A new method to obtain liquid crystal and polymer composite(LCPC) material is reported. This material is a new electro-optic material which can control scattering and transparent states in an electric field. e obtained this material by the photo-polymerization-induced phase separation from liquid crystal and prepolymer mixture where both monomer and oligonier are used as prepolymer. We have found new type of phase diagram in this mixture which has a nematicisotropic line in addition to binodal and spinodal lines. Electro-optic properties of this material are strongly affected by the point on the phase diagram at which the polymerization-induced phase separation starts. This method enables us to control these properties such as voltage-transmittance characteristics. Typical devices using these materials are also shown. They have high contrast ratio and high transmittance in ON state and are suitable for display devices. Drive voltage can be reduced by optimizing this material and the device with
high contrast ratio about 200:1 in low drive voltage below 6Vrms was obtained.
Polymer-dispersed liquid crystal (PDLC) films are useful in electro-optic applications because they can
be switched electrically between opaque and transparent states. We have prepared PDLC films using
electron-beam radiation (e-beam cure). The resulting films exhibit promising mechanical, electro-optic,
and thermal response. Compared with the ultraviolet cure process, e-beam cure has the advantage of not
requiring photoinitiators. In addition, e-beam cure is characterized by a fast cure rate. The e-beam cure
method may, therefore, be a good candidate for production of PDLC ifims.
We have measured the dielectric response of PDLC films containing liquid crystal droplets of E7 in
a polymethylmethacrylate (PMMA) matrix as a function of frequency (0-10KHz) and temperature
(25°C-11O°C). The liquid crystal composition of the films was varied from 0% to 60%. A principal
objective of this study was to understand the dissipation mechanisms in these systems in an effort to
control and reduce them.
In the light of the experimental results, we discuss the primary dissipation mechanisms, including
both DC and AC losses. The major contribution to the losses in these materials comes from the liquid
crystal conductivity. Quantitative interpretation of the results can be clouded by a number of factors
including incomplete phase separation of the liquid crystal and polymer, percolation effects and a
frequency-dependent conductivity due to charge-carrier depletion in the liquid crystal droplets. Using
simple two-phase composite formuli to model the dielectric behavior, the contributions of the real and
imaginary parts of the dielectric constant to the field inside a droplet are discussed. The model agrees
quantitatively with capacitance experiments, indicating that for frequencies below 100 Hz the field
inside of a droplet is strongly modified by charge built up at the droplet/polymer interface.
Control over the operating voltage of nematic droplet/polymer films continues to be an important area of
development in this class of devices. Our recent work in this area has included both materials modifications in order to
alter the reorientation voltages of these films, as well as efforts to tie theory to experimental results. Here, we present
evidence which shows that the shape of nematic droplets in these films is important in determining the operating
voltage of a film. Specifically, we show two film systems in which the nematic droplets adopt the shape of oblate spheroids,
but differ in the amount of eccentricity of the droplets. The more distorted droplets require higher reorientation
fields, consistent with the model of the volume elastic deformation free energy as a major factor affecting the
reorientation fields of these films.
We also demonstrate that the apparent operating voltage of a film depends on which property of the film is being
measured. Measurements based on film scattering, dichroism, and capacitance are presented, and the implications of
these measurements with regards to apparent film operating voltages discussed.
Chemically stable , wide temperature range nematic liquid crystal mixtures with
birefringence values up to almost 0 .3 are described . For applications where
high ultra-violet stability is required a range of mixtures optirnised for this
application have been developed. Chemically stable mixtures with a lc*i
threshold voltage have also been developed and are compared with standard
This paper presents the production of the a reverse-mode microdroplet liquid
crystal (RMLC) light shutter display. In this unit, the display is formed by a thin
polymer film with dispersed liquid crystal microdroplets. The display is light
transmissive in the absence of an applied electrical field. The display is converted to a
non-transmissive state (i.e. absorbing or scattering) when an electrical field is applied.
The "off' and "on" state. of this display are thus exactly opposite to that encountered in
"normal-mode" microdroplet liquid crystal display devices such as polymer dispersed
liquid crystals (PDLC)15 or Nematic Curvilinear Aligned Phase (NCAP)6.
The Reverse Mode Microdroplet Liquid Crystal is obtained by modification of
the surface energy of the polymer which encases liquid crystals via reaction of a dopant
incorporated inside of the microdroplet during the droplet formation within the inside
polymer layer. The liquid crystal used in RMLC is of negative dielectric anisotropy.
We have microscopically observed the texture of very large droplets of
chiral liquid crystal in a polymer matrix under the influence of an electric
field. The dielectric anisotropy of the liquid crystal is negative and the
pitch is made very long so that a fingerprint-like texture can be observed
within the droplet. Without the field, the droplets appear to be in a
spherulite texture: the helical axis lies everywhere along a radius and a
disclination line extends from the center to the periphery of the droplet. As
an electric field is applied, the droplet undergoes a transition to the planar
texture, the texture first occurring near the center of the droplet and
increasing in radius as the field is increased. The zero-field texture will
be discussed in terms of the Frank-Pryce spherulite model. Implication for a
polymer-dispersed chiral liquid crystal (PDCLC) display will be reviewed.
