U.S. patent application number 10/672687 was filed with the patent office on 2005-03-31 for adjustably opaque window.
Invention is credited to Clark, Noel, Fernando, Primal, Xue, Jiuzhi.
Application Number | 20050068629 10/672687 |
Document ID | / |
Family ID | 34376440 |
Filed Date | 2005-03-31 |
United States Patent
Application |
20050068629 |
Kind Code |
A1 |
Fernando, Primal ; et
al. |
March 31, 2005 |
Adjustably opaque window
Abstract
An adjustably opaque window including an external pane, an
internal pane, a light transmission control layer and a
shock-absorbing layer is provided. The external pane and the
internal pane provide a cavity between them, and the light
transmission control layer and the shock-absorbing layer are
positioned in the cavity. The shock-absorbing layer is a flexible
sheet that supports and protects the light transmission control
layer. The light transmission layer consists of liquid crystal
cells. The transmission ratio of the cells can be controlled
variably.
Inventors: |
Fernando, Primal; (Boulder,
CO) ; Clark, Noel; (Boulder, CO) ; Xue,
Jiuzhi; (Broomfield, CO) |
Correspondence
Address: |
PARK & SUTTON LLP
3255 WILSHIRE BLVD
SUITE 1110
LOS ANGELES
CA
90010
US
|
Family ID: |
34376440 |
Appl. No.: |
10/672687 |
Filed: |
September 26, 2003 |
Current U.S.
Class: |
359/609 ;
359/614 |
Current CPC
Class: |
G02B 5/208 20130101;
B32B 17/10174 20130101; B32B 17/10339 20130101; E06B 9/24 20130101;
E06B 2009/2464 20130101; Y02B 80/00 20130101; B32B 17/10036
20130101; Y02A 30/24 20180101; G02F 1/133305 20130101 |
Class at
Publication: |
359/609 ;
359/614 |
International
Class: |
G02B 027/00 |
Claims
What is claimed is:
1. An adjustably opaque window comprising: a) an external pane; b)
an internal pane; c) a light transmission control layer; and d) a
shock absorbing layer; wherein the external pane and the internal
pane provide a cavity between them, wherein the light transmission
control layer and the shock absorbing layer are positioned in the
cavity, wherein the light transmission control layer is supported
by the shock absorbing layer.
2. The adjustably opaque window of claim 1, wherein the shock
absorbing layer comprises a first flexible sheet, and the light
transmission control layer is attached to the first flexible
sheet.
3. The adjustably opaque window of claim 2, wherein the first
flexible sheet is made of polyester, or polycarbonate.
4. The adjustably opaque window of claim 2, wherein the thickness
of the first flexible sheet is in a range from about 0.1 to about
0.2 mm.
5. The adjustably opaque window of claim 2, wherein the external
pane and the internal pane are substantially hard.
6. The adjustably opaque window of claim 5, wherein the external
pane and the internal pane are made of glass.
7. The adjustably opaque window of claim 2, wherein the light
transmission control layer comprises a plurality of light
transmission control cells.
8. The adjustably opaque window of claim 7, wherein the light
transmission control cells are arranged to form a lattice.
9. The adjustably opaque window of claim 7, wherein the opacity of
the light transmission control cells is variably adjustable.
10. The adjustably opaque window of claim 9, wherein the opacity of
each of the light transmission control cells is adjusted by
changing amplitude of electric field applied on the light
transmission control cell.
11. The adjustably opaque window of claim 9, wherein each of the
light transmission control cell comprises a first electrode, a
second electrode, and an electro-optic material in between the
first and second electrodes.
12. The adjustably opaque window of claim 11, wherein the
electro-optic material comprises liquid crystal, or nonlinear
optical material.
13. The adjustably opaque window of claim 12, wherein the liquid
crystal comprises dichroic dye doped liquid crystals.
14. The adjustably opaque window of claim 12, wherein the liquid
crystal comprises nematic liquid crystals with chiral dopants.
15. The adjustably opaque window of claim 12, wherein the liquid
crystal comprises nematic liquid crystals without chiral
dopants.
16. The adjustably opaque window of claim 12, wherein the liquid
crystal comprises chiral nematic liquid crystals.
17. The adjustably opaque window of claim 12, wherein the liquid
crystal comprises polymeric liquid crystals.
18. The adjustably opaque window of claim 12, wherein the liquid
crystal comprises ferroelectric liquid crystals.
19. The adjustably opaque window of claim 12, wherein the liquid
crystal is doped with dichroic light absorbing dye.
20. The adjustably opaque window of claim 12, wherein the liquid
crystal is doped with pleochoric light absorbing dye.
21. The adjustably opaque window of claim 12, further comprising a
first polarizing layer that is positioned between the external pane
and the light transmission control layer, and a second polarizing
layer that is positioned between the first flexible sheet and the
interior pane; wherein the direction of polarization of the first
polarizing layer is substantially perpendicular to the direction of
polarization of the second polarizing layer.
22. The adjustably opaque window of claim 21, wherein the first
polarizing layer is integrated with the external pane, and the
second polarizing layer is integrated with the internal pane.
23. The adjustably opaque window of claim 21, wherein the first
polarizing layer is absorptive.
24. The adjustably opaque window of claim 21, wherein the first
polarizing layer is birefringence based.
25. The adjustably opaque window of claim 21, wherein the light
transmission cell further comprises a first electrode that is
substantially adjacent the first polarizing layer, and a second
electrode that is substantially adjacent the first flexible sheet,
wherein the liquid crystal is positioned between the first
electrode and the second electrode.
