Ppt On Led Display 236s6q
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SEMINAR ON LCD & FLAT 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
1. FLAT 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 , Bi-STABLE LCD & ORGANIC LED. 8. QUESTION & ANSWER. Edition #7 (2005)
1.0. FLAT 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 ing through
Light Light ing 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 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 IVE 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 ive design. But there are still some special design to work in the ive 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 s 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 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 ive 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
ive LCD
Projector
1/128
Portable TV
Notebook s 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 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 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 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. 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
Resistance: 1000 –1500 ohms at 10%-15% compression LCD Zebra
Mis-aligned Good
A safer way (wider on PCB)
Precautions in Assembly •Pre-clean Zebra •Three or more conductors in •PCB wraping <0.375mm / 50 mm •Bezel has opening gaps with PCB •0.3mm or 10%-15% compression •Dummy zebra use with single side 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
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 t •32 Kg/sq cm pressure is recommended •Leveling the press for even pressure along the t. •Properly select the sealing time to prevent uneven flow or wash away the conductor particles. •100pcs/mm2 particles at 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 Resistance: <0.05 ohm Precautions in Assembly: • Prolong soldering may damage the Pin to glass ---- A good LCD will add carbon cushion between pin clip and glass 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 (T IC BONDING) IC on a flexible film with conductors. The Film is heat sealed onto the LCD pinout area TAB = Tape Automation Bonding T = 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 s with Metal Pins
IC Chip
* ACF=Anisotropic Conductive Film
P.27.
6.10. TRICKS ON THE LCD 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 . 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 diff (Light Guide) and reflector are needed. Poor illumination for large
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
-
Diff 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 s. 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 t venture with the University of Hong Kong to research and develop the materials and process for OLED. The newly formed t venture company is named COLED DISPLAY LTD., established Sept 2002.
P.35.
9.0. TOUCH S 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 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 1 week 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 s 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, . 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 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: cdl@cloverdisplay,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.
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
1.0. FLAT 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 ing through
Light Light ing 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 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 IVE 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 ive design. But there are still some special design to work in the ive 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 s 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 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 ive 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
ive LCD
Projector
1/128
Portable TV
Notebook s 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 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 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 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. 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
Resistance: 1000 –1500 ohms at 10%-15% compression LCD Zebra
Mis-aligned Good
A safer way (wider on PCB)
Precautions in Assembly •Pre-clean Zebra •Three or more conductors in •PCB wraping <0.375mm / 50 mm •Bezel has opening gaps with PCB •0.3mm or 10%-15% compression •Dummy zebra use with single side 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
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 t •32 Kg/sq cm pressure is recommended •Leveling the press for even pressure along the t. •Properly select the sealing time to prevent uneven flow or wash away the conductor particles. •100pcs/mm2 particles at 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 Resistance: <0.05 ohm Precautions in Assembly: • Prolong soldering may damage the Pin to glass ---- A good LCD will add carbon cushion between pin clip and glass 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 (T IC BONDING) IC on a flexible film with conductors. The Film is heat sealed onto the LCD pinout area TAB = Tape Automation Bonding T = 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 s with Metal Pins
IC Chip
* ACF=Anisotropic Conductive Film
P.27.
6.10. TRICKS ON THE LCD 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 . 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 diff (Light Guide) and reflector are needed. Poor illumination for large
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
-
Diff 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 s. 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 t venture with the University of Hong Kong to research and develop the materials and process for OLED. The newly formed t venture company is named COLED DISPLAY LTD., established Sept 2002.
P.35.
9.0. TOUCH S 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 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 1 week 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 s 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, . 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 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: cdl@cloverdisplay,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.
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