Talk:Twisted nematic field effect

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It is amazing that the details of an electro-optical effect that has dramatically changed the way of living in the digital age and which has created an industry producing goods worth many ten billions of US$/year is rated low on the importance scale ...

panjasan (talk) 12:37, 8 January 2009 (UTC)panjasan


Even though (or just because) this seems to be a somewhat controversial subject, it would be helpful to know the identity of the person that is applying changes here and only appears as IP address.

Thanks in advance ...

panjasan 20:25, 31 January 2007 (UTC)panjasan

The unknown editor writes: "If I rermember correctly the twisted Nematic effect was discovered by Jim Fergason, who later sold the pateint to hoffman laroche after they attempted to steal his work, Jim Feragson was given a 1 million dollar cash settlement, and royalities for the discovery. Please Read spring 2002 issue of american heritage of inventions and technology volume 17 number 4, page 20 for further details."

panjasan replies: "If Martin Schadt remembers correctly, there was no such thing as "attempt to steal the work ..." involved. Please kindly identify yourself so we know who we are "talking" to and if you can possibly know the facts and details of this subject matter.

One more aspect: Fergasons patent (US 3 731 986) was filed on April 22, 1971 while the corresponding patent of Hoffmann-LaRoche (CH 532 261) was filed on December 4, 1970. Why should somebody try to steal something that was filed for patent almost 5 months earlier ? "

panjasan 21:11, 31 January 2007 (UTC) panjasan

The changes of the unidentified editor also have introduced some liguistic inconsistencies that negatively affect the article. A revision would be beneficial.

panjasan 14:24, 2 February 2007 (UTC)panjasan

Since the "disclosed editor" did not return to clean up his mess, I applied some modifications for better readability and added the filing date of the US patent US 3 731 986.

panjasan 21:21, 16 February 2007 (UTC) panjasan

Sources & references added to improve verifiablity panjasan 14:50, 8 June 2007 (UTC)panjasan

First to file is not the same as first to invent. The record indicates that Fergason did not lose his patent in the litigation with Hoffmann-LaRoche, which suggests (I haven't seen the decision) that Fergason was able to show an earlier conception and/or reduction to practice than the Hoffmann-LaRoche inventors. Also, the Fergason patent is based on a continuation-in-part of an earlier application filed in February of 1971, indicating the time between filing was only two months rather than five. (talk) 15:47, 23 May 2008 (UTC)

Citing a personal communication from an inventor who was himself involved in the dispute over who was first to invent is factually highly suspect and obviously biased. US interference proceedings in the '70s were strongly weighted procedurally in favor of the senior party (first to file). The adage among US patent attorneys was that it was better to be senior party than first to invent. In view of that, the survival of the Fergason patent is strongly suggestive that the Hoffmann-LaRoche inventors were NOT the first to invent. Someone with time on their hands should be able to research the case and get the facts as determined by the court. (talk) 15:55, 23 May 2008 (UTC)

The American Scientist article, now referenced within, was written by a 3rd party who is an expert in the field. He gives clear precedence to Hoffmann-LaRoche. It traces the history back to RCA, where the first (non-TN) LCD displays were produced.
Futhermore the patent article, also now properly referenced, gives a more in-depth examination of the issue and also clearly states that Hoffmann-LaRoche is the real inventor. It goes on to state that Fergason was introduced to the TN concept through BBC, who was working with Hoffmann-LaRoche.
Both articles state that Hoffmann-LaRoche filed first. In terms of the argument above, that's pretty much that.
The patent article also states that the US patent claims against Hoffmann-LaRoche were not based on first-to-file at all. Instead, they were based on the patent having prior art, pointing to a review article by Fergason that talked about RCA's work. Note also that the settlement was out of court, so the conclusions above cannot possibly be made.
Maury Markowitz (talk) 21:46, 12 January 2009 (UTC)

Update 2011[edit]

I plan to do the following changes :

1) It is not anymore true that TN-LCDs are largely universal in portable electronics. In the introduction I want to add: Today, a number of alternatives exist such as IPS-, AFFS- and VA-LCDs as well as OLEDs. More details will be given in the section Commercial development: Organic Light-Emitting Diode Displays (OLED and AMLED) are becoming a serious contender, replacing LCDs in some smartphones, digital cameras and laptops computers. There is more demand than OLED manufacturers Samsung, LG and Chi Mei can produce in 2011. In addition, TN-LCDs have disadvantages in touchscreen portable devices compared with other LCD technologies that are less sensitive to pressure.

2) In section Patent battle the statement This is believed to be the first fully functional twisted nematic LCD ever made is not correct. A GRUEN wristwatch was equipped with a TN-LCD and introduced in 1971. Also, an experimental TN-LCD was shown in operation at the IEE Conference on Displays, Loughborough, UK, in Sept. 1971.

Grapplang (talk) 19:55, 8 September 2011 (UTC)

1 − V[edit]

The article states, "A voltage of about 1- V is required to make the crystal align itself with the field". What is V? Or did I miss something? And why does no current flow? Is the material between the electrodes a nonconductor? I'm good at math, but know little about electronics. (The bad formatting of the formulas is deplorable -- the symbols should, at the least, be italic. I could fix it, but I have other resolutions for 2012.) Eall Ân Ûle (talk) 23:37, 29 January 2012 (UTC)

Assessment comment[edit]

The comment(s) below were originally left at Talk:Twisted nematic field effect/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Last edited at 21:04, 31 January 2007 (UTC). Substituted at 09:23, 30 April 2016 (UTC)

Alternating current device[edit]

The article speaks of 1V to drive LCDs which suggests a DC voltage, but one vendor I've found says driving with a DC voltage will cause electrochemical degradation within their displays so you're supposed to drive them at about 30--90Hz:

As is the case with conventional LCDs, in order to prevent irreversible electrochemical action from destroying the display, the voltage at all segment locations must be caused to reverse polarity periodically so that zero net DC voltage is applied ... [T]he drive frequency should be chosen to be above the flicker-fusion rate, i.e. >30 Hz. Since increasing the drive frequency significantly above this value increases current demand by the CMOS drive electronics, and to prevent problems due to the finite conductivity of the display segment and common electrodes, an upper drive frequency limit of 60-90 Hz is recommended.[1]

I am not expert enough to know if this is true for all TN LCDs or not. Can someone confirm? DLeonard (talk) 12:35, 11 May 2016 (UTC)

Can confirm the quoted reference. TN-LCDs (as well as IPS-LCDs) have to be addressed with AC voltages as described.--BBCLCD (talk) 20:32, 12 May 2016 (UTC)