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The present invention relates generally to liquid crystal, and more
particularly to a visual display device utilizing a plurality of nematic
curvilinearly aligned phases ("NCAP") liquid crystal modules.
Liquid crystals are used in a wide variety of devices, including visual
display devices. The property of liquid crystals that enables them to be
used, for example, in visual displays, is the ability of liquid crystals
to transmit light on one hand, and to scatter light and/or to absorb it
(especially when combined with an appropriate dye), on the other,
depending on whether the liquid crystals are in a relatively free, that is
de-energized or field-off state, or in a strictly aligned, that is
energized or field-on state. An electric field selectively applied across
the liquid crystals can be used to switch between field-off and field-on
states.
In the past, devices using liquid crystals (not NCAP liquid crystals), such
as visual display devices or other devices, have been of relatively small
size. Large size devices using liquid crystals, such as, for example, a
billboard display or a sign have not been able to be made satisfactorily
for a number of reasons.
One reason is the fluidity of the liquid crystals, that is, the tendency of
the liquid crystal material to flow to create areas of the display that
have different thicknesses. Such thickness variations cause undesirable
variations or gradations in the optical and electrical properties of the
liquid crystal device.
The problem of maintaining a parallel relationship between the glass plates
or substrates of a liquid crystal display device has also contributed to
the difficulty of constructing a suitable large-size display. A lack of
parallelism between the glass plates between which the liquid crystal
material is located causes the device to have non-uniform optical and
electrical characteristics, which are detrimental to its performance.
In view of the foregoing, an object of the present invention is to provide
a liquid crystal display device having a large viewing or display area as
well as a relatively high quality of operation, satisfactory contrast, and
controlled uniformity of output.
Another object of the present invention is to provide a liquid crystal
display device having a relatively large area, and which permits efficient
and high quality functioning of a liquid crystal material in response to
excitation or non-excitation by an external source.
Yet another object of the present invention is to provide a display device
comprising a plurality of NCAP liquid crystal modules that effect a
homogeneous display.
A further object of the present invention is to facilitate the
interconnection of the electrodes of a NCAP liquid crystal apparatus to a
circuit means for energizing the apparatus.
As may be seen hereinafter, the NCAP liquid crystal apparatus and display
device disclosed herein is one which includes NCAP liquid crystal. NCAP
liquid crystal comprises a liquid crystal material and containment means
for inducing a generally non-parallel alignment of the liquid crystal
material which in response to such alignment at least one of scatters and
absorbs light and which in response to a prescribed input reduces the
amount of such scattering or absorption.
The prescribed input is preferably of the electromagnetic type and, more
particularly, an electric field. A pair of electrodes may be provided to
apply the electric field. The electrodes may be located on opposite sides
of the combination of the liquid crystal material and the containment
means.
The display device of the present invention comprises a plurality of NCAP
liquid crystal modules or apparatus. The NCAP liquid crystal modules are
located adjacent to one another to effect a homogeneous display. As the
display device comprises a plurality of discrete NCAP liquid crystal
modules, it may be thought of as utilizing a segmented display.
The NCAP liquid crystal apparatus further includes flexible substrates on
which the electrodes are formed. The substrates include flexible
extensions or arms thereof. Conductive paths are formed on the substrates
and their extensions. The substrate extensions are sufficiently flexible
to facilitate and permit the interconnection of the electrodes via the
conductive paths to suitable circuit means for applying an electric field
across the electrodes.
The NCAP liquid crystal apparatus and display device of the present
invention will be described in more detail hereinafter in conjunction with
the drawings wherein:
FIG. 1 is a schematic view illustrating a NCAP liquid crystal apparatus in
accordance with the present invention;
FIG. 2 is an enlarged, schematic view of the NCAP liquid crystal apparatus
of FIG. 1 along line 2--2 thereof;
FIG. 3 is a schematic view illustrating a technique for manufacturing a
NCAP liquid crystal apparatus in accordance with the present invention;
FIG. 4 is a schematic view illustrating a substrate of a NCAP liquid
crystal apparatus made in accordance with the technique depicted in FIG.
