EP1770670B1 - Process for securing a document holographically and document thus secured - Google Patents

Abstract

The method involves superposing a marking film (1) on which a set of zero order diffraction networks are formed that are transferable on a document. The film has optically active marks that are provided in the form of numeric characters. Marks to be transferred (2, 3) are transferred on the document by applying a marking iron on the marking film. The marking iron has the shape of the marks to be transferred. The film comprises zero order diffraction networks producing their distinct optical effects. An independent claim is also included for a marking film comprising a uniform zero order diffraction network band.

Description

The invention belongs to the field of secure document marking.

• une étape de superposition dans laquelle on superpose un film de marquage sur lequel sont formés une pluralité de réseaux de diffraction d'ordre zéro transférable sur ledit document,
• une étape de transfert dans laquelle on transfère sur ledit document, ledit signe à transférer.

The invention relates to a method for securely marking at least one sign to be transferred to a document, said method comprising:

• an overlay step in which a marking film is superimposed on which a plurality of transferable zero order diffraction gratings are formed on said document,
• a transfer step in which is transferred to said document, said sign to transfer.

In these known safe marking methods, the film exhibits optically active signs including zero order diffraction gratings. These zero-order diffraction gratings are known in the field of security marking and are, for example, such that they have a well-defined color when they are observed in a first direction of observation and a distinct color when they are observed at 90 °. They have the advantage of being difficult to reproduce by possible fraudsters.

We know of the document U.S. Patent No. 6,700,705 B1 films which comprise different zones or bands whose optical configurations are different, that is to say which have diffraction properties whose optical effects are different. When such films are observed in one direction, several colors are observed.

According to the known labeling methods, the optical activation is obtained by the presence of diffraction gratings at the level of the signs. These signs have for example the form of numerical characters. The zero-order diffraction gratings corresponding to the signs to be transferred to a document are integrated into the film in relatively transparent areas called "patches" in the English language, or lozenge, covering the diffraction gratings. This pellet exceeds the diffraction grating corresponding to the sign to be applied, and generally extends over the entire width of the film.

When hot transfer, it is the entire chip that is deposited on the document. During this transfer, the area of the pellet that covers the sign and the area of the pellet that does not cover the sign are transferred together.

However, the area of the pellet which does not cover the sign reflects the light at zero order, and parasitizes the legibility of the sign, when it is in the form of a zero-order diffraction grating. The area of the pellet therefore causes a glassy reflection which hinders the zero-order reading for zero-order diffraction gratings.

The methods for securely marking at least one sign to be transferred to a document therefore have the disadvantage that the readability of the sign (s) marked in the form of a zero-order diffraction grating is poor.

The invention aims to overcome this drawback.

An object of the invention is therefore to improve the readability of the signs marked in the form of a zero-order diffraction grating during marking on a document.

Another object of the invention is to allow marking of signs in the form of a zero-order diffraction grating on a support without these elements being covered by a protective layer.

At least one of these objects is achieved by a method according to claim 1.

Thanks to such a method and in particular the fact that the iron has the shape of the sign to be transferred, it is possible to directly transfer the signs to a document without transferring any layers or pellets covering the signs on the marking film, or other disturbing elements the legibility of the signs.

Therefore, only the signs being transferred, the readability of these signs to zero order is improved.

Also known in the state of the art marking films comprising pellets, the pellets comprising at least two signs to mark, each of the signs having different optical properties.

In the case where there are two signs to be marked in the form of zero-order diffraction gratings having distinct optical properties, the problem mentioned above is even greater since the areas between these signs to be marked may be detrimental. the legibility of the signs if they are transferred together with the signs on the document.

This problem is solved by a method according to claim 2. Thanks to the two marking irons having the shape of the signs to be marked, it is possible to obtain signs having distinct optical properties of good readability.

These two marking signs are zero-order zero-order diffraction gratings in direct contrast with the substrate (scattering).

This solution makes it possible to eliminate the problem of the vitreous reflection at the zero order which parasitizes the reading.

The invention more generally relates to a method of depositing a two-color optical mark for quickly identifying and authenticating a bank note document or other document carrying a composite element requiring immediate visual identification by a person without particular qualifications or expertise. This mark must not be easily reproduced or infringed. It also offers the possibility of expert level control.

The shape of these elements is given directly by the shape of the hot stamping iron.

The invention also relates to a secure document according to claim 3.

With the marking film, no element other than zero-order diffraction gratings disturbs the legibility of the sign or signs marked by marking during the transfer.

Advantageously, the film has two uniform bands of distinct optical effects respectively on either side of a longitudinal line.

In this way, the marking with one or more irons having the shape of the signs to be transferred, is facilitated.

Preferably, said film has a transfer layer capable of transfer by means of a marking iron, and in particular with a hot-marking iron.

According to a particular embodiment, the film is in the form of a continuous coil with a sequence of separate security optical effect bands ordered longitudinally.

According to another embodiment, the film is in the form of a coil containing a succession of patches, said patches consisting of several zones of separate security optical effects. In the same way, it is the iron which will draw in each zone a precise useful surface, allowing to transfer on the document of the distinct signs having specific optical security effects.

