FR2764314A1 - Security document with integrated authentication system - Google Patents

Abstract

Security document with an authentication comprising a transparent window and a security element, where the security element cannot be photocopied and is located outside the transparent window. The transparent window co-operates with the security element to modify its appearance when viewed across the transparent window. Preferably, the security element is printed with one or more coloured inks and the window has light filtering properties to allow passage of only the wavelength corresponding to the ink colour.

Description

SECURITY DOCUMENT HAVING A MEANS OF AUTHORIZATION
COMPRISING A TRANSPARENT WINDOW
AND A SECURITY ELEMENT
The present invention relates to a security document comprising an authentication means comprising a transparent window and a security element.

 Security document means here documents such as banknotes, checks, lottery tickets, cards, payment vouchers and credit cards. It is more particularly security papers comprising a window of flexible or rigid synthetic material.

 By paper is meant here any sheet obtained by wet using a suspension of natural cellulose fibers and / or synthetic fibers that may contain various fillers and various additives commonly used in paper.

 Australian patent application AU 73 762 describes a security document, in particular a plastic banknote consisting of several layers of laminated plastic film in which a transparent window is formed by omitting to coat the corresponding surface with a layer of opacifying ink for the printability of the ticket.

 In AU 73,762, the security document consists of at least two layers of plastic film and it is intended to incorporate at the transparent window a OvD between the two plastic layers.

 In the international application WO 95/09274 the Applicant has described a security paper comprising a transparent zone. In one embodiment, this paper is obtained by the so-called bi-jet technique in which a first layer of paper is made on a round shape from an aqueous suspension of cellulose fibers, a second layer of paper is produced. on a second round shape, zones of zero thickness are formed respectively on the first and the second layers, by embossing the round-shaped canvases, said round shapes are synchronized perfectly so that the zones of zero thickness of the first layer are perfectly opposite areas of zero thickness of the second layer, is introduced between the layers of a transparent plastic band, the two layers are joined and dried.

 In these two patent applications, the transparent window constitutes a security means said level 1, that is to say, an element that can not be photocopied either because of the insertion of the OVD in the case of the Australian patent application, either because of the difference in material between the window and the rest of the document in the case of the international application.

 In WO 95/09274 it has also been proposed to incorporate at the level of the transparent window security elements such as metal prints, magnetic prints, holograms, prints using conventional ink or ink containing colored pigments, fluorescent pigments, luminescent pigments, photochromic compounds, piezo-optical or piezochromic compounds or any other security element.

 Some security features are said to be Level 2 when they can additionally be authenticated using a simple device. This is the case of micro-prints printed on security documents that can be examined using a magnifying glass of the son-counter type, or prints with an electroluminescent ink that changes luminescence under a particular lighting such as than a Uv lamp.

 An object of the present invention is to provide a security document comprising a level 2 security element whose authentication means are incorporated in the document, thus allowing authentication by the user even without ancillary equipment.

 To do this, the present invention provides a security document comprising an authentication means comprising a transparent window and a security element characterized in that said security element is a non-reproducible copy element, located outside said transparent window , and said transparent window can cooperate with said security element so as to modify the visual appearance of said security element when viewed through said transparent window.

 Thus said transparent window cooperates with said security element by folding the document so as to superpose said window and said security element, or by observing said security element on a first document through a transparent window of a second document. Preferably, said transparent window and said security element are located symmetrically on the security document.

 The use of said transparent window when folding the security document such as the ticket may constitute a tool for visually revealing or modifying an optical characteristic of said document, in particular paper or another window of said document, which is then a Level 2 security usable by the man in the street without using a material external to the ticket.

 By "non-reproducible copy element" is meant that said element can not be reproduced faithfully by commercial photocopiers involving quadrichromic printing with standard base color inks and / or that the degree of optical definition of said copiers is not able to accurately reproduce said security element.

 The security element may be a printed pattern but may also be a solid material such as wire, fibers, boards, hologram, etc. The security element may in particular comprise an optically variable device (OVD) in particular consisting of diffraction gratings.

