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2 Introduction to Reflective Displays

2.1 Reflective Displays

"Reflective displays rely on ambient light for information display" [1]. Reflective display

could be flexible or non-flexible, it is flexible if it is adopted on a plastic-board or other

flexible material, however, it is not flexible if it is adopted on a glass-board. For example

there are several types of LCD (Liquid Crystal Display) namely reflective LCD, transmissive

LCD and transflective LCD. We shall only explain reflective-LCD in this text, the rest fall

outside the scope of this project. Reflective-LCD allows ambient light to pass through the

LCD-layer to a back mirror, which subsequently reflects it back to the viewer, i.e. no obvious

backlight. Flexible-reflective displays are called Electronic papers (E-paper) because like the

conventional paper they reflect light. Generally, most reflective displays and E-papers have

deficiencies regarding contrast and color quality.

Reflective flexible display encompasses all E-Paper technologies; it is realized by

sandwiching the display material involved between two flexible board structures. The

structure of the display material is not unique as there are several types of display technology,

which also determines the driving technology applied (OTFT, Polysilicon, see figure 1).

The building block of flexible displays is divided into the front-plane and the back-plane.

The front-plane is transparent and is where different materials, which determine the display

technology (see figure 1), are applied, while the back-plane is made up of the substrate and

driving technology. The back-plane could be a passive or an active matrix. It is active matrix

if each pixels is switched on or off individually on the other hand it is passive if a group of

pixels are switched on or off by asserting power on a row and column of the transistor matrix.

Consequently, the technology applied in the production of most flexible displays (E-Paper) is

a combination of the following.

Front‐plane

1.Display technology

• Electrophoretic, Electro-wetting, Electrochromic, Cholesteric Liquid

Crystal, Bichromal, TOLED.

Back‐plane

2.Substrate technology

• Plastic, special foils etc.

3.Driving technology

• OTFT, Amorphous-Silicon, Poly-Silicon, chemical compound

semiconductors, nano, organic-semiconductors etc.

Figure 2.1: Cross-section of a Reflective Display

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