METHOD FOR MAKING WINDOW, EMBEDDED WATERMARK AND OTHER INTEGRATED SECURITY FEATURES IN A THERMOPLASTIC SECURITY DOCUMENT

Abstract

The present invention provides improved methods for making a multiple layer thermoplastic security document having a window using CO.sub.2 laser cutting and engraving in combination with a vision system for precision registration of cut windows of each layer and layer to layer registration and further provides application and registration of security features between layers within the security document body including an embedded gray scale watermark.

Claims

1. A method of making a multiple layer thermoplastic security document comprising a window using CO.sub.2 laser cutting and engraving in combination with vision system, the method comprising laser cutting windows in layers and registering the window with predetermined printed and/or marked/etched matter on the layering using the vision system, each layer further comprising one or more registration pin holes formed by laser cutting the layer in a predetermined location of the layer by vision registering the registration pin hole with preselected printed matter of the layer using the vision system; aligning the layers on a tack table by mounting each layer to match the registration pin holes of the layer to corresponding registration pins of the tack table to resist axial movement of the layer; heat tacking the layers together in register; pinning the heat tacked layers to a lamination plate using the registration pin holes; and, laminating the layers together.

2. A multiple layer laminated thermoplastic security document formed by the method of claim 1.

3. A method for making an embedded gray scale watermark in a multiple layer laminated thermoplastic security document comprising CO.sub.2 laser engraving by raster processing an image on a backside of a back layer of a multi-layer card construction, wherein the image becomes apparent to viewer of the security document only upon application of backlighting to the laminated polycarbonate card.

4. A multiple layer laminated thermoplastic security document comprising an embedded gray scale watermark and made according to the method of claim 3.

5. A method of making a multiple layer thermoplastic security document comprising complex windows using CO.sub.2 laser vector, etch and raster processing comprising laser cutting and etching a vector image on the face of a middle layer of the multiple layers of the card construction; laser cutting and etching a rasterized image on a back layer of the multiple layer card construction wherein both images are in registration.

6. A multiple layer laminated thermoplastic security document comprising a complex window comprising laser engraved vector and raster images applied according to the method of claim 3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The invention is described in detail below with reference to the following drawings drawn to facilitate illustration of features described herein and not to scale.

[0011] FIG. 1 is an enlarged partial image of an upper layer of a laminated polycarbonate card shown by FIG. 2 wherein the line beside the E is a superimposed line representing a measurement.

[0012] FIG. 2 is an enlarged front view image of a laminated polycarbonate card with laser cut window produced using a laser engraver with vision system, comprising two white printed layers in which oval windows were cut wherein the window on the back layer of the card is 10% smaller than the upper layer.

[0013] FIG. 3 illustrates an image of Einstein that becomes visible upon application of backlighting to a laminated polycarbonate card having a CO.sub.2 laser raster engraved embedded Einstein image on the backside of a white polycarbonate layer within a multi-layer card construction.

[0014] FIG. 4 illustrates on the left-hand-side a CO.sub.2 laser cut and etched (i.e. engraved) vector image on the face of a third layer of a multi-layer card construction, and on the right-hand-side a CO.sub.2 laser cut and etched raster image on a fifth layer of the multi-layer card construction wherein both images (i.e. both the third layer and fifth layer images) are in registration.

[0015] FIG. 5 illustrates the back of the multi-layer card of FIG. 4 under application of backlighting. Illustrated is a partial window with partial transparency.

DETAILED DESCRIPTION

[0016] Previously, a thermoplastic security document card having a window has been constructed using a flatbed die punching machine to cut windows in one or more white polycarbonate sheets. Typically, such a card has been constructed of five or more layers of clear and white 500 mm600 mm polycarbonate sheets having a thickness of 125-375 microns which are then, collated by manually and/or mechanically tapping against the right sheet edges against a rigid stop. In this manner, alignment of the sheets is performed on the basis of the manual/mechanical alignment of the sheet edges. Disadvantageously, however, this introduces a number of accumulative tolerances that result in a low accuracy for sheet to sheet registration, namely, in the order of +/2.0 mm between each layer. The sheets are then heat tacked together and laminated using heat and pressure. Each sheet contains a total of 48 cards.

[0017] The present invention advantageously improves the process for making a multi-layer thermoplastic security document with a window as well as improving the application and registration of security features between sheets within the security document body by using a combination of vision and laser cutting processes.

[0018] In contrast, the present invention uses a CO.sub.2 laser processing machine equipped with a vision system to both cut windows in each sheet and perform high precision sheet to sheet alignment on the basis of precision registration of the sheets to printed or marked (i.e. etched or engraved) matter of each sheet. For example, a LasX STS400-2 CO.sub.2 laser engraving machine and integrated cameras comprising the vision system.

[0019] Table 1 illustrates the length from the edge of the window of a card substrate 10 shown in FIG. 2 to location E identified by a superimposed line 20 in FIG. 1 and measured on a Keyence VHX 1000 digital microscope. The table represents 10 windows from the same location on 10 different cut sheets. The tolerance of the print to window sheet to sheet was measured to be +/95 m.