26. The adjustably opaque window of claim 25, wherein the first
electrode comprises a substantially transparent plastic substrate
coated with transparent conductive coating, and wherein the second
electrode comprises a substantially transparent plastic substrate
coated with transparent conductive coating.
27. The adjustably opaque window of claim 25, wherein the surface
of the first electrode, which is adjacent the liquid crystal, is
treated with a first polymer layer such that the first polymer
layer gives a preferential alignment to the adjacent liquid
crystal, and the surface of the second electrode, which is adjacent
the liquid crystal, is treated with a second polymer layer such
that the second polymer layer gives a preferential alignment to the
adjacent liquid crystal.
28. The adjustably opaque window of claim 27, wherein the liquid
crystals adjacent the first and second polymer layers are
pre-tilted from the planes of the first and second polymer layers,
wherein the preferential direction of the treated first polymer
layer is substantially parallel to the direction of polarization of
the first polarizing layer, and the preferential direction of the
treated second polymer layer is substantially parallel to the
direction of the second polarizing layer.
29. The adjustably opaque window of claim 28, wherein the
pre-tilting angle is in a range from 0.degree. to about forty five
degrees (45.degree.).degree..
30. The adjustably opaque window of claim 29, wherein the
pre-tilting angle is about thirty degrees (30.degree.).degree..
31. The adjustably opaque window of claim 25, wherein the light
control transmission cell further comprises a plurality of spacers,
wherein the spacers maintain predetermined distance between the
first and second electrodes.
32. The adjustably opaque window of claim 31, wherein all of the
spacers are coated with adhesive.
33. The adjustably opaque window of claim 31, wherein part of the
spacers are coated with adhesive.
34. The adjustably opaque window of claim 31, wherein the spacers
are randomly distributed within the light transmission control
cell.
35. The adjustably opaque window of claim 31, wherein each of the
spacers comprises a sphere, and the sphere contacts the first and
second electrodes.
36. The adjustably opaque window of claim 35, wherein the sphere is
coated with an adhesive layer, wherein the diameter of the sphere
is in a range from about five (5) to about thirty (30) microns, and
wherein the thickness of the adhesive layer is less than about five
(5) microns.
37. The adjustably opaque window of claim 9, wherein the first
flexible sheet is coated with transparent electrically conductive
coating.
38. The adjustably opaque window of claim 37, wherein the
transparent conductive coating is made of Indium Tin Oxide.
39. The adjustably opaque window of claim 37, wherein the
transparent conductive coating forms an electrical wiring to each
light transmission control cell.
40. The adjustably opaque window of claim 39, further comprising a
control circuit that controls each of the light transmission
control cells individually with the electrical wiring.
41. The adjustably opaque window of claim 39, further comprising a
control circuit that controls the light transmission control cells
collectively in part with the electrical wiring.
42. The adjustably opaque window of claim 39, further comprising a
control circuit that controls the light transmission control cells
in whole with the electrical wiring.
43. The adjustably opaque window of claim 9, further comprising a
light sensor that measures the intensity of the incident light,
wherein the control circuit controls the light transmission of the
light transmission control cells based on data provided by the
light sensor.
44. The adjustably opaque window of claim 9, wherein the light
transmission of the light transmission control cells is
controllable manually.
45. The adjustably opaque window of claim 9, further comprising an
array of photovoltaic cells, wherein the array provides electricity
for operation of the light transmission control layer.
46. The adjustably opaque window of claim 45, wherein the
adjustably opaque window is a vehicle window, and wherein the array
is installed in a vehicle.
47. The adjustably opaque window of claim 9, wherein the adjustably
opaque window is an architectural window, a glass door, or a
partition.
48. The adjustably opaque window of claim 9, further comprising an
ultra violet light blocking layer that is positioned between the
exterior pane and the light transmission control layer.
49. The adjustably opaque window of claim 2, wherein the opacity of
the light transmission control layer is variably adjustable.
50. The adjustably opaque window of claim 49, wherein the opacity
of the light transmission control layer is adjusted by changing
amplitude of electric field applied on the light transmission
control layer.
51. The adjustably opaque window of claim 2, wherein the shock
absorbing layer further comprises a second flexible sheet, wherein
the second flexible sheet is attached to the light transmission
control layer opposite to the first flexible sheet.
52. The adjustably opaque window of claim 1, wherein the shock
absorbing layer comprises gel that fill the cavity, and the light
transmission control layer is supported in the gel.
53. The adjustably opaque window of claim 1, wherein attachment
among the external pane, the internal pane, the light transmission
control layer, and the shock absorbing layer is done with pressure
sensitive adhesive.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a window having adjustable
opacity. More particularly, this invention relates to an adjustable
or variable window tinting system for the vehicle and architectural
industries, and further, a window system for sunlight
protection.
[0002] Vehicle and building windows that transmit a fixed fraction
of incident light are desired by many, and are currently
commercially available to control the sunlight intrusion into the
vehicles and buildings. Such windows with a fixed tint, while
desired by users during bright sunlight days, are undesirable on
cloudy days and in the evenings. Windows are needed where a
controllable fraction of incident visible light intensity can be
applicable under varying environmental as well as social conditions
and needs. A protective variable tinting that controls in
fractions, the visible light transmitting through the window, and
at the same time that can filter out UV and most of the infrared
light is highly desirable.
SUMMARY OF THE INVENTION
[0003] The present invention contrives to meet the need for an
improved light-controlling window.
[0004] An objective of the invention is to provide an adjustably
opaque window that automatically or manually changes its opacity
variably depending on ambient lighting situations.
