U.S. patent application number 10/758503 was filed with the patent office on 2004-09-02 for hybrid organic-inorganic polymer coatings with high refractive indices.
This patent application is currently assigned to Terry Brewer, Ph.D.. Invention is credited to Flaim, Tony D., Mercado, Ramil-Marcelo L., Wang, Yubao.
Application Number | 20040171743 10/758503 |
Document ID | / |
Family ID | 32776077 |
Filed Date | 2004-09-02 |
United States Patent
Application |
20040171743 |
Kind Code |
A1 |
Flaim, Tony D. ; et
al. |
September 2, 2004 |
Hybrid organic-inorganic polymer coatings with high refractive
indices
Abstract
Novel compositions and methods of using those compositions to
form metal oxide films or coatings are provided. The compositions
comprise an organometallic oligomer and an organic polymer or
oligomer dispersed or dissolved in a solvent system. The
compositions have long shelf lives and can be prepared by easy and
reliable preparation procedures. The compositions can be cured to
cause conversion of the composition into films of metal oxide
interdispersed with organic polymer or oligomer. The cured films
have high refractive indices, high optical clarities, and good
mechanical stabilities at film thicknesses of greater than about 1
.mu.m.
Inventors: |
Flaim, Tony D.; (St. James,
MO) ; Wang, Yubao; (Rolla, MO) ; Mercado,
Ramil-Marcelo L.; (Rolla, MO) |
Correspondence
Address: |
HOVEY WILLIAMS LLP
2405 GRAND BLVD., SUITE 400
KANSAS CITY
MO
64108
US
|
Assignee: |
Terry Brewer, Ph.D.
|
Family ID: |
32776077 |
Appl. No.: |
10/758503 |
Filed: |
January 15, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60441693 |
Jan 21, 2003 |
|
|
|
Current U.S.
Class: |
524/577 |
Current CPC
Class: |
C08K 5/0091 20130101;
C08L 85/00 20130101; C08K 5/56 20130101; Y10T 428/25 20150115; C08G
79/00 20130101; C08L 85/00 20130101; C08L 2666/02 20130101 |
Class at
Publication: |
524/577 |
International
Class: |
C08K 003/00 |
Claims
We claim:
1. A composition useful for forming solid-state device structures,
said composition comprising: a solvent system; an organometallic
oligomer dissolved or dispersed in said solvent system, said
organometallic oligomer comprising recurring monomers having the
formula 5wherein: n is greater than 2; each M is individually
selected from the group consisting of Groups 3-5 and 13-15 metals
other than silicon and having a combining valence of greater than
+2; and each R.sup.1 is an organic moiety covalently bonded or
coordinate-covalently bonded to M; and an organic polymer or
oligomer having a weight-average molecular weight of at least about
150 g/mol, said organic polymer or oligomer comprising a functional
group operable to form a covalent or coordinate-covalent bond with
said organometallic oligomer.
2. The composition of claim 1, wherein M is selected from the group
consisting of Group 4 metals.
3. The composition of claim 1, wherein M is selected from the group
consisting of titanium and zirconium.
4. The composition of claim 1, wherein n is 3-10.
5. The composition of claim 1, wherein each R.sup.1 is individually
selected from the group consisting of alkoxys, alkyloxyalkoxys,
beta-diketones, beta-diketonates, and alkanolamines.
6. The composition of claim 5, wherein R.sup.1 has a formula
selected from the group consisting of 6wherein: * represents the
covalent bond or coordinate covalent bond with M; and each R.sup.2
is individually selected from the group consisting of alkyls,
haloalkyls, and --OR.sup.3, wherein R.sup.3 is selected from the
group consisting of hydrogen, alkyls, aryls, and alkylaryls; and
7wherein: * represents the covalent bond or coordinate covalent
bond with M; each R.sup.4 is individually selected from the group
consisting of hydrogen, alkyls, hydroxyalkyls, aryls, and
alkylaryls, with at least one R.sup.4 being selected from the group
consisting of hydrogen, alkyls, and hydroxyalkyls; and R.sup.5 is
selected from the group consisting of hydrogen and methyl.
7. The composition of claim 6, wherein each R.sup.4 is individually
selected from the group consisting of 2-hydroxyethyl and
2-hydroxypropyl.
8. The composition of claim 7, wherein each R.sup.4 forms
coordinate-covalent bonds with at least one metal atom.
9. The composition of claim 1, wherein said organometallic oligomer
comprises poly(dibutyltitanate) reacted with ethyl
acetoacetate.
10. The composition of claim 1, wherein said organic polymer or
oligomer has a polymer backbone, and said functional group forms a
part of said polymer backbone.
11. The composition of claim 1, wherein said organic polymer or
oligomer has a polymer backbone, and said functional group is
pendantly attached to said polymer backbone.
12. The composition of claim 11, wherein said functional group is
pendantly attached to said polymer backbone via a linking group
intermediate said polymer backbone and said functional group.
13. The composition of claim 1, wherein said functional group is
selected from the group consisting of --OH, --SH, and chelating
moieties.
14. The composition of claim 13, wherein said functional group is a
chelating moiety selected from the group consisting of 8wherein: m
1 or 2; when m is 2, then x is 0; each R.sup.6 is individually
selected from the group consisting of hydrogen and methyl groups;
and each R.sup.7 is individually selected from the group consisting
of hydrogen and alkyls.
