U.S. patent application number 13/360999 was filed with the patent office on 2012-08-30 for metallic nanofiber ink, substantially transparent conductor, and fabrication method.
This patent application is currently assigned to NTHDEGREE TECHNOLOGIES WORLDWIDE INC.. Invention is credited to Jeffrey Baldridge, David Michael Chesler, Mark Allan Lewandowski, Mark David Lowenthal, Lixin Zheng.
Application Number | 20120217453 13/360999 |
Document ID | / |
Family ID | 46718354 |
Filed Date | 2012-08-30 |
United States Patent
Application |
20120217453 |
Kind Code |
A1 |
Lowenthal; Mark David ; et
al. |
August 30, 2012 |
Metallic Nanofiber Ink, Substantially Transparent Conductor, and
Fabrication Method
Abstract
An exemplary printable composition comprises a liquid or gel
suspension of a plurality of metallic nanofibers; a first solvent;
and a viscosity modifier, resin, or binder. In various embodiments,
the metallic nanofibers are between about 10 microns to about 100
microns in length, are between about 10 nm to about 120 nm in
diameter, and are typically functionalized with a coating or
partial coating of polyvinyl pyrrolidone or a similar compound. An
exemplary metallic nanofiber ink which can be printed to produce a
substantially transparent conductor comprises a plurality of
metallic nanofibers; one or more solvents such as 1-butanol,
ethanol, 1-pentanol, n-methylpyrrolidone, cyclohexanone,
cyclopentanone, 1-hexanol, acetic acid, cyclohexanol, or mixtures
thereof; and a viscosity modifier, resin, or binder such as
polyvinyl pyrrolidone or a polyimide, for example.
Inventors: |
Lowenthal; Mark David;
(Gilbert, AZ) ; Baldridge; Jeffrey; (Chandler,
AZ) ; Lewandowski; Mark Allan; (North Port, FL)
; Zheng; Lixin; (Phoenix, AZ) ; Chesler; David
Michael; (Mesa, AZ) |
Assignee: |
NTHDEGREE TECHNOLOGIES WORLDWIDE
INC.
Tempe
AZ
|
Family ID: |
46718354 |
Appl. No.: |
13/360999 |
Filed: |
January 30, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61447160 |
Feb 28, 2011 |
|
|
|
Current U.S.
Class: |
252/513 ;
252/512; 252/514; 977/762; 977/900 |
Current CPC
Class: |
B82Y 40/00 20130101;
Y10T 428/24802 20150115; B82Y 30/00 20130101; C09D 11/52 20130101;
H01B 1/22 20130101 |
Class at
Publication: |
252/513 ;
252/512; 252/514; 977/762; 977/900 |
International
Class: |
H01B 1/02 20060101
H01B001/02 |
Claims
1. A composition comprising: a plurality of metallic nanofibers,
substantially all of the metallic nanofibers at least partially
coated with a polymer; a first solvent; and a viscosity modifier,
resin or binder.
2. The composition of claim 1, wherein the plurality of metallic
nanofibers have lengths between about 1.mu. and about 250.mu. and
diameters between about 10 nm and about 500 nm.
3. The composition of claim 1, wherein the plurality of metallic
nanofibers have lengths between about 15.mu. and about 100.mu. and
diameters between about 20 nm and about 100 nm.
4. The composition of claim 1, wherein the plurality of metallic
nanofibers have lengths between about 30.mu. and about 70.mu. and
diameters between about 20 nm and about 40 nm.
5. The composition of claim 1, wherein the plurality of metallic
nanofibers have lengths between about 40.mu. and about 60.mu. and
diameters between about 25 nm and about 35 nm.
6. The composition of claim 1, wherein the plurality of metallic
nanofibers comprises at least one metal selected from the group
consisting of: aluminum, copper, silver, gold, nickel, palladium,
tin, platinum, lead, zinc, alloys thereof, and mixtures
thereof.
7. The composition of claim 1, wherein the at least a partial
coating of a polymer comprises polyvinyl pyrrolidone (PVP).
8. The composition of claim 1, wherein the first solvent comprises
at least one solvent selected from the group consisting of: water;
alcohols such as methanol, ethanol, N-propanol (including
1-propanol, 2-propanol (isopropanol or IPA), 1-methoxy-2-propanol),
butanol (including 1-butanol, 2-butanol (isobutanol)), pentanol
(including 1-pentanol, 2-pentanol, 3-pentanol), hexanol (including
1-hexanol, 2-hexanol, 3-hexanol), octanol, N-octanol (including
1-octanol, 2-octanol, 3-octanol), tetrahydrofurfuryl alcohol
(THFA), cyclohexanol, cyclopentanol, terpineol; lactones such as
butyl lactone; ethers such as methyl ethyl ether, diethyl ether,
ethyl propyl ether, and polyethers; ketones, including diketones
and cyclic ketones, such as cyclohexanone, cyclopentanone,
cycloheptanone, cyclooctanone, acetone, benzophenone,
acetylacetone, acetophenone, cyclopropanone, isophorone, methyl
ethyl ketone; esters such ethyl acetate, dimethyl adipate,
proplyene glycol monomethyl ether acetate, dimethyl glutarate,
dimethyl succinate, glycerin acetate, carboxylates; glycols such as
ethylene glycols, diethylene glycols, polyethylene glycols,
propylene glycols, dipropylene glycols, glycol ethers, glycol ether
acetates; carbonates such as propylene carbonate; glycerols such as
glycerin; n-methylpyrrolidone, acetonitrile, tetrahydrofuran (THF),
dimethyl formamide (DMF), N-methyl formamide (NMF), dimethyl
sulfoxide (DMSO); acids, including organic acids such as carboxylic
acids, dicarboxylic acids, tricarboxylic acids, alkyl carboxylic
acids, acetic acid, oxalic acid, mellitic acid, formic acid,
chloroacetic acid, benzoic acid, trifluoroacetic acid, propanoic
acid, butanoic acid; bases such as ammonium hydroxide, sodium
hydroxide, potassium hydroxide; and mixtures thereof.
9. The composition of claim 1, wherein the viscosity modifier,
resin or binder comprises at least one viscosity modifier, resin or
binder selected from the group consisting of: polymers such as
polyvinyl pyrrolidone, polyvinyl alcohol, polyimide polymers and
copolymers (including aliphatic, aromatic and semi-aromatic
polyimides), acrylate and (meth)acrylate polymers and copolymers;
glycols such as ethylene glycols, diethylene glycol, polyethylene
glycols, propylene glycols, dipropylene glycols, glycol ethers,
glycol ether acetates; clays such as hectorite clays, garamite
clays, organo-modified clays; saccharides and polysaccharides such
as guar gum, xanthan gum; celluloses and modified celluloses such
as hydroxy methylcellulose, methylcellulose, ethyl cellulose,
propyl methylcellulose, methoxy cellulose, methoxy methylcellulose,
methoxy propyl methylcellulose, hydroxy propyl methylcellulose,
carboxy methylcellulose, hydroxy ethylcellulose, ethyl
hydroxylethylcellulose, cellulose ether, cellulose ethyl ether,
chitosan; fumed silica, silica powders, modified ureas; and
mixtures thereof.
10. The composition of claim 1, wherein the first solvent comprises
1-butanol.
11. The composition of claim 1, wherein the first solvent is
present in an amount of about 3 percent to 10 percent by
weight.
12. The composition of claim 1, wherein the viscosity modifier,
resin or binder comprises a polyimide and is present in an amount
of about 0.75% to 5% by weight.
13. The composition of claim 12, wherein the first solvent
comprises cyclohexanone.
14. The composition of claim 13, wherein the first solvent is
present in an amount of about 0.05 percent to 99.95 percent by
weight.
15. The composition of claim 1, further comprising a second solvent
different from the first solvent.
16. The composition of claim 15, wherein the viscosity modifier,
resin or binder comprises polyvinyl pyrrolidone and is present in
an amount of about 0.75% to 5% by weight.
17. The composition of claim 16, wherein the first solvent
comprises 1-butanol and the second solvent comprises
cyclohexanol.
18. The composition of claim 17, wherein the first solvent is
present in an amount of about 3 percent to 10 percent by weight and
the second solvent is present in an amount of about 50 percent to
95 percent by weight.
19. The composition of claim 15, further comprising an organic acid
present in an amount of about 0.1% to 2% by weight, the organic
acid comprising at least one acid selected from the group
consisting of: carboxylic acids, dicarboxylic acids, tricarboxylic
acids, alkyl carboxylic acids, acetic acid, oxalic acid, mellitic
acid, formic acid, chloroacetic acid, benzoic acid, trifluoroacetic
acid, propanoic acid, butanoic acid; and mixtures thereof.
20. The composition of claim 15, wherein the second solvent is at
least one solvent selected from the group consisting of: water;
alcohols such as methanol, ethanol, N-propanol (including
1-propanol, 2-propanol (isopropanol or IPA), 1-methoxy-2-propanol),
butanol (including 1-butanol, 2-butanol (isobutanol)), pentanol
(including 1-pentanol, 2-pentanol, 3-pentanol), hexanol (including
1-hexanol, 2-hexanol, 3-hexanol), octanol, N-octanol (including
1-octanol, 2-octanol, 3-octanol), tetrahydrofurfuryl alcohol
(THFA), cyclohexanol, cyclopentanol, terpineol; lactones such as
butyl lactone; ethers such as methyl ethyl ether, diethyl ether,
ethyl propyl ether, and polyethers; ketones, including diketones
and cyclic ketones, such as cyclohexanone, cyclopentanone,
cycloheptanone, cyclooctanone, acetone, benzophenone,
acetylacetone, acetophenone, cyclopropanone, isophorone, methyl
ethyl ketone; esters such ethyl acetate, dimethyl adipate,
proplyene glycol monomethyl ether acetate, dimethyl glutarate,
dimethyl succinate, glycerin acetate, carboxylates; glycols such as
ethylene glycols, diethylene glycols, polyethylene glycols,
propylene glycols, dipropylene glycols, glycol ethers, glycol ether
acetates; carbonates such as propylene carbonate; glycerols such as
glycerin; n-methylpyrrolidone, acetonitrile, tetrahydrofuran (THF),
dimethyl formamide (DMF), N-methyl formamide (NMF), dimethyl
sulfoxide (DMSO); acids, including organic acids such as carboxylic
acids, dicarboxylic acids, tricarboxylic acids, alkyl carboxylic
acids, acetic acid, oxalic acid, mellitic acid, formic acid,
chloroacetic acid, benzoic acid, trifluoroacetic acid, propanoic
acid, butanoic acid; bases such as ammonium hydroxide, sodium
hydroxide, potassium hydroxide; and mixtures thereof.
21. The composition of claim 15, wherein the second solvent is at
least one cyclic alcohol.
22. The composition of claim 15, further comprising a third
solvent, the third solvent different from the first solvent and the
second solvent, the third solvent present in an amount of about
0.1% to 10% by weight.
23. The composition of claim 22, wherein the third solvent is at
least one solvent selected from the group consisting of: water;
alcohols such as methanol, ethanol, N-propanol (including
1-propanol, 2-propanol (isopropanol or IPA), 1-methoxy-2-propanol),
butanol (including 1-butanol, 2-butanol (isobutanol)), pentanol
(including 1-pentanol, 2-pentanol, 3-pentanol), hexanol (including
1-hexanol, 2-hexanol, 3-hexanol), octanol, N-octanol (including
1-octanol, 2-octanol, 3-octanol), tetrahydrofurfuryl alcohol
(THFA), cyclohexanol, cyclopentanol, terpineol; lactones such as
butyl lactone; ethers such as methyl ethyl ether, diethyl ether,
ethyl propyl ether, and polyethers; ketones, including diketones
and cyclic ketones, such as cyclohexanone, cyclopentanone,
cycloheptanone, cyclooctanone, acetone, benzophenone,
acetylacetone, acetophenone, cyclopropanone, isophorone, methyl
ethyl ketone; esters such ethyl acetate, dimethyl adipate,
proplyene glycol monomethyl ether acetate, dimethyl glutarate,
dimethyl succinate, glycerin acetate, carboxylates; glycols such as
ethylene glycols, diethylene glycols, polyethylene glycols,
propylene glycols, dipropylene glycols, glycol ethers, glycol ether
acetates; carbonates such as propylene carbonate; glycerols such as
glycerin; n-methylpyrrolidone, acetonitrile, tetrahydrofuran (THF),
dimethyl formamide (DMF), N-methyl formamide (NMF), dimethyl
sulfoxide (DMSO); acids, including organic acids such as carboxylic
acids, dicarboxylic acids, tricarboxylic acids, alkyl carboxylic
acids, acetic acid, oxalic acid, mellitic acid, formic acid,
chloroacetic acid, benzoic acid, trifluoroacetic acid, propanoic
acid, butanoic acid; bases such as ammonium hydroxide, sodium
hydroxide, potassium hydroxide; and mixtures thereof.
24. The composition of claim 22, wherein the third solvent is at
least one solvent selected from the group consisting of: acids,
including organic acids such as carboxylic acids, dicarboxylic
acids, tricarboxylic acids, alkyl carboxylic acids, acetic acid,
oxalic acid, mellitic acid, formic acid, chloroacetic acid, benzoic
acid, trifluoroacetic acid, propanoic acid, butanoic acid; bases
such as ammonium hydroxide, sodium hydroxide, potassium hydroxide;
and mixtures thereof.
25. The composition of claim 1, wherein the first solvent is
present in an amount of about 1% to 10% by weight and comprises at
least one solvent selected from the group consisting of: 1-butanol,
ethanol, 1-pentanol, 1-hexanol, n-methylpyrrolidone, acetic acid,
cyclohexanone, and mixtures thereof; wherein the viscosity
modifier, resin, or binder is present in an amount of about 0.75%
to 5.0% by weight and comprises at least one viscosity modifier,
resin, or binder selected from the group consisting of: polyvinyl
pyrrolidone, a polyimide, and mixtures thereof and further
comprising a second solvent present in an amount of about 1.75% to
98.25% by weight and comprises at least one solvent selected from
the group consisting of: cyclohexanol, cyclohexanone,
cyclopentanol, butyl lactone, and mixtures thereof.
26. A method of making the composition of claim 25, the method
comprising: mixing the plurality of metallic nanofibers with
1-butanol and cyclohexanol; mixing polyvinyl pyrrolidone and
cyclohexanol; heating the mixture of polyvinyl pyrrolidone and
cyclohexanol to between about 80.degree. C. to about 90.degree. C.;
cooling the mixture of polyvinyl pyrrolidone and cyclohexanol to
about 25.degree. C.; adding the mixture of the plurality of
metallic nanofibers with 1-butanol to the mixture of polyvinyl
pyrrolidone and cyclohexanol; and mixing the plurality of metallic
nanofibers, 1-butanol, polyvinyl pyrrolidone and cyclohexanol for
about 3 to 10 minutes in an air atmosphere.
27. The composition of claim 1, wherein the plurality of metallic
nanofibers are coated with polyvinyl pyrrolidone and the plurality
of metallic nanofibers are present in an amount of about 0.01% to
3.0% by weight; wherein the first solvent is present in an amount
of about 1% to 10% by weight and comprises at least one solvent
selected from the group consisting of: 1-butanol, ethanol,
1-pentanol, n-methylpyrrolidone, cyclohexanone, 1-hexanol, acetic
acid, and mixtures thereof; wherein the viscosity modifier, resin,
or binder is present in an amount of about 0.75% to 5.0% by weight
and comprises at least one viscosity modifier, resin, or binder
selected from the group consisting of: polyvinyl pyrrolidone, a
polyimide, and mixtures thereof; and further comprising a second
solvent present in an amount of about 2.75% to 97.25% by weight,
wherein the second solvent comprises at least one solvent selected
from the group consisting of: cyclohexanol, cyclohexanone,
cyclopentanol, butyl lactone, and mixtures thereof.
28. The composition of claim 1, wherein the plurality of metallic
nanofibers are coated with polyvinyl pyrrolidone and the plurality
of metallic nanofibers are present in an amount of about 0.01% to
3.0% by weight; wherein the first solvent is present in an amount
of about 2.5% to 8.0% by weight and comprises at least one solvent
selected from the group consisting of: 1-butanol, ethanol,
1-pentanol, n-methylpyrrolidone, cyclohexanone, 1-hexanol, acetic
acid, and mixtures thereof; wherein the viscosity modifier, resin,
or binder is present in an amount of about 1.0% to 4.5% by weight
and comprises at least one viscosity modifier, resin, or binder
selected from the group consisting of: polyvinyl pyrrolidone, a
polyimide, and mixtures thereof; and further comprising a second
solvent present in an amount of about 4.5% to 95.5% by weight,
wherein the second solvent comprises at least one solvent selected
from the group consisting of: cyclohexanol, cyclohexanone,
cyclopentanol, butyl lactone, and mixtures thereof.
29. The composition of claim 1, wherein the plurality of metallic
nanofibers are coated with polyvinyl pyrrolidone and the plurality
of metallic nanofibers are present in an amount of about 0.01% to
3.0% by weight; wherein the first solvent is present in an amount
of about 2.5% to 8.0% by weight and comprises at least one solvent
selected from the group consisting of: 1-butanol, ethanol,
1-pentanol, n-methylpyrrolidone, cyclohexanone, 1-hexanol, acetic
acid, and mixtures thereof; wherein the viscosity modifier, resin,
or binder is present in an amount of about 1.0% to 4.5% by weight
and comprises at least one viscosity modifier, resin, or binder
selected from the group consisting of: polyvinyl pyrrolidone, a
polyimide, and mixtures thereof; further comprising a second
solvent present in an amount of 0.01% to 5.0% by weight, the second
solvent comprising an acid or a base; and further comprising a
third solvent present in an amount of about 4.5% to 95.4% by
weight, the third solvent comprising at least one solvent selected
from the group consisting of: cyclohexanol, cyclohexanone,
cyclopentanol, butyl lactone, and mixtures thereof.
