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

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Liquid Crystal Switching Using Comb-on-Plane
ElectrodesM Wong, Z G Meng and H S KwokCenter
for Display ResearchHong Kong University of
Science Tech
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Outline

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

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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

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COPS structure
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COPS Structure
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Active matrix COPS
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Passive matrix COPS
row signal
column signal
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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

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COPS analysis
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Analytical solutions
Electric fields
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Electric field lines
No vertical fields
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Electric field intensity distribution
Characteristics Very intense field near the edge
only. -gt alters boundary condition of alignment
and small bulk effect
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Operation for positive anisotropic LC
V large
V0 (TN)
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Optical efficiency of COPS
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Low voltage operation
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COPS has better switching times
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Similar spectral characteristics
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Excellent viewing angles
0.7
0.5
40
0.3
10
Ton
Contrast
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Summary
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Alternate alignment for negative LC
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Transmission voltage curve
T/T(TN)99 CRgt100
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Bright state viewing angle
0.86
0.43
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Behavior in the parameter space
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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