With the popularization of LCD TV and the rapid development of LCD backlight module technology, the thickness of LCD TV is getting thinner and thinner, and the frame is getting narrower and narrower. Ultra-thin TV is gradually reduced from 15 to 10mm to 4.9mm. At the same time, LCD TV visual display area size is getting larger and larger. At present, the family with 55 inch LCD TV in the home TV accounted for nearly half of the market share, 65 inches, 75 inches and larger size of the market share is increasing year by year. From the technical point of view, the ultra-thin and ultra-narrow LCD TV faces the same technical problem: how to realize the ultra-thin and ultra-narrow TV on the premise of ensuring the TV has enough rigid strength.

Basic structure and working principle of LCD TV backlight module

Liquid crystal TV adopts liquid crystal display technology, but the liquid crystal molecular structure itself does not emit light. It is only driven by external voltage to make adjustments in different states to control the amount of light passing through pixel points. The light displays images and presents colors through color matching of color film. In addition to the LCD module, there is another important module: backlight module; the backlight module provides sufficient brightness for LCD panel display. A typical side-in backlight module is shown in Figure 1: it is composed of LCD panel 1, diaphragm combination 2 (diffusion film, prism piece, etc.), light guide plate 3, reflection piece 4, light source 5, etc.

Backlight works: light source may emit light, the light through 3 on the network structure of light guide plate, will become a diffuse light, through the role of the reflex reflector plate 4, converts side into the point light source and the display surface parallel to the surface light source, through the combination of diaphragm 2 homogenization, cover again, polymerization, such as optical effect, makes the display surface light evenly, obtain good optical subjective effect. As an important optical transmission device, light guide plate requires very high light transmittance and USES optical grade plastics, such as PMMA, MS, etc.

Characteristic analysis and contrast test of glass light guide plate

When the plastic light guide plate is applied in the super-size and ultra-thin LIQUID crystal TV, its system strength difference and large thermal deformation are the biggest disadvantages. Meanwhile, the plastic thermal expansion coefficient is large and the size is subject to the change of environmental temperature. Therefore, the structure is required to reserve large safety clearance, which is not conducive to the narrow frame design. Optical grade glass light guide plate has good light transmittance and strength, which can solve some shortcomings of plastic light guide plate.

3 Design Key Points

3.1 Overall Design Considerations

At the beginning of the design, it is necessary to determine the design indicators of the entire LIQUID crystal module, such as screen brightness, color rendering, evenness, etc., and carry out the design of each part according to these indicators. For the brightness of this most important index, to consider the LCD transmittance, generally between 5% ~ 7%, its decomposition of each layer transmittance.

Lightbars made up of LEDs and others lose 20 percent of their light as it passes through the guide plate and the bottom reflector, and 5 percent as it passes through the diffuser. The transmittance of liquid crystal panels is 5 to 7 percent, counted here as 5 percent. Then, the flux of light emitted by the lamp X1m through the entire optical path is X×80%×95%×5%=0.038X1m.Dividing this flux by the area of the screen, and then dividing it by, yields a screen with a generally lower normal brightness, so it is necessary to consider and reasonably increase the number of prism membranes and brightening membranes and LED beads to achieve the desired luminance.

3.2 Drive Control Circuit Design

General use of dedicated PWM controller driver chip. Such chips provide high precision LED current through closed-loop control of the output current. The output current can be dimmed separately by linear or PWM dimming method, and the error deviation of the output value of each current can be guaranteed within ±1%.

3.3 Heat Dissipation Design

Because LEDs produce a lot of heat when they work, they have a recommended temperature for use. If the problem of heat dissipation is not solved, it will lead to the attenuation of LED luminance and the shortening of service life. In order to suppress the heat generated by THE LED to affect the grayscale and color of the backlight module

The LED should be designed for heat dissipation. To achieve better heat dissipation, the LED array is welded to an aluminum substrate (MCPCB), which provides many times better heat dissipation than a conventional PCB. Under the aluminum substrate, a long heat dissipating aluminum strip is designed. The heat-conducting double-sided adhesive tape is applied between the heat-dissipating aluminum strip and the lamp strip, and the aluminum substrate and the heat-dissipating aluminum strip are fixed with screws.

3.4 Design and Application of Glass Light Guide Plate

In view of the advantages and disadvantages of glass light guide plate, after a large number of samples, prototype testing, glass light guide. Combining the advantages and disadvantages of MS light guide plate, MS light guide plate is suitable for some ultra-narrow frame type applications.

(1) Ultra-narrow LCD TV: Due to MS light guide plate physical characteristics,

The required safety clearance is smaller than PMMA, which is conducive to narrow edge design.

(2) Super large LCD TV: reduce the safety gap on the side, which is conducive to the design of narrow border, and use its own strength to improve the strength of the system;

(3) Ultra-thin prototype: Through the optical adhesive bonding technology: the light guide plate is bonded together with two or more materials such as optical diaphragm, reflector and back plate to further reduce the space and thickness of the structure assembly and achieve ultra-thin and ultra-narrow display effect.

LCD Light Guide Plate Assembly

Light guide plate is widely used in LCD and is one of the indispensable components in LCD panel industry.

Since LCD era development, Novo equipment and is committed to research and development a backlight module assembly equipment, and provide service for the domestic panel line companies, has accumulated a good market reputation, to promote the rapid development of the domestic LCD industry, can say the current Novo equipment has become our domestic leading edge backlight module assembly equipment local enterprise.

● Intelligent Light Guide Plate Assembly Machine

Automatic conveying and positioning of the back plate, automatic feeding, absorbing, positioning, assembling, pressing and tearing of LGP film, using visual positioning, with code scanning function, visual information can be bound to the product, with one-key replacement function.

Main Features:

1. LGP batch feeding, long replacement cycle, short feeding time;

2. LGP and back plate adopt CCD visual positioning with high precision;

3. Adopt six-axis robot for LGP assembly, which is more flexible and faster;

4. In accordance with the dust-free high standard design, ensure the internal cleanliness and yield control, cleanliness up to 1000 level;

5. With code scanning function, visual positioning data can be bound to the product, which can be traced to ensure yield control;

6. With one-button replacement function, it can quickly switch between different products;

7. Production data can be saved for 30 days and can be accessed to MES system.