3;
FIG. 5 is a schematic view which shows a NCAP liquid crystal display device
utilizing a segmented display in accordance with the present invention;
FIG. 6 is a view of the NCAP liquid crystal display device of FIG. 5 along
line 6--6 thereof;
FIG. 7 is a schematic view illustrating a number of NCAP liquid crystal
apparatus modules which may be used to form a segmented display;
FIG. 8 is a schematic view which shows a NCAP liquid crystal display device
utilizing a mosaic of NCAP liquid crystal apparatus modules to form a
segmented display;
FIG. 9 is a view along line 9--9 of FIG. 8;
FIG. 10 is a view along line 10--10 of FIG. 8; and
FIG. 11 is a schematic view of an alternate embodiment of the present
invention.
The present invention relates in the preferred embodiment described
hereinafter to the use of liquid crystal material which is operationally
nematic. By "operationally nematic" is meant that, in the absence of
external fields, structural distortion of the liquid crystal is dominated
by the orientation of the liquid crystal at its boundaries rather than by
bulk effects, such as very strong twists (as in cholesteric material) or
layering (as in smectic material). Thus, for example, a liquid crystal
material including chiral ingredients which induce a tendency to twist but
which cannot overcome the effects of the boundary alignment of the liquid
crystal material would be considered to be operationally nematic. A more
detailed explanation of operationally nematic liquid crystal material is
provided in co-pending U.S. patent application No. 477,242, filed Mar. 21,
1983, in the name of Fergason, entitled ENCAPSULATED LIQUID CRYSTAL AND
METHOD, assigned to Manchester R&D Partnership now issued as U.S. Pat. No.
4,616,903, the disclosure of which is hereby incorporated by reference.
Reference may also be made to co-pending U.S. Pat. No. 4,435,047, issued
Mar. 6, 1984, in the name of Fergason, entitled ENCAPSULATED LIQUID
CRYSTAL AND METHOD, assigned to Manchester R&D Partnership, and which
disclosure is also hereby incorporated by reference.
It is to be understood, however, that the various principles of the present
invention may be employed with any of the various types of liquid crystal
materials (cholesteric, nematic or smectic) or combinations thereof,
including combinations with dyes. Designation of the apparatus of the
present invention as a NCAP liquid crystal apparatus or NCAP display
device or any reference to NCAP liquid crystal is in no way intended to
limit such apparatus or device to use with nematic liquid crystal
materials. It is only for the sake of convenience and in an effort to use
an abbreviated term that describes the apparatus of the present invention
that it is referred to as a NCAP liquid crystal apparatus or display
device Particularly, the term NCAP is used because the preferred liquid
crystal material is nematic or operationally nematic liquid crystal and
because in the field-off condition, or any other condition which results
in the liquid crystal being in a distorted or randomly aligned state, the
liquid crystal structure is distorted to a curved form (hence
curvilinearly aligned) wherein the spatial average orientation of the
liquid crystal material over a capsule-like volume, for instance, is
strongly curved and there is no substantial parallel directional
orientation of the liquid crystal in the absence of a prescribed input,
for example, an electric field.
NCAP liquid crystals and a method of making the same and devices using NCAP
liquid crystals are described in detail in the above-identified U.S. Pat.
No. 4,435,047. Briefly, NCAP liquid crystal comprises a liquid crystal
material that is dispersed in an encapsulating medium. A NCAP liquid
crystal apparatus is an apparatus formed of NCAP liquid crystals that are
capable of providing a function of the type typically inuring to a liquid
crystal material For example, such a NCAP liquid crystal apparatus may be
a visual display device that responds to the application and removal of an
electric field to effect a selected attenuation of visible light.
Referring now to the drawings, attention is first directed to FIGS. 1 and
2. FIGS. 1 and 2 show a NCAP liquid crystal apparatus indicated generally
by reference numeral 10. The apparatus includes a layer or layers of NCAP
liquid crystal 11 supported on a substrate 12 having an electrode 13
located thereon. The apparatus further includes a second electrode 14
mounted on a second substrate 18. In the embodiment illustrated, electrode
14 comprises seven electrically isolated segments 14a-14g to form a seven
segment figure-eight pattern or arrangement 30 wherein each segment may be
selectively energized to create various numerical characters.
