Selectively presenting viewable and conductive images

A display for presenting selected images to a viewer including a substrate; a photosensitive layer provided over the substrate which is adapted to be exposed and developed to provide viewable and conductive images; and a light modulating layer formed over the photosensitive layer and effective in two conditions, in a first condition to prevent the viewing of the viewable and conductive images and in a second condition to permit viewing of the viewable and conductive images. The display includes an electrical conductive structure connected to the viewable and conductive images for applying a field to selected ones of such viewable and conductive images to cause the light modulating layer overlying the selected ones of the viewable and conductive images to change from the first condition to the second condition so as to present such viewable and conductive images for viewing to the viewer.

CROSS REFERENCE TO RELATED APPLICATIONS 
Reference is made to commonly assigned U.S. Patent application Ser. No. 
08/961,059 filed Oct. 30, 1997, entitled "Display Apparatus Using Light 
Patternable Conductive Traces" by Stanley W. Stephenson; U.S. Patent 
application Ser. No. 08/961,056 filed Oct. 30, 1997, entitled "Single 
Sheet Display Having Patternable Conductive Traces" by Stanley W. 
Stephenson; U.S. Patent application Ser. No. 08/990,891 filed Dec. 15, 
1997, entitled "Method of Producing a Display Having Patternable 
Conductive Traces" by Stanley W. Stephenson and U.S. Patent application 
Ser. No. 08/990,853 filed Dec. 15, 1997, entitled "A Sheet Having 
Patternable Conductive Traces for Use in a Display" by Stanley W. 
Stephenson, the disclosures of which are incorporated herein by reference. 
FIELD OF THE INVENTION 
The present invention relates to displays in which preformed images can be 
selectively presented to a viewer. 
BACKGROUND OF THE INVENTION 
Flat panel displays can be fabricated using many techniques. Typical 
embodiments are disclosed in Liquid Crystal Flat Panel Displays by William 
C. O'Mara (Chapman & Hall, New York, N.Y. 1993) and other similar 
publications. These displays use transparent glass plates as substrates, 
and electrical traces are sputtered in a pattern of parallel lines that 
form a first set of conductive traces. A transparent conductor such as 
Indium Tin Oxide is sputtered over the traces to disperse an electrical 
charge across transparent areas not blocked by the traces. A second 
substrate is similarly coated with a set of traces having a transparent 
conductive layer. 
Layers are applied over the substrates and patterned to orient liquid 
crystals in twisted nematic (TN) or super-twisted-nematic (STN) 
configurations. The two substrates are spaced apart and the space between 
the two substrates is filled with a liquid crystal material. Pairs of 
conductors from either set are selected and energized to alter the optical 
transmission properties of the liquid crystal material. 
In another embodiment, the traces do not define an orthogonal grid, but are 
organized to form alpha-numeric displays or graphic images. In a further 
embodiment, an active display on a transparent substrate is sputtered or 
printed and uses memory elements to continuously drive a each display 
element depending on information written to the memory element. In another 
embodiment, disclosed in SID DIGEST 90, article 12.6, the liquid crystal 
material can be polymerically dispersed to form a Liquid Crystal Polymer 
Matrix (LCPC). LCPCs are typically disposed in ultra-violet polymerized 
acrylic polymers. The liquid crystals are homogenized into the polymer, 
and the emulsion is coated onto a substrate. Ultra violet light is applied 
to the emulsion. The emulsion hardens, and bubbles of liquid crystal 
material are held in a rigid polymeric matrix. 
Reflective liquid crystal polymer matrix displays are disclosed in U.S. 
Pat. No. 4,435,047. A first sheet has transparent Indium-Tin-Oxide (ITO) 
conductive areas and a second sheet has electrically conductive inks 
printed on display areas. The sheets can be glass, but in practice have 
been formed of Mylar polyester. A dispersion of liquid crystal material in 
a binder is coated on the first sheet, and the second sheet is pressed 
onto the liquid crystal material. Electrical charges applied to opposing 
conductive areas operate on the liquid crystal material to expose display 
areas. Pleichroic dyes are added to the liquid crystal to cause the liquid 
crystal material to act as a shutter over the printed areas. The 
technology from this and related patents was licensed to the Taliq 
Corporation of Sunnyvale Calif. Currently, Taliq products form electrical 
interconnection by offsetting the two sheets and contacting trace 
conductors from each of the two sheets. 
