CA2933450C

CA2933450C - Optically variable printed feature for security documents

Info

Publication number: CA2933450C
Application number: CA2933450A
Authority: CA
Inventors: Thivaharan Thurailingam; Keith GOW
Original assignee: Canadian Bank Note Co Ltd
Current assignee: Canadian Bank Note Co Ltd
Priority date: 2014-01-14
Filing date: 2015-01-14
Publication date: 2021-06-01
Anticipated expiration: 2035-01-14
Also published as: WO2015106352A1; CA2933450A1

Abstract

The invention provides an optically variable printed feature for security documents providing a kinetic appearance of a moving image, optionally with colour shifting, as one views the feature from different angles. A plurality of substantially parallel lines (and/or line segments) are printed on a front surface of a transparent substrate and a corresponding plurality of substantially parallel lines (and/or line segments) are printed on the back surface, located in at least near perfect registration to form sets of lines, each set comprising a predetermined pattern of at least one front surface printed line and at least one back surface printed line. The image of the optically variable feature is defined by a plurality of image pixels each of which comprises a predetermined area of the substrate extending from the front surface to the back surface of the substrate and comprising one set of the predetermined pattern of lines.

Description

2 OPTICALLY VARIABLE PRINTED FEATURE
FOR SECURITY DOCUMENTS
FIELD OF THE INVENTION
[0001] The invention relates generally to a security feature for printed products. In particular, the present invention provides a printed product and method of image layering to produce an optically variable, i.e. kinetic, "moving image"
effect, for use in printed security documents including but not limited to driver's licenses, passports, and banknotes.
SUMMARY OF THE INVENTION
[0002] The present invention provides an optically variable printed feature for security documents providing a kinetic appearance of a moving image, optionally with colour shifting, as one views the feature from different angles.

[0003] According to one aspect of the invention, a security document comprises a substrate of which at least a part comprises an optically variable printed feature and is at least semi-transparent over a thickness from a front surface to a back surface of the substrate. The optically variable printed feature comprises a plurality of substantially parallel lines and/or line segments printed on the front surface and a corresponding plurality of substantially parallel lines and/or line segments printed on the back surface. The lines and/or line segments on the back surface relative to the lines and/or line segments on the front surface are located in at least near perfect registration to form sets of lines and/or line segments, each set comprising a predetermined pattern of at least one of the front surface printed lines and/or line segments and at least one of the back surface printed lines and/or line segments.
The thickness of the substrate relative to the line widths is selected such that the optically variable printed feature becomes visible upon viewing the substrate part from one angle to a different angle above the front surface.

[0004] According to another aspect of the invention a method of making a security document having an optically variable security feature is provided. A
plurality of substantially parallel lines and/or line segments are printed on a front surface of at least a part of a substrate which is at least semi-transparent over a thickness extending from the front surface to a back surface of the substrate part. A
corresponding plurality of substantially parallel lines and/or line segments are printed on the back surface of the substrate part. The lines and/or line segments on the back surface are located in at least near perfect registration relative to the lines and/or line segments on the front surface to form sets of lines and/or line segments, wherein each set comprises a predetermined pattern of at least one of the front surface printed lines and/or line segments and at least one of the back surface printed lines and/or line segments. The line widths and the thickness of the substrate part relative to the line widths are selected so that the optically variable printed feature becomes visible when the substrate part is viewed from one angle to a different angle above the front surface.

[0005] The optically variable printed feature of the security document comprises an image defined by a plurality of image pixels. Each image pixel comprises a predetermined area of the substrate extending from the front surface to the back surface of the substrate, and one the set of the predetermined pattern of lines and/or line segments.

[0006] The line(s) and/or line segments of the predetermined pattern may comprise different colours whereby the optically variable feature comprises colour shifting.

[0007] In an exemplary embodiment the predetermined pattern of printed lines and/or line segments comprise at least a 2 x 2 pattern comprising two of the front surface printed lines and/or line segments and two of the back surface printed lines and/or line segments, each the printed line comprising a different colour, the optically variable feature comprising colour shifting.

[0008] Preferably, the front surface printed lines and/or line segments are at least semi-transparent. The front surface and back surface printed lines and/or line segments may be angled up to 2 degrees relative to each other. The lines and/or line segments have a width of between 30-90 pm and the thickness of the substrate is between 25-850 pm.

