U.S. patent application number 14/044234 was filed with the patent office on 2014-09-18 for anti-glare coatings with aqueous particle dispersions and methods for forming the same.
This patent application is currently assigned to Intermolecular Inc.. The applicant listed for this patent is Intermolecular Inc.. Invention is credited to Scott Jewhurst, Nikhil Kalyankar.
Application Number | 20140272387 14/044234 |
Document ID | / |
Family ID | 51528221 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140272387 |
Kind Code |
A1 |
Jewhurst; Scott ; et
al. |
September 18, 2014 |
Anti-Glare Coatings with Aqueous Particle Dispersions and Methods
for Forming the Same
Abstract
Embodiments provided herein describe optical coatings, panels
having optical coatings thereon, and methods for forming optical
coatings and panels. A substrate is provided. A coating formulation
is applied to the substrate. The coating formulation includes an
aqueous-based suspension of particles. The particles have a
sheet-like morphology and a thickness of less than about 100
nanometers (nm). The coating formulation is cured to form an
anti-glare coating above the substrate. The anti-glare coating has
a thickness of between 1 micrometer (.mu.m) and 100 .mu.m.
Inventors: |
Jewhurst; Scott; (Redwood
City, CA) ; Kalyankar; Nikhil; (Mountain View,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Intermolecular Inc. |
San Jose |
CA |
US |
|
|
Assignee: |
Intermolecular Inc.
San Jose
CA
|
Family ID: |
51528221 |
Appl. No.: |
14/044234 |
Filed: |
October 2, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61777995 |
Mar 12, 2013 |
|
|
|
Current U.S.
Class: |
428/331 ;
427/162; 427/164; 427/165; 427/515; 427/558; 428/323 |
Current CPC
Class: |
G02B 5/0294 20130101;
G02B 1/113 20130101; Y10T 428/259 20150115; G02B 2207/109 20130101;
C09D 5/006 20130101; G02B 2207/107 20130101; Y10T 428/25 20150115;
G02B 1/12 20130101; C09D 7/63 20180101 |
Class at
Publication: |
428/331 ;
428/323; 427/162; 427/558; 427/165; 427/164; 427/515 |
International
Class: |
C09D 5/00 20060101
C09D005/00; G02B 1/11 20060101 G02B001/11 |
Claims
1. A method for coating an article, the method comprising:
providing a substrate; applying a coating formulation to the
substrate, the coating formulation comprising an aqueous-based
suspension of particles, wherein the particles have a sheet-like
morphology and a thickness of less than about 100 nanometers (nm);
and curing the coating formulation to form an anti-glare coating
above the substrate, the anti-glare coating having a thickness of
between 1 micrometer (.mu.m) and 100 .mu.m.
2. The method of claim 1, wherein the coating formulation further
comprises a hydrophilic silicone or silane emulsion, a hydrophilic
silicone or silane solution, or a combination thereof.
3. The method of claim 1, wherein the particles comprise silicon
oxide.
4. The method of claim 1, wherein the coating formulation further
comprises a plurality of nano-particles.
5. The method of claim 4, wherein each of the nano-particles has a
width of between about 3 and 50 nm.
6. The method of claim 5, wherein each of the nano-particles are
made of a metal oxide.
7. The method of claim 1, wherein the coating formulation comprises
a silane emulsion, and wherein the silane emulsion comprises an
aminoalkoxysilane, a glycidoxyalkoxysilane, a carboxylalkoxysilane,
a water soluble silicate, a hydrophilic alkoxysilane, or a
combination thereof.
8. The method of claim 5, wherein the curing the coating
formulation comprises an ultraviolet (UV) cure, a thermal cure, or
a combination thereof.
9. The method of claim 1, wherein the coating formulation is a
sol-gel formulation.
10. The method of claim 1, wherein the substrate comprises
glass.
11. A method for coating an article, the method comprising:
providing a transparent substrate; applying a coating formulation
to the transparent substrate, the coating formulation comprising an
aqueous-based suspension of particles and a hydrophilic silicone or
silane emulsion, a hydrophilic silicone or silane solution, or a
combination thereof, wherein the particles have a sheet-like
morphology and a thickness that is less than about 100 nanometers
(nm); and curing the coating formulation to form an coating above
the transparent substrate, the coating having a thickness of
between 1 micrometer (.mu.m) and 100 .mu.m.
12. The method of claim 11, wherein the particles comprise silicon
oxide.
13. The method of claim 12, wherein the coating formulation further
comprises a plurality of nano-particles, wherein each of the
nano-particles has a width of between about 3 and 50 nm.