30. The composition of claim 1, wherein the plurality of metallic
nanofibers are coated with polyvinyl pyrrolidone and the plurality
of metallic nanofibers are present in an amount of about 0.01% to
3.0% by weight; wherein the first solvent is present in an amount
of about 2.5% to 8.0% by weight and comprises at least one solvent
selected from the group consisting of: 1-butanol, ethanol,
1-pentanol, n-methylpyrrolidone, cyclohexanone, 1-hexanol, acetic
acid, and mixtures thereof; wherein the viscosity modifier, resin,
or binder is present in an amount of about 1.0% to 4.5% by weight
and comprises at least one viscosity modifier, resin, or binder
selected from the group consisting of: polyvinyl pyrrolidone, a
polyimide, and mixtures thereof; further comprising a second
solvent present in an amount of 0.01% to 5.0% by weight, wherein
the second solvent comprises at least one solvent selected from the
group consisting of: acids, including organic acids such as
carboxylic acids, dicarboxylic acids, tricarboxylic acids, alkyl
carboxylic acids, acetic acid, oxalic acid, mellitic acid, formic
acid, chloroacetic acid, benzoic acid, trifluoroacetic acid,
propanoic acid, butanoic acid; bases such as ammonium hydroxide,
sodium hydroxide, potassium hydroxide; and mixtures thereof; and
further comprising a third solvent present in an amount of about
4.5% to 95.4% by weight, the third solvent comprising at least one
solvent selected from the group consisting of: cyclohexanol,
cyclohexanone, cyclopentanol, butyl lactone, and mixtures
thereof.
31. The composition of claim 1, wherein the plurality of metallic
nanofibers are coated with polyvinyl pyrrolidone and the plurality
of metallic nanofibers are present in an amount of about 0.18% to
about 0.3% by weight; wherein the first solvent is present in an
amount of about 2.5% to 8.0% by weight and comprises at least one
solvent selected from the group consisting of: 1-butanol, ethanol,
1-pentanol, n-methylpyrrolidone, cyclohexanone, 1-hexanol, and
mixtures thereof; wherein the viscosity modifier, resin, or binder
is present in an amount of about 1.0% to 4.5% by weight and
comprises at least one viscosity modifier, resin, or binder
selected from the group consisting of: polyvinyl pyrrolidone, a
polyimide, and mixtures thereof; further comprising a second
solvent present in an amount of 0.1% to 2.0% by weight and
comprising a carboxylic acid; and further comprising a third
solvent present in an amount of about 3.7% to 96.3% by weight, the
third solvent comprising at least one solvent selected from the
group consisting of: cyclohexanol, cyclohexanone, cyclopentanol,
butyl lactone, and mixtures thereof.
32. The composition of claim 1, wherein the plurality of metallic
nanofibers are coated with polyvinyl pyrrolidone and the plurality
of metallic nanofibers are present in an amount of about 0.01% to
3.0% by weight; wherein the first solvent is present in an amount
of about 2.5% to 8.0% by weight and comprises at least one solvent
selected from the group consisting of: 1-butanol, ethanol,
1-pentanol, n-methylpyrrolidone, cyclohexanone, 1-hexanol, acetic
acid, and mixtures thereof; wherein the viscosity modifier, resin,
or binder is present in an amount of about 1.0% to 4.5% by weight
and is selected from the group consisting of: polyvinyl
pyrrolidone, a polyimide, and mixtures thereof; further comprising
a second solvent present in an amount of 0.01% to 5.0% by weight,
wherein the second solvent comprises at least one solvent selected
from the group consisting of: acids, including organic acids such
as carboxylic acids, dicarboxylic acids, tricarboxylic acids, alkyl
carboxylic acids, acetic acid, oxalic acid, mellitic acid, formic
acid, chloroacetic acid, benzoic acid, trifluoroacetic acid,
propanoic acid, butanoic acid; bases such as ammonium hydroxide,
sodium hydroxide, potassium hydroxide; and mixtures thereof;
further comprising a third solvent present in an amount of about
4.5% to 95.4% by weight, the third solvent comprising at least one
solvent selected from the group consisting of: cyclohexanol,
cyclohexanone, cyclopentanol, butyl lactone, and mixtures thereof;
and wherein the viscosity of the composition is substantially
between about 200 cps to about 20,000 cps at 25.degree. C.
33. The composition of claim 1, wherein the plurality of metallic
nanofibers are coated with polyvinyl pyrrolidone and the plurality
of metallic nanofibers are present in an amount of about 0.01% to
3.0% by weight; wherein the first solvent is present in an amount
of about 18% to 28% by weight and comprises at least one solvent
selected from the group consisting of: 1-butanol, ethanol,
1-pentanol, n-methylpyrrolidone, cyclohexanone, 1-hexanol, acetic
acid, and mixtures thereof; wherein the viscosity modifier, resin,
or binder is present in an amount of about 1.4% to 3.75% by weight
and comprises at least one viscosity modifier, resin, or binder
selected from the group consisting of: polyvinyl pyrrolidone, a
polyimide, and mixtures thereof; further comprising a second
solvent present in an amount of 0.001% to 2% by weight, wherein the
second solvent comprises at least one solvent selected from the
group consisting of: 1-octanol, acetic acid, diethylene glycol,
dipropylene glycol, propylene glycol, and mixtures thereof; and
further comprising a third solvent present in an amount of about
20.4% to 79.6% by weight, the third solvent comprising at least one
solvent selected from the group consisting of: cyclohexanol,
cyclohexanone, cyclopentanol, butyl lactone, and mixtures
thereof.
34. The composition of claim 1, wherein the composition has a
viscosity substantially between about 200 cps and about 20,000 cps
at about 25.degree. C.
35. A method of using the composition of claim 1, the method
comprising: printing the composition to form an electrical
contact.
36. The composition of claim 1, wherein the viscosity modifier,
resin or binder is present in an amount of about 0.75% to 5% by
weight and comprises a mixture of polyvinyl pyrrolidone and
polyvinyl alcohol.
37. A composition comprising: a plurality of metallic nanofibers,
substantially all of the metallic nanofibers at least partially
coated with polyvinyl pyrrolidone, the plurality of metallic
nanofibers present in an amount of about 0.01% to about 3.0% by
weight; a first solvent; a second solvent different from the first
solvent; and a viscosity modifier, resin or binder present in an
amount of about 0.75% to 5.0% by weight and comprises at least one
viscosity modifier, resin, or binder selected from the group
consisting of: polyvinyl pyrrolidone, a polyimide, and mixtures
thereof; wherein the viscosity of the composition is substantially
between about 200 cps to about 20,000 cps at 25.degree. C.
38. The composition of claim 37, wherein the first solvent
comprises at least one solvent selected from the group consisting
of: water; alcohols such as methanol, ethanol, N-propanol
(including 1-propanol, 2-propanol (isopropanol or IPA),
1-methoxy-2-propanol), butanol (including 1-butanol, 2-butanol
(isobutanol)), pentanol (including 1-pentanol, 2-pentanol,
3-pentanol), hexanol (including 1-hexanol, 2-hexanol, 3-hexanol),
octanol, N-octanol (including 1-octanol, 2-octanol, 3-octanol),
tetrahydrofurfuryl alcohol (THFA), cyclohexanol, cyclopentanol,
terpineol; lactones such as butyl lactone; ethers such as methyl
ethyl ether, diethyl ether, ethyl propyl ether, and polyethers;
ketones, including diketones and cyclic ketones, such as
cyclohexanone, cyclopentanone, cycloheptanone, cyclooctanone,
acetone, benzophenone, acetylacetone, acetophenone, cyclopropanone,
isophorone, methyl ethyl ketone; esters such ethyl acetate,
dimethyl adipate, proplyene glycol monomethyl ether acetate,
dimethyl glutarate, dimethyl succinate, glycerin acetate,
carboxylates; glycols such as ethylene glycols, diethylene glycols,
polyethylene glycols, propylene glycols, dipropylene glycols,
glycol ethers, glycol ether acetates; carbonates such as propylene
carbonate; glycerols such as glycerin; n-methylpyrrolidone,
acetonitrile, tetrahydrofuran (THF), dimethyl formamide (DMF),
N-methyl formamide (NMF), dimethyl sulfoxide (DMSO); acids,
including organic acids such as carboxylic acids, dicarboxylic
acids, tricarboxylic acids, alkyl carboxylic acids, acetic acid,
oxalic acid, mellitic acid, formic acid, chloroacetic acid, benzoic
acid, trifluoroacetic acid, propanoic acid, butanoic acid; bases
such as ammonium hydroxide, sodium hydroxide, potassium hydroxide;
and mixtures thereof.
39. The composition of claim 37, wherein the first solvent is
present in an amount of about 3 percent to 10 percent by
weight.
40. The composition of claim 37, wherein the viscosity modifier,
resin or binder comprises polyvinyl pyrrolidone.
41. The composition of claim 40, wherein the first solvent
comprises 1-butanol and the second solvent comprises
cyclohexanol.
42. The composition of claim 41, wherein the first solvent is
present in an amount of about 3 percent to 10 percent by weight and
the second solvent is present in an amount of about 50 percent to
96.3 percent by weight.
43. The composition of claim 42, further comprising acetic acid
present in an amount of about 0.1% to 2% by weight.
44. The composition of claim 37, wherein the viscosity modifier,
resin or binder comprises a polyimide and is present in an amount
of about 0.75% to 5% by weight.
45. The composition of claim 44, wherein the first solvent
comprises cyclohexanone.
46. The composition of claim 45, wherein the first solvent is
present in an amount of about 50 percent to 99.99 percent by
weight.
47. The composition of claim 44, wherein the first solvent
comprises cyclohexanone and the second solvent comprises a
crosslinking agent.
48. The composition of claim 37, wherein the viscosity modifier,
resin or binder is present in an amount of about 0.75% to 5% by
weight and comprises a mixture of polyvinyl pyrrolidone and
polyvinyl alcohol.
49. The composition of claim 37, wherein the second solvent is at
least one solvent selected from the group consisting of: water;
alcohols such as methanol, ethanol, N-propanol (including
1-propanol, 2-propanol (isopropanol or IPA), 1-methoxy-2-propanol),
butanol (including 1-butanol, 2-butanol (isobutanol)), pentanol
(including 1-pentanol, 2-pentanol, 3-pentanol), hexanol (including
1-hexanol, 2-hexanol, 3-hexanol), octanol, N-octanol (including
1-octanol, 2-octanol, 3-octanol), tetrahydrofurfuryl alcohol
(THFA), cyclohexanol, cyclopentanol, terpineol; lactones such as
butyl lactone; ethers such as methyl ethyl ether, diethyl ether,
ethyl propyl ether, and polyethers; ketones, including diketones
and cyclic ketones, such as cyclohexanone, cyclopentanone,
cycloheptanone, cyclooctanone, acetone, benzophenone,
acetylacetone, acetophenone, cyclopropanone, isophorone, methyl
ethyl ketone; esters such ethyl acetate, dimethyl adipate,
proplyene glycol monomethyl ether acetate, dimethyl glutarate,
dimethyl succinate, glycerin acetate, carboxylates; glycols such as
ethylene glycols, diethylene glycols, polyethylene glycols,
propylene glycols, dipropylene glycols, glycol ethers, glycol ether
acetates; carbonates such as propylene carbonate; glycerols such as
glycerin; n-methylpyrrolidone, acetonitrile, tetrahydrofuran (THF),
dimethyl formamide (DMF), N-methyl formamide (NMF), dimethyl
sulfoxide (DMSO); acids, including organic acids such as carboxylic
acids, dicarboxylic acids, tricarboxylic acids, alkyl carboxylic
acids, acetic acid, oxalic acid, mellitic acid, formic acid,
chloroacetic acid, benzoic acid, trifluoroacetic acid, propanoic
acid, butanoic acid; bases such as ammonium hydroxide, sodium
hydroxide, potassium hydroxide; and mixtures thereof.
50. The composition of claim 37, further comprising a third
solvent, the third solvent different from the first solvent and the
second solvent, the third solvent present in an amount of about
0.1% to 10% by weight.
51. The composition of claim 50, wherein the third solvent is at
least one solvent selected from the group consisting of: water;
alcohols such as methanol, ethanol, N-propanol (including
1-propanol, 2-propanol (isopropanol or IPA), 1-methoxy-2-propanol),
butanol (including 1-butanol, 2-butanol (isobutanol)), pentanol
(including 1-pentanol, 2-pentanol, 3-pentanol), hexanol (including
1-hexanol, 2-hexanol, 3-hexanol), octanol, N-octanol (including
1-octanol, 2-octanol, 3-octanol), tetrahydrofurfuryl alcohol
(THFA), cyclohexanol, cyclopentanol, terpineol; lactones such as
butyl lactone; ethers such as methyl ethyl ether, diethyl ether,
ethyl propyl ether, and polyethers; ketones, including diketones
and cyclic ketones, such as cyclohexanone, cyclopentanone,
cycloheptanone, cyclooctanone, acetone, benzophenone,
acetylacetone, acetophenone, cyclopropanone, isophorone, methyl
ethyl ketone; esters such ethyl acetate, dimethyl adipate,
proplyene glycol monomethyl ether acetate, dimethyl glutarate,
dimethyl succinate, glycerin acetate, carboxylates; glycols such as
ethylene glycols, diethylene glycols, polyethylene glycols,
propylene glycols, dipropylene glycols, glycol ethers, glycol ether
acetates; carbonates such as propylene carbonate; glycerols such as
glycerin; n-methylpyrrolidone, acetonitrile, tetrahydrofuran (THF),
dimethyl formamide (DMF), N-methyl formamide (NMF), dimethyl
sulfoxide (DMSO); acids, including organic acids such as carboxylic
acids, dicarboxylic acids, tricarboxylic acids, alkyl carboxylic
acids, acetic acid, oxalic acid, mellitic acid, formic acid,
chloroacetic acid, benzoic acid, trifluoroacetic acid, propanoic
acid, butanoic acid; bases such as ammonium hydroxide, sodium
hydroxide, potassium hydroxide; and mixtures thereof.
52. The composition of claim 50, wherein the third solvent is at
least one solvent selected from the group consisting of: acids,
including organic acids such as carboxylic acids, dicarboxylic
acids, tricarboxylic acids, alkyl carboxylic acids, acetic acid,
oxalic acid, mellitic acid, formic acid, chloroacetic acid, benzoic
acid, trifluoroacetic acid, propanoic acid, butanoic acid; bases
such as ammonium hydroxide, sodium hydroxide, potassium hydroxide;
and mixtures thereof.
53. The composition of claim 37, wherein the first solvent is
present in an amount of about 0.01% to 10% by weight and comprises
at least one solvent selected from the group consisting of:
1-butanol, ethanol, 1-pentanol, n-methylpyrrolidone, 1-hexanol,
acetic acid, and mixtures thereof; and wherein the second solvent
is present in an amount of about 1.75% to 98.25% by weight and
comprises at least one solvent selected from the group consisting
of: cyclohexanol, cyclohexanone, cyclopentanol, butyl lactone, and
mixtures thereof.
54. The composition of claim 37, wherein the first solvent is
present in an amount of about 2.5% to 8.0% by weight and comprises
at least one solvent selected from the group consisting of:
1-butanol, ethanol, 1-pentanol, n-methylpyrrolidone, cyclohexanone,
1-hexanol, acetic acid, and mixtures thereof; and wherein the
second solvent is present in an amount of about 4.5% to 95.5% by
weight and comprises at least one solvent selected from the group
consisting of: cyclohexanol, cyclohexanone, cyclopentanol, butyl
lactone, and mixtures thereof.
55. An apparatus comprising: a plurality of metallic nanofibers
embedded in a polymer; wherein the polymer comprises at least one
polymer selected from the group consisting of: polyvinyl
pyrrolidone, a polyimide, and mixtures thereof.
56. The apparatus of claim 55, wherein the plurality of metallic
nanofibers comprises at least one metal selected from the group
consisting of: aluminum, copper, silver, gold, nickel, palladium,
tin, platinum, lead, zinc, alloys thereof, and mixtures
thereof.
57. The apparatus of claim 55, further comprising: at least a trace
amount of a solvent.
58. The apparatus of claim 57, wherein the solvent comprises at
least one solvent selected from the group consisting of: water;
alcohols such as methanol, ethanol, N-propanol (including
1-propanol, 2-propanol (isopropanol or IPA), 1-methoxy-2-propanol),
butanol (including 1-butanol, 2-butanol (isobutanol)), pentanol
(including 1-pentanol, 2-pentanol, 3-pentanol), hexanol (including
1-hexanol, 2-hexanol, 3-hexanol), octanol, N-octanol (including
1-octanol, 2-octanol, 3-octanol), tetrahydrofurfuryl alcohol
(THFA), cyclohexanol, cyclopentanol, terpineol; lactones such as
butyl lactone; ethers such as methyl ethyl ether, diethyl ether,
ethyl propyl ether, and polyethers; ketones, including diketones
and cyclic ketones, such as cyclohexanone, cyclopentanone,
cycloheptanone, cyclooctanone, acetone, benzophenone,
acetylacetone, acetophenone, cyclopropanone, isophorone, methyl
ethyl ketone; esters such ethyl acetate, dimethyl adipate,
proplyene glycol monomethyl ether acetate, dimethyl glutarate,
dimethyl succinate, glycerin acetate, carboxylates; glycols such as
ethylene glycols, diethylene glycols, polyethylene glycols,
propylene glycols, dipropylene glycols, glycol ethers, glycol ether
acetates; carbonates such as propylene carbonate; glycerols such as
glycerin; n-methylpyrrolidone, acetonitrile, tetrahydrofuran (THF),
dimethyl formamide (DMF), N-methyl formamide (NMF), dimethyl
sulfoxide (DMSO); acids, including organic acids such as carboxylic
acids, dicarboxylic acids, tricarboxylic acids, alkyl carboxylic
acids, acetic acid, oxalic acid, mellitic acid, formic acid,
chloroacetic acid, benzoic acid, trifluoroacetic acid, propanoic
acid, butanoic acid; bases such as ammonium hydroxide, sodium
hydroxide, potassium hydroxide; and mixtures thereof.
