EP2580065B1 - Method for customizing latent embedded images and document thus produced - Google Patents

Description

Field of application of the invention

The present invention relates to a method of personalizing embedded latent images. It finds applications especially in credit cards or other official documents (identity, subscription, etc.). The invention relates more particularly to the personalization of latent images protected by a transparent mechanical protection.

State of the prior art:

Some banks offer their customers to print on their credit card an image of their choice. For this, the customer must send by email, to his bank, an image which is preferably his photo ID. During the manufacture of the card, the bank will print the image before the deposit of the protective layer.

This solution imposes an individual treatment of the credit card during its manufacture, which increases its price. Moreover, the sending by email of a photo, associated with confidential information, always presents risks of diversion.

In order to avoid these disadvantages, many companies are looking for ways to personalize credit cards at the last moment, that is, when the credit card is provided to the customer. So the mass production is the same for all credit cards, and there is no more risk of misuse of information online.

For this, some devices provide a latent image consisting of an organic layer, monochrome or a metal layer. These layers are coated with a transparent protective layer. The personalization that is to say the formation of the final image, is performed by a laser beam that burns the organic layer or engraves the metal layer, showing a certain contrast between the parts treated by the laser beam, and untreated parts. If these devices are very simple, they prohibit color, which greatly limits their application.

Other devices use several stacked sublayers, protected by a transparent layer. The stacked sub-layers having different colors, it is possible to produce color images by selective ablation of the sub-layers through the transparent layer. The patent JP2004082493 (A ), shows a similar example. If these devices make it possible to produce color images, the superposition of the sub-layers, their selective ablation, make these solutions delicate and especially very expensive.

The patent FR 2451081 proposes the personalization of a latent image coated under a protective layer, by the use of micro capsules which by mechanical pressure, show different colors. If this device seems interesting in some aspects, it does not allow to show a quality image. Moreover, the application of the mechanical force necessary for the change of color, is incompatible with shapes or patterns of small size, essential to obtain a sufficient resolution of the desired image.

US-A-5,364,829 discloses an information recording and erasing medium of the recorded information reversibly by applying heat or light radiation onto a recording medium. The recording medium comprises on a substrate (1): an optical reflection layer (2), a recording optical absorption layer (3 or 4) and a protective layer (6). The absorption layer (3, 4) contains segments (41 R, 41 V, 41 B, 41 BK) colored according to the primary colors (R, G, B) and black (41 BK). By supplying heat, the crystallo-organic particles of the colored segments change their crystalline state. The light transmission of the recording layer is then modified.

It is also known to reproduce images in a liquid crystal display by creating gray levels by a determined duration of opening of the liquid crystal with respect to the time of an image. This technology does not apply to make final images.

Object of the invention

The object of the present invention is to overcome these disadvantages by proposing a method of personalizing a recessed latent image, with a view to obtaining a final high quality and low cost color image by laser treatment on a latent image. of particular structure.

As such, the subject of the invention is a method of personalizing a latent image embedded in a transparent protective mechanical layer. The method consists in forming a latent image consisting of sub-pixels printed with primary colors uniformly distributed, these colors being reflective, then to reveal gray levels of a final image by a modulated emission of a laser beam on the sub-pixels for producing dark non-reflecting surfaces covering part or all of the surface of each sub-pixel.

• en plus des sous pixels aux couleurs primaires, des sous pixels de couleur blanche également uniformément répartis sont ajoutés pour constituer les pixels de l'image latente, chaque quadruplet de sous pixels formant un pixel ;
• les surfaces non réfléchissantes de couleur sombre recouvrant en partie ou en totalité la surface des sous pixels sont obtenues par carbonisation des sous pixels par le faisceau laser au travers de la couche transparente de protection ;
• les surfaces non réfléchissantes de couleur sombre recouvrant en partie ou en totalité la surface des sous pixels sont obtenues par effet thermo chromique ou par effet photochromique, sous l'influence du faisceau laser au travers de la couche transparente de protection.

