U.S. patent application number 12/789412 was filed with the patent office on 2010-12-02 for illumination devices and methods of fabrication thereof.
This patent application is currently assigned to QUALCOMM MEMS Technologies, Inc.. Invention is credited to Brian W. Arbuckle, Ion Bita, Clayton Ka Tsun Chan, SuryaPrakash Ganti, Sapna Patel.
Application Number | 20100302218 12/789412 |
Document ID | / |
Family ID | 42341633 |
Filed Date | 2010-12-02 |
United States Patent
Application |
20100302218 |
Kind Code |
A1 |
Bita; Ion ; et al. |
December 2, 2010 |
ILLUMINATION DEVICES AND METHODS OF FABRICATION THEREOF
Abstract
Illumination devices and methods of making same are disclosed.
In one embodiment, a display device includes a light modulating
array and a light guide configured to receive light into at least
one edge of the light guide. The display device can also include a
light turning layer disposed such that the light guide is at least
partially between the turning layer and the array. The turning
layer can comprise at least one light turning feature having at
least one curved turning surface.
Inventors: |
Bita; Ion; (San Jose,
CA) ; Patel; Sapna; (San Jose, CA) ; Chan;
Clayton Ka Tsun; (San Jose, CA) ; Ganti;
SuryaPrakash; (San Jose, CA) ; Arbuckle; Brian
W.; (San Jose, CA) |
Correspondence
Address: |
KNOBBE, MARTENS, OLSON & BEAR, LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
QUALCOMM MEMS Technologies,
Inc.
San Diego
CA
|
Family ID: |
42341633 |
Appl. No.: |
12/789412 |
Filed: |
May 27, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61182594 |
May 29, 2009 |
|
|
|
61292783 |
Jan 6, 2010 |
|
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Current U.S.
Class: |
345/204 ; 216/24;
362/607; 362/611 |
Current CPC
Class: |
G02B 6/0036 20130101;
G02B 26/001 20130101; G02F 1/133616 20210101; G02B 6/0065
20130101 |
Class at
Publication: |
345/204 ;
362/611; 362/607; 216/24 |
International
Class: |
G09G 5/00 20060101
G09G005/00; F21V 7/04 20060101 F21V007/04; B05D 5/06 20060101
B05D005/06 |
Claims
1. An illumination apparatus comprising: a light source; a light
guide having a generally planar first surface, a generally planar
second surface opposite the first surface, a first end and a second
end, and a length defined between the first end and the second end,
the light guide having an x-axis extending parallel to the first
surface between the first end and second end, a z-axis extending
normal to the first surface and the second surface, and a y-axis
extending normal to the x-axis and the z-axis, wherein the light
guide is positioned to receive light from the light source into the
light guide first end, and wherein light received from the light
source propagates through the light guide towards the second end;
and a plurality of light turning features disposed on the first
surface and protruding from the first surface into the light guide
towards the second surface, each light turning feature having at
least one curvilinear turning edge disposed on a plane that is
parallel with a plane defined by the x-axis and the z-axis, the at
least one turning edge configured to receive at least a portion of
the light which is propagating towards the second end of the light
guide and reflect at least a portion of the received light out of
the second surface of the light guide.
2. The illumination apparatus of claim 1, wherein the turning edge
of the light turning feature is configured such that the portion of
light reflected by the at least one curvilinear turning edge forms
an emission cone of light that has an angular width.
3. The illumination apparatus of claim 2, wherein the at least one
turning edge is configured to focus light that is propagating in
the light guide and incident on the at least one turning edge.
4. The illumination apparatus of claim 2, wherein the at least one
turning edge is configured to disperse light that is propagating in
the light guide and incident on the at least one turning edge.
5. The illumination apparatus of claim 1, wherein the at least one
turning edge has a convex shaped profile on the x-axis and the
z-axis defined plane on which it is disposed.
6. The illumination apparatus of claim 1, wherein the at least one
turning has a convex shaped profile on the x-axis and the z-axis
defined plane on which it is disposed.
7. The illumination apparatus of claim 1, wherein the surface of at
least one turning feature is frustum shaped.
8. The illumination apparatus of claim 7, wherein the frustum
comprises concave sides.
9. The illumination apparatus of claim 7, wherein the frustum
comprises convex sides.
10. A display device comprising: an array of light modulating
elements; a light guide disposed over the array, the light guide
having at least one edge configured to receive light into the light
guide; and a turning layer disposed such that the light guide is at
least partially between the turning layer and the array, the
turning layer having a first surface and a second surface opposite
the first surface, wherein the second surface is disposed between
the first surface and the array, wherein the turning layer further
comprises a plurality of light turning features disposed on the
first surface and protruding from the first surface into the
turning layer towards the second surface, each light turning
feature being configured to receive at least a portion of light
which is propagating through the turning layer and reflect at least
a portion of the received light toward the array, each light
turning feature having a light turning surface configured to focus
or disperse the portion of light received and reflected toward the
array.
11. The device of claim 10, wherein the curved light turning
surface of each light turning feature extends from the first
surface into the light guide and comprises a depression formed in
the first surface.
12. The device of claim 11, wherein the curved light turning
surface is frustum shaped.
13. The device of claim 11, wherein each light turning feature has
at least one sidewall and wherein at least a portion of the
sidewall is curved.
14. The device of claim 13, wherein the curved portion of the
sidewall is convex.
15. The device of claim 13, wherein the curved portion of the
sidewall is concave.
16. The device of claim 13, wherein each turning feature comprises
an optical mask disposed on at least a portion of the sidewall.
17. The device of claim 16, wherein the optical mask comprises a
first reflective layer, a second layer, and a third partially
reflective layer disposed respectively on the sidewall, wherein the
first layer is configured to receive light propagating within the
turning layer and reflect at least a portion of the received light
toward the array.
18. The device of claim 17, wherein the first, second, and third
layers are configured to absorb a portion of light incident on the
turning layer.
19. The device of claim 10, further comprising: a processor that is
configured to communicate with the array of light modulating
elements, the processor being configured to process image data; and
a memory device that is configured to communicate with the
processor.
20. The device of claim 19, further comprising a driver circuit
configured to send at least one signal to the array of light
modulating elements.
21. The device of claim 20, further comprising a controller
configured to send at least a portion of the image data to the
driver circuit.
22. The device of claim 19, further comprising an image source
module configured to send the image data to the processor.
23. The device of claim 22, wherein said image source module
comprises at least one of a receiver, transceiver, and
transmitter.
24. The device of claim 19, further comprising an input device
configured to receive input data and to communicate the input data
to the processor.
25. A method of making a light guide including turning features
that are configured to focus or disperse light incident thereon,
the method comprising: providing a substrate; depositing a layer of
material over at least a portion of the substrate; coating the
material with a layer of photoresist; exposing the photoresist to
leave a pattern of portions of the photoresist on the layer of
material; and etching the layer of material to produce one or more
depressions having curved sidewalls.
26. A method of making a turning film including turning features
that are configured to focus or disperse light incident thereon,
the method comprising: providing a substrate; depositing a layer of
material over at least a portion of the substrate; coating the
material with a layer of photoresist; exposing the photoresist to
leave portions of the photoresist on the layer of material; etching
the layer of material to produce one or more depressions having
curved sidewalls; removing the photoresist; electroplating the
surface of the layer of material and the substrate to produce a
surface relief; and using the surface relief to mold a turning
film.
27. The method of claim 26, wherein the sidewalls are convex.
28. The method of claim 26, wherein the sidewalls are concave.
29. The method of claim 26, wherein the layer of material and
substrate form at least one frustum shaped turning feature.
30. The method of claim 29, wherein the frustum shaped turning
feature comprises sidewalls that are convex.
31. The method of claim 29, wherein the frustum shaped turning
feature comprises sidewalls that are concave.
32. A display device comprising: means for modulating light; means
for guiding light disposed over the modulating means, the light
guiding means being configured to receive light; and means for
turning light disposed such that the light guiding means is at
least partially between the light turning means and the modulating
means, wherein the turning means comprises a plurality of light
turning features configured to receive at least a portion of light
received by the light guiding means and reflect at least a portion
of the received light toward the modulating means, wherein each
light turning feature is configured to focus or disperse the
portion of light received and reflected toward the modulating
means, and wherein each light turning feature comprises a
depression formed in a surface of the light turning means.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/182,594 filed on May 29, 2009, titled
"ILLUMINATION DEVICES AND METHODS OF FABRICATION THEREOF," and U.S.
Provisional Application No. 61/292,783 filed on Jan. 6, 2010,
titled "ILLUMINATION DEVICES AND METHODS OF FABRICATION THEREOF,"
both of which are hereby expressly incorporated by reference in
their entireties.
BACKGROUND
[0002] 1. Field
[0003] The field of the invention relates to electromechanical
systems.
[0004] 2. Description of the Related Art
[0005] Electromechanical systems include devices having electrical
and mechanical elements, actuators, transducers, sensors, optical
components (e.g., mirrors), and electronics. Electromechanical
systems can be manufactured at a variety of scales including, but
not limited to, microscales and nanoscales. For example,
microelectromechanical systems (MEMS) devices can include
structures having sizes ranging from about a micron to hundreds of
microns or more. Nanoelectromechanical systems (NEMS) devices can
include structures having sizes smaller than a micron including,
for example, sizes smaller than several hundred nanometers.
Electromechanical elements may be created using deposition,
etching, lithography, and/or other micromachining processes that
etch away parts of substrates and/or deposited material layers or
that add layers to form electrical and electromechanical devices.
One type of electromechanical systems device is called an
interferometric modulator. As used herein, the term interferometric
modulator or interferometric light modulator refers to a device
that selectively absorbs and/or reflects light using the principles
of optical interference. In certain embodiments, an interferometric
modulator may comprise a pair of conductive plates, one or both of
which may be transparent and/or reflective in whole or part and
capable of relative motion upon application of an appropriate
electrical signal. In a particular embodiment, one plate may
comprise a stationary layer deposited on a substrate and the other
plate may comprise a metallic membrane separated from the
stationary layer by an air gap. As described herein in more detail,
the position of one plate in relation to another can change the
optical interference of light incident on the interferometric
modulator. Such devices have a wide range of applications, and it
would be beneficial in the art to utilize and/or modify the
characteristics of these types of devices so that their features
can be exploited in improving existing products and creating new
products that have not yet been developed.
SUMMARY
[0006] The system, method, and devices of the invention each have
several aspects, no single one of which is solely responsible for
its desirable attributes. Without limiting the scope of this
invention, its more prominent features will now be discussed
briefly. After considering this discussion, and particularly after
reading the section entitled "Detailed Description of Certain
Embodiments," one will understand how the features of this
invention provide advantages over other display devices.
[0007] Various embodiments described herein comprise an
illumination device including a substrate layer and a turning layer
including light turning features coated with reflective layers
configured to turn light propagating within the substrate toward a
display.
[0008] In one embodiment, an illumination apparatus comprises a
light source, a light guide having a generally planar first
surface, a generally planar second surface opposite the first
surface, a first end and a second end, and a length defined between
the first end and the second end, the light guide having an x-axis
extending generally parallel to the first surface between the first
end and second end, a z-axis extending generally normal to the
first surface and the second surface, and a y-axis extending
generally normal to the x-axis and the z-axis, wherein the light
guide is positioned to receive light from the light source into the
light guide first end, and wherein light received from the light
source propagates through the light guide towards the second end.
This embodiment, and certain other embodiments, can also include a
plurality of light turning features disposed on the first surface
and protruding from the first surface into the light guide towards
the second surface. Each light turning feature can have at least
one curvilinear turning edge disposed on a plane that is parallel
with a plane defined by the x-axis and the z-axis wherein the at
least one turning edge is configured to receive at least a portion
of the light which is propagating towards the second end of the
light guide and reflect at least a portion of the received light
out of the second surface of the light guide.
[0009] In one aspect, the portion of light reflected by the at
least one curvilinear turning edge forms an "emission cone" of
light that has an angular width. In another aspect, the at least
one turning edge is configured to focus or disperse light
propagating in the light guide incident on the turning surface. In
yet another aspect, the at least one turning edge has a convex or
concave shaped profile and x-axis and z-axis defined plane on which
it is disposed. In one aspect, the surface of at least turning
feature forms a frustum and the frustum can have sidewalls that are
concave and/or convex relative to the light guide.
[0010] In another embodiment, a display device comprises an array
of light modulating elements, a light guide disposed over the
array, the light guide having at least one edge configured to
receive light into the light guide, and a turning layer disposed
such that the light guide is at least partially between the turning
layer and the array. The turning layer can have a first surface and
a second surface opposite the first surface wherein the second
surface is disposed between the first surface and the array. The
turning lay can include a plurality of light turning features
disposed on the first surface and protruding from the first surface
into the turning layer towards the second surface, each light
turning feature being configured to receive at least a portion of
light which is propagating through the turning layer and reflect at
least a portion of the receive light toward the array. Each light
turning feature can have a light turning surface configured to
focus or disperse the portion of light received and reflected
toward the array.
[0011] In one aspect, the curved light turning surface of each
light turning feature extends from the first surface into the light
guide and comprises a depression formed in the first surface. In
another aspect, the curved light turning surface can be frustum
shaped. In yet another aspect, each light turning feature has at
least one sidewall wherein at least a portion of the sidewall is
curved. In one aspect, the curved portion of the sidewall is
concave or convex. In one aspect, each turning feature comprises an
optical mask disposed on at least a portion of the sidewall and the
optical mask can include a first reflective layer, a second layer,
and a third partially reflective layer disposed respectively on the
tapered sidewall, wherein the first layer is configured to receive
light propagating within the turning layer and reflect at least a
portion of the received light toward the array. In one aspect, the
first, second, and third layers can be configured to absorb a
portion of light incident on the turning layer.
[0012] In one aspect, the device further comprises a processor that
is configured to communicate with the array of light modulating
elements, the processor being configured to process image data, and
a memory device that is configured to communicate with the
processor. In one aspect, the device further comprises a driver
circuit configured to send at least one signal to the array of
light modulating elements and can also include a controller
configured to send at least a portion of the image data to the
driver circuit. In another aspect, the device further comprises an
image source module configured to send image data to the processor.
In one aspect, the image source module comprises at least one of a
receiver, transceiver, and transmitter. In one aspect, the device
further comprises an input device configured to receive input data
and to communicate the input data to the processor.
[0013] In another embodiment, a method of making a light guide
including turning features that are configured to focus or disperse
light incident thereon comprises providing a substrate, depositing
a layer of material over at least a portion of the substrate,
coating the material with a layer of photoresist, exposing the
photoresist to leave portions of the photoresist layer on the
material, and etching the layer of material to produce one or more
depressions having curved sidewalls. In one aspect, the layer of
material comprises silicon oxy-nitride.
