What is an Electrophoretic Display?

An electrophoretic display is a type of low-power thin display that is considered a prime example of electronic paper, or e-paper. Electrophoretic displays are used in e-book devices such as the iLiad®, the Sony Reader®, the Cybook Gen3®, and Amazon Kindle®. The near-term goal in the display industry is to use electrophoretic displays to create e-paper that is thin, flexible, and easily visible even under glare. E-paper has long been promised by the display industry, but it has yet to take off in a big way. The long-term vision is to use e-paper to replace books and magazines.

In the most common implementation of an electrophoretic display, millions of tiny titanium dioxide (titania) particles, each about a micrometer (a thousandth of a millimeter) in diameter are suspended in a carrier solution of hydrocarbons and black dye. These titania particles are covered with charging agents to give them an electric charge.

After treatment of the particles, they are suspended in oil between two parallel conductive plates about 10 to 100 micrometers apart. The parallel conductive plates are connected to circuitry that allows external signals to manipulate the electric charge at different precise points on the display. By manipulating the charge, the particles either migrate to the surface of the display or rest near the back. This effect is called electrophoresis, after which the display is named.

While at the surface, the titania particles scatter light, appearing bright white. While near the back, the dye solution makes the pixel seem black. By manipulating charge over the entire display, an image can be created. Using color filters allows the display of the full visible spectrum.

The primary manufacturer of electrophoretic displays is E Ink Corporation, who makes the displays for the e-book devices mentioned above. A convenient aspect of electrophoretic displays is that they can be manufactured using the same manufacturing process — Electronics on Plastic by Laser Release — currently used to mass-produce LCD screens. The first cell phone to use electrophoretic display technology was the Motorola Motofone, released in 2006.