20130202828 | Laser Thermal Printing on Microporous Plastic Substrates - Disclosed herein is a process for printing on a microporous substrate using a laser to melt or soften the substrate so that the pores collapse and produce clear regions on a white background. The preferred substrate is one based on polypropylene where the microvoids are produced by orienting an extruded, precursor sheet that contains the beta crystalline form of polypropylene. A dark co-extruded layer or a pigmented adhesive can be placed on the non-laser treated side of the film, so that the treated side shows the color of the backing layer through the clear regions. This type of printing or laser marking does not require any inks, solvents, or other consumable additives, and the printing can be done at very high production rates and at low cost. The small void size of the film allows for fine print detail and excellent print contrast. | 08-08-2013 |