U.S. patent application number 15/640046 was filed with the patent office on 2018-06-07 for radiation emitting element and a method of providing it.
The applicant listed for this patent is BLACKBRITE APS. Invention is credited to Niels Agersnap LARSEN, Jens Ostergaard.
Application Number | 20180156422 15/640046 |
Document ID | / |
Family ID | 41581948 |
Filed Date | 2018-06-07 |
United States Patent
Application |
20180156422 |
Kind Code |
A1 |
Ostergaard; Jens ; et
al. |
June 7, 2018 |
RADIATION EMITTING ELEMENT AND A METHOD OF PROVIDING IT
Abstract
A radiation emitting element comprising a radiation transmissive
element having a first refractive index, a first surface, a second,
opposite surface, a radiation emitter adapted to emit radiation of
a predetermined wavelength into the radiation transmissive element,
and a plurality of radiation controlling elements, wherein each
radiation controlling element comprises: a first liquid having a
second refractive index, a second fluid having a third refractive
index being lower than the second refractive index, the second
refractive index being closer to the first refractive index than
the third refractive index, means for altering a shape of the first
liquid between two modes wherein: in a first mode, the first liquid
being in contact with the first surface at a first surface part,
and an interface between the first liquid and the second fluid, at
the first surface part, is not parallel to the first surface part
and in a second mode, a surface of the second fluid, at the first
surface part, is at least substantially parallel to the shape of
the first surface part, wherein the first liquid has a
transmittance of at least 10% at the predetermined wavelength.
Inventors: |
Ostergaard; Jens; (Roskilde,
DK) ; LARSEN; Niels Agersnap; (Lyngby, DK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BLACKBRITE APS |
Roskilde |
|
DK |
|
|
Family ID: |
41581948 |
Appl. No.: |
15/640046 |
Filed: |
June 30, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14845790 |
Sep 4, 2015 |
9696014 |
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15640046 |
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14037669 |
Sep 26, 2013 |
9176342 |
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14845790 |
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12998589 |
Dec 19, 2011 |
8559095 |
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PCT/EP2009/064753 |
Nov 6, 2009 |
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14037669 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 6/3538 20130101;
B60Q 1/076 20130101; F21S 8/04 20130101; Y10T 29/49002 20150115;
F21S 41/62 20180101; G02B 6/001 20130101; G02F 1/133605 20130101;
F21V 14/003 20130101; G02B 26/005 20130101; F21S 41/645
20180101 |
International
Class: |
F21V 14/00 20180101
F21V014/00; G02F 1/1335 20060101 G02F001/1335; G02B 26/00 20060101
G02B026/00; G02B 6/35 20060101 G02B006/35; F21V 8/00 20060101
F21V008/00; F21S 8/04 20060101 F21S008/04; F21V 9/40 20180101
F21V009/40; B60Q 1/076 20060101 B60Q001/076 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 6, 2008 |
DK |
PA200801530 |
Claims
1.-33. (canceled)
34. A radiation controlling element comprising a first optical
layer comprising a waveguide with an abutting outcoupling element,
a second optical layer comprising a refractive optical element, and
a third optical layer comprising beam shaping optics, the
outcoupling element being arranged at the waveguide for outcoupling
radiation from the waveguide, and wherein the refractive optical
element and the beam shaping optics are configured to control a
radiation propagation direction of the outcoupled radiation.
35. The radiation controlling element according to claim 34,
wherein the second optical layer is positioned between the first
optical layer and the third optical layer.
36. The radiation controlling element according to claim 34,
wherein the third optical layer is positioned between the first
optical layer and the second optical layer.
37. The radiation controlling element according to claim 34,
wherein the outcoupling element forms a dynamical shutter
element.
38. The radiation controlling element according to claim 37,
wherein the dynamical shutter element is configured to be
controllable between at least a first mode and a second mode,
wherein the waveguide has, in the first mode, an optical support
that is less than in the second mode, whereby radiation is
outcoupled from the waveguide in the first mode.
39. The radiation controlling element according to claim 37,
wherein the dynamic shutter element is a dynamic electrowetting
shutter element.
40. The radiation controlling element according to claim 34,
wherein the beam shaping optics comprise diffractive optics.
41. The radiation controlling element according to claim 34,
wherein the beam shaping optics comprise micro prisms.
42. The radiation controlling element according to claim 34,
wherein the radiation controlling element further comprises at
least one additional layer between the first optical layer and the
second optical layer.
43. The radiation controlling element according to claim 34,
wherein the radiation controlling element further comprises at
least one additional layer between the first optical layer and the
third optical layer.
44. The radiation controlling element according to claim 34,
wherein the radiation controlling element comprises: a first liquid
having a second refractive index, a second fluid having a third
refractive index being lower than the second refractive index,
shape altering arrangement for altering a shape of the first liquid
between two modes, wherein: in the first mode, the first liquid
being in contact with the first surface at a first surface part,
and an interface between the first liquid and the second fluid, at
the first surface part, is not parallel to the first surface part
and in the second mode, a surface of the second fluid, at the first
surface part, is at least substantially parallel to the shape of
the first surface part, wherein the first liquid has a
transmittance of at least 10% at the predetermined wavelength.
45. A radiation emitting element comprising the radiation
controlling element of claim 34, the radiation emitting element
comprising a radiation transmissive element as the waveguide, the
radiation transmissive element having a first refractive index, a
first surface, a second, opposite surface, a radiation emitter
adapted to emit radiation of a predetermined wavelength into the
radiation transmissive element, and a plurality of radiation
controlling elements.
46. The radiation emitting element according to claim 45, wherein
the radiation controlling elements are configured to be
individually controllable.
47. The radiation emitting element according to claim 45, wherein
the second refractive index being closer to the first refractive
index than the third refractive index.
48. The element according to claim 45, wherein at least one of the
radiation controlling elements comprises a covering element having
a fourth refractive index being lower than the first refractive
index and abutting the first surface and being positioned adjacent
to the first surface part, the shape altering arrangement of the at
least one radiation controlling element being adapted to, in the
second mode, move at least part of the first liquid to a position
overlapping the covering element.
49. The element according to claim 45, wherein the radiation
emitter comprises a plurality of radiation emitters and a
controller adapted to control the individual radiation emitters to
emit radiation into the radiation transmissive element sequentially
in time.
50. The element according to claim 49, further comprising a
controller for controlling the shape altering arrangement of the
radiation controlling elements in coordination with the controller
for controlling the radiation emitters.
51. The element according to claim 45, further comprising a
plurality of radiation converters each being adapted to receive and
convert radiation emitted from one or more radiation controlling
elements to radiation of one or more wavelengths different from the
predetermined wavelength.
52. The element according to claim 51, wherein the radiation
converting converters are adapted to convert emitted and received
radiation into at least substantially white light.
53. The radiation controlling element according to claim 34,
wherein the radiation controlling element further comprises an LCD
shutter.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 14/845,790 filed on Sep. 4, 2015 which is a
continuation of U.S. patent application Ser. No. 14/037,669 filed
on Sep. 26, 2013 (now, U.S. Pat. No. 9,176,342) which is a
continuation of U.S. patent application Ser. No. 12/998,589 filed
on Dec. 19, 2011 (now, U.S. Pat. No. 8,559,095) which is the U.S.
National Phase of International Patent Application Number
PCT/EP2009/064753 filed on Nov. 6, 2009 which claims priority to
Danish Patent Application Number PA200801530 filed on Nov. 6, 2008,
all of which said applications are herein incorporated by reference
in their entirety.
[0002] The present invention relates to improvements in lighting or
display technologies and in particular to a competitive
electrowetting lightgate in which oil or other viscous liquid is
moved by an electrical field between two positions, thereby
affecting the course of light therein. This may be used for
providing a light gate opening and closing depending on the
electrical field.
[0003] In a first aspect, the invention relates to a radiation
emitting element comprising a radiation transmissive element having
a first refractive index, a first surface, a second, opposite
surface, a radiation emitter adapted to emit radiation of a
predetermined wavelength into the radiation transmissive element,
and a plurality of radiation controlling elements, wherein each
radiation controlling element comprises: a first liquid having a
second refractive index, a second fluid having a third refractive
index being lower than the second refractive index, the second
refractive index being closer to the first refractive index than
the third refractive index, means for altering a shape of the first
liquid between two modes wherein: o in a first mode, the first
liquid being in contact with the first surface at a first surface
part, and an interface between the first liquid and the second
fluid, at the first surface part, is not parallel to the first
surface part and o in a second mode, a surface of the second fluid,
at the first surface part, is at least substantially parallel to
the shape of the first surface part, wherein the first liquid has a
transmittance of at least 10% at the predetermined wavelength.
[0004] In the present context, a radiation emitting element is an
element adapted to emit radiation in a controlled manner. One
manner of controlling the radiation may be a modulation over time,
variation of intensity, wavelength, or a combination thereof, as is
known from light sources, lamps, or the like.
[0005] Alternatively or in addition, the modulation may be over a
surface, such as when providing a display in which individual
smaller areas (such as pixels) may be controlled.
[0006] In the present context, the radiation transmissive element
is transmissive at least at the predetermined wavelength, so that
this radiation may travel in the transmissive element. Naturally,
the radiation transmissive element may have a sufficiently large
transmission (preferably more than 20%, such as 30% or more,
preferably 40% or more, such as 50% or more, preferably 60% or
more, such as 70% or more, preferably 80% or more, such as 90% or
more) at all wavelengths within a wavelength interval, especially
if the radiation emitter emits radiation at more than one
wavelength. Also, if the emitter emits radiation also at a
non-desired wavelength, the transmissive element may be provided
with a lower transmission at that wavelength in order to remove
this undesired wavelength radiation.
[0007] The transmissive element has a first refractive index, a
first surface, a second, opposite surface. The transmissive element
may then be adapted to transport the radiation from the emitter by
Total Internal Reflection, at least over parts thereof, if elements
contacting the surfaces of the transmissive element have a
sufficiently lower refractive index. In this context, it should be
noted that the transmissive element may comprise multiple parts or
layers having different refractive indexes. Normally, such layers
will be fixed to each other. Also, lower refractive layers may be
fixed to the transmissive element in order to facilitate assembly
of the product and in order to ensure optimal contact between the
layers to minimize undesired photon loss at that interface.
[0008] The transmissive element may have any desired dimensions:
the overall extent thereof defines the surface from which the
radiation is output from the multiple radiation controlling
elements, as these operate to couple radiation out from the
transmissive element. The thickness of the transmissive element may
be selected based on production parameters, ease of launching
radiation into the transmissive element or the like. When
transporting radiation by TIR, a doubling in width will double the
distance between the positions of impact of the photon on the TIR
surfaces. For that reason, it may be desired to have a slim
transmissive element.
[0009] The material of the transmissive element may also be
selected based on the transmission desired at the wavelength (or
wavelength interval) desired, as well as production parameters,
strength, availability, price, and the like. In the present
context, a radiation emitter is an element adapted to emit
radiation of a desired wavelength or with a desired wavelength
interval. This element may be a radiation generator, such as an
LED, OLED, incandescent lamp or the like, or may be an element
converting radiation with another wavelength to radiation of the
desired wavelength (interval), such as a fluorescent material. The
radiation from the emitter is launched into the transmissive
element in any suitable manner. Preferably, this launching is
performed in a manner so that as much radiation as possible is
launched within an angle supporting TIR transport within the
transmissive element.
[0010] It should be noted that the radiation emitted into the
transmissive element need not be within the visible wavelength
interval. As will be described further below, radiation of
non-visible wavelength(s) may be used and may be converted after
having been emitted from the radiation controlling means.
[0011] The difference between the refractive indexes of the first
liquid and the second fluid preferably is large enough for the
interface between the fluid and the liquid to re-direct radiation.
Preferably, the second refractive index is close to, such as close
to as possible, the first refractive index so that the interface
between the first liquid and the transmissive element does not
re-direct an excessive amount of radiation but instead lets the
radiation travel into the first liquid for the radiation to instead
be re-directed by the interface between the first liquid and the
second fluid. Thus, it may be preferred that the third refractive
index is as low as possible, taking into account the parameters of
available and suitable materials. Changing the shape of this
interface thus allows for changes of the redirection of radiation
at the position of the first surface part. In this context, the
refractive index of the transmissive element will be that at the
first surface, as the interesting part is the interaction of the
radiation and this interface.
[0012] Naturally, as the primary interest lies in the interface
between the first liquid and the second fluid, the second fluid may
be a liquid or a gas, as long as the refractive index is suitable.
Providing a liquid has certain advantages, but a gas, such as
ambient air, may also be used.
[0013] In this respect, the first liquid may be any type of liquid,
depending on the mode of operation of the altering means. In one
situation, the liquid may be magnetic, so that the movement of the
first liquid may be by magnetic forces. Preferably, the altering
means operate by providing an electrical field, where one of the
first liquid and the second fluid is more polar than the other.
Providing an electrical field to the liquid/fluid will alter the
surface characteristics thereof, and this may be taken advantage of
by providing higher affinity surfaces in contact with the
fluid/liquid. The liquid/fluid and a higher affinity surface may be
chosen so that, at the electrical field provided, the fluid has a
larger affinity to the higher affinity surface than without the
field, and where the liquid has a higher affinity then the fluid to
the higher affinity surface when the field is not provided. This
higher affinity surface may then be provided at the first surface
part, whereby providing or removing the electrical field will alter
the liquid/fluid interface at the first surface part.
[0014] Alternatively, the higher affinity surface may be provided
adjacently to the first surface part, as the fluid/liquid interface
may also be altered at this position, when the electrical field is
turned on/off.
[0015] In a particular situation, the fluid is an oil which has a
low polarity, and the fluid is water-based, which has a larger
polarity. The higher affinity surface is a hydrophobic surface, and
in this embodiment, the oil will have a higher affinity (or lower
repulsion) to the hydrophobic surface with no electrical field
provided, but the electrical field will alter the surface
characteristics of the water-based fluid so that it has a higher
affinity to the hydrophobic surface. Thus, the water-based fluid
will push the oil away from the hydrophobic surface, when the field
is provided.
[0016] As an alternative, surfaces may be used to which oil has a
large or very little affinity (so-called oilophobic surfaces or the
like), in which manner the same type of operation may be achieved
using oil as the driving force, whereby the fluid/liquid may be
replaced by other materials.
[0017] In addition, the oil/water-based fluid may be encapsulated
or contained by providing, in a closed circle around the
oil/water-based fluid and the first surface part and any covering
element (see further below), a hydrophilic material to which the
water-based fluid has a high affinity, which will ensure that the
oil does not escape.
[0018] In the second mode, the surface of the second fluid, at the
first surface part, is at least substantially parallel to the shape
of the first surface part. Thus, radiation traveling in the
transmissive element by HR will remain traveling therein, as it may
move outside the transmissive element, if the first liquid is
present in the first surface part, and be re-directed by the
interface between the first liquid and the second fluid. If no
liquid is present at the first surface part, the interface between
the fluid and the transmissive element will re-direct the
radiation. In both situations, the radiation will be re-directed by
an interface at least substantially parallel to the first surface,
whereby the TIR transport of the radiation remains.
