These three colours (Yellow, Magenta & Cyan) are the primary colours used in printing to produce all other colours including black.

The dye from the ribbon is applied to the plastic card via a multi-pass operation. This means the card will pass under the print head once for each of the three coloured ribbon panels - applying each colour separately.

"Dye Sublimation" is also referred to as Dye Diffusion. When the print head heats the dye on a ribbon, the dye is transformed from a solid to a gas and diffused onto the plastic card, which is specially coated to absorb the colour dye.

The temperature of the print head controls how much dye is converted to a gas - as the print head temperature rises; more dye can be absorbed into the plastic card. Consequently, the picture quality and continuous colour tones produced by a dye sublimation printer - at300 dpi - can outperform most laser or ink jet printers with higher resolutions. The advantage of dye sublimation is the millions of colours that can be created. Varying the heat intensity on the ribbon panels yields various shades of each colour, making colour selection virtually unlimited.

Thermal Transfer –v- Dye Sublimation
As mentioned above, thermal transfer differs from dye sublimation in that it uses ink instead of dye. However, both dye sublimation and thermal ink (sometimes referred to as Resin) can be combined in one ribbon. This ribbon is known as a YMCK Ribbon. The letter "K" designates the colour black in the printing industry.

Why do you need a separate black panel, when you can create black by mixing the three basic YMC colours together?
The answer to this question is simple. The black created by mixing the YMC colours together is referred to as "Composite Black." Composite Black typically looks muddy or has a grayish tint when compared to Thermal Transfer (TT or resin) black. Composite Black is not recommended for printing bar codes since it does not produce the sharp edge many scanners require. Although this is invisible to the naked eye, it is easily observable under magnification). Composite Black is also invisible to IR scanners since there is no carbon in the dye. Since you may not know what type of scanner will be used, the rule is to always use TT (resin) black to print bar codes.

Monochrome Printing
In general, all dye-sub printers are capable of printing in monochrome using a single colour ribbon. These ribbons are less expensive than full colour multi-panel ribbons and can be either dye or ink (thermal transfer). The most commonly used monochrome ribbon is "Black" but there are several other colours available including; Red, Green, and Blue.

Colour Image Printing
Dye Sublimation ribbons are preferred for printing pictures, since they can produce many shades of gray for a smoother look and a better picture quality. A resin black picture normally uses a dithered gray scale (gray made from a combination of pixels which limits the number of shades), producing a coarser, grainy look to the image.

Text, Barcodes, Single Colour Graphics
Thermal Transfer (resin) ribbons should be used to print text, bar codes or single colour graphics such as simple logos. The letter "K" followed by a lower case "r" or "d" (Kr or Kd) denotes black monochrome ribbons.