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Introduction to display technologiesIntroduction to display technologies
Jean-Michel LechevallierJean-Michel Lechevallier
SummarySummary
1. Introduction to LCD.1. Introduction to LCD. History.History. How it works.How it works. Optical modes.Optical modes. CCFL, EL, Led. CCFL, EL, Led. Lightguides.Lightguides. Optical films.Optical films. LED and their chromatic characteristics.LED and their chromatic characteristics.
2. Bistable LCD.2. Bistable LCD.
SummarySummary
3. LCD module architecture.3. LCD module architecture. LCD - driver connection.LCD - driver connection. Complete architecture of a module. Complete architecture of a module.
4. Color LCD.4. Color LCD. 4.1. Passive matrix.4.1. Passive matrix.
Color cell (Transmissive, Reflective, Transflective).Color cell (Transmissive, Reflective, Transflective). Optical modes comparisonOptical modes comparison Grey scale generation (FRC, PWM).Grey scale generation (FRC, PWM).
4.2. Active matrix.4.2. Active matrix. Introduction to TFT.Introduction to TFT. LTPSLTPS System on module.System on module.
SummarySummary
5. Other technologies.5. Other technologies.
5.1. Field sequential5.1. Field sequential
5.2. OLED5.2. OLED
5.3. Others.5.3. Others.
6. Display technical characteristics.6. Display technical characteristics.
6.1. Main characteristics.6.1. Main characteristics.
6.2. Measurement methods.6.2. Measurement methods.
7. Comparison.7. Comparison.
CSTN, TFT, OLED.CSTN, TFT, OLED.
1. Introduction to LCD.1. Introduction to LCD.
History.History.
1888 : discovery of liquid crystal phase by an Austrian botanist, Dr Rheinitzer
1968 : first liquid crystal display built by RCA
years 1970 : developement of first LCD for mass production in Japan.
1. Introduction to LCD.1. Introduction to LCD.
How it works (2/3).How it works (2/3).
TN, STN, DSTN, FSTN technologies.TN, STN, DSTN, FSTN technologies.
1. Introduction to LCD.1. Introduction to LCD.
How it works (3/3).How it works (3/3).
Alignment layers.Alignment layers.
1. Introduction to LCD.1. Introduction to LCD.
Optical modes.Optical modes.
ReflectiveReflectiveReflectiveReflectiveTransmissiveTransmissiveTransmissiveTransmissive TransflectiveTransflectiveTransflectiveTransflective
Backlight ONBacklight ONBacklight ONBacklight ON Backlight ONBacklight ONBacklight ONBacklight ONBacklight OFFBacklight OFFBacklight OFFBacklight OFFFrontlight ONFrontlight ONFrontlight ONFrontlight ONFrontlight OFFFrontlight OFFFrontlight OFFFrontlight OFF
= LCD panel= LCD panel= LCD panel= LCD panel = backlight or frontlight= backlight or frontlight= backlight or frontlight= backlight or frontlight
1. Introduction to LCD.1. Introduction to LCD.
sources : CCFL, EL, Led. sources : CCFL, EL, Led.
Lightguides : Lightguides : FrontlightFrontlight BacklightBacklight
1. Introduction to LCD.1. Introduction to LCD.
Optical filmsOptical films main supplier : 3M main supplier : 3M
2 technologies:
- microreplication :adjustment of the light reflection angles => ex. : BEF, xBEF
- multi layer :light filtering => ex. : DBEF
LED and chromatic characteristics.LED and chromatic characteristics.Coordonnées chromatiques
0,19
0,2
0,21
0,22
0,23
0,24
0,25
0,26
0,27
0,28
0,29
0,3
0,31
0,32
0,33
0,34
0,35
0,36
0,37
0,38
0,39
0,4
0,41
0,42
0,43
0,44
0,45
0,24 0,25 0,26 0,27 0,28 0,29 0,3 0,31 0,32 0,33 0,34 0,35 0,36 0,37 0,38 Cx
Cy
a0
b1
b2
c0
Rangs Nichia
LE
D a
nd t
heir
chro
mat
ic c
hara
cter
istic
s.LE
D a
nd t
heir
chro
mat
ic c
hara
cter
istic
s.
