System and method for forming an image on a substrate
A scanning laser having a wavelength compatible with a coating binder so as to cure it as the laser scans and irradiates the coating on a moving web. A system and method for curing flakes by providing a scanning laser which scans across a moving coated substrate in a magnetic field allows images to be formed as magnetically aligned flakes are cured into a fixed position. The images have regions of cured aligned flakes. The scanning laser cures the magnetically aligned flakes within it region it irradiates. Alternatively an array of lasers can be used wherein individual lasers can be switched on and off to fix irradiated coating as a moving web is moved at a high speed.
1. A method of forming an image on a substrate, comprising the steps of:
a) applying a coating of magnetic or electric field alignable flakes within a binder to a first region of the substrate,
b) moving the substrate at the speed of at least 25 ft/min and applying a magnetic or electric field so as to orient at least some of the flakes within the coating; and,
c) while the first region of the substrate is moving in a first downstream direction, irradiating with one or more laser beams in one or more first sub-regions of the first region of aligned flakes so as to cure the binder in the one or more sub-regions while allowing the coating of flakes in a second adjacent sub-region of the first coated region to remain uncured so as to maintain alignment of flakes within the one or more first sub-regions while not maintaining alignment of the uncured coating of flakes, wherein said irradiating includes irradiating a plurality of locations on the substrate along a predetermined direction across the downstream direction so that lines of flakes across the substrate in the one or more first sub-regions are cured in succession as the substrate is moving and wherein the length of the lines vary in a predetermined manner so as to form an image, and subsequently applying a second different magnetic field to the same coating of flakes within the first region and curing the flakes within the second sub-region of the first region, whereby a discernible image is formed dependent upon a contrast between a difference in alignment of the flakes in the first sub-region and the second sub-region.
2. A method of forming an image as defined in claim 1 wherein one of the one or more laser beams is swept across the substrate in a direction substantially transverse to the downstream direction back and forth crossing a line along the downstream direction a plurality of times, curing the coating along a path it sweeps.
3. A method as defined in claim 2 wherein the flakes are magnetically alignable flakes, wherein the field is a magnetic field and wherein the laser beam swept across the substrate irradiates the coating within the magnetic field.
4. A method as defined in claim 3 wherein the step of irradiating the one or more sub-regions results in the curing the coating in a predetermined pattern so as to provide a permanent visible image upon the substrate.
5. A method as defined in claim 4 wherein the image is a logo, or text or symbol.
6. A method as defined in claim 1 wherein the one or more laser beams includes a laser beam that irradiates the coating as a focused spot or defocused spot, or a line, wherein said line is transverse to the downstream direction.
7. A system for coating a substrate comprising:
a station for moving a substrate at a speed of at least 25 ft/min along a path;
a coater for coating the substrate with a plurality of coating regions each coating region for forming a separate image, each coating region including magnetically alignable flakes within a binder;
a first magnetic field generator positioned about a portion of the path for generating a first magnetic field for aligning magnetically alignable flakes within a each coating region as the substrate moves along the path; and,
one or more lasers for providing one or more laser beams;
a controller for controlling the one or more lasers to irradiate a plurality of locations on the substrate along a direction across the downstream direction so as to cure lines of the coating across the substrate in succession as the substrate is moving and wherein the length of the lines varies in a predetermined manner so as to form an image, wherein the one or more lasers include a laser having a beam that is moved to a plurality of positions across the path of moving substrate to cure the binder, wherein the laser is a scanning laser programmed so as to irradiate a coating region while said coating region is in the first magnetic field so as to at least partially cure the flakes in that coating region before the flakes exit the first magnetic field, and;
a second magnetic field generator disposed downstream from the first magnetic field generator and along the path for magnetically aligning flakes outside of the portion of each coating region cured by the scanning laser; and, a curing station for curing binder so as to maintain alignment of magnetically alignable flakes aligned by the second magnetic field generator.