In recent years, liquid crystal display technology has developed rapidly, whether it is applied to the display or TV, the terminal manufacturer has several important parameters in the process of customizing the LCD display module. One size, one resolution, one interface, one screen brightness.
Today, I will focus on sharing some knowledge of the brightness of the LCD display module. Electronic products have different requirements for brightness in different scenarios. Some electronic products such as home appliances, household appliances, the screen used is low-brightness 250-300Nit, with the integrated black technology to make a sense of premium. Some electronic products have very high requirements for brightness, such as outdoor logistics PDA, barrier facial recognition at the entrance of the community, and military toolbox computers, all of which require more than 1000Nit.
It can be seen that in the application fields of different environments, the selection of LCD display modules is different. If the indoor and outdoor application environments are different, different types of LCD display modules should also be selected.
First, the brightness of the LCD module in different environments
First of all, indoor and outdoor selection matching can be made through different brightness LCD screens, and the brightness reference values of two products are available for your reference:
1. X<500cd/m2: ordinary brightness, applicable to normal viewing environment, such as indoor and indoor brightness dark environment.
2. X>800cd/m2: Higher brightness, the use range is a strong light environment, such as sunlight, the visual effect is better than the general brightness.
Secondly, it can be used by full transparent and semi-trans semi-transparent type options:
1. Fully transparent type: match the ordinary brightness for indoor use, match the higher brightness for outdoor use.
2. Semi-reverse and semi-permeable type: suitable for use in outdoor strong light, clear display effect, non-reflective. But it is more expensive. Therefore, when choosing an LCD module, you not only need to choose according to the relevant circuit parameters and product parameters, but also choose the appropriate LCD module according to the use environment.
Second, 7 methods of brightening of LCD module
In addition to the abnormal increase in the working current voltage, the factors that determine the brightness of the LCD screen are: backlight brightness, whether the polarizer is brightened, and the light transmittance of liquid crystal glass.
Commonly used brightening methods are:
1. Paste sequins on the lower surface of the glass, which can increase the brightness by 20-30%.
2. The reflection of the backlight, with 3M ESR can be increased by 5-8%.
3. The brightening film with high brightness can be increased by 2-3%.
4. With V-CUT light guide plate, it can be increased by 5%.
5. With bright lights, it can be increased by 5-10%.
6. With twin heart lamps, the brightness can be increased by about 50%.
7. If the brightness should be made above 1000, open the mold to make a double row of lights
Third, share a high-brightness LCD module design scheme
High brightness module is mainly used in commercial and industrial embodiment, in addition to the brightness requirements, but also for the waterproof level and heat dissipation design has special requirements, we start from the display of the most core data, according to the human eyes and solar environment brightness, to become a high brightness display module must meet the following two requirements.
1. Key technology of high brightness module
The brightness of the LCD screen can reach 1 000 cd/m2, which can be seen in sunlight and the service life reaches the index of general LCD display.
2. Technical indicators
LCD screen brightness: > 1 000cd/m2 (9 points average brightness);
Contrast ratio: > 1 000:1;
Service life: > 50 000 hours;
LCD response speed: < 8 ms;
Power consumption: < 100 W;
Display colors: 16.7 million colors;
LCD interface: LVDS (low voltage differential signal);
Resolution: 1 366×768.
After theoretical design and simulation, the following scheme is formulated.
3. Innovative features
The design of direct LED backlight and special heat dissipation method make the brightness of the LCD screen reach the standard of high brightness and ultra-brightness, which can achieve good display effects in various complex optical environments, such as direct sunlight, window like sidewalk display, etc.
4. Key technologies
(1) LED is used as backlight, saving energy and power. The use of LED backlight, can meet the requirements of high brightness and super brightness, and LED has the characteristics of low energy consumption, high efficiency and long life, so this project is a high-end product integrating energy saving and power saving.
(2) With a direct bottom backlight design, a backlight composed of more point light sources can achieve a higher degree of integration to achieve ultra-high display brightness.
(3) Using the latest COB (Chip on Board) packaging LED, better heat dissipation, inheritance, long life, high reliability.
