U.S. patent application number 13/695674 was filed with the patent office on 2013-02-21 for articles, coating compositions, and methods.
This patent application is currently assigned to 3M INNOVATIVE PROPERTIES COMPANY. The applicant listed for this patent is Yiwen Chu, Naiyong Jing, Rui Pan, Zhigang Yu. Invention is credited to Yiwen Chu, Naiyong Jing, Rui Pan, Zhigang Yu.
Application Number | 20130045387 13/695674 |
Document ID | / |
Family ID | 44914902 |
Filed Date | 2013-02-21 |
United States Patent
Application |
20130045387 |
Kind Code |
A1 |
Chu; Yiwen ; et al. |
February 21, 2013 |
Articles, Coating Compositions, and Methods
Abstract
There is provided a coating composition comprising nonspherical
nanoparticles; spherical nanoparticles; optionally hydrophilic
groups and optional an surfactant; and a liquid medium comprising
water and no greater than 30 wt % organic solvent, if present,
based on the total weight of liquid medium, where at least a
portion of the nonspherical nanoparticles or at least a portion of
the spherical nanoparticles comprises functional groups attached to
their surface through chemical bonds, wherein the functional groups
comprise at least one group selected from the group consisting of
epoxy group, amine group, hydroxyl, olefin, alkyne, (meth)
acrylato, mercapto group, or combinations thereof. There is also
provided a method for modifying a substrate surface using the
coating composition and articles made therefrom.
Inventors: |
Chu; Yiwen; (Shanghai,
CN) ; Yu; Zhigang; (Shanghai, CN) ; Jing;
Naiyong; (Woodbury, MN) ; Pan; Rui; (Hangzhou,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Chu; Yiwen
Yu; Zhigang
Jing; Naiyong
Pan; Rui |
Shanghai
Shanghai
Woodbury
Hangzhou |
MN |
CN
CN
US
CN |
|
|
Assignee: |
3M INNOVATIVE PROPERTIES
COMPANY
ST. PAUL
MN
|
Family ID: |
44914902 |
Appl. No.: |
13/695674 |
Filed: |
April 25, 2011 |
PCT Filed: |
April 25, 2011 |
PCT NO: |
PCT/US11/33723 |
371 Date: |
November 1, 2012 |
Current U.S.
Class: |
428/410 ;
106/287.22; 106/287.24; 106/287.26; 106/287.3; 106/287.32;
106/287.34; 427/385.5; 427/386; 427/389.7; 427/393.6; 428/417;
428/426; 428/441; 428/446; 428/451; 977/773 |
Current CPC
Class: |
H01L 31/02168 20130101;
C08K 3/36 20130101; C03C 17/007 20130101; Y10T 428/31525 20150401;
Y10T 428/31645 20150401; C03C 2217/425 20130101; C08K 9/06
20130101; C09D 7/67 20180101; C09D 7/61 20180101; C03C 2217/465
20130101; C09D 7/70 20180101; C03C 2217/478 20130101; C09D 1/00
20130101; Y10T 428/315 20150115; Y10T 428/31667 20150401; Y02E
10/50 20130101 |
Class at
Publication: |
428/410 ;
106/287.22; 106/287.3; 106/287.26; 106/287.34; 106/287.24;
106/287.32; 427/385.5; 427/386; 427/389.7; 427/393.6; 428/441;
428/426; 428/446; 428/451; 428/417; 977/773 |
International
Class: |
C09D 1/00 20060101
C09D001/00; B32B 17/10 20060101 B32B017/10; B32B 27/38 20060101
B32B027/38; B32B 18/00 20060101 B32B018/00; B32B 17/06 20060101
B32B017/06 |
Foreign Application Data
Date |
Code |
Application Number |
May 11, 2010 |
CN |
201010170156.6 |
Claims
1. A method of modifying a substrate surface, the method
comprising: (a) applying a coating composition to a substrate,
wherein the coating composition comprises: (i) nonspherical
nanoparticles; (ii) spherical nanoparticles; (iii) optionally
hydrophilic groups and optionally a surfactant; and (iv) a liquid
medium comprising water and no greater than 30 wt % organic
solvent, if present, based on the total weight of liquid medium,
wherein at least a portion of the nonspherical nanoparticles or at
least a portion of the spherical nanoparticles comprises functional
groups attached to the surface of the nonspherical nanoparticles or
the spherical nanoparticles through chemical bonds, and further
wherein the functional groups comprise at least one group selected
from epoxy group, amine group, hydroxyl, olefin, alkyne, (meth)
acrylato, mercapto, or combinations thereof; and (b) drying the
coating composition to form a hydrophilic coating on the
substrate.
2. The method of claim 1 wherein all the nonspherical nanoparticles
or all the spherical nanoparticles comprise the functional
groups.
3. The method of claim 1 wherein the weight ratio of the
nonspherical nanoparticles to the spherical nanoparticles ranges
from 95:5 to 5:95.
4. The method of claim 3 wherein the weight ratio of the
nonspherical nanoparticles to the spherical nanoparticles ranges
from 80:20 to 20:80.
5. The method of claim 4 wherein the weight ratio of the
nonspherical nanoparticles to the spherical nanoparticles ranges
from 70:30 to 30:70.
6. The method of claim 1 wherein at least a portion of the
nonspherical nanoparticles comprise silica nanoparticles.
7. The method of claim 1 wherein at least a portion of the
spherical nanoparticles comprise silica nanoparticles.
8. The method of claim 1 wherein the substrate is glass or
ceramic.
9. The method of claim 1 wherein the method further comprises the
step of sintering the coated substrate at a temperature ranging
from 200 degrees C. to 750 degrees C.
10. The method of claim 1 wherein the nonspherical nanoparticles
have an average particle size between 1 and 200 nm and an aspect
ratio between 2 and 100.
11. The method of claim 1 wherein the spherical nanoparticles have
an average particle size between 1 and 120 nm.
12. The method of claim 1 wherein the coating composition comprises
at least 0.05 wt % nonspherical nanoparticles and no greater than
40 wt % nonspherical nanoparticles, based on the total weight of
the coating composition.
13. The method of claim 1 wherein the coating composition comprises
at least 0.05 wt % spherical nanoparticles and no greater than 40
wt % spherical nanoparticles, based on the total weight of the
coating composition.
14. The method of claim 1 wherein the coating composition comprises
0.01-5 wt % surfactant, based on the total weight of the coating
composition.
15. The method of claim 1 wherein the nonspherical nanoparticles
are elongated nanoparticles.
16. The method of claim 1 wherein the spherical nanoparticles
comprise the functional groups.
17. An article comprising a substrate surface modified using the
method of claim 1.
18. A coating composition comprising nonspherical nanoparticles;
spherical nanoparticles; optionally hydrophilic groups and optional
an surfactant; and a liquid medium comprising water and no greater
than 30 wt % organic solvent, if present, based on the total weight
of liquid medium, wherein at least a portion of the nonspherical
nanoparticles or at least a portion of the spherical nanoparticles
comprises functional groups attached to their surface through
chemical bonds, wherein the functional groups comprise at least one
group selected from the group consisting of epoxy group, amine
group, hydroxyl, olefin, alkyne, (meth) acrylato, mercapto group,
or combinations thereof.
19. The composition of claim 18 wherein all the nonspherical
nanoparticles or all the spherical nanoparticles comprise the
functional groups.
20. The composition of claim 18 wherein the weight ratio of the
nonspherical nanoparticles to the spherical nanoparticles ranges
from 95:5 to 5:95.
21. The composition of claim 20 wherein the weight ratio of the
nonspherical nanoparticles to the spherical nanoparticles ranges
from 70:30 to 30:70.
22. The composition of claim 18 wherein at least a portion of the
nonspherical nanoparticles comprise silica nanoparticles.
23. The composition of claim 18 wherein at least a portion of the
spherical nanoparticles comprise silica nanoparticles.
24. The composition of claim 18 wherein the substrate is glass or
ceramic.
25. The composition of claim 18 wherein the nonspherical
nanoparticles have an average particle size between 1 and 200 nm
and an aspect ratio between 2 and 100.
26. The composition of claim 18 wherein the spherical nanoparticles
have an average particle size between 1 and 120 nm.
27. The composition of claim 18 wherein the coating composition
comprises at least 0.05 wt % nonspherical nanoparticles and no
greater than 40 wt % nonspherical nanoparticles, based on the total
weight of the coating composition.
28. The composition of claim 18 wherein the coating composition
comprises at least 0.05 wt % spherical nanoparticles and no greater
than 40 wt % spherical nanoparticles, based on the total weight of
the coating composition.
29. The composition of claim 18 wherein the coating composition
comprises 0.01-5 wt % surfactant, based on the total weight of the
coating composition.
30. The composition of claim 18 wherein a dried coating provides
antireflective, easy cleaning and/or durability characteristics to
the substrate for at least 24 hours.
31. The composition of claim 18 wherein the nonspherical
nanoparticles are elongated nanoparticles.
32. The composition of claim 18 wherein the spherical nanoparticles
comprise the functional groups.
33. An article comprising a substrate surface modified using the
coating composition of claim 18.
34. The article of claim 33 which is a solar panel.
35. The article of claim 33 wherein the substrate is glass.
36. The article of claim 35 wherein the glass is tempered.
Description
FIELD OF THE INVENTION
[0001] The present application relates to a coating composition, a
method of modifying a substrate surface and articles coated with
the coating composition.
BACKGROUND
[0002] Articles having surfaces with antireflective, easy cleaning
and improved durability characteristics are desirable for a variety
of uses. For example, photoelectric conversion ratio of the solar
glass for a solar battery can be improved by a glass coating.
[0003] Some glass coating compositions have been developed. For
example, U.S. Pat. Nos. 6,040,378 and 6,352,780 disclosed a
polymeric coating composition for application onto glass substrates
for anti-reflective properties. The coating is provided via
chemical grafting that involves the use of monomers and/or
prepolymers, catalyst and graft initiator and when applied onto the
surface of the glass substrate forms a polymeric film chemically
bonded to the glass with excellent adhesion. This coating can
reduce the reflectance of the coated glass surface as close to zero
as possible, thus maximizing transmittance and providing resistance
to abrasion, water/chemical attack and UV degradation. U.S. Pat.
No. 6,838,178 disclosed a color neutral absorbing film that is
applied as a coating on a glass substrate, to which a conductive
coating is first applied. An additional metal oxide layer is
deposited on the absorbing film. The coating is suitable for use in
anti-reflective coatings containing other metal oxides to achieve a
coated glass article having a visible light transmittance of 30% or
greater and a reflectance of less than 5%. The coated glass article
is absorbing, anti-reflective and conducting. U.S. Pat. No.
6,858,306 disclosed a coated article including a glass substrate, a
coating of antimony doped tin oxide deposited on and adhering to
the glass substrate and a coating of fluorine doped tin oxide. The
low emittance of the coated glass article, when combined with the
surprisingly selective solar absorption of the multilayer stack
provides improved heat rejection in summer and heat retention in
winter, while permitting the transmittance of a relatively high
degree of visible light.
[0004] However, a need still exists for a coating composition that
will impart at least one of antireflective, easy cleaning and
improved durability to a substrate coated therewith.
SUMMARY
[0005] The invention relates to a liquid coating composition that
imparts at least one of the following characteristics
antireflective, easy cleaning and improved durability to substrates
coated therewith, as well as methods of coating and coated
articles. In some embodiments, the liquid is an aqueous-based
liquid. The coating compositions utilize nonspherical and spherical
nanoparticles, wherein a least a portion of nonspherical
nanoparticles or at least a portion of spherical nanoparticles are
functionalized with at least one group selected from the group
consisting of epoxy group, amine group, hydroxyl, olefin, alkyne,
(meth) acrylato, mercapto or combinations thereof attached to their
surfaces through chemical bonds. In some embodiments, the
nanoparticles are silica nanoparticles. In some embodiments, all of
the nonspherical nanoparticles are functionalized with at least one
group selected from the group consisting of epoxy group, amine
group, hydroxyl, olefin, alkyne, (meth) acrylato, mercapto or
combinations thereof attached to their surfaces through chemical
bonds. In some embodiments all of the spherical nanoparticles are
functionalized with at least one group selected from the group
consisting of epoxy group, amine group, hydroxyl, olefin, alkyne,
(meth) acrylato, mercapto or combinations thereof attached to their
surfaces through chemical bonds. The coating compositions are
particularly useful on solar panels, outdoor signages, automobile
bodies for easy cleaning and on a wide variety of personal
protection equipment such as face masks, shields, and protective
glasses.