[0014] In another embodiment, a method of making a turning film
including turning features that are configured to focus or disperse
light incident thereon comprises providing a substrate, depositing
a layer of material over at least a portion of the substrate,
coating the material with a layer of photoresist, exposing and
processing the photoresist to leave portions of the photoresist on
the layer of material, etching the layer of material to produce one
or more depressions having curved sidewalls, removing the
photoresist, electroplating the surface of the layer of material
and the substrate to produce a surface relief, and using the
surface relief to mold a turning film. In one aspect, the sidewalls
are convex or concave. In another aspect, the layer of material and
substrate form at least one frustum shaped turning feature and the
frustum shaped turning feature can have sidewalls that are convex
or concave.
[0015] In another embodiment, a display device includes means for
modulating light, means for guiding light disposed over the
modulating means, the light guiding means being configured to
receive light, and means for turning light disposed such that the
light guiding means is at least partially between the light turning
means and the modulating means. The turning means can include a
plurality of light turning features configured to receive at least
a portion of light received by the light guiding means and reflect
at least a portion of the received light toward the modulating
means, wherein each light turning feature is configured to focus or
disperse the portion of light received and reflected toward the
modulating means. Each light turning feature can comprise a
depression formed in a surface of the light turning means.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is an isometric view depicting a portion of one
embodiment of an interferometric modulator display in which a
movable reflective layer of a first interferometric modulator is in
a relaxed position and a movable reflective layer of a second
interferometric modulator is in an actuated position.
[0017] FIG. 2 is a system block diagram illustrating one embodiment
of an electronic device incorporating a 3.times.3 interferometric
modulator display.
[0018] FIG. 3 is a diagram of movable mirror position versus
applied voltage for one exemplary embodiment of an interferometric
modulator of FIG. 1.
[0019] FIG. 4 is an illustration of a set of row and column
voltages that may be used to drive an interferometric modulator
display.
[0020] FIGS. 5A and 5B illustrate one exemplary timing diagram for
row and column signals that may be used to write a frame of display
data to the 3.times.3 interferometric modulator display of FIG.
2.
[0021] FIGS. 6A and 6B are system block diagrams illustrating an
embodiment of a visual display device comprising a plurality of
interferometric modulators.
[0022] FIG. 7A is a cross-section of the device of FIG. 1.
[0023] FIG. 7B is a cross-section of an alternative embodiment of
an interferometric modulator.
[0024] FIG. 7C is a cross-section of another alternative embodiment
of an interferometric modulator.
[0025] FIG. 7D is a cross-section of yet another alternative
embodiment of an interferometric modulator.
[0026] FIG. 7E is a cross-section of an additional alternative
embodiment of an interferometric modulator.
[0027] FIG. 8 is a cross-section of an embodiment of a display
device having an illumination device and a reflective display.
[0028] FIG. 9A is a top plan view of an embodiment of a display
device having turning features disposed in a uniform pattern on a
turning film.
[0029] FIG. 9B is a top plan view of an embodiment of a display
device having turning features disposed in a non-uniform pattern on
a turning film.
[0030] FIG. 9C is a cross-section of an embodiment of an
illumination device having a turning film and a substrate.
[0031] FIG. 9D illustrates certain dimensions of one embodiment of
a turning feature rotationally.
[0032] FIG. 10 is a cross-section of an embodiment of an
illumination device illustrating several embodiments of light
turning features.
[0033] FIG. 11 is a cross-section of an embodiment of an
illumination device including a substrate with light turning
features.
[0034] FIG. 12 is a cross-section of an embodiment of an
illumination device having two turning films.
[0035] FIG. 13 is a cross-section of an embodiment of an
illumination device having two turning films, each turning film
having light turning features, where at least some of the light
turning features in each turning film are disposed vertically
offset from those in the other turning film.
[0036] FIG. 14 is a cross-section of an embodiment of an
illumination device having light turning features configured in the
shape of a truncated cone and a lens.
[0037] FIG. 15 is a cross-section of an embodiment of another
illumination device illustrating a turning film and a light guide
with curved edges.
[0038] FIG. 16 is a cross-section of an illumination device
illustrating an embodiment that includes a light source providing
light through an angled edge of a turning film and/or a light
guide.
[0039] FIG. 17A is a cross-section of an embodiment of an
illumination device that depicts light turning features having
multi-coated edges.
[0040] FIG. 17B is a top plan view of an embodiment of an
illumination device.
[0041] FIG. 18 is a cross-section of an embodiment of an
illumination device illustrating several examples of light turning
features with multi-coated edges.
[0042] FIG. 19A is a cross-section of a turning film during a step
of one example of a process for forming interferometric stacks on a
light turning feature.
[0043] FIG. 19B is a cross-section of the turning film of FIG. 19A
in an intermediate process step.
[0044] FIG. 19C is a cross-section of an embodiment of the turning
film of FIG. 19C resulting from further processing.
[0045] FIG. 19D is a block diagram schematically illustrating one
embodiment of a method of making the turning film of FIG. 19C.
[0046] FIGS. 20A-20E are schematic cross-sectional views
illustrating steps in a process of manufacturing an illumination
device.
[0047] FIG. 20F is a block diagram schematically illustrating one
embodiment of a method of making the illumination device of FIG.
20E.
[0048] FIGS. 21A-21H are schematic cross-sectional views
illustrating steps in a process of manufacturing an illumination
device.
[0049] FIG. 21I is a block diagram schematically illustrating one
embodiment of a method of making the illumination device of FIG.
21H.
[0050] FIG. 22A-22E are schematic cross-sectional views
illustrating steps in a process of manufacturing an illumination
device.
[0051] FIG. 22F is a block diagram schematically illustrating one
embodiment of a method of making the illumination device of FIG.
22E.
[0052] FIG. 23A-23J are schematic cross-sectional views
illustrating steps in a process of manufacturing an illumination
device.
[0053] FIG. 23K is a block diagram schematically illustrating one
embodiment of a method of making the illumination device of FIG.
23J.
[0054] FIG. 24A-24F are schematic cross-sectional views
illustrating steps in a process of manufacturing an illumination
device.
[0055] FIG. 24G is a block diagram schematically illustrating one
embodiment of a method of making the illumination device of FIG.
24F.
[0056] FIG. 25A-25G are schematic cross-sectional views
illustrating steps in a process of manufacturing an illumination
device.
[0057] FIG. 25H is a block diagram schematically illustrating one
embodiment of a method of making the illumination device of FIG.
25G.
[0058] FIG. 26A-26F are schematic cross-sectional views
illustrating steps in a process of manufacturing an illumination
device.
[0059] FIG. 26G is a block diagram schematically illustrating one
embodiment of a method of making the illumination device of FIG.
26F.
[0060] FIG. 27A-27C are schematic cross-sectional views
illustrating steps in a process of manufacturing an illumination
device.
[0061] FIG. 27D is a block diagram schematically illustrating one
embodiment of a method of making the illumination device of FIG.
27C.
[0062] FIG. 27E is a block diagram schematically illustrating one
embodiment of a method of making the illumination device of FIG.
27C.
[0063] FIG. 28 is a cross-section of an embodiment of a turning
film having tapered walls.
[0064] FIG. 29A is a schematic of a cross-section of an embodiment
of a turning film having a polygonal turning feature.
[0065] FIG. 29B is a schematic of a cross-section of an embodiment
of a turning film having a concave curvilinear turning feature.
[0066] FIG. 29C is a schematic of a cross-section of an embodiment
of a turning film having a convex curvilinear turning feature.
[0067] FIG. 29D is a schematic of a cross-section of an embodiment
of a turning film having a frustum shaped turning feature with
concave sidewalls.
[0068] FIG. 29E is a schematic of a cross-section of an embodiment
of a turning film having a frustum shaped turning feature with
convex sidewalls.
[0069] FIG. 29F is a perspective view of the turning feature of
FIG. 29D.
[0070] FIG. 29G is a perspective view of the turning feature of
FIG. 29F.
[0071] FIG. 30A is a schematic of a cross-section of an embodiment
of a turning film having a concave curvilinear turning feature with
multi-coated edges.
[0072] FIG. 30B is a schematic of a cross-section of an embodiment
of a turning film having a convex curvilinear turning feature with
multi-coated edges.
[0073] FIG. 30C is a schematic of a cross-section of an embodiment
of a turning film having a frustum shaped turning feature with
concave sidewalls and multi-coated edges.
[0074] FIG. 30D is a schematic of a cross-section of an embodiment
of a turning film having a frustum shaped turning feature with
convex sidewalls and multi-coated edges.
[0075] FIGS. 31A-31E are schematics of cross-sectional views
illustrating steps in a process of manufacturing a turning film
having convex turning features.
[0076] FIGS. 32A-32E are schematics of cross-sectional views
illustrating steps in a process of manufacturing a turning film
having a concave turning feature.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0077] The following detailed description is directed to certain
specific embodiments. However, the teachings herein can be applied
in a multitude of different ways. In this description, reference is
made to the drawings wherein like parts are generally designated
with like numerals throughout. In certain illustrated embodiments,
like numerals are used to designate generally corresponding parts;
however, it will be understood that such designated parts can vary
from embodiment to embodiment, for example as described herein.
[0078] The embodiments may be implemented in any device that is
configured to display an image, whether in motion (e.g., video) or
stationary (e.g., still image), and whether textual or pictorial.
More particularly, it is contemplated that the embodiments may be
implemented in or associated with a variety of electronic devices
such as, but not limited to, mobile telephones, wireless devices,
personal data assistants (PDAs), hand-held or portable computers,
GPS receivers/navigators, cameras, MP3 players, camcorders, game
consoles, wrist watches, clocks, calculators, television monitors,
flat panel displays, computer monitors, auto displays (e.g.,
odometer display, etc.), cockpit controls and/or displays, display
of camera views (e.g., display of a rear view camera in a vehicle),
electronic photographs, electronic billboards or signs, projectors,
architectural structures, packaging, and aesthetic structures
(e.g., display of images on a piece of jewelry). MEMS devices of
similar structure to those described herein can also be used in
non-display applications such as in electronic switching
devices.
[0079] Illumination devices can be used to provide light for
reflective displays when ambient light is insufficient. In some
embodiments, an illumination device comprises a light source and a
light guide that receives the light from the light source. Often
the light source may be positioned or offset relative to the
display, and in such a position it may not provide sufficient or
uniform light directly to the reflective display. Accordingly, an
illumination device can also include light turning features that
re-direct light from the light source towards the display, and such
turning features can be included in a turning film positioned on
the light guide. In some embodiments, turning features have
reflective coatings configured to (better) reflect light
propagating within the light guide and/or turning film towards the
reflective display. The reflective coatings could appear shiny or
bright, but they can be masked to a viewer by forming a dark
coating (e.g., black mask) over the reflective coating to absorb
light such that the turning features appear dark or black,
resulting in improving contrast of the display. The black mask can
include the reflective layer, and an absorber layer, and be
configured as a "static" interferometric modulator configured to
appear dark or black. The light guide and the turning film may be
made from an inorganic material. To facilitate light propagating
between the turning film and the light guide, the turning film may
have an index of refraction that matched to the light guide.
Embodiments disclosed herein relate to different configurations of
illumination devices that include one or more reflective coatings
on turning features. Additional embodiments disclosed herein relate
to processes of forming illumination devices that include an
inorganic light guide and/or inorganic turning film.
[0080] One interferometric modulator display embodiment comprising
an interferometric MEMS display element is illustrated in FIG. 1.
In these devices, the pixels are in either a bright or dark state.
In the bright ("relaxed" or "open") state, the display element
reflects a large portion of incident visible light to a user. When
in the dark ("actuated" or "closed") state, the display element
reflects little incident visible light to the user. Depending on
the embodiment, the light reflectance properties of the "on" and
"off" states may be reversed. MEMS pixels can be configured to
reflect predominantly at selected colors, allowing for a color
display in addition to black and white.
[0081] FIG. 1 is an isometric view depicting two adjacent pixels in
a series of pixels of a visual display, wherein each pixel
comprises a MEMS interferometric modulator. In some embodiments, an
interferometric modulator display comprises a row/column array of
these interferometric modulators. Each interferometric modulator
includes a pair of reflective layers positioned at a variable and
controllable distance from each other to form a resonant optical
gap with at least one variable dimension. In one embodiment, one of
the reflective layers may be moved between two positions. In the
first position, referred to herein as the relaxed position, the
movable reflective layer is positioned at a relatively large
distance from a fixed partially reflective layer. In the second
position, referred to herein as the actuated position, the movable
reflective layer is positioned more closely adjacent to the
partially reflective layer. Incident light that reflects from the
two layers interferes constructively or destructively depending on
the position of the movable reflective layer, producing either an
overall reflective or non-reflective state for each pixel.
[0082] The depicted portion of the pixel array in FIG. 1 includes
two adjacent interferometric modulators 12a and 12b. In the
interferometric modulator 12a on the left, a movable reflective
layer 14a is illustrated in a relaxed position at a predetermined
distance from an optical stack 16a, which includes a partially
reflective layer. In the interferometric modulator 12b on the
right, the movable reflective layer 14b is illustrated in an
actuated position adjacent to the optical stack 16b.
[0083] The optical stacks 16a and 16b (collectively referred to as
optical stack 16), as referenced herein, typically comprise several
fused layers, which can include an electrode layer, such as indium
tin oxide (ITO), a partially reflective layer, such as chromium,
and a transparent dielectric. The optical stack 16 is thus
electrically conductive, partially transparent and partially
reflective, and may be fabricated, for example, by depositing one
or more of the above layers onto a transparent substrate 20. The
partially reflective layer can be formed from a variety of
materials that are partially reflective such as various metals,
semiconductors, and dielectrics. The partially reflective layer can
be formed of one or more layers of materials, and each of the
layers can be formed of a single material or a combination of
materials.
[0084] In some embodiments, the layers of the optical stack 16 are
patterned into parallel strips, and may form row electrodes in a
display device as described further below. The movable reflective
layers 14a, 14b may be formed as a series of parallel strips of a
deposited metal layer or layers (orthogonal to the row electrodes
of 16a, 16b) to form columns deposited on top of posts 18 and an
intervening sacrificial material deposited between the posts 18.
When the sacrificial material is etched away, the movable
reflective layers 14a, 14b are separated from the optical stacks
16a, 16b by a defined gap 19. A highly conductive and reflective
material such as aluminum may be used for the reflective layers 14,
and these strips may form column electrodes in a display device.
Note that FIG. 1 may not be to scale. In some embodiments, the
spacing between posts 18 may be on the order of 10-100 um, while
the gap 19 may be on the order of <1000 Angstroms.
