Research paper on LCD displays

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Markachy

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Hi guys,

I have a short (2000) word essayto do for my physics masters, on LCD display devices in laptops/mobiles, and on reflective LCD displays (calculators etc).

I am sure there are a few experts in it here, so if you know of any good websites on these topics (fairly advanced) I would be very grateful.

To check I am on the right track, are these statements correct?:

1. All are currently active matrix displays.
2. All are thin film transistor displays - mainly 3 types - Twisted nematic (TN), Inplane swiching (IPS) and Patterned vertical alignment (PVA, basically improved MVA) (and variations thereof).
3. In laptops and mobiles its pretty much exclusively TN due to cheapenss, energy savings compared to other types and the lack of need for wide viewing angles.
4. TNs are most responsive and use less energy and are cheapest, but have narrow viewing angles, worse colours and contrast ratios
5. IPS requires more energy and are slower to switch (slower response times), but have better colours and viewing angles, but low contrast ratios.
6. PVA similar to IPS but with worse colour reproduction, and have the black crush problem where true colour is seen when you are NOT looking directly at the screen. Have better contrast ratios over IPS.

That all ok?

Bear in mind I have to cover the "current LCD display technologies used in laptops and mobiles" AND "reflective liquid crystal displays" in 2000 words, so I don't think I should go through every single variation of MVA, PVA and IPS, just the ones currently used.

You reckon it is fair to say in laptops it is only TN currently used?

Thanks guys, my masters degree will appreciate it!
 
speaking from a monitors point of view (and same should apply in other sectors), answers below:

1. All are currently active matrix displays - yes

2. All are thin film transistor displays - mainly 3 types - Twisted nematic (TN), Inplane swiching (IPS) and Patterned vertical alignment (PVA, basically improved MVA) (and variations thereof). - in monitors those are certainly 3 of the most common. PVA isn't necessarily an "improved MVA", rather a different type of VA matrix designed by Samsung. They produced it to rival MVA which was being produced by manufacturers such as AUO and CMO. They are both still used, dont discount MVA as a prevalent technology in the market still

3. In laptops and mobiles its pretty much exclusively TN due to cheapenss, energy savings compared to other types and the lack of need for wide viewing angles. - i exp[ect thats the case in mobiles, certainly mostly used in laptops. Size of the panel also comes into play as smaller screens are fine with TN Film since the viewing angles are not as important since it's not as big an area (if you see what i mean?)

4. TNs are most responsive and use less energy and are cheapest, but have narrow viewing angles, worse colours and contrast ratios - thats really the "old" view of TN Film. They are still the most responsive panels i the market, mostly because they have heavy RTC / overdrive applied to them and yes, they were traditionally the fastest panel type. VA and IPS panels are very good nowadays though with RTC. Colour accuracy and contrast ratios / black depth have acctually improved significantly. In fact many TN Film panels offer performance in these areas comparable to VA and IPS panels. TN Film actually offers black depths and contrast ratios surpassing IPS and many MVA panels now. Colour depth is still 6-bit +FRC compared with 8-bit on IPS/VA, but in practice you would rarely see a difference. Viewing angles are still inferoir on TN Film


5. IPS requires more energy and are slower to switch (slower response times), but have better colours and viewing angles, but low contrast ratios. - yes, although black depths are improving a lot with modern H-IPS panels such as in models like the NEC EA231WMi and HP LP2475W. Response times also very good now with RTC being used. See the NEC 20WGX2 for instance! Viewing angles are the widest and they are free from the off-centre contrast shift you see from VA matrices

6. PVA similar to IPS but with worse colour reproduction, and have the black crush problem where true colour is seen when you are NOT looking directly at the screen. Have better contrast ratios over IPS. - i wouldnt say worse colour reproduction, they are very good in this regard. the reason IPS is generally preferred for colour critical work is down to the viewing angles and VA black crush as you put it. that is still a problem with the technology. contrast ratios are excellent on PVA (1200:1 or more cna be reached in static values!)...
 
Forget all the bullshit truisms. There is no point throwing out "TN is faster than IPS" if you can't justify why. I suggest you account for the easy 3: TN, VA and IPS LC switching modes by explaining with an LC cell diagram their structure and how they respond to electric fields. Using these demonstrations you can then justify their image traits.

3. In laptops and mobiles its pretty much exclusively TN due to cheapenss, energy savings compared to other types and the lack of need for wide viewing angles.
Click to expand...
See, as an example, this is partly contradicted by the existence of AFFS type notebook displays.

Here are some public materials you might be able to use:

http://newton.ex.ac.uk/research/emag/pubs/pdf/Jewell_PRE_2008.pdf

http://lcd.creol.ucf.edu/publications/publication2009.htm
 
Thanks guys. That should help a lot.

What I am thinking is maybe concentrate on the TN screen, with diags of the director and field-switching etc along with the mathematics of the dipole moment and electric field, and then extend it to the 3 types of LCD lighting ie transmissive (backlit), reflective (lit from ambient light - gameboy style) to cover the reflective displays bit, and the most recent, transflective, which is a combo of the two and becoming commonplace in mobile phones.

I am just conscious of the word limit, and as PVA and IPS are not used in laptops or mobiles (with maybe one or 2 exceptions) effectively ignore them. Or, if I am ok for words, put in the basics.

What you think?
 
And the *real* reason for why IPS requires more energy is because it blocks more of the backlight - thus a stronger backlight is needed and this is also a large part of why IPS panels are so expensive.
This is also where e-IPS have made improvements and therefor is both cheaper and requires less energy due to the panel being more transparent.

I don't know how good e-IPS is compared to TN (in terms of energy and cost) but perhaps (especially when coupled with a LED backlight) it could prove to be usable in high-end notebooks.

But again, TN is dominant and should be for quite some time so I'd probably focus on that too.
 
Cheers guys.

Its so hard to find papers on the basics of TN panels! Am I right in saying that modern displays use normal TN technology and not super TN or anything like that? There seems to be tonnes of variants around, far too many to cover in a 2000 word essay.

Or does anyone know of journals dedicated to liquid crystal displays? I have found Journal of Display Technology and Society for Information Displays, and have got access through my uni.
Most seems to be dedicated to properties of individual liquid crystal types rather than on their use in displays.
 
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