U.S. patent application number 14/563962 was filed with the patent office on 2015-04-09 for coating and curing apparatus and methods.
The applicant listed for this patent is Enki Technology, Inc.. Invention is credited to Brenor L. Brophy, Peter R. Gonsalves, Patrick J. Neyman, Yu S. Yang.
Application Number | 20150099060 14/563962 |
Document ID | / |
Family ID | 51297630 |
Filed Date | 2015-04-09 |
United States Patent
Application |
20150099060 |
Kind Code |
A1 |
Brophy; Brenor L. ; et
al. |
April 9, 2015 |
COATING AND CURING APPARATUS AND METHODS
Abstract
Disclosed herein is a method of coating and curing, including
conveying a substantially flat substrate to be coated with a
conveyor system through a combination roll coating and curing
facility, wherein the combination roll coating and curing facility
comprises at least one roll coating facility and at least one
curing facility, roll coating the substantially flat substrate with
a continuous sol gel coating material with the at least one roll
coating facility, and curing the sol gel coating material on the
substantially flat substrate with an air knife of the at least one
curing facility, wherein the air knife is adapted to direct a
heated stream of air to cure the continuous sol gel coating
material while an interior of the substantially flat substrate
remains at a temperature substantially lower than a temperature of
air from the air knife.
Inventors: |
Brophy; Brenor L.; (San
Jose, CA) ; Gonsalves; Peter R.; (Santa Clara,
CA) ; Yang; Yu S.; (Pleasanton, CA) ; Neyman;
Patrick J.; (San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Enki Technology, Inc. |
San Jose |
CA |
US |
|
|
Family ID: |
51297630 |
Appl. No.: |
14/563962 |
Filed: |
December 8, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14138542 |
Dec 23, 2013 |
8960123 |
|
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14563962 |
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13835253 |
Mar 15, 2013 |
8668960 |
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14138542 |
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61762603 |
Feb 8, 2013 |
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Current U.S.
Class: |
427/8 ; 427/223;
427/299; 427/314; 427/372.2; 427/379; 427/535 |
Current CPC
Class: |
B05C 1/0834 20130101;
B05C 1/003 20130101; B05C 11/1042 20130101; B05C 11/06 20130101;
B05D 3/007 20130101; B05D 1/28 20130101; B05C 1/0878 20130101; Y10T
428/249969 20150401; B05C 1/0856 20130101; B05C 11/025 20130101;
B05D 3/002 20130101; B05D 3/08 20130101; B05C 1/0882 20130101; C23C
18/1254 20130101; B05C 1/025 20130101; B05D 3/142 20130101; C23C
18/1241 20130101; B05C 1/083 20130101; C03C 17/00 20130101; C23C
18/1283 20130101; B05C 1/0817 20130101; Y10T 428/265 20150115; B05C
1/0847 20130101 |
Class at
Publication: |
427/8 ;
427/372.2; 427/299; 427/535; 427/314; 427/379; 427/223 |
International
Class: |
B05D 1/28 20060101
B05D001/28; B05D 3/00 20060101 B05D003/00; B05D 3/08 20060101
B05D003/08; B05D 3/14 20060101 B05D003/14 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0003] This invention was made with government support under
Contract DE-EE0006040 awarded by the U.S. Department of Energy. The
government has certain rights in the invention.
Claims
1. A method of coating and curing, comprising: conveying a
substrate to be coated with a conveyor system through a combination
roll coating and curing facility, wherein the combination roll
coating and curing facility comprises at least one roll coating
facility and at least one curing facility; roll coating the
substrate with a sol gel coating material with the at least one
roll coating facility; and curing the sol gel coating material on
the substrate with an air knife of the at least one curing
facility, wherein the air knife applies a heated stream of air to
cure the sol gel coating material while an interior of the
substrate remains at a temperature substantially lower than a
temperature of air from the air knife.
2. The method of claim 1, wherein the substrate is first
pre-treated by washing with water and mechanical brushes prior to
coating.
3. The method of claim 1, wherein the substrate is first
pre-treated by gas plasma prior to coating.
4. The method of claim 1, wherein the substrate is first
pre-treated by exposure to a gas flame prior to coating.
5. The method of claim 1, wherein the substrate is pre-heated to a
temperature of between 2.degree. C. and 80.degree. C. prior to
coating.
6. The method of claim 1, wherein the substrate is coated with a
wet thickness of coating material of between 4 .mu.m and 14
.mu.m.
7. The method of claim 1, wherein a gelation of the sol-gel coating
after roll coating is controlled with a heater.
8. The method of claim 1, wherein a gelation of the sol-gel coating
after roll coating is controlled with forced air at ambient
temperature.
9. The method of claim 1, wherein a solids concentration of the
sol-gel coating material is controlled by adding make-up
solvent.
10. The method of claim 9, wherein the make-up solvent is added at
a constant rate to match a steady-state rate of evaporation.
11. The method of claim 9, wherein the make-up solvent is added
periodically based on pre-determined intervals based on time,
quantities of substrates coated, or coating material consumed.
12. The method of claim 9, wherein the make-up solvent is added
based on an active feedback loop wherein the solids concentration
of the coating material is measured and then used to control the
amount added.
13. The method of claim 12 wherein the solids concentration of the
coating material is measured by at least one of the following;
dynamic light scattering, optical adsorption, refractive index,
density, viscosity, and pH.
14. The method of claim 1, wherein the substrate is heated to a
temperature of between 25.degree. C. and 200.degree. C. after
coating and prior to the air knife.
15. The method of claim 1, wherein the surface of the substantially
flat substrate is heated to between 150.degree. C. to 600.degree.
C. while an interior temperature does not exceed about 100.degree.
C. to about 120.degree. C.
16. The method of claim 1, wherein the sol gel coating material is
continuous.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 14/138,542, now U.S. Pat. No. ______, filed Dec. 23, 2013,
which is incorporated by reference herein in its entirety.
[0002] U.S. application Ser. No. 14/138,542 is a
continuation-in-part of U.S. application Ser. No. 13/835,253, filed
Mar. 15, 2013, which is incorporated by reference in its entirety;
U.S. application Ser. No. 13/835,253 is a non-provisional of U.S.
Provisional Application No. 61/762,603, filed Feb. 8, 2013, which
is also incorporated by reference in its entirety.
BACKGROUND
[0004] 1. Field
[0005] The present disclosure relates generally to the field of
thin-film sol-gel coatings and in particular to coating on
substrates such as glass or solar panels.
[0006] 2. Description of the Related Art
[0007] Thin-film sol-gel coating refers to a technique of coating
substrates, such as optical surfaces, windows, solar panel
surfaces, and the like, using a wet chemical formulation called a
`sol` that undergoes a `gelation` process wherein it polymerizes to
form a solid thin-film on a substrate. These thin-films often
undergo a subsequent curing step to increase mechanical strength
and other properties. This curing is often accomplished by heating
or irradiating the substrate and coating. Thin-film sol-gel coating
is a very versatile process that has many industrial uses such as
formation of dielectric layers on semiconductor wafers and water
repellent layers on ceramics. There are several well documented
techniques for applying wet sol to substrates, some of which are in
widespread industry use and others that have generally been limited
to the laboratory. Industrial scale sol-gel coating is most
commonly performed by a dip, spray, aerosol deposition, spin,
meniscus, slot-die or roller process. There are also several
methods used to cure sol-gel thin films including baking in ovens,
treatment with microwave, infra-red or ultra-violet radiant energy,
and exposure to flowing hot gases. These methods may or may not
work in concert with components of the coating that catalyze or
otherwise aid the curing process.
[0008] In the dip coating process the substrate to be coated is
dipped into a tank containing the sol. It is then withdrawn at a
process dependent speed. As the substrate is slowly drawn from the
sol, the gelation process occurs just above the surface and a
thin-film layer forms. Dip coating processes are inherently two
sided in that all sides and edges of the substrate are coated. This
can be advantageous if complete sol coverage is desired but is
disadvantageous if the coating on some portion of the substrate
interferes with a later substrate processing step. The dip coating
technique requires a tank slightly larger than the substrate, which
for large substrates means the tank may hold a large volume of sol.
For sols mainly composed of organic solvents this may pose a vapor
and flammability hazard. It may also be challenging to control the
composition and quality of the sol within the large tank. Each new
substrate dipped in the tank may carry contamination that is
transferred to the sol; the sol might become depleted in some
element as more substrates are processed causing a variation in the
thin-film produced. The sol may change through evaporation of
solvent at the surface where substrates are introduced.
[0009] Spray coating exists in many forms, but generally may be
considered to be the deposition of material through a nozzle under
pressure or the atomization of material which is then entrained by
a jet of gas. In all cases the material is moved across a gap
between a nozzle and a surface to be coated. The purpose of the
spray system is to deposit a uniform layer of material over a wide
area of the substrate. In the context of sol-gel coatings on
substrates spray coating has the advantage of only applying fresh
material to the substrate. Careful selection of solvents and
control of solvent evaporation is needed to ensure that the correct
final concentration of sol is delivered to the substrate. Spraying
typically requires that either the nozzle or the substrate is moved
in order to coat an area, for example the substrate may be moved
past a line of stationary nozzles.
[0010] Spin coating is commonly used in the semiconductor wafer
processing industry and in the LCD display panel industry to apply
even layers of material to the surface of flat substrates such as
silicon wafers or large pieces of glass. It has the same advantage
as spray coating in that only fresh material is deposited. It also
has excellent uniformity control. Generally, equipment to perform
the spin coating tends to be complex and costly to maintain because
of the fine mechanical control needed to achieve uniformity. This
is particularly true as the size of the substrate increases.
[0011] Meniscus coating was historically used in the semiconductor
industry before giving way to spin coating. It remains in use by
some equipment vendors in the LCD display industry. Meniscus
coating works by passing a substrate to be coated over a narrow
slot at a very close distance such that material forced up through
the slot forms a continuous meniscus with the substrate. As the
substrate moves across the slot this meniscus deposits a layer of
material on the substrate. The technique requires fine control over
the distance between the slot and the substrate across the full
length of the slot. Generally, the substrate must be extremely flat
to avoid deviation in this distance. Additionally, this technique
works best with viscous materials that can form a large meniscus.
This limits its usability with sol-gel formulations that use
comparatively low viscosity solvents.