TABLE-US-00001 TABLE 1 Sample 1 2 3 4 5 6 7 8 9 10 Average STDEV Measurement (um) 773 974 912 1028 947 802 907 956 743 834 888 95

[0020] To precision align and register the windows of the sheets each layer to be registered has 3 registration pin holes cut in the same laser cutting processing pass. In doing so, each registration pin hole is precisely located in a predetermined location of the sheet by vision registration of the registration pin hole with preselected printed matter on the sheet. The multiple sheet layers may further include one or more optional additional security features in the form of Kinegram, hologram, color shift, ultraviolet, lenses etc. For sheet to sheet registration, a pre-lamination tack table is provided with pins corresponding to the registration pin holes to allow each sheet to be mounted on them with negligible X/Y (axial) movement. Then, in normal manner, the pin-held sheet layers are heat tacked together in register and, using the same registration pin holes, are together pinned to a lamination plate and, thereafter are laminated together to form the composite multi-layer card sheet.

[0021] After lamination, cards were examined using the Keyence VHX1000 system and measured at certain locations, namely, distances A, B, C and D identified by superimposed lines 30 of FIG. 2, between each face and back cut window. The resulting measurements for a sample of 10 cards is shown in Table 2 (of which measurements are in microns). In the result, a standard deviation of the registration between face and back window is less than 150 m for the tested 10 card samples.

TABLE-US-00002 TABLE 2 A B C D 1 1235 1641 826 1510 2 742 1328 881 1361 3 980 1461 1006 1567 4 794 1326 976 1509 5 1020 1389 758 1478 6 972 1438 937 1555 7 917 1381 773 1400 8 1039 1593 1026 1530 9 1013 1432 782 1377 10 931 1465 685 1186 Average 964 1445 865 1447 STDEVA 136 103 118 118

[0022] The present invention further provides a method for making an embedded gray scale watermark in the security document and security document formed therefrom. FIG. 3 illustrates an embodiment of such an embedded gray scale watermark comprising an embedded Einstein image that has been laser engraved on the backside of a white layer on the back layer of a multi-layer card construction, wherein an image of Einstein appears upon application of backlighting to the laminated polycarbonate card.

[0023] A CO.sub.2 laser printing process engraves (alternately referred to as etches) an image by ablating away (i.e. removing) sheet layer material one pixel at a time and a laser raster process, similar to ink jet printing of an image onto a surface but using ablation rather than depositing ink, scans the image left to right or up and down and pixelates the surface of the material with ablations to create a grey shade image. An embodiment of a raster laser engraved image of Einstein applied to a 125 micron white polycarbonate card sheet is shown in FIG. 3 of which the image is a 300 dpi (dots per inch) bitmap to provide a very high fidelity and high contrast image. The raster engraved sheet is located on the face or back of the laminated sheet and the card sheets are laminated together according to the foregoing window card construction. The laser engraved image (i.e. of Einstein in the illustrated embodiment) forms an embedded gray scale watermark that creates visible gray scale effects when held up to transmitted light.

[0024] The embedded gray scale watermark may be integrated with and registered with other security features of print and/or markings applied to the security document by using the registration process described herein to providing an increase of the level of security of the document.

[0025] FIGS. 4 and 5 illustrate a further embodiment of the invention comprising complex windows to which vector, etch and raster processing have been applied in accordance with the description herein. FIG. 4 illustrates on the left-hand-side a part of a multi-layer thermoplastic security card having a laser cut and etched vector image on the face of a third layer of the card construction, and on the right-hand-side a laser cut and etched rasterized image on a fifth and back layer of the multi-layer card construction wherein both images (i.e. both the third layer and fifth/back layer images) are in registration. FIG. 5 illustrates the back of the multi-layer card of FIG. 4 under application of backlighting.

[0026] The back layer is part of a 100 micron white polycarbonate sheet and the sequence of laser processing used to make this embodiment was to laser cut the window first, followed by the laser raster processing (marking) to form the image. This sequence is required for minimizing any burning of the card layer and maximizing vacuum of the sheet to the belt of the laser printing/engraving equipment.

[0027] It is preferable that these laser processed features in combination with a window be processed such that a raster processed feature is applied to the back of the sheet and for the embodiment of FIGS. 4 and 5 to the back of either the third or fifth layer. Registration of these features to printed matter on the face of the sheet is to have an accuracy, that is, a standard deviation of +/0.35 mm. The backside of the raster processed sheet may include lithographically printed barcode(s) and/or may also include cut marks for vision registration.

[0028] The sheet to sheet registration process described herein enables one to create complex combinations of print/marking designs, window shapes and multiple layers of security features layered in register with some being surface features and some being embedded features that are within the card body construction. A combination of a raster feature within a window produces a window of partial transparency.

[0029] Forming of the windows during lamination requires polycarbonate window plugging of a size that is at least as large as the footprint of both the face and back cut outs. Edge charring should be taken into consideration when selecting the size and shape of the plug. It is recommended that the plug be about 10% larger than the window footprint and that the edges be smooth curves, not jagged or angular.