Image displays can provide color images if a color filter array is formed 
over the pixels of the display. In U.S. Pat. No. 5,462,822, three color 
layers are formed on a transparent substrate. In this patent, a 
transparent electrode layer is formed over the color filter. The filter 
plate is aligned onto a liquid crystal layer. The plate is glass and has 
silver halide, color-forming layers. A transparent electrode material is 
sputtered at high temperature over the CFA. In practice, the presence of 
the transparent electrode material causes ionic migration of the dyes in 
the dye layers. It would be advantageous to separate the electrically 
conductive layer from the dye layers. 
The prior art requires multiple, separate layers on multiple plates to 
build up the display. The electrical traces and transparent conductive 
layers are typically formed through repeated vacuum deposition of 
materials on the substrate. These processes are expensive and require long 
processing times on capital intensive equipment. Because most display 
structures are formed of glass, two sheets are used and are offset to 
permit connection to two separate and exposed sets of traces that are 
disposed on separate sheets. It would advantageous to lower the cost of 
flat panel displays. Additionally, current structures are not amenable to 
the creation of low-cost large flat panel displays. It would be 
advantageous to be able to form low-cost, large flat-panel displays. 
In many applications it is desirable to have a number of preformed images 
which can be selectively presented to a viewer on a display. These 
displays often include a liquid crystal material and an arrangement of 
conductors which can be ITO traces on a glass support. The ITO must be 
vacuum sputtered onto the glass support using a high temperature process. 
There is a series of complex manufacturing steps which must be used in the 
process of making these displays. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a display which permit 
the selected viewing of preformed images and which minimizes the problems 
found in the prior art. 
This object is achieved in a display for presenting selected images to a 
viewer comprising: 
a substrate; 
a photosensitive layer provided over the substrate which is adapted to be 
exposed and developed to provide viewable and conductive images; 
a light modulating layer formed over the photosensitive layer and effective 
in two conditions, in a first condition to prevent the viewing of the 
viewable and conductive images and in a second condition to permit viewing 
of the viewable and conductive images; and 
electrical conduction means connected to the viewable and conductive images 
for applying a field to selected ones of such viewable and conductive 
images to cause the light modulating layer overlying the selected ones of 
the viewable and conductive images to change from the first condition to 
the second condition so as to present such viewable and conductive images 
for viewing to the viewer. 
Displays in accordance with the present invention have the advantage of 
providing a reflective display using light sensitive, conductor forming 
coatings under a liquid crystal, light modulating layer. The liquid 
crystal material and light sensitive conductor forming material is 
inexpensive when coated simultaneously using current photographic coating 
technology. Displays in accordance with the invention can be formed using 
inexpensive, fast photographic processes to expose and develop viewable 
and conductive images. The present invention can make use of high volume 
manufacturing techniques by using coating techniques.

DETAILED DESCRIPTION OF THE INVENTION 
A sectional view of the invention is shown in FIG. 1. An unassembled 
display 5 includes a sheet 10 which has a substrate 12. The substrate 12 
can be made of a polymeric material such as Kodak Estar film base formed 
of polyester plastic and with a thickness of between 20 and 200 microns. 
For a specific example, substrate 12 can be a 80 micron thick sheet of 
polyester film base. Other polymers, such as polycarbonate can also be 
used. Substrate 12 can be dyed to form a gray or black background. A 
photosensitive layer 14 is formed on the substrate 12. 
