U.S. patent number 7,206,044 [Application Number 10/001,495] was granted by the patent office on 2007-04-17 for display and solar cell device.
This patent grant is currently assigned to Motorola, Inc.. Invention is credited to Kevin W. Jelley, Zili Li, Iwona Turlik.
United States Patent |
7,206,044 |
Li , et al. |
April 17, 2007 |
Display and solar cell device
Abstract
Displays such as liquid crystal displays (10), organic light
emitting diode displays, and touch sensitive displays (41) are
stacked with one or more solar cells (15) such that light passing
through the displays will illuminate the light receiving active
surface of the solar cells (15). No reflector or polarizer need be
used when the liquid crystal display (10) uses cholesteric or
polymer dispersed liquid crystals. When using supertwist nematic or
twisted nematic liquid crystals, a reflector (21) can be used that
comprises a selective color reflector. The resultant display/solar
cell can be utilized in combination with a device such as a
wireless communications device (62) with the solar cell (15)
providing electricity to the display (61), the wireless
communications device (62), or both. A mask (71) can be used to
occlude surface features on the solar cell (15) as appropriate to
provide a substantially uniformly colored appearance.
Inventors: |
Li; Zili (Barrington, IL),
Turlik; Iwona (Barrington, IL), Jelley; Kevin W. (La
Grange, IL) |
Assignee: |
Motorola, Inc. (Schaumburg,
IL)
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Family
ID: |
21696311 |
Appl.
No.: |
10/001,495 |
Filed: |
October 31, 2001 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20030081158 A1 |
May 1, 2003 |
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Current U.S.
Class: |
349/113; 250/200;
136/244 |
Current CPC
Class: |
G02F
1/13306 (20130101); G02F 1/133553 (20130101); G02F
1/133521 (20210101); G02F 1/13324 (20210101); G02F
1/13718 (20130101); G02F 1/1334 (20130101) |
Current International
Class: |
G02F
1/1335 (20060101) |
Field of
Search: |
;348/113 ;349/113 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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4-362917 |
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Dec 1992 |
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JP |
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04362917 |
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Dec 1992 |
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JP |
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000/00300 |
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Feb 2001 |
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RU |
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WO 95/27279 |
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Oct 1995 |
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WO |
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Primary Examiner: Schechter; Andrew
Assistant Examiner: Kim; Richard
Claims
We claim:
1. A device comprising: a solar cell; a reflective liquid crystal
display having a backside and a front side and having one of
selectively reflecting cholesteric and polymer dispersed liquid
crystal such that at least some light passing from the front side
and through the backside of the reflective liquid crystal display
will illuminate a substantially uniform dark-colored
light-receiving active surface of the solar cell, wherein the solar
cell has a light-receiving inactive surface that has a different
color than the substantially uniform dark-colored light-receiving
active surface; and a mask having apertures that substantially
conform topographically to the light-receiving active surface of
the solar cell and mask surfaces that substantially conform to at
least some of the light-receiving inactive surface and that has a
color that substantially matches the substantially uniform
dark-colored light-receiving active surface of the solar cell.
2. The device of claim 1 and wherein at least some of the light
passing from the front side and through the backside of the
reflective liquid crystal display will illuminate the
light-receiving active surface without first passing through a
polarizing layer.
3. The device of claim 1 and further comprising a wireless
communications device having a user interface operably coupled to
the reflective liquid crystal display.
4. The device of claim 3 wherein the wireless communications device
further includes a battery charger that operably couples to the
solar cell.
5. The device of claim 3 wherein an electricity output of the solar
cell is operably coupled to at least one of the reflective liquid
crystal display and the wireless communications device.
6. The device of claim 1 and further comprising a plurality of
solar cells.
7. The device of claim 1 wherein the mask comprises paint deposited
on the light-receiving inactive surface of the solar cell.
