by Yan Li with editorial assistance from the Information Display staff
Each year, the Journal of Society for Information Display (JSID) recognizes a published student paper on the basis of originality, significance of results, organization, and clarity. The 2008 award went to "Fast-Response Liquid-Crystal Displays Using Crossed Fringe Fields" by Yan Li, Zhibing Ge, Ruibo Lu, Meizi Jiao, and Professor Shin-Tson Wu from the College of Optics and Photonics at the University of Central Florida.
Many of the major technical problems of liquid-crystal displays (LCDs), such as viewing angle and contrast ratio, had already been addressed to acceptable levels, but the problem of response time, however, still remained. The response time of LCDs is relatively slow, and a slow response time results in unfavorable image blur, especially for moving images.
From left to right: Professor Shin-Tson Wu, Meizi Jiao, Yan Li, and Dr. Zhibing Ge. Dr. Ruibo Lu is not pictured.
During the turn-on process, response time can be improved by using overdrive (i.e., applying a higher driving voltage pulse to generate a stronger electric field), but the turn-off time, which depends mainly on the inherent physical properties of the liquid-crystal materials, is very difficult to reduce. After studying literature describing many different approaches to this problem, the authors redesigned the electrodes of the fringe-field-switching (FFS) LCD device so that over-drive could be utilized during the turn-off process as well as to expedite the LC molecules in restoring their initial orientation. As a result, the decay time was improved by a factor of 2 compared to that of conventional FFS LCDs. Yan and the other team members believed this approach would greatly help make moving images sharper in wide-view FFS LCDs.
The team consisted of Yan Li, a second-year graduate student who is currently working toward her Ph.D. at the College of Optics and Photonics at the University of Central Florida (UCF); Dr. Zhibing Ge, research scientist at UCF; Dr. Ruibo Lu, former research scientist at UCF and current Director of Liquid Crystal Engineering at Pixel Qi; Meizi Jiao, a third-year graduate student at UCF; and thesis advisor Professor Shin-Tson Wu also from the College of Optics and Photonics at UCF.
While initially investigating the subject of slow response time in LCDs, Yan studied approaches such as the use of a thin cell gap with a low-viscosity LC material, the overdrive and undershoot voltage effect, the temperature effect and others. One idea particularly intrigued her: the crossed-field effect from the three-electrode method used in a positive VA cell (first proposed in 1975 by Channin). Based on this approach, Yan came up with the idea of using crossed fringing fields in the wide-view fringing-field-switching mode.
After Yan proposed her idea to Professor Wu, he called together a small group to further explore it. (Yan notes that Prof. Wu always encourages his students to be bold in terms of proposing new ideas.) The team identified the pros and cons of the design and came up with even better solutions.
To verify the concept, Yan and Meizi carried out computer simulations. Each time they faced obstacles, they received encouragement and constructive suggestions from the other team members. Finally, they achieved a 2x improvement in response time by applying an erasing electric field in the crossed direction.
Since this was Yan's first journal publication, Professor Wu asked her to keep in mind the critical ingredients in writing a research paper: organization, clarity, and how to present exciting results. He revised the manuscript eight times before it was finally submitted to JSID for publication. Says Yan, "His philosophy is that when your children and grandchildren read your papers 2–3 decades later, they will still be proud of you."
She adds, "The research group would like to thank the award committee. It is really a great honor for our team to receive this prestigious award." •