15. The composition of claim 1, wherein said organic polymer or
oligomer is selected from the group consisting of
poly(styrene-co-allyl alcohol), poly(ethylene glycol), glycerol
ethoxylate, pentaerythritol ethoxylate, pentaerythritol
propoxylate, and combinations thereof.
16. The composition of claim 1, wherein said composition can be
heated to a temperature of at least about 150.degree. C. for at
least about 3 minutes to yield a metal oxide film having a
refractive index of at least about 1.65 at a wavelength of about
633 nm and at a film thickness of about 0.5 .mu.m.
17. The composition of claim 1, wherein said composition can be
heated to a temperature of at least about 150.degree. C. for at
least about 3 minutes to yield a metal oxide film having a percent
transmittance of at least about 80% at a wavelength of about 633 nm
and at a film thickness of about 0.5 .mu.m.
18. The composition of claim 1, wherein said composition can be
heated to a temperature of at least about 150.degree. C. for at
least about 3 minutes to yield a metal oxide film having a metal
oxide content of from about 25-80% by weight, based upon the total
weight of the metal oxide film taken as 100% by weight.
19. The combination of: a substrate having a surface; and a layer
of a composition on said substrate surface, said composition
comprising: a solvent system; an organometallic oligomer dissolved
or dispersed in said solvent system, said organometallic oligomer
comprising recurring monomers having the formula 9wherein: n is
greater than 2; each M is individually selected from the group
consisting of Groups 3-5 and 13-15 metals other than silicon and
having a combining valence of greater than +2; and each R.sup.1 is
an organic moiety covalently bonded or coordinate-covalently bonded
to M; and an organic polymer or oligomer having a weight-average
molecular weight of at least about 150 g/mol, said organic polymer
or oligomer comprising a functional group operable to form a
covalent or coordinate-covalent bond with said organometallic
oligomer.
20. The combination of claim 19, wherein M is selected from the
group consisting of Group 4 metals.
21. The combination of claim 19, wherein M is selected from the
group consisting of titanium and zirconium.
22. The combination of claim 19, wherein n is 3-10.
23. The combination of claim 19, wherein each R.sup.1 is
individually selected from the group consisting of alkoxys,
alkyloxyalkoxys, beta-diketones, beta-diketonates, and
alkanolamines.
24. The combination of claim 23, wherein R.sup.1 has a formula
selected from the group consisting of 10wherein: * represents the
covalent bond or coordinate covalent bond with M; and each R.sup.2
is individually selected from the group consisting of alkyls,
haloalkyls, and --OR.sup.3, wherein R.sup.3 is selected from the
group consisting of hydrogen, alkyls, aryls, and alkylaryls; and
11wherein: * represents the covalent bond or coordinate covalent
bond with M; each R.sup.4 is individually selected from the group
consisting of hydrogen, alkyls, hydroxyalkyls, aryls, and
alkylaryls, with at least one R.sup.4 being selected from the group
consisting of hydrogen, alkyls, and hydroxyalkyls; and R.sup.5 is
selected from the group consisting of hydrogen and methyl.
25. The combination of claim 19, wherein said functional group is
selected from the group consisting of --OH, --SH, and chelating
moieties.
26. The combination of claim 25, wherein said functional group is a
chelating moiety selected from the group consisting of 12wherein: m
is 1 or 2; when m is 2, then x is 0; each R.sup.6 is individually
selected from the group consisting of hydrogen and methyl groups;
and each R.sup.7 is individually selected from the group consisting
of hydrogen and alkyls.
27. The combination of claim 19, wherein said organic polymer or
oligomer is selected from the group consisting of
poly(styrene-co-allyl alcohol), poly(ethylene glycol), glycerol
ethoxylate, pentaerythritol ethoxylate, pentaerythritol
propoxylate, and combinations thereof.
28. The combination of claim 19, wherein said layer can be heated
to a temperature of at least about 150.degree. C. for at least
about 3 minutes to yield a metal oxide film having a refractive
index of at least about 1.65 at a wavelength of about 633 nm and at
a film thickness of about 0.5 .mu.m.
29. The combination of claim 19, wherein said layer can be heated
to a temperature of at least about 150.degree. C. for at least
about 3 minutes to yield a metal oxide film having a percent
transmittance of at least about 80% at a wavelength of about 633 nm
and at a film thickness of about 0.5 .mu.m.
30. The combination of claim 19, wherein said layer can be heated
to a temperature of at least about 150.degree. C. for at least
about 3 minutes to yield a metal oxide film having a metal oxide
content of from about 25-80% by weight, based upon the total weight
of the metal oxide film taken as 100% by weight.
31. The combination of claim 19, wherein said substrate is selected
from the group consisting of flat panel displays, optical sensors,
integrated optical circuits, and light-emitting diodes.
32. A method of forming a solid-state device structure, said method
comprising the step of applying a composition to a substrate
surface to form a layer of said composition on said substrate
surface, said composition comprising: a solvent system; an
organometallic oligomer dissolved or dispersed in said solvent
system, said organometallic oligomer comprising recurring monomers
having the formula 13wherein: n is greater than 2; each M is
individually selected from the group consisting of Groups 3-5 and
13-15 metals other than silicon and having a combining valence of
greater than +2; and each R.sup.1 is an organic moiety covalently
bonded or coordinate-covalently bonded to M; and an organic polymer
or oligomer having a weight-average molecular weight of at least
about 150 g/mol, said organic polymer or oligomer comprising a
functional group operable to form a covalent or coordinate-covalent
bond with said organometallic oligomer.