[0085] With no applied voltage, the gap 19 remains between the
movable reflective layer 14a and optical stack 16a, with the
movable reflective layer 14a in a mechanically relaxed state, as
illustrated by the pixel 12a in FIG. 1. However, when a potential
(voltage) difference is applied to a selected row and column, the
capacitor formed at the intersection of the row and column
electrodes at the corresponding pixel becomes charged, and
electrostatic forces pull the electrodes together. If the voltage
is high enough, the movable reflective layer 14 is deformed and is
forced against the optical stack 16. A dielectric layer (not
illustrated in this Figure) within the optical stack 16 may prevent
shorting and control the separation distance between layers 14 and
16, as illustrated by actuated pixel 12b on the right in FIG. 1.
The behavior is the same regardless of the polarity of the applied
potential difference.
[0086] FIGS. 2 through 5 illustrate one exemplary process and
system for using an array of interferometric modulators in a
display application.
[0087] FIG. 2 is a system block diagram illustrating one embodiment
of an electronic device that may incorporate interferometric
modulators. The electronic device includes a processor 21 which may
be any general purpose single- or multi-chip microprocessor such as
an ARM.RTM., Pentium.RTM., 8051, MIPS.RTM., Power PC.RTM., or
ALPHA.RTM., or any special purpose microprocessor such as a digital
signal processor, microcontroller, or a programmable gate array. As
is conventional in the art, the processor 21 may be configured to
execute one or more software modules. In addition to executing an
operating system, the processor may be configured to execute one or
more software applications, including a web browser, a telephone
application, an email program, or any other software
application.
[0088] In one embodiment, the processor 21 is also configured to
communicate with an array driver 22. In one embodiment, the array
driver 22 includes a row driver circuit 24 and a column driver
circuit 26 that provide signals to a display array or panel 30. The
cross-section of the array illustrated in FIG. 1 is shown by the
lines 1-1 in FIG. 2. Note that although FIG. 2 illustrates a
3.times.3 array of interferometric modulators for the sake of
clarity, the display array 30 may contain a very large number of
interferometric modulators, and may have a different number of
interferometric modulators in rows than in columns (e.g., 300
pixels per row by 190 pixels per column).
[0089] FIG. 3 is a diagram of movable mirror position versus
applied voltage for one exemplary embodiment of an interferometric
modulator of FIG. 1. For MEMS interferometric modulators, the
row/column actuation protocol may take advantage of a hysteresis
property of these devices as illustrated in FIG. 3. An
interferometric modulator may require, for example, a 10 volt
potential difference to cause a movable layer to deform from the
relaxed state to the actuated state. However, when the voltage is
reduced from that value, the movable layer maintains its state as
the voltage drops back below 10 volts. In the exemplary embodiment
of FIG. 3, the movable layer does not relax completely until the
voltage drops below 2 volts. There is thus a range of voltage,
about 3 to 7 V in the example illustrated in FIG. 3, where there
exists a window of applied voltage within which the device is
stable in either the relaxed or actuated state. This is referred to
herein as the "hysteresis window" or "stability window." For a
display array having the hysteresis characteristics of FIG. 3, the
row/column actuation protocol can be designed such that during row
strobing, pixels in the strobed row that are to be actuated are
exposed to a voltage difference of about 10 volts, and pixels that
are to be relaxed are exposed to a voltage difference of close to
zero volts. After the strobe, the pixels are exposed to a steady
state or bias voltage difference of about 5 volts such that they
remain in whatever state the row strobe put them in. After being
written, each pixel sees a potential difference within the
"stability window" of 3-7 volts in this example. This feature makes
the pixel design illustrated in FIG. 1 stable under the same
applied voltage conditions in either an actuated or relaxed
pre-existing state. Since each pixel of the interferometric
modulator, whether in the actuated or relaxed state, is essentially
a capacitor formed by the fixed and moving reflective layers, this
stable state can be held at a voltage within the hysteresis window
with almost no power dissipation. Essentially no current flows into
the pixel if the applied potential is fixed.
[0090] As described further below, in typical applications, a frame
of an image may be created by sending a set of data signals (each
having a certain voltage level) across the set of column electrodes
in accordance with the desired set of actuated pixels in the first
row. A row pulse is then applied to a first row electrode,
actuating the pixels corresponding to the set of data signals. The
set of data signals is then changed to correspond to the desired
set of actuated pixels in a second row. A pulse is then applied to
the second row electrode, actuating the appropriate pixels in the
second row in accordance with the data signals. The first row of
pixels are unaffected by the second row pulse, and remain in the
state they were set to during the first row pulse. This may be
repeated for the entire series of rows in a sequential fashion to
produce the frame. Generally, the frames are refreshed and/or
updated with new image data by continually repeating this process
at some desired number of frames per second. A wide variety of
protocols for driving row and column electrodes of pixel arrays to
produce image frames may be used.
[0091] FIGS. 4 and 5 illustrate one possible actuation protocol for
creating a display frame on the 3.times.3 array of FIG. 2. FIG. 4
illustrates a possible set of column and row voltage levels that
may be used for pixels exhibiting the hysteresis curves of FIG. 3.
In the FIG. 4 embodiment, actuating a pixel involves setting the
appropriate column to -V.sub.bias, and the appropriate row to
+.DELTA.V, which may correspond to -5 volts and +5 volts
respectively Relaxing the pixel is accomplished by setting the
appropriate column to +V.sub.bias, and the appropriate row to the
same +.DELTA.V, producing a zero volt potential difference across
the pixel. In those rows where the row voltage is held at zero
volts, the pixels are stable in whatever state they were originally
in, regardless of whether the column is at +V.sub.bias, or
-V.sub.bias. As is also illustrated in FIG. 4, voltages of opposite
polarity than those described above can be used, e.g., actuating a
pixel can involve setting the appropriate column to +V.sub.bias,
and the appropriate row to -.DELTA.V. In this embodiment, releasing
the pixel is accomplished by setting the appropriate column to
-V.sub.bias, and the appropriate row to the same -.DELTA.V,
producing a zero volt potential difference across the pixel.
[0092] FIG. 5B is a timing diagram showing a series of row and
column signals applied to the 3.times.3 array of FIG. 2 which will
result in the display arrangement illustrated in FIG. 5A, where
actuated pixels are non-reflective. Prior to writing the frame
illustrated in FIG. 5A, the pixels can be in any state, and in this
example, all the rows are initially at 0 volts, and all the columns
are at +5 volts. With these applied voltages, all pixels are stable
in their existing actuated or relaxed states.
[0093] In the FIG. 5A frame, pixels (1,1), (1,2), (2,2), (3,2) and
(3,3) are actuated. To accomplish this, during a "line time" for
row 1, columns 1 and 2 are set to -5 volts, and column 3 is set to
+5 volts. This does not change the state of any pixels, because all
the pixels remain in the 3-7 volt stability window. Row 1 is then
strobed with a pulse that goes from 0, up to 5 volts, and back to
zero. This actuates the (1,1) and (1,2) pixels and relaxes the
(1,3) pixel. No other pixels in the array are affected. To set row
2 as desired, column 2 is set to -5 volts, and columns 1 and 3 are
set to +5 volts. The same strobe applied to row 2 will then actuate
pixel (2,2) and relax pixels (2,1) and (2,3). Again, no other
pixels of the array are affected. Row 3 is similarly set by setting
columns 2 and 3 to -5 volts, and column 1 to +5 volts. The row 3
strobe sets the row 3 pixels as shown in FIG. 5A. After writing the
frame, the row potentials are zero, and the column potentials can
remain at either +5 or -5 volts, and the display is then stable in
the arrangement of FIG. 5A. The same procedure can be employed for
arrays of dozens or hundreds of rows and columns. The timing,
sequence, and levels of voltages used to perform row and column
actuation can be varied widely within the general principles
outlined above, and the above example is exemplary only, and any
actuation voltage method can be used with the systems and methods
described herein.
[0094] FIGS. 6A and 6B are system block diagrams illustrating an
embodiment of a display device 40. The display device 40 can be,
for example, a cellular or mobile telephone. However, the same
components of display device 40 or slight variations thereof are
also illustrative of various types of display devices such as
televisions and portable media players.
[0095] The display device 40 includes a housing 41, a display 30,
an antenna 43, a speaker 45, an input device 48, and a microphone
46. The housing 41 is generally formed from any of a variety of
manufacturing processes, including injection molding, and vacuum
forming. In addition, the housing 41 may be made from any of a
variety of materials, including but not limited to plastic, metal,
glass, rubber, and ceramic, or a combination thereof. In one
embodiment the housing 41 includes removable portions (not shown)
that may be interchanged with other removable portions of different
color, or containing different logos, pictures, or symbols.
[0096] The display 30 of exemplary display device 40 may be any of
a variety of displays, including a bi-stable display, as described
herein. In other embodiments, the display 30 includes a flat-panel
display, such as plasma, EL, OLED, STN LCD, or TFT LCD as described
above, or a non-flat-panel display, such as a CRT or other tube
device. However, for purposes of describing the present embodiment,
the display 30 includes an interferometric modulator display, as
described herein.
[0097] The components of one embodiment of exemplary display device
40 are schematically illustrated in FIG. 6B. The illustrated
exemplary display device 40 includes a housing 41 and can include
additional components at least partially enclosed therein. For
example, in one embodiment, the exemplary display device 40
includes a network interface 27 that includes an antenna 43 which
is coupled to a transceiver 47. The transceiver 47 is connected to
a processor 21, which is connected to conditioning hardware 52. The
conditioning hardware 52 may be configured to condition a signal
(e.g. filter a signal). The conditioning hardware 52 is connected
to a speaker 45 and a microphone 46. The processor 21 is also
connected to an input device 48 and a driver controller 29. The
driver controller 29 is coupled to a frame buffer 28, and to an
array driver 22, which in turn is coupled to a display array 30. A
power supply 50 provides power to all components as required by the
particular exemplary display device 40 design.
[0098] The network interface 27 includes the antenna 43 and the
transceiver 47 so that the exemplary display device 40 can
communicate with one ore more devices over a network. In one
embodiment the network interface 27 may also have some processing
capabilities to relieve requirements of the processor 21. The
antenna 43 is any antenna for transmitting and receiving signals.
In one embodiment, the antenna transmits and receives RF signals
according to the IEEE 802.11 standard, including IEEE 802.11(a),
(b), or (g). In another embodiment, the antenna transmits and
receives RF signals according to the BLUETOOTH standard. In the
case of a cellular telephone, the antenna is designed to receive
CDMA, GSM, AMPS, W-CDMA, or other known signals that are used to
communicate within a wireless cell phone network. The transceiver
47 pre-processes the signals received from the antenna 43 so that
they may be received by and further manipulated by the processor
21. The transceiver 47 also processes signals received from the
processor 21 so that they may be transmitted from the exemplary
display device 40 via the antenna 43.
[0099] In an alternative embodiment, the transceiver 47 can be
replaced by a receiver. In yet another alternative embodiment,
network interface 27 can be replaced by an image source, which can
store or generate image data to be sent to the processor 21. For
example, the image source can be a digital video disc (DVD) or a
hard-disc drive that contains image data, or a software module that
generates image data.
[0100] Processor 21 generally controls the overall operation of the
exemplary display device 40. The processor 21 receives data, such
as compressed image data from the network interface 27 or an image
source, and processes the data into raw image data or into a format
that is readily processed into raw image data. The processor 21
then sends the processed data to the driver controller 29 or to
frame buffer 28 for storage. Raw data typically refers to the
information that identifies the image characteristics at each
location within an image. For example, such image characteristics
can include color, saturation, and gray-scale level.
[0101] In one embodiment, the processor 21 includes a
microcontroller, CPU, or logic unit to control operation of the
exemplary display device 40. Conditioning hardware 52 generally
includes amplifiers and filters for transmitting signals to the
speaker 45, and for receiving signals from the microphone 46.
Conditioning hardware 52 may be discrete components within the
exemplary display device 40, or may be incorporated within the
processor 21 or other components.
[0102] The driver controller 29 takes the raw image data generated
by the processor 21 either directly from the processor 21 or from
the frame buffer 28 and reformats the raw image data appropriately
for high speed transmission to the array driver 22. Specifically,
the driver controller 29 reformats the raw image data into a data
flow having a raster-like format, such that it has a time order
suitable for scanning across the display array 30. Then the driver
controller 29 sends the formatted information to the array driver
22. Although a driver controller 29, such as a LCD controller, is
often associated with the system processor 21 as a stand-alone
Integrated Circuit (IC), such controllers may be implemented in
many ways. They may be embedded in the processor 21 as hardware,
embedded in the processor 21 as software, or fully integrated in
hardware with the array driver 22.
[0103] Typically, the array driver 22 receives the formatted
information from the driver controller 29 and reformats the video
data into a parallel set of waveforms that are applied many times
per second to the hundreds and sometimes thousands of leads coming
from the display's x-y matrix of pixels.
[0104] In one embodiment, the driver controller 29, array driver
22, and display array 30 are appropriate for any of the types of
displays described herein. For example, in one embodiment, driver
controller 29 is a conventional display controller or a bi-stable
display controller (e.g., an interferometric modulator controller).
In another embodiment, array driver 22 is a conventional driver or
a bi-stable display driver (e.g., an interferometric modulator
display). In one embodiment, a driver controller 29 is integrated
with the array driver 22. Such an embodiment is common in highly
integrated systems such as cellular phones, watches, and other
small area displays. In yet another embodiment, display array 30 is
a typical display array or a bi-stable display array (e.g., a
display including an array of interferometric modulators).
[0105] The input device 48 allows a user to control the operation
of the exemplary display device 40. In one embodiment, input device
48 includes a keypad, such as a QWERTY keyboard or a telephone
keypad, a button, a switch, a touch-sensitive screen, a pressure-
or heat-sensitive membrane. In one embodiment, the microphone 46 is
an input device for the exemplary display device 40. When the
microphone 46 is used to input data to the device, voice commands
may be provided by a user for controlling operations of the
exemplary display device 40.
[0106] Power supply 50 can include a variety of energy storage
devices as are well known in the art. For example, in one
embodiment, power supply 50 is a rechargeable battery, such as a
nickel-cadmium battery or a lithium ion battery. In another
embodiment, power supply 50 is a renewable energy source, a
capacitor, or a solar cell, including a plastic solar cell, and
solar-cell paint. In another embodiment, power supply 50 is
configured to receive power from a wall outlet.
[0107] In some implementations control programmability resides, as
described above, in a driver controller which can be located in
several places in the electronic display system. In some cases
control programmability resides in the array driver 22. The
above-described optimization may be implemented in any number of
hardware and/or software components and in various
configurations.