14. The method of claim 13, wherein the curing the coating
formulation comprises an ultraviolet (UV) cure, a thermal cure, or
a combination thereof.
15. The method of claim 14, wherein the coating formulation is a
sol-gel formulation.
16. A coated article comprising: a substrate; and a coating formed
above the substrate, the coating comprising an aqueous-based
suspension of particles and having a thickness of between 1
micrometer (.mu.m) and 100 .mu.m, wherein the particles have a
sheet-like morphology and a thickness of less than about 100
nanometers (nm).
17. The coated article of claim 16, wherein the coating further
comprises at least one of a hydrophilic silicone, water soluble
silicate or silane emulsion a hydrophilic silicone or silane
emulsion, a hydrophilic silicone or silane solution, or a
combination thereof.
18. The coated article of claim 17, wherein the coating comprises a
silane emulsion, and wherein the silane emulsion comprises an
aminoalkoxysilane, a glycidoxyalkoxysilane, a carboxylalkoxysilane,
a water soluble silicate, a hydrophilic alkoxysilane, or a
combination thereof.
19. The coated article of claim 18, wherein the coating further
comprises a plurality of nano-particles, wherein each of
nano-particles has a width of between about 3 and 50 nm.
20. The coated article of claim 16, wherein each of the particles
comprises silicon oxide.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional Patent
Application No. 61/777,995, filed Mar. 12, 2013, entitled "Sol-Gel
Coatings," which is incorporated by reference herein in its
entirety.
TECHNICAL FIELD
[0002] The present invention relates to optical coatings. More
particularly, this invention relates to optical coatings that
improve, for example, the anti-glare performance of transparent
substrates and methods for forming such optical coatings.
BACKGROUND OF THE INVENTION
[0003] Anti-glare coatings, and anti-glare panels in general, are
desirable in many applications including, portrait glass, privacy
glass, and display screen manufacturing. Such optical coatings
scatter specular reflections into a wide viewing cone to diffuse
glare and reflection.
[0004] Most existing formulations (i.e., wet processing) used to
form anti-glare coatings utilize toxic and environmentally
unfriendly chemicals, such as polymer resins (e.g., urethanes,
acrylates, methacrylates, epoxies, etc.) and/or volatile organic
compound (VOC) solvents (e.g., xylene, alcohols, chlorocarbons,
etc.), leading to increased costs due to material handling and
Environmental, Health, and Safety (EHS) requirements.
[0005] Additionally, conventional anti-glare coatings produced by
wet deposition methods offer very limited thermal processing
options, requiring only low (e.g., less than 200.degree. C.) or
high (e.g., greater than 450.degree. C.) temperatures. For example,
coatings using organic particles or matrices may experience
pyrolysis (i.e., decomposition) if exposed to temperatures above
200-300.degree. C., and thus can not be used on glass that will be
tempered after coating. On the other hand, most existing inorganic
anti-glare coatings require high-temperature processing (e.g.,
greater than 450.degree. C.) to obtain adequate curing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. The drawings are not to scale and
the relative dimensions of various elements in the drawings are
depicted schematically and not necessarily to scale.
[0007] The techniques of the present invention can readily be
understood by considering the following detailed description in
conjunction with the accompanying drawings, in which:
[0008] FIG. 1 is a cross-sectional view of a substrate;
[0009] FIG. 2 is a cross-sectional view of the substrate of FIG. 1
with an anti-glare coating formed thereon according to some
embodiments of the present invention;
[0010] FIG. 3 is an isometric view of a particle within the
anti-glare coating of
[0011] FIG. 2 according to some embodiments of the present
invention;
[0012] FIG. 4 is a graph illustrating optical properties of various
anti-glare coatings formed in accordance with some embodiments of
the present invention; and
[0013] FIG. 5 is a flow chart of a method for forming an anti-glare
coating, or for forming a coated article, such as an anti-glare
panel, according to some embodiments.
DETAILED DESCRIPTION
[0014] A detailed description of one or more embodiments is
provided below along with accompanying figures. The detailed
description is provided in connection with such embodiments, but is
not limited to any particular example. The scope is limited only by
the claims and numerous alternatives, modifications, and
equivalents are encompassed. Numerous specific details are set
forth in the following description in order to provide a thorough
understanding. These details are provided for the purpose of
example and the described techniques may be practiced according to
the claims without some or all of these specific details. For the
purpose of clarity, technical material that is known in the
technical fields related to the embodiments has not been described
in detail to avoid unnecessarily obscuring the description.
