CONCEPT DIAGRAM OF LCD OPERATION
(Incident light)
(Incident light)
Polarizer A
OFF
ON
V
Liquid crystal molecules
Polarizer B
Light
Dark
When incident (natural) light reaches Polarizer A, only the light in the direction of the liquid crystal
molecules is allowed to pass.
? POWER OFF (no voltage applied)
The light passing through Polarizer A is forced to follow the twist (90?) of the liquid crystal
molecules. All of the light reaching Polarizer B from Polarizer A is allowed to pass because the
Polarizers are perpendicular to each other.
? POWER ON (voltage applied)
When voltage is applied, the liquid crystal molecules of Polarizer A do not twist the light, and so it
passes through as it is to Polarizer B. Because of this, the light reaching Polarizer B is blocked.
LCD CONSTRUCTION AND NOMENCLATURE
9
7
6
1
3
4
8
10
5
14
13
11
12
2
1) F substrate (glass)
2) Terminal
3) Segment electrode
4) Common electrode
5) B substrate (glass)
6) Upper polarizing plate
7) Orientation layer
8) Sealant
9) LC (liquid crystal)
10) Conducting material
11) Sealant
12) Inlet
13) Viewing area
14) Lower polarizing plate, or lower polarizing plate and reflecting plate
DISPLAY CONDITIONS AND VIEWING ANGLE (I)
Display Mode
Applications
Characteristics
General
Basic low-power LCD. Display
is illuminated by ambient
light, making it difficult to
read in dark environments.
Negative
display
Back light display
Multi-color display
A backlight makes characters
stand out clearer. Multi-color
display produced using color
filters.
General
Generally used in bright
environments.
External light and
back light display
Can be used as reflective type
when ambient light is bright,
and as transmissive type when
ambient light is dim.
Back light display
Used with backlight for dark
environments.
A) Display type
Positive
display
Reflecting plate
Light source
Reflective
type
Reflected light
B) Polarizing plates, reflecting plates
Polarizing plate
Transflective plate
Transflective
type
(Semitransparent)
Transmitted
light
Backlight
source
Polarizing plate
Transmissive
type
(transparent)
Backlight
source
The thickness of the polarizing plate, transflecting plate, and reflecting plate may be restricted
in order to allow optimum LCD characteristics.
Standard specification:
1) Polarizing plate thickness : 0.15mm
2) Transflecting plate thickness : 0.25mm
Reflecting plate thickness : 0.25mm
DISPLAY CONDITIONS AND VIEWING ANGLE (II)
E) Viewing direction
D) Color display
C) Wide angle viewing field display
Display Mode
Applications
Characteristics
TN
(backlight color) /
(light color)
Gray / Black
HTN
Gray / Black
Up to 1/48 duty drive possible. Wide visual field.
STN
Green / Blue
Gray / Purple
Blue / White
Up to 1/200 duty drive possible. High quality image.
FSTN
White / Black
Up to 1/200 duty drive possible. High quality image.
Viewing angle and direction somewhat limited.
Color filter
Color Filter
Backlight
source
Multi-color
12
9
7:30
1:30
3
6
Color display stands
out for alarms, etc.
Used in combination with
negative display for partial
coloring.
Example
For displays that
require high-contrast
at various angles and
directions.
Contrast characteristic
diagram for following
conditions:
9
3V, 1/3D, 1/3B
_
O= 60¢X
Viewing angle setting
12:00
12
3
10
15
20
(CR)
DRIVING SYSTEMS OF LCD
Driving systems
Characteristics
Obtainable high margin of
operating voltage allows
higher quality display.
Simple drive circuit
conditions, low-voltage
operations possible.
Static drive
system
-
Example
1F1A 1B1G 2F2A 2B 2G
7F7A 7B 7G 8F8A 8B 8G
COMMON
1E 1D1CD1 2E 2D 2CD2
Dynamic (timedivision drive
system)
When a large number of
elements are driven:
- Fewer drive circuits.
- Fewer connections between
circuit and display cells.
7E 7D 7CD7 8E 8D8CD8
COM1
COM2
COM3
S1
S2 S3S4
Dynamic (time-division) drive system
S5 S6
Vo
1. Voltage averaging method
S19 S20S21S22 S23 S24
Vo/a
-Vo/a
-Vo
This method provides optimum bias 1/a for the number of time
(a) Example of select drive waveform
divisions by weighting the drive voltage for N-1 deselects of the
(1-2/a)Vo
Vo/a
scanning side less than the drive voltage of one select of the
scanning side.