[0108] The details of the structure of interferometric modulators
that operate in accordance with the principles set forth above may
vary widely. For example, FIGS. 7A-7E illustrate five different
embodiments of the movable reflective layer 14 and its supporting
structures. FIG. 7A is a cross-section of the embodiment of FIG. 1,
where a strip of metal material 14 is deposited on orthogonally
extending supports 18. In FIG. 7B, the moveable reflective layer 14
of each interferometric modulator is square or rectangular in shape
and attached to supports at the corners only, on tethers 32. In
FIG. 7C, the moveable reflective layer 14 is square or rectangular
in shape and suspended from a deformable layer 34, which may
comprise a flexible metal. The deformable layer 34 connects,
directly or indirectly, to the substrate 20 around the perimeter of
the deformable layer 34. These connections are herein referred to
as support posts. The embodiment illustrated in FIG. 7D has support
post plugs 42 upon which the deformable layer 34 rests. The movable
reflective layer 14 remains suspended over the gap, as in FIGS.
7A-7C, but the deformable layer 34 does not form the support posts
by filling holes between the deformable layer 34 and the optical
stack 16. Rather, the support posts are formed of a planarization
material, which is used to form support post plugs 42. The
embodiment illustrated in FIG. 7E is based on the embodiment shown
in FIG. 7D, but may also be adapted to work with any of the
embodiments illustrated in FIGS. 7A-7C as well as additional
embodiments not shown. In the embodiment shown in FIG. 7E, an extra
layer of metal or other conductive material has been used to form a
bus structure 44. This allows signal routing along the back of the
interferometric modulators, eliminating a number of electrodes that
may otherwise have had to be formed on the substrate 20.
[0109] In embodiments such as those shown in FIG. 7, the
interferometric modulators function as direct-view devices, in
which images are viewed from the front side of the transparent
substrate 20, the side opposite to that upon which the modulator is
arranged. In these embodiments, the reflective layer 14 optically
shields the portions of the interferometric modulator on the side
of the reflective layer opposite the substrate 20, including the
deformable layer 34. This allows the shielded areas to be
configured and operated upon without negatively affecting the image
quality. For example, such shielding allows the bus structure 44 in
FIG. 7E, which provides the ability to separate the optical
properties of the modulator from the electromechanical properties
of the modulator, such as addressing and the movements that result
from that addressing. This separable modulator architecture allows
the structural design and materials used for the electromechanical
aspects and the optical aspects of the modulator to be selected and
to function independently of each other. Moreover, the embodiments
shown in FIGS. 7C-7E have additional benefits deriving from the
decoupling of the optical properties of the reflective layer 14
from its mechanical properties, which are carried out by the
deformable layer 34. This allows the structural design and
materials used for the reflective layer 14 to be optimized with
respect to the optical properties, and the structural design and
materials used for the deformable layer 34 to be optimized with
respect to desired mechanical properties.
[0110] Interferometric modulators are reflective elements that can
be configured to reflect ambient lighting in daylight or well-lit
environments to produce a display. When ambient light may not be
sufficient, a light source can provide the required illumination,
either directly or through a light guide that provides a
propagation path from the light source to the display elements. In
some embodiments, an illumination device provides light from a
light source to the display elements. The illumination device can
include a light guide and light turning features, which may be
disposed in or on a turning film disposed on the light guide. In
some embodiments the illumination device also includes a light
source. The light guide can be a planar optical device disposed
over and parallel to the display such that incident light passes
through the light guide to the display, and light reflected from
the display also passes through the light guide. In certain
embodiments, the light source includes an optical device (for
example, a light bar) that is configured to receive light from a
point source (e.g., a light emitting diode) and provides light as a
line source. Light entering the light bar may propagate along some
or all of the length of the bar and exit out of a surface or edge
of the light bar over a portion or all of the length of the light
bar. Light exiting the light bar may enter an edge of a light guide
and/or a turning film, and then propagate within the light guide
and/or turning film such that a portion of the light propagates in
a direction across at least a portion of the display at a low-graze
angle relative to the surface of the light guide aligned with the
display such that the light is reflected within the light guide by
total internal reflection ("TIR"). In various embodiments, turning
features in the light guide and/or turning film direct the light
towards the display elements at an angle sufficient so that at
least some of the light passes through the light guide to the
reflective display. In any of the embodiments described herein, the
turning features may include one or more coatings (or layers). The
coatings can be configured to increase reflectivity of a turning
feature and/or function as a black mask to improve contrast of the
display as seen by a viewer. In certain embodiments, the coatings
on the turning features may be configured as an interferometric
stack having a reflective layer that re-directs light propagating
within the light guide and/or turning film, a partially reflective
absorber layer disposed between the reflective layer and the
direction exposed to ambient light, and a layer disposed between
the reflective layer and the absorber layer which defines an
optical resonant cavity by its thickness.
[0111] FIG. 8 illustrates a cross-sectional view of one embodiment
of a display device 800 that includes an illumination device
configured to provide front light illumination to a reflective
display 807. The display device 800 includes a turning film 801
shown in FIG. 8 as forming a first side 800a of the device 800. The
turning, film 801 is disposed on a light guide 803. In this
embodiment, a reflective display 807 is disposed underneath the
light guide 803 and defines a second side 800b of the display
device 800. According to some embodiments, an optical isolation
layer 805 may optionally be disposed between the reflective display
807 and the light guide 803. A light source 809 may be disposed
near the light guide 803 and turning film 801 and configured to
input light into at least one edge or surface of either, or both,
the turning film 801 and the light guide 803, illustrated in FIG. 8
as providing light into both the turning film 810 and the light
guide 803. The light source 809 may comprise any suitable light
source, for example, an incandescent bulb, a light bar, a light
emitting diode ("LED"), a fluorescent lamp, an LED light bar, an
array of LEDs, and/or another light source.
[0112] In some embodiments, the reflective display 807 comprises a
plurality of reflective elements, for example, interferometric
modulators, MEMS devices, NEMS devices, reflective spatial light
modulators, electromechanical devices, liquid crystal structures,
and/or any other suitable reflective display. The reflective
elements may be configured in an array. In some embodiments, the
reflective display 807 includes a first planar side that is
configured to modulate light incident thereon and a second planar
side disposed opposite to the first planar side. The size of the
reflective display 807 can vary depending upon the application. For
example, in some embodiments, the reflective display 807 is sized
to fit within a notebook computer casing. In other embodiments, the
reflective display 807 is sized to fit within or form part of a
mobile phone or similar mobile device.
[0113] In some embodiments, the turning film 801 and light guide
803 can comprise any substantially optically transmissive material
that allows light to propagate along the length thereof. For
example, the turning film 801 and the light guide 803 may each
comprise one or more of the following materials: acrylics, acrylate
copolymers, UV-curable resins, polycarbonates, cycloolefin
polymers, polymers, organic materials, inorganic materials,
silicates, alumina, sapphire, glasses, polyethylene terephthalate
("PET"), polyethylene terephthalate glycol ("PET-G"), silicon
oxy-nitride, and/or other optically transparent materials. In some
embodiments, the turning film 801 and the light guide 803 comprise
the same material and in other embodiments, the turning film and
the light guide 803 comprise different materials. In some
embodiments, the indices of refraction of the turning film 801 and
the light guide 803 may be close or equal to one another such that
light may propagate successively through the two layers without
being substantially reflected or refracted at the interface between
the two layers. In one embodiment, the light guide 803 and the
turning film 801 each have an index of refraction of about 1.52.
According to other embodiments, the indices of refraction of the
light guide 803 and/or the turning film 801 can range from about
1.45 to about 2.05. The light guide 803 and turning film 801 may be
held together by an adhesive, which may have an index of refraction
similar or equal to the index of refraction of one or both of the
light guide and turning film. In some embodiments, the reflective
display 807 is laminated to the light guide 803 using a
refractive-index matched pressure-sensitive adhesive ("PSA") or
similar adhesive.
[0114] Both the light guide 803 and the turning film 801 can
include one or more turning features 820. In some embodiments, the
light guide 803 and the turning film 801 each comprise a single
layer. In other embodiments, the light guide 803 and/or the turning
film 801 comprise more than one layer. The light guide 803 and the
turning film 801 can have differing thicknesses and/or other
dimensions. In example embodiments, the turning film 801 can have a
thickness of between about 40 and about 100 microns, and the light
guide 803 can have a thickness of between about 40 and about 200
microns. Uniformity of brightness across the display device 800 and
efficiency of the display device may be affected by the thickness
of the light guide 803 and of the turning film 801.
[0115] In some embodiments, the turning film 801 can include one or
more turning features 820 disposed on or along the first side 800a
of the display device 800. In other embodiments, one or more
turning features 820 may be disposed on the side of the turning
film 801 and/or light guide 803 nearest to the reflective display
807. The turning features 820 depicted throughout the attached
figures are schematic and exaggerated in size and spacing
therebetween for clarity of illustration. The turning features 820
can comprise one or more angled and/or curved surfaces configured
to refract (or reflect) at least some of the light which is
traveling through the light guide (e.g., at an oblique angle) away
from the display 807 at the interface between the angled or curved
surface of the feature 820 and the air, and redirect that light
towards the reflective display 807. In certain embodiments, the
turning features can comprise a plurality of surface features or
volume features. In some embodiments, the turning features 820
comprise one or more diffractive optical elements, grooves,
depressions, and/or pits. In certain embodiments, the turning
features 820 comprise holograms or holographic features. The
holograms may include holographic volume or surface features. The
size, shape, quantity, and pattern of the turning features 820 may
vary. In some embodiments, the turning features 820 may be disposed
along the length and width of the turning film 801. In some
embodiments, turning features 820 are disposed on about 5% of the
area of the first side 800a of the turning film 801.
[0116] In some embodiments, the turning features 820 are configured
to receive light propagating along the length of the turning film
801 and turn the light through a large angle, for example, between
about 70-90.degree.. The turning features 820 can have one or more
edges shaped such that they can reflect light incident on the edges
from certain directions via total internal reflection ("TIR") and
cause the light to be turned toward the reflective display 807 at a
normal or near-normal angle of incidence (with respect to the
display). The turning features 820 illustrated and described herein
may include a reflective coating which is selected and/or
configured to increase light reflection properties (for example,
reflective coatings as described in reference to FIGS. 17A, 18,
19C, 20D, 20E, 21H, and others). The turning features 820 may be
molded, etched, or machined in the turning film 801. In some
embodiments, the turning features described herein may be molded,
etched, or machined directly in the light guide 803 and a separate
turning film 801 is not included, such that the light guide itself
forms a turning film. In some embodiments, both the light guide 803
and the turning film 801 include turning features 820. Methods for
forming turning features are described herein below in reference to
FIGS. 19A-D, 20A-F, 21.
[0117] Still referring to FIG. 8, in one embodiment, light 811
emitted from the light source 809 enters the light guide 803 and/or
the turning film 801 along one or more edges or surfaces of the
light guide and/or the turning film. A portion of light 811
propagates within the light guide 803 and turning film 801 at
shallow angles (e.g., not near-perpendicular to the reflective
display 807) and may generally remain within the light guide 803
and turning film 801 by TIR. When light 811 impinges on turning
features 820, it may be turned at a perpendicular or
near-perpendicular angle toward the display 807 allowing the light
811 to break TIR and illuminate the display 807. Light 811 that
illuminates the reflective display 811 may be reflected towards the
first side 800a and out of the display deice 800 towards a viewer.
To maximize the brightness and efficiency of the display 807, the
light turning features 820 can be configured to reflect light at an
angle normal to the display or close thereto. Light 811 that does
not at first reflect off of one of the turning features 820 may
continue to propagate through the light guide 803 and turning film
801 and subsequently reflect off another of the turning features
820 and be redirected towards the display 807, for example at a
location further from the light source 809.
[0118] In some embodiments, one or more optical isolation layers
805 may be disposed between the light guide 803 and the reflective
display 807 to improve the optical performance of the display 800.
An optical isolation layer 805 may be disposed between the light
guide 803 and an array of interferometric modulators to prevent
light propagating through the light guide 803 at shallow angles
from reaching the array, because such light would also be reflected
from the display at a shallow angle and may not reach a viewer.
According to some embodiments, the optical isolation layer 805 has
an index of refraction substantially lower than the light guide 803
such that light traveling through the light guide 803 and striking
the optical isolation layer 805 at an oblique or low grazing angle,
for example, light traveling at a lower angle than the critical
angle (which may be, for example, greater than 50.degree. or
60.degree.), will be reflected back into the light guide 803 and
turning film 801. The optical isolation layer 805 can include, for
example, silicon dioxide, fluorinated silicon dioxide, or another
material with a suitable index of refraction.
[0119] As shown in FIGS. 9A-10, the size, shape, pattern, and
quantity of the turning features 820 can vary. The quantity of
turning features 820 can vary from one turning film 801 to another
and the density of turning features 820 can vary from one portion
of a turning film 801 to another portion of the turning film. For
example, FIG. 9A illustrates an embodiment having turning features
820 disposed across a turning film 801 in a uniform pattern. In
another example, FIG. 9B illustrates an embodiment where the
density of turning features 820 is higher towards the middle or
center of the turning film 801 than near the edges of the turning
film 801. The quantity and pattern of turning features 820 can
affect the total illumination efficiency of a display device and/or
the uniformity of light extraction across a display device. An
illumination efficiency of a display device can be determined, for
example, by comparing the amount of light provided by a light
source with the amount of light reflected from the reflective
display 807. Additionally, the quantity and pattern of turning
features 820 on a given turning film 801 may depend upon the size
and/or shape of the turning features. In some embodiments, the
turning features 820 comprise between about 2% and 10% of the total
top surface area of a turning film 801 and/or light guide 803. In
one embodiment, the turning features 820 comprise about 5% of the
total top surface area of a turning film 801. In some embodiments,
turning features 820 are disposed about 100 microns from one
another on a turning film 801. In some embodiments, each turning
feature 820 on a turning film 801 can be substantially the same
size and shape. In other embodiments, the turning features 820 on a
turning film 801 may vary in size and/or shape. In some
embodiments, a turning film 801 comprises a plurality of turning
features 820 each having a generally different cross-sectional
shape. In some embodiments, a turning film 801 comprises a
plurality of turning features 820 each having a generally similar
cross-sectional shape. In some embodiments, a turning film 801
comprises a first group of turning features 820 each having a
generally similar cross-sectional shape and a second group of
turning features 820 each having a generally similar
cross-sectional shape wherein the first group of features 820 are
differently shaped than the second group of turning features. In
some embodiments, a turning feature 820 may have a generally
polygonal cross-sectional shape, for example, square, rectangular,
trapezoidal, triangular, hexagonal, octagonal, or some other
polygonal shape. In other embodiments, a turning feature 820 may
have a generally curvilinear cross-sectional shape. In some
embodiments, a turning feature 820 has an irregular cross-sectional
shape. The cross-sectional shape of a turning feature 820 may be
symmetric or asymmetric. In some embodiments, the shape formed by
the surface of a turning feature may resemble a cone, a frustum of
a cone, a pyramid, a frustum of a pyramid, a prism, a polyhedron,
or another three-dimensional shape. The shape of the turning
features 820 viewed from the top may vary. In some embodiments, the
shape of the turning features 820 viewed from the top may be
polygonal, curvilinear, irregular, generally polygonal, generally
curvilinear, square, triangular, rectangular, circular, round, or
another shape.