33. The method of claim 32, wherein M is selected from the group
consisting of Group 4 metals.
34. The method of claim 32, wherein M is selected from the group
consisting of titanium and zirconium.
35. The method of claim 32, wherein n is 3-10.
36. The method of claim 32, wherein each R.sup.1 is individually
selected from the group consisting of alkoxys, alkyloxyalkoxys,
beta-diketones, beta-diketonates, and alkanolamines.
37. The method of claim 36, wherein R.sup.1 has a formula selected
from the group consisting of 14wherein: * represents the covalent
bond or coordinate covalent bond with M; and each R.sup.2 is
individually selected from the group consisting of alkyls,
haloalkyls, and --OR.sup.3, wherein R.sup.3 is selected from the
group consisting of hydrogen, alkyls, aryls, and alkylaryls; and
15wherein: * represents the covalent bond or coordinate covalent
bond with M; each R.sup.4 is individually selected from the group
consisting of hydrogen, alkyls, hydroxyalkyls, aryls, and
arylalkyls, with at least one R.sup.4 being selected from the group
consisting of hydrogen, alkyls, and hydroxyalkyls; and R.sup.5 is
selected from the group consisting of hydrogen and methyl.
38. The method of claim 32, wherein said functional group is
selected from the group consisting of --OH, --SH, and chelating
moieties.
39. The method of claim 38, wherein said functional group is a
chelating moiety selected from the group consisting of 16wherein: m
is 1 or 2; when m is 2, then x is 0; each R.sup.6 is individually
selected from the group consisting of hydrogen and methyl groups;
and each R.sup.7 is individually selected from the group consisting
of hydrogen and alkyls.
40. The method of claim 32, wherein said organic polymer or
oligomer is selected from the group consisting of
poly(styrene-co-allyl alcohol), poly(ethylene glycol), glycerol
ethoxylate, pentaerythritol ethoxylate, pentaerythritol
propoxylate, and combinations thereof.
41. The method of claim 32, wherein said substrate is selected from
the group consisting of flat panel displays, optical sensors,
integrated optical circuits, and light-emitting diodes.
42. The method of claim 32, further comprising the step of heating
said composition to a temperature of at least about 150.degree. C.
for at least about 3 minutes to yield a metal oxide film.
43. The method of claim 42, wherein said metal oxide film has a
refractive index of at least about 1.65 at a wavelength of about
633 nm and at a film thickness of about 0.5 .mu.m.
44. The method of claim 42, wherein said metal oxide film has a
metal oxide content of from about 25-80% by weight, based upon the
total weight of the metal oxide film taken as 100% by weight.
45. The method of claim 42, wherein said metal oxide film has a
thickness of greater than about 1 .mu.m and is free of cracks when
observed under a microscope at a magnification of 200.times..
46. The method of claim 42, further comprising the step of
preheating said composition prior to said heating step, said
preheating step comprising heating said composition to a
temperature of less than about 130.degree. C. for a time of from
about 1-10 minutes.
47. The method of claim 42, wherein said metal oxide film has a
percent transmittance of at least about 80% at a wavelengths of
about 600 nm and at a film thickness of about 0.5 .mu.m.
48. A method of forming a composition for use in forming
solid-state device structures, said method comprising the steps of
dispersing or dissolving an organometallic polymer and an organic
polymer or oligomer in a solvent system, said organometallic
polymer comprising recurring monomers having the formula 17wherein:
n is greater than 2; each M is individually selected from the group
consisting of Groups 3-5 and 13-15 metals other than silicon and
having a combining valence of greater than +2; and each R.sup.1 is
an organic moiety covalently bonded or coordinate-covalently bonded
to M; and said organic polymer or oligomer comprising a functional
group operable to form a covalent or coordinate-covalent bond with
said organometallic oligomer and having a weight-average molecular
weight of at least about 150 g/mol.
49. The method of claim 48, wherein said dissolving or dispersing
step comprises dissolving or dispersing said organometallic polymer
and said organic polymer or oligomer in separate solvent systems to
yield an organometallic polymer dispersion and an organic polymer
or oligomer dispersion, said method further comprising the step of
combining said organometallic polymer dispersion and said organic
polymer or oligomer dispersion to yield the composition.
50. The method of claim 48, wherein said dissolving or dispersing
step comprises dissolving or dispersing said organometallic polymer
and said organic polymer or oligomer in the same solvent
system.
51. The method of claim 48, further comprising the step of forming
said organometallic oligomer by reacting a metal oxide precursor
with a chelating agent prior to said dispersing or dissolving step.
Description
BACKGROUND OF THE INVENTION
Related Applications
[0001] This application claims the priority benefit of a
provisional application entitled HYBRID ORGANIC-INORGANIC POLYMER
COATINGS WITH HIGH REFRACTIVE INDICES, Ser. No. 60/441,693, filed
Jan. 21, 2003, incorporated by reference herein.
FIELD OF THE INVENTION
[0002] The present invention relates to novel compositions which
can be formed into metal oxide films having high refractive
indices. The compositions are useful for forming solid-state
devices such as flat panel displays, optical sensors, integrated
optical circuits, and light-emitting diodes.