The NCAP liquid crystal 11 may include a liquid crystal material 20 more or
less contained within the confines or the interior volume 21 of a capsule
22. The NCAP liquid crystal material comprises a plurality of such
capsules or an encapsulating medium in which liquid crystal material is
dispersed.
A quantity of liquid crystal material is confined or contained in volumes
within the encapsulating medium, for example in a solid medium as
individual capsules or dried stable emulsions. Such volumes may be
discrete volumes, that is once formed, they ordinarily remain as
individually distinct entities or separate entities. Such separate
entities or discrete volumes, however, may also be interconnected, for
example, by one or more passages. The liquid crystal material would
preferably be in both the discrete volumes and in such interconnecting
passages. Thus, the internal volumes of respective capsules may be fluidly
coupled via one or more interconnecting passages. All of the aspects and
features of the present invention vis-a-vis individual unconnected
capsules have been found to be applicable to an arrangement of capsules
that have one or more interconnecting passages.
A voltage may be applied to electrodes 13 and 14, and hence across liquid
crystal 11 from an AC or DC voltage source 16. Voltage source 16 is
connected to electrode 13 by means of an electrical lead 15 and an
electrically-conductive path 31 formed on substrate 12 and a flexible arm
or extension 12a thereof Voltage 16 is connected to segments 14a-14g by
means of electrically-conductive paths 29a-29g, respectively, formed on
substrate 18 and flexible arm or extension 18a thereof. Each conductive
path is in turn interconnected to respective electrical leads 19a-19g,
which are connected to voltage source 16 through selectively closeable
switches 17a-17g, respectively. (Note the fold in substrates 12 and 18,
which may be flexible as hereinafter discussed, and in arms 12a and 18a to
facilitate interconnection of electrodes 13 and 14a-14g to voltage source
16.)
When a selected switch is closed, apparatus 10 is in an energized or
field-on state with the molecules of the liquid crystal material located
between the energized electrodes in the desired alignment to permit the
transmission of light. For example, closing switches 17f and 17g will
energize segment 14f and 14g, that is, a voltage will be applied across
electrodes 13 and 14f and 14g, and hence across the NCAP liquid crystal
material located therebetween to display the numeral "1". When all
switches are open, apparatus 10 is in a de-energized or field-off state
such that the liquid crystal material scatters and/or absorbs light. The
NCAP liquid material functions in this manner to attenuate or not to
attenuate light incident thereon depending upon whether an electric field
is applied thereacross.
Mounting substrates 12 and 18, and electrodes 13 and 14 may be optically
transmissive so that NCAP liquid crystal apparatus 10 is capable of
controlling the transmission of light therethrough in response to an
electric field applied across the electrodes. Alternatively, electrode 14
and/or substrate 18 may be optically reflective or may have thereon an
optically reflective coating so that reflection by such reflective coating
of incident light will be a function of whether there is an electric field
applied across the liquid crystal 11.
A plurality of NCAP liquid crystals 11 may be applied to substrate 12 in a
manner such that they adhere to electrode 13 and substrate 12. The
material of which capsules 22 is formed is suitable for binding or
otherwise adhering the capsule to the electrode and/or substrate. In one
embodiment, capsules 22 are formed of a polyvinyl alcohol (PVA). In the
preferred embodiment, liquid crystal material is dispersed or entrapped in
a latex medium. In either embodiment, substrate 12 and extension 12a
thereof may be formed of a flexible, polyester film, such as Mylar.RTM.,
that has been precoated with a 90 to 5000 ohms per square, and preferably
450.+-.150 ohms per square, layer of indium tin oxide (ITO). The electrode
coated surface of polyester substrate 12 is etched, as is well known in
the art, to form electrode 13. Electrode 13 preferably has a rectangular
shape that approximates the outline of figure-eight pattern 30. Conductive
path 31 is also formed on substrate 12 and extension 12a by etching the
electrode coated surface thereof to form the electrode trace 31
interconnecting electrode 13 to electrical lead 15.
The ITO coating forming electrode 13 and conductive path 31 is
substantially optically transparent to electromagnetic radiation in at
least a portion of the visible range. Such transparency is only achieved
by increasing the resistivity of the ITO coating forming the electrode and
conductive paths. A Mylar.RTM. film with a precoated ITO electrode, known
as Intrex, may be purchased from Sierracin of Sylmar, Calif. Of course,
materials other than ITO may be used to form the electrodes and conductive
paths of the apparatus of the present invention.
