Martin Schadt - Key Publications

Key Publications

KEY PUBLICATIONS BY M. SCHADT including abstracts

The numbers refer to the complete list of publications of Martin Schadt available here.

7) A Simple Organic Electroluminescence Diode; D.F. Williams and M. Schadt. IEEE 58, 476 (1970).

The first solid state, blue light emitting organic diode (OLED) is presented. The OLED is based on electron-hole recombination into single crystals of anthracene via charge carrier-injection through solid electrodes; c.f. also the corresponding Canadian patent.

9) Voltage-Dependent Optical Activity of a Twisted Nematic Liquid Crystal (TN-LCD); M. Schadt and W. Helfrich. Phys.Rev.Lett. 27, 561 (1971).

First Publication of the twisted nematic (TN)-effect after its invention and patent filing at Roche in December 1970. Based on the TN-effect and the development of TN-specific liquid crystal materials, the field-effect liquid crystal display (LCD)-industry evolved.

16) Photoresponse of Bimolecular Lipid Membranes Pigmented with Retinal and Vitamin A Acid; M. Schadt. Biophys.Acta 323, 351 (1973).

Postulation of the first electronic equivalent circuit for the visual process. The electronic model describes the photo-response of artificial lipid bilayer membranes doped with retinal and/or vitamin A.

17) Permeability of Lipid Bilayer Membranes to Biogenic Amines and Cations: Changes Induced by Ionophores and Correlations with Biological Activities: M. Schadt and G. Häusler, J. Membrane Biol. 18, 277 (1974).

Biogenic amines are found to be selectively transported across lipid bilayer membranes upon doping LB-films with specific ionophores. We show for the first time that biogenic amine transport is competitively inhibited by cations. Moreover, correlations are found between our LB-film findings and the cardiac sympathetic effects of iono-phores in dogs and the ability of specific ionophores to facilitate permeation of biogenic amines through lipid bilayers.

23) Phenyl Pyrimidines: Design, Synthesis and Physical Properties; A. Boller, M. Cereghetti, M. Schadt and H. Scherrer. Mol. Cryst. Liq. Cryst. 42, 215 (1977).

The demand for liquid crystals rendering TN-LCDs operable at very low voltages (1.5 volts) led to the design, synthesis and patenting of the first strongly polar heterocyclic liquid crystals. It is shown that strong dielectric synergies result from com-bining pyrimidine rings in the rigid cores of LC-molecules with cyano end groups without hampering mesogenic proper-ties. Phenyl-pyri-midines were the first, low operating voltage nematics enabling the development of TN-LCDs with increased information content for pocket calculators and dot-matrix digital watch TN-LCDs in the late 1970s.

25) Kerr Effect and Orientational Relaxation of Pretransitional Domains and Individual Molecules in Positive Dielectric Liquid Crystals; M. Schadt. J.Chem.Phys. 67, 210 (1977).

In the isotropic phase of polar liquid crystals exceptionally large electrically-induced optical birefringence coefficients (Kerr effect) are shown to occur.. The static and dynamic Kerr coefficients are correlated with molec-ular functional groups and are shown to be due to pre-transitional short-range order effects. Two relaxation processes with relaxation times between 10-7 - 10-8 sec are identified to govern the dynamics. The dispersion mechanisms as well as potential applications of liquid crystals in fast electro-optical shutters are outlined.

29) Field-induced Color-Switching Liquid Crystal Display; M. Schadt. J. Chem. Phys. 71, 2336 (1979).

A new electro-optical guest-host effect based on novel dichroic host molecules is presented which for the first time not only modulates light intensity but also the color of a display. A model describing the physics of the new color-switching effect is presented.

38) Class-Specific Physical Properties of Liquid Crystals and Correlations with Molecular Structure and Static Electro-Optical Performance of Twisted Nematic LCDs; M. Schadt and P. Gerber. Zeitschr. Naturforsch. 37a, 165 (1982).

For the first time complete sets of all relevant material parameters which govern the electro-optical perfor-mance of TN-LCDs are determined, including elastic constants. Specific relevant molecular functional groups of LC-molecules are identified and correlated with material properties and display performance. Heterocyclic rings are shown to induce small bend/splay elastic constant ratios. Analytical expressions are derived describing the electro-optical performance of TN-LCDs. The find-ings led to inventing and developing new LC-classes enabling increased information contents of TN-LCDs. As a result, first dot-matrix TN-displays for pocket calculators and office equipment evolved in the early 1980s.

40) Low Frequency Dielectric Relaxations in Nematics and Dual-Frequency Addressing of Field-Effects; M. Schadt. Mol. Cryst. Liq. Cryst. 89, 77 (1982).

