Reflective twisted nematic liquid crystal
display. Liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional Liquid, and those of a Solid
- Polarizing filter film with a vertical axis to polarize light as it enters. Polarization ( ''Brit'' polarisation) is a property of Waves that describes the orientation of their oscillations
- Glass substrate with ITO electrodes. Uses ITO is mainly used to make transparent conductive coatings for Liquid crystal displays Flat panel displays Plasma displays touch panels An electrode is an Electrical conductor used to make contact with a nonmetallic part of a circuit (e 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.
- Polarizing filter film with a horizontal axis to block/pass light.
- Reflective surface to send light back to viewer. (In a backlit LCD, this layer is replaced with a light source. )
A liquid crystal display (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. Liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional Liquid, and those of a Solid A display device is an Output device for presentation of Information for Visual or Tactile reception acquired stored or transmitted Monochrome comes from the Greek μονόχρωμος ( monochromos) meaning “of one color” which is a combination In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 It is often utilized in battery-powered electronic devices because it uses very small amounts of electric power. In electronics a battery is a combination of two or more Electrochemical cells which store chemical Energy which can be converted into electrical energy Electronics refers to the flow of charge (moving Electrons through Nonmetal conductors (mainly Semiconductors, whereas electrical Electric power is defined as the rate at which Electrical energy is transferred by an Electric circuit.
LCD alarm clock
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. In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by In Optics, transparency (also called pellucidity) is the Material property of allowing Polarization ( ''Brit'' polarisation) is a property of Waves that describes the orientation of their oscillations An optical filter is a device which selectively transmits light having certain properties (often a particular range of Wavelengths that is range of Colours With no liquid crystal between the polarizing filters, light passing through the first filter would be blocked by the second (crossed) polarizer. Liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional Liquid, and those of a Solid Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700
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. Electrodes are made of a transparent conductor called Indium Tin Oxide (ITO). Uses ITO is mainly used to make transparent conductive coatings for Liquid crystal displays Flat panel displays Plasma displays touch panels
Before applying an electric field, the orientation of the liquid crystal molecules is determined by the alignment at the surfaces. 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 (that can 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. A helix (pl helixes or helices) from the Greek word έλιξ, is a special kind of Space curve, i 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. Birefringence, or double refraction, is the decomposition of a ray of Light into two rays (the ordinary ray and the extraordinary ray Half of the incident light is absorbed by the first polarizing filter, but otherwise the entire assembly is reasonably transparent.
LCD with top polarizer removed from device and placed on top, such that the top and bottom polarizers are crossed.
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). Electrical tension (or voltage after its SI unit, the Volt) is the difference of electrical potential between two points of an electrical An electrode is an Electrical conductor used to make contact with a nonmetallic part of a circuit (e A torque (τ in Physics, also called a moment (of force is a pseudo- vector that measures the tendency of a force to rotate an object about 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 (that can 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. In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image Black is the Color of objects that do not emit or Reflect Light in any part of the Visible spectrum; they absorb all such frequencies of 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.
LCD with top polarizer removed from device and placed on top, such that the top and bottom polarizers are parallel.
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 variations of thickness across the device.
Both the liquid crystal material and the alignment layer material contain ionic compounds. In Chemistry, an ionic compound is a Chemical compound in which Ions are held together in a lattice structure by Ionic bonds Usually the positively 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). An alternating current ( AC) is an Electric current whose direction reverses cyclically as opposed to Direct current, whose direction remains constant
When a large number of pixels are needed in a display, it is not technically possible to drive each directly since then each pixel would require independent electrodes. Instead, the display is multiplexed. In Electronics, a multiplexer or mux ( occasionally the term muldex is also found for a combination multiplexer-demultiplexer 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. A voltage source is any device or system that produces an Electromotive force between its terminals OR derives a secondary voltage from a primary 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.
