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Finite Difference Aanalysis on Fast Response of Liquid Crystal Device Base on OCB Mode

Author: GuoQing
Tutor: ZhangHua；GaoZhiQiang
School: Nanjing University of Posts and Telecommunications
Course: Information materials
Keywords: LCD response finite-difference OCB driving nuclerization center
CLC: TN873.93
Type: Master's thesis
Year: 2011
Downloads: 37
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Abstract


Liquid Crystal Display (LCD) device is the key technology in current flat pannel displays. Fast response is one of critical standard to assess performance of LCD device. Slow respone results in the motion blur, low contrast and flash appearing on rolling screen, which really hold a block to LCD’s further development. Upon these issues, this thesis mainly focuses on:On the basis of differential equation of LC molecules’motion under external electric field, we give the analytic and numerical methods to solve these equations. Through analyzing the direct and indirect factors that influencing response time we summarize the effective approaches and pathway to improve the performance of response time, including LC cell parameter adjustment and optical mode optimization such as a reduction on cell thickness, new optical mode of as OCB, NBB, MVA.The contribution from driving method mainly include new electrode design and driving waveform adjustment.Finite-difference and iteration are the two basic mathematical methods we used in our study. Upon a derivation from a stable state LC molecule director of TN mode under fixed driving voltage, we quantitatively analyzed the influence of optimization on factors such as iterations, sublayer thickness on computational accuracy and computational reliability. Furthermore, by calculating and analyzing molecule director’s configuration under different voltage, we verify that it is hopeful to improve TN LCD’s response time by the adjustments of factors such as ratio of pitch and cell gap, voltage waveform, which results in an efficient improvment on LCD response time.Then we study the liquid crystal Optical Compensation Bend (OCB) mode and by combining with velocity gradient figure, explain the dynamic curve of director from the mutual reaction between drainage and molecule’s motion under external field. We discuss the reason of director keeping symmetry in electroptic cources, then analyze the original causes of the differences between liquid crystal molecules’rise-time and descend-time, meanwhile we predict the trend of variation of molecules’response curve’s configuration.Subsequently we study the best driving waveform from the view of energy with respect to OCB mode configuration. We also give a brief presentation on other influential factors which can improve LCD response time such as pretilt angle, anchoring energy and symmetry properties. From the point of view of display commercialization, combining with theory on geometrical optics, we discuss the suggested device response time under different viewing angle and calculate the biggest angle be at 60°under which grayscale reverse will not be occured and be accepted by users from a wild field. A mode combined symmetrical configuration from OCB and bi-nuclerization center which is easy to produce on technics is brought forward by us at last, Software-Simulation on its electric-optic course is done to assess its reponse properties. A response time at about 4.8 ms would make it compatible with techniques such as Color Field Sequential that contribute on image quality advance but has a high appeal on LCD molecule’s response. All this expedite modified-OCB-mode LCD has more broad stage on liquid crystal screen market.

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CLC: > Industrial Technology > Radio electronics, telecommunications technology > Radio equipment,telecommunications equipment > Terminal equipment > Display device,the display > LCD monitors
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