EP1042125A1

EP1042125A1 - Method for producing a particular photoluminescent polychromatic printed image, resulting image and uses

Info

Publication number: EP1042125A1
Application number: EP99950811A
Authority: EP
Inventors: François Trantoul
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-10-23
Filing date: 1999-10-22
Publication date: 2000-10-11
Anticipated expiration: 2019-10-22
Also published as: DE69917590T2; DE69917590D1; EP1042125B1; WO2000024587A1; ES2221448T5; FR2785061A1; EP1042125B2; ATE267710T1; CA2315354A1; US6494490B1; CA2315354C; DE69917590T3; FR2785061B1; ES2221448T3

Abstract

A process for producing any photoluminescent printed polychromatic image (8), and the image obtained thereby. At least one set of at least three monochromatic filtered images (6a, 6b, 6c) is prepared from any original polychromatic image (1) visible in visible light which is filtered with a spectral pass-band below or equal to 15 nm, according to at least three wavelengths of fundamental colors equal to the wavelengths of the luminescent pigments used, with the corresponding monochromatic filtered images (6a, 6b, 6c), in order to print separately, one above the other, three monochromatic printed images (8a, 8b, 8c). The invention concerns the image obtained, a protective device and a document carrying such an image.

Description

METHOD FOR PRODUCING AN IMAGE

POLYCHROMATIC PHOTOLUMINESCENT PRINT

ANYONE, IMAGE OBTAINED AND APPLICATIONS.

The invention relates to a process for producing any photoluminescent printed polychromatic image (that is to say which can incorporate all the shades of colors and of various shapes including possibly continuous color variations (gradations, fades, etc.). .) shadows, variations in intensity, speckled effects ...) invisible under lighting in visible light, and visible under lighting by at least one source of invisible light, designated below in all the text "image polychromatic printed any luminiscent photo ".

By "visible light" is meant a light whose spectral composition is located in the visible spectrum, from 0.4 μ to 0.8 μ. By "non-visible light" is meant light whose spectral composition is located outside the visible spectrum, in particular in the ultraviolet and / or infrared spectrum.

Monochromatic photoluminescent printed markings invisible under visible light illumination and visible under non-visible light illumination (ultraviolet or infrared) are often used for authentication of documents such as banknotes. Different printed monochromatic markings can be juxtaposed and / or superimposed, which creates spots of colors composed in a finite number and in a discontinuous manner. However, these photoluminescent monochromatic markings do not make it possible to produce a true polychromatic printed image of any kind reproducing, with all the nuances of colors and shapes, any polychromatic image visible in visible light such as a non-rasterized photographic image digitized.

Any such photoluminescent printed polychromatic image can have many interests and various applications, in particular as an authentication element and / or for decoration purposes. As authentication, any photoluminescent printed polychromatic image can provide at least three levels of authentication: the printing of the image creates raised patterns and / or visible opalescence in visible light; under illumination in non-visible light, we can check the conformity of the image which is extremely difficult to counterfeit perfectly given its complexity and the fact that it is applied to a background of a document with other visible patterns by transparency, unless the original visible in visible light is available, the reproduction from the visible image in non-visible light does not provide the original image; spectrophotometric analysis identifies the photoluminescent components used, and therefore their authenticity.

As a decorative feature, it turns out that such a polychromatic printed photoluminescent image of any kind illuminated in non-visible light has an unusual unusual appearance.

But the various attempts to achieve such a polychromatic photoluminescent printed image of any kind, which date back more than sixty years, have ended in failure.

In particular, traditional printed polychromatic images visible in visible light are generally made in four colors (yellow, magenta, cyan, black) on a white background. The original image is filtered with three colored filters (blue, green, red) having a spectral bandwidth of lOOμ (one third of the visible spectrum). The appearance of the colors on the printed image is due to the reflection of visible natural light (daylight or a lighting lamp) by the printed medium through transparent colored inks which selectively absorb the incident light according to the principle known as "material color" in subtractive synthesis. For each colored ink, the support reflects two-thirds of the visible spectrum, according to a spectral composition complementary to the absorption spectrum of the ink in the visible. With this technique, it is not possible to produce a photoluminescent printed polychromatic image. Indeed, if we use photoluminescent pigments corresponding to the fundamental colors of the color filters used for four-color printing, in inks that are printed from the three negatives obtained after filtering using traditional color filters , it is not possible in practice to reproduce the polychromatic image in a photoluminescent manner, in a reliable manner and with good quality.

US-2,302,645, US-2,277,169, US-2,434,019 thus describe various attempts to produce images using fluorescent pigments.

However, the methods described in these documents do not allow the production of a photoluminescent polychromatic image by automatic and reliable reproduction of a polychromatic image. In fact, the methods described in these documents consist first of all in producing a trichromic positive manually. Subsequently, this three-color positive is used to be reproduced by printing using inks, some of which incorporate fluorescent pigments. Consequently, these documents show that the automatic obtaining of a trichromic photoluminescent positive was abandoned, since these documents consider that this positive is necessarily produced manually.

Also, the document RJ TUITE "Fluorescent multicolor additive System" XP 002108747, PRODUCT LICENSING INDEX., N ° 84, pages 81-85, INDUSTRIAL OPPORTUNITIES LTD. HAVANT., GB ISSN: 0374-4353, April Issue, 1971, teaches to realize by printing using an engraving plate press, a multicolored fluorescent image under ultraviolet. The process implemented in this document consists of producing red, green and blue separation negatives from a continuous positive by exposure through a red, green and blue filter, respectively. With this process, each of the negatives not being finely filtered, the largest proportion of the surface of the final image comprises an abnormal overload of the three colors forming a dominant white. Consequently, the fluorescent image obtained is extremely pale and is in practice either invisible or a "ghost" image, despite the production of a large number of successive final layers of green ink.

The invention therefore generally aims to allow the production of any photoluminescent printed polychromatic image. Thus, the invention aims to allow the reproduction in printed and photoluminescent form, of an image of polychromatic origin formed in subtractive synthesis (principle of the color of matter), any visible in visible light (printed, painted, photographic image. ..) automatically and reliably.

The invention further aims to provide a simple and inexpensive method for quickly obtaining and reproducing such an image on an industrial scale automatically and reliably, in particular in a manner similar to traditional printing techniques, without requiring the manual creation of a tri-color positive by an artist, and providing a high quality image with high contrast.

