SEMINAR ON LCD & FLAT PANEL DISPLAYS

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Transcript SEMINAR ON LCD & FLAT PANEL DISPLAYS

SEMINAR ON LCD & FLAT PANEL DISPLAYS
BY
CLOVER DISPLAY LTD.
(HONG KONG S.A.R, CHINA)
AN LCD MANUFACTURER SINCE 1983
URL http://www.cloverdisplay.com
&
DATE :
Sept 29, 2005
SPEAKER
Mr. JOHNNY C. L. CHOU
<Topics>
1. FLAT PANEL DISPLAY
2. INTRODUCTION TO LCD TECHNOLOGY.
3. HOW LCDs ARE MADE.
4. COLOR LCD
5. TODAY’S LCD
6. CUSTOM DESIGN LCD & LCM (MODULES).
7. TOUCH PANEL, Bi-STABLE LCD & ORGANIC LED.
8. QUESTION & ANSWER.
Edition #7 (2005)
1.0. FLAT PANEL DISPLAYS
Display Types
( commonly used Display )
Emits
Light
Voltage
Current
Patterning
Flexibility
CRT ( Cathode Ray Tube )
Yes
High DC
Low
( scanning )
VFD ( Vacuum Florescent
Displays )
Yes
High DC
Low
Medium
LED ( Light Emitting Diode )
Yes
Low DC
Medium
Low
Plasma Displays
Yes
High DC
Low
Low
EL ( Electro Luminescent
Displays )
Yes
High DC
Low
High
LCD ( Liquid Crystal Display )
NO
Low AC
Low
High
OLED (Organic LED)
Yes
Low DC
Lowmedium
High
P.1.
2.0. LIQUID CRYSTAL
2.1. Three major characteristics of Liquid Crystal
2.1.1. The Thermal Nature
Solid State
Liquid Crystaline
(Crystal)
State
Liquid
State
Low Temp
High Temp
Melting Point
Clearing Point
2.1.2. The Optical Nature of a LC molecule
XXX
NO light passing through
Light
Light passing through
2.1.3. The Electrical Nature of the LC molecules
Electrodes
No potential field
AC potential
P.2.
2.2. COMMON STRUCTURAL PHASES in the Liquid Crystal State
Smectic Phase
Nematic Phase
Cholesteric phase
2.3. Two other components to make a Liquid Crystal Display Panel
2.3.1. Transparent Electrodes ---- Glass with conductive ITO layer which is
etched to form a pattern.
2.3.2. The Polarizer Film
Light wave
& its axis
Polarizer &
its light axis
Outgoing light
& its axis
P.3.
2.4. A TYPICAL TN TYPE LCD CELL
Polarizer
(Axis 0 degree)
Glass with electrodes
NO power
supply
With AC Volts
connected
Glass with electrodes
Polarizer
(Axis 90 degrees)
Cell Gap =
The separation
between two glasses
Light
Positive Mode =
Black digit on the grey background
Negative Mode =
Clear digits on the dark background
P.4.
2.5. THREE COMMON TYPES OF LCD
2.5.1. TRANSMISSIVE TYPE
LCD
Light
(Back Light)
Eyes
POLARIZER ON BOTH SIDES
2.5.2. REFLECTIVE TYPE
LCD
Incident Light
POLARIZER ON THE FRONT SIDE
REFLECTOR ON THE BACK SIDE
2.5.3. TRANSFLECTIVE TYPE
LCD
Day Light
Night Light
(Back Light)
POLARIZER ON THE FRONT SIDE
TRANSFLECTOR ON THE BACK SIDE
P.5.
2.6. CHARACTERISTIC CURVES
Vs (Saturation Voltage)
% LIGHT
ABSORPTION
(or TRANSMISSION)
At higher
Temp.
