|
|
 |
|
|
 |
 |
 |
 |
|
About Card Printers |
The Card Printing Process
Digital
card printers have been available to the public for many years
– although some companies may still use the outdated and very manual cut and paste ID card creation and lamination method. This section provides
an overview of one of the most popular technologies behind current digital card
printers and photo ID systems - dye sublimation.
The following information is provided by:
The Process of Dye Sublimation
Dye sublimation is chosen for its high quality photographic results. The dye sublimation printing process (aka, dye diffusion or dye-sub for short) involves the use of thermal transfer to transport varying amounts of colored dye pigments from a carrier ribbon or film, to the
card surface to which the dyes bond chemically.
Inside a dye-sub card printer is a roll of film or ribbon consisting of a repeating series of yellow, magenta (red), cyan (blue),
black and clear panels. The YMC (yellow, magenta and cyan) panels contain thermally sensitive dyes corresponding to the three basic colors used in subtractive printing. By combining varying amounts of these dyes, any color in the spectrum can be created, from white
(no dye transferred) to black (full transfer of each of the three dyes).
The black (K) and clear overlay (O) panels are also used in this thermal printing process, but they operate in a different way called “mass
transfer” in which ALL of the material (in this case, a plastic resin rather than a dye) is transferred once the carrier ribbon
reaches the required transfer temperature. The black resin is used to apply dense black text and barcodes on top of the
YMC color image, and the clear panel is used to put a protective overcoat over the entire printed image.
The thermal printing process uses a printhead with hundreds of individual heater elements (typically 300 per inch)
which can each be separately controlled by software to transfer varying amounts of the YMC dyes and all or none of the
black (K) and clear (O) panels as the appropriate panel passes under it.
In the case of the YMC panels, the individual temperature of the elements causes varying amounts of dye to be vaporized
and to permeate the glossy PVC card surface where they form bonds with the plastic molecules. This is the sublimation part. (Sublimation means to heat something and turn it into a vapor without going through the liquid
phase.) Because the pigments go from solid, to gas and back to solid, there is little mess compared to inkjet printing which
uses the liquid phase as part of the transfer process.
Because of the way the vaporized dyes permeate the surface of the card, a gentle gradation at the edges of each pixel is
created - not the conspicuous border between color and substrate produced by inkjets. Also, because the color infuses and
bonds with the card material, it is less vulnerable to fading and distortion over time.
The printer creates the card image by placing dye pigment and layers of acrylic resin onto the card in the following order:
- Yellow (Y)
- Magenta (M)
- Cyan (C)
- Black (K)
- Clear overcoat (O)
The colored image is formed from a combination of the Y, M, and C dye panels, which are
printed sequentially. The K layer is used to form very sharply defined black text and
barcodes and has the added advantage over YMC black that it is opaque to infrared - which
is required by barcode scanners. However, YMC black is normally used in the portrait and graphics images on the card,
because it looks more photo-realistic than the black resin. The O layer acts as a protective film against wear and UV fading.
Dye-Sub v. InkJet Printing Processes
The color produced by dye-sub printing is the result of mixing of pigments to get the actual color. This is in contrast to inkjet
printing methods which use a tight group of colored dots which, when seen by the human eye from a distance, appear
to be a particular color (a process known as dithering).
Under magnification, the inkjet dots are clearly different colors, and when seen close up with the naked eye, the picture
appears grainy. Because the dye-sub printer only prints one color in any pixel location (instead of four or even more for
the inkjet), it can place more colored pixels on a card for any given resolution.
In dye-sub printing, the color permeates the card and the edges of each pixel are blurred, rather than being laid down as little dots.
This gives the impression of blending for a more natural appearance. Dots from an inkjet
leave large white gaps in between pixels, giving the impression of a grain.
Cards printed using dye-sub technology resist fading and are colorfast; however, the best advantage of all is the bright, photo-realistic results achieved when printing on
PVC ID card material. Inkjets, by comparison, tend to produce dull, lifeless prints.
Dye-Sub: The Subtractive Color Process
Subtractive color starts with
an object (often a substrate such as paper or plastic) that reflects light and uses colorants (such as pigments or dyes) to
subtract portions of the white light illuminating an object to produce other colors. If an object reflects all the white light back
to the viewer, it appears white. If an object absorbs (subtracts) all the light illuminating it, no light is reflected back to the
viewer and it appears black. It is the subtractive process that allows everyday objects around us to show color. Color
paintings, color photography and all color printing processes use the subtractive process to reproduce color. In these cases,
the reflective substrate is canvas (paintings) or paper/plastic (photographs, prints), which is usually white.
The additive color process, RGB (Red, Green, Blue), is used in TV sets and monitors that generate light, as opposed to printing,
which reflects light.
In theory, overprinting all three colors produces black (aka, composite black). In reality, a dark gray is produced rather than true black, so resin black (aka, thermal transfer black) is used as a fourth printing
ink. Hence the ‘K’ (for monochrome black) in YMCK.
Please contact
us if we may answer any further questions. You may also
chat with us live by selecting this ‘Chat
Live' link. |
 |
 |
 |
 |
|
|
|
|
Checkout | 
