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Encyclopedia > Liquid crystal display
Reflective twisted nematic liquid crystal display. Vertical filter film to polarize the light as it enters. Glass substrate with ITO electrodes. The shapes of these electrodes will determine the dark shapes that will appear when the LCD is turned on or off. Vertical ridges etched on the surface are smooth. Twisted nematic liquid crystals. Glass substrate with common electrode film (ITO) with horizontal ridges to line up with the horizontal filter. Horizontal filter film to block/allow through light. Reflective surface to send light back to viewer. (In a backlit LCD, this layer is replaced with a light source.)
Reflective twisted nematic liquid crystal display.
  1. Vertical filter film to polarize the light as it enters.
  2. Glass substrate with ITO electrodes. The shapes of these electrodes will determine the dark shapes that will appear when the LCD is turned on or off. Vertical ridges etched on the surface are smooth.
  3. Twisted nematic liquid crystals.
  4. Glass substrate with common electrode film (ITO) with horizontal ridges to line up with the horizontal filter.
  5. Horizontal filter film to block/allow through light.
  6. Reflective surface to send light back to viewer. (In a backlit LCD, this layer is replaced with a light source.)
A subpixel of a color LCD
A subpixel of a color LCD

A liquid crystal display (commonly abbreviated LCD) is a thin, flat display device made up of any number of color or monochrome pixels arrayed in front of a light source or reflector. It is often utilized in battery-powered electronic devices because it uses very small amounts of electric power. LCD can refer to any of the following acronyms: Liquid crystal display, a type of flat-panel display device. ... Image File history File links LCD-Layers. ... Image File history File links LCD-Layers. ... Schlieren texture of Liquid Crystal nematic phase Liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional liquid, and those of a solid crystal. ... This article treats polarization in electrodynamics. ... Indium tin oxide (ITO) is a mixture of indium(III) oxide (In2O3) and tin(IV) oxide (SnO2), typically 90% In2O3, 10% SnO2 by weight. ... For other uses, see Electrode (disambiguation). ... Image File history File links Download high-resolution version (1280x1024, 249 KB) Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Liquid crystal display ... Image File history File links Download high-resolution version (1280x1024, 249 KB) Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Liquid crystal display ... Schlieren texture of Liquid Crystal nematic phase Liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional liquid, and those of a solid crystal. ... It has been suggested that this article or section be merged into output device. ... A photograph of a sign in grayscale The same photograph in black and white Monochrome comes from the two Greek words mono (μωνο, meaning one), and chroma (χρωμα, meaning surface or the color of the skin). A monochromatic object has a single color. ... This article is about the picture element. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye, or in a more general sense, any electromagnetic radiation in the range from infrared to ultraviolet. ... A reflector can mean one of several things: a reflecting telescope a device or a part of an antenna that reflects radio waves a device that causes reflection, for example, a mirror or a retroreflector a 1981 album by Pablo Cruise In LAPACK the term reflector with the types block... A battery is of one or more electrochemical cells, which store chemical energy and make it available in an electrical form. ... This article is about the engineering discipline. ... For delivered electrical power, see Electrical power industry. ...

Contents

Overview

Each pixel of an LCD typically consists of a layer of molecules aligned between two transparent electrodes, and two polarizing filters, the axes of transmission of which are (in most of the cases) perpendicular to each other. With no liquid crystal between the polarizing filters, light passing through the first filter would be blocked by the second (crossed) polarizer. This article is about the picture element. ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... In electrodynamics, polarization (also spelled polarisation) is the property of electromagnetic waves, such as light, that describes the direction of their transverse electric field. ... Coloured and Neutral Density filters An optical filter is a device which selectively transmits light having certain properties (often, a particular range of wavelengths, that is, range of colours of light), while blocking the remainder. ... Schlieren texture of Liquid Crystal nematic phase Liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional liquid, and those of a solid crystal. ... For other uses, see Light (disambiguation). ...


The surface of the electrodes that are in contact with the liquid crystal material are treated so as to align the liquid crystal molecules in a particular direction. This treatment typically consists of a thin polymer layer that is unidirectionally rubbed using, for example, a cloth. The direction of the liquid crystal alignment is then defined by the direction of rubbing.


Before applying an electric field, the orientation of the liquid crystal molecules is determined by the alignment at the surfaces. In a twisted nematic device (still the most common liquid crystal device), the surface alignment directions at the two electrodes are perpendicular to each other, and so the molecules arrange themselves in a helical structure, or twist. Because the liquid crystal material is birefringent, light passing through one polarizing filter is rotated by the liquid crystal helix as it passes through the liquid crystal layer, allowing it to pass through the second polarized filter. Half of the incident light is absorbed by the first polarizing filter, but otherwise the entire assembly is transparent. In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ... A helix (pl: helices), from the Greek word έλικας/έλιξ, is a twisted shape like a spring, screw or a spiral (correctly termed helical) staircase. ... A calcite crystal laid upon a paper with some letters showing the double refraction Birefringence, or double refraction, is the decomposition of a ray of light into two rays (the ordinary ray and the extraordinary ray) when it passes through certain types of material, such as calcite crystals, depending on... See: transparency (optics) alpha compositing GIF#Transparency transparency (overhead projector) market transparency transparency (telecommunication) transparency (computing) For X11 pseudo-transparency, see pseudo-transparency. ...


