When we buy a TV, in addition to the price, the first thing we pay attention to is the quality of the TV. As the main body of the TV, the cost of the screen occupies more than 60% of the whole machine. For a long time, the concept of “watching the screen before buying a TV” has been widely circulated among the people.
So, do you know what types of TV screens are divided into? In the current TV market, the frequency of updates is getting faster and faster. Both domestic brands and joint venture brands have launched many new categories. Like OLED, QLED…Some new image quality technologies have once again stimulated consumers’ desire to buy.
There are too many panel types and screen technologies at present, let alone ordinary consumers, even professional players are easy to confuse, today I will make a popular summary.
In fact, the mainstream screen materials on the market are only divided into two categories: LCD (liquid crystal) and OLED (organic light-emitting diode). It is generally believed that OLED is technically more advanced than LCD. However, although OLED has a strong popularity, it is limited by price. Therefore, there are still relatively more LCDs.
First look at LCD
LCD is what we usually call liquid crystal. It needs the support of backlight when displaying content, and the backlight needs to pass through glass, color filters, optical films, substrates and alignment films to generate polarized light, and it is inevitable that there will be losses in color and brightness. The full name of TFT is Thin-Film Transistor (thin film transistor). In LCD, TFT deposits a thin film on the glass substrate as a channel area to improve the image quality. The upper glass substrate is next to the color filter, and the lower glass substrate is embedded with transistors.
When the current passes through the transistor to produce a change in the electric field, it causes the LCD molecules to deflect, changing the polarization of the light, and then use the polarizer to determine the light and dark state of the pixel. At the same time, the color filter attached to the upper glass forms the three primary colors of R, G, and B contained in each LCD pixel, forming the picture displayed on the screen.
After briefly talking about LCD, then I want to talk about the panel type
The full name of TN panel is Twisted Nematic (twisted nematic panel), which is also one of many panel types. Due to the low production cost, TN has become the most widely used entry-level panel. At present, the mainstream low-end LCD TVs or monitors on the market use TN, and early tablets and mobile phones are also used. Many users now equate TN with TFT, which is actually a conceptual confusion.
TN display principleTN display principle
Due to its mature technology and low price, TN is still favored by some low-cost products. At the same time, TN with a high aperture ratio is more power-efficient under the same brightness, and the response speed of 8-15ms is also faster. Therefore, under these advantages, even if TN has disadvantages such as color distortion and narrow viewing angle, it has not faded out of the market.
The full name of VA panel is Vertical Alignment (vertical alignment panel), which is a panel type with more high-end LCD applications, and belongs to a wide viewing angle panel. There are two types of VA, Fujitsu’s MVA and Samsung’s PVA, the latter of which is an improvement and inheritance of the former. Compared with TN, VA has higher contrast, clear and sharp display text, and can also provide a wider viewing angle and better color reproduction. The disadvantages are higher power consumption and higher price, and VA is a soft screen, which is lighter by hand. Swipe will cause ripples.
VA display principle VA display principle
The full name of MVA is Multi-domain Vertical Alignment, which is a multi-quadrant vertical alignment technology, developed by Fujitsu, and licensed by Chi Mei Electronics, AU Optronics and other companies to produce it through technology. But after the financial crisis, wide-view panel manufacturers have encountered a crisis. Chi Mei and AUO felt that MVA had high cost and low profit, so they stopped supplying display manufacturers. LG and Samsung are very market-minded, using C-PVA and E-IPS, which have little difference in price from TN, to occupy the past MVA market in one fell swoop.
The feature of MVA is that the viewing angle, color and color gamut have very good performance, which is much better than the general TN, but the disadvantage is that the response time is slightly worse, but the improved P-MVA has a viewing angle close to 178°. And the response time can reach 8ms or less.
The full name of PVA is Patterned Vertical Alignment, which also belongs to the category of VA. It is the successor and pioneer of MVA, and its comprehensive quality has surpassed MVA in an all-round way. The improved S-PVA can even go hand-in-hand with P-MVA, obtaining a very short response time and a very wide viewing angle.
