U.S. patent application number 14/203630 was filed with the patent office on 2014-09-11 for method of fabricating a liquid crystal polymer film.
This patent application is currently assigned to U.S. Government as Represented by the Secretary of the Army. The applicant listed for this patent is U.S. Government as Represented by the Secretary of the Army. Invention is credited to Brian R. Kimball, Sarik R. Nersisyan, Diane M. Steeves, Nelson V. Tabirian, Rafael O. Vergara.
Application Number | 20140252666 14/203630 |
Document ID | / |
Family ID | 51486896 |
Filed Date | 2014-09-11 |
United States Patent
Application |
20140252666 |
Kind Code |
A1 |
Tabirian; Nelson V. ; et
al. |
September 11, 2014 |
METHOD OF FABRICATING A LIQUID CRYSTAL POLYMER FILM
Abstract
A method of fabricating a liquid crystal polymer film includes
providing a support substrate having a surface having a shape
arranged to define a form of a liquid crystal polymer film to be
fabricated; applying a layer of a photoaligning material over the
surface of the support substrate, the photoaligning material having
an absorption band; exposing the layer of photoaligning material to
a light having a linear polarization and the light comprising a
wavelength within the absorption band to convert the layer of
photoaligning material into a layer of photoaligned material;
applying a layer of a polymerizable liquid crystal over the layer
of photoaligned material; performing photopolymerization of the
layer of polymerizable liquid crystal to form a liquid crystal
polymer film; applying a solvent to the layer of photoaligned
material, the solvent formulated to dissolve the photoaligned
material to thereby release the liquid crystal polymer film from
the support substrate; and removing the liquid crystal polymer film
from the support substrate.
Inventors: |
Tabirian; Nelson V.; (Winter
Park, FL) ; Nersisyan; Sarik R.; (Winter Park,
FL) ; Kimball; Brian R.; (Shrewsbury, MA) ;
Steeves; Diane M.; (Franklin, MA) ; Vergara; Rafael
O.; (Winter Park, FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
U.S. Government as Represented by the Secretary of the
Army |
Natick |
MA |
US |
|
|
Assignee: |
U.S. Government as Represented by
the Secretary of the Army
Natick
MA
|
Family ID: |
51486896 |
Appl. No.: |
14/203630 |
Filed: |
March 11, 2014 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61775899 |
Mar 11, 2013 |
|
|
|
Current U.S.
Class: |
264/1.34 ;
534/577 |
Current CPC
Class: |
C09K 2219/03 20130101;
G02F 1/133711 20130101; B29D 11/00788 20130101; C07C 245/08
20130101; C09B 33/044 20130101; C09K 19/56 20130101; G02F 1/133788
20130101; C09K 19/601 20130101 |
Class at
Publication: |
264/1.34 ;
534/577 |
International
Class: |
B29D 11/00 20060101
B29D011/00; C07C 245/10 20060101 C07C245/10 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] This invention was made with Government support under
Contract No. W911QY-12-C-0016.
RIGHTS OF THE GOVERNMENT
[0003] The invention described herein may be manufactured and used
by or for the Government of the United States for all governmental
purposes without the payment of any royalty.
Claims
1. A method of fabricating a liquid crystal polymer film, the
method comprising: (a) providing a support substrate having a
surface having a shape arranged to define a form of a liquid
crystal polymer film to be fabricated; (b) applying a layer of a
photoaligning material over said surface of said support substrate,
said photoaligning material having an absorption band; (c) exposing
said layer of photoaligning material to a light having a linear
polarization and said light comprising a wavelength within said
absorption band to convert said layer of photoaligning material
into a layer of photoaligned material; (d) applying a layer of a
polymerizable liquid crystal over said layer of photoaligned
material; (e) performing photopolymerization of said layer of
polymerizable liquid crystal to form a liquid crystal polymer film;
(f) applying a solvent to said layer of photoaligned material, said
solvent formulated to dissolve said photoaligned material to
thereby release said liquid crystal polymer film from said support
substrate; and (g) removing said liquid crystal polymer film from
said support substrate.
2. A method as claimed in claim 1, wherein said photoaligning
material has a molecular structure comprising at least one
photoresponsive compound.
3. A method as claimed in claim 2, wherein said at least one
photoresponsive compound is one of azobenzene, stilbene, azoxy,
azomethine, fulgide and diarylethene.
4. A method as claimed in claim 1, wherein said photoaligning
material has a molecular structure comprising at least one
functional group for solubility in a polar solvent.
5. A method as claimed in claim 4, wherein said at least one
functional group is a sulfo group.
6. A method as claimed in claim 1, wherein the method comprises,
before exposing said layer of photoaligning material to said light,
spatially modulating said linear polarization of said light.
7. A method as claimed in claim 6, wherein said linear polarization
of said light is spatially modulated with one of a one-dimensional
polarization pattern and a two-dimensional polarization
pattern.
8. A method as claimed in claim 6, wherein said linear polarization
of said light is spatially modulated by transmitting said light
through one of a cycloidal diffractive waveplate, a vector vortex
waveplate, and an array of vector vortex waveplates.
9. A method as claimed in claim 1, wherein said solvent is a polar
solvent.
10. A method as claimed in claim 1, wherein said solvent is one of
water, Dimethylformamide, and a low molecular weight alcohol.
11. A method as claimed in claim 1, wherein after step (e) the
method comprises attaching said liquid crystal polymer film to a
carrier substrate, and where step (g) comprises removing said
liquid crystal polymer film on said carrier substrate from said
support substrate.
12. A method as claimed in claim 11, wherein said liquid crystal
polymer film is attached to said carrier substrate by applying a
layer of an adhesive onto said liquid crystal polymer film and
performing photopolymerization of said layer of said adhesive to
form said carrier substrate.
13. A method as claimed in claim 11, wherein said carrier substrate
is a polymer film which is thicker and stronger than said liquid
crystal polymer film.
14. A method as claimed in claim 11, wherein said liquid crystal
polymer film is attached to said carrier substrate by: a. applying
a layer of an adhesive onto said carrier substrate; b. bringing
said support substrate and said carrier substrate together to bring
said adhesive into contact with said liquid crystal polymer film;
and c. curing said adhesive.
15. A method as claimed in claim 1, wherein after step (e) the
method comprises adhering the liquid crystal polymer film to a
second support substrate and the method further comprises, after
step (g): a. providing a third support substrate carrying a second
layer of a photoaligned material and having a second liquid crystal
polymer film, different to the first liquid crystal polymer film,
provided over said second layer of a photoaligned material; and b.
applying a solvent to said second layer of a photoaligned material,
said solvent formulated to dissolve said photoaligned material to
thereby release said second liquid crystal polymer film from said
third support substrate.
