Flat-panel display

A flat-panel display (FPD) is an electronic display device used to enable people to see content (still images, moving images, text, or other visual material) in a range of entertainment, consumer electronics, personal computer, and mobile devices, and many types of medical, transportation and industrial equipment. They are far lighter and thinner than traditional cathode ray tube (CRT) television sets and are usually less than 10 centimetres (3.9 in) thick. Flat-panel displays can be divided into two display device categories: volatile and static. Volatile displays require that pixels be periodically electronically refreshed to retain their state (e.g. liquid-crystal displays (LCD)). A volatile display only shows an image when it has battery or AC mains power. Static flat-panel displays rely on materials whose color states are bistable (e.g., e-book reader tablets from Sony), and as such, flat-panel displays retain the text or images on the screen even when the power is off. As of 2016, flat-panel displays have almost completely replaced old CRT displays. In many 2010-era applications, specifically small portable devices such as laptops, mobile phones, smartphones, digital cameras, camcorders, point-and-shoot cameras, and pocket video cameras, any display disadvantages of flat-panels (as compared with CRTs) are made up for by portability advantages (low power consumption from batteries, thinness and lightweightness).

Most 2010s-era flat-panel displays use LCD or light emitting diode (LED) technologies, sometimes combined. Most LCD screens are back-lit as color filters are used to display colors. Flat-panel displays are thin, lightweight, provide better linearity and are capable of higher resolution than typical consumer-grade TVs from earlier eras. The highest resolution for consumer-grade CRT TVs was 1080i; in contrast, many flat-panels can display 1080p or even 4K resolution. As of 2016, some devices that use flat-panels, such as tablet computers, smartphones and, less commonly, laptops, use touchscreens, a feature that enables users to select onscreen icons or trigger actions (e.g., playing a digital video) by touching the screen. Many touchscreen-enabled devices can display a virtual QWERTY or numeric keyboard on the screen, to enable the user to type words or numbers.

A multifunctional monitor (MFM) is a flat-panel display that has additional video inputs (more than a typical LCD monitor) and is designed to be used with a variety of external video sources, such as VGA input, HDMI input from capable equipped VHS VCR or video game console and, in some cases, a USB input or card reader for viewing digital photos. In many instances, an MFM also includes a TV tuner, making it similar to a LCD TV that offers computer connectivity.

History

The first engineering proposal for a flat-panel TV was by General Electric in 1954 as a result of its work on radar monitors. The publication of their findings gave all the basics of future flat-panel TVs and monitors. But GE did not continue with the R&D required and never built a working flat panel at that time.[1] The first production flat-panel display was the Aiken tube, developed in the early 1950s and produced in limited numbers in 1958. This saw some use in military systems as a heads up display and as an oscilloscope monitor, but conventional technologies overtook its development. Attempts to commercialize the system for home television use ran into continued problems and the system was never released commercially.[2][3][4]

The Philco Predicta featured a relatively flat (for its day) cathode ray tube setup and would be the first commercially released "flat panel" upon its launch in 1958; the Predicta was a commercial failure. The plasma display panel was invented in 1964 at the University of Illinois, according to The History of Plasma Display Panels.[5]

LCD displays

The MOSFET (metal-oxide-semiconductor field-effect transistor, or MOS transistor) was invented by Mohamed M. Atalla and Dawon Kahng at Bell Labs in 1959,[6] and presented in 1960.[7] Building on their work, Paul K. Weimer at RCA developed the thin-film transistor (TFT) in 1962.[8] It was a type of MOSFET distinct from the standard bulk MOSFET.[9] The idea of a TFT-based LCD was conceived by Bernard J. Lechner of RCA Laboratories in 1968.[10] B.J. Lechner, F.J. Marlowe, E.O. Nester and J. Tults demonstrated the concept in 1968 with a dynamic scattering LCD that used standard discrete MOSFETs.[11]

The first active-matrix addressed electroluminescent display (ELD) was made using TFTs by T. Peter Brody's Thin-Film Devices department at Westinghouse Electric Corporation in 1968.[12] In 1973, Brody, J. A. Asars and G. D. Dixon at Westinghouse Research Laboratories demonstrated the first thin-film-transistor liquid-crystal display (TFT LCD).[13][14] Brody and Fang-Chen Luo demonstrated the first flat active-matrix liquid-crystal display (AM LCD) using TFTs in 1974.[10]

By 1982, pocket LCD TVs based on LCD technology were developed in Japan.[15] The 2.1-inch Epson ET-10[16] Epson Elf was the first color LCD pocket TV, released in 1984.[17] In 1988, a Sharp research team led by engineer T. Nagayasu demonstrated a 14-inch full-color LCD display,[10][18] which convinced the electronics industry that LCD would eventually replace CRTs as the standard television display technology.[10] As of 2013, all modern high-resolution and high-quality electronic visual display devices use TFT-based active-matrix displays.[19]