[0006] In one embodiment, the present invention provides a method
of modifying a substrate surface. The method includes: applying a
coating composition to a substrate; and drying the coating
composition to form a coating on the substrate; wherein the coated
substrate demonstrates improvement, relative to the uncoated
substrate, in at least one characteristic selected from the group
consisting of antireflective, dust or dirt repellent, easy cleaning
and improved durability. The coating composition includes:
nonspherical nanoparticles; spherical nanoparticles; optional
hydrophilic groups and an optional surfactant; and a liquid medium
comprising water and no greater than 30 wt % organic solvent, if
present, based on the total weight of liquid medium, wherein a
least a portion of nonspherical nanoparticles or at least a portion
of spherical nanoparticles comprises functional groups attached to
their surfaces through chemical bonds, wherein the functional
groups comprise at least one group selected from the group
consisting of epoxy group, amine group, hydroxyl, olefin, alkyne,
(meth)acrylato, mercapto, or combinations thereof. In some
embodiments, all of the nonspherical nanoparticles comprises
functional groups attached to their surfaces through chemical
bonds, wherein the functional groups comprise at least one group
selected from the group consisting of epoxy group, amine group,
hydroxyl, olefin, alkyne, (meth)acrylato, mercapto, or combinations
thereof. In some embodiments, all of the spherical nanoparticles
comprises functional groups attached to their surfaces through
chemical bonds, wherein the functional groups comprise at least one
group selected from the group consisting of epoxy group, amine
group, hydroxyl, olefin, alkyne, (meth)acrylato, mercapto, or
combinations thereof.
[0007] In one embodiment, the present invention provides a coating
composition. The coating composition includes: nonspherical
nanoparticles; spherical nanoparticles; optional hydrophilic groups
and an optional surfactant; and a liquid medium comprising water
and no greater than 30 wt % organic solvent, if present, based on
the total weight of liquid medium, wherein a least a portion of
nonspherical nanoparticles or at least a portion of spherical
nanoparticles comprises functional groups attached to their surface
through chemical bonds, wherein the functional groups comprise at
least one group selected from the group consisting of epoxy group,
amine group, hydroxyl, olefin, alkyne, (meth)acrylato, mercapto, or
combinations thereof. In some embodiments, all of the nonspherical
nanoparticles comprises functional groups attached to their
surfaces through chemical bonds, wherein the functional groups
comprise at least one group selected from the group consisting of
epoxy group, amine group, hydroxyl, olefin, alkyne, (meth)acrylato,
mercapto, or combinations thereof. In some embodiments, all of the
spherical nanoparticles comprises functional groups attached to
their surfaces through chemical bonds, wherein the functional
groups comprise at least one group selected from the group
consisting of epoxy group, amine group, hydroxyl, olefin, alkyne,
(meth)acrylato, mercapto, or combinations thereof. The coating
composition provides a coating to a substrate on which it is coated
and dried, having an improvement, relative to an uncoated
substrate, in at least one characteristic selected from the group
consisting of antireflective, easy cleaning and improved
durability.
[0008] In one embodiment, the present coating compositions may
optionally contain a curing agent or a co-curing agent including a
radical initiator, aliphatic amine, or polyamine or epoxy or
multifunctional epoxy monomer/oligomers or combinations
thereof.
[0009] In one embodiment, the present invention provides an article
comprising a substrate surface modified using the method of the
present invention. In certain embodiments, the article is a
personal protection article, an automotive vehicle or an outdoor
signage. In certain embodiments, the article is a solar panel. In
certain embodiments, the substrate is glass or ceramic.
[0010] In one embodiment, the present invention provides an article
comprising a substrate surface modified using the coating
composition of the present invention.
[0011] In some embodiments, the spherical nanoparticles have an
average particle size ranging from 1 nm to 120 nm.
DEFINITIONS
[0012] "Nanoparticles" are herein defined as nanometer-sized
particles, having, for example, an average particle size of no
greater than 200 nanometers (nm). The terms "particle size" and
"particle diameter" as used herein have the same meaning and are
used to refer to the largest dimension of a particle, or
agglomerates or agglomerations thereof. In this context,
"agglomeration" refers to a weak association between particles that
may be held together by charge or polarity and can be broken down
into smaller entities.
[0013] The term "spherical" as used herein means a three
dimensional shape, all points of which are equidistance from a
fixed point.
[0014] The term "nonspherical" as used herein means all 3
dimensional shapes other than spherical ones, including but not
limited to particles having needle-like elongated shapes,
sting-like elongated shapes, rod-like elongated shapes, chain-like
elongated shapes, filamentary elongated shapes, and the like.
[0015] "Hydrophilic groups" include water-dispersible groups,
water-soluble groups, and/or charged groups that provide
hydrophilicity to the surface of the nanoparticles. Preferably, if
such groups are attached to nanoparticles, they are capable of
reducing, and preferably preventing, excessive agglomeration and
precipitation of nanoparticles in water, and are referred to as
"water-dispersible groups."
[0016] "Charged groups" refer to groups that have one or more than
one ionizable group per functional group.
[0017] "Tempered glass" means glass that has been subjected to a
toughening process that includes heating at an elevated
temperature, for example a temperature equal to at least
500.degree. C., at least 600.degree. C., or at least 700.degree.
C., for a time up to 30 minutes, up to 20 minutes, up to 10
minutes, or up to 5 minutes and then cooling rapidly. For example,
the glass can be heated at a temperature in the range of
700.degree. C. to 750.degree. C. for about 2 to 5 minutes followed
by rapid cooling.
[0018] A "dried" coating is a coating that has been applied from a
coating composition that includes a liquid carrier (i.e., fluid or
liquid media), and the liquid carrier has been substantially
completely removed, for example, by evaporation. A dried coating is
typically also "cured" as a result of reaction between the reactive
functional groups (e.g., amine groups and epoxy groups) during the
solvent evaporation. The rate and degree of curing can be enhanced
by heating the coating composition during the drying process.
[0019] The terms "comprises" and variations thereof do not have a
limiting meaning where these terms appear in the description and
claims.
[0020] The terms "preferred" and "preferably" refer to embodiments
of the invention that may afford certain benefits, under certain
circumstances. However, other embodiments may also be preferred,
under the same or other circumstances. Furthermore, the recitation
of one or more preferred embodiments does not imply that other
embodiments are not useful, and is not intended to exclude other
embodiments from the scope of the invention.
[0021] As used herein, "a," "an," "the," "at least one," and "one
or more" are used interchangeably. Thus, for example, a
nanoparticle that comprises "a" functional group can be interpreted
to mean that the nanoparticle includes "one or more" functional
groups.
[0022] The term "and/or" means one or all of the listed
elements/characteristics or a combination of any two or more of the
listed elements/characteristics.
[0023] As used herein, the term "or" is generally employed in its
usual sense including "and/or" unless the content clearly dictates
otherwise.
[0024] Also herein, the recitations of numerical ranges by
endpoints include all numbers subsumed within that range (e.g., 1
to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).
[0025] The above summary of the present invention is not intended
to describe each disclosed embodiment or every implementation of
the present invention. The description that follows more
particularly exemplifies illustrative embodiments. In several
places throughout the application, guidance is provided through
lists of examples, which examples can be used in various
combinations. In each instance, the recited list serves only as a
representative group and should not be interpreted as an exclusive
list.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0026] The invention relates to aqueous-based coating compositions
containing functionalized nonspherical or spherical nanoparticles,
particularly silica nanoparticles, as well as methods of coating
and coated articles. At least a portion of nonspherical
nanoparticles or at least a portion of spherical nanoparticles are
functionalized with at least one group selected from the group
consisting of epoxy group, amine group, hydroxyl, olefin, alkyne,
(meth) acrylato, mercapto, or combinations thereof, and optionally
hydrophilic groups (which are water-like functionalities and may be
water-dispersible, water-soluble, and/or charged groups).
[0027] In certain embodiments, only nonspherical nanoparticles are
functionalized. It should be understood that, in these embodiments,
although a certain portion of the population of nonspherical
nanoparticles can be bare particles upon applying the coating
composition to a substrate, a large portion, and preferably a
majority, of the nonspherical nanoparticles have functionalities
(e.g., epoxy group, amine group, hydroxyl, olefin, alkyne, (meth)
acrylato, mercapto, or combinations thereof) covalently bonded
thereto.
[0028] In certain embodiments, only spherical nanoparticles are
functionalized. It should be understood that, in these embodiments,
although a certain portion of the population of shperical
nanoparticles can be bare particles upon applying the coating
composition to a substrate, a large portion, and preferably a
majority, of the shperical nanoparticles have functionalities
(e.g., epoxy group, amine group, hydroxyl, olefin, alkyne, (meth)
acrylato, mercapto, or combinations thereof) covalently bonded
thereto.
[0029] In certain embodiments, all of the nonspherical
nanoparticles or all of the spherical nanoparticles are
functionalized. It should be understood that, in other certain
embodiments, a certain portion of the population of nonspherical
nanoparticles and/or spherical nanoparticles can be bare particles
upon applying the coating composition to a substrate.
[0030] Coating compositions of the present invention impart at
least one of antireflective, easy cleaning and improved durability
to substrates coated therewith. One or more of these properties
results from the design of nanoparticle surface-chemistries that
enable assembling/interconnecting these nanoparticles together
through covalently chemical bonds, thereby forming a continuous
network structure, which contributes to the formation of coatings
with one or more of such desired properties.
[0031] Certain coating compositions of the present invention
provide "antireflective" properties to substrates coated and dried
thereon, which can be defined as follows. When the coating
compositions of the invention are applied to substrates to provide
antireflection or reduced reflection properties, glare is reduced
by increasing the light transmission of the coated substrate.
Preferably, a single-sided coated substrate exhibits an increase in
transmission of normal incident light of at least 0.5 percentage
points such as a glass substrate, at least 3 percentage points, and
up to as much as 10 percentage points or more with a double-sided
coated substrates, when compared to an uncoated substrate, at 550
mm (e.g., the wavelength at which the human eye displays peak
photo-optic response). The percent transmission is dependent upon
the angle of incidence and the wavelength of light and is
determined, for example, for plastics, using ASTM test method
D1003-92, entitled "Haze and Luminous Transmittance of Transparent
Plastics." Preferably, single-sided coated glass substrates display
an increase in percent transmission of at least 0.5 percent, and
more preferably least 3 percent, when compared with an uncoated
substrate, using 550 nm light. Preferably, single-sided coated
plastic substrates display an increase in percent transmission of
at least 2 percent for plastics, more preferably at least 5
percent, and most preferably greater than 8 percent with double
sided coated substrates, when compared with an uncoated substrate,
using 550 nm light. For double-sided coated substrates the increase
in percent transmission is typically twice these values. When the
desired usage involves significant "off-axis" (i.e., non-normal)
viewing or unwanted reflections, gains in visibility may be greater
especially where the reflections approach or exceed in brightness
the object in view.
[0032] Antireflection properties are considered over an even
broader range than 550 nm when considering solar cells. Solar cells
have been developed with a variety of semiconductor materials that
have unique absorption spectra for converting solar energy into
electricity. Each type of semiconductor material will have a
characteristic band gap energy which causes it to absorb light most
efficiently at certain wavelengths of light, or more precisely, to
absorb electromagnetic radiation over a portion of the solar
spectrum. Examples of semiconductor materials used to make solar
cells and their solar light absorption band-edge wavelengths
include, but are not limited to: crystalline silicon single
junction (about 400 nm to about 1150 nm), amorphous silicon single
junction (about 300 nm to about 720 nm), ribbon silicon (about 350
nm to about 1150 nm), CIGS (Copper Indium Gallium Selenide, about
350 nm to about 1000 nm), CdTe (Cadmium Telluride, about 400 nm to
about 895 nm), GaAs multi junction (about 350 nm to about 1750 nm).
The shorter wavelength left absorption band edge of these
semiconductor materials is typically between 300 nm and 400 nm. One
skilled in the art understands that new materials are being
developed for more efficient solar cells having their own unique
longer wavelength absorption band-edge and the multi-layer
reflective film would have a corresponding reflective
band-edge.
[0033] Certain coating compositions of the present invention
provide easy-cleaning or dust repellent properties to substrates
coated and dried thereon. Dried coatings are considered "cleanable"
or "easily cleaned" or possessing "cleanable" or "easy-cleaning"
characteristics if a coated substrate exhibits oil and/or soil
resistance. Alternatively and/or additionally, dried coatings are
considered easy-cleaning or cleanable if organic contaminates, such
as soil, food, machine oils, paints, dust, and/or dirt, may be
simply rinsed away by water. Such easy-cleaning or cleanable
characteristics typically result because the nanoporous structure
of the coatings tends to prevent penetration by oligomeric and
polymeric molecules and possibly provides unique triboelectric
properties.
[0034] Coating compositions of the present invention, when applied
to a substrate (e.g., of inorganic or organic material) and dried,
are generally durable such that handling during normal use (e.g.,
touching) does not completely remove the dried coating. Preferred
coatings are durable such that the dried coating is not completely
removed under more mechanically harsh (e.g., rubbing) conditions,
as demonstrated in the Examples Section.
[0035] Preferred dried coatings prepared from coating compositions
of the present invention can be sufficiently durable that they can
provide one or more desirable properties (antireflective, and/or
easy-cleaning characteristics) for at least 12 hours, more
preferably for at least 24 hours, even more preferably at least 120
hours, and often as long as 200 or more hours under 50.degree. C.
and 90% humidity conditions.
[0036] In preferred embodiments, a least a portion of nonspherical
nanoparticles or at least a portion of spherical nanoparticles used
in the coating compositions of the present invention are
functionalized with epoxy group, amine group, hydroxyl, olefin,
alkyne, (meth) acrylato, mercapto, or combinations thereof. Herein,
"amine" does not include quaternary ammonium. Preferably, the amine
groups are primary or secondary (i.e., nontertiary), and more
preferably, they are primary amines. They may be aliphatic or
aromatic. Optionally, the present coating compositions may contain
a curing agent or a co-curing agent including a radical initiator,
aliphatic amine, or polyamine or epoxy or multifunctional epoxy
monomer/oligomers. These curatives lead to form covalent organic
networks among these inorganic nanoparticles, thus improved
mechanical durability can be achieved.
