Institut Jozef Stefan

Kent State University

Other

Institut Josef Stefan

Janez Pirs

Bojan Marin

Robert Blinc

Silvija Pirs

Silva Pirs

Joseph W Doane

Igor Musevic

Slobodan Zumer

Matej Bazec

Dusan Ponikvar

Andrej Vrecko

Rok Petkovsek

Martin Copic

Bernarda Urankar

Sivija Pirs

A new concept of the LCD light-switching optical filter allowing for very high, electrically controlled, continuously variable light attenuation (up to &#x2267;100,000) optimized/symmetrized for the light incidence along the normal to the LCD plane is proposed. The new LCD light-switching optical filter also exhibits very low light attenuation dependence for the oblique incidence of light within a limited cone of angles off the normal incidence direction in compliance with the international safety and quality regulation EN 379 for personal protection equipment. According to the invention the problem is solved by specific, novel modification of the general principle of highly twisted nematic LCDs, allowing for the adaptation of the light transmission/driving voltage characteristics to specific requirements of the driving electronics as well as 'symmetrizing' the overall optical birefringent properties, which in turn results in a high degree of their angular compensation.

Variable contrast, wide viewing angle LCD light-switching filter

A new concept of the LCD light-switching optical filter allowing for very high, electrically controlled, continuously variable light attenuation (up to &#x2267;100.000) optimized/symmetrized for the light incidence along the normal to the LCD plane is proposed. The new LCD light-switching optical filter also exhibits very low light attenuation dependence for the oblique incidence of light within a limited cone of angles off the normal incidence direction in compliance with the international safety and quality regulation EN 379 for personal protection equipment. According to the invention the problem is solved by specific, novel modification of the general principle of highly twisted nematic LCDs, allowing for the adaptation of the light transmission/driving voltage characteristics to specific requirements of the driving electronics as well as 'symmetrizing' the overall optical birefringent properties, which in turn results in a high degree of their angular compensation.

Variable contrast, wide viewing angle liquid crystal light attenuation filter

A new concept of the normally open LCD light switching element is proposed, which allows for the superior angular compensation for the light attenuation by using a single simple negative bireffingent c-plate compensation layer. The concept is based on the simultaneous use of highly angularly symmetric STN LC-configuration (preferably 180&#xb0; twist) and maximal use of the single (preferably ordinary ray) light propagation mode. The solution is best suitable for various light switching applications like LCD automatic protective welding light filters, as well as for multi-segment large display panels, where it provides for excellent uniformity of the light-attenuation in the 'dark' state.

High contrast, wide viewing angle LCD light-switching element

This invention solves the technical problem of compensating for the angular dependence of the contrast in optical devices comprising liquid crystal displays (LC optical light shutters, which operate on the principle of electrically controlled optical birefringence), with the aid of a compensation layer exhibiting optically negative birefringence, which enables the angular compensation of the LC layer birefringence in the state in which the LC molecules are homeotropically aligned (typical optically positive birefringence). The process for the manufacture of the optically negatively birefringent compensation layer is devised on the controlled spontaneous deformation of the polymer molecules during the polymerization procedure. The manufacturing process is feasible by the employment of known and well-controllable technical procedures, and enables the mass production of compensation layers. The invention solves the problem of manufacturing a compensation layer exhibiting the required optically negative birefringence, as well as the construction/manufacturing of the optical light shutter, which utilizes such a compensation film.

Process for the manufacturing of the polymer compensation layer for LCD optical light shutter and the construction thereof

The invention relates to the problem of the driving of the LCD electrooptic-switching element () with alternating, square-wave electric signals, the amplitude of witch can vary between different voltage levels in correspondence with the actual functioning state of the LCD electrooptic-switching element. The polarity changes of the electric driving signals is controlled by the integrator (), integrating the difference of the electric potentials on the driving electrodes () of the LCD electrooptic-switching element, in such a way that the value of time integral of the driving electric field is always kept within a selected interval. Besides this the time dependence of the electric driving signals can be optionally modified so that with every change of the polarity of the electric driving signals, the potentials on both driving electrodes get the same value for a time, which is significantly shorter than the switching time of the LCD electrooptic switching element.

Driving scheme and electronic circuitry for the LCD electrooptical switching element

An oriented ferroelectric liquid crystal in the chiral smectic C phase with the smectic planes normal to bounding plates of a cell is interspersed with polymer which stabilizes and freezes the arrangement of the liquid crystal. The polymer which stabilizes the liquid crystal is formed by a method which includes introducing a mixture of a monomer and a ferroelectric liquid crystal between cell walls when the liquid crystal is in the isotropic phase, cooling the liquid crystal to a chiral nematic or smectic phase, and polymerizing the monomer. The cooling of the mixture can be done in the presence of a magnetic or electric field.

Method of making a ferroelectric liquid crystal cell including a cooling

An oriented ferroelectric liquid crystal in the chiral smectic C phase with the smectic planes normal to bounding plates of a cell is interspersed with polymer which stabilizes and freezes the arrangement of the liquid crystal.

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Ljubljana, Slovenia

Janez Pirs