Important factors to consider when evaluating an LCD monitor:
- Resolution: The horizontal and vertical size expressed in pixels (e. 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 g. , 1024x768). Unlike monochrome CRT monitors, LCD monitors have a native-supported resolution for best display effect.
- Dot pitch: The distance between the centers of two adjacent pixels. Dot pitch (sometimes called line pitch, phosphor pitch or pixel pitch) is a specification for a Computer display, Computer printer 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. In Technology, response time is the Time a System or Functional unit takes to react to a given Input. Response time is also divided into rise and fall time. For LCD Monitors, this is measured in btb (black to black) or gtg (gray to gray). These different types of measurements make comparison difficult.
- Refresh rate: The number of times per second in which the monitor draws the data it is being given. The refresh rate (most commonly the "vertical refresh rate" "vertical scan rate" for CRTs is the number of times in a second that display hardware draws A refresh rate that is too low can cause flickering and will be more noticeable on larger monitors. Many high-end LCD televisions now have a 120 Hz refresh rate (current and former NTSC countries only). NTSC ( National Television System Committee) is the Analog television system used in the United States, Canada, Japan, Mexico This allows for less distortion when movies filmed at 24 frames per second (fps) are viewed due to the elimination of telecine (3:2 pulldown). Telecine (ˈtɛləˌsɪni/ /ˌtɛləˈsɪni/ ˌtɛləˈsɪnə also /ˌtɛləˈsiːn/ — "tel-e-Sin-ee" "tel-e-Sin-a" as 'cine' is the same root as in 'cinema' The rate of 120 was chosen as the least common multiple of 24 fps (cinema) and 30 fps (TV). In Arithmetic and Number theory, the least common multiple or lowest common multiple ( lcm) or smallest common multiple of two
- Matrix type: Active or Passive.
- Viewing angle: (coll. In display technology parlance viewing angle is the maximum Angle at which a display can be viewed with acceptable visual performance , more specifically known as viewing direction).
- Color support: How many types of colors are supported (coll. , more specifically known as color gamut). In color reproduction including Computer graphics and Photography, the gamut, or color gamut (pronounced /ˈgæmət/ is a certain complete
- Brightness: The amount of light emitted from the display (coll. Brightness is an attribute of Visual perception in which a source appears to emit or reflect a given amount of Light. , more specifically known as luminance). Luminance is a photometric measure of the density of Luminous intensity in a given direction
- Contrast ratio: The ratio of the intensity of the brightest bright to the darkest dark. The contrast ratio is a measure of a display system defined as the Ratio of the Luminance of the brightest color (white to that of the darkest color (black that
- Aspect ratio: The ratio of the width to the height (for example, 4:3, 16:9 or 16:10). The aspect ratio of a Shape is the ratio of its longer Dimension to its shorter dimension
- Input ports (e. g. , DVI, VGA, LVDS, or even S-Video and HDMI). The Digital Visual Interface ( DVI) is a Video interface standard designed to maximize the visual quality of digital Display devices such as Flat panel The term Video Graphics Array ( VGA) refers specifically to the display hardware first introduced with the IBM PS/2 line of computers in 1987, but through its widespread Low-voltage differential signaling, or LVDS, is an electrical signaling system that can run at very high speeds over inexpensive Twisted-pair copper cables Super Video or Separated Video abbreviated S-Video and also known as Y/C is an analog video signal that carries the video data as two separate The High-Definition Multimedia Interface ( HDMI) is a compact audio/video connector interface for transmitting uncompressed digital streams
- 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. Year 1888 ( MDCCCLXXXVIII) was a Leap year starting on Sunday (click on link for calendar of the Gregorian calendar (or a Friedrich Richard Reinitzer ( February 25, 1857 in Prague - February 16, 1927 in Graz) was an Austrian botanist Events 1491 - Kongo monarch Nkuwu Nzinga is baptised by Portuguese missionaries adopting the baptismal name of João Year 1888 ( MDCCCLXXXVIII) was a Leap year starting on Sunday (click on link for calendar of the Gregorian calendar (or a Reinitzer: Beiträge zur Kenntniss des Cholesterins, Monatshefte für Chemie (Wien) 9, 421-441 (1888)). 
