Liquid Crystals, 2000 , Vol. 27, No. 3, 365±370
Electrically controlled director slippage over a photosensitive
aligning surface; in-plane sliding mode
DENIS ANDRIENKO†‡, FRANCOES BARBET§, DENIS BORMANN§,
YURIY KURIOZ†, SOON-BUM KWON¶, YURIY REZNIKOV†*
and MARK WARENGHEM§
†Institute of Physics, National Academy of Sciences, Prospect Nauki 46,
Kyiv 252022, Ukraine
‡H. H. Wills Physics Laboratory, University of Bristol, Royal Fort,
Tyndall Avenue, Bristol BS8 1TL, UK
§Laboratoire de Physicochimie des Interfaces et Applications, Universite ´ d’Artois,
Faculte ´ Jean Perrin, SP 18, rue Jean Souvraz, 62307 LENS Cedex, France
¶LCD Lab. of LG LCD Inc., 533 Hogae-dong, Dongan-gu, Anyang-shi,
Kyongki-do, 431-080, Korea
(Received 12 July 1999; accepted 15 October 1999 )
We have studied the electro-optical characteristics of a homogeneously aligned nematic liquid
crystal (LC) with weak planar anchoring of the director at the bounding substrates. By using
the in-plane switching (IPS) of the LC which is achieved by an in-plane electric eld, the
driving voltage was conrmed to be far less than that of the conventional IPS mode in which
both substrates possess strong anchoring characteristics. Moreover, because of the absence of
strong subsurface director deformations, the cell could operate optically in the Mauguin
regime. Using these features we propose a new type of LC switching mode—in-plane sliding
(IPSL) mode. We have realized this mode in a LC cell comprising one reference substrate
with strong director anchoring and one substrate covered with photoaligning material with
weak anchoring. In order to clarify the switching process, we derived a simplied expression
for the threshold voltage on the assumption of uniformity of the in-plane electric eld. For
the dynamical response of the LC to the in-plane electric eld, the switching on and o
relaxation times of the IPSL mode were found to be longer than for the traditional IPS
mode. However, we have proposed an optimized cell geometry for the IPSL mode with a
response time comparable to that of the IPS mode.
1. Introduction to the increased transmission in the dark state. The
The electro-optical characteristics of liquid crystals multi-domain mode devices also require a complicated
(LCs) have made them one of the most promising process in the manufacturing stage. For the phase com-
materials for practical applications in displays. A variety pensated devices it is di
cult to maintain stable control
of principles of LC displays have been proposed. They using a bias voltage.
di
er in the type of reorientation modes and design of One feasible method to solve these problems has been
the LC cell. Twisted nematic (TN) [1] and super-twisted proposed quite recently [6–12]. The idea was to use the
nematic (STN) [2] cells have been much used in practice, in-plane switching (IPS) mode. In this mode the nematic
but the viewing angle characteristics have been recognized LC is aligned homogeneously between the aligning
as a major weakness of the TN and STN based devices. substrates. Both substrates were covered with polymer
An increasing number of approaches have been tried material that provides strong anchoring of the LC.
to overcome this drawback. The most promising involve Interdigital comb shaped electrodes are placed onto one
compensation of the optical phase retardation [3] and of the substrates. The director at the initial stage (without
the multi-domain technique [4, 5]. Averaging the trans- the electric eld) coincides with the polarization axis of
mission of each domain, one can improve the viewing the polarizer. The polarizer and analyser are set at right
angle characteristics, but a decrease in the contrast ratio angles to each other, so the conguration forms the
for oblique viewing could not be prevented and is due black state when no electric eld is applied.
By applying the in-plane electric eld, the director
gradually deviates from the polarization axis while *Author for correspondence; e-mail: yuri@iop.kiev.ua
L iquid Crystals ISSN 0267-8292 print/ISSN 1366-5855 online © 2000 Taylor & Francis Ltd
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