The invention also aims to propose applications of such a polychromatic printed photoluminescent image of any kind.

To do this, the invention relates to a process for producing an arbitrary photoluminescent printed polychromatic image invisible under lighting in visible light, and visible under lighting by at least one non-visible light source, in which: - one chooses or realizes an image of polychromatic origin formed in subtractive synthesis (principle of the material color) visible in visible light,

- at least one set of at least three images, called filtered images, is produced and recorded by filtering the original image, - at least one set of at least three images, known as printed images, is printed separately, one after the other and one above the other, using and reproducing one of the images respectively filtered with a printing composition comprising a photoluminescent pigment, the different photoluminescent pigments of the different printed images of the same set emitting, under lighting by at least one invisible light source, colors capable of forming by additive synthesis all the colors visible spectrum, characterized in that:

the filtered images, known as monochromatic filtered images, are produced by filtering the original image, according to a spectral bandwidth less than or equal to 15 nm centered at a wavelength, called the filtering wavelength, chosen from the wavelengths of at least three fundamental colors, the different wavelengths of filtering of the monochromatic filtered images being two by two distinct, and being adapted to make it possible to form by additive synthesis all the colors of the visible spectrum, each of these filtering wavelengths being at least approximately equal to a wavelength of an emission peak of a photoluminescent pigment under illumination by at least one non-visible light source,

each printed image, called a monochromatic printed image, is printed using and reproducing one of the filtered monochromatic images with a printing composition comprising a photoluminescent pigment having an emission peak wavelength, under illumination by at at least one non-visible light source, which is at least approximately equal to the filtering wavelength used to obtain said monochromatic filtered image.

By "at least approximately equal" is meant either a perfect equality between wavelengths, or the fact that the wavelengths are close enough that their difference does not produce a significant effect on the image obtained. In particular, the wavelength of the emission peak can be throughout the passband less than or equal to 15 nm from the filtering wavelength. In other words, a certain margin of error is accepted for the wavelengths, and this margin of error is of the order of the bandwidth of the filters used.

Advantageously, a method according to the invention is also characterized by at least one of the following characteristics:

- to produce each of the monochromatic filtered images, an original of the image of any polychromatic origin visible in visible light is illuminated, and the polychromatic image reflected by this illuminated original is filtered, according to a spectral bandwidth less than or equal to 15 nm centered according to the filtering wavelength of the fundamental color corresponding to the monochromatic filtered image; advantageously, the reflected polychromatic image is filtered with bandpass filters having a spectral bandwidth of the order of lOnm, in particular with bandpass interference filters;

- as the filtering wavelengths and emission peaks of the photoluminescent pigments are chosen (by selecting appropriate filtering means and photoluminescent pigments), different monochromatic printed images of the same set producing a reproduction of an original image, at least one wavelength in green, at least one wavelength in red, and at least one wavelength in blue; advantageously, one chooses wavelengths adapted to be separated by the same spectral distance between 80 nm and 100 nm, in particular equal to 90 nm; in particular a wavelength in the green between 520 and 570nm, a wavelength in the red between 610 and 680nm, and a wavelength in the blue between 430 and 480nm; - the monochromatic printed images are printed so that, in the order of reception of the lighting light, they are presented in the blue, red, green order of the filtering wavelengths and of the emission peaks photoluminescent pigments; the monochromatic printed images are printed one on top of the other without an intermediate layer; - for the same game producing a reproduction of an original polychromatic image, only three monochromatic printed images are printed, one in green, one in red and one in blue; each monochromatic printed image is printed in a single printing layer;

- To make and save each monochromatic filtered image, the filtered image is captured with photosensitive means with CCD charge transfer and a corresponding digitized image is recorded; a raster image is formed from each monochromatic filtered image, which is then used to print the monochromatic printed image; advantageously, the raster image has a screen from 60 to 133, in particular of the order of 80 (this value corresponding to the number of lines of dots per inch (2.54 cm); the various monochromatic printed images are printed with a same clearance at least substantially according to the same printing thickness; each monochromatic printed image is printed so that the quantity of photoluminescent pigment at each point is a function of the light intensity of the image of polychromatic origin at this point according to the corresponding filtering wavelength (this function being proportional in the case of a positive, and inversely proportional in the case of a negative); and photoluminescent pigments with a purity factor are used (ratio of the quantity of light monochromatic according to the dominant wavelength of the emission peak on the sum of this amount of monochromatic light and the amount of white light emitted) equal at 1, quasi-monochromatic having a main emission peak, or monochromatic having one and only one emission peak;

- each monochromatic printed image is allowed to dry and / or harden after having printed it and before printing another monochromatic printed image;

- to produce the same set of printed images monochromatic, photoluminescent pigments are used under lighting by a single invisible source of light; as a variant, to produce the same set of monochromatic printed images, at least one first photoluminescent pigment is used under illumination by at least one first source of invisible light, and at least one second photoluminescent pigment is illuminated by at least one second source non-visible light of wavelength (s) distinct from that (s) of the first non-visible light source;

- One prints a set of monochromatic printed images which are positive images of an original image, adapted to reproduce in additive synthesis a positive of the original image;

- One prints a set of monochromatic printed images which are negative images of an original image, adapted to reproduce in additive synthesis a negative of the original image;

- a first set of positive monochromatic printed images is printed with luminescent photo pigments under lighting by a first non-visible light source - notably ultraviolet or infrared -, and a second set of negative monochromatic printed images is printed with photoluminescent pigments under lighting by a second non-visible light source of wavelength distinct from that of the first non-visible light source - notably infrared or ultraviolet -;

the wavelengths of the emission peaks of the photoluminescent pigments used to print the first set are at least approximately equal to the wavelengths of the emission peaks of the photoluminescent pigments used to print the second set, so that the same monochromatic filtered images can be used to print both sets;

- Furthermore, at least one image, known as an infrared image, is printed with a printing composition comprising at least one pigment having at least one emission peak wavelength situated in the infrared range but no emission in the range visible light when this pigment is activated by lighting under a visible light source; the infrared image is a monochrome image which can be of the same nature (positive or negative) as the monochromatic printed images or, preferably, of opposite nature; it is also possible to provide a first positive set and a second negative set, as indicated above, and a positive or negative infrared image;