90% changes
5v
4v
10% change
0 volt
Vth of LC
VOLTS
Vth (Threshold Voltage)
-40 deg C
+80 deg C
LC Fluid
Viscosity
mm2/sec
% Light
Absorption
10,000
At a lower
Temp.
Ton 5ms to 100ms
Toff 20ms to 300ms
Time
100
-40 deg C
+80 deg C
Depending on how the LCD fluid is formulated.
The smaller the cell gap, the faster response.
P.6.
2.7. TN & STN (Super Twisted Nematic)
The LC molecule
mid-plane tilt angle
% Light Absorption
% Light Absorption
90 deg
Twisted
Narrow View Angle
TN LCD
Grey Background
in the positive mode
Vs
% Light Absorption
240 deg
Twisted
180 deg
Twisted
V
0
Vth
0
V
0
Volts
Wide View Angle
STN LCD
Yellow Green background color
In the positive mode
P.7.
2.8. HTN (Highly Twisted Nematic) & FSTN (Film STN)
STN
180 deg or higher deg
Twisted
TN
90 deg Twisted
Wide View Angle BUT with
Darker Color Background &
Blue or dark blue patterns.
Narrow View Angle
1st Minimum TN
Little wider View
Angle than TN
(see later pages)
HTN
110 deg
Twisted
FSTN
240 deg or higher deg
Twisted
Wider View Angle than TN
but narrower than STN
View angle same as 240 deg STN
BUT in Grey Background Color
& Black patterns.
Polarizer
DSTN (Double STN Cells)
Old way
when NO
Retardation
film
1st Cell with patterns
Same as usual STN
2nd Cell without pattern
But in reverse twisting
LCD Cell
Retardation Films on Polarizers
to correct the color phase
P.8.
2.9. COMPARISON AMONG TN, HTN, STN & FSTN
2.9.1. Positive Mode (Pattern on a Clear Background)
Either
TN
HTN
STN
STN
FSTN
Deg Twisted
90
110
180
240
240
Background
Color
Grey
Grey
Yellow Green
or Grey
Grey or
Yellow Green
Grey
Pattern
Color
Black
Black
Dark Blue
or Blue
Blue or
Dark Blue
Black
Temp Range
-40C to +85C
-20C to +40C
-20C to +70C
-20C to +70C
-20C to +70C
Multiplex
Ratio
=< 1/8 duty
=<1/16 duty
=<1/32 duty
=<1/240 duty
=<1/240 duty
View Angle
60 deg
80 deg
120 deg
120 deg
110 deg
View
Direction
At 6 or 12
O’clock
ONLY
At 6 or
12 O’clock
ONLY
May specify
6 or 12 O’clock
May specify
6 or 12 O’clock
All
Voltage
2.5v min
5v typical
3v min
5v typical
3v min
5v typical
5v typical,
(higher duty,
higher volts)
5v typical,
(higher duty,
higher volts)
P.9.
2.9.2. Negative Mode (Clear Pattern on a Color Background)
TN
HTN
STN
STN
FSTN
Degree Twisted
90 deg
110 deg
180 deg
240 deg
240 deg
Background
Color
Black
Black
(Seldom used)
Dark Blue
Black
Pattern Color
Clear
Clear
(Seldom used)
Clear
Clear
Other natures same as the Positive Mode.
2.10. Gooch-Tarry Curve --- The 1st Minimum TN LCD
% Transmission
n : Birefringence (reflective indices of
12%
Light transmitted in parallel & perpendicular
To the director of LC molecules.
d : the cell gap
8%
4%
0%
0.48 (1st Min* )
1.05 (2nd Min)
*The 1st Min process is patented by E. Merck.
1.64 (3rd Min)
d n
(um)
P.10.
2.11. THE STATIC & MULTIPLEX DESIGN OF ELECTRODES
4 pairs of electrodes
8 connectors needed.
5 electrodes
5 connectors needed.
4 electrodes in matrix
4 connectors needed.