In one embodiment of the method for securely marking a document, a part of a security optical component consisting of a transparent film on which a plurality of transferable diffraction gratings are formed on a support where said networks are formed is superimposed. diffraction forms at least one pair of juxtaposed signs, each of the signs of said pair producing distinct optical effects, and transferring at least one of the two signs of said pair onto the adjacent document.

According to one variant, at least the two signs of a said pair are transferred to the document to be authenticated.

According to one variant, the shape of the hot stamping irons varies from one document to another and makes it possible to customize the authentication signs.

A film comprising a transparent substrate, an embossing layer, a high refractive index layer, an optional contrast layer, a thin layer of a preferably opaque colored varnish is prepared and said film is printed to form a series. bands having distinct optical effects with a pattern for producing two distinct optical effects for said adjacent signs of a pair when using the film.

A document secured by an optical security component consists of at least two distinct signs having different optical effects visible to the zero order transferred to said document by hot stamping.

• la figure 1 représente un film de marquage selon l'art antérieur,
• la figure 2 représente un film de marquage selon l'invention,
• la figure 3 représente un exemple d'un document marqué selon l'art antérieur,
• la figure 4 représente un exemple d'un document marqué selon l'invention.

The present invention will be better understood on reading the description which follows, with reference to the appended drawings in which:

• the figure 1 represents a marking film according to the prior art,
• the figure 2 represents a marking film according to the invention,
• the figure 3 represents an example of a document marked according to the prior art,
• the figure 4 represents an example of a document marked according to the invention.

The scale of the figures is indicated at the edge of the figure 2 .

The figure 1 presents a solution known in the state of the art. The security component is in the form of a film 1 having optically active signs 5, here in the form of numerical characters. The two characters "2" and "0" may, in the prior art be identical or different as to the optical effects they produce.

During heat transfer, the entire area 6 is deposited on the document. This zone includes, besides the 2 characters, a transparent zone which reflects the light in the zero order, parasitic by the same the readability of the characters. One of the objectives of the invention is to delete this area.

The film 1 is in the form of a coil consisting of differentiated patches.

In the solution according to the invention presented in figure 2 , the film presents the same general structure. However, the diffracting gratings spread uniformly along the coil on either side of the center line. The choice of the form of hot stamping will achieve at the time of transfer the characters here "2" and "0" suggested by the dots. Each of the characters having the predefined optical effect of each band.

The invention offers the possibility with the same film to mark distinct signs by simply changing the marking tool and limit the stock to a single stock of consumable.

It also allows the apposition of two separate effects in a single pass on machine.

The figure 3 represents an example of a document marked according to the prior art.

The marking is in the form of a transfer of an optically variable component 7 having two configurations 15, 25, of different colors possibly, but embedded in the transparent varnish deposited simultaneously at the time of transfer and which disturbs the reading at the same time. zero order.

The figure 4 represents an example of a document marked according to the invention.

The marking is in the form of a transfer of two optically variable components 2, 3, possibly of different colors, and producing distinct optical effects. They are directly transferred onto a diffusing paper substrate. The optical effect is for example obtained with a maximum intensity according to two different orientations, specific to each of the signs forming the pair 2, 3. Their readability is increased by the fact that they are no longer embedded in an important glassy reflection zone but they stand out directly on the paper that is diffusing it.

In one embodiment of the tagging method, only one sign is transferred from a film comprising a single uniform band of zero-order diffraction gratings. In this case, an iron having the shape of the sign to be transferred is used, and it is applied to the film by hot stamping.

Finally, it is also possible to carry out a marking of several signs from a film having a single uniform band of zero-order diffraction gratings. In this case, irons having the shape of the signs to be transferred are used, and they are applied to the film by hot stamping.

Claims (3)

1. A method for security marking at least one sign (5) to be transferred onto a document, said method comprising:

   - a step of superposition during which a marking film (1) is superposed, whereon a plurality of zero order diffraction gratings are formed, which can be transferred onto said document,

   - a step of transfer during which said sign (5) to be transferred is transferred onto said document,

   the method being characterized in that the step of transfer comprises steps, during which:

   • at least one marking iron is applied onto said film (1), with said marking iron having the shape of said sign (5) to be transferred.
2. A security marking method according to claim 1, wherein said marking film (1) comprises at least first zero order diffraction gratings and second zero order diffraction gratings, said first zero order diffraction gratings producing optical effects different from those produced by said second zero order diffraction gratings and wherein, during the step of transfer, at least one first sign (5) and a second sign (5) are transferred onto said document, and wherein the step of transfer includes steps wherein:

   . a first marking iron is applied onto said film (1) at the level of the first diffraction gratings, with said first marking iron having the shape of said first sign (5);

   . a second marking iron is applied onto said film (1) at the level of the second diffraction gratings, with said second marking iron having the shape of said second sign (5).
3. A secured document characterized in that it is marked using a method according to one of claims 1 or 2.

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