When a voltage is applied across the electrodes, a torque acts to align the liquid crystal molecules parallel to the electric field, distorting the helical structure (this is resisted by elastic forces since the molecules are constrained at the surfaces). This reduces the rotation of the polarization of the incident light, and the device appears gray. If the applied voltage is large enough, the liquid crystal molecules in the center of the layer are almost completely untwisted and the polarization of the incident light is not rotated as it passes through the liquid crystal layer. This light will then be mainly polarized perpendicular to the second filter, and thus be blocked and the pixel will appear black. By controlling the voltage applied across the liquid crystal layer in each pixel, light can be allowed to pass through in varying amounts thus constituting different levels of gray. International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ... Alternative meanings: There is also an Electric-type Pokémon named Electrode. ... For other senses of this word, see torque (disambiguation). ... Parallel may refer to: Parallel (geometry) Parallel (latitude), an imaginary east-west line circling a globe Parallelism (grammar), a balance of two or more similar words, phrases, or clauses Parallel (manga), a shōnen manga by Toshihiko Kobayashi Parallel (video), a video album by R.E.M. The Parallel, an... In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ... Look up constraint in Wiktionary, the free dictionary. ... Gray (Gy) is the derived SI unit for absorbed dose, specific energy and kerma (kinetic energy in matter). ... This article is about the picture element. ... This article is about the color. ...


The optical effect of a twisted nematic device in the voltage-on state is far less dependent on variations in the device thickness than that in the voltage-off state. Because of this, these devices are usually operated between crossed polarizers such that they appear bright with no voltage (the eye is much more sensitive to variations in the dark state than the bright state). These devices can also be operated between parallel polarizers, in which case the bright and dark states are reversed. The voltage-off dark state in this configuration appears blotchy, however, because of small thickness variations across the device.


Both the liquid crystal material and the alignment layer material contain ionic compounds. If an electric field of one particular polarity is applied for a long period of time, this ionic material is attracted to the surfaces and degrades the device performance. This is avoided either by applying an alternating current or by reversing the polarity of the electric field as the device is addressed (the response of the liquid crystal layer is identical, regardless of the polarity of the applied field). The crystal structure of sodium chloride, NaCl, a typical ionic compound. ... City lights viewed in a motion blurred exposure. ...


When a large number of pixels is required in a display, it is not feasible to drive each directly since then each pixel would require independent electrodes. Instead, the display is multiplexed. In a multiplexed display, electrodes on one side of the display are grouped and wired together (typically in columns), and each group gets its own voltage source. On the other side, the electrodes are also grouped (typically in rows), with each group getting a voltage sink. The groups are designed so each pixel has a unique, unshared combination of source and sink. The electronics, or the software driving the electronics then turns on sinks in sequence, and drives sources for the pixels of each sink. MUX redirects here. ... It has been suggested that this article or section be merged with Current source. ... For other uses, see Sink (disambiguation). ...


Specifications

Important factors to consider when evaluating an LCD monitor:

  • Resolution: The horizontal and vertical size expressed in pixels (e.g., 1024x768). Unlike CRT monitors, LCD monitors have a native-supported resolution for best display effect.
  • Dot pitch: The distance between the centers of two adjacent pixels. The smaller the dot pitch size, the less granularity is present, resulting in a sharper image. Dot pitch may be the same both vertically and horizontally, or different (less common).
  • Viewable size: The size of an LCD panel measured on the diagonal (more specifically known as active display area).
  • Response time: The minimum time necessary to change a pixel's color or brightness.
  • Matrix type: Active or Passive.
  • Viewing angle: (coll., more specifically known as viewing direction).
  • Color support: How many types of colors are supported (coll., more specifically known as color gamut).
  • Brightness: The amount of light emitted from the display (coll., more specifically known as luminance).
  • Contrast ratio: The ratio of the intensity of the brightest bright to the darkest dark.
  • Aspect ratio: The ratio of the width to the height (for example, 4:3, 16:9 or 16:10).
  • Input ports (e.g., DVI, VGA, LVDS, or even S-Video and HDMI).

Display standards comparison The display resolution of a digital television or computer display typically refers to the number of distinct pixels in each dimension that can be displayed. ... Dot pitch (sometimes called line pitch or phosphor pitch) is a specification for a computer display that describes the distance between phosphor dots (sub-pixels) or LCD cells of the same color on the inside of a display screen. ... In telecommunication, response time is the time a system or functional unit takes to react to a given input. ... This article is about angles in geometry. ... Image File history File links Size of this preview: 800 × 600 pixelsFull resolution (1024 × 768 pixel, file size: 120 KB, MIME type: image/png) File historyClick on a date/time to view the file as it appeared at that time. ... In color reproduction, including computer graphics and photography, the gamut, or color gamut (pronounced ), is a certain complete subset of colors. ... Brightness is an attribute of visual perception in which a source appears to emit a given amount of light. ... Luminance (also called luminosity) is a photometric measure of the density of luminous intensity in a given direction. ... The contrast ratio is a measure of a display system, defined as the ratio of the luminosity of the brightest color (white) to that of the darkest color (black) that the system is capable of producing. ... The aspect ratio of a two-dimensional shape is the ratio of its longer dimension to its shorter dimension. ... DVI redirects here. ... VGA Port VGA plug Video Graphics Array (VGA) is an analog computer display standard first marketed in 1987 by IBM. It has been technologically outdated in the PC market for some time. ... Low-voltage differential signaling, or LVDS, is an electrical signaling system that can run at very high speeds over cheap, twisted-pair copper cables. ... S-Video (also known as Y/C) is a baseband analog video format offering a higher quality signal than composite video, but a lower quality than RGB and component video. ... The High-Definition Multimedia Interface (HDMI) is a licensable audio/video connector interface for transmitting uncompressed, encrypted digital streams. ...

