Frans Leenhouts

Electro‐optical performance of a new, black‐white and highly multiplexable liquid crystal display

A new, low bias tilt field‐effect liquid crystal display (LCD) is presented with better image quality than supertwist or superbirefringence LCD’s at the same high level of multiplexing. In its positive contrast mode, the display image is black on white with virtually no inherent coloration and with a comparably large contrast as that of twisted nematic LCD’s. The viewing range of the display is as wide as that of superbirefringence LCD’s, whereas its image quality is an order of magnitude less dependent on cell gap variations. With specifically designed liquid crystal mixtures, multiplexing ratios of 1000:1 and response times below 300 ms result.

New Nematic Liquid Crystals: Influence of Rigid Cored, Alkenyl Side-Chains and Polarity on Material and Display Properties

Abstract From the design of non-polar molecular structures exhibiting different rigid cores and isolated C=C double bonds in different side-chain positions and from investigations into the static dielectric birefringence, viscous, and all three elastic constants k 1, k 2, k 3, new, negative dielectric anisotropic nenatic liqueid crystals result, namely apolar alkenyls, which are shown to cover a wide range of materail porpertie, including large twist constants k 2. The combination of double bonds in 4-position, with rigid cores comprising heterocyclic rings is shown to lead to exceptionally low elastic rations k 3/k 1 ∼ 0.4 with simultaeoulsy low optical anisotropies and low roatational viscosities γ1. Moreover, laterally substituted alkenyls are shown to exhibit large negative dielectric anisotropies rendering them applicable for low viscous, positive contrasat guest-host mixtures with high order parameters 0.72≤ S ≤ 0.78. The stability of the new nematics comprising isolated double bonds is shown to be ...

Electro‐optical characteristics of a new liquid‐crystal display with an improved gray‐scale capability

A new liquid‐crystal display (LCD) is presented with a much better gray‐scale capability than twisted nematic LCD’s and a comparably good contrast. In the not‐energized state the coloration of the display is weak, enabling full color applications. Due to its improved gray‐scale capability which results from the shallow slope of the electro‐optical characteristics, the display is particularly suited for active matrix applications.

Novel ferroelectric smectic C liquid crystal mixtures for display applications

Abstract Novel long-pitch ferroelectric smectic C liquid crystal mixtures are reported which combine a broad chiral smectic C temperature range with a low birefringe. Due to their fast response times and excellent thermal and photochemical stability, these mixtures are particularly well suited for fast switching electro-optic displays based on the surface-stabilized geometry.

Tricyclic Smectic C Compounds Incorporating a 1,3-Dioxan Ring

About 80 mesogenic achiral 1,3-dioxans substituted in the 2 position by a p-(benzoyloxy)phenyl, 4-biphenylyl, 2-phenyl-5-pyridyl, or a 2-phenyl-5-pyrimidyl core have been synthesized. Most of them ...

Compensation of the temperature dependence of the optical characteristics of twisted nematic liquid‐crystal displays using a single chiral dopant

Chiral dopants are reported which enable one to compensate for the temperature dependence of the optical characteristics of twisted nematic liquid‐crystal displays. Temperature compensation is achieved by the addition of a small amount of only one chiral compound to the liquid‐crystal mixture. This procedure is more precise and less laborious than a previously reported method, which utilizes two or more chiral dopants.

Optics of Twisted Nematic Liquid Crystal Layers

Abstract Calculations have been made of the optical properties of various liquid crystal displays (LCDs) based on twisted nematic liquid crystal layers. It is shown that the steepness of the electro-optical characteristics of TN LCDs can be reduced and consequently the gray-scale capability can be improved by decreasing the twist angle. The twist reduction permits the realization of displays which, due to their outstanding gray-scale capability and low inherent coloration, are particularly suited for active matrix TV-applications. In addition to calculations made on displays based on weakly twisted layers, a comparison is made of the optical properties of displays with a high multiplex capability, which utilize highly twisted nematic liquid crystal layers. It is shown that the brightness of the OMI LCD can be improved without deterioration of the weak inherent coloration. This renders OMI LCDs particularly well suited for applications as time-multiplexed, full colour, high information content panels.