Novel liquid crystal molecules and LC-mixtures were designed enabling pronounced dielectric dispersion already at very low (audio) frequencies, thus rendering dual-frequency addressing of LCDs feasible. Dispersive dielectric molecular functions are identified which markedly reduce the response times of displays and increase the information contents of TN-LCDs.

47) Polar Alkenyls: Physical Properties and Correlations with Molecular Structure of New Nematic Liquid Crystals; M. Schadt, M. Petrzilka, P. Gerber and A. Villiger. Mol. Cryst. Liq. Cryst. 122, 241 (1985).

For the first time it is shown that double bonds at specific sites in the hydrocarbon side-chains of liquid crystals strongly broaden the range of LC-mate-rial parameters, especially the elastic- and visco-elastic constants. First correlations between alkenyl molecules, material parameters and display performance are presented. Numerous new classes of alkenyl liquid crystals – designed and patented in our laboratories between 1984 and 1995 – are based on these findings. Alkenyl liquid crystals have become key components for achieving high information content super-twisted nematic (STN)-LCDs and fast responding, thin-film transistor (TFT)-addressed monitor- and television -LCDs.

57) Electro-Optical Performance of a New, Black-White and Highly Multi-plexible Liquid Crystal Display (OMI-LCD); M. Schadt and F. Leenhouts. Appl. Phys. Lett. 50, 236 (1987).

A new, inherently black-white (Optical Mode Interference)-effect is presented. The new OMI-supertwisted effect is shown to be less sensitive to temperature changes and to manufacturing tolerances than other, inherently colored su-pertwist configurations.

66) Material Properties, Structural Relations with Molecular Ensembles and Electro-Optical Performance of New Bicyclohexane Liquid Crystals in Field-Effect LCDs; M. Schadt, R. Buchecker and K. Müller. Liq. Cryst. 5, 293 (1989).

Several new families of fast responding alkenyl nematic liquid crystals are presented. It is shown that by shifting alkenyl double bonds from even in to odd side-chain positions, strong odd-even effects result in virtually all liquid crystal material parameters. Interactive molecular modelling indicates that the elastic constant ratios of nematic LCs are not determined by the shape of individual molecules as postulated before, but rather by the shape of molecular ensembles. Our findings led to the invention, patenting and manufacturing of new generations of (alkenyl) liquid crystals for high in-formation content displays (c.f. also ref. 96 and book ref. 3). Correlations between LC-material parameters and electro-optical performance of LCDs are derived and related with novel molecular functional groups.

68) Deformed Helix Ferroelectric Liquid Crystal Displays; a New Electro-Optical Mode in Sc* Liquid Crystals (DHF-LCDs); L.A. Beresnev, V.G. Chigrinov, I. Dergachev, E.P. Pozhidaev, J. Fünfschilling and M. Schadt. Liq.Cryst. 5, 1171 (1989).

In collaboration with researchers of NIOPIK, Moscow, a new, fast responding ferroelectric field-effect, denominated Deformed Helix Ferroelectric (DHF)-effect, is presented. Unlike other ferroelectric effects, the DHF-effect enables gray scale and rms-driving. Both properties are crucial for spatial light modulators and for very fast responding, high information con-tent displays and electronic color shutters (c.f. also ref. 111, 123).

79) New Liquid Crystal Polarized Color Projection Principle; M. Schadt and J. Fünfschilling. Jpn. J. Appl. Phys. 29, 1974 (1990).

A novel, large aperture cholesteric LCD-color projection concept is presented which converts unpolarized light into polarized light within selective wavelength ranges. All critical optical elements, i.e. color filters, polarizers and electro-optical modulators, con-sist entirely of liquid crystalline thin-films and LCDs. The new optical concept, which includes new liquid crystalline materials, con-siderably improves the brightness of displays and LCD-projectors and avoids dissipative optical elements. The first temperature-independent, short-pitch, monomeric cholesteric liquid crystals with negative dielectric anisotropy for disclocation-free, broad-band circular polarizers and cholesteric optical filters are presented (c.f. also ref. 123 and book ref. 3).

94) Surface-Induced Parallel Alignment of Liquid Crystals by Linearly Poly-merized Photopolymers (LPP-technology); M. Schadt, K. Schmitt, V. Kozinkov and V. Chigrinov. Jpn.J.Appl.Phys. 31, 2155 (1992).

For the first time simultaneous anisotropic alignment and cross-linking of initially iso-tropic photo-polymers by linearly polarized uv-light is demonstrated. The new LPP–photo-alignment technology enables non-mechanical uniaxial alignment of liquid crystal molecules. This renders photo--generation of microscopic LC-aligning patterns with arbitrary azimuthal director orientation(s) feasible. A molecular model of the new LPP-photo-alignment process is presented (c.f. also ref. 120).