[0012] Roll coating is a common application method for sol-gel
coatings on flat substrates. In one embodiment of this process,
material is deposited from a reservoir onto an application roller.
A doctor blade or doctor roller may be used to control the
thickness of the coating material placed on the application roller.
That material is then transferred directly from the application
roller to the substrate. In general, roll coating works best with
continuous substrates, such as, for example, a roll of steel. In
the case of discontinuous substrates such as pieces of glass or
wood, for example, special techniques may be employed to control
coating uniformity at the leading and trailing edges of the
substrate. These techniques include, for example, varying the
application roller contact pressure by having the coating roller
touch-down on the leading edge and lift-off the trailing edge in a
precisely controlled manner. The application roller may run in a
forward direction, i.e. rolling with the substrate direction of
movement or in a reverse direction, wherein the application roller
opposes the direction of movement of the substrate. The surface of
the application roller may be made of a compliant material that
serves to compensate for any surface or flatness variations on the
substrate and to provide a surface to which the coating material
will adhere in a reasonably uniform manner, or the application
roller may be a comparatively solid material. Depending on the
rheology of the material to be coated, the surfaces of the rollers
may be patterned with grooves or other textures to add in coating
application.
[0013] Flow coating is a technique where coating material is flowed
over a surface to be coated. The excess drips away and that which
remains on the surface forms the final coating. The surface may be
flat or irregular. In general, the substrate is oriented such that
the coating material flows due to gravity. Advantages of this
technique are its simplicity, ability to coat irregular surfaces,
and the option to use only fresh material or to recirculate the
excess material that drips off the surface.
[0014] It would also be preferable to enable drying and curing of
such coatings at relatively low temperatures, such as below
150.degree. C. so that the coatings could be applied and dried and
cured on substrates to which other temperature sensitive materials
had been previously attached, for example a fully assembled solar
panel.
[0015] The curing process for sol-gel films is a separate process
that occurs after the gelation of the sol-gel material. One common
cure method is to heat a sol-gel coated article in an oven. This
has the advantage of simplicity. The oven may be of the batch type
wherein a batch of coated material is placed in an oven that is
then sealed, and maintained for a period, then opened and the batch
removed. While in the oven, the coater material may be subject to a
varying temperature profile created by the oven's controller.
Alternatively, the oven may be of the continuous type wherein a
conveyor belt or similar transport mechanism moves coated articles
through a heated container. As the material moves through the
container it may experience different temperatures in different
zones creating a temperature profile consisting of heating, soaking
at a fixed temperature, then cooling. The profile may be a function
of the temperature zones within the oven and the speed of the
transport mechanism. Heat within the oven may be provided by
convection with hot gases created by combustion of fuel gas or by
the heating of gas by electrical elements. Alternatively, the
coated article might be heated by radiant heat.
[0016] Some types of sol-gel coatings may be cured with
ultra-violet radiation. In these types of materials, chemical
crosslinking within the material is promoted by high-energy
photons.
[0017] For the curing of thin coatings on surfaces, hot gasses may
be passed directly over the thin-film to heat the surface layer by
conduction.
[0018] Optimal methods for industrial scale sol-gel coating of flat
substrates should be capable of selectively coating just one face
of a substrate; be economical in their use of the coating material;
provide easy compositional and contamination control; be versatile
with respect to the sol-gel formulation such that solvents of
different volatilities can be used and chemically compatible with
critical equipment; be of low complexity and cost; capable of
handling large imperfections in substrate surface flatness, and
capable of achieving superior coating uniformity. Optimal curing
methods should be cost effective; not damage the coated substrate;
match the through-put of the prior coating process step and
effectively cure the coating material to its final desired
properties.
SUMMARY
[0019] In an aspect, a coating and curing apparatus may include a
conveyor system of a combination roll coating and curing facility,
wherein the combination roll coating and curing facility comprises
at least one roll coating facility and at least one curing
facility, and wherein the conveyor system is adapted to transport a
substantially flat substrate through the combination roll coating
and curing facility, a processor that controls a process parameter
of the at least one roll coating facility, and an air knife of the
at least one curing facility, wherein the air knife is adapted to
direct heated air to a portion of the flat substrate as it is
transported through the at least one curing facility, wherein the
at least one roll coating facility is adapted to coat the
substantially flat substrate with a sol gel coating material. The
substantially flat substrate may be a part of at least a partially
finished solar module. The apparatus may further include an
electrical element disposed within the air stream to heat the air
flowing through the air knife. The air may be heated to a
temperature between about 300.degree. C. and 1000.degree. C. The
apparatus may further include a fan in the air stream that directs
air to the air-knife. The apparatus may further include an
electronic controller that controls the temperature based on
readings from at least one temperature sensor located in the air
stream. The apparatus may further include an exhaust to remove
heated air from the apparatus. The apparatus may further include a
flat plate attached to the leading edge of the air-knife, wherein
the flat plate is adapted to form a pre-heat chamber with the top
surface of the substantially flat substrate. The apparatus may
further include an infra-red emitter disposed along the conveyor
system prior to the air knife, wherein the infra-red emitter is
adapted to heat the substantially flat substrate to a temperature
of between 25.degree. C. to 200.degree. C. The apparatus may
further include an infra-red emitter disposed along the conveyor
system subsequent to the air knife, wherein the infra-red emitter
is adapted to maintain the flat substrate at a temperature of
between 120.degree. C. to 400.degree. C. The process parameters may
include at least one of a doctor roller spacing and/or pressure to
an application roller, the application roller spacing or pressure
taken with respect to the substantially flat substrate, a speed at
which the substantially flat substrate is conveyed by the conveyor
system, and in the case of reverse roll-coating, a difference in
speed between the substantially flat substrate and the application
surface of the application roller. The processor may further
control a process parameter of the curing facility. A plurality of
roll coating facilities and curing facilities may be arranged
sequentially. The air-temperature exiting the air knife may be
between 500.degree. C. to 750.degree. C. The speed of the
substantially flat substrate on the conveyor system may be between
0.25 cm/s and 3.5 cm/s. The resulting temperature of a surface of
the substantially flat substrate may be between 150.degree. C. to
600.degree. C.
[0020] In an aspect, a method of coating and curing may include
conveying a substantially flat substrate to be coated with a
conveyor system through a combination roll coating and curing
facility, wherein the combination roll coating and curing facility
comprises at least one roll coating facility and at least one
curing facility, roll coating the substantially flat substrate with
a sol gel coating material with the at least one roll coating
facility, and curing the sol gel coating material on the
substantially flat substrate with an air knife of the at least one
curing facility, wherein the air knife is adapted to direct heated
air to a portion of the substantially flat substrate as it is
transported through the curing facility by the conveyor system. A
sol-gel coated substantially flat substrate may be formed by the
method, wherein a portion of the sol-gel coating material is cured
while a different portion of the sol-gel coating material remains
uncured.
[0021] In an aspect, a method of tuning the performance of a sol
gel coating may include determining a desired cure temperature
profile to achieve a specific performance metric for a sol gel
coating using at least one physical analysis method, selecting
settings for an air knife curing system's operating parameters to
achieve the desired temperature profiles for the sol gel coating on
a substantially flat substrate, and curing the sol-gel coating on
the substantially flat substrate with the air knife curing system.
The at least one physical analysis method may include at least one
of thermogravimetric analysis, Fourier transform infrared
spectroscopy, ellipsometry, nanoindentation, abrasion testing,
spectrophotometry, and a water contact angle measurement. The air
knife curing system operating parameters may include at least one
of substrate speed, air knife air-flow volume, air knife output air
temperature, air knife opening distance to substrate surface, a
temperature set-point for a pre-heating zone and a temperature set
point for a post heating zone. The performance metric for the
sol-gel coating may include at least one of hardness, abrasion
resistance, surface energy, refractive index, optical transmission,
thickness and porosity. The method may further include a step of
coating the substantially flat substrate with the sol gel coating
using a roll-coating system before the step of curing. A sol-gel
coated substantially flat substrate may be formed by the method.
The specific performance metric may include a hardness of the
sol-gel coating within a range of 0.2 GPa to 10 GPa. The specific
performance metric may include a test in which no more than 1% of
absolute optical transmission is lost after at least 500 strokes of
an abrasion test performed in accordance with specification
EN1096-2. The specific performance metric may include a water
contact angle where the water contact angle is within 60.degree. to
120.degree.. The specific performance metric may include a water
contact angle where the water contact angle is within 5.degree. to
30.degree.. The specific performance metric may include a
refractive index of the cured, coated sol gel from 1.25 to 1.45.
The thickness may be approximately 50 nm to 150 nm. A sacrificial
component of the sol-gel coating may be volatilized to form a
desired porosity.
[0022] These and other systems, methods, objects, features, and
advantages of the present disclosure will be apparent to those
skilled in the art from the following detailed description of the
preferred embodiment and the drawings.
[0023] All documents mentioned herein are hereby incorporated in
their entirety by reference. References to items in the singular
should be understood to include items in the plural, and vice
versa, unless explicitly stated otherwise or clear from the text.
Grammatical conjunctions are intended to express any and all
disjunctive and conjunctive combinations of conjoined clauses,
sentences, words, and the like, unless otherwise stated or clear
from the context.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The disclosure and the following detailed description of
certain embodiments thereof may be understood by reference to the
following figures:
[0025] FIG. 1 depicts an embodiment of flow coating;
[0026] FIG. 2 depicts a cross-sectional view of an embodiment of a
flow coating head;
[0027] FIG. 3 depicts a cross-sectional view of a second embodiment
of a flow coating head;
[0028] FIG. 4 depicts an isometric view of a flow coating head
lower slot manifold;
[0029] FIG. 5 depicts a partial view of the assembled flow coating
head of FIG. 2 and a corresponding substrate;
[0030] FIG. 6 shows a schematic cross-sectional view of a coating
slot identifying several critical dimensions and parameters;
[0031] FIGS. 7a and 7b depict a roll-coat system optimized for
coating on flat substrates;
[0032] FIG. 8 depicts an embodiment of a roll-coat system for flat
substrates;
[0033] FIG. 9 depicts an embodiment of a skin-cure system;
[0034] FIG. 10 depicts an example temperature profile for a
skin-cure system.
[0035] FIG. 11 depicts an example of thermogravimetric analysis of
representative samples of coating material.