8. A device comprising: a solar cell package; a reflective liquid
crystal display having a backside and a front side and having one
of selectively reflecting cholesteric and polymer dispersed liquid
crystal, wherein at least some light passing from the front side
and through the backside of the reflective liquid crystal display
will illuminate a substantially uniform dark-colored
light-receiving active surface of the solar cell package, and
wherein the solar cell package has a surface inactive to light that
has a different color than the substantially uniform dark-colored
light-receiving active surface; and a mask that covers at least a
portion of the surface that is inactive to light, that has
apertures that substantially conform topographically to the
substantially uniform dark-colored light-receiving active surface
of the solar cell package, and has a color that substantially
matches a color of the substantially uniform dark-colored
light-receiving active surface.
9. The device of claim 8 wherein the mask comprises paint deposited
on the solar cell package whereat the mask covers at least a
portion of the surface that is inactive to light.
10. The device of claim 8 wherein the solar cell package comprises
one or more solar cells.
Description
FIELD OF THE INVENTION
This invention relates generally to liquid crystal displays, touch
sensitive displays, and solar cells and also to wireless
communication devices having such displays and solar cells.
BACKGROUND
Various portable devices, including wireless communications
devices, utilize a portable energy source such as one or more
batteries. Notwithstanding improvements to both battery technology
and power consumption of such portable devices, batteries
nevertheless represent a finite source of power. Ways to extend
(indefinitely if possible) battery life are constantly being
sought.
For some devices, solar cells represent a viable supplemental or
alternative energy source. Some devices, such as portable
calculators, have both sufficiently large available surface area
and sufficiently low power needs that some of these devices can be
powered entirely by one or more solar cells. Unfortunately, many
devices, including for example cellular telephones and other
wireless communications devices have both higher power demands and
an often limited available surface area for locating a solar cell.
As a result, solar cells have not been viewed as a satisfactory
supplemental or alternative power source for such devices.
Some prior art suggestions have been made to combine a solar cell
with a display such as a liquid crystal display. Such a combination
seems attractive since the display will comprise an ordinary part
of the device at issue and the solar cell itself would not require
additional surface area. Unfortunately, prior art attempts in this
regard have been unsatisfactory. In particular, light that finally
reaches the active light receiving surface of the solar cell has
been sufficiently attenuated as to substantially mitigate the
quantity of electrical power that can be provided by the solar cell
even under ideal conditions. The small incremental quantities of
supplemental power provided through such prior art attempts have
been too small to warrant the additional cost and complexity of
providing such a combination in most if not all such devices.
Consequently, a continuing need exists for a way to supplement or
replace battery power in portable devices including wireless
communications devices in a commercially acceptable and
cost-effective manner.
BRIEF DESCRIPTION OF THE DRAWINGS
This need and others are substantially met through provision of the
display and solar cell device disclosed herein. Various embodiments
of this device will be better understood upon making a thorough
review and study of the following detailed description,
particularly when reviewed in conjunction with the drawings,
wherein:
FIG. 1 comprises a side elevational view of a first embodiment
configured in accordance with the invention;
FIG. 2 comprises a side elevational view of a second embodiment
configured in accordance with the invention;
FIG. 3 comprises a graph;
FIG. 4 comprises a side elevational view of a third embodiment
configured in accordance with the invention;
FIG. 5 comprises a side elevational view of a fourth embodiment
configured in accordance with the invention;
FIG. 6 comprises a block diagram depiction of a wireless
communications device including any of the first through fourth
embodiments configured in accordance with the invention; and
FIG. 7 comprises an exploded perspective view of a mask used in
conjunction with solar cells in accordance with an embodiment of
the invention.
DETAILED DESCRIPTION
Referring now to the figures, FIG. 1 depicts a first embodiment of
a display combined with at least one solar cell. In this
embodiment, a liquid crystal display 10 includes opposing
transparent plates 11 and 12 comprised of glass or suitable plastic
material. Liquid crystal 13 fills the space between these two
plates 11 and 12 in accordance with well understood prior art
knowledge and technique. In this embodiment, the liquid crystal
display 10 comprises a so-called reflective embodiment and the
liquid crystal comprises either cholesteric liquid crystal or
polymer disbursed liquid crystal. Such liquid crystal display
technology requires neither a reflector (to reflect light from the
back of the liquid crystal display towards the front) nor a
polarizer layer. Being free of both these elements, transmission of
light from the front of the liquid crystal display 10 through the
back thereof can be 75 percent or better (especially for a
monochromatic cholesteric liquid crystal display that displays only
a single color). Such transmissivisity greatly exceeds, for
example, ordinary reflective liquid crystal display technology
using super-twisted nematic liquid crystals and metallic
reflectors/transflectors that often pass less than six percent of
the light that originally enters through the front surface of the
liquid crystal display.
