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Backlighting
allows LCD modules to be viewed under variety of lighting
conditions from high ambient light sources, direct sunlight, dim
environment to total darkness.
transflective and transmissive LCD modules especially need
backlight as light source.
Po Sing utilizes three types of backlighting sources: LED,
EL & CCFL.
For common use, we will apply LED backlighting.
For thin thickness products, we will use EL backlighting
while CCFL backlighting will be introduced when large display
products involved.
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LED
(Light Emitting Diode) Backlighting
發光二極管背光源
LED
backlight is common used in character type LCD modules.
LED backlighting can be utilized in different distribution
position such as side LED backlight or bottom LED backlight
according to actual applications.
Single side or double sides LED backlight allows more
illuminuous, light weight and thin structure design.
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Advantages
:
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High luminuous and efficiency;
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Uniform illuminance in many colors e.g. yellow, green, red, white,
etc.;
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Long operating life-time of more than 100K Hrs; &
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Can be driven by DC power supply directly without inverter.
Disadvantages
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High power consumption; &
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Not suitable for high resolution graphic type LCD modules.
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EL
(Electroluminescence) Backlighting
電引發光片背光源
Soft
EL lamps built-up by capacitor format with phosphor between
conductive electrode plates. In which, AC current causes light emission by motivation of
molecules within alternating electric fields.
EL backlighting greatly help lighting of LCD modules in
darkness environment. Common
applications can be found in automotive & aircraft displays,
clocks & watches, control panels of instruments, signals &
indications, toys & gifts, etc.
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Advantages
:
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Thin & flat, thickness as thin as 0.15mm;
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Flexible & soft, can be tailored for any shapes;
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Provide even brightness in many colors e.g. blue, green,
yellow-green, amber, pink-white, etc.;
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Good moisture resistance;
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Provide non-glare lighting;
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High visibility even through smoke or fog;
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Cold light source with very low heat generation;
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Low power consumption of around 0.2mA/cm2;
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Allow thin LCD modules profile development; &
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Support wide driving power supply up to 150V AC.
Disadvantages
:
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Relative short operating life-time of approx. 10K Hrs; &
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Need external DC to AC inverters to drive.
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CCFL
(Cold Cathode Fluorescent Lamp) Backlighting
冷性陰極螢光燈背光源
CCFL
tube is made of fragile glass with lead substance that used as
light source. It is
suitable for high resolution graphic type LCD modules.
Two technologies namely direct lighting and edge lighting
will be chosen for different applications.
CCFL backlight provides two times the luminance than EL
backlight. It
improves the readability of LCD modules in brightness environment.
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Advantages
:
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Provide sharp and
uniform white backlighting color;
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High brightness up to
4,000cd/m2;
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Low heat generation
due to cold cathode fluorescent lamp;
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Intermediate
operating life-time of around 20K Hrs.
Disadvantages
:
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Available in white color only;
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Electric shock should be prevented to CCFL tube that resulting in
damage and deformation of tube.
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