[0019] In the present context, "parallel" and "not parallel" will
mean an angular difference between any part of the interface and
that of the first surface part. In this respect, even a very small
angular difference may couple out radiation in that radiation
traveling on or very close to the TIR angle will need only a very
small angular correction to be coupled out, and radiation at lower
angles will need additional corrections but will eventually also
impinge above the TIR angle. It is noted that if the radiation is
ideally transported within the transmissive element using TIR,
radiation will always only be coupled out at the first surface
areas. In this context, "not parallel" means that the angular
difference between any part of the interface (within an area
corresponding to a projection of the first surface part and onto a
plane of the first surface part) has an angle to the first surface
part being 1.degree. or more, such as 2.degree. or more, preferably
5.degree. or more, such as 10.degree. or more. Larger angles may be
obtained, depending on the altering means. In the first mode, to
the contrary, the radiation will travel into the first liquid and
interact with the interface between the fluid and the liquid, which
interface is not parallel to the first surface part, whereby the
radiation will be directed into another angle than that at which
the individual photons arrived at. Thus, the radiation may be
directed into an angle which is not supported as TTR in the
transmissive element, whereby the re-directed radiation will be
emitted from the transmissive element. Thus, the first surface part
will be a local area in which radiation, formerly transported in
the transmissive element by TIR, may be provided with a different
angle which will make the radiation escape the transmissive element
when re-introduced therein by the action of the interface. The
providing of the plurality of radiation controlling elements, such
as all radiation providing elements of the radiation emitting
element, with the same liquid, and at that with a first liquid has
a transmittance of at least 10%, a very versatile emitting element
is provided which is easily produced and which may be used for both
illumination purposes as well as displays.
[0020] It is noted that it is desired that the first liquid
transmits as much as possible of the radiation. Thus, a
transmittance of 20% or more is desired, such as 30% or more,
preferably 40% or more, such as 50% or more, preferably 60% or
more, such as 70% or more, preferably 80% or more, such as 90% or
more. Also, in the situation where the radiation emitter emits
radiation within a predetermined wavelength interval of desired
wavelengths, it is preferred that the absorption of the first
liquid over the wavelength interval is as even as possible. Thus,
it is desired that the difference in absorbance over the interval
is no more than 20%, such as no more than 20%, preferably no more
than 5%. In one embodiment, at least one of the radiation
controlling elements comprises a covering element having a fourth
refractive index being lower than the first refractive index and
abutting the first surface and being positioned adjacent to the
first surface part, the altering means of the at least one
radiation controlling element being adapted to, in the second mode,
move at least part of the first liquid to a position overlapping
the covering element. In this situation, the fourth refractive
index preferably is sufficiently low to support any TIR transport
of the radiation in the transmissive element. Thus, when moving the
fluid to the position overlapping the covering element, this liquid
will no longer affect the transport of radiation. In one
embodiment, as will also be described further below, at least
substantially all of the liquid is moved to the position
overlapping the covering element, no liquid is present at the first
surface part, and the re-direction is carried out by an interface
between the fluid and the transmissive element.
[0021] As radiation may, in the first mode, travel to the opposite
(opposite to the transmissive element) side of the covering
element, the covering element may be transmissive to the radiation
to allow this radiation to travel back to the transmissive element.
In fact, the covering element may be provided with a structure or
refractive index changes which act to direct the radiation to a
direction more across the transmissive element to further enhance
out coupling of this radiation.
[0022] In general, several manners exist of providing a display or
lighting source using the present invention.
[0023] In one manner, the radiation emitter comprises a plurality
of radiation emitters and a controlling means adapted to control
the individual radiation emitters to emit radiation into the
radiation transmissive element sequentially in time. In this
manner, visible light of different colors (such as the colors used
in normal TV's or monitors) may be emitted into the transmissive
element sequentially in time. In that manner, preferably, the
element further comprises a controller for controlling the altering
means of the radiation controlling elements in coordination with
the controlling means for controlling the radiation emitters. Thus,
a display may be provided providing any desired image, when the
opening/closing of the radiation controlling elements (knowing
these elements' positions over the surface of the display) is
coordinated with the timing of launching the different colors of
visible radiation there-into.
[0024] As an alternative manner, the element may further comprise a
plurality of radiation converting means each being adapted to
receive and convert radiation emitted from one or more radiation
controlling elements to radiation of one or more wavelengths
different from the predetermined wavelength. Thus, the radiation
emitted into the transmissive element may be the same at all times
(the same wavelength or wavelength interval), and the individual,
desired colors at the individual positions may then be provided by
the converting means. It is noted that in this situation, the
radiation emitted into the transmissive element need not be
visible. In fact, a number of advantages are obtained when
launching UV radiation or near-UV radiation into the transmissive
element. In one situation, the converting means at different
positions are different, much as the fluorescent dots on CRT's,
whereby each radiation controlling element may control the
radiation emitted toward one dot and thereby control the amount of
visible light provided at that position with the particular color.
In another situation, the radiation converting means are adapted to
convert emitted and received radiation into at least substantially
white light. In this situation, a white light source is provided,
which has a controllable white light intensity at the different
positions of the radiation controlling elements. This white light
source may be further enhanced when it comprises means for
determining a wavelength of radiation emitted by the radiation
emitter, for selecting one or more of the radiation converting
means on the basis of the determined wavelength and for controlling
the altering means accordingly. This relates to the fact that many
common radiation sources will age in a manner so that their
intensities and wavelengths or wavelength intervals will change. In
this situation, the overlap between the wavelength(s) output and
the absorption spectrum of the converting means will become less
effective. In this manner, different converting means each targeted
at a given wavelength (interval) may be used, so that different
converting means are selected over time in order to optimize the
overlap between the parameters of the radiation emitted and the
absorption parameters and thereby the intensity of white light
emitted. Different converting means all adapted to convert received
radiation to white light normally would be a blend of fluorophores.
Different blends may be optimized for different incident
wavelengths or wavelength intervals.
[0025] Another use of the white light source would be as a
so-called backlight, where the element may further comprise color
selecting means adapted to receive converted radiation from the
converting means and remove therefrom radiation of a predetermined
wavelength or radiation within a predetermined interval of
wavelengths. A particularly interesting embodiment is one in which
the converted radiation is launched through color filters, which
again makes each area, such as the area illuminated by each
radiation controlling element, controllable to have a given color,
being that of the filter at that area. A widely known array of
color filters would be the so-called Bayer filter used in e.g.
cameras. The present element may additionally be further provided
with a display element comprising a plurality of intensity
controlling elements each adapted to receive radiation from the
converting and/or selecting means and output received radiation
with a predetermined intensity. In one situation, this may be an
array of LC elements each positioned in front of a converting means
and/or a radiation controlling means for controlling the intensity
of visible radiation output thereby. One manner of obtaining this
type of display is to provide one LC element for each one or more
radiation controlling elements and/or for each converting means.
Then, the LC element will control the intensity of light provided
by the converting means/controlling element(s). Either, only
converting means and/or controlling elements are used emitting one
color or one set of colors, whereby other colors or sets of colors
are output at other points in time, or the converting
means/controlling elements emit different colors simultaneously.
One particularly interesting embodiment is one wherein the element
further comprises a backing element extending along the first
surface and delimiting a space in which the first liquids and the
second fluids are positioned, the space being further delimited by
a viscous liquid extending between the first surface and the
backing element along a closed curve encircling the radiation
controlling elements.
[0026] In this situation, the fluid and liquid are enclosed in a
space between the transmissive element, the backing element and the
viscous liquid. Thus, evaporation/escape of the fluid/liquid may be
prevented or at least substantially reduced.
[0027] In fact, this has the further advantage that the viscous
liquid may be the same as the first liquid, whereby production is
even further facilitated. Naturally, different liquids may be used,
even though this requires dosing the liquid instead of e.g. simply
pouring in on the surface.
[0028] This may be seen when the backing element or the
transmissive element is provided with a number of predetermined
areas, at least one for each radiation controlling element, of a
surface to which the liquid has a larger affinity than areas
surrounding these areas. In addition, the closed curve is provided
with a similar material. In addition, the closed curve is provided
with a width which is larger than the lowest dimension of any of
the predetermined areas. In this situation, the liquid may simply
be poured over the surface, whereby drops of the liquid will
"stick" to the predetermined areas as well as covering the closed
curve. Due to the dimensional requirements, the height of the
liquid will be higher along the closed curve compared to the
predetermined areas. This height may be controlled by acting on the
liquid with a force, such as gravity (by tilting the element), or
by rotating/moving the element. This force will then cause liquid
to fall off, reducing the height of the individual drops without
substantially changing the relative height differences.
[0029] Then, the element with the liquid drops (transmissive
element or the backing element) may be combined with the other of
the two elements so that the higher close curve touches the other
element and thereby seals the internal "chamber" without the lower
drops touching the other of the two elements. Thus, the smaller
drops will be able to move as required by the altering means while
the closed curve seals the space.
[0030] Naturally, other spacing elements may be provided, such as
larger areas inside the closed curve. Providing a larger area, also
of the higher affinity material, inside the closed curve will
provide this area with a higher drop, which may also contact the
other of the two elements after assembly. This higher drop may,
prior to assembly, be provided with a solid spacing element, such
as a ball or pellet, which has a height/diameter corresponding to
the desired space to be maintained. This ball or pellet, once
provided in the liquid, will remain there even during handling
prior to assembly, due to the surface tension of the liquid. Due to
the fact that the overall height of the liquid of the predetermined
areas and closed curve relates to the smallest dimensions thereof,
these dimensions may be adapted to the height desired. Also, the
properties of the individual areas and the areas surrounding these
will have an influence on the height obtained. This is standard
knowledge to the skilled person.
[0031] In the situation one of the liquid/fluid is water or
water-based, preferred surfaces of these high affinity surfaces are
hydrophilic, and the areas between high affinity surfaces are less
hydrophilic. In another situation, one of the liquid/fluid may be
oil, where the high affinity surfaces may again be less oliophobic
(more oliophilic) than other areas in order to bind the oil at the
desired positions. It is clear that a large variety is available as
to the altering means. In one situation, the altering means of at
least one radiation controlling element is adapted to move at least
all of the first liquid to the first surface part in the first mode
and away from the first surface part in the second mode. In this
manner, no liquid is present at the first surface part, and the
re-direction of the radiation is handled by an interface between
the transmissive element and the fluid. In general, the altering
means may be adapted to facilitate both the change from the first
mode to the second mode and vice versa, or the change from one mode
to the other may be "automatic".
[0032] In the first situation, acting on the fluid and/or liquid
with a force in both "directions" will require larger power
consumption, whereas it may provide a faster overall operation.
[0033] In the second situation, the automatic movement from one
mode to the other may e.g. be obtained if the fluid or the liquid
is e.g. water, the altering means may comprise hydrophobic surfaces
acting on the water, which will act to drive the water into a given
position, if this force is not counteracted by a greater force. In
one embodiment, at least one of the radiation controlling elements
is bistable so that altering between the first and second modes,
preferably in both directions, requires feeding an electrical
signal by the altering means and each of the first and second modes
is maintained when the electrical signal is not provided.
[0034] In this respect, the elements or forces preventing the
liquid from changing from one mode to the other may be provided in
a number of manners. In one manner, the altering means of at least
one radiation controlling element is adapted to move at least all
of the first liquid to the first surface part in the first mode and
to a second area or position, which does not overlap with the first
surface part, in the second mode, the at least one radiation
controlling element further comprising a separating element
positioned between the first surface part and the second
area/position, the separating element being adapted to prevent the
first fluid from moving to the other of the first surface part and
the second area/position, when the electrical signal is not fed.
One manner of obtaining this is to provide the fluid or liquid as
water or a water-containing liquid, and providing the separating
element as a hydrophilic surface. Thus, when provided in one mode,
the liquid may be contained in this mode by the hydrophilic surface
until provided with an additional force allowing the liquid to
overcome the retention provided by the hydrophilic surface.
[0035] In another manner, the first fluid is a dipolar liquid, the
second fluid is a fluid with a polarity lower than that of the
liquid, wherein the altering means comprise one or more electrodes
adapted to provide an electromagnetic field adapted to move the
liquid, one electrode of the altering means being positioned
adjacently to the first surface area, wherein the liquid, in the
first mode, extends over a surface of the one electrode.
[0036] If a higher affinity surface is provided on the one
electrode, and if a liquid/fluid combination is provided one of
which has a higher affinity to the surface when a predetermined
field strength is not provided and the other when the field
strength is provided, the two modes may be provided. In this
respect, the higher affinity surface may be at or adjacent to the
first surface part.
[0037] However, when the electrical field is provided, it is
attenuated by the presence of the lower polarity fluid. Thus,
providing the predetermined field strength is not sufficient to
facilitate a change in the mode.
[0038] Then, providing a higher field strength will be able to
change the affinity of the liquid/fluid and thereby have the fluid
cover the one electrode. Subsequent thereto, the predetermined
field strength is sufficient to maintain that mode. Returning to
the former mode will require the removal of the predetermined field
strength or at least the providing of a lower field strength.
Consequently, the predetermined field strength may be taken or
provided as a constant parameter, and the parameter facilitating
the change is the addition or subtraction of field strength; the
addition or subtraction of e.g. a voltage defining the field
strength.
[0039] In a preferred embodiment, the first liquid is oil and the
second fluid is a water-based liquid, where the water-based liquid,
due to the higher polarity, will change its surface characteristics
more than the oil when the electrical field is provided, as is
described further above. The covered electrode is then provided
with a higher affinity surface to which the water-based liquid has
an affinity with the predetermined field provided and to which the
oil has the larger affinity without the field.
[0040] Naturally, any of the above embodiments may be provided with
additional elements, such as different controllers for controlling
individual elements, such as coordinated operation of radiation
emission, the radiation controlling elements, any LC elements, any
sensors and the like.
[0041] Also, the radiation emitted from the element, from the
radiation controlling elements, any converting means and/or any LC
or other controlling means may be launched through additional
optical elements for directing this light or radiation toward a
single position (a single user) or broader so that other users may
also view the contents. Alternatively, different optical elements
may be provided in front of different controlling means/converting
means/LC or other controlling elements, where a selection of the
individual controlling element/converting means/LC or other
controlling element may select not only the intensity/color but
also the desired optical effect. A second aspect of the invention
relates to a method of operating a radiation emitting element
comprising a radiation transmissive element having a first
refractive index, a first surface, a second, opposite surface, a
radiation emitter adapted to emit radiation of a predetermined
wavelength into the radiation transmissive element, and a plurality
of radiation controlling elements, wherein each radiation
controlling element comprises: a first liquid having a second
refractive index and a transmittance of at least 10% at the
predetermined wavelength, a second fluid having a third refractive
index being lower than the second refractive index, the second
refractive index being closer to the first refractive index than
the third refractive index, the method comprising the radiation
emitter emitting radiation into the radiation transmissive element
and simultaneously altering a shape of the first liquid between two
modes wherein: o in a first mode, the first liquid is in contact
with the first surface at a first surface part, and an interface
between the first liquid and the second fluid, at the first surface
part, is not parallel to the first surface part and o in a second
mode, a surface of the second fluid, at the first surface part, is
at least substantially parallel to the shape of the first surface
part.