A solar cell 15 is disposed proximal to the backside of the liquid
crystal display 10 and a coupling layer 14 joins the solar cell 15
to the liquid crystal display 10. The coupling layer 14 can be, for
example, comprised of an appropriate transparent adhesive material
as appropriate to a particular application. (For some embodiments,
and particularly where vertical thickness comprises a critical form
factor, the solar cell 15 may be joined directly to the backside of
the liquid crystal display 10.) If desired, and depending upon the
area of the liquid crystal display 10 itself and/or desired total
power output, multiple solar cells 15 can be utilized as suggested
by phantom line 16.
The solar cell 15 has a light receiving active surface as
understood in the art. For most applications, the appearance of the
liquid crystal display 10 will be enhanced if the light receiving
active surface has a uniform appearance and typically a
dark-colored appearance. For most applications, a black or
substantially black colored surface will be optimum.
So configured, at least some of the light 17 passing through the
front plate 11 and through the back plate 12 of the reflective
liquid crystal display 10 will illuminate the light receiving
active surface of the solar cell 15. In this embodiment, where the
solar cell 15 has a light receiving active surface that fully
extends to the same boundaries as the liquid crystal display 10, at
least 75 percent of the light 17 so entering the liquid crystal
display 10 will reach the solar cell 15. Consequently, depending
upon the total area available, considerable electricity can be
provided by the solar cell 15 under various normal viewing
conditions.
Referring now to FIG. 2, a second embodiment will be described. In
this embodiment, the liquid crystal display 10 again includes a
front plate 11 and a back plate 12. In this embodiment, however,
the liquid crystal 13 comprises either supertwist nematic or
twisted nematic liquid crystal. Such liquid crystal requires a
reflector, and this embodiment therefore provides a reflector 21
juxtaposed substantially parallel against the back plate 12 of the
liquid crystal display 10. In this embodiment, however, the
reflector 21 does not reflect substantially all incident light 22
back through the liquid crystal display 10 towards the observer.
Instead, the reflector 21 comprises a selective color reflector.
With momentary reference to FIG. 3, this selective color reflector
reflects only a relatively narrow band of wavelengths 32 while
transmitting or passing substantially unattenuated light at other
wavelengths 31. Holographic film technology, such as Optimax
technology developed by Motorola, can serve as such a selective
color reflector. The color so selected to be reflected should match
the intended to color of the liquid crystal display 10. For
example, if the liquid crystal display 10 utilizes green as a
display color, then green constitutes the color that should be
selectively reflected by the reflector 21. For a multi-colored
display, such as a display that uses red, green, and blue, the
selective color reflector should reflect wavelengths for all
selected colors while allowing unselected colors to pass
there-through substantially unattentuated. So configured, in all
embodiments, the selective color reflector reflects at least
wavelengths that correspond to a first color but not all visible
spectrum colors; depending upon the embodiment only a single color
may be reflected or multiple colors may be reflected.
As with the first embodiment, a solar cell 15 or cells 16 is/are
disposed proximal to the backside of the reflector 21 (again using
an appropriate coupling layer 14 to maintain or provide structural
integrity). So configured, light 22 entering through the liquid
crystal display 10 will be minimally and partially reflected 24 by
the reflector 21 and the remainder of the light 22 will pass
through the reflector 21 to illuminate the light receiving active
surface of the solar cell 15. For such an embodiment, at least 30
percent of the entering light can be expected so pass through the
liquid crystal display 10 and the reflector 21. Though this
percentage is lower than that achieved with the first embodiment,
this performance still greatly exceeds the performance of
corresponding prior art displays. As with the first embodiment, the
light receiving active surface of the solar cell should again have
a substantially uniform dark-colored appearance and preferably a
uniform black appearance.