59. A composition comprising: a plurality of metallic nanofibers,
substantially all of the metallic nanofibers at least partially
coated with polyvinyl pyrrolidone, the plurality of metallic
nanofibers present in an amount of about 0.01% to 3.0% by weight; a
first solvent present in an amount of about 0.01% to 10% by weight
and comprising at least one solvent selected from the group
consisting of: 1-butanol, ethanol, 1-pentanol, n-methylpyrrolidone,
cyclohexanone, 1-hexanol, acetic acid, and mixtures thereof; a
second solvent present in an amount of about 1.75% to 98.25% by
weight and comprising at least one solvent selected from the group
consisting of: cyclohexanol, cyclohexanone, cyclopentanol, butyl
lactone, and mixtures thereof; and a viscosity modifier, resin or
binder present in an amount of about 0.75% to 5.0% by weight and
comprising at least one viscosity modifier, resin, or binder
selected from the group consisting of: polyvinyl pyrrolidone, a
polyimide, and mixtures thereof; wherein the viscosity of the
composition is substantially between about 200 cps to about 20,000
cps at 25.degree. C.
Description
CROSS-REFERENCE TO A RELATED APPLICATION
[0001] This application is a nonprovisional and conversion of and,
under 35 U.S.C. Section 119, claims the benefit of and priority to
U.S. Provisional Patent Application Ser. No. 61/447,160, filed Feb.
28, 2011, inventors Mark D. Lowenthal et al., entitled "Metallic
Nanofiber Ink, Substantially Transparent Conductor, and Fabrication
Method", which is commonly assigned herewith, the entire contents
of which are incorporated herein by reference with the same full
force and effect as if set forth in their entirety herein, and with
priority claimed for all commonly disclosed subject matter.
FIELD OF THE INVENTION
[0002] The present invention in general is related to conductive
inks and polymers utilized to produce a substantially transparent
conductor and, in particular, is related to a composition of
metallic nanofibers suspended in a liquid or gel and capable of
being printed, substantially transparent conductive films and
manufactures having the metallic nanofibers, and methods of
manufacturing a composition of metallic nanofibers suspended in a
liquid or gel to form a metallic nanofiber ink.
BACKGROUND OF THE INVENTION
[0003] Many conductive inks include a particulate metal, such as
silver or aluminum, in a binder or binding medium. While such inks
produce conductors (when cured) which are substantially conductive
and have a comparatively low electrical impedance (or resistance),
the resulting conductors are substantially opaque and do not allow
the transmission of any appreciable amount of light in the visual
spectrum or other important spectra, such as ultraviolet and
infrared spectra.
[0004] Optically transparent conductors are needed in a wide
variety of applications, however. For example, optically
transparent conductors are highly desirable for making electrical
contacts to diodes in photovoltaic and in light emitting
applications, to allow greater light input and light output,
respectively, compared to opaque conductors.
[0005] Typical printable transparent conductors, while having
reasonable optical transmissivity, unfortunately often have a
comparatively high electrical impedance and low conductivity when
cured, with resistances typically in the range of 800-1000 or more
ohms per square (e.g., polyethylene-dioxithiophene). In addition,
many such transparent conductors (e.g., indium tin oxide (ITO))
require specialized deposition techniques and very high temperature
processing to reduce impedance, or when cured in a resulting
apparatus, tend to have limited, if any, flexibility. The inks or
polymers to produce such typical transparent conductors include,
for example, polyethylene-dioxithiophene (e.g., "Orgacon" from AGFA
Corp. of Ridgefield Park, N.J., USA), a combination of
poly-3,4-ethylenedioxythiophene and polystyrenesulfonic acid
(marketed as Baytron P and available from Bayer AG of Leverkusen,
Germany), a polyaniline or polypyrrole polymer, carbon nanotubes
(CNTs), and/or antimony tin oxide (ATO) (with the CNTs, ATO or
others typically suspended as particles in any of the various
binders, polymers or carriers).
[0006] Other printable transparent conductors require significant
additional processing after printing. For example, some are created
as separate unitary sheets or films which must be laminated onto a
substrate, and then subsequently patterned to form the desired,
electrically isolated conductors having specific electrical
connections, such as through an etching process. Other printable
transparent conductors also require significant additional
processing following deposition, such as acid washing followed by
significant physical compression in nip rollers, for example, in
order to create conductive connections among metallic nanowires
forming the conductors. Other printable transparent conductors are
fragile when deposited, and may further require additional
stabilization layers to hold the deposited but unstable metallic
nanowires in place. These types of printable transparent conductors
have limited usefulness, however, as they cannot be readily
utilized to provide electrical connections to devices, such as
diodes, which are already placed on a substrate and which should
not be subjected to potentially irreparably damaging treatments
such as acid washes, etching, or compressive forces, for
example.
[0007] Accordingly, a need remains for a conductive ink, polymer or
composition which may be printed and, when cured, produces a
resulting conductor which is stable, fixed in place, and capable of
providing electrical connections to devices, and further provides a
comparatively low electrical impedance (or resistance) while
simultaneously allowing substantial light transmission in the
visual or other spectra. In addition, a need remains for such a
composition to be capable of curing into a stable conductor at
comparatively lower processing temperatures, and be suitable for a
wide variety of applications, such as for use in lighting and
photovoltaic panels.
SUMMARY
[0008] The exemplary embodiments provide a "metallic nanofiber
ink", namely, a liquid or gel suspension of metallic nanofibers
which is capable of being printed, such as through screen printing
or flexographic printing, for example and without limitation, to
produce a substantially transparent and stable conductor when cured
or solidified. An exemplary method also comprises a method of
manufacturing metallic nanofiber ink which, as discussed in greater
detail below, suspends a plurality of metallic nanofibers in a
solvent and viscous resin or polymer mixture which is capable of
being printed to manufacture various devices, such as light
emitting diode (LED) devices and photovoltaic devices. Exemplary
apparatuses and systems formed by printing such a metallic
nanofiber ink are also disclosed.
[0009] An exemplary composition comprises a plurality of metallic
nanofibers, substantially all of the metallic nanofibers at least
partially coated or functionalized with a polymer; a first solvent;
and a viscosity modifier, resin, or binder. In various exemplary
embodiments, the metallic nanofibers have lengths between about
1.mu. and about 250.mu. and diameters between about 10 nm and about
500 nm; or more particularly, the metallic nanofibers have lengths
between about 10.mu. and about 150.mu. and diameters between about
5 nm and about 250 nm; or more particularly, the metallic
nanofibers have lengths between about 10.mu. and about 100.mu. and
diameters between about 10 nm and about 100 nm; or more
particularly, the metallic nanofibers have lengths between about
10.mu. and about 80.mu. and diameters between about 10 nm and about
80 nm; or more particularly, the metallic nanofibers have lengths
between about 1.mu. and about 60.mu. and diameters between about 10
nm and about 200 nm; or more particularly, the metallic nanofibers
have lengths between about 10.mu. and about 70.mu. and diameters
between about 25 nm and about 60 nm. Lastly, in various other
exemplary embodiments, the metallic nanofibers have lengths between
about 40.mu. and about 60.mu. and diameters between about 15 nm and
about 40 nm, and/or have lengths between about 10.mu. and about
25.mu. and diameters between about 10 nm and about 15 nm.
[0010] In another exemplary embodiment, the plurality of metallic
nanofibers have an aspect ratio between about 500:1 to 100:1. In
another exemplary embodiment, the metallic nanofibers have an
aspect ratio between about 400:1 to 200:1. In another exemplary
embodiment, the metallic nanofibers have an aspect ratio between
about 350:1 to 250:1. In another exemplary embodiment, the metallic
nanofibers have an aspect ratio between about 350:1 to 275:1.
[0011] In an exemplary embodiment, the plurality of metallic
nanofibers comprises at least one metal selected from the group
consisting of: aluminum, copper, silver, gold, nickel, palladium,
tin, platinum, lead, zinc, alloys thereof, and mixtures
thereof.
[0012] In an exemplary embodiment, the metallic nanofibers are
functionalized with a coating or partial coating of a polymer. In
another exemplary embodiment, the metallic nanofibers are
functionalized with a coating or partial coating of a pyrrolidone
polymer. In another exemplary embodiment, the metallic nanofibers
are functionalized with a coating or partial coating of polyvinyl
pyrrolidone (PVP), generally in an amount of between about 0.09% to
about 0.20% by weight of the coated metallic nanofibers. In various
other exemplary embodiments, the metallic nanofibers are
functionalized with a substantial or complete coating of polyvinyl
pyrrolidone (PVP) having a comparatively low molecular weight. In
another exemplary embodiment, the metallic nanofibers are
functionalized with a substantial or complete coating of polyvinyl
pyrrolidone having a molecular weight between about 5,000 to about
50,000 MW. Other types of coatings or functionalizations, including
with different polymers, mixtures of polymers or other materials,
are also within the scope of the disclosure.
[0013] In an exemplary embodiment, the first solvent comprises at
least one solvent selected from the group consisting of: water;
alcohols such as methanol, ethanol, N-propanol (including
1-propanol, 2-propanol (isopropanol or IPA), 1-methoxy-2-propanol),
butanol (including 1-butanol, 2-butanol (isobutanol)), pentanol
(including 1-pentanol, 2-pentanol, 3-pentanol), hexanol (including
1-hexanol, 2-hexanol, 3-hexanol), octanol, N-octanol (including
1-octanol, 2-octanol, 3-octanol), tetrahydrofurfuryl alcohol
(THFA), cyclohexanol, cyclopentanol, terpineol; lactones such as
butyl lactone; ethers such as methyl ethyl ether, diethyl ether,
ethyl propyl ether, and polyethers; ketones, including diketones
and cyclic ketones, such as cyclohexanone, cyclopentanone,
cycloheptanone, cyclooctanone, acetone, benzophenone,
acetylacetone, acetophenone, cyclopropanone, isophorone, methyl
ethyl ketone; esters such ethyl acetate, dimethyl adipate,
proplyene glycol monomethyl ether acetate, dimethyl glutarate,
dimethyl succinate, glycerin acetate, carboxylates; glycols such as
ethylene glycols, diethylene glycols, polyethylene glycols,
propylene glycols, dipropylene glycols, glycol ethers, glycol ether
acetates; carbonates such as propylene carbonate; glycerols such as
glycerin; n-methylpyrrolidone, acetonitrile, tetrahydrofuran (THF),
dimethyl formamide (DMF), N-methyl formamide (NMF), dimethyl
sulfoxide (DMSO); acids, including organic acids such as carboxylic
acids, dicarboxylic acids, tricarboxylic acids, alkyl carboxylic
acids, acetic acid, oxalic acid, mellitic acid, formic acid,
chloroacetic acid, benzoic acid, trifluoroacetic acid, propanoic
acid, butanoic acid; bases such as ammonium hydroxide, sodium
hydroxide, potassium hydroxide; and mixtures thereof.
[0014] In an exemplary embodiment, the viscosity modifier, resin or
binder comprises polyvinyl pyrrolidone (also known or referred to
as polyvinyl pyrrolidinone), polyvinyl alcohol, or mixtures
thereof. In another exemplary embodiment, the viscosity modifier,
resin or binder comprises or further comprises a methylcellulose
resin, such as a hydroxy propyl methylcellulose resin, or a hydroxy
methylcellulose resin, or mixtures thereof. In another exemplary
embodiment, the viscosity modifier, resin or binder comprises a
polyimide.
[0015] In an exemplary embodiment, the viscosity modifier, resin or
binder comprises at least one viscosity modifier, resin or binder
selected from the group consisting of: polymers (or equivalently,
polymeric precursors or polymerizable precurors) such as polyvinyl
pyrrolidone (also referred to or known as polyvinyl pyrrolidinone),
polyvinyl alcohol, polyimide polymers and copolymers (including
aliphatic, aromatic and semi-aromatic polyimides), acrylate and
(meth)acrylate polymers and copolymers; glycols such as ethylene
glycols, diethylene glycol, polyethylene glycols, propylene
glycols, dipropylene glycols, glycol ethers, glycol ether acetates;
clays such as hectorite clays, garamite clays, organo-modified
clays; saccharides and polysaccharides such as guar gum, xanthan
gum; celluloses and modified celluloses such as hydroxy
methylcellulose, methylcellulose, ethyl cellulose, propyl
methylcellulose, methoxy cellulose, methoxy methylcellulose,
methoxy propyl methylcellulose, hydroxy propyl methylcellulose,
carboxy methylcellulose, hydroxy ethylcellulose, ethyl hydroxyl
ethylcellulose, cellulose ether, cellulose ethyl ether, chitosan;
fumed silica, silica powders, modified ureas; and mixtures
thereof.
[0016] In various exemplary embodiments, the composition further
comprises a second solvent different from the first solvent. In an
exemplary embodiment, the second solvent is at least one solvent
selected from the group consisting of: water; alcohols such as
methanol, ethanol, N-propanol (including 1-propanol, 2-propanol
(isopropanol or IPA), 1-methoxy-2-propanol), butanol (including
1-butanol, 2-butanol (isobutanol)), pentanol (including 1-pentanol,
2-pentanol, 3-pentanol), hexanol (including 1-hexanol, 2-hexanol,
3-hexanol), octanol, N-octanol (including 1-octanol, 2-octanol,
3-octanol), tetrahydrofurfuryl alcohol (THFA), cyclohexanol,
cyclopentanol, terpineol; lactones such as butyl lactone; ethers
such as methyl ethyl ether, diethyl ether, ethyl propyl ether, and
polyethers; ketones, including diketones and cyclic ketones, such
as cyclohexanone, cyclopentanone, cycloheptanone, cyclooctanone,
acetone, benzophenone, acetylacetone, acetophenone, cyclopropanone,
isophorone, methyl ethyl ketone; esters such ethyl acetate,
dimethyl adipate, proplyene glycol monomethyl ether acetate,
dimethyl glutarate, dimethyl succinate, glycerin acetate,
carboxylates; glycols such as ethylene glycols, diethylene glycols,
polyethylene glycols, propylene glycols, dipropylene glycols,
glycol ethers, glycol ether acetates; carbonates such as propylene
carbonate; glycerols such as glycerin; n-methylpyrrolidone,
acetonitrile, tetrahydrofuran (THF), dimethyl formamide (DMF),
N-methyl formamide (NMF), dimethyl sulfoxide (DMSO); acids,
including organic acids such as carboxylic acids, dicarboxylic
acids, tricarboxylic acids, alkyl carboxylic acids, acetic acid,
oxalic acid, mellitic acid, formic acid, chloroacetic acid, benzoic
acid, trifluoroacetic acid, propanoic acid, butanoic acid; bases
such as ammonium hydroxide, sodium hydroxide, potassium hydroxide;
and mixtures thereof. Additional different third, fourth, or more
solvents may also be utilized.
[0017] In an exemplary embodiment, the metallic nanofibers are
present in an amount between about 0.01% to 3.0% by weight. In
various other exemplary embodiments, the metallic nanofibers are
present in an amount between about 0.03% to 2.5% by weight; or more
particularly, an amount between about 0.05% to 2.0% by weight; or
more particularly, an amount between about 0.05% to 1.5% by weight;
an amount between about 0.075% to 1.0% by weight; or more
particularly, an amount between about 0.14% to 0.75% by weight; or
more particularly, an amount between about 0.15% to 0.55% by
weight; or more particularly, an amount between about 0.16% to
0.35% by weight; or more particularly, an amount between about
0.17% to 0.32% by weight; or more particularly, an amount between
about 0.18% to 0.30% by weight; or more particularly, an amount
between about 0.20% to 0.29% by weight; or more particularly, an
amount between about 0.21% to 0.25% by weight. Lastly, in another
exemplary embodiment, the metallic nanofibers are present in an
amount between about 0.22% to 0.24% by weight.
[0018] In an exemplary embodiment, the first solvent comprises
1-butanol and is present in an amount of about 3 percent to 10
percent by weight, and the viscosity modifier, resin or binder
comprises a polyimide and is present in an amount of about 0.75% to
5% by weight.
[0019] In another exemplary embodiment, the first solvent comprises
cyclohexanone, is present in an amount of about 0.05 percent to
99.95 percent by weight, and the viscosity modifier, resin or
binder comprises a polyimide and is present in an amount of about
0.75% to 5% by weight.
[0020] In another exemplary embodiment, the viscosity modifier,
resin or binder comprises polyvinyl pyrrolidone and is present in
an amount of about 0.75% to 5% by weight, the first solvent
comprises 1-butanol and the second solvent comprises cyclohexanol,
and the first solvent is present in an amount of about 3 percent to
10 percent by weight and the second solvent is present in an amount
of about 50 percent to 95 percent by weight.
