In addition to the above kinds of LCDs, you can also see other LCDs on some mobile phones, such as GF screen of Sharp in Japan and CG (Continuous Crystal Silicon) LCD. Compared with the two, they belong to completely different species. GF is an improvement of STN, which can improve the brightness of LCD, while CG is a high-precision and high-quality LCD with QVGA(240×320) pixel resolution.
Comparison of UFB, STN and TFT
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.
STN (super twisted nematic) screen, also known as super twisted nematic LCD screen. A color filter is added to the traditional monochrome liquid crystal display, and each pixel in the monochrome display matrix is divided into three pixels, and the three primary colors of red, green and blue are displayed by the color filter respectively, so as to achieve the function of displaying colors, with light green as the main color and orange as the main color. STN screen belongs to reflective LCD. Its advantage is low power consumption, but its definition is poor in dark environment.
STN is also the type of material that we contact most. At present, there are mainly CSTN and DSTN. It is a passive matrix liquid crystal device, so it consumes less power and saves electricity, but the response time is slow, 200 milliseconds.
CSTN generally adopts transmission lighting mode, and external light source must be used for lighting, which is called backlight, and the lighting source should be installed behind LCD.
TFT (thin film transistor) is a kind of thin film field effect transistor, which belongs to an active matrix liquid crystal display. It can "actively" control each independent pixel on the screen, which can greatly improve the reaction time. Generally, the reaction time of TFT is relatively fast, about 80 milliseconds, and the viewing angle is large, which can generally reach about 130 degrees, and it is mainly used in high-end products. The so-called thin film field effect transistor (TFET) means that each LCD pixel is driven by a thin film transistor integrated behind it. So that screen information can be displayed at high speed, high brightness and high contrast. TFT belongs to active matrix liquid crystal display, which is driven by "active matrix" in technology. The method is to control the opening and closing of any display point by using the transistor electrode "active pull" made by thin film technology. When the light source illuminates, it first passes through the lower polarizer, and the light is transmitted by the liquid crystal molecules, so as to achieve the purpose of display through shading and light transmission.
TFT-LCD liquid crystal display is a thin film transistor type liquid crystal display, that is, "true color" (TFT). Each pixel of TFT liquid crystal has a semiconductor switch, and each pixel can be directly controlled by point pulse, so each node is relatively independent and can be continuously controlled, which not only improves the response speed of the display screen, but also accurately controls the display color level, so the color of TFT liquid crystal is more realistic. 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. TFT liquid crystal technology accelerates the development of mobile phone color screen. Many new-generation color screen mobile phones support 65536 color display, and some even support160,000 color display. At this time, the advantages of high contrast and rich colors of TFT are very important.
TFT LCD is mainly composed of fluorescent tubes, light guide plates, polarizers, filter plates, glass substrates, alignment films, liquid crystal materials, thin transistors and so on.
TFD (thin film diode) screen, also known as thin film diode translucent liquid crystal display screen. TFD technology is jointly developed by Seiko and Epson, which is specially used on mobile phone screens. It is a compromise between TFT and STN, and its brightness and color saturation are better than STN, and it also saves electricity than TFT. The biggest feature is that it can provide high-quality and easy-to-watch display regardless of whether the backlight is turned off (reflective mode) or on (transmissive mode), and it has the advantages of low power consumption, high image quality and high response speed.
UFB LCD is a new type of mobile phone LCD released by Samsung in March 2002, which has the characteristics of ultra-thin and high brightness. UFB-LCD is a display screen specially designed for mobile phones and PDA. With ultra-thin and high brightness, it can display 65536 colors, reaching the resolution of 128 x 160. The display screen also adopts a special grating design, which can reduce the pixel spacing and get better picture 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.
Organic light emitting display (OLED) is a new product on mobile phone LCD, which is called "dream display". Organic light emitting diode display technology is different from the traditional liquid crystal display mode. It does not need backlight, and uses very thin organic material coating and glass substrate. These organic materials will emit light when current passes through them. In addition, the OLED display screen can be made lighter and thinner, with a larger viewing angle, and can significantly save power consumption.