[0120] As shown in FIG. 9C, the turning features 820 in a turning
film 801 (or in a light guide) can be configured to vary in depth
and width. In one embodiment, turning features 820 on a turning
film 801 each have a similar depth measured from the top of the
turning film 801 to the bottom of the turning features 820. In
other embodiments, a turning film 801 comprises a plurality of
turning features 820 which may be of different depths. Similarly,
the volume of each turning feature 820 can vary from turning film
801 to turning film 801 or from turning feature 820 to turning
feature 820 on a common turning film. In some embodiments, the
volume, depth, or width of turning features 820 on a given turning
film 801 may vary depending on the distance from the turning
feature to the light source. For example, in some embodiments, the
number of turning features 820 increases from the light input edge
of the turning film 801 towards the center of the turning film 801
to facilitate uniform light extraction. In some embodiments, the
width of each turning feature 820 is between about one micron and
about six microns. In some embodiment, the width of each turning
feature 820 is about two microns. The size and shape of each
turning feature 820 can be varied by using different patterns,
etching agents, process recipes, and/or different lithography and
deposition conditions of the turning film 801 and/or light guide
803. In one embodiment, a first set of turning features 820 may be
formed using a first timed etch and a differently shaped and/or
sized set of turning features 820 may be formed using a second
timed etch.
[0121] FIG. 9D illustrates additional examples of turning features
820a, 820b which are rotationally symmetrical. The turning features
820a, 820b may comprise indentations in the material comprising the
light guide and/or turning film. As illustrated, in some
embodiments, feature 820b may take on a conical shape having an
apex. In other embodiments, the cone may be truncated, removing the
apex and creating a frustoconical shape, so as to create the
structure 820a. 820a' shows a cross-sectional view of one exemplary
implementation of the feature 820a. Example dimensions of 15 .mu.m
of width and 3.5 .mu.m of depth are indicated in the
cross-sectional view shown in FIG. 9D, but other sizes and shapes
are also possible. A wide variety of other alternative
configurations are also possible. FIG. 10 shows an embodiment
comprising a plurality of variously-shaped turning features 820.
For example, components (e.g., layers) may be added, removed, or
rearranged. Also, although the terms film and layers have been used
herein, such terms as used herein include film stacks and
multilayered structures. Such film stacks and multilayered
structures can be adhered to other structures using adhesive, or
can be formed on other structures using deposition or in other
manners.
[0122] FIGS. 11 and 12 illustrate cross-sectional views of a light
guide 803 (FIG. 11) and a turning film 801 (FIG. 12) that include
one or more light turning features 820. In some embodiments, the
light turning features 820 include one or more edges that extend
from a top side or surface 823 to a bottom side or surface 825 of
the turning film 801 or light guide 803. Such a configuration can
also be referred to as "running through" the turning film 801
and/or light guide 803. For example, in FIG. 11, light turning
features 820 are shown running through a light guide 803. The light
turning features 820 may have similar cross-sectional shapes or
different cross-sectional shapes. The light turning features 820
may be formed using different etching agents and techniques, for
example, timed etching. In some embodiments, the light turning
features 820 may be formed by standard wet or dry etching
processes. In certain embodiments, the light turning features 820
may be formed by sand blast processes.
[0123] In FIG. 12, light turning features 820 are shown running
through a turning film that includes two layers 801a, 801b. The two
turning film layers 801a, 801b are disposed on light guide 803, but
the turning features 820 do not extend into the light guide 803
from the turning film layers 801a, 801b. In some embodiments, the
turning features 820 may be formed through a single or multilayer
turning film 801 into a light guide 803. In one embodiment, turning
features 820 can may be formed through a single or multilayer
turning film 801 and extend through a single or multilayer light
guide 803.
[0124] In some embodiments, a turning film may include a plurality
of layers 801a, 801b each including turning one or more turning
features 820. Referring to FIG. 13, a turning film includes a first
layer 801a and a second layer 801b. The first layer 801a is
disposed on the second layer 801b such that the second layer 801b
is disposed between the light guide 803 and the first layer 801a.
The first layer 801a and the second layer 801b may each include
separate turning features 820. The turning features 820 may be
offset from one another (e.g., laterally offset relative to the
length or width of the film turning layers) such that a turning
feature 820 in the first layer 801a is not disposed directly above
another turning feature 820 in the second layer 801b. In other
embodiments, the turning features 820 in the first layer 801a may
overlap one or more turning features 820 in the second layer 801b.
In some embodiments, the turning features 820 in the first layer
801a have a height "h" (FIG. 13) such that the turning features run
through the first layer but do not extend into the second layer
801b. Similarly, the turning features 820 in the second layer 801b
may run through the second layer but do not extend into the first
layer 801a. In other embodiments, one or more turning features 820
may be disposed in both the first layer 801a and the second layer
801b as illustrated in FIG. 12. In some embodiments, the turning
features 820 vary in shape, size, pattern, quantity, and/or volume
from layer to layer or within a single layer. For example, in one
embodiment, the turning features 820 in a first layer 801a are each
substantially the same size but vary in cross-sectional shape and
the turning features 820 in a second layer 801b are each
differently sized and differently shaped from one another and the
turning features 820 in the first layer 801a.
[0125] In some embodiments, a turning film 801 and/or light guide
803 can include additional features in addition to turning features
820. FIG. 14 illustrates a turning film 801 that includes a
plurality of turning features 820 having a first configuration. The
turning film 801 includes an additional optical device, edge 1400,
which may be configured in different shapes and sizes to optimize
performance and provide multiple operational advantages. One or
more of edges 1400 may be included in addition to turning features
820. The structure of additional edges 1400 can vary depending upon
application. In some embodiments, edge 1400 is configured as a
Fresnel lens. In some embodiments, an additional edge includes a
micro lens.
[0126] In some embodiments, the shape of one or more edges or sides
of the light guide 803 and/or turning film 801 can be configured to
affect the introduction of light from a light source into the
turning film 801 and/or light guide 803. FIG. 15 illustrates an
embodiment of a light guide 803 and a turning film 801 where the
two layers have beveled or curved edges that are not perpendicular
to the faces of the light guide 803 or turning film 801. In some
embodiments, such beveled or curved sides or edges of the turning
film 801 and/or light guide 803 may be employed to reduce or
eliminate bright spots near the edges where light is introduced by
a light source, and to increase the uniformity of light extraction
across the display. Similarly, in some embodiments, providing
unpolished edges or sides on the light guide 803 and/or turning
film 801 can serve to eliminate bright spots of light extraction by
acting as a diffuser and reflector. In some embodiments, such
beveled edges can be covered by a reflector when appropriate to
recycle light propagating within the turning film 801 and/or light
guide 803.
[0127] Turning now to FIG. 16, in some embodiments, one or more
edges or surfaces of the light guide 803 and/or turning film 801
may be angled relative to the first side 800a and/or second side
800b of the display device. In some embodiments, the edges of the
turning film 801 and the light guide 803 may be disposed at an
angle of about 45.degree. relative to the first side 800a and
second side 800b. In other embodiments, the edges of the turning
film 801 and the light guide 803 may be disposed at an angle of
between about 0.degree. and about 90.degree. relative to the first
side 800a and second side 800b. In some embodiments, a light source
809 may be configured to introduce light at an angle about normal
to the angled edges of the turning film 801 and the light guide 803
in order to increase the efficiency of the display device. In some
embodiments, when light is introduced into the light guide 803
and/or turning film 801 at an angle, the light propagates within
the light guide 803 and turning film 801 at shallow angles and more
light is turned by the light turning features 820.
[0128] As discussed above, in some embodiments, turning features
may turn light at the air/turning feature interface via TIR and
direct the light towards one or more directions (e.g., towards a
reflective display). For any of the embodiments described herein, a
turning feature may include a reflective coating configured to
provide desirable optical characteristics. The coating can include
one or more layers. One of the layers may be an additional coating
configured to increase the reflectivity of a turning feature. The
reflective coating may be metallic. In some embodiments, some of
the plurality of turning features may include a reflective coating
and others may not. In certain embodiments, a portion (or portions)
of a turning feature may be covered with a reflective coating and
another portion (or portions) of the turning feature may not be
covered with a reflective coating. Using a reflective coating can
improve the efficiency of a display device because the reflective
coatings can be configured to reflect substantially all of the
light that encounters the coatings and redirect that light toward
the display. Additionally, in some applications, it may be
desirable to add or build additional layers or features on top of
one or more turning features. In some embodiments, one or more
cover layers, for example, anti-glare layers, anti-reflection
layers, anti-scratch layers, anti-smudge layers, diffuser layers,
color filtering layers, lenses, or other layers, may be added on
top of one or more turning features. In some embodiments,
conductive electrode plates may be added on top of a turning film
including turning features. In one embodiment, a touch sensor may
be added over one or more turning features. In embodiments where
turning features rely solely on the air/feature interface to turn
light, having additional layers on the turning features may
complicate the desired optical functionality because adhesives or
laminates may cover or partially cover one or more turning features
and affect TIR characteristics of the light turning feature.
However, when reflective coatings are disposed over turning
features, one or more additional layers can be added over the
turning features without affecting the light turning properties of
the turning features because they no longer rely on the TIR
properties of a material-air interface.
[0129] Using reflective coatings on turning features can diminish
the contrast of the display if no additional coatings are disposed
between the reflective coatings and a viewer. Accordingly,
additional layers may be deposited over the reflective coating to
prevent reflection of light from the reflective coating towards a
viewer. In one embodiment, additional layers may be deposited over
the reflective coating to form a static interferometric stack that
appears dark or black to a viewer in order to improve the contrast
of the display device while reflecting light incident on the
reflective coating side of the stack towards a reflective display.
In some embodiments, a static interferometric stack may include a
reflector layer deposited on the turning film or light guide, an
absorber layer, and an optical resonant cavity defined by the
reflector layer and the absorber layer. In some embodiments, the
reflector layer is a partial reflector. In some embodiments,
reflective coatings are covered by one or more dark or black
coatings to form a black mask which prevents reflection of light
towards a viewer from the reflective coating.
[0130] FIG. 17A illustrates a turning film 801 that includes
turning features 820 (note: FIG. 17A and the other figures herein
are not drawn to scale). An interferometric stack 1707 is formed
over portions of certain surfaces of each turning feature 820. An
interferometric stack 1707 includes a reflective layer 1705
disposed on one or more portions of the turning feature 820
surface. The interferometric stack 1707 also includes an optically
resonant layer 1703 formed on top of the reflective layer 1705, and
an absorber layer 1701 disposed over the optically resonant layer
1703. The interferometric stacks 1707 can be configured to
interferometrically reflect selected wavelengths of light. This
reflected light is incident on the absorber layer 1701. The
absorber layer 1701 and the interferometric stacks 1707 are
configured such that the absorber layer 1701 absorbs light of the
reflected wavelength such that the stack 1707 appears black or
dark, which can increase the contrast of the display. In the
embodiment illustrated in FIG. 17A, the reflective layer 1705 is
formed on the tapered sidewalls 831 of each turning feature 820 but
not the bottom 833. In some embodiments, the reflective layer 1705
may be formed on portions of the tapered sidewalls 831 and/or
certain lower portions or the bottoms 833.
[0131] In some embodiments, the reflector layer 1705 includes a
single layer and in other embodiments the reflector layer 1705
includes multiple layers of material. In various embodiments, the
thicknesses of the absorber 1701 and reflective layers 1705 may be
selected to control relative amounts of reflectance and
transmittance of light. In some embodiments, both the absorber 1701
and reflective 1705 layers may comprise metal, and both can be
configured to be partially transmissive. According to certain
embodiments, the amount of light substantially reflected or
transmitted through the reflective layer 1705 can be affected by
varying the thickness and the composition of the reflective layer
1705, whereas the apparent color of reflection is largely
determined by the interference effect governed by the size or
thickness of the optically resonant layer 1703 and the material
properties of the absorber layer 1701 that determine the difference
in optical path length. In some embodiments, modulating the bottom
reflective layer 1705 thickness can modulate the intensity of the
reflected color versus the overall reflectivity of the
interferometric stack 1707.
[0132] In some embodiments, the optically resonant layer 1703 is
defined by a solid layer, for example, an optically transparent
dielectric layer, or plurality of layers. In other embodiments, the
optically transparent layer 1703 is defined by an air gap or
combination of optically transparent solid material layer(s) and an
air gap. In some embodiments, the thickness of the optically
resonant layer 1704 may be selected to maximize or minimize the
reflection of one or more specific colors of the light incident on
the absorber 1701 side of the stack 1707. In various embodiments,
the color or colors reflected by the optically resonant layer 1703
may be changed by changing the thickness of the layer.
[0133] The absorber layer 1701 can comprise various materials, for
example, molybdenum (Mo), titanium (Ti), tungsten (W), chromium
(Cr), etc., as well as alloys, for example, MoCr. The absorber 1701
can be between about 20 and about 300 .ANG. thick. In one
embodiment, the absorber 1701 is about 80 .ANG. thick. The
reflective layer 1705 may, for example, comprise a metal layer, for
example, aluminum (Al), nickel (Ni), silver (Ag), molybdenum (Mo),
gold (Au), and chromium (Cr). The reflective layer 1701 can be
between about 100 .ANG. and about 700 .ANG. thick. In one
embodiment, the reflective layer 1701 is about 300 .ANG. thick. The
optically resonant layer 1703 can comprise various optically
resonant materials, for example, air, silicon oxy-nitride
(SiO.sub.xN), silicon dioxide (SiO.sub.2), aluminum oxide
(Al.sub.2O.sub.3), titanium dioxide (TiO.sub.2), magnesium fluoride
(MgF.sub.2), chromium (III) oxide (Cr.sub.3O.sub.2), silicon
nitride (Si.sub.3N.sub.4), transparent conductive oxides (TCOs),
indium tin oxide (ITO), and zinc oxide (ZnO). In some embodiments,
any dielectric with an index of refraction (n) between 1 and 3 can
be used to form a suitable spacer layer. In some embodiments, the
optically resonant layer 1703 is between about 500 .ANG. and about
1500 .ANG. thick. In one embodiment, the optically resonant layer
1703 is about 800 .ANG. thick.
[0134] An interferometric stack 1707 as shown in FIG. 17 can be
configured to selectively produce a desired reflection output using
optical interference. As discussed above, in some embodiments, this
reflected output may be "modulated" by selection of the thickness
and optical properties of the layers that form the stack 1707. The
color observed by a viewer viewing the absorber layer 1701 side of
the stack will correspond to the frequencies which are
substantially reflected out of the interferometric stack 1707 and
which are not substantially absorbed or destructively interfered by
one or more layers in the stack 1707. As shown in FIG. 17B, the
interferometric stacks 1707 depicted in FIG. 17A can be configured
to appear dark or black to a viewer viewing the absorber layer 1701
side of the turning film 801. In some embodiments, configuring the
coated portions of the turning features 820 to appear dark or black
improves the contrast of the display device while providing other
benefits discussed above (e.g., improved light turning
functionality and easily building layers on top of the turning
features 820 without disrupting the turning functionality).