 When the security element is constituted by a printed area, the printing is carried out with a security ink, that is to say non-reproducible by photocopy with ordinary inks. As security inks are mentioned inks with optical properties that have a different appearance or appearance depending on the composition of the incident light and / or the angle of observation. In particular, inks containing iridescent, fluorescent, luminescent, photochromic, piezo-optical and piezochromic pigments, metameric inks and inks containing optical brighteners are mentioned.

 The security element may also include a printed area with micro-impressions not visible to the naked eye including applied to a material element such as a security thread. Finally, as will be seen later, the security element may also include liquid crystals.

 By "modifying the visual appearance of the security element is meant both a change of shape or a revelation of a printed pattern that a visual impression produced different due to an optical effect such as in particular an effect of The printed pattern can be printed using an ink with optical properties such that it is the visual appearance of the ink that changes and not the printed pattern itself when it is viewed at through said window.

 According to the present invention the security element can be visible to the naked eye and become invisible through the transparent window. The security element may also be invisible to the naked eye and become visible through the transparent window. Finally, the security element can be visible to the naked eye but undergo a modification so as to take on a meaning or change its meaning when seen through the window, especially when it is a motive printed.

 According to a first variant embodiment of the invention, said transparent window is provided with optical properties that make it possible to modify the visual appearance of said security element when viewed through said window.

 In one embodiment of this first variant, said transparent window is provided with light filtering properties. In this case the transparent window can be composed of a film with optical filter properties that can modify the energy curve of the illuminina, in this case daylight.

 According to a first variant of this embodiment, said security element comprises a printed area with an ink of a given color and the filtering properties of the window consist in allowing only the wavelength (s) corresponding to said color.

This means reciprocally that the wavelengths corresponding to the complementary colors of said color in the visible range are eliminated.

 Preferably, the security element comprises a printed area with at least two inks of different colors and the filtering properties of the window are such that the window passes only the wavelength (s) corresponding to one of said colors.

 By "color" is meant here the sensation that the brain receives according to the following elements: object, illuminant, observer. The tri-stimular values characteristic of a color are derived from the sum over the wavelength spectrum of these three elements. Illuminant energy curve, reflectance curve of the object, curve of the ocular filters of the 'observer. By identical colors is meant here that the reflectance curve of the ink object is identical.

 According to a second variant in this embodiment, said security element comprises an area of the document printed with an ink having optical properties so that its visual appearance changes when viewed through said transparent window endowed with Filtration properties.

 In particular, said security element may comprise at least two areas each respectively printed with an ink having different optical properties so that their visual appearance is distinguished when seen through said window.

 By ink with optical properties is meant an ink which has a different rendering or appearance depending on the composition of the incident light and / or the viewing angle.

 More particularly, the security element may comprise an area printed with an ink having a UV-sensitive optical brightener and the filtering property of the window is to not pass UV light radiation.

 Thus, the security element may comprise at least two zones each printed respectively with an ink of the same color in the light of day but one of which has an optical brightener so that through a filter that does not let the light through. UV both areas appear different appearance.

 As inks with optical properties, there may be mentioned metameric inks. In particular, the security element may comprise a zone printed with two metameric inks corresponding to two metamers of colors identical to the naked eye and the light of day, but of different hues when they are seen at through the filter of the transparent window.

Two inks are called metameric when their characteristic tri-stimular coordinates are equal but their remission or reflectance curves are different. Inks of this type have been described by
Legnetti et al. in American Ink Maker July 1995. Metameric inks are "identical" colors under the daylight illuminant but in different colors when viewed through the transparent window filter.

 More particularly, in this case, the filtering properties of the window consist in allowing only wavelengths to pass for which the differences in reflexivity intensity between the two metameric inks are the most important.

 According to another variant of filtration property, the filtration property of said transparent window may consist of passing only the light rays of a restricted range of wavelengths in the visible range, and said security element comprises a printed area using an ink that absorbs only in said restricted range of wavelengths. In this case, said security element is invisible to the naked eye and becomes visible when seen through said window.

 According to a third variant of filtration property, said filtering property of the transparent window consists in allowing only linearly polarized light to pass. In particular, it is possible to use the polariser filters made of synthetic material marketed by POLAROID.