[0036] FIGS. 12a, FIG. 12b and FIG. 12c show data for an exemplary
sol-gel coating that demonstrate control of final film thickness,
refractive index and water contact angle as a function of maximum
cure temperature.
[0037] FIG. 13 depicts an example of FT-IR analysis of
representative samples of coating material before and after the
curing process.
DETAILED DESCRIPTION
[0038] Various embodiments of the disclosure are described below in
conjunction with the Figures; however, this description should not
be viewed as limiting the scope of the present disclosure. Rather,
it should be considered as exemplary of various embodiments that
fall within the scope of the present disclosure as defined by the
claims. Further, it should also be appreciated that references to
"the disclosure" or "the present disclosure" should not be
construed as meaning that the description is directed to only one
embodiment or that every embodiment must contain a given feature
described in connection with a particular embodiment or described
in connection with the use of such phrases. In fact, various
embodiments with common and differing features are described
herein.
[0039] FIG. 1 depicts an embodiment of laboratory scale flow
coating. In embodiments, a nozzle (101) dispenses a material (102)
onto an inclined substrate (103) as it is moved across the top edge
of the substrate. The material flows down the substrate, and the
excess drips from the bottom edge of the substrate. The material
that remains adhered to the substrate undergoes a gelation process
as it dries and forms a thin-film coating on the substrate.
[0040] While the basic laboratory system shown in FIG. 1 can be
scaled up in substrate size, its rate of coating may be slow and
wasteful of coating material. It is possible to recover the coating
material that drips off the bottom edge and recycle it to the
nozzle, but this makes control of composition and contamination of
the recycled material difficult. What is needed is a flow coating
system that has a fast coating rate and that is economical with
coating material with minimal wastage dripping from the bottom
edge, without recycling of this material.
[0041] In one embodiment, a coating head such as the one shown in
FIG. 5 and in cross-section in FIG. 2 may be used in flow coating.
The coating head includes a long slot (116) formed between a lower
slot manifold (110) and an upper slot manifold (111). This slot is
positioned parallel to and extends along the length of the top edge
of an inclined substrate (120). In an embodiment, the slot is
approximately as long as the edge of the substrate to be coated.
For example, the slot may be oriented along the longer edge of a
rectangular substrate, such that the fluid flows down the substrate
along its shorter edge. This orientation minimizes the time
required for gravity to carry the fluid across the entire area of
the substrate. In an embodiment, a distribution blade (112) bridges
the gap between the slot and the top edge of the substrate such
that coating material flowing out of the slot is deposited on to
the distribution blade and then flows under gravity to the bottom
of the distribution blade, which contacts the front surface of the
substrate just below the top edge of the substrate. The coating
material then flows off the distribution blade onto the front
surface of the substrate and from there down the substrate until
eventually it either drips from the bottom edge or is removed by
other means. The length of the distribution blade is slightly
longer than the length of the slot and of the edge of the substrate
that is being coated. In an embodiment, the distribution blade
extends beyond each end of the slot manifold assemblies. For
example, the distribution blade may extend 2-100 mm beyond each end
of the slot manifold assemblies. In another example, the
distribution blade may extend 10 mm beyond the substrate.
[0042] Coating material is supplied to the slot by a dispensing
system, such as a pump (not shown) capable of transferring the
liquid coating material, and that is also capable of delivering a
measured quantity of coating material through one or more inlet
ports (113) in the lower slot manifold. The inlet port directs
material into a corresponding internal pocket (114) within the
lower slot manifold that allows the coating material to accumulate
below the lip of the slot and to spread evenly along the slot
before it begins to overflow the slot and flow onto the
distribution blade, providing a uniform fluid front of material
over the blade. FIG. 4 shows an isometric view of the internal
detail of a lower slot manifold (110). The coating material flows
from the port inlet, located in the middle of the internal pocket,
outwards toward the ends of the internal pocket and so is
distributed evenly along the back side of the slot lip (140). Once
enough material has filled the internal pocket it will begin to
overflow the slot lip evenly along the length of the slot. The
upper slot manifold (not shown in FIG. 4) forms the opposing side
of the slot. A seal channel (141) may allow the assembly to close
to the appropriate slot width, as is described herein.
[0043] Producing high quality coatings of uniform thickness onto
the substrate may depend on the rate at which the fluid flows
through the slot. In turn, the rate at which the material flows may
be highly dependent upon several factors of the design including
the slot length (l), width (w) (152) and height (h) (151), as seen
in FIG. 6, the viscosity (.mu.) and density (.rho.) of the coating
material, and the pressure differential (.DELTA.P) over the width
of the slot. In an embodiment, the fluid flow in the slot is both
laminar and has a fully developed velocity profile upon exit onto
the distribution blade. Laminar flow in the slot can be achieved by
ensuring the fluid has a Reynolds number less than 1,400. In an
embodiment, the Reynolds number (Re) of the coating fluid within
the slot is less than 100. The coating fluid may exit the slot with
a velocity profile that is independent of subtle edge effects,
turbulence and other disturbances present at the coating fluid's
entry into the slot. This condition can be achieved by ensuring the
width of the slot is significantly longer than the flow's
characteristic entrance length (L.sub.e). In an embodiment, the
slot width is equal to at least 10 times the entrance length. Such
a condition is governed in the following relation, which uses the
Blasius approximation to solve for the entrance length between
parallel surfaces:
L e = hRe h 100 ##EQU00001##
[0044] The volumetric rate at which the coating fluid flows through
the slot is closely approximated by the following relation:
Q = l .DELTA.Ph 3 12 w .mu. ##EQU00002##
[0045] With average flow speed, V, determined by:
V = Q lh ##EQU00003##
[0046] In an embodiment, sol coating flow rates per unit slot
length of between 5.times.10.sup.-9 and 5.times.10.sup.-4 m.sup.2/s
are useful for coating glass substrates of high quality, and
uniform thickness. In an embodiment with a 2 meter long slot, this
equates to a volumetric flow rate between 1.times.10.sup.-7 and
1.times.10.sup.-3 m.sup.3/s. To prevent splatter or turbulent flow
or other undesirable phenomena from impacting the distribution
blade or substrate, coating material may not be forced from the
slot under high pressure or flow rates. For example, gravity force
may be used to drive fluid from the internal pocket to the
distribution blade. In an embodiment, the slot is designed such
that for the chosen coating material properties, the flow rate out
of the slot is less than the flow rate into the internal pocket.
This has the effect of building a reservoir of coating material
behind the slot in the internal pocket, forcing it to spread evenly
under the influence of gravity along the entire length of the slot
and to build up a head height H (150), as in FIG. 6, inside the
internal pocket. If the flow rate through the slot is too high,
then coating material will completely flow through part of the slot
before spreading along the entire length of the slot and reaching
the ends furthest away from the inlet port. If the flow rate is too
low, then the internal pocket may completely fill with coating
material causing an increase in pressure that will create uneven
flow rates and excessive back pressure on the coating fluid, and
adversely affect the flow rate through the slot. All of these
issues can cause the slot flow rate to vary and can affect the
quality and uniformity of the coating. The pressure drop over the
slot width, .DELTA.P, can be related the fluid head height within
the interior pocket, H (150), the internal pocket pressure P.sub.o
(154), pressure at the entrance to the narrow slot, P.sub.1 (153),
and the pressure at the exit of the slot, P.sub.2 (155), the fluid
material density .rho. and the gravitational constant g according
to the following relationship:
.DELTA.P=P.sub.1-P.sub.2
.DELTA.P=.rho.gH+P.sub.o
[0047] This pressure input as a function of head height, combined
with the desired flow rate drives the desired slot height, h (151).
As a result, careful consideration should be paid to the pressure
in the internal pocket. Some embodiments keep the internal pocket
sealed via a gasket, o-ring or sealant such that pressure is
controlled by the relative flow rates of coating material into and
out of the pocket. Other embodiments may include vents between the
internal pocket and ambient pressure or to an auxiliary
pressurization system. In an embodiment, pressure inside the pocket
is vented to the atmosphere and slot height, h, is determined by
the following relationship:
h = 12 Q w .mu. lpgH 3 ##EQU00004##
[0048] Given the above parameters, for a typical sol coating, the
width of the slot is between 0.05 and 2 mm, and preferably 0.1 to
0.5 mm. This width may be controlled by placing shims between the
upper and lower slot manifolds. Alternative embodiments may use
machined steps or other gap control methods. The assembly of upper
and lower slot manifolds may have a gasket-like seal along the top
and sides to ensure material is directed towards the slot. An
O-ring or similar internal pocket seal may allow the assembly to
close to the appropriate slot width, and may be facilitated with
the use of a seal channel (141).
[0049] The distribution blade may serve at least three functions in
enabling consistent and uniform coating thickness; 1) it provides a
path for coating material to flow from the slot to the substrate;
2) it has a high energy surface that causes the material to spread
evenly by surface tension during its travel from the slot to the
substrate; and 3) it provides an interface to the substrate surface
that is tolerant of imperfections in flatness or warping of the
substrate. In one embodiment, the distribution blade is relatively
more flexible than the substrate and is able to conform to an
uneven or warped substrate. For example, the distribution blade is
316L stainless steel, 2020 mm long, 45 mm wide and 0.38 mm thick
and the substrate is tempered soda-lime glass 1970 mm long, 984 mm
wide and 3.2 mm thick. In another embodiment, the distribution
blade is relatively more rigid than the substrate and a mechanism
clamps the substrate to the back surface such that it is held flat
against the distribution blade. In one embodiment, the distribution
blade has a surface energy between 25 mN/m and 100 mN/m.
[0050] The coating material exiting the head slot may not naturally
form a continuous curtain or `waterfall` of coating material in the
absence of the distribution blade, and instead, the coating
material may exit the slot with many drips or small rivulets of
material all along the length of the slot which may not result in a
consistent or uniform thickness coating on the substrate. To
achieve a curtain or "waterfall" out of the slot head in the
absence of the distribution blade would require significantly
greater flow rates of coating material, and could therefore result
in significant waste of coating material. Thus, the distribution
blade enables a consistent and uniform thickness coating with
minimal material waste.
