1. 1 Examples of flat-panel liquid crystal displays

2. 2 Display design

3. 3 Display elementEfficiency (%) individualcumulative lamp reflector + in-coupling8080 backlight waveguide 7056 diffuser + air gap9050 back polarizer 4020 display aperture8016 color filters28 5 effective area for color33 2 front polar95 1 Display elementEfficiency (%) individualcumulative lamp reflector + in-coupling8080 backlight waveguide 7056 diffuser + air gap9050 back polarizer 4020 display aperture8016 color filters28 5 effective area for color33 2 front polar95 1 Light efficiency of flat-panel TN LCDs

4. 4 Optical films for LCDs

5. 5 Polymers in LCD displays Polarizers Color Filters Viewing angle compensation Prism films Multi-layer optical films Specular reflectors Liquid crystal alignment layers

6. 6 Ceramics in LCD displays Display quality glass Transparent conductive oxides Spacers Viewing angle compensation Prism films Multi-layer optical films Specular reflectors

7. 7 Quenched-in misorientation of InO 6 structural units leads to amorphous films Bixbyite crystal structure: c-type rare earth sesquioxide Ia3 with 80 atom unit cell consisting of InO 6 structural units Indium oxide

8. 8 Sputter Target Qualification Film purity Film properties Step coverage System throughput Uniformity of deposition Target integrity (& utilization) Process repeatability Sputter Deposition Challenges Compositional analysis standard test conditions: Sputter system Power density Voltage Sputter gas Film thickness Resistivity (film) Surface asperities (nodules) Sputter rate Time dependence of... Transparent Conducting Oxides

9. 9 N S N S N S DC Power supply erosion center substrate target sputtered atoms incident ion Target Sequence of collisions results in ejection of target atom (sputtering) sputtered atom reflected ions and neutrals secondary electrons implanted ion Magnetron Sputter Deposition

10. 10 Crystalline and wt%SnO 2 Indium Oxide CrystallinityWt% SnO 2

11. 11 Erosion profile Surface profile Nodule formation Composition Toughness Sputter target removed from service Sputter target characterization

12. 12 TFT Foils TFT Structure Flexible polyimide substrates On surface minimum radius of curvature depends on TFT strain to failure Inside substrate minimum radius of curvature depends on substrate

13. 13 By an external field electrical field (e.g. 1 V/  m) magnetic field (e.g. 5 kG) mechanical field (e.g. flow) At an oriented surface buffed substrate for planar alignment surfactants for homeotropic alignment form anisotropy anisotropic molecular properties combined action of sterical and dispersive interfacial interactions E Liquid crystal alignment

14. 14 Rubbing directions and chiral dopants determines rotation direction Twisted nematic displays

15. 15 rubbing Tilt angle  by selection of alignment material and rubbing  Rubbing direction in accordance with twist sense 90 o twist by adding chiral dopant Pretilt and chiral additives to prevent domain formation Tilt, twist and rubbing directions

16. 16 Alignment mechanism: at nano grooves by excluded volume effects of rod-like molecules at interface at preferentially orientated chain segments by anisotropic dispersive interactions with LC molecules apolar side/end groups provide pre-tilt control n Rubbing of polyimide provides liquid crystal orientation

17. 17 Use polarized UV light to modify polymer surface in order to control liquid-crystal alignment linearly polarized UV-light      * Recent development: photo-alignment

18. 18 Problems with mechanical rubbing: static electricity dust formation uniform rubbing of large surface area uniform rubbing of irregular surface Photo-alignment is a non-contact method that avoids these problems ! Why photoalignment ?

19. 19 Orientation perpendicular to polarization direction No or small pretilt () n O CO C C () n O CO C C () n () n O O CO CO LP-UV Photo-alignment using polyvinylcinnamates

20. 20 Orientation parallel to polarization direction Pretilt O O O O O O O O LP-UV Coumarin-based photoalignment (Rolic)

21. 21 Multi-component mix for: low melting temperature high nematic to isotropic transition temperature optimized optical anisotropy small dispersion of refractive indices low viscosity for fast response small elastic constants high dielectric anisotropy / low threshold voltage low conductivity LC mixtures for displays contain many components

22. 22 Example of LC mixture

23. 23 Column electrodes Row electrodes Active matrix LCD (TN) Direct addressing Passive matrix LCD (STN) - row and column electrodes - LC responds to RMS voltage switch at each pixel Passive plate with counter electrode Drive Schemes

24. 24 macroorganisch 6C275 / kernkeuze college 6C270 24-04-01 home TNSTN for  polars:(Super Twisted Nematic) 90 o twist180 o -270 o twist white off statecolored on/off state black-on statecompensation foil for B/W for // polars: (poor) black off white on state twist angle Electro-optic response of TN and STN LCD’s

25. 25 active matrix:high end computer monitors, video ‘emissive’ by back light passive matrix: simpler displays ?? passive matrix, bistable effect, reflective color: simpler displays, extremely low power consumption paper-white reflective effects Polarizer-based LC effects Twisted-nematic In-plane switching of nematics Vertically aligned nematics Ferroelectric (S C *) Supertwisted-nematic Polarizer-free LC effects Polymer dispersed liquid crystals LC gels surface or polymer-stabilized cholesterics guest-host LC’s Other liquid crystal display effects

26. 26 h E transparent scattering Polymer stabilized liquid crystals

27. 27 Schematic representation of different types of liquid crystal polymers Network formation by photo-initiated polymerization Formation of ordered networks by photopolymerization of liquid-crystalline monomers Example of photo-initiated polymerization in the liquid-crystalline state Typical processing sequence Reactive liquid crystals Influence of functional moiety on mesomorphism of reactive liquid crystals Refractive indices before and after polymerization Order parameter of LC diacrylates before and after polymerization Liquid crystalline networks for advanced optics Three-dimensional polymer architectures Combination of different alignment principles Photopolymerization of a chiral monomer Pitch of the helix can be freely chosen by blending chiral with nematic monomers Reflection band of sample containing 62 % chiral diacrylate Photo-induced diffusion in z-direction Gradient in UV light by strong absorbing dye Modulation of properties in z-direction Cholesteric network with a pitch gradient Polymeric liquid crystals and liquid crystal networks

28. 28 rod rigid main chain flexible main chain disk LC MAIN CHAIN POLYMERS LC SIDE CHAIN POLYMERS LC NETWORKS Schematic representation of different types of liquid crystal polymers

29. 29 O O O O O O O O O O h aligned LC monomer Formation of LC networks by photopolymerization of LC monomers

30. 30 Iso-contrast lines Grey scale inversion Contrast and grey-scale inversion as function of viewing angle

31. 31 high contrastlow contrast low V medium V high V lowlow contrasthigh d  n >> 0d  n = 0  Grey scale inversion Contrast degradation Viewing angle of TN-LCD’s

32. 32 towards homeotropic orientation at air interface planar orientation at rubbed substrate with WVA without WVA Compensation foils to improve on viewing angle

33. 33 Tilted discotic networks to improve on viewing angle Fuji film

34. 34 Reflecting polarizer, e.g. wide-band cholesteric film Depolarizing or polarization converting reflector 100% polarized light instead of 50% by recycling principle Non-absorbing polarizer improves on light-efficiency

35. 35 wideband cholesteric polarizer Display partly provided with wide-band cholesteric polarizer

36. 36 u monomer with steep temperature dependence u polymer with flat temperature dependence monomer polymer 1 polymer 2 polymer 3 Cholesteric color filters: color generation without absorption improves LCD’s on light efficiency