No time sharing for
the input signals –
The STATIC Design
1/4 time sharing for
the input signals to
each of the top electrode.
No time sharing for
the bottom glass.
We call the top electrodes
the SEGMENT while
the bottom electrodes
the COMMON.
1/2 time sharing for
the input signals to
both the top and
bottom electrodes---The MULTIPLEX Design.
We call it 1/2 duty if the
1/2 time sharing is used
on the Common.
PROBLEM:
The higher the duty ratio, the shorter time the power signal goes into each electrode pair.
Finally the power rms value may NOT be enough to fully drive the LC twisting properly.
P.11.
2.12. THE PASSIVE AND ACTIVE LCD
Y1
Y2
Signal
X1
Time
X2
Signal
Time
An ACTIVE Component ;
MIM (metal insulator metal) Diode
Or
TFT (thin film transistor)
The LCD Pixel
The TFT method is commonly used today on the large DOT MATRIX LCD,
we call it the ACTIVE MATRIX LCD, or AMLCD
The LCD built together with the Active Component is not only the TFT LCD. The LCOS
is also an LCD built on a silicon wafer with active components to control the LCD.
In general, the duty ratio over 1/256 may not give a good contrast in the Passive design.
But there are still some special design to work in the Passive way, such as;
Dual Scan STN (DSTN), High Performance Addressing (HPA), …. etc
P.12.
2.13. THE HISTORY OF LC & LCD
Application
Thermometer
Approx Year
Major Development
1888
Liquid Crystalline initially described by an Austrian Scientist,
Mr. Friedrich Reinitzer.
1904
E. Merck sold the first Liquid Crystal substrates to the research market.
1960
Westinghouse used the cholesteric LC as a temperature indicator.
1965
RCA demonstrated a dynamic scattering LCD to show numeric symbols.
Kent State Univ. in Ohio USA presented an LCD operated at room temp.
Rockwell (USA) and Sharp (Japan) made LCD Calculators.
Hull Univ. in England synthesised new biphenyls with excellent physical
properties for display use.
1970
Calculator
Higher Contrast Twisted Nematic Mode in use.
OCLI (USA) coated ITO on glass as electrodes.
BDH (UK) sold LC to LCD manufacturers.
Time pieces
1975
Instruments
Hamlin Inc (USA) in TN LCD mass production.
E. Merck introduced Biphenylcyclohexanes LC for higher multiplex.
Data bank & PDA
Motorola built LCD on 4 ½”x 4 ½” glass substrates
Microma (USA) further improved the mass production technique and
Fairchild Semiconductor Inc. moved LCD production to Hong Kong.
Timex (USA) bought RCA LCD facility and merged with Fairchild.
The Japanese developed a Chemical Sealing process for cost reduction.
P.13.
2.13. THE HISTORY (continued)
Application
Approx Year
Major Development
The first LCD scriber made by Villa Precision Inc. (USA)
1980
Roche, BDH, E.Merck improve LC mixtures for TN, STN
5x7 Character
Fairchild scaled up to 14x14” substrates
Dot Matrix Graphic
Word Processor
Clover Display Ltd established in May 1983
Full Dot Matrix &
TV Panels
1985
PDA, Laptop &
Notebook PC
MIM & TFT AMLCD invented
Brewer Science Inc. & OIS of Troy, USA developed colour
AMLCD for space shuttle use.
Full color TFT panel for Notebook PC
1990
Mobile phones
1995
Bi-stable Cholesteric LCD
E Books
2000
New Display to replace LCD ?---- OLED, PLED
P.14.
3.0. HOW LCDs ARE MADE
3.1. THE FRONT END PROCESS
ITO Glass
ITO = Indium Tin Oxide, a transparent conductive layer coated on the
Sodium Lime Glass. Its resistance is from 10 Ohms to 120 Ohms/square.
