1. 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

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

3. 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

4. HKUST COPS structure

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

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

7. HKUST Passive matrix COPS row signal column signal

8. 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

9. HKUST COPS analysis y x

10. HKUST Analytical solutions Electric fields

11. HKUST (b) Electric field lines No vertical fields

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

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

14. HKUST Optical efficiency of COPS

15. HKUST Low voltage operation

16. HKUST COPS has better switching times

17. HKUST Similar spectral characteristics

18. HKUST Excellent viewing angles T on Contrast 0.7 0.5 0.3 40 10

19. HKUST Summary

20. HKUST Alternate alignment for negative LC

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

22. HKUST Bright state viewing angle 0.86 0.43

23. HKUST Behavior in the parameter space D G T

24. 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