The voltage averaging method 1/a bias is calculated -(1-2/a)Vo -Vo/a
?
(b) Example of deselect drive waveform
according to the following formula:
Example waveforms using 1/a bias method
a = ? N + 1 ……… N : number of time divisions
The resulting value for “a” is generally truncated to an integer.
2. Operating voltage range
The lighting condition of the liquid crystal depends on the effective value of the drive voltage. The
maximum operating margin α is expressed as follows:
α = ? ((? N + 1) / (? N – 1)) = (Vth2) / (Vth1)
Vth1 : Voltage representing 50% of luminance characteristics of select waveform.
Vth2 : Voltage representing 74% of luminance characteristics of deselect waveform.
Lighting voltage range
with no crosstalk
100%
Luminance
74%
Deselect waveform
50%
-V
4
Operating voltage
Select waveform
B
0
Com1 -1/2V
0
Com2 -1/2V
-V
3
α= Vth2/Vth1
2
Seg
0
-V
+V
Seg vs Com1 + 1/2V
0
(Select) -1/2V
1
-V
Vth1
Vth2 Drive voltage V
Luminance characteristics
by time-division drive
0 1 2 3 4 5 6 7 8 9
Number of time divisions N
Operating margin α in
1/a bias method
Seg vs Com2 + 1/2V
0
(Deselect) -1/2V
Waveforms for 1/2 duty, 1/2 bias
liquid crystal drive
LCD CONNECTION TYPES
ELASTOMER CONNECTOR
- Connection method
Mechanical compression
- Structure
Alternate laminations of conductive and
insulating rubber
- Contact pitch
Min. 0.5mm recommended
PIN CONNECTOR
- Connection method
Solder
- Structure
Plated metal pins
- Contact pitch
1.5, 1.8, 2.0, 2.54mm
FLEX CONNECTOR
- Connection method
Heat seal (heat + pressure), solder or
mechanical compression
- Structure
Base film with electro-conductive traces
- Contact pitch
Heat seal type 0.28mm Min.
Solder type 0.8mm Min.
TCP STRUCTURE
Tape carrier package (with driver)
- Connection method
Heat and pressure fitting (ACF),
soldering
COG STRUCTURE
Chip on glass
- Connection method
Heat and pressure fitting (ACF), heatseal,
FPC, rubber, socket or pin
LCD BASIC DESIGN RULES
FEATURE
Glass thickness
Polarizer thickness
Total display thickness
Seal width
Contact ledge width
For DIL pins type
For DIL pins type
For elastomer type
For heat seal type
Pin length
Minimum track widths
General design
- Line
-
Space
Graphic
- Line
- Space
Front
Back (RF)
G=1.10
G=0.70
G=0.55
G=1.10
G=0.70
G=0.55
MIN
----------------1.80
1.50
1.20
TYP
1.10
0.70
0.55
0.20
0.20
2.60
1.80
1.50
2.00
2.00
2.00
MAX
--------0.30
------3.00
3.00
3.00
P=2.51
P=1.80
2.20
2.00
2.50
2.50
3.50
3.50
G=1.10
G=0.70
G=0.55
2.00
1.20
1.00
2.50
2.00
2.00
-------
P=2.54
P=1.80
2.00
3.20
3.20
3.00
6.35
6.35
--20.00
22.00
L<3mm
L>3mm
L<3mm
L>3mm
0.05
0.06
0.05
0.06
0.20
0.02
OPTIMUM GLASS SIZES
D
B
C
SINGLE EDGE CONNECT
A
A
170
if D = 2.5
B
C
114
111.5
113
85
68
56
48
42
37
34
86
83.5
69
66.5
57
54.5
49
46.5
43
41.5
39
36.5
35
32.5
32
29.5
30
D
C
B
D
DOUBLE EDGE CONNECT
A
A
170
if D = 2.5
B
C
115
110
113
85
68
56
48
42
37
34
30
87
82
70
65
59
54
51
46
45
40
40
35
36
31
33
28
28
23
TYPICAL CUSTOM LCDS