The photocopier, although the invention of the printing process dates back to the late 1930s, is still one of the most widely used office machines in the world. Of course, digital technology has made some elements obsolete, but the operation of a photocopier has remained the same. Currently, analog technology still equips several models of photocopiers.
A printing process based on the elementary principle of electricity
A photocopier, also called a photocopier machine or simply a copier, is a machine designed to reproduce a paper document in one or more identical copies. Basically, in electricity, it is the attraction of opposite charges that was exploited in the 1930s by scientists, and then innovation gave birth to the process called electrophotography which is also called xerography today. It is from this name that the name and brand “Xerox” were born. It is the pioneer manufacturer of duplicators since the end of the 1950s. Since then, the process has evolved a lot, but the operation of a photocopier has remained the same despite digital technology.
In fact, until now, the photocopier has always been equipped with a drum. It is a positively charged cylindrical photoconductive device. Originally, selenium was used as the semiconductor element, but it has now been replaced by silicon. If we briefly present how a black and white photocopier works: a very high-intensity light is used to illuminate the original document. On the drum, the dark parts, i.e. the image of the original document, will be impregnated with the negatively charged ink toner. In the meantime, the sheet that will receive the copy, charged with static electricity, comes into contact with the drum and attracts the ink particles, i.e. the very image of the document. Before leaving the photocopier, the new copy passes through two heated rollers to finalize the printing. Once the photocopy is complete, the drum is automatically “cleaned” to receive a new copy.
What about other types of photocopiers?
Compared to the classic black and white photocopier, the operation of a color photocopier is the same principle, but obviously, the mechanism is rather different. Manufacturers use two different techniques, either 4 drums are used to each receive the primary colors cyan, magenta, yellow, and black – CMYK – or the image of the original document is deposited on a device called a “transfer cloth”, then transferred to the sheet. It is this last technique that is used in most current color photocopiers. The 4-drum technology is still used to have color photocopies on heavy-weight paper. It is an almost obsolete technology, but it offers exceptional image quality.
The different types of photocopiers, including blueprint copiers, duplicators, and high-volume copiers all use the same operating principle. As for digital photocopiers and other laser printers, manufacturers have taken the operation of a traditional photocopier, but the process is reversed due to the use of the laser beam. The ink particles are instead attracted to the drum by the illuminated parts of the laser. The power of the latter varies according to the intensity of the scanned pixels.