Additionally, selectively coating only portions of the turning
features 820, for example, the side-walls, with interferometric
stack layers can limit the total area of the turning film 801 that
appears dark to a viewer due to interferometric disruption.
[0135] Turning now to FIG. 18, an embodiment of a turning film 801
is depicted including various turning features 820. Each turning
feature 820 differs in size and cross-sectional shape.
Additionally, each turning feature includes an interferometric
stack 1707 covering at least a portion of the turning feature 820
surface. As discussed above, turning features 820 that include
interferometric stacks 1707 can vary in size, shape, quantity, and
pattern depending on the application. For example, in some
embodiments, some turning features 820 on a turning film 801 can be
covered at least partially by an interferometric stack 1707 and
other turning features 820 on the film 801 may not be covered by an
interferometric stack. In other embodiments, each turning feature
820 can vary in shape and/or size but each turning feature 820 may
be covered at least partially by an interferometric stack 1707. In
some embodiments, each turning feature 820 can be covered at least
partially by an interferometric stack 1707 but the coverage may
vary from one turning feature 820 to another.
[0136] Turning now to FIGS. 19A-19C, one method of forming
interferometric stacks 1707 over turning features 820 is depicted
in three steps. FIG. 19A shows an embodiment of a turning film 801
including turning features 820 formed thereon. The turning features
820 may be etched, molded, machined, or otherwise formed in or on
the turning layer 801 using known methods. In some embodiments, the
turning film 801 can include multiple layers. In one embodiment,
the turning features 820 are formed directly on a light guide or on
a turning film 801 that comprises a light guide. FIG. 19B shows an
embodiment of a turning film 801 with an interferometric stack 1707
deposited on the turning feature 820 side of the turning film 801.
As discussed above, the interferometric stack 1707 may contain a
plurality of layers configured to produce a desired reflection
output using optical interference. In one embodiment, the
interferometric stack includes a reflective layer 1701 deposited on
the turning feature 820 side of the turning film 801, an optically
resonant layer 1703 deposited on the reflective layer 1701, and an
absorber layer 1707 deposited on the optically resonant cavity
layer.
[0137] Methods of depositing the layers of an interferometric stack
1707 are known to those of skill in the art and include, for
example, physical vapor deposition, chemical vapor deposition,
electro-chemical vapor deposition, plasma-enhanced chemical vapor
deposition, and/or other deposition techniques. As shown in FIG.
19B, a single interferometric stack 1707 covers the entire turning
feature 820 surface of the turning film 801. In some embodiments,
the interferometric stack 1707 is configured to appear dark or
black to a viewer and thus, the entire turning film 801 shown in
FIG. 19B would appear dark or black to viewer looking at the
turning feature side of the turning film. In some embodiments, it
is important to limit the coverage of the interferometric stack
1707 to one or more portions of the turning film 801 surface. In
one embodiment, one or more interferometric stacks 1707 are
disposed near or over only the turning features 820. The turning
film 801 in FIG. 19B can be processed further to limit the coverage
of the interferometric stack 1707.
[0138] FIG. 19C shows an embodiment of the turning film 801
depicted in FIGS. 19A and 19B with interferometric stacks 1707
disposed only over portions of the turning features 820. In some
embodiments, the turning film 801 depicted in FIG. 19C can be
formed by polishing the turning feature side of the turning film
801 depicted in FIG. 19B and thinning the opposite side. The
turning feature side of the turning film 801 may be polished until
the interferometric stack 1707 is removed from surfaces other than
the turning features 820. Similarly, the opposite side of the
turning film 801 may be optionally thinned until the
interferometric stack 1707 is removed from a portion of the turning
features 820, for example, a bottom portion. In one embodiment, the
turning film 801 depicted in FIG. 19B may be polished and/or
thinned such that the interferometric stack 1707 is divided into
separate interferometric stacks that cover only a portion or
portions of the turning features 820 resulting in a turning film
801 similar to the turning film schematically depicted in FIG.
19C.
[0139] FIG. 19D is a block diagram depicting a method 1920 of
manufacturing the turning film shown in FIG. 19C, according to one
embodiment. Method 1920 includes providing a turning film having a
first side and a second side opposite the first side, the turning
film including turning features formed on the first side as
illustrated in block 1921, depositing an interferometric stack on
the first side of the turning film as illustrated in block 1923,
polishing the first side of the turning film until the
interferometric stack is removed from surfaces other than the
turning features as illustrated in block 1925, and thinning the
second side until the interferometric stack is removed from at
least the bottom portion of each turning features as illustrated in
block 1927.
[0140] FIGS. 20A-20E illustrate an embodiment of another method of
forming interferometric stacks 1707 over turning features 820. FIG.
20A shows an embodiment of a light guide 803 and a turning film 801
disposed on the light guide 803. In some embodiments, a dissolvable
layer 2001, for example, a photoresist coating or layer, can be
formed or deposited over the turning film 801 as shown in FIG. 20B.
In some embodiments, a plurality of light turning features 820 can
then be formed in the dissolvable layer 2001 and the turning film
801 as shown in FIG. 20C. According to certain embodiments, the
turning features 820 can have varying shapes and sizes. In some
embodiments, the turning features 820 are formed by etching or
embossing. In some embodiments, the turning features 820 run
through the turning film 801 to the light guide 803. In other
embodiments, the turning features 820 are shallower and do not run
through the turning film 801.
[0141] Turning now to FIG. 20D, an interferometric stack 1707 is
formed over the dissolvable layer 2001, the exposed portions of the
turning film 801, and the exposed portions of the light guide 803
shown in FIG. 20C, such that the interferometric stack 1707 covers
the turning feature 820 side of the light guide 803 and turning
film 801 stack. According to some embodiments, the interferometric
stack 1707 includes an aluminum layer, a silicon dioxide layer, and
a molybdenum-chromium alloy. In some embodiments, portions of the
deposited interferometric stack 1707 are removed from the turning
feature side of the turning film 801 by stripping or dissolving the
dissolvable layer 2001. FIG. 20E shows an embodiment of the light
guide 803 and turning film 801 depicted in FIG. 20D with the
portions of the interferometric stack 1707 removed from portions of
the turning film 801. In some embodiments, the turning film 801 and
light guide 803 shown in FIG. 20E can be used to efficiently turn
light towards a reflective display while still allowing a viewer to
see the reflection from the display through the two layers. In some
embodiments, additional layers, for example, a cover, can be added
to the turning film 801 with adhesives or by lamination without
sacrificing the light turning performance of the light turning
features 820.
[0142] FIG. 20F is a block diagram depicting a method 2020 of
manufacturing the illumination device shown in FIG. 20E, according
to one embodiment. Method 2020 includes the steps of providing a
light guide with a light turning film disposed thereon as
illustrated in block 2021, depositing a dissolvable layer over the
turning film as illustrated in block 2023, etching one or more
turning features in the dissolvable layer and turning film as
illustrated in block 2025, depositing an interferometric stack over
the dissolvable layer and exposed portions of the turning film and
light guide as illustrated in block 2027, and removing the
dissolvable layer as illustrated in block 2029.
[0143] FIGS. 21A-21H illustrate an embodiment of a method of
forming interferometric stacks 1707 over different portions of
turning features 820. As shown in FIGS. 20A-20C, according to one
embodiment, the process begins by providing a light guide 803,
depositing a turning film 801 onto the light guide 803, and then
depositing a dissolvable layer 2001 over certain portions of the
turning film 801. In some embodiments, the light guide 803 and the
turning film can comprise any optically transparent material. In
one embodiment, the dissolvable layer 2001 comprises a
light-sensitive material, for example, a photoresist. In some
embodiments, a dissolvable layer 2001a is deposited across an
entire side or surface of the turning film 801 and then portions of
the photoresist layer are removed by etching. According to certain
embodiments, the dissolvable layer 2001a is selectively deposited
on portions of the turning film 801.
[0144] Turning now to FIG. 21D-21E, in some embodiments, turning
features 820 may be formed in the turning film 801 in portions of
the turning film 801 that are not covered by the dissolvable layer
2001a. In certain embodiments, the turning features 820 are formed
by various etching processes including dry etch processes and/or
wet etch processes. As discussed above, the turning features 820
can vary at least in size, shape, quantity, and/or pattern. In some
embodiments, after the turning features 820 are formed in the
turning film 801, the dissolvable layer 2001a is stripped or
dissolved and another dissolvable layer 2001b is added to certain
portions of the turning film 801 and/or the light guide 803. In
some embodiments, the dissolvable layer 2001b may be a photoresist
layer that is patterned over certain portions of the turning film
801 and the light guide 803 by a spin-coat, expose, and develop
process. In some embodiments, a photoresist layer can be deposited
using known methods to leave a resist pattern that serves as a
physical mask to cover surfaces that are desired to be protected
from subsequent etching, implantation, lift-off, and/or deposition
steps. As shown in FIG. 21E, portions of the turning features 820
are exposed and other portions of the turning features 820, light
guide 803, and turning film 801 are covered by the dissolvable
layer 2001b.
[0145] As shown in FIGS. 21F-21H, in some embodiments, an
interferometric stack 1707 can be deposited layer by layer over a
dissolvable layer 2001b and the exposed portions of the turning
film 801. In one embodiment, the interferometric stack 1707
includes a reflective layer, an optically resonant layer, and an
absorber layer. In some embodiments, a reflective layer and black
coating layer may be deposited over the dissolvable layer 2001b and
the exposed portions of the turning film 801. In some embodiments,
once the interferometric stack 1707 has been deposited, the
dissolvable layer 2001b may be removed or lifted-off from the
turning film 801 and the light guide 803. When the dissolvable
layer 2001b is lifted-off, the layers deposited onto the
dissolvable layer 2001b can also be removed. As shown in FIG. 21G,
in some embodiments, interferometric stacks 1707 may remain over
certain portions of turning features 1707 and/or the turning film
801 and light guide 803 after the dissolvable layer 2001 is
removed. Limiting interferometric stack 1707 coverage to certain
portions of the turning features 820 and/or turning film 801 can be
used to balance contrast concerns with the light turning benefits
provided by a reflective layer included as part of the
interferometric stacks 1707. In some embodiments, interferometric
stacks 1707 are deposited over the side-walls of the turning
features 820 and are configured to appear as black or dark rings to
a viewer. In other embodiments, interferometric stacks 1707 are
deposited over the entire surfaces of the turning features 820 and
appear as black or dark circles or dots to a viewer.
[0146] In some embodiments, a passivation layer 2101 can be added
over a turning film 801 that includes interferometric stack 1707
coated turning features 820. FIG. 21H shows an embodiment where a
passivation layer 2101 has been added over the embodiment shown in
FIG. 21G. In some embodiments, the passivation layer 2101 can
include silicon dioxide, silicon oxy-nitride, aluminum oxide,
and/or any optically transparent material. In some embodiments, the
passivation layer 2101 includes more than one layer. In some
embodiments, the passivation layer 2101 includes an anti-glare
layer, an anti-reflection layer, an anti-scratch layer, an
anti-smudge layer, a diffuser layer, a color filtering layer,
and/or a lens. In some embodiments, additional layers can be added
over the passivation layer 2101. In some embodiments, the
passivation layer 2101 can comprise an adhesive or material used to
couple an additional layer (not shown) with the turning film
801.
[0147] FIG. 21J is a block diagram depicting a method 2120 of
manufacturing the illumination device shown in FIG. 21H, according
to one embodiment. Method 2120 includes the steps of providing a
light guide at block 2121, disposing a turning film on one surface
of the light guide at block 2123, depositing a first dissolvable
layer on the turning film at block 2125, etching one or more
turning features in the first dissolvable layer and turning film at
block 2127, removing the first dissolvable layer at block 2129,
depositing a second dissolvable layer over exposed portions of the
light guide and portions of the turning film where a light turning
feature is not formed at block 2131, depositing an interferometric
stack over the second dissolvable layer and exposed portions of the
turning film at block 2133, removing the second dissolvable layer
at block 2135, and depositing a passivation layer over the turning
film and turning features at block 2137.
[0148] FIGS. 22A-22E illustrate another embodiment of a method of
forming interferometric stacks 1707 over turning features 820. The
method depicted in FIGS. 22A-22E is similar to the method depicted
in FIGS. 21A-21H except that a dissolvable layer 2001 is not
deposited within the turning features 820. As shown in FIG. 22C, an
interferometric stack 1707 is then deposited directly onto the
entire surface of each turning feature 820 and also onto the
dissolvable layer 2001. In some embodiments, the dissolvable layer
2001 is then lifted-off or removed resulting in the embodiment
shown in FIG. 22D. Because the interferometric stack 1707 in FIG.
22D covers the entire surface of each turning feature 820, the
turning features appear as black or dark shapes to a viewer instead
of rings. As discussed above, in some embodiments, interferometric
stacks 1707 can be added to the same portions of each turning
feature 820 or different portions. Additionally, in some
embodiments, turning features 820 can vary in size, shape,
quantity, and pattern and the coverage of these turning features
820 by interferometric stacks 1707 can also vary. For example, in
one embodiment, a first turning feature 820 may not be covered by
an interferometric stack 1707, a second turning feature 820 may be
completely covered by an interferometric stack 1707, and a third
turning feature 820 may be covered partially by one or more
interferometric stacks 1707. As discussed above, in some
embodiments, a reflective layer and one or more dark coating layers
may be deposited over turning features or portions of turning
features.
[0149] FIG. 22F is a block diagram depicting a method 2220 of
manufacturing the illumination device shown in FIG. 22E, according
to one embodiment. Method 2220 includes the steps of providing a
light guide at block 2221, disposing a turning film on one surface
of the light guide at block 2223, depositing a dissolvable layer on
the turning film at block 2225, etching one or more turning
features in the dissolvable layer and turning film at block 2227,
depositing an interferometric stack over the dissolvable layer and
the light turning features at block 2229, removing the dissolvable
layer at block 2231, and depositing a passivation layer over the
turning film and turning features at block 2233.
[0150] Turning now to FIGS. 23A-23J, an embodiment of a method of
forming a reflective coating over turning features 820 is shown. As
shown in FIGS. 23A-23D, in some embodiments, the process begins by
adding a turning film 801 to a light guide 803, applying a
dissolvable layer 2001 in a particular pattern over the turning
film 801, etching turning features 820 into the turning film 801,
and stripping the dissolvable layer 2001 from the turning film 801.