- To print each monochromatic printed image, a printing composition is used which incorporates a photoluminescent pigment, but which is, at least after drying, transparent or translucent for visible light when it is placed under lighting by the non-light source visible or by each of the non-visible light sources; in addition, advantageously, for printing each monochromatic printed image, a printing composition is used which, at least after drying, is transparent or translucent for visible light when it is placed under visible light lighting;

- the monochromatic printed images are printed by screen printing; advantageously, a printing composition is used which is formed from a serigraphic varnish for polymerization under ultraviolet rays; a screen printing screen is produced from each monochromatic filtered image, and the various screen printing screens are produced from the same fabric;

- Photoluminescent pigments are used under lighting by at least one non-visible light source whose spectral composition is located in the ultraviolet or infrared range;

- mineral photoluminescent pigments are used, in particular from the rare earth family; alternatively, organic photoluminescent pigments are used with better transparency (less opalescence) but which are less durable than mineral pigments;

- the monochromatic printed images are successively printed on the free external face of a transparent film in the visible comprising at least one layer formed by a continuous printing of a printing composition, for example a film as described in EP- 0 271 941 or US-5,232,527.

The invention thus makes it possible for the first time to automatically obtain any polychromatic printed photoluminescent image which is a faithful reproduction, with all the nuances of colors and the shapes which can vary infinitely continuously, from a original of any polychromatic image visible in visible light. This original can be printed or a stored analog image (photographic, cinematographic, video ...), or a digitized image stored on a computer mass memory or other. It should be noted that this result is obtained by implementing not broadband filtering as in traditional printing, but on the contrary a selective narrowband filtering in visible light and a three-color additive synthesis under lighting in non-visible light.

The invention also extends to the printed image obtained by a method according to the invention.

The invention therefore relates to any photoluminescent printed polychromatic image invisible under lighting in visible light, and visible under lighting by at least one non-visible light source, comprising at least one set of at least three images, called printed images, printed one above the other, each printed image comprising a photoluminescent pigment emitting a color under lighting by a non-visible light source, the different colors of the printed images of the same set being adapted so as to be able to form by additive synthesis all the colors of the spectrum visible under lighting by at least one non-visible light source, characterized in that each printed image, called monochromatic printed image corresponds to the filtering of a polychromatic image in subtractive synthesis visible in visible light, according to a spectral bandwidth less than or equal to 15 nm centered on a wavelength , called filtering wavelength, chosen from the wavelengths of at least three fundamental colors, the different lengths filter wavelength being two by two distinct and adapted to allow to form by additive synthesis all the colors of the visible spectrum, each of these filter wavelengths being at least approximately equal to a wavelength of a peak emission of the photoluminescent pigment from the corresponding monochromatic printed image.

Advantageously, an image according to the invention is also characterized by at least one of the following characteristics: it comprises at least one printed monochromatic image having at least one emission peak wavelength in the green, at least one image monochromatic print having at least one emission peak wavelength in red, and at least one monochromatic print image having at least one emission peak wavelength in blue; for the same set of monochromatic printed images reproducing an original image, it includes three monochromatic printed images, one in green, one in red and one in blue;

- The wavelengths of the emission peaks of the monochromatic printed images are separated by the same spectral distance between 80 nm and 100 nm, in particular of the order of 90 nm; advantageously, it comprises a printed monochromatic image having a wavelength of emission peak in the green between 520 and 570nm, a monochromatic image having a wavelength of emission peak in the red between 610 and 680nm , and a monochromatic printed image having a blue emission peak wavelength between 430 and 480nm;

- the monochromatic printed images of the same set follow one another in the order of reception of the light in the blue, red, green order of the wavelengths of the emission peaks; advantageously, the monochromatic printed images are stacked on one another without an intermediate layer; the monochromatic printed images have at least substantially the same printing thickness; each monochromatic printed image is formed of a printing composition which is transparent or translucent for visible light when it is placed under illumination by the non-visible light source or by each of the non-visible light sources, and which incorporates a photoluminescent pigment; each monochromatic printed image is formed of a printing composition which is transparent or translucent for visible light when placed under visible light illumination;

- the luminescent photo pigments of at least one and the same set of monochromatic printed images emit under illumination by at least one source of non-visible light whose spectral composition is located in the ultraviolet or infrared range; the various monochromatic printed images of the same set include photoluminescent pigments emitting under lighting by at least one source of non-visible monochromatic light; advantageously, the various photoluminescent pigments of at least one and the same set of monochromatic printed images are adapted to present a wavelength of emission peak under lighting by one and only one and the same source of non-visible light; as a variant, for at least one and the same set of monochromatic printed images, at least one first pigment is photoluminescent under lighting by at least one first source of invisible light, and at least one second pigment is photoluminescent under lighting by at least one second non-visible light source of wavelength (s) distinct from that (s) of the first non-visible light source;

- It includes several sets of monochromatic printed images visible under lighting by different light sources (for example a set forming a visible reproduction under ultraviolet and a set forming a visible reproduction under infrared);

- it includes a first set of positive monochromatic printed images comprising photoluminescent pigments under lighting by a first source of non-visible light - notably ultraviolet or infrared- and adapted to reproduce in additive synthesis, a positive of an image of polychromatic origin, and a second set of negative monochromatic printed images comprising photoluminescent pigments under lighting by a second source of invisible light of lengths wave distinct from that of the first non-visible light source - notably infrared or ultraviolet - and adapted to reproduce in additive synthesis, a negative of an image of polychromatic origin; these two sets can be superimposed and are reproductions of the same image of polychromatic origin, one in negative and the other in positive; alternatively, they are reproductions of two images of different origin;

- It further comprises at least one image, called an infrared image, visible in the infrared range but invisible in the field of visible light under lighting by a visible light source; this infrared image can be a reverse reproduction of a reproduction of an image of polychromatic origin produced by a set of monochromatic printed images on the same support, and can be superimposed on this set.

The invention also extends to the applications of an image according to the invention. The invention extends in particular to the application of an image according to the invention for the protection of a document, in particular a passport, an identity card, a driving license, a vehicle registration card or other official identification and / or authentication document, a fiduciary document such as a bank note, check, card or other payment instrument.

The invention thus relates to a document protection device comprising at least one transparent protective film making it possible to cover and protect at least one surface portion of a document, in which the film comprises at least one image according to the invention.