[0021] Another exemplary composition further comprises an organic
acid present in an amount of about 0.1% to 2% by weight, the
organic acid comprising at least one acid selected from the group
consisting of: carboxylic acids, dicarboxylic acids, tricarboxylic
acids, alkyl carboxylic acids, acetic acid, oxalic acid, mellitic
acid, formic acid, chloroacetic acid, benzoic acid, trifluoroacetic
acid, propanoic acid, butanoic acid; and mixtures thereof.
[0022] Another exemplary composition further comprises a third
solvent, the third solvent different from the first solvent and the
second solvent, the third solvent present in an amount of about
0.1% to 10% by weight. In an exemplary embodiment, the third
solvent is at least one solvent selected from the group consisting
of: acids, including organic acids such as carboxylic acids,
dicarboxylic acids, tricarboxylic acids, alkyl carboxylic acids,
acetic acid, oxalic acid, mellitic acid, formic acid, chloroacetic
acid, benzoic acid, trifluoroacetic acid, propanoic acid, butanoic
acid; bases such as ammonium hydroxide, sodium hydroxide, potassium
hydroxide; and mixtures thereof.
[0023] In an exemplary embodiment, the first solvent is present in
an amount of about 1% to 10% by weight and comprises at least one
solvent selected from the group consisting of: 1-butanol, ethanol,
1-pentanol, 1-hexanol, acetic acid, cyclohexanone, cyclopentanone,
and mixtures thereof; the viscosity modifier, resin, or binder is
present in an amount of about 0.75% to 5.0% by weight and comprises
at least one viscosity modifier, resin, or binder selected from the
group consisting of: polyvinyl pyrrolidone, a mixture of polyvinyl
pyrrolidone with polyvinyl alcohol, and/or a polyimide; and the
second solvent is present in an amount of about 1.75% to 98.25% by
weight and comprises at least one solvent selected from the group
consisting of: cyclohexanol, cyclohexanone, cyclopentanol, butyl
lactone, and mixtures thereof. Additional third, fourth or more
solvents may also be utilized. A method of making the composition
is also disclosed, with the method comprising, for a polyvinyl
pyrrolidone embodiment: mixing the plurality of metallic nanofibers
with 1-butanol and cyclohexanol, for example; mixing polyvinyl
pyrrolidone and cyclohexanol; heating the mixture of polyvinyl
pyrrolidone and cyclohexanol to between about 80.degree. C. to
about 90.degree. C.; cooling the mixture of polyvinyl pyrrolidone
and cyclohexanol to about 25.degree. C.; adding the mixture of the
plurality of metallic nanofibers with 1-butanol and cyclohexanol to
the mixture of polyvinyl pyrrolidone and cyclohexanol; and mixing
the plurality of metallic nanofibers, 1-butanol, polyvinyl
pyrrolidone and cyclohexanol for about 3 to 10 minutes in an air
atmosphere at standard temperature (about 25.degree. C.) and
pressure (about one atmosphere). In an exemplary embodiment, about
0.1% to 2% of acetic acid is also added.
[0024] In yet another exemplary embodiment, the plurality of
metallic nanofibers are coated with polyvinyl pyrrolidone and the
plurality of metallic nanofibers are present in an amount of about
0.01% to 3.0% by weight; the first solvent is present in an amount
of about 1% to 10% by weight and comprises at least one solvent
selected from the group consisting of: 1-butanol, ethanol,
1-pentanol, n-methylpyrrolidone, cyclohexanone, 1-hexanol, acetic
acid, and mixtures thereof; the viscosity modifier, resin, or
binder is present in an amount of about 0.75% to 5.0% by weight and
comprises at least one viscosity modifier, resin, or binder
selected from the group consisting of: polyvinyl pyrrolidone, a
polyimide, and mixtures thereof; and further comprising a second
solvent present in an amount of about 2.75% to 97.25% by weight,
wherein the second solvent comprises at least one solvent selected
from the group consisting of: cyclohexanol, cyclohexanone,
cyclopentanol, butyl lactone, and mixtures thereof.
[0025] In another exemplary embodiment, the plurality of metallic
nanofibers are coated with polyvinyl pyrrolidone and the plurality
of metallic nanofibers are present in an amount of about 0.01% to
3.0% by weight; the first solvent is present in an amount of about
2.5% to 8.0% by weight and comprises at least one solvent selected
from the group consisting of: 1-butanol, ethanol, 1-pentanol,
n-methylpyrrolidone, cyclohexanone, 1-hexanol, acetic acid, and
mixtures thereof; the viscosity modifier, resin, or binder is
present in an amount of about 1.0% to 4.5% by weight and comprises
at least one viscosity modifier, resin, or binder selected from the
group consisting of: polyvinyl pyrrolidone, a polyimide, and
mixtures thereof; and further comprising a second solvent present
in an amount of about 4.5% to 95.5% by weight, wherein the second
solvent comprises at least one solvent selected from the group
consisting of: cyclohexanol, cyclohexanone, cyclopentanol, butyl
lactone, and mixtures thereof.
[0026] In another exemplary composition, the plurality of metallic
nanofibers are coated with polyvinyl pyrrolidone and the plurality
of metallic nanofibers are present in an amount of about 0.01% to
3.0% by weight; the first solvent is present in an amount of about
2.5% to 8.0% by weight and comprises at least one solvent selected
from the group consisting of: 1-butanol, ethanol, 1-pentanol,
n-methylpyrrolidone, cyclohexanone, 1-hexanol, acetic acid, and
mixtures thereof; the viscosity modifier, resin, or binder is
present in an amount of about 1.0% to 4.5% by weight and comprises
at least one viscosity modifier, resin, or binder selected from the
group consisting of: polyvinyl pyrrolidone, a polyimide, and
mixtures thereof; further comprising a second solvent present in an
amount of 0.01% to 5.0% by weight, the second solvent comprising an
acid or a base; and further comprising a third solvent present in
an amount of about 4.5% to 95.4% by weight, the third solvent
comprising at least one solvent selected from the group consisting
of: cyclohexanol, cyclohexanone, cyclopentanol, butyl lactone, and
mixtures thereof.
[0027] In an additional exemplary composition, the plurality of
metallic nanofibers are coated with polyvinyl pyrrolidone and the
plurality of metallic nanofibers are present in an amount of about
0.01% to 3.0% by weight; the first solvent is present in an amount
of about 2.5% to 8.0% by weight and comprises at least one solvent
selected from the group consisting of: 1-butanol, ethanol,
1-pentanol, n-methylpyrrolidone, cyclohexanone, 1-hexanol, acetic
acid, and mixtures thereof; the viscosity modifier, resin, or
binder is present in an amount of about 1.0% to 4.5% by weight and
comprises at least one viscosity modifier, resin, or binder
selected from the group consisting of: polyvinyl pyrrolidone, a
polyimide, and mixtures thereof; further comprising a second
solvent present in an amount of 0.01% to 5.0% by weight, wherein
the second solvent comprises at least one solvent selected from the
group consisting of: acids, including organic acids such as
carboxylic acids, dicarboxylic acids, tricarboxylic acids, alkyl
carboxylic acids, acetic acid, oxalic acid, mellitic acid, formic
acid, chloroacetic acid, benzoic acid, trifluoroacetic acid,
propanoic acid, butanoic acid; bases such as ammonium hydroxide,
sodium hydroxide, potassium hydroxide; and mixtures thereof; and
further comprising a third solvent present in an amount of about
4.5% to 95.4% by weight, the third solvent comprising at least one
solvent selected from the group consisting of: cyclohexanol,
cyclohexanone, cyclopentanol, butyl lactone, and mixtures
thereof.
[0028] In another exemplary embodiment, the plurality of metallic
nanofibers are coated with polyvinyl pyrrolidone and the plurality
of metallic nanofibers are present in an amount of about 0.18% to
about 0.3% by weight; the first solvent is present in an amount of
about 2.5% to 8.0% by weight and comprises at least one solvent
selected from the group consisting of: 1-butanol, ethanol,
1-pentanol, n-methylpyrrolidone, cyclohexanone, 1-hexanol, and
mixtures thereof; the viscosity modifier, resin, or binder is
present in an amount of about 1.0% to 4.5% by weight and comprises
at least one viscosity modifier, resin, or binder selected from the
group consisting of: polyvinyl pyrrolidone, a polyimide, and
mixtures thereof; further comprising a second solvent present in an
amount of 0.1% to 2.0% by weight and comprising a carboxylic acid;
and further comprising a third solvent present in an amount of
about 3.7% to 96.3% by weight, the third solvent comprising at
least one solvent selected from the group consisting of:
cyclohexanol, cyclohexanone, cyclopentanol, butyl lactone, and
mixtures thereof.
[0029] In another exemplary composition, the plurality of metallic
nanofibers are coated with polyvinyl pyrrolidone and the plurality
of metallic nanofibers are present in an amount of about 0.01% to
3.0% by weight; the first solvent is present in an amount of about
2.5% to 8.0% by weight and comprises at least one solvent selected
from the group consisting of: 1-butanol, ethanol, 1-pentanol,
n-methylpyrrolidone, cyclohexanone, 1-hexanol, acetic acid, and
mixtures thereof; the viscosity modifier, resin, or binder is
present in an amount of about 1.0% to 4.5% by weight and is
selected from the group consisting of: polyvinyl pyrrolidone, a
polyimide, and mixtures thereof; further comprising a second
solvent present in an amount of 0.01% to 5.0% by weight, wherein
the second solvent comprises at least one solvent selected from the
group consisting of: acids, including organic acids such as
carboxylic acids, dicarboxylic acids, tricarboxylic acids, alkyl
carboxylic acids, acetic acid, oxalic acid, mellitic acid, formic
acid, chloroacetic acid, benzoic acid, trifluoroacetic acid,
propanoic acid, butanoic acid; bases such as ammonium hydroxide,
sodium hydroxide, potassium hydroxide; and mixtures thereof;
further comprising a third solvent present in an amount of about
4.5% to 95.4% by weight, the third solvent comprising at least one
solvent selected from the group consisting of: cyclohexanol,
cyclohexanone, cyclopentanol, butyl lactone, and mixtures thereof;
and wherein the viscosity of the composition is substantially
between about 200 cps to about 20,000 cps at 25.degree. C.
[0030] In another exemplary composition, the plurality of metallic
nanofibers are coated with polyvinyl pyrrolidone and the plurality
of metallic nanofibers are present in an amount of about 0.01% to
3.0% by weight; the first solvent is present in an amount of about
18% to 28% by weight and comprises at least one solvent selected
from the group consisting of: 1-butanol, ethanol, 1-pentanol,
n-methylpyrrolidone, cyclohexanone, 1-hexanol, acetic acid, and
mixtures thereof; the viscosity modifier, resin, or binder is
present in an amount of about 1.4% to 3.75% by weight and comprises
at least one viscosity modifier, resin, or binder selected from the
group consisting of: polyvinyl pyrrolidone, a polyimide, and
mixtures thereof; further comprising a second solvent present in an
amount of 0.001% to 2% by weight, wherein the second solvent
comprises at least one solvent selected from the group consisting
of: 1-octanol, acetic acid, diethylene glycol, dipropylene glycol,
propylene glycol, and mixtures thereof; and further comprising a
third solvent present in an amount of about 20.4% to 79.6% by
weight, the third solvent comprising at least one solvent selected
from the group consisting of: cyclohexanol, cyclohexanone,
cyclopentanol, butyl lactone, and mixtures thereof.
[0031] In another exemplary embodiment, the viscosity modifier,
resin or binder is present in an amount of about 0.75% to 5% by
weight and comprises a mixture of polyvinyl pyrrolidone and
polyvinyl alcohol.
[0032] Another exemplary embodiment comprises: a plurality of
metallic nanofibers, substantially all of the metallic nanofibers
at least partially coated with polyvinyl pyrrolidone, the plurality
of metallic nanofibers present in an amount of about 0.01% to about
3.0% by weight; a first solvent; a second solvent different from
the first solvent; and a viscosity modifier, resin or binder
present in an amount of about 0.75% to 5.0% by weight and comprises
at least one viscosity modifier, resin, or binder selected from the
group consisting of: polyvinyl pyrrolidone, a polyimide, and
mixtures thereof; wherein the viscosity of the composition is
substantially between about 200 cps to about 20,000 cps at
25.degree. C.
[0033] In an exemplary embodiment the viscosity modifier, resin or
binder comprises polyvinyl pyrrolidone, the first solvent comprises
1-butanol and the second solvent comprises cyclohexanol. In another
exemplary embodiment, the viscosity modifier, resin or binder
comprises a polyimide and is present in an amount of about 0.75% to
5% by weight, and the first solvent comprises cyclohexanone and is
present in an amount of about 50 percent to 99.99 percent by
weight. In another exemplary embodiment, the first solvent
comprises cyclohexanone and the second solvent comprises a
crosslinking agent. In another exemplary composition, the viscosity
modifier, resin or binder is present in an amount of about 0.75% to
5% by weight and comprises a mixture of polyvinyl pyrrolidone and
polyvinyl alcohol.
[0034] Another exemplary embodiment comprises: a plurality of
metallic nanofibers, substantially all of the metallic nanofibers
at least partially coated with polyvinyl pyrrolidone, the plurality
of metallic nanofibers present in an amount of about 0.01% to 3.0%
by weight; a first solvent present in an amount of about 0.01% to
10% by weight and comprising at least one solvent selected from the
group consisting of: 1-butanol, ethanol, 1-pentanol,
n-methylpyrrolidone, cyclohexanone, 1-hexanol, acetic acid, and
mixtures thereof; a second solvent present in an amount of about
1.75% to 98.25% by weight and comprising at least one solvent
selected from the group consisting of: cyclohexanol, cyclohexanone,
cyclopentanol, butyl lactone, and mixtures thereof; and a viscosity
modifier, resin or binder present in an amount of about 0.75% to
5.0% by weight and comprising at least one viscosity modifier,
resin, or binder selected from the group consisting of: polyvinyl
pyrrolidone, a polyimide, and mixtures thereof; wherein the
viscosity of the composition is substantially between about 200 cps
to about 20,000 cps at 25.degree. C.
[0035] Various percentages of the constituents and various
viscosities of the exemplary compositions are also disclosed.
[0036] In an exemplary embodiment, the viscosity modifier, resin,
or binder, when dried or cured, forms a polymer or resin lattice or
structure substantially about the periphery of each metallic
nanofiber of the plurality of metallic nanofibers. In an exemplary
embodiment, the composition is substantially optically transparent
when dried or cured. In another exemplary embodiment, the
composition has a relative evaporation rate less than one, wherein
the evaporation rate is relative to butyl acetate having a rate of
one.
[0037] A method of using the composition is also disclosed, with
the method comprising: printing the composition to form an
electrical contact.
[0038] An exemplary apparatus is also disclosed, comprising: a
plurality of metallic nanofibers embedded in a polymer; wherein the
polymer comprises at least one polymer selected from the group
consisting of: polyvinyl pyrrolidone, a polyimide, and mixtures
thereof.
[0039] In an exemplary embodiment, the cured or polymerized resin
or polymer comprises polyvinyl pyrrolidone, or a mixture of
polyvinyl pyrrolidone and polyvinyl alcohol. In another exemplary
embodiment, the cured or polymerized resin or polymer comprises a
cellulose resin such as hydroxy methylcellulose, methylcellulose,
ethyl cellulose, propyl methylcellulose, methoxy cellulose, methoxy
methylcellulose, methoxy propyl methylcellulose, hydroxy propyl
methylcellulose, carboxy methylcellulose, hydroxy ethylcellulose,
or mixtures thereof. In another exemplary embodiment, the cured or
polymerized resin or polymer comprises a polyimide.
[0040] The exemplary apparatus may further comprise: at least a
trace amount of a solvent; and/or at least a trace amount of a
viscosity modifier; and/or at least trace amounts of a
surfactant.
[0041] Numerous other advantages and features of the present
invention will become readily apparent from the following detailed
description of the invention and the embodiments thereof, from the
claims and from the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] The objects, features and advantages of the present
invention will be more readily appreciated upon reference to the
following disclosure when considered in conjunction with the
accompanying drawings, wherein like reference numerals are used to
identify identical components in the various views, and wherein
reference numerals with alphabetic characters are utilized to
identify additional types, instantiations or variations of a
selected component embodiment in the various views, in which:
[0043] FIG. 1 is a perspective view illustrating an exemplary
apparatus embodiment.
[0044] FIG. 2 is a cross-sectional view illustrating the exemplary
apparatus embodiment.
[0045] FIG. 3 is a photograph of an exemplary apparatus embodiment
fabricated with an exemplary metallic nanofiber ink at a
magnification of 880.times..
[0046] FIG. 4 is a perspective view illustrating an exemplary
functionalized metallic nanofiber embodiment.
[0047] FIG. 5 is a cross-sectional view illustrating an exemplary
functionalized metallic nanofiber embodiment.
[0048] FIG. 6 is a flow diagram illustrating an exemplary method
embodiment for metallic nanofiber ink fabrication.
[0049] FIG. 7 is a graphical diagram illustrating sheet resistance
and optical transmissivity for an exemplary apparatus embodiment
fabricated with an exemplary metallic nanofiber ink.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0050] While the present invention is susceptible of embodiment in
many different forms, there are shown in the drawings and will be
described herein in detail specific exemplary embodiments thereof,
with the understanding that the present disclosure is to be
considered as an exemplification of the principles of the invention
and is not intended to limit the invention to the specific
embodiments illustrated. In this respect, before explaining at
least one embodiment consistent with the present invention in
detail, it is to be understood that the invention is not limited in
its application to the details of construction and to the
arrangements of components set forth above and below, illustrated
in the drawings, or as described in the examples. Methods and
apparatuses consistent with the present invention are capable of
other embodiments and of being practiced and carried out in various
ways. Also, it is to be understood that the phraseology and
terminology employed herein, as well as the abstract included
below, are for the purposes of description and should not be
regarded as limiting.