- 1904: Otto Lehmann publishes his work "Liquid Crystals". Year 1904 ( MCMIV) was a Leap year starting on Friday (link will display calendar of the Gregorian calendar (or a Leap year starting on Otto Lehmann (born January 13, 1855 in Konstanz, Germany; died June 17, 1922 in Karlsruhe) was a German
- 1911: Charles Mauguin first experiments of liquids crystals confined between plates in thin layers. Year 1911 ( MCMXI) was a Common year starting on Sunday (link will display the full calendar of the Gregorian calendar (or a Common year French professor of Mineralogy Charles-Victor Mauguin ( July 19, 1878 &ndash April 25, 1958) was a founder of the
- 1922: George Friedel describes the structure and properties of liquid crystals and classified them in 3 types (nematics, smectics and cholesterics). Year 1922 ( MCMXXII) was a Common year starting on Sunday of the Gregorian calendar.
- 1936: The Marconi Wireless Telegraph company patents the first practical application of the technology, "The Liquid Crystal Light Valve". Year 1936 ( MCMXXXVI) was a Leap year starting on Wednesday (link will display the full calendar of the Gregorian calendar. The Marconi Company Ltd was founded by Guglielmo Marconi in 1897 as The Wireless Telegraph & Signal Company (sometimes presented as Wireless
- 1962: The first major English language publication on the subject "Molecular Structure and Properties of Liquid Crystals", by Dr. Year 1962 ( MCMLXII) was a Common year starting on Monday (the link is to a full 1962 calendar of the Gregorian calendar. George W. Gray. George William Gray CBE, FRS (born 4 September 1926 is a Professor of Organic Chemistry at the University of Hull who was instrumental in developing the 
- 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. Year 1962 ( MCMLXII) was a Common year starting on Monday (the link is to a full 1962 calendar of the Gregorian calendar. This effect is based on an electro-hydrodynamic instability forming what is now called “Williams domains” inside the liquid crystal. 
- 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. Year 1964 ( MCMLXIV) was a Leap year starting on Wednesday (link will display full calendar of the 1964 Gregorian calendar. George Harry Heilmeier (born May 22 1936 is an American Engineer and businessman who was a pioneering contributor to Liquid crystal displays Biography 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. 
Pioneering work on liquid crystals was undertaken in the late 1960s by the UK's Royal Radar Establishment at Malvern. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located The Royal Radar Establishment, or RRE, was a renaming of the Radar Research Establishment, which was formed in 1953 from the merger of the Telecommunications Great Malvern is a Town in Worcestershire, England, positioned at the foot and partly on the sides of the Malvern Hills. 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). The University of Hull, also known as Hull University, is an English University, founded in 1927 located in Hull (or Kingston upon Hull) a
- 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 Wolfgang Helfrich and Martin Schadt (then working for the Central Research Laboratories) listed as inventors. Year 1970 ( MCMLXX) was a Common year starting on Thursday (link shows full calendar of the Gregorian calendar. The twisted nematic effect ( TN-effect) in Liquid crystals is claimed to be first discovered by James Fergason in 1970 at the International Liquid Xtal Martin Schadt ( 1938) PhD is a Swiss Physicist and Inventor. Biography In 1970 the physicists Martin Schadt and Wolfgang Helfrich invented  Hoffmann-La Roche then licensed the invention to the Swiss manufacturer Brown, Boveri & Cie who produced displays for wrist watches during the 1970s 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 the Westinghouse Research Laboratories in Pittsburgh while working with Sardari Arora and Alfred Saupe at Kent State University Liquid Crystal Institute filed an identical patent in the USA on April 22, 1971. James Fergason (born Wakenda Missouri, January 12, 1934) is an inventor of an improved Liquid Crystal Display, or LCD Kent State University (also known as Kent, Kent State, or KSU) is one of America’s largest university systems the third largest university  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. 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
- 1972: The first active-matrix liquid crystal display panel was produced in the United States by T. Year 1972 ( MCMLXXII) was a Leap year starting on Saturday (link will display full calendar of the Gregorian calendar. Peter Brody. 
