We would introduce the TN lcd,STN lcd, FSTN,FFSTN LCD technology and types of lcd panel available for lcd technology in nowadays. how the lcd panel display working. what is difference of FSTN and FFSTN lcd display definition? what does STN stand for? you would find all these answers in the following:
How many types of lcd available? (monochrome lcd and color lcd)
LCD is including monochrome lcd and color lcd types, monochrome lcd have TN LCD, STN LCD (yellow-green mode, blue mode, gray mode, black-white mode/FSTN,FFSTN), color lcd including color STN LCD and color TFT lcd types, CSTN lcd is almost phase out because it is no better than TFT in contrast, almost all the CSTN LCD manufacturer closed their CSTN LCD lines in the past 10 years.
What is TN LCD?
TN lcd means (twisted nematic) LCD, the namatic liquid crystal elements inside the lcd glass cell,its twisted angle is 90 degree, intergrated the front and rear polarizes on the lcd, the polarized angle is also in 90 degree in cross, it control the light transmission and make the tn lcd display on and off. TN display is based on the precisely controlled realignment of liquid crystal molecules between different ordered molecular configurations under the action of an applied electric field. This is achieved with little power consumption and at low operating voltages.
In the TN lcd display panel OFF state, i.e., when no electrical field is applied, a twisted configuration (aka helical structure or helix) of nematic liquid crystal molecules is formed between two glass plates, G in the figure, which are separated by several spacers and coated with transparent electrodes, E1 and E2. The electrodes themselves are coated with alignment layers (not shown) that precisely twist the liquid crystal by 90° when no external field is present (left diagram). If a light source with the proper polarization (about half) shines on the front of the TN LCD, the light will pass through the first polarizer, P2 and into the liquid crystal, where it is rotated by the helical structure. The light is then properly polarized to pass through the second polarizer, P1, set at 90° to the first. The light then passes through the back of the cell and the image, I, appears transparent.
In the TN LCD display panel ON state, i.e., when a field is applied between the two electrodes, the crystal re-aligns itself with the external field (right diagram). This "breaks" the careful twist in the crystal and fails to re-orient the polarized light passing through the crystal. In this case the light is blocked by the rear polarizer, P1, and the image, I, appears opaque. The amount of opacity can be controlled by varying the voltage. At voltages near the threshold, only some of the crystals will re-align, and the display will be partially transparent. As the voltage is increased, more of the crystals will re-align until it becomes completely "switched". A voltage of about 1 V is required to make the crystal align itself with the field, and no current passes through the crystal itself. Thus the electrical power required for that action is very low.
To display information with a TN liquid crystal, the transparent electrodes are structured by photo-lithography to form a matrix or other pattern of electrodes. Only one of the electrodes has to be patterned in this way, the other can remain continuous (common electrode). For low information content numerical and alpha-numerical TN-LCDs, like digital watches or calculators, segmented electrodes are sufficient. If more complex data or graphics information have to be displayed, a matrix arrangement of electrodes is used. Obviously, the voltage controlled addressing ofmatrix displays, such as in LCD-screens for computer monitors or flat television screens, is more complex than with segmented electrodes. These matrix LCDs necessitate integration of additional non-linear electronic elements into each picture element of the display (e.g., thin-film diodes, TFDs, or thin-film transistors, TFTs) in order to allow the addressing of individual picture elements without crosstalk (unintended activation of non-addressed pixels).
What is STN LCD?
STN lcd is super-twisted nematic lcd display, it is a type of monochrome passive-matrix liquid crystal display (LCD). compare to TN lcd, STN LCD twist angle is 240 degree, instead of 90 degree of TN LCD, so we call it STN LCD, This new type of LCD was invented at the Brown Boveri Research Center, Baden, Switzerland, in 1983. For years a better scheme for multiplexing was sought. Standard twisted nematic (TN) LCDs with a 90 degrees twisted structure of the molecules have a contrast vs. voltage characteristic unsuitable for passive-matrix addressing as there is no distinct threshold voltage. STN displays, with the molecules twisted from 180 to 270 degrees, have superior characteristics. The main advantage of STN LCD is their more pronounced electro-optical threshold allowing for passive-matrix addressing with many more lines and columns. For the first time, a prototype STN matrix display with 540x270 pixels was made by Brown Boveri in 1984, which was considered a breakthrough for the industry.
STN LCD display require less power and are less expensive to manufacture than TFT LCDs, another popular type of LCD that has largely superseded STN for mainstream laptops. STN displays typically suffer from lower image quality and slower response time than TFT displays. STN LCDs can be made purely reflective for viewing under direct sunlight. STN displays are used in some inexpensive mobile phones and informational screens of some digital products.
What is FSTN LCD?
FSTN lcd display mode is the profession name for black-white STN mode, it is white background and black display characters. it is the nearest color to paper in monochrome lcd, even its real background is a little near to gray. FSTN LCD mode is one of STN mode, instead of the background color to yellow-green color or blue color, FSTN LCD add a optics compensator on the front of FSTN LCD, the optics compensator compensate the linear polarize light and color from STN LCD, the STN LCD color turn to white background after light through the optics compensator film. so we also call it is white-black lcd mode. it is the display mode that near to paper. FSTN lcd is widely used in many display application because of its background.
What is FFSTN LCD?
FFSTN is FSTN LCD in negative display mode, it is also a kind of white-black stn lcd mode, FFSTN lcd is negative background with white display characters, while FSTN lcd is white background with black characters, its background would be in black, and display white characters. FSTN lcd would need one layer polarized light compensation, FFSTN would need two layers polarized light compensation on the front and rear polarizers, it would need higher cost than other STN LCD, but FFSTN LCD is best lcd soluton in STN LCD. it is higher contrast than other types of lcd.
What is CSTN LCD?
CSTN lcd means color STN LCD, its display technology is based on FFSTN mode, but it have a RGB color filter in side the lcd glass, so it can realize to color display, and because FFSTN have high contrast, so instead lcd font display to other STN LCD, CSTN LCD is better in image display than other monochrome lcd. but CSTN lcd is still type of stn lcd, it have cross-talk effect, which decreased the contrast than TFT LCD which is active display mode without cross-talk.
TFT VS LCD
TFT (thin film transistor) is still one kinds of lcd, but it active matrix lcd which without cross-talk with higher contrast than STN LCD or monochrome TN LCD. because of the thin film transistor inside, it is without cross-talk problem, and easily to get the high contrast. besides IPS tft, most of tft lcd is still TN LCD display mode, that is 90 degree twist angle to the liquid crystal.
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