Editing TFT LCD (section)

==Types==

===Twisted nematic (TN){{anchor|TN}}===
<!-- This section is quite biased, it requires someone to make a note of some more positive aspects of the technology -->
[[File:Dell axim LCD under microscope.jpg|thumb|TN display under a microscope, with the transistors visible at the bottom]]

The [[twisted nematic]] (TN) display is one of the oldest and frequently cheapest kind of liquid crystal display technologies. TN displays have fast pixel response times and less smearing than other types of LCDs like [[IPS display]]s, but suffer from poor color reproduction and limited viewing angles, especially in the vertical direction. When viewed at an angle that is not perpendicular to the display, colors will shift, sometimes to the point of completely inverting. Modern, high end consumer products have developed methods to overcome the technology's shortcomings, such as [[Response Time Compensation|RTC (Response Time Compensation / Overdrive) technologies]]. Modern TN displays can look significantly better than older TN displays from decades earlier, but overall TN has inferior viewing angles and poor color in comparison to other technology like IPS.

Most TN panels can represent colors using only six [[bit]]s per RGB channel, or 18 bit in total, and are unable to display the 16.7 million color shades (24-bit [[24-bit color|truecolor]]) that are available using 24-bit color. Instead, these panels display interpolated 24-bit color using a [[dither]]ing method that combines adjacent pixels to simulate the desired shade. They can also use a form of temporal dithering called [[Frame Rate Control]] (FRC), which cycles between different shades with each [[refresh rate|new frame]] to simulate an intermediate shade. Such 18 bit panels with dithering are sometimes advertised as having "16.2 million colors". These color simulation methods are noticeable to many people and highly bothersome to some.<ref>{{cite web|url=http://www.xbitlabs.com/articles/monitors/display/lcd-guide_11.html|title=X-bit's Guide: Contemporary LCD Monitor Parameters and Characteristics (page 11)|author=Oleg Artamonov|publisher=Xbitlabs.com|date=2004-10-26|access-date=2009-08-05|url-status=dead|archive-url=https://web.archive.org/web/20090519104937/http://www.xbitlabs.com/articles/monitors/display/lcd-guide_11.html|archive-date=2009-05-19}}</ref> FRC tends to be most noticeable in darker tones, while dithering appears to make the individual pixels of the LCD visible. Overall, color reproduction and linearity on TN panels is poor. Shortcomings in display color [[gamut]] (often referred to as a percentage of the [[RGB color space|NTSC 1953 color gamut]]) are also due to backlighting technology. It is common for older displays to range from 10% to 26% of the NTSC color gamut, whereas other kind of displays, utilizing more complicated CCFL or LED [[phosphor]] formulations or RGB LED backlights, may extend past 100% of the NTSC color gamut, a difference that is easily seen by the human eye.

The [[transmittance]] of a pixel of an LCD panel typically does not change linearly with the applied voltage,<ref name="matuszczyk">Marek Matuszczyk, [http://www.mc2.chalmers.se/pl/lc/engelska/applications/Displays.html Liquid crystals in displays] {{Webarchive|url=https://web.archive.org/web/20041223045600/http://www.mc2.chalmers.se/pl/lc/engelska/applications/Displays.html |date=2004-12-23 }}. Chalmers University Sweden, c. 2000.</ref> and the [[sRGB]] standard for computer monitors requires a specific nonlinear dependence of the amount of emitted light as a function of the [[RGB]] value.

===In-plane switching (IPS){{Anchor|IPS}}===
{{Main|IPS panel}}
[[IPS panel|In-plane switching]] (IPS) was developed by [[Hitachi]] in 1996 to improve on the poor viewing angle and the poor color reproduction of TN panels at that time.<ref name="tftcentral">{{cite web|title=TN Film, MVA, PVA and IPS - Panel Technologies|publisher=TFT Central|url=http://www.tftcentral.co.uk/articles/panel_technologies.htm|access-date=9 September 2009}}</ref><ref name="esportsource">{{cite web|title=IPS or TN panel?|publisher=eSport Source|url=https://www.esportsource.net/monitors/ips-tn-panel/|access-date=23 May 2016}}</ref> Its name comes from the main difference from TN panels, that the crystal molecules move parallel to the panel plane instead of perpendicular to it. This change reduces the amount of light scattering in the matrix, which gives IPS its characteristic wide viewing angles and good color reproduction.<ref name="philips">{{cite web|title=Enhanced Super IPS - Next Generation Image Quality|publisher=LG Display|url=http://www.tftcentral.co.uk/downloads/enhanced_s-ips.pdf|access-date=9 September 2009}}</ref>

Initial iterations of IPS technology were characterised by slow response time and a low contrast ratio but later revisions have made marked improvements to these shortcomings. Because of its wide viewing angle and accurate color reproduction (with almost no off-angle color shift), IPS is widely employed in high-end monitors aimed at professional graphic artists, although with the recent fall in price it has been seen in the mainstream market as well. IPS technology was sold to [[Panasonic]] by Hitachi.

