2. Liquid crystals : The fourth state of matter Thierry Chuard, Universität Bern

3. What is a liquid crystal ? Crystal Highly organized solid Liquid Non-organized fluid Liquid crystal Organized fluid heat

4. Example for a liquid crystal 4-methoxybenzilidene-4'-butylaniline CrystalLiquid crystal 20 °C 47 °C

5. How do liquid crystals organize ?

6. The nematic phase Director + + + + + + + + + - - - -- - -- - + + + - - + + + + + + + - - - - - - - - Random orientation of the dipoles

7. Heating a nematic phase The less organized material is the most fluid 

8. The cholesteric phase A cholesteric phase is a chiral nematic phase

9. Twisted nematic (TN) cell Front glass Rear glass Contacts Electrode Counter-electrode Alignment layers LC

10. Twisted nematic (TN) cell Front glass Rear glass LC Polarizer

11. TN cells switching Front glass Rear glass Electrode Counter-Electrode Alignment layer Polarizer

12. The plane of the polarized light is turned by 90° by the LC The light can go through the 2nd polarizer Only the polarized Light in the plane of the polarizer goes through

13. The plane of the polarized light is not turned by the LC The light cannot go through the 2nd polarizer 

14. How can we obtain a white pixel on a black background with the same disposal ?

15. The plane of the polarized light is turned by 90° by the LC The light cannot go through the 2nd polarizer

16. The plane of the polarized light is not turned by the LC The light can go through the 2nd polarizer 

17. ITO electrodes

19. Progress in LC displays  Faster switching time  Lower switching voltage  Larger screen size  Higher resolution  Better color quality ans greyscale