Date Visited: October 7, 1991
Report Author: A. Firester
We were hosted by Mr. Ota. He first explained to us the organization of the Matsushita LC Display Strategic Unit for Development and Manufacturing (LCD SUM). This is an internal organization of both development and manufacturing functions. LCD SUM is a profit center; sales of products supports R&D. Figure Matsushita.1 outlines the structure. Matsushita prepared an excellent detailed written response to the questions we submitted in advance.
All Matsushita R&D is funded by the company. They have some connections with Osaka Industrial University for basic R&D. The flat-display strategy is first internal use only and OEM only if there is excess capacity. First-stage applications are workstations, followed by AV (projection) and direct-view TV.
Matsushita will focus only on large-size panels in their new line.
High-temperature p-Si cannot be used to fabricate HiVision drive circuitry (projection discussion, Takeda).
They are investigating both high-temperature and low-temperature processes. HT suitable only for small sizes (viewfinders) and LT for 1- to 3-inch diagonal applications (projection).
Matsushita is studying excimer laser recrystalization of PECVD silicon. Uniformity is difficult; using multishot methods. Experiments only. Requires about 200 seconds for a 6-inch diameter wafer; not optimized. Mobilities achieved are 50-100 cm2/V-sec N-type and 20-50 cm2/V-sec P-type. Achieved high mobility using sputtered silicon, but there are many pinholes; sputtering is not suitable for large sizes.
For EDTV, mobilities of 50 (N) and 20-30 (P) are all that is needed. V(subscript T) is more critical. Currently V(subscript T) = 10 to -15 (P) and V(subscript T) = 0 to +2 (N).
They expect to be able to use p-Si on glass for peripheral drivers by 1995.
LPCVD is difficult to use for sizes larger than 300 mm x 300 mm; therefore, interest in PECVD.
Many approaches are under study for doping: ion shower, n-type amorphous silicon, gas-phase doping; ion implantation too expensive.
Gate insulator processes are under study are LTD, APCVD SiO2, and PECVD SiN. Problems still exist with interface states and bulk defects. Best so far is APCVD SiO2.
a-Si is suitable for projection. Optimum size is 3-inch diagonal.
Aperture ratio 30-40% @ 3-inch diagonal achieved 1 lumen/watt with an experimental transmissive system (Reflective LCD - 0.2 lumen/watt)
Light output is limited by a-Si photo conductivity. For home use the goal is 250 ft-lamberts on a 40-inch diagonal screen. This results in 400,000-lux blue light on a 3-inch diagonal light value. This value is safe.
Demonstrated 200 lumens output using a 250-watt metal halide lamp. This lamp provides 80 lumens/watt.
Maximum LV temperature should be less than 70 degrees centigrade with air cooling. The LC would operate up to 100 degrees centigrade but reliability is a concern at temperature > 70 degrees centigrade. Using the above lamp, the LV temperature is approx. 60 degrees centigrade.
Projector lens f/# = 4.5
Progressive scan using two-line driving method. Matsushita prefers two-line drive for moving images and single line drive progressive (using a frame store) for static images.
They have an interest in single LV color sequential projection to reduce the cost of the projector.
Matsushita has been working on FELCD for many years.
They have fabricated a 10-inch diagonal view display and a four megapixel projection display, which requires 500 msec for complete refresh.
They favor FLC for high-information-capacity static displays, and use partial addressing to handle mouse movements.
To achieve gray scale, possible techniques are frame rate modulation, subpixels. However, their ultimate goal is multidomain gray scale.
Expect use for projection in 1995.
Note: Matsushita manufactures and OEMs hot cathode fluorescent lamps and inverters.
Their 3 mm diameter lamps have an efficiency of < 35 lumens/watt. They would like to use cold cathode lamps for color sequential.