Brief history

  • 1888: Friedrich Reinitzer (1858-1927) discovers the liquid crystalline nature of cholesterol extracted from carrots (that is, two melting points and generation of colors) and published his findings at a meeting of the Vienna Chemical Society on May 3, 1888 (F. Reinitzer: Beiträge zur Kenntniss des Cholesterins, Monatshefte für Chemie (Wien) 9, 421-441 (1888)).[1]
  • 1904: Otto Lehmann publishes his work "Liquid Crystals".
  • 1911: Charles Mauguin describes the structure and properties of liquid crystals.
  • 1936: The Marconi Wireless Telegraph company patents the first practical application of the technology, "The Liquid Crystal Light Valve".
  • 1962: The first major English language publication on the subject "Molecular Structure and Properties of Liquid Crystals", by Dr. George W. Gray.[2]
  • 1962: Richard Williams of RCA found that liquid crystals had some interesting electro-optic characteristics and he realized an electro-optical effect by generating stripe-patterns in a thin layer of liquid crystal material by the application of a voltage. This effect is based on an electro-hydrodynamic instability forming what is now called “Williams domains” inside the liquid crystal.[3]
  • 1964: In the fall of 1964 George H. Heilmeier, then working in the RCA laboratories on the effect discovered by Williams realized the switching of colors by field-induced realignment of dichroic dyes in a homeotropically oriented liquid crystal. Practical problems with this new electro-optical effect made Heilmeier to continue work on scattering effects in liquid crystals and finally the realization of the first operational liquid crystal display based on what he called the dynamic scattering mode (DSM). Application of a voltage to a DSM display switches the initially clear transparent liquid crystal layer into a milky turbid state. DSM displays could be operated in transmissive and in reflective mode but they required a considerable current to flow for their operation.[4][5][6]

Pioneering work on liquid crystals was undertaken in the late 1960s by the UK's Royal Radar Establishment at Malvern. The team at RRE supported ongoing work by George Gray and his team at the University of Hull who ultimately discovered the cyanobiphenyl liquid crystals (which had correct stability and temperature properties for application in LCDs). For the toll-free telephone number see Toll-free telephone number Year 1888 (MDCCCLXXXVIII) was a leap year starting on Sunday (click on link for calendar) of the Gregorian calendar (or a leap year starting on Friday of the 12-day slower Julian calendar). ... Friedrich Reinitzer Friedrich Richard Reinitzer (February 25, 1857 in Prague - February 16, 1927 in Graz) was an Austrian botanist and chemist. ... is the 123rd day of the year (124th in leap years) in the Gregorian calendar. ... For the toll-free telephone number see Toll-free telephone number Year 1888 (MDCCCLXXXVIII) was a leap year starting on Sunday (click on link for calendar) of the Gregorian calendar (or a leap year starting on Friday of the 12-day slower Julian calendar). ... 1904 (MCMIV) was a leap year starting on a Friday (see link for calendar). ... Otto Lehmann (born January 13, 1855 in Konstanz, Germany; died June 17, 1922 in Karlsruhe) was a German physicist and father of liquid crystal technology. ... Year 1911 (MCMXI) was a common year starting on Sunday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Saturday of the 13-day-slower Julian calendar). ... French professor of mineralogy Charles-Victor Mauguin (July 19, 1878 – April 25, 1958) was a founder of the International Union of Crystallography (IUCr), and inventor (with Carl Hermann) of an international standard notation for crystallographic groups. ... Year 1936 (MCMXXXVI) was a leap year starting on Wednesday (link will display the full calendar) of the Gregorian calendar. ... The Marconi Company Ltd. ... Year 1962 (MCMLXII) was a common year starting on Monday (the link is to a full 1962 calendar) of the Gregorian calendar. ... George William Gray (born 4 September 1926) is a Professor of Organic Chemistry at the University of Hull who was instrumental in developing the long-lasting materials which made liquid crystal displays possible. ... Year 1962 (MCMLXII) was a common year starting on Monday (the link is to a full 1962 calendar) of the Gregorian calendar. ... Also Nintendo emulator: 1964 (emulator). ... Dr. George Harry Heilmeier (May 22, 1936 - ) is a notable American engineer and businessman, perhaps best known for his pioneering contributions to liquid crystal displays. ... This article needs cleanup. ... Great Malvern is a town in Worcestershire, England positioned at the foot of, and partly on the sides of, the Malvern Hills. ... The Venn Building The University of Hull, also known as Hull University, is an English university located in Hull (or Kingston upon Hull), a city in the East Riding of Yorkshire. ...

  • 1970: On December 4, 1970, the twisted nematic field effect in liquid crystals was filed for patent by Hoffmann-LaRoche in Switzerland, (Swiss patent No. 532 261) with Martin Schadt and Wolfgang Helfrich (then working for the Central Research Laboratories) listed as inventors.[4] Hoffmann-La Roche then licensed the invention to the Swiss manufacturer Brown, Boveri & Cie who produced displays for wrist watches during the 1970's and also to Japanese electronics industry which soon produced the first digital quartz wrist watches with TN-LCDs and numerous other products. James Fergason at Kent State University filed an identical patent in the USA on April 22, 1971. In 1971 the company of Fergason ILIXCO (now LXD Incorporated) produced the first LCDs based on the TN-effect, which soon superseded the poor-quality DSM types due to improvements of lower operating voltages and lower power consumption.
  • 1972: The first active-matrix liquid crystal display panel was produced in the United States by T. Peter Brody.[7]