[0009] The substrate comprising the front surface and back surface printed lines and/or line segments may be provided as an intermediary layer located in a composite substrate comprising multiple layers.

[00010] A layer of lenticular lenses configured and arranged for enhancing the optically variable printed feature may be provided.

[00011] Preferably, the front surface and the back surface printed lines and/or line segments are printed simultaneously using a Giori Simultan press.

[00012] Further features and advantages of the invention will be apparent from the detailed description which follows together with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS

[00013] A better understanding of the invention will be obtained by considering the detailed description below, with reference to the following drawings.

[00014] Figure 1 is a side angle, enlarged perspective view of a part of an exemplary security document substrate comprising an optically variable printed feature depicting a maple leaf image in accordance with the invention and a lens layer there over for enhancing and magnifying the optical effect.

[00015] Figure 2 is a side angle, enlarged perspective view of a part of a different exemplary security document substrate comprising an optically variable printed feature which includes a phase shifted image of a maple leaf in accordance with the invention (a lens layer is not included in this embodiment).

[00016] Figure 3 is a side view of an expanded part of another exemplary security document substrate comprising an optically variable printed feature, illustrating a visual effect when viewed from different side angles above the substrate when light impinges upon a substrate surface.

[00017] Figure 4 is an exploded view of an exemplary security document substrate comprising multiple substrate layers that are combined to form the security document substrate, wherein the second substrate layer from the front comprises an optically variable printed feature in accordance with the invention.

[00018] Figure 5 is an enlarged side view of a part of a further exemplary security document substrate comprising an optically variable printed feature in accordance with the invention and a front lens layer there over, showing sets of four print lines of different colours below each lens of the lens layer, each set having two lines of different colours printed on the front surface and two lines of different colours printed between them on the back surface.

[00019] Figure 6 is a side angle perspective view of an exemplary banknote in a folded over configuration, the lower part of the banknote comprising an optically variable printed feature in accordance with the invention and the upper folded over part of the banknote comprising a lens for use to improve the visibility of the optically variable feature, and an exploded view "A" of the part of the substrate comprising the optically variable printed feature.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[00020] The invention provides a product in the form of a security document, including but not limited to driver's licenses, passports, banknotes and other secure instruments, comprising an optically variable feature 10 printed on a transparent or semi-transparent substrate 20 of the product, and a method for making the product.

[00021] Exemplary embodiments of the product are illustrated by the drawings of which Figure 1 shows a part of an exemplary security document substrate 20 having an optically variable printed feature 10 comprising printed front surface lines 40 and printed back surface lines 60 each set of lines 40, 60 forming a part of a visible image, being a maple leaf in this example, and having a lens layer 100 there over for magnifying the variable optical effect of feature 10. As shown, the lines 60 printed on the back surface 24 of the substrate 20 are located directly below the spaces between the lines 40 on the front surface 22 such that, if combined together in a single plane, there would be no spaces (or smaller spaces) between the lines 40, 60 and, together, the lines 40, 60 would form the whole of the distinct image.
The distance between the front and back surface lines 40, 60 corresponding to the thickness of the substrate 20, relative to the widths of those lines 40, 60, produces a parallax effect which causes the optically variable printed feature 10, being an appearance of movement of the visible image, to become visible to a viewer upon viewing the substrate from different angles above the front surface 22.

[00022] The printed lines 40 and 60 include a very large number of very thin, precisely printed lines, arranged according any one of different predetermined patterns on a pixel-by-pixel basis. Due to their thinness, in the order of tens of microns, the discrete lines are not apparent when one views the feature 10 and, instead, the viewer sees a macro-image formed by the combination of the front and back printed line patterns 40, 60 (the lines shown in the drawing are depicted in an exaggerated large form for purposes of illustration only). The printed lines 40 and 60 may be of different colours as shown in this example of which lines 40a are blue, lines 40b are red, lines 60a are green and lines 60b are yellow, in which case the optical variable feature 10 includes a visible colour shifting effect when viewed from different angles. For example, when one views the printed feature 10 at an angle of -45 degrees from the vertical the image of the maple leaf appears to the viewer to be blue, but then when the viewing angle is moved to +45 degrees from the vertical the apparent colour of the maple leaf image, to the viewer, changes from blue to red.

