Conducting substrate, liquid crystal device made therefrom and liquid crystalline composition in contact therewith

Conducting substrate for use in display device having a conducting polymer on the surface of a rigid or flexible, flat, curved or bent substrate.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to conducting substrates for use in, e.g., 
liquid crystalline devices, to liquid crystalline devices comprising 
conducting substrates and to liquid crystalline compositions in contact 
with conducting substrates. 
2. Discussion of the Background 
Liquid crystalline-based display devices generally rely upon the 
application of an electrical field to a liquid crystalline compound or 
liquid crystalline composition. This electric field is typically generated 
by using substrates which encase the liquid crystalline 
compound/composition and which have on their surface a conducting layer of 
indium tin oxide (ITO). The substrates typically are made of glass and 
have a thin layer of ITO coated directly thereon. Common liquid 
crystalline devices in use today comprise two such substrates coated with 
ITO and having a liquid crystalline compound/composition sandwiched 
therebetween. When a voltage is applied to the conducting surfaces of the 
substrates the electric field passing through the liquid crystal 
compound/composition exerts an orienting effect which can block or 
transmit light passing through the liquid crystalline compound/composition 
depending upon the particular characteristics of the given device. 
The fabrication of ITO coatings on, e.g., glass is carried out at 
temperatures on the order of 250.degree. C. in order to provide an 
acceptably short deposition time. While this process has received wide 
acceptance, a serious problem is encountered when relatively low melting 
point materials (e.g., polymers, etc.) are to be used as a base for 
conducting substrates. Further, ITO coatings on e.g., flexible substrates 
are brittle, and they fail by, e.g., cracking when the substrate on which 
it is deposited is purposefully flexed or bent, or when the substrate 
undergoes dimensional change due to thermal gradients, etc. While 
conducting polymers have been mentioned as candidates for substrates this 
has never been realized. See Cao et al, App. Phys. Lett 60, 271, 1992. 
SUMMARY OF THE INVENTION 
Accordingly, one object of this invention is to provide a novel electrode 
substrate for use in display devices such as liquid crystalline display 
devices, electrochromic display devices, etc. which are flexible, bendable 
and/or which may be provided in various curved shapes while avoiding the 
problems encountered with ITO coatings. 
Another object of this invention is to provide colored or transparent, 
preferably transparent, films of conducting polymers on substrate bases so 
as to provide conducting electrode substrates for use in display devices, 
etc. 
Another object of this invention is to provide a method for preparing 
lightweight, transparent or colored electrode substrates comprising a 
layer of conducting polymer at low cost using room temperature processing 
and simple manufacturing steps such as dipping or coating from solution. 
Another object of this invention is to provide a curved and/or flexible 
display device having flat and/or curved surfaces for use in automobile 
windshields and moon/sun roofs, aircraft canopies, helmet visors, 
television screens, etc.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention, which relates to conducting substrates and their use 
in display devices such as liquid crystal devices, comprises a substrate, 
which may be made of any material, and which is coated with a layer of 
conducting polymer. The conducting substrates are useful as electrodes in 
display devices. The substrate is preferably one capable of maintaining 
its shape at temperatures of 100.degree. C. and greater and may be 
transparent, translucent or opaque, and may be colored or colorless. 
Preferably, the substrate is flexible and/or curved and may be made of 
glass or plastic, preferably silica glass, pyrex glass, 
poly(ethyleneterephthalate) (PET), Mylar, 
hexafluoropropylene-co-tetrafluoroethylene (fluorinated ethylene propylene 
or FEP), poly(meth)-C.sub.1 -C.sub.16 acrylate, poly(meth)acrylic acid, 
polyethers, polyethyleneoxide, polycarbonates, polyimines, polyamines, 
polyesters etc. Alternatively, the substrate may be bent. Bendable 
materials useful as substrates in the present invention include metals 
such as copper, aluminum, etc., glass, etc. If the substrate is 
electrically conducting, an insulating material such as a non-conductive 
polymer may be placed between the substrate and the conducting polymer. 
The substrate may be of any thickness, such as, for example 
1.times.10.sup.-8 cm-1 cm including all values in between and all ranges 
therebetween. Thicker and thinner layers may be used. The substrate need 
not have a uniform thickness. The preferred shape is square or 
rectangular, although any shape may be used. Before the substrate is 
coated with conducting polymer it may be physically and/or optically 
patterned, for example by rubbing, by the application of an image, by the 
application of patterned electrical contact areas, by the presence of one 
or more colors in distinct regions, etc., or may be treated by radio 
frequency glow discharge treatment, etc. 