[0051] In FIG. 2, the distribution blade is a thin piece of
material that is held in place by a backing plate (118) that along
with the distribution blade is attached to the upper slot manifold
(111) by a plurality of bolts or other fastening means (119). This
backing plate also serves to tension the distribution blade by
forcing it forward at a slight angle. This reduces warping of the
thin distribution blade along its length. The upper and lower slot
manifolds are held together by a plurality of bolts or other
fastening means (117). In some embodiments the bottom edge of the
thin distribution blade may be beveled or rounded. In a preferred
embodiment it is beveled between 15.degree. and 60.degree..
[0052] In some embodiments the distribution blade is made from a
stainless steel alloy such as 316L. In other embodiments it could
be made from titanium, chrome or nickel plated steel, various
corrosion resistant alloys, glass, ceramics, polymer or composite
materials such as a metal coated polymer. The material may be
chosen to be chemically resistant to the composition of the coating
material such that it is not damaged by the coating material and
such that it does not contaminate the coating material in any
way.
[0053] In FIG. 2, the lower slot manifold has a notch (115) just
below the slot. The purpose of this notch is to prevent the flow of
coating material from the slot along the bottom edge of the lower
slot manifold and from there dripping on to the distribution blade
or the substrate.
[0054] FIG. 3 shows an alternative embodiment of a distribution
blade (130) wherein the blade is a solid piece of material that
also forms the upper slot manifold. The front surface of the blade
(132) acts to distribute the coating material evenly from the slot
to the substrate. The bottom edge of the blade is profiled (133) to
facilitate the flow of coating material from the blade onto the
substrate. It should be understood that the exact shape of this
profile can include curved or angled flat bevels and that the
transition of angle from the face of the distribution blade can
range from gradual to abrupt and that the final angle that the edge
makes with the substrate surface can be from 10.degree. (sharp) to
110.degree. degrees (obtuse). In another embodiment, the thick or
solid distribution blade does not also form the upper slot
manifold, but is instead a separate piece that is bolted onto the
slot manifold in a manner similar to the thin distribution blade
shown in FIG. 2.
[0055] Some embodiments of the distribution blade include coatings
or surface treatments on the front side (that is the wet side) and
on the back side. For example, a front side surface treatment may
enhance the spreading of the coating material as it flows to the
substrate. A back-side treatment might repel the coating material
to suppress material gathering on the backside due to capillary
action that then dripped onto the substrate as it was removed from
the distribution or gather on the backside and contaminate the next
substrate positioned against the blade. Other embodiments of the
distribution blade include laminates and composites where
dissimilar materials are fused or assembled together to provide
differences between the front and backside surface properties as
might also be achieved in the case of a coated metal blade.
[0056] Some embodiments of the coating head manifolds may have
coatings or surface treatments to protect them from adverse
chemical reactions with the coating material or to change how the
coating material flows within the internal pocket or over the slot
lip.
[0057] A full coating head may be composed of a plurality of slot
manifold assemblies. For example each slot manifold assembly might
be 50 cm long. Four such assemblies may be mounted on a supporting
structure such that they form a 200 cm long coating head. The
dimensions of the slot manifold assembly and the number of such
assemblies used for a particular length of coating head may be
selected to manage the cost of manufacturing the slot manifolds
themselves and the complexity of constructing the coating head from
multiple slot manifold assemblies. In the case where multiple slot
manifold assemblies are used to assemble a coating head, it is
advantageous to have a single distribution blade that is continuous
over the entire length of the coating head. However, multiple
adjacent or overlapping segments of distribution blade comprising
the length of the coating head are not precluded.
[0058] It should be understood that the number of internal pockets
and inlet ports within a slot manifold is variable and may be more
or less than the two shown in FIG. 4. The number of pockets and
inlet ports may be selected to manage the manufacturing complexity
of the slot manifold and the uniformity of flow of coating material
from the slot.
[0059] In the slot manifold, the wall between internal pockets may
be kept as thin as possible. This wall affects the flow of material
over the slot lip in its immediate vicinity. By keeping the wall as
thin as is practical, the effect is minimized.
[0060] The method of coating using the apparatus may include the
following steps. First, optionally, the substrate may be prepared
for the coating by increasing the surface energy of the surface to
be coated, thus making it possible for the coating material to
spread evenly on the substrate surface by surface tension. In one
embodiment, the substrate is glass and the surface energy is
increased by washing vigorously with water and/or mechanical
brushes. In other embodiments, the substrate surface may be
prepared using gas plasma such as oxygen or by treatment with a gas
flame. Other pre-treatments are described further herein.
[0061] As an initial step, the substrate is pre-treated or
pre-cleaned to remove surface impurities and to activate the
surface by generating a fresh surface or new binding sites on the
surface. The substrate pre-treatment steps may provide uniform
spreading and deposition of the sol, effective bonding interactions
between the substrate and coating material for Si--O--Si linkage
formation, and prevention of defects and imperfections at the
coating-substrate interface because of uneven spreading and/or
diminished bonding interactions due to surface inhomogeneities.
[0062] In particular, it is desirable to increase the surface
energy of the substrate through pre-treatment or cleaning of the
substrate surface to form an "activated" surface. For example an
activated surface may be one with many exposed Si--OH moieties. An
activated surface reduces the contact angle of the sol and enables
effective wetting of the sol on the surface. In some embodiments, a
combination of physical polishing or cleaning and/or chemical
etching is sufficient to provide even wetting of the sol. In cases,
where the surface tension would need to be further lowered, the
substrate, such as glass, may be pretreated with a dilute
surfactant solution (low molecular weight surfactants such as
surfynol; long chain alcohols such as hexanol or octanol; low
molecular weight ethylene oxide or propylene oxide; or a commercial
dishwasher detergent such as CASCADE, FINISH, or ELECTRASOL to
further help the sol spread better on the glass surface.
[0063] Accordingly, surface preparation may involve a combination
of chemical and physical treatment of the surface. The chemical
treatment steps may include (1) cleaning the surface with a solvent
or combination of solvents, detergents, mild bases like sodium
carbonate or ammonium carbonate (2) cleaning the surface with a
solvent along with an abrasive pad, (3) optionally chemically
etching the surface, and (4) washing the surface with water. The
physical treatment steps may include (1) cleaning the surface with
a solvent or combination of solvents, (2) cleaning the surface with
a solvent along with particulate abrasives, and (3) washing the
surface with water. It should be appreciated that a substrate can
be pre-treated by using only the chemical treatment steps or only
the physical treatment steps. Alternatively, both chemical and
physical treatment steps could be used in any combination. It
should be further appreciated that the physical cleaning action of
friction between a cleaning brush or pad and the surface may be an
important aspect of the surface preparation.
[0064] In the first chemical treatment step, the surface is treated
with a solvent or combination of solvents with variable
hydrophobicity. Typical solvents used are water, ethanol,
isopropanol, acetone, and methyl ethyl ketone. A commercial glass
cleaner (e.g., WINDEX) can also be employed for this purposes. The
surface may be treated with an individual solvent separately or by
using a mixture of solvents. In the second step, an abrasive pad
(e.g., SCOTCHBRITE) is rubbed over the surface with the use of a
solvent, noting that this may be performed in conjunction with the
first step or separately after the first step. In the last step,
the surface is washed or rinsed with water.
[0065] One example of substrate preparation by this method involves
cleaning the surface with an organic solvent such as ethanol,
isopropanol, or acetone to remove organic surface impurities, dirt,
dust, and/or grease (with or without an abrasive pad) followed by
cleaning the surface with water. Another example involves cleaning
the surface with methyl ethyl ketone (with or without an abrasive
pad) followed by washing the surface with water. Another example is
based on using a 1:1 mixture of ethanol and acetone to remove
organic impurities followed by washing the surface with water.
[0066] In some instances an additional, optional step of chemically
etching the surface by means of concentrated nitric acid, sulfuric
acid, or piranha solution (1:1 mixture of 96% sulfuric acid and 30%
H.sub.2O.sub.2) may be necessary to make the surface suitable for
bonding to the deposited sol. Typically this step would be
performed prior the last step of rinsing the surface with water. In
one embodiment, the substrate may be placed in piranha solution for
20 minutes followed by soaking in deionized water for 5 minutes.
The substrate may then be transferred to another container holding
fresh deionized water and soaked for another 5 minutes. Finally,
the substrate is rinsed with deionized water and air-dried.
[0067] The substrate may alternatively or additionally be prepared
by physical treatment. In the physical treatment case, the surface
may simply be cleaned with a solvent and the mechanical action of a
cleaning brush or pad, optionally a surfactant or detergent can be
added to the solvent, after which the substrate is rinsed with
water and air dried. In another embodiment, the surface is first
cleaned with water followed by addition of powdered abrasive
particles such as ceria, titania, zirconia, alumina, aluminum
silicate, silica, magnesium hydroxide, aluminum hydroxide
particles, silicon carbide, or combinations thereof onto the
surface of the substrate to form a slurry or paste on the surface.
The abrasive media can be in the form a powder or it can be in the
form of slurry, dispersion, suspension, emulsion, or paste. The
particle size of the abrasives can vary from 0.1 to 10 microns and
in some embodiments from 1 to 5 microns. The substrate may be
polished with the abrasive slurry via rubbing with a pad (e.g., a
SCOTCHBRITE pad), a cloth, a foam, or paper pad. Alternatively, the
substrate may be polished by placement on the rotating disc of a
polisher followed by application of abrasive slurry on the surface
and rubbing with a pad as the substrate rotates on the disc.
Another alternative method involves use of an electronic polisher
that can be used as a rubbing pad in combination with abrasive
slurry to polish the surface. The substrates polished with the
slurry are cleaned by pressurized water jet and air-dried.
[0068] Next, the substrate to be coated may be positioned with its
top edge aligned with and parallel to the bottom edge of the
distribution blade. The bottom edge of the distribution blade may
overlap slightly with the top edge of the substrate. The amount of
overlap is dependent upon the coating requirements but may be at
least 0.1 mm and in a preferred embodiment be approximately 3 mm.