[0005] Another objective of the invention is to provide an
adjustably opaque window that is durable and thin enough for a
vehicle window.
[0006] Still another objective of the invention is to filter the UV
and infrared light out of vehicle or building either by absorption
or reflection.
[0007] Still another objective of the invention is to provide an
adjustably opaque window that can gradually change its color or
tint.
[0008] Still another objective of the invention is to provide a
robust and dimensionally flexible enclosure for electro-optic
materials such as liquid crystal for window applications.
[0009] To achieve the above objectives, an adjustably opaque window
including an external pane, an internal pane, a light transmission
control layer, and a shock absorbing layer is provided. The
external pane and the internal pane provide a cavity between them,
and the light transmission control layer and the shock absorbing
layer are positioned in the cavity. The light transmission control
layer is supported by the shock absorbing layer. The attachment
among the external pane, the internal pane, and the light
transmission control layer, and the shock absorbing layer is done
with techniques often employed by glass lamination processes, such
as those using polyvinyl butyral (PVB), or optically clear UV
curable resins such as those under the trade name of Astrocure
1000G, and may further include the use of pressure sensitive
adhesive.
[0010] The shock absorbing layer includes the lamination materials
such as polyvinyl butyral (PVB), UV curable clear resins such as
Astrocure 1000G, and or pressure sensitive adhesives that are
further designed to have or to enhance their shock absorbing
properties while providing the function of attachment among various
layers.
[0011] Alternatively, the shock absorbing layer includes gel that
fills the cavity, and the light transmission control layer is
supported in the gel.
[0012] Alternatively, the shock absorbing layer includes a first
flexible sheet, and the light transmission control layer is
attached to the first flexible sheet. The shock absorbing layer may
further include a second flexible sheet, and the second flexible
sheet is attached to the light transmission control layer opposite
to the first flexible sheet.
[0013] Preferably, the first and second flexible sheets are made of
polyester or polycarbonate, and the thickness of them should be in
a range from about 0.1 to about 0.2 mm.
[0014] The external pane and the internal pane are substantially
hard. Preferably, the external pane and the internal pane are made
of glass.
[0015] In a preferred embodiment, the light transmission control
layer includes a plurality of light transmission control cells that
are arranged to form a seamlessly tiled lattice structure.
[0016] The opacity of the light transmission control cells is
variably adjustable. The opacity of each of the light transmission
control cells, or of the light transmission control layer, is
adjusted by applying an external stimulus such as an external
electric field and by changing the amplitude of such an electric
field applied to the light transmission control cell.
[0017] Each of the light transmission control cells comprises a
first electrode, a second electrode, and an electro-optic material
in between the first and second electrodes. The electro-optic
material may be, and not limited to liquid crystals, nonlinear
optical material, and other optical materials having similar
characteristics.
[0018] The types of liquid crystal which forms the light
transmission layer may include but not limited to nematic liquid
crystals with or without chiral dopants, chiral nematic liquid
crystals, polymeric liquid crystals, ferroelectric liquid crystals.
Such liquid crystal may be doped with dichroic light absorbing dye,
or with pleochoric light absorbing dye.
[0019] The adjustably opaque window further includes a first
polarizing layer that is positioned between the external pane and
the light transmission control layer, and a second polarizing layer
that is positioned between the first flexible sheet and the
interior pane. The direction of polarization of the first
polarizing layer is substantially perpendicular to the direction of
polarization of the second polarizing layer.
[0020] The first and second polarizing layers may be integrated
with the external and the internal pane, respectively. The first
polarizing layer is absorptive, or birefringence based. Also, the
first polarizing layer may include wire grids of metals.
[0021] In the light transmission cell, the first electrode is
substantially adjacent the first polarizing layer, and the second
electrode is substantially adjacent the first flexible sheet.
[0022] The first electrode includes a substantially transparent
plastic substrate coated with transparent conductive coating, and
the second electrode includes a substantially transparent plastic
substrate coated with transparent conductive coating.
[0023] The first electrode, which is adjacent the liquid crystals,
is treated with a first polymer layer such that the first polymer
layer gives a preferential alignment to the adjacent liquid
crystal, and the surface of the second electrode, which is adjacent
liquid crystal, is treated with a second polymer layer such that
the second polymer layer gives a preferential alignment to the
adjacent liquid crystal.
[0024] The liquid crystals adjacent the first and second polymer
layers are pre-tilted from the planes of the first and second
polymer layers. The preferential direction of the treated first
polymer layer is substantially parallel to the direction of
polarization of the first polarizing layer, and the preferential
direction of the treated second polymer layer is substantially
parallel to the direction of the second polarization layer.
[0025] Preferably, the pre-tilting angle is in a range from
0.degree. to about forty five degrees (45.degree.). More
preferably, the pre-tilting angle is about thirty degrees
(30.degree.).
[0026] The light control transmission cell further includes a
plurality of spacers, and the spacers maintain predetermined
distance between the first and second electrodes. Part or all of
the spacers are coated with adhesive. The spacers are randomly
distributed within the light transmission control cell. Each of the
spacers includes a sphere, and the sphere contacts the first and
second electrodes. The sphere is coated with an adhesive layer. The
diameter of the sphere is in a range from about five (5) to about
thirty (30) microns, and the thickness of the adhesive layer is
less than about five (5) microns.
[0027] The first flexible sheet is coated with transparent
electrically conductive coating, which is made of Indium Tin Oxide.
The transparent conductive coating of the first flexible sheet
forms an electrical wiring to each light transmission control
cell.