Glass area usually in 14x16”. Thickness in 1.1, 0.7, 0.5, 0.4, 0.3mm
Clean Glass
with DI water
Artwork & Mask Design
Patterning the
Electrodes on ITO
Methods: Photo Masking, Resist Ink Printing,
ITO Ink direct Printing, Laser Cutting.
Alignment Layer
To form a rough surface to hold the LC molecule chains
Sealing Frame &
Silver Dot Printing
To form the cell and the inter-connections between the top and bottom glasses
Top/bottom Glass
Alignment and Seal
The Laminated pairs
P.15.
3.2. THE BACK END PROCESS
Laminated Pair
Cutting into cells
Liquid Crystal Mixture
Formulation
Liquid Crystal Filling
End Sealing & Cleaning
Testing & Inspection
Polarizer Cutting
Polarizer Fixing
Metal Pin or Heat Seal Connector fixing
Cosmetic Check
Shipments
Optional Process
LCD Module Assembly (COB, TAB, COG, COF)
P.16.
4.0. THE COLOR LCD
4.1. THE FULL COLOR LCD
Black and White LCD
Segments
Common
Full Color LCD
Slice ITO
into narrow
sections
RGB
Color
Filter
Common
In order to give a better color mixing,
the RGB line widths are usually less
than 30 micron in width per color.
Hence the same for the ITO electrodes.
The color LCD can be built as a Passive LCD.
But most large size Dot Matrix Color LCDs
are built in the Active design.
P.17.
4.0. THE COLOR LCD (continued)
4.2. THE ECB (ELECTRICALLY CONTROLLED
BIREFRINGENCE) COLOR LCD
% Light
Absorption
Various ECB Types;
1) Homogeneous Type
Red->Yellow->Green->Blue
0
Clear
Dark
Grey
Y O R P B G
Color around
2.4v to 3.7v
Dark
V
2) Deformation of Vert Aligned
Plane (DAP) Type
Blue->Green->Yellow->Red
3) Hybrid Aligned Nematic
(HAN) Type
Green->Red->Blue
4) Vertical Aligned Nematic
(VAN) Type
V
No pure color,
50% Green + 25% Red + 25% Blue at this point
P.18.
4.3. DOUBLE CELL COLOR LCD
There are two kinds of double cell can generate colors;
A) With Color Polarizer
B) With usual Polarizers at certain angles
(Only working in Transmissive Mode)
(Reflective Mode is also possible)
4.4. GUEST HOST LCD (Single fixed color)
Mixing color dye in the LC fluid and build LCD in Negative Mode.
It will show clear pattern on a color background.
Such method was used in the early date.
4.5. LCD WITH COLOR POLARIZER, COLOR FILM OR
COLOR REFLECTOR IN CERTAIN AREA (fixed color)
Pre-printed color polarizer is expensive.
4.6. COLOR INK PRINTING ON THE BOTTOM GLASS SURFACE
(fixed color)
This is the cheapest way to make LCD with fixed colors.
The LC image & color area may not coincide well due to the glass thickness.
P.19.
5.0. TODAY’S LCD
Active LCD
Duty Ratio
LCD TV & Monitors
1/256
Passive LCD
Projector
1/128
Portable TV
Notebook Panels
1M+ Pixels
Digital Camera
Office Equipment
1/64
PDA
100K Pixels
1/32
Mobile Phone
Digital Instruments
1/16
10K Pixels
Data Bank
1/8
1/4
Film Camera
1/3
Calculator
STN
TN
1K Pixels
100 Pixels
1/2
Time pieces
Hand Held Games
Panel
Size
1/1
Static
10 mm2
100
1,000
10,000
100,000 mm2
P.20.
6.0. CUSTOM DESIGN LCD & LCM --- The factors to consider
6.1. LCD PANEL DIMENSIONS
Outer Dimensions (Be economical size)
View Area (normally 2mm from the edges)
End Seal (0.5mm thick)
Active Area (Area with patterns)
Pinout or Connection Area (2 to 2.5mm)
Glass Thickness (1.1, 0.7, 0.5, 0.4 or 0.3mm/one side)
( Glass Material: Sodium Lime Glass with SiO2 barrier, surface polished for STN use )
Economical Panel Size: The outer dimension may use up most the raw glass sheet area.
