SECURE DOCUMENT AND METHOD FOR MANUFACTURING A SECURE DOCUMENT
The present invention relates to a secure document and to a method for manufacturing a secure document. The secure document comprises: a metal layer or metal oxide layer, a lenticular array comprising converging lenses positioned facing the metal layer or metal oxide layer, at least one transparent layer on which the metal layer or metal oxide layer is arranged such that said metal layer or metal oxide layer is interposed between the lenticular array and the transparent layer; wherein the metal layer or metal oxide layer comprises perforations formed by focusing a plurality of laser radiations through the lenticular array onto the metal layer or metal oxide layer, the plurality of laser radiations being directed at a plurality n of angles of incidence in order to form said perforations so as to reveal n personalized images when the secure document is observed at the n angles of incidence, said perforations being produced in contiguous or overlapping perforation areas so as to form visual continuity between the n personalized images when said document is tilted.
1 . A secure document comprising:
a metal layer or metal oxide layer,
a lenticular array comprising converging lenses positioned facing the metal layer or metal oxide layer,
at least one transparent layer on which the metal layer or metal oxide layer is arranged such that said metal layer or metal oxide layer is interposed between the lenticular array and the transparent layer;
wherein the metal layer or metal oxide layer comprises perforations formed by focusing a plurality of laser radiations through the lenticular array onto the metal layer or metal oxide layer, the plurality of laser radiations being directed at a plurality n of angles of incidence in order to form said perforations so as to reveal n personalized images when the secure document is observed at the n angles of incidence,
said perforations being produced in contiguous or overlapping perforation areas so as to form visual continuity between the n personalized images when said document is tilted.
2 . The document according to claim 1 , wherein the thickness of the metal layer is between 10 and 20 nanometres.
3 . The document according to claim 1 , comprising a black opaque layer under the metal layer, said black layer not being perforated by said plurality of laser radiations.
4 . The document according to claim 3 , wherein the perforations reveal black areas when the metal layer is exposed to incident light through said lenticular array.
5 . The document according to claim 1 , wherein the perforations reveal white areas when the metal layer is exposed to incident light through the transparent layer.
6 . The document according to claim 1 , wherein said metal layer or metal oxide layer comprises one or more areas comprising one or more second metal perforations to allow adhesion between said metal layer and the at least one transparent layer.
7 . The document according to claim 1 , wherein
said lenses are spherical, and
the maximum angle of incidence of said laser beams between the centre of one of said lenses and the radius of the lens is in a range of 14 degrees to 20 degrees,
the number of perforation areas under each lens being between 5 and 7.
8 . The document according to claim 1 , such that the distance d between the centres of two contiguous perforation areas is given by the following formula
d
=
(
λ
2
+
1
)
*
y
in which the pitch x of the displacement of the laser in one direction is equal to λ times the pitch y in the other direction.
9 . A method for manufacturing a secure document, comprising
forming a metal layer on a transparent layer,
positioning a lenticular layer comprising converging lenses, facing the metal layer, the metal layer being interposed between the lenticular array and the transparent layer; and
forming perforations by focusing a plurality of laser radiations through the lenticular array onto the metal layer, the plurality of laser radiations being directed at a plurality n of angles of incidence in order to form said perforations so as to reveal n personalized images when the secure document is observed at the n angles of incidence,
said perforations being produced in contiguous or overlapping perforation areas so as to form visual continuity between the n personalized images when said document is tilted.
10 . The method according to claim 8 , comprising, prior to forming perforations and to lamination-based assembly of said layers, partially destroying the metal layer by way of laser radiation or by way of insolation so as to selectively remove at least portions of the metal layer so as to form demetallized areas in the metal layer.
11 . The method according to claim 7 , wherein said plurality of laser radiations passes through said metal layer in a first direction and in a second direction perpendicular to the first, the pitch x of the displacement of the laser in one direction being equal to λ times the pitch y in the other direction, the minimum diameter d of a perforation for achieving ablation of the width of the pitch being determined by
d =(√{square root over (λ 2 +1)})* y