In a preferred arrangement, the photosensitive layer 14 can be an emulsion 
of silver halide grains in gelatin. Alternatively, other light sensitive, 
metal forming materials can be used such as gold or copper salts. In the 
case of silver halide emulsions, high concentrations of silver halide 
salts in a binder such as gelatin or polyvinyl alcohol (PVA) are used to 
improve conductivity over conventional imaging emulsions. Conductive 
additives such as fine Indium-Tin-Oxide or fine silver with particle sizes 
between 0.5 and 2 microns can be added to the emulsion to improve 
conductivity of photographically produced metallic silver. The 
photosensitive layer 14 must be exposed and developed to provide viewable 
and conductive images. When silver halide grains in gelatin are used the 
conductive images are formed of silver. 
Over the first photosensitive layer 14 is coated a light modulating layer 
30. Light modulating layer 30 can be a liquid crystal of conventional 
design. Such material should exhibit high optical and electrical 
anisotropy and match the index of refraction of the carrier polymer, in 
this case gelatin, when the material is electrically oriented. Examples of 
such materials are Merck MLC-6406, MLC-6422, MLC6436-000, 6436-100, 
9300-100. The liquid crystal material is dispersed in a polymeric binder 
such as gelatin or polyvinyl alcohol (PVA). It is advantageous that the 
binder have a low ionic content. The presence of ions in such a binder 
hinders the development of and electrical field across the dispersed 
liquid crystal material. Additionally, ions in the binder can migrate in 
the presence of an electrical field, chemically damaging the light 
modulating layer 30. Light modulating layer 30 must be formed of materials 
that permit penetration by an electrical conductor. The liquid crystal and 
gelatin emulsion is coated to a thickness of between 1 and 30 microns to 
optimize light modulating of light modulating layer 30. Pleichroic dyes 
can be added to the liquid crystal material to create a colored, or 
neutral light modulating layer 30. Other light-modulating, electrically 
operated materials can also be coated such as a micro-encapsulated 
ferroelectric (FLC) material. The light modulating layer 30 is effective 
in two conditions. In the first condition, the light modulating layer 30 
prevents viewing the viewable and conductive silver images and in the 
second condition permits viewing of the viewable and conductive silver 
images as will become clearer hereinafter. 
A transparent substrate shown as cover glass 24 is bonded over sheet 10. 
Cover glass 24 can be made of glass or a transparent polymeric film such 
as Mylar polyester. Cover glass 24 has a transparent electrically 
conductive layer 24a, which is an optically transparent, electrically 
conductive coating formed of Indium-Tin-Oxide (ITO). A typical sheet 
resistance of transparent electrically conductive layer 24a can be less 
than 250 ohms per square. 
FIG. 2 is a sectional view of an assembled display 5. Photosensitive layer 
14 has been exposed and processed to create viewable and conductive images 
16 and non-conductive areas 18. Viewable and conductive images 16 are 
metallic silver formed from exposed silver halide grains in the sheet 10. 
The effective sheet conductivity of viewable and conductive images 16 is 
less than 250 ohms per square. Viewable and conductive images 16 appear 
black, having an optical density of greater than 2.0 D. Unexposed silver 
halide in non-conductive areas 18 has been removed by conventional 
photographic processes to define the extent of viewable and conductive 
images 16. Alternatively, non-conductive area 18 can be small gaps in 
developed silver that electrically isolates electrically viewable and 
conductive images 16. 
In FIG. 2, cover glass 24 has been bonded onto sheet 10. Transparent 
electrically conductive layer 24a provides a continuous electrode across 
cover glass 24. Transparent electrically conductive layer 24a works in 
conjunction with viewable and conductive images 16 to impose an electrical 
field across selected portions of light modulating layer 30. Piercing pins 
20 are supported by circuit board 40, shown in FIG. 2 and 3a. Separate 
piercing pins 20 are pressed through substrate 12 and into each viewable 
and conductive image 16 to provide selectively imposed electrical fields 
between viewable and conductive images 16 and transparent electrically 
conductive layer 24a. 
FIGS. 3a, 3b and 3c show views of each of the three parts of display 5. In 
FIG. 3a is circuit board 40, which has circuit board traces 45 running 
from a position under each viewable and conductive images 16 to a 
connection point. Piercing pins 20 are located under each viewable and 
conductive images 16 and are soldered to each circuit board trace 45 to 
provide electrical interconnect to each viewable and conductive images 16 
on sheet 10. 