5. Technical route
This project adopts LED backlight, light weight, thin thickness, low power consumption, low heat, high brightness and wide temperature work, long life and easy reinforcement. In addition, cold cathode lamps contain heavy metal mercury and are driven by high pressure, while LEDs, in addition to low energy consumption and no toxic substances, are low-voltage devices, and their safety is far better than that of cold cathode lamps.
Traditional direct-down cold cathode fluorescent lamps are highly bright backlit, doubling in thickness, and high power consumption causes high heat, which makes high-temperature operation difficult, and for large-size LCD backlights, longer lamps and higher voltage inverter power supplies are required. This project uses LED backlight, which neither increases the appearance size, nor does it increase the thickness of the original screen, nor does it cause high heat in the LCD module. It really achieves light weight, thin thickness, low power consumption, low heat, high brightness and wide temperature work, long life and easy reinforcement.
In terms of design, it adopts a straight down method. The straight-down method is to evenly distribute the LEDs behind the panel, and the light emitted by the light source can be evenly transmitted to the entire picture. Experts generally believe that direct backlighting can present images more accurately and show excellent color and chiaroscuro.
The emission of LED light requires a certain amount of space, and if the direct backlight technology wants to reduce the thickness, it is necessary to install more LEDs more tightly to minimize the light diffusion space or separate the substrate parts such as the tuner and the power regulator part. However, if you want to use LED backlight to achieve a high-brightness display, you must adopt a bottom-side design.
LED backlight is DC power supply, no longer use inverter power supply, greatly improve the power conversion efficiency, but also greatly improve the reliability of the product, and modular backlight design, no need to use high-power LED driver module and power supply, so that the manufacture of large-size LCD backlight is no longer an unattainable problem.
This project uses light-emitting diodes as the backlight of the LCD screen, which is more environmentally friendly than the traditional cold cathode lamp, and the light-emitting diode is more energy-saving because the luminous efficiency is higher than that of the traditional cold cathode lamp.
The traditional design is achieved by adding many cold cathodes, in addition to power consumption and harmful substances, but also using high-voltage drive. Light-emitting diodes are low-voltage devices that are far safer than cold cathode lamps. This is why we can see high-voltage warnings behind traditional LCD TVs, while LED TVs do not need to worry about this safety.
Generally, the mixing effect of the LED array is improved by using a lens that facilitates light divergence for direct type, which reduces the thickness of the backlight module to a certain extent, and makes the LCD structure with direct backlight thinner.
At the same time, compared with the side backlight structure, which requires a high-cost light guide plate, the direct structure only needs to consider the cost of the lens and diffuser plate, and the number of LEDs used in the same brightness is small, and even ultra-high brightness performance requirements can be achieved. Therefore, the use of direct backlight structure has obvious advantages in cost and energy consumption, especially for large-size liquid crystal displays, the disadvantages of thick structure are less obvious, and the advantages of low cost and low energy consumption are more prominent.
Fourth, the market expectation of high-brightness LCD modules
Liquid crystal technology is becoming more mature and stable, high-brightness ultra-bright LED backlit liquid crystal display due to its high-definition display in strong sunlight and cold environment, greatly improving the application range of liquid crystal display products. It is a dream product for outdoor image display and commercial advertisers. It can be widely used in aviation, ships, oil fields, trains, urban buses and long-distance buses mobile multimedia display, public venue commercial advertising display, industrial control industry, image surveillance system and other special requirements of image display, is national defense and all walks of life indispensable high-tech products, market demand is increasing day by day.
The Internet era multiplied by the Internet of Things, and driven by industrial upgrades, the demand for high-brightness display has been greatly increased, the future in semi-outdoor and outdoor, high-brightness display is a necessary product, with the national strategic development and transformation, high-brightness display module from the previous small workshop will enter the batch workshop of large companies, there is reason to believe that the entire high-brightness display module will be promising. From the maturity of display technology, TFT-LCD high-brightness module will be the mainstream of the market.
Saishida focuses on LCD modules, with high-brightness screen customization, the corresponding size resolution has corresponding high-brightness screen in trial production or mass production, we have successfully helped customers customize LCD screen brightness in many fields.