TFT-LCD liquid crystal display is a thin film transistor type liquid crystal display, that is, "true color" (TFT), which not only improves the response speed of the display, but also accurately controls the display color scale. TFT liquid crystal display is characterized by good brightness, high contrast, strong layering and bright colors, but it also has the disadvantages of high power consumption and high cost. UFB LCD has the characteristics of ultra-thin and high brightness. UFB-LCD is a display screen specially designed for mobile phones and PDA, which has the characteristics of ultra-thin and high brightness. The display screen can reduce the pixel spacing to obtain better image quality.
The contrast of UFB LCD screen is twice that of STN LCD screen, and its brightness is equivalent to that of TFT display screen in 65536 colors, but its power consumption is less than that of TFT display screen, and its price is similar to that of STN display screen, which can be said to combine the advantages of these two existing products. STN is the abbreviation of super twisted nematic. The gray-scale mobile phone screens we used in the past are all STN, which has the advantage of low power consumption, and the biggest advantage is power saving. Generally speaking, the performance of STN screen in color is still far less than the above screens.
In addition to gray level STN, there are two main types of STN: CSTN and DSTN. CSTN (Color STN) transmissive LCD displays well in normal light and dark light, but it is difficult to distinguish the display contents outdoors, especially in the sun, and the backlight needs power to generate illumination light, which consumes electric energy. Active matrix organic light emitting diode panel (AMOLED) is called the next generation display technology, and Samsung Electronics, LG and Philips all attach great importance to this new display technology.
At present, in addition to Samsung Electronics, LG and Philips, which mainly focus on developing large-size AMOLED products, Samsung SDI and AUO both focus on developing small and medium-sized products. On the mainland, Foshan Rainbow is building a production line, which is expected to be officially put into production within two years.
Among the above-mentioned manufacturers, only Samsung SDI has been mass-produced, and the size is between 3 inches and 4 inches.
Recently, the president of Sharp, Kazuo Katayama, was asked about the future development of organic light-emitting diodes. He said it was impossible in five years. Personally, what he said may be true in the TV market, but in the small and medium-sized market, AMOLED has a good chance to coexist with TFTLCD in two years. If the yield of AMOLED can reach the same level as that of TFT LCD in the future, it is definitely just around the corner to replace TFT LCD.
Because AMOLED has many advantages over TFT LCD in terms of image quality, efficiency and cost. This is also the reason why many international manufacturers still don't give up the research and development of AMOLED when the yield is difficult to break through. At present, manufacturers who continue to invest in research and development of AMOLED include Sony, which has announced the time of product launch, Toshiba, which has invested in Toshiba Panasonic Display (TMD), Panasonic, which independently develops products, and Sharp, which claims that it is not optimistic. Both Nokia N85 released in August 2008 and Nokia N86 launched in the first quarter of 2009 adopted AMOLED.
In terms of display efficiency, AMOLED has the advantages of faster response speed, higher contrast and wider viewing angle, which are inherently superior to TFT LCD. In addition, AMOLED has self-luminous characteristics, so it can be made thinner and more power-saving than TFT. Another more important feature is that AMOLED without backlight can save the cost of backlight module, which accounts for 3 ~ 4% of TFT LCD.
AMOLED is indeed a very attractive product. Many international manufacturers like it very much. Even iPhone, the most popular product in the mobile phone market, is interested in AMOLED. I believe that after the yield is improved, the iPhone will also consider adopting AMOLED, especially its power-saving feature, which is very suitable for mobile phones. At present, the power consumption of AMOLED panel is only about 60% of that of TFT LCD, and there is still room for further decline in future technology.
Of course, the biggest problem with AMOLED is the yield. With the current yield, the price of AMOLED panel is 50% higher than that of TFT LCD, which is definitely a threshold for customers to adopt in large quantities. For Qi Jing, it is still in the training period to adjust the yield, so it is not easy to take a large number of orders.
After understanding the main performance differences between AMOLED and TFT LCD, we analyzed the main reasons for the differences through technical aspects. Because AMOLED is an organic light-emitting diode technology, we analyze it according to the working principle of organic light-emitting diodes. STN is the main equipment of early color screen, which can only display 256 colors at first. Although it can display 4096 colors or even 65536 colors after technical transformation, the general STN is still 256 colors, which is cheap and low in energy consumption.
TFT has good brightness, high contrast, strong layering and bright colors. Disadvantages are high power consumption and high cost.
UFB is a display screen specially designed for mobile phones and PDA, which is characterized by ultra-thin and high brightness. It can display 65536 colors with a resolution of 128× 160. UFB display adopts special grating design to reduce pixel spacing and obtain better picture quality. UFB combines the advantages of STN and TFT: the power consumption is smaller than TFT, and the price is similar to STN.
If the display effect is good or bad, it is ASV, TFT, organic light emitting diode, TFD, UFB, STN and CSTN in turn.
Organic Light-Emitting Display refers to the phenomenon that organic semiconductor materials and luminescent materials emit light through carrier injection and recombination driven by electric field. The light-emitting principle of organic light-emitting diode is that ITO transparent electrode and metal electrode are used as anode and cathode of the device respectively. At a certain voltage, electrons and holes are injected into the electron and hole transport layer from the cathode and anode, respectively. Electrons and holes migrate to the luminescent layer through the electron and hole transport layers respectively, where they meet to form excitons and excite luminescent molecules. The latter emits visible light after radiation relaxation. The radiated light can be observed from the ITO side, and the metal electrode film also acts as a reflective layer. For TFT liquid crystal, we take TN liquid crystal panel as a representative to introduce its working principle. TN liquid crystal module structure: nematic liquid crystal sandwiched between two pieces of glass. The surface of this glass is coated with transparent conductive film (ITO) as an electrode. The glass with ITO is coated with a surface orientation agent, so that the liquid crystal is oriented in a specific direction parallel to the glass surface. Based on the principle that electric field can make liquid crystal rotate, applying voltage to two electrodes will make the polarization direction of liquid crystal parallel to the direction of electric field. Because the refractive index of liquid crystal changes with the direction of liquid crystal, the polarization of light will change after passing through TN liquid crystal. Electrical switches can be used to control the brightness of lights. In this way, when it is transparent, it will form white, when it is opaque, it will form black, and the characters can be displayed on the screen.
Obviously, the two panels use different light sources, the organic light emitting diode emits light by itself, and TN uses backlight. The imaging mechanisms of the two panels are completely different. By comparison, it is not difficult to find that organic light-emitting diodes are thinner, emit light actively (without backlight), have no viewing angle problem, have high definition, high brightness, fast response, low energy consumption, wide temperature range, strong earthquake resistance, low cost, flexible display and other characteristics, many of which are difficult for TFT liquid crystal panels to achieve.