School of Mathematics UNIVERSITY OF SOUTHAMPTON
Episodes From The History Of Liquid Crystals
Tim Sluckin University of Southampton
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School of Mathematics CONTENTS UNIVERSITY OF SOUTHAMPTON • Liquid crystal physics • Early German and French History • Optical devices and all that • Non-optical applications • Some brief comments about current work in the field • Commercial
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School of Mathematics UNIVERSITY OF SOUTHAMPTON This is the Isaac Newton Institute for Mathematical Sciences, so I thought I would show you some equations
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OK…
That’s all for equations today
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• This is a story of some accidental and some deliberate discoveries
• A large part of the early story is a German story
• I shall try to talk about some of the personalities, some of the physics and some of the social history
• As with all history, I have to select, and others would select differently!
• At the end is a commercial for the books I have written on this subject
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A brief summary of liquid crystal physics
Much more in the next 10 days
1. Liquid crystals are structurally intermediate between liquid and crystalline phases (except when they are not…) 2. They are not crystals! 3. Rich panoply of “mesomorphic phases” 4. Non-Newtonian hydrodynamics 5. Broken symmetry statistical mechanics phases 6. ∃ topological defects whose nature depends on the phase symmetry 7. Optically birefringent
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SOME FACTS ABOUT LIQUID CRYSTALS
• Liquid crystals are not crystals, but liquids with some remnant of crystalline order • Liquid crystals are usually made from rod-like molecules, but are sometimes made from disc-like molecules • Liquid crystal phases are optically anisotropic • Between crossed polarisers, liquid crystals produce brightly coloured patterns known as textures • Liquid crystal phase diagrams are complex, with often many phases between liquid and crystalline solid • Two flavours: thermotropic (change temperature) and lyotropic (change concentration in a water solution) • Inhomogeneous liquid crystal phases sustain topological defects where the order is not defined
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Molecular organisation (after Friedel 1922)
Nematic phase Smectic A (layered) phase
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School of Mathematics UNIVERSITY OF SOUTHAMPTON Chiral and tilted phases
• The cholesteric (or chiral nematic) phase is chiral. • The director configuration is helical • Repeat length is known as the pitch. The smectic C phase is tilted.
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TNI
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Friedrich Reinitzer (1857-1927)
About 1½ years ago, I reported the results of some studies of a cholesterol occurring in the root of the carrot. Husemann [1] named this compound hydrocarotene. …….
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School of Mathematics UNIVERSITY OF SOUTHAMPTON The first experiment - 1888
• Friedrich Reinitzer(1857-1927) Imperial Institute for Plant Physiology German University of Prague COO • Studies of cholesteryl benzoate Interested in cholesterol compounds from • Double melting – carrots. (i) crystal to cloudy fluid Cholesteryl benzoate the first liquid crystal (ii) cloudy fluid to clear liquid C27H45 . C7H5O2 (iii) colours close to clearing point (iv) Lehmann has observed Crystal melts to liquid crystal 145.5°C crystallites Liquid crystal clears to liquid 178.5 °C
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A liquid crystal sample
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School of Mathematics QUESTION No.1 UNIVERSITY OF SOUTHAMPTON
THE BOTTLE ON THE DESK CONTAINS:
A. A sample of bull’s semen from a farm in Granchester
B. Milk from the fridge upstairs containing coloured chocolate nanodroplets
C. A cholesteric liquid crystal with a formula to long to fit into the margin of this slide
D. White paint scooped up from my floor because I am a hopeless experimentalist
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School of Mathematics UNIVERSITY OF SOUTHAMPTON REINITZER’S PUZZLES
What is causing the peculiar double melting?
What is causing the peculiar colours?
Must be some pigment somewhere…
Thank you Dr Lehmann for some microscopy!
