Applications of amorphous semiconductors to pickup and display devices are reviewed. Amorphous semiconductors can be obtained as large-area thin films, and are suitable for photo-electric conversion devices such as vidicon target and solid-state image sensor. Thin film transistor and electroluminescent panel are promising applications to display devices.
In order to improve the performance of HDTV cameras, we have been studying and developing the high-performance camera tube combined a 1-inch all electrostatic focusing and deflecting electron optics with a 4μm HARP. This paper describes the basic specification and the characteristics of the prototype tube at first. And we proposed several new technologies of a tube and a new operation method of a camera which enabled to attain the higher picture quality than ever.
A 15 inch-diagonal full-color a-Si TFT - LCD with 1152×900 pixels by non-interlace driving has been developed. In the TFT array of this LCD panel, the double layer gate constraction of TaOx and SiNx contributes to high production yield. Also, the double layer gate line of A1 (200nm thick) and Cr lowers the gate bus line resistance, decreasing the gate pulse signal distortion. The LCD panel with the storage capacitance structure formed on the gate lines is driven by a "capacitively coupled driving method", achieving a high aperture ratio at the TFT array (34%) and a low signal amplitude (5v).
A 13.8-inch a-Si TFT-LCD with 1152×900 pixels has been developed by using some new technologies which incorporate a low-resistance gate-line structure, a self-aligned TFT with improved gate-insulator, a high pre-tilt alignment layer and high resistivity liquid crystal material. As the result, a 30% aperture ratio and excellent 4096-color graghic displays have been achieved.
When moving images are displayed on matrix display panels, we sometimes observe pixels that appear at places where they should not. For instance, red pixels appear at the places of green or blue pixels, or even at places between two pixels. We named this phenomenon "false pixels". These false pixels are found to be originated from the after-image of human eyes and stimulation pattern from light-emitting pixels. Also, when the displays have extended light-emission periods, we observe extension of apparent pixel size. Because of these phenomenon, quality degradation occurs to moving images in the matrix displays.
An experimental 17-in. dc plasma display panel (PDP) with the average cell pitch of 0.58×0.54mm^2 is presented. A stable memory operation has been demonstrated by use of a pulse-memory technique. A full-screen video image has been reproduced with white. luminance up to 70cd/m^2. The number of display cells is 448×640. This performance has been brought about by a peculiar fine screen-printing technology for patterning the narrow width cathodes as well as for barrier ribs.
A full color gas discharge panel is Still insufficiently bright for use as a high definition display, so increasing contrast or reducing reflectance should be regarded with more importance than increasing brightness, especially for viewing in a light illuminated room. We proposed a panel which has micro color filters coated on inner surface of the faceplate. A 25-in. panel has been developed with 512×768 cells of 0.7mm pitch. Size and power consumption of new display system is about half of these of a conventional system. A HDTV picture is displayed on the panel with the following performance ; luminance 90cd/m^2, gray level 256, contrast 50 in a 200lux environment.
Short life is one of the problems for a DC discharge color panel. The life in this case is limited by the decrease of luminance. Experimentally, following results are obtained: (1) The life of a panel (Ne-Xe) is proportional to X^<1.5>P^6I^<-3>,where P:total pressure, X:Xe partial pressure ratio, I:discharge current. (2) TV pictures have been reproduced on a panel (Ne-Xe (10%)-Kr (10%), 200 Torr) that is provided resistors in each cell. The life of this panel is estimated at 14000 hours. (3) It is found that the life of a panel operated with pulse memory drive or one line at a time drive can be estimated from that of DC drive operation. (4) Resistance maps are obtained by measuring value of all resistors in panels.