[00023] As will be understood by the skilled reader, while continuous printed lines are depicted in the drawings of the exemplary embodiments herein to illustrate the optically variable feature of the invention, it is not necessary that continuous lines be used. Rather, line segments, including dashes, dots and other elements providing in combination an appearance of a line, may be printed on the substrate as described instead of continuous lines. Throughout this description the term "lines" is intended to refer to both continuous lines and such line segments.

[00024] Figure 2 shows a part of another exemplary security document substrate having a different optically variable printed feature 10 comprising printed front 40 and back 60 surface lines, coloured as in the example of Figure 1, of which the front lines 40 (only) form a distinct embedded image (viz, in this example a maple leaf) and excluding the lens layer 100 which, though preferred to enhance the visual effect of the optical variable feature 10, is not required in order for the optical effect of the feature 10 to be visible.

[00025] To produce the optically variable feature 10 each pixel of the image of the feature must include a set of front and back printed lines 40 and 60. The front and back printed lines must be printed in perfect or near perfect registration in order to ensure they fall within the area of one image pixel and thereby define the pixel image. Within each pixel, the printed lines are parallel or substantially (i.e. near) parallel, with parallel lines producing a greater optical effect (e.g. if different coloured lines are use, the strongest colour shift effect). If non-parallel and too much tilt is present, an undesirable Moir_ effect will be produced. Non-parallel lines, tilting relative to each other up to 1 or 2 degrees may produce an acceptable optically variable feature depending upon the application.

[00026] The part of the substrate 20 comprising the optically variable feature 10 is transparent or at least semi-transparent over the thickness of the substrate from the front surface 22 to the back surface 24 so that light impinging on those surfaces produces varying levels of absorbed and reflected light depending on the impinged surface whereby, in the area of the printed optically variable feature 10, these levels are determined by the grey scale level or colour of the printed lines 40, 60.
Figure 3 illustrates a reflected light effect of light (L) passing through the front surface spaces (i.e. between print lines 40) onto the back print lines 60, impinging on the printed substrate surfaces, to appear as lines 1 and 3 when viewed from different side angles ( e from the vertical) above the substrate and produce the optically variable visual effect.

[00027] In these embodiments, the inks used to print at least the front surface lines 40 are semi-transparent so light will pass from at least the front of the printed feature though both the ink of the printed lines 40 and the spaces between them, the light passing though the ink being filtered in a manner which depends on the color of the ink. The filtered light interacts with the printed lines 60 on the back surface 22 and some gets absorbed, some reflects back and gets transmitted. Where the feature is incorporated into a window portion of a product, being substantially transparent throughout, light will also from the back of the printed feature 10. The differing degrees of absorption/reflection/transmission, depending on the grey scale level or colour of the printed lines 40, 60 and the angle from which the printed feature 10 is viewed, produces a visible optically variable (i.e. kinetic or moving image) effect when the substrate is viewed from one angle to another, and this which includes a color shifting effect where the lines 40, 60 are of different colours.

[00028] The substrate 20 is comprised of a material that is either transparent or semi-transparent and is capable of accepting printing such as polycarbonate, polyester, polypropylene, and other similar materials. It may be formed as a single layer or as multiple layers, as illustrated by Figure 4 which shows an exploded view of an exemplary security document substrate 20 comprising multiple substrate layers that are combined to form the security document substrate 20. In this example, the second substrate layer 20a from the front comprises an optically variable printed feature 10, comprising back and front print lines 40, 60, in accordance with the invention. Substrate layer 20a is a non-laser-engravable (nLE) material of 250 pm thickness, while the other substrate layers vary in thickness from 100 ¨ 150 pm and each of the outer layers is laser-engravable (LE). In at least the area of the optically variable feature 10 all of the layers making up the substrate 20, must be substantially transparent (i.e. transparent or semi-transparent).

[00029] The visual effect of the optically variable feature 10 may be enhanced through the addition of a lenticular lens layer 100 above the substrate layer 20 on which the lines 40, 60 of the optically variable feature 10 are printed, as illustrated by Figures 1 and 5. Such a lens layer 100 is comprised of lenticular lenses or equipped with lenticular lenses on its upper surface. As shown in Figure 5, each of the lenses 110 is oriented parallel to the printed lines 40, 60. To obtain an optimal visual effect, the distance between the upper surface of the lens layer 100 and the center of the substrate layer 20 should be approximately equal to the focal length of the lenticular lenses.