[0028] The adjustably opaque window further includes a control
circuit that controls each of the light transmission control cells
individually, collectively in part, or in whole with the electrical
wiring.
[0029] The adjustably opaque window further includes a light sensor
that measures the intensity of the incident light, and the control
circuit controls the light transmission of the light transmission
control cells based on data provided by the light sensor. The light
transmission of the light transmission control cells may be
controlled manually.
[0030] The adjustably opaque window further includes an array of
photovoltaic cells, and the array provides electricity for
operation of the light transmission control layer. The adjustably
opaque window may be a vehicle window, and the array may be
installed in a vehicle. Other applications of the adjustably opaque
window includes an architectural window, a glass door, or a
partition.
[0031] The adjustably opaque window further includes an ultra
violet light blocking layer that is positioned between the exterior
pane and the light transmission control layer.
[0032] The present invention is summarized in a different aspect
below.
[0033] A controllable protective tinting window allows the
transmission of visible light to be adjusted by external means,
while the UV and infrared light are absorbed or reflected out of
the vehicle. An important mode of control in tinting applications
is the electrical manipulation of optical properties of an active
layer.
[0034] This is the central layer of the light control layer shown
in FIG. 1, and with which transmittance of light through the active
layer is controlled. An expanded view of the light control layer is
shown in FIG. 2. Films of electrically active material such as
liquid crystals, and often in combination with auxiliary layers can
change the transmittance of light in a way that depends on the
external electrical stimulus applied.
[0035] Auxiliary layers can be comprised of layers such as
polarizers of various types, layers necessary for application of
external stimulus such as an electric field, and layers necessary
for proper operation of active layers, such as alignment layers and
compensation layers to enhance the light attenuation effects for
obliquely incident light, when the active layer is liquid
crystal.
[0036] The unwanted visible light can be reflected, diffracted to
the exterior of the vehicle, or absorbed, and/or a combination of
all these modes, by the active layer and its auxiliary
elements.
[0037] The control of visible light transmittance through the light
control layer derives from the ability that the optical properties
of the active layer can be manipulated using an external stimulus
such as an electrical field. Active layers, such as liquid
crystals, can change their optical properties such as their
birefringence and hence the polarization state of the light
traveling through the active layer, when an external stimulus such
as an electrical field is applied.
[0038] More explicitly, the application of an external stimulus
such as an external electrical field to the liquid crystal layer
causes liquid crystal molecules, such as those liquid crystals
composed of rod-shaped molecules, to reorient. This molecular
reorientation in the liquid crystal layer causes a change in the
index of refraction of the light traveling through the glass. As a
result, there is a change in the polarization of light exiting the
liquid crystal layer, due to the application of the external
stimulus to the liquid crystal active layer.
[0039] Still more explicitly and more generally, the degree of
liquid crystal molecular reorientation is dependent on the
amplitude of the external stimulus, and the polarization state of
light traveling through the liquid crystal layer can be manipulated
continuously by manipulating the external stimulus.
[0040] Auxiliary layers such as polarizers can then be used to
absorb or reflect a fraction of visible light depending on the
choice of polarizers and depending on the polarization state of the
light, which is controlled by the active layer. Active layers, such
as dichroic dye doped liquid crystals can change their absorbance
of light upon the application of an external stimulus such as an
electrical field, and therefore control the transmittance of light
through the active layer using an external stimulus.
[0041] The filtering, that is, the reflection or absorption of UV
and or infrared light, can be achieved by auxiliary layers, such as
an additional UV absorption layer, polarizers, and or other active
layers, depending on the choice of such materials. External
stimulus applied to the active layer to achieve transmittance
change in the visible spectrum will have little or no effects on
the filtering of UV and infrared by the light control layer.
[0042] A variety of window sizes are employed in commercial
applications and specifically in vehicle, land, marine or air,
applications. For large windows, according to the current
invention, the active layer is structured such that several smaller
active layers joined seamlessly together for a tiled structure and
the collection of these smaller tiles, acts as one single active
layer that controls the passage of light of the whole panel, as
depicted in FIG. 3.
[0043] Protective adjustably opaque windows according to the
present invention offer a number of advantages.
[0044] Natural sunlight radiation has a broad spectrum in the
optical frequency regime, ranging from ultraviolet to infrared
beams. Ultraviolet (UV) light can induce photochemical reactions,
particularly in organic systems, and are harmful to passengers as
well as the interior of a vehicle or building. UV filtering feature
provided by the protective adjustably opaque window is an added
environmental safety feature to, for example the occupants of a
vehicle, and alleviates the problem of use of sunscreen products
for the occupants. UV radiation damage to active layers, such as
active layers made using liquid crystals, can also be minimized or
eliminated by preventing UV from entering the active layers.
[0045] The infrared spectrum of sunlight radiation can be absorbed
by materials that make up the interior of a vehicle or building,
and is a very significant portion of heat converted from absorption
of light. According to the present invention, the light control
layer can filter out the infrared by reflection or absorption or a
combination of both. The filtering of this infrared spectrum can
reduce the temperature rise of the interior of a vehicle or
building due to this converted heat, and reduce the energy and cost
of desired cooling of a vehicle or building on a hot day.
[0046] The primary function, and thus the advantage of the
adjustably opaque window is that it reduces the transmission of
unwanted light when the light setting is too bright, and it can be
tuned for maximum transmission in a darker light setting. An
additional advantage of the use of the protective adjustably opaque
window is that they can provide privacy under a wide range of
natural lighting conditions. Unless a near perfect reflection
mirror is placed in the interior of the setting protected by the
window, the reflected light is stronger than that passing through a
window from behind in typical applications. Thus objects on the
dimmer interior side of the window will be obscured to observers on
the brighter side by the reflected exterior light. Privacy can be
further enhanced by controlling the tint, to reduce the
transmission of light through the window.