[0037] Preferred compositions of the present invention can have a
relatively long shelf-life, preferably up to several months even
when stored in liquid form, or impregnated in an applicator
substrate in a sealed container, under ambient conditions (e.g., at
Room Temperature).
Nanoparticles
[0038] Nanoparticles that are surface modified in accordance with
the present invention comprise nanometer-sized particles. The term
"nanometer-sized" refers to particles that are characterized by an
average particle size (i.e., the average of the largest dimension
of the particles, or the average particle diameter for spherical
particles) in the nanometer range, often no greater than 200
nanometers (nm), and preferably no greater than 100 nm (prior to
surface modification, i.e., functionalization).
[0039] Average particle size of the nanoparticles can be measured
using transmission electron microscopy. In the practice of the
present invention, particle size may be determined using any
suitable technique. Preferably, particle size refers to the number
average particle size and is measured using an instrument that uses
transmission electron microscopy or scanning electron microscopy.
Another method to measure particle size is dynamic light scattering
that measures weight average particle size. One example of such an
instrument found to be suitable is the N4 PLUS SUB-MICRON PARTICLE
ANALYZER available from Beckman Coulter Inc. of Fullerton,
Calif.
[0040] It is also preferable that the nanoparticles be relatively
uniform in size. Uniformly sized nanoparticles generally provide
more reproducible results. Preferably, variability in the size of
the nanoparticles is less than 25% of the mean particle size.
[0041] Herein, bare nanoparticles (prior to functionalization) are
water-dispersible to reduce, and preferably prevent, excessive
agglomeration and precipitation of the particles in an aqueous
environment. If necessary, water-dispersibility can be enhanced by
functionalizing the nanoparticles with water-dispersible groups.
Nanoparticle aggregation can result in undesirable precipitation,
gellation, or a dramatic increase in viscosity; however, small
amounts of agglomeration can be tolerated when the nanoparticles
are in an aqueous environment as long as the average size of the
agglomerates (i.e., agglomerated particles) is no greater than 200
nm. Thus, the nanoparticles are preferably referred to herein as
colloidal nanoparticles since they can be individual particles or
small agglomerates thereof.
[0042] The nanoparticles preferably have a surface area of at least
10 m.sup.2/gram, more preferably at least 20 m.sup.2/gram, and even
more preferably at least 25 m.sup.2/gram. The nanoparticles
preferably have a surface area of greater than 750 m.sup.2/gram.
Nanoparticles of the present invention can be porous or
nonporous.
[0043] Suitable glass and ceramic nanoparticles can include, for
example, sodium, silicon, aluminum, lead, boron, phosphorous,
zirconium, magnesium, calcium, arsenic, gallium, titanium, copper,
or combinations thereof. Glasses typically include various types of
silicate-containing materials.
[0044] The unmodified nanoparticles can be provided as a sol rather
than as a powder. Preferred sols generally contain from 15 wt % to
50 wt % of colloidal particles dispersed in a fluid medium.
Representative examples of suitable fluid media for the colloidal
particles include water, aqueous alcohol solutions, lower aliphatic
alcohols, ethylene glycol, N,N-dimethylacetamide, formamide, or
combinations thereof. The preferred fluid medium is aqueous, e.g.,
water and optionally one or more alcohols. When the colloidal
particles are dispersed in an aqueous fluid, the particles can be
stabilized due to common electrical charges that develop on the
surface of each particle. The common electrical charges tend to
promote dispersion rather than agglomeration or aggregation,
because the similarly charged particles repel one another.
[0045] Inorganic silica sols in aqueous media are well known in the
art and available commercially. Silica sols in water or
water-alcohol solutions are available commercially under such trade
names as LUDOX (manufactured by E.I. duPont de Nemours and Co.,
Inc., Wilmington, Del.), NYACOL (available from Nyacol Co.,
Ashland, Mass.) or NALCO (manufactured by Nalco Chemical Co., Oak
Brook, Ill.). Some useful silica sols are NALCO 1115, 2326, 1050,
2327, and 2329 available as silica sols with mean particle sizes of
4 nanometers (nm) to 77 nm. Another useful silica sol is NALCO
1034a available as a silica sol with mean particle size of 20
nanometers. Another useful silica sol is NALCO 8699 available as a
silica sol with mean particle size of 2-4 nanometers. Additional
examples of suitable colloidal silicas are described in U.S. Pat.
No. 5,126,394.
[0046] The sols used in the present invention generally can include
counter cations, in order to counter the surface charge of the
colloids. Depending upon pH and the kind of colloids being used,
the surface charges on the colloids can be negative or positive.
Thus, either cations or anions are used as counter ions. Examples
of cations suitable for use as counter ions for negatively charged
colloids include Na.sup.+, K.sup.+, Li.sup.+, a quaternary ammonium
cation such as NR.sub.4.sup.+, wherein each R can be any monovalent
moiety, but is preferably H or lower alkyl, such as --CH.sub.3,
combinations of these, and the like.
[0047] A variety of methods are available for modifying the
surfaces of nanoparticles, depending on the functionality of the
surface. Of the suggested reaction below, it is understood that
when working in aqueous media there is a strong preference for
groups stable or metastable in water.
[0048] Various mixtures of different types of nanoparticles can be
used if desired (even including "bare" or "naked", i.e.,
nonfunctionalized nanoparticles or nanoparticles functionalized
with only hydrophilic groups). The nanoparticles used in the
coating composition of the present invention include not only
nonspherical nanoparticles but also spherical nanoparticles. In
certain preferred embodiments, the weight ratio of the nonspherical
nanoparticles to the spherical nanoparticles ranges from 95:5 to
5:95, more preferably, 80:20 to 20:80, most preferably, 70:30 to
30:70.
[0049] The nanoparticle concentration in coating compositions of
the present invention, in total, is preferably at least 0.1 percent
by weight (wt %), more preferably at least 0.2 wt %, even more
preferably at least 0.5 wt %, even more preferably at least 1 wt %,
even more preferably at least 2 wt %, even more preferably greater
than 2 wt %, even more preferably at least 3 wt %, even more
preferably at least 4 wt %, even more preferably at least 5 wt %,
and even more preferably at least 10 wt %, based on the total
weight of the coating composition. The nanoparticle concentration
is preferably no greater than 45 wt %, more preferably no greater
than 40 wt %, and even more preferably no greater than 10 wt %,
based on the total weight of the coating composition. Above about
45 percent by weight the coating composition becomes difficult to
apply in the desired thickness range and below about 0.1 percent by
weight, excessive time periods may be required for the coating to
dry after application to the substrate. The terms "composition" and
"solution" as used herein include dispersions or suspensions of
nanoparticles in a liquid medium. In certain preferred embodiments,
the coating composition comprises at least 0.05 wt % nonspherical
nanoparticles and no greater than 40 wt % nonspherical
nanoparticles, based on the total weight of the coating
composition. In certain preferred embodiments, the coating
composition comprises at least 0.05 wt % spherical nanoparticles
and no greater than 40 wt % spherical nanoparticles, based on the
total weight of the coating composition.
Nonspherical Nanoparticles
[0050] The nonspherical nanoparticles (preferably, elongated
colloidal silica particles) may have an average diameter of 5 to 60
nm, a length, D.sub.1, of 40 to 500 nm (as measured by dynamic
light-scattering method) and a degree of elongation D.sub.1/D.sub.2
of 5 to 30, wherein D.sub.2 means a diameter in nm calculated by
the equation D.sub.2=2720/S and S means specific surface area in
m.sup.2/g of the particle, as is disclosed in the specification of
U.S. Pat. No. 5,221,497. According to certain embodiments,
nonspherical silica particles may have a diameter of 5.about.20 nm,
a length of 50.about.200 nm.
[0051] U.S. Pat. No. 5,221,497 discloses a method for producing
nonspherical silica nanoparticles by adding water-soluble calcium
salt, magnesium salt or mixtures thereof to an aqueous colloidal
solution of active silicic acid or acidic silica sol having a mean
particle diameter of 3 to 30 nm in an amount of 0.15 to 1.00 wt. %
based on CaO, MgO or both to silica, then adding an alkali metal
hydroxide so that the molar ratio of SiO.sub.2/M.sub.2O (M: alkali
metal atom) becomes 20 to 300, and heating the obtained liquid at
60 to 300.degree. C. for 0.5 to 40 hours. The colloidal silica
particles obtained by this method are elongate-shaped silica
particles that have elongations of a uniform thickness within the
range of 5 to 40 nm extending in only one plane. The nonspherical
silica sol may also be prepared as described by Watanabe et al. in
U.S. Pat. No. 5,597,512. Briefly stated, the method comprises: (a)
mixing an aqueous solution containing a water-soluble calcium salt
or magnesium salt or a mixture of said calcium salt and said
magnesium salt with an aqueous colloidal liquid of an active
silicic acid containing from 1 to 6% (w/w) of SiO.sub.2 and having
a pH in the range of from 2 to 5 in an amount of 1500 to 8500 ppm
as a weight ratio of CaO or MgO or a mixture of CaO and MgO to
SiO.sub.2 of the active silicic acid; (b) mixing an alkali metal
hydroxide or a water-soluble organic base or a water-soluble
silicate of said alkali metal hydroxide or said water-soluble
organic base with the aqueous solution obtained in step (a) in a
molar ratio of SiO.sub.2/M.sub.2O of from 20 to 200, where
SiO.sub.2 represents the total silica content derived from the
active silicic acid and the silica content of the silicate and M
represents an alkali metal atom or organic base molecule; and (c)
heating at least a part of the mixture obtained in step (b) to
60.degree. C. or higher to obtain a heel solution, and preparing a
feed solution by using another part of the mixture obtained in step
(b) or a mixture prepared separately in accordance with step (b),
and adding said feed solution to said heel solution while
vaporizing water from the mixture during the adding step until the
concentration of SiO.sub.2 is from 6 to 30% (w/w). The silica sol
produced in step (c) typically has a pH of from 8.5 to 11.
[0052] Useful nonspherical silica particles may be obtained as an
aqueous suspension under the trade name SNOWTEX-OUP, SNOWTEX-UP, by
Nissan Chemical Industries (Tokyo, Japan). The SNOWTEX-OUP consists
of 15-16% (w/w) of nonspherical silica, less than 0.03% (w/w) of
Na.sub.2O, and water. The particles are 9 to 15 nanometers in
diameter and have lengths of 40 to 300 nanometers. The suspension
has a viscosity of less than 20 mPas at 25.degree. C., a pH of 2 to
4, and a specific gravity of 1.10 at 20.degree. C. The SNOWTEX-UP
consists of 20-21% (w/w) of nonspherical silica, less than 0.35%
(w/w) of Na.sub.2O, and water. The particles are 9 to 15 nanometers
in diameter and have lengths of 40 to 300 nanometers. The
suspension has a viscosity of less than 100 mPas at 25.degree. C.,
a pH of 9 to 10.5, and a specific gravity of 1.13 at 20.degree.
C.
[0053] Other useful nonspherical silica particles may be obtained
as an aqueous suspension under the trade name SNOWTEX-PS-S and
SNOWTEX-PS-M by Nissan Chemical Industries. SNOWTEX-PS-S has a
morphology of a string of pearls comprised of nanoparticles. The
mixture consists of 20-21% (w/w) of silica, less than 0.2% (w/w) of
Na.sub.2O, and water. The SNOWTEX-PS-M particles are 18 to 25
nanometers in diameter and have lengths of 80 to 150 nanometers.
The particle size is 80 to 150 nanometers by dynamic light
scattering methods. The suspension has a viscosity of less than 100
mPas at 25.degree. C., a pH of 9 to 10.5, and a specific gravity of
1.13 at 20.degree. C. The SNOWTEX-PS-S has a particle diameter of
10-15 nm and a length of 80-120 nm.
Spherical Nanoparticles
[0054] The term "spherical" is taken to include nominally spherical
particles. The term "spherical nanometer-sized" refers to particles
that are characterized by an average particle diameter (particle
size) in the nanometer range, often no greater than 200 nanometers
(nm), and preferably no greater than 60 nm (prior to surface
modification, i.e., functionalization). More preferably, the
average particle size is no greater than 45 nm (prior to surface
modification), even more preferably no greater than 20 nm (prior to
surface modification), even more preferably no greater than 10 nm
(prior to surface modification), and even more preferably no
greater than 5 nm (prior to surface modification). Preferably,
prior to surface modification, the average particle size of the
silica nanoparticles is at least 1 nm, more preferably at least 2
nm. A particularly preferred particle size is 2 nm to 5 nm.
Functionalized Nanoparticles
[0055] At least a portion of nonspherical nanoparticles or at least
a portion of spherical nanoparticles used in coating compositions
of the present invention include at least one group selected from
the group consisting of epoxy group, amine group, hydroxyl, olefin,
alkyne, (meth) acrylato, mercapto, or combinations thereof. If two
or more kinds of functional groups are present, these functional
groups may be on the same nanoparticle or on different
nanoparticles. In one embodiment, only one of the functional groups
is included in the nanoparticles.