[0042] Most of the definitions and descriptions relating to the
first aspect of the invention are also relevant to the second
aspect of the invention.
[0043] Thus, in one embodiment, at least one of the radiation
controlling elements comprises a covering element having a fourth
refractive index being lower than the first refractive index and
abutting the first surface and being positioned adjacent to the
first surface part, the altering step comprises, in the at least
one radiation controlling element, moving, when altering to the
second mode, at least part of the first liquid to a position
overlapping the covering element. Thus, this covering element may
be used for rendering the liquid inoperable in the second mode, and
it may be transmissive to the radiation and may have a structure
aiding in the out coupling of radiation.
[0044] In another embodiment, the emitting step comprises a
plurality of radiation emitters emitting radiation into the
radiation transmissive element sequentially in time. In this
manner, the visible colors desired may be emitted into the
transmissive element one at the time, the radiation controlling
elements ensure that the colors are emitted where desired when the
altering step comprises coordinating altering with the sequence of
the radiation emitters. In another embodiment, the method further
comprises the step of a plurality of radiation converting means
each receiving and converting radiation emitted from one or more
radiation controlling elements to radiation of one or more
wavelengths different from the predetermined wavelength. Then, the
converting step could comprise converting emitted and received
radiation into at least substantially white light. In that
situation, the method could further comprise the steps of
determining a wavelength of radiation emitted by the radiation
emitter, selecting one or more of the radiation converting means on
the basis of the determined wavelength and altering the individual
radiation converting means. Also or alternatively, the method could
further comprise the step of color selecting means receiving
converted radiation from the converting means and removing
therefrom radiation of a predetermined wavelength or radiation
within a predetermined interval of wavelengths.
[0045] Also or alternatively, the method could further comprise the
step of a display element comprising a plurality of intensity
controlling elements each receiving radiation from the converting
and/or selecting step and output received radiation with a
predetermined intensity.
[0046] In one embodiment, the altering step, in at least one
radiation controlling element, comprises moving at least all of the
first liquid to the first surface part in the first mode and away
from the first surface part in the second mode.
[0047] In that or another embodiment, at least one of the radiation
controlling elements is bistable so that the altering step
comprises feeding an electrical signal by the altering means and
each of the first and second modes is maintained when the
electrical signal is not provided.
[0048] In one situation, the altering step, in at least one
radiation controlling element, comprises moving at least all of the
first liquid to the first surface part in the first mode and to a
second area or position, which does not overlap with the first
surface part, in the second mode, the at least one radiation
controlling element further comprising a separating element
positioned between the first surface part and the second
area/position, the separating element preventing the first fluid
from moving to the other of the first surface part and the second
area/position, when the electrical signal is not fed
[0049] In another situation, the first fluid is a dipolar liquid,
the second fluid is a fluid with a polarity lower than that of the
liquid, wherein the altering step comprises providing, using one or
more electrodes, an electromagnetic field so as to move the liquid,
wherein one of the electrodes being positioned adjacently to the
first surface area, where the liquid, in the first mode, extends
over a surface of the one electrode.
[0050] As described above, preferably, the first fluid is a
water-based liquid, the second fluid is oil, and the first surface
part is provided with higher affinity surfaces for water and oil
respectively.
[0051] As described in relation to the first aspect, different
optical post-treatments or operations may be provided or desired,
depending on the use of the element and the position of any
viewer(s).
[0052] A third aspect of the invention relates to a method of
assembling a radiation emitting element, the method comprising:
providing a radiation transmissive element having a first surface
and a second, opposite surface providing, on the first surface, a
first plurality of higher affinity surface areas, providing on the
first surface, a closed curve of a higher affinity material, the
closed surface encircling the first plurality of higher affinity
surface areas, providing, on the first surface a liquid having a
high affinity toward the higher affinity surface areas and the
higher affinity material, and providing a backing element and
positioning the backing element so as to contact the liquid of the
closed curve but not contact the liquid of the first plurality of
higher affinity surface areas wherein the liquid provided on the
closed curve extends farther from the first surface than the liquid
provided on the first plurality of surface areas. Naturally, this
radiation emitting element may be that of the first aspect, where
the present liquid may be the first liquid or the second fluid of
the first aspect element.
[0053] In this aspect, all parameters and operations of the
transmissive element of the first aspect are equally valid in
relation to the third aspect of the invention. Naturally, the high
affinity surface areas and high affinity material correspond to the
liquid in question. A high affinity relates to the liquid wishing
to attach itself or deposit itself on the material/surface area
compared to other parts of the first surface. Then, the high
affinity areas/material will depend on the liquid used. If water is
used, hydrophilic materials may be used, whereas oliophilic
materials may be preferred, if an oil is used.
[0054] In this context, the high affinity material and the high
affinity surface areas may be of the same or different
materials.
[0055] Naturally, as the height of the liquid drop or curve will
depend on the affinity of the liquid and the dimensions of the
material, different liquids may be used as may different materials
and/or different dimensions. Thus, a larger height of the closed
curve may actually be obtained with a narrower width, if the liquid
and/or material is suitably selected. It is noted that the higher
affinity is relative to other areas of the first surface, and that
e.g. the term "hydrophilic" may relate to a wide interval of
contact angles of a drop of water on the surface.
[0056] In this context, a first plurality of higher affinity
surface areas is provided. In the context of the first aspect, each
such surface area may correspond to a radiation controlling
element.
[0057] Naturally, a closed curve may have any shape, such as
square, circular, oval, star-shaped, triangular or any type of
shape.
[0058] Due to the different in height of the liquid, subsequent to
assembly, the liquid of the closed curve will span and enclose the
remaining liquid parts, if the assembly is stopped when only the
layer at the closed curve contacts both elements. It should be
noted that the present technology works equally well with the high
affinity areas/material positioned on the backing element. When the
closed curve has a lowest width being larger than the lowest
dimension, such as in the plane of the first surface, of any of the
first plurality of higher affinity surface areas, the resulting
thickness of the liquid deposited on the closed curve may be
higher, even if the same high affinity material is used, whereby
the thicker layers will contact the other of the backing element
and the first element before the thinner layers.
[0059] In one embodiment, the method further comprises the step of
providing, within the closed curve, a fluid. This fluid may be used
for filling the space between the backing element, first surface
and the closed curve. This filling may be performed before or after
assembly. If performed subsequent to assembly, it may be performed
by positioning a hollow element, such as a hollow needle, through
the closed curve and providing the fluid. Optionally, another
hollow element may be used for simultaneously removing e.g. ambient
air during providing of the fluid. In another embodiment, the
method further comprises providing, on the first surface and within
the closed curve, a second plurality of higher affinity surface
areas each having a lowest dimension being larger than the lowest
dimension of the first plurality of higher affinity surface
areas.
[0060] Also, the method may further comprise providing, on the
first surface and within the closed curve, a second plurality of
higher affinity surface areas each having a lowest dimension being
larger than the lowest dimension of the first plurality of higher
affinity surface areas. Alternatively, another fluid or other high
affinity material may be used to ensure that the liquid height is
higher than that of the first plurality of surface areas.
[0061] This second plurality may be used as spacer elements
provided inside the closed curve.
[0062] In a particular situation, the method further comprises the
step of providing, at each of the second plurality of higher
affinity surface areas and subsequent to the providing of the
liquid, a distance defining element, such as a ball. This element
is maintained in place at the individual area due to the surface
tension of the liquid and may be used to provide a more precise and
more rugged spacing element. In yet an embodiment, the method
further comprises the step of providing an acceleration force to
the liquid subsequent to the step of providing the liquid and prior
to the step of providing the backing element. In this manner, the
overall thickness of the liquid at the curve and first/second
pluralities may be reduced while maintaining a relative height
difference, so that the above purpose may still be served.
BRIEF DESCRIPTION OF THE DRAWINGS
[0063] In the following, preferred embodiments are described with
reference to the drawing, wherein:
[0064] FIG. 1 shows an electrowetting optical device in side view
cross section and top view depicting the position of the lightgates
and the fluid spacers and the solid barrier and the fluid barrier
and filling with dipolar fluid while gas is vented out through a
tube;
[0065] FIG. 2 shows a number of different arrangements of
electrodes;
[0066] FIG. 3 shows four principal arrangements of electrodes that
constitute different ways of addressing lightgates;
[0067] FIG. 4 shows an essentially round lightgate with a low n
island in center in shut state;
[0068] FIG. 5 shows an essentially round lightgate with a low n
island in center in open state;
[0069] FIG. 6 shows a push & flush lightgate in shut state;
[0070] FIG. 7 shows a push & flush lightgate in open state;
[0071] FIG. 8 shows a bistable push & flush lightgate in shut
state;
[0072] FIG. 9 shows a bistable push & flush lightgate in open
state;
[0073] FIG. 10 shows a push & push lightgate in shut state;
[0074] FIG. 11 shows a push & push lightgate in open state;
[0075] FIG. 12 shows a push & push binary lightgate in shut
state;
[0076] FIG. 13A shows a push & push binary lightgate in open
state;
[0077] FIG. 13B Shows a push & push binary lightgate (a) in
open and (b) shut state;
[0078] FIG. 14 shows a Lightgate in the shape of a torus in shut
state;
[0079] FIG. 15 shows a Lightgate in the shape of a torus in open
state;
[0080] FIG. 16 shows a Lightgate with conductive spacer dots in
shut state;
[0081] FIG. 17 shows a Lightgate with conductive spacer dots in
open state;
[0082] FIG. 18 shows a nanoimprint with characteristics usable to
produce lightgates;
[0083] FIG. 19 shows a number of different layers that are
applicable to modulate light extracted from the waveguide;
[0084] FIG. 20A shows a lightgate with inverted droplet in shut and
open state;
[0085] FIG. 20B shows a lightgate with inverted droplet in (a) open
and (b) shut state;
[0086] FIG. 21A shows an illumination unit;
[0087] FIG. 21B shows an illumination unit waveguide;
[0088] FIG. 21C shows an illumination unit spacer layer;
[0089] FIG. 21D shows an illumination unit top surface;
[0090] FIG. 21E shows an illumination unit barrier layer;
[0091] FIG. 21F shows an illumination unit protective upper
surface;
[0092] FIG. 21G shows an illumination unit protective lower
surface;
[0093] FIG. 22 shows an inverted lightgate based on topologic
suspension of fluids;
DETAILED DESCRIPTION OF THE DRAWINGS
[0094] FIG. 1 shows the basic configuration of an electrowetting
optical device according to the invention. The waveguide 10 and
lower substrate 42 are joined by the solid evaporation barrier 90.
Inside the cavity created a fluid evaporation barrier 91 consisting
of the same less polar liquid 35 used in the 94 lightgates contains
the 30 dipolar fluid. The dipolar liquid 30 will usually be water
and water is difficult to contain. The solid evaporation barrier 90
will in case a polymer is used leave small crack where water vapor
can escape and the glue used to attach the lower substrate 42 and
waveguide 10 can also form small channels where water can escape.
With a fluid evaporation barrier 91 inside a non dimensional
stabile but highly water impermeable barrier can be established.
The electrowetting optical device is produced by controlling the
surface energy of the waveguide 10 and lower substrate 42 such that
a pattern of oliophilic areas are surrounded by oliophobic areas.
The less polar liquid 35 is then spin coated upon the waveguide 10
which deposits defined amounts of less polar liquid 35 upon the
oliophilic areas. The oliophilic areas that are not part of the
lightgate apertures 96 can be optically decoupled from the
radiation trapped inside the waveguide 10 by a low n cladding 5
with low n. Due to the surface tension of the less polar liquid 35
it will strive after forming droplets with the same angles so
droplets formed on larger oliophilic areas will become slightly
higher than droplets formed on smaller areas. In some instances the
less polar liquid 35 spacers can be fitted with polymer or glass
ball spacers with similar surface energy that will ensure that it
will be completely covered by less polar liquid 35. When the
waveguide 10 is assembled with the lower substrate 42 the larger
droplets formed at waveguide 10 will connect between the two planar
plates. In the areas surrounding the oliophilic areas less polar
liquid 35 will not assemble and they are therefore ready for gluing
the solid evaporation barrier 90 securely in place. The demands for
the less polar liquid 35 are high transparency, low diffusion and
low UV photoluminescence. The 30 dipolar fluid is supplied to the
electrowetting optical device by a fluid pump 92 through a prepared
channel in the solid evaporation barrier 90 and an intermediate
channel through the fluid evaporation barrier 91. Capillary forces
will draw the dipolar liquid 30 in provided that fluid tube 93 is
connected to allow contained gas to escape. The process can be
accelerated by doing it in low pressure surroundings such that a
minimum of gas is contained inside the electro wetting optical
device. When the filling is completed the fluid pump 92 and fluid
tube 93 are removed and the fluid evaporation barrier 91 will seal
the channels.
[0095] A way to counteract the evaporation is to replenish the
water inside the electrowetting optical device is to leave the
fluid pump 92 in place and to maintain a pressure such that the
liquid pressure inside the electrowetting optical device is kept
constant. Alternatively the electrowetting optical device can be
fitted with an osmotic gradient by supplying salt or sugar to the
dipolar liquid 30. To prevent dipolar liquid 30 to escape through
the connection an aquaporin filter similar to the filters found in
the cells of all living organisms is usable. Alternatively to an
external reservoir a dew collector design based on nanostructures
similar to the surface design of desert plants can be attached to
enable the electrowetting optical device to self-replenish the
water content.
[0096] A way to counteract problems with gas entrapped in the
liquids is to process the liquids in low pressure champers at all
times. Gas inside the liquids may in some instance create bubbles
or corrosive effects.
[0097] FIG. 2 shows a number of different arrangements of
electrodes. In FIG. 2 a. two charge electrodes opposite each other
in the same level form a torus with an outer electrode and an inner
electrode. On the opposite side the selector electrode 24 is
positioned, oliophobic passivation areas 62 are used to control
that parts of the lightgate are inactive optically and mechanically
because there are no 35 less polar fluid and therefore no
competitive electrowetting and in the absence of less polar liquid
35 dipolar liquid 30 with low n will secure that the area will not
interact optically with the radiation trapped by TIR inside the
waveguide. Oliophobic passivation areas 62 are usable to avoid
optical edge effects and also to create channels for turbulent
liquid flow around the less polar liquid 35 movement.
[0098] In FIG. 2 a. the oliophobic passivation area 62 creates
turbulence went and avoid unwanted optical edge effects. The torus
shape creates a line that is at the same time optically
omni-directional except for the effect of the oliophobic
passivation area 62. If the internal electrode is connected through
the outer electrode via a sufficiently thin line that enters
through the outer ring electrode in a skewed angle it is possible
to create a torus without the need for (oliophobic passivation
areas 62). An advantage of a torus with push & push electrode
configuration is that it is feasible to design the system such that
there will be no net movement of fluids in the horizontal plane.