Description of the Prior Art
[0003] The performance of many solid-state devices including flat
panel displays, optical sensors, integrated optical (photonic)
circuits, and light-emitting diodes (LEDs) can be improved by
applying a transparent, high refractive index coating onto the
light-emitting or light-sensing portion of the device structure.
Organic polymer coatings offer easy, low-temperature application
and robust mechanical properties, including good surface adhesion,
when used on such devices. However, few organic polymers have
refractive indices greater than 1.65 at visible wavelengths, and
fewer still have indices of 1.70 or greater. Those polymers that do
have higher indices generally contain a high concentration of large
polarizable atoms such as bromine, iodine, or sulfur, which limits
their thermal and chemical stability.
[0004] On the other hand, certain metal oxides, most notably those
of titanium and zirconium, possess excellent optical clarity when
applied as thin films and exhibit refractive indices of 2.0 or more
at visible wavelengths. They, unfortunately, must be deposited by
expensive and inefficient methods such as evaporation or
sputtering, and then can only be applied as thin films (less than 1
.mu.m in thickness) whereas device makers are often seeking films
of several microns to several tens of microns in thickness.
Moreover, the deposited metal oxide coatings are brittle and may
not adhere well to device surfaces without high-temperature
annealing, which may degrade device operation.
[0005] The well known sol-gel coating method has been used to
deposit high index metal oxide coatings from solution. However, the
coatings tend to be brittle and subject to cracking and require
long, complicated curing schedules. Sol-gel coating solutions also
have limited pot life, making the method difficult to practice on a
commercial scale. More recently, the sol-gel method has been
combined with conventional polymer chemistry to prepare
inorganic-organic hybrid coatings in which the metal oxide phase,
formed by in situ hydrolysis and condensation of a metal alkoxide,
is chemically bonded to an organic polymer phase to obtain
materials with greater toughness and durability. However, they are
still prone to the pot life problems associated with sol-gel
compositions and lend themselves best to silicon dioxide
incorporation, which does not promote a high refractive index.
[0006] Inorganic-organic hybrid coatings have also been prepared by
dispersing nanosized (1 to 50 nm in diameter) metal oxide particles
in a polymer vehicle to produce transparent film compositions.
However, the refractive indices of these compositions are largely
restricted to the range of 1.55 to 1.70 unless very high metal
oxide loadings (80%) are utilized. Moreover, preparation of the
coatings requires many steps, including particle synthesis and
purification, surface treatment, and dispersion, often under a non-
ambient environment.
[0007] Therefore, in light of the shortcomings of the prior art, a
need exists for coatings that have a refractive index greater than
about 1.7, and preferably greater than about 1.75, at visible and
near infrared wavelengths (from about 400-1700 nm), and that
provide high optical clarity along with easy and reliable
preparation, long shelf life, and good mechanical stability at film
thicknesses of greater than 1 micron.
SUMMARY OF THE INVENTION
[0008] The present invention fills this need by broadly providing
novel coating compositions for use in optical device
applications.
[0009] In more detail, the compositions comprise an organometallic
oligomer and an organic polymer or oligomer dispersed or dissolved
in a solvent system. The organometallic oligomer can be linear or
branched and will thermally decompose to a high refractive index
metal oxide. Preferred organometallic oligomers comprise monomers
having the structure 1
[0010] where:
[0011] n is greater than 2 and more preferably 3-10;
[0012] each M is individually selected from the group consisting of
Groups 3-5 and 13-15 metals from the Periodic table of elements
(more preferably Group 4 and even more preferably titanium or
zirconium) other than silicon and having a combining valence of
greater than +2; and
[0013] each R.sup.1 is an organic moiety covalently bonded or
coordinate-covalently bonded to M.
[0014] Preferred R.sup.1 groups include those which form a
--CH.sub.2--O--M bond (where M is the metal atom as discussed
above) such as those selected from the group consisting of alkoxys
(preferably C.sub.1-C.sub.12, and more preferably C.sub.1-C.sub.8),
alkyloxyalkoxys (preferably C.sub.1-C.sub.12, and more preferably
C.sub.1-C.sub.8), beta-diketones, beta-diketonates, and
alkanolamines.
[0015] In another embodiment, preferred R.sup.1 groups have a
formula selected from the group consisting of 2
[0016] where:
[0017] * represents the covalent bond or coordinate-covalent bond
with M; and
[0018] each R.sup.2 is individually selected from the group
consisting of alkyls (preferably C.sub.1-C.sub.12, and more
preferably C.sub.1-C.sub.8, with methyl and ethyl being the most
preferred), haloalkyls (preferably C.sub.1-C.sub.12, and more
preferably C.sub.1-C.sub.8; preferably fluoroalkyls with
trifluoromethyl being the most preferred), and --OR.sup.3, where
R.sup.3 is selected from the group consisting of hydrogen, alkyls
(preferably C.sub.1-C.sub.12, and more preferably C.sub.1-C.sub.8),
aryls (preferably C.sub.6-C.sub.18, and more preferably
C.sub.6-C.sub.12), and alkylaryls (preferably C.sub.1-C.sub.12, and
more preferably C.sub.1-C.sub.8 for the alkyl component and
preferably C.sub.6-C.sub.18, and more preferably C.sub.6-C.sub.12
for the aryl component); and 3
[0019] where:
[0020] * represents the covalent bond or coordinate-covalent bond
with M;
[0021] each R.sup.4 is individually selected from the group
consisting of hydrogen, alkyls (preferably C.sub.1-C.sub.12, and
more preferably C.sub.1-C.sub.8), hydroxyalkyls (preferably
C.sub.1-C.sub.12, and more preferably C.sub.1-C.sub.8), aryls
(preferably C.sub.6-C.sub.18, and more preferably
C.sub.6-C.sub.12), and alkylaryls (preferably C.sub.1-C.sub.12, and
more preferably C.sub.1-C.sub.8 for the alkyl component and
preferably C.sub.6-C.sub.18, and more preferably C.sub.6-C.sub.12
for the aryl component), with at least one R.sup.4 being selected
from the group consisting of hydrogen, alkyls, (preferably
C.sub.1-C.sub.12, and more preferably C.sub.1-C.sub.8) and
hydroxyalkyls (preferably C.sub.1-C.sub.12, and more preferably
C.sub.1-C.sub.8); and
[0022] R.sup.5 is selected from the group consisting of hydrogen
and methyl.