[0015] The term "horizontal" as used herein will be understood to
be defined as a plane parallel to the plane or surface of the
substrate, regardless of the orientation of the substrate. The term
"vertical" will refer to a direction perpendicular to the
horizontal as previously defined. Terms such as "above", "below",
"bottom", "top", "side" (e.g. sidewall), "higher", "lower",
"upper", "over", and "under", are defined with respect to the
horizontal plane. The term "on" means there is direct contact
between the elements. The term "above" will allow for intervening
elements.
[0016] Embodiments described herein provide optical coatings, and
methods for forming optical coatings, that improve the anti-glare
performance of, for example, transparent substrates. In some
embodiments, this is accomplished by using water-based suspensions
of sheet-like particles, or "sheet particles," in the optical
coatings. The thickness of the sheet particles is relatively small
compared to the length and width of the particles. The sheet
particles form durable coatings in which the particles may be
arranged in an irregular manner, resulting in porosity within the
coating. In some embodiments, a hydrophilic silicone or silane
emulsion, a hydrophilic silicone or silane solution, or a
combination thereof is used as a binder, and in some embodiments, a
surfactant as well.
[0017] The anti-glare coating may have an effective surface
roughness between 0.2 and 5.0 micrometers (.mu.m). The surface
roughness and other properties of the coating may be influenced by
processing parameters such as particle size, particle shape,
loading, binder level, the addition of fillers, curing method,
etc.
[0018] FIG. 1 illustrates a transparent substrate 100 according to
some embodiments of the present invention. In some embodiments, the
transparent substrate 100 is made of glass and has an upper surface
102 and a thickness 104 of, for example, between 0.1 and 2.0
centimeters (cm). Although only a portion of the substrate 100 is
shown, it should be understood that the substrate 100 may have a
width of, for example, between 5.0 cm and 2.0 meters (m). In some
embodiments, the substrate 100 is made of a transparent polymer,
such as polyethylene terephthalate (PET), poly(methyl methacrylate)
(PMMA), polycarbonate (PC), and polyimide (PI). In some
embodiments, an optical coating, as described below, is formed
above the substrate 100 to create a coated article.
[0019] FIG. 2 illustrates a coated article (or anti-glare panel)
200. The coated article 200 includes the transparent substrate 100
and an anti-glare coating 202. The anti-glare coating 202 is formed
above the upper surface 102 of the substrate 100 and includes
sheet-shaped particles (or sheet particles or nano-sheets) 204,
nano-particles 206, and a binder material (or binder) 208. The
coating 202 has a thickness 210 of between about 1 and 100 .mu.m.
In some embodiments, an upper surface 212 of the coating 202 has a
surface roughness of between 0.2 .mu.m and 5.0 .mu.m due to a
series of surfaces formations formed thereon because of the
presence of the sheet particles 204 and the nano-particles 206. It
should be noted that in FIG. 2 the binder 208 may appear to
substantially form the structure of the coating 202. However, the
actual structure of the coating 202 may be substantially formed by
the particles 204 and 206, which are held together, or in place, by
the binder 208.
[0020] FIG. 3 illustrates one of the sheet particles 204, according
to some embodiments, in greater detail. The sheet particle 204 is
substantially plate-shaped and has, for example, a length 300 of
between 300 and 500 nanometers (nm), a width 302 of between 150 and
250 nm, and a thickness 304 of less than 100 nm (e.g., less than 10
nm, such as between about 1 nm and 10 nm). It should be understood
that the sheet particles 204 may vary in size. In some embodiments,
the sheet particle(s) 204 is made of substantially pure silicon
dioxide (i.e., no other materials may be present). In some
embodiments in which the coating 202 is formed using a sol-gel
system, the sheet particles 204 may be added via an aqueous
solution/slurry, such as SUNLOVELY LFS HN-050 available from AGC
Chemicals Americas, Inc., Exton, Pa. In some embodiments, the sheet
particles are nano-clays, LAPONITE available from Southern Clay
Products, Inc., Gonzales, Tex., or a combination of any of the
previously-mentioned particles.
[0021] Referring again to FIG. 2, in some embodiments, the
nano-particles 206 are spherical particles having a width of, for
example, between 3 and 50 nm. The nano-particles 206 may be made
of, for example, metals oxides, such as titanium oxide, silica, and
fluorine-doped silica, metal fluorides, such as magnesium fluoride,
and combinations thereof. Although shown in FIG. 2, it should be
understood that in some embodiments, the nano-particles 206 are
elongated, while in some embodiments, the nano-particles 206 are
not included in the coating 202.