The molecular anchoring strength for the liquid crystal E7 (EM Chemicals) confined to
spherical cavities dispersed in the polyurethane TU5OA (CONAP) is measured. The anchoring
strength values result from a study of the radial-to-axial configuration transition when
perpendicular anchoring conditions exist at the polymer/liquid crystal interface. This transition is
also a function of droplet radius, temperature, and the strength of any external fields present. A
study of field-induced configuration transitions provides values for the reduced local electric fields
inside droplets. Computer simulated pictures of nematic droplets are formed to identify director
Polymer dispersed liquid crystal (PDLC) devices modulate light through electrically controlled light
scattering. Colored PDLCs are formed by incorporation ofdichroic dyes. The efficiency ofthe dichroic dye,
PDLC films depend on the scattering efficiency of the films, the dichroic ratio of the dichroic dye, the order
parameter ofthe dichroic dye in the liquid crystal used, and the fraction ofdye dissolved in the liquid crystal
droplets. The efficiency of these films can be measured using a UV/visible spectrometer. Incorporation of
dichroic dye in the PDLC film increases the refractive indices of the liquid crystal droplet affecting the
scattering efficiency ofthe PDLC film.
Liquid crystalline materials with high optical anisotropy are of great interest for many electrooptical devices, such
as STN and 2'-Mithmum Active Matrix Displays. Use of these materials leads to improved response times by
using smaller cell gaps as well as enhanced contrast.
As standard materials for achieving high optical anisotropy cyanobiphenyls and cyanoterphenyls are used at
present. The demand for materials with lower viscosity as well as improved stability and resistivity has led us to
develop new materials to meet these requirements.
Introduction offluorine and fluorine containing substituents (CF3, OCF3, OCHF2) in terminal position ofhigh nstructures
leads to new liquid crystals with high positive dielectiic anisotropy and good stability. Also liquid
crystals with negative dielectñ anisotropy can be obtained by the incorporation of an 2,3-difluoro-l,4-phenylene
A full-color miniature light valve is being investigated for
display applications. The light valve is based on a subtractive
rather than an additive approach to color mixture. In utilizing
a subtractive color approach, a full-color information display is
created using a single broadband light source whose energy passes
through a stack of three thin liquid crystal cells. Each cell
contains a different dichroic dye (e.g. cyan, magenta, and yellow)
in a guest/host arrangement with the liquid crystal medium. Each
dichroic guest/host liquid crystal cell constitutes an electronic
color filter, switchable by the application of an appropriate
voltage across the two plates of the cell. In one extreme state,
the cells simply pass all spectral components of the light, while
in the other extreme state the spectral composition of light
passing through the cells is altered by the particular dichroic dye
so that the complementary color of the dye is blocked or subtracted
from passage through the cell. Voltages between the extremes
produce the gradations in spectral throughput required for fullcolor
operation. The achievable color gamut will be approximately
equal to a shadow-mask color CRT. With a pixel addressing
mechanism in each of the cells, a full color information display
is created with complete color control at each individual pixel.
Ferroelectric liquid-crystal gray-scale effects are reviewed. The experimental behavior of a charge-controlled surfacestabilized
ferroelectric liquid crystal pixel of area 1 mm2 is reported. Obliquely evaporated silicon-oxide alignment is
compared with rubbed-nylon alignment. The experimental behavior of a deformable helix ferroelectric liquid crystal cell
The recent development of large multiplex and active matrix liquid crystal displays (LCD's) has increased the need for
efficient automation. Spacing and plate-to-plate alignment control both have to be improved and cost effective production
of these high information content systems requires efficient processing and high yields. Yield is dependent on process and
contamination control and can only be effectively improved by process development and automation.
While automation is necessary, a key problem is designing the production facility to be cost effective. This has been
achieved in the past by producing large quantities of the same product in order to avoid costs associated with changing
machine set-ups. The array process for standard LCD's was developed to minimise handling costs and to minimise
investment by designing the production line to work with one substrate size. This system allows production of different
sizes and styles of product within the line substrate size limitation, the major constraint being efficiency of fit. Substrate
handling problems and tighter process control requirements now require the development of standardised systems to cope
with the large substrate sizes.
The design of automated LCD production equipment is discussed in relation to the problems of automating in a cost
This paper reports on a study of the three basic parameters involved in bonding heat
seal connectors to flat panel displays. Those parameters are: temperature. at the bond,
pressure at the bond, and the time that the temperature and pressure are applied to the
The background color of a TN LCD is one of the important issues of the liquid crystal flat panel display technology,
especially as the panel size gets bigger and the displayed information content gets larger. Therefore, in the first part
of this paper, we carried out (1) a theoretical calculation of the color coordinates as a function of And for the range
of the ind from 0. 1 jm to 2.0 jtm, which cover the first, second, and third Gooch and Tarry minima; and (2) theoretical
calculations for the color coordinates as a function of viewing angle near the first, second and third Gooch
and Tarry minima. Our experimental results corresponding to the above two cases will also be presented for cornparison.
Our data shows that our theoretical results agree reasonably well with the experimental ones. In the second
part of this paper, we will use the above experimentally verified theoretical method to study and compare the color
quality of the single-gap NB mode, the multi-gap NB mode, and the NW mode LCDs. The result will provide
important information for LCD design and the selection of a mode of operation.
In tilted smectic phases C Sm C, Sm 1, Sm F and Sm / ) consisting of
polar non-centrosymmetric molecules, a pronounced contribution to the dielectric
permittivity is observed, which can be assigned to the Goldstone mode. It is a
collective process showing a non-Arrhenius type behaviour in the temperature
dependence of the relaxation time . By applying a bias electrical field, which is
strong enough to unwind the helix, the Goldstone mode contribution can be suppressed
. In all smectic phases there are high frequency relaxations arising from
the principal molecular motions, i. e. from the reorientations about the long and
short molecular axes. In the vicinity of the Sm A* Sm C* phase transition the
so-called soft mode appears obeying Curie-Weiss behavior of the dielectric increment.
Application aspects of different chiral smectics will be discussed in view of
the different relaxation mechanisms by taking the recent experimental studies into