The ends of the distribution blade may extend slightly beyond the
left and right edges of the substrate, between 2 and 100 mm on each
side. In an embodiment, it extends by 10 mm on each side. The
substrate may be inclined at an angle of 60.degree. to 85.degree.
relative to horizontal. In the case of a flexible thin distribution
blade, the angle between the surface of the substrate and the
surface of the distribution blade may be between 0.degree. and
5.degree.. The substrate can be pushed slightly against the
distribution blade to apply pressure to the contact area such that
the distribution blade conforms to any gross irregularity or
deviation from flatness of the substrate. In the case of a rigid
distribution blade, the substrate may be positioned with its front
surface parallel to the back surface of the distribution blade and
a clamping mechanism may hold the substrate to the distribution
blade such that any warping or deviation from flatness of the
substrate is eliminated against the flat back side of the
distribution blade. In one embodiment, the coating head is
stationary and the substrate is brought to it. However, in other
embodiments, the substrate may be stationary and the coating head
moved to position or both elements may move together to arrive at
the final coating position. It is also possible for both elements
to be stationary relative to each other but to be moving relative
to the larger coating system.
[0069] Next, the front surface of the substrate may be completely
wetted with a pre-wet solution. This pre-wet solution is dispensed
in a manner that quickly wets the entire substrate surface rapidly,
such as in less than 30 seconds. In one embodiment, a plurality of
fan nozzles positioned on a rotatable mechanism above and in front
of the substrate and along its length aligned to the coating head
starts spraying pre-wet solution such that it first wets the
distribution blade along it entire length. Then the nozzle assembly
rotates such that the fan shaped jets of pre-wet solution from the
nozzles travel down the substrate from its top edge to its bottom
edge and in the process deposit pre-wet solution on the full
surface of the distribution blade and the substrate. When employed,
the pre-wet step decreases the time for the coating material to
completely wet the substrate to between 1 and 25 seconds; improves
the uniformity of distribution of the coating material on the
substrate to .+-.25% by volume per unit area and reduces the amount
of coating material needed to completely coat the substrate by up
to 90%. The composition of the pre-wet solution is chosen to
provide a number of properties: The viscosity is within .+-.50% of
the viscosity of the coating material and more preferably within
.+-.10% and even more preferably within .+-.2% and/or the surface
tension is within .+-.50% of the surface tension of the coating
material and more preferably within .+-.10% and even more
preferably within .+-.2% and/or the vapor pressure is within
.+-.50% of the vapor pressure of the coating material and more
preferably within .+-.10% and even more preferably within .+-.2%.
In one embodiment, the pre-wet solution comprises the same mixture
of solvents, mixed in the same ratios as the coating material. For
example, the pre-wet solution might be composed of 90% isopropyl
alcohol and 10% water that approximately matches the ratio of
isopropyl alcohol and water in a sol-gel coating material. In an
alternative embodiment, the pre-wet solution could be a non-ionic,
cationic or anionic surfactant, such as for example Sodium dodecyl
sulfate or perfluoroalkyl sulfonate.
[0070] Next or some time shortly after the pre-wet step has
commenced, a pre-determined amount of coating material may be
dispensed from the coating head on to the substrate. The coating
material flows down the substrate completely covering the front
surface of the substrate. Excess coating material may drip from the
bottom edge or be wicked away from bottom edge by capillary action
onto a mechanism designed for that purpose. In some embodiments,
excess coating material may be collected at the bottom of the
substrate for reuse. The decision to reuse this material or not
depends on the composition of the coating material and substrate.
For example, if the coating material is quite stable and does not
significantly change during the time it travels down the substrate
and if the substrate does not contaminate the coating material then
a decision might be made to reuse excess material collected from
the bottom edge.
[0071] Next, optionally, there may be a pause of between 1 and 600
seconds after the dispensing of coating material has finished while
excess coating material is able to drain out of the internal pocket
and from the wet surface of the distribution blade onto the
substrate. The length of this pause may be optimized to reduce the
possibility of drips from the distribution blade after the
substrate is removed from the coating head. In some embodiments,
this pause may be long enough to allow the distribution blade
and/or the top area of the substrate to dry or partially dry.
[0072] Next, the substrate may be withdrawn from the coating head.
In some embodiments, if the coating head is still wet, a drip guard
may quickly move into place between the substrate and the bottom
edge of the distribution blade. This drip guard may optionally
touch the bottom edge of the blade to wick away excess material in
which case the surface of the drip guard may have similar surface
characteristics to the front surface of the distribution blade to
encourage the coating material to easily flow off the distribution
blade.
[0073] Finally, the substrate may be allowed to dry in a manner
that allows the coating material to undergo gelation such that a
uniform high quality coating is formed on the substrate
surface.
[0074] This coating method, enabled by the novel design of the
coating head can have several of the following advantages over
alternative coating techniques. First, by dispensing material
simultaneously across the full width of the substrate the time to
dispense can be greatly shortened. Second, by pre-wetting the
substrate the amount of time for the coating material to flow down
the substrate can be greatly shortened and the amount of coating
material required to fully wet the substrate surface is greatly
reduced. Third, if coating material is not collected at the bottom
of the substrate for reuse then only fresh (virgin) material can be
deposited on the substrate so control of coating material purity
and composition can be greatly increased. Fourth, by utilizing a
distribution blade in conjunction with a properly sized slot
dispenser, the uniformity of flow of material on to the substrate
can be greatly increased at very low cost and with a very simply
system. Fifth, the technique can be very tolerant of deviation of
flatness on the substrate without requiring any precision
mechanical control or design. Sixth, the method does not
necessarily pose any significant chemical compatibility challenges
where it may be difficult to identify critical coating components
with properties that are not sensitive to or contaminate the
coating material. Finally, the method can be inherently single
sided allowing the flexibility to coat one side of the substrate or
both (in a second coating step) if needed.
[0075] Is should also be understood that in some embodiments the
formulation of the coating material will have a significant effect
on the uniformity of the thin-film. In particular, in a sol-gel
coating material the ratio of solids or particle content to solvent
in conjunction with the ambient conditions during drying may affect
the gelation process that occurs as the thin-film forms. Careful
control of these elements will enhance the uniformity of the final
thin-film especially in the top to bottom direction on the
substrate.
[0076] FIG. 7a shows a simplified schematic of a forward roll
coating apparatus. FIG. 7b shows a simplified schematic of a
reverse roll-coating apparatus. In both figures, a flat substrate
(160) is fed from left to right. A counter pressure roller (163)
supports the substrate from the bottom and moves in a complementary
direction to the movement of the substrate. A coating material
(164) is deposited in a reservoir created between a doctor roller
(162) and an application roller (161). The pressure or spacing of
the doctor roller to application roller controls the amount of
coating material that is transferred to the application roller. The
surfaces of the doctor and application rollers may be smooth or
textured, soft or hard. The roller surfaces need not be the same.
For example, the doctor roller may be compliant and textured while
the application roller could be hard and smooth and vice versa. The
application roller transfers coating material to the surface of the
substrate. The pressure or distance between the application roller
and the substrate surface is adjustable to facilitate control of
the final wet-coating thickness and/or uniformity of the material
on the substrate. In forward roll-coating, the application roller
(161) moves in the same direction as the direction of motion of the
substrate. In reverse roll-coating, the application roller (161)
moves in the opposite direction to the motion of the substrate.
[0077] The substrate may be continuous, such as for example a roll
of polymer sheet or steel, or it may be discontinuous, such as
discrete pieces of glass or wood or individual solar panels. In the
case of discontinuous substrates, the application roller assembly
may be moved in a vertical direction such that it touches down on
the leading edge of the substrate as it enters the roll-coater and
then lifts off the trailing edge as the substrate exits the
roll-coater. This technique may reduce uniformity on the leading
and trailing edges.
[0078] Selection of the materials within the roll-coater that come
into contact with the liquid coating material are a consideration.
In some embodiments, the coating material may be corrosive, having
either a high or low pH. In an embodiment, the pH of the coating
material is between 1.8 and 2.8. Additionally, in some embodiments,
the coating material contains organic solvents such as iso-propyl
alcohol, methanol, ethanol, propylene glycol monomethyl ether,
propylene glycol monomethyl ether acetate, and the like. All
materials may be selected to withstand both the organic solvents
and pH conditions used. For metallic components, stainless steel is
preferential with chrome-plated steel, for example. In selecting
polymer materials for pipes, fittings and seals made from
polytetrafluoroethylene, polypropylene, polyether ether ketone, and
polyvinylidene difluoride may be considered. For polymer coatings
on the rollers polyurethane, EPDM (ethylene propylene diene
monomer) rubber and nitrile rubber are suitable. The particular
embodiment of a roll-coater selected for a specific sol-gel coating
application depends upon a number of factors. The wet film
thickness is a process parameter to consider in achieving the final
cured film thickness. The desired wet thickness may be dependent on
the desired final dry thickness, the solids content of the coating
material and the target porosity of the final dry film. In one
embodiment, the desired final thickness is 120 nm (DT), the solids
content (SC) of the coating material is between 1% and 3% by volume
and the target porosity (P) is 10%. The target wet thickness (WT)
may be calculated with the following formula:
WT = DT SC * ( 1 - P ) ##EQU00005##
[0079] For example, the equation yields a target wet thickness
between approximately 4 .mu.m and 14 .mu.m using the input
parameters above. Wet thickness can be controlled by a number of
process controls on the roll-coater system. Selection of which
parameters are most important is dependent upon the characteristics
of the coating material, such as for example its viscosity, and the
architecture or operation mode of the roll-coater, such as forward
or reverse. Typically, the parameters adjusted are the doctor
roller spacing and/or pressure to the application roller; the
application roller spacing/pressure to the substrate; the speed at
which the substrate moves and in the case of reverse roll-coating
the difference in speed between the substrate and the application
roller. The speed at which the doctor roller moves relative to the
application roller is also a process parameter. FIG. 8 shows an
embodiment of a roll-coater used for sol-gel coating of flat
substrates such as glass or solar panels. The roll-coater (170) is
positioned after a feed-in conveyor (171) and ahead of a feed-out
conveyor (172). In FIG. 8, substrates move from right to left.