16. A method as claimed in claim 15, wherein said first liquid
crystal polymer film has a first alignment pattern and said second
liquid crystal polymer film has a second alignment pattern, said
second alignment pattern being one of a different pattern to said
first alignment pattern and a different orientation to said first
alignment pattern.
17. A method as claimed in claim 1, wherein said support substrate
is a first mold segment and step (a) further comprises providing a
second mold segment having a surface having a shape arranged to
cooperate with said surface of said first mold segment, said
surfaces of said first and second mold segments together defining a
cavity defining said shape of said liquid crystal polymer film and
wherein step (d) comprises arranging said first and second mold
segments together to form said cavity and filling said cavity with
said polymerizable liquid crystal.
18. A method as claimed in claim 17, wherein step (b) further
comprises applying a layer of said photoaligning material over said
surface of said second mold segment and step (c) comprises exposing
both said layers of photoaligning material to a light having a
linear polarization and said light comprising a wavelength within
said absorption band to convert each said layer of photoaligning
material into a layer of photoaligned material.
19. A method as claimed in claim 17, wherein step (b) further
comprises applying a layer of said photoaligning material over said
surface of said second mold segment and step (c) comprises exposing
said layer of photoaligning material on said first mold segment to
a first linearly polarized light having a first polarization
spatial modulation and exposing said layer of photoaligning
material on said second mold segment to a second linearly polarized
light having a second polarization spatial modulation, different to
said first polarization spatial modulation, each said linearly
polarized light comprising a wavelength within said absorption band
to convert each said layer of photoaligning material into a
respective layer of photoaligned material.
20. A method as claimed in claim 1, wherein said polymerizable
liquid crystal comprises functional groups, copolymers and
additives to control its optical, electro-optical, mechanical,
thermodynamic, and chemical properties.
21. A liquid crystal polymer release material having a molecular
structure comprising: a first functional group characterised for
photoalignment of liquid crystal materials; a second functional
group characterised for solubility in a polar solvent; and a third
functional group characterised for adhesion to a substrate
material.
22. A liquid crystal polymer release material as claimed in claim
21, wherein said first functional group is a photoresponsive
compound.
23. A liquid crystal polymer release material as claimed in claim
21, wherein said first functional group is one of Azobenzene,
Stilbene, Azoxy, Azomethine, Fulgide and Diarylethene.
24. A liquid crystal polymer release material as claimed in claim
21, wherein said second functional group is a sulfo group.
25. A liquid crystal polymer release material as claimed in claim
21, wherein said second functional group is characterised for
solubility in one of water, Dimethylformamide, and a low molecular
weight alcohol.
26. A liquid crystal polymer release material as claimed in claim
21, wherein said substrate material is an optical substrate.
27. A liquid crystal polymer release material as claimed in claim
21, wherein said substrate material is one of glass, polycarbonate,
fused silica, Zinc selenide and Barium fluoride.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application No. 61/775,899, filed Mar. 11, 2013, and which is
hereby incorporated by reference.
TECHNICAL FIELD
[0004] The invention relates to a method of fabricating a liquid
crystal polymer film. The field of applications of liquid crystal
polymer films includes, for example, variable transmission lenses,
flexible displays, laser beam steering and positioning systems,
patterned phase-retardation films, diffractive waveplates, and
polarization holograms.
BACKGROUND
[0005] Application of polymers in optical technologies is expanding
due to low cost manufacturing, improved quality, and small weight.
Polymers bring new qualities and opportunities in optical devices
such as mechanical flexibility. Liquid crystal polymers, LCPs, have
made it possible to inexpensively transform conventional liquid
crystal displays, LCDs, into three-dimensional displays by
application of half-wave phase retardation films with patterned
optical axis orientation. Azobenzene polymer films have been used
as optically deformable membrane mirrors.
[0006] Polymer optical components such as lenses are often
fabricated by molding, and need to be released from the mold used
for shaping them. Certain optical components such as phase
retardation films and polarizers do not require molding into a
complex shape, however they still need to be fabricated on a
variety of substrates for mechanical stability and need releasing
from their support substrates for transfer onto the devices and
components they are designed for. A typical LCD, for example,
comprises both a phase retardation film, for viewing angle
enhancement, and polarizers, for contrast. Fabrication of polymer
optical components in the form of coatings directly on the
substrate they are intended for may be prohibited by technological
and cost limitations.
[0007] The manufacturer of a final product often lacks the
expertise, capability, resources and commercial incentives for
expanding their manufacturing processes to all component materials.
Just like computer manufacturers use processors and displays
developed and produced by other companies, the LCD manufacturers
use phase-retardation films and polarizers produced by specialized
suppliers. Apart from those considerations, many of the substrates
for polymer optics, such as those used for flexible displays, are
not compatible with the organic solvents and processes used for
their fabrication thus also requiring separate film fabrication,
release and transfer techniques.
SUMMARY
[0008] The variety of materials and techniques developed for
releasing polymer optics from their molds or substrates did not
address the specifics and requirements of the class of polymer
optics comprising liquid crystal polymers in the prior art, some
examples of them are cited in the cross-references. LCPs are
typically used for fabricating optical films with spatial
modulation of optical axis orientation, such as vector vortex
waveplates, cycloidal diffractive waveplates and polarization
gratings, as discussed in N. V. Tabiryan, S. R. Nersisyan, D. M.
Steeves and B. R. Kimball, "The Promise of Diffractive Waveplates",
Optics and Photonics News, volume 21, number 3, pages 41-45, 2010.
The orientation of molecules in LCPs is often coupled with the
shape and form of the polymer film.
[0009] Thus, in the case of LCPs, substrates are can be needed not
only for providing a form or support, but also for inducing the
local orientation direction for the LCP molecules. This is achieved
by coating the substrate, typically glass, with so-called alignment
layer capable of producing anisotropic boundary conditions for the
molecules of the polymerizable liquid crystal, LC.
[0010] The anisotropy axis that determines the orientation
direction of LC molecules is typically created by mechanically
buffing the alignment film. Buffing creates nano/microgrooves in
the alignment materials such as a polyimide. An alternative to
mechanical buffing is the photoalignment technique, which offers
the advantages of being a non-contact method, and allowing complex
orientation patterns to be achieved. It is based on coatings that
produce an anisotropy axis under the influence of a linear
polarized light. Certain azobenzene dyes, including sulfonic
bisazodyes are well suited for the photoalignment technique
reported by S. R. Nersisyan, N. V. Tabiryan, D. M. Steeves, B. R.