[0051] Exemplary embodiments of the invention provide a liquid
and/or gel suspension of metallic nanofibers 100 which is capable
of being printed, and may be referred to equivalently herein as
"metallic nanofiber ink", it being understood that "metallic
nanofiber ink" means and refers to a liquid and/or gel suspension
of metallic nanofibers (also referred to equivalently as metallic
nanowires), such as exemplary metallic nanofibers 100. An exemplary
method of the invention also comprises a method of manufacturing
metallic nanofiber ink which, as discussed in greater detail below,
suspends a plurality of metallic nanofibers 100 in one or more
solvents and a viscous resin or polymer mixture which is capable of
being printed, for example, to produce a substantially transparent
conductor when cured or solidified, such as for the manufacture of
LED-based devices and photovoltaic devices, for example and without
limitation. Exemplary conductors, apparatuses and systems formed by
printing such an exemplary metallic nanofiber ink are also
disclosed.
[0052] The metallic nanofiber ink disclosed herein may be
deposited, printed or otherwise applied to any substrate, device,
or may be deposited, printed or otherwise applied to any product of
any kind or to form any product of any kind, including lighting,
photovoltaic panels, electronic displays such as computer,
television, tablet and mobile device displays, packaging, signage
or indicia for product packaging, or as a conductor for any other
product or device, such as a consumer product, a personal product,
a business product, an industrial product, an architectural
product, a building product, etc. The metallic nanofiber ink may be
printed onto the substrate, device, article, or packaging thereof,
as either a functional or decorative component of the article,
package, or both. In one embodiment, the metallic nanofiber ink is
printed in the form of indicia and combined with light emitting
diodes. In another embodiment, the metallic nanofiber ink is
printed to form electrical contacts for light emitting diodes or
photovoltaic diodes. In another embodiment, the metallic nanofiber
ink is printed to form electrical contacts for any two, three or
more terminal device, such as a transistor or RFID tag. The article
or package may be formed from any consumer-acceptable material.
[0053] For example and without limitation, the metallic nanofiber
ink disclosed herein may be utilized to form any of the conductors
or conductive layers, transparent or otherwise, for the
apparatuses, methods, and systems referred to and disclosed in the
following U.S. patent applications, U.S. patents, and PCT patent
applications, the entire contents of each of which are incorporated
herein by reference with the same full force and effect as if set
forth in their entireties herein, and with priority claimed for all
commonly disclosed subject matter (individually and collectively
referred to as the "related patent applications"): U.S. patent
application Ser. No. 13/223,279; U.S. patent application Ser. No.
13/223,286; U.S. patent application Ser. No. 13/223,289; U.S.
patent application Ser. No. 13/223,293; U.S. patent application
Ser. No. 13/223,294; U.S. patent application Ser. No. 13/223,297;
U.S. patent application Ser. No. 13/223,302; U.S. patent
application Ser. No. 12/753,888; U.S. patent application Ser. No.
12/753,887; U.S. Pat. No. 7,719,187; U.S. Pat. No. 7,972,031; U.S.
Pat. No. 7,992,332; U.S. patent application Ser. No. 12/560,334;
U.S. patent application Ser. No. 12/560,340; U.S. patent
application Ser. No. 12/560,355; U.S. patent application Ser. No.
12/560,364; U.S. patent application Ser. No. 12/560,371; U.S.
patent application Ser. No. 13/025,137; U.S. patent application
Ser. No. 13/025,138; PCT patent application Ser. No.
PCT/US2011/50168; PCT patent application Ser. No.
PCT/US2011/50174.
[0054] FIG. 1 is a perspective view illustrating an exemplary
substantially transparent conductor (or conductive apparatus) 150
embodiment. FIG. 2 is a cross-sectional view (through the 20-20'
plane of FIG. 1) illustrating the exemplary substantially
transparent conductor (or conductive apparatus) 150. FIG. 3 is a
photograph of an exemplary substantially transparent conductor (or
conductive apparatus) 150A embodiment. FIG. 4 is a perspective view
illustrating an exemplary functionalized metallic nanofiber 100B
embodiment. FIG. 5 is a cross-sectional view (through the 30-30'
plane of FIG. 4) illustrating an exemplary functionalized metallic
nanofiber 100B embodiment. In addition, referring to FIGS. 1-5,
those having skill in the art will also recognize that the various
Figures are for purposes of description and explanation, are not
drawn to scale, and further may not illustrate any actual or
preferred densities or curvatures of the metallic nanofibers 100;
for example and without limitation, both the densities and the
curvatures of the metallic nanofibers 100 may be considerably
greater than that illustrated in FIGS. 1, 2, 4 and 5, and with
various densities and percentages in the metallic nanofiber ink
described in greater detail below.
[0055] Referring to FIGS. 1-2, the exemplary metallic nanofibers
100 are illustrated as at least partially embedded, primarily, in a
polymerized or cured polymer or resin 110 (discussed in greater
detail below), which to some extent possibly may also include
residual or trace amounts of other components of the metallic
nanofiber ink as discussed in greater detail below, such as
depending upon cure time, to form an exemplary, substantially
transparent conductor (or conductive apparatus) 150. An exemplary
conductor (or conductive apparatus) 150 is typically a
substantially transparent conductive film, layer, strip, electrode,
wire or conductive line or trace, having any shape or form factor,
such as those illustrated and discussed in the related patent
applications, although other conductor (or conductive apparatus)
150 shapes and form factors are considered equivalent and within
the scope of the disclosure. The substantially transparent
conductor (or conductive apparatus) 150 is illustrated as an
exemplary conductive line or wire in FIG. 1. An exemplary apparatus
150A is illustrated in the photograph of FIG. 3, with exemplary
metallic nanofibers 100A having a length on the order of between
about twenty to sixty microns (10.mu.-60.mu.) and a diameter on the
order of between about twenty to one hundred nanometers (10-120
nm).
[0056] The substantially transparent conductor (or conductive
apparatus) 150 may be deposited to have any width and length, with
the resulting depth depending to some extent upon the viscosity of
the metallic nanofiber ink and the sizes (length and diameters) of
the metallic nanofibers 100. Referring to FIG. 2, in exemplary
embodiments, the substantially transparent conductor (or conductive
apparatus) 150, once cured or dried, generally has a substantially
thin form factor, generally between about 100 to 300 nm thick (or
deep), or more particularly, between about 150 to 250 nm thick, or
more particularly, between about 175 to 225 nm, or more
particularly, on the order of about 200 nm thick when the applied
metallic nanofiber ink has a viscosity on the order of 500 cps
using metallic nanofibers 100 having a length on the order of
between about twenty to sixty microns (10.mu.-60.mu.) and a
diameter on the order of between about twenty to one hundred
nanometers (10-120 nm). As a result, many of the metallic
nanofibers 100 become and are at least partially exposed on the
surfaces of the substantially transparent conductor (or conductive
apparatus) 150.
[0057] Referring to FIG. 4, exemplary metallic nanofibers 100 may
have a wide variety of shapes and sizes, and are generally or
roughly cylindrically or rod-shaped, with any of various
cross-sectional shapes (such as a hexagonal rod shape illustrated
in FIG. 4), also may be solid or hollow (tubular), and generally
having a length dimension substantially greater than a diameter
dimension (also referred to as anisotropic), i.e., an aspect ratio
greater than one. As illustrated in FIG. 4, for example and without
limitation, an exemplary metallic nanofiber 100B is substantially
hexagonal in diameter (or cross-section), having a plurality of
substantially flat sides, and further may have one or more
curvatures along its length dimension, as illustrated. A complete,
substantial or at least a partial polymer coating 125 or other
functionalization is illustrated in FIG. 4 and in cross-section in
FIG. 5, as discussed in greater detail below. As mentioned above,
in a first exemplary embodiment, the exemplary metallic nanofibers
100A may have a length on the order of about 10.mu. to about
100.mu. and a diameter on the order of about 10 nm to about 120 nm.
More particularly, in various exemplary embodiments, the lengths
and diameters of the metallic nanofibers may vary, for example: the
plurality of metallic nanofibers may have lengths between about
1.mu. and about 250.mu. and diameters between about 10 nm and about
500 nm; or more particularly, may have lengths between about 10.mu.
and about 150.mu. and diameters between about 5 nm and about 250
nm; or more particularly, may have lengths between about 10.mu. and
about 100.mu. and diameters between about 10 nm and about 100 nm;
or more particularly, may have lengths between about 10.mu. and
about 80.mu. and diameters between about 10 nm and about 80 nm; or
more particularly, may have lengths between about 1.mu. and about
60.mu. and diameters between about 10 nm and about 200 nm; or more
particularly, may have lengths between about 10.mu. and about
70.mu. and diameters between about 25 nm and about 60 nm; or more
particularly, the plurality of metallic nanofibers may have lengths
between about 40.mu. and about 60.mu. and diameters between about
15 nm and about 40 nm and/or have lengths between about 10.mu. and
about 25.mu. and diameters between about 10 nm and about 15 nm
[0058] In addition, the selection of the lengths of the metallic
nanofibers 100 for a metallic nanofiber ink may also depend upon
the type of printing to be utilized. For example and without
limitation, for screen printing, the lengths of the metallic
nanofibers 100 may be selected for the pore or hole size of the
screen or mesh, to pass through and not become caught in the
screen.
[0059] In various exemplary embodiment, the plurality of metallic
nanofibers may have an aspect ratio between about 500:1 to 100:1,
for example and without limitation. In various other exemplary
embodiments, the plurality of metallic nanofibers may have an
aspect ratio between about 400:1 to 200:1; an aspect ratio between
about 350:1 to 250:1; and/or an aspect ratio between about 350:1 to
275:1, all also for example and without limitation. With the length
dimension substantially greater than the diameter (or width)
dimension, such as having lengths 10 to about 6000 times greater
than the diameter, the exemplary metallic nanofibers 100 have some
rigidity but are also flexible, which aids in the creation of
electrical contacts with each other to form a conductive film,
trace or line, in any form factor, and to facilitate the creation
of electrical contacts with other system components, such as
diodes, as illustrated in the related patent applications, to
provide corresponding electrical connections to these other system
components.
[0060] The dimensions of the exemplary metallic nanofibers 100 may
be measured, for example, using a light microscope (which may also
include measuring software). As additional examples, the dimensions
of the exemplary metallic nanofibers 100 may be measured using, for
example, a scanning electron microscope (SEM), or Horiba's LA-920.
The Horiba LA-920 instrument uses the principles of low-angle
Fraunhofer Diffraction and Light Scattering to measure the particle
size and distribution in a dilute solution of particles, such as
when embodied in a metallic nanofiber ink. All particle sizes are
measured in terms of their number average particle diameters and
lengths, as there may be significant outliers in the fabrication of
metallic nanofibers.
[0061] The exemplary metallic nanofibers 100 may be comprised of a
wide variety of materials, and a referred to as "metallic" to
indicate substantially high conductivity. In an exemplary
embodiment, metallic nanofibers 100 are comprised of one or more
metals (e.g., aluminum, copper, silver, gold, nickel, palladium,
tin, platinum, lead, zinc, etc.), alone or in combination with each
other, such as an alloy, for example and without limitation.
Combinations of different types of conductors and/or conductive
compounds or materials (e.g., ink, polymer, carbon nanotubes,
elemental metal, etc.) may also be utilized to form metallic
nanofibers 100. Multiple layers and/or types of metal or other
conductive materials may be combined to form the metallic
nanofibers 100.
[0062] As illustrated in FIG. 5, the exemplary metallic nanofibers
100 may also be functionalized with a wide variety of compounds to
aid their dispersion in a liquid or gel. In an exemplary
embodiment, metallic nanofibers 100 are functionalized by having a
complete or full coating, a substantial coating, or at least a
partial coating 125 of a polymer, including a pyrrolidone polymer
such as polyvinyl pyrrolidone ("PVP") or any other polymer, for
example and without limitation, such as to facilitate dispersion of
the metallic nanofibers 100 in the metallic nanofiber ink, also for
example.
[0063] The exemplary metallic nanofibers 100 may be fabricated
using any fabrication techniques which are known currently or which
are developed in the future. Exemplary metallic nanofibers 100,
such as silver nanofibers, including metallic nanofibers in a
functionalized form with PVP coatings, are commercially available
and have been obtained from several suppliers, including NanoGap
Subnmparticles of Spain, US and UK and having an office in San
Francisco, Calif. USA; Blue Nano Inc. of Charlotte and Cornelius,
N.C. USA; Zhejiang Kechuang Advanced Materials Technology Co. Ltd.
of Zhejiang, China; and ACS Material LLC, having offices in
Medford, Mass. and Ames, Iowa, USA. For example, metallic
nanofibers 100 exemplary include AW030 silver fibers obtained from
Zhejiang Kechuang Advanced Materials Technology Co. Ltd.
[0064] Metallic Nanofiber Ink Example 1: [0065] A composition
comprising: [0066] a plurality of functionalized metallic
nanofibers, substantially all of the metallic nanofibers having at
least a partial coating of a polymer; [0067] a solvent; and [0068]
a viscosity modifier.
[0069] Metallic Nanofiber Ink Example 2: [0070] A composition
comprising: [0071] a plurality of functionalized metallic
nanofibers, substantially all of the metallic nanofibers having at
least a partial coating of a polymer; [0072] a solvating agent; and
[0073] a viscosity modifier.
[0074] Metallic Nanofiber Ink Example 3: [0075] A composition
comprising: [0076] a plurality of functionalized metallic
nanofibers, substantially all of the metallic nanofibers having at
least a partial coating of a polymer; [0077] a wetting or rewetting
solvent; and [0078] a viscosity modifier.
[0079] Metallic Nanofiber Ink Example 4: [0080] A composition
comprising: [0081] a plurality of functionalized metallic
nanofibers, substantially all of the metallic nanofibers having at
least a partial coating of a polymer; [0082] a first solvent;
[0083] a first viscosity modifier; and [0084] a second, adhesion
promoting solvent or a second, adhesive viscosity modifier.
[0085] Metallic Nanofiber Ink Example 5: [0086] A composition
comprising: [0087] a plurality of functionalized metallic
nanofibers, substantially all of the metallic nanofibers having at
least a partial coating of a polymer; [0088] a first solvent having
a comparatively high melting point and comprising a solid at room
temperature (about 25.degree. C.); [0089] a first viscosity
modifier; [0090] a second, adhesion promoting solvent or a second,
adhesive viscosity modifier; and [0091] a third solvent to lower
the melting point and liquefy the first solvent at room temperature
(about 25.degree. C.).
[0092] Metallic Nanofiber Ink Example 6: [0093] A composition
comprising: [0094] a plurality of functionalized metallic
nanofibers, substantially all of the metallic nanofibers having at
least a partial coating of a polyvinyl pyrrolidone polymer and
having lengths between about 40.mu. and about 60.mu. and diameters
between about 25 nm and about 35 nm; [0095] a first solvent having
a comparatively high melting point and comprising a solid at room
temperature (about 25.degree. C.); [0096] a viscosity modifier;
[0097] a second, adhesion promoting solvent; and [0098] a third
solvent to lower the melting point and liquefy the first solvent at
room temperature (about 25.degree. C.).
[0099] Metallic Nanofiber Ink Example 7: [0100] A composition
comprising: [0101] a plurality of functionalized metallic
nanofibers, substantially all of the metallic nanofibers having at
least a partial coating of a polyvinyl pyrrolidone polymer; [0102]
a first solvent comprising cyclohexanol or cyclohexanone; [0103] a
viscosity modifier comprising polyvinyl pyrrolidone or a polyimide;
[0104] a second, adhesion promoting solvent comprising acetic acid;
and [0105] a third solvent comprising 1-butanol,
n-methylpyrrolidone or cyclopentanone.
[0106] In various exemplary embodiments, such as in Examples 1-7
and the additional Examples below, a metallic nanofiber ink
comprises a plurality of functionalized metallic nanofibers 100,
each or most having at least a partial coating of a polymer such as
PVP, and which are dispersed in a solvent (such as cyclohexanol,
1-butanol, n-methylpyrrolidone, cyclohexanone, cyclopentanone,
acetic acid, ethanol, 1-pentanol or 1-hexanol) and a viscosity
modifier, such as PVP. One or more solvents (as first, second or
third solvents) may be used equivalently, for example and without
limitation: water; alcohols such as methanol, ethanol, N-propanol
(including 1-propanol, 2-propanol (isopropanol or IPA),
1-methoxy-2-propanol), butanol (including 1-butanol, 2-butanol
(isobutanol)), pentanol (including 1-pentanol, 2-pentanol,
3-pentanol), hexanol (including 1-hexanol, 2-hexanol, 3-hexanol),
octanol, N-octanol (including 1-octanol, 2-octanol, 3-octanol),
tetrahydrofurfuryl alcohol (THFA), cyclohexanol, cyclopentanol,
terpineol; lactones such as butyl lactone; ethers such as methyl
ethyl ether, diethyl ether, ethyl propyl ether, and polyethers;
ketones, including diketones and cyclic ketones, such as
cyclohexanone, cyclopentanone, cycloheptanone, cyclooctanone,
acetone, benzophenone, acetylacetone, acetophenone, cyclopropanone,
isophorone, methyl ethyl ketone; esters such ethyl acetate,
dimethyl adipate, proplyene glycol monomethyl ether acetate,
dimethyl glutarate, dimethyl succinate, glycerin acetate,
carboxylates; glycols such as ethylene glycols, diethylene glycols,
polyethylene glycols, propylene glycols, dipropylene glycols,
glycol ethers, glycol ether acetates; carbonates such as propylene
carbonate; glycerols such as glycerin; n-methylpyrrolidone,
acetonitrile, tetrahydrofuran (THF), dimethyl formamide (DMF),
N-methyl formamide (NMF), dimethyl sulfoxide (DMSO); acids,
including organic acids such as carboxylic acids, dicarboxylic
acids, tricarboxylic acids, alkyl carboxylic acids, acetic acid,
oxalic acid, mellitic acid, formic acid, chloroacetic acid, benzoic
acid, trifluoroacetic acid, propanoic acid, butanoic acid; bases
such as ammonium hydroxide, sodium hydroxide, potassium hydroxide;
and mixtures thereof. In addition, a solvent may also function as a
viscosity modifier and vice-versa, such as cyclohexanol, terpineol
and n-methyl pyrrolidone, for example and without limitation.