The invention also relates to a document - in particular a passport, an identity card, a driving license, a vehicle registration card or other official document of identification and / or authentication, a fiduciary document, a bank note, a check, a card or other payment instrument comprising at least one image according to the invention. Advantageously and according to the invention, at least one image according to the invention is carried by at least one transparent protective film applied to at least one face of the document. The invention also relates to a process, any photoluminescent printed polychromatic image, a protection device and a document characterized in combination for all or part of the characteristics mentioned above or below.

Other objects, characteristics and advantages of the invention will appear on reading the following description which refers to the appended figures in which:

FIG. 1 is a diagram illustrating an installation allowing the implementation of a method according to the invention,

FIG. 2 is a diagram illustrating various stages of a method according to the invention,

FIG. 3 is a diagram showing an example of a document protected by a protection device according to the invention, seen lit in visible light,

- Figure 4 is a diagram showing the document of Figure 3 illuminated in non-visible light.

In FIG. 1, a polychromatic original image 1 is represented, colored according to the principle of the material color (subtractive synthesis), visible in visible light such as a photograph or an image printed in traditional four-color process, as desired. reproduce with all shades of color and shape, obtaining any photoluminescent printed polychromatic image invisible under lighting in visible light and visible under lighting by at least one non-visible light source. An original of this original image 1 is illuminated from a visible light source 2 such as an incandescent lamp or daylight. Light illuminating the original image 1 is visible white light which is reflected by the original image 1 towards a CCD camera 3 connected to a microcomputer 4 making it possible to memorize the images captured by the camera 3. On the optical path of the light reflected, a bandpass filter 5 is interposed. This filter 5 is chosen from at least three interference filters 5a, 5b, 5c bandpass whose spectral bandwidth is less than 15nm - in particular of the order of lOnm-, and whose filtering wavelength is chosen at less approximately equal to the wavelength of an emission peak of a photoluminescent pigment under lighting by at least one non-visible light source, this pigment being moreover adapted to be able to allow subsequent printing of the image polychromatic, that is to say to be compatible with the printing means and techniques used as described below. The filtering wavelengths are chosen from the wavelengths of at least three fundamental colors which can form all the colors of the visible spectrum by additive synthesis. In particular, three wavelengths are sufficient provided that each fundamental color cannot be balanced by the other two. It is also possible to use more than three wavelengths.

The monochromatic image from filter 5 is a contrasted monochromatic filtered image. Camera 3 is therefore a monochrome camera. Three monochromatic filtered images 6a, 6b, 6c are thus produced, with, respectively, each of the three filters 5a, 5b, 5c, monochromators from the same original image 1. These three monochromatic filtered images 6a, 6b, 6c are digitized images recorded in the microcomputer 4. Each monochromatic filtered image 6a, 6b, 6c captured and digitized by the CCD camera 3 is recorded by the microcomputer 4. In a variant not shown, the image of polychromatic origin may be a recorded digital image and digital filtering means are used to produce, by software calculation, each monochromatic filtered image 6a, 6b, 6c. It is also possible to use the digital filtering of a scanner having a transfer function adapted to the filtering wavelengths. Next, from the three monochromatic filtered images 6a, 6b 6c, three printing frames 7a, 7b, 7c, flashed in the traditional way in the field of screen printing, are produced, using a frame of 60 to 133 - in particular around 80-. The fineness of the weft is adapted according to the viscosity of the printing composition and its dry extract in a manner known per se in the field of screen printing.

These printing screens 7a, 7b, 7c are each formed of a film carrying a contrasting image, the density of screen points at each point of the image corresponds to the light intensity of the polychromatic image which is wish to reproduce.

In the case where it is desired to produce a positive reproduction of the original image 1, the density of halftone dots at each point of the contrasted image of the print halftone which is in negative corresponds to the light flux the original polychromatic image 1 reflected at this point, respectively according to each filtering wavelength. It is therefore necessary in this case to invert the filtered monochromatic images 6a, 6b, 6c, which are positive, in order to obtain negative screens for screen printing 7a, 7b, 7c. This reversal can be carried out either by the software for capturing the image by the CCD3 camera, or using traditional image processing software from the scanned and recorded images, or by the image processing software. the flashing machine for producing the printing frames.

On the contrary, in the case where it is desired to produce a negative reproduction of the original image 1, the inversion of the monochromatic filtered images 6a, 6b, 6c is not carried out, and the screen printing frames 7a, 7b, 7c are positive

The printing screens 7a, 7b, 7c are produced on transparent films then making it possible to produce, by exposure to a photopolymer, screen printing screens, one for each monochromatic filtered image 6a, 6b, 6c. Each screen printing screen is produced for example from a fabric whose mesh comprises 165 threads / cm, the threads having a diameter of 27 μ. A layer of photopolymer material 18 μ thick is used.

Each screen screen is thus representative, for each filtering wavelength, of a light flux reflected by the original polychromatic image 1 in the filtering wavelength corresponding to the filter used, or of the inverse of this luminous flux.

One prints then, separately, one after the other, and one above the other (with or without the interposition of a transparent intermediate layer) on a printing medium, three images, called images monochromatic prints 8a, 8b 8c, of the same format corresponding to the format of any photoluminescent printed polychromatic image 8 that one wishes to form. The printing medium 9 can be of any kind as long as it is compatible with the printing technique used. Advantageously, this printing support 9 is itself non-photo luminescent, in particular devoid of optical brightener, so as not to disturb the chromatic balance of the image 8 to be formed. For each monochromatic printed image 8a, 8b, 8c, the screen screen produced from one of the monochromatic filtered images 6a, 6b, 6c is used and a transparent printing composition comprising a photoluminescent pigment the length of which emission peak wave, under lighting by at least one non-visible light source 14, is equal to the filtering wavelength used to obtain said monochromatic filtered image. By successively using the three serigraphic screens corresponding to the three filtered monochromatic images 6a, 6b, 6c, the three monochromatic printed images 8a, 8b, 8c are successively printed.

As photoluminescent pigments, mineral pigments are used, in particular chosen from rare earths, which are well suited for being printed by screen printing, and resist radiation from the non-visible light source, which ensures resistance in the time to chromatic balance. You can also choose organic pigments whose resistance over time is a little less good, but which have better transparency.

As a monochromator filter 5, it is possible to use, for example, the bandpass interference filters sold by the company LOT ORIEL (Courtaboeuf, France) as mentioned in the table below, and in which are also given examples of references of corresponding photoluminescent pigments which can be used, sold by the company RIEDEL DE HAN (Germany) (RDH in the table) or the company USR OPTONICS (New Jersey, USA) (USR in the table).