According to particular implementations:

• in addition to sub pixels with primary colors, sub pixels of white color equally uniformly distributed are added to constitute the pixels of the latent image, each quadruplet of sub-pixels forming a pixel;
• the non-reflecting surfaces of dark color covering part or all of the surface of the sub-pixels are obtained by carbonization of the sub-pixels by the laser beam through the transparent protective layer;
• the non-reflective dark-colored surfaces covering part or all of the surface of the sub-pixels are obtained by thermochromic effect or by photochromic effect, under the influence of the laser beam through the transparent protective layer.

The invention also relates to the document comprising an image produced according to the method above. In this document, the image being arranged under a mechanical protection layer, the embedded image is formed of sub-pixels which have printed surfaces with primary reflective colors and are regularly distributed on a support, these surfaces being covered with non-reflective surfaces. dark.

• les surfaces non réfléchissantes sombres sont de couleur noire et les sous pixels sont aux couleurs primaires et également blanches régulièrement réparties ;
• la surface de l'image latente est courbe afin de permettre une incrustation d'image dans un document souple.

According to particular embodiments:

• the dark non-reflective surfaces are black in color and the sub-pixels are in primary colors and also regularly distributed white;
• the surface of the latent image is curved to allow image embedding in a flexible document.

The invention thus proposes to make, during the mass production of the image support object, which may be a credit card, a latent image, deposited on this support and mechanically protected by a transparent layer, this image latent being printed according to the same manufacturing processes as those used for the standard manufacture of credit cards. At this stage of production, all latent images are identical and appear as white. Then in a second step, a laser beam, through the transparent protective layer, transforms the latent image into a personalized final color image.

Indeed, the latent image consists of small surfaces with primary colors (RGB): Red, Green and Blue, surfaces that will be called "sub pixels", each set (triplet) sub pixels (RGB) forms a pixel of the image. These sub-pixels are printed by inkjet, or any other technique known to those skilled in the art during the mass production of the carrier object, which may be a credit card or other identity document. This latent image, formed of regularly distributed sub pixels, is identical for all the objects of the same series. The latent image is then mechanically protected by a transparent coating.

Subsequently, in a second phase, the customization of the latent image is effected by a laser beam which, by thermal effect or photosensitive effect, reveals a dark color, preferably black, covering partially or totally the sub pixels surface. The dark coloration being formed between the surface of the sub-pixels and the field of view, the recovery of the sub-pixels by this coloration appears in the field of view by reflection of the light on the sub-pixels.

More specifically, the subject of the invention is a method of personalizing a latent image embedded in a transparent mechanical protection layer. The latent image consists of a regular set of small primary-color printed surfaces, essentially including red, green, and blue colors. In order to reinforce the white dominance, the invention advantageously provides for regularly adding small white areas. Each small surface constitutes a sub-pixel of the image, and a set (quadruplet) of sub-pixel red, green, blue and white constitutes a pixel of the image.

Each image can contain several million pixels, depending on the definition. The sub-pixels are arranged regularly to form the latent image. They are printed by any technique known to those skilled in the art, such as inkjet, for example. The support surface of the latent image may be flat or curved. The colors of the sub pixels are reflective, in order to give the final image, once personalized, the maximum brightness in ambient light.

At this level of manufacture, the latent image consisting of all the pixels described above, appears as a white surface to the observer. The latent image is then coated with a transparent protective layer. All of these manufacturing steps, are common to all objects in the same series.

In a second step, the customization is carried out by a laser beam which through the protective transparent layer, reveals non-reflecting surfaces, dark colors, preferably black, which more or less cover the surface of the sub-pixels thus forming the gray levels of the final custom color image. The non-reflective surfaces made by the laser beam are obtained by thermal or photochromic effect.