Coating material (173) is fed to the roll-coater from a storage
tank at a controlled rate by a pump (174). Excess material is
collected (177) off the ends of the rollers and recirculated. An
optional pre-heater (175) may be positioned such that it can heat
the substrate prior to the roll-coater. The substrate may be heated
to a temperature, such as a temperature between 2.degree. C. and
80.degree. C. In some embodiments, this pre-heat step can serve to
reduce thermal stress during the very rapid heating of subsequent
process step. In other embodiments, it is used to control
evaporation rates of the coating material placed on the substrate
to achieve specific process targets such as uniformity,
film-thickness, porosity or process speed. Careful consideration
should be paid regarding heat transfer from warmed substrates to
the application roller such that it is accounted for in the
process. In one embodiment, a flash-off heater (176) is positioned
at the output of the roll-coater to control evaporation of the
solvent of the coating material to facilitate the gelation of the
thin-film. In some embodiments, the pre-heater and the flash-off
heater may be radiant infra-red or in other embodiments they may be
electric or fuel fired convection heaters. In another embodiment
forced air at ambient or close to ambient temperature could be used
to accomplish the flash-off process by accelerating solvent
evaporation.
[0080] The conveyor systems used to move substrates between process
stages may be continuous belt driven systems. In some embodiments
robots might be used to convey substrates between process stages.
In other embodiment substrates might be conveyed by humans using
carts. In any case it should be understood that substrates may be
conveyed between process steps by many means known in the art.
[0081] An important consideration when using roll-coaters is
accommodating or controlling for evaporation of coating material
solvent from the equipment itself as the machine is running. To
mitigate this evaporation, it can be advantageous to add make-up
solvent to the coating material such that the solids concentration
is controlled within a workable range. Make-up solvent can be added
at a constant rate known to match the steady-state rate of
evaporation; it can be added periodically based on pre-determined
intervals based on time, quantities of substrates coated, or
coating material consumed. Make-up solvent can be added based on an
active feedback loop wherein the solids concentration is measured
directly or indirectly and then used to control the amount added.
Solids concentration might be measured by optical means such as
dynamic light scattering or adsorption or refractive index; it
could be measured by physical properties such as for example
density or viscosity; it could be measured chemically such as for
example monitoring pH.
[0082] Sol-gel materials used for coatings are often sensitive to
environmental conditions such as relative humidity and temperature
during the gelation process. Additionally, sol-gel materials may
release significant amounts of solvent vapor prior to or during
cure. It is therefore desirable to engineer the environment around
the roll-coating system such as that temperature and humidity are
controlled, and solvent vapor is removed. In some embodiments a
containment chamber is built around the complete roll-coater system
with a dedicated HVAC unit to control temperature and relative
humidity. In an embodiment, there is a secondary interior
containment around the coater application roller and the flash-off
area that is small in volume such that its temperature and relative
humidity can be controlled more easily. This interior containment
area is also used to collect solvent vapor for venting, destruction
or recycling. This has an additional advantage to prevent people
working inside the primary containment area from being subjected to
elevated levels of solvent vapor. Such an environmental chamber
system would have safety interlocks such that the tool could be
stopped and any coating material safely contained if the solvent
vapors approached flammability safety limits.
[0083] FIG. 9 shows a cross-sectional schematic view of one
embodiment of a curing apparatus and method for skin-cure. In this
apparatus, an air-knife (180) directs heated air on to the surface
of a substrate (181) presented to the air-knife by a feed-in
conveyor (182) and extracted by a feed-out conveyor (183). The air
may be heated by an electrical element (184), as shown in FIG. 9,
may also be heated by any other method known in the art. The air
may be heated to any temperature useful in the method, such as to a
temperature of 300.degree. C. to 1000.degree. C. Air may be forced
through the heating element and air-knife by a fan (185). The
temperature of the air is controlled by an electronic controller
(186) and temperature sensor (188) located in the heated air
stream. Optionally, overheat protection of the heating element may
be provided by the electronic controller and, optionally, a second
temperature sensor (187) located close to the heating element. When
no substrate is present, air may flow from the fan through the
heating element, through the air-knife and then directly to the
exhaust (197). When a substrate is present, the air flows along the
top surface of the substrate. In an embodiment, a pre-heating stage
(189), for example an infra-red emitter, heats the substrate prior
to the air-knife. The pre-heat temperature is controlled by an
electronic controller (190) and a temperature sensor (191) with an
optional safety over-heat sensor (192). In another embodiment a
flat plate attached to the leading edge of the air-knife forms a
pre-heat chamber (189) with the top surface of substrate. This
pre-heat chamber traps the hot air close to the substrate surface
for a longer period allowing the hot air more time to pre-heat the
substrate surface. A post-heating stage (193), for example an
infra-red emitter (190), located subsequent to the air-knife
provides additional heat that can extend the time that the
substrate stays at an elevated temperature. The post-heating
temperature is controlled by an electronic controller (194) and a
temperature sensor (195), with an optional safety over-heat sensor
(196). In another embodiment, there is a heating element in place
of the pre-heat chamber. The pre-heating of the substrate can serve
to reduce thermal stress during the very rapid heating under the
air-knife and to provide an additional control on the peak
temperature the substrate reaches under the air-knife, the peak
temperature being a function of the initial temperature plus the
temperature rise due to the air-knife.
[0084] A major advantage of this embodiment of a skin-cure system
is that it allows the curing of a thin-film sol-gel coating without
heating the entire substrate to a high temperature. A properly
configured air-knife is able to heat the surface very fast (high
power) without imparting a great deal of heat (energy) to the full
substrate. Thus while the surface heats rapidly to a high
temperature the overall substrate does not heat up excessively. In
one embodiment the substrate is glass coated on one side with
thin-film solar cells, and the opposing side of the glass is the
desired surface for the sol coating. In this case, it is desirable
to avoid heating and raising the temperature of the semiconductor
photovoltaic material as much as possible while curing the sol
coating. Thin-film solar materials such as CdTe, CIGS or amorphous
silicon can be quite sensitive to elevated temperatures. High
temperatures can cause dopants within the material to defuse in a
detrimental manner or can cause metal electrode materials to defuse
into the photovoltaic material. In some embodiments, the
temperature of the photovoltaic cell may be kept from exceeding
100.degree. C. to 120.degree. C. as the sol is cured. Additionally,
polymer materials within the finished solar panel such as
encapsulates may be kept from exceeding their glass transition
temperature of 150.degree. C. to 200.degree. C.
[0085] FIG. 10 shows an example temperature profile for a skin-cure
system. In this example the substrate is a dummy thin-film solar
module consisting of two pieces of glass typical of those used in
thin-film module manufacturing, laminated together with temperature
sensors embedded between the glass sheets such that they measure
the interior temperature of the dummy module and temperature
sensors attached to the top surface. The module was moved at a
speed of 1 cm/s under an air-knife set to an exit air temperature
of approximately 650.degree. C. and a gap distance (from substrate
top surface to the air-knife opening) of approximately 1 cm. Two
temperatures are shown, the top surface temperature representing
the temperature reached by the interior of the dummy module. In
this example the pre-heat chamber embodiment was used. From the
profile, the pre-heat chamber caused an initial rise in temperature
of the top surface (202) to approximately 100.degree. C., there
after the air-knife caused a very rapid temperature rise (200) to
approximately 300.degree. C. after which the post-heat infra-red
emitter set to a temperature of 300.degree. C. as measured by a
sensor placed between the substrate and the IR emitter, maintains
the top surface temperature (201) at approximately 200.degree. C.
Through-out the process the interior temperature never exceeds
approximately 90.degree. C.
[0086] In one embodiment, the substrate is glass of thickness 1 mm
to 4 mm. In an embodiment of a skin-cure apparatus, the
air-temperature exiting the air knife is between 500.degree. C. to
750.degree. C. as controlled by the power setting of the heating
element and the volume of air provided by the fan. The speed of the
substrate is between 0.25 cm/s and 3.5 cm/s. The resulting
temperature of the substrate surface is between 150.degree. C. to
600.degree. C. and this temperature is attained between the start
of the pre-heat chamber and the end of the air-knife. In other
embodiments the substrate is pre-heated by an infra-red emitter to
approximately 25.degree. C. to 200.degree. C. prior to the
air-knife wherein it is further heated to approximately 150.degree.
C. to 600.degree. C. Thereafter, the substrate is maintained at a
temperature of between 120.degree. C. to 400.degree. C. until the
end of the post-heat section. Such a configuration of the skin-cure
apparatus has been shown to cure the sol coating while leaving the
opposing surface at a temperature below 120.degree. C.
[0087] The process of rapidly heating the substrate using the
air-knife and then maintaining that temperature with radiant heat
facilitates the curing of the sol-gel material. In an embodiment,
the curing is achieved by providing sufficient energy so that a
sufficient portion of the remaining Si--OH moieties within the
coating undergo a condensation reaction and form Si--O--Si
crosslinks that greatly strengthen the material enabling it to pass
Taber abrasion testing to standard EN-1096-2 with no more than 0.5%
loss of absolute transmission. In other embodiments, the curing
temperature is used to facilitate other processes such as
volatizing a sacrificial component of the coating to form a desired
porosity or a desired surface morphology. Other embodiments may use
very high temperatures to completely oxidize all organic components
in the coating creating a hydrophilic pure silica film. Yet further
embodiments may use the heat and/or reactive gas composition of the
air-knife to initiate chemical reactions that modify the properties
of the coating, such as for example, surface energy, color,
refractive index, surface morphology and surface chemistry. In
embodiments, the skin-cure process works in concert with the
composition and properties of the coating material to facilitate
tuning of the properties of the final thin-film coating.
[0088] FIG. 11 shows a thermogravimetric analysis of representative
samples of coating material. Thermogravimetric analysis is
performed by heating a sample gradually and recording the loss of
mass as various components of the sample volatize. When performed
on coating materials such as these example sol-gel coatings for
glass, it can be used to determine critical temperatures required
to cure the coating material. The figure shows three temperatures
of interest. Using Sample 1 in FIG. 11 as an illustrative example,
there is a point of inflection (210) at approximately 125.degree.
C., another much steeper point of inflection (211) at approximately
450.degree. C. finally there is a flattening out (212) above
500.degree. C. Without being bound by theory, these three points
are interpreted as follows. As temperature increases to point 210
any residual water and solvent is volatilized and all easily
accessible Si--OH moieties react and release water. This represents
a substantially cured film that has attained a useful hardness and
abrasion resistance at a relatively low temperature. Further
heating in the range from point 210 until point 211 represents an
approximately linear reduction in mass as additional remaining
Si--OH moieties condense and release water. This temperature range
represents increasing hardness and abrasion resistance of the
material with increasing temperature, without detrimental effects
on the coating. This reduction in mass causes a corresponding
decrease in density and hence a decrease in refractive index. In
coating materials that form hydrophobic films, the reduction in
Si--OH will also result in an increase of the hydrophobic effect as
measured by increasing water contact angle. Heating beyond point
211 begins to oxidize organic moieties within the coating, the
byproducts of which may then volatilize. In some embodiments these
moieties may be methyl groups or other hydro-carbon groups or
fluoro-carbon chains or any combination thereof. Other reactions
may also occur such as for example the formation of SiC and SiOC.
