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does anyone know what is exact name(s) of liquid crystal material used in modern LCD's and how big should be electric field to make it change polarization?

Update for the second bounty: My idea is that I want to make LCD at home. I can get everything except these twisted nematic crystals, and I haven't found any papers or information on how they should be used (like required electric field, preventing electrolysis, required thinkness), or under which names I can buy them.

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  • \$\begingroup\$ lots of materials, but it's built on glass of semiconductor material. \$\endgroup\$ – kenny Aug 10 '11 at 14:20
  • \$\begingroup\$ It's not really a crystal structure but borrows its name from the anisotropic properties (different depending on the angle you look at it), which are typical for crystals. Glass for instance is amorphous, which implies isotropy, and indeed the optical properties of glass are the same for all directions. \$\endgroup\$ – stevenvh Aug 10 '11 at 16:17
  • \$\begingroup\$ Regarding anisotropy in crystals: evilmadscientist.com/article.php/pennmuseum \$\endgroup\$ – jpc Aug 22 '11 at 21:31
  • \$\begingroup\$ Here's a good link originally submitted by parulpatel with background and assembly information, and quite a few sources in books and periodicals: madehow.com/Volume-1/Liquid-Crystal-Display-LCD.html \$\endgroup\$ – Kevin Vermeer Aug 22 '11 at 22:04
  • \$\begingroup\$ Will try and hunt down my 3rd year project notes. I built some bistable lcd's from scratch - pretty straightforward. If I find them I'll POP info up here, but this was 19 years ago... \$\endgroup\$ – Rory Alsop Aug 23 '11 at 11:32
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This site (in German) has info, and kits, for building your own LCDs: http://fluessigkristalle.com/

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The crystal substance is known as "Twisted Nematic" crystal. These operate by twisting between 0° and 90° thus polarizing the light as it passes through. A second polarizing filter either allows or blocks the polarized light, thus making the black areas you see on the LCD.

A Twisted Nematic crystal typically requires a potential of around 1V to twist fully through 90°.

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  • \$\begingroup\$ Yes, I am particularly interested in names of specific "Twisted Nematic" crystals used. LCD structure itself is pretty clear. \$\endgroup\$ – BarsMonster Aug 10 '11 at 14:58
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    \$\begingroup\$ I've always wondered, where can you buy Liquid Twisted Nematic crystals? \$\endgroup\$ – user3045 Aug 10 '11 at 15:58
  • \$\begingroup\$ @kurtnelle - yeah, this is also what I am interested in :-D \$\endgroup\$ – BarsMonster Aug 10 '11 at 16:00
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Some Web search fun turns up:

4'-Propoxy-[1,1'-Biphenyl]-4-carbonitrile (C16H15NO), which is a powder

Trans-1-(bromomethyl)-4-propylcyclohexane (C10H19Br), which is a liquid

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  • \$\begingroup\$ Here's an answer that the answerer doesn't understand himself and that doesn't help the asker... ;-) \$\endgroup\$ – Federico Russo Aug 10 '11 at 17:54
  • \$\begingroup\$ @Federico Well, this allows me to find a supplier to buy 25kg of this thing :-) \$\endgroup\$ – BarsMonster Aug 11 '11 at 9:22
  • \$\begingroup\$ @Linker3000 Could you suggest any references which tells that this is the one used in LCD's and any details about it? Also, not sure how powder might be used in LCD. \$\endgroup\$ – BarsMonster Aug 11 '11 at 9:23
  • \$\begingroup\$ @Federico Russo - with chemical names like that, it helps me understand I don't ever want to crack one open and find out what effects it might have on things =P \$\endgroup\$ – JustJeff Aug 14 '11 at 3:36
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Another common chemical to use in LCD screens is MBBA, or N-(4-Methoxybenzylidene)-p-n-butylaniline.

If you do experiment with this substance, please heed these warnings. From this MSDS, you can see that while the material is poisonus if you ingest/inhale it (or get it in an open wound or your eyes), it just causes some skin irritation if you get it on you. If you do happen to get the material inside of your body, then you should seek medical assistance (as it will begin to make methemoglobin in your blood). However, if you get just a bit on your finger (externally only), wash your hands with soap and water and you should be fine.

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