For small order size or pilot run,
7x8 inches sheets are used to boost
up the yield and save the tool cost.
or
Raw Glass Sheet
7x8 inches
(178x203mm)
14x16 inches
(355x406 mm)
(The usable area is 7mm off the edge)
P.21.
6.2. PANEL CONFIGURATIONS
A
B
C
The thick lines representing
the pinout areas.
D
Connectors suitable:
Zebra (Silicone Rubber) – A, B,
Heat Seal or TAB – A, B, C, D,
Metal Pins – C, D,
Eyes
All the above 4 models required Ag (silver) connections inside the LCD cell.
If such Ag connection not to be used or unable to be used, the configurations will be as follows;
E
G
F
Models E, F & G are good for combination use of Zebra and Heat Seal connectors together.
Most TAB connections are also applying on such models.
For TN LCD, don’t forget to
specify the View Direction
45+deg
15+deg
12 O’clock
15+deg
40+deg
40+deg
45+deg
6 O’clock
P.22.
6.3. PATTERN LAYOUT
Too Long Trace
Cross Over
Narrow down trace
Good
Bad
Layout Layout
C S1 S2 S3 S4 S5 S6
S6 S3 C S1 S2 S4 S5
+
P.23.
6.4. ZEBRA CONNECTORS
Three kinds of Rubber
Side Wall Insulators
Conductive Layers
1. Sponge Rubber
2. Silicon Rubber
Insulation Layers
3. Super Soft Rubber
Metal Mounting Bezel
Pitch: (Conductor/Insulator Layers)
Low Cost Type --- 0.25+-0.05mm
General Type ----- 0.18+-0.04 mm
Dot Matrix Type – 0.10+-0.03 mm
Graphic Type ------0.05+-0.025 mm
LCD
Assembly
Zebra
PCB
Contact Resistance:
1000 –1500 ohms at 10%-15% compression
LCD
Zebra
Mis-aligned Good
A safer way
(wider contact on PCB)
Precautions in Assembly
•Pre-clean Zebra
•Three or more conductors in contact
•PCB wraping <0.375mm / 50 mm
•Bezel has opening gaps with PCB
•0.3mm or 10%-15% compression
•Dummy zebra use with single side
contact LCD.
•Insulation side wall quality.
P.24.
6.5. HEAT SEAL CONNECTORS
Conductors (~20 um particles) printed on a Polyester (PET) Film of 20 -25um
Contact Resistance
&
Graphite Type --- 35 to 100 ohms/sq
Silver Graphite Type ---- 0.5 ohm/sq
Silver Type ------ 0.05 ohm/sq
Hot Press
Choose proper LCD configuration:
LCD
PET film
Conductor side
PET side
PCB
Welded
Precautions in Assembly
PCB
LCD
Pitch
0.40, 0.60, 2.80 mm
0.23, 0.35, 2.80 mm
0.23 mm
PET side
PCB
PET side
•The Hot Press head temperature 120-140 deg C at joint
•32 Kg/sq cm pressure is recommended
•Leveling the press for even pressure along the joint.
•Properly select the sealing time to prevent uneven flow or
wash away the conductor particles.
•100pcs/mm2 particles at contact area is suggested.
•Peeling off strength be >200gm (Vertical)
& >500gm (Horizontal)
P.25.
6.6. METAL PIN CONNECTORS ( for 0.7 & 1.1mm glass )
LCD
Epoxy enforcement
Wider seal area is
required.