Liquid crystal displays using supertwist nematic or twisted nematic
liquid crystals utilize a polarizing layer. For most if not all
applications such a polarizing layer is necessary. In that event,
the front plate 11 of the liquid crystal display 10 can be
configured as a polarizing layer, or a polarizing layer can be
disposed outwardly of the front plate 11. In the alternative, or in
addition, the back plate 12 of the liquid crystal display 10 can
also be configured as a polarizing layer, or a polarizing layer can
be disposed inwardly of the back plate 12.
Organic Light Emitting Diodes are another type of display that can
support a relevant embodiment in accordance with the invention.
Unlike the reflective liquid crystal displays that are discussed
above, OLED's do not depend on ambient light to form an image on
the display. Instead, OLED's emit their own light to form a desired
image. In a conventional OLED, a transparent top electrode (most
commonly a thin Indium-Tin-Oxide layer) and a highly reflective
bottom electrode (most commonly an aluminum layer) are disposed on
either side of a layer of light emitting organic material. When
powered, electrons ejected from the bottom electrode and holes
ejected from the top electrode move towards the center OLED
material layer. Recombination of the electrons and holes in the
OLED material creates visible light.
Upward emission of the light will pass directly through the
transparent top electrode. The downward emission of light will
reflect back from the reflective bottom electrode to combine with
the upward emission and travel through the top electrode. As
understood in the art, one modulates the degree of power applied to
the electrodes to generate the desired image.
The aluminum layer that serves as a mirror in a typical OLED blocks
all light (ambient or otherwise) from passing any further.
Consequently, a solar cell could not be placed behind such a
display with any expectation that any amount of useful light would
reach the solar cell. In this embodiment, however, just as with the
super twisted nematic and nematic LCD cases described above, a
selective color reflector can be substituted for the bottom
metallic reflector and a solar cell can then be usefully placed
behind the selective color reflector. The reflective wavelength of
the selective color reflector should be chosen to correspond to the
emission spectrum of the OLED itself. Pursuant to such an
embodiment, an acceptable OLED display can be realized while
simultaneously allowing an increased amount of non-image forming
light (such as ambient light) to pass through the selective color
reflector and contact the light receiving surfaces of the solar
panel. Transmissivity of the same or more light than is achieved
with a reflective super twisted nematic liquid crystal display is
reasonably to be expected.
Fully transparent OLED's have also been demonstrated quite
recently. With such a device, ambient light can readily pass
through the display and contact a solar cell as disposed on the
backside of the display. Consequently, this invention can readily
be extended to transparent OLED's in a similar fashion as taught
below as applied in the context of touch sensitive devices.
Touch sensitive displays are well understood in the art. Touch
sensitive displays ordinarily have a back surface that is colored
relatively dark with most consumer products having such a display
using a gray color. Pursuant to a third embodiment as depicted in
FIG. 4, this back surface of a touch sensitive display 41 can be
transparent instead such that light 43 can pass through the back of
the touch sensitive display 41 to illuminate the light receiving
active surface of a solar cell 15 that is disposed proximal to the
backside of the touch sensitive display 41. Again, a coupling layer
14 can be provided to integrate the solar cell 15 with the touch
sensitive display 41. So configured, a significant percentage of
light 43 entering the touch sensitive display 41 will pass through
the transparent backside of the touch sensitive display 41 and
illuminate the light receiving active surface of the solar cell 15.
The surface of the solar cell 15 should again be substantially
uniformly colored and can be whatever color is appropriate as the
background color for the touch sensitive display (such as
gray).
A fourth embodiment as depicted in FIG. 5 provides a device having
both a liquid crystal display 10 and a touch sensitive display 41.
Each display can be configured as described above. In the
particular embodiment depicted, the liquid crystal display 10
comprises a reflective liquid crystal display using supertwist
nematic or twisted nematic liquid crystals. Consequently, this
embodiment depicts the liquid crystal display 10 in conjunction
with a reflector 21 that comprises a selective color reflector as
described above. If this embodiment were to use cholesteric or
polymer dispersed liquid crystals, then this reflector 21 could be
eliminated. In this embodiment, the liquid crystal display 10 and
the touch sensitive display 41 are positioned substantially
contiguous to one another. When these displays are contiguous as
depicted (or are at least relatively close together) a common
coupling layer 14 can be utilized to join a solar cell 15 or solar
cells 16 to both displays 10 and 41. As before, the solar cell 15
or solar cells 16 preferably have a substantially uniform
dark-colored light-receiving active surface such as a black
light-receiving active surface.