The conducting electrode substrates of the present invention further 
comprise an electrically conducting polymer on a surface of the substrate. 
The conducting polymer is a layer deposited directly on the substrate 
and/or deposited on any material which has first been applied to the 
substrate. The term "on a surface of the substrate" as used herein refers 
to both situations. Any thickness of conducting polymer can be used. 
Preferably, the conducting polymer is formed as a layer having a thickness 
of from 1-1000 nanometers, more preferably 5-100 nm including all values 
and ranges therebetween. The conducting polymer layer need not form an 
integral whole, need not have a uniform thickness and need not be 
contiguous with the base substrate. In fact, in a preferred embodiment, 
the conducting polymer layer is formed in a pattern on the substrate base. 
The invention conducting electrode comprising a substrate base and a layer 
of conducting polymer may be formed into any desired shape. As shown in 
FIG. 1, the generally planar electrode substrate 1 (shown in 
cross-section) may be curved in any manner desirable. The curvature of the 
substrate can be characterized by a radius of curvature r, depicted in 
FIG. 1. r may have any value since the electrode substrates according to 
the present invention may be flat or may be curved to any desired degree. 
Preferred values of r are from 0.01 mm-1,000 mm, including all values 
therebetween and all ranges therebetween. In addition, the electrode 
substrates according to the present invention may be bent so as to form an 
angle. As shown in FIG. 2 this angle (.alpha.) may be any angle of from 
0.degree.-360.degree., including all angles therebetween and all ranges 
therebetween. In both FIGS. 2a and 2b the substrate 1 has, on the surface 
indicated by the arrow, a conducting polymer layer. The conducting 
electrode substrates of the present invention are not limited to articles 
of manufacture wherein a substrate has on only one of its surfaces a 
conducting polymer but includes conducting electrodes wherein a base 
substrate has conducting polymer on more than one surface thereof. For 
example, a conducting electrode according to the invention could be 
prepared where a base substrate is coated with conducting polymer on the 
side to which the arrow points in FIG. 1 as well as to the opposite side. 
The conducting polymer layer of the present invention preferably comprises 
aniline, pyrrole, thiophene, dithiophene, etc., monomers, and is 
preferably a homopolymer of these monomers (polyaniline, polypyrrole, 
polythiophene, polydithiophene, etc.). Derivatives of these monomers can 
also be used. Any derivative that produces a conducting polymer can be 
used. Such derivatives include the C.sub.1 -C.sub.10 alkyl-, C.sub.1 
-C.sub.10 alkoxy-, halo-, nitro-, cyano-, ester-, etc., substituted 
monmoners. These monomers are commercially available or made by simple 
organic reactions well within the skill of the ordinary artisan. Mixtures 
may be used. The conducting polymer layer preferably has a conductivity 
ranging from 0.01 S/cm to 5.times.10.sup.3 S/cm, including all 
conductivity values therebetween and all ranges therebetween. The 
conducting polymer film is preferably doped with any type of a salt, such 
as an anthroquinone salt, in any amount including amounts of 1 mole of 
salt for every 1-10, preferably every 2-3, moles of monomeric units 
constituting the conducting polymer. Other conducting polymers and dopant 
salts which may be used in the present invention conducting electrodes are 
those described in the Kirk-Othmer Encyclopedia of Chemical Technology, 
vol. 18, 3ed., p. 755-793, John Wiley & Sons, Inc., 1982, incorporated 
herein by reference. 
The conducting polymer of the present invention may be applied to a surface 
of the substrate or to any material, layer, etc. present on the base 
substrate by any method known in the art. A preferred method according to 
the present invention is an in situ deposition method wherein the 
substrate to be coated, optionally having any further material on the 
surface thereof which is intended to be over-coated with conducting 
polymer, is placed in an aqueous solution of monomer(s) which form a 
conducing polymer layer as they undergo polymerization. See, for example, 
A. G. MacDiarmid in "Conjugated Polymers and Related Materials", Ch. 6, W. 
R. Salanek et al, Eds., Oxford University Press, 1993, A. G. MacDiarmid et 
al, MRS PROC. Boston, Nov. 1993, Manohar et al, Bull. Am. Phys. Soc., 34, 
582 (1989), Manohar, S. K. et al, Synth. Met., 241-43, 711 (1991) and 
Manohar, S. K., Ph.D. Dissertation, University of Pennsylvania, 1992, all 
incorporated herein by reference. 