 In this case, said security element may be constituted by a material having undergone irreversible mechanical or thermal stress, which may be especially created in a second transparent window, and said stress being visible through said first polarizing window.

 Said security element may comprise liquid crystals which reveal an irreversible mechanical or thermal stress when viewed through said polarizing window.

 The use of the transparent window which acts as a polarizer in transmissive light makes it possible to visualize, by a particular iridescence effect, the phenomenon of bi-refringence brought by said security element consisting of a zone having undergone an irreversible mechanical or thermal stress. . The mechanical or thermal stress experienced in particular by a film or liquid crystals at this point leads to an orientation of the molecules which modifies the refractive index according to the angle of the light and is at the origin of the birefringence phenomenon. In the same way, a birefringence can be created from an anisotropic transparent film. Anisotropy can also be created by using liquid crystals which are permanently oriented by photo-crosslinking of polymers. Oriented areas create a colorful effect through a polarizing window.

 More generally, said security element may consist of a material with anisotropic optical properties. These materials modify the phase of the incident light, in particular delay the phase, so that said security element changes its appearance when viewed through a so-called polarizing window.

 As materials having anisotropic optical properties, mention is made in particular of liquid crystals which can be applied to an opaque support of the security document or to a second transparent window or to a portion of said first transparent window of the security document.

 SCHATD et al., Described in Day. APPL. PHYS. flight.

34 1995 pages 3240-3249 Part 1. Nos. 6A and pages L764-L767
Part 2, No. 6B and in the patent application EP 689,065 thin films with an optical effect based on liquid crystal polymers. These thin layers called HLPP (Hybrid
Linearly Photopolimerizable Polymers) are likely to be disposed on any substrate. These liquid crystals are oriented and polymerized in the same step and thus record an image formed of points of different orientations may be subsequently revealed with one or two polarizers depending on the case. The so-called HLPP system comprises an orienting layer LPP (Linearly
Polymerizable Process) with an LCP (Liquid Crystal Polymer) optical effect layer. The LPP layer serves only to orient the molecules of the LCP top layer with optical properties. The LPP layer (Linearly polymerizable process) is obtained by crosslinking in particular PVMC under a linearly polarized W illumination which simultaneously aligns and crosslinks the polymer. An oriented LPP film transmits its orientation to a layer of liquid crystal prepolymer (LCP) which is in contact with it. This orientation of the LCP is preserved during the polymerization under UV unpolarized up to thicknesses of several microns. The LPP and LCP combination makes it possible to obtain HLPP (Hybrid linearly photopolymerizable) materials. An image can be recorded by a photolithographic process with UV mask polarized on the LPP thin film. Depending on the thickness and nature of the LCP polymer layer it is possible to obtain phase retardant or polarizer properties. This HLPP technology makes it possible to obtain, by a photolithographic process, an image such as a face photograph or a text having the function of a polarizer of light. It is possible to visualize between two crossed polarizers an image consisting of black and white pixels, for example a symbol, the portrait of a person or a text with the definition of a transmission or viewing photograph with a single polarizer if the complex also includes a complex layer of polarizing HLPP liquid crystal, in transmission or in reflection.

 In one embodiment of the invention, the security element comprises a light phase retarding layer consisting of a complex layer of HLPP crystals in which the LPP orienting layer incorporates the recording of an image.

 The HLPP complex layer may be applied on a light-reflecting support such as a metallized support or on a transparent window, that is to say not necessarily on a reflecting support.

 In the case where the HLPP complex layer incorporating an image is applied to a second transparent window without a reflective support, it can be visualized by transmissive light. If the HLPP complex layer incorporating an LPP orienting layer comprising the recording of an image, is applied alone, this layer is transparent and an image is revealed by its observation through two crossed polarization external polarizers, one on each side of the complex layer HLPP. These crossed external polarizers can be provided for at least one of them by said first transparent polarizing windows of the same security document and another security document.

 When applied to a second transparent window, a film of a complex layer HLPP may also be associated with a polarizing film, the two films being superimposed. If the HLPP complex layer comprises an LPP orienting layer incorporating the recording of an image, the image will be revealed by observation through an outer polarization polarizer. This external polarizer may consist of a said first transparent window of said security document or another security document. It may also be constituted by another polarizing HLPP layer.

