TN, STN LCD, FSTN LCD Display

Blaze Display Technology Co., Ltd. | Updated: Nov 27, 2018

This article is introduces what is TN LCD and STN display, what is difference for FSTN and FFSTN? What types of lcd panel available for lcd technology?  How the lcd panel display working. What is difference between FSTN and FFSTN lcd display definition? What does STN stand for? Let's see the introduction as 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), monochrome tft lcd.  Color lcd including color STN LCD and color TFT lcd types, color STN LCD (CSTN lcd) is almost phase out because it is no better than TFT in contrast, Now all CSTN LCDs were replaced by tft lcd dsiplay.

 

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, integrated 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.

 

What is STN LCD?

 

STN lcd is super-twisted nematic lcd display, it is a type of monochrome lcd display, it is also passive 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. STN lcd have yellow-green display mode, gray, black-white mode, blue display mode, available.

STN lcd structure:

The STN LCD is not only difference on twist angle in 240 °, in the same time, because the liquid crystal has the double-reflective characteristic, the ambient light through the polarizer, it would change to linear polarized light, the linear polarized light go through the STN LCD cell with 240° twist angle, it would turn to oval polarized light because of the double-reflective of liquid crystal characteristic （the linear polarized light turn to two group lights via 240° twist angle liquid crystal, and the two group light intervened to oval polarized light）. The oval polarized lights are always with colors, that is the reason of yellow-green or blue color come from for the STN LCD.

Contrast and viewing angle of STN LCD:

With the twist angle in 240°, it bring higher display contrast as the twist angle from TN 90° to STN 240°, as see the graph as below, as the increasing about the lcd contrast in twist angle, when TN lcd can support 8 commons driver (1/8 duty), such as segment lcd, because the TN liquid crystal sharpness is less than STN LCD, if the commons higher than 8, the TN lcd contrast would be decreased dramatically. While STN lcd could support 240 commons (1/240 duty) in maximum. STN not only support 16x2, 20x4 characters lcd, and could support 128x64, 320x240 graphic lcd as well, it is all because the contrast increased due to liquid crystal's twist angle for STN lcd.

 

Meanwhile, as the display contrast increased for the STN LCD, it bring wider viewing angle for STN lcd than TN lcd display. STN lcd viewing angle could be reach 120 degree, while TN lcd viewing angle around 90 degree.

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, it is mean film STN, instead of the background color to yellow-green color or blue color, FSTN LCD add a optics compensating film on the front of FSTN LCD, the optics compensating film 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. That is the compensating film turn the oval polarized light to the linear polarized light again, then we could get the white and black lcd display. It is the display mode that near to paper. FSTN lcd is widely used in many display application because of its background.

FSTN LCD module:

FSTN LCD structure:

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.