[0047] Furthermore, the tiled structure of the active layer for
large windows is advantageous in several ways. The yield, and thus
the associated costs, of active layers is typically a nonlinear
function of its area size. For example, the cost of a semiconductor
IC chip grows exponentially as a function of the area, due to
unavoidable contaminations and defects. Smaller active layers have
much higher yield ratios and the material costs will be lower. In
addition, many supply materials and tools necessary to make the
active layers may not be able to handle large sizes even if it is
chosen to do so. The overall handling of smaller but very thin
active layers can be easier compared to handling the larger ones.
Thus the cost is cheaper and the windows are easier to manufacture.
In the larger size windows, the active layer is a collection of
seamlessly tiled smaller pieces of active layers. Due to a higher
yield in the smaller tiles, the tooling is readily available, and
it is easier to handle.
[0048] Although the present invention is briefly summarized, the
fuller understanding of the invention can be obtained by the
following drawings, detailed description and appended claims.
DESCRIPTION OF THE FIGURES
[0049] These and other features, aspects and advantages of the
present invention will become better understood with reference to
the accompanying drawings, wherein:
[0050] FIG. 1 is a schematic diagram of an adjustably opaque window
with its principal functions depicted;
[0051] FIG. 2 is an expanded view of the light control layer;
[0052] FIG. 3 is a schematic diagram showing a tiling structure of
the active layers;
[0053] FIG. 4 is an elevation view showing an adjustably opaque
window according to the present invention;
[0054] FIG. 5 is a partial cross-sectional view of the window taken
along the line 5-5 of FIG. 4;
[0055] FIG. 6 is a view similar to FIG. 5 showing a cavity between
internal and external panes;
[0056] FIG. 7 is a view similar to FIG. 5 showing a shock absorbing
layer;
[0057] FIG. 8 is an elevation view of the window showing a lattice
of light transmission control cells;
[0058] FIG. 9 is a cross-sectional view of the light transmission
control cell within the window;
[0059] FIG. 10 is a plan view of spacers in the light transmission
control cell;
[0060] FIG. 11 is a partial cross-sectional view taken along the
line 11-11 of FIG. 10;
[0061] FIG. 12 is a cross-sectional view taken along the line 12-12
of FIG. 11;
[0062] FIG. 13 is a schematic circuit diagram that shows
controlling of the light transmission control cells;
[0063] FIG. 14 is a view similar to FIG. 7 showing that the shock
absorbing layer includes gel;
[0064] FIG. 15 is an elevation view of the window showing a
different partition with the cells;
[0065] FIG. 16 is a partial cross-sectional view taken along the
line 16-16 of FIG. 15;
[0066] FIG. 17 is an elevation view of the window showing a
different partition with the cells; and
[0067] FIG. 18 is an elevation view of the window showing a
different partition with the cells.
DETAILED DESCRIPTION OF THE INVENTION
[0068] The control of visible light transmittance through the light
transmission control layer derives from the ability that the
optical properties of an active layer, which is the central layer
of the light transmission control layer, can be manipulated using
an external stimulus such as an electrical field. Active layers,
such as liquid crystals, can change their optical properties such
as their birefringence and hence the polarization state of the
light traveling through the active layer, when an external stimulus
such as an electrical field is applied.
[0069] More explicitly, the application of an external stimulus
such as an external electrical field to the liquid crystal layer
causes liquid crystal molecules, such as those liquid crystals
composed of rod-shaped molecules, to reorient. This molecular
reorientation in the liquid crystal layer causes a change in the
index of refraction of the light traveling through the glass. As a
result, there is a change in the polarization of light exiting the
liquid crystal layer, due to the application of the external
stimulus to the liquid crystal active layer.
[0070] Still more explicitly and more generally, the degree of
liquid crystal molecular reorientation is dependent on the
amplitude of the external stimulus, and the polarization state of
light traveling through the liquid crystal layer can be manipulated
continuously by manipulating the external stimulus.
[0071] Auxiliary layers such as polarizers can then be used to
absorb or reflect a fraction of visible light depending on the
choice of polarizers and depending on the polarization state of the
light, which is controlled by the active layer. Active layers, such
as dichroic dye doped liquid crystals can change their absorbance
of light upon the application of an external stimulus such as an
electrical field, and therefore control the transmittance of light
through the active layer using an external stimulus.
[0072] The filtering, that is, the reflection or absorption of UV
and or infrared light, can be achieved by auxiliary layers, such as
an additional UV absorption layer, polarizers, and or other active
layers, depending on the choice of such materials. External
stimulus applied to the active layer to achieve transmittance
change in the visible spectrum will have little or no effects on
the filtering of UV and infrared by the light control layer.
[0073] A variety of window sizes are employed in commercial
applications and specifically in vehicle, land, marine or air,
applications. For large windows, according to the current
invention, the active layer is structured such that several smaller
active layers joined seamlessly together for a tiled structure and
the collection of these smaller tiles, acts as one single active
layer that controls the passage of light of the whole panel, as
depicted in FIG. 3.
[0074] The light control layer, comprising an active layer, can
assume a variety of layered structures with varying layer thickness
and layer structures. A variety of electrooptic materials can be
used as the active layers. Such layers can be made up of liquid
crystals, polymer liquid crystals, or other optical materials such
as nonlinear optical materials.