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School of Mathematics Letter from Reinitzer to Herr UNIVERSITY OF SOUTHAMPTON Otto Lehmann (Aachen)
Dr Knoll in Karlsruhe interpreted these letters
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School of Mathematics UNIVERSITY OF SOUTHAMPTON Otto Lehmann (1855-1922) Professor at Technische Hochschule, Karlsruhe, 1890-1922
• Fliessende Krystalle (1890) Schleimig flüssige kristalle • Krystalline Flüssigkeit (1890) • Flüssige Kristalle (1900) Tropfbar flüssige kristalle
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School of Mathematics UNIVERSITY OF SOUTHAMPTON Lehmann’s studies 1889 -
• Otto Lehmann (1855 – 1922) Institute of Physics University of Karlsruhe
• Developed the use of the polarising microscope with heating stage – applied it to Reinitzer’s cholesteryl benzoate
• Identified birefringence (a property of crystals) and flow (a property of liquids)
• Coined the phrase Flowing Crystals
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School of Mathematics UNIVERSITY OF SOUTHAMPTON The Lehmann microscope
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The title page of Lehmann’s 1904 book on liquid crystals
There is not time to do justice to Lehmann’s catholic interests
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Lehmann’s microscopic observations (from 1904 book)
artificial colour, photos in b/w
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School of Mathematics UNIVERSITY OF SOUTHAMPTON Ludwig gattermann (1860-1920)
Gattermann and Ritschke On azoxyphenyl ethers Berichte der Deutschen chemischen Gesellschaft 23, 1738-40 (1890) Gattermann was the first to synthesise a liquid crystal Para-azoxyanisole K-116ºC-cloudy -134 ºC-clear liquid PAA became the experimental liquid crystal of choice Gattermann later became a famous organic chemist, and authored the premier textbook of the day (“Gattermanns Kochbuch”) The Dye Company thought that the bright colours in the liquid crystal displays under the microscope could be used in dyes and colourings. So they funded Gattermann’s work…
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School of Mathematics UNIVERSITY OF SOUTHAMPTON Son of a Baker (!) Gattermann reaction (1890) Gattermann-Koch reaction (1897) Gattermann aldehyde synthesis (1898) Gattermann-Stika pyridine synthesis (1916) Pure explosive nitrogen trichloride
Liquid Crystal work sponsored by Bayer’s Dyeworks in Elderfeld
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Lehmann’s drops can merge……….. The patterns deform………..very quickly…………. No-one understood Lehmann’s patterns. They saw ‘lines of force’ and ‘Schliere’ Gattermann had a vivid imagination…
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After the drops amalgamate the molecules reorient according to the mutual lines of force. I call this process copulation. If the merging drops are very small then the copulation proceeds so quickly that it cannot be separated from the amalgamation
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School of Mathematics Textures UNIVERSITY OF SOUTHAMPTON The term “texture”, for the brilliant coloured patterns observed between crossed nicols, entered the field very early.
• Texture below was a liquide à fils or liquide à noyaux, Schlieren texture., also flüssige Kristalle • Textures on the right were batonnets, liquides à coniques, also fliessende Kristalle
Each texture was associated with a phase. Flow properties and patterns seemed to be related
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School of Mathematics Gustav Tammann UNIVERSITY OF SOUTHAMPTON (1861-1938) •Two articles in Annalen der Physik 1900-1 •“On the so-called liquid crystals” •Intense controversy with Lehmann •Liquid crystals are cloudy for the same reason that milk is. •Professor of Physical Chemistry at Göttingen •Founder of modern metallurgy
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School of Mathematics WHAT IS GOING UNIVERSITY OF SOUTHAMPTON ON (1890-1900)? • Two (or even three) melting points • Cloudy and birefringent phase • Structural and flow properties between solid and liquid Eureka! A liquid crystal!
• Maybe the system is impure? (Quincke, Tammann) • Maybe a suspension of crystals inside a liquid? (Quincke, Wulff ) • Maybe an emulsion of two liquids? (Tammann, Nernst) • No, a liquid crystal ! (Schenck,Lehmann) But what is a liquid crystal?
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School of Mathematics UNIVERSITY OF SOUTHAMPTON Tammann’s controversy with Lehmann continued for several years (1901-1906) with great bitterness.
Lehmann referred to Tammann as “my opponent”
Tammann did not believe that crystals could be liquid, because he believed in the lattice theory of solids, which at that time had not been experimentally proved.
He thought liquid crystals were mixtures, which could be separated
Lehmann was convinced that he had actually seen liquid crystals, and so Tammann’s preconceptions were clouding his judgement.
He was also angry that his experimental skill was being criticized.
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School of Mathematics The showdown UNIVERSITY OF SOUTHAMPTON
Karlsruhe June 3 1905
Rudolf Schenck (1870-1965), (then) Lecturer in Physical Chemistry, University of Marburg
German Physical Chemistry Society Meeting, Karlsruhe
‘Liquid Crystals’ cannot be colloidal mixtures.
