Table of Contents (click to expand)
A laser printer turns your file into a print by using electrostatic charge: a primary charge roller lays a uniform negative charge on the photoreceptor drum, the laser discharges the spots where the image should appear, negatively charged toner sticks to those discharged spots, a positively charged sheet of paper pulls the toner off the drum, and a heated fuser unit melts the toner permanently into the paper.
From school papers to corporate reports and everything in between, we use printers when it comes to creating any form of hard documented material. Most of the printers today also come with a myriad of color options, which allow for HD-quality pictures to be printed with precision and ease. The levels of technology the printer progressed through on its journey to reach such sophistication is quite interesting. Let’s look at some of the history that came before the advent of the modern printer.
Recommended Video for you:
History Of The Printer
Before our modern-day printer with its incredible level of precision, the field of printing materials used very draconian methods and machinery. Until the 1980s, the concept of a personal computer was basically non-existent. There were only a few who had “hard copies” or the infamous dot matrix printers. These made horrendous screeching noises during the process of printing. The dot matrix printer used a grid of tiny metal needles, pressed against an inked ribbon, to form the shapes of letters, numbers and symbols on the page. They printed each character individually, line by line, at a typical speed of about 80 characters (one line of text) per second, so a page would take about a minute to print. These dot matrix printers can still be seen in use, as they are today used for printing bills and address labels.
The funny thing is that laser printers were already in development as early as the 1960s. The basic principles were worked out by Gary Starkweather at Xerox PARC in 1971, leading to an internal research printer called the Xerox Dover (which was never sold commercially). The first commercial laser printer was the Xerox 9700, launched in 1977 for roughly $300,000 per unit. What made it so special at the time was the fact that it could print up to 120 pages per minute, around two pages every second.
However, it was two companies that were responsible for the laser printer becoming a mass public commodity. Those two companies were HP and Apple. HP sold their version of a laser printer named ‘Laserjet’, which sold for a price $3,495. The Apple counterpart to this is the “Apple LaserWriter”, which sold for almost double the amount at $6,995.
Working Of A Laser Printer
Whenever you print something, the laptop or computer you use sends a large stream of data to your printer. Typically, a few megabytes or a million characters. There is an onboard electronic motherboard that receives this signal from the laptop or computer. It then decodes all the data sent into simple machine-level language, which is used for making the different components of the laser printer act in a certain way.
The electronic motherboard then activates the primary charge roller (a refined replacement for the older corona wire used in early laser printers). The charge roller is a high-voltage component whose job is to lay down a uniform negative electrostatic charge of around -600 to -900 volts across the entire surface of the photoreceptor drum.
At the same time, the electronic motherboard activates the laser. The laser itself stays put and is steered onto the spinning drum by a fast-rotating polygon mirror, drawing the page image one scan line at a time. Wherever the laser hits the drum, it discharges that spot, leaving it nearly neutral, while the parts of the drum that should print white stay at their original strong negative charge. The resulting electrostatic “latent image” on the drum is the layout for the printable material.
Next, the developer roller (sometimes called the ink roller) presses against the photoreceptor drum, coated with toner: tiny particles of powdered plastic-and-pigment ink. The toner is negatively charged, just like the unexposed parts of the drum, but since like charges repel, the toner is pulled off the developer roller and onto the discharged (less negative) parts of the drum, where the laser previously hit. The toner sticks to exactly the pattern of the page you want to print.
A sheet of paper is then rolled under the drum. A transfer corona (or transfer roller) gives the back of the paper a strong positive charge that easily overpowers the toner’s grip on the drum, so the toner jumps from drum to paper. The paper then passes through two hot rollers, the fuser unit, which heats the toner above its melting point (typically around 180 °C / 356 °F) and presses it permanently into the fibres of the paper. That is how a laser printer turns ones and zeros into a physical page. So, the next time you print out a report, take a moment to appreciate the elegant electrostatic ballet that goes into every copy.
