Presentation on theme: "Bring polarizing film Palffy – Muhorray, “The Diverse World of Liquid Crystals”, Physics Today, Sept. 2007 1 Some slides need re-organizing and tighter."— Presentation transcript:
Bring polarizing film Palffy – Muhorray, “The Diverse World of Liquid Crystals”, Physics Today, Sept Some slides need re-organizing and tighter message.
LC = a misnomer. These systems are not crystals…. and the study is not necessarily confined to liquids either. First related observations: Myelin 1700s –1850 2
Discovery due to Reinitzer & Lehman = Botanist & Physicist Irridescent beetle colors may Trace to “liquid” “crystal” behavior. (from a beetle wiki) See also Srinivasarao Science 2009 Discovery is usually associated with the behavior of cholesteryl benzoate, which by ~1888 was known to have two melting points. Note the rather extended shape! 3
1949 Onsager > 4/x (x = L/d) kind of a pure packing argument, logs in a river photo Maier Saupe extend to temperature; anisotropic polarizability below some crit temperature 1965 Kent State Glenn Brown 6
8 The "Great Raft," a huge mass of timber that formed a logjam, dammed up the Red River and flooded the surrounding area. Photo by R. B. Taylor, courtesy Louisiana State University, Shreveport, Noel Memorial Library Archives.
Biaxial nematic 10
LC’s as displays. Why do we need something besides the CRT? Vacuum! How heavy does a CRT have to be to be strong enough to maintain vacuum, since the e-beam has to travel from gun to phosphor screen? This is a fundamental limitation. By contrast, the limiting size of LCD’s = production yields of large, defect-free films. There is no fundamental limitation, merely a matter of engineering. 12 The problem is CRTs have a heart of glass!
Casio Hybrid Projector Actually, this isn’t an LCD display. Doesn’t use a lamp either…. $800 gets you a “hybrid” light source with DLP technology. Animated GIF of how it works. LG HS201 Slim Sort of 6” x 6” size Not an LCD No lamp $550 Even so, very huge LCD displays are not with us yet; we use projection. For now. 13
DIY LCD Projector Videos 1Vmo&feature=related Heart of Glass doesn’t cut it in the plastics world: Cracker box: OHP e=relatedhttp://www.youtube.com/watch?v=n6n6jW0XIV0&featur e=related DIY LCD Projector > views 14
The idea of using LCs for light display goes back to simple rubbing of glass experiments It is found that rubbing glass can align the LC molecules; crossed rubbing leads to no transmission of light through the objects word mesomorphic coined 1935 Freedericksz finds E field can align LCs 1936 patent (British) to Marconi for “light valves….for use in television, facsimile telegraph and other systems” Postwar: synthesis of mesogens By 1950s, a thriving subject 15
Twisted nematic LC (Saupe 1969, KSU) How to twist it? How to switch it? 16
From PC World ~2000 (I think) 17
The invention of the TFT made this practical in large arrays. The TFT was invented in 1973 by Westinghouse (120 x 120 pixels in 6” x 6” array = 0.05”/pixel). By this time, the USA had already ceded other video technology, such as video tape recording, to the Japanese. TFT/LCD panels met the same fate. 19
About 40% of Corning’s $4.6B revenues in 2006 came from LCD glass. So…how do you make a perfectly flat, bubble-free piece of glass? Plastics’ role: under 30” the sandwich can be made from plastic. From some website: The liquid crystal is placed between the two sheets in a patterned plastic sheet that divides the liquid into individual shutters and keeps the sheets at a precise distance from each other. There are opportunities for polymers in this game. 20
Plasma….its days probably also numbered. Probably better quality than LCD, though. Plasma 21
Research continues. This Fabry-Perot interferometer device requires poly(ethylene napthalate) which deflects to create a light gate at a particular color. 22 This color display is flexible! Harry Potter-Style Newspapers a Reality article /Harry-Potter-meets-Minority- Report-video-adverts-magazines-reality.html article /Harry-Potter-meets-Minority- Report-video-adverts-magazines-reality.html PEN, even better barrier properties than PET
The future is probably with these technologies: OLED FED SED The LCD is limited by energy cost—tosses away an awful lot of light; 40” display about 250 W, same as CRT. Organic LEDs will light up just where/when you need. FED/SED display = array of nanotubes that makes electrons for phosphors just where/when you need them. 23
Even others can be considered. Electronic paper Wiki Palfy-Muhorray review article m