[0022] The sheet particles 204 are arranged in various ways within
the anti-glare coating 202. For, example, some of the sheet
particles 204 are essentially stacked in a "flat" manner, while
others interact in such a way that irregular structures are formed,
resulting in "pores" (i.e., spaces between the particles) being
formed. For example, some of the sheet particles 204 may form
relatively organized arrangements, similar to a "house of cards"
due to differences between the surface charges at the edges and
faces thereof, resulting in a large, regular porosity. The
nano-particles 206 are dispersed throughout the coating 202, within
the various spaces and/or pores formed between the sheet particles
204.
[0023] The sheet particles 204 have surface chemistries that are
easily manipulated in aqueous systems to allow control over coating
and gelation behavior, allowing them to produce dense conformal
coatings or particles of aggregated nano-sheets without use of
organic additives which require removal from the coating to produce
a durable coating.
[0024] The anti-glare coating 202 may be deposited and/or formed
using various methods. In some embodiments, the coating 202 is
deposited on the transparent substrate 100 using a sol-gel system
in which a sol-gel formulation is prepared and deposited onto the
substrate 100 using, for example, spin coating, spray coating,
slot-die coating, curtain coating, meniscus coating, dip coating,
roller coating, draw down coating, or doctor blade coating. In some
embodiments, the anti-glare coating 202 is applied directly to the
upper surface 102 of the substrate 100. However, in other
embodiments, other materials or layers may be formed between the
substrate 100 and the anti-glare coating 202. Solvents in the
formulation may be removed and/or the coating 202 may be cured
using, for example, a thermal cure, a UV cure, or a combination
thereof. In some embodiments utilizing a thermal cure, depending on
the chemistry used, the coating 202 may be rapidly cured during
tempering of the glass substrate (e.g., 650.degree. C.-700.degree.
C.) or at lower temperatures (e.g., 100.degree. C.-500.degree. C.)
when it is not desirable for the particular substrate to reach
annealing temperatures.
[0025] In some embodiments, the sheet particles 204 (perhaps in
combination with the nano-particles 206) are provided in a
water-based suspension combined a hydrophilic silicone or silane
emulsion, a hydrophilic silicone or silane solution, or a
combination thereof, which is used as the binder 208, but may also
serve as a surfactant. As will be appreciated by one skilled in the
art, emulsions are two-phase mixtures of liquids in which the two
liquids are usually immiscible, while solutions are single-phase
mixtures of solutions. Examples of suitable binder materials
include water-soluble dipodal reactive silanes, such as
aminoalkoxysilanes, glycidoxyalkoxysilanes, carboxylalkoxysilanes,
hydrophilic alkoxysilanes, and combinations thereof. These
materials increase durability by increasing the adhesion and
cohesion of the coating 202, while also decreasing the porosity of
the coating 202. These materials also act as wetting agents and as
effective binders for low and high temperature manufacturing
processing, as the alkoxy groups form a thermally stable network
through the sol-gel reaction, which also bond to the metal oxide
nano-particles 206 and substrate 100. Catalysts, such as acids,
bases, and metal carboxylates, may be used to enhance the rate of
the sol-gel reaction.
[0026] Additionally, glycidoalkoxysilanes may also be cross-linked
using the terminal epoxide (glycido) group, forming an organic
polyether (epoxy) linkage, using suitable catalysts, such as
ultra-violet (UV) catalysts, peroxides, and metal carboxylates.
Further, glycidoalkoxysilanes may be cross-linked with dipodal
alkoxysilanes that have a terminal amine or carboxyl group through
the reaction between the epoxide and amine or carboxyl groups,
requiring only modest heating to drive the reaction.
Glycidoalkoxysilanes and aminoalkoxysilanes may also act as a
coupling agent for forming strongly adhering coatings using these
formulations on transparent polymer substrates. Such coatings may
be cured at relatively low temperatures (e.g., less than
150.degree. C.).
[0027] Aqueous solutions or emulsions of hydrophilic silicone
surfactants may act as wetting agents during coating and convert
into a silica binder when the coatings are heat treated above
300.degree. C. in air or oxygen. They may not provide suitable
binder properties until oxidized to silica, which may also be
achieved using a UV-ozone treatment or an oxidizing plasma
treatment. Hydrophilic silicones may also be used in conjunction
with hydrophilic reactive silanes, in both low and high temperature
processing methods.
[0028] Surface modification of the substrate 100 (e.g., a glass
substrate) with a cationic (e.g. amine or ammonium) or an anionic
(e.g. carboxylate) layer may be used to manipulate the structure of
the interfacial layer by exploiting electrostatic effects between
the charged surfaces of the particles and the substrate. Use of
water as the primary solvent leads to significant cost savings when
compared with organic solvents.