Kimball, V. G. Chigrinov, and H.-S. Kwok, "Study of azo dye surface
command photoalignment material for photonics applications",
Applied Optics, volume 49, number 10, pages 1720-1727, 2010. Due to
absorption dichroism, highly efficient photoisomerization processes
drive the azobenzene dyes to align perpendicular to the
polarization direction of the light. Even a few nanometer thin
films of thus photoaligned azobenzene dyes create anisotropic
boundary conditions strong enough for alignment of LCP layers
deposited on them.
[0011] Thus, the substrates used for fabrication of LCP optical
structures, such as waveplates, and mirrors, etc., preferably
should be able to carry an alignment layer that fulfilling one or
more of the following: compatibility with the substrate, so that no
deterioration of the optical qualities of the substrate occurs in
the process of subjecting the substrate to the organic solvents
used for coating the alignment material (this is a particular issue
for flexible polymer substrates and polycarbonate); capability of
producing a homogeneous thin film coating on a substrate; ability
to provide adequate physical adhesion to the substrate; capability
of creating anisotropic boundary conditions for a LC controlled by
external influences; ability to exhibit strong orienting action on
the LC; and the ability to withstand the fabrication process
conditions of the LCP film and the component.
[0012] Naturally, the alignment materials that meet the
requirements listed above are rather unique and have undergone
decades of development. This is particularly true for
photoalignment materials due to the complex processes involving
their interaction both with light and with LCs. Incorporating a
release film for LCPs may introduce a myriad of new variables in
the fabrication process of LCP optics. To avoid it, in some cases,
it was preferred to fabricate the LCP using known materials and
processes and then dissolve the substrates in hazardous solvents
rather than to try adapting a release film to the process.
Mechanical stresses applied when separating LCP films from
substrates without proper release layers affect their optical
quality and the optical modulation patterns, and compromise the
mechanical integrity of the LCP films, that, for example, are only
a few micrometer thick in case of waveplates.
[0013] It is an object of the present invention to provide an
improved method of fabricating a liquid crystal polymer film. It is
a further object of the present invention to provide an improved
liquid crystal polymer release material.
[0014] A first aspect of the invention provides a method of
fabricating a liquid crystal polymer film. The method comprises
steps (a) to (g). Step (a) comprises providing a support substrate
having a surface having a shape arranged to define a form of a
liquid crystal polymer film to be fabricated. Step (b) comprises
applying a layer of a photoaligning material over said surface of
said support substrate. Said photoaligning material has an
absorption band. Step (c) comprises exposing said layer of
photoaligning material to a light having a linear polarization and
said light comprising a wavelength within said absorption band.
Exposing said layer of photoaligning material to the light converts
the layer of photoaligning material into a layer of photoaligned
material. Step (d) comprises applying a layer of a polymerizable
liquid crystal over said layer of photoaligned material. Step (e)
comprises performing photopolymerization of said layer of
polymerizable liquid crystal to form a liquid crystal polymer film.
Step (f) comprises applying a solvent to said layer of photoaligned
material. Said solvent is formulated to dissolve said photoaligned
material, to thereby release said liquid crystal polymer film from
said support substrate. Step (g) comprises removing said liquid
crystal polymer film from said support substrate.
[0015] The photoaligned material layer may both perform alignment
of the polymerisable liquid crystal and act as a release layer for
the liquid crystal polymer, LCP, film from the substrate. The
method may thus enable fabrication of a LCP film using materials
that combine photoalignment capability with LCP release function.
The method may enable non-contact release of LCPs from substrates
without affecting their optical quality and alignment properties.
The method may enable LCPs to be released from a support substrate
while maintaining their mechanical and optical characteristics and
without a direct physical influence or a mechanical stress. The
method may enable the release of LCPs onto substrates made of
materials that are not suitable for direct fabrication of LCP
optical components due to poor chemical resistivity to solvents
involved in the process and/or poor mechanical strength. The method
may enable LCP films to be provided on substrates of complex shape,
such as lenses.
[0016] In an embodiment, said photoaligning material has a
molecular structure comprising at least one photoresponsive
compound. The photoresponsive compound may ensure that the
photoaligning material is able to provide photoalignment for liquid
crystal molecules including monomers.
[0017] In an embodiment, said at least one photoresponsive compound
is one of azobenzene, stilbene, azoxy, azomethine, fulgide and
diarylethene. Use of the identified photoresponsive compounds may
ensure that the photoaligning material is able to provide
photoalignment for liquid crystal molecules including monomers.
[0018] In an embodiment, said solvent is a polar solvent and said
photoaligning material has a molecular structure comprising at
least one functional group for solubility in a polar solvent. In an
embodiment, said solvent is one of water, Dimethylformamide, and a
low molecular weight alcohol.
[0019] In an embodiment, said at least one functional group is a
sulfo group. This may provide adhesion of the photoaligning
material to the support substrate.
[0020] In an embodiment, said support substrate is chemically
resistant to said solvent. This may ensure that the support
substrate does not deteriorate during the fabrication of the LCP
film.
[0021] In an embodiment, the method comprises, before exposing said
layer of photoaligning material to said light, spatially modulating
said linear polarization of said light. This may enable complex
alignment patterns, and thus complex orientation patterns in the
LCP film, to be produced.
[0022] In an embodiment, said linear polarization of said light is
spatially modulated by transmitting said light through a spatial
light polarization modulator. This may enable complex alignment
patterns, and thus complex orientation patterns in the LCP film, to
be produced.
[0023] In an embodiment, said spatial light polarization modulator
is configured to apply one of a one-dimensional polarization
pattern and a two-dimensional polarization pattern.
[0024] In an embodiment, said linear polarization of said light is
spatially modulated with one of a one-dimensional polarization
pattern and a two-dimensional polarization pattern.
[0025] In an embodiment, said linear polarization of said light is
spatially modulated by transmitting said light through one of a
cycloidal diffractive waveplate, a vector vortex waveplate, and an
array of vector vortex waveplates. This may enable complex
alignment patterns, and thus complex orientation patterns in the
LCP film, to be produced.
[0026] In an embodiment, said photoaligned material is insoluble in
at least one of hexanes, cyclohexane, ketones such as
cyclopenthanone, and esthers such as Propylene glycol monomethyl
ether acetate, PGMEA. The photoaligned material is therefore
insoluble in many organic solvents often used for polymerizable
liquid crystals.