[0056] The present invention involves the design of nanoparticle
surface-chemistries that enable assembling/interconnecting the
nanoparticles together through covalent chemical bonds (which can
include a combination of organic-organic, organic-inorganic (e.g.,
C--N), or inorganic-inorganic bonds (e.g., Si--O--Si)), thereby
forming a dendritic network. This network is believed to include a
generally continuous phase of interbonded nanoparticles (which may
be the same or different). Such structure contributes to the
formation of coatings with improved properties relative to uncoated
substrates.
[0057] Coatings resulting from nonspherical particles alone or
spherical particles alone or the combination of functionalized
nonspherical particles and functionalized spherical particles may
not give the desired balance of mechanical durability,
antireflective, and easy cleaning. Even if the combination of
functionalized nonspherical particles and functionalized spherical
particles can provide desired properties, the production cost of
the coating composition will be abruptly increased as a result of
excess functionalization, as compared with the present invention.
Surprisingly, it was found that the combination of the
functionalized nanoparticles in one shape and the
non-functionalized nanoparticles in another shape can provide
improved properties for the coating. For example, improved
mechanical durability, antireflective, easy cleaning and control of
porosity can be obtained by such a novel combination. As our
assumption, the reasons may be explained as follows. For example,
improved mechanical properties may be obtained by mixing the
nonspherical particles with smaller functionalized spherical
particles in certain ratios, which may help to achieve particle
packing and coating topology which are important for mechanical
durability. For example, when epoxy-functionalized nanoparticles
having a diameter of 4 nm are mixed with non-functionalized
nonspherical nanoparticles, improved durability can be obtained
relative to mixtures of bared particles having the same weight
ratio.
Epoxy Functional Groups
[0058] In some embodiments, a portion of the nanoparticles of the
present invention are functionalized with organic groups, such as
epoxy groups, which can be formed, for example, using epoxy
alkoxysilane chemistry. The epoxy groups are covalently bonded to a
preferred silica surface of individual nanoparticles, preferably
through Si--O--Si bonds. Other nanoparticles containing zirconia,
alumina, ceria, tin oxide, or titanium dioxide, may similarly be
attached to epoxy alkoxysilanes by the chemical bonds Zr--O--Si,
Al--O--Si, Ce--O--Si, Sn--O--Si, and Ti--O--Si, respectively. These
chemical bonds may not be as strong as the siloxane bond,
Si--O--Si, however, their bond strength is suitable for the present
coating applications.
[0059] The level of coverage of the epoxy-functionalized
nanoparticles herein is reported in terms of the concentration of
epoxy groups in the coating composition, assuming 100% of the
amount of epoxy groups in the coating composition would be
covalently bonded to surfaces of the silica particles. Preferably,
the epoxy groups are present on a particle surface in the coating
composition in an amount equivalent to at least 3 mole-% of the
total molar functional groups on said surface.
[0060] In some embodiments, the epoxy groups are present on a
particle surface in the coating composition in an amount equivalent
to at least 5 mole-%, even more preferably at least 10 mole-%, and
even more preferably at least 25 mole-%, of total molar functional
groups on the particle surface. Higher molar equivalents of epoxy
groups can contribute to more bonds between particles, thereby
forming a coating with a more dense particle network. In certain
situations, an excess of epoxy groups (i.e., greater than 100%) can
be desirable; however, typically the amount of epoxy groups on a
particle surface in the coating composition is no more than 150
mole-% of the total molar functional groups on the particle
surface. Due to the multifunctionality of the epoxy alkoxysilanes,
when the coating composition includes more than 100 mole-% epoxy
groups, more than a monolayer of the epoxysiloxane is created on
the particle surface. An excess of hydrolyzed epoxy alkoxysilane,
when present, can also function as a primer on the surface of the
substrate.
[0061] The nanoparticle functionalization with epoxy groups can be
accomplished using conventional techniques. For silica
nanoparticles, however, it has been discovered that this can be
advantageously accomplished by functionalizing the nanoparticles
using epoxy functional compounds under acidic conditions.
Preferably, the pH is no greater than 6, more preferably at a pH of
no more than 5, even more preferably at a pH of no more than 3, and
even more preferably at a pH of 1 to 3. Such pH is maintained for
at least 3 hours, preferably at least 8 hours, and more preferably
at least 12 hours. The desired pH and time of reaction are ones
that enhance functionalization, enhance stability of the
composition (e.g., reduce precipitation and/or agglomeration of the
particles), and enhance antifogging characteristics of the
resultant coating. For nanoparticles of 4-5 nm, the preferred pH
range for the functionalization reaction is 1 to 3. After the
functionalization reaction is carried out to the desired level
(preferably, completed), the pH of the coating solution may be
brought to a desired pH (e.g., to a range of 5 to 8).
[0062] The functional groups include various chemical groups that
allow for binding to the nanoparticles. Such groups are typically
provided by functional compound represented by the formula A-L-F1.
The functional group F3 includes the epoxy groups. In this
representation, the group A is the nanoparticle surface-bonding
group, and L can be a bond or any of a variety of organic linkers.
Organic linkers L can be linear or branched alkylene, arylene, or a
combination of alkylene and arylene groups, optionally including
heteroatoms.
[0063] Exemplary epoxy functional compounds include:
##STR00001##
[0064] A variety of methods are available for modifying the surface
of nanoparticles including, e.g., adding a surface modifying agent
to nanoparticles (e.g., in the form of a powder or a colloidal
dispersion) and allowing the surface modifying agent to react with
the nanoparticles. For epoxy functional compounds A-L-F1, the
surface-bonding groups A are typically silanols, alkoxysilanes, or
chlorosilanes, which can be monofunctional, difunctional, or
trifunctional. For example, the silanol groups on the surfaces of
the silica nanoparticles are reacted with at least one silanol,
alkoxysilane, or chlorosilane group of a functional compound to
form a functionalized nanoparticle. Exemplary conditions for
reacting functional compounds with silica nanoparticles are
described in the Examples Section.
Amine Functional Groups
[0065] In certain embodiments, a portion of the nanoparticles of
the present invention are functionalized with amine groups, which
can be formed typically using aminosiloxane chemistry. The amine
groups can be protected if desired. Combinations of protected amine
groups and unprotected amine groups can be used if desired.
[0066] The amine groups are covalently bonded to a preferred silica
surface of individual nanoparticles, preferably through Si--O--Si
bonds. Other nanoparticles containing zirconia, alumina, ceria, tin
oxide, or titanium dioxide, may similarly be attached to
aminosiloxanes by the chemical bonds Zr--O--Si, Al--O--Si,
Ce--O--Si, Sn--O--Si, and Ti--O--Si, respectively. These chemical
bonds may not be as strong as the siloxane bond, Si--O--Si,
however, their bond strength can be enough for the present coating
applications.
[0067] The level of coverage of the amine-functionalized
nanoparticles herein is reported in terms of the concentration of
amine groups in the coating composition, assuming 100% of the
amount of amine groups in the coating composition would be
covalently bonded to surfaces of the silica particles. Preferably,
the amine groups are present on a particle surface in the coating
composition in an amount equivalent to at least 3 mole-% of the
total molar functional groups on said surface.
[0068] More preferably, the amine groups are present on a particle
surface in the coating composition in an amount equivalent to at
least 5 mole-%, even more preferably at least 10 mole-%, and even
more preferably at least 25 mole-%, of total molar functional
groups on said surface. Higher molar equivalents of amine groups
can contribute to more bonds between particles, thereby forming a
coating with a more dense particle network. In certain situations,
an excess of amine groups (i.e., greater than 100%) can be
desirable; however, typically the amount of amine groups are
present on a particle surface in the coating composition in an
amount equivalent to no more than 150 mole-% of the total molar
functional groups on said particle surface. Due to the
multifunctionality of the amine alkoxysilanes, when the coating
composition includes more than 100 mole-% amine groups, more than a
monolayer of the aminosiloxane is created on the particle surface.
An excess of hydrolyzed amine alkoxysilane, when present, can also
function as a primer on the surface of the substrate.
[0069] The nanoparticle functionalization with amine groups can be
accomplished using conventional techniques. For silica
nanoparticles, however, it has been discovered that reacting amine
alkoxysilanes to create amino functionality on the surface of the
silica nanoparticles can be advantageously accomplished (for
example, without gelling) using basic conditions. Preferably, this
is accomplished at a pH of at least 10.5, even more preferably at a
pH of at least 11.0, even more preferably at a pH of at least 11.5,
even more preferably at a pH of at least 12.0, and even more
preferably at a pH of at least 12.5. A typically upper pH is 14.0.
In a typical method, the pH of an aqueous dispersion of silica
nanoparticles is initially adjusted to this pH to generate
negatively charged silica particles. Then the amine alkoxysilane is
combined with the negatively charged silica nanoparticles and
allowed to react for a time effective for the alkoxysilyl end of
the amine alkoxysilane to preferentially react with the negatively
charged silica surface. Such pH is maintained for a time effective
to cause reaction between the alkoxysilyl end of the amine
alkoxysilane and the silica nanoparticles. Typically, this is at
least 2 hours, preferably at least 8 hours, and more preferably at
least 12 hours. Temperatures above room temperature (e.g.,
60.degree. C.-80.degree. C.) can be used to reduce the reaction
time. The desired pH and time of reaction are ones that enhance
functionalization and enhance stability of the composition (e.g.,
reduce precipitation and/or agglomeration of the particles). After
the functionalization reaction is carried out to the desired level
(preferably, completed), the pH of the coating solution may be
brought to a desired pH (e.g., to a range of 5 to 8).
[0070] The functional groups include various chemical groups that
allow for binding to the nanoparticles. Such groups are typically
provided by functional compound represented by the formula A-L-F2.
The functional group F1 includes the amine groups. In this
representation, the group A is the nanoparticle surface-bonding
group, and L can be a bond or any of a variety of organic linkers.
Organic linkers L can be linear or branched alkylene, arylene, or a
combination of alkylene and arylene groups, optionally including
heteroatoms.
[0071] Exemplary amine functional compounds include:
##STR00002##
[0072] A variety of methods are available for modifying the surface
of nanoparticles including, e.g., adding a surface modifying agent
to nanoparticles (e.g., in the form of a powder or a colloidal
dispersion) and allowing the surface modifying agent to react with
the nanoparticles. For amine functional compounds A-L-F2, the
surface-bonding groups A are typically silanols, alkoxysilanes, or
chlorosilanes, which can be monofunctional, difunctional, or
trifunctional. For example, the silanol groups on the surfaces of
the silica nanoparticles are reacted with at least one silanol,
alkoxysilane, or chlorosilane group of a functional compound to
form a functionalized nanoparticle. Exemplary conditions for
reacting functional compounds with silica nanoparticles are
described in the Examples Section. The surface-bonding groups in
the described in invention may not be limited to silanols or alkoxy
silanes. Ionic bonds or hydrogen bonds and other types of covalent
bonds to nanoparticle surfaces may also be included.
[0073] The amine groups can be protected if desired. Typically,
amine groups may be converted to a protected form by reaction with
a suitable reagent that reacts with (i.e., protects) the amine and
converts it to a form without hydrogen atoms bonded to the nitrogen
atom. Subsequent deprotection regenerates the original amine group.
Methods for protecting amine groups, and deprotecting the
corresponding protected amine groups, are widely known and are
described, for example, by P. J. Kocienski in "Protecting Groups",
3rd ed., Stuttgart: Thieme, 2004 and by T. W. Greene and P. G. M.
Wuts in "Protective Groups in Organic Synthesis", 2nd ed., New
York: Wiley-Interscience, 1991. Suitable protecting groups include
CH.sub.3C(O)--, CF.sub.3C(O)--, (CH.sub.3).sub.3Si--,
(CH.sub.3).sub.2CH--O--C(O)--, CH.sub.3--O--C(O)--C(O)--, --C(O)OH,
--C(O)O.sup.-, alkyl-NH--C(O)--, wherein "--" represents a bond to
the Nitrogen.
Olefin, Alkyne, (Meth) Acrylato, Mercapto Group
[0074] In certain preferred embodiments, a portion of the
nanoparticles of the present invention are functionalized with at
least one of selecting from the group consisting of olefin, alkyne,
(meth) acrylato, and mercapto groups, which can be formed typically
using olefin, alkyne, (meth) acrylato, mercapto siloxane
chemistry.
[0075] The olefin, alkyne, (meth) acrylato, mercapto groups are
covalently bonded to a preferred silica surface of individual
nanoparticles, preferably through Si--O--Si bonds. Other
nanoparticles containing zirconia, alumina, ceria, tin oxide, or
titanium dioxide, may similarly be attached to olefin, alkyne,
(meth) acrylato, mercapto siloxanes by the chemical bonds
Zr--O--Si, Al--O--Si, Ce--O--Si, Sn--O--Si, and Ti--O--Si,
respectively. These chemical bonds may not be as strong as the
siloxane bond, Si--O--Si, however, their bond strength can be
enough for the present coating applications.