PVA uses transparent ITO electrodes instead of LCD protrusions in MVA. The transparent electrodes can achieve better aperture ratio, minimize the waste of backlight, and reduce the possibility of LCD “bright spots”. It has a similar position in the LCD era. The “long tube” in the CRT era.
The full name of IPS is In-Plane Switching, which is a wide viewing angle technology launched by Hitachi in 1996. It can effectively improve the problems of TN chromatic aberration and narrow field of view when the viewing angle is not good. IPS can get a viewing angle of almost 180°, which greatly improves the deficiency of TN.
IPS display principle IPS display principle
Hitachi introduced S-IPS (Super-IPS) in 1998. In addition to the original advantages of IPS, it also improved the response speed. LG-PHIHIPS joined the IPS camp as a joint venture in 1999. After declaring bankruptcy in 2006, the IPS business was mainly handled by LG Display.
During this period, Hitachi launched the AS-IPS in 2002, which greatly improved the contrast. In the same year, Hitachi also launched IPS-PRO, which is divided into E-IPS, H-IPS and S-IPS.
E-IPS is considered an economical version of H-IPS. The contrast and color are slightly worse than H-IPS, but the color gamut reaches 72%, and the reduction in aperture ratio increases the viewing angle.
The most obvious difference of H-IPS (Horizontal IPS) is that it has changed the fish-scale sub-pixel arrangement of S-IPS. Each pixel is arranged in a straight line, and the pixels are connected in a straight line from top to bottom. At the same time, each pixel has Smaller electrode width.
Compared with S-IPS, H-IPS has slightly improved contrast and color performance. It is a relatively high-priced product, while S-IPS has a good price/performance ratio due to its lower price.
Later, LG Display, which took on the responsibility of IPS, launched AH-IPS in 2012. Compared with E-IPS, it has made significant upgrades in contrast and power consumption, bringing greater improvements in display effects.
LG Display LG Display
With the continuous advancement of technology, there has also been a better display effect of AIPS, with optimized brightness and clarity. The difference between AIPS and IPS is that instead of pre-orienting the LCD molecules into light-transmitting mode, they are oriented into opaque mode. The amount of light transmitted is determined by the electrode perpendicular to the orientation direction of the LCD molecules. The higher the voltage, the twisted LCD The more molecules there are, the precise control of light can be achieved.
AIPS only controls one deflection angle of the LCD, and the number of deflection molecules can be close to the voltage, which makes it easier for LCD to achieve level control, and the improvement of dynamic contrast also makes the motion picture perform better.
The advantages of IPS are cheap price, high viewing angle and accurate color reproduction, but the disadvantage is that the black purity is not enough, slightly worse than PVA, so it needs to rely on the compensation of the optical film to achieve a purer black. The IPS screen is more “hard”, and it is not easy to appear ripples when you swipe it with your hand. It is also what we usually call a “hard screen.”
Finally, let’s take a look at OLED
The full name of OLED is Organic Light-Emitting Diode (Organic Light-Emitting Diode). Unlike the aforementioned LCD, OLED does not require backlight support. OLED is an innate surface light source technology. The light emitted can be red, green, blue, white and other monochromatic colors, and then achieve a full-color effect, which belongs to a new light-emitting principle. The reason why the picture quality of plasma technology, OLED technology and even the early CRT technology is praised is mainly because they all have the characteristic of “self-luminous”.
OLED technology can turn off individual pixels and return their brightness to zero. In theory, the contrast ratio of OLED technology can be infinite. Therefore, it is impossible for OLEDs to leak light in the black field, thereby improving the contrast and image quality performance.
In addition, since OLED technology does not require backlight support, it eliminates the need for liquid crystal and backlight modules. The structure is very simple, and the body can naturally be extremely ultra-thin, which can be about 1/3 of the thickness of a traditional LED screen.
OLED also has flexible and bendable characteristics, not only can be applied to TV, the future may be able to make smart devices full of imagination. Combining the thin characteristics of OLED, the screen can be made as thin as a piece of paper and can be bent and folded at will, which is unimaginable in the LCD era.
Finally, I want to say that whether it is LCD or OLED, as long as it exists, it has its meaning. As consumers, we don’t have to get lost in a bunch of parameters. It is better to try more and experience the real effect in the store, so that we can choose the product that suits our eyes.