Patent ID: 7968173

Claim:
A printable security paper comprising: a first paper portion which is a vellum part having a first paper thickness defined between a front side and a reverse side of said paper, a second paper portion which is a continuous screened region capable of receiving printed indicia on a front side and on a reverse side of said screened region which are observable in reflected light and form an image observable in transmitted light, as security element protecting against two-sided copying, wherein the screened region has an average overall opacity less than an opacity of the vellum part of the paper, said screened region consisting of alternations of (i) vellum paper miniregions, having an approximately constant paper thickness defined between the front side and the reverse side of the paper and equal to the first paper thickness of the vellum part of the paper, and (ii) reduced opacity paper miniregions, having a smaller paper thickness defined between the front side and the reverse side of the paper, as compared to the vellum paper miniregions, said paper miniregions being of reduced opacity because of their smaller thickness as compared to the vellum paper miniregions, and printed indicia on the front side and on the reverse side of the screened region of said security paper, wherein these indicia form patterns that are observed in reflected light and said patterns make up a final representation that is observed in transmitted light through said screened paper region.