The less polar liquid 35 will merely be moving at the same spot
spreading and contracting and the dipolar liquid 30 inside the
lagoon will just change form with no net movement of volume across
the atoll. The same stationary movement can be achieved with a push
& flush electrode if it is curled up as a essentially circular
or elliptical shape this will however be at the expense of
switchtime because the oliophilic area will increase and attract a
larger amount of less polar fluid.
[0099] In FIG. 2 b. two comb shaped electrodes are intertwined to
form the lightgate and oliophobic passivation areas 62 are utilized
to separate the dynamic areas where fluid turbulence is created by
the electrowetting. The result is a design where the lightgate
essentially constitutes a line of sub lightgates arranged as linear
micro lightgates. The purpose of this design to create lightgates
with the smallest possible horizontal cross section because this
minimize fluid movement and thus in turn both expended energy and
switchtime. The oliophobic passivation area 62 is also usable as a
means of controlling the fill factor of the apertures that out
couple light from the waveguide and thereby the light extraction
efficiency in specific areas.
[0100] In FIG. 2 c. lower electrodes 41 are arranged in a saw tooth
like pattern that is addressed by selector electrode 24. Here there
are shown no oliophobic passivation areas 62 so the system must
rely on common directional pressure build up and release.
[0101] In FIG. 2 d. lower electrodes 41 are arranged in a double
spiral. There are no oliophobic passivation areas 62 shown but
there could have been a few small ones to secure pressure vents
that would offset the negative effects of turbulence and local
pressure build up.
[0102] Not shown in the figure it is feasible to create lightgates
where the electrodes are positioned in several layers separated by
dielectric layers and therefore allowable to cross each other.
Crossing electrodes opens for designs with multiple electrodes. The
general principle for lightgates is that any figure that is
possible to draw with a line (representing aligned aperture and low
n island 60 with surrounding hydrophilic areas) and an eraser
(oliophobic passivation areas 62) is also possible to produce in a
single layer provided that there is access for the upper electrode
25 and upper electrode2 26 to be aligned.
[0103] Transparent electrodes are relevant whenever electrodes are
positioned in the optical pathway between the waveguide 10 and the
beholder. Alternatively to transparent electrodes mirroring
electrodes in a mesh can be employed as the openings in the mesh
will allow radiation from the waveguide 10 to reach the beholder.
Most transparent materials suited for electrodes such as ITO will
provide a high refractive index that cause potentially unwanted
Fresnel reflection if the layer is sufficiently thick to be
experienced by passing light as a high refractive material, so a
thin deposition layer in 20-40 nm will prevent Fresnel
reflections.
[0104] Electrodes that are not in the optical pathway between the
waveguide 10 and the beholder may be mirroring or absorbing
depending upon whether the object is to recycle photons or rather
absorb photons. For all electrodes it is feasible to reduce their
optical interaction with impinging radiation by a low n cladding 5
layer with low n which will serve as a highly effective TIR mirror
in angle above the critical angle formed by the refractive indices
between the low n cladding 5 and adjacent surface such as for
instance the waveguide 10. In this way electrodes will limit
unwanted absorption of light.
[0105] FIG. 3 shows four principal arrangements of electrodes that
constitute different ways of addressing lightgates.
[0106] In FIG. 3 a. the push & flush row selector 70 selects a
push & flush lightgate. The column electrodes are controlled by
the drive circuitry not shown so the system is a passive matrix
with two electrodes per lightgate.
[0107] In FIG. 3 b. push & push selector electrode 71 selects a
push & push lightgate. Designs with three electrodes per
lightgate allow differentially driven lightgates. Passive matrix
usually is prone by crosstalk and heightened levels of Electro
Magnetic Interference emission. Electrowetting is almost completely
symmetric between positive and negative electric field potentials
In push & push designs each lightgate has three electrodes one
push & push ground selector 71 on top of the lower substrate 42
and two upper electrodes 25 and upper electrode2 26 beneath the
waveguide 10. How the electrodes are patterned within the pixel (be
it rectangles, torus', islands, spirals, etc.) does not matter in
this respect, as long as the capacitances between each of the two
upper electrodes and the selector electrode are the same (within
each pixel).
[0108] Upper electrode 25 and upper electrode2 26 are either driven
at Ov or 1Ov depending upon whether the less polar liquid 35 is to
be pushed onto the aperture 96 or the low n island 60 and the push
& push ground selector 71 is driven at 1Ov every time it
selects a row similar to one of the upper electrodes and 5 v
similar to the average charge of the two upper electrodes when it
is not selecting (it can also be driven at Ov when selecting rows
the important thing is that it match one of upper electrode 25 or
upper electrode2 26 when selecting rows and has the average charge
of the two upper electrodes when not selecting). This means that
the lightgates when updated will see an electric field of a
magnitude proportional to the difference in potential between the
each of the upper electrode 25 and upper electrode2 26 and the push
& push ground selector 71.
[0109] When the row is not selected the row electrode is a 5V. This
means each of the halves of the pixel will have a field-strength
with the same magnitude, but with opposing sign. The difference in
potential between the push & push ground selector 71 and the
two upper electrodes must be kept so small that the less polar
liquid 35 is able to flush out to the bordering hydrophilic area
surrounding the lightgate. If the potential difference becomes too
big the less polar liquid 35 will be pushed up into high contact
angles but the less polar liquid 35 will centralize in the middle
of the lateral plane because the push is in balance from both
sides. The latter is however not true if the lightgate has the
barrier 63 area because this will result in high contact angles but
at one side of the barrier 63 area.
[0110] No matter how the column electrodes are switching the net
average of the changes will be 0 within each lightgate, and
therefore zero within each push & push ground selector row 71,
and that (zero) is the net amount of capacitively coupled noise
that the non-selected row electrodes will be subject to.
[0111] Within each lightgate the switching of the column electrodes
will induce a capacitively coupled current to the push & push
ground selector row 71, but that current will stay local intra
lightgate thanks to the symmetric differential drive of the upper
electrode 25 and upper electrode2 26.
[0112] Further as the push & push ground selector row 71 can be
stable at mid-rail (5V) when not selected to update lightgates, it
can be driven actively to that voltage, making the non-selected
rows forming a low-impedance plane, acting as an RF shielding
ground plane and reducing RF emissions from the driving of the
electrowetting optical device.
[0113] In FIG. 3 c. the push & flush common ground electrode 72
is constantly on and can be galvanically connected to the dipolar
liquid 30. The column electrodes are controlled by the drive
circuitry not shown so the system is a passive matrix with two
electrodes per lightgate and each lightgate stretch the entire
length of the column.
[0114] In FIG. 3 d. push & push active matrix ground selector
electrode 73 selects a number of lightgates spread across the
entire electrowetting optical device simultaneously.
[0115] It should be noted that is possible to address with the
columns and use the rows as lower electrodes 41 and that the
potential of the electrodes at the waveguide 10 side and lower
substrate 42 side can be reversed as well.
[0116] FIG. 4 shows an essentially round lightgate with a low n
island in center in shut state.
[0117] The top surface 1 protects the electrowetting optical
device, low n cladding 5 on top of the waveguide 10 ensures a
critical angle inside the waveguide 10. low n cladding 5 in
patterns above the electrodes and the low n island 60 maintain the
critical angle except in the aperture 96. On top of the low n
island 60 there are out coupling structures 61 that ensures that
radiation impinging upon the low n island 60 from the less polar
liquid 35 side will pass through the low n island 60. Radiation
having passed through the low n island 60 cannot become trapped by
HR since the low n of the low n island 60 prevent it from entering
radiation above the critical angle formed between the waveguide 10
and the low n cladding. Radiation from light source 20 is entered
into the waveguide in angles that are above the critical angle
between the waveguide 10 and the low n cladding 5. The beam of
light 15 impinges upon the low n island 60 and continue trapped by
TIR. Had the beam of light 15 impinged upon the aperture then the
dipolar liquid 30 would have provided a sufficiently low n to match
the low n cladding 5 such that the radiation would continue HR
reflected inside the waveguide. In the figure the upper electrode
25 is situated beneath the dielectric layer 3 and it is not
covering the aperture 96. If a transparent upper electrode 25 or a
mirroring mesh upper electrode 25 had been employed the upper
electrode 25 could have covered some or the whole aperture 96 area.
The less polar liquid 35 is pressed up upon the low n island 60 by
applied charge over absorbing electrode 43 and upper electrode 25
because the dipolar liquid 30 develop an affinity for hydrophobic
surfaces when the polarization of the water molecules are changed
by the applied electric field. The main principle of competitive
electrowetting is that the dipolar liquid 30 pushes the less polar
liquid 35 away and up in high contact angles. The lower substrate
42 supports the absorbing electrode 43 circuitry.
[0118] FIG. 5 shows an essentially round lightgate with a low n
island in center in open state.
[0119] The beam of light 15 impinge on aperture 96 and enters into
less polar liquid 35 because there is a match of refractive indices
between the waveguide 10 and the less polar liquid 35. The beam of
light 15 is reflected upon a TIR mirror formed between the less
polar liquid 35 and the dipolar liquid 30 and continues towards the
underside of the low n island 60 where out coupling structures 61
send it into the waveguide 10 below the critical angle.
[0120] The general principle for the waveguide 10 is a design that
ensures photon recycling. The photon recycling is achieved by low n
cladding 5 on the upper side of the waveguide 10 can be of lower
refractive index than the low n cladding 5 on the lower side of the
waveguide 10 such that the critical angle at the upper side of the
waveguide 10 is lower than at the lower side of the waveguide 10.
This difference in critical angle will result in that radiation
deflected below the critical angle inside the waveguide 10 will
leave the waveguide 10 downwards. Flexible materials such as
polymers or thin glass are usable for the waveguide 10 and will
together with the low n cladding 5 arrangement with lower
refractive index at the upper side allow electro wetting optical
devices with flexible waveguides 10. The waveguide 10 can be made
of materials that feature high transmissivity in the wavelengths to
be used. The upper and lower surfaces of the waveguide 10 are
important as any surface imperfection will result in deflection
that accumulated can result in that light trapped by TIR drop below
the critical angle and therefore exit the waveguide 10. The
waveguide 10 must also be free of diffusion that can effect
radiation to go below the critical angle. Edges of the waveguide 10
have to be cut with exactly 90 degrees and all edges has to be
perfectly plane in order to reflect the impinging radiation without
bringing the impinging angles below the critical angle. The
thickness of waveguide 10 is significant for the fill factor of
lightgate apertures 96 as the amount photons impinging on a given
area scale linearly with the thickness of the waveguide 10 such
that a waveguide 10 that is halved in thickness will have the
double amount of photons impinging on a given waveguide 10 area and
thus demand 50% less aperture fill factor to have the same
effective fill factor. In order to enhance reflectivity low n
cladding 5 is added to the edges so impinging radiation above the
critical angle will be TIR reflected with 100% efficiency and
behind the low n cladding 5 a high quality specular mirror is
positioned to reflect light that impinge upon the edges below the
critical angle. The edge mirror is shielded from oxygen by a
dielectric layer 3 and a protective lacquer. The metal layer can be
co-processed with 25 electrodes provided they also are made of
mirroring material. Among mirroring materials aluminum, silver,
gold, chrome and other metals are usable as the main attribute is
high reflectivity.
[0121] The incoupling of light not shown in figure enters light
above the critical angle and the design of the waveguide 10 will
allow the radiation to recycle inside the waveguide 10 until it is
either absorbed or deflected below the critical angle or deflected
out of the electrowetting optical device by a lightgate. The effect
of this is that light entered into the waveguide by a light source
20 can be parceled into small portions of photons that can be
treated by optical modulation means particular to the specific
lightgate or the specific lightgate area which enables a multitude
of different optical modulation principles and optical
applications.
[0122] Among the suitable waveguide 10 polymer materials are
optical PMMA, PET and Polycarbonate and among suitable glass BK
270, fused silica, LCD glass substrates, etc. all made in fused
glass processing for perfect surface characteristics. A special
consideration has to be afforded to the refractive index of the
waveguide 10 material as a higher refractive index will provide
higher refractive difference between the waveguide 10 and the low n
cladding 5 which enables lower critical angle and thus facilitate
efficient incoupling of light from the light source 20. Another
consideration is however at there must be index match between the
less polar liquid 35 in order to facilitate out coupling into the
less polar liquid 35 from the waveguide 10 without TIR cutting a
high angle span of due to TIR between the waveguide 10 and the less
polar liquid 35.
[0123] The optical function of absorbing electrode 43 is to ensure
that light escaping from the waveguide 10 will not be reflected
towards the beholder and that ambient light impinging upon the
electrowetting optical device will be absorbed without causing
unwanted reflectance. The absorbing electrode 43 is mainly relevant
in display applications.
[0124] A black matrix not shown in the figure can be inserting
between the lightgates and allow space for circuitry. The combined
effect of the low refractive indices differences between the
materials employed in the layers constituting the electrowetting
optical device and the high absorptance achieved by the absorbing
electrode 43 and the black matrix.
[0125] The mirror electrode 40 not shown in figure is an
alternative in electrowetting optical devices intended for
illumination because it will allow radiation out coupled downwards
by FTIR from the lightgates to be reflected towards the beholder.
The combination of TIR and FTIR out coupling is very efficient. It
should be noted that although the preferred embodiments of the
invention all feature front light then it quite feasible to combine
the elements such that the system can be a backlight solution. This
is especially true for solutions intended for illumination
applications.
[0126] FIG. 6 shows a push & flush lightgate in shut state.
[0127] The push & flush lightgate is identical to the above
design with the difference that the design does not curl up and
form an essentially round figure but stay a line where the
transverse movement of fluids are minimized and the amount of 35
less polar fluid and dipolar liquid 30 that is required to move is
minimal due to reduced cross sectional dimensions.
[0128] FIG. 7 shows a push & flush lightgate in open state.
[0129] The lightgate opens when the less polar liquid 35 flush into
the aperture 96 area after the applied charge to the upper
electrode 25 is released. As all other electro wetting optical
devices according to the invention the push & flush lightgate
is a capacitor with two liquids inside. When a charge potential is
applied across the lightgate the polarity of the dipolar liquid 30
will change and its affinity to the hydrophobic surfaces will
change such that it will push the less polar liquid 35 away from
hydrophobic areas. The push & flush lightgate is somewhat slow
because only the push is caused by an applied field whereas the
flush is not helped by an electric field.
[0130] FIG. 8 shows a push & flush lightgate in shut state with
electrical controlled bistability.
[0131] In a design very similar to the ordinary push & flush
lightgate it is feasible to utilize the less polar liquid 35 as an
additional dielectric layer that decrease the electric field
strength when the less polar liquid 35 flood the upper electrode
25. The decreased electric field strength match the electric field
strength needed to prevent the less polar liquid 35 from flushing
into the aperture 96 and this allows a bistability to be created by
applying an electric charge across the lightgate when one of the
two situations occur.
[0132] FIG. 9 shows a push & flush lightgate in open state with
electrical controlled bistability.