A detailed description of the origins and the complex history of liquid crystal displays from the perspective of an insider during the early days has been published by Joseph A. Castellano in "Liquid Gold, The Story of Liquid Crystal Displays and the Creation of an Industry" [8]. Year 1970 (MCMLXX) was a common year starting on Thursday (link shows full calendar) of the Gregorian calendar. ... The twisted nematic effect in liquid crystals has been developed in the Central Research Laboratories of Hoffmann-LaRoche (Switzerland) by Martin Schadt and Wolfgang Helfrich and a patent application was filed for it in Switzerland with the priorty date of December 4, 1970 (Swiss patent No. ... Martin Schadt, PhD, is a Swiss physicist // In 1970 the physicists Martin Schadt and Wolfgang Helfrich invented and patented the twisted nematic (TN)-effect in the Central Research Laboratories of F. Hoffmann-La Roche Ltd, in Basel, Switzerland. ... James Fergason (born Wakenda, Missouri, January 12, 1934) is the inventor of an improved Liquid Crystal Display, or LCD. After obtaining a Bachelors Degree in physics from the University of Missouri in 1956, Fergason began his work on the practical uses of liquid crystals at the Westinghouse Research Laboratories... For the events of May 4, 1970, see Kent State shootings Kent State University (also known as Kent, Kent State or KSU) is one of America’s largest university systems, the third largest university in Ohio after Ohio State University (57,748) and the University of Cincinnati (35,364), and... LXD, Incorporated is one of the first Liquid Crystal Display Manufacturers in the world. ... LXD, Incorporated is one of the first Liquid Crystal Display Manufacturers in the world. ... Year 1972 (MCMLXXII) was a leap year starting on Saturday (link will display full calendar) of the Gregorian calendar. ...


The same history seen from a different perspective has been described and published by Hiroshi Kawamoto (The History of Liquid-Crystal Displays, Proc. IEEE, Vol. 90, No. 4, April 2002[9]), This paper is publicly available at the IEEE History Center.


Color displays

Wikipedia's logo displayed on an LCD monitor.
Wikipedia's logo displayed on an LCD monitor.

In color LCDs each individual pixel is divided into three cells, or subpixels, which are colored red, green, and blue, respectively, by additional filters (pigment filters, dye filters and metal oxide filters). Each subpixel can be controlled independently to yield thousands or millions of possible colors for each pixel. Older CRT monitors employ a similar 'subpixel' structures via the use of phosphors, although the analog electron beam employed in CRTs do not hit exact 'subpixels'. Image File history File links Download high resolution version (1162x1027, 818 KB) Summary Macro shot of an LCD monitor showing the red, green and blue elements. ... Image File history File links Download high resolution version (1162x1027, 818 KB) Summary Macro shot of an LCD monitor showing the red, green and blue elements. ... This article is about the picture element. ... Cathode ray tube employing electromagnetic focus and deflection Cutaway rendering of a color CRT: 1. ...


Color components may be arrayed in various pixel geometries, depending on the monitor's usage. If software knows which type of geometry is being used in a given LCD, this can be used to increase the apparent resolution of the monitor through subpixel rendering. This technique is especially useful for text anti-aliasing. The components of the pixels (primary colors red, green and blue) in an image sensor or display can be ordered in different patterns, called pixel geometry. ... Subpixel rendering works by increasing the luminance reconstruction points of a color subpixelated screen, such as a liquid crystal display (LCD). ... In digital signal processing, anti-aliasing is the technique of minimizing the distortion artifacts known as aliasing when representing a high-resolution signal at a lower resolution. ...


Passive-matrix and active-matrix addressed LCDs

A general purpose alphanumeric LCD, with two lines of 16 characters.

LCDs with a small number of segments, such as those used in digital watches and pocket calculators, have individual electrical contacts for each segment. An external dedicated circuit supplies an electric charge to control each segment. This display structure is unwieldy for more than a few display elements. Image File history File links Download high resolution version (1374x732, 151 KB) Summary This is an general-purpose alphanumeric LCD display, like you might see on a vending machine or suchlike. ... Image File history File links Download high resolution version (1374x732, 151 KB) Summary This is an general-purpose alphanumeric LCD display, like you might see on a vending machine or suchlike. ... Generally speaking, the term alphanumeric refers to anything that consists of only letters and numbers. ... Pocket watch A watch is a small portable clock that displays the current time and sometimes the current day, date, month and year. ... A basic arithmetic calculator. ... An electronic circuit is an electrical circuit that also contains active electronic devices such as transistors or vacuum tubes. ...


Small monochrome displays such as those found in personal organizers, or older laptop screens have a passive-matrix structure employing super-twisted nematic (STN) or double-layer STN (DSTN) technology (DSTN corrects a color-shifting problem with STN), and (CSTN) color-STN (a technology where color is added by using an internal color filter). 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 passive-matrix addressed 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 less feasible. Very slow response times and poor contrast are typical of passive-matrix addressed LCDs. For the band, see Laptop (band). ... This article or section does not cite any references or sources. ... In telecommunication, response time is the time a system or functional unit takes to react to a given input. ... Look up Contrast in Wiktionary, the free dictionary. ...


High-resolution color displays such as modern LCD computer monitors and televisions use an active matrix structure. A matrix of thin-film transistors (TFTs) is added to the polarizing and color filters. Each pixel has its own dedicated transistor, allowing each column line to access one pixel. When a row line is activated, all of the column lines are connected to a row of pixels and the correct voltage is driven onto all of the column lines. The row line is then deactivated and the next row line is activated. All of the row lines are activated in sequence during a refresh operation. Active-matrix addressed displays look "brighter" and "sharper" than passive-matrix addressed displays of the same size, and generally have quicker response times, producing much better images. Display standards comparison The display resolution of a digital television or computer display typically refers to the number of distinct pixels in each dimension that can be displayed. ... A computer display monitor, usually called simply a monitor, is a piece of electrical equipment which displays viewable images generated by a computer without producing a permanent record. ... This article does not cite any references or sources. ... This article is about TFT technology. ... Assorted discrete transistors A transistor is a semiconductor device, commonly used as an amplifier or an electrically controlled switch. ... The refresh rate (or vertical refresh rate, vertical scan rate for CRTs) is the number of times in a second that a display is illuminated. ...


Active matrix technologies

Main article: TFT LCD, Active-matrix liquid crystal display

A 15 TFT-LCD TFT-LCD (thin film transistor liquid crystal display) is a variant of liquid crystal display (LCD) which uses thin film transistor (TFT) technology to improve image quality. ... This article does not cite any references or sources. ...