[0107] In various exemplary embodiments, the selection of a first
(or second) solvent is based upon at least two properties or
characteristics. A first characteristic of the solvent is its
ability be soluble in or to solubilize a binder, a viscosity
modifier or an adhesive viscosity modifier such as PVP, PVA,
methoxy cellulose or hydroxy propyl methylcellulose resin. A second
characteristic or property is its evaporation rate, which should be
slow enough to allow sufficient screen residence (for screen
printing) of the metallic nanofiber ink or to meet other printing
parameters. In various exemplary embodiments, an exemplary
evaporation rate is less than one (<1, as a relative rate
compared with butyl acetate), or more specifically, between 0.0001
and 0.9999.
[0108] One or more viscosity modifiers, binders, resins or
thickeners (as a viscosity modifier) may be used, for example and
without limitation: polymers (or equivalently, polymeric precursors
or polymerizable precurors) such as polyvinyl pyrrolidone (also
referred to or known as polyvinyl pyrrolidinone), polyvinyl
alcohol, polyimide polymers and copolymers (including aliphatic,
aromatic and semi-aromatic polyimides), acrylate and (meth)acrylate
polymers and copolymers; glycols such as ethylene glycols,
diethylene glycol, polyethylene glycols, propylene glycols,
dipropylene glycols, glycol ethers, glycol ether acetates; clays
such as hectorite clays, garamite clays, organo-modified clays;
saccharides and polysaccharides such as guar gum, xanthan gum;
celluloses and modified celluloses such as hydroxy methylcellulose,
methylcellulose, ethyl cellulose, propyl methylcellulose, methoxy
cellulose, methoxy methylcellulose, methoxy propyl methylcellulose,
hydroxy propyl methylcellulose, carboxy methylcellulose, hydroxy
ethylcellulose, ethyl hydroxylethylcellulose, cellulose ether,
cellulose ethyl ether, chitosan; fumed silica (such as Cabosil),
silica powders and modified ureas such as BYK.RTM. 420 (available
from BYK Chemie GmbH); and mixtures thereof. As mentioned above,
some of the viscosity modifiers may also function as solvents and
vice-versa, such as the various glycols, and therefore are included
in the various listings of exemplary solvents and viscosity
modifiers. In several Examples discussed below, E-3 and E-10
cellulose resins available from The Dow Chemical Company
(www.dow.com) and Hercules Chemical Company, Inc. (www.herchem.com)
are utilized. In an exemplary embodiment, the PVP utilized has a
molecular weight between about 50,000 to about 3 million MW, or
more particularly between about 100,000 to 2 million MW, or more
particularly between about 500,000 to 1.5 million MW, or more
particularly between about 750,000 to 1.25 million MW, while the
PVA has a molecular weight of about 133K, or more generally between
about 50,000 to 250K MW, and may be obtained from Polysciences,
Inc. of Warrington, Pa. USA. Other viscosity modifiers may be used,
as well as particle addition to control viscosity, as described in
Lewis et al., Patent Application Publication Pub. No. US
2003/0091647. Other viscosity modifiers or binders may also be
utilized. As mentioned above, the metallic nanofibers 100 are
functionalized with a substantial, complete or at least a partial
coating of polyvinyl pyrrolidone (PVP) having a molecular weight
between about 5,000 to about 50,000 MW.
[0109] Referring to Metallic Nanofiber Ink Examples 1-7 and the
additional Examples described below, there are a wide variety of
exemplary metallic nanofiber ink compositions within the scope of
the present disclosure. Generally, as in Example 1, a liquid
suspension of metallic nanofibers 100 comprises a plurality of
functionalized metallic nanofibers 100, a first solvent (such as
1-butanol, ethanol, 1-pentanol, n-methylpyrrolidone, cyclohexanone,
1-hexanol, acetic acid, or other solvents discussed herein), which
also may be an adhesion promoting solvent as in Examples 5-7, and a
viscosity modifier, resin or binder (such those discussed above,
which may also be an adhesive viscosity modifier, resin or binder
as in Example 5); and as in Examples 2 and 3, a liquid suspension
of metallic nanofibers 100 comprises a plurality of functionalized
metallic nanofibers 100, a solvating agent or a wetting or
rewetting solvent (such as one of the second solvents discussed
herein), and a viscosity modifier, resin or binder. More
particularly, such as in Examples 4-7, a liquid suspension of
metallic nanofibers 100 comprises a plurality of functionalized
metallic nanofibers 100, a first solvent (such as 1-butanol,
ethanol, 1-pentanol, n-methylpyrrolidone, cyclohexanone, 1-hexanol,
or acetic acid), a viscosity modifier, resin or binder (or
equivalently, a viscous compound, a viscous resin, a viscous agent,
a viscous polymer, a viscous resin, a viscous binder, a thickener,
and/or a rheology modifier) such as PVP or a polyimide, and a
second, adhesion promoting solvent or a second, adhesive viscosity
modifier, to provide a metallic nanofiber ink having a viscosity
between about 100 centipoise (cps) and 20,000 cps at room
temperature (about 25.degree. C.), or more preferably between about
200-1000 centipoise (cps) cps at room temperature (about 25.degree.
C.), or more preferably between about 400-600 centipoise (cps) cps
at room temperature (about 25.degree. C.) for a screen printable
ink (or between about 500 cps to 60,000 cps at a refrigerated
temperature (e.g., 5-10.degree. C.)). Depending upon the viscosity,
the resulting composition may be referred to equivalently as a
liquid or as a gel suspension of metallic nanofibers, and any
reference to liquid or gel herein shall be understood to mean and
include the other.
[0110] In addition, the resulting viscosity of the metallic
nanofiber ink will generally vary depending upon the type of
printing process to be utilized and may also vary depending upon
the metallic nanofiber composition and size. For example, a
metallic nanofiber ink for screen printing may have a viscosity
between about 100 centipoise (cps) and 25,000 cps at room
temperature, or more specifically between about 200 centipoise
(cps) and 5,000 cps at room temperature, or more specifically
between about 200 centipoise (cps) and 1,000 cps at room
temperature, or more specifically between about 300 centipoise
(cps) and 800 cps at room temperature, or more specifically between
about 400 centipoise (cps) and 600 cps at room temperature, or more
specifically between about 450 centipoise (cps) and 550 cps at room
temperature. Also for example, a metallic nanofiber ink for
flexographic printing may have a viscosity between about 100
centipoise (cps) and 10,000 cps at room temperature, or more
specifically between about 200 centipoise (cps) and 4,000 cps at
room temperature, or more specifically between about 500 centipoise
(cps) and 3,000 cps at room temperature, or more specifically
between about 1,800 centipoise (cps) and 2,200 cps at room
temperature, or more specifically between about 2,000 centipoise
(cps) and 6,000 cps at room temperature, or more specifically
between about 2,500 centipoise (cps) and 4,500 cps at room
temperature, or more specifically between about 2,000 centipoise
(cps) and 4,000 cps at room temperature.
[0111] Viscosity may be measured in a wide variety of ways. For
purposes of comparison, the various specified and/or claimed ranges
of viscosity herein have been measured using a Brookfield
viscometer (available from Brookfield Engineering Laboratories of
Middleboro, Mass., USA) at a shear stress of about 200 pascals (or
more generally between 190 and 210 pascals), in a water jacket at
about 25.degree. C., using a spindle SC4-27 at a speed of about 10
rpm (or more generally between 1 and 30 rpm, particularly for
refrigerated fluids, for example and without limitation).
[0112] Referring to Metallic Nanofiber Ink Examples 4-7, the liquid
suspension of metallic nanofibers 100 may further comprise a
second, adhesion promoting solvent or a second, adhesive viscosity
modifier, namely, any of the solvents or viscosity modifiers
mentioned above which have the additional property of adhesion
promotion, including modification of a substrate surface to allow
or promote adherence of the metallic nanofiber ink and resulting
film or trace (150). Such an adhesion promoting solvent or adhesive
viscosity modifier may provide for any of the following: adhering
the metallic nanofibers 100 to another conductor (e.g., a diode
contact); adhering the film or trace (150) to a substrate (e.g.,
during device fabrication (e.g., printing)) such as plastic, glass,
silicon, polyethylene terephthalates (PET), polycarbonate,
polymethyl methacrylate (PMMA), etc.; and/or an infrastructure
(e.g., polymeric) (when dried or cured) for holding the metallic
nanofibers 100 in place in an apparatus (150, 150A). While
providing such adhesion, such a viscosity modifier, resin or binder
should also have some capability to de-wet from inter-fiber
contacts of the metallic nanofibers 100 to each other (i.e. to
de-wet from the contact points between the various metallic
nanofibers 100) and thereby help to decrease the sheet resistance
of the apparatus 150. Such adhesive, viscosity and de-wetting
properties are among the reasons methoxyl cellulose or other
cellulose resins have been utilized in various exemplary
embodiments. In addition, such adhesion promoting to a substrate is
also a reason a solvent such as acetic acid (or another acid or
base) may be utilized in exemplary embodiments. Other suitable
viscosity modifiers or binders may also be selected
empirically.
[0113] Additional properties of the viscosity modifier, resin or
binder are also useful and within the scope of the disclosure.
First, such a viscosity modifier, resin or binder should prevent
the suspended metallic nanofibers 100 from settling out or prevent
hard caking of the metallic nanofibers 100 at a selected
temperature, and potentially further allow comparatively easy
redispersion of the metallic nanofibers 100 with minor agitation or
stirring. Second, such a viscosity modifier, resin or binder should
aid in printing the metallic nanofibers 100 in a uniform manner
during apparatus (150, 150A) fabrication. Third, the viscosity
modifier, resin or binder may also serve to cushion or otherwise
protect the metallic nanofibers 100 during the printing
process.
[0114] Referring to Examples 2-7, the liquid suspension of metallic
nanofibers 100 may further comprise a second solvent (Examples 4-7)
or a solvating agent or a wetting solvent (Examples 2 and 3), with
many examples discussed in greater detail below. Such a (first or
second) solvent is selected as a wetting (equivalently, solvating)
or rewetting agent or adhesion promoting for facilitating ohmic or
electrical contact between metallic nanofibers 100 and other
devices, such as diodes or transistors, and between the metallic
nanofibers 100 themselves, also for example and without
limitation.
[0115] The balance of the liquid or gel suspension of metallic
nanofibers 100 is generally another, second solvent, such as
cyclohexanol, cyclohexanone, cyclopentanone and/or a third solvent
(or fourth or more solvents), such as 1-butanol,
n-methylpyrrolidone, or deionized water, and any descriptions of
percentages herein shall assume that the balance of the liquid or
gel suspension of metallic nanofibers 100 is such a second, third
or fourth solvent such as cyclohexanol, cyclohexanone,
cyclopentanone, n-methylpyrrolidone, 1-butanol or water, and all
described percentages are based on weight, rather than volume or
some other measure. It should also be noted that the various
metallic nanofiber ink suspensions may all be mixed in a typical
atmospheric setting, without requiring any particular composition
of air or other contained or filtered environment.
[0116] Solvent selection may also be based upon the polarity of the
solvent. In an exemplary embodiment, a first solvent such as an
alcohol may be selected as a polar or hydrophilic solvent, to
facilitate de-wetting off of the metallic nanofibers 100 and other
conductors during apparatus 150, 150A, fabrication, while
concomitantly being able to be soluble in or solubilize a viscosity
modifier.
[0117] Another useful property of an exemplary metallic nanofiber
ink is that the dried or cured metallic nanofiber ink is
substantially clear at visible wavelengths, to substantially allow
or not interfere with the emission of visible light generated by
devices such as LEDs. Various transmissivity percentages and
corresponding sheet resistances for different densities of metallic
nanofibers 100 are provided in Table I below and illustrated in
FIG. 7.
[0118] Another way to characterize an exemplary metallic nanofiber
ink is based upon the size of the metallic nanofibers 100, as
discussed above. As illustrated in Example 6, the metallic
nanofibers 100 generally may be between about 40-60 microns in
length, and have a diameter between about 25 nm to about 35 nm.
Additional size ranges also may be provided as previously
discussed.
[0119] The metallic nanofiber ink may also be characterized by its
electrical properties. For example, the metallic nanofibers 100 may
be suspended in at least one substantially non-insulating carrier
or solvent, in contrast with an insulating binder, for example.
[0120] Metallic Nanofiber Ink Example 8: [0121] A composition
comprising: [0122] a plurality of metallic nanofibers,
substantially all of the metallic nanofibers having at least a
partial coating of polyvinyl pyrrolidone; [0123] a first solvent
comprising about 1% to 10% 1-butanol, ethanol, 1-pentanol,
n-methylpyrrolidone, 1-hexanol, or acetic acid, or mixtures
thereof; [0124] a viscosity modifier, resin, or binder comprising
about 0.75% to 5.0% PVP, polyvinyl alcohol, or a polyimide, or
mixtures thereof; and [0125] with the balance comprising a second
solvent such as cyclohexanol, cyclohexanone, cyclopentanone,
cyclopentanol, butyl lactone, or mixtures thereof
[0126] Metallic Nanofiber Ink Example 9: [0127] A composition
comprising: [0128] about 0.01% to 3.0% of a plurality of
functionalized metallic nanofibers, substantially all of the
metallic nanofibers having at least a partial coating of a
polyvinyl pyrrolidone polymer; [0129] a first solvent comprising
about 2.5% to 8% 1-butanol, ethanol, 1-pentanol,
n-methylpyrrolidone, 1-hexanol, or acetic acid, or mixtures
thereof; [0130] a viscosity modifier, resin, or binder comprising
about 1.0% to 4.5% PVP, polyvinyl alcohol, or a polyimide, or
mixtures thereof; and [0131] with the balance comprising a second
solvent such as cyclohexanol, cyclohexanone, cyclopentanone,
cyclopentanol, butyl lactone, or mixtures thereof.
[0132] Metallic Nanofiber Ink Example 10: [0133] A composition
comprising: [0134] about 0.01% to 3.0% of a plurality of
functionalized metallic nanofibers, substantially all of the
metallic nanofibers having at least a partial coating of a
polyvinyl pyrrolidone polymer; [0135] a first solvent comprising
about 2.5% to 8% 1-butanol, ethanol, 1-pentanol,
n-methylpyrrolidone, or 1-hexanol, or mixtures thereof; [0136] a
second solvent comprising about 0.01% to 5% of an acid or base, or
mixtures thereof; [0137] a viscosity modifier, resin, or binder
comprising about 1.0% to 4.5% PVP, polyvinyl alcohol, or a
polyimide, or mixtures thereof; and [0138] with the balance
comprising a third solvent such as cyclohexanol, cyclohexanone,
cyclopentanone, cyclopentanol, butyl lactone, or mixtures
thereof.
[0139] Metallic Nanofiber Ink Example 11: [0140] A composition
comprising: [0141] about 0.01% to 3.0% of a plurality of
functionalized metallic nanofibers, substantially all of the
metallic nanofibers having at least a partial coating of a
polyvinyl pyrrolidone polymer; [0142] a first solvent comprising
about 2.5% to 8% of a first alcohol; [0143] a second solvent
comprising about 0.01% to 5% of an acid or base, or mixtures
thereof; [0144] a viscosity modifier, resin, or binder comprising
about 1.0% to 4.5% PVP, polyvinyl alcohol, or a polyimide, or
mixtures thereof; and [0145] with the balance comprising a second
alcohol different from the first alcohol.
[0146] Metallic Nanofiber Ink Example 12: [0147] A composition
comprising: [0148] about 0.01% to 3.0% of a plurality of
functionalized metallic nanofibers, substantially all of the
metallic nanofibers having at least a partial coating of a
polyvinyl pyrrolidone polymer; [0149] a first solvent comprising
about 2.5% to 8% 1-butanol, ethanol, 1-pentanol,
n-methylpyrrolidone, or 1-hexanol, or mixtures thereof; [0150] a
second solvent comprising about 0.01% to 5% of an acid or bases,
including organic acids such as carboxylic acids, dicarboxylic
acids, tricarboxylic acids, alkyl carboxylic acids, acetic acid,
oxalic acid, mellitic acid, formic acid, chloroacetic acid, benzoic
acid, trifluoroacetic acid, propanoic acid, butanoic acid, or bases
such as ammonium hydroxide, sodium hydroxide, potassium hydroxide,
or mixtures thereof; [0151] a viscosity modifier, resin, or binder
comprising about 1.0% to 4.5% PVP, polyvinyl alcohol, or a
polyimide, or mixtures thereof; and [0152] with the balance
comprising a third solvent such as cyclohexanol, cyclohexanone,
cyclopentanone, cyclopentanol, butyl lactone, or mixtures
thereof.
