Types and working principle of LCD panel
Date:2019-07-22
The main component of the industrial display is the industrial LCD screen. About 80% of the cost of a LCD is spent on the LCD panel. The quality of the industrial LCD screen will directly affect the effect and use of the industrial LCD screen, so what kind of influence is the parameter effect of the industrial LCD screen?
The type of LCD panel will directly affect the brightness, contrast, color, visual angle and other parameters of LCD. LCD panel production, advantages and disadvantages, market environment and other factors are related to the quality, price and market trend of LCD. Let's introduce the main types of LCD panel
The types of LCD panel are: TN panel, VA panel, IPS panel, CPA panel, adsds panel, etc. the common types are TN, VA, IPS panel, etc
TN panel:
TN is fully known as twisted nematic (twisted nematic) panel, low production cost makes TN become the most widely used entry-level LCD panel, which is widely used in the mainstream low-end LCD in the market. Most of the TN panels we see are improved TN + film. Film is compensation film, which is used to make up for the lack of viewing angle of TN panel. The viewing angle of improved TN panel reaches 160 °， Of course, this is the limit value measured by the manufacturer when the contrast is 10:1. In fact, when the contrast drops to 100:1, the image has been distorted or even biased.
VA panel
VA panel is a kind of panel with high-end LCD applications, which belongs to wide view panel. Compared with TN panel, 8bit panel can provide 16.7M color and large viewing angle, which is the high-end capital of this kind of panel, but the price is also higher than TN panel. VA panel can be divided into MVA panel dominated by Fujitsu and PVA panel developed by Samsung. The latter is the inheritance and improvement of the former. The front (front) contrast of the VA panel is the highest, but the uniformity of the screen is not good enough, which often leads to color drift. Sharp text is its killer, black and white contrast is quite high.
IPS panel
IPS (in plane switching) technology is a liquid crystal panel technology launched by Hitachi in 2001, commonly known as "super TFT". Led by Hitachi, the IPS camp has gathered a number of manufacturers such as LG Philips, Hanyu Caijing, idtech (a joint venture between Chimei electronics and IBM in Japan), but not many models can be seen in the market. The biggest feature of IPS panel is that its two poles are on the same surface, unlike other liquid crystal mode, the electrodes are arranged on the top and bottom in three-dimensional arrangement. Because the electrodes are in the same plane, no matter in what state, the liquid crystal molecules are always parallel to the screen, which will reduce the opening rate and reduce the light transmittance, so IPS application in LCD TV will need more backlights. In addition, there is an improved S-IPS panel
CPA panel
CPA (continuous pinwheel alignment) mode wide view technology (soft screen). Strictly speaking, CPA mode wide view technology is also a member of VA camp. The liquid crystal molecules radiate toward the central electrode in a fireworks like arrangement. Because the electric field on the pixel electrode changes continuously, this wide view mode is called "continuous fireworks arrangement" mode. However, CPA is mainly promoted by sharp, the "father of liquid crystal". It should be noted that the ASV that sharp has always promoted does not refer to a specific wide view technology. It refers to the products that have used TN + film, VA and CPA wide view technology as ASV. In fact, only CPA mode is sharp's own wide perspective technology, and its products are basically equivalent to MVA and PVA. In other words, sharp's LCD TV may not use the CPA mode LCD panel produced by sharp itself, it may use the VA mode panel of Taiwan manufacturers or the LCD panel of other manufacturers. Sharp's CPA panel color restoration is true, visual angle is excellent, image is delicate, the price is relatively expensive, and sharp rarely sells CPA panel to other manufacturers. The CPA panel is also a soft screen. If you scratch it with your hand, similar water marks will appear. If you look at the screen carefully, it's like this:
Adsds panel
Adsds (advanced super dimension switch) advanced super dimension field conversion technology (hard screen), strictly belongs to the IPS camp, is the technical improvement of the traditional IPS panel. But different from IPS, adsds panel uses ITO transparent electrode instead of traditional metal electrode to increase the opening rate and transmittance. With the arrangement of liquid crystal molecules similar to IPS panel, the color expressiveness of liquid crystal panel can be improved. Adsds is mainly promoted by Chinese LCD panel suppliers and is mainly used in LCD TV of private brand.
Now the main panel types on the market are TN and IPS panels. Compared with the VA and IPS panels, the TN panel is at the low end. In terms of the color performance of the panel, the jitter is raised to 8bit, but after all, the color calculated by the IC circuit can not compare with the original in terms of accuracy and naturalness, so it is poor in terms of color. In terms of price and power consumption, it is ahead of the VA and IPS panels, which is the main reason why it occupies the vast majority of the market share. Compared with the VA and IPS panels, the two have their own advantages and disadvantages. Generally speaking, the response time and visual angle of IPS are slightly better at the same price, while the VA panel is slightly better in contrast and uniformity. However, it is difficult to distinguish between the two, because in addition to the panel factor, the image processing engine and the panel IC driver are also the key factors to determine the effect.