Turning to FIG. 23E, in one embodiment, an electroplating process
may start by applying a seed layer 2301 over the turning film 801
and the surfaces of the turning features 820. The seed layer may
comprise any suitable material, for example, copper or silver. In
some embodiments, a stick layer (not shown) may optionally be added
over the turning film 801 and the turning features 820. Examples of
suitable stick layers include tantalum, titanium, and molybdenum.
In some embodiments, once the seed layer 2301 is added over the
turning film 801 and the turning features 820, a dissolvable layer
2001 may be added over the turning film 801 and the portions of the
turning features 820. In one embodiment, the dissolvable layer 2001
includes a photoresist layer that is spin-coated, exposed, and
developed. In some embodiments, the dissolvable layer 2001 may be
applied in a pattern to expose all, or certain portions, of the
turning features 820. In one embodiment, the dissolvable layer 2001
is patterned to leave the sidewalls of one or more turning features
820 exposed.
[0151] Turning now to FIG. 23G and 23H, in certain embodiments,
portions of the seed layer 2301 that are not covered by the
dissolvable layer 2001 are electroplated and the dissolvable layer
2001 is stripped or removed from the turning film 801 and the
turning features 820. In some embodiments, portions of the seed
layer 2301 may then be etched or removed with another process
resulting in the turning film 801 and light guide stack 803 shown
in FIG. 23I. In some embodiments, portions of the seed layer 2301
that are not over turning features 820 may be removed by etching or
another process. In certain embodiments, portions of the seed layer
2301 that have not been electroplated are removed by etching. In
some embodiments, portions of the seed layer 2301 that were
electroplated may be removed using various methods known in the
art. In some embodiments, once portions of the seed layer 2301 have
been removed, a passivation layer 2101 can optionally be applied
over the turning film 801 and turning features 820 as schematically
depicted in FIG. 23J. Because the turning features 820 rely on a
reflective coating applied to at least a portion of the turning
features 820 surfaces to turn light instead of total internal
reflection, an air pocket over the turning features 820 does not
necessarily have to be maintained.
[0152] FIG. 23K is a block diagram depicting a method 2320 of
manufacturing the illumination device shown in FIG. 23J, according
to one embodiment. Method 2320 includes the steps of providing a
light guide at block 2321, disposing a turning film on one surface
of the light guide at block 2323, depositing a first dissolvable
layer on the turning film at block 2325, etching one or more
turning features in the first dissolvable layer and turning film at
block 2327, removing the first dissolvable layer at block 2329,
depositing a seed layer over the dissolvable layer and the light
turning features at block 2331, depositing a second dissolvable
layer over portions of the seed layer at block 2333, electroplating
exposed portions of the seed layer at block 2335, removing the
second dissolvable layer at block 2337, etching portions of the
seed layer that are not electroplated at block 2339, and depositing
a passivation layer over the turning film and turning features at
block 2341.
[0153] FIGS. 24A-24F depict an embodiment of a method of forming
turning features 820 with a reflective coating on the side of a
light guide 803 opposite a reflective display. In some embodiments,
a reflective display may include the light guide 803 and thus, the
light guide 803 can be used both for light turning and as part of
the reflective display assembly. In some embodiments, the process
begins in FIGS. 24A and 24B by depositing a seed layer 2301 onto a
light guide 803. The light guide 803 may comprise any suitable
material, for example, inorganic materials and/or organic
materials. In some embodiments, the seed layer 2301 may comprise
any suitable material, for example, tantalum, titanium, and
molybdenum. As shown in FIG. 24C, in one embodiment, a dissolvable
layer 2001 may be added over the seed layer 2301 in a pattern
leaving certain portions of the seed layer 2301 exposed. Turning to
FIG. 24D, in some embodiments, the exposed portions of the seed
layer 2301 may be electroplated using known methods, resulting in
an electroplate layer 2303 disposed over at least a portion of the
seed layer 2301. In some embodiments, the dissolvable layer 2001
may then be removed and portions of the seed layer 2301 that were
not electroplated may be etched or otherwise removed resulting in
the light guide 803, seed layer 2301, and electroplate 2303 stack
depicted in FIG. 24E. In some embodiments, the dissolvable layer
2001 comprises a photoresist and the photoresist is removed using
known methods.
[0154] Turning to FIG. 24F, a turning film 801 can then be added
over the light guide 803 surrounding-the seed layer 2301 portions
and electroplate portions 2303. In some embodiments, the light
guide 803 may comprise material that is index matched to the light
guide 803. In some embodiments, the light guide 803 and the turning
film 803 have about the same index of refraction. In some
embodiments, the light guide 803 and the turning film 801 each have
an index of refraction between about 1.45 and 2.05. In some
embodiments, the light turning film 801 comprises the same
material(s) as the light guide 803. In some embodiments, the
surface or side of the turning film 801 opposite the light guide
803 may be substantially planar. In some embodiments, additional
layers (not shown), for example, a cover layer, may be added over
the turning film 801. One advantage of the embodiment shown in
FIGS. 24A-24F is that it allows the use of only a single
dissolvable layer 2001 mask instead of multiple dissolvable layer
2001 masks.
[0155] FIG. 24G is a block diagram depicting a method 2420 of
manufacturing the illumination device shown in FIG. 24F, according
to one embodiment. Method 2420 includes the steps of providing a
light guide 2421, depositing a seed layer on one surface of the
light guide 2423, depositing a dissolvable layer on the seed layer
2425, etching one or more turning features in the dissolvable layer
2427, electroplating exposed portions of the seed layer 2429,
removing the dissolvable layer 2431, etching portions of the seed
layer that are not electroplated 2433, and depositing a turning
film layer on the light guide over portions of the seed layer that
are not electroplated 2435.
[0156] FIGS. 25A-25G show another embodiment of a method of forming
turning features 820 with a reflective coating on the side of a
light guide 803 opposite a reflective display. Referring to FIGS.
25A-25C, in some embodiments, the method includes providing a light
guide 803, depositing a seed layer 2301 on one surface of the light
guide 803, and adding a dissolvable layer 2001 over the seed layer
2301. In some embodiments, the dissolvable layer 2001 may be added
in a certain pattern or it may be deposited over the entire surface
of the seed layer 2301 and have certain portions removed to create
a desired pattern. Comparing FIG. 25C to 24C, it can be appreciated
by those of skill in the art that the dissolvable layer 2001
pattern can be used to create differently shaped voids defined by
sides or surfaces of different portions of the dissolvable layer
2001 and the seed layer 2301. For example, in some embodiments,
voids may be formed with generally trapezoidal cross-sectional
shapes or inverted trapezoidal cross-sectional shapes. Turning to
FIG. 25D, in some embodiments, exposed portions of the seed layer
2301 may be electroplated, resulting in an electroplate layer 2303
that partially fills the voids shown in FIG. 25C. In some
embodiments, the dissolvable layer 2001 may then be removed and
portions of the seed layer 2301 that were not electroplated may be
etched or otherwise removed resulting in the light guide 803, seed
layer 2301, and electroplate 2303 stack depicted in FIG. 25E.
Turning to FIGS. 25F and 25G, in certain embodiments, a turning
film 801 may be added over the light guide 803 and surround the
seed layer 2301 portions and electroplate layers 2303. In some
embodiments, a buffering layer 2501 may be added on top of the
turning film 801. In certain embodiments, the buffering layer 2501
may comprise varying materials or layers configured to protect the
turning film 801 from scratches or other damage.
[0157] FIG. 25H is a block diagram depicting a method 2520 of
manufacturing the illumination device shown in FIG. 25G, according
to one embodiment. Method 2520 includes the steps of providing a
light guide at block 2521, depositing a seed layer on one surface
of the light guide at block 2523, depositing a dissolvable layer on
the seed layer at block 2525, etching one or more turning features
in the dissolvable layer at block 2527, electroplating exposed
portions of the seed layer at block 2529, removing the dissolvable
layer at block 2531, etching portions of the seed layer that are
not electroplated at block 2533, depositing a turning film layer on
the light guide over portions of the seed layer that are not
electroplated at block 2535, and depositing a buffering layer over
the turning film layer at block 2537.
[0158] Turning now to FIGS. 26A-26F, another embodiment of a method
of forming turning features 820 with a reflective coating on a
turning film 801 is shown. In some embodiments, the method begins
with providing a turning film 801 and forming turning features 820
on at least one surface of the turning film 801. In some
embodiments, a light guide may be provided and turning features 820
may be formed on the light guide using known methods. As shown in
FIG. 26C, in some embodiments, an interferometric stack 1707 is
deposited over the turning feature 820 side of the turning film
801. In certain embodiments, a reflective coating is applied
instead of an interferometric stack and a dark coating layer is
applied over the reflective coating. In some embodiments, a
dissolvable layer 2001 is then formed in a pattern covering certain
portions of the interferometric stack 1707 as shown in FIG. 26D. In
some embodiments, the dissolvable layer 2001 includes a photoresist
material. In certain embodiments, portions of the interferometric
stack 1707 that are not covered by the dissolvable layer 2001 are
removed. In some embodiments, the portions of the interferometric
stack 1707 that are not covered by the dissolvable layer 2001 are
etched away using known methods and the dissolvable layer 2001 is
then removed resulting in the embodiment shown in FIG. 26E. In some
embodiments, an additional layer 2101, for example, a passivation
layer or cover layer, may then be added over the turning film 801
and the interferometric stacks 1707. One of skill in the art will
understand that there are numerous methods and processes to form
reflective layers and/or interferometric stacks over turning
features or portions of turning features on a substrate layer.
[0159] FIG. 26G is a block diagram depicting a method 2620 of
manufacturing the illumination device shown in FIG. 26F, according
to one embodiment. Method 2620 includes the steps of providing a
turning film having a first side and a second side opposite the
first side at block 2621, etching turning features in the first
side at block 2623, depositing an interferometric stack over the
first side of the turning film at block 2625, depositing a
dissolvable layer over the sidewalls of the turning features at
block 2627, etching exposed portions of the interferometric stack
at block 2629, removing the dissolvable layer at block 2631, and
depositing a passivation layer over the turning film and turning
features at block 2633.
[0160] As discussed above, turning films and light guides can
comprise various materials. Light guides or turning films are
commonly formed by organic materials such as polymers or plastics.
Using plastics in the light guide and/or turning film, however, can
limit the mechanical, environmental, and/or chemical robustness of
an illumination device. Certain molded plastics, for example,
acrylics, polycarbonates, and cyclooelfin polymers, have low
scratch resistance, limited chemical resistance, and have limited
lifetime, as their optical properties can degrade from exposure to
environmental stress factors. In some cases, cleaning and/or
exposure to ultraviolet rays, temperature, and humidity, can cause
molded plastics to degrade over time. In some embodiments of the
invention, inorganic materials, for example, silicates and alumina,
can be used to form one or more layers of a display device to
increase the robustness of an illumination device. For example, in
some embodiments, a substrate, light guide, turning feature, or
other layers of the device can comprise an inorganic material. In
some embodiments, inorganic materials can also provide superior
optical properties, for example, higher transparency and higher
refractive indices, than those of organic materials. In some
embodiments, an inorganic turning film can be formed on an
inorganic light guide using the methods disclosed below.
[0161] Turning now to FIGS. 27A-27C, one embodiment of a method of
building an illumination device incorporating an inorganic light
guide and turning film is depicted. FIG. 27A shows an embodiment of
a light guide 803 comprising an inorganic material. In some
embodiments, the light guide 803 comprises an aluminosilicate or
sapphire. In some embodiments, a mixture of high purity silane
(SiH.sub.4 dilute in argon), nitrous oxide (N.sub.2O), and ammonia
(NH.sub.3) gases may be mixed to form an illumination device
comprising silicon oxy-nitride having a desired refractive index.
In some embodiments, the refractive index of the silicon
oxy-nitride can be adjusted to a desired level, for example, to
match the index of the light guide 803. In certain embodiments, the
refractive index of the silicon oxy-nitride can be adjusted to the
desired level by adjusting the N.sub.2O:NH.sub.3 molar ratio. In
one embodiment, the N.sub.2O:NH.sub.3 molar ratio may be adjusted
by controlling the flow rates of the respective gases. Example
refractive indices of materials used in some embodiments include
indices ranging from about 1.46 to about 2.05 as the
N.sub.2O:NH.sub.3 molar ratio increases from 0 to 100%.
[0162] Turning now to FIG. 27B, silicon oxy-nitride can be
deposited on the light guide 803 to form a turning film 801 which
can be configured with an index of refraction matched to that of
the light guide 803. In one embodiment, a silicon oxy-nitride
material can be deposited on the light guide 803 using plasma
enhanced chemical vapor deposition ("PECVD"). In some embodiments,
turning features 820 can then be formed in the surface of the
turning film 801 opposite the light guide 803, for example as
illustrated in FIG. 27C. In one embodiment, the turning features
820 can be etched to form sloped side-walls, for example using a
photolithographically patterned mask layer and a suitable wet or
dry etching method. Differently sized and shaped turning features
820 can be formed in the turning film 801 using various
manufacturing methods. In some embodiments, the shape formed by the
surface of a turning feature 820 may comprise a cone, a frustum of
a cone, a pyramid, a frustum of a pyramid, a prism, a polyhedron,
or another three-dimensional shape. In some embodiments, additional
coatings, for example, reflective coatings, interferometric stacks,
and/or dark coatings may be added over the turning features 820 or
portions of the turning features.
[0163] In some embodiments, an illumination device comprising an
inorganic light guide and turning film can be made using a sol-gel
precursor mixture to form the light turning film. In some
embodiments, the sol-gel precursor mixture can comprise
organosilicon and organotitanium compounds which, when combined,
form mixtures of silicon oxide and titanium dioxide. In some
embodiments, the index of refraction of the structure produced from
a sol-gel precursor mixture can be adjusted by adjusting the ratios
of the precursors and/or by applying heat treatment. In some
embodiments, the index of refraction of a structure produced from a
sol-gel precursor mixture can be adjusted to a level anywhere
between about 1.4 to about 2.4. In some embodiments, the light
guide can comprise glass (e.g., TFT substrate type or
aluminosilicate) having a refractive index of about 1.52. In other
embodiments, a light guide can comprise sapphire having a
refractive index of about 1.77. In some embodiments, a sol-gel
precursor mixture can comprise tetraethaoxysilane (TEOS or
tetraethyl orthosilicate), titanium isopropoxide, solvents, for
example, ethanol, isopropanol, or mixtures thereof, and can also
include one or more additives, for example, hydrochloric acid,
acetic acid, and titanium chloride.
[0164] In one embodiment, a sol-gel precursor mixture is formed by
hydrolyzing TEOS and titanium isopropoxide, at a ratio chosen to
match the refractive index of the light guide, along with
TiCl.sub.4 in an ethanol/IPA mixture with water at an acidic pH of
about 1 (which can be obtained, for example, by addition of HCl),
and aging the solution at about 40 C. In some embodiments, the
sol-gel precursor mixture can then be coated over the light guide.