 When the HLPP complex layer constituting the security element is applied to a second transparent window, it can also be interposed between two cross-polarized films integrated in the transparent window on either side of the complex layer HLPP. If the complex layer HLPP contains an orienting layer LPP incorporating the recording of an image, this image disappears (becomes black) by observation through a third polarizer outside polarization appropriate. This third external polarizer can be adapted to said first transparent window of said security document or another security document.

 It is also possible to apply two different HLPP layers on either side of a polarizing film constituting a said second transparent window, a different image can thus be revealed by observation through a crossed external polarizer placed below or above above said document at the location of said transparent window, the outer polarizer being constituted by a said first transparent window of said security document or another security document.

 When said HLPP complex layer is applied to a reflective support such as a metallized support, an image is revealed if the HLPP complex layer comprises an LPP orienting layer incorporating the recording of an image, using an outer polarizer completely covering the area so that the ray of incident light and of light reflected on the layer HLPP applied on metallized support passes through said polarizer twice, said polarizer being constituted by the or said first transparent window of the same ticket or another note. In reflection both polarizers must have the same orientation.

 If the complex layer HLPP incorporating the recording of an image is applied on a metallized support combined with an integrated polarizing film, said image appears by observation through an external polarizer interposed between said HLPP layer (on the opposite side to the integrated polarizer film) and the source of light. In this case, said outer polarizer does not necessarily cover the entire area and is not placed between the HLPP complex layer incorporating the recorded image and the observer. Said external polarizer can be integrated on the or said first transparent window of the same bill or another ticket and this external polarizer can be obtained with a polarizing HLPP layer.

 The outer polarizer may also be placed between the reflective support complex layer HLPP and the observer, the incident ray between the light source and the reflective support not traveling through said polarizer.

 Finally, it is possible to apply a HLPP complex layer, an integrated polarizer film, over the HLPP complex layer to the reflective support, in particular metallized, so that if the HLPP layer incorporates the recording of an image, the image disappears by observation. through an outer polarizer, said outer polarizer can be applied to a said first transparent window of the same ticket or another ticket.

 In another variant embodiment of transparent window with optical properties, said transparent window comprises a magnifying glass.

 In a particular embodiment, said magnifying glass is constituted by a holographic embossing. Preferably, said magnifying glass is constituted by a longitudinal holographic embossing consisting of a series of parallel lines on a strip of synthetic material introduced into said embossed document longitudinally with respect to the strip. When the security document is constituted by a security paper, this band can be incorporated between two jets of fibrous structure constituting the paper without the need for tracking and synchronization so that the magnifying glass coincides with the windows provided in the fibrous structure of the paper.

 In this embodiment where the transparent window includes a magnifying glass, suitably the security element is constituted by a micro-printing of a pattern such as a text or a drawing, including a symbol. In this case, an invisible or almost invisible element to the naked eye can become visible through the transparent window.

 According to the second main variant of the present invention, said transparent window does not have intrinsic optical properties. In this case, said transparent window may comprise a first printed pattern and said security element may comprise a second printed pattern. Preferably, the security element reveals a third pattern consisting of a different symbol, text or pattern when viewed through said window, said third pattern resulting from the superposition of said first and second patterns.

 The pattern printed on said transparent window may constitute a complementary frame of a printed frame constituting said security element so that by superposition of the two frames a hidden symbol is revealed.

 The pattern printed on said window may constitute a frame, in particular of parallel lines or concentric circles, identical to a printed frame constituting said security element so that the superposition of the two frames and displacement of one with respect to the another produces a moire effect or a transition from transparent to complete black.

 Said frame may be a frame constituting a diffraction grating.

 In all the embodiments according to the invention, said security element can be included in a second transparent window.

 Suitably the security document according to the invention is a paper document comprising a transparent plastic window, in particular made of polypropylene.