LED displays

The first usable LED display was developed by Hewlett-Packard (HP) and introduced in 1968.[20] It was the result of research and development (R&D) on practical LED technology between 1962 and 1968, by a research team under Howard C. Borden, Gerald P. Pighini, and Mohamed M. Atalla, at HP Associates and HP Labs. In February 1969, they introduced the HP Model 5082-7000 Numeric Indicator.[21] It was the first alphanumeric LED display, and was a revolution in digital display technology, replacing the Nixie tube for numeric displays and becoming the basis for later LED displays.[22] In 1977, James P Mitchell prototyped and later demonstrated what was perhaps the earliest monochromatic flat panel LED television display.

Ching W. Tang and Steven Van Slyke at Eastman Kodak built the first practical organic LED (OLED) device in 1987.[23] In 2003, Hynix produced an organic EL driver capable of lighting in 4,096 colors.[24] In 2004, the Sony Qualia 005 was the first LED-backlit LCD display.[25] The Sony XEL-1, released in 2007, was the first OLED television.[26]

Common types

Liquid crystal display (LCD)
An LCD screen used as an information display for travellers.

LCDs are lightweight, compact, portable, cheap, more reliable, and easier on the eyes than CRT screens. LCD screens use a thin layer of liquid crystal, a liquid that exhibits crystalline properties. It is sandwiched between two electrically conducting plates. The top plate has transparent electrodes deposited on it, and the back plate is either fitted with a reflector or is illuminated from behind so that the viewer can see the images on the screen. By applying controlled electrical signals across the plates, various segments of the liquid crystal can be activated, causing changes in their light diffusing or polarizing properties. These segments can either transmit or block light. An image is produced by passing light through selected segments of the liquid crystal to the viewer. They are used in various electronics like watches, calculators, and notebook computers.

LCD with backlit light-emitting diode (LED)

Some LCD screens are back-lit with a number of LEDs. LEDs are two-lead semiconductor light sources. The image is still generated by the LCD. LED-backlit LCD displays are the most prevalent in the 2010s.

Plasma panel

A plasma display consists of two glass plates separated by a thin gap filled with a gas such as neon. Each of these plates has several parallel electrodes running across it. The electrodes on the two plates are at right angles to each other. A voltage applied between the two electrodes one on each plate causes a small segment of gas at the two electrodes to glow. The glow of gas segments is maintained by a lower voltage that is continuously applied to all electrodes. By 2010, consumer plasma displays had been discontinued by numerous manufacturers.

Electroluminescent panel

In an electroluminescent display (ELD), the image is created by applying electrical signals to the plates which makes the phosphor glow.

Organic light-emitting diode

An OLED (organic light-emitting diode) is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound which emits light in response to an electric current. This layer of organic semiconductor is situated between two electrodes; typically, at least one of these electrodes is transparent. OLEDs are used to create digital displays in devices such as television screens, computer monitors, portable systems such as mobile phones, handheld game consoles and PDAs.

Quantum dot light emitting diode

QLED or quantum dot LED is a flat panel display technology introduced by Samsung under this trademark. Other television set manufacturers such as Sony have used the same technology to enhance the backlighting of LCD TVs already in 2013.[27][28] Quantum dots create their own unique light when illuminated by a light source of shorter wavelength such as blue LEDs. This type of LED TV enhances the color gamut of LCD panels, where the image is still generated by the LCD. In the view of Samsung, quantum dot displays for large-screen TVs are expected to become more popular than the OLED displays in the coming years; Firms like Nanoco and Nanosys compete to provide the QD materials. In the meantime, Samsung Galaxy devices such as smartphones are still equipped with OLED displays manufactured by Samsung as well. Samsung explain on their website that the QLED TV they produce can determine what part of the display needs more or less contrast. Samsung also announced a partnership with Microsoft that will promote the new Samsung QLED TV.

Volatile
A large LED display at the Taipei Arena displays commercials and movie trailers.

Volatile displays require that pixels be periodically refreshed to retain their state, even for a static image. As such, a volatile screen needs electrical power, either from mains electricity (being plugged into a wall socket) or a battery to maintain an image on the display or change the image. This refresh typically occurs many times a second. If this is not done, for example, if there is a power outage, the pixels will gradually lose their coherent state, and the image will "fade" from the screen.

Examples
Further information: Comparison CRT, LCD, Plasma

The following flat-display technologies have been commercialized in 1990s to 2010s:

Technologies that were extensively researched, but their commercialization was limited or has been ultimately abandoned:

Static
Amazon's Kindle Keyboard e-reader displaying a page of an e-book. The Kindle's image of the book's text will remain onscreen even if the battery runs out, as it is a static screen technology. Without power, however, the user cannot change to a new page.