FIG. 3b is a top view of sheet 10 with light modulating layer 30 sectioned 
away to show viewable and conductive images 16. 
FIG. 3c is a top view of cover glass 24. Cover glass 24 will appear to be 
transparent. Cover glass 24 has ground connection 50 soldered to an edge 
outside of the display area. 
Top views of display 5 are shown in FIGS. 4a and 4b. Circuit board 40 has a 
series of the circuit board traces 45 that provide interconnection to 
external drive electronics. Each circuit board trace 45 terminates under a 
separate viewable and conductive image 16. Piercing pins 20 press through 
sheet 10 into viewable and conductive images 16. 
In FIG. 4a, which shows a de-energized state or condition, viewable and 
conductive images 16 are obscured by light modulating layer 30 which 
covers viewable and conductive images 16. Cover glass 24 is bonded over 
sheet 10 and ground connection 50 has been soldered onto the transparent 
electrically conductive layer 24a. 
FIG. 4b shows the activation of one area of display 5. One of the circuit 
board traces 45 (see circuit board trace 45a) is shown to be electrically 
connected to a source of potential, +e. It will be understood by those 
skilled in the art that a control circuit should actually be interposed 
between the potential source e+ and the conductive traces 45 to 
selectively apply potential to viewable and conductive images 16 which are 
to be displayed. Similarly, the other circuit board traces 45 are 
connected to appropriate electrical potentials. Circuit board trace 45 
carries the charge to piercing pins 20 and into viewable and conductive 
images 16. The other electrical connection for a viewable and conductive 
image 16 is shown as ground connection 50. The potential is selectively 
applied across appropriate circuit board traces to a viewable and 
conductive image 16. A field is produced which causes liquid crystal 
material in light modulating layer 30 to align with the imposed electrical 
field. Areas of light modulating layer 30 overlying selected viewable and 
conductive images 16 becomes transparent and viewable and conductive 
images 16 are exposed. 
FIGS. 5a-e are schematic representations of how viewable and conductive 
images 16 are formed in photosensitive layer 14. Unexposed silver halide 
92 is the light sensitive material. 
In FIG. 5a, photo mask 80 selectively blocks a source of light that strikes 
and exposes silver halide 94 while unexposed silver halide 92 remains 
inactivated. A photo mask conductive coating 80a works in conjunction with 
a grounding plate on the other side of sheet 10 to drive light modulating 
layer 30 to a transparent condition or state. The photo mask conductive 
coating 80a can be a sputtered coating of indium-tin-oxide (ITO) or 
tin-oxide having optical transparency greater than 85% and electrical 
conductivity greater than 250 ohms per square. 
In FIG. 5b sheet 10 is photographically developed to convert exposed silver 
halide 94 to metallic silver 96. Metallic silver 96 forms viewable and 
conductive images 16 in sheet 10. 
In FIG. 5c, a conventional photographic fixing step has removed the 
unexposed silver halide 92. Removal of unexposed silver halide 92 leaves 
non-conductive areas 18 in sheet 10. 
In FIG. 5d, cover glass 24 has been adhesively bonded to sheet 10. 
In FIG. 5e, piercing pins 20 on circuit board 40 have been driven through 
sheet 10 and into photosensitive layer 14 to electrically connect with 
viewable and conductive images 16 in photosensitive layer 14. 
The invention has been described in detail with particular reference to 
certain preferred embodiments thereof, but it will be understood that 
variations and modifications can be effected within the spirit and scope 
of the invention. 
______________________________________ 
TS LIST 
______________________________________ 
5 display 
10 sheet 
12 substrate 
14 photosensitive layer 
16 viewable and conductive images 
18 non-conductive areas 
20 piercing pins 
24 cover glass 
24a transparent electrically conductive layer 
30 light modulating layer 
40 circuit board 
45 circuit board traces 
45a circuit board trace 
50 ground connection 
80 photo mask 
80a photo mask conductive coating 
92 unexposed silver halide 
94 exposed silver halide 
96 metallic silver 
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