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Das alte Schloß, Baden- Der Stadtgarten in Karlsruhe Baden. Spaziergang, Sonntag den 4. Juni, 1905
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School of Mathematics UNIVERSITY OF SOUTHAMPTON ‘Liquid Crystals’ cannot be colloidal mixtures!
•No miscibility gap at clearing. •Discontinuity in density/viscosity at clearing point •Surface tension obeys law of corresponding states •Mixtures cannot explain birefringence
I have worked with Herr Tammann’s materials. He says they are not pure. He is right - but they can be purified When purified the liquid crystal phenomenon remains!
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School of Mathematics Tammann’s reply UNIVERSITY OF SOUTHAMPTON
• …..Has birefringence in these cloudy liquids been conclusively established ?….
• I an happy to concede flowing crystals but not liquid crystals!
The discussion ran out of time and was closed by the chairman. As a result, a reply to Professor Tammann’s points was impossible. …. … Herr Professor van’t Hoff proposed the formation of a committee of experts who could examine the liquid crystal question further. The committee would include, inter alia, Professors Lehmann and Tammann……
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School of Mathematics QUESTION No.2 UNIVERSITY OF SOUTHAMPTON
LIQUID CRYSTALS ARE:
A. A type of dish-washing liquid which look crystalline when you blow bubbles
B. A magic type of gooey crystal which will give you good luck
C. Neither liquid nor crystal, but something altogether different and more interesting
D. A material with some liquid and some crystalline properties
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Merck advertisement (1907) Lehmann developed a close relationship with Merck. As a physicist he needed a reliable source for new materials.
Merck are still the leading producers of industrial liquid crystals.
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Much controversy and argument
Controversy between Lehmann and the chemist Daniel Vorländer (Halle) Controversy between Lehmann and Reinitzer Controversy between Georges Friedel and Lehmann Controversy between Vorländer and Friedel Long correspondence between Ernst Haeckel and Lehmann
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Vorländer’s molecules Daniel Vorländer (1869-1941). Created the Halle school of liquid crystals which exists to this day.
1906-7 : First to use systematic methods of synthetic chemistry to investigate “crystalline liquids”.
Meta-azoxyanisole, ortho-azoxyanisole do not exhibit double melting, but para-azoxyanisole does.
Only rod-like molecules from liquid crystals!
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School of Mathematics linear molecules UNIVERSITY OF SOUTHAMPTON
(a) The cyanobiphenyl series (Gray 1972); (b) para-azoxyanizole (PAA) (Gattermann 1890) (c) spherocylinder .. model used by theoretical physicists (Onsager 1949)
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School of Mathematics UNIVERSITY OF SOUTHAMPTON The history of liquid crystals O. Lehmann Annalen der Physik 25, pp852-60 (1908) In a book published recently, the origin of the liquid crystal concept was described………It presents a seriously misleading picture of the origin of the liquid crystal concept. One might suspect from this book that Herr Fried. Reinitzer, professor in the Botanical Institute at the University of Graz, had actually discovered this phenomenon in 1888 and I had merely renamed it. I present here, for the first time, the full story.
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School of Mathematics QUESTION No.3 UNIVERSITY OF SOUTHAMPTON THE REAL DISCOVERER OF LIQUID CRYSTALS WAS:
A. Rudolf Virchow (because in retrospect he was the first to observe them)
B. Friedrich Reinitzer (because we can trace liquid crystal science continuously back to a paper by him)
C. Otto Lehmann (because he was the first to realise that they were a special phase and to investigate their properties)
D. Ludwig Gattermann (because he was the first to synthesise a liquid crystal in the lab)
E. Georges Friedel (because he was the first to understand liquid crystal structures)
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Haeckel invoked liquid crystals as an intermediate stage between the living and the non-living. Lehmann’s credibility was reduced
What’s this about your liquid crystals? Can they now eat?
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School of Mathematics Liquid crystals and UNIVERSITY OF SOUTHAMPTON life • 1854 – The distinguished physiologist Rudolf Virchow observed nerve fibres in water under the microscope
• 1888 – Lehmann noted that “…the myelin forms first found by Virchow are liquid crystals.”