[0133] Bistability is an advantage in display designs based on
binary principles with multiple frames that create a binary
Grayscale and color depth by use of three light sources 20 with RGB
primary colors that output energy amounts going from
1-2-4-8-16-32-64-128. Each of the RGB primary colors will feature a
.delta.bit resolution and combined they will deliver 24 bit true
color with 16.777.216 colors. For the system to accomplish this it
is necessary to show 24 frames within the time span where a display
normally show a frame. Video framerate is 24 which indicate that
the system must switch from off to on within 1 ms and also allow
the light source to output within that time span. If we are dealing
with a high definition television then there are 1.080 rows and
1.920 columns. In a passive matrix each row can be selected
exclusively once and all other rows can be selected collectively at
the same time. This means that the system needs to address
1.080.times.24=25.920 times per frame. At video framerate each
frame last 41.6 ms so the each row has to be completed within
1000/24/25.920/1.000=0.0016 ms
[0134] 100 Hz framerate requires linearly faster switching. The
bistable push & flush lightgate is most likely unable to reach
this switching speed and is thus more useful in illumination
applications where switching speed is not as important.
[0135] FIG. 10 shows a push & push lightgate in shut state.
[0136] The push & push lightgate is faster because the amount
of less polar liquid 35 becomes smaller as the entire less polar
liquid 35 is moved from the low n island 60 to the aperture 96 with
the same geometry within the less polar liquid 35 contain 75% less
fluid. Also the added force achieved by having both upper electrode
25 pushing into the low n island 60 and upper electrode2 26 pushing
into the aperture 96 increase switch speed.
[0137] FIG. 11 shows a push & push lightgate in open state.
[0138] The less polar liquid 35 is pushed into the aperture 96.
When the 71 push and push selector row electrode is charged the
lightgate switch according to the potential on either upper
electrode 25 or upper electrode2 26 but as soon as the charge on
either electrode change the lightgate switch again. This makes this
particular lightgate useful only in designs where a temporary on or
of state is required fast and it is accepted that the state vanish
after the charge to one of the three electrodes is removed. These
characteristics are befitting for electro wetting optical devices
based on a common ground where the upper electrode 25 and the upper
electrode2 26 selects an entire column.
[0139] FIG. 12 shows a push & push binary lightgate in shut
state. The push & push binary lightgate resemble the push &
push lightgate except for a barrier 63 area inserted between the
aperture 96 and the low n island 60. The barrier 63 is either
hydrophilic or a combination of hydrophobic and oliophobic such
that when either of the electrodes upper electrode 25 or upper
electrode2 26 push the less polar liquid 35 to the low n island 60
or the 35 low n island to the aperture 96 it will first push the
less polar liquid 35 up in a high contact angle before it flush
across the barrier 63. When more than 50% of the less polar liquid
35 is moved across the barrier 63 the less polar liquid 35 attach
stronger to the largest area on either side of the barrier 63 which
will draw it across the barrier 63. Due to this self-completion
effect the required time where charge has to be applied to switch
the lightgate is reduced and the lightgate is inherently bistable
as well as truly binary because only one or the other state open or
shut is feasible.
[0140] Due to fast switch speed and the bistability and the binary
nature this lightgate is ideally suitable for truly digital
displays and equally suited for illumination where analogue
intensity levels are not required.
[0141] FIG. 13A shows a push & push binary lightgate in open
state. The need for high switch speed can be relaxed slightly by a
few techniques that are enabled better due to the binary nature of
this particular lightgate that allows the lightgate to stay in the
state is has once been updated to.
[0142] The digital display principle is based on time modulation
over several frames and is in its basic concept fixed to a certain
framerate as for instance video framerate at 24 frames per second
or classic CRT framerate at 50 frames per second or modern LCD
framerate at 100 frames per second. There is however no reason that
the time modulation should not be slower or faster depending upon
the video content such that video sequences with slow movements are
modulated over more frames than video sequences with fast movement
which creates higher color depth and better grayscale for slow
moving images. The result of this approach is that it becomes
feasible to show for instance 24 bit true color in slow moving
video content and 8 bit in fast moving video content. This coincide
with human color and Grayscale perception which is low for fast
moving objects and high for slow moving objects.
[0143] The color field sequential mode in its pure form is based
upon the concept that each lightgate is also a single pixel but it
is feasible to let the lightgates work ensemble as pixels. If you
join two lightgates into one pixel you double the Grayscale and the
color depth. In this particular design it is feasible to join
several lightgates into virtual pixels that can have any number of
lightgates so an increase in Grayscale and color depth can be
achieved by lowering the resolution in particular areas of the
display. This will go unnoticed by the human eye however because
human vision system is mainly sensitive to contrast which will not
be impacted by this strategy provided that the high contrast area
of the image is shown with optimum resolution.
[0144] Another option is to Bin lightgates together such that you
sacrifice Grayscale and color depth for speed along particular rows
and/or columns. If you for instance watch television content in 4:3
format on a widescreen display you do not need any resolution
outside the 4:3 image so you simply bin these areas into a single
black pixel which will leave you with more time for modulating the
actual active 4:3 content area and thus with better Grayscale and
color depth. Also you can fit the display resolution to lower
resolution content by binning the lightgates to emulate the lower
resolution.
[0145] Another option which is feasible for all lightgates with two
charge electrodes is to employ an active matrix ground. The
configuration with the binary lightgate design is close to full
active matrix performance because it can simultaneously address all
lightgates but it is required to update both those lightgates that
are to be shut and those that are to be opened while those that are
not required to alter state are not addressed. Two frames per bit
is required which entails that 48 frames are needed to create a
full 24 bit true color digital lightgate display. 48 frames is
substantially less than a passive matrix update that requires 540
times more frames and the lessened number of frames translates into
less switch speed requirement and consequently allows larger
lightgate features. Ground electrodes controlled by an active
matrix placed select all lightgates that are to be switched to the
low n island 60 and when this is done then all lightgates that are
to be switched to the aperture 96 are selected. The lightgates that
does not require switching are not selected. Obviously it is
feasible to choose addressing via columns instead of rows and it is
likewise possible to let individual pairs of charge electrodes
update selected lightgates alternating between opening and shutting
lightgates independently of what is done on other pairs of charge
electrodes. Due to the binary principle the active matrix can be
simplified to only being able to send three instructions to each
controlled ground electrode, charge matching the charge electrode
with the highest potential, charge matching the charge electrode
with the lowest potential and no charge. In a display application
it is feasible to employ absorbing electrode 43 to enhance
blacklevel whereas in illumination applications it feasible to
employ mirror electrode 40.
[0146] FIG. 13B Shows a push & push binary lightgate (a) in
open and (b) shut state. The less polar liquid 35 is in figure a.
positioned in the low n island 60 where the radiation inside the
waveguide 10 cannot enter due to TIR created by the refractive
index difference between the low n material used for the low n
island 60 and the high n material used for the waveguide 10. The
less polar liquid 35 forms a droplet due to the surface tension
inside the less polar liquid 35 and the surrounding dipolar liquid
30, and the droplet is kept in place by the indention between the
low n island 60 and the aperture 96. Due to the indention the less
polar liquid 35 will either form a droplet in the 35 low n island
or in the aperture 96. And while in transition from either the low
n island 60 to the aperture 96 or vice versa the less polar liquid
35 will complete a movement from one side to the other if more than
less polar liquid 35 attaches itself to position from which the
transition has been initiated from. Due to the binary character of
the design the switching requires electrodes beneath both the low n
island 60 and the aperture 96. The indention principle may also
apply to the other binary pixel designs. The depicted design could
be different as there is no requirement of rounded forms on both
sides or any sides of the indention. Any indentions between two
bordering areas will create a bistable situation provided that the
contact angle between the less polar liquid 35 and the underlying
surface is sufficiently small so that it will not exert and outward
pressure that exceeds the surface tension forces. The balance
between hydrophobicity, hydrophilicity, oliophobicity and
oliophilicity has to be such that the less polar liquid 35 will be
contained by the indentions. A less polar liquid 35 can also be
contained inside a form with several points that among them create
multitudes of indentions through which the liquid can move. In a
particular design the indentions could create a circular lightgate
where the low n island is surrounded by an aperture 96 such as
shown in FIG. 4 and FIG. 5. The design shown in FIG. 4 and FIG. 5
does not show the indentions and the needed double set of
electrodes is not shown either.
[0147] FIG. 14 shows a Lightgate in the shape of a torus in shut
state.
[0148] The torus lightgate design is a particular embodiment of
either a push & push lightgate or a push & flush
lightgate.
[0149] In the first case with a push & push design the less
polar liquid 35 will remain with the same center point but expand
into aperture 96 area outside the low n island 60 that in this
connection is an atoll or contract onto the atoll such as it is
shown in the figure.
[0150] FIG. 15 shows a Lightgate in the shape of a torus in open
state. The less polar liquid 35 is expanded into the aperture 96
area which in this particular design also covers part of the lagoon
inside the atoll. Due to the geometry of the torus design it is
feasible to design a large omni directional lightgate with small
feature sizes in the important lateral dimension.
[0151] FIG. 16 shows a Lightgate with conductive spacer dots in
shut state. The spacer dot design introduce the spacer dot
electrode 27 which as the figure show protrudes up through a layer
of less polar liquid 35 covered with a layer of dipolar liquid 30.
The boundary between less polar liquid 35 and dipolar liquid 30 is
in balance around the spacer dot electrode 27 because the surface
energy of the spacer dot electrode 27 average the surface energies
of the less polar liquid 35 and the dipolar liquid 30. If the
balance is not perfect the interface between less polar liquid 35
and dipolar liquid 30 around spacer dot electrode 27 will show a
topology change. Any topology change will result in TIR and FTIR
out coupling from the electrowetting optical device. If however the
balance between less polar liquid 35 and dipolar liquid 30 is not
right it is possible to feed a bias charge to spacer dot electrode
27 that will recreate the balance and thus enable a waveguide 10
which partly consist of the less polar liquid 35.
[0152] FIG. 17 shows a Lightgate with conductive spacer dots in
open state. When charge is applied the boundary between the less
polar liquid 35 and the dipolar liquid 30 around the surface of
spacer dot electrode 27 shifts position which result in a topology
change that create HR and FTIR out coupling from the waveguide 10.
The out coupled light will move either towards mirror electrode 40
where it will be reflected upwards through the waveguide 10 or it
will move upwards through the waveguide 10. As the spacer dot
electrode 27 provides an upright surface for the competitive
electro wetting the demanded change in contact angle for the two
fluids is rather small relative to the topology change which result
in a system that require rather low electric field strength change
to output light from the waveguide 10. The spacer dot electrode 27
cause constant light leakages from the waveguide 10 because they
are constant imperfections in the waveguide.
[0153] The leakages effect makes the spacer dot design usable for
illumination only whereas the design is less useful for display
application say for backlight.
[0154] FIG. 18 shows a nanoimprint with characteristics usable to
produce lightgates. There are two ways to produce surfaces with
controlled hydrophilic/hydrophobic/oliophilic/oliophobic/refractive
indices surfaces. The first approach utilizes print of different
materials inherent surface properties and the second approach
engineer surface properties by use of nanostructures created by
nanoimprint techniques.
[0155] The approaches can be combined and will indeed always be a
combination for nanoimprint solutions as the surface
characteristics inherent to materials always will play a role for
nanoengineered surfaces.
[0156] The print process needed in the inherent properties set
demands for a good alignment which are difficult to attain.
Therefore the feature size must be enlarged which slow down
lightgate switch speed. Also the yield is depending upon many
different materials being able to adhere to each other which is a
complication. The dielectric layer required has to be beneath the
surface property controlling materials unless the characteristics
of the dielectric layer itself is useful in the construction and
therefore the electric field strength will be lessened which also
cause slower lightgates and require higher voltage applied to
achieve the electrowetting actuation of the two fluids.
[0157] The nanoimprint approach creates special nanostructures that
control the surface characteristics. If the nanostructure of a
material is controlled the inherent surface characteristics are
changed. As the nanoimprint is done in a single process step there
is no alignment issue between the surface characteristics which
entails that smaller feature size is attainable. The alignment
between electrodes and surface characteristics is how ever still
critical and so is the integrity of both electrodes and the
dielectric layer 3.
[0158] The dielectric layer 3 is important for preserving the
electric field strength. Tantalum dioxide, Hafnium dioxide and
Silicon dioxide are usable alternatives. Especially Tantalum
dioxide and Hafnium dioxide are interesting due to high dielectric
constants that allow layers as thin as 20-40 nm to be used which is
both an advantage for the electric field strength and for the
optical performance of the electrowetting optical device because a
layer that thin will not be seen by passing radiation as a material
with a refractive index.
[0159] The hydrophilic structures 83 are used in lightgate design
to contain less polar liquid 35 simply by providing a surface where
dipolar liquid 30 which is usually water based will have an
affinity for whereas less polar liquid 35 which is usually oil
based will deter. The refractive engineering structures 84 function
by mixing two materials with different refractive indices together
such that light will see the layer with mixed materials as a layer
with the combined refractive index of the two materials respective
refractive index. The diffractive structures 81 are large light
controlling structures that always require print process to be
created in a controlled fashion. The hydrophobic structures 82 are
used to attract the less polar liquid 35. It should be noted that
other particular surface properties such as oliophilic, oliophobic
also can be created by nanoimprint and that surfaces that combine
the different surface properties can be created too such as a
surface that is both hydrophobic and oliophobic and refractive
index engineered and fitted with diffractive structures. Also the
different properties can be controlled such that they are not only
blended together but also such that it is feasible make the
different properties weaker or stronger according to specific
design preferences. The reason for this versatility is the
difference of scale of the different structures.
[0160] A key advantage of nanoimprint is that it is benign for thin
film processing. In a preferred embodiment the waveguide 10 is a
thin film with printed structures that create a hydrophilic area
that is also oliophobic such that it can contain areas where the
less polar liquid 35 will attach itself to, areas with low n
refractive index that are also hydrophobic and oliophilic such that
less polar liquid 35 will attach itself to it and at the same time
will be prevented from optical interaction with light trapped by
TIR inside the waveguide 10, areas with a refractive index matched
to the less polar liquid 35 and the waveguide 10 that are also
hydrophobic and oliophilic such that less polar liquid 35 will
attach itself to it and be able to interact optically with light
trapped by TIR inside the waveguide 10.
[0161] These three kinds of areas with different grades of the
properties are sufficient to design the disclosed lightgate
designs. In the preferred embodiment electrodes and the dielectric
layer 3 are situated on top of the nanoengineered structures but it
will be noted that the both the electrodes and the dielectric layer
3 can be placed on the other side of the thin film. Also the thin
film can be made from PET or another polymer suitable as a
dielectric layer 3.
[0162] The production process could be as follows:
[0163] A thin film is cladded with photo resist.
[0164] Structures are imprinted into the photoresist with a stamp
containing nanostructures and microstructures.
[0165] UV curing is done while the stamp is in contact with the
photoresist.
[0166] On top of the structures a conductive surface is
deposited.
[0167] The conductive surface is cladded with a photoresist.