{| class="wikitable" style="font-size: 90%; text-align:left;"
|+ Hitachi IPS technology development<ref>[http://www.ips-alpha.co.jp/en/technology/ips.html IPS-Pro (Evolving IPS technology)] {{webarchive|url=https://web.archive.org/web/20100329145251/http://www.ips-alpha.co.jp/en/technology/ips.html |date=2010-03-29 }}</ref><ref>{{cite web |url=http://www.barco.be/barcoview/downloads/IPS-Pro_LCD_technology.pdf |title=Archived copy |access-date=2013-11-24 |url-status=dead |archive-url=https://web.archive.org/web/20121115091442/http://www.barco.be/barcoview/downloads/IPS-Pro_LCD_technology.pdf |archive-date=2012-11-15 }}</ref>
|-
! style="width:12%;"|Name
!Nickname
!Year
! style="width:12%;"|Advantage
!Transmittance/<br />contrast ratio
!Remarks
|-
| Super TFT || IPS || 1996 || Wide viewing angle || 100/100<br />Base level || Most panels also support true [[24-bit color|8-bit per channel color]]. These improvements came at the cost of a higher response time, initially about 50&nbsp;ms. IPS panels were also extremely expensive.
|-
| Super-IPS || S-IPS || 1998 || Color shift free || 100/137 || IPS has since been superseded by '''S-IPS''' (Super-IPS, [[Hitachi]] in 1998), which has all the benefits of IPS technology with the addition of improved pixel refresh timing.{{quantify|date=September 2014}}
|-
| Advanced Super-IPS || AS-IPS || 2002 || High transmittance || 130/250 || AS-IPS, also developed by [[Hitachi]] in 2002, improves substantially{{quantify|date=September 2014}} on the contrast ratio of traditional S-IPS panels to the point where they are second only to some S-PVAs.{{citation needed|date=September 2014}}
|-
| IPS-Provectus || IPS-Pro || 2004 || High contrast ratio || 137/313 || The latest panel from IPS Alpha Technology with a wider color gamut{{quantify|date=September 2014}} and contrast ratio{{quantify|date=September 2014}} matching PVA and ASV displays without off-angle glowing.{{citation needed|date=September 2014}}
|-
| IPS alpha || IPS-Pro || 2008 || High contrast ratio ||  || Next generation of IPS-Pro
|-
| IPS alpha next gen || IPS-Pro || 2010 || High contrast ratio ||  || 
|}

{|class="wikitable" style="font-size: 90%; text-align:left;"
|+ LG IPS technology development
|-
! style="width:15%;"|Name
!Nickname
!Year
!Remarks
|-
|Horizontal IPS||H-IPS||2007||Improves{{quantify|date=January 2012}} contrast ratio by twisting electrode plane layout.  Also introduces an optional Advanced True White polarizing film from NEC, to make white look more natural{{quantify|date=January 2012}}. This is used in professional/photography LCDs.{{Citation needed|date=January 2012}}
|-
|Enhanced IPS||E-IPS||2009||Wider{{quantify|date=January 2012}} aperture for light transmission, enabling the use of lower-power, cheaper backlights.  Improves{{quantify|date=January 2012}} diagonal viewing angle and further reduce response time to 5ms.{{Citation needed|date=January 2012}}
|-
|Professional IPS||P-IPS||2010||Offer 1.07 billion colors (10-bit color depth).{{Citation needed|date=January 2012}} More possible orientations per sub-pixel (1024 as opposed to 256) and produces a better{{quantify|date=January 2012}} true color depth.
|-
|Advanced High Performance IPS||AH-IPS||2011||Improved color accuracy, increased resolution and PPI, and greater light transmission for lower power consumption.<ref>{{cite web |author=tech2 News Staff |url=http://tech2.in.com/news/tablets/lg-announces-super-high-resolution-ahips-displays/219942 |title=LG Announces Super High Resolution AH-IPS Displays |publisher=Tech2.in.com |access-date=2013-07-21 |url-status=dead |archive-url=https://web.archive.org/web/20130606135240/http://tech2.in.com/news/tablets/lg-announces-super-high-resolution-ahips-displays/219942 |archive-date=2013-06-06 }}</ref>
|}

===Advanced fringe field switching (AFFS){{anchor|AFFS}}===
This is an LCD technology derived from the IPS by Boe-Hydis of Korea. Known as fringe field switching (FFS) until 2003,<ref>{{cite web
 | url = http://vertexlcd.com/technology.htm#point04
 | title = AFFS & AFFS+
 | publisher = Vertex LCD
 | work = Technology
 | access-date = 2010-08-12
 | archive-date = 2016-05-18
 | archive-url = http://arquivo.pt/wayback/20160518020420/http://vertexlcd.com/technology.htm#point04
 | url-status = dead
 }}</ref> advanced fringe field switching is a technology similar to IPS or S-IPS offering superior performance and color gamut with high luminosity. Color shift and deviation caused by light leakage is corrected by optimizing the white gamut, which also enhances white/grey reproduction. AFFS is developed by Hydis Technologies Co., Ltd, Korea (formally Hyundai Electronics, LCD Task Force).<ref>{{cite journal
 | title = A Novel Outdoor Readability of Portable TFT-LCD with AFFS Technology
 | journal = SID Symposium Digest of Technical Papers
 | date = June 2006
 | volume = 37
 | issue = 1
 | publisher = AIP
 | pages = 1079–82
 |author1=K. H. Lee |author2=H. Y. Kim |author3=K. H. Park |author4=S. J. Jang |author5=I. C. Park |author6=J. Y. Lee  |name-list-style=amp | doi = 10.1889/1.2433159| s2cid = 129569963
 }}</ref>

