OCDIS: Optical compensation for displays

• Research unit: EU RFP
• Project number: 99.0266-1

Key words (English)

Liquid crystal displays; viewing angle enhancement; compensation films

Alternative project number (English)

EU project number: IST-1999-12085

Research programs (English)

EU-programme: 5. Frame Research Programme - 1.2.4 Essential technologies and infrastructures

Short description (English)

See abstract

Partners and International Organizations (English)

Coordinator: Thomson CSF (F)

Abstract (English)

The objective of the 'OCDIS' project is to develop technologies which allow to improve the optical performance of different types of liquid crystal displays (LCDs) on the basis of specifically designed birefringent compensation films. Two competing technological approaches are applied in comparison: holographic retarders (Thales R&T) and linearly photopolymerized polymer / liquid crystal polymer (LPP/LCP) technology (ROLIC Research Ltd.). Besides the technology providers there are two end users participating in the project, Thales LCD and Optrex Europe, both are display manufacturers. Each of the end user partners specified an LCD type to be improved with the novel films: Thales LCD chose active matrix TN (twisted nematic) displays for avionic applications and Optrex Europe decided on DSTN (double supertwisted nematic) displays for automotive applications. Vantico AG as the producer and distributor of ROLIC´s LPP/ LCP materials represents the fifth project partner.
The introductory task within the first year (2000) of the project concentrated on defining the target specifications of the optical performance for both the compensated TN and DSTN displays. The specifications included the viewing angle dependency of the contrast ratio, the tolerable color shifts under specific viewing angles and the desired gray level stability (for TN displays only). Subsequently, extensive computer simulations were performed by ROLIC and Thales R&T (each taking into account the specific parameters of their technology) to find the optimum material and design parameters of the compensation films. From the results of the simulations a number of compensator configurations were proposed, all of which theoretically met the specified targets. In a second step the experimental realization of compensation films with the chosen configuration was started. At the end of the first year a set of samples which were prepared on 2.5x2.5 cm2 glass substrates were provided to the display manufacturers.
At the beginning of the second year (2001) Optrex Europe and Thales LCD characterized the first compensation film samples in combination with the repective displays. The characterization met the theoretical expectations except for minor deviations. In accordance with the original schedule the next working step would have been the preparation of compensation films on plastic subtrates. To shorten the time required to realize large area demonstration displays which allow better visual inspection of the compensation performance the partners agreed to prepare 7x7 cm2 samples on thin glass substrates as an additional, intermediate step. During the preparation of this second set of samples the characterization and preparation methods were further improved to fully meet the desired properties and to remedy the remaining deviations from the simulation results. The subsequent characterization of the large area samples by the display manufacturers confirmed the superior optical performance of ROLIC's compensators compared with commercial compensators. In parallel, the technology providing companies worked successfully on the adaption of the process parameters for coating of the birefringent films on plastic substrates.
Because the holographic retarders did not improve DSTN displays significantly, the holographic project part of Thales R&T was stopped for DSTN-compensation.
Until the end of the project at the 31st of June 2002 large area compensation films on plastic substrates will be manufactured and integrated in demonstration displays. These will be utilized by the display producers to convince their customers of the benefits of the novel LCD compensation technologies.

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: 99.0266-1