Generally, in the invention method an aqueous solution is prepared by 
dissolving in water one or more types of monomer which, when polymerized, 
form a conducting polymer in an amount of from about 0.01 g-50 g/100 ml. 
For, e.g., polypyrrole films in a separate container, ferric chloride is 
dissolved in water in an amount of from 0.1 g-35 g/100 ml. A dopant salt 
may be added to the ferric chloride solution, for example, 
anthraquinone-2-sulfonic acid sodium salt (AQ2SA) in amounts of from 
0.1-10 g/100 ml of ferric chloride solution. If desired, a second, third, 
etc., dopant salt, such as, for example, 5-sulfosalicylic acid sodium salt 
(SSA) may be added to the ferric chloride solution in an amount of from 
0.1-10 g/100 ml. 
The substrate to be coated with conducting polymer is placed in the ferric 
chloride solution optionally containing one or more dopant salts in a 
manner such that the substrate is covered by solution on those surfaces 
where the conducting polymer film is desired. The aqueous monomer solution 
is then added to the ferric chloride solution into which the substrate has 
been placed, and the substrate is removed after an appropriate amount of 
time depending on the thickness, etc. of the conducting polymer layer 
desired. Typical time periods for immersion range from about 1-60 minutes. 
The monomer solution can be added to the ferric chloride solution before 
the substrate is dipped therein. After the desired conducting polymer 
layer has been deposited on a surface of the substrate, the substrate is 
removed and washed with distilled water and, if desired, may be sonicated 
in methyl/alcohol for cleaning. The substrate is then dried, for example, 
in air. For, e.g., polyaniline films the procedure and amounts are 
similar. Aniline is dissolved in 0.1-5M orthophosphoric acid, and a second 
solution of 0.001-1M ammonium metavanadate in 0.1-5M orthophosphoric acid 
is prepared. The two solutions are cooled to -10.degree.-10.degree. C. and 
combined. The substrate is placed in the combined solutions for deposition 
and then optionally placed in a solution of 1-50 ml aniline in 500 ml 
0.1-2 HCl at 0.degree. C. to reduce any pernigraniline polymer. The 
substrate is then washed in 0.1-2M HCl and dried. The HCl tends to 
exchange orthophosphate anions for chloride ions in the deposited film. 
More than one monomer may be used in the monomer solution and the 
thickness of the deposited conducting polymer film may be measured by 
using an atomic force microscopy instrument. Typical surface resistivities 
obtained by the above-described methods range from 5 to 1.times.10.sup.5 
ohms/square. Bulk conductivities typically range from 10-1000 s/cm. 
Thus the deposition of the conducting polymer layer on the substrate in the 
present invention is easily controlled by varying the concentration of 
monomer, polymerization initiator, optional dopant salt, etc. in solution 
as well as the time the base substrate is present therein. In this manner 
the thickness, transparency, physical characteristics, etc. of the 
deposited conducting polymer layer can be controlled. 
The invention conducting substrates are preferably used in optical 
recording media and devices such as liquid crystalline devices comprising 
one or more conducting electrodes. The present invention conducting 
electrodes may simply be substituted for any one or more conducting 
electrodes present in such prior art devices. As mentioned above, curved, 
flexible or permanently or impermanently bent displays are particularly 
preferred, but flat-panel displays, particularly those having large areas, 
are also preferred. 
The invention conducting substrates preferably have at least one electric 
lead attached to (in contact with) the conducting polymer material on the 
substrate for the application of current, voltage, etc. to said conducting 
polymer (i.e. electrically connected). The lead(s) is/are preferably not 
in electrical contact with the substrate or any material applied to said 
substrate other than the conducting polymer and may be made of patterned 
deposited metal, may be a simple wire in contact with the conducting 
polymer, etc. Devices according to the invention preferably also include a 
current or a voltage source electrically connected to the conducting 
electrode through the lead(s). A power source, battery, etc. may be used. 