In the most economical form of the invention, the colored surface of each sub-pixel is carbonized in part or in whole by the laser beam. In a more elaborate form, the ink used to color the sub-pixels has thermochromic properties or photochromic properties, known to those skilled in the art who, under the influence of either a thermal effect or a radiation effect of the laser beam causes a non-reflecting, preferably black, coloration on the treated parts.

Presentation of the figures:

• La figure 1 montre une carte de crédit comprenant l'image latente selon l'invention.
• La figure 2 montre la même carte de crédit une fois personnalisée par le faisceau laser au travers de la couche de protection.
• La figure 3 montre les « sous pixels » de l'image latente.
• La figure 4 montre la coupe de l'image latente protégée sous la couche de protection transparente.
• La figure 5 montre la personnalisation par le faisceau laser de l'image latente.
• La figure 6 montre un exemple de niveaux de gris obtenus par le faisceau laser, de l'image personnalisée.

In any case, the features and advantages of the invention will appear better after the description which follows, given for explanatory purposes and in no way limiting. This description refers to the accompanying drawings, in which:

• The figure 1 shows a credit card including the latent image according to the invention.
• The figure 2 shows the same credit card once personalized by the laser beam through the protective layer.
• The figure 3 shows the "sub pixels" of the latent image.
• The figure 4 shows the section of the protected latent image under the transparent protective layer.
• The figure 5 shows the personalization by the laser beam of the latent image.
• The figure 6 shows an example of gray levels obtained by the laser beam, the personalized image.

Detailed description :

The figure 1 shows a credit card (11) on which, during its mass production, the latent image (12) has been printed. Any printing technique known to those skilled in the art can be used, including techniques commonly used to print the color patterns of credit cards. The latent image (12) may be located on a flat portion of the credit card, or on a curved surface, or in relief, such as, for example, the raised portions of the credit card numbers. At the end of manufacturing, the credit card is coated with a transparent protective layer like the current credit cards. At this level, standard credit card manufacturing processes are not modified.

The figure 2 , shows the same credit card, including the latent image (11) of the figure 1 , has been customized, showing the final color image (21). If this image is a photo ID, it can preferably have the standardized dimensions of photo ID, 35mm by 45mm.

The figure 3 , shows a detailed view of the latent image (12). It consists of small areas that we call "sub-pixels", regularly arranged. Each quadruplet of "sub-pixels" (31) of red color, (32) of green color, (33) of blue color, and (34) of white color form a pixel which may have a square shape according to the example of the figure 3 . The "subpixels" can also be aligned forming monochrome bands in the previously described colors. The ink used to print the "sub-pixels" is preferably reflective. According to the example of the figure 3 , the "sub pixels" are squares of 16μm side. The pixel comprising the four "sub-pixels" according to this example has a square shape of 32 μm on the side.

The figure 4 shows the section of a credit card (11) comprising the latent image (12), the assembly being coated with the transparent protective layer (41).

The figure 5 , shows a credit card (11) comprising the latent image (12) coated with the protective layer (41). A laser beam (51) scans the entire surface of the latent image (12) to customize it through the protective layer (41), showing the gray levels of the final image, by performing dark, preferably black, non-reflective surfaces that partially or wholly cover the surface of each "sub-pixel". In its most economical form, the gray levels are obtained by carbonization of the color of the subpixels. other methods, known to those skilled in the art, use photochromic or thermochromic colors, which under the influence of the wavelength of the laser beam, or under the thermal influence of the laser beam, make it possible to reveal a color dark, which reflects very little light.

The reproduction of an image, for example a digital image, according to the invention, consists in producing by laser beam (51) the gray level of each pixel of the digitized image by partial or total darkening, in particular by darkening, of one or several sub pixels of each pixel of the reproduced image corresponding to a pixel of the digital image to be reproduced.