95) Strongly Nonlinear Optical (NLO)-Ferroelectric Liquid Crystals for Frequency Doubling; K. Schmitt, R.P. Herr, M. Schadt, J. Fünfschilling, R. Buchecker, X.H. Chen and C. Benecke. Liq.Cryst. 14, 1735 (1993).

Novel synergies are shown to result from combining the non-centro symmetry and the large spontaneous polarization Ps of short pitch ferroelectric smectic C* liquid crystals with another molecular function, namely with optical non-linearity. From coupling NLO properties with Ps and optical bi-stability result molecular configurations with exceptional ?2 -coefficients which are 500 times larger than those of the best NLO-Sc*-materials known at the time. The NLO-activity of our new materials and molecular configuration is competitive with the best inorganic NLO-materials (LiNO3). Moreover, from combining for the first time the optical bi-stability of an electro-optical effect with NLO-activity, follow the first thermally stable inorganic NLO-configurations (c.f. also ref. 112).

119) Photo-Generation of Linearly Polymerized Liquid Crystal Aligning Layers with Integrated Optically Patterned Retarders and Color Filters. M. Schadt, H. Seiberle, A. Schuster and S.M. Kelly, Jpn. J. Appl. Phys. Pact 1, 34, 3240 (1995).

For the first time uniaxial planar alignment of liquid crystal polymer (LCP)-films on single substrates is shown. Photo-alignment of single- and stacked LCP-layers is shown to enable LCP-thin-film configurations with freely adjustable optical axes and novel optical functions. The molecular photo-mechanisms generating anisotropic optical film-properties are outlined. The new LPP/LCP technology enables a plethora of novel photo-patternable thin-films, such as interference color filters, wide-view films to broaden the field of view of LCDs, photo-structured polarisers as well as a novel optical security elements (c.f. also ref. 120, 157, 159).

127) Optical Patterning of Multi-Domain Liquid Crystals with Wide Viewing Angles; M. Schadt, H. Seiberle and A. Schuster. NATURE 381, 212 (1996).

Photo-induced uniaxial liquid crystal alignment in a single exposure step is for the first time shown to generate defined LC bias-tilt angles. Prerequisite is non-centro-symmetric LPP-photo-alignment achieved by photo-polymerizable molecules with novel photo-reactive symmetry. This extension of our LPP-photo-alignment technology is crucial for enabling dislocation-free photo-aligned LCDs (c.f. also ref. 94). Moreover, LPP-photo-alignment enables angular independent high information-content monitor- and television-LCDs via control of molecular alignment within each pixture element. This is demonstrated by the first four-domain LPP-photo-aligned and photo-patterned TN-LCD.

164) Novel Optical Thin-Films with Isotropic and Anisotropic Nano-Corrugated Surface Topologies; M. Ibn-Elhaj and M. Schadt. NATURE 410, 796 – 799 (2001).

Nano- and Micro-topologies are shown to result from optically-induced monomer phase-separation on polymer surfaces. Our novel monomer-corrugation (MC)-technology enables high-performance antireflection coatings for optical components of virtually any size, shape and material. It also enables a plethora of other functional polymer thin-films with isotropic as well as anisotropic topologies. Examples are films whose birefringence exceeds the birefringence of the polymer material itself, diffractive thin-films, diffusors, directional-reflectors which preserve light-polarisation as well as films which align LCDs and simultaneously exhibit optical and electrical functions.

BOOKS

1) M. Schadt Liquid Crystal Displays. in: Liquid Crystals; ed. H. Stegemeyer, Steinkopff/Springer, New York, pp. 195–226 (1994)

2) M. v. Zedtwitz, M. Brauchli and M. Schadt Ueberwindung nationaler Grenzen dargestellt am Beispiel der Liquid Crystal Display (LCD)-Technologie. in: Internationales Innovations Management; ed. O. Gassmann und M. v. Zedtwitz, Vahlen Verlag, Muenchen, pp. 143–154 (1996)

3) M. Schadt Liquid Crystal Materials and Liquid Crystal Displays. in: Annual Review of Materials Sciences, Vol 27; ed. E.N. Kaufmann, guest ed. Ch.J. Summers. New York, pp. 305–375, (1997)

4) M. Schadt Recent Advances in LPP-Photo-Alignment of Liquid Crystals Applied to the Phase-Retarder Image of Alfred Saupe. in: Dynamics and Defects in Liquid Crystals; ed. P.E. Cladis and P. Palffy-Muhoray, Gordon and Breach Science Publishers, Amsterdam, pp 263–271 (1998)

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