Pioneering passive-matrix STN LCD, Brown Boveri, Switzerland, 1984 A super-twisted nematic display (STN) is a type of

monochrome A monochrome or monochromatic image, object or palette is composed of one color (or values of one color). Images using only shades of grey are called grayscale (typically digital) or black-and-white (typically analog). In physics, monochr ...

liquid crystal display A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liquid crystals do not emit light directly but ...

(LCD).

History

This 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 unfavorable 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.

Features

The main advantage of STN LCDs 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 (today ABB) in 1984, which was considered a breakthrough for the industry. STN LCDs require less power and are less expensive to manufacture than

TFT LCD A thin-film-transistor liquid-crystal display (TFT LCD) is a variant of a liquid-crystal display that uses thin-film-transistor technology to improve image qualities such as addressability and contrast. A TFT LCD is an active matrix LCD, in con ...

s, another popular type of LCD that has largely superseded STN for mainstream

laptop A laptop, laptop computer, or notebook computer is a small, portable personal computer (PC) with a screen and alphanumeric keyboard. Laptops typically have a clam shell form factor with the screen mounted on the inside of the upper li ...

s. STN displays typically suffer from lower image quality and slower

response time Response time may refer to: *The time lag between an electronic input and the output signal which depends upon the value of passive components used. * Responsiveness, how quickly an interactive system responds to user input * Response time (biolog ...

than TFT displays. However, 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. In the early 1990s, they had been used in some portable computers such as Amstrad's PPC512 and PPC640, and in Nintendo's

Game Boy The is an 8-bit fourth generation handheld game console developed and manufactured by Nintendo. It was first released in Japan on April 21, 1989, in North America later the same year, and in Europe in late 1990. It was designed by the same t ...

Variants

A 12 bit CSTN in a

thumb The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front), the thumb is the outermost digit. The Medical Latin English noun for thumb ...

''CSTN'' (

color Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are associ ...

super-twist nematic) is a color form for electronic display screens originally developed by

Sharp Electronics is a Japanese multinational corporation that designs and manufactures electronics, electronic products, headquartered in Sakai-ku, Sakai, Sakai-ku, Sakai, Osaka Prefecture. Since 2016 it has been majority owned by the Taiwan-based Foxconn Grou ...

. The CSTN uses red,

green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a combin ...

and

blue Blue is one of the three primary colours in the RYB colour model (traditional colour theory), as well as in the RGB (additive) colour model. It lies between violet and cyan on the spectrum of visible light. The eye perceives blue when ...

filters Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component that ...

to display color. The original CSTN displays developed in the early 1990s suffered from slow response times and ghosting (where text or graphic changes are blurred because the

pixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the ...

s cannot turn off and on fast enough). Recent advances in the technology, however, have made CSTN a viable alternative to

active matrix Active matrix is a type of addressing scheme used in flat panel displays. In this method of switching individual elements (pixels), each pixel is attached to a transistor and capacitor ''actively'' maintaining the pixel state while other pixels ar ...

displays. New CSTN displays offer 100ms response times (for comparison TFT displays offer 8ms or less), a 140 degree viewing angle and high-quality color rivaling TFT displays – all at about half the cost. A newer passive-matrix technology called

High-Performance Addressing High-performance addressing (HPA) is an LCD passive-matrix display technology commonly found on low-end portable computers; versions of HPA have been developed by Hitachi and by Sharp. HPA enables higher response rates and contrast, displaying up t ...

(HPA) offers even better response times and contrast than CSTN. Samsung had two proprietary technologies for STN LCDs, Ultra Fine & Bright (UFB), which delivered wide viewing angle (about 120 degrees), faster response time (about 60 ms) and less power consumption, while Ultra Fine & High Speed (UFS), delivered almost same color depths as TFT LCDs, greater color purity, much faster response time (about 14 ms) and same contrast ratio as TFT LCDs. Other STN displays include: * Double layer STN: An earlier passive matrix LCD technology that used an extra compensating layer to provide a sharper image. *

Dual Scan Dual Scan, also known as dual-scan supertwist nematic or DSTN, is an LCD technology in which a screen is divided in half, which are simultaneously refreshed giving faster refresh rate than traditional passive matrix screens. It is an improved for ...

STN: An enhanced STN passive matrix LCD. The screen is divided into halves, and each half is scanned simultaneously, thereby doubling the number of lines refreshed per second and providing a sharper appearance. DSTN was widely used on earlier laptops. See STN and LCD. * FRSTN: Fast Response STN * FSTN: Film compensated STN, Formulated STN or Filtered STN. A passive matrix LCD technology that uses a film compensating layer between the STN display and rear polarizer for added sharpness and contrast. It was used in laptops before the DSTN method became popular and many early 21st Century cellphones. * FFSTN: Double film super-twist nematic * MSTN:

Monochrome A monochrome or monochromatic image, object or palette is composed of one color (or values of one color). Images using only shades of grey are called grayscale (typically digital) or black-and-white (typically analog). In physics, monochr ...

super-twist nematic * CCSTN:

Color Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are associ ...

Coded Super Twist Nematic. An LCD capable of displaying a limited range of colours, used in some digital organisers and graphic calculators in the 1990s

References

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External links

Display Types and Technologies
Display technology Swiss inventions