For each impression of a monochromatic printed image 8a, 8b, 8c, the chosen pigment is incorporated into a varnish screen printing chosen to be able to be transparent, or at least translucent, when dry and placed under lighting by the light source (s) 14 not visible, at least for the light of wavelength corresponding to the length of the emission peak of this photoluminescent pigment, and for each of the emission peak wavelengths of the photoluminescent pigment (s) of the printed image (s) ) monochromatic (s) previously printed (s) on the printing support 9. In this way, the light emitted by each of the photoluminescent pigments will be able to pass through the printed serigraphic varnish to be visible from the outside, and this without color imbalance. For example, with the pigments CD 144, CD 166 and CD 105, the concentrations of each pigment in the screen varnish can be as follows: 27% for the blue pigment, 27% for the red pigment and 13.5% for the pigment green. These values can be reduced or increased (provided that the composition can be printed) provided that the relative proportions of the different colors are respected for the chromatic balance.

We print the three monochromatic printed images 8a, 8b, 8c blue, red, green, on the support 9 starting with the monochromatic printed image 8a whose photoluminescent pigment emits in green (wavelength of 530nm in the example above), then by printing the monochromatic printed image 8b whose photoluminescent pigment emits in red (wavelength of 620nm in the example above), and ending with the monochromatic printed image 8c whose photoluminescent pigment emits in blue (wavelength 440nm in the example above).

Thus, the various monochromatic printed images 8a, 8b, 8c are presented in the order 8c blue, 8b red, 8a green of the wavelengths of emission of the photoluminescent pigments, in the order of reception of the non-visible light causing this show.

The screen printing varnish used must also be transparent for light at the wavelength of non-light source 14 visible (or sources of light not visible when several sources are used), so as to allow photoluminescence of the different pigments.

The different monochromatic printed images 8a, 8b, 8c are printed successively, either directly one above the other, respecting a drying time between each layer, or possibly interposing between them continuous transparent layers. Such a transparent layer is for example a layer of polymerizable bicomponent printing composition containing a hydroxylated polyol and an isocyanate or a polyisocyanate so as to cause the polymerization in situ of the mixture leading to a thin transparent film of polyurethane, as described for example by EP-0 271 941 or US-5 232 527.

The monochromatic printed images 8a, 8b, 8c are all three printed with the same printing tools (the serigraphic screens used are made from the same fabrics and with the same photopolymer material). In particular, the monochromatic printed images 8a, 8b, 8c are printed with the same printing thickness. This thickness is advantageously between 3μ and 12μ depending on the characteristics of the screen printing screen used, in particular and is of the order of 5μ in the example above. Of course, the actual thickness of the monochromatic image 8a, 8b, 8c at each point depends on the pattern of the image, as is always the case in screen printing. Thus, for each monochromatic printed image 8a, 8b, 8c in positive, the quantity of photoluminescent pigment at each point is a function of the light intensity of the image of polychromatic origin at this point according to the corresponding filtering wavelength . The screen printing varnish used incorporating the photoluminescent pigment is chosen to be itself non-photoluminescent so as to allow the formation of image 8 by additive synthesis subsequently by the three pigments of the three monochromatic images 8a, 8b, 8c. In addition, advantageously, the different monochromatic printed images 8a, 8b, 8c are transparent or translucent in visible light when they are placed under visible light illumination, so that the image 8 formed is itself, in total, transparent or translucent for visible light when it is placed under light illumination visible. In this way, it allows the visualization of any mentions 12 previously written on the support 9, by transparency. The screen printing varnish used is advantageously a varnish for polymerization under ultraviolet rays. In fact, mineral photoluminescent pigments are generally sensitive to temperature.

In the example given above, the luminescent photo pigments all have the same absorption spectrum, and emit visible light according to a single emission peak under lighting by a non-visible light source 14, for example ultraviolet of wavelength equal to 365nm. However, nothing prevents combining different pigments whose absorption spectra may be different, for example a photoluminescent pigment whose absorption spectrum is included in long ultraviolet rays (the non-visible light source being able to emit at a length of wave of around 365nm) and / or a photoluminescent pigment whose absorption spectrum is located in short ultraviolet (the corresponding non-visible light source can emit at an emission wavelength of around 250nm) and / or a photoluminescent pigment whose absorption spectrum is located in the infrared (the corresponding non-visible light source being able to emit at a wavelength of the order of 950nm). The advantage of using photoluminescent pigments having different absorption spectra is to require the use of several different sources of non-visible light to view the image later, which reinforces the protection obtained against falsification.

We have described above the production of a polychromatic photo luminescent image 8 formed by a set of three monochromatic printed images 8a, 8b, 8c. It is possible to make several sets of similar images on the same printing medium 9, from several images of polychromatic origin 1 and / or with photoluminescent pigments visible under lighting by different non-visible light sources (of different wavelengths) and / or of different natures (negative or positive). In particular, it is possible for example to produce a first set of photo luminescent images under ultraviolet with photoluminescent pigments under ultraviolet which form a positive of the original image 1, visible under ultraviolet lighting but invisible under lighting in visible light; and a second set of luminescent photo images under infrared with photoluminescent pigments under infrared which form a negative of the same original image 1, visible under infrared lighting but invisible under visible light lighting. Thus, when viewing the support 9 under lighting by a source of ultraviolet, a positive of the original image 1 appears, while when viewing the support 9 under lighting by a source of infrared, a negative of the original image 1 appears.

Other similar variants are possible. For example, two successive positives can be produced on the same support 9, one visible under ultraviolet, the other under infrared. It is also possible to make more than two reproductions, by printing more than two sets of images, supeφosed or not supeφosed. The number of sets of images that can be assumed is limited by the transparency properties of the different printed layers, and by the number of different excitation light sources available.

The different sets of monochromatic printed images can be printed successively, the two photoluminescent reproductions thus formed being superposed one on the other. On the contrary, as a variant, the monochromatic printed images of the different sets can be nested. For example, you can first print the different monochromatic printed images with green pigments, then the different monochromatic printed images with red pigments, then the different monochromatic printed images with blue pigments.

