The uses of static electricity in photocopies and laser printers

THE USES OF STATIC ELECTRICITY IN PHOTOCOPIERS AND LASER PRINTERS OUR OBJECTIVE FOR YOU/WHAT WE WANT YOU TO UNDERSTAND We see it everywhere and every day. It can even build up on us. It’s (Static Electricity). We see it when our hair gets charged and sticks straight up or when our pant legs keep sticking to our legs. This is all static electricity that has built up on the surface of an object. In this PowerPoint we'll unravel the mystery behind the photocopier and laser printer, tracing a page's path from the characters on your computer screen to printed letters on paper. Understand that the printing process is based on some very basic scientific principles applied in an exceptionally innovative way. REMEMBER! The primary principle at work here is static electricity, the same energy that makes clothes in the dryer stick together or a lightning bolt travel from a thundercloud to the ground. Static electricity is an imbalance of electric charges within or on the surface of a material. The charge remains until it is able to move away by means of an electric discharge. Static electricity is simply an electrical charge built up on an insulated object, such as a balloon or your body. INTRODUCTION: Have you ever tried writing with a beam of light? Sounds impossible doesn't it, but it's exactly what a printer does when it makes a permanent copy of information from your computer onto a piece of paper. Thanks to sci-fi and spy movies we tend to think of lasers as incredibly powerful light beams that can slice through chunks of metal or blast enemy spaceships into smithereens. They are actually much more than that and in fact they are useful too in a much more exciting way. They're vital parts of most office computers printers. Many people use them in their day-to-day lives, but most probably never think about the technology that turns those bits of digital data into a legible images and text. All set? Okay, let's take a closer look at how these printers work! THE LASER PRINTER WHO INVENTED THE LASER PRINTER AND WHEN WAS IT DISCOVERED? Until the early 1980s, hardly anyone had a personal or office computer. Laser printers are a lot like photocopiers and use the same basic technology. Indeed, as we describe later, the first laser printers were actually built from modified photocopiers. In 1938, American physicist and inventor Chester Carlson invented a dry printing process, called later Xerography, the word comes from the Greek word for dry writing, this formed the foundation of technology for copiers and laser printers to come. The first designs for a laser printer were developed by Gary Starkweather, at Xerox’s research facility in New York. Gary Starkweather worked in Xerox's product development department and came up with the idea of using a laser beam to draw an image of what was to be copied directly onto it’s drum in the year 1969. He worked with Butler Lampson and Ronald Rider as well to add a control system and character generator. Gary Starkweather Chester Carlson HOW IS STATIC ELECTRICITY INCORPORATED IN THE PROCESS? When you print something, your computer sends a vast stream of data (typically a few megabytes or million characters) to your laser printer. An electronic circuit in the printer figures out what all this data means and what it needs to look like on the page. It makes a laser beam scan back and forth across a drum inside the printer building up a pattern of static electricity. The static electricity attracts onto the page a kind of powdered ink called toner. EXAMINE THIS INTERACTIVE DIAGRAM AND THE FOLLOWING: How it works (10 processes): 1) Millions of bytes (characters) of data stream into the printer from your computer. 2) An electronic circuit in the printer figures out how to print this data so it looks correct on the page. 3) The electronic circuit activates the corona wire, a highvoltage wire that gives a static electric charge to anything nearby. 4)The corona wire charges up the photoreceptor drum so the drum gains a positive charge spread across its surface. 5)At the same time, the circuit activates the laser to make it draw the image of the page onto the drum. The laser beam doesn't actually move it bounces off a moving mirror that scans it over the drum. Where the laser beam hits the drum, it erases the positive charge that was there and creates an area of negative charge instead. Gradually, an image of the entire page builds up on the drum where the page should be white, there are areas with a positive charge where the page should be black, there are areas of negative charge. EXAMINE THIS INTERACTIVE DIAGRAM AND THE FOLLOWING CONTINUED..: How it works (10 processes): 6)An ink roller touching the drum coats it with tiny particles of powdered ink (toner). The toner has been given a positive electrical charge, so it sticks to the parts of the photoreceptor drum that have a negative charge No ink is attracted to the parts of the drum that have a positive charge. An inked image of the page builds up on the drum. 7) A sheet of paper on the other side of the printer feeds up toward the drum. As it moves along, the paper is given a strong positive electrical charge by another corona wire. 8) When the paper moves near the drum, its positive charge attracts the negatively charged toner particles away from the drum. The image is transferred from the drum onto the paper but for the moment the toner particles are just resting lightly on the paper's surface. 