[0076] The level of coverage of the olefin, alkyne, (meth)
acrylato, mercapto functionalized nanoparticles herein is reported
in terms of the concentration of unsaturated alkene, alkyne,
acryl(metha) groups in the coating composition, assuming 100% of
the amount of olefin, alkyne, (meth) acrylato, mercapto groups in
the coating composition would be covalently bonded to surfaces of
the silica particles. Preferably, the olefin, alkyne, (meth)
acrylato, mercapto groups are present on a particle surface in the
coating composition in an amount equivalent to at least 3 mole-% of
the total molar functional groups on said surface.
[0077] More preferably, the olefin, alkyne, (meth) acrylato,
mercapto groups are present on a particle surface in the coating
composition in an amount equivalent to at least 5 mole-%, even more
preferably at least 10 mole-%, and even more preferably at least 25
mole-%, of total molar functional groups on said surface. Higher
molar equivalents of olefin, alkyne, (meth) acrylato, mercapto
groups can contribute to more bonds between particles, thereby
forming a coating with a more dense particle network. In certain
situations, an excess of olefin, alkyne, (meth) acrylato, mercapto
groups (i.e., greater than 100%) can be desirable; however,
typically the amount of olefin, alkyne, (meth) acrylato, mercapto
groups are present on a particle surface in the coating composition
in an amount equivalent to no more than 150 mole-% of the total
molar functional groups on said particle surface. Due to the
multifunctionality of the olefin, alkyne, (meth) acrylato, mercapto
alkoxysilanes, when the coating composition includes more than 100
mole-% olefin, alkyne, (meth) acrylato, mercapto groups, more than
a monolayer of the olefin, alkyne, (meth) acrylato, mercapto
siloxane is created on the particle surface. An excess of
hydrolyzed olefin, alkyne, (meth) acrylato, mercapto alkoxysilane,
when present, can also function as a primer on the surface of the
substrate.
[0078] The nanoparticle functionalization with olefin, alkyne,
(meth) acrylato, mercapto groups can be accomplished using
conventional techniques. For silica nanoparticles, however, it has
been discovered that reacting olefin, alkyne, (meth) acrylato,
mercapto alkoxysilanes to create amino functionality on the surface
of the silica nanoparticles can be advantageously accomplished (for
example, without gelling) using basic conditions. Preferably, this
is accomplished at a pH of at least 10.5, even more preferably at a
pH of at least 11.0, even more preferably at a pH of at least 11.5,
even more preferably at a pH of at least 12.0, and even more
preferably at a pH of at least 12.5. A typically upper pH is 14.0.
In a typical method, the pH of an aqueous dispersion of silica
nanoparticles is initially adjusted to this pH to generate
negatively charged silica particles. Then the alkene, alkyne,
acryl(Metha) alkoxysilane are combined with the negatively charged
silica nanoparticles and allowed to react for a time effective for
the alkoxysilyl end of the alkene, alkyne, acryl(Metha)
alkoxysilane to preferentially react with the negatively charged
silica surface. Such pH is maintained for a time effective to cause
reaction between the alkoxysilyl end of the olefin, alkyne, (meth)
acrylato, mercapto alkoxysilane and the silica nanoparticles.
Typically, this is at least 2 hours, preferably at least 8 hours,
and more preferably at least 12 hours. Temperatures above room
temperature (e.g., 60.degree. C.-80.degree. C.) can be used to
reduce the reaction time. The desired pH and time of reaction are
ones that enhance functionalization and enhance stability of the
composition (e.g., reduce precipitation and/or agglomeration of the
particles). After the functionalization reaction is carried out to
the desired level (preferably, completed), the pH of the coating
solution may be brought to a desired pH (e.g., to a range of 5 to
8).
[0079] The functional groups include various chemical groups that
allow for binding to the nanoparticles. Such groups are typically
provided by functional compound represented by the formula A-L-F3.
The functional group F3 includes the olefin, alkyne, (meth)
acrylato, mercapto groups. In this representation, the group A is
the nanoparticle surface-bonding group, and L can be a bond or any
of a variety of organic linkers. Organic linkers L can be linear or
branched alkylene, arylene, or a combination of alkylene and
arylene groups, optionally including heteroatoms.
[0080] Exemplary alkene, alkyne, acryl(metha) functional compounds
are shown as follows in this order:
##STR00003##
[0081] A variety of methods are available for modifying the surface
of nanoparticles including, e.g., adding a surface modifying agent
to nanoparticles (e.g., in the form of a powder or a colloidal
dispersion) and allowing the surface modifying agent to react with
the nanoparticles. For alkene, alkyne, acryl(metha) functional
compounds A-L-F3, the surface-bonding groups A are typically
silanols, alkoxysilanes, or chlorosilanes, which can be
monofunctional, difunctional, or trifunctional. For example, the
silanol groups on the surfaces of the silica nanoparticles are
reacted with at least one silanol, alkoxysilane, or chlorosilane
group of a functional compound to form a functionalized
nanoparticle. Exemplary conditions for reacting functional
compounds with silica nanoparticles are described in the Examples
Section.
Optional Hydrophilic Groups
[0082] If desired, to enhance hydrophilicity of the functionalized
nanoparticles of the present invention, additional hydrophilic
(e.g., water-dispersible, water-soluble, and/or charged) groups can
be covalently attached to individual particles. Hydrophilic groups
(e.g., water-dispersible groups, water-soluble, and/or charged
groups) are monovalent groups that are capable of providing
hydrophilic characteristics to the nanoparticle surface, thereby
reducing, and preferably preventing, excessive agglomeration and/or
precipitation of the nanoparticles in an aqueous environment
(although small amounts of agglomeration can be tolerated when the
nanoparticles are in an aqueous environment as long as the average
size of the agglomerates is preferably no greater than 80 nm).
[0083] As used herein, the term "hydrophilic compound" (e.g.,
"water-dispersible compound," "water-soluble" and/or charged)
describes a compound that can react with a surface of the
nanoparticles to modify it with hydrophilic groups (e.g.,
water-dispersible groups). It can be represented by the formula
A-L-WD, wherein A are the surface-bonding groups, which may be the
same or different as other surface-bonding groups described herein,
WD represents the hydrophilic groups (e.g., water-dispersible
groups, water-soluble groups, and/or charged groups), and L
represents an organic linker or a bond. Organic linkers L can be
linear or branched alkylene, arylene, or a combination of alkylene
and arylene groups, optionally including heteroatoms.
[0084] The hydrophilic groups are water-like groups. They typically
include, for example, anionic groups, cationic groups, groups that
are capable of forming an anionic group or cationic group when
dispersed in water (e.g., salts or acids), or mixtures thereof. The
anionic or anion-forming groups can be any suitable groups that
contribute to anionic ionization of the surface. For example,
suitable groups include: carboxylate groups and structural units
bearing multiple carboxylate groups, exemplified by bonded
ethylenediamine triacetatic acid group and by bonded citric acid;
sulfate half-ester groups and structural units bearing multiple
sulfate half-ester groups; sulfonate groups and structural units
bearing multiple sulfonate groups; phosphate mono- and/or diester
groups and structural units bearing multiple phosphate mono and/or
diester groups; phosphonate groups and structural units bearing
multiple phosphonate groups; and similar groups, and acids
thereof.
[0085] The cationic or cation-forming groups can be any suitable
groups that contribute to cationic ionization of the surface. For
example, suitable groups include quaternary ammonium groups,
quaternary phosphonium groups, tertiary sulfonium groups,
combinations thereof, and structural units bearing multiples
thereof.
[0086] Other suitable hydrophilic groups include hydroxyl groups,
polyethylene oxide groups, combinations thereof, and structural
units bearing multiples thereof.
[0087] The hydrophilic groups may be neutral, but many are charged.
"Charged groups" refer to groups that have one or more than one
ionizable group per functional group.
[0088] In certain embodiments, preferred hydrophilic groups include
carboxylic acid groups, sulfonic acid groups, phosphonic acid
groups, or combinations thereof.
[0089] In certain embodiments, the attachment of water-dispersible
groups on the surface of nanoparticles, significantly, means that
dispersions thereof do not require external emulsifiers, such as
surfactants, for stability. However, if desired anionic and
cationic water-dispersible compounds can also be used in a
composition that includes the functionalized nanoparticles to
function as an external emulsifier and assist in the dispersion of
the nanoparticles.
[0090] The hydrophilic groups can be provided using hydrophilic
compounds of the formula A-L-WD. Suitable surface-bonding groups A
of the hydrophilic compounds are described herein for the epoxy
functional compounds, for example. Examples include silanols,
alkoxysilanes, or chlorosilanes.
[0091] Some preferred hydrophilic compounds include the
following:
##STR00004##
as well as other known compounds.
[0092] Those of ordinary skill in the art will recognize that a
wide variety of other hydrophilic compounds are useful in the
present invention as external emulsifiers or as compounds that can
be used to modify the nanoparticles with water-dispersible
groups.
[0093] Preferably, a sufficient amount of hydrophilic compound is
reacted with the nanoparticles to provide the desired level of
hydrophilicity without interfering with the antifogging,
antireflective, and cleanable characteristics of the compositions
of the present invention.
[0094] The level of coverage of the nanoparticles by hydrophilic
groups herein is reported in terms of the concentration of
hydrophilic groups in the coating composition, assuming 100% of the
amount of hydrophilic groups in the coating composition would be
covalently bonded to surface of the particles. If used, the
hydrophilic groups are preferably present on a nanoparticle surface
in the coating composition in an amount equivalent to at least 1
mole-%, and more preferably at least 10 mole-%, of the total molar
functional groups on said surface. If used, the hydrophilic groups
are preferably present on a nanoparticle surface in the coating
composition in an amount equivalent to no more than 60 mole-%, more
preferably no more than 50 mole-%, more preferably, no more than 20
mole-%, and even more preferably no more than 10 mole-%, of the
total molar functional groups on said surface.
[0095] Preferably, the desired level of hydrophilicity is such that
an external emulsifier is not necessary for preparing a
storage-stable dispersion.
Optional Additives
[0096] In certain embodiments, the compositions of the present
invention include one or more surfactants. The term "surfactant" as
used herein describes molecules that reduce the surface tension of
the coating composition and provide a coating which imparts
desirable easy-cleaning, antireflective, and improved durability
characteristics to substrates or articles coated therewith.
Surfactants described in this invention may also be used as
leveling agents for coating uniformity. Useful surfactants of the
present invention include anionic, cationic, nonionic, or
amphoteric surfactants. Examples include the following:
TABLE-US-00001 Surfactant Type Surfactant Name Product Name Source
Anionic Sodium dodecyl DS-10 Rhone-Poulenc benzene sulfonate
Amphoteric N-coco-aminopropionic MIRATAINE Rhone-Poulenc acid AP-C
Amphoteric Cocaamidopropyl CAPB-30S Shanghai betaine Gaowei
Chemical Co. Nonionic Lauryl dimethylamine RRODAMOX- Rhone-Poulenc
oxide LO Nonionic Alkyl polyglucoside TRITON BG10 Dow Chemical
Nonionic PEG/PPG/PEG block PLURONIC BASF Corp. copolymer F38
Nonionic Organosilicone BYK-333 BYK surfactant Nonionic
Organosilicone Q2-5211 Dow-Corning surfactant Nonionic
Fluorochemical FC-4430 3 M surfactant Nonionic Fluorochemical
FC-4432 3 M surfactant Nonionic Polyoxyethylene AEO7-24S Sasol
(China) (7) lauryl ether Chemical Co., Ltd. Nonionic
Polyoxyethylene AEO7-24S Sasol (China) (9) lauryl ether Chemical
Co., Ltd. Nonionic Polyoxyethylene AEO7-24S Sasol (China) (18)
lauryl ether Chemical Co., Ltd. Cationic Di-oleic acid PRAEPAGEN
Clariant triethanolamine 4317 Chemicals esterquat (China) Ltd.
Cationic Di-tallow dimethyl PRAEPAGEN Clariant ammonium chloride
3345 Chemicals (China) Ltd. Cationic Alkyldimethylbenzyl- DODIGEN
226 Clariant ammonium chloride Chemicals (China) Ltd.
TABLE-US-00002 Surfactant Type Surfactant Product and Class Name
Name Source Anionic Dioctyl ester AEROSOL OT Cytec Sulfosuccinate
of sodium Industries sulfosuccinic acid Anionic Alkyl benzene-
POLYSTEP Stepan Sulfosuccinates sulfonic A-13 Company acid
(C10-C16) Anionic Sodium branched POLYSTEP Stepan Alkylbenzene
alkyl (C12) A-16 Company sulfonates and benzene sulfonate sulfates
Anionic Sodium dodecyl RHODOCAL Rhone- Alkylbenzene benzene
sulfonate DS-10 Poulenc sulfonates and sulfates Anionic
Polyethoxylated STEOL CA-460 Stepan Polyethoxylated alkyl Company
derivatives of (C12) ether sulfate, straight or branched ammonium
salt chain aliphatic sulfate Anionic Aliphatic sulfates HOSTASTAT
Hoechst Straight or HS-1 Celanese branched chain Corp. aliphatic
sulfates and sulfonates Anionic Sodium linear alkyl POLYSTEP Stepan
Alkylbenzene (C12) benzene A-15 Company sulfonates and sulfonate
sulfates Anionic Sodium stearate Witco Alkyl carboxylate Amphoteric
N-coco-amino- MIRATAINE Rhone- Alkyl carboxylates propionic acid
AP-C Poulenc Anionic Ethoxylated RRODAFAC Rhone- Alkyl phosphate
dodecyl MC-470 Poulenc mono-or di-ester alcohol phosphate ester,
sodium salt Nonionic Polyoxyethylene BRIJ 35 ICI Americas
Polyethoxylated (23) lauryl ether Inc. alkyl alcohol Nonionic
Plyoxyethylene BRIJ 30 ICI Americas Polyethoxylated (4) laury
lether Inc. alkyl alcohol Nonionic Polyoxyethylene AEO7-24S Sasol
(China) Polyethoxylated (7) lauryl ether Chemical Co., alkyl
alcohol Ltd. Nonionic Polyoxyethylene AEO9-24S Sasol (China)
Polyethoxylated (9) lauryl ether Chemical Co., alkyl alcohol Ltd.