- 2008: LCD TVs are the main stream with 50% market share of the 200 million TVs forecasted to ship globally in 2008 according to Display Bank. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common
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" .
The same history seen from a different perspective has been described and published by Hiroshi Kawamoto, available at the IEEE History Center. 
A subpixel of a color LCD
Simulation of an LCD monitor up close
Comparison of the OLPC XO-1
display (left) with a typical color LCD. The XO-1, previously known as the $100 Laptop or Children's Machine, is an inexpensive Laptop computer intended to be distributed to children in developing
The images show 1×1 mm
of each screen. The Millimetre ( American spelling: millimeter, symbol mm) is a unit of Length in the Metric system, equal to
A typical LCD addresses groups of 3 locations as pixels. The XO-1 display addresses each location as a separate pixel.
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). In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image Each subpixel can be controlled independently to yield thousands or millions of possible colors for each pixel. CRT monitors employ a similar 'subpixel' structures via phosphors, although the electron beam employed in CRTs do not hit exact 'subpixels'. The cathode ray tube (CRT is a Vacuum tube containing an Electron gun (a source of electrons and a Fluorescent screen with internal or
Color components may be arrayed in various pixel geometries, depending on the monitor's usage. The components of the Pixels ( Primary colors red green and blue in an Image Sensor or display can be ordered in different Patterns 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. Subpixel rendering is a way to increase the apparent resolution of a computer's Liquid crystal display (LCD by rendering pixels to take account the screen type's physical properties This technique is especially useful for text anti-aliasing. In Digital signal processing, anti-aliasing is the technique of minimizing the distortion artifacts known as Aliasing when representing a high-resolution signal
To reduce smudging in a moving picture when pixels do not respond quickly enough to color changes, so-called pixel overdrive may be used. Pixel overdrive is a method used to make video on LCD screens look better
Passive-matrix and active-matrix addressed LCDs
A general purpose alphanumeric
LCD, with two lines of 16 characters. Alphanumeric is a is Portmanteau of Alphabetic and Numeric and is used to describe the collection of Latin letters and Arabic digits
LCDs with a small number of segments, such as those used in digital watches and pocket calculators, have individual electrical contacts for each segment. A watch is a timepiece that is made to be worn on a person The term now usually refers to a wristwatch, which is worn on the wrist with a strap or Bracelet. A calculator is device for performing mathematical calculations distinguished from a Computer by having a limited problem solving ability and an interface optimized for interactive An external dedicated circuit supplies an electric charge to control each segment. An electronic circuit is a closed path formed by the interconnection of Electronic components through which an Electric current can flow This display structure is unwieldy for more than a few display elements.
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—the latter of which addresses a color-shifting problem with the former—and color-STN (CSTN)—wherein color is added by using an internal filter. A laptop computer, also known as a notebook computer, is a small Personal computer designed for mobile use. A super-twisted nematic display (STN is a type of Monochrome passive matrix Liquid crystal display (LCD 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. About CONTRAST CONTRAST is a Multidisciplinary alliance bringing together key skills and expertise to generate new knowledge on biological environmental
High-resolution color displays such as modern LCD computer monitors and televisions use an active matrix structure. 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 visual display unit, often called simply a monitor or display, is a piece of Electrical equipment which displays images generated from the Video Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic An active matrix Liquid crystal display ( AMLCD) is a type of Flat panel display, currently the overwhelming choice of Notebook computer 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. In Electronics, a transistor is a Semiconductor device commonly used to amplify or switch electronic signals 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. The refresh rate (most commonly the "vertical refresh rate" "vertical scan rate" for CRTs is the number of times in a second that display hardware draws 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.