[0027] In an embodiment, after step (e) the method comprises
attaching said liquid crystal polymer film to a carrier substrate.
Step (g) comprises removing said liquid crystal polymer film on
said carrier substrate from said support substrate. The method may
enable the LCP film to be fabricated on one substrate, typically
made of mechanically strong and chemically resistant materials,
onto a substrate which may be difficult to handle or otherwise not
compatible with the LCP fabrication process due to wettability,
temperature, solvents, or a complex shape and surface topology.
[0028] In an embodiment, said liquid crystal polymer film is
attached to said carrier substrate by applying a layer of an
adhesive onto said liquid crystal polymer film and performing
photopolymerization of said layer of said adhesive to form said
carrier substrate. This may enable the LCP film to be attached to a
carrier substrate without any mechanical stress being applied to
the LCP film, which may reduce risk of damage to the LCP film
during the attachment process.
[0029] In an embodiment, said carrier substrate is a polymer film
which is thicker and stronger than said liquid crystal polymer
film. Such a carrier substrate may act as a support backbone for
the LCP film.
[0030] In an embodiment, said liquid crystal polymer film is
attached to said carrier substrate by applying a layer of an
adhesive onto said carrier substrate, and then bringing said
support substrate and said carrier substrate together to bring said
adhesive into contact with said liquid crystal polymer film. Said
adhesive is then cured. This may enable the LCP film to be attached
to a more substantial carrier substrate still without any
mechanical stress being applied to the LCP film, which may reduce
risk of damage to the LCP film during the attachment process.
[0031] In an embodiment, after step (e) the method comprises
adhering the liquid crystal polymer film to a second support
substrate. The method further comprises performing additional steps
a. and b. after step (g). Step a. comprises providing a third
support substrate carrying a second layer of a photoaligned
material. The third support substrate has a second liquid crystal
polymer film, different to the first liquid crystal polymer film,
provided over said second layer of a photoaligned material. Step b.
comprises applying a solvent to said second layer of a photoaligned
material. Said solvent is formulated to dissolve said photoaligned
material to thereby release said second liquid crystal polymer film
from said third support substrate. A support substrate carrying two
overlaid LCP films may therefore be formed, which may enable a
composite LCP film having a varying or more complex orientation
pattern to be formed.
[0032] In an embodiment, said first liquid crystal polymer film has
a first alignment pattern and said second liquid crystal polymer
film has a second alignment pattern. Said second alignment pattern
is one of a different pattern to the first alignment pattern and a
different orientation to said first alignment pattern. A support
substrate carrying two overlaid LCP films may therefore be formed,
which may enable a composite LCP film having a varying or more
complex orientation pattern to be formed. A composite LCP film may
be formed in this way in which the two alignment patterns have
mutually perpendicular orientation patterns, to thereby produce a
photonic bandgap structure described in H. Sarkissian, B.
Zeldovich, N. Tabiryan, "Longitudinally modulated bandgap nematic
structure", JOSA B 23, 1712-1717, 2006.
[0033] In an embodiment, said support substrate is a first mold
segment and step (a) further comprises providing a second mold
segment. The second mold segment has a surface which has a shape
arranged to cooperate with said surface of said first mold segment.
Said surfaces of said first and second mold segments together
define a cavity which defines said shape of said liquid crystal
polymer film to be fabricated. Step (d) comprises arranging said
first and second mold segments together to form said cavity and
then filling said cavity with said polymerizable liquid crystal.
This may enable LCP films having a complex, non-planar shapes, such
as a spherical lens, to be formed.
[0034] In an embodiment, step (b) further comprises applying a
layer of said photoaligning material over said surface of said
second mold segment. Step (c) comprises exposing both said layers
of photoaligning material to a light having a linear polarization
and said light comprising a wavelength within said absorption band
to convert each said layer of photoaligning material into a layer
of photoaligned material.
[0035] In an embodiment, step (b) further comprises applying a
layer of said photoaligning material over said surface of said
second mold segment. Step (c) comprises exposing said layer of
photoaligning material on said first mold segment to a first
linearly polarized light having a first polarization spatial
modulation. Step (c) additionally comprises exposing said layer of
photoaligning material on said second mold segment to a second
linearly polarized light having a second polarization spatial
modulation, different to said first polarization spatial
modulation. Each said linearly polarized light comprises a
wavelength within said absorption band to convert each said layer
of photoaligning material into a respective layer of photoaligned
material.
[0036] In an embodiment, said absorption band comprises a
wavelength in the ultra-violet, UV, or visible part of the optical
spectrum.
[0037] In an embodiment, step (c) comprises providing an exposure
dose of said light in dependence on at least one of a
characteristic of said photoaligning material and a wavelength of
said light.
[0038] In an embodiment, step (b) comprises applying said
photoaligning material over said surface of said support substrate
by one of dip coating, printing, stamping and spin coating. This
may ensure that the resulting photoalignment layer has a thickness
capable of being effectively dissolved in said solvent,
particularly water.
[0039] In an embodiment, step (d) comprises applying said layer of
said polymerizable liquid crystal by spin coating.
[0040] In an embodiment, said polymerizable liquid crystal
comprises functional groups, copolymers and additives to control
its optical, electro-optical, mechanical, thermodynamic, and
chemical properties.
[0041] A second aspect of the invention provides a liquid crystal
polymer release material comprising a first functional group, a
second functional group and a third functional group. The first
functional group is characterised for photoalignment of liquid
crystal materials. The second functional group is characterised for
solubility in a polar solvent. The third functional group is
characterised for adhesion to a substrate material.
[0042] The LCP release material may perform alignment of the
polymerisable liquid crystal and act as a release layer for the
liquid crystal polymer, LCP, from, for example, a substrate. The
LCP release material may enable non-contact release of LCPs from
substrates without affecting their optical quality and alignment
properties. The LCP release material may enable LCPs to be released
from a support substrate while maintaining their mechanical and
optical characteristics and without a direct physical influence or
a mechanical stress. The LCP release material combines LCP
alignment capabilities, in particular capability for
photoalignment, with a release function. The LCP release material
may enable the release of LCPs onto substrates made of materials
that are not suitable for direct fabrication of LCP optical
components due to poor chemical resistivity to solvents involved in
the process and/or poor mechanical strength. The LCP release
material may enable LCP films to be provided on substrates of
complex shape, such as lenses.
[0043] In an embodiment, said first functional group is a
photoresponsive compound. The photoresponsive compound may ensure
that the photoaligning material is able to provide photoalignment
for liquid crystal molecules including monomers.