Preferably, to carry out on the same support 9 two photoluminescent polychromatic reproductions under lighting by two different sources, photoluminescent pigments are chosen whose wavelengths of the emission peaks are at least approximately equal, so as to use the same monochromatic filtered images 6a, 6b, 6c to produce these two photoluminescent reproductions. It suffices to invert these filtered monochromatic images during the preparation of the printing screens to obtain the polychromatic reproductions in positive, and not to carry out this inversion to obtain the polychromatic reproduction in negative.

It should be noted that the emission intensities of pigments with infrared excitation being lower than those of pigments with ultraviolet excitation, the concentration of pigments with infrared excitation must be greater in the printing varnish than that of pigments with infrared excitation under ultraviolet.

In addition, at least one image, known as an infrared image, can be printed with a printing composition comprising at least one pigment, called an infrared pigment, having at least one emission peak wavelength situated in the infrared range. , but no emission in visible light, when this pigment is activated by lighting under a visible light source. Such an infrared image is a monochrome image which will be visible in the infrared range but will remain invisible in the visible light range. On the same support 9, one prints either a single infrared image, or several infrared images juxtaposed or offset (that is to say not supeφosés).

For example, a photoluminescent polychromatic reproduction 8 is produced under ultraviolet or under infrared as indicated above which is a positive reproduction of the original image, then an infrared image which is a negative reproduction of the original image. origin. Alternatively, the infrared image is a positive while the photoluminescent polychromatic reproductions is a negative. The sources of excitation of the pigments being different, nothing even prevents printing on the same printing medium 9 an infrared image in positive or in negative on two polychromatic photoluminescent reproductions 8 supeφosées carried out as indicated above.

To produce an infrared image, a printing composition is used comprising, for example, the varnish reference CD 170 sold by the company RIEDEL DE HAN (Germany). In addition, the reflected image of the original image 1, captured by the CCD3 camera is used without filtering, and the steps of screening, possible inversion, flashing, exposure, revelation and printing are carried out as described above. . To read such an infrared image, the support 9 is illuminated with a visible light source. Preferably, a light source filtered using a spectral band of 40 nm to 100 nm centered on 585 nm is used. We then read the infrared image formed for example by an infrared camera, or a CCD camera via a high-pass filter having a cut-off threshold of 800 nm filtering the light directly coming from the visible light source. of excitement.

The printing support 9 can be a transparent protective film or a transparent film of such a film, so that the image 8 according to the invention is carried by or incoφorated in a protective film. For example, the image 8 according to the invention can be formed inside a transparent protective film as described by EP-0 271 941 or US-5 232 527.

Figures 3 and 4 show an example of application of a transparent protective film 9 carrying a photoluminescent printed polychromatic image 8 according to the invention. This film 9 is applied to part of a face 13 of a document 10 to serve as a means of authentication. The face 13 of the document 10 is coated with an image 11 visible in visible light and with common or variable indications 12 visible by transparency through the film 9 when the latter is illuminated in visible light. As seen in Figure 3 where the document 10 is only illuminated by a visible light source 15, the image 8 carried by the film 9 is not visible in visible light. In fact, image 8 is formed of a transparent composition in visible light, and the photoluminescent pigments do not emit light in visible light. The presence of photoluminescent pigments in image 8 has the consequence in practice, in general, of making it slightly whitish and translucent. In addition, in particular when the monochromatic printed images 8a, 8b, 8c are printed in serigraphy and with mineral pigments, the variations in thicknesses of the patterns of these different images create an opalescence on the surface (represented schematically by dotted lines in FIG. 3) allowing to distinguish certain contours of image 8, but without allowing precise vision of the contours, nor especially of the colors of the polychromatic image.

In the situation represented in FIG. 4, the document 10 is illuminated by a source 14 of non-visible light corresponding to the absorption spectrum of the various photoluminescent pigments of a set of monochromatic printed images 8a, 8b, 8c of image 8. If necessary, several non-visible light sources must be used to excite the photoluminescent pigments of image 8. Thus, the polychromatic image 8 appears in photoluminescent manner with all of its shades of color, identical to the image. of polychromatic origin 1. Photoluminescence also creates a certain decorative and su effetrenant effect, the colors appearing with an unusual brightness and chromatic purity according to the principle of light color. The photoluminescent polychromatic image 8 is superimposed on the mentions 12 carried by the face 13 of the document, which are still visible by transparency through the film 9 and the image 8. The document 10 thus protected may be a passport, a card identity, driver's license, vehicle registration card or other official identification and / or authentication documents, a fiduciary document such as a bank note, check, card or other payment instrument.

The film 9 can be applied to the face 13 of the document 10 of in the traditional way, by means of an adhesive layer, for example by cold dry transfer or hot rolling. The film 9 can itself be an anti-forgery film which can incoφor other authentication marks or prevent its reproduction by optical reading. The transparent image 8 being applied to the document cannot be counterfeited because of the other mentions 12 of the document or of incoφorated mentions in the film 9 which, by combining with image 8, prevent its reproduction by illumination in non-light visible and filtering. The photoluminescent printed polychromatic image 8 also protects the document 10 against any reproduction by optical reading in visible light, for example by photocopying or other. Furthermore, it is possible to combine, on the same document, several images according to the invention. For example, the mentions 12 of the document can themselves be formed at least in part from an image according to the invention printed on the face 13 of the document. In this case, it is advantageous to use pigments different from those of the first image for the second image.

The invention is also applicable purely for decorative or advertising purposes to produce images 8 that are particularly aesthetic and providing a suφrenant effect. Depending on whether the invisible source of light is turned on or off to excite the photoluminescent pigments, image 8 can appear or disappear, intermittently.

EXAMPLE 1:

With the method described above, a photoluminescent polychromatic photoluminescent image under ultraviolet light was printed on a white paper devoid of optical brightener according to the invention from an original four-color printed image formed from a full continuous visible color spectrum. . The mineral pigments CD 144, CD 105 and CD 166 are used. It can be seen that the image according to the invention perfectly reproduces the colored spectrum under illumination in ultraviolet light. EXAMPLE 2:

A four-color A4 printed landscape image is used which is reproduced by a process according to the invention as described above on the free face of a transparent adhesive polyurethane protective film sold by the company FASVER (France) under the name FASPROTEK ®, of corresponding format. This transparent film is then applied to an official document to be protected bearing a pre-printed text. We see that the film does not prevent the reading of the pre-printed text. The screen-printed image forms opalescent reliefs visible at low incidence. It is not visible in visible white light. Under lighting by an ultraviolet lamp, the image appears with all its nuances of colors.