[0153] Metallic Nanofiber Ink Example 13: [0154] A composition
comprising: [0155] about 0.18% to 0.3% of a plurality of
functionalized metallic nanofibers, substantially all of the
metallic nanofibers having at least a partial coating of a
polyvinyl pyrrolidone polymer; [0156] about 2.5% to 8% of
1-butanol; [0157] about 0.1% to 2% of acetic acid; [0158] about
1.0% to 4.5% polyvinyl pyrrolidone; and [0159] with the balance
comprising cyclohexanol, cyclohexanone, cyclopentanone,
cyclopentanol, or butyl lactone, or mixtures thereof.
[0160] Metallic Nanofiber Ink Example 14: [0161] A composition
comprising: [0162] about 0.01% to 3.0% of a plurality of
functionalized metallic nanofibers; [0163] a first solvent
comprising about 3% to 28% 1-butanol, ethanol, 1-pentanol,
n-methylpyrrolidone, or 1-hexanol, or mixtures thereof; [0164] a
viscosity modifier, resin, or binder comprising about 1.4% to 3.75%
PVP, polyvinyl alcohol, or a polyimide, or mixtures thereof; and
[0165] with the balance comprising a second solvent such as
cyclohexanol, cyclohexanone, cyclopentanone, cyclopentanol, butyl
lactone, or mixtures thereof
[0166] Metallic Nanofiber Ink Example 15: [0167] A composition
comprising: [0168] about 0.01% to 3.0% of a plurality of
functionalized metallic nanofibers; [0169] a first solvent
comprising about 3.0% to 7% 1-butanol, ethanol, 1-pentanol,
n-methylpyrrolidone, 1-hexanol, or acetic acid, or mixtures
thereof; [0170] a viscosity modifier, resin, or binder comprising
about 1.4% to 3.75% PVP, polyvinyl alcohol, or a polyimide, or
mixtures thereof; [0171] a second solvent comprising about 0.001%
to 2% of 1-octanol, acetic acid, diethylene glycol, dipropylene
glycol, propylene glycol, potassium hydroxide or sodium hydroxide,
or mixtures thereof; and [0172] with the balance comprising a third
solvent such as cyclohexanol, cyclohexanone, cyclopentanone,
cyclopentanol, butyl lactone, or mixtures thereof.
[0173] Metallic Nanofiber Ink Example 16: [0174] A composition
comprising: [0175] about 0.01% to 3.0% of a plurality of
functionalized metallic nanofibers; [0176] a first solvent
comprising about 2.5% to 28% 1-butanol, ethanol, 1-pentanol,
1-hexanol, acetic acid, 2-propanol (isopropyl alcohol or IPA),
1-methoxy-2-propanol, diethylene glycol, or mixtures thereof;
[0177] a viscosity modifier, resin, or binder comprising about
0.05% to 5.0% cellulose resin such as hydroxy methylcellulose,
methylcellulose, ethyl cellulose, propyl methylcellulose, methoxy
cellulose, methoxy methylcellulose, methoxy propyl methylcellulose,
hydroxy propyl methylcellulose, carboxy methylcellulose, hydroxy
ethylcellulose, ethyl hydroxylethylcellulose, or mixtures thereof;
[0178] a second solvent comprising about 5% to 50% of n-propanol,
2-propanol, propylene glycol, or diethylene glycol, or mixtures
thereof; and [0179] with the balance comprising a third solvent
such as 1-methoxy-2-propanol, cyclohexanol, cyclohexanone,
cyclopentanone, cyclopentanol, butyl lactone, or mixtures
thereof.
[0180] Metallic Nanofiber Ink Example 17: [0181] A composition
comprising: [0182] about 0.01% to 3.0% of a plurality of
functionalized metallic nanofibers 100; [0183] a first solvent
comprising about 18% to 28% 2-propanol (isopropyl alcohol or IPA),
1-methoxy-2-propanol, 1-butanol, ethanol, diethylene glycol,
1-pentanol or 1-hexanol, or mixtures thereof; [0184] a viscosity
modifier, resin, or binder comprising about 1.5% to 2.5% cellulose
resin such as propoxymethyl cellulose, methoxyl cellulose or
hydroxypropyl cellulose resin, or mixtures thereof; [0185] a second
solvent comprising about 15% to 25% of n-propanol, 2-propanol, or
diethylene glycol, or mixtures thereof; and [0186] with the balance
comprising a third solvent such as (deionized) water,
1-methoxy-2-propanol, cyclohexanol, cyclohexanone, cyclopentanone,
cyclopentanol, butyl lactone, or mixtures thereof.
[0187] Metallic Nanofiber Ink Example 18: [0188] A composition
comprising: [0189] about 0.01% to 3.0% of a plurality of
functionalized metallic nanofibers 100; [0190] a first solvent
comprising about 2.0% to 10.0% n-methylpyrrolidone, 2-propanol
(isopropyl alcohol or IPA), 1-methoxy-2-propanol, 1-butanol,
ethanol, diethylene glycol, 1-pentanol, n-methylpyrrolidone, or
1-hexanol, or mixtures thereof; [0191] a first viscosity modifier,
resin, or binder comprising about 0.75% to 5.0% PVP, polyvinyl
alcohol, or a polyimide, or mixtures thereof; [0192] a second
viscosity modifier, resin, or binder comprising about 7% to 12%
alpha-terpineol; [0193] a second solvent comprising about 1% to 5%
of n-propanol, 2-propanol, or diethylene glycol, or mixtures
thereof; and [0194] with the balance comprising a third solvent
such as n-methylpyrrolidone, cyclohexanol, cyclohexanone,
cyclopentanone, cyclopentanol, butyl lactone, or mixtures
thereof.
[0195] Metallic Nanofiber Ink Example 19: [0196] A composition
comprising: [0197] about 0.01% to 3.0% of a plurality of
functionalized metallic nanofibers 100; [0198] a first solvent
comprising about 18% to 28% n-methylpyrrolidone, 2-propanol
(isopropyl alcohol or IPA), 1-methoxy-2-propanol, 1-butanol,
ethanol, diethylene glycol, 1-pentanol, n-methylpyrrolidone, or
1-hexanol, or mixtures thereof; [0199] a first viscosity modifier,
resin, or binder comprising about 0.75% to 5.0% PVP, polyvinyl
alcohol (PVA), or a polyimide, or mixtures thereof (e.g., about 60%
PVA with 40% PVP or about 80% PVA with 20% PVP in
n-methylpyrrolidone); and [0200] with the balance comprising a
second solvent such as n-methyl pyrrolidone, cyclohexanol,
cyclohexanone, cyclopentanone, cyclopentanol, butyl lactone, or
mixtures thereof.
[0201] Metallic Nanofiber Ink Example 20: [0202] A composition
comprising: [0203] about 0.01% to 3.0% of a plurality of
functionalized metallic nanofibers, substantially all of the
metallic nanofibers having at least a partial coating of a
polyvinyl pyrrolidone polymer; [0204] a first solvent comprising
about 2.5% to 8% 1-butanol, ethanol, 1-pentanol,
n-methylpyrrolidone, or 1-hexanol, or mixtures thereof [0205] a
second solvent comprising about 0.01% to 5% of acetic acid, nitric
acid, sulfuric acid, hydrochloric acid, hydrofluoric acid, ammonium
hydroxide, sodium hydroxide, or potassium hydroxide, or mixtures
thereof; [0206] a viscosity modifier, resin, or binder comprising
about 1.0% to 4.5% PVP, polyvinyl alcohol, or a polyimide, or
mixtures thereof; and [0207] with the balance comprising a third
solvent such as cyclohexanol, cyclohexanone, cyclopentanone,
cyclopentanol, butyl lactone, or mixtures thereof; [0208] wherein
the viscosity of the composition is substantially between about 200
cps to about 20,000 cps at 25.degree. C.
[0209] Metallic Nanofiber Ink Example 21: [0210] A composition
comprising: [0211] about 0.01% to 3.0% of a plurality of
functionalized metallic nanofibers, substantially all of the
metallic nanofibers having at least a partial coating of a
polyvinyl pyrrolidone polymer and having lengths between about
40.mu. and about 60.mu. and diameters between about 25 nm and about
35 nm; [0212] a plurality of metallic particles about 20-30 nm in
any dimension; [0213] a first solvent comprising about 2.5% to 8%
1-butanol, ethanol, 1-pentanol, n-methylpyrrolidone, or 1-hexanol,
or mixtures thereof; [0214] a second solvent comprising about 0.01%
to 5% of an acid or base, or mixtures thereof; [0215] a viscosity
modifier, resin, or binder comprising about 1.0% to 4.5% PVP,
polyvinyl alcohol, or a polyimide, or mixtures thereof; and [0216]
with the balance comprising a third solvent such as cyclohexanol,
cyclohexanone, cyclopentanone, cyclopentanol, butyl lactone, or
mixtures thereof.
[0217] Metallic Nanofiber Ink Example 22: [0218] A composition
comprising: [0219] about 0.01% to 3.0% of a plurality of
functionalized metallic nanofibers, substantially all of the
metallic nanofibers having at least a partial coating of a
polyvinyl pyrrolidone polymer; [0220] a plurality of carbon
nanotubes; [0221] a first solvent comprising about 2.5% to 8%
1-butanol, ethanol, 1-pentanol, n-methylpyrrolidone, or 1-hexanol,
or mixtures thereof; [0222] a second solvent comprising about 0.01%
to 5% of acetic acid, nitric acid, sulfuric acid, hydrochloric
acid, hydrofluoric acid, ammonium hydroxide, sodium hydroxide, or
potassium hydroxide, or mixtures thereof; [0223] a viscosity
modifier, resin, or binder comprising about 1.0% to 4.5% PVP,
polyvinyl alcohol, or a polyimide, or mixtures thereof; and [0224]
with the balance comprising a third solvent such as cyclohexanol,
cyclohexanone, cyclopentanone, cyclopentanol, butyl lactone, or
mixtures thereof.
[0225] Metallic Nanofiber Ink Example 23: [0226] A composition
comprising: [0227] about 0.01% to 3.0% of a plurality of
functionalized metallic nanofibers, substantially all of the
metallic nanofibers having at least a partial coating of a
polyvinyl pyrrolidone polymer; [0228] about 0.5% to 5.0% polyimide;
and [0229] with the balance comprising a ketone, including
diketones and cyclic ketones, such as cyclohexanone,
cyclopentanone, cycloheptanone, cyclooctanone, acetone,
benzophenone, acetylacetone, acetophenone, cyclopropanone,
isophorone, methyl ethyl ketone, or mixtures thereof.
[0230] Metallic Nanofiber Ink Example 24: [0231] A composition
comprising: [0232] about 0.01% to 3.0% of a plurality of
functionalized metallic nanofibers, substantially all of the
metallic nanofibers having at least a partial coating of a
polyvinyl pyrrolidone polymer; [0233] about 1.0% to 4.5% polyimide;
and [0234] with the balance comprising cyclohexanone.
[0235] Referring to Metallic Nanofiber Ink Examples 8-24, in an
exemplary embodiment, a plurality of (functionalized) metallic
nanofibers 100 are suspended in a first solvent, such as 1-butanol,
ethanol, 1-pentanol, 1-hexanol, 2-propanol (isopropyl alcohol or
IPA), 1-methoxy-2-propanol, cyclohexanol, cyclohexanone,
cyclopentanone, cyclopentanol, butyl lactone, diethylene glycol, or
n-methylpyrrolidone, other solvents discussed above, or mixtures
thereof, such that the functionalized metallic nanofibers 100
typically comprise between about 3% to 10% by weight of this
intermediate mixture, e.g., 4% to 5% by weight metallic nanofibers
100 suspended in a solvent mixture comprising about 80%
cyclohexanol and about 20% 1-butanol. A first or second solvent may
then be added to further reduce the percentage (by weight) of
functionalized metallic nanofibers 100 by about 50-75%, to between
about 0.01% to 3.0% functionalized metallic nanofibers 100. A third
solvent such as acetic acid may also be added. A viscosity
modifier, resin or binder comprising about 1.0% to 8.5% PVP,
polyvinyl alcohol, or a polyimide is dissolved in a first or second
solvent (such as cyclohexanol, cyclohexanone, cyclopentanone,
cyclopentanol, butyl lactone, 1-butanol, ethanol, 1-pentanol or
1-hexanol, other viscosity modifiers, resins or binders discussed
above, or mixtures thereof), typically at 80-90.degree. C. with an
impeller or stirring bead, then allowed to cool to room
temperature. (For consistency between batches, the PVP is typically
heated and dessicated prior to use, and is reflected in all PVP
weight percentages described herein). The metallic nanofibers 100
in the first (or second) solvent are then added to the viscosity
modifier, resin or binder mixture, mixing with a helical impeller
for 3 to 10 minutes, depending on the batch size, at a moderate
speed to avoid damaging the metallic nanofibers 100, at standard
atmospheric pressure and at room temperature (about 25.degree. C.),
which further serves to avoid any harm or damage to the PVP
functionalization of the metallic nanofibers 100.
[0236] A particular advantage of this formulation using
cyclohexanol and 1-butanol is that the various percentages of
metallic nanofibers 100 and solvents such as 1-butanol may be
adjusted independently of the other.
[0237] The viscosity modifier, resin or binder provides sufficient
viscosity for the metallic nanofibers 100 that they are
substantially maintained in suspension and do not settle out of the
liquid or gel suspension, particularly under refrigeration.
[0238] A second or third (or fourth) solvent such as deionized
water also may be added, to adjust the relative percentages and
reduce viscosity, as may be necessary or desirable. In addition,
other first, second or third solvents which may be utilized
equivalently include, for example and without limitation, water;
alcohols such as methanol, ethanol, N-propanol (including
1-propanol, 2-propanol (isopropanol or IPA), 1-methoxy-2-propanol),
butanol (including 1-butanol, 2-butanol (isobutanol)), pentanol
(including 1-pentanol, 2-pentanol, 3-pentanol), hexanol (including
1-hexanol, 2-hexanol, 3-hexanol), octanol, N-octanol (including
1-octanol, 2-octanol, 3-octanol), tetrahydrofurfuryl alcohol
(THFA), cyclohexanol, cyclopentanol, terpineol; lactones such as
butyl lactone; ethers such as methyl ethyl ether, diethyl ether,
ethyl propyl ether, and polyethers; ketones, including diketones
and cyclic ketones, such as cyclohexanone, cyclopentanone,
cycloheptanone, cyclooctanone, acetone, benzophenone,
acetylacetone, acetophenone, cyclopropanone, isophorone, methyl
ethyl ketone; esters such ethyl acetate, dimethyl adipate,
proplyene glycol monomethyl ether acetate, dimethyl glutarate,
dimethyl succinate, glycerin acetate, carboxylates; glycols such as
ethylene glycols, diethylene glycols, polyethylene glycols,
propylene glycols, dipropylene glycols, glycol ethers, glycol ether
acetates; carbonates such as propylene carbonate; glycerols such as
glycerin; n-methylpyrrolidone, acetonitrile, tetrahydrofuran (THF),
dimethyl formamide (DMF), N-methyl formamide (NMF), dimethyl
sulfoxide (DMSO); acids, including organic acids such as carboxylic
acids, dicarboxylic acids, tricarboxylic acids, alkyl carboxylic
acids, acetic acid, oxalic acid, mellitic acid, formic acid,
chloroacetic acid, benzoic acid, trifluoroacetic acid, propanoic
acid, butanoic acid; bases such as ammonium hydroxide, sodium
hydroxide, potassium hydroxide; and mixtures thereof.
[0239] While generally the various metallic nanofiber inks are
mixed in the order described above, it should also be noted that
the various first solvent, viscosity modifier, second solvent, and
third solvent (such as water) may be added or mixed together in
other orders, any and all of which are within the scope of the
disclosure.
[0240] Additional surfactants or non-foaming agents for printing
may be utilized as an option, but are not required for proper
functioning and exemplary printing.
[0241] FIG. 6 is a flow diagram illustrating an exemplary method
embodiment for manufacturing metallic nanofiber ink, and provides a
useful summary. The method begins, start step 200, with suspending
or dispersing the metallic nanofibers 100 in a first solvent, step
205. A viscosity modifier or binder is then dissolved or mixed with
a first or second solvent, step 210, heating as necessary or
desirable, followed by cooling to room temperature (about
25.degree. C.). The method then adds the metallic nanofibers 100 in
the first solvent to the mixture of the viscosity modifier or
binder and first or second solvent, step 215. Any weight
percentages may be adjusted using a first, second or third solvent
such as deionized water, step 220. In step 225, the method then
mixes the plurality of metallic nanofibers 100, first solvent,
viscosity modifier or binder, second solvent, and any additional
first, second or third solvents for about 3-10 minutes at room
temperature (about 25.degree. C.) in an air atmosphere, with a
resulting viscosity between about 200 cps to about 25,000 cps,
e.g., 500 cps for screen printing. The method may then end, return
step 230. It should also be noted that steps 205, 210, and 220 may
occur in other orders, as described above, and may be repeated as
needed, and that optional, additional mixing steps may also be
utilized.