Prior art devices which are improved by substituting at least one invention 
conducting substrate electrode for an existing conducting substrate 
include displays, spatial light modulators, phase shifting devices, 
non-linear optical devices, twisted nematic devices, supertwisted nematic 
devices, double layer supertwisted nematic devices, triple layer 
supertwisted nematic devices, active matrix displays, multiplexed versions 
of the above-described devices, etc. In addition, polymer dispersed liquid 
crystal (PDLC) devices surface stabilized ferroelectric liquid crystal 
(SSFLC) devices, electrically controlled birefringence (ECB) devices and 
memory devices using smectic or nematic liquid crystals are preferred. If 
desired, the conducting polymer of the present invention conducting 
electrode substrate may be modified to provide alignment of, e.g., liquid 
crystalline molecules, by, for example, rubbing, by the alignment 
technique described in U.S. Ser. No. 08/375,997 filed Jan. 20, 1995), etc. 
In addition, the conducting polymer can be applied in a pattern on the 
base substrate. The method described in U.S. Ser. No. 08/308,917, filed 
Dec. 20, 1994 can be used. Both the above-identified applications are 
incorporated herein by reference. 
Liquid crystalline materials useful in display devices comprising one or 
more conducting electrode substrates according to the present invention 
are not particularly limited and includes those exhibiting nematic, 
cholesteric, smectic, discotic, etc. phases, including ferroelectric 
materials (particularly those with lateral fluorine substitution). The 
liquid crystals may be used singly or in mixture, including eutectic 
mixtures. Superfluorinated nematic mixtures may be used. Compositions 
comprising two or more different liquid crystalline materials are 
preferred. Examples of liquid crystals and their mixtures are described in 
Liquid Crystals in Tabellen, VOLS. I and II VEB Deutscher Verlag fur 
Grundstoffindustrie, Leipzig, Germany, 1974 and 1984 both volumes 
incorporated herein by reference, in U.S. Pat. No. 5,032,099, incorporated 
herein by reference, etc. Guest host compositions may also be used wherein 
mixtures of liquid crystal(s) with, e.g., dyes, non-linear optical 
compounds, etc. are provided. 
The present invention will now be further described by reference to 
Examples. The invention is not limited to the Examples. 
General Method for Film Deposition 
POLYPYRROLE FILMS 
0.6 ml of pyrrole (monomer) was dissolved under magnetic stirring in 100 ml 
of distilled water (200 ml beaker, room temperature) during 15 minutes. 
3.5 g of ferric chloride was dissolved under magnetic stirring in 100 ml 
of distilled water in 400 ml beaker. After 5 minutes stirring at room 
temperature 0.98 g of Anthraquinone-2-sulfonic acid sodium salt (AQ2SA) 
was added to the 100 ml of ferric chloride solution. This solution was 
stirred for 5 more minutes. After complete dissolving of AQ2SA 5.34 g of 
5-sulfosalicylic acid sodium SSA was placed into above solution. After 
addition of SSA, the solution became red in color. The solution (mixture) 
was stirred for 5 more minutes in order to dissolve SSA completely. 
A substrate (overhead transparency, FEP, pyrex glass or 
polymethylmethacrylate sheet) was situated by using plastic clamps above 
(FeC13+AQ2SA+SSA) solution level inside the 400 ml beaker. 
100 ml of pyrrole solution was added quickly (during 1-2 seconds) into the 
beaker containing mixture of FeC13+AQ2SA+SSA. Simultaneously at that 
moment a stop watch was started. During dipping (reaction) time substrates 
were immersed completely into polymerizing solution. After 1-60 minutes of 
reaction, substrates with thin polyppyrrole films on them were removed 
from the polymerizing solution and immediately washed in the 400 ml beaker 
with 300 ml of distilled water for 20 minutes. The polypyrrole deposit was 
rinsed with distilled water for 2-3 minutes. If necessary substrate was 
sonicated for 30 seconds in an 80 ml beaker containing 40 ml of methyl 
alcohol. The deposit on the substrate was then dried under air flow for 20 
minutes. 
POLYANILINE FILM 
Aniline (Aldrich Company) was freshly distilled under vacuum prior to use. 
All other chemical were of the highest grade and used as received. 
Deionized, filtered water (Fisher Company) was used in all studies. 
Commercially available glass microscope slides were used as substrates 
without any additional treatment. 