 Preferably, the security document according to the invention consists of a paper obtained by the bi-jet technique comprising two layers of fibrous structure comprising a strip of plastic material interposed between zones of zero thickness which coincide between the two layers of fibrous structure and with said strip so that it is wider than said areas, so as to form said transparent windows.

 Other features and advantages of the present invention will become apparent in light of the detailed examples of embodiments that follow.

Example l
This example illustrates the embodiment of the invention wherein the security element comprises a printed area using a given color ink and the window of the filter characteristics changing the color of the ink.

 The window in the banknote consists of a filter which is a red polyester plastic film sold under the reference 250 of GamColor (w) which allows light transmission beyond 600 mm.

 On the sheet of paper is printed, for example by gravure printing, a drawing composed of points of different sizes and colors. The dots are arranged to form light areas and dark areas as the pattern is viewed through the filter window.

The colors are referenced according to the PANTONE O index
MATCHING SYSTEM 1000 (marketed by the French company
SOCIETE DES ENCRES G. AND P. BRANCHER FRERES).

The colors and their tones after observation through the red filter window are shown in the table below.

<Tb>

COLOR <SEP> DSS <SEP> POINTED <SEP><SEP> Reference <SEP> PANTONE <SEP> s <SEP><SEP> TON <SEP> observed <SEP> at <SEP> through
<tb><SEP> the <SEP> filter
<tb><SEP> Orange <SEP> clear <SEP> 144 <SEP> U <SEP> Gray <SEP> clear
<tb><SEP> Red <SEP> 180 <SEP> U <SEP> Gray <SEP> clear
<tb><SEP> Pink <SEP> 699 <SE> U <SEP> Gray <SEP> clear
<tb><SEP> Brown <SEP> Clear <SEP> 723 <SEP> U <SEP> Gray <SEP> Dark
<tb><SEP> Brown <SEP> dark <SEP> 725 <SEP> U <SEP> Gray <SEP> Dark
<tb><SEP> Green <SEP> dark <SEP> 347 <SEP> U <SEP> Gray <SEP> very <SEP> dark
<tb><SEP> Green <SEP> clear <SEP> 458 <SE> U <SEP> Gray <SEP> Dark
<tb><SEP> Gray <SEP> 415 <SEP> U <SEP> Gray <SEP> Dark
<Tb>
All the tones observed through the filter are monochrome red with shades of intensity called light gray or dark gray, the tone "very dark gray" corresponding in fact to black.

 Thus, the parts composed of light orange, red and pink dots form by observation through the red window, folding said window on the drawing, a light gray area while the parts composed of light brown or dark, light green or dark and of gray form a dark gray area.

 The design can be composed to form a particular pattern when viewed through the filter window. It can also form a particular pattern under direct observation and another pattern, possibly complementary to it by observation through the window.

 This pattern will further authenticate the security document.

The printed area can be a security element in two ways - either using security inks - or the size of the printing dots is thinner
that corresponding to the degree of resolution of the
photocopier.

Example 2
This example illustrates the use of metameric inks.

Example 2 A
Prints were made with two yellow metameric inks and a transparent window was made with filters consisting of the plastic films of the range marketed by GamColor ("), refs 395 or 1565. The inks used had the composition next
Ink A TI02 RL 18 10.4%
Kaolin 4.7
Yellow ARC 29 20 Lead Chromate - PbCrO4 - PbSO4
Yellow G6593 1,6 {Color INDEX PY 34 nO 77603
Yellow GM15 11
Ink B TI02 RL 18 9.5 W
Kaolin 9
Yellow NCG LA 13 DIAZOIC - COLOR INDEX PY NO 20040
Yellow YFD 1128 0.420 DIAZOIC - COLOR INDEX PY 83
TI02 RL 18 72.5
Yellow GM15 0.715 {Lead Chromate - PbCr04 - PbSO4
Yellow G6593 1,135 {Color INDEX PY 34 nO 77603
Ink D
TI02 RL 18 70
Orange 943 0.47 Iron Oxide - Fe203 (Color INDEX PY 42
No. 77492)
Yellow 0.82 DIAZOIC ESOD - (Color INDEX PY 155 - NO no
communicated
Formulation C corresponds to a cream shade which remains the most lemon yellow under a neon-type illuminant.

