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Martin Schadt (born 1938) is a Swiss physicist and inventor.
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Martin Schadt (born 1938) is a Swiss physicist and inventor.
In 1970, the physicists Martin Schadt and Wolfgang Helfrich invented the twisted nematic field effect (TN-effect) in the Central Research Laboratories of F. Hoffmann-La Roche Ltd, in Basel, Switzerland. The resulting patent CH532261 was licensed worldwide to electronics and watch industries and thus initiated a paradigm change towards flat panel field effect liquid crystal (LC) displays.
In the early 1970s, Martin Schadt started to investigate correlations between liquid crystal molecular structures, material properties, electro-optical effects and display performance to obtain criteria for novel, effect-specific liquid crystal materials for TN- and subsequent field-effect applications. His interdisciplinary approach involving physics and chemistry became the basis for modern industrial LC-materials research and led to the discovery and production of numerous new functional molecules and new electro-optical effects. In 1970, shortly after the invention of the TN-effect, he developed the first commercial room temperature nematic liquid crystal mixture with positive dielectric anisotropy, [1] used in the displays of the first Japanese digital TN-LCD watches. The pharmaceutical company Roche established itself as a major supplier of liquid crystal materials for the emerging LCD-industry.
Apart from his pioneering work on the TN-effect (i.e.e twisted nematic field effect), novel liquid crystal materials, organic semiconductors and biophysics, he invented or co-invented the following effects and technologies:
As principal inventor and head of Roche LC research he promoted the development of LPP-Photoalignment into manufacturing (1992–2002). As a key technology it enables contact free alignment and photo-patterning of monomeric and polymeric liquid crystals by optical means instead of mechanically. This has opened up novel display configurations as well as a wide range of new optical thin-film elements on single substrates, such as LC-interference color filters, optical retarders, cholesteric optical filters, wide-view films to enhance the field of view of LCDs, novel optical security elements for document and brand protection, stereo-polarizers as well as nano-and micro-corrugated optical polymer thin-film elements enabling polymeric antireflective and directional light scattering coatings.
The molecular design approach of Martin Schadt and his team has led to the discovery, patenting and production of the following commercially important liquid crystal classes: alkyl cyano Schiff'bases and esters (1971), [2] phenyl-pyrimidines (1977), alkenyl liquid crystals which have become key for all state-of-the-art high-information content LCDs (1985–1995), numerous halogenated liquid crystals (1989–1995) as well as the first strongly non-linear optical (NLO)-ferroelectric liquid crystals (1992).
Until 1994 Martin Schadt was the head of the Liquid Crystal Research division of F. Hoffmann-La Roche Ltd. As a spin-off from Hoffmann-La Roche in 1994 he founded the interdisciplinary research and development company ROLIC Ltd. From 1994 until his retirement from the operating business in October 2002 Martin Schadt was CEO of ROLIC Ltd. and delegate of the board of directors. He retired from ROLIC in 2005 and is now active as a scientific advisor to various research groups and governmental agencies.
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A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liquid crystals do not emit light directly, instead using a backlight or reflector to produce images in color or monochrome. LCDs are available to display arbitrary images or fixed images with low information content, which can be displayed or hidden. For instance: preset words, digits, and seven-segment displays, as in a digital clock, are all good examples of devices with these displays. They use the same basic technology, except that arbitrary images are made from a matrix of small pixels, while other displays have larger elements. LCDs can either be normally on (positive) or off (negative), depending on the polarizer arrangement. For example, a character positive LCD with a backlight will have black lettering on a background that is the color of the backlight, and a character negative LCD will have a black background with the letters being of the same color as the backlight. Optical filters are added to white on blue LCDs to give them their characteristic appearance.
Liquid crystals (LCs) are a state of matter which has properties between those of conventional liquids and those of solid crystals. For instance, a liquid crystal may flow like a liquid, but its molecules may be oriented in a crystal-like way. There are many different types of liquid-crystal phases, which can be distinguished by their different optical properties. The contrasting areas in the textures correspond to domains where the liquid-crystal molecules are oriented in different directions. Within a domain, however, the molecules are well ordered. LC materials may not always be in a liquid-crystal state of matter.
A thin-film-transistor liquid-crystal display is a variant of a liquid-crystal display (LCD) that uses thin-film-transistor (TFT) technology to improve image qualities such as addressability and contrast. A TFT LCD is an active matrix LCD, in contrast to passive matrix LCDs or simple, direct-driven LCDs with a few segments.
A super-twisted nematic display (STN) is a type of monochrome passive-matrix liquid crystal display (LCD). This type of LCD was invented at the Brown Boveri Research Center, Baden, Switzerland, in 1983. For years a better scheme for multiplexing was sought. Standard twisted nematic (TN) LCDs with a 90 degrees twisted structure of the molecules have a contrast vs. voltage characteristic unfavorable for passive-matrix addressing as there is no distinct threshold voltage. STN displays, with the molecules twisted from 180 to 270 degrees, have superior characteristics. The main advantage of STN LCDs is their more pronounced electro-optical threshold allowing for passive-matrix addressing with many more lines and columns. For the first time, a prototype STN matrix display with 540x270 pixels was made by Brown Boveri in 1984, which was considered a breakthrough for the industry.
