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13 results on '"Desimpel, C."'

1. Lateral ion transport in nematic liquid-crystal devices.

Author

Neyts, K., Vermael, S., Desimpel, C., Stojmenovik, G., Verschueren, A.R.M., de Boer, D.K.G., Snijkers, R., Machiels, P., and van Brandenburg, A.

Subjects
LIQUID crystals, INFORMATION display systems, ELECTRIC fields
Abstract

Reports on liquid crystals used in electronic displays which usually contain small amounts of ions that move under the influence of the varying applied electric field. Modified electric fields resulting in image sticking effects from the motion of ions perpendicular to the substrates; Image sticking effects near the pixel edge observed in supertwisted nematic cells.

Published
2003
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2. Vloeibaar-kristaltoepassingen met in-het-vlak draaiende director

Author

Desimpel, C and Neyts, K

Abstract

Vloeibare kristallen zijn een veel gebruikt materiaal in tal van optische toepassingen door een aantal unieke eigenschappen. Ze zijn optisch dubbelbrekend en kunnen door hun elektrisch anisotropie op eenvoudige wijze geschakeld worden met behulp van elektrische of magnetische velden. De meest bekende toepassing is het vloeibaar-kristalbeeldscherm of Liquid Crystal Display (LCD). Het onderzoek van Chris Desimpel is begonnen als een studie van de optische eigenschappen van LCD’s met als belangrijkste aandachtspunt de in-het-vlak draaiende of in-plane switching (ips) mode. In de ips-mode wordt de gemiddelde richting van de moleculen in het vloeibaar kristal gedraaid in een vlak parallel met de substraten. Doorheen het doctoraat komt zowel modellering, optica als technologie van vloeibare kristallen aan bod. Na een inleiding tot vloeibare kristallen wordt aandacht besteed aan verschillende optische algoritmes die gebruikt worden om de transmissie doorheen vloeibare kristallen te berekenen. Vervolgens gaat het doctoraat dieper in op de oppervlakteverankering van vloeibare kristallen, een belangrijk aspect bij toepassingen. Gebruik makend van de ips-mode is uiteindelijk een nieuw vloeibaar-kristalcomponent ontwikkeld met een aantal opvallende eigenschappen.

Published
2006

5. A four-electrode liquid crystal device for 2 pi in-plane director rotation

Author

UCL, Desimpel, C., Beeckman, J., Desmet, H., Neyts, K., James, R., Fernandez, F. A., UCL, Desimpel, C., Beeckman, J., Desmet, H., Neyts, K., James, R., and Fernandez, F. A.

Abstract

A novel type of liquid crystal device is described, based on a four-electrode unit, arranged in a hexagonal array. Full three-dimensional simulations were performed using a finite elements algorithm demonstrating a 2 pi rotation of the director in the plane parallel to the substrate surface. Applications for the device are situated in the field of multistable wave plates, spatial light modulators and electrically controllable anchoring.

Published
2005

6. Lateral ion transport in nematic liquid-crystal devices

Author

Neyts, Kristiaan, Vermael, S., Desimpel, C., Stojmenovik, G., Verschueren, A.R.M., De Boer, D.K.G., Snijkers, R., Machiels, P., Van Brandenburg, A., Neyts, Kristiaan, Vermael, S., Desimpel, C., Stojmenovik, G., Verschueren, A.R.M., De Boer, D.K.G., Snijkers, R., Machiels, P., and Van Brandenburg, A.

Abstract

The lateral ion transport in nematic liquid-crystal devices was studied. It was observed that the liquid crystals used in electronic displays contains small amount of ions that move under the influence of the varying applied electric field. It was found that the modulation in the director tilt angle could lead to a net residual lateral component of the ion motion parallel with the glass plates.

Published
2003

7. Ion currents in in-plane switching liquid crystal displays

Author

Vermael, Stefaan, Stojmenovik, G., Desimpel, C., Adamski, A., Neyts, Kristiaan, De Boer, D.K.G., Vermael, Stefaan, Stojmenovik, G., Desimpel, C., Adamski, A., Neyts, Kristiaan, and De Boer, D.K.G.

Abstract

In liquid crystal (LC) devices where the electrode structure has a microscopic pattern, as in In-Plane-Switching (IPS), ion transport is essentially two-dimensional. In this paper we report the measurements of ion transport currents in IPS devices. The time dependency of these currents is explained qualitatively.

Published
2002

8. The non-uniform theory simulations of the continuous director rotation mode of FLCD's

Author

Adamski, A., Pauwels, H., Neyts, Kristiaan, Desimpel, C., Stojmenovik, G., Vermael, S., Adamski, A., Pauwels, H., Neyts, Kristiaan, Desimpel, C., Stojmenovik, G., and Vermael, S.

Abstract

We introduce the theoretical model of LC material with the phase sequence I-N*-SmC* as a material having suitable properties for multimedia applications (fast speed, high contrast and full grey scale capabilities). We present the structure and investigate the switching and the optical response of the device taking into account material and technological parameters. We explain the mechanism of the continuous switching mode and prove the ability of using grey levels.

Published
2002

9. Two-dimensional Monte Carlo based ion transport algorithm in liquid crystals

Author

Vermael, Stefaan, Neyts, Kristiaan, Desimpel, C., De Boer, D.K.G., Day, S.E., Fernandez, A.F., Trwoga, P.F., Lanowith, F., Vermael, Stefaan, Neyts, Kristiaan, Desimpel, C., De Boer, D.K.G., Day, S.E., Fernandez, A.F., Trwoga, P.F., and Lanowith, F.

Abstract

The two-dimensional Monte Carlo based ion transport algorithm for calculating ionic transport in liquid crystals were described. The Monte Carlo based algorithms calculates the position of 'meta-ions' by using the principles of drift and diffusion. It was found that the downward electrical field attracts the meta-ions towards the negative electrode.

Published
2001

10. Polarization state of the diffraction peaks in in-plane switching cells

Author

Desimpel, C., Neyts, Kristiaan, Janevska, I., Gjurcinovski, A., De Boer, D.K.G., Cortie, R., Desimpel, C., Neyts, Kristiaan, Janevska, I., Gjurcinovski, A., De Boer, D.K.G., and Cortie, R.

Abstract

In-Plane Switching LCD's are an example of microscopic 2-dimensional structures. Because of their inherent periodicity in the cell structure, an incoming plane wave is split up in several diffraction orders. Our goal is to determine the polarization state of these different peaks and compare them with numerical simulations.

Published
2001

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