[0044] In an embodiment, said first functional group is one of
Azobenzene, Stilbene, Azoxy, Azomethine, Fulgide and Diarylethene.
The photoresponsive compound may ensure that the photoaligning
material is able to provide photoalignment for liquid crystal
molecules including monomers.
[0045] In an embodiment, said second functional group is a sulfo
group. This may provide adhesion of the photoaligning material to
the substrate material.
[0046] In an embodiment, second functional group is characterised
for solubility in one of water, Dimethylformamide, and a low
molecular weight alcohol. The photoresponsive compound may ensure
that the photoaligning material is able to provide photoalignment
for liquid crystal molecules including monomers.
[0047] In an embodiment, said substrate material is an optical
substrate.
[0048] In an embodiment, said substrate material is one of glass,
polycarbonate, fused silica, Zinc selenide, ZnSe, and Barium
fluoride, BaF2.
[0049] A third aspect of the invention provides a method for
preparing a liquid crystal polymer film comprising the steps of:
[0050] (a) providing a substrate; [0051] (b) dispensing a
photoaligning release material layer over said substrate; [0052]
(c) exposing said photoaligning release material layer to a linear
polarized light; [0053] (d) dispensing a polymerizable liquid
crystal over the photoaligned release material layer; [0054] (e)
in-situ reacting said polymerizable liquid crystal to form a
polymer film; [0055] (f) immersing said substrate comprising said
photoaligned release material layer and said polymerized liquid
crystal layer into a solvent, said solvent capable of dissolving
said photoaligned release material layer; [0056] (g) separating the
polymerized liquid crystal film from the substrate.
[0057] In an embodiment, the molecular structure of said
photoaligning release material comprises at least one
photoresponsive core such as azobenzene, stilbene, azoxy,
azomethine, fulgide and diarylethene.
[0058] In an embodiment, the molecular structure of said
photoaligning release material comprises special groups for water
solubility such as sulfo groups.
[0059] In an embodiment, linear polarization of said polarized
light is modulated by a spatial light polarization converter.
[0060] In an embodiment, said spatial light polarization converter
is a cycloidal diffractive waveplate, vector vortex waveplate,
arrays of vector vortex waveplates, or other 1- or 2-D polarization
patterns.
[0061] In an embodiment, said solvent is a polar like water, DMF,
or a low molecular weight alcohol.
[0062] A fourth aspect of the invention provides a method for
preparing a liquid crystal polymer film comprising the steps of:
[0063] (a) providing a mold, including at least two cooperating
mold segments, having a cavity therein for forming the molded
liquid crystal polymer film; [0064] (b) dispensing a photoaligning
release material layer over the surfaces of at least one of the
segments of the mold; [0065] (c) exposing the photoaligning release
material layers at least on one of the segments of the mold to a
linear polarized light that is, generally, spatially modulated and
different for each segment of the mold; [0066] (d) closing the
mold; [0067] (e) injecting liquid crystal polymeric precursor
materials into the mold cavity; [0068] (f) reacting in situ the
liquid crystal polymeric precursor materials to form the molded
polymer; [0069] (g) immersing the mold into a solvent, said solvent
capable of dissolving said photoaligned release material layers;
[0070] (h) parting at least one of the mold sections.
[0071] In an embodiment, said polymerizable liquid crystal contains
functional groups, copolymers and additives to control its optical,
electro-optical, mechanical, thermodynamic, and chemical
properties.
[0072] A fifth aspect of the invention provides a method for
preparing a liquid crystal polymer film comprising the steps of:
[0073] (a) providing a mold comprising the first and the second
segments that are congruent at least in part; [0074] (b) dispensing
a photoaligning release material layer over the surface of the
first segment of the mold; [0075] (c) exposing said photoaligning
release material layer to a pattern of linear polarized light;
[0076] (d) dispensing a polymerizable liquid crystal precursor over
the photoaligned release material layer; [0077] (e) in-situ
reacting said polymerizable liquid crystal to form a polymer film;
[0078] (f) dispensing an adhesive layer over the second segment of
the mold; [0079] (g) closing the mold; [0080] (h) curing the
adhesive; [0081] (f) immersing the mold into a solvent, said
solvent capable of dissolving said photoaligned release material
layer; [0082] (g) parting the first segment of the mold.
[0083] In an embodiment, said polymerizable liquid crystal contains
functional groups, copolymers and additives to control its optical,
electro-optical, mechanical, thermodynamic, and chemical
properties.
[0084] A sixth aspect of the invention provides a mold release
material comprising at functional groups in their molecular
structure, said functional groups providing: [0085] (a)
photoalignment for liquid crystalline materials; [0086] (b)
solubility in polar solvents like water, DMF, and low molecular
weight alcohols; [0087] (c) adhesion to a substrate made of a
material selected from the group consisting of glass,
polycarbonate, fused silica, ZnSe, BaF2, and other materials
commonly used in optics, including infra-red, IR, and Terahertz,
THz, optics.
[0088] Several aspects of the invention are described above, in
varying detail as to the features of each of the aspects. Any of
the features of one of the aspects can be included as an additional
or alternative feature of any of the other aspects, practices or
embodiments of the disclosure described herein, except where
clearly mutually exclusive with another feature of an aspect,
practice or embodiment or where a statement is explicitly made
herein that certain features will not work in such a combination.
To avoid undue repetition and length of the disclosure, every
possible combination is not explicitly recited. Furthermore, as the
skilled worker can ascertain, a method of the present disclosure
can comprise the steps relating to the function or operation of the
features of apparatus and systems disclosed herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0089] FIG. 1 shows the steps of a method according to a first
embodiment of the invention of fabricating a liquid crystal polymer
film;
[0090] FIG. 2 schematically shows a method according to a second
embodiment of the invention of fabricating a liquid crystal polymer
film;
[0091] FIG. 3 schematically shows a method according to a third
embodiment of the invention of fabricating a liquid crystal polymer
film;
[0092] FIG. 4 shows the steps of a method according to a fourth
embodiment of the invention of fabricating a liquid crystal polymer
film;
[0093] FIG. 5 schematically shows a method according to a fifth
embodiment of the invention of fabricating a liquid crystal polymer
film;
[0094] FIG. 6 shows a photo of a homogeneously aligned LCP film
transferred onto a flexible polymer support film;
[0095] FIG. 7 shows (a) a photo of a LCP film with an array of
axially modulated optical axis orientation fabricated on a fused
silica substrate and (b) a photo of the LCP film transferred onto a
polycarbonate substrate;
[0096] FIG. 8 shows the steps of a method according to a sixth
embodiment of the invention of fabricating a liquid crystal polymer
film;
[0097] FIG. 9 schematically shows a method according to a seventh
embodiment of the invention of fabricating a liquid crystal polymer
film;
[0098] FIG. 10 schematically shows a method according to an eighth
embodiment of the invention of fabricating a liquid crystal polymer
film;
[0099] FIG. 11 shows a photo a molded LCP film fabricated using the
method illustrated in FIG. 10; and
[0100] FIG. 12 shows a molecular structure of a liquid crystal
polymer release material according to a tenth embodiment of the
invention.