This temperature regime may be generalized as the oxidation of the
organic components of the coating, reactions between byproducts of
that oxidation with each other and with components of the film
itself and the transformation of the coating to a substantially
inorganic silica coating. At this point further heating no longer
causes significant mass loss and the curve flattens out as
indicated by point 212. Sample 2 is a different sol-gel coating
material for glass, however, it also exhibits approximately the
same shape and inflection points as Sample 1. It also illustrates
that when more complex organic moieties are present in the coating
the transformation that occurs after the second inflection point
can be more complex and more prolonged. Therefore for the purposes
of developing a process for curing these coatings we can determine
from this analysis that a first low temperature cure can be
accomplished at a temperature of approximately 125.degree. C., that
is the first point of inflection. A second higher temperature cure
at the second point of inflection (approximately 450.degree. C. for
the material in Sample 1 and 350.degree. C. for the material in
Sample 2) results in increased hardness, abrasion resistance and
hydrophobicity. Temperatures beyond the second inflection point
result in the breakdown and modification of organic moieties that
may in some embodiments be useful.
[0089] The curing process parameters including substrate speed, air
knife output air temperature, air knife air flow volume, air knife
opening distance to substrate surface, pre and post heating set
temperatures are used to control process cure parameters including
maximum temperature, rate of heating, duration at temperature,
cumulative temperature exposure and rate of cooling that can be
used to tune specific properties of the final cured film. One
property is hardness as measured by nanoindentation methods. In
some embodiments, the curing system described herein may cure
sol-gel coatings on glass substrates to a hardness of approximately
0.2 GPa to 10 GPa and preferably to a hardness of approximately 2
GPa to 4 GPa. Another property is abrasion resistance. In some
embodiments, the curing system described herein may cure sol-gel
coatings on glass substrates to an abrasion resistance whereby they
lose no more than 1% of absolute optical transmission as measured
by spectrophotometer after 500 strokes of an abrasion test
performed in accordance with specification EN1096-2 and preferably
no more than 0.5% loss of absolute optical transmission after 1000
strokes. Such a test can be performed using a Taber reciprocating
abrader model 5900 with a ratcheting arm assembly. A third property
is surface energy as measured by water contact angle (WCA). In some
embodiments the curing system described herein may cure sol-gel
coatings to a WCA of approximately 60.degree. to 120.degree. and
preferably to a WCA of approximately 70.degree. to 100.degree.. In
other embodiments the film can be cured to a WCA of approximately
5.degree. to 30.degree. and preferably a WCA of approximately
10.degree. to 20.degree.. A fourth property is refractive index
(RI) as measured by ellipsometer. In some embodiments curing system
described herein may cure sol-gel coatings to a RI of approximately
1.25 to 1.45 and preferably a RI of approximately 1.35 to 1.42. A
fifth property is final film thickness as measured by ellipsometer.
The final film thickness is a function of the initial (pre-cure)
dry film thickness and the cure parameters such that the cure
parameters modify the initial dry thickness. In some embodiments
the curing system described herein may cure sol-gel coatings to a
thickness of 50 nm to 150 nm and to a preferred thickness of 70 nm
to 130 nm.
[0090] FIGS. 12a, FIG. 12b and FIG. 12c depict data for an
exemplary sol-gel coating that demonstrate control of final film
thickness, refractive index and water contact angle as a function
of maximum cure temperature.
[0091] FIG. 13 shows Fourier transform infrared spectroscopy data
for an exemplary sol-gel coating material taken before and after a
cure process step. This analysis technique shows how chemical bonds
within the material change during the curing process. In particular
the spectral peaks denoted by points 220, 221 & 222 have
changed during the process. Without being bound by theory, these
changes can be interpreted as the reduction of Si--OH bonds through
condensation causing the reduction of the peaks at points 220 and
222. These bonds are converted to Si--O--Si bonds causing the
increase in the peak at point 221. This analysis technique can be
used to quantify the proportion of Si--OH bonds that condense and
hence to quantify the degree to which the film is cured.
[0092] The coating and curing process steps may further be
configured in to create coatings of varying complexity and
structure. In embodiments, any combination of coating technique and
curing technique may be used to achieve a final coating for a
substrate. Embodiments of such combinations may include coating via
a flow coating technique followed by a skin cure process or cure by
conventional means, coating via a roll coating technique followed
by a skin cure process or cure by conventional means, and the like.
To generate multilayer coatings, any combination of coating and
curing apparatus may be used sequentially to generate such a
coating. The sequential use of such apparatus may be enabled by an
arrangement that places multiple coating apparatus and curing
apparatus in sequence. Alternatively, handling facilities may exist
for handling the substrate between one or more coating and curing
apparatus. For example, two roll-coaters may be placed in sequence
with an optional flash-off heater in between. This facilitates
coating of a first layer by the first roll-coater, drying of the
layer by the flash-off station, then deposition of a second layer
by the second roll-coater before curing in a skin-cure station or
in a simple oven. Alternatively, a high temperature skin-cure step
may be interposed between the roll-coaters to enable a high
temperature heat treatment to the first layer before application of
the second layer. It is understood that this technique for multiple
layer coatings may be extended to more than two layers. Multi-layer
coatings manufactured by this technique may be high performance
anti-reflective interference type coatings or multiple layers
coatings could be used to modify the surface energy of the top
surface coating by for example adding a fluorinated silane
mono-layer to an underlying layer to make the final coating
hydrophobic and oleophobic on the environmentally exposed surface.
The multi-layer coatings may be used to enhance single layer
anti-reflective coatings by adding a lower refractive index
material on the environmentally exposed surface to create a graded
index coating between the environment and the underlying
substrate.
[0093] The foregoing apparatus and methods are particularly well
suited to the application of sol-gel thin-films to glass. In an
embodiment, the glass to be coated is the front (sun facing)
surface of a solar panel and the sol-gel thin-film is an
anti-reflective coating. Either bare glass may be coated and/or
cured by the apparatus or fully assembled solar panels or solar
panels at any intermediate stage of manufacture. In other
embodiments, the apparatus may be used to coat and/or cure windows,
architectural glass, displays, lenses, mirrors or other electronic
devices.
[0094] Embodiments described herein are well suited to performing
various other steps or variations of the steps recited herein, and
in a sequence other than that depicted and/or described herein.
[0095] It should be appreciated that reference throughout this
specification to "one embodiment" or "an embodiment" means that a
particular feature, structure or characteristic described in
connection with the embodiment is included in at least one
embodiment of the present disclosure. Therefore, it is emphasized
and should be appreciated that two or more references to "an
embodiment" or "one embodiment" or "an alternative embodiment" in
various portions of this specification are not necessarily all
referring to the same embodiment. Furthermore, the particular
features, structures or characteristics may be combined as suitable
in one or more embodiments of the disclosure.
[0096] Similarly, it should be appreciated that in the foregoing
description of exemplary embodiments of the disclosure, various
features of the disclosure are sometimes grouped together in a
single embodiment, figure, or description thereof for the purpose
of streamlining the disclosure aiding in the understanding of one
or more of the various inventive aspects. This method of
disclosure, however, is not to be interpreted as reflecting an
intention that the claimed disclosure requires more features than
are expressly recited in each claim. Rather, as the following
claims reflect, inventive aspects lie in less than all features of
a single foregoing disclosed embodiment. Thus, the claims following
the detailed description are hereby expressly incorporated into
this detailed description, with each claim standing on its own as a
separate embodiment of this disclosure.
[0097] While only a few embodiments of the present disclosure have
been shown and described, it will be obvious to those skilled in
the art that many changes and modifications may be made thereunto
without departing from the spirit and scope of the present
disclosure as described in the following claims. All patent
applications and patents, both foreign and domestic, and all other
publications referenced herein are incorporated herein in their
entireties to the full extent permitted by law.
[0098] The methods and systems described herein may be deployed in
part or in whole through a machine that executes computer software,
program codes, and/or instructions on a processor. The present
disclosure may be implemented as a method on the machine, as a
system or apparatus as part of or in relation to the machine, or as
a computer program product embodied in a computer readable medium
executing on one or more of the machines. In embodiments, the
processor may be part of a server, cloud server, client, network
infrastructure, mobile computing platform, stationary computing
platform, or other computing platform. A processor may be any kind
of computational or processing device capable of executing program
instructions, codes, binary instructions and the like. The
processor may be or may include a signal processor, digital
processor, embedded processor, microprocessor or any variant such
as a co-processor (math co-processor, graphic co-processor,
communication co-processor and the like) and the like that may
directly or indirectly facilitate execution of program code or
program instructions stored thereon. In addition, the processor may
enable execution of multiple programs, threads, and codes. The
threads may be executed simultaneously to enhance the performance
of the processor and to facilitate simultaneous operations of the
application. By way of implementation, methods, program codes,
program instructions and the like described herein may be
implemented in one or more thread. The thread may spawn other
threads that may have assigned priorities associated with them; the
processor may execute these threads based on priority or any other
order based on instructions provided in the program code. The
processor, or any machine utilizing one, may include memory that
stores methods, codes, instructions and programs as described
herein and elsewhere. The processor may access a storage medium
through an interface that may store methods, codes, and
instructions as described herein and elsewhere. The storage medium
associated with the processor for storing methods, programs, codes,
program instructions or other type of instructions capable of being
executed by the computing or processing device may include but may
not be limited to one or more of a CD-ROM, DVD, memory, hard disk,
flash drive, RAM, ROM, cache and the like.
[0099] A processor may include one or more cores that may enhance
speed and performance of a multiprocessor. In embodiments, the
process may be a dual core processor, quad core processors, other
chip-level multiprocessor and the like that combine two or more
independent cores (called a die).