[0023] When R.sup.1 is structure (II), particularly preferred
R.sup.4 groups include 2-hydroxyethyl and 2-hydroxypropyl. In these
instances, the R.sup.4 groups may optionally form
coordinate-covalent bonds with the same or different metal
atoms.
[0024] The organometallic oligomer is preferably present in the
composition at a level of at least about 15% by weight, preferably
from about 15-35% by weight, and more preferably from about 24-35%
by weight, based upon the total weight of the composition taken as
100% by weight.
[0025] The organic polymer or oligomer can be either branched or
linear. An organic oligomer rather than an organic polymer would
typically be used, but the scope of this invention is intended to
include both so long as the organic polymer or oligomer comprises a
functional group (and preferably three such functional groups)
capable of forming covalent or coordinate-covalent bonds with the
organometallic oligomer.
[0026] The functional group can be present within the backbone of
the organic polymer or oligomer, or it can be present as a group
pendantly attached (either directly or through a linking group) to
the polymer backbone, provided the functional group meets the other
requirements discussed herein.
[0027] Preferred functional groups on the organic polymer or
oligomer include those selected from the group consisting of --OH,
--SH, and chelating moieties. Preferred chelating moieties include
those selected from the group consisting of 4
[0028] where:
[0029] m is 1 or 2;
[0030] when m is 2, then x is 0;
[0031] each R.sup.6 is individually selected from the group
consisting of hydrogen and methyl groups; and
[0032] each R.sup.7 is individually selected from the group
consisting of hydrogen and alkyls (preferably C.sub.1-C.sub.12,
more preferably C.sub.1-C.sub.8, and even more preferably
methyl).
[0033] Particularly preferred organic polymers or oligomers include
those selected from the group consisting of poly(styrene-co-allyl
alcohol), poly(ethylene glycol), glycerol ethoxylate,
pentaerythritol ethoxylate, pentaerythritol propoxylate, and
combinations thereof. The organic polymer or oligomer is preferably
present in the composition at a level of at least about 3% by
weight, preferably from about 3-35% by weight, and more preferably
from about 3-20% by weight, based upon the total weight of the
composition taken as 100% by weight. Finally, the organic polymer
or oligomer preferably has a weight-average molecular weight of at
least about 150 g/mol, preferably at least about 500 g/mol, and
more preferably from about 1500-2500 g/mol.
[0034] Suitable solvent systems include most organic solvents such
as those selected from the group consisting of alcohols, glycol
ethers, esters, aromatic solvents, ketones, ethers, and mixtures
thereof. Particularly preferred solvents are ethyl lactate,
ethylene glycol ethers, and propylene glycol ethers (e.g.,
1-propoxy-2-propanol). The solvent system is preferably present in
the composition at a level of at least about 10% by weight,
preferably from about 10-35% by weight, and more preferably from
about 10-28% by weight, based upon the total weight of the
composition taken as 100% by weight.
[0035] The compositions can include other solvent-soluble
ingredients to modify the optical or physical properties of the
coatings formed from the compositions. For example, the
compositions can include other organic polymers and resins, low
molecular weight (less than about 500 g/mol) organic compounds such
as dyes, surfactants, and chelating agents (e.g., alkanolamines),
and non-polymeric metal chelates such as metal alkoxides or metal
acetylacetonates.
[0036] The compositions are prepared by dissolving/dispersing the
organometallic oligomer and organic polymer or oligomer in the
solvent system. This can be done simultaneously, or it can be
carried out in two separate vessels followed by combining of the
two dispersions or solutions. Any optional ingredients are added in
a similar manner. The total solids content in the composition can
vary from about 1-50% by weight, and more preferably from about
10-40% by weight, based upon the total weight of the composition
taken as 100% by weight.
[0037] The compositions are applied to a substrate by any known
method to form a coating layer or film thereon. Suitable coating
techniques include dip coating, draw- down coating, or spray
coating. A preferred method involves spin coating the composition
onto the substrate at a rate of from about 500-4000 rpm (preferably
from about 1000-3000 rpm) for a time period of from about 30-90
seconds to obtain uniform films. Substrates to which the coatings
can be applied include flat panel displays, optical sensors,
integrated optical circuits, and light-emitting diodes.
