SALC-NET: Liquid crystals - Surface properties from basic to applications

• Research unit: EU RFP
• Project number: 98.0063

Key words (English)

Liquid crystal; liquid crystal display; photo alignment; orientation; surfaces; surface treatments; bistability

Alternative project number (English)

EU project number: BRRT-CT97-5003

Research programs (English)

EU-programme: 4. Frame Research Programme - 2.1 Industrial and materials technologies

Short description (English)

See abstract

Partners and International Organizations (English)

Calpark (I), INFM (I), Thomson-CSF (F), REOSC (F), MOD (UK), UPS.LPS (F), CNRS.CRPP (F), MPG (D), TECDIS (I), THDAR.IAP (D), USTRAT (UK)

Abstract (English)

All of today's field effect Liquid Crystal Displays (LCDs) require alignment of liquid crystal molecules at the display boundaries. The market for flat panel displays is dominated by LCDs which are based on the twisted nematic field effect (TN-LCDs). For optimising the performance of TN-LCDs, optical compensations films which improve their field of view are key. Optical compensation films are based on Liquid Crystal Polymer (LCP) films which broaden the field of view of flat computer monitors and television screens. Control of the anchoring forces between the liquid crystal molecules at the surface and those in the bulk determine display performance as well as the performance of optical compensation films. The role of SALC-NET, a thematic network, is to provide a platform to establish contacts between academic and industrial laboratories investigating interactions between liquid crystal molecules and surfaces. Many of the results obtained by the different groups within this network further advance the LCD technology and enable novel applications in the future. Therefore, and due to pending patents, most of the information is confidential and cannot be published at this stage.At the annual plenary meeting in Moena (Italy) in March 2001, ROLIC gave a presentation entitled 'Director Distributions in Liquid Crystal Polymer-Films' illustrating the potential of ROLIC's LPP/LCP photo-aligning technology (LPP: Linear Photo-Polymerization). LPP-photo-alignment enables generating any bias tilt and any azimuthal angle distribution in monomeric or polymeric liquid crystal films. Moreover, with its high optical resolution and its capability to generate azimuthal LC-alignment patterns and multi-domain LCDs have become feasible. For the first time arbitrary tilt angle distributions are achieved. Moreover, control of the tilt distribution within thin LCP-films on single substrates was shown to be essential for many applications, for instance for the design of novel LPP/LCP wide-view films for computer monitors or displays for airplane cockpits.Apart from ROLIC's contribution the following highlights were presented in Moena :- The concept of anchoring competition which was first introduced within this SALC-NET project is now generally accepted by the scientific community. It illustrates the possibility to modify LC alignment by two subsequent surface treatments exhibiting different anchoring interactions.- Several solutions to achieve very weak surface anchoring were presented. For example via slippery surfaces by DERA, via surface passivation by the ORSAY-Group, via polymer coating with polymerisation gradients by the COSENZA-Group.- New photopolymers for weak as well as strong photo-alignment of LCs (ROLIC and THALES).- Banana shaped mesogenic molecules with improved thermal stability and lower phase transition temperatures (CRPP).- Surface treatment based on the use of silane coupling agents to get rid of anchoring memory (NEMOPTIC).- The following demonstrators were presented: i) a 5 x 5 cm auto-stereoscopic display (DARMSTADT University); ii) a truly bi-stable nematic demonstrator (TECDIS and COSENZA-Group); iii) a zenithal bi-stable nematic display by DERA.

References in databases (English)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 98.0063