HKUST Liquid Crystal Switching Using Comb-on-Plane Electrodes M Wong, Z G Meng and H S Kwok Center for Display Research Hong Kong University of Science & Tech

HKUST Outline  Introduction  Comb-on-plane electrode analysis  Performance of a wide viewing angle LCD  Other applications

HKUST In-plane switching  IPS is good for wide viewing angle  But IPS has many shortcomings - low transmission, easy shorts and opens, high voltages...  COPS is planar in structure and easy to made with no defects

HKUST COPS structure

HKUST COPS Structure WcWc Plane electrode Glass WsWs CsCs CsCs LTO ITO Comb electrodes

HKUST Active matrix COPS (a) ITO plane electrode Data line Gate line x ITO comb electrode

HKUST Passive matrix COPS row signal column signal

HKUST Major advantages over IPS  Much better layout than IPS - chance of shorts and opens much reduced  Large storage capacitance (useful for active matrix)  Lower voltage operation  Faster response times  Higher brightness  Excellent viewing angles - same as IPS

HKUST COPS analysis y x

HKUST Analytical solutions Electric fields

HKUST (b) Electric field lines No vertical fields

HKUST Electric field intensity distribution Characteristics: Very intense field near the edge only. -> alters boundary condition of alignment and small bulk effect

HKUST Operation for positive anisotropic LC Incident light E C E E C V=0 (TN) V large

HKUST Optical efficiency of COPS

HKUST Low voltage operation

HKUST COPS has better switching times

HKUST Similar spectral characteristics

HKUST Excellent viewing angles T on Contrast

HKUST Summary

HKUST Alternate alignment for negative LC

HKUST Transmission voltage curve T/T(TN)= 99% CR>100

HKUST Bright state viewing angle

HKUST Behavior in the parameter space D G T

HKUST Conclusions  A new electrode geometry has been proposed and demonstrated  It is easier to make, more reliable and performs better than conventional IPS  It can be used in passive matrix as well as active matrix situations