[0168] The photoresist is masked and developed.
[0169] The undeveloped photoresist is removed.
[0170] The conductive surface not protected by photoresist is
lifted off.
[0171] The photoresist above the conductive area is removed.
[0172] The dielectric layer 3 is deposited above the conductive
area.
[0173] Anti-charge trapping
[0174] The dielectric layer 3 is influenced by the presence of ions
because the voltage across will attract ions and lead to charge
trapping that will disrupt the electrowetting actuation. As a means
of preventing the charge trapping long polymer chains that readily
trap charges can be added to the water as a soluble or be printed
to surfaces. Colloids are useful in this capacity.
[0175] FIG. 19 Auxiliary layers
[0176] It is feasible to insert auxiliary layers in the
electrowetting optical devices below the top surface 1 to control
the emission of light.
[0177] By employing the phosphors 100, beam shaping optics 101
and/or LC elements 104 in combinations with the described
electrowetting optical devices it becomes feasible to create
various applications.
[0178] An example of such an application is a scanning backlight
where a phosphor 100 layer can be placed above the low n cladding 5
over the waveguide 10 and beneath the top surface 1. The scanning
backlight application can be realized with all types of
electrowetting optical devices where the lightgates stretch the
entire length of either a row or a column. The phosphor layer will
convert short wavelengths from the light source 20 to visible
spectrum which enables the use of high brightness UV LED's that are
very much more efficient than primary color LED's and very much
more powerful. Further by separating the phosphors from the LED it
becomes possible to avoid the mutually harmful heat generation
inside both the LED chip and the phosphor layer and it becomes
feasible to achieve better LED thermal management. Also it should
be noted that the heat generation from the phosphors brings the
temperature above the max for the LED chip earlier and thus reduce
the max LED output. Also increased heat generation accelerate
degradation of both LED chip and phosphors. It should however be
noted that the electrowetting optical device is also adaptable to
fluorescent tubes. As the phosphors are essentially isotropic the
radiation will go in all directions but the low n cladding 5 has a
low n that will TIR reflect the majority of the converted light in
the direction toward the beholder. The part of the radiation that
continues downwards can be recycled by use of mirror electrode 40.
When the converted radiation pass through the phosphor layer the
phosphor layer will act as a diffuser. Above the top surface 1 a
normal LCD design beginning with a DBEF film can be placed.
[0179] In another embodiment of the scanning backlight it is
possible to extend the functionality with lOlbeam shaping optics
layer such as prism sheet or a diffractive optical element that
control where light from a particular area of the phosphor will be
directed. Combined with the area selective nature of the backlight
design it becomes possible to select rows or columns that transmit
light that spread in a wide view angle or a narrow view angle. This
functionality is especially useful for power savings because the
energy send in other directions than towards the beholder(s) is
lost.
[0180] In an embodiment of the scanning backlight specific rows or
columns lightgates select phosphor 100 layers below beam shaping
optics 101 layer that direct emission to the left or to the right
directions such that a scanning backlight that alternating output
an image to the left eye and the right eye is realized and thereby
a backlight that can convert any normal 104 LC element into a
Liquid crystal display that can display stereoscopic content.
[0181] In an embodiment of the scanning backlight the rows that
transmit left and right are subdivided into rows where the
phosphors above exclusively convert UV into red light or green
light or blue light such that it becomes feasible to remove the
Bayer filter from the LCD and run it in color field sequential
mode. The Bayer filter consumes approximately 75% of the photons
emitted from normal LCD backlight units so the advantage is
significant. Also the number of pixels required in a
1.080.times.1.920 HDTV is lowered by a factor 4 when you switch to
color field sequential mode which allows the design to reduce the
complexity even though an active backlight is added. Auxiliary
lightgates with deep saturated blue and red phosphors can be added
and used in specific frames to accentuate parts of images where
extra saturated colors are desirable. Further the selected
phosphors can be chosen for narrowband emission and through this
increase the beholders perceived brightness through the Helmholtz
kohlraus effect.
[0182] In an embodiment of the scanning backlight the rows also
choose between phosphors with slightly different excitation spectra
such that good match to the light source 20 output spectrum is
achievable. To harvest the advantage a measure of the match between
the LED emission spectrum and the excitation spectra of the
phosphors has to be carried out and this can be done by adding one
or more photo sensors to the top surface 1 and by either introduce
slight topology similar to antiglare to the top surface 1 or by
tapering the top surface 1 slightly such that a small portion of
the light passing through the top surface 1 continue to the rim of
the top surface 1 where photo sensors measure the energy. The best
match is simply the match that makes the photo sensors output most
energy. A further use of the photo sensors is to match the timing
of the LED emission to the LCD update including the time span the
phosphors require to respond with emission from when UV impinge
upon them.
[0183] In an embodiment of the scanning backlight all the above
options including are combined in a single package where there are
also added lightgate rows or columns that select phosphors 100
beneath beam shaping optics 101 layer that output in either wide
angle or narrow angle. If all the features are combined including
wide and narrow view angle, RGB phosphors, two sets of phosphors
with different excitation spectra and left and right optics
elements then the design is required to have
2.times.3.times.2.times.2=24 lightgates in sequential repetition
that choose different optical modulations according to the desires
of the beholder. In order to avoid too large distance between the
backlight unit the 24 repeated lightgates are made in a jig saw
pattern.
[0184] Another consideration regarding possible Moire effects
dictates that the repetitive patterns in all layers above the
phosphors should be varied such that Moire patterns are avoided.
The above different backlight designs are all feasible to combine
with advanced algorithms that foresee the needed backlight
intensity above each lightgate and this is of cause also feasible
to do including the RGB color field sequential mode. The intensity
can be varied by pulsing the light source 20 in different duty
cycles and/or by varying the energy applied to the light source 20
and or by varying the duration of a scan position. The latter will
require that the scan rate of the LCD is co-controlled to match
such that the scanning backlight continue to be on only where the
LCD is actually updated.
[0185] Above it has been detailed how a scanning backlight can be
made with different levels of refinement. The same refinements can
be employed in a dynamic backlight where the backlight is designed
with a push & push active matrix ground selector 73 which
enable addressing lightgates in a matrix behind LC elements 104.
All the elements shown in the above scanning backlight application
including selection of wide or narrow view angle, left or right
emission, R or G or B color field sequentially, saturated frames
addition, matching of phosphors excitation spectra to LED's
emission spectra can be utilized combined with active matrix
selection of single lightgates which enable that the intensity of
the backlight emission can be co-modulated by both the backlight
unit and the LC elements 104 to match the dynamics required by the
video content.
[0186] The backlight design principles are also employable in other
applications such as for instance car headlamps.
[0187] In a car headlight the electrowetting optical device is
required to: [0188] Balance light according to the balance of the
car that will affect the up down direction of the headlights.
[0189] Shift between close up light (naerlys?) and distance light
and mist light and position light. [0190] Turn lights into left and
right curves. [0191] set the headlights for left road driving or
right road driving [0192] Blink light left or right [0193]
Distribute intensity from the headlights such that the close field
get less photons and the far field get progressively more in order
to compensate for the distance law and though this enable best
possible illumination of the road and obstacles ahead. [0194] Show
decorative elements in multiple colors
[0195] All the above settings and more can be fashioned using the
very same techniques as employed to create the scanning backlight.
If we provide three different balance settings combined with near
field lighting, far field lighting, mist lighting and position
lighting combined with left road and right road settings combined
with left turn and right turn settings+added blink light to both
left and right then we in total need 3.times.4.times.2.times.2=48
lightgates in repetition and as we want to add left and right blink
light it is preferable to address active column lightgates.
[0196] In a headlight the top surface 1 needs to be very tough
which is not a problem using for instance press glass or molded
polycarbonate as top surface 1. Mounting the headlight is very easy
compared to standard headlights as the form factor provide low
depth that allow a design where the car body only has small holes
for electrical connection of the headlights. The employed beam
shaping optics 101 layer can allow a very slanted profile that
improves design aesthetics as well as aerodynamics. Also the before
mentioned opportunity to create a curvable electrowetting optical
device affords designers good opportunities.
[0197] In an embodiment of the invention the electrowetting optical
device similar to the scanning backlight is utilized to create a
tuneable LED that can output colored light across the visible
spectrum and also output white light with a Color Rendering Index
CRI>95% A normal high brightness UV LED has a fixed mix of
phosphors that are co-located in close proximity to the LED chip
and is therefore unable to tune the color of the converted
emission. When a batch of high brightness LED's is produced there
will for many reasons always be a variation of the emission spectra
and the Im/W. As white phosphors mixes usually require an accurate
match to their excitation spectrum the LED's has to be sorted
according to performance and especially according to emission
spectra. The LED's that does not meet requirements are sold at a
discount and the process steps required to sort the LED's into
different bins is costly. The electrowetting optical device can
employ all high brightness UV LED's in a batch and thus increase
yield and lower costly sorting into different bins.
[0198] Due to the inherent accuracy of match between emission and
excitation spectra based on computation of sensor readings it is
feasible to match the same color and intensity for a multitude of
individual electrowetting optical devices. Most light sources loose
efficiency over their lifespan and experience ageing degradation
with color temperature shift as well. LED's are no exception so it
is almost impossible to have several LED based lamps in the same
lighting design that output even color and intensity which is a
major problem for lighting designers. The built in sensors can also
measure ambient light level in dark cycles between LED emissions
and the tuneable LED can output light that is blended with the
ambient light such that the light intensity is kept at a predefined
level.
[0199] The CPU that calculate the color match and the ambient blend
is fitted with a transceiver running for instance Z-wave or Zigbee
such that it becomes feasible to remote control the tuneable
electrowetting optical device. This facility enable performance
control where max output is probed by first matching CRI to a
preferred level and second increase intensity until it reaches a
peak output. When the max output is found the max output efficiency
is probed by measuring when the best Im/W ratio with the preferred
CRI is obtained by varying duty cycle, voltage and ampere. The
information will be extremely useful for cost and environmental
conscious facility managers because the tuneable electrowetting
optical device should be replaced when it is too expensive to keep
and not when it stops working. The equation needed to process in
order to decide a replacement can be part of software supplied to
the facility managers and can be kept updated via the internet so
every time a novel electrowetting optical device with better
performance becomes available as a consequence of the constant
improvements of LED efficiency the equation changes and facility
managers will be able to get a reliable payback time calculation
that explain both the economics of replacement and the
environmental benefits. Data collected to facility managers about
tuneable electrowetting optical devices can be used to establish
how real life lighting schemes are operated and based on these data
research into different programming of the lighting can form the
basis for further energy savings on a system basis.
[0200] The remote control enables users to set the light according
to their wishes including color temperature and intensity.
[0201] Proximity sensors commonly used in other lamps are also
feasible to connect via the wireless communication or build into
the tuneable electrowetting optical device. In the absence of
humans in the proximity the response can be either to shut the
light down entirely, to dim light or to set the CRI to a lower
value where the Im/W ratio is better than for high CRI values.
[0202] In another embodiment of the invention the electrowetting
optical device serve as a display. All the described lightgates
shown in FIGS. 2 and 4 to FIG. 17 with different arrangements of
the electrodes shown in FIG. 3 (except for c) will function in
display applications but there are considerable differences in the
performance of displays that employ the different lightgates. The
push & flush lightgate type will when it expands increase the
covered aperture area. The round and torus shaped push & flush
designs increase area exponentially which is a better match to the
logarithmic human vision system than linear pixels such as they are
found in Plasma displays, Liquid crystal displays, OLED displays
and other contemporary displays. Linear pixels have a problem with
Grayscale because the uncertainty of applied charge and pixel
performance is equally large regardless of the emission which means
that the relative inaccuracy is significantly higher in low level
emission where the human vision system is most adapt to register
flaws. For an exponential lightgate such as the round lightgate
best precision is achieved when a high amount of charge is utilized
to push the less polar liquid 35 into high contact angles where it
covers the least area of the aperture 96. As both the round and the
torus shaped push & flush lightgates requires exact positioning
of the less polar liquid 35 it is required to use active matrix to
control the display. Differences in output can be mitigated by use
of coupling sensors to the display either to each lightgate or to
regions of the display and then compensate surplus or deficit
output by time modulating the output from the lightgate over
several frames. The time modulation also makes a better Grayscale
feasible because the LED's can be driven in alternating intensity
in sequential frames such that finer differences in intensity can
be realized. Color field sequential mode is feasible provided that
at least
[0203] RGB light sources 20 are connected to the waveguide 10.
Frames with deeper saturated colors are feasible to insert in
between the normal RGB frames provided light sources 20 with deeper
saturated colors are attached to the waveguide. The deeper
saturated colors will be employed to accentuate specific parts of
the image.
[0204] All displays where the pixel fill factor is lower than 100%
will close up show a pixilation effect and for round push flush
lightgates design the fill factor has to be low to design a
lightgate with sufficiently fast switch speed. To counteract
pixilation a beam shaping optics 101 layer can be adapted to
diffuse light from the lightgates and a 103 beam shaping optics
Iayer2 can be adapted to control the view angle. The appearance of
the display will be that the pixels overlap seamlessly.
[0205] In another embodiment of the invention passive matrix push
& flush lightgates are utilized to create a binary display
based on passive matrix instead of the above described. All the
color field sequential mode techniques are applicable and so is the
anti-pixilation design. A passive matrix display is limited to only
update a single row or a single column at a time. For HDTV 1.080
rows.times.1.920 columns have to be updated per frame. A 24 bit
true color mode will require 25.920 updates per color sequential
image frame. The number of updates can be lessened if the
lightgates are operated as sub-pixels. Two lightgate pixels design
half the needed updates and four lightgate pixels design half it
once more. Floating pixels with varying numbers of lightgates are
feasible. The binary principle requires that the lightgate is only
to be in one of two states which are shut or open. In the push
& flush design a binary state can be created by introducing a
bias charge to rows that are not updated. The binary charge has to
equal the force needed to push the less polar liquid 35 onto the
low n island 60 shown in FIG. 8 where the lightgate is shut and at
the same time be less than the maximal force needed to the push the
less polar liquid 35 away from the far border of the aperture 96.
The design rely on the less polar liquid 35 layer on top of the
upper electrode 25 below the dielectric layer 3 to become a part of
the dielectric layer 3 that due to its thicker dimension creates a
lowered electric field strength that require a voltage difference
higher than created by the bias charge to actuate the less polar
liquid 35 that covers the entire aperture 96. The bias charge is
able to push the less polar liquid 35 up upon the low n island 60
as long as the electric field strength is not limited by less polar
liquid 35 thickening the dielectric layer 3 so once a lightgate is
shut the time before the bias charge has to be applied equals the
time required for the first updated to flush the less polar liquid
35 back past the upper electrode 25. The bias charge can only be
applied when the lightgate is either shut or open. Therefore in
push & flush designs it is required not to begin the update of
lightgates before the last aperture 96 is fully covered by less
polar liquid 35. Then by applying charge to the upper electrode 25
the less polar liquid 35 is pushed onto the low n island 60. In
order to prevent less polar liquid 35 flush it is feasible to apply
charge to all upper electrodes 25 while all push & flush row
selector electrodes 70 are charged with bias charge.