Formulation D turns red under this same illuminant.

 A security document according to the invention can be produced with a zone printed with these two inks and a transparent window made with a filter film marketed by GamColor under the references 835 to 845.

Example 3
This example illustrates the use of liquid crystals described by the articles of SCHADT et al. already mentioned and in
EP 689,065. Reference will be made to these documents for more details on the realization of the complex layers HLPP and
LCP.

 A paper banknote is made comprising a transparent polypropylene plastic window.

 A film comprising a polarizing single-oriented liquid crystal complex layer HLPP is applied to the transparent window. The window being polarizing, it is slightly colored because a polarizer absorbs any light that is not oriented in its direction of orientation.

A HLPP liquid crystal complex layer comprising the recording of an image is applied to a metal support applied to the bill. When folding the ticket and looking at the second complex layer
HLPP through the window, an image is revealed. Layer
HLPP deposited on the surface of the paper on the metallized reflective medium does not reveal any image until it is viewed through the window. When the polarizer of the transparent window completely covers the area incorporating the recording of an image, the image is revealed because the ray of incident light and of light reflected on the metallized support passes through the polarizing filter twice.

 In a variant of this example, a hidden image is distributed between the transparent window and the reflection patch comprising an HLPP layer. In this case, the window is not only polarizing but the polarizing layer is superimposed on a complex layer incorporating the recording of an image corresponding to a portion of information, while having the same smooth and slightly colored appearance. To see a meaningful full image, we look at the patch through the window once it is properly positioned.

 In another variant, a ticket is made with two transparent windows. A polarizing HLPP complex layer (P1) is applied to the first window and a film with a second phase-retarding HLPP complex layer is provided on the second transparent window comprising recording a superimposed image with a cross polarization complex layer HLPP. (P2) and one or two other same notes are used to reveal the hidden image, by transmitted light observation by superimposing said second window and said first window so that the second complex layer HLPP has the function of delaying the phase is interposed between two polarizing films.

 The LCP layer which is the only one to have optical properties by its thickness (2y m) and the choice of the liquid crystal polymer diacrylate goes, in the zone where the liquid crystal polymers are oriented at 450 with respect to the angle of the light polarized by the filter (P1), delay the latter by 900. The light leaving the LCP layer is therefore in the same orientation as that of the second crossed polarizer P2 and can then reveal a "color" through bright pixels. On the other hand, in the zone where the liquid crystal polymers of the LCP layer are oriented parallel to the light polarized by the filter (P1), there is no phase shift so that the second crossed polarizer (P2) causes an extinction of the light producing black pixels.

Claims (34)