Nonionic Polyoxyethylene AEO18-24S Sasol (China) Polyethoxylated
(18) lauryl ether Chemical Co., alkyl alcohol Ltd. Nonionic Block
copolymer of TETRONIC BASF Corp. Block copolymers ethylene oxide
and 1502 of polyethylene propylene oxide oxide and polypropylene
oxide Nonionic PEG-PPG-PEG PLURONIC BASF Corp. Block copolymers
block copolymer F38 of polyethylene oxide and polypropylene oxide
Nonionic PEG-PPG-PEG TETRONIC BASF Corp. Block copolymers block
copolymer 908 of polyethylene oxide and polypropylene oxide
Nonionic Lauryl dime- RHODAMOX- Rhone- Amine oxide thylamine oxide
LO Poulenc Nonionic Ethoxylated TERGITOL Union Carbide
Polyethoxylated trimethylnonanol TMN-6 Chemical & alkyl alcohol
Plastics Co.,
[0097] If used, the surfactant concentration in coating
compositions of the present invention is preferably at least 0.01
percent by weight of the coating composition, more preferably at
least 0.04 wt %, and even more preferably at least 0.1 wt %. If
used, the surfactant concentration is preferably no greater than 10
wt % of the coating composition, more preferably no greater than 5
wt % of the coating composition.
[0098] Another optional but preferred additive is an antimicrobial
agent. Examples include the following (with information with
respect to solubility in water):
TABLE-US-00003 Soluble in Product Name Composition Company Water
KATHON 5-Chloro-2-methyl-4- Rohm & Haas Good CG
isothiazolin-3-one 2-Methyl-4-isothiazolin- 3-one Magnesium
chloride Magnesium nitrate Water C302 1,3-Dimethylol-5,5- Shanghai
JiuXin Good dimethylhydantoin Chem. Co. Ltd. PROTECTOL
2-Phenoxyethanol BASF Dissolves PE/PES in hot water METHYL-SAR
Methyl-p-hydrobenzoate Taizhou Necchem Dissolves ABEN Company
(China) in hot water PROPYL-SAR Propyl-p- hydrobenzoate Taizhou
Necchem Does not ABEN Company (China) dissolve in hot water DODIGEN
226 Alkyldimethylbenzylam Clariant Good monium chloride Chemicals
(China) Ltd. NIPACIDE Benzisothiazolinone Clariant Good BIT20
Chemicals (China) Ltd.
[0099] If used, the antimicrobial concentration in coating
compositions of the present invention is preferably at least 0.0005
percent by weight (wt %) of the total weight of the coating
composition, more preferably at least 0.001 wt %, and even more
preferably at least 0.002 wt %. If used, the antimicrobial
concentration is preferably no greater than 1 wt %, and more
preferably no greater than 0.1 wt % of the total weight of the
coating composition.
[0100] Typically, the coating compositions of the present invention
include water as the liquid carrier (i.e., fluid media); however,
organic solvents can be used in addition to the water. Suitable
organic solvents in the present invention include methanol,
ethanol, isopropanol, butanol, propylene glycol and its monomethyl
ether, ethylene glycol and its monomethyl ether, ketones such as
acetone and methyl ethyl ketone, and ethers such as tetrahydrofuran
(THF), N,N-dimethylacetamide, formamide, or combinations thereof.
If present, typically the organic solvent is an alcohol or
combination of alcohols. The amount of organic solvent in the
coating composition is typically no more than 30 wt %, preferably
no more than 10 wt %, more preferably no more than 5 wt %, even
more preferably no more than 2 wt %, and even more preferably no
more than 1 wt %, based on the total weight of the liquid medium.
The most preferred liquid medium is 100% water.
Articles
[0101] The coatings, when applied to a substrate (e.g., of
inorganic and/or organic material) and dried, are removable or
permanent. Substrates to which the coating compositions of the
invention can be applied are preferably transparent or translucent
to visible light. They include organic, inorganic materials, or
combinations thereof. Exemplary substrates are made of polyester
(e.g., polyethylene terephthalate (PET), polybutylene
terephthalate), polycarbonate (PC), allyldiglycolcarbonate,
polyacrylates such as polymethylmethacrylate, polystyrene,
polysulfone, polyethersulfone, cellulose acetate butyrate, glass,
polyolefin, PVC and the like, including blends and laminates
thereof.
[0102] Typically the substrate is in the form of a film, sheet,
panel or pane of material and is part of an article such as a solar
panel, protective eye wear, face masks, face shields, surgical
masks, and various other types of personal protection equipment,
particularly for eyes, as well as mirrors, motor vehicle windows
and windshields. The coatings may, if desired, cover only a portion
of the article, e.g., only the section immediately adjacent the
eyes in a face shield may be coated. The substrate may be flat,
curved, or shaped. The article to be coated may be produced by any
method such as by blowing, casting, extruding, or injection
molding.
[0103] The compositions can be coated on a substrate as a fluid
coating composition such as in the form of a liquid-based coating
composition (e.g., in a pourable form or sprayable form) using
conventional techniques, for example, such as bar, roll, curtain,
rotogravure, spray, or dip coating techniques. Sprayers and nozzle
systems suitable for use in this application are known to one
skilled in the art and include, for example, hydraulic, pneumatic,
rotary and ultrasonic nozzles and associated sprayer systems. An
example of a hydraulic sprayer is the MSO sprayer available for US
Global Resources (Seattle, Wash.). Examples of suitable pneumatic
sprayers include the EGA Manual Touch-Up Gun available from
DeVilbiss Corporation (Glendale Hts., IL) or the AJ-401-LH sprayer
available from Jacto (Tualaltin, Oreg.). Rotary atomizers use a
high speed rotating disk, cup or wheel to disperse the liquid into
a hollow cone spray. The rotational speed controls the drop size.
Examples of rotary atomizers include PROPTEC and PENGUIN atomizers
available from Ledebuhr Industries (Williamston, Mich.). Ultrasonic
atomizers use a high (20 kHz to 50 kHz) frequency vibration of a
piezoelectric crystal to produce narrow drop size distribution and
low velocity spray. Examples of suitable sprayers with ultrasonic
atomizer nozzles include models VC5020AT and VC5040AT available
from Sonics and Materials, Inc. (Newtown, Conn.).
[0104] Alternatively, the compositions of the present invention can
be coated on a substrate by simply wiping a pad, cloth, paper
towel, or other application device/material over the surface of the
substrate, wherein the composition is contained within the pad,
cloth, etc. or applied to the surface of the substrate surface.
Suitable applicator substrates can be in the form of a sponge,
foam, woven, nonwoven, or knit material, for example. The term
"nonwoven web" or "nonwoven fabric" refers to a web or fabric
having a structure of individual fibers that are interlaid in an
irregular manner. In contrast, knit or woven fabrics have fibers
that are interlaid in a regular manner. Materials of the applicator
substrate (e.g., applicator pad or wipe) can include synthetic or
natural fibers, filaments, or yarns. Suitable materials include,
but are not limited to, polyolefins, polyesters, polyamides (e.g.,
nylons), polyurethanes, halogenated polyolefins, polyacrylates,
polyureas, polyacrylonitriles, cellulose, cotton, rayon, jute,
hemp, as well as copolymers and polymer blends thereof. Various
combinations of materials in various shapes can be used for
applicator substrates if desired. The most typical substrate is a
paper wipe containing the coating composition (soaked or
impregnated into the wipe).
[0105] The coatings of the present invention can be coated on one
side or both sides of a substrate. The coatings of the present
invention may be coated on one side of the substrate and the
opposite side of the substrate may be uncoated or coated with a
wide variety of conventional compositions, particularly
conventional antifogging compositions. Preferably, the coating
surface should face the direction of higher humidity, e.g., on a
face shield the side having an antifog coating should face the
wearer.
[0106] A coated surface may be dried at room temperature (e.g.,
over a 15 minute period) or if desired, at elevated temperatures,
to dry more quickly (such as within 5 minutes). For coating
compositions of the present invention, drying conditions can
impact, for example, the durability, removability, and permanency
of the dried coating. A "dried" coating (i.e., one in which the
liquid carrier (i.e., fluid media) has been substantially
completely removed, for example, by evaporation, from the coating
composition) is typically also "cured" as a result of reaction
between the reactive functional groups (e.g., amine groups and
epoxy groups). Such curing can be enhanced by heating the coating
composition during the drying process. For example, drying
conditions can include a temperature of at least 80.degree. C., or
a temperature of at least 100.degree. C., or at a temperature of at
least 120.degree. C. The substrate on which the coating composition
is applied typically controls the temperature of drying. For
example, for glass substrates, coatings can generally be dried at
temperatures of 120.degree. C. to 160.degree. C. Generally, for
plastic substrates, coatings can be dried at temperatures of
120.degree. C. to 140.degree. C., and more specifically, for PET
substrates, coatings can be dried at temperatures of 120.degree. C.
to 135.degree. C., and for PMMA substrates, coatings can be dried
at temperatures of only up to 80.degree. C.
[0107] Additionally, the coatings can be heated at temperatures and
times typical of glass tempering (e.g., temperatures such as 700 to
750.degree. C. for 2 to 5 minutes) do not destroy the properties
important to solar cell coatings (high light transmittance,
antireflection, anti-soiling, and anti-abrasion) even though
Transmission Electron Microscopy (TEM) and ESCA do indicate some
changes to the shape of the particles and the elemental composition
of the coatings on the particles after the tempering process.
However, the specific tempering conditions mentioned do not appear
to sinter the particles. Tempering may be necessary for
commercialized solar glass and thus the coating compositions may be
applied before or after tempering. The relatively lower refractive
index caused by the nanostructure imparts antireflection properties
which can, at least in some embodiments, improve light
transmittance by 2.0 to 3.0 percent and thus improves light to
power conversion by 2.0 to 2.5 percent. Even under these high
temperature tempering conditions, the resulting coatings can impart
higher power conversion than naked silica particles.
[0108] The functional groups on the nanoparticles can contribute to
adhesion of the coating to a substrate. For example, functional
such as epoxy groups and/or amine groups can react with
functionalities of a surface to form covalent bonds between the
nanoparticles and the substrate. Alternatively or additionally, a
substrate can be treated to improve adhesion between the substrate
and the coating, using, e.g., chemical treatment, mechanical
roughening, corona treatment such as air or nitrogen corona,
plasma, flame, or actinic radiation. If desired, an optional tie
layer can also be applied between the substrate and the coating to
increase the interlayer adhesion.
[0109] An example of another article that can include a coating
composition of the present invention includes a solar panel (e.g.,
a photovoltaic cell module) comprising: a photovoltaic cell or an
array of photovoltaic cells (a series of interconnected
photovoltaic cells); and a coating composition disposed on the
front side of solar panel for tansmission increase and for
antisoiling and rinse-away cleaning.
[0110] In general, photovoltaic cells are semiconductor devices
used to convert light into electricity and may be referred to as
solar cells. Upon exposure to light, a photovoltaic cell generates
a voltage across its terminals resulting in a consequent flow of
electrons, the size of which is proportional to the intensity of
the light impinging on the photovoltaic junction formed at the
surface of the cell. Typically, a series of solar cell modules are
interconnected to form a solar array (i.e., solar panel), which
functions as a single electricity producing unit wherein the cells
and modules are interconnected in such a way as to generate a
suitable voltage in order to power a piece of equipment or supply a
battery for storage, etc.
[0111] Semiconductor materials used in photovoltaic cells include
crystalline or polycrystalline silicon or thin film silicon (e.g.,
amorphous, semicrystalline silicon) as well as non-silicon
materials such as gallium arsenide, copper indium diselenide,
organic semiconductors, CIGS, and the like. There are two types of
photovoltaic cells, wafers and thin films. A wafer is a thin sheet
of semiconductor material made by mechanically sawing it from a
single crystal or multicrystal ingot or casting. Thin film based
photovoltaic cells are continuous layers of semiconducting
materials typically deposited on a substrate or substrate using
sputtering or chemical vapour deposition processes or the like.
[0112] Wafer and thin film photovoltaic cells are often fragile
enough such that a module may require one or more supports. The
support may be rigid, e.g., a glass plate rigid material, or it may
be a flexible material, e.g., a metallic film and/or sheet of
suitable polymer material such as a polyimide or polyethylene
terephthalate. The support may be a top layer or substrate, i.e.,
positioned between the photovoltaic cell and the light source, and
which is transparent to light coming from the light source.
Alternatively or in addition thereto, the support may be a bottom
layer positioned behind the photovoltaic cell.