[0206] In another embodiment of the electrowetting optical device
the push & push design shown in FIG. 10 and FIG. 11 is
employed. The flush to cover the aperture 96 is speeded up by an
additional upper electrode2 26. The differential drive scheme
described can be employed.
[0207] In another embodiment of the electrowetting optical device
the push & push design shown in FIG. 12 and FIG. 13A is
employed. Due to the barrier 63 area that is slightly less
oliophobic than the oliophobic 62 areas surrounding the lightgate
the less polar liquid 35 will be contained either upon the aperture
96 or the low n island 60. When the less polar liquid 35 is in
transition from either side across the barrier 63 then either of
the sides which the less polar liquid 35 is most in contact with
will draw the less polar liquid 35 across the barrier 63 even
though the charge is annulled. This self-completion effect reduces
the time needed to update the lightgate and due to the binary
nature of the system no bias charge upon the push & push row
selector electrode 71 is required. The binary state enables longer
time to fire light source 20 energy through the lightgates.
[0208] In another embodiment of the electrowetting optical device
the push & push design shown in FIG. 12 and FIG. 13A is
employed together with a push & push active matrix ground
selector electrode 73 shown in FIG. 3d. In this design the switch
speed required is lowered because only a total of 48 sub-frames are
needed to create one frame with 24 bit true color. First upper
electrode 25 and upper electrode2 26 select whether the next update
open or shut the lightgates and then the push & push active
matrix ground selector electrodes 73 select which lightgates should
to be updated. Second the potential of upper electrode 25 and upper
electrode2 26 is reversed before push & push active matrix
ground selector electrodes 73 select which lightgates should to be
updated. The lightgates that needs no update is left unaltered.
[0209] FIG. 20A shows a lightgate with inverted droplet in shut and
open state. The top surface 1 has a cladding with hydrophobic
structures 82 that attach the base of a droplet with less polar
liquid 35 to the top surface 1. The hydrophobic structures 82 that
serve as aperture 96 areas are divided by hydrophilic structures 83
that prevent the less polar liquid 35 to attach there. By
controlling where the respective hydrophobic structures 82 and
hydrophilic structures 83 are printed the form of less polar liquid
35 droplet in contact with the top surface 1 can be designed. The
upper electrodes 26 are connected galvanically to the less polar
liquid 35 that is made conductive by use of filler materials based
on carbon nano tubes or large polymer chains molecules containing
carbon. The surrounding dipolar liquid 30 is made electrically
insulating by removing ions which will make the dipolar liquid 30 a
poor electric conductor. The lower electrodes 41 area made such
that each row is subdivided into an uneven number of electrodes
that are aligned. The aligned electrodes are addressable such that
every second electrode can have a potential that is different from
the immediate neighboring electrode in a row while the outer
electrodes in a row always are equal to the outer electrodes of
adjourning row electrodes when the adjourning rows are of. When the
aligned electrodes in a single row are addressed with different
electric potentials horizontal electrowetting will draw water to
aperture 96 areas that are created by nano-imprinting of
hydrophobic structures 82 that are surrounded by hydrophilic
structures 83. The form and extent of the aperture 96 areas can
vary. The aperture 96 areas and the low n island 60 area created by
spin coating a low n cladding material onto the waveguide 10 and
then nanoimprinting hydrophobic structures 82 such that the low n
low n cladding 5 material becomes so thin in the aperture 96 areas
that the combined refractive index of the low n low n cladding 5
layer, the ITO lower electrodes 41 layer on top of the
nanoimprinted structures and the dielectric layer 3 and the less
polar liquid 35 match the refractive index of the waveguide 10. The
low n island 60 is in fact as shown in FIG. 20A a surrounding "sea"
consisting of hydrophilic structures 83 that attract dipolar liquid
30. The low n island 60 area is co-produced in the same low n low n
cladding 5 and the same nanoimprint process by applying
nanoimprinted hydrophilic structures 83 on top of a low n low n
cladding 5 layer that is sufficiently thick to maintain the low n
of the low n cladding 5 and thus create a critical angle between
the low n low n cladding 5 and the waveguide 10 that will prevent
light trapped by TIR inside the waveguide 10 from exiting via low n
island 60 areas.
[0210] When the lightgate is addressed with a potential difference
laterally between the aligned lower electrodes 41 it will be shut
as shown in FIG. 20B.
[0211] When the aligned electrodes in a row all have the same
electric potential the row can be addressed through the upper
electrodes 25 in the column direction because electric potential
difference will drive the electrowetting and shut the lightgate as
shown in FIG. 20B. and equal electric potential will open the
lightgate as shown in FIG. 20B. When the electrowetting is on all
surfaces including the aperture 96 areas are wetted as shown in
FIG. 20B. and the added dipolar liquid 30 layer will lower the
refractive index such that radiation trapped by TlR inside the
waveguide 10 will not exit. When all electrodes 41 in the row have
equal potential and the 26 upper column electrode also have an
equal potential the aperture 96 areas will be index matched to the
less polar liquid 35 and the waveguide 10 such that radiation
inside the waveguide 10 can enter into the less polar liquid 35.
When the radiation enters into the inverted droplet of less polar
liquid 35 it will be reflected by TIR at the walls of the less
polar liquid 35 because it is bordered by dipolar liquid 30 which
is low n such as water. The hydrophilic structures 83 will
constantly be flooded with a dipolar liquid 30 which serves as a
reservoir for the 82 hydrophobic areas that draw dipolar liquid 30
when the lightgate is shut as shown in FIG. 20B. Shutting the
lightgate by increasing the thickness of the dipolar liquid 30
layer is dependent upon the wavelength of light to be shut off. The
longer the wavelength light the thicker the layer needs to be in
order to TIR reflect light and therefore also the corresponding
volume of dipolar liquid 30 that has to be moved increase with
wavelength. Volume movement is part of the equation that determine
how fast the lightgate can be operated it follows that the
lightgate is speedier for short wavelength light and thus better
adapted for blue and UV wavelengths.
[0212] Movement of the droplet with less polar liquid 35 is also
part of the equation and in this design the movement is minimized
to a theoretical minimum by holding the less polar liquid 35
droplet still in the lateral plane while only moving a few
nanometers up and down in the vertical plane. The result is that
the relative speed of fluids is limited to a minimum which prevent
friction between the liquids and the thereof following mixing of
the liquids that can create emulsion which basically resemble
mayonnaise. The emulsion risk is an upper speed limit so the
operation of shutting and opening the lightgate is increased to a
maximum via this design. The emulsion risk can be reduced by
selection of liquids that are mutually repellent and by selecting
liquids with near identical density and by selecting liquids with
as little as possible solubility in each other.
[0213] The aperture 96 areas can be dispersed across an area such
that each aperture 96 is in fact an island within a sea consisting
of an area that does change wettability. When the there is a
potential difference driving the electro wetting effect only the
wetting of the aperture 96 areas will be affected such that a
change in refractive index occur. The nano imprint structures that
create the differing hydrophobic and hydrophilic properties can be
optimized to be filled with dipolar liquid 30 rather than with less
polar liquid 35. Multiple aperture 96 areas creates the least
possible travel distance over ground and relative to the inverted
droplet lower contact area shown in FIG. 20.1. The shown aperture
areas are round but there are in fact no limiting factors that
prevent them from having different forms and from an optimization
of least speed over ground perspective the cross section of the
aperture 96 areas should be as small as possible whereas the length
does not matter since it is the shortest distance from the edge to
the center that counts.
[0214] The inverted droplets shown in FIG. 20A are dimensional
stable in themselves but the dimension stability can be enhanced by
inserting an oliophilic spacer, similar to the description of FIG.
1, inside such that the top surface 1 and the waveguide 10 cannot
be pressed together. When no vertical pressure is applied to the
unit the top surface 1 and waveguide 10 will float on a film of
less polar liquid 35.
[0215] FIG. 21A shows a illumination unit 270.
[0216] A number of layers shown in top view in FIGS. 21.1, 21.2,
21.3, 21.4, 21.5, and 21.6 with different functions are stacked and
assembled with high precision alignment due to alignment markers
240 that are either cut in the surface or drilled through the
layers surfaces using laser or high pressure water cutting. The
protective upper surface 230 shown in FIG. 21F seals the
illumination unit 270 upwards. The lower surface of the protective
upper surface 230 is preferably plane while the upper surface of
the protective upper surface 230 can have any form desired. At the
lower side of the protective upper surface 230 one or more thin
layers can be deposited including phosphor 100 layer, beam shaping
optics 101 layer or auxiliary layer 102 and the order of their
relative position can vary according to purpose. The upper surface
may be contoured with macro and micro prisms, diffractive optics,
contour text, and may comprise thin layers that for instance apply
scratch resistance, graded index match to prevent avoid Fresnel
reflections, hydrophobic or hydrophilic properties, absorptive
color filter text or ornamentation and interference filters.
[0217] The top surface 1 shown in FIG. 21D may comprise beam
shaping optics 101 that may consist of a layer with micro prisms or
81 diffractive optics structures, and/or phosphor 100 layer that
convert short wavelength light to visible wavelengths and/or a
layer patterned with upper electrodes 26 and/or a layer patterned
with a dielectric layer 3. The top surface 1 may be produced of any
transparent material but due to considerations regarding thermal
expansion it will be advantageous if it has similar temperature
dependent expansion as the waveguide 10 material shown in FIG. 21B
and preferably as little expansion as possible. Also the material
should preferably be a thermal conductor as it is important that
the heat generated inside the illumination unit 270 can be
dissipated. Materials such as fused silicon and Pyrex glass fit the
requirements but also other glass types and polymers are usable. At
the lower side of the top surface 1 a barrier layer 210 shown in
FIG. 21E comprising a sheet of glass or polymer featuring alignment
markers 240 matching the other layers in the stack and an open cut
matching the zone where the electrowetting lightgates are
positioned and a rim that covers the outer perimeter of the
waveguide 10 in such as fashion that the barrier layer 210
constitute a solid evaporation barrier 90 containing the fluids
active in the competitive electrowetting lightgates. The waveguide
10 comprise a low n low n cladding 5 material that provide a
critical angle between the waveguide 10 and the low n cladding 5
except in the aperture 96 areas where there should be index match
between the less polar liquid 35 the aperture area and the
waveguide 10. One way to achieve this is to contour the low n low n
cladding 5 such that surrounding the aperture 96 areas the low n
cladding 5 is thick enough to provide a low n while the low n
cladding 5 in the aperture 96 areas is thin enough to blend with
other layers to form a mixed refractive index that match the
refractive indices of the waveguide 10 and the less polar liquid
35. The contouring of the low n low n cladding 5 can be done by
imprinting. Alternatively the contouring to create index match
between the waveguide 10 and the aperture 96 and the less polar
liquid 35 could be done by applying a PMMA photo resist in a spin
coating process to the entire waveguide 10 above the low n cladding
5, UV cure the resist around the aperture 96 areas and remove the
photoresist above the aperture 96 areas. For better adhesion of the
low n low n cladding 5 a primer can be used on top of the waveguide
10 and for better adhesion between the low n cladding 5 and the
PMMA photoresist a plasma etch of the low n cladding 5 can be used
or a thin layer of material in the 10 nm range such as Hafnium
dioxide can be added.
[0218] The waveguide 10 comprise 82 hydrophobic and 83 hydrophilic
areas that defines the lightgates and surrounding passivated
hydrophilic areas that will not accept other than dipolar liquid 30
which can be made by nanoimprinted structures. PMMA is well suited
for nanoimprint and the UV curing described above can be made such
that the PMMA is soft due to incomplete curing which may enhance
the nanoimprint quality as well as the speed with which it can be
performed. After the nanoimprinting or indeed while the nanoimprint
stamp is in contact with the PMMA the UV curing can take place.
Alternatively to creating hydrophobic and hydrophilic properties by
nanoimprinting either hydrophobic or hydrophilic structures can
rely on inherent properties of the dielectric layer 3 and these
properties may be accentuated or manipulated by adding chemical
impurities to the dielectric layer 3 as for instance is well known
with silicon dioxide where an increase of carbon impurities create
a hydrophilic surface. The waveguide 10 further comprise electrodes
41 below the dielectric layer 3 that are typically either rows or
columns. The electrodes 41 for transmissive displays are usually
made out of transparent materials such as ITO that is widely used
in the display industry due to its transparent properties and well
known controllable qualities. The electrodes 41 are applied by for
instance a sputtering process whereafter photo resist is spin
coated onto the electrodes 41 and thereafter patterned using UV
lithography, thereafter the none UV cured photoresist is removed,
thereafter the exposed 41 electrode layer is etched away,
thereafter the remaining photo resist is removed and finally the
waveguide 10 is rinsed and dried before further process steps which
will leave the waveguide 10 with row electrodes in any of the forms
described in the present patent application. In order to fortify
the quality and conductivity of the electrodes 41 it is feasible to
insert a electroplating process where a solution with ions is
poured on top of the waveguide 10 whereafter the electrodes 41 are
charged with a potential that attract ions to the electrodes 41 and
thus increase the electric conductivity. After the electroplating
the waveguide 10 is rinsed and dried. The waveguide 10 also
comprise a dielectric layer 3 which is preferably made from a
material with as high as electric constants as possible and as good
an integrity as possible with as thin a layer as possible because
the electric field strength that drives the electrowetting process
depend on these qualities. Further the transparency is important
even though the layer may only span 20 to 40 nm. Alternatives are
among others hafnium dioxide, Tantalum dioxide and silicon dioxide.
The dielectric layer 3 serves an important purpose by toughening
the nanoimprinted structures as well as the ITO. When the waveguide
10 is readied in the above process it can be in the form of a sheet
of glass or polymer or in the form of a roll of glass or polymer
and many waveguides 10 for illumination units 270 may be cut from
the sheet or roll employed. Cutting the waveguide 10 can be done
with a number of high precision techniques such as water cutting or
laser cutting. The key property of the cut is that the cut leaves a
perfect edge because the edge of the waveguide 10 TIR reflects the
revolving photons inside the waveguide 10 shown in FIG. 21.1. The
underside and the edges of the waveguide 10 does not require any
low n cladding 5 as it will be bordering air with a refractive
index at 1 which decrease the critical. At the edges the combined
angles x, y & z act together which allow photons to be TIR
reflected even though the x,y angle is below the critical angle.