As noted, latex entrapped NCAP liquid crystal is used in the preferred
embodiment. Latex entrapped NCAP liquid crystal comprises the entrapment
of liquid crystal in a latex medium. The latex is a suspension of
particles. The particles may be natural rubber or synthetic polymers or
copolymers. A latex medium is formed by drying a suspension of such
particles. A further explanation of latex entrapped NCAP liquid crystal
and methods of making the same are provided in U.S. Pat. No. 591,433,
filed Mar. 20, 1984, now abandoned in the name of Pearlman, entitled LATEX
ENTRAPPED NCAP LIQUID CRYSTAL COMPOSITION, METHOD AND APPARATUS, assigned
to the assignee of the present invention, and which disclosure is hereby
incorporated by reference.
Briefly, latex entrapped NCAP liquid crystal may be formed by mixing a
suspension of latex particles and liquid crystal material wherein the
liquid crystal material has been previously emulsified in an aqueous
phase. Alternatively, all components may be combined prior to emulsifying
the liquid crystal material. The mixture may then be applied to substrate
12 and electrode 13. As the mixture dries, it adheres to the electrode
coated side of the polyester film. When dried, the latex particles form a
latex medium with particles of liquid crystal dispersed therein.
A specific method for making latex entrapped NCAP liquid crystal may
comprise first emulsifying 36 grams of the liquid crystal ROTN701
(manufactured by Hoffman La Roche of New York, N.Y.) in a solution
containing 14 grams of a 12% aqueous solution of PVA and 1 gram of the
surfactant TWEEN 20 (available through ICI Americas Incorporated of
Wilmington, Del.) The liquid crystal is added continuously while the
solution is mixed with an impeller blade at 3500 RPM. When the particle
size of the liquid crystal is about 1-5 microns, 49 grams of Neorez R-967
(manufactured by Polyvinyl Chemical Industries, Wilmington, Mass.),
containing 40% latex particles by weight, is added with slow mixing of
less than 1000 RPM until the mixture is homogeneous. This material may
then be cast with a doctor blade or other suitable means onto substrate 12
and electrode 13.
After the NCAP liquid crystal material has dried on electrode 13 and
substrate 12, substrate 18 and electrode 14 formed thereon may be
laminated onto the surface of the latex entrapped NCAP liquid crystal.
Substrate 18 and its extension 18a may also be a flexible, Mylar.RTM. film
precoated with a 90 to 5000 ohms per square, and preferably a 450.+-.150
ohms per square, layer of ITO. The electrode segments 14a-14g are formed
by etching the electrode coated surface of film 18 to delineate the
prescribed pattern. Various other patterns, of course, could be formed.
Conductive paths 29a-29g are also formed on the surface of substrate 18 and
extension or arm 18a by etching the ITO coated surface thereof to define
these conductive paths that interconnect the electrode segments to the
circuit means for applying an electric field. As discussed, the ITO
coating forming electrode segments 14a-14g and conductive paths 29a-29g is
substantially optically transparent. As such, the coating has a high
resistance. It should be understood that the circuit means may comprise
the electrical leads and voltage source shown in FIG. 1 or any other means
for energizing the electrodes, such as a printed circuit board including
appropriate driver electronics (see FIG. 6).
Flexible arm 18a on which a portion of conductive paths 29a-29g are formed
(as well as arm 12a on which a portion of trace 31 is formed) is
sufficiently flexible to permit interconnection of the conductive paths to
a circuit means for energizing the electrodes. As shown in FIG. 2 (see
also FIGS. 3, 4 and 6), arm 18a may be folded or bent to essentially act
as an interconnect cable. Such an arrangement offers the distinct
advantage of eliminating the need for a separate interconnect means, such
as an elastomeric connector, for connecting the electrodes of a liquid
crystal apparatus to the circuit used to drive the apparatus. In
accordance with the present invention, such interconnect means is
integrated into the respective substrates of NCAP liquid crystal apparatus
10.
