The International Technical Level And Present Situation Of TFT LCD Screen

- Jul 19, 2018 -

TFT-LCD technology has matured, the long-term puzzle LCD flat panel display three major problems: perspective, color saturation, brightness has been resolved. Multi-area vertical arrangement mode (MVA mode) and in-line switching mode (IPS mode) so that the LCD flat panel display of the horizontal angle of view has reached 170 degrees (the current major LCD TV manufacturers using a hard screen, the perspective has reached 178 degrees, almost the level are visible).

The MVA model also shortens response time to 20ms. From a technical point of view, the Tn+film solution is the simplest one, TFT display manufacturers used to use the old LCD display of the Twisted column (tn:twisted nematic) technology, with the TFT technology, thus having tn+film technology. The technique is to expand the visual angle by covering a particular layer of film through a screen--to extend the visual angle from 90 degrees to about 140 degrees. As shown in Figure 6: Tn+film, like a standard TFT display, is to control the image by arranging the liquid crystal molecule, which covers a layer of film on the upper surface to increase the visual angle. However, the relative weak contrast and slow reaction time of TFT display are still unchanged.

So tn+film this way is not a good solution, in addition to its cost is the cheapest there is no merit. IPS is the abbreviation of In-plane switching, which means flat switch, also known as Super TFT. First developed by Hitachi (Hitachi), it is understood that NEC and Nokia also use this technology to make displays.

This technique differs from a twisted nematic display (tn-film) in that the liquid crystal molecule is different from the basic arrangement, and the liquid crystal molecule is arranged in parallel with the substrate when the voltage is added. With this technique, the visual angle of the display reaches 170 degrees, has been comparable to the visual angle of cathode ray tubes, but the technique also has drawbacks: in order to allow the liquid crystal molecules to be arranged in parallel, the electrodes cannot be as twisted to the column display (Tn-film), on both substrates, and can only be placed on the base plate of the lower layer- The direct result is a noticeable decrease in brightness and contrast of the display, which enhances the brightness and contrast of the backlight source. Thus, the reaction time and contrast are more difficult to improve than the ordinary TFT display.

So this technology does not seem to be the best solution. MVA multi-area vertical arrangement technology, is developed by Fujitsu of Japan (Fujitsu), from a technical point of view, it takes into account the visual angle and reaction time two aspects. A compromise solution was found.

The MVA technology allows a visual angle of 160 degrees--although not as much as the 170-degree perspective that IPs can achieve-but it's still good because it provides better contrast and shorter response times. The M generation in MVA refers to "multi-domains"-the meaning of multiple regions. As shown in Figure 8, those purple protrusions (protrusion) Form the so-called region.

There are 4 areas in the MAV display that Fujitsu produces. VA is the abbreviation of "vertical alignment", meaning vertical arrangement. However, there is a literal misunderstanding because the liquid crystal molecule is not exactly perpendicular to the "protuberance" (protrusion) shown in the picture. Take a look at the black sketch shown in Figure 8.

When the voltage generates an electric field, the liquid crystal molecules are arranged in parallel with each other so that the backlight light source can pass through, and the light can diverge in all directions, thus widening the visual angle. In addition, MVA provides faster response times than IPs and Tn+film technologies, which are important for good video retrieval and residual visual effects.

The contrast of MVA is also improved, but it also changes with the change of visibility. The field sequence full color (FSFC) LCD technology, developed on the basis of optical compensation bending technology (OCB), not only cancels the color filter film (CF), which takes up one-third of the cost, it can also increase the resolution by 3 times times, increase the transmission rate by 5 times times, and simplify the process and reduce the cost. The development of color film technology and backlight technology makes the color reproduction ability of TFT-LCD reach even more than CRT. As a commodity display TFT-LCD, the main technical indicators of comprehensive performance in various types of display devices is the best, especially the TFT-LCD products of large-scale production technology, many varieties, many series of product development space, the scope of application thoughtfulness.

and Korea Samsung Electronics has produced a 38-inch single substrate TFT-LCD TV and 40-inch TFT-LCD display, with its excellent performance to the recognized should be the PDP occupied large size color TV market March. LCD is the lowest-consumption product in all monitors, taking the 13.3-inch XGA TFT-LCD as an example, Its power consumption of 1998 to 4.4 Watts, 1999 to 3.3 Watts, to 2001 will be less than 2.5 watts, especially the reflective TFT-LCD development success, due to the cancellation of backlight, its power consumption than the transmission of TFT-LCD lower a order of magnitude. At the same time, due to several improvements, low temperature laser annealing polysilicon (p-si) technology mature, and the development of monocrystalline silicon technology makes TFT-LCD response faster, higher circuit integration level, phase-locked loop technology applications, a function update, a more complete peripheral circuit adoption, system integration (systems on The development of glass technology makes TFT-LCD lighter and thinner. The thickness of 13.3 TFT-LCD in 1998 for the 7.2mm,1999 year for 5.5mm,2001 year to below 5mm, its weight 1998 to 580 grams, 1999 to 450 grams, to 2001 to 400 grams below. TFT-LCD Production technology has matured, has been fully automated production, the fifth generation of production lines in 2002 will enter a practical production phase, production costs will continue to decline.

The maturity and progress of TFT-LCD technology and its unique performance have confirmed the pattern of TFT-LCD replacing CRT eventually.