EXAMPLE 3:

With the process described above, the following were printed on the same white paper devoid of optical brightener: - a polychromatic photo luminescent reproduction under ultraviolet reproducing in positive the complete continuous visible color spectrum, with the pigments CD329, CD308 and CD335,

- a photoluminescent polychromatic reproduction under infrared reproducing in negative the complete continuous visible color spectrum, with the pigments red UC6, green UC6, blue UC6,

- an infrared image reproducing in negative the full continuous visible color spectrum, with the pigment CD 170.

Under illumination by an ultraviolet light source, the polychromatic image of the spectrum appears in positive. Under illumination by an infrared light source, the polychromatic image of the spectrum appears in negative. Under visible light lighting, no visible light image appears. Under lighting in visible light filtered at 585 nm and detection in infrared by means of a high pass filter at 800 nm by a CCD camera, an image is observed which is a monochromatic negative of the spectrum. The invention can be the subject of multiple variant embodiments with respect to the embodiments described and shown. In particular, other printing techniques than screen printing can be used, provided that the photoluminescent pigments used are compatible with these printing techniques. Printing can be carried out on a support other than a transparent film 9, and the original polychromatic image 1 can not be a photographic or printed image, but an image previously scanned in a computer system which is printed. for example using a color laser printer to allow its filtering by filters 5, or even that one filters by numerical calculation.

Claims

CLAIMS 1 / - Method for producing an arbitrary photoluminescent printed polychromatic image (8) invisible under lighting in visible light, and visible under lighting by at least one source (14) of non-visible light, in which:

- a polychromatic original image (1) is chosen or produced in subtractive synthesis visible in visible light,

- at least one set of at least three images is produced and recorded, called filtered images (6a, 6b, 6c), by filtering the original image (1), - one prints separately, one after the other and one above the other, at least one set of at least three images, called printed images (8a, 8b, 8c), using and respectively reproducing one of the filtered images ( 6a, 6b, 6c), with a printing composition comprising a photoluminescent pigment, the different photoluminescent pigments of the different printed images of the same set emitting, under lighting by at least one source (14) of non-visible light, colors able to form by additive synthesis all the colors of the visible spectrum, characterized in that:

- the filtered images are produced, called monochromatic filtered images (6a, 6b, 6c), by filtering the original image (1), according to a spectral bandwidth less than or equal to 15nm centered along a wavelength, said filtering wavelength, chosen from the wavelengths of at least three fundamental colors, the different filtering wavelengths of the monochromatic filtered images being two by two distinct, and being adapted to allow formation by synthesis additive all the colors of the visible spectrum, each of these filtering wavelengths being at least approximately equal to a wavelength of an emission peak of a photoluminescent pigment under illumination by at least one source (14) invisible light,

- we print each printed image, called printed image monochromatic (8a, 8b, 8c), using and reproducing one of the monochromatic filtered images (6a, 6b, 6c) with a printing composition comprising a photoluminescent pigment having an emission peak wavelength, under illumination by at least one source (14) of non-visible light, which is at least approximately equal to the filtering wavelength used to obtain said filtered monochromatic image (6a, 6b, 6c).

2 / - Method according to claim 1, characterized in that to produce each of the monochromatic filtered images (6a, 6b, 6c), an original of the original image (1) any polychromatic visible in visible light is illuminated, and the polychromatic image reflected by this illuminated original is filtered, according to a spectral bandwidth less than or equal to 15nm centered according to the filtering wavelength of the fundamental color corresponding to the monochromatic filtered image (6a, 6b, 6c).

3 / - Method according to claim 2, characterized in that the image (1) polychromatic reflected is filtered with monochromator filters (5a, 5b, 5c) having a spectral bandwidth of the order of lOnm -in particular filters (5a, 5b, 5c) interference bandpass.

4 / - Method according to one of claims 1 to 3, characterized in that one chooses, as filter wavelengths and emission peaks of photoluminescent pigments, at least one wavelength in the green, at least one wavelength in red, and at least one wavelength in blue.

5 / - Method according to claim 4, characterized in that the wavelengths are chosen so that they are separated by the same spectral distance between 80nm and lOOnm, in particular equal to 90nm. 6 / - Method according to one of claims 4 or 5, characterized in that a wavelength in the green of between 520 and 570nm is chosen, a wavelength in the red of between 610 and 680nm, and a wavelength in the blue between 430 and 480nm.

II - Method according to one of claims 4 to 6, characterized in what we print the monochromatic printed images (8a, 8b, 8c) so that, in the order of reception of the lighting light, they appear in the blue, red, green wavelength order filtering and emission peaks of photoluminescent pigments. 8 / - Method according to one of claims 1 to 7, characterized in that, to record the monochromatic filtered images (6a, 6b, 6c), the filtered image is captured with photosensitive means (3) of charge transfer CCD, we record a corresponding digitized image, and in that we form, from each monochromatic filtered image, a digitized (7a, 7b, 7c) and rasterized image which has a frame of 60 to 133, and that the we then use to print the monochromatic printed image (8a, 8b, 8c).

9 / - Method according to one of claims 1 to 8, characterized in that one prints the monochromatic printed images (8a, 8b, 8c) at least substantially according to the same printing thickness, and so that the amount of photo luminescent pigment at each point is a function of the light intensity of the original image (1) polychromatic at this point according to the corresponding filtering wavelength, and in that photoluminescent pigments having a factor are used of purity equal to 1.

10 / - Method according to one of claims 1 to 9, characterized in that each monochromatic printed image (8a, 8b, 8c) is allowed to dry and / or harden after having printed it and before printing another image monochromatic print (8a, 8b, 8c).

11 / - Method according to one of claims 1 to 10, characterized in that to produce the same set of monochromatic printed images (8a, 8b, 8c) using photoluminescent pigments under lighting by a single source (14 ) invisible light.

12 / - Method according to one of claims 1 to 10, characterized in that to achieve the same set of monochromatic printed images (8a, 8b, 8c) using at least a first photoluminescent pigment under lighting by at at least a first source of non-visible light, and at least a second photoluminescent pigment under illumination by at least a second source of non-visible light of wavelength (s) distinct from that (s) of the first source of invisible light. 13 / - Method according to one of claims 1 to 12, characterized in that one prints a set of monochromatic printed images (8a, 8b, 8c) which are positive images of an original image (1) , adapted to reproduce in additive synthesis a positive of the original image (1).