• 1906 – Lehmann publishes monograph entitled “Liquid crystals and theories of life”
• 1936 – Bawden, Pirie, Bernal and Fankuchen identify solutions of Tobacco Mosaic Virus as liquid crystals
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School of Mathematics Applications of UNIVERSITY OF SOUTHAMPTON liquid crystals
“ I have been asked if the crystalline-liquid substances may be technically exploited. I do not see any such possibility”
Daniel Vorländer
Chemische Kristallographie der Flüssigkeiten (Leipzig 1924)
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Theoretical attempts: 1908 Bose (failed, inconsistent) 1916 Born (failed, experimentally wrong) 1917 Grandjean (succeeded, paper remained unread until 1971)
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School of Mathematics UNIVERSITY OF SOUTHAMPTON The French school
• Visit of Lehmann to Paris and Geneva 1909
• Two competing French groups
• Frédéric Wallérant …Charles Mauguin was his assistant, at ENS, Paris
• Georges Friedel, and his assistant François Grandjean at the Écoles des Mines at St. Étienne.
• Both groups started work on liquid crystals
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Georges Friedel (1865-1933)
The mesomorphic states of matter
Annales de Physique 18 , pp 273-474 (1922)
This is the most cited article on liquid crystals
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School of Mathematics UNIVERSITY OF SOUTHAMPTON Friedel and Grandjean published several papers before 1914 on the structure of “liquid crystals”, identifying phases (or “stases”) through their textures.
Liquides à noyaux
Liquides à fils
On a larger scale, the collection of droplets looks cloudy.
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School of Mathematics Friedel’s review article UNIVERSITY OF SOUTHAMPTON
• Introduced modern terminology (smectic, nematic, cholesteric)
• Identified liquid crystals as distinct new phases (also stases)
• Tried to replace the term liquid crystal by mesomorphic phase • Realised that structure, rather than degree of fluidity, was crucial property which identified particular phases • Described qualitatively the main structural features of each phase
• Explained the origin of the optical signatures of each phase
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Friedel’s monograph was not only a great scientific work, but also a great piece of literature.
He was known for his strong opinions and acerbic style.
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School of Mathematics UNIVERSITY OF SOUTHAMPTON Pr. Friedel’s article
I use the term mesomorphic to designate those states of matter observed by Lehmann in the years following 1889 and for which he invented the terms liquid crystal and crystalline fluid. Lehmann had the great merit of drawing attention to these substances, but he erred seriously in naming them wrongly. The terminology is inapt, despite having been ceaselessly repeated over the last thirty years. His terminology might lead many people to suppose that these materials are just crystals, albeit differing from those hitherto known by their degree of fluidity. In fact, it is entirely otherwise, and indeed something infinitely more interesting than would be the case if we were considering simple crystals exhibiting some unexpected degree of fluidity.
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And it goes on…..
As to the detailed study of the mesomorphic phases…., and the need to establish any order in this jungle of new facts, the German authors seem to be little concerned. An exception must be made for Lehmann, whose large number of publications contain many observations with the microscope. However, these are confused, and rendered still more unclear by the theoretical considerations which accompany them. It has been in France above all that the main steps in understanding the principal concepts have been made, although understanding is still far from complete. We need to recall…… (p282)
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School of Mathematics QUESTION No. 4 UNIVERSITY OF SOUTHAMPTON NATIONALISM AND SCIENCE: A. Friedel was right: Germans really are stupid.
B. Friedel was wrong: Germans are very smart and should be given credit for discovering liquid crystals
C. Scientists are human and carry the same prejudices as other humans
D. These questions are not of interest to us; we are here to do science and not sociology
E. Both Germans and French people are equally stupid; actually Koreans are smarter than everyone else, which is why modern display devices are mainly made by Samsung.
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School of Mathematics QUESTION No.5 UNIVERSITY OF SOUTHAMPTON THE BEST-LOOKING LIQUID CRYSTAL PIONEER WAS: A. Otto Lehmann (1855-1922) Sorry… in those days there were very few women in B. Rudolf Schenck (1870-1965) science..
C. Gustav Tammann Interesting question, − (1861-1938) which we postpone − why D. Otto Vorlander (1869-1941)
E. Georges Friedel (1866-1933)
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Vsevolod Konstantinovich Frederiks (1885-1944) Created the first liquid crystal group in Russia. Married the sister of the composer Shostakovich Was deported by Stalin and died in the Gulag.