Twisted nematic (TN)

Twisted nematic displays contain liquid crystal elements which twist and untwist at varying degrees to allow light to pass through. When no voltage is applied to a TN liquid crystal cell, the light is polarized to pass through the cell. In proportion to the voltage applied, the LC cells twist up to 90 degrees changing the polarization and blocking the light's path. By properly adjusting the level of the voltage almost any grey level or transmission can be achieved.


For a more comprehensive description refer to the section on the twisted nematic field effect. The twisted nematic effect in liquid crystals has been developed in the Central Research Laboratories of Hoffmann-LaRoche (Switzerland) by Martin Schadt and Wolfgang Helfrich and a patent application was filed for it in Switzerland with the priorty date of December 4, 1970 (Swiss patent No. ...


In-plane switching (IPS)

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 two transistors for each pixel instead of the single transistor needed for a standard thin-film transistor (TFT) display. This results in blocking more transmission area, thus requiring a brighter backlight, which will consume more power, making this type of display less desirable for notebook computers.


Vertical alignment (VA)

Vertical alignment displays are a form of LC displays in which the liquid crystal material naturally exists in a horizontal state removing the need for extra transistors (as in IPS). When no voltage is applied the liquid crystal cell, it remains perpendicular to the substrate creating a black display. When voltage is applied, the liquid crystal cells shift to a horizontal position, parallel to the substrate, allowing light to pass through and create a white display. VA liquid crystal displays provide some of the same advantages as IPS panels, particularly an improved viewing angle and improved black level.


Quality control

Some LCD panels have defective transistors, causing permanently lit or unlit pixels which are commonly referred to as stuck pixels or dead pixels respectively. Unlike integrated circuits, LCD panels with a few defective pixels are usually still usable. It is also economically prohibitive to discard a panel with just a few defective pixels because LCD panels are much larger than ICs. Manufacturers have different standards for determining a maximum acceptable number of defective pixels. The maximum acceptable number of defective pixels for LCD varies greatly. At one point, Samsung held a zero-tolerance policy for LCD monitors sold in Korea.[10] Currently, though, Samsung adheres to the less restrictive ISO 13406-2 standard.[11] Other companies have been known to tolerate as many as 11 dead pixels in their policies.[12] Dead pixel policies are often hotly debated between manufacturers and customers. To regulate the acceptability of defects and to protect the end user, ISO released the ISO 13406-2 standard.[13] However, not every LCD manufacturer conforms to the ISO standard and the ISO standard is quite often interpreted in different ways. Assorted discrete transistors A transistor is a semiconductor device, commonly used as an amplifier or an electrically controlled switch. ... A stuck pixel is a common pixel defect on LCD screens. ... Close-up of an LCD display, showing a dead green subpixel A dead pixel is a defective pixel that remains unlit on an LCD screen or a CCD or CMOS sensor in a digital camera. ... An integrated circuit (IC) is a thin chip consisting of at least two interconnected semiconductor devices, mainly transistors, as well as passive components like resistors. ...

Examples of defects in LCDs
Examples of defects in LCDs

LCD panels are more likely to have defects than most ICs due to their larger size. In this example, a 300 mm SVGA LCD has 8 defects and a 150 mm 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. Some manufacturers, notably in South Korea where some of the largest LCD panel manufacturers, such as LG, are located, now have "zero defective pixel guarantee" and would replace a product even with one defective pixel. Even where such guarantees do not exist, the location of defective pixels is 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. Image File history File links LCD defects. ... Image File history File links LCD defects. ...


LCD panels also have defects known as mura, which look like a small-scale crack with very small changes in luminance or color.[14] Mura (æ–‘) is a Japanese term for unevenness. ... Luminance (also called luminosity) is a photometric measure of the density of luminous intensity in a given direction. ... Color is an important part of the visual arts. ...


Zero-power (bistable) displays

The zenithal bistable device (ZBD), developed by QinetiQ (formerly DERA), can retain an image without power. The crystals may exist in one of two stable orientations (Black and "White") and power is only required to change the image. ZBD Displays is a spin-off company from QinetiQ who manufacture both grayscale and color ZBD devices. , QinetiQ (LSE: QQ.) (pronounced [], as in kinetic energy) is a British defence technology company, formed from the greater part of the former government agency DERA when it was split up in June 2001 (with the smaller part becoming Dstl). ... The Defence Evaluation and Research Agency (normally known as DERA), was a part of the UK Ministry of Defence (MOD) until July 2, 2001. ...


A French company, Nemoptic, has developed another zero-power, paper-like LCD technology which has been mass-produced since July 2003. This technology is intended for use in applications such as Electronic Shelf Labels, E-books, E-documents, E-newspapers, E-dictionaries, Industrial sensors, Ultra-Mobile PCs, etc. Zero-power LCDs are a category of electronic paper. For other uses, see Paper (disambiguation). ... A prototype electronic paper display. ...


Kent Displays has also developed a "no power" display that uses Polymer Stabilized Cholesteric Liquid Crystals (ChLCD). The major drawback to the ChLCD is slow refresh rate, especially with low temperatures.


In 2004 researchers at the University of Oxford also demonstrated two new types of Zero Power bistable LCDs based on Zenithal bistable techniques.[15]


Several bistable technologies, like the 360° BTN and the bistable cholesteric, depend mainly on the bulk properties of the liquid crystal (LC) and use standard strong anchoring, with alignment films and LC mixtures similar to the traditional monostable materials. Other bistable technologies (i.e. Binem Technology) are based mainly on the surface properties and need specific weak anchoring materials.


Drawbacks

Laptop LCD screen viewed at an extreme angle.
Laptop LCD screen viewed at an extreme angle.