Active matrix technologies
1. ( is a Japanese electronic devices manufacturing company founded in 1946 with its Headquarters in Tokyo.
8" colour TFT liquid crystal display which equips the Sony
Cyber-shot DSC-P93A digital compact cameras
- Main article: TFT LCD, Active-matrix liquid crystal display
Twisted nematic (TN)
Twisted nematic displays contain liquid crystal elements which twist and untwist at varying degrees to allow light to pass through. is a multinational conglomerate corporation headquartered in Minato Tokyo, Japan, and one of the world's largest Media conglomerates with Many compact digital still cameras can record Sound and moving Video as well as still Photograph. A thin film transistor liquid crystal display ( TFT-LCD) is a variant of Liquid crystal display (LCD which uses Thin film transistor (TFT technology to An active matrix Liquid crystal display ( AMLCD) is a type of Flat panel display, currently the overwhelming choice of Notebook computer 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 ( TN-effect) in Liquid crystals is claimed to be first discovered by James Fergason in 1970 at the International Liquid Xtal
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.
Blue Phase mode
In blue phase based LC-displays for TV applications it is not the selective reflection of light according the lattice pitch (Bragg reflection), but an electric field deforms the lattice which results in anisotropy of the refractive indices of the layer, followed by a change of transmission between crossed polarizers. Liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional Liquid, and those of a Solid Anisotropy (pronounced with stress on the third syllable ˌænaɪˈsɒtrəpi is the property of being directionally dependent as opposed to Isotropy, which means homogeneity A polarizer is a device that converts an unpolarized or mixed- Polarization beam of Electromagnetic waves (e
Developed with a look at cost-efficiency, blue phase mode LCDs do not require liquid crystal alignment layers, unlike today’s most widely used LCD modes such as Twisted Nematic (TN), In-Plane Switching (IPS) or Vertical Alignment (VA) modes. History In Reinitzer 's reports from 1888 on the melting behaviour of Cholesteryl benzoate there is a note that the substance briefly turned blue as it changed The twisted nematic effect ( TN-effect) in Liquid crystals is claimed to be first discovered by James Fergason in 1970 at the International Liquid Xtal The blue phase mode can make its own alignment layers, eliminating the need for any mechanical alignment and rubbing processes. History In Reinitzer 's reports from 1888 on the melting behaviour of Cholesteryl benzoate there is a note that the substance briefly turned blue as it changed This reduces the number of required fabrication steps, resulting in savings on production costs. Additionally is has been claimed that blue phase panels will reduce sensitivity of the LC-layer to mechanical pressure which can impair the lateral uniformity of display luminance.
Overdrive circuits that are currently applied to many LCD panels with 120Hz frame frequency for improvement of the display of moving images in premium LCD TVs will become obsolete since the blue phase mode features a superior response speed, allowing images to be reproduced at 240Hz frame rate or higher without the need for any overdrive circuit . Frequency is a measure of the number of occurrences of a repeating event per unit Time.
Some LCD panels have defective transistors, causing permanently lit or unlit pixels which are commonly referred to as stuck pixels or dead pixels respectively. In Electronics, a transistor is a Semiconductor device commonly used to amplify or switch electronic signals Defective pixels are pixels on a crystal display (LCD not performing as expected Defective pixels are pixels on a crystal display (LCD not performing as expected Unlike integrated circuits (ICs), LCD panels with a few defective pixels are usually still usable. Microchipsjpg|right|thumb|200px|Microchips ( EPROM memory with a transparent window showing the integrated circuit inside 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.  Currently, though, Samsung adheres to the less restrictive ISO 13406-2 standard. ISO 13406-2 is an ISO standard with the full title "Ergonomic requirements for work with visual displays based on flat panels -- Part 2 Ergonomic requirements for flat  Other companies have been known to tolerate as many as 11 dead pixels in their policies.  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. ISO 13406-2 is an ISO standard with the full title "Ergonomic requirements for work with visual displays based on flat panels -- Part 2 Ergonomic requirements for flat  However, not every LCD manufacturer conforms to the ISO standard and the ISO standard is quite often interpreted in different ways.