A solution was made containing 2 mL (0.02M) aniline in 100 mL of 4M 
orthophosphoric acid at room temperature. Another solution was made 
containing 1.2 g (0.01M) of ammonium metavanadate in 100 mL of 4M 
orthophosphoric acid at room temperature. Both solutions were stirred for 
10 minutes and then cooled to -2C. in an ice bath. Using plastic clamps, 
several substrates were suspended in 400 mL beaker containing 100 mL of 
the magnetically stirred ammonium metavanadate/orthophoshoric acid 
solution. The dipping solution was prepared by pouring the 100 mL solution 
containing aniline into this beaker. Dipping times were registered 
relative to the time of initial mixing of the aniline/orthophosphoric acid 
and ammonium metavanadate/orthophosphoric acid solutions. Substrates on 
which polyaniline films were being deposited were withdrawn form the 
dipping solution at different time intervals and quickly placed in a 
beaker containing a solution of 10 mL aniline in 500 mL 1M HCl at 
0.degree. C. This step reduced any oxidized pernigraniline form of polymer 
in the emeraldine oxidation state. After soaking for 30 minutes, the 
substrates covered with the films were washed for 60 seconds in 1M HCl and 
then placed in a solution of 1M HCl at room temperature for 30 minutes. 
The substrates were subsequently washed again in 1M HCl for 30 seconds and 
dried using an air jet for 20 minutes. The HCl tended to exchange 
orthophosphospate anions to chloride anions in the deposited polyaniline 
films. 
General Method for Determination of Film Thickness 
Films were deposited on a commercial (NASHUA R brand) overhead transparency 
substrates to which a strip of commercial adhesive tape had previously 
been affixed. After washing and drying as described above and recording 
the vis/UV spectra for each deposit (varying from 2 to 60 minutes) the 
thickness of the same sample was determined as follows: the adhesive tape 
was carefully removed from the substrate thus exposing the substrate on 
which the polymer had not been deposited. The thickness of the deposited 
film was measured by an Atomic Force Microscopy instrument (Nanoscope III 
model). From the above data, a working curve plotting thickness vs. 
minimum optic absorbance (at 600 mm) was constructed to facilitate rapid 
estimation of film thickness for future studies. 
EXAMPLE A1 
(Substrate: Untreated Glass Microscope Slide) 
By using the procedure described above for depositing polypyrrole, a 
polypyrrole film was deposited into microscope glass slide (no cleaning of 
substrate). 
Reaction conditions: Dipping time 5 minutes (at room temperature). 
Results: R.sub.s =7.4.times.10.sup.3 ohm/square .delta.=100 s/cm; 
T=1.2.times.10.sup.-6 cm; 
where: R.sub.s is surface resistivity(ohms/square) .delta. is bulk 
conductivity. 
T is thickness in cm. 
EXAMPLE A2 
(Substrate: Hydrophobic Microscope Slide) 
Using procedure from example A1, a polypyrrole film was deposited onto a 
hydrophobic microscope glass slide (treated with 1,1,1,3,3,3,-hexamethyl 
disilazane). 
Reaction conditions: Dipping time was 10 minutes. 
Results: R.sub.s =1.4.times.10.sup.3 ohms/square; .delta.=232 s/cm; 
T=3.times.10.sup.-6 cm. 
EXAMPLE A# 
Substrate: Overhead transparency: Water Contact Angle -110.degree. 
Using procedure from Example A1, a polypyrrole film was deposited onto the 
non-treated substrate. 
Dipping time: 5 minutes. 
Results: R.sub.s =1.4.times.10.sup.3 ohms/square; .delta.=235 s/cm; 
T=3.times.10.sup.-6 cm. 
EXAMPLE A4 
(Substrate: Radio Frequency Glow Discharge Modifed FEP; Water Contact Angle 
Approx. 65.60) 
Polypyrrole was deposited on FEP as in example A1. 
Dipping time: 5 minutes. 
Results: R.sub.s =2.times.10.sup.3 ohms/square; .delta.=327.times./cm; 
T=1.4.times.10.sup.-6 s/cm 
EXAMPLE A5 
(Substrate: Radio Frequency Glow Discharge Modified FEP; Water Contact 
Angle -56.degree.) 
Procedure as in example A1. Deposition onto treated FEP. 
Dipping time 30 minutes. 