Static flat-panel displays rely on materials whose color states are bistable. This means that the image they hold requires no energy to maintain, but instead requires energy to change. This results in a much more energy-efficient display, but with a tendency toward slow refresh rates which are undesirable in an interactive display. Bistable flat-panel displays are beginning deployment in limited applications (cholesteric liquid crystal displays, manufactured by Magink, in outdoor advertising; electrophoretic displays in e-book reader devices from Sony and iRex; anlabels; interferometric modulator displays in a smartwatch).

See also

References
  1. "Proposed Television Sets Would Feature Thin Screens." Popular Mechanics, November 1954, p. 111.
  2. William Ross Aiken, "History of the Kaiser-Aiken, thin cathode ray tube", IEEE Transactions on Electron Devices, Volume 31 Issue 11 (November 1984), pp. 1605-1608.
  3. "Flat Screen TV in 1958 - Popular Mechanics (Jan, 1958)".
  4. "Geer Experimental Color CRT". www.earlytelevision.org.
  5. Plasma TV Science.org - The History of Plasma Display Panels
  6. "1960 - Metal Oxide Semiconductor (MOS) Transistor Demonstrated". The Silicon Engine. Computer History Museum. Retrieved 29 July 2019.
  7. Atalla, M.; Kahng, D. (1960). "Silicon-silicon dioxide field induced surface devices". IRE-AIEE Solid State Device Research Conference.
  8. Weimer, Paul K. (June 1962). "The TFT A New Thin-Film Transistor". Proceedings of the IRE. 50 (6): 1462–1469. doi:10.1109/JRPROC.1962.288190. ISSN 0096-8390. S2CID 51650159.
  9. Kimizuka, Noboru; Yamazaki, Shunpei (2016). Physics and Technology of Crystalline Oxide Semiconductor CAAC-IGZO: Fundamentals. John Wiley & Sons. p. 217. ISBN 9781119247401.
  10. Kawamoto, H. (2012). "The Inventors of TFT Active-Matrix LCD Receive the 2011 IEEE Nishizawa Medal". Journal of Display Technology. 8 (1): 3–4. doi:10.1109/JDT.2011.2177740. ISSN 1551-319X.
  11. Castellano, Joseph A. (2005). Liquid Gold: The Story of Liquid Crystal Displays and the Creation of an Industry. World Scientific. pp. 41–2. ISBN 9789812389565.
  12. Castellano, Joseph A. (2005). Liquid gold: the story of liquid crystal displays and the creation of an industry ([Online-Ausg.] ed.). New Jersey [u.a.]: World Scientific. pp. 176–7. ISBN 981-238-956-3.
  13. Kuo, Yue (1 January 2013). "Thin Film Transistor Technology—Past, Present, and Future" (PDF). The Electrochemical Society Interface. 22 (1): 55–61. doi:10.1149/2.F06131if. ISSN 1064-8208.
  14. Brody, T. Peter; Asars, J. A.; Dixon, G. D. (November 1973). "A 6 × 6 inch 20 lines-per-inch liquid-crystal display panel". IEEE Transactions on Electron Devices. 20 (11): 995–1001. doi:10.1109/T-ED.1973.17780. ISSN 0018-9383.
  15. Morozumi, Shinji; Oguchi, Kouichi (12 October 1982). "Current Status of LCD-TV Development in Japan". Molecular Crystals and Liquid Crystals. 94 (1–2): 43–59. doi:10.1080/00268948308084246. ISSN 0026-8941.
  16. Souk, Jun; Morozumi, Shinji; Luo, Fang-Chen; Bita, Ion (2018). Flat Panel Display Manufacturing. John Wiley & Sons. pp. 2–3. ISBN 9781119161356.
  17. "ET-10". Epson. Retrieved 29 July 2019.
  18. Nagayasu, T.; Oketani, T.; Hirobe, T.; Kato, H.; Mizushima, S.; Take, H.; Yano, K.; Hijikigawa, M.; Washizuka, I. (October 1988). "A 14-in.-diagonal full-color a-Si TFT LCD". Conference Record of the 1988 International Display Research Conference: 56–58. doi:10.1109/DISPL.1988.11274. S2CID 20817375.
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  20. Kramer, Bernhard (2003). Advances in Solid State Physics. Springer Science & Business Media. p. 40. ISBN 9783540401506.
  21. Borden, Howard C.; Pighini, Gerald P. (February 1969). "Solid-State Displays" (PDF). Hewlett-Packard Journal: 2–12.
  22. "Hewlett-Packard 5082-7000". The Vintage Technology Association. Retrieved 15 August 2019.
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  25. Wilkinson, Scott (19 November 2008). "Sony KDL-55XBR8 LCD TV". Sound & Vision. Retrieved 3 October 2019.
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