James Lee Fergason was an American inventor and business entrepreneur. A member of the National Inventors Hall of Fame, Fergason is best known for his work on an improved Liquid Crystal Display, or LCD. He held over one hundred U.S. patents at the time of his death.
Edward Peter Raynes FInstP, FRS is Professor of Optoelectronic Engineering at the University of Oxford. He was, and continues to be, an early developer and advocate of liquid crystal displays (LCDs).
The twisted nematic effect (TN-effect) was a main technology breakthrough that made LCDs practical. Unlike earlier displays, TN-cells did not require a current to flow for operation and used low operating voltages suitable for use with batteries. The introduction of TN-effect displays led to their rapid expansion in the display field, quickly pushing out other common technologies like monolithic LEDs and CRTs for most electronics. By the 1990s, TN-effect LCDs were largely universal in portable electronics, although since then, many applications of LCDs adopted alternatives to the TN-effect such as in-plane switching (IPS) or vertical alignment (VA).
Large-screen television technology developed rapidly in the late 1990s and 2000s. Prior to the development of thin-screen technologies, rear-projection television was used for many larger displays, and jumbotron, a non-projection video display technology, was used at stadiums and concerts. Various thin-screen technologies are being developed, but only liquid crystal display (LCD), plasma display (PDP) and Digital Light Processing (DLP) have been released on the public market. However, recently released technologies like organic light-emitting diode (OLED), and not-yet-released technologies like surface-conduction electron-emitter display (SED) or field emission display (FED), are on their way to replacing the first flat-screen technologies in picture quality.
In chemistry and chemical physics, a mesophase is a state of matter intermediate between liquid and solid. Gelatin is a common example of a partially ordered structure in a mesophase. Further, biological structures such as the lipid bilayers of cell membranes are examples of mesophases.
A blue phase mode LCD is a liquid crystal display (LCD) technology that uses highly twisted cholesteric phases in a blue phase. It was first proposed in 2007 to obtain a better display of moving images with, for example, frame rates of 100–120 Hz to improve the temporal response of LCDs. This operational mode for LCDs also does not require anisotropic alignment layers and thus theoretically simplifies the LCD manufacturing process.
There are various classifications of the electro-optical modes of liquid crystal displays (LCDs).
Ferroelectric Liquid Crystal Display (FLCD) is a display technology based on the ferroelectric properties of chiral smectic liquid crystals as proposed in 1980 by Clark and Lagerwall.
Electrically operated display devices have developed from electromechanical systems for display of text, up to all-electronic devices capable of full-motion 3D color graphic displays. Electromagnetic devices, using a solenoid coil to control a visible flag or flap, were the earliest type, and were used for text displays such as stock market prices and arrival/departure display times. The cathode ray tube was the workhorse of text and video display technology for several decades until being displaced by plasma, liquid crystal (LCD), and solid-state devices such as thin-film transistors (TFTs), LEDs and OLEDs. With the advent of metal-oxide-semiconductor field-effect transistors (MOSFETs), integrated circuit (IC) chips, microprocessors, and microelectronic devices, many more individual picture elements ("pixels") could be incorporated into one display device, allowing graphic displays and video.
IPS is a screen technology for liquid-crystal displays (LCDs). It was designed to solve the main limitations of the twisted nematic field effect (TN) matrix LCDs which were prevalent in the late 1980s. These limitations included strong viewing angle dependence and low-quality color reproduction. In-plane switching involves arranging and switching the orientation of the molecules of the liquid crystal (LC) layer between the glass substrates. This is done, essentially, parallel to these glass plates.
Shin-Tson Wu, is an American physicist and inventor of Taiwanese origin. He is currently a Pegasus professor at CREOL, The College of Optics and Photonics, University of Central Florida. Wu's contributions to liquid-crystal research and the resulting patent portfolio for next-generation liquid crystal displays (LCDs), adaptive optics, laser-beam steering, biophotonics, and new photonic materials, have had a major impact on display technology worldwide.
Wolfgang Helfrich is a German physicist and inventor recognized for his contributions to twisted-nematic liquid crystal technology, which is used to produce a variety of modern LCD electronic displays.
Guest Host Displays, Dichroic Displays, Polymer Dispersed Displays
During the 20th century, dichroic dyes had been used as electric field responsive colorants for rugged avionics and armored vehicle electronic displays. In general, dichroic dye displays had more predictable performance than twisted nematic liquid crystal displays or plasma displays, until technological advances in nematic displays surpassed the performance of dichroic dyes.
Photoalignment is a technique for orienting liquid crystals to desired alignment by exposure to polarized light and a photo reactive alignment chemical. It is usually performed by exposing the alignment chemical to polarized light with desired orientation which then aligns the liquid crystal cells or domains to the exposed orientation. The advantages of photoalignment technique over conventional methods are non-contact high quality alignment, reversible alignment and micro-patterning of liquid crystal phases.
Yuriy Reznikov was a Ukrainian physicist, Head of the Department of Crystals at NASU Institute of Physics and a world-renown expert in the field of liquid crystals. He is known for his work on photoalignment, "giant" optical non-linearity of liquid crystals and nano-colloids.
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