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'''Ferroelectric liquid crystal display''' (FLCD) is a display technology based on the [[ferroelectricity|ferroelectric]] properties of chiral smectic [[liquid crystal]]s as proposed in 1980 by Clark and Lagerwall.<ref>Noel A. Clark, Sven Torbjörn Lagerwall (1980). "Submicrosecond Bistable Electro-Optic Switching in Liquid Crystals". Applied Physics Letters 36 (11): 899. {{Bibcode|1980ApPhL..36..899C}}. {{doi|10.1063/1.91359}}</ref>
{{redirect|FLD|Fisher's linear discriminant|Linear discriminant analysis}}
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==Overview==
'''Ferro Liquid Display''' or Ferro-electric Liquid Display (FLD) or Ferro Fluid Display (FFD) is based on Ferro electric properties of
Reportedly discovered in 1975, several companies pursued the development of FLCD technologies, notably [[Canon Inc.|Canon]] and [[Central Research Laboratories]] (CRL), along with others including [[Seiko]], [[Sharp Corporation|Sharp]], [[Mitsubishi]] and [[General Electric Company|GEC]]. Canon and CRL pursued different technological approaches with regard to the switching of display cells, these providing the individual [[pixel|pixels]] or subpixels, and the production of intermediate pixel intensities between full transparency and full opacity, these differing approaches being adopted by other companies seeking to develop FLCD products.<ref name="pcw199310_crt">{{cite magazine |title=The CRT challenge |magazine=Personal Computer World |last1=Cole |first1=George |date=October 1993 |pages=362-365 }}</ref>
certain liquids. Not all such fluids are [[crystals|crystal]] but they are generically referred to as Ferro Liquid Crystal Display (FLCD) also.


==Description==
==Development==
By 1985, Seiko had already demonstrated a colour FLCD panel able to display a 10-inch diagonal still image with a resolution of {{nowrap|640 x 400}}. By 1993, Canon had delivered the first commercial application of the technology in its EZPS Japanese-language desktop publishing system in the form of a 15-inch monochrome display with a reported cost of around £2,000, and the company demonstrated a 21-inch 64-colour display and a 24-inch 16-greyscale display, both with a {{nowrap|1280 x 1024}} resolution and able to show "GUI software with multiple windows". Other applications included projectors, viewfinders and printers.<ref name="pcw199310_crt" />
[[Image:Ferrofluid Magnet under glass edit.jpg|thumb|Ferrofluid on glass, with a magnet underneath.]]


The FLCD did not make many inroads as a direct view display device. Manufacturing of larger FLCDs was problematic making them unable to compete against direct view LCDs based on nematic liquid crystals using the [[Twisted nematic field effect]] or [[IPS panel|In-Plane Switching]]. Today, the FLCD is used in reflective microdisplays based on [[Liquid Crystal on Silicon]] technology.{{cn|date=July 2024}} Using ferroelectric liquid crystal (FLC) in F[[LCoS]] technology allows a much smaller display area which eliminates the problems of manufacturing larger area FLC displays. Additionally, the [[dot pitch]] or pixel pitch of such displays can be as low as 6 μm giving a very high [[Display resolution|resolution]] display in a small area. To produce color and grey-scale, time multiplexing is used, exploiting the sub-millisecond switching time of the ferroelectric liquid crystal.
These fluids have bistable properties that can be switched with a magnetic field. The switching time is much shorter than that of a typical [[LCD]] that twist/untwist due to electric rather than magnetic interactions.<ref>[http://inst.eecs.berkeley.edu/~ee290d/sp99/ho17/ Berkeley (University of California) notes]</ref>
These microdisplays find applications in 3D [[head mounted display]]s (HMDs), image insertion in [[microsurgery|surgical microscopes]], and electronic [[viewfinder]]s where direct-view LCDs fail to provide more than 600 ppi resolution.


Ferroelectric LCoS also finds commercial uses in [[Structured illumination]] for 3D-[[Metrology]] and [[Super-resolution microscopy]]. Some commercial products use FLCD.<ref>[http://www.yunamoptics.com/main.htm?page=menu2_e&sub=yunam_m2_e FLCD : Ferro-Electric Liquid Crystal Display - Yunam Optics]</ref><ref>[http://www.forthdd.com Forth Dimension Displays]</ref> High switching speed allows building [[optical switch]]es and shutters in [[Computer printer|printer]] heads.<ref>[http://www.wtec.org/loyola/dsply_jp/c4_s6.htm WTEC Library]</ref>
Also see [[Ferro fluid|Ferrofluid]] for how some liquids behave in presence of a [[magnetic field]]. Practically the switching time is just the same as the time it takes for the electric signal to switch (the magnetic field). The ferro liquid reacts almost instantly when used in µg quantities (thin layer) as in a typical LCD's crystal layer.


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==References==
The [[dot pitch]] of such displays can be as low as 10 µm giving a very dense high [[Display resolution|resolution]] display on a small area. These might find applications in 3D displays and head mounted displays ([[HMD]]) where typical LCDs have failed to provide anything better than a 640x480 (RGB pixel) resolution on a sq.cm display area.
{{Reflist}}


==External links==
Displays based on these are still experimental or of less commercial value only due to the costs. Gradual adoption in consumer electronics is expected to bring the costs down.
*[https://lamomoneon.com/ LED Neon Signs]


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{{Display technology}}
A major drawback is that the angle of twist is not easily controlled by intensity of magnetic field. To produce color scales, time multiplexing might be used exploiting the quick switching time. The materials found so far are sensitive to vibration and shock.
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{{emerging technologies|displays=yes}}

== Working of Ferro Electric Crystals ==

[[Image:LCD subpixel (en).png|thumb|200px|A single pixel]]

Those based on crystals can retain polarisation permanently. FLCDs are [[smectic]] liquid crystals that have a natural layered order. Most FLCDs are
* of the smectic C phase (SmC<sup>*</sup>)
** i.e., they are tilted away from the layer normal (90°) and
* possess a [[Chirality (chemistry)|chiral]] behaviour
** i.e., they have a layered structure with the molecules at some angle (the "cone angle") away from the layer normal, and there is some inherent twist in the structure.