[00030] The embodiment of Figure 5 uses a preferred 2x2 line pattern whereby each image pixel comprises 2 front lines 40a,b and 2 back lines 60a,b. Four different colours are used for each set of pixel lines, namely, line 40a is blue, line 40b is red, line 60a is green and line 60b is yellow. The width of each line 40a,b, 60a,b is 90 pm so the pixel size is 360 pm (i.e. 4 x 90 pm) and all four lines must be printed, including any desired adjustment to thickness such as to incorporate a phase shifted image (e.g. the maple leaf in Figure 2) and/or angle, within that pixel size on the substrate. As illustrated, each lens 100 has a diameter corresponding to the width of each set of 4 lines i.e. to each image pixel.

[00031] As stated, the optically variable feature 10 depicted in each of Figures 1, 2, and 6 comprises a number of sets of four lines of different colours, each arranged in a predetermined pattern whereby two of the line colours are printed on the front surface 22 of the substrate 20 with the other two line colours are printed on the back surface 24 of the substrate 20. For each set of four print lines, the lines printed on the front surface must be parallel to each other and the lines printed on the back surface must also be parallel to each other. The lines printed on the front surface are not required to be parallel to the sets of lines printed on the back surface and may be angled at 1 or 2 degrees, or they may be parallel. The two front surface lines and the two back surface lines of each set of four coloured lines must be printed in perfect or near perfect registration so that they are perfectly spaced relative to each other. As such these line sets of four lines there may be printed according to either of two predetermined patterns, namely, either the 2 sets of lines are butted side by side or they are evenly spaced. That is, on the front surface a pattern of line, line, space, space is printed, or a pattern of line, space, line, space and, on the back surface a pattern of space, space, line, line is printed, or a pattern of space, line, space, line, respectively.

[00032] The transparent or semi-transparent substrate layer 20 has a thickness in the range of 25 to 850 pm. To obtain an optimal visual effect, the width of the lines 40, 60 printed on both the upper and the lower surfaces should be the same.
However, while not optimal some kinetic visual effect will be obtained using lines of different widths, the back lines 60 of the embodiment shown by Figure 3 illustrating an example of such different widths, the back lines 60 having a smaller width than the front lines 40. While the width of the lines is limited only by the size of the medium, it has been found that using a line width between 30 to 90 pm produces a high quality visual effect, with a strong flip effect (colour shift) where different front and back line colours are used, while at the same time keeping the visibility of the line arrangement (as opposed to the macro image created by the line combination as a whole). If desired, lines with angles of 1 or 2 degrees, preferably between 0 ¨
1.124 may be used to increase the rainbow, or sweeping, effect of the feature 10.
To do so, either of the front surface lines, or back surface lines, may be printed at such an angle relative to the other line.

[00033] Various technologies may be utilized in the printing of the lines 40, 60. For the illustrated embodiments a Giori Simultan press was used to print the front surface and back surface lines simultaneously with very high resolution and having a width as small as 20 pm. This type of press, provided by the manufacturers KOMORI Corporation (i.e. its LT-83211A product) and KBA-NotaSys SA (i.e. its Simultan product), is able to print as many as four different colours of lines with perfect registration of the front and back printing on a pixel-by-pixel basis.
Referring to the embodiment of Figure 5, having a 2 x 2 print pattern of four print lines per pixel, this means that for each image pixel the two back surface lines 60 is/are precisely located directly below the space between the two front surface lines 40.

[00034] Any type of ink may be utilized for the printing of the lines 40, 60 including invisible fluorescent inks. However, an optimal kinetic effect results when visible, semi-transparent ink is used whereby the transparency of the printed lines acts as filter for light. The best results are typically achieved through the use of visible inks mostly made up of organic pigments. Inks made up of organic pigments usually have better transparency (lower optical density) and produce a better color shifting effect. However, metallic pigment having a high optical density may also produce an acceptable kinetic effect depending upon the image design and application.

[00035] As a result of many tests run by the applicant to test embodiments of the printed optical variable feature of the invention a Giori Simultan Press was chosen for printing the feature lines because it enables the back surface lines 60 to be printed in perfect registration with the front surface lines 40. Due to the mechanical nature of a normal offset press, if such a press is used to print the front surface and back surface lines over two passes an undesirable pixel migration may occur whereby the printing on the second pass migrates towards the next pixel. Since the Giori Simultan type, common blanket, presses are only available for security printers, counterfeiting will be difficult.

