

Other aspects, objectives and advantages of the invention will appear with the reading of the following description of different embodiments of the invention.

According to a first embodiment of the invention, a banknote is processed placing it in a first time in an evaporation enclosure in the which has established an extremely low pressure that can be assimilated under vacuum This ticket can be a paper ticket of fibrous weft

The ticket is placed in front of a crucible that It contains a hydrophobic substance that can be:

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organic (silane, fluorinated silane, xylene type polymer - for example parylene (registered trademark), other polymers ...);

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inorganic (SiO2, Si3 {N4} or well TiO 2, ZnO, SnO 2 for example),

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or of organic / inorganic hybrid type (mixtures of SiO2 and silanes fluoridated, or other).

The crucible is then heated which it contains the substance, bringing it to a temperature that can be of the order of 1000 degrees Celsius so that the substance pass in gas phase. Once the substance passed to the gas phase, it is released on the premises and will be deposited on the ticket according to a noticeably rectilinear trajectory due to the almost absence of pressure in the enclosure. Among the substances mentioned, you may use a polymer of the xylene type or SiO2 that have advantageous hydrophobic properties.

In the case of known techniques of varnish printing on a bill, the pores of the bill (whose diameter is of the order of 1 to 20 micrometers) may not be plugged by varnish, and the quality of protection is in this bad case.

In the case of the low evaporation procedure vacuum described above, on the contrary, the substance protective impregnates the fibrous weft of the paper in all its thickness, so that the fibers of this weft are coated by said substance, and the areas of union between these fibers are also Coated by this substance.

And by this procedure the pores of the ticket they are tightly plugged, which increases considerably the quality of protection (in particular against moisture and particles carried by a humid atmosphere).

To characterize this improvement the applicant has in particular, quantification tests of the evolution of whiteness at the level of the filigree of banknotes Bank; said test consists of an accelerated aging of the ticket (exposure to water and dirt ...) and in a optical determination of the whiteness of the paper.

Treating a ticket according to the known technique of varnish printing, the whiteness results were improved in a few tens of percent points against a ticket not treaty. Treating the ticket by deposit of a polymer according to a procedure as described above, the improvement was considerably higher.

The applicant has also carried out some tests of duration of life (based on the characterization of the state banknote mechanic after accelerated aging). In In this case too, the varnished bill allowed to obtain a gain of the order of some tens of points percent with regarding an untreated ticket, while in the case of a ticket treated according to the invention, the gain was of the order of some of some hundreds of percentage points, corresponding typically a triplicate of the life of the ticket.

It is also possible according to the invention to carry out a coating of the weft fibers of a bill that it allows to clog the pores of the ticket and thus improve very significant its robustness, making a deposit under vacuum by pulverization of a target subjected to the bombardment of exiting ions of a plasma.

In this case, the ticket is placed in a plasma chamber inside which a pressure close to that of the vacuum, the target can be performed in metal, for example silicon, the plasma may be constituted by a mixture of argon and oxygen. Bombarded by the ions of oxygen, the target emits silicon particles that are going to combine on the surface of the bill with oxygen ions to form silicon oxide SiO2 (not performing this combination in the absence of solid support).

It will be observed on the other hand that it is possible make a deposit of substance on a ticket by creating a plasma in an enclosure whose pressure is not close to that of the vacuum, if not more important, even close to atmospheric pressure.

According to another embodiment of the invention, you can also proceed to the coating of the ticket by deposit chemical in vapor phase (known procedure under the term Anglo-Saxon "chemical vapor deposition"). In this case, the banknote is exposed to the vapor phase substance (which thus forms a gaseous precursor), condensing the vapor in contact with the ticket to form a deposit on the ticket.

This embodiment also allows get a very good impregnation of the bill by coating the fibers and thus a clogging of the pores of the paper, the gaseous precursor spread in all free volumes and condense on all exposed surfaces.

It should be noted that the last procedure mentioned above must be performed at temperatures that do not exceed a high limit of the order of 200 degrees Celsius, so that they do not harm the role (training or other disturbance). This embodiment of the invention can be performed at atmospheric pressure, or at reduced pressure.

Finally, it is also possible to perform the invention by a deposit of the "solution-gel" type when takes place which the bill is immersed in a solution of viscosity low enough for the ticket frame to be fully impregnated, and then the ticket is annealed thus impregnated to fix the solution in the paper frame of the ticket. This procedure is particularly well suited for the use of hybrid substances to coat the surface of the ticket.

The different embodiments of the invention described above allow deposit on the fibrous weft structure of the bill a substance of protective coating that completely seals the pores of the paper and thus constitutes an extremely effective moisture barrier and dirt, such as the tests performed by the applicant have shown. In addition, said coating allows to increase considerably the mechanical robustness of the ticket.

The substance coating should be quite thick to constitute an effective and lasting barrier; in the practice, the thickness equivalent to the amount of matter deposited (i.e. the thickness that would form the amount of substance effectively deposited on a support perfectly flat and not porous) should be of the order of some micrometers, for 0.2 to 30 micrometer example.

However, it is possible to effectively apply the invention with lower thickness coatings for some substances (for example equivalent thickness of the order of 5 micrometers, even 1 micrometer in the case of type polymers xylene presenting advantageous characteristics of tightness and mechanical behavior at these thicknesses reduced).

It will also be noted that if the substances used for coating the fibrous weft structure of the ticket are generally optically transparent, you can also take advantage of the optical features (coloring ...) of some coating substances to obtain an advantageous aesthetic effect on a ticket treated according to the invention.

Claims (13)

1. Procedure for preparing security documents comprising a support on a sheet of fibrous weft paper, characterized in that the process comprises impregnating said fibrous weft in its entire thickness by a protective substance, so that said substance covers the fibers of the weft and covers the joining areas of these fibers, the pores of said support being tightly clogged by the coating. 2. Method according to claim 1, characterized in that the protective substance comprises an organic substance. 3. Method according to the preceding claim, characterized in that the organic substance is a silane, a fluorinated silane, a xylene-type polymer, or another polymer. Method according to one of the preceding claims, characterized in that the protective substance comprises an inorganic substance. 5. Method according to claim 4, characterized in that the inorganic substance is SiO2, Si3 {N4}, TiO2, ZnO or SnO2. Method according to one of the preceding claims, characterized in that the protective substance has been deposited on the paper sheet support by evaporation under vacuum. Method according to one of claims 1 to 5, characterized in that the protective substance is deposited on the paper sheet support by decomposing a plasma on the surface of the support. 8. Method according to claim 7, characterized in that the decomposition of the plasma is carried out under a pressure close to that of the vacuum. Method according to one of claims 1 to 5, characterized in that the protective substance is deposited on the paper sheet support by chemical vapor deposition. Method according to one of claims 1 to 5, characterized in that the protective substance is deposited on the paper sheet support by impregnating the support by a solution of low viscosity and then by performing an annealing cap that allows the solution to be fixed. in the frame of the support. Method according to one of the preceding claims, characterized in that the equivalent thickness of the coating is between 0.2 and 30 micrometers. 12. Method according to claim 11, characterized in that the equivalent thickness of the coating is between 1 and 5 micrometers. 13. Method according to one of the preceding claims, characterized in that the protective substance is colored.