[0038] The applied coatings are preferably first baked at low
temperatures (e.g., less than about 130.degree. C., preferably from
about 60-130.degree. C., and more preferably from about
100-130.degree. C.) for a time period of from about 1-10 minutes to
remove the casting solvents. To effect curing or conversion of the
organometallic oligomer to a metal oxide/organic polymer hybrid
film, the coating is then baked at temperatures of at least about
150.degree. C., and more preferably from about 150-300.degree. C.
for a time period of at least about 3 minutes (preferably at least
about 5 minutes). Baking at the curing temperature for longer than
5 minutes will produce further small reductions in film thickness
and small increases in refractive index.
[0039] In another embodiment, the film is heated to a temperature
of at least about 300.degree. C. for a time period of from about
5-10 minutes in order to thermally decompose essentially all (i.e.,
at least about 95% by weight, and preferably at least about 99% by
weight) of the organic polymer or oligomer so that extremely high
metal oxide content (at least about 95% by weight metal oxide)
films are formed. This high-temperature baking can be carried out
after a hybrid conversion bake step as discussed above, or in lieu
of such a bake step.
[0040] The baking processes are conducted preferably on a hot
plate-style baking apparatus, though oven baking may be applied to
obtain equivalent results. The initial drying bake may not be
necessary if the final curing process is conducted in such a way
that rapid evolution of the solvents and curing by-products is not
allowed to disrupt the film quality. For example, a ramped bake
beginning at low temperatures and then gradually increasing to the
range of 150-300.degree. C. can give acceptable results. The choice
of final bake temperature depends mainly upon the curing rate that
is desired. If curing times of less than 5 minutes are desired,
then final baking should be conducted at temperatures greater than
about 200.degree. C., and more preferably greater than about
225.degree. C.
[0041] Though not wishing to be bound by theory, it is believed
that the conversion of the organometallic oligomer to metal oxide
involves its hydrolysis by moisture that is contained in the
coating and/or adsorbed from the atmosphere during the casting and
curing processes. Therefore, the curing process is preferably
carried out in air or in an atmosphere where moisture is present to
facilitate complete conversion to metal oxide. The curing process
can also be aided by exposure of the coating to ultraviolet
radiation, preferably in a wavelength range of from about 200-400
nm. The exposure process can be applied separately or in
conjunction with a thermal curing process.
[0042] Cured coatings prepared according to the instant invention
will have superior properties, even at final thicknesses of greater
than 1 .mu.m. For example, the cured coatings or films will have a
refractive index of at least about 1.65, more preferably at least
about 1.70, and even more preferably from about 1.75-2.00, at
wavelengths of about 633 nm and thicknesses of about 0.5 .mu.m or
about 1 .mu.m. Furthermore, cured coatings or films having a
thickness of about 0.5 .mu.m or about 1 .mu.m will have a percent
transmittance of at least about 80%, preferably at least about 90%,
and even more preferably least about 95% at wavelengths of from
about 633 nm. Finally, the curing process will yield films having a
metal oxide content of from about 25-80% by weight, more preferably
from about 25-75% by weight, and even more preferably from about
35-75% by weight, based upon the total weight of the cured film or
layer taken as 100% by weight. Each of the foregoing properties can
be achieved while yielding cured films having extremely good
mechanical stabilities (i.e., no cracking of the films is visible
when observed under a microscope at a magnification of
200.times.).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
EXAMPLES
[0043] The following examples set forth preferred methods in
accordance with the invention. It is to be understood, however,
that these examples are provided by way of illustration and nothing
therein should be taken as a limitation upon the overall scope of
the invention.
Examples 1 Through 6
Preparation and Application of Hybrid Coatings
[0044] 1. Coating Preparation
[0045] A series of hybrid coatings were prepared by first reacting
poly(dibutyltitanate) with ethyl acetoacetate to form a
beta-diketonate-chelated organometallic oligomer and then combining
this product in solution with different proportions of
poly(styrene-co-allyl alcohol) as the organic oligomer.
[0046] In this preparation method, 108.00 g of
poly(dibutyltitanate) were weighed into a 500-ml closed container,
followed by 54.00 g propylene glycol n-propyl ether. The contents
were stirred until a clear, homogeneous solution was obtained.
Next, over a period of 2 hours, 140.44 g of ethyl acetoacetate were
added through a dropping funnel into the solution while constant
stirring was carried out. The contents were allowed to stir
overnight after completing the addition to yield an organometallic
oligomer solution.
[0047] In the next step, 22.15 g of poly(styrene-co-allyl alcohol)
(SAA 101, Mw=2200 g/mol) were dissolved by stirring in 22.15 g of
propylene glycol n-propyl ether to yield an organic oligomer
solution. The organic oligomer solution was then added in different
proportions to the organometallic oligomer solution to give hybrid
coating solutions containing the amounts of materials shown in
Table 1. The resulting mixtures, which were clear and free of any
gelled materials, were stirred for 4 hours and then filtered
through a 0.1-.mu.m Teflon.RTM. filter. The theoretical weight
ratio of titanium dioxide to organic oligomer for the cured film
product prepared from each coating solution also appears in Table
1.
