What is backlight module ?
Jan 07, 2022
The backlight module is one of the key components of the LCD panel. The function is to supply sufficient brightness and evenly distributed light source, so that it can display images normally
Introduction
The so-called BackLight is a light source located behind the liquid crystal display (LCD ""), and its luminous effect will directly affect the visual effect of the liquid crystal display module (LCM). The liquid crystal itself does not emit light, it displays graphics or characters as a result of its modulation of light. The development of the backlight can be traced back to the Second World War. At that time, ultra-small tungsten filament lamps were used as the backlight of aircraft instruments. This is the initial stage of the development of the backlight. After half a century of development, the backlight has now become an independent subject of electronics, and has gradually formed a research and development hotspot.
With the continuous development of liquid crystal display technology, the application fields of liquid crystal displays, especially color liquid crystal displays, are constantly expanding. Driven by the liquid crystal display market, the backlight industry is showing a booming scene. The LCD is a non-luminous display device, which requires the use of a backlight to achieve the display function. The performance of the backlight source will directly affect the display quality of the LCD. The cost of the backlight source accounts for 30-50% of the LCD module, and the power consumed accounts for 75% of the module. It can be said to be a very important part of the LCD module. Components. High-definition, large-size LCDs must be matched with high-performance backlight technology. Therefore, as the LCD industry strives to open up new application areas, the high-performance backlight technology (such as high brightness, low cost, low power consumption) It also plays the role of behind-the-scenes heroes.
The backlight is the light source that provides the LCD panel. Mainly composed of light source, light guide plate, optical diaphragm, plastic frame, etc. The backlight has the characteristics of high brightness, long life and uniform light emission. At present, there are mainly three types of backlight sources: EL, CCFL and LED. According to the different light source distribution positions, they are divided into side-light type and direct-light type (backlight type). As LCD modules continue to develop in the direction of being brighter, lighter, and thinner, edge-lit CCFL backlights have become the mainstream of backlight development.
principle
The liquid crystal display is a passive light-emitting element, the display itself does not emit light, but is illuminated by the backlight system below it. The backlight source and the liquid crystal display are combined to form a liquid crystal display module. The following figure shows the common structure of the backlight of a liquid crystal display. The liquid crystal backlight is a flat, uniform lighting device. The cold cathode fluorescent tubes or LED strips as the light source are arranged on both sides or one side of the whole backlight (it may be the long side or the short side). The cold cathode tube is a linear light source, and the LED is a point light source. A light guide plate is required to convert this light source into a surface light source. The light guide plate is generally made of acrylic plastic with high light transmittance, and the surface is very smooth and flat, so that most of the internal light will be regularly and totally reflected on the flat surface, and will not be emitted to the outside of the light guide plate. The bottom of the light guide plate of the liquid crystal display is printed with white dots. At the position where the light guide plate is printed with dots, the light will no longer be totally reflected regularly but will be emitted from the top of the light guide plate. Controlling the density of dots at each location can control how much light the light guide plate emits at this location. Precisely designed light guide plate dots can spread the incident light on both sides evenly on the entire plane. Optical films will be placed above the light guide plate. These films can uniform light and converge large-angle light for frontal observation.
The light source, the light guide plate, the reflective sheet, and the optical film constitute the backlight source of the liquid crystal display. When the light emitted by it is irradiated on the liquid crystal panel, the light will first pass through the lower polarizer and pass through upwards. At this time, different liquid crystal panels will change the polarization direction of the light according to their own mechanism. The light then touches the color filter to produce color, and finally enters the upper polarizer. After the polarization direction is changed by the liquid crystal, part of the light can be emitted, and part of it will be absorbed. Each pixel on the entire LCD panel can individually determine the intensity of the emitted light. Resulting in an image.