[00036] Various implementations of the invention included the following specifications:
Press: Giori Simultan offset press Plates: (Dry plates) P1SD1 ¨ Mounted at the front of the press P2SD1 ¨ Mounted at the front of the press P1SD2 ¨ Mounted at the back of the press P2SD2 ¨ Mounted at the back of the press Line work: (Thicker and thinner background/ Regular and thicker relief) 1 front surface line/1 back surface line (1 x 1) 1 front surface line/2 back surface lines (1 x 2) 2 front surface lines/2 back surface line (2 x 2) 2/2 Even /Odd 2/2 Line Pair 2/2 Criss Cross Concentric Circles Substrates:
Bayer Clear 100um LE (14179) Bayer Clear 150um LE (14180) Sabic Clear 250um nLE (15711) Sabic Clear 375um nLE (15254) Inks:
Metallic Inks Invisible Fluorescent Inks Silver 877 Invisible Blue 9455 Gold 871 Invisible Red 9025 Invisible Yellow 9960 Invisible Green 9475 Standard Inks Standard Inks with 10% TiO2 5853 Blue 5853 Blue + 10% TiO2 Red 1853 Red 1853 + 10% TiO2 Yellow 3853 Yellow 3853 + 10% TiO2 Green 4853 Green 4853 + 10% TiO2

[00037] Tests conducted by the applicant using standard lithographic inks, with and without Ti02, printed over 250 pm polycarbonate substrate sheets showed strong kinetic effects. The tests also demonstrated that the greater the distance between the front and back surface lines (i.e. the greater the thickness of the substrate layer upon which they are printed) the stronger the parallax effect and, in turn, the greater the kinetic effect and, where different colours are used for the lines of the two print levels, the better the colour shifting effect. While many combinations of line arrangements achieve the desired result, arrangements of at least 2 x 2 parallel lines and odd/even lines were found to provide an optimal color shift. Lines of 30 to 90 pm width provide a strong flip effect while at the same time keeping the visibility of the lines minimal. The kinetic color shifting effect can also be further enhanced by utilizing lighter back surface lines, as compared to the use of a darker lines.

[00038] The optically variable feature 10 of the invention can also be utilized to enhance the security of banknotes as illustrated by the embodiment shown in Figure 6. In this embodiment, a banknote 200 includes a transparent and/or semi-transparent window, shown by the exploded view "A" included in Figure 6 comprising a transparent or semi-transparent substrate 20. The front 40 and back 60 surface print lines of the feature 10 are applied to the substrate 10 by either the banknote printer or the substrate manufacturer. The registration between the front set of lines 40 to the back set of lines 60 should be perfect or near perfect to avoid an undesirable Moir_ effect. For this banknote application, applying a lens layer directly over the printed line pattern of the feature 10, although possible, may be too costly so, instead, a lenticular lens layer 100 is provided on a second transparent or semi-transparent window by the substrate manufacturer during the process of manufacturing the substrate. In use, to authenticate the feature, the user folds over the banknote as shown by Figure 6 so that the lenses of the lens layer 100 are placed over and in front of the printed optically variable feature 10, to verify the genuineness of the banknote 200 by determining a kinetic effect, and colour shifting effect if the feature 10 uses colour, upon viewing the feature 10 from different angles.

[00039] As will be recognized by persons skilled in the art, many other combinations and materials will yield similar results and are within the scope of this invention, and the invention is not limited to any particular substrate (which may be of various thicknesses an appropriately selected by the skilled person for a given application), combination or arrangement of print lines (which may include embedded images of any form) or type of ink and/or ink colours.

[00040] Although various exemplary embodiments of the invention have been disclosed, it is to be understood that various changes and modifications can be made to achieve the invention without departing from the scope thereof, which is defined by the appended claims.