[0113] The coating composition of the present invention may be
coated on the front side of a solar panel. The preferred coating
thickness is in a range of 100 nm to 200 nm for antireflective
coatings.
EXEMPLARY EMBODIMENTS
[0114] 1. A method of modifying a substrate surface, the method
comprising: [0115] (a) applying a coating composition to a
substrate, wherein the coating composition comprises: [0116] (i)
nonspherical nanoparticles; [0117] (ii) spherical nanoparticles;
[0118] (iii) optionally hydrophilic groups and optionally a
surfactant; and [0119] (iv) a liquid medium comprising water and no
greater than 30 wt % organic solvent, if present, based on the
total weight of liquid medium, [0120] wherein at least a portion of
the nonspherical nanoparticles or at least a portion of the
spherical nanoparticles comprises functional groups attached to the
surface of the nonspherical nanoparticles or the spherical
nanoparticles through chemical bonds, and further wherein the
functional groups comprise at least one group selected from epoxy
group, amine group, hydroxyl, olefin, alkyne, (meth) acrylato,
mercapto, or combinations thereof; and [0121] (b) drying the
coating composition to form a hydrophilic coating on the
substrate.
[0122] 2. The method of claim 1 wherein all the nonspherical
nanoparticles or all the spherical nanoparticles comprise the
functional groups.
[0123] 3. The method of claim 1 wherein the weight ratio of the
nonspherical nanoparticles to the spherical nanoparticles ranges
from 95:5 to 5:95.
[0124] 4. The method of claim 3 wherein the weight ratio of the
nonspherical nanoparticles to the spherical nanoparticles ranges
from 80:20 to 20:80.
[0125] 5. The method of claim 4 wherein the weight ratio of the
nonspherical nanoparticles to the spherical nanoparticles ranges
from 70:30 to 30:70.
[0126] 6. The method of claim 1 wherein at least a portion of the
nonspherical nanoparticles comprise silica nanoparticles.
[0127] 7. The method of claim 1 wherein at least a portion of the
spherical nanoparticles comprise silica nanoparticles.
[0128] 8. The method of claim 1 wherein the substrate is glass or
ceramic.
[0129] 9. The method of claim 1 wherein the method further
comprises the step of sintering the coated substrate at a
temperature ranging from 200 degrees C. to 750 degrees C.
[0130] 10. The method of claim 1 wherein the nonspherical
nanoparticles have an average particle size between 1 and 200 nm
and an aspect ratio between 2 and 100.
[0131] 11. The method of claim 1 wherein the spherical
nanoparticles have an average particle size between 1 and 120
nm.
[0132] 12. The method of claim 1 wherein the coating composition
comprises at least 0.05 wt % nonspherical nanoparticles and no
greater than 40 wt % nonspherical nanoparticles, based on the total
weight of the coating composition.
[0133] 13. The method of claim 1 wherein the coating composition
comprises at least 0.05 wt % spherical nanoparticles and no greater
than 40 wt % spherical nanoparticles, based on the total weight of
the coating composition.
[0134] 14. The method of claim 1 wherein the coating composition
comprises 0.01-5 wt % surfactant, based on the total weight of the
coating composition.
[0135] 15. The method of claim 1 wherein the nonspherical
nanoparticles are elongated nanoparticles.
[0136] 16. The method of claim 1 wherein the spherical
nanoparticles comprise the functional groups.
[0137] 17. An article comprising a substrate surface modified using
the method of claim 1.
[0138] 18. A coating composition comprising [0139] nonspherical
nanoparticles; [0140] spherical nanoparticles; [0141] optionally
hydrophilic groups and optional an surfactant; and [0142] a liquid
medium comprising water and no greater than 30 wt % organic
solvent, if present, based on the total weight of liquid medium,
[0143] wherein at least a portion of the nonspherical nanoparticles
or at least a portion of the spherical nanoparticles comprises
functional groups attached to their surface through chemical bonds,
wherein the functional groups comprise at least one group selected
from the group consisting of epoxy group, amine group, hydroxyl,
olefin, alkyne, (meth) acrylato, mercapto group, or combinations
thereof
[0144] 19. The composition of claim 18 wherein all the nonspherical
nanoparticles or all the spherical nanoparticles comprise the
functional groups.
[0145] 20. The composition of claim 18 wherein the weight ratio of
the nonspherical nanoparticles to the spherical nanoparticles
ranges from 95:5 to 5:95.
[0146] 21. The composition of claim 20 wherein the weight ratio of
the nonspherical nanoparticles to the spherical nanoparticles
ranges from 70:30 to 30:70.
[0147] 22. The composition of claim 18 wherein at least a portion
of the nonspherical nanoparticles comprise silica
nanoparticles.
[0148] 23. The composition of claim 18 wherein at least a portion
of the spherical nanoparticles comprise silica nanoparticles.
[0149] 24. The composition of claim 18 wherein the substrate is
glass or ceramic.
[0150] 25. The composition of claim 18 wherein the nonspherical
nanoparticles have an average particle size between 1 and 200 nm
and an aspect ratio between 2 and 100.
[0151] 26. The composition of claim 18 wherein the spherical
nanoparticles have an average particle size between 1 and 120
nm.
[0152] 27. The composition of claim 18 wherein the coating
composition comprises at least 0.05 wt % nonspherical nanoparticles
and no greater than 40 wt % nonspherical nanoparticles, based on
the total weight of the coating composition.
[0153] 28. The composition of claim 18 wherein the coating
composition comprises at least 0.05 wt % spherical nanoparticles
and no greater than 40 wt % spherical nanoparticles, based on the
total weight of the coating composition.
[0154] 29. The composition of claim 18 wherein the coating
composition comprises 0.01-5 wt % surfactant, based on the total
weight of the coating composition.
[0155] 30. The composition of claim 18 wherein a dried coating
provides antireflective, easy cleaning and/or durability
characteristics to the substrate for at least 24 hours.
[0156] 31. The composition of claim 18 wherein the nonspherical
nanoparticles are elongated nanoparticles.
[0157] 32. The composition of claim 18 wherein the spherical
nanoparticles comprise the functional groups.
[0158] 33. An article comprising a substrate surface modified using
the coating composition of claim 18.
[0159] 34. The article of claim 33 which is a solar panel.
[0160] 35. The article of claim 33 wherein the substrate is
glass.
[0161] 36. The article of claim 35 wherein the glass is
tempered.
EXAMPLES
[0162] Unless otherwise indicated, all chemical reagents and
solvents were or can be obtained from Aldrich Chemical Co.,
Milwaukee, Wis. All parts, percentages, or ratios specified in the
examples are by weight, unless specified otherwise. All
temperatures specified in the examples are in degrees Celsius,
unless specified otherwise.
[0163] Spherical silica nanoparticles dispersions 1115 (4-nm), 2326
(5-nm), 8699 (2.about.4-nm), were obtained from Nalco Company,
Naperville, Ill.
[0164] Nonspherical silica nanoparticles dispersions IPA-ST-UP,
ST-OUP, ST-UP and ST-PS-S were obtained from Nissan Chemical
Industries, LTD.
[0165] 3-(glycidoxypropyl)-trimethoxysilane (KH560, 97%),
aminoethylaminopropyltrimethoxysilane (Z-6020, 85%), and
.gamma.-methacryloxypropyltrimethoxysilane (Z-6030, 98%) were
obtained from Zhejiang Chem-Tech Group Co., Ltd. Hangzhou, Zhejiang
Province, China, or from Dow Corning Company, Midland, Mich.
[0166] Solar glass was obtained by CSG Holding Co. Ltd.
Antireflection Test
[0167] Total transmittance measurements were made on a HAZE-GARD
DUAL haze and transmittance meter (BYK-Gardner, Columbia, Md.,
USA). The % transmission was directly read from the instrument as
the average of the solar daylight wavelength range (CIE D65
standard illuminant) according to ASTM D1003.
[0168] The light transmission spectrum in 400.about.1200 nm was
performed on Lambda 900, PerkinElmer.
Durability Test
[0169] The mechanical durability was evaluated by wet and dry
scrubbing. The dry scrubbing was performed by rubbing (by hand,
with strong pressure) the coated surface 100 times with a paper
towel. The wet scrubbing was preformed on a Sheen Wet Abrasion
Scrub Tester using 1 kg weight pressure with dishcloth and a 1.0%
by weight detergent water solution (commercial dish detergent with
anionic and nonionic surfactants from Shanghai Baimao Company) for
1000 cycles. (See table 2).
Easy Cleaning Test
[0170] This test was carried out by immersing the coated substrate
sample into Gorecki Standard Carpet Soil available from Gorecki
Manufacturing Inc., Milaca, Minn. and shaking it for 30 seconds.
The sample was removed from the soil container and rinsed with tap
water for 1 minute at a speed of 750 millimeters per minute
(mL/min). The samples were rated based on their appearance. A
rating of "good" was given if the sample was completely clean, and
a rating of "bad" was given if the sample was not clean (see tables
3).
Hardness Test
[0171] The hardness was tested simply by personal nail and pencil
by Test Method for film hardness coating (ASTM D 3363). If there is
no scraping trace by scratching the coating with nail, we value the
coating "pass", or else "fail". (See table 4)
85.degree. C./85% RH Test of IEC 61215
[0172] Coated glass samples were put in climatic chamber under
85%.+-.5% RH and 85.degree. C. after 1250 hours and the light
transmission was tracked to determine the effect of damp heat aging
durability. (See table 5)
Surface Modified Nanoparticle (SMN) 1 (Epoxy Functionalized--5-nm
Spherical Nanoparticles):
[0173] Nalco 2326 silica nanoparticles (20 grams (g), 15 wt %) and
deionized water (40 g) were stirred together in a glass jar for 15
minutes (min) Concentrated H.sub.3PO.sub.4 was dropped into the
dispersion to adjust pH value to 1.5.about.2.0. 0.85 g
3-(glycidoxypropyl)-trimethoxysilane (KH560) was slowly added to
the solution. Then the solution was heated to 60 C and kept
reaction for 10 hours. Coating solution concentrations were about 5
wt % and were used in the preparation of coating samples for
examples described in Tables 1.
Surface Modified Nanoparticle (SMN) 2 (Epoxy Functionalized--4 nm
Spherical Nanoparticles):
[0174] Nalco 2326 silica nanoparticles (20 grams (g), 15 wt %) and
deionized water (40 g) were stirred together in a glass jar for 15
minutes (min) Concentrated H.sub.2SO.sub.4 was dropped into the
dispersion to adjust pH value to 1.5.about.2.0. 0.85 g
3-(glycidoxypropyl)-trimethoxysilane (KH560) was slowly added to
the solution. Then the solution was heated to 60 C and kept
reaction for 10 hours. Coating solution concentrations were about 5
wt % and were used in the preparation of coating samples for
examples described in Tables 1.
Surface Modified Nanoparticle (SMN) 3 (Epoxy Functionalized--4 nm
Spherical Nanoparticles):
[0175] Nalco 1115 silica nanoparticles (20 g, 15 wt %) and
deionized water (40 g) were stirred together in a glass jar for 15
min. Concentrated H.sub.2SO.sub.4 was dropped into the dispersion
to adjust pH value to 1.5.about.2.0. 1.06 g
3-(glycidoxypropyl)-trimethoxysilane (KH560) was slowly added to
the solution. Then the solution was heated to 60 C and kept
reaction for 10 hours. Coating solution concentrations were about 5
wt % and were used in the preparation of coating samples for
examples described in Tables 1.
Surface Modified Nanoparticle (SMN) 4 (Epoxy Functionalized--40-100
nm Nonspherical Nanoparticles):
[0176] Nissan SNOWTEX-OUP nonspherical nanoparticles (20 g, 15 wt
%) and deionized water (40 g) were stirred together in a glass jar
for 15 min. Concentrated H.sub.3PO.sub.4 was dropped into the
dispersion to adjust pH value to 1.5.about.2.0. 0.21 g
3-(glycidoxypropyl)-trimethoxysilane (KH560) was slowly added to
the solution. Then the solution was heated to 60 C and kept
reaction for 10 hours. Coating solution concentrations were about 5
wt % and were used in the preparation of coating samples for
examples described in Tables 1.
Surface Modified Nanoparticle (SMN) 5 (Epoxy Functionalized--2-4 nm
Silica Spherical Nanoparticles):
[0177] Nalco 8699 silica nanoparticles (20 g, 15 wt %) and
deionized water (40 g) were stirred together in a glass jar for 15
min. Concentrated H.sub.3PO.sub.4 was dropped into the dispersion
to adjust pH value to 1.5.about.2.0. 1.06 g
3-(glycidoxypropyl)-trimethoxysilane (KH560) was slowly added to
the solution. Then the solution was heated to 60 C and kept
reaction for 10 hours. Coating solution concentrations were about 5
wt % and were used in the preparation of coating samples for
examples described in Tables 1.
Surface Modified Nanoparticle (SMN) 6 (Amine Functionalized--40-100
nm Nonspherical Nanoparticles)
[0178] Nissan SNOWTEX-UP (20 g, 20 wt %) nonspherical nanoparticles
and deionized water (60 g) were stirred together in a glass jar for
15 min. The pH of this mixture was adjusted to about 12 using 0.1N
sodium hydroxide. 0.06 g aminoethylaminopropyltrimethoxysilane
(Z-6020) in ethanol (5 g) was added drop-wise with stirring over a
period of 1 to 1.5 hrs and the resulting mixture was continuously
stirred at 20.degree. C. for an additional 14 hrs. The resulting
solution (5 wt %) was used in the preparation of coating samples
for examples described in Tables 1.