Examples of defects in LCDs
LCD panels are more likely to have defects than most ICs due to their larger size. In the example to the right, 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", which is an extra screening process which can then determine "A" and "B" grade panels. Many manufacturers 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.
LCD panels also have defects known as mura, which look like a small-scale crack with very small changes in luminance or color. Mura (斑 or ムラ is traditional general Japanese term for unevenness inconsistency in physical matter or human spiritual condition Luminance is a photometric measure of the density of Luminous intensity in a given direction  It is most visible in dark or black areas of displayed scenes. Defects in various LCD panel components can cause mura effect.
Zero-power (bistable) displays
The zenithal bistable device (ZBD), developed by QinetiQ (formerly DERA), can retain an image without power. QinetiQ ( (pronounced, as in Kinetic energy) is a British defence technology company, formed from the greater part of the former government agency The Defence Evaluation and Research Agency (normally known as DERA) was a part of the UK Ministry of Defence (MoD until July 2, 2001. 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.
A French company, Nemoptic, has developed another zero-power, paper-like LCD technology which has been mass-produced since July 2003. Paper is thin material mainly used for writing upon printing upon or packaging 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. Electronic paper, also called e-paper, is a display technology designed to mimic the appearance of ordinary Ink on Paper.
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 demonstrated two new types of zero-power bistable LCDs based on Zenithal bistable techniques. The University of Oxford (informally "Oxford University" or simply "Oxford" located in the city of Oxford, Oxfordshire, England is the 
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.
Two IBM ThinkPad
laptop screens viewed at an extreme angle. ThinkPad is a brand of portable Laptop and Notebook Personal computers originally designed manufactured and sold by IBM.
LCD technology still has a few drawbacks in comparison to some other display technologies:
- 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. The native resolution of a LCD, LCoS or other flat panel display refers to its single fixed 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. 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 The following factors are generally the primary or secondary Many LCDs are incapable of displaying very low resolution screen modes (such as 320x200) due to these scaling limitations.
- 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. The contrast ratio is a measure of a display system defined as the Ratio of the Luminance of the brightest color (white to that of the darkest color (black that 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. However, as of December 2007, the very best LCDs can approach the contrast ratios of plasma displays in terms of delivering a deep black.
- 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. A first-person shooter ( FPS) is an action Video game from the Shooter game The initial development of Maze War Short lag times are sometimes emphasized in marketing.
- LCD panels using TN tend to have a limited viewing angle relative to CRT and plasma displays. A thin film transistor liquid crystal display ( TFT-LCD) is a variant of Liquid crystal display (LCD which uses Thin film transistor (TFT technology to In display technology parlance viewing angle is the maximum Angle at which a display can be viewed with acceptable visual performance This reduces the number of people able to conveniently view the same image – laptop screens are a prime example. Usually when looking below the screen, it gets much darker; looking from above makes it look lighter. Many panels which are based on the IPS, MVA, or PVA panels have much improved viewing angles; typically the color only gets a little brighter when viewing at extreme angles.
- 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 can occur when the screen is damaged or pressure is put upon the screen; few manufacturers replace screens with dead pixels for free. Defective pixels are pixels on a crystal display (LCD not performing as expected
- 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 manufacturer's quality control procedures. In Engineering and Manufacturing, quality control and quality engineering are involved in developing systems to ensure products or services
- The cold cathode fluorescent bulbs typically used for back-lights in LCDs contain mercury. A cold cathode is an element used within some Nixie tubes Gas discharge lamps Gas filled tubes and Vacuum tubes Cold cathodes do not LED backlit LCD displays are mercury-free.
