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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>
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==Overview==
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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>
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==Development==
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'''Ferroelectric Liquid Crystal Display''' (FLCD) is a display technology based on the [[ferroelectricity|ferroelectric]] properties of chrial smectic [[liquid crystal]]s. It has been 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>
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" />


As direct-view displays, the FLCD could not displace the LCDs based on nematic liquid crystals using the [[Twisted nematic field effect]] or [[IPS panel|In-Plane Switching]]. Today, the FLCD is not used as direct-view display but in microdisplays based on [[Liquid Crystal on Silicon]] devices. Used in [[LCoS]] the [[dot pitch]] of such displays can be as low as 8 µm giving a very high [[Display resolution|resolution]] display on a small area. To produce color and grey-scale, time multiplexing is used, exploiting the sub-millisecond switching time.
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 find applications in 3D head mounted displays ([[Head-mounted display|HMD]]), image insertion in [[microsurgery|surgical microscopes]] and electronic view finders where direct-view LCDs fail to provide more than 600 ppi resolution.
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 find commercial use also in [[Structured illumination]] in 3D-[[Metrology]] and [[Super-resolution microscopy]].
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>


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==References==
== Working of Ferroelectric Liquid Crystals ==
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{{Reflist}}


==External links==
Ferroelectric liquid crystals are [[chiral]] [[smectic]] [[liquid crystals]] that have a layered order. Within the layer the liquid crystal molecules (called mesogenes) are tilted away from the layer normal (90°), forming a so-called smectic C liquid crystal. [[Chirality (chemistry)|Chiral]] behavior is introduced by inserting asymmetric carbon atom into the mesogenic molecule, termed now smectic C* (the asterix denotes the chirality). The chirality causes a smectic layer to exhibit a permanent spontaneous polarization at right angle to the tilt plane, giving rise to the term ferroelectric. In an unconstrained system a helical twist in the structure lowers the energy of the structure, i.e. the tilt direction changes from layer to layer by some degree. In other words, the azimuthal direction in which the molecules tilt away from the layer normal will differ slightly from one layer to the next. Therefore the overall polarization of an unconstrained smectic C* phase will be zero.
*[https://lamomoneon.com/ LED Neon Signs]


Typically, the FLCDs are built with cell gaps less than 2 µm for stable molecular alignment. In this constraint system the interaction between the alignment layers and the smectic C* liquid crystal suppress the helical superstructure. Proper [[ferroelectricity]] now forms in domains. The spontaneous polarization of the smectic C* layer interacts with the electric field applied to the electrodes. Depending on the direction of the electric field the mesogenes are titled either to left or the right side of the layer normal. This in turn results in opaque or transparent state when used in combination with crossed polarizers as in [[LCD]].

== Properties and uses ==
* Very thin layer (less than 2 µm thick) produce a 90° polarisation twist.
* High density [[LCoS]] displays with small display areas can be produced.
* Switching time is less than 50 µs
* High frame rate video displays are possible.
* Polarization effect is [[Bistability|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.
* In-plane Switching provides reduced viewing angle dependence of contrast and color.

Some commercial products utilize FLCD.<ref>[http://www.yunamoptics.com/main.htm?page=menu2_e&sub=yunam_m2_e Yunam Optics]</ref><ref>[http://www.forthdd.com Forth Dimension Displays]</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==
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{{Reflist|30em}}

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{{Display technology}}
{{Display technology}}
{{Emerging technologies}}
{{emerging technologies|displays=yes}}


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

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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