[0075] In one of the preferred embodiments, the active layer is
comprised of a liquid crystal layer, which is bounded by substrates
such as a pair of non-intersecting glass or flexible polymer
substrates like polyester or polycarbonate films. The substrates
are generally further comprised of transparent conductive layers,
through which external stimulus such as electricity can be applied
to liquid crystals, and other overcoats such as polymer or
inorganic thin layers for various purposes including alignment of
liquid crystals, prevention of electrically shorting the two
substrates, and prevention of penetration of moisture to the active
liquid crystal layers. The substrates may further be doped with
metallic materials such as silver or conducting polymers such as
polyaniline to increase the electrical conductivity of the
substrates. The liquid crystal layer is bounded by a pair of
polarizers, with their polarization selection direction nominally
at 0 or 90 degrees to each other.
[0076] In this preferred embodiment of using liquid crystal as an
active layer, the liquid crystals can be nematic, with or without
chiral dopants, or the liquid crystal active layer can be a layer
of chiral nematic liquid crystals. Further, the liquid crystal
active layer can be other forms of liquid crystals such as
polymeric liquid crystals or ferroelectric liquid crystals.
Further, the liquid crystal layer may be doped with dichroic or
pleochroic light absorbing dyes. Addition of such dyes can assist
with needed transmission control for the variable tinting
applications.
[0077] Still in this preferred embodiment, the polarizers can be
reflective in nature, where the reflective polarizers can be
birefringence based or wire grids of metals which further can
reflect infrared light and at least partially block the UV light.
Further, the polarizers can be absorptive in nature, where the
selection of polarization is achieved by absorbing light in the
unwanted polarization direction by the polarizing film.
[0078] In another preferred embodiment of using liquid crystal as
the active layer, the liquid crystals can be nematic doped with
dichroic or pleochroic light absorbing dyes, and the dielectric
anisotropy is negative. In this preferred embodiment, no polarizers
may be necessary to achieve tinting control.
[0079] In another preferred embodiment, the light control layer, in
addition to the active layer such as liquid crystal layer discussed
above, is comprised of a UV layer and a IR filtering layer with
proper filtering functions laminated to the window glass or the
active layer assembly.
[0080] In one preferred embodiment, the protective variable tinting
window can be fabricated by first making the light control layer
and then laminated in between two panes of window glasses, using
such adhesive layers such as pressure sensitive adhesive layers.
Yet in another embodiment, the light control layer can be laminated
onto the inner side of a window glass in a way similar to the
lamination of a fixed sheet window tint material. The adhesive
material can again be such material as pressure sensitive adhesive
films.
[0081] Still in another preferred embodiment, smaller light control
layer or active layers are arranged in two rolls or two columns so
that the active layers can be tiled seamlessly in the interior of
the window while the means of applying external stimulus can be
conveniently hidden along the edges of the window.
[0082] Still in another preferred embodiment, the external stimulus
can be an electric stimulus, which can be an oscillatory electrical
field from a circuitry that is powered by the battery system of the
vehicle. Alternatively, the circuitry may be powered by solar cells
that are laminated on the top section of the windshield glass.
[0083] The present invention is further explained with reference to
FIGS. 4-18.
[0084] FIGS. 4 and 5 show an adjustably opaque window 50 according
to the present invention. The window 50 includes an external pane
52, an internal pane 54, a light transmission control layer 56, and
a shock absorbing layer 58. The light transmission control layer 56
is supported by the shock absorbing layer 58. For the effectiveness
of illustration, the elements are not drawn to scale throughout the
drawings. Attachment among the external pane 52, the internal pane
54, the light transmission control layer 56, and the shock
absorbing layer 58 is done with pressure sensitive adhesive.
[0085] FIG. 6 shows that the external pane 52 and the internal pane
54 provide a cavity 60 between them. The light transmission control
layer 56 and the shock absorbing layer 58 are positioned in the
cavity 60 as shown in FIG. 5.
[0086] FIG. 7 shows that the shock absorbing layer 58 comprises a
first flexible sheet 62, and an optional second flexible sheet 64.
The light transmission control layer 56 is attached to the first
flexible sheet 62. The second flexible sheet 64 is attached to the
light transmission control layer 56 opposite to the first flexible
sheet 62. Moreover, a plurality of flexible sheets may be added on
the either side of the light transmission control layer to
strengthen and toughen the window. Preferably, the material for the
flexible sheets 62, 64 is polyester or polycarbonate, and the
thickness of the flexible sheets is in a range from about 0.1 to
about 0.2 mm. The first flexible sheet 62 protects the light
transmission control layer 56, which may include a fragile material
including liquid crystal, from external shock.
[0087] Preferably, the external pane 52 and the internal pane 54
are substantially hard to provide structural rigidity required for
various applications. For example, the panes 52, 54 are made of
glass or plastic. Other light transmitting panes are also
acceptable.
[0088] FIG. 8 shows that the light transmission control layer 56
includes a plurality of light transmission control cells 66. The
light transmission control cells 66 are arranged to form a lattice
68. Although a lesser number of the light transmission control
cells 66 may be used when larger cells are used, it is preferable
to use smaller light transmission control cells 66 to provide more
redundancy and flexibility. The opacity of the light transmission
control cell 66 is variably adjustable by changing amplitude of
electric field applied on the light transmission control cell 66.
Tiling the window 50 with the light transmission control cells 66
makes manufacturing of the window 50 substantially easier.