 A security document comprising an authentication means comprising a transparent window and a security element characterized in that said security element is a non-reproducible copy element located outside said transparent window, and said transparent window can cooperate. with said security element so as to modify the visual appearance of said security element when viewed through said transparent window.  2. Security document according to claim 1, characterized in that said transparent window is provided with optical properties which make it possible to modify the visual appearance of said security element when viewed through said window.  3. Security document according to claim 2, characterized in that said transparent window is provided with light filtering properties.  Security document according to claim 3, characterized in that the security element comprises an area printed with an ink of a given color and the filtering properties of the window consist in allowing only the length or lengths of waves corresponding to said color.  5. Security document according to claim 4, characterized in that the security element comprises a printed area with at least two inks of different colors and the filtering properties of the window are such that the window passes only the or the wavelengths corresponding to one of said colors.  6. Security document according to one of claims 1 to 5, characterized in that said security element comprises an area of the document printed with an ink with optical properties so that its visual appearance changes when it is seen through said transparent window.  7. Security document according to claim 6, characterized in that said security element comprises at least two areas each printed respectively with an ink having different optical properties so that their visual appearance is distinguished when viewed through said window.  8. Security document according to claim 6 or 7, characterized in that the security element comprises an area printed with an ink comprising an optical brightener sensitive to UV rays and the filtering properties of the window consist not to let the Uv light rays pass.  9. Security document according to claim 8, characterized in that the security element comprises two zones each printed respectively with an ink of the same color in the light of day but one of which comprises an optical brightener so that Through a filter that does not let the UV ray pass, the two zones appear different in appearance.  10. Security document according to claim 6, characterized in that the security element comprises an area printed with two metameric inks corresponding to two metamers of colors identical to the naked eye and the light of day, but of different hues when viewed through the filter of the transparent window.  11. Security document according to claim 10, characterized in that the filtering properties of the window consist in passing only wavelengths for which the differences in reflectance intensity between the two metamers of the ink are the same. more important.  12. Security document according to claim 4, characterized in that said transparent window consists in passing only the light rays of a restricted range of wavelengths in the visible range, and said security element comprises a zone printed with an ink that absorbs only in said restricted range of wavelengths.  13. Security document according to claim 3, characterized in that the filtering property of the transparent window consists of passing only linearly polarized light.  14. Security document according to claim 13, characterized in that said security element is constituted by a material having undergone irreversible mechanical or thermal stress visible through said first polarizing window.  15. Security document according to claim 13 or 14, characterized in that said security element comprises liquid crystals which reveal an irreversible mechanical or thermal stress when viewed through a said polarizing transparent window.  Security document according to claim 13, characterized in that said security element consists of an anisotropic material having optical properties which modify the phase of the incident light so that said security element changes its appearance when it is seen through said polarizing window.  17. Security document according to claim 16, characterized in that the security element comprises liquid crystals.  18. Security document according to claim 17, characterized in that the security element comprises a phase-retarding layer consisting of HLPP crystals in which the LPP orienting layer incorporates the recording of an image.  19. Security document according to claim 18, characterized in that the security element comprises a said layer of crystals HLPP and an integrated polarizer film, superimposed.  20. Security document according to claim 18, characterized in that the security element comprises a said HLPP crystal layer and two integrated polarizer films, on either side of said HLPP layer.  21. Security document according to one of claims 19 or 20, characterized in that said HLPP crystal layer and optionally an integrated polarizer film are applied on a light reflecting medium.  22. Security document according to one of claims 18 to 20, characterized in that the security element comprises a said HLPP crystal layer and optionally one or two integrated polarizers, applied on a second transparent window.  23. Security document according to one of claims 16 to 22, characterized in that the polarizing window consists of a window comprising a polarizing liquid crystal layer HLPP.  24. Security document according to claim 23, characterized in that the polarizing window further comprises a HLPP layer incorporating a recorded image.  25. Security document according to claim 1 or 2, characterized in that said transparent window comprises a magnifying glass.  26. Security document according to claim 25, characterized in that said magnifying glass is constituted by a longitudinal holographic embossing on a strip of a plastic film introduced into the document, said embossing consisting of a series of longitudinal parallel lines relative to each other. to the said band.  27. Security document according to claim 25 or 26, characterized in that the security element is constituted by a micro-printing of a pattern invisible or almost invisible to the naked eye.  28. Security document according to claim 1, characterized in that said transparent window comprises a first printed pattern, and said security element comprises a second printed pattern.  29. Security document according to claim 28, characterized in that the security element reveals a third motif consisting of a symbol, text or different drawing when seen through said window, said third pattern resulting from the superposition of said first and second reasons.  30. Security document according to claim 28, characterized in that the pattern printed on said transparent window constitutes a complementary frame of a printed frame constituting said security element so that by the superposition of the two frames, a hidden symbol be revealed.  31. Security document according to claim 30, characterized in that the pattern printed on said window is a frame in particular of parallel lines or concentric circles, identical to a printed frame constituting said security element so that the superposition of the two frames and displacement of one relative to the other produce a phenomenon of moiré or a transition from transparent to complete black.  32. Security document according to one of claims 1 to 31, characterized in that said security element is included in a second transparent window.  33. Security document according to one of claims 1 to 32, characterized in that it is a paper document comprising at least one transparent plastic window.  34. Security document according to claim 33, characterized in that it consists of a paper obtained by the twin jet technique comprising two layers of fibrous structure comprising a strip of plastic material interposed between zones of zero thickness which coincide between the two layers of fibrous structure and with said strip, the latter being wider than said zones, so as to form said transparent windows.