Other display technologies
- ^ Tim Sluckin: Ueber die Natur der kristallinischen Flüssigkeiten und flüssigen Kristalle (The early history of liquid crystals), Bunsen-Magazin, 7. This is an incomplete list of LCD matrices. TN+Film Matrices IPS Matrices S-IPS Matrices DD-IPS Matrices A thin film transistor liquid crystal display ( TFT-LCD) is a variant of Liquid crystal display (LCD which uses Thin film transistor (TFT technology to An active matrix Liquid crystal display ( AMLCD) is a type of Flat panel display, currently the overwhelming choice of Notebook computer Anisotropic Conductive Film (ACF, is a lead-free and environmentally-friendly epoxy system that has been used in Liquid Crystal Display manufacturing to make the electrical A backlight is the form of illumination used in a Liquid crystal display (LCD HDTV blur is a common term used to describe a number of different artifacts on consumer modern high-definition television sets The following factors are generally the primary or secondary This is a comparison of various properties of different display technologies The cathode ray tube (CRT is a Vacuum tube containing an Electron gun (a source of electrons and a Fluorescent screen with internal or Digital Light Processing (DLP is a Trademark owned by Texas Instruments, representing a technology used in projectors and Video projectors It was A field emission display ( FED) is a Flat panel display technology based on field emitting cathodes to bombard Phosphor coatings as the light emissive Liquid crystal on silicon ( LCOS or LCoS) is a "micro-projection" or "micro-display" Technology typically applied in projection An Organic Light Emitting Diode ( OLED) also Light Emitting Polymer ( LEP) and Organic Electro Luminescence ( OEL) is any 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 A vacuum fluorescent display (VFD is a Display device used commonly on consumer-electronics equipment such as Video cassette recorders Car radios Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic Digital television (DTV is the sending and receiving of moving images and sound by discrete ( digital) signals in contrast to the analog signals used by Liquid-crystal display televisions ( LCD TV) are Television sets that use LCD technology to produce images An LCD projector is a type of Video projector for displaying video images or computer data on a screen or other flat surface A visual display unit, often called simply a monitor or display, is a piece of Electrical equipment which displays images generated from the Video Acer Incorporated ( ( is a Taiwanese multinational electronics manufacturer AU Optronics Corp (AUO ( is one of the top 3 worldwide manufacturers of thin film transistor liquid crystal display panels ( TFT LCD) and is the largest in Taiwan Barco NV ( is a display Hardware manufacturer specialising in CRT projectors LCD projectors DLP projectors, LCoS projectors BenQ Corporation (ˌbɛn ˈkjuː 明基電通股份有限公司 is a Taiwanese company that sells and markets consumer electronics computing and communications devices under the ( is a Japanese electronic devices manufacturing company founded in 1946 with its Headquarters in Tokyo. Chi Mei Corporation (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 Corning Incorporated ( is an American manufacturer of Glass, Ceramics and related materials primarily for industrial and scientific applications ( or EIZO, is a manufacturer of high quality Computer displays A Japanese corporation it was founded in March 1968 but did not adopt its current name or Epson, is a Japanese company and one of the world's largest manufacturers of inkjet, dot matrix and Laser printers scanners is a Japanese company specializing in Semiconductors Computers ( Supercomputers Personal computers, servers, Telecommunications is a manufacturer of high end computer monitors medical monitors and televisions named after the city Iiyama in Nagano, Japan. This article is about the Corporation known as IDWK } International DisplayWorks Inc ( usually referred to as JVC, is an International consumer and professional electronics Corporation based in Yokohama, Japan which was founded is a Japanese company based in Kyoto, Japan. The company was founded as in 1959 by Kazuo Inamori. Lenovo Group Limited (,) is China's largest and the world's fourth largest Personal computer manufacturer after Hewlett-Packard and Dell of the U