[0029] It should also be noted that UV curing options exist for
binders containing alkoxy and/or glycido (epoxy) groups. UV curing
may be used to selectively form organic network, siloxane network,
or both by choice of UV photo-initiator. UV-curing may also be used
in conjunction with lower temperature (e.g., less than 300.degree.
C.) thermal treatments (post-UV) to further promote formation of
the siloxane network. UV-ozone or oxidizing plasma may be used to
rapidly calcinate the binder into a pure silica binder at very low
temperatures (e.g., less than 100.degree. C.).
[0030] Using the methods described herein, dense anti-glare
coatings may be provided, which do not require the use of toxic or
environmentally hazardous during manufacturing. Anti-glare (light
scattering) properties may be derived solely from the dispersed and
aggregated sheet particles 204, perhaps in combination with the
nano-particles 206. In some embodiments, larger particles (e.g.,
0.1-2 .mu.m) may also be used in the coating 202 to modify the
anti-glare properties. The sheet particles 204 form extremely
durable coatings due to the very high specific surface area and the
high silanol (--Si--OH) density, which results in strong
interfacial bonding between the sheet particles 204, the binder
208, and substrate 100.
[0031] FIG. 4 graphically depicts the haze and 60 degree gloss for
various experimental anti-glare coatings formed in accordance with
embodiments described herein. The anti-glare coatings were formed
on 3.2 mm thick, solar float glass substrates using SUNLOVELY
nano-sheet aqueous slurry, with 0%-0.10% SILWET L-77 hydrophilic
silicone (available from Momentive Specialty Chemicals Inc.,
Columbus, Ohio) as wetting agent and sol stabilizer and binder. The
coatings were processed at approximately 300.degree. C. for about
10 minutes. Region 400 in FIG. 4 indicates desirable haze and gloss
values for anti-glare coatings. As shown, at least some of the
experimental coatings have these desirable properties. The
embodiments described herein allow for precise control over
important optical properties, which is beneficial because depending
on the particular application, different combinations of haze-gloss
may be desirable.
[0032] The sheet particle-based formulations exhibit improved
durability over formulations based on submicron to micron scale
light scattering particles due to greater interfacial area
promoting improved cohesion and adhesion. Additionally, the
durability of the anti-glare coatings described herein may be
controlled by binder level, the addition of fillers, and method of
curing. Additionally, the use of "green" aqueous formulation
chemistry, including non-flammable and non-toxic materials, results
in lower total manufacturing costs than traditional organic
solvent-based formulations due to, for example, reduced solvent
cost as well as reduced hazardous waste and material handling
costs.
[0033] FIG. 5 illustrates a method 500 for forming an anti-glare
coating, or for forming a coated article, such as an anti-glare
panel, according to some embodiments. At step 502, the method 500
begins by providing a substrate, such as the transparent substrate
100 described above. At step 504, a coating formulation is applied
to the substrate. The coating formulation includes an aqueous-based
suspension of particles, such as those described above. At step
506, the coating formulation is cured (e.g., via thermal, UV, or a
combination cure) to form an anti-glare coating above the
substrate. At step 508, the method 500 ends.
[0034] Thus, in some embodiments, a method for coating an article
is provided. A substrate is provided. A coating formulation is
applied to the substrate. The coating formulation includes an
aqueous-based suspension of particles. The particles have a
sheet-like morphology and a thickness of less than about 100 nm.
The coating formulation is cured to form an anti-glare coating
above the substrate. The anti-glare coating has a thickness of
between 1 .mu.m and 100 .mu.m.
[0035] In some embodiments, a method for coating an article is
provided. A transparent substrate is provided. A coating
formulation is applied to the transparent substrate. The coating
formulation includes an aqueous-based suspension of particles and a
hydrophilic silicone or silane emulsion, a hydrophilic silicone or
silane solution, or a combination thereof. The particles have a
sheet-like morphology and a thickness of less than about 100 nm.
The coating formulation is cured to form an anti-glare coating
above the transparent substrate. The anti-glare coating has a
thickness of between 1 .mu.m and 100 .mu.m.
[0036] In some embodiments, a coated article is provided. The
coated article includes a substrate and a coating formed above the
substrate. The coating includes an aqueous-based suspension of
particles and has a thickness of between 1 .mu.m and 100 .mu.m. The
particles have a sheet-like morphology and a thickness of less than
about 100 nm.
[0037] Although the foregoing examples have been described in some
detail for purposes of clarity of understanding, the invention is
not limited to the details provided. There are many alternative
ways of implementing the invention. The disclosed examples are
illustrative and not restrictive.
* * * * *