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Laser Printing
Laser Printing is the dominant technology for commercial, government and educational printing. In the corporate sector people use laser printers as typically they are faster, quieter and cost less to print. The initial cost of the cartridge may be more but typically these cartridges last for a lot longer meaning that the cost per page is greatly reduced. With the increasing launch of cheaper laser printers sales of inkjet printers at the higher end of the market have fallen and for colour printing laser printing can be substantially faster.
Technical Summary:
Static electricity is the
principle behind laser printing which uses a revolving cylinder, a laser
beam, fine powder toner, and heat to create images on paper. Black and
white lasers (black toner) are relatively inexpensive and common in many
homes and small offices. Colour lasers were once seldom found outside
service bureaux and commercial
printers, but falling prices have made them standard for most offices and
attractive to home users for their cheap running costs.
Adobe
PostScript capabilities found in many laser printers make them popular
with graphic designers and desktop publishers who often utilize EPS images
and PostScript files. Hewlett-Packard's PCL language is another popular
command language used by laser printers.
What's the difference between LED and laser?
The main mechanical difference between the printers is that rather than using a single laser to create the image on the page, an LED array is used, which is the width of the page. That's just about it.
LED printers were the first printers to employ "single pass" technology. That is rather than having a single drum to create the images from the four colours, one drum is assigned to each colour making the process quicker. See "How it works" below for more information about this.
Traditionally, manufacturing constraints meant that LED heads were only capable of producing a 600x600 dpi image, and the impression was that they were inferior in quality to a laser. Nowadays however, improvements in technology mean that LED printers are comparable to their laser equivalents. In fact, they are virtually identical in performance and we believe they should all just be called laser printers!
How it works
The basic underlying concept behind laser printers is static electricity. On a small scale, it's what makes your woolly jumper crackle when you take it off, on a larger scale, it's lightening! This charge can either be positive or negative.
Laser printers use this natural phenomenon as a kind of temporary glue. First of all the drum/ OPC Belt/ Photoconductor is given a clean and then a total positive charge by traditionally a corona wire, but nowadays a charge roller.
As the drum revolves, a tiny laser beam writes the characters and images to the drum, now making the written area negatively charged. The drum is then coated with positively charged toner, however under the opposites attract theory, it only sticks to the negatively charged area written by the laser beam.
Now for the paper, this is given a stronger negative charge than the drum which allows the paper to draw the toner from the drum. As the paper is moving at the same speed as the drum, the exact image from the drum is transferred to the paper. The paper is then discharged using a discharge roller to prevent it sticking to the drum. Finally the paper passes through the fuser, which is a pair of heated rollers that apply heat and pressure, which in turn melts the toner and fuses it into the fibres of the paper. This is the basic process for a mono laser, and the process for colour follows the same process, except for the following subtle differences. In a 4 pass laser printer, the process is repeated 4 times using 1 drum, once for each colour (CMYK). In a single pass laser printer, the process is performed once on 4 (CMYK) drums.
When printing with a laser people tend to expect ultra sharp high quality printing. To this end we only supply toner cartridges which use the very highest grades of micro fine toner to ensure consistent high quality printed text and images.