Super-twisted nematic LCDs

Twisted nematic displays rotate the director of the liquid crystal by 90° , but super-twisted nematic displays employ up to a 270° rotation. This extra rotation gives the crystal a much steeper voltage-brightness response curve and also widens the angle at which the display can be viewed before losing much contrast. With the sharper response, it is possible to achieve higher contrast with the same voltage selection ratio. Therefore, the degree to which multiplexing is possible is greatly increased. The largest common super-twist displays have up to 500 rows.

Difference between LCD and CRT

LCDs (Liquid Crystal Display) are displays that use liquid crystals sandwiched between two sheets of polarizing material. The images are displayed when electrical charge is applied to the crystals. An LCD uses a select type of liquid crystal known as twisted nematics (TN), which are twisted in shape. Applying a current to these crystals causes them to unwind to a certain degree depending on the voltage. A LCD is in a layer formation, it starts with a mirror on the back for reflection, followed by a piece of glass that has a polarizing film on the bottom side, and a common electrode plane made of indium-tin oxide on top. After that is a layer of liquid crystals, followed by another piece of glass with an electrode and another polarizing film, which is at a right angle to the first one. The LCD is then hooked up to power source that provides a charge to the crystals and causes them to create an image on the screen. LCDs also have a backlight that makes the image visible to the user

CRTs (Cathode Ray Tube) are vacuum tubes that use electron guns and fluorescent screens to display images. A heated filament or ‘cathode’ is in a vacuum in a glass tube, while an electron gun pours electrons into the tube and the electrons are attracted by the positive anode in the tubes. The screen is coated with phosphor, which glows after is hit by the electron gun. Color CRTs have three different electron guns, one for each primary color. A shadow mask, thin metal screen filled with holes, is used to control the points where the electron beams passes to focus on a single point on the CRT’s phosphor surface. Another method is an aperture-grill, which uses tiny vertical wires. Aperture-grill displays are more expensive compared to shadow mask CRTs. However, CRTs are becoming obsolete as it is being replaced by LCDs, OLEDs, Plasmas, etc

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CRT monitors are less expensive than LCDs, though LCD prices continue to fall.CRT monitors typically produce more accurate colors, though LCDs are improving.CRT monitors don't usually exhibit the blurring and ghosting that LCDs do, because they can redraw the screen faster.CRT monitors support multiple resolutions without a decrease in picture quality.CRT monitors are sturdier and more difficult to damage

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