Dye-sublimation printing (or dye-sub printing) is a term that covers several distinct digital computer printing techniques that involve using heat to transfer dye onto a substrate.
The sublimation name was first applied because the dye was thought to make the transition between the solid and gas states without going through a liquid stage. This understanding of the process was later shown to be incorrect, as there is some liquefication of the dye. Since then, the proper name for the process has become known as dye diffusion, though this technically correct term has not supplanted the original name.
Historically, "dye sublimation" referred to page printers that use a thermal printhead to transfer dye from a ribbon directly onto the print media via sublimation. While it originally was used in creating prepress proofs, today this technology survives in ID card printers and dedicated photo printers, often under the name dye diffusion thermal transfer (D2T2).
The term was later also applied to the indirect sublimation transfer printing process, which uses a standard printer to deposit sublimation-capable toner or ink onto a transfer sheet. The printed transfer sheet is then pressed with the substrate with heat, transferring the dye to the substrate, such as plastic or fabric, via sublimation. Thus, this process is indirect, since the final substrate does not pass through the printer, and the sublimation step occurs separately.
The term direct dye sublimation is sometimes applied to a variant of digital textile printing using dye-sublimation inks printed directly onto fabric, which must then be heated to set the dyes, without the use of a transfer sheet.
Dye-sublimation page printing
Process
Using a mechanism which is a variant of the thermal-transfer printer, the most common direct process lays down one color at a time, the dye being stored on a polyester ribbon that has each color on a separate panel. Each colored panel is the size of the medium that is being printed on; for example, a 4x6 in (10x15cm) dye-sub printer would have four 4x6 in (10x15cm) panels.
During the printing cycle, the printer rollers will move the medium and one of the colored panels together under a thermal printing head, which is usually the same width as the shorter dimension of the print medium. Tiny heating elements on the head change temperature rapidly, laying different amounts of dye depending on the amount of heat applied. Some of the dye diffuses into the printing medium.
After the printer finishes printing the medium in one color, it advances the ribbon to the next color panel and partially ejects the medium from the printer to prepare for the next cycle. The entire process is repeated four or five times in total: the first three lay the colors onto the medium to form a complete image; there may or may not then be a (wax ink) black thermal transfer process; the last pass lays the laminate over top. This layer protects the dyes from UV light and moisture.
For ID card printing, sharp text and bar codes are necessary, and they are printed by means of an additional wax-based black panel on the (YMCKO) ribbon. This extra panel works by thermal transfer printing instead of dye diffusion: a whole layer, instead of just some of the dye in the layer, transfers from the ribbon to the substrate at the pixels defined by the thermal head.
Applications
Industrial and Commercial Settings
Previously, the use of dye-sub printing was limited to industrial or high-end commercial printing. Dye-sub photo printing has been used in medical imaging, graphic arts proofing, security, and broadcast-related applications.
Rising Popularity: Dye-Sublimation in Event Photography
Today, it is extremely popular in event photography and photo booths or kiosks that require high-speed, on-demand printing.
Affordable Dye-Sublimation: Home Consumers and Postcard-Sized
Alps Electric produced the first quality dye-sub printers for home consumers in the $500–$1,000 price range, bringing dye-sublimation technology within the reach of a wider audience. (These models were, however, not true page printers, since they used a narrow printhead that swept across the page, like most inkjet printers.) Now there are many dye-sublimation printers on the market starting from as low as $100, especially postcard-sized mobile photo printers.
ID Photography and Card Printing
The ability to produce instant photo prints inexpensively from a small printer has led to dye sublimation solutions supplanting traditional instant photos in some applications, such as ID photography with a card printer.