When reading about ID card printing processes, you will often encounter the term, dye sublimation. Find out how printing is done on ID cards in this article.
Dye-sublimation printing involves the use of heat to transfer dye onto a print surface such as a plastic card. If you looked inside a dye-sublimation printer, you would see a long roll of transparent film that resembles sheets of red, blue, yellow, and grey coloured cellophane stuck together end to end. Embedded in this film are solid dyes corresponding to the four basic colours used in printing: cyan, magenta, yellow and black. As it passes over the film the print head heats up, causing the dyes to vaporize and permeate the glossy surface of the paper before returning to solid form.
Dye-sublimation is done on surfaces with a special coating (such as polyester, polymer, hardboard, ceramic, glass, or metal). Run your finger over the transferred surface and you will feel nothing. This happens because, during the printing process, the high heat causes the solid dye to convert into a gas without ever becoming a liquid. The high temperature also opens the pores of the print surface and allows the gas into the pores. When the temperature drops, the pores close and the gas reverts to a solid state, leaving the image on the chosen surface.
Offset Printing – Lithography
Lithography is mainly used by commercial printers, printing companies that print thousands of copies of the same item in one production run. Lithography machines can print on both sides of a card and rely on four basic colours: yellow, cyan (type of blue), magenta (type of red) and black.
This is also known as the CYMK process.
- The printing plate has the image to be printed, in relief, on its surface (the image stands out slightly from the printing plate surface).
- The printing plate is kept dampened. Ink is applied to the plate but it is repelled from the dampened surfaces, which are the non-image areas.
- As the printing cylinder rotates the ink is transferred to the rubber blanket cylinder.
- The ink, now on the rubber blanket cylinder, is pressed onto the paper or card as it is pulled through the machine (The paper is trapped between the blanket cylinder and the impression cylinder - these pull the paper through the machine).
Some modern lithography printing machines have refined the process:
- The image is put onto the printing plate by shining ultra violet light through a negative (similar to a photograph negative).
- The plate is coated with a chemical which allows the ink - made from oil - to attach to the image area.
- If different colours are needed for the final print, the same card or paper will be sent through the machine and each time different negatives and colours will be applied. This is done until the print (a poster, for example) is completed.