DETAILED DESCRIPTION
[0101] Before explaining the disclosed embodiment of the present
invention in detail it is to be understood that the invention is
not limited in its application to the details of the particular
arrangement shown since the invention is capable of other
embodiments. Also, the terminology used herein is for the purpose
of description and not limitation.
[0102] Referring to FIG. 1, a first preferred embodiment of the
invention provides a method 10 of fabricating a liquid crystal
polymer film 121.
[0103] The method comprises steps (a) to (g), as follows. In step
(a) 12 a support substrate is provided. The support substrate has a
surface which has a shape arranged to define a form of the liquid
crystal polymer, LCP, film that is to be fabricated. In step (b) 14
a layer of a photoaligning material is applied over the surface of
the support substrate. The photoaligning material has an absorption
band. In step (c) 16 the said layer of photoaligning material is
exposed to a light having a linear polarization to convert the
layer of photoaligning material into a layer of photoaligned
material. The light comprises a wavelength within the absorption
band of the photoaligning material.
[0104] In step (d) 18 of the method, a layer of a polymerizable
liquid crystal is applied over the layer of photoaligned material
111. In step (e) 20 photopolymerization of the layer of
polymerizable liquid crystal is performed, to form a liquid crystal
polymer, LCP, film.
[0105] Step (f) 22 comprises releasing the liquid crystal polymer
film from the support substrate by applying a solvent to the layer
of photoaligned material. The solvent is formulated to dissolve the
photoaligned material, to thereby release the LCP film. In the
final step (g) 24, the liquid crystal polymer film is removed from
the support substrate.
[0106] In a second embodiment, illustrated in FIG. 2, the invention
provides a method of fabricating a liquid crystal polymer film 121.
The method of this embodiment is similar to the method 10 of the
first embodiment, with the following modifications.
[0107] In this embodiment, the photoaligning material comprises an
azobenzene dye based on chromocentranine R structures which
comprise a sulfo group. An example of such a dye is sulfonic
bisazodye SD1:
##STR00001##
[0108] Such materials meet the key conditions required for the
preferred embodiment of the current invention: 1) solubility in
water and other polar (hydrophilic) solvents such as DMF and low
molecular weight alcohols; 2) insolubility in organic solvents
often used for polymerizable liquid crystals, among them, hexanes,
cyclohexane, ketones like cyclopenthanone, esthers like PGMEA,
etc.; and 3) capability of providing photoalignment for liquid
crystal molecules, including, monomers due to the presence of
azobenzene group in their molecular structure. Other
photoresponsive cores such as azoxy, azomethine, fulgide and
diarylethene, could be used as well.
[0109] Typically, azobenzene dyes meeting all the conditions above
are in the form of a powder at room temperature, and they can be
used for coating by dissolving them in a variety of solvents,
including water. The concentration of the azo dye in the solvent
determines film thickness and the coating technique. Variety of
coating techniques are applicable, including dip coating, printing,
stamping, and spin coating. In the latter case, approximately 1 wt.
% of said azo dye can be used in a DMF as solvent. Spinning at 3000
rpm for 60 s provides thus a photoalignment layer of a few tens of
nm thickness capable of being effectively dissolved in water.
[0110] The photoalignment film 110 is coated on a substrate 100
that is chemically resistive to the solvents used in the process,
glass, for example. The photoalignment film 110 is exposed to
polarized light comprising a wavelength in the absorption band of
the photoalignment material. The absorption band can be in the UV
or visible part of the spectrum. The light is generally polarized
by a polarizer and a spatial light polarization modulator. The
exposure dose depends on the specific photoalignment material and
the radiation wavelength. For example, PAAD-72 azobenzene
(available at www.beamco.com), for example, produces high quality
alignment conditions for common liquid crystals such as
4-pentyl-4'-cyanobiphenyl (5CB) as well as for Merck's RMS series
reactive mesogens within a 5 minute exposure time to a UV radiation
of 325 nm wavelength and 10 mW/cm2 power density.
[0111] The substrate coated by the photoaligned azobenzene dye
layer 111 is further coated with a polymerizable liquid crystal, LC
120. For example, an RMS series LC material available from Merck
can be used and may be applied on the photoalignment layer 111 by
spin coating. The spinning regime is chosen from considerations of
required film thickness or phase retardation. As an example, an
approximately half-wavelength phase retardation for a light beam of
400 nm wavelength is obtained by spin coating at 3000 rpm for 60s.
The polymerizable liquid crystal layer 120 thus aligned can be
crosslinked by photopolymerization with an unpolarized UV
light.
[0112] The crosslinked polymer film 121 thus obtained is released
from the substrate 100 by submerging the substrate in water, which
causes dissolution of the azobenzene dye layer. The release takes
place within minutes affecting neither the alignment conditions nor
the mechanical properties of the crosslinked polymer film 121.
[0113] In a third embodiment, illustrated in FIG. 3, the invention
provides a method of fabricating a liquid crystal polymer film 221.
The method of this embodiment is similar to the previous
embodiments, with the following modifications.
[0114] In this embodiment, the layer photoaligning material is
exposed to light having a spatially modulated linear polarization.
The method comprises, before exposing the layer of photoaligning
material to the light, spatially modulating the linear polarization
of the light.
[0115] The linear polarization of the light may be spatially
modulated with either a one-dimensional polarization pattern or a
two-dimensional polarization pattern. In this example, the linear
polarization of the light is spatially modulated by transmitting
the light through a cycloidal diffractive waveplate. The light may
alternatively be transmitted through a vector vortex waveplate or
an array of vector vortex waveplates.
[0116] In contrast to the homogeneous alignment of the LCP
molecules shown in FIG. 2, spatially modulating the polarization of
the light used to expose the photoaligning material enables one to
produce more complex orientation patterns. For example, using
diffractive waveplates as linear-to-radial or linear-to-cycloidal
polarization converters, as disclosed in U.S. patent application
Ser. No. 12/662,525, and described in Sarik R. Nersisyan, Nelson V.