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FREDEERICKSZ EFFECT (1927)
Boundaries align molecules ←→ These effects compete Electric Fields align molecules ↑
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Devices and technological applications of liquid crystals
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School of Mathematics UNIVERSITY OF SOUTHAMPTON Early Devices • 1933 First liquid crystal patent granted to Marconi (London) for a light valve
• 1960 Patent application for thermochromic thermometer from Westinghouse Electric Corporation
• 1963 First Thermochromic patent granted
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School of Mathematics UNIVERSITY OF SOUTHAMPTON • Marconi company • TV research • Turning electric currents into light beams • Kerr constants of nematic liquid crystals 106 higher than in Nitrobenzene
• The device would not have worked in practice
• Research was interrupted by war
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Thermochromic thermometers 1960
J.L. Fergason, T.P. Vogl and M. Garbuny Westinghouse Electric Corporation Thermal imaging devices utilizing a cholesteric liquid crystalline phase material Patent application March 4 1960 Patent granted December 17 1963
James L. Fergason (1935-2008)
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School of Mathematics UNIVERSITY OF SOUTHAMPTON Thermochromic thermometers: example
• The temperature changes across the sample. • Temperature changes are echoed by a change in colour. • Thermometers using this principle are now very common, particularly in the home for measuring body temperature
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School of Mathematics UNIVERSITY OF SOUTHAMPTON Display Devices • 1963-8 Pioneering work at RCA (Princeton) under Heilmeier leads to first liquid crystal display • 1970-1 Invention of twisted nematic (TN) display by Helfrich and Schadt (Hoffman-LaRoche) and Fergason(USA) • 1971-2 Invention of cyanobiphenyls by Gray (UK) • 1973- Beginning of Japanese lcd work • 1988 First small flat screen liquid crystal TVs
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School of Mathematics UNIVERSITY OF SOUTHAMPTON LIGHT TRANSMISSION THROUGH CROSSED POLARISERS
• Screen polarisation governs transmission. • Extinction can be tuned by rotating the director.
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This pattern is characteristic of The view through crossed polars slabs of nematic liquid crystal.
It is known as the Schlieren texture.
These are the Schliere seen by Gatterman in 1890.
The patterns betray a network of topological defects at which the nematic director is not defined.
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School of Mathematics UNIVERSITY OF SOUTHAMPTON Twisted Nematic Cell (Schadt &Helfrich 1970) • Physics dates back to Mauguin effect 1911 • Twisted director field wave-guides light
• No field light transmission; transparent • Above threshold voltage (thickness-independent, ∼1 volt) no light transmission; black • Other devices can reverse this effect
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Twisted Nematic Cell
a) Zero voltage. Polarisation rotates ⇒ transmission b) High voltage. Polarisation unchanged ⇒ extinction
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Wolfgang Helfrich Worked for RCA and then for Hoffman-LaRoche in Switzerland George Heilmeier (b 1935) Created dynamic scattering displays in 1960s while working for RCA Later worked for Department of Martin Schadt Defense and President of Texas worked with Instruments. Helfrich to Blamed by some for the demise of produce a viable the US lcd industry TN display
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George Gray (1927-2013) University of Hull 1946-90 Technical Director BDH, Merck UK
Inventor of Cyanobiphenyls (room temperature liquid crystals)
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School of Mathematics James L Fergason constructedUNIVERSITY a OF TN SOUTHAMPTON device at roughly the same time in the USA.
There followed mighty patent wars….
Frank Leslie (1935-2000) created the modern continuum theory of liquid crystals and calculated the properties of a TN cell ….. Switched by a magnetic field !
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School of Mathematics Display issues UNIVERSITY OF SOUTHAMPTON
• Chemical Stability / lack of toxicity • Wide nematic temperature range (-20 C < T <60 C) • tailor mixtures for correct properties • Low elasticity ⇒ low threshold voltage • Optical contrast • Orientational viscosity • Addressing Getting the right message to each pixel (electronics problem, common to many display technologies) • Refreshing Changing the picture often enough • Contrast Important if no light source • Brightness Do I need to close the curtains? • Colour Colour filters ( but reduce brightness!) • Grey Scale Temporal or spatial dither • Viewing Angle A peculiar liquid crystal problem
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School of Mathematics UNIVERSITY OF SOUTHAMPTON LC television
• Large area
• Wall-mounted
• Fast response
• High definition
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School of Mathematics …Small area… UNIVERSITY OF SOUTHAMPTON
Displaytech (Boulder, Colorado) Ferroelectric liquid crystal (FLC) microscreen
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School of Mathematics UNIVERSITY OF SOUTHAMPTON SOCIAL ISSUES • The major industrial success has been Japanese (and more recently Taiwan and China)
• Why could the US and Europe do the science but not do the engineering?
