Plastic ID card printers use two types of printing. Thermal transfer printing and dye sublimation printing are used in both direct to card printers and retransfer printers. Direct to card printers merge the image directly on the surface of the card. Retransfer printing deposits the image on the back of a clear plastic film. This film is then bonded to the surface of a plastic card. Retransfer printing is the newest of these printing types and results in a better image result. The card design is applied to specialized cards and does not require a perfectly smooth card as the direct to card printers require.
Thermal Transfer Printing
Thermal printing is when resin or ink is melted off of a printer ribbon and is directly transferred to the retransfer film or the surface of the card. To melt the ink, a print head is used. The print head has heated pins that are aligned across a ceramic plate. In the correct sequence, the pins in the print head receive instructions to heat and release ink at just the right moment. The desired digital image created in the software is recreated on the card or ribbon.
Colored prints require the use of Y, M and C panels. As each panel passes over the card, dots of color are released resulting in the completed image. The K panel produces needed black printing on the card. Dithering allows the dots of different colors to be placed close together to create a blended shade when observed.
Monochrome printing is also available. This single color ribbon produces clear results with standard text and with bar codes. Monochrome printing is completed at high speeds and is often used to customize a preprinted card. The thermal ribbons provide durable print that resists fading. The resin dries quickly.
Sublimation is when a solid is heated directly into a gaseous state. The solid bypasses the liquid state during heating. With this printing, the dye is heated to about 250 degrees Fahrenheit while the polymers in the PVC card are heated to 350 degrees. The gaseous dye penetrates the plastic and as the card cools, the dye chemically bonds with the plastic card.
Crisp, sharp images are printed with dye sublimation printing. Photographic images are printed with accuracy. The higher heat levels allow more dye to be released into the card surface. The result is the colors blend into a pleasing result as there is control over the opacity and transparency of the printing result.
Colors in this printing method are applied one panel at a time- the Y, M and C. This type of print is prone to fading when exposed to UV rays from the sun. Often a UV resistant topcoat is recommended to help protect the dye printed cards.