[0089] FIG. 9 shows that the light transmission control cell
includes a first electrode 70, a second electrode 72, and an
electro-optic material 73 in between the first and second
electrodes 70, 72.
[0090] The electro-optic material 73 includes liquid crystal 74, or
nonlinear optical material. The liquid crystal includes dichroic
dye doped liquid crystals, nematic liquid crystals with or without
chiral dopants, chiral nematic liquid crystals, polymeric liquid
crystals, and ferroelectric liquid crystals. The liquid crystal may
be doped with dichroic light absorbing dye, or pleochoric light
absorbing dye.
[0091] More general description of liquid crystal used in light
transmission control is given in U.S. Pat. No. 5,197,242, the
disclosure of which is incorporated by reference into this
application.
[0092] The window 50 further includes a first polarizing layer 76
that is positioned between the external pane 52 and the light
transmission control layer 56, and a second polarizing layer 78
that is positioned between the first flexible sheet 62 and the
interior pane 54.
[0093] The direction of polarization of the first polarizing layer
76 is substantially perpendicular to the direction of polarization
of the second polarizing layer 78.
[0094] The first polarizing layer 76 and the second polarizing
layer 78 may be integrated with, within, as a part of, or alongside
the external pane 52 and internal pane 54, respectively.
[0095] The first polarizing layer 76, which receives the incident
light from outside, may be absorptive, birefringence based, or
include wire grids of metals for better filtering effect against
unwanted lights.
[0096] In the light transmission control cell 66, the first
electrode 70 is substantially adjacent the first polarizing layer
76, and the second electrode 72 is substantially adjacent the first
flexible sheet 62. The liquid crystal 74 is positioned between the
first electrode 70 and the second electrode 72.
[0097] The first electrode 70 includes a substantially transparent
plastic substrate 80 coated with transparent conductive coating 82,
and the second electrode 72 includes a substantially transparent
substrate plate 80 coated with transparent conductive coating
82.
[0098] The surface of the first electrode 70, which is adjacent the
liquid crystal 74, is treated with a first polymer layer 86 such
that the first polymer layer 86 gives a preferential alignment to
the adjacent liquid crystal 74. The surface of the second electrode
72, which is adjacent the liquid crystal 74, is treated with a
second polymer layer 88 such that the second polymer layer 88 gives
a preferential alignment to the adjacent liquid crystal.
[0099] Preferential alignment means that the liquid crystal
molecules that are adjacent the polymer layers 86, 88 tend to
orient with their long axes parallel to the direction to which the
polymer layers 86, 88 are rubbed or brushed. The brushed direction
of the first polymer layer 86 is substantially perpendicular to the
brushed direction of the second polymer layer 88.
[0100] The preferential direction of the treated first polymer
layer 86 should be substantially parallel to the direction of
polarization of the first polarizing layer 76, and the preferential
direction of the treated second polymer layer 88 should be
substantially parallel to the direction of the second polarizing
layer 78.
[0101] The liquid crystals 74 adjacent the first and second polymer
layers 86, 88 are pre-tilted from the planes of the first and
second polymer layers 86, 88. That is, in FIG. 9, the rod-like
liquid crystals 74 make an angle with the first and second polymer
layers 86, 88.
[0102] This pre-tilting of the liquid crystals adjacent the treated
polymer layers facilitates the variable control of the alignment of
the liquid crystals 74, and thus the variable control of the
opacity of the light transmission control cell 66. A zero or small
angle pre-tilt of liquid crystals adjacent to the places of polymer
layers typically result in a device where a small change in
externally applied stimulus such as an external electric field will
cause a significant change in light transmission. A higher
pre-tilt, in particular, a pre-tilt that is about 30.degree. or
more, will result in a light transmission control device whose
light transmittance will changes smoothly when the external
stimulus is changed.
[0103] Preferably, the pre-tilting angle is in a range from
0.degree. to about forty-five degrees (45.degree.). More
preferably, the pre-tilting angle is about thirty degrees
(30.degree.).
[0104] FIG. 10 shows that the light control transmission cell 66
further includes a plurality of spacers 90. The spacers 90 are
coated with adhesive. The spacers 90 may be randomly or uniformly
distributed within the light transmission control cell 66.
[0105] As shown in FIG. 11, the spacers 90 contact the first and
second electrodes 70, 72 and maintain predetermined distance
between the first and second electrodes 70, 72. The boundaries of
the light transmission control cell 66 is sealed by adhesive
92.
[0106] As shown in FIG. 12, the cross-section of the spacer 90
includes a sphere 94, and the sphere 94 is coated with an adhesive
layer 96. The diameter of the sphere 94 should be in a range from
about five (5) to about thirty (30) microns, and the thickness of
the adhesive layer 96 is less than about five (5) microns. The
spacer 90 having the adhesive layer 96 effectively maintains the
distance between the first and second electrodes 70, 72, and
protects the liquid crystal 74 against external force, so that the
cell 66, and thus the window 50 may be curved, bent or flexed. More
particularly, since the first and second electrodes 70, 72 of the
light transmission control cell 66 are supported at multiple
points, at which the randomly distributed spacers 94 are
positioned, even though the cell 66 as a whole is bent, the
distance between the first and second electrodes 70, 72, and hence
the thickness of the cell 66 is kept constant throughout the cell
66, thereby protecting the cell 66 and the liquid crystal 74
inside.
[0107] Referring back to FIG. 9, the first flexible sheet 62 is
coated with transparent electrically conductive coating 98.