• Manufacturing display devices Long-term investment required `.. Suitable technology for the Japanese mentality..’ (Shirano Hirano, I.B.M. Japan 1990) (seems unlikely to be racial factors!)
• US had prior investments which needed defending.
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WORLD DISPLAY MARKET Now about $150B pa
Heilmeier’s original dream of a TV hanging on wall took 25 years to achieve. Now other technology is beginning to be competitive again.
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School of Mathematics QUESTION No. 6 UNIVERSITY OF SOUTHAMPTON ENGINEERING, SCIENCE AND FUNDING RESEARCH: A. Governments should fund basic liquid crystal research because science is an important part of culture.
B. Governments should fund basic liquid crystal research because historically liquid crystals have turned out to be useful.
C. Governments should fund basic liquid crystal research because liquid crystals are at the heart of understanding life (but should not necessarily find all science in this way)
D. Industrial companies should fund liquid crystal research only if it can see a short-term application.
E. Industrial companies should fund liquid crystal research because liquid crystals have such a good applications track record. 26/06/2013 question I-CAMP, Cambridge 2013 74
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NON-OPTICAL APPLICATIONS
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School of Mathematics Liquid crystals as structural UNIVERSITY OF SOUTHAMPTON materials - polymers
Main-chain lc polymer Side-chain lc polymer
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School of Mathematics Synthetic high strength liquid UNIVERSITY OF SOUTHAMPTON crystal fibres e.g. Kevlar
Nematic solution of polyamide in conc. sulphuric acid Kevlar fibre
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School of Mathematics …..and bridges UNIVERSITY OF SOUTHAMPTON
Rion-Antirion bridge Suspension foot-bridge (Greece) (Scotland)
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School of Mathematics Structure of Kevlar UNIVERSITY OF SOUTHAMPTON fibres
Fibre axis
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LIQUID CRYSTALS AND LIFE
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School of Mathematics …or naturally UNIVERSITY OF SOUTHAMPTON
Kevlar fibres resemble molecules in naturally occurring strong materials such as wood or spider silk
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School of Mathematics Liquid crystals as UNIVERSITY OF SOUTHAMPTON structural materials – cell membranes
hydrophilic region hydrophobic region
phosphol ipid bilayer
integral protein peripheral protein
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Tobacco mosaic virus (TMV) molecules can form liquid crystalline solutions in water
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THE FUTURE FOR LIQUID CRYSTALS
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School of Mathematics The future for liquid UNIVERSITY OF SOUTHAMPTON crystals • Faster and more versatile displays • Tunable liquid crystal lenses • Better spying & snooping at NSF and GCHQ • The electronic book (I-pod is LC, Kindle is not) • Combination of electro-activity and high strength fibres might result in ….. Artificial Muscles • Liquid crystals and life
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• Colloids and Liquid Crystals are culturally important, because they were the first exceptions to the classification of solid-liquid-gas (earth-water-air).
• Liquid crystals and colloids were the beginning of “Soft- matter studies”.
• First stones in the philosophical grave of Dualism (distinction between living and non-living substances)
• Liquid crystalline ideas (and the coupling of orientational and spatial degrees of freedom) underlie much current biophysics
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LIQUID CRYSTAL SCIENCE Computer Chemistry Biology
Mathematics Engineering Physics
Art
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School of Mathematics UNIVERSITY OF SOUTHAMPTON Acknowledgements
• David Dunmur, Horst Stegemeyer (collaborators on history project)
• Geoffrey Luckhurst (years of tutorials) • Taylor and Francis, OUP (publishers) • Peter Knoll and Anatoli Sonin (who wrote the key books in German and Russian and sent me copies!) • Many senior colleagues and informants including several present today (and particularly Jacques Friedel and Jerry Ericksen who wrote me long letters) • The late…Frank Leslie, Charles Frank, Yves Bouligand, George Gray • Everyone who helped me understand Otto Lehmann’s labyrinthine German sentences
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Commercial break !
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Reprints (and translations) of key papers with commentary
Taylor and Francis 2004
A must for your university or company library!
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Social and intellectual history of liquid crystals OUP 2011 A must for your personal library!
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