Laser Marking of Pigment Layers on Documents
A laser markable document material comprises a binder sensitive to laser energy, a pigment interspersed in the binder, and a document substrate. One example of the pigment is a pearlescent silicate, which has optically varying effects. The binder is applied to the document substrate using a form of printing or other means of applying a coating. This coating provides a first indicia of fixed or variable information, such as the seal of the document issuer or personal information of a document bearer. A laser engraver writes a second indicia into the coating.
1 . A laser markable document material comprising:
a binder sensitive to laser energy;
a pigment interspersed in the binder; and
a document substrate, the binder applied to the document substrate.
2 . The material of claim 1 wherein the binder comprise a polymer that carbonizes in response to laser engraving.
3 . The material of claim 2 wherein the laser engraving comprises carbonizing with a YAG laser.
4 . The material of claim 2 wherein the pigment comprises a silicate pigment.
5 . The material of claim 2 wherein the pigment comprises a pearlescent pigment.
6 . The material of claim 2 wherein the pigment comprises an optically variable pigment, wherein the pigment comprises particles that have a structure causing the particles to align substantially along an orientation such that viewing information printed with this pigment shifts when viewed at different viewing angles.
7 . The material of claim 1 wherein a blocking layer is applied over the binder, the blocking layer comprising a material that is substantially opaque to visible light, yet at least partially transparent to non visible light, the binder being marked with laser light through the blocking layer.
8 . The material of claim 1 wherein a laminate is applied over the binder, the binder being marked with laser light through the laminate.
9 . The material of claim 1 wherein the binder comprises a coating.
10 . The material of claim 1 wherein the coating is printed on the substrate.
11 . The material of claim 10 wherein the coating is printed with an offset press.
12 . The material of claim 10 wherein the coating is applied with a gravure press.
13 . The material of claim 10 wherein the coating is applied with a screening process.
14 . A method for marking indicia on a document, the method comprising:
applying a coating of pigment dispersed in a binder; and
laser engraving the coating.
15 . The method of claim 14 including applying the coating to form a first indicia, and laser engraving the coating to form a second indicia within the first indicia.
16 . The method of claim 15 wherein the first indicia comprised fixed information common to documents issued from an issuer, and the second indicia comprises personalized information of a bearer of the document.
17 . The method of claim 15 wherein both the first and second indicia comprise personalized information of a bearer of the document.
18 . The method of claim 14 comprising applying a laminate over the coating, and laser engraving the coating through the laminate.
19 . The method of claim 14 comprising applying a blocking layer over the coating, and laser engraving the coating through the blocking layer, the blocking layer being substantially opaque to visible light.
20 . The method of claim 14 wherein the laser marking forms a variable indicia depicting biometric information of a bearer of the document.
21 . The method of claim 19 wherein the laser engraving forming a variable indicia of personal information of a bearer of the document.
22 . The method of claim 21 wherein the variable indicia of personal information comprises biometric information of the bearer.
23 . A method for authenticating a laser marked document, the laser marked document including a laser marked indicia in a carrier indicia, the method comprising:
illuminating the document with a light source in a band corresponding to optical property of a laser marked indicia in the document;
capturing one or more images of the document, including the laser marked indicia;
analyzing the laser marked indicia and the carrier indicia; and
providing a measure of validity based on the analyzing.
24 . The method of claim 23 wherein the laser marked indicia comprises biometric information of a document bearer, and the analyzing includes comparing the biometric information from the laser marked indicia with biometric information elsewhere on the document.
25 . The method of claim 23 wherein the carrier indicia comprises variable information related to a bearer of the document.