Tetsu Ogawa

Plasma-Enhanced Chemical Vapor Deposition of Silicon Nitride

The optimum condition of plasma-enhanced chemical vapor deposition to deposite silicon nitride (SiNx) film and its application as a gate insulator of a-Si thin-film transistor (TFT) have been investigated. The internal stress of SiNx in the range of 4.3×109 dyn/cm2 tensile to 8.0×109 dyn/cm2 compressive is found to be controllable by changing the ratio of H2 and N2 in the source gases without affecting the optical band gap. Satisfactory TFT characteristics and high reliability are realized by using a gate insulator of SiNx having either stoichiometric or N-rich composition which shows the large optical band gap.

16.1: Invited Paper; The Trends of Reflective LCDs for Future Electronic Paper

One of the biggest challenges for LCD technologies is to realize true “Electronic Paper”. The most appropriate solution for it will be reflective color LCDs. Various types of them will be reviewed, and especially single polarizer modes will be emphasized. The trends to go ahead and key technologies will be also discussed.

Threshold Voltage Shifts in Amorphous Silicon Thin Film Transistors under Bias Stress

Through the time and temperature dependence measurements on threshold voltage shifts (Δ V T ) in amorphous silicon thin film transistors, it has been found that two separate instability mechanisms exist; within short stress time ranges Δ V τ increases as log t and this behavior corresponds to charge trapping in SiN. On the other hand, in long stress time ranges Δ V T increases as t t/4 and can be explained by time-dependent creation of trap in a-Si.

A reflective color STN‐LCD with a single polarizer and double retardation films

— A reflective color STN-LCD with a single polarizer and double retardation films has been investigated. The double retardation films arranged in front of the LC layer enabled the LCD to contain reflective electrodes inside the panel. This configuration achieves a bright image with no parallax. A new construction of a reflective STN-LCD with a single polarizer has been developed by means of our own method in which the color difference ΔE* as the optimizing parameter has been used. Further, RGB color filters have been newly designed for our reflective LCD, and an aluminum (Al) layer has been introduced as a reflective electrode. As a result, we have realized a 7.8-in.-diagonal reflective color STN-LCD (640 × 480) which has 15% reflectance, 14:1 contrast ratio, 4096-color capability, and sufficient color gamut. It has been confirmed that the single-polarizer reflective color STN-LCD has sufficient performance for mobile business tools. We believe that it will be a key device for this application.

P-8: A Novel Bright Reflective Color STN-LCD with the ISR (Inner Scattering Reflector) Structure

A novel bright reflective color STN-LCD with the ISR (Inner Scattering Reflector) structure has been developed for the first time in reflective color STN-LCDs. The adoption of the ISR structure enables the LCD to obtain not only clear image without blur but also 2.5 times brightness as high as that of conventional reflective color STN-LCDs.

Reflective color STN-LCD technologies

Reflective color STN-LCDs should be one of the most promising devices for mobile business tools (MBT), because the demand such as low cost, low power consumption, light weight and compact size is especially strong for this application. A reflective color STN-LCD with a single polarizer and double retardation films has been investigated. The double retardation films arranged in front of LC-layer enabled the LCD to contain reflective electrodes inside the panel. This configuration achieves the bright image with no parallax. A new construction of a reflective STN-LCD with a single polarizer has been decided by means of our own method in which the color difference (Delta) E* as the optimizing parameter has been used. Further, RGB color filters has been newly designed for our reflective LCD, and the aluminum (Al) layer has been introduced as reflective electrodes. As a result, we have realized 7.8-in.-diagonal refractive color STN-LCD(640 by 480) which has 15% reflectance, 1:14 contrast ratio, 4096 color capability and the sufficient color gamut. It has been confirmed that the single polarizer reflective color STN-LCD has sufficient enough performance for MBT use. We believe that it will be a key device for this application.