14 / - Method according to one of claims 1 to 13, characterized in that one prints a set of monochromatic printed images which are negative images of an original image (1), adapted to reproduce in additive synthesis a negative of the original image (1).

15 / - A method according to claims 13 and 14, characterized in that a first set of positive monochromatic printed images (8a, 8b, 8c) is printed with photolummescent pigments under lighting by a first source of non-visible light - in particular ultraviolet or infrared-, and in that a second set of negative monochromatic printed images (8a, 8b, 8c) is printed with photoluminescent pigments under illumination by a second non-visible light source of wavelength distinct from that from the first non-visible light source - notably infrared or ultraviolet -.

16 / - Method according to claim 15, characterized in that the wavelengths of the emission peaks of the photoluminescent pigments used to print the first set are at least approximately equal to the wavelengths of the emission peaks of the photoluminescent pigments used to print the second set, so that the same monochromatic filtered images (6a, 6b, 6c) can be used to print both sets.

17 / - Method according to one of claims 13 to 16, characterized in that one further prints at least one image, called infrared image, with a printing composition comprising at least one pigment having at least an emission peak wavelength situated in the infrared range but no emission in the visible light range when this pigment is activated by lighting under a visible light source.

18 / - Method according to one of claims 1 to 17, characterized in that, to print each monochromatic printed image (8a, 8b, 8c), a printing composition is used which incorporates a photoluminescent pigment, but which is, at least after drying, transparent or translucent for visible light when it is placed under lighting by the source (14) of non-visible light or by each of the non-visible light sources. 19 / - Method according to one of claims 1 to 18, characterized in that, to print each monochromatic printed image (8a, 8b, 8c), a printing composition is used which, at least after drying, is transparent or translucent for visible light when placed under visible light. 20 / - Method according to one of claims 1 to 19, characterized in that the monochromatic printed images (8a, 8b, 8c) are printed by screen printing, in that a screen printing screen is produced, from each monochromatic filtered image (6a, 6b, 6c), and the various screen printing screens are produced from the same fabric, and in that a printing composition is used formed from a polymerization screen printing varnish under ultraviolet rays.

21 / - Method according to one of claims 1 to 20, characterized in that photoluminescent pigments are used under lighting by at least one source (14) of non-visible light whose spectral composition is located in the ultraviolet range or infrared.

22 / - Any photoluminescent printed polychromatic image invisible under lighting in visible light, and visible under lighting by at least one source (14) of non-visible light, comprising at least one set of at least three images, called printed images (8a, 8b, 8c), printed one on the other above the others, each printed image (8a, 8b, 8c) comprising a photoluminescent pigment emitting a color under lighting by a non-visible light source, the different colors of the printed images (8a, 8b, 8c) of the same set being adapted to be able to form by additive synthesis all the colors of the visible spectrum under lighting by at least one source (14) of non-visible light, characterized in that each printed image, called monochromatic printed image (8a, 8b, 8c) corresponds to the filtering an original image (1) polychromatic in subtractive synthesis visible in visible light, according to a spectral bandwidth less than or equal to 15 nm centered on a wavelength, called filtering wavelength, chosen from the lengths of at least three fundamental colors, the different filtering wavelengths being two by two distinct and adapted to allow all additive synthesis to form urs of the visible spectrum, each of these filtering wavelengths being at least approximately equal to a wavelength of an emission peak of the photoluminescent pigment of the corresponding monochromatic printed image (8a, 8b, 8c).

23 / - polychromatic image according to claim 22, characterized in that it comprises at least one monochromatic printed image (8a) having at least one emission peak wavelength in the green, at least one monochromatic printed image ( 8b) having at least one emission peak wavelength in red, and at least one monochromatic printed image (8c) having at least one emission peak wavelength in blue.

24 / - polychromatic image according to one of claims 22 or 23, characterized in that the wavelengths of the emission peaks of the monochromatic printed images (8a, 8b, 8c) are separated by the same spectral distance between 80nm and 100nm, in particular of the order of 90nm.

25 / - polychromatic image according to one of claims 23 and 24, characterized in that the monochromatic images (8a, 8b, 8c) of the same game follow one another, in the order of reception of the light, in the blue, red, green order of the wavelengths of the emission peaks.

26 / - Polychromatic image according to one of claims 22 to 25, characterized in that the photoluminescent pigments of at least one and the same set of monochromatic printed images (8a, 8b, 8c) emit under illumination by at least one source ( 14) of non-visible light whose spectral composition is located in the ultraviolet or infrared range.

27 / - polychromatic image according to one of claims 22 to 26, characterized in that the various photoluminescent pigments are adapted to present an emission peak wavelength under lighting by one and only one and the same source (14) invisible light.

28 / - polychromatic image according to one of claims 22 to 26, characterized in that it comprises at least a first photoluminescent pigment under lighting by at least a first source of invisible light, and at least a second photoluminescent pigment under lighting by at least one second non-visible light source of wavelength (s) distinct from that (s) of the first non-visible light source.

29 / - Image according to one of claims 22 to 28, characterized in that it comprises a first set of positive monochromatic printed images (8a, 8b, 8c) comprising photoluminescent pigments under lighting by a first non-light source visible - notably ultraviolet or infrared - and suitable for reproducing in additive synthesis, a positive of an original polychromatic image (1), and a second set of negative monochromatic printed images (8a, 8b, 8c) comprising photoluminescent pigments under lighting by a second source of non-visible light of wavelengths distinct from that of the first source of non-visible light - notably infrared or ultraviolet - and adapted to reproduce in additive synthesis, a negative of an original image (1) polychromatic.

30 / - Image according to one of claims 22 to 29, characterized in that it further comprises at least one image, called an infrared image, visible in the infrared range but invisible in the field of visible light under illumination by a visible light source.

31 / - Device for protecting a document comprising at least one transparent protective film (9) making it possible to cover and protect at least a surface portion (13) of a document (10), in which the film (9) comprises at least one image (8) according to one of claims 22 to 30.

32 / - Document -in particular a passport, an identity card, a driving license, a vehicle registration card or other official document of identification and / or authentication, a fiduciary document, a banknote, a check, card or other payment instrument comprising at least one image (8) according to one of claims 22 to 30.

33 / - Document according to claim 32, characterized in that at least one image (8) according to one of claims 22 to 30 is carried by at least one transparent protective film (9) applied to at least one face (13 ) of document (10).