How Inkjet Printers and Laser Printers Work

I think it's important to understand the mechanism of color printing and why you get dithering and jaggies on some printers and why dye sublimation printers such as the Alps give you continuous tone or photographic quality prints. Color printing uses four separate pigments: cyan, yellow, magenta, and black. This system is called CYMK. (K stands for black.) Some low-end color inkjet printers save the cost of a black ink print head by using equal portions of magenta, yellow, and cyan to produce black. But the resulting black lacks density, which is why better personal printers include a print head for black ink. All color printers use tiny dots of those four inks to create various shades of color on the page. Lighter shades are created by leaving dots of unprinted white. Some printers, such as dye-sublimation, control the size of the dots and produce continuous-tone images that rival photography. But most printers create dots that are essentially the same size no matter how much of a particular color is needed. For all shades beyond the eight that are produced by overlaying the primaries, the printer generates a varied pattern of differently colored dots. For example, the printer uses a combination of 1 magenta dot to two of cyan to produce a deep purple. For most shades of color, the dots of ink are not printed on top of each other. Instead, they are offset slightly, a process called dithering. The eye accommodatingly blends the dots to form the desired shade as it hides the jagged edges, or jaggies, produced by the dots. Dithering can produce nearly 17 million colors. The type of paper used in color printing affects the quality of the hard copy. Dithering is more apparent on inkjets

Inkjet printers spray ink through tiny jets, or nozzles, onto the paper. All in all, inkjet printers deliver great and affordable results, but there are some downsides. The ink from an inkjet printer tends to migrate, or spread out, on the paper, making the print look less sharp because the "dot" is less defined. This is where you get jaggies or jagged text. A harder, less absorbable paper, such as paper with a glossy surface, helps contain ink migration, but the ink might take a few minutes to dry. You should handle a page, especially one with a lot of dense color on it, with care. Inkjets can be slow. It takes a lot of time for the print head to scan across the page and deliver ink. There are printers that are designed specifically for printing photos which give good detail and very accurate color. Although you can use plain paper to get a quick draft image printed, a better paper grade, such as a good-quality laser paper, yields better results. Inkjet prints fade quickly and smear easily unless they have a protective coating. A good photographic inkjet printer can give you outstanding quality images on special paper. They are also good for general office work where you want an inexpensive printer that can handle volume. Many of the older versions used only one cartridge filled with cyan, magenta, and yellow ink and one cartridge filled with black ink. You would have to throw out the whole cartridge if you ran out of even one color. Numerous new inkjets come with separate color cartridges and this is a consideration if you do any volume printing. Also many of the newer inkjets can give you good quality output on laser paper.

Color Laser Printers have a drum that is charged with static electricity. The drum picks up colored toner, which sticks to the static. The drum transfers the toner to the paper. The toner is then thermally fixed to the paper. Color laser printers deliver great color, but they are expensive. You can use plain paper but a better quality paper will produce better results. Laser printers produce great looking and crisp text, but are not noted for the quality of printed photographs as they are not continuous tone printers.

Micro-Dry is a computer printing system developed by the ALPS corporation of Japan. It is a resin-transfer system using individual colored thermal ribbon cartridges, and can print in process color using cyan, magenta, yellow, and black cartridges, as well as such spot-color cartridges as white, metallic silver, and metallic gold, on a wide variety of paper and transparency stock. Certain Micro-Dry printers can also operate in dye sublimation mode, using special cartridges and paper.

A typical Micro-Dry printer includes a moving carriage containing the printhead, which is capable of taking cartridges from a rack on the front cover of the machine, printing with them, and returning them to the rack, without human intervention. Printing is normally done one color at a time, printing the entire cyan portion of the page, then retracting the page to print the entire magenta portion, then yellow, then black (or yellow, magenta, cyan, and a protective overcoat, in dye sublimation mode). When multiple spot colors are used in addition to CMYK, the printer can be manually directed to retract the page at the end of the printing cycle, instead of ejecting it, thus assuring that the spot colors remain in registration.

Because ALPS had little name recognition among United States consumers, because it could not interest other major printer manufacturers in its system, and because it is considerably slower than most ink-jet systems, the Micro-Dry system never achieved wide acceptance, despite its ability to produce clear, waterproof, fade-resistant hardcopy. It has found a niche market in certain types of plotters used in the signage industry, as well as an extremely loyal following among those who understand its capabilities, and ALPS does continue to produce mechanisms for use in plotters, as well as supplies, and has pledged to continue doing so for as long as there is a significant demand

Micro-Dry printers are much like dye-sub printers delivering resin-based ink via thermal transfer from a ribbon. You can use any paper with a micro-dry printer. There is a slight banding. It is questionable whether this is from where the half-inch ribbon swaths stitch together or from thermal technology, but this banding is common to many printers that print in a row, so some banding is natural. The banding can be avoided by selecting different backgrounds or subjects. The MD-5000 can produce vivid and photographic quality prints because it is a variable dot printer. The Alps patented printer insures exact control of dot diameter, resulting in superior print quality. This unique technology combines a thermal controller chip and an Alps Micro DOS (Deposit on Silicon) print head. The controller creates a precision, high-density print pattern for each dot, selects the correct ink and fuses the image to the print surface. The printer is able to size the pixel into three perfectly shaped dots, accurately registered. Have you ever designed an image, picked great colors, and then printed the image on colored paper and you get totally different shades of the colors. Well, with the Alps this doesn't happen. Since the ink stays on the surface, you can print on colored paper without the color changing the color of the ink. We tested the MD-5000 against other laser and inkjet printers and it produced excellent results in the micro-dry mode. The text was clear, the colors were sharp and vivid, even on just laser paper such as Hammermill. The inks cost under $10 per color and seem to last.

Dye-sub printers work by transferring colored dyes by heat (for this reason, you might also have seen these printers referred to as thermal dye sublimation printers) The dyes are held on a ribbon or roll and transferred to the paper when heated. When the dye hits the paper, it sublimates, or sinks into the paper--it does not sit on the paper surface. You cannot use plain paper in this process; you must use paper that is made especially for this process. When you use the proper paper, the dye spreads out a bit on the paper's glossy surface and mixes with the other colors, producing a continuous tone much like that found in a traditional color print. The prints from the MD-5000 using this mode were outstanding. You get an extremely professional look from just a desktop printer. Until now, a full-page dye sublimation printer has been to expensive for most people. The cheaper models printed only smaller pages.