Liquid Crystal Display Module

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Liquid Crystal Display Module
Gregory P. Crawford Brown University NSF MRSEC
Center Division of Engineering Providence, RI
02912
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Education Outreach Philosophy
Teach and inspire basic science concepts through
modern technology!
Science Invention Products
Benefits
Innovation starts with basic science
Engineering Constraints --- Basic Science !
Technology Platform Flat Panel Displays
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What is a Display?
http//www.thesatelliteguy.com/media/tel_LC26GD4U_
pic1.jpeg
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Three Phases of Matter ???????
Solid Liquid Gas
Increasing Temperature
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What is a liquid crystal molecule ?
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The Liquid Crystal Phase
n
Crystal Nematic LC Isotropic
Temperature
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Anisotropy The Dielectric Constant
E

e


positive
- -
-
- -
e
De e - e gt 0
E
E

- - - -
negative
all angles in the plane ? to E are possible for
the -De materials
De e - e lt 0
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Anisotropy The Dielectric Constant
ordinary ray (n
, ordinary index of refraction)
o
extraordinary ray (
n
, extraordinary index
e
of refraction)
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Polarizers
Transmission Axis
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Twisted Nematic Liquid Crystal Displays
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Visualize a Phase Transition
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Color Addition
Yellow
RED
GREEN
WHITE
CYAN
MAGENTA
BLUE
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How to produce colors on your laptop
Spatial color synthesis
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How to produce colors on your laptop
How to create yellow ?
How
YELLOW
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CRT versus LCD
LCD polymer filters CRT phosphor
dots
300 mm
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Reflective Displays
Next Major Paradigm Shift in Display Technology
Backlit
Reflective
LCD
LCD

• Low power
• Low volume weight
• Naturally adaptive to
• changes in ambient
• illumination
• Low cost

backlight
absorber
Backlit
scan drivers data drivers controller grayscale
backlight
Power
Reflective
Reflective
bistable
2.6 W
mW
1.2 W
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The Chiral Nematic
Ordinary Nematic
Chiral Nematic
CN
director
pitch
n
P
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Bistable Cholesteric Display

• Polymer Stabilized Cholesteric Texture (PSCT)
• Pitch length tuned to reflect visible
• Contrast ratio 20-301
• Photopic reflectance 20-25
• Peak reflectance 40-45
• Driving voltage V120 Volts
• and V235 Volts
• Color monochrome

V1
V2
V
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l and Dl Properties of Cholesterics
Predicting reflection peak
Reflectance (arb. units)
Dl
Predicting reflection band
Wavelength
l
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The Future Electronic Books
Courtesy of Kent Displays (Ohio)
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The Future
?
CRT
LCD
100 years old 25 years old
Future
Transformation
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The Future
Howard, Scientific American, 290, 64 (2004).
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The Future ????
ITO Plastic
Display Materials
Roll Display
ITO Plastic
UV Cure
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Relate to MRSEC Research
ITO on PET
PEDOT on PET
ITO
substrate
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Thank you
Gregory P. Crawford Division of Engineering, Box
D 182 Hope Street Providence, RI
02912 Gregory_Crawford_at_Brown.Edu 401-863-2858
(voice) 401-863-9120 (fax) http//display.engin.br
own.edu