1. I
ntr
od
uct
ion
to
LC
D.
1. I
ntr
od
uct
ion
to
LC
D.
2. Bistable LCD.2. Bistable LCD.
Bistable LCD - BiNem technology from NemopticBistable LCD - BiNem technology from Nemoptic
3. LCD module architecture.3. LCD module architecture.
LCD - driver connection.LCD - driver connection.
COBCOB : Chip On Board, : Chip On Board,
TABTAB : Tape Automated Bonding (TCP : Tab Carrier Package), : Tape Automated Bonding (TCP : Tab Carrier Package),
COFCOF : Chip On Foil - Flex, : Chip On Foil - Flex,
COGCOG : Chip On Glass. : Chip On Glass.
3. LCD module architecture.3. LCD module architecture.
Complete architecture of a module. Complete architecture of a module. TAB
COG
Driver
Driver
4. Color LCD4. Color LCD4.1. Passive matrix4.1. Passive matrix
Color cellColor cell
Transmissive display
4. Color LCD4. Color LCD4.1. Passive matrix4.1. Passive matrix
Color cellColor cell
Reflective display
4. Color LCD4. Color LCD4.1. Passive matrix4.1. Passive matrix
Color cellColor cell
Transflective displaysolution 1 : with a transflective sheet
The display reflectivity is adjusted by changing the reflectivity (transmissivity) of the transflector.
4. Color LCD4. Color LCD4.1. Passive matrix4.1. Passive matrix
Color cellColor cell
Transflective displaysolution 2 : reflective surface on color filters
Reflective areaReflective area
Transmissive areaTransmissive area
surfacetotale
surfacevetransmissiRatioOpen
..
....
4. Color LCD4. Color LCD4.1. Passive matrix4.1. Passive matrix
Optical modes comparisonOptical modes comparison
Transmissive Reflective Transflective
Indoorreadability
+++ + ++
Outdoorreadability
+ +++ ++
contrast +++ + ++
Colorgamut
(saturation)+++ + ++
4. Color LCD4. Color LCD4.1. Passive matrix4.1. Passive matrix
Grey scale generatorGrey scale generator
FRC = Frame Rate ControlFRC = Frame Rate Control
alternatively light on and off pixels alternatively light on and off pixels during several frames => the average during several frames => the average
light creates the grey level.light creates the grey level.
Advantages:Advantages:lower power consumptionlower power consumption
better contrastbetter contrastless flickeringless flickering
Disadvantage :Disadvantage :jitteringjittering
PWM = Pulse Width ModulationPWM = Pulse Width Modulation
Advantage:Advantage:No jitteringNo jittering
Disadvantage:Disadvantage:higher power consumptionhigher power consumption
ONON OFFOFF OFFOFFONON OFFOFFONONOFFOFF TframeTframe
tHtH
Duty cycle=tH/TframeDuty cycle=tH/Tframe
ExampleExampleGL=3/7GL=3/7
ExampleExampleGL=3/7GL=3/7
Frames 1 2 3 4 5 6 7Frames 1 2 3 4 5 6 7Frames 1 2 3 4 5 6 7Frames 1 2 3 4 5 6 7
4. Color LCD4. Color LCD4.2. Active matrix4.2. Active matrix
Introduction to TFT Introduction to TFT
4. Color LCD4. Color LCD4.2. Active matrix4.2. Active matrix
Introduction to TFTIntroduction to TFT
TFT cell structure TFT cell structure
4. Color LCD4. Color LCD4.2. Active matrix4.2. Active matrix
Advantages of TFT Advantages of TFT compared to CSTNcompared to CSTN
contrastcontrast
color saturationcolor saturation
response timeresponse time
viewing anglesviewing angles
Disadvantages of TFT Disadvantages of TFT compared to CSTNcompared to CSTN
power consumptionpower consumption
costcost
4. Color LCD4. Color LCD4.2. Active matrix4.2. Active matrix
TFT LTPS (Low temperature Poly Silicon) TFT LTPS (Low temperature Poly Silicon)
LTPS : electron mobility increased compared to amorphous TFT technology :
electron mobility
p-SI TFT = 200cm²/V.S
a-Si TFT = 0.5cm²/V.S
=> enable to reduce transistor size and embed more electronic functions on the glass substrate.