The waveguide 10 design shown in FIG. 21B is roundish and in a
round planar waveguide each reflection of incident radiation will
in the x,y plane be determined by the tangent to the circular form
and as the edges are slightly skewed relative to a perfect circle
by the addition of appendices 250 that for stability each
reflection increase the angle in x,y plane. Appendices 250 can be
connected to the sheet of glass or polymer that the waveguide 10 is
cut out of. The various layers of glass or polymer that the
illumination unit 270 consist of can comprise 240 alignment marks
in the form of holes, marks etc. that ensure assembly with perfect
alignment to other sheets of glass or polymer that are laminated to
construct the illumination unit 270. To each of the appendices 250
a light source 20 can be connected and the light sources 20 can be
either of same wavelengths or different wavelength. The preferred
lightgate design for out coupling of radiation is the inverted
droplet out coupling shown in FIG. 20A and FIG. 20B because this
design has a high out coupling efficiency and because light that is
not out coupled through the apertures 96 continue in the same
optical pathway which ensures that photons will stay strapped
inside the waveguide 10 until they exit via apertures 96. All other
lightgate designs allow photons to enter and output a percentage of
the entered photon while a percentage is returned into the
waveguide 10 where it may bounce in different angles. The reason
why photons once injected via one or more 96 appendices into the
waveguide 10 by one or more light sources 20 will not exit except
through apertures 96 is that the round form with appendices 250
pointing backwards relative to the direction photons spin around in
the waveguide ensures that the photons once injected will be TIR
reflected by all surface except when it comes to the apertures 96.
Other lightgates described in the present innovation are feasible
to employ but are not preferred because the diffusive property of
the lightgates with respect to non out coupled photons will require
mirroring below and at the edges to ensure that the scattered
photons that are not out coupled can be directed to out couple.
While it is entirely feasible to position high quality mirrors at
the edges and surfaces it is however a complexity in the design and
relative to TIR mirrors constitutes a loss factor. Usually a photon
injected into a round waveguide will gradually be reflected in more
and more open angles until it nears the most open angle possible
inside a circle. The design requires that we also find place for
solid evaporation barrier 90 and fluid evaporation barrier 91 shown
in FIG. 1. The connected appendices 250 which will throw photons
into a spin inside the waveguide 10 that is more centralized with
fewer bounces per circulation. In one embodiment the light sources
20 can be visible color light sources and the color and intensity
of the emission from the illumination unit 270 can be controlled by
mixing the photons from each of the light sources 20 to blend a
desired color with a desired intensity. The light sources 20 in
this set up may comprise light sources 20 that emit white light
with different color temperature. The TIR mirroring inside the
inverted droplets avoids prismatic effects and ensures that the
light will blend such that the emitted light comes from the same
points without color fringing phenomenon. The light from the
illumination unit 270 will be emitted from a ring at the perimeter
of the rounded waveguide 10 and the directionality of the light
will match the predominant direction of the light circulation
inside the waveguide 10 so it will be very predictable where the
light will be emitted. The predictability of emission is well
suited for a beam shaping optics 101 layer. The beam shaping optics
101 layer can be placed at the top surface 1 and be either
diffractive optic structures or micro prisms. The beam shaping
optics 101 diffractive structures 81 can be combined with
nanoimprint of hydrophobic structures 82 and hydrophilic structures
83 necessary for the inverted droplet lightgate design shown in
FIG. 20 and in FIG. 18 it is shown design that a nano imprinted
surface can combine hydrophobic 82, hydrophilic 83 and diffractive
structures 81. An alternative is to place the hydrophobic
structures 82 and hydrophilic structures 83 at the lower side of
the top surface 1 facing towards the inverted droplets and the
diffractive structures 81 at the opposite side of the top surface 1
with the advantage that the diffractive structures 81 can be more
efficient if they are not combined with hydrophobic structures 82
and hydrophilic structures 83 and if they are made from high index
material that border air.
[0219] Further by placing the diffractive structures 81 at the
upper side of the top surface 1 it is feasible to use the top
surface thickness as a spacer part of the optical system which will
result in disintegrate the emission into various angles that could
be optimally handled by diffractive structures 81 aligned to
received light in specific angles. In another embodiment the light
extracted from the waveguide is UV and phosphor 100 layer is
positioned to convert the UV light to visible light. In this
embodiment the phosphor 100 layer can be added as an inserted layer
of its own. The phosphor 100 can be arranged with a palette of
phosphors that emit different narrowband or wideband wavelengths
and the phosphors in the palette can be adapted to have different
excitation wavelengths such that if the short wavelength radiation
emitted from the light source 20 vary in emission wavelength it
will be possible to match the phosphor excitation to the LED
emission as described previously. The phosphor 100 layer can
further comprise areas that match lightgates but without phosphors
such that primary light sources 20 can draw out of the waveguide 10
without being diffused or absorbed by the phosphors. This will
allow a blend of light from both phosphors and primary color light
sources 20 that will enable better blending possibilities and thus
greater ability to blend the desired colors. As primary colors have
longer wavelengths than for instance UV it is feasible to shut a
lightgate for UV while it is kept open for visible light because
the refractive index is depending upon wavelength and upon the
thickness of the low n material providing the critical angle and
upon the incident angle of the radiation. In the inverted droplet
lightgate the shutter mechanism is a thin layer of dipolar liquid
30 injected in between the aperture 96 area and the less polar
liquid 35 inside the inverted droplet. The thickness of the dipolar
liquid 30 layer will first block UV radiation and it will block
radiation in high incident angles before it block radiation in low
incident angles. This means that a lightgate can be open for long
visible wavelengths while it is shut for UV radiation in shorter
wavelengths. When longer wavelength radiation enters a phosphor 100
layer it is diffused but not converted in wavelengths. Beneath the
phosphor 100 layer a low n low n cladding 5 can be inserted. The
low n low n cladding 5 will not affect radiation from the 30 less
polar liquid inside the inverted droplet lightgates because the
geometry of the inverted droplet will direct radiation towards the
low n low n cladding 5 layer in angles below the critical angle.
When UV radiation enters the phosphor 100 layer it is converted and
reemitted as Lambertian radiation. At least 50% will therefore
propagate upwards and of the 50% of the radiation that will
propagate downwards a large proportion will be TIR reflected and
re-enter the phosphor 100 layer where it will be diffused in the
general direction that it has been TIR reflected of the low n low n
cladding 5. The combined refractive index of the phosphors and the
material containing the phosphors in the phosphor 100 layer should
be as high as possible to ensure as low a critical angle between
the low n low n cladding 5 and the phosphor 100 layer as this
enhanced the proportion of radiation that is TIR reflected. The
converted radiation backscatter from the phosphor 100 layer below
the critical angle can be blocked to a great extent by inserting a
multilayer interference filter designed to reflect the visible
light converted by the phosphor 100 layer while allowing direct UV
radiation in low angles to pass straight through such that the
proportion of radiation that backscatter is limited. Backscattered
radiation can be reemitted by use of mirrors below the waveguide
and the mirror can for instance be placed on top of the lower
protective surface 200. The light sources 20 can be side emitting
LED(s) that are attached to the appendices 250 surfaces. In order
to prevent loss of radiation that is not TIR reflected at the
waveguide 10 edges the light source 20 can be mirrored such that
radiation only will exit the edge that is directed into the
appendices 250 and thus is send on a course that will ensure that
the radiation circulate inside the waveguide 10. Controlling the
correct angle span inside the waveguide can be done by use of
diffractive structures 81. The spacer layer 220 is primarily used
to ensure that the lower surface of the waveguide 10 is facing air
such that a low critical angle is ensured. Secondary the spacer
layer 220 provides partly support to the waveguide 10 and creates a
cavity between the waveguide 10 and the protective lower layer 200.
The cavity can be used for several purposes such as for containing
low n liquid with high heat conductivity and good electric
insulation such as the dipolar liquid 30 when all ions are removed.
Inside the cavity with or without the dipolar liquid 30 electronic
components such as the light sources 20 and various electronics
that can comprise 2D or 3D accelerometer, light sensors, cameras,
wireless communication transceiver, memory, programmable CPU etc.
The purpose of the electronics is to control the color tuning, the
match between LED emission spectra and phosphor excitation spectra,
the emission intensity, the spot width etc. through addressing
different lightgates that connect radiation to different light
modulations arrangements such as diffractive structures 81 and/or
micro prisms and/or phosphor 100 layer and/or LC elements 104.
[0220] FIG. 22 shows an inverted lightgate based on topologic
suspension of fluids. The key idea in the inverted droplet
lightgate is that radiation that enters the lightgate will be TIR
reflected at the boundary between the less polar liquid 35 inside
the inverted droplet and the low n dipolar liquid 30 at the outside
due to the critical angle formed as a result of the difference in
refractive indices. In the single sided version of the inverted
droplet lightgate the droplet is not created by suspending it
between two surfaces but merely by controlling the topology and
distribution of dipolar liquid 30 and less polar liquid 35 via
printed indents in the low n cladding 5 above the waveguide 10 that
are designed with ridges, that repel the dipolar liquid 30 but
attract the 25 less polar liquid, going to the bottom of the
indents where the apertures 96 are situated. In between the ridges
the sidewalls of the indent have surfaces that repel the less polar
liquid 35 but attract the dipolar liquid 30. In between the indents
the waveguide 10 surface is nanoengineered to increased affinity
for the dipolar liquid 30 except for small areas that are also
elevated where there is less or no affinity for the dipolar liquid
30. These elevated areas form spacer dots that are adapted to
support and/or adhere to the top surface 1. The less polar liquid
35 will when it is brought in contact with the waveguide 10 surface
with printed indents and nanoengineered properties connect to the
areas that are nanoengineered to increased affinity for the less
polar liquid 35 and the dipolar liquid 30 will adhere to the areas
that is nanoengineered to have affinity for dipolar liquid 30. In
the indents the less polar liquid 35 will for a droplet suspended
by the ridges and the aperture 96 and surrounded at all other sides
by dipolar liquid 30. The walls of the suspended droplet of less
polar liquid 35 are designed to be above 90 degrees such that the
radiation escaping from the waveguide 10 due to frustrated total
reflection in general be TIR reflected at the boundary between less
polar liquid 35 and the dipolar liquid 30 and the boundary between
the less polar liquid 35 and the low n cladding 5. At the same time
the angle of the droplet walls will reflect escaping radiation
upwards in lower angles. The 41 lower
[0221] Electrode is situated below the dielectric layer 3. The
lower electrode 41 can either be a common ground or patterned with
rows or columns or be part of an active matrix. The lower electrode
41 and the dielectric layer 3 can be placed on top of the low n
cladding 5 and the waveguide 10 or it can be placed directly on top
of the waveguide 10. If the lower electrode 41 and the dielectric
layer 3 is situated on top of the waveguide 10 with low n cladding
5 on top there is a high probability that the low n cladding 5
print process leaves residual materials on top of the bottom of the
indents where the apertures 96 are situated which will result in a
decrease of electric field strength and will increase the risk of
charge trapping. One way to handle the problem is by etching the
residual material away in a process where the entire waveguide 10
with the low n cladding 5 is put through an etch process. This etch
process must however not ruin the nanoengineered properties and
this entails that the nanoengineered properties has to be created
in a scale large enough to withstand etching without changing its
desired properties. A way to achieve this is to nanoengineer one
property or in some instances two properties only while the
intrinsic properties to the material with the nanoengineered
surfaces provide yet a desired property. Clearly this process is
only applicable for surfaces before the 41 electrode and the
dielectric layer 3 is applied to the top of the surfaces. In an
alternative production method the lower electrode 41 and the
dielectric layer 3 is applied directly to the waveguide 10 and the
dielectric layer 3 is of a material that after having been etched
will have a greater affinity for the less polar liquid 35 than for
the dipolar liquid 30.
[0222] In some instances a primer is required to ensure that the
low n cladding 5 can adhere to the waveguide 10 surface directly or
the dielectric layer 3. The primer can be spin coated onto the
desired surface or alternatively both the low n cladding 5 and the
primer can be printed onto the desired surface by a multilayer
print process where the low n cladding 5 is first supplied to the
print matrix whereafter surplus low n cladding 5 is removed and the
primer is then supplied to the low n cladding 5 whereafter the
matrix apply both primer and the low n cladding 5 to the surface
desired. Curing is preferably UV curing and the curing is
preferably done while the matrix is still in contact with the
desired surface. The described process can be enhanced with a
material that allows safe removal of the matrix and yet a material
that is better adapted to form the required nanoengineered
structures. In this case the print process will deliver a
multilayered print to the desired surface and the low n cladding 5
will exhibit its desired property from inside a sandwich
construction. The advantage of this approach is that each of the
layers in the sandwich is applied in the same print process and
each enhances performance by having properties designed for the
specific task.
[0223] The print matrices employed in the process can be a roll
which enables fast roll to roll manufacture. For fast roll to roll
manufacture it is important that the curing is equally fast and
accurate which entails that the curing should take place while the
print is confined within the print matrices.
[0224] The nanoengineered surface can be absorptive or diffuse
reflective according to the purpose of the electrowetting unit. For
illumination purposes it will usually be valuable to reflect
impinging photons while it for display applications can be more
valuable to be absorptive to enhance blacklevel.
[0225] In order to secure the distribution of less polar liquid 35
and dipolar liquid 30 inside the electrowetting unit, the top
surface 1 underside has an affinity for the 30 less polar
liquid.
[0226] The 30 less polar liquid can be engineered to become more
electric conductive by additives such as carbon nanotubes or
metallic ions. With conductive 30 less polar liquid the electric
field strength can be increased and the voltage required can be
lowered.
[0227] As there is oil at the lower side of the top surface 1 the
upper electrode 25 can be in direct galvanic contact with the oil
with little risk of exposure to oxygen. This protected position for
the upper electrode 25 can be utilized to place an active matrix on
the underside of the top surface 1. An active matrix can have a
print that could be oil based that repel dipolar liquid 30 and
enhances affinity for less polar liquid 35 and form an oxygen
barrier and act as an insulator. The insulating print could in
conjunction with a conductive print in patterns define where the
electric interaction between the less polar liquid 35 with
conductive properties takes place. Active matrix based on polymorph
silicon or crystalline silicon is able to withstand exposure to
oxygen while cheaper printed electronics active matrix is made from
materials that are unable to withstand exposure to oxygen for a
prolonged period without degradation. The print and oil layer that
protect the active matrix can prolong the lifetime before a printed
active matrix succumb to the oxygen exposure. Radiation from the
waveguide 10 exit through the top surface 1 and if there is an
active matrix situated at the lower top surface 1 then it should be
partially transmissive. Transistors and other elements in circuitry
needed for active matrix are available in transparent version.
[0228] An entire electrowetting unit based on printed electronics
is therefore feasible.
[0229] Electric control of the lightgates is done by employing a
potential difference which change the aperture 96 areas from an
affinity for less polar liquid 35 to an affinity for dipolar liquid
30 which shut the lightgate due to the low n property of the
dipolar liquid 30 and by aligning the potential which will allow
the aperture 96 area to exhibit its affinity for less polar liquid
35 and thus create index match between the waveguide 10 and the
less polar liquid 35.
[0230] In an embodiment with active matrix as well as with active
rows or columns there will be crosstalk but it will be limited as a
result of the low conductivity of the less polar liquid 35 and the
mush thinner and longer connection in the vertical plane relative
to the more direct connection through the inverted droplet to the
aperture 96 area. The crosstalk between a shut lightgate to an
adjacent open lightgate will be below a level where the aperture 96
area switch affinity to dipolar liquid 30 which ensures that even
though there will be crosstalk the crosstalk is insufficient to
cause problems with controlling open and shut states.
* * * * *