Results: R.sub.s =687 ohms/square; .delta.=362 s/cm; T=4.times.10.sup.-6 
cm; 
EXAMPLE A6 
(Substrate: Untreated Polymethylmethacrylate Sheet) 
Exactly as in Example A1, 
Dipping time: 10 minutes 
Results R.sub.s 1.3.times.10.sup.3 ohms/square .delta.=380 s/cm 
T=2.times.10.sup.6- cm; 
EXAMPLE A7 
(Substrate: Untreated Overhead Transparency) 
Exactly as in Example A1 
Substrate: Overhead transparency Nashua.RTM. brand 
Results: R.sub.s 2.3.times.10.sup.3 ohms/square .delta.=190 s/cm 
T=2.times.10.sup.-6 cm; 
EXAMPLE A8 
(Substrate: Specially Cleaned Flat Pyrex Glass) 
Substrate Pyrex glass (cleaned in 50% NH.sub.4 OH at 60.degree. C. and then 
in 0.25 NaOH). 
Dipping time: 10 minutes 
Results: R.sub.s =3.times.10.sup.3 ohms/square .delta.=230 s/cm 
T=1.4.times.10.sup.-6 cm; 
EXAMPLE A9 
(Substrate: Non-cleaned Pyrex Glass) 
Pyrex glass not cleaned 
Results: R.sub.s =1.8.times.10.sup.3 ohms/square .delta.=260 s/cm 
T=2.times.10.sup.-6 cm; 
EXAMPLE 2 
Fabrication of Polyaniline Films on PET/FEP Substrates 
Polyaniline films were deposited on PET or FEP by the in-situ deposition 
method described in Example 1. The surface resistance as well as the 
optical absorption of the deposited films was varied by deposition 
conditions. The efficacy of this process to control both the electrical 
conductivity and the optical absorption (and hence optical transmission) 
is shown by the data in FIG. 3. Strongly adhering doped polyaniline films 
ranging from 50 to 300 Angstroms thick with conductivity ranging from 0.1 
S/cm to 5.0 S/cm were obtained. Typical optical transparency was about 60% 
for films on PET while it was about 80% for films on FEP. 
EXAMPLE 3 
Polypyrrole Films on PET/FEP 
Polypyrrole was deposited on PET/FEP substrate using the in-situ process. 
The electrical conductivity depended greatly on the nature of the dopant 
anion. The conductivity was about 0.1 S/cm when the dopant was 
methanesulfonate while it was much higher (about 230 S/cm) when 
anthraquinone-2-sulfonate ion was the dopant (FIG. 4). The optical 
transparency for the film with the highest conductivity was about 62% on 
PET and about 78% for FEP. 
EXAMPLE 4 
Patterned Attachment of Polyaniline on FEP 
For fabrication of addressable passive matrix liquid crystal devices from 
conducting polymer substrates, it is essential to deposit conducting 
polymer films in patterns. Hexafluoroproylene-co-tetrafluoroethylene 
(fluorinated ethylene propylene) or FEP materials were modified as per 
Science, 262, 1711 (1993), Langmuir, 8, 130 (1992) and J. Polym. Sci. Part 
A. Polym. Chem. 29, 555 (1991), all incorporated herein by reference to 
achieve selective adsorption of both polyaniline and polypyrrole to only 
modified areas of the FEP film. FIG. 5 illustrates the deposition of 
polyaniline to 400 .mu.m regions bordered by 450 .mu.m regions of 
unmodified FEP. Thus the creation of a patterned conducting polymer 
surface suitable for display devices is demonstrated. It should also be 
mentioned that other surface patterning methods are also known and can be 
applied for producing patterns of conducting polymers. See, for example, 
J. Vac. Sci. Tech., 11, 2155 (1993) and U.S. Pat. No. 5,079,600, both 
incorporated herein by reference. 
EXAMPLE 5 
PDLC Device From Polypyrrole Films on PET 
A PDLC device was fabricated using polypyrrole coated PET as described in 
Ex 2. A schematic diagram of this device (the diagram is generic for any 
type of conducting polymer film) is shown in FIG. 6. The electrically 
conducting surfaces by which the voltage is applied to the device are 
conducting polymer films. Thus, the ITO coated glass or plastic conducting 
substrates of typical PDLC devices are replaced by conducting polymer 
films in the present invention. 
The conducting polymer (polypyrrole) coated PET was cut into strips of 
appropriate size (eg, 5.times.5 cm.sup.2) for the PDLC cell fabrication. 
