LED printing (LED)

Principle of work

The principle of operation of LED printers is in many respects similar to the principle of work of laser. Operation of the printer is based on the principle of dry electrostatic transfer — the light source lights a surface of a photosensitive shaft, influence of light causes change of a charge in the lit parts of a drum at the expense of what to them the powdery toner is pasted.

Methods of transfer of a toner on a drum, on paper, and its fixing in the oven, are identical to the similar methods which are applied in a laser printing — the shaft is rolled according to paper, pressing into it a toner then the paper is transferred to the device of thermal fixing (oven) where due to high temperature and pressure the toner is fixed on paper, being literally soldered in in it (the best effect of fixing of a toner is reached when using the spherical toner developed in 1996 by OKI company (OKI Sistems Rus), at present is applied in printers and the OKI and Xerox MFP).

The fundamental difference of the LED printer from laser consists in the mechanism of illumination of a photosensitive shaft. In case of laser technology it becomes one light source (laser) which using the scanning system of prisms and mirrors runs on all surface of a shaft. In LED printers instead of the laser the LED line located along all surface of a shaft is used. The quantity of LEDs in a line is from 2.5 to 10 thousand pieces, depending on resolution of the printer.

History

The first LED printer was put on the market by OKI company in 1987, and in 1998 the same company released the first color LED printer.

LED printers came to Russia in the 1996th year when OKI opened representation in Moscow. In 1999 the LED printers to Russia begin to sell Panasonic and Kyocera, however OKI continues to remain the largest producer of LED printers, and their printers are remembered first of all, at the mention of LED technology.

In 1996 OKI begins sales in Russia of the most running printer, OkiPage 4W, and representatives of OKI in Russia make the largest mistake which effects are still felt in the market of LED printing. The printer developed by the Japanese specialists of OKI for home use in Russia having tough times is positioned as the cheapest printer for office.

As OkiPage 4W costs much cheaper than the laser analogs, it begins to be bought up in large quantities in offices of small, average, and at times and large business. Where the inexpensive printer expected house volumes of printing quickly fails, without coping with office requirements. The maximum allowed volume of printing on OkiPage 4W — 2500 of sheets in a month. In practice at the Russian offices on it printed in two — three times more.

In the printer it was supposed to use development of OKI new for those times — a spherical toner, however in Russia practice of use of original supplies did not get accustomed yet, and printers filled, significantly reducing printing quality.

Advantages of LED technology

The LED technology has the following advantages in comparison with laser:

• The LED line is much more compact than the scanning system of laser printers that affects also the sizes of printers. Color LED printers are almost twice less than the laser analogs, for monochrome models the difference in the amount of is noticeable, but is not so brightly expressed;

• Owing to absence in the mechanism of image generation of moving parts, a system is much simpler and more reliable;

• Because of use of a motionless line where each LED is over a certain section of a photodrum, problems with image quality at the edges of the sheet, inherent in systems with laser development are removed, and also allows to achieve a print speed bigger, than from laser printers;

• Instead of the laser point sizes on a photosensitive shaft, so and on the sheet of paper allow to change use of LEDs that gives the chance to apply technologies of smoothing. Brightness variation of a LED is also possible that also allows to increase image quality.

• In LED printers the principle of separation of a photodrum and a toner cartridge is used that allows to replace any of these elements in process of expenditure of its resource. The toner cartridge represents a plastic cylinder with a toner  which 90% of cost value are made by a toner, but not packaging at the expense of what any meaning in gas station of a cartridge is lost. Possible economy of means will not be able to offset image quality losses.

Shortcomings of LED technology

Lack of LED printing only one. It is impossible to create two absolutely identical LED lines, and as a result, the image printed on one printer will be though a little, but nevertheless to differ from the same image output on other printer. This shortcoming extends also to printers with laser technology of printing.

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