Standard Pitch: 1.27mm, 1.8mm, 2.0mm, 2.54mm
Pin Length:
20mm, 30mm, & 45mm max
Clip Depth
2.0mm to 2.4mm max
Contact Resistance: <0.05 ohm
Precautions in Assembly:
• Prolong soldering may damage the Pin contact to glass
---- A good LCD will add carbon cushion between pin
clip and glass contact area.
• Care on bending the pins ---- LCD maker provides pin
lead forming.
• Pin length under 4.0mm is not recommended.
• Wave solder is not recommended ---- Polarizer is weak
• Mechanical stress on pin or temperature changes may
cause LCD background color changed.
All the above connections may have IC on PCB by SMT, Wire Bonding (COB) or Insert & Solder.
6.7. TAB (TCP IC BONDING)
IC on a flexible film
with conductors.
The Film is heat sealed
onto the LCD pinout area
TAB = Tape Automation Bonding
TCP = Tape Carrier Package
LCD
P.26.
6.8. CHIP ON FILM (COF)
LCD
Same as TAB, but with more
components on the film like
a circuitry on PCB
6.9. CHIP ON GLASS (COG)
The IC Chip
for COG is
different from
those for usual
wire bonding
on PCB.
Same as an
usual LCD
LCD
Glass with
Fine traces
Fan-in &
Fan-out
ACF* film is used to fix the
COG chip onto the glass.
The ACF film is similar to
Heat Seal but with much finer
Pitch and conductive particles.
Most panels with
Metal Pins
IC Chip
* ACF=Anisotropic Conductive Film
P.27.
6.10. TRICKS ON THE LCD PANEL DESIGN
6.10.1. THE BIAS VOLTAGE
Recommended Driving Freq
60 Hz to 120 Hz
Theoretical Driving Waveform
% LIGHT
ABSORPTION
Applied to
Segment
90%
Applied to
Common
10%
0 volt
Vth
Volts
Volts
Resulting
Waveform
to LCD
Off
On
Practical Design Waveform
(Example: Waveform to LCD at 1/3 Bias)
The Bias
Voltage
Time
The driving
Voltage
V
2/3V
1/3V
0
-1/3V
-2/3V
-V
Off
On
Off
P.28.
6.10.1. THE BIAS VOLTAGE (continued)
The formula and design facts;
N: Multiplex Rate. Example: N=3 for 1/3 duty
S: Bias The ideal design S=1+ N
Vd: The supply voltage to the panel.
Von = ( Vd / S ) x
2
( N-1+S ) / N
Voff = ( Vd / S ) x
[ N – 1 + ( S – 2 )2 ] / N
N
2
3
4
8
16
S
2
2
3
4
5
Vd
3 volts
3 volts
3 volts
3 volts
5 volts
Voff
1.06 v
1.22 v
1.00 v
0.88 v
1.22 v
Von
2.37 v
2.12 v
1.73 v
1.27 v
1.58 v
Von – Voff
1.31 v
0.90 v
0.73 v
0.39 v
0.36 v
Less than 1 volt !
Beware the drifting under temp changes
P.29.
6.10.2. CROSS OVER LAYOUT
S1
Ag Dot
Connection
S2
S3
Epoxy Sealing Frame
S4
C1
Hided under Frame
C2
C1
2 cross over points
6.10.3. THE POLARIZER SELECTION
•The Glue Type or Non-glue Type polarizer.
•The Polarizer with the UV Barrier may extend the LCD Life under strong UV exposure.
•The Anti Glare Polarizer may improve the contrast.
•The high durability polarizer may stand for wider temperature environment.
•The slightly orientation of Polarizer axis may change the background color.
6.11. THE THERMAL COMPENSATION
It is recommended to use the thermal compensation circuit when a LCD will be operated under
a wide temperature range.
P.30.
6.12. TEMPERATURE RANGE
Wide Temp Type
Melting
point
Clearing
point
Low Temp Type
General purpose
Temp
Deg C
Operating
Temp.
