Security document including a laserizable layer and a pattern for illuminating in order to color a grayscale image, and corresponding fabrication and reading methods
A security document may include a laserizable first layer including a grayscale image formed by laserizing; a color pattern that is in alignment with the grayscale image; and a second layer arranged between the first layer and the pattern, such that the first layer is above the second layer, and the pattern is below the second layer. The second layer may be more opaque than the first layer, such that when observing the security document from the top, the grayscale image appears to be colored by the color pattern only when the bottom of the security document is being illuminated.
1. A security document comprising:
a laserizable first layer including a grayscale image formed by laserizing;
a color pattern in alignment with said grayscale image;
a second layer arranged between said laserizable first layer and said color pattern, the laserizable first layer being above the second layer, and said color pattern being below the second layer, the second layer being more opaque than the laserizable first layer, the second layer comprising an additive that adjusts opacity or being covered in printing using an ink filled with the additive; and
a third layer below said color pattern, the third layer being more opaque than the laserizable first layer, the third layer comprising the additive that adjusts opacity or being covered in printing using an ink filled with the additive;
wherein the opacity of the second layer and the opacity of the third layer are such that when observing the security document from a top, said grayscale image appears to be colored by the color pattern only when a bottom of the security document is being illuminated.
2. The security document according to claim 1 , wherein the color pattern includes at least two elements of different colors, and the laserizable first layer is laserized while taking account of the colors of said two elements of different colors.
3. The security document according to claim 2 , wherein the color pattern is a matrix of color pixels, each pixel comprising a plurality of sub-pixels of different colors, and the grayscale image includes grayscale pixels comprising grayscale sub-pixels in alignment with the sub-pixels of different colors in the color pattern.
4. The security document according to claim 1 , including a laserizable fourth layer below said color pattern or below said third layer.
5. The security document according to claim 4 , wherein the laserizable first layer is a window arranged within a fifth layer that is more opaque than the laserizable first layer.
6. The security document according to claim 5 , wherein an additional pattern is formed above said fifth layer.
7. The security document according to claim 1 , wherein an additional pattern is formed below said third layer.
8. The security document according to claim 4 , wherein the laserizable fourth layer includes an additional grayscale image formed by laserizing, wherein the additional grayscale image of the laserizable fourth layer is in alignment with said color pattern.
9. The security document according to claim 8 , wherein the grayscale image of the laserizable first layer is associated with the additional grayscale image of the laserizable fourth layer in such a manner that when observing the security document from the top, a complete colored image appears only when the bottom of the security document is being illuminated.
10. The security document according to claim 1 , wherein the third layer lacks holes.
11. A fabrication method for fabricating a security document, the method comprising:
assembling together a laserizable first layer and a second layer below the laserizable first layer, the second layer being more opaque than the laserizable first layer, the second layer comprising an additive that adjusts opacity or being covered in printing using an ink filled with the additive;
forming a color pattern below the second layer;
assembling a third layer below the color pattern, the third layer being more opaque than the laserizable first layer, the third layer comprising the additive that adjusts opacity or being covered in printing using an ink filled with the additive; and
laserizing a grayscale image within the laserizable first layer, the color pattern being in alignment with said grayscale image;
wherein when observing the security document from a top, said grayscale image appears to be colored by the color pattern only when a bottom of the security document is being illuminated.
12. The fabrication method according to claim 11 , wherein the color pattern is formed by forming a color pattern having at least two elements of different colors, and the laserizable first layer is laserized while taking account of the colors of said two elements of different colors.
13. The fabrication method according to claim 12 , wherein the color pattern is a matrix of color pixels, each pixel comprising a plurality of sub-pixels of different colors, and the grayscale image is formed by laserizing so that it includes grayscale pixels comprising grayscale sub-pixels in alignment with the sub-pixels of different colors in the color pattern.
14. The fabrication method according to claim 11 , wherein a laserizable fourth layer is also assembled below said color pattern or below said third layer.
15. The fabrication method according to claim 14 , wherein the laserizable first layer is a window that is arranged within a fifth layer that is more opaque than the laserizable first layer.
16. The fabrication method according to claim 15 , wherein an additional pattern is formed above said fifth layer.
17. The fabrication method according to claim 11 , wherein an additional pattern is formed below said third layer.
18. The fabrication method according to claim 14 , wherein an additional grayscale image is laserized in the laserizable fourth layer, wherein the additional grayscale image in the laserizable fourth layer is in alignment with said color pattern.
19. The fabrication method according to claim 18 , wherein the grayscale image of the laserizable first layer is associated with the additional grayscale image of the laserizable fourth layer in such a manner that when observing the security document from the top, a complete colored image appears only when the bottom of the security document is being illuminated.
20. The fabrication method according to claim 11 , wherein the laserizable first layer is laserized while the bottom of the security document is being illuminated.
21. A method of reading a security document obtained by the method according to claim 11 , wherein the security document is illuminated from the bottom and the security document is observed from the top.
22. The fabrication method according to claim 11 , wherein the third layer lacks holes.