LCD technology still has a few drawbacks in comparison to some other display technologies: Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ...

  • While CRTs are capable of displaying multiple video resolutions without introducing artifacts, LCDs produce crisp images only in their "native resolution" and, sometimes, fractions of that native resolution. Attempting to run LCD panels at non-native resolutions usually results in the panel scaling the image, which introduces blurriness or "blockiness" and is susceptible in general to multiple kinds of HDTV Blur.
  • Although LCDs typically have more vibrant images and better "real-world" contrast ratios (the ability to maintain contrast and variation of color in bright environments) than CRTs, they do have lower contrast ratios than CRTs in terms of how deep their blacks are. A contrast ratio is the difference between a completely on (white) and off (black) pixel, and LCDs can have "backlight bleed" where light (usually seen around corners of the screen) leaks out and turns black into gray. Nowadays the very best LCDs can approach the contrast ratios of plasma displays in terms of delivering a deep black, but most LCDs still lag behind. The very best plasma displays such as the Pioneer Kuro models still lead the way with black levels, which are simply not possible with todays LCD technology. [16]
  • LCDs which use cheap parts cannot "truly" display as many colors as their CRT and plasma counterparts, typically ones that have lower-end panel types (see List of LCD matrices) such as Twisted Nematic panels (TN).
  • LCDs typically have longer response times than their plasma and CRT counterparts, especially older displays, creating visible ghosting when images rapidly change. For example, when moving the mouse quickly on an LCD, multiple cursors can sometimes be seen.
  • Some LCDs have significant input lag. If the lag delay is large enough, such displays can be unsuitable for fast and time-precise mouse operations (CAD, FPS gaming) as compared to CRT displays or smaller LCD panels with negligible amounts of input lag. Short lag times are sometimes emphasized in marketing.
  • LCD panels tend to have a limited viewing angle relative to CRT and plasma displays. This reduces the number of people able to conveniently view the same image – laptop screens are a prime example. As this lack of ambient radiation is what gives LCDs their reduced power consumption in comparison to CRTs and plasma displays, it is unavoidable.
    • While improved viewing angles mean that grossly incorrect color is now uncommon in normal use, viewing an LCD at ranges typical of computer use still allows small shifts in the user's posture, and even the difference in position between their eyes, to produce noticeable color distortion from even the best LCDs on the market.
  • Some LCD monitors can cause migraines and eyestrain problems due to flicker from fluorescent backlights fed at 50 or 60 Hz.
  • A small percentage of LCD screens suffer from image persistence, which is similar to screen burn on CRT and plasma displays, though in LCD monitors, this condition can be repaired very easily.
  • Many LCDs are incapable of displaying very low resolution screen modes (such as 320x200) due to scaling limitations.
  • Consumer LCD monitors tend to be more fragile than their CRT counterparts. The screen may be especially vulnerable due to the lack of a thick glass shield as in CRT monitors.
  • Dead pixels are a common occurrence and few manufacturers replace screens with dead pixels for free.
  • Horizontal and/or vertical banding is a problem in some LCD screens. This flaw occurs as part of the manufacturing process, and cannot be repaired (short of total replacement of the screen). Banding can vary substantially even among LCD screens of the same make and model. The degree is determined by the manufacture's quality control procedures.
  • Color metering is a common problem often not thought about. For a realistic image the frequency range of each of the 3 colors should match the color perception (frequency range) of the human eye. CRT monitors generally do a better job than that of LCD screens. (ref:http://www.sencore.com/newsletter/Mar05/Why%20You%20Need%20a%20CP5000.htm)

It has been suggested that this article or section be merged into Liquid crystal display. ... In computer graphics, image scaling is the process of resizing a digital image. ... HDTV Blur is a common term used to describe a number of different artifacts on consumer modern high definition television sets: Pixel response time on LCD displays (blur in the color response of the active pixel) Slower camera Shutter speeds common in hollywood production films (blur in the HDV content... The contrast ratio is a measure of a display system, defined as the ratio of the luminosity of the brightest color (white) to that of the darkest color (black) that the system is capable of producing. ... This is an incomplete list of LCD matrices. ... In telecommunication, response time is the time a system or functional unit takes to react to a given input. ... Ghosting can have different meanings: ghosting (television), a double image when receiving a distorted or multipath input signal in analog television broadcasting. ... Input lag is a phenomenon associated with some types of LCD displays that refers to latency, or lag measured by the difference between the time a signal is inputted into a display and the time it is shown by the display. ... CAD is a TLA that may stand for: Cadiz Railroad (AAR reporting mark CAD) Canadian dollar – ISO 4217-code Capital Adequacy Directive Card Acceptance Device Children of the Anachronistic Dynasty Computer-aided design Computer-aided detection (medical) Computer-aided diagnosis (medical) Computer-assisted dispatch Computer-assisted drafting Coronary artery disease... This article is about video games. ... This article is about angles in geometry. ... Image Persistence is the term used for LCD Screen Burn. Like the burn-in on CRT monitors, image persistence on LCD monitors is caused by the continuous display of static graphics on the screen for extended periods of time. ... Phosphor burn-in seen at an airport terminal. ... Close-up of an LCD display, showing a dead green subpixel A dead pixel is a defective pixel that remains unlit on an LCD screen or a CCD or CMOS sensor in a digital camera. ... An example of a photo in JPEG format (24bit colour or 16. ... For the Jurassic 5 album, see Quality Control (album) In engineering and manufacturing, quality control and quality engineering are involved in developing systems to ensure products or services are designed and produced to meet or exceed customer requirements. ... Color vision is a psychophysical phenomenon that exists only in our minds. ...