Claims

What is claimed is:

1. A security document comprising a substrate of which at least a part comprises an optically variable printed feature, said part of said substrate being at least semi-transparent over a thickness from a front surface to a back surface of said substrate, said optically variable printed feature comprising a plurality of substantially parallel lines and/or line segments printed on said front surface and a corresponding plurality of substantially parallel lines and/or line segments printed on said back surface, wherein said lines and/or line segments on said back surface relative to said lines and/or line segments on said front surface are located in at least near perfect registration to form sets of lines and/or line segments, each set comprising a predetermined pattern of at least one of said front surface printed lines and/or line segments and at least one of said back surface printed lines and/or line segments, said thickness of said substrate relative to said line widths selected such that said optically variable printed feature becomes visible upon viewing said substrate part from one angle to a different angle above said front surface.

2. A security document according to claim 1 wherein said optically variable printed feature comprises an image defined by a plurality of image pixels, each said image pixel comprising a predetermined area of said substrate extending from the front surface to the back surface of said substrate, and comprising one said set of said predetermined pattern of lines and/or line segments.

3. A security document according to claim 2 wherein said line(s) and/or line segments of said predetermined pattern comprise different colours, said optically variable feature comprising colour shifting.

4. A security document according to claim 2 wherein said predetermined pattern of printed lines and/or line segments comprises at least a 2 x 2 pattern comprising two of said front surface printed lines and/or line segments and two of said back surface printed lines and/or line segments, each said printed line and/line segments comprising a different colour, said optically variable feature comprising colour shifting.

5. A security document according to claim 4 wherein at least said front surface printed lines and/or line segments are at least semi-transparent.

6. A security document according to claim 2 wherein said front surface and back surface printed lines and/or line segments are angled up to 2 degrees relative to each other.

7. A security document according to claim 1 wherein said lines and/or line segments have a width of between 30-90 pm and said thickness of said substrate is between 25-850 pm.

8. A security document according to claim 1 wherein said substrate comprising said front surface and back surface printed lines and/or line segments is an intermediary layer located in a composite substrate comprising multiple layers.

9. A security document according to claim 2 comprising a layer of lenticular lenses configured and arranged for enhancing said optically variable printed feature.

10. A method of making a security document having an optically variable security feature, said method comprising:
(a) printing a plurality of substantially parallel lines and/or line segments on a front surface of at least a part of a substrate which is at least semi-transparent over a thickness extending from said front surface to a back surface of said substrate part;
and, (b) printing a corresponding plurality of substantially parallel lines and/or line segments on said back surface of said substrate part, said lines and/or line segments on said back surface located in at least near perfect registration relative to said lines and/or line segments on said front surface to form sets of lines and/or line segments wherein each set comprises a predetermined pattern of at least one of said front surface printed lines and/or line segments and at least one of said back surface printed lines and/or line segments;
wherein said line widths and said thickness of said substrate part relative to said line widths are selected so that said optically variable printed feature becomes visible when said substrate part is viewed from one angle to a different angle above said front surface.

11. A method according to claim 10 wherein said optically variable printed feature comprises an image defined by a plurality of image pixels, each said image pixel comprising one said set of lines and/or line segments located within a predetermined area of said substrate extending from the front surface to the back surface of said substrate, and comprising one said set of said predetermined pattern of lines and/or line segments.

12. A method according claim 11 wherein said front surface and said back surface printed lines and/or line segments are printed simultaneously.

13. A method according to claim 12 wherein said printed lines and/or line segments are printed by a Giori Simultan press.

14. A method according to claim 11 wherein said line(s) and/or line segments of said predetermined pattern comprise different colours, said optically variable feature comprising colour shifting.

15. A method according to claim 11 wherein said predetermined pattern of printed lines and/or line segments comprises at least a 2 x 2 pattern comprising two of said front surface printed lines and/or line segments and two of said back surface printed lines and/or line segments, each said printed line and/or line segments comprising a different colour, said optically variable feature comprising colour shifting.

16. A method according to claim 15 wherein at least said front surface printed lines and/or line segments are at least semi-transparent.

17. A method according to claim 16, wherein said front surface and back surface printed lines and/or line segments are angled up to 2 degrees relative to each other.

18. A method according to claim 11 wherein said lines and/or line segments have a width of between 30-90 µm and said thickness of said substrate is between µm.

19. A method according to claim 11 comprising incorporating said substrate comprising said front surface and back surface printed lines and/or line segments as an intermediary layer of a composite substrate comprising multiple layers.

20. A method according to claim 11 comprising providing said security document with a layer of lenticular lenses configured and arranged for enhancing said optically variable printed feature.