The surface area to be blackened above each subpixel ("above" means between the surface of subpixels (12) and the laser beam (51), (i.e. the field of view of the image by reflection of light) corresponds to that of the image to reproduce in order to reconstruct the same level of gray as that of this image for each of its sub-pixels.

The figure 6 , shows examples of gray levels on the four "sub pixels" (31), (32), (33), and (34) of a pixel. According to this example, the laser beam (51) of the figure 5 , scan the latent image from left to right. By way of example, the impact of the laser beam on the surface of the "sub-pixel" (31) has generated a black surface (61) of 1 μm × 1 μm. Sweeping the "sub-pixels" from left to right for example, the laser beam, when the surface to be treated is larger, can leave a rectilinear trace (62) of 1 μm wide, and of length proportionate to the non-reflective surface required. For example, on the "sub-pixel" (32), the non-reflecting surface has a dimension of 1 μm × 12 μm. Other non-reflective surfaces (63) and (64) are shown on the "sub pixels" (33), and (34) respectively. At the extreme, some "sub pixels" can be completely covered with non-reflective surface, or conversely not be covered at all. According to the example given of the figure 6 each "sub-pixel" can be covered with 16 x 16 laser impacts, thus forming 256 gray levels per sub-pixel. According to the example of the figure 6 , the identity photo of 35mm X 45mm, will then consist of more than 6 million pixels.

To reproduce the darkening of each sub-pixel, which will provide the gray level corresponding to each sub-pixel of the image to be reproduced, the intensity of the laser beam is programmed according to the gray levels of the image to be reproduced. These gray levels are recorded with their address in a memory of a digital processing unit. The predetermined scans are also recorded according to the image to be embedded on the document medium (global dimension, size of the sub-pixels, type of organization of the sub-pixels). Depending on the choice of scanning, the unit then controls the emission and displacement of the laser beam through suitable equipment, known to those skilled in the art, in order to reproduce the gray levels stored in a given image .

Claims (7)

1. A method of personalizing a latent image (12) embedded under a transparent mechanical protection layer (41), the method being characterized in that it consists in forming a latent image (12) constituted by uniformly distributed subpixels (31 to 33) printed in primary colors, these colors being reflecting, and then in causing gray levels of a final image (21) to appear by modulated emission of a laser beam (51) on the subpixels (31 to 33) in order to make dark non-reflecting surfaces (61 to 64) covering the surface of each subpixel (31 to 34) in part or in full.
2. A method of personalizing a latent image embedded under a transparent mechanical protection layer according to claim 1, characterized in that, in addition to the subpixels (31 to 33) in primary colors, subpixels of white color (34) that are likewise uniformly distributed are added to constitute the pixels of the latent image.
3. A method of personalizing a latent image embedded under a transparent mechanical protection layer according to claim 1 or claim 2, characterized in that the non-reflecting surfaces (61 to 64) of dark color covering the surface of the subpixels in part or in full are obtained by the laser beam (51) carbonizing subpixels through the transparent protection layer (41).
4. A method of personalizing a latent image embedded under a transparent mechanical protection layer (41) according to any one of claims 1 to 3, characterized in that the non-reflecting surfaces (61 to 64) of dark color covering the surface of the subpixels in part or in full are obtained by a thermochromic effect or by a photochromic effect, under the influence of the laser beam (51) acting through the transparent protection layer (41).
5. A document having embedded therein a final image (21) obtained by the method according to any preceding claim, the final image (21) being arranged under the mechanical protection layer (41), the document being characterized in that the embedded final image (21) is formed of printed subpixels (31 to 33) having reflecting surfaces of primary colors and that are regularly distributed over a medium (11), these surfaces being covered by dark non-reflecting surfaces (61 to 63).
6. A document according to the preceding claim, wherein the dark non-reflecting surfaces (61 to 64) are black in color and the subpixels (31 to 33) are of primary colors and also white (34) and being regularly distributed.
7. A document according to claim 5 or claim 6, characterized in that the surface of the latent image is curved.

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