The Introduction for Backlight Unit Structure
Backlight module is mainly composed of light source (LED lamps), light guide plate, reflection film, diffusion film, brightness enhancement film / prism sheet, light shade film, etc. Therefore, we can see that backlight module consists of many optical films and the light which is emitted by LED lamps goes through these optical films and has been redistributed. And the light is fading at the same time. According to the research, if the light from the traditional backlight source is 100%, only about 60% of the light could reach the polarizing film after going through reflection film, diffusion film and other optical films, and finally, only about 4-8% light could pass through the liquid crystal and the polarizing films.
The backlight unit is the highest cost component in the LCD panel (about 20-30%). The larger the LCD panel, the greater the proportion of the cost the backlight module. For example: it is about 20-25% in the cost of 15 inches – 17 inches LCD panel and it is more than 25% in the 30 inches or above. With the popular trend of large size LCD panel, backlight module is becoming more important than ever. And optical films which are very important occupy about 40% in the cost of backlight module.
The Cost Composition of Backlight Module
| Size(inch) | 15.4 | 17 | 26 | 32 | 40-42 | 46-47 |
| LED | 9 | 17 | 23 | 22 | 19 | 23 |
| Light Guide Plate | 10 | 12 | 0 | 0 | 0 | 0 |
| Diffusion Film | 13 | 8 | 13 | 17 | 19 | 18 |
| Reflection Film | 6 | 6 | 2 | 5 | 3 | 2 |
| Brightness Enhancement Film / Prism Sheet | 25 | 12 | 11 | 9 | 24 | 20 |
| Outer Frame | 12 | 13 | 8 | 7 | 5 | 5 |
| Other Material | 25 | 32 | 43 | 40 | 30 | 32 |
| Total | 100 | 100 | 100 | 100 | 100 | 100 |
Light Source
Backlight unit is the most power consumption part of LCD panel. LED backlight unit can reach higher color saturation and brightness in lower power consumption. Also, the LCD panel can be made thinner than ever. There are many light sources for backlight.
LED light source is the best so far. The LED backlight is divided into bottom led backlight and edge led backlight.
Light Guide Plate
A great majority of light guide plates are made from PMMA. It can improve the brightness and uniformity of the light by guiding the direction of the light. It is the most important technology and the major cost of the backlight unit.