To be able to control the spacing of the cell between the electrodes, one 
of the substrates was treated with 15 micron mylar spacers. The PDLC 
device was fabricated by mixing equal weight percentages of eutectic 
nematic liquid crystal mixture E7 (EM Chemicals) and UV curable optical 
adhesive, Norland Optical Adhesive #65. The ordinary refractive index of 
the liquid crystal is nearly equal to that of the polymer (n=1.524), a 
prerequisite to fabricating a PDLC light shutter. Before polymerization of 
the Norland adhesive, the liquid crystal was dissolved in a prepolymer and 
a small amount of this homogeneous mixture was placed on the conducting 
polymer substrate with the spacers. The substrates were placed on top of 
each other with the conducting surfaces facing toward the inside of the 
cell with a small offset, such that electrical contact can be made. The 
sample was photopolymerized for approximately twenty minutes in UV light 
(360 nm). As the pre-polymer moiety polymerized, the low molecular weight 
liquid crystal was no longer soluble in the polymer binder and it phase 
separated out of the polymer binder. Liquid crystal droplet morphology 
forms. The PDLC device, fabricated in this manner using the polypyrrole 
film as the conducting substrate, exhibited electro-optic switching. The 
voltage dependence of the intensity of transmission of the PDLC device 
with polypyrrole substrates showed a threshold voltage of about 15 volts 
beyond which the intensity attains a saturation value (FIG. 7). This 
behavior, the qualitative nature of the variation of the intensity with 
applied voltage, as well as the magnitude of the threshold voltage, are 
very similar to those in currently used PDLC devices with ITO based 
substrates. 
EXAMPLE 6 
Twisted Nematic (TN) Device From Polypyrrole Films on PET 
A TN cell using polypyrrole films deposited on PET as in Ex. 2 was 
fabricated. The cell consists of two conducting substrates, two polarizes, 
spacers to control the cell thickness, and eutectic nematic liquid crystal 
material (E7). The conducting polypyrrole substrates were treated 
(unidirectional rubbed with filter paper) to create uniform parallel 
alignment. The substrates were sandwiched together with the conducting 
sides facing each other, a small offset to allow for electric connections, 
and with the alignment direction at the top substrates rotated at 
90.degree. with respect to the bottom substrates. Spacers (usually 3-10 
microns) were placed in between the substrates so as to control the cell 
thickness. The two opposing side edges were sealed with an epoxy glue and 
the liquid crystal was capillary filled into the cell. Placing the cell 
between crossed polarizers completes the fabrication process of the TN 
display. 
The electro-optic characteristics of the TN device, fabricated using 
conducting polymer (polypyrrole) films deposited on PET as the electrode 
surfaces were investigated. Typical curves showing the electro-optic 
response for a TN cell (approximately 10 microns thick) are shown in FIG. 
7. The applied voltage was 24 volts across the thickness of the cell. The 
rise time and the off-time, evaluated from the value of the optical 
intensity at 10% and 90% of the intensity, are 35 ms and 54 ms. Thus, the 
functioning and the characteristics of a working TN device fabricated with 
an optically transparent conducting polymer as the conducting substrate 
has been demonstrated. An important feature of this device is that the 
conducting polymer film not only acts as the conducting substrate but also 
as the aligning layer. Thus, the conducting polymer film replaces the ITO 
substrates as well as the polyimide aligning layer used in conventional 
devices. This reduces the steps involved in the device fabrication. 
EXAMPLE 7 
PDLC Device From Polyaniline Films Deposited on PET 
The fabrication procedure was the same as that used for the 
polypyrrole-based PDLC device described as Example 4. The thickness of the 
PDLC device was 18 microns. Electro-optical switching was clearly 
observed. The applied voltage (200 volts across 18 microns) was higher 
than that used for the polypyrrole-based PDLC device. This is due to a 
higher surface resistance of the polyaniline films compared to polypyrrole 
films on the same PET substrate. Other than this difference, all the 
electro-optic characteristics of the polyaniline based PDLC device were 
similar to the polypyrrole-based PDLC device described in Example 4. 
EXAMPLE 8 
Twisted Nematic (TN) Device From Polypyrrole Films on Glass 
A TN device was fabricated from polypyrrole films deposited on glass. The 
cell thickness was 8 microns. E7 was the nematic material used. 
Electrooptic switching was observed. 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described herein.