Preferably, the transparent conductive coating 98 is made of Indium
Tin Oxide. The transparent conductive coating 98 forms an
electrical wiring 102 (refer to FIG. 13) to each light transmission
control cell 66.
[0108] FIG. 13 schematically shows how the light transmission
control cells 66 are controlled. The adjustably opaque window 50
further includes a control circuit 100 that controls each of the
light transmission control cells 66 individually with the
electrical wiring 102. The control circuit 100 may also control the
light transmission control cells 66 collectively in part or in
whole depending on the requirements on the window 50 such as
blocking most of the incident light, partial or gradual tinting of
the window, or displaying specific images on the window.
[0109] The adjustably opaque window 50 may further include a light
sensor 104 that measures the intensity of the incident light. The
control circuit 100 controls the light transmission, or the opacity
of the light transmission control cells 66, and thus of the light
transmission control layer 56, based on data provided by the light
sensor 104. On the other hand, the control of the light
transmission control cells 66 may be overridden manually.
[0110] The adjustably opaque window further includes a power source
106 for supplying power to operate the light transmission control
layer 56. In one application, the window 50 may be a vehicle
window, and the power source 106 may be an array of photovoltaic
cells (not shown) installed on a vehicle such as the upper portion
of the windshield glass to harness and collect the sunlight, or may
be simply the battery used in the vehicle.
[0111] In other applications, the adjustably opaque window 50 is an
architectural window, a glass door, a partition, a mirror, a sun
roof, a moon roof, or anywhere windows are used.
[0112] Referring back to FIG. 9, the adjustably opaque window 50
further includes an ultra violet light blocking layer 108 that is
positioned between the exterior pane 52 and the light transmission
control layer 56.
[0113] FIG. 14 shows another embodiment of the shock absorbing
layer 58. The shock absorbing layer 58 includes gel 110 filled in
the cavity 60, and the light transmission control layer 56 is
supported in the gel 110.
[0114] The light transmission control cells and their arrangement
are such that the said window seem seamless to human eyes. Also,
the spacers within the light transmission control cells are
microscopic in size and are not visible to human eye.
[0115] FIGS. 15-18 show another embodiment of the invention. In
this embodiment, the cells are arranged so that part of the
periphery of each cell is positioned at the periphery of the
window. The wiring for each cell is positioned at the periphery of
the window, and thus conductive coating on the shocking absorbing
layer is not required. FIG. 15 shows that six horizontal light
transmission control cells 112 cover a whole adjustably opaque
window 111. FIG. 17 shows that six vertical light transmission
control cells 114 cover the whole window. FIG. 18 shows six pairs
of horizontal light transmission control cells 116 cover the whole
window.
[0116] FIG. 16 shows the structure common to the light transmission
cells 112, 114, 116. The adjustably opaque window 111 includes an
external pane 118 and an internal pane 120. Between the external
pane 118 and the internal pane 120, an ultra violet light blocking
layer 122, a shock absorbing layer 124, a first polarizing layer
126, the light transmission control cell 112, and a second
polarizing layer 127 are positioned in the order according to which
they are listed. The light transmission control cell 112 includes a
first electrode 128, and a second electrode 130 oppositely
positioned with each other. Each of the first and second electrodes
128, 130 includes flexible plastic substrate 132, and a transparent
conductive coating 133, which is made of, for example, Indium Tin
Oxide, coated on the plastic substrate 132. Between the electrodes
128, 130, liquid crystal 74 is filled. A first polymer layer 134,
which is brushed horizontally, is attached to the first electrode
128, and a second polymer layer 136, which is brushed vertically,
is attached to the second electrode 130. The spacer 90 with the
adhesive layer 96 is positioned between the electrodes 128, 130 and
supports them. An adhesive 140 forms a seamless wall between the
cells 112. Pressure sensitive adhesive 142 combines the exterior
pane 118, the ultra violet light blocking layer 122, the shock
absorbing layer 124, the first polarizing layer 126, the light
transmission control cell 112, and the second polarizing layer
127.
[0117] The panes, layers and cell of this embodiment have
constructions similar to those explained with reference to FIG.
4-14.
[0118] Light incident on the window 111 is unpolarized. The light
is first transmitted through the exterior pane 118, and then
through the ultra violet light blocking layer 122, in which the
ultra violet light is prevented from further transmitting. Then the
light is transmitted through the shock absorbing layer 124, which
support and protect the light transmission control cells 112. Then
the light transmission control cell 112 together with the
polarizing layers 126, 127 control the opacity of the window 111,
or transmission ratio of the incident light. Then the light, which
is allowed to be transmitted further, is tranmitted inside the
window through the interior pane 120.
[0119] With the above construction, a stable and robust light
transmission layer is achieved using liquid crystals. The liquid
crystal cells constructing the light transmission layer are
protected from external force by the shock absorbing layer, and
also protected from adverse energy such as ultraviolet light or
high temperature. When the adjustably opaque window is used in
automotive application, the window may be generally clear, when no
electricity is applied, that is, the dormant state; such as when a
vehicle is in parking state. When a driver gets in the vehicle, the
control circuit senses the ambient lighting condition and adjusts
the opacity of the window, or the driver may manually adjust the
opacity for privacy purpose, etc. Alternately, the vehicle window
may be totally dark and allow no light to enter when no electricity
is applied, that is, the dormant state, by reverse arranging of the
polarizing layers.
[0120] While the invention has been shown and described with
reference to different embodiments thereof, it will be appreciated
by those skilled in the art that variations in form, detail,
compositions and operation may be made without departing from the
spirit and scope of the invention as defined by the accompanying
claims.
* * * * *