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Smoother toner could lead to smaller, cheaper color laser printers
June
2007 -The much-trumpeted paperless office was last reported vanishing
under a tidal wave of documents back in the early 80s. After extensive
investigations, the culprit was found to be the laser printer. These
printers had the advantage of being relatively inexpensive with
reasonable print quality and were heavy enough that the boss could use
it to anchor his fifty-foot yacht. The black-and-white laser printer
has continued to improve: small footprint, better quality output at a
faster speed, and much, much cheaper. Color laser printers have lagged
behind their black-and-white brethren, and the reason, apparently, is
in the toner. But Science has a review article that hints at much
cheaper and smaller color laser printers in the pipeline.The article in
question is a review of electrostatics, which one of my university
lecturers described as a necessary evil on the way to electrodynamics.
One recent discovery in the field is that, given a certain value of
charge and a certain surface area, the strength of the adhesion will
vary depending on the number of contact points, even though the charge
is still evenly distributed. This is due to the fact that charge comes
in fixed units of electrons (and protons, but electrostatics is almost
entirely about electrons).Small points of contact act to magnify the
effects of charge differences, as even a single electron difference
creates a large electric field in its immediate vicinity. Put simply,
spiky contacts are held very strongly, while smooth contacts adhere to
each other much more weakly. Here’s how it could lead to cheaper laser
printers.
Svelte color laser printers
This
strong adhesion, when combined with the poor precision control in
today’s color laser printers are what make them bulky and expensive.
The current generation avoids this problem by using a combination of
magnetic particles that have smaller polymeric particles adhering to
them as “ink.” The adhesion between the big and small particles is a
product of their mutual electrostatic charge, making the whole
electrically neutral.The particles are then steered using the magnetic
properties of the inner particle to the correct region on a drum, which
has been charged in a mirror image of the desired print pattern. This
strips off the large inner particle while leaving the toner particles
stuck to the correct region of the drum. Finally, the charged polymers
are stuck on the paper and cooked. The requirements for both
electrostatic and magnetic control systems are what make color laser
printers expensive and bulky.To avoid using a magnetic field to control
the toner deposition, the researchers have developed a new toner that
comes wrapped in its own shell, giving it a very smooth surface that is
much less sticky. This much weaker adhesion means that the positioning
of the toner can be done using electrostatics alone. In turn, the laser
printer can be much smaller using a control system that is very similar
to normal laser printer—though with a touch of the three headed ink-jet
printer thrown in.It was bad enough to be drowning in black and white
copies of rubbish, now we will have to contend with colored bits of
paper flying around the office too—if the new toner works out.
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