LXD Incorporated is one of the first Liquid Crystal Display Manufacturers in the world Medion AG 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 Polaroid Corporation was founded in 1937 by Edwin H Land. It is most famous for its Instant film Cameras which reached the market in 1948 and Samsung Electronics (SEC Hangul:삼성전자,,,) is the world's largest Consumer electronics company headquartered in Seocho Samsung Town in () is a Japanese Electronics manufacturer founded in 1912 It takes its name from one of its founder's first inventions the Ever-Sharp Mechanical pencil, which S-LCD Corporation ( Hangul: 에스 엘시디 Japanese: エス・エルシーディー is a joint venture between the Korean Samsung Electronics Co is a multinational conglomerate corporation headquartered in Minato Tokyo, Japan, and one of the world's largest Media conglomerates with ( is a multinational conglomerate manufacturing company headquartered in Tokyo, Japan. Videocon is an industrial conglomerate with interests all over the world and based in India. ViewSonic Corporation is a manufacturer and provider of visual technology specifically CRT monitors Liquid crystal displays Projectors Plasma Vizio, is a privately-held producer of consumer electronics based in Irvine California, USA. Xerox Corporation ( (name ˈziːrɒks is a global document management company which manufactures and sells a range of color and black-and-white printers, multifunction Jahrgang, 5/2005
- ^ George W. Gray, Stephen M. Kelly: "Liquid crystals for twisted nematic display devices", J. Mater. Chem. , 1999, 9, 2037–2050
- ^ R. Williams, “Domains in liquid crystals,” J. Phys. Chem. , vol. 39, pp. 382–388, July 1963
- ^ a b Castellano, Joseph A. (2006), “Modifying Light”, American Scientist 94 (5): pp. 438-445
- ^ 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
- ^ 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
- ^ Modifying Light. American Scientist Online.
- ^ Brody, T. P. , "Birth of the Active Matrix", Information Display, Vol. 13, No. 10, 1997, pp. 28-32.
- ^ 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
- ^ Hiroshi Kawamoto: The History of Liquid-Crystal Displays, Proc. IEEE, Vol. 90, No. 4, April 2002
- ^ Samsung Develops World’s First 'Blue Phase' Technology , retrieved May 2008
- ^ Samsung to Offer 'Zero-PIXEL-DEFECT' Warranty for LCD Monitors. Forbes. com (December 30, 2004). Retrieved on 2007-09-03. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 36 BC - In the Battle of Naulochus, Marcus Vipsanius Agrippa, Admiral of Octavian, defeats Sextus Pompeius
- ^ What is Samsung's Policy on dead pixels?. Samsung (February 5, 2005). Retrieved on 2007-08-03. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 8 - Roman Empire General Tiberius defeats Dalmatians on the river Bathinus.
- ^ Display (LCD) replacement for defective pixels - ThinkPad. Lenovo (June 25, 2007). Retrieved on 2007-07-13. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1174 - William I of Scotland, a key rebel in the Revolt of 1173-1174, is captured at Alnwick by forces loyal to
- ^ What is the ISO 13406-2 standard for LCD screen pixel faults?. Anders Jacobsen's blog (January 4, 2006).
- ^ EBU – TECH 3320, "User requirements for Video Monitors in Television Production", EBU/UER, May 2007, p. 11.
- ^ Dr Chidi Uche. Development of bistable displays. University of Oxford. Retrieved on 2007-07-13. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1174 - William I of Scotland, a key rebel in the Revolt of 1173-1174, is captured at Alnwick by forces loyal to
External links - Tutorials
Color LCD Interfacing,LCD Interfacing with microcontroller
- 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
- Oleg Artamonov (2007-01-23). Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 393 - Roman Emperor Theodosius I proclaims his nine year old son Honorius co-emperor Contemporary LCD Monitor Parameters: Objective and Subjective Analysis. X-bit labs. Retrieved on 2008-05-17. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1521 - Edward Stafford 3rd Duke of Buckingham, is executed for Treason.
- 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 About. com: PC Support
- TFT CentralLCD Monitor Reviews, Specs, Articles and News
- Interfacing Alphanumeric LCD to Microcontroller
© 2009 citizendia.org; parts available under the terms of GNU Free Documentation License, from http://en.wikipedia.org
network: | |