[0242] Additional components may also be included in the metallic
nanofiber ink, such as CNTs or particulate materials. For example,
in the embodiment of Example 21, metallic particles have also been
added, such as silver nanoparticles having a size on the order of
about 20-30 nm in any dimension, such as substantially spherical or
oblong, available as 010 nanosilver from Ink Tec of Korea. When
such particles are also included, the printed film (discussed
below) may also be sintered as part of the curing process at about
130.degree. C. to couple the particles to the metallic nanofibers
100. Also for example, in the embodiment of Example 22, carbon
nanotubes have also been added, such as carbon nanotubes in a
liquid carrier available from SouthWest NanoTechnologies, Inc.,
Norman, Okla., USA. It should be noted that for added robustness,
the various cured metallic nanofiber inks of the Examples may be
overprinted with a stabilizing uv curable sealant of polymer as
discussed below.
[0243] Dried or Cured Metallic Nanofiber Ink Example 1: [0244] A
composition comprising: [0245] a plurality of metallic nanofibers
100; and [0246] a cured or polymerized resin or polymer.
[0247] Dried or Cured Metallic Nanofiber Ink Example 2: [0248] A
composition comprising: [0249] a plurality of metallic nanofibers
100; [0250] a cured or polymerized resin or polymer; and [0251] at
least trace amounts of a solvent.
[0252] Dried or Cured Metallic Nanofiber Ink Example 3: [0253] A
composition comprising: [0254] a plurality of metallic nanofibers
100; [0255] a cured or polymerized resin or polymer; [0256] at
least trace amounts of a solvent; and [0257] at least trace amounts
of a surfactant.
[0258] The metallic nanofiber ink may then be deposited in any
pattern (e.g, as a sheet, conformal coating, lines or wires), such
as through printing, to a wet film thickness of about 4.mu.-25.mu.,
depending upon the type of printing or other deposition (such as
screen or flexographic printing), and more preferably to about
16.mu., such as through screen printing using a 280-500 mesh
polyester, or PTFE-coated, or stainless steel screen having open
areas large enough to permit substantially free passage of the
longer metallic nanofibers 100 through the screen, and the volatile
or evaporative components are dissipated, such as through a
heating, uv cure, a radiation cure, or any drying process, for
example and without limitation, to leave the metallic nanofibers
100 in the cured or polymerized resin or polymer. Depending upon
the selected viscosity modifier, resin or polymer, curing of a
polymer or polymerization of a polymer precursor may occur, and
additionally may be crosslinked, such as by the addition of a
crosslinking agent in the various exemplary compositions.
[0259] In an exemplary embodiment, the wet film is then cured or
polymerized by heating for about 4-6 minutes, using a ramp cure,
starting at about 65.degree. C. to about 140-160.degree. C., such
as up to about 150.degree. C. During such curing at these
temperatures and with the exemplary combinations of solvents
described above (e.g., cyclohexanol, cyclohexanone, cyclopentanone,
1-butanol, n-methylpyrrolidone), the PVP functionalization of the
metallic nanofibers 100 dewets or pulls away from the metallic
nanofibers 100, such that a sufficient number of the metallic
nanofibers 100 form direct contacts with each other to form a
conductive mesh and provide for sufficient conductivity at the
various sheet resistances discussed and illustrated in Table 1
below, and further provide for electrical contacts with other
system components, both generally without intervening or sandwiched
PVP or other interference from the PVP coating on the metallic
nanofibers 100. As a further consequence, the apparatus 150 does
not require further processing, such as compression through nip
rollers, to be sufficiently conductive with comparatively low sheet
resistance while maintaining substantial transparency. The
remaining dried or cured metallic nanofiber ink, as in Dried or
Cured Metallic Nanofiber Ink Example 1, generally comprises a
plurality of metallic nanofibers 100 and a cured or polymerized
resin or polymer (which, as mentioned above, generally secures or
holds the metallic nanofibers 100 in place). While the volatile or
evaporative components (such as first and/or second solvents and/or
surfactants) are substantially dissipated, trace or more amounts
may remain, as illustrated in Dried or Cured Metallic Nanofiber Ink
Examples 2 and 3. As used herein, a "trace amount" of an ingredient
should be understood to be an amount greater than zero and less
than or equal to 5% of the amount of the ingredient originally
present in the metallic nanofiber ink when initially deposited.
[0260] Several novel, highly beneficial and synergistic effects
have been empirically observed using the formulations of Examples
7-13 when cyclohexanol is used as a solvent and a comparatively
high molecular weight PVP is utilized as the viscosity modifier,
resin, or binder (e.g., 750,000 to 1.25 million MW). First, the use
of cyclohexanol in the metallic nanofiber ink does not dissolve or
otherwise remove the comparatively lower molecular weight PVP
coating (functionalization) from the metallic nanofibers 100 at
room temperature, but also does maintain the higher molecular
weight PVP polymer in solution at room temperature. This promotes a
long shelf life of the metallic nanofiber ink, as the PVP coating
(functionalization) on the metallic nanofibers 100 serves to
prevent the metallic nanofibers 100 from agglomerating, allowing
comparatively easy redispersion after any settling during storage
of the metallic nanofiber ink, such as simply shaking the ink
bottle or other container.
[0261] Second, at the elevated temperatures described above for
curing the deposited metallic nanofiber ink, the cyclohexanol in
the metallic nanofiber ink does dissolve or otherwise remove the
comparatively lower molecular weight PVP coating
(functionalization) from the metallic nanofibers 100, allowing the
metallic nanofibers 100 to make direct contact with each other,
without any intervening PVP, and thereby reducing the sheet
resistance of the apparatus 150, 150A. Third, the cyclohexanol also
helps to reduce or remove oxide formation on the surfaces of the
metallic nanofibers 100, also enhancing the quality of the contacts
of the metallic nanofibers 100 with each other. Fourth, during the
cure process described above, the cured PVP (as the viscosity
modifier, resin, or binder) tends to force the metallic nanofibers
100 together, also enhancing the inter-fiber contacts and reducing
the sheet resistance of the apparatus 150, 150A.
[0262] The cured metallic nanofiber ink (forming an apparatus 150,
150A) results in a dried film thickness of between about 80 nm to
about 300 nm, such as about 200 nm. For thicker optically
transmissive, conductive films (150, 150A), additional layers of
metallic nanofiber ink may be overprinted or otherwise deposited.
An exemplary resistivity is about 15-60 ohms/square, with optical
transmissivity from about 93% to over about 97%, depending on the
formulation, with a higher percentage of metallic nanofibers 100
decreasing resistance but also decreasing optical transmissivity,
as illustrated in Table 1, below. A graph of resistivity versus
transmissivity is illustrated in FIG. 7, using these formulations
based on Example 13, the AW030 metallic nanofibers mentioned above,
and deposited using screen printing with a 305 mesh. It should be
noted that the haze data in Table 1 is based upon a linear model
model fit to measured haze data (rather than the actual or raw haze
data).
TABLE-US-00001 TABLE 1 Metallic Optical Nanofibers Optical
Ohms/square Density % Weight Transmissivity % Haze % 5 0.103 0.94
78.8 29.7 10 0.056 0.51 87.9 16.4 20 0.032 0.29 92.9 9.2 30 0.024
0.22 94.6 6.7 40 0.020 0.18 95.5 5.5 50 0.018 0.16 96.0 4.7 60
0.016 0.15 96.3 4.2 70 0.015 0.14 96.6 3.8 80 0.014 0.13 96.8 3.6
90 0.014 0.12 96.9 3.4 100 0.013 0.12 97.0 3.2 150 0.012 0.10 97.4
2.7 200 0.011 0.10 97.6 2.4 400 0.010 0.09 97.8 2.0 800 0.009 0.09
98.0 1.8
[0263] As mentioned above, metallic nanofibers 100 may also be
sonicated to break longer metallic nanofibers 100 into shorter
metallic nanofibers 100. The resulting mixture of metallic
nanofibers 100 having longer and shorter metallic nanofibers 100
may be utilized to produce better and more flexible surface
coverage, and improve electrical contacts with other devices, such
as diodes, for example.
[0264] The resulting substantially optically transmissive,
conductive film, illustrated as apparatus 150, 150, typically
comprises the metallic nanofibers 100 embedded in a binder, resin
or polymer (resulting from the curing of the viscosity modifier,
resin or binder), such as metallic nanofibers 100 embedded or
emeshed with PVP, PVA or a polyimide, potentially also with
residual or trace amounts of the other metallic nanofiber ink
components, such as the various solvents or other additives
mentioned above. The optically transmissive, conductive film (150,
150A) may then be overprinted as necessary or desirable, such as
printing or deposition of additional layers or features, such as
phosphors, stabilization or sealing layers (e.g., DuPont 5018 or
Nazdar 3529 polymers), or other components, as discussed in greater
detail below and in the related applications.
[0265] Any types of deposition processes may be utilized. As a
consequence, as used herein, "deposition" includes any and all
printing, coating, rolling, spraying, layering, sputtering,
plating, spin casting (or spin coating), vapor deposition,
lamination, affixing and/or other deposition processes, whether
impact or non-impact, known in the art. "Printing" includes any and
all printing, coating, rolling, spraying, layering, spin coating,
lamination and/or affixing processes, whether impact or non-impact,
known in the art, and specifically includes, for example and
without limitation, screen printing, inkjet printing,
electro-optical printing, electroink printing, photoresist and
other resist printing, thermal printing, laser jet printing,
magnetic printing, pad printing, flexographic printing, hybrid
offset lithography, Gravure and other intaglio printing, for
example. All such processes are considered deposition processes
herein and may be utilized. The exemplary deposition or printing
processes do not require significant manufacturing controls or
restrictions. No specific temperatures or pressures are required.
Some clean room or filtered air may be useful, but potentially at a
level consistent with the standards of known printing or other
deposition processes. For consistency, however, such as for proper
alignment (registration) of the various successively deposited
layers forming the various embodiments, relatively constant
temperature (with a possible exception, discussed below) and
humidity may be desirable. In addition, the various compounds
utilized may be contained within various polymers, binders or other
dispersion agents which may be heat-cured or dried, air dried under
ambient conditions, or IR or uv cured.
[0266] It should also be noted, generally for any of the
applications of various compounds herein, such as through printing
or other deposition, the surface properties or surface energies may
also be controlled, such as through the use of resist coatings or
by otherwise modifying the "wetability" of such a surface, for
example, by modifying the hydrophilic, hydrophobic, or electrical
(positive or negative charge) characteristics, or by a corona
treatment, for example. In conjunction with the characteristics of
the compound, suspension, polymer or ink being deposited, such as
the surface tension, the deposited compounds may be made to adhere
to desired or selected locations, and effectively repelled from
other areas or regions.
[0267] For example and without limitation, the plurality of
metallic nanofibers 100 are suspended in a liquid, semi-liquid or
gel carrier using any evaporative or volatile organic or inorganic
compound, such as water, an alcohol, an ether, etc., which may also
include an adhesive component, such as a resin, and/or a surfactant
or other flow aid. In an exemplary embodiment, for example and
without limitation, the plurality of metallic nanofibers 100 are
suspended as described above in the Examples. A surfactant or flow
aid may also be utilized, such as octanol, methanol, isopropanol,
or deionized water, and may also use a binder such as an
anisotropic conductive binder containing substantially or
comparatively small nickel beads (e.g., 1 micron) (which provides
conduction after compression and curing and may serve to improve or
enhance creation of ohmic contacts, for example), or any other uv,
heat or air curable binder or polymer, including those discussed in
greater detail below (and which also may be utilized with
dielectric compounds, lenses, and so on).
[0268] The optically transmissive, conductive film (150, 150A)
formed from the cured or dried metallic nanofiber ink may be
utilized in a wide variety of applications, namely, an application
involving a conductor, a conductive ink or polymer or more
preferably, an optically transmissive conductor. Various
applications are also illustrated in the related applications,
incorporated by reference herein in their entireties. Numerous
additional applications will be apparent to those having skill in
the art.
[0269] Various textures may be provided for the optically
transmissive, conductive film embodiment 150, such as having a
comparatively smooth surface, or conversely, a rough or spiky
surface, or an engineered micro-embossed structure (e.g., available
from Sappi, Ltd.) to potentially improve the adhesion of other
layers and/or to facilitate subsequent forming of ohmic contacts
with other components such as diodes 120. The optically
transmissive, conductive film embodiment 150 may also be given a
corona treatment prior to deposition of other components, which may
tend to remove any oxides which may have formed, and also
facilitate subsequent forming of ohmic contacts. Those having skill
in the electronic or printing arts will recognize innumerable
variations in the ways in which the optically transmissive,
conductive film embodiment 150 may be formed, with all such
variations considered equivalent and within the scope of the
disclosure. In addition, for other various embodiments, the
optically transmissive, conductive film embodiment 150 may be
deposited as a single or continuous layer, such as through coating
or printing, for example.
[0270] As may be apparent from the disclosure, an exemplary
apparatus 150, 150A, may be designed and fabricated to be highly
flexible and deformable, potentially even foldable, stretchable and
potentially wearable, rather than rigid. For example, an exemplary
apparatus 150, 150A, may comprise flexible, foldable, and wearable
clothing, or a flexible lamp, or a wallpaper lamp, without
limitation. With such flexibility, an exemplary apparatus 150,
150A, may be rolled, such as a poster, or folded like a piece of
paper, and fully functional when re-opened. Also for example, with
such flexibility, an exemplary apparatus 150, 150A, may have many
shapes and sizes, and be configured for any of a wide variety of
styles and other aesthetic goals. Such an exemplary apparatus 150,
150A, is also considerably more resilient than prior art
devices.
[0271] Although the invention has been described with respect to
specific embodiments thereof, these embodiments are merely
illustrative and not restrictive of the invention. In the
description herein, numerous specific details are provided, such as
examples of electronic components, electronic and structural
connections, materials, and structural variations, to provide a
thorough understanding of embodiments of the present invention. One
skilled in the relevant art will recognize, however, that an
embodiment of the invention can be practiced without one or more of
the specific details, or with other apparatus, systems, assemblies,
components, materials, parts, etc. In other instances, well-known
structures, materials, or operations are not specifically shown or
described in detail to avoid obscuring aspects of embodiments of
the present invention. One having skill in the art will further
recognize that additional or equivalent method steps may be
utilized, or may be combined with other steps, or may be performed
in different orders, any and all of which are within the scope of
the claimed invention. In addition, the various Figures are not
drawn to scale and should not be regarded as limiting.
[0272] Reference throughout this specification to "one embodiment",
"an embodiment", or a specific "embodiment" means that a particular
feature, structure, or characteristic described in connection with
the embodiment is included in at least one embodiment and not
necessarily in all embodiments, and further, are not necessarily
referring to the same embodiment. Furthermore, the particular
features, structures, or characteristics of any specific embodiment
may be combined in any suitable manner and in any suitable
combination with one or more other embodiments, including the use
of selected features without corresponding use of other features.
In addition, many modifications may be made to adapt a particular
application, situation or material to the essential scope and
spirit of the present invention. It is to be understood that other
variations and modifications of the embodiments of the present
invention described and illustrated herein are possible in light of
the teachings herein and are to be considered part of the spirit
and scope of the present invention.
[0273] It will also be appreciated that one or more of the elements
depicted in the Figures can also be implemented in a more separate
or integrated manner, or even removed or rendered inoperable in
certain cases, as may be useful in accordance with a particular
application. Integrally formed combinations of components are also
within the scope of the invention, particularly for embodiments in
which a separation or combination of discrete components is unclear
or indiscernible. In addition, use of the term "coupled" herein,
including in its various forms such as "coupling" or "couplable",
means and includes any direct or indirect electrical, structural or
magnetic coupling, connection or attachment, or adaptation or
capability for such a direct or indirect electrical, structural or
magnetic coupling, connection or attachment, including integrally
formed components and components which are coupled via or through
another component.
[0274] The dimensions and values disclosed herein are not to be
understood as being strictly limited to the exact numerical values
recited. Instead, unless otherwise specified, each such dimension
is intended to mean both the recited value and a functionally
equivalent range surrounding that value. For example, a dimension
disclosed as "40 mm" is intended to mean "about 40 mm."
[0275] All documents cited in the Detailed Description of the
Invention are, in relevant part, incorporated herein by reference;
the citation of any document is not to be construed as an admission
that it is prior art with respect to the present invention. To the
extent that any meaning or definition of a term in this document
conflicts with any meaning or definition of the same term in a
document incorporated by reference, the meaning or definition
assigned to that term in this document shall govern.
[0276] Furthermore, any signal arrows in the drawings/Figures
should be considered only exemplary, and not limiting, unless
otherwise specifically noted. Combinations of components of steps
will also be considered within the scope of the present invention,
particularly where the ability to separate or combine is unclear or
foreseeable. The disjunctive term "or", as used herein and
throughout the claims that follow, is generally intended to mean
"and/or", having both conjunctive and disjunctive meanings (and is
not confined to an "exclusive or" meaning), unless otherwise
indicated. As used in the description herein and throughout the
claims that follow, "a", "an", and "the" include plural references
unless the context clearly dictates otherwise. Also as used in the
description herein and throughout the claims that follow, the
meaning of "in" includes "in" and "on" unless the context clearly
dictates otherwise.
[0277] The foregoing description of illustrated embodiments of the
present invention, including what is described in the summary or in
the abstract, is not intended to be exhaustive or to limit the
invention to the precise forms disclosed herein. From the
foregoing, it will be observed that numerous variations,
modifications and substitutions are intended and may be effected
without departing from the spirit and scope of the novel concept of
the invention. It is to be understood that no limitation with
respect to the specific methods and apparatus illustrated herein is
intended or should be inferred. It is, of course, intended to cover
by the appended claims all such modifications as fall within the
scope of the claims.
* * * * *