Principles of Functioning
"paper like" screens based on E-Ink technology
Work on creating "electronic book" gadgets is held for a long time already.
Several companies are involved in the production. The most visible success has
been achieved by American firm E-Ink. It developed electronic-ink displays which
are already used in devices by Sony, Fujitsu (Fujitsu-Siemens) and some other
big corporations. At the first stage E-Ink screen production is the same with
TFT screens. Here they use matrix similar to that in LCD panels. And then
the matrix is covered with a layer of microscopical capsules which contain
viscous fluid and positively and negatively charged particles with black and
white pigments. The functioning of such displays is based on a well known in
physics effect of electrophoresis - the property of charged particles to
move in fluid from one electrode to another (see picture).
If an area under a capsule on TFT-matrix gets positive
charge, negatively charged black particles are gravitated towards the charge and
descend to the bottom of the capsule. Positively charged white particles, on the
contrary, are repelled and emerge, i.e. they become visible. At this time the
reader sees a white point on the screen.
If a negative charge is given under the capsule the situation repeats vice
versa and we see a black point on the screen. Managing the degree of charge on
TFT-matrix we can get half-tints. The colour in this case will depend on
the number of transferred particles.
A very important peculiarity of electronic ink is that we can reach a very
high quality of resolution due to changing the colour of every single particle
of the pigment. As the particles diameter is measured in microns
screen resolution is actually determined by the
resolution of the electronic matrix managing the state of capsules. That's why
size and shape of capsules is not of great importance as well as colour
continuity of each one, consequently production becomes cheaper. Besides ink
optical state after the impulse applied is very stable. The formed image can be
kept for months!
The merits of E-Ink technology are also comfortable
reading (no flickering or letters shape change, independence on conditions of
lighting and visual angle) and ultra low power consumption if image on the
screen is static. This means that power supply is taken only when the
image is renewed, e.g. while turning a page.The power consumption of electronic
book main display is approximately 100 times lower than a mobile phone
screen. More over E-Ink displays possess six times higher reflectance and they
have two times more contrastihg range than LCD screens.
Electronic Paper in Work