1TABLE 1 Component Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6
Poly(dibutyltitanate) 108.00 g 108.00 g 108.00 g 108.00 g 108.00 g
108.00 g Ethyl acetoacetate 140.44 g 140.44 g 140.44 g 140.44 g
140.44 g 40.44 g Poly(styrene-co-allyl 10.29 g 13.71 g 17.63 g
22.15 g 41.09 g 76.23 g alcohol) Propylene glycol 64.29 g 67.71 g
71.63 g 76.15 g 95.09 g 130.21 g propyl ether TiO.sub.2/SAA101 w/w
80/20 75/25 70/30 65/35 50/50 35/65 ratio
[0048] 2. Application and Properties
[0049] The coating solutions were applied onto quartz and silicon
substrates by spin-coating, soft-baked on a 130.degree. C. hot
plate for 120 seconds, and then cured by baking on a 225.degree. C.
hot plate for 10 minutes. This cycle was repeated for some of the
compositions to increase film thickness. The thickness of each
resulting film was measured with an ellipsometer (633-nm light
source) or by profilometry, and coating transparency (reported as
percent transmission at 633 nm) was measured using a UV-visible
spectrophotometer with no corrections for scattering or reflective
losses. The refractive index of each coating was determined with
the aid of a variable-angle scanning ellipsometer (VASE). The
results are summarized in Table 2.
2TABLE 2 Property Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Refractive
Index (400 nm) 2.01 1.94 1.90 1.86 1.78 1.72 Refractive Index (633
nm) 1.88 1.83 1.80 1.77 1.71 1.66 Film Thickness 0.88 1.10 1.85
2.15 2.50 4.28 (microns) % Transmittance at 85.8 86.6 95.7 94.0
96.1 94.5 633 nm TiO.sub.2/SAA101 w/w 80/20 75/25 70/30 65/35 50/50
35/65 ratio
Example 7
Effect of Lower Curing Temperature on Hybrid Coating Refractive
Index
[0050] The composition corresponding to Example 5 was applied as
described above but cured at lower temperatures to show that a
comparable refractive index could be obtained using sub-200.degree.
C. curing conditions. The results obtained for 150.degree. C.
curing (1 hour) and 175.degree. C. curing (1 hour) were comparable
to those obtained at 225.degree. C. (10 min.), as can be seen in
Table 3.
3TABLE 3 Refractive Index Curing Conditions (400 nm) Refractive
Index (633 nm) 225.degree. C./10 min. 1.78 1.71 175.degree. C./60
min. 1.75 1.68 150.degree. C./60 min. 1.73 1.66
Example 8
Preparation of a Hybrid Coating Composition from Modified
Styrene-Allyl Alcohol Copolymer Having Acetoacetic Ester Chelating
Groups
[0051] A hybrid coating composition resembling that in Example 4
was prepared but, in this instance, poly(styrene-co-allyl alcohol)
[SAA101] was first reacted with t-butyl acetoacetate to esterify a
portion of the alcohol groups on the polymer, thus creating
acetoacetic ester pendant groups that could form chelating bonds
with the organometallic oligomer.
[0052] 1. Modification of SAA101 with t-Butyl Acetoacetate
[0053] In this procedure, 50 g SAA101 powder were charged into a
500-ml, three-neck flask containing 275 g toluene and equipped with
a distillation head, thermometer, and dropping funnel. The solution
was heated to 50.degree. C. while stirring to increase the
dissolution rate of the SAA101. Once it had dissolved, 14.38 g of
t-butyl acetoacetate were added to the solution through a dropping
funnel over a period of 10 minutes. The mixture was heated to
100.degree. C. after completing the addition, whereupon the
evolution of by-product t-butyl alcohol was observed. The
temperature of the contents was held at 100.degree. C. for 1 extra
hour to ensure complete reaction, during which time t-butyl alcohol
was removed continuously from the reaction mixture. The reaction
mixture was allowed to cool to room temperature, and the toluene
was removed by rotating vacuum distillation. The residual material
was further dried in a vacuum oven, yielding 52 g of the modified
SAA101 product.
[0054] 2. Coating Formulation
[0055] In this preparation, 7.00 g poly(dibutyltitanate) were
weighed into a 60-ml closed container, followed by the addition of
7.00 g propylene glycol n-propyl ether. The contents were stirred
at room temperature until a clear, homogeneous solution was
obtained. Then, 6.90 g ethyl acetoacetate were slowly added with
constant stirring to the solution prepared in procedure 1. The
contents were allowed to stir overnight after completing the
addition. Modified SAA101 (1.44 g) was dissolved in an equivalent
amount of propylene glycol n-propyl ether and then added to the
solution prepared in procedure 2. The mixture was stirred for 4
hours and then filtered through a 0.1-.mu.m Teflon.RTM. filter. The
values in Table 4 were obtained when the coating composition was
applied and cured as described in Example 1.
4 TABLE 4 Property Ex. 8 Refractive Index (400 nm) 1.88 Refractive
Index (633 nm) 1.78 Film Thickness (microns) 0.43 % Transmittance
at 633 nm 89.5 TiO2/SAA101 w/w ratio 65/35
Example 9
Preparation of a Hybrid Coating Composition from an Acrylic
Copolymer Having Pendant Acetoacetic Ester Functional Groups
[0056] An acrylic copolymer having pendant acetoacetic ester
functional groups was combined with poly(dibutyltitanate) to form a
hybrid coating solution.
