The response time for each TFT-LCD display mode, such as twisted nematic (TN), multi-domain vertical align (MVA), and in-plane switching (IPS) mode, has been measured and analyzed especially in grayscale. The characterization of each display mode has clarified the panel design dependence, especially that of IPS mode LCD. Several display modes have also been subjectively evaluated in view of moving picture appearance by comparing each LCD display monitor to CRT monitor. For moving picture image, subjective evaluation performed by selecting three display test patterns with two moving speeds. Subjective evaluation result is related to the three response parameters, 1) bi-level response time between L255 (brightest) and L0 (darkest), which is conventional definition of response time, 2) sum of average and variance of all response times including gray-levels (calculated twenty response times), and 3) average response time between middle and gray-level and next levels (L127 (reversible reaction) L191 and L127 (reversible reaction) L63). Among above parameters, the average response time of middle grayscales (to and from L127) shows good relationship with subjective evaluation result. The perception speed of each LCD monitor has been also subjectively evaluated to verify the relation to each response parameter. The target for the appropriated response parameter will be discussed.
Control of the seal edge of LC cells with super narrow periphery is very important for the application to compact AM-LCD designs. Several thermal cure epoxy resins have been studied as candidates for LC panel seal materials, with emphasis on characterizing the seal edge. The factors affecting material selection are its effect on LC alignment, the seal edge waviness or straightness, the formation of the seal edge boundary during lamination and cure and finally, its compatibility with standard cell processing techniques. Optimal seal material selection is discussed in view of its application to the design and fabrication of super narrow periphery LC cells. Cell design of seal edge control is also discussed in view of application of seal characterization and structural contribution, including material and process matching.
The multi-domain technology of UV light modified method has been further studied for the application to TFT/LCDs. The additional process is only UV light irradiation through the sub-pixel mask onto the polyimide film. The cell design of pre-tilt control and LC alignment optimization has been studied. The pre-tilt angle difference and the lower pre- tilt angle between the upper and the lower glass substrate are the key to apply this technology to TFT/LCD, the value are more than 2 degree and less than 1 degree, respectively. The process dependency of this technology has also been evaluated and proved its application to TFT/LCD cell process. The opto-electrical characteristics will be described including charge retention, transmittance-voltage curve, and driving life issue.