At present, among the two technical systems of organic light-emitting diodes, the technology of low-molecular-weight organic light-emitting diodes is mastered by Japan, while the technology and patents of polymer PLED (the so-called OEL of LG mobile phone is the product of this system) are mastered by British technology company CDT. Compared with PLED products, colorization is still difficult.
However, although the OLED with better technology may replace LCD such as TFT in the future, the OLED display technology still has shortcomings such as short service life and difficult screen enlargement.
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Three indicators of a mobile phone LCD screen are more important.
The first is the problem of color depth, which is what we often say: 65k 26w ==. The screen consists of images.
The pixel color depth here refers to how many hours a pixel can display colors, so the above-mentioned 65k means that a pixel can display 65536 colors. More colors can show better transition colors. As for the transition color, everyone knows that the face in the photo is not represented by one color. The dark spots or light spots of one color from deep to light or from shallow to deep are actually another color. Therefore, people with more colors show more delicate colors on their faces, but they will become stiff. There is little difference between 65536 and 262 144, mainly due to the limited color resolution of human eyes. If you look carefully, you can clearly see the color transition on the car body.
However, there is still a gap between 4096 and 65536. Of course, there is absolutely no problem in displaying animation in 4096, and there is less requirement for color. Real people think that at least 65536 colors can achieve real visual effects.
As for 256 colors, in a classic phrase, it is what the computer graphics card looks like when it is not installed. But at present, there is no new 256-color machine, and even the external screen does not use 256 colors.
second
Screen material
We often say tft or stn refers to the screen material.
We don't care about his working principle and display effect.
Tft & gttfd & gtufb & gt stone with the best screen effect at present.
There are also things like
At present, many technologies such as oled are used as external screens. For example, v868 8280 has a high self-luminous contrast, but it is said that its life span is not long. At present, Samsung's newly developed models have used oled as the main screen.
Tfd display effect is good, but the brightness is still darker than tft, but it is relatively power-saving.
Ufb is also particular. The original ufb effect is not ideal, such as lg7 100 Samsung t208.
However, the new 65536ufb such as x608 has been greatly improved compared with the previous products.
Stn is likely to be replaced at present, and some low-end machines have begun to use tft.
There are low-temperature polysilicon such as ltps in tft, which not only saves energy but also highlights Sharp's ace technology cg-slicon tft continuous polysilicon technology. The display effect is better, and the number of points per unit area can be higher.
If the above content confuses everyone, you can basically consider it this way.
CG-slicon & gt； Ltps & gttft & gttfd & gtufb & gt stone
In terms of display effect.
Another point is the difference between the transflective tft and the transmissive tft of moto v303 and v300, which is concerned by many people. It is said that the former has better definition, while the latter can see the screen clearly in the sun, so each has its own advantages.
Compared with tft, stn is not bright enough, its color is prone to color cast, and it is particularly prone to yellow paste.
The last one is the most easily overlooked.
In fact, screen resolution is also an important aspect.
At present, the screen resolution of mainstream models is 160* 128. In fact, if you look carefully, you can still see the pixel lattice on the screen. Screen size is more important than resolution.
In fact, a small screen with high resolution looks more comfortable (personal opinion)
The resolution of 160* 128 is normal.
For high resolution, for example, moto v303 /v600 adopts the resolution of 220* 176, and its display area is the same as the general 160*. 128 is almost the same, and better results can be obtained. The image is more delicate and can show the luster on the corners of people's mouths. It should also be said here that the mobile phone screen with qvga resolution, such as Sharp gx22, has excellent display effect, reaching the resolution of 320*240, but the display area is relatively large. And the screen resolution of nec n820 is 320*240. At present, this is the standard of mainstream machines in Japan.
I have a picture here. From left to right, the resolution is
moto v303 65536 tft 220* 176
Mitsubishi M720 262144 TFT160 *128
Sony Ericsson z60865536tfd160 *128