Tabiryan, Diane M. Steeves, and Brian R. Kimball, "Characterization
of optically imprinted polarization gratings", Applied Optics,
volume 48, number 21, pages 4062-4067, 2009, the method of this
embodiment may be used to fabricate a diffractive waveplate LCP
films. FIG. 3 shows a substrate 100 on which a cycloidal aligned
photoalignment-release layer coating 211 is provided and a
cycloidal aligned crosslinked liquid crystal polymer 221. A
cycloidal diffractive waveplate LCP film is released in this
case.
[0117] In a fourth embodiment, illustrated in FIG. 4, the invention
provides a method 30 of fabricating a liquid crystal polymer film
121. The method 30 of this embodiment is similar to the method 10
of the first embodiment, with the following modifications. The same
reference numbers are retained for corresponding steps.
[0118] In this embodiment, after step (e) the method 30 comprises
attaching said liquid crystal polymer film to a carrier substrate
32. Step (g) comprises removing said liquid crystal polymer film on
said carrier substrate from said support substrate 34.
[0119] In a fifth embodiment, illustrated in FIGS. 5 to 7, the
invention provides a method of fabricating a liquid crystal polymer
film 121. The method of this embodiment is similar to the method of
the second embodiment, with the following modifications.
[0120] The opportunity of releasing LCP films produced on
substrates coated with photoaligning release layers can be used for
transferring the films produced on a given substrate, typically
made of mechanically strong and chemically resistant materials,
onto substrates that are either difficult to handle or otherwise
are not compatible with LCP fabrication processes due to
wettability, temperature, solvents, or complex shape and surface
topology.
[0121] In this embodiment, the LCP film 121 is transferred to
another polymer film 131 that may generally be thicker and stronger
mechanically to act as a support backbone for the LCP film 121. The
method of this embodiment is the same as the method illustrated in
FIG. 2, up to the stage of obtaining the crosslinked optical
polymer film 121. In this embodiment, an optical adhesive 130, for
example NOA-68 (available from Norland), is coated on top of the
crosslinked optical film 121 by spin coating at 4000 rpm for 60s.
The layer of optical adhesive 130 is then exposed to a UV light of
365 nm wavelength for 10 minutes to cause photopolymerization of
the optical adhesive 130, to thereby form the support film 131. The
support substrate 100, photoalignment layer 111, LCP film 121 and
support film 131 are then submersed in water, which results in
releasing the optical film 121, carried by the support film 131,
from the support substrate 100.
[0122] FIG. 6 shows an example of an anisotropic optical film of
approximately 1 .mu.m thickness attached to a thick polymer backing
and FIGS. 7a and 7b show the transfer of an LCP film 421 in the
form of an array of vector vortex waveplates produced on a fused
silica substrate onto a polycarbonate support film 422.
[0123] In a sixth embodiment, illustrated in FIG. 8, the invention
provides a method 40 of fabricating a liquid crystal polymer film
which is similar to the method 10 of the first embodiment, with the
following modifications.
[0124] In this embodiment, after step (e) the method 40 comprises,
after step (e), the step of adhering the liquid crystal polymer
film to a second support substrate 42. Solvent is then applied to
the layer of photoaligned material, to dissolve the photoaligned
material and release the LCP film from the support substrate 22 and
the LCP film attached to the second support substrate is removed
from the support substrate on which it was formed.
[0125] The method further comprises, after step (g), providing a
third support substrate carrying a second layer of a photoaligned
material 46. The third support substrate has a second liquid
crystal polymer film, different to the first liquid crystal polymer
film, provided over the second layer of a photoaligned material. A
solvent is then applied to the second layer of a photoaligned
material. The solvent is formulated to dissolve the photoaligned
material to thereby release the second LCP film from the third
support substrate. The two LCP films are thereby left on the second
support substrate.
[0126] Referring to FIG. 9, a seventh embodiment of the invention
provides a method of fabricating a liquid crystal polymer film
which is similar to the method of the illustrated in FIG. 2, with
the following modifications. The same reference numbers are
retained for corresponding features.
[0127] In this embodiment, a first LCP film 121 is transferred onto
a second LCP film 122, as follows. The substrate 100 carrying the
photoalignment layer 111 and the cross-linked LCP film 121 with
optical axis aligned according to the photoalignment pattern
produced on said photoalignment layer 111 is attached to a second
support substrate 101 by an adhesive layer (not shown). Submersion
in water then releases the original support substrate 100 by
dissolving the photoalignment layer 111. The LCP film 121, carried
by the second support substrate 101, is then attached to a second
LCP film 122 of generally different pattern or different
orientation. The second LCP film 122 is carried on a third support
substrate 102 via a further photoalignment layer 112.
[0128] The third support substrate 102 is then released by
dissolving the further photoalignment layer 112, resulting in the
second support substrate 101 carrying both of the LCP films 121,
122. As an example, the two LOP films could be homogeneously
aligned LCP films having a mutually perpendicular orientation of
their optical axes, to produce a photonic bandgap structure such as
the one described in H. Sarkissian, B. Zeldovich, N. Tabiryan,
"Longitudinally modulated bandgap nematic structure", Journal of
the Optical Society of America B, volume 23, pages 1712-1717,
2006.
[0129] FIG. 10 illustrates a method according to an eighth
embodiment of the invention of fabricating a liquid crystal polymer
film. The method of this embodiment is similar to the method 10 of
the first embodiment, with the following modifications.
[0130] In this embodiment, the support substrate is a first mold
segment 601 and step (a) further comprises providing a second mold
segment 602 which has a surface having a shape arranged to
cooperate with the surface of the first mold segment 601. The
surfaces of the first and second mold segments together define a
cavity which defines the shape with which the LCP film 620 is to be
fabricated. Step (b) further comprises applying a layer of the
photoaligning material over the surface of the second mold segment
602 and in step (c) the layer of photoaligning material on each of
the first and second mold segments is exposed to the light having a
linear polarization. Each layer of photoaligning material is
thereby converted into a layer of photoaligned material 611 on the
respective mold segment 601, 602.
[0131] Step (d) comprises arranging the first and second mold
segments together to form the cavity and then filling the cavity
with the polymerizable liquid crystal. Steps (e) to (g) are then
performed to form the LCP film 620 and release the LCP film from
the two mold segments 601, 602. FIG. 11 shows an example resulting
azobenzene LCP film molded in the form of a spherical lens 622.