See also

LCD technologies

This is an incomplete list of LCD matrices. ... A 15 TFT-LCD TFT-LCD (thin film transistor liquid crystal display) is a variant of liquid crystal display (LCD) which uses thin film transistor (TFT) technology to improve image quality. ... A transreflective liquid crystal display is a liquid crystal display (LCD) that reflects most of the sunlight the monitor is exposed to, and automatically increases or decreases the light emanating from the screen depending on how much light shines on it. ... This article does not cite any references or sources. ... Anisotropic Conductive Film (ACF), is a lead-free and environmentally-friendly epoxy system that has been used in the Liquid Crystal Display manufacturing to make the electrical and mechanical connections from the driver electronics to the glass substrates of the LCD. ACF technology is used in chip-on-glass (COG... Backlights are lights that are attached to LCD displays so that they can be seen at night. ... HDTV Blur is a common term used to describe a number of different artifacts on consumer modern high definition television sets: Pixel response time on LCD displays (blur in the color response of the active pixel) Slower camera Shutter speeds common in hollywood production films (blur in the HDV content...

Other display technologies

This is a comparison of various properties of different display technologies. ... Cathode ray tube employing electromagnetic focus and deflection Cutaway rendering of a color CRT: 1. ... For political parties using this acronym, see Democratic Labour Party. ... A field emission display (FED) is a type of flat panel display using phosphor coatings as the emissive medium. ... “LED” redirects here. ... Liquid crystal on silicon (LCOS or LCoS) is a micro-projection or micro-display technology typically applied in projection televisions. ... A 3. ... An example of a plasma display A plasma display panel (PDP) is a type of flat panel display now commonly used for large TV displays (typically above 37-inch or 940 mm). ... A surface-conduction electron-emitter display (SED) is a flat panel display technology that uses surface conduction electron emitters for every individual display pixel. ... A full view of a typical vacuum fluorescent display used in a videocassette recorder A close-up of the VFD highlighting the multiple filaments, tensioned by the sheet metal springs at the right of the image A vacuum fluorescent display (VFD) is a type of display used commonly on consumer...

Display applications

Digital television (DTV) is a telecommunication system for broadcasting and receiving moving pictures and sound by means of digital signals, in contrast to analog signals used by analog (traditional) TV. DTV uses digital modulation data, which is digitally compressed and requires decoding by a specially designed television set, or a... Liquid crystal display television (LCD TV) is television that uses LCD technology for its visual output. ... An LCD projector is a type of video projector for displaying video, images or computer data on a screen or other flat surface. ... Nineteen inch (48 cm) CRT computer monitor A computer display, monitor or screen is a computer peripheral device capable of showing still or moving images generated by a computer and processed by a graphics card. ...

Manufacturers

Acer (LSE: ACID) (Traditional Chinese: ) is a Taiwanese multinational electronics manufacturer. ... AU Optronics Corp. ... Barco N.V. (Euronext: BAR) is a display hardware manufacturer specialising in CRT projectors, LCD projectors, DLP projectors, LED displays and flat panel displays. ... BenQ Corporation (IPA: ; Chinese: ) is a Taiwanese company specializing in the manufacturing of computing, communications, and consumer electronics devices. ... Casio Computer Co. ... Chi Mei Corporation (Chinese: 奇美實業廠) is a plastics producer in Taiwan. ... CoolTouch Monitors LLC is a private company based in Southern California that was founded in 2005[1]. CoolTouch Monitors designs and manufactures standalone and 19-inch rack mounted LCD video monitoring products for the Television Broadcast, Film, CCTV and multimedia markets. ... Corning Glass Works (NYSE: GLW) is a U.S. manufacturer of glass, ceramics and related materials, primarily for technical and scientific applications. ... Eizo Nanao Corporation ) (TYO: 6737 ), or EIZO, is a manufacturer of computer displays. ... A four colour Epson Stylus C45 inkjet printer Epson is one of the worlds largest manufacturers of inkjet, dot-matrix and laser printers, scanners, desktop computers, business, multimedia and home theatre projectors, point of sale docket printers and cash registers, laptops, integrated circuits, LCD components and other associated electronic... For the district in Saga, Japan, see Fujitsu, Saga. ... The Hewlett-Packard Company (NYSE: HPQ), commonly known as HP, is a very large, global company headquartered in Palo Alto, California, United States. ... International DisplayWorks, Inc. ... Victor Company of Japan, Limited ) (TYO: 6792 ), usually referred to as JVC, is an international consumer and professional electronics corporation based in Yokohama, Japan which was founded in 1927. ... LG.Philips LCD (hangul:엘지필립스엘씨디, LG필립스LCD) was formed as a joint venture by the Korean electronics company LG Electronics and the Dutch company Koninklijke Philips Electronics in 1999 to manufacture active matrix liquid crystal displays (LCDs). ... LXD, Incorporated is one of the first Liquid Crystal Display Manufacturers in the world. ... Medion is a German company which sells consumer electronics products. ... NEC Display Solutions is a manufacturer of computer monitors and large screen public information displays and has sold and marketed products under the NEC brand globally for over 20 years. ... Panasonic is an international brand name for Japanese electric products manufacturer Matsushita Electric Industrial Co. ... Samsung Electronics (SEC, Hangul:삼성전자; KSE: 005930, KSE: 005935, LSE: SMSN, LSE: SMSD) is a South Korean multinational corporation and the worlds largest and leading electronics and information technology company. ... Sharp Corporation ) (TYO: 6753 , LuxSE: SRP) is a Japanese electronics manufacturer, founded in 1912. ... S-LCD Corporation (Japanese:エス・エルシーディー) is an electronic company of Japan and Korea. ... Sony Corporation ) is a Japanese multinational corporation and one of the worlds largest media conglomerates with revenue of $66. ... Toshiba Corporations headquarters (Center) in Hamamatsucho, Tokyo Toshiba Corporation sales by division for year ending March 31, 2005 Toshiba Corporation ) (TYO: 6502 ) is a Japanese multinational conglomerate manufacturing company, headquartered in Tokyo, Japan. ... ViewSonic is a manufacturer and provider of visual technology, specifically CRT monitors, liquid crystal displays, projectors, plasma displays, HDTV technology, and mobile products, including tablet PCs and wireless monitors. ... Vizio, a privately-held company, is a marketer of consumer electronics based in California, USA. In 2005, Vizio was founded with the goal of providing top tier performance while allowing their technology to be sold at lesser prices. ... Xerox Corporation (NYSE: XRX) (name pronounced ) is a global document management company, which manufactures and sells a range of color and black-and-white printers, multifunction systems, photo copiers, digital production printing presses, and related consulting services and supplies. ...