The high resistance electrode traces or conductive paths 29a-29g may be
overprinted with a low resistance conductive ink, such as Acheson
Electrodag 427SS manufactured by Acheson Colloids of Port Huron, Mich., at
the point where the respective electrical leads 19a-19g are connected to
the conductive paths. The conductive ink is applied to the conductive
paths outside of the viewing area of apparatus 10 so as not to interfere
with the display. The use of conductive ink in this manner decreases the
voltage drop along the conductive paths, especially at the point of
interconnection with the electrical leads.
The conductive paths 29a-29g are adapted to be compatible with existing
electrical connectors to facilitate connection of appropriate circuit
means to the conductive paths for applying an electrical field across the
electrodes of the apparatus. For instance, electrical connectors such as
those manufactured by Berg Electronics of Willimington, Del., Part No.
Series 65801 and staple style crimp connectors could be used to
interconnect the conductive paths to the electrical leads.
FIG. 3 illustrates a technique for producing NCAP liquid crystal apparatus
in accordance with the present invention. As shown, a sheet 38 of an
electrode-coated flexible film, such as Intrex, has formed therein, as by
stamping, a plurality flexible substrates 40 including flexible arms or
extensions 40a thereof. In the embodiment illustrated, four figure-eight
patterns 30 are formed on each substrate 40. As discussed, each
figure-eight pattern is ordinarily divided into seven electrically
isolated conductive segments, each of which may be selectively energized.
Each segment of each pattern is to be connected to an appropriate driver
circuit such as might be mounted on a printed circuit board (PCB) 42 (See
FIG. 4) for driving the NCAP liquid crystal apparatus.
As shown in FIG. 4, transparent conductive paths or electrode traces,
indicated generally by reference numeral 44, are provided for
interconnecting the individual electrode segments of the various
figure-eight patterns to an appropriate circuit for energizing the
segments. The conductive paths are formed on the surface of flexible
substrates 40 and flexible extensions 40a thereof. The conductive paths
are thus formed in the same plane as the segmented electrodes, and
preferably they are formed by etching the electrode coated surface of the
substrate and its extension. Extensions or arms 40a are sufficiently
flexible or foldable such that arms 40a in effect act as a flexible flat
cable that permits the conductive paths formed thereon to be directly
interconnected to a circuit means on PCB 42 for applying an electric field
across the electrodes of the NCAP liquid crystal apparatus. As discussed
heretofore, the conductive paths on arms 40a are adapted to be compatible
with existing electrical connector means for proper connection to the PCB.
Although not illustrated, it would be understood that the other substrate
of the NCAP liquid crystal apparatus on which typically a single electrode
is mounted would be formed in the same manner. That is, the substrate and
its extension or arm thereof would be die cut from a sheet of etched
Intrex material, and the electrode and conductive path thereto would be
formed on the electrode coated surface thereof.
FIGS. 5 and 6 illustrate a NCAP liquid crystal display device utilizing
display segmentation The particular display 50 illustrated comprises a
plurality of NCAP liquid crystal apparatus 52a-52f similar to the type
heretofore described. However, rather than a figure-eight display, each
NCAP liquid crystal apparatus is configured to comprise a dot matrix
display. Of course, each NCAP liquid crystal apparatus could be adapted to
display a figure-eight pattern or any other preestablished pattern. In the
embodiment illustrated, 6.times.8 dot matrices may be used for each
character, and there are a plurality of character positions for each NCAP
apparatus 52a-52c. For instance, each NCAP apparatus 52a-52c could display
20 characters. The respective NCAP apparatus may be driven so that
continuous information in a line format is displayed across the display
area of display device 50, as illustrated by the visual output depicted in
the upper half of device 50 (NCAP apparatus 52a-52c). Alternatively,
adjacent NCAP apparatus may be driven and appropriate matrices or patterns
formed so that their respective display areas are combined to effect a
visual output that is additive of two or more individual displays, for
example, as shown in the lower third (NCAP apparatus 52e-52f) of display
device 50.
As illustrated, the displays are positioned adjacent to one another and the
distance therebetween, represented by reference numeral 54, is minimized.
The minimization of this distance 54 is achieved because each NCAP
apparatus includes flexible extensions 56a and 58a, discussed in more
detail below, which allow adjacent apparatus to be positioned very close
to one another. The particular display illustrated comprises six NCAP
liquid crystal a | | |
