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PROBLEM SHOOTING
2000-10-29 13:57:01
In this chapter, we provide our customer a tool to shoot the problems during
the sample stage, I would hereby emphasize this is very important to shorten
the delivering time of our customer’s sample to the market.
As we all known, your approval of our sample is prerequisite for your product
delivered to the market, but in many case, a bad communication between the
two sides, takes a lot of time, to be specific, that’s an inaccurate description
of the problem lead to such a boring situation, actually, the problem as simple
as picking up an object under your feet, in this sense, we strongly recommend
you read this article carefully, because which is mostly helpful to realize our
philosophy so-called: shorten the time to the market.
We hope a quick approval of our sample as well as your sample by your
customer with the help of this paper. So I list below most problems you
will meet in the sample stage, based on our past experience.

Problems
Phenomenon
Potential reasons
Solutions
Lower
contrast
The characters
are haze in
the range of
promised view
cone.
1)The operation voltage is
lower than the desired one.
2)The Vth of LCD is too
higher than the desired one.
3)The steepness (V90/V10)
is too higher than the
desired one.
4)The retardation of LC
layer is not suitable.
5)The driving method
doesn’t match the
LCD.
1)Increase the
operation voltage.
2)Decrease the
Vth of LCD.
3)Decrease the
steepness of
LCD.
4)Adjust the
retardation of LCD.
5)Adjust the bias
circuit or driving
frequency.
Ghosting
(cross-talk)
The off-segments
are visible in the
range of promised
view cone
1)The operation voltage is
too higher.
2)The Vth of LCD is too
lower.
3)The steepness of LCD
is too higher.
4)The view cone of LCD
is too smaller.
5)The LC contaminated.
6)The driving doesn't
match the LCD.
1)Decrease the
operation voltage.
2)Increase the
Vth of LCD.
3)Decrease the
steepness of LCD.
4)Enlarge the view
cone of LCD.
5)More strict control
on LC and LC filling
process.
6)Adjust the driving
circuit.
 
Uneven
contrast
The displayed
characters are
uneven.
1)The LC is contaminated.
2)The alignment layer of
LCD has some problem.
3)The dopant content
isn't suitable.
4)The driving frequency
is too higher.
5)The contacting- resistance
of the according segments
is too higher.
1)More strict control
on LC and LC filling
process.
2)The more strict
control on PI curing,
and rubbing process.
3)Adjust the dopant
content.
4)Decrease the
driving frequency.
5) Improve the
connections of
electrodes.
Flicker
The displayed
characters or
pictures are
flickering
1)The driving frequency
is too  lower.
2)The response time
is too faster of LCD.
1)Increase the
driving frequency.
2)Increase the
response time.
Over
power
The power
consumption
is too bigger.
1)The driving voltage is
too higher.
2)The driving frequency
is too higher.
3)The capacitance of
LCD is too higher.
4)The ion content is too
higher in the LC.
5)There are short between
some electrodes.
1)Decrease the
driving voltage.
2)Decrease the
driving frequency.
3)Decrease the
capacitance of LCD.
4)Decrease the ion
content in LCD.
5)Check the
electrodes to find
out what happened.
Small
view
cone
The character
can’t be seen
clearly when
beyond some
angle
1)The retardation of LC
isn't suitable.
2)The steepness is
too higher.
3)The driving circuit
settings isn't perfect.
1)Adjust the
Retardation of LC
layer.
2)Increase the
twist angle of
LC layer.
3)Optimize the
driving circuit
settings.
The
background
of LCD isn't
desirable
The color of
LCD is different
with the desired
one.
1)The polarizer property
isn't the desired one.
2)The ITO glass isn't
suitable.
3)The PI property and
thickness isn't suitable.
4)The △n of LC isn't
suitable.
1)Change to the
suitable polarizer.
2)Change to the
suitable ITO glass.
3)Change to the
suitable PI film.
4)Select the
suitable △n  of  LC. 
Too strong
parallax
The color change
too much when
side-view the
LCD in off-state
1)The d of LCD cell
is too bigger.
2)The polarizer setting
isn't suitable.
1)Decrease the
cell gap of LCD.
2)Adjust the
polarizer setting.
Trailing
There is trail
when displaying
a moving picture.
1)Too slowly switch
off of LCD.
2)Too higher driving
voltage.
1)Decrease the
cell gap.
2)Decrease the
twist angle.
3)Decrease the
driving voltage.
Narrow
operation
temperature
The LCD can't
normally operate
at higher or lower
temperature.
1)The temperature
coefficient of LC is
too bigger.
2)The steepness is
too bigger of LCD.
3)The driving circuit
setting unreasonable.
1)Select a LC with
smaller temperature
coefficient.
2)Decrease the
steepness of
LC layer.
3)Add temperature-
compensation circuit
if necessary.
Cold
bubble
The LCD appear
bubbles in a cold
circumstance
1) Higher tension or
less flexibility with
the LCD cell.
1) Optimize the
cell-making process
of LCD.
Imagine
retention
The undesired
off-segment or
parts displayed
when the LCD
addressed for
a long time.
1)There is DC component
in the driving signals.
2)There is too much ions
in the LC.
1)Decrease the DC
component in the
driving signals.
2)More strict control
on the LC and LC
filling process.
3)Select the PI with
less polar-groups.
Lower
Resistance
to Electrical-
Magnetic
interference.
The LCD is
susceptible
to the electrical-
magnetic field.
There is no electrical-
magnetic shield in
the application circuits.
Add the grounded
circuits.
Lower
resistance
to the
outside force.
The displayed
character would
move when a
outside force
applied.
Too flexible of the
LCD structure.
1) Add the spacer
density and
pressing after
filling process.

Remark: The harder of LCD cell, the narrower of LCD storage and operation
temperature range, so the balance need take care.
 



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