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Due to the immense cost of building TFT factories, the number of major OEM panel vendors probably does not exceed four or five. Several of the most well-known are Samsung, LG.Philips LCD and AU Optronics. Due to the immense cost of building TFT factories, the number of major OEM panel vendors probably does not exceed four or five. Several of the most well-known are Samsung, LG.Philips LCD and AU Optronics. Small monochrome displays such as those found in personal organizers, or older laptop screens have a passive-matrix structure employing supertwist nematic (STN) or double-layer STN (DSTN) technology (DSTN corrects a color-shifting problem with STN). Each row or column of the display has a single electrical circuit. The pixels are addressed one at a time by row and column addresses. This type of display is called a passive matrix because the pixel must retain its state between refreshes without the benefit of a steady electrical charge. As the number of pixels (and, correspondingly, columns and rows) increases, this type of display becomes increasingly less feasible. Very slow response times and poor contrast are typical of passive-matrix LCDs. MVA (Multi-domain Vertical Alignment) was originally developed in 1998 by Fujitsu as a compromise between TN and IPS. It achieved fast pixel response (at the time), wide viewing angles, and high contrast at the cost of brightness and color reproduction.
Small monochrome displays such as those found in personal organizers, or older laptop screens have a passive-matrix structure employing supertwist nematic (STN) or double-layer STN (DSTN) technology (DSTN corrects a color-shifting problem with STN). Each row or column of the display has a single electrical circuit. The pixels are addressed one at a time by row and column addresses. This type of display is called a passive matrix because the pixel must retain its state between refreshes without the benefit of a steady electrical charge. As the number of pixels (and, correspondingly, columns and rows) increases, this type of display becomes increasingly less feasible. Very slow response times and poor contrast are typical of passive-matrix LCDs. Reflective LCDs, often found in digital watches and calculators, are illuminated by external light reflected by a (sometimes) diffusing reflector behind the display. This type of LCD can produce darker 'blacks' than the transmissive type since light must pass through the liquid crystal layer twice and thus is attenuated twice, however because the reflected light is also attenuated twice in the translucent parts of the display image contrast is usually poorer than a transmissive display. The absence of a lamp significantly reduces power consumption, allowing for longer battery life in battery-powered devices; small reflective LCDs consume so little power that they can rely on a photovoltaic cell, as often found in pocket calculators. * LCD screens occasionally suffer from image persistence, which is similar to screen burn on CRT displays. Contrast ratio claims The xenon and neon gas in a plasma television is contained in hundreds of thousands of tiny cells positioned between two plates of glass. Long electrodes are also sandwiched between the glass plates, on both sides of the cells. The address electrodes sit behind the cells, along the rear glass plate. The transparent display electrodes, which are surrounded by an insulating dielectric material and covered by a magnesium oxide protective layer, are mounted above the cell, along the front glass plate.
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LCD technology still has a few drawbacks in comparison to some other display technologies: A diagram of the Pixel layout In-plane switching is an LCD technology which aligns the liquid crystal cells in a horizontal direction. In this method, the electrical field is applied through each end of the crystal, but this requires the need for two transistors for each pixel instead of the one needed for a standard thin-film transistor (TFT) display. This results in blocking more transmission area requiring brighter backlights, which consume more power making this type of display undesirable for notebook computers.
The TN display suffers from limited viewing angles, especially in the vertical direction, and some are unable to display the full 16.7 million colors (24-bit truecolor) available from modern graphics cards. These particular panels, with 6 bits per color channel as opposed to 8, can approach true 24-bit color using a dither method which quickly cycles pixels to simulate a given shade, which are noticeable to some and discomforting to others. Overall, color reproduction and linearity on TN panels is poor. Shortcomings in display color gamut (often referred to as a percentage of the NTSC color gamut) can also be attributed to backlighting technology. It is not uncommon for displays with CCFL (Cold Cathode Fluorescent Lamps) based lighting to range from 40% to 76% of the NTSC color gamut, whereas displays utilizing white LED backlights may extend past 100% of the NTSC color gamut -a difference quite perceivable by the human eye. LCD panels are more likely to have defects than most ICs due to their larger size. In this example, a 12" SVGA LCD has 8 defects and a 6" wafer has only 3 defects. However, 134 of the 137 dies on the wafer will be acceptable, whereas rejection of the LCD panel would be a 0% yield. The standard is much higher now due to fierce competition between manufacturers and improved quality control. An SVGA LCD panel with 4 defective pixels is usually considered defective and customers can request an exchange for a new one. The location of defective pixels is also important. A display with only a few defective pixels may be unacceptable if the defective pixels are near each other. Manufacturers may also relax their replacement criteria when defective pixels are in the center of the viewing area. 1911: Charles Mauguin describes the structure and properties of Liquid Crystals. IPS (In-Plane Switching) was developed by Hitachi in 1996 to improve on the poor viewing angles and color reproduction of TN panels. These improvements came at a loss of response time, which was initially on the order of 50ms. IPS panels were also extremely expensive.