So, an unconstrained system, the azimuthal direction in which the molecules tilt away from the layer normal will differ slightly from one layer to the next.

Typically, the FLCDs are built with cell gaps less than 2 µm for stable molecular alignment. Alignment layer causes perpendicular stacked alignment. The cell's polarisation is determined by the magnetic field applied. That in turn results in opaque or transparent layer when used in combination with polarised layers as in [[LCD]].

== Properties and uses ==
* Very thin layer (less than 2 µm thick) can help produce a 90° polarisation twist.
** High density displays with small display areas can be produced.
** DisplayTECH claims that a stamp sized FLCD can drive resolutions needed for 50&nbsp;inch screens.<ref>[http://electronicdesign.com/Articles/Index.cfm?AD=1&ArticleID=1286 External article on Display Tech]</ref>
* Switching time is less than 100 µs
** High frame rate video displays are possible.
* Magnetic polarisation effect is [[bistable]].
** Can be used for low frame rate displays that can run on very low power
** This property can help build display with non-volatile memory with the advantage that the memory can be changed easily.
* Viewing angle is greater than 120°
** This makes it suitable for commercial TV applications.

Some commercial products do seem to utilize FLCD.<ref>[http://www.yunamoptics.com/main.htm?page=menu2_e&sub=yunam_m2_e Yunam Optics]</ref><ref>[http://www.displaytech.com/newsite/060501_pr_first_half.html DisplayTECH PR]</ref>

High switching allows building [[optical switch]]es and shutters in [[Computer printer|printer]] heads.<ref>[http://www.wtec.org/loyola/dsply_jp/c4_s6.htm WTEC Library]</ref>

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==References==
{{reflist|2}}

<br>
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{{Display Technology}}
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{{Emerging technologies}}


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[[Category:Liquid crystal displays]]
[[Category:Display technology]]
[[Category:Display technology]]
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[[Category:Liquid crystal displays]]
[[Category:Emerging technology]]

[[de:Ferroelektrische Flüssigkristallanzeige]]

Revision as of 05:22, 27 July 2024

Ferroelectric liquid crystal display (FLCD) is a display technology based on the ferroelectric properties of chiral smectic liquid crystals as proposed in 1980 by Clark and Lagerwall.[1]

Übersicht

Reportedly discovered in 1975, several companies pursued the development of FLCD technologies, notably Canon and Central Research Laboratories (CRL), along with others including Seiko, Sharp, Mitsubishi and GEC. Canon and CRL pursued different technological approaches with regard to the switching of display cells, these providing the individual pixels or subpixels, and the production of intermediate pixel intensities between full transparency and full opacity, these differing approaches being adopted by other companies seeking to develop FLCD products.[2]

Development

By 1985, Seiko had already demonstrated a colour FLCD panel able to display a 10-inch diagonal still image with a resolution of 640 x 400. By 1993, Canon had delivered the first commercial application of the technology in its EZPS Japanese-language desktop publishing system in the form of a 15-inch monochrome display with a reported cost of around £2,000, and the company demonstrated a 21-inch 64-colour display and a 24-inch 16-greyscale display, both with a 1280 x 1024 resolution and able to show "GUI software with multiple windows". Other applications included projectors, viewfinders and printers.[2]

The FLCD did not make many inroads as a direct view display device. Manufacturing of larger FLCDs was problematic making them unable to compete against direct view LCDs based on nematic liquid crystals using the Twisted nematic field effect or In-Plane Switching. Today, the FLCD is used in reflective microdisplays based on Liquid Crystal on Silicon technology.[citation needed] Using ferroelectric liquid crystal (FLC) in FLCoS technology allows a much smaller display area which eliminates the problems of manufacturing larger area FLC displays. Additionally, the dot pitch or pixel pitch of such displays can be as low as 6 μm giving a very high resolution display in a small area. To produce color and grey-scale, time multiplexing is used, exploiting the sub-millisecond switching time of the ferroelectric liquid crystal. These microdisplays find applications in 3D head mounted displays (HMDs), image insertion in surgical microscopes, and electronic viewfinders where direct-view LCDs fail to provide more than 600 ppi resolution.

Ferroelectric LCoS also finds commercial uses in Structured illumination for 3D-Metrology and Super-resolution microscopy. Some commercial products use FLCD.[3][4] High switching speed allows building optical switches and shutters in printer heads.[5]

References

  1. ^ Noel A. Clark, Sven Torbjörn Lagerwall (1980). "Submicrosecond Bistable Electro-Optic Switching in Liquid Crystals". Applied Physics Letters 36 (11): 899. Bibcode:1980ApPhL..36..899C. doi:10.1063/1.91359
  2. ^ a b Cole, George (October 1993). "The CRT challenge". Personal Computer World. pp. 362–365.
  3. ^ FLCD : Ferro-Electric Liquid Crystal Display - Yunam Optics
  4. ^ Forth Dimension Displays
  5. ^ WTEC Library
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