9)The inked paper passes through two hot rollers (the fuser unit). The heat and pressure from the rollers fuse the toner particles permanently into the fibers of the paper. 10) The printout emerges from the side of the copier. Thanks to the fuser unit, the paper is still warm. It's literally hot off the press! THE PHOTOCOPIER WHO INVENTED THE PHOTOCOPIER AND WHEN WAS IT DISCOVERED? James Watt invented an early version of the photocopier called the document copier in and patented it in1780. Chester Carlson invented the powder that helps copy it onto the paper in 1938 and it didn't hit the market until 1959 more then 20 years later. He made the first photocopy using a zinc plate covered with sulfur. Chester Carlson tried to sell his invention to some companies, but failed because the process was still underdeveloped. Even as a young boy, he had always been curious about how things work. He was especially fascinated with Chemistry. Back when he was a teenager, he used to work for a local printer. Chester Carlson used this opportunity to publish a little magazine for amateur chemists. James Watt Chester Carlson HOW IS STATIC ELECTRICITY INCORPORATED IN THE PROCESS? There are multiple components inside of a photocopier, including a drum and toner. The drum is selectively charged with static electricity to mirror the image that is being copied. The toner, which is black powder, then adheres to the charged areas of the drum. Finally, a blank piece of paper is charged with static electricity. As the paper pulls through, the toner image transfers onto it. Note that while digital copiers do not use static electricity, older photocopiers do. EXAMINE THIS INTERACTIVE DIAGRAM AND THE FOLLOWING: How it works (10 processes): 1) You place the document you want to copy upside down on the glass 2) An extremely bright light scans across the document. Much more light reflects off the white areas (where there is no ink) than off the black, inked areas. 3) An electrical shadow of the page forms on the photoconductor. The photoconductor in a photocopier is a rotating conveyor belt coated with a chemical called selenium. 4) As the belt rotates, it carries the electrical shadow around with it. 5) An ink drum touching the belt coats it with tiny particles of powdered ink (toner). 6) The toner has been given an electrical charge, so it sticks to the electrical shadow and makes an inked image of the original page on the belt. EXAMINE THIS INTERACTIVE DIAGRAM AND THE FOLLOWING CONTINUED..: How it works (10 processes): 7) A sheet of paper from a hopper on the other side of the copier feeds up toward the first belt on another conveyor belt. As it moves along, the paper is given a strong electrical charge. 8) When the paper moves near the upper belt, its strong charge attracts the charged toner particles away from the belt. The image is rapidly transferred from the belt onto the paper. 9) The inked paper passes through two hot rollers (the fuser unit). The heat and pressure from the rollers fuse the toner particles permanently onto the paper. 10) The final copy emerges from the side of the copier. Thanks to the fuser unit, the paper is still warm. It may still have enough static electric charge to stick to your pullover. Try it (but make sure the ink is dry first). WELL WHAT’S THE DIFFERENCE? The major difference between the two is in how the image is formed on the photosensitive drum. A laser printer uses a low power sharply focused laser beam to scan one line at a time on the drum, the laser must therefore write it out from scratch. IN CONCLUSION: As you can see static electricity is used in photocopiers and laser printers through a lot of it’s parts in a variety of ways and is very helpful to modern society even to this day. Again the reason why static electricity works on these machines or on any object in general is because there is an imbalance between positive and negative charges in objects, meaning there is more of one charge than the other, which either attracts or repels them from other objects. Remember, you should also take great care when changing toner cartridges or handling empty ones. 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