[0100] The methods and systems described herein may be deployed in
part or in whole through a machine that executes computer software
on a server, client, firewall, gateway, hub, router, or other such
computer and/or networking hardware. The software program may be
associated with a server that may include a file server, print
server, domain server, internet server, intranet server, cloud
server, and other variants such as secondary server, host server,
distributed server and the like. The server may include one or more
of memories, processors, computer readable media, storage media,
ports (physical and virtual), communication devices, and interfaces
capable of accessing other servers, clients, machines, and devices
through a wired or a wireless medium, and the like. The methods,
programs, or codes as described herein and elsewhere may be
executed by the server. In addition, other devices required for
execution of methods as described in this application may be
considered as a part of the infrastructure associated with the
server.
[0101] The server may provide an interface to other devices
including, without limitation, clients, other servers, printers,
database servers, print servers, file servers, communication
servers, distributed servers, social networks, and the like.
Additionally, this coupling and/or connection may facilitate remote
execution of program across the network. The networking of some or
all of these devices may facilitate parallel processing of a
program or method at one or more location without deviating from
the scope of the disclosure. In addition, any of the devices
attached to the server through an interface may include at least
one storage medium capable of storing methods, programs, code
and/or instructions. A central repository may provide program
instructions to be executed on different devices. In this
implementation, the remote repository may act as a storage medium
for program code, instructions, and programs.
[0102] The software program may be associated with a client that
may include a file client, print client, domain client, internet
client, intranet client and other variants such as secondary
client, host client, distributed client and the like. The client
may include one or more of memories, processors, computer readable
media, storage media, ports (physical and virtual), communication
devices, and interfaces capable of accessing other clients,
servers, machines, and devices through a wired or a wireless
medium, and the like. The methods, programs, or codes as described
herein and elsewhere may be executed by the client. In addition,
other devices required for execution of methods as described in
this application may be considered as a part of the infrastructure
associated with the client.
[0103] The client may provide an interface to other devices
including, without limitation, servers, other clients, printers,
database servers, print servers, file servers, communication
servers, distributed servers and the like. Additionally, this
coupling and/or connection may facilitate remote execution of
program across the network. The networking of some or all of these
devices may facilitate parallel processing of a program or method
at one or more location without deviating from the scope of the
disclosure. In addition, any of the devices attached to the client
through an interface may include at least one storage medium
capable of storing methods, programs, applications, code and/or
instructions. A central repository may provide program instructions
to be executed on different devices. In this implementation, the
remote repository may act as a storage medium for program code,
instructions, and programs.
[0104] The methods and systems described herein may be deployed in
part or in whole through network infrastructures. The network
infrastructure may include elements such as computing devices,
servers, routers, hubs, firewalls, clients, personal computers,
communication devices, routing devices and other active and passive
devices, modules and/or components as known in the art. The
computing and/or non-computing device(s) associated with the
network infrastructure may include, apart from other components, a
storage medium such as flash memory, buffer, stack, RAM, ROM and
the like. The processes, methods, program codes, instructions
described herein and elsewhere may be executed by one or more of
the network infrastructural elements. The methods and systems
described herein may be adapted for use with any kind of private,
community, or hybrid cloud computing network or cloud computing
environment, including those which involve features of software as
a service (SaaS), platform as a service (PaaS), and/or
infrastructure as a service (IaaS).
[0105] The methods, program codes, and instructions described
herein and elsewhere may be implemented on a cellular network
having multiple cells. The cellular network may either be frequency
division multiple access (FDMA) network or code division multiple
access (CDMA) network. The cellular network may include mobile
devices, cell sites, base stations, repeaters, antennas, towers,
and the like. The cell network may be a GSM, GPRS, 3G, EVDO, mesh,
or other networks types.
[0106] The methods, program codes, and instructions described
herein and elsewhere may be implemented on or through mobile
devices. The mobile devices may include navigation devices, cell
phones, mobile phones, mobile personal digital assistants, laptops,
palmtops, netbooks, pagers, electronic books readers, music players
and the like. These devices may include, apart from other
components, a storage medium such as a flash memory, buffer, RAM,
ROM and one or more computing devices. The computing devices
associated with mobile devices may be enabled to execute program
codes, methods, and instructions stored thereon. Alternatively, the
mobile devices may be configured to execute instructions in
collaboration with other devices. The mobile devices may
communicate with base stations interfaced with servers and
configured to execute program codes. The mobile devices may
communicate on a peer-to-peer network, mesh network, or other
communications network. The program code may be stored on the
storage medium associated with the server and executed by a
computing device embedded within the server. The base station may
include a computing device and a storage medium. The storage device
may store program codes and instructions executed by the computing
devices associated with the base station.
[0107] The computer software, program codes, and/or instructions
may be stored and/or accessed on machine readable media that may
include: computer components, devices, and recording media that
retain digital data used for computing for some interval of time;
semiconductor storage known as random access memory (RAM); mass
storage typically for more permanent storage, such as optical
discs, forms of magnetic storage like hard disks, tapes, drums,
cards and other types; processor registers, cache memory, volatile
memory, non-volatile memory; optical storage such as CD, DVD;
removable media such as flash memory (e.g. USB sticks or keys),
floppy disks, magnetic tape, paper tape, punch cards, standalone
RAM disks, Zip drives, removable mass storage, off-line, and the
like; other computer memory such as dynamic memory, static memory,
read/write storage, mutable storage, read only, random access,
sequential access, location addressable, file addressable, content
addressable, network attached storage, storage area network, bar
codes, magnetic ink, and the like.
[0108] The methods and systems described herein may transform
physical and/or or intangible items from one state to another. The
methods and systems described herein may also transform data
representing physical and/or intangible items from one state to
another.
[0109] The elements described and depicted herein, including in
flow charts and block diagrams throughout the figures, imply
logical boundaries between the elements. However, according to
software or hardware engineering practices, the depicted elements
and the functions thereof may be implemented on machines through
computer executable media having a processor capable of executing
program instructions stored thereon as a monolithic software
structure, as standalone software modules, or as modules that
employ external routines, code, services, and so forth, or any
combination of these, and all such implementations may be within
the scope of the present disclosure. Examples of such machines may
include, but may not be limited to, personal digital assistants,
laptops, personal computers, mobile phones, other handheld
computing devices, medical equipment, wired or wireless
communication devices, transducers, chips, calculators, satellites,
tablet PCs, electronic books, gadgets, electronic devices, devices
having artificial intelligence, computing devices, networking
equipment, servers, routers and the like. Furthermore, the elements
depicted in the flow chart and block diagrams or any other logical
component may be implemented on a machine capable of executing
program instructions. Thus, while the foregoing drawings and
descriptions set forth functional aspects of the disclosed systems,
no particular arrangement of software for implementing these
functional aspects should be inferred from these descriptions
unless explicitly stated or otherwise clear from the context.
Similarly, it will be appreciated that the various steps identified
and described above may be varied, and that the order of steps may
be adapted to particular applications of the techniques disclosed
herein. All such variations and modifications are intended to fall
within the scope of this disclosure. As such, the depiction and/or
description of an order for various steps should not be understood
to require a particular order of execution for those steps, unless
required by a particular application, or explicitly stated or
otherwise clear from the context.
[0110] The methods and/or processes described above, and steps
associated therewith, may be realized in hardware, software or any
combination of hardware and software suitable for a particular
application. The hardware may include a general-purpose computer
and/or dedicated computing device or specific computing device or
particular aspect or component of a specific computing device. The
processes may be realized in one or more microprocessors,
microcontrollers, embedded microcontrollers, programmable digital
signal processors or other programmable device, along with internal
and/or external memory. The processes may also, or instead, be
embodied in an application specific integrated circuit, a
programmable gate array, programmable array logic, or any other
device or combination of devices that may be configured to process
electronic signals. It will further be appreciated that one or more
of the processes may be realized as a computer executable code
capable of being executed on a machine-readable medium.
[0111] The computer executable code may be created using a
structured programming language such as C, an object oriented
programming language such as C++, or any other high-level or
low-level programming language (including assembly languages,
hardware description languages, and database programming languages
and technologies) that may be stored, compiled or interpreted to
run on one of the above devices, as well as heterogeneous
combinations of processors, processor architectures, or
combinations of different hardware and software, or any other
machine capable of executing program instructions.
[0112] Thus, in one aspect, methods described above and
combinations thereof may be embodied in computer executable code
that, when executing on one or more computing devices, performs the
steps thereof. In another aspect, the methods may be embodied in
systems that perform the steps thereof, and may be distributed
across devices in a number of ways, or all of the functionality may
be integrated into a dedicated, standalone device or other
hardware. In another aspect, the means for performing the steps
associated with the processes described above may include any of
the hardware and/or software described above. All such permutations
and combinations are intended to fall within the scope of the
present disclosure.
[0113] While the disclosure has been disclosed in connection with
the preferred embodiments shown and described in detail, various
modifications and improvements thereon will become readily apparent
to those skilled in the art. Accordingly, the spirit and scope of
the present disclosure is not to be limited by the foregoing
examples, but is to be understood in the broadest sense allowable
by law.
[0114] The use of the terms "a" and "an" and "the" and similar
referents in the context of describing the disclosure (especially
in the context of the following claims) is to be construed to cover
both the singular and the plural, unless otherwise indicated herein
or clearly contradicted by context. The terms "comprising,"
"having," "including," and "containing" are to be construed as
open-ended terms (i.e., meaning "including, but not limited to,")
unless otherwise noted. Recitation of ranges of values herein are
merely intended to serve as a shorthand method of referring
individually to each separate value falling within the range,
unless otherwise indicated herein, and each separate value is
incorporated into the specification as if it were individually
recited herein. All methods described herein can be performed in
any suitable order unless otherwise indicated herein or otherwise
clearly contradicted by context. The use of any and all examples,
or exemplary language (e.g., "such as") provided herein, is
intended merely to better illuminate the disclosure and does not
pose a limitation on the scope of the disclosure unless otherwise
claimed. No language in the specification should be construed as
indicating any non-claimed element as essential to the practice of
the disclosure.
[0115] While the foregoing written description enables one of
ordinary skill to make and use what is considered presently to be
the best mode thereof, those of ordinary skill will understand and
appreciate the existence of variations, combinations, and
equivalents of the specific embodiment, method, and examples
herein. The disclosure should therefore not be limited by the above
described embodiment, method, and examples, but by all embodiments
and methods within the scope and spirit of the disclosure.
[0116] All documents referenced herein are hereby incorporated by
reference.
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