-30
Storage
Temp
-20
0 deg
+50
10 deg C lower
+60
+75 deg
10 deg C higher
The STN temp is 10 deg narrower than TN
Problem
when exceeds
rated temp.
Background blackened
Cross Talk
Black Spots
Slow response
All the above defects are reversible at room temp
Possible design
Specific for High Temp
Specific for Low Temp
Temp
-40 deg
+10
+30 deg
+100
P.31.
6.13. BACK LIGHTS
Choice of
Back Light
Descriptions
Common
Color
Side LED Type
( Fig. 1 )
Wedge diffuser (Light Guide) and reflector are
needed.
Poor illumination for large panel
Yellow Green,
Blue, White
Array LED Type
( Fig. 2 )
Consuming more power and generating more heat.
Beware the difference in supply voltages of each
model. Easy assembly
Yellow Green,
Red.
EL (ElectroLuminescent)
The best in even brightness and light weight. But
less brighter than LED Backlight. High voltage and
EMC consideration.
Green, Blue,
White.
CCFL (Cold Cathode
Fluorescent Lamp)
The strongest illumination.
High voltage and EMC consideration.
White.
Important: The Transmissive and the Transflective Type LCD absorb the different light intensity.
Light
Light
-
Diffuser Paper
Light Guide
LED wiring
LEDs
Fig. 1.
Reflector domes
Reflector Paper
+
Fig. 2.
P. 32.
7.0. BI-STABLE LCD
Bi-stable Cholesteric Display, or
SSCT – Surface Stabilised Cholestric Texture Display, or
Multi-stable Chiral Nematic Display, or
E-Book Display
This is a new technology in LCD making use of the Cholesteric Liquid Crystal. Mr. John West
and Mr. D. K. Yang of Kent State University, Ohio, USA filed the patent in 1995.
The display image is retentive in the absence of an electric field. It has a excellent readability
and wide view angle under the daylight or strong ambient light.
No Polarizer is required on this kind of display panels.
The Liquid Crystal is switchable and stable in two kinds of texture.
(a) The Twisted Planar Texture, which has the LC layers parallel to the display surface,
reflects the incident light.
(b) The Focal Conic Texture, whose LC is in fragmentary, scatters the incident light.
Switch-able
(a)
(b)
The above two textures are switch-able under 30V to 180V pulse of 10ms to 100ms,
and stable in zero electric field.
By properly adjust the pitch of the Twisted Planar Texture, it can reflect R, G, B lights.
P.33.
8.0. ORGANIC LED
The Organic Electro Luminescent Displays (OELD) , or The Organic Light Emitting Devices (OLED)
The EL ( Electro-luminescence ) Back Light for LCD has been used for many years. It operates
at high voltage (>100V). In 1987, Tang and Van Slyke in Kodak, USA reported a low voltage (<10V)
Organic EL. It comes a new display ---- the OELD.
8.1. THE BASIC STRUCTURE
Metal Cathode
Electron Transport Layer
Re-combination and Emission Layer
DC
volt
Hole Transport Layer
ITO Layer (Anode)
Glass Substrate
Light emits
8.2. THE DIFFERENCE BETWEEN LCD & OLED
LCD
OLED
No Light emission
Emits light in colours (100cd/sqm)
Narrow view angle
Wide view angle (>150 degrees)
Slow response
Fast response (<10 microsec)
OLED has most the advantage of LCD such as;
Easy patterning
Low operating voltage but at high current ( 20ma/cm2)
Low manufacturing cost
Thin and light weight
P.34.
8.0. ORGANIC LED (continued)
8.3. THE OLED & PLED
a.
b.
There are two major ways to build the OLED;
The small molecule process ---- by spluttering the organic materials onto the ITO patterns.
Kodak uses such way.
The large molecule process, or the polymer process ---- by spin coating, dip coating or screen
printing the organic pastes layer by layer. Cavendish Lab in Cambridge, UK and Dow
Corning, USA developed such process and materials in ’90s.
