**1.1.1 Gyricon**

Historically, the very first flexible display system was realized with "Gyricon" media by Sheridon and Berlovitz in 1977 and its conceptual cross-sectional view is illustrated in Figure 1. This kind of material contains black and white colored beads (balls) with averaged size of 100m. Since different colors on the bead carry different charge polarity and the beads are enclosed in liquid, specific color can be directed to specific direction by outside electric field. This kind of system can perform either binary (black and white) data or gray scale reflective light. This system also mimics the printing process on papers by putting this Gyricon sheet into programmable electric field "printer". Unfortunately this project was closed in 2005 for not profitable reasons by Xerox. Some main advantages and disadvantages of electrophoretic system are listed below:


Disadvantage

370 Microelectromechanical Systems and Devices

also be with compact size when folded or rolled, and must be supporting large area when unfolded or unrolled. Hence the first idea within its applications is focused on electronic paper (e-paper). With the arising of the attitude towards ecological friendliness, the demands of paper reduction also transfer to and stress on the development of flexible display as an e-paper. A successfully flexible display is thus expected to be bendable, portable, light weigh, low cost, durable, and even disposable. On the other hand, from the technology point of view, to manufacture a flexible display typically requires a flexible substrate such as polymer plastic material, which adds more complicated factors into

From the process flow we understand that there are several disadvantages when use polymer plastic material as flexible substrate. For example, high temperature thin film deposition will cause material deformation since most polymers' glass transition temperatures (*Tg*); points or even melting point are below 200°C. Some polymer materials are also weak to chemical treatment or plasma bombardment which usually carries ultraviolet (UV) light. Thus, in order to successfully handle flexible substrate during production, a new process system should be set up. This process system is expected to take advantage of substrate's flexibility for variety and to avoid previously mentioned drawbacks on polymer materials. As discussed before, the flexible display has to support large display area thus a large substrate also introduces process difficulties in a production line. Take current semiconductor apparatus as an example, up to 12-inch circular substrate can be supported with lowest unit cost. However, a 12-inch diameter area cannot be called large area display. The latest 8th generation LCD apparatus which supports up to 2160×2460mm substrate size will be very helpful for large area display but its transportation is always a problem. To overcome these issues, traditional printing processes are taken into consideration because flexible polymer substrate is just like paper, which can be bent during process and can be produced continuously. Both the material flexibility and process

Historically, the very first flexible display system was realized with "Gyricon" media by Sheridon and Berlovitz in 1977 and its conceptual cross-sectional view is illustrated in Figure 1. This kind of material contains black and white colored beads (balls) with averaged size of 100m. Since different colors on the bead carry different charge polarity and the beads are enclosed in liquid, specific color can be directed to specific direction by outside electric field. This kind of system can perform either binary (black and white) data or gray scale reflective light. This system also mimics the printing process on papers by putting this Gyricon sheet into programmable electric field "printer". Unfortunately this project was closed in 2005 for not profitable reasons by Xerox. Some main advantages and

traditional electronic device's production line.

continuity are positive factors for large area device realization.

disadvantages of electrophoretic system are listed below:

3. Pattern is programmable by controller (computer),

5. Zero power consumption for static display.

1. The first demonstration of e-paper with little flexibility,

**1.1 Flexible display systems** 

**1.1.1 Gyricon** 

Advantage

2. Supports A4 size,

4. Supports gray scale display.


Fig. 1. Schematic cross-sectional view of Gyricon system.