References

  1. ^ Tim Sluckin: Ueber die Natur der kristallinischen Flüssigkeiten und flüssigen Kristalle (The early history of liquid crystals), Bunsen-Magazin, 7.Jahrgang, 5/2005
  2. ^ George W. Gray, Stephen M. Kelly: "Liquid crystals for twisted nematic display devices", J. Mater. Chem., 1999, 9, 2037–2050
  3. ^ R. Williams, “Domains in liquid crystals,” J. Phys. Chem., vol. 39, pp. 382–388, July 1963
  4. ^ a b Castellano, Joseph A. (2006), "Modifying Light", American Scientist 94 (5): pp. 438-445
  5. ^ G. H. Heilmeier and L. A. Zanoni, “Guest-host interactions in nematic liquid crystals. A new electro-optic effect,” Appl. Phys. Lett., vol. 13, no. 3, pp. 91–92, 1968
  6. ^ G. H. Heilmeier, L. A. Zanoni, and L. A. Barton, “Dynamic scattering: A new electrooptic effect in certain classes of nematic liquid crystals,” Proc. IEEE, vol. 56, pp. 1162–1171, July 1968
  7. ^ Brody, T.P., "Birth of the Active Matrix", Information Display, Vol. 13, No. 10, 1997, pp. 28-32.
  8. ^ LIQUID GOLD, The Story of Liquid Crystal Displays and the Creation of an Industry, 2005 World Scientific Publishing Co. Pte. Ltd., ISBN 981-238-956-3
  9. ^ Hiroshi Kawamoto: The History of Liquid-Crystal Displays, Proc. IEEE, Vol. 90, No. 4, April 2002
  10. ^ Samsung to Offer 'Zero-PIXEL-DEFECT' Warranty for LCD Monitors. Forbes.com (December 30, 2004). Retrieved on 2007-09-03.
  11. ^ What is Samsung's Policy on dead pixels?. Samsung (February 5, 2005). Retrieved on 2007-08-03.
  12. ^ Display (LCD) replacement for defective pixels - ThinkPad. Lenovo (June 25, 2007). Retrieved on 2007-07-13.
  13. ^ What is the ISO 13406-2 standard for LCD screen pixel faults?. Anders Jacobsen's blog (January 4, 2006).
  14. ^ EBU – TECH 3320, "User requirements for Video Monitors in Television Production", EBU/UER, May 2007, p. 11.
  15. ^ Dr Chidi Uche. Development of bistable displays. University of Oxford. Retrieved on 2007-07-13.
  16. ^ David Katzmaier. Flat-panel TVs: plasma and LCD. CNET.com. Retrieved on 2007-06-08.

Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 246th day of the year (247th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 215th day of the year (216th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 194th day of the year (195th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 194th day of the year (195th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 159th day of the year (160th in leap years) in the Gregorian calendar. ...

External links - Tutorials

Wikimedia Commons has media related to:
Liquid Crystal Displays

Image File history File links Commons-logo. ...

General information

  • How LCDs are made, an interactive demonstration from AUO (LCD manufacturer).
  • Development of Liquid Crystal Displays: Interview with George Gray, Hull University, 2004 – Video by the Vega Science Trust.
  • History of Liquid Crystals – Presentation and extracts from the book Crystals that Flow: Classic papers from the history of liquid crystals by its co-author Timothy J. Sluckin
  • Display Technology, by Geoff Walker in the September 2001 issue of Pen Computing
  • Overview of 3LCD technology, Presentation Technology
  • LCD Module technical resources and application notes, Diamond Electronics
  • LCD Phase and Clock Adjustment, Techmind offers a free test screen to get a better LCD picture quality than the LCDs "auto-tune" function.
  • How to clean your LCD screen? The Walyou Blog
  • TFT CentralLCD Monitor Reviews, Specs, Articles and News
  • Pictures of LCD bulbsInterlight

  Results from FactBites:
 
Patents in Class 349/187 (2533 words)
An LCD device and a method of manufacturing the same are disclosed, in which a sealant concentrated upon the end of a dispensing device is formed in a dummy region on a substrate, so that a liquid crystal layer is not contaminated when b...
An LCD device and a method of manufacturing the same are disclosed, which prevents a liquid crystal from being filled imperfectly or excessively in an active region, thereby obtaining a uniform cell gap and improving picture quality char...
A liquid crystal display and a method of fabricating such a liquid crystal display wherein a buffer layer having a hydrophilic property is formed at normal (atmospheric) pressure on the exposed surface of a hydrophobic organic passivatio...
How liquid crystal display (lcd) is made - Background, Raw materials, The manufacturing process of liquid crystal ... (2181 words)
The basis of LCD technology is the liquid crystal, a substance made of complicated molecules.
In an LCD, an electric current is used to switch segments of liquid crystals from a transparent phase to a cloudy phase, each segment forming part of a number or letter.
Most LCDs today also use a source of light coming from the rear of the display (backlight), such as a fluorescent light, to make the liquid crystal appear darker against the screen when in its cloudy phase.
  More results at FactBites »

 
 

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