In 2004, Hydis Technologies Co., Ltd licensed its AFFS patent to Japan's Hitachi Displays. Hitachi is using AFFS to manufacture high end panels in their product line. In 2006, Hydis also licensed its AFFS to Sanyo Epson Imaging Devices Corporation.

Hydis introduced AFFS+ which improved outdoor readability in 2007.{{Citation needed|date=January 2012}}

===Multi-domain vertical alignment (MVA){{anchor|MVA}}===
It achieved pixel response which was fast for its time, wide viewing angles, and high contrast at the cost of brightness and color reproduction.{{Citation needed|date=January 2012}} Modern MVA panels can offer wide viewing angles (second only to S-IPS technology), good black depth, good color reproduction and depth, and fast response times due to the use of RTC ([[Response Time Compensation]]) technologies.{{Citation needed|date=January 2012}}  When MVA panels are viewed off-perpendicular, colors will shift, but much less than for TN panels.{{Citation needed|date=January 2012}}

There are several "next-generation" technologies based on MVA, including AU Optronics' '''P-MVA''' and '''AMVA''', as well as Chi Mei Optoelectronics' '''S-MVA'''.

===Patterned vertical alignment (PVA){{anchor|PVA}}===
<!-- This section is linked from [[PVA]] -->
Less expensive PVA panels often use dithering and [[Frame Rate Control|FRC]], whereas super-PVA (S-PVA) panels all use at least 8 bits per color component and do not use color simulation methods.{{Citation needed|date=January 2012}}S-PVA also largely eliminated off-angle glowing of solid blacks and reduced the off-angle gamma shift. Some high-end Sony [[BRAVIA]] LCD TVs offer 10-bit and xvYCC color support, for example, the Bravia X4500 series.  S-PVA also offers fast response times using modern RTC technologies.{{Citation needed|date=January 2012}}

===Advanced super view (ASV){{anchor|ASV}}===
Advanced super view, also called ''axially symmetric vertical alignment'' was developed by [[Sharp Corporation|Sharp]].<ref>{{cite web|url=https://www.sharpsma.com/advanced-super-view-asv-|title=Sharp Advanced Super View (ASV) - Sharp|website=www.sharpsma.com|access-date=2019-06-12}}</ref>  It is a VA mode where liquid crystal molecules orient perpendicular to the substrates in the off state. The bottom sub-pixel has continuously covered electrodes, while the upper one has a smaller area electrode in the center of the subpixel.

When the field is on, the liquid crystal molecules start to tilt towards the center of the sub-pixels because of the electric field; as a result, a continuous pinwheel alignment (CPA) is formed; the azimuthal angle rotates 360 degrees continuously resulting in an excellent viewing angle. The ASV mode is also called CPA mode.<ref>[http://www.personal.kent.edu/%7Emgu/LCD/asv.htm The World of Liquid Crystal Displays] from personal.kent.edu/%7Emgu</ref>

===Plane line switching (PLS){{anchor|PLS}}===
{{seealso|IPS panel#PLS}}
A technology developed by [[Samsung]] is Super PLS, which bears similarities to IPS panels, has wider viewing angles, better image quality, increased brightness, and lower production costs. PLS technology debuted in the PC display market with the release of the Samsung S27A850 and S24A850 monitors in September 2011.<ref>{{cite web|url=http://www.xbitlabs.com/articles/monitors/display/samsung-sa850.html |title=Samsung SyncMaster SA850: World's First Monitor on PLS Matrix |publisher=X-bit labs |date=2011-05-30 |access-date=2013-07-21}}</ref>

===TFT dual-transistor pixel (DTP) or cell technology{{anchor|PLS}}===
[[File:Patent TFT SES.pdf|thumb|Patent TFT Store Electronic Systems]]
TFT dual-transistor pixel or cell technology is a reflective-display technology for use in very-low-power-consumption applications such as electronic shelf labels (ESL), digital watches, or metering. DTP involves adding a secondary transistor gate in the single TFT cell to maintain the display of a pixel during a period of 1s without loss of image or without degrading the TFT transistors over time. By slowing the refresh rate of the standard frequency from 60&nbsp;Hz to 1&nbsp;Hz, DTP claims to increase the power efficiency by multiple orders of magnitude.