What are the advantages and disadvantages of the side-type LED backlight and the direct-type LED backlight?
May 27, 2021
Side-type LED backlight is a kind of backlight product of common technology, and it is also one of the two broad types of LED backlight, just like direct-type LED backlight. What are the characteristics of the side-type LED backlight, where are the advantages and disadvantages, and what can be improved? This article focuses on explaining and analyzing for you, and I hope it will be helpful to you.
Analysis of the advantages and disadvantages of side-type LED backlight modules
advantage
1. Can use fewer LED dies, saving cost
2. It can create a relatively thin body, so that the rear of the LED TV LCD panel does not need to be equipped with an LED module, but placed on the side, which can reduce the overall thickness of the screen and create a thinner machine than a direct-lit LED backlight LCD TV. Planted.
Disadvantage
1. The coupling efficiency of the LED package and the light guide plate can also be improved;
2. It is challenging when applied to large sizes;
3. Local control is not possible.
4. Traditional side-type LED backlight module structure
The structure of the traditional side-type LED backlight module
The structure of the traditional side-lit LED backlight module includes that the LED light source is arranged on the side of the light guide plate, and dots are formed on the bottom surface of the light guide plate. The light emitted by the LED package is coupled into the light guide plate, and propagates toward the liquid crystal screen through the reflection and scattering of the reflective sheet and the dots.
Structural shortcomings
For traditional edge-lit LED backlight modules, all the light emitted by the LED chip cannot enter the light guide plate. On the one hand, a part of the light (large-angle light, about 20%-30%, depending on the package structure) is caused by total internal reflection. It cannot be emitted from the light-emitting surface of the LED package. On the other hand, even if the light has been emitted from the light-emitting surface of the LED package, part of the light cannot enter the light-guide plate due to the reflection of the light-incident surface of the light-guide plate. The coupling method and efficiency between the LED package and the light-guide plate need to be further improved.
Side-in LED backlight improvement method
1. Improve the coupling efficiency between the LED package and the light guide plate
In order to make all the light emitted by the LED chip enter the light guide plate, transparent glue 210 is used to stick the light exit surface of the LED package 102 to the light entrance surface of the light guide plate, as shown in Figure 2. Due to the refractive index of the silica gel, transparent glue, and light guide plate of the LED package It is basically the same. Therefore, there is basically no total internal reflection at the light exit surface of the LED package, and there is basically no reflection at the light entrance surface of the light guide plate. The light emitted by the LED chip basically enters the light guide plate, and the coupling efficiency is improved. Reach 100%. In addition, because there is no total internal reflection, the large-angle light emitted by the LED chip also enters the light guide plate, which is easy to achieve the uniformity of brightness.
Advantages after improvement:
(1) The coupling efficiency between the LED package and the light guide plate is improved.
(2) The light extraction efficiency of the LED package is increased by about 20%-30%.
(3) The heat generated by each LED package is reduced by about 8%-13%.
(4) Under the condition of ensuring the same brightness, the number of LED packages used is reduced by about 16%-23%, reducing costs.
(5) The total heat generated by the LED backlight module is reduced by approximately 23%-33%.
(6) Energy consumption is reduced by approximately 16%-23%.
(7) The light-emitting angle of the LED package is increased.
2. Light guide plate with V groove suitable for large size TV
The side-mounted LED backlight module with the light guide plate of the V-shaped groove enables the LED backlight to be applied to any large-size display screen without the need to use higher-brightness LED chips.
A V-shaped groove 402 is formed in the middle part of the top of the light guide plate 401, and an LED light source 408b is arranged at the position corresponding to the V-shaped groove at the bottom of the light guide plate. When the light 425 emitted by the LED light source propagates upward, it is completely inside the V-shaped groove 402. Reflect, so as to propagate on the side of the light guide plate and stick to the bottom of the light guide plate to increase the light extraction efficiency.
Advantages after improvement:
(1) Suitable for display screens of any large size.
(2) Thinning. The thickness of the SMD form of the LED package can be 0.7mm, and the PCB thickness can be 1mm. Therefore, the thickness of the LED backlight module is only 1.7mm more than the thickness of the traditional edge-type LED backlight module.
(3) The light extraction efficiency of the LED package is high.
(4) Better heat dissipation.
(5) The light-emitting angle of the LED package is increased.
3. The side-entry LED backlight module without light guide plate that reduces the number of LED packages used
An embodiment of a side-lit LED backlight module without a light guide plate: an LED light source 205 is provided on one side, and a side reflector 204b is opposite to it, and dots 203 are formed on the main reflector 204a and the side reflector 204b to adjust the dots Structure and distribution, making the brightness distribution uniform
Advantages after improvement:
(1) There is no light guide plate and light attenuation in the light guide plate, therefore, the number of LED packages used is reduced.
(2) Reduce the heat generated.
(3) Reduce costs.
(4) Reduce weight.
Although there are many shortcomings in the edge-type LED backlight, it cannot prevent it from becoming a commonly used LED backlight. It is also because of its cost and size advantages. If the above-mentioned improvements can be used to overcome or reduce the edge-type LED backlight The negative impact of module shortcomings on its performance, the market space it possesses will be broader
