Print PageElectrophoretic displays electrically turn vast numbers of tiny spheres in a viscous medium to create and destroy images. The principle is that balls or microencapsulated particles rotate or move within a viscous medium when a voltage is applied. The displays may be passive or active. Companies such as E-ink develop these displays.
Advantages of electophoretic displays are:
- Strong scattering effect - wide viewing angles.
- Long-term image stability.
- Large area manufacturability.
- Print onto most surfaces easily.
- Thin
Disadvantages include:
- Slow response (current speed <200m/s - not video rate)
- High power (>15 Volts)
- Moving parts
- Colours limited
The principal components of E-Ink are the millions of tiny microcapsules, about the diameter of a human hair. In one incarnation, each microcapsule contains positively charged white particles and negatively charged black particles suspended in a clear fluid. When a negative electric field is applied, the white particles move to the top of the microcapsule, where they become visible to the user. This makes the surface appear white at that spot. At the same time, an opposite electric field pulls the black particles to the bottom of the microcapsules, where they are hidden. By reversing this process, the black particles appear at the top of the capsule, which now makes the surface appear dark at that spot.
Lucent, Toppan Printing and Dai Nippon Printing have also been researching electrophoretic displays.