Some people now call the OLED made under polymer process the PLED.
The small molecule process is also applying to making the ACTIVE OLED.
Pioneer, Japan seems the first one in mass production for the OLED.
It is expected the OLED will replace the LCD step by step from 2005.
CLOVER DISPLAY GROUP has started a joint venture with the University of Hong Kong to research
and develop the materials and process for OLED.
The newly formed joint venture company is named COLED DISPLAY LTD., established Sept 2002.
P.35.
9.0. TOUCH PANELS
9.1. ANALOG TYPE
A PE film with ITO layer is sealed
onto an ITO Glass with epoxy dots as
Spacer to maintain a gap.
When the external pressure of
touching makes contact of two ITO
layers, the sensing IC circuit with give
an analog reading corresponding to the
touch position.
PE Film
With ITO
Ra
Rb
Silver
Conductors
Epoxy dots
As Spacer
Glass with
ITO
Rd
Rc
Pin out
Area
9.2. DIGITAL TYPE
The ITO on the PE Film and the
ITO Glass are etched out into sectors.
When touched, the corresponding
sectors are shorted circuit and reflected
to the pins concerned.
PE Film
With ITO
Epoxy dots
As Spacer
Glass with
ITO
Pin out
Area
P.36.
10.0. CUSTOM LCD/LCM DEVELOPMENT GUIDE.
Enquiry from Customer
Feasibility Study & NRE
Charge / Unit Price Quoted
Free quote in 2-4 working days
NRE Order Confirmation
NRE payment in advance
LCD Panel
1 week
Panel Drawing
for Approval
PCB & Circuit
1 week
Circuit diagram
& PCB Layout
External Casing
1-3 weeks
Case Drawing
** normally 10-20 LCD
or 3-5 LCM samples
will be free. For more qty,
please notice us in advance
when confirm the NRE order.
3-6 weeks
3-4 weeks
Mask Design
& Samples**
for Approval
3-10 weeks
PCB Tool Design
& Samples** for
Approval
Hand mould up sample
Final Case
Mould
3-9 weeks
Primary Sample
Final Sample
Total development time;
LCD Panels 4-7 weeks, LCM Modules 4-10 weeks; With External Case 7-18 weeks
P.37.
11.0. ACKNOWLEDGEMENT & DECLAIMER
We have tried our best to present up-to-date and correct information here. Some of them to be
explained together with photographs and demonstration samples to form a complete part of the
Introduction.
We wish that the information discussed in this seminar may help the design engineers to make
a cost effective and quality custom design in an easier and logical way.
However, this is not an academic seminar that we have used a simply way in the presentation.
All information here is provided in good faith without any expressed or implied warranty. The reader
should seek for more detail advice from the industry.
1.
2.
3.
The information in above are partly referring to the following documents;
Proceedings of the Liquid Crystal Seminar HK by E. Merck, Darmstadt, Germany.
Various articles in the SID International Symposium and Information Display by the Society for
Information Display, Inc. USA
LCD Displays, the leading edge in flat panel displays, by Sharp Technical Library, Vol. 1, of
Sharp Corporation, Osaka, Japan.
Prepared by;
Johnny C. L. Chou,
Clover Display Ltd.
Room 1006, 26 Hung To Road, 10/F, Kwun Tong, Hong Kong
Tel: 23428228, 23413238
Fax: 23418785, 23574237
email: [email protected],com
URL: http://www.cloverdisplay.com (in English)
http://www.cloverdisplay.com.hk (in Japanese)
http://www.cloverchina.com (in Chinese)
Editions:
7th edition Sept 29, 2005
6th edition Mar 13, 2003.
5th edition Sept 19, 2001.
4th edition Apr 16, 2000.
3rd edition Sept 6, 1999.
2nd edition Sept 1, 1998.
1st edition May 19,1997.
All copy rights reserved
Clover Display Ltd. H.K.
P.38.