Surface Modified Nanoparticle (SMN) 7 (Amine Functionalized--2-4 nm
Silica Spherical Nanoparticles)
[0179] Nalco 8699 silica nanoparticles (20 g, 15 wt %) and
deionized water (40 g) were stirred together in a glass jar for 15
min. The pH of this mixture was adjusted to about 12 using 0.1N
sodium hydroxide. 0.20 g aminoethylaminopropyltrimethoxysilane
(Z-6020) in ethanol (5 g) was added drop-wise with stirring over a
period of 1 to 1.5 hrs and the resulting mixture was continuously
stirred at 20.degree. C. for an additional 14 hrs. The resulting
solution (5 wt %) was used in the preparation of coating samples
for examples described in Tables 1.
Surface Modified Nanoparticle (SMN) 8 (Acrylate
Functionalized--40-100 nm Nonspherical Nanoparticles)
[0180] Nissan SNOWTEX-OUP nonspherical nanoparticles (20 g, 15 wt
%) and deionized water (40 g) were stirred together in a glass jar
for 15 min. Concentrated H.sub.3PO.sub.4 was dropped into the
dispersion to adjust pH value to 1.5.about.2.0. 0.5 g
.gamma.-methacryloxypropyltrimethoxysilane (Z6030) was slowly added
to the solution. Then the solution was heated to 60 C and kept
reaction for 10 hours. Coating solution concentrations were about 5
wt % and were used in the preparation of coating samples for
examples described in Tables 1.
Bared Nanoparticle (BN) 1 (4 nm Silica Spherical Nanoparticle)
[0181] Nalco 1115 silica nanoparticles (20 g, 15 wt %) and
deionized water (80 g) were stirred together in a glass jar for 15
min. Concentrated H.sub.2SO.sub.4 was dropped into the dispersion
to adjust pH value to 1.5.about.2.0. Coating solution
concentrations were about 3 wt % and were used in the preparation
of coating samples for examples described in Tables 1.
Bared Nanoparticle (BN) 2 (5 nm Silica Spherical Nanoparticle)
[0182] Nalco 2326 silica nanoparticles (20 g, 15 wt %) and
deionized water (80 g) were stirred together in a glass jar for 15
min. Concentrated H.sub.3PO.sub.4 was dropped into the dispersion
to adjust pH value to 1.5.about.2.0. Coating solution
concentrations were about 3 wt % and were used in the preparation
of coating samples for examples described in Tables 1.
Bared Nanoparticle (BN) 3 (2-4 nm Silica Spherical
Nanoparticle)
[0183] Nalco 8699 silica nanoparticles (20 g, 15 wt %) and
deionized water (80 g) were stirred together in a glass jar for 15
min. Concentrated H.sub.3PO.sub.4 was dropped into the dispersion
to adjust pH value to 1.5.about.2.0. Coating solution
concentrations were about 3 wt % and were used in the preparation
of coating samples for examples described in Tables 1.
Bared Nanoparticle (BN) 4 (40-100 nm Nonspherical Nanoparticles in
IPA/H2O)
[0184] Nissan IPA-ST-UP nonspherical nanoparticles (20 g, 15 wt %)
and deionized water (80 g) were stirred together in a glass jar for
15 min. Coating solution concentrations were about 3 wt % and were
used in the preparation of coating samples for examples described
in Tables 1.
Bared Nanoparticle (BN) 5 (Acidic 40-100 nm Nonspherical
Nanoparticles)
[0185] Nissan SNOWTEX-OUP nonspherical nanoparticles (20 g, 15 wt
%) and deionized water (80 g) were stirred together in a glass jar
for 15 min. Coating solution concentrations were about 3 wt % and
were used in the preparation of coating samples for examples
described in Tables 1.
Bared Nanoparticle (BN) 6 (Alkaline 40-100 nm Nonspherical
Nanoparticles)
[0186] Nissan SNOWTEX-UP (30 g, 20 wt %) nonspherical nanoparticles
and deionized water (170 g) were stirred together in a glass jar
for 15 min. Coating solution concentrations were about 3 wt % and
were used in the preparation of coating samples for examples
described in Tables 1.
TABLE-US-00004 Exam- ple 5:95 20:80 30:70 40:60 50:50 1 SMN1:BN4 2
SMN2:BN4 3 SMN3:BN5 4 BN1:SMN4 5 BN3:SMN8 6 BN3:BN5 7 BN3:SMN4 8
BN3:SMN4 9 BN3:SMN4 10 SMN5:BN5 11 SMN5:BN5 12 SMN5:- BN5 13
BN3:SMN6 14 BN3:SMN6 15 SM7:BN6 16 SM7:BN6 17 BN3:SMN8 18 BN3:SMN8
19 BN3:- SMN8 20 SMN4:BN3 21 SMN4:BN3 22 SMN5:BN5 23 SMN5:BN5 24
BN5:SMN5 25 BNS:SMN5 26 BN3:SMN6 27 BN3:SMN6 28 SMN6:BN3 29
SMN6:BN3 30 SM7:BN6 31 SM7:BN6 32 BN6:SM7 33 BN6:SM7 34 SMN8:BN3 35
SMN8:BN3
Examples 1 to 37
[0187] Coating solutions (3 wt %) were prepared by mixing
appropriate amounts of SMN and BN solutions with water and
surfactants to improve wetting as indicated in Table 1.
[0188] Example 1 was prepared by gradually adding 9.0 g SMN 1 to
35.0 g BN4. Then 6.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0189] Example 2 was prepared by gradually adding 9.0 g SMN 2 to
35.0 g BN4. Then 6.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0190] Example 3 was prepared by gradually adding 1.5 g SMN 3 to
45.0 g BN4. Then 3.5 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0191] Example 4 was prepared by gradually adding 2.5 g BN1 to 28.5
g SMN4. Then 19.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0192] Example 5 was prepared by gradually adding 2.5 g BN3 to 28.5
g SMN8. Then 19.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0193] Example 6 was prepared by gradually adding 2.5 g BN3 to 47.5
g BN 5. Then 0.75 g of a 10% solution of TRITON BG10 was added to
the coating solution.
[0194] Example 7 was prepared by gradually adding 2.5 g BN3 3 to
28.5 g SMN 4. Then 19.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0195] Example 8 was prepared by gradually adding 15.0 g BN3 to
21.0 g SMN 6. Then 14.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0196] Example 9 was prepared by gradually adding 20.0 g BN3 to
18.0 g SMN 6. Then 12.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0197] Example 10 was prepared by gradually adding 6.0 g SMN5 to
40.0 g BN5. Then 4.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0198] Example 11 was prepared by gradually adding 12.0 g SMN5 to
30.0 g BN 5. Then 8.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0199] Example 12 was prepared by gradually adding 15.0 g SMN5 to
25.0 g BN 5. Then 10.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0200] Example 13 was prepared by gradually adding 10.0 g BN3 to
24.0 g SMN6. Then 16.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0201] Example 14 was prepared by gradually adding 20.0 g BN3 to
18.0 g SMN6. Then 12.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0202] Example 15 was prepared by gradually adding 6.0 g SMN7 to
40.0 g BN6. Then 4.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0203] Example 16 was prepared by gradually adding 12.0 g SMN7 to
30.0 g BN6. Then 8.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0204] Example 17 was prepared by gradually adding 5.0 g BN3 to
27.0 g SMN8. Then 18.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0205] Example 18 was prepared by gradually adding 15.0 g BN3 to
21.0 g SMN8. Then 14.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0206] Example 19 was prepared by gradually adding 25.0 g BN3 to
15.0 g SMN8. Then 10.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0207] Example 20 was prepared by gradually adding 15.0 g BN3 to
21.0 g SMN4. Then 14.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0208] Example 21 was prepared by gradually adding 47.5 g BN3 to
1.5 g SMN4. Then 1.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0209] Example 22 was prepared by gradually adding 2.5 g BN5 to
28.5 g SMN5. Then 19.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0210] Example 23 was prepared by gradually adding 15.0 g BN5 to
21.0 g SMN5. Then 14.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0211] Example 24 was prepared by gradually adding 35.0 g BN5 to
9.0 g SMN5. Then 6.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0212] Example 25 was prepared by gradually adding 47.5 g BN5 to
1.5 g SMN5. Then 1.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0213] Example 26 was prepared by gradually adding 2.5 g BN3 to
28.5 g SMN6. Then 19.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0214] Example 27 was prepared by gradually adding 15.0 g BN3 to
21.0 g SMN6. Then 14.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0215] Example 28 was prepared by gradually adding 35.0 g BN3 to
9.0 g SMN6. Then 6.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0216] Example 29 was prepared by gradually adding 47.5 g BN3 to
1.5 g SMN6. Then 1.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0217] Example 30 was prepared by gradually adding 47.5 g BN6 to
1.5 g SMN7. Then 1.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0218] Example 31 was prepared by gradually adding 35.0 g BN6 to
9.0 g SMN7. Then 6.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0219] Example 32 was prepared by gradually adding 15.0 g BN6 to
21.0 g SMN7. Then 14.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0220] Example 33 was prepared by gradually adding 2.5 g BN6 to
28.5 g SMN7. Then 19.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0221] Example 34 was prepared by gradually adding 47.5 g BN3 to
1.5 g SMN8. Then 1.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0222] Example 35 was prepared by gradually adding 35.0 g BN3 to
9.0 g SMN8. Then 6.0 g deionized water was added to dilute the
solution by the addition of 0.75 g of a 10% solution of TRITON
BG10.
[0223] Example 36 was prepared by adding 12.5 g BN6 into solution
of example 19. Example 37 was prepared by adding 5.0 g SMN7 into
solution of example 27.
[0224] Coating solutions were coated on the smooth side of solar
glass substrates (CSG Holding Co. Ltd) by using a dip coater to
obtain a dry coating thickness of about 100-200 nm. The coated
samples were then dried at 100.degree. C. for 10 minutes. After
that, the coated samples were tempered at 750.degree. C. for 3
minutes. The % transmittance increased after coating and tempering
was 2.0-3.5 vs the uncoated glass in the case of all the examples.
Example 6 is prepared by bared nanoparticles, used here as a
control example.
TABLE-US-00005 TABLE 2 Durability Dry Wet Increased Increased
Increased Increased T(%)- T(%) -After T(%)- T(%) -After Example
original 100 times original 1000 times 1 2.2 -0.2 2.6 0 2 2.3 -0.2
2.4 0 3 2.3 -0.1 2.3 -0.1 4 2.0 0 2.2 -0.1 5 2.9 -0.5 NT NT 6 3.1
-1.0 2.4 -0.7 7 2.8 -0.3 NT NT 8 2.5 -0.2 NT NT 9 2.6 -0.1 NT NT 10
2.5 -0.2 NT NT 11 2.6 -0.2 NT NT 12 2.4 -0.1 NT NT 13 3.2 -0.2 NT
NT 14 2.6 -0.2 NT NT 15 2.8 -0.4 NT NT 16 2.6 -0.4 NT NT 17 2.8
-0.4 NT NT 18 2.5 -0.3 NT NT 19 2.2 -0.3 NT NT 20 2.5 -0.2 NT NT 21
2.2 -0.3 NT NT 22 2.8 -0.3 NT NT 23 2.6 -0.2 NT NT 24 2.5 -0.2 NT
NT 25 2.3 -0.4 NT NT 26 2.9 -0.4 NT NT 27 2.7 -0.3 NT NT 28 2.5
-0.2 NT NT 29 2.4 -0.3 NT NT 30 2.8 -0.4 NT NT 31 2.6 -0.2 NT NT 32
2.5 -0.2 NT NT 33 2.3 -0.3 NT NT 34 2.4 -0.4 NT NT 35 2.6 -0.3 NT
NT 36 2.7 -0.3 NT NT 37 2.8 -0.2 NT NT
TABLE-US-00006 TABLE 3 Example Cleanability Blank glass Bad 1 Good
3 Good 6 Good 7 Good 10 Good 13 Good 15 Good 17 Good
TABLE-US-00007 TABLE 4 Example Hardness Nail Scratch 1 3H Pass 2 3H
Pass 4 2H~3H Fail 6 1H Fail 9 3H Pass 12 3H Pass 14 3H Pass 15
2H~3H Fail 19 3H Pass
TABLE-US-00008 TABLE 5 Example Increased T(%) -Original Increased
T(%) -After 1250 h 1 2.2 -0.3 4 2.0 +0.2 6 2.4 -0.9 9 2.5 -0.1
[0225] The complete disclosures of the patents, patent documents,
and publications cited herein are incorporated by reference in
their entirety as if each were individually incorporated. Various
modifications and alterations to this invention will become
apparent to those skilled in the art without departing from the
scope and spirit of this invention. It should be understood that
this invention is not intended to be unduly limited by the
illustrative embodiments and examples set forth herein and that
such examples and embodiments are presented by way of example only
with the scope of the invention intended to be limited only by the
claims set forth herein as follows.
* * * * *