So configured, a significant part of the light entering both
through the liquid crystal display 10 and the touch sensitive
display 41 will pass therethrough and illuminate the light
receiving active surface of the solar cell 15 or solar cells
16.
Depending upon ambient light conditions, the electricity generated
by the solar cell 15 in the above embodiments can be considerable.
FIG. 6 depicts some ways by which these resultant devices can be
utilized. In this embodiment, a wireless communications device 62
such as a cellular telephone, a dispatch two-way radio, a one-way
or two-way pager, a wireless personal digital assistant, or the
like has a user interface 63 that couples to and drives a display
61. This display 61 can be a liquid crystal display using
cholesteric or polymer dispersed liquid crystal, a liquid crystal
display using supertwist nematic or twisted nematic liquid crystal,
or a pressure sensitive display 41 as disclosed above (or
juxtaposed combinations as appropriate to a given application). The
display 61 passes light to a corresponding solar cell 15 as taught
above. Electricity from this solar cell 15 can be coupled 64 to the
display 61 to supplement battery power or to substitute for battery
power (either temporarily or permanently). In addition, or in the
alternative, electricity from this solar cell 15 can be coupled 65
to the wireless communications device 62 to supplement or
substitute for battery power as utilized to power the wireless
communications device 62. As one particular example, electricity
from the solar cell 15 can be coupled to a battery charger circuit
and used to charge the batteries for the device in question.
Although only a single solar cell 15 has been depicted for ease of
description, it will be readily recognized that a plurality of
solar cells could be utilized to provide increased quantities of
electricity.
Many solar cells 15 are provided in an integrated package that does
not offer a uniformly colored active surface area. Instead, and
referring now to FIG. 7, many such packages provide a plurality of
solar cells 15 that are separated by inactive areas 74 made of, for
example, copper or other metal. Not only are such materials usually
comprised on a color that does not match the color of the active
surface regions, but such materials are also usually relatively
reflective. As a result, when placing such a package behind a
display surface as taught above, under at least some viewing
conditions these inactive surface regions can be visible through
the display. When visible in this way, the resultant display can be
very distracting to a user.
When using such a package, it may therefore be desired to modify
the package in order to ensure that the package has a substantially
uniform color across at least that part of the package surface that
will be at least partially visible through the display. Pursuant to
one embodiment, paint masking technologies can be used to deposit
paint on the inactive surfaces to thereby match the color of the
solar cells 15. Pursuant to another embodiment, a permanent mask 71
matching the color of the active regions of the solar cells 15 can
be provided between the solar cells 15 and the display itself. Such
a mask 71 should have apertures 72 and 73 to allow light to pass
therethrough and contact the active areas 15A and 15B and of the
solar cells. So configured, the mask 71 will cooperate with the
solar cell package to allow light to pass through to the active
regions while presenting a substantially uniformly colored surface
as a background to the display. If desired, the permanent mask 71
can be formed as an integral part of the coupling layer 14
described above.
The devices described provide a more commercially acceptable
solution than that offered by the prior art. No surface space of
the device to be powered need be uniquely dedicated to one or more
solar cells. Instead, the surface space dedicated to the display
can serve a parallel purpose in serving as a light collection
portal for illuminating the active surfaces of the solar cells.
Furthermore, relatively ordinary and cost effective liquid crystal
display technologies can now be utilized successfully to provide an
acceptable display and nevertheless provide an acceptable level of
light to a stacked solar cell. As yet one other advantage, the
display will offer protection for the solar cell (such protection
will likely be especially meaningful for high efficiency solar
panels).
Those skilled in the art will recognize that various alterations
and substitutions can be made with respect to the embodiments
described without departing from the spirit and scope of the
inventive concepts set forth. It is understood that the breadth and
scope of the invention is defined only by the following claims.
* * * * *