[0132] A ninth embodiment of the invention provides a method of
fabricating a liquid crystal polymer film which is similar to the
method of the previous embodiment and will be described with
reference to FIG. 10 also.
[0133] In this embodiment, step (c) comprises exposing the layer of
photoaligning material on the first mold segment 601 to a first
linearly polarized light having a first polarization spatial
modulation. The layer of photoaligning material on the second mold
segment 602 is exposed to a second linearly polarized light having
a second polarization spatial modulation, different to the first
polarization spatial modulation.
[0134] A tenth embodiment of the invention provides a liquid
crystal polymer release material comprising three functional
groups: a first functional group characterised for photoalignment
of liquid crystal materials; a second functional group
characterised for solubility in a polar solvent; and a third
functional group characterised for adhesion to a substrate
material.
[0135] FIG. 12 illustrates the molecular structure 700 of sulfonic
bisazodye SD1, an azobenzene dye based on chromocentranine R
structures which comprise a sulfo group, which is an example of a
LCP release material according to this embodiment of the
invention.
[0136] The LCP release material molecular structure 700 comprises:
a first functional group 701 characterised for photoalignment of
liquid crystal materials; a second functional group 702
characterised for solubility in a polar solvent; and a third
functional group 703 characterised for adhesion to a substrate
material. It will however be appreciated that there may not be
strict differentiation of the group functionality, and some groups
may take part in different functions.
[0137] It will be appreciated that the specific orientations used
within these FIGURES to demonstrate the apparatus functionality are
by way of example only.
[0138] The present disclosure is directed to each individual
feature, system, material, and/or method described herein. In
addition, any combination of two or more such features, systems,
materials, and/or methods, if such features, systems, materials,
and/or methods are not mutually inconsistent, is included within
the scope of the present invention. To avoid undue repetition, not
all features are discussed in conjunction with every aspect,
embodiment or practice of the disclosure. Features described in
conjunction with one aspect, embodiment or practice are deemed to
be includable with others absent mutual inconsistency or a clear
teaching to the contrary. In some instances, features will be
discussed generally rather than in detail in conjunction with a
specific aspect, embodiment or practice, and it is understood that
such features can be included in any aspect, embodiment or
practice, again absent mutual inconsistency or a clear teaching to
the contrary.
[0139] Those of ordinary skill in the art will readily envision a
variety of other means and structures for performing the functions
and/or obtaining the results or advantages described herein and
each of such variations or modifications is deemed to be within the
scope of the present invention. More generally, those skilled in
the art would readily appreciate that all parameters, dimensions,
materials and configurations described herein are meant to be
exemplary and that actual parameters, dimensions, materials and
configurations will depend on specific applications for which the
teachings of the present invention are used.
[0140] Those skilled in the art will recognize or be able to
ascertain using no more than routine experimentation many
equivalents to the specific embodiments of the invention described
herein. It is therefore to be understood that the foregoing
embodiments are presented by way of example only and that within
the scope of the appended claims, and equivalents thereto, the
invention may be practiced otherwise than as specifically
described.
[0141] In the claims as well as in the specification above all
transitional phrases such as "comprising", "including", "carrying",
"having", "containing", "involving" and the like are understood to
be open-ended. Only the transitional phrases "consisting of" and
"consisting essentially of" shall be closed or semi-closed
transitional phrases, respectively, as set forth in the U.S. Patent
Office Manual of Patent Examining Procedure .sctn.2111.03, 8th
Edition, Revision 8. Furthermore, statements in the specification,
such as, for example, definitions, are understood to be open ended
unless otherwise explicitly limited.
[0142] The phrase "A or B" as in "one of A or B" is generally meant
to express the inclusive "or" function, meaning that all three of
the possibilities of A, B or both A and B are included, unless the
context clearly indicates that the exclusive "or" is appropriate
(i.e., A and B are mutually exclusive and cannot be present at the
same time). "At least one of A, B or C" (as well as "at least one
of A, B and C") reads on any combination of one or more of A, B and
C, including, for example the following: A; B; C; A & B; A
& C; B & C; A & B; as well as on A, B & C.
[0143] It is generally well accepted in patent law that "a" means
"at least one" or "one or more." Nevertheless, there are
occasionally holdings to the contrary. For clarity, as used herein
"a" and the like mean "at least one" or "one or more." The phrase
"at least one" may at times be explicitly used to emphasize this
point. Use of the phrase "at least one" in one claim recitation is
not to be taken to mean that the absence of such a term in another
recitation (e.g., simply using "a") is somehow more limiting.
Furthermore, later reference to the term "at least one" as in "said
at least one" should not be taken to introduce additional
limitations absent express recitation of such limitations. For
example, recitation that an apparatus includes "at least one
widget" and subsequent recitation that "said at least one widget is
colored red" does not mean that the claim requires all widgets of
an apparatus that has more than one widget to be red. The claim
shall read on an apparatus having one or more widgets provided
simply that at least one of the widgets is colored red. Similarly,
the recitation that "each of a plurality" of widgets is colored red
shall also not mean that all widgets of an apparatus that has more
than two red widgets must be red; plurality means two or more and
the limitation reads on two or more widgets being red, regardless
of whether a third is included that is not red, absent more
limiting explicit language (e.g., a recitation to the effect that
each and every widget of a plurality of widgets is red).
ADDITIONAL REFERENCES
[0144] [1] N. V. Tabiryan, S. R. Nersisyan, D. M. Steeves and B. R.
Kimball, The Promise of Diffractive Waveplates, Optics and
Photonics News, 21 (3), 41-45, 2010. [0145] [2] S. R. Nersisyan, N.
V. Tabiryan, D. M. Steeves, B. R. Kimball, V. G. Chigrinov, and
H.-S. Kwok, Study of azo dye surface command photoalignment
material for photonics applications, Appl. Opt. 49 (10), 1720-1727,
2010. [0146] [3] Sarik R. Nersisyan, Nelson V. Tabiryan, Diane M.
Steeves, and Brian R. Kimball, Characterization of optically
imprinted polarization gratings, Appl. Optics 48 (21), 4062-4067,
2009. [0147] [4] H. Sarkissian, B. Zeldovich, N. Tabiryan,
"Longitudinally modulated bandgap nematic structure", JOSA B 23,
1712-1717, 2006.
U.S. Patent Documents
TABLE-US-00001 [0148] 4,956,141 September 1990 Allen et al.
4,983,332 January 1991 Hahn et al. 6,551,531 April 2003 Ford et al.
7,094,304 August 2006 Nystrom et al. 12/662,525 April 2010 Tabirian
et al.
* * * * *
References