4. Color LCD4. Color LCD4.2. Active matrix4.2. Active matrix
Advantages and disadvantages of LTPSAdvantages and disadvantages of LTPS
Advantages:
higher electron mobility
higher aperture ratio => enable to increase the resolution
Disadvantages :
production yield
cost
4. Color LCD4. Color LCD4.2. Active matrix4.2. Active matrix
System On Module System On Module
Display areaSensor
MemoriesInterface
Controller Driver,DAC
Embedded functions :
- driver / controller- memories- peripheral audio functions- scanner- finger print recognition- etc.
5. Other technologies.5. Other technologies.5.1. Field sequential5.1. Field sequential
IntroductionIntroduction
5. Other technologies.5. Other technologies.5.1. Field sequential5.1. Field sequential
Advantages:
up to 85% of NTSC color gamut
High resolution (1dot/pixel)
Disadvantages:
the display is black and white in reflective mode
dedicated controller
specific LC cells (very fast response time)
a sorting of tricolor LED is necessary to reduce color variations
Necessary to adjust the color balance
Advantages / DisadvantagesAdvantages / Disadvantages
5. Other technologies.5. Other technologies.5.2. OLED.5.2. OLED.
IntroductionIntroduction
Anode (ITO)
Glass Substrate
Cathode (AL:Li)
+
-
Hole
Electron
Hole Injection Layer
Emission Layers
Light
----------
+ + + + + + + + + + +
CurrentLight
5. Other technologies.5. Other technologies.5.2. OLED.5.2. OLED.
Advantages / DisadvantagesAdvantages / Disadvantages
Advantages
contrast
viewing angles
very thin module (no backlight)
response time (1µs)
color saturation
Disadvantages
lifetime (especially for blue)
Brightness is a bit low
power consumption
emissive technology
6. Display technical characteristics6. Display technical characteristics6.1. Characteristics6.1. Characteristics
Contrast (transmissive and reflective)
Transmittance (%)
Reflectance (%)
Response time (ms)
Viewing angles (transmissive and reflective) (degrees)
Chromatic co-ordinates (transmissive and reflective) (defined in CIE 1931 diagram)
Color gamut (surface or % of NTSC triangle)
Open ratio (%)
Aperture ratio (%)
Brightness (cd/m²)
Backlight uniformity (%)
Power consumption (mW)
6. Display technical characteristics 6. Display technical characteristics 6.2. Measurement methods6.2. Measurement methods
2 methods for measurements in reflective mode (contrast, reflectivity, …) 2 methods for measurements in reflective mode (contrast, reflectivity, …)
Specular diffuse
Use a sphere to diffuse the light in every direction => this method is the
most representative of normal lighting condition.
Use a point light source.
7. Comparison7. Comparison
CSTN TFT AM OLED Thickness 2.7mm with backlight 2.7mm with backlight 1.7 Brightness TF : 70cd/m²
TM : 170cd/m² TF : 100cd/m² TM : 250cd/m²
150 to 200 cd/m²
Response time 150 à 300ms 30ms 1µs NTSC ratio TF : 15%
TM : 35% TF : 40%
TM : 60% (up to) 65%
(50% for PM OLED) Contrast TF : 20
TM : 30 TF : 70
TM : 300 500
Viewing angles 60 à 90 degres 60 à 160 degres 180 degres Power consumption (all on) based on 96*64 display
BL off : 2mW BL on : 180mW
BL off : 3~4mW BL on : 180mW
200mW
Lifetime (defined at half brightness)
>30K hrs >30K hrs <5 to 10 K hrs (with color deviation)