In certain embodiments, turning features may be formed in the
sol-gel precursor mixture layer by pressing a mold onto the gelled
ceramic coating, ramping the temperature to increase cross-link
density, and drying at about 110 C. In some embodiments, the
turning film comprising the sol-gel mixture can be further
processed by densifying the sol-gel precursor mixture between about
600 C and about 800 C, so that the final refractive index of the
turning film matches the refractive index of the light guide.
[0165] FIG. 27D is a block diagram depicting a method 2720 of
manufacturing the illumination device shown in FIG. 27C, according
to one embodiment. Method 2720 includes the steps of providing a
light guide comprising an inorganic material, the light guide
having a known index of refraction at block 2721, mixing high
purity silane, nitrous oxide, and ammonia to create a silicon
oxy-nitride having the same index of refraction as the light guide
at block 2723, depositing the silicon oxy-nitride on one surface of
the light guide at block 2725, and etching turning features in the
silicon oxy-nitride layer at block 2727. FIG. 27E is a block
diagram depicting a method at block 2750 of manufacturing the
illumination device shown in FIG. 27C, according to one embodiment.
Method 2750 includes the steps of providing a light guide
comprising an inorganic material, the light guide having a known
index of refraction at block 2751, mixing organosilicon and
organotitanium compounds to form a sol-gel precursor having the
same index of refraction as the light guide at block 2753,
depositing the sol-gel precursor on one surface of the light guide
at block 2755, and molding turning features in the sol-gel
precursor layer at block 2757.
[0166] Turning now to FIG. 28, a cross-sectional view of an
embodiment of a turning film 801 is depicted. In some embodiments,
the turning film 801 comprises silicon oxy-nitride and includes one
or more turning feature 820. In some embodiments, the one or more
turning features 820 can be formed by an etching process. In one
embodiment, the etching process uses an etching gas comprising a
mixture of SiON etchant, for example, CF.sub.4, and a mask material
etchant, for example, O.sub.2 for photoresist. In some embodiments,
the silicon oxy-nitride is pulled back from its initial profile
2801 as it is removed during etching, resulting in one or more
light turning features 820 with tapered side walls. In some
embodiments, the turning film 801 can be disposed on a light guide
803. In some embodiments, the turning film 801 can have an index of
refraction that is, or is about, the same as the index of
refraction of the light guide 803. In some embodiments, a
reflective layer (not shown), an interferometric stack (not shown),
and/or a black or dark coating (not shown) can be disposed over
portions of the turning film 801 including portions of the turning
features 820.
[0167] As indicated herein, in some embodiments turning films can
include turning features having curvilinear cross-sectional shapes.
In the absence of curved edges or sidewalls, each edge extracts
light and produces an emission cone based on the collimation of the
light propagating in the turning film. Turning features with curved
edges can be configured to adjust the angular width of the
illumination cone of light produced by the turning features. Thus,
curved edges can be configured to focus (e.g., reduce the angular
width of the emission cone) or to disperse (e.g., increase the
angular width of the emission cone) light propagating inside the
turning film. These configurations can allow for the optimization
of the emission properties of the turning film for a variety of
input light sources and other geometrical constraints.
[0168] Adjusting (e.g., increasing or decreasing) the angular width
of the illumination cone can enable embodiments of displays to have
thinner front lights by abrogating the need for a diffusing
isolation layer that is sometimes used to produce a uniform
display. Additionally, in some embodiments, turning features having
curved edges can be placed farther apart from one another than
turning features with straight edges because each curved turning
feature illuminates a larger area of the display due to the
increased width of the illumination cone. Turning films configured
with increased spatial separation between light turning features
can also be configured such that the thickness of the turning film
is decreased.
[0169] FIG. 29A illustrates a cross-sectional view of one
embodiment of a turning film 2901a that includes a turning feature
2920a. The turning film 2901a is illustrated with an x-axis
extending generally parallel to a bottom surface of the turning
film, a z-axis extending generally normal to the bottom surface and
a top surface of the turning film, and a y-axis extending generally
normal to the x-axis and z-axis. Turning feature 2920a is v-shaped
and includes a left edge 2921a and a right edge 2923a configured to
direct light towards the bottom of the turning film 2901a. Also
shown is a first ray of light 2911a and a second ray of light
2911a'. Both light rays 2911a, 2911a' are propagating within the
turning film 2901a at the same angle relative to the top and bottom
of the turning film and the light rays 2911a, 2911a' are offset or
spaced apart from one another. Because the left edge 2921a of the
turning feature 2920a is at a constant angle relative to the top of
the turning film 2901a, the light rays 2911a, 2911a' reflect off of
the left edge 2921a at the same angle towards the bottom of the
turning film 2901a (in this illustration, downward). Thus, the
illumination cone of light produced by the turning feature 2920a is
collimated (e.g., the rays of light that form the cone are
substantially parallel to one another) as the light travels away
from the turning feature 2920a. While only the cross-section of the
prismatic turning feature 2920a is shown in FIG. 29A, it should be
understood by those of skill in the art that the in-plane
distribution of the light turning features disclosed herein can be
linear, curvilinear, etc., so that a variety of front light
configurations can be implemented, for example, light bar sources
or LED sources.
[0170] FIG. 29B illustrates a cross-sectional view of another
embodiment of a turning film 2901b that includes a turning feature
2920b. Turning feature 2920b includes a left curved edge 2921b and
a right curved edge 2923b. Edges 2921b, 2923b form a turning
feature 2920b that is concave relative to the turning film 2901b.
Curved edges 2921b, 2923b can be disposed in the turning film in
one or more planes that are at least substantially parallel to the
illustrated x-z plane of the turning film. Also shown are rays of
light 2911b, 2911b' that are propagating within the turning film
2901b at the same angles relative to the top and bottom of the
turning film. The rays 2911b, 2911b' are directed away from one
another after reflecting off of the left edge 2921b because the
edge is curved. Thus, the curved turning feature 2920b can create
an illumination cone of light with an angular width that is greater
than the cone of light produced by the turning feature 2920a shown
in FIG. 29A (e.g., an illumination cone of light that is not
collimated).
[0171] FIG. 29C illustrates a cross-sectional view of another
embodiment of a turning film 2901c that includes a turning feature
2920c. Turning feature 2920c includes a left curved edge 2921c and
a right curved edge 2923c. Edges 2921c, 2923c form a turning
feature 2920c that is convex relative to the turning film 2901c.
Curved edges 2921c, 2923c can be disposed in the turning film in
one or more planes that are at least substantially parallel to the
illustrated x-z plane of the turning film. Rays of light 2911c,
2911c' are directed away from one another after reflecting off the
left edge 2921c because the edge is curved. Similarly to the
turning feature illustrated in FIG. 29B, this results in an
illumination cone of light that has an angular width that is
greater than the cone of light produced by the turning feature
2920a shown in FIG. 29A (e.g., an illumination cone of light that
is not collimated).
[0172] FIG. 29D illustrates a cross-sectional view of another
embodiment of a turning film 2901d that includes a turning feature
2920d. Turning feature 2920d includes a left curved edge 2921d and
a right curved edge 2923d. Turning feature 2920d also includes a
substantially straight edge 2925d between the left and right edges
and disposed substantially parallel to the top and bottom of the
turning film. Edges 2921d, 2923d, and 2925d form a turning feature
2920d with sidewalls that are convex relative to the turning film
2901d and disposed in the turning film in one or more planes that
are at least substantially parallel to the illustrated x-z plane of
the turning film. Rays of light 2911d, 2911d' are directed away
from one another after reflecting off the left edge 2921d because
the edge is curved. Similarly to the turning features illustrated
in FIGS. 29B and 29C this results in an illumination cone of light
that has an angular width that is greater than the cone of light
produced by the turning feature 2920a shown in FIG. 29A (e.g., an
illumination cone of light that is not collimated).
[0173] FIG. 29E illustrates a cross-sectional view of another
embodiment of a turning film 2901e that includes a turning feature
2920e. Turning feature 2920e includes a left curved edge 2921e and
a right curved edge 2923e. Turning feature 2920e also includes a
substantially straight edge 2925e between the left and right edges
and disposed substantially parallel to the top and bottom of the
turning film. Edges 2921e, 2923e, and 2925e form a turning feature
2920e with sidewalls that are concave relative to the turning film
2901e and disposed in the turning film in one or more planes that
are at least substantially parallel to the illustrated x-z plane of
the turning film. Rays of light 2911e, 2911e' are directed away
from one another after reflecting off the left edge 2921e because
the edge is curved. Similarly to the turning features illustrated
in FIGS. 29B and 29C this results in an illumination cone of light
that has an angular width that is greater than the cone of light
produced by the turning feature 2920a shown in FIG. 29A (e.g., an
illumination cone of light that is not collimated).
[0174] FIG. 29F illustrates a perspective view of the turning
feature 2920d of FIG. 29D. The surfaces of the turning feature
2920d form a truncated curvilinear shape or frustum having
sidewalls that are concave relative to the space adjacent the
turning feature. FIG. 29G illustrates a perspective view of the
turning feature 2920e of FIG. 29E. The surfaces of the turning
feature 2920e form a truncated curvilinear shape or frustum having
sidewalls that are convex relative to the space adjacent the
turning feature.
[0175] As discussed above, turning features can be coated with
reflective layers or coatings to provide desirable optical
characteristics and additional layers can be deposited over the
reflective coating to prevent the reflection of light from the
reflective coating towards a viewer. In some embodiments,
additional layers can be deposited over the reflective coating to
form a static interferometric stack, or optical mask, that appears
dark or black to a viewer in order to improve the contrast of the
display device while reflecting light incident on the reflective
coating side of the stack towards a reflective display. FIGS.
30A-30D illustrate embodiments of turning features 3020 that have
curved sidewalls or edges 3021, 3023 with reflective coatings 3003
deposited over the curved sidewalls. An optically resonant layer
3005 and absorber layer 3007 can optionally be deposited over the
reflective coating 3003 to form an interferometric stack 3009. The
interferometric stacks 3009 can be configured such that the
absorber layers 3007 absorb light of the reflected wavelength such
that the stack 3009 appears black or dark, which can increase the
contrast of the display. As discussed above, the reflective
coatings 3003 and/or interferometric stacks 3009 can be disposed
over only a portion or portions of the surface of a turning feature
3020 or they can be disposed over the entire surface of a turning
feature.
[0176] In some instances, frustum shaped turning features similar
to turning feature 2920d of FIG. 29F and turning feature 2920e of
FIG. 29G can be easier to manufacture or produce than the turning
features shown in FIGS. 29B and 29C which do not have flat bottom
edges. All of the turning features discussed herein can be
manufactured, fabricated, or produced using plastic molding or by
using the inorganic material system deposition and etching
techniques discussed above. In some embodiments, a thin film front
light can be manufactured using known film embossing techniques,
for example hot or UV embossing, using a master mold tool produced
by diamond turning techniques. A diamond tool can be machined so
that its tip has a curved-wall cross-section and can be used to cut
into a substrate (e.g., metals or alloys based on copper or nickel)
to fabricate a mold with the desired curved sidewall grooves. In
another example of making master tools, photolithography and
etching techniques can be used to produce wafers with desired
surface topography. Photolithography and etching can be used to
produce a light guide by producing one or more turning features
directly in a substrate, or such techniques can be used to produce
a surface relief that can be used to produce turning films. By
properly designing the lithography mask, turning features with
concave and/or convex sidewalls or edges can be produced. For
example, an etchant can be chosen that etches the photoresist
material and another layer of material in order to control the
curvature of the etching.
[0177] FIGS. 31A-31E illustrate one example of a process for
fabricating a turning film or light guide including convex turning
features. As shown in FIG. 31A, a process for fabricating a turning
film or light guide can begin by providing a substrate 3101. In
some embodiments, the substrate 3101 comprises silicon or silicon
dioxide. With reference to FIG. 31B, a layer of material 3103 can
then be deposited on the substrate. As discussed below, the layer
of material 3103 can later be etched and can comprise, for example,
silicon oxy-nitride, aluminum, and other suitable materials.
[0178] Referring now to FIG. 31C, the layer of material 3103 can
then be coated with a photoresist 3105. After coating the layer of
material 3103, the photoresist 3105 can be exposed and patterned
through a specially designed photolithographic mask and developed
to leave portions of the coat of photoresist 3105 on the layer of
material 3103. Turning now to FIG. 31D, the layer of material 3103
can then be etched to produce curved sidewalls or edges. The
etching process can be controlled to pull-back or etch certain
portions of the photoresist in addition to the material 3103 to
produce curved sidewalls (edges). For example, the material 3103
can be etched isotropically or with a combination of isotropic with
anisotropic etching for tailoring the curved shape of the
sidewalls. After etching, the photoresist layer can be removed
resulting in a light guide or a surface relief that can be used to
manufacture a turning film. When manufacturing a turning film, the
surface relief can be electroplated to produce a mold that can be
used to manufacture turning films that match the surface relief. As
shown in FIG. 31E, with the surface relief replicated, a front
light turning film 3110 including convex turning features 3120 can
be tooled and embossed.
[0179] FIGS. 32A-32E illustrate one example of a process for
fabricating a turning film including concave turning features. As
shown in FIG. 32A, a process for fabricating a turning film can
begin by providing a substrate 3201. In some embodiments, the
substrate 3201 comprises silicon or silicon dioxide. With reference
to FIG. 32B, a layer of material 3203 can then be deposited on the
substrate. As discussed below, the layer of material 3203 can later
be etched and can comprise, for example, silicon dioxide, aluminum,
silicon nitride, and other suitable materials.
[0180] Referring now to FIG. 32C, the layer of material 3203 can
then be coated with a photoresist 3205. After coating the layer of
material 3203, the photoresist 3205 can be exposed through a
specially designed photolithographic mask and developed to leave
portions of the coat of photoresist 3205 on the layer of material
3203. Turning now to FIG. 32D, the layer of material 3203 can then
be etched to produce curved sidewalls or edges. In some
embodiments, the material 3203 can be etched isotropically or with
a combination of isotropic with anisotropic etching for tailoring
the curved shape of the sidewalls. After etching, the photoresist
layer can be removed and the surface relief can be replicated by
electroforming the surface. As shown in FIG. 32E, with the surface
relief replicated, a front light film 3210 including a convex
turning feature 3220 can be tooled and embossed.
[0181] The foregoing description details certain embodiments of the
invention. It will be appreciated, however, that no matter how
detailed the foregoing appears in text, the invention can be
practiced in many ways. As is also stated above, it should be noted
that the use of particular terminology when describing certain
features or aspects of the invention should not be taken to imply
that the terminology is being re-defined herein to be restricted to
including any specific characteristics of the features or aspects
of the invention with which that terminology is associated. The
scope of the invention should therefore be construed in accordance
with the appended claims and any equivalents thereof.
* * * * *