[0057] 1. Preparation of Methyl Methyacrylate/2-Acetoacetoxyethyl
Methacrylate Copolymer
[0058] In this procedure, 20 g (0.198 mol) methyl methacrylate,
22.30 g (0.0989 mol) 2-acetoacetoxyethyl methacrylate, and 170 g
tetrahyrdrofuran (THF) were placed in a 250-ml, 3-necked flask with
a nitrogen inlet, condenser, glass stopper, and stir bar. The
mixture was stirred until well mixed. Next, 0.4 g
2,2'-azobis(2-methylpropionitrile) (AIBN) were added, and the
resulting mixture was stirred until homogeneous. The resulting
solution was heated to reflux for 24 hours under a flow of
nitrogen. A colorless, viscous liquid was obtained after the
reaction period. Thermogravimetric analysis (TGA) showed this to
contain 40% copolymer solids.
[0059] 2. Coating Formulation
[0060] About 1.0 g of the above copolymer solution was placed in a
glass vial and diluted by the addition of 2 g of THF. A stir bar
was placed in the vial. In a separate glass vial 1.0 g of
poly(dibutyltitanate) was placed followed by dilution with 2 g of
THF. The diluted solution of poly(dibutyltitanate) was added
dropwise to the stirred copolymer solution. A slight yellow
coloration formed in the solution, finally giving a light yellow
solution after all the organotitanate solution had been added. A
freestanding thick film was prepared by casting the coating mixture
onto the bottom of a polypropylene beaker and air-drying for 15
minutes, followed by hot blow drying for another 5 minutes. The
coating was then peeled from the plastic surface. The film had a
light yellow color and was brittle to touch.
Example 10
Use of Ultraviolet Radiation to Cure a Hybrid Coating
Composition
[0061] The purpose of this example was to demonstrate how exposure
to ultraviolet radiation can effect the conversion of the
organometallic oligomer used in the new compositions to the final
metal oxide component. Four silicon wafers were coated with an
ethyl lactate solution of poly(butyltitanate) to which had been
added two equivalents of ethyl acetoacetate per equivalent of
titanium to form a chelated organotitanium polymer product. The
coated wafers were soft-baked on a hot plate and then hard-baked at
205.degree. C. for 60 seconds to partially cure the organotitanium
polymer. The respective average film thicknesses for the four
wafers at that point was 1266 .ANG. as determined by ellipsometry.
Three of the wafers were then exposed to ultraviolet light from a
500-W mercury-xenon arc lamp for 30, 60, or 90 seconds,
respectively, after which the respective film thicknesses were
redetermined. The results are listed in Table 5.
5 TABLE 5 Exposure Time (sec) Film Thickness (.ANG.) 0 1266 30 1084
60 943 90 873
[0062] The continuous reduction in film thickness as exposure time
increased indicated that curing was proceeding, and volatile
by-products were being expelled from the coating in the absence of
heating. The occurrence of curing was also confirmed by placing
droplets of aqueous tetramethylammonium hydroxide (TMAH) solution
on the specimens at 30-second intervals. The unexposed coating
etched completely away in less than 30 seconds, whereas the exposed
coatings showed no evidence of etching, even when in contact with
the etchant for 1 to 2 minutes. The inability of the etchant to
dissolve the exposed coatings was evidence of their higher degree
of curing than the unexposed specimen.
Example 11
[0063] 1. Coating Preparation
[0064] Coatings were prepared by first reacting
poly(dibutyltitanate) with ethyl acetoacetate to form a
beta-diketonate-chelated organometallic oligomer and then combining
this product in solution with one of two different organic
oligomers.
[0065] In this preparation method, the poly(dibutyltitanate) was
weighed into a 500-ml closed container, followed by addition of the
propylene glycol n-propyl ether. The contents were stirred until a
clear, homogeneous solution was obtained. Next, over a period of 2
hours, the ethyl acetoacetate was added through a dropping funnel
into the solution while constant stirring was carried out. The
contents were allowed to stir overnight after completing the
addition to yield the organometallic oligomer solution.
[0066] In the next step, the particular organic oligomer was added
to the organometallic oligomer solution to give hybrid coating
solutions containing the amounts of materials shown in Table 6. The
resulting mixtures, which were clear and free of any gelled
materials, were stirred for 4 hours and then filtered through a
0.1-.mu.m Teflon.RTM. filter.
6 TABLE 6 Component Ex. 1 Ex. 2 Poly(dibutyltitanate) 300.07 g
300.08 g Ethyl acetoacetate 390.88 g 390.88 g Poly(ethylene
glycol), Mw = 600 g/mol 38.09 g -- Glycerol propoxylate, Mn = 725
g/mol -- 38.09 g Propylene glycol propyl ether 150.06 g 150.03 g
TiO.sub.2/organic polymer or oligomer 75/25 75/25 ratio w/w
ratio
[0067] 2. Application and Properties
[0068] The coating solutions were applied onto quartz and silicon
substrates by spin-coating, soft-baked on a 130.degree. C. hot
plate for 120 seconds, baked at 225.degree. C. for 10 minutes, and
then baked at 300.degree. C. for 10 minutes to thermally decompose
the organic oligomer, thus yielding an extremely high metal oxide
content film. The properties are summarized in Table 7.
7 TABLE 7 Property Ex. 1 Ex. 2 Refractive Index (400 nm) 2.20 2.16
Refractive Index (633 nm) 2.01 1.98 Film Thickness (microns) 0.24
0.24 % Transmittance at 633 nm 90 90
* * * * *